Light-emitting element, display device, electronic device, and lighting device

Abstract

To provide a light-emitting element with high luminous efficiency.SOLUTION: A light-emitting element includes first to third organic compounds. The first organic compound has the function of converting triplet excitation energy into luminescence. Preferably, the second organic compound is a TADF material. The third organic compound is a fluorescent compound. Light emitted by the light-emitting element is obtained from the third organic compound. The triplet excitation energy in the light-emitting layer is transferred to the third organic compound through reverse intersystem crossing by the second organic compound or through the first organic compound.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] One aspect of the present invention relates to a light-emitting element, or a display device, an electronic device, and a lighting device having the light-emitting element. Note that one aspect of the present invention is not limited to the above technical field. The technical field of one aspect of the invention disclosed in this specification or the like relates to an article, a method, or a manufacturing method. Alternatively, one aspect of the present invention relates to a process, a machine, a manufacture, or a composition of matter. Therefore, more specifically, examples of the technical field of one aspect of the invention disclosed in this specification include semiconductor devices, display devices, liquid crystal display devices, light-emitting devices, lighting devices, power storage devices, memory devices, their driving methods, or their manufacturing methods.

[0002] Note that one aspect of the present invention is not limited to the above technical field. The technical field of one aspect of the invention disclosed in this specification or the like relates to an article, a method, or a manufacturing method. Alternatively, one aspect of the present invention relates to a process, a machine, a manufacture, or a composition of matter. Therefore, more specifically, examples of the technical field of one aspect of the invention disclosed in this specification include semiconductor devices, display devices, liquid crystal display devices, light-emitting devices, lighting devices, power storage devices, memory devices, their driving methods, or their manufacturing methods. Note that one aspect of the present invention is not limited to the above technical field. The technical field of one aspect of the invention disclosed in this specification or the like relates to an article, a method, or a manufacturing method. Alternatively, one aspect of the present invention relates to a process, a machine, a manufacture, or a composition of matter. Therefore, more specifically, examples of the technical field of one aspect of the invention disclosed in this specification include semiconductor devices, display devices, liquid crystal display devices, light-emitting devices, lighting devices, power storage devices, memory devices, their driving methods, or their manufacturing methods. Note that one aspect of the present invention is not limited to the above technical field. The technical field of one aspect of the invention disclosed in this specification or the like relates to an article, a method, or a manufacturing method. Alternatively, one aspect of the present invention relates to a process, a machine, a manufacture, or a composition of matter. Therefore, more specifically, examples of the technical field of one aspect of the invention disclosed in this specification include semiconductor devices, display devices, liquid crystal display devices, light-emitting devices, lighting devices, power storage devices, memory devices, their driving methods, or their manufacturing methods. Note that one aspect of the present invention is not limited to the above technical field. The technical field of one aspect of the invention disclosed in this specification or the like relates to an article, a method, or a manufacturing method. Alternatively, one aspect of the present invention relates to a process, a machine, a manufacture, or a composition of matter. Therefore, more specifically, examples of the technical field of one aspect of the invention disclosed in this specification include semiconductor devices, display devices, liquid crystal display devices, light-emitting devices, lighting devices, power storage devices, memory devices, their driving methods, or their manufacturing methods. Note that one aspect of the present invention is not limited to the above technical field. The technical field of one aspect of the invention disclosed in this specification or the like relates to an article, a method, or a manufacturing method. Alternatively, one aspect of the present invention relates to a process, a machine, a manufacture, or a composition of matter. Therefore, more specifically, examples of the technical field of one aspect of the invention disclosed in this specification include semiconductor devices, display devices, liquid crystal display devices, light-emitting devices, lighting devices, power storage devices, memory devices, their driving methods, or their manufacturing methods. Note that one aspect of the present invention is not limited to the above technical field. The technical field of one aspect of the invention disclosed in this specification or the like relates to an article, a method, or a manufacturing method. Alternatively, one aspect of the present invention relates to a process, a machine, a manufacture, or a composition of matter. Therefore, more specifically, examples of the technical field of one aspect of the invention disclosed in this specification include semiconductor devices, display devices, liquid crystal display devices, light-emitting devices, lighting devices, power storage devices, memory devices, their driving methods, or their manufacturing methods. Note that one aspect of the present invention is not limited to the above technical field. The technical field of one aspect of the invention disclosed in this specification or the like relates to an article, a method, or a manufacturing method. Alternatively, one aspect of the present invention relates to a process, a machine, a manufacture, or a composition of matter. Therefore, more specifically, examples of the technical field of one aspect of the invention disclosed in this specification include semiconductor devices, display devices, liquid crystal display devices, light-emitting devices, lighting devices, power storage devices, memory devices, their driving methods, or their manufacturing methods.

Background Art

[0003] In recent years, research and development of light-emitting elements using electroluminescence (EL) have been actively conducted. The basic configuration of these light-emitting elements is a configuration in which a layer (EL layer) containing a light-emitting substance is sandwiched between a pair of electrodes. By applying a voltage between the electrodes of this element, light emission from the light-emitting substance can be obtained. Since the above-described light-emitting element is a self-luminous type, a display device using the same has advantages such as excellent visibility, no need for a backlight, and low power consumption. Furthermore, it also has advantages such as being able to be manufactured in a thin and lightweight manner and having a high response speed. Since the above-described light-emitting element is a self-luminous type, a display device using the same has advantages such as excellent visibility, no need for a backlight, and low power consumption. Furthermore, it also has advantages such as being able to be manufactured in a thin and lightweight manner and having a high response speed. Since the above-described light-emitting element is a self-luminous type, a display device using the same has advantages such as excellent visibility, no need for a backlight, and low power consumption. Furthermore, it also has advantages such as being able to be manufactured in a thin and lightweight manner and having a high response speed.

[0004] Since the above-described light-emitting element is a self-luminous type, a display device using the same has advantages such as excellent visibility, no need for a backlight, and low power consumption. Furthermore, it also has advantages such as being able to be manufactured in a thin and lightweight manner and having a high response speed. Since the above-described light-emitting element is a self-luminous type, a display device using the same has advantages such as excellent visibility, no need for a backlight, and low power consumption. Furthermore, it also has advantages such as being able to be manufactured in a thin and lightweight manner and having a high response speed. Since the above-described light-emitting element is a self-luminous type, a display device using the same has advantages such as excellent visibility, no need for a backlight, and low power consumption. Furthermore, it also has advantages such as being able to be manufactured in a thin and lightweight manner and having a high response speed.

[0005] An organic compound is used as the light-emitting substance, and an EL layer containing the light-emitting organic compound is provided between a pair of electrodes. In the case of a light-emitting element (e.g., an organic EL element) provided with a layer, when a voltage is applied between a pair of electrodes, electrons are injected from the cathode and holes are injected from the anode into the light-emitting EL layer, respectively, and a current flows. Then, the injected electrons and holes recombine, causing the light-emitting organic compound to enter an excited state, and light can be obtained from the excited light-emitting organic compound.

[0006] The types of excited states formed by the organic compound include the singlet excited state (S * ) and the triplet excited state (T * ). The light emitted from the singlet excited state is called fluorescence, and the light emitted from the triplet excited state is called phosphorescence. Also, their statistical generation ratio in the light-emitting element is S * :T * = 1:3. Therefore, a light-emitting element using a compound that emits phosphorescence (phosphorescent compound) can achieve higher luminous efficiency than a light-emitting element using a compound that emits fluorescence (fluorescent compound). Therefore, in recent years, the development of light-emitting elements using phosphorescent compounds capable of converting the energy of the triplet excited state into light has been actively carried out.

[0007] Among the light-emitting elements using phosphorescent compounds, especially in the case of light-emitting elements that exhibit blue light emission, it is difficult to develop a stable compound having a high triplet excitation energy level, and thus it has not yet reached practical use. Therefore, the development of light-emitting elements using more stable fluorescent compounds has been carried out, and methods for increasing the luminous efficiency of light-emitting elements using fluorescent compounds (fluorescent light-emitting elements) have been explored.

[0008] As an example, thermally activated delayed fluorescence (Thermally Activated Del ​​​​​Light-emitting devices using TADF (Transparent Adhesion Fuel) materials are known. In thermally activated delayed fluorescent materials, the singlet excited state is generated from the triplet excited state by reverse intersystem crossing. The singlet excited state is converted into light emission.

[0009] In addition, in a light-emitting device having a thermally activated delayed fluorescent material and a fluorescent compound, The singlet excitation energy of the delayed fluorescent material is transferred to the fluorescent compound, and the fluorescent compound emits light. A method for obtaining luminescence has been proposed (see Patent Document 1). [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-45179 [Non-patent literature]

[0011] [Non-Patent Document 1] T. Sajoto et al.,J. Am. Chem. Soc.,2009,131,9813 Summary of the Invention [Problem to be solved by the invention]

[0012] Fluorescent materials cannot convert triplet excitation energy into luminescence. The luminous efficiency tends to be lower than that of light-emitting elements. Also, a large current is required to obtain high brightness. However, this requires a large amount of heat and current load, making it difficult to achieve good reliability. do.

[0013] In order to increase the luminous efficiency of a fluorescent light-emitting device, it is necessary to efficiently disperse triplet excitation energy in the luminescent layer. The triplet excitation energy can be converted into singlet excitation energy, or the triplet excitation energy can be converted into fluorescent material. Therefore, it is desirable to transfer energy efficiently from the triplet excited state to the singlet excited state. Development of methods and materials for efficiently generating excited states and further improving the luminous efficiency of light-emitting devices In addition, the material used in the light-emitting layer must have a high carrier transport property in order to reduce the driving voltage. Therefore, materials with good properties are required.

[0014] Therefore, an object of one embodiment of the present invention is to provide a light-emitting element with high emission efficiency. Another object of one embodiment of the present invention is to provide a light-emitting element with low driving voltage. Another object of one embodiment of the present invention is to provide a light-emitting element with high reliability. Another object of one embodiment of the present invention is to provide a light-emitting element with reduced power consumption. Another object of one embodiment of the present invention is to provide a light-emitting element with high color purity. Another object of one embodiment of the present invention is to provide a novel light-emitting element. An object of one embodiment of the present invention is to provide a novel light-emitting device. The object of the present invention is to provide a novel electronic device.

[0015] Note that the above description of the object does not preclude the existence of other objects. It is not necessary to solve all of these problems. Problems other than those mentioned above can be solved by the description of the specification, etc. It is obvious from the description of the specification, etc. that other problems can be extracted. do. [Means for solving the problem]

[0016] As described above, in a fluorescent light-emitting element, triplet excitation energy can be efficiently converted into light emission. There is a demand for the development of a conversion method. Therefore, it is required to enhance the energy transfer efficiency between the materials used in the light-emitting layer.

[0017] Accordingly, one aspect of the present invention is a light-emitting device having a light-emitting layer between a pair of electrodes, the light-emitting layer including a first organic compound, a second organic compound, and a third organic compound, the first organic compound having a function of converting triplet excitation energy into light, the difference between the singlet excitation energy and the triplet excitation energy of the second organic compound being 0 eV or more and 0.2 eV or less, and the third organic compound having a function of converting singlet excitation energy into light, and the light emitted by the light-emitting layer including the light emitted by the third organic compound.

[0018] Further, another aspect of the present invention is a light-emitting device having a light-emitting layer between a pair of electrodes, the light-emitting layer including a first organic compound, a second organic compound, and a third organic compound, the first organic compound having a function of converting triplet excitation energy into light, the second organic compound having a π-electron-excessive skeleton and a π-electron-deficient skeleton, the third organic compound having a function of converting singlet excitation energy into light, and the light emitted by the light-emitting layer including the light emitted by the third organic compound.

[0019] Furthermore, another aspect of the present invention is a light-emitting device having a light-emitting layer between a pair of electrodes, the light-emitting layer including a first organic compound, a second organic compound, and a third organic compound, the first organic compound and the second organic compound being capable of forming an exciplex, the first organic compound having a function of converting triplet excitation energy into light, and the singlet excitation energy of the second organic compound ​​​​​​​​​​​​​​The difference between the level and the triplet excitation energy level of the second organic compound is 0 eV or more and 0.2 eV or less, and the third organic compound has a function of converting singlet excitation energy into light emission The light emission exhibited by the light-emitting layer is the light emission exhibited by the third organic compound, and it is a light-emitting device.

[0020] Further, another aspect of the present invention has a light-emitting layer between a pair of electrodes, and the light-emitting layer includes a first organic compound a second organic compound, and a third organic compound, and the first organic compound and the second organic compound can form an exciplex. The first organic compound has a function of converting triplet excitation energy into light emission, and the second organic compound has a π-electron-rich skeleton and a π-electron-deficient skeleton. The third organic compound has a function of converting singlet excitation energy into light emission, and the light emission exhibited by the light-emitting layer is the light emission exhibited by the third organic compound, and it is a light-emitting device. In the above configuration, it is preferable that the first organic compound has a function of donating excitation energy to the third organic compound.

[0021] In the above configuration, it is preferable that the exciplex has a function of donating excitation energy to the third organic compound. In the above configuration, it is preferable that the π-electron-rich skeleton and the π-electron-deficient skeleton are directly bonded.

[0022] In the above configuration, it is preferable that the triplet excitation energy level of the first organic compound is equal to or higher than the singlet excitation energy level of the third organic compound. In the above configuration, it is preferable that the first organic compound is Ru, Rh, Pd, Os, Ir, or

[0023] In the above configuration, it is preferable that the π-electron-rich skeleton and the π-electron-deficient skeleton are directly bonded. In the above configuration, it is preferable that the π-electron-rich skeleton and the π-electron-deficient skeleton are directly bonded.

[0024] In the above configuration, it is preferable that the triplet excitation energy level of the first organic compound is equal to or higher than the singlet excitation energy level of the third organic compound. In the above configuration, it is preferable that the triplet excitation energy level of the first organic compound is equal to or higher than the singlet excitation energy level of the third organic compound.

[0025] In the above configuration, the first organic compound is Ru, Rh, Pd, Os, Ir, or Preferably, it has Pt.

[0026] In addition, in the above configuration, the first organic compound preferably has a function of exhibiting phosphorescence.

[0027] In addition, in the above configuration, the lowest excited triplet energy level of the first organic compound is preferably equal to or lower than the lowest excited triplet energy level of the second organic compound.

[0028] In addition, in the above configuration, the emission spectrum exhibited by the exciplex preferably has a region overlapping with the absorption band on the longest wavelength side of the absorption spectrum of the third organic compound.

[0029] In addition, in the above configuration, the first organic compound preferably has a luminescence quantum yield of 0% or more and 40% or less at room temperature.

[0030] In addition, in the above configuration, the third organic compound preferably exhibits fluorescence.

[0031] Another aspect of the present invention is a display device having the light-emitting element of each of the above configurations and at least one of a color filter or a transistor. Another aspect of the present invention is an electronic device having the display device and at least one of a housing or a touch sensor. Another aspect of the present invention is a lighting device having the light-emitting element of each of the above configurations and at least one of a housing or a touch sensor. One aspect of the present invention includes not only a light-emitting device having a light-emitting element but also an electronic device having a light-emitting device. Therefore, the light-emitting device described in this specification refers to an image display device or a light source (including a lighting device). In addition, a connector, for example, an FPC (Flexible Printed Circui is connected to the light-emitting element. In addition, a light-emitting device having a light-emitting element and an electronic device having a light-emitting device are also included in the scope. Therefore, the light-emitting device described in this specification refers to an image display device or a light source (including a lighting device). Also, a connector, for example, an FPC (Flexible Printed Circuit is connected to the light-emitting element. t), a display module to which a TCP (Tape Carrier Package) is attached ule, a display module provided with a printed wiring board at the tip of the TCP, or a C display module in which an IC (integrated circuit) is directly mounted by a COG (Chip On Glass) method may also be included in the light-emitting device.

Advantages of the Invention

[0032] According to one aspect of the present invention, a light-emitting element with high luminous efficiency can be provided. Or, according to one aspect of the present invention, a light-emitting element with a low driving voltage can be provided. Or, according to the present invention, a light-emitting element with good reliability can be provided. Or, according to one aspect of the present invention a light-emitting element with reduced power consumption can be provided. Or, according to the present invention, a light-emitting element with high color purity can be provided. Or, according to one aspect of the present invention a novel light-emitting element can be provided. Or, according to one aspect of the present invention a novel light-emitting device can be provided. Or, according to one aspect of the present invention, a new type of electronic device can be provided.

[0033] Note that the description of these effects does not prevent the existence of other effects. Note that one aspect of the present invention does not necessarily have to have all of these effects. Note that other effects can be clearly understood from the description in the specification, drawings, claims, etc., and it is possible to extract these other effects from the description in the specification, drawings, claims, etc.

Brief Description of the Drawings

[0034]

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Modes for Carrying Out the Invention

[0035] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and its form and details can be variously changed without departing from the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited to the description of the embodiments and examples shown below. Note that the positions, sizes, ranges, etc. of the respective components shown in the drawings and the like may not represent the actual positions, sizes, ranges, etc. for the sake of easy understanding. For this reason, the disclosed invention is

[0036] not necessarily limited to the positions, sizes, ranges, etc. disclosed in the drawings and the like. not necessarily limited to the positions, sizes, ranges, etc. disclosed in the drawings and the like.

[0037] In addition, in this specification and the like, ordinal numbers such as first, second, etc. are used for convenience, and may not indicate the process order or the stacking order. Therefore, for example, "the first" can be appropriately replaced with "the second" or "the third" and so on for explanation. Also, the ordinal numbers described in this specification and the like may not match the ordinal numbers used to specify an aspect of the present invention.

[0038] In addition, in this specification and the like, when explaining the configuration of the invention using drawings, the reference signs indicating the same thing may be commonly used among different drawings.

[0039] In addition, in this specification and the like, the term "film" and the term "layer" can be interchanged with each other. For example, the term "conductive layer" may be changed to the term "conductive film". Or, for example, the term "insulating film" may be changed to the term "insulating layer".

[0040] In addition, in this specification and the like, the singlet excited state (S * ) is a singlet state having excitation energy. Also, the S1 level is the lowest level of the singlet excitation energy levels, and is the excitation energy level of the lowest singlet excited state (S1 state). Also, the triplet excited state (T * ) is a triplet state having excitation energy. Also, the T1 level is the lowest level of the triplet excitation energy levels, and is the excitation energy level of the lowest triplet excited state (T1 state). Note that in this specification and the like, simply the singlet excitation ​​Even when written as S1 state and singlet excited energy level, Also, the triplet excited state and triplet excited energy level are sometimes used. Even in this case, it may refer to the T1 state and T1 level.

[0041] In this specification and the like, a fluorescent compound is a compound that relaxes from a singlet excited state to a ground state. Phosphorescent compounds are compounds that emit light in the visible light region when excited into a triplet state. It is a compound that emits light in the visible light region at room temperature when it relaxes to the bottom state. A phosphorescent compound is a compound that can convert triplet excitation energy into visible light.

[0042] In this specification, room temperature refers to a temperature in the range of 0°C or higher and 40°C or lower.

[0043] In this specification, the blue wavelength range is 400 nm or more and less than 490 nm. The blue light emission has at least one emission spectrum peak in the wavelength region. The green wavelength region is 490 nm or more and less than 580 nm, and green light is emitted in this wavelength region. It has at least one emission spectrum peak. The red wavelength region is 580 nm. The red light has at least one emission spectrum in the wavelength range of 680 nm or more and 680 nm or less. It has a peak.

[0044] (Embodiment 1) In this embodiment, a light-emitting element of one embodiment of the present invention will be described below with reference to FIGS. Reveal.

[0045] <Configuration example 1 of light-emitting element> First, the structure of a light-emitting element of one embodiment of the present invention will be described below with reference to FIG.

[0046] FIG. 1(A) is a schematic cross-sectional view of a light-emitting element 150 according to one embodiment of the present invention.

[0047] The light-emitting element 150 has a pair of electrodes (electrode 101 and electrode 102), and has an EL layer 100 provided between the pair of electrodes. The EL layer 100 has at least a light-emitting layer 130. .

[0048] In addition, the EL layer 100 shown in FIG. 1(A) has functional layers such as a hole injection layer 111, a hole transport layer 112, an electron transport layer 118, and an electron injection layer 119 in addition to the light-emitting layer 130. Note that in the present embodiment, among the pair of electrodes, electrode 101 is described as the anode and electrode 102 is described as the cathode, but the configuration of the light-emitting element 150 is not limited thereto. That is, electrode 101 may be the cathode, electrode 102 may be the anode, and the lamination of each layer between the electrodes may be in the reverse order. That is, from the anode side, the hole injection layer 111, the hole transport layer 112, the light-emitting layer 130, the electron transport layer 118, and the electron injection layer 119 may be laminated in this order.

[0049] Note that the configuration of the EL layer 100 is not limited to the configuration shown in FIG. 1(A), and may be a configuration having at least one selected from the hole injection layer 111, the hole transport layer 112, the electron transport layer 118, and the electron injection layer 119. Alternatively, the EL layer 100 may have a functional layer having a function such as reducing a hole or electron injection barrier, improving hole or electron transportability, inhibiting hole or electron transportability, or suppressing a quenching phenomenon by an electrode. Note that each functional layer may be a single layer or a configuration in which a plurality of layers are laminated. That is, the light-emitting element 150 may have a configuration in which electrode 101 is the cathode, electrode 102 is the anode, and the lamination of each layer between the electrodes is in the reverse order. That is, from the anode side, the hole injection layer 111, the hole transport layer 112, the light-emitting layer 130, the electron transport layer 118, and the electron injection layer 119 may be laminated in this order. That is, electrode 101 may be the cathode, electrode 102 may be the anode, and the lamination of each layer between the electrodes may be in the reverse order. That is, from the anode side, the hole injection layer 111, the hole transport layer 112, the light-emitting layer 130, the electron transport layer 118, and the electron injection layer 119 may be laminated in this order. That is, electrode 101 may be the cathode, electrode 102 may be the anode, and the lamination of each layer between the electrodes may be in the reverse order. That is, from the anode side, the hole injection layer 111, the hole transport layer 112, the light-emitting layer 130, the electron transport layer 118, and the electron injection layer 119 may be laminated in this order. That is, from the anode side, the hole injection layer 111, the hole transport layer 112, the light-emitting layer 130, the electron transport layer 118, and the electron injection layer 119 may be laminated in this order. .

[0050] Note that the configuration of the EL layer 100 is not limited to the configuration shown in FIG. 1(A), and may be a configuration having at least one selected from the hole injection layer 111, the hole transport layer 112, the electron transport layer 118, and the electron injection layer 119. Note that the configuration of the EL layer 100 is not limited to the configuration shown in FIG. 1(A), and may be a configuration having at least one selected from the hole injection layer 111, the hole transport layer 112, the electron transport layer 118, and the electron injection layer 119. Note that the configuration of the EL layer 100 is not limited to the configuration shown in FIG. 1(A), and may be a configuration having at least one selected from the hole injection layer 111, the hole transport layer 112, the electron transport layer 118, and the electron injection layer 119. Note that the configuration of the EL layer 100 is not limited to the configuration shown in FIG. 1(A), and may be a configuration having at least one selected from the hole injection layer 111, the hole transport layer 112, the electron transport layer 118, and the electron injection layer 119. Note that the configuration of the EL layer 100 is not limited to the configuration shown in FIG. 1(A), and may be a configuration having at least one selected from the hole injection layer 111, the hole transport layer 112, the electron transport layer 118, and the electron injection layer 119. Note that the configuration of the EL layer 100 is not limited to the configuration shown in FIG. 1(A), and may be a configuration having at least one selected from the hole injection layer 111, the hole transport layer 112, the electron transport layer 118, and the electron injection layer 119. Note that the configuration of the EL layer 100 is not limited to the configuration shown in FIG. 1(A), and may be a configuration having at least one selected from the hole injection layer 111, the hole transport layer 112, the electron transport layer 118, and the electron injection layer 119.

[0051] Next, the light-emitting layer 130 will be described below.

[0052] In one aspect of the present invention, the light-emitting element 150 has a fluorescent compound in the light-emitting layer 130. It is a fluorescent light-emitting element. Fluorescent light-emitting elements have good reliability, and furthermore, since the emission spectrum tends to be sharper compared to phosphorescent light-emitting elements, it is possible to obtain a light-emitting element with high color purity. However, in the case of an organic EL element, the generation ratio of singlet excitons and triplet excitons (hereinafter, exciton generation probability) is 1:3 according to statistical probability. Therefore, generally, in a fluorescent light-emitting element using light emission from singlet excitons, only 25% of the generated excitons can contribute to light emission. Therefore, in order to improve the efficiency of the fluorescent light-emitting element, it is important to make the triplet excitons contribute to light emission. Here, the present inventors have found that by using an organic compound capable of converting triplet excitation energy into light emission in the light-emitting layer, an organic compound having a difference between singlet excitation energy and triplet excitation energy of 0 eV or more and 0.2 eV or less, and an organic compound exhibiting fluorescent light emission, it is possible to efficiently make triplet excitons contribute to fluorescent light emission, that is, a highly efficient fluorescent element can be obtained.

[0053] In addition, the organic compound having a difference between singlet excitation energy and triplet excitation energy of 0 eV or more and 0.2 eV or less may be an organic compound having both a π-electron excess skeleton and a π-electron deficient skeleton in one molecule. In addition, examples of the organic compound having a difference between singlet excitation energy and triplet excitation energy of 0 eV or more and 0.2 eV or less include thermally activated delayed fluorescence (TADF) materials. Note that heat

[0054] In addition, examples of the organic compound having a difference between singlet excitation energy and triplet excitation energy of 0 eV or more and 0.2 eV or less include thermally activated delayed fluorescence (TADF) materials. A thermally activated delayed fluorescence material has a small energy difference between the S1 level and the T1 level, and can convert the triplet excitation energy into singlet excitation energy through reverse intersystem crossing. Therefore, the triplet excitation energy can be upconverted (reverse intersystem crossing) into singlet excitation energy by a small amount of thermal energy, and the singlet excited state can be efficiently generated. An exciplex (also called an exciplex or exciplex) that forms an excited state with two types of substances has a very small energy difference between the S1 level and the T1 level, and can convert the triplet excitation energy into singlet excitation energy. It has the function as a thermally activated delayed fluorescence material. Moreover, an organic compound having a π-electron rich skeleton and a π-electron deficient skeleton in one molecule has bipolar properties and good carrier (electron and hole) transport properties. Therefore, by using it in a light-emitting device, the carrier balance can be improved. In addition, the driving voltage can be lowered.

[0055] Further, when the organic compound having such a structure has TADF properties, it is preferable that the π-electron rich skeleton and the π-electron deficient skeleton are directly bonded. By adopting such a structure, the efficiency of reverse intersystem crossing is increased, so that a TADF material with good luminous efficiency can be obtained. Moreover, a TADF material has an organic compound having a π-electron rich skeleton and a π-electron deficient skeleton in one molecule. Therefore, the TADF material has good carrier transport properties as described above, and by using it in a light-emitting device, the carrier balance can be improved. In addition, the driving voltage of the light-emitting device can be lowered.

[0056]

[0057] ​​​​​​An organic compound having a function capable of converting the above-mentioned triplet excitation energy into light, and a compound capable of emitting phosphorescence (hereinafter also referred to as a phosphorescent compound) can be mentioned. In this specification and the like, a phosphorescent compound refers to a temperature range from a low temperature (for example, 77K) to room temperature or lower (that is, from 77K to 313K), which exhibits phosphorescence and does not exhibit fluorescence of a compound. In order for a phosphorescent compound to efficiently convert triplet excitation energy into light, it preferably has a heavy atom. When a phosphorescent compound has a heavy atom, spin -orbit interaction (interaction between the spin angular momentum and orbital angular momentum of electrons) allows the transition between the singlet ground state and the triplet excited state. Therefore, since the transition probability between the singlet ground state and the triplet excited state of the phosphorescent compound increases, the efficiency of light emission and the probability of absorption related to the transition can be increased. In addition, energy transfer by the Förster mechanism from the triplet excitation energy level of the phosphorescent compound to the singlet excitation energy level of the fluorescent compound is also allowed. For this purpose, it is preferable that the phosphorescent compound has a metal element with a large spin-orbit interaction. Specifically, a transition metal element is preferable, and particularly a platinum group element ( ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), or platinum (Pt)) is preferably included. Among them, having iridium can increase the transition probability related to the direct transition between the singlet ground state and the triplet excited state, which is preferable. In addition, as a material having a function capable of converting triplet excitation energy into light, the above-mentioned TADF material can also be mentioned.

[0058] ​​​​​​​​​​Figure 1(B) is a schematic cross-sectional view showing an example of the light-emitting layer 130 shown in Figure 1(A). Figure 1( The light-emitting layer 130 shown in B) has compound 131, compound 132, and compound 133. In one aspect of the present invention, compound 131 has a function capable of converting triplet excitation energy into light emission. Also, compound 132 is preferably a TADF material. Compound 133 is a guest material that exhibits fluorescence emission.

[0059] <Example 1 of the configuration of the light-emitting layer> Figure 1(C) is an example of the energy level correlation in the light-emitting layer in a light-emitting device according to one aspect of the present invention. This configuration example shows the case where a phosphorescent compound is used for compound 131.

[0060] Also, the energy level correlation among compound 131, compound 132, and compound 133 in the light-emitting layer 130 is shown in Figure 1(C). Note that the notations and symbols in Figure 1(C) are as follows. ·Comp(131): Compound 131 ·Comp(132): Compound 132 ·Guest(133): Compound 133 ·Comp(132): Compound 132 ·Guest(133): Compound 133 ·T C1 : T1 level of compound 131 ·S C2 : S1 level of compound 132 ·T C2 : T1 level of compound 132 ·S G : S1 level of compound 133 ·T G : T1 level of compound 133

[0061] In Figure 1(C), compound 131 or compound 132 receives holes and electrons to form an excited state. Here, since compound 131 is a phosphorescent compound, the singlet state and the triplet Intersystem crossing between the singlet state and the 132 singlet state is allowed. Both the valence and triplet excitation energy can be rapidly transferred to compound 131 (Figure 1). 1(C) Root A1). At this time, S C2 ≧T C1 , T C2 ≧T C1 It is preferable that The light-emitting layer 130 is formed by mixing compounds 131, 132, and 133. However, it is preferable that the compound 132 is mixed in a larger amount than the compound 131. Specifically, the weight ratio of Compound 131:Compound 132 is preferably 1:9 to 3:7. This configuration allows compound 131 to be excited efficiently. Since 31 is a phosphorescent compound, it can efficiently utilize the triplet excitation energy of compound 131. The singlet excitation energy of compound 133 can be converted to the hydroxyl group (Figure 1(C) Route A). 2) Here, as shown in Figure 1(C), S C2 ≧T C1 ≧S G If so, the singlet excited This is preferable because the energy is efficiently transferred to the guest material, compound 133. C 2≧T C1 ≧S G When the triplet excitation energy is This is preferable because it moves to the guest material, compound 133.

[0062] Also, T C1 From T G When triplet excited energy transfer occurs to is deactivated (Fig. 1(C) Route A3). Therefore, the energy transfer of Route A3 The less the better. To inhibit route A3, the more effective the compound 131 and compound 132 are. The weight ratio of the total amount to Compound 133 preferably has a low weight ratio of Compound 133. Specifically, the weight ratio of Compound 133 to the total amount of Compound 131 and Compound 132 is preferably 0.001 or more and 0.05 or less, more preferably 0.001 or more and 0.01 or less. .

[0063] In addition, when the direct recombination process of the carrier dominates in Compound 133, a large number of triplet excitons are generated in Compound 13 3, which impairs the luminescence efficiency due to thermal deactivation. Therefore, it is preferable that the ratio of the energy transfer process via Route A 2 is larger than the direct recombination process of the carrier in Compound 133, because the generation probability of the triplet excited state of Compound 133 can be reduced and thermal deactivation can be suppressed. For this purpose, the weight ratio of the total amount of Compound 131 and Compound 132 to Compound 133 preferably has a low weight ratio of Compound 133. Specifically, the weight ratio of Compound 133 to the total amount of Compound 131 and Compound 132 is preferably 0.001 or more and 0.05 or less, more preferably 0 .001 or more and 0.01 or less. .

[0064] In addition, in the light-emitting device of one aspect of the present invention, Compound 132 has a function of exhibiting thermally activated delayed fluorescence ( TADF property). That is, Compound 132 has a function of converting triplet excitation energy into singlet excitation energy by upconversion version (Route A 4 in Fig. 1(C)). The singlet excitation energy possessed by Compound 132 can quickly move to Compound 133 (Route A5 in Fig. 1(C)). At this time, it is preferable that S C2 ≧S G .

[0065] ​Note that route A1 can occur even if no inverse term crossing represented by route A4 occurs. That is, the energy transfer represented by route A1 can occur whether or not the inverse term crossing represented by route A4 occurs.

[0066] As described above, in the light-emitting element of one aspect of the present invention, the triplet excitation energy moves to compound 133, which is a guest material, through route A1 and route A2 in FIG. 1(C), and there is a route that moves to compound 133 through route A4 and route A5 in FIG. 1 (C). The existence of a route through which triplet excitation energy moves to a fluorescent compound can increase the luminescence efficiency of the fluorescent light-emitting element. Further, the existence of a plurality of routes through which triplet excitation energy moves to a fluorescent compound can further increase the luminescence efficiency. By configuring the light-emitting layer 130 as described above, luminescence from the fluorescent compound in the light-emitting layer 130 can be obtained efficiently.

[0067]

[0068] Also, T G is preferably 2.0 eV or less. By adopting such a configuration, a light-emitting element with good reliability can be obtained.

[0069] In the above configuration, since it is not necessary to use a material with a high luminescence quantum yield for the phosphorescent compound, material design becomes easy and the range of material selection expands. Specifically, the luminescence quantum yield of the compound may be 0% or more and 50% or less, 0% or more and 40% or less at room temperature or normal temperature, 0% or more and 25% or less, 0% or more and 10% or less , or even 0% or more and 1% or less. Further, the compound may have a heavy atom. ​​​​​​​is preferable. Examples of the heavy atom include Ru, Rh, Pd, Os, Ir, Pt, etc. .

[0070] <Example 2 of the structure of the light-emitting layer> Figure 2(B) shows the energy levels in the light-emitting layer 130 of the light-emitting element 150 according to one embodiment of the present invention. This is an example of the correlation of. In this configuration example, a phosphorescent compound is used for compound 131, and the case where compound 131 and compound 132 form an exciplex is shown.

[0071] The combination of compound 131 and compound 132 may be any combination capable of forming an exciplex, but it is more preferable that one is a compound having hole-transporting properties and the other is a compound having electron-transporting properties. In this case, a donor-acceptor type exciplex is easily formed, and the exciplex can be efficiently formed. Further, when the combination of compound 131 and compound 132 is a combination of a compound having hole-transporting properties and a compound having electron-transporting properties, the carrier balance can be easily controlled by the mixing ratio. Specifically, the range of compound having hole-transporting properties: compound having electron-transporting properties = 1 :9 to 9:1 (weight ratio) is preferable. Further, by having this configuration, the carrier balance can be easily controlled, so that the control of the carrier recombination region can also be easily performed. Note that the formation of the exciplex can be confirmed, for example, by comparing the emission spectrum of compound 131, the emission spectrum of compound 132, and the emission spectrum of a mixed film obtained by mixing these compounds, and if the emission spectrum of the mixed film shows a longer wavelength shift (or a longer wavelength than the emission spectra of the respective compounds).

[0072] spectrum, and the emission spectrum of the mixed film shifts to a longer wavelength than the emission spectra of the respective compounds (or has a longer wavelength ​​It can be confirmed by observing the phenomenon of having a new peak on the side). Alternatively, The transient photoluminescence (PL) of Compound 131, the transient PL of Compound 132, and the transient PL of a mixed film obtained by mixing these compounds are compared, and the transient PL lifetime of the mixed film has a longer lifetime component than the transient PL lifetime of each compound, or the difference in transient response such as an increase in the ratio of the delayed component is observed, [[ID=We can confirm by observing the difference in transient response such as an increase in the ratio of the delayed component. In addition, the above-mentioned transient PL may be read as transient electroluminescence (EL). That is, the transient EL of Compound 131, the transient EL of Compound 132, and the transient EL of a mixed film of these are compared, and the formation of an exciplex can also be confirmed by observing the difference in transient response.

[0073] In addition, as a combination of materials that efficiently form an exciplex, the HOMO (Highest Occupied Molecular Orbital, also referred to as the highest occupied orbital) level of one of Compound 131 and Compound 132 is preferably higher than the HOMO level of the other, and the LUMO (Lowest Unoccupied Molecular Orbita l, also referred to as the lowest unoccupied orbital) level of one is preferably higher than the LUMO level of the other. Specifically, the energy difference between the HOMO level of Compound 131 and the HOMO level of Compound 132 is preferably 0.1 eV or more, more preferably 0.2 eV or more, and even more preferably 0.3 eV or more. Also, the energy difference between the LUMO level of Compound 131 and the LUMO level of Compound 132 is preferably 0.1 eV or more, more preferably 0.2 eV or more, and even more preferably 0.3 eV or more. Such a correlation of energy levels By doing so, holes and electrons, which are carriers injected from a pair of electrodes (electrode 101 and electrode 102), are likely to be injected into Compound 131 and Compound 132, respectively, which is preferable. Note that the HOMO level of Compound 131 may be equivalent to the HOMO level of Compound 132, or the LUMO level of Compound 131 may be equivalent to the LUMO level of Compound 132. It is suitable. Note that the HOMO level of Compound 131 may be equivalent to the HOMO level of Compound 132, or the LUMO level of Compound 131 may be equivalent to the LUMO level of Compound 132.

[0074] Note that the LUMO level and HOMO level of a compound can be derived from the electrochemical properties (reduction potential and oxidation potential) of the compound measured by cyclic voltammetry (CV) measurement.

[0075] For example, when Compound 131 has hole transporting properties and Compound 132 has electron transporting properties, as shown in the energy band diagram of Fig. 2(A), it is preferable that the HOMO level of Compound 131 is higher than the HOMO level of Compound 132, and it is preferable that the LUMO level of Compound 131 is higher than the LUMO level of Compound 132. With such a correlation of energy levels, holes and electrons, which are carriers injected from a pair of electrodes (electrode 101 and electrode 102), are likely to be injected into Compound 131 and Compound 132, respectively, which is preferable.

[0076] Note that in Fig. 2(A), Comp(131) represents Compound 131, Comp(1 32) represents Compound 132, ΔE C1 represents the energy difference between the LUMO level and the HOMO level of Compound 131, ΔE represents the energy difference between the LUMO level and the HOMO level of Compound 132, and ΔE C2 represents the energy difference between the LUMO level of Compound 132 and the HOMO level of Compound 131. These are notations and symbols. E ​​​​​​​​​​

[0077] In addition, the exciplex formed by Compound 131 and Compound 132 is an exciplex having the HOMO molecular orbital of Compound 131 and the LUMO molecular orbital of Compound 132. Also, the excitation energy of the exciplex is approximately equivalent to the energy difference (ΔE ) between the LUMO level of Compound 132 and the HOMO E level of Compound 131, and is smaller than the energy difference (ΔE ) between the LUMO level and the HOMO C1 level of Compound 131 and the energy difference (ΔE ) between the LUMO level and the HOMO level of Compound 132. Therefore, by forming an exciplex with Compound 131 and Compound 132 C2 , it becomes possible to form an excited state with a lower excitation energy . Also, since it has a lower excitation energy, the exciplex can form a stable excited state .

[0078] In addition, the correlation of the energy levels of Compound 131, Compound 132, and Compound 133 in the light-emitting layer 130 is shown in FIG. 2(B). Note that the notations and symbols in FIG. 2(B) are as follows , and other notations and symbols are the same as those shown in FIG. 1(C). ·S : S1 level of Compound 131 C1 ·S E : S1 level of the exciplex ·T E : T1 level of the exciplex

[0079] In the light-emitting element according to one aspect of the present invention shown in this configuration example, an exciplex is formed by Compound 131 and Compound 132 included in the light-emitting layer 130. The S1 level (S ) of the exciplex and the T1 level (T E ) of the exciplex E ​​​is an energy level adjacent to each other (Figure 2(B), Route A See 6).

[0080] When the exciplex generated by the above process emits light or loses excitation energy, such as donating the excitation energy to another material, and returns to the ground state, the two substances that formed the exciplex behave as the original separate substances again. When the exciplex generated by the above process emits light or loses excitation energy, such as donating the excitation energy to another material, and returns to the ground state, the two substances that formed the exciplex behave as the original separate substances again. When the exciplex generated by the above process emits light or loses excitation energy, such as donating the excitation energy to another material, and returns to the ground state, the two substances that formed the exciplex behave as the original separate substances again.

[0081] The excitation energy levels (S E and T E ) of the exciplex are lower than the S1 levels (S and S C1 and S C2 ) of each substance (Compound 131 and Compound 132) that forms the exciplex. Therefore, it is possible to form an excited state with a lower excitation energy. As a result, the driving voltage of the light-emitting element 150 can be reduced. it is possible to form an excited state with a lower excitation energy. As a result, the driving voltage of the light-emitting element 150 can be reduced.

[0082] The S1 level (S E ) and the T1 level (T E ) of the exciplex are adjacent energy levels to each other and thus have a function of exhibiting thermally activated delayed fluorescence. That is, the exciplex has a function of converting triplet excitation energy into singlet excitation energy by upconversion . Therefore, a part of the triplet excitation energy generated in the light-emitting layer 130 is converted into singlet excitation energy by the exciplex. For this purpose, the energy difference between the S1 level (S ) and the T1 level (T ) of the exciplex is preferably greater than 0 eV and 0.2 eV or less, more preferably E greater than 0 eV and 0.1 eV or less. In addition, in order to efficiently cause intersystem crossing , the T1 level (T E ) of the exciplex is preferably lower than the S1 level (S ) of each substance (Compound 131 and Compound 132) that forms the exciplex. And the energy difference between the S1 level (S E ) and the T1 level (T and the T1 level (T C1 and T C2 ) of the compound 132) is preferably lower. This makes it less likely for quenching of the triplet excitation energy of the exciplex formed by the compound 131 and the compound 132 to occur, and efficient reverse intersystem crossing from the triplet excitation energy to the singlet excitation energy occurs by the exciplex. Moreover, the singlet excitation energy level (S ) of the exciplex is preferably higher than the singlet excitation energy level (S

[0083] ) of the compound 133 which is the luminescent material. By having such a correlation of energy levels, the singlet excitation energy of the generated exciplex can transfer energy from the singlet excitation energy level (S E ) of the exciplex to the singlet excitation energy level (S ) of the compound 133. G At this time, the correlation of the energy levels between the compound 131 and the compound 132 is not limited to FIG. 2(B). That is, the singlet excitation energy level (S ) of the compound 131 may be higher or lower than the singlet excitation energy level (S ) of the compound 132. Also, the triplet excitation energy level (T E ) of the compound 131 may be higher or lower than the triplet excitation energy level (T G ) of the compound 132. Moreover, in one aspect of the present invention, since a phosphorescent compound is used for one of the compounds forming the exciplex, intersystem crossing between the singlet state and the triplet state is allowed. Therefore, the triplet

[0084] C1 ) of the compound 131 may be higher or lower than the triplet excitation energy level (T 132 of the compound. C2 ) may be higher or lower. 131 of the compound. C1 ) is the triplet excitation energy of the compound 132 Level (T C2 ) may be higher or lower.

[0085] Also, in one aspect of the present invention, since a phosphorescent compound is used for one of the compounds forming the exciplex, intersystem crossing between the singlet state and the triplet state is allowed. Therefore, the triplet state. It is possible to form an exciplex that can undergo a transition from the excited state to the singlet ground state. In this case, the triplet excited energy level (T E ) is one of the luminescent materials, Compound 133. Singlet excited energy level (S G ) is preferable. By using correlation, the triplet excitation energy of the generated exciplex is Energy level (T E ) to the singlet excited energy level (S G ) to energy The S1 level (S E ) and T1 level (T E )teeth, The adjacent energy levels allow for distinct fluorescence and phosphorescence in the emission spectrum. In some cases, it is difficult to distinguish between fluorescence and phosphorescence. It may be possible to distinguish between them.

[0086] Through the energy transfer process described above, compound 133 enters a singlet excited state and emits light. (See route A7 in Figure 2(B)).

[0087] Also, T E From T G When triplet excitation energy transfer occurs to This results in inactivation (Fig. 2(B) Route A8). Therefore, the energy transfer along Route A8 is small. In order to inhibit route A8, the total amount of compound 131 and compound 132 is preferably The weight ratio of the amount of the compound 133 to the amount of the compound 133 is preferably low, specifically The weight ratio of compound 133 to the total amount of compound 131 and compound 132 is preferably 0. It is 0.001 or more and 0.05 or less, and more preferably 0.001 or more and 0.01 or less.

[0088] In addition, when the direct recombination process of carriers dominates in Compound 133, a large number of triplet excitons will be generated in Compound 133, which will reduce the luminescence efficiency due to thermal deactivation. Therefore, it is preferable that the ratio of the energy transfer process (Route A7 in Fig. 2(B)) through the formation process of the exciplex is higher than the direct recombination process of carriers in Compound 133, because it can reduce the generation probability of the triplet excited state of Compound 133 and suppress thermal deactivation. For this purpose, the weight ratio of the total amount of Compound 131 and Compound 132 to Compound 133 is preferably low. Specifically, the weight ratio of Compound 133 to the total amount of Compound 131 and Compound 132 is preferably 0.001 or more and 0.05 or less, and more preferably 0.001 or more and 0.01 or less. Also, T is preferably 2.0 eV or less. With such a configuration, a light-emitting device with good reliability can be obtained. In addition, it may be a configuration in which Compound 131 has electron transporting properties and Compound 132 has hole transporting properties. In that case, it is preferable that the HOMO level of Compound 132 is higher than the HOMO level of Compound 131, and it is preferable that the LUMO level of Compound 132 is higher than the LUMO level of Compound 131. Also, the weight ratio of Compound 131 to Compound 132 is preferably low. Specifically, the weight ratio of Compound 131 to Compound 132 is preferably 0.0 1 or more and 0.5 or less, and more preferably 0.05 or more and 0.3 or less.

[0089] G

[0090]

[0091] ​​​​​​​​​​​

[0092] As described above, if all the energy transfer processes of the above-mentioned routes A6 and A7 occur efficiently, both the singlet excitation energy and the triplet excitation energy generated in the light-emitting layer 130 can be efficiently converted into the energy of the singlet excited state of compound 133, so the light-emitting device 150 can emit light with high luminous efficiency.

[0093] Further, in the light-emitting device according to one aspect of the present invention, it is preferable that compound 132 has a π-electron deficient skeleton. With this configuration, the LUMO level of compound 132 becomes lower, which is suitable for the formation of an exciplex.

[0094] Further, in the light-emitting device according to one aspect of the present invention, it is preferable that compound 132 has a π-electron rich skeleton. With this configuration, the HOMO level of compound 132 becomes higher, which is suitable for the formation of an exciplex.

[0095] Further, in the light-emitting device according to one aspect of the present invention, compound 132 has a function of exhibiting thermally activated delayed fluorescence ( TADF property). Therefore, in compound 132 in which no exciplex is formed, as shown in the above-described configuration example of the light-emitting layer, it has a function of converting triplet excitation energy into singlet excitation energy by upconversion (Route A9 in FIG. 2(B)). The singlet excitation energy possessed by compound 132 can quickly move to compound 133 (Route A 10 ) in FIG. 2(B). At this time, it is preferable that S C2 ≧S G .

[0096] As described above, in the light-emitting device according to one aspect of the present invention, Routes A6 and A7 in FIG. 2(B) Through this process, the triplet excitation energy moves to compound 133, which is the guest material, and the route is shown in FIG. 2 (B) Routes A9 and A 10 There is a route through which the energy moves to compound 133 Similar to the previous example of the structure of the light-emitting layer, there is a route through which the triplet excitation energy moves to the fluorescent compound By virtue of this, the luminous efficiency of the fluorescent light-emitting device can be enhanced. Also, since there are multiple routes through which the triplet excitation energy moves to the fluorescent compound the luminous efficiency can be further enhanced

[0097] In this specification etc., the processes of Routes A6 and A7 shown above may be referred to as ExSET (Exciplex-Singlet Energy Transfer) or ExEF (Exciplex-Enhanced Fluorescence). In other words, in the light-emitting layer 130, there is donation of excitation energy from the exciplex to the fluorescent compound

[0098] By configuring the light-emitting layer 130 as described above, efficient light emission from the fluorescent compound can be obtained

[0099] <Example of the structure of the light-emitting layer 3> FIG. 3 shows an example of the correlation of energy levels in the light-emitting layer of a light-emitting device according to an aspect of the present invention. In this example, the case where TADF material is used for compound 131 is shown. Note that the notations and symbols in FIG. 3 are the same as those shown in FIG. 1(C). ·S C1 : S1 level of compound 131

[0100] In FIG. 3, when compound 131 or compound 132 receives holes and electrons, they are in an excited state ​​​​​​In addition, the excitation energy of compound 132 is rapidly transferred to compound 131. (Fig. 3 Route A 11 ). At this time, S C2 ≧S C1 , T C2 ≧T C1 in Here, since Compound 131 is a thermally activated delayed fluorescent material, Compound 13 The triplet excitation energy of 1 is upconverted to singlet excitation energy at room temperature. Version (Fig. 3 Route A 12 ) In addition, the singlet excitation energy of compound 131 Level (S C1 ) to the singlet excited energy level (S G ) energy transfer Movement (Fig. 3 Route A 13 ) is admissible, so the root A 11 Route A 13 Through the process By this, the triplet excitation energy of compound 131 is converted to the singlet excitation energy of compound 133. Energy level (S G ) where, as shown in Figure 3, T C2 ≧T C1 ≧S G and both the singlet excitation energy and the triplet excitation energy are In order to efficiently transfer from compounds 131 and 132 to the guest material, compound 133, This is preferable.

[0101] In order to efficiently proceed with the above-mentioned upconversion, the S1 level ( S C2 ) and T1 level (T C2 ) is preferably greater than 0 eV and less than 0.2 eV. eV or less, and more preferably, greater than 0 eV and less than 0.1 eV.

[0102] Also, TC1 From T G When triplet excitation energy transfer occurs to T, the triplet excitation energy is deactivated (Fig. 3, Route A 14 ). Therefore, it is preferable that the energy transfer of Route A 14 is less. To suppress the energy transfer of Route A, it is preferable that the energy difference between T and T is large. For this purpose, it is preferable 14 that T is 2.0 eV or less. By adopting such a configuration, a light-emitting C1 element with good luminous efficiency and good reliability can be obtained. G G .

[0103] Also, as shown in the above-described configuration example of the light-emitting layer, since Compound 132 is a TADF material, it has a function of converting triplet excitation energy into singlet excitation energy by upconversion (Fig. 15 3, Route A). The singlet excitation energy possessed by Compound 132 can quickly move to Compound 133 (Fig. 3, Route A). At this time, it is 16 preferable that S ≧ S. C2 G

[0104] Similar to the above-described configuration example of the light-emitting 11 layer, in the light-emitting element according to one embodiment of the present invention, through Route A to Route A in Fig. 3, the triplet excitation 13 energy moves to Compound 133, which is a guest material, and through Route A and Route A in Fig. 3, there is a path for moving to Compound 133. 15 Also, since there is a path for the triplet excitation energy to move to the 16 fluorescent compound, the luminous efficiency of the fluorescent light-emitting element can be increased. Since there is a path for the triplet excitation energy to move to the fluorescent compound, The presence of multiple paths for movement can further enhance the luminous efficiency.

[0105] Note that Route A 11 is Route A 15 can occur even without the occurrence of the inverse term crossing represented by it. That is, that is, the energy transfer represented by Route A 11 can occur whether or not the inverse term crossing 15 represented by Route A occurs.

[0106] <Constitution Example 4 of Light Emitting Layer> FIG. 4(A) shows the case where four kinds of materials are used for the light emitting layer 130. In FIG. 4(A), the light emitting layer 130 has Compound 131, Compound 132, Compound 133, and Compound 134. In one aspect of the present invention, Compound 131 has a function of converting triplet excitation energy into light emission. Also, Compound 132 is preferably a TADF material. Compound 13 3 is a guest material that exhibits fluorescence emission. Further, Compound 134 is an organic compound that forms an exciplex with Compound 132.

[0107] Also, the correlation of the energy levels of Compound 131, Compound 132, Compound 133, and Compound 134 in the light emitting layer 130 is shown in FIG. 4(B). Note that the notations and symbols in FIG. 4(B) are as follows, and other notations and symbols are the same as the notations and symbols shown in FIG. 2(B). ·S C3 : S1 level of Compound 134 ·T C3 : T1 level of Compound 134

[0108] In the light emitting element of one aspect of the present invention shown in this constitution example, the compounds included in the light emitting layer 130 132 and compound 134 form an exciplex. The S1 level (S E ) of the exciplex and the T1 level (T ) of the exciplex are adjacent energy levels to each other (Figure 4(B), Route A E 17 17 17

[0109] The exciplex generated by the above process, as described above, loses its excitation energy, and thus the two substances that formed the exciplex behave as the original separate substances again.

[0110]

[0110] The excitation energy levels (S E and T E ) of the exciplex are lower than the S1 levels (S ) of each substance (compound 132 and compound 134) that forms the exciplex. Therefore, it becomes possible to form an excited state with a lower excitation energy. As a result, the driving voltage of the light-emitting element 150 can be reduced. C2 and S C3 ) of each substance (compound 132 and compound 134) that forms the exciplex. Therefore, it becomes possible to form an excited state with a lower excitation energy. As a result, the driving voltage of the light-emitting element 150 can be reduced.

[0111] Here, since compound 131 is a phosphorescent compound, intersystem crossing between the singlet state and the triplet state is allowed. Therefore, both the singlet excitation energy and the triplet excitation energy of the exciplex quickly move to compound 131 (Route A ) 18 18 ). At this time, it is preferable that T E ≧T C1 . Also, the triplet excitation energy of compound 131 can be efficiently converted into the singlet excitation energy of compound 133 (Route A ) 19 19 . [[ID=5۳]] E [[ID=5۶]] E [[ID=5۷]] C1 [[ID=5۸]] C1 [[ID=5۹]] G [[ID=6۰]] G [[ID=6۱]] It is preferable that the energy of the triplet state of the ruthenium complex efficiently transfers to Compound 133, which is a guest material, as singlet excitation energy. This is preferable.

[0112] At this time, the combination of Compound 132 and Compound 134 may be any combination that can form an exciplex, but it is more preferable that one is a compound having hole transporting properties and the other is a compound having electron transporting properties. In this case, it becomes easier to form a donor-acceptor type exciplex, and an exciplex can be efficiently formed. Further, when the combination of Compound 132 and Compound 134 is a combination of a compound having hole transporting properties and a compound having electron transporting properties, the carrier balance can be easily controlled by the mixing ratio. Specifically, the range of the compound having hole transporting properties: the compound having electron transporting properties = 1:9 to 9:1 (weight ratio) is preferable. Further, since the carrier balance can be easily controlled by having this configuration, the control of the carrier recombination region can also be easily performed. Moreover, as a combination of materials that efficiently form an exciplex, it is preferable that the HOMO level of one of Compound 132 and Compound 134 is higher than the HOMO level of the other, and the LUMO level of one is higher than the LUMO level of the other. Specifically, the energy difference between the HOMO level of Compound 132 and the HOMO level of Compound 134 is preferably 0.1 eV or more, more preferably 0.2 eV or more, and still more preferably 0.3 eV or more. Also, the energy difference between the LUMO level of Compound 132 and the LUMO level of Compound 134 is preferably 0.1 eV or more, more preferably 0.2 eV or more, and still more preferably 0.3 eV or more. In this case, it becomes easier to form a donor-acceptor type exciplex, and an exciplex can be efficiently formed. Further, when the combination of Compound 132 and Compound 134 is a combination of a compound having hole transporting properties and a compound having electron transporting properties, the carrier balance can be easily controlled by the mixing ratio. In this case, it becomes easier to form a donor-acceptor type exciplex, and an exciplex can be efficiently formed. Further, when the combination of Compound 132 and Compound 134 is a combination of a compound having hole transporting properties and a compound having electron transporting properties, the carrier balance can be easily controlled by the mixing ratio. Moreover, as a combination of materials that efficiently form an exciplex, it is preferable that the HOMO level of one of Compound 132 and Compound 134 is higher than the HOMO level of the other, and the LUMO level of one is higher than the LUMO level of the other. Specifically, the energy difference between the HOMO level of Compound 132 and the HOMO level of Compound 134 is preferably 0.1 eV or more, more preferably 0.2 eV or more, and still more preferably 0.3 eV or more. Also, the energy difference between the LUMO level of Compound 132 and the LUMO level of Compound 134 is preferably 0.1 eV or more, more preferably 0.2 eV or more, and still more preferably 0.3 eV or more. In this case, it becomes easier to form a donor-acceptor type exciplex, and an exciplex can be efficiently formed. Further, when the combination of Compound 132 and Compound 134 is a combination of a compound having hole transporting properties and a compound having electron transporting properties, the carrier balance can be easily controlled by the mixing ratio. Specifically, the range of the compound having hole transporting properties: the compound having electron transporting properties = 1:9 to 9:1 (weight ratio) is preferable. Also, since the carrier balance can be easily controlled by having this configuration, the control of the carrier recombination region can also be easily performed.

[0113] Moreover, as a combination of materials that efficiently form an exciplex, it is preferable that the HOMO level of one of Compound 132 and Compound 134 is higher than the HOMO level of the other, and the LUMO level of one is higher than the LUMO level of the other. Specifically, the energy difference between the HOMO level of Compound 132 and the HOMO level of Compound 13... It is preferable that the HOMO level of one of Compound 132 and Compound 134 is higher than the HOMO level of the other, and the LUMO level of one is higher than the LUMO level of the other. Specifically, the energy difference between the HOMO level of Compound 132 and the HOMO level of Compound 134 is preferably 0.1 eV or more, more preferably 0.2 eV or more, and still more preferably 0.3 eV or more. <\ Also, the energy difference between the LUMO level of Compound 132 and the LUMO level of Compound 134 is preferably 0.1 eV or more, more preferably 0.2 eV or more, and still more preferably 0.3 eV or more. Specifically, the energy difference between the HOMO level of Compound 132 and the HOMO level of Compound 134 is preferably 0.1 eV or more, more preferably 0.2 eV or more, and still more preferably 0.3 eV or more. Also, the energy difference between the LUMO level of Compound 132 and the LUMO level of Compound 134 is preferably 0.1 eV or more, more preferably 0.2 eV or more, and still more preferably 0.3 eV or more. It is 0.3 eV or more. By setting such a correlation of energy levels, holes and electrons, which are carriers injected from a pair of electrodes (electrode 101 and electrode 102), are likely to be injected into Compound 132 and Compound 134, respectively, which is preferable. Note that the HOMO level of Compound 132 may be equivalent to the HOMO level of Compound 134, or the LUMO level of Compound 132 may be equivalent to the LUMO level of Compound 134. Also, the holes and electrons, which are carriers injected from the pair of electrodes (electrode 101 and electrode 102), are preferably easily injected into Compound 132 and Compound 134. Note that the HOMO level of Compound 132 may be equivalent to the HOMO level of Compound 134, or the LUMO level of Compound 132 may be equivalent to the LUMO level of Compound 134. The HOMO level of Compound 132 may be equivalent to the HOMO level of Compound 134, or the LUMO level of Compound 132 may be equivalent to the LUMO level of Compound 134.

[0114] In addition, the correlation of the energy levels between Compound 132 and Compound 134 is not limited to that shown in Fig. 4(B). That is, the singlet excitation energy level (S ) of Compound 132 may be higher or lower than the singlet excitation energy level (S C2 ) of Compound 13 4. Also, the triplet excitation energy level (T C3 ) of Compound 13 2 may be higher or lower than the triplet excitation energy level C2 of Compound 134 (T ). C3

[0115] In addition, in the light-emitting element according to one aspect of the present invention, it is preferable that Compound 132 has a π-electron-deficient skeleton. With such a configuration, the LUMO level of Compound 132 becomes lower, which is suitable for the formation of an exciplex. With such a configuration, the LUMO level of Compound 132 becomes lower, which is suitable for the formation of an exciplex.

[0116] In addition, in the light-emitting element according to one aspect of the present invention, it is preferable that Compound 132 has a π-electron-excessive skeleton. With such a configuration, the HOMO level of Compound 132 becomes higher, which is suitable for the formation of an exciplex. With such a configuration, the HOMO level of Compound 132 becomes higher, which is suitable for the formation of an exciplex.

[0117] In addition, as shown in the above-described configuration example of the light-emitting layer, since Compound 132 is a TADF material, Compound 132 that does not form an exciplex up-converts triplet excitation energy ​​​​​ (Figure 4(B) Route A) 21 ). The singlet excitation energy of compound 132 is rapidly transferred to compound 133. (Fig. 4(B) Route A 22 ). At this time, S C2 ≧S G It is preferable that:

[0118] As in the previous structural example of the light-emitting layer, in the light-emitting element of one embodiment of the present invention, the route A in FIG. 17 Route A 19 The triplet excitation energy is transferred to the guest material, compound 133. The route to travel and Route A in Figure 4(B) 21 and Route A 22 Transferred to compound 133 via There is also a pathway for triplet excitation energy to be transferred to fluorescent compounds. The presence of triplet excitation energy can increase the luminous efficiency of the fluorescent light-emitting device. The existence of multiple pathways for transfer to fluorescent compounds can further increase the luminescence efficiency. do.

[0119] Also, T C1 From T G When triplet excited energy transfer occurs to is inactivated (Fig. 4(B) Route A 20 ) Therefore, root A 20 Energy transfer Less movement is preferable. Route A 20 To suppress this, Compound 131 and Compound 13 The weight ratio of the total amount of Compound 2 and Compound 134 to Compound 133 was low. Specifically, the total amount of Compound 131, Compound 132 and Compound 134 is preferably The weight ratio of Compound 133 is preferably 0.001 or more and 0.05 or less, more preferably 0.001 or more and 0.01 or less.

[0120] Also, T G is preferably 2.0 eV or less. By adopting this configuration, a light-emitting device with good reliability can be obtained.

[0121] <Energy transfer mechanism> Here, the governing factors of the intermolecular energy transfer process will be described. As the mechanism of intermolecular energy transfer, two mechanisms, the Förster mechanism (dipole-dipole interaction) and the Dexter mechanism (electron exchange interaction), have been proposed. Here, regarding the donation of excitation energy from the first material in the excited state to the second material in the ground state, the intermolecular energy transfer process between the first material and the second material will be described, but the same applies when either one is an exciplex.

[0122] ≪Förster mechanism≫ In the Förster mechanism, energy transfer does not require direct contact between molecules, and energy transfer occurs through the resonance phenomenon of the dipole vibrations of the first material and the second material. Due to the resonance phenomenon of the dipole vibrations, the first material transfers energy to the second material, the first material in the excited state returns to the ground state, and the second material in the ground state becomes excited. The rate constant k of the Förster mechanism is shown in Equation (1). h*→g

[0123]

Equation

[0124] In Equation (1), ν represents the frequency, and f’ h ​(ν) represents the normalized emission spectrum of the first material (fluorescence spectrum when discussing energy transfer from the singlet excited state, phosphorescence spectrum when discussing energy transfer from the triplet excited state), ε whereas ε ( g (ν) represents the molar extinction coefficient of the second material, N represents Avogadro's number, n represents the refractive index of the medium, R represents the intermolecular distance between the first material and the second material, τ represents the measured lifetime of the excited state (fluorescence lifetime or phosphorescence lifetime), c represents the speed of light, φ represents the emission quantum yield (fluorescence quantum yield when discussing energy transfer from the singlet excited state, phosphorescence quantum yield when discussing energy transfer from the triplet excited state), and K ( ν) represents the molar extinction coefficient of the second material, N represents Avogadro's number, n represents the refractive index of the medium, R represents the intermolecular distance between the first material and the second material, τ represents the measured lifetime of the excited state (fluorescence lifetime or phosphorescence lifetime), c represents the speed of light, φ represents the emission quantum yield (fluorescence quantum yield when discussing energy transfer from the singlet excited state, phosphorescence quantum yield when discussing energy transfer from the triplet excited state), and K is a coefficient (ranging from 0 to 4) representing the orientation of the transition dipole moments of the first material and the second material. In the case of random orientation, K = 2 / 3. is a coefficient (ranging from 0 to 4) representing the orientation of the transition dipole moments of the first material and the second material. In the case of random orientation, K 2 is a coefficient (ranging from 0 to 4) representing the orientation of the transition dipole moments of the first material and the second material. In the case of random orientation, K = 2 / 3. = 2 / 3. 2 = 2 / 3.

[0125] ≪Dexter mechanism≫ In the Dexter mechanism, the first material and the second material approach within the contact effective distance where orbital overlap occurs, and energy transfer occurs through the exchange of electrons between the electron of the excited-state first material and the electron of the ground-state second material. The rate constant k of the Dexter mechanism is shown in Equation (2). In Equation (2), h is Planck's constant, K is a constant with the dimension of energy, ν represents the frequency, and f’ h*→g (ν) represents the normalized emission spectrum of the first material. is shown in Equation (2).

[0126]

Equation

[0127] In Equation (2), h is Planck's constant, K is a constant with the dimension of energy, ν represents the frequency, and f’ is a constant with the dimension of energy, ν represents the frequency, and f’ h (ν) represents the normalized emission spectrum of the first material. When discussing energy transfer from the singlet excited state, it is the fluorescence spectrum; when discussing energy transfer from the triplet excited state, it is the phosphorescence spectrum (), and ε’ (ν) represents the normalized absorption spectrum of the second g material, L represents the effective molecular radius, and R represents the intermolecular distance between the first material and the second material. Here, the energy transfer efficiency φ

[0128] from the first material to the second material is expressed by Equation (3). k ET is the rate constant of the emission process of the first material (fluorescence when discussing energy transfer from the singlet excited state, phosphorescence when discussing energy transfer from the triplet excited state), and k r is the rate constant of the non-emission process (thermal deactivation or intersystem crossing) of the second material, and τ represents the measured lifetime of the excited state of the first material. From Equation (3), it can be seen that to increase the energy transfer efficiency φ n , the rate constant k of energy transfer should be increased, and the other competing rate constant k

[0129]

Equation

[0130] + k ET (=1 / τ) should be relatively small. h*→g r n [[ID=A50]]

[0131] ≪Concepts for enhancing energy transfer≫ First, consider 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 ​​​​​is independent of the lifetime τ of the excited state of the first material. Also, the energy transfer efficiency φ ET should preferably be high when discussing energy transfer from the singlet excited state (in this case, it is the fluorescence quantum yield) or from the triplet excited state (in this case, it is the phosphorescence quantum yield) of the first material to the second material. is the fluorescence quantum yield when discussing energy transfer from the singlet excited state, and the phosphorescence quantum yield when discussing energy transfer from the triplet excited state). It can be said that the higher the better.

[0132] Also, it is preferable that the overlap between the emission spectrum of the first material (the fluorescence spectrum when discussing energy transfer from the singlet excited state, and the phosphorescence spectrum when discussing energy transfer from the triplet excited state) and the absorption spectrum of the second material (the absorption corresponding to the transition from the singlet ground state to the singlet excited state) is large. Furthermore, it is preferable that the molar absorption coefficient of the second material is also high. This means that the emission spectrum of the first material overlaps with the absorption band that appears on the longest wavelength side of the second material. Note that since the direct transition from the singlet ground state to the triplet excited state in the second material is forbidden, the molar absorption coefficient related to the triplet excited state in the second material can be ignored. From this, the energy transfer process from the excited state of the first material to the triplet excited state of the second material by the Förster mechanism can be ignored, and only the energy transfer process to the singlet excited state of the second material needs to be considered. is the fluorescence spectrum when discussing energy transfer from the singlet excited state, and the phosphorescence spectrum when discussing energy transfer from the triplet excited state). to the absorption of the second material (the absorption corresponding to the transition from the singlet ground state to the singlet excited state) is large. Furthermore, it is preferable that the molar absorption coefficient of the second material is also high. This means that the emission spectrum of the first material overlaps with the absorption band that appears on the longest wavelength side of the second material. Note that since the direct transition from the singlet ground state to the triplet excited state in the second material is forbidden, the molar absorption coefficient related to the triplet excited state in the second material can be ignored. From this, the energy transfer process from the excited state of the first material to the triplet excited state of the second material by the Förster mechanism can be ignored, and only the energy transfer process to the singlet excited state of the second material needs to be considered. to the absorption of the second material (the absorption corresponding to the transition from the singlet ground state to the singlet excited state) is large. Furthermore, it is preferable that the molar absorption coefficient of the second material is also high. This means that the emission spectrum of the first material overlaps with the absorption band that appears on the longest wavelength side of the second material. Note that since the direct transition from the singlet ground state to the triplet excited state in the second material is forbidden, the molar absorption coefficient related to the triplet excited state in the second material can be ignored. From this, the energy transfer process from the excited state of the first material to the triplet excited state of the second material by the Förster mechanism can be ignored, and only the energy transfer process to the singlet excited state of the second material needs to be considered. to the absorption of the second material (the absorption corresponding to the transition from the singlet ground state to the singlet excited state) is large. Furthermore, it is preferable that the molar absorption coefficient of the second material is also high. This means that the emission spectrum of the first material overlaps with the absorption band that appears on the longest wavelength side of the second material. Note that since the direct transition from the singlet ground state to the triplet excited state in the second material is forbidden, the molar absorption coefficient related to the triplet excited state in the second material can be ignored. From this, the energy transfer process from the excited state of the first material to the triplet excited state of the second material by the Förster mechanism can be ignored, and only the energy transfer process to the singlet excited state of the second material needs to be considered. to the absorption of the second material (the absorption corresponding to the transition from the singlet ground state to the singlet excited state) is large. Furthermore, it is preferable that the molar absorption coefficient of the second material is also high. This means that the emission spectrum of the first material overlaps with the absorption band that appears on the longest wavelength side of the second material. Note that since the direct transition from the singlet ground state to the triplet excited state in the second material is forbidden, the molar absorption coefficient related to the triplet excited state in the second material can be ignored. From this, the energy transfer process from the excited state of the first material to the triplet excited state of the second material by the Förster mechanism can be ignored, and only the energy transfer process to the singlet excited state of the second material needs to be considered. to the absorption of the second material (the absorption corresponding to the transition from the singlet ground state to the singlet excited state) is large. Furthermore, it is preferable that the molar absorption coefficient of the second material is also high. This means that the emission spectrum of the first material overlaps with the absorption band that appears on the longest wavelength side of the second material. Note that since the direct transition from the singlet ground state to the triplet excited state in the second material is forbidden, the molar absorption coefficient related to the triplet excited state in the second material can be ignored. From this, the energy transfer process from the excited state of the first material to the triplet excited state of the second material by the Förster mechanism can be ignored, and only the energy transfer process to the singlet excited state of the second material needs to be considered. to the absorption of the second material (the absorption corresponding to the transition from the singlet ground state to the singlet excited state) is large. Furthermore, it is preferable that the molar absorption coefficient of the second material is also high. This means that the emission spectrum of the first material overlaps with the absorption band that appears on the longest wavelength side of the second material. Note that since the direct transition from the singlet ground state to the triplet excited state in the second material is forbidden, the molar absorption coefficient related to the triplet excited state in the second material can be ignored. From this, the energy transfer process from the excited state of the first material to the triplet excited state of the second material by the Förster mechanism can be ignored, and only the energy transfer process to the singlet excited state of the second material needs to be considered. to the absorption of the second material (the absorption corresponding to the transition from the singlet ground state to the singlet excited state) is large. Furthermore, it is preferable that the molar absorption coefficient of the second material is also high. This means that the emission spectrum of the first material overlaps with the absorption band that appears on the longest wavelength side of the second material. Note that since the direct transition from the singlet ground state to the triplet excited state in the second material is forbidden, the molar absorption coefficient related to the triplet excited state in the second material can be ignored. From this, the energy transfer process from the excited state of the first material to the triplet excited state of the second material by the Förster mechanism can be ignored, and only the energy transfer process to the singlet excited state of the second material needs to be considered. to the absorption of the second material (the absorption corresponding to the transition from the singlet ground state to the singlet excited state) is large. Furthermore, it is preferable that the molar absorption coefficient of the second material is also high. This means that the emission spectrum of the first material overlaps with the absorption band that appears on the longest wavelength side of the second material. Note that since the direct transition from the singlet ground state to the triplet excited state in the second material is forbidden, the molar absorption coefficient related to the triplet excited state in the second material can be ignored. From this, the energy transfer process from the excited state of the first material to the triplet excited state of the second material by the Förster mechanism can be ignored, and only the energy transfer process to the singlet excited state of the second material needs to be considered.

[0133] Next, consider the energy transfer by the Dexter mechanism. According to Equation (2), to increase the rate constant k h*→g the overlap between the emission spectrum of the first material (the fluorescence spectrum when discussing energy transfer from the singlet excited state, and the phosphorescence spectrum when discussing energy transfer from the triplet excited state) and the absorption spectrum of the second material (the absorption corresponding to the transition from the singlet ground state to the singlet excited state) should be large. the overlap between the emission spectrum of the first material (the fluorescence spectrum when discussing energy transfer from the singlet excited state, and the phosphorescence spectrum when discussing energy transfer from the triplet excited state) and the absorption spectrum of the second material (the absorption corresponding to the transition from the singlet ground state to the singlet excited state) should be large. the overlap between the emission spectrum of the first material (the fluorescence spectrum when discussing energy transfer from the singlet excited state, and the phosphorescence spectrum when discussing energy transfer from the triplet excited state) and the absorption spectrum of the second material (the absorption corresponding to the transition from the singlet ground state to the singlet excited state) should be large. It can be seen that it is better for the overlap with (absorption corresponding to the transition to the state) to be larger. Therefore, Optimization of the energy transfer efficiency is achieved by the overlap between the emission spectrum of the first material and the absorption band appearing on the longest wavelength side of the second material.

[0134] Also, substituting Equation (2) into Equation (3), it can be seen that the energy transfer efficiency φ in the Dexter mechanism depends on τ. Since the Dexter mechanism is an energy transfer process based on electron exchange, similar to the energy transfer from the singlet excited state of the first material to the singlet excited state of the second material, energy transfer from the triplet excited state of the first material to the triplet excited state of the second material also occurs. ET

[0135] In addition, similar to the energy transfer from the first material to the second material, for the energy transfer process from the exciplex to the fluorescent compound, energy transfer occurs by both the Förster mechanism and the Dexter mechanism.

[0136] In the light-emitting element according to one aspect of the present invention, since the second material is a fluorescent compound, it is preferable that the energy transfer efficiency to the triplet excited state of the second material is low. That is, it is preferable that the energy transfer efficiency based on the Dexter mechanism from the first material to the second material is low, and it is preferable that the energy transfer efficiency based on the Förster mechanism from the first material to the second material is high.

[0137] Also, as already described, the energy transfer efficiency in the Förster mechanism does not depend on the lifetime τ of the excited state of the first material. On the other hand, the energy transfer efficiency in the Dexter mechanism ​​​​​​​​​​​​depends on the excitation lifetime τ of the first material and, in order to reduce the energy transfer efficiency in the Dexter mechanism, it is preferable that the excitation lifetime τ of the first material be short. Therefore, in one aspect of the present invention, an exciplex or a TADF material is used as the first material, and one of the compounds forming the exciplex has a function of converting triplet excitation energy into light emission.

[0138] According to the configuration of one aspect of the present invention, reverse intersystem crossing from the triplet excited state to the singlet excited state of the exciplex (first material) is promoted, and the excitation lifetime of the triplet excited state of the exciplex (first material) can be shortened. Further, the transition from the triplet excited state to the singlet ground state of the exciplex (first material) is promoted, and the excitation lifetime τ of the triplet excited state of the exciplex (first material) can be shortened. As a result, since the energy transfer efficiency in the Dexter mechanism from the triplet excited state of the exciplex (first material) to the triplet excited state of the fluorescent compound (second material) can be reduced, in one aspect of the present invention, a light-emitting device with high luminous efficiency can be provided.

[0139]

[0140] Also, among the light emissions exhibited by the exciplex, the fluorescence lifetime in the thermally activated delayed fluorescence component is preferably short, specifically, preferably 10 ns or more and 50 μs or less, more preferably 10 ns or more and 20 μs or less, and even more preferably of 10 ns or more and 10 μs or less.

[0140] Note that the rate constant of the Förster mechanism is inversely proportional to the sixth power of the distance between the first material and the second material, and the rate constant of the Dexter mechanism is inversely proportional to the exponential function of the distance between the first material and the second material. Therefore, when the distance between the two molecules is approximately 1 nm or less, the Dexter mechanism becomes dominant. When it is more than about 1 nm, the Förster mechanism becomes dominant. Therefore, in order to reduce the energy transfer efficiency in the Dexter mechanism, it is preferable to increase the distance between the first material and the second material. Specifically, it is preferably 0.7 nm or more, more preferably 0.9 nm or more, and still more preferably 1 nm or more. Also, in order for the Förster mechanism to occur efficiently, the distance between the first material and the second material is preferably 5 nm or less. Therefore, in one aspect of the present invention, the compound 133, which is a fluorescent compound, preferably has at least two or more alkyl groups having 2 or more carbon atoms. Alternatively, the compound 133 preferably has at least two or more alkyl groups having a branch with 3 to 10 carbon atoms. Alternatively, the compound 133 preferably has at least two or more cyclic hydrocarbon groups having 3 to 10 carbon atoms, or at least two or more bridged cyclic hydrocarbon groups having 3 to 10 carbon atoms. Further, the compound 133 preferably has a condensed aromatic hydrocarbon having 3 to 12 carbon atoms. When it is more than about 1 nm, the Förster mechanism becomes dominant. Therefore, in order to reduce the energy transfer efficiency in the Dexter mechanism, it is preferable to increase the distance between the first material and the second material. Specifically, it is preferably 0.7 nm or more, more preferably 0.9 nm or more, and still more preferably 1 nm or more. Also, in order for the Förster mechanism to occur efficiently, the distance between the first material and the second material is preferably 5 nm or less. When it is more than about 1 nm, the Förster mechanism becomes dominant. Therefore, in order to reduce the energy transfer efficiency in the Dexter mechanism, it is preferable to increase the distance between the first material and the second material. Specifically, it is preferably 0.7 nm or more, more preferably 0.9 nm or more, and still more preferably 1 nm or more. Also, in order for the Förster mechanism to occur efficiently, the distance between the first material and the second material is preferably 5 nm or less. When it is more than about 1 nm, the Förster mechanism becomes dominant. Therefore, in order to reduce the energy transfer efficiency in the Dexter mechanism, it is preferable to increase the distance between the first material and the second material. Specifically, it is preferably 0.7 nm or more, more preferably 0.9 nm or more, and still more preferably 1 nm or more. Also, in order for the Förster mechanism to occur efficiently, the distance between the first material and the second material is preferably 5 nm or less.

[0141] Therefore, in one aspect of the present invention, the compound 133, which is a fluorescent compound, preferably has at least two or more alkyl groups having 2 or more carbon atoms. Alternatively, the compound 133 preferably has at least two or more alkyl groups having a branch with 3 to 10 carbon atoms. Alternatively, the compound 133 preferably has at least two or more alkyl groups having a branch with 3 to 10 carbon atoms. Alternatively, the compound 133 preferably has at least two or more cyclic hydrocarbon groups having 3 to 10 carbon atoms, or at least two or more bridged cyclic hydrocarbon groups having 3 to 10 carbon atoms. Alternatively, the compound 133 preferably has at least two or more cyclic hydrocarbon groups having 3 to 10 carbon atoms, or at least two or more bridged cyclic hydrocarbon groups having 3 to 10 carbon atoms. Further, the compound 133 preferably has a condensed aromatic hydrocarbon having 3 to 12 carbon atoms.

[0142] <Material> Next, the details of the components of the light-emitting element according to one aspect of the present invention will be described below.

[0143] ≪Light-emitting layer≫ The materials that can be used for the light-emitting layer 130 will be described below, respectively.

[0144] The compound 132 is, for example, a TADF material. The energy difference between the S1 level and the T1 level of the compound 132 is preferably small, specifically, more than 0 eV and 0.2 eV or less. The energy difference between the S1 level and the T1 level of the compound 132 is preferably small, specifically, more than 0 eV and 0.2 eV or less. The energy difference between the S1 level and the T1 level of the compound 132 is preferably small, specifically, more than 0 eV and 0.2 eV or less.

[0145] Compound 132 has a skeleton with hole-transporting properties and a skeleton with electron-transporting properties. This is preferable. Alternatively, compound 132 preferably has a π-electron-excessive skeleton or an aromatic amine skeleton and a π-electron-deficient skeleton. By doing so, it becomes easier to form a donor-acceptor type excited state within the molecule. Furthermore, so that both the donor property and the acceptor property within the molecule of compound 132 become strong, it preferably has a structure in which a skeleton with electron-transporting properties and a skeleton with hole-transporting properties are directly bonded. Alternatively, it is preferable to have a structure in which a π-electron-excessive skeleton or an aromatic amine skeleton and a π-electron-deficient skeleton are directly bonded. By strengthening both the donor property and the acceptor property within the molecule, the overlap between the region where the molecular orbitals of the HOMO of compound 132 are distributed and the region where the molecular orbitals of the LUMO are distributed can be reduced, and the energy difference between the singlet excitation energy level and the triplet excitation energy level of compound 132 can be made small. Also, the triplet excitation energy level of compound 132 can be kept at a high energy. When a thermally activated delayed fluorescence material is composed of one type of material, for example, the following materials can be used. First, fullerenes and their derivatives, acridine derivatives such as proflavine, and eosin etc. can be mentioned. Also, metal-containing porphyrins containing magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), or palladium (Pd) etc. can be mentioned. Examples of the metal-containing porphyrin include protoporphyrin-tin fluoride complex (SnF2(Proto IX)), mesoporphyrin-fluoride and so on.

[0146] When a thermally activated delayed fluorescence material is composed of one type of material, for example, the following materials can be used.

[0147] First, fullerenes and their derivatives, acridine derivatives such as proflavine, and eosin etc. can be mentioned. Also, metal-containing porphyrins containing magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), or palladium (Pd) etc. can be mentioned. Examples of the metal-containing porphyrin include protoporphyrin-tin fluoride complex (SnF2(Proto IX)), mesoporphyrin-fluoride and so on. As the metal-containing porphyrin, for example, protoporphyrin-tin fluoride complex (SnF2(Proto IX)), mesoporphyrin-fluoride Tin complex (SnF2(Meso IX)), hematoporphyrin-tin fluoride complex (Sn F2(Hemato IX)), coproporphyrin tetramethyl ester-tin fluoride complex (SnF2(Copro III-4Me)), octaethylporphyrin-tin fluoride complex (SnF2(OEP)), etioporphyrin-tin fluoride complex (SnF2(E tio I)), octaethylporphyrin-platinum chloride complex (PtCl2OEP), etc. are cited as examples.

[0148]

Chemical formula

[0149] In addition, as a thermally activated delayed fluorescence material composed of a single material, heterocyclic compounds having a π-electron rich skeleton and a π-electron deficient skeleton can also be used. Specifically, 2-(biphenyl -4-yl)-4,6-bis(12-phenylindolo[2,3-a]carbazole -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-phenoxazine-10-yl)phenyl]-4,6-diphenyl- 1,3,5-triazine (abbreviation: PXZ-TRZ), 3-[4-(5-phenyl-5,1 0-dihydro-phenazine-10-yl)phenyl]-4,5-diphenyl-1,2,4- triazole (abbreviation: PPZ-3TPT), 3-(9,9-dimethyl-9H-acridine -10-yl)-9H-xanthene-9-one (abbreviation: ACRXTN), bis[4-(9 -yl)phenyl]amine (abbreviation: BPA), etc. are cited ,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone (abbreviation: DMAC -DPS), 10-phenyl-10H,10'H-spiro[acridine-9,9'-an thracen]-10'-one (abbreviation: ACRSA), 4-(9'-phenyl-3,3'-biphenyl)- -9H-carbazol-9-yl)benzofuro[3,2-d]pyrimidine (abbreviation: 4PC CzBfpm), 4-[4-(9'-phenyl-3,3'-bi-9H-carbazole-9 -yl)phenyl]benzofuro[3,2-d]pyrimidine (abbreviation: 4PCCzPBfpm ), 9-[3-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl] -9'-phenyl-2,3'-bi-9H-carbazole (abbreviation: mPCCzPTzn-0 2) and the like. Since the heterocyclic compound has a π-electron rich skeleton and a π-electron deficient skeleton, Therefore, the electron transport property and the hole transport property are high, and it is preferable. Diazine skeleton (pyrimidine skeleton, pyrazine skeleton, pyridazine skeleton), and triazine skeleton The triazine skeleton is preferred because it is stable and reliable. In particular, the benzofuropyrimidine skeleton is preferred. , benzothienopyrimidine skeleton, benzofuropyrazine skeleton, benzothienopyrazine skeleton Among the π-electron-rich skeletons, the following are preferred because they have high acceptor properties and good reliability. Acridine skeleton, phenoxazine skeleton, phenothiazine skeleton, furan skeleton, thiophene skeleton Since the pyrrole skeleton and the pyrrole skeleton are stable and reliable, It is preferable that the furan skeleton is a dibenzofuran skeleton, and the thiophene skeleton is As the pyrrole skeleton, a dibenzothiophene skeleton is preferred. Dole skeleton, carbazole skeleton, bicarbazole skeleton, 3-(9-phenyl-9H-carbazole) A (1-benzazol-3-yl)-9H-carbazole skeleton is particularly preferred. The π-electron rich skeleton A substance in which a π-electron rich skeleton and a π-electron deficient skeleton are directly bonded has both a strong donor property of the π-electron rich skeleton and an acceptor property of the π-electron deficient skeleton And the difference between the singlet excited state level and the triplet excited state level is small Therefore, it is particularly preferred. An aromatic ring to which an electron-withdrawing group such as a cyano group is bonded may be used as the π-electron deficient skeleton.

[0150]

Chemical formula

[0151] Next, as Compound 131, as described above, it preferably has a function capable of converting triplet excitation energy into light emission. Examples of the organic compound having this function include a phosphorescent material and a thermally activated delayed fluorescence material.

[0152] Examples of the phosphorescent compound include an iridium, rhodium, or platinum-based organometallic complex, or a metal complex. Also, a platinum complex having a porphyrin ligand and an organoiridium complex are included. Among them, for example, an organoiridium complex such as an iridium-based orthometalated complex is preferred. Examples of the ligand for orthometalation include a 4H-triazole ligand, a 1H-triazole ligand, an imidazole ligand, a pyridine ligand, a pyrimidine ligand, a pyrazine ligand, or an isoquinoline ligand. In this case, Compound 131 (phosphorescent compound) has an absorption band of triplet MLCT (Metal to Ligand Charge Transfer) transition. Compound) has an absorption band of triplet MLCT (Metal to Ligand Charge Tran sfer) transition.

[0153] Examples of substances having an emission peak in blue or green include, for example, tris{2-[5-(2​​​​​​​​ -methylphenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazo 3-yl-κN 2 ]phenyl-κC}iridium(III) (abbreviation: Ir(mpp tz-dmp)3), tris(5-methyl-3,4-diphenyl-4H-1,2,4-trimethyl- Triazolato)iridium(III) (abbreviation: Ir(Mptz)3), tris[4-(3- Biphenyl)-5-isopropyl-3-phenyl-4H-1,2,4-triazolato]i Iridium(III) (abbreviation: Ir(iPrptz-3b)3), tris[3-(5-biphenyl] (phenyl)-5-isopropyl-4-phenyl-4H-1,2,4-triazolato]irid Ir(III) (abbreviated as Ir(iPr5btz)3), a 4H-triazole skeleton and organometallic iridium complexes with 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-Triazolate)iridium(III) (abbreviation: Ir(Prtz1-Me) 3) and fac-triazole-based organometallic iridium complexes. S[1-(2,6-diisopropylphenyl)-2-phenyl-1H-imidazole]isopropyl Iridium(III) (abbreviation: Ir(iPrpmi)3), tris[3-(2,6-dimethyl phenyl)-7-methylimidazo[1,2-f]phenanthridinato]iridium(I II) Imidazole skeleton-containing compounds such as Ir(dmpimpt-Me) Organic metal iridium complexes and bis[2-(4',6'-difluorophenyl)pyridinato- N,C 2’Iridium(III) tetrakis(1 - pyrazolyl)borate (abbreviation: FI r6), bis[2-(4’,6’-difluorophenyl)pyridinato-N,C 2’ Iri dium(III) picolinate (abbreviation: FIrpic), bis{2-[3’,5’-bis (trifluoromethyl)phenyl]pyridinato-N,C 2’}iridium(III) pico linate (abbreviation: Ir(CF3ppy)2(pic)), bis[2-(4’,6’-dif luorophenyl)pyridinato-N,C 2’ iridium(III) acetylacetonate (abbreviation: FIr(acac)) and other organometallic iridium complexes having a phenylpyridine derivative with an electron-withdrawing group as a ligand are mentioned. Among the above, organometallic iridium complexes having a nitrogen-containing five-membered heterocyclic skeleton such as a 4H-triazole skeleton, a 1H-triazole skeleton, and an imidazole skeleton have high triplet excitation energy and are also excellent in reliability and luminescence efficiency , so they are particularly preferred.

[0154] In addition, as substances having a luminescence peak in green or yellow, for example, tris(4-methyl -6-phenylpyrimidinato)iridium(III) (abbreviation: Ir(mppm)3), tris(4-t-butyl-6-phenylpyrimidinato)iridium(III) (abbreviation: I r(tBuppm)3), (acetylacetonato)bis(6-methyl-4-phenylpyr imidinato)iridium(III) (abbreviation: Ir(mppm)2(acac)), (acetyl acetonato)bis(6-tert-butyl-4-phenylpyrimidinato)iridium( III) (abbreviation: Ir(tBuppm)2(acac)), (acetylacetonato)bis [4-(2-Norbornyl)-6-phenylpyrimidinato]iridium(III) (abbreviation : Ir(nbppm)2(acac)), bis[5-methyl-6 -(2-methylphenyl)-4-phenylpyrimidinato]iridium(III) (abbreviation: Ir(mpmppm)2(acac)), bis{4,6-dimethyl -2-[6-(2,6-dimethylphenyl)-4-pyrimidinyl-κN 3 phenyl- κC}iridium(III) (abbreviation: Ir(dmppm-dmp)2(acac)), acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III) ( abbreviation: Ir(dppm)2(acac)) and other organometallic iridium complexes having a pyrimidine skeleton, such as (acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazinato )iridium(III) (abbreviation: Ir(mppr-Me)2(acac)), (acetyl acetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazinato)iridium (III) (abbreviation: Ir(mppr-iPr)2(acac)) and other organometallic iridium complexes having a pyrazine skeleton, and tris(2-phenylpyridinato-N,C 2’ ) iridium(III) (abbreviation: Ir(ppy)3), bis(2-phenylpyridinato-N ,C 2’ )iridium(III) acetylacetonate (abbreviation: Ir(ppy)2(ac ac)), 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(ac ac)) and other organometallic iridium complexes having a pyridine skeleton, bis(2,4-dif enyl-1,3-oxazolato-N,C 2’ ) Iridium(III) acetylacetonate (abbreviation: Ir(dpo)2(acac)), bis{2-[4’-(perfluorophen yl)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(a cac)) and other organometallic iridium complexes, tris(acetylacetonato)(monophen anthrolin) terbium(III) (abbreviation: Tb(acac)3(Phen)) and the like rare earth metal complexes are mentioned. Among the above, organometallic iri dium complexes having a pyrimidine skeleton are particularly preferred because they are outstanding in reliability and luminescence efficiency.

[0155] Further, as substances having a luminescence peak in yellow or red, for example, (diisobutyryl methanato)bis[4,6-bis(3-methylphenyl)pyrimidinato]iridium(II I) (abbreviation: Ir(5mdppm)2(dibm)), bis[4,6-bis(3-methyl phenyl)pyrimidinato](dipivaloyl methanato)iridium(III) (abbreviation: Ir (5mdppm)2(dpm)), bis[4,6-di(naphthalen-1-yl)pyrimidin Sodium](dipivaloylmethanato)iridium(III) (abbreviation: Ir(d1npm)2( dpm)), an organometallic iridium complex having a pyrimidine skeleton, or (acetylacet onato)bis(2,3,5-triphenylpyrazinato)iridium(III) (abbreviation: I r(tppr)2(acac)), bis(2,3,5-triphenylpyrazinato)(dip ivaloylmethanato)iridium(III) (abbreviation: Ir(tppr)2(dpm)), ( acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]i ridium(III) (abbreviation: Ir(Fdpq)2(acac)), an organometallic iridium complex having a pyrazine skeleton, or 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)), an organometallic iridium complex having a pyridine skeleton, in addition to 2,3,7, 8,12,13,17,18-octaethyl-21H,23H-porphyrin platinum(II )(abbreviation: PtOEP), a platinum complex, or tris(1,3-diphenyl-1,3-prop anedionato)(monophenanthroline)europium(III) (abbreviation: Eu(DB M)3(Phen)), tris[1-(2-thenoyl)-3,3,3-trifluoroac etonato)(monophenanthroline)europium(III) (abbreviation: Eu(TTA)3( Phen)), a rare earth metal complex. Among the above, the organometallic iridium complex having a pyrimidine skeleton is particularly preferable because of its outstanding reliability and luminescence efficiency. Moreover, an organometallic iridium complex having a pyrazine skeleton can obtain red emission with good chromaticity. is obtained.

[0156] In addition, examples of the material that can be used as Compound 131 include the above-described thermally activated delayed fluorescence materials. are mentioned.

[0157] In the light-emitting layer 130, as Compound 133, a fluorescent compound is preferable. Although there is no particular limitation on the fluorescent compound, anthracene derivatives, tetracene derivatives, chrysene derivatives, phenanthrene derivatives, pyrene derivatives, perylene derivatives, stilbene derivatives, acridine derivatives, coumarin derivatives, phenoxazine derivatives, phenothiazine derivatives, etc. are preferable. Although there is no particular limitation on the fluorescent compound, anthracene derivatives, tetracene derivatives, chrysene derivatives, phenanthrene derivatives, pyrene derivatives, perylene derivatives, stilbene derivatives, acridine derivatives, coumarin derivatives, phenoxazine derivatives, phenothiazine derivatives, etc. are preferable. derivatives, phenanthrene derivatives, pyrene derivatives, perylene derivatives, stilbene derivatives, acridine derivatives, coumarin derivatives, phenoxazine derivatives, pheno thiazine derivatives, etc. are preferable.

[0158] Specifically, 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: PAPP2 BPy), N,N'-diphenyl-N,N'-bis[4-(9-phenyl-9H-fluoro ren-9-yl)phenyl]pyrene-1,6-diamine (abbreviation: 1,6FLPAPrn) , N,N'-bis(3-methylphenyl)-N,N'-bis[3-(9-phenyl-9H -fluorene-9-yl)phenyl]pyrene-1,6-diamine (abbreviation: 1,6mMem FLPAPrn), N,N'-bis[4-(9-phenyl-9H-fluorene-9-yl )phenyl]-N,N'-bis(4-tert-butylphenyl)pyrene-1,6-dia mine (abbreviation: 1,6tBu-FLPAPrn), N,N'-diphenyl-N,N'-bis [4-(9-Phenyl-9H-fluoren-9-yl)phenyl]-3,8-dicyclohe xylpyrene-1,6-diamine (abbreviation: ch-1,6FLPAPrn), N,N’-bi s[4-(9H-carbazol-9-yl)phenyl]-N,N’-diphenylstilbe ne-4,4’-diamine (abbreviation: YGA2S), 4-(9H-carbazol-9-yl) -4’-(10-phenyl-9-anthryl)triphenylamine (abbreviation: YGAPA) 、4-(9H-carbazol-9-yl)-4’-(9,10-diphenyl-2-anth ryl)triphenylamine (abbreviation: 2YGAPPA), N,9-diphenyl-N-[4- (10-phenyl-9-anthryl)phenyl]-9H-carbazole-3-amine (abbre viation: PCAPA), perylene, 2,5,8,11-tetra(tert-butyl)perylene (abbreviation: TBP), 4-(10-phenyl-9-anthryl)-4’-(9-phenyl- 9H-carbazol-3-yl)triphenylamine (abbreviation: PCBAPA), N,N’ ’-(2-tert-butylanthracene-9,10-diyl-di-4,1-phenylene) bis[N,N’,N’-triphenyl-1,4-phenylenediamine] (abbreviation: DPAB PA), N,9-diphenyl-N-[4-(9,10-diphenyl-2-anthryl)ph[[ID=2,7]] enyl]-9H-carbazole-3-amine (abbreviation: 2PCAPPA), N-[4-(9 ,10-diphenyl-2-anthryl)phenyl]-N,N’,N’-triphenyl-1 ,4-phenylenediamine (abbreviation: 2DPAPPA), N,N,N’,N’,N’’,N ’’,N’’’,N’’’-octaphenyldibenz[g,p]chrysene-2,7,10 ,15-tetraamine (abbreviation: DBC1), coumarin 30, N-(9,10-diphenyl -2-anthryl)-N,9-diphenyl-9H-carbazol-3-amine (abbreviation: 2 PCAPA), N-[9,10-bis(1,1'-biphenyl-2-yl)-2-anth ryl]-N,9-diphenyl-9H-carbazol-3-amine (abbreviation: 2PCABPh A), N-(9,10-diphenyl-2-anthryl)-N,N',N'-triphenyl -1,4-phenylenediamine (abbreviation: 2DPAPA), N-[9,10-bis(1,1 '-biphenyl-2-yl)-2-anthryl]-N,N',N'-triphenyl-1, 4-phenylenediamine (abbreviation: 2DPABPhA), 9,10-bis(1,1'-bip henyl-2-yl)-N-[4-(9H-carbazol-9-yl)phenyl]-N-f henylanthracen-2-amine (abbreviation: 2YGABPhA), N,N,9-triphenyl luanthracen-9-amine (abbreviation: DPhAPhA), coumarin 6, coumarin 545T 、N,N'-diphenylquinacridone (abbreviation: DPQd), rubrene, 2,8-di-te rt-butyl-5,11-bis(4-tert-butylphenyl)-6,12-diphenyl lutetracene (abbreviation: TBRb), Nile Red, 5,12-bis(1,1'-biphenyl -4-yl)-6,11-diphenyltetracene (abbreviation: BPT), 2-(2-{2- [4-(dimethylamino)phenyl]ethenyl}-6-methyl-4H-pyran-4-ylidene propanedinitrile (abbreviation: DCM1), 2-{2-methyl-6-[2-(2,3 ,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl -4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCM2), N,N,N ’,N’-Tetrakis(4-methylphenyl)tetracene-5,11-diamine (abbreviation: p-mPhTD), 7,14-diphenyl-N,N,N’,N’-tetrakis(4-methyl phenyl)acenaphtho[1,2-a]fluoranthene-3,10-diamine (abbreviation: p -mPhAFD), 2-{2-isopropyl-6-[2-(1,1,7,7-tetramethyl -2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl )ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCJTI) 、2-{2-tert-butyl-6-[2-(1,1,7,7-tetramethyl-2,3, 6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl] -4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCJTB), 2-(2, 6-bis{2-[4-(dimethylamino)phenyl]ethenyl}-4H-pyran-4-i lidene)propanedinitrile (abbreviation: BisDCM), 2-{2,6-bis[2-(8- methoxy-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H -benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}p ropanedinitrile (abbreviation: BisDCJTM), 5,10,15,20-tetraphenyl bisbenzo[5,6]indeno[1,2,3-cd:1’,2’,3’-lm]perylene 、etc. can be mentioned.

[0159] In addition, when an exciplex is formed between Compound 131 and Compound 132, the emission peak of the formed exciplex is preferably selected for Compound 131, Compound 132, and Compound 133 so as to overlap with the absorption band on the longest wavelength side (low energy side) of Compound 133 which is a luminescent material. This makes it possible to obtain a light-emitting element with a dramatically improved luminous efficiency.

[0160] Note that the light-emitting layer 130 may also be composed of two or more layers. For example, when the first light-emitting layer and the second light-emitting layer are laminated in order from the hole transport layer side to form the light-emitting layer 130, a substance having hole transport properties is used as the host material of the first light-emitting layer, and a substance having electron transport properties is used as the host material of the second light-emitting layer and the like.

[0161] Also, as shown in FIG. 4, in the light-emitting layer 130, it may have a material (compound 134) other than the compound 131, the compound 132, and the compound 133. In that case, it is preferable to form an exciplex with the compound 132 and the compound 134. To achieve this configuration, the HOMO level of one of the compound 132 and the compound 134 is the highest HO MO level among the materials in the light-emitting layer 130, and the LUMO level of the other is the lowest LUMO level among the materials in the light-emitting layer 130. That is, the HOMO level of one of the compound 132 and the compound 134 is higher than the HOMO level of the other and the HOMO level of the compound 131, and the LUMO level of the other is lower than the LUMO level of one and the LUMO level of the compound 131. With this configuration, the reaction of forming an exciplex between the compound 132 and the compound 131 can be suppressed .

[0162] As the compound 134, for example, the following hole transport materials and electron transport materials can be used .

[0163] As the hole transport material, a material with higher hole transportability than electrons can be used, 1 ×10 -6 cm 2It is preferably a material having a hole mobility of 0 / Vs or more. Specifically, aromatic amines, carbazole derivatives, etc. can be used. Further, the hole transporting material may be a polymer compound.

[0164] As these materials with high hole transport properties, for example, as aromatic amine compounds, N,N’ -di(p-tolyl)-N,N’-diphenyl-p-phenylenediamine (abbreviation: DTDP PA), 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’-di amine (abbreviation: DNTPD), 1,3,5-tris[N-(4-diphenylaminophenyl l)-N-phenylamino]benzene (abbreviation: DPA3B), etc. can be mentioned.

[0165] Further, as carbazole derivatives, specifically, 3-[N-(4-diphenylamino phenyl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzDPA1 ), 3,6-bis[N-(4-diphenylaminophenyl)-N-phenylamino]-9 -phenylcarbazole (abbreviation: PCzDPA2), 3,6-bis[N-(4-diphenyl laminophenyl)-N-(1-naphthyl)amino]-9-phenylcarbazole (abbreviation : PCzTPN2), 3-[N-(9-phenylcarbazol-3-yl)-N-phenyl lamino]-9-phenylcarbazole (abbreviation: PCzPCA1), 3,6-bis[N- (9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole Zol (abbreviation: PCzPCA2), 3-[N-(1-naphthyl)-N-(9-phenylcarb azol-3-yl)amino]-9-phenylcarbazole (abbreviation: PCzPCN1) and the like can be mentioned.

[0166] In addition, as the carbazole derivative, 4,4'-di(N-carbazolyl)biphe nyl (abbreviation: CBP), 1,3,5-tris[4-(N-carbazolyl)phenyl]ben zene (abbreviation: TCPB), 1,4-bis[4-(N-carbazolyl)phenyl]-2,3 ,5,6-tetraphenylbenzene and the like can be used.

[0167] In addition, as materials with high hole transport properties, for example, 4,4'-bis[N-(1-naphthyl )-N-phenylamino]biphenyl (abbreviation: NPB or α-NPD) and N,N'-bi s(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4 '-diamine (abbreviation: TPD), 4,4',4''-tris(carbazol-9-yl) triphenylamine (abbreviation: TCTA), 4,4',4''-tris[N-(1-naphth yl)-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]tri phenylamine (abbreviation: m-MTDATA), 4,4'-bis[N-(spiro-9,9 '-bifluorene-2-yl)-N-phenylamino]biphenyl (abbreviation: BSPB), 4-phenyl-4'-(9-phenylfluorene-9-yl)triphenylamine (abbreviation :BPAFLP), 4-phenyl-3'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: 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 (abbreviation: DFLADFL), N-(9,9-dimethyl-2-diphenylamino-9H-fluoren-7-yl)diphenylamine (abbreviation: DPNF), 2-[N-(4-diphenylaminophenyl)-N-phenylamino]spiro-9,9'-bifluorene (abbreviation: DPASF), 4-phenyl-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4'-diphenyl-4''-(9-phenyl-9H-carbazol-… enylamine (abbreviation: mBPAFLP), N-(9,9-dimethyl-9H-fluoren- 2-yl)-N-{9,9-dimethyl-2-[N'-phenyl-N'-(9,9-dimethyl yl-9H-fluoren-2-yl)amino]-9H-fluoren-7-yl}phenylamine (abbreviation: DFLADFL), N-(9,9-dimethyl-2-diphenylamino-9H -fluoren-7-yl)diphenylamine (abbreviation: DPNF), 2-[N-(4-dip enylaminophenyl)-N-phenylamino]spiro-9,9'-bifluorene (abbreviation : DPASF), 4-phenyl-4'-(9-phenyl-9H-carbazol-3-yl )triphenylamine (abbreviation: PCBA1BP), 4,4'-diphenyl-4''-(9 -phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBBi1 BP), 4-(1-naphthyl)-4'-(9-phenyl-9H-carbazol-3-yl )triphenylamine (abbreviation: PCBANB), 4,4'-di(1-naphthyl)-4'' -(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCB NBB), 4-phenyldiphenyl-(9-phenyl-9H-carbazol-3-yl) amine (abbreviation: PCA1BP), N,N'-bis(9-phenylcarbazol-3-yl )-N,N'-diphenylbenzene-1,3-diamine (abbreviation: PCA2B), N,N' ,N''-triphenyl-N,N',N''-tris(9-phenylcarbazol-3- yl)benzene-1,3,5-triamine (abbreviation: PCA3B), N-(4-biphenyl )-N-(9,9-dimethyl-9H-fluoren-2-yl)-9-phenyl-9H-ca Rubazole-3-amine (abbreviation: PCBiF), N-(1,1'-biphenyl-4-yl )-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9- dimethyl-9H-fluorene-2-amine (abbreviation: PCBBiF), 9,9-dimethyl- N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl] fluorene-2-amine (abbreviation: PCBAF), N-phenyl-N-[4-(9-phenyl -9H-carbazol-3-yl)phenyl]spiro-9,9'-bifluorene-2- amine (abbreviation: PCBASF), 2-[N-(9-phenylcarbazol-3-yl)- N-phenylamino]spiro-9,9'-bifluorene (abbreviation: PCASF), 2,7- bis[N-(4-diphenylaminophenyl)-N-phenylamino]-spiro-9,9 '-bifluorene (abbreviation: DPA2SF), 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), etc., aromatic amine compounds such as these can be used. Also, 3-[4-(1-naphthyl)-phenyl]-9-phenyl -9H-carbazole (abbreviation: PCPN), 3-[4-(9-phenanthryl)-f enyl]-9-phenyl-9H-carbazole (abbreviation: PCPPn), 3,3'-bis( 9-phenyl-9H-carbazole) (abbreviation: PCCP), 1,3-bis(N-carbazol yl)benzene (abbreviation: mCP), 3,6-bis(3,5-diphenylphenyl)-9- Phenylcarbazole (abbreviation: CzTP), 4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran (abbreviation: mmDBFFLBi -II), 4,4’,4’’-(benzene-1,3,5-triyl)tri(dibenzofuran (abbreviation: DBF3P-II), 1,3,5-tri(dibenzothiophen-4-yl) -benzene (abbreviation: DBT3P-II), 2,8-diphenyl-4-[4-(9-phenyl -9H-fluoren-9-yl)phenyl]dibenzothiophene (abbreviation: DBTFLP -III), 4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6 -phenyl dibenzothiophene (abbreviation: DBTFLP-IV), 4-[3-(triphenyl (1888897)ylene-2-yl)phenyl]dibenzothiophene (abbreviation: mDBTPTp-II), etc. of amine compounds, carbazole compounds, thiophene compounds, furan compounds, fluorene compounds , triphenylene compounds, phenanthrene compounds, etc. can be used. The substances described here are substances mainly having a hole mobility of 1×10 cm -6 / Vs or more. However, as long as the substance has higher hole transportability than electrons, substances other than these can also be used. 2 For the electron transport material, a material having higher electron transportability than holes can be used, and it is preferably a material having an electron mobility of 1× 10

[0168] cm 10 -6 / Vs or more. As a compound (material having electron transportability) that easily accepts electrons, a π-electron deficient heteroaromatic such as a nitrogen-containing heteroaromatic compound or a metal complex can be used. Specific examples include quinone 2 For the electron transport material, a material having higher electron transportability than holes can be used, and it is preferably a material having an electron mobility of 1× 10 cm A metal complex having a phosphorus ligand, a benzoquinoline ligand, an oxazole ligand, or a thiazole ligand is exemplified. Also, oxadiazole derivatives, triazole derivatives, phenanthroline derivatives, pyridine derivatives, bipyridine derivatives, pyrimidine derivatives, benzo[f]pyrimidine derivatives, or benzothieno[2,3-d]pyrimidine derivatives, etc. are exemplified. Note that as long as the substance has higher electron transport property than the hole, substances other than the above may be used as the electron transport layer. Specific examples of the electron transport material include tris(8-quinolinolato)aluminum(III) (abbreviation: Alq), tris(4-methyl-8-quinolinolato)aluminum(III) (abbreviation: Almq3), bis(10-hydroxybenzo[h]quinolinato)beryllium(II) (abbreviation: BeBq2), bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III) (abbreviation: BAlq), bis(8-quinolinolato)zinc(II) (abbreviation: Znq), etc., which are metal complexes having a quinoline skeleton or a benzoquinoline skeleton. Also, in addition to metal complexes, 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, etc.

[0169] ​​​​​​​​​​​​​​​​​4-Oxadiazol-2-yl)phenyl]-9H-carbazole (abbreviation: CO11) , 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)- 1,2,4-triazole (abbreviation: TAZ), 2,2',2''-(1,3,5-benzene) (1-phenyl-1H-benzimidazole) (TPBI), 2-[3-(dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzo Imidazole (abbreviation: mDBTBIm-II), bathophenanthroline (abbreviation: BPhe n), bathocuproine (abbreviation: BCP), 2,9-bis(naphthalen-2-yl)-4 Heterocyclization of 7-diphenyl-1,10-phenanthroline (abbreviation: NBPhen) compounds and 2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]ky Noxaline (abbreviation: 2mDBTPDBq-II), 2-[3'-(dibenzothiophene- 4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBT BPDBq-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]quino Xaline (abbreviation: 2CzPDBq-III), 7-[3-(dibenzothiophene-4-yl) phenyl]dibenzo[f,h]quinoxaline (abbreviation: 7mDBTPDBq-II), 6-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxalate (abbreviation: 6mDBTPDBq-II), 4,6-bis[3-(phenanthrene-9-yl)] phenyl]pyrimidine (abbreviation: 4,6mPnP2Pm), 4,6-bis[3-(4- Dibenzo[b,d]thiophen-2-yl)phenyl]pyrimidine (abbreviation: 4,6mDBTP2Pm-II), 4 ,6-bis[3-(9H-carbazol-9-yl)phenyl]pyrimidine (abbreviation: 4, 6mCzP2Pm), and other heterocyclic compounds having a diazine skeleton, such as PCCzPTzn and other heterocyclic compounds having a triazine skeleton, 3,5-bis[3-(9H-carbazol- 9-yl)phenyl]pyridine (abbreviation: 35DCzPPy), 1,3,5-tri[3-( 3-pyridyl)phenyl]benzene (abbreviation: TmPyPB), and other heterocyclic compounds having a pyridine skeleton such as 4,4'-bis(5-methylbenzoxazol-2-yl)stilbene (abbreviation: BzOs) and other heteroaromatic compounds can also be used. In addition, poly(2,5 -pyridinediyl) (abbreviation: PPy), poly[(9,9-dihexylfluorene-2,7 -diyl)-co-(pyridine-3,5-diyl)] (abbreviation: PF-Py), poly[(9 ,9-dioctylfluorene-2,7-diyl)-co-(2,2'-bipyridine-6, 6'-diyl)] (abbreviation: PF-BPy) and other polymer compounds can also be used. The substances described here mainly have an electron mobility of 1×10 -6 cm 2 / Vs or more. As long as the substance has higher electron transportability than holes, substances other than the above can also be used. If the substance has higher electron transportability than holes, substances other than the above can also be used.

[0170] In addition, when an exciplex is formed between Compound 134 and Compound 132, it is preferable to select Compound 131, Compound 132, and Compound 134 such that the emission peak of the formed exciplex overlaps with the absorption band on the longest wavelength side (low energy side) of Compound 131. ​​​As a result, a light-emitting element with dramatically improved luminous efficiency can be obtained.

[0171] <Pair of electrodes> The electrode 101 and the electrode 102 have the function of injecting holes and electrons into the light-emitting layer 130. The electrodes 101 and 102 are made of metals, alloys, conductive compounds, and mixtures or laminates thereof. It can be formed using aluminum (Al) as a typical example of a metal. , and other transition metals such as silver (Ag), tungsten, chromium, molybdenum, copper, and titanium. , alkali metals such as lithium (Li) and cesium, calcium, magnesium (Mg) Group 2 metals such as ytterbium (Yb) can be used as transition metals. A rare earth metal may be used. As the alloy, an alloy containing the above metals may be used. Examples of the conductive compound include MgAg and AlLi. Indium tin oxide (ITO), silicon or silicon oxide Including indium tin oxide (ITSO), indium zinc oxide (Indium Zinc Oxide) inc Oxide), tungsten and zinc-containing indium oxide, etc. As the conductive compound, an inorganic carbon material such as graphene may be used. As described above, electrodes 101 and 102 are formed by stacking multiple layers of these materials. 2 or both may be formed.

[0172] The light emitted from the light-emitting layer 130 is emitted from one or both of the electrodes 101 and 102. Therefore, at least one of the electrodes 101 and 102 is visible. Conductive materials that have the function of transmitting light include those that transmit visible light. The transmittance is 40% or more and 100% or less, preferably 60% or more and 100% or less, and the resistivity is 1×10 -2 Ω·cm or less. Examples of the conductive material include those. Also, the electrode on the light extraction side may be formed of a conductive material having a function of transmitting light and a function of reflecting light. Examples of the conductive material include those with a visible light reflectance of 20% or more and 80% or less, preferably 40% or more and 70% or less, and a resistivity of 1×10 -2 Ω·cm or less. When a material with low light transmittance such as metal or alloy is used for the electrode on the light extraction side it is sufficient to form one or both of electrode 101 and electrode 102 with a thickness that allows visible light to pass through (for example, a thickness of 1 nm to 10 nm).

[0173] In addition, in this specification and the like, for an electrode having a function of transmitting light, a material having a function of transmitting visible light and having conductivity may be used. For example, in addition to an oxide conductor layer typified by ITO as described above, it includes an oxide semiconductor layer or an organic conductor layer containing an organic substance. Examples of the organic conductor layer containing an organic substance include a layer containing a composite material formed by mixing an organic compound and an electron donor (donor), a layer containing a composite material formed by mixing an organic compound and an electron acceptor (acceptor), and the like. Also, the resistivity of the transparent conductive layer is preferably 1×10 Ω·cm or less, more preferably 1×10 Ω·cm or less. 5 4

[0174] Also, the film formation methods of electrode 101 and electrode 102 include sputtering method, evaporation method, printing method, coating method, MBE (Molecular Beam Epitaxy) method, CVD method, pulse Laser deposition method, ALD (Atomic Layer Deposition) method, etc. can be appropriately used. It can be used as appropriate.

[0175] ≪Hole injection layer≫ The hole injection layer 111 has a function of promoting hole injection by reducing the hole injection barrier from one of the pair of electrodes (electrode 101 or electrode 102), and is formed by, for example, transition metal oxides, phthalocyanine derivatives, or aromatic amines. Examples of transition metal oxides include molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, and manganese oxide. Examples of phthalocyanine derivatives include phthalocyanine and metal phthalocyanine. Examples of aromatic amines include benzidine derivatives and phenylenediamine derivatives. Polymer compounds such as polythiophene and polyaniline can also be used, and for example, poly(ethylenedioxythiophene) / poly(styrenesulfonic acid), which is self-doped polythiophene, is a typical example. For example, transition metal oxides, phthalocyanine derivatives, or aromatic amines can be used. Examples of transition metal oxides include molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, and manganese oxide. Examples of phthalocyanine derivatives include phthalocyanine and metal phthalocyanine. Examples of aromatic amines include benzidine derivatives and phenylenediamine derivatives. Polymer compounds such as polythiophene and polyaniline can also be used. For example, poly(ethylenedioxythiophene) / poly(styrenesulfonic acid), which is self-doped polythiophene, is a typical example. As the hole injection layer 111, a layer having a composite material of a hole transporting material and a material showing electron accepting property can also be used. Alternatively, a laminate of a layer containing a material showing electron accepting property and a layer containing a hole transporting material may be used.

[0176] Charge transfer is possible between these materials in a steady state or in the presence of an electric field. Examples of materials showing electron accepting property include organic acceptors such as quinodimethane derivatives, chloranil derivatives, and hexaazatriphenylene derivatives. Specifically, 7,7,8,8-tetracyano-2,3,5,6-tetrafluorobenzoquinodimethane (abbreviation: F4-TCNQ), chloranil, 2,3,6,7, etc. Organic acceptors such as quinodimethane derivatives, chloranil derivatives, and hexaazatriphenylene derivatives can be mentioned. Specifically, 7,7,8,8-tetracyano-2,3,5,6-tetrafluorobenzoquinodimethane (abbreviation: F4-TCNQ), chloranil, 2,3,6,7, tetrafluorobenzoquinodimethane (abbreviation: F4-TCNQ), 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 - naphtho quinodimethane (abbreviation: F6 - TCNNQ), etc., compounds having an electron - withdrawing group (especially a halogen group such as a fluoro group or a cyano group) can be mentioned. In particular, a compound in which an electron - withdrawing group is bonded to a condensed aromatic ring having a plurality of heteroatoms, such as HAT - CN, is thermally stable and preferable. Also, a [3]radialene derivative having an electron - withdrawing group (especially a halogen group such as a fluoro group or a cyano group) is preferable because of its very high electron - accepting property. Specifically, α,α’ ,α’’ - 1,2,3 - cyclopropanetriylidene tris[4 - cyano - 2,3,5, 6 - tetrafluorobenzeneacetonitrile], α,α’,α’’ - 1,2,3 - cyclo propane triylidene tris[2,6 - dichloro - 3,5 - difluoro - 4 - (triflu oromethyl)benzeneacetonitrile], α,α’,α’’ - 1,2,3 - cyclopropa ne triylidene tris[2,3,4,5,6 - pentafluorobenzeneacetonitrile] and the like can be mentioned. Further, transition metal oxides, for example, oxides of metals from Group 4 to Group 8 can be used. Specifically, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide , molybdenum oxide, tungsten oxide, manganese oxide, rhenium oxide, etc. Among them, molybdenum oxide is stable in the atmosphere, has low hygroscopicity, and is easy to handle, so it is preferable. As the hole - transporting material, a material having higher hole - transporting property than electrons can be used, and it is preferably a material having a hole mobility of 1

[0177] ×10 cm -6 / Vs or more. Specifically 2 The aromatic amines and carbazole derivatives mentioned as hole transporting materials that can be used in the light emitting layer 130 can be used. Also, aromatic hydrocarbons and stilbene derivatives etc. can be used. Further, the hole transporting material may be a polymer compound.

[0178] Examples of the aromatic hydrocarbon include 2-tert-butyl-9,10-di(2-naphthyl l)anthracene (abbreviation: t-BuDNA), 2-tert-butyl-9,10-di(1 -naphthyl)anthracene, 9,10-bis(3,5-diphenylphenyl)anthracene (abbreviation: DPPA), 2-tert-butyl-9,10-bis(4-phenylphenyl )anthracene (abbreviation: t-BuDBA), 9,10-di(2-naphthyl)anthracene (abbreviation: DNA), 9,10-diphenylanthracene (abbreviation: DPAnth), 2-t ert-butylanthracene (abbreviation: t-BuAnth), 9,10-bis(4-methyl -1-naphthyl)anthracene (abbreviation: DMNA), 2-tert-butyl-9,10- bis[2-(1-naphthyl)phenyl]anthracene, 9,10-bis[2-(1-naph thyl)phenyl]anthracene, 2,3,6,7-tetramethyl-9,10-di(1-naph thyl)anthracene, 2,3,6,7-tetramethyl-9,10-di(2-naphthyl) anthracene, 9,9’-bianthryl, 10,10’-diphenyl-9,9’-bian thryl, 10,10’-bis(2-phenylphenyl)-9,9’-bianthryl, 10 ,10’-bis[(2,3,4,5,6-pentaphenyl)phenyl]-9,9’-bia nthryl, anthracene, tetracene, rubrene, perylene, 2,5,8,11-tetra Examples include (tert-butyl)perylene and the like. In addition, pentacene, coronene, etc. can also be used. Thus, it is more preferable to use an aromatic hydrocarbon having a hole mobility of 1×10 -6 cm 2 / Vs or more and having 14 to 42 carbon atoms.

[0179] Note that the aromatic hydrocarbon may have a vinyl skeleton. Examples of the aromatic hydrocarbon having a vinyl group include 4,4'-bis(2,2-diphenylvinyl)biphenyl (abbreviation: DPVBi), 9,10-bis[4-(2,2-diphenylvinyl)phenyl] anthracene (abbreviation: DPVPA), etc.

[0180] In addition, high molecular compounds such as poly(N-vinylcarbazole) (abbreviation: PVK), poly(4-vinyltriphenylamine) (abbreviation: PVTPA), poly[N-(4-{N'-[4-(4-diphenyl amino)phenyl]phenyl-N'-phenylamino}phenyl)methacrylamide]( (abbreviation: PTPDMA), poly[N,N'-bis(4-butylphenyl)-N,N'-bis (phenyl)benzidine] (abbreviation: Poly-TPD) can also be used.

[0181] ≪Hole transport layer≫ The hole transport layer 112 is a layer containing a hole transporting material, and the materials exemplified as the material of the hole injection layer 111 can be used. Since the hole transport layer 112 has a function of transporting the holes injected into the hole injection layer 111 to the light emitting layer 130, it preferably has the same or a nearly the same HOMO level as that of the hole injection layer 111.

[0182] As the hole transport material, the materials exemplified as the materials for the hole injection layer 111 and the compound 134 can be used. Materials can be used. Also, 1 × 10 -6 cm 2 / Vs or higher hole mobility However, any material that has a higher hole transporting property than electron transporting property may be used. Note that the layer containing a substance with a high hole transporting property may be a single layer or an upper layer. Two or more layers made of the above substances may be laminated.

[0183] ≪Electron transport layer≫ The electron transport layer 118 is connected to the other of the pair of electrodes (electrode 101 or electrode 102) via the electron injection layer 119. The electron transport material has the function of transporting electrons injected from the electrode 102 to the light-emitting layer 130. As the material, a material with higher electron transportability than holes can be used, and the -6 cm 2 It is preferable that the material has an electron mobility of 1 / Vs or more. Any other substance may be used as long as it has high transportability.

[0184] As the electron transporting material, the materials exemplified as the material for Compound 134 can be used. Also, 1×10 -6 cm 2 It is preferable that the material has an electron mobility of 1 / Vs or more. The electron transport layer 118 may be formed not only as a single layer, but also as a laminate of two or more layers made of the above-mentioned materials. You may do so.

[0185] In addition, a layer for controlling the movement of electron carriers is provided between the electron transport layer 118 and the light emitting layer 130. The layer for controlling the movement of electron carriers may be made of a material having high electron transport properties as described above. A small amount of material with high electron trapping properties is added to the layer, which suppresses the movement of electron carriers. This makes it possible to adjust the carrier balance. Such a configuration is effective in suppressing problems (such as a reduction in device lifetime) caused by electrons passing through the light-emitting layer.

[0186] ≪Electron injection layer≫ The electron injection layer 119 has a function of promoting electron injection by reducing the electron injection barrier from the electrode 102. For example, Group 1 metals, Group 2 metals, or their oxides, halides, carbonates, etc. can be used. Also, a composite material of the electron-transporting material shown above and a material exhibiting electron-donating properties can be used. Examples of materials exhibiting electron-donating properties include Group 1 metals, Group 2 metals, or their oxides. Specifically, alkali metals such as lithium fluoride (LiF), sodium fluoride (NaF), cesium fluoride (CsF ), calcium fluoride (CaF2), lithium oxide (LiO ), etc., alkaline earth metals, or their compounds can be used. Also, rare earth metal compounds such as erbium fluoride (ErF3) can be used. Further, an electride may be used for the electron injection layer 119. Examples of such electrides include substances obtained by adding electrons at a high concentration to a mixed oxide of calcium and aluminum. Also, a substance that can be used in the electron transport layer 118 may be used for the electron x injection layer 119. Moreover, a composite material formed by mixing an organic compound and an electron donor may be used for the electron injection layer 119. Such a composite material has excellent electron injection and electron transport properties because electrons are generated in the organic compound by the electron donor. In this case, examples of the organic compound include

[0187] It is preferable that the material is excellent in transporting the generated electrons. Specifically, for example, the above-mentioned The material constituting the electron transport layer 118 (metal complex, heteroaromatic compound, etc.) can be used. The electron donor may be any substance that exhibits electron donating properties to organic compounds. For the metal, alkali metals, alkaline earth metals and rare earth metals are preferred, and lithium, cesium, Examples include magnesium, calcium, erbium, and ytterbium. Preferred are lithium metal oxides and alkaline earth metal oxides, and lithium oxide and calcium oxide are preferred. , barium oxide, etc. Also, Lewis bases such as magnesium oxide are used. It is also possible to use organic compounds such as tetrathiafulvalene (abbreviation: TTF). It can also be done as follows.

[0188] The above-mentioned light-emitting layer, hole-injection layer, hole-transport layer, electron-transport layer, and electron-injection layer are These are deposition method (including vacuum deposition method), inkjet method, coating method, and nozzle printing method, respectively. The light-emitting layer and the hole-injection layer can be formed by a method such as gravure printing. In addition to the above-mentioned materials, the hole transport layer, the electron transport layer, and the electron injection layer may contain other materials such as quantum dots. Inorganic compounds or polymeric compounds (oligomers, dendrimers, polymers, etc.) may be used. stomach.

[0189] Quantum dots include colloidal quantum dots, alloy quantum dots, and core-shell quantum dots. It is also possible to use quantum dots of the 2nd group and the 16th group, quantum dots of the 13th group, and the like. Contains element groups from group 15, 13 and 17, 11 and 17, or 14 and 15 Quantum dots may also be used. Alternatively, cadmium (Cd), selenium (Se), zinc (Zn ) Sulfur (S), phosphorus (P), indium (In), tellurium (Te), lead (Pb), gallium (Ga), arsenic (As), aluminum (Al), and other elements may be used.

[0190] As the liquid medium used in the wet process, for example, methyl ethyl ketone, cyclohe tones such as xanone, fatty acid esters such as ethyl acetate, halogenated hydrocarbons such as dichlorobenzene, aromatic hydrocarbons such as toluene, xylene, mesitylene, cyclohexylbenzene aliphatic hydrocarbons such as cyclohexane, decalin, dodecane, and organic solvents such as dimethylform amide (DMF) and dimethyl sulfoxide (DMSO) can be used.

[0191] Further, as the polymer compound that can be used in the light-emitting layer, for example, poly[2-methoxy -5-(2-ethylhexyloxy)-1,4-phenylene vinylene] (abbreviation: MEH -PPV), polyphenylene vinylene (PPV) derivatives such as poly(2,5-dioctyl-1,4-phenylene vinylene), poly(9,9-di-n-octylfluorenyl-2,7 -diyl) (abbreviation: PF8), poly[(9,9-di-n-octylfluorenyl-2,7 -diyl)-alt-(benzo[2,1,3]thiadiazole-4,8-diyl)] (abbreviation : F8BT), poly[(9,9-di-n-octylfluorenyl-2,7-diyl)- alt-(2,2'-bithiophene-5,5'-diyl)] (abbreviation: F8T2), poly (9,9-dioctyl-2,7-divinylenefluorenylene)-alt-(9,10-a nthracene)], poly[(9,9-dihexylfluorenyl-2,7-diyl)-alt- (2,5-Dimethyl-1,4-phenylene)] and other polyfluorene derivatives, poly(3-he xylthiophene-2,5-diyl) (abbreviation: P3HT) and other polyalkylthiophene ( PAT) derivatives, polyphenylene derivatives, and the like. In addition, these polymer compounds and , PVK, poly(2-vinylnaphthalene), poly[bis(4-phenyl)(2,4,6- trimethylphenyl)amine] (abbreviation: PTAA) and other polymer compounds may be doped with a light-emitting compound and used in the light-emitting layer. As the light-emitting compound, the light-emitting compounds listed above can be used.

[0192] As one aspect of the present invention, an organic compound having a benzofuropyrimidine skeleton or a benzothienopyrimidine skeleton , an organic compound capable of converting triplet excitation energy into light emission, and an organic compound exhibiting fluorescence emission are mixed and used in the light-emitting layer 130. However, a polymer compound having the above skeleton or function can also be used. For example, a polymer compound having a benzofuropyrimidine skeleton or a benzothienopyrimidine skeleton, a substituent capable of converting triplet excitation energy into light emission, and a substituent exhibiting fluorescence emission may be used as the light-emitting layer 130. Further, a polymer compound having a benzofuropyrimidine skeleton or a benzothienopyrimidine skeleton and a substituent capable of converting triplet excitation energy into light emission, and a low molecule exhibiting fluorescence emission are mixed to produce the light-emitting layer 130. By using the polymer compound, the utilization efficiency of the material can be improved, and the manufacturing cost can be reduced.

[0193] <<Substrate>> Further, the light-emitting element according to one aspect of the present invention is formed on a substrate made of glass, plastic, or the like. It suffices to fabricate it. As for the order of fabrication on the substrate, they may be laminated in order from the side of electrode 101, or may be laminated in order from the side of electrode 102.

[0194] Note that as the substrate on which the light-emitting element according to one embodiment of the present invention can be formed, for example, glass, quartz, or plastic can be used. A flexible substrate may also be used. A flexible substrate refers to a substrate that can be bent (flexible), and examples thereof include plastic substrates made of polycarbonate, polyarylate, etc. Also, a film, an inorganic vapor deposition film, etc. can be used. Note that as long as it functions as a support in the manufacturing process of the light-emitting element, those other than these may be used. Alternatively, as long as it has a function of protecting the light-emitting element, it may be used.

[0195] For example, in this specification and the like, a light-emitting element can be formed using various substrates. The type of the substrate is not particularly limited. As an example of the substrate, a semiconductor substrate (for example, 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 a stainless steel foil, a tungsten substrate, a substrate having a tungsten foil, a flexible substrate, a bonded film, a cellulose nanofiber (CNF) containing a fibrous material, paper, or a base film, etc. are available. As an example of the glass substrate, there are barium borosilicate glass, aluminoborosilicate glass, or soda lime glass, etc. Examples of the flexible substrate, the bonded film, the base film, etc. include the following. For example, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), polytetrafluoro​​​​ There is plastic represented by polytetrafluoroethylene (PTFE). Or, as an example, there is resin such as acrylic. Or, as an example, polypropylene, polyester, polyvinyl fluoride, or polyvinyl chloride, etc. Or, as an example, polyamide , polyimide, aramid, epoxy, inorganic vapor deposition film, or papers, etc.

[0196] Also, as the substrate, a flexible substrate may be used, and a light-emitting element may be directly formed on the flexible substrate. Or, a release layer may be provided between the substrate and the light-emitting element. The release layer is used to separate from the substrate after partially or completely completing the light-emitting element thereon and transfer it to another substrate. At that time, the light-emitting element can be transferred to a substrate with poor heat resistance or a flexible substrate. In addition, for the above-mentioned release layer, for example, a laminated structure of an inorganic film of a tungsten film and a silicon oxide film , or a structure in which a resin film such as polyimide is formed on the substrate can be used. That is, a light-emitting element is formed using a certain substrate, and then the light-emitting element is transposed to another substrate

[0197] and the light-emitting element may be arranged on another substrate. As an example of the substrate on which the light-emitting element is transposed, in addition to the above-mentioned substrate, a cellophane substrate, a stone substrate, a wood substrate, a cloth substrate (including natural fibers (silk, cotton, hemp), synthetic fibers (nylon, polyurethane, polyester) or regenerated fibers (acetate tow, cupra, rayon, regenerated polyester), etc.), a leather substrate, or a rubber substrate, etc. By using these substrates, a light-emitting element that is not easily broken, a light-emitting element with high heat resistance, a light-emitting element with reduced weight, or a light-emitting element with reduced thickness can be obtained.

[0198] Furthermore, for example, a field effect transistor (FET) is formed on the above-mentioned substrate, and the FET and The light emitting element 150 may be fabricated on the electrically connected electrodes. In this way, an active matrix display device that controls the driving of the light emitting element 150 can be fabricated.

[0199] As described above, the structure shown in this embodiment mode can be used in appropriate combination with other embodiment modes. Cut.

[0200] (Embodiment 2) In this embodiment mode, a light-emitting element having a different structure from that of the light-emitting element shown in Embodiment 1 is The following will be explained with reference to FIG. 5. In FIG. 5, the symbols shown in FIG. 1(A) Parts with the same function may be marked with the same hatch pattern and the reference numerals may be omitted. In addition, parts having similar functions are denoted by similar reference numerals, and detailed descriptions thereof may be omitted. There is a match.

[0201] <Configuration example 2 of light-emitting element> FIG. 5 is a schematic cross-sectional view of the light emitting element 250. As shown in FIG.

[0202] The light-emitting element 250 shown in FIG. 5 has a plurality of electrodes between a pair of electrodes (electrode 101 and electrode 102). The light-emitting unit 106 and the light-emitting unit 108 are light-emitting units. One of the light-emitting units in the unit is the same as the EL layer 100 shown in FIG. That is, the light emitting element 150 shown in FIG. It is preferable that the light emitting element 250 has a plurality of light emitting units. In the optical element 250, the electrode 101 functions as an anode and the electrode 102 functions as a cathode. However, the following description will be given assuming that the light emitting element 250 has the same structure as the light emitting element 250, and the structure of the light emitting element 250 may be reversed.

[0203] Also, in the light-emitting element 250 shown in FIG. 5, the light-emitting unit 106 and the light-emitting unit 108 are laminated, and a charge generation layer 1 15 is provided between the light-emitting unit 106 and the light-emitting unit 108. Note that the light-emitting unit 106 and the light-emitting unit 108 may have the same configuration or different configurations. For example, it is preferable to use a configuration similar to that of the EL layer 100 for the light-emitting unit 108.

[0204] Also, the light-emitting element 250 has a light-emitting layer 120 and a light-emitting layer 170. In addition to the light-emitting layer 120, the light-emitting unit 106 has a hole injection layer 111, a hole transport layer 112, an electron transport layer 113, and an electron injection layer 114. In addition to the light-emitting layer 170, the light-emitting unit 108 has a hole injection layer 116, a hole transport layer 117, an electron transport layer 118, and an electron injection layer 11 9.

[0205] The light-emitting element 250 may contain an organic compound according to an aspect of the present invention in any layer included in the light-emitting unit 106 and the light-emitting unit 108. Note that the layer in which the organic compound is contained is preferably the electron transport layer 113 or the electron transport layer 118, and more preferably the light-emitting layer 120 or the light-emitting layer 170.

[0206] The charge generation layer 115 may have a configuration in which an acceptor substance, which is an electron acceptor, is added to a hole transporting material, or a configuration in which a donor substance, which is an electron donor, is added to an electron transporting material. Alternatively, a configuration in which both of these are laminated may be used.

[0207] When the charge generation layer 115 contains a composite material of an organic compound and an acceptor substance, the ​​​​​A composite material that can be used for the hole injection layer 111 shown in Embodiment 1 may be used in the composite material. As the organic compound, various compounds such as aromatic amine compounds, carbazole compounds, aromatic hydrocarbons, high molecular compounds (oligomers, dendrimers, polymers, etc.) can be used. Note that, as the organic compound, those having a hole mobility of 1×10 -6 cm 2 / Vs or more are preferably applied. However, as long as the substance has higher hole transportability than electrons, substances other than these may be used. Since the composite material of the organic compound and the acceptor material is excellent in carrier injection property and carrier transport property, low voltage driving and low current driving can be realized. When the surface on the anode side of the light emitting unit is in contact with the charge generation layer 115, since the charge generation layer 115 can also serve as the hole injection layer or the hole transport layer of the light emitting unit, the light emitting unit may be configured without providing a hole injection layer or a hole transport layer. Alternatively, when the surface on the cathode side of the light emitting unit is in contact with the charge generation layer 115, since the charge generation layer 115 can also serve as the electron injection layer or the electron transport layer of the light emitting unit, the light emitting unit may be configured without providing an electron injection layer or an electron transport layer.

[0208] Note that the charge generation layer 115 may be formed as a laminated structure combining a layer containing a composite material of an organic compound and an acceptor material and a layer composed of other materials. For example, it may be formed by combining a layer containing a composite material of an organic compound and an acceptor material and a layer containing one compound selected from electron donating substances and a compound having high electron transportability. Also, ​A layer containing a composite material of an organic compound and an acceptor material and a layer containing a transparent conductive film may be combined. It may be formed.

[0209] Note that the charge generation layer 115 sandwiched between the light-emitting unit 106 and the light-emitting unit 108 when a voltage is applied between the electrode 101 and the electrode 102, it may inject electrons into one light-emitting unit and holes into the other light-emitting unit. For example, in FIG. 5, when a voltage is applied such that the potential of the electrode 1 01 is higher than the potential of the electrode 102, the charge generation layer 115 injects electrons into the light-emitting unit 106 and holes into the light-emitting unit 108. .

[0210] Note that the charge generation layer 115 preferably has light transmittance with respect to visible light (specifically the transmittance of visible light with respect to the charge generation layer 115 is 40% or more) from the viewpoint of light extraction efficiency. Also, the charge generation layer 115 functions even if it has a lower conductivity than a pair of electrodes (electrode 101 and electrode 102).

[0211] By forming the charge generation layer 115 using the above-described materials, an increase in the driving voltage in the case where the light-emitting layer is laminated can be suppressed.

[0212] Also, in FIG. 5, a light-emitting device having two light-emitting units has been described, but the same can be similarly applied to a light-emitting device in which three or more light-emitting units are laminated. As shown in the light-emitting device 250, by arranging a plurality of light-emitting units between a pair of electrodes with a charge generation layer interposed therebetween , high-brightness light emission can be enabled while keeping the current density low, and furthermore, a long-life light-emitting device can be realized. Also, a light-emitting device with low power consumption can be realized.

[0213] In each of the above configurations, the gates used in the light-emitting units 106 and 108 The light emitting colors of the light emitting materials may be the same or different. The guest unit 106 and the light-emitting unit 108 have the function of emitting light of the same color. When the material is included, the light emitting element 250 becomes a light emitting element that exhibits high light emitting luminance with a small current value. It is more preferable that the light-emitting units 106 and 108 emit light of different colors. When the light-emitting element 250 includes a guest material having a light-emitting function, the light-emitting element 250 can emit multicolor light. In this case, either one of the light-emitting layer 120 and the light-emitting layer 170 or In both cases, the light emitting element 250 is formed by using a plurality of light emitting materials with different emission wavelengths. The emission spectrum is a composite of light with different emission peaks, so Both result in an emission spectrum with two maxima.

[0214] The above-mentioned structure is also suitable for obtaining white light emission. By making the lights complementary to each other, white light can be emitted. The resulting white light is highly luminescent, or at least has red, green, and blue components. It is preferable to select a suitable material.

[0215] The light-emitting layer 130 shown in the first embodiment may be formed in one or both of the light-emitting layers 120 and 170. By using this configuration, it is possible to obtain light emitting devices with good luminous efficiency and reliability. The guest material contained in the light-emitting layer 130 is a fluorescent material. Therefore, the light-emitting layer 120 and / or the light-emitting layer 170 may be formed by the light-emitting layer shown in the first embodiment. By using the configuration of 130, a light-emitting element with a sharp emission spectrum and high color purity can be obtained. It is possible.

[0216] Also, in the case of a light-emitting element in which three or more light-emitting units are stacked, the emission colors exhibited by the guest materials used in the respective light-emitting units may be the same or different from each other. When there are a plurality of light-emitting units exhibiting the same color emission, the emission colors exhibited by these plurality of light-emitting units can obtain a high emission luminance at a low current value as compared with other colors. Such a configuration can be suitably used for adjusting the emission color. In particular, it is suitable when using guest materials having different emission efficiencies and exhibiting different emission colors. For example, in the case of having three layers of light-emitting units, two layers of light-emitting units having the same color fluorescent material and one layer of light-emitting unit having a phosphorescent material exhibiting a different emission color from the fluorescent material, the emission intensities of fluorescence emission and phosphorescence emission can be adjusted. That is, the emission intensity of each color can be adjusted according to the number of light-emitting units. The emission colors exhibited by the guest materials used in the respective light-emitting units may be the same or different from each other. When there are a plurality of light-emitting units exhibiting the same color emission, the emission colors exhibited by these plurality of light-emitting units can obtain a high emission luminance at a low current value as compared with other colors. Such a configuration can be suitably used for adjusting the emission color. In particular, it is suitable when using guest materials having different emission efficiencies and exhibiting different emission colors. For example, in the case of having three layers of light-emitting units, two layers of light-emitting units having the same color fluorescent material and one layer of light-emitting unit having a phosphorescent material exhibiting a different emission color from the fluorescent material, the emission intensities of fluorescence emission and phosphorescence emission can be adjusted. That is, the emission intensity of each color can be adjusted according to the number of light-emitting units. When there are a plurality of light-emitting units exhibiting the same color emission, the emission colors exhibited by these plurality of light-emitting units can obtain a high emission luminance at a low current value as compared with other colors. Such a configuration can be suitably used for adjusting the emission color. In particular, it is suitable when using guest materials having different emission efficiencies and exhibiting different emission colors. For example, in the case of having three layers of light-emitting units, two layers of light-emitting units having the same color fluorescent material and one layer of light-emitting unit having a phosphorescent material exhibiting a different emission color from the fluorescent material, the emission intensities of fluorescence emission and phosphorescence emission can be adjusted. That is, the emission intensity of each color can be adjusted according to the number of light-emitting units. When there are a plurality of light-emitting units exhibiting the same color emission, the emission colors exhibited by these plurality of light-emitting units can obtain a high emission luminance at a low current value as compared with other colors. Such a configuration can be suitably used for adjusting the emission color. In particular, it is suitable when using guest materials having different emission efficiencies and exhibiting different emission colors. For example, in the case of having three layers of light-emitting units, two layers of light-emitting units having the same color fluorescent material and one layer of light-emitting unit having a phosphorescent material exhibiting a different emission color from the fluorescent material, the emission intensities of fluorescence emission and phosphorescence emission can be adjusted. That is, the emission intensity of each color can be adjusted according to the number of light-emitting units. When there are a plurality of light-emitting units exhibiting the same color emission, the emission colors exhibited by these plurality of light-emitting units can obtain a high emission luminance at a low current value as compared with other colors. Such a configuration can be suitably used for adjusting the emission color. In particular, it is suitable when using guest materials having different emission efficiencies and exhibiting different emission colors. For example, in the case of having three layers of light-emitting units, two layers of light-emitting units having the same color fluorescent material and one layer of light-emitting unit having a phosphorescent material exhibiting a different emission color from the fluorescent material, the emission intensities of fluorescence emission and phosphorescence emission can be adjusted. That is, the emission intensity of each color can be adjusted according to the number of light-emitting units. When there are a plurality of light-emitting units exhibiting the same color emission, the emission colors exhibited by these plurality of light-emitting units can obtain a high emission luminance at a low current value as compared with other colors. Such a configuration can be suitably used for adjusting the emission color. In particular, it is suitable when using guest materials having different emission efficiencies and exhibiting different emission colors. For example, in the case of having three layers of light-emitting units, two layers of light-emitting units having the same color fluorescent material and one layer of light-emitting unit having a phosphorescent material exhibiting a different emission color from the fluorescent material, the emission intensities of fluorescence emission and phosphorescence emission can be adjusted. That is, the emission intensity of each color can be adjusted according to the number of light-emitting units. When there are a plurality of light-emitting units exhibiting the same color emission, the emission colors exhibited by these plurality of light-emitting units can obtain a high emission luminance at a low current value as compared with other colors. Such a configuration can be suitably used for adjusting the emission color. In particular, it is suitable when using guest materials having different emission efficiencies and exhibiting different emission colors. For example, in the case of having three layers of light-emitting units, two layers of light-emitting units having the same color fluorescent material and one layer of light-emitting unit having a phosphorescent material exhibiting a different emission color from the fluorescent material, the emission intensities of fluorescence emission and phosphorescence emission can be adjusted. That is, the emission intensity of each color can be adjusted according to the number of light-emitting units. When there are a plurality of light-emitting units exhibiting the same color emission, the emission colors exhibited by these plurality of light-emitting units can obtain a high emission luminance at a low current value as compared with other colors. Such a configuration can be suitably used for adjusting the emission color. In particular, it is suitable when using guest materials having different emission efficiencies and exhibiting different emission colors. For example, in the case of having three layers of light-emitting units, two layers of light-emitting units having the same color fluorescent material and one layer of light-emitting unit having a phosphorescent material exhibiting a different emission color from the fluorescent material, the emission intensities of fluorescence emission and phosphorescence emission can be adjusted. That is, the emission intensity of each color can be adjusted according to the number of light-emitting units. When there are a plurality of light-emitting units exhibiting the same color emission, the emission colors exhibited by these plurality of light-emitting units can obtain a high emission luminance at a low current value as compared with other colors. Such a configuration can be suitably used for adjusting the emission color. In particular, it is suitable when using guest materials having different emission efficiencies and exhibiting different emission colors. For example, in the case of having three layers of light-emitting units, two layers of light-emitting units having the same color fluorescent material and one layer of light-emitting unit having a phosphorescent material exhibiting a different emission color from the fluorescent material, the emission intensities of fluorescence emission and phosphorescence emission can be adjusted. That is, the emission intensity of each color can be adjusted according to the number of light-emitting units. When there are a plurality of light-emitting units exhibiting the same color emission, the emission colors exhibited by these plurality of light-emitting units can obtain a high emission luminance at a low current value as compared with other colors. Such a configuration can be suitably used for adjusting the emission color. In particular, it is suitable when using guest materials having different emission efficiencies and exhibiting different emission colors. For example, in the case of having three layers of light-emitting units, two layers of light-emitting units having the same color fluorescent material and one layer of light-emitting unit having a phosphorescent material exhibiting a different emission color from the fluorescent material, the emission intensities of fluorescence emission and phosphorescence emission can be adjusted. That is, the emission intensity of each color can be adjusted according to the number of light-emitting units.

[0217] In the case of a light-emitting element having two layers of such fluorescence emission units and one layer of phosphorescence emission units, a light-emitting element containing two layers of light-emitting units containing a blue fluorescent material and one layer of light-emitting unit containing a yellow phosphorescent material, a light-emitting element having two layers of light-emitting units containing a blue fluorescent material and one layer of light-emitting unit containing a red phosphorescent material and a green phosphorescent material, or a light-emitting element having two layers of light-emitting units containing a blue fluorescent material and one layer of light-emitting unit containing a red phosphorescent material, a yellow phosphorescent material and a green phosphorescent material is preferable because white light emission can be efficiently obtained. In the case of a light-emitting element having two layers of such fluorescence emission units and one layer of phosphorescence emission units, a light-emitting element containing two layers of light-emitting units containing a blue fluorescent material and one layer of light-emitting unit containing a yellow phosphorescent material, a light-emitting element having two layers of light-emitting units containing a blue fluorescent material and one layer of light-emitting unit containing a red phosphorescent material and a green phosphorescent material, or a light-emitting element having two layers of light-emitting units containing a blue fluorescent material and one layer of light-emitting unit containing a red phosphorescent material, a yellow phosphorescent material and a green phosphorescent material is preferable because white light emission can be efficiently obtained. In the case of a light-emitting element having two layers of such fluorescence emission units and one layer of phosphorescence emission units, a light-emitting element containing two layers of light-emitting units containing a blue fluorescent material and one layer of light-emitting unit containing a yellow phosphorescent material, a light-emitting element having two layers of light-emitting units containing a blue fluorescent material and one layer of light-emitting unit containing a red phosphorescent material and a green phosphorescent material, or a light-emitting element having two layers of light-emitting units containing a blue fluorescent material and one layer of light-emitting unit containing a red phosphorescent material, a yellow phosphorescent material and a green phosphorescent material is preferable because white light emission can be efficiently obtained. In the case of a light-emitting element having two layers of such fluorescence emission units and one layer of phosphorescence emission units, a light-emitting element containing two layers of light-emitting units containing a blue fluorescent material and one layer of light-emitting unit containing a yellow phosphorescent material, a light-emitting element having two layers of light-emitting units containing a blue fluorescent material and one layer of light-emitting unit containing a red phosphorescent material and a green phosphorescent material, or a light-emitting element having two layers of light-emitting units containing a blue fluorescent material and one layer of light-emitting unit containing a red phosphorescent material, a yellow phosphorescent material and a green phosphorescent material is preferable because white light emission can be efficiently obtained. In the case of a light-emitting element having two layers of such fluorescence emission units and one layer of phosphorescence emission units, a light-emitting element containing two layers of light-emitting units containing a blue fluorescent material and one layer of light-emitting unit containing a yellow phosphorescent material, a light-emitting element having two layers of light-emitting units containing a blue fluorescent material and one layer of light-emitting unit containing a red phosphorescent material and a green phosphorescent material, or a light-emitting element having two layers of light-emitting units containing a blue fluorescent material and one layer of light-emitting unit containing a red phosphorescent material, a yellow phosphorescent material and a green phosphorescent material is preferable because white light emission can be efficiently obtained. In the case of a light-emitting element having two layers of such fluorescence emission units and one layer of phosphorescence emission units, a light-emitting element containing two layers of light-emitting units containing a blue fluorescent material and one layer of light-emitting unit containing a yellow phosphorescent material, a light-emitting element having two layers of light-emitting units containing a blue fluorescent material and one layer of light-emitting unit containing a red phosphorescent material and a green phosphorescent material, or a light-emitting element having two layers of light-emitting units containing a blue fluorescent material and one layer of light-emitting unit containing a red phosphorescent material, a yellow phosphorescent material and a green phosphorescent material is preferable because white light emission can be efficiently obtained.

[0218] Also, at least one of the light-emitting layer 120 or the light-emitting layer 170 is further divided into layers, and the You may also make it such that different light-emitting materials are contained in each of the divided layers. That is, the light-emitting layer 12 0, or at least one of the light-emitting layer 170 may be composed of two or more layers. For example, when stacking a first light-emitting layer and a second light-emitting layer in order from the hole transport layer side to form a light-emitting layer, a material having hole transport properties is used as the host material of the first light-emitting layer, and a material having electron transport properties is used as the host material of the second light-emitting layer. There are configurations such as this. In this case, the light-emitting materials of the first light-emitting layer and the second light-emitting layer may be the same material or different materials, and may be materials having a function of emitting light of the same color or materials having a function of emitting light of different colors. With a configuration having a plurality of light-emitting materials having functions of emitting light of mutually different colors, it is possible to obtain white light emission with high color rendering composed of three primary colors or four or more emission colors.

[0219] Note that this embodiment can be appropriately combined with other embodiments.

[0220] (Embodiment 3) In this embodiment, a light-emitting device using the light-emitting element described in Embodiment 1 and Embodiment 2 will be described with reference to FIGS. 6(A) and 6(B).

[0221] FIG. 6(A) is a top view showing the light-emitting device, and FIG. 6(B) is a cross-sectional view obtained by cutting FIG. 6(A) along A-B and C-D. This light-emitting device includes a drive circuit unit (source-side drive circuit) 601, a pixel unit 602, and a drive circuit unit (gate-side drive circuit) 603, which are indicated by dotted lines, for controlling the light emission of the light-emitting element. Further, 604 is a sealing substrate, 625 is a drying material, and 605 is a sealing material. The inside surrounded by the sealing material 605 is a space 607.

[0222] Note that the routing wiring 608 is wiring for transmitting signals input to the source-side drive circuit 601 and the gate-side drive circuit 603, and is an FPC (flexible printed circuit) 609 serving as an external input terminal that receives a video signal, a clock signal, a start signal, a reset signal, etc. Although only the FPC is illustrated here, a printed wiring board (PWB) may be attached to this FPC. The light-emitting device in this specification includes not only the light-emitting device main body but also a state in which an FPC or a PWB is attached thereto. Next, the cross-sectional structure of the above light-emitting device will be described with reference to FIG. 6(B). A drive circuit section and a pixel section are formed on the element substrate 610. Here, one pixel in the source-side drive circuit 601, which is a drive circuit section, and the pixel section 602 is shown.

[0223] Note that the source-side drive circuit 601 is formed of a CMOS circuit combined with an n-channel type TFT 623 and a p-channel type TFT 624. Also, the drive circuit may be formed of various CMOS circuits, P MOS circuits, and NMOS circuits. In this embodiment, a driver integrated type in which a drive circuit is formed on a substrate is shown, but this is not necessarily required, and the drive circuit can be formed outside the substrate instead of on the substrate.

[0224] Also, the pixel section 602 is formed of pixels including a switching TFT 611, a current control TFT 612, and a first electrode 613 electrically connected to the drain thereof. Note that an insulator 614 is formed so as to cover an end portion of the first electrode 613. The insulator 614 is a positive type. type. type.

[0225] type. type. type. It can be formed by using a photosensitive resin film of a certain type.

[0226] In addition, in order to improve the coating property of the film formed on the insulator 614, a surface with a curvature is formed at the upper end or the lower end of the insulator 614. For example, when photosensitive acrylic is used as the material of the insulator 614, it is preferable to provide a curved surface only at the upper end of the insulator 614. The radius of curvature of the curved surface is preferably 0.2 μm or more and 0.3 μm or less. Also, as the insulator 614, either a negative-type or a positive-type photosensitive material can be used.

[0227] An EL layer 616 and a second electrode 617 are respectively formed on the first electrode 613. Here, as the material used for the first electrode 613 that functions as an anode, it is desirable to use a material with a large work function. For example, an ITO film, an indium tin oxide film containing silicon, an indium oxide film containing 2 wt% or more and 20 wt% or less of zinc oxide, a titanium nitride film, a chromium film, a tungsten film, a Zn film, a Pt film, etc. In addition to single-layer films, a laminate of a titanium nitride film and a film mainly composed of aluminum, a three-layer structure of a titanium nitride film, a film mainly composed of aluminum, and a titanium nitride film can be used. When a laminated structure is used, the resistance as a wiring is low, good ohmic contact can be achieved, and it can further function as an anode.

[0228] Also, the EL layer 616 is formed by various methods such as a vapor deposition method using a vapor deposition mask, an inkjet method, and a spin coating method. As the material constituting the EL layer 616, a low molecular compound or a high molecular compound (including oligomers and dendrimers) may be used.

[0229] Furthermore, the material used for the second electrode 617 formed on the EL layer 616 and functioning as a cathode is preferably a material with a small work function (Al, Mg, Li, Ca, or their alloys and compounds, MgAg, MgIn, AlLi, etc.). When the light generated in the EL layer 616 passes through the second electrode 617, it is preferable to use a stacked layer of a thin metal film with a reduced thickness and a transparent conductive film (ITO, indium oxide containing 2 wt% or more and 20 wt% or less of zinc oxide, indium tin oxide containing silicon, zinc oxide (ZnO), etc.) as the second electrode 617. Note that the light generated in the EL layer 616 is transmitted through the second electrode 617. When this occurs, it is preferable to use a stacked layer of a thin metal film with a reduced thickness and a transparent conductive film (ITO, indium oxide containing 2 wt% or more and 20 wt% or less of zinc oxide, indium tin oxide containing silicon, zinc oxide (ZnO), etc.) as the second electrode 617. When the light generated in the EL layer 616 passes through the second electrode 617, it is preferable to use a stacked layer of a thin metal film with a reduced thickness and a transparent conductive film (ITO, indium oxide containing 2 wt% or more and 20 wt% or less of zinc oxide, indium tin oxide containing silicon, zinc oxide (ZnO), etc.) as the second electrode 617. When the light generated in the EL layer 616 passes through the second electrode 617, it is preferable to use a stacked layer of a thin metal film with a reduced thickness and a transparent conductive film (ITO, indium oxide containing 2 wt% or more and 20 wt% or less of zinc oxide, indium tin oxide containing silicon, zinc oxide (ZnO), etc.) as the second electrode 617. When the light generated in the EL layer 616 passes through the second electrode 617, it is preferable to use a stacked layer of a thin metal film with a reduced thickness and a transparent conductive film (ITO, indium oxide containing 2 wt% or more and 20 wt% or less of zinc oxide, indium tin oxide containing silicon, zinc oxide (ZnO), etc.) as the second electrode 617. When the light generated in the EL layer 616 passes through the second electrode 617, it is preferable to use a stacked layer of a thin metal film with a reduced thickness and a transparent conductive film (ITO, indium oxide containing 2 wt% or more and 20 wt% or less of zinc oxide, indium tin oxide containing silicon, zinc oxide (ZnO), etc.) as the second electrode 617.

[0230] Note that the light-emitting element 618 is formed by the first electrode 613, the EL layer 616, and the second electrode 617. The light-emitting element 618 preferably has the configuration of the light-emitting element in Embodiment 1 and Embodiment 2. Note that although the pixel portion is formed of a plurality of light-emitting elements, in the light-emitting device in this embodiment, both the light-emitting element having the configuration described in Embodiment 1 and Embodiment 2 and the light-emitting element having other configurations may be included. Note that the light-emitting element 618 is formed by the first electrode 613, the EL layer 616, and the second electrode 617. The light-emitting element 618 preferably has the configuration of the light-emitting element in Embodiment 1 and Embodiment 2. Note that although the pixel portion is formed of a plurality of light-emitting elements, in the light-emitting device in this embodiment, both the light-emitting element having the configuration described in Embodiment 1 and Embodiment 2 and the light-emitting element having other configurations may be included. Note that the light-emitting element 618 is formed by the first electrode 613, the EL layer 616, and the second electrode 617. The light-emitting element 618 preferably has the configuration of the light-emitting element in Embodiment 1 and Embodiment 2. Note that although the pixel portion is formed of a plurality of light-emitting elements, in the light-emitting device in this embodiment, both the light-emitting element having the configuration described in Embodiment 1 and Embodiment 2 and the light-emitting element having other configurations may be included. Note that the light-emitting element 618 is formed by the first electrode 613, the EL layer 616, and the second electrode 617. The light-emitting element 618 preferably has the configuration of the light-emitting element in Embodiment 1 and Embodiment 2. Note that although the pixel portion is formed of a plurality of light-emitting elements, in the light-emitting device in this embodiment, both the light-emitting element having the configuration described in Embodiment 1 and Embodiment 2 and the light-emitting element having other configurations may be included. Note that the light-emitting element 618 is formed by the first electrode 613, the EL layer 616, and the second electrode 617. The light-emitting element 618 preferably has the configuration of the light-emitting element in Embodiment 1 and Embodiment 2. Note that although the pixel portion is formed of a plurality of light-emitting elements, in the light-emitting device in this embodiment, both the light-emitting element having the configuration described in Embodiment 1 and Embodiment 2 and the light-emitting element having other configurations may be included.

[0231] Furthermore, by bonding the sealing substrate 604 to the element substrate 610 with the sealing material 605, a structure is formed in which the light-emitting element 618 is provided in the space 607 surrounded by the element substrate 610, the sealing substrate 604, and the sealing material 605. Note that the space 607 is filled with a filling material, and in addition to the case where an inert gas (such as nitrogen or argon) is filled, it may also be filled with a resin or a drying material or both. Furthermore, by bonding the sealing substrate 604 to the element substrate 610 with the sealing material 605, a structure is formed in which the light-emitting element 618 is provided in the space 607 surrounded by the element substrate 610, the sealing substrate 604, and the sealing material 605. Note that the space 607 is filled with a filling material, and in addition to the case where an inert gas (such as nitrogen or argon) is filled, it may also be filled with a resin or a drying material or both. Furthermore, by bonding the sealing substrate 604 to the element substrate 610 with the sealing material 605, a structure is formed in which the light-emitting element 618 is provided in the space 607 surrounded by the element substrate 610, the sealing substrate 604, and the sealing material 605. Note that the space 607 is filled with a filling material, and in addition to the case where an inert gas (such as nitrogen or argon) is filled, it may also be filled with a resin or a drying material or both. Furthermore, by bonding the sealing substrate 604 to the element substrate 610 with the sealing material 605, a structure is formed in which the light-emitting element 61 is provided in the space 607 surrounded by the element substrate 610, the sealing substrate 604, and the sealing material 605. Note that the space 607 is filled with a filling material, and in addition to the case where an inert gas (such as nitrogen or argon) is filled, it may also be filled with a resin or a drying material or both. Furthermore, by bonding the sealing substrate 604 to the element substrate 610 with the sealing material 605, a structure is formed in which the light-emitting element 618 is provided in the space 607 surrounded by the element substrate 610, the sealing substrate 604, and the sealing material 605. Note that the space 607 is filled with a filling material, and in addition to the case where an inert gas (such as nitrogen or argon) is filled, it may also be filled with a resin or a drying material or both. Furthermore, by bonding the sealing substrate 604 to the element substrate 610 with the sealing material 605, a structure is formed in which the light-emitting element 618 is provided in the space 607 surrounded by the element substrate 610, the sealing substrate 604, and the sealing material 605. Note that the space 607 is filled with a filling material, and in addition to the case where an inert gas (such as nitrogen or argon) is filled, it may also be filled with a resin or a drying material or both.

[0232] Note that it is preferable to use an epoxy-based resin or glass frit for the sealing material 605. Also, it is desirable that these materials be as impermeable to moisture and oxygen as possible. Also, As materials for the sealing substrate 604, in addition to glass substrates and quartz substrates, FRP (Fiber R einforced Plastics), PVF (polyvinyl fluoride), polyester or plastic substrates made of acrylic or the like can be used.

[0233] In the above manner, a light-emitting device using the light-emitting elements described in Embodiment 1 and Embodiment 2 can be obtained.

[0234] <Configuration Example 1 of Light-Emitting Device> FIG. 7 shows an example of a light-emitting device in which a light-emitting element exhibiting white light emission is formed and a coloring layer (color filter ter) is formed.

[0235] In FIG. 7(A), a substrate 1001, an underlying insulating film 1002, a gate insulating film 1003, gate electrodes 1006, 1007, 1008, a first interlayer insulating film 1020, a second interlayer insulating film 1021 , a peripheral portion 1042, a pixel portion 1040, a driving circuit portion 1041, first electrodes 102 4W, 1024R, 1024G, 1024B of the light-emitting element, a partition wall 1026, an EL layer 1028, the light-emitting element second electrode 1029, a sealing substrate 1031, a sealing material 1032, a red pixel 1044R, green pixel 1044G, blue pixel 1044B, white pixel 1044W, etc. are shown.

[0236] Also, in FIG. 7(A), coloring layers (a red coloring layer 1034R, a green coloring layer 1034G, blue coloring layer 1034B) are provided on a transparent base material 1033. Also, a black layer (black matrix rix) 1035 may be further provided. The transparent base material 1 on which the coloring layer and the black layer are provided 033 is aligned and fixed to the substrate 1001. Note that the colored layer and the black layer are covered with an overcoat layer 1036. In FIG. 7(A), there are a light-emitting layer that allows light to exit to the outside without passing through the colored layer and a light-emitting layer that allows light to exit to the outside through the colored layers of each color. Since the light that does not pass through the colored layer is white, and the light that passes through the colored layer is red, blue, or green, an image can be represented by four-color pixels.

[0237] In FIG. 7(B), an example is shown in which a red colored layer 1034R, a green colored layer 1034G, and a blue colored layer 1034B are formed between the gate insulating film 1003 and the first interlayer insulating film 1020. As shown in FIG. 7(B), the colored layer may be provided between the substrate 1001 and the sealing substrate 1031.

[0238] In addition, in the light-emitting device described above, a light-emitting device having a structure (bottom emission type) that extracts light from the side of the substrate 1001 on which the TFT is formed is used. However, a light-emitting device having a structure (top emission type) that extracts light from the side of the sealing substrate 1031 may also be used.

[0239] <Configuration Example 2 of Light-Emitting Device> Cross-sectional views of a top emission type light-emitting device are shown in FIGS. 8(A) and (B). In this case, a substrate that does not transmit light can be used as the substrate 1001. Until a connection electrode that connects the TFT and the anode of the light-emitting element is fabricated, it is formed in the same manner as the bottom emission type light-emitting device. After that, a third interlayer insulating film 1037 is formed to cover the electrode 1022. This insulating film may serve as a planarization film. The third interlayer insulating film 1037 can be formed using various materials other than the same material as the second interlayer insulating film 1021.

[0240] ​​​​​​​​​​​The lower electrodes 1025W, 1025R, 1025G, and 1025B of the light-emitting element are anodes here, but they may be cathodes. Also, in the case of a top-emission type light-emitting device as shown in FIGS. 8(A) and (B ), the lower electrodes 1025W, 1025R, 1025G, and 1025B are preferably reflective electrodes . Note that the second electrode 1029 preferably has a function of reflecting light and a function of transmitting light . Also, it is preferable that a microcavity structure is applied between the second electrode 1029 and the lower electrodes 1025W, 1025R, 1025G, and 1025B to have a function of amplifying light of a specific wavelength . The configuration of the EL layer 1028 is the same as the configuration described in Embodiment 1 and Embodiment 2, and the element structure is such that white light emission can be obtained . In FIGS. 7(A), 7(B), 8(A), and (B), as the configuration of the EL layer from which white light emission can be obtained, it may be realized by using a plurality of light-emitting layers, using a plurality of light-emitting units, etc . Note that the configuration for obtaining white light emission is not limited to these

[0241] . In the top-emission structure as shown in FIGS. 8(A) and (B), sealing can be performed with a sealing substrate 1031 provided with a coloring layer (red coloring layer 103 4R, green coloring layer 1034G, blue coloring layer 1034B) . A black layer (black matrix) 1035 may be provided on the sealing substrate 1031 so as to be located between pixels

[0242] . The coloring layer (red coloring layer 1034R , green coloring layer 1034G, blue coloring layer 1034B) and the black layer (black matrix ) may be covered with an overcoat layer . Note that the sealing substrate 1031 has translucency . . A substrate is used.

[0243] In addition, in Fig. 8(A), a configuration for performing full-color display in three colors of red, green, and blue is shown. However, as shown in Fig. 8( B), full-color display may be performed in four colors of red, green, blue, and white. Also, The configuration for performing full-color display is not limited to these. For example, full-color display may also be performed in four colors of red, green, blue, and yellow.

[0244] The light-emitting element according to one aspect of the present invention uses a fluorescent material as a guest material. Since the spectrum of the fluorescent material is sharper compared to the phosphorescent material, light emission with high color purity can be obtained. Therefore, by using the light-emitting element in the light-emitting device shown in this embodiment, a light-emitting device with high color reproducibility can be obtained.

[0245] As described above, a light-emitting device using the light-emitting element described in Embodiment 1 and Embodiment 2 can be obtained.

[0246] Note that this embodiment can be appropriately combined with other embodiments.

[0247] (Embodiment 4) In this embodiment, an electronic device and a display device according to one aspect of the present invention will be described.

[0248] According to one aspect of the present invention, an electronic device and a display device having a flat surface, good luminous efficiency, and high reliability can be manufactured. Also, according to one aspect of the present invention, an electronic device and a display device having a curved surface, good luminous efficiency, and high reliability can be manufactured. The light-emitting element according to one aspect of the present invention can obtain light emission with high color purity Therefore, by using the light-emitting element in the light-emitting device shown in this embodiment, an electronic device and a display device with high color reproducibility can be obtained. ​

[0249] Examples of electronic devices include, for example, television sets, desktop or notebook personal computers, monitors for computers, digital cameras, digital video cameras, digital photo frames, mobile phones, portable game machines, portable information terminals, audio playback devices, and large game machines such as pachinko machines.

[0250] The portable information terminal 900 shown in FIGS. 9(A) and 9(B) includes a housing 901, a housing 902, a display unit 90 3, and a hinge unit 905 and the like.

[0251] The housing 901 and the housing 902 are connected by a hinge unit 905. The portable information terminal 900 can be expanded from the folded state (FIG. 9(A)) as shown in FIG. 9(B). Thereby, it has excellent portability when carried, and excellent visibility due to a large display area when used.

[0252] The portable information terminal 900 is provided with a flexible display unit 903 across the housing 901 and the housing 902 connected by the hinge unit 905.

[0253] The light-emitting device manufactured using one aspect of the present invention can be used for the display unit 903. Thus, a portable information terminal having high reliability can be manufactured.

[0254] The display unit 903 can display at least one of document information, still images, moving images, and the like. When displaying document information on the display unit, the portable information terminal 900 can be used as an electronic book terminal.

[0255] ​When the mobile information terminal 900 is unfolded, the display unit 903 is held in a gently curved form. For example, it is curved with a radius of curvature of 1 mm or more and 50 mm or less, preferably 5 mm or more and 30 mm or less and the display unit 903 is held including the curved portion. A part of the display unit 903 has pixels continuously arranged from the housing 901 to the housing 902, and can perform a curved surface display.

[0256] The display unit 903 functions as a touch panel and can be operated by a finger, a stylus, or the like. It can be done.

[0257] The display unit 903 is preferably composed of a single flexible display. This makes it possible to perform a continuous display without interruption between the housing 901 and the housing 902. Note that a configuration in which a display is provided on each of the housing 901 and the housing 902 may also be used. It may be.

[0258] The hinge portion 905 preferably has a locking mechanism so that when the mobile information terminal 900 is unfolded, the angle between the housing 901 and the housing 902 does not become larger than a predetermined angle. For example, the angle at which the lock is applied (it cannot be opened further) is preferably 90 degrees or more and less than 180 degrees. Typically, it can be 90 degrees, 120 degrees, 135 degrees, 150 degrees, or 17 5 degrees, etc. This can improve the convenience, safety, and reliability of the mobile information terminal 900. When the hinge portion 905 has a locking mechanism, it is possible to prevent the display unit 903 from being damaged without applying excessive force to the display unit 903. Therefore, a highly reliable mobile information terminal can be realized.

[0259] When the hinge portion 905 has a locking mechanism, it is possible to prevent the display unit 903 from being damaged without applying excessive force to the display unit 903. Therefore, a highly reliable mobile information terminal can be realized. realized.

[0260] The housing 901 and the housing 902 may have a power button, operation buttons, external connection ports, speakers, a microphone, etc.

[0261] A wireless communication module is provided in either the housing 901 or the housing 902, and it is possible to transmit and receive data via a computer network such as the Internet, a LAN (Local Area Network), or Wi-Fi (registered trademark).

[0262] The portable information terminal 910 shown in Fig. 9(C) includes a housing 911, a display unit 912, operation buttons 913, external connection ports 914, speakers 915, a microphone 916, a camera 917, etc.

[0263] The light-emitting device manufactured using one aspect of the present invention can be used for the display unit 912. As a result, a portable information terminal can be manufactured with a high yield.

[0264] The portable information terminal 910 is provided with a touch sensor on the display unit 912. Any operation such as making a call or inputting characters can be performed by touching the display unit 912 with a finger or a stylus.

[0265] Also, by operating the operation buttons 913, it is possible to turn the power on and off and switch the types of images displayed on the display unit 912. For example, it is possible to switch from the mail creation screen to the main menu screen. [[ID=o36]]

[0266] Also, by providing a detection device such as a gyro sensor or an acceleration sensor inside the portable information terminal 910, the orientation (portrait or landscape) of the portable information terminal 910 can be determined, and the screen of the display unit 912 ​​​​​​​​The display orientation can be automatically switched. Also, the switching of the screen display orientation can be performed by touching the display unit 912, operating the operation button 913, or voice input using the microphone 916, etc. The portable information terminal 910 has one or more functions selected from, for example, a telephone, a notebook, or an information browsing device, etc. Specifically, it can be used as a smartphone. The portable information terminal 910 can execute various applications such as mobile phones, e-mails, text browsing and creation, music playback, video

[0267] playback, Internet communication, games, etc. The camera 920 shown in FIG. 9(D) has a housing 921, a display unit 922, an operation button 923, a shutter button 924, etc. Also, a detachable lens 926 is attached to the camera 920. A light-emitting device manufactured using one aspect of the present invention can be used for the display unit 922. Thereby, a camera with high reliability can be manufactured.

[0268] Here, the camera 920 is configured such that the lens 926 can be removed from the housing 921 and replaced, but the lens 926 and the housing 921 may be integrated.

[0269] The camera 920 can capture a still image or a moving image by pressing the shutter button 924. Also, the display unit 922 has a function as a touch panel, and it is also possible to capture an image by touching the display unit 922.

[0270]

[0271]

[0272] The camera 920 can be equipped with a strobe device, a viewfinder, etc. Alternatively, these may be incorporated into the housing 921.

[0273] FIG. 10(A) is a schematic diagram showing an example of a cleaning robot.

[0274] The cleaning robot 5100 has a display 5101 on the top surface and multiple The camera 5102, the brush 5103, and the operation button 5104 are also shown. However, the underside of the cleaning robot 5100 is provided with tires, a suction port, etc. The robot 5100 also has an infrared sensor, an ultrasonic sensor, an acceleration sensor, a piezo sensor, It is equipped with various sensors such as a sensor, a light sensor, and a gyro sensor. 100 is equipped with wireless communication means.

[0275] The cleaning robot 5100 moves by itself, detects the dust 5120, and sucks it out from the suction port on the bottom. It can suck up dirt.

[0276] In addition, the cleaning robot 5100 analyzes the image captured by the camera 5102 and detects the wall, furniture, or It can detect obstacles such as steps. Image analysis can also detect obstacles such as wiring. If an object that may get tangled in the brush 5103 is detected, the rotation of the brush 5103 can be stopped. can.

[0277] The display 5101 can display the remaining battery level and the amount of dust sucked. The route traveled by the cleaning robot 5100 can be displayed on the display 5101. In addition, the display 5101 is a touch panel, and the operation button 5104 is It may be provided in the ray 5101.

[0278] The cleaning robot 5100 can communicate with a mobile electronic device 5140 such as a smartphone. The image captured by the camera 5102 can be displayed on the mobile electronic device 5140. Therefore, the owner of the cleaning robot 5100 can know the state of the room even when away from home. Also, the display on the display 5101 can be confirmed on a mobile electronic device 5140 such as a smartphone.

[0279] The light-emitting device according to one aspect of the present invention can be used for the display 5101.

[0280] The robot 2100 shown in FIG. 10(B) includes an arithmetic unit 2110, an illuminance sensor 2101, a microphone 2102, an upper camera 2103, a speaker 2104, a display 2105, a lower camera 2106, an obstacle sensor 2107, and a moving mechanism 2108.

[0281] The microphone 2102 has a function of detecting the user's voice and environmental sounds, etc. Also the speaker 2104 has a function of emitting sound. The robot 2100 can communicate with the user using the microphone 2102 and the speaker 2104.

[0282] The display 2105 has a function of displaying various information. The robot 2100 can display the information desired by the user on the display 2105. The display 2105 may be equipped with a touch panel. Also, the display 2105 may be a removable information terminal, and by installing it at a fixed position of the robot 2100, charging and data transfer are made possible. ​

[0283] The upper camera 2103 and the lower camera 2106 have the function of imaging the surroundings of the robot 2100. In addition, the obstacle sensor 2107 can detect the presence or absence of obstacles in the traveling direction when the robot 2100 moves forward using the moving mechanism 2108. The robot 21 00 can recognize the surrounding environment and move safely by using the upper camera 2103, the lower camera 2106, and the obstacle sensor 2107. The light-emitting device according to one aspect of the present invention can be used for the display 2105.

[0284] The light-emitting device according to one aspect of the present invention can be used for the display 2105.

[0285] FIG. 10(C) is a diagram showing an example of a goggle-type display. The goggle-type display includes, for example, a housing 5000, a display unit 5001, a speaker 5003, an LED lamp 5004 , an operation key 5005 (including a power switch or an operation switch), a connection terminal 5006, a sensor 5007 (having a function of measuring 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, inclination , vibration, odor, or infrared rays), a microphone 5008, a second display unit 5002, a support unit 5012, earphones 5013, and the like.

[0286] The light-emitting device according to one aspect of the present invention can be used for the display unit 5001 and the second display unit 5002.

[0287] Further, FIGS. 11(A) and (B) show a foldable portable information terminal 5150. The foldable portable information terminal 5150 includes a housing 5151, a display area 5152, and a bending portion 515 It has 3. FIG. 11(A) shows the portable information terminal 5150 in the unfolded state. FIG. 11( B) shows the portable information terminal 5150 in the folded state. Although the portable information terminal 5150 has a large display area 5152, it is compact and excellent in portability when folded.

[0288] The display area 5152 can be folded in half by the bending portion 5153. The bending portion 515 3 is composed of a stretchable member and a plurality of support members. When folding, the stretchable member extends, and the bending portion 5153 has a curvature radius of 2 mm or more, preferably 5 mm or more and is folded.

[0289] Note that the display area 5152 may be a touch panel (input / output device) equipped with a touch sensor (input device). The light-emitting device according to one aspect of the present invention can be used for the display area 5152.

[0290] This embodiment can be appropriately combined with other embodiments.

[0291] (Embodiment 5) In this embodiment, an example of applying the light-emitting element according to one aspect of the present invention to various lighting devices will be described with reference to FIG. 12. By using the light-emitting element which is one aspect of the present invention, a lighting device with good luminous efficiency and high reliability can be manufactured.

[0292] By manufacturing the light-emitting element according to one aspect of the present invention on a flexible substrate, an electronic device and a lighting device having a light-emitting area with a curved surface can be realized.

[0293] In addition, the light-emitting device to which the light-emitting element according to one aspect of the present invention is applied is also applicable to vehicle lighting. ​​​For example, lighting can be installed on the windshield, ceiling, etc.

[0294] FIG. 12 shows an example in which the light-emitting element is used as an indoor lighting device 8501. Since the surface area can be increased, a large-area lighting device can be formed. By using a housing having the above structure, a lighting device 8502 having a curved light-emitting area can be formed. The light-emitting element shown in this embodiment mode has a thin film shape, and the housing can be designed with a high degree of freedom. Therefore, it is possible to create lighting devices with various elaborate designs. A large lighting device 8503 may be provided on the wall. A touch sensor may be provided in 503 to turn the power on or off.

[0295] In addition, by using light-emitting elements on the surface of the table, it has the function of a table. The lighting device 8504 can be used as a lighting device. This allows the lighting device to function as furniture.

[0296] In this manner, a lighting device and an electronic device can be obtained by applying a light-emitting element of one embodiment of the present invention. Note that the lighting devices and electronic devices to which the present invention can be applied are the same as those described in this embodiment. The present invention can be applied to lighting devices and electronic devices in a wide range of fields.

[0297] The structure described in this embodiment mode may be used in appropriate combination with structures described in other embodiments. You can be there. [Example]

[0298] In this example, a manufacturing example of a light-emitting element according to one embodiment of the present invention will be described. The structure of the optical element is the same as that in Fig. 1(A). The details of the element structure are shown in Table 1. Also, the structures and abbreviations of the compounds used are shown below. For the structures and abbreviations of other compounds, refer to the previous embodiments.

[0299] [Chemical Formula]

[0300] [Table 1]

[0301] [Fabrication of Light-Emitting Element] The fabrication method of the light-emitting element fabricated in this example is shown below.

[0302] [[Fabrication of Light-Emitting Element 1]] On a glass substrate, an ITSO film was formed as electrode 101 to a thickness of 70 nm. Note that the electrode area of electrode 101 was 4 mm 2 (2 mm × 2 mm).

[0303] Next, as a hole injection layer 111 on electrode 101, DBT3P-II and molybdenum oxide (MoO₃) were co-evaporated so that the weight ratio (DBT3P-II:MoO₃) was 1:0.5 and the thickness was 40 nm.

[0304] Next, as a hole transport layer 112 on the hole injection layer 111, 9-[3-(9-phenyl-9 H-fluoren-9-yl)phenyl]-9H-carbazole (abbreviation: mCzFLP) was evaporated to a thickness of 20 nm.

[0305] Next, as a light-emitting layer 130 on the hole transport layer 112, 4PCCzBfpm and tris[2 -(1H-pyrazol-1-yl-κN 2Phenyl-κC]iridium(III) (abbreviation : Ir(ppz)3), and 10-(2-benzothiazolyl)-2,3,6,7-tetra hydro-1,1,7,7-tetramethyl-1H,5H,11H-[1]benzopyrano[6 ,7,8-ij]quinolizin-11-one (abbreviation: coumarin545T), and were co-evaporated at a weight ratio (4PCCzBfpm:Ir(ppz)3:coumarin545T) of 0.8: 0.2:0.005 and a thickness of 30 nm. In the light-emitting layer 130, coumarin545T is a fluorescent compound and Ir(ppz)3 is a phosphorescent compound.

[0306] Next, on the light-emitting layer 130, as the electron transport layer 118, 4,6mCzP2Pm was sequentially evaporated to a thickness of 2 0 nm and NBPhen was evaporated to a thickness of 10 nm. Next , on the electron transport layer 118, as the electron injection layer 119, LiF was evaporated to a thickness of 1 nm on it.

[0307] Next, on the electron injection layer 119, as the electrode 102, aluminum (Al) was formed to a thickness of 20 0 nm.

[0308] Next, in a glove box under a nitrogen atmosphere, a glass substrate for sealing was fixed to the glass substrate on which the organic material was formed using an organic EL sealing material, thereby sealing the light-emitting element 1 . Specifically, the sealing material was applied around the organic material formed on the glass substrate, and the glass substrate and the glass substrate for sealing were bonded together, irradiated with ultraviolet light having a wavelength of 〈0000204〉 365 nm at 6 J / cm 2 and heat-treated at 80 °C for 1 hour. The light-emitting element 1 was obtained through the above steps.

[0309] <<Fabrication of Comparative Light-Emitting Device 2>> Comparative Light-Emitting Device 2 is different from the previously shown Light-Emitting Device 1 only in the formation process of the light-emitting layer 130, and the other processes were carried out using the same fabrication method as that of Light-Emitting Device 1.

[0310] As the light-emitting layer 130 of Comparative Light-Emitting Device 2, 4PCCzBfpm, Ir(ppz)3, and were co-evaporated so that the weight ratio (4PCCzBfpm:Ir(ppz)3) was 0.8:0.2 and the thickness was 30 nm. The difference between Comparative Light-Emitting Device 2 and Light-Emitting Device 1 is the presence or absence of the fluorescent compound, and the other structures are the same.

[0311] <<Fabrication of Light-Emitting Device 3>> Light-Emitting Device 3 is different from the previously shown Light-Emitting Device 1 only in the formation process of the light-emitting layer 130, and the other processes were carried out using the same fabrication method as that of Light-Emitting Device 1.

[0312] As the light-emitting layer 130 of Light-Emitting Device 3, 4-[4-(9'-phenyl-3,3'-bi-9H -carbazol-9-yl)phenyl]benzofuro[3,2-d]pyrimidine (abbreviation: 4 PCCzPBfpm), Ir(ppz)3, and coumarin545T were co-evaporated so that the weight ratio (4PCCzPBfpm:Ir(ppz)3:coumarin545T) was 0.8:0 .2:0.005 and the thickness was 30 nm.

[0313] <<Fabrication of Comparative Light-Emitting Device 4>> Comparative Light-Emitting Device 4 is different from the previously shown Light-Emitting Device 3 only in the formation process of the light-emitting layer 130, and the other processes were carried out using the same fabrication method as that of Light-Emitting Device 3.

[0314] As the light-emitting layer 130 of Comparative Light-Emitting Device 4, 4PCCzPBfpm and Ir(ppz)3 , with a weight ratio (4PCCzPBfpm:Ir(ppz)3) of 0.8:0.2 , and co-evaporated to a thickness of 30 nm. The difference between Comparative Light-Emitting Device 4 and Light-Emitting Device 3 is the presence or absence of the fluorescent compound, and the other structures are the same.

[0315] ≪Fabrication of Comparative Light-Emitting Device 5≫ Comparative Light-Emitting Device 5 is different only in the formation process of the light-emitting layer 130 and the electron transport layer 11 8, and the other processes were the same as those of Light-Emitting Device 1.

[0316] As the light-emitting layer 130 of Comparative Light-Emitting Device 5, 4,4'-bis(9-carbazolyl)biphenyl (abbreviation: CBP), Ir(ppz)3, and coumarin545T were co-evaporated with a weight ratio ( CBP:Ir(ppz)3:coumarin545T) of 0.8:0.2:0.005 , and to a thickness of 30 nm. The difference between Comparative Light-Emitting Device 5 and Light-Emitting Device 1 is the host material, and in Comparative Light-Emitting Device 5, CBP, which is not a TADF material, is used as the host material.

[0317] Next, on the light-emitting layer 130, as the electron transport layer 118, bathocuproine (abbreviation: BCP ) was sequentially evaporated to a thickness of 10 nm and NBPhen was evaporated to a thickness of 15 nm.

[0318] <Characteristics of the Light-Emitting Device> Next, the characteristics of the fabricated Light-Emitting Devices 1, 3 and Comparative Light-Emitting Devices 2, 4, 5 were measured. For the measurement of luminance and CIE chromaticity, a color luminance meter (Topcon Corporation, BM-5A) was used, and for the measurement of the electroluminescence spectrum, a multi-channel spectrometer (Hamamatsu Photonics, PMA-11) was used.

[0319] The current efficiency of the light-emitting element 1, the light-emitting element 3, the comparative light-emitting element 2, the comparative light-emitting element 4, and the comparative light-emitting element 5 - luminance characteristics are shown in FIG. 13, the current-voltage characteristics are shown in FIG. 14, and the external quantum efficiency-luminance characteristics are shown in FIG. 15 respectively. Also, for the light-emitting element 1, the light-emitting element 3, the comparative light-emitting element 2, the comparative light-emitting element 4, and the comparative light-emitting element 5, when a current is passed at a current density of 2.5 mA / cm respectively, the electroluminescence spectrum is shown in FIG. 16. The measurement of each light-emitting element was performed at room temperature (in an atmosphere maintained at 23°C 2 ). ) )

[0320] Also, near 1000 cd / m 2 , the element characteristics of the light-emitting element 1, the light-emitting element 3, the comparative light-emitting element 2, the comparative light-emitting element 4, and the comparative light-emitting element 5 are shown in Table 2

[0321]

Table 2

[0322] From FIG. 16, the electroluminescence spectra of the light-emitting element 1, the light-emitting element 3, and the comparative light-emitting element 5 each showed green emission derived from coumarin545T, a fluorescent compound, with a peak wavelength of 509 nm . Thus, the light-emitting element 1 and the light-emitting element 3, which are one aspect of the present invention, can exhibit emission with a shorter peak wavelength and a smaller full width at half maximum in the electroluminescence spectrum and higher color purity than the comparative light-emitting element 2 and the comparative light-emitting element 4 . Therefore, the light-emitting element of one aspect of the present invention is suitable for a display device .

[0323] Also, as shown in FIGS. 13, 15, and Table 2, the light-emitting element 1 and the light-emitting element 3 exhibit high luminous efficiency (current efficiency, power efficiency, and external quantum efficiency). Here, injection from a pair of electrodes The generation probability of singlet excitons generated by the recombination of the injected carriers (holes and electrons) is at most 25%. Therefore, when the external light extraction efficiency is 25%, the external quantum efficiency is , at most 6.25%. In light-emitting element 1 and light-emitting element 3, despite being fluorescent light-emitting elements , an efficiency higher than 6.25% is obtained for the external quantum efficiency. This is because in light-emitting element 1 and light-emitting element 3 according to one aspect of the present invention, in addition to the light emission derived from singlet excitons , due to the heavy atom effect derived from the phosphorescent compound Ir(ppz)3 and the reverse intersystem crossing derived from the TADF material , triplet excitons can contribute to fluorescent light emission .

[0324] Also, the light emission efficiency of light-emitting element 1 and light-emitting element 3 is higher than that of comparative light-emitting element 5. As described above , CBP, which is not a TADF material, is used for the light-emitting layer 130 of comparative light-emitting element 5. Therefore , comparative light-emitting element 5 does not have the function of converting triplet excitons into singlet excitons by reverse intersystem crossing by a TADF material . On the other hand, light-emitting element 1 and light-emitting element 3, which are one aspect of the present invention, have a TADF material in the light-emitting layer 130 . Therefore, light-emitting element 1 and light-emitting element 3 can convert triplet excitons into singlet excitons by reverse intersystem crossing , and can achieve high light emission efficiency .

[0325] <Time-resolved luminescence measurement> Next, time-resolved luminescence measurements of light-emitting element 1, light-emitting element 3, comparative light-emitting element 2, and comparative light-emitting element 4 were performed .

[0326] A picosecond fluorescence lifetime measurement system (manufactured by Hamamatsu Photonics) was used for the measurement. In this measurement , in order to measure the fluorescence lifetime in the light-emitting element, a rectangular pulse voltage was applied to the light-emitting element The light emission that decays from the voltage drop was measured by a streak camera in a time-resolved manner. The pa rse voltage was applied with a period of 10 Hz, and data obtained from repeated measurements were integrated to obtain data with a high S / N ratio. The measurement was also carried out at room temperature (300 K), and the applied pulse voltage was applied in the range of 3 V to around 4 V so that the luminance of the light-emitting element was around 100 0 cd / m 2 . The pulse width during application was 100 μsec, the negative bias voltage was -5 V (when the element drive was OFF), and the measurement time range was 20 μsec. The measurement results are shown in Fig. 17. In Fig. 17, the vertical axis represents the intensity normalized by the light emission intensity in the state where carriers are constantly injected (when the pulse voltage is ON). The horizontal axis represents the elapsed time from the voltage drop of the pulse voltage. As shown in Fig. 17, the light-emitting elements 1 and 3 have a faster decay rate of light emission compared to the comparative light-emitting elements 2 and 4. This means that the excitation energy is quickly converted into light emission. Therefore, in the light-emitting layer, even in a state where the exciton density is high (a state where a large amount of current is flowing), light emission can be efficiently extracted. Therefore, as shown in Figs. 13 and 15, the light-emitting elements 1 and 3 have little roll-off. Also, the external quantum efficiency around 15000 cd / m

[0327] in the high luminance region is 8. 0% for the light-emitting element 1, 7.3% for the comparative light-emitting element 2, 4.8% for the light-emitting element 3, and 4. 2% for the comparative light-emitting element 4. That is, the light-emitting element 1 has higher efficiency than the comparative light-emitting element 2, and the light-emitting element 3 has higher efficiency than the comparative light-emitting element 4. Thus, the fact that there is little roll-off is one of the characteristics of the light-emitting element according to one aspect of the present invention. Furthermore, around 15000 cd / m 2 in the high luminance region, the external quantum efficiency is 8. 0% for the light-emitting element 1, 7.3% for the comparative light-emitting element 2, 4.8% for the light-emitting element 3, and 4. 2% for the comparative light-emitting element 4. That is, the light-emitting element 1 has higher efficiency than the comparative light-emitting element 2, and the light-emitting element 3 has higher efficiency than the comparative light-emitting element 4. Thus, the fact that there is little roll-off is one of the characteristics of the light-emitting element according to one aspect of the present invention.

[0328] ​​​​ <CV Measurement Results> Next, the electrochemical properties (oxidation reaction properties and reduction reaction properties) of the materials used in the light-emitting layer of the above-described light-emitting element were measured by cyclic voltammetry (CV). For the measurement, an electrochemical analyzer (manufactured by BAS Inc., model number: ALS model 600A or 600C) was used, and a solution in which each material was dissolved in N,N-dimethylformamide (abbreviation: DMF) was measured. In the measurement, the potential of the working electrode with respect to the reference electrode was changed within an appropriate range to obtain the oxidation peak potential and the reduction peak potential, respectively. Also, since it is estimated that the redox potential of the reference electrode is -4.94 eV, the HOMO level and LUMO level of each compound were calculated from this value and the obtained peak potential. The HOMO level of Ir(ppz)3 calculated from the CV measurement was -5.39 eV, and the LUMO level was -1.77 eV. Also, the HOMO level of 4PCCzBfpm was -5.70 eV and the LUMO level was -2.84 eV. Also, the HOMO level of 4PCCzPBfpm was -5.64 eV and the LUMO level was -3.01 eV.

[0329] As described above, the LUMO levels of 4PCCzBfpm and 4PCCzPBfpm are lower than the LUMO level of Ir (ppz)3, and the HOMO level of Ir(ppz)3 is higher than the HOMO levels of 4PCCz Bfpm and 4PCCzPBfpm. Therefore, when the compound is used in the light-emitting layer as in Light-Emitting Element 1 and Light-Emitting Element 3, electrons and holes, which are carriers injected from a pair of electrodes, can efficiently recombine with 4PCCzBfpm and 4PCCzPBfpm.

[0330] (ppz)3, and the HOMO level of Ir(ppz)3 is higher than the HOMO levels of 4PCCz Bfpm and 4PCCzPBfpm. Therefore, when the compound is used in the light-emitting layer as in Light-Emitting Element 1 and Light-Emitting Element 3, electrons and holes, which are carriers injected from a pair of electrodes, can efficiently recombine with 4PCCzBfpm and 4PCCzPBfpm. ​Each is injected into Ir(ppz)3, and 4PCCzBfpm and 4PCCzPBfpm can form an exciplex with Ir(ppz)3. Therefore, the light-emitting element 1 and the light-emitting element 3 can be said to be light-emitting elements using ExEF.

[0331] In addition, the exciplex formed by 4PCCzBfpm and Ir(ppz)3 is an exciplex having a LUMO level in 4PCCzB fpm and a HOMO level in Ir(ppz)3. In addition, the energy difference between the LUMO level of 4PCCzBfpm and the HOMO level of Ir(ppz)3 is 2.55 eV. This value is approximately consistent with the emission energy (2.42 eV) calculated from the peak wavelength of the emission spectrum of the comparative light-emitting element 2 shown in FIG. 16 . From this, it can be said that the emission spectrum of the comparative light-emitting element 2 is emission based on the exciplex formed by 4PCCzBfpm and Ir(p pz)3. Note that since the difference between the S1 level and the T1 level of the exciplex is small, the emission energy can be regarded as the energy of the S1 level and the T1 level of the exciplex (2.42 eV).

[0332] Similarly, the exciplex formed by 4PCCzPBfpm and Ir(ppz)3 is an exciplex having a LUMO level in 4PCC zPBfpm and a HOMO level in Ir(ppz)3. In addition, the energy difference between the LUMO level of 4PCCzPBfpm and the HOMO level of Ir(ppz)3 is 2.38 eV. This value is approximately consistent with the emission energy (2.30 eV) calculated from the peak wavelength of the emission spectrum of the comparative light-emitting element 4 shown in FIG. 16. From this, it can be said that the emission spectrum of the comparative light-emitting element 4 is 4PCCzPBfpm and It can be said that the emission is based on an exciplex formed by Ir(ppz)3. The exciplex has a small energy difference between the S1 level and the T1 level, so the emission energy can be regarded as the energy of the S1 level and the T1 level (2.30 eV) of the exciplex.

[0333] <Relationship between the emission spectrum of the exciplex and the absorption spectrum of the guest material> Next, the absorption spectrum in a toluene solution of coumarin545T was measured and the results are shown in Fig. 18. Also, in accordance with Fig. 18, the emission spectra of the exciplexes exhibited by Comparative Light Emitting Element 2 and Comparative Light Emitting Element 4 are shown. For the measurement of the absorption spectrum, a UV-visible spectrophotometer (manufactured by JASCO Corporation, model V550) was used and the measurement was performed at room temperature (in an atmosphere maintained at 23 °C).

[0334] As shown in Fig. 18, the absorption spectrum of coumarin545T and the emission spectra of the exciplexes exhibited by Comparative Light Emitting Element 2 and Comparative Light Emitting Element 4 have an overlapping region. Therefore, it is possible to efficiently transfer excitation energy from the exciplexes formed by 4PCCzBfpm and Ir(ppz)3 and the exciplexes formed by 4PCCzPBfpm and Ir(ppz)3 to the fluorescent compound coumarin5 45T. Also, thereby, it is possible to provide a light emitting element that exhibits emission having a peak wavelength shorter than the peak wavelength of the electroluminescence spectrum of the exciplex, like the electroluminescence spectra of Light Emitting Element 1 and Light Emitting Element 3 shown in Fig. 1 6.

[0335] <Measurement of the T1 level> Next, the T1 levels of 4PCCzBfpm and 4PCCzPBfpm were determined. The measurement method is ​​​​​​​​This will be described later. As a result, the T1 level of 4PCCzBfpm was calculated to be 2.58 eV, and that of 4PCCzPBf pm was calculated to be 2.46 eV.

[0336] In addition, in order to estimate the T1 level of Ir(ppz)3, absorption spectra and emission spectra were measured. A dichloromethane solution in which Ir(ppz)3 was dissolved was prepared, and an absorption spectrum was measured using a quartz cell . An ultraviolet-visible spectrophotometer (manufactured by JASCO Corporation, model V550) was used for the measurement of the absorption spectrum. From the spectrum of the measured sample, the absorption spectra of the quartz cell and the solvent were subtracted. The measurement was performed at room temperature (an atmosphere maintained at 23 °C).

[0337] Based on the above absorption spectrum data, the absorption edge was determined, and the transition energy assuming a direct transition was estimated. As a result, the transition energy of Ir(ppz)3 was calculated to be 3.27 eV. Since Ir(ppz)3 is a phosphorescent compound, the absorption edge on the lowest energy side is an absorption band based on the transition from the triplet excited state. Therefore, the T1 level of Ir(ppz)3 was calculated to be 3.27 eV from the absorption edge.

[0338] From the above measurement results, the T1 level (2.58 eV) of 4PCCzBfpm and the T1 level (2.46 eV) of 4PCCz PBfpm are lower than the T1 level (3.27 eV ) of Ir(ppz)3, and the T1 level (2.58 eV) of 4PCCzBfpm and the T1 level (2.46 eV) of 4PCCzPBfpm are higher than the T1 level (2.42 eV) of the excited complex formed by 4PCCzBfpm and Ir(ppz)3 and the T1 level (2.30 eV) of the excited complex formed by 4PCCzPBfpm and Ir(ppz)3. Therefore, 4PCCzBfpm and ​​​​​​​​​ The triplet excitation energy of the exciplex formed by Ir(ppz)3 and 4PCCzPBfpm with Ir(ppz)3 is not quenched by 4PCCzBfpm, 4PCCzPBfpm, and Ir(pp z)3 respectively. Therefore, the triplet excitation energy of the exciplex can be converted into singlet excitation energy by reverse intersystem crossing to be converted into luminescence, or transferred to a fluorescent compound.

[0339] In addition, when attempting to measure the emission spectrum of Ir(ppz)3 at room temperature, no emission of Ir(pp )3 was observed. Non-Patent Document 1 describes that the emission quantum yield of Ir(ppz)3 is less than 1% at room temperature. From this, it can be seen that Ir(ppz)3 is a material that does not emit light at room temperature. That is, even when using a compound with a low emission quantum yield of less than 1%, a light-emitting device having a high emission efficiency can be obtained.

[0340] <Transient Fluorescence Characteristics of Host Material> Here, in order to confirm that 4PCCzBfpm and 4PCCzPBf pm used in Light-Emitting Device 1 and Light-Emitting Device 3 are TADF materials, the transient fluorescence characteristics were measured by time-resolved luminescence measurement.

[0341] For the time-resolved luminescence measurement, a thin film sample co-evaporated on a quartz substrate so that the weight ratio of bis[2-(diphenylphosphino)phenyl] ether oxide (abbreviation: DPEPO) to 4PCCzPBfpm is 0.8:0.2 and the thickness is 50 nm, and a thin film sample co-evaporated so that the weight ratio of DPEPO to 4PCCzBfpm (DPE O:4PCCzPBfpm) is 0.8:0.2 and the thickness is 50 nm, The thin film sample co-evaporated so that PO:4PCCzBfpm) becomes 0.8:0.2 and the thickness becomes 50 nm was used for the measurement. The measurement was carried out using the thin film sample co-evaporated as described above.

[0342] For the measurement, a picosecond fluorescence lifetime measurement system (manufactured by Hamamatsu Photonics) was used. In this measurement, To measure the lifetime of the fluorescence emission exhibited by the thin film, the thin film was irradiated with a pulsed laser, and the emission that decayed after the laser irradiation was time-resolvedly measured by a streak camera. As the pulsed laser, a nitrogen gas laser with a wavelength of 337 nm was used, and a 500 ps pulsed laser was irradiated onto the thin film at a cycle of 10 Hz. By integrating the repeatedly measured data, data with a high S / N ratio was obtained. Also, the measurement was carried out at room temperature (an atmosphere maintained at 23°C).

[0343] The transient fluorescence characteristics of 4PCCzBfpm obtained by the measurement are shown in FIGS. 19(A) and (B). Note that FIG. 19(A) shows the measurement results of the emission component with a short emission lifetime, and FIG. 19(B) shows the measurement results of the emission component with a long emission lifetime. The transient fluorescence characteristics of 4PCCzPBfpm are not particularly shown, but the measurement and the following calculations were performed in the same manner as for 4PCCzBfpm.

[0344] Also, for the decay curves shown in FIGS. 19(A) and (B), fitting was performed using the following mathematical formula (4).

[0345]

Equation

[0346] In the mathematical formula (4), L represents the normalized emission intensity, and t represents the elapsed time. As a result of performing the fitting of the decay curve, for the thin films of 4PCCzBfpm and 4PCCzPBfpm, The luminescence exhibited by the film sample contains a plurality of luminescent components having different fluorescence lifetimes. It was found that. The luminescent components of the thin film sample of 4PCCzBfpm include at least an initial fluorescence component with a fluorescence lifetime of 11.7 ns and a delayed fluorescence component with the longest lifetime of 217 μs. The luminescent components of the thin film sample of 4PCCzPBfpm include at least an initial fluorescence component of 11.0 ns and a delayed fluorescence component with the longest lifetime of 301 μs. That is, it can be said that 4PCCzBfpm and 4PCCzPBfpm are thermally activated delayed fluorescence materials that exhibit delayed fluorescence at room temperature.

[0347] <Measurement of S1 level and T1 level> In addition, in order for inverse intersystem crossing to occur efficiently and exhibit thermally activated delayed fluorescence, the energy difference between the S1 level and the T1 level is preferably greater than 0 eV and less than or equal to 0.3 eV, and more preferably greater than 0 eV and less than or equal to 0.2 eV. Therefore, next, measurements were performed to calculate the S1 level and T1 level of 4PCCzBfpm and 4P CCzPBfpm.

[0348] To calculate the S1 level and T1 level, the emission spectra of 4PCCzBfpm and 4PCCzPBfp m were measured. The measurement results of the emission spectrum of 4PCCzBfpm are shown in Fig. 2 0, and the measurement results of the emission spectrum of 4PCCzPBfpm are shown in Fig. 21, respectively.

[0349] For the measurement of the emission spectrum, a microscopic PL device LabRAM HR-PL (manufactured by Horiba, Ltd.) was used. The measurement temperature was 10 K, and a He-Cd laser (325 nm) was used as the excitation light. A CCD detector was used as the detector. The thin film for measurement was deposited on a quartz substrate with a thickness of A film was formed at 50 nm, and another quartz substrate was attached to the quartz substrate from the vapor deposition surface side in a nitrogen atmosphere, and then it was used for measurement. After attachment, it was used for measurement.

[0350] In addition to the measurement of the normal emission spectrum, the measurement of the time-resolved emission spectrum focusing on the long-lived emission was also performed for the measurement of the emission spectrum. The measurement of this emission spectrum was carried out at a low temperature (10 K). Therefore, in the measurement of the normal emission spectrum, in addition to fluorescence, which is the main emission component, a part of phosphorescence was also observed. Also, in the measurement of the time-resolved emission spectrum focusing on the long-lived emission, mainly phosphorescence was observed. From the results of the measured emission spectra above, the wavelengths of the fluorescence component and the shortest-wavelength side peak (including shoulder) of the phosphorescence component of the emission spectrum of 4PCCzBfpm were 45

[0351] 5 nm and 480 nm, respectively. Also, the wavelengths of the fluorescence component and the shortest-wavelength side peak (including shoulder) of the phosphorescence component of the emission spectrum of 4PCCzPBfpm were 480 nm and 505 nm, respectively. Therefore, the S1 level of 4PCCzBfpm calculated from the wavelengths of the above peaks (including shoulders) was 2.72 eV, the T1 level was 2.58 eV, and the energy difference between the S1 level and the T1 level was calculated to be 0.14 eV. Also, the S1 level of 4PCCzPBfpm was 2 .58 eV, the T1 level was 2.46 eV, and the energy difference between the S1 level and the T1 level was calculated to be

[0352] 0.12 eV. Moreover, from the results of the measured emission spectra above, the wavelengths of the rise on the short-wavelength side of the fluorescence component and the phosphorescence component of the emission spectrum of 4PCCzBfpm were 435 nm and 46 respectively. Calculated.

[0353] In addition, from the results of the measured emission spectra above, the fluorescence component and the phosphorescence component of the emission spectrum of 4PCCzBfpm It was 4 nm. Also, the fluorescence component and phosphorescence component of the emission spectrum of 4PCCzPBfpm The wavelengths of the rise on the short-wavelength side were 458 nm and 491 nm, respectively. Note that As the wavelength of the rise on the short-wavelength side of the emission spectrum, a tangent was drawn at the wavelength where the slope of the tangent in the spectrum has a maximum value, and the wavelength of the intersection of the tangent and the horizontal axis was taken as the wavelength.

[0354] The S1 level of 4PCCzBfpm calculated from the rise wavelength as described above was 2.85 eV, the T1 level was 2.67 eV, and the energy difference between the S1 level and the T1 level was 0.1 8 eV was calculated. Also, the S1 level of 4PCCzPBfpm was 2.71 eV, and the T1 level was 2.53 eV, and the energy difference between the S1 level and the T1 level was calculated to be 0.18 eV was calculated.

[0355] As described above, the wavelengths of the peaks (including shoulders) on the shortest-wavelength side of the emission spectrum and the energy differences between the S1 level and the T1 level of 4PCCzPBfpm and 4PCCzBfpm calculated from the wavelengths of the rise on the short-wavelength side were all greater than 0 eV and less than or equal to 0.2 eV and were very small values. Therefore, both 4PCCzPBfpm and 4PCCzBfpm have the function of converting triplet excitation energy into singlet excitation energy by reverse intersystem crossing and have the function of exhibiting thermally activated delayed fluorescence.

[0356] <Reliability of the light-emitting device> Fig. 22 shows the results of the constant-current drive test at 0.5 mA for the light-emitting device 1, the comparative light-emitting device 2, the light-emitting device 3, the comparative light-emitting device 4, and the comparative light-emitting device 5 From Fig. 22, the light-emitting device 1 has better reliability than the comparative light-emitting device 2, and the light-emitting device 3 has better reliability than the comparative light-emitting device 4 has. It has been found that. The difference between the light-emitting element 1 and the comparative light-emitting element 2, and the difference between the light-emitting element 3 and the comparative light-emitting element 4 are respectively the presence or absence of the fluorescent compound. As described above, light emission from the fluorescent compound is obtained from the light-emitting element 1 and the light-emitting element 3, and light emission from the excitation complex is obtained from the comparative light-emitting element 2 and the comparative light-emitting element 4. Therefore, as in the light-emitting element of one aspect of the present invention, it has been found that obtaining light emission from a fluorescent compound has better reliability. Also, it has been found that the light-emitting element 1 and the light-emitting element 3 have better reliability than the comparative light-emitting element 5. By using a host material having TADF properties as the host material, a light-emitting element having high reliability can be obtained.

Example

[0357] In this example, an example of manufacturing a light-emitting element of one aspect of the present invention and a comparative light-emitting element will be described. The configuration of the light-emitting element manufactured in this example is the same as that in FIG. 1(A). The details of the element structure are shown in Table 3. Also, the structures and abbreviations of the compounds used are shown below. For the structures and abbreviations of other compounds, refer to Example 1 and the previous embodiments.

[0358]

Chemical formula

[0359]

Table 3

[0360] <Manufacture of the light-emitting element> The manufacturing method of the light-emitting element manufactured in this example is shown below.

[0361] ≪Manufacture of the light-emitting element 6≫ ​​​​​On a glass substrate, an ITSO film was formed as electrode 101 to a thickness of 70 nm. . The electrode area of electrode 101 was 4 mm 2 (2 mm × 2 mm).

[0362] Next, as a hole injection layer 111 on electrode 101, DBT3P-II and molybdenum oxide (MoO3) were co-evaporated so that the weight ratio (DBT3P-II:MoO3) was 1:0.5 and the thickness was 45 nm.

[0363] Next, as a hole transport layer 112 on hole injection layer 111, PCBBi1BP was evaporated to a thickness of 20 nm.

[0364] Next, as a light-emitting layer 130 on hole transport layer 112, 4PCCzBfpm, GD270 (manufactured by Jilin OLED Co., Ltd.), and 2,8-di-tert-butyl-5,11-bis(4-ter t-butylphenyl)-6,12-diphenyltetracene (abbreviation: TBRb) were co-evaporated so that the weight ratio (4PCCzBfpm:GD270:TBRb) was 0.8:0.2:0.01 and the thickness was 40 nm. In light-emitting layer 130, GD27 0 is a phosphorescent compound and TBRb is a fluorescent compound.

[0365] Next, on light-emitting layer 130, as an electron transport layer 118, 4,6mCzP2Pm was evaporated to a thickness of 2 0 nm and NBPhen was evaporated to a thickness of 10 nm in sequence. Next , on electron transport layer 118, as an electron injection layer 119, LiF was evaporated to a thickness of 1 nm .

[0366] Next, on electron injection layer 119, as electrode 102, aluminum (Al) was deposited to a thickness of 20 It was formed to be 0 nm.

[0367] Next, in a glove box under a nitrogen atmosphere, a glass substrate for sealing was fixed to the glass substrate on which the organic material was formed using an organic EL sealing material, thereby sealing the light-emitting element 6. Specifically, the sealing material was applied around the organic material formed on the glass substrate, and the glass substrate and the glass substrate for sealing were bonded together, and ultraviolet light with a wavelength of 365 nm was irradiated at 6 J / cm 2 and heat-treated at 80 °C for 1 hour. The light-emitting element 6 was obtained through the above steps.

[0368] ≪Fabrication of Comparative Light-Emitting Element 7≫ Comparative light-emitting element 7 differed only in the formation process of the light-emitting layer 130 from the light-emitting element 6 shown above, and the other processes were the same as those of the light-emitting element 6.

[0369] As the light-emitting layer 130 of the comparative light-emitting element 7, 4PCCzBfpm and GD270 were co-evaporated so that the weight ratio (4PCCzBfpm:GD270) was 0.8:0.2 and the thickness was 40 nm. Compared with the light-emitting layer 130 of the light-emitting element 6, the light-emitting layer 130 of the comparative light-emitting element 7 does not contain TBRb, which is a fluorescent compound.

[0370] ≪Fabrication of Comparative Light-Emitting Element 8≫ On the glass substrate, an ITSO film was formed as the electrode 101 to a thickness of 70 nm. Note that the electrode area of the electrode 101 was 4 mm 2 (2 mm × 2 mm).

[0371] Next, as the hole injection layer 111 on the electrode 101, DBT3P-II and molybdenum oxide (MoO3) were used so that the weight ratio (DBT3P-II:MoO3) was 1:0.5. And co-evaporated so that the thickness becomes 45 nm.

[0372] Next, as a hole transport layer 112 on the hole injection layer 111, mCzFLP was deposited so that the thickness becomes 20 nm thereby.

[0373] Next, as a light-emitting layer 130 on the hole transport layer 112, CBP, GD270, and TBRb were co-evaporated so that the weight ratio (CBP:GD270:TBRb) becomes 0.8:0.2:0.01 and the thickness becomes 30 nm. The difference in the light-emitting layer 130 between the light-emitting device 6 and the comparative light-emitting device 8 is the host material. The light-emitting device 6 uses a TADF material, and the comparative light-emitting device 8 uses CBP which is not a TADF material.

[0374] Next, on the light-emitting layer 130, as an electron transport layer 118, bathocuproine (abbreviation: BCP ) was sequentially deposited so that the thickness becomes 10 nm and the thickness of NBPhen becomes 15 nm. Next, on the electron transport layer 118, as an electron injection layer 119, LiF was deposited so that the thickness becomes 1 nm thereby.

[0375] Next, on the electron injection layer 119, as an electrode 102, aluminum (Al) was formed so that the thickness becomes 20 0 nm.

[0376] Next, in a glove box under a nitrogen atmosphere, a glass substrate for sealing was fixed to the glass substrate on which an organic material was formed using an organic EL sealing material, thereby sealing the comparative light-emitting device 8. Specifically, a sealing material was applied around the organic material formed on the glass substrate , the glass substrate and the glass substrate for sealing were bonded together, and ultraviolet light having a wavelength of 365 nm was irradiated at 6 J / cm 2Irradiated and heat-treated at 80°C for 1 hour. Through the above process, the comparative light-emitting element 8 was obtained.

[0377] ≪Fabrication of Comparative Light-Emitting Element 9≫ Comparative light-emitting element 9 is different from the previously shown comparative light-emitting element 8 only in the forming process of the light-emitting layer 130 and the electron transport layer 118, and the other processes were carried out in the same manufacturing method as that of comparative light-emitting element 8. For the light-emitting layer 130 of comparative light-emitting element 9, bis[2-(diphenylphosphino)phenyl

[0378] ether oxide (abbreviation: DPEPO), 4PCCzBfpm, and TBRb were co-evaporated so that the weight ratio (DPEPO:4PCCzBfpm:TBRb) became 0.8:0.2:0.01 and the thickness became 30 nm. Comparing the light-emitting layer 130 of light-emitting element 6 with the light-emitting layer 130 of comparative light-emitting element 9, the light-emitting layer 130 of comparative light-emitting element 9 does not contain a phosphorescent compound. ether oxide (abbreviation: DPEPO), 4PCCzBfpm, and TBRb were co-evaporated so that the weight ratio (DPEPO:4PCCzBfpm:TBRb) became 0.8:0.2:0.01 and the thickness became 30 nm. Comparing the light-emitting layer 130 of light-emitting element 6 with the light-emitting layer 130 of comparative light-emitting element 9, the light-emitting layer 130 of comparative light-emitting element 9 does not contain a phosphorescent compound. weight ratio (DPEPO:4PCCzBfpm:TBRb) became 0.8:0.2:0.01 and the thickness became 30 nm. Comparing the light-emitting layer 130 of light-emitting element 6 with the light-emitting layer 130 of comparative light-emitting element 9, the light-emitting layer 130 of comparative light-emitting element 9 does not contain a phosphorescent compound. Next, on the light-emitting layer 130, as the electron transport layer 118, DPEPO was deposited to a thickness of 5 nm and 1,3,5-tri[3-(3-pyridyl)phenyl]benzene (abbreviation: TmP yPB) was deposited to a thickness of 20 nm in sequence. Next, on the light-emitting layer 130, as the electron transport layer 118, DPEPO was deposited to a thickness of 5 nm and 1,3,5-tri[3-(3-pyridyl)phenyl]benzene (abbreviation: TmP

[0379] Next, on the light-emitting layer 130, as the electron transport layer 118, DPEPO was deposited to a thickness of 5 nm and 1,3,5-tri[3-(3-pyridyl)phenyl]benzene (abbreviation: TmP yPB) was deposited to a thickness of 20 nm in sequence. yPB) was deposited to a thickness of 20 nm in sequence.

[0380] <Characteristics of the Light-Emitting Element> Next, the characteristics of the fabricated light-emitting element 6 and comparative light-emitting elements 7 to 9 were measured. The measurement method was the same as that in Example 1.

[0381] The current efficiency-luminance characteristics of light-emitting element 6 and comparative light-emitting elements 7 to 9 are shown in Fig. 23, the current-voltage characteristics are shown in Fig. 24, and the external quantum efficiency-luminance characteristics are shown in Fig. 25, respectively. Also, For light-emitting element 6 and comparative light-emitting elements 7 to 9, 2.5 mA / cm2 Electricity The electroluminescence spectrum when a current was applied at a current density is shown in Figure 26. was carried out at room temperature (atmosphere maintained at 23°C).

[0382] Also, 1000cd / m 2 Light-emitting element 6 and comparative light-emitting element 7 to comparative light-emitting element 8 are The device characteristics of Device 9 are shown in Table 4.

[0383] [Table 4]

[0384] As shown in FIG. 26, the emission spectra of the light-emitting element 6, the comparative light-emitting element 8, and the comparative light-emitting element 9 are The peak wavelengths are 565 nm, 562 nm, and 561 nm, respectively, and the full width at half maximum is The light-emitting element 6 and the comparative light-emitting element 8 emitted yellow light at wavelengths of 72 nm, 67 nm, and 69 nm, respectively. The light emitted by the light-emitting element 8 and the comparative light-emitting element 9 is derived from the fluorescent compound TBRb. The emission spectrum of the comparative light-emitting element 7 has a peak wavelength of 528 nm. The comparative light-emitting element 7 emitted green light with a full width at half maximum of 76 nm. As described above, the light-emitting element 6 according to one embodiment of the present invention has a relatively low The full width at half maximum of the peak wavelength of the emission spectrum is smaller than that of comparative light emitting element 7, and the emission has high color purity. Therefore, the light-emitting element of one embodiment of the present invention is suitable for a display device.

[0385] 23 and 25 and Table 4, the external quantum efficiency of the light-emitting element 6 was Although it is an optical element, its external quantum efficiency is lower than the maximum value of 6.25% for fluorescent light-emitting elements. This is because the light-emitting element 6 according to one embodiment of the present invention exhibits high efficiency due to the singlet excitation. In addition to the light emission derived from the screwdriver, triplet excitons can contribute to fluorescence emission by passing through GD270, which is a phosphorescent compound. This is because. In addition, as described above, 4PCCzBfpm included in the light emitting element 6 is a TADF material. Therefore, triplet excitons can contribute to fluorescence emission by reverse intersystem crossing derived from the TADF material, and thus the luminous efficiency can be improved. Moreover, the luminous efficiency of the light emitting element 6 is higher than that of the comparative light emitting element 8. As described above, CBP, which is not a TADF material, is used for the light emitting layer 130 of the comparative light emitting element 8. Therefore, the comparative light emitting element 8 does not have the function of converting triplet excitons into singlet excitons by reverse intersystem crossing by the TADF material.

[0386] On the other hand, the light emitting element 6, which is one aspect of the present invention, has a TADF material in the light emitting layer 130. Therefore, the light emitting element 6 can convert triplet excitons into singlet excitons by utilizing reverse intersystem crossing by the TADF material, and can achieve higher luminous efficiency than the comparative light emitting element 8. Moreover, the luminous efficiency of the light emitting element 6 is higher than that of the comparative light emitting element 9. As described above, although the light emitting layer 130 of the comparative light emitting element 9 contains a TADF material, it does not contain a phosphorescent compound. Therefore, the comparative light emitting element 9 cannot contribute triplet excitons to fluorescence emission via a phosphorescent compound. On the other hand, the light emitting element 6, which is one aspect of the present invention, contains a phosphorescent compound in addition to the TADF material in the light emitting layer 130. Therefore, in addition to the high-efficiency effect due to reverse intersystem crossing derived from the TADF material, the light emitting element 6 can contribute triplet excitons to fluorescence emission via a phosphorescent compound.

[0387] Moreover, the luminous efficiency of the light emitting element 6 is higher than that of the comparative light emitting element 9. As described above, although the light emitting layer 130 of the comparative light emitting element 9 contains a TADF material, it does not contain a phosphorescent compound. Therefore, the comparative light emitting element 9 cannot contribute triplet excitons to fluorescence emission via a phosphorescent compound. On the other hand, the light emitting element 6, which is one aspect of the present invention, contains a phosphorescent compound in addition to the TADF material in the light emitting layer 130. Therefore, in addition to the high-efficiency effect due to reverse intersystem crossing derived from the TADF material, the light emitting element 6 can contribute triplet excitons to fluorescence emission via a phosphorescent compound. In addition, the light emitting element 6 contains a phosphorescent compound in addition to the TADF material in the light emitting layer 130. Therefore, in addition to the high-efficiency effect due to reverse intersystem crossing derived from the TADF material, the light emitting element 6 can contribute triplet excitons to fluorescence emission via a phosphorescent compound. ​It is possible to achieve a luminous efficiency higher than that of the comparative light-emitting element 9.

[0388] <Time-resolved luminescence measurement> Next, time-resolved luminescence measurements of the light-emitting element 6 and the comparative light-emitting element 7 were performed. The results are shown in Fig. 27 as shown. The measurement method is the same as the method shown in Example 1.

[0389] As shown in Fig. 27, the light-emitting element 6 has a faster decay rate of luminescence compared to the comparative light-emitting element 7 This means that the excitation energy is quickly converted into luminescence. Therefore , even in a state where the exciton density is high (a state where a large amount of current is flowing) in the light-emitting layer luminescence can be efficiently extracted. Therefore, as shown in Figs. 23 and 25, the light-emitting element 6 has little roll-off. Also, the light-emitting element 6 has a higher luminous efficiency than the comparative light-emitting element 7 The light-emitting layer 130 of the light-emitting element 6 has a configuration in which TBRb, which is a fluorescent compound, is added to the light-emitting layer of the comparative light-emitting element 7 From Fig. 27, it can be seen that by adding the fluorescent compound, the decay rate of luminescence is improved. Therefore, the deactivation of excitons is suppressed, and it can be said that the light-emitting element 6 has an improved luminous efficiency compared to the comparative light-emitting element 7. <Reliability of the light-emitting element>

[0390] <Reliability of the light-emitting element> Fig. 28 shows the results of the constant-current drive test at 2.0 mA for the light-emitting element 6, the comparative light-emitting element 7, and the comparative light-emitting element 8. From Fig. 28, it was found that the light-emitting element 6 has better reliability than the comparative light-emitting element 7 The difference between the light-emitting element 6 and the comparative light-emitting element 7 is the presence or absence of the fluorescent compound. As described above, luminescence from the fluorescent compound is obtained from the light-emitting element 6, and luminescence from the phosphorescent compound is obtained from the comparative light-emitting element 7 Therefore, like the light-emitting element of one aspect of the present invention, a fluorescent compound It was found that obtaining light emission from the object has better reliability. Also, the light-emitting element 6 was found to have better reliability than the comparative light-emitting element 8. By using a host material having TADF properties as the host material, a light-emitting element having high reliability can be obtained .

Example

[0391] In this example, an example of manufacturing a light-emitting element and a comparative light-emitting element according to one aspect of the present invention will be described. The configuration of the light-emitting element manufactured in this example is the same as that in FIG. 1(A). The details of the element structure are shown in Table 5. Also, the structures and abbreviations of the compounds used are shown below. For the structures and abbreviations of other compounds, refer to the previous examples and embodiments.

[0392]

Chemical formula

[0393]

Table 5

[0394] <Manufacture of light-emitting element> Below, the manufacturing method of the light-emitting element manufactured in this example is shown.

[0395] ≪Manufacture of light-emitting element 10≫ As the electrode 101 on the glass substrate, an ITSO film was formed to a thickness of 70 nm . The electrode area of the electrode 101 was 4 mm 2 (2 mm × 2 mm).

[0396] Next, as the hole injection layer 111 on the electrode 101, DBT3P-II and molybdenum oxide (MoO3) were used in a weight ratio (DBT3P-II:MoO3) of 1:0.5 And co-evaporated so that the thickness becomes 45 nm.

[0397] Next, as the hole transport layer 112 on the hole injection layer 111, PCBBi1BP was evaporated so that the thickness becomes 20 nm.

[0398] Next, as the light emitting layer 130 on the hole transport layer 112, PCCzPTzn, GD270 ( manufactured by Jilin OLED Co., Ltd.), TBRb, were co-evaporated so that the weight ratio (PCCzPTzn:GD270:TBR b) becomes 0.8:0.2:0.01 and the thickness becomes 40 nm. In the light emitting layer 130, GD270 is a phosphorescent compound and TBRb is a fluorescent compound.

[0399] Next, on the light emitting layer 130, as the electron transport layer 118, PCCzPTzn was evaporated so that the thickness becomes 20 n m, and then NBPhen was evaporated so that the thickness becomes 10 nm. Next, on the electron transport layer 118, as the electron injection layer 119, LiF was evaporated so that the thickness becomes 1 nm.

[0400] Next, on the electron injection layer 119, as the electrode 102, aluminum (Al) was formed so that the thickness becomes 20 0 nm.

[0401] Next, in a glove box under a nitrogen atmosphere, a glass substrate for sealing was fixed to the glass substrate on which the organic material was formed using an organic EL sealing material, thereby sealing the light emitting element 1 0. Specifically, a sealing material was applied around the organic material formed on the glass substrate, the glass substrate and the glass substrate for sealing were bonded together, irradiated with ultraviolet light having a wavelength of 365 nm at 6 J / cm 6J / cm 2 and heat-treated at 80 °C for 1 hour. Through the above steps, the light emitting element 10 was obtained. ​​​​Done.

[0402] <<Fabrication of Comparative Light-Emitting Element 11>> Comparative light-emitting element 11 is different from the light-emitting element 10 shown above only in the formation process of the light-emitting layer 130, and the other processes were the same as those of the light-emitting element 10.

[0403] As the light-emitting layer 130 of the comparative light-emitting element 11, PCCzPTzn and GD270 were co-evaporated so that the weight ratio (PCCzPTzn:GD270) was 0.8:0.2 and the thickness was 40 nm. When compared with the light-emitting layer 130 of the light-emitting element 10, the light-emitting layer 130 of the comparative light-emitting element 1 1 does not contain the fluorescent compound TBRb.

[0404] <<Fabrication of Comparative Light-Emitting Element 12>> Comparative light-emitting element 12 is different from the light-emitting element 10 shown above only in the formation processes of the hole transport layer 112 and the light-emitting layer 130, and the other processes were the same as those of the light-emitting element 10.

[0405] As the hole transport layer 112 of the comparative light-emitting element 12, PCCP was evaporated on the hole injection layer 111 to a thickness of 2 0 nm.

[0406] Next, as the light-emitting layer 130, PCCzPTzn and TBRb were co-evaporated so that the weight ratio (PCCzP Tzn:TBRb) was 1:0.01 and the thickness was 30 nm. When compared with the light-emitting layer 130 of the light-emitting element 10, the light-emitting layer 130 of the comparative light-emitting element 12 does not contain the phosphorescent compound GD270.

[0407] <Characteristics of Light-Emitting Elements> Next, the characteristics of the above-fabricated light-emitting element 10, comparative light-emitting element 11, comparative light-emitting element 12, and the aforementioned comparative light-emitting element 8 were measured. The measurement method was the same as that in Example 1. ​​

[0408] Current efficiency of light-emitting element 10, comparative light-emitting element 11, comparative light-emitting element 12, and comparative light-emitting element 8 - The luminance characteristics are shown in Fig. 29, the current-voltage characteristics are shown in Fig. 30, and the external quantum efficiency-luminance characteristics are shown in Fig. 31, respectively. Further, for light-emitting element 10, comparative light-emitting element 11, comparative light-emitting element 12, and comparative light-emitting element 8, the electroluminescence spectra 2 when current is passed at a current density of 2.5 mA / cm are shown in Fig. 32. The measurement of each light-emitting element was performed at room temperature (an atmosphere maintained at 23°C) .

[0409] Also, the device characteristics of light-emitting element 10, comparative light-emitting element 11, and comparative light-emitting 2 element 12 in the vicinity of 1000 cd / m are shown in Table 6.

[0410]

Table 6

[0411] As shown in Fig. 32, the emission spectra of light-emitting element 10, comparative light-emitting element 8, and comparative light-emitting element 12 have peak wavelengths of 566 nm, 562 nm, and 560 nm, respectively, and show yellow emission with full widths at half maximum of about 74 nm, 67 nm, and 69 nm, respectively. Therefore, the emission exhibited by light-emitting element 10 , comparative light-emitting element 8, and comparative light-emitting element 12 is emission derived from the fluorescent compound TBRb. Note that the emission spectrum of comparative light-emitting element 11 shows green emission with a peak wavelength of 533 nm and a full width at half maximum of 78 nm. Therefore, the emission exhibited by comparative light-emitting element 11 is emission derived from GD270. Thus, the light-emitting element 10, which is one aspect of the present invention, has a smaller full width at half maximum of the peak wavelength of the emission spectrum than comparative light-emitting element 11, and has higher color purity. can exhibit high-intensity light emission. Therefore, the light-emitting element according to one aspect of the present invention is suitable for a display device is suitable for.

[0412] Also, as shown in FIGS. 29 and 31 and Table 6, although the light-emitting element 10 is a fluorescent light-emitting element a higher efficiency than 6.25% in external quantum efficiency has been obtained. This is because in the light-emitting element 10 according to one aspect of the present invention, in addition to the light emission derived from singlet excitons, triplet excitons can be made to contribute to fluorescent light emission by passing through GD270, which is a phosphorescent compound In addition, as will be described later, PCCzPTz n contained in the light-emitting element 10 is a TADF material. Therefore, triplet excitons can be made to contribute to fluorescent light emission by reverse intersystem crossing derived from the TADF material, and thus the light emission efficiency can be improved

[0413] Also, the light emission efficiency of the light-emitting element 10 is higher than that of the comparative light-emitting element 8. As described above, CBP, which is not a TADF material, is used for the light-emitting layer 130 of the comparative light-emitting element 8. Therefore, the comparative light-emitting element 8 does not have the function of converting triplet excitons into singlet excitons by reverse intersystem crossing by a TADF material. On the other hand, the light-emitting element 10, which is one aspect of the present invention, has a TADF material in the light-emitting layer 130 Therefore, the light-emitting element 10 can convert triplet excitons into singlet excitons by utilizing reverse intersystem crossing by a TADF material, and can achieve a higher light emission efficiency than the comparative light-emitting element 8 efficiency

[0414] Also, the light emission efficiency of the light-emitting element 10 is higher than that of the comparative light-emitting element 12. As described above, although the light-emitting layer 130 of the comparative light-emitting element 12 contains a TADF material, it does not contain a phosphorescent compound ​​​​No. Therefore, the comparative light-emitting element 12 cannot contribute triplet excitons to fluorescence emission through a phosphorescent compound. On the other hand, in the light-emitting element 10 according to one aspect of the present invention, the light-emitting layer 130 contains a phosphorescent compound in addition to the TADF material. Therefore, in addition to the high-efficiency effect due to reverse intersystem crossing derived from the TADF material, the light-emitting element 10 can contribute triplet excitons to fluorescence emission through a phosphorescent compound, and can achieve higher luminous efficiency than the comparative light-emitting element 12. No. In the light-emitting element 10 according to one aspect of the present invention, the light-emitting layer 130 contains a phosphorescent compound in addition to the TADF material. No. Therefore, in addition to the high-efficiency effect due to reverse intersystem crossing derived from the TADF material, the light-emitting element 10 can contribute triplet excitons to fluorescence emission through a phosphorescent compound, and can achieve higher luminous efficiency than the comparative light-emitting element 12. No. In addition to the high-efficiency effect due to reverse intersystem crossing derived from the TADF material, the light-emitting element 10 can contribute triplet excitons to fluorescence emission through a phosphorescent compound, and can achieve higher luminous efficiency than the comparative light-emitting element 12. No. In addition to the high-efficiency effect due to reverse intersystem crossing derived from the TADF material, the light-emitting element 10 can contribute triplet excitons to fluorescence emission through a phosphorescent compound, and can achieve higher luminous efficiency than the comparative light-emitting element 12. No.

[0415] <Time-resolved luminescence measurement> Next, time-resolved luminescence measurements of the light-emitting element 10 and the comparative light-emitting element 11 were performed. The results are shown in FIG. 33. The measurement method is the same as the method shown in the previous example. No. As shown in FIG. 33, the decay rate of luminescence of the light-emitting element 10 is faster than that of the comparative light-emitting element 11. This means that the excitation energy is quickly converted into luminescence. Therefore, even in a state where the exciton density is high (a state where a large amount of current is flowing) in the light-emitting layer, luminescence can be efficiently extracted. Therefore, as shown in FIGS. 29 and 31, the light-emitting element 10 has less roll-off. In addition, the light-emitting element 10 has higher luminous efficiency than the comparative light-emitting element 11. The light-emitting layer 130 of the light-emitting element 10 has a configuration in which TBRb, which is a fluorescent compound, is added to the light-emitting layer 130 of the comparative light-emitting element 11. It can be seen from FIG. 33 that adding the fluorescent compound improves the decay rate of luminescence. Therefore, it can be said that the deactivation of excitons is suppressed and the luminous efficiency of the light-emitting element 10 is improved compared to the comparative light-emitting element 11.

[0416] No. As shown in FIG. 33, the decay rate of luminescence of the light-emitting element 10 is faster than that of the comparative light-emitting element 11. This means that the excitation energy is quickly converted into luminescence. Therefore, even in a state where the exciton density is high (a state where a large amount of current is flowing) in the light-emitting layer, luminescence can be efficiently extracted. Therefore, as shown in FIGS. 29 and 31, the light-emitting element 10 has less roll-off. In addition, the light-emitting element 10 has higher luminous efficiency than the comparative light-emitting element 11. The light-emitting layer 130 of the light-emitting element 10 has a configuration in which TBRb, which is a fluorescent compound, is added to the light-emitting layer 130 of the comparative light-emitting element 11. It can be seen from FIG. 33 that adding the fluorescent compound improves the decay rate of luminescence. Therefore, it can be said that the deactivation of excitons is suppressed and the luminous efficiency of the light-emitting element 10 is improved compared to the comparative light-emitting element 11. No. This means that the excitation energy is quickly converted into luminescence. Therefore, even in a state where the exciton density is high (a state where a large amount of current is flowing) in the light-emitting layer, luminescence can be efficiently extracted. No. Therefore, even in a state where the exciton density is high (a state where a large amount of current is flowing) in the light-emitting layer, luminescence can be efficiently extracted. No. Therefore, as shown in FIGS. 29 and 31, the light-emitting element 10 has less roll-off. In addition, the light-emitting element 10 has higher luminous efficiency than the comparative light-emitting element 11. The light-emitting layer 130 of the light-emitting element 10 has a configuration in which TBRb, which is a fluorescent compound, is added to the light-emitting layer 130 of the comparative light-emitting element 11. It can be seen from FIG. 33 that adding the fluorescent compound improves the decay rate of luminescence. Therefore, it can be said that the deactivation of excitons is suppressed and the luminous efficiency of the light-emitting element 10 is improved compared to the comparative light-emitting element 11. No. Therefore, as shown in FIGS. 29 and 31, the light-emitting element 10 has less roll-off. In addition, the light-emitting element 10 has higher luminous efficiency than the comparative light-emitting element 11. The light-emitting layer 130 of the light-emitting element 10 has a configuration in which TBRb, which is a fluorescent compound, is added to the light-emitting layer 130 of the comparative light-emitting element 11. It can be seen from FIG. 33 that adding the fluorescent compound improves the decay rate of luminescence. Therefore, it can be said that the deactivation of excitons is suppressed and the luminous efficiency of the light-emitting element 10 is improved compared to the comparative light-emitting element 11. No. In addition, the light-emitting element 10 has higher luminous efficiency than the comparative light-emitting element 11. The light-emitting layer 130 of the light-emitting element 10 has a configuration in which TBRb, which is a fluorescent compound, is added to the light-emitting layer 130 of the comparative light-emitting element 11. No. It can be seen from FIG. 33 that adding the fluorescent compound improves the decay rate of luminescence. No. It can be seen from FIG. 33 that adding the fluorescent compound improves the decay rate of luminescence. No. Therefore, it can be said that the deactivation of excitons is suppressed and the luminous efficiency of the light-emitting element 10 is improved compared to the comparative light-emitting element 11.

[0417] <Transient fluorescence characteristics of host material> Here, it is confirmed that the PCCzPTzn used in the light-emitting element 10 is a TADF material. Therefore, transient fluorescence characteristics were measured by time-resolved luminescence measurement. The time-resolved luminescence measurement was carried out in the same manner as the method shown in Example 1. Also, the measured sample was a thin film in which PCCzPT zn was vapor-deposited to a thickness of 50 nm on a quartz substrate.

[0418] The transient fluorescence characteristics of PCCzPTzn obtained by the measurement are shown in FIG. 34.

[0419] Also, fitting was performed on the decay curve shown in FIG. 34 using Equation (4). As a result, it was found that the emission exhibited by the thin film sample of PCCzPTzn contains a plurality of emission components having different fluorescence lifetimes. The emission components of the thin film sample of PCCzPTzn were found to contain at least an initial fluorescence component with a fluorescence lifetime of 15.0 ns and a delayed fluorescence component with the longest lifetime of 1.5 μs. That is, it can be said that PCCzPTzn is a thermally activated delayed fluorescence material that exhibits delayed fluorescence at room temperature.

[0420] <Measurement of S1 level and T1 level> Next, in order to calculate the S1 level and T1 level of PCCzPTzn, the emission spectrum of PCCzPTzn at low temperature (10 K) was measured. The measurement method is the same as the method shown in Example 1. The measurement results are shown in FIG. 35.

[0421] From FIG. 35, the wavelengths of the peaks (including shoulders) on the shortest wavelength side of the fluorescence component and the phosphorescence component of the emission spectrum of PCCzPTzn were 472 nm and 491 nm, respectively. .

[0422] Therefore, the S1 level and T1 level of PCCzPTzn calculated from the wavelengths of the above peaks (including shoulders) The S1 level is 2.63 eV and the T1 level is 2.53 eV. The energy difference was calculated to be 0.10 eV.

[0423] In addition, from Figure 35, the short wavelengths of the fluorescent and phosphorescent components of the emission spectrum of PCCzPTzn The wavelengths of the longer wavelengths were 450 nm and 477 nm, respectively. The wavelength at the beginning of the spectrum on the short wavelength side is determined by t...

Claims

1. A light-emitting layer is provided between a pair of electrodes, the light-emitting layer includes a first organic compound, a second organic compound, and a third organic compound, the first organic compound is a TADF material, the difference between the S1 level and the T1 level of the second organic compound is 0 eV or more and 0.2 eV or less, the third organic compound has a function of converting singlet excitation energy into light emission, a light-emitting device.

2. A light-emitting layer is provided between a pair of electrodes, the light-emitting layer includes a first organic compound, a second organic compound, and a third organic compound, the difference between the S1 level of the first organic compound and the T1 level of the second organic compound is 0 eV or more and 0.2 eV or less, the difference between the S1 level and the T1 level of the second organic compound is 0 eV or more and 0.2 eV or less, the third organic compound has a function of converting singlet excitation energy into light emission, a light-emitting device.

3. A light-emitting layer is provided between a pair of electrodes, the light-emitting layer includes a first organic compound, a second organic compound, and a third organic compound, the first organic compound is a TADF material, the second organic compound has a π-electron rich skeleton and a π-electron deficient skeleton, the third organic compound has a function of converting singlet excitation energy into light emission, a light-emitting device.

4. A light-emitting layer is provided between a pair of electrodes, the light-emitting layer includes a first organic compound, a second organic compound, and a third organic compound, the difference between the S1 level of the first organic compound and the T1 level of the second organic compound is 0 eV or more and 0.2 eV or less, the second organic compound has a π-electron rich skeleton and a π-electron deficient skeleton, the third organic compound has a function of converting singlet excitation energy into light emission, a light-emitting device.

5. In any one of Claims 1 to 4, the S1 level of the second organic compound is equal to or higher than the S1 level of the first organic compound, a light-emitting device.

6. In any one of Claims 1 to 5, the T1 level of the second organic compound is equal to or higher than the T1 level of the first organic compound, a light-emitting device.

7. In any one of Claims 1 to 6, the third organic compound exhibits fluorescence, a light-emitting device.

8. In any one of Claims 1 to 7, light emission derived from the third organic compound is obtained, a light-emitting device.

9. A light-emitting element according to any one of Claims 1 to 8, at least one of a color filter or a transistor, and a display device having the same.

10. A display device according to Claim 9, at least one of a housing or a touch sensor, and an electronic device having the same.

11. A light-emitting element according to any one of Claims 1 to 8, at least one of a housing or a touch sensor, and a lighting device having the same.

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