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

Abstract

To provide a light-emitting device with high light-emitting efficiency.SOLUTION: The light-emitting device has a fluorescence emitting substance and a phosphorescence emitting substance, or a thermally activated delayed phosphor. The fluorescent emitting substance has a luminophore and five or more protective groups. The luminophore is a fused aromatic ring or fused heteroaromatic ring. The five or more protective groups have one of the following: an alkyl group with a carbon number of 1 to 10, a substituted or unsubstituted cycloalkyl group with a carbon number of 3 to 10, or a trialkylsilyl group with a carbon number of 3 to 12. The lowest singlet excitation energy level of the fluorescent emitting substance is higher than the lowest triplet excitation energy level of the phosphorescent emitting substance or thermally activated delayed fluorescence substance. The light-emitting device emits light from both the fluorescent emitting substance and the phosphorescent emitting substance or thermally activated delayed fluorescence substance.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] An aspect of the present invention relates to a light-emitting device, a light-emitting apparatus, an electronic device, and a lighting apparatus. However, an aspect of the present invention is not limited thereto. That is, an aspect of the present invention relates to an object, a method, a manufacturing method, or a driving method. Alternatively, an aspect of the present invention relates to a process, a machine, a manufacture, or a composition of matter. [Background technology]

[0002] In recent years, there has been much research into light-emitting devices that utilize electroluminescence (EL). These light-emitting devices have a structure in which an EL layer (containing a light-emitting substance) is sandwiched between a pair of electrodes. When a voltage is applied between the pair of electrodes, electrons and holes injected from each electrode recombine in the EL layer, causing the light-emitting substance (organic compound) contained in the EL layer to enter an excited state, and light is emitted when the excited state returns to the ground state. There are several types of excited states, including singlet excited states (S * ) and triplet excited states (T * ) Emission from the singlet excited state is called fluorescence, and emission from the triplet excited state is called phosphorescence. The statistical generation ratio of these in a light-emitting device is S * :T * = 1: 3. For this reason, light-emitting devices using phosphorescent materials that can convert the energy of triplet excited states into light emission are expected to achieve high efficiency, and have been actively developed in recent years.

[0003] In addition to phosphorescent materials, thermally activated delayed fluorescence (TADF) materials are known as materials capable of converting part or all of the energy of a triplet excited state into light emission. TADF materials can generate a singlet excited state from a triplet excited state by reverse intersystem crossing.

[0004] As a light-emitting device using TADF material, a method has been proposed in which the TADF material is combined with a fluorescent substance to transfer the singlet excitation energy of the TADF material to the fluorescent substance, thereby causing the fluorescent substance to emit light efficiently (see Patent Document 1 and Non-Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2014-45179 A [Non-patent literature]

[0006] [Non-Patent Document 1] Hiroki Noda et al., “SCIENCE ADVANCES”, 2018, vol. 4, no. 6, eaao6910 Summary of the Invention [Problem to be solved by the invention]

[0007] In order to efficiently utilize the energy of the excited state generated in the EL layer of a light-emitting device, it is necessary to generate the singlet excited state (S * ) to the fluorescent material, and the triplet excited state (T * It is preferable that the energy from the triplet excitation energy (hereinafter referred to as triplet excitation energy) can be transferred to the phosphorescent material or the TADF material, respectively.

[0008] However, when a plurality of guest materials are used in the EL layer of a light-emitting device, the excitation energy of the host material usually moves to the material with a lower energy level. Therefore, when a phosphorescent material or a TADF material is used as a guest material together with a fluorescent material, the singlet excitation energy and triplet excitation energy of the host material both move to the material with a lower energy level, making it difficult to simultaneously emit light from both the fluorescent material and the phosphorescent material or the TADF material. In addition, the triplet excitation level of the fluorescent material does not contribute to light emission, but serves as a deactivation path for the triplet excitation energy. Therefore, it is difficult to efficiently emit light from both the fluorescent material and the phosphorescent material or the TADF material.

[0009] Therefore, one embodiment of the present invention aims to improve the luminous efficiency of the light-emitting device by transferring the singlet excitation energy of a host material to the S1 level of a fluorescent material and transferring the triplet excitation energy of the host material to the T1 level of a phosphorescent material or a TADF material in an EL layer (particularly one light-emitting layer) of a light-emitting device, thereby causing both the fluorescent material and the phosphorescent material or the TADF material to emit light.

[0010] Therefore, an object of one embodiment of the present invention is to provide a light-emitting device in which a plurality of emissions having different wavelengths (peak emission wavelengths) are obtained from one light-emitting layer included in an EL layer. Another object of one embodiment of the present invention is to provide a light-emitting device with high emission efficiency. Another object of one embodiment of the present invention is to provide a novel light-emitting device. Another object of one embodiment of the present invention is to provide a novel light-emitting device. Another object of one embodiment of the present invention is to provide a novel electronic device. Another object of one embodiment of the present invention is to provide a novel lighting device.

[0011] Note that the description of these problems does not preclude the existence of other problems. Note that one embodiment of the present invention does not necessarily solve all of these problems. Note that problems other than these will become apparent from the description of the specification, drawings, claims, etc., and it is possible to extract problems other than these from the description of the specification, drawings, claims, etc. [Means for solving the problem]

[0012] As mentioned above, there is a demand for the development of a method for efficiently converting triplet excitation energy into light emission in fluorescent light-emitting devices. Therefore, it is necessary to improve the efficiency of energy transfer between materials used in the light-emitting layer. To achieve this, it is necessary to suppress the transfer of triplet excitons between energy donors and energy acceptors by the Dexter mechanism.

[0013] One embodiment of the present invention is a light-emitting device having an EL layer between a pair of electrodes. The EL layer has a light-emitting layer. The light-emitting layer has a first organic compound having a function of converting singlet excitation energy into light emission and a second organic compound having a function of converting triplet excitation energy into light emission. The first organic compound has a luminophore and five or more protecting groups. The luminophore is a fused aromatic ring or a fused heteroaromatic ring. The five or more protecting groups are any one of an alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, and a trialkylsilyl group having 3 to 12 carbon atoms. The first organic compound has a lowest singlet excitation energy level (S1 level) higher than a lowest triplet excitation energy level (T1 level) of the second organic compound.

[0014] Another embodiment of the present invention is a light-emitting device having an EL layer between a pair of electrodes, the EL layer having an emission layer, the emission layer having a first organic compound having a function of converting singlet excitation energy into light emission, and a second organic compound having a function of converting triplet excitation energy into light emission, the first organic compound having a luminophore and five or more protecting groups, the luminophore is a fused aromatic ring or a fused heteroaromatic ring, the five or more protecting groups are any one of an alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, or a trialkylsilyl group having 3 to 12 carbon atoms, and the second organic compound has an emission spectrum with a peak wavelength longer than the peak wavelength of the emission spectrum of the first organic compound.

[0015] In each of the above structures, the light-emitting layer further contains a third organic compound, the lowest singlet excitation energy level (S1 level) of the third organic compound being higher than the lowest singlet excitation energy level (S1 level) of the first organic compound, and the lowest triplet excitation energy level (T1 level) of the third organic compound being higher than the lowest triplet excitation energy level (T1 level) of the second organic compound.

[0016] Another embodiment of the present invention is a light-emitting device having an EL layer between a pair of electrodes. The EL layer has a light-emitting layer. The light-emitting layer has a first organic compound having a function of converting singlet excitation energy into light emission, a second organic compound having a function of converting triplet excitation energy into light emission, a fourth organic compound, and a fifth organic compound. The first organic compound has a luminophore and five or more protecting groups. The luminophore is a condensed aromatic ring or a condensed heteroaromatic ring. The five or more protecting groups are any one of an alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, and a trialkylsilyl group having 3 to 12 carbon atoms. The lowest singlet excitation energy level (S1 level) of the first organic compound is higher than the lowest triplet excitation energy level (T1 level) of the second organic compound. The fourth organic compound and the fifth organic compound form an exciplex.

[0017] Another embodiment of the present invention is a light-emitting device having an EL layer between a pair of electrodes, the EL layer having an emission layer, the emission layer having a first organic compound having a function of converting singlet excitation energy into light emission, a second organic compound having a function of converting triplet excitation energy into light emission, a fourth organic compound, and a fifth organic compound, the first organic compound having a luminophore and five or more protecting groups, the luminophore is a condensed aromatic ring or a condensed heteroaromatic ring, the five or more protecting groups are any one of an alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, and a trialkylsilyl group having 3 to 12 carbon atoms, the peak wavelength of the emission spectrum of the second organic compound is longer than the peak wavelength of the emission spectrum of the first organic compound, and the fourth organic compound and the fifth organic compound form an exciplex.

[0018] In each of the above structures, light is emitted from both the first organic compound and the second organic compound.

[0019] In each of the above structures, the first organic compound has a plurality of diarylamino groups, the luminophore and the protecting group are bonded via the diarylamino groups, and there are a plurality of protecting groups bonded to the diarylamino groups.

[0020] In each of the above structures, the diarylamino group is a diphenylamino group, and the multiple protecting groups are each independently bonded to the 3-position and the 5-position of the diphenylamino group.

[0021] In each of the above structures, the alkyl group is a branched chain alkyl group.

[0022] In each of the above structures, the condensed aromatic ring or the condensed heteroaromatic ring is any one of naphthalene, anthracene, fluorene, chrysene, triphenylene, tetracene, pyrene, perylene, coumarin, quinacridone, and naphthobisbenzofuran.

[0023] In each of the above structures, the first organic compound is represented by the following general formula (G1).

[0024] [ka]

[0025] In the formula, A represents a substituted or unsubstituted fused aromatic ring having 10 to 30 carbon atoms or a substituted or unsubstituted fused heteroaromatic ring having 10 to 30 carbon atoms; Ar 1 ~Ar 4 each independently represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 13 carbon atoms; 1 ~X 8 each independently represents one of an alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, or a trialkylsilyl group having 3 to 10 carbon atoms.

[0026] In the above structure, the first organic compound is represented by the following general formula (G2).

[0027] [ka]

[0028] In the formula, Ar 5 or Ar 6 each independently represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 13 carbon atoms; 9 ~X 12 each independently represents one of an alkyl group having from 1 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having from 3 to 10 carbon atoms, and a trialkylsilyl group having from 3 to 10 carbon atoms; R 1 ~R 10 each independently represents one of a hydrogen atom, an alkyl group having from 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having from 3 to 10 carbon atoms, and a trialkylsilyl group having from 3 to 12 carbon atoms.

[0029] In each of the above structures, the first organic compound is represented by the following general formula (G3).

[0030] [ka]

[0031] In the formula, A represents a substituted or unsubstituted fused aromatic ring having 10 to 30 carbon atoms or a substituted or unsubstituted fused heteroaromatic ring having 10 to 30 carbon atoms; X 1 ~X 8 each independently represents one of an alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, or a trialkylsilyl group having 3 to 10 carbon atoms.

[0032] In the above structure, the first organic compound is represented by the following general formula (G4).

[0033] [ka]

[0034] In the formula, X 9 ~X 12 R each independently represents one of an alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, or a trialkylsilyl group having 3 to 10 carbon atoms. 1 , R 3 , R 6 and R 8 each independently represents one of a hydrogen atom, an alkyl group having from 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having from 3 to 10 carbon atoms, and a trialkylsilyl group having from 3 to 12 carbon atoms.

[0035] In each of the above structures, the alkyl group is a branched chain alkyl group.

[0036] In addition to the above-described light-emitting device (also referred to as a light-emitting element), one embodiment of the present invention also includes a light-emitting device having a transistor, a substrate, or the like in the scope of the invention. Furthermore, in addition to these light-emitting devices, electronic devices and lighting devices having any of a microphone, a camera, an operation button, an external connection portion, a housing, a cover, a support base, a speaker, or the like are also included in the scope of the invention. That is, one embodiment of the present invention includes a light-emitting device having a light-emitting device, and further includes electronic devices and lighting devices to which a light-emitting device is applied in the scope of the invention. Therefore, the light-emitting device in this specification refers to an image display device or a light source (including a lighting device). In addition, a connector (for example, a module to which an FPC (Flexible Printed Circuit) or a TCP (Tape Carrier Package) is attached to a light-emitting device, a module to which a printed wiring board is provided at the end of a TCP, or a module to which an IC (Integrated Circuit) is directly mounted by a COG (Chip On Glass) method, etc.) are all included in the light-emitting device. Effect of the Invention

[0037] According to one embodiment of the present invention, a light-emitting device with high emission efficiency can be provided. Alternatively, according to one embodiment of the present invention, a light-emitting device with high reliability can be provided. Alternatively, according to one embodiment of the present invention, a light-emitting device with reduced power consumption can be provided. Alternatively, according to one embodiment of the present invention, a novel light-emitting device can be provided. Alternatively, according to one embodiment of the present invention, a novel display device can be provided. Alternatively, a novel organic compound can be provided.

[0038] Note that the description of these effects does not preclude the existence of other effects. Note that one embodiment of the present invention does not necessarily have all of these effects. Note that effects other than these are self-evident from the description in the specification, drawings, claims, etc., and it is possible to extract effects other than these from the description in the specification, drawings, claims, etc. [Brief description of the drawings]

[0039] [Figure 1] Fig. 1A is a diagram showing the structure of a light-emitting device, and Fig. 1B is a diagram explaining a light-emitting layer. [Diagram 2] FIG. 2 is a conceptual diagram of energy transfer between a host material and a guest material in an emitting layer. [Diagram 3] Fig. 3A is a conceptual diagram of energy transfer between a general guest material and a host material, and Fig. 3B is a conceptual diagram of energy transfer between a guest material and a host material used in an emitting layer. [Figure 4] Figure 4A shows the structural formula of the guest material used in the light-emitting layer, and Figure 4B shows a ball-and-stick model of the guest material used in the light-emitting layer. [Diagram 5] 5A and 5B are diagrams illustrating the structure of a light-emitting device. [Figure 6] 6A, 6B, and 6C are diagrams illustrating a light emitting device. [Figure 7] Fig. 7A is a top view illustrating the light emitting device, and Fig. 7B is a cross-sectional view illustrating the light emitting device. [Figure 8] Fig. 8A is a diagram for explaining a mobile computer. Fig. 8B is a diagram for explaining a portable image reproducing device. Fig. 8C is a diagram for explaining a digital camera. Fig. 8D is a diagram for explaining a portable information terminal. Fig. 8E is a diagram for explaining a portable information terminal. Fig. 8F is a diagram for explaining a television device. Fig. 8G is a diagram for explaining a portable information terminal. [Figure 9] 9A, 9B, and 9C are diagrams illustrating a foldable portable information terminal. [Figure 10] 10A and 10B are diagrams illustrating an automobile. [Figure 11] 11A and 11B are diagrams illustrating a lighting device. [Figure 12] FIG. 12 is a diagram illustrating a light-emitting device. [Figure 13]FIG. 13 is a graph showing the current density-luminance characteristics of the light-emitting device 1 and the comparative light-emitting device 2. As shown in FIG. [Figure 14] FIG. 14 is a graph showing the voltage-luminance characteristics of the light-emitting device 1 and the comparative light-emitting device 2. As shown in FIG. [Figure 15] FIG. 15 is a graph showing the luminance-current efficiency characteristics of the light-emitting device 1 and the comparative light-emitting device 2. As shown in FIG. [Figure 16] FIG. 16 is a graph showing the voltage-current density characteristics of the light-emitting device 1 and the comparative light-emitting device 2. As shown in FIG. [Figure 17] FIG. 17 is a graph showing the luminance-power efficiency characteristics of the light-emitting device 1 and the comparative light-emitting device 2. As shown in FIG. [Figure 18] FIG. 18 is a graph showing the luminance-external quantum efficiency characteristics of the light-emitting device 1 and the comparative light-emitting device 2. As shown in FIG. [Figure 19] FIG. 19 shows the electroluminescence spectra of Light-Emitting Device 1 and Comparative Light-Emitting Device 2. As shown in FIG. [Figure 20] Figure 20 shows the ultraviolet-visible absorption and emission spectra of 2TMS-mmtBuDPhA2Anth and [Ir(dmdppr-dmp)2(dpm)] in solution. [Figure 21] FIG. 21 is a graph showing current density-luminance characteristics of the light-emitting device 3, the comparative light-emitting device 4, and the comparative light-emitting device 5. In FIG. [Figure 22] FIG. 22 is a graph showing the voltage-luminance characteristics of the light-emitting device 3, the comparative light-emitting device 4, and the comparative light-emitting device 5. In FIG. [Figure 23] FIG. 23 is a graph showing the luminance-current efficiency characteristics of the light-emitting device 3, the comparative light-emitting device 4, and the comparative light-emitting device 5. In FIG. [Figure 24] FIG. 24 is a graph showing the voltage-current density characteristics of the light-emitting device 3, the comparative light-emitting device 4, and the comparative light-emitting device 5. In FIG. [Diagram 25] FIG. 25 is a graph showing the luminance-power efficiency characteristics of the light-emitting device 3, the comparative light-emitting device 4, and the comparative light-emitting device 5. In FIG. [Figure 26]FIG. 26 is a graph showing the luminance-external quantum efficiency characteristics of the light-emitting device 3, the comparative light-emitting device 4, and the comparative light-emitting device 5. In FIG. [Figure 27] FIG. 27 shows the electroluminescence spectra of Light-Emitting Device 3, Comparative Light-Emitting Device 4, and Comparative Light-Emitting Device 5. As shown in FIG. [Figure 28] FIG. 28 is a graph showing the current density-luminance characteristics of the light-emitting device 6 and the light-emitting device 7. As shown in FIG. [Figure 29] FIG. 29 is a diagram showing the voltage-luminance characteristics of the light-emitting device 6 and the light-emitting device 7. As shown in FIG. [Diagram 30] FIG. 30 is a graph showing the luminance-current efficiency characteristics of the light-emitting device 6 and the light-emitting device 7. As shown in FIG. [Diagram 31] FIG. 31 is a graph showing the voltage-current density characteristics of the light-emitting device 6 and the light-emitting device 7. As shown in FIG. [Diagram 32] FIG. 32 is a diagram showing the luminance-power efficiency characteristics of the light-emitting device 6 and the light-emitting device 7. As shown in FIG. [Diagram 33] FIG. 33 is a graph showing the luminance-external quantum efficiency characteristics of the light-emitting device 6 and the light-emitting device 7. As shown in FIG. [Diagram 34] FIG. 34 shows the electroluminescence spectra of light-emitting device 6 and light-emitting device 7. As shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] Hereinafter, the embodiment of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and the form and details can be changed in various ways without departing from the spirit and scope of the present invention. Therefore, the present invention should not be interpreted as being limited to the description of the embodiment shown below.

[0041] In addition, for ease of understanding, the position, size, range, etc. of each component shown in the drawings, etc. may not represent the actual position, size, range, etc. Therefore, the disclosed invention is not necessarily limited to the position, size, range, etc. disclosed in the drawings, etc.

[0042] In addition, in this specification and the like, when describing the configuration of the invention using drawings, the same reference numerals are used in common between different drawings.

[0043] In the present specification and the like, the singlet excited state (S * ) is a singlet state with excitation energy. The S1 level is the lowest singlet excited energy level, and is the lowest singlet excited state (S1 state) excitation energy level. The triplet excited state (T * ) refers to a triplet state having an excitation energy. The T1 level is the lowest level of triplet excitation energy levels, and refers to the lowest triplet excitation energy level (T1 state). In this specification and the like, even when simply referring to a singlet excitation state and a singlet excitation energy level, it may refer to an S1 state and an S1 level. Even when referring to a triplet excitation state and a triplet excitation energy level, it may refer to a T1 state and a T1 level.

[0044] In the present specification and the like, a fluorescent substance is a compound that emits light in the visible light region or near infrared region when relaxing from a singlet excited state to a ground state. A phosphorescent substance is a compound that emits light in the visible light region or near infrared region at room temperature when relaxing from a triplet excited state to a ground state. In other words, a phosphorescent substance is one of the compounds that can convert triplet excitation energy into light emission.

[0045] (Embodiment 1) In this embodiment, a light-emitting device according to one embodiment of the present invention will be described. As shown in Fig. 1A, the light-emitting device has a structure in which an EL layer 103 is sandwiched between a pair of electrodes, which are a first electrode 101 (anode in Fig. 1A) and a second electrode 102 (cathode in Fig. 1A), and the EL layer 103 has at least a light-emitting layer 113, and may also have functional layers such as a hole injection layer 111, a hole transport layer 112, an electron transport layer 114, and an electron injection layer 115.

[0046] The light-emitting layer 113 is a layer containing a light-emitting substance (guest material) and preferably contains a host material in addition to the light-emitting substance. The light-emitting layer 113 of the light-emitting device according to one embodiment of the present invention contains an organic compound functioning as a host material and a plurality of light-emitting substances (guest materials). Specifically, as shown in FIG. 1B, the light-emitting layer 113 contains at least a first organic compound 121 having a function of converting singlet excitation energy into light emission and a second organic compound 122 having a function of converting triplet excitation energy into light emission. The light-emitting layer 113 also contains a third organic compound 123 functioning as a host material. The light-emitting layer 113 may contain a plurality of organic compounds functioning as host materials.

[0047] The light emission of the light-emitting device is achieved in the light-emitting layer 113 by energy transfer from an excited host material (including cases where multiple host materials form an exciplex or not) generated by recombination of carriers (holes and electrons) to a guest material, causing the guest material to emit light.

[0048] Note that the light-emitting device of one embodiment of the present invention has a structure in which energy transfer occurs from an excited state of a third organic compound 123 functioning as a host material to a first organic compound (guest material that is a fluorescent substance) 121 having a function of converting singlet excitation energy into light emission, and energy transfer occurs to a second organic compound (guest material that is a phosphorescent substance) 122 having a function of converting triplet excitation energy into light emission, thereby obtaining fluorescent emission from the first organic compound 121 and phosphorescent emission from the second organic compound 122. Note that since a TADF material can be used instead of a phosphorescent substance as the second organic compound 122, the phosphorescent substance can be interpreted as a TADF material, and phosphorescent emission can be interpreted as fluorescent emission.

[0049] In order to obtain both fluorescent emission from the first organic compound 121 serving as a guest material and phosphorescent emission from the second organic compound 122 serving as a guest material by energy transfer from the excited state of the third organic compound 123 serving as a host material, as in the light-emitting device of one embodiment of the present invention, it is necessary that the lowest singlet excitation energy level (S1 level) of the third organic compound 123 serving as a host material is higher than the S1 level of the first organic compound 121 having a function of converting singlet excitation energy into light emission, and that energy transfer from the T1 level of the host material and the phosphorescent light-emitting substance to the T1 level of the fluorescent light-emitting substance is unlikely to occur, as shown in FIG. 2 .

[0050] 2 shows an example of the correlation of energy levels in the light-emitting layer 113 of the light-emitting device according to one embodiment of the present invention. Note that in FIG. 2, the same symbols as those in FIG. 1B are used, but for convenience, the third organic compound 123 functioning as a host material is shown as Host (123), the first organic compound 121 having the function of converting singlet excitation energy into light emission is shown as Fluorescent Guest (121), and the second organic compound 122 having the function of converting triplet excitation energy into light emission is shown as Phosphorecent Guest (122). Other notations and symbols are as follows. ·S H1 : S1 level of the third organic compound 123 T H1 :T1 level of the third organic compound 123 ·S FG : S1 level of the first organic compound 121 T FG :T1 level of the first organic compound 121 ·S PG : T1 level of the second organic compound 122 T PG : T1 level of the second organic compound 122

[0051] When the third organic compound 123 is excited, the singlet excitation energy can be rapidly transferred to the first organic compound 121. (FIG. 2 Route A 1). At this time, S H1 ≧S FG Specifically, a tangent line is drawn at the base of the fluorescence spectrum of the third organic compound 123 on the short wavelength side, and the energy of the wavelength of the extrapolated line is S H1 The energy of the wavelength at the absorption edge of the absorption spectrum of the first organic compound 121 is S FG When this is done, S H1 ≧S FG It is preferable that:

[0052] In addition, since the second organic compound 122 is a phosphorescent material, it can receive the singlet excitation energy and triplet excitation energy of the third organic compound 123 (see FIG. 2, Route A). 2 ). At this time, T H1 ≧T PG It is preferable that the energy of the wavelength at the absorption edge of the absorption spectrum of the second organic compound 122 is T PG The wavelength energy of the emission edge on the short wavelength side of the emission spectrum of the third organic compound 123 at a low temperature (for example, 10 K) can be regarded as T H1 In order to obtain a good ratio of both the light emission from the first organic compound 121 and the light emission from the second organic compound 122, it is necessary to consider S FG ≧T PG It is preferable that:

[0053] In the light-emitting layer 113, the third organic compound 123, the first organic compound 121, and the second organic compound 122 are mixed together. Therefore, between the third organic compound 123 and the first organic compound 121, route A 1 The triplet excitation energy of the third organic compound 123 is converted to the triplet excitation energy of the first organic compound 121 in competition with the first organic compound 122 (Figure 2, Route A). 3 Since the first organic compound 121 is a fluorescent material, the triplet excitation energy of the first organic compound 121 does not contribute to light emission. That is, route A 3 When energy transfer occurs, the light-emitting efficiency of the light-emitting device decreases. H1 From T FGEnergy transfer process A to 3 is not directly, but the T of the first organic compound 121 FG Energy is transferred once to a triplet excited state higher than T, and then internal conversion occurs. FG However, this process is omitted in the figure. FG The deactivation process for all of them is similar.

[0054] In addition, as shown in Figure 2, S FG ≧T PG In the case of T, the singlet excitation energy of the first organic compound 121 is converted into fluorescent light and T PG The process of energy transfer to (Route A in Figure 2) 4 In other words, the route through which the second organic compound 122 receives the excitation energy is route A. 2 and A 4 Therefore, in order to obtain both the light emissions from the first organic compound 121 and the second organic compound 122 at a good ratio, it is preferable that the concentration of the first organic compound 121 in the light-emitting layer 113 is higher than the concentration of the second organic compound 122. In addition, it is preferable that the concentration of the second organic compound 122 in the light-emitting layer 113 is lower, because this makes it difficult for carriers to recombine in the second organic compound 122.

[0055] In addition, the triplet excitation energy of the second organic compound 122 is converted into light emission, and the triplet excitation energy of the second organic compound 122 is converted into the triplet excitation energy of the first organic compound 121 (Route A in FIG. 2). 5 ) may occur in competition with each other. Since the first organic compound 121 is a fluorescent material, the triplet excitation energy of the first organic compound 121 does not contribute to light emission. That is, route A 5 When this energy transfer occurs, the light emitting efficiency of the light emitting device decreases.

[0056] A compound that emits light with a shorter wavelength is excited with higher energy. Therefore, in order to obtain good reliability in a light-emitting device, it is preferable to use a light-emitting substance with a high emission rate constant for a compound that emits light with a short wavelength, and it is preferable to use a fluorescent light-emitting substance. In other words, it is preferable that the emission spectrum of the second organic compound 122 has an emission peak at a longer wavelength than the peak wavelength of the emission spectrum of the first organic compound 121.

[0057] Generally, the Förster mechanism (dipole-dipole interaction) and the Dexter mechanism (electron exchange interaction) are known as intermolecular energy transfer mechanisms. Since the first organic compound 121, which is the energy acceptor, is a fluorescent material, route A 3 and Route A 5 The Dexter mechanism is dominant in the energy transfer in the above. In general, the Dexter mechanism occurs significantly when the distance between the third organic compound 123, which is the energy donor, and the first organic compound 121, which is the energy acceptor, is 1 nm or less. The Dexter mechanism also occurs significantly when the distance between the first organic compound 121 and the second organic compound 122 is 1 nm or less. Therefore, route A 3 and Route A 5 In order to suppress this, it is important to increase the distance between the energy donor and the energy acceptor.

[0058] In addition, the singlet excited energy level (S H1 ) to obtain the triplet excited energy level (T FG ) is not shown in the figure because it is unlikely to be a major energy transfer process since a direct transition from the singlet ground state to the triplet excited state in the first organic compound 121 is prohibited.

[0059] T in Figure 2 FG is often an energy level derived from the luminophore of the fluorescent material, which is the first organic compound 121. Therefore, route A 3 and Route A 5In order to suppress the energy transfer by the Dexter mechanism, it is important to suppress the energy transfer by increasing the distance between the third organic compound 123 or the second organic compound 122, which are the energy donors, and the luminophore contained in the first organic compound 121, which is the energy acceptor.

[0060] A method for increasing the distance between the energy donor and the luminophore contained in the first organic compound 121 serving as the energy acceptor is generally to reduce the concentration of the first organic compound 121 in the mixed film of these organic compounds. However, reducing the concentration of the first organic compound 121 in the mixed film suppresses not only the energy transfer based on the Dexter mechanism from the energy donor to the luminophore contained in the first organic compound 121 serving as the energy acceptor, but also the energy transfer based on the Förster mechanism. In that case, route A 1 However, because this is based on the Förster mechanism, problems such as reduced light emission efficiency and reduced reliability of the light emitting device occur.

[0061] The present inventors have found that the use of a fluorescent substance having a protecting group as the first organic compound 121, which is an energy acceptor, in order to increase the distance between the first organic compound 121, which is an energy acceptor, and the third organic compound 123 and the second organic compound 122, which are energy donors, can suppress the decrease in luminous efficiency caused by the energy transfer described above. In addition, the present inventors have found that the use of the first organic compound 121 having the protecting group makes it possible to obtain both luminescence (fluorescence) derived from the first organic compound 121 and luminescence (phosphorescence or fluorescence) derived from the second organic compound 122 from the luminescent layer 113 having the first organic compound 121 and the second organic compound 122.

[0062] Next, the concept of energy transfer between a host material and a guest material in a light-emitting layer of the light-emitting device according to one embodiment of the present invention will be described with reference to FIGS. 3A and 3B. FIG.

[0063] 3A shows the presence of a third organic compound 123 as a host material and a fluorescent material 124 as a guest material. Note that the fluorescent material 124 is a general fluorescent material, and has a luminophore 130a but no protecting group.

[0064] 3B shows a state in which the third organic compound 123, which is a host material, and the first organic compound (fluorescent material) 121, which is a guest material, are present. Note that the first organic compound 121 is a fluorescent material used as an energy acceptor in the light-emitting device of one embodiment of the present invention, and has a luminophore 130b and a protecting group 131. Note that the protecting group 131 has a function of separating the third organic compound (host material) 123 and the luminophore 130b by providing a distance therebetween that makes it difficult for energy transfer based on the Dexter mechanism to occur.

[0065] 3A and 3B, in the light-emitting layer, the third organic compound 123 as the host material and the fluorescent material 124 as the guest material or the first organic compound (fluorescent material) 121 are all located close to each other. Therefore, as shown in FIG. 3A, when the fluorescent material 124 does not have a protecting group, the distance between the luminophore 130a and the third organic compound 123 becomes short, and energy transfer from the third organic compound 123 to the fluorescent material 124 occurs by the Forster mechanism (Route A in FIG. 3A). 6 ) and energy transfer via the Dexter mechanism (Route A in Figure 3A). 7 Even if triplet excitation energy is transferred from the host material to the guest material by the Dexter mechanism and a triplet excited state is generated in the guest material, if the guest material is a fluorescent material, the triplet excitation energy is non-radiatively deactivated, which is one of the causes of a decrease in the luminous efficiency of the light-emitting device.

[0066] On the other hand, in FIG. 3B, the first organic compound (fluorescent material) 121, which is a guest material, has a protecting group 131, so that the distance between the luminophore 130b and the third organic compound 123, which is a host material, can be increased. This allows energy transfer by the Dexter mechanism (Route A 7 ) can be suppressed. Therefore, by using the first organic compound (fluorescent substance) 121 having the protecting group 131 as a guest material in the light-emitting layer of the light-emitting device according to one embodiment of the present invention, energy transfer from the host material (third organic compound 123) present in the light-emitting layer to the first organic compound 121 (Route A in FIG. 2) can be suppressed. 3 ) can be suppressed. The same applies to another guest material (the second organic compound 122 described in FIG. 2) present in the light-emitting layer, and energy transfer from the second organic compound 122 to the first organic compound 121 (Route A in FIG. 2) can be suppressed. 3 ) can be suppressed.

[0067] Here, the luminophore 130a of the fluorescent material 124 shown in FIG. 3A and the luminophore 130b of the first organic compound (fluorescent material) 121 shown in FIG. 3B will be described. The luminophore (130a, 130b) refers to an atomic group (skeleton) that causes light emission in a fluorescent material. The luminophore (130a, 130b) generally has a π bond and preferably contains an aromatic ring, preferably a condensed aromatic ring or a condensed heteroaromatic ring. In another embodiment, an atomic group (skeleton) containing an aromatic ring whose transition dipole vector exists on the ring plane can be regarded as the luminophore (130a, 130b). In addition, when one fluorescent material has a plurality of condensed aromatic rings or condensed heteroaromatic rings, the skeleton having the lowest S1 level among the plurality of condensed aromatic rings or condensed heteroaromatic rings may be regarded as the luminophore of the fluorescent material. In addition, when a compound has a plurality of condensed rings or condensed heteroaromatic rings, the skeleton having the absorption edge on the longest wavelength side may be regarded as the luminophore of the fluorescent substance. In addition, when a compound has a plurality of condensed rings or condensed heteroaromatic rings, the luminophore of the fluorescent substance may be predicted from the shape of each emission spectrum.

[0068] Examples of the condensed aromatic ring or condensed heteroaromatic ring include a phenanthrene skeleton, a stilbene skeleton, an acridone skeleton, a phenoxazine skeleton, a phenothiazine skeleton, etc. In particular, fluorescent substances having a naphthalene skeleton, an anthracene skeleton, a fluorene skeleton, a chrysene skeleton, a triphenylene skeleton, a tetracene skeleton, a pyrene skeleton, a perylene skeleton, a coumarin skeleton, a quinacridone skeleton, or a naphthobisbenzofuran skeleton are preferred because they have a high fluorescence quantum yield.

[0069] In addition, the protecting group 131 of the first organic compound (fluorescent material) 121 shown in FIG. 3B preferably has a T1 level higher than the T1 levels of the luminophore 130b and the third organic compound 123, which is the host material. Therefore, a saturated hydrocarbon group can be suitably used as the protecting group. The saturated hydrocarbon group has a high T1 level and a low function of transporting carriers (electrons or holes) because it does not have a π bond. Therefore, by having the saturated hydrocarbon group as the protecting group 131 in the first organic compound 121, the distance between the luminophore 130b and the third organic compound 123, which is the host material, can be increased without affecting the excited state or carrier transportability of the third organic compound 123, which is the host material.

[0070] In addition, when the first organic compound (fluorescent material) 121 has both a substituent that does not have a π bond and a substituent that has a π-conjugated system, the frontier orbital {HOMO (Highest Occupied Molecular Orbital) and LUMO (Lowest Unoccupied Molecular Orbital)} are often present on the side of the substituent that has the π-conjugated system, and in particular, the luminophore 130b often has a frontier orbital. As will be described later, the overlap of the HOMOs of both the energy donor and the energy acceptor and the overlap of the LUMOs of both are important for the energy transfer by the Dexter mechanism. Therefore, by using a saturated hydrocarbon group as a protecting group, the distance between the frontier orbital of the third organic compound 123, which is the energy donor, and the frontier orbital of the first organic compound 121, which is the energy acceptor, can be increased, and the energy transfer by the Dexter mechanism can be suppressed.

[0071] A specific example of the protective group 131 is an alkyl group having 1 to 10 carbon atoms. In addition, since it is necessary to increase the distance between the luminophore 130b of the first organic compound 121, which is a guest material, and the third organic compound 123, which is a host material, the protective group 131 preferably has a bulky structure. For this reason, an alkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, or a trialkylsilyl group having 3 to 10 carbon atoms can be preferably used. In particular, a bulky branched alkyl group is preferable as the alkyl group. In addition, it is particularly preferable that the substituent has a quaternary carbon, since it becomes a bulky substituent.

[0072] In addition, it is preferable that the protecting group 131 has five or more for one luminophore 130b. By adopting this structure, the entire luminophore 130b can be covered with the protecting group 131, so that the distance between the third organic compound 123 and the luminophore can be appropriately adjusted. In addition, it is preferable that the protecting group 131 does not directly bond to the luminophore 130b. For example, it is preferable that the protecting group 131 and the luminophore 130b are bonded via a divalent or higher substituent such as an arylene group or an amino group. By bonding the protecting group 131 and the luminophore 130b via the substituent, the distance between the luminophore 130b and the third organic compound 123 can be effectively increased. Note that, when the protecting group 131 and the luminophore 130b are bonded via the substituent, it is preferable to have four or more protecting groups for one luminophore, since the Dexter mechanism can be effectively suppressed.

[0073] In addition, the divalent or higher substituent linking the luminophore 130b and the protecting group 131 is preferably a substituent having a π-conjugated system. This configuration makes it possible to adjust the physical properties such as the emission color, HOMO level, and glass transition point of the first organic compound 121, which is the guest material. Note that the protecting group 131 is preferably positioned on the outermost side when the molecular structure is viewed from the luminophore in the center.

[0074] As described above, the first organic compound 121 is suppressed in energy transfer by the Dexter mechanism, so that the first organic compound 121 needs to receive energy from the third organic compound 123 by the Förster mechanism in order to emit light. In other words, it is preferable to efficiently utilize the energy transfer by the Förster mechanism while suppressing the energy transfer by the Dexter mechanism. It is known that the energy transfer by the Förster mechanism is also affected by the distance between the host material and the guest material. In general, when the distance between the host material and the guest material is 1 nm or less, the Dexter mechanism predominates, and when the distance is 1 nm or more and 10 nm or less, the Förster mechanism predominates. However, it is said that energy transfer is difficult to occur when the distance between the host material and the guest material is 10 nm or more.

[0075] In this specification, the distance between the third organic compound 123, which is the host material, and the first organic compound 121, which is the guest material, is equal to the distance between the third organic compound 123 and the luminophore 130b of the first organic compound 121. Therefore, it is preferable that the protective group 131 of the first organic compound 121 extends from the luminophore 130b of the first organic compound 121 to a range of 1 nm to 10 nm, so that the Förster mechanism can be dominant. It is more preferable that the extension of the protective group 131 of the first organic compound 121 is in a range of 1 nm to 5 nm. With this configuration, it is possible to efficiently transfer energy by the Förster mechanism while suppressing the energy transfer by the Dexter mechanism from the third organic compound 123, which is the host material, to the first organic compound 121, so that a light-emitting device with high luminous efficiency can be manufactured.

[0076] In general, in order to increase the efficiency of energy transfer by the Förster mechanism (to improve the energy transfer speed), it is preferable to increase the concentration ratio of a fluorescent substance as a guest material relative to a host material, but there is a trade-off relationship in that increasing the concentration ratio of the guest material increases the transfer speed of energy transfer by the Dexter mechanism, resulting in a decrease in luminous efficiency. Therefore, increasing the concentration ratio of the guest material has not been considered an effective means for improving luminous efficiency.

[0077] In contrast, the first organic compound 121 used in the light-emitting device according to one embodiment of the present invention has a structure capable of suppressing energy transfer from a host material by the Dexter mechanism, and therefore, when used as a guest material in a light-emitting layer, the efficiency of energy transfer by the Förster mechanism (the rate of energy transfer) can be increased by increasing the concentration ratio of the first organic compound 121 to the host material. By increasing the concentration ratio of the first organic compound 121 to the host material and increasing the rate of energy transfer by the Förster mechanism, the excitation lifetime of the guest material (energy acceptor) in the light-emitting layer can be shortened, and the reliability of the light-emitting device can be improved.

[0078] In the light-emitting layer of the light-emitting device according to one embodiment of the present invention, the concentration of the first organic compound 121 as a guest material is preferably 2 wt % to 30 wt %, more preferably 5 wt % to 20 wt %, and further preferably 5 wt % to 15 wt %, based on the third organic compound 123 as a host material. This structure can increase the rate of energy transfer by the Forster mechanism, and thus a light-emitting device with high emission efficiency can be obtained. In addition to the above structure, the light-emitting layer of the light-emitting device according to one embodiment of the present invention includes, as a guest material, the second organic compound 122 having a function of converting triplet excitation energy into light emission. Therefore, the light-emitting device according to one embodiment of the present invention can obtain both fluorescent emission from the first organic compound 121 and light emission (phosphorescence or fluorescence) from the second organic compound 122 with high emission efficiency. In this case, in order to obtain a good ratio of the emissions from both the first organic compound 121 and the second organic compound 122, it is preferable that the concentration of the first organic compound 121 in the light-emitting layer 113 is higher than the concentration of the second organic compound 122.

[0079] In a light-emitting device, the above-mentioned energy transfer always competes with the quenching process caused by the influence of degradation products and impurities. In other words, when the quenching rate constant of the quenching process increases over time, the rate of light emission in the light-emitting device decreases, causing the luminance degradation of the light-emitting device. However, as described above, the light-emitting device according to one embodiment of the present invention can suppress the energy transfer by the Dexter mechanism while increasing the energy transfer rate by the Förster mechanism compared to conventional devices, thereby reducing the influence of the competition with the quenching process and enabling the light-emitting device to have a long life.

[0080] Here, the above-mentioned Förster mechanism and Dexter mechanism will be explained. Here, with regard to the donation of excitation energy from a first organic compound in an excited state to a second organic compound in a ground state, the energy transfer process between the molecules of a first organic compound and a second organic compound will be explained, but the same applies when either one of them is an exciplex.

[0081] <Förster mechanism> In the Förster mechanism, energy transfer does not require direct contact between molecules, but occurs through the resonance phenomenon of the dipole vibration of the third organic compound and the first organic compound. The third organic compound transfers energy to the first organic compound through the resonance phenomenon of the dipole vibration, and the third organic compound in the excited state goes to the ground state, and the first organic compound in the ground state goes to the excited state. The rate constant k of the Förster mechanism is h*→g is shown in Equation (1).

[0082]

number

[0083] In formula (1), ν represents the frequency, and f' h (ν) represents the normalized emission spectrum of the third organic compound (fluorescence spectrum when discussing energy transfer from a singlet excited state, and phosphorescence spectrum when discussing energy transfer from a triplet excited state), and ε g (ν) represents the molar absorption coefficient spectrum of the first organic compound, N represents Avogadro's number, n represents the refractive index of the medium, R represents the intermolecular distance between the third organic compound and the first organic compound, τ represents the measured excited state lifetime (fluorescence lifetime or phosphorescence lifetime), c represents the speed of light, φ represents the luminescence quantum yield (fluorescence quantum yield when discussing energy transfer from a singlet excited state, and phosphorescence quantum yield when discussing energy transfer from a triplet excited state), and K 2 is a coefficient (0 to 4) that represents the orientation of the transition dipole moment of the third organic compound and the first organic compound. In the case of random orientation, K 2 =2 / 3.

[0084] In this case, when the energy donor is a third organic compound and the energy acceptor is a first organic compound, if the emission colors of the third organic compound and the first organic compound are close to each other, then according to the above formula (1), f' h (ν) and ε g (ν) overlap becomes smaller (ε gSince (ν) exists on the longer wavelength side than the emission spectrum of the first organic compound), k h*→g However, in the light-emitting device according to one embodiment of the present invention, the concentration of the energy donor in the light-emitting layer can be increased as described above, so that the value of R in formula (1) can be increased, and k h*→g Therefore, in the light-emitting device according to one embodiment of the present invention, a fluorescent substance having an emission color close to that of the energy donor can be used as a light-emitting material. Note that the light-emitting device according to one embodiment of the present invention can be used even if the emission colors of the energy donor and the energy acceptor are different.

[0085] <Dexter System> In the Dexter mechanism, when the third organic compound and the first organic compound approach the effective contact distance where orbital overlap occurs, energy transfer occurs through the exchange of electrons between the excited third organic compound and the ground state first organic compound. The rate constant of the Dexter mechanism, k h*→g is shown in formula (2).

[0086]

number

[0087] In formula (2), h is the Planck constant, K is a constant with the dimension of energy, ν is the frequency, and f' h (ν) represents the normalized emission spectrum of the third organic compound (fluorescence spectrum when discussing energy transfer from a singlet excited state, phosphorescence spectrum when discussing energy transfer from a triplet excited state). In addition, ε' g (ν) represents the normalized absorption spectrum of the first organic compound, L represents the effective molecular radius, and R represents the intermolecular distance between the third organic compound and the first organic compound.

[0088] Energy transfer efficiency φ from the third organic compound to the first organic compound ET is expressed by the formula (3).r represents the rate constant of the emission process of the third organic compound (fluorescence when considering energy transfer from a singlet excited state, phosphorescence when considering energy transfer from a triplet excited state), and k n represents the rate constant of the non-radiative process (thermal deactivation or intersystem crossing) of the first organic compound, and τ represents the measured lifetime of the excited state of the third organic compound.

[0089]

number

[0090] From equation (3), the energy transfer efficiency φ ET To increase the rate constant of energy transfer, k h*→g By increasing the other competing rate constants k r +k n It can be seen that it is good if (=1 / τ) becomes relatively small.

[0091] Next, a concept for increasing the energy transfer efficiency in the above energy transfer mechanisms (Förster mechanism and Dexter mechanism) will be described.

[0092] First, consider the energy transfer by the Förster mechanism. By substituting equation (1) into equation (3), τ can be eliminated. Therefore, in the case of the Förster mechanism, the energy transfer efficiency φ ET It can be seen that the excited state of the third organic compound does not depend on the lifetime τ. In addition, the energy transfer efficiency φ ET It can be said that a higher luminescence quantum yield φ is better.

[0093] In addition, it is preferable that the emission spectrum of the third organic compound and the absorption spectrum of the first organic compound (absorption corresponding to the transition from the singlet ground state to the singlet excited state) overlap greatly. Furthermore, it is preferable that the molar absorption coefficient of the first organic compound is also high. This means that the emission spectrum of the third organic compound overlaps with the absorption band appearing on the longest wavelength side of the first organic compound. Since the direct transition from the singlet ground state to the triplet excited state in the first organic compound is prohibited, the molar absorption coefficient related to the triplet excited state in the first organic compound is a negligible amount. For this reason, the energy transfer process from the excited state of the third organic compound to the triplet excited state to the first organic compound by the Förster mechanism can be ignored, and only the energy transfer process to the singlet excited state of the first organic compound needs to be considered.

[0094] According to formula (1), the rate of energy transfer by the Förster mechanism is inversely proportional to the sixth power of the intermolecular distance R between the third organic compound and the first organic compound. As described above, when R is 1 nm or less, energy transfer by the Dexter mechanism predominates, so in order to increase the rate of energy transfer by the Förster mechanism while suppressing energy transfer by the Dexter mechanism, the intermolecular distance is preferably 1 nm or more and 10 nm or less. Therefore, since it is required that the above-mentioned protecting group is not too bulky, the number of carbon atoms constituting the protecting group is preferably 3 to 10.

[0095] Next, consider the energy transfer via the Dexter mechanism. According to equation (2), the rate constant k h*→g It can be seen that in order to increase the efficiency of energy transfer, it is better to have a large overlap between the emission spectrum of the third organic compound (fluorescence spectrum when discussing energy transfer from a singlet excited state, and phosphorescence spectrum when discussing energy transfer from a triplet excited state) and the absorption spectrum of the first organic compound (absorption corresponding to the transition from the singlet ground state to the singlet excited state). Therefore, the optimization of the energy transfer efficiency is realized by overlapping the emission spectrum of the third organic compound with the absorption band that appears on the longest wavelength side of the first organic compound.

[0096] In addition, by substituting equation (2) into equation (3), the energy transfer efficiency in the Dexter mechanism, φ ET It can be seen that depends on τ. Since the Dexter mechanism is an energy transfer process based on electron exchange, energy transfer occurs not only from the singlet excited state of the third organic compound to the singlet excited state of the first organic compound, but also from the triplet excited state of the third organic compound to the triplet excited state of the first organic compound.

[0097] In the light-emitting device according to one embodiment of the present invention, since the first organic compound is a fluorescent substance, it is preferable that the efficiency of energy transfer to the triplet excited state of the first organic compound is low. In other words, it is preferable that the efficiency of energy transfer from the third organic compound to the first organic compound based on the Dexter mechanism is low, and it is preferable that the efficiency of energy transfer from the third organic compound to the first organic compound based on the Förster mechanism is high.

[0098] As already mentioned, the efficiency of energy transfer in the Förster mechanism does not depend on the lifetime τ of the excited state of the third organic compound. On the other hand, the efficiency of energy transfer in the Dexter mechanism depends on the excited-state lifetime τ of the third organic compound. Therefore, in order to reduce the efficiency of energy transfer in the Dexter mechanism, it is preferable that the excited-state lifetime τ of the third organic compound is short.

[0099] In a light-emitting device according to one embodiment of the present invention, a fluorescent substance having a protecting group is used as the first organic compound. This increases the intermolecular distance between the third organic compound and the first organic compound, and suppresses the energy transfer due to the Dexter mechanism. This makes it possible to suppress the triplet excitation energy of the third organic compound from being transferred to the first organic compound by the Dexter mechanism and being non-radiatively deactivated. This makes it possible to provide a light-emitting device with high luminous efficiency.

[0100] (Embodiment 2) The light-emitting layer of the light-emitting device according to one embodiment of the present invention includes a host material and a guest material, and the guest materials include a first organic compound 121 that is a material (fluorescent material) having a function of converting singlet excitation energy into light emission, and a second organic compound 122 that is a material (phosphorescent material or TADF material) having a function of converting triplet excitation energy into light emission. In this embodiment, the first organic compound 121 will be described in detail.

[0101] The first organic compound 121, which is a material (fluorescent material) having a function of converting singlet excitation energy into luminescence, has a luminophore 130b and a protecting group 131. Note that a condensed aromatic ring or a condensed heteroaromatic ring can be used as the luminophore 130b.

[0102] The protecting group 131 contained in the first organic compound 121 is preferably an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, a branched-chain alkyl group having 3 to 10 carbon atoms, or a trialkylsilyl group having 3 to 12 carbon atoms. When the first organic compound 121 has the protecting group 131, it is possible to suppress energy transfer from the host material to the first organic compound 121, which is a guest material, by the Dexter mechanism in the light-emitting layer.

[0103] In addition, the first organic compound 121 preferably has two or more diarylamino groups having an aryl group bonded to the luminophore 130b, and each of the aryl groups has at least two protective groups 131. By bonding two or more diarylamino groups to symmetrical positions with respect to the luminophore 130b, the quantum yield of the first organic compound 121 can be increased. A specific example of the diarylamino group possessed by the first organic compound 121 is preferably a diphenylamino group. By using a diphenylamino group, it is possible to suppress an increase in the molecular weight of the first organic compound 121 and maintain the sublimability.

[0104] As described above, the diarylamino group is bonded to the protecting group 131 via an aryl group, so that the protecting group 131 can be arranged so as to cover the luminophore 130b, and therefore the distance between the host material and the luminophore 130b can be increased from any direction, which is preferable. Note that the first organic compound 121 is preferably structured so that one luminophore 130b has four or more protecting groups 131.

[0105] Furthermore, when a diphenylamino group is used as a specific example of the diarylamino group contained in the first organic compound 121, it is preferable that the phenyl group in the diphenylamino group has protective groups 131 at the 3rd and 5th positions. In this case, the luminophore 130b contained in the first organic compound 121 is covered with protective groups 131 from above and below in the planar direction, so that energy transfer from the host material to the luminophore 130b by the Dexter mechanism can be suppressed.

[0106] One embodiment of the first organic compound 121 shown above is represented by the following general formula (G1).

[0107] [ka]

[0108] In the above general formula (G1), A represents a substituted or unsubstituted fused aromatic ring having 10 to 30 carbon atoms or a substituted or unsubstituted fused heteroaromatic ring having 10 to 30 carbon atoms; 1 ~Ar 4 each independently represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 13 carbon atoms; 1 ~X 8 each independently represents one of an alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, or a trialkylsilyl group having 3 to 10 carbon atoms.

[0109] Another embodiment of the first organic compound 121 is represented by the following general formula (G2).

[0110] [ka]

[0111] In the above general formula (G2), Ar 5 or Ar 6 each independently represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 13 carbon atoms; 9 ~X 12 each independently represents one of an alkyl group having from 1 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having from 3 to 10 carbon atoms, and a trialkylsilyl group having from 3 to 10 carbon atoms; R 1 ~R 10 each independently represents one of a hydrogen atom, an alkyl group having from 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having from 3 to 10 carbon atoms, and a trialkylsilyl group having from 3 to 12 carbon atoms.

[0112] The first organic compound 121 represented by the general formula (G2) is 9 ~X 12 The protecting group 131 represented by the formula 5 or Ar 6 The luminophore 130b has a structure in which the protecting group 131 is bonded to the quinacridone skeleton of the luminophore 130b via an aromatic hydrocarbon group represented by the following formula: By using this structure, the protecting group 131 can be arranged so as to cover the luminophore 130b, thereby suppressing energy transfer by the Dexter mechanism. The protecting group 131 may be bonded directly to the luminophore 130b.

[0113] Another embodiment of the first organic compound 121 shown above is represented by the following general formula (G3).

[0114] [ka]

[0115] In the above general formula (G3), A represents a substituted or unsubstituted fused aromatic ring having 10 to 30 carbon atoms or a substituted or unsubstituted fused heteroaromatic ring having 10 to 30 carbon atoms; 1 ~X 8 each independently represents one of an alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, or a trialkylsilyl group having 3 to 10 carbon atoms.

[0116] The first organic compound 121 represented by the general formula (G3) is X 1 ~X 8 The protecting group 131 has a structure in which the protecting group 131 represented by the formula (I) is bonded to the luminophore 130b represented by A via a phenylene group. In addition, it is preferable that the two protecting groups 131 bonded to one phenylene group are bonded at the meta-position of the phenylene group. By using this structure, the protecting group 131 can be arranged so as to cover the luminophore 130b, thereby suppressing energy transfer by the Dexter mechanism. Note that the protecting group 131 may be directly bonded to the luminophore 130b.

[0117] Another embodiment of the first organic compound 121 is represented by the following general formula (G4).

[0118] [ka]

[0119] In the general formula (G4) above, X 9 ~X 12 R each independently represents one of an alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, or a trialkylsilyl group having 3 to 10 carbon atoms. 1 , R 3 , R 6 and R 8 each independently represents one of a hydrogen atom, an alkyl group having from 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having from 3 to 10 carbon atoms, and a trialkylsilyl group having from 3 to 12 carbon atoms.

[0120] The first organic compound 121 represented by the general formula (G4) is X 9 ~X 12 The protective group 131 has a structure in which the protective group 131 represented by the formula (I) is bonded to the quinacridone skeleton, which is the luminophore 130b, via a phenylene group. It is also preferable that the two protective groups 131 bonded to one phenylene group are bonded at the meta-position of the phenylene group. This structure allows the protective group 131 to be arranged so as to cover the luminophore 130b, thereby suppressing energy transfer by the Dexter mechanism. The protective group 131 may be directly bonded to the luminophore 130b.

[0121] Another embodiment of the first organic compound 121 is represented by the following general formula (G5).

[0122] [ka]

[0123] In the above general formula (G5), X 1 ~X 8 each independently represents one of an alkyl group having from 1 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having from 3 to 10 carbon atoms, and a trialkylsilyl group having from 3 to 10 carbon atoms; R 11 ~R 18 each independently represents one of hydrogen, a branched alkyl group having from 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having from 3 to 10 carbon atoms, a trialkylsilyl group having from 3 to 10 carbon atoms, or a substituted or unsubstituted aryl group having from 6 to 25 carbon atoms.

[0124] The luminophore 130b contained in the first organic compound 121 represented by the general formula (G1) and the general formula (G3) is represented by a substituted or unsubstituted fused aromatic ring having 10 to 30 carbon atoms or a substituted or unsubstituted fused heteroaromatic ring having 10 to 30 carbon atoms. The luminophore 130b contained in the first organic compound 121 represented by the general formula (G2), the general formula (G4) and the general formula (G5) is a quinacridone skeleton as shown in the formula. In addition, X in the general formula (G1), the general formula (G2), the general formula (G3), the general formula (G4) and the general formula (G5) 1 ~X 12 represents the protecting group 131 that the first organic compound 121 has.

[0125] In the above general formula (G1) and general formula (G3), examples of the substituted or unsubstituted fused aromatic ring having 10 to 30 carbon atoms or the substituted or unsubstituted fused heteroaromatic ring having 10 to 30 carbon atoms include a phenanthrene skeleton, a stilbene skeleton, an acridone skeleton, a phenoxazine skeleton, a phenothiazine skeleton, etc. In addition, examples of skeletons that can further increase the fluorescence quantum yield include a naphthalene skeleton, an anthracene skeleton, a fluorene skeleton, a chrysene skeleton, a triphenylene skeleton, a tetracene skeleton, a pyrene skeleton, a perylene skeleton, a coumarin skeleton, a quinacridone skeleton, a naphthobisbenzofuran skeleton, etc.

[0126] In the above general formulae (G1), (G2), (G3), and (G4), examples of the aromatic hydrocarbon group having 6 to 13 carbon atoms include a phenyl group, a biphenyl group, a naphthyl group, and a fluorenyl group.

[0127] In the above general formulae (G1), (G2), (G3), and (G4), specific examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, a propyl group, a pentyl group, and a hexyl group.

[0128] In the above general formulae (G1), (G2), (G3), (G4), and (G5), specific examples of the cycloalkyl group having 3 to 10 carbon atoms include, for example, a cyclopropyl group, a cyclobutyl group, a cyclohexyl group, a norbornyl group, and an adamantyl group. Specific examples of the cycloalkyl group having a substituent include an alkyl group having 1 to 7 carbon atoms, such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, or a hexyl group, a cycloalkyl group having 5 to 7 carbon atoms, such as a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, or a 8,9,10-trinorbornanyl group, and an aryl group having 6 to 12 carbon atoms, such as a phenyl group, a naphthyl group, or a biphenyl group.

[0129] In addition, in general formula (G5), specific examples of the branched alkyl group having 3 to 10 carbon atoms include an isopropyl group, a sec-butyl group, an isobutyl group, a tert-butyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a neopentyl group, an isohexyl group, a 3-methylpentyl group, a 2-methylpentyl group, a 2-ethylbutyl group, a 1,2-dimethylbutyl group, and a 2,3-dimethylbutyl group.

[0130] In addition, in the above general formulae (G1), (G2), (G3), (G4), and (G5), specific examples of the trialkylsilyl group having 3 to 12 carbon atoms include a trimethylsilyl group, a triethylsilyl group, and a tert-butyldimethylsilyl group.

[0131] In the above general formulae (G1), (G2), (G3), and (G4), when the fused aromatic ring, the fused heteroaromatic ring, the aromatic hydrocarbon group having 6 to 13 carbon atoms, or the cycloalkyl group having 3 to 10 carbon atoms has a substituent, examples of the substituent include alkyl groups having 1 to 7 carbon atoms such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, and a hexyl group; cycloalkyl groups having 5 to 7 carbon atoms such as a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a 8,9,10-trinorbornanyl group; and aryl groups having 6 to 12 carbon atoms such as a phenyl group, a naphthyl group, and a biphenyl group.

[0132] In the above general formula (G5), specific examples of the aryl group having 6 to 25 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, a fluorenyl group, a spirofluorenyl group, etc. When the aryl group has a substituent, examples of the substituent include the above-mentioned alkyl group having 1 to 10 carbon atoms, a branched alkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, and a trialkylsilyl group having 3 to 10 carbon atoms.

[0133] The first organic compound 121 represented by the general formula (G5) is X 1 ~X 8 The protecting group 131 represented by the formula (I) is bonded to the anthracene skeleton, which is the luminophore 130b, via a phenylene group. The two protecting groups 131 bonded to one phenylene group are preferably bonded at the meta-position of the phenylene group. In this structure, since the anthracene skeleton has a small light-emitting surface area, the protecting group 131 can efficiently cover the luminophore 130b, and energy transfer by the Dexter mechanism can be suppressed.

[0134] Next, specific examples of the first organic compound 121 represented by the above general formulae (G1) to (G5) are shown in the following structural formulae (100) to (105) and structural formulae (200) to (284). Note that specific examples of the first organic compound 121 represented by the general formulae (G1) to (G5) are not limited to these.

[0135] [ka]

[0136] [ka]

[0137] [ka]

[0138] [ka]

[0139] [ka]

[0140] [ka]

[0141] [ka]

[0142] [ka]

[0143] [ka]

[0144] [ka]

[0145] [ka]

[0146] [ka]

[0147] [ka]

[0148] [ka]

[0149] Among the specific examples of the first organic compound 121 described above, N,N'-[(2-tert-butylanthracene)-9,10-diyl]-N,N'-bis(3,5-di-tert-butylphenyl)amine (abbreviation: 2tBu-mmtBuDPhA2Anth) represented by the following structural formula (102) will be used to explain the structure of the first organic compound 121. Note that the luminophore 130b in 2tBu-mmtBuDPhA2Anth is an anthracene ring, and the protecting group 131 is a tertiary butyl group (tBu).

[0150] [ka]

[0151] FIG. 4A shows 2tBu-mmtBuDPhA2Anth, and FIG. 4B shows a ball-and-stick model of 2tBu-mmtBuDPhA2Anth when viewed from the direction of the arrow in FIG. 4A (horizontal to the plane of the anthracene ring).

[0152] The shaded portion in FIG. 4B represents the portion directly above the surface of the anthracene ring, which is the luminophore 130b, and it can be seen that the portion directly above has an area where the tBu group, which is the protecting group, overlaps. For example, in FIG. 4B, the atom indicated by the arrow (a) is the carbon atom of the tBu group that overlaps with the shaded portion, and the atom indicated by the arrow (b) is the hydrogen atom of the tBu group that overlaps with the shaded portion. That is, in 2tBu-mmtBuDPhA2Anth, the atom constituting the protecting group 131 is located directly above one surface of the luminophore 130b, and the atom constituting the protecting group 131 is also located directly above the other surface of the luminophore 130b. By adopting this configuration, even if the first organic compound 121, which is the guest material, is dispersed in the third organic compound 123, which is the host material, the distance between the host material and both the planar direction and the vertical direction of the anthracene ring, which is the luminophore 130b, can be increased, and energy transfer by the Dexter mechanism can be suppressed.

[0153] In the case of energy transfer by the Dexter mechanism, for example, when the transition related to the energy transfer is between HOMO and LUMO, the Dexter mechanism occurs significantly when the HOMO and LUMO of both the host material and the guest material overlap. Therefore, the Dexter mechanism can be suppressed by suppressing the overlap of the HOMO and LUMO of both materials. In other words, the Dexter mechanism can be suppressed by increasing the distance between the skeleton related to the excited state and the guest material. Here, in the second organic compound 121, which is a fluorescent material, the luminophore 130b often has a HOMO and a LUMO. Therefore, in 2tBu-mmtBuDPhA2Anth shown in FIG. 4B, it is important to have a molecular structure in which the HOMO and LUMO extending above and below the anthracene ring, which is the luminophore 130b, are covered with the protecting group 131 in order to suppress the Dexter mechanism.

[0154] In addition, when the luminophore 130b of the first organic compound 121 is a fused aromatic ring or a fused heteroaromatic ring such as a pyrene ring or an anthracene ring, the transition dipole vector exists on the plane of the ring. Therefore, as shown in FIG. 4B, it is preferable that 2tBu-mmtBuDPhA2Anth has a region where the tBu group, which is the protecting group 131, overlaps with the plane where the transition dipole vector exists, i.e., the plane of the anthracene ring, which is the luminophore 130b. Specifically, it is preferable that at least one of the atoms constituting the multiple protecting groups 131 (tBu group in FIG. 4B) is located directly above one surface of the fused aromatic ring or the fused heteroaromatic ring (anthracene ring in FIG. 4B), and at least one of the atoms constituting the multiple protecting groups 131, excluding the previous atom, is located directly above the other surface of the fused aromatic ring or the fused heteroaromatic ring.

[0155] Next, a method for synthesizing the first organic compound 121 represented by the following general formula (G1) will be described.

[0156] [ka]

[0157] In the above general formula (G1), A represents a substituted or unsubstituted fused aromatic ring having 10 to 30 carbon atoms or a substituted or unsubstituted fused heteroaromatic ring having 10 to 30 carbon atoms; 1 ~Ar 4 each independently represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 13 carbon atoms; 1 ~X 8 each independently represents one of an alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, or a trialkylsilyl group having 3 to 10 carbon atoms.

[0158] The first organic compound 121 represented by the above general formula (G1) can be synthesized, for example, by the methods shown in the following synthesis schemes (S-1) and (S-2).

[0159] First, as shown in the synthesis scheme (S-1), compound 1, compound 2 (arylamine), and compound 3 (arylamine) are coupled to obtain compound 4 (diamine compound).

[0160] [ka]

[0161] Subsequently, as shown in the synthesis scheme (S-2), the compound 4 (diamine compound), the compound 5 (aryl halide), and the compound 6 (aryl halide) are coupled to obtain the first organic compound 121 represented by the general formula (G1).

[0162] [ka]

[0163] In the above synthesis schemes (S-1) and (S-2), A represents a substituted or unsubstituted fused aromatic ring having 10 to 30 carbon atoms or a substituted or unsubstituted fused heteroaromatic ring having 10 to 30 carbon atoms; Ar 1 ~Ar 4 each independently represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 13 carbon atoms; 1 ~X 8 each independently represents any one of an alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, and a trialkylsilyl group having 3 to 12 carbon atoms. Examples of the condensed ring or condensed heteroaromatic ring include chrysene, phenanthrene, stilbene, acridone, phenoxazine, and phenothiazine. In particular, anthracene, pyrene, coumarin, quinacridone, perylene, tetracene, and naphthobisbenzofuran are preferred.

[0164] In the above synthesis schemes (S-1) and (S-2), when the Buchwald-Hartwig reaction is carried out using a palladium catalyst, X 10~X 13 represents a halogen group or a triflate group, and the halogen is preferably iodine, bromine, or chlorine. In this reaction, palladium compounds such as bis(dibenzylideneacetone)palladium(0) and palladium(II) acetate, and ligands such as tri(tert-butyl)phosphine, tri(n-hexyl)phosphine, tricyclohexylphosphine, di(1-adamantyl)-n-butylphosphine, and 2-dicyclohexylphosphino-2',6'-dimethoxy-1,1'-biphenyl can be used. In addition, organic bases such as sodium tert-butoxide, and inorganic bases such as potassium carbonate, cesium carbonate, and sodium carbonate can be used. In addition, toluene, xylene, mesitylene, benzene, tetrahydrofuran, dioxane, and the like can be used as a solvent. It should be noted that the reagents that can be used in this reaction are not limited to these reagents.

[0165] The reaction carried out in the above synthesis schemes (S-1) and (S-2) is not limited to the Buchwald-Hartwig reaction, and may be, for example, the Migita-Kosugi-Still coupling reaction using an organotin compound, a coupling reaction using a Grignard reagent, or the Ullmann reaction using copper or a copper compound.

[0166] In addition, in the above synthesis scheme (S-1), when compound 2 and compound 3 have different structures, it is preferable to first react compound 1 with compound 2 to form a coupling product, and then react the resulting coupling product with compound 3. When compound 1 is reacted stepwise with compound 2 and compound 3, compound 1 is preferably a dihalogen product, and X 10 and X 11 It is preferred to carry out the amination reaction selectively one by one using different halogens.

[0167] In addition, in the above synthesis scheme (S-2), when compound 5 and compound 6 have different structures, it is preferable to first react compound 4 with compound 5 to form a coupling product, and then react the obtained coupling product with compound 6.

[0168] The synthesis method of the first organic compound 121 represented by General Formula (G1), which is an example of the first organic compound 121 that can be used for the light-emitting layer of the light-emitting device of one embodiment of the present invention, has been described above. However, the present invention is not limited thereto, and the compound may be synthesized by another synthesis method.

[0169] (Embodiment 3) In this embodiment, a light-emitting device which is one embodiment of the present invention will be described.

[0170] <Example of light-emitting device configuration> FIG. 5A shows an example of a light-emitting device having an EL layer including a light-emitting layer between a pair of electrodes. Specifically, the EL layer 103 is sandwiched between a first electrode 101 and a second electrode 102. For example, when the first electrode 101 is an anode, the EL layer 103 has a structure in which a hole injection layer 111, a hole transport layer 112, a light-emitting layer 113, an electron transport layer 114, and an electron injection layer 115 are sequentially laminated as functional layers. The light-emitting layer 113 has a host material and a guest material, and uses a third organic compound 123 as the host material, a first organic compound 121 that is a material (fluorescent material) having a function of converting singlet excitation energy into light emission, and a second organic compound 122 that is a material (phosphorescent material or TADF material) having a function of converting triplet excitation energy into light emission as the guest material.

[0171] Other light-emitting device structures include a light-emitting device having a structure (tandem structure) in which a charge generation layer is sandwiched between a pair of electrodes to enable low-voltage operation, and a light-emitting device having improved optical characteristics by forming a micro-optical resonator (microcavity) structure between a pair of electrodes, etc. The charge generation layer has a function of injecting electrons into one of the adjacent EL layers and injecting holes into the other EL layer when a voltage is applied between the first electrode 101 and the second electrode 102.

[0172] At least one of the first electrode 101 and the second electrode 102 of the light-emitting device is an electrode having translucency (transparent electrode, semi-transmissive / semi-reflective electrode, etc.). When the electrode having translucency is a transparent electrode, the visible light transmittance of the transparent electrode is 40% or more. When the electrode is a semi-transmissive / semi-reflective electrode, the visible light reflectance of the semi-transmissive / semi-reflective electrode is 20% or more and 80% or less, preferably 40% or more and 70% or less. Furthermore, these electrodes have a resistivity of 1×10 -2 It is preferable to set it to Ωcm or less.

[0173] In the above-described light-emitting device according to one embodiment of the present invention, when one of the first electrode 101 and the second electrode 102 is a reflective electrode (reflective electrode), the electrode has a visible light reflectance of 40% to 100%, preferably 70% to 100%. -2 It is preferable to set it to Ωcm or less.

[0174] <First Electrode and Second Electrode> As the material for forming the first electrode 101 and the second electrode 102, the following materials can be used in appropriate combination as long as the above-mentioned functions of both electrodes are satisfied. For example, metals, alloys, electrically conductive compounds, and mixtures thereof can be used appropriately. Specific examples include In-Sn oxide (also called ITO), In-Si-Sn oxide (also called ITSO), In-Zn oxide, and In-W-Zn oxide. In addition, metals such as aluminum (Al), titanium (Ti), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), gallium (Ga), zinc (Zn), indium (In), tin (Sn), molybdenum (Mo), tantalum (Ta), tungsten (W), palladium (Pd), gold (Au), platinum (Pt), silver (Ag), yttrium (Y), and neodymium (Nd), as well as alloys containing these in appropriate combinations, can also be used. Other examples that can be used include elements belonging to Group 1 or 2 of the periodic table (e.g., lithium (Li), cesium (Cs), calcium (Ca), and strontium (Sr)) that are not listed above, rare earth metals such as europium (Eu) and ytterbium (Yb), and alloys containing appropriate combinations of these, as well as graphene.

[0175] These electrodes can be fabricated by sputtering or vacuum deposition.

[0176] <Hole injection layer> The hole injection layer 111 is a layer that injects holes from the first electrode 101, which is an anode, to the EL layer 103, and is a layer that contains an organic acceptor material or a material with high hole injection properties.

[0177] An organic acceptor material is a material that can generate holes in an organic compound by charge separation between the organic compound and another organic compound whose LUMO level and HOMO level are close to each other. Therefore, as an organic acceptor material, a compound having an electron-withdrawing group (a halogen group or a cyano group), such as a quinodimethane derivative, a chloranil derivative, or a hexaazatriphenylene derivative, can be used. For example, 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation: F 4 -TCNQ), 3,6-difluoro-2,5,7,7,8,8-hexacyanoquinodimethane, chloranil, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviation: HAT-CN), 1,3,4,5,7,8-hexafluorotetracyano-naphthoquinodimethane (abbreviation: F6-TCNNQ), etc. can be used. Among organic acceptor materials, HAT-CN is particularly suitable because it has high acceptor properties and its film quality is stable against heat. In addition, [3] radialene derivatives are preferable because of their extremely high electron-accepting properties. Specifically, α,α',α''-1,2,3-cyclopropane triylidene tris[4-cyano-2,3,5,6-tetrafluorobenzeneacetonitrile], α,α',α''-1,2,3-cyclopropane triylidene tris[2,6-dichloro-3,5-difluoro-4-(trifluoromethyl)benzeneacetonitrile], α,α',α''-1,2,3-cyclopropane triylidene tris[2,3,4,5,6-pentafluorobenzeneacetonitrile], and the like can be used.

[0178] Examples of materials with high hole injection properties include transition metal oxides such as molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, and manganese oxide. 2 Pc) and copper phthalocyanine (abbreviation: CuPc) and other phthalocyanine-based compounds can be used.

[0179] In addition to the above materials, the following low molecular weight compounds have been developed: 4,4',4''-tris(N,N-diphenylamino)triphenylamine (abbreviation: TDATA), 4,4',4''-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine (abbreviation: MTDATA), 4,4'-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation: DPAB), 4,4'-bis(N-{4-[N'-(3-methylphenyl)-N'-phenylamino]phenyl}-N-phenylamino)biphenyl (abbreviation: DNTPD), 1,3,5-tris(N-{4-[N'-(3-methylphenyl)-N'-phenylamino]phenyl}-N-phenylamino)biphenyl (abbreviation: DNTPD), Aromatic amine compounds such as [N-(4-diphenylaminophenyl)-N-phenylamino]benzene (abbreviation: DPA3B), 3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA1), 3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA2), and 3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole (abbreviation: PCzPCN1) can be used.

[0180] Also, polymer compounds (oligomers, dendrimers, polymers, etc.) such as poly(N-vinylcarbazole) (abbreviation: PVK), poly(4-vinyltriphenylamine) (abbreviation: PVTPA), poly[N-(4-{N'-[4-(4-diphenylamino)phenyl]phenyl-N'-phenylamino}phenyl)methacrylamide] (abbreviation: PTPDMA), poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine] (abbreviation: Poly-TPD), etc. can be used. Alternatively, polymer compounds to which an acid has been added, such as poly(3,4-ethylenedioxythiophene) / poly(styrenesulfonic acid) (abbreviation: PEDOT / PSS) and polyaniline / poly(styrenesulfonic acid) (PAni / PSS), etc. can also be used.

[0181] As a material with high hole injection properties, a composite material containing a hole transport material and an acceptor material (electron accepting material) can also be used. In this case, electrons are extracted from the hole transport material by the acceptor material, generating holes in the hole injection layer 111, and the holes are injected into the light emitting layer 113 via the hole transport layer 112. Note that the hole injection layer 111 may be formed as a single layer made of a composite material containing a hole transport material and an acceptor material (electron accepting material), or may be formed by laminating the hole transport material and the acceptor material (electron accepting material) in separate layers.

[0182] The hole transport material is 1×10 -6 cm 2 A substance having a hole mobility of / Vs or more is preferable. Note that other substances can be used as long as they have a higher hole transporting property than an electron transporting property.

[0183] As the hole transporting material, a material having a high hole transporting property, such as a π-electron-rich heteroaromatic compound (for example, a carbazole derivative or a furan derivative) or an aromatic amine (a compound having an aromatic amine skeleton), is preferable.

[0184] Examples of the carbazole derivative (a compound having a carbazole skeleton) include a bicarbazole derivative (for example, a 3,3'-bicarbazole derivative) and an aromatic amine having a carbazolyl group.

[0185] Specific examples of the bicarbazole derivative (e.g., 3,3'-bicarbazole derivative) include 3,3'-bis(9-phenyl-9H-carbazole) (abbreviation: PCCP), 9,9'-bis(1,1'-biphenyl-4-yl)-3,3'-bi-9H-carbazole, 9,9'-bis(1,1'-biphenyl-3-yl)-3,3'-bi-9H-carbazole, 9-(1,1'-biphenyl-3-yl)-9'-(1,1'-biphenyl-4-yl)-9H,9'H-3,3'-bicarbazole (abbreviation: mBPCCBP), and 9-(2-naphthyl)-9'-phenyl-9H,9'H-3,3'-bicarbazole (abbreviation: βNCCP).

[0186] Specific examples of the aromatic amine having a carbazolyl group include 4-phenyl-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBA1BP), N-(4-biphenyl)-N-(9,9-dimethyl-9H-fluoren-2-yl)-9-phenyl-9H-carbazol-3-amine (abbreviation: PCBiF), N-(1,1'-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)]- 4,4'-diphenyl-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBBi1BP), 4-(1-naphthyl)-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBAB), 4,4'-di(1-naphthyl)-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBANB), PCBNBB, 4-phenyldiphenyl-(9-phenyl-9H-carbazol-3-yl)amine (PCA1BP), N,N'-bis(9-phenylcarbazol-3-yl)-N,N'-diphenylbenzene-1,3-diamine (PCA2B), N,N',N''-triphenyl-N,N',N''-tris(9-phenylcarbazol-3-yl)benzene-1,3,5-triamine (PCA3B), 9 ,9-Dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]fluoren-2-amine (abbreviation: PCBAF), N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]spiro-9,9'-bifluoren-2-amine (abbreviation: PCBASF), 3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA1), 3,6-Bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA2), 3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole (abbreviation: PCzPCN1), 3-[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzDPA1), 3,6-bis[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzDPA2), 3,6-bis[N-(4-diphenylaminophenyl)-N-(1 -naphthyl)amino]-9-phenylcarbazole (abbreviation: PCzTPN2), 2-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]spiro-9,9'-bifluorene (abbreviation: PCASF), N-[4-(9H-carbazol-9-yl)phenyl]-N-(4-phenyl)phenylaniline (abbreviation: YGA1BP), N,N'-bis[4-(carbazol-9-yl)phenyl]-N,N'-diphenyl-9,9-dimethylfluorene-2,7-diamine (abbreviation: YGA2F), 4,4',4''-tris(carbazol-9-yl)triphenylamine (abbreviation: TCTA), etc.

[0187] In addition to the above, examples of the carbazole derivative include 3-[4-(9-phenanthryl)-phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPPn), 3-[4-(1-naphthyl)-phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPN), 1,3-bis(N-carbazolyl)benzene (abbreviation: mCP), 4,4'-di(N-carbazolyl)biphenyl (abbreviation: CBP), 3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviation: CzTP), 1,3,5-tris[4-(N-carbazolyl)phenyl]benzene (abbreviation: TCPB), and 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation: CzPA).

[0188] Specific examples of the furan derivative (compound having a furan skeleton) include compounds having a thiophene skeleton such as 4,4',4''-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation: DBT3P-II), 2,8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene (abbreviation: DBTFLP-III), and 4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviation: DBTFLP-IV), 4,4',4''-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation: DBF3P-II), and 4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran (abbreviation: mmDBFFLBi-II).

[0189] Specific examples of the aromatic amine include 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB or α-NPD), N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (abbreviation: TPD), 4,4'-bis[N-(spiro-9,9'-bifluoren-2-yl)-N-phenylamino]biphenyl (abbreviation: BSPB), 4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP ... mBPAFLP, N-(9,9-dimethyl-9H-fluoren-2-yl)-N-{9,9-dimethyl-2-[N'-phenyl-N'-(9,9-dimethyl-9H-fluoren-2-yl)amino]-9H-fluoren-7-yl}phenylamine (DFLADFL), N-(9,9-dimethyl-2-diphenylamino-9H-fluoren-7-yl)diphenylamine (DPNF), 2-[N-(4-diphenylaminophenyl)-N-phenylamino] ]spiro-9,9'-bifluorene (abbreviation: DPASF), 2,7-bis[N-(4-diphenylaminophenyl)-N-phenylamino]-spiro-9,9'-bifluorene (abbreviation: DPA2SF), 4,4',4''-tris[N-(1-naphthyl)-N-phenylamino]triphenylamine (abbreviation: 1'-TNATA), 4,4',4''-tris(N,N-diphenylamino)triphenylamine (abbreviation: TDATA), 4,4',4''-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine (abbreviation: m- MTDATA), N,N'-di(p-tolyl)-N,N'-diphenyl-p-phenylenediamine (abbreviation: DTDPPA), 4,4'-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation: DPAB), N,N'-bis{4-[bis(3-methylphenyl)amino]phenyl}-N,N'-diphenyl-(1,1'-biphenyl)-4,4'-diamine (abbreviation: DNTPD), 1,3,5-tris[N-(4-diphenylaminophenyl)-N-phenylamino]benzene (abbreviation: DPA3B), etc.

[0190] As the hole transporting material, polymer compounds such as poly(N-vinylcarbazole) (abbreviation: PVK), poly(4-vinyltriphenylamine) (abbreviation: PVTPA), poly[N-(4-{N'-[4-(4-diphenylamino)phenyl]phenyl-N'-phenylamino}phenyl)methacrylamide] (abbreviation: PTPDMA), and poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine] (abbreviation: Poly-TPD) can also be used.

[0191] However, the hole transporting material is not limited to the above, and one or a combination of various known materials may be used as the hole transporting material.

[0192] As an acceptor material used for the hole-injection layer 111, an oxide of a metal belonging to Groups 4 to 8 of the periodic table can be used. Specific examples include molybdenum oxide, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, tungsten oxide, manganese oxide, and rhenium oxide. Among them, molybdenum oxide is particularly preferable because it is stable in the air, has low hygroscopicity, and is easy to handle. In addition, the above-mentioned organic acceptors can also be used.

[0193] The hole injection layer 111 can be formed by using various known film formation methods, for example, by using a vacuum deposition method.

[0194] <Hole transport layer> The hole transport layer 112 is a layer that transports holes injected from the first electrode 101 by the hole injection layer 111 to the light emitting layer 113. The hole transport layer 112 is a layer that contains a hole transport material. Therefore, the hole transport layer 112 can be made of the same material as the hole injection layer 111.

[0195] Note that in the light-emitting device of one embodiment of the present invention, the light-emitting layer 113 preferably uses the same organic compound as that used for the hole-transport layer 112. By using the same organic compound for the hole-transport layer 112 and the light-emitting layer 113, holes can be efficiently transported from the hole-transport layer 112 to the light-emitting layer 113.

[0196] <Light-emitting layer> The light-emitting layer 113 is a layer containing a light-emitting substance. The light-emitting layer 113 in the light-emitting device according to one embodiment of the present invention includes a host material and a guest material. The host material includes a third organic compound 123, and the guest materials include a first organic compound 121 that is a material (fluorescent material) having a function of converting singlet excitation energy into light emission and a second organic compound 122 that is a material (phosphorescent material or TADF material) having a function of converting triplet excitation energy into light emission. Note that the light-emitting substance that can be used for the light-emitting layer 113 is not particularly limited as long as it satisfies the above conditions, and a substance that emits light of blue, purple, blue-purple, green, yellow-green, yellow, orange, red, or the like can be appropriately used.

[0197] However, the host material used in the light-emitting layer 113 may be a mixture of a plurality of organic compounds, or may be an exciplex formed by these compounds. The third organic compound 123 used as the host material is preferably a substance having a larger energy gap than the energy gaps of the first organic compound 121 and the second organic compound 122 used as the guest materials. The lowest singlet excitation energy level (S1 level) of the third organic compound 123 is preferably higher than the S1 level of the first organic compound 121, and the lowest triplet excitation energy level (T1 level) of the third organic compound 123 is preferably higher than the T1 level of the first organic compound 121. The lowest triplet excitation energy level (T1 level) of the third organic compound 123 is preferably higher than the T1 level of the second organic compound 122.

[0198] As the one or more organic compounds used as the host material, as long as they satisfy the conditions as a host material used in the light-emitting layer, examples of the organic compounds include a hole transporting material that can be used in the hole transporting layer 112 described above and an electron transporting material that can be used in the electron transporting layer 114 described below, and may be an exciplex consisting of multiple organic compounds. An exciplex (also called an exciplex) that forms an excited state with multiple organic compounds has an extremely small difference between the S1 level and the T1 level, and functions as a TADF material that can convert triplet excitation energy into singlet excitation energy. As a combination of multiple organic compounds that form an exciplex, for example, one of them has a π-electron-deficient heteroaromatic ring and the other has a π-electron-rich heteroaromatic ring. As a combination that forms an exciplex, a phosphorescent material such as an iridium, rhodium, or platinum-based organometallic complex or a metal complex may be used on one side.

[0199] Note that the first organic compound 121 and the second organic compound 122 used as guest materials in the light-emitting layer 113 preferably emit different light colors. Alternatively, white light may be emitted by combining complementary light colors.

[0200] The first organic compound 121, which is a first guest material of the light-emitting layer 113 and has a function of converting singlet excitation energy into light emission, can be any of the materials shown in embodiment 2 in a combination that satisfies the conditions for a guest material used in the light-emitting layer. In addition, the second organic compound 122, which is a second guest material of the light-emitting layer 113 and has a function of converting triplet excitation energy into light emission, can be, for example, a phosphorescent substance or a thermally activated delayed fluorescence (TADF) material that exhibits thermally activated delayed fluorescence. These can also be used in a combination that satisfies the conditions for a guest material used in the light-emitting layer. In addition, the lowest singlet excitation energy level (S1 level) of the first organic compound 121 is higher than the T1 level of the second organic compound 122. That is, the light emission obtained from the second organic compound 122 has a longer peak wavelength in the emission spectrum than the light emission obtained from the first organic compound 121.

[0201] A phosphorescent material is a compound that exhibits phosphorescence but does not exhibit fluorescence in a temperature range from low temperature (e.g., 77 K) to room temperature (i.e., 77 K to 313 K). The phosphorescent material preferably has a metal element with a large spin-orbit interaction, and examples of the phosphorescent material include an organometallic complex, a metal complex (platinum complex), and a rare earth metal complex. Specifically, a transition metal element is preferable, and it is particularly preferable to have a platinum group element (ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), or platinum (Pt)). Among these, it is preferable to have iridium, since it can increase the transition probability related to the direct transition between the singlet ground state and the triplet excited state.

[0202] Examples of phosphorescent substances that exhibit blue or green light and have an emission spectrum with a peak wavelength of 450 nm or more and 570 nm or less include the following substances.

[0203] For example, tris{2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazol-3-yl-κN2]phenyl-κC}iridium(III) (abbreviation: [Ir(mpptz-dmp) 3 ]), tris(5-methyl-3,4-diphenyl-4H-1,2,4-triazolato)iridium(III) (abbreviation: [Ir(Mptz) 3 ]), tris[4-(3-biphenyl)-5-isopropyl-3-phenyl-4H-1,2,4-triazolato]iridium(III) (abbreviation: [Ir(iPrptz-3b) 3 ]), tris[3-(5-biphenyl)-5-isopropyl-4-phenyl-4H-1,2,4-triazolato]iridium(III) (abbreviation: [Ir(iPr5btz) 3 ]), organometallic complexes with a 4H-triazole skeleton such as tris[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-triazolato]iridium(III) (abbreviation: [Ir(Mptz1-mp) 3 ]), tris(1-methyl-5-phenyl-3-propyl-1H-1,2,4-triazolato)iridium(III) (abbreviation: [Ir(Prptz1-Me) 3 ]), organometallic complexes with a 1H-triazole skeleton such as fac-tris[1-(2,6-diisopropylphenyl)-2-phenyl-1H-imidazole]iridium(III) (abbreviation: [Ir(iPrpmi) 3 ]), tris[3-(2,6-dimethylphenyl)-7-methylimidazo[1,2-f]phenanthridinato]iridium(III) (abbreviation: [Ir(dmpimpt-Me 3 Organometallic complexes with imidazole skeletons such as bis[2-(4',6'-difluorophenyl)pyridinato-N,C 2’ ]iridium(III) tetrakis(1-pyrazolyl)borate (abbreviation: FIr6), bis[2-(4',6'-difluorophenyl)pyridinato-N,C 2’ ]iridium(III) picolinate (abbreviation: FIrpic), bis{2-[3',5'-bis(trifluoromethyl)phenyl]pyridinato-N,C2’}Iridium(III) picolinate (abbreviation: [Ir(CF 3 ppy) 2 (pic)]), bis[2-(4',6'-difluorophenyl)pyridinato-N,C 2’ ] Examples include organometallic complexes with phenylpyridine derivatives having electron-withdrawing groups as ligands, such as iridium(III) acetylacetonate (abbreviation: FIr(acac)).

[0204] Examples of phosphorescent substances that exhibit green or yellow light and have an emission spectrum with a peak wavelength of 495 nm or more and 590 nm or less include the following substances.

[0205] For example, tris(4-methyl-6-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(mppm) 3 ]), tris(4-t-butyl-6-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(tBuppm) 3 ]), (acetylacetonato)bis(6-methyl-4-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(mppm) 2 (acac)]), (acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(tBuppm) 2 (acac)]), (acetylacetonato)bis[6-(2-norbornyl)-4-phenylpyrimidinato]iridium(III) (abbreviation: [Ir(nbppm) 2 (acac)]), (acetylacetonato)bis[5-methyl-6-(2-methylphenyl)-4-phenylpyrimidinato]iridium(III) (abbreviation: [Ir(mpmppm) 2 (acac)]), (acetylacetonato)bis{4,6-dimethyl-2-[6-(2,6-dimethylphenyl)-4-pyrimidinyl-κN3]phenyl-κC}iridium(III) (abbreviation: [Ir(dmppm-dmp) 2 (acac)]), (acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III) (abbreviation: [Ir(dppm) 2(Acac)]), (acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazinato)iridium(III) (abbreviation: [Ir(mppr-Me 2 (acac)]), (acetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazinate)iridium(III) (abbreviation: [Ir(mppr-iPr) 2 Organometallic iridium complexes with pyrazine skeletons such as tris(2-phenylpyridinato-N,C(acac)]) 2’ ) Iridium(III) (abbreviation: [Ir(ppy) 3 ]), bis(2-phenylpyridinato-N,C 2’ ) Iridium(III) acetylacetonate (abbreviation: [Ir(ppy) 2 (acac)]), bis(benzo[h]quinolinato)iridium(III) acetylacetonate (abbreviation: [Ir(bzq) 2 (acac)]), tris(benzo[h]quinolinato)iridium(III) (abbreviation: [Ir(bzq) 3 ]), tris(2-phenylquinolinato-N,C 2’ ) Iridium(III) (abbreviation: [Ir(pq) 3 ]), bis(2-phenylquinolinato-N,C 2’ ) Iridium(III) acetylacetonate (abbreviation: [Ir(pq) 2 (acac)]), bis[2-(2-pyridinyl-κN)phenyl-κC][2-(4-phenyl-2-pyridinyl-κN)phenyl-κC]iridium(III) (abbreviation: [Ir(ppy) 2 (4dppy)]), organometallic iridium complexes with pyridine skeletons such as bis[2-(2-pyridinyl-κN)phenyl-κC][2-(4-methyl-5-phenyl-2-pyridinyl-κN)phenyl-κC], and bis(2,4-diphenyl-1,3-oxazolato-N,C 2’ ) Iridium(III) acetylacetonate (abbreviation: [Ir(dpo) 2 (acac)]), bis{2-[4'-(perfluorophenyl)phenyl]pyridinato-N,C 2’}Iridium(III) acetylacetonate (abbreviation: [Ir(p-PF-ph) 2 (acac)]), bis(2-phenylbenzothiazolato-N,C 2’ ) Iridium(III) acetylacetonate (abbreviation: [Ir(bt) 2 In addition to organometallic complexes such as tris(acetylacetonato)(monophenanthroline)terbium(III) (abbreviation: [Tb(acac)]), 3 Examples of rare earth metal complexes include those described above.

[0206] Examples of phosphorescent substances that exhibit yellow or red light and have an emission spectrum with a peak wavelength of 570 nm or more and 750 nm or less include the following substances.

[0207] For example, (diisobutyrylmethanato)bis[4,6-bis(3-methylphenyl)pyrimidinato]iridium(III) (abbreviation: [Ir(5mdppm) 2 (dibm)]), bis[4,6-bis(3-methylphenyl)pyrimidinato](dipivaloylmethanato)iridium(III) (abbreviation: [Ir(5mdppm) 2 (dpm)]), (dipivaloylmethanato)bis[4,6-di(naphthalen-1-yl)pyrimidinato]iridium(III) (abbreviation: [Ir(d1npm) 2 (acetylacetonato)bis(2,3,5-triphenylpyrazinate)iridium(III) (abbreviation: [Ir(tppr)]) 2 (acac)]), bis(2,3,5-triphenylpyrazinate)(dipivaloylmethanato)iridium(III) (abbreviation: [Ir(tppr) 2 (dpm)]), bis{4,6-dimethyl-2-[3-(3,5-dimethylphenyl)-5-phenyl-2-pyrazinyl-κN]phenyl-κC}(2,6-dimethyl-3,5-heptanedionato-κ 2 O,O') Iridium(III) (abbreviation: [Ir(dmdppr-P) 2(dibm)]), bis{4,6-dimethyl-2-[5-(4-cyano-2,6-dimethylphenyl)-3-(3,5-dimethylphenyl)-2-pyrazinyl-κN]phenyl-κC}(2,2,6,6-tetramethyl-3,5-heptanedionato-κ 2 O,O') Iridium(III) (abbreviation: [Ir(dmdppr-dmCP) 2 (dpm)]), bis[2-(5-(2,6-dimethylphenyl)-3-(3,5-dimethylphenyl)-2-pyrazinyl-κN)-4,6-dimethylphenyl-κC](2,2',6,6'-tetramethyl-3,5-heptadionato-κ20,0')iridium(III) (abbreviation: [Ir(dmdppr-dmp) 2 (dpm)]), (acetylacetonato)bis[2-methyl-3-phenylquinoxalinato-N,C 2’ ]Iridium(III) (abbreviation: [Ir(mpq) 2 (acac)]), (acetylacetonato)bis(2,3-diphenylquinoxalinato-N,C 2’ ) Iridium(III) (abbreviation: [Ir(dpq) 2 (acac)]), (acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III) (abbreviation: [Ir(Fdpq) 2 Organometallic complexes with pyrazine skeletons such as tris(1-phenylisoquinolinato-N,C 2’ ) Iridium(III) (abbreviation: [Ir(piq) 3 ]), bis(1-phenylisoquinolinato-N,C 2’ ) Iridium(III) acetylacetonate (abbreviation: [Ir(piq) 2 (acac)]), bis[4,6-dimethyl-2-(2-quinolinyl-κN)phenyl-κC](2,4-pentanedionato-κ 2 O,O') Iridium(III) (abbreviation: [Ir(dmpqn) 2(acac)]), platinum complexes such as 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrinplatinum(II) (abbreviation: [PtOEP]), tris(1,3-diphenyl-1,3-propanedionato)(monophenanthroline)europium(III) (abbreviation: [Eu(DBM) 3 (Phen)]), tris[1-(2-thenoyl)-3,3,3-trifluoroacetonato](monophenanthroline)europium(III) (abbreviation: [Eu(TTA) 3 Examples of rare earth metal complexes include those described above.

[0208] The following materials can be used as TADF materials. TADF materials are materials in which the difference between the S1 level and the T1 level is small (preferably 0.2 eV or less), the triplet excited state can be upconverted to the singlet excited state by a small amount of thermal energy (reverse intersystem crossing), and the material efficiently emits light (fluorescence) from the singlet excited state. Conditions for efficiently obtaining thermally activated delayed fluorescence include an energy difference between the triplet excited level and the singlet excited level of 0 eV or more and 0.2 eV or less, preferably 0 eV or more and 0.1 eV or less. The delayed fluorescence in TADF materials refers to light emission that has a spectrum similar to that of normal fluorescence, but has a significantly long lifespan. The lifespan is 1×10 -6 sec or more, preferably 1×10 -3 More than seconds.

[0209] Examples of TADF materials include fullerene and its derivatives, acridine derivatives such as proflavine, and eosin. Examples of metal-containing porphyrins include those containing magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), or palladium (Pd). Examples of metal-containing porphyrins include protoporphyrin-tin fluoride complexes (abbreviated as SnF 2 (Proto IX)), mesoporphyrin-tin fluoride complex (abbreviation: SnF 2(Meso IX)), hematoporphyrin-tin fluoride complex (abbreviation: SnF 2 (Hemato IX)), coproporphyrin tetramethyl ester-tin fluoride complex (abbreviation: SnF 2 (Copro III-4Me)), octaethylporphyrin-tin fluoride complex (abbreviation: SnF 2 (OEP)), etioporphyrin-tin fluoride complex (abbreviation: SnF 2 (Etio I)), octaethylporphyrin-platinum chloride complex (abbreviation: PtCl 2 OEP) etc.

[0210] [ka]

[0211] In addition, 2-(biphenyl-4-yl)-4,6-bis(12-phenylindolo[2,3-a]carbazol-11-yl)-1,3,5-triazine (abbreviation: PIC-TRZ), 2-{4-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: PCCzPTzn), 2-[4-(10H-phenyl 3-[4-(5-phenyl-5,10-dihydrophenazin-10-yl)phenyl]-4,5-diphenyl-1,2,4-triazole (abbreviation: PPZ-3TPT), 3-(9,9-dimethyl-9H-acridin-10-yl)-9H-xanthen-9-one (abbreviation: ACRXTN), bis[4 -(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone (abbreviation: DMAC-DPS), 10-phenyl-10H,10'H-spiro[acridine-9,9'-anthracen]-10'-one (abbreviation: ACRSA), 4-(9'-phenyl-3,3'-bi-9H-carbazol-9-yl)benzofuro[3,2-d]pyrimidine (abbreviation: 4PCCzBfpm), 4-[4-(9'-phenyl Heterocyclic compounds having a π-electron rich heteroaromatic ring and a π-electron deficient heteroaromatic ring, such as 9-[3-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]-9'-phenyl-2,3'-bi-9H-carbazole (abbreviation: mPCCzPTzn-02), may also be used.

[0212] In addition, a substance in which a π-electron-rich heteroaromatic ring and a π-electron-deficient heteroaromatic ring are directly bonded to each other is particularly preferable because the donor property of the π-electron-rich heteroaromatic ring and the acceptor property of the π-electron-deficient heteroaromatic ring are both strong, and the energy difference between the singlet excited state and the triplet excited state is small.

[0213] [ka]

[0214] In addition to the above, the second organic compound 122, which is a material having a function of converting triplet excitation energy into luminescence, may be a nanostructure of a transition metal compound having a perovskite structure. In particular, a nanostructure of a metal halide perovskite is preferable. As the nanostructure, nanoparticles and nanorods are preferable.

[0215] In addition to the above, other light-emitting materials that can be used in the light-emitting layer 113 and convert singlet excitation energy into light emission include the following fluorescent materials (fluorescent materials). For example, pyrene derivatives, anthracene derivatives, triphenylene derivatives, fluorene derivatives, carbazole derivatives, dibenzothiophene derivatives, dibenzofuran derivatives, dibenzoquinoxaline derivatives, quinoxaline derivatives, pyridine derivatives, pyrimidine derivatives, phenanthrene derivatives, and naphthalene derivatives are listed. In particular, pyrene derivatives are preferable because of their high light emission quantum yield. Specific examples of pyrene derivatives include N,N'-bis(3-methylphenyl)-N,N'-bis[3-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine (abbreviation: 1,6mMemFLPAPrn), (N,N'-diphenyl-N,N'-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine) (abbreviation: 1,6FLPAPrn), N,N'-bis(dibenzofuran-2-yl)-N,N'-diphenylpyrene-1,6-diamine (abbreviation: 1,6FrAPrn), N,N'-bis(dibenzothiophene-2-yl)-N ,N'-diphenylpyrene-1,6-diamine (abbreviation: 1,6ThAPrn), N,N'-(pyrene-1,6-diyl)bis[(N-phenylbenzo[b]naphtho[1,2-d]furan)-6-amine] (abbreviation: 1,6BnfAPrn), N,N'-(pyrene-1,6-diyl)bis[(N-phenylbenzo[b]naphtho[1,2-d]furan)-8-amine] (abbreviation: 1,6BnfAPrn-02), N,N'-(pyrene-1,6-diyl)bis[(6,N-diphenylbenzo[b]naphtho[1,2-d]furan)-8-amine] (abbreviation: 1,6BnfAPrn-03), etc.

[0216] In addition, 5,6-bis[4-(10-phenyl-9-anthryl)phenyl]-2,2'-bipyridine (abbreviation: PAP2BPy), 5,6-bis[4'-(10-phenyl-9-anthryl)biphenyl-4-yl]-2,2'-bipyridine (abbreviation: PAPP2BPy), N,N'-bis[4-(9H-carbazol-9-yl)phenyl]-N,N'-diphenylstilbene-4,4'-diamine (abbreviation: YGA2S), 4-(9H-carbazol-9-yl)phenyl]- N,9-diphenyl-N-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine (abbreviation: PCAPA), 4-(10-phenyl-9-anthryl)-4'-(9,10-diphenyl-2-anthryl)triphenylamine (abbreviation: YGAPA), 4-(9H-carbazol-9-yl)-4'-(9,10-diphenyl-2-anthryl)triphenylamine (abbreviation: 2YGAPPA), N,9-diphenyl-N-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine (abbreviation: PCAPA), 4-(10-phenyl-9-anthryl)-4 '-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBAPA), 4-[4-(10-phenyl-9-anthryl)phenyl]-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBAPBA), perylene, 2,5,8,11-tetra-tert-butylperylene (abbreviation: TBP), N,N''-(2-tert-butylanthracene-9,10-diyldi-4,1-phenyl) N,9-diphenyl-N-[4-(9,10-diphenyl-2-anthryl)phenyl]-9H-carbazole-3-amine (abbreviation: 2PCAPPA), N-[4-(9,10-diphenyl-2-anthryl)phenyl]-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviation: 2DPAPPA), and the like can be used.

[0217] Next, examples of the third organic compound 123 that is the host material of the light-emitting layer 113 include condensed polycyclic aromatic compounds such as anthracene derivatives, tetracene derivatives, phenanthrene derivatives, pyrene derivatives, chrysene derivatives, and dibenzo[g,p]chrysene derivatives.

[0218] Specific examples of the above include 9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: PCzPA), 3,6-diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: DPCzPA), 3-[4-(1-naphthyl)-phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPN), 9,10-diphenylanthracene (abbreviation: DPAnth), N,N-diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole-3-a amine (abbreviation: CzA1PA), 4-(10-phenyl-9-anthryl)triphenylamine (abbreviation: DPhPA), YGAPA, PCAPA, N,9-diphenyl-N-{4-[4-(10-phenyl-9-anthryl)phenyl]phenyl}-9H-carbazol-3-amine (abbreviation: PCAPBA), N-(9,10-diphenyl-2-anthryl)-N,9-diphenyl-9H-carbazol-3-amine (abbreviation: 2PCAPA), 6,12-dimethoxy-5,11-diphenylchrysene, N,N,N',N',N'',N'',N''',N'', '-Octaphenyldibenzo[g,p]chrysene-2,7,10,15-tetraamine (abbreviation: DBC1), 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation: CzPA), 7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole (abbreviation: cgDBCzPA), 6-[3-(9,10-diphenyl-2-anthryl)phenyl]-benzo[b]naphtho[1,2-d]furan (abbreviation: 2mBnfPPA), 9-phenyl-10-{4-(9-phenyl-9H-fluorene) 9,10-bis(3,5-diphenylphenyl)anthracene (abbreviation: DPPA), 9,10-di(2-naphthyl)anthracene (abbreviation: DNA), 2-tert-butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA), 9,9'-bianthryl (abbreviation: BANT), 9,9'-(stilbene-3,3'-diyl)diphenanthrene (abbreviation: DPNS), 9,9'-(stilbene-4,4'-diyl)diphenanthrene (abbreviation: DPNS2), 1,Examples include 3,5-tri(1-pyrenyl)benzene (abbreviation: TPB3), 5,12-diphenyltetracene, and 5,12-bis(biphenyl-2-yl)tetracene.

[0219] In addition, as the third organic compound 123 which is a host material of the light-emitting layer 113, for example, aromatic amines, carbazole derivatives, dibenzothiophene derivatives, dibenzofuran derivatives, zinc- or aluminum-based metal complexes, oxadiazole derivatives, triazole derivatives, benzimidazole derivatives, quinoxaline derivatives, dibenzoquinoxaline derivatives, pyrimidine derivatives, pyrazine derivatives, triazine derivatives, pyridine derivatives, bipyridine derivatives, phenanthroline derivatives, and the like can be used.

[0220] Specific examples of these include 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene (abbreviation: OXD-7), 9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole (abbreviation: CO11), 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviation: TAZ), Triazole derivatives such as 3-(4-tert-butylphenyl)-4-(4-ethylphenyl)-5-(4-biphenylyl)-1,2,4-triazole (abbreviation: p-EtTAZ), 2,2',2''-(1,3,5-benzenetriyl)tris(1-phenyl-1H-benzimidazole) (abbreviation: TPBI), 2-[3-(dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzimidazole (abbreviation: mDBTBIm-II), 4,4'-bis(5-methylbenzoxazol-2-yl)stilbene (abbreviation: BzOs, Bathofena 2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTPDBq-II), 2-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTBPDBq-II), 2-[3'-(9H-carbazol-9-yl)biphenyl-3-yl]dibenzo [f,h]quinoxaline (abbreviation: 2mCzBPDBq), 2-[4-(3,6-diphenyl-9H-carbazol-9-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2CzPDBq-III), 7-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 7mDBTPDBq-II), and 6-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 6mDBTPDBq-II) and other quinoxaline derivatives or dibenzoquinoxaline derivatives.

[0221] Furthermore, pyrimidine derivatives such as 4,6-bis[3-(phenanthren-9-yl)phenyl]pyrimidine (abbreviation: 4,6mPnP2Pm), 4,6-bis[3-(4-dibenzothienyl)phenyl]pyrimidine (abbreviation: 4,6mDBTP2Pm-II), and 4,6-bis[3-(9H-carbazol-9-yl)phenyl]pyrimidine (abbreviation: 4,6mCzP2Pm), 2-{4-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}-4,6-diphenyl-1, Examples of the compound include triazine derivatives such as 3,5-triazine (abbreviation: PCCzPTzn), triazine derivatives such as 9-[3-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]-9'-phenyl-2,3'-bi-9H-carbazole (abbreviation: mPCCzPTzn-02), and pyridine derivatives such as 3,5-bis[3-(9H-carbazol-9-yl)phenyl]pyridine (abbreviation: 35DCzPPy) and 1,3,5-tri[3-(3-pyridyl)phenyl]benzene (abbreviation: TmPyPB).

[0222] In addition, polymer compounds such as poly(2,5-pyridinediyl) (abbreviation: PPy), poly[(9,9-dihexylfluorene-2,7-diyl)-co-(pyridine-3,5-diyl)] (abbreviation: PF-Py), and poly[(9,9-dioctylfluorene-2,7-diyl)-co-(2,2'-bipyridine-6,6'-diyl)] (abbreviation: PF-BPy) can also be used.

[0223] <Electron transport layer> The electron transport layer 114 is a layer that transports electrons injected from the second electrode 102 by the electron injection layer 115 described later to the light emitting layer 113. The electron transport layer 114 is a layer that contains an electron transport material. The electron transport material used for the electron transport layer 114 has a concentration of 1×10 -6 cm 2A substance having an electron mobility of 1 / Vs or more is preferable. Note that other substances can be used as long as they have a higher electron transporting property than holes. Although the electron transporting layer (114, 114a, 114b) functions as a single layer, the device characteristics can be improved by forming a stacked structure of two or more layers as necessary.

[0224] Examples of organic compounds that can be used for the electron-transport layer 114 include organic compounds having a structure in which an aromatic ring is condensed to a furan ring of a furodiazine skeleton, metal complexes having a quinoline skeleton, metal complexes having a benzoquinoline skeleton, metal complexes having an oxazole skeleton, and metal complexes having a thiazole skeleton. In addition, materials with high electron transport properties (electron-transport materials) such as oxadiazole derivatives, triazole derivatives, imidazole derivatives, oxazole derivatives, thiazole derivatives, phenanthroline derivatives, quinoline derivatives having a quinoline ligand, benzoquinoline derivatives, quinoxaline derivatives, dibenzoquinoxaline derivatives, pyridine derivatives, bipyridine derivatives, pyrimidine derivatives, and other nitrogen-containing heteroaromatic compounds and other π-electron-deficient heteroaromatic compounds can be used.

[0225] Specific examples of the electron transport material include 2-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTBPDBq-II), 2-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTBPDBq-II), 5-[3-(4,6-diphenyl-1,3,5-triazin-2yl)furan-2-yl]phenyl-1,3,5-triazin ... phenyl]-7,7-dimethyl-5H,7H-indeno[2,1-b]carbazole (abbreviation: mINc(II)PTzn), 4-[3-(dibenzothiophen-4-yl)phenyl]-8-(naphthalen-2-yl)-[1]benzofuro[3,2-d]pyrimidine (abbreviation: 8βN-4mDBtPBfpm), 3,8-bis[3-(dibenzothiophen-4-yl)phenyl]benzofuro[2,3-b]pyrazine (abbreviation 4,8-Bis[3-(dibenzothiophen-4-yl)phenyl]-[1]benzofuro[3,2-d]pyrimidine (abbreviation: 4,8mDBtP2Bfpm), 9-[(3'-dibenzothiophen-4-yl)biphenyl-3-yl]naphtho[1',2':4,5]furo[2,3-b]pyrazine (abbreviation: 9mDBtBPNfpr), 8-[3'-(dibenzothiophen-4-yl) (1,1'-biphenyl-3-yl)]naphtho[1',2':4,5]furo[3,2-d]pyrimidine (abbreviation: 8mDBtBPNfpm), 8-[(2,2'-binaphthalene)-6-yl]-4-[3-(dibenzothiophene-4-yl)phenyl-[1]benzofuro[3,2-d]pyrimidine (abbreviation: 8(βN2)-4mDBtPBfpm), tris(8-quinolinolato)aluminum(III) (abbreviation: Alq 3 ), tris(4-methyl-8-quinolinolato)aluminum (abbreviation: Almq 3 ), Bis(10-hydroxybenzo[h]quinolinato)beryllium (abbreviation: BeBq 2), bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III) (abbreviation: BAlq), bis(8-quinolinolato)zinc(II) (abbreviation: Znq), and other metal complexes having a quinoline skeleton or a benzoquinoline skeleton; and metal complexes having an oxazole skeleton or a thiazole skeleton, such as bis[2-(2-benzoxazolyl)phenolato]zinc(II) (abbreviation: ZnPBO), bis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ), and other metal complexes having an oxazole skeleton or a thiazole skeleton.

[0226] In addition to metal complexes, oxadiazole derivatives such as PBD, OXD-7, and CO11, triazole derivatives such as TAZ and p-EtTAZ, imidazole derivatives (including benzimidazole derivatives) such as TPBI and mDBTBIm-II, oxazole derivatives such as BzOs, phenanthroline derivatives such as Bphen, BCP, and NBphen, quinoxaline derivatives such as 2mDBTPDBq-II, 2mDBTBPDBq-II, 2mCzBPDBq, 2CzPDBq-III, 7mDBTPDBq-II, and 6mDBTPDBq-II, or dibenzoquinoxaline derivatives, pyridine derivatives such as 35DCzPPy and TmPyPB, pyrimidine derivatives such as 4,6mPnP2Pm, 4,6mDBTP2Pm-II, and 4,6mCzP2Pm, and triazine derivatives such as PCCzPTzn and mPCCzPTzn-02 can also be used.

[0227] Moreover, polymer compounds such as PPy, PF-Py, and PF-BPy can also be used.

[0228] <Electron injection layer> The electron injection layer 115 is a layer for increasing the efficiency of electron injection from the cathode 102. When comparing the work function value of the cathode 102 material and the LUMO level value of the material used for the electron injection layer 115, it is preferable to use a material having a small difference (0.5 eV or less) between them. Therefore, the electron injection layer 115 is preferably made of lithium, cesium, lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF 2), 8-(hydroxyquinolinato)lithium (abbreviation: Liq), 2-(2-pyridyl)phenolatolithium (abbreviation: LiPP), 2-(2-pyridyl)-3-pyridinolatolithium (abbreviation: LiPPy), 4-phenyl-2-(2-pyridyl)phenolatolithium (abbreviation: LiPPP) lithium oxide (LiO x ), cesium carbonate, and other alkali metals, alkaline earth metals, and compounds thereof can be used. Also, erbium fluoride (ErF 3 ) can be used.

[0229] Also, as in the light-emitting device shown in Fig. 5B, a charge generating layer 104 is provided between two EL layers (103a, 103b), so that a structure in which a plurality of EL layers are stacked between a pair of electrodes (also called a tandem structure) can be formed. Note that the hole injection layer (111), hole transport layer (112), light-emitting layer (113), electron transport layer (114), and electron injection layer (115) described in Fig. 5A in this embodiment have the same functions and materials as the hole injection layer (111a, 111b), hole transport layer (112a, 112b), light-emitting layer (113a, 113b), electron transport layer (114a, 114b), and electron injection layer (115a, 115b) described in Fig. 5B.

[0230] <Charge generation layer> The charge generation layer 104 in the light-emitting device of FIG. 5B has a function of injecting electrons into the EL layer 103a and injecting holes into the EL layer 103b when a voltage is applied between the first electrode (anode) 101 and the second electrode (cathode) 102. The charge generation layer 104 may be a structure in which an electron acceptor is added to a hole transporting material, or a structure in which an electron donor is added to an electron transporting material. In addition, both of these structures may be laminated. By forming the charge generation layer 104 using the above-mentioned material, it is possible to suppress an increase in driving voltage when EL layers are laminated.

[0231] In the case where the charge generation layer 104 has a structure in which an electron acceptor is added to a hole-transporting material, the material described in this embodiment mode can be used as the hole-transporting material. In addition, 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation: F 4 -TCNQ), chloranil, etc. Also included are oxides of metals belonging to Groups 4 to 8 of the periodic table. Specific examples include vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide, and rhenium oxide.

[0232] In the case where the charge generation layer 104 has a structure in which an electron donor is added to an electron transporting material, the material shown in this embodiment can be used as the electron transporting material. In addition, as the electron donor, an alkali metal, an alkaline earth metal, a rare earth metal, or a metal belonging to Groups 2 and 13 of the periodic table, and an oxide or carbonate thereof can be used. Specifically, it is preferable to use lithium (Li), cesium (Cs), magnesium (Mg), calcium (Ca), ytterbium (Yb), indium (In), lithium oxide, cesium carbonate, or the like. In addition, an organic compound such as tetrathianaphthacene may be used as the electron donor.

[0233] Although FIG. 5B shows a configuration in which two EL layers 103 are stacked, a stacked structure of three or more EL layers may be used by providing a charge generating layer between different EL layers.

[0234] <Substrate> The light-emitting device shown in this embodiment mode can be formed on various substrates. The type of substrate is not limited to a specific one. Examples of the substrate include a semiconductor substrate (e.g., a single crystal substrate or a silicon substrate), an SOI substrate, a glass substrate, a quartz substrate, a plastic substrate, a metal substrate, a stainless steel substrate, a substrate having stainless steel foil, a tungsten substrate, a substrate having tungsten foil, a flexible substrate, a laminated film, a paper containing a fibrous material, or a base film.

[0235] Examples of glass substrates include barium borosilicate glass, aluminoborosilicate glass, soda lime glass, etc. Examples of flexible substrates, laminated films, base films, etc. include plastics such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polyethersulfone (PES), synthetic resins such as acrylic resins, polypropylene, polyester, polyvinyl fluoride, polyvinyl chloride, polyamide, polyimide, aramid resin, epoxy resin, inorganic deposition film, and paper.

[0236] In addition, the light-emitting device shown in this embodiment can be manufactured by a vacuum process such as a deposition method, or a solution process such as a spin coating method or an ink-jet method. When a deposition method is used, a physical deposition method (PVD method) such as a sputtering method, an ion plating method, an ion beam deposition method, a molecular beam deposition method, or a vacuum deposition method, a chemical deposition method (CVD method), or the like can be used. In particular, the functional layers (hole injection layer (111, 111a, 111b), hole transport layer (112, 112a, 112b), light-emitting layer (113, 113a, 113b, 113c), electron transport layer (114, 114a, 114b), electron injection layer (115, 115a, 115b), and charge generation layer (104, 104a, 104b)) included in the EL layer of the light-emitting device can be formed by a deposition method (vacuum deposition method, etc.), a coating method (dip coating method, die coating method, bar coating method, spin coating method, spray coating method, etc.), a printing method (inkjet method, screen (screen printing) method, offset (lithographic printing) method, flexo (relief printing) method, gravure method, microcontact method, nanoimprint method, etc.), or the like.

[0237] The functional layers constituting the EL layer (103, 103a, 103b) of the light-emitting device shown in this embodiment (hole injection layer (111, 111a, 111b), hole transport layer (112, 112a, 112b), light-emitting layer (113, 113a, 113b), electron transport layer (114, 114a, 114b), electron injection layer (115, 115a, 115b), and charge generation layer 104 are not limited to the above-mentioned materials, and other materials can be used in combination as long as they can fulfill the functions of each layer. As an example, a polymer compound (oligomer, dendrimer, polymer, etc.), a medium molecular compound (a compound in the intermediate range between a low molecular weight and a polymer: molecular weight 400 to 4000), an inorganic compound (quantum dot material, etc.), etc. can be used. As the quantum dot material, a colloidal quantum dot material, an alloy type quantum dot material, a core-shell type quantum dot material, a core type quantum dot material, etc. can be used.

[0238] The structure described in this embodiment mode can be used in appropriate combination with structures described in other embodiments.

[0239] (Embodiment 4) In this embodiment, a light-emitting device according to one embodiment of the present invention will be described. The light-emitting device shown in Fig. 6A is an active matrix type light-emitting device in which a transistor (FET) 202 and light-emitting devices (203R, 203G, 203B, 203W) on a first substrate 201 are electrically connected, and the light-emitting devices (203R, 203G, 203B, 203W) have a common EL layer 204 and a microcavity structure in which the optical distance between the electrodes of each light-emitting device is adjusted according to the emission color of each light-emitting device. The light-emitting device is a top-emission type light-emitting device in which light emitted from the EL layer 204 is emitted through color filters (206R, 206G, 206B) formed on a second substrate 205.

[0240] In the light-emitting device shown in Fig. 6A, the first electrode 207 is formed to function as a reflective electrode. The second electrode 208 is formed to function as a semi-transmissive / semi-reflective electrode having both the functions of transparency and reflectivity to light (visible light or near-infrared light). Note that the electrode materials for forming the first electrode 207 and the second electrode 208 can be appropriately selected by referring to the descriptions of other embodiments.

[0241] 6A, for example, when light emitting device 203R is a red light emitting device, light emitting device 203G is a green light emitting device, light emitting device 203B is a blue light emitting device, and light emitting device 203W is a white light emitting device, as shown in FIG 6B, light emitting device 203R is adjusted so that the optical distance between first electrode 207 and second electrode 208 is 200R, light emitting device 203G is adjusted so that the optical distance between first electrode 207 and second electrode 208 is 200G, and light emitting device 203B is adjusted so that the optical distance between first electrode 207 and second electrode 208 is 200B. Note that, as shown in FIG 6B, optical adjustment can be performed by stacking conductive layer 210R on first electrode 207 in light emitting device 203R and stacking conductive layer 210G in light emitting device 203G.

[0242] Color filters (206R, 206G, 206B) are formed on the second substrate 205. The color filters are filters that pass a specific wavelength range of visible light and block a specific wavelength range. Therefore, as shown in FIG. 6A, by providing a color filter 206R that passes only a red wavelength range at a position overlapping the light emitting device 203R, red light can be emitted from the light emitting device 203R. By providing a color filter 206G that passes only a green wavelength range at a position overlapping the light emitting device 203G, green light can be emitted from the light emitting device 203G. By providing a color filter 206B that passes only a blue wavelength range at a position overlapping the light emitting device 203B, blue light can be emitted from the light emitting device 203B. However, the light emitting device 203W can emit white light without providing a color filter. A black layer (black matrix) 209 may be provided at the end of one type of color filter. Furthermore, the color filters (206R, 206G, 206B) and the black layer 209 may be covered with an overcoat layer made of a transparent material.

[0243] FIG. 6A shows a light-emitting device having a structure (top emission type) in which light is extracted on the second substrate 205 side, but as shown in FIG. 6C, a light-emitting device having a structure (bottom emission type) in which light is extracted on the first substrate 201 side on which the FET 202 is formed may be used. In the case of a bottom emission type light-emitting device, the first electrode 207 is formed to function as a semi-transmissive / semi-reflective electrode, and the second electrode 208 is formed to function as a reflective electrode. The first substrate 201 is at least a light-transmitting substrate. The color filters (206R', 206G', 206B') may be provided on the first substrate 201 side of the light-emitting devices (203R, 203G, 203B) as shown in FIG. 6C.

[0244] 6A shows the case where the light-emitting device is a red light-emitting device, a green light-emitting device, a blue light-emitting device, and a white light-emitting device, but the light-emitting device according to one embodiment of the present invention is not limited to these configurations, and may be a configuration having a yellow light-emitting device or an orange light-emitting device. Note that the materials used in the EL layer (light-emitting layer, hole injection layer, hole transport layer, electron transport layer, electron injection layer, charge generation layer, etc.) for producing these light-emitting devices may be appropriately selected by referring to the descriptions of other embodiments. Note that in this case, it is necessary to appropriately select a color filter according to the emission color of the light-emitting device.

[0245] With the above-mentioned configuration, a light emitting device including light emitting devices that emit light of a plurality of colors can be obtained.

[0246] Note that the structure described in this embodiment mode can be used in appropriate combination with structures described in other embodiments.

[0247] (Embodiment 5) In this embodiment, a light-emitting device which is one embodiment of the present invention will be described.

[0248] By applying the device configuration of the light-emitting device which is one embodiment of the present invention, an active matrix light-emitting device or a passive matrix light-emitting device can be manufactured. Note that an active matrix light-emitting device has a configuration in which a light-emitting device and a transistor (FET) are combined. Therefore, both a passive matrix light-emitting device and an active matrix light-emitting device are included in one embodiment of the present invention. Note that the light-emitting device described in the other embodiments can be applied to the light-emitting device shown in this embodiment.

[0249] In this embodiment mode, an active matrix light emitting device will be described with reference to FIG.

[0250] 7A is a top view showing the light-emitting device, and FIG. 7B is a cross-sectional view taken along dashed line A-A' in FIG. 7A. The active matrix light-emitting device has a pixel portion 302, a driver circuit portion (source line driver circuit) 303, and a driver circuit portion (gate line driver circuit) (304a, 304b) provided on a first substrate 301. The pixel portion 302 and the driver circuit portion (303, 304a, 304b) are sealed between the first substrate 301 and a second substrate 306 by a sealant 305.

[0251] Moreover, on the first substrate 301, lead wiring 307 is provided. The lead wiring 307 is electrically connected to an FPC 308 which is an external input terminal. The FPC 308 transmits signals (e.g., video signals, clock signals, start signals, reset signals, etc.) and potentials from the outside to the drive circuit units (303, 304a, 304b). A printed wiring board (PWB) may be attached to the FPC 308. The state in which the FPC and PWB are attached is included in the light-emitting device.

[0252] Next, a cross-sectional structure is shown in FIG. 7B.

[0253] The pixel section 302 is formed by a plurality of pixels each having a FET (switching FET) 311, a FET (current control FET) 312, and a first electrode 313 electrically connected to the FET 312. The number of FETs each pixel has is not particularly limited, and may be appropriately provided as necessary.

[0254] The FETs 309, 310, 311, and 312 are not particularly limited, and may be, for example, staggered or inverted staggered transistors, or may have a top-gate or bottom-gate transistor structure.

[0255] Note that the crystallinity of a semiconductor that can be used for these FETs 309, 310, 311, and 312 is not particularly limited, and any of an amorphous semiconductor and a semiconductor having crystallinity (a microcrystalline semiconductor, a polycrystalline semiconductor, a single crystal semiconductor, or a semiconductor having a crystalline region in a part) may be used. Note that the use of a semiconductor having crystallinity is preferable because it can suppress deterioration of transistor characteristics.

[0256] Examples of the semiconductor that can be used include Group 14 elements, compound semiconductors, oxide semiconductors, and organic semiconductors. Typically, a semiconductor containing silicon, a semiconductor containing gallium arsenide, and an oxide semiconductor containing indium can be used.

[0257] The driver circuit unit 303 has an FET 309 and an FET 310. The driver circuit unit 303 may be formed of a circuit including transistors of the same polarity (either N-type or P-type), or may be formed of a CMOS circuit including N-type transistors and P-type transistors. Also, the driver circuit unit 303 may be configured to have an external driver circuit.

[0258] The end of the first electrode 313 is covered with an insulator 314. For the insulator 314, organic compounds such as negative photosensitive resin and positive photosensitive resin (acrylic resin) or inorganic compounds such as silicon oxide, silicon oxynitride, and silicon nitride can be used. The upper end or lower end of the insulator 314 preferably has a curved surface having a curvature. This can improve the coverage of the film formed on the upper layer of the insulator 314.

[0259] An EL layer 315 and a second electrode 316 are stacked over the first electrode 313. The EL layer 315 has a light-emitting layer, a hole injection layer, a hole transport layer, an electron transport layer, an electron injection layer, a charge generation layer, and the like.

[0260] Note that the structures and materials described in the other embodiments can be applied to the structure of the light-emitting device 317 shown in this embodiment. Although not shown here, the second electrode 316 is electrically connected to the FPC 308 which is an external input terminal.

[0261] In addition, although only one light-emitting device 317 is illustrated in the cross-sectional view shown in FIG. 7B, a plurality of light-emitting devices are arranged in a matrix in the pixel section 302. In the pixel section 302, light-emitting devices capable of obtaining three types of light emission (R, G, B) can be selectively formed, respectively, to form a light-emitting device capable of full-color display. In addition to the light-emitting devices capable of obtaining three types of light emission (R, G, B), light-emitting devices capable of obtaining light emission of, for example, white (W), yellow (Y), magenta (M), cyan (C), etc. may be formed. For example, by adding the light-emitting devices capable of obtaining the above-mentioned several types of light emission to the light-emitting device capable of obtaining three types of light emission (R, G, B), effects such as improved color purity and reduced power consumption can be obtained. In addition, a light-emitting device capable of full-color display may be formed by combining with a color filter. Note that the types of color filters that can be used are red (R), green (G), blue (B), cyan (C), magenta (M), yellow (Y), etc.

[0262] The FETs (309, 310, 311, 312) on the first substrate 301 and the light emitting device 317 have a structure in which they are provided in a space 318 surrounded by the first substrate 301, the second substrate 306, and the sealant 305, by bonding the second substrate 306 and the first substrate 301 with the sealant 305. The space 318 may be filled with an inert gas (nitrogen, argon, etc.) or an organic substance (including the sealant 305).

[0263] The sealing material 305 can be made of epoxy resin or glass frit. It is preferable to use a material that is as impermeable to moisture and oxygen as possible for the sealing material 305. The second substrate 306 can be made of the same material as the first substrate 301. Therefore, it is possible to use various substrates described in other embodiments as appropriate. As the substrate, in addition to a glass substrate or a quartz substrate, a plastic substrate made of FRP (Fiber-Reinforced Plastics), PVF (Polyvinyl Fluoride), polyester, acrylic resin, or the like can be used. When glass frit is used as the sealing material, it is preferable that the first substrate 301 and the second substrate 306 are glass substrates from the viewpoint of adhesion.

[0264] In this manner, an active matrix light emitting device can be obtained.

[0265] In addition, when forming an active matrix type light emitting device on a flexible substrate, the FET and the light emitting device may be formed directly on the flexible substrate, or the FET and the light emitting device may be formed on another substrate having a peeling layer, and then the FET and the light emitting device may be peeled off at the peeling layer by applying heat, force, laser irradiation, or the like, and then transferred to the flexible substrate to fabricate the device. As the peeling layer, for example, a laminate of inorganic films of a tungsten film and a silicon oxide film, or an organic resin film such as polyimide, etc. may be used. In addition to substrates on which transistors can be formed, examples of the flexible substrate include paper substrates, cellophane substrates, aramid film substrates, polyimide film substrates, cloth substrates (including natural fibers (silk, cotton, hemp), synthetic fibers (nylon, polyurethane, polyester) or regenerated fibers (acetate, cupra, rayon, regenerated polyester), etc.), leather substrates, and rubber substrates. By using these substrates, it is possible to achieve excellent durability and heat resistance, and to achieve lighter weight and thinner thickness.

[0266] In addition, the light-emitting device of the active matrix type light-emitting device may be driven in a pulsed manner (using a frequency of, for example, kHz or MHz) to be used for display. The light-emitting device formed using the above organic compound has excellent frequency characteristics, so that the time for driving the light-emitting device can be shortened and power consumption can be reduced. In addition, the shortened driving time suppresses heat generation, so that deterioration of the light-emitting device can be reduced.

[0267] Note that the structure described in this embodiment mode can be used in appropriate combination with structures described in other embodiment modes.

[0268] (Embodiment 6) In this embodiment, examples of various electronic devices and automobiles completed by applying a light-emitting device according to one embodiment of the present invention and a light-emitting device having a light-emitting device according to one embodiment of the present invention will be described. Note that the light-emitting device can be applied mainly to a display portion in the electronic devices described in this embodiment.

[0269] The electronic device shown in Figures 8A to 8C may have a housing 7000, a display unit 7001, a speaker 7003, an LED lamp 7004, operation keys 7005 (including a power switch or an operation switch), a connection terminal 7006, a sensor 7007 (including a function to measure force, displacement, position, speed, acceleration, angular velocity, rotation speed, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, gradient, vibration, odor, or infrared rays), a microphone 7008, etc.

[0270] FIG. 8A is a mobile computer, which may have, in addition to those mentioned above, a switch 7009, an infrared port 7010, etc.

[0271] FIG. 8B shows a portable image reproducing device (for example, a DVD reproducing device) equipped with a recording medium, which may further include a second display unit 7002, a recording medium reading unit 7011, and the like in addition to the above-mentioned components.

[0272] FIG. 8C shows a digital camera with a television receiving function, which may further include an antenna 7014, a shutter button 7015, an image receiving unit 7016, and the like in addition to the components described above.

[0273] 8D shows a portable information terminal. The portable information terminal has a function of displaying information on three or more sides of a display unit 7001. Here, an example is shown in which information 7052, information 7053, and information 7054 are displayed on different sides. For example, a user can check information 7053 displayed in a position that can be observed from above the portable information terminal while the portable information terminal is stored in a breast pocket of clothes. The user can check the display without taking the portable information terminal out of the pocket and decide, for example, whether or not to answer a call.

[0274] FIG. 8E shows a mobile information terminal (including a smartphone), and a housing 7000 may have a display unit 7001, operation keys 7005, and the like. The mobile information terminal may also have a speaker 7003, a connection terminal 7006, a sensor 7007, and the like. The mobile information terminal may also display text and image information on a plurality of surfaces. Here, an example is shown in which three icons 7050 are displayed. Information 7051, indicated by a dashed rectangle, may also be displayed on another surface of the display unit 7001. Examples of the information 7051 include notifications of incoming e-mail, SNS, and phone calls, titles of e-mail and SNS, sender name, date and time, time, remaining battery level, and antenna reception strength. Alternatively, an icon 7050 or the like may be displayed at the position where the information 7051 is displayed.

[0275] FIG. 8F shows a large television device (also called a television or a television receiver), which may have a housing 7000, a display unit 7001, and the like. Here, a configuration in which the housing 7000 is supported by a stand 7018 is shown. The television device can be operated by a separate remote control unit 7111, and the like. Note that the display unit 7001 may be provided with a touch sensor, and may be operated by touching the display unit 7001 with a finger or the like. The remote control unit 7111 may have a display unit that displays information output from the remote control unit 7111. The channel and volume can be operated by the operation keys or touch panel provided in the remote control unit 7111, and the image displayed on the display unit 7001 can be operated.

[0276] The electronic devices shown in FIGS. 8A to 8F can have various functions. For example, they can have a function of displaying various information (still images, videos, text images, etc.) on the display unit, a touch panel function, a function of displaying a calendar, date or time, etc., a function of controlling processing by various software (programs), a wireless communication function, a function of connecting to various computer networks using the wireless communication function, a function of transmitting or receiving various data using the wireless communication function, a function of reading out a program or data recorded on a recording medium and displaying it on the display unit, etc. Furthermore, in an electronic device having multiple display units, they can have a function of displaying image information mainly on one display unit and text information mainly on another display unit, or a function of displaying a stereoscopic image by displaying an image taking into account parallax on multiple display units, etc. Furthermore, in an electronic device having an image receiving unit, they can have a function of taking still images, a function of taking videos, a function of automatically or manually correcting the taken images, a function of saving the taken images on a recording medium (external or built-in to the camera), a function of displaying the taken images on the display unit, etc. Note that the functions that the electronic devices shown in FIGS. 8A to 8F can have are not limited to these, and they can have various functions.

[0277] FIG. 8G shows a wristwatch-type portable information terminal, which can be used as, for example, a watch-type electronic device. This wristwatch-type portable information terminal includes a housing 7000, a display unit 7001, operation buttons 7022 and 7023, a connection terminal 7024, a band 7025, a microphone 7026, a sensor 7029, a speaker 7030, and the like. The display unit 7001 has a curved display surface, and can display information along the curved display surface. This portable information terminal can also perform hands-free conversation by mutual communication with, for example, a headset capable of wireless communication. Note that the connection terminal 7024 can also perform data transmission between the portable information terminal and another information terminal, and can also perform charging. Charging can also be performed by wireless power supply.

[0278] A display unit 7001 mounted on a housing 7000 that also serves as a bezel has a non-rectangular display area. The display unit 7001 can display an icon indicating the time, other icons, etc. The display unit 7001 may be a touch panel (input / output device) equipped with a touch sensor (input device).

[0279] The watch-type electronic device shown in Fig. 8G can have various functions, such as a function to display various information (still images, videos, text images, etc.) on the display unit, a touch panel function, a function to display a calendar, date or time, etc., a function to control processing by various software (programs), a wireless communication function, a function to connect to various computer networks using the wireless communication function, a function to transmit or receive various data using the wireless communication function, a function to read out a program or data recorded on a recording medium and display it on the display unit, etc.

[0280] The housing 7000 may also have a speaker, sensors (including functions to measure force, displacement, position, speed, acceleration, angular velocity, rotation speed, distance, light, liquid, magnetism, temperature, chemical substances, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, gradient, vibration, odor, or infrared rays), microphone, etc. inside the housing 7000.

[0281] Note that the light-emitting device which is one embodiment of the present invention can be used in each display portion of the electronic devices described in this embodiment, and the electronic devices can have a long lifetime.

[0282] An example of an electronic device to which a light-emitting device is applied is a foldable portable information terminal as shown in Fig. 9A to Fig. 9C. Fig. 9A shows a portable information terminal 9310 in an unfolded state. Fig. 9B shows the portable information terminal 9310 in a state in the process of changing from one of an unfolded state and a folded state to the other. Fig. 9C shows the portable information terminal 9310 in a folded state. The portable information terminal 9310 has excellent portability in a folded state, and has excellent viewability of a display due to a seamless wide display area in an unfolded state.

[0283] The display portion 9311 is supported by three housings 9315 connected by hinges 9313. Note that the display portion 9311 may be a touch panel (input / output device) equipped with a touch sensor (input device). The display portion 9311 can be reversibly transformed from an unfolded state of the portable information terminal 9310 to a folded state by bending the two housings 9315 via the hinges 9313. Note that the light-emitting device of one embodiment of the present invention can be used for the display portion 9311. In addition, an electronic device with a long life can be realized. A display region 9312 in the display portion 9311 is a display region located on a side surface of the portable information terminal 9310 in the folded state. In the display region 9312, information icons, frequently used apps, shortcuts to programs, and the like can be displayed, and thus information can be checked and apps can be started smoothly.

[0284] 10A and 10B show automobiles to which the light emitting device is applied. That is, the light emitting device can be provided integrally with the automobile. Specifically, the light emitting device can be applied to the exterior lights 5101 (including the rear of the vehicle body), the wheels 5102 of the tires, a part or the whole of the door 5103, and the like, of the automobile shown in FIG. 10A. The light emitting device can also be applied to the interior display unit 5104, steering wheel 5105, shift lever 5106, seat 5107, inner rear view mirror 5108, windshield 5109, and the like, shown in FIG. 10B. It may also be applied to parts of other glass windows.

[0285] In the above manner, an electronic device or an automobile to which the light-emitting device according to one embodiment of the present invention is applied can be obtained. In that case, an electronic device with a long life can be realized. The electronic devices and automobiles to which the light-emitting device according to one embodiment of the present invention can be applied are not limited to those described in this embodiment, and can be applied in any field.

[0286] Note that the structure described in this embodiment mode can be used in appropriate combination with structures described in other embodiment modes.

[0287] (Embodiment 7) In this embodiment, a structure of a lighting device manufactured using a light-emitting device which is one embodiment of the present invention or a light-emitting device which is a part of the light-emitting device will be described with reference to FIGS.

[0288] 11A and 11B are cross-sectional views of an example of a lighting device. Fig. 11A shows a bottom emission type lighting device that extracts light on the substrate side, and Fig. 11B shows a top emission type lighting device that extracts light on the sealing substrate side.

[0289] 11A includes a light-emitting device 4002 on a substrate 4001. The substrate 4001 also includes a substrate 4003 having projections and recesses on its outer surface. The light-emitting device 4002 includes a first electrode 4004, an EL layer 4005, and a second electrode 4006.

[0290] The first electrode 4004 is electrically connected to an electrode 4007, and the second electrode 4006 is electrically connected to an electrode 4008. In addition, an auxiliary wiring 4009 electrically connected to the first electrode 4004 may be provided. Note that an insulating layer 4010 is formed over the auxiliary wiring 4009.

[0291] The substrate 4001 and the sealing substrate 4011 are bonded together with a sealant 4012. A desiccant 4013 is preferably provided between the sealing substrate 4011 and the light-emitting device 4002. Since the substrate 4003 has projections and recesses as shown in FIG. 11A, the efficiency of extracting light generated in the light-emitting device 4002 can be improved.

[0292] 11B includes a light emitting device 4202 on a substrate 4201. The light emitting device 4202 includes a first electrode 4204, an EL layer 4205, and a second electrode 4206.

[0293] The first electrode 4204 is electrically connected to the electrode 4207, and the second electrode 4206 is electrically connected to the electrode 4208. In addition, an auxiliary wiring 4209 electrically connected to the second electrode 4206 may be provided. In addition, an insulating layer 4210 may be provided under the auxiliary wiring 4209.

[0294] The substrate 4201 and a sealing substrate 4211 having projections and recesses are bonded with a sealant 4212. A barrier film 4213 and a planarization film 4214 may be provided between the sealing substrate 4211 and the light-emitting device 4202. Since the sealing substrate 4211 has projections and recesses as shown in FIG. 11B, the efficiency of extracting light generated in the light-emitting device 4202 can be improved.

[0295] An example of the application of these lighting devices is a ceiling light for indoor lighting. Ceiling lights include a direct ceiling type and a ceiling recessed type. Such lighting devices are constructed by combining a light-emitting device with a housing and a cover.

[0296] In addition, it can be applied to footlights that can irradiate light onto the floor surface and increase the safety of the feet. Footlights are effective for use in bedrooms, stairs, and corridors, for example. In such cases, the size and shape can be changed appropriately according to the size and structure of the room. It is also possible to make a stationary lighting device that is configured by combining a light-emitting device with a support base.

[0297] It can also be used as a sheet-type lighting device (sheet lighting). Sheet lighting is attached to a wall surface, so it does not take up much space and can be used for a wide range of purposes. It can also be easily made larger. It can also be used on curved walls and housings.

[0298] In addition to the above, the light-emitting device according to one embodiment of the present invention or a light-emitting device that is a part of the light-emitting device can be used as a lighting device having a function as the furniture in a room.

[0299] As described above, various lighting devices using the light-emitting device can be obtained. Note that these lighting devices are included in one embodiment of the present invention.

[0300] The structure described in this embodiment mode can be used in appropriate combination with structures described in other embodiment modes. EXAMPLES

[0301] In this example, a light-emitting device according to one embodiment of the present invention and a comparative light-emitting device were fabricated, and their operating characteristics were measured. Note that the light-emitting device 1 according to one embodiment of the present invention uses 4,6-bis[3-(9H-carbazol-9-yl)phenyl]pyrimidine (abbreviation: 4,6mCzP2Pm) as a host material in the light-emitting layer, and 2-trimethylsilyl-N,N,N',N'-tetrakis(3,5-di-tert-butylphenyl)-9,10-anthracene as a guest material, which is an organic compound having a function of converting singlet excitation energy into light emission and has a protecting group. The diamine (abbreviation: 2TMS-mmtBuDPhA2Anth) and bis[2-(5-(2,6-dimethylphenyl)-3-(3,5-dimethylphenyl)-2-pyrazinyl-κN)-4,6-dimethylphenyl-κC](2,2',6,6'-tetramethyl-3,5-heptadionato-κ20,0')iridium(III) (abbreviation: [Ir(dmdppr-dmp 2 (dpm)] was used, and in the comparative light-emitting device 2, which is a comparative device, 9,10-bis[phenyl(p-tolyl)-anilino]anthracene (abbreviation: MeDPhA2A) was used instead of 2TMS-mmtBuDPhA2Anth in the light-emitting device 1.

[0302] 12 shows the element structure of the light emitting device used in this example, and its specific configuration is shown in Table 1. The chemical formulas of the materials used in this example are shown below.

[0303] [Table 1]

[0304] [ka]

[0305] <Fabrication of light-emitting devices> The light-emitting device shown in this embodiment has a structure in which a hole injection layer 911, a hole transport layer 912, a light-emitting layer 913, an electron transport layer 914, and an electron injection layer 915, which constitute an EL layer 902, are sequentially stacked on a first electrode 901 formed on a substrate 900 as shown in FIG. 12, and a second electrode 903 is stacked on the electron injection layer 915.

[0306] First, a first electrode 901 was formed on a substrate 900. The electrode area was 4 mm 2 The dimensions were (2 mm×2 mm). A glass substrate was used for the substrate 900. The first electrode 901 was formed by depositing indium tin oxide containing silicon oxide (ITSO) to a thickness of 70 nm by a sputtering method.

[0307] As a pretreatment, the surface of the substrate was washed with water, baked at 200°C for 1 hour, and then subjected to UV ozone treatment for 370 seconds. -4 The substrate was introduced into a vacuum deposition apparatus whose inside had been reduced in pressure to about Pa, and vacuum baking was carried out at 170° C. for 30 minutes in a heating chamber in the vacuum deposition apparatus, and then the substrate was allowed to cool for about 30 minutes.

[0308] Next, a hole injection layer 911 was formed on the first electrode 901. The hole injection layer 911 was formed by evaporating 1×10 -4 After reducing the pressure to 10 Pa, 1,3,5-tri(dibenzothiophen-4-yl)benzene (abbreviation: DBT3P-II) and molybdenum oxide were co-evaporated in a ratio of DBT3P-II:molybdenum oxide = 1:0.5 (mass ratio) to a film thickness of 40 nm.

[0309] Next, a hole transport layer 912 was formed on the hole injection layer 911. The hole transport layer 912 was formed by vapor deposition using 9-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]9H-carbazole (abbreviation: mCzFLP) to a thickness of 20 nm.

[0310] Next, a light-emitting layer 913 was formed on the hole-transporting layer 912 .

[0311] In the case of the light-emitting device 1, the light-emitting layer 913 uses 4,6mCzP2Pm as a host material, and uses, as guest materials, 2TMS-mmtBuDPhA2Anth, an organic compound having a function of converting singlet excitation energy into light emission and having a protecting group, and [Ir(dmdppr-dmp) 2 (dpm)] with a weight ratio of 4,6mCzP2Pm:2TMS-mmtBuDPhA2Anth:[Ir(dmdppr-dmp) 2 (dpm)] = 1:0.025:0.005. The film thickness was 40 nm.

[0312] In the case of the comparative light-emitting device 2, 4,6mCzP2Pm was used as the host material, and MeDPhA2A, an organic compound having a function of converting singlet excitation energy into light emission, and [Ir(dmdppr-dmp) 2 (dpm)] and the weight ratio is 4.6mCzP2Pm:MeDPhA2A:[Ir(dmdppr-dmp) 2 (dpm)] = 1:0.05:0.01. The film thickness was 40 nm.

[0313] Next, an electron transport layer 914 was formed on the light emitting layer 913. The electron transport layer 914 was formed by sequentially depositing 4,6mCzP2Pm to a thickness of 20 nm and 2,9-bis(naphthalene-2-yl)-4,7-diphenyl-1,10-phenanthroline (abbreviation: NBphen) to a thickness of 10 nm.

[0314] Next, the electron injection layer 915 was formed on the electron transport layer 914. The electron injection layer 915 was formed by vapor deposition using lithium fluoride (LiF) so as to have a film thickness of 1 nm.

[0315] Next, a second electrode 903 was formed on the electron injection layer 915. The second electrode 903 was formed by vapor deposition of aluminum so as to have a film thickness of 200 nm. In this embodiment, the second electrode 903 functions as a cathode.

[0316] Through the above steps, a light-emitting device including an EL layer sandwiched between a pair of electrodes was formed over a substrate 900. Note that the hole injection layer 911, the hole transport layer 912, the light-emitting layer 913, the electron transport layer 914, and the electron injection layer 915 described in the above steps are functional layers that constitute the EL layer in one embodiment of the present invention. In addition, in all of the deposition steps in the above-described manufacturing method, deposition by resistance heating was used.

[0317] The light emitting device fabricated as described above is sealed with another substrate (not shown). When sealing is performed using another substrate (not shown), another substrate (not shown) coated with a sealant that is hardened by ultraviolet light is fixed on the substrate 900 in a glove box with a nitrogen atmosphere, and the substrates are bonded together so that the sealant adheres to the periphery of the light emitting device formed on the substrate 900. During sealing, 365 nm ultraviolet light is applied at 6 J / cm. 2 The sealant was solidified by irradiation and then heat-treated at 80° C. for 1 hour to stabilize the sealant.

[0318] <Operation characteristics of each light-emitting device> The operating characteristics of the fabricated light-emitting devices were measured. A color luminance meter (Topcon, BM-5A) was used to measure the luminance and chromaticity (CIE chromaticity), and a multichannel spectrometer (Hamamatsu Photonics, PMA-11) was used to measure the electroluminescence (EL) spectrum. The measurements were performed at room temperature (an atmosphere maintained at 23°C). As the operating characteristics of light-emitting device 1 and comparative light-emitting device 2, the current density-luminance characteristics are shown in Figure 13, the voltage-luminance characteristics in Figure 14, the luminance-current efficiency characteristics in Figure 15, the voltage-current density characteristics in Figure 16, the luminance-power efficiency characteristics in Figure 17, and the luminance-external quantum efficiency characteristics in Figure 18, respectively.

[0319] In addition, each light-emitting device is supplied with 2.5mA / cm 2 19 shows electroluminescence spectra (EL spectra) obtained when a current was applied at a current density of 1000 .mu.m. FIG. 20 shows the ultraviolet-visible absorption spectrum and emission spectrum of 2TMS-mmtBuDPhA2Anth in a toluene solution, and the emission spectrum of [Ir(dmdppr-dmp) 2 The ultraviolet-visible absorption spectrum and emission spectrum of 4,6mCzP2Pm in a dichloromethane solution are shown in Fig. 20, and the ultraviolet-visible absorption spectrum of 4,6mCzP2Pm in a toluene solution are shown in Fig. 20. The absorption spectrum in Fig. 20 was measured using an ultraviolet-visible spectrophotometer (V550 model, manufactured by JASCO Corporation), and the emission spectrum was measured using a fluorometer (FS920, manufactured by Hamamatsu Photonics Corporation). From Fig. 20, it can be seen that the phosphorescent material Ir(dmdppr-dmp) 2 It can be seen that the peak wavelength of the emission spectrum of (dpm) is longer than the peak wavelength of the emission spectrum of the fluorescent substance 2TMS-mmtBuDPhA2Anth.

[0320] In addition, the absorption edge of the absorption spectrum or the emission edge on the short wavelength side of the emission spectrum of the fluorescent material 2TMS-mmtBuDPhA2Anth is the same as that of the phosphorescent material Ir(dmdppr-dmp) 2Since the S1 level of the fluorescent material 2TMS-mmtBuDPhA2Anth is shorter than the absorption edge of the absorption spectrum or the emission edge on the short wavelength side of the emission spectrum of (dpm), the S1 level of the phosphorescent material Ir(dmdppr-dmp) 2 It can be seen that the S1 level of the host material 4,6mCzP2Pm is higher than the S1 level of the fluorescent material 2TMS-mmtBuDPhA2Anth, because the absorption edge of the absorption spectrum of the host material 4,6mCzP2Pm is at a shorter wavelength than the absorption edge of the absorption spectrum of the fluorescent material 2TMS-mmtBuDPhA2Anth or the emission edge on the short-wavelength side of the emission spectrum.

[0321] In order to obtain the T1 level of 4,6mCzP2Pm, a thin film of 4,6mCzP2Pm was formed on a quartz substrate by vacuum deposition, and the emission spectrum of the thin film was measured at a low temperature (10K). For the measurement, a micro PL device LabRAM HR-PL (Horiba, Ltd.) was used, the measurement temperature was 10K, a He-Cd laser with a wavelength of 325 nm was used as the excitation light, and a CCD was used as the detector. A tangent line was drawn to the short-wavelength side of the emission spectrum measured at a low temperature, and the T1 level was calculated from the energy of the wavelength of the extrapolated line, resulting in a T1 level of 2.79 eV (444 nm). Therefore, from FIG. 20, the T1 level of the host material 4,6mCzP2Pm was calculated by the energy of the phosphorescent material Ir(dmdppr-dmp) 2 It can be seen that this is higher than the T1 level of (dpm).

[0322] Also, 1000cd / m 2 The main initial characteristic values ​​of each light-emitting device in the vicinity are shown in Table 2 below.

[0323] [Table 2]

[0324] As shown in Fig. 19, the EL spectra of each light-emitting device all have two peaks around 530 nm and around 610 nm. The peak around 530 nm of the light-emitting device 1 is derived from 2TMS-mmtBuDPhA2Anth, and the peak around 610 nm is from 2 [Ir(dmdppr-dmp) 2 (dpm)]. Also, the peak around 530 nm of the comparative light-emitting device 2 is derived from MeDPhA2A, and the peak around 610 nm is from [[Ir(dmdppr-dmp) 2 (dpm)]. That is, in the light-emitting device 1, both light emission (fluorescent emission) derived from 2TMS-mmtBuDPhA2Anth and light emission (phosphorescent emission) derived from [[Ir(dmdppr-dmp) 2 (dpm) are obtained. It can be seen that in the comparative light-emitting device 2, both light emission (fluorescent emission) derived from MeDPhA2A and light emission (phosphorescent emission) derived from [[Ir(dmdppr-dmp)

[0325] (dpm) are obtained. Therefore, from the results of the EL spectra, it was confirmed that in both cases of the light-emitting devices, light emission from different guest materials was obtained simultaneously.

[0326] <CV measurement results> Next, the host material (first organic compound) 4,6mCzP2Pm, the guest material (second organic compound) 2TMS-mmtBuDPhA2Anth, and the guest material (third organic compound) [Ir(dmdppr-dmp) 2 The electrochemical properties (oxidation and reduction properties) of the compound (dpm) were measured by cyclic voltammetry (CV).

[0327] The measurement device used was an electrochemical analyzer (manufactured by BAS Co., Ltd., model number: ALS model 600A or 600C). The solution used in the CV measurement was dehydrated dimethylformamide (DMF) (manufactured by Aldrich Co., Ltd., 99.8%, catalog number: 22705-6) as the solvent and tetra-n-butylammonium perchlorate (n-Bu 4 NClO 4 ) (Tokyo Chemical Industry Co., Ltd., catalog number: T0836) was dissolved to a concentration of 100 mmol / L, and the measurement target was further dissolved to a concentration of 2 mmol / L. The working electrode was a platinum electrode (BAS Co., Ltd., PTE platinum electrode), the auxiliary electrode was a platinum electrode (BAS Co., Ltd., Pt counter electrode (5 cm) for VC-3), and the reference electrode was an Ag / Ag + An electrode (RE7 non-aqueous solvent reference electrode, manufactured by BAS Co., Ltd.) was used. The measurements were performed at room temperature (20 to 25° C.). The scan speed during CV measurement was standardized to 0.1 V / sec, and the oxidation potential Ea [V] and reduction potential Ec [V] relative to the reference electrode were measured. Ea was the midpoint potential of the oxidation-reduction wave, and Ec was the midpoint potential of the reduction-oxidation wave. Here, since the potential energy of the reference electrode used in this example relative to the vacuum level is known to be −4.94 [eV], the HOMO level and the LUMO level can be calculated from the formulas HOMO level [eV] = −4.94-Ea and LUMO level [eV] = −4.94-Ec, respectively.

[0328] As a result of CV measurement, the oxidation potential of 4,6mCzP2Pm was 0.95V and the reduction potential was -2.06V. In addition, the HOMO level of 4,6mCzP2Pm calculated from the CV measurement was -5.89eV and the LUMO level was -2.88eV. In addition, the oxidation potential of 2TMS-mmtBuDPhA2Anth was 0.45V and the reduction potential was -2.12V. In addition, the HOMO level of 2TMS-mmtBuDPhA2Anth calculated from the CV measurement was -5.39eV and the LUMO level was -2.82eV. In addition, [Ir(dmdppr-dmp) 2 (dpm)] had an oxidation potential of 0.54 V and a reduction potential of -2.06 V. In addition, [Ir(dmdppr-dmp) 2 (dpm)] had a HOMO level of -5.48 eV and a LUMO level of -2.89 eV. EXAMPLES

[0329] In this example, a light-emitting device according to one embodiment of the present invention and a comparative light-emitting device were manufactured, and their operating characteristics were measured. Note that the light-emitting device 3 according to one embodiment of the present invention uses 2-[4'-(9-phenyl-9H-carbazol-3-yl)-3,1'-biphenyl-1-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mpPCBPDBq) as a host material in the light-emitting layer, and uses 2TMS-mmtBuDPhA2Anth, an organic compound having a function of converting singlet excitation energy into light emission and having a protecting group, and [Ir(dmdppr-dmp) 2 (dpm)] was used, and in comparative light-emitting device 4 and comparative light-emitting device 5, which are comparative devices, MeDPhA2A was used instead of 2TMS-mmtBuDPhA2Anth of light-emitting device 3.

[0330] The element structures of the light-emitting device 3, the comparative light-emitting device 4, and the comparative light-emitting device 5 produced in this example are similar to those shown in Fig. 12 in Example 1, but the specific configurations of the layers constituting the element structures are as shown in Table 3. The chemical formulas of the materials used in this example are shown below.

[0331] [Table 3]

[0332] [ka]

[0333] <Operation characteristics of each light-emitting device> The operating characteristics of the fabricated light-emitting devices were measured. A color luminance meter (Topcon, BM-5A) was used to measure the luminance and chromaticity (CIE chromaticity), and a multichannel spectrometer (Hamamatsu Photonics, PMA-11) was used to measure the electroluminescence (EL) spectrum. The measurements were performed at room temperature (an atmosphere maintained at 23°C). As the operating characteristics of light-emitting device 3, comparative light-emitting device 4, and comparative light-emitting device 5, the current density-luminance characteristics are shown in Figure 21, the voltage-luminance characteristics in Figure 22, the luminance-current efficiency characteristics in Figure 23, the voltage-current density characteristics in Figure 24, the luminance-power efficiency characteristics in Figure 25, and the luminance-external quantum efficiency characteristics in Figure 26, respectively.

[0334] In addition, each light-emitting device is supplied with 2.5mA / cm 2 FIG. 27 shows the electroluminescence spectrum (EL spectrum) when a current was passed at a current density of 1000 .mu.m.

[0335] Also, 1000cd / m 2 The main initial characteristic values ​​of each light-emitting device in the vicinity are shown in Table 4 below.

[0336] [Table 4]

[0337] 27, the EL spectrum of each light-emitting device has two peaks at around 530 nm and 610 nm. The peak at around 530 nm of light-emitting device 3 is due to 2TMS-mmtBuDPhA2Anth, and the peak at around 610 nm is due to [Ir(dmdppr-dmp) 2 In the comparative light-emitting devices 4 and 5, the peak near 530 nm is due to MeDPhA2A, and the peak near 610 nm is due to [Ir(dmdppr-dmp) 2 In other words, in the light-emitting device 3, the emission (fluorescence emission) originates from 2TMS-mmtBuDPhA2Anth and the emission (fluorescence emission) originates from Ir(dmdppr-dmp) 2 In the comparative light-emitting device 4 and the comparative light-emitting device 5, both the emission (fluorescence emission) originating from MeDPhA2A and the emission (phosphorescence emission) originating from Ir(dmdppr-dmp) were obtained. 2 It can be seen that both luminescence (phosphorescence) originating from (dpm) and luminescence (phosphorescence) originating from (dpm) are obtained. Therefore, the EL spectrum results confirmed that luminescence from different guest materials was obtained simultaneously in both devices.

[0338] 23, 25, and 26, the efficiency value with respect to luminance was higher in the light-emitting device 3 than in the comparative light-emitting device 4 and the comparative light-emitting device 5, and the light-emitting device 3 showed a high external quantum efficiency exceeding 10% despite using a fluorescent material as a guest material. That is, by using an organic compound having a protecting group (the first organic compound 121 described in the second embodiment) as an organic compound having a function of converting singlet excitation energy into light emission, which is a guest material in the light-emitting layer, it was confirmed that the transfer of triplet excitation energy from the host material to the fluorescent material by the Dexter mechanism can be suppressed, and the deactivation of triplet excitation energy accompanying the energy transfer can be suppressed, and as a result, the decrease in the light-emitting efficiency of the light-emitting device can be suppressed.

[0339] The light-emitting device 3 and the comparative light-emitting device 4 have different guest materials that have the function of converting singlet excitation energy into light emission, but the concentrations of each guest material relative to the host material are the same. However, when comparing the EL spectra of the light-emitting device 3 and the comparative light-emitting device 4, the comparative light-emitting device 4 has a higher EL spectrum than the light-emitting device 3, which is the guest material that has the function of converting triplet excitation energy into light emission, [Ir(dmdppr-dmp) 2 It can be seen that the peak at around 610 nm originating from [Ir(dmdppr-dmp) 2 In comparison, by increasing the concentration of 1,3-dichlorophenyl ether (dpm)], the relative intensity of the spectrum near 610 nm is increased, and an EL spectrum shape close to that of the light-emitting device 3 is obtained. However, in reality, this is due to a decrease in the spectral intensity near 530 nm, and the efficiency of the comparative light-emitting device 5 is lower than that of the comparative light-emitting device 4. As described above, in a comparative light-emitting device using a fluorescent substance having no protecting group, it is difficult to efficiently emit both a fluorescent substance and a phosphorescent substance in a desired balance. On the other hand, the light-emitting device of one embodiment of the present invention can suppress the deactivation of triplet excitation energy, and therefore can efficiently emit both a fluorescent substance and a phosphorescent substance in a desired balance. EXAMPLES

[0340] In this example, a light-emitting device according to one embodiment of the present invention was manufactured, and its operating characteristics were measured. Note that the light-emitting device 6 according to one embodiment of the present invention uses 9-[3-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]-9'-phenyl-2,3'-bi-9H-carbazole (abbreviation: mPCCzPTzn-02) as a host material in the light-emitting layer, and 2TMS-mmtBuDPhA2Anth, an organic compound having a function of converting singlet excitation energy into light emission and having a protecting group, and [Ir(dmdppr-dmp) 2 (dpm)] was used, and in light-emitting device 7, 9-phenyl-9'-(4-phenyl-2-quinazolinyl)-3,3'-bi-9H-carbazole (abbreviation: PCCzQz) was used instead of mPCCzPTzn-02, which was the host material in light-emitting device 6.

[0341] The element structures of the light-emitting devices 6 and 7 fabricated in this example are similar to those shown in Fig. 12 in Example 1, but the specific configurations of the layers constituting the element structures are as shown in Table 5. The chemical formulas of the materials used in this example are shown below.

[0342] [Table 5]

[0343] [ka]

[0344] <Operation characteristics of each light-emitting device> The operating characteristics of the fabricated light-emitting devices were measured. A color luminance meter (Topcon, BM-5A) was used to measure the luminance and chromaticity (CIE chromaticity), and a multichannel spectrometer (Hamamatsu Photonics, PMA-11) was used to measure the electroluminescence (EL) spectrum. The measurements were performed at room temperature (an atmosphere maintained at 23°C). As the operating characteristics of light-emitting device 6 and light-emitting device 7, the current density-luminance characteristics are shown in Figure 28, the voltage-luminance characteristics in Figure 29, the luminance-current efficiency characteristics in Figure 30, the voltage-current density characteristics in Figure 31, the luminance-power efficiency characteristics in Figure 32, and the luminance-external quantum efficiency characteristics in Figure 33, respectively.

[0345] In addition, each light-emitting device is supplied with 2.5mA / cm 2 FIG. 34 shows the electroluminescence spectrum (EL spectrum) when a current was applied at a current density of 1000 .mu.m.

[0346] Also, 1000cd / m 2 The main initial characteristic values ​​of each light-emitting device in the vicinity are shown in Table 6 below.

[0347] [Table 6]

[0348] 34, the EL spectrum of each light-emitting device has two peaks at around 530 nm and 610 nm. The peak at around 530 nm of light-emitting device 6 and light-emitting device 7 is due to 2TMS-mmtBuDPhA2Anth, and the peak at around 610 nm is due to [Ir(dmdppr-dmp) 2 That is, in the light-emitting devices 6 and 7, the emission (fluorescence emission) originates from 2TMS-mmtBuDPhA2Anth and the emission (fluorescence emission) originates from Ir(dmdppr-dmp) 2 It can be seen that both luminescence (phosphorescence) originating from (dpm) and luminescence (phosphorescence) originating from (dpm) are obtained. Therefore, the EL spectrum results confirmed that luminescence from different guest materials was obtained simultaneously in both devices.

[0349] As shown in FIG. 33, both the light-emitting device 6 and the light-emitting device 7 showed high external quantum efficiency exceeding 10% at maximum, even though the fluorescent material was used as the guest material. This is because the organic compound having a protective group (the first organic compound 121 described in the second embodiment) was used as the guest material of the light-emitting layer, which is an organic compound having a function of converting singlet excitation energy into light emission, thereby suppressing the triplet excitation energy transfer from the host material to the fluorescent material by the Dexter mechanism and suppressing the deactivation of the triplet excitation energy accompanying the energy transfer, and as a result, the decrease in the light-emitting efficiency of the light-emitting device was suppressed. As can be seen from FIG. 30, FIG. 32, and FIG. 33, the efficiency of each light-emitting device with respect to luminance was higher in the light-emitting device 6 than in the light-emitting device 7. In this embodiment, the light-emitting device 6 and the light-emitting device 7 have structures that differ only in the host material of the light-emitting layer. The host material used in the light-emitting layer of the light-emitting device 6 was mPCCzPTzn-02, and the host material used in the light-emitting layer of the light-emitting device 7 was PCCzQz. In order to obtain the T1 level of the host material, a thin film of each organic compound was formed on a quartz substrate by vacuum deposition, and the emission spectrum of the thin film was measured at a low temperature (10K). For the measurement, a micro PL device LabRAM HR-PL (Horiba, Ltd.) was used, the measurement temperature was 10K, a He-Cd laser with a wavelength of 325 nm was used as the excitation light, and a CCD was used as the detector. A tangent line was drawn at the short wavelength side of the emission spectrum measured at a low temperature, and the T1 level was calculated from the energy of the wavelength of the extrapolated line. As a result, the T1 level of mPCCzPTzn-02 was 2.59 eV (478 nm), and the T1 level of PCCzQz was 2.38 eV (521 nm). Since the T1 level of mPCCzPTzn-02 is higher than the T1 level of PCCzQz, it can be said that the efficiency of the light-emitting device 6 is higher than that of the light-emitting device 7. Furthermore, a constant current drive test at 2.0 mA was performed on the light-emitting devices 6 and 7, and the time (LT80) until the relative luminance reached 80% (relative luminance of 100%) was 39 hours for the light-emitting device 6 and 156 hours for the light-emitting device 7. In this manner, a light-emitting device with good reliability can be obtained by using the light-emitting device according to one embodiment of the present invention.

[0350] (Reference synthesis example 1) In this Reference Synthesis Example, a method for synthesizing the organic compound used in the above Examples, 2-trimethylsilyl-N,N,N',N'-tetrakis(3,5-di-tert-butylphenyl)-9,10-anthracenediamine (abbreviation: 2TMS-mmtBuDPhA2Anth) (structural formula (229)) will be described.

[0351] <Step 1: Synthesis of 9,10-dibromo-2-trimethylsilyl anthracene> 2.7g (11mmol) of 2-trimethylsilyl anthracene was placed in a 500mL three-neck flask, and the flask was replaced with nitrogen. 110mL of N,N-dimethyl sulfoxide was added thereto and stirred at room temperature. 4.0g (23mmol) of N-bromosuccinimide was added thereto and stirred at room temperature for 15 hours. After stirring, water was added to the reaction mixture to obtain an aqueous layer and an organic layer. The aqueous layer was extracted with toluene, and the obtained extract and organic layer were combined. The mixed solution of the extract and organic layer was washed with water and a saturated aqueous solution of sodium thiosulfate, and then dried with magnesium sulfate. This mixture was filtered by gravity, and the filtrate was concentrated to obtain a yellow-brown solid. 450mL of hexane and 50mL of toluene were added to the obtained yellow-brown solid, and then the mixture was suction-filtered through Florisil (Wako Pure Chemical Industries, Ltd., catalog number: 066-05265), Celite (Wako Pure Chemical Industries, Ltd., catalog number: 537-02305), and aluminum oxide to obtain a filtrate. The obtained filtrate was concentrated to obtain a yellowish brown solid. The obtained solid was recrystallized with ethyl acetate / ethanol to obtain 2.4 g of a yellow solid in a yield of 54%. The synthesis scheme of step 1 is shown below in (F-1).

[0352] [ka]

[0353] In addition, the yellow solid obtained in step 1 above 1 The measurement results by H-NMR are shown below. From the results, it was found that 9,10-dibromo-2-trimethylsilyl anthracene was obtained.

[0354] 1 H-NMR (CDCl 3 ,300MHz):σ=8.74(s,1H),8.63-8.56(m,2H),8.55(d,J=8.8Hz,1H),7.75(d,J=8.3Hz,1H),7.68-7.61(m,2H),0.42(s,9H).

[0355] <Step 2: Synthesis of 2TMS-mmtBuDPhA2Anth> 1.4g (3.3mmol) of 9,10-dibromo-2-trimethylsilyl anthracene, 2.6g (6.6mmol) of bis(3,5-tert-butylphenyl)amine, 1.3g (14mmol) of sodium t-butoxide, and 60mg (0.15mmol) of 2-dicyclohexylphosphino-2',6'-dimethoxy-1,1'-biphenyl (abbreviation: SPhos) were placed in a 200mL three-neck flask, and the flask was replaced with nitrogen. 33mL of xylene was added to this mixture, and the mixture was degassed under reduced pressure, and then 40mg (70μmol) of bis(dibenzylideneacetone)palladium(0) was added to the mixture, and the mixture was stirred at 150°C for 6 hours under a nitrogen stream. After stirring, 400mL of toluene was added to the obtained mixture, and the mixture was suction filtered through Florisil, Celite, and aluminum oxide to obtain a filtrate. The obtained filtrate was concentrated to obtain a brown solid. This solid was purified by silica gel column chromatography (developing solvent: hexane:toluene 9:1) to obtain a yellow solid. The obtained yellow solid was recrystallized with ethyl acetate and ethanol to obtain 0.40 g of the target yellow solid in a yield of 12%. The synthesis scheme of step 2 is shown below in (F-2).

[0356] [ka]

[0357] The yellow solid thus obtained (0.40 g) was purified by train sublimation. The yellow solid was heated at 260°C for 15 hours under a pressure of 3.5 Pa. After the sublimation purification, the target yellow solid was obtained in an amount of 0.35 g with a recovery rate of 87%.

[0358] In addition, the yellow solid obtained in step 2 above 1 The measurement results by H-NMR are shown below. From these results, it was found that 2TMS-mmtBuDPhA2Anth was obtained.

[0359] 1 H-NMR (CDCl 3 ,300MHz):σ=8.25(s,1H),8.24-8.21(m,1H),8.15-8.11(m,2H),7.40-7.37(m,1H),7.30-7 .27(m,2H),6.97-6.94(m,8H),6.92-6.91(m,4H),1.14(s,36H),1.12(m,36H),0.09(s,9H). [Explanation of symbols]

[0360] 101: first electrode, 102: second electrode, 103: EL layer, 103a, 103b: EL layer, 104: charge generation layer, 111, 111a, 111b: hole injection layer, 112, 112a, 112b: hole transport layer, 113, 113a, 113b: light emitting layer, 114, 114a, 114b: electron transport layer, 115, 115a, 115b: electron injection layer, 121: first organic compound, 122: second organic compound, 123: third organic compound, 124: fluorescent material, 130a, 130b: luminophore, 131: protecting group, 200R, 200G, 200B: optical path, 201: first the substrate, 202: transistor (FET), 203R, 203G, 203B, 203W: light emitting device, 204: EL layer, 205: second substrate, 206R, 206G, 206B: color filter, 206R', 206G', 206B': color filter, 207: first electrode, 208: second electrode, 209: black layer (black matrix), 210R, 210G: conductive layer, 301: first substrate, 302: pixel section, 303: drive circuit section (source line drive circuit), 304a, 304b: drive circuit section (gate line drive circuit), 305: seal material, 306: second Substrate, 307: wiring, 308: FPC, 309: FET, 310: FET, 311: FET, 312: FET, 313: first electrode, 314: insulator, 315: EL layer, 316: second electrode, 317: light-emitting device, 318: space, 900: substrate, 901: first electrode, 902: EL layer, 903: second electrode, 911: hole injection layer, 912: hole transport layer, 913: light-emitting layer, 914: electron transport layer, 915: electron injection layer, 4000: lighting device, 4001: substrate, 4002: light-emitting device, 4003: substrate, 4004: first electrode, 4005: EL layer , 4006: second electrode, 4007: electrode, 4008: electrode, 4009: auxiliary wiring, 4010: insulating layer, 4011: sealing substrate, 4012: sealing material, 4013: desiccant, 4200: lighting device, 4201: substrate, 4202: light-emitting device, 4204: first electrode, 4205: EL layer, 4206: second electrode, 4207: electrode, 4208: electrode, 4209: auxiliary wiring, 4210: insulating layer, 4211: sealing substrate, 4212: sealing material, 4213: barrier film, 4214: planarization film, 5101: light, 5102: wheel, 5103: door, 5104: display unit,5105: steering wheel, 5106: shift lever, 5107: seat, 5108: inner rear view mirror, 5109: windshield, 7000: housing, 7001: display unit, 7002: second display unit, 7003: speaker, 7004: LED lamp, 7005: operation key, 7006: connection terminal, 7007: sensor, 7008: microphone, 7009: switch, 7010: infrared port, 7011: recording medium reading unit, 70 13: Earphone, 7014: Antenna, 7015: Shutter button, 7016: Image receiving unit, 7018: Stand, 7020: Camera, 7022, 7023: Operation buttons, 7024: Connection terminal, 7025: Band, 7026: Microphone, 7029: Sensor, 7030: Speaker, 7052, 7053, 7054: Information, 9310: Portable information terminal, 9311: Display unit, 9312: Display area, 9313: Hinge, 9315: Housing,

Claims

1. A light-emitting layer is disposed between a pair of electrodes, the light-emitting layer comprises a first organic compound having a function of converting singlet excitation energy into luminescence, and a second organic compound having a function of converting triplet excitation energy into luminescence; the first organic compound has a luminophore and five or more protecting groups; the luminophore is a fused aromatic ring or a fused heteroaromatic ring; the protecting group is any one of an alkyl group having from 1 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having from 3 to 10 carbon atoms, and a trialkylsilyl group having from 3 to 12 carbon atoms; A light-emitting device, wherein the S1 level of the first organic compound is higher than the T1 level of the second organic compound.

2. A light-emitting layer is disposed between a pair of electrodes, the light-emitting layer comprises a first organic compound having a function of converting singlet excitation energy into luminescence, and a second organic compound having a function of converting triplet excitation energy into luminescence; the first organic compound has a luminophore and five or more protecting groups; the luminophore is a fused aromatic ring or a fused heteroaromatic ring; the protecting group is any one of an alkyl group having from 1 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having from 3 to 10 carbon atoms, and a trialkylsilyl group having from 3 to 12 carbon atoms; A light-emitting device, wherein the peak wavelength of the emission spectrum of the second organic compound is longer than the peak wavelength of the emission spectrum of the first organic compound.

3. A light-emitting layer is disposed between a pair of electrodes, the light-emitting layer comprises a first organic compound having a function of converting singlet excitation energy into luminescence, and a second organic compound having a function of converting triplet excitation energy into luminescence; the first organic compound has five or more of any one of an alkyl group having from 1 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having from 3 to 10 carbon atoms, and a trialkylsilyl group having from 3 to 12 carbon atoms, and a condensed aromatic ring or a condensed heteroaromatic ring; A light-emitting device, wherein the S1 level of the first organic compound is higher than the T1 level of the second organic compound.

4. A light-emitting layer is disposed between a pair of electrodes, the light-emitting layer comprises a first organic compound having a function of converting singlet excitation energy into luminescence, and a second organic compound having a function of converting triplet excitation energy into luminescence; the first organic compound has five or more of any one of an alkyl group having from 1 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having from 3 to 10 carbon atoms, and a trialkylsilyl group having from 3 to 12 carbon atoms, and a condensed aromatic ring or a condensed heteroaromatic ring; A light-emitting device, wherein the peak wavelength of the emission spectrum of the second organic compound is longer than the peak wavelength of the emission spectrum of the first organic compound.

5. In any one of claims 1 to 4, the light-emitting layer further contains a third organic compound, the S1 level of the third organic compound is higher than the S1 level of the first organic compound; A light-emitting device, wherein the T1 level of the third organic compound is higher than the T1 level of the second organic compound.

6. In any one of claims 1 to 4, the light-emitting layer further comprises a fourth organic compound and a fifth organic compound, A light-emitting device, wherein the fourth organic compound and the fifth organic compound are a combination that forms an exciplex.

7. In any one of claims 1 to 6, The light-emitting device, wherein the fused aromatic ring or the fused heteroaromatic ring is any one of naphthalene, anthracene, fluorene, chrysene, triphenylene, tetracene, pyrene, perylene, coumarin, quinacridone, and naphthobisbenzofuran.

8. In any one of claims 1 to 7, A light-emitting device in which light is emitted from both the first organic compound and the second organic compound.

9. A light-emitting device according to any one of claims 1 to 8; at least one of a transistor or a substrate; A light emitting device having the

10. The light emitting device according to claim 9 ; At least one of a microphone, a camera, an operation button, an external connection part, or a speaker; An electronic device having:

11. A light-emitting device according to any one of claims 1 to 8; At least one of a housing, a cover, or a support base; A lighting device having:

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