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

Abstract

A light-emitting device comprising a light-emitting layer between a pair of electrodes, wherein the light-emitting layer contains a first material, a second material and a third material, wherein the first material can convert the triplet excitation energy into light emission and has a five-membered ring framework, wherein the first material is a metal complex, wherein the second material can convert the singlet excitation energy into light emission and has a luminophore and five or more protecting groups, wherein the luminophore is a condensed aromatic ring or a condensed heteroaromatic ring, wherein the five or more protecting groups each independently comprise an alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms or a trialkylsilyl group having 3 to 12 carbon atoms, wherein the third material comprises a diazine framework or a triazine framework, and wherein a T1 level of the first material is higher than an S1 level of the second material.

Description

Technical area

[0001] An embodiment of the present invention relates to a light-emitting device or a display device, an electronic device and a lighting device, each including the light-emitting device. State of the art

[0002] In recent years, intensive research and development has been conducted on light-emitting devices that utilize electroluminescence (EL). A basic structure of these light-emitting devices involves a layer containing a light-emitting substance (an EL layer) sandwiched between a pair of electrodes. By applying a voltage between the electrodes of this device, light emission from the light-emitting substance can be obtained.

[0003] Since the above light-emitting device is a self-luminous type, a display device using this light-emitting device has the following advantages: high visibility, no need for a backlight, and low power consumption. Furthermore, such a light-emitting device is also advantageous in that the device can be manufactured thinly and lightweight, and it has a high response speed.

[0004] In a light-emitting device whose EL layer contains a light-emitting organic compound as the light-emitting substance and is provided between a pair of electrodes (e.g., an organic EL device), applying a voltage between the pair of electrodes causes the injection of electrons from a cathode and holes from an anode into the EL layer having a light-emitting property, thereby causing a current to flow. By recombination of the injected electrons and holes, the light-emitting organic compound is excited, and light emission can be obtained from the excited light-emitting organic compound.

[0005] The excited states that can be formed by an organic compound are a singlet excited state (S*) and a triplet excited state (T*). Light emission from the singlet excited state is called fluorescence, and light emission from the triplet excited state is called phosphorescence. The statistical generation ratio of S* to T* in the light-emitting device is 1:3. Therefore, it is possible for a light-emitting device containing a compound that emits phosphorescence (a phosphorescent material) to have higher emission efficiency than a light-emitting device containing a compound that emits fluorescence (a fluorescent material).Accordingly, light-emitting devices containing phosphorescent materials that can convert the energy of the triplet excited state into light emission have been intensively developed in recent years.

[0006] Among light-emitting devices containing phosphorescent materials, a light-emitting device emitting blue light, in particular, has not yet been put into practical use due to the difficulty of developing a stable compound with a high triplet excitation energy level. For this reason, a light-emitting device containing a more stable fluorescent material has been developed, and a technique for increasing the emission efficiency of a light-emitting device containing a fluorescent material (a fluorescent device) has been researched.

[0007] In addition to phosphorescence, thermally activated delayed fluorescence (TADF) materials are known as materials that can convert part or all of the energy of the triplet excited state into light emission. In a thermally activated delayed fluorescence material, a singlet excited state is generated from a triplet excited state through reverse intersystem crossing, and the singlet excited state is converted into light emission.

[0008] To increase the emission efficiency of a light-emitting device using a thermally activated, delayed-fluorescent material, not only efficient generation of a singlet excited state from a triplet excited state but also efficient light emission from a singlet excited state—that is, a high fluorescence quantum yield—is important. However, it is difficult to create a light-emitting material that meets these two criteria.

[0009] A method is disclosed in which, in a light-emitting device containing a thermally activated delayed fluorescent material and a fluorescent material, the singlet excitation energy of the thermally activated delayed fluorescent material is transferred to the fluorescent material, and light emission is obtained from the fluorescent material (see Patent Document 1). In other words, a light-emitting device has been proposed in which a thermally activated delayed fluorescent material is used as a host material and a fluorescent material is used as a guest material. Other examples of light-emitting devices are disclosed in Patent Documents 2 and 3. [Reference][Patent document] [Patent document 1] JP 2014 - 45 179 A [Patent document 2] US 2019 / 0 280 236 A1 [Patent document 3] US 2016 / 0 172 602 A1 Summary of the inventionProblem to be solved by the invention

[0010] For example, the efficiency of a fluorescent device is increased by a process in which, in a light-emitting layer containing a host material and a guest material, the triplet excitation energy of the host material is converted into the singlet excitation energy and then the singlet excitation energy is transferred to a fluorescent material that is the guest material, thereby increasing the emission efficiency of the fluorescent device. However, the process in which the triplet excitation energy of the host material is converted into the singlet excitation energy competes with a process in which the triplet excitation energy is deactivated. Therefore, in some cases, the triplet excitation energy of the host material is not sufficiently converted into the singlet excitation energy.One possible deactivation pathway for triplet excitation energy is, for example, a deactivation pathway in which, when a fluorescent material is used as a guest material in a light-emitting layer of a light-emitting device, the triplet excitation energy of the host material is transferred to the lowest triplet excitation energy level (T1 level) of the fluorescent material. Energy transfer through this deactivation pathway does not contribute to light emission, resulting in a reduction in the emission efficiency of a fluorescent device. This deactivation pathway can be suppressed by reducing the concentration of the guest material. However, in this case, the rate of energy transfer from the host material to the singlet excitation state of the guest material is also reduced. This makes quenching due to degraded substances and impurities more likely.As a result, the luminance of the light-emitting device is more likely to be reduced, which reduces reliability.

[0011] Therefore, an object of an embodiment of the present invention is to increase the fluorescence efficiency and the reliability of a light-emitting device by suppressing, with respect to a host material and a guest material of a light-emitting layer of the light-emitting device, the transfer of the triplet excitation energy of the host material to the T1 level of the guest material and efficiently converting the triplet excitation energy of the host material into the singlet excitation energy of the guest material.

[0012] Another object of an embodiment of the present invention is to provide a light-emitting device with high emission efficiency. Another object of an embodiment of the present invention is to provide a light-emitting device with high reliability. Another object of an embodiment of the present invention is to provide a light-emitting device with low power consumption. Another object of an embodiment of the present invention is to provide a novel light-emitting device. Another object of an embodiment of the present invention is to provide a novel light-emitting apparatus. Another object of an embodiment of the present invention is to provide a novel display device.

[0013] It should be noted that the description of the above objects does not preclude the existence of further objects. In one embodiment of the present invention, it is not necessarily required to fulfill all of the objects. Further objects will become apparent from the explanation of the description and the like and can be derived therefrom. Means to solve the problem

[0014] An embodiment of the present invention provides a light-emitting device including a light-emitting layer in which, with respect to energy transfer between a host material (energy donor) and a guest material (energy acceptor), energy transfer can be mainly suppressed by the Dexter mechanism to suppress the transfer of the triplet excitation energy of the host material to the T1 level of the guest material.

[0015] To suppress energy transfer by the Dexter mechanism, it is preferable that the energy donor and the energy acceptor in the light-emitting layer be sufficiently separated from each other to prevent energy transfer. Therefore, one embodiment of the present invention provides a light-emitting device containing an energy donor with a bulky structure and an energy acceptor with protecting groups so that the energy donor and a luminophore of the energy acceptor are sufficiently separated from each other to prevent energy transfer. Furthermore, in one embodiment of the present invention, the triplet level (T1 level) of the energy donor is preferably higher than the singlet level (S1 level) of the energy acceptor.

[0016] It should be noted that in one embodiment of the present invention, a material having a substituent in a five-membered ring framework is used as the energy donor with a voluminous structure. Furthermore, a fluorescent material is used as the energy acceptor, and the protecting groups of the fluorescent material result in a voluminous structure. An imidazole framework or a triazole framework is particularly preferred as the five-membered ring framework of the energy donor.

[0017] Therefore, one embodiment of the present invention is a light-emitting device including a light-emitting layer between a pair of electrodes. The light-emitting layer contains a first material, a second material, and a third material. The first material is a metal complex, can convert triplet excitation energy into light emission, and has a five-membered ring framework. The second material can convert singlet excitation energy into light emission and has a luminophore and five or more protecting groups. The luminophore is a condensed aromatic ring or a condensed heteroaromatic ring. The five or more protecting groups each independently comprise an alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, or a trialkylsilyl group having 3 to 12 carbon atoms.The T1 level of the first material is higher than the S1 level of the second material. The third material comprises a diazine framework or a triazine framework.

[0018] In the above structure, it is preferable that at least four protecting groups among the five or more protecting groups are each independently an alkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, or a trialkylsilyl group having 3 to 10 carbon atoms.

[0019] Another embodiment of the present invention is a light-emitting device including a light-emitting layer between a pair of electrodes. The light-emitting layer contains a first material, a second material, and a third material. The first material is a metal complex, can convert triplet excitation energy into light emission, and has a five-membered ring framework. The second material can convert singlet excitation energy into light emission and has a luminophore and at least four protecting groups. The luminophore is a fused aromatic ring or a fused heteroaromatic ring. The four protecting groups are not directly bonded to the fused aromatic ring or the fused heteroaromatic ring.The four protecting groups each independently comprise an alkyl group with 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group with 3 to 10 carbon atoms, or a trialkylsilyl group with 3 to 12 carbon atoms. The T1 level of the first material is higher than the S1 level of the second material. The third material comprises a diazine scaffold or a triazine scaffold.

[0020] Another embodiment of the present invention is a light-emitting device including a light-emitting layer between a pair of electrodes. The light-emitting layer contains a first material and a second material. The first material is a metal complex, can convert triplet excitation energy into light emission, and has a five-membered ring framework. The second material can convert singlet excitation energy into light emission and has a luminophore and two or more diarylamino groups. The luminophore is a condensed aromatic ring or a condensed heteroaromatic ring. The condensed aromatic ring or the condensed heteroaromatic ring is bonded to the two or more diarylamino groups. Aryl groups of the two or more diarylamino groups each independently have at least one protecting group.The protecting groups each independently comprise an alkyl group with 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group with 3 to 10 carbon atoms, or a trialkylsilyl group with 3 to 12 carbon atoms. The T1 level of the first material is higher than the S1 level of the second material.

[0021] Another embodiment of the present invention is a light-emitting device including a light-emitting layer between a pair of electrodes. The light-emitting layer contains a first material and a second material. The first material is a metal complex, can convert triplet excitation energy into light emission, and has a five-membered ring framework. The second material can convert singlet excitation energy into light emission and has a luminophore and two or more diarylamino groups. The luminophore is a fused aromatic ring or a fused heteroaromatic ring. The fused aromatic ring or the fused heteroaromatic ring is bonded to the two or more diarylamino groups. Aryl groups in the two or more diarylamino groups each independently have at least two protecting groups.The protecting groups each independently comprise an alkyl group with 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group with 3 to 10 carbon atoms, or a trialkylsilyl group with 3 to 12 carbon atoms. The T1 level of the first material is higher than the S1 level of the second material.

[0022] In the above structure, it is preferred that the diarylamino group is a diphenylamino group.

[0023] Another embodiment of the present invention is a light-emitting device including a light-emitting layer between a pair of electrodes. The light-emitting layer contains a first material and a second material. The first material is a metal complex, can convert triplet excitation energy into light emission, and has a five-membered ring framework. The second material can convert singlet excitation energy into light emission and has a luminophore and a plurality of protecting groups. The protecting groups each independently comprise an alkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, or a trialkylsilyl group having 3 to 12 carbon atoms. The luminophore is a condensed aromatic ring or a condensed heteroaromatic ring.At least one of the atoms of the protecting groups is positioned directly on one face of the fused aromatic ring or the fused heteroaromatic ring, and at least one of the atoms of the plurality of protecting groups is positioned directly on the other face of the fused ring or the fused heteroaromatic ring. The T1 level of the first material is higher than the S1 level of the second material.

[0024] Another embodiment of the present invention is a light-emitting device including a light-emitting layer between a pair of electrodes. The light-emitting layer contains a first material and a second material. The first material is a metal complex, can convert triplet excitation energy into light emission, and has a five-membered ring framework. The second material can convert singlet excitation energy into light emission and has a luminophore and two or more diphenylamino groups. The luminophore is a condensed aromatic ring or a condensed heteroaromatic ring. The condensed aromatic ring or the condensed heteroaromatic ring is bonded to the two or more diphenylamino groups. Phenyl groups in the two or more diphenylamino groups each independently have protecting groups at the 3- and 5-positions.The protecting groups each independently comprise an alkyl group with 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group with 3 to 10 carbon atoms, or a trialkylsilyl group with 3 to 12 carbon atoms. The T1 level of the first material is higher than the S1 level of the second material.

[0025] In any of the above structures, it is preferred that the five-membered ring skeleton comprises a pyrazole skeleton, an imidazole skeleton, or a triazole skeleton. It is more preferred that a nitrogen atom not involved in a double bond contained in the imidazole skeleton and the triazole skeleton has a substituted or unsubstituted aromatic hydrocarbon group having 6 to 13 carbon atoms.

[0026] Another embodiment of the present invention is a light-emitting device including a light-emitting layer between a pair of electrodes. The light-emitting layer contains a first material and a second material. The first material is a metal complex, can convert triplet excitation energy into light emission, and has a five-membered ring framework. The second material can convert singlet excitation energy into light emission and has a luminophore and two or more protecting groups. The luminophore is a condensed aromatic ring or a condensed heteroaromatic ring. The two or more protecting groups each independently comprise an alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, or a trialkylsilyl group having 3 to 12 carbon atoms.The first material has a five-membered ring structure. The five-membered ring structure comprises an imidazole structure and / or a triazole structure. A nitrogen atom not involved in a double bond contained in the imidazole structure and the triazole structure has a substituted or unsubstituted aromatic hydrocarbon group with 6 to 13 carbon atoms. The T1 level of the first material is higher than the S1 level of the second material.

[0027] In the above structure, it is preferred that the aromatic hydrocarbon group is a phenyl group.

[0028] In any of the above structures, it is preferred that the alkyl group is a branched chain alkyl group.

[0029] In the above structure, it is preferred that the branched chain alkyl group has a quaternary carbon.

[0030] In any of the above structures, it is preferred that the fused aromatic ring or the fused heteroaromatic ring comprises naphthalene, anthracene, fluorene, chrysene, triphenylene, pyrene, tetracene, perylene, coumarin, quinacridone or naphthobisbenzofuran.

[0031] In the above structure, it is preferable that the light-emitting layer further contains a third material, and the first material and the third material form an exciplex.

[0032] In the above structure, it is preferred that the emission spectrum of the exciplex overlaps with the absorption band on the longest wavelength side of the second material.

[0033] In the above structure, it is preferred that the five-membered ring skeleton comprises a pyrazole skeleton, an imidazole skeleton or a triazole skeleton.

[0034] In any of the above structures, it is preferred that the metal complex comprises a metal of one of Groups 8 to 10 and Periods 5 and 6 and the five-membered ring framework is coordinated to the metal.

[0035] In any of the above structures, it is preferred that the first material emits phosphorescence.

[0036] In any of the above structures, it is preferred that the emission spectrum of the first material overlaps with the absorption band on the longest wavelength side of the second material.

[0037] In any of the above structures, it is preferable that the concentration of the second material in the light-emitting layer is higher than or equal to 2 wt% and lower than or equal to 30 wt%.

[0038] Another embodiment of the present invention is an electronic device that includes the display device and a housing and / or a touch sensor. Another embodiment of the present invention is a lighting device that includes the light-emitting device having any of the above structures and a housing and / or a touch sensor. The present invention can be used in a light-emitting device. The light-emitting device in this specification therefore refers to an image display device or a light source (including a lighting device). The light-emitting device may be a display module in which a connector, such as a connector, is used.a flexible printed circuit (FPC) or a tape carrier package (TCP) connected to a light-emitting device, a display module in which a printed circuit board is provided at the end of a TCP, and a display module in which an integrated circuit (IC) is directly mounted on a light-emitting device by a chip-on-glass (COG) method. Effect of the invention

[0039] One embodiment of the present invention can provide a light-emitting device with high emission efficiency. Another embodiment of the present invention can provide a light-emitting device with high reliability. Another embodiment of the present invention can provide a light-emitting device with low power consumption. Another embodiment of the present invention can provide a novel light-emitting device. Another embodiment of the present invention can provide a novel light-emitting device. Another embodiment of the present invention can provide a novel display device. Another embodiment of the present invention can provide a novel organic compound.

[0040] It should be noted that the description of these effects does not preclude the existence of further effects. In one embodiment of the present invention, it is not necessarily required to achieve all of the effects. Further effects will become apparent from and can be derived from the explanation of the description, the drawings, the claims, and the like. Short description of the drawings Fig. 1A and Fig. 1B are schematic cross-sectional views of a light-emitting layer of a light-emitting device of an embodiment of the present invention. Fig. 1C is a diagram showing the correlation of energy levels of the light-emitting device of one embodiment of the present invention. Fig. Figure 2A is a conceptual diagram of a conventional guest material. Fig. 2B is a conceptual diagram of a guest material used for a light-emitting device of an embodiment of the present invention. Fig. 3A is a structural formula of a guest material used for a light-emitting device of one embodiment of the present invention. Fig. 3B is a ball-and-stick diagram of the guest material used for the light-emitting device of one embodiment of the present invention. Fig. 4A is a schematic cross-sectional view of a light-emitting layer of a light-emitting device of an embodiment of the present invention. Fig. 4B and Fig. 4C are diagrams showing the correlation of energy levels of the light-emitting device of one embodiment of the present invention. Fig. 5A is a schematic cross-sectional view of a light-emitting layer of a light-emitting device of an embodiment of the present invention. Fig. 5B and Fig. 5C are diagrams showing the correlation of energy levels of the light-emitting layer of the light-emitting device of one embodiment of the present invention. Fig. 6 is a schematic cross-sectional view of a light-emitting device of an embodiment of the present invention. Fig. 7A is a plan view illustrating a display device of an embodiment of the present invention. Fig. 7B is a schematic cross-sectional view illustrating the display device of an embodiment of the present invention. Fig. 8A and Fig. 8B are schematic cross-sectional views illustrating display devices of embodiments of the present invention. Fig. 9A and Fig. 9B are schematic cross-sectional views illustrating display devices of embodiments of the present invention. Fig. 10A to Fig. 10D are perspective views illustrating display modules of embodiments of the present invention. Fig. 11A to Fig. 11C are diagrams illustrating electronic devices of embodiments of the present invention. Fig. 12A and Fig. 12B are perspective views illustrating a display device of an embodiment of the present invention. Fig. 13 is a diagram illustrating lighting devices of embodiments of the present invention. Fig. 14 is a diagram showing the external quantum efficiency-luminance characteristics of light-emitting devices of an example. Fig. 15 is a diagram showing the electroluminescence spectra of light-emitting devices of an example. Fig. 16 is a diagram showing the external quantum efficiency-luminance characteristics of light-emitting devices of an example. Fig. 17 is a diagram showing the electroluminescence spectra of light-emitting devices of an example. Fig. 18 is a diagram showing the external quantum efficiency-luminance characteristics of light-emitting devices of an example. Fig. 19 is a diagram showing the electroluminescence spectra of light-emitting devices of an example. Fig. 20 is a diagram showing the external quantum efficiency-luminance characteristics of light-emitting devices of an example. Fig. 21 is a diagram showing the electroluminescence spectra of light-emitting devices of an example. Fig. 22 is a diagram showing the external quantum efficiency-luminance characteristics of light-emitting devices of an example. Fig. 23 is a diagram showing the electroluminescence spectra of light-emitting devices of an example. Fig. 24 is a diagram showing the external quantum efficiency-luminance characteristics of light-emitting devices of an example. Fig. 25 is a diagram showing the electroluminescence spectra of light-emitting devices of an example. Fig. 26 is a diagram showing the external quantum efficiency-luminance characteristics of light-emitting devices of an example. Fig. 27 is a diagram showing the electroluminescence spectra of light-emitting devices of an example. Fig. 28 is a graph showing the external quantum efficiency-luminance characteristics of comparative light-emitting devices of an example. Fig. 29 is a diagram showing the electroluminescence spectra of comparative light-emitting devices of an example. Fig. 30 is a diagram showing a relationship between an emission spectrum and an absorption spectrum of an example. Fig. 31 is a diagram showing a relationship between an emission spectrum and an absorption spectrum of an example. Fig. 32 is a diagram showing a relationship between an emission spectrum and an absorption spectrum of an example. Fig. 33 is a diagram showing a relationship between an emission spectrum and an absorption spectrum of an example. Fig. 34 is a diagram showing a relationship between an emission spectrum and an absorption spectrum of an example. Fig. 35 is a diagram showing a relationship between an emission spectrum and an absorption spectrum of an example. Fig. 36 is a diagram showing a relationship between an emission spectrum and an absorption spectrum of an example. Fig. Figure 37 is a graph showing a relationship between the external quantum efficiency and the concentration of the guest material of an example. Fig. Figure 38 is a graph showing the reliability test results of an example. Fig. Figure 39 is a graph showing the reliability test results of an example. Fig. Figure 40 is a graph showing the reliability test results of an example. Fig. Figure 41 is a graph showing the reliability test results of an example. Fig. Figure 42 is a graph showing the reliability test results of an example. Fig. Figure 43 is a graph showing the reliability test results of an example. Fig. Figure 44 is a graph showing the reliability test results of an example. Fig. 45A and Fig. 45B are NMR diagrams of compounds of a reference example. Fig. Figure 46 is an NMR diagram of a compound of a reference example. Fig. Figure 47 is an NMR diagram of a compound of a reference example. Fig. Figure 48 is an NMR diagram of a compound of a reference example. Fig. 49 is a graph showing the measurement results of the emission lifetime of light-emitting devices of an example. Fig. 50 is a graph showing the measurement results of the emission lifetime of light-emitting devices of an example. Fig. 51 is a graph showing the measurement results of the emission lifetime of light-emitting devices of an example. Fig. 52 is a diagram showing the external quantum efficiency-luminance characteristics of light-emitting devices of an example. Fig. 53 is a diagram showing the electroluminescence spectra of light-emitting devices of an example. Fig. Figure 54 is a graph showing the reliability test results of an example. Fig. 55 is a graph showing the measurement results of the emission lifetime of light-emitting devices of an example. Fig. 56A and Fig. 56B are NMR diagrams of compounds of a reference example. Fig. Figure 57 is an NMR diagram of a compound of a reference example. Embodiments of the invention

[0041] Embodiments of the present invention will be described in detail below with reference to the drawings.

[0042] Note that the position, size, range, or the like of each component illustrated in drawings and the like may not be precisely illustrated in some cases for ease of understanding. Therefore, the disclosed invention is not necessarily limited to the position, size, range, or the like disclosed in the drawings and the like.

[0043] Furthermore, the ordinal numbers such as "first" and "second" in this specification and the like are used for convenience, and in some cases, they do not indicate the order of steps or the arrangement order of layers. Therefore, for example, an appropriate description can be made even if "first" is replaced with "second" or "third." Furthermore, the ordinal numbers in this specification and the like do not correspond to the ordinal numbers used to specify an embodiment of the present invention in some cases.

[0044] In explaining the structures of the invention in this specification and the like with reference to drawings, in some cases, the same components in different drawings are generally denoted by the same reference numerals.

[0045] Furthermore, in this description and the like, the term "film" and the term "layer" may be interchanged. For example, the term "conductive layer" may be replaced with the term "conductive film" in some cases. For example, the term "insulating film" may also be replaced with the term "insulating layer" in some cases.

[0046] In this specification and the like, a singlet excited state (S*) refers to a singlet state with excitation energy. An S1 level means the lowest level of the singlet excitation energy level, that is, the excitation energy level of the lowest singlet excited state (S1 state). A triplet excited state (T*) refers to a triplet state with excitation energy. A T1 level means the lowest level of the triplet excitation energy level, that is, the excitation energy level of the lowest triplet excited state (T1 state). Note that in this specification and the like, simple terms such as a "singlet excited state" and a "singlet excited energy level" in some cases mean the S1 state and the S1 level, respectively. Furthermore, terms such as "singlet excited state" and "singlet excited energy level" refer to the S1 state and the S1 level, respectively. B. “triplet excited state” and “triplet excited energy level”, in some cases the T1 state or the T1 level.

[0047] In this specification and the like, a fluorescent material refers to a compound that emits light in the visible light range when relaxing from the singlet excitation state to the ground state. A phosphorescent material refers to a compound that emits light in the visible light range at room temperature when relaxing from the triplet excitation state to the ground state. That is, a phosphorescent material refers to a compound that can convert triplet excitation energy into visible light.

[0048] In this specification and the like, a wavelength range of blue refers to a wavelength range greater than or equal to 400 nm and less than 490 nm, and blue light has at least one peak in this wavelength range in an emission spectrum. A wavelength range of green refers to a wavelength range greater than or equal to 490 nm and less than 580 nm, and green light has at least one peak in this wavelength range in an emission spectrum. A wavelength range of red refers to a wavelength range greater than or equal to 580 nm and less than or equal to 680 nm, and red light has at least one peak in this wavelength range in an emission spectrum. (Embodiment 1)

[0049] In this embodiment, a light-emitting device of one embodiment of the present invention will be described below with reference to Fig. 1 to Fig. 5 described. <Strukturbeispiel der Licht emittierenden Vorrichtung>

[0050] First, a structure of the light-emitting device of an embodiment of the present invention will be described below with reference to Fig. 1A to Fig. 1C described.

[0051] Fig. 1A is a schematic cross-sectional view of a light-emitting device 150 of an embodiment of the present invention.

[0052] The light-emitting device 150 includes a pair of electrodes (an electrode 101 and an electrode 102) and an EL layer 100 between the pair of electrodes. The EL layer 100 includes at least one light-emitting layer 130.

[0053] The EL layer 100, which is Fig. 1A, in addition to the light-emitting layer 130, comprises 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.

[0054] Although in this embodiment, a description is given assuming that the electrode 101 and the electrode 102 of the pair of electrodes serve as the anode and the cathode, respectively, the structure of the light-emitting device 150 is not limited to this. That is, the electrode 101 may serve as the cathode and the electrode 102 may serve as the anode, and the arrangement order of the layers between the electrodes may be reversed. In other words, 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 arranged in this order from the anode side.

[0055] It should be noted that the structure of the EL layer 100 is not limited to the structure shown in Fig. 1A, and a structure including at least one layer selected from the hole injection layer 111, the hole transport layer 112, the electron transport layer 118, and the electron injection layer 119 may be employed. Alternatively, the EL layer 100 may include, for example, a functional layer having a function of lowering a hole or electron injection barrier, improving a hole or electron transport property, reducing a hole or electron transport property, or suppressing quenching by an electrode. Note that the functional layers may each be a single layer or a multilayer. <Lichtemissionsmechanismus der Licht emittierenden Vorrichtung>

[0056] Next, a light emission mechanism of the light-emitting layer 130 will be described below.

[0057] In the light-emitting device 150 of one embodiment of the present invention, applying a voltage between the pair of electrodes (electrodes 101 and 102) causes electrons and holes to be injected from the cathode and anode, respectively, into the EL layer 100, causing a current to flow. The ratio (hereinafter, the exciton generation probability) of singlet excitons to triplet excitons generated by the recombination of charge carriers (electrons and holes) is 1:3 according to the statistically obtained probability. In other words, the generation probability of singlet excitons is 25%, and the generation probability of triplet excitons is 75%. Thus, triplet excitons are important for contributing to light emission to increase the emission efficiency of the light-emitting device.Accordingly, a material having a function of converting triplet excitation energy into light emission is preferably used for the light-emitting layer 130.

[0058] As a material having a function of converting triplet excitation energy into light emission, a compound capable of emitting phosphorescence (hereinafter also referred to as a phosphorescent material) can be specified. A phosphorescent material in this specification and the like is a compound that emits phosphorescence but does not emit fluorescence in a temperature range from higher than or equal to a low temperature obtainable with liquid nitrogen (e.g., 77 K) to lower than or equal to room temperature. The phosphorescent material preferably contains a metal element with a large spin-orbit interaction, particularly a transition metal element.In particular, a platinum group element (an element of one of groups 8 to 10 and periods 5 and 6 (ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir) or platinum (Pt)), in particular iridium, is preferably included, since the probability of direct transition between a singlet ground state and a triplet excited state can be increased.

[0059] A TADF material can be specified as a material with the function of converting triplet excitation energy into light emission. Note that the TADF material is a material that has a small difference between the S1 level and the T1 level and has the function of converting triplet excitation energy into singlet excitation energy through reverse intersystem crossing. Therefore, the triplet excitation energy can be upconverted to singlet excitation energy using a small amount of thermal energy (e.g., at room temperature) (i.e., reverse intersystem crossing), and a singlet excited state can be efficiently generated.An exciplex in which an excited state is formed by two types of substances has a very small difference between the S1 level and the T1 level and serves as a TADF material that can convert the triplet excitation energy into the singlet excitation energy.

[0060] Note that a phosphorescence spectrum observed at a low temperature (e.g., 10K) can be used as an index of the T1 level. The difference between the S1 level and the T1 level of the TADF material is preferably less than or equal to 0.2 eV when the energy level with a wavelength of the line obtained by extrapolating a tangent to the fluorescence spectrum at a tail on the short wavelength side is the S1 level, and the energy level with a wavelength of the line obtained by extrapolating a tangent to the phosphorescence spectrum at a tail on the short wavelength side is the T1 level.

[0061] Fig. 1B is a schematic cross-sectional view illustrating the light-emitting layer 130 of the light-emitting device of one embodiment of the present invention. In one embodiment of the present invention, the light-emitting layer 130 includes a compound 131, a compound 132, and a compound 133. The compound 133 has a function of converting triplet excitation energy into light emission and has a five-membered ring framework. The compound 132 has a function of converting singlet excitation energy into light emission and has protecting groups. A fluorescent material having high stability is preferably used as the compound 132 to provide a light-emitting device with high reliability. The compound 131 is a host material. It is preferable that charge carrier recombination occurs in the compound 131.In the light-emitting device of one embodiment of the present invention, it is preferred that both the singlet excitation energy and the triplet excitation energy of excitons generated by charge carrier recombination in compound 131 are ultimately transferred to the singlet excited state of compound 132 via compound 133, so that compound 132 emits light. In the light-emitting layer 130, compound 133 serves as an energy donor, and compound 132 serves as an energy acceptor. Fig. 1B, the light-emitting layer 130 is a fluorescent layer containing compound 131 as the host material and compound 132 as the guest material. Compound 133 serves as an energy donor. Furthermore, the light-emitting layer 130 can emit light originating from compound 132, which is a guest material. <Strukturbeispiel 1 der Licht emittierenden Schicht>

[0062] Fig. Figure 1C is an example of the correlation of energy levels in the light-emitting layer 130 of the light-emitting device 150 of an embodiment of the present invention. The light-emitting layer 130 shown in Fig. 1B contains compound 131, compound 132, and also compound 133. In one embodiment of the present invention, compound 132 is a fluorescent material with protecting groups. Furthermore, compound 133 has a function of converting triplet excitation energy into light emission. In this structural example, compound 133 is a phosphorescent material.

[0063] Fig. Figure 1C shows the correlation of the energy levels of compounds 131 and 132 in the light-emitting layer 130. The following explains what the terms and symbols in Fig. 1C. • Comp (131): the connection 131 • Comp (133): the connection 133 • Guest (132): the connection 132 • S C1 : the S1 level of compound 131 • T C1 : the T1 level of compound 131 • T C3 : the T1 level of compound 133 • T G : the T1 level of compound 132 • S G : the S1 level of compound 132

[0064] In the light-emitting device of one embodiment of the present invention, singlet excitons and triplet excitons are generated by recombining charge carriers mainly in the compound 131 contained in the light-emitting layer 130. Since the compound 133 is a phosphorescent material, both the singlet excitation energy and the triplet excitation energy generated in the compound 131 can be applied to the T C3-level of the compound 133 by selecting materials such that they have a relationship T C3 ≤ T C1 (Route A1 in Fig. 1C). It should be noted that some of the charge carriers in compound 133 can recombine.

[0065] It should be noted that the phosphorescent material used in the above structure preferably contains a heavy atom, such as Ir, Pt, Os, Ru, or Pd. As described above, a phosphorescent material of this structural example serves as an energy donor; therefore, the quantum yield can be high or low. A phosphorescent material is preferably used as compound 133 (energy donor) because the energy transfer from the triplet excitation energy level of the energy donor to the singlet excitation energy level of the guest material (energy acceptor) is a permitted transition. Therefore, the triplet excitation energy of compound 133 can be transferred to the S1 level (S G ) of compound 132, which is a guest material, are transferred through the process of route A2. In route A2, compound 133 serves as an energy donor and compound 132 serves as an energy acceptor. In this case, T C3 ≥ S Gpreferred because the excitation energy of compound 133 is efficiently transferred to the singlet excited state of compound 132, which is a guest material. In particular, T C3 ≥ S G preferably fulfilled when the level of energy having a wavelength of the line obtained by extrapolating a tangent to the phosphorescence spectrum of compound 133 at a tail on the short wavelength side is T C3 and the level of energy with a wavelength of the absorption edge of the absorption spectrum of compound 132 or the level of energy with a wavelength of the line obtained by extrapolating a tangent to the emission spectrum at a tail on the short wavelength side, S G is.

[0066] Here, in the light-emitting layer 130, the compound 131, the compound 132, and the compound 133 are mixed. Therefore, a process can occur in which the triplet excitation energy of the compound 133 is converted into the triplet excitation energy of the compound 132 (route A3 in Fig. 1C), whereby this process competes with route A1 and route A2. Since compound 132 is a fluorescent material, the triplet excitation energy of compound 132 does not contribute to light emission. This means that when energy transfer occurs through route A3, the emission efficiency of the light-emitting device is reduced. It should be noted that in practice, the energy transfer process A3 from T C3 on T G may not be a direct path, but a path where the energy is once reduced to a triplet excited state higher than T Gthe connection 132, and then through the internal conversion into T G is converted; this process is not shown in the drawing. In the following, the same applies to all undesirable thermal deactivation processes, ie all processes of energy transfer to T G , in this description.

[0067] Fluorescence resonance energy transfer (also known as FRET or Förster mechanism (dipole-dipole interaction)) and the Dexter mechanism (electron exchange interaction) are known as intermolecular energy transfer mechanisms. Since compound 132, an energy acceptor, is a fluorescent material, the Dexter mechanism is dominant for energy transfer through route A3. Generally, the Dexter mechanism significantly occurs when the distance between compound 131, an energy donor, and compound 132, an energy acceptor, is 1 nm or smaller. Therefore, it is important to keep the host material and the guest material—that is, the energy donor and the energy acceptor—away from each other to suppress route A3.

[0068] Since the direct transition from a singlet ground state to a triplet excited state is forbidden in compound 132, it is less likely that energy transfer from the singlet excited energy level (S C1 ) of compound 131 to the triplet excitation energy level (T G ) of the compound 132 becomes a major energy transfer process; thus, this process is not shown.

[0069] T G in Fig. 1C is often the energy level originating from a luminophore in the energy acceptor. Therefore, especially to suppress route A3, it is important to separate the energy donor and the luminophore in the energy acceptor from each other. A general method for separating the energy donor and the luminophore in the energy acceptor from each other is to reduce the concentration of the energy acceptor in a mixed film of these compounds. However, if the concentration of the energy acceptor in the mixed film is reduced, not only the energy transfer by the Dexter mechanism from the energy donor to the energy acceptor but also the energy transfer by the Förster mechanism are suppressed. In this case, since route A2 is based on the Förster mechanism, problems such as lower emission efficiency or lower reliability of the light-emitting device are caused.

[0070] In view of the foregoing, the inventors of this invention have found that by using a fluorescent material having protecting groups to maintain distance from the energy donor as an energy acceptor, the reduction in emission efficiency can be suppressed. With the protecting groups, the fluorescent material can be a bulky energy acceptor. <Konzept eines fluoreszierenden Materials mit Schutzgruppen>

[0071] Fig. Figure 2A is a conceptual diagram illustrating the case where a non-protecting fluorescent material, which is a general fluorescent material, is dispersed as a guest material in a host material. Fig. Figure 2B is a conceptual diagram illustrating the case where a fluorescent material with protecting groups, used for the light-emitting device of one embodiment of the present invention, is dispersed as a guest material in a host material. The host material can be replaced with an energy donor, and the guest material can be replaced with an energy acceptor. Here, the protecting groups have a function of separating the luminophore and the host material from each other. Fig. 2A, a guest material 301 has a luminophore 310. The guest material 301 serves as an energy acceptor. In Fig. 2B, a guest material 302 comprises the luminophore 310 and protecting groups 320. In Fig. 2A and Fig. 2B, the guest material 301 and the guest material 302 are enclosed by host materials 330. Since Fig. 2A the luminophore is located close to the host materials, the energy transfer from the host materials 330 to the guest material 301 can be either the energy transfer by the Förster mechanism (route B1 in Fig. 2A and Fig. 2B) and the energy transfer through the Dexter mechanism (route B2 in Fig. 2A and Fig. 2B). If the guest material is a fluorescent material, the transfer of triplet excitation energy from the host material to the guest material occurs through the Dexter mechanism and the triplet excited state of the guest material is generated, causing non-radiative deactivation of the triplet excitation energy, resulting in a decrease in emission efficiency.

[0072] In Fig. 2B, the guest material 302 has protecting groups 320. Therefore, the luminophore 310 and the host materials 330 can be separated from each other. Consequently, energy transfer by the Dexter mechanism (Route B2) can be suppressed.

[0073] For the guest material 302 to emit light, the guest material 302 must receive energy from the host materials 330 through the Förster mechanism, since the Dexter mechanism is suppressed. In other words, it is preferable that the energy transfer through the Förster mechanism is efficiently utilized while the energy transfer through the Dexter mechanism is suppressed. It is known that the energy transfer through the Förster mechanism is also affected by the distance between a host material and a guest material. Generally, the Dexter mechanism is dominant when the distance between the host material 330 and the luminophore 310 of the guest material 302 is less than or equal to 1 nm, and the Förster mechanism is dominant when the distance between them is greater than or equal to 1 nm and less than or equal to 10 nm.In general, energy transfer is less likely to occur when the distance between the host material 330 and the luminophore 310 of the guest material 302 is greater than or equal to 10 nm.

[0074] Therefore, the protecting groups 320 preferably extend within a range of greater than or equal to 1 nm and less than or equal to 10 nm, more preferably within a range of greater than or equal to 1 nm and less than or equal to 5 nm, from the luminophore 310. With such a structure, the energy transfer by the Förster mechanism from the host material 330 to the guest material 302 can be efficiently utilized while suppressing the energy transfer by the Dexter mechanism. In this way, a light-emitting device with high emission efficiency can be manufactured.

[0075] Furthermore, the concentration of the guest material 301 or the guest material 302 relative to the host material 330 is preferably increased to increase the energy transfer efficiency (the rate of energy transfer) by the Förster mechanism. However, when the concentration of the guest material is increased, the rate of energy transfer by the Dexter mechanism is usually increased, resulting in a decrease in emission efficiency. Therefore, it is difficult to increase the concentration of the guest material. As a fluorescent device using a material having a function of converting triplet excitation energy into light emission as the host material, a light-emitting device in which the concentration of the guest material is low, that is, less than or equal to 1 wt%, is reported.

[0076] In contrast, in the light-emitting device of one embodiment of the present invention, a guest material in which the luminophore has protecting groups is used for the light-emitting layer. Therefore, energy transfer by the Förster mechanism can be efficiently utilized while energy transfer by the Dexter mechanism is suppressed. Consequently, the concentration of the guest material, which is an energy acceptor, can be increased. As a result, the phenomena that originally compete with each other, that is, the rate of energy transfer by the Förster mechanism is increased while energy transfer by the Dexter mechanism is suppressed, can be caused. The concentration of the guest material with respect to the host material is preferably higher than or equal to 2 wt% and lower than or equal to 30 wt%, more preferably higher than or equal to 5 wt% and lower than or equal to 20 wt%.-%, more preferably higher than or equal to 5 wt% and lower than or equal to 15 wt%. With such a structure, the rate of energy transfer by the Förster mechanism can be increased; therefore, a light-emitting device with high emission efficiency can be obtained. Furthermore, by using a material having a function of converting triplet excitation energy into light emission as a host material, a fluorescent device with an emission efficiency as high as that of a phosphorescent device can be manufactured. Since the emission efficiency can be increased by using a fluorescent material with high stability, a light-emitting device with high reliability can be manufactured.

[0077] In particular, the effect of the light-emitting device of one embodiment of the present invention is not only to increase reliability by using a fluorescent material with high stability. The above-described energy transfer always competes with a quenching process due to the influence of deteriorating substances and impurities. As the quenching rate constant of the quenching process increases over time, the proportion of light emission from the light-emitting device decreases. This means that the luminance of the light-emitting device deteriorates.However, as described above, in one embodiment of the present invention, the rate of energy transfer through the Förster mechanism can be increased compared to a conventional light-emitting device while suppressing energy transfer through the Dexter mechanism. Consequently, the influence of competition with the quenching process can be reduced, so that the lifetime of the light-emitting device can be extended.

[0078] Here, the luminophore in a fluorescent material refers to an atomic group (backbone) that emits light. The luminophore generally has a π bond and preferably comprises an aromatic ring, more preferably a fused aromatic ring or a fused heteroaromatic ring. As a further embodiment, the luminophore can be considered an atomic group (backbone) comprising an aromatic ring with a transition dipole vector on one face of the ring.

[0079] Examples of the fused aromatic ring or the fused heteroaromatic ring include a phenanthrene skeleton, a stilbene skeleton, an acridone skeleton, a phenoxazine skeleton, and a phenothiazine skeleton. In particular, a fluorescent material having a naphthalene skeleton, an anthracene skeleton, a fluorene skeleton, a chrysene skeleton, a triphenylene skeleton, a tetracene skeleton, a pyrene skeleton, a perylene skeleton, a coumarin skeleton, a quinacridone skeleton, or a naphthobisbenzofuran skeleton is preferred because the fluorescence quantum yield is high.

[0080] The protecting groups must have a triplet excitation energy level higher than the T1 levels of the luminophore and the host material. Therefore, a saturated hydrocarbon group is preferable. This is because a substituent without a π bond has a high triplet excitation energy level. Furthermore, a substituent without a π bond lacks a charge carrier (electron or hole) transport function. As a result, a saturated hydrocarbon group can separate the luminophore and the host material without significantly affecting the excited state or charge carrier transport property of the host material.In an organic compound containing both a substituent without a π bond and a substituent with a π-conjugated system, in many cases the frontier orbitals (the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO)) are located on the side of the substituent with a π-conjugated system; in particular, there is a tendency for the luminophore to have the frontier orbitals. As described below, the overlap of the HOMO of the energy donor and the HOMO of the energy acceptor, as well as the overlap of the LUMO of the energy donor and the LUMO of the energy acceptor, are important for energy transfer by the Dexter mechanism.Therefore, by using a saturated hydrocarbon group as a protecting group, the frontier orbitals of the host material, which is an energy donor, and the frontier orbitals of the guest material, which is an energy acceptor, can be removed, thereby suppressing the energy transfer by the Dexter mechanism.

[0081] A specific example of the protecting group is an alkyl group having 1 to 10 carbon atoms. Furthermore, the protecting group is preferably a bulky substituent because the luminophore and the host material must be separated from each other. In other words, a substituent with large steric hindrance is preferred. Therefore, an alkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, or a trialkylsilyl group having 3 to 10 carbon atoms can be preferably used. In particular, the alkyl group is preferably a bulky branched-chain alkyl group. This substituent is particularly preferred because it becomes bulky with a quaternary carbon.

[0082] A luminophore preferably has five or more protecting groups. With such a structure, the luminophore can be completely covered with the protecting groups, so that the distance between the host material and the luminophore can be appropriately controlled. Fig. 2B, the protecting groups are directly bonded to the luminophore; however, the protecting groups are preferably not directly bonded to the luminophore. For example, the protecting groups can each be bonded to the luminophore via a substituent with a valence of 2 or more, such as an arylene group or an amino group. When each of the protecting groups is bonded to the luminophore via the substituent, the luminophore can be effectively removed from the host material. Therefore, in the case where the protecting groups are not directly bonded to the luminophore and a luminophore has four or more protecting groups, energy transfer by the Dexter mechanism can be effectively suppressed.

[0083] Furthermore, the substituent with a valence of 2 or more that binds the luminophore to one of the protecting groups is preferably a substituent with a π-conjugated system. With such a structure, the physical properties of the guest material, such as the emission color, HOMO level, and glass transition temperature, can be controlled. It should be noted that the protecting groups are preferably positioned on the outermost side when observing the molecular structure around the luminophore. <Beispiele für ein fluoreszierendes Material mit Schutzgruppen und dessen Molekularstruktur>

[0084] Here, a structure of N,N'-[(2-tert-butylanthracene)-9,10-diyl]-N,N'-bis(3,5-di-tert-butylphenyl)amine (abbreviation: 2tBu-mmtBuDPhA2Anth) is shown, which is a fluorescent material represented by the following structural formula (102) and can be used for the light-emitting device of one embodiment of the present invention. In 2tBu-mmtBuDPhA2Anth, an anthracene ring is a luminophore, and a tertiary butyl group (tBu group) serves as a protecting group.

[0085] Fig. Figure 3B shows a rod model of 2tBu-mmtBuDPhA2Anth. It should be noted that Fig. 3B shows the state in which 2tBu-mmtBuDPhA2Anth is oriented in the direction of the arrow Fig. 3A (from the direction parallel to the surface of the anthracene ring). The hatched part in Fig. Figure 3B shows a blanket portion of the anthracene ring surface, which is a luminophore, and the blanket portion includes an area overlapping with tBu groups, which are protecting groups. For example, in Fig. In Figure 3B, an atom represented by arrow (a) is a carbon atom of the tBu group, which overlaps with the hatched part, and an atom represented by arrow (b) is a hydrogen atom of the tBu group, which overlaps with the hatched part. This means that in 2tBu-mmtBuDPhA2Anth, atoms contained in protecting groups are positioned directly on one face of the luminophore, and atoms contained in protecting groups are also positioned directly on the other face. With such a structure, even when the guest material is dispersed in the host material, the anthracene ring, which is a luminophore, and the host material can be separated from each other in both the horizontal and vertical directions of the anthracene ring, resulting in the suppression of energy transfer by the Dexter mechanism.

[0086] Furthermore, for example, when the transition involving energy transfer is a HOMO-LUMO transition, the overlap between the HOMO of the host material and the HOMO of the guest material, as well as the overlap between the LUMO of the host material and the LUMO of the guest material, are important for energy transfer through the Dexter mechanism. The overlap between the HOMOs of the two materials and the overlap between their LUMOs largely cause the Dexter mechanism. Therefore, it is important to avoid the overlap between the HOMOs of the two materials and the overlap between their LUMOs to suppress the Dexter mechanism. This means that it is important to keep the excited-state framework and the host material separate from each other. In a fluorescent material, both the HOMO and the LUMO are often present in the luminophore.For example, in the case where the HOMO and LUMO of the guest material extend above and below the luminophore face (above and below the anthracene ring in 2tBu-mmtBuDPhA2Anth), it is important that the molecular structure covers the top and bottom surfaces of the luminophore with protecting groups.

[0087] A fused aromatic ring and a fused heteroaromatic ring serving as a luminophore, such as a pyrene ring and an anthracene ring, have a transition dipole vector on the ring face. Therefore, Fig. 3B 2tBu-mmtBuDPhA2Anth preferably has a region overlapping with the tBu group, which is a protecting group, directly on a face where a transition dipole vector is located, i.e., directly on the face of the anthracene ring. In particular, at least one of atoms of a plurality of protecting groups (the tBu groups in Fig. 3A and Fig. 3B) directly onto a surface of a fused aromatic ring or a fused heteroaromatic ring (the anthracene ring in Fig. 3A and Fig. 3B), and at least one of the atoms of the plurality of protecting groups is positioned directly on the other face of the fused aromatic ring or the fused heteroaromatic ring. With such a structure, even in the state where the guest material is dispersed in the host material, the luminophore and the host material can be separated from each other, resulting in the suppression of energy transfer by the Dexter mechanism. Furthermore, the tBu groups are preferably positioned to cover a luminophore, such as an anthracene ring. <Grund für die Verwendung eines phosphoreszierenden Materials mit einem fünfgliedrigen Ring-Gerüst>

[0088] Next, an energy donor is discussed. The present inventors have discovered that when a material with a five-membered ring framework is used as a phosphorescent material used as an energy donor, energy transfer through the Förster mechanism can be effectively utilized. As described below, a phosphorescent material with a five-membered ring framework can be advantageously used as a bulk energy donor.

[0089] A heteroaromatic ring structure is preferred as the five-membered ring structure. Examples include a pyrrole structure, a pyrazole structure, an imidazole structure, a triazole structure, a tetrazole structure, a benzimidazole structure, and a naphthoimidazole structure. Particularly, a phosphorescent material having an imidazole structure, a triazole structure, a benzimidazole structure, or a naphthoimidazole structure is preferred. A metal complex having the structure as a ligand is used. It is preferred that the metal complex has the structure as a ligand and comprises a metal from one of Groups 8 to 10 and Periods 5 and 6 (Ru, Rh, Pd, Os, Ir, or Pt) as the central metal; among these, an Ir complex is particularly preferred. It should be noted that a benzimidazole skeleton and a naphthoimidazole skeleton are examples of a skeleton having an imidazole skeleton.

[0090] A phosphorescent material having a five-membered ring framework as a ligand tends to have a high HOMO level. In the case where a material having a high HOMO level is used as the above-described compound 133 (energy donor) in the light-emitting layer 130, when a current flows through the light-emitting device 150, hole capture by compound 132, which is the guest material (energy acceptor), can be prevented, that is, compound 132 can be prevented from becoming positively charged. Except for the above-mentioned exciplex, excitation of a compound due to current is caused by the capture of a hole and an electron on the same molecule. Therefore, when a material having a high HOMO level is used as compound 133, current excitation in compound 132 (direct excitation of compound 132) can be prevented.Since compound 132 is a fluorescent material, when compound 132 is directly excited, triplet excitons generated do not contribute to light emission, resulting in a reduction in emission efficiency. Therefore, in the case where the HOMO level of the phosphorescent material with a five-membered ring framework is high, using the phosphorescent material as compound 133 can suppress a reduction in the emission efficiency of the light-emitting device 150. <Phosphoreszierendes Material mit einem fünfgliedrigen Ring-Gerüst als voluminöser Energiedonator>

[0091] The following describes examples of the Ir complex having a five-membered ring framework as a ligand as a phosphorescent material having a five-membered ring framework as a ligand that can be used in one embodiment of the present invention. Ir(mpptz-diPrp)3 is an Ir complex having a triazole framework as a five-membered ring framework, and fac-Ir(pbi-diBup)3 is an Ir complex having an imidazole framework as a five-membered ring framework.

[0092] In the case where, as in the case of the above Ir complex, a skeleton containing two or more nitrogen atoms in a five-membered ring skeleton, such as an imidazole skeleton or a triazole skeleton, is used as the five-membered ring skeleton of a ligand, nitrogen is present that is not coordinated to a metal. At least one nitrogen that is not coordinated to the metal does not participate in a double bond; therefore, it can have a substituent while maintaining an aromatic ring (a nitrogen atom indicated by a circle in each of the above Ir complexes). Various substituents, such as hydrogen, an alkyl group, and an aromatic hydrocarbon group, can be specified as the substituent, and a substituted or unsubstituted aromatic hydrocarbon group having 6 to 13 carbon atoms is preferred.In particular, an unsubstituted phenyl group or a phenyl group comprising one or more alkyl groups having 1 to 6 carbon atoms is preferred. An electron-withdrawing group, such as fluorine, a cyano group, or an alkyl fluoride group, may be further bonded to the phenyl group. With such a structure, the thermal stability and sublimability of the Ir complex can be increased.

[0093] Therefore, in the case where the compound having a five-membered ring structure is used as the ligand of the Ir complex, the nitrogen atom preferably has a substituted or unsubstituted aromatic hydrocarbon group having 6 to 13 carbon atoms as a substituent. With the substituent, the ligand has a bulky structure with large steric hindrance. As a result, the Ir complex has a bulky structure. In other words, in the case where the compound having a five-membered ring structure is used as the ligand of the phosphorescent material, there is a tendency for the Ir complex to have a bulky structure.

[0094] Here, the case where the Ir complex is excited is described. In the Ir complex, which is a phosphorescent material, the lowest triplet excitation level often originates from the triplet MLCT. Therefore, in many cases, the triplet excitation energy is present near an Ir atom and a portion coordinated to an Ir atom in a ligand (a nitrogen atom coordinated to Ir or an ortho-metalated carbon atom).

[0095] Here, the case is described in which the Ir complex is dispersed in the light-emitting layer with a bulky ligand. Thanks to the bulky ligand, an Ir atom in the Ir complex and a material surrounding the Ir complex can be separated from each other. This means that the deactivation of the triplet excitation energy can be suppressed by the Dexter mechanism.

[0096] Here, the case where the bulky Ir complex is used as the above-described compound 133 is described. As described above, the deactivation of the excitation energy by the Dexter mechanism from compound 133 to compound 132 (Route A3) can be suppressed. Therefore, the energy transfer by Route A2 (energy transfer by the Förster mechanism) can be efficiently utilized. Consequently, a light-emitting device with high emission efficiency can be obtained by using the Ir complex having a five-membered ring framework as a ligand.

[0097] When the Ir complex having a five-membered ring framework as a ligand, as described above, is used as an energy donor, the excitation energy transfer by the Dexter mechanism can be suppressed. Therefore, in the case where the Ir complex having a five-membered ring as a ligand is used as an energy donor, energy transfer by route A2 can be efficiently utilized even when the number of protecting groups of the energy acceptor, which is the guest material, is small. In this case, the energy acceptor preferably has at least two protecting groups, more preferably three or more protecting groups, even more preferably four or more protecting groups for a luminophore. As the five-membered ring framework used as a ligand of the Ir complex, an imidazole framework or a triazole framework is preferred.It is more preferable that the Ir complex has a structure in which a substituted or unsubstituted aromatic hydrocarbon group having 6 to 13 carbon atoms is bonded to a nitrogen atom that is not bonded to Ir and does not participate in a double bond. In the case where the aromatic hydrocarbon group is a phenyl group and the phenyl group has a substituent, it is more preferable that an alkyl group having 1 to 6 carbon atoms is included as a substituent.

[0098] Specific examples of the aromatic hydrocarbon group having 6 to 13 carbon atoms include a phenyl group, a biphenyl group, a naphthyl group, and a fluorenyl group. Examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, a pentyl group, a hexyl group, a cyclohexyl group, a norbornyl group, an adamantyl group, an isopropyl group, a sec-butyl group, an isobutyl group, a tert-butyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a neopentyl group, an isohexyl group, a 3-methylpentyl group, a 2-methylpentyl group, a 2-ethylbutyl group, a 1,2-dimethylbutyl group, and a 2,3-dimethylbutyl group. Note that the aromatic hydrocarbon group having 6 to 13 carbon atoms and the alkyl group having 1 to 6 carbon atoms are not limited thereto.

[0099] The triplet excitation energy of the Ir complex having a five-membered ring framework as a ligand tends to be higher than that of an Ir complex consisting only of a six-membered ring framework. Therefore, in the case where a fluorescent material that emits light with a relatively short wavelength, such as green or blue light, is used as compound 132, which is an energy acceptor, the Ir complex having a five-membered ring framework as a ligand can be advantageously used as an energy donor.

[0100] As described below, with respect to energy transfer by the Förster mechanism, it is preferable that the absorption spectrum (absorption band on the longest wavelength side (absorption band originating mainly from the S1 level)) of the energy acceptor largely overlaps with the emission spectrum of the energy donor. In the case where a fluorescent material is used that has an emission peak on a relatively short wavelength side (400 nm to 580 nm), that is, in the blue to green range, the absorption band of the fluorescent material is also located on the short wavelength side. Therefore, an energy donor with high triplet excitation energy is preferably used so that the absorption band largely overlaps with the emission spectrum of the energy donor.

[0101] When a phosphorescent material having a five-membered ring framework is used as compound 133, energy transfer by the Förster mechanism can be efficiently utilized while energy transfer by the Dexter mechanism is suppressed; therefore, in the case where compound 133, which is the energy donor, is added to the light-emitting layer 130, the concentration of the compound 133 can be increased. As a result, the phenomena that originally compete with each other can be caused, that is, the rate of energy transfer by the Förster mechanism is increased while energy transfer by the Dexter mechanism is suppressed. The concentration of compound 133 with respect to the host material is preferably higher than or equal to 2 wt% and lower than or equal to 30 wt%, more preferably higher than or equal to 5 wt% and lower than or equal to 20 wt%.-%, more preferably higher than or equal to 5 wt% and lower than or equal to 15 wt%. With such a structure, the rate of energy transfer by the Förster mechanism can be increased; therefore, a light-emitting device with high emission efficiency can be obtained. Since the emission efficiency can be increased using a fluorescent material with high stability, a light-emitting device with high reliability can be manufactured. The concentration of compound 133 and the concentration of compound 132, which is a fluorescent material, are preferably high. In addition, the concentration of compound 133 is preferably as high as the concentration of compound 132.In particular, the concentration ratio of compound 133 to compound 132 is greater than or equal to 1:0.2 and less than or equal to 1:5, more preferably greater than or equal to 1:0.5 and less than or equal to 1:2. <Strukturbeispiel 2 der Licht emittierenden Schicht>

[0102] Fig. Figure 4C shows an example of the correlation of energy levels in the light-emitting layer 130 of the light-emitting device 150 of an embodiment of the present invention. The light-emitting layer 130 shown in Fig. 4A contains compound 131, compound 132, and also compound 133. In one embodiment of the present invention, compound 132 is preferably a fluorescent material. In this structural example, the combination of compounds 131 and 133 forms an exciplex. Note that the case where compound 133 is a phosphorescent material having a five-membered ring framework will be described below.

[0103] As long as the combination of compounds 131 and 133 can form an exciplex, it is acceptable; however, preferably, one of them is a compound with a function of transporting holes (a hole-transport property) and the other is a compound with a function of transporting electrons (an electron-transport property). In this case, a donor-acceptor exciplex is easily formed; thus, an exciplex can be formed efficiently. In the case where the combination of compounds 131 and 133 is a combination of a compound with a hole-transport property and a compound with an electron-transport property, the carrier balance can be easily controlled by the mixing ratio.In particular, the weight ratio of the compound with a hole-transport property to the compound with an electron-transport property is preferably within a range of 1:9 to 9:1. Since the charge carrier balance can be easily controlled by this structure, a charge carrier recombination range can also be easily controlled. The phosphorescent material with a five-membered ring framework is more likely to exhibit a high HOMO level. Therefore, it can be advantageously used as a material with a hole-transport property.

[0104] For the combination of host materials to efficiently form an exciplex, the following conditions are preferably met: the HOMO level of one of the compounds 131 and 133 is higher than that of the other compound, and the LUMO level of one of the compounds is higher than that of the other compound. Note that the HOMO level of compound 131 may be the same as the HOMO level of compound 133, or the LUMO level of compound 131 may be the same as the LUMO level of compound 133.

[0105] It should be noted that the LUMO levels and HOMO levels of the compounds can be obtained from the electrochemical properties (reduction potentials and oxidation potentials) of the compounds measured by cyclic voltammetry (CV) measurement.

[0106] For example, in the case where compound 133 has a hole transport property and compound 131 has an electron transport property, the HOMO level of compound 133 is preferably higher than the HOMO level of compound 131, and the LUMO level of compound 133 is preferably higher than the LUMO level of compound 131, as shown in an energy band diagram in Fig. 4B. Such a correlation of energy levels is suitable because holes and electrons, which serve as charge carriers, are easily injected from the pair of electrodes (electrode 101 and electrode 102) into junction 133 and junction 131, respectively.

[0107] In Fig. 4B, “Comp (131)” represents compound 131, “Comp (133)” represents compound 133, ΔE C1 represents the energy difference between the LUMO level and the HOMO level of compound 131, ΔE C3represents the energy difference between the LUMO level and the HOMO level of compound 133 and represents ΔE E the energy difference between the LUMO level of compound 131 and the HOMO level of compound 133.

[0108] The exciplex formed by compound 131 and compound 133 has the HOMO in compound 133 and the LUMO in compound 131. The excitation energy of the exciplex essentially corresponds to the energy difference between the LUMO level of compound 131 and the HOMO level of compound 133 (ΔE E ), which is smaller than the energy difference between the LUMO level and the HOMO level of compound 131 (ΔE C1 ) and is smaller than the energy difference between the LUMO level and the HOMO level of compound 133 (ΔE C3). Thus, when compound 131 and compound 133 form an exciplex, an excited state with a lower excitation energy can be formed. The exciplex can form a stable excited state because it has a lower excitation energy.

[0109] Fig. Figure 4C shows the correlation of the energy levels of compounds 131, 132 and 133 in the light-emitting layer 130. The following explains what the terms and symbols in Fig. 4C. • Comp (131): the connection 131 • Comp (133): the connection 133 • Guest (132): the connection 132 • S C1 : the S1 level of compound 131 • T C1 : the T1 level of compound 131 • S C3 : the S1 level of compound 133 • T C3 : the S1 level of compound 133 • S G : the S1 level of compound 132 • T G: the T1 level of compound 132 • S E : the S1 level of the exciplex • T E : the T1 level of the exciplex

[0110] In the light-emitting device of one embodiment of the present invention, compound 131 and compound 133 contained in light-emitting layer 130 form an exciplex. The S1 level (S E ) of the exciplex and the T1 level (T E ) of the exciplex are close to each other (see route A4 in Fig. 4C).

[0111] Since the excitation energy levels (S E and T E ) of the exciplex is lower than the S1 levels (S C1 and S C3 ) of the substances (compounds 131 and 133) forming an exciplex, an excited state with lower excitation energy can be formed. Consequently, the operating voltage of the light-emitting device 150 can be reduced.

[0112] Since the S1 level (S E ) and the T1 level (T E ) of the exciplex are close to each other, the reverse intersystem crossing occurs with a higher probability and the exciplex exhibits a TADF property. Therefore, the exciplex has a function of converting the triplet excitation energy into the singlet excitation energy by upconversion (route A5 in Fig. 4C). The singlet excitation energy of the exciplex can be rapidly transferred to compound 132 (route A6 in Fig. 4C). S E ≥ S G preferably fulfilled. In route A6, the exciplex serves as the energy donor and compound 132 serves as the energy acceptor. In particular, S E ≥ S G preferably fulfilled when the level of energy with a wavelength of the line obtained by extrapolating a tangent to the fluorescence spectrum of the exciplex at a tail on the short wavelength side, SE and the level of energy with a wavelength of the absorption edge of the absorption spectrum of compound 132 or the level of energy with a wavelength of the line obtained by extrapolating a tangent to the fluorescence spectrum at a tail on the short wavelength side, S G is.

[0113] To improve the TADF property, the T1 levels of the two compounds 131 and 133, ie T C1 and T C3 , higher than or equal to T E. As an index of this, the emission peak wavelengths of the phosphorescence spectra of compounds 131 and 133 on the shortest wavelength side are each preferably less than or equal to the maximum emission peak wavelength of the exciplex. When the energy level having a wavelength of the line obtained by extrapolating a tangent to the emission spectrum of the exciplex at a tail on the short wavelength side, T E is the level of energy with a wavelength of the line obtained by extrapolating a tangent to the phosphorescence spectrum of compound 131 at a tail on the short wavelength side, T C1 and the level of energy with a wavelength of the line obtained by extrapolating a tangent to the phosphorescence spectrum of compound 133 at a tail on the short wavelength side, T C3 is, T E -T C1 ≤ 0.2 eV and T E -TC3 ≤ 0.2 eV is preferably fulfilled.

[0114] A compound containing a heavy atom is used in this structural example as one of the compounds forming an exciplex. Therefore, intersystem crossing between a singlet state and a triplet state is promoted. Therefore, an exciplex can be formed that can convert the energy of the triplet excited state into light emission. In this case, the triplet excited energy level (T E ) of the exciplex will be the level of the energy donor, and therefore T E preferably higher than or equal to the singlet excitation energy level (S G ) of compound 132, which is a light-emitting material. In particular, T E ≥ S Gpreferably fulfilled when the level of energy with a wavelength of the line obtained by extrapolating a tangent to the emission spectrum of the exciplex containing a heavy atom at a tail on the short wavelength side, T E and the level of energy with a wavelength of the absorption edge of the absorption spectrum of compound 132 or the level of energy with a wavelength of the line obtained by extrapolating a tangent to the emission spectrum at a tail on the short wavelength side, S G is.

[0115] With such a correlation of energy levels, the triplet excitation energy of the formed exciplex can be determined from the triplet excitation energy level (T E ) of the exciplex directly or via the singlet excitation energy level (S E ) to the singlet excitation energy level (S G) of compound 132. It should be noted that in some cases it is difficult to clearly distinguish fluorescence and phosphorescence in an emission spectrum because the S1 level (S E ) and the T1 level (T E ) of the exciplex are close to each other. In this case, fluorescence and phosphorescence can sometimes be distinguished by their emission lifetimes.

[0116] The energy transfer process of the triplet excitation energy generated in the light-emitting layer 130 through routes A4 and A6, i.e., from the S1 level of the exciplex to the S1 level of the guest material, enables light emission from the guest material. Therefore, by using a combination of the materials forming an exciplex in the light-emitting layer 130, the emission efficiency of the fluorescent device can be increased.

[0117] Note that the heavy atom-containing compound used in the above structure preferably contains a heavy atom, such as Ir, Pt, Os, Ru, or Pd. The heavy atom-containing compound is preferably a phosphorescent material. In contrast, in this structural example, a phosphorescent material serves as an energy donor and is one of the materials forming an exciplex; therefore, the quantum yield can be high or low. That is, energy transfer from the triplet excitation energy level of the exciplex to the singlet excitation energy level of the guest material, directly or via the singlet excitation energy level, is preferably a permitted transition.Energy transfer from the exciplex formed using a phosphorescent material or from the phosphorescent material to the guest material is preferred because energy transfer from the triplet excitation energy level of the energy donor to the singlet excitation energy level of the guest material (energy acceptor) is a permitted transition. Therefore, there is also a route in which the triplet excitation energy of the exciplex can be transferred without undergoing the process of route A5 in [Figure 1]. Fig. 4C to the S1 level (S G ) of the guest material is transferred through the process of route A5. In route A5, the exciplex serves as the energy donor and compound 132 serves as the energy acceptor.

[0118] In the light-emitting device of one embodiment of the present invention, a guest material in which the luminophore has protecting groups is used as compound 132. With such a structure, energy transfer by the Dexter mechanism represented by route A7 as described above can be suppressed; thus, deactivation of the triplet excitation energy can be suppressed. Therefore, a fluorescent device with high emission efficiency can be obtained.

[0119] In one embodiment of the present invention, the phosphorescent material having a five-membered ring framework is further used. With such a structure, energy transfer by the Dexter mechanism represented by route A7 can be suppressed as described above; thus, the deactivation of the triplet excitation energy can be suppressed. Furthermore, charge carrier recombination in compound 132 can be suppressed. Therefore, a fluorescent device with high emission efficiency can be obtained.

[0120] The processes described above through routes A4 to A6 may be referred to in this specification and the like as exciplex-singlet energy transfer (ExSET) or exciplex-enhanced fluorescence (ExEF). In other words, in the light-emitting layer 130, the excitation energy is transferred from the exciplex to the fluorescent material. <Strukturbeispiel 3 der Licht emittierenden Schicht>

[0121] Fig. Figure 5A illustrates the light-emitting layer 130, which contains four types of materials. Fig. 5A, the light-emitting layer 130 contains compound 131, compound 132, compound 133, and compound 134. In one embodiment of the present invention, compound 133 has a function of converting triplet excitation energy into light emission. In this structural example, compound 133 is a phosphorescent material with a five-membered ring framework. Compound 132 is a guest material that emits fluorescence. Compound 131 is an organic compound that forms an exciplex with compound 134.

[0122] Fig. Figure 5B shows the correlation of the energy levels of compounds 131, 132, 133 and 134 in the light-emitting layer 130. The terms and symbols in Fig. 5B represent the following levels, and the other terms and symbols are the same as those used in Fig. 2B are shown. • S C4 : the S1 level of compound 134 • T C4 : the T1 level of compound 134

[0123] In the light-emitting device of one embodiment of the present invention in this structural example, the compound 131 and the compound 134 contained in the light-emitting layer 130 form an exciplex. The S1 level (S E ) of the exciplex and the T1 level (T E ) of the Exciplex are close to each other (see route A8 in Fig. 5B).

[0124] As described above, when the exciplex formed by the above-mentioned process loses the excitation energy, the two kinds of substances constituting the exciplex behave individually as original separate substances.

[0125] Since the excitation energy levels (S E and T E ) of the exciplex is lower than the S1 levels (S C1 and S C4) of the substances (compounds 131 and 134) forming an exciplex, an excited state with lower excitation energy can be formed. Consequently, the operating voltage of the light-emitting device 150 can be reduced.

[0126] Here, if compound 133 is a phosphorescent material, intersystem crossing between a singlet state and a triplet state is allowed. Thus, both the singlet excitation energy and the triplet excitation energy of the exciplex are rapidly transferred to compound 133 (route A9). At this time, T E ≥ T C3 preferably fulfilled. In addition, the triplet excitation energy of compound 133 can be efficiently converted into the singlet excitation energy of compound 132 (Route A 10 ). Here T E ≥ T C3 ≥ S G , as in Fig. 5B, in which case the excitation energy of compound 133 is efficiently transferred as singlet excitation energy to compound 132, which is a guest material. In particular, T C3 ≥ S G preferably fulfilled when the level of energy having a wavelength of the line obtained by extrapolating a tangent to the phosphorescence spectrum of compound 133 at a tail on the short wavelength side is T C3 and the level of energy with a wavelength of the absorption edge of the absorption spectrum of compound 132 or the level of energy with a wavelength of the line obtained by extrapolating a tangent to the fluorescence spectrum at a tail on the short wavelength side, S G is. In Route A 10 Compound 133 serves as an energy donor and compound 132 serves as an energy acceptor.

[0127] As long as the combination of compounds 131 and 134 can form an exciplex, it is acceptable; however, preferably one of them is a compound with a hole-transport property and the other is a compound with an electron-transport property.

[0128] For the combination of materials to efficiently form an exciplex, the following is preferably satisfied: the HOMO level of one of the compounds 131 and 134 is higher than that of the other compound, and the LUMO level of one of the compounds is higher than that of the other compound.

[0129] The correlation of the energy levels of compounds 131 and 134 is not due to the Fig. 5B. In other words, the singlet excitation energy level (S C1 ) of compound 131 can be higher or lower than the singlet excitation energy level (S C4) of compound 134 and the triplet excitation energy level (T C1 ) of compound 131 can be higher or lower than the triplet excitation energy level (T C4 ) of compound 134.

[0130] Furthermore, in the light-emitting device of one embodiment of the present invention, compound 131 preferably has a π-electron-deficient framework. Such a composition reduces the LUMO level of compound 131, which is suitable for the formation of an exciplex.

[0131] Furthermore, in the light-emitting device of one embodiment of the present invention, compound 131 preferably has a π-electron-rich framework. Such a composition increases the HOMO level of compound 131, which is suitable for the formation of an exciplex.

[0132] In the light-emitting device of one embodiment of the present invention, a guest material in which the luminophore has protecting groups is used as compound 132. With such a structure, the energy transfer by the Dexter mechanism, which is achieved by route A 11 As described above, the deactivation of the triplet excitation energy can be suppressed. Therefore, a fluorescent device with high emission efficiency can be obtained.

[0133] In one embodiment of the present invention, a phosphorescent material having a five-membered ring framework is used as compound 133. With such a structure, the energy transfer by the Dexter mechanism, which is achieved by route A 11represented as described above; thus, the deactivation of the triplet excitation energy can be suppressed. Furthermore, charge carrier recombination in compound 132 can be suppressed. Therefore, a fluorescent device with high emission efficiency can be obtained.

[0134] Note that in this specification and the like, the processes described above through routes A8 and A9 may be referred to as exciplex triplet energy transfer (ExTET). In other words, in the light-emitting layer 130, the excitation energy is transferred from the exciplex to the compound 133. Therefore, this structural example can be regarded as a structure in which a fluorescent material with protecting groups is mixed into the light-emitting layer, which can utilize ExTET. <Strukturbeispiel 4 der Licht emittierenden Schicht>

[0135] In this structural example, the case where a TADF material is used as compound 134 described in the structural example 3 of the light-emitting layer is described.

[0136] Fig. Figure 5C illustrates the light-emitting layer 130, which contains four types of materials. Fig. 5C, the light-emitting layer 130 contains compound 131, compound 132, compound 133, and compound 134. In one embodiment of the present invention, compound 133 has a function of converting triplet excitation energy into light emission. Compound 132 is a guest material that emits fluorescence. Compound 131 is an organic compound that forms an exciplex with compound 134. In this structural example, compound 133 is a phosphorescent material with a five-membered ring framework.

[0137] Since compound 134 is a TADF material, compound 134, which does not form an exciplex, has a function of converting the triplet excitation energy into the singlet excitation energy by upconversion (Route A 12 in Fig. 5C). The singlet excitation energy of compound 134 can be rapidly transferred to compound 132 (Route A 13 in Fig. 5C). S C4 ≥ S G preferably fulfilled. In particular, S C4 ≥ S G preferably satisfied when the level of energy having a wavelength of the line obtained by extrapolating a tangent to the fluorescence spectrum of compound 134 at a tail on the short wavelength side is S C4and the level of energy with a wavelength of the absorption edge of the absorption spectrum of compound 132 or the level of energy with a wavelength of the line obtained by extrapolating a tangent to the fluorescence spectrum at a tail on the short wavelength side, S G is.

[0138] As described in the above structural example of the light-emitting layer, in the light-emitting device of one embodiment of the present invention, there is a path through which the triplet excitation energy is applied to the compound 132, which is a guest material, via the routes A8 to A 10 in Fig. 5B, and a path through which the triplet excitation energy is transferred to compound 132 via routes A 12 and A 13 in Fig. 5C. The variety of pathways by which the triplet excitation energy is transferred to a fluorescent material can further increase the emission efficiency. In route A 10 Compound 133 serves as an energy donor and compound 132 serves as an energy acceptor. In route A 13 Compound 134 serves as an energy donor and compound 132 serves as an energy acceptor.

[0139] In the light-emitting device of one embodiment of the present invention, a guest material in which the luminophore has protecting groups is used as compound 132. With such a structure, the energy transfer by the Dexter mechanism, which is achieved by route A 11 As described above, the deactivation of the triplet excitation energy can be suppressed. Therefore, a fluorescent device with high emission efficiency can be obtained.

[0140] In one embodiment of the present invention, a phosphorescent material having a five-membered ring framework is used as compound 133. With such a structure, the energy transfer by the Dexter mechanism, which is achieved by route A 11 represented as described above; thus, the deactivation of the triplet excitation energy can be suppressed. Furthermore, charge carrier recombination in compound 132 can be suppressed. Therefore, a fluorescent device with high emission efficiency can be obtained. <Energieübertragungsmechanismus>

[0141] The Förster mechanism and the Dexter mechanism are described below. Here, an intermolecular energy transfer process between the first material and the second material is described, with respect to the transfer of excitation energy from a first material in an excited state to a second material in a ground state. The same can also apply to the case where one of them is an exciplex. <<Förster-Mechanismus> >

[0142] In the Förster mechanism, no direct contact between molecules is necessary for energy transfer, and the energy is transferred through a resonance phenomenon of dipole vibration between the first material and the second material. Through the resonance phenomenon of dipole vibration, the first material transfers the energy to the second material, and thus the first material, which is in an excited state, is brought to a ground state, and the second material, which is in a ground state, is brought to an excited state. Note that the rate constant k h*→g of the Förster mechanism is represented by formula (1). [Formula 1] kh*→g=900c4K2ϕ ln10128π5n4NτR6∫f'h(v)εg(v)v4dv

[0143] In formula (1) v represents a frequency, f' h(v) represents a normalized emission spectrum of the first material (a fluorescence spectrum at energy transfer from a singlet excited state, and a phosphorescence spectrum at energy transfer from a triplet excited state), ε g (v) represents a molar absorption coefficient of the second material, N represents the Avogadro number, n represents a refractive index of a medium, R represents an intermolecular distance between the first material and the second material, r represents a measured lifetime of an excited state (fluorescence lifetime or phosphorescence lifetime), c represents the speed of light, ϕ represents a luminescence quantum yield (a fluorescence quantum yield in the energy transfer from a singlet excited state, and a phosphorescence quantum yield in the energy transfer from a triplet excited state), and K 2represents a coefficient (0 to 4) for the orientation of a transition dipole moment between the first material and the second material. It should be noted that for random orientation K 2 = 2 / 3 applies. < <dexter-mechanismus>>

[0144] In the Dexter mechanism, the first material and the second material are near a contact-effective region where their orbitals overlap, and the first material, which is in an excited state, and the second material, which is in a ground state, exchange their electrons, resulting in energy transfer. Note that the rate constant k h*→g of the Dexter mechanism is represented by formula (2). [Formula 2] kh*→g=(2πh)K2 exp(−2RL)∫f'h(v)ε'g(v)dv

[0145] In formula (2), h represents a Planck constant, K represents a constant with an energy dimension, v represents a frequency, f' h (v) represents a normalized emission spectrum of the first material (the fluorescence spectrum at energy transfer from a singlet excited state, and the phosphorescence spectrum at energy transfer from a triplet excited state), ε' g (v) represents a normalized absorption spectrum of the second material, L represents an effective molecular radius, and R represents an intermolecular distance between the first material and the second material.

[0146] Here, the energy transfer efficiency ϕ ET from the first material to the second material is represented by formula (3). k r represents a rate constant of a light emission process (fluorescence in the energy transfer from a singlet excited state, and phosphorescence in the energy transfer from a triplet excited state) of the first material, k n represents a rate constant of a process without light emission (thermal deactivation or intersystem crossing) of the second material, and τ represents a measured lifetime of an excited state of the first material. [Formula 3] ϕET=kh*→gkr+kn+kh*→g=kh*→g(1π)+kh*→g

[0147] According to formula (3), it has been found that the energy transfer efficiency ϕ ET by increasing the rate constant k h*→g in the energy transfer can be increased, so that another competing rate constant k r + k n (= 1 / τ) becomes relatively small. <<Konzept zur Förderung der Energieübertragung> >

[0148] First, the energy transfer through the Förster mechanism is considered. If formula (1) is substituted into formula (3), it can be eliminated. Thus, in the Förster mechanism, the energy transfer efficiency ϕ ET does not depend on the lifetime τ of the excited state of the first material. Furthermore, it can be stated that the energy transfer efficiency ϕ ET is higher when the luminescence quantum yield ϕ is higher.

[0149] Preferably, the emission spectrum of the first material largely overlaps with the absorption spectrum (the absorption corresponding to the transition from a singlet ground state to a singlet excited state) of the second material. Furthermore, it is preferred 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 of the second material, which is located on the longest wavelength side. Since the direct transition from the singlet ground state to the triplet excited state of the second material is forbidden, the molar absorption coefficient of the second material in the triplet excited state is negligible.Therefore, a process of energy transfer from an excited state of the first material to a triplet excited state of the second material by the Förster mechanism is negligible, and only a process of energy transfer to a singlet excited state of the second material is considered.

[0150] The rate of energy transfer through the Förster mechanism is inversely proportional to the sixth power of the intermolecular distance R between the first material and the second material, according to formula (1). Furthermore, when R is less than or equal to 1 nm, as described above, energy transfer through the Dexter mechanism is dominant. Therefore, the intermolecular distance is preferably greater than or equal to 1 nm and less than or equal to 10 nm to increase the rate of energy transfer through the Förster mechanism while suppressing energy transfer through the Dexter mechanism. Therefore, the above protecting groups should not be so bulky; thus, the number of carbon atoms of the protecting groups is preferably 3 to 10.

[0151] Next, energy transfer through the Dexter mechanism is considered. To determine the rate constant k h*→9 To increase the energy transfer efficiency, according to formula (2), the emission spectrum (the fluorescence spectrum upon energy transfer from a singlet excited state, and the phosphorescence spectrum upon energy transfer from a triplet excited state) of the first material preferably overlaps largely with the absorption spectrum (the absorption corresponding to the transition from a singlet ground state to a singlet excited state) of the second material. Accordingly, the energy transfer efficiency can be optimized by ensuring that the emission spectrum of the first material overlaps with the absorption band of the second material located on the longest wavelength side.

[0152] When formula (2) is inserted into formula (3), it becomes clear that the energy transfer efficiency ϕ ET in the Dexter mechanism depends on τ. In the Dexter mechanism, which is an energy transfer process based on electron exchange, energy transfer occurs from the triplet excited state of the first material to the triplet excited state of the second material, as well as energy transfer from the singlet excited state of the first material to the singlet excited state of the second material.

[0153] In the light-emitting device of one embodiment of the present invention, in which the second material is a fluorescent material, the energy transfer efficiency to the triplet excited state of the second material is preferably low. That is, the energy transfer efficiency based on the Dexter mechanism from the first material to the second material is preferably low, and the energy transfer efficiency based on the Förster mechanism from the first material to the second material is preferably high.

[0154] As described above, in the Förster mechanism, the energy transfer efficiency does not depend on the lifetime τ of the excited state of the first material. In contrast, the energy transfer efficiency in the Dexter mechanism depends on the excitation lifetime τ of the first material. To reduce the energy transfer efficiency in the Dexter mechanism, the excitation lifetime τ of the first material is preferably short.

[0155] Therefore, in one embodiment of the present invention, an exciplex, a phosphorescent material, or a TADF material is used as the first material. These materials each have a function of converting triplet excitation energy into light emission. The energy transfer efficiency through the Förster mechanism depends on the luminescence quantum yield of the energy donor; therefore, the excitation energy of the first material capable of converting the triplet excited state into light emission, such as a phosphorescent material, an exciplex, or a TADF material, can be transferred to the second material through the Förster mechanism.In contrast, in the structure of one embodiment of the present invention, reverse intersystem crossing from the triplet excited state to the singlet excited state of the first material (the exciplex or the TADF material) can be promoted, and the excitation lifetime τ of the triplet excited state of the first material can be short. Furthermore, the transition from the triplet excited state to the singlet ground state of the first material (the phosphorescent material or the exciplex using the phosphorescent material) can be promoted, and the excitation lifetime τ of the triplet excited state of the first material can be short. As a result, the energy transfer efficiency from the triplet excited state of the first material to the triplet excited state of the fluorescent material (the second material) in the Dexter mechanism can be reduced.

[0156] As described above, in the light-emitting device of one embodiment of the present invention, a fluorescent material having protecting groups is used as the second material. Therefore, the intermolecular distance between the first material and the second material can be large. Therefore, in the light-emitting device of one embodiment of the present invention, a material having a function of converting triplet excitation energy into light emission is used as the first material and a fluorescent material having protecting groups is used as the second material, whereby the energy transfer efficiency by the Dexter mechanism can be reduced. As a result, non-radiative deactivation of the triplet excitation energy in the light-emitting layer 130 can be suppressed, and a light-emitting device with high emission efficiency can be provided. <materialien>

[0157] Next, components of the light-emitting device of one embodiment of the present invention will be described in detail below. <<Licht emittierende Schicht> >

[0158] Materials that can be used for the light-emitting layer 130 are described below. For the light-emitting layer of the light-emitting device of one embodiment of the present invention, an energy acceptor with a function of converting triplet excitation energy into light emission and an energy donor in which a luminophore has protecting groups are used. A TADF material, a phosphorescent material, and the like can be specified as a material with a function of converting triplet excitation energy into light emission.

[0159] Examples of the luminophore contained in compound 132 serving as an energy acceptor include a phenanthrene skeleton, a stilbene skeleton, an acridone skeleton, a phenoxazine skeleton, and a phenothiazine skeleton. In particular, a fluorescent compound having a naphthalene skeleton, an anthracene skeleton, a fluorene skeleton, a chrysene skeleton, a triphenylene skeleton, a tetracene skeleton, a pyrene skeleton, a perylene skeleton, a coumarin skeleton, a quinacridone skeleton, or a naphthobisbenzofuran skeleton is preferred because the fluorescence quantum yield is high.

[0160] The protecting group is preferably an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, a branched-chain alkyl group having 3 to 10 carbon atoms or a trialkylsilyl group having 3 to 12 carbon atoms.

[0161] Examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, a propyl group, a pentyl group, and a hexyl group, and a branched-chain alkyl group having 3 to 10 carbon atoms, which will be described below, is particularly preferred. Note that the alkyl group is not limited to this.

[0162] Examples of the cycloalkyl group having 3 to 10 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclohexyl group, a norbornyl group, and an adamantyl group. The cycloalkyl group is not limited to these. In the case where the cycloalkyl group has a substituent, examples of the substituent include an alkyl group having 1 to 7 carbon atoms such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, or a hexyl group; a cycloalkyl group having 5 to 7 carbon atoms such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, or a hexyl group; and B. a cyclopentyl group, a cyclohexyl group, a cycloheptyl group or an 8,9,10-trinorbornanyl group, and an aryl group having 6 to 12 carbon atoms, such as a phenyl group, a naphthyl group or a biphenyl group.

[0163] Examples of the branched-chain alkyl group having 3 to 10 carbon atoms include an isopropyl group, a sec-butyl group, an isobutyl group, a tert-butyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a neopentyl group, an isohexyl group, a 3-methylpentyl group, a 2-methylpentyl group, a 2-ethylbutyl group, a 1,2-dimethylbutyl group, and a 2,3-dimethylbutyl group. The branched-chain alkyl group is not limited to these.

[0164] Examples of the trialkylsilyl group having 3 to 12 carbon atoms include a trimethylsilyl group, a triethylsilyl group, and a tert-butyldimethylsilyl group. The trialkylsilyl group is not limited to these.

[0165] In the molecular structure of the energy acceptor, it is preferable that two or more diarylamino groups are bonded to the luminophore, and aryl groups in the diarylamino groups each have at least one protecting group. It is more preferable that at least two protecting groups are bonded to each of the aryl groups. This is because, in the case where the guest material is used for the light-emitting layer, a large number of protecting groups more effectively suppresses energy transfer by the Dexter mechanism. To suppress an increase in molecular weight and maintain sublimation ability, the diarylamino groups are preferably diphenylamino groups.

[0166] Furthermore, when two or more amino groups are bonded to the luminophore, a fluorescent material whose emission color can be controlled and which exhibits a high quantum yield can be obtained. The amino groups are preferably bonded to the luminophore in symmetrical positions. With such a structure, the fluorescent material can exhibit a high quantum yield.

[0167] The protecting groups cannot be introduced directly into the luminophore, but rather into the luminophore via the aryl groups in the diarylamine. This structure is preferred because the protecting groups can be arranged to cover the luminophore, allowing the host material and the luminophore to be removed from each other in any direction. In the case where the protecting groups are not directly attached to the luminophore, four or more protecting groups are preferably introduced into one luminophore.

[0168] In addition, as in Fig. 3B, at least one of atoms of a plurality of protecting groups is positioned directly on one face of a luminophore, that is, a fused aromatic ring or a fused heteroaromatic ring, and at least one of atoms of the plurality of protecting groups is positioned directly on the other face of the fused aromatic ring or the fused heteroaromatic ring. The following structure is given as a specific method. The fused aromatic ring or the fused heteroaromatic ring, which is a luminophore, is bonded to two or more diphenylamino groups, and the phenyl groups of the two or more diphenylamino groups each independently have protecting groups at the 3- and 5-positions.

[0169] Such a structure allows a steric configuration in which, as in Fig. As shown in Figure 3B, the protecting groups at the 3- and 5-positions of the phenyl groups are positioned directly on the fused aromatic ring or the fused heteroaromatic ring, which is a luminophore. As a result, the upper and lower surfaces of the fused aromatic ring or the fused heteroaromatic ring can be efficiently covered, suppressing energy transfer by the Dexter mechanism.

[0170] As the energy acceptor described above, an organic compound represented by the following general formula (G1) or (G2) can be preferably used.

[0171] In the general formulas (G1) and (G2), A represents a substituted or unsubstituted condensed aromatic ring having 10 to 30 carbon atoms or a substituted or unsubstituted condensed heteroaromatic ring having 10 to 30 carbon atoms, Ar 1 to Ar 6 each independently represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 13 carbon atoms, X 1 to X 12 each independently represents a branched-chain alkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms or a trialkylsilyl group having 3 to 10 carbon atoms, and R 1 to R 10 each independently represents hydrogen, an alkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms or a trialkylsilyl group having 3 to 12 carbon atoms.

[0172] Examples of the aromatic hydrocarbon group having 6 to 13 carbon atoms include a phenyl group, a biphenyl group, a naphthyl group, and a fluorenyl group. Note that the aromatic hydrocarbon group is not limited to these. In the case where the aromatic hydrocarbon group has a substituent, examples of the substituent include an alkyl group having 1 to 7 carbon atoms such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, or a hexyl group; a cycloalkyl group having 5 to 7 carbon atoms such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, or a hexyl group; and B. a cyclopentyl group, a cyclohexyl group, a cycloheptyl group or an 8,9,10-trinorbornanyl group, and an aryl group having 6 to 12 carbon atoms, such as a phenyl group, a naphthyl group or a biphenyl group.

[0173] In the general formula (G1), the substituted or unsubstituted condensed aromatic ring having 10 to 30 carbon atoms or the substituted or unsubstituted condensed heteroaromatic ring having 10 to 30 carbon atoms represents the luminophore, and any of the above frameworks can be used. In the general formulas (G1) and (G2), X represents 1 to X 12 Protecting groups.

[0174] In the general formula (G2), the protecting groups are each bonded to a quinacridone backbone, which is a luminophore, via an arylene group. In this structure, the protecting groups can be arranged to cover the luminophore; therefore, energy transfer can be suppressed by the Dexter mechanism. Note that any of the protecting groups can be bonded directly to the luminophore.

[0175] As the energy acceptor, an organic compound represented by the following general formula (G3) or (G4) can be preferably used.

[0176] In the general formulas (G3) and (G4), A represents a substituted or unsubstituted condensed aromatic ring having 10 to 30 carbon atoms or a substituted or unsubstituted condensed heteroaromatic ring having 10 to 30 carbon atoms, and X 1 to X 12 each independently represents a branched-chain alkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms or a trialkylsilyl group having 3 to 10 carbon atoms.

[0177] The protecting groups are each preferably bonded to the luminophore via a phenyl group. In this structure, the protecting groups can be arranged to cover the luminophore; therefore, energy transfer by the Dexter mechanism can be suppressed. In the case where the protecting groups are each bonded to the luminophore via a phenylene group and two protecting groups are bonded to the phenylene group, as shown in general formulas (G3) and (G4), the two protecting groups are preferably bonded to the phenylene group in the meta positions. With such a structure, the luminophore can be efficiently covered; therefore, energy transfer by the Dexter mechanism can be suppressed. An example of the organic compound represented by general formula (G3) is 2tBu-mmtBuDPhA2Anth, which has been described above.That is, in one embodiment of the present invention, (G3) is particularly preferred.

[0178] As the energy acceptor, an organic compound represented by the following general formula (G5) can be preferably used.

[0179] In the general formula (G5) X 1 to X 8 each independently represents a branched-chain alkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms or a trialkylsilyl group having 3 to 10 carbon atoms, and R 11 to R 18 each independently represents hydrogen, a branched-chain alkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, a trialkylsilyl group having 3 to 10 carbon atoms or a substituted or unsubstituted aryl group having 6 to 25 carbon atoms.

[0180] Examples of the aryl group having 6 to 25 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, a fluorenyl group, and a spirofluorenyl group. Note that an aryl group having 6 to 25 carbon atoms is not limited to this. In the case where the aryl group has a substituent, the alkyl group having 1 to 10 carbon atoms, the branched-chain alkyl group having 3 to 10 carbon atoms, the substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, and the trialkylsilyl group having 3 to 10 carbon atoms described above can be cited.

[0181] An anthracene compound exhibits a high luminescence quantum yield and a small luminophore area; therefore, the upper and lower surfaces of anthracene can be efficiently covered with protecting groups. An example of the organic compound represented by the general formula (G5) is 2tBummtBuDPhA2Anth, which was described above.

[0182] Examples of the compounds represented by general formulas (G1) to (G5) are represented by the following structural formulas (102) to (105) and (200) to (249). Note that the compounds represented by general formulas (G1) to (G5) are not limited thereto. The compounds represented by structural formulas (102) to (105) and (200) to (249) can be advantageously used as the guest material of the light-emitting device of one embodiment of the present invention. Note that the guest material is not limited thereto.

[0183] Examples of materials that can be advantageously used as the guest material of the light-emitting device of one embodiment of the present invention are represented by structural formulas (100) and (101). Note that the guest material is not limited thereto.

[0184] As compound 133, a phosphorescent material having a five-membered ring framework can be used. An iridium-, rhodium-, or platinum-based organometallic complex or metal complex can be used as the phosphorescent material. Another example is a platinum complex or an organoiridium complex with a porphyrin ligand; in particular, an organoiridium complex, such as an iridium-based ortho-metalated complex, is preferred. Examples of an ortho-metalated ligand include a pyrrole ligand, a pyrazole ligand, a 4H-triazole ligand, a 1H-triazole ligand, an imidazole ligand, a benzimidazole ligand, and a naphthoimidazole ligand. In this case, compound 133 (the phosphorescent material) exhibits an absorption band of a triplet metal-to-ligand charge transfer (MLCT) transition.Preferably, compound 133 and compound 132 (the fluorescent material) are selected such that the emission peak of compound 133 overlaps with an absorption band on the longest wavelength side (low energy side) of compound 132 (the fluorescent material). This makes it possible to provide a light-emitting device with drastically improved emission efficiency. Even in the case where compound 133 is a phosphorescent material, it can form an exciplex with compound 131. When an exciplex is formed, the phosphorescent material does not need to emit light at room temperature and emits light at room temperature after an exciplex is formed. In this case, for example, tris[2-(1H-pyrazol-1-yl-κN2)phenyl-κC]iridium(III) (abbreviation: Ir(ppz)3) can be used as the phosphorescent material.

[0185] Examples of a substance that exhibits an emission peak in blue or green include organometallic iridium complexes with a 4H-triazole framework, such as: B. Tris{2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazol-3-yl-κN2]phenyl-κC}iridium(III) (abbreviation: Ir(mpptz-dmp)3), Tris(5-methyl-3,4-diphenyl-4H-1,2,4-triazolato)iridium(III) (abbreviation: Ir(Mptz)3), Tris[4-(3-biphenyl)-5-isopropyl-3-phenyl-4H-1,2,4-triazolato]iridium(III) (Abbreviation: Ir(iPrptz-3b)3), Tris[3-(5-biphenyl)-5-isopropyl-4-phenyl-4H-1,2,4-triazolato]iridium(III) (Abbreviation: Ir(iPr5btz)3), Tris{2-[4-(4-cyano-2,6-diisobutylphenyl)-5-(2-methylphenyl)-4H-1,2,4-triazol-3-yl-κN2]phenyl-κC}iridium(III) (abbreviation: Ir(mpptz-diBuCNp)3) and Tris{2-[5-(2-methylphenyl)-4-(2,6-diisopropylphenyl)-4H-1,2,4-triazol-3-yl-κN2]phenyl-κC}iridium(III) (abbreviation: Ir(mpptzdiPrp)3), organometallic iridium complexes with a 1H-triazole framework, such asTris[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-triazolato]iridium(III) (abbreviation: Ir(Mptz1-mp)3) and tris(1-methyl-5-phenyl-3-propyl-1H-1,2,4-triazolato)iridium(III) (abbreviation: Ir(Prptz1-Me)3), organometallic iridium complexes with an imidazole framework, such as. B. fac-Tris[1-(2,6-diisopropylphenyl)-2-phenyl-1H-imidazole]iridium(III) (abbreviation: Ir(iPrpmi)3) and Tris[3-(2,6-dimethylphenyl)-7-methylimidazo[1,2-f]phenanthridinato]iridium(III) (abbreviation: Ir(dmpimpt-Me)3), organometallic iridium complexes with a benzimidazole framework, such as. B. Tris{2-[1-(4-cyano-2,6-diisobutylphenyl)-1H-benzimidazol-2-yl-κN3]phenyl-κC}iridium(III) (abbreviation: Ir(pbi-diBuCNp)3) and (OC-6-22)-Tris{2-[1-(2,6-diisobutylphenyl)-1H-benzimidazol-2-yl-κN3]phenyl-κC}iridium(III) (abbreviation: Ir(pbi-diBup)3), and organometallic iridium complexes with a naphthoimidazole framework, such asBis{2-[1-(2,6-diisobutylphenyl)-1H-naphtho[1,2-d]imidazol-2-yl-κN3]phenyl-κC}[2-(4-methyl-5-phenyl-2-pyridyl-κN2)phenyl-κC]iridium(III) (abbreviation: Ir(pni-diBup)2(mdppy)) and tris{2-[1-(2,6-diisobutylphenyl)-1H-naphtho[1,2-d]imidazol-2-yl-κN3]phenyl-κC}iridium(III) (abbreviation: [Ir(pni-diBup)3]). Among the materials listed above, the organometallic iridium complexes containing a five-membered nitrogen-containing heterocyclic framework, such as [Ir(pni-diBup)3], are particularly noteworthy. B. a 4H-triazole framework, a 1H-triazole framework, an imidazole framework, a benzimidazole framework, or a naphthoimidazole framework, exhibit high triplet excitation energy, reliability, and emission efficiency and are therefore particularly preferred. It should be noted that a platinum complex such as 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin platinum(II) (abbreviation: PtOEP) and a rare earth metal complex such asTris[1-(2-thenoyl)-3,3,3-trifluoroacetonato](monophenanthroline)europium(III) (abbreviation: Eu(TTA)3(Phen)), can also be used.

[0186] For example, a TADF material can be used as compound 134. The energy difference between the S1 level and the T1 level of compound 134 is preferably small, and in particular, it is greater than 0 eV and less than or equal to 0.2 eV.

[0187] Compound 134 preferably has a framework with a hole-transport property and a framework with an electron-transport property. Alternatively, compound 134 preferably has a π-electron-rich framework or an aromatic amine framework and a π-electron-deficient framework. Accordingly, a donor-acceptor excited state is easily formed in one molecule. Furthermore, a structure in which the framework with an electron-transport property is directly bonded to the framework with a hole-transport property is preferably included to increase both the donor property and the acceptor property in the molecule of compound 134. Alternatively, a structure in which a π-electron-rich framework or an aromatic amine framework is directly bonded to a π-electron-deficient framework is preferably included.By increasing both the donor property and the acceptor property in the molecule, the overlap between a region where the HOMO is distributed and a region where the LUMO is distributed in compound 134 can be small, and the energy difference between the singlet excitation energy level and the triplet excitation energy level of compound 134 can be small. Furthermore, the triplet excitation energy level of compound 134 can be maintained at a high energy level.

[0188] For example, in the case where the TADF material is made of one type of material, any of the following materials can be used.

[0189] First, a fullerene, a derivative thereof, an acridine derivative such as proflavin, eosin, and the like may be mentioned. Further, a metal-containing porphyrin, such as a porphyrin containing magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), or palladium (Pd), may be mentioned. Examples of the metal-containing porphyrin include a protoporphyrin-tin fluoride complex (SnF2(Proto IX)), a mesoporphyrin-tin fluoride complex (SnF2(Meso IX)), a hematoporphyrin-tin fluoride complex (SnF2(Hemato IX)), a coproporphyrin-tetramethyl ester-tin fluoride complex (SnF2(Copro III-4Me)), an octaethylporphyrin-tin fluoride complex (SnF2(OEP)), an etioporphyrin-tin fluoride complex (SnF2(Etio I)), and an octaethylporphyrin-platinum chloride complex (PtCl2OEP).

[0190] For the thermally activated, delayed-release fluorescent material, which consists of one type of material, a heterocyclic compound having a π-electron-rich framework and a π-electron-poor framework is used. Specific examples include heterocyclic compounds having a π-electron-rich heteroaromatic ring and / or a π-electron-poor heteroaromatic ring, such as:2-(Biphenyl-4-yl)-4,6-bis(12-phenylindolo[2,3-a]carbazol-11-yl)-1,3,5-triazine (abbreviation: PIC-TRZ), 2-{4-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: PCCzPTzn), 2-[4-(10H-phenoxazin-10-yl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviation: PXZ-TRZ), 3-[4-(5-phenyl-5,10-dihydrophenazin-10-yl)phenyl]-4,5-diphenyl-1,2,4-triazole (abbreviation: PPZ-3TPT), 3-(9,9-Dimethyl-9H-acridin-10-yl)-9H-xanthen-9-one (abbreviation: ACRXTN), bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone (abbreviation: DMAC-DPS), 10-phenyl-10H,10'H-spiro[acridin-9,9'-anthracene]-10'-one (abbreviation: ACRSA), and 9-[3-(4,6-Diphenyl-1,3,5-triazin-2-yl)phenyl]-9'-phenyl-2,3'-bi-9H-carbazole (abbreviation: mPCCzPTzn-02). Since the heterocyclic compound has the π-electron-rich heteroaromatic ring and the π-electron-poor heteroaromatic ring, it has a high electron transport property and a high hole transport property and is therefore preferred.As scaffolds containing the π-electron-deficient heteroaromatic ring, a diazine scaffold (a pyrimidine scaffold, a pyrazine scaffold, or a pyridazine scaffold) and a triazine scaffold exhibit high stability and high reliability and are therefore used. A benzofuropyrimidine scaffold, a benzothienopyrimidine scaffold, a benzofuropyrazine scaffold, and a benzothienopyrazine scaffold are particularly preferred because they exhibit high acceptor property and high reliability. Among scaffolds containing the π-electron-rich heteroaromatic ring, an acridine scaffold, a phenoxazine scaffold, a phenothiazine scaffold, a furan scaffold, a thiophene scaffold, and a pyrrole scaffold exhibit high stability and high reliability; therefore, at least one of these scaffolds is preferably included. A dibenzofuran framework is preferred as the furan framework. A dibenzothiophene framework is preferred as the thiophene framework.As the pyrrole skeleton, an indole skeleton, a carbazole skeleton, a bicarbazole skeleton, and a 3-(9-phenyl-9H-carbazol-3-yl)-9H-carbazole skeleton are particularly preferred. Note that a substance in which the π-electron-rich heteroaromatic ring is directly bonded to the π-electron-deficient heteroaromatic ring is particularly preferred because both the donor property of the π-electron-rich heteroaromatic ring and the acceptor property of the π-electron-deficient heteroaromatic ring are enhanced, and the difference between the singlet excited state level and the triplet excited state level becomes small. Note that an aromatic ring to which an electron-withdrawing group, such as a cyano group, is bonded can be used instead of the π-electron-deficient heteroaromatic ring. An aromatic amine framework, a phenazine framework, or the like can be used as the π-electron-rich framework.As the π-electron-deficient skeleton, a xanthene skeleton, a thioxanthene skeleton, a dioxide skeleton, an oxadiazole skeleton, a triazole skeleton, an imidazole skeleton, an anthraquinone skeleton, a boron-containing skeleton such as phenylborane or boranthrene, an aromatic ring or a heteroaromatic ring having a nitrile group or a cyano group such as benzonitrile or cyanobenzene, a carbonyl skeleton such as benzophenone, a phosphine oxide skeleton, a sulfone skeleton, or the like can be used. As described above, a π-electron-deficient skeleton and a π-electron-rich skeleton can be used instead of the π-electron-deficient heteroaromatic ring and / or the π-electron-rich heteroaromatic ring.

[0191] In the case where compound 134 does not have a function of converting triplet excitons into light emission, compounds that form an exciplex in combination are preferably used as compounds 131 and 133 or as compounds 131 and 134; however, they are not limited thereto. It is preferable that one of the compounds has a function of transporting electrons and the other has a function of transporting holes.

[0192] Examples of Compound 131 include a zinc- or aluminum-based metal complex, an oxadiazole derivative, a triazole derivative, a benzimidazole derivative, a quinoxaline derivative, a dibenzoquinoxaline derivative, a dibenzothiophene derivative, a dibenzofuran derivative, a pyrimidine derivative, a triazine derivative, a pyridine derivative, a bipyridine derivative, and a phenanthroline derivative. Other examples include an aromatic amine, a carbazole derivative, and the like.

[0193] Alternatively, any of the following hole transport materials and electron transport materials can be used.

[0194] A material with a property of transporting more holes than electrons can be used as a hole transport material, whereby a material with a hole mobility of 1 × 10 -6 cm 2 / Vs or higher is preferred. In particular, an aromatic amine, a carbazole derivative, an aromatic hydrocarbon, a stilbene derivative, or the like can be used. Furthermore, the hole-transporting material can be a high-molecular compound.

[0195] Examples of the aromatic amine compound, which is a material with a high hole-transport property, include N,N'-di(p-tolyl)-N,N'-diphenyl-p-phenylenediamine (abbreviation: DTDPPA), 4,4'-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation: DPAB), N,N'-bis{4-[bis(3-methylphenyl)amino]phenyl}-N,N'-diphenyl-(1,1'-biphenyl)-4,4'-diamine (abbreviation: DNTPD), and 1,3,5-tris[N-(4-diphenylaminophenyl)-N-phenylamino]benzene (abbreviation: DPA3B).

[0196] Specific examples of the carbazole derivative include 3-[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzDPA1), 3,6-bis[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzDPA2), 3,6-bis[N-(4-diphenylaminophenyl)-N-(1-naphthyl)amino]-9-phenylcarbazole (abbreviation: PCzTPN2), 3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA1), 3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA2) and 3-[N-(1-Naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole (abbreviation: PCzPCN1).

[0197] Other examples of the carbazole derivative include 4,4'-di(N-carbazolyl)biphenyl (abbreviation: CBP), 1,3,5-tris[4-(N-carbazolyl)phenyl]benzene (abbreviation: TCPB), 9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: CzPA) and 1,4-bis[4-(N-carbazolyl)phenyl]-2,3,5,6-tetraphenylbenzene.

[0198] Examples of the aromatic hydrocarbon include 2-tert-butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA), 2-tert-butyl-9,10-di(1-naphthyl)anthracene, 9,10-bis(3,5-diphenylphenyl)anthracene (abbreviation: DPPA), 2-tert-butyl-9,10-bis(4-phenylphenyl)anthracene (abbreviation: t-BuDBA), 9,10-di(2-naphthyl)anthracene (abbreviation: DNA), 9,10-diphenylanthracene (abbreviation: DPAnth), 2-tert-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-naphthyl)phenyl]anthracene, 2,3,6,7-tetramethyl-9,10-di(1-naphthyl)anthracene, 2,3,6,7-Tetramethyl-9,10-di(2-naphthyl)anthracene, 9,9'-bianthryl, 10,10'-diphenyl-9,9'-blanthryl, 10,10'-bis(2-phenylphenyl)-9,9'-bianthryl, 10,10'-Bis[(2,3,4,5,6-pentaphenyl)phenyl]-9,9'bianthryl, anthracene, tetracene, rubrene, perylene and 2,5,8,11-Tetra(tert-butyl)perylene. Other examples include pentacene and coronene.The aromatic hydrocarbon, which has a hole mobility of 1 × 10. -6 cm 2 / Vs or higher and 14 to 42 carbon atoms is more preferred.

[0199] The aromatic hydrocarbon may have a vinyl backbone. Examples of aromatic hydrocarbons with a vinyl group include 4,4'-bis(2,2-diphenylvinyl)biphenyl (abbreviation: DPVBi) and 9,10-bis[4-(2,2-diphenylvinyl)phenyl]anthracene (abbreviation: DPVPA).

[0200] Further examples include high molecular weight compounds such as poly(N-vinylcarbazole) (abbreviation: PVK), poly(4-vinyltriphenylamine) (abbreviation: PVTPA), poly[N-(4-{N-[4-(4-diphenylamino)phenyl]phenyl-N'-phenylamino}phenyl)methacrylamide] (abbreviation: PTPDMA) and poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine] (abbreviation: poly-TPD).

[0201] Examples of the material with a high hole transport property further include aromatic amine compounds such as: B. 4,4'-Bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB or α-NPD), N,N'-Bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (abbreviation: TPD), 4,4',4''-Tris(carbazol-9-yl)triphenylamine (abbreviation: TCTA), 4,4',4''-Tris[N-(1-naphthyl)-N-phenylamino]triphenylamine (abbreviation: 1'-TNATA), 4,4',4''-Tris(N,N-diphenylamino)triphenylamine (abbreviation: TDATA), 4,4',4''-Tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine (abbreviation: MTDATA), 4,4'-Bis[N-(spiro-9,9'-bifluoren-2-yl)-N-phenylamino]biphenyl (abbreviation: BSPB), 4-Phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP), 4-Phenyl-3'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: 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-3-yl)triphenylamine (abbreviation: PCBBi1BP), 4-(1-Naphthyl)-4'-(9-phenyl-9H-carbazol-3-yl)-triphenylamine (abbreviation: PCBANB), 4,4'-Di(1-naphthyl)-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBNBB), 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-carbazol-3-amine (abbreviation: PCBiF), N-(1,1'-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: PCBBiF), 9,9-Dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-fluoren-2-amine (abbreviation: PCBAF), N-Phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-spiro-9,9'-bifluoren-2-amine (abbreviation: PCBASF), 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) and N,N-Bis[4-(carbazol-9-yl)phenyl]-N,N-diphenyl-9,9-dimethylfluorene-2,7-diamine (abbreviation: YGA2F). Other examples include amine compounds, carbazole compounds, thiophene compounds, furan compounds, fluorene compounds, triphenylene compounds, phenanthrene compounds, and the like, such as 3-[4-(1-naphthyl)phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPN), 3-[4-(9-phenanthryl)phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPPn), 3,3'-bis(9-phenyl-9H-carbazole) (abbreviation: PCCP), 1,3-bis(N-carbazolyl)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-phenyldibenzothiophene (abbreviation: DBTFLP-IV) and 4-[3-(Triphenylen-2-yl)phenyl]dibenzothiophene (abbreviation: mDBTPTp-II). The substances described here are mainly substances with a hole mobility of 1 × 10, -6 cm 2 / Vs or higher. It should be noted that other substances can also be used, as long as they have the ability to transport more holes than electrons.

[0202] A material with a property of transporting more electrons than holes can be used as an electron transport material, whereby a material with an electron mobility of 1 × 10 -6 cm 2 / Vs or higher is preferred. As a material that readily accepts electrons (material with an electron-transport property), for example, a π-electron-deficient heteroaromatic compound such as a nitrogen-containing heteroaromatic compound or a metal complex can be used. Specific examples include a metal complex containing a quinoline ligand, a benzoquinoline ligand, an oxazole ligand, or a thiazole ligand, an oxadiazole derivative, a triazole derivative, a phenanthroline derivative, a pyridine derivative, a bipyridine derivative, and a pyrimidine derivative.

[0203] Examples include metal complexes with a quinoline framework or a benzoquinoline framework, such as 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), and bis(8-quinolinolato)zinc(II) (abbreviation: Znq). Alternatively, a metal complex with an oxazole-based ligand or a thiazole-based ligand, such as B. Bis[2-(2-benzoxazolyl)phenolato]zinc(II) (abbreviation: ZnPBO) or Bis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ) can be used. In addition to the metal complexes, any of the following compounds can also be used: heterocyclic compounds, such as2-(4-Biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD), 1,3-Bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene (abbreviation: OXD-7), 9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole (abbreviation: CO11), 3-(4-Biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviation: TAZ), 2,2',2''-(1,3,5-Benzenetriyl)tris(1-phenyl-1H-benzimidazole) (abbreviation: TPBI), 2-[3-(Dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzimidazole (abbreviation: mDBTBIm-II), bathophenanthroline (abbreviation: BPhen), 2,9-bis(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline (abbreviation: NBPhen) and bathocuproine (abbreviation: BCP), heterocyclic compounds with a diazine skeleton, such as2-[3-(Dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTPDBq-II), 2-[3'-(Dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTBPDBq-II), 2-[3'-(9H-Carbazol-9-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mCzBPDBq), 2-[4-(3,6-Diphenyl-9H-carbazol-9-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2CzPDBq-III), 7-[3-(Dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 7mDBTPDBq-II), 6-[3-(Dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 6mDBTPDBq-II), 4,6-bis[3-(phenanthren-9-yl)phenyl]pyrimidine (abbreviation: 4,6mPnP2Pm), 4,6-bis[3-(4-dibenzothienyl)phenyl]pyrimidine (abbreviation: 4,6mDBTP2Pm-II) and 4,6-bis[3-(9H-carbazol-9-yl)phenyl]pyrimidine (abbreviation: 4,6mCzP2Pm), heterocyclic compounds with a triazine skeleton, such as. B. 2-{4-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: PCCzPTzn), heterocyclic compounds with a pyridine skeleton, such as3,5-bis[3-(9H-carbazol-9-yl)phenyl]pyridine (abbreviation: 35DCzPPy) and 1,3,5-tri[3-(3-pyridyl)phenyl]benzene (abbreviation: TmPyPB), and heteroaromatic compounds such as 4,4'-bis(5-methylbenzoxazol-2-yl)stilbene (abbreviation: BzOs). Furthermore, a high-molecular compound such as B. Poly(2,5-pyridinediyl) (abbreviation: PPy), poly[(9,9-dihexylfluorene-2,7-diyl)-co-(pyridine-3,5-diyl)] (abbreviation: PF-Py), or poly[(9,9-dioctylfluorene-2,7-diyl)-co-(2,2'-bipyridine-6,6'-diyl)] (abbreviation: PF-BPy). The substances mentioned here are mainly those with an electron mobility of 1 × 10 -6 cm 2 / Vs or higher. Note that a substance other than the above substances can be used as long as it has the property of transporting more electrons than holes.

[0204] As compound 134, a substance capable of forming an exciplex with compound 131 is preferably used. Specifically, the hole-transport material and the electron-transport material described above can be used. In this case, compound 131, compound 134, and compound 133 (the phosphorescent material having a five-membered ring skeleton) are preferably selected such that the emission peak of the exciplex formed by compound 131 and compound 134 overlaps with the absorption band on the longest wavelength side (low energy side) of compound 133 (the phosphorescent material having a five-membered ring skeleton). This makes it possible to provide a light-emitting device with drastically improved emission efficiency.

[0205] The light-emitting layer 130 may include two or more layers. For example, in the case where the light-emitting layer 130 is formed by stacking a first light-emitting layer and a second light-emitting layer in this order from the hole-transport layer side, the first light-emitting layer is formed using a substance having a hole-transport property as a host material, and the second light-emitting layer is formed using a substance having an electron-transport property as a host material.

[0206] The light-emitting layer 130 may contain another material (a compound 135) in addition to the compounds 131, 132, 133, and 134. In this case, in order for the compound 131 and the compound 133 (or the compound 134) to efficiently form an exciplex, the following preferably applies: the HOMO level of one of the compound 131 and the compound 133 (or the compound 134) is the highest among the materials in the light-emitting layer 130, and the LUMO level of the other is the lowest among the materials in the light-emitting layer 130. With such a correlation of energy levels, a reaction to form an exciplex by the compound 131 and the compound 135 can be suppressed.

[0207] For example, in the case where compound 131 has a hole transport property and compound 133 (or compound 134) has an electron transport property, the HOMO level of compound 131 is preferably higher than the HOMO level of compound 133 and the HOMO level of compound 135, and the LUMO level of compound 133 is preferably lower than the LUMO level of compound 131 and the LUMO level of compound 135. In this case, the LUMO level of compound 135 may be higher or lower than the LUMO level of compound 131. Furthermore, the HOMO level of compound 135 may be higher or lower than the HOMO level of compound 133.

[0208] Although there is no particular limitation on a material (the compound 135) that can be used in the light-emitting layer 130, for example, any of the following materials can be used: metal complexes such as: B. 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), bis[2-(2-benzoxazolyl)phenolato]zinc(II) (abbreviation: ZnPBO) and bis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ), heterocyclic compounds, such as B. 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), 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviation: TAZ), 2,2',2''-(1,3,5-Benzenetriyl)tris(1-phenyl-1H-benzimidazole) (abbreviation: TPBI), bathophenanthroline (abbreviation: BPhen), bathocuproine (abbreviation: BCP) and 9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole (abbreviation: CO11), and aromatic amine compounds, such as. B. 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB or α-NPD), N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (abbreviation: TPD), and 4,4'-bis[N-(spiro-9,9'-bifluoren-2-yl)-N-phenylamino]biphenyl (abbreviation: BSPB). Additionally, condensed polycyclic aromatic compounds, such as B. Anthracene derivatives, phenanthrene derivatives, pyrene derivatives, chrysene derivatives and dibenzo[g,p]chrysene derivatives, and specific examples include 9,10-diphenylanthracene (abbreviation: DPAnth), N,N-diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine (abbreviation: CzA1PA), 4-(10-phenyl-9-anthryl)triphenylamine (abbreviation: DPhPA),4-(9H-carbazol-9-yl)-4'-(10-phenyl-9-anthryl)triphenylamine (abbreviation: YGAPA), N,9-diphenyl-N-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine (abbreviation: PCAPA), N,9-Diphenyl-N-{4-[4-(10-phenyl-9-anthryl)phenyl]phenyl}-9H-carbazol-3-amine (abbreviation: PCAPBA), N,9-diphenyl-N-(9,10-diphenyl-2-anthryl)-9H-carbazol-3-amine (abbreviation: 2PCAPA), 6,12-dimethoxy-5, 11-diphenylchrysene, N,N,N',N',N'',N'',N''',N'''-Octaphenyldibenzo[g,p]chrysene-2,7,10,15-tetraamine (abbreviation: DBC1), 9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: CzPA), 3,6-diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: DPCzPA), 9,10-bis(3,5-diphenylphenyl)anthracene (abbreviation: DPPA), 9,10-di(2-naphthyl)anthracene (abbreviation: DNA), 2-tert-butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA), 9,9'-bianthryl (abbreviation: BANT), 9,9'-(stilbene-3,3'-diyl)diphenanthrene (abbreviation: DPNS), 9,9'-(stilbene-4,4'-diyl)diphenanthrene (abbreviation: DPNS2) and 1,3,5-Tri(1-pyrenyl)benzene (abbreviation: TPB3). One or more substances with a larger energy gap than compound 131 and compound 132 can be selected from these and known substances. <<Paar von Elektroden> >

[0209] The electrode 101 and the electrode 102 have functions of injecting holes and electrons into the light-emitting layer 130. The electrodes 101 and 102 can be formed, for example, using a metal, an alloy, a conductive compound, or a mixture or layer arrangement of these. A typical example of the metal is aluminum (Al); in addition, a transition metal such as silver (Ag), tungsten, chromium, molybdenum, copper, or titanium; an alkali metal such as lithium (Li) or cesium; or a Group 2 metal such as calcium or magnesium (Mg) can also be used. As the transition metal, a rare earth metal such as ytterbium (Yb) can be used. An alloy containing any of the above metals can be used as an alloy; examples include MgAg and AlLi. Examples of the conductive compound include metal oxides such as:Indium tin oxide (hereinafter referred to as ITO), indium tin oxide containing silicon or silicon oxide (abbreviation: ITSO), indium zinc oxide, and indium oxide containing tungsten and zinc. It is also possible to use an inorganic carbon-based material such as graphene as the conductive compound. As described above, the electrode 101 and / or the electrode 102 can be formed by stacking two or more of these materials.

[0210] Light emitted from the light-emitting layer 130 is extracted via the electrode 101 and / or the electrode 102. Accordingly, at least one of the electrode 101 and the electrode 102 transmits visible light. As the conductive material that transmits light, a conductive material whose visible light transmittance is higher than or equal to 40% and lower than or equal to 100%, preferably higher than or equal to 60% and lower than or equal to 100%, and whose specific resistance is lower than or equal to 1 × 10 -2 Ω cm. The electrode on the light extraction side can be formed using a conductive material with light transmitting and light reflecting functions. As the conductive material, a conductive material whose visible light reflectance is higher than or equal to 20% and lower than or equal to 80%, preferably higher than or equal to 40% and lower than or equal to 70%, and whose resistivity is lower than or equal to 1 × 10 -2 Ω cm. In the case where the electrode on the light extraction side is formed using a material with low light transmittance, such as a metal or an alloy, the electrode 101 and / or the electrode 102 are / is formed to a thickness thin enough to transmit visible light (e.g., a thickness of 1 nm to 10 nm).

[0211] In this specification and the like, as the light-transmitting electrode, a material that transmits visible light and has conductivity is preferably used. Examples of the material include, in addition to the above-described oxide conductive layer, of which ITO is a typical example, an oxide semiconductor layer and an organic conductive layer containing an organic substance. Examples of the organic conductive layer containing an organic substance include a layer containing a composite material in which an organic compound and an electron donor (donor) are mixed, and a layer containing a composite material in which an organic compound and an electron acceptor (acceptor) are mixed. The specific resistance of the transparent conductive layer is preferably less than or equal to 1 × 10 5 Ω·cm, more preferably less than or equal to 1 × 10 4 Ω·cm.

[0212] As a method for forming the electrode 101 and the electrode 102, a sputtering method, an evaporation method, a printing method, a coating method, a molecular beam epitaxy (MBE) method, a CVD method, a pulse laser deposition method, an atomic layer deposition (ALD) method, or the like can be used as needed. < <lochinjektionsschicht>>

[0213] The hole-injection layer 111 has a function of reducing a barrier to hole injection from one of the pair of electrodes (the electrode 101 or the electrode 102) to promote hole injection, and is formed using, for example, a transition metal oxide, a phthalocyanine derivative, or an aromatic amine. Molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, manganese oxide, or the like can be cited as the transition metal oxide. Phthalocyanine, metal phthalocyanine, or the like can be cited as the phthalocyanine derivative. A benzidine derivative, a phenylenediamine derivative, or the like can be cited as the aromatic amine. It is also possible to use a high-molecular compound such as polythiophene or polyaniline. A typical example is poly(ethylenedioxythiophene) / poly(styrenesulfonic acid), which is a self-doped polythiophene.

[0214] As the hole-injection layer 111, a layer containing a composite material of a hole-transporting material and a material having an electron-accepting property of the hole-transporting material can also be used. Alternatively, a layer arrangement of a layer containing a material having an electron-accepting property and a layer containing a hole-transporting material can also be used. In a stable state or in the presence of an electric field, charges can be transferred between these materials. As examples of the material having an electron-accepting property, organic acceptors such as a quinodimethane derivative, a chloranil derivative, and a hexaazatriphenylene derivative can be given. A specific example is a compound having an electron-withdrawing group (particularly a cyano group or a halogen group such as a fluorine group), such as7,7,8,8-Tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation: F4-TCNQ), chloranil, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviation: HAT-CN), and 1,3,4,5,7,8-hexafluorotetracyano-naphthoquinodimethane (abbreviation: F6-TCNNQ). In particular, a compound in which electron-withdrawing groups are bonded to a condensed aromatic ring containing a plurality of heteroatoms, such as HAT-CN, is preferred because of its thermal stability. A [3]radialene derivative comprising an electron-withdrawing group (particularly a cyano group or a halogen group, such as a fluorine group) exhibits a very high electron-accepting property and is thus preferred. Specific examples include α,α',α''-1,2,3-cyclopropanetriylidene tris[4-cyano-2,3,5,6-tetrafluorobenzene acetonitrile], α,α',α''-1,2,3-cyclopropanetriylidene tris[2,6-dichloro-3,5-difluoro-4-(trifluoromethyl)benzene acetonitrile] and α,α',α''-1,2,3-cyclopropanetriylidene tris[2,3,4,5,6-pentafluorobenzene acetonitrile].Alternatively, a transition metal oxide, such as an oxide of a metal from Group 4 to Group 8, can also be used. Specifically, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide, rhenium oxide, or the like can be used. Among these, molybdenum oxide is preferred because it is stable in air, has low hygroscopicity, and is easy to handle.

[0215] A material with a property of transporting more holes than electrons can be used as a hole transport material, whereby a material with a hole mobility of 1 × 10 -6 cm 2 / Vs or higher is preferred. Specifically, any of the aromatic amines and carbazole derivatives mentioned as hole-transporting materials that can be used in the light-emitting layer 130 can be used. Alternatively, an aromatic hydrocarbon, a stilbene derivative, or the like can be used. Furthermore, the hole-transporting material can be a high-molecular compound.

[0216] Examples of the aromatic hydrocarbon include 2-tert-butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA), 2-tert-butyl-9,10-di(1-naphthyl)anthracene, 9,10-bis(3,5-diphenylphenyl)anthracene (abbreviation: DPPA), 2-tert-butyl-9,10-bis(4-phenylphenyl)anthracene (abbreviation: t-BuDBA), 9,10-di(2-naphthyl)anthracene (abbreviation: DNA), 9,10-diphenylanthracene (abbreviation: DPAnth), 2-tert-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-naphthyl)phenyl]anthracene, 2,3,6,7-tetramethyl-9,10-di(1-naphthyl)anthracene, 2,3,6,7-Tetramethyl-9,10-di(2-naphthyl)anthracene, 9,9'-bianthryl, 10,10'-diphenyl-9,9'-bianthryl, 10,10'-bis(2-phenylphenyl)-9,9'-bianthryl, 10,10'-Bis[(2,3,4,5,6-pentaphenyl)phenyl]-9,9'-bianthryl, anthracene, tetracene, rubrene, perylene and 2,5,8,11-Tetra(tert-butyl)perylene. Other examples include pentacene and coronene.The aromatic hydrocarbon, which has a hole mobility of 1 × 10. -6 cm 2 / Vs or higher and 14 to 42 carbon atoms is more preferred.

[0217] The aromatic hydrocarbon may have a vinyl backbone. Examples of aromatic hydrocarbons with a vinyl group include 4,4'-bis(2,2-diphenylvinyl)biphenyl (abbreviation: DPVBi) and 9,10-bis[4-(2,2-diphenylvinyl)phenyl]anthracene (abbreviation: DPVPA).

[0218] Further examples include high molecular weight compounds such as poly(N-vinylcarbazole) (abbreviation: PVK), poly(4-vinyltriphenylamine) (abbreviation: PVTPA), poly[N-(4-{N'-[4-(4-diphenylamino)phenyl]phenyl-N'-phenylamino}phenyl)methacrylamide] (abbreviation: PTPDMA) and poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine] (abbreviation: poly-TPD). < <lochtransportschicht>>

[0219] The hole-transport layer 112 is a layer containing a hole-transport material and can be formed using any of the materials given as examples of the material of the hole-injection layer 111. In order for the hole-transport layer 112 to have a function of transporting holes injected into the hole-injection layer 111 to the light-emitting layer 130, the HOMO level of the hole-transport layer 112 is preferably equal to or close to the HOMO level of the hole-injection layer 111.

[0220] Any of the materials given as examples for the material of the hole injection layer 111 can be used as the hole transport material. Furthermore, a substance having a hole mobility of 1 × 10 -6 cm 2 / Vs or higher is used. Note that, in addition to these substances, any substance that has the property of transporting more holes than electrons can be used. The layer containing a substance with a high hole-transport property is not limited to a single layer, and two or more layers containing the above substances can be stacked. < <elektronentransportschicht>>

[0221] The electron-transport layer 118 has a function of transporting electrons injected from the other electrode of the pair of electrodes (the electrode 101 or the electrode 102) via the electron-injection layer 119 to the light-emitting layer 130. A material having a property of transporting more electrons than holes can be used as the electron-transport material, and a material having an electron mobility of 1 × 10 -6 cm 2 / Vs or higher is preferred. As a compound that readily accepts electrons (material with an electron-transport property), for example, a π-electron-deficient heteroaromatic compound such as a nitrogen-containing heteroaromatic compound or a metal complex can be used. Specifically, a metal complex having a quinoline ligand, a benzoquinoline ligand, an oxazole ligand, or a thiazole ligand can be cited, which has been described as an electron-transport material that can be used in the light-emitting layer 130. In addition, an oxadiazole derivative, a triazole derivative, a phenanthroline derivative, a pyridine derivative, a bipyridine derivative, a pyrimidine derivative, and the like can be cited. Further, a substance having an electron mobility of 1 × 10 -6 cm 2 / Vs or higher is used. Note that a substance other than the above substances can be used as the electron-transport layer as long as it has a property of transporting more electrons than holes. The electron-transport layer 118 is not limited to a single layer, and it may be a stacked arrangement of two or more layers containing the above-mentioned substances.

[0222] Between the electron-transport layer 118 and the light-emitting layer 130, a layer that controls the transfer of electron carriers can be provided. The layer that controls the transfer of electron carriers is formed by adding a small amount of a substance with a high electron-capturing property to the above-mentioned material with a high electron-transporting property, and the layer can control the carrier balance by suppressing the transfer of electron carriers. Such a structure is very effective in preventing a problem (such as a shortening of the device's lifetime) that occurs when electrons pass through the light-emitting layer. < <elektroneninjektionsschicht>>

[0223] The electron injection layer 119 has a function of reducing a barrier to electron injection from the electrode 102 to promote electron injection, and can be formed, for example, using a Group 1 metal or a Group 2 metal, or using an oxide, a halide, or a carbonate of these metals. Alternatively, a composite material containing the above-mentioned electron-transport material and a material having an electron-donating property with respect to the electron-transport material can also be used. As the material having an electron-donating property, a Group 1 metal, a Group 2 metal, an oxide of these metals, or the like can be specified. Specifically, an alkali metal, an alkaline earth metal, or a compound thereof, such as hydroxide, can be used.Lithium fluoride (LiF), sodium fluoride (NaF), cesium fluoride (CsF), calcium fluoride (CaF2) or lithium oxide (LiO). x ), can be used. A rare earth metal compound such as erbium fluoride (ErF3) can also be used. An electride can also be used for the electron-injection layer 119. Examples of the electride include a substance in which electrons are added at a high concentration to calcium oxide-alumina. The substance that can be used for the electron-transport layer 118 can be used for the electron-injection layer 119.

[0224] A composite material in which an organic compound and an electron donor (donor) are mixed can also be used for the electron injection layer 119. Such a composite material has excellent electron injection properties and electron transport properties because electrons are generated in the organic compound by the electron donor. In this case, the organic compound is preferably a material that can excellently transport the generated electrons. Specifically, for example, the substances listed above (e.g., the metal complexes and heteroaromatic compounds) can be used for forming the electron transport layer 118. A substance that has an electron donation property with respect to an organic compound can be used as the electron donor. Preferred examples are an alkali metal, an alkaline earth metal, and a rare earth metal.Specifically, lithium, cesium, magnesium, calcium, erbium, ytterbium, and the like can be mentioned. Furthermore, an alkali metal oxide and an alkaline earth metal oxide are preferred, and lithium oxide, calcium oxide, barium oxide, and the like can be mentioned. Alternatively, a Lewis base such as magnesium oxide can be used. As a further alternative, an organic compound such as tetrathiafulvalene (abbreviation: TTF) can be used.

[0225] Note that the light-emitting layer, hole-injection layer, hole-transport layer, electron-transport layer, and electron-injection layer described above can each be formed by an evaporation method (including a vacuum evaporation method), an inkjet method, a coating method, a jet printing method, a gravure printing method, or the like. In addition to the above-mentioned materials, an inorganic compound such as a quantum dot or a high-molecular compound (e.g., an oligomer, a dendrimer, and a polymer) can be used in the light-emitting layer, the hole-injection layer, the hole-transport layer, the electron-transport layer, and the electron-injection layer.

[0226] The quantum dot can be, for example, a gelatinous quantum dot, an alloyed quantum dot, a core-shell quantum dot, or a core quantum dot. The quantum dot containing elements belonging to groups 2 and 16, elements belonging to groups 13 and 15, elements belonging to groups 13 and 17, elements belonging to groups 11 and 17, or elements belonging to groups 14 and 15 can be used. Alternatively, the quantum dot containing an element such as cadmium (Cd), selenium (Se), zinc (Zn), sulfur (S), phosphorus (P), indium (In), tellurium (Te), lead (Pb), gallium (Ga), arsenic (As), or aluminum (Al) can be used.

[0227] As the liquid medium used for the wet process, organic solvents can be used, for example, ketones such as methyl ethyl ketone and cyclohexanone, fatty acid esters such as ethyl acetate, halogenated hydrocarbons such as dichlorobenzene, aromatic hydrocarbons such as toluene, xylene, mesitylene and cyclohexylbenzene, aliphatic hydrocarbons such as cyclohexane, decalin and dodecane, dimethylformamide (DMF) and dimethyl sulfoxide (DMSO).

[0228] Examples of the high molecular compound that can be used for the light-emitting layer include a polyphenylenevinylene (PPV) derivative such as poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (abbreviation: MEH-PPV) or poly(2,5-dioctyl-1,4-phenylenevinylene), a polyfluorene derivative such as poly(ethylenediamine dimethyl ether), and a poly(ethylenediamine dimethyl ether). B. Poly(9,9-din-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-anthracene)] or poly[(9,9-dihexylfluorene-2,7-diyl)-alt-(2,5-dimethyl-1,4-phenylene)], a polyalkylthiophene (PAT) derivative, such as B. Poly(3-hexylthiophene-2,5-diyl) (abbreviation: P3HT), and a polyphenylene derivative. These high-molecular-weight compounds and high-molecular-weight compounds, such asPoly(N-vinylcarbazole) (abbreviation: PVK), poly(2-vinylnaphthalene), and poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (abbreviation: PTAA) can be doped with a light-emitting compound and used for the light-emitting layer. Any of the light-emitting compounds described above can be used as the light-emitting compound. < <substrat>>

[0229] The light-emitting device of one embodiment of the present invention can be formed over a substrate made of glass, plastic, or the like. Regarding the order of layer stacking over the substrate, layers can be stacked sequentially from the electrode 101 side or sequentially from the electrode 102 side.

[0230] For the substrate over which the light-emitting device of one embodiment of the present invention can be formed, for example, glass, quartz, plastic, or the like can be used. Alternatively, a flexible substrate can be used. The flexible substrate is a substrate that can be bent, such as a plastic substrate made of polycarbonate or polyarylate. Alternatively, a film, an inorganic film formed by evaporation, or the like can be used. Another material can be used as long as the substrate serves as a support in the manufacturing process of the light-emitting device and an optical device. Another material having a function of protecting the light-emitting device and the optical device can also be used.

[0231] For example, in this specification and the like, a light-emitting device can be formed using various substrates. The type of substrate is not particularly limited. Examples of the substrate include a semiconductor substrate (e.g., a single-crystal substrate or a silicon substrate), an SOI substrate, a glass substrate, a quartz substrate, a plastic substrate, a metal substrate, a stainless steel substrate, a substrate containing a stainless steel foil, a tungsten substrate, a substrate containing a tungsten foil, a flexible substrate, an attachment film, a cellulose nanofiber (CFN) and paper containing a fiber material, and a base material film. Examples of the glass substrate include barium borosilicate glass, aluminoborosilicate glass, and soda-lime glass.Examples of the flexible substrate, the fixing film, the base material film, and the like include plastic substrates, typical examples being polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), and polytetrafluoroethylene (PTFE). Other examples include a resin such as acrylic. Other examples include polypropylene, polyester, polyvinyl fluoride, and polyvinyl chloride. Other examples include polyamide, polyimide, aramid, epoxy, an evaporation-formed inorganic film, and paper.

[0232] Alternatively, a flexible substrate may be used as the substrate, and the light-emitting device may be formed directly over the flexible substrate. Alternatively, a separation layer may be provided between the substrate and the light-emitting device. The separation layer may be used when a part or all of the light-emitting device formed over the separation layer is completed, separated from the substrate, and transferred to another substrate. In such a case, the light-emitting device may also be transferred to a substrate with low heat resistance or to a flexible substrate. For the above separation layer, for example, a layer assembly comprising inorganic films, namely a tungsten film and a silicon oxide film, or a resin film of polyimide or the like formed over a substrate may be used.

[0233] In other words, after the light-emitting device is formed using one substrate, the light-emitting device can be transferred to another substrate. Examples of the substrate to which the light-emitting device is transferred include, in addition to the substrates described above, a cellophane substrate, a stone substrate, a wood substrate, a fabric substrate (including a natural fiber (e.g., silk, cotton, or hemp), a synthetic fiber (e.g., nylon, polyurethane, or polyester), a regenerated fiber (e.g., acetate, cupro, viscose, or regenerated polyester), or the like), a leather substrate, and a rubber substrate.When such substrates are used, a light-emitting device with high durability, a light-emitting device with high heat resistance, a light-emitting device with reduced weight, or a light-emitting device with reduced thickness can be formed.

[0234] The light-emitting device 150 can, for example, be formed over an electrode electrically connected to a field-effect transistor (FET) formed over one of the substrates described above. In this way, an active matrix display device can be fabricated in which the FET controls the operation of the light-emitting device.

[0235] The structure described above in this embodiment can be appropriately combined with any of the other embodiments. (Embodiment 2)

[0236] In this embodiment, examples of a method for synthesizing an organic compound preferably used for the light-emitting device of one embodiment of the present invention will be described, with the organic compounds represented by general formulas (G1) and (G2) being given as examples. <Verfahren zum Synthetisieren der durch die allgemeine Formel (G1) dargestellten organischen Verbindung>

[0237] The organic compound represented by the general formula (G1) can be prepared by a synthetic method utilizing any of various reactions. For example, the organic compound can be synthesized by the following synthesis schemes (S-1) and (S-2). A compound 1, an arylamine (compound 2), and an arylamine (compound 3) are coupled to obtain a diamine compound (compound 4).

[0238] Next, the diamine compound (compound 4), a halogenated aryl (compound 5) and a halogenated aryl (compound 6) are coupled, whereby the organic compound represented by the general formula (G1) can be obtained.

[0239] In the synthesis schemes (S-1) and (S-2), A represents a substituted or unsubstituted condensed aromatic ring having 10 to 30 carbon atoms or a substituted or unsubstituted condensed heteroaromatic ring having 10 to 30 carbon atoms, Ar 1 to Ar 4 each independently represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 13 carbon atoms, X 1 to X 8 each independently represents an alkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, or a trialkylsilyl group having 3 to 12 carbon atoms. Examples of the condensed ring or the condensed heteroaromatic ring include chrysene, phenanthrene, stilbene, acridone, phenoxazine, and phenothiazine. Anthracene, pyrene, coumarin, quinacridone, perylene, tetracene, and naphthobisbenzofuran are particularly preferred.

[0240] In the case where a Buchwald-Hartwig reaction using a palladium catalyst is applied in the synthesis schemes (S-1) and (S-2), X 10 to X 13 each preferably represents a halogen group or a triflate group, and the halogen is preferably iodine, bromine, or chlorine. In the reaction, a palladium compound such as bis(dibenzylideneacetone)palladium(0) or palladium(II) acetate and a ligand such as tri(tert-butyl)phosphine, tri(n-hexyl)phosphine, tricyclohexylphosphine, di(1-adamantyl)-n-butylphosphine, or 2-dicyclohexylphosphino-2',6'-dimethoxy-1,1'-biphenyl can be used. In addition, an organic base such as sodium tert-butoxide, an inorganic base such as potassium carbonate, cesium carbonate, or sodium carbonate, or the like can be used. Furthermore, toluene, xylene, mesitylene, benzene, tetrahydrofuran, dioxane, or the like can be used as a solvent. Reagents that can be used in the reaction are not limited to this.

[0241] The reaction used in synthesis schemes (S-1) and (S-2) is not limited to the Buchwald-Hartwig reaction. The Migita-Kosugi-Stille coupling reaction using an organotin compound, a coupling reaction using a Grignard reagent, the Ullmann reaction using copper or a copper compound, or the like can be used.

[0242] In the case where compound 2 and compound 3 in the synthesis scheme (S-1) have different structures, it is preferable that compound 1 and compound 2 first react to form a coupling product, and then the resulting coupling product and compound 3 react. In the case where compound 1 reacts with compound 2 and with compound 3 in different phases, it is preferable that compound 1 is a dihalogen compound and that X 10 and X 11 are different halogens and are selectively subjected to successive amination reactions.

[0243] Furthermore, in the case where Compound 5 and Compound 6 in the synthesis scheme (S-2) have different structures, it is preferable that Compound 4 and Compound 5 first react to form a coupling product, and then the obtained coupling product and Compound 6 react. <Verfahren zum Synthetisieren der durch die allgemeine Formel (G2) dargestellten organischen Verbindung>

[0244] The organic compound of one embodiment of the present invention, represented by general formula (G2), can be synthesized using various organic reactions. Two methods are described below as examples.

[0245] The first method includes the following synthesis schemes (S-3) to (S-8). In the first step, an amine compound (Compound 9) is obtained by a condensation reaction of an aniline compound (Compound 7) and a 1,4-cyclohexadiene-1,4-dicarboxylic acid compound (Compound 8). This step is shown in Scheme (S-3). In the case where two aniline compounds (Compound 7) with the same substituent can be condensed in a single phase and an amino group with the same substituent is introduced, two equivalents of the aniline compound (Compound 7) are preferably added to conduct this reaction. In this case, a target substance can be obtained even if a carbonyl group of Compound 8 lacks reaction selectivity.

[0246] Subsequently, the amine compound (Compound 9) and an aniline derivative (Compound 10) are condensed to obtain a 1,4-cyclohexadiene compound (Compound 11). A step for obtaining Compound 11 is shown in Scheme (S-4).

[0247] Subsequently, the 1,4-cyclohexadiene compound (Compound 11) is oxidized in air to obtain a terephthalic acid compound (Compound 12). A step for obtaining Compound 12 is shown in Scheme (S-5).

[0248] Subsequently, the terephthalic acid compound (Compound 12) is condensed using an acid to obtain a quinacridone compound (Compound 13). A step for obtaining Compound 13 is shown in Scheme (S-6).

[0249] Subsequently, the quinacridone compound (Compound 13) and a halogenated aryl (Compound 14) are coupled, whereby a quinacridone compound (Compound 15) can be obtained. A step for obtaining Compound 15 is shown in Scheme (S-7). In the case where two halogenated aryls (Compounds 8) with the same substituent can be coupled in a single phase and an amino group with the same substituent is introduced, two equivalents of the halogenated aryl (Compound 14) are preferably added to conduct this reaction. In this case, a target substance can be obtained even if an amino group of Compound 14 lacks reaction selectivity.

[0250] Subsequently, the quinacridone compound (compound 15) and a halogenated aryl (compound 16) are coupled to obtain the organic compound represented by the general formula (G2). This step is shown in Scheme (S-8).

[0251] The second method includes synthesis schemes (S-3) to (S-5) and the following synthesis schemes (S-9), (S-10), and (S-11). The description of (S-3) to (S-5) is the same as described above. The terephthalic acid compound (Compound 12) and the halogenated aryl (Compound 14) are coupled, whereby a diamine compound (Compound 17) can be obtained. A step for obtaining Compound 17 is shown in Scheme (S-9). In the case where two halogenated aryl molecules with the same substituent can be coupled in a single phase and an amino group with the same substituent is introduced, two equivalents of the halogenated aryl (Compound 14) are preferably added to conduct this reaction. In this case, a target substance can be obtained even if an amino group of Compound 12 lacks reaction selectivity.

[0252] Subsequently, the diamine compound (compound 17) and the halogenated aryl (compound 16) are coupled to yield a diamine compound (compound 18). A step for obtaining compound 18 is shown in Scheme (S-10).

[0253] Finally, the diamine compound (Compound 18) is condensed using an acid, whereby the organic compound represented by the general formula (G2) can be obtained. This step is shown in Scheme (S-11). It should be noted that in the condensation reaction, hydrogen is present in the ortho position of Ar. 5 or Ar 6 could react to produce an isomer of the organic compound represented by the general formula (G2).

[0254] In Scheme (S-11), using the diamine compound (Compound 18) having a symmetrical structure, the organic compound represented by the general formula (G2) can be synthesized.

[0255] In each of the synthesis schemes (S-3) to (S-6) and (S-9) to (S-11), Al 1 an alkyl group, such as a methyl group.

[0256] In each of the synthesis schemes (S-7) to (S-10), Y 1 and Y 2 each represents chlorine, bromine, iodine or a triflate group.

[0257] In the synthesis schemes (S-7) to (S-10), the Ullmann reaction can be used because the reaction can take place at high temperature and a target compound can be obtained in a relatively high yield. Examples of the reagent that can be used in the reaction include copper and a copper compound, and examples of the base that can be used in the reaction include an inorganic base such as potassium carbonate and sodium hydride. Examples of the solvent that can be used in the reaction include 2,2,6,6-tetramethyl-3,5-heptanedione, 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)pyrimidinone (DMPU), toluene, xylene, and benzene. In the Ullmann reaction, the target substance can be obtained in a shorter time and in a higher yield when the reaction temperature is 100°C or higher; Therefore, 2,2,6,6-tetramethyl-3,5-heptanedione, DMPU or xylene, which have high boiling points, are preferably used.A reaction temperature of 150 °C or higher is more preferred, and therefore DMPU is more preferable. The reagents that can be used in the reaction are not limited to the above reagents.

[0258] In the synthesis schemes (S-7) to (S-10), the Buchwald-Hartwig reaction can be used using a palladium catalyst. The reaction can involve a palladium compound such as bis(dibenzylideneacetone)palladium(0), palladium(II) acetate, [1,1'-bis(diphenylphosphino)ferrocene]palladium(II) dichloride, tetrakis(triphenylphosphine)palladium(0), or allylpalladium(II) chloride (dimer), and a ligand such as phenyl palladium(II). B. Tri(tert-butyl)phosphine, tri(n-hexyl)phosphine, tricyclohexylphosphine, di(1-adamantyl)-n-butylphosphine, 2-dicyclohexylphosphino-2',6'-dimethoxybiphenyl, tri(ortho-tolyl)phosphine, or (S)-(6,6'-dimethoxybiphenyl-2,2'-diyl)bis(diisopropylphosphine) (abbreviation: cBRIDP (registered trademark)) can be used. An organic base such as sodium tert-butoxide, an inorganic base such as potassium carbonate, cesium carbonate, or sodium carbonate, or the like, can be used in the reaction.Toluene, xylene, benzene, tetrahydrofuran, dioxane, or the like can be used as solvents in the reaction. Reagents that can be used in the reaction are not limited to the above reagents.

[0259] The method for synthesizing the organic compound of the present invention represented by the general formula (G2) is not limited to the synthesis schemes (S-1) to (S-11).

[0260] Specific examples for R 1 to R 10 that are bonded to the quinacridone skeleton include an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a trimethylsilyl group, a triethylsilyl group, and a tributylsilyl group.

[0261] Specific examples of Ar 5 , to the X 9 and X 10 be bound, and for Ar 6 to the X 11 and X 12 are bonded include a 2-isopropylphenyl group, a 2-butylphenyl group, a 2-isobutylphenyl group, a 2-tert-butylphenyl group, a 2-isopropylphenyl group, a 2-butylphenyl group, a 3-propylphenyl group, a 3-isobutylphenyl group, a 3-tert-butylphenyl group, a 4-propylphenyl group, a 4-isopropylphenyl group, a 4-butylphenyl group, a 4-isobutylphenyl group, a 4-tert-butylphenyl group, a 3,5-dipropylphenyl group, a 3,5-di-isopropylphenyl group, a 3,5-dibutylphenyl group, a 3,5-diisobutylphenyl group, a (3,5-di-tert-butyl)phenyl group, a 1,3-dipropylphenyl group, a 1,3-di-isopropylphenyl group, a 1,3-dibutylphenyl group, a 1,3-di-isobutylphenyl group, a (1,3-di-tert-butyl)phenyl group, a 1,3,5-triisopropylphenyl group, a (1,3,5-tri-tert-butyl)phenyl group and a 4-cyclohexylphenyl group.

[0262] The above is the description of the methods for synthesizing the organic compounds which are embodiments of the present invention and represented by the general formulas (G1) and (G2); however, the present invention is not limited thereto, and other synthesis methods may be used. (Embodiment 3)

[0263] In this embodiment, a light-emitting device having a structure different from that of the light-emitting device described in Embodiment 1 will be described below with reference to Fig. 6 described. In Fig. 6, in some cases, a section with a similar function to that in Fig. 1A by the same hatching pattern as in Fig. 1A and are not specifically designated with a reference symbol. In addition, the same reference symbols are used for sections with similar functions, and a detailed description of the sections is omitted in some cases. <Strukturbeispiel 2 einer Licht emittierenden Vorrichtung>

[0264] Fig. 6 is a schematic cross-sectional view of a light-emitting device 250.

[0265] The light emitting device 250, which in Fig. 6 includes a plurality of light-emitting units (a light-emitting unit 106 and a light-emitting unit 108) between a pair of electrodes (the electrode 101 and the electrode 102). Any one of the plurality of light-emitting units preferably has the same structure as the EL layer 100 shown in Fig. 1A. That is, the light-emitting device 150 in Fig. 1A preferably includes one light-emitting unit, and the light-emitting device 250 preferably includes a plurality of light-emitting units. Note that in the following description of the light-emitting device 250, the electrode 101 serves as the anode and the electrode 102 serves as the cathode; however, the functions of these can be interchanged in the light-emitting device 250.

[0266] In the light-emitting device 250, which is in Fig. As shown in FIG. 6, the light-emitting unit 106 and the light-emitting unit 108 are stacked, and a charge generation layer 115 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 structure or may have different structures. For example, the light-emitting unit 108 preferably uses a structure similar to that of the EL layer 100.

[0267] The light-emitting device 250 includes a light-emitting layer 120 and a light-emitting layer 170. The light-emitting unit 106 includes, in addition to the light-emitting layer 120, the hole-injection layer 111, the hole-transport layer 112, an electron-transport layer 113, and an electron-injection layer 114. The light-emitting unit 108 includes, in addition to the light-emitting layer 170, a hole-injection layer 116, a hole-transport layer 117, an electron-transport layer 118, and an electron-injection layer 119.

[0268] In the light-emitting device 250, any layer in each of the light-emitting units 106 and 108 contains the compound of one embodiment of the present invention. Note that the layer containing the compound is preferably the light-emitting layer 120 or the light-emitting layer 170.

[0269] The charge generation layer 115 may have either a structure in which an acceptor substance, which is an electron acceptor, is added to a hole-transporting material, or a structure in which a donor substance, which is an electron donor, is added to an electron-transporting material. Alternatively, both of these structures may be arranged one above the other.

[0270] In the case where the charge generation layer 115 contains a composite material of an organic compound and an acceptor substance, the composite material that can be used for the hole injection layer 111 described in Embodiment 1 can be used for the composite material. As the organic compound, various compounds such as an aromatic amine compound, a carbazole compound, an aromatic hydrocarbon, and a high-molecular compound (such as an oligomer, a dendrimer, or a polymer) can be used. An organic compound with a hole mobility of 1 × 10 -6 cm 2 / Vs or higher is preferably used. Note that any substance can be used as long as it has a property of transporting more holes than electrons. Since the composite material of an organic compound and an acceptor substance has excellent charge injection and charge transport properties, low-voltage operation or low-current operation can be achieved. Note that when a surface of a light-emitting unit on the anode side is in contact with the charge generation layer 115, the charge generation layer 115 can also serve as a hole injection layer or a hole transport layer of the light-emitting unit; therefore, a hole injection layer or a hole transport layer may not necessarily be included in the light-emitting unit.Alternatively, when a surface of a light-emitting unit on the cathode side is in contact with the charge generation layer 115, the charge generation layer 115 can also serve as an electron injection layer or an electron transport layer of the light-emitting unit; therefore, an electron injection layer or an electron transport layer may not necessarily be included in the light-emitting unit.

[0271] The charge generation layer 115 may have a multilayer structure composed of a layer containing the composite material of an organic compound and an acceptor substance and a layer containing another material. For example, the charge generation layer 115 may be formed by combining a layer containing the composite material of an organic compound and an acceptor substance with a layer containing a compound selected from among substances having an electron-donating property and a compound having a high electron-transporting property. Furthermore, the charge generation layer 115 may be formed using a combination of a layer containing the composite material of an organic compound and an acceptor substance with a layer including a transparent conductive film.

[0272] The charge generation layer 115 provided between the light-emitting unit 106 and the light-emitting unit 108 may have any structure as long as electrons can be injected into the light-emitting unit on one side and holes can be injected into the light-emitting unit on the other side when a voltage is applied between the electrode 101 and the electrode 102. For example, Fig. 6 the charge generation layer 115 electrons into the light-emitting unit 106 and holes into the light-emitting unit 108 when a voltage is applied such that the potential of the electrode 101 is higher than that of the electrode 102.

[0273] Note that in terms of light extraction efficiency, the charge generation layer 115 preferentially transmits visible light (specifically, it has a visible light transmittance greater than or equal to 40%). The charge generation layer 115 operates even if it has a lower conductivity than the pair of electrodes (electrodes 101 and 102).

[0274] By forming the charge generation layer 115 using any of the above materials, an increase in the operating voltage caused by the stacking of the light-emitting layers can be suppressed.

[0275] The light-emitting device, which includes two light-emitting units, is identified by Fig. 6; however, a similar structure can also be applied to a light-emitting device in which three or more light-emitting units are stacked. By placing a plurality of light-emitting units separated by the charge generation layer between a pair of electrodes, as in the light-emitting device 250, a light-emitting device capable of emitting light with high luminance while keeping the current density low and having a long lifetime can be provided. A light-emitting device with low power consumption can also be provided.

[0276] Note that, in each of the structures described above, the emission colors of the guest materials used in the light-emitting unit 106 and the light-emitting unit 108 may be the same or different. When guest materials emitting light of the same color are used for the light-emitting unit 106 and the light-emitting unit 108, the light-emitting device 250 can exhibit high emission luminance at a small current value, which is preferable. When guest materials emitting light of different colors are used for the light-emitting unit 106 and the light-emitting unit 108, the light-emitting device 250 can exhibit multi-color light emission, which is preferable.In this case, when a plurality of light-emitting materials with different emission wavelengths are used in one or both of the light-emitting layers 120 and 170, the light-emitting device 250 emits light obtained by synthesizing light with different emission peaks. That is, the emission spectrum of the light-emitting device 250 has at least two local maximum values.

[0277] The above structure is also suitable for obtaining white light emission. If the light-emitting layer 120 and the light-emitting layer 170 emit light of complementary colors, white light emission can be obtained. Preferably, the guest materials are particularly selected such that white light emission with high color rendering properties or light emission of at least red, green, and blue can be obtained.

[0278] One or both of the light-emitting layers 120 and 170 preferably has / have the structure of the light-emitting layer 130 described in Embodiment 1. With such a structure, a light-emitting device with high emission efficiency and high reliability can be obtained. The guest material contained in the light-emitting layer 130 is a fluorescent material. Thus, when the structure of the light-emitting layer 130 described in Embodiment 1 is used in one or both of the light-emitting layers 120 and 170, a light-emitting device with high efficiency and high reliability can be obtained.

[0279] In the case of a light-emitting device in which three or more light-emitting units are stacked, the colors of light emitted by guest materials in the light-emitting units may be the same or different from each other. In the case where a light-emitting device includes a plurality of light-emitting units having the same emission color, the plurality of light-emitting units can emit light with high intensity at a smaller current value. Such a structure can be suitably used to adjust emission colors. The structure is particularly suitable when guest materials with different emission efficiencies and different emission colors are used.For example, if the light-emitting device includes three light-emitting units, the intensity of fluorescence and phosphorescence can be adjusted by providing two light-emitting units containing a fluorescent material of the same color and one light-emitting unit containing a phosphorescent material that emits light in a color different from the emission color of the fluorescent material. This means that the emission intensity of light of each color can be adjusted by the number of light-emitting units.

[0280] When a light-emitting device includes two light-emitting units for fluorescence and one light-emitting unit for phosphorescence in the above manner, the following light-emitting devices that efficiently emit white light are preferred: a light-emitting device comprising two light-emitting units containing a blue fluorescent material and one light-emitting unit containing a yellow phosphorescent material, a light-emitting device comprising two light-emitting units containing a blue fluorescent material and one light-emitting unit containing a red phosphorescent material and a green phosphorescent material, and a light-emitting device comprising two light-emitting units containing a blue fluorescent material and one light-emitting unit containing a red phosphorescent material,a yellow phosphorescent material and a green phosphorescent material. Thus, the light-emitting device of one embodiment of the present invention can be combined with a phosphorescent layer as needed.

[0281] In the above-described light-emitting device including two light-emitting units for fluorescence and one light-emitting unit for phosphorescence, the light-emitting unit for phosphorescence can be replaced with a light-emitting unit having the structure of the light-emitting layer 130 described in Embodiment 1. This is because, by using the structure of the light-emitting layer 130 described in Embodiment 1, a fluorescent layer with an emission efficiency as high as that of a phosphorescent layer can be obtained.

[0282] At least one of the light-emitting layers 120 and 170 may be divided into layers, and the divided layers may contain different light-emitting materials from each other. That is, at least one of the light-emitting layers 120 and 170 may be composed of two or more layers. For example, in the case where the light-emitting layer is formed by stacking a first light-emitting layer and a second light-emitting layer in this order from the hole-transport layer side, the first light-emitting layer is formed using a material having a hole-transport property as a host material, and the second light-emitting layer is formed using a material having an electron-transport property as a host material.In this case, a light-emitting material contained in the first light-emitting layer may be the same as or different from a light-emitting material contained in the second light-emitting layer. Furthermore, the materials may have functions of emitting light of the same color or light of different colors. A white light emission with a high color rendering property formed from three primary colors or four or more colors can be obtained by using a plurality of light-emitting materials that emit light of different colors.

[0283] For example, any of the following phosphorescent materials can be used as the guest material of the light-emitting layer of the light-emitting unit for phosphorescence described in Embodiment 3.

[0284] Examples of the phosphorescent material exhibiting an emission peak in blue or green include organometallic iridium complexes having a 4H-triazole skeleton, such as: B. Tris{2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazol-3-yl-κN2]phenyl-κC}iridium(III) (abbreviation: Ir(mpptz-dmp)3), Tris(5-methyl-3,4-diphenyl-4H-1,2,4-triazolato)iridium(III) (abbreviation: Ir(Mptz)3), Tris[4-(3-biphenyl)-5-isopropyl-3-phenyl-4H-1,2,4-triazolato]iridium(III) (abbreviation: Ir(iPrptz-3b)3) and Tris[3-(5-biphenyl)-5-isopropyl-4-phenyl-4H-1,2,4-triazolato]iridium(III) (abbreviation: Ir(iPr5btz)3), organometallic Iridium complexes with a 1H-triazole skeleton, such as tris[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-triazolato]iridium(III) (abbreviation: Ir(Mptz1-mp)3) and tris(1-methyl-5-phenyl-3-propyl-1H-1,2,4-triazolato)iridium(III) (abbreviation: Ir(Prptz1-Me)3), organometallic iridium complexes with an imidazole skeleton, such asfac-Tris[1-(2,6-diisopropylphenyl)-2-phenyl-1H-imidazole]iridium(III) (abbreviation: Ir(iPrpmi)3) and tris[3-(2,6-dimethylphenyl)-7-methylimidazo[1,2-f]phenanthridinato]iridium(III) (abbreviation: Ir(dmpimpt-Me)3), and organometallic iridium complexes in which a phenylpyridine derivative with an electron-withdrawing group is a ligand, such as bis[2-(4',6'-difluorophenyl)pyridinato-N,C. 2' ]iridium(III)tetrakis(1-pyrazolyl)borate (abbreviation: Flr6), bis[2-(4',6'-difluorophenyl)pyridinato-N,C 2' ]iridium(III)picolinate (abbreviation: Flrpic), bis{2-[3',5'-bis(trifluoromethyl)phenyl]pyridinato-N,C 2' }iridium(III)picolinate (abbreviation: Ir(CF3ppy)2(pic)) and bis[2-(4',6'-difluorophenyl)pyridinato-N,C 2' ]iridium(III) acetylacetonate (abbreviation: Flr(acac)). Among the above-mentioned materials, organometallic iridium complexes having a five-membered nitrogen-containing heterocyclic framework, such as a 4H-triazole framework, a 1H-triazole framework, or an imidazole framework, exhibit high triplet excitation energy, reliability, and emission efficiency and are therefore particularly preferred. It should be noted that platinum complexes, such as 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrinplatinum(II) (abbreviation: PtOEP), and rare earth metal complexes, such as 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrinplatinum(II) (abbreviation: PtOEP), are also suitable. B. Tris[1-(2-thenoyl)-3,3,3-trifluoroacetonato](monophenanthroline)europium(III) (abbreviation: Eu(TTA)3(Phen)), can also be used.

[0285] Examples of the substance that exhibits an emission peak in green or yellow include organometallic iridium complexes with a pyrimidine skeleton, such asTris(4-methyl-6-phenylpyrimidinato)iridium(III) (abbreviation: Ir(mppm)3), Tris(4-t-butyl-6-phenylpyrimidinato)iridium(III) (abbreviation: Ir(tBuppm)3), (Acetylacetonato)bis(6-methyl-4-phenylpyrimidinato)iridium(III) (abbreviation: Ir(mppm)2(acac)), (Acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidinato)iridium(III) (abbreviation: Ir(tBuppm)2(acac)), (Acetylacetonato)bis[4-(2-norbornyl)-6-phenylpyrimidinato]iridium(III) (abbreviation: Ir(nbppm)2(acac)), (Acetylacetonato)bis[5-methyl-6-(2-methylphenyl)-4-phenylpyrimidinato]iridium(III) (abbreviation: Ir(mpmppm)2(acac)), (Acetylacetonato)bis{4,6-dimethyl-2-[6-(2,6-dimethylphenyl)-4-pyrimidinyl-κN3]phenyl-κC}iridium(III) (abbreviation: Ir(dmppm-dmp)2(acac)) and (Acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III) (abbreviation: Ir(dppm)2(acac)), organometallic iridium complexes with a pyrazine framework, such as(Acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazinato)iridium(III) (abbreviation: Ir(mppr-Me)2(acac)) and (acetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazinato)iridium(III) (abbreviation: Ir(mppr-iPr)2(acac)), organometallic iridium complexes with a pyridine framework, such as 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(acac)), bis(benzo[h]quinolinato)iridium(III)acetylacetonate (abbreviation: Ir(bzq)2(acac)), tris(benzo[h]quinolinato)iridium(III) (abbreviation: Ir(bzq)3), tris(2-phenylquinolinato-N,C 2' )iridium(III) (abbreviation: Ir(pq)3) and bis(2-phenylquinolinato-N,C 2' )iridium(III)acetylacetonate (abbreviation: Ir(pq)2(acac)), organometallic iridium complexes, such as bis(2,4-diphenyl-1,3-oxazolato-N,C 2' )iridium(III)acetylacetonate (abbreviation: Ir(dpo)2(acac)), bis{2-[4'-(perfluorophenyl)phenyl]pyridinato-N,C 2'}iridium(III)acetylacetonate (abbreviation: Ir(p-PF-ph)2(acac)) and bis(2-phenylbenzothiazolato-N,C 2' iridium(III) acetylacetonate (abbreviation: Ir(bt)2(acac)), and a rare earth metal complex, such as tris(acetylacetonato)(monophenanthroline)terbium(III) (abbreviation: Tb(acac)3(Phen)). Among the materials listed above, the organometallic iridium complexes with a pyrimidine framework exhibit very high reliability and very high emission efficiency and are therefore particularly preferred.

[0286] Examples of the substance exhibiting an emission peak in yellow or red include organometallic iridium complexes having a pyrimidine skeleton such as (diisobutyrylmethanato)bis[4,6-bis(3-methylphenyl)pyrimidinato]iridium(III) (abbreviation: Ir(5mdppm)2(dibm)), bis[4,6-bis(3-methylphenyl)pyrimidinato](dipivaloylmethanato)iridium(III) (abbreviation: Ir(5mdppm)2(dpm)) and bis[4,6-di(naphthalen-1-yl)pyrimidinato](dipivaloylmethanato)iridium(III) (abbreviation: Ir(d1npm)2(dpm)), organometallic iridium complexes having a pyrazine skeleton such as (diisobutyrylmethanato)bis[4,6-bis(3-methylphenyl)pyrimidinato]iridium(III) (abbreviation: Ir(5mdppm)2(dpm)), and organometallic iridium complexes having a pyrazine skeleton such as (diisobutyrylmethanato)bis[4,6-bis(3-methylphenyl)pyrimidinato]iridium(III) (abbreviation: Ir(5mdppm)2(dpm)). B. (Acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III) (abbreviation: Ir(tppr)2(acac)), bis(2,3,5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III) (abbreviation: Ir(tppr)2(dpm)) and (Acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III) (abbreviation: Ir(Fdpq)2(acac)), organometallic iridium complexes with a pyridine framework, such as tris(1-phenylisoquinolinato-N,C 2' )iridium(III) (abbreviation: Ir(piq)3) and bis(1-phenylisoquinolinato-N,C 2' )iridium(III) acetylacetonate (abbreviation: Ir(piq)2(acac)), a platinum complex such as 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrinplatinum(II) (abbreviation: PtOEP), and rare earth metal complexes such as tris(1,3-diphenyl-1,3-propanedionato)(monophenanthroline)europium(III) (abbreviation: Eu(DBM)3(Phen)) and tris[1-(2-thenoyl)-3,3,3-trifluoroacetonato](monophenanthroline)europium(III) (abbreviation: Eu(TTA)3(Phen)). Among the materials listed above, organometallic iridium complexes with a pyrimidine framework exhibit very high reliability and very high emission efficiency and are therefore particularly preferred. Furthermore, an organometallic iridium complex with a pyrazine framework can emit red light with favorable chromaticity.

[0287] As the host material of the light-emitting unit for phosphorescence, the hole transport material described above and / or the electron transport material described above can be used.

[0288] A structure different from the structure of the light-emitting layer 130 described in Embodiment 1 can also be used for the fluorescent light-emitting unit. Although there is no particular limitation on the guest material for the fluorescent light-emitting unit, an anthracene derivative, a tetracene derivative, a chrysene derivative, a phenanthrene derivative, a pyrene derivative, a perylene derivative, a stilbene derivative, an acridone derivative, a coumarin derivative, a phenoxazine derivative, a phenothiazine derivative, or the like is preferably used as the fluorescent compound, and for example, any of the following substances can be used.

[0289] Specific examples include 5,6-bis[4-(10-phenyl-9-anthryl)phenyl]-2,2'-bipyridine (abbreviation: PAP2BPy), 5,6-bis[4'-(10-phenyl-9-anthryl)biphenyl-4-yl]-2,2'-bipyridine (abbreviation: PAPP2BPy), N,N'-diphenyl-N,N'-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine (abbreviation: 1,6FLPAPrn), N,N'-bis(3-methylphenyl)-N,N'-bis[3-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine (abbreviation: 1,6mMemFLPAPrn), N,N'-Bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-N,N'-bis(4-tert-butylphenyl)-pyrene-1,6-diamine (abbreviation: 1,6tBu-FLPAPrn), N,N-Bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-N,N'-diphenyl-3,8-dicyclohexylpyrene-1,6-diamine (abbreviation: ch-1,6FLPAPrn), N,N'-Bis[4-(9H-carbazol-9-yl)phenyl]-N,N'-diphenylstilbene-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-anthryl)triphenylamine (abbreviation: 2YGAPPA), N,9-diphenyl-N-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine (abbreviation: 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-diyldi-4,1-phenylene)bis[N,N',N'-triphenyl-1,4-phenylenediamine] (abbreviation: DPABPA), N,9-Diphenyl-N-[4-(9,10-diphenyl-2-anthryl)phenyl]-9H-carbazol-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''-Octaphenyldibenzo[g,p]chrysen-2,7,10,15-tetraamine (abbreviation: DBC1), Coumarin 30, N-(9,10-Diphenyl-2-anthryl)-N,9-diphenyl-9H-carbazol-3-amine (abbreviation: 2PCAPA), N-[9,10-Bis(1,1'-biphenyl-2-yl)-2-anthryl]-N,9-diphenyl-9H-carbazol-3-amine (abbreviation: 2PCABPhA), 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'-biphenyl-2-yl)-N-[4-(9H-carbazol-9-yl)phenyl]-N-phenylanthracene-2-amine (abbreviation: 2YGABPhA), N,N,9-triphenylanthracene-9-amine (abbreviation: DPhAPhA), coumarin 6, coumarin 545T, N,N'-diphenylquinacridone (abbreviation: DPQd), rubrene, 2,8-di-tert-butyl-5,11-bis(4-tert-butylphenyl)-6,12-diphenyltetracene (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)tetracen-5,11-diamine (abbreviation: p-mPhTD), 7,14-Diphenyl-N,N,N',N'-tetrakis(4-methylphenyl)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-ylidene)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}propanedinitrile (abbreviation: BisDCJTM) and 5,10,15,20-Tetraphenylbisbenzo[5,6]indeno[1,2,3-cd:1',2',3'-lm]perylene (abbreviation: DBP).

[0290] The above-described hole-transport material and / or the above-described electron-transport material can be used as the host material of the light-emitting unit for fluorescence. Note that this embodiment can be combined with any of the other embodiments as needed. (Embodiment 4)

[0291] In this embodiment, a light-emitting device including the light-emitting device described in Embodiment 1 and Embodiment 3 is described by Fig. 7A and Fig. 7B.

[0292] Fig. 7A is a plan view of the light-emitting device and Fig. Figure 7B is a cross-sectional view along AB and CD in Fig. 7A. This light-emitting device includes a driver circuit section (source driver circuit) 601, a pixel section 602, and a driver circuit section (gate driver circuit) 603, indicated by dashed lines, which control the light emission of light-emitting devices. Reference numeral 604 denotes a sealing substrate, reference numeral 605 denotes a desiccant, and reference numeral 605 denotes a sealant. A portion surrounded by the sealant 605 is a space 607.

[0293] Note that a lead line 608 is a line for transmitting signals input to the source drive circuit 601 and the gate drive circuit 603, and for receiving a video signal, a clock signal, a start signal, a reset signal, and the like from a flexible printed circuit (FPC) 609 serving as an external input terminal. Although only the FPC is illustrated here, a printed wiring board (PWB) may be attached to the FPC. A light-emitting device in this specification includes within its category not only a light-emitting device per se but also a light-emitting device provided with an FPC or a PWB.

[0294] Next, a cross-sectional structure of the above light-emitting device is shown by Fig. 7B. Here, the source driver circuit 601, which is the driver circuit section, and one pixel of the pixel section 602 are shown.

[0295] In the source driver circuit 601, a CMOS circuit consisting of an n-channel TFT 623 and a p-channel TFT 624 is formed. The driver circuit can be formed using any of various circuits, such as a CMOS circuit, a PMOS circuit, and an NMOS circuit. Although this embodiment shows a driver-integrated light-emitting device in which the driver circuit is formed above the substrate, the driver circuit does not necessarily have to be formed above the substrate and may be formed outside the substrate.

[0296] The pixel section 602 consists of pixels, each including a switching TFT 611, a current control TFT 612, and a first electrode 613 electrically connected to a drain of the current control TFT 612. Note that an insulator 614 is formed to cover an end portion of the first electrode 613. The insulator 614 can be formed using a positive photosensitive resin film.

[0297] To improve coverage with a film formed over the insulator 614, the insulator 614 is formed to have a surface with a curvature at its upper or lower end portion. For example, when a photosensitive acrylic is used for a material of the insulator 614, preferably only the upper end portion of the insulator 614 has a curved surface. The radius of curvature of the curved surface is preferably greater than or equal to 0.2 µm and less than or equal to 0.3 µm. Either a negative photosensitive material or a positive photosensitive material can be used for the insulator 614.

[0298] An EL layer 616 and a second electrode 617 are formed over the first electrode 613. For the first electrode 613, which serves as an anode, a material with a high work function is preferably used. For example, a single-layer film such as an ITO film, an indium tin oxide film containing silicon, an indium oxide film containing 2 wt% to 20 wt% zinc oxide, a titanium nitride film, a chromium film, a tungsten film, a Zn film, or a Pt film, a stacked film of a titanium nitride film and a film containing aluminum as the main component, or a stacked film of three layers, namely a titanium nitride film, a film containing aluminum as the main component, and a titanium nitride film, can be used. The multilayer structure enables low conduction resistance and good ohmic contact, and it can serve as an anode.

[0299] The EL layer 616 is formed by one of various methods, such as an evaporation method using an evaporation mask, an inkjet method, and a spin coating method. The material contained in the EL layer 616 can be a low-molecular compound or a high-molecular compound (including an oligomer or a dendrimer).

[0300] As the material used for the second electrode 617 formed over the EL layer 616 and serving as a cathode, a material with a low work function (e.g., Al, Mg, Li, Ca, or an alloy or compound thereof, such as MgAg, Mgln, or AlLi) is preferably used. In the case where light generated in the EL layer 616 passes through the second electrode 617, a stacked arrangement of a thin metal film and a transparent conductive film (e.g., ITO, indium oxide containing 2 wt% to 20 wt% zinc oxide, indium tin oxide containing silicon, or zinc oxide (ZnO)) is preferably used for the second electrode 617.

[0301] A light-emitting device 618 is composed of the first electrode 613, the EL layer 616, and the second electrode 617. The light-emitting device 618 preferably has the structure described in Embodiment 1 and Embodiment 2. In the light-emitting device of this embodiment, the pixel section composed of a plurality of light-emitting devices may include both the light-emitting device having the structure described in Embodiment 1 and Embodiment 3 and a light-emitting device having a different structure.

[0302] The sealing substrate 604 is attached to a light-emitting device substrate 610 with the sealant 605, so that the light-emitting device 618 is provided in the space 607 surrounded by the substrate 610, the sealing substrate 604, and the sealant 605. The space 607 is filled with a filler, and may be filled with an inert gas (e.g., nitrogen or argon) or a resin and / or a desiccant.

[0303] Note that an epoxy-based resin or a glass frit is preferably used for the sealant 605. It is preferable that such a material permits as little moisture or oxygen permeation as possible. A glass substrate, a quartz substrate, or a plastic substrate formed from fiber-reinforced plastics (FRP), polyvinyl fluoride (PVF), polyester, acrylic, or the like can be used as the sealant substrate 604.

[0304] As described above, the light-emitting device including the light-emitting device described in Embodiment 1 and Embodiment 3 can be obtained. <Strukturbeispiel 1 einer Licht emittierenden Vorrichtung>

[0305] As an example of a display device, Fig. 8 illustrates an example of a light-emitting device including a light-emitting device having a white light emission and a color layer (a color filter).

[0306] Fig. 8A illustrates a substrate 1001, a base insulating film 1002, a gate insulating film 1003, gate electrodes 1006, 1007, and 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 1024W, 1024R, 1024G, and 1024B of light-emitting devices, an EL layer 1028, a second electrode 1029 of the light-emitting devices, a sealing substrate 1031, a sealing agent 1032, a red pixel 1044R, a green pixel 1044G, a blue pixel 1044B, a white pixel 1044W and the like.

[0307] In Fig. 8A and Fig. 8B, color layers (a red color layer 1034R, a green color layer 1034G, and a blue color layer 1034B) are provided on a transparent base material 1033. A black layer (black matrix) 1035 may be additionally provided. The transparent base material 1033, provided with the color layers and the black layer, is properly aligned and attached to the substrate 1001. The color layers and the black layer are covered with a cover layer 1036. Furthermore, Fig. 8A illustrates a light-emitting layer whose light is not transmitted to the outside through a color layer and a light-emitting layer whose light is transmitted to the outside through a corresponding color layer. Since light that is not transmitted through a color layer is white, and light that is transmitted through a color layer is red, blue, or green, an image can be displayed using pixels of the four colors.

[0308] Fig. 8B illustrates an example in which the red color layer 1034R, the green color layer 1034G, and the blue color layer 1034B are formed between the gate insulating film 1003 and the first interlayer insulating film 1020. As shown in Fig. 8B, the color layers may be provided between the substrate 1001 and the sealing substrate 1031.

[0309] The light-emitting device described above is a light-emitting device having a structure in which light is extracted from the side of the substrate 1001 where the TFTs are formed (bottom-emission structure), but it may also be a light-emitting device having a structure in which light is extracted from the side of the sealing substrate 1031 (top-emission structure). <Strukturbeispiel 2 einer Licht emittierenden Vorrichtung>

[0310] Fig. 9A and Fig. 9B are cross-sectional views of top-emission light-emitting devices. In this case, a substrate that does not transmit light can be used as the substrate 1001. The process up to the step of forming a connection electrode that connects the TFT and the anode of the light-emitting device is performed in the same manner as in the bottom-emission light-emitting device. Next, a third interlayer insulating film 1037 is formed to cover an electrode 1022. This insulating film may have a planarization function. The third interlayer insulating film 1037 may be formed using a material that can be used for the second interlayer insulating film 1021 or a different material from other materials.

[0311] The lower electrodes 1025W, 1025R, 1025G, and 1025B of the light-emitting device serve as anodes here, but they can also serve as cathodes. In the top-emission light-emitting device, as shown in Fig. 9A and Fig. 9B, 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. It is preferable that a microcavity structure is used between the second electrode 1029 and the lower electrodes 1025W, 1025R, 1025G, and 1025B, in which case, light with a specific wavelength is amplified. The EL layer 1028 has a device structure similar to that described in Embodiment 1 and Embodiment 3, so that white light emission can be obtained.

[0312] In Fig. 8A, Fig. 8B, Fig. 9A and Fig. 9B, the structure of the EL layer for providing white light emission can be achieved by, for example, using a plurality of light-emitting layers or a plurality of light-emitting units. Note that the structure for providing white light emission is not limited to the above.

[0313] In the Fig. 9A and Fig. In the top-emission structure illustrated in FIG. 9B, sealing may be performed with the sealing substrate 1031 on which the color layers (the red color layer 1034R, the green color layer 1034G, and the blue color layer 1034B) are provided. The sealing substrate 1031 may be provided with a black layer (black matrix) 1030 positioned between pixels. The color layers (the red color layer 1034R, the green color layer 1034G, and the blue color layer 1034B) and the black layer (black matrix) may be covered with the capping layer. Note that a light-transmitting substrate is used as the sealing substrate 1031.

[0314] Fig. 9A illustrates a structure in which a full-color display is performed using three colors, namely red, green, and blue; a full-color display may alternatively be performed using four colors, namely red, green, blue, and white, as shown in Fig. 9B. The structure for performing a full-color display is not limited to the above. For example, a full-color display can be performed using four colors, namely red, green, blue, and yellow.

[0315] In the light-emitting device of one embodiment of the present invention, a fluorescent material is used as the guest material. Since a fluorescent material has a sharper spectrum than a phosphorescent material, light emission with high color purity can be obtained. Accordingly, by using the light-emitting device for the light-emitting device described in this embodiment, the light-emitting device can have high color reproducibility. (Embodiment 5)

[0316] In this embodiment, electronic devices and display devices of embodiments of the present invention are described.

[0317] According to one embodiment of the present invention, an electronic device and a display device can be manufactured that have a flat surface and high emission efficiency, as well as high reliability. Furthermore, according to one embodiment of the present invention, an electronic device and a display device can be manufactured that have a curved surface and high emission efficiency, as well as high reliability. Furthermore, a light-emitting device that has high color reproducibility as described above can be obtained.

[0318] Examples of the electronic devices include a television set, a desktop or notebook personal computer, a monitor of a computer or the like, a digital camera, a digital video camera, a digital photo frame, a mobile phone, a portable game console, a portable information terminal, an audio playback device, and a large gaming machine such as a pinball machine.

[0319] A portable information terminal 900 which is Fig. 10A and Fig. 10B includes a housing 901, a case 902, a display portion 903, a hinge portion 905, and the like.

[0320] The housing 901 and the housing 902 are connected to each other via the hinge portion 905. The portable information terminal 900 can, as in Fig. 10B, from a closed state ( Fig. 10A). Thus, the portable information terminal 900 has high portability when worn and excellent visibility when used thanks to its large display area.

[0321] In the portable information terminal 900, the flexible display section 903 is provided across the case 901 and the case 902, which are connected to each other via the hinge section 905.

[0322] The light-emitting device manufactured using an embodiment of the present invention can be used for the display section 903. Therefore, the portable information terminal can have high reliability.

[0323] The display section 903 can display at least one of a text, a still image, a moving image, and the like. When a text is displayed on the display section, the portable information terminal 900 can be used as an e-book reader.

[0324] When the portable information terminal 900 is opened, the display portion 903 is maintained in a state with a large radius of curvature. For example, the display portion 903 is maintained in a state where it includes a curved portion with a radius of curvature greater than or equal to 1 mm and less than or equal to 50 mm, preferably greater than or equal to 5 mm and less than or equal to 30 mm. A portion of the display portion 903 can display an image in the curved state because pixels are continuously arranged from the housing 901 to the housing 902.

[0325] The display section 903 serves as a touch screen and can be operated with a finger, a pen or the like.

[0326] The display section 903 is preferably formed using a flexible display. Thus, a seamless, continuous image can be displayed between the housing 901 and the housing 902. Note that both the housing 901 and the housing 902 may be provided with a display.

[0327] The hinge portion 905 preferably includes a locking mechanism so that the angle formed between the housing 901 and the housing 902 does not exceed a predetermined angle when the portable information terminal 900 is opened. For example, the locking angle (beyond which the device cannot be opened further) is preferably greater than or equal to 90° and less than 180°, and may typically be 90°, 120°, 135°, 150°, 175°, or the like. In this case, the convenience, safety, and reliability of the portable information terminal 900 can be improved.

[0328] When the hinge portion 905 includes a locking mechanism, excessive force is not applied to the display portion 903; thus, damage to the display portion 903 can be prevented. Consequently, a portable information terminal with high reliability can be provided.

[0329] The housings 901 and 902 may include a power button, a control button, an external connection port, a speaker, a microphone, and the like.

[0330] Either the housing 901 or the housing 902 is provided with a wireless communication module, and data can be transmitted and received via a computer network such as the Internet, a local area network (LAN), or Wi-Fi (registered trademark).

[0331] A portable information terminal 910 which is Fig. 10C includes a housing 911, a display section 912, an operation button 913, an external connection terminal 914, a speaker 915, a microphone 916, a camera 917, and the like.

[0332] The light-emitting device manufactured using an embodiment of the present invention can be used for the display section 912. Thus, the portable information terminal can be manufactured with high yield.

[0333] The portable information terminal 910 includes a touch sensor in the display section 912. Various operations, such as making a call and entering text, can be performed by touching the display section 912 with a finger, a stylus, or the like.

[0334] The control buttons 913 can be used to turn the power on / off and switch the types of images displayed on the display section 912. For example, an email writing screen can be switched to a main menu screen.

[0335] When a sensing device such as a gyroscope sensor or an acceleration sensor is provided within the portable information terminal 910, the direction of the display on the screen of the display section 912 can be automatically changed by determining the orientation of the portable information terminal 910 (whether the portable information terminal 910 is arranged horizontally or vertically). The direction of the display on the screen can also be changed by touching the display section 912, operating the operation buttons 913, inputting sound with the microphone 916, or the like.

[0336] The portable information terminal 910 has, for example, one or more functions as a telephone, notebook, information search system, and the like. In particular, the portable information terminal can be used as a smartphone. The portable information terminal 910 can execute various applications, such as making mobile phone calls, sending and receiving emails, displaying and editing text, playing music, playing moving images, Internet communication, and running computer games.

[0337] A camera 920 that is in Fig. 10D includes a housing 921, a display section 922, operation buttons 923, a shutter button 924, and the like. Furthermore, an attachable lens 926 is attached to the camera 920.

[0338] The light-emitting device manufactured using an embodiment of the present invention can be used for the display section 922. Therefore, the camera can have high reliability.

[0339] Although the lens 926 of the camera 920 is removable from the housing 921 for replacement, the lens 926 may be integrated into the housing 921.

[0340] A still image or a moving image can be captured with the camera 920 when the shutter button 924 is pressed. In addition, images can also be captured by touching the display section 922, which has a touchscreen function.

[0341] It should be noted that the camera 920 may additionally be provided with a strobe light, a viewfinder, or the like. Alternatively, they may be incorporated into the housing 921.

[0342] Fig. 11A is a schematic view showing an example of a cleaning robot.

[0343] A cleaning robot 5100 includes a display 5101 on its top surface, a plurality of cameras 5102 on its side surface, a brush 5103, and control buttons 5104. Although not shown, the bottom of the cleaning robot 5100 is provided with a tire, an intake port, and the like. The cleaning robot 5100 further includes various sensors, such as an infrared sensor, an ultrasonic sensor, an acceleration sensor, a piezoelectric sensor, an optical sensor, and a gyroscope sensor. The cleaning robot 5100 has a wireless communication means.

[0344] The 5100 cleaning robot is self-propelled, captures dust 5120 and sucks up the dust through the inlet provided on the bottom.

[0345] The cleaning robot 5100 can determine whether an obstacle, such as a wall, a piece of furniture, or a step, is present by analyzing images captured by the cameras 5102. If the cleaning robot 5100 detects an object that may become entangled in the brush 5103 (e.g., a wire) by analyzing an image, the rotation of the brush 5103 can be stopped.

[0346] The display 5101 can display the remaining battery power, the amount of dust collected, and the like. The display 5101 can display a route that the cleaning robot 5100 has traveled. The display 5101 can be a touchscreen, and the control buttons 5104 can be provided on the display 5101.

[0347] The cleaning robot 5100 can communicate with a portable electronic device 5140, such as a smartphone. The portable electronic device 5140 can display images captured by the cameras 5102. Accordingly, an owner of the cleaning robot 5100 can monitor their room even when the owner is not at home. The owner can also check the display 5101 using the portable electronic device 5140, such as a smartphone.

[0348] The light-emitting device of one embodiment of the present invention can be used for the display 5101.

[0349] A robot 2100 that is in Fig. 11B includes an arithmetic device 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.

[0350] The microphone 2102 has a function of detecting a user's speaking voice, ambient noise, and the like. The speaker 2104 also has a function of outputting a sound. The robot 2100 can communicate with a user using the microphone 2102 and the speaker 2104.

[0351] The display 2105 has the function of displaying various types of information. The robot 2100 can display information requested by a user on the display 2105. The display 2105 can be equipped with a touchscreen. Furthermore, the display 2105 can be a detachable information terminal, in which case charging and data communication can be performed when the display 2105 is adjusted to the predetermined position of the robot 2100.

[0352] The upper camera 2103 and the lower camera 2106 each have a function for capturing an image of the surroundings of the robot 2100. The obstacle sensor 2107 can detect an obstacle in the direction in which the robot 2100 moves forward with the movement mechanism 2108. The robot 2100 can move safely by detecting the surroundings with the upper camera 2103, the lower camera 2106, and the obstacle sensor 2107.

[0353] The light-emitting device of one embodiment of the present invention can be used for the display 2105.

[0354] Fig. 11C illustrates an example of a glasses-type display. The glasses-type display includes, for example, a housing 5000, a display portion 5001, a speaker 5003, an LED lamp 5004, operation buttons (including a power button or an operation switch), a connection terminal 5006, a sensor 5007 (a sensor having a function of measuring force, displacement, position, speed, acceleration, angular velocity, rotational speed, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current, voltage, electric energy, radiation, flow rate, humidity, gradient, vibration, odor, or infrared ray), a microphone 5008, a second display portion 5002, a support 5012, and an earphone 5013.

[0355] The light-emitting device of one embodiment of the present invention can be used for the display section 5001 and the second display section 5002.

[0356] Fig. 12A and Fig. 12B illustrates a foldable portable information terminal 5150. The foldable portable information terminal 5150 includes a housing 5151, a display portion 5152, and a bending portion 5153. Fig. 12A illustrates the portable information terminal 5150 in the opened state. Fig. 12B illustrates the portable information terminal 5150 in the folded state. Despite its large display area 5152, the portable information terminal 5150 is compact and has high portability when folded.

[0357] The display area 5152 can be folded twice with the bending section 5153. The bending section 5153 includes a flexible element and a plurality of support elements. When the display area is folded, the flexible element expands, and the bending section 5153 has a radius of curvature of 2 mm or more, preferably 5 mm or more.

[0358] Note that the display area 5152 may be a touchscreen (an input / output device) that includes a touch sensor (an input device). The light-emitting device of one embodiment of the present invention may be used for the display area 5152.

[0359] This embodiment can be combined with any of the other embodiments as required. (Embodiment 6)

[0360] In this embodiment, examples in which the light-emitting device of one embodiment of the present invention is used for various lighting devices will be explained with reference to Fig. 13. Using the light-emitting device of one embodiment of the present invention, a highly reliable lighting device with high emission efficiency can be manufactured.

[0361] By forming the light-emitting device of one embodiment of the present invention over a flexible substrate, an electronic device or a lighting device having a light-emitting region with a curved surface can be obtained.

[0362] Furthermore, a light-emitting device using the light-emitting apparatus of one embodiment of the present invention can also be used for lighting for vehicles; examples include lighting for a windshield, a vehicle ceiling, and the like.

[0363] Fig. 13 illustrates an example in which the light-emitting device is used for an indoor lighting device 8501. Since the light-emitting device can have a larger area, a lighting device with a large area can also be formed. In addition, a lighting device 8502 in which a light-emitting region has a curved surface can also be formed using a housing with a curved surface. The light-emitting device described in this embodiment is in the form of a thin film, which makes it possible to design the housing more freely. Consequently, the lighting device can be artistically designed in various ways. Furthermore, the wall of a room can be provided with a large lighting device 8503.Touch sensors may be provided in the lighting devices 8501, 8502 and 8503 to control the switching on or off of the lighting devices.

[0364] Furthermore, when the light-emitting device is used on the surface side of a table, a lighting device 8504 having a function as a table can be obtained. When the light-emitting device is used as part of another piece of furniture, a lighting device having a function as the relevant piece of furniture can be obtained.

[0365] As described above, lighting devices and electronic devices can be obtained using the light-emitting device of one embodiment of the present invention. Note that the light-emitting device for electronic devices can be used in various fields, without being limited to the lighting devices and electronic devices described in this embodiment.

[0366] The structure described in this embodiment may be used in a suitable combination with any of the structures described in the other embodiments. [Example 1]

[0367] In this example, examples of manufacturing light-emitting devices of embodiments of the present invention and comparative light-emitting devices, as well as the characteristics of the light-emitting devices, are described. The structure of each of the light-emitting devices manufactured in this example is the same as that described in Fig. 1A. Tables 1 to 6 show the details of the device structures. Note that values ​​represented by x1 in Tables 1 to 4 correspond to values ​​shown in Table 5, and values ​​represented by x2 correspond to values ​​shown in Table 6. In addition, the structures and abbreviations of compounds used herein are given below. [Table 1] Schicht Bezugszeichen Dicke(nm) Material Gewichtsverhältnis LichtemittierendeVergleichsvorrichtung 1 Elektrode 102 200 Al - Elektroneninjektionsschicht 119 1 LiF - Elektronentransportschicht 118(2) 10 NBphen - 118(1) 20 mPCCzPTzn-02 - LichtemittierendeSchicht 130(2) 10 mPCCzPTzn-02: PCCP: Ir(mpptz-diBuCNp)3 0,8:0,2:0,1 130(1) 30 mPCCzPTzn-02: PCCP: Ir(mpptz-diBuCNp)3 0,5:0,5:0,1 Hole transport layer 112 20 PCCP - Hole injection layer 111 20 DBT3P-II: MoO3 1:0,5 anode 101 70 ITSO - Light-emitting devices 2-5 electrode 102 200 Al - Electron injection layer 119 1 LiF - Electron transport layer 118(2) 10 NBphen - 118(1) 20 mPCCzPTzn-02 - Light-emitting layer 130(2) 10 mPCCzPTzn-02: PCCP:Ir(mpptz-diBuCNp)3: 2tBu-ptBuDPhA2Anth 0,8:0,2:0,1:x1 130(1) 30 mPCCzPTzn-02: PCCP:Ir(mpptz-diBuCNp)3: 2tBu-ptBuDPhA2Anth 0,5:0,5:0,1:x1 Hole transport layer 112 20 PCCP - Hole injection layer 111 40 DBT3P-II: MoO3 1:0,5 anode 101 70 ITSO - Light-emitting comparison device 6 electrode 102 200 Al - Electron injection layer 119 1 LiF - Electron transport layer 118(2) 10 NBphen - 118(1) 20 4.6mCzP2Pm - Light-emitting layer 130(2) 20 4.6mCzP2Pm: PCCP: Ir(mpptz-diPrp)3 0,8:0,2:0,1 130(1) 20 4.6mCzP2Pm: PCCP: Ir(mpptz-diPrp)3 0,5:0,5:0,1 Hole transport layer 112 20 PCCP - Hole injection layer 111 20 DBT3P-II: MoO3 1:0,5 anode 101 70 ITSO - Light-emitting devices 7-10 electrode 102 200 Al - Electron injection layer 119 1 LiF - Electron transport layer 118(2) 10 NBphen - 118(1) 20 4.6mCzP2Pm - Light-emitting layer 130(2) 20 4.6mCzP2Pm: PCCP:Ir(mpptz-diPrp)3: 2tBu-ptBuDPhA2Anth 0,8:0,2:0,1:x1 130(1) 20 4.6mCzP2Pm2: PCCP:Ir(mpptz-diPrp)3: 2tBu-ptBuDPhA2Anth 0,5:0,5:0,1:x1 Hole transport layer 112 20 PCCP - Hole injection layer 111 40 DBT3P-II: MoO3 1:0,5 anode 101 70 ITSO - [Table 2] layer Reference symbol Thickness (nm) material Weight ratio Light-emitting comparison device 11 electrode 102 200 Al - Electron injection layer 119 1 LiF - Electron transport layer 118(2) 10 NBphen - 118(1) 20 4.6mCzP2Pm - Light-emitting layer 130 40 4.6mCzP2Pm : Ir(Mptz1-mp)3 0,8:0,2 Hole transport layer 112 20 PCCP - Hole injection layer 111 40 DBT3P-II: MoO3 1:0,5 anode 101 70 ITSO - Light-emitting devices 12-15 electrode 102 200 Al - Electron injection layer 119 1 LiF - Electron transport layer 118(2) 10 NBphen - 118(1) 20 4.6mCzP2Pm - Light-emitting layer 130 40 4.6mCzP2Pm : Ir(Mptz1-mp)3: 2tBu-ptBuDPhA2Anth 0,8:0,2:x1 Hole transport layer 112 20 PCCP - Hole injection layer 111 40 DBT3P-II: MoO3 1:0,5 anode 101 70 ITSO - Light-emitting comparison device 16 electrode 102 200 Al - Electron injection layer 119 1 LiF - Electron transport layer 118(2) 10 NBphen - 118(1) 20 4.6mCzP2Pm - Light-emitting layer 130 40 mPCCzPTzn-02 : PCCP : Ir(pbi-diBuCNp)3 0,5:0,5:0,1 Hole transport layer 112 20 PCBBi1BP - Hole injection layer 111 40 DBT3P-II: MoO3 1:0,5 anode 101 70 ITSO - Light-emitting devices 17-19 electrode 102 200 Al - Electron injection layer 119 1 LiF - Electron transport layer 118(2) 10 NBphen - 118(1) 20 4.6mCzP2Pm - Light-emitting layer 130 40 mPCCzPTzn-02 : PCCP : Ir(pbidiBuCNp)3 : 2tBu-ptBuDPhA2Anth 0,5:0,5:x2 Hole transport layer 112 20 PCBBi1BP - Hole injection layer 111 40 DBT3P-II: MoO3 1:0,5 anode 101 70 ITSO - [Table 3] layer Reference symbol Thickness (nm) material Weight ratio Light-emitting comparison device 20 electrode 102 200 Al - Electron injection layer 119 1 LiF - Electron transport layer 118(2) 10 NBphen - 118(1) 20 mPCCzPTzn-02 - Light-emitting layer 130 40 mPCCzPTzn-02: PCCP:fac-Ir(pbi-diBup)3 0,5:0,5:0,1 Hole transport layer 112 20 PCBBi1BP - Hole injection layer 111 40 DBT3P-II: MoO3 1:0,5 anode 101 70 ITSO - Light-emitting devices 21-24 electrode 102 200 Al - Electron injection layer 119 1 LiF - Electron transport layer 118(2) 10 NBphen - 118(1) 20 mPCCzPTzn-02 - Light-emitting layer 130 40 mPCCzPTzn-02: PCCP : fac-I r(pbi-diBup)3: 2tBu-ptBuDPhA2Anth 0,5:0,5:x1 Hole transport layer 112 20 PCBBi1BP - Hole injection layer 111 40 DBT3P-II: MoO3 1:0,5 anode 101 70 ITSO - Light-emitting comparison device 25 electrode 102 200 Al - Electron injection layer 119 1 LiF - Electron transport layer 118(2) 10 NBphen - 118(1) 20 mPCCzPTzn-02 - Light-emitting layer 130 40 mPCCzPTzn-02 : PCCP: Ir(pni-diBup)2(mdppy) 0,5:0,5:0,1 Hole transport layer 112 20 PCBBi1BP - Hole injection layer 111 40 DBT3P-II: MoO3 1:0,5 anode 101 70 ITSO - Light-emitting devices 26-28 electrode 102 200 Al - Electron injection layer 119 1 LiF - Electron transport layer 118(2) 10 NBphen - 118(1) 20 mPCCzPTzn-02 - Light-emitting layer 130 40 mPCCzPTzn-02: PCCP: Ir(pnidiBup)2(mdppy) : 2tBu-ptBuDPhA2Anth 0,5:0,5:0,1:x2 Hole transport layer 112 20 PCBBi1BP - Hole injection layer 111 40 DBT3P-II: MoO3 1:0,5 anode 101 70 ITSO - [Table 4] layer Reference symbol Thickness (nm) material Weight ratio Light-emitting comparison device 29 electrode 102 200 Al - Electron injection layer 119 1 LiF - Electron transport layer 118(2) 10 NBphen - 118(1) 20 mPCCzPTzn-02 - Light-emitting layer 130 40 mPCCzPTzn-02: PCCP: Ir(pni-diBup)3 0,5:0,5:0,1 Hole transport layer 112 20 PCBBi1BP - Hole injection layer 111 40 DBT3P-II: MoO3 1:0,5 anode 101 70 ITSO - Light-emitting devices 30-33 electrode 102 200 Al - Electron injection layer 119 1 LiF - Electron transport layer 118(2) 10 NBphen - 118(1) 20 mPCCzPTzn-02 - Light-emitting layer 130 40 mPCCzPTzn-02: PCCP: Ir(pni-diBup)3: 2tBu-ptBuDPhA2Anth 0,5:0,5:x1 Hole transport layer 112 20 PCBBi1BP - Hole injection layer 111 40 DBT3P-II: MoO3 1:0,5 anode 101 70 ITSO - Light-emitting comparison device 34 electrode 102 200 Al - Electron injection layer 119 1 LiF - Electron transport layer 118(2) 10 NBphen - 118(1) 20 4.6mCzP2Pm - Light-emitting layer 130 40 mPCCzPTzn-02: PCCP: Ir(ppy)3 0,5:0,5:0,1 Hole transport layer 112 20 PCBBi1BP - Hole injection layer 111 40 DBT3P-II: MoO3 1:0,5 anode 101 70 ITSO - Light-emitting comparison devices 35-38 electrode 102 200 Al - Electron injection layer 119 1 LiF - Electron transport layer 118(2) 10 NBphen - 118(1) 20 4.6mCzP2Pm - Light-emitting layer 130 40 mPCCzPTzn-02: PCCP: Ir(ppy)3: 2tBu-ptBuDPhA2Anth 0,5:0,5:0,1:x1 Hole transport layer 112 20 PCBBi1BP - Hole injection layer 111 40 DBT3P-II: MoO3 1:0,5 anode 101 70 ITSO - [Table 5] Light-emitting devices 2, 7, 12, 21, 30 Light-emitting comparison device 35 Light-emitting devices 3, 8, 13, 22, 31 Light-emitting comparison device 36 Light-emitting devices 4, 9, 14, 23, 32 Light-emitting comparison device 37 Light-emitting devices 5, 10, 15, 24, 33 Light-emitting comparison device 38 x1 0,01 0,025 0,05 0,1 [Table 6] Light-emitting devices17,26 Light-emitting devices18,27 Light-emitting devices19,28 x2 0,01 0,05 0,1 <Herstellung der Licht emittierenden Vorrichtungen>

[0368] Methods for manufacturing the light-emitting devices of this example are described below. <<Herstellung von Licht emittierenden Vorrichtungen 2 bis 5> >

[0369] An ITSO film with a thickness of 70 nm was formed over a glass substrate as electrode 101. Note that the electrode area of ​​electrode 101 was set to 4 mm 2 (2 mm × 2 mm) was set.

[0370] As hole injection layer 111, DBT3P-II and molybdenum oxide (MoO3) were then deposited by co-evaporation in a weight ratio of 1:0.5 (DBT3P-II: MoO3) in a thickness of 40 nm over the electrode 101.

[0371] Next, PCCP was deposited as hole transport layer 112 by evaporation to a thickness of 20 nm over the hole injection layer 111.

[0372] Next, as the light-emitting layer 130, mPCCzPTzn-02, PCCP, Ir(mpptz-diBuCNp)3 and 2tBu-ptBuDPhA2Anth were co-evaporated in a weight ratio of 0.5:0.5:0.1:x1 (mPCCzPTzn-02:PCCP:Ir(mpptz-diBuCNp)3:2tBu-ptBuDPhA2Anth) to a thickness of 30 nm over the hole transport layer 112. Subsequently, mPCCzPTzn-O2, PCCP, Ir(mpptz-diBuCNp)3, and 2tBu-ptBuDPhA2Anth were co-evaporated in a weight ratio of 0.8:0.2:0.1:x1 (mPCCzPTzn-O2:PCCP:Ir(mpptz-diBuCNp)3:2tBu-ptBuDPhA2Anth) to a thickness of 10 nm. In the light-emitting layer 130, Ir(mpptz-diBuCNp)3 is a phosphorescent material with a five-membered ring. Furthermore, 2tBu-ptBuDPhA2Anth is a fluorescent material with protecting groups. Note that the value of x1 depends on the light-emitting device, and Table 5 shows the value of x1 for each light-emitting device.

[0373] Next, mPCCzPTzn-02 and NBPhen were successively deposited by evaporation to a thickness of 20 nm and 10 nm, respectively, over the light-emitting layer 130 as the electron-transport layer 118. Subsequently, LiF was deposited by evaporation to a thickness of 1 nm over the electron-transport layer 118 as the electron-injection layer 119.

[0374] Next, aluminum (Al) was deposited as electrode 102 to a thickness of 200 nm over the electron injection layer 119.

[0375] Subsequently, light-emitting devices 2 to 5 were sealed in a glove box having a nitrogen atmosphere by fixing a glass substrate for sealing to the glass substrate on which the organic materials were deposited using a sealant for organic EL. Specifically, after the sealant was applied to enclose the organic materials deposited on the glass substrate and the glass substrate was fixed to the glass substrate for sealing, irradiation with UV light having a wavelength of 365 nm at 6 J / cm 2 and heat treatment at 80 °C for one hour. Through the above steps, light-emitting devices 2 to 5 were obtained. <<Herstellung von Licht emittierenden Vorrichtungen 7 bis 10, Licht emittierenden Vorrichtungen 12 bis 15, Licht emittierenden Vorrichtungen 17 bis 19, Licht emittierenden Vorrichtungen 21 bis 24, Licht emittierenden Vorrichtungen 26 bis 28, Licht emittierenden Vorrichtungen 30 bis 33, Licht emittierenden Vergleichsvorrichtungen 1, 6, 11, 16, 20, 25 und 29 sowie Licht emittierenden Vergleichsvorrichtungen 34 bis 38>>

[0376] Light-emitting devices 7 to 10, light-emitting devices 12 to 15, light-emitting devices 17 to 19, light-emitting devices 21 to 24, light-emitting devices 26 to 28, light-emitting devices 30 to 33, comparative light-emitting devices 1, 6, 11, 16, 20, 25, and 29, and comparative light-emitting devices 34 to 38 were formed by a vacuum evaporation method in the same manner as the above-described light-emitting devices 2 to 5. The details of the manufacturing process will not be described because the details of the structures of the light-emitting devices are as shown in Tables 1 to 4. It should be noted that the values ​​each represented by x1 in Tables 1 to 4 are as shown in Table 5 and the values ​​each represented by x2 are as shown in Table 6.

[0377] Comparative light-emitting devices 1, 6, 11, 16, 20, 25, and 29, as well as comparative light-emitting device 34, are light-emitting devices that do not contain any fluorescent material in the light-emitting layers 130. Therefore, the phosphorescent material contained in each of the light-emitting layers emits light. These light-emitting devices are light-emitting devices in which the phosphorescent material serves as a guest material (energy acceptor), and they are shown as comparative examples of the light-emitting device of one embodiment of the present invention in which the phosphorescent material serves as an energy donor.

[0378] Light-emitting devices 2 to 5, light-emitting devices 7 to 10, light-emitting devices 12 to 15, light-emitting devices 21 to 24, light-emitting devices 26 to 28, and light-emitting devices 30 to 33 are the light-emitting devices of embodiments of the present invention. The light-emitting layer 130 of each device contains 2tBu-ptBuDPhA2Anth, which is a fluorescent material with protecting groups. Therefore, the light-emitting devices emit fluorescence. Similarly, comparative light-emitting devices 35 to 38 are also fluorescent devices, each of which has a light-emitting layer 130 containing 2tBu-ptBuDPhA2Anth, which is a fluorescent material with protecting groups.

[0379] Ir(mpptz-diBuCNp)3 is used as a five-membered ring phosphorescent material in light-emitting devices 2 to 5, Ir(mpptz-diPrp)3 is used as a five-membered ring phosphorescent material in light-emitting devices 7 to 10, Ir(Mptz1-mp)3 is used as a five-membered ring phosphorescent material in light-emitting devices 12 to 15, Ir(pbi-diBuCNp)3 is used as a five-membered ring phosphorescent material in light-emitting devices 17 to 19, fac-Ir(pbi-diBup)3 is used as a five-membered ring phosphorescent material in light-emitting devices 20 to 24, Ir(pni-diBup)2(mdppy) is used as phosphorescent material having a five-membered ring is used in the light-emitting devices 26 to 28,and Ir(pni-diBup)3 is used as a phosphorescent material having a five-membered ring in the light-emitting devices 30 to 33. The above-described phosphorescent materials, each comprising a five-membered ring, are examples of a phosphorescent material having a triazole skeleton or an imidazole skeleton. Note that Ir(ppy)3, which is a phosphorescent material without a five-membered ring skeleton, is used for the comparative light-emitting devices 35 to 38, which were prepared for comparing the device characteristics with those of the light-emitting device of one embodiment of the present invention.

[0380] It should be noted that mPCCzPTzn-02 and PCCP are a combination forming an exciplex, and 4,6mCzP2Pm and PCCP are a combination forming an exciplex. <Eigenschaften der Licht emittierenden Vorrichtungen>

[0381] Next, the characteristics of light-emitting devices 2 to 5, light-emitting devices 7 to 10, light-emitting devices 12 to 15, light-emitting devices 17 to 19, light-emitting devices 21 to 24, light-emitting devices 26 to 28, light-emitting devices 30 to 33, comparative light-emitting devices 1, 6, 11, 16, 20, 25, and 29, and comparative light-emitting devices 34 to 38, which were prepared in the above manner, were measured. The luminance and CIE chromaticity were measured using a luminance colorimeter (BM-5A, manufactured by TOPCON TECHNOHOUSE CORPORATION). The electroluminescence spectrum was measured using a multichannel spectrometer (PMA-11, manufactured by Hamamatsu Photonics KK).

[0382] Fig. 14, Fig. 16, Fig. 18, Fig. 20, Fig. 22, Fig. 24, Fig. 26 and Fig. 28 shows the external quantum efficiency-luminance characteristics of light-emitting devices 2 to 5, light-emitting devices 7 to 10, light-emitting devices 12 to 15, light-emitting devices 17 to 19, light-emitting devices 21 to 24, light-emitting devices 26 to 28, light-emitting devices 30 to 33, comparative light-emitting devices 1, 6, 11, 16, 20, 25 and 29, and comparative light-emitting devices 34 to 38. Fig. 15, Fig. 17, Fig. 19, Fig. 21, Fig. 23, Fig. 25, Fig. 27 and Fig. 29 show the electroluminescence spectra obtained when a current with a current density of 2.5 mA / cm 2 to light-emitting devices 2 to 5, light-emitting devices 7 to 10, light-emitting devices 12 to 15, light-emitting devices 17 to 19, light-emitting devices 21 to 24, light-emitting devices 26 to 28, light-emitting devices 30 to 33, comparative light-emitting devices 1, 6, 11, 16, 20, 25, and 29, and comparative light-emitting devices 34 to 38. The measurement of the light-emitting devices was conducted at room temperature (in an atmosphere maintained at 23°C).

[0383] Table 7 and Table 8 show the device characteristics at about 1000 cd / m 2 the light-emitting devices 2 to 5, the light-emitting devices 7 to 10, the light-emitting devices 12 to 15, the light-emitting devices 17 to 19, the light-emitting devices 21 to 24, the light-emitting devices 26 to 28, the light-emitting devices 30 to 33, the comparative light-emitting devices 1, 6, 11, 16, 20, 25 and 29, and the comparative light-emitting devices 34 to 38. [Table 7] Voltage (V) Current density (mA / cm 2 ) CIE chromaticity (x, y) Luminance (cd / m 2 ) Power efficiency (cd / A) Power efficiency (Im / W) external quantum efficiency (%) Light-emitting comparison device 1 3,10 1,42 (0,204, 0.516) 981 69,0 69,9 25,9 Light-emitting device 2 3,10 1,25 (0.269, 0.638) 980 78,2 79,2 22,6 Light-emitting device 3 3,10 1,39 (0.289, 0.655) 1124 80,8 81,9 22,1 Light-emitting device 4 3,10 1,47 (0.300, 0.661) 1178 80,0 81,1 21,3 Light-emitting device 5 3,00 1,11 (0.312, 0.659) 839 75,6 79,2 19,9 Light-emitting comparison device 6 3,50 1,72 (0.220, 0.491) 916 53,2 47,7 19,7 Light-emitting device 7 3,40 1,24 (0.287, 0.613) 916 73,7 68,1 21,2 Light-emitting device 8 3,40 1,14 (0.296, 0.633) 944 82,7 76,4 22,7 Light-emitting device 9 3,40 1,32 (0.306, 0.646) 1114 84,5 78,1 22,4 Light-emitting device 10 3,30 1,16 (0.324, 0.646) 893 77,2 73,5 20,0 Light-emitting comparison device 11 3,50 2,22 (0.213, 0.468) 1087 49,0 44,0 18,4 Light-emitting device 12 3,10 0,94 (0.272, 0.613) 839 88,8 90,0 25,4 Light-emitting device 13 3,10 0,92 (0.291, 0.639) 892 96,8 98,1 26,3 Light-emitting device 14 3,00 0,72 (0.307, 0.647) 696 97,0 101,6 25,6 Light-emitting device 15 3,00 0,96 (0,321, 0.648) 821 85,2 89,2 22,0 Light-emitting comparison device 16 3,00 1,02 (0.305, 0.651) 1010 98,9 103,5 27,7 Light-emitting device 17 3,00 1,05 (0.308, 0.653) 992 94,8 99,3 25,9 Light-emitting device 18 3,00 1,16 (0.322, 0.650) 943 81,4 85,3 21,4 Light-emitting device 19 3,00 1,29 (0,327, 0.649) 912 70,6 73,9 18,3 [Table 8] Voltage (V) Current density (mA / cm 2 ) CIE chromaticity (x, y) Luminance (cd / m 2 ) Power efficiency (cd / A) Power efficiency (Im / W) external quantum efficiency (%) Light-emitting comparison device 20 3,40 1,00 (0.310, 0.634) 873 87,0 80,4 25,3 Light-emitting device 21 3,20 0,99 (0.304, 0.650) 856 86,6 85,0 24,6 Light-emitting device 22 3,20 1,17 (0,310, 0.652) 982 83,8 82,3 23,4 Light-emitting device 23 3,20 1,19 (0.320, 0.651) 927 77,8 76,4 21,3 Light-emitting device 24 3,20 1,39 (0,324, 0.651) 1002 72,1 70,8 18,7 Light-emitting comparison device 25 3,20 1,23 (0.331, 0.640) 988 80,6 79,1 21,8 Light-emitting device 26 3,20 1,52 (0.328, 0.643) 1167 76,6 75,2 20,5 Light-emitting device 27 3,30 1,60 (0.337, 0.640) 1028 64,1 61,0 16,9 Light-emitting device 28 3,20 1,73 (0.339, 0.640) 936 54,3 53,3 14,1 Light-emitting comparison device 29 3,60 1,25 (0.285, 0.628) 977 77,9 68,0 23,6 Light-emitting device 30 3,60 1,22 (0.295, 0.647) 990 81,3 71,0 23,1 Light-emitting device 31 3,60 1,34 (0.304, 0.654) 1101 82,2 71,8 22,4 Light-emitting device 32 3,60 1,41 (0,315, 0.653) 1120 79,5 69,4 21,2 Light-emitting device 33 3,60 1,50 (0,323, 0.652) 1122 75,0 65,5 19,8 Light-emitting comparison device 34 3,20 1,26 (0.298, 0.656) 1036 81,9 80,4 22,6 Light-emitting comparison device 35 3,20 1,23 (0.313, 0.647) 908,3 74,1 72,7 20,0 Light-emitting comparison device 36 3,30 1,73 (0.320, 0.646) 1074 62,2 59,3 16,5 Light-emitting comparison device 37 3,30 1,90 (0.326, 0.645) 984 51,9 49,4 13,6 Light-emitting comparison device 38 3,30 2,27 (0,333, 0.642) 908,7 40,0 38,0 10,3 <Energieübertragung von einem Energiedonator (einem phosphoreszierenden Material mit einem fünfgliedrigen Ring-Gerüst) auf einen Energieakzeptor (ein fluoreszierendes Material mit Schutzgruppen)>

[0384] As in Fig. As shown in Figure 15, the emission spectra of the light-emitting devices 2 to 5 each have a peak at a wavelength of approximately 528 nm and a half-width of approximately 62 nm, indicating green light originating from 2tBu-ptBuDPhA2Anth. In contrast, the emission spectrum of the comparative light-emitting device 1 has a peak at a wavelength of 492 nm and a half-width of 67 nm, indicating light originating from Ir(mpptz-diBuCNp)3. Thus, it was found that energy transfer from the phosphorescent material to the fluorescent material occurs in the light-emitting device of one embodiment of the present invention.

[0385] As in Fig. As shown in Figure 17, the emission spectra of the light-emitting devices 7 to 10 each have a peak at a wavelength of approximately 530 nm and a half-width of approximately 66 nm, indicating green light originating from 2tBu-ptBuDPhA2Anth. In contrast, the emission spectrum of the comparative light-emitting device 6 has a peak at a wavelength of 508 nm and a half-width of 85 nm, indicating light originating from Ir(mpptz-diPrp)3. Thus, it was found that energy transfer from the phosphorescent material to the fluorescent material occurs in the light-emitting device of one embodiment of the present invention.

[0386] As in Fig. As shown in Figure 19, the emission spectra of the light-emitting devices 12 to 15 each have a peak at a wavelength of approximately 529 nm and a half-width of approximately 64 nm, indicating green light originating from 2tBu-ptBuDPhA2Anth. In contrast, the emission spectrum of the comparative light-emitting device 11 has a peak at a wavelength of 502 nm and a half-width of 91 nm, indicating light originating from Ir(Mptz1-mp)3. Thus, it was found that energy transfer from the phosphorescent material to the fluorescent material occurs in the light-emitting device of one embodiment of the present invention.

[0387] As in Fig. As shown in Figure 21, the emission spectrum of the comparative light-emitting device 16 has the maximum peak at a wavelength of 513 nm and a half-width of 64 nm, indicating light originating from Ir(pbi-diBuCNp)3. The emission spectrum of the light-emitting device 17 differs from that of the comparative light-emitting device 16. This is because both the light emission originating from Ir(pbi-diBuCNp)3 and the light emission originating from 2tBu-ptBuDPhA2Anth are observed. Therefore, it is determined that fluorescence is emitted from the light-emitting device 17. The emission spectra of the light-emitting devices 18 and 19 each have a peak at a wavelength of approximately 535 nm and a half-width of approximately 69 nm, indicating green light originating from 2tBu-ptBuDPhA2Anth.Thus, it was found that energy transfer from the phosphorescent material to the fluorescent material occurs in the light-emitting device of one embodiment of the present invention.

[0388] As in Fig. As shown in Figure 23, the emission spectrum of the comparative light-emitting device 20 has the maximum peak at a wavelength of 508 nm and a half-width of 64 nm, indicating light originating from fac-Ir(pbi-diBup)3. The emission spectrum of the light-emitting device 21 differs from that of the comparative light-emitting device 20. This is because both the light emission originating from fac-Ir(pbi-diBup)3 and the light emission originating from 2tBu-ptBuDPhA2Anth are observed. Therefore, it is determined that fluorescence is emitted from the light-emitting device 21. The emission spectra of the light-emitting devices 22 to 24 each have a peak at a wavelength of approximately 538 nm and a half-width of approximately 69 nm, indicating green light originating from 2tBu-ptBuDPhA2Anth.Thus, it was found that energy transfer from the phosphorescent material to the fluorescent material occurs in the light-emitting device of one embodiment of the present invention.

[0389] As in Fig. As shown in Figure 25, the emission spectrum of the comparative light-emitting device 25 has the maximum peak at a wavelength of 525 nm and a half-width of 73 nm, indicating light originating from Ir(pni-diBup)2(mdppy). The emission spectrum of the light-emitting device 26 differs from that of the comparative light-emitting device 25. This is because both the light emission originating from Ir(pni-diBup)2(mdppy) and the light emission originating from 2tBu-ptBuDPhA2Anth are observed. Therefore, it is determined that fluorescence is emitted from the light-emitting device 26. The emission spectra of the light-emitting devices 27 and 28 each have a peak at a wavelength of approximately 535 nm and a half-width of approximately 69 nm, indicating green light originating from 2tBu-ptBuDPhA2Anth.Thus, it was found that energy transfer from the phosphorescent material to the fluorescent material occurs in the light-emitting device of one embodiment of the present invention.

[0390] As in Fig. As shown in Figure 27, the emission spectrum of the comparative light-emitting device 29 has the maximum peak at a wavelength of 500 nm and a half-width of 59 nm, indicating light originating from Ir(pni-diBup)3. The emission spectrum of the light-emitting device 30 differs from that of the comparative light-emitting device 29. This is because both the light emission originating from Ir(pni-diBup)3 and the light emission originating from 2tBu-ptBuDPhA2Anth are observed. Therefore, it is determined that fluorescence is emitted from the light-emitting device 29. The emission spectra of the light-emitting devices 31 to 33 each have a peak at a wavelength of approximately 536 nm and a half-width of approximately 65 nm, indicating green light originating from 2tBu-ptBuDPhA2Anth.Thus, it was found that energy transfer from the phosphorescent material to the fluorescent material occurs in the light-emitting device of one embodiment of the present invention.

[0391] As in Fig. As shown in Figure 29, the emission spectrum of the comparative light-emitting device 34 has the maximum peak at a wavelength of 517 nm and a half-width of 70 nm, indicating light originating from Ir(ppy)3. Furthermore, the emission spectra of the comparative light-emitting devices 35 to 38 each have a peak at a wavelength of approximately 535 nm and a half-width of approximately 69 nm, indicating green light originating from 2tBu-ptBuDPhA2Anth.

[0392] Although the light-emitting devices 2 to 5, the light-emitting devices 7 to 10, the light-emitting devices 12 to 15, the light-emitting devices 17 to 19, the light-emitting devices 21 to 24, the light-emitting devices 26 to 28 and the light-emitting devices 30 to 33 emit light originating from the respective fluorescent material, they have, as shown in Fig. 16, Fig. 18, Fig. 20, Fig. 22, Fig. 24, Fig. 26, Table 7, and Table 8, an external quantum efficiency of at least above 14%, that is, a high emission efficiency, even with a high concentration of 2tBu-ptBuDPhA2Anth, which is a fluorescent material. Furthermore, light-emitting devices 2 to 5, light-emitting devices 7 to 10, light-emitting devices 12 to 15, light-emitting devices 17 to 19, light-emitting devices 21 to 24, light-emitting devices 26 to 28, and light-emitting devices 30 to 33, which are the light-emitting devices of embodiments of the present invention, have a higher external quantum efficiency than the comparative light-emitting device 37 at each concentration.

[0393] The maximum generation probability of singlet excitons generated by recombination of carriers (holes and electrons) injected from the pair of electrodes is 25%, and therefore, the maximum external quantum efficiency of a fluorescent device is 7.5% when the external light extraction efficiency is 30%. However, for light-emitting devices 2 to 5, light-emitting devices 7 to 10, light-emitting devices 12 to 15, light-emitting devices 21 to 24, light-emitting devices 26 to 28, and light-emitting devices 30 to 33, the external quantum efficiency is higher than 7.5%.This is because, in addition to light originating from singlet excitons generated by the recombination of charge carriers (holes and electrons) injected from the pair of electrodes, light originating from the energy transfer of triplet excitons is emitted from the fluorescent material. As a result, it is found that in the light-emitting device of one embodiment of the present invention, by using a fluorescent material with protecting groups and a phosphorescent material with a five-membered ring framework, the non-radiative deactivation of triplet excitons is suppressed, and both the singlet excitation energy and the triplet excitation energy generated in the light-emitting layer are efficiently converted into light emission from the fluorescent material. <Overlap between the absorption spectrum of the fluorescent material and the emission spectrum of the phosphorescent material with a five-membered ring>

[0394] Next, the relationship between the absorption spectrum of 2tBu-ptBuDPhA2Anth, which is a fluorescent material, and the EL emission spectrum of the phosphorescent material used in each of the light-emitting devices was investigated. The results are presented in Fig. 30 to Fig. 36 shown.

[0395] As described above, the comparative light-emitting devices 1, 6, 11, 16, 20, 25, and 29 emit light originating from the phosphorescent materials used in the respective light-emitting layers. Fig. 30 to Fig. 36 indicate that the emission spectrum of each of the phosphorescent materials overlaps with the absorption spectrum of 2tBu-ptBuDPhA2Anth. Accordingly, in the case where both the phosphorescent material and 2tBu-ptBuDPhA2Anth are used in each of the light-emitting layers, energy transfer from the phosphorescent material to 2tBu-ptBuDPhA2Anth can occur. Here, as described above, the light-emitting devices of embodiments of the present invention have high emission efficiency. That is, the deactivation of triplet excitons in the light-emitting layer, which might be caused in a normal fluorescent element, is suppressed. This is an effect of using the fluorescent material with protecting groups.This is also an effect of using the phosphorescent material with a five-membered ring, where the phosphorescent material suppresses the following: the charge carrier recombination in the fluorescent material, the energy transfer of triplet excitons from the phosphorescent material to the fluorescent material through the Dexter mechanism, and the deactivation of the energy of triplet excitons. <Change in external quantum efficiency due to the concentration of the guest material>

[0396] Fig. Figure 37 shows the relationship between the concentration of the guest material and the external quantum efficiency in the light-emitting devices using the phosphorescent materials. Fig. 37 indicates that in the light-emitting devices of embodiments of the present invention each containing the phosphorescent material having a five-membered ring, compared with the comparative light-emitting devices 34 to 38 each containing Ir(ppy)3, which is a phosphorescent material without a five-membered ring framework, the reduction in the external quantum efficiency due to the increase in the concentration of the fluorescent material is suppressed.This is because, by using the guest material with protecting groups for the light-emitting layer and the phosphorescent material having a five-membered ring, the transfer of triplet excitation energy by the Dexter mechanism from the host material to the guest material and the deactivation of the triplet excitation energy are suppressed. Furthermore, by increasing the concentration of the guest material, the transfer of excitation energy by the Förster mechanism from the host material to the guest material can be efficiently utilized, whereby both the triplet excitation energy and the singlet excitation energy in the light-emitting layer can be efficiently converted into light emission from the fluorescent material. In this way, according to one embodiment of the present invention, a light-emitting device with a high guest material concentration and high emission efficiency can be obtained.

[0397] It was also found that increasing the concentration of the guest material increased the emission efficiency of the light-emitting devices containing Ir(mpptz-diPrp)3 or Ir(Mptz1-mp)3, respectively. <Messung der Zuverlässigkeit der Licht emittierenden Vorrichtungen>

[0398] Next, operation tests were conducted at a constant current of 2.0 mA on light-emitting devices 2 to 5, light-emitting devices 7 to 10, light-emitting devices 12 to 15, light-emitting devices 17 to 19, light-emitting devices 21 to 24, light-emitting devices 26 to 28, light-emitting devices 30 to 33, and comparative light-emitting devices 1, 6, 11, 16, 20, 25, and 29. The results are shown in Fig. 38 to Fig. 44 shown. Fig. 38 to Fig. 44 illustrate that increasing the concentration of the guest material increases reliability. This suggests that increasing the concentration of the guest material can efficiently convert the excitation energy in the light-emitting layer into light emission from the guest material. This means that increasing the concentration of the guest material can increase the transfer rate of triplet excitation energy from a host material to a guest material through the Förster mechanism.

[0399] Here, in the light-emitting layer, the energy transfer from the energy donor to the guest material, i.e., the energy transfer related to light emission, competes with the quenching process due to the influence of impurities and degraded substances. Therefore, it is important to increase the rate of energy transfer related to light emission to obtain a highly reliable light-emitting device. <Messung der Fluoreszenzlebensdauer der Licht emittierenden Vorrichtungen>

[0400] Subsequently, the fluorescence lifetimes of light-emitting devices 2 to 5, light-emitting devices 7 to 10, light-emitting devices 12 to 15, and comparative light-emitting devices 1, 6, and 11 were measured to investigate the different emission rates of the guest materials depending on the concentration. A picosecond fluorescence lifetime measurement system (manufactured by Hamamatsu Photonics KK) was used for the measurement. To measure the fluorescence lifetime of the light-emitting device, a pulse voltage with a square wave was applied to the light-emitting device, and a time-resolved measurement of light attenuated by the voltage drop was performed using a streak camera. The pulse voltage was applied at a frequency of 10 Hz.By integrating data obtained through repeated measurements, data with a high S / N ratio were obtained. The measurement was performed at room temperature (300 K) under the following conditions: A pulse voltage of approximately 3 V to 4 V was applied, so that the luminance of the light-emitting devices was close to 1000 cd / m. 2 the pulse time width was 100 µs, the negative bias was -5 V (at the time the elements were not driven) and the measurement time was 10 µs. Fig. 49 to Fig. 51 shows the measurement results. It should be noted that in Fig. 49 to Fig. 51 the vertical axis represents the emission intensity normalized to that in a state where carriers are continuously injected (ie, the pulse voltage is applied), and the horizontal axis represents the time elapsed after the pulse voltage decays.

[0401] The adjustment of the attenuation curves in Fig. 49 to Fig. 51 to the exponential function indicates that light-emitting devices 2 to 5 and light-emitting devices 7 to 10 emit light including a fast fluorescence component of 0.4 μs or less and a delayed fluorescence component of approximately 2 μs, and light-emitting devices 12 to 15 emit light including a fast fluorescence component of 0.4 μs or less and a delayed fluorescence component of approximately 4 μs. When a fluorescent material is added as a guest material, as the concentration of the fluorescent material increases, the proportion of the fast fluorescence component increases and the proportion of the delayed fluorescence component decreases.In addition, the comparative light-emitting device 1 emits light from the phosphorescent material and light including a fast fluorescence component of 0.5 µs or less and a delayed fluorescence component of about 4 µs, and the comparative light-emitting devices 6 and 11 emit light from the phosphorescent material and light including a fast fluorescence component of 0.5 µs or less and a delayed fluorescence component of about 2 µs.

[0402] This indicates that by adding the fluorescent material as a guest material to the light-emitting layer, the emission speed is increased and therefore the proportion of light emission of the fast fluorescent component originating from the fluorescent material is increased. As described above, the light-emitting devices 2 to 5, the light-emitting devices 7 to 10, and the light-emitting devices 12 to 15 of embodiments of the present invention have high external quantum efficiency even when the concentration of the fluorescent material is high. That is, in the light-emitting device of one embodiment of the present invention, the emission efficiency is high even when the proportion of light originating from the fluorescent material is increased.As a result, in the light-emitting device of one embodiment of the present invention, the transfer of triplet excitation energy from a host material to a guest material by the Dexter mechanism and the deactivation of the triplet excitation energy can be suppressed. Therefore, it is suggested that the concentration of the guest material can be increased, thus increasing the transfer efficiency of the excitation energy by the Förster mechanism. Therefore, in the light-emitting device of one embodiment of the present invention, both the singlet excitation energy and the triplet excitation energy can be efficiently converted into light emission in the light-emitting layer.

[0403] To increase the speed of energy transfer, as in Fig. 49 to Fig. 51, the concentration of the guest material in the light-emitting layer is preferably increased. In the light-emitting device of one embodiment of the present invention, the rate of energy transfer by the Förster mechanism can be increased while suppressing the energy transfer by the Dexter mechanism, and a light-emitting device with high emission efficiency and high reliability can be obtained by reducing the influence of competition with the quenching process. In addition, the comparative light-emitting devices have a long emission lifetime because phosphorescence is observed therein, while the light-emitting devices of embodiments of the present invention have a short emission lifetime because they emit fluorescence. Accordingly, the above-described influence of competition with the quenching process can be reduced.Therefore, in the light-emitting device of one embodiment of the present invention, the concentration of the guest material can be increased and the emission efficiency and reliability are advantageous. [Example 2]

[0404] In this example, examples of manufacturing light-emitting devices of embodiments of the present invention and comparative light-emitting devices different from those in Example 1, as well as the characteristics of the light-emitting devices, are described. The structure of each of the light-emitting devices manufactured in this example is the same as that described in Fig. 1A. Table 9 shows the details of the device structures. In addition, the structures and abbreviations of compounds used herein are given below. Note that for the other organic compounds, reference may be made to the above examples and embodiments. [Table 9] layer Reference symbol Thickness (nm) material Weight ratio Light-emitting comparison device 39 cathode 102 200 Al - Electron injection layer 119 1 LiF - Electron transport layer 118(2) 10 NBPhen - 118(1) 20 4.6mCzP2Pm - Light-emitting layer 130 40 mPCCzPTzn-02: PCCP: Ir(pbi-diBuCNp)3 0,5:0,5:0,1 Hole transport layer 112 20 PCCP - Hole injection layer 111 40 DBT3P-II: MoO3 1:0,5 anode 101 70 ITSO - Light-emitting devices 40-43 cathode 102 200 Al - Electron injection layer 119 1 LiF - Electron transport layer 118(2) 10 NBPhen - 118(1) 20 4.6mCzP2Pm - Light-emitting layer 130 40 mPCCzPTzn-02 : PCCP: Ir(pbi-diBuCNp)3: 2.6tBu-mmtBuDPhA2Anth 0,5:0,5:0,1:x3 Hole transport layer 112 20 PCCP - Hole injection layer 111 40 DBT3P-II: MoO3 1:0,5 anode 101 70 ITSO - [Table 10] Light-emitting device 40 Light-emitting device 41 Light-emitting device 42 Light-emitting device 43 X3 0,05 0,10 0,15 0,2 < <Herstellung einer Licht emittierenden Vergleichsvorrichtung 39 und von Licht emittierenden Vorrichtungen 40 bis 43> >

[0405] A comparative light-emitting device 39 and light-emitting devices 40 to 43 were formed in the same manner as the above-described light-emitting devices 2 to 5 by a vacuum evaporation method. The details of the manufacturing process will not be described because the details of the structures of the light-emitting devices are as shown in Tables 9 and 10. Note that a value represented by x3 in Table 9 is as shown in Table 10.

[0406] Note that in the comparative light-emitting device 39, Ir(pbi-diBuCNp)3, which is a phosphorescent material, serves as the energy acceptor. The comparative light-emitting device 39 is shown as a comparative example of the light-emitting device of an embodiment of the present invention in which the phosphorescent material serves as the energy donor. <Eigenschaften der Licht emittierenden Vorrichtungen>

[0407] Next, the characteristics of the comparative light-emitting device 39 and the light-emitting devices 40 to 43 manufactured in the above manner were measured. Note that the measurement method is the same as that of Example 1.

[0408] Fig. 52 shows the external quantum efficiency-luminance characteristics of the comparative light-emitting device 39 and the light-emitting devices 40 to 43. Fig. Figure 53 shows the electroluminescence spectra obtained when a current with a current density of 2.5 mA / cm 2 to the comparative light-emitting device 39 and the comparative light-emitting devices 40 to 43. The measurement of the light-emitting devices was conducted at room temperature (in an atmosphere maintained at 23°C).

[0409] Table 11 shows the device characteristics at about 1000 cd / m 2 the comparison light-emitting device 39 and the comparison light-emitting devices 40 to 43. [Table 11] Voltage (V) Current density (mA / cm 2 ) CIE chromaticity (x, y) Luminance (cd / m 2 ) Power efficiency (cd / A) Power efficiency (Im / W) external quantum efficiency (%) Light-emitting comparison device 39 3,00 0,96 (0.303, 0.652) 1000 104,4 109,3 29,2 Light-emitting device 40 3,10 1,05 (0.315, 0.643) 903 86,0 87,2 23,7 Light-emitting device 41 3,20 1,31 (0.313, 0.646) 961 73,5 72,2 20,1 Light-emitting device 42 3,30 1,56 (0.309, 0.650) 1001 64,2 61,1 17,3 Light-emitting device 43 3,40 1,90 (0.309, 0.650) 1074 56,4 52,1 15,2 <Energieübertragung von einem Energiedonator (einem phosphoreszierenden Material mit einem fünfgliedrigen Ring-Gerüst) auf einen Energieakzeptor (ein fluoreszierendes Material mit Schutzgruppen)>

[0410] As in Fig. As shown in Figure 53, the emission spectra of the light-emitting devices 40 to 43 each have a peak at a wavelength of approximately 520 nm and a half-width of approximately 69 nm, indicating green light originating from 2,6tBu-mmtBuDPhA2Anth. In contrast, the emission spectrum of the comparative light-emitting device 39 has a peak at a wavelength of 513 nm and a half-width of 63 nm, indicating light originating from Ir(pbi-diBuCNp)3. Thus, it was determined that energy transfer from the phosphorescent material to the fluorescent material occurs in the light-emitting device of one embodiment of the present invention.

[0411] Although the light-emitting devices 40 to 43 emit light originating from the respective fluorescent material, they have, as shown in Fig. 52 and Table 11, an external quantum efficiency of at least over 15%, that is, a high emission efficiency, even with a high concentration of the fluorescent material. As a result, it is found that in the light-emitting device of one embodiment of the present invention, by using a fluorescent material with protecting groups and a phosphorescent material having a five-membered ring framework, the non-radiative deactivation of triplet excitons is suppressed, and both the singlet excitation energy and the triplet excitation energy generated in the light-emitting layer are efficiently converted into light emission from the fluorescent material. <Messung der Zuverlässigkeit der Licht emittierenden Vorrichtungen>

[0412] Next, operation tests were conducted at a constant current of 2.0 mA on the comparison light-emitting device 39 and the light-emitting devices 40 to 43. The results are shown in Fig. 54 shown. Fig. Figure 54 illustrates that increasing the concentration of the guest material increases the reliability. This suggests that increasing the concentration of the guest material can efficiently convert the excitation energy in the light-emitting layer into light emission from the guest material. This means that increasing the concentration of the guest material can increase the transfer rate of triplet excitation energy from a host material to a guest material through the Förster mechanism. <Messung der Fluoreszenzlebensdauer der Licht emittierenden Vorrichtungen>

[0413] Subsequently, the fluorescence lifetimes of the comparative light-emitting device 39 and the light-emitting devices 40 to 43 were measured to investigate the different emission rates of the guest materials as a function of concentration. The measurement was carried out as in Example 1. The results are shown in Fig. 55 shown.

[0414] Fig. Figure 55 illustrates that with increasing the concentration of the fluorescent material (guest material), the proportion of the high-emission fluorescent component increases and the proportion of the delayed fluorescent component decreases. This indicates that adding the fluorescent material as a guest material to the light-emitting layer increases the emission speed and therefore increases the proportion of light emission of the fast fluorescent component originating from the fluorescent material.

[0415] As described above, the light-emitting devices 40 to 43 of embodiments of the present invention have high external quantum efficiency even when the concentration of the fluorescent material is high. That is, in the light-emitting device of one embodiment of the present invention, the emission efficiency is high even when the proportion of light originating from the fluorescent material is increased. Therefore, in the light-emitting device of one embodiment of the present invention, the transfer of triplet excitation energy by the Dexter mechanism from a host material to a guest material and the deactivation of the triplet excitation energy can be suppressed; therefore, it is suggested that the concentration of the guest material can be increased, and thus the transfer efficiency of the excitation energy by the Förster mechanism can be increased.Therefore, in the light-emitting device of one embodiment of the present invention, both the singlet excitation energy and the triplet excitation energy in the light-emitting layer can be efficiently converted into light emission. (Reference example 1)

[0416] In this Reference Example, a method for synthesizing 2tBu-ptBuDPhA2Anth, which is a fluorescent material with protecting groups and was used in Example 1, is described.

[0417] 1.2 g (3.1 mmol) of 2-tert-butylanthracene, 1.8 g (6.4 mmol) of bis(4-tert-butylphenyl)amine, 1.2 g (13 mmol) of sodium t-butoxide, and 60 mg (0.15 mmol) of 2-dicyclohexylphosphino-2',6'-dimethoxy-1,1'-biphenyl (abbreviation: SPhos) were added to a 200 mL three-necked flask, and the air in the flask was replaced with nitrogen. 35 mL of mesitylene was added to this mixture, and the mixture was degassed under reduced pressure. 40 mg (70 μmol) of bis(dibenzylideneacetone)palladium(0) was then added to this mixture, and it was stirred for 4 hours under a nitrogen stream at 170 °C.

[0418] After stirring, 400 ml of toluene was added to the resulting mixture, and the mixture was subjected to suction filtration through Florisil (manufactured by Wako Pure Chemical Industries, Ltd., Catalog No. 066-05265), Celite (manufactured by Wako Pure Chemical Industries, Ltd., Catalog No. 537-02305), and alumina to obtain a filtrate. The resulting filtrate was concentrated to obtain a brown solid.

[0419] This solid was purified by silica gel column chromatography (hexane:toluene = 9:1 as eluent) to obtain a yellow target solid. The resulting yellow solid was recrystallized from toluene / hexane / ethanol to obtain 1.5 g of a yellow target solid in 61% yield. This synthesis scheme is shown below in (A-1).

[0420] Using a train sublimation method, 1.5 g of the resulting yellow solid was sublimated. The sublimation purification was carried out under a pressure of 4.5 Pa by heating the yellow solid at 315 °C for 15 hours. After sublimation purification, 1.3 g of a target yellow solid was obtained with a collection rate of 89%.

[0421] The 1 H-NMR measurements of the yellow solid obtained in this synthesis are shown below. Fig. 45 and Fig. 46 the 1 H-NMR diagrams. It should be noted that Fig. Figure 45B is a diagram showing an enlarged part of the range from 6.5 ppm to 9.0 ppm in Fig. 45A shows. In addition, Fig. 46 a diagram showing an enlarged part of the range from 0.5 ppm to 2.0 ppm in Fig. 45A. These results revealed that 2tBuptBuDPhA2Anth, which is the target compound, was obtained.

[0422] 1 H-NMR (CDCl3, 300 MHz): σ = 8.20-8.13 (m, 2H), 8.12 (d, J = 8.8 Hz, 1H), 8.05 (d, J = 2.0 Hz, 1H), 7.42 (dd, J = 9.3 Hz, 2.0 Hz, 1H), 7.32-7.26 (m, 2H) 7.20 (d, J = 8.8 Hz, 8H), 7.04 (dd, J = 8.8 Hz, 2.4 Hz, 8H), 1.26 (s, 36H), 1.18 (s, 9H). (Reference example 2)

[0423] In this Reference Example, a method for synthesizing Ir(pnidiBup)3, which is an example of the phosphorescent material having a five-membered ring and used in Example 1, is described. <Schritt 1: Synthese von 2,6-Diisobutylanilin>

[0424] In a 5000 mL three-necked flask, 100 g (617 mmol) of 2,6-dichloroaniline, 230 g (2256 mmol) of isobutylboronic acid, 479 g (2256 mmol) of tripotassium phosphate, 10 g (24.7 mmol) of 2-dicyclohexylphosphino-2',6'-dimethoxybiphenyl (S-phos), and 3000 mL of toluene were added. The air in the flask was replaced with nitrogen, and the mixture was degassed with stirring under reduced pressure. After degassing, 11 g (11.5 mmol) of tris(dibenzylideneacetone)dipalladium(0) was added, and the mixture was stirred for 12 hours under a nitrogen stream at 120 °C. After a predetermined time, the resulting reaction solution was subjected to suction filtration. The resulting filtrate was purified by extraction with toluene. Purification was then carried out by silica gel column chromatography. Hexane and toluene were used as eluents in a ratio of 15:1.The resulting fraction was concentrated to obtain 79 g of a black oily target substance in a yield of 62%. The synthesis scheme of step 1 is shown in the following formula (B-1). <Schritt 2; Synthese von 2-Nitronaphthalen-1-trifluormethansulfonat>

[0425] 35 g (182 mmol) of 2-nitro-1-naphthol, 500 mL of anhydrous dichloromethane, and 51 mL (365 mmol) of triethylamine were added to a 1000 mL three-necked flask. The air in the flask was replaced with nitrogen, and the mixture was cooled to 0 °C. Then, 40 mL (243 mmol) of trifluoromethanesulfonic anhydride (abbreviation: Tf2O) was added dropwise, and the mixture was stirred at 0 °C for 1 hour and then at room temperature for 20 hours. After a predetermined time, 300 mL of water and 30 mL of 1M hydrochloric acid were added to the resulting mixture. This mixture was then purified by extraction with dichloromethane. Purification was then carried out by silica gel column chromatography. The eluent used was hexane and dichloromethane in a ratio of 5:1. The obtained fraction was concentrated to obtain 47 g of a yellow oily target substance in a yield of 80%.The synthesis scheme of step 2 is shown in the following formula (B-2). <Schritt 3; Synthese von N-(2,6-Diisobutylphenyl)-2-nitro-1-naphthalenamin>

[0426] In a 2000 mL three-necked flask, 30 g (146 mmol) of 2,6-diisobutylaniline synthesized in Step 1, 47 g (146 mmol) of 2-nitronaphthalene-1-trifluoromethanesulfonate synthesized in Step 2, 81 g (248 mmol) of cesium carbonate, and 750 mL of toluene were added. The air in the flask was replaced with nitrogen, and the mixture was degassed with stirring under reduced pressure. After degassing, 4.8 g (11.7 mmol) of S-phos and 2.7 g (2.9 mmol) of tris(dibenzylideneacetone)dipalladium(0) were added, and the mixture was stirred for 28 hours under a nitrogen stream at 130 °C. After a predetermined time, the resulting reaction mixture was purified by extraction with toluene. Purification was then carried out by silica gel column chromatography. Hexane and ethyl acetate were used as eluents in a ratio of 15:1.The resulting fraction was concentrated to obtain 13 g of a yellow oily substance in a yield of 23%. The synthesis scheme of step 3 is shown in the following formula (B-3). <Schritt 4; Synthese von N-(2,6-Diisobutylphenyl)-1,2-naphthalendiamin>

[0427] In a 1000 mL three-necked flask, 13 g (34 mmol) of N-(2,6-diisobutylphenyl)-2-nitro-1-naphthalenamine synthesized in Step 3, 6.1 mL (0.34 mol) of water, and 400 mL of ethanol were added, and the mixture was stirred. 32 g (0.17 mol) of stannous chloride was added to this mixture, and the mixture was stirred for 5 hours under a nitrogen stream at 80 °C. After a predetermined time, the resulting reaction mixture was poured into 500 mL of a 2M sodium hydroxide aqueous solution and stirred for 2 hours at room temperature. A precipitated sediment was subjected to suction filtration and washed with chloroform to obtain a filtrate. The resulting filtrate was then purified by extraction with chloroform. Purification was then carried out by silica gel column chromatography. Hexane and ethyl acetate were used as eluent in a ratio of 15:1.The resulting fraction was concentrated to obtain 9.5 g of a black oily target substance in 81% yield. The synthesis scheme of step 4 is shown in the following formula (B-4). <Schritt 5; Synthese von 1-(2,6-Diisobutylphenyl)-2-phenyl-1H-naphtho[1,2-d]imidazol (Abkürzung: Hpni-diBup)>

[0428] In a 300-ml recovery flask, 9.5 g (27 mmol) of N-(2,6-diisobutylphenyl)-1,2-naphthalenediamine synthesized in Step 4, 100 ml of acetonitrile, and 2.9 g (27 mmol) of benzaldehyde were added, and the mixture was stirred at 100 °C for 6 hours. Then, 0.044 g (0.274 mmol) of ferric chloride was added to this mixture, and the mixture was stirred at 100 °C for 16 hours. After a predetermined time, the resulting reaction mixture was subjected to extraction with ethyl acetate. The resulting oily substance, 100 ml of toluene, and 10 g of manganese (IV) oxide were added to a 300-ml recovery flask and stirred at 130 °C for 7 hours. After a predetermined time, the obtained reaction mixture was subjected to suction filtration through Celite (manufactured by Wako Pure Chemical Industries, Ltd., Catalog No. 537-02305), Florisil (manufactured by Wako Pure Chemical Industries, Ltd., Catalog No. 066-05265) and alumina.The resulting filtrate was concentrated to obtain an oily substance. The resulting oily substance was purified by silica gel column chromatography. Toluene was used as the eluent. The resulting fraction was concentrated to obtain 7.9 g of a white target solid in a yield of 66%. The synthesis scheme of step 5 is shown in the following formula (B-5). <Schritt 6; Synthese von Di-µ-chlor-tetrakis{2-[1-(2,6-diisobutylphenyl)-1H-naphtho[1,2-d]imidazol-2-yl-κN3]phenyl-κC}diiridium(III) (Abkürzung: [Ir(pni-diBup)2Cl]2)>

[0429] In a 100 mL round-bottom flask, 3.3 g (7.7 mmol) of 1-(2,6-diisobutylphenyl)-2-phenyl-1H-naphtho[1,2-d]imidazole (abbreviation: Hpni-diBup) synthesized in Step 5, 1.6 g (3.7 mmol) of iridium chloride monohydrate, 30 mL of 2-ethoxyethanol, and 10 mL of water were added, and the air in the flask was replaced with argon. This reaction vessel was subjected to microwave irradiation (2.45 GHz, 100 W) for 2 hours to induce a reaction. After the reaction, the reaction solution was subjected to suction filtration to obtain 2.8 g of a yellow target solid in a yield of 69%. The synthesis scheme of Step 6 is shown in the following formula (B-6). <Schritt 7; Synthese von Tris{2-[1-(2,6-diisobutylphenyl)-1H-naphtho[1,2-d]imidazol-2-yl-κN3]phenyl-κC}iridium(III) (Abkürzung: [Ir(pni-diBup)3])>

[0430] In a 500 mL three-necked flask, 2.0 g (0.92 mmol) of di-μ-chloro-tetrakis{2-[1-(2,6-diisobutylphenyl)-1H-naphtho[1,2-d]imidazol-2-yl-κN3]phenyl-κC}diiridium(III) (abbreviation: [Ir(pni-diBup)2Cl]2), synthesized by the method in steps 1 to 6, and 150 mL of dichloromethane were added, and the mixture was stirred under a nitrogen stream. A mixed solution of 0.72 g (2.8 mmol) of silver trifluoromethanesulfonate and 150 mL of methanol was added dropwise to this mixed solution, and the solution was stirred in a dark place for three days. After reacting for a predetermined time, the reaction mixture was filtered through Celite. The resulting filtrate was concentrated to obtain 2.7 g of a yellow solid.In a 500-mL recovery flask, 2.7 g of the obtained solid, 50 mL of ethanol, and 1.6 g (3.7 mmol) of 1-(2,6-diisobutylphenyl)-2-phenyl-1H-naphtho[1,2-d]imidazole (abbreviation: Hpni-diBup), synthesized by the method in steps 1 to 5, were added, and the mixture was heated and stirred under a nitrogen stream for 20 hours. After reacting for a predetermined time, the reaction mixture was subjected to suction filtration to obtain a solid. The obtained solid was dissolved in dichloromethane and subjected to suction filtration through Celite, neutral silica, and Celite. The obtained filtrate was concentrated to obtain a solid. The obtained solid was purified by silica gel column chromatography. As the eluent, dichloromethane and hexane were used in a ratio of 1:3. The obtained fraction was concentrated to obtain a solid.The resulting solid was recrystallized from ethyl acetate / hexane to obtain 1.1 g of a solid in 40% yield. The synthesis scheme is shown in the following formula (B-7).

[0431] Using a train sublimation process, 1.1 g of the resulting solid was purified by sublimation. The sublimation purification was carried out under conditions where the pressure was 2.6 Pa and the argon flow rate was 10.5 ml / min by heating the resulting solid at 340 °C for 41 hours. After sublimation purification, 0.93 g of a yellow solid was obtained with a collection rate of 88%.

[0432] The resulting yellow solid was subjected to proton NMR ( 1 H-NMR measurement. The obtained values ​​are shown below. Fig. 47 shows the 1 H-NMR diagram. Fig. 47 found that Ir(pni-diBup)3, which is the organometallic complex of one embodiment of the present invention, was obtained.

[0433] 1 H-NMR. δ (CD2Cl2): 0.15 (d, 9H), 0.39-0.42 (m, 18H), 0.59 (d, 9H), 1.27-1.35 (m, 3H), 1.78-1.86 (m, 3H), 1.93-2.02 (m, 6H), 2.33 (d, 6H), 6.35-6.40 (m, 6H), 6.56-6.61 (m, 6H), 7.04-7.07 (m, 6H), 7.16 (t, 3H), 7.25 (d, 3H), 7.30 (t, 3H), 7.40 (d, 3H), 7.48 (d, 3H), 7.63 (t, 3H), 7.73 (d, 3H). (Reference example 3)

[0434] In this Reference Example, a method for synthesizing Ir(pnidiBup)2(mdppy), which is an example of the phosphorescent material having a five-membered ring and used in Example...

Claims

[1] Light-emitting device comprising a light-emitting layer between a pair of electrodes, wherein the light-emitting layer contains a first material, a second material and a third material, wherein the first material can convert the triplet excitation energy into light emission and has a five-membered ring framework, wherein the first material is a metal complex, wherein the second material can convert the singlet excitation energy into light emission and has a luminophore and five or more protecting groups, wherein the luminophore is a condensed aromatic ring or a condensed heteroaromatic ring, wherein the five or more protecting groups each independently comprise an alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms or a trialkylsilyl group having 3 to 12 carbon atoms, wherein the third material comprises a diazine framework or a triazine framework, and wherein a T1 level of the first material is higher than an S1 level of the second material. [2] The light-emitting device according to claim 1, wherein at least four protecting groups among the five or more protecting groups are each independently an alkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, or a trialkylsilyl group having 3 to 12 carbon atoms. [3] A light-emitting device comprising a light-emitting layer between a pair of electrodes, wherein the light-emitting layer contains a first material, a second material and a third material, wherein the first material is a metal complex, wherein the first material can convert the triplet excitation energy into light emission and has a five-membered ring framework, wherein the second material can convert the singlet excitation energy into light emission and has a luminophore and at least four protecting groups, wherein the luminophore is a condensed aromatic ring or a condensed heteroaromatic ring, wherein the four protecting groups are not directly bonded to the fused aromatic ring or the fused heteroaromatic ring, wherein the four protecting groups each independently comprise an alkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms or a trialkylsilyl group having 3 to 12 carbon atoms, wherein the third material comprises a diazine framework or a triazine framework, and wherein a T1 level of the first material is higher than an S1 level of the second material. [4] A light-emitting device comprising a light-emitting layer between a pair of electrodes, wherein the light-emitting layer contains a first material and a second material, wherein the first material can convert the triplet excitation energy into light emission and has a five-membered ring framework, wherein the first material is a metal complex, wherein the second material can convert the singlet excitation energy into light emission, wherein the second material comprises a luminophore and two or more diarylamino groups, wherein the luminophore is a condensed aromatic ring or a condensed heteroaromatic ring, wherein the fused aromatic ring or the fused heteroaromatic ring is bonded to the two or more diarylamino groups, wherein aryl groups of the two or more diarylamino groups each independently have at least one protecting group, wherein the protecting group comprises an alkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms or a trialkylsilyl group having 3 to 12 carbon atoms, and where a T1 level of the first material is higher than an S1 level of the second material. [5] The light-emitting device according to claim 4, wherein the aryl groups of the two or more diarylamino groups each independently have at least two protecting groups. [6] The light-emitting device according to claim 4, wherein the diarylamino groups are diphenylamino groups. [7] A light-emitting device according to claim 1, wherein the five or more protecting groups each independently comprise an alkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, or a trialkylsilyl group having 3 to 12 carbon atoms, and wherein at least one of the atoms of the five or more protecting groups is positioned directly on one face of the fused aromatic ring or the fused heteroaromatic ring and at least one of the atoms of the five or more protecting groups is positioned directly on the other face of the fused aromatic ring or the fused heteroaromatic ring. [8] The light-emitting device according to claim 6, wherein phenyl groups in the two or more diphenylamino groups each independently have protecting groups in the 3- and 5-positions. [9] The light-emitting device according to any one of claims 1, 3 and 4, wherein the five-membered ring skeleton comprises a pyrazole skeleton, an imidazole skeleton or a triazole skeleton. [10] The light-emitting device according to claim 9, wherein a nitrogen atom not involved in a double bond contained in the imidazole skeleton and the triazole skeleton is bonded to a substituted or unsubstituted aromatic hydrocarbon group having 6 to 13 carbon atoms. [11] A light-emitting device comprising a light-emitting layer between a pair of electrodes, wherein the light-emitting layer contains a first material, a second material and a third material, wherein the first material can convert the triplet excitation energy into light emission, wherein the first material is a metal complex, wherein the second material can convert the singlet excitation energy into light emission and has a luminophore and two or more protecting groups, wherein the luminophore is a condensed aromatic ring or a condensed heteroaromatic ring, wherein the two or more protecting groups each independently comprise an alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms or a trialkylsilyl group having 3 to 12 carbon atoms, wherein the first material has a five-membered ring framework, wherein the five-membered ring skeleton comprises an imidazole skeleton and / or a triazole skeleton, wherein a nitrogen atom not involved in a double bond and contained in the imidazole skeleton and the triazole skeleton is bonded to a substituted or unsubstituted aromatic hydrocarbon group having 6 to 13 carbon atoms, wherein the third material comprises a diazine framework or a triazine framework, and wherein a T1 level of the first material is higher than an S1 level of the second material. [12] The light-emitting device according to claim 11, wherein the aromatic hydrocarbon group is a phenyl group. [13] The light-emitting device according to any one of claims 1, 3, 4 and 11, wherein the alkyl group is a branched-chain alkyl group. [14] A light-emitting device according to any one of claims 1, 3, 4 and 11, wherein the condensed aromatic ring or the condensed heteroaromatic ring comprises naphthalene, anthracene, fluorene, chrysene, triphenylene, tetracene, pyrene, perylene, coumarin, quinacridone or naphthobisbenzofuran. [15] Light-emitting device according to claim 4, wherein the light-emitting layer further contains a third material, and wherein the first material and the third material form an exciplex. [16] A light-emitting device according to any one of claims 1, 3, 4 and 11, wherein an emission spectrum of the first material overlaps with an absorption band on the longest wavelength side of the second material. [17] Electronic device comprising: the light-emitting device according to any one of claims 1, 3, 4 and 11; and a housing and / or a touch sensor. [18] Lighting device comprising: the light-emitting device according to any one of claims 1, 3, 4 and 11; and a housing and / or a touch sensor.

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