Light-emitting device

Abstract

To provide a light-emitting element which has low driving voltage and high emission efficiency.SOLUTION: A light-emitting element includes, between a pair of electrodes, a hole-transport layer and a light-emitting layer formed over the hole-transport layer. The light-emitting layer contains a first organic compound having an electron-transport property, a second organic compound having a hole-transport property, and a light-emitting third organic compound converting triplet excitation energy into light emission. A combination of the first organic compound and the second organic compound forms an exciplex. The hole-transport layer contains at least a fourth organic compound whose HOMO level is lower than or equal to that of the second organic compound and a fifth organic compound whose HOMO level is higher than that of the second organic compound.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] One embodiment of the present invention is a semiconductor device comprising: a semiconductor device including a pair of electrodes and an organic compound that emits light when an electric field is applied thereto; A light-emitting device having such a light-emitting element, an electronic device, and a lighting device are also provided. Regarding the lighting device. [Background technology]

[0002] The organic compound used as the light emitter has characteristics such as being thin and lightweight, having high-speed response, and being driven by low DC voltage. The light-emitting element used is expected to be applied to next-generation flat panel displays. In addition, a display device in which light-emitting elements are arranged in a matrix has a higher viewing angle than a conventional liquid crystal display device. It is believed that its advantages lie in its wide viewing angle and excellent visibility.

[0003] The light-emitting mechanism of a light-emitting element is to sandwich a light-emitting layer containing a light-emitting body between a pair of electrodes and apply a voltage. As a result, electrons injected from the cathode and holes injected from the anode are emitted at the luminescence center of the luminescent layer. recombines to form molecular excitons, which then lose energy as they relax to the ground state. It is said that the electrons emit light by emitting light. There are two types of excited states: singlet excited states and triplet excited states. It is believed that emission can occur through either excited state, and the singlet excited state (S * ) is emitted from the triplet excited state (T * ) is called phosphorescence.

[0004] Regarding such light-emitting devices, improvements in the device structure and materials have been made in order to improve the device characteristics. Materials development and the like are being actively conducted (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2010-182699 A Summary of the Invention [Problem to be solved by the invention]

[0006] As reported in Patent Document 1, improvements in element structure have progressed, but However, there is still room for improvement in terms of light emission efficiency, reliability, and light emission characteristics, and There is a demand for the development of light-emitting devices having such properties.

[0007] In view of the above, one embodiment of the present invention provides a light-emitting element which has a low driving voltage and high emission efficiency. One of the objectives of the Society is to [Means for solving the problem]

[0008] One embodiment of the present invention is a light-emitting element including a hole transport layer between a pair of electrodes and a light-emitting layer formed on the hole transport layer. The light-emitting layer comprises a first organic compound having an electron transporting property and a second organic compound having a hole transporting property. and a third organic compound having a light-emitting property that converts triplet excitation energy into light emission. The first organic compound and the second organic compound are combined to form an exciplex, The hole transport layer comprises at least a fourth organic compound having a HOMO level equal to or lower than the HOMO level of the second organic compound, The present invention is characterized in that the fifth organic compound has a higher HOMO level than the second organic compound. It is a light emitting element.

[0009] Another embodiment of the present invention is a semiconductor device including a hole injection layer between a pair of electrodes and a semiconductor device formed on the hole injection layer. a hole transport layer formed on the hole transport layer, a light emitting layer formed on the hole transport layer, and an electron transport layer formed on the light emitting layer. and an electron injection layer formed on the electron transport layer. The light emitting layer is a first layer having an electron transport property. The organic compound of the first embodiment, the second organic compound having a hole transport property, and the compound emitting triplet excitation energy are mixed. and a third organic compound that emits light and converts the light into light. is a combination that forms an exciplex, and the hole transport layer is a combination of at least a second organic compound A fourth organic compound with a HOMO level lower than that of the first organic compound and a HOMO level higher than that of the second organic compound. The light-emitting element is characterized by having a fifth organic compound.

[0010] In each of the above structures, the first organic compound is used as a host material, and the second organic compound is used as a It is preferable to use the compound as an assist material and a third organic compound as a guest material. That is, the mass fraction (or volume fraction) of the third organic compound in the light-emitting layer is It is preferably less than that of the first organic compound and the second organic compound.

[0011] In each of the above structures, the first organic compound (host material) and the second organic compound (a The emission wavelength of the exciplex formed by the first organic compound (host material) is and the second organic compound (assist material) have a longer wavelength than the emission wavelength (fluorescence wavelength) of the first organic compound (assist material). Since the first organic compound (host material) and the second organic compound (host material) are on the long side, The fluorescence spectrum of the compound (assist material) is changed to an emission spectrum located on the longer wavelength side. can be exchanged.

[0012] Therefore, in the light-emitting element of one embodiment of the present invention, an exciplex is formed in the light-emitting layer. As a result, the first organic compound (host material) and the second organic compound (assist material) The emission spectrum of the exciplex that exists on the longer wavelength side than the emission wavelength (fluorescence wavelength) of the third Energy transfer is performed by utilizing the overlap of the absorption spectrum with that of the organic compound (guest material). This makes it possible to realize a light-emitting element with high energy transfer efficiency and high luminous efficiency. Cut.

[0013] In addition, in the hole transport layer, the hole transport layer contains at least a second organic compound (assist The fourth organic compound is located below the HOMO level of the first organic compound (assist material) and the second organic compound is located below the HOMO level of the second organic compound (assist material). The fourth organic compound in the hole transport layer has a higher HOMO level than the fifth organic compound in the hole transport layer. The holes are injected into the second organic compound (assist material) of the light-emitting layer, The hole transport layer is also formed in the first region of the light emitting layer. Since the organic compound 5 has a higher HOMO level than the second organic compound (assist material), The driving voltage (also simply referred to as voltage) of the light-emitting layer, particularly the driving start voltage, can be reduced. This effect is achieved when the hole transport layer contains two or more of the above organic compounds and the HOMO level is This is an effect that can only be achieved through relationships.

[0014] In each of the above configurations, the fourth organic compound is a mixture of the first organic compound and the second organic compound. It is preferable that the lowest triplet excitation energy level (T1 level) of such a compound is higher than that of the compound having such a structure. By using this structure, it is possible to suppress the triplet excitation energy of the light-emitting layer from diffusing to the hole transport layer. Since the triplet excitation of the light-emitting layer can be suppressed, the light-emitting efficiency of the device can be improved. In order to prevent the energy from diffusing to the hole transport layer, the fourth The mass fraction (or volume fraction) of organic compounds must be 20% or more (less than 100%). preferable.

[0015] In each of the above structures, the first organic compound (host material) is a π-deficient heteroaromatic compound. The second organic compound (assist material) is a π-excess heteroaromatic compound or an aromatic It is preferable that the third organic compound (guest material) is an aromatic amine compound and the third organic compound (guest material) is a phosphorescent compound. stomach.

[0016] Another embodiment of the present invention is a light-emitting device having a light-emitting element, an electronic device having a light-emitting device, and Therefore, the term "light-emitting device" in this specification includes: This refers to an image display device or a light source (including lighting equipment). Also, a light-emitting device with a connector For example, FPC (Flexible printed circuit) or TAB (Tape Automated Bonding) Tape or TCP (Tape Carrier Package) attached modules, TAB tape and TCP A module with a printed wiring board on the end of the light emitting element, or a COG (Chip On Glass) The modules with ICs directly mounted using the OLED Glass method are all luminous. This is included in the location. Effect of the Invention

[0017] In the light-emitting element of one embodiment of the present invention, an exciplex is formed in the light-emitting layer, The emission waves of the first organic compound (host material) and the second organic compound (assist material) The emission spectrum of the exciplex that exists on the longer wavelength side than the long (fluorescence wavelength) and the third organic compound This allows energy transfer by utilizing the overlap of the absorption spectrum with the guest material. Therefore, it is possible to realize a light-emitting element having high energy transfer efficiency and high luminous efficiency. . [Brief description of the drawings]

[0018] [Figure 1] 1A to 1C illustrate a light-emitting element of one embodiment of the present invention. [Diagram 2] FIG. 1 illustrates a concept of one embodiment of the present invention. [Diagram 3] A diagram explaining the energy levels of one DBq (abbreviation) molecule, one TPA (abbreviation) molecule, and a dimer of DBq (abbreviation) and TPA (abbreviation). [Figure 4] FIG. 1 is a diagram illustrating the distribution of HOMO and LUMO for one DBq (abbreviation) molecule, one TPA (abbreviation) molecule, and a dimer of DBq (abbreviation) and TPA (abbreviation). [Diagram 5] FIG. 2 illustrates a concept of energy levels of a hole-transport layer and a light-emitting layer according to one embodiment of the present invention. [Figure 6] 1A to 1C illustrate a light-emitting element of one embodiment of the present invention. [Figure 7] 1A to 1C are diagrams illustrating a structure of a light-emitting element. [Figure 8] 1A to 1C are diagrams illustrating a structure of a light-emitting element. [Figure 9] 1A and 1B are diagrams illustrating a light-emitting device. [Figure 10] 1A to 1C are diagrams illustrating electronic devices. [Figure 11] 1A to 1C are diagrams illustrating electronic devices. [Figure 12] FIG. [Figure 13] 1A to 1C are diagrams illustrating a structure of a light-emitting element in an embodiment. [Figure 14] FIG. 1 shows current density-luminance characteristics of the light-emitting element shown in Example 1. [Figure 15] FIG. 1 shows voltage-luminance characteristics of the light-emitting element shown in Example 1. [Figure 16] FIG. 1 shows luminance-current efficiency characteristics of the light-emitting element shown in Example 1. [Figure 17] FIG. 2 shows voltage-current characteristics of the light-emitting element shown in Example 1. [Figure 18] FIG. 2 shows an emission spectrum of the light-emitting element shown in Example 1. [Figure 19]FIG. 13 shows luminance-power efficiency characteristics of the light-emitting element shown in Example 1. [Figure 20] FIG. 1 shows the phosphorescence emission spectrum of 2mDBTPDBq-II (abbreviation). [Figure 21] FIG. 1 shows the phosphorescence emission spectrum of PCBA1BP (abbreviation). [Figure 22] FIG. 1 shows the phosphorescence emission spectrum of BPAFLP (abbreviation). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, the embodiment of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the above description, and the embodiments and details thereof are not limited to those described above without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited to the embodiments described below. It is not to be construed as being limited to the content.

[0020] In addition, the position, size, range, etc. of each component shown in the drawings are not necessarily shown in order to facilitate understanding. The actual position, size, range, etc. may not be shown. The present invention is not necessarily limited to the position, size, range, etc. disclosed in the drawings, etc.

[0021] In this specification, ordinal numbers such as "first," "second," and "third" refer to the number of components. It should be noted that this is added to avoid confusion and is not intended to limit the number.

[0022] (Embodiment 1) In this embodiment, a concept and specific examples of forming a light-emitting element according to one embodiment of the present invention will be described. First, the structure of a light-emitting element according to one embodiment of the present invention will be described. This will be explained with reference to FIG.

[0023] The element structure shown in FIG. 1 has a hole The light-emitting layer 11 has a hole transport layer 112 and a light-emitting layer 113 formed on the hole transport layer 112. 3 is a first organic compound 120 having an electron transporting property and a second organic compound 121 having a hole transporting property. and a third organic compound 124 that converts triplet excitation energy into light emission. The first organic compound 120 and the second organic compound 122 are a compound that forms an exciplex. The hole transport layer 112 is a combination of at least the HOMO level of the second organic compound 122. A fourth organic compound 126 having a lower HOMO level than the second organic compound 122 and a fourth organic compound 126 having a higher HOMO level than the second organic compound 122. The fifth organic compound 128 is included.

[0024] In FIG. 1, the region between the first electrode 101 and the hole transport layer 112 has A hole injection layer and a hole transport layer can be formed as necessary. In the region between the second electrode 103 and the light-emitting layer 113, an electron injection layer and an electron transport layer are provided. can be formed as needed.

[0025] The first organic compound 120 is used as a host material, and the second organic compound 122 is used as an The first organic compound 123 may be used as a host material and the second organic compound 124 may be used as a guest material. That is, the mass fraction (or volume fraction) of the third organic compound in the light-emitting layer is It is preferable that the amount of the first organic compound is less than that of the second organic compound. The first organic compound 120 is a host material, the second organic compound 122 is an assist material, and the third organic compound 123 is an auxiliary material. The organic compound 124 may be referred to as a guest material.

[0026] The first organic compound 120 (host material) is, for example, 10-6 cm 2 / Vs or more An electron transporting material having high mobility can be used. Cyst material) is, for example, 10 -6 cm 2 Hole transport material with hole mobility of ≥ 100 / Vs can be used.

[0027] In the above structure, the first organic compound 120 (host material) and the second organic compound The lowest triplet excitation energy level (T1 level) of each of the substances 122 (assist materials) is , is preferably higher than the T1 level of the third organic compound 124 (guest material). The T1 standard of the organic compound 120 (host material) and the second organic compound 122 (assist material) If the T1 level of the third organic compound 124 (guest material) is lower than the T1 level of the third organic compound 124, the T1 level of the third organic compound 124 (guest material) contributes to light emission. The triplet excitation energy of the third organic compound 124 (guest material) is calculated by the 0 (host material) and the second organic compound 122 (assist material) are quenched. This leads to a decrease in luminous efficiency.

[0028] In addition, in order to increase the efficiency of energy transfer from the host material to the guest material, intermolecular transfer Mechanisms known as Förster mechanism (dipole-dipole interaction) and Dexter Taking into account the mechanism (electron exchange interaction), the emission spectrum (singlet excited state) of the host material When discussing energy transfer from the triplet excited state, use the fluorescence spectrum. The phosphorescence spectrum when discussing the transfer of the guest material) and the absorption spectrum of the guest material (more specifically, The overlap with the spectrum of the absorption band on the longest wavelength (lowest energy) side becomes large. is preferred.

[0029] However, when a phosphorescent compound is used as a guest material, the phosphorescence of the host material The optical spectrum is the absorption spectrum in the longest wavelength (lowest energy) absorption band of the guest material. It is difficult to layer the ZnO vector on the host material because doing so would The phosphorescence spectrum is located on the longer wavelength (lower energy) side than the fluorescence spectrum. The T1 level of the photoluminescent material falls below that of the phosphorescent compound, causing the quenching problem mentioned above. On the other hand, to avoid the quenching problem, the T1 standard of the host material is If the level is designed to be higher than the T1 level of the phosphorescent compound used as the guest material, The fluorescence spectrum of the host material is shifted to the short wavelength (high energy) side, The spectrum is the absorption spectrum of the longest wavelength (lowest energy) absorption band of the guest material. Therefore, the fluorescence spectrum of the host material is aligned to the longest wavelength of the guest material. The absorption spectrum of the host material was superimposed on the absorption band on the (lower energy) side. It is usually difficult to maximize the energy transfer from the

[0030] Therefore, in the present invention, the first organic compound 120 and the second organic compound 122 are , a combination that forms an exciplex (also called an exciplex) The exciplex will be described below with reference to FIG. 2(A) and FIG. 2(B).

[0031] FIG. 2(A) is a schematic diagram showing the concept of an exciplex. The fluorescence spectrum of the first organic compound 120 (or the second organic compound 122), The phosphorescence spectrum of the third organic compound 122, the absorption spectrum of the third organic compound 124, and the exciplex Represents the emission spectrum of the body.

[0032] For example, in the light-emitting layer 113, the fluorescent spectrum of the first organic compound 120 (host material) The fluorescence spectra of the toru and the second organic compound 122 (assist material) are on the longer wavelength side. The emission spectrum of the exciplex is converted to the emission spectrum of the exciplex located at the In order to increase the overlap with the absorption spectrum of the third organic compound 124 (guest material), A first organic compound 120 (host material) and a second organic compound 122 (assist material) are mixed. By selecting the appropriate fluorine atom, it is possible to maximize the energy transfer from the singlet excited state (Figure 2). (See (A)).

[0033] Regarding the triplet excited state, the energy transfer occurs not from the host material but from the exciplex. It is believed that the following will occur.

[0034] Therefore, the emission wavelength of the formed exciplex is determined by the first organic compound 120 (host material ) and the emission wavelength (fluorescence wavelength) of the second organic compound 122 (assist material). Since all of the emission spectra are on the long wavelength side, the fluorescence spectrum of the first organic compound 120 (host material) is The fluorescence spectrum of the 122nd organic compound (assist material) is shifted to the longer wavelength side. The emission spectrum may be located at

[0035] Furthermore, the difference between the singlet and triplet excitation energies of exciplexes is extremely small. In other words, the emission spectrum from the singlet state of the exciplex and that from the triplet state are The emission spectra of these are very close to each other. The emission spectrum of the complex (generally the emission spectrum from the singlet state of the exciplex) is The absorption band of the organic compound 124 (guest material) was designed to overlap with the absorption band located at the longest wavelength side. In this case, the emission spectrum from the triplet state of the exciplex (which is not observed at room temperature but is observed at low temperatures) The third organic compound 124 (guest material) is located on the longest wavelength side. In other words, the absorption band is not only the energy transfer from the singlet excited state. In addition, the efficiency of energy transfer from the triplet excited state is also increased, resulting in a singlet-triplet Both of these can be efficiently emitted.

[0036] In this manner, the light-emitting element according to one embodiment of the present invention can be obtained by using the excitation light emitting layer 113. The emission spectrum of the complex and the absorption spectrum of the third organic compound 124 (guest material) Energy transfer is achieved by utilizing overlap, resulting in high energy transfer efficiency.

[0037] In addition, since exciplexes exist only in excited states, there is no ground state that can absorb energy. Therefore, the singlet excited state and triplet excited state of the third organic compound 124 (guest material) are not present. The third organic compound 124 (guest material) was generated by energy transfer from the singlet excited state to the exciplex. In principle, the phenomenon that the phosphorus (a phosphorus compound) becomes inactive before it emits light (i.e., the luminous efficiency is reduced) does not occur. It is thought that this is not the case.

[0038] The above-mentioned exciplexes are formed by interactions between different molecules in an excited state. In addition, exciplexes have relatively low LUMOs (Lowest Unoccupied Orbitals). Materials with low unoccupied molecular orbital (LDO) levels and high いHOMO(HOMO:Hightest Occupied Molecular O It is generally known that it is easy to form between materials with the highest occupied molecular orbital (RBIT) level. It is being done.

[0039] Here, the energies of the first organic compound 120, the second organic compound 122, and the exciplex are The concept of the first level will be explained with reference to FIG. 2(B). 1 shows a schematic diagram of the energy levels of an organic compound 120, a second organic compound 122, and an exciplex. This is a diagram.

[0040] A first organic compound 120 (host material) and a second organic compound 122 (assist material). The HOMO level and the LUMO level of the first organic compound 1 are different from each other. HOMO level of 20 < HOMO level of second organic compound 122 < HOMO level of first organic compound 120 The energy levels of the first organic compound are different from that of the second organic compound, 122. When these two organic compounds form an exciplex, the LU of the exciplex is The MO level is due to the first organic compound 120 (host material), and the HOMO level is due to the second organic compound 121 (host material). It originates from organic compound 122 (assist material) (see FIG. 2(B)).

[0041] The emission wavelength of an exciplex depends on the energy difference between the HOMO and LUMO levels. Generally speaking, the larger the energy difference, the shorter the emission wavelength. The smaller it is, the longer the emission wavelength will be.

[0042] Therefore, the energy difference of the exciplex is the energy difference of the first organic compound 120 (host material). and the energy difference of the second organic compound 122 (assist material). That is, the emission wavelengths of the first organic compound 120 and the second organic compound 122 are The emission wavelength of the exciplex is longer than that of the

[0043] Here, molecular orbital calculations are carried out to determine whether exciplexes actually have such properties. In general, the combination of a heteroaromatic compound and an aromatic amine is The LUMO level of heteroaromatic compounds is lower than that of amines (electrons can easily enter properties) and the higher HOMO levels of aromatic amines ( In many cases, exciplexes are formed due to the effect of the property that holes can easily enter the molecule. In one embodiment, the LUMO of a heteroaromatic compound is constructed as a model for the first organic compound 120. The present invention uses dibenzo[f,h]quinoxaline (abbreviation: DBq), which is a representative skeleton that forms In one embodiment, the HOMO of an aromatic amine is configured as a model for the second organic compound 122. We use triphenylamine (TPA), a representative skeleton, and combine these to I did the calculations.

[0044] First, the lowest excited singlet state (S1) of one DBq (abbreviation) molecule and one TPA (abbreviation) molecule The optimal molecular structure and excitation energy in the lowest excited triplet state (T1) are calculated using the time-dependent density The calculations were performed using the TD-DFT functional method. In addition, DBq (abbreviation) and TPA (abbreviation) The excitation energies of the dimer of

[0045] The total energy of DFT (density functional theory) is the potential energy, the interelectronic electrostatic energy, energy, the kinetic energy of the electrons, and the exchange-correlation energy, which includes all the complex interactions between electrons. In DFT, the exchange-correlation interaction is expressed as a one-electron potential represented by the electron density. The calculation is fast and highly accurate because it is approximated by a functional of a function. Here, we use the mixed functional B3LYP to estimate the parameters related to the exchange and correlation energies. The weight of the meter was specified.

[0046] In addition, the basis functions are 6-311 (three contraction functions are used for each valence orbital). The triple split valence basis set was applied to all atoms. .

[0047] With the above-mentioned basis functions, for example, in the case of a hydrogen atom, the 1s to 3s orbitals are taken into account, In addition, in the case of a carbon atom, the orbitals 1s to 4s and 2p to 4p are taken into consideration. In order to improve the accuracy of the calculation, the polarization basis set is p function for hydrogen atoms and d function for other atoms. Added function.

[0048] The quantum chemical calculation program used was Gaussian 09. The experiment was carried out using a high-performance computer (SGI, Altix 4700). .

[0049] First, one molecule of DBq (abbreviation), one molecule of TPA (abbreviation), and the combination of DBq (abbreviation) and TPA ( The HOMO and LUMO levels of the dimer of The UMO levels are shown in Figure 3.

[0050] As shown in Figure 3, the dimer of DBq (abbreviation) and TPA (abbreviation) is The LUMO level of DBq (abbreviation) (-1.99 eV) is lower than the UMO level, and the The HOMO level of TPA (abbreviation) is higher than that of It is suggested that the influence of this leads to the formation of an exciplex of DBq (abbreviation) and TPA (abbreviation).

[0051] Next, one molecule of DBq (abbreviation), one molecule of TPA (abbreviation), and the combination of DBq (abbreviation) and TPA ( The HOMO and LUMO distributions of the dimer of (abbreviation) are shown in Figure 4.

[0052] In addition, Fig. 4(A) shows the LUMO distribution of one molecule of DBq (abbreviation), and Fig. 4(B) shows the LUMO distribution of one molecule of DB The distribution of the HOMO of one molecule of q (abbreviation) is shown in Fig. 4(C), and the LUM of one molecule of TPA (abbreviation) is shown in Fig. 4(D). Fig. 4(D) shows the distribution of the HOMO of one molecule of TPA (abbreviation), and Fig. 4(E) shows the distribution of the HOMO of one molecule of TPA (abbreviation). ) shows the distribution of LUMOs of the dimers of DBq (abbreviation) and TPA (abbreviation), and Fig. 4(F) shows the distribution of LUMOs of the dimers of DBq (abbreviation) and TPA (abbreviation), and Fig. 4(C) shows the distribution of LUMOs of the dimers of DBq (abbreviation) and TPA (abbreviation), and Fig. 4(D) shows the distribution of LUMOs The HOMO distributions of the dimers of Bq (abbreviation) and TPA (abbreviation), respectively, are shown.

[0053] As shown in Figure 4(E) and Figure 4(F), the dimer of DBq (abbreviation) and TPA (abbreviation) The LUMO is distributed on the DBq (abbreviation) side, and the HOMO is distributed on the TPA (abbreviation) side. The results are shown in Figure 3. This suggests that...

[0054] In addition, the formation process of the exciplex in one embodiment of the present invention can be considered to be the following two processes. do.

[0055] The first exciplex formation process is carried out by reacting a first organic compound 120 (host material) with a second organic compound 121 (host material). Is the organic compound 122 (assist material) in a carrier state (cation or anion)? This is the process of forming an exciplex.

[0056] In general, when electrons and holes recombine in a host material, they are released from the host material in an excited state. The excitation energy is transferred from the hologram to the guest material, and the guest material reaches an excited state and emits light. The host material itself emits light before the excitation energy is transferred from the host material to the guest material. Or, the excitation energy becomes thermal energy, and some of the excitation energy is deactivated. Wow.

[0057] However, in one embodiment of the present invention, a first organic compound 120 (host material) and a second The organic compound 122 (assist material) has a carrier (cation or anion) ) to form an exciplex, the singlet excitons of the first organic compound 120 (host material) are In other words, it is possible to suppress the formation of excitons directly without forming singlet excitons. There may be a process of forming a complex, which also suppresses the deactivation of the singlet excitation energy. Therefore, a light emitting element having a long life can be realized.

[0058] For example, the first organic compound 120 captures electrons (carriers) even in the electron transport material. It is a compound with electron trapping properties that has a low LUMO level and is easy to dissociate. The organic compound 122 has the property of easily capturing holes (carriers) among hole transporting materials. In the case where the first organic compound is a hole trapping compound (having a high HOMO level), A direct exciplex is formed from the anion of 120 and the cation of a second organic compound 122. The exciplex formed in this process is called an electroplex ( We will call this the "electroplex."

[0059] In this way, the generation of a singlet excited state of the first organic compound 120 (host material) is suppressed. Then, energy is transferred from the electroplex to a third organic compound 124 (guest material). By carrying out the above steps, a light-emitting element with high luminous efficiency can be obtained. The generation of triplet excited states in compound 120 (host material) was also suppressed, and direct exciplexes were formed. As a result, energy is transferred from the exciplex to the third organic compound 124 (guest material). It is thought that this is the case.

[0060] The formation process of the second exciplex is carried out by reacting a first organic compound 120 (host material) with a second organic compound 121 (host material). After one of the organic compounds 122 (assist materials) forms a singlet exciton, it is in the ground state with the other. This is the elementary process by which electrons interact with each other to form an exciplex. Unlike electroplexes, In this case, the first organic compound 120 (host material) or the second organic compound 122 (a However, this is quickly converted to an exciplex. Therefore, the deactivation of the singlet excitation energy can be suppressed. The first organic compound 120 or the second organic compound 122 is prevented from quenching the excitation energy. In this case, the triplet state of the first organic compound 120 (host material) can be suppressed. The excited state is also rapidly converted to an exciplex, which is then converted to a third organic compound, 124. It is believed that energy is transferred to the guest material.

[0061] The first organic compound 120 (host material) is an electron trapping compound, while The second organic compound 122 (assist material) is a compound with hole trapping properties. When the difference between the HOMO and LUMO levels of the compound is large (specifically, the difference is 0.3e V or higher), electrons selectively enter the first organic compound 120 (host material) and holes selectively In this case, the electron enters the second organic compound 122 (assist material). The process of electroplex formation takes precedence over the process of complex formation. It is thought that.

[0062] The calculation results of the excitation energy are shown below. The excitation energy of S1 of one molecule of DBq (abbreviation) The energy of the electron beam was 3.294 eV and the fluorescence wavelength was 376.4 nm. The excitation energy of T1 of one molecule is 2.460 eV, and the phosphorescence wavelength is 504.1 nm. On the other hand, the excitation energy of S1 of one TPA molecule is 3.508 eV The fluorescence wavelength was 353.4 nm. The electromotive energy was 2.610 eV and the phosphorescence wavelength was 474.7 nm.

[0063] Here, the optimal molecular structure of the dimer of DBq (abbreviation) and TPA (abbreviation) at S1 and T1 The excitation energies obtained from the dimers DBq (abbreviation) and TPA (abbreviation) are shown. The excitation energy was 2.036 eV and the fluorescence wavelength was 609.1 nm. The T1 excitation energy of the DBq (abbreviation) and TPA (abbreviation) dimer is 2.030 eV. The phosphorescence wavelength was 610.0 nm.

[0064] From the above, the fluorescence wavelength of the dimer of DBq (abbreviation) and TPA (abbreviation) is It has been found that the fluorescence wavelengths of the single molecule of 1,2-dichlorophenyl phosphate (TPA) are longer than those of the single molecule of 1,2-dichlorophenyl phosphate (TPA). The difference between the fluorescence and phosphorescence wavelengths of the dimers of DBq (abbreviation) and TPA (abbreviation) is small. It can be seen that the wavelengths are almost the same, being only 0.9 nm.

[0065] From these results, it can be seen that the exciplex has almost the same excitation energy for singlet and triplet. Therefore, as mentioned above, the exciplex is Efficient energy transfer from both the singlet and triplet states of It was suggested that it could be moved.

[0066] This effect is a unique effect that results from using exciplexes as a medium for energy transfer. Generally, phosphorescence occurs from the singlet or triplet excited state of the host material. On the other hand, in one embodiment of the present invention, the energy transfer to the host material and the other compound is taken into consideration. First, an exciplex is formed with the material, and then energy transfer from the exciplex is used. This difference makes it possible to achieve unprecedentedly high luminous efficiency. There is.

[0067] Generally, when an exciplex is used in the light-emitting layer of a light-emitting device, it is possible to control the color of emitted light. Although they have utility, the luminescence efficiency is usually significantly reduced. The light-emitting element used here has been considered to be unsuitable for obtaining a highly efficient light-emitting element. However, as shown in one embodiment of the present invention, an exciplex can be used as a medium for energy transfer. However, the inventors have found that it is possible to increase the luminous efficiency to the maximum extent. This is a technological concept that contradicts conventional stereotypes.

[0068] The emission spectrum of the exciplex and the absorption spectrum of the third organic compound 124 (guest material) were In order to overlap the spectra sufficiently, the energy values ​​of the peaks in the emission spectrum and the absorption spectrum must be The difference between the energy value of the absorption band peak on the lowest energy side of the It is preferable that the difference is within 0.2 eV, more preferable that the difference is within 0.1 eV. Within.

[0069] In the light-emitting element of one embodiment of the present invention, the excitation energy of the exciplex is a third The energy transfer to the organic compound 124 (guest material) was sufficient, and the emission from the exciplex was substantial. Therefore, it is preferable that the third organic compound 124 is not observed through the exciplex. (guest material) to transfer energy, and the third organic compound 124 emits phosphorescence. The third organic compound 124 is preferably an organic compound that converts triplet excitation energy into light emission. Any luminescent material capable of emitting light capable of emitting light of this kind may be used, and phosphorescent compounds are particularly preferred.

[0070] Next, the concept of energy levels of the hole-transport layer 112 and the light-emitting layer 113 according to one embodiment of the present invention will be described. The following will be described with reference to Figs. 5(A), 5(B), and 5(C). 5A), 5B, and 5C show the hole transport layer 112 (hole transport layers 112a, 112 11 is a diagram showing the energy levels of the light-emitting layer 113 and the light-emitting layer 112b and 112c.

[0071] The light-emitting layer 113 shown in FIG. 5(A), FIG. 5(B), and FIG. 5(C) is the same as that described above. A combination of a first organic compound 120 and a second organic compound 122 that form an exciplex be.

[0072] The energy level of the hole transport layer 112a shown in FIG. 5(A) is The T1 level is higher than that of the second organic compound 122 (assist material) and is lower than that of the second organic compound 123 (assist material). In the present embodiment, the hole transport layer 112a is formed of one organic compound having a lower HOMO level than that of the conventional hole transport layer 112a. An example is given here.

[0073] In the case of the configuration shown in FIG. 5A, the HOMO level of the light-emitting layer 113 that forms an exciplex is higher than that of the light-emitting layer 113. Since the HOMO level of the hole transport layer 112a is low, the electrons from the hole transport layer 112a to the light emitting layer 113 This allows holes to enter the inside more easily, and the luminous efficiency of the light-emitting layer 113 can be improved. The driving start voltage is E1 (LUMO of the light-emitting layer 113 forming an exciplex) shown in FIG. The energy is determined by the energy difference between the HOMO level and the For example, if E1 is 2 eV, the drive open The starting voltage cannot be lower than 2 V. In the configuration shown in Figure 5(A), the energy Compared to LG, E 2a (LUMO level of the light-emitting layer 113 forming an exciplex and the hole-transport layer 1 This is because the energy difference between the HOMO level of 12a and that of 12b is larger.

[0074] Next, the energy level of the hole transport layer 112b shown in FIG. 5B is changed to that of the second organic compound 1. The T1 level is higher than that of the second organic compound 122 (assist material). The hole transport layer 112b is formed of one kind of organic compound having a higher HOMO level than the material. The configuration is illustrated.

[0075] In the case of the configuration shown in FIG. 5B, the HOMO level of the light-emitting layer 113 that forms an exciplex is higher than that of the light-emitting layer 113. Since the HOMO level of the hole transport layer 112b is high, the driving voltage (particularly, the driving start voltage) is It is affected by the HOMO level of the hole transport layer 112b. Specifically, E 2b ( The LUMO level of the light-emitting layer 113 and the HOMO level of the hole transport layer 112b form an exciplex. The drive start voltage is determined by the energy of (energy difference between the In the case of the configuration shown in (B), E1 (LUMO level of the light-emitting layer 113 forming an exciplex) and HO The energy difference between the electron and the MO level is smaller than the E 2b Since the energy of the drive is small, However, the onset voltage can be reduced. This makes it difficult for holes to move to the luminous efficiency, which decreases especially in the high luminance (practical luminance) region.

[0076] Next, the energy level of the hole-transport layer 112c shown in FIG. 5C is This represents the idea of ​​at least the HOMO level of the second organic compound 122 (assist material) or higher. The fourth organic compound 126 below and the second organic compound 122 (assist material) are more HOM Regarding the structure in which the hole transport layer 112c having the fifth organic compound 128 with a high O level is formed, The following examples are given:

[0077] In the case of the structure shown in FIG. 5C, the HOMO level of the hole transport layer 112c is Due to the influence of the substance 126, the HOMO level of the second organic compound 122 (assist material) is lower than the HOMO level. Therefore, holes can be transported from the hole transport layer 112c to the inside of the light emitting layer 113. This makes it easier for the light to enter the light emitting layer 113, thereby improving the light emitting efficiency of the light emitting layer 113. In particular, the driving start voltage is affected by the HOMO level of the hole transport layer 112c. In the case of 12c, the HOMO level is determined by the influence of the fifth organic compound 128. The LUMO level of the transport layer 112c is determined by the influence of the fourth organic compound 126. (C) E 2c (LUMO level of the light-emitting layer 113 forming an exciplex and the fifth organic compound The drive voltage is determined by the energy difference between the HOMO level of the substance 128 and the Therefore, in the case of the configuration shown in FIG. 5(C), E1 (light-emitting layer 1 in which an exciplex is formed) The energy difference between the LUMO level and the HOMO level of 13 is smaller than the energy E 2c Energy Since the energy is small, the drive start voltage can be reduced.

[0078] By using the structure shown in FIG. 5C, the electric energy lower than the light emission energy of the light-emitting layer 113 is generated. Generally, the driving start voltage is set to 100 V. The voltage is equivalent to the light emission energy of 1000mV, and it will not start operating at a voltage lower than that. However, in one embodiment of the present invention, the driving start voltage is Since it is determined by the fifth organic compound 128 contained in 2c, the driving open In addition, at the start of driving, the fifth organic compound 128 is excited. Since it contributes to the formation of photovoltaic energy, the luminous efficiency is thought to be low, but at the beginning of operation, Since the brightness is barely visible, there is no problem in practical use. is 1 cd / m 2 In the above, the main mechanism is hole injection from the fourth organic compound 126 to the light-emitting layer 113. The fifth organic compound 128 is unlikely to be involved in hole injection into the light-emitting layer 113 or in an excited state. Therefore, high luminous efficiency can be obtained.

[0079] In this manner, the light-emitting element described in this embodiment has a hole transport layer 112c. The layer 112c has a HOMO level lower than the HOMO level of the second organic compound 122 (assist material). The fourth organic compound 126 has a HOMO higher than that of the second organic compound 122 (assist material). The fourth organic compound 128 of the hole transport layer 112c has a high level. Holes are injected from the second organic compound 122 (assist material) of the light-emitting layer 113. In addition, the fifth organic layer of the hole transport layer 112c can be formed by the above-mentioned method. The compound 128 has a higher HOMO level than the second organic compound 122 (assist material). Therefore, the driving voltage of the light-emitting layer, especially the driving start voltage, can be reduced. The transport layer has two or more of the above organic compounds, and the above HOMO level relationship is obtained only. This is the effect.

[0080] In the light-emitting element according to one embodiment of the present invention, the first organic compound 120 (host material When a phosphorescent compound is used for the first organic compound 120, the first organic compound 120 itself becomes more likely to emit light, and the third In this case, the energy is hardly transferred to the organic compound 124 (guest material). It is sufficient for the first organic compound 120 to emit light efficiently. Due to the problem of concentration quenching, it is difficult to achieve high luminous efficiency. A first organic compound 120 (host material) and a second organic compound 122 (assist material). At least one of the compounds is a fluorescent compound (i.e., a compound that emits light or undergoes thermal deactivation from a singlet excited state). Therefore, the first organic compound 120 and the second organic compound 130 are preferably the same or different from each other. At least one of the two organic compounds 122 is preferably a fluorescent compound.

[0081] As described above, the light-emitting element described in this embodiment has an emission spectrum of the exciplex and a third Energy transfer using the overlap with the absorption spectrum of the organic compound (guest material) Since the efficiency of energy transfer can be improved, a light-emitting element with high luminous efficiency can be realized. This can be done.

[0082] In addition, the light-emitting element described in this embodiment mode has a second conductive layer having a hole-transporting property. A fourth organic compound with a HOMO level lower than the HOMO level of the organic compound and a fourth organic compound with a HOMO level lower than the HOMO level of the second organic compound. In the above-mentioned structure, the hole transport layer contains a fifth organic compound having a high molecular weight. As a result, the current efficiency of the light emitting element is increased, and the voltage of the light emitting element, particularly the driving start voltage, is reduced. It is possible.

[0083] Note that the structure described in this embodiment mode may be used in appropriate combination with structures described in other embodiments. It is possible.

[0084] (Embodiment 2) In this embodiment mode, a modification of the light-emitting element shown in Embodiment 1 will be described with reference to FIG. Note that a portion having a function similar to that of the light-emitting element shown in Embodiment 1 may be formed in the same manner. The reference symbols are used and the repeated explanation is omitted.

[0085] The light-emitting element shown in this embodiment has a pair of electrodes (a first electrode 101, A hole injection layer 111 is formed between the second electrode 103) and a hole transport layer 112 formed on the hole injection layer 111. a layer 112, a light-emitting layer 113 formed on the hole-transporting layer 112, and a light-emitting layer 114 formed on the light-emitting layer 113. and an electron injection layer 115 formed on the electron transport layer 114. The light-emitting layer 113 is made of a first organic compound 120 having an electron transporting property and a second organic compound 121 having a hole transporting property. The second organic compound 122 and the luminescent third organic compound that converts triplet excitation energy into light emission. and a compound 124, in which the first organic compound 120 and the second organic compound 122 form an exciplex. The hole transport layer 112 is a combination of at least a second organic compound 122 A fourth organic compound 126 has a HOMO level lower than that of the second organic compound 122. The fifth organic compound 128 has a high O level.

[0086] In the light-emitting layer 113, the third organic compound 124 (guest material) is The composition is made of a compound 120 (host material) and a second organic compound 122 (assist material). By using this composition, concentration quenching caused by the high concentration of the light-emitting layer 113 can be suppressed, and the light-emitting device The luminous efficiency can be improved.

[0087] In addition, a first organic compound 120 (host material) and a second organic compound 122 (assist material) are The combination of the cations (electron emitting materials) forms an exciplex.

[0088] A specific example of manufacturing the light-emitting element described in this embodiment mode will be described below.

[0089] The substrate 100 is used as a support for the light-emitting device. The substrate 100 is, for example, glass. , quartz, plastic, etc. Also, a flexible substrate may be used. A flexible substrate is a substrate that can be bent (flexible). For example, a flexible substrate is a polyimide. Plastic substrates made of carbonate, polyarylate, polyethersulfone, etc. In addition, films (polypropylene, polyester, polyvinyl fluoride, poly It is also possible to use an inorganic deposition film, etc. Any other material may be used as long as it functions as a support in the preparation process.

[0090] The first electrode 101 and the second electrode 103 may be made of a metal, an alloy, an electrically conductive compound, or A mixture of these materials can be used. Specifically, indium oxide-tin oxide (I TO: Indium Tin Oxide, an indium oxide containing silicon or silicon oxide. Contains indium-tin oxide, indium-zinc oxide, tungsten oxide and zinc oxide. Indium oxide, gold (Au), platinum (Pt), nickel (Ni), tungsten (W) , Chromium (Cr), Molybdenum (Mo), Iron (Fe), Cobalt (Co), Copper (Cu), In addition to palladium (Pd) and titanium (Ti), elements in the first or second groups of the periodic table The elements are alkali metals such as lithium (Li) and cesium (Cs), and magnesium. Alkaline earth metals such as magnesium (Mg), calcium (Ca), and strontium (Sr), and alloys containing these (MgAg, AlLi), europium (Eu), ytterbium ( Rare earth metals such as Yb) and alloys containing these, as well as graphene, etc. can be used. The first electrode 101 and the second electrode 103 are formed by, for example, a sputtering method or a vapor deposition method. The insulating film can be formed by a method including a vacuum deposition method. The first electrode 101 is used as an anode and the second electrode 103 is used as a cathode.

[0091] The hole-injection layer 111 and the hole-transport layer 112 may be formed of a material having a high hole-transporting property. For example, 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB or α-NPD) and N,N'-bis(3-methylphenyl)-N,N'-diphenyl Nyl-[1,1'-biphenyl]-4,4'-diamine (abbreviation: TPD), 4,4',4 ''-Tris(carbazol-9-yl)triphenylamine (abbreviation: TCTA), 4, 4',4''-Tris(N,N-diphenylamino)triphenylamine (abbreviation: TDA TA), 4,4',4''-tris[N-(3-methylphenyl)-N-phenylamino ]triphenylamine (abbreviation: MTDATA), 4,4'-bis[N-(spiro-9,9 '-Bifluoren-2-yl)-N-phenylamino]biphenyl (abbreviation: BSPB) Which aromatic amine compound, 3-[N-(9-phenylcarbazol-3-yl)-N-phenyl phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA1), 3,6-bis[ N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazol Rubazol (abbreviation: PCzPCA2), 3-[N-(1-naphthyl)-N-(9-phenyl PCzPCN 1) and others. Other examples include 4,4'-di(N-carbazolyl)biphenyl (abbreviation: C BP), 1,3,5-tris[4-(N-carbazolyl)phenyl]benzene (abbreviation: T CPB), 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-cal Carbazole derivatives such as CzPA (abbreviation: CzPA) can also be used. The hole transporting material described below can also be used. -6 cm 2 A material that has a hole mobility of 1 / Vs or more. However, it has a higher hole transporting capacity than electron transporting capacity. Other materials may be used as long as they are of the same quality.

[0092] Furthermore, the hole injection layer 111 and the hole transport layer 112 are made of poly(N-vinylcarbazolyl) Poly(4-vinyltriphenylamine) (abbreviation: PVTPA), Poly[N-(4-{N'-[4-(4-diphenylamino)phenyl]phenyl-N'- (phenylamino)phenyl)methacrylamide (abbreviation: PTPDMA), poly[N,N '-Bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine] (abbreviation: P Polymer compounds such as poly-TPD can also be used.

[0093] In addition, examples of acceptor substances that can be used in the hole injection layer 111 include transition metals, Examples of the oxides include oxides of metals belonging to groups 4 to 8 of the periodic table. Specifically, molybdenum oxide is particularly preferred.

[0094] The hole transport layer 112 is made of the second organic compound 122 (acis) from among the above-mentioned substances. A fourth organic compound 126 below the HOMO level of the second organic compound 122 (a By selecting a material for the fifth organic compound 128 that has a higher HOMO level than the cis material, The substances used for the fourth organic compound 126 and the fifth organic compound 128 are the same as those described above. The second organic compound 122 (assist material) may be any material. , the implementer can select as appropriate.

[0095] The light-emitting layer 113 is made of a first organic compound 120 (host material), a second organic compound 1 22 (assist material), and a third organic compound 124 (guest material).

[0096] As the first organic compound 120 (host material), it is preferable to use an electron transporting material. In addition, a hole transporting material is used as the second organic compound 122 (assist material). In addition, the third organic compound 124 (guest material) is preferably a triplet excited Luminescent materials that convert energy into light emission are preferred.

[0097] The electron transport material may be a π-deficient heteroaromatic compound such as a nitrogen-containing heteroaromatic compound. Compounds such as 2-(4-biphenylyl)-5-(4-tert-butylphenyl)- 3-(4-biphenylyl)-1,3,4-oxadiazole (abbreviation: PBD), 4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviation Name: TAZ), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxo oxadiazol-2-yl]benzene (abbreviation: OXD-7), 9-[4-(5-phenyl -1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole (abbreviation: CO11), 2,2',2''-(1,3,5-benzenetriyl)tris(1-phenyl 1H-benzimidazole (abbreviation: TPBI), 2-[3-(dibenzothiophene -4-yl)phenyl]-1-phenyl-1H-benzimidazole (abbreviation: mDBTB Heterocyclic compounds having a polyazole skeleton (oxadiazole derivatives, Imidazole derivatives, triazole derivatives, etc.) and 2-[3-(dibenzothiophene-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- [f,h]quinoxaline (abbreviated as [furan-9-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline :2mCzBPDBq), 4,6-bis[3-(phenanthren-9-yl)phenyl] Pyrimidine (abbreviation: 4,6mPnP2Pm), 4,6-bis[3-(4-dibenzothienyl Diazine skeleton such as 4,6mDBTP2Pm-II Heterocyclic compounds having the formula (pyrazine derivatives, pyrimidine derivatives, pyridazine derivatives, quinoxa Sarin derivatives, dibenzoquinoxaline derivatives, etc.) and 3,5-bis[(3-9H-carba 35DCzPPy, 1,3,5-Triphenylpyridine (abbreviation: 35DCzPPy), Pyridine skeleton such as [3-(3-pyridyl)phenyl]benzene (abbreviation: TmPyPB) Heterocyclic compounds (pyridine derivatives, quinoline derivatives, dibenzoquinoline derivatives, etc.) Among the above, heterocyclic compounds having a diazine skeleton and heterocyclic compounds having a pyridine skeleton are preferred. Heterocyclic compounds having such a structure are preferred because of their excellent reliability. Heterocyclic compounds having a dimethylamino group skeleton have high electron transport properties and contribute to reducing the driving voltage.

[0098] In addition, the hole transport material may be a π-excess heteroaromatic compound (e.g., carbazole Derivatives and indole derivatives) and aromatic amine compounds are preferred, for example, 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'-bifluor

[0113] -N-phenylamino]biphenyl (abbreviation: BSPB), 4-phenyl 4'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAF LP), 4-phenyl-3'-(9-phenylfluoren-9-yl)triphenylamine mBPAFLP, 4-phenyl-4'-(9-phenyl-9H-carbazolyl PCBA1BP, 4,4'-diphenyl-3-yltriphenylamine 4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBBi1BP), 4-(1-naphthyl)-4'-(9-phenyl-9H-carbazol PCBANOB, 4,4'-di(1-naphthalene-3-yl)-triphenylamine 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: PCB AF), N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl] phenyl]spiro-9,9'-bifluorene-2-amine (abbreviation: PCBASF) Compounds with aromatic amine skeletons and 1,3-bis(N-carbazolyl)benzene (abbreviation: mCP), 4,4'-di(N-carbazolyl)biphenyl (abbreviation: CBP), 3,6-biphenyl CzTP, 3 ,3'-bis(9-phenyl-9H-carbazole) (abbreviation: PCCP) and other carbazo Compounds with a triol skeleton and 4,4',4''-(benzene-1,3,5-triyl) Di(dibenzothiophene) (abbreviation: DBT3P-II), 2,8-diphenyl-4-[4 -(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene (abbreviation :DBTFLP-III), 4-[4-(9-phenyl-9H-fluoren-9-yl) Thiothiophene such as phenyl-6-phenyldibenzothiophene (abbreviation: DBTFLP-IV) Compounds with a phene skeleton 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: mmDB Among the above, aromatic compounds having a furan skeleton such as FFLBi-II are also suitable. Compounds having an aromatic amine skeleton and compounds having a carbazole skeleton have good reliability. In addition, it has a high hole transporting property and contributes to a reduction in the driving voltage, which is preferable.

[0099] These electron transport materials and hole transport materials have absorption spectra in the blue region. Specifically, the absorption edge of the absorption spectrum is 440 nm or less. It is preferable.

[0100] On the other hand, examples of luminescent materials that convert triplet excitation energy into luminescence include phosphorescent materials. and thermally activated delayed fluorescence (TADF) materials that exhibit thermally activated delayed fluorescence.

[0101] As the phosphorescent material, for example, a phosphorescent material having an emission peak at 440 nm to 520 nm Tris{2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl] (1,2,4-triazol-3-yl)-κN 2 ]phenyl-κC}iridiu Ir(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(iPrtz -3b) Organometallic iridium complexes having a 4H-triazole skeleton such as 3) and tri S[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-trimethyl Azolate]iridium(III) (abbreviation: [Ir(Mptz1-mp)3]), tris( 1-Methyl-5-phenyl-3-propyl-1H-1,2,4-triazolato)iridium 1H-triazole skeleton such as Ir(III) (abbreviation: Ir(Prtz1-Me)3) Organometallic iridium complexes with fac-tris[1-(2,6-diisopropyl fluorene] Iridium(III) (abbreviation: Ir(i Prpmi)3), tris[3-(2,6-dimethylphenyl)-7-methylimidazo[ 1,2-f]phenanthridinato]iridium(III) (abbreviation: Ir(dmpimpt iridium complexes with imidazole skeletons such as bis[2- (4',6'-Difluorophenyl)pyridinato-N,C 2’ ]Iridium(III) tetrachloride Trachys(1-pyrazolyl)borate (abbreviation: FIr6), bis[2-(4',6'-di Fluorophenyl)pyridinato-N,C 2’ ]Iridium(III) picolinate (abbreviation :FIrpic), bis{2-[3',5'-bis(trifluoromethyl)phenyl]pi Lysinato-N,C 2’}Iridium(III) picolinate (abbreviation: Ir(CF3ppy )2(pic)), bis[2-(4',6'-difluorophenyl)pyridinato-N,C 2’ ]Iridium(III) acetylacetonate (abbreviation: FIr(acac)) Organometallic iridium complexes with phenylpyridine derivatives bearing electron-withdrawing groups as ligands have been developed. Among the above, organometallic iridium complexes having a 4H-triazole skeleton are is particularly preferred because it is excellent in reliability and luminous efficiency.

[0102] For example, phosphorescent materials having an emission peak at 520 nm to 600 nm include trifluoromethane. Iridium(III) (abbreviation: Ir(mp pm)3), tris(4-t-butyl-6-phenylpyrimidinato)iridium(III ) (abbreviation: Ir(tBuppm)3), (acetylacetonato)bis(6-methyl-4- Phenylpyrimidinato)iridium(III) (abbreviation: Ir(mppm)2(acac) ), (acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidinato) Iridium(III) (abbreviation: Ir(tBuppm)2(acac)), ((acetylated cetonato)bis[4-(2-norbornyl)-6-phenylpyrimidinato]iridium( III) (endo-, exo-mixture) (abbreviation: Ir(nbppm)2(acac)) , (acetylacetonato)bis[5-methyl-6-(2-methylphenyl)-4-phenyl Rupyrimidinato]iridium(III) (abbreviation: Ir(mpmppm)2(acac)) , (acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III ) (abbreviation: Ir(dppm)2(acac)) Iridium complexes and (acetylacetonato)bis(3,5-dimethyl-2-phenylpyridine) iridium(III) (abbreviation: Ir(mppr-Me)2(acac)), (A Cetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazinate)iso Pyridine such as Ir(III) (abbreviation: Ir(mppr-iPr)2(acac)) Organometallic iridium complexes with a phenyl skeleton and tris(2-phenylpyridinato-N,C 2 ’ ) Iridium(III) (abbreviation: Ir(ppy)3), bis(2-phenylpyridinato -N,C 2’ ) Iridium(III) acetylacetonate (abbreviation: Ir(ppy)2a cac), bis(benzo[h]quinolinato)iridium(III) acetylacetonate (abbreviation: Ir(bzq)2(acac)), tris(benzo[h]quinolinato)iridium Ir(III) (abbreviation: Ir(bzq)3), tris(2-phenylquinolinato-N,C 2 ’ ) Iridium(III) (abbreviation: Ir(pq)3), bis(2-phenylquinolinato- N,C 2’ ) Iridium(III) acetylacetonate (abbreviation: Ir(pq)2(ac In addition to organometallic iridium complexes with pyridine skeletons such as tris(acetyl)-(1,2-diphenylphosphine) Acetonato)(monophenanthroline)terbium(III) (abbreviation: Tb(acac) Among the above, pyrimidine skeleton complexes such as rare earth metal complexes are also useful. Organometallic iridium complexes, which have excellent reliability and luminescence efficiency, are particularly preferable.

[0103] For example, a phosphorescent material having an emission peak at 600 nm to 700 nm is bismuth. [4,6-bis(3-methylphenyl)pyrimidinato](diisobutyrylmethanate)yl Ir(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(naphthalene-1-yl) Ir(d1 Organometallic iridium complexes with pyrimidine skeletons such as (npm)2(dpm)) and ( Acetylacetonato)bis(2,3,5-triphenylpyrazinate)iridium(III) ) (abbreviation: Ir(tppr)2(acac)), bis(2,3,5-triphenylpyrazine nato)(dipivaloylmethanato)iridium(III) (abbreviation: Ir(tppr)2(d pm)), (acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxa Salinato]iridium(III) (abbreviation: Ir(Fdpq)2(acac)) Organometallic iridium complexes with a radicandine skeleton and tris(1-phenylisoquinolinato- N,C 2’ ) Iridium(III) (abbreviation: Ir(piq)3), bis(1-phenyli Sokinorinato-N,C 2’ ) Iridium(III) acetylacetonate (abbreviation: Ir( In addition to organometallic iridium complexes with pyridine skeletons such as piq) and 2acac), 2, 3,7,8,12,13,17,18-Octaethyl-21H,23H-porphyrin white Platinum complexes such as gold(II) (abbreviation: PtOEP) and tris(1,3-diphenyl-1 ,3-Propanedionato)(monophenanthroline)europium(III)(abbreviation:E u(DBM)3(Phen)), Tris[1-(2-thenoyl)-3,3,3-trifluoro

[0026] (monophenanthroline)europium(III) (abbreviation: Eu(TT A) 3(Phen)) and other rare earth metal complexes. Organometallic iridium complexes with an iridium skeleton are extremely reliable and have excellent luminescence efficiency. In particular, organometallic iridium complexes having a pyrazine skeleton are preferred. Light emission is obtained.

[0104] The delayed fluorescence in TADF materials has the same spectrum as normal fluorescence, but Its lifetime is approximately 10 -6 seconds or more, preferably 10 -3 seconds That's all. TADF materials include fullerene and its derivatives, proflavin, etc. acridine derivatives such as eosin, etc. Magnesium (Mg), zinc ( Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), if Examples of the metal-containing porphyrin include metal-containing porphyrins containing palladium (Pd) and the like. Examples of the porphyrin include protoporphyrin-tin fluoride complex (SnF2 (Protoporphyrin-tin fluoride complex) IX), mesoporphyrin-tin fluoride complex (SnF2(Meso IX)), hema Toporphyrin-Tin Fluoride Complex (SnF2(Hemato IX)), Coproporphyrin Phosphorus tetramethyl ester-tin fluoride complex (SnF2(Copro III-4Me) ), Octaethylporphyrin-Tin Fluoride Complex (SnF2(OEP)), Ethioporphyrin Porphyrin-Tin Fluoride Complex (SnF2(Etio I)), Octaethylporphyrin-Salt and 2-biphenyl-4,6 -Bis(12-phenylindolo[2,3-a]carbazol-11-yl)-1,3, π-rich heteroaromatic rings and π-deficient heteroaromatic rings such as 5-triazine (abbreviation: PIC-TRZ) It is also possible to use a heterocyclic compound having a π-rich heteroaromatic ring and a π-deficient heteroaromatic ring. The substance in which the aromatic ring is directly bonded to the π-rich heteroaromatic ring exhibits the donor property of the π-deficient heteroaromatic ring. This is particularly favorable because the acceptor properties of both are strong and the energy difference between S1 and T1 is small. I wish.

[0105] However, the first organic compound 120 (host material) and the second organic compound 122 ( The third organic compound 123 (assist material) and the third organic compound 124 (guest material) can be used, respectively. The materials that can be used are not limited to these, but are combinations that can form exciplexes. The emission spectrum of the photoinduced complex was similar to the absorption spectrum of the third organic compound 124 (guest material). The emission spectrum peak of the exciplex overlaps with that of the third organic compound 124 (guest material). Any wavelength longer than the peak of the absorption spectrum may be used.

[0106] In addition, an electron transporting material is used as the first organic compound 120 (host material), and When a hole transporting material is used for the compound 122 (assist material), the carrier Specifically, the first organic compound 120: the second organic compound The ratio of compound 122 is preferably in the range of 1:9 to 9:1.

[0107] The electron transport layer 114 is a layer containing a substance with a high electron transport property. In addition to the above-mentioned electron transport materials, tris(8-quinolinolato)aluminum (Alq 3), tris(4-methyl-8-quinolinolato)aluminum (abbreviation: Almq3), bi 10-hydroxybenzo[h]quinolinato)beryllium (BeBq2), BA lq, Zn(BOX)2, bis[2-(2-hydroxyphenyl)benzothiazolato] Metal complexes such as lead (abbreviation: Zn(BTZ)2) can be used. Biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazo PBD, 1,3-bis[5-(p-tert-butylphenyl)-1,3, 4-Oxadiazol-2-yl]benzene (abbreviation: OXD-7), 3-(4-tert -butylphenyl)-4-phenyl-5-(4-biphenylyl)-1,2,4-triazo (abbreviation: TAZ), 3-(4-tert-butylphenyl)-4-(4-ethylphenyl) p-EtTAZ ), Bathophenanthroline (abbreviation: BPhen), Bathocuproine (abbreviation: BCP), 4,4'-Bis(5-methylbenzoxazol-2-yl)stilbene (abbreviation: BzO Heteroaromatic compounds such as poly(2,5-pyridine-diphenylphosphine) can also be used. Poly[(9,9-dihexylfluorene-2,7-diyl)- co-(pyridine-3,5-diyl)] (abbreviation: PF-Py), poly[(9,9-diox 2,2'-bipyridine-6,6'-diyl)-co-(2,2'-bipyridine-6,6'-diyl) )] (abbreviation: PF-BPy) can also be used. The material is mainly 10 -6 cm 2 / Vs or higher. As long as the substance has a higher electron transporting property than the above, the electron transporting layer 114 may be formed using any substance other than the above. Good too.

[0108] In addition, the electron transport layer 114 may be a single layer or may be a laminate of two or more layers made of the above-mentioned materials. It may also be layered.

[0109] The electron injection layer 115 is a layer containing a substance with high electron injection properties. Lithium fluoride (LiF), Cesium fluoride (CsF), Calcium fluoride (CaF2) , lithium oxide (LiO x ) and other compounds of alkali metals or alkaline earth metals. Also, rare earth metal compounds such as erbium fluoride (ErF3) can be used. In addition, the above-mentioned material constituting the electron transport layer 114 may be used. can.

[0110] Alternatively, the electron injection layer 115 may be formed by mixing an organic compound and an electron donor. Composite materials may also be used. Such composite materials are made by adding electrons to organic compounds by electron donors. In this case, the organic compound is In particular, the material is preferably one that is excellent in transporting the generated electrons. The material constituting the electron transport layer 114 (metal complex, heteroaromatic compound, etc.) can be used. The electron donor may be any substance that exhibits electron donating properties to organic compounds. Specifically, alkali metals, alkaline earth metals and rare earth metals are preferred, and lithium, cesium, etc. Examples of the elements include aluminum, magnesium, calcium, erbium, and ytterbium. Alkali metal oxides and alkaline earth metal oxides are preferred, and lithium oxide, calcium oxide, Examples of the cations include barium oxide and barium phosphate. In addition, Lewis bases such as magnesium oxide are used. It is also possible to use organic compounds such as tetrathiafulvalene (TTF). It is also possible.

[0111] The hole injection layer 111, the hole transport layer 112, the light emitting layer 113, and the electron transport layer 11 4. The electron injection layer 115 is formed by a deposition method (including a vacuum deposition method), an inkjet method, The layer can be formed by a coating method or the like.

[0112] The light emitted from the light-emitting layer 113 of the light-emitting element is transmitted through the first electrode 101 and the second electrode 102. The electric current is taken out through one or both of the electrodes 103. In the embodiment, either or both of the first electrode 101 and the second electrode 103 This results in an electrode having light-transmitting properties.

[0113] As described above, the light-emitting element described in this embodiment has an emission spectrum of the exciplex and a third Energy transfer using the overlap with the absorption spectrum of the organic compound (guest material) Since the efficiency of energy transfer can be improved, a light-emitting element with high luminous efficiency can be realized. This can be done.

[0114] In addition, the light-emitting element described in this embodiment mode has a second conductive layer having a hole-transporting property. A fourth organic compound with a HOMO level lower than the HOMO level of the organic compound and a fourth organic compound with a HOMO level lower than the HOMO level of the second organic compound. In the above-mentioned structure, the hole transport layer contains a fifth organic compound having a high molecular weight. As a result, the current efficiency of the light emitting element is increased, and the voltage of the light emitting element, particularly the driving start voltage, is reduced. It is possible.

[0115] The light-emitting element described in this embodiment is one embodiment of the present invention, and in particular, The structure of the light-emitting layer is characteristic. Therefore, by applying the structure shown in this embodiment mode, , passive matrix type light emitting devices, active matrix type light emitting devices, etc. and all of these are intended to be included in the present invention.

[0116] In the case of an active matrix type light emitting device, the structure of the TFT is not particularly limited. For example, a staggered or inverted staggered TFT can be used as appropriate. The driver circuit formed on the FT substrate may consist of N-type and P-type TFTs. Alternatively, it may be composed of only one of N-type TFTs or P-type TFTs. Furthermore, there is no particular limitation on the crystallinity of the semiconductor film used in the TFT. An amorphous semiconductor film, a crystalline semiconductor film, an oxide semiconductor film, or the like can be used.

[0117] Note that the structure described in this embodiment mode may be used in appropriate combination with structures described in other embodiments. It is possible.

[0118] (Embodiment 3) In this embodiment, as one embodiment of the present invention, a structure having a plurality of light-emitting layers sandwiching a charge generation layer is described. A light emitting device having this structure (hereinafter referred to as a tandem type light emitting device) will be described.

[0119] The light-emitting element shown in this embodiment has a pair of electrodes (first electrode 30) as shown in FIG. A plurality of light-emitting layers (first light-emitting layer 311, second light-emitting layer 31 2) is a tandem-type light-emitting device having the above structure.

[0120] In this embodiment, the first electrode 301 is an electrode that functions as an anode, and the second The electrode 303 functions as a cathode. 03 can have the same structure as in the embodiment 2. In addition, a plurality of light-emitting layers (first The light-emitting layer 311 and the second light-emitting layer 312 are the same as those shown in the first embodiment or the second embodiment. The first layer may have a similar structure, or either of them may have a similar structure. The first light-emitting layer 311 and the second light-emitting layer 312 may have the same structure or different structures. In addition, the configuration may be the same as that of the first or second embodiment. However, either or both of the first light-emitting layer 311 and the second light-emitting layer 312 are This has a configuration including the hole transport layer described in the first or second embodiment.

[0121] In addition, between the plurality of light-emitting layers (the first light-emitting layer 311 and the second light-emitting layer 312), a charge generation The charge generating layer 313 is disposed between the first electrode 301 and the second electrode 303. When a voltage is applied to the two layers, electrons are injected into one light-emitting layer and holes are injected into the other light-emitting layer. In the present embodiment, the first electrode 301 is electrically charged more than the second electrode 303. When a voltage is applied so that the potential becomes high, electrons are transferred from the charge generating layer 313 to the first light emitting layer 311. is injected into the second light-emitting layer 312, and holes are injected into the second light-emitting layer 312.

[0122] From the viewpoint of light extraction efficiency, the charge generating layer 313 is transparent to visible light. (Specifically, the transmittance of visible light through the charge generating layer 313 is preferably 40% or more.) In addition, the charge generating layer 313 has a lower conductivity than the first electrode 301 and the second electrode 303. It also works as a percentage.

[0123] The charge generation layer 313 is made of an organic compound having a high hole transporting property to which an electron acceptor is added. Even in the case of a structure in which an electron donor is added, the electron donor is added to an organic compound with high electron transport properties. Alternatively, both of these configurations may be laminated.

[0124] In the case where an electron acceptor is added to an organic compound having a high hole transporting property, Examples of organic compounds with high transportability include NPB, TPD, TDATA, and MTDATA. , 4,4'-bis[N-(spiro-9,9'-bifluoren-2-yl)-N-phenyl Aromatic amine compounds such as bisaminobiphenyl (abbreviation: BSPB) can be used. The substances mentioned here are mainly -6 cm 2 / Vs or more. However, if an organic compound has a higher hole transporting property than an electron transporting property, a substance other than the above may be used. That's fine.

[0125] In addition, 7,7,8,8-tetracyano-2,3,5,6-tetracyanophenylacetate can be used as an electron acceptor. Examples include fluoroquinodimethane (abbreviation: F4-TCNQ) and chloranil. Further, transition metal oxides can be used. Specifically, vanadium oxide, niobium oxide, etc. , Tantalum oxide, Chromium oxide, Molybdenum oxide, Tungsten oxide, Manganese oxide, Oxide Rhenium is preferred because of its high electron-accepting property. In particular, molybdenum oxide is stable even in the atmosphere. It is preferable because it is stable, has low hygroscopicity, and is easy to handle.

[0126] On the other hand, in the case where an electron donor is added to an organic compound having high electron transport properties, Examples of organic compounds with high electron transport properties include Alq, Almq3, BeBq2, and B Metal complexes having a quinoline or benzoquinoline skeleton, such as Alq, can be used. In addition, oxazole-based compounds such as Zn(BOX)2 and Zn(BTZ)2, Metal complexes having azole-based ligands can also be used. However, PBD, OXD-7, TAZ, BPhen, BCP, etc. can also be used. The substances mentioned in are mainly -6 cm 2 / Vs or higher. Any organic compound having a higher electron transporting property than a hole transporting property may be used. stomach.

[0127] The electron donor may be an alkali metal, an alkaline earth metal, a rare earth metal, or or metals belonging to Group 13 of the periodic table and their oxides and carbonates. Specifically, lithium (Li), cesium (Cs), magnesium (Mg), Calcium (Ca), Ytterbium (Yb), Indium (In), Lithium oxide, Carbonate It is preferable to use cesium, etc. Also, organic compounds such as tetrathianaphthacene may be used as the electron donor.

[0128] In addition, by forming the charge generating layer 313 using the above-mentioned material, the light emitting layer is laminated. In this case, the increase in the driving voltage can be suppressed.

[0129] In addition, in FIG. 7(A), a light-emitting element having two light-emitting layers has been described. As shown in (B), a light-emitting device having n light-emitting layers (where n is 3 or more) stacked As in the light emitting device according to the present embodiment, a pair of When a plurality of light-emitting layers are provided between the electrodes, a charge generating layer 313 is disposed between the light-emitting layers. By doing so, it is possible to emit light in a high brightness range while keeping the current density low. In addition, when applied to lighting, the electrode material Since the voltage drop due to resistance can be reduced, uniform light emission is possible over a large area. It is possible to realize a light emitting device that can be pressure driven and has low power consumption.

[0130] In addition, by making the emission colors of the respective light-emitting layers different, the light-emitting device as a whole can For example, in a light-emitting device having two light-emitting layers, the first By making the emission color of the first light-emitting layer and the emission color of the second light-emitting layer complementary to each other, It is also possible to obtain a light-emitting element that emits white light as a whole. In other words, the color that becomes achromatic when it is combined with the color that is complementary is called the color of the substance that emits the color. When the resulting light is mixed, white light can be obtained.

[0131] The same applies to a light-emitting element having three light-emitting layers. For example, The emission color of the first light-emitting layer is red, the emission color of the second light-emitting layer is green, and the emission color of the third light-emitting layer is blue. In this case, the light emitting element as a whole can emit white light.

[0132] Note that the structure described in this embodiment mode may be used in appropriate combination with structures described in other embodiments. There can be.

[0133] (Embodiment 4) In this embodiment, a light-emitting device which is one embodiment of the present invention will be described.

[0134] The light-emitting device described in this embodiment mode is a micro-optical resonance device that utilizes the optical resonance effect between a pair of electrodes. As shown in Figure 8, the reflector has a microcavity structure and a pair of electrodes (reflection electrodes 4 A light-emitting device having at least an EL layer 455 between the light-emitting element 51 and the semi-transmissive / semi-reflective electrode 452, The EL layer 455 includes at least a hole transport layer (not shown) and a light emitting layer. Layer 454 (454R, 454G, 454B), as well as a hole injection layer, an electron transport layer, An electron injection layer, a charge generation layer, etc. may be included.

[0135] The first light emitting element 450R has a first transparent conductive layer 453a and a first The EL layer 45 includes the light-emitting layer 454B, the second light-emitting layer 454G, and the third light-emitting layer 454R. The second light emitting element 5 and the semi-transmissive / semi-reflective electrode 452 are laminated in this order. The element 450G includes a second transparent conductive layer 453b, an EL layer 455, and a semi-transparent The third light emitting element 450B has a structure in which a transparent electrode 451 and a semi-reflective electrode 452 are sequentially stacked. In the example shown in FIG. 1, an EL layer 455 and a semi-transmissive / semi-reflective electrode 452 are laminated in this order on a reflective electrode 451. It has a structure.

[0136] In addition, the above-mentioned light emitting elements (first light emitting element 450R, second light emitting element 450G, third light emitting element In the element 450B), the reflective electrode 451, the EL layer 455, and the semi-transmissive / semi-reflective electrode 452 are The first light-emitting layer 454B emits light in a wavelength range of 420 nm to 480 nm. Light with a peak in the region (λ B ) is emitted, and in the second light-emitting layer 454G, Light with a peak in the wavelength region below 50 nm (λ G ) is made to emit light, and the third light-emitting layer 454R is the light (λ) that has a peak in the wavelength range of 600 nm to 760 nm. R ) will light up. As a result, all of the light emitting elements (the first light emitting element 450R, the second light emitting element 450G, The third light-emitting element 450B also has a first light-emitting layer 454B, a second light-emitting layer 454G, and a third light-emitting layer 454G. The light emitted from the light-emitting layer 454R is overlapped, that is, a broad light that covers the visible light region. From the above, the wavelength is λ B <λ G <λ R Relationship Let us assume that.

[0137] Each of the light-emitting elements shown in this embodiment has a reflective electrode 451 and a semi-transmissive / semi-reflective electrode 45 2 and an EL layer 455 is sandwiched between the EL layer 455 and the The light emitted from the layer in all directions functions as a micro-optical resonator (microcavity) The reflection electrode 451 and the semi-transmissive and semi-reflective electrode 452 are resonated. The electrode 451 is formed of a conductive material having reflectivity, and the reflection of visible light on the film is The rate is 40% to 100%, preferably 70% to 100%, and the resistivity is 1×10 -2 The semi-transmissive / semi-reflective electrode 452 has a reflectivity of Ωcm or less. The film is made of a conductive material and a conductive material having optical transparency, and the reflection of visible light on the film is The emissivity is 20% to 80%, preferably 40% to 70%, and the resistivity is 1×10 - 2 It is assumed that the film has a resistance of less than Ωcm.

[0138] In this embodiment, the first light emitting element 450R and the second light emitting element 4 50G, the transparent conductive layers (first transparent conductive layer 453a, second transparent conductive layer By changing the thickness of 453b), the reflective electrode 451 and the semi-transmissive / semi-reflective electrode 452 can be formed for each light-emitting element. The optical distance between the electrodes 452 is changed. The light with a wavelength that resonates between the reflective electrode 451 and the semi-transparent and semi-reflective electrode 452 is The reflector 45 is connected to each element to enhance the light of the resonant wavelength and attenuate the light of the non-resonant wavelength. By changing the optical distance between the reflective electrode 452 and the reflective electrode 452, light of different wavelengths can be captured. It can be brought out.

[0139] The optical distance (also called the optical path length) is the actual distance multiplied by the refractive index. In the embodiment, it is expressed by multiplying the actual film thickness by n (refractive index). Optical distance = actual film thickness x n.

[0140] In the first light emitting element 450R, the reflective electrode 451 to the semi-transmissive and semi-reflective electrode 452 The optical distance at R / 2 (where m is a natural number equal to or greater than 1), the second light-emitting element 450G Let mλ be the optical distance from the reflective electrode 451 to the semi-transmissive and semi-reflective electrode 452. G / 2( In the third light emitting element 450B, a semi-transparent light emitting element is formed from a reflective electrode 451. The optical distance to the semi-reflective electrode 452 is mλ. B / 2 (where m is a natural number greater than or equal to 1). is.

[0141] As a result, the first light-emitting element 450R emits the third luminescent light mainly contained in the EL layer 455. The light emitted in the optical layer 454R (λ R) is extracted, and from the second light emitting element 450G, The light (λ G ) is taken out, The third light-emitting element 450B is mainly composed of the first light-emitting layer 454B included in the EL layer 455. The light emitted at (λ B The light extracted from each light-emitting element is semi-transmitted. The light is emitted from the semi-reflective electrode 452 side.

[0142] In the above configuration, the optical path from the reflective electrode 451 to the semi-transmissive and semi-reflective electrode 452 is Strictly speaking, the distance is from the reflective area of ​​the reflective electrode 451 to the semi-transparent and semi-reflective electrode 452. However, in the reflective electrode 451 and the semi-transmissive / semi-reflective electrode 452, Since it is difficult to precisely determine the position of the reflective region in the reflective electrode 451, The above-mentioned effect can be obtained by assuming that any position of the semi-reflective electrode 452 is a reflective area. It is assumed that this is possible.

[0143] Next, in the first light emitting element 450R, the reflected light from the third light emitting layer 454R is The light reflected by the reflective electrode 451 and returned (first reflected light) is incident on the third light emitting layer 454. This causes interference with the light (first incident light) that is directly incident on the semi-transmissive / semi-reflective electrode 452 from R. The optical distance between the reflective electrode 451 and the third light-emitting layer 454R is (2n R -1)λ R / 4(just S,n R is a natural number equal to or greater than 1. By adjusting the optical distance, the first reflection and amplifying the light emitted from the third light-emitting layer 454R by adjusting the phase of the light and the first incident light. can be done.

[0144] Strictly speaking, the optical distance between the reflective electrode 451 and the third light-emitting layer 454R is The optical distance between the reflection area in the third light-emitting layer 451 and the light-emitting area in the third light-emitting layer 454R is called However, the reflection area of ​​the reflective electrode 451 and the third light-emitting layer 454R may be Since it is difficult to precisely determine the position of the light-emitting region, the reflective electrode 451 and the third light-emitting It is sufficient to assume that any position on the layer 454R is a reflective region and a light-emitting region, respectively, in order to understand the above. The effect can be obtained.

[0145] Next, in the second light emitting element 450G, the reflected light from the second light emitting layer 454G is The light reflected by the reflective electrode 451 and returned (second reflected light) is incident on the second light emitting layer 454. Because interference occurs with the light (second incident light) that is directly incident on the semi-transmissive / semi-reflective electrode 452 from G, The optical distance between the reflective electrode 451 and the second light-emitting layer 454G is (2n G -1)λ G / 4(just S,n G By adjusting the optical distance, the second reflection and amplifying light emitted from the second light-emitting layer 454G by adjusting the phase of the light and the second incident light. can be done.

[0146] Strictly speaking, the optical distance between the reflective electrode 451 and the second light-emitting layer 454G is The optical distance between the reflection area in the second light-emitting layer 451 and the light-emitting area in the second light-emitting layer 454G is However, the reflection area of ​​the reflective electrode 451 and the second light-emitting layer 454G may be Since it is difficult to precisely determine the position of the light-emitting region, the reflective electrode 451 and the second light-emitting It is sufficient to assume that any position on the layer 454G is a reflective region and a light-emitting region, respectively, in order to realize the above-mentioned The effect can be obtained.

[0147] Next, in the third light emitting element 450B, the reflected light from the first light emitting layer 454B is The light reflected by the reflective electrode 451 and returned (third reflected light) is incident on the first light emitting layer 454. This causes interference with the light (third incident light) that is directly incident on the semi-transmissive / semi-reflective electrode 452 from B. The optical distance between the reflective electrode 451 and the first light-emitting layer 454B is (2n B -1)λ B / 4(just S,n B By adjusting the optical distance, the third reflection and amplifying the light emitted from the first light-emitting layer 454B by adjusting the phase of the light and the third incident light. can be done.

[0148] Strictly speaking, the optical distance between the reflective electrode 451 and the first light-emitting layer 454B is The optical distance between the reflection area in 451 and the light-emitting area in the first light-emitting layer 454B is called However, the reflection area of ​​the reflective electrode 451 and the first light-emitting layer 454B may be Since it is difficult to precisely determine the position of the light-emitting region, the reflective electrode 451 and the first light-emitting It is sufficient to assume that any position on layer 454B is a reflective region and a light-emitting region, respectively, in order to understand the above. The effect can be obtained.

[0149] In the above configuration, each of the light-emitting elements has a structure in which the EL layer has a plurality of light-emitting layers. However, the present invention is not limited to this. For example, the tank described in the third embodiment may be used. In combination with the structure of a DEM type (stacked type) light-emitting element, a charge generating layer is sandwiched between one light-emitting element. A configuration in which a plurality of light emitting layers are formed may also be used.

[0150] The light-emitting device shown in this embodiment has a microcavity structure. Even if the device has an EL layer, it is possible to extract light of different wavelengths from each light-emitting element, so it is possible to Therefore, it is easy to achieve high definition. This is advantageous in realizing full color. It also strengthens the emission intensity of a specific wavelength in the front direction. This configuration allows for three or more color pixels to be used, resulting in low power consumption. This is particularly useful when applied to color displays (image display devices) using It may also be used for purposes such as illumination.

[0151] Note that the structure described in this embodiment mode may be used in appropriate combination with structures described in other embodiments. It is possible.

[0152] (Embodiment 5) In this embodiment, a light-emitting device including a light-emitting element which is one embodiment of the present invention will be described. .

[0153] The light emitting device may be a passive matrix light emitting device or an active matrix light emitting device. The light emitting device shown in this embodiment may be the light emitting device described in the other embodiment. A light emitting element can be applied.

[0154] In this embodiment mode, an active matrix light emitting device will be described with reference to FIG. .

[0155] 9(A) is a top view showing a light emitting device, and FIG. 9(B) is a top view showing FIG. 9(A) along a chain line A- FIG. 1 is a cross-sectional view taken along line B of the active matrix light emitting device according to the present embodiment. A pixel section 502 and a driver circuit section (source line driver circuit) 503 are provided on an element substrate 501. and a driver circuit section (gate line driver circuit) 504 (504a and 504b). The element portion 502, the driving circuit portion 503, and the driving circuit portion 504 are sealed by a sealing material 505. It is sealed between the child substrate 501 and a sealing substrate 506 .

[0156] In addition, on the element substrate 501, a driving circuit section 503 and a driving circuit section 504 are provided. Signals (e.g., video signals, clock signals, start signals, reset signals, etc.) and potentials A wiring 507 is provided for connecting an external input terminal for transmitting the signal. An example of providing an FPC (flexible printed circuit) 508 as an external input terminal is shown below. Although only the FPC is shown here, the FPC also has a printed wiring board. The light emitting device in this specification may include a light emitting device itself. This includes not only the body but also the state in which an FPC or PWB is attached to it.

[0157] Next, the cross-sectional structure will be described with reference to FIG. A driver circuit portion 503 which is a source line driver circuit is formed in the pixel portion. 5, a pixel portion 502 is shown.

[0158] The driving circuit section 503 is a combination of an n-channel TFT 509 and a p-channel TFT 510. The circuit forming the driver circuit section is shown in FIG. It may be formed of various CMOS circuits, PMOS circuits, or NMOS circuits. In the embodiment, a driver integrated type in which a driving circuit is formed on a substrate is shown, but this is not necessarily required. In addition, the driving circuit can be formed externally instead of on the substrate.

[0159] The pixel section 502 includes a switching TFT 511, a current control TFT 512, and a current A first TFT 512 electrically connected to the wiring (source electrode or drain electrode) of the control TFT 512 The pixel electrode 513 is formed of a plurality of pixels including the first electrode 513. The insulating material 514 is formed by the insulating material 514. Here, a positive photosensitive acrylic resin is used. In this embodiment, the first electrode 513 is used as an anode. .

[0160] In order to improve the coverage of the film to be laminated on the upper layer, the upper end of the insulator 514 It is preferable that a curved surface having a curvature is formed at the upper or lower end. When a positive photosensitive acrylic resin is used as the material of the insulating material 514, the upper end of the insulating material 514 It is preferable that the insulating layer has a curved surface with a radius of curvature (0.2 μm to 3 μm). Either a negative photosensitive resin or a positive photosensitive resin can be used as the material 514. It is possible to use not only organic compounds but also inorganic compounds such as silicon oxide and silicon oxynitride. Both of these can be used.

[0161] On the first electrode 513, an EL layer 515 and a second electrode 516 are laminated. The EL layer 515 includes at least a hole transport layer and a light emitting layer. The structure shown in Embodiment 1 or 2 can be applied to the light-emitting layer. In this embodiment, the second electrode 516 is used as a cathode.

[0162] The first electrode 513, the EL layer 515, and the second electrode 516 are stacked to form a light-emitting element. The first electrode 513, the EL layer 515 and the second electrode 516 are formed on the substrate 511. As the material, the material shown in the embodiment 2 can be used. However, the second electrode 516 is electrically connected to the FPC 508 which is an external input terminal. do.

[0163] In addition, although only one light-emitting element 517 is shown in the cross-sectional view shown in FIG. In the pixel section 502, a plurality of light emitting elements are arranged in a matrix. 02, selectively forming light-emitting elements that can emit three types of light (R, G, B), It is possible to form a light-emitting device capable of full color display. By combining these, a light emitting device capable of full color display may be obtained.

[0164] Furthermore, a sealing substrate 506 is bonded to the element substrate 501 with a sealant 505. The light is emitted into a space 518 surrounded by the element substrate 501, the sealing substrate 506, and the sealant 505. The structure is provided with an element 517. The space 518 is filled with an inert gas (such as nitrogen, etc.). In addition to the case where the cavity is filled with a gas such as argon, the cavity may also be filled with a sealing material 505. .

[0165] It is preferable to use an epoxy resin for the sealing material 505. It is preferable that the sealing substrate 506 is made of a material that is as impermeable to moisture and oxygen as possible. In addition to glass and quartz substrates, FRP (Fiberglass-Reinforced Plastics) is also used as a material for unforced Plastics), PVF (Polyvinyl fluoride), Polyester Alternatively, a plastic substrate made of acrylic or the like can be used.

[0166] In this manner, an active matrix light emitting device can be obtained.

[0167] Note that the structure described in this embodiment mode may be used in appropriate combination with structures described in other embodiment modes. There can be.

[0168] (Embodiment 6) In this embodiment, a light-emitting device according to one embodiment of the present invention shown in the above embodiment is included as a part of the light-emitting device. The electronic devices are described below. The electronic devices are cameras such as video cameras and digital cameras. goggle-type displays, navigation systems, audio playback devices (car audio , audio components, computers, game devices, mobile information terminals (mobile computers computers, mobile phones, smartphones, handheld game consoles, e-books, or tablet devices etc.), image reproducing devices equipped with recording media (specifically, Digital Versatile A display device capable of playing recording media such as eDisc (DVD) and displaying the images. Specific examples of these electronic devices are shown in Figures 10 and 11. I will explain it below.

[0169] FIG. 10A illustrates a television device according to one embodiment of the present invention. The television device includes a housing 611 and a support stand 612. , a display unit 613, a speaker unit 614, a video input terminal 615, etc. In this case, the light-emitting device according to one embodiment of the present invention can be applied to the display portion 613. The light-emitting device of one embodiment of the present invention can achieve high current efficiency at a low driving voltage. By using the light emitting device, a television device with reduced power consumption can be obtained.

[0170] FIG. 10B shows a computer according to one embodiment of the present invention, which includes a main body 621, a housing 622, and a , a display unit 623, a keyboard 624, an external connection port 625, a pointing device 6 In this computer, the display unit 623 includes a light-emitting device according to one embodiment of the present invention. The light-emitting device according to one embodiment of the present invention can achieve high current efficiency at a low driving voltage. Therefore, by using the light-emitting device of one embodiment of the present invention, it is possible to reduce power consumption. You can get a computer.

[0171] FIG. 10C shows a mobile phone according to one embodiment of the present invention. The mobile phone includes a main body 631, a housing 632, a front display unit 633, audio input unit 634, audio output unit 635, operation keys 636, external connection port 6 37, an antenna 638, etc. In this mobile phone, the display unit 633 includes one of the features of the present invention. The light-emitting device according to one embodiment of the present invention can be applied to a light-emitting device that can be driven at a low voltage. Since high current efficiency can be obtained, power consumption can be reduced by using the light-emitting device of one embodiment of the present invention. A reduced mobile phone charge can be obtained.

[0172] FIG. 10D illustrates a camera according to one embodiment of the present invention. The camera includes a main body 641, a display unit 642, a housing body 643, external connection port 644, remote control receiver 645, image receiver 646, battery 6 47, a voice input section 648, operation keys 649, an eyepiece section 650, etc. The light-emitting device according to one embodiment of the present invention can be applied to the display portion 642. Such a light-emitting device can achieve high current efficiency at a low driving voltage. By applying this arrangement, a camera with reduced power consumption can be obtained.

[0173] FIG. 11 shows an example of a mobile terminal according to an embodiment of the present invention. 11(C) shows a portable terminal 5000, and FIG. 11(D) shows a portable terminal 60 It shows 00.

[0174] In the mobile terminal 5000 shown in FIG. 11(A), FIG. 11(B), and FIG. 11(C), FIG. 11(A) is a front view, FIG. 11(B) is a side view, and FIG. 11(C) is a rear view. In addition, in the mobile terminal 6000 shown in FIG. 11(D), a front view is shown. There are.

[0175] The portable terminal 5000 includes a housing 5001, a display unit 5003, a power button 5005, a front cover, and a 5007, a rear camera 5009, a first external connection terminal 5011, and a second external connection It is composed of terminals 5013 and the like.

[0176] The display unit 5003 is incorporated in the housing 5001 and can also be used as a touch panel. For example, an icon 5015 or the like can be displayed on the display unit 5003 to In addition, the housing 5001 is equipped with a A front camera 5007 is built into the face side, allowing the user to take pictures. In addition, a rear camera 5009 is built into the rear side of the housing 5001, The camera can capture an image on the opposite side. The camera also has a first external connection terminal 5 011 and a second external connection terminal 5013. For example, the first external connection terminal 5 011 outputs audio to earphones or the like, and the second external connection terminal 5013 outputs data. It is possible to move around etc.

[0177] Next, a portable terminal 6000 shown in FIG. 11(D) is made up of a first housing 6001 and a second housing 6002. 003, hinge portion 6005, first display portion 6007, second display portion 6009, power button It is composed of a camera 6011, a first camera 6013, a second camera 6015, etc.

[0178] The first display unit 6007 is incorporated in the first housing 6001, and the second display The first display unit 6007 and the second display unit 6009 are incorporated in the second housing 6003. The second display unit 6009 uses, for example, the first display unit 6007 as a display panel, The second display unit 6009 is a touch panel. The icon 6017 is checked, and the icon 6019 is displayed on the second display unit 6009. using a keyboard 6021 (keyboard image displayed on the second display unit 6009), It is possible to select an image, input text, etc. The first display unit 6001 is a touch panel, and the second display unit 6009 is a display panel. Both the display unit 6007 and the second display unit 6009 may be configured as touch panels. .

[0179] The first housing 6001 and the second housing 6003 are connected by a hinge portion 6005. The first housing 6001 and the second housing 6003 can be opened and closed. With this configuration, when carrying the portable terminal 6000, the first housing 600 A first display unit 6007 is incorporated in the first housing 6001, and a second display unit 6008 is incorporated in the second housing 6003. The first display unit 6007 and the second display unit 6009 are combined to form a first display unit 6007 and a second display unit 6009. This is preferable because it can protect the surface of the substrate (for example, a plastic substrate, etc.).

[0180] In addition, the first housing 6001 and the second housing 6003 can be separated by a hinge portion 6005. It is also possible to use a structure that allows the use of a convertible type. For example, the first housing 6001 is used in a vertical position and the second housing 6003 is used in a horizontal position. As described above, this is preferable since it broadens the range of use.

[0181] In addition, a first camera 6013 and a second camera 6015 are used to capture 3D images. It is also possible.

[0182] In addition, the portable terminal 5000 and the portable terminal 6000 are configured to be able to transmit and receive information wirelessly. For example, the device may be connected to the Internet wirelessly and the desired information may be purchased. It is also possible to configure the information to be downloaded.

[0183] In addition, the mobile terminal 5000 and the mobile terminal 6000 can store various information (still images, videos, Functions for displaying text images, calendars, dates, or times on the display A touch input function that allows you to operate or edit the information displayed on the display unit, and various software It can also have a function to control processing by software (programs), etc. Light sensors that can optimize display brightness according to the amount of external light, gyros, and accelerometers A detection device such as a sensor for detecting the inclination of the sensor may be built in.

[0184] The display unit 5003 of the portable terminal 5000 and the first display unit 60 of the portable terminal 6000 07 or / and the second display portion 6009, a light-emitting device according to one embodiment of the present invention is applied. The light-emitting device according to one embodiment of the present invention can achieve high current efficiency at a low driving voltage. Therefore, by using the light-emitting device of one embodiment of the present invention, a portable terminal with reduced power consumption can be realized. can be obtained.

[0185] As described above, the light-emitting device of one embodiment of the present invention has an extremely wide range of application. The light-emitting device according to one embodiment of the present invention can be used in electronic devices in various fields. This makes it possible to obtain an electronic device with reduced power consumption.

[0186] The light-emitting device of one embodiment of the present invention can also be used as a lighting device. A specific example will be described with reference to FIG.

[0187] FIG. 12A illustrates a liquid crystal display device using a light-emitting device according to one embodiment of the present invention as a backlight. The liquid crystal display device shown in FIG. 12A includes a housing 701, a liquid crystal panel 702, The liquid crystal panel 702 has a backlight 703 and a housing 704, and is connected to a driver IC 705. The backlight 703 is formed using the light-emitting device of one embodiment of the present invention. A current is supplied through a terminal 706. In this manner, the light-emitting device according to one embodiment of the present invention is By using it as a backlight for a liquid crystal display device, a backlight with low power consumption can be obtained. In addition, the light-emitting device of one embodiment of the present invention is a surface-emitting lighting device and can be made large in area. Therefore, it is possible to increase the area of ​​the backlight. A liquid crystal display device having such a structure can be obtained.

[0188] FIG. 12B shows a case in which the light-emitting device of one embodiment of the present invention is used as a desk lamp, which is a lighting device. The desk lamp shown in FIG. 12B has a housing 801 and a light source 802. The light-emitting device of one embodiment of the present invention is used as the light source 802. Since current efficiency can be obtained, the use of the light-emitting device according to one embodiment of the present invention can achieve low power consumption. You can get a stand.

[0189] FIG. 12C shows an example in which the light-emitting device of one embodiment of the present invention is used as an indoor lighting device 901. The light-emitting device of one embodiment of the present invention can be made large in area, and therefore can be used as a large-area lighting device. In addition, the light-emitting device of one embodiment of the present invention can be used at a low driving voltage and with high current efficiency. Therefore, by using the light-emitting device of one embodiment of the present invention, a lighting device with low power consumption can be obtained. In this way, the light-emitting device according to one embodiment of the present invention can be used as an indoor lighting device 9. In the room used as the room 01, a television set according to one embodiment of the present invention as described in FIG. You can install 902 and watch public broadcasts and movies.

[0190] Note that this embodiment mode can be appropriately combined with other embodiment modes. EXAMPLES

[0191] In this example, a light-emitting element of one embodiment of the present invention (light-emitting element 1) and a light-emitting element for comparison (light-emitting element 2) were The comparative light emitting element 2) will be described with reference to FIG. 13. The chemistry of the materials used in this embodiment will be described. The formula is shown below.

[0192] [ka]

[0193] [ka]

[0194] A method for fabricating the light-emitting element 1 of this example and the comparative light-emitting element 2 will be described below.

[0195] (Light emitting element 1) First, on a substrate 1100, indium oxide-tin oxide containing silicon or silicon oxide is A compound (ITO-SiO2, hereafter abbreviated as ITSO) was formed into a film by sputtering. The composition of the target used was In2O3:Sn The ratio of O2 to SiO2 was 85:10:5 [wt %]. The thickness of the first electrode 1101 was , 110 nm, and the electrode area was 2 mm × 2 mm. Here, the first electrode 1101 is This electrode functions as an anode of the light-emitting element.

[0196] Next, as a pretreatment for forming a light emitting element on the substrate 1100, the substrate surface is washed with water. After baking at 200°C for 1 hour, UV ozone treatment was performed for 370 seconds.

[0197] Then, 10 -4 The substrate is introduced into a vacuum deposition apparatus whose inside has been reduced in pressure to about Pa. After vacuum baking at 170° C. for 30 minutes in a heating chamber in the deposition apparatus, the substrate 1100 is It was left to cool for about 30 minutes.

[0198] Next, the first electrode 1101 is placed on the substrate 1101 so that the surface on which the first electrode 1101 is formed faces downward. The substrate 1100 thus formed is fixed to a substrate holder provided in a vacuum deposition apparatus, and -4 After the pressure was reduced to about Pa, 4 ,4',4''-(benzene-1,3,5-triyl)tri(dibenzothiophene)(abbreviation The hole injection layer 1111 is formed by co-evaporating the SiO2 (DBT3P-II) and molybdenum oxide. The film thickness was 40 nm, and the ratio of DBT3P-II (abbreviation) to molybdenum oxide was was adjusted to a weight ratio of 4:2 (=DBT3P-II:molybdenum oxide).

[0199] Next, 4-phenyl-4'-(9-phenylfluorene-9 -yl)triphenylamine (abbreviation: BPAFLP) and 3-[N-(9-phenylcarbamoyl) PC(3-yl)-N-phenylamino]-9-phenylcarbazole The hole transport layer 1112 was formed by co-evaporation of ZnPCA1). 0 nm, and the ratio of BPAFLP (abbreviation) to PCzPCA1 (abbreviation) was 0.5 by weight. :0.5 (=BPAFLP:PCzPCA1).

[0200] In addition, in the hole transport layer 1112, BPAFLP (abbreviation) is a fourth organic compound. PCzPCA1 (abbreviation) is the fifth organic compound.

[0201] Next, on the hole transport layer 1112, 2mDBTPDBq-II (abbreviation) and 4-phenyl -4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBA1BP) and (acetylacetonato)bis(6-tert-butyl-4-phenyl Rupyrimidinato)iridium(III) (abbreviation: [Ir(tBuppm)2(acac) ]) was co-evaporated to form the first light-emitting layer 1113a. -II (abbreviation), PCBA1BP (abbreviation), and [Ir(tBuppm)2(acac) The weight ratio of 2mDBTPDBq-II:PC BA1BP: [Ir(tBuppm)2(acac)]). The thickness of the first light emitting layer 1113a was set to 20 nm.

[0202] In the first light-emitting layer 1113a, 2mDBTPDBq-II (abbreviation) is The first organic compound (host material) is PCBA1BP (abbreviation), and the second organic compound ( The third organic compound, [Ir(tBuppm)2(acac)] (abbreviation) Compound (guest material).

[0203] Next, 2mDBTPDBq-II (abbreviation) and PCBA 1BP (abbreviation) and [Ir(tBuppm)2(acac)] (abbreviation) are co-evaporated, The second light-emitting layer 1113b was formed. The weight ratio of BA1BP (abbreviation) and [Ir(tBuppm)2(acac)] (abbreviation) is , 0.8:0.2:0.05(=2mDBTPDBq-II:PCBA1BP:[Ir( tBuppm)2(acac)]). The second light-emitting layer 1113 The film thickness of b was set to 20 nm.

[0204] In the second light-emitting layer 1113b, 2mDBTPDBq-II (abbreviation) is The first organic compound (host material) is PCBA1BP (abbreviation), and the second organic compound ( The third organic compound, [Ir(tBuppm)2(acac)] (abbreviation) Compound (guest material).

[0205] Next, 2mDBTPDBq-II (abbreviation) was applied to the second light-emitting layer 1113b to a thickness of 10 nm. A film was formed so as to form a first electron-transporting layer 1114a.

[0206] Next, bathophenanthroline (abbreviation: BPhen) was applied onto the first electron transport layer 1114a. A film was formed to a thickness of 20 nm to form the second electron transport layer 1114b.

[0207] Next, lithium fluoride (LiF) was deposited on the second electron transport layer 1114b to a thickness of 1 nm. An electron injection layer 1115 was formed by evaporation.

[0208] Finally, a second electrode 1103 functioning as a cathode was prepared by depositing 20% ​​aluminum (Al). The light-emitting element 1 of this example was fabricated by depositing the layer so as to have a film thickness of 0 nm.

[0209] In the above-mentioned deposition process, the deposition was all performed by a resistance heating method.

[0210] (Comparative light-emitting element 2) The comparative light-emitting element 2 is different from the light-emitting element 1 in the configuration of the hole transport layer 1112. Only the different configurations will be described below.

[0211] BPAFLP (abbreviation) is deposited on the hole injection layer 1111 to form a hole transport layer 111 2 was formed. The film thickness was set to 20 nm.

[0212] The element structures of the thus obtained light-emitting element 1 and comparative light-emitting element 2 are shown in Table 1.

[0213] [Table 1]

[0214] Next, the hole transport layer and the first light-emitting layer used in the light-emitting element 1 of this example and the comparative light-emitting element 2 were and BPAFLP (abbreviation), PCzPCA1 (abbreviation), and PCB used in the second emitting layer. The electrochemical properties (HOMO and LUMO levels) of each thin film of A1BP (abbreviation) were measured. (Measuring equipment: Riken Keiki Co., Ltd., AC-2). was carried out as follows.

[0215] The HOMO level was measured by photoelectron spectroscopy (Riken Keiki, AC-2) in air. The ionization potential value was converted to a negative value. The LUMO level value was also calculated. The absorption spectrum data of each thin film is measured, and the direct transfer is performed using the absorption spectrum data. The absorption edge is calculated from the Tauc plot assuming a transition of the absorption edge. The value was obtained by adding it to the value of the HOMO level as a loop.

[0216] The measurement results of the electrochemical properties of each thin film are shown in Table 2.

[0217] [Table 2]

[0218] From Table 2, the HOMO level of BPAFLP (abbreviation) is -5.63 eV, and the LUMO level is - The optical density (Vd) of PCzPC was 2.29 eV, and the band gap (Bg) was 3.34 eV. The HOMO level of A1 (abbreviation) is -5.17 eV, the LUMO level is -2.26 eV, and The band gap (Bg) was 2.91 eV. O level is -5.42 eV, LUMO level is -2.21 eV, and band gap (Bg) was 3.21 eV.

[0219] In addition, from Tables 1 and 2, the hole transport layers of the light-emitting element 1 of this example and the comparative light-emitting element 2, Table 3 shows the materials and HOMO levels of the light-emitting layer (second organic compound).

[0220] [Table 3]

[0221] As shown in Table 3, the hole transport layer of the light-emitting element 1 of this example contains the second organic compound (acis The fourth organic compound below the HOMO level of PCBA1BP (abbreviation), which is a 100% organic compound, is B Using PAFLP (abbreviation), the second organic compound (assist material), PCBA1BP ( The fifth organic compound with a higher HOMO level than On the other hand, the comparative light-emitting element 2 is configured to have a structure in which the second organic compound (assist material) is PC One organic compound (BPAFLP (abbreviation)) with a lower HOMO level than BA1BP (abbreviation) )) is used.

[0222] Next, the light-emitting element 1 and the comparative light-emitting element 2 were placed in a glove box with a nitrogen atmosphere. The process of sealing each light-emitting element with a glass substrate so that it is not exposed to the atmosphere (sealing material is applied to the element) The luminescent element was then coated with a fluorine-containing resin and heat-treated at 80°C for 1 hour. The operating characteristics of the device were measured. The measurements were performed at room temperature (25°C). I did.

[0223] FIG. 14 shows the current density-luminance characteristics of the light-emitting element 1 and the comparative light-emitting element 2. The horizontal axis is the current density (mA / cm 2 ) and the vertical axis is luminance (cd / m 2 ) and also represents light emission. FIG. 15 shows the voltage-luminance characteristics of the element 1 and the comparative light-emitting element 2. In FIG. The vertical axis represents voltage (V) and the vertical axis represents brightness (cd / m 2 ) are shown. The luminance-current efficiency characteristics of 2 are shown in FIG. 16. In FIG. 16, the horizontal axis is luminance (cd / m 2 ), The vertical axis represents the current efficiency (cd / A). The current characteristics are shown in Fig. 17. In Fig. 17, the horizontal axis represents voltage (V) and the vertical axis represents current (mA). FIG. 18 shows the emission spectra of the light-emitting element 1 and the comparative light-emitting element 2. In FIG. 18, the horizontal axis represents the wavelength (nm) and the vertical axis represents the emission intensity (arbitrary unit). The data for each light-emitting element are shown overlapping each other. The luminance-power efficiency characteristics (lm / W) of element 2 are shown in FIG.

[0224] As shown in FIG. 19, the luminance of the light-emitting element 1 is 1000 cd / m 2 The power efficiency in the vicinity is 105(l m / W), and that of Comparative Light-emitting Device 2 was 1000 cd / m 2 The power efficiency in the vicinity is 93 (lm / As described above, the light-emitting element of one embodiment of the present invention had a luminance of 12 W compared to the comparative light-emitting element 2. (lm / W) was confirmed to be a high-performance element.

[0225] In addition, the luminance of each light-emitting element is 1000 cd / m 2 Voltage (V) and current density near (mA / cm 2 ), CIE chromaticity coordinates (x, y), current efficiency (cd / A), external quantum efficiency ( %) are shown in Table 4.

[0226] [Table 4]

[0227] As shown in Table 4, the luminance is 1112cd / m 2 The CIE chromaticity coordinates of light-emitting element 1 are (x,y )=(0.43,0.56). The luminance was 1037cd / m 2 Comparison of light-emitting elements 2 The CIE chromaticity coordinates of are (x,y) = (0.43,0.56).

[0228] Also, the brightness is 1112cd / m 2 The voltage of the light-emitting element 1 is 2.6 V, and the current efficiency is 87 cd / A. The brightness was 1037cd / m 2 The voltage of the comparison light-emitting element 2 is 2.9V. The current efficiency was 85 cd / A.

[0229] Therefore, the light-emitting element 1 of one embodiment of the present invention has a lower voltage than the comparative light-emitting element 2. It was confirmed that the voltage could be reduced by 0.3 V and the current efficiency was equal to or higher. As shown in FIG. 17, the light-emitting element 1 can have a lower driving start voltage than the comparative light-emitting element 2. It was confirmed that.

[0230] As described above, the light-emitting element of one embodiment of the present invention has a hole-transporting property used in the light-emitting layer. A fourth organic compound that is lower than the HOMO level of the second organic compound and has a higher H The hole transport layer includes a fifth organic compound having a high OMO level. This makes it possible to reduce the driving voltage of the light emitting element and increase the current efficiency.

[0231] The first organic compound (2mDBTPDB The PL peak wavelength of the thin film of q-II) is 426 nm, and the second organic compound (PCBA1BP) The PL peak wavelength of the mixed film is 519 nm. It was found that the wavelengths of the two organic compounds were shifted to longer wavelengths. is a combination that forms an exciplex.

[0232] In this way, in the light-emitting element 1, the second The fifth organic compound (PCzPC A1) is added to the hole transport layer, so that the light-emitting element is lighter than the comparative light-emitting element 2, which does not contain A1). The drive start voltage can be reduced even further.

[0233] As a second organic compound, PCzPCA1 was added to the light-emitting layer instead of PCBA1BP. When the voltage applied to the light-emitting element 1 is increased, the driving start voltage can be reduced as in the light-emitting element 1. However, when the voltage applied to the light-emitting element 1 is increased, the driving start voltage can be reduced as in the light-emitting element 1. Since CzPCA1 has a higher HOMO level than PCBA1BP, the first organic compound (2m The emission wavelength of the exciplex formed by DBTPDBq-II) and PCzPCA1 is 571 nm. m, which is a longer wavelength shift compared to PCBA1BP (519 nm). Therefore, However, when a green phosphorescent material is used in the light-emitting layer as in this embodiment, the green phosphorescent material is difficult to excite. On the other hand, in the present invention (light-emitting element 1), In other words, the configuration of one embodiment of the present invention has an energy gap In green and blue light-emitting elements, which have a large driving voltage (i.e., a high driving start voltage in principle), It can also be said to be a particularly effective means of lowering voltage without compromising efficiency.

[0234] (Reference example 1) The (acetylacetonato)bis(6-tert-butyl-4-phenyl) Rupyrimidinato)iridium(III) (abbreviation: [Ir(tBuppm)2(acac) A specific example of the synthesis of [Ir(tBuppm)2(acac)] is given below. The structure is shown below.

[0235] [ka]

[0236] <Step 1: 4-tert-butyl-6-phenylpyrimidine (abbreviation: HtBuppm ) Synthesis Method> First, 22.5 g of 4,4-dimethyl-1-phenylpentane-1,3-dione and formamide were 50 g of amide was placed in a recovery flask equipped with a reflux condenser, and the inside of the flask was replaced with nitrogen. The reaction solution was refluxed for 5 hours by heating the vessel. Then, the solution was diluted with sodium hydroxide. The organic layer was extracted with dichloromethane. The solution was washed with ethyl acetate and dried over magnesium sulfate. The dried solution was filtered. After distilling off the solvent, the residue was extracted with hexane:ethyl acetate = 10:1 (volume ratio). The pyrimidine derivative HtBup was purified by silica gel column chromatography using the solvent pm was obtained (colorless oil, 14% yield). The synthesis scheme of step 1 is shown below (a-1). show.

[0237] [ka]

[0238] <Step 2: Di-μ-chloro-bis[bis(6-tert-butyl-4-phenylpyridine] Synthesis of [midinato)iridium(III)] (abbreviation: [Ir(tBuppm)2Cl]2) Law> Next, 15 mL of 2-ethoxyethanol, 5 mL of water, and the HtBup obtained in step 1 above were Add 1.49g of pm, 1.04g of iridium chloride hydrate (IrCl3·H2O) and a reflux condenser. The flask was then purged with argon. After that, the mixture was heated in a microwave oven (2. The mixture was irradiated with a 45 GHz 100 W power source for 1 hour to cause a reaction. After removing the solvent, the resulting residue was The mixture was filtered with suction and washed with ethanol to obtain the binuclear complex [Ir(tBuppm)2Cl]2 ( Yellow-green powder, 73% yield. The synthesis scheme of step 2 is shown in (a-2) below.

[0239] [ka]

[0240] <Step 3; (acetylacetonato)bis(6-tert-butyl-4-phenylpyridine) Iridium(III) (abbreviation: [Ir(tBuppm)2(acac)] Law> Furthermore, 40 mL of 2-ethoxyethanol and the binuclear complex [Ir(t Buppm)2Cl]21.61g, acetylacetone 0.36g, sodium carbonate 1 0.27g was placed in a recovery flask equipped with a reflux condenser, and the atmosphere in the flask was replaced with argon. Thereafter, the mixture was irradiated with microwaves (2.45 GHz, 100 W) for 60 minutes to cause a reaction. The resulting residue was filtered off with ethanol and washed with water and ethanol. Dissolve in dichloromethane and filter with Celite (Wako Pure Chemical Industries, Ltd., catalog number: 531- The mixture was filtered through a filter aid consisting of a layer of 16855), alumina, and celite. The solid obtained by distillation was recrystallized in a mixed solvent of dichloromethane and hexane. The target product was obtained as a yellow powder (yield 68%). The synthesis scheme of step 3 is shown below (a- 3) is shown.

[0241] [ka]

[0242] The compound obtained by the above synthesis method was analyzed by nuclear magnetic resonance spectroscopy ( 1 H-NMR From the measurement results, [Ir(tBuppm)2(acac)] (abbreviation) was obtained. It was discovered that...

[0243] The obtained material 1 The H-NMR data is shown below. 1 H-NMR.δ(CDCl3):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).

[0244] (Reference example 2) In the above-mentioned embodiment, 2mDBTPDBq-II (abbreviation) was used as the light-emitting element. The T1 levels of A1BP (abbreviation) and BPAFLP (abbreviation) were measured. The measurement of the first level is done by measuring the phosphorescence emission of each substance and converting the phosphorescence emission wavelength into electron volts. The measurement conditions were as follows: each substance was irradiated with 325 nm excitation light, and the measurement The measurements were performed at a temperature of 10 K. The energy levels were calculated from the emission wavelength and the absorption wavelength. However, the absorption at the T1 level is extremely weak and difficult to measure. Therefore, here, the peak wavelength located on the shortest wavelength side of the phosphorescence spectrum is measured. Therefore, the measured values ​​may contain some error.

[0245] The measured phosphorescence emission of 2mDBTPDBq-II (abbreviation) is shown in Figure 20. The phosphorescence emission measured by BPAFLP (abbreviation) is shown in Figure 21, and the phosphorescence emission measured by BPAFLP (abbreviation) is shown in Figure 2 The measurement results are summarized in Table 5. As can be seen from the results, In the above examples, 2mDBTPDBq-II (abbreviation) was used as the first organic compound. Compared with PCBA1BP (abbreviation) used as the second organic compound, It can be seen that BPAFLP (abbreviation), which corresponds to the organic compound 4, has a high T1 level.

[0246] [Table 5] [Explanation of symbols]

[0247] 100 Substrates 101 First electrode 103 Second electrode 111 Hole injection layer 112 Hole transport layer 112a Hole transport layer 112b Hole transport layer 112c Hole transport layer 113 Light-emitting layer 114 Electron transport layer 115 Electron injection layer 120 The first organic compound 122 Second organic compound 124 The third organic compound 126 The fourth organic compound 128 The fifth organic compound 301 First electrode 303 Second electrode 311 First light-emitting layer 312 Second light-emitting layer 313 Charge generation layer 450R First light emitting element 450G Second light emitting element 450B Third light-emitting element 451 Reflecting electrode 452 Semi-transparent / semi-reflective electrode 453a First transparent conductive layer 453b Second transparent conductive layer 454 Light-emitting layer 454B First light-emitting layer 454G Second light-emitting layer 454R Third luminescent layer 455 EL layer 501 Element substrate 502 Pixel section 503 Drive circuit section 504 Drive circuit section 505 Sealing material 506 Sealing substrate 507 Wiring 508 FPC 509 n-channel TFT 510 p-channel TFT 511 Switching TFT 512 Current control TFT 513 First electrode 514 Insulation 515 EL layer 516 Second Electrode 517 Light emitting element 518 Space 611 Case 612 Support stand 613 Display section 614 Speaker section 615 Video input terminal 621 Main unit 622 Case 623 Display section 624 Keyboard 625 External connection port 626 Pointing Device 631 Main unit 632 Case 633 Display section 634 Audio input section 635 Audio output section 636 Operation Key 637 External connection port 638 Antenna 641 Main unit 642 Display section 643 Case 644 External connection port 645 Remote control receiver 646 Image receiving unit 647 Battery 648 Audio Input Unit 649 Operation Key 650 Eyepiece 701 Case 702 Liquid crystal panel 703 Backlight 704 Case 705 Driver IC 706 Terminal 801 Case 802 light source 901 Lighting equipment 902 Television equipment 1100 Substrate 1101 First electrode 1103 Second electrode 1111 Hole injection layer 1112 Hole transport layer 1113a First light-emitting layer 1113b Second light-emitting layer 1114a First electron transport layer 1114b Second electron transport layer 1115 Electron injection layer 5000 Portable Devices 5001 Case 5003 Display section 5005 Power button 5007 Front Camera 5009 Rear Camera 5011 External connection terminal 5013 External connection terminal 5015 Icon 6000 Portable Devices 6001 Case 6003 Case 6005 Hinge part 6007 Display section 6009 Display section 6011 Power button 6013 Camera 6015 Camera 6017 Text Icon 6019 Icon 6021 Keyboard

Claims

1. a hole injection layer, a hole transport layer, a light emitting layer, a first electron transport layer, and a second electron transport layer between an anode and a cathode; the hole transport layer is in contact with the light emitting layer, the light-emitting layer includes a first organic compound, a second organic compound, and a third organic compound that converts triplet excitation energy into light emission; the first organic compound and the second organic compound are a combination that forms an exciplex, the HOMO level of the first organic compound is lower than the HOMO level of the second organic compound; a LUMO level of the first organic compound is lower than a LUMO level of the second organic compound; the hole transport layer comprises a fourth organic compound having a HOMO level higher than a HOMO level of the second organic compound; the fourth organic compound is at least one of a π-excessive heteroaromatic compound and an aromatic amine compound; At least one of the first electron transport layer and the second electron transport layer comprises a heteroaromatic compound; A light-emitting device, wherein the difference between the energy value of the peak of the emission spectrum of the exciplex and the energy value of the peak of the absorption band located on the lowest energy side of the absorption spectrum of the third organic compound is within 0.2 eV.

2. A device comprising a hole injection layer, a hole transport layer, a light emitting layer, a first electron transport layer, and a second electron transport layer between an anode and a cathode, the hole transport layer is in contact with the light emitting layer, the light-emitting layer includes a first organic compound, a second organic compound, and a third organic compound that converts triplet excitation energy into light emission; the first organic compound and the second organic compound are a combination that forms an exciplex, the HOMO level of the first organic compound is lower than the HOMO level of the second organic compound; a LUMO level of the first organic compound is lower than a LUMO level of the second organic compound; the hole transport layer comprises a fourth organic compound having a HOMO level higher than a HOMO level of the second organic compound; the fourth organic compound has at least one of an aromatic amine skeleton, a carbazole skeleton, a thiophene skeleton, and a furan skeleton; At least one of the first electron transport layer and the second electron transport layer comprises a heteroaromatic compound; A light-emitting device, wherein the difference between the energy value of the peak of the emission spectrum of the exciplex and the energy value of the peak of the absorption band located on the lowest energy side of the absorption spectrum of the third organic compound is within 0.2 eV.

3. a hole injection layer, a hole transport layer, a light emitting layer, a first electron transport layer, and a second electron transport layer between an anode and a cathode; the hole transport layer is in contact with the light emitting layer, the light-emitting layer includes a first organic compound, a second organic compound, and a third organic compound that converts triplet excitation energy into light emission; the first organic compound and the second organic compound are a combination that forms an exciplex, the HOMO level of the first organic compound is lower than the HOMO level of the second organic compound; a LUMO level of the first organic compound is lower than a LUMO level of the second organic compound; the hole transport layer comprises a fourth organic compound having a HOMO level higher than a HOMO level of the second organic compound; the fourth organic compound is at least one of a π-excessive heteroaromatic compound and an aromatic amine compound; At least one of the first electron transport layer and the second electron transport layer comprises a heteroaromatic compound; A light-emitting device, wherein the difference between the energy value of the peak of the emission spectrum of the exciplex and the energy value of the peak of the absorption band located on the lowest energy side of the absorption spectrum of the third organic compound is within 0.1 eV.

4. A device comprising a hole injection layer, a hole transport layer, a light emitting layer, a first electron transport layer, and a second electron transport layer between an anode and a cathode, the hole transport layer is in contact with the light emitting layer, the light-emitting layer includes a first organic compound, a second organic compound, and a third organic compound that converts triplet excitation energy into light emission; the first organic compound and the second organic compound are a combination that forms an exciplex, the HOMO level of the first organic compound is lower than the HOMO level of the second organic compound; a LUMO level of the first organic compound is lower than a LUMO level of the second organic compound; the hole transport layer comprises a fourth organic compound having a HOMO level higher than a HOMO level of the second organic compound; the fourth organic compound has at least one of an aromatic amine skeleton, a carbazole skeleton, a thiophene skeleton, and a furan skeleton; At least one of the first electron transport layer and the second electron transport layer comprises a heteroaromatic compound; A light-emitting device, wherein the difference between the energy value of the peak of the emission spectrum of the exciplex and the energy value of the peak of the absorption band located on the lowest energy side of the absorption spectrum of the third organic compound is within 0.1 eV.

5. a hole injection layer, a hole transport layer, a light emitting layer, a first electron transport layer, and a second electron transport layer between an anode and a cathode; the hole transport layer is in contact with the light emitting layer, the light-emitting layer includes a first organic compound, a second organic compound, and a third organic compound that converts triplet excitation energy into light emission; the first organic compound and the second organic compound are a combination that forms an exciplex, the T1 level of the first organic compound is higher than the T1 level of the third organic compound; the T1 level of the second organic compound is higher than the T1 level of the third organic compound; the HOMO level of the first organic compound is lower than the HOMO level of the second organic compound; a LUMO level of the first organic compound is lower than a LUMO level of the second organic compound; the hole transport layer comprises a fourth organic compound having a HOMO level higher than a HOMO level of the second organic compound; the fourth organic compound is at least one of a π-excessive heteroaromatic compound and an aromatic amine compound; At least one of the first electron transport layer and the second electron transport layer comprises a heteroaromatic compound; A light-emitting device, wherein the difference between the energy value of the peak of the emission spectrum of the exciplex and the energy value of the peak of the absorption band located on the lowest energy side of the absorption spectrum of the third organic compound is within 0.2 eV.

6. A device comprising a hole injection layer, a hole transport layer, a light emitting layer, a first electron transport layer, and a second electron transport layer between an anode and a cathode, the hole transport layer is in contact with the light emitting layer, the light-emitting layer includes a first organic compound, a second organic compound, and a third organic compound that converts triplet excitation energy into light emission; the first organic compound and the second organic compound are a combination that forms an exciplex, the T1 level of the first organic compound is higher than the T1 level of the third organic compound; the T1 level of the second organic compound is higher than the T1 level of the third organic compound; the HOMO level of the first organic compound is lower than the HOMO level of the second organic compound; a LUMO level of the first organic compound is lower than a LUMO level of the second organic compound; the hole transport layer comprises a fourth organic compound having a HOMO level higher than a HOMO level of the second organic compound; the fourth organic compound has at least one of an aromatic amine skeleton, a carbazole skeleton, a thiophene skeleton, and a furan skeleton; At least one of the first electron transport layer and the second electron transport layer comprises a heteroaromatic compound; A light-emitting device, wherein the difference between the energy value of the peak of the emission spectrum of the exciplex and the energy value of the peak of the absorption band located on the lowest energy side of the absorption spectrum of the third organic compound is within 0.2 eV.

7. a hole injection layer, a hole transport layer, a light emitting layer, a first electron transport layer, and a second electron transport layer between an anode and a cathode; the hole transport layer is in contact with the light emitting layer, the light-emitting layer includes a first organic compound, a second organic compound, and a third organic compound that converts triplet excitation energy into light emission; the first organic compound and the second organic compound are a combination that forms an exciplex, the T1 level of the first organic compound is higher than the T1 level of the third organic compound; the T1 level of the second organic compound is higher than the T1 level of the third organic compound; the HOMO level of the first organic compound is lower than the HOMO level of the second organic compound; a LUMO level of the first organic compound is lower than a LUMO level of the second organic compound; the hole transport layer comprises a fourth organic compound having a HOMO level higher than a HOMO level of the second organic compound; the fourth organic compound is at least one of a π-excessive heteroaromatic compound and an aromatic amine compound; At least one of the first electron transport layer and the second electron transport layer comprises a heteroaromatic compound; A light-emitting device, wherein the difference between the energy value of the peak of the emission spectrum of the exciplex and the energy value of the peak of the absorption band located on the lowest energy side of the absorption spectrum of the third organic compound is within 0.1 eV.

8. A device comprising a hole injection layer, a hole transport layer, a light emitting layer, a first electron transport layer, and a second electron transport layer between an anode and a cathode, the hole transport layer is in contact with the light emitting layer, the light-emitting layer includes a first organic compound, a second organic compound, and a third organic compound that converts triplet excitation energy into light emission; the first organic compound and the second organic compound are a combination that forms an exciplex, the T1 level of the first organic compound is higher than the T1 level of the third organic compound; the T1 level of the second organic compound is higher than the T1 level of the third organic compound; the HOMO level of the first organic compound is lower than the HOMO level of the second organic compound; a LUMO level of the first organic compound is lower than a LUMO level of the second organic compound; the hole transport layer comprises a fourth organic compound having a HOMO level higher than a HOMO level of the second organic compound; the fourth organic compound has at least one of an aromatic amine skeleton, a carbazole skeleton, a thiophene skeleton, and a furan skeleton; At least one of the first electron transport layer and the second electron transport layer comprises a heteroaromatic compound; A light-emitting device, wherein the difference between the energy value of the peak of the emission spectrum of the exciplex and the energy value of the peak of the absorption band located on the lowest energy side of the absorption spectrum of the third organic compound is within 0.1 eV.

9. a hole injection layer, a hole transport layer, a light emitting layer, a first electron transport layer, and a second electron transport layer between an anode and a cathode; the hole transport layer is in contact with the light emitting layer, the light-emitting layer includes a first organic compound, a second organic compound, and a third organic compound that is a phosphorescent compound; the first organic compound and the second organic compound are a combination that forms an exciplex, the HOMO level of the first organic compound is lower than the HOMO level of the second organic compound; a LUMO level of the first organic compound is lower than a LUMO level of the second organic compound; the hole transport layer comprises a fourth organic compound having a HOMO level higher than a HOMO level of the second organic compound; the fourth organic compound is at least one of a π-excessive heteroaromatic compound and an aromatic amine compound; At least one of the first electron transport layer and the second electron transport layer comprises a heteroaromatic compound; A light-emitting device, wherein the difference between the energy value of the peak of the emission spectrum of the exciplex and the energy value of the peak of the absorption band located on the lowest energy side of the absorption spectrum of the third organic compound is within 0.2 eV.

10. A device comprising a hole injection layer, a hole transport layer, a light emitting layer, a first electron transport layer, and a second electron transport layer between an anode and a cathode, the hole transport layer is in contact with the light emitting layer, the light-emitting layer includes a first organic compound, a second organic compound, and a third organic compound that is a phosphorescent compound; the first organic compound and the second organic compound are a combination that forms an exciplex, the HOMO level of the first organic compound is lower than the HOMO level of the second organic compound; a LUMO level of the first organic compound is lower than a LUMO level of the second organic compound; the hole transport layer comprises a fourth organic compound having a HOMO level higher than a HOMO level of the second organic compound; the fourth organic compound has at least one of an aromatic amine skeleton, a carbazole skeleton, a thiophene skeleton, and a furan skeleton; At least one of the first electron transport layer and the second electron transport layer comprises a heteroaromatic compound; A light-emitting device, wherein the difference between the energy value of the peak of the emission spectrum of the exciplex and the energy value of the peak of the absorption band located on the lowest energy side of the absorption spectrum of the third organic compound is within 0.2 eV.

11. a hole injection layer, a hole transport layer, a light emitting layer, a first electron transport layer, and a second electron transport layer between an anode and a cathode; the hole transport layer is in contact with the light emitting layer, the light-emitting layer includes a first organic compound, a second organic compound, and a third organic compound that is a phosphorescent compound; the first organic compound and the second organic compound are a combination that forms an exciplex, the HOMO level of the first organic compound is lower than the HOMO level of the second organic compound; a LUMO level of the first organic compound is lower than a LUMO level of the second organic compound; the hole transport layer comprises a fourth organic compound having a HOMO level higher than a HOMO level of the second organic compound; the fourth organic compound is at least one of a π-excessive heteroaromatic compound and an aromatic amine compound; At least one of the first electron transport layer and the second electron transport layer comprises a heteroaromatic compound; A light-emitting device, wherein the difference between the energy value of the peak of the emission spectrum of the exciplex and the energy value of the peak of the absorption band located on the lowest energy side of the absorption spectrum of the third organic compound is within 0.1 eV.

12. A device comprising a hole injection layer, a hole transport layer, a light emitting layer, a first electron transport layer, and a second electron transport layer between an anode and a cathode, the hole transport layer is in contact with the light emitting layer, the light-emitting layer includes a first organic compound, a second organic compound, and a third organic compound that is a phosphorescent compound; the first organic compound and the second organic compound are a combination that forms an exciplex, the HOMO level of the first organic compound is lower than the HOMO level of the second organic compound; a LUMO level of the first organic compound is lower than a LUMO level of the second organic compound; the hole transport layer comprises a fourth organic compound having a HOMO level higher than a HOMO level of the second organic compound; the fourth organic compound has at least one of an aromatic amine skeleton, a carbazole skeleton, a thiophene skeleton, and a furan skeleton; At least one of the first electron transport layer and the second electron transport layer comprises a heteroaromatic compound; A light-emitting device, wherein the difference between the energy value of the peak of the emission spectrum of the exciplex and the energy value of the peak of the absorption band located on the lowest energy side of the absorption spectrum of the third organic compound is within 0.1 eV.

13. a hole injection layer, a hole transport layer, a light emitting layer, a first electron transport layer, and a second electron transport layer between an anode and a cathode; the hole transport layer is in contact with the light emitting layer, the light-emitting layer includes a first organic compound, a second organic compound, and a third organic compound that is a phosphorescent compound; the first organic compound and the second organic compound are a combination that forms an exciplex, the T1 level of the first organic compound is higher than the T1 level of the third organic compound; the T1 level of the second organic compound is higher than the T1 level of the third organic compound; the HOMO level of the first organic compound is lower than the HOMO level of the second organic compound; a LUMO level of the first organic compound is lower than a LUMO level of the second organic compound; the hole transport layer comprises a fourth organic compound having a HOMO level higher than a HOMO level of the second organic compound; the fourth organic compound is at least one of a π-excessive heteroaromatic compound and an aromatic amine compound; At least one of the first electron transport layer and the second electron transport layer comprises a heteroaromatic compound; A light-emitting device, wherein the difference between the energy value of the peak of the emission spectrum of the exciplex and the energy value of the peak of the absorption band located on the lowest energy side of the absorption spectrum of the third organic compound is within 0.2 eV.

14. A device comprising a hole injection layer, a hole transport layer, a light emitting layer, a first electron transport layer, and a second electron transport layer between an anode and a cathode, the hole transport layer is in contact with the light emitting layer, the light-emitting layer includes a first organic compound, a second organic compound, and a third organic compound that is a phosphorescent compound; the first organic compound and the second organic compound are a combination that forms an exciplex, the T1 level of the first organic compound is higher than the T1 level of the third organic compound; the T1 level of the second organic compound is higher than the T1 level of the third organic compound; the HOMO level of the first organic compound is lower than the HOMO level of the second organic compound; a LUMO level of the first organic compound is lower than a LUMO level of the second organic compound; the hole transport layer comprises a fourth organic compound having a HOMO level higher than a HOMO level of the second organic compound; the fourth organic compound has at least one of an aromatic amine skeleton, a carbazole skeleton, a thiophene skeleton, and a furan skeleton; At least one of the first electron transport layer and the second electron transport layer comprises a heteroaromatic compound; A light-emitting device, wherein the difference between the energy value of the peak of the emission spectrum of the exciplex and the energy value of the peak of the absorption band located on the lowest energy side of the absorption spectrum of the third organic compound is within 0.2 eV.

15. a hole injection layer, a hole transport layer, a light emitting layer, a first electron transport layer, and a second electron transport layer between an anode and a cathode; the hole transport layer is in contact with the light emitting layer, the light-emitting layer includes a first organic compound, a second organic compound, and a third organic compound that is a phosphorescent compound; the first organic compound and the second organic compound are a combination that forms an exciplex, the T1 level of the first organic compound is higher than the T1 level of the third organic compound; the T1 level of the second organic compound is higher than the T1 level of the third organic compound; the HOMO level of the first organic compound is lower than the HOMO level of the second organic compound; a LUMO level of the first organic compound is lower than a LUMO level of the second organic compound; the hole transport layer comprises a fourth organic compound having a HOMO level higher than a HOMO level of the second organic compound; the fourth organic compound is at least one of a π-excessive heteroaromatic compound and an aromatic amine compound; At least one of the first electron transport layer and the second electron transport layer comprises a heteroaromatic compound; A light-emitting device, wherein the difference between the energy value of the peak of the emission spectrum of the exciplex and the energy value of the peak of the absorption band located on the lowest energy side of the absorption spectrum of the third organic compound is within 0.1 eV.

16. A device comprising a hole injection layer, a hole transport layer, a light emitting layer, a first electron transport layer, and a second electron transport layer between an anode and a cathode, the hole transport layer is in contact with the light emitting layer, the light-emitting layer includes a first organic compound, a second organic compound, and a third organic compound that is a phosphorescent compound; the first organic compound and the second organic compound are a combination that forms an exciplex, the T1 level of the first organic compound is higher than the T1 level of the third organic compound; the T1 level of the second organic compound is higher than the T1 level of the third organic compound; the HOMO level of the first organic compound is lower than the HOMO level of the second organic compound; a LUMO level of the first organic compound is lower than a LUMO level of the second organic compound; the hole transport layer comprises a fourth organic compound having a HOMO level higher than a HOMO level of the second organic compound; the fourth organic compound has at least one of an aromatic amine skeleton, a carbazole skeleton, a thiophene skeleton, and a furan skeleton; At least one of the first electron transport layer and the second electron transport layer comprises a heteroaromatic compound; A light-emitting device, wherein the difference between the energy value of the peak of the emission spectrum of the exciplex and the energy value of the peak of the absorption band located on the lowest energy side of the absorption spectrum of the third organic compound is within 0.1 eV.

17. In any one of claims 1 to 16, the first organic compound is an electron transporting material, The light-emitting device, wherein the second organic compound is a hole transporting material.

18. In any one of claims 1 to 16, the first organic compound is a π-deficient heteroaromatic compound, The light-emitting device, wherein the second organic compound is a π-excess heteroaromatic compound.

19. In any one of claims 1 to 16, the first organic compound is a nitrogen-containing heteroaromatic compound; The second organic compound has at least one of an aromatic amine skeleton, a carbazole skeleton, a thiophene skeleton, and a furan skeleton.

20. In any one of claims 1 to 16, the first organic compound is a nitrogen-containing heteroaromatic compound; The second organic compound has a carbazole skeleton.

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