Light-emitting element, light-emitting device, electronic apparatus, and lighting apparatus

Abstract

To provide a light-emitting element which has low driving voltage and high luminous efficiency.SOLUTION: A light-emitting element comprises between a pair of electrodes, a hole transport layer; and a light-emitting layer formed on the hole transport layer. The light-emitting layer comprises a first organic compound having electron transport property, a second organic compound having hole transport property, and a luminescent third organic compound which converts triplet excitation energy into light emission. The first organic compound and the second organic compound are combination forming an excited complex. The hole transport layer is formed of two or more organic compounds and contains at least 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 is made of two or more organic compounds (e.g., a second organic compound and a hole transporting compound). and a fifth organic compound, characterized in that the composition has at least a second organic compound. This 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 made of two or more organic compounds (e.g. For example, the second organic compound and the fifth organic compound having a hole transporting property are used. The light-emitting element is characterized by having at least a second 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 their respective emission wavelengths (fluorescence wavelengths). Since the first organic compound (host material) and the second organic compound are present side by side, Converts the fluorescence spectrum of the object (assist material) into an emission spectrum located on the longer wavelength side. It is possible.

[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, the hole transport layer is formed of two or more organic compounds, and By including at least a second organic compound (assist material), the luminous efficiency of the luminescent layer can be improved. First, the hole transport layer is used in the light emitting layer, and the driving voltage of the light emitting layer can be reduced. By having a second organic compound (assist material) that Since holes are transported via the HOMO level, there is no hindrance to hole injection from the hole transport layer to the light emitting layer. The wall becomes extremely small. This reduces the driving voltage of the device. In addition, the hole transport layer By including an organic compound other than the second organic compound (assist material), the triple layer of the light-emitting layer can be formed. It is possible to suppress the diffusion of the excitation energy to the hole transport layer. The luminous efficiency of the element can be improved.

[0014] This effect is achieved when the hole transport layer is formed of two or more organic compounds, and the second organic compound For example, the hole transport layer is the first In the case where the organic compound of 2 is not included, the hole transport layer and the light emitting layer are separated by different HOMO levels. The driving voltage increases due to hole transport. On the other hand, the hole transport layer is made of the second organic compound. In the case where the layer is a layer consisting of only the second organic compound contained in both the light-emitting layer and the hole-transporting layer, The triplet excitation energy of the light-emitting layer is diffused to the hole transport layer through the material, so the light-emitting efficiency is improved. decreases.

[0015] In each of the above structures, the hole transport layer is a layer having a smaller thickness than the first organic compound (host material). It is preferable to have a fourth organic compound with a high low triplet excitation energy level (T1 level). The hole transport layer is made of a fourth organic compound (assist material) having a higher T1 level than the second organic compound (assist material). It is preferred to have an organic compound.

[0016] In this case, in order to obtain the effect of reducing the driving voltage, the second organic compound ( The mass fraction (or volume fraction) of the assist material is preferably 20% or more. In order to prevent the triplet excitation energy of the ZnO from diffusing to the hole transport layer, The mass fraction (or volume fraction) of the second organic compound (assist material) in the Therefore, the mass fraction (or volume fraction) of the fourth organic compound in the hole transport layer is preferably The percentage is also preferably 20% or more and 80% or less.

[0017] 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 The third organic compound (guest material) is a phosphorescent organometallic complex. preferable.

[0018] 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 , e.g. FPC (Flexible printed circuit) or TCP Module with (Tape Carrier Package) attached, TCP A module with a printed wiring board or a light emitting element with COG (Chip On Gate) All modules with ICs directly mounted using the Glass method are light-emitting devices. This includes: Effect of the Invention

[0019] Note that 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) and the third Energy transfer is performed by utilizing the overlap with the absorption spectrum 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. can.

[0020] Furthermore, in the light-emitting element of one embodiment of the present invention, the second By using the organic compound (assist material) The driving voltage (particularly the driving start voltage) of the element can be reduced. [Brief description of the drawings]

[0021] [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. 1 illustrates a concept of 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 current density-luminance characteristics of the light-emitting element shown in Example 2. [Figure 20] FIG. 13 shows voltage-luminance characteristics of the light-emitting element shown in Example 2. [Figure 21] FIG. 13 shows luminance-current efficiency characteristics of the light-emitting element shown in Example 2. [Figure 22] FIG. 13 shows voltage-current characteristics of the light-emitting element shown in Example 2. [Figure 23] FIG. 13 shows an emission spectrum of the light-emitting element shown in Example 2. [Figure 24] FIG. 13 shows current density-luminance characteristics of the light-emitting element shown in Example 3. [Diagram 25] FIG. 13 shows voltage-luminance characteristics of the light-emitting element shown in Example 3. [Figure 26] FIG. 13 shows luminance-current efficiency characteristics of the light-emitting element shown in Example 3. [Figure 27] FIG. 13 shows voltage-current characteristics of the light-emitting element shown in Example 3. [Figure 28] FIG. 13 shows an emission spectrum of the light-emitting element shown in Example 3. [Figure 29] FIG. 13 shows current density-luminance characteristics of the light-emitting element shown in Example 4. [Diagram 30] FIG. 13 shows voltage-luminance characteristics of the light-emitting element shown in Example 4. [Diagram 31] FIG. 13 shows luminance-current efficiency characteristics of the light-emitting element shown in Example 4. [Diagram 32] FIG. 13 shows voltage-current characteristics of the light-emitting element shown in Example 4. [Diagram 33] FIG. 13 shows an emission spectrum of the light-emitting element shown in Example 4. [Diagram 34] FIG. 13 is a graph showing drive time vs. normalized luminance characteristics of the light-emitting element shown in Example 4. [Diagram 35] FIG. 13 shows current density-luminance characteristics of the light-emitting element shown in Example 5. [Diagram 36] FIG. 13 shows voltage-luminance characteristics of the light-emitting element shown in Example 5. [Figure 37] FIG. 13 shows luminance-current efficiency characteristics of the light-emitting element shown in Example 5. [Figure 38] FIG. 13 shows voltage-current characteristics of the light-emitting element shown in Example 5. [Figure 39] FIG. 13 shows an emission spectrum of the light-emitting element shown in Example 5. [Diagram 40] FIG. 13 is a graph showing drive time vs. normalized luminance characteristics of the light-emitting element shown in Example 5. [Diagram 41] FIG. 13 shows current density-luminance characteristics of the light-emitting element shown in Example 6. [Diagram 42] FIG. 13 shows voltage-luminance characteristics of the light-emitting element shown in Example 6. [Diagram 43] FIG. 13 shows luminance-current efficiency characteristics of the light-emitting element shown in Example 6. [Diagram 44] FIG. 13 shows voltage-current characteristics of the light-emitting element shown in Example 6. [Diagram 45] FIG. 13 shows an emission spectrum of the light-emitting element shown in Example 6. [Figure 46]FIG. 13 shows current density-luminance characteristics of the light-emitting element shown in Example 7. [Figure 47] FIG. 13 shows voltage-luminance characteristics of the light-emitting element shown in Example 7. [Figure 48] FIG. 13 shows luminance-current efficiency characteristics of the light-emitting element shown in Example 7. [Figure 49] FIG. 13 shows voltage-current characteristics of the light-emitting element shown in Example 7. [Figure 50] FIG. 13 shows an emission spectrum of the light-emitting element shown in Example 7. [Figure 51] FIG. 1 shows the phosphorescence emission spectrum of 2mDBTPDBq-II (abbreviation). [Figure 52] FIG. 1 shows the phosphorescence emission spectrum of PCzPCN1 (abbreviation). [Figure 53] FIG. 1 shows the phosphorescence emission spectrum of DPA2SF (abbreviation). [Figure 54] FIG. 1 shows the phosphorescence emission spectrum of BPAFLP (abbreviation). [Figure 55] FIG. 1 shows the phosphorescence emission spectrum of PCPPn (abbreviation). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] 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.

[0023] 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.

[0024] 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.

[0025] (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.

[0026] 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 two or more organic compounds (e.g., a second organic compound and a fifth organic compound having a hole transporting property), Contains organic compound 122.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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

[0033] 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).

[0034] 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.

[0035] 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)).

[0036] 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.

[0037] 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

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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)).

[0044] 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.

[0045] 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

[0046] 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 The calculations were done.

[0047] 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

[0048] 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.

[0049] 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. .

[0050] 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.

[0051] The quantum chemical calculation program used was Gaussian 09. The experiment was carried out using a high-performance computer (SGI, Altix 4700). .

[0052] 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.

[0053] 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 DBq ( 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).

[0054] 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

[0055] 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 of the dimers of DBq (abbreviation) and TPA (abbreviation), and Fig. 4(F ... The HOMO distributions of the dimers of Bq (abbreviation) and TPA (abbreviation), respectively, are shown.

[0056] 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...

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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."

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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 ...

[0073] 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.

[0074] 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.

[0075] 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.

[0076] In the case of the structure shown in FIG. 5A, the T1 level of the hole transport layer 112a is the same as that of the second organic compound 12. 2 (assist material), the excitation energy is transferred from the light-emitting layer 113 to the hole transport layer 112a. This makes it difficult for the light to diffuse, and the light emitting efficiency of the light emitting layer 113 can be improved. The pressure can be controlled by appropriately selecting the second organic compound (to appropriately control the emission wavelength of the exciplex). However, the driving voltage in the practical luminance range of the element is The electromotive voltage is also affected by the HOMO level of the hole transport layer 112a. Since the HOMO level of the hole transport layer 112a is lower than that of the light emitting layer 1, the The movement of holes to 13 does not proceed smoothly, and the IV characteristics are poor, especially in the high brightness (practical brightness) region. As a result, it becomes difficult to reduce the driving voltage.

[0077] Next, the energy level of the hole transport layer 112b shown in FIG. 5B is changed to that of the second organic compound 1. 22 (assist material) and one organic compound with the same T1 level and HOMO level The structure in which the transport layer 112b is formed is illustrated. That is, the hole transport layer 112b This is the case where the second organic compound 122 is formed from the same type of material as the second organic compound 122 (assist material).

[0078] In the case of the configuration shown in FIG. 5B, the HOMO level of the light-emitting layer 113 that forms an exciplex and a hole Since the HOMO level of the transport layer 112b is the same, the driving voltage of the light-emitting layer 113 can be reduced to the limit. However, a phenomenon that the luminous efficiency of the light-emitting layer 113 decreases is observed. This phenomenon occurs when the second organic compound 122 (assist material) in the light-emitting layer 113 and the same kind of material In order to use a material for the hole transport layer 112b, the triplet excitation energy of the light emitting layer 113 is This is believed to be because the electrons diffuse to the transport layer 112b.

[0079] Next, the energy level of the hole-transport layer 112c shown in FIG. 5C is one embodiment of the present invention. The organic compound 122 is formed of two or more organic compounds, and at least the second organic compound 122 (aza The hole transport layer 112c having a silicon nitride film (a silicon nitride material) is formed. The energy level of the hole transport layer 112c shown in FIG. 5C is The T1 level is higher than that of the second organic compound 122, and the HO level is higher than that of the second organic compound 122. The hole transport layer 112c includes a fourth organic compound 126 having a low MO level. do.

[0080] In the case of the structure shown in FIG. 5C, due to the influence of the fourth organic compound 126 having a high T1 level, The HOMO level can be lower than that of the second organic compound 122. The excitation energy is less likely to diffuse from the layer 113 to the hole transport layer 112c, and the light emission of the light emitting layer 113 In addition, the hole transport layer 112c has a fourth fluorine atom having a low HOMO level. Although the organic compound 126 is included, the second organic compound 122 is included. It is possible to reduce not only the drive start voltage but also the drive voltage in the practical brightness range.

[0081] 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.

[0082] 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.

[0083] In addition, the light-emitting element described in this embodiment mode has a second conductive layer having a hole-transporting property. The organic compound is also contained in the hole transport layer. The driving voltage of the optical element, particularly the driving start voltage, is lowered by the second organic compound contained in the hole transport layer. In addition, the light-emitting element according to one embodiment of the present invention can be formed only from the second organic compound. Compared with the hole transport layer formed in the first organic layer, the layer also contains materials other than the second organic compound, so that the three The diffusion of the doublet excitation energy is suppressed by a material other than the second organic compound, and the luminescence efficiency is high. An excellent light emitting element can be obtained.

[0084] Note that the structure described in this embodiment mode may be used in appropriate combination with structures described in other embodiments. It is possible.

[0085] (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.

[0086] 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 formed of two or more organic compounds. and has at least a second organic compound 122 .

[0087] 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.

[0088] 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.

[0089] A specific example of manufacturing the light-emitting element described in this embodiment mode will be described below.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] 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.

[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, it is preferable that the absorption edge of the absorption spectrum is 440 nm or less. It is preferable that

[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 Tris(4-methyl-6-phenylpyrimidinato)iridium(III) (abbreviation: Ir(m ppm)3), tris(4-t-butyl-6-phenylpyrimidinato)iridium(II I) (abbreviation: Ir(tBuppm)3), (acetylacetonato)bis(6-methyl-4 -phenylpyrimidinato)iridium(III) (abbreviation: Ir(mppm)2(acac )), (acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidinate ) 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] In addition, examples of phosphorescent materials having an emission peak at 600 nm to 700 nm include biphenyls. S[4,6-bis(3-methylphenyl)pyrimidinato](diisobutyrylmethanato) Ir(III) (abbreviation: Ir(5mdppm)2(dibm)), bis[4,6-bi bis(3-methylphenyl)pyrimidinato](dipivaloylmethanato)iridium(III) ) (abbreviation: Ir(5mdppm)2(dpm)), bis[4,6-di(naphthalene-1- Ir(dyl)pyrimidinato](dipivaloylmethanato)iridium(III) Organometallic iridium complexes with pyrimidine skeletons such as 1npm)2(dpm) and (Acetylacetonato)bis(2,3,5-triphenylpyrazinate)iridium(II I) (abbreviation: Ir(tppr)2(acac)), bis(2,3,5-triphenylpyridine) dipivaloylmethanato)iridium(III) (abbreviation: Ir(tppr)2( dpm), (acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoline xalinato]iridium(III) (abbreviation: Ir(Fdpq)2(acac)) Organometallic iridium complexes with pyrazine skeletons and tris(1-phenylisoquinolinato -N,C 2’ ) Iridium(III) (abbreviation: Ir(piq)3), bis(1-phenyl Isoquinolinato-N,C 2’) Iridium(III) acetylacetonate (abbreviation: Ir In addition to organometallic iridium complexes with pyridine skeletons such as (piq)2acac), 2 ,3,7,8,12,13,17,18-Octaethyl-21H,23H-porphyrin Platinum complexes such as platinum(II) (abbreviation: PtOEP) and tris(1,3-diphenyl- 1,3-Propanedionato)(monophenanthroline)europium(III)(abbreviation: Eu(DBM)3(Phen)), tris[1-(2-thenoyl)-3,3,3-triphenylphosphine]

[0046] (monophenanthroline)europium(III) (abbreviation: Eu(T Among the above, rare earth metal complexes such as pyrimidinium phosphate (TA)3(Phen) are also available. Organometallic iridium complexes with an iridium skeleton have outstanding reliability and luminescence efficiency. In addition, organometallic iridium complexes having a pyrazine skeleton are particularly preferred. Colored 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. The organic compound is also contained in the hole transport layer. The driving voltage of the optical element, particularly the driving start voltage, is lowered by the second organic compound contained in the hole transport layer. In addition, the light-emitting element according to one embodiment of the present invention can be formed only from the second organic compound. Compared with the hole transport layer formed in the first organic layer, the layer also contains materials other than the second organic compound, so that the three The diffusion of the doublet excitation energy is suppressed by a material other than the second organic compound, and the luminescence efficiency is high. An excellent light emitting element can be obtained.

[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.

[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 FIG. 7A, a light emitting element having two light emitting layers has been described. In FIG. As shown in the figure, for a light-emitting device having n light-emitting layers (where n is 3 or more), The same can be applied to the light emitting device according to the present embodiment. When the device has a plurality of light-emitting layers, the charge generating layer 313 is disposed between the light-emitting layers. This allows light emission in a high brightness range while keeping the current density low. In addition, when applied to lighting, the resistance of the electrode material is This reduces the voltage drop caused by the driving voltage, enabling uniform light emission over a large area. It is possible to realize a light emitting device that is capable of realizing a light emitting device with 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 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 this in more detail.

[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 and a housing 622. , 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 according to 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 ( Comparative light-emitting element 2, comparative light-emitting element 3, and comparative light-emitting element 4 will be described with reference to FIG. 13. The chemical formulas of the materials used in this example are shown below.

[0192] [ka]

[0193] [ka]

[0194] The light-emitting element 1 of this example, the comparative light-emitting element 2, the comparative light-emitting element 3, and the comparative light-emitting element are described below. The method for producing 4 is shown 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 The weight ratio of DBT3P-II to molybdenum oxide was adjusted to 4:2 (=DBT3P-II:molybdenum oxide). The co-evaporation method is a method in which deposition is performed simultaneously from multiple evaporation sources in one processing chamber. .

[0199] Next, 4-phenyl-4'-(9-phenylfluorene-9 -yl)triphenylamine (abbreviation: BPAFLP) and 3-[N-(1-naphthyl)-N -(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole (abbreviation A hole transport layer 1112 was formed by co-evaporating ZnPCN1 and ZnO. 20 nm, and the ratio of BPAFLP (abbreviation) to PCzPCN1 (abbreviation) was 0. The ratio was adjusted to 5:0.5 (=BPAFLP:PCzPCN1).

[0200] Next, on the hole transport layer 1112, 2-[3-(dibenzothiophen-4-yl)phenyl 2mDBTPDBq-II and PCzP CN1 (abbreviation) and bis{2-[6-(3,5-dimethylphenyl)-4-pyrimidinyl -κN3]-4,6-dimethylphenyl-κC}(2,6-dimethyl-3,5-heptane Geonath-κ 2 O,O') Iridium(III) (abbreviation: [Ir(dmdppm)2(d ibm)]) was co-evaporated to form the first light-emitting layer 1113a. PDBq-II (abbreviation), PCzPCN1 (abbreviation), and [Ir(dmdppm)2(d The weight ratio of 2mDBTPDBq-I I:PCzPCN1:[Ir(dmdppm)2(dibm)]) The thickness of the first light emitting layer 1113a was set to 20 nm.

[0201] In the first light-emitting layer 1113a, 2mDBTPDBq-II (abbreviation) is The first organic compound (host material) is PCzPCN1 (abbreviation), and the second organic compound ( The third organic compound, [Ir(dmdppm)2(dibm)] (abbreviation) Compound (guest material).

[0202] Next, 2mDBTPDBq-II (abbreviation) and PCzP CN1 (abbreviation) and [Ir(dmdppm)2(dibm)] (abbreviation) are co-evaporated, The second light-emitting layer 1113b was formed. The weight ratio of zPCN1 (abbreviation) and [Ir(dmdppm)2(dibm)] (abbreviation) is , 0.8:0.2:0.05(=2mDBTPDBq-II:PCzPCN1:[Ir( dmdppm)2(dibm)]). The second light-emitting layer 1113 The film thickness of b was set to 20 nm.

[0203] In the second light-emitting layer 1113b, 2mDBTPDBq-II (abbreviation) is The first organic compound (host material) is PCzPCN1 (abbreviation), and the second organic compound ( The third organic compound, [Ir(dmdppm)2(dibm)] (abbreviation) Compound (guest material).

[0204] 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.

[0205] 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.

[0206] 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.

[0207] 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.

[0208] In the above-mentioned deposition process, the deposition was all performed by a resistance heating method.

[0209] (Comparative light-emitting element 2) The comparative light-emitting element 2 includes the light-emitting element 1, a hole-transport layer 1112, a first light-emitting layer 1113a, and The configuration of the second light emitting layer 1113b is different, and the other configurations are the same. The following is described below.

[0210] 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.

[0211] On the hole transport layer 1112, 2mDBTPDBq-II (abbreviation) and 4-phenyl-4' -(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCB A1BP) and [Ir(dmdppm)2(dibm)] (abbreviation) were co-evaporated to form the first The light-emitting layer 1113a was formed using the following: 2mDBTPDBq-II (abbreviation), PCBA The weight ratio of 1BP (abbreviation) and [Ir(dmdppm)2(dibm)] (abbreviation) is 0. .7:0.3:0.06(=2mDBTPDBq-II:PCBA1BP:[Ir(dm The first light-emitting layer 1113a was adjusted to have a refractive index of 1.25 ppm / dppm. The film thickness was 20 nm.

[0212] 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(dmdppm)2(dibm)] (abbreviation) Compound (guest material).

[0213] On the first light-emitting layer 1113a, 2mDBTPDBq-II (abbreviation) and PCBA1BP (abbreviation) and [Ir(dmdppm)2(dibm)] (abbreviation) were co-evaporated to form the second The light-emitting layer 1113b was formed. The weight ratio of BP (abbreviation) and [Ir(dmdppm)2(dibm)] (abbreviation) is 0. 8:0.2:0.05(=2mDBTPDBq-II:PCBA1BP:[Ir(dmd The film of the second light-emitting layer 1113b was adjusted to have a concentration of 1 ppm (dibm). The thickness was set to 20 nm.

[0214] 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(dmdppm)2(dibm)] (abbreviation) Compound (guest material).

[0215] (Comparative light-emitting element 3) The comparative light-emitting element 3 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.

[0216] 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.

[0217] (Comparative light-emitting element 4) The comparative light-emitting element 4 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.

[0218] PCzPCN1 (abbreviation) is deposited on the hole injection layer 1111 to form a hole transport layer 11 12 was formed. The film thickness was set to 20 nm.

[0219] The light-emitting element 1, the comparative light-emitting element 2, the comparative light-emitting element 3, and the comparative light-emitting element obtained above The element structure of 4 is shown in Table 1.

[0220] [Table 1]

[0221] The light-emitting element 1, the comparative light-emitting element 2, the comparative light-emitting element 3, and the comparative light-emitting element 4 were In the glove box, each light-emitting element is sealed with a glass substrate to prevent it from being exposed to the atmosphere. The sealing process is carried out (sealing material is applied around the element, and heat treatment is performed at 80°C for 1 hour during sealing). After that, the operating characteristics of these light-emitting devices were measured. The experiment was carried out in an atmosphere maintained at 5°C.

[0222] Current density vs. luminance of light-emitting element 1, comparative light-emitting element 2, comparative light-emitting element 3, and comparative light-emitting element 4 The characteristics are shown in Figure 14. In Figure 14, the horizontal axis represents the current density (mA / cm 2 ) and the vertical axis is brightness. (cd / m 2 ) are represented as light-emitting element 1, comparative light-emitting element 2, comparative light-emitting element 3, and comparative 15 shows the voltage-luminance characteristics of the light-emitting element 4. In FIG. 15, the horizontal axis represents voltage (V) and the vertical axis represents The axis is luminance (cd / m 2 ) are represented as follows: Light-emitting element 1, comparative light-emitting element 2, comparative light-emitting element 3, 16 shows the luminance-current efficiency characteristics of the light-emitting element 1 and the comparative light-emitting element 4. In FIG. (cd / m 2 ), and the vertical axis represents current efficiency (cd / A). FIG. 17 shows the voltage-current characteristics of the light-emitting element 2, the comparative light-emitting element 3, and the comparative light-emitting element 4. In the graph, the horizontal axis represents voltage (V) and the vertical axis represents current (mA). FIG. 18 shows the emission spectra of the light-emitting element 2, the comparative light-emitting element 3, and the comparative light-emitting element 4. 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 is shown roughly overlapping.

[0223] In addition, the luminance of each light-emitting element is 1000 cd / m 2Voltage (V) and current density near (mA / cm 2 ), CIE chromaticity coordinates (x, y), current efficiency (cd / A), external quantum efficiency ( %) are shown in Table 2.

[0224] [Table 2]

[0225] As shown in Table 2, the luminance is 1036cd / m 2 The CIE chromaticity coordinates of light-emitting element 1 are (x,y )=(0.63,0.38). The luminance was 1162cd / m 2 Comparison of light-emitting elements 2 The CIE chromaticity coordinates of are (x,y)=(0.63,0.37). The luminance is 841 cd / m 2 The CIE chromaticity coordinates of the comparative light-emitting element 3 are (x,y)=(0.63,0.37). The brightness was 1217cd / m 2 The CIE chromaticity coordinates of the comparative light-emitting element 4 are (x, y)=(0.63,0.37).

[0226] The brightness is 1036cd / m 2 The voltage of the light-emitting element 1 is 2.6 V, and the current efficiency is 53 cd / A. The brightness was 1162cd / m 2 The voltage of the comparison light-emitting element 2 is 3.0V. The current efficiency was 53 cd / A. The luminance was 841 cd / m 2 Comparison of light-emitting elements 3 The voltage was 2.9 V, and the current efficiency was 53 cd / A. The luminance was 1217 cd / A. m 2 The voltage of the comparative light-emitting element 4 was 2.6 V, and the current efficiency was 47 cd / A.

[0227] Therefore, the light-emitting element 1 which is one embodiment of the present invention is similar to the comparative light-emitting element 2 and the comparative light-emitting element 3. Compared to the previous model, the voltage can be reduced by 0.3V to 0.4V while maintaining the same current efficiency. In addition, it was confirmed that the light-emitting element 1 of one embodiment of the present invention had a higher It was confirmed that the voltage could be reduced to the same extent and the current efficiency could be increased by 6 cd / A.

[0228] This result can be explained as follows. First, PCzPCN1 (abbreviation The HOMO levels of the thin films of PCBA1BP (abbreviation) and BPAFLP (abbreviation) are as follows: The HOMO levels are -5.15 eV, -5.42 eV, and -5.63 eV, respectively. The value of the ionization potential was measured by photoelectron spectroscopy in air (Riken Keiki Co., Ltd., AC-2). The same applies to the following examples.

[0229] The HOMO of the second organic compound (PCBA1BP) used in the light-emitting layer of the comparative light-emitting element 2 The level is lower than that of the second organic compound (PCzPCN1) used in the light-emitting element 1. As a result, the first organic compound (2mDBTPDBq-II) was formed with As a result, the driving start voltage of the comparative light-emitting element 2 is On the other hand, the comparative light-emitting elements 3 and 4 have the same light-emitting layer configuration as the light-emitting element 1. Since they are the same, the drive start voltages are almost the same.

[0230] However, in the comparative light-emitting element 3, the hole transport layer is made of the second organic compound (PCzPC Since it is composed only of BPAFLP, which has a much lower HOMO level than N1), it is a hole transport The movement of holes from the layer to the light-emitting layer does not proceed smoothly, and the voltage-current characteristics in the high brightness (practical brightness) range are poor. As a result, the image quality is worse at 1000cd / m 2The driving voltage in the vicinity is As a result, a high voltage shift occurs as in the comparative light-emitting element 2.

[0231] For the comparative light-emitting element 4, the second organic compound (PCzPCN1) of the light-emitting layer was added to the hole transport layer. ) is used, the voltage-current characteristics are generally the same as those of the light-emitting element 1. However, However, since the hole transport layer is made of only PCzPCN1, the triplet excitation energy of the emission layer is Energy diffuses into the hole transport layer, resulting in low external quantum efficiency (luminous efficiency) and current efficiency. It is clear that it is declining.

[0232] As described above, the light-emitting element 1 according to one embodiment of the present invention has a lower The voltage was maintained and the current efficiency was high.

[0233] As described above, the light-emitting element of one embodiment of the present invention has a light-emitting layer (the first light-emitting layer 1113a and The second organic compound having a hole transporting property used in the second light emitting layer 1113b) is a hole transporting compound. In this element configuration, the light-emitting element is also included in the layer 1112. (both the driving voltage at the driving start and the driving voltage in the practical luminance region) The light-emitting element according to one embodiment of the present invention can be made lower by using an organic compound. Compared with a hole transport layer formed only of an organic compound, the hole transport layer also contains a material other than the second organic compound. Therefore, the diffusion of triplet excitation energy from the light-emitting layer is suppressed by a material other than the second organic compound. In addition, an excellent light-emitting element with high luminous efficiency can be obtained.

[0234] The first organic compound (2mDBTPDB The PL peak wavelength of the thin film of q-II) is 426 nm, and the second organic compound (PCzPCN1) The PL peak wavelength of the mixed film is 571 nm. It was found that the wavelengths of the two organic compounds were shifted to longer wavelengths. is a combination that forms an exciplex. EXAMPLES

[0235] In this example, a light-emitting element of one embodiment of the present invention (light-emitting element 5) and a comparative light-emitting element ( Comparative light-emitting element 6 and comparative light-emitting element 7 will be described with reference to FIG. The chemical formulas of the materials used in the examples are given below.

[0236] [ka]

[0237] [ka]

[0238] The methods for fabricating the light-emitting element 5 of this example, the comparative light-emitting element 6, and the comparative light-emitting element 7 are described below. vinegar.

[0239] (Light emitting element 5) First, on a substrate 1100, indium oxide-tin oxide containing silicon or silicon oxide is A compound (ITSO) was deposited by sputtering to form a first electrode 1101. The composition of the target used was In2O3:SnO2:SiO2=85:10:5 [weight The thickness of the first electrode 1101 was 110 nm, and the area of ​​the electrode was 2 mm The first electrode 1101 is an electrode that functions as an anode of the light-emitting element. be.

[0240] 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.

[0241] 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.

[0242] 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 is reduced to about Pa, a deposition method using resistance heating is used to deposit D The hole injection layer 1111 is formed by co-evaporating BT3P-II (abbreviation) 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).

[0243] Next, on the hole injection layer 1111, BPAFLP (abbreviation) and 2,7-bis[N-(4-di phenylaminophenyl)-N-phenylamino]-spiro-9,9'-bifluorene ( The hole transport layer 1112 was formed by co-evaporation of 2,4-dichloroethane (abbreviation: DPA2SF). , 20nm, and the ratio of BPAFLP (abbreviation) to DPA2SF (abbreviation) is 0. The ratio was adjusted to 5:0.5 (=BPAFLP:DPA2SF).

[0244] Next, on the hole transport layer 1112, 2mDBTPDBq-II (abbreviation) and DPA2SF (abbreviation) and [Ir(dmdppm)2(dibm)] (abbreviation) were co-evaporated to form a first The light-emitting layer 1113a was formed. The weight ratio of F (abbreviation) and [Ir(dmdppm)2(dibm)] (abbreviation) is 0.7 :0.3:0.06(=2mDBTPDBq-II:DPA2SF:[Ir(dmdpp The thickness of the first light-emitting layer 1113a was adjusted to be 2(dibm). The thickness was set to 20 nm.

[0245] In the first light-emitting layer 1113a, 2mDBTPDBq-II (abbreviation) is The first organic compound (host material) is DPA2SF (abbreviation), and the second organic compound (acid [Ir(dmdppm)2(dibm)] (abbreviation) is the third organic compound. The guest material is a

[0246] Next, 2mDBTPDBq-II (abbreviation) and DPA2 SF (abbreviation) and [Ir(dmdppm)2(dibm)] (abbreviation) are co-evaporated, and the first The light-emitting layer 1113b of 2 was formed. The weight ratio of 2SF (abbreviation) and [Ir(dmdppm)2(dibm)] (abbreviation) is 0. .8:0.2:0.05(=2mDBTPDBq-II:DPA2SF:[Ir(dmd The film of the second light-emitting layer 1113b was adjusted to have a concentration of 1 ppm (dibm). The thickness was set to 20 nm.

[0247] In the second light-emitting layer 1113b, 2mDBTPDBq-II (abbreviation) is The first organic compound (host material) is DPA2SF (abbreviation), and the second organic compound (acid [Ir(dmdppm)2(dibm)] (abbreviation) is the third organic compound. The guest material is a

[0248] 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.

[0249] Next, BPhen (abbreviation) was deposited on the first electron transport layer 1114a to a thickness of 20 nm. A second electron-transporting layer 1114b was formed.

[0250] 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.

[0251] Finally, a second electrode 1103 functioning as a cathode was prepared by depositing 20% ​​aluminum (Al). The light-emitting element 5 of this example was fabricated by depositing the layer so as to have a film thickness of 0 nm.

[0252] In the above-mentioned deposition process, the deposition was all performed by a resistance heating method.

[0253] (Comparative light-emitting element 6) The comparative light-emitting element 6 is different from the light-emitting element 5 in the configuration of the hole transport layer 1112. Only the different configurations will be described below.

[0254] 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.

[0255] (Comparative light-emitting element 7) The comparative light-emitting element 7 is different from the light-emitting element 5 in the configuration of the hole transport layer 1112. Only the different configurations will be described below.

[0256] DPA2SF (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.

[0257] The device structures of the thus obtained light-emitting element 5, comparative light-emitting element 6, and comparative light-emitting element 7 are shown below. Shown in 3.

[0258] [Table 3]

[0259] The light-emitting element 5, the comparative light-emitting element 6, and the comparative light-emitting element 7 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) The sealing material was applied around the element, and heat treatment was performed at 80°C for 1 hour during sealing. The operating characteristics of these light-emitting devices were measured. The measurements were performed at room temperature (25°C). The experiment was conducted in an atmospheric condition.

[0260] FIG. 19 shows current density-luminance characteristics of the light-emitting element 5, the comparative light-emitting element 6, and the comparative light-emitting element 7. In Figure 19, the horizontal axis represents the current density (mA / cm 2 ) and the vertical axis is luminance (cd / m 2 )of FIG. 2 shows the voltage-luminance characteristics of the light-emitting element 5, the comparative light-emitting element 6, and the comparative light-emitting element 7. 0. In FIG. 20, the horizontal axis represents voltage (V) and the vertical axis represents luminance (cd / m 2 ) is represented. FIG. 21 shows the luminance-current efficiency characteristics of the light-emitting element 5, the comparative light-emitting element 6, and the comparative light-emitting element 7. In FIG. 21, the horizontal axis is luminance (cd / m 2 ), and the vertical axis represents the current efficiency (cd / A). FIG. 22 shows the voltage-current characteristics of the light-emitting element 5, the comparative light-emitting element 6, and the comparative light-emitting element 7. In FIG. 22, the horizontal axis represents voltage (V) and the vertical axis represents current (mA). FIG. 23 shows the emission spectra of the light-emitting element 5, the comparative light-emitting element 6, and the comparative light-emitting element 7. In FIG. 23, the horizontal axis represents the wavelength (nm) and the vertical axis represents the emission intensity (arbitrary unit). The data for each light emitting element is shown roughly overlapping.

[0261] 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.

[0262] [Table 4]

[0263] As shown in Table 4, the luminance is 1025cd / m 2 The CIE chromaticity coordinates of the light-emitting element 5 are (x, y )=(0.62,0.38). The luminance was 875cd / m 2 Comparison of light-emitting element 6 The CIE chromaticity coordinates are (x,y)=(0.62,0.38). The luminance is 739c d / m 2 The CIE chromaticity coordinates of the comparative light-emitting element 7 are (x,y)=(0.62,0.38). there were.

[0264] Also, the brightness is 1025cd / m 2 The voltage of the light-emitting element 5 is 2.7 V, and the current efficiency is 50 cd / A. The brightness was 875cd / m 2 The voltage of the comparative light-emitting element 6 is 2.9V. The current efficiency was 53 cd / A. The luminance was 739 cd / m 2 Comparison of light-emitting element 7 The voltage was 2.5 V and the current efficiency was 44 cd / A.

[0265] Therefore, the light-emitting element 5 of one embodiment of the present invention has a lower voltage than the comparative light-emitting element 6. It was confirmed that the voltage can be reduced by 0.2 V while maintaining the same current efficiency. The light-emitting element 5 according to one embodiment of the present invention has a voltage equivalent to that of the comparative light-emitting element 7, and It was confirmed that the current efficiency could be increased by 6 cd / A.

[0266] This result can be explained as follows. First, DPA2SF (abbreviation) used in this example The HOMO levels of the thin films of , and BPAFLP (abbreviation) are -5.09 eV, -5.63 eV.

[0267] The comparative light-emitting elements 6 and 7 have the same light-emitting layer configuration as the light-emitting element 5. However, in the comparative light-emitting element 6, the hole transport layer is the second organic layer of the light-emitting layer. The compound consists only of BPAFLP, which has a much lower HOMO level than the compound (DPA2SF). Therefore, the movement of holes from the hole transport layer to the light emitting layer does not proceed smoothly, and the high brightness (practical brightness) region is As a result, the voltage-current characteristics at 1000cd / m 2 Nearby The driving voltage at has shifted to a higher voltage.

[0268] On the other hand, in the comparative light-emitting element 7, the second organic compound (DPA2 Since the same material as that of the light-emitting element 5 is used, the voltage-current characteristics are almost the same as those of the light-emitting element 5. However, since the hole transport layer is made of only DPA2SF, the triplet excited electrons in the emission layer The energy diffuses to the hole transport layer, resulting in a decrease in the external quantum efficiency (luminous efficiency) and current efficiency. As a result, the light-emitting element 5 has the highest power efficiency.

[0269] As described above, the light-emitting element 5 according to one embodiment of the present invention is similar to the comparative light-emitting element 6 and the comparative light-emitting element 7. Compared to the conventional method, it maintained a low voltage and had a high current efficiency.

[0270] As described above, the light-emitting element of one embodiment of the present invention has a light-emitting layer (the first light-emitting layer 1113a and The second organic compound having a hole transporting property used in the second light emitting layer 1113b) is a hole transporting compound. In this element configuration, the light-emitting element is also included in the layer 1112. (both the driving voltage at the driving start and the driving voltage in the practical luminance region) The light-emitting element according to one embodiment of the present invention can be made lower by using an organic compound. Compared with a hole transport layer formed only of an organic compound, the hole transport layer also contains a material other than the second organic compound. Therefore, the diffusion of triplet excitation energy from the light-emitting layer is suppressed by a material other than the second organic compound. In addition, an excellent light-emitting element with high luminous efficiency can be obtained.

[0271] The first organic compound (2mDBTPDB The PL peak wavelength of the thin film of q-II) is 426 nm, and that of the second organic compound (DPA2SF) is The PL peak wavelength of these mixed films is 579 nm, while that of the other films is 433 nm. It was found that the emission wavelengths of these two organic compounds are shifted to longer wavelengths. , a combination that forms an exciplex. EXAMPLES

[0272] In this example, a light-emitting element of one embodiment of the present invention (light-emitting element 8) and a comparative light-emitting element ( The comparative light-emitting element 9 and the comparative light-emitting element 10 will be described with reference to FIG. The chemical formulas of the materials used in the examples are given below.

[0273] [ka]

[0274] [ka]

[0275] The methods for fabricating the light-emitting element 8 of this example, the comparative light-emitting element 9, and the comparative light-emitting element 10 are described below. show.

[0276] (Light emitting element 8) First, on a substrate 1100, indium oxide-tin oxide containing silicon or silicon oxide is A compound (ITSO) was deposited by sputtering to form a first electrode 1101. The composition of the target used was In2O3:SnO2:SiO2=85:10:5 [weight The thickness of the first electrode 1101 was 110 nm, and the area of ​​the electrode was 2 mm The first electrode 1101 is an electrode that functions as an anode of the light-emitting element. be.

[0277] 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.

[0278] 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.

[0279] 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 is reduced to about Pa, a deposition method using resistance heating is used to deposit D The hole injection layer 1111 is formed by co-evaporating BT3P-II (abbreviation) 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).

[0280] Next, BPAFLP (abbreviation) and PCzPCN1 (abbreviation) were co-formed on the hole injection layer 1111. The hole transport layer 1112 was formed by vapor deposition. The thickness of the layer was set to 20 nm. The weight ratio of LP (abbreviation) to PCzPCN1 (abbreviation) was 0.5:0.5 (=BPAF The concentration was adjusted to be LP:PCzPCN1).

[0281] Next, on the hole transport layer 1112, 2mDBTPDBq-II (abbreviation) and PCzPCN 1 (abbreviation) and (acetylacetonato)bis(4,6-diphenylpyrimidinato)iridine Ir(dppm)2(acac)] and 1H2O3 were co-evaporated to form the first The light-emitting layer 1113a was formed. Here, 2mDBTPDBq-II (abbreviation), PCzPC The weight ratio of N1 (abbreviation) and [Ir(dppm)2(acac)] (abbreviation) was 0.7: 0.3:0.06(=2mDBTPDBq-II:PCzPCN1:[Ir(dppm) 2(acac)]). The thickness of the first light-emitting layer 1113a was adjusted to 20 nm.

[0282] In the first light-emitting layer 1113a, 2mDBTPDBq-II (abbreviation) is The first organic compound (host material) is PCzPCN1 (abbreviation), and the second organic compound ( The third organic compound is [Ir(dppm)2(acac)] (abbreviation). The guest material is

[0283] Next, 2mDBTPDBq-II (abbreviation) and PCzP CN1 (abbreviation) and [Ir(dppm)2(acac)] (abbreviation) are co-evaporated to form a second The light-emitting layer 1113b was formed using the following: 2mDBTPDBq-II (abbreviation), PCzP The weight ratio of CN1 (abbreviation) and [Ir(dppm)2(acac)] (abbreviation) is 0.8 :0.2:0.05(=2mDBTPDBq-II:PCzPCN1:[Ir(dppm The thickness of the second light-emitting layer 1113b was adjusted to 2(acac). The thickness was set to 0 nm.

[0284] In the second light-emitting layer 1113b, 2mDBTPDBq-II (abbreviation) is The first organic compound (host material) is PCzPCN1 (abbreviation), and the second organic compound ( The third organic compound is [Ir(dppm)2(acac)] (abbreviation). The guest material is

[0285] 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.

[0286] Next, BPhen (abbreviation) was deposited on the first electron transport layer 1114a to a thickness of 20 nm. A second electron-transporting layer 1114b was formed.

[0287] 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.

[0288] Finally, a second electrode 1103 functioning as a cathode was prepared by depositing 20% ​​aluminum (Al). The light-emitting element 8 of this example was fabricated by depositing the layer so as to have a film thickness of 0 nm.

[0289] In the above-mentioned deposition process, the deposition was all performed by a resistance heating method.

[0290] (Comparative light-emitting element 9) The comparative light-emitting element 9 includes the light-emitting element 8 and a hole-transport layer 1112, a first light-emitting layer 1113a, and The configuration of the second light emitting layer 1113b is different, and the other configurations are the same. The following is described below.

[0291] 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.

[0292] On the hole transport layer 1112, 2mDBTPDBq-II (abbreviation) and PCBA1BP (abbreviation) were [Ir(dppm)2(acac)] (abbreviation) was co-deposited to form a first light-emitting layer 1 113a was formed. Here, 2mDBTPDBq-II (abbreviation), PCBA1BP (abbreviation The weight ratio of [Ir(dppm)2(acac)] (abbreviation) was 0.7:0.3: 0.06(=2mDBTPDBq-II:PCBA1BP:[Ir(dppm)2(ac The thickness of the first light emitting layer 1113a was adjusted to 20 nm. Ta.

[0293] 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 is [Ir(dppm)2(acac)] (abbreviation). The guest material is

[0294] On the first light-emitting layer 1113a, 2mDBTPDBq-II (abbreviation) and PCBA1BP (abbreviation) and [Ir(dppm)2(acac)] (abbreviation) were co-evaporated to obtain the second emission A layer 1113b was formed. Here, 2mDBTPDBq-II (abbreviation), PCBA1BP The weight ratio of [Ir(dppm)2(acac)] (abbreviation) was 0.8:0. 2:0.05(=2mDBTPDBq-II:PCBA1BP:[Ir(dppm)2( The thickness of the second light emitting layer 1113b was adjusted to 20 nm. It was decided.

[0295] 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 is [Ir(dppm)2(acac)] (abbreviation). The guest material is

[0296] (Comparative light-emitting element 10) The comparative light-emitting element 10 differs from the light-emitting element 8 in the configuration of the hole transport layer 1112. The configuration is the same, and only the different configurations are described below.

[0297] 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.

[0298] The element structures of the light-emitting element 8, the comparative light-emitting element 9, and the comparative light-emitting element 10 obtained above were As shown in Table 5.

[0299] [Table 5]

[0300] The light-emitting element 8, the comparative light-emitting element 9, and the comparative light-emitting element 10 were placed in a glove box in a nitrogen atmosphere. The process of sealing each light-emitting element in the device with a glass substrate to prevent it from being exposed to the atmosphere (sealing). The sealing material was applied around the element and heat-treated at 80°C for 1 hour. The operating characteristics of these light-emitting devices were measured. The measurements were performed at room temperature (25°C). I went there for the atmosphere.

[0301] FIG. 24 shows the current density-luminance characteristics of the light-emitting element 8, the comparative light-emitting element 9, and the comparative light-emitting element 10. In FIG. 24, the horizontal axis represents the current density (mA / cm 2 ) and the vertical axis is luminance (cd / m 2 ) The voltage-luminance characteristics of the light-emitting element 8, the comparative light-emitting element 9, and the comparative light-emitting element 10 are shown below. This is shown in Figure 25. In Figure 25, the horizontal axis represents voltage (V) and the vertical axis represents luminance (cd / m 2 ) In addition, the luminance-current efficiency characteristics of the light-emitting element 8, the comparative light-emitting element 9, and the comparative light-emitting element 10 are shown in FIG. In FIG. 26, the horizontal axis is luminance (cd / m 2 ), and the vertical axis is current efficiency (cd / A) The voltage-current characteristics of the light-emitting element 8, the comparative light-emitting element 9, and the comparative light-emitting element 10 are shown below. This is shown in FIG. 27. In FIG. 27, the horizontal axis represents voltage (V) and the vertical axis represents current (mA). FIG. 28 shows the emission spectra of the light-emitting element 8, the comparative light-emitting element 9, and the comparative light-emitting element 10. In FIG. 28, the horizontal axis represents wavelength (nm) and the vertical axis represents emission intensity (arbitrary unit). In FIG. 28, the data for each light emitting element is shown roughly overlapping.

[0302] 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 6.

[0303] [Table 6]

[0304] As shown in Table 6, the luminance is 791cd / m 2 The CIE chromaticity coordinates of the light-emitting element 8 are (x, y) =(0.57,0.43). The luminance was 1029 cd / m 2 Comparison of light-emitting elements 9 The CIE chromaticity coordinates are (x,y)=(0.56,0.44). The luminance is 1211 cd / m 2 The CIE chromaticity coordinates of the comparative light-emitting element 10 are (x, y) = (0.57, 0.43 ) was.

[0305] The brightness is 791cd / m 2 The voltage of the light-emitting element 8 is 2.5 V, and the current efficiency is 76 d / A. The brightness was 1029cd / m 2 The voltage of the comparative light-emitting element 9 is 2.9V. The current efficiency was 74 cd / A. The luminance was 1211 cd / m 2 Comparison of light-emitting element 1 The zero voltage was 2.9 V and the current efficiency was 73 cd / A.

[0306] Therefore, the light-emitting element 8 according to one embodiment of the present invention is similar to the comparative light-emitting element 9 and the comparative light-emitting element 1. Compared to 0, the voltage can be reduced by 0.4V while maintaining the same current efficiency. Confirmed.

[0307] This result can be explained as follows. First, PCzPCN1 (abbreviation The HOMO levels of the thin films of PCBA1BP (abbreviation) and BPAFLP (abbreviation) are as follows: These are -5.15 eV, -5.42 eV, and -5.63 eV, respectively.

[0308] The HOMO of the second organic compound (PCBA1BP) used in the light-emitting layer of the comparative light-emitting element 9 The level is lower than that of the second organic compound (PCzPCN1) used in the light-emitting element 8. As a result, the first organic compound (2mDBTPDBq-II) was formed with As a result, the driving start voltage of the comparative light-emitting element 9 is On the other hand, the comparative light-emitting element 10 has the same structure of the light-emitting layer as the light-emitting element 8. Therefore, the drive start voltage is almost the same.

[0309] However, in the comparative light-emitting element 10, the hole transport layer is made of the second organic compound (PCzP Since it is composed only of BPAFLP, which has a much lower HOMO level than CN1), hole transport The movement of holes from the transport layer to the light-emitting layer does not proceed smoothly, and the voltage-current in the high brightness (practical brightness) region is As a result, the characteristics have deteriorated. 2 The driving voltage near As a result, a high voltage shift occurs as in the comparative light-emitting element 9.

[0310] Thus, the light-emitting element 8 according to one embodiment of the present invention is similar to the comparative light-emitting element 9 and the comparative light-emitting element 1. Compared to 0, a lower voltage was maintained and the current efficiency was higher.

[0311] As described above, the light-emitting element of one embodiment of the present invention has a light-emitting layer (the first light-emitting layer 1113a and The second organic compound having a hole transporting property used in the second light emitting layer 1113b) is a hole transporting compound. In this element configuration, the light-emitting element is also included in the layer 1112. (both the driving voltage at the driving start and the driving voltage in the practical luminance region) The light-emitting element according to one embodiment of the present invention can be made lower by using an organic compound. Compared with a hole transport layer formed only of an organic compound, the hole transport layer also contains a material other than the second organic compound. Therefore, the diffusion of triplet excitation energy from the light-emitting layer is suppressed by a material other than the second organic compound. In addition, an excellent light-emitting element with high luminous efficiency can be obtained.

[0312] The first organic compound (2mDBTPDB The PL peak wavelength of the thin film of q-II) is 426 nm, and the second organic compound (PCzPCN1) The PL peak wavelength of the mixed film is 571 nm. It was found that the wavelengths of the two organic compounds were shifted to longer wavelengths. is a combination that forms an exciplex. EXAMPLES

[0313] In this example, a light-emitting element of one embodiment of the present invention (light-emitting element 11) and a light-emitting element for comparison ( The comparative light-emitting element 12) will be described with reference to FIG. The chemical formula is shown below.

[0314] [ka]

[0315] [ka]

[0316] A method for fabricating the light-emitting element 11 of this example and the comparative light-emitting element 12 will be described below.

[0317] (Light emitting element 11) First, on a substrate 1100, indium oxide-tin oxide containing silicon or silicon oxide is A compound (ITSO) was deposited by sputtering to form a first electrode 1101. The composition of the target used was In2O3:SnO2:SiO2=85:10:5 [weight The thickness of the first electrode 1101 was 110 nm, and the area of ​​the electrode was 2 mm The first electrode 1101 is an electrode that functions as an anode of the light-emitting element. be.

[0318] 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.

[0319] 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.

[0320] 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 is reduced to about Pa, a deposition method using resistance heating is used to deposit D The hole injection layer 1111 is formed by co-evaporating BT3P-II (abbreviation) 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).

[0321] Next, BPAFLP (abbreviation) and PCzPCN1 (abbreviation) were co-formed on the hole injection layer 1111. The hole transport layer 1112 was formed by vapor deposition. The thickness of the layer was set to 20 nm. The weight ratio of LP (abbreviation) to PCzPCN1 (abbreviation) was 0.5:0.5 (=BPAF The concentration was adjusted to be LP:PCzPCN1).

[0322] Next, on the hole transport layer 1112, 2mDBTPDBq-II (abbreviation) and PCzPCN 1 (abbreviation) and (dipivaloylmethanato)bis(2,3,5-triphenylpyrazinato) Iridium (III) (abbreviation: [Ir(tppr)2(dpm)]) and The light-emitting layer 1113a was formed using the following: 2mDBTPDBq-II (abbreviation), PCzP The weight ratio of CN1 (abbreviation) and [Ir(tppr)2(dpm)] (abbreviation) was 0.7: 0.3:0.06(=2mDBTPDBq-II:PCzPCN1:[Ir(tppr) 2 (dpm)]. The thickness of the first light-emitting layer 1113a was adjusted to 20n The value was m.

[0323] In the first light-emitting layer 1113a, 2mDBTPDBq-II (abbreviation) is The first organic compound (host material) is PCzPCN1 (abbreviation), and the second organic compound ( The third organic compound is [Ir(tppr)2(dpm)] (abbreviation). (guest material).

[0324] Next, 2mDBTPDBq-II (abbreviation) and PCzP CN1 (abbreviation) and [Ir(tppr)2(dpm)] (abbreviation) were co-evaporated to form the second The light-emitting layer 1113b was formed. Here, 2mDBTPDBq-II (abbreviation), PCzPC The weight ratio of N1 (abbreviation) and [Ir(tppr)2(dpm)] (abbreviation) was 0.8:0 .2:0.05(=2mDBTPDBq-II:PCzPCN1:[Ir(tppr)2 The thickness of the second light-emitting layer 1113b was adjusted to 20 nm. It was decided.

[0325] In the second light-emitting layer 1113b, 2mDBTPDBq-II (abbreviation) is The first organic compound (host material) is PCzPCN1 (abbreviation), and the second organic compound ( The third organic compound is [Ir(tppr)2(dpm)] (abbreviation). (guest material).

[0326] 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.

[0327] Next, BPhen (abbreviation) was deposited on the first electron transport layer 1114a to a thickness of 20 nm. A second electron-transporting layer 1114b was formed.

[0328] 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.

[0329] Finally, a second electrode 1103 functioning as a cathode was prepared by depositing 20% ​​aluminum (Al). The light-emitting element 11 of this example was fabricated by depositing the layer so as to have a film thickness of 0 nm.

[0330] In the above-mentioned deposition process, the deposition was all performed by a resistance heating method.

[0331] (Comparative light-emitting element 12) The comparative light-emitting element 12 is different from the light-emitting element 11 in the configuration of the hole transport layer 1112. The configuration is the same, and only the different configurations will be described below.

[0332] 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.

[0333] Table 7 shows the element structures of the thus obtained light-emitting element 11 and comparative light-emitting element 12.

[0334] [Table 7]

[0335] The light-emitting element 11 and the comparative light-emitting element 12 were placed in a glove box with a nitrogen atmosphere. The process of sealing each light-emitting element with a glass substrate to prevent it from being exposed to the atmosphere (applying a sealant to the element) The surrounding area was coated with the resin, and the resin was then heat-treated at 80°C for 1 hour during sealing. The operating characteristics of the device were measured. The measurements were performed at room temperature (an atmosphere maintained at 25°C). Ta.

[0336] FIG. 29 shows the current density-luminance characteristics of the light-emitting element 11 and the comparative light-emitting element 12. The horizontal axis is the current density (mA / cm 2 ) and the vertical axis is luminance (cd / m 2 ) Also, FIG. 30 shows voltage-luminance characteristics of the light-emitting element 11 and the comparative light-emitting element 12. , the horizontal axis is voltage (V) and the vertical axis is luminance (cd / m 2 ) is represented. The luminance-current efficiency characteristic of the comparative light emitting element 12 is shown in FIG. 31. In FIG. 31, the horizontal axis is the luminance (c d / m 2 The vertical axis represents the current efficiency (cd / A), and the vertical axis represents the current efficiency (cd / A). The voltage-current characteristics of the element 12 are shown in FIG. 32. In FIG. 32, the horizontal axis represents voltage (V) and the vertical axis represents The figure shows the emission spectra of the light-emitting element 11 and the comparative light-emitting element 12. In FIG. 33, the horizontal axis represents wavelength (nm) and the vertical axis represents emission intensity (arbitrary unit). In FIG. 33, the data for each light-emitting element is shown roughly overlapping.

[0337] 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 8.

[0338] [Table 8]

[0339] As shown in Table 8, the luminance is 1002 cd / m 2 The CIE chromaticity coordinates of the light-emitting element 11 are (x, y)=(0.66,0.34). The luminance was 947cd / m 2 Comparison of light-emitting element 1 The CIE chromaticity coordinates of 2 are (x,y) = (0.66,0.34).

[0340] The brightness is 1002cd / m 2 The voltage of the light-emitting element 11 is 2.9 V, and the current efficiency is 2 5cd / A. The brightness was 947cd / m 2The voltage of the light-emitting element 12 is 3.3V. The current efficiency was 25 cd / A.

[0341] Therefore, the light-emitting element 11 which is one embodiment of the present invention has a lower electric field than the comparative light-emitting element 12. It was confirmed that the voltage could be reduced by 0.4 V while maintaining the same current efficiency.

[0342] This result can be explained as follows. First, PCzPCN1 (abbreviation The HOMO levels of the thin films of BPAFLP and BPAFLP (abbreviation) are -5.15 eV, respectively. , -5.63 eV.

[0343] The comparative light-emitting element 12 has the same structure of the light-emitting layer as the light-emitting element 11, and therefore the driving start voltage is However, in the comparative light-emitting element 12, the hole transport layer is the second organic compound of the light-emitting layer. The compound (PCzPCN1) consists of only BPAFLP, which has a much lower HOMO level. Therefore, the movement of holes from the hole transport layer to the light emitting layer does not proceed smoothly, and the high brightness (practical brightness) region is As a result, the voltage-current characteristics at 1000cd / m 2 Nearby The driving voltage at has shifted to a higher voltage.

[0344] As described above, the light-emitting element 11 according to one embodiment of the present invention has a lower The voltage was maintained and the current efficiency was high.

[0345] As described above, the light-emitting element of one embodiment of the present invention has a light-emitting layer (the first light-emitting layer 1113a and The second organic compound having a hole transporting property used in the second light emitting layer 1113b) is a hole transporting compound. In this element configuration, the light-emitting element is also included in the layer 1112. (both the driving voltage at the driving start and the driving voltage in the practical luminance region) The light-emitting element according to one embodiment of the present invention can be made lower by using an organic compound. Compared with a hole transport layer formed only of an organic compound, the hole transport layer also contains a material other than the second organic compound. Therefore, the diffusion of triplet excitation energy from the light-emitting layer is suppressed by a material other than the second organic compound. In addition, an excellent light-emitting element with high luminous efficiency can be obtained.

[0346] The first organic compound (2mDBTPD The PL peak wavelength of the thin film of Bq-II is 426 nm, and the second organic compound (PCzPCN1 The PL peak wavelength of the mixed film is 571 nm. m and was shifted to longer wavelengths. The substances are in combination to form exciplexes.

[0347] Next, the light-emitting element 11 and the comparative light-emitting element 12 were subjected to a reliability test. The results of the reliability test are shown in FIG.

[0348] In FIG. 34, the reliability test was performed with an initial luminance of 5000 cd / m 2 Set it to Each light-emitting element was driven under a constant current density condition. The horizontal axis represents the driving time (h) of the element, and the vertical axis represents the initial The normalized luminance (%) is calculated based on the initial luminance of 100%. From Figure 34, the operating time was 219 hours. After the lapse of time, the normalized luminance of the light-emitting element 11 was 82%, and the normalized luminance of the comparative light-emitting element 12 was 8 The rate was 2%.

[0349] As shown in FIG. 34, the light-emitting element 11 of one embodiment of the present invention is a light-emitting element with a long lifetime. It was found that... EXAMPLES

[0350] In this example, a light-emitting element of one embodiment of the present invention (light-emitting element 13) and a light-emitting element for comparison ( Comparative light-emitting element 14 and comparative light-emitting element 15 will be described with reference to FIG. The chemical formulas of the materials used in the examples are shown below.

[0351] [ka]

[0352] [ka]

[0353] The methods for fabricating the light-emitting element 13 of this example, the comparative light-emitting element 14, and the comparative light-emitting element 15 are described below. Show the law.

[0354] (Light emitting element 13) First, on a substrate 1100, indium oxide-tin oxide containing silicon or silicon oxide is A compound (ITSO) was deposited by sputtering to form a first electrode 1101. The composition of the target used was In2O3:SnO2:SiO2=85:10:5 [weight The thickness of the first electrode 1101 was 110 nm, and the area of ​​the electrode was 2 mm The first electrode 1101 is an electrode that functions as an anode of the light-emitting element. be.

[0355] 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.

[0356] Then, 10 -4The 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.

[0357] 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 is reduced to about Pa, a deposition method using resistance heating is used to deposit D The hole injection layer 1111 is formed by co-evaporating BT3P-II (abbreviation) 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).

[0358] Next, BPAFLP (abbreviation) and DPA2SF (abbreviation) are co-evaporated on the hole injection layer 1111. The hole transport layer 1112 was formed by depositing the ZnO film on the hole transport layer 1112. The thickness of the film was set to 20 nm. The weight ratio of P (abbreviation) to DPA2SF (abbreviation) is 0.5:0.5 (=BPAFLP :DPA2SF).

[0359] Next, on the hole transport layer 1112, 2mDBTPDBq-II (abbreviation) and DPA2SF (abbreviation) and [Ir(tppr)2(dpm)] (abbreviation) were co-evaporated to form a first light-emitting layer. 1113a was formed. Here, 2mDBTPDBq-II (abbreviation), DPA2SF (abbreviation The weight ratio of [Ir(tppr)2(dpm)] (abbreviation) was 0.7:0.3:0. .06(=2mDBTPDBq-II:DPA2SF:[Ir(tppr)2(dpm) The thickness of the first light-emitting layer 1113a was adjusted to 20 nm.

[0360] In the first light-emitting layer 1113a, 2mDBTPDBq-II (abbreviation) is The first organic compound (host material) is DPA2SF (abbreviation), and the second organic compound (acid The third organic compound, [Ir(tppr)2(dpm)] (abbreviation) guest material).

[0361] Next, 2mDBTPDBq-II (abbreviation) and DPA2 SF (abbreviation) and [Ir(tppr)2(dpm)] (abbreviation) are co-evaporated, and the second The optical layer 1113b was formed. (abbreviation) and [Ir(tppr)2(dpm)] (abbreviation) weight ratio is 0.8:0.2 :0.05(=2mDBTPDBq-II:DPA2SF:[Ir(tppr)2(dp The thickness of the second light-emitting layer 1113b was adjusted to 20 nm. .

[0362] In the second light-emitting layer 1113b, 2mDBTPDBq-II (abbreviation) is The first organic compound (host material) is DPA2SF (abbreviation), and the second organic compound (acid The third organic compound, [Ir(tppr)2(dpm)] (abbreviation) guest material).

[0363] 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.

[0364] Next, BPhen (abbreviation) was deposited on the first electron transport layer 1114a to a thickness of 20 nm. A second electron-transporting layer 1114b was formed.

[0365] 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.

[0366] Finally, a second electrode 1103 functioning as a cathode was prepared by depositing 20% ​​aluminum (Al). The light-emitting element 13 of this example was fabricated by depositing the layer so as to have a film thickness of 0 nm.

[0367] In the above-mentioned deposition process, the deposition was all performed by a resistance heating method.

[0368] (Comparative light-emitting element 14) The comparative light-emitting element 14 includes the light-emitting element 13, a hole transport layer 1112, a first light-emitting layer 1113a, and The configuration of the first and second light emitting layers 1113b is different, and the other configurations are the same. Only the following are described below.

[0369] 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.

[0370] On the hole transport layer 1112, 2mDBTPDBq-II (abbreviation) and PCBA1BP (abbreviation) were [Ir(tppr)2(dpm)] (abbreviation) was co-deposited to form a first light-emitting layer 11. 13a was formed. Here, 2mDBTPDBq-II (abbreviation), PCBA1BP (abbreviation ) and [Ir(tppr)2(dpm)] (abbreviation) in a weight ratio of 0.7:0.3:0. 06(=2mDBTPDBq-II:PCBA1BP:[Ir(tppr)2(dpm) The thickness of the first light-emitting layer 1113a was adjusted to 20 nm.

[0371] 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 is [Ir(tppr)2(dpm)] (abbreviation). (guest material).

[0372] On the first light-emitting layer 1113a, 2mDBTPDBq-II (abbreviation) and PCBA1BP (abbreviation) and [Ir(tppr)2(dpm)] (abbreviation) were co-evaporated to form a second light-emitting layer. 1113b was formed. Here, 2mDBTPDBq-II (abbreviation), PCBA1BP ( The weight ratio of [Ir(tppr)2(dpm)] (abbreviation) was 0.8:0.2: 0.05(=2mDBTPDBq-II:PCBA1BP:[Ir(tppr)2(dp The thickness of the second light-emitting layer 1113b was adjusted to 20 nm. .

[0373] 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 is [Ir(tppr)2(dpm)] (abbreviation). (guest material).

[0374] (Comparative light-emitting element 15) The comparative light-emitting element 15 is different from the light-emitting element 13 in the configuration of the hole transport layer 1112. The configuration is the same, and only the different configurations will be described below.

[0375] 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.

[0376] The element structures of the light-emitting element 13, the comparative light-emitting element 14, and the comparative light-emitting element 15 obtained above were The structure is shown in Table 9.

[0377] [Table 9]

[0378] The light-emitting element 13, the comparative light-emitting element 14, and the comparative light-emitting element 15 were placed in a globe box in a nitrogen atmosphere. The process of sealing each light-emitting element with a glass substrate inside the box to prevent it from being exposed to the atmosphere. (Sealing material was applied around the element, and heat treatment was performed at 80°C for 1 hour during sealing.) The operating characteristics of these light-emitting devices were then measured. The event was held in a relaxed atmosphere.

[0379] FIG. 3 shows the current density-luminance characteristics of the light-emitting element 13, the comparative light-emitting element 14, and the comparative light-emitting element 15. 5. In FIG. 35, the horizontal axis represents the current density (mA / cm 2 ) and the vertical axis is luminance (cd / m 2 The voltage-luminance relationship of the light-emitting element 13, the comparative light-emitting element 14, and the comparative light-emitting element 15 is shown in FIG. The luminance characteristics are shown in Figure 36. In Figure 36, the horizontal axis represents voltage (V) and the vertical axis represents luminance (cd / m 2 The luminance vs. current of the light-emitting element 13, the comparative light-emitting element 14, and the comparative light-emitting element 15 are shown in Table 1. The efficiency characteristics are shown in Figure 37. In Figure 37, the horizontal axis is the luminance (cd / m 2 ), the vertical axis is the current efficiency (cd / A). The voltage-current characteristics are shown in Figure 38. In Figure 38, the horizontal axis represents voltage (V) and the vertical axis represents current (m A) is shown. The emission spectra of the light-emitting element 13, the comparative light-emitting element 14, and the comparative light-emitting element 15 are shown. The spectrum is shown in Figure 39. In Figure 39, the horizontal axis is the wavelength (nm) and the vertical axis is the emission intensity (arbitrary unit In FIG. 39, the data for each light-emitting element is shown overlapping each other.

[0380] 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 10.

[0381] [Table 10]

[0382] As shown in Table 10, the luminance is 995cd / m 2 The CIE chromaticity coordinates of the light-emitting element 13 are (x, y)=(0.66,0.34). The luminance was 1019cd / m 2 Comparison of light-emitting elements The CIE chromaticity coordinates of 14 are (x,y)=(0.66,0.34). 050cd / m 2 The CIE chromaticity coordinates of the comparative light-emitting element 15 are (x,y)=(0.66,0 .34).

[0383] The brightness is also 995cd / m 2 The voltage of the light-emitting element 13 is 2.9 V, and the current efficiency is 25 cd / A. The brightness was 1019cd / m 2 The voltage of the light-emitting element 14 is 3.3V. The current efficiency was 25 cd / A. The luminance was 1050 cd / m 2 Comparison of luminescent elements The voltage of the electrode 15 was 3.3 V, and the current efficiency was 25 cd / A.

[0384] Therefore, the light-emitting element 13 which is one embodiment of the present invention is Compared to the 15-Volt MOSFET, the voltage can be reduced by 0.4V while maintaining the same current efficiency. It was confirmed that:

[0385] This result can be explained as follows. First, DPA2SF (abbreviation) used in this example The HOMO levels of the thin films of PCBA1BP (abbreviation) and BPAFLP (abbreviation) are as follows: These are -5.09 eV, -5.42 eV, and -5.63 eV, respectively.

[0386] The HOM of the second organic compound (PCBA1BP) used in the light-emitting layer of the comparative light-emitting element 14 The O level is higher than that of the second organic compound (DPA2SF) used in the light-emitting element 13. Since the ion exchange reaction is low, the ion exchange reaction between the first organic compound (2mDBTPDBq-II) and the As a result, the driving start voltage of the comparative light-emitting element 14 is On the other hand, the comparative light-emitting element 15 has the same structure of the light-emitting layer as the light-emitting element 13. Since they are the same, the drive start voltages are almost the same.

[0387] However, in the comparative light-emitting element 15, the hole transport layer is made of the second organic compound (DPA2 Since it is composed only of BPAFLP, which has a much lower HOMO level than SF), it is a hole transport The movement of holes from the layer to the light-emitting layer does not proceed smoothly, and the voltage-current characteristics in the high brightness (practical brightness) range are poor. As a result, the image quality is worse at 1000cd / m 2 The driving voltage in the vicinity is As a result, a high voltage shift occurs as in the comparative light emitting element 14.

[0388] Thus, the light-emitting element 13 which is one embodiment of the present invention is similar to the comparative light-emitting element 14 and the comparative light-emitting element 15. Compared to element 15, it maintained a lower voltage and had a higher current efficiency.

[0389] As described above, the light-emitting element of one embodiment of the present invention has a light-emitting layer (the first light-emitting layer 1113a and The second organic compound having a hole transporting property used in the second light emitting layer 1113b) is a hole transporting compound. In this element configuration, the light-emitting element is also included in the layer 1112. (both the driving voltage at the driving start and the driving voltage in the practical luminance region) The light-emitting element according to one embodiment of the present invention can be made lower by using an organic compound. Compared with a hole transport layer formed only of an organic compound, the hole transport layer also contains a material other than the second organic compound. Therefore, the diffusion of triplet excitation energy from the light-emitting layer is suppressed by a material other than the second organic compound. In addition, an excellent light-emitting element with high luminous efficiency can be obtained.

[0390] The first organic compound (2mDBTPD The PL peak wavelength of the thin film of Bq-II is 426 nm, and the second organic compound (DPA2SF) The PL peak wavelength of the mixed film is 579 nm. It was found that the wavelengths of the two organic compounds were shifted to longer wavelengths. is a combination that forms an exciplex.

[0391] Next, the reliability test was performed on the light-emitting element 13, the comparative light-emitting element 14, and the comparative light-emitting element 15. The results of the reliability test are shown in Figure 40.

[0392] In FIG. 40, the reliability test was performed with an initial luminance of 5000 cd / m 2Set it to Each light-emitting element was driven under a constant current density condition. The horizontal axis represents the driving time (h) of the element, and the vertical axis represents the initial The normalized luminance (%) is calculated based on the initial luminance of 100%. After the lapse of time, the normalized luminance of the light-emitting element 13 was 85%, and the normalized luminance of the comparative light-emitting element 14 was 6 9%, and the normalized luminance of the comparative light-emitting element 15 was 81%.

[0393] As shown in FIG. 40, the light-emitting element 13 of one embodiment of the present invention is a light-emitting element with a long lifetime. It was found that... EXAMPLES

[0394] In this example, a light-emitting element of one embodiment of the present invention (light-emitting element 16) and a light-emitting element for comparison ( The comparative light-emitting element 17) will be described with reference to FIG. The chemical formula is shown below.

[0395] [ka]

[0396] [ka]

[0397] A method for fabricating the light-emitting element 16 of this example and the comparative light-emitting element 17 will be described below.

[0398] (Light emitting element 16) First, on a substrate 1100, indium oxide-tin oxide containing silicon or silicon oxide is A compound (ITSO) was deposited by sputtering to form a first electrode 1101. The composition of the target used was In2O3:SnO2:SiO2=85:10:5 [weight The thickness of the first electrode 1101 was 110 nm, and the area of ​​the electrode was 2 mm The first electrode 1101 is an electrode that functions as an anode of the light-emitting element. be.

[0399] 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.

[0400] 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.

[0401] 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 is reduced to about Pa, a deposition method using resistance heating is used to deposit D The hole injection layer 1111 is formed by co-evaporating BT3P-II (abbreviation) and molybdenum oxide. The film thickness was 30 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).

[0402] Next, 3-[4-(9-phenanthryl)-phenyl]-9 -Phenyl-9H-carbazole (abbreviation: PCPPn) and PCzPCN1 (abbreviation) were co-evaporated. The hole transport layer 1112 was formed by depositing the film of PCPPn The weight ratio of PCPPn (abbreviation) and PCzPCN1 (abbreviation) is 1:1 (=PCPPn:PCzP The concentration was adjusted to CN1.

[0403] Next, on the hole transport layer 1112, 2mDBTPDBq-II (abbreviation) and PCzPCN 1 (abbreviation) and [Ir(tppr)2(dpm)] (abbreviation) were co-evaporated to obtain the first light-emitting A layer 1113a was formed. Here, 2mDBTPDBq-II (abbreviation), PCzPCN1 (abbreviation) and [Ir(tppr)2(dpm)] (abbreviation) weight ratio is 0.5:0.5 :0.05(=2mDBTPDBq-II:PCzPCN1:[Ir(tppr)2(d The thickness of the first light-emitting layer 1113a was adjusted to 20 nm. Ta.

[0404] In the first light-emitting layer 1113a, 2mDBTPDBq-II (abbreviation) is The first organic compound (host material) is PCzPCN1 (abbreviation), and the second organic compound ( The third organic compound is [Ir(tppr)2(dpm)] (abbreviation). (guest material).

[0405] Next, 2mDBTPDBq-II (abbreviation) and PCzP CN1 (abbreviation) and [Ir(tppr)2(dpm)] (abbreviation) were co-evaporated to form the second The light-emitting layer 1113b was formed. Here, 2mDBTPDBq-II (abbreviation), PCzPC The weight ratio of N1 (abbreviation) and [Ir(tppr)2(dpm)] (abbreviation) was 0.8:0 .2:0.05(=2mDBTPDBq-II:PCzPCN1:[Ir(tppr)2 The thickness of the second light-emitting layer 1113b was adjusted to 20 nm. It was decided.

[0406] In the second light-emitting layer 1113b, 2mDBTPDBq-II (abbreviation) is The first organic compound (host material) is PCzPCN1 (abbreviation), and the second organic compound ( The third organic compound is [Ir(tppr)2(dpm)] (abbreviation). (guest material).

[0407] 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.

[0408] 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.

[0409] 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.

[0410] Finally, a second electrode 1103 functioning as a cathode was prepared by depositing 20% ​​aluminum (Al). The light emitting element 16 of this example was fabricated by depositing the layer so as to have a film thickness of 0 nm.

[0411] In the above-mentioned deposition process, the deposition was all performed by a resistance heating method.

[0412] (Comparative light-emitting element 17) The comparative light-emitting element 17 is different from the light-emitting element 16 in the configuration of the hole transport layer 1112. The configuration is the same, and only the different configurations will be described below.

[0413] A hole transport layer 1112 is formed by evaporating PCPPn (abbreviation) on the hole injection layer 1111. The thickness of the film was 20 nm.

[0414] Table 11 shows the element structures of the thus obtained light-emitting element 16 and comparative light-emitting element 17.

[0415] [Table 11]

[0416] The light-emitting element 16 and the comparative light-emitting element 17 were placed in a glove box with a nitrogen atmosphere. The process of sealing each light-emitting element with a glass substrate to prevent it from being exposed to the atmosphere (applying a sealant to the element) The surrounding area was coated with the resin, and the resin was then heat-treated at 80°C for 1 hour during sealing. The operating characteristics of the device were measured. The measurements were performed at room temperature (an atmosphere maintained at 25°C). Ta.

[0417] FIG. 41 shows the current density-luminance characteristics of the light-emitting element 16 and the comparative light-emitting element 17. The horizontal axis is the current density (mA / cm 2 ) and the vertical axis is luminance (cd / m 2 ) Also, FIG. 42 shows voltage-luminance characteristics of the light-emitting element 16 and the comparative light-emitting element 17. , the horizontal axis is voltage (V) and the vertical axis is luminance (cd / m 2 ) In addition, the light emitting element 16 and the The luminance-current efficiency characteristic of the comparative light emitting element 17 is shown in FIG. 43. In FIG. 43, the horizontal axis is the luminance (c d / m 2 The vertical axis represents the current efficiency (cd / A), and the vertical axis represents the current efficiency (cd / A). The voltage-current characteristics of the element 17 are shown in FIG. 44. In FIG. 44, the horizontal axis represents voltage (V) and the vertical axis represents The figure shows the emission spectra of the light-emitting element 16 and the comparative light-emitting element 17. In FIG. 45, the horizontal axis represents wavelength (nm) and the vertical axis represents emission intensity (arbitrary unit). In FIG. 45, the data for each light-emitting element is shown roughly overlapping.

[0418] 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 12.

[0419] [Table 12]

[0420] As shown in Table 12, the luminance is 1095cd / m 2 The CIE chromaticity coordinates of the light-emitting element 16 are (x ,y)=(0.66,0.34). The luminance was 910cd / m 2 Comparison of light-emitting elements The CIE chromaticity coordinates of 17 are (x,y) = (0.66,0.34).

[0421] Also, the brightness is 1095cd / m 2 The voltage of the light-emitting element 16 is 2.9 V, and the current efficiency is 3 1cd / A. The brightness was 910cd / m 2 The voltage of the comparison light-emitting element 17 is 3.2V. The current efficiency was 30 cd / A.

[0422] Therefore, the light-emitting element 16 which is one embodiment of the present invention has a lower electric field than the comparative light-emitting element 17. It was confirmed that the voltage could be reduced by 0.3 V while maintaining the same current efficiency.

[0423] This result can be explained as follows. First, PCzPCN1 (abbreviation The HOMO levels of the thin films of PCPPn and PCPPn (abbreviation) are -5.15 eV and -5.78 eV.

[0424] The comparative light-emitting element 17 has the same structure of the light-emitting layer as the light-emitting element 16, and therefore the driving start voltage is However, in the comparative light-emitting element 17, the hole transport layer is the second organic compound of the light-emitting layer. It consists of only PCPPn, which has a much lower HOMO level than the compound (PCzPCN1). Therefore, the movement of holes from the hole transport layer to the light emitting layer does not proceed smoothly, and in the high brightness (practical brightness) region, As a result, the voltage-current characteristics of 1000cd / m 2 Nearby The driving voltage of the MOSFET has shifted to a higher voltage.

[0425] As described above, the light-emitting element 16 which is one embodiment of the present invention has a lower The voltage was maintained and the current efficiency was high.

[0426] As described above, the light-emitting element of one embodiment of the present invention has a light-emitting layer (the first light-emitting layer 1113a and The second organic compound having a hole transporting property used in the second light emitting layer 1113b) is a hole transporting compound. In this element configuration, the light-emitting element is also included in the layer 1112. (both the driving voltage at the driving start and the driving voltage in the practical luminance region) The light-emitting element according to one embodiment of the present invention can be made lower by using an organic compound. Compared with a hole transport layer formed only of an organic compound, the hole transport layer also contains a material other than the second organic compound. Therefore, the diffusion of triplet excitation energy from the light-emitting layer is suppressed by a material other than the second organic compound. In addition, an excellent light-emitting element with high luminous efficiency can be obtained.

[0427] The first organic compound (2mDBTPD The PL peak wavelength of the thin film of Bq-II is 426 nm, and the second organic compound (PCzPCN1 The PL peak wavelength of the mixed film is 571 nm. m and was shifted to longer wavelengths. The substances are in combination to form exciplexes. EXAMPLES

[0428] In this example, a light-emitting element of one embodiment of the present invention (light-emitting element 18) and a light-emitting element for comparison ( The comparative light-emitting element 19) will be described with reference to FIG. 13. The chemical formula is shown below.

[0429] [ka]

[0430] [ka]

[0431] A method for fabricating the light-emitting element 18 of this example and the comparative light-emitting element 19 will be described below.

[0432] (Light emitting element 18) First, on a substrate 1100, indium oxide-tin oxide containing silicon or silicon oxide is A compound (ITSO) was deposited by sputtering to form a first electrode 1101. The composition of the target used was In2O3:SnO2:SiO2=85:10:5 [weight The thickness of the first electrode 1101 was 110 nm, and the area of ​​the electrode was 2 mm The first electrode 1101 is an electrode that functions as an anode of the light-emitting element. be.

[0433] 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.

[0434] 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.

[0435] 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 is reduced to about Pa, a deposition method using resistance heating is used to deposit D The hole injection layer 1111 is formed by co-evaporating BT3P-II (abbreviation) and molybdenum oxide. The film thickness was 30 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).

[0436] Next, PCPPn (abbreviation) and PCzPCN1 (abbreviation) are co-evaporated on the hole injection layer 1111. The hole transport layer 1112 was formed by depositing the film of PCPPn The weight ratio of PCPPn (abbreviation) and PCzPCN1 (abbreviation) is 1:1 (=PCPPn:PCzP The concentration was adjusted to CN1.

[0437] Next, on the hole transport layer 1112, 2mDBTPDBq-II (abbreviation) and PCzPCN 1 (abbreviation) and [Ir(dmdppm)2(dibm)] (abbreviation) were co-evaporated to form a first The light-emitting layer 1113a was formed using the following: 2mDBTPDBq-II (abbreviation), PCzP The weight ratio of CN1 (abbreviation) and [Ir(dmdppm)2(dibm)] (abbreviation) is 0 .5:0.5:0.05(=2mDBTPDBq-II:PCzPCN1:[Ir(dm The first light-emitting layer 1113a was adjusted to have a refractive index of 1.25 ppm / dppm. The film thickness was 20 nm.

[0438] In the first light-emitting layer 1113a, 2mDBTPDBq-II (abbreviation) is The first organic compound (host material) is PCzPCN1 (abbreviation), and the second organic compound ( The third organic compound, [Ir(dmdppm)2(dibm)] (abbreviation) Compound (guest material).

[0439] Next, 2mDBTPDBq-II (abbreviation) and PCzP CN1 (abbreviation) and [Ir(dmdppm)2(dibm)] (abbreviation) are co-evaporated, The second light-emitting layer 1113b was formed. The weight ratio of zPCN1 (abbreviation) and [Ir(dmdppm)2(dibm)] (abbreviation) is , 0.8:0.2:0.05(=2mDBTPDBq-II:PCzPCN1:[Ir( dmdppm)2(dibm)]). The second light-emitting layer 1113 The film thickness of b was set to 20 nm.

[0440] In the second light-emitting layer 1113b, 2mDBTPDBq-II (abbreviation) is The first organic compound (host material) is PCzPCN1 (abbreviation), and the second organic compound ( The third organic compound, [Ir(dmdppm)2(dibm)] (abbreviation) Compound (guest material).

[0441] 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.

[0442] 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.

[0443] 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.

[0444] Finally, a second electrode 1103 functioning as a cathode was prepared by depositing 20% ​​aluminum (Al). The light-emitting element 18 of this example was fabricated by depositing the layer so as to have a film thickness of 0 nm.

[0445] In the above-mentioned deposition process, the deposition was all performed by a resistance heating method.

[0446] (Comparative light-emitting element 19) The comparative light-emitting element 19 is different from the light-emitting element 18 in the configuration of the hole transport layer 1112. The configuration is the same, and only the different configurations will be described below.

[0447] A hole transport layer 1112 is formed by evaporating PCPPn (abbreviation) on the hole injection layer 1111. The thickness of the film was 20 nm.

[0448] Table 13 shows the element structures of the thus obtained light-emitting element 18 and comparative light-emitting element 19.

[0449] [Table 13]

[0450] The light-emitting element 18 and the comparative light-emitting element 19 were placed in a glove box with a nitrogen atmosphere. The process of sealing each light-emitting element with a glass substrate to prevent it from being exposed to the atmosphere (applying a sealant to the element) The surrounding area was coated with the resin, and the resin was then heat-treated at 80°C for 1 hour during sealing. The operating characteristics of the device were measured. The measurements were performed at room temperature (an atmosphere maintained at 25°C). Ta.

[0451] FIG. 46 shows the current density-luminance characteristics of the light-emitting element 18 and the comparative light-emitting element 19. The horizontal axis is the current density (mA / cm 2 ) and the vertical axis is luminance (cd / m 2 ) Also, FIG. 47 shows the voltage-luminance characteristics of the light-emitting element 18 and the comparative light-emitting element 19. , the horizontal axis is voltage (V) and the vertical axis is luminance (cd / m 2 ) In addition, the light emitting element 18 and the The luminance-current efficiency characteristic of the comparative light emitting element 19 is shown in FIG. 48. In FIG. 48, the horizontal axis is the luminance (c d / m 2 The vertical axis represents the current efficiency (cd / A), and the vertical axis represents the current efficiency (cd / A). The voltage-current characteristics of the element 19 are shown in FIG. 49. In FIG. 49, the horizontal axis represents voltage (V) and the vertical axis represents The figure shows the emission spectra of the light-emitting element 18 and the comparative light-emitting element 19. In FIG. 50, the horizontal axis represents wavelength (nm) and the vertical axis represents emission intensity (arbitrary unit). In FIG. 50, the data for each light-emitting element is shown roughly overlapping.

[0452] 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 14.

[0453] [Table 14]

[0454] As shown in Table 14, the luminance is 931cd / m 2 The CIE chromaticity coordinates of the light-emitting element 18 are (x, y)=(0.61,0.39). The luminance was 941cd / m 2 Comparison of light-emitting element 1 The CIE chromaticity coordinates of 9 are (x,y) = (0.61,0.39).

[0455] The brightness is 931cd / m 2 The voltage of the light-emitting element 18 is 2.6 V, and the current efficiency is 62 cd / A. The brightness was 941cd / m 2 The voltage of the comparison light-emitting element 19 is 3.0V. The current efficiency was 59 cd / A.

[0456] Therefore, the light-emitting element 18 which is one embodiment of the present invention has a lower current density than the comparative light-emitting element 19. It was confirmed that the voltage could be reduced by 0.4 V while maintaining the same current efficiency.

[0457] This result can be explained as follows. First, PCzPCN1 (abbreviation The HOMO levels of the thin films of PCPPn and PCPPn (abbreviation) are -5.15 eV and -5.78 eV.

[0458] The comparative light-emitting element 19 has the same structure of the light-emitting layer as the light-emitting element 18, and therefore the driving start voltage is However, in the comparative light-emitting element 19, the hole transport layer is the second organic compound of the light-emitting layer. It consists of only PCPPn, which has a much lower HOMO level than the compound (PCzPCN1). Therefore, the movement of holes from the hole transport layer to the light emitting layer does not proceed smoothly, and in the high brightness (practical brightness) region, As a result, the voltage-current characteristics of 1000cd / m2 Nearby The driving voltage of the MOSFET has shifted to a higher voltage.

[0459] As described above, the light-emitting element 18 of one embodiment of the present invention has a lower The voltage was maintained and the current efficiency was high.

[0460] As described above, the light-emitting element of one embodiment of the present invention has a light-emitting layer (the first light-emitting layer 1113a and The second organic compound having a hole transporting property used in the second light emitting layer 1113b) is a hole transporting compound. In this element configuration, the light-emitting element is also included in the layer 1112. (both the driving voltage at the driving start and the driving voltage in the practical luminance region) The light-emitting element according to one embodiment of the present invention can be made lower by using an organic compound. Compared with a hole transport layer formed only of an organic compound, the hole transport layer also contains a material other than the second organic compound. Therefore, the diffusion of triplet excitation energy from the light-emitting layer is suppressed by a material other than the second organic compound. In addition, an excellent light-emitting element with high luminous efficiency can be obtained.

[0461] The first organic compound (2mDBTPD The PL peak wavelength of the thin film of Bq-II is 426 nm, and the second organic compound (PCzPCN1 The PL peak wavelength of the mixed film is 571 nm. m and was shifted to longer wavelengths. The substances are in combination to form exciplexes.

[0462] (Reference example 1) The bis{2-[6-(3,5-dimethylphenyl)-4-pyrimidinyl] {2,6-dimethyl-3,5-heptyl-κN3}-4,6-dimethylphenyl-κC ndionate-κ 2 O,O') Iridium(III) (abbreviation: [Ir(dmdppm)2( The synthesis method of [Ir(dmdppm)2(di The structure of [bm)] (abbreviation) is shown below.

[0463] [ka]

[0464] <Step 1: 4,6-bis(3,5-dimethylphenyl)pyrimidine (abbreviation: Hdmd ppm) synthesis method> First, 5.97 g of 4,6-dichloropyrimidine and 1 g of 3,5-dimethylphenylboronic acid were 2.04g, sodium carbonate 8.48g, bis(triphenylphosphine)palladium ( II) Dichloride (Pd(PPh3)2Cl2) 0.34g, water 20mL, 1,3-dimethyl Chil-3,4,5,6-tetrahydro-2(1H)pyrimidinone (abbreviation: DMPU) 20 1 mL was placed in a recovery flask equipped with a reflux condenser, and the inside of the flask was replaced with argon. The mixture was heated by irradiating it with microwaves (2.45 GHz, 100 W) for 60 minutes. 2.58 g of 3,5-dimethylphenylboronic acid, 1.78 g of sodium carbonate, Pd(P Put 0.070 g of Ph3)2Cl2, 5 mL of water, and 5 mL of DMPU into the flask and mix again. The material was heated by exposure to microwaves (2.45 GHz, 100 W) for 60 minutes.

[0465] The resulting residue was then suction filtered with water and washed with water and ethanol. Dissolve in dichloromethane and pass through a filter aid consisting of layers of Celite, alumina, and Celite. The pyrimidine derivative Hdmdp was isolated by filtration and washing with ethanol. pm was obtained (white powder, yield 56%). Note that microwave irradiation was performed using a microwave synthesis apparatus ( The synthesis scheme for step 1 is shown below (a-1). As shown in.

[0466] [ka]

[0467] <Step 2: Di-μ-chloro-tetrakis{2-[6-(3,5-dimethylphenyl) -4-pyrimidinyl-κN3]-4,6-dimethylphenyl-κC}diiridium(II Synthesis of Ir(dmdppm)2Cl2 Next, 15 mL of 2-ethoxyethanol, 5 mL of water, and the Hdmdp obtained in step 1 above were pm (abbreviation) 2.10 g, iridium chloride hydrate (IrCl3·H2O) (Sigma-Aldrich Put 1.07 g of ... The atmosphere was replaced with argon. After that, microwaves (2.45 GHz, 100 W) were irradiated for 1 hour. After the solvent was distilled off, the resulting residue was suction filtered and washed with ethanol to obtain a binuclear complex. The compound [Ir(dmdppm)2Cl]2 (abbreviation) was obtained (reddish brown powder, 74% yield). The synthesis scheme of trip 2 is shown in (a-2) below.

[0468] [ka]

[0469] <Step 3: Bis{2-[6-(3,5-dimethylphenyl)-4-pyrimidinyl-κ N3]-4,6-dimethylphenyl-κC}(2,6-dimethyl-3,5-heptanediol Nat-κ 2 O,O') Iridium(III) (abbreviation: [Ir(dmdppm)2(dib m)] Synthesis Method In addition, 30 mL of 2-ethoxyethanol and the binuclear complex [Ir(d mdppm)2Cl]2 (abbreviation) 1.09 g, diisobutyrylmethane (abbreviation: Hdibm 0.32 g of sodium carbonate and 0.72 g of sodium carbonate were placed in a recovery flask equipped with a reflux condenser. The inside of the scope was replaced with argon. Then, microwaves (2.45 GHz, 120 W) were used for 60 minutes. The mixture was heated by irradiating with light for 1 hour. The solvent was removed by distillation, and the resulting residue was subjected to suction filtration with ethanol. The obtained solid was washed with water and ethanol, and then reconstituted with a mixed solvent of dichloromethane and ethanol. By crystallizing, the organometallic complex [Ir(dmdppm)2(dibm )] (abbreviation) was obtained as a red powder (yield 62%). The synthesis scheme of step 3 is shown below ( As shown in a-3).

[0470] [ka]

[0471] The compound obtained by the above synthesis method was analyzed by nuclear magnetic resonance spectroscopy ( 1 H-NMR The measurement results showed that [Ir(dmdppm)2(dibm)] (abbreviation) It was discovered that...

[0472] The obtained material 1 The H-NMR data is shown below. 1 H-NMR.δ(CDCl3):0.69(d,6H),0.82(d,6H),1. 51(s,6H),2.17-2.23(m,2H),2.31(s,6H),2.45 (s,12H),5.19(s,1H),6.61(s,2H),7.17(s,2H) ,7.56(s,2H),7.82(s,4H),8.11(d,2H),8.88(d ,2H).

[0473] (Reference example 2) The 3-[4-(9-phenanthryl)-phenyl]-9-phenyl- The synthesis method of 9H-carbazole (abbreviation: PCPPn) is specifically explained. The structure of Pn (abbreviation) is shown below.

[0474] [ka]

[0475] <Step 1: Synthesis of 3-(4-bromophenyl)-9-phenyl-9H-carbazole Law> In a 300 mL three-neck flask, 14 g (50 mmol) of 4-bromoiodobenzene and 9 -Phenyl-9H-carbazole-3-boronic acid 14g (50mmol), palladium acetate 110 mg (0.5 mmol) of ruthenium(II), 300 mg of tri(o-tolyl)phosphine ( 1.0mmol), toluene 50mL, ethanol 10mL, 2mol / L potassium carbonate A mixture of 25 mL of the aqueous solution was degassed under reduced pressure while stirring, and then heated at 80°C under a nitrogen atmosphere. The mixture was reacted with heating and stirring for 6 hours.

[0476] After the reaction, 200 mL of toluene was added to the reaction mixture, and the suspension was dissolved in Florisil and Ce The filtrate was washed with water and magnesium sulfate was added to reduce the moisture content. The suspension was filtered to obtain a filtrate. The filtrate was concentrated and then applied to a silica gel column. The mixture was purified by column chromatography. A mixed solvent of toluene and hexane (toluene:hexane = 1:4) was used. The fraction was concentrated, hexane was added, and the mixture was sonicated. The recrystallization showed that The target product was obtained as a white powder in an amount of 15 g and a yield of 75%. The reaction scheme of step 1 is shown below. Shown in (b-1).

[0477] [ka]

[0478] <Step 2: 4-(9-phenyl-9H-carbazol-3-yl)phenylboronic acid Synthesis method of In a 300 mL three-neck flask, 3-(4-bromo 8.0 g (20 mmol) of 9-phenyl-9H-carbazole was added to the flask. After replacing the atmosphere in the scope with nitrogen, 100 ml of dehydrated tetrahydrofuran (abbreviation: THF) was added. The mixture was cooled to -78°C and 1.65 mol / L n-butyllithium hexahydrate was added. 15 mL (24 mmol) of the dimethylformamide solution was added dropwise and stirred for 2 hours. 3.4 mL (30 mmol) of methyl was added, and the mixture was stirred at -78°C for 2 hours and at room temperature for 18 hours. After the reaction, 1M dilute hydrochloric acid was added to the reaction solution until it became acidic, and the mixture was stirred for 7 hours. The organic layer was washed with saturated saline. After washing, the organic layer was added with mag- nesium sulfate. The suspension was filtered, and the filtrate was concentrated to obtain hexane. After adding 1,000 mg of ethyl acetate and applying ultrasonic waves, the mixture was recrystallized to obtain the desired white powder with a yield of 6.4 g. The reaction scheme of step 2 above is shown below in (b-2).

[0479] [ka]

[0480] <Step 2: 3-[4-(9-phenanthryl)-phenyl]-9-phenyl-9H- Synthesis of Carbazole (abbreviation: PCPPn)> Add 9-phenyl-9H-carbazol-3-yl-phenyl- 1.5 g (5.0 mmol) of 4-boronic acid and 3.2 g (1 1 mmol), palladium(II) acetate 11 mg (0.1 mmol), tri(o-tri 30 mg (0.1 mmol) of phosphine, 30 mL of toluene, 3 mL of ethanol, A mixture of 5 mL of 2 mol / L potassium carbonate aqueous solution was degassed under reduced pressure while stirring, The mixture was reacted under nitrogen atmosphere with stirring at 90° C. for 6 hours.

[0481] After the reaction, 200 mL of toluene was added to the reaction mixture, and the organic layer of the mixture was separated by The filtrate was washed with water and magnesium sulfate was added. The suspension was filtered to obtain a filtrate. The filtrate was concentrated. The mixture was purified by silica gel column chromatography. A mixture of toluene and hexane (toluene:hexane = 1:4) was used as the developing solvent for the fee. The obtained fraction was concentrated, and acetone and methanol were added and the mixture was sonicated. After the mixture was cooled, it was recrystallized to obtain 2.2 g of the desired white powder in a yield of 75%. The reaction scheme of Step 3 is shown below in (b-3).

[0482] [ka]

[0483] The compound obtained by the above synthesis method was analyzed by nuclear magnetic resonance spectroscopy ( 1 H-NMR The measurement results showed that PCPPn (abbreviation) was obtained.

[0484] The obtained material 1 The H-NMR data is shown below. 1 H-NMR(CDCl3,300MHz):δ(ppm)=7.30-7.35(m, 11H),7.43-7.78(m,16H),7.86-7.93(m,3H),8. 01(dd,J=0.9Hz,7.8Hz,1H),8.23(d,J=7.8Hz,1 H),8.47(d,J=1.5Hz,1H),8.74(d,J=8.1Hz,1H) ,8.80(d,J=7.8Hz,1H).

[0485] (Reference example 3) In the above-mentioned examples, 2mDBTPDBq-II (abbreviation) and P CzPCN1 (abbreviation), DPA2SF (abbreviation), BPAFLP (abbreviation), and PCPP The T1 level of n (abbreviation) was measured. The T1 level was measured by measuring the phosphorescence of each substance. The phosphorescence emission wavelength was measured and converted into electron volts. The materials were irradiated with 325 nm excitation light and measured at a temperature of 10 K. The measurement of the energy level is more accurate when calculated from the absorption wavelength rather than the emission wavelength. Since the absorption at the T1 level is extremely weak and difficult to measure, we will focus on the phosphorescence spectrum here. The T1 level was obtained by measuring the peak wavelength located on the shortest wavelength side of the tor. Therefore, the measured values ​​may contain some error.

[0486] The measured phosphorescence emission of 2mDBTPDBq-II (abbreviation) is shown in Figure 51. The phosphorescence emission of CN1 (abbreviation) is shown in Figure 52, and the phosphorescence emission of DPA2SF (abbreviation) is shown in Figure 5 3 shows the measured phosphorescence emission of BPAFLP (abbreviation), and FIG. 54 shows the measured phosphorescence emission of PCPPn (abbreviation). The phosphorescence emission of each of the compounds is shown in FIG. 55. The measurement results are summarized in Table 15. As can be seen from the above, 2mDBTPD used as the first organic compound in the above-mentioned examples Bq-II (abbreviation), PCzPCN1 (abbreviation) and D Compared to PA2SF (abbreviation), BPAFLP (abbreviation) added to the hole transport layer and the fourth organic compound It can be seen that the compound PCPPn (abbreviation) has a high T1 level.

[0487] [Table 15] [Explanation of symbols]

[0488] 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 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 section 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, and an electron transport layer are provided between a pair of electrodes, the light-emitting layer includes a first organic compound, a second organic compound, and a third organic compound; the first organic compound is a π-deficient heteroaromatic compound, the second organic compound is a compound having an aromatic amine skeleton or a compound having a carbazole skeleton, the third organic compound is an organometallic iridium complex; the first organic compound and the second organic compound are a combination that forms an exciplex, The hole transport layer is a layer of the first organic compound T １ level and the T of the second organic compound １ T higher than the level １ a fourth organic compound having a level; the hole injection layer has a fifth organic compound different from the fourth organic compound, the electron transport layer comprises a metal complex or a heteroaromatic compound; a difference between a peak energy value of an emission spectrum of the exciplex and a peak energy value of an absorption band on the lowest energy side of an absorption spectrum of the third organic compound is within 0.2 eV.

2. A hole injection layer, a hole transport layer, a light emitting layer, and an electron transport layer are provided between a pair of electrodes, the light-emitting layer includes a first organic compound, a second organic compound, and a third organic compound; the first organic compound is a π-deficient heteroaromatic compound, the second organic compound is a compound having an aromatic amine skeleton or a compound having a carbazole skeleton, the third organic compound is an organometallic iridium complex; the first organic compound and the second organic compound are a combination that forms an exciplex, The hole transport layer is a layer of the first organic compound T １ level and the T of the second organic compound １ T higher than the level １ a fourth organic compound having a level; the hole injection layer has a fifth organic compound different from the fourth organic compound, the electron transport layer comprises a metal complex or a heteroaromatic compound; a difference between a peak energy value of an emission spectrum of the exciplex and a peak energy value of an absorption band on the lowest energy side of an absorption spectrum of the third organic compound is within 0.2 eV; T of the first organic compound １ level and the T of the second organic compound １ The level is T １ A light-emitting element having a higher level than the

3. A hole injection layer, a hole transport layer, a light emitting layer, and an electron transport layer are provided between a pair of electrodes, the light-emitting layer includes a first organic compound, a second organic compound, and a third organic compound; the first organic compound is a π-deficient heteroaromatic compound, the second organic compound is a compound having an aromatic amine skeleton or a compound having a carbazole skeleton, the third organic compound is an organometallic iridium complex; the first organic compound and the second organic compound are a combination that forms an exciplex, The hole transport layer is a layer of the first organic compound T １ level and the T of the second organic compound １ T higher than the level １ a fourth organic compound having a level; the hole injection layer has a fifth organic compound different from the fourth organic compound, the electron transport layer comprises a metal complex or a heteroaromatic compound; a difference between a peak energy value of an emission spectrum of the exciplex and a peak energy value of an absorption band on the lowest energy side of an absorption spectrum of the third organic compound is within 0.1 eV.

4. A hole injection layer, a hole transport layer, a light emitting layer, and an electron transport layer are provided between a pair of electrodes, the light-emitting layer includes a first organic compound, a second organic compound, and a third organic compound; the first organic compound is a π-deficient heteroaromatic compound, the second organic compound is a compound having an aromatic amine skeleton or a compound having a carbazole skeleton, the third organic compound is an organometallic iridium complex; the first organic compound and the second organic compound are a combination that forms an exciplex, The hole transport layer is a layer of the first organic compound T １ level and the T of the second organic compound １ T higher than the level １ a fourth organic compound having a level; the hole injection layer has a fifth organic compound different from the fourth organic compound, the electron transport layer comprises a metal complex or a heteroaromatic compound; a difference between an energy value of a peak in an emission spectrum of the exciplex and an energy value of a peak in an absorption band on the lowest energy side in an absorption spectrum of the third organic compound is within 0.1 eV; T of the first organic compound １ level and the T of the second organic compound １ The level is T １ A light-emitting element having a higher level.

5. In any one of claims 1 to 4, The light-emitting element, wherein the hole injection layer contains an acceptor material.

6. A light emitting device comprising the light emitting element according to claim 1 .

7. An electronic device comprising the light emitting device according to claim 6.

8. A lighting device comprising the light-emitting device according to claim 6.

Images