JP2017120867A - Light-emitting element, display device, electronic device, and illuminating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-emitting element having a material emitting fluorescence as a luminescent material, and having a high light emission efficiency.SOLUTION: A light-emitting element is provided, in which an EL layer between a pair of electrodes includes an organic compound; the organic compound has a first skeleton and a second skeleton; and the light emission that the EL layer exhibits has a delay fluorescence component according to triplet-triplet annihilation. In the organic compound, a first triplet excitation state has a molecular orbital in the first skeleton. In the organic compound, a second triplet excitation state has a molecular orbital in the second skeleton. In the organic compound, a third triplet excitation state has a molecular orbital in the first skeleton. An energy of the third triplet excitation state having the most stable structure of the third triplet excitation state is higher than an energy of the first triplet excitation state having the most stable structure of the third triplet excitation state and lower than an energy of the second triplet excitation state having the most stable structure of the third triplet excitation state.SELECTED DRAWING: Figure 1

Description

  One embodiment of the present invention relates to a light-emitting element in which a light-emitting layer that can emit light by applying an electric field is sandwiched between a pair of electrodes, or a display device, an electronic device, and a lighting device each having the light-emitting element.

  Note that one embodiment of the present invention is not limited to the above technical field. The technical field of one embodiment of the invention disclosed in this specification and the like relates to an object, a method, or a manufacturing method. Alternatively, one embodiment of the present invention relates to a process, a machine, a manufacture, or a composition (composition of matter). Therefore, the technical field of one embodiment of the present invention disclosed in this specification more specifically includes a semiconductor device, a display device, a liquid crystal display device, a light-emitting device, a lighting device, a power storage device, a memory device, a driving method thereof, Alternatively, the production method thereof can be given as an example.

  In recent years, research and development of light-emitting elements using electroluminescence (EL) have been actively conducted. The basic structure of these light-emitting elements is such that a layer containing a light-emitting substance (EL layer) is sandwiched between a pair of electrodes. Light emission from a light-emitting substance can be obtained by applying a voltage between the electrodes of this element.

  Since the above light-emitting element is a self-luminous type, a display device using the light-emitting element has advantages such as excellent visibility, no need for a backlight, and low power consumption. Furthermore, it has advantages such as being thin and light and capable of high response speed.

  In the case of a light-emitting element (for example, an organic EL element) in which an organic compound is used as a light-emitting substance and an EL layer including the light-emitting substance is provided between a pair of electrodes, a voltage is applied between the pair of electrodes, thereby However, holes are injected from the anode into the light-emitting EL layer, and current flows. Then, when the injected electrons and holes are recombined, the light-emitting organic compound is in an excited state, and light emission can be obtained from the excited light-emitting organic compound.

The types of excited states formed by an organic compound include a singlet excited state (S ^* ) and a triplet excited state (T ^* ). The emission from the singlet excited state is fluorescence, and the emission from the triplet excited state is It is called phosphorescence. In addition, the statistical generation ratio of the light emitting elements is considered to be S ^* : T ^* = 1: 3. Therefore, a light emitting element using a phosphorescent compound can obtain higher light emission efficiency than a light emitting element using a fluorescent compound. Therefore, development of a light-emitting element using a phosphorescent compound capable of converting a triplet excited state into light emission has been actively performed in recent years.

  Among light-emitting elements using phosphorescent compounds, in particular, light-emitting elements that emit blue light have not yet been put into practical use because it is difficult to develop a stable compound having a high triplet excitation energy level. Therefore, for light emitting elements that emit blue light, a light emitting element using a more stable fluorescent compound has been developed, and a method for increasing the light emission efficiency of the light emitting element (fluorescent light emitting element) using the fluorescent compound has been developed. Has been explored.

  A triplet-triplet annihilation (TTA) is known as a light emission mechanism capable of converting a part of the triplet excited state into light emission. TTA is an exchange and exchange of excitation energy and spin angular momentum by the proximity of two triplet excitons. As a result, singlet excitons are generated.

  A compound having an anthracene skeleton is known as a compound that generates TTA. In Non-Patent Document 1, it is reported that a compound having an anthracene skeleton is used as a host material of a light-emitting element, whereby a light-emitting element exhibiting blue light emission exhibits an external quantum efficiency higher than 10%. Further, it has been reported that the proportion of the delayed fluorescent component due to TTA is about 10% of the light emitting component exhibited by the light emitting element using the compound having an anthracene skeleton.

  On the other hand, a compound having a tetracene skeleton is known as a compound having a high ratio of delayed fluorescent component by TTA. In Non-Patent Document 2, it is reported that the ratio of the delayed fluorescent component due to TTA in the emission from the compound having a tetracene skeleton is higher than that of the compound having an anthracene skeleton.

Tsunori Suzuki, 6 others, Japanese Journal of Applied Physics, vol. 53, 052102 (2014) D. Y. Kondakov, 3 others, Journal of Applied Physics, vol. 106, 124510 (2009)

  In order to increase luminous efficiency in a light-emitting element having a fluorescent compound, the energy of triplet excitons that do not contribute to light emission is converted to the energy of luminescent singlet excitons and the conversion efficiency is increased. Is important. That is, it is important to convert triplet exciton energy into singlet exciton energy by TTA. In order to increase luminous efficiency in a light-emitting element having a fluorescent compound, it is important to increase the proportion of delayed fluorescent components based on TTA among the light-emitting components exhibited by the light-emitting elements. This is because a high ratio of delayed fluorescent components based on TTA means that the generation ratio of luminescent singlet excitons is increasing.

  Note that not all compounds having an anthracene skeleton or a tetracene skeleton efficiently generate TTA, and some compounds generate TTA, but some compounds hardly generate TTA. However, the reason is not clear. Therefore, there is a need for a method of designing a compound that produces TTA or a compound that has a high proportion of delayed fluorescent components based on TTA. In addition, when a compound having high carrier transportability is used for the host material of the light-emitting layer in the light-emitting element, the driving voltage of the light-emitting element can be reduced. Therefore, if a compound with high carrier transportability and TTA can be designed, a light-emitting element with low driving voltage and high light emission efficiency, that is, a light-emitting element with reduced power consumption can be manufactured. Since a method for designing a compound that generates TTA has not been clarified, it is difficult to design a compound that has high carrier transportability and that generates TTA.

  Therefore, an object of one embodiment of the present invention is to provide a light-emitting element having a high emission efficiency in a light-emitting element having a fluorescent compound. Another object of one embodiment of the present invention is to provide a light-emitting element that emits blue light and has high emission efficiency. Another object of one embodiment of the present invention is to provide a light-emitting element with a high ratio of delayed fluorescent components due to TTA among light-emitting components. Another object of one embodiment of the present invention is to provide a light-emitting element with reduced power consumption. Another object of one embodiment of the present invention is to provide a novel light-emitting element. Another object of one embodiment of the present invention is to provide a novel light-emitting device. Another object of one embodiment of the present invention is to provide a novel display device.

  Note that the description of the above problems does not disturb the existence of other problems. Note that one embodiment of the present invention does not necessarily have to solve all of these problems. Problems other than those described above are naturally apparent from the description of the specification and the like, and it is possible to extract problems other than the above from the description of the specification and the like.

  In one embodiment of the present invention, a light-emitting element includes at least an EL layer, and triplet excitons that do not contribute to light emission are converted into singlet excitons by efficiently generating TTA in the EL layer. Luminescence efficiency of the light-emitting element is improved by emitting light from a child or emitting light from a guest material (fluorescent material) by energy transfer from singlet excitons.

  Further, in order to efficiently generate TTA in the EL layer, it is important to use as the host material a compound in which the proportion of the delayed fluorescent component due to TTA is high in the light emitting component. In particular, in a light-emitting element exhibiting a blue color, it is important to use a compound having high excitation energy as a host material.

  Therefore, one embodiment of the present invention is a light-emitting element including a pair of electrodes and an EL layer sandwiched between the pair of electrodes, the EL layer including an organic compound, The luminescence of the EL layer has a delayed fluorescence component due to triplet-triplet annihilation, and the first triplet excited state in the organic compound is in the organic compound. The first triplet excited state has a molecular orbital in the first skeleton, and the second triplet excited state in the organic compound is in the second skeleton. Among triplet excited states having a molecular orbital and having a molecular orbital in the second skeleton, the triplet excited state having the lowest excitation energy level, and the third triplet excited state in the organic compound is Having a molecular orbital in the first skeleton, and Among triplet excited states having a molecular orbital in the first skeleton other than the triplet excited state, the triplet excited state having the lowest excitation energy level and the most stable structure of the third triplet excited state Is higher than the energy of the first triplet excited state having the most stable structure of the third triplet excited state, and is most stable in the third triplet excited state. The light-emitting element has a lower energy than that of a second triplet excited state having a structure.

  Another embodiment of the present invention is a light-emitting element including a pair of electrodes and an EL layer sandwiched between the pair of electrodes, the EL layer including an organic compound, The light emitted from the EL layer having a first skeleton and a second skeleton has a delayed fluorescence component due to triplet-triplet annihilation, and the first triplet excited state in the organic compound is organic An excited state having the lowest excitation energy level in the compound, the first triplet excited state has a molecular orbital in the first skeleton, and the second triplet excited state in the organic compound is the second A triplet excited state having the lowest excitation energy level among triplet excited states having a molecular orbital in the skeleton and a molecular orbital in the second skeleton, and the third triplet excitation in the organic compound The state has molecular orbitals in the first skeleton and Among the triplet excited states having a molecular orbital in the first skeleton other than the triplet excited state, the triplet excited state having the lowest excitation energy level and the singlet having the lowest excitation energy level in the organic compound The light emission characterized in that the term excited state has an excitation energy level higher than the excitation energy level of the second triplet excited state and lower than or equal to the excitation energy level of the third triplet excited state. It is an element.

  In the above structure, the energy of the singlet excited state is higher than the energy of the second triplet excited state having the most stable structure of the third triplet excited state, and is highest in the third triplet excited state. The energy of the second triplet excited state having the most stable structure of the third triplet excited state is less than or equal to the energy of the third triplet excited state having a stable structure. The energy is preferably higher than the energy of the first triplet excited state having the most stable structure.

  In the above structure, the energy conversion value of the absorption edge in the absorption spectrum of the organic compound is higher than the energy of the second triplet excited state having the most stable structure of the third triplet excited state, and The energy of the second triplet excited state having the most stable structure in the third triplet excited state is equal to or lower than the energy of the third triplet excited state having the most stable structure in the triplet excited state. It is preferable that the energy is higher than the energy of the first triplet excited state having the most stable structure of the triplet excited state.

  In each of the above structures, the first skeleton preferably has an anthracene skeleton, and the second skeleton is preferably bonded to the first skeleton.

  In each of the above structures, light emitted by the EL layer is preferably blue with an emission spectrum peak.

  In each of the above structures, the EL layer preferably includes a guest material that exhibits fluorescence.

  In the above structure, light emitted from the guest material is preferably blue with an emission spectrum peak. In the above structure, the light emitted by the guest material preferably has a delayed fluorescence component. In the above structure, the guest material preferably has a pyrene skeleton.

  Another embodiment of the present invention is a display device including the light-emitting element having any of the above structures and a color filter, a seal, or a transistor. Another embodiment of the present invention is an electronic device including the display device and a housing or a touch sensor. Another embodiment of the present invention is a lighting device including the light-emitting element having any of the above structures and a housing or a touch sensor. Further, one embodiment of the present invention includes not only a light-emitting device having a light-emitting element but also an electronic device having a light-emitting device. Therefore, a light-emitting device in this specification refers to an image display device or a light source (including a lighting device). In addition, a connector in which a light emitting device, for example, FPC (Flexible Printed Circuit), TCP (Tape Carrier Package) is attached, a module in which a printed wiring board is provided at the end of TCP, or COG (Chip On Glass) in a light emitting element It is assumed that the light emitting device also includes all modules on which IC (integrated circuit) is directly mounted by the method.

  According to one embodiment of the present invention, a light-emitting element having a high emission efficiency in a light-emitting element including a fluorescent compound can be provided. Alternatively, according to one embodiment of the present invention, a light-emitting element that emits blue light and has high emission efficiency can be provided. Alternatively, according to one embodiment of the present invention, a light-emitting element with a high ratio of delayed fluorescent components due to TTA among light-emitting components can be provided. Alternatively, according to one embodiment of the present invention, a light-emitting element with reduced power consumption can be provided. Alternatively, according to one embodiment of the present invention, a novel light-emitting element can be provided. Alternatively, according to one embodiment of the present invention, a novel light-emitting device can be provided. Alternatively, according to one embodiment of the present invention, a novel display device can be provided.

  Note that the description of these effects does not disturb the existence of other effects. Note that one embodiment of the present invention does not necessarily have all of these effects. It should be noted that the effects other than these are naturally obvious from the description of the specification, drawings, claims, etc., and it is possible to extract the other effects from the descriptions of the specification, drawings, claims, etc. It is.

FIGS. 3A and 3B are a schematic cross-sectional view of a light-emitting element of one embodiment of the present invention and a schematic diagram illustrating correlation of energy levels. FIGS. 4A and 4B illustrate molecular orbitals of compounds according to one embodiment of the present invention. 4A and 4B illustrate molecular orbitals of compounds according to one embodiment of the present invention. 4A and 4B illustrate molecular orbitals of compounds according to one embodiment of the present invention. 4A and 4B illustrate molecular orbitals of compounds according to one embodiment of the present invention. 4A and 4B illustrate molecular orbitals of compounds according to one embodiment of the present invention. 6A and 6B illustrate energy levels of a compound according to one embodiment of the present invention. 6A and 6B illustrate energy levels of a compound according to one embodiment of the present invention. FIGS. 3A and 3B are a schematic cross-sectional view of a light-emitting element of one embodiment of the present invention and a schematic diagram illustrating correlation of energy levels. FIGS. FIGS. 3A and 3B are a schematic cross-sectional view of a light-emitting element of one embodiment of the present invention and a schematic diagram illustrating correlation of energy levels. FIGS. FIG. 9 is a schematic cross-sectional view of a light-emitting element of one embodiment of the present invention. FIG. 9 is a schematic cross-sectional view of a light-emitting element of one embodiment of the present invention. FIG. 6 is a schematic cross-sectional view illustrating a method for manufacturing a light-emitting element according to one embodiment of the present invention. FIG. 6 is a schematic cross-sectional view illustrating a method for manufacturing a light-emitting element according to one embodiment of the present invention. 4A and 4B are a top view and cross-sectional schematic views illustrating a display device of one embodiment of the present invention. FIG. 10 is a schematic cross-sectional view illustrating a display device of one embodiment of the present invention. FIG. 10 is a schematic cross-sectional view illustrating a display device of one embodiment of the present invention. FIG. 10 is a schematic cross-sectional view illustrating a display device of one embodiment of the present invention. FIG. 10 is a schematic cross-sectional view illustrating a display device of one embodiment of the present invention. FIG. 10 is a schematic cross-sectional view illustrating a display device of one embodiment of the present invention. FIG. 10 is a schematic cross-sectional view illustrating a display device of one embodiment of the present invention. 4A and 4B are a block diagram and a circuit diagram illustrating a display device of one embodiment of the present invention. FIG. 10 is a circuit diagram illustrating a pixel circuit of a display device of one embodiment of the present invention. FIG. 10 is a circuit diagram illustrating a pixel circuit of a display device of one embodiment of the present invention. The perspective view which shows an example of a touch panel. Sectional drawing which shows an example of a display apparatus and a touch sensor. Sectional drawing which shows an example of a touch panel. The block diagram and timing chart figure of a touch sensor. The circuit diagram of a touch sensor. The perspective view explaining a display module. 6A and 6B illustrate electronic devices. 4A and 4B are a perspective view and a cross-sectional view illustrating a light-emitting device of one embodiment of the present invention. FIG. 10 is a cross-sectional view illustrating a light-emitting device of one embodiment of the present invention. 6A and 6B illustrate a lighting device and an electronic device of one embodiment of the present invention. FIG. 10 illustrates a lighting device of one embodiment of the present invention. FIG. 6 is a diagram for explaining the fluorescence lifetime characteristics of the light emitting element according to Example 1; 6A and 6B illustrate current efficiency-luminance characteristics of a light-emitting element according to Example 1. FIG. FIG. 6 is a diagram illustrating external quantum efficiency-luminance characteristics of a light-emitting element according to Example 1. 6A and 6B illustrate luminance-voltage characteristics of a light-emitting element according to Example 1. FIG. FIG. 6 illustrates an electroluminescence spectrum of a light-emitting element according to Example 1. 6A and 6B illustrate current efficiency-luminance characteristics of a light-emitting element according to Example 2. FIG. FIG. 6 is a diagram illustrating external quantum efficiency-luminance characteristics of a light-emitting element according to Example 2. 6A and 6B illustrate luminance-voltage characteristics of a light-emitting element according to Example 2. FIG. 10 illustrates an electroluminescence spectrum of a light-emitting element according to Example 2. 6A and 6B illustrate a light emission angle distribution of a light emitting element according to Example 2. FIG. 6A and 6B illustrate a reliability test result of a light-emitting element according to Example 2. FIG. 6 is a schematic cross-sectional view illustrating a light-emitting element according to Example 3. FIG. 6A and 6B illustrate current efficiency-luminance characteristics of a light-emitting element according to Example 3. FIG. 6A and 6B illustrate current efficiency-luminance characteristics of a light-emitting element according to Example 3. FIG. 6A and 6B illustrate luminance-voltage characteristics of a light-emitting element according to Example 3. 6A and 6B illustrate luminance-voltage characteristics of a light-emitting element according to Example 3. FIG. 10 illustrates an electroluminescence spectrum of a light-emitting element according to Example 3. FIG. 10 illustrates an electroluminescence spectrum of a light-emitting element according to Example 3. FIG. 10 illustrates an electroluminescence spectrum of a light-emitting element according to Example 3. FIG. 10 illustrates an electroluminescence spectrum of a light-emitting element according to Example 3. FIG. 6 is a diagram for explaining chromaticity angle dependency of a light emitting element according to Example 3; 6A and 6B illustrate a reliability test result of a light-emitting element according to Example 3. FIG. 6A and 6B illustrate a reliability test result of a light-emitting element according to Example 3. FIG. 6A and 6B illustrate a reliability test result of a light-emitting element according to Example 3. FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and various changes can be made in form and details without departing from the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited to the description of the embodiments below.

  Note that the position, size, range, and the like of each component illustrated in the drawings and the like may not represent the actual position, size, range, or the like for easy understanding. Therefore, the disclosed invention is not necessarily limited to the position, size, range, or the like disclosed in the drawings and the like.

  In this specification and the like, the ordinal numbers attached as the first and second are used for convenience and may not indicate the order of steps or the order of lamination. Therefore, for example, the description can be made by appropriately replacing “first” with “second” or “third”. In addition, the ordinal numbers described in this specification and the like may not match the ordinal numbers used to specify one embodiment of the present invention.

  Further, in this specification and the like, in describing the structure of the invention with reference to drawings, the same reference numerals may be used in common among different drawings.

  In this specification and the like, the terms “film” and “layer” can be interchanged with each other. For example, the term “conductive layer” may be changed to the term “conductive film”. Alternatively, for example, the term “insulating film” may be changed to the term “insulating layer” in some cases.

In this specification and the like, a singlet excited state (S ^* ) is a singlet state having excitation energy. Of the singlet excited states, the excited state having the lowest energy is referred to as the lowest singlet excited state. The singlet excitation energy level is an excitation energy level in a singlet excited state. Of the singlet excitation energy levels, the lowest excitation energy level is referred to as the lowest singlet excitation energy (S1) level.

In this specification and the like, the triplet excited state (T ^* ) is a triplet state having excitation energy. Of the triplet excited states, the excited state having the lowest energy is referred to as the lowest triplet excited state. A triplet excited state having higher energy than the lowest triplet excited state is referred to as a high triplet excited state. The triplet excitation energy level is an excitation energy level in a triplet excited state. Among triplet excitation energy levels, the lowest excitation energy level is referred to as the lowest triplet excitation energy (T1) level. An energy level higher than the lowest triplet excitation energy level is referred to as a high triplet excitation energy level.

  In this specification and the like, a fluorescent material is a material that emits light in the visible light region when relaxing from a singlet excited state to a ground state. A phosphorescent material is a material that emits light in the visible light region at room temperature when relaxing from a triplet excited state to a ground state. In other words, a phosphorescent material is one of materials that can convert triplet excitation energy into visible light.

  Note that in this specification and the like, room temperature refers to any temperature of 0 ° C. to 40 ° C.

  In this specification and the like, a blue wavelength region is a wavelength region of 400 nm to 550 nm, and blue light emission is light emission having at least one emission spectrum peak in the region.

(Embodiment 1)
In this embodiment, a light-emitting element of one embodiment of the present invention will be described below with reference to FIGS.

<Configuration example of light emitting element>
First, the structure of the light-emitting element of one embodiment of the present invention is described below with reference to FIGS.

  FIG. 1A is a schematic cross-sectional view of a light-emitting element 120 of one embodiment of the present invention.

  The light-emitting element 120 includes a pair of electrodes (the electrode 101 and the electrode 102) and the EL layer 100 provided between the pair of electrodes. The EL layer 100 includes at least a light emitting layer 130.

  In addition, the EL layer 100 illustrated in FIG. 1A includes a functional layer in addition to the light-emitting layer 130. The functional layer includes a hole injection layer 111, a hole transport layer 112, an electron transport layer 118, and an electron injection layer 119.

  Note that in this embodiment, the electrode 101 is an anode and the electrode 102 is a cathode among the pair of electrodes, but the structure of the light-emitting element 120 is not limited thereto. That is, the electrode 101 may be a cathode, the electrode 102 may be an anode, and the layers stacked between the electrodes may be reversed. That is, from the anode side, the hole injection layer 111, the hole transport layer 112, the light emitting layer 130, the electron transport layer 118, and the electron injection layer 119 may be stacked.

  Note that the structure of the EL layer 100 is not limited to the structure shown in FIG. 1A, and is selected from the hole injection layer 111, the hole transport layer 112, the electron transport layer 118, and the electron injection layer 119. What is necessary is just to set it as the structure which has at least one. Alternatively, the EL layer 100 reduces a hole or electron injection barrier, improves a hole or electron transport property, inhibits a hole or electron transport property, or suppresses a quenching phenomenon caused by an electrode. It is good also as a structure which has a functional layer which has the function of being able to do. Note that the light-emitting layer 130 or the functional layer may be a single layer or a structure in which a plurality of layers are stacked.

  FIG. 1B is a schematic cross-sectional view illustrating an example of the light-emitting layer 130 illustrated in FIG. A light-emitting layer 130 illustrated in FIG. 1B includes a host material 131 and a guest material 132.

  The host material 131 preferably has a function of converting triplet excitation energy into singlet excitation energy by TTA. By doing so, part of the triplet excitation energy generated in the light-emitting layer 130 can be converted into singlet excitation energy by TTA in the host material 131 and transferred to the guest material 132, so that it can be extracted as fluorescent light emission. It becomes. For that purpose, the lowest singlet excitation energy (S1) level of the host material 131 is preferably higher than the S1 level of the guest material 132. The lowest triplet excitation energy (T1) level of the host material 131 is preferably lower than the T1 level of the guest material 132.

  The host material 131 may be composed of a single compound or a plurality of compounds. As the guest material 132, a light-emitting organic compound may be used, and the light-emitting organic compound is preferably a substance that can emit fluorescence (hereinafter also referred to as a fluorescent material). In the following description, a structure using a fluorescent material as the guest material 132 will be described. Note that the guest material 132 may be read as a fluorescent material.

<Light emitting mechanism of light emitting element>
First, the light emission mechanism of the light emitting element 120 will be described below.

  In the light-emitting element 120 of one embodiment of the present invention, by applying voltage between a pair of electrodes (the electrode 101 and the electrode 102), electrons from the cathode and holes from the anode are applied to the EL layer 100, respectively. It is injected and current flows. The injected electrons and holes recombine to form excitons. Of excitons generated by carrier recombination, the ratio of singlet excitons to triplet excitons (hereinafter, exciton generation probability) is 1: 3 due to statistical probability.

Note that singlet excitons are generated in the EL layer 100 through the following two processes, and light emission from the guest material 132 is obtained.
(Α) Direct generation process (β) TTA process

<(Α) Direct generation process>
First, the case where carriers (electrons and holes) recombine in the light-emitting layer 130 included in the EL layer 100 to form singlet excitons will be described.

  An exciton is a carrier (electron and hole) pair. Since excitons have energy, the material from which the excitons are generated is in an excited state.

  When carriers recombine in the host material 131, an excited state (singlet excited state or triplet excited state) of the host material 131 is formed by the generation of excitons. At this time, when the excited state of the host material 131 is a singlet excited state, the singlet excitation energy is transferred from the S1 level of the host material 131 to the S1 level of the guest material 132, and the singlet of the guest material 132 is single-ended. A term excited state is formed. In addition, when the excited state of the host material 131 is a triplet excited state, it demonstrates in the below-mentioned ((beta)) TTA process.

  In addition, when carriers recombine in the guest material 132, an excited state (singlet excited state or triplet excited state) of the guest material 132 is formed by generation of excitons.

  When the excited state of the formed guest material 132 is a singlet excited state, light emission can be obtained from the singlet excited state of the guest material 132. At this time, in order to obtain high luminous efficiency, the guest material 132 preferably has a high fluorescence quantum yield. Specifically, the fluorescence quantum yield of the guest material 132 is preferably 50% or more, more preferably 70% or more, and further preferably 90% or more.

  On the other hand, when the triplet excited state of the guest material 132 is formed, the triplet excited state of the guest material 132 does not contribute to light emission because it is thermally deactivated. However, when the T1 level of the host material 131 is lower than the T1 level of the guest material 132, the triplet excitation energy of the guest material 132 changes from the T1 level of the guest material 132 to the T1 level of the host material 131. Energy transfer becomes possible. In that case, conversion from triplet excitation energy to singlet excitation energy becomes possible by the (β) TTA process described later.

<(Β) TTA process>
Next, a case where singlet excitons are formed by triplet excitons formed in the carrier recombination process in the light emitting layer 130 will be described.

Here, the case where the T1 level of the host material 131 is lower than the T1 level of the guest material 132 will be described. A schematic diagram showing the correlation of energy levels at this time is shown in FIG. In addition, notations and symbols in FIG. 1C are as follows. Note that the T1 level of the host material 131 may be higher than the T1 level of the guest material 132.
Host (131): Host material 131
Guest (132): Guest material 132 (fluorescent material)
S _FH : S1 level of the host material 131 T _FH : T1 level of the host material 131 S _FG : S1 level of the guest material 132 (fluorescent material) T _FG : T1 of the guest material 132 (fluorescent material) Level

  Carriers recombine in the host material 131, and an excited state of the host material 131 is formed by the generation of excitons. At this time, when the generated exciton is a triplet exciton, due to the proximity of the two generated triplet excitons, a part of their triplet excitation energy is converted to singlet excitation energy, A singlet excited state of the host material 131 is generated (see TTA in FIG. 1C). This is represented by the following general formula (G1).

^{3 H + 3 H → 1 H} * + 1 H (G1)
^{3 H + 3 H → 3 H} * + 1 H (G2)

The general formula (G1) is a reaction in which singlet excitons ( ¹ H ^* ) are generated from two triplet excitons ( ³ H) in the host material 131. The general formula (G2) is a reaction in which triplet excitons ( ³ H ^* ) excited electronically or vibrationally are generated from two triplet excitons ( ³ H) in the host material 131. . Note that in the general formulas (G1) and (G2), ¹ H represents a singlet ground state in the host material 131.

When the density of triplet excitons in the light-emitting layer 130 is sufficiently high (1 × 10 ⁻¹² cm ⁻³ or more), deactivation of the singlet excitons alone is ignored, and two adjacent triplet excitons are ignored. Only the reaction by can be considered.

Further, the triplet exciton ( ³ H ^* ) excited by electronic or vibration formed by the general formula (G2) can be rapidly converted into a triplet exciton ( ³ H) or Converted to singlet excitons ( ¹ H ^* ). Therefore, in the general formula (G2), if all the electronically or vibrationally excited triplet excitons ( ³ H ^* ) are converted into singlet excitons ( ¹ H ^* ), two triplets One singlet exciton ( ¹ H ^* ) is generated at maximum from the term exciton ( ³ H).

On the other hand, the statistical generation ratio of singlet excitons ( ¹ H ^* ) and triplet excitons ( ³ H) directly generated by recombination of carriers injected from a pair of electrodes is ¹ H ^* : ³ H = 1: 3. That is, the probability that singlet excitons are directly generated by recombination of carriers injected from a pair of electrodes is 25%.

  Therefore, by combining singlet excitons generated directly by recombination of carriers injected from a pair of electrodes with singlet excitons generated by TTA, direct recombination of carriers injected from the pair of electrodes directly Five singlet excitons can be generated from the generated eight excitons (total of singlet excitons and triplet excitons) (general formula (G3)). That is, TTA can improve the singlet exciton generation probability from the conventional 25% to a maximum of 62.5%.

2 ¹ H ^* + 6 ³ H → 2 ¹ H ^* + (3 ¹ H ^* + 3 ¹ H) (G3)

In the singlet excited state of the host material 131 formed by singlet excitons generated by the above process, the guest material 132 having an excitation energy level lower than that of the host material 131 from the S1 level (S _FH ). Energy transfer to the S1 level (S _FG ) occurs (see FIG. 1 (C) Route A). Then, the guest material 132 in a singlet excited state emits fluorescence.

Note that in the case where the excited state formed by the excitons generated by recombination of carriers in the guest material 132 is a triplet excited state, the T1 level (T _FH ) of the host material 131 is changed to the T1 level (T _FH ) of the guest material ( When T _FG is lower than T _FG , T _FG transfers energy to T _FH without being deactivated (see Route B in FIG. 1C) and is used for TTA.

In the case where the T1 level (T _FG ) of the guest material 132 is lower than the T1 level (T _FH ) of the host material 131, the weight ratio of the host material 131 to the guest material 132 is the weight of the guest material 132. A lower ratio is preferred. Specifically, the weight ratio of the guest material 132 to the host material 131 of 1 is preferably greater than 0 and 0.05 or less. By doing so, the probability that carriers are recombined in the guest material 132 can be reduced. In addition, the probability of energy transfer from the T1 level (T _FH ) of the host material 131 to the T1 level (T _FG ) of the guest material 132 can be reduced.

  As described above, triplet excitons formed in the light-emitting layer 130 are converted into singlet excitons by TTA, and thus light emission from the guest material 132 can be efficiently obtained.

<About TTA efficiency>
As described above, TTA can improve the generation probability of singlet excitons and improve the light emission efficiency of the light-emitting element. However, in order to obtain high light emission efficiency, the probability of TTA generation (TTA efficiency). It is important to increase the level of That is, it is important that the proportion of the delayed fluorescent component due to TTA is high in the light emitted by the light emitting element.

  In order to increase the probability of occurrence of TTA, the host material 131 preferably has higher singlet excited state energy and lower triplet excited state energy than the guest material 132. As such a compound, the host material 131 preferably has a condensed aromatic ring skeleton, and more preferably an acene skeleton such as an anthracene skeleton or a tetracene skeleton.

  In a light-emitting element that emits blue light, a compound having large excitation energy needs to be used as the host material 131. That is, a compound having an anthracene skeleton is preferable as a compound that can be used as the light-emitting material or the host material 131 in a light-emitting element that emits blue light and exhibits delayed fluorescence due to TTA. Among them, in order to obtain high luminous efficiency, a compound having an anthracene skeleton and showing high TTA efficiency is preferable.

  When holes from the anode and electrons from the cathode are injected into the EL layer and current flows, the holes and electrons are respectively the highest occupied orbitals (also referred to as Highest Occupied Molecular Orbital, HOMO) of the compound of the EL layer. And injected into the lowest unoccupied orbit (also called Lowest Unoccupied Molecular Orbital, LUMO) and transported.

  When the injected holes and electrons recombine with the host material, the HOMO orbital and LUMO orbitals in the host material have molecular orbitals in the same region, which corresponds to the energy gap between the HOMO level and the LUMO level. Excitons having energy are generated.

  When the injected holes and electrons recombine with the host material, if the host material has molecular orbitals in different regions, the LUMO + n orbital (the molecular orbitals in the same region as the HOMO orbitals). Excitons having an energy corresponding to the energy gap between the HOMO orbital and the orbital having higher energy than the LUMO orbital, where n is a natural number, or HOMO-n ′ orbitals (molecules in the same region as the LUMO orbitals) An exciton having an orbit and having an energy lower than that of the HOMO orbit (where n ′ is a natural number) and an energy gap corresponding to the energy gap between the LUMO orbits is generated.

  The energy corresponding to the energy gap in the host material corresponds to the energy of the lowest singlet excited state. Therefore, the singlet excited state of the host material formed by carrier recombination is the lowest singlet excited state.

  Similarly, the triplet excited state of the host material formed by carrier recombination is a first triplet excited state having a molecular orbital in the same region as the lowest singlet excited state. The first triplet excited state is the lowest triplet excited state.

  The molecular orbital represents the probability of finding a region in a compound where an electron is likely to be found or an electron. With molecular orbitals, it is possible to describe in detail the electronic configuration (spatial distribution and energy of electrons) of molecules.

  The second triplet excited state and the third triplet excited state of the host material are a high triplet excited state (a triplet excited state having higher energy than the first triplet excited state) and the second triplet excited state. The triplet excited state is a triplet excited state having the lowest excitation energy among high triplet excited states having molecular orbitals in a region different from the first triplet excited state, and the third triplet excited state is the first triplet excited state. It is assumed that the triplet excited state has the lowest excitation energy among the high triplet excited states having molecular orbitals in the same region as the triplet excited state. In the case where a high triplet excited state is generated by TTA, the first triplet excited state is present in the same region as the second triplet excited state having a molecular orbital in a region different from the first triplet excited state. A third triplet excited state having a molecular orbital is more easily formed. This is because TTA is a reaction that occurs from the first triplet excited state, which is the lowest triplet excited state. Note that even if the formed third triplet excited state is a state further excited by vibration, the third triplet excited state having the vibration state with the most stable energy can be obtained by quickly relaxing the vibration. Can be formed.

  Note that the three-dimensional structure in the ground state of the compound in the most stable state (hereinafter, the most stable structure) and the most stable structure in the excited state (singlet excited state and triplet excited state) have different three-dimensional structures. Further, the most stable structures in different excited states have different three-dimensional structures. Further, when the compound is in the ground state or the electronic state of an excited state (singlet excited state or triplet excited state) and further has vibration energy or rotational energy, it is in a vibrationally excited or rotationally excited state. When a compound is vibrationally excited in a certain electronic state, the three-dimensional structure is different from the most stable energy state of the electronic state even though the molecular structure is the same. For example, the most stable structure in the first triplet excited state (the three-dimensional structure in the most energy stable state) and the most stable structure in the third triplet excited state are different structures. The structure of the first triplet excited state that is vibrationally excited in the first triplet excited state and has the most stable structure of the third triplet excited state is the same as that in the first triplet excited state. The structure is different from the most stable structure. In other words, if a compound has different steric structures in a certain electronic state, it has different energies.

  In one embodiment of the present invention, the energy of the third triplet excited state having the most stable structure in the third triplet excited state is the second triplet having the most stable structure in the third triplet excited state. It is preferably lower than the energy in the excited state. By doing so, internal conversion from the third triplet excited state having the most stable structure to the second triplet excited state is less likely to occur. Note that the third triplet excited state has a molecular orbital in the same region as the first triplet excited state, and the first triplet excited state has a molecular orbital in the same region as the lowest singlet excited state. . That is, the third triplet excited state has a molecular orbital in the same region as the lowest singlet excited state. Therefore, the probability of occurrence of intersystem crossing and energy transfer from the formed third triplet excited state to the lowest singlet excited state is increased. That is, it is preferable because the probability that a singlet excited state is generated by TTA increases. At this time, the energy of the third triplet excited state having the most stable structure in the third triplet excited state is equal to that of the second triplet excited state having the most stable structure in the third triplet excited state. It is preferably lower than energy by 0.1 eV or more, more preferably 0.2 eV or more.

  On the other hand, the energy of the third triplet excited state having the most stable structure in the third triplet excited state is greater than or equal to the energy of the second triplet excited state having the most stable structure in the third triplet excited state. In some cases, the formed third triplet excited state is likely to transition to the second triplet excited state by internal conversion. Note that the second triplet excited state has a molecular orbital in a region different from the first triplet excited state, and the first triplet excited state has a molecular orbital in the same region as the lowest singlet excited state. . That is, the second triplet excited state has a molecular orbital in a region different from the lowest singlet excited state. Therefore, the probability of occurrence of intersystem crossing and energy transfer from the second triplet excited state to the lowest singlet excited state is low. That is, the probability that a singlet excited state is generated by TTA is lowered.

  Note that since the third triplet excited state has a molecular orbital in the same region as the lowest singlet excited state, the energy of the third triplet excited state having the most stable structure of the third triplet excited state is Even when the energy is higher than the energy of the second triplet excited state having the most stable structure of the third triplet excited state, the energy of the lowest singlet excited state is higher than the energy of the second triplet excited state. And it is preferable that it is below the energy of the third triplet excited state. More preferably, the energy of the lowest singlet excited state is higher than the energy of the second triplet excited state having the most stable structure of the third triplet excited state, and the most stable structure of the third triplet excited state. Or less than the energy of the third triplet excited state having. By doing so, the probability of occurrence of intersystem crossing and energy transfer from the formed third triplet excited state to the lowest singlet excited state is increased. That is, it is preferable because the probability that a singlet excited state is generated by TTA increases. At this time, the energy of the third triplet excited state having the most stable structure in the third triplet excited state is equal to that of the second triplet excited state having the most stable structure in the third triplet excited state. It is preferably higher than energy by 0.1 eV or more, more preferably 0.2 eV or more.

  In order to efficiently generate TTA, an organic compound in which TTA is generated preferably has an energy difference of 0.5 eV or more between the lowest singlet excitation energy level and the lowest triplet excitation energy level. In addition, the lowest singlet excitation energy level is preferably energy that is twice or less the lowest triplet excitation energy level.

  Note that the lowest singlet excitation energy level can be observed from an absorption spectrum when the organic compound transitions from the singlet ground state to the lowest singlet excited state. Alternatively, the lowest singlet excitation energy level may be estimated from the peak wavelength of the fluorescence emission spectrum of the organic compound. The lowest triplet excitation energy level can be observed from the absorption spectrum when the organic compound transitions from the singlet ground state to the lowest triplet excited state, but is observed because the transition is forbidden. It can be difficult. In that case, the lowest triplet excitation energy level may be estimated from the phosphorescence spectrum peak wavelength of the organic compound.

  Therefore, the energy conversion value difference between the peak wavelength of the fluorescence emission spectrum and the peak wavelength of the phosphorescence emission spectrum in the organic compound included in the light-emitting element of one embodiment of the present invention is preferably 0.5 eV or more.

<Calculation of molecular orbitals by quantum chemical calculation>
Next, an example of calculation of molecular orbitals by quantum chemical calculation and calculation of triplet excitation energy levels of a compound that can be used for one embodiment of the present invention will be described. The structures and abbreviations of the compounds used for the calculation are shown below.

  The calculation method is as follows. Gaussian 09 was used as the quantum chemistry calculation program. The calculation was performed using a high performance computer (ICE X, manufactured by SGI).

  First, the most stable structure in the singlet ground state was calculated by the density functional theory (DFT). 6-311G (d, p) was used as a basis function. As the functional, CAM-B3LYP was used. Next, the energy and molecular orbital distribution related to the transition from the most stable structure of the singlet ground state to the triplet excited state were calculated using a time-dependent density functional method (TD-DFT). Note that the total energy of DFT is represented by the sum of potential energy, electrostatic energy between electrons, and exchange correlation energy including all the interactions between kinetic energy of electrons and complex electrons. In DFT, the exchange correlation interaction is approximated by a functional of one electron potential expressed by electron density (meaning a function of a function), and thus the calculation is highly accurate.

  FIG. 2 to FIG. 6 show distributions of molecular orbitals having a large contribution among the molecular orbitals related to the transition from the singlet ground state to the triplet excited state.

  As shown in FIGS. 2A to 2C, in 9- [4- (10-phenyl-9-anthryl) phenyl] -9H-carbazole (abbreviation: CzPA), from a singlet ground state to a triplet excited state. The transition to 151 is a transition between a HOMO orbital and a LUMO orbital, and each has a molecular orbital in the anthracene skeleton. The transition from the singlet ground state to the triplet excited state 152 is a transition between the HOMO-2 orbital and LUMO + 1 orbitals, and each has a molecular orbital on a substituent (here, phenylcarbazole skeleton) bonded to the anthracene skeleton. have. The transition from the singlet ground state to the triplet excited state 153 is a transition between the HOMO orbital and the LUMO + 8 orbital, and a transition between the HOMO-5 orbital and the LUMO orbital. have. Therefore, the triplet excited state 151 has a molecular orbital in the anthracene skeleton, the triplet excited state 152 has a molecular orbital in a substituent bonded to the anthracene skeleton, and the triplet excited state 153 has a molecular orbital in the anthracene skeleton. Triplet excited state. Note that the HOMO-2 and HOMO-5 orbits represent the second and fifth orbits having lower energy than the HOMO orbit, and the LUMO + 1 and LUMO + 8 orbits have the first and higher energies than the LUMO orbit. Represents the eighth trajectory. In addition, the energy related to the transition from the singlet ground state to the triplet excited state increases in the order of the triplet excited states 151, 152, and 153, and the triplet excited state 151 is the lowest triplet excited state in CzPA.

  In addition, as shown in FIGS. 3A to 3D, triplet excitation from a singlet ground state in 2-tert-butyl-9,10-di (2-naphthyl) anthracene (abbreviation: t-BuDNA) is performed. The transition to the state 161 is a transition between the HOMO orbital and the LUMO orbital, and each has a molecular orbital in the anthracene skeleton. The transition from the singlet ground state to the triplet excited state 162 is a transition between the HOMO-1 orbital and the LUMO + 2 orbital, and the molecular orbitals are attached to the substituents (here, the naphthalene skeleton) bonded to the anthracene skeleton. Have. In addition, the transition from the singlet ground state to the triplet excited state 163 is a transition between the HOMO-2 orbital and LUMO + 1 orbitals, and the molecular orbitals are respectively attached to the substituents (here, the naphthalene skeleton) bonded to the anthracene skeleton. Have. The transition from the singlet ground state to the triplet excited state 164 is a transition between the HOMO-6 orbit and the LUMO orbital, and a transition between the HOMO and LUMO + 6 orbitals. have. Therefore, the triplet excited state 161 has a molecular orbital in the anthracene skeleton, the triplet excited states 162 and 163 have a molecular orbital in a substituent bonded to the anthracene skeleton, and the triplet excited state 164 has a molecular orbital in the anthracene skeleton. Is a triplet excited state. Note that the HOMO-1 orbit, the HOMO-2 orbit, and the HOMO-6 orbit represent the first, second and sixth orbits having lower energy than the HOMO orbit, and the LUMO + 1 orbit, LUMO + 2 and LUMO + 6 orbits, Represents the first, second and sixth trajectories with higher energy than the LUMO trajectory. The energy related to the transition from the singlet ground state to the triplet excited state is larger in the order of the triplet excited states 161, 162, 163, and 164. The triplet excited state 161 is the lowest triplet excited state in t-BuDNA. is there.

  As shown in FIGS. 4A to 4D, in 7- [4- (10-phenyl-9-anthryl) phenyl] -7H-dibenzo [c, g] carbazole (abbreviation: cgDBCzPA), The transition from the term ground state to the triplet excited state 171 is a transition between the HOMO-1 orbital and the LUMO orbital, and each has a molecular orbital in the anthracene skeleton. Further, the transition from the singlet ground state to the triplet excited state 172 is a transition between the HOMO orbital and LUMO + 1 orbitals, and each has a molecular orbital on a substituent (here, phenyldibenzocarbazole skeleton) bonded to the anthracene skeleton. Have. The transition from the singlet ground state to the triplet excited state 173 is a transition between the HOMO orbital and the LUMO + 3 orbital, and a transition between the HOMO-3 orbital and the LUMO + 1 orbital, which is coupled to the anthracene skeleton. The substituent (here, phenyldibenzocarbazole skeleton) has a molecular orbital. The transition from the singlet ground state to the triplet excited state 174 is a transition between the HOMO-1 orbital and the LUMO + 10 orbital, and a transition between the HOMO-7 orbital and the LUMO orbital. Has molecular orbitals. Therefore, the triplet excited state 171 has a molecular orbital in the anthracene skeleton, the triplet excited states 172 and 173 have a molecular orbital in a substituent bonded to the anthracene skeleton, and the triplet excited state 174 has a molecular orbital in the anthracene skeleton. Is a triplet excited state. Note that the HOMO-1 orbit, the HOMO-3 orbit, and the HOMO-7 orbit represent the first, third and seventh orbits having lower energy than the HOMO orbit, and the LUMO + 1 orbit, LUMO + 3 and LUMO + 10 orbits Represents the first, third and tenth orbits having higher energy than the LUMO orbitals. In addition, the energy related to the transition from the singlet ground state to the triplet excited state increases in the order of triplet excited states 171, 172, 173, and 174, and the triplet excited state 171 is the lowest triplet excited state in cgDBCzPA.

  In addition, as illustrated in FIGS. 5A to 5D, in 9- (2-naphthyl) -10- [4- (1-naphthyl) phenyl] anthracene (abbreviation: BH-1), a singlet ground state The transition from the triplet excited state 181 to the triplet excited state 181 is a transition between the HOMO orbital and LUMO orbitals, and each has a molecular orbital in the anthracene skeleton. The transition from the singlet ground state to the triplet excited state 182 is a transition between the HOMO-1 orbital and LUMO + 1 orbitals, and each has a molecular orbital on a substituent (here, phenylnaphthalene skeleton) bonded to the anthracene skeleton. have. The transition from the singlet ground state to the triplet excited state 183 is a transition between a HOMO-2 orbital and a LUMO + 2 orbital, and each has a molecular orbital on a substituent (here, a naphthalene skeleton) bonded to an anthracene skeleton. Have. The transition from the singlet ground state to the triplet excited state 184 is a transition between the HOMO orbital and the LUMO + 8 orbital, and a transition between the HOMO-7 orbital and the LUMO orbital. have. Therefore, the triplet excited state 181 has a molecular orbital in the anthracene skeleton, the triplet excited states 182 and 183 have a molecular orbital in a substituent bonded to the anthracene skeleton, and the triplet excited state 184 has a molecular orbital in the anthracene skeleton. Is a triplet excited state. Note that the HOMO-1 orbit, the HOMO-2 orbit, and the HOMO-7 orbit represent the first, second and seventh orbits having lower energy than the HOMO orbit. Represents the first, second and eighth trajectories with higher energy than the LUMO trajectory. The energy related to the transition from the singlet ground state to the triplet excited state is larger in the order of the triplet excited states 181, 182, 183, and 184, and the triplet excited state 181 is the lowest triplet excited state in BH-1. is there.

  In addition, as shown in FIGS. 6A to 6D, in 9- (1-naphthyl) -10- (2-naphthyl) anthracene (abbreviation: α, β-ADN), a triplet from a singlet ground state is obtained. The transition to the excited state 191 is a transition between the HOMO orbital and the LUMO orbital, and each has a molecular orbital in the anthracene skeleton. The transition from the singlet ground state to the triplet excited state 192 is a transition between the HOMO-1 orbital and the LUMO + 2 orbital, and each has a molecular orbital on the substituent (here, the naphthalene skeleton) bonded to the anthracene skeleton. Have. The transition from the singlet ground state to the triplet excited state 193 is a transition between the HOMO-2 orbital and LUMO + 1 orbitals, and the molecular orbitals are attached to the substituents (here, the naphthalene skeleton) bonded to the anthracene skeleton. Have. The transition from the singlet ground state to the triplet excited state 194 is a transition between the HOMO-6 orbit and the LUMO orbital, and a transition between the HOMO and LUMO + 6 orbitals. have. Therefore, the triplet excited state 191 has a molecular orbital in the anthracene skeleton, the triplet excited states 192 and 193 have a molecular orbital in a substituent bonded to the anthracene skeleton, and the triplet excited state 194 has a molecular orbital in the anthracene skeleton. Is a triplet excited state. Note that the HOMO-1 orbit, the HOMO-2 orbit, and the HOMO-6 orbit represent the first, second, and sixth orbits having lower energy than the HOMO orbit. Represents the first, second and sixth trajectories with higher energy than the LUMO trajectory. The energy related to the transition from the singlet ground state to the triplet excited state is large in the order of the triplet excited states 191, 192, 193, 194, and the triplet excited state 191 is the lowest triplet excitation in α, β-ADN. State.

  Next, in each compound, the triplet excited state (triple excited state) having the lowest excitation energy among the high triplet excited states having a molecular orbital in the anthracene skeleton (triplet excited state having higher excitation energy than the lowest triplet excited state). The most stable structure in the term excited states 153, 164, 174, 184, 194) was calculated by the time-dependent density functional theory (TD-DFT). 6-311G (d, p) was used as a basis function. As the functional, CAM-B3LYP was used. Further, the energy of the high triplet excited state having the most stable structure of the triplet excited state was calculated based on the energy of the most stable structure of the singlet ground state. Here, the lowest triplet excited state is the first triplet excited state (triplet excited states 151, 161, 171, 181, 191). The triplet excited state having the lowest excitation energy among the triplet excited states having a molecular orbital in the substituent bonded to the anthracene skeleton and the molecular orbital in the substituent bonded to the anthracene skeleton is the second triplet excited state. It is a term excited state (triplet excited state 152, 162, 172, 182, 192). Triplet excitation having the lowest excitation energy among triplet excited states having molecular orbitals in the anthracene skeleton and having molecular orbitals in the anthracene skeleton other than the first triplet excited state (lowest triplet excited state). The state is the third triplet excited state (triplet excited states 153, 164, 174, 184, 194).

  The excitation energy levels of the second triplet excited state having the most stable structure of the third triplet excited state and the third triplet excited state of each compound estimated as described above are shown in FIGS. And in Table 1. In the above calculation method, since the triplet excitation energy level tends to be underestimated, the calculated value is corrected by 1.066 times.

  In CzPA and t-BuDNA, the energy of the third triplet excited state having the most stable structure in the third triplet excited state is the second triplet having the most stable structure in the third triplet excited state. Lower than excited state energy. Therefore, internal conversion from the third triplet excited state having the most stable structure to the second triplet excited state hardly occurs. The third triplet excited state has a molecular orbital in the same region as the first triplet excited state, and the first triplet excited state has a molecular orbital in the same region as the lowest singlet excited state. That is, the third triplet excited state has a molecular orbital in the same region as the lowest singlet excited state. Therefore, the probability of occurrence of intersystem crossing and energy transfer from the formed third triplet excited state to the lowest singlet excited state is increased. That is, it is preferable because the probability that a singlet excited state is generated by TTA increases.

  On the other hand, in BH-1 and α, β-ADN, the energy of the third triplet excited state having the most stable structure of the third triplet excited state is the most stable structure of the third triplet excited state. It is more than the energy of the second triplet excited state. Therefore, the formed third triplet excited state easily transitions to the second triplet excited state quickly by internal conversion. The second triplet excited state has a molecular orbital in a region different from the first triplet excited state, and the first triplet excited state has a molecular orbital in the same region as the lowest singlet excited state. That is, the second triplet excited state has a molecular orbital in a region different from the lowest singlet excited state. Therefore, the probability of occurrence of intersystem crossing and energy transfer from the second triplet excited state to the lowest singlet excited state is low. That is, the probability that a singlet excited state is generated by TTA is lowered.

  In cgDBCzPA, the energy of the third triplet excited state having the most stable structure in the third triplet excited state is the second triplet excited state having the most stable structure in the third triplet excited state. More than energy. The energy difference is 0.2 eV or more. As will be described later, the lowest singlet excitation energy level calculated from the measurement of the absorption spectrum of cgDBCzPA is 2.95 eV. Therefore, the energy of the lowest singlet excited state of cgDBCzPA is higher than the energy of the second triplet excited state and less than or equal to the energy of the third triplet excited state, or the energy of the lowest singlet excited state is The energy of the third triplet excited state which is higher than the energy of the second triplet excited state having the most stable structure of the third triplet excited state and has the most stable structure of the third triplet excited state. It is as follows. As described above, since the third triplet excited state has molecular orbitals in the same region as the lowest singlet excited state, the intersystem crossing from the formed third triplet excited state to the lowest singlet excited state. And the probability that energy transfer will occur. That is, it is preferable because the probability that a singlet excited state is generated by TTA increases.

  As will be described later, the lowest triplet excitation energy levels calculated from phosphorescence emission spectrum measurements at low temperatures (10K) of CzPA, t-BuDNA, and cgDBCzPA are 1.72 eV, 1.70 eV, and 1.72 eV, respectively. It is. Therefore, the second triplet excited state having the most stable structure of the third triplet excited state and the third triplet excited state having the most stable structure of the third triplet excited state in the compound are respectively This is a triplet excited state having higher energy than the first triplet excited state (lowest triplet excited state).

<Material>
Next, details of components of the light-emitting element according to one embodiment of the present invention are described below.

≪Luminescent layer≫
As a material that can be used for the host material 131 in the light-emitting layer 130, an organic compound having a delayed fluorescence component due to triplet-triplet annihilation (TTA) among the emitted light is preferable. Specifically, a compound having an anthracene skeleton as the first skeleton is preferable, and a compound having a substituent bonded to the anthracene skeleton as the second skeleton is preferable. The substituent bonded to the anthracene skeleton (second skeleton) preferably has a carbazole skeleton, and may be bonded to the anthracene skeleton which is the first skeleton or an aryl group bonded to the anthracene skeleton by the 9-position of the carbazole skeleton. More preferred. Alternatively, the substituent (second skeleton) bonded to the anthracene skeleton has a naphthyl group, and the second position of the naphthyl group is bonded to the anthracene skeleton which is the first skeleton or the aryl group bonded to the anthracene skeleton. Is preferred. The aryl group may have another substituent.

  In the organic compound having an anthracene skeleton, the triplet excitation energy level of the substituent bonded to the anthracene skeleton is preferably higher than the triplet excitation energy level of the anthracene skeleton, and the energy difference from the excitation energy level Is more preferably 0.5 eV or more.

  In the light emitting layer 130, the host material 131 may be composed of one kind of compound, or may be composed of a plurality of compounds.

  In the light-emitting layer 130, the guest material 132 is not particularly limited, but anthracene derivatives, tetracene derivatives, chrysene derivatives, phenanthrene derivatives, pyrene derivatives, perylene derivatives, stilbene derivatives, acridone derivatives, coumarin derivatives, phenoxazine derivatives, A phenothiazine derivative or the like is preferable. For example, the following materials can be used.

  5,6-bis [4- (10-phenyl-9-anthryl) phenyl] -2,2′-bipyridine (abbreviation: PAP2BPy), 5,6-bis [4 ′-(10-phenyl-9-anthryl) Biphenyl-4-yl] -2,2′-bipyridine (abbreviation: PAPP2BPy), N, N′-diphenyl-N, N′-bis [4- (9-phenyl-9H-fluoren-9-yl) phenyl] Pyrene-1,6-diamine (abbreviation: 1,6FLPAPrn), N, N′-bis (3-methylphenyl) -N, N′-bis [3- (9-phenyl-9H-fluoren-9-yl) Phenyl] pyrene-1,6-diamine (abbreviation: 1,6 mM emFLPAPrn), N, N′-bis [4- (9H-carbazol-9-yl) phenyl] -N, N′-diphenylstilbene-4,4 -Diamine (abbreviation: YGA2S), 4- (9H-carbazol-9-yl) -4 '-(10-phenyl-9-anthryl) triphenylamine (abbreviation: YGAPA), 4- (9H-carbazole-9- Yl) -4 ′-(9,10-diphenyl-2-anthryl) triphenylamine (abbreviation: 2YGAPPA), N, 9-diphenyl-N- [4- (10-phenyl-9-anthryl) phenyl] -9H -Carbazole-3-amine (abbreviation: PCAPA), perylene, 2,5,8,11-tetra (tert-butyl) perylene (abbreviation: TBP), 4- (10-phenyl-9-anthryl) -4'- (9-phenyl-9H-carbazol-3-yl) triphenylamine (abbreviation: PCBAPA), N, N ″-(2-tert-butylanthrace -9,10-diyldi-4,1-phenylene) bis [N, N ', N'-triphenyl-1,4-phenylenediamine] (abbreviation: DPABPA), N, 9-diphenyl-N- [4- (9,10-diphenyl-2-anthryl) phenyl] -9H-carbazol-3-amine (abbreviation: 2PCAPPA), N- [4- (9,10-diphenyl-2-anthryl) phenyl] -N, N ′ , N′-triphenyl-1,4-phenylenediamine (abbreviation: 2DPAPPA), N, N, N ′, N ′, N ″, N ″, N ′ ″, N ′ ″-octaphenyldibenzo [G, p] Chrysene-2,7,10,15-tetraamine (abbreviation: DBC1), coumarin 30, N- (9,10-diphenyl-2-anthryl) -N, 9-diphenyl-9H-carbazole-3 − Amine (abbreviation: 2PCAPA), N- [9,10-bis (1,1′-biphenyl-2-yl) -2-anthryl] -N, 9-diphenyl-9H-carbazol-3-amine (abbreviation: 2PCABPhA) ), N- (9,10-diphenyl-2-anthryl) -N, N ′, N′-triphenyl-1,4-phenylenediamine (abbreviation: 2DPAPA), N- [9,10-bis (1, 1′-biphenyl-2-yl) -2-anthryl] -N, N ′, N′-triphenyl-1,4-phenylenediamine (abbreviation: 2DPABPhA), 9,10-bis (1,1′-biphenyl) -2-yl) -N- [4- (9H-carbazol-9-yl) phenyl] -N-phenylanthracen-2-amine (abbreviation: 2YGABPhA), N, N, 9-triphenylanthra -9-amine (abbreviation: DPhAPhA), coumarin 6, coumarin 545T, N, N'-diphenylquinacridone (abbreviation: DPQd), rubrene, 5,12-bis (1,1'-biphenyl-4-yl)- 6,11-diphenyltetracene (abbreviation: BPT), 2- (2- {2- [4- (dimethylamino) phenyl] ethenyl} -6-methyl-4H-pyran-4-ylidene) propanedinitrile (abbreviation: DCM 1), 2- {2-methyl-6- [2- (2,3,6,7-tetrahydro-1H, 5H-benzo [ij] quinolizin-9-yl) ethenyl] -4H-pyran-4-ylidene } Propanedinitrile (abbreviation: DCM2), N, N, N ′, N′-tetrakis (4-methylphenyl) tetracene-5,11-diamine (abbreviation: p-mPhTD), , 14-diphenyl-N, N, N ′, N′-tetrakis (4-methylphenyl) acenaphtho [1,2-a] fluoranthene-3,10-diamine (abbreviation: p-mPhAFD), 2- {2- Isopropyl-6- [2- (1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H, 5H-benzo [ij] quinolizin-9-yl) ethenyl] -4H-pyran- 4-Ilidene} propanedinitrile (abbreviation: DCJTI), 2- {2-tert-butyl-6- [2- (1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H) , 5H-benzo [ij] quinolizin-9-yl) ethenyl] -4H-pyran-4-ylidene} propanedinitrile (abbreviation: DCJTB), 2- (2,6-bis {2- [4- (dimethylamino) ) Phenyl ] Ethenyl} -4H-pyran-4-ylidene) propanedinitrile (abbreviation: BisDCM), 2- {2,6-bis [2- (8-methoxy-1,1,7,7-tetramethyl-2, 3,6,7-tetrahydro-1H, 5H-benzo [ij] quinolizin-9-yl) ethenyl] -4H-pyran-4-ylidene} propanedinitrile (abbreviation: BisDCJTM), 5,10,15,20- And tetraphenylbisbenzo [5,6] indeno [1,2,3-cd: 1 ′, 2 ′, 3′-lm] perylene.

  Note that the light-emitting layer 130 may include a material other than the host material 131 and the guest material 132.

Note that there is no particular limitation on a material that can be used for the light-emitting layer 130; for example, tris (8-quinolinolato) aluminum (III) (abbreviation: Alq), tris (4-methyl-8-quinolinolato) aluminum. (III) (abbreviation: Almq ₃ ), bis (10-hydroxybenzo [h] quinolinato) beryllium (II) (abbreviation: BeBq ₂ ), bis (2-methyl-8-quinolinolato) (4-phenylphenolato) aluminum (III) (abbreviation: BAlq), bis (8-quinolinolato) zinc (II) (abbreviation: Znq), bis [2- (2-benzoxazolyl) phenolato] zinc (II) (abbreviation: ZnPBO), bis [2- (2-benzothiazolyl) phenolate] metal complexes such as zinc (II) (abbreviation: ZnBTZ), 2- (4-biphenyl) Ryl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole (abbreviation: PBD), 1,3-bis [5- (p-tert-butylphenyl) -1,3, 4-oxadiazol-2-yl] benzene (abbreviation: OXD-7), 3- (4-biphenylyl) -4-phenyl-5- (4-tert-butylphenyl) -1,2,4-triazole ( Abbreviation: TAZ), 2,2 ′, 2 ″-(1,3,5-benzenetriyl) tris (1-phenyl-1H-benzimidazole) (abbreviation: TPBI), bathophenanthroline (abbreviation: BPhen), Heterocyclic compounds such as bathocuproin (abbreviation: BCP), 9- [4- (5-phenyl-1,3,4-oxadiazol-2-yl) phenyl] -9H-carbazole (abbreviation: CO11), 4, 4'- Bis [N- (1-naphthyl) -N-phenylamino] biphenyl (abbreviation: NPB or α-NPD), N, N′-bis (3-methylphenyl) -N, N′-diphenyl- [1,1 '-Biphenyl] -4,4'-diamine (abbreviation: TPD), 4,4'-bis [N- (spiro-9,9'-bifluoren-2-yl) -N-phenylamino] biphenyl (abbreviation: Aromatic amine compounds such as BSPB). In addition, condensed polycyclic aromatic compounds such as anthracene derivatives, phenanthrene derivatives, pyrene derivatives, chrysene derivatives, and dibenzo [g, p] chrysene derivatives can be given. Specifically, 9,10-diphenylanthracene (abbreviation: DPAnth) N, N-diphenyl-9- [4- (10-phenyl-9-anthryl) phenyl] -9H-carbazol-3-amine (abbreviation: CzA1PA), 4- (10-phenyl-9-anthryl) triphenyl Amine (abbreviation: DPhPA), 4- (9H-carbazol-9-yl) -4 ′-(10-phenyl-9-anthryl) triphenylamine (abbreviation: YGAPA), N, 9-diphenyl-N- [4 -(10-phenyl-9-anthryl) phenyl] -9H-carbazol-3-amine (abbreviation: PCAPA), N, 9-diphenyl-N- {4- [4- (10-phenyl-9-anthryl) phenyl] phenyl} -9H-carbazol-3-amine (abbreviation: PCAPBA), N, 9-diphenyl-N- ( 9,10-diphenyl-2-anthryl) -9H-carbazol-3-amine (abbreviation: 2PCAPA), 6,12-dimethoxy-5,11-diphenylchrysene, N, N, N ′, N ′, N ″ , N ″, N ′ ″, N ′ ″-octaphenyldibenzo [g, p] chrysene-2,7,10,15-tetraamine (abbreviation: DBC1), 9- [4- (10-phenyl- 9-anthryl) phenyl] -9H-carbazole (abbreviation: CzPA), 3,6-diphenyl-9- [4- (10-phenyl-9-anthryl) phenyl] -9H-carbazole (abbreviation: DPCzPA), 9 10-bis (3,5-diphenylphenyl) anthracene (abbreviation: DPPA), 9,10-di (2-naphthyl) anthracene (abbreviation: DNA), 2-tert-butyl-9,10-di (2-naphthyl) ) Anthracene (abbreviation: t-BuDNA), 9,9′-bianthryl (abbreviation: BANT), 9,9 ′-(stilbene-3,3′-diyl) diphenanthrene (abbreviation: DPNS), 9,9′- (Stilbene-4,4′-diyl) diphenanthrene (abbreviation: DPNS2), 3,3 ′, 3 ″-(benzene-1,3,5-triyl) tripylene (abbreviation: TPB3), and the like can be given. . In addition, one or more kinds of substances having an energy gap larger than that of the guest material 132 may be selected and used from these and known substances.

  Note that the light-emitting layer 130 can be formed of a plurality of layers of two or more layers. For example, when the first light-emitting layer and the second light-emitting layer are sequentially stacked from the hole transport layer side to form the light-emitting layer 130, a substance having a hole-transport property is used as the host material of the first light-emitting layer, There is a structure in which a substance having an electron transporting property is used as a host material of the second light emitting layer.

≪A pair of electrodes≫
The electrode 101 and the electrode 102 have a function of injecting holes and electrons into the light-emitting layer 130. The electrode 101 and the electrode 102 can be formed using a metal, an alloy, a conductive compound, a mixture or a stacked body thereof. Typical examples of the metal include aluminum (Al), transition metals such as silver (Ag), tungsten, chromium, molybdenum, copper, and titanium, alkali metals such as lithium (Li) and cesium, calcium, magnesium (Mg Group 2 metals such as) can be used. A rare earth metal such as ytterbium (Yb) may be used as the transition metal. As the alloy, an alloy containing the above metal can be used, and examples thereof include MgAg and AlLi. Examples of the conductive compound include indium tin oxide (hereinafter referred to as ITO), indium tin oxide containing silicon or silicon oxide (abbreviation: ITSO), indium zinc oxide (indium zinc oxide), and tungsten oxide. And metal oxides such as indium oxide containing zinc oxide. An inorganic carbon-based material such as graphene may be used as the conductive compound. As described above, one or both of the electrode 101 and the electrode 102 may be formed by stacking a plurality of these materials.

Light emitted from the light-emitting layer 130 is extracted through one or both of the electrode 101 and the electrode 102. Therefore, at least one of the electrode 101 and the electrode 102 has a function of transmitting visible light. The conductive material having a function of transmitting light has a visible light transmittance of 40% to 100%, preferably 60% to 100%, and a resistivity of 1 × 10 ⁻² Ω · cm. The following conductive materials are mentioned. The electrode from which light is extracted may be formed of a conductive material having a function of transmitting light and a function of reflecting light. Examples of the conductive material include a conductive material having a visible light reflectance of 20% to 80%, preferably 40% to 70%, and a resistivity of 1 × 10 ⁻² Ω · cm or less. Can be mentioned. In the case where a material having low light transmission property such as a metal or an alloy is used for the electrode from which light is extracted, the electrode 101 and the electrode 102 have a thickness that can transmit visible light (for example, a thickness of 1 nm to 10 nm). One or both may be formed.

Note that in this specification and the like, an electrode having a function of transmitting light may be formed using a material having a function of transmitting visible light and having conductivity, and is represented by, for example, ITO as described above. In addition to the oxide conductor layer, an oxide semiconductor layer or an organic conductor layer containing an organic substance is included. Examples of the organic conductor layer containing an organic material include a layer containing a composite material obtained by mixing an organic compound and an electron donor (donor), and a composite material obtained by mixing an organic compound and an electron acceptor (acceptor). And the like. Further, the resistivity of the transparent conductive layer is preferably 1 × 10 ⁵ Ω · cm or less, and more preferably 1 × 10 ⁴ Ω · cm or less.

  The electrode 101 and the electrode 102 can be formed by sputtering, evaporation, printing, coating, MBE (Molecular Beam Epitaxy), CVD, pulsed laser deposition, ALD (Atomic Layer Deposition), or the like. It can be used as appropriate.

≪Hole injection layer≫
The hole injection layer 111 has a function of promoting hole injection by reducing a hole injection barrier from one of the pair of electrodes (the electrode 101 or the electrode 102). For example, a transition metal oxide, a phthalocyanine derivative, or an aromatic Formed by a group amine. Examples of the transition metal oxide include molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, and manganese oxide. Examples of the phthalocyanine derivative include phthalocyanine and metal phthalocyanine. Examples of aromatic amines include benzidine derivatives and phenylenediamine derivatives. High molecular compounds such as polythiophene and polyaniline can also be used. For example, self-doped polythiophene poly (ethylenedioxythiophene) / poly (styrenesulfonic acid) is a typical example.

As the hole-injecting layer 111, a layer including a composite material of a hole-transporting material and a material that exhibits an electron-accepting property can be used. Alternatively, a stack of a layer containing a material showing an electron accepting property and a layer containing a hole transporting material may be used. Charges can be transferred between these materials in a steady state or in the presence of an electric field. Examples of the material exhibiting electron acceptability include organic acceptors such as quinodimethane derivatives, chloranil derivatives, and hexaazatriphenylene derivatives. Specifically, 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation: F ₄ -TCNQ), chloranil, 2,3,6,7,10,11 -A compound having an electron withdrawing group (halogen group or cyano group) such as hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviation: HAT-CN). Transition metal oxides such as Group 4 to Group 8 metal oxides can also be used. Specifically, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide, rhenium oxide, and the like. Among these, molybdenum oxide is preferable because it is stable in the air, has a low hygroscopic property, and is easy to handle.

As the hole transporting material, a material having a hole transporting property higher than that of electrons can be used, and a material having a hole mobility of 1 × 10 ⁻⁶ cm ² / Vs or more is preferable. Specifically, aromatic amines, carbazole derivatives, aromatic hydrocarbons, stilbene derivatives, and the like can be used. The hole transporting material may be a polymer compound.

  As these materials having a high hole transporting property, for example, aromatic amine compounds include N, N′-di (p-tolyl) -N, N′-diphenyl-p-phenylenediamine (abbreviation: DTDPPA), 4, 4′-bis [N- (4-diphenylaminophenyl) -N-phenylamino] biphenyl (abbreviation: DPAB), N, N′-bis {4- [bis (3-methylphenyl) amino] phenyl} -N , N′-diphenyl- (1,1′-biphenyl) -4,4′-diamine (abbreviation: DNTPD), 1,3,5-tris [N- (4-diphenylaminophenyl) -N-phenylamino] Benzene (abbreviation: DPA3B) and the like can be given.

  As the carbazole derivative, specifically, 3- [N- (4-diphenylaminophenyl) -N-phenylamino] -9-phenylcarbazole (abbreviation: PCzDPA1), 3,6-bis [N- ( 4-diphenylaminophenyl) -N-phenylamino] -9-phenylcarbazole (abbreviation: PCzDPA2), 3,6-bis [N- (4-diphenylaminophenyl) -N- (1-naphthyl) amino] -9 -Phenylcarbazole (abbreviation: PCzTPN2), 3- [N- (9-phenylcarbazol-3-yl) -N-phenylamino] -9-phenylcarbazole (abbreviation: PCzPCA1), 3,6-bis [N- ( 9-phenylcarbazol-3-yl) -N-phenylamino] -9-phenylcarbazole (abbreviation: PCzPCA2 , 3- [N- (1- naphthyl)-N-(9-phenyl-3-yl) amino] -9-phenylcarbazole (abbreviation: PCzPCN1), and the like.

  As other carbazole derivatives, 4,4′-di (N-carbazolyl) biphenyl (abbreviation: CBP), 1,3,5-tris [4- (N-carbazolyl) phenyl] benzene (abbreviation: TCPB) ), 9- [4- (10-phenyl-9-anthryl) phenyl] -9H-carbazole (abbreviation: CzPA), 1,4-bis [4- (N-carbazolyl) phenyl] -2,3,5, 6-tetraphenylbenzene or the like can be used.

Examples of the aromatic hydrocarbon include 2-tert-butyl-9,10-di (2-naphthyl) anthracene (abbreviation: t-BuDNA), 2-tert-butyl-9,10-di (1- Naphthyl) anthracene, 9,10-bis (3,5-diphenylphenyl) anthracene (abbreviation: DPPA), 2-tert-butyl-9,10-bis (4-phenylphenyl) anthracene (abbreviation: t-BuDBA), 9,10-di (2-naphthyl) anthracene (abbreviation: DNA), 9,10-diphenylanthracene (abbreviation: DPAnth), 2-tert-butylanthracene (abbreviation: t-BuAnth), 9,10-bis (4) -Methyl-1-naphthyl) anthracene (abbreviation: DMNA), 2-tert-butyl-9,10-bis [2- (1-naphthy ) Phenyl] anthracene, 9,10-bis [2- (1-naphthyl) phenyl] anthracene, 2,3,6,7-tetramethyl-9,10-di (1-naphthyl) anthracene, 2,3,6 , 7-Tetramethyl-9,10-di (2-naphthyl) anthracene, 9,9′-bianthryl, 10,10′-diphenyl-9,9′-bianthryl, 10,10′-bis (2-phenylphenyl) ) -9,9′-bianthryl, 10,10′-bis [(2,3,4,5,6-pentaphenyl) phenyl] -9,9′-bianthryl, anthracene, tetracene, rubrene, perylene, 2, Examples include 5,8,11-tetra (tert-butyl) perylene. In addition, pentacene, coronene, and the like can also be used. Thus, it is more preferable to use an aromatic hydrocarbon having a hole mobility of 1 × 10 ⁻⁶ cm ² / Vs or more and having 14 to 42 carbon atoms.

  The aromatic hydrocarbon may have a vinyl skeleton. As the aromatic hydrocarbon having a vinyl group, for example, 4,4′-bis (2,2-diphenylvinyl) biphenyl (abbreviation: DPVBi), 9,10-bis [4- (2,2- Diphenylvinyl) phenyl] anthracene (abbreviation: DPVPA) and the like.

  In addition, poly (N-vinylcarbazole) (abbreviation: PVK), poly (4-vinyltriphenylamine) (abbreviation: PVTPA), poly [N- (4- {N ′-[4- (4-diphenylamino)] Phenyl] phenyl-N′-phenylamino} phenyl) methacrylamide] (abbreviation: PTPDMA), poly [N, N′-bis (4-butylphenyl) -N, N′-bis (phenyl) benzidine] (abbreviation: Polymer compounds such as Poly-TPD can also be used.

≪Hole transport layer≫
The hole transport layer 112 is a layer including a hole transport material, and the materials exemplified as the material of the hole injection layer 111 can be used. Since the hole transport layer 112 has a function of transporting holes injected into the hole injection layer 111 to the light emitting layer 130, the hole transport layer 112 may have a HOMO level that is the same as or close to the HOMO level of the hole injection layer 111. preferable.

In addition to the materials exemplified as the material of the hole injection layer 111 as the hole transporting material, examples of the substance having a high hole transporting property include 4,4′-bis [N- (1-naphthyl)- N-phenylamino] biphenyl (abbreviation: NPB or α-NPD) and N, N′-bis (3-methylphenyl) -N, N′-diphenyl- [1,1′-biphenyl] -4,4′- Diamine (abbreviation: TPD), 4,4 ′, 4 ″ -tris (carbazol-9-yl) triphenylamine (abbreviation: TCTA), 4,4 ′, 4 ″ -tris [N- (1-naphthyl) ) -N-phenylamino] triphenylamine (abbreviation: 1'-TNATA), 4,4 ', 4 "-tris (N, N-diphenylamino) triphenylamine (abbreviation: TDATA), 4,4' , 4 ″ -Tris [N- (3-methylphenyl) -N-fur Nylamino] triphenylamine (abbreviation: MTDATA), 4,4′-bis [N- (spiro-9,9′-bifluoren-2-yl) -N-phenylamino] biphenyl (abbreviation: BSPB), 4-phenyl -4 ′-(9-phenylfluoren-9-yl) triphenylamine (abbreviation: BPAFLP), 4-phenyl-3 ′-(9-phenylfluoren-9-yl) triphenylamine (abbreviation: mBPAFLP), N -(9,9-dimethyl-9H-fluoren-2-yl) -N- {9,9-dimethyl-2- [N'-phenyl-N '-(9,9-dimethyl-9H-fluoren-2- Yl) amino] -9H-fluoren-7-yl} phenylamine (abbreviation: DFLADFL), N- (9,9-dimethyl-2-diphenylamino-9H-fluoren-7-yl) Diphenylamine (abbreviation: DPNF), 2- [N- (4-diphenylaminophenyl) -N-phenylamino] spiro-9,9′-bifluorene (abbreviation: DPASF), 4-phenyl-4 ′-(9-phenyl) -9H-carbazol-3-yl) triphenylamine (abbreviation: PCBA1BP), 4,4′-diphenyl-4 ″-(9-phenyl-9H-carbazol-3-yl) triphenylamine (abbreviation: PCBBi1BP) 4- (1-naphthyl) -4 ′-(9-phenyl-9H-carbazol-3-yl) triphenylamine (abbreviation: PCBANB), 4,4′-di (1-naphthyl) -4 ″- (9-phenyl-9H-carbazol-3-yl) triphenylamine (abbreviation: PCBNBB), 4-phenyldiphenyl- (9-phenyl-9H-carba -3-yl) amine (abbreviation: PCA1BP), N, N′-bis (9-phenylcarbazol-3-yl) -N, N′-diphenylbenzene-1,3-diamine (abbreviation: PCA2B), N, N ′, N ″ -triphenyl-N, N ′, N ″ -tris (9-phenylcarbazol-3-yl) benzene-1,3,5-triamine (abbreviation: PCA3B), N- ( 4-biphenyl) -N- (9,9-dimethyl-9H-fluoren-2-yl) -9-phenyl-9H-carbazol-3-amine (abbreviation: PCBiF), N- (1,1′-biphenyl- 4-yl) -N- [4- (9-phenyl-9H-carbazol-3-yl) phenyl] -9,9-dimethyl-9H-fluoren-2-amine (abbreviation: PCBBiF), 9,9-dimethyl -N-phenyl-N- [ -(9-phenyl-9H-carbazol-3-yl) phenyl] fluoren-2-amine (abbreviation: PCBAF), N-phenyl-N- [4- (9-phenyl-9H-carbazol-3-yl) phenyl ] Spiro-9,9′-bifluoren-2-amine (abbreviation: PCBASF), 2- [N- (9-phenylcarbazol-3-yl) -N-phenylamino] spiro-9,9′-bifluorene (abbreviation) : PCASF), 2,7-bis [N- (4-diphenylaminophenyl) -N-phenylamino] -spiro-9,9'-bifluorene (abbreviation: DPA2SF), N- [4- (9H-carbazole- 9-yl) phenyl] -N- (4-phenyl) phenylaniline (abbreviation: YGA1BP), N, N′-bis [4- (carbazol-9-yl) phenyl]- , N'- diphenyl-9,9-dimethyl-2,7-diamine (abbreviation: YGA2F) can be used aromatic amine compounds such as. 3- [4- (1-naphthyl) -phenyl] -9-phenyl-9H-carbazole (abbreviation: PCPN), 3- [4- (9-phenanthryl) -phenyl] -9-phenyl-9H-carbazole (Abbreviation: PCPPn), 3,3′-bis (9-phenyl-9H-carbazole) (abbreviation: PCCP), 1,3-bis (N-carbazolyl) benzene (abbreviation: mCP), 3,6-bis ( 3,5-diphenylphenyl) -9-phenylcarbazole (abbreviation: CzTP), 4- {3- [3- (9-phenyl-9H-fluoren-9-yl) phenyl] phenyl} dibenzofuran (abbreviation: mmDBFFLBi-II) ), 4,4 ′, 4 ″-(benzene-1,3,5-triyl) tri (dibenzofuran) (abbreviation: DBF3P-II), 1,3,5-tri (dibenzo) Thiophen-4-yl) -benzene (abbreviation: DBT3P-II), 2,8-diphenyl-4- [4- (9-phenyl-9H-fluoren-9-yl) phenyl] dibenzothiophene (abbreviation: DBTFLP-III) ), 4- [4- (9-phenyl-9H-fluoren-9-yl) phenyl] -6-phenyldibenzothiophene (abbreviation: DBTFLP-IV), 4- [3- (triphenylene-2-yl) phenyl] An amine compound such as dibenzothiophene (abbreviation: mDBTPTp-II), a carbazole compound, a thiophene compound, a furan compound, a fluorene compound, a triphenylene compound, a phenanthrene compound, or the like can be used. The substances described here are mainly substances having a hole mobility of 1 × 10 ⁻⁶ cm ² / Vs or higher. Note that other than these substances, any substance that has a property of transporting more holes than electrons may be used. Note that the layer containing a substance having a high hole-transport property is not limited to a single layer, and two or more layers containing the above substances may be stacked.

  Note that a compound that can be used for the hole-transport layer 112 may be used for the hole-injection layer 111.

≪Electron transport layer≫
The electron transport layer 118 has a function of transporting electrons injected from the other of the pair of electrodes (the electrode 101 or the electrode 102) through the electron injection layer 119 to the light emitting layer 130. As the electron transporting material, a material having a higher electron transporting property than holes can be used, and a material having an electron mobility of 1 × 10 ⁻⁶ cm ² / Vs or more is preferable. As a compound that easily receives electrons (a material having an electron transporting property), a π-electron deficient heteroaromatic such as a nitrogen-containing heteroaromatic compound, a metal complex, or the like can be used. Specifically, metal complexes having quinoline ligand, benzoquinoline ligand, oxazole ligand, or thiazole ligand, oxadiazole derivatives, triazole derivatives, phenanthroline derivatives, pyridine derivatives, bipyridine derivatives, pyrimidine derivatives Etc.

For example, tris (8-quinolinolato) aluminum (III) (abbreviation: Alq), tris (4-methyl-8-quinolinolato) aluminum (III) (abbreviation: Almq ₃ ), bis (10-hydroxybenzo [h] quinolinato) Beryllium (II) (abbreviation: BeBq ₂ ), bis (2-methyl-8-quinolinolato) (4-phenylphenolato) aluminum (III) (abbreviation: BAlq), bis (8-quinolinolato) zinc (II) (abbreviation) : Znq) or the like, a layer made of a metal complex having a quinoline skeleton or a benzoquinoline skeleton. In addition, bis [2- (2-benzoxazolyl) phenolato] zinc (II) (abbreviation: ZnPBO), bis [2- (2-benzothiazolyl) phenolato] zinc (II) (abbreviation: ZnBTZ), etc. A metal complex having an oxazole-based or thiazole-based ligand can also be used. In addition to metal complexes, 2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole (abbreviation: PBD), 1,3-bis [5 -(P-tert-butylphenyl) -1,3,4-oxadiazol-2-yl] benzene (abbreviation: OXD-7), 9- [4- (5-phenyl-1,3,4-oxa) Diazol-2-yl) phenyl] -9H-carbazole (abbreviation: CO11), 3- (4-biphenylyl) -4-phenyl-5- (4-tert-butylphenyl) -1,2,4-triazole ( Abbreviation: TAZ), 2,2 ′, 2 ″-(1,3,5-benzenetriyl) tris (1-phenyl-1H-benzimidazole) (abbreviation: TPBI), 2- [3- (dibenzothiophene) -4-yl) phenyl] -1 Heterocyclic compounds such as phenyl-1H-benzimidazole (abbreviation: mDBTBIm-II), bathophenanthroline (abbreviation: BPhen), bathocuproin (abbreviation: BCP), and 2- [3- (dibenzothiophen-4-yl) phenyl] Dibenzo [f, h] quinoxaline (abbreviation: 2mDBTPDBq-II), 2- [3 ′-(dibenzothiophen-4-yl) biphenyl-3-yl] dibenzo [f, h] quinoxaline (abbreviation: 2mDBTPBPDBq-II), 2- [3 ′-(9H-carbazol-9-yl) biphenyl-3-yl] dibenzo [f, h] quinoxaline (abbreviation: 2mCzBPDBq), 2- [4- (3,6-diphenyl-9H-carbazole- 9-yl) phenyl] dibenzo [f, h] quinoxaline (abbreviation: 2CzPDBq-I) II), 7- [3- (dibenzothiophen-4-yl) phenyl] dibenzo [f, h] quinoxaline (abbreviation: 7mDBTPDBq-II) and 6- [3- (dibenzothiophen-4-yl) phenyl] Dibenzo [f, h] quinoxaline (abbreviation: 6mDBTPDBq-II), 4,6-bis [3- (phenanthrene-9-yl) phenyl] pyrimidine (abbreviation: 4,6mPnP2Pm), 4,6-bis [3- ( Diazine skeletons such as 4-dibenzothienyl) phenyl] pyrimidine (abbreviation: 4,6mDBTP2Pm-II) and 4,6-bis [3- (9H-carbazol-9-yl) phenyl] pyrimidine (abbreviation: 4,6mCzP2Pm) Or a heterocyclic compound having 2- {4- [3- (N-phenyl-9H-carbazol-3-yl) -9H-cal A heterocyclic compound having a triazine skeleton such as zol-9-yl] phenyl} -4,6-diphenyl-1,3,5-triazine (abbreviation: PCCzPTzn), or 3,5-bis [3- (9H-carbazole) Heterocyclic compounds having a pyridine skeleton such as -9-yl) phenyl] pyridine (abbreviation: 35DCzPPy) and 1,3,5-tri [3- (3-pyridyl) phenyl] benzene (abbreviation: TmPyPB); Heteroaromatic compounds such as' -bis (5-methylbenzoxazol-2-yl) stilbene (abbreviation: BzOs) can also be used. In addition, poly (2,5-pyridinediyl) (abbreviation: PPy), poly [(9,9-dihexylfluorene-2,7-diyl) -co- (pyridine-3,5-diyl)] (abbreviation: PF -Py), poly [(9,9-dioctylfluorene-2,7-diyl) -co- (2,2′-bipyridine-6,6′-diyl)] (abbreviation: PF-BPy) Molecular compounds can also be used. The substances mentioned here are mainly substances having an electron mobility of 1 × 10 ⁻⁶ cm ² / Vs or higher. Note that other than the above substances, any substance that has a property of transporting more electrons than holes may be used for the electron-transport layer. Further, the electron-transport layer 118 is not limited to a single layer, and two or more layers including the above substances may be stacked.

  Further, a layer for controlling the movement of electron carriers may be provided between the electron transport layer 118 and the light emitting layer 130. This is a layer obtained by adding a small amount of a substance having a high electron trapping property to a material having a high electron transporting property as described above. By suppressing the movement of electron carriers, the carrier balance can be adjusted. Such a configuration is very effective in suppressing problems that occur when electrons penetrate through the light emitting layer (for example, a reduction in device lifetime).

≪Electron injection layer≫
The electron injection layer 119 has a function of promoting electron injection by reducing an electron injection barrier from the electrode 102. For example, a Group 1 metal, a Group 2 metal, or an oxide, halide, carbonate, or the like thereof is used. Can be used. Alternatively, a composite material of the electron transporting material described above and a material exhibiting an electron donating property can be used. Examples of the material exhibiting electron donating properties include Group 1 metals, Group 2 metals, and oxides thereof. Specifically, lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride _(CaF 2), lithium oxide (LiO _x) an alkali metal, alkaline earth metal or a compound thereof, such as Can be used. Alternatively, a rare earth metal compound such as erbium fluoride (ErF ₃ ) can be used. Further, electride may be used for the electron injection layer 119. Examples of the electride include a substance obtained by adding a high concentration of electrons to a mixed oxide of calcium and aluminum. Alternatively, a substance that can be used for the electron-transport layer 118 may be used for the electron-injection layer 119.

  Alternatively, a composite material obtained by mixing an organic compound and an electron donor (donor) may be used for the electron injection layer 119. Such a composite material is excellent in electron injecting property and electron transporting property because electrons are generated in the organic compound by the electron donor. In this case, the organic compound is preferably a material excellent in transporting the generated electrons. Specifically, for example, a substance (metal complex, heteroaromatic compound, or the like) constituting the electron transport layer 118 described above is used. Can be used. The electron donor may be any substance that exhibits an electron donating property to the organic compound. Specifically, alkali metals, alkaline earth metals, and rare earth metals are preferable, and lithium, cesium, magnesium, calcium, erbium, ytterbium, and the like can be given. Alkali metal oxides and alkaline earth metal oxides are preferable, and lithium oxide, calcium oxide, barium oxide, and the like can be given. A Lewis base such as magnesium oxide can also be used. Alternatively, an organic compound such as tetrathiafulvalene (abbreviation: TTF) can be used.

  Note that the light emitting layer, the hole injection layer, the hole transport layer, the electron transport layer, and the electron injection layer described above are formed by a vapor deposition method (including a vacuum vapor deposition method), an inkjet method, a coating method, a gravure printing, and the like, respectively. Can be formed by a method. In addition, the light emitting layer, the hole injection layer, the hole transport layer, the electron transport layer, and the electron injection layer described above include, in addition to the materials described above, inorganic compounds or polymer compounds such as quantum dots (oligomers, dendrimers, A polymer or the like) may be used.

  As the quantum dot material, a colloidal quantum dot material, an alloy type quantum dot material, a core / shell type quantum dot material, a core type quantum dot material, or the like may be used. Alternatively, a material including an element group of Group 2 and Group 16, Group 13 and Group 15, Group 13 and Group 17, Group 11 and Group 17, or Group 14 and Group 15 may be used. Alternatively, cadmium (Cd), selenium (Se), zinc (Zn), sulfur (S), phosphorus (P), indium (In), tellurium (Te), lead (Pb), gallium (Ga), arsenic (As ), A quantum dot material having an element such as aluminum (Al) may be used.

<< Board >>
The light-emitting element according to one embodiment of the present invention may be manufactured over a substrate formed of glass, plastic, or the like. As the order of manufacturing on the substrate, the layers may be sequentially stacked from the electrode 101 side or may be sequentially stacked from the electrode 102 side.

  Note that as the substrate over which the light-emitting element according to one embodiment of the present invention can be formed, glass, quartz, plastic, or the like can be used, for example. A flexible substrate may be used. The flexible substrate is a substrate that can be bent (flexible), and examples thereof include a plastic substrate made of polycarbonate or polyarylate. Moreover, a film, an inorganic vapor deposition film, etc. can also be used. Note that other materials may be used as long as they function as a support in the manufacturing process of the light-emitting element and the optical element. Or what is necessary is just to have a function which protects a light emitting element and an optical element.

  For example, in the present invention and the like, a light-emitting element can be formed using various substrates. The kind of board | substrate is not limited to a specific thing. Examples of the substrate include a semiconductor substrate (for example, a single crystal substrate or a silicon substrate), an SOI substrate, a glass substrate, a quartz substrate, a plastic substrate, a metal substrate, a stainless steel substrate, a substrate having stainless steel foil, and a tungsten substrate. , A substrate having a tungsten foil, a flexible substrate, a laminated film, a paper containing a fibrous material, or a base film. Examples of the glass substrate include barium borosilicate glass, aluminoborosilicate glass, and soda lime glass. Examples of the flexible substrate, the laminated film, and the base film include the following. For example, there are plastics represented by polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), and polytetrafluoroethylene (PTFE). Another example is a resin such as acrylic. Alternatively, examples include polypropylene, polyester, polyvinyl fluoride, and polyvinyl chloride. As an example, there are polyamide, polyimide, aramid, epoxy, an inorganic vapor deposition film, papers, and the like.

  Alternatively, a flexible substrate may be used as the substrate, and the light-emitting element may be formed directly on the flexible substrate. Alternatively, a separation layer may be provided between the substrate and the light-emitting element. The release layer can be used to separate a part from the substrate after the light emitting element is partially or wholly formed thereon, and to transfer the light emitting element to another substrate. At that time, the light-emitting element can be transferred to a substrate having poor heat resistance or a flexible substrate. Note that, for example, a structure of a laminated structure of an inorganic film of a tungsten film and a silicon oxide film or a structure in which a resin film such as polyimide is formed over a substrate can be used for the above-described release layer.

  That is, a light-emitting element may be formed using a certain substrate, and then the light-emitting element may be transferred to another substrate, and the light-emitting element may be disposed on another substrate. As an example of a substrate to which the light emitting element is transferred, in addition to the above-described substrate, a cellophane substrate, a stone substrate, a wood substrate, a cloth substrate (natural fiber (silk, cotton, hemp), synthetic fiber (nylon, polyurethane, polyester) or There are recycled fibers (including acetate, cupra, rayon, recycled polyester), leather substrates, rubber substrates, and the like. By using these substrates, a light-emitting element that is not easily broken, a light-emitting element with high heat resistance, a light-emitting element that is reduced in weight, or a light-emitting element that is thinned can be obtained.

  Further, for example, a field effect transistor (FET) may be formed on the above-described substrate, and the light-emitting element 120 may be formed on an electrode electrically connected to the FET. Accordingly, an active matrix display device in which driving of the light emitting element 120 is controlled by the FET can be manufactured.

  Note that one embodiment of the present invention is described in this embodiment. Alternatively, in another embodiment, one embodiment of the present invention will be described. Note that one embodiment of the present invention is not limited thereto. For example, in one embodiment of the present invention, an example in which the organic compound included in the EL layer has an anthracene skeleton and light emission exhibited by the EL layer has a delayed fluorescence component due to triplet-triplet annihilation is shown. However, one embodiment of the present invention is not limited thereto. Depending on circumstances or conditions, in one embodiment of the present invention, for example, the organic compound included in the EL layer may not have an anthracene skeleton. Alternatively, the light emitted by the EL layer may not have a delayed fluorescence component. Alternatively, for example, in one embodiment of the present invention, in the organic compound included in the EL layer, the first triplet excited state has a molecular orbital in an anthracene skeleton, and the second triplet excited state has a molecule in a substituent. An example of the case where the third triplet excited state has an orbital and a molecular orbital in the anthracene skeleton is shown; however, one embodiment of the present invention is not limited thereto. Depending on circumstances or conditions, in one embodiment of the present invention, for example, in the organic compound included in the EL layer, the first triplet excited state may not have a molecular orbital in the anthracene skeleton. Alternatively, in the second triplet excited state, the substituent does not have to have a molecular orbital. Alternatively, the third triplet excited state may not have a molecular orbital in the anthracene skeleton. Alternatively, for example, in one embodiment of the present invention, in the organic compound included in the EL layer, the energy of the third triplet excited state in the most stable structure of the third triplet excited state is equal to that of the third triplet excited state. An example is shown in which the energy is higher than the energy of the first triplet excited state in the most stable structure and lower than the energy of the second triplet excited state in the most stable structure of the third triplet excited state. One embodiment of the invention is not limited to this. Depending on circumstances or circumstances, in one embodiment of the present invention, for example, in the organic compound included in the EL layer, the energy of the third triplet excited state in the most stable structure of the third triplet excited state is The energy of the first triplet excited state in the most stable structure of the third triplet excited state may not be higher. Alternatively, the energy of the third triplet excited state in the most stable structure in the third triplet excited state is not lower than the energy of the second triplet excited state in the most stable structure in the third triplet excited state. Also good. Alternatively, for example, in one embodiment of the present invention, in the organic compound included in the EL layer, the energy of the singlet excited state is higher than the energy of the second triplet excited state in the most stable structure of the third triplet excited state. In addition, although an example in which the energy is not more than the energy of the third triplet excited state in the most stable structure of the third triplet excited state is shown, one embodiment of the present invention is not limited thereto. Depending on circumstances or conditions, in one embodiment of the present invention, for example, in the organic compound included in the EL layer, the energy in the singlet excited state is higher than that in the most stable structure in the third triplet excited state. The energy of the triplet excited state may not be higher. Alternatively, the energy of the singlet excited state may not be equal to or lower than the energy of the third triplet excited state in the most stable structure of the third triplet excited state.

  As described above, the structure described in this embodiment can be combined as appropriate with any of the other embodiments.

(Embodiment 2)
In this embodiment, a light-emitting element having a structure different from that described in Embodiment 1 and a light-emitting mechanism of the light-emitting element will be described below with reference to FIGS. 9 and 10, portions having the same functions as those shown in FIG. 1A have the same hatch pattern, and the symbols may be omitted. Moreover, the same code | symbol is attached | subjected to the location which has the same function, and the detailed description may be abbreviate | omitted.

<Configuration Example 1 of Light-Emitting Element>
FIG. 9A is a schematic cross-sectional view of the light-emitting element 450.

  A light-emitting element 450 illustrated in FIG. 9A includes a plurality of light-emitting units (in FIG. 9A, the light-emitting units 441 and 442) between a pair of electrodes (the electrodes 401 and 402). One light emitting unit has a configuration similar to that of the EL layer 100 shown in FIG. That is, the light-emitting element 120 illustrated in FIG. 1 includes one light-emitting unit, and the light-emitting element 450 includes a plurality of light-emitting units. Note that in the light-emitting element 450, the electrode 401 functions as an anode and the electrode 402 functions as a cathode, which will be described below. However, the structure of the light-emitting element 450 may be reversed.

  Further, in the light-emitting element 450 illustrated in FIG. 9A, a light-emitting unit 441 and a light-emitting unit 442 are stacked, and a charge generation layer 445 is provided between the light-emitting unit 441 and the light-emitting unit 442. Note that the light-emitting unit 441 and the light-emitting unit 442 may have the same configuration or different configurations. For example, it is preferable to use the EL layer 100 shown in FIG. 1 for the light-emitting unit 441 and a light-emitting layer including a phosphorescent material as the light-emitting material for the light-emitting unit 442.

  That is, the light emitting element 450 includes a light emitting layer 420 and a light emitting layer 430. In addition to the light-emitting layer 420, the light-emitting unit 441 includes a hole injection layer 411, a hole transport layer 412, an electron transport layer 413, and an electron injection layer 414. In addition to the light-emitting layer 430, the light-emitting unit 442 includes a hole injection layer 416, a hole transport layer 417, an electron transport layer 418, and an electron injection layer 419.

  The charge generation layer 445 has a configuration in which an acceptor substance that is an electron acceptor is added to a hole transport material, but a donor substance that is an electron donor is added to the electron transport material. May be. Moreover, both these structures may be laminated | stacked.

In the case where the charge-generation layer 445 includes a composite material of an organic compound and an acceptor substance, a composite material that can be used for the hole-injection layer 111 described in Embodiment 1 may be used as the composite material. As the organic compound, various compounds such as an aromatic amine compound, a carbazole compound, an aromatic hydrocarbon, and a high molecular compound (oligomer, dendrimer, polymer, etc.) can be used. Note that an organic compound having a hole mobility of 1 × 10 ⁻⁶ cm ² / Vs or higher is preferably used. Note that other than these substances, any substance that has a property of transporting more holes than electrons may be used. Since a composite material of an organic compound and an acceptor substance is excellent in carrier injecting property and carrier transporting property, low voltage driving and low current driving can be realized. Note that when the surface of the light emitting unit on the anode side is in contact with the charge generation layer 445 as in the light emitting unit 442, the charge generation layer 445 also serves as a hole injection layer or a hole transport layer of the light emitting unit. Therefore, it is not necessary to provide a hole injection layer or a hole transport layer in the light emitting unit.

  Note that the charge generation layer 445 may be formed as a stacked structure in which a layer including a composite material of an organic compound and an acceptor substance and a layer formed using another material are combined. For example, a layer including a composite material of an organic compound and an acceptor substance may be formed in combination with a layer including one compound selected from electron donating substances and a compound having a high electron transporting property. Alternatively, a layer including a composite material of an organic compound and an acceptor substance may be combined with a layer including a transparent conductive film.

  Note that the charge generation layer 445 sandwiched between the light-emitting units 441 and 442 injects electrons into one light-emitting unit and applies holes to the other light-emitting unit when voltage is applied to the electrodes 401 and 402. As long as it injects. For example, in FIG. 9A, when a voltage is applied so that the potential of the electrode 401 is higher than the potential of the electrode 402, the charge generation layer 445 injects electrons into the light-emitting unit 441, and Inject holes into

  Note that the charge generation layer 445 preferably has a property of transmitting visible light from the viewpoint of light extraction efficiency (specifically, the visible light transmittance to the charge generation layer 445 is 40% or more). Further, the charge generation layer 445 functions even when it has lower conductivity than the pair of electrodes (the electrode 401 and the electrode 402).

  By forming the charge generation layer 445 using the above-described material, an increase in driving voltage when the light-emitting layer is stacked can be suppressed.

  9A illustrates a light-emitting element having two light-emitting units, the present invention can be similarly applied to a light-emitting element in which three or more light-emitting units are stacked. As shown in the light-emitting element 450, a plurality of light-emitting units are partitioned and arranged between a pair of electrodes by a charge generation layer, thereby enabling high-intensity light emission while maintaining a low current density, and a long-life light-emitting element Can be realized. In addition, a light-emitting element with low power consumption can be realized.

  Note that a light-emitting element with high emission efficiency can be provided by applying the structure of the EL layer 100 illustrated in FIG. 1 to at least one of the plurality of units.

  In addition, the light-emitting layer 420 includes a host material 421 and a guest material 422. In addition, the light-emitting layer 430 includes a host material 431 and a guest material 432. The host material 431 includes an organic compound 431_1 and an organic compound 431_2.

  In this embodiment mode, the light-emitting layer 420 has a structure similar to that of the light-emitting layer 130 illustrated in FIG. That is, the host material 421 and the guest material 422 included in the light emitting layer 420 correspond to the host material 131 and the guest material 132 included in the light emitting layer 130, respectively. The guest material 432 included in the light-emitting layer 430 will be described below as a phosphorescent material. Note that the electrode 401, the electrode 402, the hole injection layers 411 and 416, the hole transport layers 412 and 417, the electron transport layers 413 and 418, and the electron injection layers 414 and 419 are the same as the electrode 101 and the electrode described in Embodiment 1. 102, a hole injection layer 111, a hole transport layer 112, an electron transport layer 118, and an electron injection layer 119, respectively. Therefore, detailed description thereof is omitted in the present embodiment.

<< Light-Emitting Mechanism of Light-Emitting Layer 420 >>
The light emitting mechanism of the light emitting layer 420 is the same as that of the light emitting layer 130 shown in FIG.

<< Light-Emitting Mechanism of Light-Emitting Layer 430 >>
Next, the light emission mechanism of the light emitting layer 430 will be described below.

  The organic compound 431_1 and the organic compound 431_2 included in the light-emitting layer 430 form an exciplex.

  The combination of the organic compound 431_1 and the organic compound 431_2 that form the exciplex in the light-emitting layer 430 may be a combination that can form an exciplex, but one is a compound having a hole-transport property, and the other Is more preferably a compound having an electron transporting property.

FIG. 9B shows the correlation of energy levels among the organic compound 431_1, the organic compound 431_2, and the guest material 432 in the light-emitting layer 430. Note that the notations and symbols in FIG. 9B are as follows.
Host (431_1): Host material (organic compound 431_1)
Host (431_2): Host material (organic compound 431_2)
Guest (432): Guest material 432 (phosphorescent material)
· _{S PH:} host material lowest level · _{T PH} of the singlet excited state of (organic compound 431_1): host material lowest level · _{T PG} triplet excited state of the (organic compound 431_1): guest material 432 ( The lowest level of the triplet excited state of the phosphorescent material) S _PE : the lowest level of the singlet excited state of the exciplex • T _PE : the lowest level of the triplet excited state of the exciplex

An exciplex is formed by the organic compound 431_1 and the organic compound 431_2. The lowest level (S _PE ) of the singlet excited state of the exciplex and the lowest level (T _PE ) of the triplet excited state of the exciplex are adjacent to each other (FIG. 9 (B) Route C reference).

Then, the energy of both the _SPE and _TPE of the exciplex is transferred to the lowest level (T _PG ) of the triplet excited state of the guest material 432 (phosphorescent material), and light emission is obtained (FIG. 9B ) See Route D).

  Note that the process of Route C and Route D described above may be referred to as ExTET (Exciplex-Triple Energy Transfer) in this specification and the like.

  One of the organic compound 431_1 and the organic compound 431_2 forms an exciplex by receiving holes and the other receiving electrons. Alternatively, when one is in an excited state, an exciplex is formed by interacting with the other. Therefore, most excitons in the light emitting layer 430 exist as exciplexes. Since the exciplex has a smaller band gap than both the organic compound 431_1 and the organic compound 431_2, the exciplex is formed by recombination of one hole and the other electron, whereby the driving voltage can be lowered.

  When the light-emitting layer 430 has the above structure, light emission from the guest material 432 (phosphorescent material) of the light-emitting layer 430 can be efficiently obtained.

  Note that light emission from the light-emitting layer 420 preferably has a light emission peak on a shorter wavelength side than light emission from the light-emitting layer 430. A light-emitting element using a phosphorescent material that emits light having a short wavelength tends to deteriorate in luminance. Therefore, a light-emitting element with small luminance deterioration can be provided by using short-wavelength light emission as fluorescent light emission.

  In addition, by obtaining light with different emission wavelengths in the light-emitting layer 420 and the light-emitting layer 430, a multicolor light-emitting element can be obtained. In this case, since the emission spectrum is light in which emission having different emission peaks is synthesized, it becomes an emission spectrum having at least two maximum values.

  The above configuration is also suitable for obtaining white light emission. White light emission can be obtained by making the light of the light emitting layer 420 and the light emitting layer 430 have complementary colors.

  In addition, by using a plurality of light-emitting substances having different emission wavelengths in one or both of the light-emitting layer 420 and the light-emitting layer 430, white light emission having high color rendering properties composed of three primary colors or four or more emission colors can be obtained. it can. In this case, one or both of the light-emitting layer 420 and the light-emitting layer 430 may be further divided into layers, and a different light-emitting material may be included in each of the divided layers.

<Configuration Example 2 of Light-Emitting Element>
Next, a structural example different from the light-emitting element illustrated in FIG. 9 is described below with reference to FIGS.

  FIG. 10A is a schematic cross-sectional view of the light-emitting element 452.

  A light-emitting element 452 illustrated in FIG. 10A has a structure in which an EL layer 400 is sandwiched between a pair of electrodes (an electrode 401 and an electrode 402). Note that in the light-emitting element 452, the electrode 401 functions as an anode and the electrode 402 functions as a cathode.

  The EL layer 400 includes a light-emitting layer 420 and a light-emitting layer 430. In the light-emitting element 452, the EL layer 400 includes a hole-injection layer 411, a hole-transport layer 412, an electron-transport layer 418, and an electron-injection layer 419 in addition to the light-emitting layer 420 and the light-emitting layer 430. However, these stacked structures are examples, and the structure of the EL layer 400 in the light-emitting element 452 is not limited thereto. For example, in the EL layer 400, the stacking order of the above layers may be changed. Alternatively, a functional layer other than the above layers may be provided in the EL layer 400. For example, the functional layer may have a function of injecting carriers (electrons or holes), a function of transporting carriers, a function of suppressing carriers, and a function of generating carriers.

  In addition, the light-emitting layer 420 includes a host material 421 and a guest material 422. In addition, the light-emitting layer 430 includes a host material 431 and a guest material 432. The host material 431 includes an organic compound 431_1 and an organic compound 431_2. Note that the guest material 422 is a fluorescent material and the guest material 432 is a phosphorescent material.

<< Light-Emitting Mechanism of Light-Emitting Layer 420 and Light-Emitting Layer 430 >>
The light-emitting mechanism of the light-emitting layer 420 is the same as that of the light-emitting layer 130 illustrated in FIG. The light-emitting mechanism of the light-emitting layer 430 is the same as that of the light-emitting layer 430 illustrated in FIG.

  As illustrated in the light-emitting element 452, in the case where the light-emitting layer 420 and the light-emitting layer 430 are in contact with each other, energy transfer from the exciplex to the host material 421 of the light-emitting layer 420 at the interface between the light-emitting layer 420 and the light-emitting layer 430 Even when triplet excitation level energy transfer occurs, the light emission layer 420 can convert the triplet excitation energy into light emission.

  Note that the T1 level of the host material 421 in the light-emitting layer 420 is preferably lower than the T1 levels of the organic compound 431_1 and the organic compound 431_2 included in the light-emitting layer 430. In the light-emitting layer 420, the S1 level of the host material 421 is higher than the S1 level of the guest material 422 (fluorescent material), and the T1 level of the host material 421 is the T1 level of the guest material 422 (fluorescent material). Is preferably lower than the position.

Specifically, FIG. 10B shows the correlation of energy levels when TTA is used for the light-emitting layer 420 and ExTET is used for the light-emitting layer 430. In addition, the notation and code | symbol in FIG. 10 (B) are as follows.
Fluorescence EML (420): fluorescent light emitting layer (light emitting layer 420)
Phosphorescence EML (430): phosphorescent light emitting layer (light emitting layer 430)
S _FH : lowest level of singlet excited state of host material 421 T _FH : lowest level of triplet excited state of host material 421 S _FG : singlet excited state of guest material 422 (fluorescent material) T _FG : the lowest level of the triplet excited state of the guest material 422 (fluorescent material) • S _PH : the lowest level of the singlet excited state of the host material (organic compound 431_1) • T _PH : Lowest level of triplet excited state of host material (organic compound 431_1) · T _PG : lowest level of triplet excited state of guest material 432 (phosphorescent material) · S _E : singlet excited state of excited complex Lowest level of T _E : lowest level of triplet excited state of exciplex

As shown in FIG. 10B, since the exciplex exists only in an excited state, exciton diffusion is hardly generated between the exciplex and the exciplex. In addition, the excitation level (S _E , T _E ) of the exciplex is lower than the excitation level (S _PH , T _PH ) of the organic compound 431_1 (that is, the host material of the phosphorescent material) in the light-emitting layer 430. Energy diffusion from the complex to the organic compound 431_1 does not occur. That is, since the exciton diffusion distance of the exciplex is short in the phosphorescent light emitting layer (light emitting layer 430), the efficiency of the phosphorescent light emitting layer (light emitting layer 430) can be maintained. In addition, at the interface between the fluorescent light-emitting layer (light-emitting layer 420) and the phosphorescent light-emitting layer (light-emitting layer 430), part of the triplet excitation energy of the exciplex of the phosphorescent light-emitting layer (light-emitting layer 430) is Even if it diffuses to 420), the triplet excitation energy of the fluorescent light-emitting layer (light-emitting layer 420) generated by the diffusion is emitted through TTA, so that energy loss can be reduced.

  As described above, the light-emitting element 452 uses ExTET for the light-emitting layer 430 and TTA for the light-emitting layer 420, so that energy loss is reduced. Therefore, the light-emitting element 452 can be a light-emitting element with high emission efficiency. . In the case where the light-emitting layer 420 and the light-emitting layer 430 are in contact with each other as illustrated in the light-emitting element 452, the energy loss is reduced and the number of layers of the EL layer 400 can be reduced. Therefore, a light-emitting element with low manufacturing cost can be obtained.

  Note that the light-emitting layer 420 and the light-emitting layer 430 may not be in contact with each other. In this case, the excited state of the organic compound 431_1, the organic compound 431_2, or the guest material 432 (phosphorescent material) generated in the light-emitting layer 430 is changed to the host material 421 or the guest material 422 (fluorescent material) in the light-emitting layer 420. Energy transfer (particularly triplet energy transfer) by the Dexter mechanism can be prevented. Therefore, the layer provided between the light-emitting layer 420 and the light-emitting layer 430 may have a thickness of about several nm.

  The layer provided between the light-emitting layer 420 and the light-emitting layer 430 may be formed of a single material, but may include both a hole transporting material and an electron transporting material. In the case of a single material, a bipolar material may be used. Here, the bipolar material refers to a material having a mobility ratio of electrons and holes of 100 or less. Further, a hole transporting material or an electron transporting material may be used. Alternatively, at least one of them may be formed using the same material as the host material (the organic compound 431_1 or the organic compound 431_2) of the light-emitting layer 430. This facilitates the production of the light emitting element and reduces the driving voltage. Further, an exciplex may be formed by the hole transporting material and the electron transporting material, thereby effectively preventing exciton diffusion. Specifically, energy transfer from the excited state of the host material (organic compound 431_1) or the guest material 432 (phosphorescent material) of the light-emitting layer 430 to the host material 421 or the guest material 422 (fluorescent material) of the light-emitting layer 420 is prevented. be able to.

  Note that in the light-emitting element 452, the carrier recombination region is preferably formed to have a certain distribution. Therefore, the light-emitting layer 420 or the light-emitting layer 430 preferably has an appropriate carrier trapping property. In particular, the guest material 432 (phosphorescent material) included in the light-emitting layer 430 preferably has an electron-trapping property.

  Note that a structure in which light emission from the light-emitting layer 420 has a light emission peak on a shorter wavelength side than light emission from the light-emitting layer 430 is preferable. A light-emitting element using a phosphorescent material that emits light having a short wavelength tends to deteriorate in luminance. Therefore, a light-emitting element with small luminance deterioration can be provided by using short-wavelength light emission as fluorescent light emission.

  In addition, by obtaining light with different emission wavelengths in the light-emitting layer 420 and the light-emitting layer 430, a multicolor light-emitting element can be obtained. In this case, since the emission spectrum is light in which emission having different emission peaks is synthesized, it becomes an emission spectrum having at least two maximum values.

  The above configuration is also suitable for obtaining white light emission. White light emission can be obtained by making the light of the light emitting layer 420 and the light emitting layer 430 have complementary colors.

  In addition, by using a plurality of light-emitting substances having different emission wavelengths for the light-emitting layer 420, white light emission with high color rendering properties composed of three primary colors or four or more emission colors can be obtained. In this case, the light emitting layer 420 may be further divided into layers, and a different light emitting material may be included in each of the divided layers.

<Examples of materials that can be used for the light emitting layer>
Next, materials that can be used for the light-emitting layer 420 and the light-emitting layer 430 are described below.

<< Materials that can be used for light-emitting layer 420 >>
In the light emitting layer 420, the host material 421 is present in the largest amount by weight ratio, and the guest material 422 (fluorescent material) is dispersed in the host material 421. The S1 level of the host material 421 is preferably higher than the S1 level of the guest material 422 (fluorescent material), and the T1 level of the host material 421 is preferably lower than the T1 level of the guest material 422 (fluorescent material). .

  As a material that can be used for the light-emitting layer 420, a material that can be used for the light-emitting layer 130 described in Embodiment 1 above may be used. By doing so, it is possible to manufacture a light-emitting element with a high ratio of delayed fluorescence of light emission and high light emission efficiency.

<< Material that can be used for light-emitting layer 430 >>
In the light emitting layer 430, the host material 431 is present in the largest amount by weight, and the guest material 432 (phosphorescent material) is dispersed in the host material 431. The T1 level of the host material 431 (the organic compound 431_1 and the organic compound 431_2) of the light-emitting layer 430 is preferably higher than the T1 level of the guest material 422 (fluorescent material) of the light-emitting layer 420.

  As the organic compound 431_1, in addition to zinc and aluminum-based metal complexes, oxadiazole derivatives, triazole derivatives, benzimidazole derivatives, quinoxaline derivatives, dibenzoquinoxaline derivatives, dibenzothiophene derivatives, dibenzofuran derivatives, pyrimidine derivatives, triazine derivatives, pyridine derivatives, Bipyridine derivatives, phenanthroline derivatives and the like can be mentioned. Other examples include aromatic amines and carbazole derivatives. Specifically, the electron transporting material and the hole transporting material described in Embodiment 1 can be used.

  The organic compound 431_2 is a combination that can form an exciplex with the organic compound 431_1. Specifically, the electron transporting material and the hole transporting material described in Embodiment 1 can be used. In this case, the emission peak of the exciplex formed by the organic compound 431_1 and the organic compound 431_2 has an absorption band of a triplet MLCT (Metal to Ligand Charge Transfer) transition of the guest material 432 (phosphorescent material), more specifically, The organic compound 431_1, the organic compound 431_2, and the guest material 432 (phosphorescent material) are preferably selected so as to overlap with the absorption band on the longest wavelength side. Thereby, it can be set as the light emitting element which luminous efficiency improved greatly. However, when a thermally activated delayed fluorescent material is used instead of the phosphorescent material, it is preferable that the absorption band on the longest wavelength side is a singlet absorption band.

  Examples of the guest material 432 (phosphorescent material) include iridium, rhodium, or platinum-based organometallic complexes, or metal complexes. Among these, organic iridium complexes such as iridium-based orthometal complexes are preferable. Examples of orthometalated ligands include 4H-triazole ligands, 1H-triazole ligands, imidazole ligands, pyridine ligands, pyrimidine ligands, pyrazine ligands, and isoquinoline ligands. Can be mentioned. Examples of the metal complex include a platinum complex having a porphyrin ligand.

As a substance having an emission peak in blue or green, for example, tris {2- [5- (2-methylphenyl) -4- (2,6-dimethylphenyl) -4H-1,2,4-triazole-3 -Yl- [kappa] N2] phenyl- [kappa] C} iridium (III) (abbreviation: Ir (mppptz-dmp) ₃ ), tris (5-methyl-3,4-diphenyl-4H-1,2,4-triazolate) iridium (III ) (Abbreviation: Ir (Mptz) ₃ ), tris [4- (3-biphenyl) -5-isopropyl-3-phenyl-4H-1,2,4-triazolato] iridium (III) (abbreviation: Ir (iPrptz- 3b) ₃ ), tris [3- (5-biphenyl) -5-isopropyl-4-phenyl-4H-1,2,4-triazolato] iridium (III) (abbreviation: Ir (IPr5btz) ₃ ) or an organometallic iridium complex having a 4H-triazole skeleton, or tris [3-methyl-1- (2-methylphenyl) -5-phenyl-1H-1,2,4-triazolate] iridium (III) (abbreviation: Ir (Mptz1-mp) ₃ ), tris (1-methyl-5-phenyl-3-propyl-1H-1,2,4-triazolato) iridium (III) (abbreviation: Ir (Prptz1- Me) ₃ ), an organometallic iridium complex having a 1H-triazole skeleton, fac-tris [1- (2,6-diisopropylphenyl) -2-phenyl-1H-imidazole] iridium (III) (abbreviation: Ir) _{(iPrpmi) 3),} tris [3- (2,6-dimethylphenyl) -7-methylimidazo [1, 2-f] off Nantorijinato] iridium (III) _{(abbreviation: Ir (dmpimpt-Me) 3} ) or an organic iridium complex having an imidazole skeleton, such as bis [2- (4 ', 6'-difluorophenyl) pyridinato -N, ^{C 2 '} ] Iridium (III) tetrakis (1-pyrazolyl) borate (abbreviation: FIr6), bis [2- (4 ′, 6′-difluorophenyl) pyridinato-N, C ^{2 ′} ] iridium (III) picolinate (abbreviation: FIrpic) ), Bis {2- [3 ′, 5′-bis (trifluoromethyl) phenyl] pyridinato-N, C ^{2 ′} } iridium (III) picolinate (abbreviation: Ir (CF ₃ ppy) ₂ (pic)), bis [2- (4 ', 6'-difluorophenyl) pyridinato -N, C ^2'] iridium (III) acetylacetonate ( Universal: FIr (acac)) organometallic iridium complex having a ligand of phenylpyridine derivative having an electron-withdrawing group such as and the like. Among the above, an organometallic iridium complex having a 4H-triazole skeleton is particularly preferable because it is excellent in reliability and luminous efficiency.

Examples of a substance having an emission peak in green or yellow include tris (4-methyl-6-phenylpyrimidinato) iridium (III) (abbreviation: Ir (mppm) ₃ ), tris (4-t-butyl). -6-phenylpyrimidinato) iridium (III) (abbreviation: Ir (tBupppm) ₃ ), (acetylacetonato) bis (6-methyl-4-phenylpyrimidinato) iridium (III) (abbreviation: Ir (mppm) ) ₂ (acac)), (acetylacetonato) bis (6-tert-butyl-4-phenylpyrimidinato) iridium (III) (abbreviation: Ir (tBupppm) ₂ (acac)), (acetylacetonato) bis [6- (2-norbornyl) -4-phenylpyrimidinato] iridium (III) (abbreviation: Ir (nbppm) ₂ (Acac)), (acetylacetonato) bis [5-methyl-6- (2-methylphenyl) -4-phenylpyrimidinato] iridium (III) (abbreviation: Ir (mpmppm) ₂ (acac)), ( Acetylacetonato) bis {4,6-dimethyl-2- [6- (2,6-dimethylphenyl) -4-pyrimidinyl-κN3] phenyl-κC} iridium (III) (abbreviation: Ir (dmppm-dmp) ₂ (Acac)), (acetylacetonato) bis (4,6-diphenylpyrimidinato) iridium (III) (abbreviation: Ir (dppm) ₂ (acac)), an organometallic iridium complex having a pyrimidine skeleton, (Acetylacetonato) bis (3,5-dimethyl-2-phenylpyrazinato) iridium (III) (abbreviation: Ir (mppr -Me) ₂ (acac)), (acetylacetonato) bis (5-isopropyl-3-methyl-2-phenylpyrazinato) iridium (III) (abbreviation: Ir (mppr-iPr) ₂ (acac)) Organometallic iridium complexes having such a pyrazine skeleton, tris (2-phenylpyridinato-N, C ^{2 ′} ) iridium (III) (abbreviation: Ir (ppy) ₃ ), bis (2-phenylpyridinato- N, C ^{2 ′} ) iridium (III) acetylacetonate (abbreviation: Ir (ppy) ₂ (acac)), bis (benzo [h] quinolinato) iridium (III) acetylacetonate (abbreviation: Ir (bzq) ₂ ( acac)), tris (benzo [h] quinolinato) iridium (III) (abbreviation: Ir _(bzq) 3), tris (2-Fenirukino Isocyanato -N, C ^{2 ')} iridium (III) (abbreviation: Ir _(pq) 3), bis (2-phenylquinolinato--N, C ^2') iridium (III) acetylacetonate (abbreviation: Ir (pq) ₂ (acac)), an organometallic iridium complex having a pyridine skeleton, or bis (2,4-diphenyl-1,3-oxazolate-N, C ^{2 ′} ) iridium (III) acetylacetonate (abbreviation: Ir ( dpo) ₂ (acac)), bis {2- [4 ′-(perfluorophenyl) phenyl] pyridinato-N, C ^{2 ′} } iridium (III) acetylacetonate (abbreviation: Ir (p-PF-ph) ₂ (Acac)), bis (2-phenylbenzothiazolate-N, C ^{2 ′} ) iridium (III) acetylacetonate (abbreviation: Ir (bt) ₂ (acac )) And other rare earth metal complexes such as tris (acetylacetonato) (monophenanthroline) terbium (III) (abbreviation: Tb (acac) ₃ (Phen)). Among the above-described compounds, organometallic iridium complexes having a pyrimidine skeleton are particularly preferable because they are remarkably excellent in reliability and luminous efficiency.

As a substance having an emission peak in yellow or red, for example, (diisobutyrylmethanato) bis [4,6-bis (3-methylphenyl) pyrimidinato] iridium (III) (abbreviation: Ir (5 mdppm) ₂ ( dibm)), bis [4,6-bis (3-methylphenyl) pyrimidinato] (dipivaloylmethanato) iridium (III) (abbreviation: Ir (5 mdppm) ₂ (dpm)), bis [4,6-di (Naphthalen-1-yl) pyrimidinato] (dipivaloylmethanato) iridium (III) (abbreviation: Ir (d1npm) ₂ (dpm)), an organometallic iridium complex having a pyrimidine skeleton, and (acetylacetonato) bis (2,3,5-triphenylpyrazinato) iridium (III) (abbreviation: Ir _(tppr) 2 (ac c)), bis (2,3,5-triphenylpyrazinato) (dipivaloylmethanato) iridium (III) (abbreviation: Ir _(tppr) 2 (dpm)), (acetylacetonato) bis [2 , 3-bis (4-fluorophenyl) quinoxalinato] iridium (III) (abbreviation: [Ir (Fdpq) ₂ (acac)]), organometallic iridium complexes having a pyrazine skeleton, tris (1-phenylisoquino Linato-N, C ^{2 ′} ) iridium (III) (abbreviation: Ir (piq) ₃ ), bis (1-phenylisoquinolinato-N, C ^{2 ′} ) iridium (III) acetylacetonate (abbreviation: Ir (piq) ) other organometallic iridium complex having a pyridine skeleton, such as ₂ (acac)), 2,3,7,8,12,13,17,18-octaethyl Platinum complexes such as 21H, 23H-porphyrin platinum (II) (abbreviation: PtOEP), tris (1,3-diphenyl-1,3-propanedionate) (monophenanthroline) europium (III) (abbreviation: Eu ( DBM) ₃ (Phen)), tris [1- (2-thenoyl) -3,3,3-trifluoroacetonato] (monophenanthroline) europium (III) (abbreviation: Eu (TTA) ₃ (Phen)) Such rare earth metal complexes are mentioned. Among the above-described compounds, organometallic iridium complexes having a pyrimidine skeleton are particularly preferable because they are remarkably excellent in reliability and luminous efficiency. An organometallic iridium complex having a pyrazine skeleton can emit red light with good chromaticity.

  The light-emitting material included in the light-emitting layer 430 may be a material that can convert triplet excitation energy into light emission. Examples of the material that can convert the triplet excitation energy into light emission include a thermally activated delayed fluorescence (TADF) material in addition to a phosphorescent material. Therefore, the portion described as phosphorescent material may be read as thermally activated delayed fluorescent material. Note that the thermally activated delayed fluorescent material has a small difference between the triplet excitation energy level and the singlet excitation energy level, and the function of converting energy from the triplet excited state to the singlet excited state by crossing between inverses. It is the material which has. Therefore, the triplet excited state can be up-converted (reverse intersystem crossing) into a singlet excited state with a slight thermal energy, and light emission (fluorescence) from the singlet excited state can be efficiently exhibited. As a condition for efficiently obtaining thermally activated delayed fluorescence, the energy difference between the triplet excitation energy level and the singlet excitation energy level is preferably greater than 0 eV but not greater than 0.2 eV, more preferably greater than 0 eV and not greater than 0. 0.1 eV or less.

  In addition, the material that exhibits thermally activated delayed fluorescence may be a material that can generate a singlet excited state from a triplet excited state alone by crossing between reverse terms, or an exciplex (also referred to as an exciplex or exciplex). It may be composed of a plurality of materials that form

  When the thermally activated delayed fluorescent material is composed of one type of material, for example, the following materials can be used.

First, fullerene and its derivatives, acridine derivatives such as proflavine, eosin and the like can be mentioned. In addition, metal-containing porphyrins including magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), palladium (Pd), and the like can be given. Examples of the metal-containing porphyrin include a protoporphyrin-tin fluoride complex (SnF ₂ (Proto IX)), a mesoporphyrin-tin fluoride complex (SnF ₂ (Meso IX)), and a hematoporphyrin-tin fluoride complex (SnF). ₂ (Hemato IX)), coproporphyrin tetramethyl ester-tin fluoride complex (SnF ₂ (Copro III-4Me)), octaethylporphyrin-tin fluoride complex (SnF ₂ (OEP)), etioporphyrin-tin fluoride And a complex (SnF ₂ (Etio I)), octaethylporphyrin-platinum chloride complex (PtCl ₂ OEP), and the like.

  In addition, as the thermally activated delayed fluorescent material composed of a kind of material, a heterocyclic compound having a π-electron rich heteroaromatic ring and a π-electron deficient heteroaromatic ring can also be used. Specifically, 2- (biphenyl-4-yl) -4,6-bis (12-phenylindolo [2,3-a] carbazol-11-yl) -1,3,5-triazine (abbreviation: PIC-TRZ), 2- {4- [3- (N-phenyl-9H-carbazol-3-yl) -9H-carbazol-9-yl] phenyl} -4,6-diphenyl-1,3,5- Triazine (abbreviation: PCCzPTzn), 2- [4- (10H-phenoxazin-10-yl) phenyl] -4,6-diphenyl-1,3,5-triazine (abbreviation: PXZ-TRZ), 3- [4 -(5-phenyl-5,10-dihydrophenazin-10-yl) phenyl] -4,5-diphenyl-1,2,4-triazole (abbreviation: PPZ-3TPT), 3- (9,9-dimethyl- 9H-acridine- 0-yl) -9H-xanthen-9-one (abbreviation: ACRXTN), bis [4- (9,9-dimethyl-9,10-dihydroacridine) phenyl] sulfone (abbreviation: DMAC-DPS), 10-phenyl -10H, 10'H-spiro [acridine-9,9'-anthracene] -10'-one (abbreviation: ACRSA) and the like. Since the heterocyclic compound has a π-electron rich heteroaromatic ring and a π-electron deficient heteroaromatic ring, it is preferable because of its high electron transporting property and hole transporting property. A substance in which a π-electron rich heteroaromatic ring and a π-electron deficient heteroaromatic ring are directly bonded has both a donor property of a π-electron rich heteroaromatic ring and an acceptor property of a π-electron deficient heteroaromatic ring, This is particularly preferable because the difference between the level of the singlet excited state and the level of the triplet excited state becomes small.

  In addition, when a thermally activated delayed fluorescent material is used as a host material, it is preferable to use a combination of two types of compounds that form an exciplex. In this case, it is particularly preferable to use a compound that easily receives electrons, which is a combination that forms the exciplex shown above, and a compound that easily receives holes.

  Further, there is no limitation on the light emission color of the light emitting material included in the light emitting layer 420 and the light emitting material included in the light emitting layer 430, and they may be the same or different. Since the light emission obtained from each is mixed and taken out of the device, the light emitting device can give white light when, for example, the light emission colors of both are complementary colors. In consideration of the reliability of the light emitting element, the emission peak wavelength of the light emitting material included in the light emitting layer 420 is preferably shorter than that of the light emitting material included in the light emitting layer 430.

  Note that the light-emitting unit 441, the light-emitting unit 441, and the charge generation layer 445 can be formed by a method such as a vapor deposition method (including a vacuum vapor deposition method), an inkjet method, a coating method, or gravure printing.

  Note that the structure described in this embodiment can be combined as appropriate with any of the structures described in the other embodiments.

(Embodiment 3)
In this embodiment, examples of light-emitting elements having different structures from those described in Embodiments 1 and 2 are described below with reference to FIGS.

<Configuration Example 1 of Light-Emitting Element>
11A and 11B are cross-sectional views illustrating a light-emitting element of one embodiment of the present invention. Note that in FIGS. 11A and 11B, portions having the same functions as those illustrated in FIG. 1A are denoted by the same hatch patterns, and the symbols may be omitted. Moreover, the same code | symbol is attached | subjected to the location which has the same function, and the detailed description may be abbreviate | omitted.

  The light-emitting elements 250 and 252 illustrated in FIGS. 11A and 11B may be bottom emission light-emitting elements that extract light to the substrate 200 side, and emit light in a direction opposite to the substrate 200. A top emission type light emitting element may be used. Note that one embodiment of the present invention is not limited thereto, and may be a dual emission type light-emitting element that extracts light emitted from the light-emitting element both above and below the substrate 200.

  In the case where the light-emitting element 250 and the light-emitting element 252 are bottom emission types, the electrode 101 preferably has a function of transmitting light. The electrode 102 preferably has a function of reflecting light. Alternatively, in the case where the light-emitting element 250 and the light-emitting element 252 are top emission types, the electrode 101 preferably has a function of reflecting light. The electrode 102 preferably has a function of transmitting light.

  The light-emitting element 250 and the light-emitting element 252 include the electrode 101 and the electrode 102 over the substrate 200. In addition, the light-emitting layer 123B, the light-emitting layer 123G, and the light-emitting layer 123R are provided between the electrode 101 and the electrode 102. In addition, the hole injection layer 111, the hole transport layer 112, the electron transport layer 118, and the electron injection layer 119 are included.

  The light-emitting element 252 includes a conductive layer 101a, a conductive layer 101b over the conductive layer 101a, and a conductive layer 101c under the conductive layer 101a as part of the structure of the electrode 101. That is, the light-emitting element 252 has a structure of the electrode 101 in which the conductive layer 101a is sandwiched between the conductive layer 101b and the conductive layer 101c.

  In the light-emitting element 252, the conductive layer 101b and the conductive layer 101c may be formed using different materials or the same material. In the case where the electrode 101 has a configuration in which the electrode 101 is sandwiched between the same conductive materials, it is preferable because pattern formation by an etching process becomes easy.

  Note that the light-emitting element 252 may have only one of the conductive layer 101b and the conductive layer 101c.

  Note that the conductive layers 101a and 101b and the conductive layer 101c included in the electrode 101 can each have the same structure and material as the electrode 101 or the electrode 102 described in Embodiment 1.

  11A and 11B, a partition 140 is provided between the region 221B, the region 221G, and the region 221R sandwiched between the electrode 101 and the electrode 102. The partition 140 has an insulating property. The partition wall 140 covers an end portion of the electrode 101 and has an opening overlapping with the electrode. By providing the partition wall 140, the electrodes 101 included in the substrate 200 in each region can be separated into island shapes.

  Note that the light-emitting layer 123B and the light-emitting layer 123G may have regions that overlap with each other in a region overlapping with the partition wall 140. Alternatively, the light-emitting layer 123G and the light-emitting layer 123R may have regions that overlap each other in a region that overlaps with the partition wall 140. Alternatively, the light-emitting layer 123 </ b> R and the light-emitting layer 123 </ b> B may have regions that overlap each other in a region overlapping with the partition wall 140.

  The partition 140 only needs to be insulative and is formed using an inorganic material or an organic material. Examples of the inorganic material include silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, aluminum oxide, and aluminum nitride. As this organic material, photosensitive resin materials, such as an acrylic resin or a polyimide resin, are mentioned, for example.

  In addition, the light-emitting layer 123R, the light-emitting layer 123G, and the light-emitting layer 123B preferably include light-emitting materials having a function of exhibiting different colors. For example, when the light-emitting layer 123R includes a light-emitting material having a function of exhibiting red, the region 221R exhibits red light emission, and the light-emitting layer 123G includes a light-emitting material having a function of exhibiting green, so that the region 221G has a green color. The region 221 </ b> B emits blue light when the light-emitting layer 123 </ b> B includes a light-emitting material having a function of exhibiting blue. By using the light-emitting element 250 or the light-emitting element 252 having such a structure for a pixel of the display device, a display device capable of full color display can be manufactured. Moreover, the film thickness of each light emitting layer may be the same, and may differ.

  In addition, any one or a plurality of light-emitting layers of the light-emitting layer 123B, the light-emitting layer 123G, and the light-emitting layer 123R preferably include the compound having a delayed fluorescence component by TTA described in Embodiment 1. By doing so, it is possible to manufacture a light-emitting element with favorable emission efficiency among the light emitted by the light-emitting layer.

  Note that one or a plurality of light-emitting layers of the light-emitting layer 123B, the light-emitting layer 123G, and the light-emitting layer 123R may have a structure in which two or more layers are stacked.

  As described above, at least one light-emitting layer includes the compound having a delayed fluorescent component by TTA described in Embodiment 1, and the light-emitting element 250 or the light-emitting element 252 including the light-emitting layer is used for a pixel of a display device. Thus, a display device with high emission efficiency can be manufactured. That is, a display device including the light-emitting element 250 or the light-emitting element 252 can reduce power consumption.

  Note that the color purity of the light-emitting element 250 and the light-emitting element 252 can be improved by providing a color filter over the electrode from which light is extracted. Therefore, the color purity of the display device including the light-emitting element 250 or the light-emitting element 252 can be increased.

  In addition, by providing a polarizing plate over the electrode from which light is extracted, reflection of external light from the light-emitting element 250 and the light-emitting element 252 can be reduced. Therefore, the contrast ratio of the display device including the light-emitting element 250 or the light-emitting element 252 can be increased.

  Note that as for other structures of the light-emitting element 250 and the light-emitting element 252, the structure of the light-emitting element in Embodiment 1 or 2 may be referred to.

<Configuration Example 2 of Light-Emitting Element>
Next, a structural example different from the light-emitting element illustrated in FIGS. 11A to 11C is described below with reference to FIGS.

  12A and 12B are cross-sectional views illustrating a light-emitting element of one embodiment of the present invention. Note that in FIGS. 12A and 12B, portions having the same functions as those shown in FIG. Moreover, the same code | symbol is attached | subjected to the location which has the same function, and the detailed description may be abbreviate | omitted.

  12A and 12B are configuration examples of a tandem light-emitting element in which a plurality of light-emitting layers are stacked with a charge generation layer 115 interposed between a pair of electrodes. A light-emitting element 254 illustrated in FIG. 12A is a top emission light-emitting element that extracts light in a direction opposite to the substrate 200, and a light-emitting element 256 illustrated in FIG. This is a bottom emission type light emitting device for taking out the light. Note that one embodiment of the present invention is not limited to this, and a dual emission type in which light emitted from a light-emitting element is extracted both above and below the substrate 200 over which the light-emitting element is formed may be used.

  The light-emitting element 254 and the light-emitting element 256 include the electrode 101, the electrode 102, the electrode 103, and the electrode 104 over the substrate 200. In addition, the light-emitting layer 160, the charge generation layer 115, and the light-emitting layer 170 are provided between the electrode 101 and the electrode 102, between the electrode 102 and the electrode 103, and between the electrode 102 and the electrode 104. . In addition, the hole injection layer 111, the hole transport layer 112, the electron transport layer 113, the electron injection layer 114, the hole injection layer 116, the hole transport layer 117, the electron transport layer 118, and the electron injection A layer 119.

  The electrode 101 includes a conductive layer 101a and a conductive layer 101b in contact with the conductive layer 101a. The electrode 103 includes a conductive layer 103a and a conductive layer 103b in contact with the conductive layer 103a. The electrode 104 includes a conductive layer 104a and a conductive layer 104b in contact with the conductive layer 104a.

  A light-emitting element 254 illustrated in FIG. 12A and a light-emitting element 256 illustrated in FIG. 12B each include a region 222B sandwiched between the electrode 101 and the electrode 102, a region 222G sandwiched between the electrode 102 and the electrode 103, In addition, a partition wall 140 is provided between the region 222 </ b> R sandwiched between the electrode 102 and the electrode 104. The partition 140 has an insulating property. The partition 140 covers the ends of the electrode 101, the electrode 103, and the electrode 104 and has an opening overlapping with the electrode. By providing the partition wall 140, the electrodes of the substrate 200 in each region can be separated into island shapes.

  In addition, the light-emitting element 254 and the light-emitting element 256 include the substrate 220 including the optical element 224B, the optical element 224G, and the optical element 224R, respectively, in the direction in which light emitted from the region 222B, the region 222G, and the region 222R is extracted. . Light presented from each region is emitted to the outside of the light emitting element through each optical element. That is, the light presented from the region 222B is emitted through the optical element 224B, the light presented from the region 222G is emitted through the optical element 224G, and the light presented from the region 222R is emitted from the optical element 224R. Is injected through.

  Further, the optical element 224B, the optical element 224G, and the optical element 224R have a function of selectively transmitting light having a specific color from incident light. For example, light presented from the region 222B emitted through the optical element 224B becomes blue light, and light presented from the region 222G emitted through the optical element 224G becomes green light. The light presented from the region 222R emitted through the optical element 224R becomes red light.

  For the optical element 224R, the optical element 224G, and the optical element 224B, for example, a colored layer (also referred to as a color filter), a bandpass filter, a multilayer filter, or the like can be used. Further, a color conversion element can be applied to the optical element. The color conversion element is an optical element that converts incident light into light having a wavelength longer than the wavelength of the light. The color conversion element is preferably an element using a quantum dot method. By using the quantum dot method, the color reproducibility of the display device can be improved.

  Note that a plurality of optical elements may be overlaid on the optical element 224R, the optical element 224G, and the optical element 224B. As another optical element, for example, a circularly polarizing plate or an antireflection film can be provided. If a circularly polarizing plate is provided on the side from which light emitted from the light emitting element of the display device is extracted, light incident from the outside of the display device is reflected inside the display device and prevented from being emitted to the outside. it can. In addition, when an antireflection film is provided, external light reflected on the surface of the display device can be weakened. Thereby, the light emission which a display apparatus emits can be observed clearly.

  In FIGS. 12A and 12B, light emitted from each region through each optical element is light that exhibits blue (B), light that exhibits green (G), and light that exhibits red (R). , As schematically shown by broken arrows.

  Further, a light shielding layer 223 is provided between the optical elements. The light shielding layer 223 has a function of shielding light emitted from adjacent regions. Note that the light-blocking layer 223 may not be provided.

  The light shielding layer 223 has a function of suppressing reflection of external light. Alternatively, the light-blocking layer 223 has a function of preventing color mixture of light emitted from adjacent light-emitting elements. As the light-blocking layer 223, a metal, a resin containing a black pigment, carbon black, a metal oxide, a composite oxide containing a solid solution of a plurality of metal oxides, or the like can be used.

  Note that Embodiment 1 may be referred to for the substrate 220 and the substrate 200 each including an optical element.

≪Microcavity structure≫
Further, the light emitting element 254 and the light emitting element 256 have a microcavity structure.

  Light emitted from the light-emitting layer 160 and the light-emitting layer 170 is resonated between a pair of electrodes (for example, the electrode 101 and the electrode 102). In addition, the light emitting layer 160 and the light emitting layer 170 are formed at a position where light having a desired wavelength out of the emitted light is strengthened. For example, the light is emitted from the light emitting layer 160 by adjusting the optical distance from the reflective region of the electrode 101 to the light emitting region of the light emitting layer 160 and the optical distance from the reflective region of the electrode 102 to the light emitting region of the light emitting layer 160. It is possible to intensify light having a desired wavelength among the light to be transmitted. Further, by adjusting the optical distance from the reflective region of the electrode 101 to the light emitting region of the light emitting layer 170 and the optical distance from the reflective region of the electrode 102 to the light emitting region of the light emitting layer 170, the light is emitted from the light emitting layer 170. It is possible to intensify light having a desired wavelength among the light to be transmitted. That is, in the case of a tandem light-emitting element in which a plurality of light-emitting layers (here, the light-emitting layer 160 and the light-emitting layer 170) are stacked via the charge generation layer 115, the optical distances of the light-emitting layer 160 and the light-emitting layer 170 are optimal Is preferable.

  In the light-emitting element 254 and the light-emitting element 256, the thickness of the conductive layer (the conductive layer 101b, the conductive layer 103b, and the conductive layer 104b) is adjusted in each region to be exhibited from the light-emitting layer 160 and the light-emitting layer 170. It is possible to intensify light having a desired wavelength among the light to be transmitted. Note that light emitted from the light-emitting layer 160 and the light-emitting layer 170 may be strengthened by changing the thickness of at least one of the hole injection layer 111 and the hole transport layer 112 in each region.

For example, in the electrodes 101 to 104, when the refractive index of the conductive material having a function of reflecting light is smaller than the refractive index of the light-emitting layer 160 or the light-emitting layer 170, the film of the conductive layer 101b included in the electrode 101 The thickness is adjusted so that the optical distance between the electrode 101 and the electrode 102 is mλ _B / 2 (m represents a natural number, and λ _B represents the wavelength of light to be strengthened in the region 222B). Similarly, the thickness of the conductive layer 103b included in the electrode 103 is set such that the optical distance between the electrode 103 and the electrode 102 is m′λ _G / 2 (m ′ is a natural number, and λ _G is the wavelength of light that is strengthened in the region 222G. , Respectively). Further, the thickness of the conductive layer 104b of the electrode 104 has an optical distance m''λ _R / 2 (m '' is a natural number between electrode 104 and the electrode 102, lambda _R is the wavelength of the light to enhance the region 222R Are expressed respectively).

  As described above, by providing a microcavity structure and adjusting the optical distance between a pair of electrodes in each region, light scattering and light absorption near each electrode can be suppressed, and high light extraction efficiency can be realized. Can do. Note that in the above structure, the conductive layer 101b, the conductive layer 103b, and the conductive layer 104b preferably have a function of transmitting light. The materials forming the conductive layer 101b, the conductive layer 103b, and the conductive layer 104b may be the same as or different from each other. The conductive layer 101b, the conductive layer 103b, and the conductive layer 104b may each have a structure in which two or more layers are stacked.

  Note that since the light-emitting element 254 illustrated in FIG. 12A and a top emission light-emitting element, the conductive layer 101a, the conductive layer 103a, and the conductive layer 104a preferably have a function of reflecting light. The electrode 102 preferably has a function of transmitting light and a function of reflecting light.

  12B is a bottom emission light-emitting element, the conductive layer 101a, the conductive layer 103a, and the conductive layer 104a each have a function of transmitting light and a function of reflecting light. It is preferable to have. The electrode 102 preferably has a function of reflecting light.

  In the light-emitting element 254 and the light-emitting element 256, the same material may be used for the conductive layer 101a, the conductive layer 103a, or the conductive layer 104a, or different materials may be used. In the case where the same material is used for the conductive layer 101a, the conductive layer 103a, and the conductive layer 104a, manufacturing costs of the light-emitting element 254 and the light-emitting element 256 can be reduced. Note that the conductive layer 101a, the conductive layer 103a, and the conductive layer 104a may each have a structure in which two or more layers are stacked.

  In addition, for the light-emitting layer 160 or the light-emitting layer 170, it is preferable to use the compound having a delayed fluorescence component by TTA described in Embodiment Mode 1 for the light-emitting layer 160. By doing so, a light-emitting element exhibiting high light emission efficiency can be manufactured. In particular, in the region 222B, a light-emitting element having an emission spectrum peak in blue with favorable emission efficiency can be obtained.

  The light-emitting layer 160 and the light-emitting layer 170 can have a structure in which two layers are stacked, such as the light-emitting layer 170a and the light-emitting layer 170b. By using two types of light-emitting materials having a function of exhibiting different colors, ie, a first compound and a second compound, in the two light-emitting layers, a plurality of light emissions can be obtained simultaneously. In particular, it is preferable to select a light-emitting material used for each light-emitting layer so that the light-emitting layer 160 and the light-emitting layer 170 emit white light.

  The light-emitting layer 160 or the light-emitting layer 170 may have a structure in which three or more layers are stacked, or may include a layer that does not have a light-emitting material.

  As described above, the light-emitting element 254 or the light-emitting element 256 including the light-emitting layer that includes the compound having the delayed fluorescent component by TTA described in Embodiment 1 in at least one light-emitting layer is used for a pixel of the display device. Thus, a display device with high emission efficiency can be manufactured. In other words, a display device including the light-emitting element 254 or the light-emitting element 256 can reduce power consumption.

  Note that as for other structures of the light-emitting element 254 and the light-emitting element 256, the structure of the light-emitting element 250 or the light-emitting element 252 or the light-emitting element described in Embodiment 1 or 2 may be referred to.

<Constituent elements of light emitting layer>
Next, details of components of the light emitting layer in the light emitting element shown in FIGS. 11 and 12 will be described below.

  The light-emitting layer 123B, the light-emitting layer 123G, the light-emitting layer 123R, the light-emitting layer 160, or the light-emitting layer 170 is a first guest material having a function of emitting at least one selected from purple, blue, and blue-green. It has a certain luminescent substance. Alternatively, the light-emitting substance includes a light-emitting substance that is a second guest material having a function of emitting at least one selected from green, yellow-green, yellow, orange, and red. Each light-emitting layer includes one or both of an electron transporting material and a hole transporting material in addition to the light-emitting substance that is the first guest material. Each light-emitting layer includes one or both of an electron transporting material and a hole transporting material in addition to the light-emitting substance that is the second guest material.

  As the first guest material, a light-emitting substance having a function of converting singlet excitation energy into light emission can be used. As the second guest material, a light-emitting substance having a function of converting singlet excitation energy into light emission or a light-emitting substance having a function of converting triplet excitation energy into light emission can be used. Examples of the luminescent substance include the following.

  As a light-emitting substance that changes singlet excitation energy into light emission, a substance that can be used for the guest material 132 described in Embodiment 1 can be given.

  Examples of the light-emitting substance that changes triplet excitation energy into light emission include a substance that emits phosphorescence.

  There is no particular limitation on a material that can be used as the host material for the light-emitting layer; for example, the host material 131, the organic compound 431_1, and the organic compound 431_2 described in Embodiments 1 and 2 can be used. Possible substances are listed. One or a plurality of substances having an energy gap larger than that of the light-emitting material may be selected from these and various substances. When the light-emitting substance is a substance that emits phosphorescence, a host material that has a triplet excitation energy higher than the triplet excitation energy (the energy difference between the ground state and the triplet excited state) of the light-emitting substance is selected. It ’s fine.

  Further, when a plurality of materials are used as the host material of the light emitting layer, it is preferable to use a combination of two types of compounds that form an exciplex. In this case, various carrier transport materials can be used as appropriate. However, in order to efficiently form an exciplex, a compound that easily receives electrons (a material having an electron transport property) and a compound that easily receives holes (holes) It is particularly preferred to combine with a material having transportability.

  This is because when a material having an electron transporting property and a material having a hole transporting property are combined to form a host material that forms an exciplex, the mixing ratio of the material having the electron transporting property and the material having the hole transporting property is By adjusting, it becomes easy to optimize the carrier balance of holes and electrons in the light emitting layer. By optimizing the carrier balance between holes and electrons in the light emitting layer, it is possible to suppress the bias of the region where recombination of electrons and holes occurs in the light emitting layer. By suppressing the bias of the region where recombination occurs, the reliability of the light-emitting element can be improved.

  As a compound that easily receives electrons (a material having an electron transporting property), a π-electron deficient heteroaromatic such as a nitrogen-containing heteroaromatic compound, a metal complex, or the like can be used. Among them, a heterocyclic compound having a diazine skeleton and a triazine skeleton and a heterocyclic compound having a pyridine skeleton are preferable because they have good reliability. In particular, a heterocyclic compound having a diazine (pyrimidine or pyrazine) skeleton and a triazine skeleton has a high electron transport property and contributes to a reduction in driving voltage.

  As a compound that easily accepts holes (a material having a hole transporting property), a π-electron rich heteroaromatic (for example, a carbazole derivative or an indole derivative) or an aromatic amine can be preferably used. In addition, a compound having a thiophene skeleton and a compound having a furan skeleton can be given. Among these, a compound having an aromatic amine skeleton and a compound having a carbazole skeleton are preferable because they have good reliability, have high hole transportability, and contribute to a reduction in driving voltage.

  Note that the host material combination for forming the exciplex is not limited to the above-described compounds, and is a combination capable of transporting carriers and forming an exciplex. The emission of the exciplex is absorbed by the luminescent substance. As long as it overlaps with the absorption band on the longest wavelength side in the spectrum (absorption corresponding to the transition from the singlet ground state to the singlet excited state of the light-emitting substance), other materials may be used.

  Further, a thermally activated delayed fluorescent material may be used as the light emitting material or host material of the light emitting layer.

<Method for Manufacturing Light-Emitting Element>
Next, a method for manufacturing the light-emitting element of one embodiment of the present invention is described below with reference to FIGS. Note that here, a method for manufacturing the light-emitting element 254 illustrated in FIG. 12A will be described.

  13 and 14 are cross-sectional views illustrating a method for manufacturing a light-emitting element of one embodiment of the present invention.

  A method for manufacturing the light-emitting element 254 described below includes first to seventh steps.

≪First step≫
In the first step, an electrode of a light-emitting element (specifically, a conductive layer 101a constituting the electrode 101, a conductive layer 103a constituting the electrode 103, and a conductive layer 104a constituting the electrode 104) is formed over the substrate 200. This is a forming step (see FIG. 13A).

  In this embodiment, a conductive layer having a function of reflecting light is formed over the substrate 200, and the conductive layer is processed into a desired shape, so that the conductive layer 101a, the conductive layer 103a, and the conductive layer 104a are processed. Form. As the conductive layer having a function of reflecting light, an alloy film of silver, palladium, and copper (also referred to as an Ag—Pd—Cu film or APC) is used. As described above, it is preferable to form the conductive layer 101a, the conductive layer 103a, and the conductive layer 104a through the process of processing the same conductive layer because manufacturing costs can be reduced.

  Note that a plurality of transistors may be formed over the substrate 200 before the first step. The plurality of transistors may be electrically connected to the conductive layer 101a, the conductive layer 103a, and the conductive layer 104a.

≪Second step≫
In the second step, a conductive layer 101b having a function of transmitting light is formed on the conductive layer 101a constituting the electrode 101, and a conductive layer 103b having a function of transmitting light is formed on the conductive layer 103a constituting the electrode 103. In this step, a conductive layer 104b having a function of transmitting light is formed over the conductive layer 104a included in the electrode 104 (see FIG. 13B).

  In this embodiment, conductive layers 101b, 103b, and 104b having a function of transmitting light are formed over the conductive layers 101a, 103a, and 104a having a function of reflecting light, respectively. Are processed into desired shapes, whereby the electrode 101, the electrode 103, and the electrode 104 are formed. As the conductive layers 101b, 103b, and 104b, ITSO films are used.

  Note that the conductive layers 101b, 103b, and 104b having a function of transmitting light may be formed in multiple steps. By forming in multiple steps, the conductive layers 101b, 103b, and 104b can be formed with a film thickness that provides a suitable microcavity structure in each region.

≪Third step≫
The third step is a step of forming a partition 140 that covers an end portion of each electrode of the light emitting element (see FIG. 13C).

  The partition 140 has an opening so as to overlap with the electrode. The conductive film exposed through the opening functions as an anode of the light emitting element. In this embodiment, polyimide resin is used for the partition wall 140.

  Note that in the first to third steps, since there is no possibility of damaging the EL layer (a layer containing an organic compound), various film formation methods and microfabrication techniques can be applied. In this embodiment mode, a reflective conductive layer is formed using a sputtering method, the conductive layer is patterned using a lithography method, and then the conductive layer is formed using a dry etching method or a wet etching method. Is processed into an island shape, whereby a conductive layer 101a that forms the electrode 101, a conductive layer 103a that forms the electrode 103, and a conductive layer 104a that forms the electrode 104 are formed. Thereafter, a conductive film having transparency is formed using a sputtering method, a pattern is formed on the conductive film having transparency using a lithography method, and then the transparent conductive film is formed using a wet etching method. The electrode 101, the electrode 103, and the electrode 104 are formed by processing into an island shape.

≪Fourth Step≫
The fourth step is a step of forming the hole injection layer 111, the hole transport layer 112, the light emitting layer 170, the electron transport layer 113, the electron injection layer 114, and the charge generation layer 115 (see FIG. 14A). ).

  The hole injection layer 111 can be formed by co-evaporation of a hole transporting material and a material containing an acceptor substance. Note that co-evaporation is an evaporation method in which a plurality of different substances are simultaneously evaporated from different evaporation sources. The hole transport layer 112 can be formed by vapor deposition of a hole transport material.

  The light emitting layer 170 can be formed by vapor-depositing a second guest material that emits at least one selected from green, yellow-green, yellow, orange, and red. As the second guest material, a light-emitting organic compound exhibiting fluorescence or phosphorescence can be used. The light-emitting organic compound may be vapor-deposited alone, but may be vapor-deposited by mixing with other substances. Alternatively, a light-emitting organic compound may be used as a guest material, and the guest material may be dispersed and evaporated in a host material having a higher excitation energy than the guest material. The light-emitting layer 170 preferably has a two-layer structure of a light-emitting layer 170a and a light-emitting layer 170b. In that case, the light-emitting layer 170a and the light-emitting layer 170b each preferably include a light-emitting substance that exhibits different emission colors.

  The electron transport layer 113 can be formed by evaporating a substance having a high electron transport property. Further, the electron injection layer 114 can be formed by vapor deposition of a substance having a high electron injection property.

  The charge generation layer 115 is formed by vapor deposition of a material in which an electron acceptor (acceptor) is added to a hole transporting material, or a material in which an electron donor (donor) is added to an electron transporting material. Can do.

≪Fifth step≫
The fifth step is a step of forming the hole injection layer 116, the hole transport layer 117, the light emitting layer 160, the electron transport layer 118, the electron injection layer 119, and the electrode 102 (see FIG. 14B).

  The hole injection layer 116 can be formed using the same material and the same method as those of the hole injection layer 111 described above. Further, the hole transport layer 117 can be formed using a material and a method similar to those of the hole transport layer 112 described above.

  The light-emitting layer 160 can be formed by vapor-depositing a first guest material that exhibits at least one light emission selected from purple, blue, and blue-green. As the first guest material, a fluorescent organic compound can be used. The fluorescent organic compound may be vapor-deposited alone, or may be vapor-deposited by mixing with other materials. Alternatively, a fluorescent organic compound may be used as a guest material, and the guest material may be dispersed and evaporated in a host material having a higher excitation energy than the guest material.

  The electron transport layer 118 can be formed by vapor deposition of a substance having a high electron transport property. Further, the electron injection layer 119 can be formed by vapor-depositing a substance having a high electron injection property.

  The electrode 102 can be formed by stacking a conductive film having reflectivity and a conductive film having a light-transmitting property. The electrode 102 may have a single-layer structure or a stacked structure.

  Through the above steps, a light-emitting element having a region 222B, a region 222G, and a region 222R is formed over the substrate 200 over the electrode 101, the electrode 103, and the electrode 104, respectively.

≪Sixth Step≫
The sixth step is a step of forming the light shielding layer 223, the optical element 224B, the optical element 224G, and the optical element 224R over the substrate 220 (see FIG. 14C).

  As the light shielding layer 223, a resin film containing a black pigment is formed in a desired region. After that, the optical element 224B, the optical element 224G, and the optical element 224R are formed over the substrate 220 and the light shielding layer 223. As the optical element 224B, a resin film containing a blue pigment is formed in a desired region. As the optical element 224G, a resin film containing a green pigment is formed in a desired region. As the optical element 224R, a resin film containing a red pigment is formed in a desired region.

≪Seventh Step≫
In the seventh step, the light-emitting element formed over the substrate 200 and the light-shielding layer 223, the optical element 224B, the optical element 224G, and the optical element 224R formed over the substrate 220 are bonded together, and a sealing material is attached. It is the process of sealing using (not shown).

  Through the above steps, the light-emitting element 254 illustrated in FIG. 12A can be formed.

  Note that the structure described in this embodiment can be combined as appropriate with any of the structures described in the other embodiments.

(Embodiment 4)
In this embodiment, a display device of one embodiment of the present invention will be described with reference to FIGS.

<Configuration Example 1 of Display Device>
15A is a top view of the display device 600, and FIG. 15B is a cross-sectional view taken along the dashed-dotted line AB and the dashed-dotted line CD in FIG. The display device 600 includes a driver circuit portion (a signal line driver circuit portion 601 and a scan line driver circuit portion 603) and a pixel portion 602. Note that the signal line driver circuit portion 601, the scan line driver circuit portion 603, and the pixel portion 602 have a function of controlling light emission of the light-emitting element.

  In addition, the display device 600 includes an element substrate 610, a sealing substrate 604, a sealant 605, a region 607 surrounded by the sealant 605, a lead wiring 608, and an FPC 609.

  Note that the lead wiring 608 is a wiring for transmitting a signal input to the signal line driver circuit portion 601 and the scanning line driver circuit portion 603, and a video signal, a clock signal, a start signal, an FPC 609 serving as an external input terminal, Receive a reset signal. Note that only the FPC 609 is illustrated here, but a printed wiring board (PWB) may be attached to the FPC 609.

  In the signal line driver circuit portion 601, a CMOS circuit in which an N-channel transistor 623 and a P-channel transistor 624 are combined is formed. Note that the signal line driver circuit portion 601 or the scan line driver circuit portion 603 can use various CMOS circuits, PMOS circuits, or NMOS circuits. In this embodiment mode, a display device in which a driver and a pixel in which a driver circuit portion is formed over a substrate is provided on the same surface is not necessarily required; It can also be formed.

  The pixel portion 602 includes a switching transistor 611, a current control transistor 612, and a lower electrode 613 electrically connected to the drain of the current control transistor 612. A partition wall 614 is formed so as to cover an end portion of the lower electrode 613. As the partition wall 614, a positive photosensitive acrylic resin film can be used.

  In addition, a curved surface having a curvature is formed at the upper end portion or the lower end portion of the partition wall 614 in order to improve the coverage. For example, when positive photosensitive acrylic is used as the material of the partition wall 614, it is preferable that only the upper end portion of the partition wall 614 has a curved surface having a curvature radius (0.2 μm or more and 3 μm or less). As the partition wall 614, either a negative photosensitive resin or a positive photosensitive resin can be used.

  Note that there is no particular limitation on the structure of the transistor (the transistors 611, 612, 623, and 624). For example, a staggered transistor may be used. There is no particular limitation on the polarity of the transistor, and a structure including N-channel and P-channel transistors and a structure including only one of an N-channel transistor and a P-channel transistor may be used. . There is no particular limitation on the crystallinity of a semiconductor film used for the transistor. For example, an amorphous semiconductor film or a crystalline semiconductor film can be used. As the semiconductor material, a group 14 (silicon, etc.) semiconductor, a compound semiconductor (including an oxide semiconductor), an organic semiconductor, or the like can be used. As the transistor, for example, an oxide semiconductor with an energy gap of 2 eV or more, preferably 2.5 eV or more, more preferably 3 eV or more can be used because off-state current of the transistor can be reduced. Examples of the oxide semiconductor include In—Ga oxide, In—M—Zn oxide (M is Al, Ga, yttrium (Y), zirconium (Zr), lanthanum (La), cerium (Ce), Sn, Hafnium (Hf) or neodymium (Nd)).

  An EL layer 616 and an upper electrode 617 are formed on the lower electrode 613, respectively. Note that the lower electrode 613 functions as an anode, and the upper electrode 617 functions as a cathode.

  The EL layer 616 is formed by various methods such as an evaporation method using an evaporation mask, an inkjet method, and a spin coating method. Further, as another material forming the EL layer 616, a low molecular compound or a high molecular compound (including an oligomer and a dendrimer) may be used.

  Note that the light-emitting element 618 is formed by the lower electrode 613, the EL layer 616, and the upper electrode 617. A light-emitting element 618 is a light-emitting element having the structure of Embodiment 1 or 2. Note that in the case where a plurality of light-emitting elements are formed, the pixel portion may include both the light-emitting elements described in Embodiment 1 or 2 and light-emitting elements having other structures.

  Further, the sealing substrate 604 is attached to the element substrate 610 with the sealant 605, whereby the light-emitting element 618 is provided in the region 607 surrounded by the element substrate 610, the sealing substrate 604, and the sealant 605. ing. Note that the region 607 is filled with a filler and is filled with an ultraviolet curable resin or a thermosetting resin that can be used for the sealant 605 in addition to a case where an inert gas (such as nitrogen or argon) is filled. For example, PVC (polyvinyl chloride) resin, acrylic resin, polyimide resin, epoxy resin, silicone resin, PVB (polyvinyl butyral) resin, or EVA (ethylene vinyl acetate) resin may be used. Can be used. When a recess is formed in the sealing substrate and a desiccant is provided therein, deterioration due to the influence of moisture can be suppressed, which is a preferable configuration.

  In addition, the optical element 621 is provided below the sealing substrate 604 so as to overlap with the light emitting element 618. Further, a light shielding layer 622 is provided below the sealing substrate 604. The optical element 621 and the light-blocking layer 622 may have structures similar to those of the optical element and the light-blocking layer described in Embodiment 3, respectively.

  Note that an epoxy resin or glass frit is preferably used for the sealant 605. Moreover, it is desirable that these materials are materials that are as difficult to permeate moisture and oxygen as possible. In addition to a glass substrate or a quartz substrate, a plastic substrate made of FRP (Fiber Reinforced Plastics), PVF (polyvinyl fluoride), polyester, acrylic, or the like can be used as a material for the sealing substrate 604.

  As described above, a display device including the light-emitting element and the optical element described in any of Embodiments 1 to 3 can be obtained.

<Configuration Example 2 of Display Device>
Next, another example of the display device will be described with reference to FIGS. 16A and 16B and 17 are cross-sectional views of a display device of one embodiment of the present invention.

  FIG. 16A shows a substrate 1001, a base insulating film 1002, a gate insulating film 1003, gate electrodes 1006, 1007, and 1008, a first interlayer insulating film 1020, a second interlayer insulating film 1021, a peripheral portion 1042, and a pixel portion. 1040, a driver circuit portion 1041, a light emitting element lower electrode 1024R, 1024G, 1024B, a partition wall 1025, an EL layer 1028, a light emitting element upper electrode 1026, a sealing layer 1029, a sealing substrate 1031, a sealing material 1032, and the like Yes.

  In FIG. 16A, a colored layer (a red colored layer 1034R, a green colored layer 1034G, and a blue colored layer 1034B) is provided over a transparent base material 1033 as an example of an optical element. Further, a light shielding layer 1035 may be further provided. The transparent base material 1033 provided with the coloring layer and the light shielding layer is aligned and fixed to the substrate 1001. Note that the coloring layer and the light shielding layer are covered with an overcoat layer 1036. In FIG. 16A, since light transmitted through the colored layer is red, green, and blue, an image can be expressed with pixels of three colors.

  In FIG. 16B, as an example of the optical element, a colored layer (a red colored layer 1034R, a green colored layer 1034G, and a blue colored layer 1034B) is provided between the gate insulating film 1003 and the first interlayer insulating film 1020. An example of forming is shown. As described above, the coloring layer may be provided between the substrate 1001 and the sealing substrate 1031.

  In FIG. 17, as an example of the optical element, a colored layer (a red colored layer 1034R, a green colored layer 1034G, and a blue colored layer 1034B) is provided between the first interlayer insulating film 1020 and the second interlayer insulating film 1021. An example of forming is shown. As described above, the coloring layer may be provided between the substrate 1001 and the sealing substrate 1031.

  In the display device described above, a display device having a structure in which light is extracted to the substrate 1001 side where the transistor is formed (bottom emission type) is used. However, a structure in which light emission is extracted to the sealing substrate 1031 side (top emission type). ) Display device.

<Configuration Example 3 of Display Device>
An example of a cross-sectional view of a top emission type display device is shown in FIGS. 18A and 18B are cross-sectional views illustrating a display device of one embodiment of the present invention, in which the driver circuit portion 1041, the peripheral portion 1042, and the like shown in FIGS. 16A and 16B are omitted. It is illustrated as an example.

  In this case, a substrate that does not transmit light can be used as the substrate 1001. Until the connection electrode for connecting the transistor and the anode of the light-emitting element is manufactured, the transistor is formed in the same manner as the bottom emission display device. Thereafter, a third interlayer insulating film 1037 is formed so as to cover the electrode 1022. This insulating film may play a role of planarization. The third interlayer insulating film 1037 can be formed using various other materials in addition to the same material as the second interlayer insulating film.

  The lower electrodes 1024R, 1024G, and 1024B of the light-emitting elements are anodes here, but may be cathodes. In the case of a top-emission display device as shown in FIGS. 18A and 18B, the lower electrodes 1024R, 1024G, and 1024B preferably have a function of reflecting light. An upper electrode 1026 is provided over the EL layer 1028. The upper electrode 1026 has a function of reflecting light and a function of transmitting light, and adopts a microcavity structure between the lower electrodes 1024R, 1024G, and 1024B and the upper electrode 1026, and increases the light intensity at a specific wavelength. Increasing is preferable.

  In the top emission structure as shown in FIG. 18A, sealing is performed with a sealing substrate 1031 provided with colored layers (a red colored layer 1034R, a green colored layer 1034G, and a blue colored layer 1034B). it can. A light-blocking layer 1035 may be provided on the sealing substrate 1031 so as to be positioned between the pixels. Note that a light-transmitting substrate is preferably used as the sealing substrate 1031.

  FIG. 18A illustrates a plurality of light-emitting elements and a structure in which a colored layer is provided for each of the plurality of light-emitting elements; however, the present invention is not limited to this. For example, as shown in FIG. 18B, a red colored layer 1034R and a blue colored layer 1034B are provided without providing a green colored layer, and full color display is performed with three colors of red, green, and blue. It is good also as a structure. As shown in FIG. 18A, when a light-emitting element and a structure in which a colored layer is provided for each of the light-emitting elements are provided, there is an effect that external light reflection can be suppressed. On the other hand, as shown in FIG. 18B, when a light emitting element and a red colored layer and a blue colored layer are provided without providing a green colored layer, the light is emitted from the green light emitting element. Since the energy loss of the light is small, the power consumption can be reduced.

<Configuration Example 4 of Display Device>
Although the display device described above has a configuration including sub-pixels of three colors (red, green, and blue), sub-pixels of four colors (red, green, blue, yellow, or red, green, blue, and white) It is good also as a structure which has. 19 to 21 illustrate a structure of a display device including lower electrodes 1024R, 1024G, 1024B, and 1024Y. 19A, 19B, and 20 show a display device having a structure (bottom emission type) in which light is extracted to the substrate 1001 side where a transistor is formed. FIGS. This is a display device having a structure in which light emission is extracted from the substrate 1031 side (top emission type).

  FIG. 19A illustrates an example of a display device in which an optical element (a colored layer 1034R, a colored layer 1034G, a colored layer 1034B, and a colored layer 1034Y) is provided over a transparent base material 1033. FIG. 19B illustrates a display device in which an optical element (colored layer 1034R, colored layer 1034G, colored layer 1034B, and colored layer 1034Y) is formed between the gate insulating film 1003 and the first interlayer insulating film 1020. It is an example. 20 illustrates a display device in which an optical element (colored layer 1034R, colored layer 1034G, colored layer 1034B, and colored layer 1034Y) is formed between the first interlayer insulating film 1020 and the second interlayer insulating film 1021. It is an example.

  The colored layer 1034R has a function of transmitting red light, the colored layer 1034G has a function of transmitting green light, and the colored layer 1034B has a function of transmitting blue light. The colored layer 1034Y has a function of transmitting yellow light or a function of transmitting a plurality of lights selected from blue, green, yellow, and red. When the colored layer 1034Y has a function of transmitting a plurality of lights selected from blue, green, yellow, and red, the light transmitted through the colored layer 1034Y may be white. Since a light-emitting element that emits yellow or white light has high emission efficiency, the display device including the colored layer 1034Y can reduce power consumption.

  In the top emission display device illustrated in FIG. 21, the light-emitting element having the lower electrode 1024Y also has a microcavity structure between the upper electrode 1026 and the display device in FIG. A configuration is preferred. In the display device in FIG. 21A, sealing is performed with a sealing substrate 1031 provided with colored layers (a red colored layer 1034R, a green colored layer 1034G, a blue colored layer 1034B, and a yellow colored layer 1034Y). It can be performed.

  The light emitted through the microcavity and the yellow colored layer 1034Y becomes light having an emission spectrum in the yellow region. Since yellow is a color with high visibility, a light-emitting element that emits yellow light has high light emission efficiency. That is, the display device having the structure illustrated in FIG. 21A can reduce power consumption.

  FIG. 21A illustrates a plurality of light-emitting elements and a structure in which a colored layer is provided for each of the plurality of light-emitting elements; however, the present invention is not limited to this. For example, as shown in FIG. 21B, a red colored layer 1034R, a green colored layer 1034G, and a blue colored layer 1034B are provided without providing a yellow colored layer, and red, green, blue, yellow The full color display may be performed with the four colors of red, green, blue, and white. As shown in FIG. 21A, when a light emitting element and a structure in which a colored layer is provided for each light emitting element are provided, an effect that external light reflection can be suppressed is obtained. On the other hand, as shown in FIG. 21B, when a light emitting element and a yellow colored layer are not provided, a red colored layer, a green colored layer, and a blue colored layer are provided. Since there is little energy loss of the light inject | emitted from the white light emitting element, there exists an effect that power consumption can be made low.

  Note that the structure described in this embodiment can be combined as appropriate with any of the other embodiments and the other structures in this embodiment.

(Embodiment 5)
In this embodiment, a display device including the light-emitting element of one embodiment of the present invention will be described with reference to FIGS.

  22A is a block diagram illustrating a display device of one embodiment of the present invention, and FIG. 22B illustrates a pixel circuit included in the display device of one embodiment of the present invention. It is a circuit diagram.

<Description of display device>
A display device illustrated in FIG. 22A includes a region having a pixel of a display element (hereinafter referred to as a pixel portion 802) and a circuit portion (hereinafter, referred to as a pixel portion 802) that includes a circuit for driving the pixel. , A driver circuit portion 804), a circuit having an element protection function (hereinafter referred to as a protection circuit 806), and a terminal portion 807. Note that the protection circuit 806 may not be provided.

  Part or all of the driver circuit portion 804 is preferably formed over the same substrate as the pixel portion 802. Thereby, the number of parts and the number of terminals can be reduced. When part or all of the driver circuit portion 804 is not formed over the same substrate as the pixel portion 802, part or all of the driver circuit portion 804 is formed by COG or TAB (Tape Automated Bonding). Can be implemented.

  The pixel portion 802 includes a circuit (hereinafter referred to as a pixel circuit 801) for driving a plurality of display elements arranged in X rows (X is a natural number of 2 or more) and Y columns (Y is a natural number of 2 or more). The driver circuit portion 804 supplies a signal for selecting a pixel (scanning signal) (hereinafter referred to as a scanning line driving circuit 804a) and a signal (data signal) for driving a display element of the pixel. A driver circuit such as a circuit (hereinafter, a signal line driver circuit 804b) is included.

  The scan line driver circuit 804a includes a shift register and the like. The scan line driver circuit 804a receives a signal for driving the shift register via the terminal portion 807 and outputs a signal. For example, the scan line driver circuit 804a receives a start pulse signal, a clock signal, and the like and outputs a pulse signal. The scan line driver circuit 804a has a function of controlling the potential of a wiring to which a scan signal is supplied (hereinafter referred to as scan lines GL_1 to GL_X). Note that a plurality of scan line driver circuits 804a may be provided, and the scan lines GL_1 to GL_X may be divided and controlled by the plurality of scan line driver circuits 804a. Alternatively, the scan line driver circuit 804a has a function of supplying an initialization signal. Note that the present invention is not limited to this, and the scan line driver circuit 804a can supply another signal.

  The signal line driver circuit 804b includes a shift register and the like. In addition to a signal for driving the shift register, the signal line driver circuit 804b receives a signal (image signal) that is a source of a data signal through the terminal portion 807. The signal line driver circuit 804b has a function of generating a data signal to be written in the pixel circuit 801 based on the image signal. In addition, the signal line driver circuit 804b has a function of controlling output of a data signal in accordance with a pulse signal obtained by inputting a start pulse, a clock signal, or the like. The signal line driver circuit 804b has a function of controlling the potential of a wiring to which a data signal is supplied (hereinafter referred to as data lines DL_1 to DL_Y). Alternatively, the signal line driver circuit 804b has a function of supplying an initialization signal. Note that the present invention is not limited to this, and the signal line driver circuit 804b can supply another signal.

  The signal line driver circuit 804b is configured using a plurality of analog switches, for example. The signal line driver circuit 804b can output a signal obtained by time-dividing an image signal as a data signal by sequentially turning on a plurality of analog switches. Alternatively, the signal line driver circuit 804b may be formed using a shift register or the like.

  Each of the plurality of pixel circuits 801 receives a pulse signal through one of the plurality of scanning lines GL to which the scanning signal is applied, and receives the data signal through one of the plurality of data lines DL to which the data signal is applied. Entered. In each of the plurality of pixel circuits 801, writing and holding of data signals is controlled by the scanning line driver circuit 804a. For example, the pixel circuit 801 in the m-th row and the n-th column receives a pulse signal from the scan line driver circuit 804a through the scan line GL_m (m is a natural number equal to or less than X), and the data line DL_n according to the potential of the scan line GL_m. A data signal is input from the signal line driver circuit 804b through (n is a natural number equal to or less than Y).

  The protection circuit 806 illustrated in FIG. 22A is connected to, for example, the scanning line GL which is a wiring between the scanning line driver circuit 804a and the pixel circuit 801. Alternatively, the protection circuit 806 is connected to the data line DL that is a wiring between the signal line driver circuit 804 b and the pixel circuit 801. Alternatively, the protection circuit 806 can be connected to a wiring between the scan line driver circuit 804 a and the terminal portion 807. Alternatively, the protection circuit 806 can be connected to a wiring between the signal line driver circuit 804 b and the terminal portion 807. Note that the terminal portion 807 is a portion where a terminal for inputting a power supply, a control signal, and an image signal from an external circuit to the display device is provided.

  The protection circuit 806 is a circuit that brings a wiring into a conductive state when a potential outside a certain range is applied to the wiring to which the protection circuit 806 is connected.

  As shown in FIG. 22A, by providing a protection circuit 806 in each of the pixel portion 802 and the driver circuit portion 804, resistance of the display device to an overcurrent generated by ESD (Electro Static Discharge) or the like is increased. be able to. However, the structure of the protection circuit 806 is not limited thereto, and for example, a structure in which the protection circuit 806 is connected to the scan line driver circuit 804a or a structure in which the protection circuit 806 is connected to the signal line driver circuit 804b can be employed. Alternatively, the protective circuit 806 can be connected to the terminal portion 807.

  FIG. 22A illustrates an example in which the driver circuit portion 804 is formed using the scan line driver circuit 804a and the signal line driver circuit 804b; however, the present invention is not limited to this structure. For example, a structure in which only the scan line driver circuit 804a is formed and a substrate on which a separately prepared signal line driver circuit is formed (for example, a driver circuit substrate formed of a single crystal semiconductor film or a polycrystalline semiconductor film) is mounted. Also good.

<Configuration example of pixel circuit>
The plurality of pixel circuits 801 illustrated in FIG. 22A can have a structure illustrated in FIG.

  A pixel circuit 801 illustrated in FIG. 22B includes transistors 852 and 854, a capacitor 862, and a light-emitting element 872.

  One of a source electrode and a drain electrode of the transistor 852 is electrically connected to a wiring (data line DL_n) to which a data signal is supplied. Further, the gate electrode of the transistor 852 is electrically connected to a wiring (scanning line GL_m) to which a gate signal is supplied.

  The transistor 852 has a function of controlling data writing of the data signal.

  One of the pair of electrodes of the capacitor 862 is electrically connected to a wiring to which a potential is applied (hereinafter referred to as a potential supply line VL_a), and the other is electrically connected to the other of the source electrode and the drain electrode of the transistor 852. Is done.

  The capacitor 862 functions as a storage capacitor for storing written data.

  One of a source electrode and a drain electrode of the transistor 854 is electrically connected to the potential supply line VL_a. Further, the gate electrode of the transistor 854 is electrically connected to the other of the source electrode and the drain electrode of the transistor 852.

  One of an anode and a cathode of the light-emitting element 872 is electrically connected to the potential supply line VL_b, and the other is electrically connected to the other of the source electrode and the drain electrode of the transistor 854.

  As the light-emitting element 872, the light-emitting element described in Embodiment 1 can be used.

  Note that one of the potential supply line VL_a and the potential supply line VL_b is supplied with the high power supply potential VDD, and the other is supplied with the low power supply potential VSS.

  In the display device including the pixel circuit 801 in FIG. 22B, for example, the pixel circuit 801 in each row is sequentially selected by the scan line driver circuit 804a illustrated in FIG. Write data.

  The pixel circuit 801 in which data is written is brought into a holding state when the transistor 852 is turned off. Further, the amount of current flowing between the source electrode and the drain electrode of the transistor 854 is controlled in accordance with the potential of the written data signal, and the light-emitting element 872 emits light with luminance corresponding to the flowing current amount. An image can be displayed by sequentially performing this for each row.

  Further, the pixel circuit may have a function of correcting the influence of fluctuations such as the threshold voltage of the transistor. FIGS. 23A and 23B and FIGS. 24A and 24B show examples of pixel circuits.

  A pixel circuit illustrated in FIG. 23A includes six transistors (transistors 303_1 to 303_6), a capacitor 304, and a light-emitting element 305. In addition, wirings 301_1 to 301_5, a wiring 302_1, and a wiring 302_2 are electrically connected to the pixel circuit illustrated in FIG. Note that as the transistors 303_1 to 303_6, for example, p-channel transistors can be used.

  The pixel circuit illustrated in FIG. 23B has a structure in which a transistor 303_7 is added to the pixel circuit illustrated in FIG. In addition, the wiring 301_6 and the wiring 301_7 are electrically connected to the pixel circuit illustrated in FIG. Here, the wiring 301_5 and the wiring 301_6 may be electrically connected to each other. Note that for the transistor 303_7, for example, a p-channel transistor can be used.

  A pixel circuit illustrated in FIG. 24A includes six transistors (transistors 308_1 to 308_6), a capacitor 304, and a light-emitting element 305. In addition, wirings 306_1 to 306_3 and wirings 307_1 to 307_3 are electrically connected to the pixel circuit illustrated in FIG. Here, the wiring 306_1 and the wiring 306_3 may be electrically connected to each other. Note that as the transistors 308_1 to 308_6, for example, p-channel transistors can be used.

  A pixel circuit illustrated in FIG. 24B includes two transistors (a transistor 309_1 and a transistor 309_2), two capacitors (a capacitor 304_1 and a capacitor 304_2), and a light-emitting element 305. In addition, wirings 311_1 to 311_3, a wiring 312_1, and a wiring 312_2 are electrically connected to the pixel circuit illustrated in FIG. In addition, with the structure of the pixel circuit illustrated in FIG. 24B, for example, a voltage input-current driving method (also referred to as a CVCC method) can be employed. Note that as the transistors 309_1 and 309_2, for example, p-channel transistors can be used.

  The light-emitting element of one embodiment of the present invention can be applied to an active matrix method in which an active element is included in a pixel of a display device or a passive matrix method in which an active element is not included in a pixel of a display device. .

  In the active matrix system, not only transistors but also various active elements (active elements and nonlinear elements) can be used as active elements (active elements and nonlinear elements). For example, MIM (Metal Insulator Metal) or TFD (Thin Film Diode) can be used. Since these elements have few manufacturing steps, manufacturing cost can be reduced or yield can be improved. Alternatively, since these elements have small element sizes, the aperture ratio can be improved, and power consumption and luminance can be increased.

  As a method other than the active matrix method, a passive matrix type that does not use an active element (an active element or a non-linear element) can be used. Since no active element (active element or non-linear element) is used, the number of manufacturing steps is small, so that manufacturing costs can be reduced or yield can be improved. Alternatively, since an active element (an active element or a non-linear element) is not used, an aperture ratio can be improved, power consumption can be reduced, or luminance can be increased.

  The structure described in this embodiment can be combined as appropriate with any of the structures described in the other embodiments.

(Embodiment 6)
In this embodiment, a display device including the light-emitting element of one embodiment of the present invention and an electronic device in which the input device is attached to the display device will be described with reference to FIGS.

<Description 1 regarding touch panel>
Note that in this embodiment, a touch panel 2000 including a display device and an input device is described as an example of an electronic device. A case where a touch sensor is provided as an example of the input device will be described.

  25A and 25B are perspective views of the touch panel 2000. FIG. 25A and 25B, typical components of the touch panel 2000 are shown for clarity.

  The touch panel 2000 includes a display device 2501 and a touch sensor 2595 (see FIG. 25B). The touch panel 2000 includes a substrate 2510, a substrate 2570, and a substrate 2590. Note that the substrate 2510, the substrate 2570, and the substrate 2590 are all flexible. Note that any one or all of the substrate 2510, the substrate 2570, and the substrate 2590 may not have flexibility.

  The display device 2501 includes a plurality of pixels over the substrate 2510 and a plurality of wirings 2511 that can supply signals to the pixels. The plurality of wirings 2511 are routed to the outer periphery of the substrate 2510, and a part of them constitutes a terminal 2519. A terminal 2519 is electrically connected to the FPC 2509 (1). The plurality of wirings 2511 can supply a signal from the signal line driver circuit 2503s (1) to the plurality of pixels.

  The substrate 2590 includes a touch sensor 2595 and a plurality of wirings 2598 electrically connected to the touch sensor 2595. The plurality of wirings 2598 are drawn around the outer periphery of the substrate 2590, and a part of them constitutes a terminal. The terminal is electrically connected to the FPC 2509 (2). Note that in FIG. 25B, for clarity, electrodes, wirings, and the like of the touch sensor 2595 provided on the back surface side of the substrate 2590 (the surface side facing the substrate 2510) are shown by solid lines.

  As the touch sensor 2595, for example, a capacitive touch sensor can be used. Examples of the electrostatic capacity method include a surface electrostatic capacity method and a projection electrostatic capacity method.

  As the projected capacitance method, there are mainly a self-capacitance method and a mutual capacitance method due to a difference in driving method. The mutual capacitance method is preferable because simultaneous multipoint detection is possible.

  Note that a touch sensor 2595 illustrated in FIG. 25B has a structure to which a projected capacitive touch sensor is applied.

  Note that as the touch sensor 2595, various sensors that can detect the proximity or contact of a detection target such as a finger can be used.

  The projected capacitive touch sensor 2595 includes an electrode 2591 and an electrode 2592. The electrode 2591 is electrically connected to any of the plurality of wirings 2598, and the electrode 2592 is electrically connected to any other of the plurality of wirings 2598.

  As shown in FIGS. 25A and 25B, the electrode 2592 has a shape in which a plurality of quadrilaterals repeatedly arranged in one direction are connected at corners.

  The electrode 2591 has a quadrangular shape and is repeatedly arranged in a direction intersecting with the direction in which the electrode 2592 extends.

  The wiring 2594 is electrically connected to two electrodes 2591 that sandwich the electrode 2592. At this time, a shape in which the area of the intersection of the electrode 2592 and the wiring 2594 is as small as possible is preferable. Thereby, the area of the area | region where the electrode is not provided can be reduced, and the dispersion | variation in the transmittance | permeability can be reduced. As a result, variation in luminance of light transmitted through the touch sensor 2595 can be reduced.

  Note that the shapes of the electrode 2591 and the electrode 2592 are not limited thereto, and various shapes can be employed. For example, a plurality of electrodes 2591 may be arranged so as not to have a gap as much as possible, and a plurality of electrodes 2592 may be provided apart from each other so as to form a region that does not overlap with the electrodes 2591 with an insulating layer interposed therebetween. At this time, it is preferable to provide a dummy electrode electrically insulated from two adjacent electrodes 2592 because the area of regions having different transmittances can be reduced.

<Description of display device>
Next, details of the display device 2501 will be described with reference to FIG. FIG. 26A corresponds to a cross-sectional view taken along dashed-dotted line X1-X2 in FIG.

  The display device 2501 includes a plurality of pixels arranged in a matrix. The pixel includes a display element and a pixel circuit that drives the display element.

  In the following description, a case where a light-emitting element that emits white light is applied to a display element will be described; however, the display element is not limited to this. For example, light emitting elements having different emission colors may be applied so that the color of light emitted from each adjacent pixel is different.

For example, the substrate 2510 and the substrate 2570 have a water vapor transmission rate of 1 × 10 ⁻⁵ g · m ⁻² · day ⁻¹ or less, preferably 1 × 10 ⁻⁶ g · m ⁻² · day ⁻¹ or less. A flexible material can be preferably used. Alternatively, a material in which the thermal expansion coefficient of the substrate 2510 and the thermal expansion coefficient of the substrate 2570 are approximately equal is preferably used. For example, a material having a linear expansion coefficient of 1 × 10 ⁻³ / K or less, preferably 5 × 10 ⁻⁵ / K or less, more preferably 1 × 10 ⁻⁵ / K or less can be suitably used.

  Note that the substrate 2510 is a stack including an insulating layer 2510a that prevents diffusion of impurities into the light-emitting element, a flexible substrate 2510b, and an adhesive layer 2510c that bonds the insulating layer 2510a and the flexible substrate 2510b. . The substrate 2570 is a stack including an insulating layer 2570a that prevents diffusion of impurities into the light-emitting element, a flexible substrate 2570b, and an adhesive layer 2570c that bonds the insulating layer 2570a and the flexible substrate 2570b. .

  As the adhesive layer 2510c and the adhesive layer 2570c, for example, polyester, polyolefin, polyamide (nylon, aramid, or the like), polyimide, polycarbonate, acrylic resin, polyurethane, or epoxy resin can be used. Alternatively, a material including a resin having a siloxane bond such as silicone can be used.

  In addition, a sealing layer 2560 is provided between the substrate 2510 and the substrate 2570. The sealing layer 2560 preferably has a refractive index larger than that of air. In addition, as illustrated in FIG. 26A, in the case where light is extracted to the sealing layer 2560 side, the sealing layer 2560 can also serve as an optical bonding layer.

  Further, a sealing material may be formed on the outer peripheral portion of the sealing layer 2560. By using the sealant, the light-emitting element 2550R can be provided in a region surrounded by the substrate 2510, the substrate 2570, the sealing layer 2560, and the sealant. Note that the sealing layer 2560 may be filled with an inert gas (such as nitrogen or argon). In addition, a drying material may be provided in the inert gas to adsorb moisture or the like. Moreover, as the above-mentioned sealing material, for example, it is preferable to use an epoxy resin or glass frit. As a material used for the sealant, a material that does not transmit moisture and oxygen is preferably used.

  In addition, the display device 2501 includes a pixel 2502R. In addition, the pixel 2502R includes a light emitting module 2580R.

  The pixel 2502R includes a light-emitting element 2550R and a transistor 2502t that can supply power to the light-emitting element 2550R. Note that the transistor 2502t functions as part of the pixel circuit. The light emitting module 2580R includes a light emitting element 2550R and a colored layer 2567R.

  The light-emitting element 2550R includes a lower electrode, an upper electrode, and an EL layer between the lower electrode and the upper electrode. As the light-emitting element 2550R, for example, the light-emitting element described in any of Embodiments 1 to 3 can be used.

  Further, a microcavity structure may be employed between the lower electrode and the upper electrode to increase the light intensity at a specific wavelength.

  In the case where the sealing layer 2560 is provided on the light extraction side, the sealing layer 2560 is in contact with the light-emitting element 2550R and the coloring layer 2567R.

  The coloring layer 2567R is in a position overlapping with the light-emitting element 2550R. Thus, part of the light emitted from the light emitting element 2550R passes through the colored layer 2567R and is emitted to the outside of the light emitting module 2580R in the direction of the arrow shown in the drawing.

  The display device 2501 is provided with a light-blocking layer 2567BM in the direction of emitting light. The light-blocking layer 2567BM is provided so as to surround the colored layer 2567R.

  The coloring layer 2567R may have a function of transmitting light in a specific wavelength band, for example, a color filter that transmits light in a red wavelength band, a color filter that transmits light in a green wavelength band, A color filter that transmits light in the blue wavelength band, a color filter that transmits light in the yellow wavelength band, and the like can be used. Each color filter can be formed using a variety of materials by a printing method, an inkjet method, an etching method using a photolithography technique, or the like.

  In addition, the display device 2501 is provided with an insulating layer 2521. The insulating layer 2521 covers the transistor 2502t. Note that the insulating layer 2521 has a function of planarizing unevenness caused by the pixel circuit. Further, the insulating layer 2521 may have a function of suppressing impurity diffusion. Accordingly, a decrease in reliability of the transistor 2502t and the like due to impurity diffusion can be suppressed.

  The light-emitting element 2550R is formed above the insulating layer 2521. In addition, the lower electrode included in the light-emitting element 2550R is provided with a partition wall 2528 which overlaps with an end portion of the lower electrode. Note that a spacer for controlling the distance between the substrate 2510 and the substrate 2570 may be formed over the partition wall 2528.

  The scan line driver circuit 2503g (1) includes a transistor 2503t and a capacitor 2503c. Note that the driver circuit can be formed over the same substrate in the same process as the pixel circuit.

  A wiring 2511 capable of supplying a signal is provided over the substrate 2510. A terminal 2519 is provided over the wiring 2511. In addition, the FPC 2509 (1) is electrically connected to the terminal 2519. The FPC 2509 (1) has a function of supplying a video signal, a clock signal, a start signal, a reset signal, and the like. Note that a printed wiring board (PWB) may be attached to the FPC 2509 (1).

  Further, transistors with various structures can be used for the display device 2501. FIG. 26A illustrates the case where a bottom-gate transistor is used; however, the invention is not limited to this. For example, a top-gate transistor illustrated in FIG. It is good also as a structure applied to.

  There is no particular limitation on the polarity of the transistor 2502t and the transistor 2503t, and a structure including an N-channel transistor and a P-channel transistor, or a structure including only one of an N-channel transistor and a P-channel transistor is used. It may be used. Further, there is no particular limitation on the crystallinity of the semiconductor film used for the transistors 2502t and 2503t. For example, an amorphous semiconductor film or a crystalline semiconductor film can be used. As the semiconductor material, a Group 14 semiconductor (for example, a semiconductor containing silicon), a compound semiconductor (including an oxide semiconductor), an organic semiconductor, or the like can be used. By using an oxide semiconductor with an energy gap of 2 eV or more, preferably 2.5 eV or more, more preferably 3 eV or more for either or both of the transistor 2502t and the transistor 2503t, the off-state current of the transistor can be reduced. Therefore, it is preferable. Examples of the oxide semiconductor include In—Ga oxide and In—M—Zn oxide (M represents Al, Ga, Y, Zr, La, Ce, Sn, Hf, or Nd).

<Explanation about touch sensor>
Next, details of the touch sensor 2595 will be described with reference to FIG. FIG. 26C corresponds to a cross-sectional view taken along dashed-dotted line X3-X4 in FIG.

  The touch sensor 2595 includes electrodes 2591 and electrodes 2592 that are arranged in a staggered pattern on the substrate 2590, an insulating layer 2593 that covers the electrodes 2591 and 2592, and wiring 2594 that electrically connects adjacent electrodes 2591.

  The electrodes 2591 and 2592 are formed using a light-transmitting conductive material. As the light-transmitting conductive material, a conductive oxide such as indium oxide, indium tin oxide, indium zinc oxide, zinc oxide, or zinc oxide to which gallium is added can be used. Note that a film containing graphene can also be used. The film containing graphene can be formed, for example, by reducing a film containing graphene oxide formed in a film shape. Examples of the reduction method include a method of applying heat.

  For example, after forming a light-transmitting conductive material over the substrate 2590 by a sputtering method, unnecessary portions are removed by various pattern formation techniques such as a photolithography method, so that the electrode 2591 and the electrode 2592 are formed. can do.

  As a material used for the insulating layer 2593, for example, a resin such as an acrylic resin or an epoxy resin, a resin having a siloxane bond such as silicone, or an inorganic insulating material such as silicon oxide, silicon oxynitride, or aluminum oxide is used. You can also.

  An opening reaching the electrode 2591 is provided in the insulating layer 2593 so that the wiring 2594 is electrically connected to the adjacent electrode 2591. Since the light-transmitting conductive material can increase the aperture ratio of the touch panel, it can be preferably used for the wiring 2594. A material having higher conductivity than the electrodes 2591 and 2592 can be preferably used for the wiring 2594 because electric resistance can be reduced.

  The electrode 2592 extends in one direction, and a plurality of electrodes 2592 are provided in a stripe shape. The wiring 2594 is provided so as to intersect with the electrode 2592.

  A pair of electrodes 2591 is provided with one electrode 2592 interposed therebetween. The wiring 2594 electrically connects the pair of electrodes 2591.

  Note that the plurality of electrodes 2591 are not necessarily arranged in a direction orthogonal to the one electrode 2592, and may be arranged to form an angle greater than 0 degree and less than 90 degrees.

  The wiring 2598 is electrically connected to the electrode 2591 or the electrode 2592. In addition, part of the wiring 2598 functions as a terminal. As the wiring 2598, for example, a metal material such as aluminum, gold, platinum, silver, nickel, titanium, tungsten, chromium, molybdenum, iron, cobalt, copper, or palladium, or an alloy material containing the metal material is used. it can.

  Note that an insulating layer that covers the insulating layer 2593 and the wiring 2594 may be provided to protect the touch sensor 2595.

  The connection layer 2599 electrically connects the wiring 2598 and the FPC 2509 (2).

  As the connection layer 2599, an anisotropic conductive film (ACF: Anisotropic Conductive Film), an anisotropic conductive paste (ACP: Anisotropic Conductive Paste), or the like can be used.

<Description 2 regarding touch panel>
Next, details of the touch panel 2000 will be described with reference to FIG. FIG. 27A corresponds to a cross-sectional view taken along dashed-dotted line X5-X6 in FIG.

  A touch panel 2000 illustrated in FIG. 27A has a structure in which the display device 2501 described in FIG. 26A and the touch sensor 2595 described in FIG.

  In addition to the structure described in FIGS. 26A and 26C, the touch panel 2000 illustrated in FIG. 27A includes an adhesive layer 2597 and an antireflection layer 2567p.

  The adhesive layer 2597 is provided in contact with the wiring 2594. Note that the adhesive layer 2597 attaches the substrate 2590 to the substrate 2570 so that the touch sensor 2595 overlaps the display device 2501. The adhesive layer 2597 preferably has a light-transmitting property. For the adhesive layer 2597, a thermosetting resin or an ultraviolet curable resin can be used. For example, an acrylic resin, a urethane resin, an epoxy resin, or a siloxane resin can be used.

  The antireflection layer 2567p is provided at a position overlapping the pixel. As the antireflection layer 2567p, for example, a circularly polarizing plate can be used.

  Next, a touch panel having a structure different from that illustrated in FIG. 27A will be described with reference to FIG.

  FIG. 27B is a cross-sectional view of the touch panel 2001. A touch panel 2001 illustrated in FIG. 27B is different from the touch panel 2000 illustrated in FIG. 27A in the position of the touch sensor 2595 with respect to the display device 2501. Here, different configurations will be described in detail, and the description of the touch panel 2000 is used for a portion where a similar configuration can be used.

  The coloring layer 2567R is in a position overlapping with the light-emitting element 2550R. In addition, the light-emitting element 2550R illustrated in FIG. 27B emits light to the side where the transistor 2502t is provided. Thus, part of the light emitted from the light emitting element 2550R passes through the colored layer 2567R and is emitted to the outside of the light emitting module 2580R in the direction of the arrow shown in the drawing.

  The touch sensor 2595 is provided on the substrate 2510 side of the display device 2501.

  An adhesive layer 2597 is provided between the substrate 2510 and the substrate 2590, and the display device 2501 and the touch sensor 2595 are attached to each other.

  As shown in FIGS. 27A and 27B, light emitted from the light-emitting element may be emitted through one or both of the substrate 2510 side and the substrate 2570 side.

<Explanation regarding touch panel drive method>
Next, an example of a touch panel driving method will be described with reference to FIGS.

  FIG. 28A is a block diagram illustrating a structure of a mutual capacitive touch sensor. FIG. 28A shows a pulse voltage output circuit 2601 and a current detection circuit 2602. Note that in FIG. 28A, the electrode 2621 to which a pulse voltage is applied is represented by X1-X6, and the electrode 2622 for detecting a change in current is represented by Y1-Y6. FIG. 28A illustrates a capacitor 2603 formed by overlapping an electrode 2621 and an electrode 2622. Note that the functions of the electrode 2621 and the electrode 2622 may be interchanged.

  The pulse voltage output circuit 2601 is a circuit for sequentially applying pulses to the wiring lines X1 to X6. When a pulse voltage is applied to the wiring of X1-X6, an electric field is generated between the electrode 2621 and the electrode 2622 forming the capacitor 2603. By utilizing the fact that the electric field generated between the electrodes causes a change in the mutual capacitance of the capacitor 2603 due to shielding or the like, it is possible to detect the proximity or contact of the detection object.

  The current detection circuit 2602 is a circuit for detecting a change in current in the wiring of Y1-Y6 due to a change in mutual capacitance in the capacitor 2603. In the wiring of Y1-Y6, there is no change in the current value detected when there is no proximity or contact with the detected object, but the current value when the mutual capacitance decreases due to the proximity or contact with the detected object. Detect changes that decrease. Note that current detection may be performed using an integration circuit or the like.

  Next, FIG. 28B shows a timing chart of input / output waveforms in the mutual capacitance type touch sensor shown in FIG. In FIG. 28B, it is assumed that the detection target is detected in each matrix in one frame period. FIG. 28B shows two cases, that is, a case where the detected object is not detected (non-touch) and a case where the detected object is detected (touch). In addition, about the wiring of Y1-Y6, the waveform made into the voltage value corresponding to the detected electric current value is shown.

  A pulse voltage is sequentially applied to the X1-X6 wiring, and the waveform of the Y1-Y6 wiring changes according to the pulse voltage. When there is no proximity or contact of the detection object, the waveform of Y1-Y6 changes uniformly according to the change of the voltage of the wiring of X1-X6. On the other hand, since the current value decreases at the location where the detection object is close or in contact, the waveform of the voltage value corresponding to this also changes.

  In this way, by detecting the change in mutual capacitance, the proximity or contact of the detection target can be detected.

<Explanation about sensor circuit>
28A illustrates a passive matrix touch sensor in which only a capacitor 2603 is provided at a wiring intersection as a touch sensor; however, an active matrix touch sensor including a transistor and a capacitor may be used. An example of a sensor circuit included in the active matrix touch sensor is shown in FIG.

  The sensor circuit illustrated in FIG. 29 includes a capacitor 2603, a transistor 2611, a transistor 2612, and a transistor 2613.

  The gate of the transistor 2613 is supplied with the signal G2, the voltage VRES is supplied to one of a source and a drain, and the other is electrically connected to one electrode of the capacitor 2603 and the gate of the transistor 2611. In the transistor 2611, one of a source and a drain is electrically connected to one of a source and a drain of the transistor 2612, and the voltage VSS is supplied to the other. In the transistor 2612, the gate is supplied with the signal G1, and the other of the source and the drain is electrically connected to the wiring ML. The voltage VSS is applied to the other electrode of the capacitor 2603.

  Next, the operation of the sensor circuit shown in FIG. 29 will be described. First, a potential for turning on the transistor 2613 is supplied as the signal G2, so that a potential corresponding to the voltage VRES is applied to the node n to which the gate of the transistor 2611 is connected. Next, a potential for turning off the transistor 2613 is supplied as the signal G2, so that the potential of the node n is held.

  Subsequently, the potential of the node n changes from VRES as the mutual capacitance of the capacitor 2603 changes due to the proximity or contact of a detection object such as a finger.

  In the reading operation, a potential for turning on the transistor 2612 is supplied to the signal G1. The current flowing through the transistor 2611, that is, the current flowing through the wiring ML is changed in accordance with the potential of the node n. By detecting this current, the proximity or contact of the detection object can be detected.

  As the transistor 2611, the transistor 2612, and the transistor 2613, an oxide semiconductor layer is preferably used for a semiconductor layer in which a channel region is formed. In particular, when such a transistor is used as the transistor 2613, the potential of the node n can be held for a long time, and the frequency of the operation of supplying VRES to the node n (refresh operation) can be reduced. it can.

  The structure described in this embodiment can be combined as appropriate with any of the structures described in the other embodiments.

(Embodiment 7)
In this embodiment, a display module and an electronic device each including the light-emitting element of one embodiment of the present invention will be described with reference to FIGS.

<Explanation about display module>
A display module 8000 illustrated in FIG. 30 includes a touch sensor 8004 connected to the FPC 8003, a display device 8006 connected to the FPC 8005, a frame 8009, a printed circuit board 8010, and a battery 8011 between an upper cover 8001 and a lower cover 8002. .

  The light-emitting element of one embodiment of the present invention can be used for the display device 8006, for example.

  The shapes and dimensions of the upper cover 8001 and the lower cover 8002 can be changed as appropriate in accordance with the sizes of the touch sensor 8004 and the display device 8006.

  As the touch sensor 8004, a resistive touch sensor or a capacitive touch sensor can be used by being superimposed on the display device 8006. In addition, the counter substrate (sealing substrate) of the display device 8006 can have a touch sensor function. In addition, an optical sensor may be provided in each pixel of the display device 8006 to provide an optical touch sensor.

  The frame 8009 has a function as an electromagnetic shield for blocking electromagnetic waves generated by the operation of the printed board 8010 in addition to a protective function of the display device 8006. The frame 8009 may have a function as a heat sink.

  The printed board 8010 includes a power supply circuit, a signal processing circuit for outputting a video signal and a clock signal. As a power supply for supplying power to the power supply circuit, an external commercial power supply may be used, or a power supply using a battery 8011 provided separately may be used. The battery 8011 can be omitted when a commercial power source is used.

  The display module 8000 may be additionally provided with a member such as a polarizing plate, a retardation plate, or a prism sheet.

<Explanation about electronic equipment>
FIG. 31A to FIG. 31G illustrate electronic devices. These electronic devices include a housing 9000, a display portion 9001, a speaker 9003, operation keys 9005 (including a power switch or operation switch), a connection terminal 9006, and a sensor 9007 (force, displacement, position, speed, acceleration, angular velocity, Includes functions to measure rotation speed, distance, light, liquid, magnetism, temperature, chemical, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, gradient, vibration, odor or infrared ), A microphone 9008, and the like.

  The electronic devices illustrated in FIGS. 31A to 31G can have a variety of functions. For example, a function for displaying various information (still images, moving images, text images, etc.) on the display unit, a touch sensor function, a function for displaying a calendar, date or time, etc., a function for controlling processing by various software (programs) , Wireless communication function, function to connect to various computer networks using wireless communication function, function to transmit or receive various data using wireless communication function, read program or data recorded in recording medium A function of displaying on the display portion can be provided. Note that the functions which the electronic devices illustrated in FIGS. 31A to 31G can have are not limited to these, and can have various functions. Although not illustrated in FIGS. 31A to 31G, the electronic device may have a plurality of display portions. In addition, the electronic device is equipped with a camera, etc., to capture still images, to capture moving images, to store captured images on a recording medium (externally or built into the camera), and to display captured images on the display unit And the like.

  Details of the electronic devices illustrated in FIGS. 31A to 31G are described below.

  FIG. 31A is a perspective view showing a portable information terminal 9100. FIG. A display portion 9001 included in the portable information terminal 9100 has flexibility. Therefore, the display portion 9001 can be incorporated along the curved surface of the curved housing 9000. Further, the display portion 9001 includes a touch sensor and can be operated by touching the screen with a finger, a stylus, or the like. For example, an application can be activated by touching an icon displayed on the display unit 9001.

  FIG. 31B is a perspective view showing the portable information terminal 9101. The portable information terminal 9101 has one or a plurality of functions selected from, for example, a telephone, a notebook, an information browsing device, or the like. Specifically, it can be used as a smartphone. Note that the portable information terminal 9101 is illustrated with the speaker 9003, the connection terminal 9006, the sensor 9007, and the like omitted, but can be provided at the same position as the portable information terminal 9100 illustrated in FIG. Further, the portable information terminal 9101 can display characters and image information on the plurality of surfaces. For example, three operation buttons 9050 (also referred to as operation icons or simply icons) can be displayed on one surface of the display portion 9001. Further, information 9051 indicated by a broken-line rectangle can be displayed on another surface of the display portion 9001. As an example of the information 9051, a display for notifying an incoming call such as an e-mail, SNS (social networking service), a telephone call, a title such as an e-mail or SNS, a sender name such as an e-mail or SNS, a date and time, and a time , Battery level, antenna reception strength and so on. Alternatively, an operation button 9050 or the like may be displayed instead of the information 9051 at a position where the information 9051 is displayed.

  FIG. 31C is a perspective view showing the portable information terminal 9102. The portable information terminal 9102 has a function of displaying information on three or more surfaces of the display portion 9001. Here, an example is shown in which information 9052, information 9053, and information 9054 are displayed on different planes. For example, the user of the portable information terminal 9102 can check the display (information 9053 here) in a state where the portable information terminal 9102 is stored in the chest pocket of clothes. Specifically, the telephone number or name of the caller of the incoming call is displayed at a position where it can be observed from above portable information terminal 9102. The user can check the display and determine whether to receive a call without taking out the portable information terminal 9102 from the pocket.

  FIG. 31D is a perspective view showing a wristwatch-type portable information terminal 9200. The portable information terminal 9200 can execute various applications such as a mobile phone, electronic mail, text browsing and creation, music playback, Internet communication, and computer games. Further, the display portion 9001 is provided with a curved display surface, and can perform display along the curved display surface. In addition, the portable information terminal 9200 can execute short-range wireless communication with a communication standard. For example, it is possible to talk hands-free by communicating with a headset capable of wireless communication. In addition, the portable information terminal 9200 includes a connection terminal 9006 and can directly exchange data with other information terminals via a connector. Charging can also be performed through the connection terminal 9006. Note that the charging operation may be performed by wireless power feeding without using the connection terminal 9006.

  31E, 31F, and 31G are perspective views illustrating a foldable portable information terminal 9201. FIG. FIG. 31E is a perspective view of a state in which the portable information terminal 9201 is expanded, and FIG. 31F is a state in the middle of changing from one of the expanded state or the folded state of the portable information terminal 9201 to the other. FIG. 31G is a perspective view of the portable information terminal 9201 folded. The portable information terminal 9201 is excellent in portability in the folded state, and in the expanded state, the portable information terminal 9201 is excellent in display listability due to a seamless wide display area. A display portion 9001 included in the portable information terminal 9201 is supported by three housings 9000 connected by a hinge 9055. By bending between the two housings 9000 via the hinge 9055, the portable information terminal 9201 can be reversibly deformed from the expanded state to the folded state. For example, the portable information terminal 9201 can be bent with a curvature radius of 1 mm to 150 mm.

  The electronic device described in this embodiment includes a display portion for displaying some information. Note that the light-emitting element of one embodiment of the present invention can also be applied to an electronic device having no display portion. In addition, in the display portion of the electronic device described in this embodiment, an example of a configuration that has flexibility and can display along a curved display surface, or a configuration of a foldable display portion is given. However, the present invention is not limited to this, and may have a configuration in which display is performed on a flat portion without having flexibility.

  The structure described in this embodiment can be combined as appropriate with any of the structures described in the other embodiments.

(Embodiment 8)
In this embodiment, a light-emitting device including the light-emitting element of one embodiment of the present invention will be described with reference to FIGS.

  FIG. 32A shows a perspective view of the light-emitting device 3000 shown in this embodiment mode, and FIG. 32B shows a cross-sectional view corresponding to the area between dashed-dotted lines EF shown in FIG. Note that in FIG. 32A, some components are displayed with broken lines in order to avoid complexity of the drawing.

  A light-emitting device 3000 illustrated in FIGS. 32A and 32B includes a substrate 3001, a light-emitting element 3005 over the substrate 3001, a first sealing region 3007 provided on the outer periphery of the light-emitting element 3005, and a first seal. And a second sealing region 3009 provided on the outer periphery of the stop region 3007.

  Light emission from the light-emitting element 3005 is emitted from one or both of the substrate 3001 and the substrate 3003. 32A and 32B, a structure in which light emitted from the light-emitting element 3005 is emitted downward (substrate 3001 side) will be described.

  32A and 32B, the light-emitting device 3000 includes two light-emitting elements 3005 that are surrounded by a first sealing region 3007 and a second sealing region 3009. It is a heavy sealing structure. With the double sealing structure, external impurities (for example, water, oxygen, and the like) that enter the light-emitting element 3005 side can be preferably suppressed. Note that the first sealing region 3007 and the second sealing region 3009 are not necessarily provided. For example, only the first sealing region 3007 may be configured.

  Note that in FIG. 32B, the first sealing region 3007 and the second sealing region 3009 are provided in contact with the substrate 3001 and the substrate 3003. However, the invention is not limited to this. For example, one or both of the first sealing region 3007 and the second sealing region 3009 are provided in contact with an insulating film or a conductive film formed over the substrate 3001. It is good also as a structure. Alternatively, one or both of the first sealing region 3007 and the second sealing region 3009 may be provided in contact with an insulating film or a conductive film formed below the substrate 3003.

  The substrate 3001 and the substrate 3003 may have structures similar to those of the substrate 200 and the substrate 220 described in Embodiment 3, respectively. The light-emitting element 3005 may have a structure similar to that of the light-emitting element described in the above embodiment.

  As the first sealing region 3007, a material containing glass (eg, a glass frit, a glass ribbon, or the like) may be used. For the second sealing region 3009, a material containing a resin may be used. By using a material containing glass for the first sealing region 3007, productivity and sealing performance can be improved. In addition, by using a material containing a resin for the second sealing region 3009, impact resistance and heat resistance can be improved. Note that the first sealing region 3007 and the second sealing region 3009 are not limited to this, and the first sealing region 3007 is formed of a material containing a resin. May be formed of a material including glass.

  Examples of the glass frit include magnesium oxide, calcium oxide, strontium oxide, barium oxide, cesium oxide, sodium oxide, potassium oxide, boron oxide, vanadium oxide, zinc oxide, tellurium oxide, aluminum oxide, silicon dioxide, Lead oxide, tin oxide, phosphorus oxide, ruthenium oxide, rhodium oxide, iron oxide, copper oxide, manganese dioxide, molybdenum oxide, niobium oxide, titanium oxide, tungsten oxide, bismuth oxide, zirconium oxide, lithium oxide, antimony oxide, boric acid Including lead glass, tin phosphate glass, vanadate glass or borosilicate glass. In order to absorb infrared light, it is preferable to include at least one kind of transition metal.

  As the above-mentioned glass frit, for example, a frit paste is applied on a substrate, and heat treatment or laser irradiation is performed on the frit paste. The frit paste includes the glass frit and a resin diluted with an organic solvent (also called a binder). Alternatively, a glass frit to which an absorbent that absorbs light having a wavelength of laser light is added may be used. As the laser, for example, an Nd: YAG laser or a semiconductor laser is preferably used. Further, the laser irradiation shape during laser irradiation may be circular or quadrangular.

  Moreover, as a material containing the above-mentioned resin, polyester, polyolefin, polyamide (nylon, aramid etc.), a polyimide, a polycarbonate or an acrylic resin, a polyurethane, and an epoxy resin can be used, for example. Alternatively, a material including a resin having a siloxane bond such as silicone can be used.

  Note that in the case where a material containing glass is used for one or both of the first sealing region 3007 and the second sealing region 3009, the coefficient of thermal expansion between the material containing glass and the substrate 3001 is close. preferable. By setting it as the said structure, it can suppress that a crack enters into the material or board | substrate 3001 containing glass with a thermal stress.

  For example, when a material containing glass is used for the first sealing region 3007 and a material containing resin is used for the second sealing region 3009, the following excellent effects are obtained.

  The second sealing region 3009 is provided closer to the outer peripheral portion of the light emitting device 3000 than the first sealing region 3007. As the light emitting device 3000 moves toward the outer periphery, distortion due to external force or the like increases. Therefore, the first sealing provided on the outer peripheral side of the light-emitting device 3000 where the distortion increases, that is, the second sealing region 3009, is sealed with a material containing resin and is provided on the inner side of the second sealing region 3009. By sealing the stop region 3007 with a material containing glass, the light-emitting device 3000 is less likely to be broken even when distortion such as external force occurs.

  As shown in FIG. 32B, a first region 3011 is formed in a region surrounded by the substrate 3001, the substrate 3003, the first sealing region 3007, and the second sealing region 3009. The A second region 3013 is formed in a region surrounded by the substrate 3001, the substrate 3003, the light-emitting element 3005, and the first sealing region 3007.

  The first region 3011 and the second region 3013 are preferably filled with an inert gas such as a rare gas or nitrogen gas, for example. Note that the first region 3011 and the second region 3013 are preferably in a reduced pressure state rather than an atmospheric pressure state.

  A modified example of the structure illustrated in FIG. 32B is illustrated in FIG. FIG. 32C is a cross-sectional view illustrating a modified example of the light-emitting device 3000.

  FIG. 32C illustrates a structure in which a recess is provided in part of the substrate 3003 and a desiccant 3018 is provided in the recess. The other structure is the same as the structure shown in FIG.

  As the desiccant 3018, a substance that adsorbs moisture or the like by chemical adsorption, or a substance that adsorbs moisture or the like by physical adsorption can be used. For example, substances that can be used as the desiccant 3018 include alkali metal oxides, alkaline earth metal oxides (such as calcium oxide and barium oxide), sulfates, metal halides, perchlorates, zeolites, Examples include silica gel.

  Next, a modification of the light-emitting device 3000 illustrated in FIG. 32B will be described with reference to FIGS. 33A, 33B, 33C, and 33D. 33A, 33B, 33C, and 33D are cross-sectional views illustrating a modification of the light-emitting device 3000 illustrated in FIG.

  The light-emitting device shown in FIGS. 33A, 33B, 33C, and 33D has a structure in which the second sealing region 3009 is not provided and the first sealing region 3007 is used. In addition, the light-emitting device illustrated in FIGS. 33A, 33B, 33C, and 33D includes a region 3014 instead of the second region 3013 illustrated in FIG.

  As the region 3014, for example, polyester, polyolefin, polyamide (nylon, aramid, or the like), polyimide, polycarbonate, acrylic resin, polyurethane, or epoxy resin can be used. Alternatively, a material including a resin having a siloxane bond such as silicone can be used.

  When the above-described material is used for the region 3014, a so-called solid-sealed light-emitting device can be obtained.

  The light-emitting device illustrated in FIG. 33B has a structure in which the substrate 3015 is provided on the substrate 3001 side of the light-emitting device illustrated in FIG.

  The substrate 3015 has unevenness as illustrated in FIG. By providing the uneven substrate 3015 on the light extraction side of the light-emitting element 3005, the light extraction efficiency from the light-emitting element 3005 can be improved. Note that a substrate functioning as a diffusion plate may be provided instead of the structure having unevenness as illustrated in FIG.

  A light-emitting device illustrated in FIG. 33C has a structure in which light is extracted from the substrate 3003 side, whereas the light-emitting device in FIG. 33A extracts light from the substrate 3001 side.

  A light-emitting device illustrated in FIG. 33C includes a substrate 3015 on the substrate 3003 side. Other structures are similar to those of the light-emitting device illustrated in FIG.

  In addition, the light-emitting device illustrated in FIG. 33D has a structure in which the substrate 3016 is provided without providing the substrates 3003 and 3015 of the light-emitting device shown in FIG.

  The substrate 3016 has a first unevenness located on the side closer to the light emitting element 3005 and a second unevenness located on the side farther from the light emitting element 3005. With the structure illustrated in FIG. 33D, the light extraction efficiency from the light-emitting element 3005 can be further improved.

  Therefore, by implementing the structure described in this embodiment, a light-emitting device in which deterioration of the light-emitting element due to impurities such as moisture and oxygen is suppressed can be realized. Alternatively, by performing the structure described in this embodiment, a light-emitting device with high light extraction efficiency can be realized.

  Note that the structure described in this embodiment can be combined as appropriate with any of the structures described in the other embodiments.

(Embodiment 9)
In this embodiment, an example in which the light-emitting element of one embodiment of the present invention is applied to various lighting devices and electronic devices will be described with reference to FIGS.

  By manufacturing the light-emitting element of one embodiment of the present invention over a flexible substrate, an electronic device or a lighting device having a light-emitting region having a curved surface can be realized.

  In addition, the light-emitting device to which one embodiment of the present invention is applied can also be used for lighting of a car. For example, lighting can be provided on a dashboard, a windshield, a ceiling, or the like.

  34A shows a perspective view of one surface of the multi-function terminal 3500, and FIG. 34B shows a perspective view of the other surface of the multi-function terminal 3500. In the multi-function terminal 3500, a display portion 3504, a camera 3506, an illumination 3508, and the like are incorporated in a housing 3502. The light-emitting device of one embodiment of the present invention can be used for the lighting 3508.

  The illumination 3508 functions as a surface light source by using the light-emitting device of one embodiment of the present invention. Therefore, unlike a point light source typified by an LED, light emission with less directivity can be obtained. For example, when the lighting 3508 and the camera 3506 are used in combination, the lighting 3508 can be turned on or blinked and an image can be captured by the camera 3506. Since the illumination 3508 has a function as a surface light source, it can capture a photograph taken under natural light.

  Note that the multi-function terminal 3500 illustrated in FIGS. 34A and 34B can have various functions in a manner similar to that of the electronic devices illustrated in FIGS. 31A to 31G.

  In addition, a speaker, a sensor (force, displacement, position, velocity, acceleration, angular velocity, rotation speed, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current are provided inside the housing 3502. , Voltage, power, radiation, flow rate, humidity, gradient, vibration, odor or infrared measurement function), microphone, and the like. Further, by providing a detection device having a sensor for detecting inclination such as a gyroscope and an acceleration sensor inside the multi-function terminal 3500, the orientation (vertical or horizontal) of the multi-function terminal 3500 is determined, and a display unit 3504 is provided. The screen display can be automatically switched.

  The display portion 3504 can also function as an image sensor. For example, personal authentication can be performed by touching the display portion 3504 with a palm or a finger and capturing a palm print, a fingerprint, or the like. In addition, when a backlight that emits near-infrared light or a sensing light source that emits near-infrared light is used for the display portion 3504, finger veins, palm veins, and the like can be imaged. Note that the light-emitting device of one embodiment of the present invention may be applied to the display portion 3054.

  FIG. 34C is a perspective view of a crime prevention light 3600. The light 3600 includes an illumination 3608 outside the housing 3602, and the housing 3602 incorporates a speaker 3610 and the like. The light-emitting device of one embodiment of the present invention can be used for the lighting 3608.

  As the light 3600, for example, light can be emitted by gripping, holding, or holding the illumination 3608. Further, an electronic circuit that can control a light emission method from the light 3600 may be provided inside the housing 3602. As the electronic circuit, for example, a circuit that can emit light once or intermittently a plurality of times may be used, or a circuit that can adjust the light emission amount by controlling the light emission current value. Good. In addition, a circuit that outputs a loud alarm sound from the speaker 3610 at the same time as the light emission of the illumination 3608 may be incorporated.

  Since the light 3600 can emit light in all directions, for example, it can be threatened with light or light and sound toward a thief or the like. The light 3600 may be provided with a camera such as a digital still camera and a function having a photographing function.

  FIG. 35 illustrates an example in which the light-emitting element is used as an indoor lighting device 8501. Note that since the light-emitting element can have a large area, a large-area lighting device can be formed. In addition, by using a housing having a curved surface, the lighting device 8502 in which the light-emitting region has a curved surface can be formed. The light-emitting element described in this embodiment is thin and has a high degree of freedom in housing design. Therefore, it is possible to form a lighting device with various designs. Further, a large lighting device 8503 may be provided on the indoor wall surface. Alternatively, the lighting devices 8501, 8502, and 8503 may be provided with touch sensors to turn the power on or off.

  In addition, by using the light-emitting element on the surface side of the table, the lighting device 8504 having a function as a table can be obtained. Note that a lighting device having a function as furniture can be obtained by using a light-emitting element as part of other furniture.

  As described above, a lighting device and an electronic device can be obtained by using the light-emitting device of one embodiment of the present invention. Note that applicable lighting devices and electronic devices are not limited to those described in this embodiment and can be applied to electronic devices in various fields.

  The structure described in this embodiment can be combined as appropriate with any of the structures described in the other embodiments.

  In this example, manufacturing examples of a light-emitting element (light-emitting element 1 to light-emitting element 3) and a comparative light-emitting element (comparative light-emitting element 1 and comparative light-emitting element 2) which are one embodiment of the present invention will be described. A cross-sectional schematic view of the light-emitting element manufactured in this example is the same as the light-emitting element shown in FIG. Details of the element structure are shown in Table 2. The structures and abbreviations of the compounds used in this example are shown below. Note that the compound described in Embodiment 1 was used as a host material for the light-emitting layer.

<Preparation of Light-Emitting Element 1>
An ITSO film was formed as an electrode 101 on the substrate so as to have a thickness of 110 nm. The electrode area of the electrode 101 was 4 mm ² (2 mm × 2 mm).

Next, the EL layer 100 was formed over the electrode 101. As the hole injection layer 111, PCPPn and molybdenum oxide (MoO ₃ ) were co-deposited so that the weight ratio (PCPPn: MoO ₃ ) was 1: 0.5 and the thickness was 50 nm. Further, as the hole transport layer 112, PCPPn was deposited so as to have a thickness of 30 nm.

  Next, as the light emitting layer 130, CzPA and 1,6mMemFLPAPrn were co-deposited so that the weight ratio (CzPA: 1,6mMemFLPAPrn) was 1: 0.04 and the thickness was 25 nm. In the light emitting layer 130, CzPA is a host material and 1,6mMemFLPAPrn is a fluorescent material (guest material).

  Further, BPhen was deposited as an electron transport layer 118 on the light emitting layer 130 so as to have a thickness of 25 nm. Next, lithium fluoride (LiF) was deposited as the electron injection layer 119 so as to have a thickness of 1 nm.

  As the electrode 102, aluminum (Al) was formed to a thickness of 200 nm.

Next, the light-emitting element 1 was sealed by fixing the sealing substrate to the substrate on which the EL layer 100 was formed using a sealing material for organic EL in a glove box in a nitrogen atmosphere. Specifically, a sealing material is applied around the EL layer 100 formed on the substrate, the substrate and the sealing substrate are bonded, ultraviolet light having a wavelength of 365 nm is irradiated with 6 J / cm ² , and 80 Heat treatment was performed at 0 ° C. for 1 hour. The light emitting element 1 was obtained through the above steps.

<Preparation of Light-Emitting Element 2>
The light-emitting element 2 is different from the light-emitting element 1 described above only in the steps of forming the hole injection layer 111 and the light-emitting layer 130, and the other steps are the same as those for the light-emitting element 1.

As the hole injection layer 111 of the light-emitting element 2, PCPPn and MoO ₃ were co-deposited so that the weight ratio (PCPPn: MoO ₃ ) was 1: 0.5 and the thickness was 60 nm.

  In addition, as the light emitting layer 130 of the light emitting element 2, t-BuDNA and 1,6mMemFLPAPrn are formed so that the weight ratio (t-BuDNA: 1,6mMemFLPAPrn) is 1: 0.03 and the thickness is 25 nm. Co-deposited. In the light emitting layer 130, t-BuDNA is a host material, and 1,6 mM emFLPAPrn is a fluorescent material (guest material).

<Preparation of Light-Emitting Element 3, Comparative Light-Emitting Element 1, and Comparative Light-Emitting Element 2>
The light-emitting element 3, the comparative light-emitting element 1, and the comparative light-emitting element 2 are different from the light-emitting element 2 described above only in the process of forming the light-emitting layer 130, and other processes are the same as those in the light-emitting element 2. did.

  As the light-emitting layer 130 of the light-emitting element 3, cgDBCzPA and 1,6mMemFLPAPrn were co-deposited so that the weight ratio (cgDBCzPA: 1,6mMemFLPAPrn) was 1: 0.03 and the thickness was 25 nm. In the light-emitting layer 130, cgDBCzPA is a host material, and 1,6 mM emFLPAPrn is a fluorescent material (guest material).

  As the light emitting layer 130 of the comparative light emitting element 1, the weight ratio of BH-1 and 1,6mMemFLPAPrn (BH-1: 1,6mMemFLPAPrn) is 1: 0.03 and the thickness is 25 nm. Co-deposited. In the light emitting layer 130, BH-1 is a host material, and 1,6 mM emFLPAPrn is a fluorescent material (guest material).

  As the light-emitting layer 130 of the comparative light-emitting element 2, α, β-ADN and 1,6 mM emFLPAPrn have a weight ratio (α, β-ADN: 1,6 mM emFLPAPrn) of 1: 0.03 and a thickness of 25 nm. Co-deposited so that In the light emitting layer 130, α, β-ADN is a host material, and 1,6 mM emFLPAPrn is a fluorescent material (guest material).

<Measurement of fluorescence lifetime>
36A and 36B illustrate fluorescence lifetimes of the light-emitting elements (light-emitting element 1 to light-emitting element 3) and comparative light-emitting elements (comparative light-emitting element 1 and comparative light-emitting element 2) which are embodiments of the present invention. It is the result. In the measurement of the fluorescence lifetime, blue light emission exhibited by the fluorescent material 1,6 mM emFLPAPrn was observed.

  For the measurement, a picosecond fluorescence lifetime measurement system (manufactured by Hamamatsu Photonics) was used. In this measurement, in order to measure the lifetime of fluorescence emission in the light-emitting element, a rectangular pulse voltage was applied to the light-emitting element, and light emission attenuated from the fall of the voltage was time-resolved measured with a streak camera. A pulse voltage was applied at a cycle of 10 Hz, and data with a high S / N ratio were obtained by integrating the data measured repeatedly. The measurement was performed at room temperature (300 K) under conditions of an applied pulse voltage of 3.5 V, an applied pulse time width of 100 μsec, a negative bias voltage of −5 V, and a measurement time range of 50 μsec. The measurement results are shown in FIGS. 36A and 36B, the vertical axis indicates the intensity normalized with the light emission intensity in a state where carriers are constantly injected (when the pulse voltage is ON). The horizontal axis represents the elapsed time from the fall of the pulse voltage.

  The attenuation curves shown in FIGS. 36 (A) and 36 (B) were fitted with an exponential function. As a result, the fluorescence lifetimes τ of the light-emitting element 1, the light-emitting element 2, and the light-emitting element 3 were estimated to be 2.5 μsec, 3.5 μsec, and 2.3 μsec, respectively. In addition, the fluorescence lifetimes τ of the comparative light-emitting element 1 and the comparative light-emitting element 2 could be estimated to be 4.7 μsec and 3.8 μsec, respectively. Usually, the lifetime of fluorescence emission is several nsec. Therefore, since it has a fluorescence lifetime of 1 μsec or more, all of the light-emitting element 1, the light-emitting element 2, the light-emitting element 3, the comparative light-emitting element 1, and the comparative light-emitting element 2 have been observed to emit fluorescence containing a delayed fluorescent component. It can be said.

  Note that in the fluorescence measurement shown in FIGS. 36A and 36B, the cause of delayed fluorescence is not only singlet exciton generation due to triplet-triplet annihilation (TTA) but also the inside of the light-emitting element when the pulse voltage is OFF In the case where the carriers remain in the substrate, delayed fluorescence due to the generation of singlet excitons due to recombination of the remaining carriers may occur. However, this measurement is a measurement under a condition in which recombination of the remaining carriers is suppressed because a negative bias voltage (−5 V) is applied under the measurement conditions. Therefore, it can be said that the delayed fluorescence component shown in the measurement results of FIGS. 36A and 36B is due to light emission derived from triplet-triplet annihilation (TTA).

  Next, the ratio of the delayed fluorescent component to the total light emitting component was calculated by fitting with an exponential function. As a result, the light-emitting element 1, the light-emitting element 2, and the light-emitting element 3 had a delayed fluorescence component ratio of 10%, 20%, and 12%, respectively, and the delayed fluorescence ratio was high. On the other hand, Comparative Light-Emitting Element 1 and Comparative Light-Emitting Element 2 both had a delayed fluorescence component of less than 1%, indicating that the ratio of delayed fluorescence was very low.

  Therefore, it can be said that the light emitting element 1, the light emitting element 2, and the light emitting element 3 have higher TTA efficiency than the comparative light emitting element 1 and the comparative light emitting element 2.

<Operating characteristics of light emitting element>
Next, light emission characteristics of the manufactured light-emitting element 1, light-emitting element 2, light-emitting element 3, comparative light-emitting element 1, and comparative light-emitting element 2 were measured. The measurement was performed at room temperature (atmosphere kept at 25 ° C.).

Here, the light emission characteristics of the light emitting element in the vicinity of 1000 cd / m ² are shown in Table 3 below. FIG. 37 shows the current efficiency-luminance characteristics of the light-emitting element, FIG. 38 shows the external quantum efficiency-luminance characteristics, and FIG. 39 shows the luminance-voltage characteristics. In addition, FIG. 40 shows an electroluminescence spectrum when current is passed through the light-emitting element at a current density of ^2.5 mA / cm ² .

  As shown in FIG. 40, the electroluminescence spectrum peaks of the light-emitting element 1, the light-emitting element 2, the light-emitting element 3, the comparative light-emitting element 1, and the comparative light-emitting element 2 are 462 nm, 461 nm, 464 nm, 464 nm, and 463 nm, respectively. Blue luminescence exhibited by the material 1,6mMemFLPAPrn was observed. That is, each light emitting element emits blue light having an emission spectrum peak in a wavelength band of 400 nm or more and 550 nm or less. In addition, since light emission of the fluorescent material was observed in the light-emitting elements 1 to 3, it can be said that singlet excitation energy generated by TTA is transferred from the host material to the fluorescent material.

  37 and 38 and Table 3 show that the light-emitting elements 1 to 3 have higher current efficiency and external quantum efficiency than the comparative light-emitting element 1 and the comparative light-emitting element 2. Note that in a fluorescent light-emitting element that does not use TTA, the generation probability of singlet excitons generated by recombination of carriers (holes and electrons) injected from a pair of electrodes is 25% at the maximum. When the light extraction efficiency is 25%, the external quantum efficiency is 6.25% at the maximum. In the light-emitting elements 1 to 3, the external quantum efficiency is higher than 6.25%. This is based on singlet excitons generated by TTA in addition to singlet excitons generated by recombination of carriers (holes and electrons) injected from a pair of electrodes in the light-emitting elements 1 to 3. This is because light emission is obtained.

  Therefore, as shown in Embodiment Mode 1, the energy of the third triplet excited state having the most stable structure of the third triplet excited state of the compound used for the host material is equal to that of the third triplet excited state. It is preferably higher than the energy of the first triplet excited state having the most stable structure and lower than the energy of the second triplet excited state having the most stable structure of the third triplet excited state. Alternatively, the energy of the singlet excited state of the compound used for the host material is higher than the energy of the second triplet excited state having the most stable structure of the third triplet excited state, and the third triplet excited state. The energy of the second triplet excited state having the most stable structure of the third triplet excited state is equal to or lower than the energy of the third triplet excited state having the most stable structure. It is preferable that the energy is higher than the energy of the first triplet excited state having the most stable structure. With such a structure, a blue light-emitting element having a delayed fluorescence component due to TTA and exhibiting high light emission efficiency can be manufactured.

  Moreover, in the light emitting element 1, the outstanding light emission efficiency in which external quantum efficiency exceeds 9% is obtained. Therefore, the energy of the third triplet excited state having the most stable structure in the third triplet excited state is lower than the energy of the second triplet excited state having the most stable structure in the third triplet excited state. More preferably, it is more preferably 0.2 eV or more lower than the energy.

  As shown in FIG. 39 and Table 3, the light-emitting elements 1 to 3 are driven at a lower voltage than the comparative light-emitting elements 1 and 2. That is, by using a host material having a delayed fluorescence component by TTA, a blue light-emitting element driven at a low voltage can be manufactured.

  As described above, by using a host material having a delayed fluorescence component by TTA, a blue light-emitting element with reduced power consumption can be manufactured.

<Measurement of singlet and triplet excitation energy levels>
In the fluorescence measurement shown in FIGS. 36 (A) and 36 (B), as a factor that causes delayed fluorescence, a reverse intersystem crossing from the triplet excited state to the singlet excited state occurs and exhibits thermally activated delayed fluorescence. There is also a possibility. In order for the reverse intersystem crossing to occur efficiently, the difference between the S1 level and the T1 level is preferably greater than 0 eV and not greater than 0.2 eV. Therefore, in order to confirm that the delayed fluorescence shown in FIGS. 36A and 36B is caused by TTA, the S1 level and the material used for the light-emitting layer 130 of the light-emitting element manufactured above are The T1 level was measured.

  The measurement of the S1 level and the T1 level was performed for CzPA, t-BuDNA, cgDBCzPA, and 1,6 mM emFLPAPrn.

  First, in order to estimate the S1 level, a thin film (about 50 nm) was formed on a quartz substrate by a vacuum evaporation method to form a thin film sample, and an absorption spectrum was measured. An ultraviolet-visible spectrophotometer (manufactured by JASCO Corporation, model V550) was used for measuring the absorption spectrum. The absorption spectrum of quartz was subtracted from the measured spectrum of the sample. From the data of the absorption spectrum of the thin film, the absorption edge was obtained from the Tauc plot assuming direct transition, and the S1 level was estimated using the absorption edge as the optical band gap.

  Next, phosphorescence measurement was performed to estimate the T1 level. Note that a fluorescent compound is unlikely to cross between terms, and light emission from the T1 level is weak, so that measurement of the T1 level may be difficult. In addition, the substance used for the light-emitting element which is one embodiment of the present invention has a very high fluorescence quantum yield, and it is very difficult to directly observe phosphorescence by a low-temperature PL measurement method in a thin film sample using a single material. . Therefore, phosphorescence measurement was performed by a technique using a triplet sensitizer described below, and the T1 level was estimated.

A co-deposited film was prepared by adding Ir (ppy) ₃ as a triplet sensitizer to the material for measuring the T1 level, measured by a low-temperature PL measurement method, and the T1 level was determined from the measured phosphorescence spectrum. Estimated. For the measurement, a micro-PL apparatus LabRAM HR-PL (Horiba, Ltd.) was used, the measurement temperature was 10K, He-Cd laser (325 nm) was used as excitation light, and a CCD detector was used as the detector. By co-evaporating Ir (ppy) ₃ , it is possible to increase the probability of intersystem crossing of the fluorescent material to be measured, and to measure phosphorescence emission from the fluorescent material, which is difficult without co-evaporation.

  The thin film was formed to a thickness of about 50 nm on a quartz substrate, and another quartz substrate was attached to the quartz substrate from the vapor deposition surface side in a nitrogen atmosphere, and then used for measurement.

  Table 4 shows the measurement result of the S1 level and the measurement result of the T1 level estimated as described above.

  From Table 4, the S1 level of CzPA, t-BuDNA, and cgDBCzPA is higher than the S1 level of 1,6mMemFLPAPrn, which is a guest material that emits blue light, and has a sufficient S1 level as a host material. I understand.

  Table 4 shows that the energy difference between the S1 level and the T1 level of CzPA, t-BuDNA, and cgDBCzPA is 0.5 eV or more. As a factor that causes delayed fluorescence, there can be thermally activated delayed fluorescence derived from the reverse intersystem crossing from the triplet excited state to the singlet excited state, but in order for the reverse intersystem crossing to occur efficiently, the S1 quasi- The difference between the position and the T1 level is preferably greater than 0 eV and not greater than 0.2 eV. Therefore, in the material used for the light-emitting layer 130 of the light-emitting element in this example and Embodiment 1, the delayed fluorescence component cannot be said to be derived from thermally activated delayed fluorescence, but is derived from TTA. It can be said that. Further, since the energy of the S1 level is twice or less than the energy of the T1 level, it can be said that energy transfer from the triplet excited state to the singlet excited state can be performed by TTA.

  The spectral peaks of fluorescence emission of the thin films of CzPA, t-BuDNA, and cgDBCzPA were 451 nm (2.75 eV), 442 nm (2.81 eV), and 442 nm (2.81 eV), respectively. Therefore, the energy conversion value difference between the peak wavelength of the fluorescence emission spectra of CzPA, t-BuDNA and cgDBCzPA and the peak wavelength of the phosphorescence emission spectrum was 0.5 eV or more. Also from this, in the material used for the light-emitting layer 130 of the light-emitting element in this example and Embodiment 1, the delayed fluorescence component is not derived from thermally activated delayed fluorescence but derived from TTA. It can be said that there is. In addition, the PL-EL measuring apparatus (made by Hamamatsu Photonics) was used for the measurement of a fluorescence spectrum.

  As described above, the structure described in this example can be combined with any of the other embodiments as appropriate.

  In this example, an example of manufacturing a light-emitting element (light-emitting element 4) which is one embodiment of the present invention will be described. A cross-sectional schematic view of the light-emitting element manufactured in this example is similar to the light-emitting element shown in FIG. Details of the element structure are shown in Table 5. The compounds used in this example are those shown in Embodiment Mode 1 and Example 1.

<Preparation of Light-Emitting Element 4>
An ITSO film was formed as an electrode 101 on the substrate so as to have a thickness of 70 nm. The electrode area of the electrode 101 was 4 mm ² (2 mm × 2 mm).

Next, the EL layer 100 was formed over the electrode 101. As the hole injection layer 111, PCPPn and MoO ₃ were co-deposited so that the weight ratio (PCPPn: MoO ₃ ) was 1: 0.5 and the thickness was 10 nm. Further, as the hole transport layer 112, PCPPn was deposited so as to have a thickness of 30 nm.

  Next, as the light emitting layer 130, cgDBCzPA and 1,6mMemFLPAPrn were co-deposited so that the weight ratio (cgDBCzPA: 1,6mMemFLPAPrn) was 1: 0.03 and the thickness was 25 nm. In the light-emitting layer 130, cgDBCzPA is a host material, and 1,6 mM emFLPAPrn is a fluorescent material (guest material).

  Further, on the light emitting layer 130, cgDBCzPA and BPhen were sequentially deposited as the electron transport layer 118 so as to have a thickness of 10 nm, respectively. Next, lithium fluoride (LiF) was deposited as the electron injection layer 119 so as to have a thickness of 1 nm.

  As the electrode 102, aluminum (Al) was formed to a thickness of 200 nm.

  Next, the light-emitting element 4 was sealed by fixing the sealing substrate to the substrate on which the EL layer 100 was formed using an organic EL sealing material in a glove box in a nitrogen atmosphere. The specific method is the same as that in the first embodiment. The light emitting element 4 was obtained through the above steps.

<Operation Characteristics of Light-Emitting Element 4>
Next, the light emission characteristics of the manufactured light-emitting element 4 were measured. The measurement was performed at room temperature (atmosphere kept at 23 ° C.).

Here, the light emission characteristics of the light-emitting element 4 around 1000 cd / m ² are shown in Table 6 below. 41 shows current efficiency-luminance characteristics of the light-emitting element 4, FIG. 42 shows external quantum efficiency-luminance characteristics, and FIG. 43 shows luminance-voltage characteristics. In addition, FIG. 44 shows an electroluminescence spectrum when a current is passed through the light-emitting element 4 at a current density of ^2.5 mA / cm ² . In addition, FIG. 45 shows the result of measuring the angular distribution of light emission exhibited by the light emitting element 4.

  As shown in FIG. 44, the electroluminescence spectrum peak of the light-emitting element 4 was 465 nm, and blue light emission exhibited by the fluorescent material 1,6 mM emFLPAPrn was observed. That is, the light emitting element 4 emits blue light having an emission spectrum peak in a wavelength band of 400 nm or more and 550 nm or less. In addition, since light emission exhibited by the fluorescent material was observed in the light-emitting element 4, it can be said that the singlet excitation energy generated by TTA is transferred from the host material to the fluorescent material.

  41 and 42 and Table 6, it can be seen that the light-emitting element 4 exhibits high current efficiency and external quantum efficiency efficiency. In the light emitting element 4, excellent efficiency with an external quantum efficiency exceeding 13% is obtained. This is because, in the light-emitting element 4, light is emitted based on singlet excitons generated by TTA in addition to singlet excitons generated by recombination of carriers (holes and electrons) injected from a pair of electrodes. It is because it is obtained.

  Note that as a result of measuring the angle distribution of light emission of the light emitting element 4, as shown in FIG. 45, the difference (also referred to as Lambertian ratio) between the light emission angle distribution of the light emitting element 4 and the complete diffusion surface (also referred to as Lambertian or Lambertian). ) Was 97.5%. The external quantum efficiencies shown in FIG. 42 and Table 6 are the products of the external quantum efficiencies calculated from the measurement results of the current efficiency in the front and assuming the Lambertian light distribution, and the Lambertian ratio. This is an estimated external quantum efficiency.

  Further, as shown in FIG. 43 and Table 6, the light emitting element 4 is driven at a low voltage. That is, by using a host material having a delayed fluorescence component by TTA, a blue light-emitting element driven at a low voltage can be manufactured.

Next, the measurement result of the reliability test of the light-emitting element 4 is shown in FIG. In the reliability test, the initial luminance of the light-emitting element 4 was set to 5000 cd / m ² and the light-emitting element 4 was driven under the condition of a constant current density.

  As a result, the time (LT90) at which the initial luminance was degraded to 90% was 180 hours, and the light-emitting element 4 showed excellent reliability.

  Therefore, as shown in Embodiment Mode 1, the energy of the lowest singlet excited state of the compound used for the host material is higher than the energy of the second triplet excited state having the most stable structure of the third triplet excited state. A second triplet excited state that is high and less than or equal to the energy of the third triplet excited state having the most stable structure of the third triplet excited state and having the most stable structure of the third triplet excited state. Is preferably higher than the energy of the first triplet excited state having the most stable structure of the third triplet excited state.

  As described above, by using a host material having a delayed fluorescence component by TTA, a blue light-emitting element with reduced power consumption and excellent reliability can be manufactured. The structure described in this example can be used in appropriate combination with any of the other embodiments.

  In this example, manufacturing examples of light-emitting elements (light-emitting elements 5 to 11) which are one embodiment of the present invention will be described. FIG. 47 shows a schematic cross-sectional view of the light-emitting element manufactured in this example, and Tables 8 to 10 show details of the element structure. The structures and abbreviations of the compounds used are shown below. Note that Embodiment 1 and Example 1 may be referred to for other compounds.

<Production of Light-Emitting Elements 5 to 11>
<< Production of Light-Emitting Element 5 >>
An alloy film of silver, palladium, and copper (also referred to as an Ag—Pd—Cu film or APC) was formed to a thickness of 100 nm over the substrate 510 as the conductive layer 501a included in the electrode 501. Next, an ITSO film was formed to a thickness of 85 nm as the conductive layer 501b in contact with the conductive layer 501a. Through the above steps, an electrode 501 having a function of reflecting light was formed. The electrode area of the electrode 501 was 4 mm ² (2 mm × 2 mm).

Next, a hole injection layer 531 is formed on the electrode 501 so that the weight ratio of PCPPn and MoO ₃ (PCPPn: MoO ₃ ) is 1: 0.5 and the thickness is 20 nm. Vapor deposited. Further, as the hole transport layer 532, PCPPn was deposited so as to have a thickness of 15 nm.

  Next, as the light emitting layer 521, cgDBCzPA and 1,6mMemFLPAPrn were co-deposited so that the weight ratio (cgDBCzPA: 1,6mMemFLPAPrn) was 1: 0.03 and the thickness was 25 nm. In the light-emitting layer 521, cgDBCzPA is a host material, and 1,6 mM emFLPAPrn is a fluorescent material (guest material).

  Further, on the light-emitting layer 521, cgDBCzPA and BPhen were sequentially deposited as the electron transport layer 533 so that the thicknesses were 10 nm and 15 nm, respectively.

Next, lithium oxide (Li ₂ O) and copper phthalocyanine (abbreviation: CuPc) were sequentially deposited as an electron injection layer 534 over the electron transport layer 533 so that the thicknesses were 0.1 nm and 2 nm, respectively.

Next, as a charge generation layer 535 that also serves as a hole injection layer, 4,4 ′, 4 ″-(benzene-1,3,5-triyl) tri (dibenzothiophene) (abbreviation: DBT3P-II), MoO ₃ was co-evaporated so that the weight ratio (DBT3P-II: MoO ₃ ) was 1: 0.5 and the thickness was 10 nm.

  Next, 4-phenyl-4 ′-(9-phenylfluoren-9-yl) triphenylamine (abbreviation: BPAFLP) was deposited as the hole-transporting layer 537 so as to have a thickness of 15 nm.

Next, as the light-emitting layer 522, 2- [3 ′-(dibenzothiophen-4-yl) biphenyl-3-yl] dibenzo [f, h] quinoxaline (abbreviation: 2mDBTBPDBq-II) and N- (1,1 '-Biphenyl-4-yl) -N- [4- (9-phenyl-9H-carbazol-3-yl) phenyl] -9,9-dimethyl-9H-fluoren-2-amine (abbreviation: PCBBiF); (Acetylacetonato) bis (6-tert-butyl-4-phenylpyrimidinato) iridium (III) (abbreviation: Ir (tBupppm) ₂ (acac)) and a weight ratio (2mDBTBBPDBq-II: PCBiF: Ir ( _tBuppm) 2 _(acac)) is 0.8: 0.2: to be 0.06, and thickness were co-deposited so as to 20 nm, followed by, 2m BTBPDBq-II, PCBBiF, and bis [2- (5- (2,6-dimethylphenyl) -3- (3,5-dimethylphenyl) -2-pyrazinyl-κN) -4,6-dimethylphenyl-κC ] (2,2,6,6-tetramethyl-3,5-heptanedionato-κ ² O, O ′) iridium (III) (abbreviation: Ir (dmdppr-dmp) ₂ (dpm)) and a weight ratio ( 2mDBTBPDBq-II: PCBBiF: Ir (dmdppr-dmp) ₂ (dpm)) is co-evaporated to 0.8: 0.2: 0.05 and to a thickness of 10 nm, followed by 2mDBTBPDBq-II, PCBBiF, and Ir (tBupppm) ₂ (acac) are used in a weight ratio (2mDBTBPDBq-II: PCBBiF: Ir (tBupppm) _2. Co-deposition was performed so that (acac)) was 0.8: 0.2: 0.05 and the thickness was 10 nm.

  Next, 2mDBTBPDBq-II and 2,9-bis (naphthalen-2-yl) -4,7-diphenyl-1,10-phenanthroline (abbreviation: NBPhen) are formed over the light-emitting layer 522 as the electron transport layer 538. The films were sequentially deposited so as to have thicknesses of 30 nm and 15 nm, respectively. Further, lithium fluoride (LiF) was deposited as an electron injection layer 539 on the electron transport layer 538 so as to have a thickness of 1 nm.

  Next, silver (Ag) and magnesium (Mg) were co-deposited as an electrode 502 on the electron injection layer 539 so as to have a thickness of 15 nm, and an ITO film was formed so as to have a thickness of 70 nm. . Through the above steps, an electrode 502 having a function of reflecting light and a function of transmitting light was formed. The co-deposited film of Ag and Mg was deposited so that the volume ratio (Ag: Mg) was 1: 0.1.

  Through the above steps, a pair of electrodes and an EL layer formed over the substrate 510 were formed. Note that, in the above-described film formation process, all vapor deposition was performed by a resistance heating method. Further, the ITO film of the electrode 502 was formed by a sputtering method.

  In addition, a red color filter (CF Red) having a thickness of 2.1 μm was formed as the optical element 514 on the sealing substrate 512 of the light emitting element 5.

Next, the light emitting element 5 was sealed by fixing the sealing substrate 512 on the substrate 510 using an organic EL sealing material in a glove box in a nitrogen atmosphere. Specifically, a sealing material is applied around the EL layer formed on the substrate 510, the substrate 510 and the sealing substrate 512 are bonded together, ultraviolet light having a wavelength of 365 nm is irradiated with 6 J / cm ² , and 80 ° C. 1 hour heat treatment. The light emitting element 5 was obtained through the above steps.

<< Production of Light-Emitting Element 6 >>
The light-emitting element 6 is different from the above-described manufacturing of the light-emitting element 5 only in the steps of the hole injection layer 531 and the light-emitting layer 522, and the other manufacturing steps are the same as those of the light-emitting element 5.

As the hole injection layer 531 on the electrode 501, PCPPn and MoO ₃ were co-deposited so that the weight ratio (PCPPn: MoO ₃ ) was 1: 0.5 and the thickness was 10 nm.

As the light-emitting layer 522, a weight ratio of 2mDBTBPDBq-II, PCBBiF, and Ir (tBupppm) ₂ (acac) (2mDBTBBPDBq-II: PCBBiF: Ir (tBupppm) ₂ (acac)) is 0.8: 0.2. : Co-evaporated to a thickness of 0.06 and a thickness of 20 nm, followed by 2mDBTBBPDBq-II, PCBBiF, bis {4,6-dimethyl-2- [5- (2,6 -Dimethylphenyl) -3- (3,5-dimethylphenyl) -2-pyrazinyl-κN] phenyl-κC} (2,4-pentanedionato-κ ² O, O ′) iridium (III) (abbreviation: Ir _{(dmdppr-dmp) 2 (acac} )), bis {4,6-dimethyl-2- [5- (2,6-dimethylphenyl) -3- (3,5-dimethyl Eniru) -2-pyrazinyl -KappaN] phenyl-KC} (2,8-dimethyl-4,6-nonanedionato -κ ² O, O ') iridium (III) _{(abbreviation: Ir (dmdppr-dmp) 2} (divm) ) And so that the weight ratio (2mDBTBPDBq-II: PCBiF: Ir (dmdppr-dmp) ₂ (divm)) is 0.8: 0.2: 0.05 and the thickness is 10 nm. Co-deposited, followed by 2mDBTBPDBq-II, PCBBiF, and Ir (tBupppm) ₂ (acac) to a weight ratio (2mDBTBPDBq-II: PCBBiF: Ir (tBupppm) ₂ (acac)) of 0.8: 0 2: Co-deposited so that the thickness was 0.05 and the thickness was 10 nm.

<< Production of Light-Emitting Element 7 >>
The light-emitting element 7 is different from the manufacturing of the light-emitting element 5 described above in the steps of the conductive layer 501b, the hole injection layer 531, and the optical element 514. The other processes are the same as the manufacturing method of the light-emitting element 5.

  An ITSO film was formed to a thickness of 45 nm as the conductive layer 501b included in the electrode 501.

On the electrode 501, as a hole injection layer 531, PCPPn and MoO ₃ were co-deposited so that the weight ratio (PCPPn: MoO ₃ ) was 1: 0.5 and the thickness was 10 nm.

  A green color filter (CF Green) having a thickness of 1.2 μm was formed as the optical element 514 on the sealing substrate 512 of the light emitting element 7.

<< Production of Light-Emitting Element 8 >>
The light-emitting element 8 is different from the manufacturing of the light-emitting element 7 described above in the process of the hole injection layer 531, and the other processes are the manufacturing methods of the light-emitting element 7.

On the electrode 501, as a hole injection layer 531, PCPPn and MoO ₃ were co-deposited so that the weight ratio (PCPPn: MoO ₃ ) was 1: 0.5 and the thickness was 15 nm.

<< Production of Light-Emitting Element 9 >>
The light-emitting element 9 is different from the above-described manufacturing of the light-emitting element 6 in the steps of the conductive layer 501b, the hole injection layer 531, and the optical element 514. The other processes are the same as the manufacturing method of the light-emitting element 6.

  An ITSO film was formed to a thickness of 45 nm as the conductive layer 501b included in the electrode 501.

On the electrode 501, as a hole injection layer 531, PCPPn and MoO ₃ were co-deposited so that the weight ratio (PCPPn: MoO ₃ ) was 1: 0.5 and the thickness was 10 nm.

  In addition, a green color filter (CF Green) having a thickness of 1.2 μm was formed as the optical element 514 on the sealing substrate 512 of the light emitting element 9.

<< Production of Light-Emitting Element 10 >>
In the light-emitting element 10, the manufacturing process of the light-emitting element 5 described above is different from the processes of the conductive layer 501 b, the hole injection layer 531, and the optical element 514.

  As the conductive layer 501b included in the electrode 501, an ITSO film was formed to a thickness of 110 nm.

On the electrode 501, as a hole injection layer 531, PCPPn and MoO ₃ were co-deposited so that the weight ratio (PCPPn: MoO ₃ ) was 1: 0.5 and the thickness was 15 nm.

  In addition, a blue color filter (CF Blue) having a thickness of 0.8 μm was formed as the optical element 514 on the sealing substrate 512 of the light emitting element 7.

<< Production of Light-Emitting Element 11 >>
The light-emitting element 11 is different from the above-described manufacturing of the light-emitting element 6 in the steps of the conductive layer 501b, the hole injection layer 531, and the optical element 514, and the other steps are the manufacturing methods of the light-emitting element 6.

  As the conductive layer 501b included in the electrode 501, an ITSO film was formed to a thickness of 115 nm.

On the electrode 501, as a hole injection layer 531, PCPPn and MoO ₃ were co-deposited so that the weight ratio (PCPPn: MoO ₃ ) was 1: 0.5 and the thickness was 5 nm.

  Further, a blue color filter (CF Blue) having a thickness of 0.8 μm was formed as the optical element 514 on the sealing substrate 512 of the light emitting element 9.

<Characteristics of Light-Emitting Elements 5 to 11>
Current efficiency-luminance characteristics of the manufactured light-emitting elements 5 to 11 are shown in FIGS. Further, the luminance-voltage characteristics are shown in FIGS. Note that each light-emitting element was measured at room temperature (atmosphere kept at 23 ° C.).

Table 11 shows element characteristics of the light-emitting elements 5 to 11 around 1000 cd / m ² .

In addition, FIGS. 52 and 53 show electroluminescence spectra (EL spectra) when current is supplied to the light-emitting elements 5 to 11 at a current density of ^2.5 mA / cm ² .

  As shown in FIGS. 48 to 53 and Table 11, the light-emitting element 5 and the light-emitting element 6 were able to obtain red light emission with high current efficiency and high color purity. The light-emitting elements 7 to 9 emitted green light with high current efficiency and high color purity. The light emitting element 10 and the light emitting element 11 emitted blue light with high current efficiency and high color purity.

<Angle dependence of chromaticity of light emitting element>
Next, FIG. 54 shows the result of measuring the electroluminescence spectrum of the light emitting element 10 from the front direction (0 °) to the oblique direction (70 °). In addition, FIG. 55 shows the result of measuring the electroluminescence spectrum from the front direction (0 °) to the oblique direction (70 °) in the light emitting element (light emitting element 12) which is different from the light emitting element 10 only in the configuration of the optical element 514. As the optical element 514 of the light emitting element 12, a blue color filter (CF Blue) was formed with a thickness of 1.5 μm.

  As shown in FIGS. 54 and 55, in the light emitting element 10, light emission near 550 nm appears strongly at an oblique direction of 70 °. On the other hand, in the light emitting element 12, light emission near 550 nm is weaker than that of the light emitting element 10 in an oblique direction of 70 °.

  FIG. 56 shows the result of calculating the chromaticity difference Δu′v ′ from the front direction in the oblique direction with respect to the viewing angle dependency of the chromaticity of the light emitting element 10 and the light emitting element 12.

  As shown in FIG. 56, the light emitting element 12 has a chromaticity difference Δu′v ′ of less than 0.2 at an angle of 0 ° to 70 °, and the viewing angle dependency of chromaticity is smaller than that of the light emitting element 10. Obtained. That is, the light emitting element 12 has better angle dependency of chromaticity than the light emitting element 10.

<Estimation of power consumption of display devices using light-emitting elements>
Next, the power consumption of the display device when the display device was manufactured using the manufactured light-emitting elements 5 to 11 was estimated.

In a display device having an aspect ratio of 16: 9, a diagonal size of 4.5 inches, and an area of 55.82 cm ² , the power consumption of the display device is estimated on the assumption that the aperture ratio is 35%. It was. Table 12 shows the characteristics of the light emitting element and the display device when used in the display device of the specification. In this embodiment, a display device using the light emitting elements 5, 7, and 10 as display elements is a display device 1, and a display device using light emitting elements 5, 8, and 10 as display elements is a light emitting device. A display device using the elements 6, 9, and 11 as display elements is displayed on the display device 3, a display device using the light emitting elements 5, 7, and 12 as display elements is displayed on the display device 4, and the light emitting elements 5, 8, and 12 are displayed on the display device 3. A display device used as an element is referred to as a display device 5.

As shown in Table 12, when the light emitting elements 5, 7, and 10 are used as display elements of the display device having the above specifications (display apparatus 1), the luminance of the display element having the structure of the light emitting element 5 is 675 cd / m ² , When the luminance of the display element having the structure of the light-emitting element 7 is 1631 cd / m ² and the luminance of the display element having the structure of the light-emitting element 10 is 266 cd / m ² , a white color having a color temperature of 6500 K (chromaticity (x, y) (0.313, 0.329)) can be displayed on the entire display area at 300 cd / m ^2. At this time, the power consumption of these display elements can be estimated to be 427 mW. The area ratio (NTSC ratio) of CIE 1976 chromaticity that can be displayed by the display device to the color gamut standard established by the National Television Broadcasting Standards Committee (NTSC) was estimated to be 102%.

When the light emitting elements 5, 8, and 10 are used as the display elements of the display device having the above specifications (display device 2), the luminance of the display element having the structure of the light emitting element 5 is 576 cd / m ² , and When the luminance of the display element having the structure is 1728 cd / m ² and the luminance of the display element having the structure of the light-emitting element 10 is 267 cd / m ² , white (chromaticity (x, y)) of 6500K is (0. 313, 0.329)) can be displayed on the entire display area at 300 cd / m ² , and at this time, the power consumption of these display elements can be estimated to be 393 mW. The NTSC ratio was estimated to be 95%.

When the light emitting elements 6, 9, and 11 are used as the display elements of the display device having the above specifications (display device 3), the luminance of the display element having the structure of the light emitting element 6 is 658 cd / m ² , When the luminance of the display element having the structure is 1620 cd / m ² and the luminance of the display element having the structure of the light-emitting element 11 is 294 cd / m ² , white (chromaticity (x, y)) of 6500K is (0. 313, 0.329)) can be displayed on the entire display area at 300 cd / m ² , and the power consumption of these display elements can be estimated to be 476 mW. The NTSC ratio was estimated to be 98%.

When the light emitting elements 5, 7, and 12 are used as the display elements of the display device having the above specifications (display device 4), the luminance of the display element having the structure of the light emitting element 5 is 697 cd / m ² , When the luminance of the display element having the structure is 1640 cd / m ² and the luminance of the display element having the structure of the light-emitting element 10 is 234 cd / m ² , white (chromaticity (x, y)) having a color temperature of 6500 K is (0. 313, 0.329)) can be displayed on the entire display area at 300 cd / m ² , and at this time, the power consumption of these display elements was estimated to be 447 mW. The NTSC ratio was estimated to be 106%.

In addition, when the light-emitting elements 5, 8, and 12 are used as display elements of the display device having the above specifications (display apparatus 5), the luminance of the display element having the structure of the light-emitting element 5 is 598 cd / m ² , When the luminance of the display element having the structure is 1739 cd / m ² and the luminance of the display element having the structure of the light-emitting element 10 is 235 cd / m ² , white (chromaticity (x, y)) of 6500K is (0. 313, 0.329)) can be displayed on the entire display area at 300 cd / m ² , and at this time, the power consumption of these display elements can be estimated to be 413 mW. The NTSC ratio was estimated to be 100%.

  As described above, it was shown that the display element having the structure of the light-emitting elements 5 to 12 is a display element with reduced power consumption. Further, it was shown that a display device with reduced power consumption can be provided by using the display element as described above.

<Reliability test results>
Next, results of reliability tests of the light-emitting element 5, the light-emitting element 7, the light-emitting element 8, and the light-emitting element 10 are shown in FIGS. Note that the initial luminance of the light-emitting element in the reliability test was the initial luminance assumed for the display device 1 and the display device 2, and the light-emitting element was driven under a constant current density condition. In addition, a reliability test was performed on each of the two light emitting elements.

In the light-emitting element 5, the light-emitting elements tested at the initial luminance of the display device 1 (initial luminance 675 cd / m ² ) are the light-emitting elements 5 (1) and 5 (2), and the initial luminance of the display device 2. The light-emitting elements tested at (initial luminance 576 cd / m ² ) were light-emitting elements 5 (3) and 5 (4). In the light-emitting element 7, light-emitting elements tested at the initial luminance (initial luminance 1631 cd / m ² ) of the display device 1 were referred to as a light-emitting element 7 (1) and a light-emitting element 7 (2). In the light-emitting element 8, the light-emitting elements tested at the initial luminance of the display device 2 (initial luminance 1728cd / m ² ) were referred to as the light-emitting element 8 (1) and the light-emitting element 8 (2). In the light-emitting element 10, the light-emitting elements tested at the initial luminance (initial luminance 267 cd / m ² ) of the display device 1 and the display device 2 were referred to as the light-emitting element 10 (1) and the light-emitting element 10 (2).

  The results of the reliability test of the light-emitting elements 5 (1), (2), (3), and (4) are shown in FIGS. 57 (A) and 57 (B). 58 (A) and (B) of the reliability test of FIG. 59, and the results of the reliability test of the light emitting elements 10 (1) and (2) are shown in FIGS. 59 (A) and (B), respectively. Note that FIGS. 57A, 58A, and 59A show changes in normalized luminance over time when the initial luminance is 100%, and FIGS. 58B and 59B are shown. FIG. 59B shows a voltage change when the initial voltage is 0V.

  As shown in FIGS. 57 to 59, each of the light-emitting elements 5, 7, 8, and 10 that is a light-emitting element of one embodiment of the present invention has a luminance deterioration of 95% or more after an elapse of 800 hours and little deterioration in luminance. In addition, the voltage rise after 800 hours was 0.2 V or less and the voltage change was small, and the light emitting device was excellent in reliability. That is, the light-emitting element of one embodiment of the present invention is suitable as a display element of a display device.

  As described above, by using the structure of one embodiment of the present invention, a light-emitting element that exhibits high current efficiency and emits blue light with high color purity can be provided. In addition, by using the light-emitting element having the structure of one embodiment of the present invention, a display device with excellent reliability can be provided. In addition, by using the light-emitting element having the structure of one embodiment of the present invention, a display device with low power consumption and high color purity can be provided.

  As described above, the structure described in this example can be combined with any of the other examples and embodiments as appropriate.

100 EL layer 101 Electrode 101a Conductive layer 101b Conductive layer 101c Conductive layer 102 Electrode 103 Electrode 103a Conductive layer 103b Conductive layer 104 Electrode 104a Conductive layer 104b Conductive layer 111 Hole injection layer 112 Hole transport layer 113 Electron transport layer 114 Electron injection layer 115 charge generation layer 116 hole injection layer 117 hole transport layer 118 electron transport layer 119 electron injection layer 120 light emitting element 123B light emitting layer 123G light emitting layer 123R light emitting layer 130 light emitting layer 131 host material 132 guest material 140 partition 151 triplet excited state 152 Triplet excited state 153 Triplet excited state 160 Light emitting layer 161 Triplet excited state 162 Triplet excited state 163 Triplet excited state 164 Triplet excited state 170 Light emitting layer 170a Light emitting layer 170b Light emitting layer 171 Triplet excited state 172 Triplet Excited state 1 3 Triplet excited state 174 Triplet excited state 181 Triplet excited state 182 Triplet excited state 183 Triplet excited state 184 Triplet excited state 191 Triplet excited state 192 Triplet excited state 193 Triplet excited state 194 Triplet excited state 200 substrate 220 substrate 221B region 221G region 221R region 222B region 222G region 222R region 223 light shielding layer 224B optical element 224G optical element 224R optical element 250 light emitting element 252 light emitting element 254 light emitting element 256 light emitting element 301_1 wiring 301_5 wiring 301_6 wiring 301_7 wiring 302_7 wiring 302_2 wiring 303_1 transistor 303_6 transistor 303_7 transistor 304 capacitor 304_1 capacitor 304_2 capacitor 305 light-emitting element 306_1 wiring 306 3 wiring 307_1 wiring 307_3 wiring 308_1 transistor 308_6 transistor 309_1 transistor 309_2 transistor 311_1 wiring 311_3 wiring 312_1 wiring 312_2 wiring 400 EL layer 401 electrode 402 electrode 411 hole injection layer 412 hole transport layer 413 electron transport layer 414 electron injection layer 416 hole Injection layer 417 Hole transport layer 418 Electron transport layer 419 Electron injection layer 420 Light emission layer 421 Host material 422 Guest material 430 Light emission layer 431 Host material 431_1 Organic compound 431_2 Organic compound 432 Guest material 441 Light emission unit 442 Light emission unit 445 Charge generation layer 450 Light-emitting element 452 Light-emitting element 501 Electrode 502 Electrode 501a Conductive layer 501b Conductive layer 510 Substrate 512 Sealing substrate 514 Optical element 52 Light emitting layer 522 Light emitting layer 531 Hole injection layer 532 Hole transport layer 533 Electron transport layer 534 Electron injection layer 535 Charge generation layer 537 Hole transport layer 538 Electron transport layer 539 Electron injection layer 600 Display device 601 Signal line driver circuit portion 602 Pixel portion 603 Scanning line driver circuit portion 604 Sealing substrate 605 Seal material 607 Region 608 Wiring 609 FPC
610 element substrate 611 transistor 612 transistor 613 lower electrode 614 partition 616 EL layer 617 upper electrode 618 light emitting element 621 optical element 622 light shielding layer 623 transistor 624 transistor 801 pixel circuit 802 pixel unit 804 driving circuit unit 804a scanning line driving circuit 804b signal line driving Circuit 806 Protection circuit 807 Terminal portion 852 Transistor 854 Transistor 862 Capacitance element 872 Light emitting element 1001 Substrate 1002 Base insulating film 1003 Gate insulating film 1006 Gate electrode 1007 Gate electrode 1008 Gate electrode 1020 Interlayer insulating film 1021 Interlayer insulating film 1022 Electrode 1024B Lower electrode 1024G Lower electrode 1024R Lower electrode 1024Y Lower electrode 1025 Partition 1026 Upper electrode 1028 EL layer 1029 Sealing layer 1031 Sealing substrate 1032 Sealing material 1033 Base material 1034B Colored layer 1034G Colored layer 1034R Colored layer 1034Y Colored layer 1035 Light-shielding layer 1036 Overcoat layer 1037 Interlayer insulating film 1040 Pixel portion 1041 Drive circuit portion 1042 Peripheral portion 2000 Touch panel 2001 Touch panel 2501 Display device 2502R Pixel 2502t Transistor 2503c Capacitance element 2503g Scan line driver circuit 2503s Signal line driver circuit 2503t Transistor 2509 FPC
2510 Substrate 2510a Insulating layer 2510b Flexible substrate 2510c Adhesive layer 2511 Wiring 2519 Terminal 2521 Insulating layer 2528 Partition 2550R Light emitting element 2560 Sealing layer 2567BM Light shielding layer 2567p Antireflection layer 2567R Colored layer 2570 Substrate 2570a Insulating layer 2570b Flexible substrate 2570c Adhesive layer 2580R Light emitting module 2590 Substrate 2591 Electrode 2592 Electrode 2593 Insulating layer 2594 Wiring 2595 Touch sensor 2597 Adhesive layer 2598 Wiring 2599 Connection layer 2601 Pulse voltage output circuit 2602 Current detection circuit 2603 Capacitance 2611 Transistor 2612 Transistor 2613 Transistor 2621 Electrode 2622 Electrode 3000 Light emission Device 3001 Substrate 3003 Substrate 3005 Light emitting element 3007 Sealing region 3009 Sealing region 3011 region 3013 region 3014 region 3015 substrate 3016 substrate 3018 desiccant 3054 display unit 3500 multifunctional terminal 3502 housing 3504 display unit 3506 Camera 3508 Lighting 3600 light 3602 housing 3608 Lighting 3610 speaker 8000 display module 8001 top cover 8002 lower cover 8003 FPC
8004 Touch sensor 8005 FPC
8006 Display device 8009 Frame 8010 Printed circuit board 8011 Battery 8501 Illumination device 8502 Illumination device 8503 Illumination device 8504 Illumination device 9000 Case 9001 Display unit 9003 Speaker 9005 Operation key 9006 Connection terminal 9007 Sensor 9008 Microphone 9050 Operation button 9051 Information 9052 Information 9053 Information 9054 Information 9055 hinge 9100 portable information terminal 9101 portable information terminal 9102 portable information terminal 9200 portable information terminal 9201 portable information terminal

Claims (13)

A pair of electrodes;
An EL layer sandwiched between the pair of electrodes;
A light emitting device comprising:
The EL layer has an organic compound,
The organic compound has a first skeleton and a second skeleton,
The light emitted by the EL layer has a delayed fluorescence component due to triplet-triplet annihilation,
The first triplet excited state in the organic compound is an excited state having the lowest excitation energy level in the organic compound,
The first triplet excited state has a molecular orbital in the first skeleton,
The second triplet excited state in the organic compound has the lowest excitation energy level among triplet excited states having a molecular orbital in the second skeleton and a molecular orbital in the second skeleton. A triplet excited state having
The third triplet excited state in the organic compound is a triplet excited having a molecular orbital in the first skeleton and a molecular orbital in the first skeleton other than the first triplet excited state. The triplet excited state having the lowest excitation energy level among the states,
The energy of the third triplet excited state having the most stable structure of the third triplet excited state is the energy of the first triplet excited state having the most stable structure of the third triplet excited state. Higher and lower than the energy of the second triplet excited state having the most stable structure of the third triplet excited state;
A light emitting element characterized by the above. A pair of electrodes;
An EL layer sandwiched between the pair of electrodes;
A light emitting device comprising:
The EL layer has an organic compound,
The organic compound has a first skeleton and a second skeleton,
The light emitted by the EL layer has a delayed fluorescence component due to triplet-triplet annihilation,
The first triplet excited state in the organic compound is an excited state having the lowest excitation energy level in the organic compound,
The first triplet excited state has a molecular orbital in the first skeleton,
The second triplet excited state in the organic compound has the lowest excitation energy level among triplet excited states having a molecular orbital in the second skeleton and a molecular orbital in the second skeleton. A triplet excited state having
The third triplet excited state in the organic compound is a triplet excited having a molecular orbital in the first skeleton and a molecular orbital in the first skeleton other than the first triplet excited state. The triplet excited state having the lowest excitation energy level among the states,
The singlet excited state having the lowest excitation energy level in the organic compound is higher than the excitation energy level of the second triplet excited state and not more than the excitation energy level of the third triplet excited state. Having an excitation energy level of
A light emitting element characterized by the above. In claim 2,
The energy of the singlet excited state is higher than the energy of the second triplet excited state having the most stable structure of the third triplet excited state, and the most stable structure of the third triplet excited state. Or less of the energy of the third triplet excited state having
The energy of the second triplet excited state having the most stable structure in the third triplet excited state is the energy of the first triplet excited state having the most stable structure in the third triplet excited state. taller than,
A light emitting element characterized by the above. In claim 2,
The energy conversion value of the absorption edge in the absorption spectrum of the organic compound is higher than the energy of the second triplet excited state having the most stable structure of the third triplet excited state, and the third triplet. Less than the energy of the third triplet excited state having the most stable structure of the excited state;
The energy of the second triplet excited state having the most stable structure in the third triplet excited state is the energy of the first triplet excited state having the most stable structure in the third triplet excited state. taller than,
A light emitting element characterized by the above. In any one of Claims 1 thru | or 4,
The first skeleton has an anthracene skeleton,
The second skeleton is bonded to the first skeleton;
A light emitting element characterized by the above. In any one of Claims 1 thru | or 5,
The light emitted by the EL layer has an emission spectrum peak in blue.
A light emitting element characterized by the above. In any one of Claims 1 thru | or 5,
The EL layer has a guest material that exhibits fluorescence,
A light emitting element characterized by the above. In claim 7,
The light emitted by the guest material has an emission spectrum peak in blue.
A light emitting element characterized by the above. In claim 7 or claim 8,
The light emitted by the guest material has a delayed fluorescent component,
A light emitting element characterized by the above. In any one of Claims 7 to 9,
The guest material has a pyrene skeleton,
A light emitting element characterized by the above. The light emitting device according to any one of claims 1 to 10,
With color filters, seals, or transistors,
A display device. A display device according to claim 11;
A housing or touch sensor;
Electronic equipment having The light emitting device according to any one of claims 1 to 10,
A housing or touch sensor;
A lighting device.