JP7362959B2 - Light emitting elements, lighting devices, light emitting devices, display devices and electronic equipment - Google Patents

Description

The present invention relates to a light emitting element, a display device, a light emitting device, an electronic device, and a lighting device using an organic compound as a light emitting substance.

In recent years, research and development of light emitting elements using electroluminescence (EL) has been actively conducted. The basic configuration of these light emitting elements is
A layer containing a light emitting substance (EL layer) is sandwiched between a pair of electrodes. By applying a voltage to this element, light emission from the luminescent substance can be obtained.

Since such light-emitting elements are self-luminous, they have advantages such as higher pixel visibility than liquid crystal displays and no need for a backlight, and are considered suitable as flat panel display elements. Another great advantage of a display using such a light emitting element is that it can be made thin and lightweight. Another feature is that the response speed is extremely fast.

Since these light-emitting elements can form a light-emitting layer in the form of a film, they can emit light in a planar manner. Therefore, a large-area element can be easily formed. This is a characteristic that is difficult to obtain with point light sources such as incandescent bulbs and LEDs, or line light sources such as fluorescent lamps, and therefore has high utility value as a surface light source that can be applied to lighting.

In the case of an organic EL element in which an organic compound is used as a light emitting substance and the EL layer is provided between a pair of electrodes,
By applying a voltage between the pair of electrodes, electrons are injected from the cathode and holes are injected from the anode into the luminescent EL layer, causing current to flow. Then, the injected electrons and holes recombine to bring the luminescent organic compound into an excited state, and light emission can be obtained from the excited luminescent organic compound.

The types of excited states formed by organic compounds include singlet excited states and triplet excited states.Emission from the singlet excited state (S ^* ) is fluorescent, and emission from the triplet excited state (T ^* ) is It's called phosphorescence. Moreover, the statistical generation ratio in the light emitting element is S ^* :T ^* =
It is believed that the ratio is 1:3.

For compounds that emit light from the singlet excited state (hereinafter referred to as fluorescent compounds), at room temperature, emission from the triplet excited state (phosphorescence) is usually not observed, and only emission from the singlet excited state (fluorescence) is observed. is observed. Therefore, the theoretical limit of internal quantum efficiency (ratio of photons generated to injected carriers) in a light-emitting device using a fluorescent compound is S ^* :T ^* =
It is assumed to be 25% based on the ratio of 1:3.

On the other hand, if a compound that emits light from a triplet excited state (hereinafter referred to as a phosphorescent compound) is used,
Emission (phosphorescence) from the triplet excited state is observed. In addition, phosphorescent compounds have intersystem crossing (
(transition from singlet excited state to triplet excited state) is likely to occur, so the internal quantum efficiency is 1
Theoretically, it is possible to reach 0.00%. In other words, higher luminous efficiency than fluorescent compounds can be achieved. For these reasons, in order to realize highly efficient light emitting devices, development of light emitting devices using phosphorescent compounds has been actively conducted in recent years.

Patent Document 1 discloses a white light-emitting element that has a light-emitting region containing a plurality of light-emitting dopants, and in which the light-emitting dopants emit phosphorescence.

Special Publication No. 2004-522276

Although phosphorescent compounds are theoretically capable of achieving 100% internal quantum efficiency, it is difficult to achieve high efficiency without optimizing the device structure and combination with other materials. In particular, in light-emitting devices that use multiple types of phosphorescent compounds with different bands (emission colors) as light-emitting dopants, it is of course necessary to consider energy transfer, but it is difficult to optimize the efficiency of the energy transfer itself. Obtaining efficient light emission is difficult. In fact, in Patent Document 1, even if all the light-emitting dopants are phosphorescent elements, the external quantum efficiency is about 3 to 4%. This means that even if light extraction efficiency is taken into consideration, the internal quantum efficiency is considered to be 20% or less, which is a low value for a phosphorescent light emitting device.

Furthermore, in addition to increasing the luminous efficiency, in a multicolor light emitting element using dopants of different luminescent colors, it is necessary that the dopants of each luminescent color emit light in a well-balanced manner. It is not easy to achieve high luminous efficiency while also maintaining the luminous balance of each dopant.

Therefore, an object of one embodiment of the present invention is to provide a light-emitting element that uses a plurality of light-emitting dopants and has high luminous efficiency. Another object of one embodiment of the present invention is to provide a light-emitting device, a display device, an electronic device, and a lighting device each having reduced power consumption using the above-described light-emitting element.

The present invention is intended to solve any one of the above-mentioned problems.

In the present invention, we focus on the Förster mechanism, which is one of the energy transfer mechanisms between molecules. By applying a combination of molecules such that peaks having maxima on the longest wavelength side in the multiplied characteristic curves overlap, energy transfer in the Forster mechanism can be efficiently performed. Here, one of the characteristics of the energy transfer is that it is not a general energy transfer from a host to a dopant, but an energy transfer between dopants. In this way, the light-emitting element of one embodiment of the present invention can be manufactured by using a combination of dopants that increases the efficiency of energy transfer between dopants and by designing a device structure that appropriately isolates each dopant molecule. can be obtained.

That is, in one embodiment of the present invention, the first phosphorescent compound is located between the pair of electrodes, the first light-emitting layer is dispersed in the first host material, and the first phosphorescent compound is longer than the first phosphorescent compound. a second phosphorescent compound exhibiting emission ^at a wavelength, the second phosphorescent compound comprising a second emissive layer dispersed in a second host material; This is a light emitting element in which the wavelength of the maximum value located on the longest wavelength side of the function overlaps with the phosphorescent emission spectrum F(λ) of the first phosphorescent compound. (However, ε(λ) represents the molar extinction coefficient of each phosphorescent compound and is a function of wavelength λ.)

Further, in another embodiment of the present invention, the first phosphorescent compound is formed between the first light-emitting layer, which is dispersed in the first host material, and the first phosphorescent compound, between the pair of electrodes. a second phosphorescent compound that emits light at a longer wavelength; a second emissive layer dispersed in a second host material; This is a light-emitting element in which a peak containing ε(λ)λ ⁴ of the second phosphorescent compound and a peak containing a maximum value located on the longest wavelength side of the function represented by ε(λ)λ 4 overlap. (However, ε(λ) represents the molar extinction coefficient of each phosphorescent compound and is a function of wavelength λ.)

Further, in another aspect of the present invention, in the above structure, the first light emitting layer further includes a first organic compound, the first host material and the first organic compound form an exciplex, and the first light emitting layer further includes a first organic compound, and the first host material and the first organic compound form an exciplex. This is a light-emitting element in which the light emission of the phosphorescent compound No. 1 has a longer wavelength than the light emission of the exciplex.

Another aspect of the present invention is that in the above structure, the emission spectrum of the exciplex and the maximum located on the longest wavelength side of the function expressed by ε(λ)λ ⁴ of the first phosphorescent compound These are light emitting elements whose wavelengths overlap. (However, ε(λ) represents the molar extinction coefficient of each phosphorescent compound,
A function of wavelength λ. )

Another aspect of the present invention is that in the above configuration, the peak including the maximum value of the emission spectrum of the exciplex and the maximum value of the function represented by ε(λ)λ ⁴ of the first phosphorescent compound are provided. This is a light-emitting element in which peaks including maximum values located on the long wavelength side overlap. (However, ε(λ) represents the molar extinction coefficient of each phosphorescent compound and is a function of wavelength λ.)

Further, in another aspect of the present invention, in the above structure, the first phosphorescent compound has a wavelength of 500 nm.
The second phosphorescent compound has a phosphorescent emission peak in the range of 600 nm to 600 nm.
The light-emitting element has a phosphorescent emission peak in the range of m to 700 nm.

Another embodiment of the present invention is a light-emitting element in which the recombination region of electrons and holes is a first light-emitting layer in the above structure.

Another aspect of the present invention is that in the above structure, the first light-emitting layer is located closer to the anode than the second light-emitting layer, and at least the second light-emitting layer has electron transport properties rather than hole transport properties. It is a light-emitting element with high performance.

Further, in another aspect of the present invention, in the above structure, the first light emitting layer is located closer to the anode than the second light emitting layer, and both the first host material and the second host material are electron transporting. It is a light-emitting element that has properties. Note that as the material having electron transport properties, it is preferable to use a material that has higher electron transport properties than hole transport properties.

Another aspect of the present invention is that in the above structure, the first light-emitting layer is located closer to the cathode than the second light-emitting layer, and at least the second light-emitting layer has hole transport properties rather than electron transport properties. It is a light-emitting element with high performance.

In addition, in another aspect of the present invention, in the above structure, the first light emitting layer is located closer to the cathode than the second light emitting layer, and both the first host material and the second host material contain holes. It is a light emitting element that has transport properties. Note that as the material having hole transporting properties, a material having hole transporting properties higher than electron transporting properties is preferable.

Another embodiment of the present invention is a light-emitting element in which the first light-emitting layer and the second light-emitting layer are stacked in contact with each other in the above structure.

Another embodiment of the present invention is a light-emitting device, a light-emitting display device, an electronic device, and a lighting device including a light-emitting element having the above structure.

Note that the light-emitting device in this specification includes an image display device using a light-emitting element. In addition, a connector such as an anisotropic conductive film or TCP (Tape C) is attached to the light emitting element.
A module with a printed wiring board attached to the end of the TCP, or a module with an IC (integrated circuit) directly mounted on the light emitting element using the COG (Chip On Glass) method can all be used as a light emitting device. shall be included. Furthermore, the term also includes light emitting devices used in lighting equipment and the like.

One embodiment of the present invention can provide a light-emitting element with high luminous efficiency. One embodiment of the present invention can provide a light-emitting device, a light-emitting display device, an electronic device, and a lighting device with reduced power consumption by using the light-emitting element.

A conceptual diagram of a light emitting element. Diagram showing energy transfer in the light emitting layer A diagram explaining Förster movement. A conceptual diagram of an active matrix light emitting device. Conceptual diagram of a passive matrix light emitting device. A conceptual diagram of an active matrix light emitting device. A conceptual diagram of an active matrix light emitting device. Conceptual diagram of a lighting device. A diagram representing electronic equipment. A diagram representing electronic equipment. A diagram showing a lighting device. FIG. 3 is a diagram showing a lighting device and a display device. FIG. 3 is a diagram showing an in-vehicle display device and a lighting device. A diagram representing electronic equipment. Brightness-current efficiency characteristics of light-emitting element 1. Voltage-luminance characteristics of light emitting element 1. Brightness-external quantum efficiency characteristics of light emitting element 1. Brightness-power efficiency characteristics of light emitting element 1. Emission spectrum of light emitting element 1. FIG. 3 is a diagram illustrating Förster movement of the light emitting element 1. FIG. 3 is a diagram illustrating Förster movement of the light emitting element 1. FIG. 3 is a diagram illustrating Förster movement of the light emitting element 1. PL spectra of 2mDBTPDBq-II, PCBA1BP and their mixed film. Brightness-current efficiency characteristics of light-emitting element 2. Voltage-luminance characteristics of light emitting element 2. Brightness-external quantum efficiency characteristics of light emitting element 2. Brightness-power efficiency characteristics of light emitting element 2. Emission spectrum of light emitting element 2. FIG. 3 is a diagram showing reliability test results of the light emitting element 2. Brightness-current efficiency characteristics of light emitting element 3. Voltage-luminance characteristics of light emitting element 3. Brightness-external quantum efficiency characteristics of light emitting element 3. Brightness-power efficiency characteristics of light emitting element 3. Emission spectrum of light emitting element 3. Brightness-current efficiency characteristics of light emitting element 4. Voltage-luminance characteristics of light emitting element 4. Brightness-external quantum efficiency characteristics of light emitting element 4. Brightness-power efficiency characteristics of light emitting element 4. Emission spectrum of light emitting element 4. Brightness-current efficiency characteristics of light emitting element 5. Voltage-luminance characteristics of light emitting element 5. Brightness-external quantum efficiency characteristics of light emitting element 5. Brightness-power efficiency characteristics of light emitting element 5. Emission spectrum of light emitting element 5. FIG. 4 is a diagram illustrating Förster movement of the light emitting element 4. FIG. FIG. 4 is a diagram illustrating Förster movement of the light emitting element 4. FIG. FIG. 5 is a diagram illustrating Förster movement of the light emitting element 5. FIG. FIG. 5 is a diagram illustrating Förster movement of the light emitting element 5. FIG. FIG. 5 is a diagram illustrating Förster movement of the light emitting element 5. FIG.

Embodiments of the present invention will be described in detail below with reference to the drawings. However, those skilled in the art will easily understand that the present invention is not limited to the following description, and that the form and details thereof can be changed in various ways without departing from the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited to the contents described in the embodiments shown below.

(Embodiment 1)
First, the operating principle of a light-emitting element according to one embodiment of the present invention will be described. The gist of the present invention is to use a first phosphorescent compound and a second phosphorescent compound that emits light with a longer wavelength than that of the first phosphorescent compound; By efficiently causing both of the phosphorescent compounds (2) to emit light, a highly efficient multicolor light emitting device can be obtained.

As a general method for obtaining a multicolor light emitting device using a phosphorescent compound, a method can be considered in which a plurality of phosphorescent compounds having different emission colors are dispersed in an appropriate ratio in some kind of host material. However, in the case of such a method, the phosphorescent compound that emits light with the longest wavelength tends to emit light. ) is extremely difficult to design and control.

Another method for obtaining a multicolor light emitting device is a so-called tandem structure in which light emitting devices emitting different colors are stacked in series. For example, if three light-emitting elements, a blue light-emitting element, a green light-emitting element, and a red light-emitting element, are stacked in series and emitted simultaneously, polychromatic light (white light in this case) can be easily obtained. As for the element structure, it is only necessary to optimize each blue, green, and red element individually, so the design and
Control is relatively easy. However, since three elements are stacked, the number of layers increases and manufacturing becomes complicated. Further, if a problem occurs in electrical contact at the connection portion (so-called intermediate layer) of each element, an increase in driving voltage, that is, power loss may occur.

On the other hand, a light-emitting element according to one embodiment of the present invention includes a first light-emitting layer in which a first phosphorescent compound is dispersed in a first host material, and a first phosphorescent compound dispersed in a first host material between a pair of electrodes. This is a light-emitting element in which a second light-emitting layer in which a second phosphorescent compound that emits light with a long wavelength is dispersed in a second host material is laminated. At this time, the first light emitting layer and the second light emitting layer may be provided in contact with each other, unlike the tandem structure.

FIG. 1 schematically shows the element structure of the light-emitting element of one embodiment of the present invention described above. In FIG. 1C, a first electrode 101, a second electrode 102, and an EL layer 103 are illustrated. The EL layer 103 is provided with at least a light emitting layer 113, and other layers may be provided as appropriate.
FIG. 1C temporarily shows a structure in which a hole injection layer 111, a hole transport layer 112, an electron transport layer 114, and an electron injection layer 115 are provided. Note that the first electrode 101 functions as an anode, and the second electrode 102 functions as a cathode.

Further, FIGS. 1A and 1B are enlarged views of the light emitting layer 113 in the light emitting element. 1A and 1B, the first light emitting layer 113a, the second light emitting layer 113b, and the second light emitting layer 113a, the second light emitting layer 113b,
A light-emitting layer 113 in which the layers are combined, a first phosphorescent compound 113Da, and a second phosphorescent compound 1
13Db, a first host material 113Ha, and a second host material 113Hb.
In addition, FIG.1(b) is a schematic diagram when the 1st organic compound 113A is further contained in the 1st light emitting layer 113a. In either case, each phosphorescent compound (first and second
The phosphorescent compounds) are dispersed in the host material, so that each phosphorescent compound is separated from each other by each host material. Note that the first and second host materials may be the same or different. Further, either the first light emitting layer 113a or the second light emitting layer 113b may be on the anode side or the cathode side.

In this case, electron exchange interactions (so-called Dexter mechanism) occur between each phosphorescent compound.
The energy transfer due to this is suppressed. That is, after the first phosphorescent compound 113Da is excited, the excitation energy is transferred to the second phosphorescent compound 113Db by the Dexter mechanism.
This can prevent the phenomenon of movement. Therefore, it is possible to suppress a phenomenon in which the second phosphorescent compound 113Db that emits light with the longest wavelength mainly emits light. In addition, the second
If excitons are directly generated in the light emitting layer 113b, the second phosphorescent compound 113Db will mainly emit light. It is preferable that the phosphorescent compound 113Da be mainly excited.

However, if the energy transfer from the first phosphorescent compound 113Da is completely suppressed, the second phosphorescent compound 113Db will no longer emit light. Therefore, in one aspect of the present invention, the excitation energy of the first phosphorescent compound 113Da is partially
A device design is performed in which the phosphorescent compound 113Db is transferred. Such energy transfer between isolated molecules is possible by utilizing dipole-dipole interaction (Förster mechanism).

Here, the Förster mechanism will be explained. Hereinafter, the molecule giving excitation energy will be referred to as an energy donor, and the molecule receiving excitation energy will be referred to as an energy acceptor. That is, in one embodiment of the present invention, both the energy donor and the energy acceptor are phosphorescent compounds and are separated from each other by the host material.

The Förster mechanism does not require direct contact between molecules for energy transfer. Energy transfer occurs through the resonance phenomenon of dipole vibrations between an energy donor and an energy acceptor. The energy donor transfers energy to the energy acceptor by the resonance phenomenon of dipole vibration, and the excited state energy donor becomes the ground state, and the ground state energy acceptor becomes the excited state. The rate constant _kF of energy transfer by the Förster mechanism is shown in equation (1).

In formula (1), ν represents the vibration frequency, and F(ν) is the normalized emission spectrum of the energy donor (fluorescence spectrum when discussing energy transfer from the singlet excited state, and fluorescence spectrum from the triplet excited state). When discussing the energy transfer of phosphorescence spectrum), ε(
ν) represents the molar extinction coefficient of the energy acceptor, N represents Avogadro's number, and n
represents the refractive index of the medium, R represents the intermolecular distance between the energy donor and energy acceptor, τ represents the actually measured lifetime of the excited state (fluorescence lifetime or phosphorescence lifetime), and c represents the speed of light , φ represents the emission quantum yield (fluorescence quantum yield when discussing energy transfer from a singlet excited state, phosphorescence quantum yield when discussing energy transfer from a triplet excited state), and K ² is a coefficient (0 to 4) representing the orientation of the transition dipole moments of the energy donor and energy acceptor. Note that in the case of random orientation, K ² =2/3.

As can be seen from equation (1), the conditions for energy transfer by the Förster mechanism (Förster transfer) are: 1. Energy donor and energy acceptor are not too far apart (related to distance R); 2. The energy donor emits light (related to the luminescence quantum yield φ); 3. An example of this is that the emission spectrum of the energy donor and the absorption spectrum of the energy acceptor overlap (related to the integral term).

Here, as explained in FIG. 1, each phosphorescent compound (first and second phosphorescent compound)
are dispersed in each host material, and each phosphorescent compound is isolated from each other by each host material, so the distance R is at least one molecule or more (1 nm or more).
Therefore, all of the excitation energy generated in the first phosphorescent compound is not transferred to the second phosphorescent compound by the Förster mechanism. On the other hand, R is 1
Forster movement is possible up to about 0 nm to 20 nm. In order to ensure a distance R of at least one molecule between the first and second phosphorescent compounds, it is preferable that the volume of each phosphorescent compound dispersed in the host material is below a certain level. The corresponding concentration of each phosphorescent compound in the light emitting layer is 10 wt% or less. If the concentration of the phosphorescent compound is too low, it is difficult to obtain good characteristics, so the concentration of the phosphorescent compound in this embodiment is preferably 0.1 wt% or more and 10 wt% or less. In particular, it is more preferable that the first phosphorescent compound is contained in the first light emitting layer 113a at a concentration of 0.1 wt% or more and 5 wt% or less.

Each of the phosphorescent properties in the light-emitting element of one embodiment of the present invention using the first phosphorescent compound 113Da and the second phosphorescent compound 113Db that emits light with a longer wavelength than the first phosphorescent compound. A schematic diagram of Förster transfer between compounds is shown in FIG. FIG. 2 shows a structure in which a first light emitting layer 113a and a second light emitting layer 113b are stacked between the electrode 10 and the electrode 11. Note that one of the electrodes 10 and 11 functions as an anode, and the other functions as a cathode. As shown in FIG. 2(A), first, the singlet excited state (S _a ) generated in the first phosphorescent compound 113Da is converted to the triplet excited state (T _a ) by intersystem crossing.
That is, excitons in the first light emitting layer 113a are basically concentrated in _Ta .

Next, part of the exciton energy in the _Ta state is converted directly into light emission, but by using the Förster mechanism, part of the energy is converted into the triplet excited state of the second phosphorescent compound 113Db. (T _b ). This is because the first phosphorescent compound 113Da is luminescent (phosphorescence quantum yield φ is high) and the second phosphorescent compound 113Db undergoes an electronic transition from the singlet ground state to the triplet excited state. This is due to the fact that it has a direct absorption corresponding to (absorption spectrum of triplet excited state exists). If these conditions are met, T
Triplet-triplet Förster transfer from _a to T _b becomes possible.

Note that the singlet excited state (S _b ) of the second phosphorescent compound 113Db often has higher energy than the triplet excited state (T _a ) of the first phosphorescent compound 113Da, so the above-mentioned In many cases, it does not contribute much to energy transfer. Therefore, it is omitted here.
Of course, if the singlet excited state (S _b ) of the second phosphorescent compound 113Db is lower in energy than the triplet excited state (T _a ) of the first phosphorescent compound 113Da, energy transfer occurs in the same way. sell. In this case, the singlet excited state of the second phosphorescent compound 113Db (
The energy transferred to S _b ) is transferred to the triplet excited state (T _b ) of the second phosphorescent compound 113Db through intersystem crossing, and is involved in light emission.

In addition, in order to efficiently generate the Förster transfer described above between the phosphorescent compounds that are dopants, and to design the device so that energy does not transfer to the host material, the first and second host materials must be It is preferable that the phosphorescent compound does not have an absorption spectrum in the emission region of 113Da. In this way, by directly transferring energy between dopants without going through the host material (specifically, the second host material), it is possible to suppress the generation of extra energy transfer paths and achieve high luminous efficiency. This is a preferable configuration because it can be tied together.

Further, the first host material preferably has a higher triplet excitation energy than the first phosphorescent compound so as not to quench the first phosphorescent compound.

As described above, the basic concept of one embodiment of the present invention is to first isolate each of the first and second phosphorescent compounds using a host material and a stacked structure, and then to separate the first and second phosphorescent compounds, which emit light at a short wavelength. The object of the present invention is to provide an element structure that mainly excites a phosphorescent compound. In such a device structure, Förster-type energy transfer occurs partially within a certain distance (~20 nm), so the excitation energy of the first phosphorescent compound is partially transferred to the second phosphorescent compound. It is possible to move to the phosphorescent compound and obtain light emission from each of the first and second phosphorescent compounds.

However, what is more important in one aspect of the present invention is the selection of materials and element structure in consideration of energy transfer.

First, in order to generate Förster transfer, the emission quantum yield φ on the energy donor side needs to be high, but in one embodiment of the present invention, a phosphorescent compound (specifically, a phosphorescence quantum yield Since a luminescent compound of 0.1 or more is used, no problem occurs. The important point is that the formula (1
), that is, to make the emission spectrum F(ν) of the energy donor and the molar absorption coefficient ε(ν) of the energy acceptor overlap well.

In general, it is sufficient to overlap the emission spectra F(ν) of the energy donor in the wavelength region where the molar extinction coefficient ε(ν) of the energy acceptor is large (that is, by increasing the product of F(ν)ε(ν)). It is believed that However, this is not necessarily true in Förster mechanisms. This is because the integral term in equation (1) is inversely proportional to the fourth power of the frequency ν,
This is because wavelength dependence exists.

In order to make it easier to understand, equation (1) is first transformed. If the wavelength of light is λ, ν=c
/λ, equation (1) can be rewritten as equation (2) below.

In other words, it can be seen that the integral term becomes larger as the wavelength λ becomes larger. Simply put, this means that energy transfer occurs more easily on the longer wavelength side. That is, molar extinction coefficient ε(λ)
It is not as simple as just having F(λ) overlap in a wavelength region where ε(λ)λ4 is large, but it is necessary to make F(λ) overlap in a region where ε(λ) ^λ4 is large.

Therefore, in the light-emitting element of one embodiment of the present invention, the second phosphorescent compound 113Db is used to increase the efficiency of energy transfer from the first phosphorescent compound 113Da. The peak of the spectrum where the maximum value of the spectrum exists and the second
A phosphorescent compound is used in which the peaks of the function represented by ε(λ)λ ⁴ of the phosphorescent compound 113Db have peaks located on the longest wavelength side that overlap.

Note that the wavelength of the maximum value located on the longest wavelength side of the function represented by ε(λ)λ ⁴ of the second phosphorescent compound is the phosphorescent emission spectrum F(λ) of the first phosphorescent compound. It is preferable that they overlap. Further, a wavelength range having an intensity of half of the maximum value at the peak where the maximum value of the emission spectrum of the first phosphorescent compound 113Da exists, and ε(λ)λ ⁴ of the second phosphorescent compound It is more preferable if the wavelength ranges having half the intensity of the maximum value in the peak where the maximum value of the function expressed by is present overlap because the overlap between the spectra becomes large.

A light-emitting element having the above configuration can be a light-emitting element that has high luminous efficiency and can obtain light from each phosphorescent compound in a well-balanced manner.

In order to better understand the structure of such a phosphorescent compound, specific examples will be used below. Here, the following compound (1) (bis[
2-(6-tert-butyl-4-pyrimidinyl-κN3)phenyl-κC](2,4-
Pentanedionato-κ ² O, O') Iridium (III) (abbreviation: Ir(tBuppm)
₂ (acac))) as a second phosphorescent compound that emits light at a longer wavelength than the first phosphorescent compound 113Da.
As the phosphorescent compound 113Db, the following compound (2) (bis(2,3,5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III) (abbreviation: Ir(tppr
) ₂ (dpm))) will be explained using an example.

Figure 3(a) shows the molar extinction coefficient ε(λ) of compound (2), which is the second phosphorescent compound, and ε
(λ)λ ⁴ . The molar extinction coefficient ε(λ) decreases toward longer wavelengths, but ε(λ) ^λ4 has a maximum value around 550 nm (corresponding to the triplet MLCT absorption band of compound (2)). are doing. As can be seen from this example, due to the influence of the term λ ⁴ , ε(λ) λ ⁴ of the second phosphorescent compound has a maximum value in the absorption band located on the longest wavelength side (triplet MLCT absorption band). has.

On the other hand, FIG. 3(b) shows the photoluminescence (PL) spectrum F(λ) of compound (1).
and ε(λ)λ ⁴ of compound (2). Compound (1) is a first phosphorescent compound and emits green light with an emission peak around 545 nm. The PL spectrum F(λ) of the first phosphorescent compound has a large overlap with ε(λ)λ ⁴ of the second phosphorescent compound near the maximum value of ε(λ)λ ⁴ . As a result, energy transfer occurs from the first phosphorescent compound to the second phosphorescent compound by the Förster mechanism. In this case, since the maximum value corresponds to the triplet MLCT absorption band, it is a triplet-triplet Förster type energy transfer (T _a -T _b energy transfer in FIG. 2). At this time, the emission peak wavelength of the PL spectrum F(λ) of the first phosphorescent compound and ε(
When the difference in wavelength between the maximum values of λ) ^λ4 is 0.2 eV or less, energy transfer is performed efficiently, which is a preferable configuration. The emission peak wavelength of the PL spectrum F(λ) of compound (1) is 546 nm, and the wavelength of the maximum value of ε(λ)λ ⁴ of compound (2) is 543 nm, and the difference therebetween is 3 nm, which corresponds to 0.01 eV. Therefore, it can be seen that energy transfer between compound (1) and compound (2) is carried out very efficiently.

In addition, from the above, the second phosphorescent compound has direct absorption corresponding to electronic transition from the singlet ground state to the triplet excited state (for example, triplet ML
CT absorption). With such a configuration, triplet-triplet energy transfer as shown in FIG. 2 occurs efficiently.

Further, in order to obtain the above-mentioned recombination region, when the first light emitting layer 113a is located on the anode side, it is preferable that at least the second light emitting layer 113b has an electron transporting property, and the first light emitting layer 1
Both the light emitting layer 13a and the second light emitting layer 113b may have electron transport properties. Further, when the first light emitting layer 113a is located on the cathode side, it is preferable that at least the second light emitting layer 113b has hole transport properties, and both the first light emitting layer 113a and the second light emitting layer 113b have positive hole transport properties. It may also have pore transport properties.

Here, in the first light-emitting layer 113a, there is also a peak where the maximum value of the photoluminescence (PL) spectrum F(λ) of the first host material 113Ha exists, and ε( λ) It is preferable that the peaks where the maximum value located on the longest wavelength side of the function represented by ⁴ exists have a large overlap.

However, typically the photoluminescence (PL) spectrum F(λ) of the host material
The peak where the maximum value of exists and ε(λ)λ of the guest material (first phosphorescent compound 113Da)
It is difficult to overlap the peak where the maximum value located on the longest wavelength side of the function represented by ⁴ exists. This is because the photoluminescence (PL) of the host material is usually fluorescence emission, and fluorescence emission is emission from a higher energy level than phosphorescence emission, so the fluorescence spectrum is the absorption of the longest wavelength side of the guest material. This is because the triplet excitation energy level of the host material at a wavelength close to the spectrum (the triplet excited state of the guest material) is highly likely to be lower than the triplet excitation energy level of the guest material. If the triplet excitation energy level of the host material is lower than the triplet excitation energy level of the guest material, the triplet excitation energy of the guest material will be transferred to the host material, resulting in a decrease in luminous efficiency.

Therefore, in this embodiment, the first light emitting layer 113a further includes the first organic compound 113.
A, the first host material 113Ha and the first organic compound 113A contain the exciplex 11
A combination that forms 3Ec (also referred to as exciplex) is preferable (FIG. 1(b), FIG. 2(B)). In FIG. 2(B), 10 and 11 are electrodes, and one of the electrodes 10 and 11 functions as an anode and the other functions as a cathode. In addition, in the figure, exciplex 113E
The singlet excited state of c is represented by Se, the triplet excited state is represented by Te, and the first phosphorescent compound 11
The singlet excited state of 3Da is represented by Sa, the triplet excited state by Ta, the singlet excited state of the second phosphorescent compound 113Db is represented by Sb, and the triplet excited state is represented by Tb.

In this case, when carriers (electrons and holes) recombine in the first light emitting layer 113a, the first organic compound 113A and the first host material 113Ha obtain energy by recombining electrons and holes. The exciplex 113Ec is formed. The fluorescence emission from the exciplex 113Ec has a spectrum on the longer wavelength side than the fluorescence spectra of the first organic compound 113A alone and the first host material 113Ha alone, but the singlet excited state Se of the exciplex 113Ec and the triplet excited state Te have a characteristic that their energies are very close. Therefore, the PL spectrum F(λ) which is the emission from the singlet excited state of exciplex 113Ec
The peak where the maximum value of exists and ε(λ)λ of the guest material (first phosphorescent compound 113Da)
By overlapping the peak where the maximum value is located on the longest wavelength side of the function represented by ⁴ (corresponding to the absorption spectrum of the triplet excited state Ta of the guest material), energy transfer from Se to Ta, Both energy transfer from Te to Ta can be maximized. At this time, the emission peak wavelength of the exciplex 113Ec and the guest material (first phosphorescent compound 113
If the difference in wavelength between the maximum values of ε(λ)λ ⁴ of Da) is 0.2 eV or less, energy transfer is efficiently performed, which is a preferable configuration. Further, it is preferable to keep the triplet excitation energy level of the first organic compound 113A and the first host material 113Ha higher than the triplet excitation energy level of the first phosphorescent compound 113Da.

As described above, part of the energy transferred to the first phosphorescent compound 113Da is transferred to the second phosphorescent compound 113Db, and the energy transferred to the first phosphorescent compound 113Da is transferred to the second phosphorescent compound 113Db.
and the second phosphorescent compound 113Db both emit light efficiently.

In addition, from the triplet excited state (Te) of the exciplex 113Ec, the first phosphorescent compound 113D
Energy transfer to a occurs efficiently by the Dexter mechanism. Singlet excited state (Se
) is efficiently transferred by the Förster mechanism having the above configuration, so that total efficient energy transfer is achieved.

The first organic compound 113A and the first host material 113Ha may be any combination that produces an exciplex, but a compound that easily accepts electrons (electron-trapping compound),
It is preferable to combine it with a compound that easily accepts holes (a hole-trapping compound).

Compounds that easily accept electrons include bis(10-hydroxybenzo[h]quinolinato) beryllium(II) (abbreviation: BeBq ₂ ), bis(2-methyl-8-quinolinato)(
4-phenylphenolato)aluminum(III) (abbreviation: BAlq), bis(8-quinolinolato)zinc(II) (abbreviation: Znq), bis[2-(2-benzooxazolyl)phenolato]zinc(II) (abbreviation: ZnPBO), metal complexes such as bis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ), and 2-(4-biphenylyl)-5-(4-tert-butylphenyl). -1,3,4-oxadiazole (abbreviation: P
BD), 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviation: TAZ), 1,3-bis[5-(p- tert
-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene (abbreviation: OX
D-7), 9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole (abbreviation: CO11), 2,2',2''- (1,3,5-benzentriyl)tris(1-phenyl-1H-benzimidazole) (abbreviation: TPBI
), 2-[3-(dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzimidazole (abbreviation: mDBTBIm-II) and other heterocyclic compounds having a polyazole skeleton, 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: 2mD
BTBPDBq-II), 2-[3'-(9H-carbazol-9-yl)biphenyl-
3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mCzBPDBq), 4,6-bis[3-(phenanthren-9-yl)phenyl]pyrimidine (abbreviation: 4,6mPnP2
Pm), 4,6-bis[3-(4-dibenzothienyl)phenyl]pyrimidine (abbreviation: 4
, 6mDBTP2Pm-II), and 3,5-bis[3-(9H-carbazol-9-yl)phenyl]pyridine (abbreviation: 35DCzPP).
y), 1,3,5-tri[3-(3-pyridyl)-phenyl]benzene (abbreviation: TmPy
Examples include heterocyclic compounds having a pyridine skeleton such as PB). Among the above, heterocyclic compounds having a diazine skeleton and heterocyclic compounds having a pyridine skeleton are preferable because of their good reliability. In particular, a heterocyclic compound having a diazine (pyrimidine or pyrazine) skeleton has high electron transport properties and contributes to reducing the driving voltage.

Compounds that easily accept holes include 4,4'-bis[N-(1-naphthyl)-N-
phenylamino]biphenyl (abbreviation: NPB), N,N'-bis(3-methylphenyl)
-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (abbreviation: TP
D), 4,4'-bis[N-(spiro-9,9'-bifluoren-2-yl)-N-phenylamino]biphenyl (abbreviation: BSPB), 4-phenyl-4'-(9-phenyl fluoren-9-yl)triphenylamine (abbreviation: BPAFLP), 4-phenyl-3'-
(9-phenylfluoren-9-yl)triphenylamine (abbreviation: mBPAFLP),
4-phenyl-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4'-diphenyl-4''-(9-phenyl-9H
-carbazol-3-yl)triphenylamine (abbreviation: PCBBi1BP), 4-(1
-naphthyl)-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBANB), 4,4'-di(1-naphthyl)-4''-(9-phenyl- 9H-carbazol-3-yl)triphenylamine (abbreviation: PCBNBB), 9,9
-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]fluoren-2-amine (abbreviation: PCBAF), N-phenyl-N-[4-
Compounds having an aromatic amine skeleton such as (9-phenyl-9H-carbazol-3-yl)phenyl]spiro-9,9'-bifluoren-2-amine (abbreviation: PCBASF),
1,3-bis(N-carbazolyl)benzene (abbreviation: mCP), 4,4'-di(N-carbazolyl)biphenyl (abbreviation: CBP), 3,6-bis(3,5-diphenylphenyl)
-9-phenylcarbazole (abbreviation: CzTP), 3,3'-bis(9-phenyl-9H
-Carbazole) (abbreviation: PCCP) and other compounds with a carbazole skeleton, 4,4
',4''-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation:
DBT3P-II), 2,8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene (abbreviation: DBTFLP-III), 4-[
Compounds having a thiophene skeleton such as 4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviation: DBTFLP-IV), 4,
4',4''-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation: D
Compounds having a furan skeleton such as BF3P-II) and 4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran (abbreviation: mmDBFFLBi-II) can be mentioned. Among the above-mentioned compounds, compounds having an aromatic amine skeleton and compounds having a carbazole skeleton are preferable because they have good reliability, high hole transportability, and contribute to reduction in driving voltage.

The first organic compound 113A and the first host material 113Ha are combinations that can form an exciplex, without being limited to these, and the photoluminescence (PL) of the exciplex
) The peak where the maximum value of the spectrum F(λ) exists and the peak where the maximum value located on the longest wavelength side of the function expressed by ε(λ)λ ⁴ of the first phosphorescent compound exists. It is sufficient that the peak of the emission spectrum of the exciplex has a longer wavelength than the peak of the emission spectrum of the first phosphorescent compound 113Da.

Note that when the first organic compound 113A and the first host material 113Ha are composed of a compound that easily accepts electrons and a compound that easily accepts holes, the carrier balance can be controlled by the mixing ratio thereof. Specifically, it is preferable that the first organic compound 113A and the first host material 113Ha be in the range of 1:9 to 9:1.

Here, in this configuration, the peak where the maximum value of the photoluminescence (PL) spectrum F(λ) of the exciplex exists, and the peak of the function expressed by ε(λ)λ ⁴ of the first phosphorescent compound First host material 1 constituting an exciplex in which peaks with maximum values located on the long wavelength side overlap
13Ha and the first organic compound 113A are selected. The larger the overlap of these mountains, the better.

Note that the wavelength of the maximum value located on the longest wavelength side of the function expressed by ε(λ)λ ⁴ of the first phosphorescent compound overlaps with the photoluminescence (PL) spectrum F(λ) of the exciplex. It is preferable that In addition, the photoluminescence (PL) spectrum F(λ
) at the peak where the maximum value exists, the wavelength range having half the intensity of the above maximum value, and at the peak where the maximum value of the function represented by ε(λ) ^λ4 of the first phosphorescent compound exists. It is more preferable if the wavelength ranges having an intensity that is half the maximum value overlap because the overlap between the spectra becomes large.

In this configuration, since it becomes possible to efficiently transfer energy from the exciplex consisting of the first host material 113Ha and the first organic compound 113A to the first phosphorescent compound 113Da, the energy transfer efficiency can be further improved. Therefore, it is possible to realize a light emitting element with even higher external quantum efficiency.

(Embodiment 2)
In this embodiment, a detailed structure example of the light-emitting element described in Embodiment 1 will be described below with reference to FIG.

The light emitting element in this embodiment has an EL layer formed of a plurality of layers between a pair of electrodes.
In this embodiment, the light emitting element includes a first electrode 101, a second electrode 102, and an EL layer 103 provided between the first electrode 101 and the second electrode 102. There is.
Note that in this embodiment, the following description will be made assuming that the first electrode 101 functions as an anode and the second electrode 102 functions as a cathode. In other words, the first electrode 101 is better than the second electrode 10.
The structure is such that light emission is obtained when a voltage is applied to the first electrode 101 and the second electrode 102 so that the potential is higher than 2.

Since the first electrode 101 functions as an anode, it has a large work function (specifically, 4.0e
V or more) It is preferable to form using a metal, an alloy, a conductive compound, a mixture thereof, or the like. Specifically, for example, indium oxide-tin oxide (ITO)
in Oxide), indium oxide-tin oxide containing silicon or silicon oxide,
Indium oxide - Indium oxide containing zinc oxide, tungsten oxide and zinc oxide (
IWZO), etc. These conductive metal oxide films are usually formed by a sputtering method, but they may also be formed by applying a sol-gel method or the like. An example of a manufacturing method is a method in which indium oxide-zinc oxide is formed by a sputtering method using a target in which 1 to 20 wt % of zinc oxide is added to indium oxide. In addition, indium oxide (IWZO) containing tungsten oxide and zinc oxide is formed by a sputtering method using a target containing 0.5 to 5 wt% of tungsten oxide and 0.1 to 1 wt% of zinc oxide relative to indium oxide. You can also. In addition, gold (Au), platinum (
Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo)
, iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), or a nitride of a metal material (eg, titanium nitride). Graphene can also be used. Note that by using a composite material to be described later for the layer in contact with the first electrode 101 in the EL layer 103, the electrode material can be selected regardless of the work function.

The stacked structure of the EL layer 103 is not particularly limited as long as the light emitting layer 113 has the structure shown in Embodiment Mode 1. For example, it can be configured by appropriately combining a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, a carrier block layer, an intermediate layer, and the like. In this embodiment, the EL layer 103 includes a hole injection layer 111, a hole transport layer 112, a light emitting layer 113, an electron transport layer 114, and an electron injection layer 115, which are stacked in this order on the first electrode 101.
A configuration having the following will be explained. The materials constituting each layer are specifically shown below.

The hole injection layer 111 is a layer containing a substance with high hole injection properties. Molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, manganese oxide, etc. can be used. In addition, phthalocyanine (abbreviation: H ₂ Pc) and copper phthalocyanine (CuPC)
Phthalocyanine compounds such as 4,4'-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation: DPAB), N,N'-bis{4-[bis(3- Aromatic amine compounds such as methylphenyl)amino]phenyl}-N,N'-diphenyl-(1,1'-biphenyl)-4,4'-diamine (abbreviation: DNTPD), or poly(ethylenedioxythiophene) /Poly(styrene sulfonic acid) (PEDOT/PSS
The hole injection layer 111 can also be formed of a polymer such as ).

Further, as the hole injection layer 111, a composite material in which a hole transporting substance contains an acceptor substance can be used. Note that by using a hole-transporting substance containing an acceptor substance, the material for forming the electrode can be selected regardless of the work function of the electrode. In other words, not only a material with a large work function but also a material with a small work function can be used for the first electrode 101. As acceptor substances, 7, 7, 8
,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation: F ₄ -TC
NQ), chloranil, and the like. Further, transition metal oxides can be mentioned. Further, oxides of metals belonging to Groups 4 to 8 in the periodic table of elements can be mentioned. Specifically, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide, and rhenium oxide are preferable because they have high electron-accepting properties. Among these, molybdenum oxide is particularly preferred because it is stable in the atmosphere, has low hygroscopicity, and is easy to handle.

Various organic compounds such as aromatic amine compounds, carbazole derivatives, aromatic hydrocarbons, and polymer compounds (oligomers, dendrimers, polymers, etc.) can be used as the hole-transporting substance used in the composite material. Note that the organic compound used in the composite material is preferably an organic compound with high hole transport properties. Specifically, a substance having a hole mobility of 10 ⁻⁶ cm ² /Vs or more is preferable. Below, organic compounds that can be used as hole-transporting substances in composite materials are specifically listed.

For example, aromatic amine compounds include N,N'-di(p-tolyl)-N,N'-diphenyl-p-phenylenediamine (abbreviation: DTDPPA), 4,4'-bis[N-(4-
Diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation: DPAB), N
, N'-bis{4-[bis(3-methylphenyl)amino]phenyl}-N,N'-diphenyl-(1,1'-biphenyl)-4,4'-diamine (abbreviation: DNTPD), 1 ,3
, 5-tris[N-(4-diphenylaminophenyl)-N-phenylamino]benzene (abbreviation: DPA3B).

Specifically, carbazole derivatives that can be used in composite materials include 3-[N-
(9-phenylcarbazol-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-phenylcarbazol-3-yl)amino]
-9-phenylcarbazole (abbreviation: PCzPCN1) and the like can be mentioned.

In addition, other carbazole derivatives that can be used in composite materials include 4,4'-
Di(N-carbazolyl)biphenyl (abbreviation: CBP), 1,3,5-tris[4-(N-
Carbazolyl)phenyl]benzene (abbreviation: TCPB), 9-[4-(10-phenyl-)
9-anthryl)phenyl]-9H-carbazole (abbreviation: CzPA), 1,4-bis[
4-(N-carbazolyl)phenyl]-2,3,5,6-tetraphenylbenzene and the like can be used.

In addition, examples of aromatic hydrocarbons that can be used in composite materials include 2-tert
-Butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA), 2-
tert-butyl-9,10-di(1-naphthyl)anthracene, 9,10-bis(3,
5-diphenylphenyl)anthracene (abbreviation: DPPA), 2-tert-butyl-9
, 10-bis(4-phenylphenyl)anthracene (abbreviation: t-BuDBA), 9,1
0-di(2-naphthyl)anthracene (abbreviation: DNA), 9,10-diphenylanthracene (abbreviation: DPAnth), 2-tert-butylanthracene (abbreviation: t-BuAn)
th), 9,10-bis(4-methyl-1-naphthyl)anthracene (abbreviation: DMNA)
, 2-tert-butyl-9,10-bis[2-(1-naphthyl)phenyl]anthracene, 9,10-bis[2-(1-naphthyl)phenyl]anthracene, 2,3,6,7-
Tetramethyl-9,10-di(1-naphthyl)anthracene, 2,3,6,7-tetramethyl-9,10-di(2-naphthyl)anthracene, 9,9'-biantryl, 10,1
0'-diphenyl-9,9'-bianthryl, 10,10'-bis(2-phenylphenyl)-9,9'-bianthryl, 10,10'-bis[(2,3,4,5,6- pentaphenyl) phenyl]-9,9'-biantryl, anthracene, tetracene, rubrene,
Examples include perylene, 2,5,8,11-tetra(tert-butyl)perylene, and the like. In addition, pentacene, coronene, etc. can also be used. In this way, 1×10 ⁻⁶
It is more preferable to use an aromatic hydrocarbon having a hole mobility of cm ² /Vs or more and having 14 to 42 carbon atoms.

Note that the aromatic hydrocarbon that can be used in the composite material may have a vinyl skeleton. Examples of aromatic hydrocarbons having a vinyl group include 4,4'-bis(2,2-
diphenylvinyl)biphenyl (abbreviation: DPVBi), 9,10-bis[4-(2,2-
Examples include diphenylvinyl)phenyl]anthracene (abbreviation: DPVPA).

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

By forming the hole injection layer, hole injection properties are improved, and it becomes possible to obtain a light emitting element with low driving voltage.

The hole transport layer 112 is a layer containing a hole transporting substance. As hole-transporting substances,
For example, 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB) and N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[ 1,
1'-biphenyl]-4,4'-diamine (abbreviation: TPD), 4,4',4''-tris(N,N-diphenylamino)triphenylamine (abbreviation: TDATA), 4,4', 4
''-Tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine (abbreviation: MTDATA), 4,4'-bis[N-(spiro-9,9'-bifluorene-2)
-yl)-N-phenylamino]biphenyl (abbreviation: BSPB), 4-phenyl-4'-
Aromatic amine compounds such as (9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP) can be used. The substances described herein have high hole transport properties, and mainly have a hole mobility of 10 ⁻⁶ cm ² /Vs or more. Furthermore, the organic compounds listed as hole-transporting substances in the above-described composite material can also be used for the hole-transporting layer 112. Further, polymer compounds such as poly(N-vinylcarbazole) (abbreviation: PVK) and poly(4-vinyltriphenylamine) (abbreviation: PVTPA) can also be used. Note that the layer containing the hole-transporting substance is not limited to a single layer, and may be a stack of two or more layers made of the above-mentioned substance.

The light emitting layer 113 is a layer containing a first phosphorescent compound and a second phosphorescent compound. Since the light-emitting layer 113 has the structure described in Embodiment 1, the light-emitting element in this embodiment can have very high light-emitting efficiency. Light emitting layer 113
Please refer to the description of Embodiment 1 for the main configuration.

In the light-emitting layer 113, there are no particular limitations on the materials that can be used as the first phosphorescent compound and the second phosphorescent compound, as long as the combination has the relationship as described in Embodiment 1. None. Examples of the first phosphorescent compound and the second phosphorescent compound include the following.

Tris {2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)-4H
-1,2,4-triazol-3-yl-κN ² ]phenyl-κC}iridium (III
) (abbreviation: Ir(mpptz-dmp) ₃ ), tris(5-methyl-3,4-diphenyl-4H-1,2,4-triazolato)iridium(III) (abbreviation: Ir(Mptz) ₃
), tris[4-(3-biphenyl)-5-isopropyl-3-phenyl-4H-1,2
,4-triazolato]iridium(III) (abbreviation: Ir(iPrptz-3b) ₃ ), an organometallic iridium complex having a 4H-triazole skeleton, and tris[3-methyl-1-(2-methylphenyl)- 5-phenyl-1H-1,2,4-triazolato]iridium(III) (abbreviation: Ir(Mptz1-mp) ₃ ), tris(1-methyl-5-phenyl-3-propyl-1H-1,2, Organometallic iridium complexes having a 1H-triazole skeleton such as Ir(Prptz1-Me) ₃ ), fac-tris[1-(2,6-diisopropylphenyl)-2 -phenyl-1H-imidazole]iridium(III) (abbreviation: Ir(iPrpmi) ₃ ),
An imidazole skeleton such as tris[3-(2,6-dimethylphenyl)-7-methylimidazo[1,2-f]phenanthridinato]iridium(III) (abbreviation: Ir(dmpimpt-Me) ₃ ) Organometallic iridium complexes containing bis[2-(4',6'-difluorophenyl)pyridinato-N,C ^2' ]iridium(III) tetrakis(1-pyrazolyl)borate (abbreviation: FIr6), bis[2- (4',6'-difluorophenyl)
Pyridinato-N,C ^2' ]iridium(III) picolinate (abbreviation: FIrpic),
Bis{2-[3',5'-bis(trifluoromethyl)phenyl]pyridinato-N,C ^2
' }Iridium (III) picolinate (abbreviation: Ir(CF ₃ ppy) ₂ (pic)),
Bis[2-(4',6'-difluorophenyl)pyridinato-N,C ^2' ]iridium (
III) An organometallic iridium complex having a phenylpyridine derivative having an electron-withdrawing group such as acetylacetonate (abbreviation: FIracac) as a ligand can be mentioned. These are compounds that emit blue phosphorescence, and have an emission peak from 440 nm to 520 nm. Among the above-mentioned, organometallic iridium complexes having a polyazole skeleton such as 4H-triazole, 1H-triazole, and imidazole have high hole-trapping properties. Therefore, these compounds are used as the first phosphorescent compound in the light-emitting element of one embodiment of the present invention, the first light-emitting layer is provided closer to the cathode than the second light-emitting layer, and the second light-emitting layer is provided closer to the cathode than the second light-emitting layer. When the layer is hole-transporting (specifically, when the second host material is a hole-transporting material), it becomes easy to control the carrier recombination region within the first light-emitting layer. Therefore, it is preferable.
Note that organometallic iridium complexes having a 4H-triazole skeleton are particularly preferred because they are excellent in reliability and luminous efficiency.

Also, tris(4-methyl-6-phenylpyrimidinato)iridium(III) (abbreviation:
Ir(mppm) ₃ ), tris(4-t-butyl-6-phenylpyrimidinato)iridium(III) (abbreviation: Ir(tBuppm) ₃ ), (acetylacetonato)bis(6-methyl-4-phenyl) pyrimidinato) iridium(III) (abbreviation: Ir(mppm) ₂ (
acac)), (acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidinato)iridium(III) (abbreviation: Ir(tBuppm) ₂ (acac)), (acetylacetonato)bis[6- (2-norbornyl)-4-phenylpyrimidinato]iridium(III) (abbreviation: Ir(nbppm) ₂ (acac)), (acetylacetonato)bis[5-methyl-6-(2-methylphenyl)- 4-phenylpyrimidinato]iridium(III) (abbreviation: Ir(mpmppm) ₂ (acac)), (acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III) (abbreviation: Ir(dpp
Organometallic iridium complexes having a _pyrimidine skeleton such as
II) (abbreviation: Ir(mppr-Me) ₂ (acac)), (acetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazinato)iridium(III) (abbreviation: Ir(mppr- Organometallic iridium complexes having a pyrazine skeleton such as iPr) ₂ (acac)) and tris(2-phenylpyridinato-N,C ^2' )iridium
) (abbreviation: Ir(ppy) ₃ ), bis(2-phenylpyridinato-N,C ^2' )iridium(III) acetylacetonate (abbreviation: Ir(ppy) ₂ (acac)), bis(benzo[ h] quinolinato) iridium (III) acetylacetonate (abbreviation: Ir(bz
q) ₂ (acac)), tris(benzo[h]quinolinato)iridium(III) (abbreviation: Ir(bzz) ₃ ), tris(2-phenylquinolinato-N,C ^2' )iridium(I
II) (abbreviation: Ir(pq) ₃ ), pyridine skeleton such as bis(2-phenylquinolinato-N,C ^2' )iridium(III) acetylacetonate (abbreviation: Ir(pq) ₂ (acac)) In addition to organometallic iridium complexes having the following, examples include rare earth metal complexes such as tris(acetylacetonato)(monophenanthroline)terbium(III) (abbreviation: Tb(acac) ₃ (Phen)). These are compounds that mainly emit green phosphorescence, and have an emission peak at 500 nm to 600 nm. Among the above-mentioned, organometallic iridium complexes having a diazine skeleton such as pyrimidine and pyrazine have weak hole-trapping properties;
High electron trapping property. Therefore, these compounds are used as the first phosphorescent compound in the light-emitting element of one embodiment of the present invention, the first light-emitting layer is provided closer to the anode than the second light-emitting layer, and the second light-emitting layer is provided closer to the anode than the second light-emitting layer. It is preferable when the layer is electron transporting (specifically, when the second host material is an electron transporting material) because it is easy to control the carrier recombination region within the first light emitting layer. . Note that an organometallic iridium complex having a pyrimidine skeleton is particularly preferable because it has outstanding reliability and luminous efficiency.

Also, bis[4,6-bis(3-methylphenyl)pyrimidinato](diisobutyrylmethano)iridium(III) (abbreviation: Ir(5mdppm) ₂ (dibm)), bis[4,
6-bis(3-methylphenyl)pyrimidinato](dipivaloylmethanato)iridium (
III) (abbreviation: Ir(5mdppm) ₂ (dpm)), bis[4,6-di(naphthalen-1-yl)pyrimidinato](dipivaloylmethanato)iridium(III) (abbreviation: I
Organometallic iridium complexes with a pyrimidine skeleton such as r(d1npm) ₂ (dpm)) and (acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III) (abbreviation: Ir( tppr) ₂ (acac)), bis(2,3,5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III) (abbreviation: Ir(tppr)
) ₂ (dpm)), having a pyrazine skeleton such as (acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III) (abbreviation: Ir(Fdpq) ₂ (acac)) Organometallic iridium complexes, tris(1-phenylisoquinolinato-N,C ^2' )iridium(III) (abbreviation: Ir(piq) ₃ ), bis(1-phenylisoquinolinato-N,C ^2' ) In addition to organometallic iridium complexes with a pyridine skeleton such as iridium (III) acetylacetonate (abbreviation: Ir(piq) ₂ (acac)), 2,3,7,8,12,13,17,18-octaethyl Platinum complexes such as -21H,23H-porphyrin platinum (II) (abbreviation: PtOEP) and tris(1,3-diphenyl-1,3-propanedionato) (monophenanthroline) europium (III)
) (abbreviation: Eu(DBM) ₃ (Phen)), tris[1-(2-thenoyl)-3,3,
Examples include rare earth metal complexes such as 3-trifluoroacetonato] (monophenanthroline) europium (III) (abbreviation: Eu(TTA) ₃ (Phen)). These are compounds that emit red phosphorescence, and have an emission peak between 600 nm and 700 nm. Among the above-mentioned, organometallic iridium complexes having a diazine skeleton such as pyrimidine and pyrazine have weak hole trapping properties and high electron trapping properties. Therefore, an organometallic iridium complex having a diazine skeleton is used as the second phosphorescent compound, the first light-emitting layer is provided closer to the cathode than the second light-emitting layer, and the second light-emitting layer If the second host material is a hole transporting material (specifically, if the second host material is a hole transporting material), the carrier recombination region is
This is preferable because it is easy to control the luminescent layer. Note that an organometallic iridium complex having a pyrimidine skeleton is particularly preferable because it has outstanding reliability and luminous efficiency. Furthermore, since an organometallic iridium complex having a pyrazine skeleton can provide red light emission with good chromaticity, color rendering properties can be improved when applied to a white light emitting element.

In addition to the phosphorescent compounds described above, from among known phosphorescent materials, a first phosphorescent material and a second phosphorescent material having the relationship as shown in Embodiment 1 may be used. You may choose and use it.

Note that the phosphorescent compounds (first phosphorescent compound 113a and second phosphorescent compound 1
13b), a material exhibiting thermally activated delayed fluorescence, namely thermally activated delayed fluorescence (TADF).
) materials may be used. Here, delayed fluorescence refers to light emission that has a spectrum similar to normal fluorescence but has an extremely long lifetime. Its lifetime is more than 10 ⁻⁶ seconds, preferably 10 ⁻³
It is more than seconds. Specific examples of the thermally activated delayed fluorescent material include fullerene and derivatives thereof, acridine derivatives such as proflavin, eosin, and the like. In addition, magnesium (Mg
), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (I
n) or a metal-containing porphyrin containing palladium (Pd) or the like. As the metal-containing porphyrin, for example, protoporphyrin-tin fluoride complex (abbreviation: Sn
F ₂ (Proto IX)), mesoporphyrin-tin fluoride complex (abbreviation: SnF ₂ (M
eso IX)), hematoporphyrin-tin fluoride complex (abbreviation: SnF ₂ (Hemat
o IX)), coproporphyrin tetramethyl ester-tin fluoride complex (abbreviation: Sn
F ₂ (Copro III-4Me)), octaethylporphyrin-tin fluoride complex (
Abbreviation: SnF ₂ (OEP)), ethioporphyrin-tin fluoride complex (abbreviation: SnF ₂ (
Etio I)), octaethylporphyrin-platinum chloride complex (abbreviation: PtCl ₂ (OE
P)) etc. Furthermore, 2-(biphenyl-4-yl)-4,6-bis(12-
Heterocycles having a π-excessive heteroaromatic ring and a π-deficient heteroaromatic ring such as phenylindolo[2,3-a]carbazol-11-yl)-1,3,5-triazine (abbreviation: PIC-TRZ) Compounds can also be used. In addition, in a substance in which a π-excessive heteroaromatic ring and a π-deficient heteroaromatic ring are directly bonded, both the donor property of the π-excessive heteroaromatic ring and the acceptor property of the π-deficient heteroaromatic ring become strong, and _S1 and This is particularly preferable because the energy difference in T ₁ becomes small.

There are no particular limitations on the materials that can be used as the first and second host materials, and various carrier transport materials may be selected and combined as appropriate to obtain the device structure shown in FIG. .

For example, as a host material having electron transport properties, bis(10-hydroxybenzo[h]
quinolinato) beryllium(II) (abbreviation: BeBq ₂ ), bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III) (abbreviation: BAlq), bis(8-quinolinolato)zinc(II) (abbreviation: Znq), bis[2-(2-benzooxazolyl)phenolato]zinc(II) (abbreviation: ZnPBO), bis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ) metal complexes such as 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD), 3-(4-biphenylyl)-4- Phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviation: TAZ), 1,3-bis[5-(p
-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene (
Abbreviation: OXD-7), 9-[4-(5-phenyl-1,3,4-oxadiazole-2-
phenyl]-9H-carbazole (abbreviation: CO11), 2,2',2''-(1,
3,5-benzentriyl)tris(1-phenyl-1H-benzimidazole) (abbreviation: TPBI), 2-[3-(dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzimidazole ( Heterocyclic compounds having a polyazole skeleton such as (abbreviation: mDBTBIm-II), 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-[3'-(9H-carbazol-9-yl)biphenyl-3 -yl]dibenzo[f,h]quinoxaline (abbreviation: 2mCzBPDBq),
4,6-bis[3-(phenanthren-9-yl)phenyl]pyrimidine (abbreviation: 4,6
Heterocyclic compounds having a diazine skeleton such as mPnP2Pm), 4,6-bis[3-(4-dibenzothienyl)phenyl]pyrimidine (abbreviation: 4,6mDBTP2Pm-II),
3,5-bis[3-(9H-carbazol-9-yl)phenyl]pyridine (abbreviation: 35
Examples include heterocyclic compounds having a pyridine skeleton, such as DCzPPy) and 1,3,5-tri[3-(3-pyridyl)-phenyl]benzene (abbreviation: TmPyPB). Among the above, heterocyclic compounds having a diazine skeleton and heterocyclic compounds having a pyridine skeleton are preferable because of their good reliability. In particular, a heterocyclic compound having a diazine (pyrimidine or pyrazine) skeleton has high electron transport properties and contributes to reducing the driving voltage.

In addition, as a host material having hole transport properties, 4,4'-bis[N-(1-naphthyl)
-N-phenylamino]biphenyl (abbreviation: NPB), N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (abbreviation) :TPD), 4,4'-bis[N-(spiro-9,9'-bifluoren-2-yl)-N
-phenylamino]biphenyl (abbreviation: BSPB), 4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP), 4-phenyl-
3'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: mBPAFL)
P), 4-phenyl-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4'-diphenyl-4''-(9-phenyl-9H- carbazol-3-yl)triphenylamine (abbreviation: PCBBi1BP), 4
-(1-naphthyl)-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBANB), 4,4'-di(1-naphthyl)-4''-(9 -phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBNBB),
9,9-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazole-3
-yl)phenyl]fluorene-2-amine (abbreviation: PCBAF), N-phenyl-N-
[4-(9-phenyl-9H-carbazol-3-yl)phenyl]spiro-9,9'-
Compounds with an aromatic amine skeleton such as bifluoren-2-amine (abbreviation: PCBASF), 1,3-bis(N-carbazolyl)benzene (abbreviation: mCP), 4,4'-di(N
-carbazolyl)biphenyl (abbreviation: CBP), 3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviation: CzTP), 3,3'-bis(9-phenyl-9H-carbazole) ( Compounds having a carbazole skeleton such as (abbreviation: PCCP),
4,4',4''-(benzene-1,3,5-triyl)tri(dibenzothiophene) (
Abbreviation: DBT3P-II), 2,8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene (abbreviation: DBTFLP-III),
Compounds with a thiophene skeleton such as 4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviation: DBTFLP-IV), and 4,4',4'' -(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation: DBF3P-II), 4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran (abbreviation: mmDBFFLBi-II) and other compounds having a furan skeleton are included. Among the above-mentioned compounds, compounds having an aromatic amine skeleton and compounds having a carbazole skeleton are preferable because they have good reliability, high hole transportability, and contribute to reduction in driving voltage.

Further, in addition to the host materials described above, host materials from among known substances may be used. Note that as the host material, it is preferable to select a substance having a triplet level (energy difference between the ground state and triplet excited state) that is larger than the triplet level (energy difference between the ground state and triplet excited state) of the phosphorescent compound. Also,
Preferably, these host materials do not have an absorption spectrum in the blue region. Specifically, it is preferable that the absorption edge of the absorption spectrum is 440 nm or less.

The light emitting layer 113 having the above structure can be manufactured by co-evaporation using a vacuum evaporation method, or by using a mixed solution using an inkjet method, a spin coating method, a dip coating method, or the like.

The electron transport layer 114 is a layer containing an electron transport substance. For example, tris(8-quinolinolato)aluminum (abbreviation: Alq), tris(4-methyl-8-quinolinolato)aluminum (abbreviation: Almq ₃ ), bis(10-hydroxybenzo[h]quinolinato) beryllium (abbreviation: BeBq ₂ ), bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum (abbreviation: BAlq), etc., is a layer made of a metal complex having a quinoline skeleton or benzoquinoline skeleton. In addition, bis[2-(2-hydroxyphenyl)benzoxazolato]zinc (abbreviation: Zn(BOX) ₂ ), bis[2-(2-hydroxyphenyl)benzothiazolato]zinc (abbreviation: Zn(BTZ)) Metal complexes having oxazole-based or thiazole-based ligands such as ₂ ) can also be used. Furthermore, in addition to metal complexes, 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3
,4-oxadiazole (abbreviation: PBD) and 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene (abbreviation: OXD- 7
), 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)
-1,2,4-triazole (abbreviation: TAZ), bathophenanthroline (abbreviation: BPhe)
n), bathocuproine (abbreviation: BCP), etc. can also be used. The substances described herein have high electron transport properties and mainly have an electron mobility of 10 ⁻⁶ cm ² /Vs or more. Note that the electron-transporting host material described above may be used for the electron-transporting layer 114.

Further, the electron transport layer 114 is not limited to a single layer, and may be a stack of two or more layers made of the above substances.

Further, a layer for controlling movement of electron carriers may be provided between the electron transport layer and the light emitting layer.
This is a layer in which a small amount of a substance with high electron trapping properties is added to the above-mentioned material with high electron transport properties, and by suppressing the movement of electron carriers, it is possible to adjust the carrier balance. Such a configuration is highly effective in suppressing problems caused by electrons penetrating the light-emitting layer (for example, reduction in device life).

Further, an electron injection layer 115 may be provided between the electron transport layer 114 and the second electrode 102 and in contact with the second electrode 102. As the electron injection layer 115, lithium fluoride (LiF),
Alkali metals or alkaline earth metals or compounds thereof such as cesium fluoride (CsF), calcium fluoride (CaF ₂ ), etc. can be used. For example, a layer containing an alkali metal, an alkaline earth metal, or a compound thereof in a layer made of a substance having electron transport properties can be used. Note that by using a layer containing an alkali metal or alkaline earth metal in a layer made of a substance having electron transport properties as the electron injection layer 115, electron injection from the second electrode 102 is efficiently performed. more preferable.

The material forming the second electrode 102 has a small work function (specifically, 3.8 eV
(below) Metals, alloys, electrically conductive compounds, mixtures thereof, etc. can be used. Specific examples of such cathode materials include alkali metals such as lithium (Li) and cesium (Cs), as well as magnesium (Mg), calcium (Ca), and strontium (Sr).
Elements belonging to Group 1 or Group 2 of the periodic table of elements such as
, AlLi), europium (Eu), ytterbium (Yb), and alloys containing these metals. However, by providing an electron injection layer between the second electrode 102 and the electron transport layer, indium oxide-tin oxide containing Al, Ag, ITO, silicon or silicon oxide can be used regardless of the size of the work function. A variety of conductive materials such as
It can be used as the electrode 102 of. These conductive materials can be formed into films using a sputtering method, an inkjet method, a spin coating method, or the like.

Furthermore, various methods can be used to form the EL layer 103, regardless of whether it is a dry method or a wet method. For example, a vacuum deposition method, an inkjet method, a spin coating method, etc. may be used. Further, each electrode or each layer may be formed using a different film forming method.

The electrodes may also be formed by a wet method using a sol-gel method, or may be formed by a wet method using a paste of a metal material. Alternatively, it may be formed using a dry method such as a sputtering method or a vacuum evaporation method.

In the light-emitting element having the above configuration, a current flows due to the potential difference generated between the first electrode 101 and the second electrode 102, and holes are generated in the light-emitting layer 113, which is a layer containing a highly luminescent substance. and electrons recombine and emit light. In other words, the structure is such that a light emitting region is formed in the light emitting layer 113.

The emitted light is extracted to the outside through either or both of the first electrode 101 and the second electrode 102. Therefore, either one or both of the first electrode 101 and the second electrode 102 is made of a light-transmitting electrode. When only the first electrode 101 is a translucent electrode, emitted light is extracted through the first electrode 101. Furthermore, when only the second electrode 102 is a translucent electrode, light emission is extracted through the second electrode 102. When the first electrode 101 and the second electrode 102 are both light-transmitting electrodes, the emitted light passes through the first electrode 101 and the second electrode 102 and is extracted from both.

Note that the structure of the layer provided between the first electrode 101 and the second electrode 102 is not limited to the above. However, in order to suppress the quenching caused by the close proximity of the light emitting region to the metal used for the electrode or carrier injection layer, holes and electrons are placed in a region away from the first electrode 101 and the second electrode 102. It is preferable to have a configuration in which a light emitting region is provided in which the rays are recombined.

In addition, the hole transport layer and electron transport layer in contact with the light emitting layer 113, especially the carrier transport layer in contact with the side near the light emitting region of the light emitting layer 113, suppress energy transfer from excitons generated in the light emitting layer. It is preferable to use a substance having a band gap larger than that of a light-emitting substance constituting the light-emitting layer or a luminescent center substance included in the light-emitting layer.

The light emitting element in this embodiment may be manufactured on a substrate made of glass, plastic, or the like. The order in which they are formed on the substrate may be stacked sequentially from the first electrode 101 side or stacked sequentially from the second electrode 102 side. The light emitting device may be one in which one light emitting element is formed on one substrate, or a plurality of light emitting elements may be formed on one substrate. By manufacturing a plurality of such light emitting elements on one substrate, a lighting device with divided elements or a passive matrix type light emitting device can be manufactured. Alternatively, for example, a thin film transistor (TFT) may be formed on a substrate made of glass, plastic, or the like, and a light emitting element may be produced on an electrode electrically connected to the TFT. As a result, an active matrix light-emitting device in which driving of a light-emitting element is controlled by TFTs can be manufactured. Note that the structure of the TFT is not particularly limited. Staggered TF
It may be a TFT or an inverted staggered TFT. Furthermore, the crystallinity of the semiconductor used in the TFT is not particularly limited, and either an amorphous semiconductor or a crystalline semiconductor may be used. Furthermore, the driving circuit formed on the TFT substrate may be composed of N-type and P-type TFTs, or may be composed only of either N-type TFTs or P-type TFTs. good.

Note that this embodiment can be combined with other embodiments as appropriate.

(Embodiment 3)
In this embodiment, a light-emitting device using the light-emitting element described in Embodiment 1 and Embodiment 2 will be described.

In this embodiment, a light-emitting device manufactured using the light-emitting elements described in Embodiment 1 and 2 will be described with reference to FIGS. Note that FIG. 4(A) is a top view showing the light emitting device, and FIG. 4(B) is a cross-sectional view taken along AB and CD in FIG. 4(A). This light emitting device includes a drive circuit section (source line drive circuit) 601, a pixel section 602, and a drive circuit section (gate line drive circuit) 603, which are shown by dotted lines, to control light emission of the light emitting element. Further, 604 is a sealing substrate, 625 is a desiccant, 605 is a sealing material, and the inside surrounded by the sealing material 605 is a space 607.

Note that the routing wiring 608 is a wiring for transmitting signals input to the source line driving circuit 601 and the gate line driving circuit 603, and is used to transmit video signals, clock signals, Receives start signals, reset signals, etc. Note that although only the FPC is illustrated here, a printed wiring board (PWB) may be attached to the FPC. The light emitting device in this specification includes not only a light emitting device main body but also a state in which an FPC or PWB is attached to the light emitting device.

Next, the cross-sectional structure will be explained using FIG. 4(B). A drive circuit section and a pixel section are formed on the element substrate 610, but here, the source line drive circuit 601, which is the drive circuit section, is formed on the element substrate 610.
, one pixel in the pixel portion 602 is shown.

Note that the source line drive circuit 601 includes an n-channel type TFT 623 and a p-channel type TFT 62.
A CMOS circuit is formed by combining 4 and 4. Furthermore, the drive circuit may be formed of various CMOS circuits, PMOS circuits, or NMOS circuits. Furthermore, although this embodiment shows a driver-integrated type in which a drive circuit is formed on a substrate, this is not necessarily necessary, and the drive circuit can be formed outside instead of on the substrate.

Further, the pixel portion 602 is formed of a plurality of pixels including a switching TFT 611, a current control TFT 612, and a first electrode 613 electrically connected to the drain thereof.
Note that an insulator 614 is formed to cover the end of the first electrode 613. Here, it is formed using a positive type photosensitive acrylic resin film.

Further, in order to obtain good coverage, a curved surface having a curvature is formed at the upper end or lower end of the insulator 614. For example, when positive photosensitive acrylic is used as the material for the insulator 614, it is preferable that only the upper end of the insulator 614 has a curved surface with a radius of curvature (0.2 μm to 3 μm). Further, as the insulator 614, a negative photosensitive resin,
Alternatively, any positive type photosensitive resin can be used.

An EL layer 616 and a second electrode 617 are formed on the first electrode 613, respectively. Here, as the material used for the first electrode 613 that functions as an anode, it is desirable to use a material with a large work function. For example, an ITO film, an indium tin oxide film containing silicon, an indium oxide film containing 2 to 20 wt% zinc oxide, a titanium nitride film,
In addition to single-layer films such as chromium film, tungsten film, Zn film, and Pt film, laminated films of titanium nitride and aluminum-based films, titanium nitride films, aluminum-based films, and titanium nitride films are also available. A three-layer structure or the like can be used. Note that if the layered structure is used, the resistance as a wiring is low, good ohmic contact can be made, and furthermore, it can function as an anode.

Further, the EL layer 616 is formed by various methods such as a vapor deposition method using a vapor deposition mask, an inkjet method, and a spin coating method. The EL layer 616 is the same as in Embodiment 1 and Embodiment 2.
It includes the configuration described in . In addition, other materials constituting the EL layer 616 include:
It may be a low molecular compound or a high molecular compound (including oligomers and dendrimers).

Furthermore, the material used for the second electrode 617, which is formed on the EL layer 616 and functions as a cathode, may be a material with a small work function (Al, Mg, Li, Ca, or an alloy or compound thereof, MgAg, MgIn, It is preferable to use AlLi, etc.). Note that the EL layer 616
When the light generated in the above is transmitted through the second electrode 617, the second electrode 617 is made of a thin metal film and a transparent conductive film (ITO, indium oxide containing 2 to 20 wt% zinc oxide). , silicon-containing indium tin oxide, zinc oxide (ZnO), etc.) is preferably used.

Note that the first electrode 613, the EL layer 616, and the second electrode 617 form a light emitting element. The light-emitting element is the light-emitting element described in Embodiment 1 and Embodiment 2. Note that although the pixel portion includes a plurality of light emitting elements, the light emitting device in this embodiment uses the light emitting elements described in Embodiment 1 and Embodiment 2, and a light emitting element having a structure other than that. Both elements may be included.

Furthermore, by bonding the sealing substrate 604 to the element substrate 610 using a sealing material 605,
The structure is such that a light emitting element 618 is provided in a space 607 surrounded by an element substrate 610, a sealing substrate 604, and a sealant 605. Note that the space 607 is filled with a filler, and in addition to being filled with an inert gas (nitrogen, argon, etc.), the space 607 may also be filled with a sealing material 605. If a recess is formed in the sealing substrate and a drying material 625 is provided there, deterioration due to the influence of moisture can be suppressed, which is a preferable configuration.

Note that it is preferable to use epoxy resin or glass frit for the sealing material 605. Further, it is desirable that these materials are as impervious to moisture and oxygen as possible. In addition to glass substrates and quartz substrates, materials used for the sealing substrate 604 include FRP (Fiberg
A plastic substrate made of lass-reinforced plastics, PVF (polyvinyl fluoride), polyester, acrylic, or the like can be used.

As described above, a light-emitting device manufactured using the light-emitting element described in Embodiment 1 and Embodiment 2 can be obtained.

Since the light-emitting device in this embodiment uses the light-emitting element described in Embodiment 1 and 2, a light-emitting device with good characteristics can be obtained. Specifically, the light-emitting element shown in Embodiment 1 and Embodiment 2 has good luminous efficiency, and a light-emitting device with reduced power consumption can be obtained. Further, since the light emitting element has a low driving voltage, it is possible to obtain a light emitting device with a low driving voltage.

As described above, in this embodiment, an active matrix type light emitting device has been described, but a passive matrix type light emitting device may also be used. FIG. 5 shows a passive matrix type light emitting device manufactured by applying the present invention. Note that FIG. 5(A) is a perspective view showing the light emitting device, and FIG. 5(B) is a cross-sectional view taken along XY in FIG. 5(A). In Figure 5,
An EL layer 955 is provided on the substrate 951 between an electrode 952 and an electrode 956.
The end of the electrode 952 is covered with an insulating layer 953. A partition layer 9 is provided on the insulating layer 953.
54 are provided. The side walls of the partition layer 954 have an inclination such that the distance between one side wall and the other side wall becomes narrower as the side wall approaches the substrate surface. In other words, the cross section of the partition layer 954 in the short side direction is trapezoidal, and the bottom side (the side facing in the same direction as the surface direction of the insulating layer 953 and touching the insulating layer 953) is closer to the top side (the side facing the surface of the insulating layer 953). The insulating layer 9 is oriented in the same direction as the
53). By providing the partition layer 954 in this manner, defects in the light emitting element due to static electricity or the like can be prevented. Furthermore, a passive matrix light-emitting device can also be driven with low power consumption by including the light-emitting element described in Embodiment 1 and Embodiment 2 that operates at a low driving voltage. Further, by including the light-emitting elements described in Embodiments 1 and 2, a highly reliable light-emitting device can be obtained.

Further, in order to display in full color, a colored layer or a color conversion layer may be provided on the optical path through which light from the light emitting element exits to the outside of the light emitting device. An example of a full-color light emitting device by providing a colored layer or the like is shown in FIGS. 6(A) and 6(B). In FIG. 6(A), a substrate 1001,
Base insulating film 1002, gate insulating film 1003, gate electrodes 1006, 1007, 1008
, first interlayer insulating film 1020, second interlayer insulating film 1021, peripheral part 1042, pixel part 10
40, drive circuit section 1041, first electrodes 1024W, 1024R, 1024G of light emitting element
, 1024B, a partition wall 1025, an EL layer 1028, a second electrode 1029 of a light emitting element, a sealing substrate 1031, a sealant 1032, and the like are illustrated. In addition, a colored layer (red colored layer 10
34R, a green colored layer 1034G, and a blue colored layer 1034B) are provided on a transparent base material 1033. Further, a black layer (black matrix) 1035 may be further provided. A transparent base material 1033 provided with a colored layer and a black layer is aligned and fixed to the substrate 1001.
Note that the colored layer and the black layer are covered with an overcoat layer 1036. Furthermore, in this embodiment, there are a light-emitting layer in which light does not pass through the colored layer and exits to the outside, and a light-emitting layer in which light passes through the colored layer of each color and exits to the outside, and the light does not pass through the colored layer. The light is white, and the light that passes through the colored layer is red, blue, and green, so images can be expressed using pixels of four colors.

In addition, the light emitting device described above has a structure (bottom emission type) in which light is extracted from the substrate 1001 side where the TFT is formed, but a structure (top emission type) in which light emission is extracted from the sealing substrate 1031 side. ) may be used as a light emitting device. FIG. 7 shows a cross-sectional view of a top emission type light emitting device. In this case, a substrate that does not transmit light can be used as the substrate 1001. The manufacturing process is similar to that of a bottom emission type light emitting device until the connection electrode that connects the TFT and the anode of the light emitting element is manufactured. After that, a third interlayer insulating film 1037 is formed to cover the electrode 1022. This third interlayer insulating film 1037 may play the role of planarization. The third interlayer insulating film 1037 can be formed using the same material as the second interlayer insulating film, as well as other known materials.

Although the first electrodes 1024W, 1024R, 1024G, and 1024B of the light emitting elements are assumed to be anodes here, they may be cathodes. Further, in the case of a top emission type light emitting device as shown in FIG. 7, it is preferable that the first electrode is a reflective electrode. The structure of the EL layer 1028 is as described in Embodiment Modes 1 and 2, and has an element structure that can emit white light. A configuration that can obtain white light emission is such that when two EL layers are used, blue light is obtained from the light emitting layer in one EL layer, and orange light is obtained from the light emitting layer in the other EL layer. Blue light from the light-emitting layer in one EL layer is emitted from the other EL layer.
A conceivable configuration is such that red and green light can be obtained from the light emitting layer in the L layer. Furthermore, when three EL layers are used, a light-emitting element that emits white light can be obtained by making red, green, and blue light emitted from each light-emitting layer. Note that as long as the structures shown in Embodiments 1 and 2 are applied, the structure for obtaining white light emission is of course not limited to this.

The colored layer is provided on the optical path through which light from the light emitting element exits to the outside. In the case of a bottom emission type light emitting device as shown in FIG. 6(A), colored layers 1034R, 1034
This can be provided by providing G and 1034B and fixing them to the substrate 1001. Alternatively, a colored layer may be provided between the gate insulating film 1003 and the first interlayer insulating film 1020 as shown in FIG. 6B. In the case of a top emission structure as shown in FIG. 7, sealing can be performed using a sealing substrate 1031 provided with colored layers (a red colored layer 1034R, a green colored layer 1034G, and a blue colored layer 1034B). A black layer (black matrix) 1035 may be provided on the sealing substrate 1031 so as to be located between pixels. The colored layers (red colored layer 1034R, green colored layer 1034G, blue colored layer 1034B) and the black layer (black matrix) 1035 may be covered with an overcoat layer 1036.
Note that the sealing substrate 1031 is a transparent substrate.

When a voltage is applied between the pair of electrodes of the organic light emitting device thus obtained, a white light emitting region 10 is generated.
44W is obtained. In addition, by combining with a colored layer, a red light emitting region 1044R,
A blue light emitting region 1044B and a green light emitting region 1044G are obtained. Since the light-emitting device of this embodiment uses the light-emitting elements described in Embodiments 1 and 2, it is possible to realize a light-emitting device with low power consumption.

Further, although an example in which full-color display is performed using four colors of red, green, blue, and white is shown here, there is no particular limitation, and full-color display may be performed using three colors of red, green, and blue. Furthermore, color purity may be improved by providing a microcavity structure. At this time, the microcavity structure may be provided in all pixels, or may be provided only in blue pixels.

Furthermore, this embodiment can be freely combined with other embodiments.

(Embodiment 4)
In this embodiment, an example in which the light-emitting elements described in Embodiments 1 and 2 are used as a lighting device will be described with reference to FIG. 8. FIG. 8(B) is a top view of the illumination device, and FIG. 8(A) is a sectional view taken along line ef in FIG. 8(B).

In the lighting device in this embodiment, a first
An electrode 401 is formed. The first electrode 401 is the first electrode 1 in the third embodiment.
Corresponds to 01.

An auxiliary electrode 402 is provided on the first electrode 401 . In this embodiment, an example is shown in which light emission is extracted from the first electrode 401 side, so the first electrode 401 is formed of a light-transmitting material. The auxiliary electrode 402 is provided to compensate for the low conductivity of the transparent material, and suppresses uneven brightness within the light emitting surface caused by voltage drop due to the high resistance of the first electrode 401. It has the function of The auxiliary electrode 402 is formed using a material having higher conductivity than at least the material of the first electrode 401, preferably a material having high conductivity such as aluminum. Note that the surface of the auxiliary electrode 402 other than the portion in contact with the first electrode 401 is preferably covered with an insulating layer. This is to suppress light emission from the upper part of the auxiliary electrode 402, which cannot be taken out, to reduce reactive current, and to suppress a decrease in power efficiency. Note that the second electrode 404 is formed at the same time as the auxiliary electrode 402 is formed.
A pad 412 may be formed for supplying voltage to.

An EL layer 403 is formed on the first electrode 401 and the auxiliary electrode 402. EL layer 40
3 has the configuration described in Embodiment 1 and Embodiment 2. In addition, please refer to the said description regarding these structures. Note that it is preferable that the EL layer 403 be formed slightly larger than the first electrode 401 in plan view, since it can also play the role of an insulating layer that suppresses short circuits between the first electrode 401 and the second electrode 404. It is the composition.

A second electrode 404 is formed covering the EL layer 403. The second electrode 404 is the third embodiment
It corresponds to the second electrode 102 in , and has a similar configuration. In this embodiment, since light is extracted from the first electrode 401 side, the second electrode 404 is preferably formed of a material with high reflectance. In this embodiment, the second electrode 404 is connected to the pad 4
12, voltage is supplied.

As described above, the first electrode 401, the EL layer 403, and the second electrode 404 (and the auxiliary electrode 402
) The lighting device described in this embodiment mode includes a light-emitting element having the following structure. Since the light-emitting element is a light-emitting element with high luminous efficiency, the lighting device in this embodiment can be a lighting device with low power consumption. Furthermore, since the light-emitting element is a highly reliable light-emitting element, the lighting device in this embodiment can be a highly reliable lighting device.

A lighting device is completed by fixing the light emitting element having the above configuration to a sealing substrate 407 using sealants 405 and 406 and sealing it. Either one of the sealing materials 405 and 406 may be used. Further, a desiccant can be mixed into the inner sealing material 406, which allows moisture to be adsorbed, leading to improved reliability.

In addition, a part of the pad 412, the first electrode 401, and the auxiliary electrode 402 is replaced with a sealing material 405,
By extending and providing it outside of 406, it can be used as an external input terminal. Furthermore, an IC chip 420 having a converter or the like mounted thereon may be provided.

As described above, since the lighting device described in this embodiment includes the light-emitting element described in Embodiment 1 and Embodiment 2 as an EL element, it can be a lighting device with low power consumption. Further, it is possible to provide a lighting device with low driving voltage. Moreover, a highly reliable lighting device can be obtained.

(Embodiment 5)
In this embodiment, an example of an electronic device including a part of the light-emitting element described in Embodiment 1 or 2 will be described. The light-emitting elements described in Embodiments 1 and 2 have good luminous efficiency and reduced power consumption. As a result, the electronic device described in this embodiment can have a light emitting portion with reduced power consumption. Further, since the light-emitting elements described in Embodiments 1 and 2 are light-emitting elements with a low driving voltage, they can be used as electronic devices with a low driving voltage.

Electronic devices to which the above-mentioned light-emitting elements are applied include, for example, television devices (also referred to as televisions or television receivers), computer monitors, digital cameras, digital video cameras, digital photo frames, mobile phones (mobile phones, Examples include mobile phone devices (also referred to as mobile phone devices), portable game machines, personal digital assistants, audio playback devices, and large game machines such as pachinko machines. Specific examples of these electronic devices are shown below.

FIG. 9A shows an example of a television device. The television device has a housing 710
1 has a display section 7103 incorporated therein. Further, here, a configuration in which the housing 7101 is supported by a stand 7105 is shown. Images can be displayed on the display portion 7103, and the display portion 7103 is configured by arranging the light-emitting elements described in Embodiment 1 and 2 in a matrix. The light emitting element can have good luminous efficiency. Further, it is possible to provide a light emitting element with low driving voltage. Further, it is possible to provide a light emitting element with a long life. Therefore, the display section 7 configured with the light emitting element
The television device having the television set 103 can be a television device with reduced power consumption. Further, it is possible to provide a television device with low driving voltage. Furthermore, a highly reliable television device can be achieved.

The television device can be operated using an operation switch included in the housing 7101 or a separate remote controller 7110. Operation keys 7109 included in remote control operating device 7110
, the channel and volume can be controlled, and the video displayed on the display section 7103 can be controlled. In addition, the remote control operation device 7110
A configuration may also be provided in which a display section 7107 is provided to display information output from.

Note that the television device is configured to include a receiver, a modem, and the like. The receiver can receive general television broadcasts, and can be connected to a wired or wireless communication network via a modem, allowing one-way (sender to receiver) or two-way (sender to receiver) It is also possible to communicate information between recipients or between recipients.

FIG. 9B1 shows a computer, which includes a main body 7201, a housing 7202, a display portion 7203, a keyboard 7204, an external connection port 7205, a pointing device 7206, and the like. Note that this computer is manufactured by using light-emitting elements similar to those described in Embodiment Mode 2 or 3, which are arranged in a matrix and used for the display portion 7203. Figure 9 (
The computer in B1) may have a form as shown in FIG. 9 (B2). The computer in FIG. 9B2 is provided with a second display portion 7210 instead of the keyboard 7204 and pointing device 7206. The second display section 7210 is a touch panel type, and input can be performed by operating the input display displayed on the second display section 7210 with a finger or a special pen. Furthermore, the second display section 7210 can display not only input images but also other images. Further, the display portion 7203 may also be a touch panel. By connecting the two screens with a hinge, it is possible to prevent problems such as scratching or damaging the screens during storage or transportation. The light emitting element can have good luminous efficiency. Therefore, a computer including the display portion 7203 including the light-emitting element can have reduced power consumption.

FIG. 9C shows a portable gaming machine, which is composed of two housings, a housing 7301 and a housing 7302, which are connected by a connecting portion 7303 so as to be openable and closable. A display portion 7304, which is manufactured by arranging the light-emitting elements described in Embodiment Modes 1 and 2 in a matrix, is incorporated into the housing 7301, and a display portion 7305 is incorporated into the housing 7302. . In addition, the portable gaming machine shown in FIG. 9(C) also includes a speaker section 7306, a recording medium insertion section 7307,
, LED lamp 7308, input means (operation key 7309, connection terminal 7310, sensor 73
11 (force, displacement, position, velocity, acceleration, angular velocity, rotation speed, distance, light, liquid, magnetism, temperature, chemical substances, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, (includes the function of measuring tilt, vibration, odor, or infrared rays), a microphone 7312), etc. Of course, the configuration of the portable gaming machine is not limited to that described above, and at least the display section 73
04 and the display portion 7305, or a display portion manufactured by arranging the light-emitting elements described in Embodiment Modes 1 and 2 in a matrix, and other accessory equipment may be provided as appropriate. It can be configured as follows. The portable gaming machine shown in FIG. 9(C) has a function of reading out a program or data recorded on a recording medium and displaying it on a display unit, and sharing information by wirelessly communicating with other portable gaming machines. Has a function. Note that the functions of the portable gaming machine shown in FIG. 9(C) are not limited to these, and can have various functions. The portable gaming machine having the display section 7304 as described above can be a portable gaming machine with reduced power consumption because the light emitting elements used in the display section 7304 have good luminous efficiency. can. Further, since the light emitting element used in the display portion 7304 can be driven with a low driving voltage, it is possible to provide a portable gaming machine with a low driving voltage. Further, since the light emitting element used in the display portion 7304 is a light emitting element with a long life, it is possible to provide a highly reliable portable gaming machine.

FIG. 9(D) shows an example of a mobile phone. The mobile phone has a display section 7402 built into a housing 7401, an operation button 7403, an external connection port 7404, and a speaker 74.
05, a microphone 7406, etc. Note that the mobile phone 7400 includes a display portion 7402 in which the light-emitting elements described in Embodiment 1 and 2 are arranged in a matrix. The light emitting element can have good luminous efficiency. Also,
It is possible to provide a light emitting element with low driving voltage. Further, it is possible to provide a light emitting element with a long life. Therefore, a mobile phone including the display portion 7402 including the light-emitting element can have reduced power consumption. Furthermore, it is possible to make a mobile phone with a low driving voltage. Furthermore, it is possible to provide a highly reliable mobile phone.

The mobile phone shown in FIG. 9D can also be configured so that information can be input by touching the display portion 7402 with a finger or the like. In this case, operations such as making a phone call or composing an email can be performed by touching the display portion 7402 with a finger or the like.

The screen of the display section 7402 mainly has three modes. The first is a display mode that mainly displays images, and the second is an input mode that mainly inputs information such as characters. The third mode is a display+input mode, which is a mixture of two modes: a display mode and an input mode.

For example, when making a phone call or composing an email, the display unit 7402 may be set to a character input mode that mainly inputs characters, and the user may input the characters displayed on the screen. In this case, it is preferable to display a keyboard or number buttons on most of the screen of the display section 7402.

Furthermore, by providing a detection device having a sensor such as a gyro or an acceleration sensor for detecting inclination inside the mobile phone, the orientation of the mobile phone (vertical or horizontal) can be determined and the screen display on the display unit 7402 can be automatically changed. It is possible to switch between the two.

Further, switching of the screen mode is performed by touching the display portion 7402 or operating the operation button 7403 on the housing 7401. Further, it is also possible to switch depending on the type of image displayed on the display section 7402. For example, if the image signal to be displayed on the display section is video data, the mode is switched to display mode, and if it is text data, the mode is switched to input mode.

In addition, in the input mode, a signal detected by the optical sensor of the display section 7402 is detected, and if there is no input by touch operation on the display section 7402 for a certain period of time, the screen mode is switched from the input mode to the display mode. May be controlled.

The display portion 7402 can also function as an image sensor. For example, the display section 74
02 with the palm or fingers and capture an image of a palm print, fingerprint, etc., to authenticate the person. Furthermore, if a backlight that emits near-infrared light or a sensing light source that emits near-infrared light is used in the display section, it is also possible to image finger veins, palm veins, and the like.

Note that the structure shown in this embodiment can be used by appropriately combining the structures shown in Embodiments 1 to 4.

As described above, the range of application of the light-emitting device including the light-emitting element described in Embodiment 1 and Embodiment 2 is extremely wide, and this light-emitting device can be applied to electronic devices in all fields.
By using the light-emitting elements described in Embodiments 1 and 2, an electronic device with reduced power consumption can be obtained.

FIG. 10 is an example of a liquid crystal display device in which the light-emitting elements described in Embodiments 1 and 2 are applied to a backlight. The liquid crystal display device shown in FIG. 10 includes a housing 901, a liquid crystal layer 902,
, a backlight unit 903, and a housing 904, and the liquid crystal layer 902 includes a driver IC 90.
5 is connected. Further, the light emitting element described in Embodiment 1 and Embodiment 2 is used in the backlight unit 903, and current is supplied through the terminal 906.

By applying the light-emitting elements described in Embodiments 1 and 2 to a backlight of a liquid crystal display device, a backlight with reduced power consumption can be obtained. Furthermore, by using the light-emitting element described in Embodiment 2, a surface-emitting lighting device can be manufactured, and the area can also be increased. This makes it possible to increase the area of the backlight and also to increase the area of the liquid crystal display device. Furthermore, the thickness of a light-emitting device to which the light-emitting element described in Embodiment 2 is applied can be reduced compared to a conventional device, so that a display device can be made thinner.

FIG. 11 is an example in which the light-emitting elements described in Embodiments 1 and 2 are used in a desk lamp that is a lighting device. The desk lamp shown in FIG. 11 includes a housing 2001 and a light source 2002.
The light emitting device described in Embodiment 4 is used as the light source 2002.

FIG. 12 shows the light-emitting elements described in Embodiment Modes 1 and 2 used in an indoor lighting device 300.
1 and a display device 3002. Since the light-emitting elements described in Embodiments 1 and 2 are light-emitting elements with reduced power consumption, a lighting device with reduced power consumption can be obtained. Further, since the light-emitting elements described in Embodiments 1 and 2 can be made to have a large area, they can be used as a large-area lighting device. Further, since the light-emitting elements described in Embodiments 1 and 2 are thin, they can be used as a thin lighting device.

The light-emitting elements described in Embodiments 1 and 2 can also be mounted on the windshield or dashboard of an automobile. FIG. 13 shows one mode in which the light-emitting element described in Embodiment 2 is used for a windshield or a dashboard of an automobile. Display 5000 to display 5005
is a display provided using the light-emitting element described in Embodiment 1 and Embodiment 2.

Display 5000 and display 5001 are display devices equipped with the light-emitting elements described in Embodiment 1 and Embodiment 2, which are provided on the windshield of an automobile. The light-emitting element described in Embodiment 1 and 2 is a so-called see-through display device in which the opposite side can be seen through the first electrode and the second electrode using light-transmitting electrodes. It can be done. If the display is see-through, it can be installed on the windshield of a car without obstructing the view. Note that when a driving transistor or the like is provided, it is preferable to use a light-transmitting transistor such as an organic transistor made of an organic semiconductor material or a transistor made of an oxide semiconductor.

A display 5002 is a display device in which the light-emitting elements described in Embodiment Modes 1 and 2 are provided in pillar portions. The display 5002 can complement the view blocked by the pillars by displaying an image from an imaging means provided on the vehicle body. Similarly, a display 5003 provided on the dashboard can compensate for blind spots and improve safety by projecting images from an imaging means installed outside the vehicle to cover the field of view obstructed by the vehicle body. can. By projecting images to supplement the invisible parts, safety confirmation can be performed more naturally and without any discomfort.

Display 5004 and display 5005 can provide various other information such as navigation information, speedometer, tachometer, mileage, amount of fuel, gear status, and air conditioner settings. The display items and layout can be changed as appropriate to suit the user's preferences. Note that this information can also be provided in the displays 5000 to 5003.
Further, the displays 5000 to 5005 can also be used as lighting devices.

The light-emitting elements described in Embodiments 1 and 2 can have high luminous efficiency. Further, a light emitting element with low power consumption can be obtained. From this, display 5
Even if a large number of large screens such as 000 to 5005 are provided, there is little load on the battery and the use can be made comfortably. The device or lighting device can be suitably used as a vehicle-mounted light emitting device or lighting device.

14(A) and 14(B) are examples of tablet-type terminals that can be folded into two. Figure 1
4(A) is an open state, and the tablet type terminal has a housing 9630 and a display portion 9631a.
, a display portion 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. Note that the tablet terminal is manufactured by using a light-emitting device including the light-emitting element described in Embodiment 1 or 2 for one or both of the display portion 9631a and the display portion 9631b.

A portion of the display portion 9631a can be a touch panel area 9632a, and data can be input by touching the displayed operation keys 9637. Note that the display section 963
1a shows, as an example, a configuration in which half of the area has a display-only function and the other half has a touch panel function, but the configuration is not limited to this. Display section 963
The entire area of 1a may have a touch panel function. For example, the display section 96
The entire surface of 31a can be used as a touch panel by displaying keyboard buttons, and the display section 9631b can be used as a display screen.

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

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

Further, a display mode changeover switch 9034 can switch the display orientation such as portrait display or landscape 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, which is detected by an optical sensor built into the tablet terminal. The tablet terminal may include not only a light sensor but also other detection devices such as a sensor that detects tilt, such as a gyro or an acceleration sensor.

Further, although FIG. 14A shows an example in which the display area of the display portion 9631b and the display portion 9631a are the same, this is not particularly limited, and the size of one and the other may be different, and the quality of the display may also be affected. May be different. For example, one display panel may be capable of displaying higher definition than the other.

FIG. 14B shows a closed state, and the tablet terminal according to this embodiment includes a housing 9630, a solar cell 9633, a charge/discharge control circuit 9634, a battery 9635, a DC
An example including a C converter 9636 is shown. In addition, in FIG. 14(B), the charge/discharge control circuit 963
4 shows a configuration including a battery 9635 and a DC/DC converter 9636.

Note that since the tablet terminal can be folded in two, the housing 9630 can be kept in a closed state when not in use. Therefore, since the display portion 9631a and the display portion 9631b can be protected,
It is possible to provide a tablet device that is highly durable and highly reliable from the standpoint of long-term use.

In addition, the tablet terminals shown in FIGS. 14(A) and 14(B) have functions to display various information (still images, videos, text images, etc.), a calendar, date or time, etc. It can have a function of displaying on the display, a touch input function of performing a touch input operation or editing the information displayed on the display, a function of controlling processing by various software (programs), and the like.

A solar cell 9633 attached to the surface of the tablet terminal can supply power to a touch panel, a display section, a video signal processing section, or the like. Note that the solar cell 9633 can be provided on one or both sides of the housing 9630, and the battery 9635 can be charged efficiently.

Further, regarding the configuration and operation of the charge/discharge control circuit 9634 shown in FIG. 14(B), FIG.
C) shows a block diagram and will be explained. In FIG. 14(C), a solar cell 9633, a battery 9
635, DCDC converter 9636, converter 9638, switches SW1 to SW3
, a display section 9631, a battery 9635, a DCDC converter 963
6. The converter 9638 and switches SW1 to SW3 correspond to the charging/discharging control circuit 9634 shown in FIG. 14(B).

First, an example of the operation when the solar cell 9633 generates power using external light will be described. The electricity generated by the solar cells is converted to DC voltage to charge the battery 9635.
A DC converter 9636 performs voltage step-up or step-down. When the power charged by the solar cell 9633 is used to operate the display section 9631, the switch SW1 is turned on, and the converter 9638 steps up or steps down the voltage necessary for the display section 9631. Further, when not displaying information on the display section 9631, the configuration may be such that SW1 is turned off and SW2 is turned on to charge the battery 9635.

Although the solar cell 9633 is shown as an example of a power generation means, the power generation means is not particularly limited, and the battery 9635 can be charged by other power generation means such as a piezoelectric element (piezo element) or a thermoelectric conversion element (Peltier element). It may also be configured to perform the following. A non-contact power transmission module that wirelessly (contactlessly) transmits and receives power for charging, or a combination of other charging means may be used, and the power generation means may not be provided.

Further, as long as the display section 9631 is included, the tablet terminal is not limited to the shape shown in FIG. 14.

In this example, a manufacturing method and characteristics of a light-emitting element corresponding to one embodiment of the present invention described in Embodiment Modes 1 and 2 will be described. The structural formula of the organic compound used in this example is shown below.

Next, a method for manufacturing the light emitting device of this example will be described.

First, a film of indium tin oxide containing silicon oxide (ITSO) was formed on a glass substrate by sputtering to form the first electrode 101. Note that the film thickness was 110 nm, and the electrode area was 2 mm x 2 mm. Here, the first electrode 101 is an electrode that functions as an anode of a light emitting element.

Next, as a pretreatment for forming a light emitting element on the substrate, the surface of the substrate is washed with water,
After baking at ℃ for 1 hour, UV ozone treatment was performed for 370 seconds.

Thereafter, the substrate was introduced into a vacuum evaporation apparatus whose internal pressure was reduced to about 10 ^-4 Pa, and vacuum baking was performed at 170°C for 30 minutes in the heating chamber of the vacuum evaporation apparatus, followed by leaving the substrate for about 30 minutes. It got cold.

Next, the substrate on which the first electrode 101 was formed was fixed to a substrate holder provided in a vacuum evaporation apparatus so that the surface on which the first electrode 101 was formed faced downward, and the substrate was heated to about 10 ⁻⁴ Pa. After reducing the pressure to 4,4',4''-(benzene-1,3,5-triyl ) Tri(dibenzothiophene) (abbreviation: DBT3P-II) and molybdenum oxide (VI) were co-evaporated to form the hole injection layer 111. The film thickness was 33 nm, and the weight ratio of DBT3P-II to molybdenum oxide was adjusted to be 4:2 (=DBT3P-II:molybdenum oxide). Note that the co-evaporation method is a vapor deposition method in which vapor deposition is performed simultaneously from a plurality of evaporation sources in one processing chamber.

Next, on the hole injection layer 111, 4-phenyl-4'-(
9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP) at 20
A film was formed to have a film thickness of nm to form a hole transport layer 112.

Furthermore, 2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBT) represented by the above structural formula (iii) is formed on the hole transport layer 112.
PDBq-II), 4-phenyl-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBA1BP) represented by the above structural formula (iv), and the above structural formula (v) Bis[2-(6-tert-butyl-4-pyrimidinyl-κN3)
) phenyl-κC](2,4-pentanedionato-κ ² O,O')iridium(III)
(abbreviation: Ir(tBuppm) ₂ (acac)) at a weight ratio of 0.8:0.2:0.05
(=2mDBTPDBq-II:PCBA1BP:Ir(tBuppm) ₂ (acac)
) to form the first light-emitting layer 113a, and 2mDBTPDBq-I
I and bis(2,3,5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III) (abbreviation: Ir(tppr) ₂ (dpm)) represented by the above structural formula (vi). , weight ratio 1:0.06 (=2mDBTPDBq-II:Ir(tppr) ₂ (dpm))
The second light-emitting layer 113b was formed by co-evaporation to a thickness of 20 nm. Note that the host material 2mDBTPDBq-II and PCBA1BP form an exciplex.

Thereafter, 2mDBTPDBq-II was formed on the light emitting layer 113 to a thickness of 15 nm, and bathophenanthroline (abbreviation: BPhen) represented by the above structural formula (vii) was further formed.
was deposited to a thickness of 15 nm to form an electron transport layer 114.

After forming the electron transport layer 114, lithium fluoride (LiF) was deposited to a thickness of 1 nm to form an electron injection layer 115.

Finally, aluminum was deposited to a thickness of 200 nm as the second electrode 102 functioning as a cathode, thereby manufacturing the light emitting element 1 of this example.

In addition, in the vapor deposition process mentioned above, the resistance heating method was used for all vapor deposition.

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

The light-emitting element 1 was sealed with a glass substrate in a glove box with a nitrogen atmosphere so as not to be exposed to the atmosphere (a sealing material was applied around the element, and heat treatment was performed at 80°C for 1 hour during sealing). Ta.

In the light emitting element 1, Ir(tBuppm) ₂ (ac
ac), and Ir(tppr) ₂ (dpm) is used as the second phosphorescent compound 113Db. Here, the PL spectrum of Ir(tBuppm) ₂ (acac) and the Ir(tp
The relationship between ε(λ)λ ⁴ of pr) ₂ (dpm) will be described. Note that λ is the wavelength and ε(λ) is the molar absorption coefficient.

First, Figure 20(a) shows the molar extinction coefficient ε(λ) of Ir(tppr) ₂ (dpm) and ε(λ
) A graph representing λ ⁴ is shown. While the molar extinction coefficient ε(λ) does not have a noticeable peak in the long wavelength region, in the graph of ε(λ)λ ⁴ , there is a peak (mountain) having a maximum value at 543 nm. This peak is the triplet ML of Ir(tppr) ₂ (dpm)
This is CT absorption, and by superimposing the emission peak of the first phosphorescent compound 113Da on this peak, it becomes possible to greatly increase the efficiency of energy transfer.

FIG. 20(b) shows the first phosphorescent compound 113Da, Ir(tBuppm) ₂ (ac
ac) and the second phosphorescent compound 113Db, Ir(tpp
A graph representing ε(λ)λ ⁴ of r) ₂ (dpm) is shown. From this graph, Ir(tBu
ppm) ₂ (acac) and the mountain where the peak of F(λ) exists and Ir(tpp
r) ₂ (dpm) and the peak having the maximum value on the longest wavelength side of ε(λ)λ ⁴ , it can be seen that this is a combination in which energy transfer is performed very efficiently. Also,
The peak of the emission of Ir(tBuppm) ₂ (acac), which is the first phosphorescent compound 113Da, exists at 546 nm, and the peak of the emission of Ir(tppr) _{2 which} is the second phosphorescent compound 113Db exists at 546 nm.
Since the maximum on the long wavelength side in the spectrum representing ε(λ)λ ⁴ of (dpm) exists at 543 nm, the difference therebetween is 3 nm. 546nm is 2.27eV, 543nm is 2.28eV
Since it corresponds to V, the difference is 0.01 eV, which is smaller than 0.2 eV, suggesting that efficient energy transfer is also performed from the peak position.

Subsequently, in FIG. 21(a), the first phosphorescent compound 113Da Ir(tBuppm) ₂
A graph showing the molar extinction coefficient ε(λ) of (acac) and ε(λ)λ ⁴ is shown. In the graph representing molar extinction coefficient ε(λ), the peak in the longer wavelength region has a lower intensity than the peak in the shorter wavelength region, whereas in the graph of ε(λ)λ ⁴ , the peak in the region of 494 nm There is a local maximum with a large intensity. The peak (mountain) where this maximum value exists is Ir(tBu
ppm) ₂ (acac), and by superimposing the emission peak of the energy donor on this peak, it becomes possible to greatly increase the efficiency of energy transfer.

Here, in the light emitting device 1 of this example, 2mDBTPDBq-II which is the first host material
and PCBA1BP, which is the first organic compound, form an exciplex 113Ec, and energy is supplied from the exciplex 113Ec to the first phosphorescent compound 113Da. FIG. 23 is a diagram showing PL spectra of 2mDBTPDBq-II, PCBA1BP, and a mixed film thereof (mass ratio of 0.8:0.2).
It can be seen that -II and the first organic compound PCBA1BP form an exciplex 113Ec. Furthermore, FIG. 21(b) shows a graph showing the PL spectrum F(λ) of the exciplex and ε(λ)λ ⁴ of Ir(tBuppm) ₂ (acac), which is the first phosphorescent compound 113Da. Ta. From this graph, the peak where the peak of the PL spectrum F(λ) of the exciplex exists and the peak with the maximum value on the longest wavelength side of ε(λ)λ ⁴ of Ir(tBuppm) ₂ (acac) overlap. It can be seen that this is a combination that allows efficient energy transfer. In addition, the peak of the PL spectrum of the exciplex exists at 519 nm, and the maximum on the long wavelength side in the spectrum representing ε(λ)λ ⁴ of Ir(tBuppm) ₂ (acac), which is the first phosphorescent compound 113Da. exists at 494 nm, so the difference is 25 nm. 519nm corresponds to 2.39eV when converted to energy, and 494nm corresponds to 2.51eV when converted to energy, so the difference is 0.12eV, which is smaller than 0.2eV, so it is efficient from the peak position. This suggests that energy transfer occurs.

In addition, as can be seen from FIG. 23, 2mDBTPDBq, which is the first host material 113Ha,
The peak of the PL spectrum of -II is 426 nm, which is 2.91 when converted to energy.
Corresponds to eV. Furthermore, the peak of the PL spectrum of PCBA1BP, which is the first organic compound 113A, is 405 nm, which corresponds to 3.06 eV when converted to energy. Ir
In the spectrum representing ε(λ)λ ⁴ of (tBuppm) ₂ (acac), the maximum value on the long wavelength side exists at 494 nm, which corresponds to 2.51 eV when converted to energy, and the difference between each is 0.4 eV (first host material 113Ha:2mDBTPDBq-II),
0.55 eV (first organic compound 113A: PCBA1BP), both are 0.2e
Since the energy difference is greater than V, it can be seen that energy transfer from 2mDBTPDBq-II and PCBA1BP to Ir(tBuppm) ₂ (acac) is difficult.

In addition, FIG. 22 shows the PL spectrum F(λ) of the exciplex, Ir(tBuppm) ₂ (acac
) PL spectrum F(λ), PL spectrum F(λ) of Ir(tppr) ₂ (dpm)
, Ir(tBuppm) ₂ (acac) ε(λ)λ ⁴ , Ir(tppr) ₂ (dpm)
A graph is shown in which ε(λ)λ ⁴ of 4 are combined into one. PL spectrum of exciplex and Ir(tB
uppm) ₂ (acac) with ε(λ)λ ⁴ (near the maximum value A) from the exciplex to Ir(tBuppm) ₂ (acac), and then Ir(tBuppm) ₂ (acac).
c) Using the overlap between the PL spectrum of Ir(tppr) ₂ (dpm) and ε(λ)λ ⁴ (near the maximum value B), Ir(tBuppm) ₂ (acac) to Ir(tppr) ₂ (dp
It can be seen that stepwise energy transfer is possible to m). In addition, from the exciplex, the second
Energy can also be transferred directly to the phosphorescent compound Ir(tppr) ₂ (dpm). As can be seen from FIG. 22, this is the triplet ML of Ir(tppr) ₂ (dpm)
On the short wavelength side of the CT absorption band (near the maximum value B), both the PL spectrum F(λ) of the exciplex and Ir
This is because ε(λ)λ ⁴ of (tppr) ₂ (dpm) overlaps.

The device characteristics of this light emitting device were measured. Note that the measurement was performed at room temperature (atmosphere maintained at 25° C.).

FIG. 15 shows the luminance-current efficiency characteristics of the light-emitting element 1. In FIG. 15, the horizontal axis is the luminance (cd/
m ² ), and the vertical axis represents current efficiency (cd/A). Further, the voltage-luminance characteristics are shown in FIG. In FIG. 16, the horizontal axis represents voltage (V), and the vertical axis represents brightness (cd/m ² ). Further, the luminance-external quantum efficiency characteristics are shown in FIG. In FIG. 17, the horizontal axis shows luminance (cd/m ² ), and the vertical axis shows external quantum efficiency (%). Further, the luminance-power efficiency characteristics are shown in FIG. In FIG.
The horizontal axis shows luminance (cd/m ² ), and the vertical axis shows power efficiency (%).

As described above, it was found that the light emitting device 1 exhibited good device characteristics. In particular, Fig. 15, Fig. 1
7. As can be seen from Figure 18, it has very good luminous efficiency, and the external quantum efficiency is lower than the practical luminance (
1000 cd/m ² ), it showed a high value of 20% or more. Similarly, the current efficiency is around 60 cd/A, and the power efficiency is around 60 lm/W, which are very good values.

Further, FIG. 19 shows an emission spectrum when a current of 0.1 mA is passed through the light emitting element 1. In FIG. 19, the horizontal axis represents wavelength (nm), and the vertical axis represents emission intensity (arbitrary unit). From Figure 19,
Light-emitting element 1 is bis[2-(6-tert-butyl-4-pyrimidinyl-κN3)phenyl-κC](2,4-pentanedionato-κ ² O,O')iridium(III) (abbreviation: I
r(tBuppm) ₂ (acac)) and bis(2,3,5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III) (abbreviation: Ir(tp)
pr) ₂ (dpm)) was found to exhibit an emission spectrum containing well-balanced red wavelength light.

Thus, it was found that the light-emitting element 1, which corresponds to one embodiment of the present invention, has good luminous efficiency and is a light-emitting element that can obtain light from two types of luminescent center substances in a well-balanced manner.

In this example, a manufacturing method and characteristics of a light-emitting element corresponding to one embodiment of the present invention described in Embodiment Modes 1 and 2 will be described. The structural formula of the organic compound used in this example is shown below.

Next, a method for manufacturing the light emitting device of this example will be described.

First, a film of indium tin oxide containing silicon oxide (ITSO) was formed on a glass substrate by sputtering to form the first electrode 101. Note that the film thickness was 110 nm, and the electrode area was 2 mm x 2 mm. Here, the first electrode 101 is an electrode that functions as an anode of a light emitting element.

Next, as a pretreatment for forming a light emitting element on the substrate, the surface of the substrate is washed with water,
After baking at ℃ for 1 hour, UV ozone treatment was performed for 370 seconds.

Thereafter, the substrate was introduced into a vacuum evaporation apparatus whose internal pressure was reduced to about 10 ^-4 Pa, and vacuum baking was performed at 170°C for 30 minutes in the heating chamber of the vacuum evaporation apparatus, followed by leaving the substrate for about 30 minutes. It got cold.

Next, the substrate on which the first electrode 101 was formed was fixed to a substrate holder provided in a vacuum evaporation apparatus so that the surface on which the first electrode 101 was formed faced downward, and the substrate was heated to about 10 ⁻⁴ Pa. After reducing the pressure to 100, the above structural formula (viii
) and molybdenum oxide (VI), the hole injection layer 111 was formed. The film thickness was 33.3 nm, and the weight ratio of PCPPn to molybdenum oxide was adjusted to be 1:0.5 (=PCPPn:molybdenum oxide). Note that the co-evaporation method is a vapor deposition method in which vapor deposition is performed simultaneously from a plurality of evaporation sources in one processing chamber.

Next, on the hole injection layer 111, 4-phenyl-4'-(
9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP) at 20
A film was formed to have a film thickness of nm to form a hole transport layer 112.

Furthermore, 2-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTBPDBq-II) and 4,4'-di(1-naphthyl)-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBNBB) and bis[2-(6-tert-butyl-4-pyrimidinyl-κN3)phenyl-κC](2,4-pentanedionato-κ ² O
, O') and iridium (III) (abbreviation: Ir(tBuppm) ₂ (acac)) at a weight ratio of 0.8:0.2:0.06 (=2mDBTBPDBq-II:PCBNBB:Ir(
The first light emitting layer 113a is co-deposited to a thickness of 20 nm so that tBuppm) ₂ (acac)).
and 2mDBTBPDBq-II and bis(2,3,5-
triphenylpyrazinato)(dipivaloylmethanato)iridium(III) (abbreviation: Ir
(tppr) ₂ (dpm)) at a weight ratio of 1:0.06 (=2mDBTBPDBq-II
: Ir(tppr) ₂ (dpm)) by co-evaporating 20 nm to form the second light emitting layer 113.
b was formed. Note that the host material 2mDBTBPDBq-II and PCBNBB form an exciplex.

Thereafter, 2mDBTBPDBq-II was formed on the light emitting layer 113 to a thickness of 15 nm, and bathophenanthroline (abbreviation: BPhen) represented by the above structural formula (vii) was further formed.
) was deposited to a thickness of 15 nm to form an electron transport layer 114.

After forming the electron transport layer 114, lithium fluoride (LiF) was deposited to a thickness of 1 nm to form an electron injection layer 115.

Finally, aluminum was deposited to a thickness of 200 nm as the second electrode 102 functioning as a cathode, thereby manufacturing the light emitting element 2 of this example.

In addition, in the vapor deposition process mentioned above, the resistance heating method was used for all vapor deposition.

Table 2 shows the element structure of the light emitting element 2 obtained as described above.

The light emitting element 2 was sealed with a glass substrate in a glove box with 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 during sealing). Ta.

In the light emitting element 2, as in the light emitting element 1, Ir(tB
uppm) ₂ (acac) as Ir(tppr) as the second phosphorescent compound 113Db.
₂ (dpm) is used. Therefore, regarding the relationship between the PL spectrum of Ir(tBuppm) ₂ (acac) and ε(λ)λ ⁴ of Ir(tppr) ₂ (dpm), the light emitting element 1
Since it is the same as , we will omit the repetitive explanation. Please refer to the description regarding FIGS. 20(a) and 20(b) in Example 1. In this way, the first phosphorescent compound 113 in the light emitting element 2
It is suggested that energy transfer between Da and the second phosphorescent compound 113Db is performed efficiently.

The device characteristics of this light emitting device were measured. Note that the measurement was performed at room temperature (atmosphere maintained at 25° C.).

FIG. 24 shows the luminance-current efficiency characteristics of the light emitting element 2. Further, the voltage-luminance characteristics are shown in FIG. Further, the luminance-external quantum efficiency characteristics are shown in FIG. In addition, the luminance-power efficiency characteristics are shown in Figure 27.
Shown below.

As described above, it was found that the light emitting element 2 exhibited good device characteristics. In particular, Fig. 24, Fig. 2
6. As can be seen from Figure 27, it has very good luminous efficiency, and the external quantum efficiency is lower than the practical luminance (
1000 cd/m ² ), it showed a high value of 20% or more. Similarly, the current efficiency is around 60 cd/A, and the power efficiency is around 60 lm/W, which are very good values.

Further, FIG. 28 shows an emission spectrum when a current of 0.1 mA is passed through the light emitting element 2. From FIG. 28, light emitting element 2 is bis[2-(6-tert-butyl-4-pyrimidinyl-κN3
) phenyl-κC](2,4-pentanedionato-κ ² O,O')iridium(III)
(abbreviation: Ir(tBuppm) ₂ (acac)) and bis(2,3,
5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III) (abbreviation:
It was found that the light emission spectrum contained well-balanced red wavelength light derived from Ir(tppr) ₂ (dpm)).

In addition, the initial brightness was set to 5000 cd/ ^m2 , and the initial brightness was set to 100 cd/m2 under conditions of constant current density.
FIG. 29 shows the results of a reliability test in the case where: From FIG. 29, despite the reliability test with an initial luminance of 5000 cd/ ^m2 , the luminance of light emitting element 2 was 96% of the initial luminance after 70 hours.
It was found that the light-emitting element had good reliability.

Thus, it was found that the light-emitting element 2, which corresponds to one embodiment of the present invention, has good luminous efficiency and is a light-emitting element that can obtain light from two types of luminescent center substances in a well-balanced manner. Furthermore, it was found that the light emitting element has good reliability and a long life.

In this example, a manufacturing method and characteristics of a light-emitting element corresponding to one embodiment of the present invention described in Embodiment Modes 1 and 2 will be described. The structural formula of the organic compound used in this example is shown below.

Next, a method for manufacturing the light emitting device of this example will be described.

First, a film of indium tin oxide containing silicon oxide (ITSO) was formed on a glass substrate by sputtering to form the first electrode 101. Note that the film thickness was 110 nm, and the electrode area was 2 mm x 2 mm. Here, the first electrode 101 is an electrode that functions as an anode of a light emitting element.

Next, as a pretreatment for forming a light emitting element on the substrate, the surface of the substrate is washed with water,
After baking at ℃ for 1 hour, UV ozone treatment was performed for 370 seconds.

Thereafter, the substrate was introduced into a vacuum evaporation apparatus whose internal pressure was reduced to about 10 ^-4 Pa, and vacuum baking was performed at 170°C for 30 minutes in the heating chamber of the vacuum evaporation apparatus, followed by leaving the substrate for about 30 minutes. It got cold.

Next, the substrate on which the first electrode 101 was formed was fixed to a substrate holder provided in a vacuum evaporation apparatus so that the surface on which the first electrode 101 was formed faced downward, and the substrate was heated to about 10 ⁻⁴ Pa. After reducing the pressure to 4,4',4''-(benzene-1,3,5-triyl ) Tri(dibenzothiophene) (abbreviation: DBT3P-II) and molybdenum (VI) oxide were co-evaporated to form the hole injection layer 111. The film thickness was 40 nm, and DBT3P-II and molybdenum oxide The ratio of molybdenum was adjusted to be 4:2 (=DBT3P-II: molybdenum oxide) by weight.The co-evaporation method refers to simultaneous evaporation from multiple evaporation sources in one processing chamber. This is a vapor deposition method.

Next, on the hole injection layer 111, 4,4',4''-tri(N-carbazolyl)triphenylamine (abbreviation: TCTA), which is represented by the above structural formula (xi), is deposited to a thickness of 10 nm. The hole transport layer 112 was formed by forming a film so as to have the following properties.

Further, on the hole transport layer 112, TCTA and bis(2,3
,5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III) (abbreviation: Ir(tppr) ₂ (dpm)) at a weight ratio of 1:0.1 (=TCTA:Ir(tpp
r) ₂ (dpm)) to form the second light emitting layer 113b, and 2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo represented by the above structural formula (iii). [f,h]quinoxaline (abbreviation: 2mDBTPDBq-II) and the above structural formula (iv)
4-phenyl-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBA1BP) represented by and bis[2-(6
-tert-butyl-4-pyrimidinyl-κN3)phenyl-κC](2,4-pentanedionato-κ ² O,O')iridium(III) (abbreviation: Ir(tBuppm) ₂ (ac
ac)) at a weight ratio of 0.8:0.2:0.05 (=2mDBTPDBq-II:PCB
A1BP:Ir(tBuppm) ₂ (acac)) was codeposited to a thickness of 5 nm to form the first light emitting layer 113a. In addition, the host material 2mDBTPDBq-II and PCB
It forms an exciplex with A1BP.

After that, 2mDBTPDBq-II and Ir(tBuppm) ₂ (aca
c) and 1:0.05 (=2mDBTPDBq-II:Ir(tBuppm) ₂ (aca
c)) Co-evaporated to a thickness of 20 nm to form a 10 nm film of 2mDBTPDBq-II, and further bathophenanthroline (abbreviation: BPhen) represented by the above structural formula (vii)
The electron transport layer 114 was formed by forming a film to have a thickness of 0 nm.

After forming the electron transport layer 114, lithium fluoride (LiF) was deposited to a thickness of 1 nm to form an electron injection layer 115.

Finally, aluminum was deposited to a thickness of 200 nm as the second electrode 102 functioning as a cathode, thereby manufacturing the light emitting element 3 of this example.

In addition, in the vapor deposition process mentioned above, the resistance heating method was used for all vapor deposition.

Table 3 shows the element structure of the light emitting element 3 obtained as described above. The light-emitting element 3 is a light-emitting element manufactured using materials for the hole transport layer and the second host material that are significantly different from those of the light-emitting elements 1 and 2. Furthermore, the positions of the first light-emitting layer and the second light-emitting layer with respect to the electrodes and the structure of the electron transport layer are also significantly different.

The light emitting element 3 was sealed with a glass substrate in a glove box with a nitrogen atmosphere so as not to be exposed to the atmosphere (sealing material was applied around the element and heat treatment was performed at 80°C for 1 hour during sealing). Ta.

In the light emitting element 3, as in the light emitting element 1, Ir(tB
uppm) ₂ (acac) as Ir(tppr) as the second phosphorescent compound 113Db.
₂ (dpm) is used. Therefore, regarding the relationship between the PL spectrum of Ir(tBuppm) ₂ (acac) and ε(λ)λ ⁴ of Ir(tppr) ₂ (dpm), the light emitting element 1
Since it is the same as , we will omit the repetitive explanation. Please refer to the description regarding FIGS. 20(a) and 20(b) in Example 1. In this way, the first phosphorescent compound 113 in the light emitting element 3
It is suggested that energy transfer between Da and the second phosphorescent compound 113Db is performed efficiently.

The device characteristics of this light emitting device were measured. Note that the measurement was performed at room temperature (atmosphere maintained at 25° C.).

FIG. 30 shows the luminance-current efficiency characteristics of the light emitting element 3. Further, the voltage-luminance characteristics are shown in FIG. Further, the luminance-external quantum efficiency characteristics are shown in FIG. In addition, the luminance-power efficiency characteristics are shown in Figure 33.
Shown below.

As described above, it was found that the light emitting element 3 exhibited good device characteristics. In particular, Figure 30, Figure 3
2. As can be seen from Figure 33, it has very good luminous efficiency, and the external quantum efficiency is lower than the practical luminance (
1000 cd/m ² ), it showed a high value of 20% or more. Similarly, the current efficiency is around 60 cd/A, and the power efficiency is around 70 lm/W, which are very good values.

Further, FIG. 34 shows an emission spectrum when a current of 0.1 mA is passed through the light emitting element 3. From FIG. 34, the light emitting element 3 is bis[2-(6-tert-butyl-4-pyrimidinyl-κN3
) phenyl-κC](2,4-pentanedionato-κ ² O,O')iridium(III)
(abbreviation: Ir(tBuppm) ₂ (acac)) and bis(2,3,
5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III) (abbreviation:
It was found that the light emission spectrum contained well-balanced red wavelength light derived from Ir(tppr) ₂ (dpm)).

Although light-emitting element 3, which corresponds to one embodiment of the present invention, uses a different host material from light-emitting element 1 and light-emitting element 2, it has good luminous efficiency and is composed of two types of luminescent center substances. It was found that this light-emitting element can provide a well-balanced amount of light.

In this example, a manufacturing method and characteristics of a light-emitting element corresponding to one embodiment of the present invention described in Embodiment Modes 1 and 2 will be described. The structural formula of the organic compound used in this example is shown below.

Next, a method for manufacturing the light emitting elements (light emitting element 4, light emitting element 5) of this example will be described.

First, a film of indium tin oxide containing silicon oxide (ITSO) was formed on a glass substrate by sputtering to form the first electrode 101. Note that the film thickness was 110 nm, and the electrode area was 2 mm x 2 mm. Here, the first electrode 101 is an electrode that functions as an anode of a light emitting element.

Next, as a pretreatment for forming a light emitting element on the substrate, the surface of the substrate is washed with water,
After baking at ℃ for 1 hour, UV ozone treatment was performed for 370 seconds.

Thereafter, the substrate was introduced into a vacuum evaporation apparatus whose internal pressure was reduced to about 10 ^-4 Pa, and vacuum baking was performed at 170°C for 30 minutes in the heating chamber of the vacuum evaporation apparatus, followed by leaving the substrate for about 30 minutes. It got cold.

Next, the substrate on which the first electrode 101 was formed was fixed to a substrate holder provided in a vacuum evaporation apparatus so that the surface on which the first electrode 101 was formed faced downward, and the substrate was heated to about 10 ⁻⁴ Pa. After reducing the pressure to The hole injection layer 111 was formed by co-evaporating phenylamine (abbreviation: BPAFLP) and molybdenum oxide (VI). The film thickness was 33.3 nm, and the weight ratio of BPAFLP to molybdenum oxide was adjusted to be 1:0.5 (=BPAFLP:molybdenum oxide). Note that the co-evaporation method is a vapor deposition method in which vapor deposition is performed simultaneously from a plurality of evaporation sources in one processing chamber.

Next, BPAFLP was formed into a film with a thickness of 20 nm on the hole injection layer 111 to form the hole transport layer 112.

Furthermore, 2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBT) represented by the above structural formula (iii) is formed on the hole transport layer 112.
PDBq-II), 4-phenyl-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBA1BP) represented by the above structural formula (iv), and the above structural formula (v) Bis[2-(6-tert-butyl-4-pyrimidinyl-κN3)
) phenyl-κC](2,4-pentanedionato-κ ² O,O')iridium(III)
(abbreviation: Ir(tBuppm) ₂ (acac)) at a weight ratio of 0.8:0.2:0.06
(=2mDBTPDBq-II:PCBA1BP:Ir(tBuppm) ₂ (acac)
) to form the first light-emitting layer 113a, and 2mDBTPDBq-I
I and bis{4,6-dimethyl-2-[3-(3,5-dimethylphenyl)-5-phenyl-2-pyrazinyl-κN]phenyl-κC} (2 ,6-
Dimethyl-3,5-heptanedionato-κ ² O,O'')iridium(III) (abbreviation:
[Ir(dmdppr-P) ₂ (dibm)]) at a weight ratio of 1:0.06 (=2mDB
TPDBq-II: 20n so that [Ir(dmdppr-P) ₂ (dibm)])
A second light-emitting layer 113b was formed by co-evaporation. In addition, the host material 2mDBTPD
Bq-II and PCBA1BP form an exciplex.

Thereafter, 2mDBTPDBq-II was formed on the light emitting layer 113 to a thickness of 15 nm, and bathophenanthroline (abbreviation: BPhen) represented by the above structural formula (vii) was further formed.
was deposited to a thickness of 15 nm to form an electron transport layer 114.

After forming the electron transport layer 114, lithium fluoride (LiF) was deposited to a thickness of 1 nm to form an electron injection layer 115.

Finally, aluminum was deposited to a thickness of 200 nm as the second electrode 102 functioning as a cathode, thereby manufacturing the light emitting element 4 of this example.

The light-emitting element 5 replaces [Ir(tBuppm) ₂ (acac)] in the first light-emitting layer 113a with tris[2-(6-tert-butyl-4-pyrimidinyl-κN3) represented by the above structural formula (xiii). ) phenyl-κC]iridium(III) (abbreviation: [Ir(tBuppm)
₃ )]) was manufactured in the same manner as Light-emitting Element 4 except that it was manufactured in place of 3)]).

In addition, in the vapor deposition process mentioned above, the resistance heating method was used for all vapor deposition.

Table 4 shows the element structure of light emitting element 4 obtained above, and Table 5 shows the element structure of light emitting element 5.

The work of sealing the light-emitting elements 4 and 5 with a glass substrate in a glove box with a nitrogen atmosphere so that they are not exposed to the atmosphere (a sealing material is applied around the elements,
Heat treatment was performed at 0° C. for 1 hour.

In the light emitting element 4, Ir(tBuppm) ₂ (ac
ac) as the second phosphorescent compound 113Db [Ir(dmdppr-P) ₂ (di
bm)] is used. Here, the relationship between the PL spectrum of Ir(tBuppm) ₂ (acac) and ε(λ)λ ⁴ of [Ir(dmdppr-P) ₂ (dibm)] will be described. Note that λ is the wavelength and ε(λ) is the molar absorption coefficient.

First, FIG. 45(a) shows the second phosphorescent compound 113Db of the light emitting element 4 [Ir(dmd
A graph showing the molar extinction coefficient ε(λ) and ε(λ)λ ⁴ of [ppr-P) ₂ (dibm)] is shown. While the molar extinction coefficient ε(λ) does not have a noticeable peak in the long wavelength region, in the graph of ε(λ)λ ⁴ , there is a maximum value at 509 nm, 550 nm, and 605 nm.
There is a peak (mountain) with a shoulder around m. This peak is [Ir(dmdppr-P)
₂ (dibm)], and this peak contains the first phosphorescent compound 11.
By overlapping the 3Da emission peaks, it becomes possible to greatly increase the efficiency of energy transfer.

FIG. 45(b) shows Ir(tBupp), which is the first phosphorescent compound 113Da of the light emitting element 4.
A graph showing the PL spectrum F(λ) of m) ₂ (acac) and ε(λ)λ ⁴ of [Ir(dmdppr-P) ₂ (dibm)], which is the second phosphorescent compound 113Db, is shown. From this graph, the peak where the peak of the PL spectrum F(λ) of Ir(tBuppm) ₂ (acac) exists and the longest wavelength side of ε(λ)λ ⁴ of [Ir(dmdppr-P) ₂ (dibm)] There is a large overlap with the peak having the maximum value of , and it can be seen that this is a combination in which energy transfer is carried out very efficiently. In addition, Ir, which is the first phosphorescent compound 113Da,
The emission peak of (tBuppm) ₂ (acac) is present at 546 nm, which is the peak in the spectrum representing ε(λ)λ ⁴ of [Ir(dmdppr-P) ₂ (dibm)], which is the second phosphorescent compound 113Db. The maximum on the long wavelength side exists at 509 nm, so the difference is 37 nm.
It is. Since 546 nm corresponds to 2.27 eV and 509 nm corresponds to 2.44 eV, the difference is 0.17 eV, which is smaller than 0.2 eV, suggesting that efficient energy transfer occurs from the peak position as well. be done. Note that [Ir(dmdppr-P) ₂
The maximum on the long wavelength side (maximum C) in the spectrum representing ε(λ)λ ⁴ of Ir(tBuppm) _{2 (acac) hardly overlaps with the spectrum F(λ) of the emission of Ir(tBuppm) 2} (acac). The peak having the maximum value C in the spectrum representing ε(λ)λ ⁴ of Ir(dmdppr-P) ₂ (dibm)] has a broad shape on the long wavelength side, and the spectrum on the long wavelength side and Ir( The emission spectra F(λ) of tBuppm) ₂ (acac) have a large overlap. This results in very good energy transfer.

In the light emitting element 4, the first host material 2mDBTPDBq-II and the first organic compound PCBA1BP form an exciplex, and the first phosphorescent compound 113Da Ir
Energy is efficiently transferred to (tBuppm) ₂ (acac). These relationships are the same as those in the light emitting element 1 and have been explained in detail in Example 1, so a repeated description will be omitted. Please refer to the corresponding description of Example 1.

In addition, FIG. 46 shows the PL spectrum F(λ) of the exciplex, Ir(tBuppm) ₂ (acac
), PL spectrum F(λ) of [Ir(dmdppr-P) ₂ (dibm)], ε(λ)λ ⁴ of Ir(tBuppm) ₂ (acac), [Ir(dmd
A graph is shown in which ε(λ)λ ⁴ of [ppr-P) ₂ (dibm)] are combined into one. Using the overlap between the PL spectrum of the exciplex and ε(λ)λ ⁴ of Ir(tBuppm) ₂ (acac) (near the maximum value A), the exciplex is converted to Ir(tBuppm) 2 (acac), and Ir(tBuppm) ₂ (acac) is
The PL spectrum of r(tBuppm) ₂ (acac) and [Ir(dmdppr-P) ₂ (
dibm)] with ε(λ)λ ⁴ (around 650 nm from the maximum value C)
It can be seen that energy can be transferred stepwise from tBuppm) ₂ (acac) to [Ir(dmdppr-P) ₂ (dibm)]. Note that energy can also be directly transferred from the exciplex to the second phosphorescent compound [Ir(dmdppr-P) ₂ (dibm)]. As can be seen from FIG. 46, [Ir(dmdppr-P) ₂ (dib
m)] triplet MLCT absorption band (near the maximum value C), the PL spectrum of the exciplex F(λ)
This is because ε(λ)λ ⁴ of [Ir(dmdppr-P) ₂ (dibm)] overlaps in both cases.

In the light emitting element 5, Ir(tBuppm) ₃ is used as the first phosphorescent compound 113Da, and [Ir(dmdppr-P) ₂ (dibm)] is used as the second phosphorescent compound 113Db. Here, the PL spectrum of Ir(tBuppm) ₃ and [Ir(dmdppr
-P) ₂ (dibm)], the relationship between ε(λ)λ ⁴ will be described. Note that λ is the wavelength and ε(λ
) is the molar extinction coefficient.

First, FIG. 47(a) shows the second phosphorescent compound 113Db of the light emitting element 4 [Ir(dmd
A graph showing the molar extinction coefficient ε(λ) and ε(λ)λ ⁴ of [ppr-P) ₂ (dibm)] is shown. While the molar extinction coefficient ε(λ) does not have a noticeable peak in the long wavelength region, in the graph of ε(λ)λ ⁴ , there is a maximum value at 509 nm, 550 nm, and 605 nm.
There is a peak (mountain) with a shoulder around m. This peak is [Ir(dmdppr-P)
₂ (dibm)], and this peak contains the first phosphorescent compound 11.
By overlapping the 3Da emission peaks, it becomes possible to greatly increase the efficiency of energy transfer.

FIG. 47(b) shows Ir(tBupp), which is the first phosphorescent compound 113Da of the light emitting element 5.
m) PL spectrum F(λ) of ₃ and the second phosphorescent compound 113Db [Ir(dm
A graph representing ε(λ)λ ⁴ of dppr-P) ₂ (dibm)] is shown. From this graph, we can see that the peak of the PL spectrum F(λ) of Ir(tBuppm) ₃ exists and the peak of [Ir(dm
dppr-P) ₂ (dibm)] and the peak having the maximum value on the longest wavelength side of ε(λ)λ ⁴ , it can be seen that this is a combination in which energy transfer is performed very efficiently. Furthermore, the emission peak of the first phosphorescent compound 113Da, Ir(tBuppm) ₃ , exists at 540 nm, and the second phosphorescent compound 113Db, [Ir(dmdp
The maximum on the long wavelength side in the spectrum representing ε(λ)λ ⁴ of [pr-P) ₂ (dibm)] exists at 509 nm, so the difference therebetween is 31 nm. 540nm is 2.30eV, 50
Since 9 nm corresponds to 2.44 eV, the difference is 0.14 eV, which is smaller than 0.2 eV, suggesting that efficient energy transfer is performed also from the peak position. In addition, the maximum on the long wavelength side in the spectrum representing ε(λ)λ ⁴ of [Ir(dmdppr-P) ₂ (dibm)] (maximum value C) and the emission spectrum F(λ) of Ir(tBuppm) ₃ are as follows. There is almost no overlap, but the ε of [Ir(dmdppr-P) ₂ (dibm)]
The peak with the maximum value C in the spectrum representing (λ) ^λ4 has a broad shape on the long wavelength side, and the spectrum on the long wavelength side and the emission _spectrum F(
λ) have a large overlap. This results in very good energy transfer.

Subsequently, in FIG. 48(a), Ir(tB
A graph showing the molar extinction coefficient ε(λ) of uppm) ₃ and ε(λ)λ ⁴ is shown. ε(λ
) In the graph of λ ⁴ , there are local maxima with large intensities at 409 and 465 nm, and 49
A peak with a shoulder exists at 4 nm. This peak (mountain) is triplet MLCT absorption of Ir(tBuppm) ₃ , and by superimposing the emission peak of the energy donor on this peak, it becomes possible to greatly increase the efficiency of energy transfer.

Here, in the light emitting element 5 of this example, 2mDBTPDBq-II which is the first host material
and PCBA1BP, which is the first organic compound, form an exciplex 113Ec, and energy is supplied from the exciplex 113Ec to the first phosphorescent compound 113Da. FIG. 23 is a diagram showing PL spectra of 2mDBTPDBq-II, PCBA1BP, and a mixed film thereof (mass ratio of 0.8:0.2).
It can be seen that -II and the first organic compound PCBA1BP form an exciplex 113Ec. Further, FIG. 48(b) shows a graph showing the PL spectrum F(λ) of the exciplex and ε(λ)λ ⁴ of Ir(tBuppm) ₃ which is the first phosphorescent compound 113Da. From this graph, we can see that there is a part of the wavelength range that has half the intensity of the peak of the PL spectrum F(λ) of the exciplex, and a maximum on the longest wavelength side of ε(λ)λ ⁴ of Ir(tBuppm) ₃ . It can be seen that a part of the wavelength range having half the intensity in the peak having the high value overlaps with the peak, and this is a combination in which energy transfer is performed efficiently.

In addition, Fig. 49 shows the PL spectrum F(λ) of the exciplex, the PL spectrum F(λ) of Ir(tBuppm) ₃ , and the PL spectrum F(λ) of [Ir(dmdppr-P) ₂ (dibm)].
), Ir(tBuppm) ₃ 's ε(λ)λ ⁴ , [Ir(dmdppr-P) ₂ (dibm
)] ε(λ)λ ⁴ are combined into one graph. PL spectrum of exciplex and Ir(
Ir from the exciplex using the overlap of ε(λ)λ of tBuppm) ₃ with ^λ4 (near the maximum value A).
(tBuppm) ₃ , and the PL spectrum of Ir(tBuppm) ₃ and [Ir(d
mdppr-P) ₂ (dibm)] overlaps with ε(λ)λ ⁴ (650 nm from the maximum value C
from Ir(tBuppm) ₃ to [Ir(dmdppr-P) ₂ (dibm)
] It can be seen that energy transfer is possible in stages. Note that energy can also be directly transferred from the exciplex to the second phosphorescent compound [Ir(dmdppr-P) ₂ (dibm)]. As can be seen from FIG. 49, [Ir(dmdppr-P) ₂
(dibm)], the PL spectrum F(λ) of the exciplex and the ε(λ)λ ⁴ of [Ir(dmdppr-P) ₂ (dibm)] overlap. This is because there is.

The device characteristics of these light emitting devices were measured. Note that the measurement was performed at room temperature (atmosphere maintained at 25° C.).

FIG. 35 shows the luminance-current efficiency characteristics of the light emitting element 4. Further, the voltage-luminance characteristics are shown in FIG. Further, the luminance-external quantum efficiency characteristics are shown in FIG. In addition, the luminance-power efficiency characteristics are shown in Figure 38.
Shown below.

As described above, it was found that the light emitting element 4 exhibited good device characteristics. In particular, Figure 35, Figure 3
7. As can be seen from Figure 38, it has very good luminous efficiency, and the external quantum efficiency is lower than the practical luminance (
1000 cd/m ² ), it showed a high value of 20% or more. Similarly, the current efficiency is around 50 cd/A, and the power efficiency is around 50 lm/W, which are very good values.

Further, FIG. 39 shows an emission spectrum when a current of 0.1 mA is passed through the light emitting element 4. In FIG. 39, the horizontal axis represents wavelength (nm), and the vertical axis represents emission intensity (arbitrary unit). From Figure 39,
The light emitting element 4 emits green wavelength light derived from [Ir(tBuppm) ₂ (acac)] and [Ir(tBuppm) 2 (acac)].
dmdppr-P) ₂ (dibm)] was found to exhibit an emission spectrum containing well-balanced red wavelength light.

FIG. 40 shows the luminance-current efficiency characteristics of the light emitting element 5. Further, the voltage-luminance characteristics are shown in FIG. Further, the luminance-external quantum efficiency characteristics are shown in FIG. In addition, the luminance-power efficiency characteristics are shown in Figure 43.
Shown below.

As described above, it was found that the light emitting element 5 exhibited good device characteristics. In particular, FIGS. 40 and 4
2. As can be seen from Figure 43, it has very good luminous efficiency, and the external quantum efficiency is lower than the practical luminance (
1000 cd/m ² ), it showed a high value of around 25%. Similarly, the current efficiency is around 65 cd/A, and the power efficiency is around 70 lm/W, which are very good values.

Further, FIG. 44 shows an emission spectrum when a current of 0.1 mA is passed through the light emitting element 5. In FIG. 44, the horizontal axis represents wavelength (nm), and the vertical axis represents emission intensity (arbitrary unit). From Figure 44,
The light emitting element 5 emits green wavelength light derived from [Ir(tBuppm) ₂ (acac)] and [Ir(tBuppm) 2 (acac)].
dmdppr-P) ₂ (dibm)] was found to exhibit an emission spectrum containing well-balanced red wavelength light.

As described above, it was found that Light-emitting Element 4 and Light-emitting Element 5, which correspond to one embodiment of the present invention, have good luminous efficiency and are light-emitting elements that can obtain light from two types of luminescence center substances in a well-balanced manner. Ta.

(Reference example 1)
The organometallic complex used in the above embodiment is bis[2-(6-tert-butyl-4-pyrimidinyl-κN3)phenyl-κC](2,4-pentanedionato-κ ² O,O')iridium ( A synthesis example of III) (abbreviation: [Ir(tBuppm) ₂ (acac)]) is shown. Note that the structure of [Ir(tBuppm) ₂ (acac)] is shown below.

<Step 1; 4-tert-butyl-6-phenylpyrimidine (abbreviation: HtBuppm
) synthesis>
First, 22.5 g of 4,4-dimethyl-1-phenylpentane-1,3-dione and 50 g of formamide were placed in a round bottom flask equipped with a reflux tube, and the inside was purged with nitrogen. The reaction solution was refluxed for 5 hours by heating this reaction vessel. Thereafter, this solution was poured into an aqueous sodium hydroxide solution, and the organic layer was extracted with dichloromethane. The obtained organic layer was washed with water and saturated brine, and dried over magnesium sulfate. After drying, the solution was filtered. After distilling off the solvent of this solution, the obtained residue was purified by silica gel column chromatography using hexane:ethyl acetate = 10:1 (volume ratio) as a developing solvent to obtain a pyrimidine derivative HtBupp.
m (colorless oil, yield 14%) was obtained. The synthesis scheme for step 1 is shown below.

<Step 2; Synthesis of di-μ-chloro-bis[bis(6-tert-butyl-4-phenylpyrimidinato)iridium(III)] (abbreviation: [Ir(tBuppm) ₂ Cl] ₂ )>
Next, add 15 mL of 2-ethoxyethanol and 5 mL of water to the HtBupp obtained in step 1 above.
1.49 g of iridium chloride hydrate (IrCl ₃ .H ₂ O) were placed in an eggplant flask equipped with a reflux tube, and the inside of the flask was replaced with argon. After that, microwave (2.4
5 GHz 100 W) for 1 hour to cause a reaction. After distilling off the solvent, the resulting residue was suction-filtered and washed with ethanol to obtain a dinuclear complex [Ir(tBuppm) ₂ Cl] ₂ (yellow-green powder, yield 73%). The synthesis scheme for step 2 is shown below.

<Step 3; Synthesis of (acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(tBuppm) ₂ (acac)])>
Furthermore, 40 mL of 2-ethoxyethanol, the dinuclear complex [Ir(tB
uppm) ₂ Cl] ₂ 1.61 g, acetylacetone 0.36 g, sodium carbonate 1.
27 g was placed in an eggplant flask equipped with a reflux tube, and the inside of the flask was purged with argon. Thereafter, microwave (2.45 GHz 120 W) was irradiated for 60 minutes to cause a reaction. The solvent was distilled off, and the resulting residue was suction-filtered with ethanol and washed with water and ethanol. This solid was dissolved in dichloromethane and dissolved in Celite (Wako Pure Chemical Industries, Ltd., catalog number: 531-1).
6855), alumina, and Celite in this order. By distilling off the solvent and recrystallizing the obtained solid from a mixed solvent of dichloromethane and hexane,
The desired product was obtained as a yellow powder (yield 68%). The synthesis scheme for step 3 is shown below.

The analysis results of the yellow powder obtained in step 3 above by nuclear magnetic resonance spectroscopy ( ¹ H NMR) are shown below. From this result, it was found that the organometallic complex Ir(tBuppm) ₂ (acac) was obtained.

^1H NMR. δ (CDCl ₃ ): 1.50 (s, 18H), 1.79 (s, 6H),
5.26 (s, 1H), 6.33 (d, 2H), 6.77 (t, 2H), 6.85 (t,
2H), 7.70 (d, 2H), 7.76 (s, 2H), 9.02 (s, 2H).

(Reference example 2)
In this reference example, the organometallic iridium complex used in the example, bis{4,6-dimethyl-2
-[3-(3,5-dimethylphenyl)-5-phenyl-2-pyrazinyl-κN]phenyl-κC}(2,6-dimethyl-3,5-heptanedionato-κ ² O,O'') Iridium ( III) (abbreviation: [Ir(dmdppr-P) ₂ (dibm)]) will be described. The structure of [Ir(dmdppr-P) ₂ (dibm)] (abbreviation) is shown below.

<Step 1: 2,3-bis(3,5-dimethylphenyl)pyrazine (abbreviation: Hdmdp
synthesis of pr)>
First, 5.00 g of 2,3-dichloropyrazine and 10 g of 3,5-dimethylphenylboronic acid.
．． 23g, sodium carbonate 7.19g, bis(triphenylphosphine)palladium(I
I) 0.29 g of dichloride (abbreviation: Pd(PPh ₃ ) ₂ Cl ₂ ), 20 mL of water, and 20 mL of acetonitrile were placed in a round bottom flask equipped with a reflux tube, and the inside was purged with argon. This reaction vessel was heated by irradiating it with microwaves (2.45 GHz, 100 W) for 60 minutes. Here, 2.55 g of 3,5-dimethylphenylboronic acid and 1.80 g of sodium carbonate are added.
, 0.070 g of Pd(PPh ₃ ) ₂ Cl ₂ , 5 mL of water, and 5 mL of acetonitrile were placed in a flask, and heated by irradiating with microwave (2.45 GHz 100 W) for 60 minutes again.

Thereafter, water was added to this solution, and the organic layer was extracted with dichloromethane. The obtained organic layer was washed with a saturated aqueous sodium bicarbonate solution, water, and saturated brine, and dried over magnesium sulfate. The solution after drying was filtered. After distilling off the solvent of this solution, the obtained residue was purified by flash column chromatography using hexane:ethyl acetate=5:1 (volume ratio) as a developing solvent. The solvent was distilled off, and the obtained solid was dichloromethane:ethyl acetate=10:
1 (volume ratio) as a developing solvent to obtain the desired pyrazine derivative Hdmdppr (abbreviation) (white powder, yield 44%). Note that a microwave synthesizer (Discover manufactured by CEM) was used for the microwave irradiation. The synthesis scheme of Step 1 is shown in (a-1) below.

<Step 2: Synthesis of 2,3-bis(3,5-dimethylphenyl)-5-phenylpyrazine (abbreviation: Hdmdppr-P)>
First, 4.28g of Hdmdppr (abbreviation) obtained in step 1 above and 80m of dryTHF
L was placed in a three-necked flask, and the inside was replaced with nitrogen. After cooling the flask on ice, add phenyllithium (
9.5 mL of 1.9M butyl ether solution) was added dropwise, and the mixture was stirred at room temperature for 23 and a half hours. The reaction solution was poured into water and extracted with chloroform. The obtained organic layer was washed with water and saturated brine, and dried over magnesium sulfate. Manganese oxide was added to the resulting mixture and stirred for 30 minutes. Thereafter, the solution was filtered and the solvent was distilled off. The obtained residue was purified by silica gel column chromatography using dichloromethane as a developing solvent to obtain the desired pyrazine derivative Hdmdppr.
-P (abbreviation) was obtained (orange oil, yield 26%). The synthesis scheme for step 2 is shown below (a
-2).

<Step 3: Di-μ-chloro-tetrakis {4,6-dimethyl-2-[3-(3,5-
Synthesis of dimethylphenyl)-5-phenyl-2-pyrazinyl-κN]phenyl-κC}diiridium(III) (abbreviation: [Ir(dmdppr-P) ₂ Cl] ₂ )>
Next, add 15 mL of 2-ethoxyethanol and 5 mL of water to the Hdmdp obtained in step 2 above.
pr-P (abbreviation) 1.40 g, iridium chloride hydrate (IrCl ₃ H ₂ O) (Sigma
a-Aldrich) was placed in an eggplant flask equipped with a reflux tube, and the inside of the flask was replaced with argon. Thereafter, microwave (2.45 GHz 100 W) was irradiated for 1 hour to cause a reaction. After distilling off the solvent, the resulting residue was suction-filtered and washed with ethanol to obtain a dinuclear complex [Ir(dmdppr-P) ₂ Cl] ₂ (abbreviation) (reddish brown powder, yield 58%).
). The synthesis scheme of Step 3 is shown in (a-3) below.

<Step 4: Bis{4,6-dimethyl-2-[3-(3,5-dimethylphenyl)-5
-Phenyl-2-pyrazinyl-κN]phenyl-κC}(2,6-dimethyl-3,5-heptanedionato-κ ² O,O'') Iridium(III) (abbreviation: [Ir(dmdppr
-P) ₂ (dibm)] synthesis>
Furthermore, 30 mL of 2-ethoxyethanol, the dinuclear complex [Ir(d
mdppr-P) ₂ Cl] ₂ 0.94 g, diisobutyrylmethane (abbreviation: Hdibm)
0.23 g and 0.52 g of sodium carbonate were placed in an eggplant flask equipped with a reflux tube, and the inside of the flask was replaced with argon. Thereafter, it was heated by irradiating it with microwaves (2.45 GHz 120 W) for 60 minutes. The solvent was distilled off, and the resulting residue was suction-filtered with ethanol. The obtained solid was washed with water and ethanol, and recrystallized with a mixed solvent of dichloromethane and ethanol to obtain the organometallic complex [Ir(dmdppr-P) ₂ (dibm)] of the present invention.
(abbreviation) was obtained as a dark red powder (yield 75%). The synthesis scheme for step 4 is shown below (a
-4).

The analysis results of the dark red powder obtained by the above synthesis method by nuclear magnetic resonance spectroscopy ( ¹ H-NMR) are shown below. From this result, in this synthesis example, the organometallic complex [Ir(dmdp
It was found that pr-P) ₂ (dibm)] (abbreviation) was obtained.

^1H -NMR. δ (CDCl ₃ ): 0.79 (d, 6H), 0.96 (d, 6H), 1
．． 41 (s, 6H), 1.96 (s, 6H), 2.24-2.28 (m, 2H), 2.4
1 (s, 12H), 5.08 (s, 1H), 6.46 (s, 2H), 6.82 (s, 2H
), 7.18 (s, 2H), 7.39-7.50 (m, 10H), 8.03 (d, 4H)
, 8.76 (s, 2H).

10 Electrode 11 Electrode 101 First electrode 102 Second electrode 103 EL layer 111 Hole injection layer 112 Hole transport layer 113 Light emitting layer 113a First light emitting layer 113Da First phosphorescent compound 113Ha First host material 113b Second light emitting layer 113Db Second phosphorescent compound 113Hb Second host material 113A First organic compound 113Ec Exciplex 114 Electron transport layer 115 Electron injection layer 400 Substrate 401 First electrode 402 Auxiliary electrode 403 EL layer 404 Second electrode 405 Sealing material 406 Sealing material 407 Sealing substrate 412 Pad 420 IC chip 601 Drive circuit section (source line drive circuit)
602 Pixel section 603 Drive circuit section (gate line drive circuit)
604 Sealing substrate 605 Sealing material 607 Space 608 Wiring 609 FPC (flexible printed circuit)
610 Element substrate 611 Switching TFT
612 Current control TFT
613 First electrode 614 Insulator 616 EL layer 617 Second electrode 618 Light emitting element 623 N-channel TFT
624 p-channel TFT
625 Drying material 901 Housing 902 Liquid crystal layer 903 Backlight unit 904 Housing 905 Driver IC
906 Terminal 951 Substrate 952 Electrode 953 Insulating layer 954 Partition layer 955 EL layer 956 Electrode 1001 Substrate 1002 Base insulating film 1003 Gate insulating film 1006 Gate electrode 1007 Gate electrode 1008 Gate electrode 1020 First interlayer insulating film 1021 Second interlayer insulating film 1022 Electrode 1024W First electrode of light emitting element 1024R First electrode of light emitting element 1024G First electrode of light emitting element 1024B First electrode of light emitting element 1025 Partition wall 1028 EL layer 1029 Second electrode of light emitting element 1031 Sealing Substrate 1032 Sealing material 1033 Transparent base material 1034R Red colored layer 1034G Green colored layer 1034B Blue colored layer 1035 Black layer (black matrix)
1036 Overcoat layer 1037 Third interlayer insulating film 1040 Pixel portion 1041 Drive circuit portion 1042 Peripheral portion 1044W White light emitting region 1044R Red light emitting region 1044B Blue light emitting region 1044G Green light emitting region 2001 Housing 2002 Light source 3001 Lighting device 3002 Display device 5000 Display 5001 Display 5002 Display 5003 Display 5004 Display 5005 Display 7101 Housing 7103 Display portion 7105 Stand 7107 Display portion 7109 Operation keys 7110 Remote control unit 7201 Main body 7202 Housing 7203 Display portion 7204 Keyboard 7205 External connection port 720 6 Pointing device 7210 Second display section 7301 Housing 7302 Housing 7303 Connecting section 7304 Display section 7305 Display section 7306 Speaker section 7307 Recording medium insertion section 7308 LED lamp 7309 Operation key 7310 Connection terminal 7311 Sensor 7400 Mobile phone 7401 Housing 7402 Display section 7403 Operation Button 7404 External connection port 7405 Speaker 7406 Microphone 9033 Fastener 9034 Switch 9035 Power switch 9036 Switch 9038 Operation switch 9630 Housing 9631 Display section 9631a Display section 9631b Display section 9632a Touch panel area 9632b Touch panel area 9633 Solar cell 9634 Charge/discharge control circuit 9 635 battery 9636 DCDC converter 9637 Operation key 9638 Converter 9639 Button

Claims (7)

A light-emitting layer having a phosphorescent compound, a host material, and an organic compound is provided between the first electrode and the second electrode,
The host material and the organic compound are a combination that forms an exciplex,
The difference between the energy value of the emission peak wavelength of the PL spectrum of the exciplex and the energy value of the wavelength of the maximum value on the longest wavelength side of the function expressed by ε(λ)λ ⁴ of the phosphorescent compound is 0. .2 eV or less, a light emitting element.
(However, ε(λ) represents the molar extinction coefficient and is a function of the wavelength λ.) A light emitting layer including an iridium complex, a host material, and an organic compound is provided between the first electrode and the second electrode,
The host material and the organic compound are a combination that forms an exciplex,
The difference between the energy value of the emission peak wavelength of the PL spectrum of the exciplex and the energy value of the wavelength of the maximum value on the longest wavelength side of the function expressed by ε(λ)λ ⁴ of the iridium complex is 0.2 eV. A light emitting element as follows.
(However, ε(λ) represents the molar extinction coefficient and is a function of the wavelength λ.) In claim 2,
A light-emitting device, wherein two of the three ligands that the iridium complex has are the same ligand and one is a different ligand. A lighting device comprising the light emitting element according to any one of claims 1 to 3. A light-emitting device comprising the light-emitting element according to claim 1 and means for controlling the light-emitting element. A display device comprising the light emitting element according to any one of claims 1 to 3 in a display section, and having means for controlling the light emitting element. An electronic device comprising the light emitting element according to any one of claims 1 to 3.

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