JP2021180332A - Light-emitting element, light-emitting device, electronic apparatus, and illuminating device - Google Patents

Abstract

To provide a light-emitting element with high external quantum efficiency, and a light-emitting element with long life.SOLUTION: A light-emitting element includes a light-emitting layer between an anode and a cathode. The light-emitting layer includes a stack of a first light-emitting layer and a second light-emitting layer. The first light-emitting layer includes at least a first light-emitting substance that changes triplet excitation energy into light emission, a first organic compound with an electron transport property, and a second organic compound with a hole transport property and formed on the anode side. The second light-emitting layer includes at least a second light-emitting substance that changes triplet excitation energy into light emission, a second organic compound, and a third organic compound with an electron transport property. The first organic compound has higher LUMO level than the third organic compound. The first light-emitting substance emits light with a shorter wavelength than that of the second light-emitting substance. The first organic compound and the second organic compound, and the second organic compound and the third organic compound form an excited complex, respectively.SELECTED DRAWING: None

Description

One aspect of the present invention relates to a light emitting element in which an organic compound capable of emitting light by applying an electric field is sandwiched between a pair of electrodes, and a light emitting device, an electronic device, and a lighting device having such a light emitting element.

Light emitting devices that use organic compounds as light emitters, which are thin and lightweight, have high-speed responsiveness, and are driven by DC low voltage, are expected to be applied to next-generation flat panel displays. In particular, a display device in which light emitting elements are arranged in a matrix is considered to be superior in that it has a wide viewing angle and excellent visibility as compared with a conventional liquid crystal display device.

In the light emitting mechanism of the light emitting element, by sandwiching an EL layer containing a light emitting body between a pair of electrodes and applying a voltage, electrons injected from the cathode and holes injected from the anode are regenerated at the light emitting center of the EL layer. It is said that they combine to form a molecular exciter, and when the molecular excitator relaxes to the ground state, it releases energy and emits light. Singlet and triplet excitations are known as excited states, and it is considered that light emission is possible through either excited state.

With respect to such a light emitting element, in order to improve the element characteristics, improvement of the element structure, material development and the like are actively carried out (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2010-182699

However, the light extraction efficiency of the light emitting element at present is said to be about 20% to 30%, and even considering the absorption of light by the reflective electrode and the transparent electrode, the external quantum efficiency of the light emitting element using the phosphorescent compound. The limit of is considered to be about 25%.

Therefore, in one aspect of the present invention, a light emitting device having high external quantum efficiency is provided. Further, one aspect of the present invention provides a light emitting device having a long life.

One aspect of the present invention has a light emitting layer between a pair of electrodes (anolyde and cathode), and the light emitting layer is a first light emitting substance (guest material) that converts triple-term excitation energy into light emission, and has electron transportability. A first light emitting layer containing at least a first organic compound (host material) and a second organic compound (assist material) having a hole transport property and formed on the anode side, and triple-term excitation energy. Formed containing at least a second luminescent substance (guest material) that converts to luminescence, a third organic compound having electron transportability (host material), and a second organic compound having hole transportability (assist material). It is a laminated structure with a second light emitting layer, and in the first light emitting layer, the first organic compound (host material) and the second organic compound (assist material) are a combination forming an excitation complex. The second light emitting layer is a light emitting element characterized in that the third organic compound (host material) and the second organic compound (assist material) are a combination forming an excitation complex.

Further, another aspect of the present invention has a light emitting layer between the anode and the cathode, a hole transport layer between the anode and the light emitting layer, and electron transport between the cathode and the light emitting layer. The light emitting layer has at least a first luminescent substance that converts triplet excitation energy into light emission, a first organic compound having electron transporting property, and a second organic compound having hole transporting property. A first light emitting layer containing and in contact with the hole transporting layer, a second light emitting substance that converts triplet excitation energy into light emission, a third organic compound having electron transporting property, and hole transporting. It is a laminate with a second light emitting layer that contains at least a second organic compound having a property and is formed in contact with an electron transport layer. In the first light emitting layer, the first organic compound (host material) is used. And the second organic compound (assist material)
It is a combination that forms an excited complex, and in the second light emitting layer, the third organic compound (host material) and the second organic compound (assist material) are a combination that forms an excited complex. It is a light emitting element.

In each of the above configurations, the emission wavelength of the excitation complex formed by the first organic compound (host material) and the second organic compound (assist material) of the first light emitting layer is the first organic compound (host). Emission wavelength (fluorescence wavelength) of each of the material) and the second organic compound (assist material)
Since it exists on the long wavelength side, the fluorescence spectrum of the first organic compound (host material) and the fluorescence spectrum of the second organic compound (assist material) can be made longer by forming an excitation complex. It can be converted into an emission spectrum located on the wavelength side. Further, the emission wavelengths of the excitation complex formed by the third organic compound (host material) and the second organic compound (assist material) of the second light emitting layer are the third organic compound (host material) and the second. Organic compounds (
Since it exists on the longer wavelength side than each emission wavelength (fluorescence wavelength) of the assist material), the fluorescence spectrum of the third organic compound (host material) and the second organic can be obtained by forming an excitation complex. The fluorescence spectrum of the compound (assist material) can be converted into an emission spectrum located on the longer wavelength side.

In each of the above configurations, in the first light emitting layer, the anion of the first organic compound and the second
The excitation complex is formed from the cations of the organic compound of the above, and the second light emitting layer is characterized in that the excitation complex is formed from the anion of the third organic compound and the cation of the second organic compound.

Further, in the above configuration, each of the first light emitting layer and the second light emitting layer contains the same second organic compound (assist material), and the first organic compound (host material) contained in the first light emitting layer is contained. ) Is characterized in that the minimum empty orbital level (LUMO level) is higher than that of the third organic compound (host material) contained in the second light emitting layer.

Further, in the above configuration, the first luminescent substance contained in the first light emitting layer is characterized by being a substance exhibiting light emission having a shorter wavelength than the second luminescent substance contained in the second light emitting layer. And.

Further, in the above configuration, the first luminescent substance and the second luminescent substance are luminescent substances that convert triplet excitation energy into luminescence, and are phosphorescent compounds such as organic metal complexes and thermally activated delayed fluorescence. Materials that indicate Thermally Activated Delayed Fluorescence (TADF: Thermally A).
Activated Fluorescence) materials can be used. The first organic compound and the third organic compound are mainly ^10-6 cm ² / V.
An electron transporting material having an electron mobility of s or more, specifically, a π-deficient heteroaromatic compound, and the second organic compound mainly has a ^{hole mobility of 10-6} cm ² / Vs or more. It is characterized by being a hole-transporting material, specifically, a π-excessive heteroaromatic compound or an aromatic amine compound.

Further, one aspect 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 and a lighting device. Therefore, the light emitting device in the present specification refers to an image display device, a light emitting device, or a light source (including a lighting device). again,
A connector to the light emitting device, for example, FPC (Flexible printed circu)
It) or a module with TCP (Tape Carrier Package) attached, a module with a printed wiring board at the end of TCP, or a C
All modules in which ICs (integrated circuits) are directly mounted by the OG (Chip On Glass) method are also included in the light emitting device.

Since the light emitting element according to one aspect of the present invention can form an excited complex in each of the first light emitting layer and the second light emitting layer constituting the light emitting layer, the energy transfer efficiency is high and the external quantum. It is possible to realize a highly efficient light emitting element.

Further, in the light emitting element according to one aspect of the present invention, the excitation complex formed in the first light emitting layer by having the above-mentioned element structure has higher excitation energy than the excitation complex formed in the second light emitting layer. As a first luminescent material (guest material) that converts the triplet excitation energy contained in the first light emitting layer into light emission, the triplet excitation energy contained in the second light emitting layer is converted into light emission. By using a substance that emits light having a shorter wavelength than the second light emitting substance (guest material) to be changed, it is possible to simultaneously obtain light emission from the first light emitting layer and the second light emitting layer, and further, the first light emitting layer. A second luminescent material (guest material) that converts some of the excitation energies of the excitation complex formed in the light emitting layer of the above into light emission, and converts the triplet excitation energy in the second light emitting layer into light emission. ) Can be used as excitation energy, so that the light emission efficiency in the light emitting element can be further improved.

The figure explaining the concept of one aspect of this invention. The figure explaining the concept of one aspect of this invention. The figure which shows the calculation result which concerns on one aspect of this invention. The figure which shows the calculation result which concerns on one aspect of this invention. The figure explaining the structure of a light emitting element. The figure explaining the structure of a light emitting element. The figure explaining the light emitting device. The figure explaining the light emitting device. The figure explaining the electronic device. The figure explaining the electronic device. The figure explaining the lighting apparatus. The figure explaining the light emitting element. The figure which shows the current density-luminance characteristic of a light emitting element 1. The figure which shows the voltage-luminance characteristic of a light emitting element 1. The figure which shows the luminance-current efficiency characteristic of a light emitting element 1. The figure which shows the voltage-current characteristic of a light emitting element 1. The figure which shows the emission spectrum of a light emitting element 1. The figure which shows the emission spectrum of the substance used for a light emitting element 1. The figure which shows the emission spectrum of the substance used for a light emitting element 1.

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 its form and details can be variously changed without departing from the spirit and scope of the present invention. Therefore, the present invention is not construed as being limited to the description of the embodiments shown below.

(About the elementary process of light emission in the light emitting element)
First, a general elementary process of light emission in a light emitting device using a luminescent substance (including a phosphorescent compound and a thermal activated delayed fluorescent (TADF) material) that converts triplet excitation energy into light emission will be described. Here, the molecule that gives the excitation energy is referred to as a host molecule, and the molecule that receives the excitation energy is referred to as a guest molecule.

(1) When electrons and holes (holes) are recombined in the guest molecule and the guest molecule is in an excited state (direct recombination process).

(1-1) When the excited state of the guest molecule is the triplet excited state, the guest molecule emits phosphorescence.

(1-2) When the excited state of the guest molecule is the singlet excited state The guest molecule in the singlet excited state crosses the triplet excited state between the terms and emits phosphorescence.

That is, in the direct recombination process of (1) above, high luminous efficiency can be obtained as long as the intersystem crossing efficiency of the guest molecule and the phosphorescence quantum yield are high. The host molecule T1
The level is preferably higher than the T1 level of the guest molecule.

(2) When electrons and holes (holes) are recombined in the host molecule and the host molecule is in an excited state (energy transfer process).

(2-1) When the excited state of the host molecule is the triple-term excited state When the T1 level of the host molecule is higher than the T1 level of the guest molecule, the excitation energy is transferred from the host molecule to the guest molecule, and the guest molecule moves. It becomes a triplet excited state. The guest molecule in the triplet excited state emits phosphorescence. It should be noted that energy transfer from the T1 level of the host molecule to the level (S1 level) of the single-term excitation energy of the guest molecule is prohibited unless the host molecule emits phosphorescence, and is unlikely to become the main energy transfer process. It is omitted here. That is, as shown in the following equation (2-1), the energy transfer from the triplet excited state (3H *) of the host molecule to the triplet excited state (3G *) of the guest molecule is important (in the equation, 1G is the guest). The singlet ground state of the molecule, 1H represents the singlet ground state of the host molecule).

3H * + 1G → 1H + 3G * (2-1)

(2-2) When the excited state of the host molecule is the single-term excited state When the S1 level of the host molecule is higher than the S1 level and T1 level of the guest molecule, the excited energy is transferred from the host molecule to the guest molecule. , The guest molecule is in a single-term excited state or a triple-term excited state. The guest molecule in the triplet excited state emits phosphorescence. In addition, the guest molecule in the singlet excited state crosses the triplet excited state between the terms and emits phosphorescence.

That is, as shown in the following equation (2-2A), energy is transferred from the singlet excited state (1H *) of the host molecule to the singlet excited state (1G *) of the guest molecule, and then the triplet of the guest molecule is transferred by intersystem crossing. The process of generating the excited state (3G *) and the direct energy transfer from the singlet excited state (1H *) of the host molecule to the triplet excited state (3G *) of the guest molecule as shown in the following equation (2-2B). The process is conceivable.

1H * + 1G → 1H + 1G * → (intersystem crossing) → 1H + 3G * (2-2A)
1H * + 1G → 1H + 3G * (2-2B)

If all the energy transfer processes described in (2) above occur efficiently, both the triplet excited energy and the singlet excited energy of the host molecule are efficiently converted into the triplet excited state (3G *) of the guest molecule. Therefore, highly efficient light emission is possible. On the contrary, if the host molecule itself emits the excitation energy as light or heat and is inactivated before the excitation energy is transferred from the host molecule to the guest molecule, the luminous efficiency is lowered.

Next, the governing factors of the energy transfer process between the host molecule and the guest molecule described above will be described. The following two mechanisms have been proposed as the mechanism of energy transfer between molecules.

First, the Felster mechanism (dipole-dipole interaction), which is the first mechanism, does not require direct contact between molecules for energy transfer, and the resonance of dipole vibration between host and guest molecules. It is a mechanism in which energy transfer occurs through a phenomenon. Due to the resonance phenomenon of bipolar vibration, the host molecule transfers energy to the guest molecule, the host molecule becomes the ground state, and the guest molecule becomes the excited state. The rate constant kh _{* → g} of the Felster mechanism is shown in the equation (1).

In Equation (1), [nu denotes a frequency, f _{'h (ν)} is the fluorescence spectrum in energy transfer from the normalized emission spectrum (singlet excited state of the host molecules, the triplet excited Represents the phosphorescence spectrum when discussing energy transfer from a state), ε _g (
ν) represents the molar absorbance coefficient of the guest molecule, N represents the avocadro number, n represents the refractive index of the medium, R represents the intermolecular distance between the host molecule and the guest molecule, and τ is the actual measurement. The lifetime of the excited state (fluorescence lifetime or phosphorescent lifetime) is represented, c represents the light velocity, and φ is the emission quantum yield (fluorescence quantum yield, triple term when discussing energy transfer from the single-term excited state). When discussing energy transfer from an excited state, it represents phosphorous quantum yield), and K ² is a coefficient (0-4) that represents the orientation of the transition dipole moment between the host molecule and the guest molecule. In the case of random orientation, K ² = 2/3.

Next, in the second mechanism, the Dexter mechanism (electron exchange interaction), the host molecule and the guest molecule approach the contact effective distance where the orbital overlap occurs, and the electron in the excited state and the guest molecule in the ground state are approached. Energy transfer occurs through the exchange of electrons in. The speed constant kh _{* → g} of the Dexter mechanism is shown in the equation (2).

In Equation (2), h is Planck's constant, K 'is the constant with the dimension of energy, [nu denotes a frequency, f' _{h (ν)} is normalized host molecules (a fluorescence spectrum in energy transfer from a singlet excited state, in energy transfer from a triplet excited state phosphorescence spectrum) emission spectra represent, epsilon _{'g ([nu)} is normalized guest molecule The absorption spectrum is represented, L represents the effective molecular radius, and R represents the intermolecular distance between the host molecule and the guest molecule.

_{Here, the energy transfer efficiency Φ ET} from the host molecule to the guest molecule is considered to be expressed by the mathematical formula (3). k _r is (in energy transfer from a singlet excited state fluorescence and phosphorescence if the energy transfer from a triplet excited state) emission process of the host molecule represents the rate constant, k _n, the host molecule Represents the rate constant of the non-fluorescent process (heat deactivation and intersystem crossing), and τ represents the lifetime of the measured excited state of the host molecule.

From equation (3), _{in order to increase the energy transfer efficiency Φ ET} , the energy transfer rate constant kh _{* → g} is increased, and other competing rate constants _kr + k _n (= 1 / τ) are relative. It turns out that it should be smaller.

(About the energy transfer efficiency of (2-1))
First, consider the energy transfer process of (2-1). In this case, the Felster type (formula (1)) is forbidden, so only the Dexter type (formula (2)) needs to be considered.
According to equation (2), in order to increase the velocity constant kh _{* → g} , the emission spectrum of the host molecule (phosphorescence spectrum because we are discussing the energy transfer from the triplet excited state) and the absorption spectrum of the guest molecule (single). It can be seen that the larger the overlap with the absorption) corresponding to the direct transition from the ground state of the term to the excited state of the triplet, the better.

In one aspect of the present invention, a luminescent material (including a phosphorescent compound and a heat-activated delayed fluorescence (TADF) material) that converts triplet excitation energy into light emission is used as a guest material, but in the absorption spectrum of the phosphorescent compound, it is used. , Absorption corresponding to the direct transition from the singlet ground state to the triplet excited state may be observed, which is the absorption band that appears on the longest wavelength side. In particular, in a luminescent iridium complex, the absorption band on the longest wavelength side often appears as a broad absorption band in the vicinity of 500 to 600 nm (of course, depending on the emission wavelength, it appears on the shorter wavelength side or the longer wavelength side. In some cases). This absorption band is mainly a triplet MLCT (Metalt).
o Ligand Charge Transfer) Derived from the transition. However, the absorption band also includes some absorption derived from the triplet π-π * transition and the singlet MLCT transition, and these overlap to form a broad absorption band on the longest wavelength side of the absorption spectrum. It is thought that there is. In other words, the difference between the lowest singlet excited state and the lowest triplet excited state is small, and it is considered that the absorptions derived from these overlap to form a broad absorption band on the longest wavelength side of the absorption spectrum. Therefore, the guest material, when using the organometallic complex (especially iridium complex), and absorption band broad present in this way the longest wavelength side by phosphorescence spectrum of the host material overlaps significantly, the rate constant k _{h * → G} can be increased to improve energy transfer efficiency.

Further, usually, since the host material used fluorescent compound, phosphorescence lifetime (tau) is (small k r ₊ k _n) or more milliseconds and very long. This is because the transition from the triplet excited state to the ground state (singlet state) is a forbidden transition. From equation (3), this means energy transfer efficiency Φ
It works in favor of _ET.

Considering the above, the energy transfer from the triplet excited state of the host material to the triplet excited state of the guest material, that is, the process of equation (2-1) is the phosphorescence spectrum of the host material and the singlet of the guest material. As long as the absorption spectrum corresponding to the direct transition from the ground state to the triplet excited state is superimposed, it tends to occur as a whole.

(About the energy transfer efficiency of (2-2))
Next, consider the energy transfer process of (2-2). The process of equation (2-2A) is affected by the intersystem crossing efficiency of the guest material. Therefore, in order to increase the luminous efficiency to the utmost limit, the process of equation (2-2B) is considered to be important. In this case, the Dexter type (formula (formula)
Since 2)) is prohibited, only the Felster type (formula (1)) needs to be considered.

Eliminating τ from equations (1) and (3), the energy transfer efficiency Φ _ET has a higher quantum yield φ (because we are discussing energy transfer from a singlet excited state). It can be said that it is good. However, in reality, as more important factors, the emission spectrum of the host molecule (fluorescence spectrum because we are discussing the energy transfer from the singlet excited state) and the absorption spectrum of the guest molecule (directly from the singlet ground state to the triplet excited state). It is also necessary that the overlap with the absorption corresponding to the transition is large (note that it is preferable that the molar absorption coefficient of the guest molecule is also high). This means that the fluorescence spectrum of the host material and the absorption band appearing on the longest wavelength side of the phosphorescent compound, which is the guest material, overlap.

However, it has been very difficult to achieve this in the past. because,
In order to efficiently perform both the process (2-1) and the process (2-2) described above, from the above discussion, not only the phosphorescence spectrum of the host material but also the fluorescence spectrum is the longest wavelength of the guest material. This is because it must be designed to overlap the absorption band on the side. In other words, the host material must be designed so that the fluorescence spectrum of the host material is at a position similar to the phosphorescence spectrum.

However, in general, the S1 level and the T1 level are significantly different (S1 level> T1 level).
The emission wavelengths of fluorescence and phosphorescence are also significantly different (fluorescence emission wavelength <phosphorescence emission wavelength).
For example, in a light emitting device using a phosphorescent compound, it is often used as a host material 4,
4'-di (N-carbazolyl) biphenyl (abbreviation: CBP) has a phosphorescence spectrum near 500 nm, while the fluorescence spectrum is around 400 nm, with a gap of 100 nm. Considering this example as well, it is extremely difficult to design the host material so that the fluorescence spectrum of the host material is located at the same position as the phosphorescence spectrum. Therefore, improving the efficiency of energy transfer from the singlet excited state of the host material to the guest material is very important.

Therefore, one aspect of the present invention provides a useful method capable of overcoming the problem of energy transfer efficiency from the singlet excited state of the host material to the guest material. The specific embodiment will be described below.

(Embodiment 1)
In the present embodiment, a concept and a specific configuration of the light emitting element in constituting the light emitting element, which is one aspect of the present invention, will be described. The light emitting element according to one aspect of the present invention is formed by sandwiching an EL layer including a light emitting layer between a pair of electrodes (anolyde and cathode), and the light emitting layer converts the triplet excitation energy into light emission. Contains at least 1 luminescent substance (guest material), a first organic compound having electron transportability (host material), and a second organic compound having hole transportability (assist material), and is formed on the anode side. It has a first light emitting layer, a second light emitting substance (guest material) that converts triple-term excitation energy into light emission, a third organic compound having electron transport property (host material), and a hole transport property. It has a laminated structure with a second light emitting layer formed by containing at least a second organic compound (assist material).

The first organic compound (host material) contained in the first light emitting layer has the lowest unoccupied molecular orbital level (LUMO level) than the third organic compound (host material) contained in the second light emitting layer. Is high. Accordingly, the excitation energy of the exciplex formed in the first light-emitting layer (E _A)
It can be designed to be larger than the second excitation energy of the exciplex formed in the light-emitting layer (E _B).

Further, the first luminescent substance contained in the first light emitting layer is a substance exhibiting light emission having a shorter wavelength than the second luminescent substance contained in the second light emitting layer.

First, the element structure of the light emitting element, which is an example of the present invention, will be described with reference to FIG. 1 (A).

The element structure shown in FIG. 1A has a light emitting layer 10 between a pair of electrodes (anode 101, cathode 102).
The EL layer 103 including 6 is sandwiched, and the EL layer 103 includes a hole injection layer 104, a hole transport layer 105, and a light emitting layer 106 (106a, 106b) from the anode 101 side.
It has a structure in which an electron transport layer 107, an electron injection layer 108, and the like are sequentially laminated.

Further, as shown in FIG. 1A, the light emitting layer 106 in one aspect of the present invention is a first light emitting substance (guest material) 109a that converts triplet excitation energy into light emission, and a first electron transporting property. An organic compound (host material) 110 and a second organic compound having a hole transporting property (host material)
A first light emitting layer 106a containing at least 111 as an assist material and formed on the anode side.
A second luminescent substance (guest material) 109b that converts triplet excitation energy into light emission, a third organic compound (host material) 112 having electron transportability, and a second organic compound having hole transportability. Second light emitting layer 10 formed to include at least 111 (assist material)
As the first organic compound 110 and the third organic compound 112, which have a structure in which 6b is laminated, an electron transporting material having an electron mobility of ^10-6 cm ^{2 / Vs or more is mainly used, and a second organic compound is used.} As the organic compound 111, a hole transporting material having a hole mobility of ^10-6 cm ^{2 / Vs or more is mainly used.} Further, in the present specification, the first organic compound 110 and the third organic compound 112 are referred to as host materials, and the second organic compound 1
11 will be referred to as an assist material.

Further, the combination of the first organic compound (host material) 110 and the second organic compound (assist material) 111 in the first light emitting layer 106a is a combination forming an excited complex (also referred to as excimlex). It is characterized by being. Further, the emission wavelengths of the excitation complex formed by the first organic compound (host material) 110 and the second organic compound (assist material) 111 are the first organic compound (host material) 110 and the second organic compound. Since it exists on the longer wavelength side than the respective emission wavelengths (fluorescence wavelengths) of the (assist material) 111, the fluorescence spectrum of the first organic compound (host material) 110 and the second organic compound (assist material) The fluorescence spectrum of 111 can be converted into an emission spectrum located on the longer wavelength side.

This also applies to the second light emitting layer 106b. Therefore, the second light emitting layer 10
The combination of the third organic compound (host material) 112 and the second organic compound (assist material) 111 in 6b is characterized in that it is a combination that forms an excited complex (also referred to as excimlex). Further, the emission wavelength of the excitation complex formed by the third organic compound (host material) 112 and the second organic compound (assist material) 111 is such that the third organic compound (host material) 112 and the second organic compound have different emission wavelengths. (Assist material) 1
Since it exists on the longer wavelength side than each emission wavelength (fluorescence wavelength) of 11, the fluorescence spectrum of the third organic compound (host material) 112 and the fluorescence of the second organic compound (assist material) 111 The spectrum can be converted into an emission spectrum located on the longer wavelength side.

In the above configuration, the triplet excitation energy level (T1 level) of each of the first organic compound (host material) 110 and the second organic compound (assist material) 111 emits the triplet excitation energy. It is preferably higher than the T1 level of the first luminescent substance (guest material) 109a to be converted into. When the T1 level of the first organic compound 110 (or the second organic compound 111) is lower than the T1 level of the first luminescent substance (guest material) 109a, the first luminescent substance that contributes to luminescence. This is because the triple-term excitation energy of the (guest material) 109a is extinguished (quenched) by the first organic compound 110 (or the second organic compound 111), resulting in a decrease in light emission efficiency.

Similarly, each triplet excitation energy level (T1 level) of the third organic compound (host material) 112 and the second organic compound (assist material) 111 converts the triplet excitation energy into light emission. It is preferably higher than the T1 level of the second luminescent substance (guest material) 109b. When the T1 level of the third organic compound 112 (or the second organic compound 111) is lower than the T1 level of the second luminescent substance (guest material) 109b, the second luminescent substance contributes to light emission. (Guest material) The triple-term excitation energy of 109b is applied to the third organic compound 112 (
Alternatively, the second organic compound 111) is quenched, resulting in a decrease in luminous efficiency.

Further, the ratio of the first organic compound (host material) 110 and the second organic compound (assist material) 111 contained in the first light emitting layer 106a constituting the light emitting layer 106, and the second light emitting layer 106 constituting the light emitting layer 106. Regarding the ratio of the third organic compound (host material) 112 and the second organic compound (assist material) 111 contained in the light emitting layer 106b of 2, either may be larger, and in the present invention, both cases are included. I will do it.

The light emitting layer 106 having the above structure (first light emitting layer 106a and second light emitting layer 106b).
The first organic compound (host material) 110 and the second organic compound (assist material) in
FIG. 1B shows a band diagram illustrating the energy relationship between 111 and the third organic compound (host material) 112.

In the first light-emitting layer 106a, as shown in FIG. 1 (B), the first organic compound (host material) 110 and the excitation energy _{(E A} exciplex formed by the second organic compound (assist material) 111 ) Indicates the HOMO level of the second organic compound (assist material) 111, and
It is determined by the LUMO level of the first organic compound (host material) 110. Further, in the second light-emitting layer 106b, the third organic compound (host material) 112 and the second organic compound excitation energy of the exciplex formed by (assist material) 111 _{(E B),} the second organic The HOMO level of compound (assist material) 111 and the third organic compound (host material) 1
Determined by 12 LUMO levels. The first organic compound (host material) 110 contained in the first light emitting layer 106a has a higher LUMO level than the third organic compound (host material) 112 contained in the second light emitting layer 106b. from it can be designed to be larger than the first excitation energy of the exciplex which excitation energy of the exciplex formed in the light-emitting layer 106a of the (E _a) is formed in the second light-emitting layer 106b (E _B) I understand.

In addition, since the excitation complex formed by the first light emitting layer 106a has a higher excitation energy than the excitation complex formed by the second light emitting layer 106b by adopting the above-mentioned element structure, the first First, which converts the triplet excitation energy contained in the light emitting layer 106a into light emission.
As the luminescent substance (guest material) 109a, a substance that emits light having a shorter wavelength than that of the second luminescent substance (guest material) 109b that converts the triplet excitation energy contained in the second light emitting layer 106b into light emission is used. Thereby, at the same time, the first light emitting layer 106a and the second light emitting layer 10
Light emission from 6b can be obtained. Further, of the excitation energies of the excitation complex formed in the first light emitting layer 106a, a second energy that cannot contribute to light emission is converted into light emission by converting the triplet excitation energy in the second light emitting layer 106b into light emission. Since it can be used as excitation energy for the light emitting substance (guest material) 109b, the light emission efficiency in the light emitting element can be further improved.

The light emitting element described in the present embodiment has a configuration in which the light emitting layer 106 (first light emitting layer 106a, second light emitting layer 106b) forms an excitation complex, respectively, but the first organic compound (host material). ) 110, the fluorescence spectrum of the third organic compound (host material) 112, or the fluorescence spectrum of the second organic compound (assist material) 111 can be converted into an emission spectrum located on the longer wavelength side. That is possible, as shown in FIG. 2, the first organic compound 110, the second organic compound 111, or the third organic compound 112.
Luminescent substance 109 (first luminescent substance (guest material) 109a, and second luminescent substance (guest material) 109, even if the fluorescence spectrum of the above converts triplet excitation energy into light emission.
The luminescent material 109 (first luminescent material (guest material) 109a, and the second luminescent material 109a, which is located on the short wavelength side as compared with the absorption band located on the longest wavelength side of b) and converts the triplet excitation energy into light emission. Even if there is no overlap with the absorption band located on the longest wavelength side of the luminescent material (guest material) 109b), it means that the overlap can be increased by forming an excited complex. This makes it possible to increase the energy transfer efficiency of the above-mentioned equation (2-2B).

Furthermore, it is considered that the difference between the singlet excitation energy and the triplet excitation energy of the excitation complex is extremely small. In other words, the emission spectra from the singlet state and the emission spectra from the triplet state of the excited complex are very close to each other. Therefore, as described above, the absorption band located on the longest wavelength side of the luminescent substance 109 that converts the luminescence spectrum of the excited complex (generally, the luminescence spectrum from the single-term state of the excited complex) into luminescence. When designed to superimpose on, the emission spectrum from the triplet state of the excited complex (not observed at room temperature and often not observed at low temperature) is also the longest wavelength of the luminescent material 109 that converts the triplet excitation energy into emission. It will overlap the absorption band located on the side. That is, not only the energy transfer from the singlet excited state ((2-2)) but also the efficiency of the energy transfer from the triplet excited state ((2-1)) is increased, and as a result, the singlet / triplet Energy from both excited states can be efficiently converted to light emission.

Therefore, whether or not the excited complex actually has such characteristics is verified below using molecular orbital calculation. In general, the combination of a heteroaromatic compound and an aromatic amine is the lowest empty molecular orbital (LUMO: Lowest Unoccuped) of the aromatic amine.
The LUMO level (property that electrons can easily enter) of the complex aromatic compound deeper than the Molecular Orbital level and the highest occupied orbital (HOMO: High) of the complex aromatic compound.
Excited complexes are often formed due to the influence of the HOMO level (property of easily entering holes) of aromatic amines, which are shallower than the est Occupied Molecular Orbital) level. Therefore, as a model of the first organic compound 110 (or the third organic compound 112) in one embodiment of the present invention, dibenzo [f, h] quinoxalin having a typical skeleton constituting the LUMO level of the heteroaromatic compound (Abbreviation: DBq) is used, and triphenylamine (abbreviation: TPA) having a typical skeleton constituting the HOMO level of aromatic amine is used as a model of the second organic compound 111 in one embodiment of the present invention. Was combined and calculated.

First, the time-dependent density functional theory (TD) is used to determine the optimum molecular structure and excitation energy of one DBq (abbreviation) molecule and one TPA (abbreviation) molecule in the lowest excited singlet state (S1) and the lowest excited triplet state (T1). -DFT) was used for calculation. Furthermore, DBq (abbreviation) and TPA (abbreviation)
The excitation energies were also calculated for the dimer of.

The total energy of DFT (density general function method) is expressed by the sum of potential energy, electron-electron electrostatic energy, electron kinetic energy, and exchange correlation energy including all complex electron-electron interactions. 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), so that the calculation is fast and highly accurate. Here, the weight of each parameter related to exchange and correlation energy is defined by using B3LYP which is a mixed functional.

In addition, as a basis function, 6-311 (a basis function of a triple split value basis set using three abbreviated functions for each valence orbital) was applied to all atoms.

According to the above-mentioned basis function, for example, in the case of a hydrogen atom, the orbitals of 1s to 3s are considered, and in the case of a carbon atom, the orbitals of 1s to 4s and 2p to 4p are considered. Furthermore, in order to improve the calculation accuracy, as a polarization basis set, a p function is used for hydrogen atoms, and d is used for other than hydrogen atoms.
Added a function.

Gaussian 09 was used as the quantum chemistry calculation program. The calculation was performed using a high performance computer (SGI, Altix4700).

First, one molecule of DBq (abbreviation), one molecule of TPA (abbreviation), and DBq (abbreviation) and TPA (
The HOMO level and LUMO level were calculated for the dimer of (abbreviation). HOMO level and L
The UMO level is shown in FIG. 3, and the distribution of the HOMO level and the LUMO level is shown in FIG. 4, respectively.

FIG. 4 (A1) shows the distribution of the LUMO level of one molecule of DBq (abbreviation), FIG. 4 (A2) shows the distribution of the HOMO level of one molecule of DBq (abbreviation), and FIG. 4 (B1) shows the distribution. , TPA (abbreviation)
The distribution of the LUMO level of one molecule is shown, FIG. 4 (abbreviation) (B2) shows the distribution of the HOMO level of one molecule of TPA (abbreviation), and FIG. 4 (C1) shows DBq (abbreviation) and TPA (abbreviation). The distribution of LUMO levels of the dimer of (abbreviation) is shown, and FIG. 4 (C2) shows the distribution of HOMO levels of the dimer of DBq (abbreviation) and TPA (abbreviation).

As shown in FIG. 3, the dimer of DBq (abbreviation) and TPA (abbreviation) is L of TPA (abbreviation).
The LUMO level (-1.99eV) of DBq (abbreviation), which is deeper (lower) than the UMO level,
Shallow (high) TPA (abbreviation) HOMO level (-) compared to DBq (abbreviation) HOMO level
It is suggested that the influence of 5.21eV) forms an excited complex of DBq (abbreviation) and TPA (abbreviation). As can be seen from FIG. 4, the LUMO levels of the dimers of DBq (abbreviation) and TPA (abbreviation) are distributed on the DBq (abbreviation) side, and the HOMO levels are distributed on the TPA (abbreviation) side.

Next, the excitation energies obtained from the optimum molecular structure at the S1 level and the T1 level of one DBq (abbreviation) molecule are shown. Here, the excitation energies of the S1 level and the T1 level correspond to the wavelengths of fluorescence and phosphorescence emitted by one molecule of DBq (abbreviation), respectively. The excitation energy of the S1 level of one DBq (abbreviation) molecule was 3.294 eV, and the fluorescence wavelength was 376.4 nm.
The excitation energy of the T1 level of one molecule of DBq (abbreviation) was 2.460 eV, and the phosphorescence wavelength was 504.1 nm.

Further, the excitation energies obtained from the optimum molecular structure at the S1 level and the T1 level of one TPA (abbreviation) molecule are shown. Here, the excitation energies of the S1 level and the T1 level correspond to the wavelengths of fluorescence and phosphorescence emitted by one TPA (abbreviation) molecule, respectively. The excitation energy of the S1 level of one TPA (abbreviation) molecule was 3.508 eV, and the fluorescence wavelength was 353.4 nm.
The excitation energy of the T1 level of one TPA (abbreviation) molecule was 2.610 eV, and the phosphorescence wavelength was 474.7 nm.

Further, the excitation energies obtained from the optimum molecular structures at the S1 and T1 levels of the DBq (abbreviation) and TPA (abbreviation) dimers are shown. The excitation energies of the S1 and T1 levels are
It corresponds to the wavelengths of fluorescence and phosphorescence emitted by the dimers of DBq (abbreviation) and TPA (abbreviation), respectively. The excitation energy of the S1 level of the dimer of DBq (abbreviation) and TPA (abbreviation) is 2.036.
It was eV and the fluorescence wavelength was 609.1 nm. The excitation energy of the T1 level of the dimer of DBq (abbreviation) and TPA (abbreviation) is 2.030 eV, and the phosphorescence wavelength is 61.
It was 0.0 nm.

From the above, in both DBq (abbreviation) one molecule and TPA (abbreviation) one molecule,
It can be seen that the phosphorescence wavelength has a long wavelength shift of nearly 100 nm. This is the CBP mentioned above
It has the same tendency as (abbreviation) (actual measurement value), and is a result that supports the validity of the calculation.

On the other hand, it can be seen that the fluorescence wavelength of the dimer of DBq (abbreviation) and TPA (abbreviation) exists on the longer wavelength side than the fluorescence wavelength of one molecule of DBq (abbreviation) or one molecule of TPA (abbreviation). In addition, the difference between the fluorescence wavelength and the phosphorescence wavelength of the dimer of DBq (abbreviation) and TPA (abbreviation) is only 0.9n.
It is m, and it can be seen that the wavelengths are almost the same.

From this result, it can be said that the singlet excitation energy and the triplet excitation energy of the excitation complex are almost the same energy. Therefore, as mentioned above, the excited complex is in its singlet state,
From both the triplet state and the triplet state, it was suggested that the energy can be efficiently transferred to the luminescent substance (the guest material containing the first luminescent substance and the second luminescent substance described above) that converts the triplet excited energy into luminescence. ..

As described above, the light emitting element according to one aspect of the present invention is a luminescent substance that converts the emission spectrum of the excitation complex formed in the light emitting layer and the triplet excitation energy into light emission (the first light emitting substance and the second light emitting substance described above). Utilizing the overlap with the absorption spectrum of the guest material (guest material containing luminescent material),
Since energy transfer is performed, energy transfer efficiency is high. Therefore, it is possible to realize a light emitting device having high external quantum efficiency.

Moreover, since the excited complex exists only in the excited state, there is no ground state that can absorb energy. Therefore, a luminescent substance (guest material) that converts triplet excitation energy into luminescence.
A phenomenon in which a luminescent substance (guest material) that converts triplet excited energy into light emission due to energy transfer from the singlet excited state and triplet excited state to light emission is deactivated (that is, the light emission efficiency is impaired). Is not considered to occur in principle. This is also one of the reasons why the external quantum efficiency can be increased.

The above-mentioned excited complex is formed by the interaction between different molecules in the excited state. Further, it is generally known that the excited complex is easily formed between a material having a relatively deep LUMO level and a material having a shallow HOMO level.

The emission wavelength of the excited complex depends on the energy difference between the HOMO level and the LUMO level. As a general tendency, when the energy difference is large, the emission wavelength becomes short, and when the energy difference is small, the emission wavelength becomes long.

Therefore, the HOMO level and LUMO level of the first organic compound (host material) 110, the second organic compound (assist material) 111, and the third organic compound (host material) 112 in the present embodiment are shown in FIG. As shown in 1 (B), they are different from each other. Specifically, the HOMO level of the first organic compound 110 and the HOMO level of the third organic compound 112 <HOMO level of the second organic compound 111 <LUMO level of the third organic compound 112 <th. The energy levels differ in the order of the LUMO level of the organic compound 110 of 1 <the LUMO level of the second organic compound 111.

Then, in each light emitting layer, two organic compounds (the first organic compound 110 and the second organic compound 111 in the first light emitting layer 106a, and the third organic compound 112 in the second light emitting layer 106b) are used. When the excited complex is formed by the second organic compound 111), the HOMO level of the excited complex in the first light emitting layer 106a and the second light emitting layer 106b is set to the second organic compound (assist material) 111. The LUMO level of the excited complex in the first light emitting layer 106a is derived from the first organic compound (host material) 110, and the second light emitting layer 1 is derived.
The LUMO level of the excited complex at 06b is L of the third organic compound (host material) 112.
Derived from the UMO level. Accordingly, the excitation energy of the exciplex in the first light-emitting layer 106a _{(E A)} is larger than the excitation energy of the exciplex in the second light-emitting layer 106b _{(E B).} That is, as the first luminescent material 109a that converts the triplet excitation energy contained in the first light emitting layer into light emission, the second luminescent material 109b that converts the triplet excitation energy contained in the second light emitting layer into light emission. By using a substance that emits light having a shorter wavelength than that of the above, it is possible to form a light emitting element having high light emission efficiency. In addition, light emitting materials having different emission wavelengths can be efficiently emitted at the same time.

The following two processes can be considered as the process of forming the excited complex in one aspect of the present invention.

The first formation process is a formation process of forming an excited complex from a state in which the second organic compound (assist material) has a carrier (specifically, a cation).

Generally, when electrons and holes (holes) are recombined in the host material, the excitation energy is transferred from the excited state host material to the guest material, and the guest material reaches the excited state and emits light. Before the excitation energy is transferred to the guest material, the host material itself emits light, or the excitation energy becomes heat energy, so that a part of the excitation energy is deactivated. In particular, when the host material is in a singlet excited state, energy transfer is unlikely to occur as described in (2-2). Such deactivation of excitation energy is one of the factors leading to a decrease in the life of the light emitting device.

However, in one aspect of the invention, the first organic compound (or the third organic compound) (
The first organic compound (or the third organic compound) (host material) in order to form an excited complex from the state (cation or anion) in which the host material) and the second organic compound (assist material) have carriers. The formation of single-term excitons can be suppressed. That is, there may be a process of directly forming an excited complex without forming singlet excitons. Thereby, the deactivation of the singlet excitation energy can also be suppressed. Therefore, it is possible to realize a light emitting element having a long life.

For example, the first organic compound (or the third organic compound) is an electron-trapping compound (with a deep LUMO level) having a property of easily capturing electrons (carriers) among electron-transporting materials. When the organic compound 2 is a hole-trapping compound having a property of easily capturing holes (carriers) among the hole-transporting materials (shallow HOMO level), the first organic compound (or A direct excitation complex is formed from the anion of the third organic compound) and the cation of the second organic compound. The excited complex formed in such a process is particularly called an electroplex. In this way, a luminescent substance (guest material) that suppresses the generation of the singlet excited state of the first organic compound (or the third organic compound) (host material) and converts the triplet excited energy from the electroplex into light emission. By performing energy transfer to, a light emitting element having high light emitting efficiency can be obtained. In this case, the generation of the triplet excited state of the first organic compound (or the third organic compound) (host material) is similarly suppressed, and the direct excited complex is formed. Therefore, the triplet excited from the excited complex. It is thought that energy is transferred to a luminescent substance (guest material) that converts energy into luminescence.

The second formation process is after any one of the first organic compound (host material), the second organic compound (assist material), or the third organic compound (host material) forms a single-term excitator. , Is an elementary process that interacts with the other of the ground states to form an excited complex. Unlike Electroplex, in this case, once the first organic compound (host material) and the second organic compound (
The singlet excited state of the assist material) or the third organic compound (host material) is generated, but since this is rapidly converted into an excited complex, the deactivation of the singlet excited energy is also suppressed. Can be done. Therefore, it is possible to suppress the deactivation of the excitation energy of the first organic compound (host material), the second organic compound (assist material), or the third organic compound (host material). In this case, it is considered that the triplet excited state of the host material is also rapidly converted into the excited complex, and the energy is transferred from the excited complex to the luminescent substance (guest material) that converts the triplet excited energy into light emission.

The first organic compound (or the third organic compound) (host material) is an electron trapping compound, while the second organic compound (assisting material) is a whole trapping compound, and these compounds. When the difference in HOMO level and the difference in LUMO level are large (specifically, the difference is 0.3 eV or more), the electron is selectively the first organic compound (or the third organic compound) (host material). ), And the hole selectively enters the second organic compound (assist material).
In this case, it is considered that the process of forming the electroplex is prioritized over the process of forming the excited complex via the singlet excitons.

A luminescent substance that converts the emission spectrum of the excitation complex and triplet excitation energy into emission (
In order to sufficiently overlap the absorption spectra of the guest material), the difference between the energy value of the peak of the emission spectrum and the energy value of the peak of the absorption band on the lowest energy side of the absorption spectrum must be within 0.3 eV. preferable. It is more preferably within 0.2 eV, and most preferably within 0.1 eV.

Further, in the light emitting element according to one aspect of the present invention, the excitation energy of the excitation complex is sufficiently transferred to a luminescent substance (guest material) that converts triple-term excitation energy into light emission, and the light emission from the excitation complex is substantially. It is preferable not to be observed. Therefore, it is preferable that the luminescent substance that transfers energy to a luminescent substance that converts triplet excitation energy into luminescence via an excitation complex and converts the triplet excitation energy into luminescence emits light. The luminescent substance that converts triplet excitation energy into light emission is preferably a phosphorescent compound (organic metal complex or the like), a thermal activated delayed fluorescent (TADF) material, or the like.

Further, in the first light emitting layer 106a of the light emitting element according to one aspect of the present invention, triple term excitation is performed on the first organic compound (the third organic compound in the case of the second light emitting layer 106b) (host material). When a luminescent substance that converts energy into luminescence is used, a first organic compound (second luminescent layer 10) is used.
In the case of 6b, the third organic compound) (host material) itself tends to emit light, and energy is less likely to be transferred to a luminescent substance (guest material) that converts triplet excitation energy into light emission.
In this case, the first organic compound (the third organic compound in the case of the second light emitting layer 106b) may emit light efficiently, but the host material has a problem of concentration quenching, so that high luminous efficiency is achieved. It is difficult to achieve. Therefore, at least one of the first organic compound (third organic compound in the case of the second light emitting layer 106b) (host material) and the second organic compound (assist material) is a fluorescent compound (that is, a single term). It is effective when the compound is liable to emit light or heat deactivate from the excited state). Therefore, at least one of the first organic compound (the third organic compound in the case of the second light emitting layer 106b) (host material) and the second organic compound (assist material) is a fluorescent compound and is an excitation complex. Is preferably used as a medium for energy transfer.

The configuration shown in this embodiment can be used in combination with the configurations shown in other embodiments as appropriate.

(Embodiment 2)
In the present embodiment, an example of a light emitting device, which is one aspect of the present invention, will be described with reference to FIG.

The light emitting element shown in the present embodiment has a pair of electrodes (first electrode (anode) 2) as shown in FIG.
An EL layer 203 including a light emitting layer 206 is sandwiched between 01 and a second electrode (cathode) 202), and the EL layer 203 has a laminated structure of a first light emitting layer 206a and a second light emitting layer 206b. In addition to the light emitting layer 206, the hole (or hole) injection layer 204, the hole (or hole) transport layer 205, the electron transport layer 207, the electron injection layer 208, and the like are included.

The light emitting layer 206 shown in the present embodiment includes a first light emitting layer 206a and a second light emitting layer 20.
Although it has a laminated structure with 6b, the first light emitting layer 206a of the light emitting layer 206 contains a first light emitting substance (guest material) 209a that converts triplet excitation energy into light emission, and has electron transportability. The organic compound (host material) 210 of 1 and the second organic compound (assist material) 211 having a hole transport property are contained, and the second light emitting layer 206b converts triplet excitation energy into light emission. A second luminescent substance (guest material) 209b, a third organic compound having electron transportability (host material) 212, and a second organic compound having hole transportability ()
Assist material) 211 is included.

The first organic compound (host material) contained in the first light emitting layer has the lowest unoccupied molecular orbital level (LUMO level) than the third organic compound (host material) contained in the second light emitting layer. Is high. Accordingly, the excitation energy of the exciplex formed in the first light-emitting layer (E _A)
It can be designed to be larger than the second excitation energy of the exciplex formed in the light-emitting layer (E _B).

In the light emitting layer 206 (first light emitting layer 206a and second light emitting layer 206b),
In the case of the first light emitting layer 206a, the first light emitting substance 209a that converts the triplet excitation energy into light emission is contained in the first organic compound (host material) 210 and the second organic compound (assist material) 211. In the case of the second light emitting layer 206b, the second light emitting substance 209b which is dispersed and converts the triplet excitation energy into light emission is used as the third organic compound (host material) 212 and the second organic compound (assist material). ) The light emitting layer 20 is dispersed in 211.
6 (first light emitting layer 206a and second light emitting layer 206b) can be suppressed from crystallization. Further, it is possible to suppress the concentration quenching due to the high concentration of the luminescent substance 209 (209a, 209b) and increase the luminous efficiency of the light emitting element.

Further, the first organic compound 210, the second organic compound 211, and the third organic compound 2
The triplet excitation energy level (T1 level) of each of the twelve is preferably higher than the T1 level of the luminescent substance 209 (209a, 209b) that converts the triplet excitation energy into light emission. The first organic compound 210, the second organic compound 211, and the third organic compound 21
Luminescent substance 209 (209a, 20) in which the T1 level of 2 converts triplet excitation energy into luminescence.
When it is lower than the T1 level of 9b), the triplet excitation energy of the luminescent substance 209 (209a, 209b) that converts the triplet excitation energy contributing to light emission into light emission is changed to the first organic compound 21.
This is because 0 (or the second organic compound 211 or the third organic compound 212) is quenched, resulting in a decrease in luminous efficiency.

In the present embodiment, in the light emitting layer 206, in the first light emitting layer 206a, when the carriers (electrons and holes) injected from both electrodes are recombined, the first organic compound 210
And the second organic compound 211 form an excited complex (exciplex), and in the second light emitting layer 206b, an excited complex is formed from the third organic compound 212 and the second organic compound 211. Thereby, the fluorescence spectrum of the first organic compound 210 and the fluorescence spectrum of the second organic compound 211 in the first light emitting layer 206a can be converted into the emission spectrum of the excitation complex located on the longer wavelength side. , The fluorescence spectrum of the third organic compound 212 in the second light emitting layer 206b, and the fluorescence spectrum of the second organic compound 211 are
It can be converted into the emission spectrum of the excitation complex located on the longer wavelength side. Therefore, in order to maximize the energy transfer from the singlet excited state, the overlap between the emission spectrum of the excitation complex and the absorption spectrum of the luminescent substance (guest material) 209 that converts the triplet excitation energy into emission is increased. In the first light emitting layer 206a, the first organic compound 210 and the second organic compound 211 are selected, and in the second light emitting layer 206b, the third organic compound 212 and the second organic compound 211 are selected. And. That is, here, it is considered that energy transfer occurs not from the host material but from the excited complex even in the triplet excited state.

A luminescent substance 209 that converts triplet excitation energy into luminescence (first luminescent substance 20).
9a, the second luminous substance 209b) is preferably a phosphorescent compound (organic metal complex or the like), a thermally activated delayed fluorescent (TADF) material, or the like. Further, it is preferable to use an electron transporting material as the first organic compound (host material) 210 and the third organic compound (host material) 212. Further, as the second organic compound (assist material) 211,
It is preferable to use a hole transporting material.

Examples of the organometallic complex include 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'-bistrifluoromethylphenyl) pyridinato-N, C ^2' ] iridium (III) picolinate (abbreviation: Ir (CF ₃ ppy) ₂ (pic)), bis [2- (4)
', 6'-Difluorophenyl) iridium-N, C ^2' ] Iridium (III) Acetylacetonate (abbreviation: FIracac), Tris (2-phenylpyridinato) iridium (III) (abbreviation: Ir (ppy) ₃ ), Bis (2-phenylpyridinato) iridium (III) acetylacetonate (abbreviation: Ir (ppy) ₂ (acac)), bis (benzo [h] quinolinato) iridium (III) acetylacetonate (abbreviation: Ir) (Bzq
) ₂ (acac)), bis (2,4-diphenyl-1,3-oxazolato-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-phenylbenzothiazolato-N, C ^2' ) Iridium (III) Acetylacetonate (abbreviation: Ir (bt) ₂ (acac)), Bis [2- (2'-benzo [4,)
5-α] thienyl) pyridinato-N, C ^3' ] iridium (III) acetylacetonate (abbreviation: Ir (btp) ₂ (acac)), bis (1-phenylisoquinolinato-N,
C ^2' ) Iridium (III) Acetylacetonate (abbreviation: Ir (piq) ₂ (aca)
c)), (Acetylacetonato) bis [2,3-bis (4-fluorophenyl) quinoxalinato] iridium (III) (abbreviation: Ir (Fdpq) ₂ (acac)), (acetylacetonato) bis (2, 3,5-Triphenylpyrazinato) Iridium (III) (abbreviation: Ir (tppr) ₂ (acac)), 2,3,7,8,12,13,17,18-octaethyl-21H, 23H-porphyrin Platinum (II) (abbreviation: PtOEP), Tris (
Acetylacetone) (monophenanthroline) Terbium (III) (abbreviation: Tb (a)
cac) ₃ (Phen)), Tris (1,3-diphenyl-1,3-propanedionat)
(Monophenanthroline) Europium (III) (abbreviation: Eu (DBM) ₃ (Phen)
)), Tris [1- (2-tenoyl) -3,3,3-trifluoroacetonato] (monophenanthroline) Europium (III) (abbreviation: Eu (TTA) ₃ (Phen)) and the like.

Further, as the electron transporting material, a π-deficient heteroaromatic compound such as a nitrogen-containing heteroaromatic compound is preferable, and for example, 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: 2mDBTBPDBq-II), 2- [4- (3,6-diphenyl-9H-)
Carbazole-9-yl) Phenyl] dibenzo [f, h] quinoxaline (abbreviation: 2CzP)
DBq-III), 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: 6mDB)
Examples thereof include quinoxaline or dibenzoquinoxaline derivatives such as TPDBq-II).

Further, as the hole transporting material, a π-excessive heteroaromatic compound (for example, a carbazole derivative or an indole derivative) or an aromatic amine compound is preferable, and for example, 4-.
Phenyl-4'-(9-phenyl-9H-carbazole-3-yl) triphenylamine (abbreviation: PCBA1BP), 4,4'-di (1-naphthyl) -4''-(9-phenyl-)
9H-carbazole-3-yl) triphenylamine (abbreviation: PCBNBB), 3- [N
-(1-naphthyl) -N- (9-phenylcarbazole-3-yl) amino] -9-phenylcarbazole (abbreviation: PCzPCN1), 4,4', 4''-tris [N- (1-naphthyl) -N-Phenylamino] Triphenylamine (abbreviation: 1'-TNATA), 2,
7-Bis [N- (4-diphenylaminophenyl) -N-Phenylamino] -Spiro-9
, 9'-bifluorene (abbreviation: DPA2SF), N, N'-bis (9-phenylcarbazole-3-yl) -N, N'-diphenylbenzene-1,3-diamine (abbreviation: PCA2)
B), N- (9,9-dimethyl-2-diphenylamino-9H-fluorene-7-yl)
Diphenylamine (abbreviation: DPNF), N, N', N''-triphenyl-N, N', N
'' -Tris (9-phenylcarbazole-3-yl) benzene-1,3,5-triamine (abbreviation: PCA3B), 2- [N- (9-phenylcarbazole-3-yl) -N-phenylamino] Spiro-9,9'-bifluorene (abbreviation: PCASF), 2- [N- (4)
-Diphenylaminophenyl) -N-Phenylamino] Spiro-9,9'-bifluorene (abbreviation: DPASF), N, N'-bis [4- (carbazole-9-yl) phenyl]-
N, N'-diphenyl-9,9-dimethylfluorene-2,7-diamine (abbreviation: YGA)
2F), 4,4'-bis [N- (3-methylphenyl) -N-phenylamino] biphenyl (abbreviation: TPD), 4,4'-bis [N- (4-diphenylaminophenyl) -N- Phenylamino] Biphenyl (abbreviation: DPAB), N- (9,9-dimethyl-9H-fluorene-2-yl) -N- {9,9-dimethyl-2- [N'-phenyl-N'-(9) , 9-
Dimethyl-9H-fluorene-2-yl) amino] -9H-fluorene-7-yl} phenylamine (abbreviation: DFLADFL), 3- [N- (9-phenylcarbazole-3-yl) -N-phenylamino] -9-Phenylcarbazole (abbreviation: PCzPCA1), 3
-[N- (4-Diphenylaminophenyl) -N-Phenylamino] -9-Phenylcarbazole (abbreviation: PCzDPA1), 3,6-bis [N- (4-diphenylaminophenyl) -N-Phenylamino]- 9-Phenylcarbazole (abbreviation: PCzDPA2), 4
, 4'-Bis (N- {4- [N'-(3-Methylphenyl) -N'-Phenylamino] phenyl} -N-Phenylamino) Biphenyl (abbreviation: DNTPD), 3,6-Bis [N −
(4-Diphenylaminophenyl) -N- (1-naphthyl) amino] -9-Phenylcarbazole (abbreviation: PCzTPN2), 3,6-bis [N- (9-phenylcarbazole-)
3-Il) -N-Phenylamino] -9-Phenylcarbazole (abbreviation: PCzPCA2)
).

However, a luminescent substance (guest material) 209 that converts the above-mentioned triplet excitation energy into light emission.
(First luminescent substance 209a, second luminescent substance 209b), first organic compound (host material) 210, second organic compound (assist material) 211, and third organic compound (host material). The materials that can be used for each of the 212 are not limited to these.
A combination capable of forming an excited complex, wherein the emission spectrum of the excitation complex is a luminescent substance (guest material) 209 (first luminescent substance 209a or second luminescent substance 209b) that converts triple-term excitation energy into luminescence. Luminescent substance (guest material) 209 (first) that overlaps with the absorption spectrum and the peak of the emission spectrum of the excitation complex converts the triplet excitation energy into emission.
The wavelength may be longer than the peak of the absorption spectrum of the luminescent substance 209a or the second luminescent substance 209b).

Further, when an electron transporting material is used for the first organic compound 210 and a hole transporting material is used for the second organic compound 211, the carrier balance can be controlled by the mixing ratio thereof. Specifically, the first organic compound 210: the second organic compound 211 = 1: 9.
It is preferably in the range of ~ 9: 1.

A specific example for manufacturing the light emitting device shown in the present embodiment will be described below.

Metals, alloys, electrically conductive compounds, mixtures thereof, and the like can be used for the first electrode (anode) 201 and the second electrode (cathode) 202. Specifically, indium-tin oxide (ITO: Indium Tin Oxide), indium-tin oxide containing silicon or silicon oxide, indium-zinc oxide-zinc oxide (Indium Zi).
nc Oxide), indium oxide containing tungsten oxide and zinc oxide, gold (A)
u), platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), titanium ( In addition to Ti), elements belonging to Group 1 or Group 2 of the Periodic Table of the Elements, that is, lithium (L)
Alkali metals such as i) and cesium (Cs), and magnesium (Mg) and calcium (
Alkaline earth metals such as Ca) and strontium (Sr), and alloys containing them (Mg).
Rare earth metals such as Ag, AlLi), europium (Eu), ytterbium (Yb), alloys containing these, graphene and the like can be used. The first electrode (anode) 201 and the second electrode (cathode) 202 can be formed by, for example, a sputtering method, a vapor deposition method (including a vacuum vapor deposition method), or the like.

Examples of the highly hole-transporting substance used for the hole injection layer 204 and the hole transport layer 205 include 4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (abbreviation: NPB). Or α-NPD) or N, N'-bis (3-methylphenyl) -N, N'-diphenyl- [1,1'-biphenyl] -4,4'-diamine (abbreviation: TPD), 4,4 ',,
4''-Tris (carbazole-9-yl) triphenylamine (abbreviation: TCTA), 4
, 4', 4''-Tris (N, N-diphenylamino) Triphenylamine (abbreviation: TD)
ATA), 4,4', 4''-tris [N- (3-methylphenyl) -N-phenylamino] triphenylamine (abbreviation: MTDATA), 4,4'-bis [N- (spiro-9) ， ，
9'-Bifluoren-2-yl) -N-Phenylamino] Biphenyl (abbreviation: BSPB)
Aromatic amine compounds such as 3- [N- (9-phenylcarbazole-3-yl) -N-
Phenylamino] -9-Phenylcarbazole (abbreviation: PCzPCA1), 3,6-bis [N- (9-phenylcarbazole-3-yl) -N-phenylamino] -9-phenylcarbazole (abbreviation: PCzPCA2), 3 -[N- (1-naphthyl) -N- (9-phenylcarbazole-3-yl) amino] -9-Phenylcarbazole (abbreviation: PCzPC)
N1) and the like can be mentioned. In addition, 4,4'-di (N-carbazolyl) biphenyl (abbreviation: abbreviation:)
CBP), 1,3,5-tris [4- (N-carbazolyl) phenyl] benzene (abbreviation:
TCPB), carbazole derivatives such as 9- [4- (10-phenyl-9-anthrasenyl) phenyl] -9H-carbazole (abbreviation: CzPA), and the like can be used. The substances described here are mainly substances having a hole mobility of ^10-6 cm ^{2 / Vs or more.} However, any substance other than these may be used as long as it is a substance having a higher hole transport property than electrons.

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

Examples of the acceptor substance that can be used for the hole injection layer 204 include transition metal oxides and oxides of metals belonging to Groups 4 to 8 in the Periodic Table of the Elements. Specifically, molybdenum oxide is particularly preferable.

The light emitting layer 206 (206a, 206b) is as described above, and the first light emitting layer 206a
Has at least a first luminescent material 209a, a first organic compound (host material) 210, and a second organic compound (assist material) 211, and the second light emitting layer 206b has a second luminescent material. It is formed with at least the substance 209b, the third organic compound (host material) 212, and the second organic compound (assist material) 211.

The electron transport layer 207 is a layer containing a substance having a high electron transport property. The electron transport layer 207 has
Alq ₃ , Tris (4-methyl-8-quinolinolat) aluminum (abbreviation: Almq ₃ )
, Bis (10-hydroxybenzo [h] quinolinato) beryllium (abbreviation: BeBq ₂ ),
Metal complexes such as BAlq, Zn (BOX) ₂ , bis [2- (2-hydroxyphenyl) benzothiazolato] zinc (abbreviation: Zn (BTZ) ₂ ) can be used. Also, 2- (
4-Biphenylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole (abbreviation: PBD), 1,3-bis [5- (p-tert-butylphenyl) -1,
3,4-oxadiazole-2-yl] benzene (abbreviation: OXD-7), 3- (4-te
rt-Butylphenyl) -4-phenyl-5- (4-biphenylyl) -1,2,4-triazole (abbreviation: TAZ), 3- (4-tert-butylphenyl) -4- (4-ethylphenyl) -5- (4-biphenylyl) -1,2,4-triazole (abbreviation: p-EtT)
AZ), Basophenanthroline (abbreviation: BPhen), Basocuproin (abbreviation: BCP)
), 4,4'-Bis (5-methylbenzoxazole-2-yl) stilbene (abbreviation: B)
Heteroaromatic compounds such as zOs) 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) A polymer compound such as 6'-diyl)] (abbreviation: PF-BPy) can also be used. The substances described here are mainly substances having electron mobilities of ^10-6 cm ^{2 / Vs or more.} A substance other than the above may be used as the electron transport layer 207 as long as it is a substance having a higher electron transport property than holes.

Further, the electron transport layer 207 may be not only a single layer but also a layer in which two or more layers made of the above substances are laminated.

The electron injection layer 208 is a layer containing a substance having a high electron injection property. The electron injection layer 208
Lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF ₂ )
, Alkaline metals such as lithium oxide (LiOx), alkaline earth metals, or compounds thereof can be used. In addition, rare earth metal compounds such as erbium fluoride (ErF _{3) can be used.} Further, the substance constituting the electron transport layer 207 described above can also be used.

Alternatively, a composite material obtained by mixing an organic compound and an electron donor (donor) may be used for the electron injection layer 208. Such a composite material is excellent in electron injecting property and electron transporting property because electrons are generated in an organic compound by an electron donor. In this case, the organic compound is preferably a material excellent in transporting generated electrons, and specifically, for example, a substance (metal complex, heteroaromatic compound, etc.) constituting the electron transport layer 207 described above is used. Can be used. The electron donor may be any substance that exhibits 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 mentioned. Further, alkali metal oxides and alkaline earth metal oxides are preferable, and lithium oxides, calcium oxides, barium oxides and the like can be mentioned. It is also possible to use a Lewis base such as magnesium oxide. Further, an organic compound such as tetrathiafulvalene (abbreviation: TTF) can also be used.

The hole injection layer 204, the hole transport layer 205, and the light emitting layer 206 (206a, 20) described above.
6b), the electron transport layer 207, and the electron injection layer 208 can be formed by a vapor deposition method (including a vacuum vapor deposition method), an inkjet method, a coating method, or the like, respectively.

The light emitted from the light emitting layer 206 of the light emitting element described above is taken out to the outside through either or both of the first electrode 201 and the second electrode 202. Therefore, one or both of the first electrode 201 and the second electrode 202 in the present embodiment is a translucent electrode.

The light emitting element shown in the present embodiment enhances energy transfer efficiency by energy transfer using the overlap between the emission spectrum of the excitation complex and the absorption spectrum of the luminescent substance (guest material) that converts triple-term excitation energy into emission. Therefore, it is possible to realize a light emitting element having high external quantum efficiency.

The light emitting device shown in the present embodiment is one aspect of the present invention, and is particularly characterized by the configuration of the light emitting layer. Therefore, by applying the configuration shown in the present embodiment, a passive matrix type light emitting device, an active matrix type light emitting device, and the like can be manufactured, both of which are included in the present invention. ..

In the case of the active matrix type light emitting device, the structure of the TFT is not particularly limited. For example, a staggered type or reverse staggered type TFT can be appropriately used. Also, T
The drive circuit formed on the FT substrate may also be composed of N-type and P-type TFTs, or may be composed of only one of N-type TFTs and P-type TFTs. Further, the crystallinity of the semiconductor film used for the TFT is not particularly limited. For example, an amorphous semiconductor film, a crystalline semiconductor film, an oxide semiconductor film, or the like can be used.

The configuration shown in this embodiment can be used in combination with the configurations shown in other embodiments as appropriate.

(Embodiment 3)
In the present embodiment, as one aspect of the present invention, a light emitting device having a structure having a plurality of EL layers with a charge generation layer interposed therebetween (hereinafter, referred to as a tandem type light emitting device) will be described.

The light emitting element shown in the present embodiment has a pair of electrodes (first electrode 30) as shown in FIG. 6 (A).
A plurality of EL layers (first EL layer 302 (1), second E) between the first and second electrodes 304).
It is a tandem type light emitting device having an L layer 302 (2)).

In the present embodiment, the first electrode 301 is an electrode that functions as an anode, and the second electrode 304 is an electrode that functions as a cathode. The first electrode 301 and the second electrode 304 can use the same configuration as that of the first embodiment. In addition, a plurality of EL layers (first)
The EL layer 302 (1) and the second EL layer 302 (2)) may have the same configuration as the EL layer shown in the first embodiment or the second embodiment, but any one of them is the same. It may be configured. That is, the first EL layer 302 (1) and the second EL layer 302 (2) may have the same configuration or different configurations, and the configurations are the same as those of the first embodiment or the second embodiment. Similar ones can be applied.

Further, a charge generation layer (I) 305 is provided between the plurality of EL layers (first EL layer 302 (1), second EL layer 302 (2)). The charge generation layer (I) 305 has a function of injecting electrons into one EL layer and injecting holes into the other EL layer when a voltage is applied to the first electrode 301 and the second electrode 304. Have. In the case of the present embodiment, when a voltage is applied to the first electrode 301 so that the potential is higher than that of the second electrode 304, the charge generation layer (I) 30
Electrons are injected into the first EL layer 302 (1) from 5 and holes are injected into the second EL layer 302 (2).

The charge generation layer (I) 305 has light transmittance with respect to visible light from the viewpoint of light extraction efficiency (specifically, the transmittance of visible light with respect to the charge generation layer (I) 305 is determined. 40% or more) is preferable. Further, the charge generation layer (I) 305 includes the first electrode 301 and the second electrode 3.
It works even with a conductivity lower than 04.

The charge generation layer (I) 305 has a structure in which an electron acceptor is added to an organic compound having a high hole transport property, but an electron donor is added to the organic compound having a high electron transport property. It may be a configured configuration. Further, both of these configurations may be laminated.

In the case where an electron acceptor is added to an organic compound having a high hole transport property, examples of the organic compound having a high hole transport property include NPB, TPD, TDATA, and MTDATA.
, 4,4'-Bis [N- (spiro-9,9'-bifluoren-2-yl) -N-phenylamino] Biphenyl (abbreviation: BSBP) and other aromatic amine compounds can be used. The substances described here are mainly substances having a hole mobility of ^10-6 cm ^{2 / Vs or more.} However, a substance other than the above may be used as long as it is an organic compound having a higher hole transport property than electrons.

Examples of the electron acceptor include 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation: F4-TCNQ), chloranil and the like.
Also, transition metal oxides can be mentioned. Further, the oxides of metals belonging to Group 4 to Group 8 in the Periodic Table of the Elements can be mentioned. Specifically, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide, and renium oxide are preferable because they have high electron acceptability. Among them, molybdenum oxide is particularly preferable because it is stable in the atmosphere, has low hygroscopicity, and is easy to handle.

On the other hand, in the case where the electron donor is added to the organic compound having high electron transport property, examples of the organic compound having high electron transport property include Alq, Almq ₃ , BeBq ₂ and B.
A metal complex having a quinoline skeleton or a benzoquinoline skeleton such as Alq can be used. In addition, a metal complex having an oxazole-based ligand such as Zn (BOX) ₂ or Zn (BTZ) _{2 or a thiazole-based ligand can also be used.} Further, in addition to the metal complex, PBD, OXD-7, TAZ, BPhen, BCP and the like can also be used. The substances described here are mainly substances having electron mobilities of ^10-6 cm ^{2 / Vs or more.} A substance other than the above may be used as long as it is an organic compound having a higher electron transport property than holes.

Further, as the electron donor, an alkali metal, an alkaline earth metal, a rare earth metal, a metal belonging to Group 13 in the Periodic Table of the Elements, an oxide thereof, or a carbonate can be used. Specifically, it is preferable to use lithium (Li), cesium (Cs), magnesium (Mg), calcium (Ca), ytterbium (Yb), indium (In), lithium oxide, cesium carbonate and the like. Further, an organic compound such as tetrathianaphthalene may be used as an electron donor.

By forming the charge generation layer (I) 305 using the above-mentioned material, it is possible to suppress an increase in the drive voltage when the EL layers are laminated.

In the present embodiment, a light emitting device having two EL layers has been described, but as shown in FIG. 6B, a light emitting device in which n layers (where n is 3 or more) are laminated is also used. , Can be applied as well. When a plurality of EL layers are provided between a pair of electrodes as in the light emitting element according to the present embodiment, by arranging the charge generation layer (I) between the EL layers, the charge generation layer (I) can be arranged.
It is possible to emit light in a high brightness region while keeping the current density low. Since the current density can be kept low, a long-life element can be realized. Further, when lighting is used as an application example, the voltage drop due to the resistance of the electrode material can be reduced, so that uniform light emission over a large area becomes possible. In addition, it is possible to realize a light emitting device that can be driven at a low voltage and has low power consumption.

Further, by making the emission color of each EL layer different, it is possible to obtain emission of a desired color as the entire light emitting element. For example, in a light emitting element having two EL layers, a light emitting element that emits white light as a whole by making the light emitting color of the first EL layer and the light emitting color of the second EL layer have a complementary color relationship. It is also possible to obtain. The complementary color refers to the relationship between colors that become achromatic when mixed. That is, when a color having a complementary color relationship is mixed with light obtained from a substance that emits light, white light emission can be obtained.

The same applies to a light emitting element having three EL layers. For example, the light emitting color of the first EL layer is red, the light emitting color of the second EL layer is green, and the third EL layer. When the emission color of is blue, white emission can be obtained for the entire light emitting element.

The configuration shown in this embodiment can be used in combination with the configurations shown in other embodiments as appropriate.

(Embodiment 4)
In this embodiment, a light emitting device which is one aspect of the present invention will be described.

The light emitting device shown in the present embodiment has a micro-optical cavity structure that utilizes the resonance effect of light between a pair of electrodes, and has a pair of electrodes (reflection) as shown in FIG. Electrode 4
It has a plurality of light emitting elements having a structure having at least an EL layer 405 between 01 and the semi-transmissive / semi-reflective electrode 402). Further, the EL layer 405 is a light emitting layer 4 which is at least a light emitting region.
It has 04 (404R, 404G, 404B), and may also include a hole injection layer, a hole transport layer, an electron transport layer, an electron injection layer, a charge generation layer (E), and the like. The light emitting layer 404
(404R, 404G, 404B) can include a configuration of a light emitting layer which is one aspect of the present invention as described in the first and second embodiments.

In the present embodiment, as shown in FIG. 7, a light emitting element having a different structure (first light emitting element (R) 4)
A light emitting device including 10R, a second light emitting element (G) 410G, and a third light emitting element (B) 410B) will be described.

The first light emitting element (R) 410R has a first transparent conductive layer 403a on the reflective electrode 401 and a first transparent conductive layer 403a.
First light emitting layer (B) 404B, second light emitting layer (G) 404G, third light emitting layer (R) 404
It has a structure in which an EL layer 405 containing R as a part and a semi-transmissive / semi-reflective electrode 402 are sequentially laminated. Further, the second light emitting element (G) 410G has a second transparent conductive layer 4 on the reflective electrode 401.
It has a structure in which 03b, an EL layer 405, and a semi-transmissive / semi-reflective electrode 402 are sequentially laminated. Further, the third light emitting element (B) 410B has a structure in which the EL layer 405 and the semi-transmissive / semi-reflective electrode 402 are sequentially laminated on the reflective electrode 401.

The above light emitting element (first light emitting element (R) 410R, second light emitting element (G) 410G)
, In the third light emitting element (B) 410B), the reflective electrode 401, the EL layer 405, and the transflective
The semi-reflecting electrode 402 is common. Further, in the first light emitting layer (B) 404B, light (λ _B ) having a peak in a wavelength region of 420 nm or more and 480 nm or less is emitted, and the second light emitting layer (G) is emitted.
The 404G emits light having a peak in the wavelength region of 500 nm or more and 550 nm or less (λ _G ), and the third light emitting layer (R) 404R emits light having a peak in the wavelength region of 600 nm or more and 760 nm or less (λ _R ). To emit light. As a result, in any of the light emitting elements (first light emitting element (R) 410R, second light emitting element (G) 410G, third light emitting element (B) 410B), the first light emitting layer (B) 404B, Second light emitting layer (G) 404G, and third light emitting layer (R)
) It is possible to emit a broad light in which the light emitted from the 404R is superimposed, that is, over the visible light region. From the above, it is assumed that the wavelength length has a relationship of _{λ B} <λ _G <λ _R.

Each light emitting element shown in this embodiment has a reflective electrode 401 and a semi-transmissive / semi-reflective electrode 40, respectively.
It has a structure in which the EL layer 405 is sandwiched between the two and the light emitting layer emitted from each light emitting layer contained in the EL layer 405 in all directions, and functions as a micro optical resonator (microcavity). It is resonated by the reflective electrode 401 having the above and the semi-transmissive / semi-reflective electrode 402. The reflective electrode 401 is formed of a conductive material having reflectivity, and the reflectance of visible light to the film thereof is 40% to 100%, preferably 70% to 100%, and the resistivity thereof is 1 ×. 10
^-2 with Ωcm or less of the membrane. Further, the semi-transmissive / semi-reflective electrode 402 is formed of a conductive material having reflectivity and a conductive material having light transmissivity, and the reflectance of visible light to the film thereof is 20% to 80%, preferably 40. % To 70%, and its reflectance is 1 × 10 ⁻
It is assumed that the film is ^{2 Ω cm or less.}

Further, in the present embodiment, in each light emitting element, the transparent conductive layers (first transparent conductive layer 403a, first transparent conductive layer 403a, first) provided on the first light emitting element (R) 410R and the second light emitting element (G) 410G, respectively. 2
By changing the thickness of the transparent conductive layer 403b), the optical distance between the reflective electrode 401 and the semi-transmissive / semi-reflective electrode 402 is changed for each light emitting element. That is, the broad light emitted from each light emitting layer of each light emitting element is generated between the reflecting electrode 401 and the semitransmissive / semi-reflecting electrode 402.
Since light with a wavelength that resonates can be strengthened and light with a wavelength that does not resonate can be attenuated, light with different wavelengths can be produced by changing the optical distance between the reflective electrode 401 and the transflective / semi-reflective electrode 402 for each element. Can be taken out.

The optical distance (also referred to as an optical path length) is an actual distance multiplied by a refractive index, and in the present embodiment, represents an actual film thickness multiplied by n (refractive index). .. That is, "
Optical distance = actual film thickness x n ".

Further, in the first light emitting element (R) 410R, the semi-transmissive / semi-reflective electrode 4 is transmitted from the reflective electrode 401.
The total thickness up to 02 is mλ _R / 2 (however, m is a natural number), and in the second light emitting element (G) 410G, the total thickness from the reflective electrode 401 to the transflective / semi-reflective electrode 402 is mλ _G / 2 (mλ G / 2). However, m
Is a natural number), and in the third light emitting element (B) 410B, the total thickness from the reflecting electrode 401 to the semi-transmissive / semi-reflective electrode 402 is mλ _B / 2 (where m is a natural number).

_{From the above, the light (λ R} ) emitted mainly by the third light emitting layer (R) 404R contained in the EL layer 405 is extracted from the first light emitting element (R) 410R, and the second light emitting element (G) is taken out. ) 4
_{Light (λ G} ) emitted mainly by the second light emitting layer (G) 404G contained in the EL layer 405 is extracted from 10G, and mainly the EL layer 405 is extracted from the third light emitting element (B) 410B.
_{The light (λ B} ) emitted by the first light emitting layer (B) 404B contained in the above is taken out. The light taken out from each light emitting element is emitted from the semitransparent / semi-reflecting electrode 402 side, respectively.

Further, in the above configuration, the total thickness from the reflective electrode 401 to the semi-transmissive / semi-reflective electrode 402 is, strictly speaking, the total thickness from the reflective region of the reflective electrode 401 to the reflective region of the semi-transmissive / semi-reflective electrode 402. can. However, the reflective electrode 401 and the semi-transmissive / semi-reflective electrode 40
Since it is difficult to accurately determine the position of the reflection region in 2, the above-mentioned effect can be sufficiently obtained by assuming an arbitrary position of the reflection electrode 401 and the semi-transmissive / semi-reflection electrode 402 as the reflection region. It should be possible.

Next, in the first light emitting element (R) 410R, the reflection electrode 401 to the third light emitting layer (R)
) Amplify the emission from the third light emitting layer (R) 404R by adjusting the optical distance to the 404R to the desired film thickness ((2m'+ 1) λ _{R / 4 (where m'is a natural number)).} Can be made to. Of the light emitted from the third light emitting layer (R) 404R, the light reflected and returned by the reflective electrode 401 (first reflected light) is semi-transmitted / semi-reflected from the third light emitting layer (R) 404R. Since it causes interference with the light directly incident on the electrode 402 (first incident light), the optical distance from the reflecting electrode 401 to the third light emitting layer (R) 404R is set to a desired value ((2 m'+ 1) λ _R /. By adjusting to 4 (however, m'is a natural number)), the phases of the first reflected light and the first incident light are matched, and the light emitted from the third light emitting layer (R) 404R is amplified. be able to.

Strictly speaking, the optical distance between the reflecting electrode 401 and the third light emitting layer (R) 404R is the optical distance between the reflecting region of the reflecting electrode 401 and the light emitting region of the third light emitting layer (R) 404R. Can be done. However, the reflection region in the reflection electrode 401 and the third light emitting layer (R)
Since it is difficult to accurately determine the position of the light emitting region in the 404R, the reflective electrode 40
It is assumed that the above-mentioned effect can be sufficiently obtained by assuming that an arbitrary position of 1 is a reflection region and an arbitrary position of the third light emitting layer (R) 404R is a light emitting region.

Next, in the second light emitting element (G) 410G, the reflection electrode 401 to the second light emitting layer (G).
) Light emission from the second light emitting layer (G) 404G by adjusting the optical distance to the desired film thickness ((2 m'' + 1) λ _G / 4 (where m'' is a natural number)). Can be amplified. Of the light emitted from the second light emitting layer (G) 404G, the light reflected and returned by the reflective electrode 401 (second reflected light) is semi-transmitted / semi-reflected from the second light emitting layer (G) 404G. Reflective electrode 401 because it causes interference with light directly incident on the electrode 402 (second incident light).
The optical distance from the second light emitting layer (G) 404G to the desired value ((2m'' + 1) λ _G / 4 (
However, by adjusting m'' to a natural number)), the phase of the second reflected light and the second incident light are matched, and the light emitted from the second light emitting layer (G) 404G is amplified. Can be done.

Strictly speaking, the optical distance between the reflecting electrode 401 and the second light emitting layer (G) 404G is the optical distance between the reflecting region of the reflecting electrode 401 and the light emitting region of the second light emitting layer (G) 404G. Can be done. However, the reflection region in the reflection electrode 401 and the second light emitting layer (G)
Since it is difficult to accurately determine the position of the light emitting region in the 404G, the reflective electrode 40
It is assumed that the above-mentioned effect can be sufficiently obtained by assuming that an arbitrary position of 1 is a reflection region and an arbitrary position of the second light emitting layer (G) 404G is a light emitting region.

Next, in the third light emitting element (B) 410B, the reflection electrode 401 to the first light emitting layer (B).
) The optical distance to 404B is the desired film thickness ((2m'''+ 1) λ _B / 4 (however, m'''.
Is a natural number)), the light emission from the first light emitting layer (B) 404B can be amplified. Of the light emitted from the first light emitting layer (B) 404B, the light reflected and returned by the reflective electrode 401 (third reflected light) is semi-transmitted / semi-reflected from the first light emitting layer (B) 404B. Since it causes interference with the light directly incident on the electrode 402 (third incident light), the reflective electrode 4
The optical distance from 01 to the first light emitting layer (B) 404B is set to a desired value ((2m'''+ 1) λ _B.
By adjusting to / 4 (however, m'''is a natural number), the third reflected light and the third
The light emitted from the first light emitting layer (B) 404B can be amplified by matching the phase with the incident light of.

In the third light emitting element, the optical distance between the reflecting electrode 401 and the first light emitting layer (B) 404B is, strictly speaking, the light emitting region in the reflecting electrode 401 and the light emitting in the first light emitting layer (B) 404B. It can be said that it is the optical distance from the area. However, since it is difficult to precisely determine the positions of the reflection region on the reflection electrode 401 and the light emission region on the first light emitting layer (B) 404B, any position of the reflection electrode 401 can be set as the reflection region and the first light emission. It is assumed that the above-mentioned effect can be sufficiently obtained by assuming an arbitrary position of the layer (B) 404B as a light emitting region.

In the above configuration, each light emitting element has a structure having a plurality of light emitting layers in the EL layer, but the present invention is not limited to this, and for example, the tandem type described in the third embodiment is described. Multiple ELs with a charge generation layer sandwiched between one light emitting element in combination with the configuration of the light emitting element
A layer may be provided, and a single or a plurality of light emitting layers may be formed on each EL layer.

The light emitting device shown in this embodiment has a microcavity structure and has the same EL.
Even if it has a layer, it is possible to extract light having a different wavelength for each light emitting element, so that it is not necessary to separately paint RGB. Therefore, it is advantageous to realize full color because it is easy to realize high definition. It can also be combined with a colored layer (color filter). In addition, since it is possible to increase the emission intensity in the front direction of a specific wavelength, it is possible to reduce power consumption. This configuration is particularly useful when applied to a color display (image display device) using pixels of three or more colors, but it may also be used for applications such as lighting.

(Embodiment 5)
In the present embodiment, a light emitting device having a light emitting element, which is one aspect of the present invention, will be described.

Further, the light emitting device may be a passive matrix type light emitting device or an active matrix type light emitting device. The light emitting element described in another embodiment can be applied to the light emitting device shown in the present embodiment.

In the present embodiment, the active matrix type light emitting device will be described with reference to FIG.

8 (A) is a top view showing a light emitting device, and FIG. 8 (B) shows FIG. 8 (A) as a chain line A-.
It is sectional drawing cut in A'. The active matrix type light emitting device according to the present embodiment has a pixel unit 502 provided on the element substrate 501 and a drive circuit unit (source line drive circuit) 50.
3 and a drive circuit unit (gate line drive circuit) 504 (504a and 504b).
The pixel unit 502, the drive circuit unit 503, and the drive circuit unit 504 are formed by the sealing material 505.
It is sealed between the element substrate 501 and the sealing substrate 506.

Further, on the element substrate 501, an external input terminal for transmitting an external signal (for example, a video signal, a clock signal, a start signal, a reset signal, etc.) or a potential to the drive circuit unit 503 and the drive circuit unit 504 is provided. A routing wire 507 for connection is provided. here,
An example of providing an FPC (flexible printed circuit) 508 as an external input terminal is shown. Although only the FPC is shown here, a printed wiring board (PWB) may be attached to the FPC. The light emitting device in the present specification includes not only the light emitting device main body but also a state in which an FPC or a PWB is attached to the light emitting device main body.

Next, the cross-sectional structure will be described with reference to FIG. 8 (B). A drive circuit unit and a pixel unit are formed on the element substrate 501, but here, the drive circuit unit 503, which is a source line drive circuit, is formed.
, The pixel unit 502 is shown.

The drive circuit unit 503 shows an example in which a CMOS circuit in which an n-channel type TFT 509 and a p-channel type TFT 510 are combined is formed. The circuit forming the drive circuit section is
It may be formed by various CMOS circuits, polyclonal circuits or nanotube circuits. Further, in the present embodiment, the driver integrated type in which the drive circuit is formed on the substrate is shown, but it is not always necessary, and the drive circuit can be formed on the outside instead of on the substrate.

Further, the pixel unit 502 has a plurality of pixels including a switching TFT 511 and a first electrode (anode) 513 electrically connected to the wiring (source electrode or drain electrode) of the current control TFT 512 and the current control TFT 512. Is formed by. The first electrode (anode) 5
Insulation 514 is formed over the end of 13. Here, it is formed by using a positive type photosensitive acrylic resin.

Further, in order to improve the covering property of the film laminated and formed on the upper layer, it is preferable to form a curved surface having a curvature on the upper end portion or the lower end portion of the insulating material 514. For example, when a positive photosensitive acrylic resin is used as the material of the insulating material 514, it is preferable to have a curved surface having a radius of curvature (0.2 μm to 3 μm) at the upper end portion of the insulating material 514. Further, as the insulator 514, either a negative type photosensitive resin or a positive type photosensitive resin can be used, and not only organic compounds but also inorganic compounds such as silicon oxide and silicon oxynitride can be used.
Both can be used.

An EL layer 515 and a second electrode (cathode) 516 are laminated and formed on the first electrode (anode) 513. The EL layer 515 is provided with at least a light emitting layer, and the light emitting layer has a laminated structure as shown in the first embodiment. In addition to the light emitting layer, the EL layer 515 can be appropriately provided with a hole injection layer, a hole transport layer, an electron transport layer, an electron injection layer, a charge generation layer, and the like.

The light emitting element 517 is formed by a laminated structure of the first electrode (anode) 513, the EL layer 515, and the second electrode (cathode) 516. First electrode (anode) 513, EL layer 515
As the material used for the second electrode (cathode) 516, the material shown in the second embodiment can be used. Further, although not shown here, the second electrode (cathode) 516 is electrically connected to the FPC 508 which is an external input terminal.

Further, although only one light emitting element 517 is shown in the cross-sectional view shown in FIG. 8B, it is assumed that a plurality of light emitting elements are arranged in a matrix in the pixel unit 502. Pixel part 5
In 02, light emitting elements capable of obtaining three types of light emission (R, G, B) are selectively formed.
It is possible to form a light emitting device capable of displaying in full color. Further, it may be a light emitting device capable of full-color display by combining with a colored layer (color filter).

Further, by bonding the sealing substrate 506 to the element substrate 501 with the sealing material 505, the light emitting element 517 is provided in the space 518 surrounded by the element substrate 501, the sealing substrate 506, and the sealing material 505. ing. In addition to the case where the space 518 is filled with an inert gas (nitrogen, argon, etc.), it is assumed that the space 518 is filled with the sealing material 505.

It is preferable to use an epoxy resin, low melting point glass, or the like for the sealing material 505. Further, it is desirable that these materials are materials that do not allow moisture or oxygen to permeate as much as possible. In addition to glass substrates and quartz substrates, FRP (Fiberg) can be used as the material for the sealing substrate 506.
A plastic substrate made of lass-Reinforced Plastics), PVF (polyvinyl fluoride), polyester, acrylic or the like can be used.

As described above, an active matrix type light emitting device can be obtained.

In addition, the configuration shown in this embodiment can be used in combination with the configurations shown in other embodiments as appropriate.

(Embodiment 6)
In the present embodiment, examples of various electronic devices completed by using a light emitting device manufactured by applying a light emitting element according to one aspect of the present invention will be described with reference to FIGS. 9 and 10.

Electronic devices to which the light emitting device is applied include, for example, television devices (also referred to as televisions or television receivers), monitors for computers, digital cameras, digital video cameras, digital photo frames, mobile phones (mobile phones, mobile phones). (Also called a telephone device),
Examples include portable game machines, mobile information terminals, sound reproduction devices, and large game machines such as pachinko machines. Specific examples of these electronic devices are shown in FIG.

FIG. 9A shows an example of a television device. The television device 7100 is
The display unit 7103 is incorporated in the housing 7101. The display unit 7103 can display an image, and the light emitting device can be used for the display unit 7103. Further, here, a configuration in which the housing 7101 is supported by the stand 7105 is shown.

The operation of the television device 7100 can be performed by an operation switch included in the housing 7101 or a separate remote controller operating device 7110. The operation key 7109 included in the remote controller 7110 can be used to operate the channel and volume, and can operate the image displayed on the display unit 7103. Further, the remote controller 7110 may be provided with a display unit 7107 for displaying information output from the remote controller 7110.

The television device 7100 is configured to include a receiver, a modem, and the like. The receiver can receive general television broadcasts, and by connecting to a wired or wireless communication network via a modem, it can be unidirectional (sender to receiver) or bidirectional (sender to receiver).
It is also possible to perform information communication between the sender and the receiver, or between the receivers.

FIG. 9B is a computer, which includes a main body 7201, a housing 7202, a display unit 7203, a keyboard 7204, an external connection port 7205, a pointing device 7206, and the like. The computer is manufactured by using a light emitting device for the display unit 7203.

FIG. 9C shows a portable gaming machine, which is composed of two housings, a housing 7301 and a housing 7302, and is connected by a connecting portion 7303 so as to be openable and closable. The display unit 7304 is incorporated in the housing 7301, and the display unit 7305 is incorporated in the housing 7302. In addition, the portable gaming machine shown in FIG. 9C has a speaker unit 7306 and a recording medium insertion unit 7307.
, LED lamp 7308, input means (operation key 7309, connection terminal 7310, sensor 73
11 (force, displacement, position, speed, acceleration, angular velocity, rotation speed, distance, light, liquid, magnetism, temperature, chemical substance, voice, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, It includes a function to measure inclination, vibration, odor or infrared rays), a microphone 7312) and the like. Of course, the configuration of the portable game machine is not limited to the above, and at least the display unit 73.
A light emitting device may be used for both or one of the 04 and the display unit 7305, and other auxiliary equipment may be appropriately provided. The portable gaming machine shown in FIG. 9C has a function of reading a program or data recorded on a recording medium and displaying it on a display unit, and wirelessly communicates with other portable gaming machines to share information. Has a function. The functions of the portable gaming machine shown in FIG. 9C are not limited to this, and can have various functions.

FIG. 9D shows an example of a mobile phone. The mobile phone 7400 has a housing 7401.
In addition to the display unit 7402 built into the unit, it is equipped with an operation button 7403, an external connection port 7404, a speaker 7405, a microphone 7406, and the like. The mobile phone 7400 is manufactured by using a light emitting device for the display unit 7402.

In the mobile phone 7400 shown in FIG. 9D, information can be input by touching the display unit 7402 with a finger or the like. In addition, operations such as making a phone call or composing an e-mail can be performed by touching the display unit 7402 with a finger or the like.

The screen of the display unit 7402 mainly has three modes. The first is a display mode mainly for displaying an image, and the second is an input mode mainly for inputting information such as characters. The third is a display + input mode in which two modes, a display mode and an input mode, are mixed.

For example, when making a phone call or composing an e-mail, the display unit 7402 may be set to a character input mode mainly for inputting characters, and the characters displayed on the screen may be input. In this case, it is preferable to display the keyboard or the number button on most of the screen of the display unit 7402.

Further, by providing a detection device having a sensor for detecting the inclination of a gyro, an acceleration sensor, etc. inside the mobile phone 7400, the orientation (vertical or horizontal) of the mobile phone 7400 can be determined.
The screen display of the display unit 7402 can be automatically switched.

Further, the screen mode can be switched by touching the display unit 7402 or by operating the operation button 7403 of the housing 7401. It is also possible to switch depending on the type of the image displayed on the display unit 7402. For example, if the image signal displayed on the display unit is moving image data, the display mode is switched, and if the image signal is text data, the input mode is switched.

Further, in the input mode, the signal detected by the optical sensor of the display unit 7402 is detected, and if there is no input by the touch operation of the display unit 7402 for a certain period of time, the screen mode is switched from the input mode to the display mode. You may control it.

The display unit 7402 can also function as an image sensor. For example, display unit 7
The person can be authenticated by touching the 402 with his / her palm or finger and taking an image of a palm print, a fingerprint, or the like.
Further, if a backlight that emits near-infrared light or a sensing light source that emits near-infrared light is used for the display unit, the finger vein, palm vein, and the like can be imaged.

10 (A) and 10 (B) are tablet terminals that can be folded in half. FIG. 10 (A
) Is in the open state, and the tablet-type terminal has a housing 9630, a display unit 9631a, a display unit 9631b, a display mode changeover switch 9034, a power switch 9035, a power saving mode changeover switch 9036, a fastener 9033, and an operation switch 9038. , Have. The tablet terminal is manufactured by using a light emitting device for one or both of the display unit 9631a and the display unit 9631b.

A part of the display unit 9631a can be a touch panel area 9632a, and data can be input by touching the displayed operation key 9637. The display unit 96
In 31a, as an example, a configuration in which half of the area has a display-only function and the other half of the region has a touch panel function are shown, but the configuration is not limited to this. Display 96
All areas of 31a may be configured to have a touch panel function. For example, display unit 9
The entire surface of 631a can be displayed as a keyboard button to form a touch panel, and the display unit 9631b can be used as a display screen.

Further, in the display unit 9631b as well, a part of the display unit 9631b can be a touch panel area 9632b, similarly to the display unit 9631a. Further, the keyboard button can be displayed on the display unit 9631b by touching the position where the keyboard display switching button 9639 on the touch panel is displayed with a finger or a stylus.

Further, touch input can be simultaneously performed on the touch panel area 9632a and the touch panel area 9632b.

Further, the display mode changeover switch 9034 can switch the display direction such as vertical display or horizontal display, and can select switching between black-and-white display and color display. The power saving mode changeover switch 9036 can optimize the brightness of the display according to the amount of external light during use detected by the optical sensor built in the tablet terminal. The tablet-type terminal may incorporate not only an optical sensor but also another detection device such as a sensor for detecting tilt such as a gyro and an acceleration sensor.

Further, FIG. 10A shows an example in which the display areas of the display unit 9631b and the display unit 9631a are the same, but the display area is not particularly limited, and one size and the other size may be different, and the display quality is also good. It may be different. For example, one may be a display panel capable of displaying a higher definition than the other.

FIG. 10B shows a closed state, and the tablet-type terminal has a housing 9630 and a solar cell 9.
It has 633, a charge / discharge control circuit 9634, a battery 9635, and a DCDC converter 9636. In FIG. 10B, the battery 963 is an example of the charge / discharge control circuit 9634.
5. The configuration having the DCDC converter 9636 is shown.

Since the tablet terminal can be folded in half, the housing 9630 can be closed when not in use. Therefore, since the display unit 9631a and the display unit 9631b can be protected,
It is possible to provide a tablet-type terminal that has excellent durability and is highly reliable from the viewpoint of long-term use.

In addition to this, the tablet-type terminals shown in FIGS. 10 (A) and 10 (B) have a function of displaying various information (still images, moving images, text images, etc.), a calendar, a date, a time, and the like. It can have a function of displaying on a display unit, a touch input function of performing a touch input operation or editing information displayed on the display unit, a function of controlling processing by various software (programs), and the like.

The solar cell 9633 mounted on the surface of the tablet terminal can supply electric power to the touch panel, the display unit, the video signal processing unit, or the like. The solar cell 9633 can be provided on one side or both sides of the housing 9630, and can be configured to efficiently charge the battery 9635. As the battery 9635, if a lithium ion battery is used, there is an advantage that the size can be reduced.

Further, the configuration and operation of the charge / discharge control circuit 9634 shown in FIG. 10B will be described in FIG. 10 (B).
A block diagram will be shown and described in C). In FIG. 10C, the solar cell 9633 and the battery 9 are shown.
635, DCDC converter 9636, converter 9638, switches SW1 to SW3
, Display unit 9631, battery 9635, DCDC converter 963.
6. The converter 9638 and the switches SW1 to SW3 correspond to the charge / discharge control circuit 9634 shown in FIG. 10B.

First, an example of operation when power is generated by the solar cell 9633 by external light will be described. The electric power generated by the solar cell 9633 is stepped up or down by the DCDC converter 9636 so as to be a voltage for charging the battery 9635. And the display unit 9631
When the power from the solar cell 9633 is used for the operation, the switch SW1 is turned on, and the converter 9638 steps up or down the voltage required for the display unit 9631. When not displaying on the display unit 9631, the switch SW1 is turned off and the switch S is turned off.
W2 may be turned on to charge the battery 9635.

The solar cell 9633 is shown as an example of power generation means, but is not particularly limited.
The battery 9635 may be charged by another power generation means such as a piezoelectric element (piezo element) or a thermoelectric conversion element (Peltier element). For example, a non-contact power transmission module that wirelessly (non-contactly) transmits and receives power for charging may be used, or a configuration may be performed in combination with other charging means.

Further, it goes without saying that the electronic device shown in FIG. 10 is not particularly limited as long as it is provided with the display unit described in the above embodiment.

As described above, an electronic device can be obtained by applying the light emitting device according to one aspect of the present invention. The range of application of the light emitting device is extremely wide, and it can be applied to electronic devices in all fields.

The configuration shown in this embodiment can be used in combination with the configurations shown in other embodiments as appropriate.

(Embodiment 7)
In the present embodiment, an example of a lighting device to which a light emitting device including a light emitting element, which is one aspect of the present invention, is applied will be described with reference to FIG.

FIG. 11 shows an example in which the light emitting device is used as the indoor lighting device 8001. Since the light emitting device can have a large area, it is possible to form a lighting device having a large area. In addition, by using a housing having a curved surface, it is possible to form a lighting device 8002 having a curved light emitting region. The light emitting element included in the light emitting device shown in the present embodiment is in the form of a thin film, and has a high degree of freedom in the design of the housing. Therefore, it is possible to form a lighting device with various elaborate designs. Further, a large lighting device 8003 may be provided on the wall surface of the room.

Further, by using the light emitting device on the surface of the table, the lighting device 8004 having a function as a table can be obtained. By using a light emitting device for a part of other furniture, it is possible to obtain a lighting device having a function as furniture.

As described above, various lighting devices to which the light emitting device is applied can be obtained. It should be noted that these lighting devices are included in one aspect of the present invention.

Moreover, the configuration shown in this embodiment can be used in combination with the configuration shown in other embodiments as appropriate.

In this embodiment, the light emitting device 1 which is one aspect of the present invention will be described with reference to FIG. The chemical formulas of the materials used in this example are shown below.

<< Fabrication of light emitting element 1 >>
First, indium tin oxide (ITSO) containing silicon oxide was formed on a glass substrate 1100 by a sputtering method to form a first electrode 1101 that functions as an anode. The film thickness was 110 nm, and the electrode area was 2 mm × 2 mm.

Next, as a pretreatment for forming the light emitting element 1 on the substrate 1100, the surface of the substrate was washed with water, fired at 200 ° C. for 1 hour, and then subjected to UV ozone treatment for 370 seconds.

After that, the ^{substrate was introduced into a vacuum vapor deposition apparatus whose internal pressure was reduced to about 10-4} Pa, vacuum fired at 170 ° C. for 30 minutes in a heating chamber inside the vacuum vapor deposition apparatus, and then the substrate 1100 was placed for about 30 minutes. It was allowed to cool.

Next, the substrate 1100 was fixed to a holder provided in the vacuum vapor deposition apparatus so that the surface on which the first electrode 1101 was formed was facing downward. In this embodiment, the EL layer 1 is obtained by the vacuum vapor deposition method.
A case where the hole injection layer 1111, the hole transport layer 1112, the light emitting layer 1113, the electron transport layer 1114, and the electron injection layer 1115 constituting the 102 are sequentially formed will be described.

After depressurizing the inside of the vacuum device to 10 ^-4 Pa, 1,3,5-tri (dibenzothiophene-4)
-Il) benzene (abbreviation: DBT3P-II) and molybdenum oxide (VI), DBT3
The hole injection layer 1111 was formed on the first electrode 1101 by co-depositing so that P-II (abbreviation): molybdenum oxide = 4: 2 (mass ratio). The film thickness was 20 nm. Co-deposited is a vapor deposition method in which a plurality of different substances are simultaneously evaporated from different evaporation sources.

Next, a hole transport layer 1112 was formed by depositing 4-phenyl-4'-(9-phenylfluorene-9-yl) triphenylamine (abbreviation: BPAFLP) at 20 nm.

Next, a light emitting layer 1113 was formed on the hole transport layer 1112. 4,6-bis [3- (9H)
-Carbazole-9-yl) Phenyl] Pyrimidine (abbreviation: 4.6mCzP2Pm), N
-(1,1'-biphenyl-4-yl) -N- [4- (9-phenyl-9H-carbazole-3-yl) phenyl] -9,9-dimethyl-9H-fluorene-2-amine (abbreviation) :
PCBBiF), Tris (2-phenylpyridinato) Iridium (III) (abbreviation: [I]
r (ppy) ₃ ]), 4,6mCzP2Pm (abbreviation): PCBBiF (abbreviation): [Ir
(Ppy) ₃ ] (abbreviation) = 0.7: 0.3: 0.05 (mass ratio), co-deposited to form the first light emitting layer 1113a with a film thickness of 20 nm, and then 2- [ 3'-(dibenzothiophen-4-yl) biphenyl-3-yl] dibenzo [f, h] quinoxaline (abbreviation: 2mD)
BTBPDBq-II), PCBBiF (abbreviation), bis {4,6-dimethyl-2- [5-]
(2,6-Dimethylphenyl) -3- (3,5-Dimethylphenyl) -2-pyrazinyl-
κN] Phenyl-κC} (2,8-dimethyl-4,6-nonandionato-κ ² O, O')
Iridium (III) (abbreviation: [Ir (dmdppr-dmp) ₂ (divm)]),
2mDBTBPDBq-II (abbreviation): PCBBiF (abbreviation): [Ir (dmdppr-)
dmp) ₂ (divm)] (abbreviation) = 0.9: 0.1: 0.05 (mass ratio) by co-depositing to form the second light emitting layer 1113b with a film thickness of 20 nm. A light emitting layer 1113 having a laminated structure was formed.

Next, 2mDBTBPDBq-II (abbreviation) was vapor-deposited on the light emitting layer 1113 at 15 nm, and then bassophenanthroline (abbreviation: Bphen) was vapor-deposited at 10 nm to form an electron transport layer 1114. Further, an electron injection layer 1115 was formed by depositing lithium fluoride at 1 nm on the electron transport layer 1114.

Finally, aluminum was deposited on the electron injection layer 1115 so as to have a film thickness of 200 nm to form a second electrode 1103 to be a cathode, and a light emitting device 1 was obtained. In the above-mentioned vapor deposition process, the resistance heating method was used for all the vapor deposition.

Table 1 shows the element structure of the light emitting element 1 obtained as described above.

Further, the produced light emitting element 1 was sealed in a glove box having a nitrogen atmosphere so as not to be exposed to the atmosphere (a sealing material was applied around the element and heat-treated at 80 ° C. for 1 hour at the time of sealing).

<< Operating characteristics of light emitting element 1 >>
The operating characteristics of the manufactured light emitting device 1 were measured. The measurement was performed at room temperature (atmosphere maintained at 25 ° C.).

First, FIG. 13 shows the current density-luminance characteristic of the light emitting element 1. In FIG. 13, the vertical axis represents the luminance (cd / m ² ) and the horizontal axis represents the current density (mA / cm ² ). Further, the voltage-luminance characteristic of the light emitting element 1 is shown in FIG. In FIG. 14, the vertical axis is the luminance (cd / m ² ).
The horizontal axis represents the voltage (V). Further, the luminance-current efficiency characteristic of the light emitting element 1 is shown in FIG. In FIG. 15, the vertical axis represents current efficiency (cd / A) and the horizontal axis represents luminance (cd / m ² ). Further, the voltage-current characteristic of the light emitting element 1 is shown in FIG. In FIG. 16, the vertical axis represents current (mA) and the horizontal axis represents voltage (V).

From FIG. 15, it was found that the light emitting device 1 according to one aspect of the present invention is a highly efficient device. Also, Table 2 below shows initial values of main characteristics of the light-emitting element 1 at around 1000 cd / ^{m 2.}

From the above results, it can be seen that the light emitting device 1 manufactured in this embodiment shows high external quantum efficiency, and therefore shows high light emitting efficiency.

Further, FIG. 17 shows an emission spectrum when a current is passed through the light emitting element 1 at ^{a current density of 25 mA / cm 2.} As shown in FIG. 17, the emission spectra of the light emitting element 1 are 519 nm and 615.
It has two peaks near nm, each of which is a phosphorescent organometallic iridium complex [Ir (Ir).
It is suggested that it is derived from the emission of poly) ₃ ] and [Ir (dmdppr-dmp) _{2 (divm)].}

From the cyclic voltammetry measurement, the LUMO level of 4.6 mCzP2Pm, which is the first organic compound having electron transportability, is -2.88eV, and 2mDBTBPDBq, which is the third organic compound having electron transportability. The LUMO level of -II was estimated to be -2.94 eV. Therefore, the LUMO of the first organic compound is higher than that of the third organic compound.
It has a high level structure.

Here, FIG. 18 shows 4,6 mCzP2Pm, which is the first organic compound having electron transportability.
The emission spectrum of the thin film, the emission spectrum of the thin film of PCBiF which is the second organic compound having hole transport property, and the emission spectrum of the mixed film (co-deposited film) of 4.6 mCzP2Pm and PCBBiF are shown. Further, in FIG. 19, it is a third organic compound having electron transporting property 2
Emission spectrum of the thin film of mDBTBPDBq-II, emission spectrum of the thin film of PCBBiF which is a second organic compound having hole transportability, and 2mDBTBPDBq-II and PC.
The emission spectrum of the mixed film (co-deposited film) of BBiF is shown.

From FIGS. 18 and 19, since the emission wavelength of the mixed film is located at a longer wavelength than the emission wavelength of the single film of each material, the first organic compound (4.6 mCzP2Pm) and the second organic compound (P).
It can be seen that the CBBiF), the third organic compound (2mDBTBPDBq-II) and the second organic compound (PCBBiF) each form an excited complex.

101 First electrode 102 Second electrode 103 EL layer 104 Hole injection layer 105 Hole transport layer 106 Light emitting layer 106a First light emitting layer 106b Second light emitting layer 107 Electron transport layer 108 Electron injection layer 109 Luminous substance 109a First luminescent material that converts triple-term excitation energy into light emission 109b Second luminescent material that converts triple-term excitation energy into light emission 110 First organic compound 111 Second organic compound 112 Third organic compound 201 No. Electrode of 1 (electron hole)
202 Second electrode (cathode)
203 EL layer 204 Hole injection layer 205 Hole transport layer 206 Light emitting layer 206a First light emitting layer 206b Second light emitting layer 207 Electron transport layer 208 Electron injection layer 209 Luminescent substance 209a Converting triplet excitation energy into light emission Luminescent substance 209b Second luminescent substance that converts triple-term excitation energy into light emission 210 First organic compound 211 Second organic compound 212 Third organic compound 301 First electrode 302 (1) First EL layer 302 (2) Second EL layer 302 (n-1) EL layer 302 (n) of the second (n-1) EL layer 304 of the second (n) Second electrode 305 Charge generation layer (I)
305 (1) First charge generation layer (I)
305 (2) Second charge generation layer (I)
305 (n-2) No. (n-2) charge generation layer (I)
305 (n-1) Third (n-1) charge generation layer (I)
401 Reflective electrode 402 Semi-transmissive / semi-reflective electrode 403a First transparent conductive layer 403b Second transparent conductive layer 404B First light emitting layer (B)
404G Second light emitting layer (G)
404R Third light emitting layer (R)
405 EL layer 410R First light emitting element (R)
410G Second light emitting element (G)
410B Third light emitting element (B)
501 Element board 502 Pixel unit 503 Drive circuit unit (source line drive circuit)
504a, 504b drive circuit section (gate line drive circuit)
505 Sealing material 506 Sealing substrate 507 Routing wiring 508 FPC (Flexible printed circuit)
509 n-channel TFT
510 p-channel TFT
511 Switching TFT
512 Current control TFT
513 First electrode (anode)
514 Insulation 515 EL layer 516 Second electrode (cathode)
517 Light emitting element 518 Space 7100 Television device 7101 Housing 7103 Display unit 7105 Stand 7107 Display unit 7109 Operation key 7110 Remote control operation machine 7201 Main unit 7202 Housing 7203 Display unit 7204 Keyboard 7205 External connection port 7206 Pointing device 7301 Housing 7302 Housing 7303 Connection unit 7304 Display unit 7305 Display unit 7306 Speaker unit 7307 Recording medium insertion unit 7308 LED lamp 7309 Operation key 7310 Connection terminal 7311 Sensor 7312 Microphone 7400 Mobile phone 7401 Housing 7402 Display unit 7403 Operation button 7404 External connection port 7405 Speaker 7406 Microphone 8001 Lighting device 8002 Lighting device 8003 Lighting device 8004 Lighting device 9033 Fastener 9034 Display mode changeover switch 9035 Power switch 9036 Power saving mode changeover switch 9038 Operation switch 9630 Housing 9631 Display unit 9631a Display unit 9631b Display unit 9632a Touch panel area 9632b Touch panel Area 9633 Solar Battery 9634 Charge / Discharge Control Circuit 9635 Battery 9636 DCDC Converter 9637 Operation Key 9638 Converter 9339 Button

Claims (5)

It has a light emitting layer between the anode and the cathode,
The light emitting layer has a first light emitting layer and a second light emitting layer.
The first light emitting layer is located between the anode and the second light emitting layer.
The first light emitting layer contains a first light emitting substance, a first organic compound, and a second organic compound.
The second light emitting layer contains the second light emitting substance, the second organic compound, and the third organic compound.
The emission spectrum of the mixed film of the first organic compound and the second organic compound is located at a longer wavelength than the emission spectrum of the first organic compound, and is from the emission spectrum of the second organic compound. Is located at a long wavelength,
The emission spectrum of the mixed film of the first organic compound and the second organic compound has an overlap with the absorption spectrum of the first luminescent substance.
The emission spectrum of the mixed film of the second organic compound and the third organic compound is located at a longer wavelength than the emission spectrum of the second organic compound, and is from the emission spectrum of the third organic compound. Is located at a long wavelength,
The emission spectrum of the mixed film of the second organic compound and the third organic compound has an overlap with the absorption spectrum of the second luminescent substance.
The first organic compound has a higher minimum unorbital level (LUMO level) than the third organic compound.
The first luminescent substance is a light emitting device which is a substance that emits light having a shorter wavelength than the second luminescent substance. It has a light emitting layer between the anode and the cathode,
The light emitting layer has a first light emitting layer and a second light emitting layer.
The first light emitting layer is located between the anode and the second light emitting layer.
The first light emitting layer contains a first light emitting substance, a first organic compound, and a second organic compound.
The second light emitting layer contains the second light emitting substance, the second organic compound, and the third organic compound.
The first organic compound and the second organic compound are combinations that form a first excitation complex.
The emission spectrum of the first excitation complex has an overlap with the absorption spectrum of the first luminescent substance.
The second organic compound and the third organic compound are combinations that form a second excitation complex.
The emission spectrum of the second excitation complex has an overlap with the absorption spectrum of the second luminescent substance.
The first organic compound has a higher minimum unorbital level (LUMO level) than the third organic compound.
The first luminescent substance is a light emitting device which is a substance that emits light having a shorter wavelength than the second luminescent substance. A light emitting device having the light emitting element according to claim 1 or 2. An electronic device having the light emitting device according to claim 3. A lighting device having the light emitting device according to claim 3.

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