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

Abstract

Provided is a light-emitting element having high luminous efficiency and reliability. The light-emitting element is a light-emitting element containing a material used as an energy donor and a light-emitting material in a light-emitting layer. The material used as the energy donor has the function of converting triplet excitation energy into luminescence, and the luminescent material emits fluorescence. The molecular structure of the light-emitting material has a light-emitting body and protecting groups, and one molecule of the guest material contains five or more protecting groups. By introducing a protecting group into the molecule, the energy transfer of triplet excitation energy based on the Texester mechanism from a material used as an energy donor to a luminescent material is inhibited. An alkyl group or a branched alkyl group is used as the protecting group. Light is emitted from both a light-emitting material and a material that is used as an energy donor.

Description

This application is a divisional application of an application with an application date of April 26, 2019, application number "201980031762.9", and invention name "Light-emitting element, display device, electronic device, organic compound and lighting device". Technical Field

[0001] One embodiment of the present invention relates to a light-emitting element or a display device, an electronic device, an organic compound, and a lighting device including the light-emitting element.

[0002] Note that one embodiment of the present invention is not limited to the above-mentioned technical field. The technical field of one embodiment of the invention disclosed in this specification, etc., relates to an object, method, or manufacturing method. In addition, one embodiment of the present invention relates to a process, machine, product, or composition of matter. Therefore, more specifically, as examples of the technical field of one embodiment of the present invention disclosed in this specification, semiconductor devices, display devices, liquid crystal display devices, light-emitting devices, lighting devices, power storage devices, storage devices, and driving methods or manufacturing methods of these devices can be cited. Background Art

[0003] In recent years, research and development of light-emitting elements using electroluminescence (EL) has become increasingly popular. The basic structure of these light-emitting elements is a structure in which a layer containing a light-emitting substance (EL layer) is sandwiched between a pair of electrodes. By applying voltage between the electrodes of the element, light from the light-emitting substance can be obtained.

[0004] Since the light-emitting element is a self-luminous light-emitting element, a display device using the light-emitting element has the following advantages: good visibility; no backlight source is required; low power consumption, etc. Moreover, the display device also has the following advantages: it can be made thin and light; and has a fast response speed, etc.

[0005] When a light-emitting element (e.g., an organic EL element) is used in which an organic compound is used as a light-emitting substance and an EL layer containing the light-emitting substance is provided between a pair of electrodes, a voltage is applied between the pair of electrodes, and electrons and holes are injected from the cathode and the anode into the light-emitting EL layer, respectively, so that a current flows. Furthermore, the injected electrons and holes are recombined to make the light-emitting organic compound into an excited state, and light emission can be obtained.

[0006] As the types of excited states formed by organic compounds, there are singlet excited states (S ＊ ) and triplet excited state (T ＊), the emission from the singlet excited state is called fluorescence, and the emission from the triplet excited state is called phosphorescence. In addition, in this light-emitting element, the statistical generation ratio of the singlet excited state to the triplet excited state is S ＊ :T ＊ =1:3. Therefore, compared with the light-emitting element using the compound emitting fluorescence (fluorescent material), the light-emitting element using the compound emitting phosphorescence (phosphorescent material) has a higher luminous efficiency. Therefore, in recent years, the research and development of light-emitting elements using phosphorescent materials that can convert triplet excitation energy into luminescence has become increasingly hot.

[0007] Among light-emitting elements using phosphorescent materials, especially light-emitting elements emitting blue light, it is difficult to develop stable compounds with high triplet excitation energy levels, so they have not yet been put into practical use. For this reason, light-emitting elements using more stable fluorescent materials have been developed, and methods for improving the luminous efficiency of light-emitting elements using fluorescent materials (fluorescent light-emitting elements) have been sought.

[0008] As a material capable of converting part or all of triplet excitation energy into luminescence, in addition to phosphorescent materials, thermally activated delayed fluorescence (TADF) materials are known. In TADF materials, a singlet excited state is generated from a triplet excited state by anti-intersystem crossing, and the singlet excited state is converted into luminescence.

[0009] In order to improve the luminous efficiency in a light-emitting element using a TADF material, it is important not only to efficiently generate a singlet excited state from a triplet excited state in the TADF material, but also to efficiently obtain luminescence from the singlet excited state, that is, to achieve a high fluorescence quantum yield. However, it is difficult to design a luminescent material that satisfies both of the above conditions.

[0010] In addition, a method is also known in which, in a light-emitting element including 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 to obtain light emission from the fluorescent material (see Patent Document 1). [Prior technical literature] [Patent Document]

[0011] [Patent Document 1] Japanese Patent Application Publication No. 2014-45179 [Non-patent literature]

[0012] [Non-patent document 1] Hiroki Noda et al., “SCIENCE ADVANCES”, 2018, vol. 4, no. 6, eaao6910 Summary of the invention Technical problem to be solved by the invention

[0013] Multicolor light-emitting elements represented by white light-emitting elements are light-emitting elements that are expected to be used in displays and the like. As an element structure for obtaining the multicolor light-emitting element, a light-emitting element (also called a tandem element) having a plurality of EL layers disposed across a charge generation layer can be cited. Since the tandem element can use materials exhibiting different luminous colors for different EL layers, it is suitable for the manufacture of multicolor light-emitting elements. However, the number of layers of the tandem element is large, resulting in a problem of more manufacturing processes.

[0014] Therefore, a light-emitting element that can emit multiple colors from one EL layer is required. In order to obtain multiple colors of light, two or more light-emitting materials are used in the light-emitting layer, but from the viewpoint of reliability, the development of a multi-color light-emitting element using fluorescent materials is required.

[0015] As described above, as a method for improving the efficiency of a fluorescent light-emitting element, for example, the following method can be cited: in a light-emitting layer comprising a host material and a guest material, the triplet exciton of the host material is converted into a singlet exciton, and then the singlet excitation energy is transferred to the fluorescent material as the guest material. However, the process of converting the triplet excitation energy of the host material into the singlet excitation energy competes with the process of deactivating the triplet excitation energy. Therefore, sometimes the conversion of the triplet excitation energy of the host material to the singlet excitation energy is insufficient. For example, as a path for deactivating the triplet excitation energy, the following deactivation path is considered: when a fluorescent material is used as a guest material in the 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 (T 1 Energy level). The energy transfer through this deactivation pathway does not contribute to luminescence, thus resulting in a decrease in the luminescence efficiency of the fluorescent light-emitting device.

[0016] Therefore, in order to improve the luminous efficiency and reliability of the fluorescent light-emitting element, it is preferred that the triplet excitation energy in the light-emitting layer is efficiently converted into singlet excitation energy and efficiently transferred to the fluorescent light-emitting material as singlet excitation energy. To this end, it is necessary to develop a method that efficiently generates the singlet excited state of the guest material from the triplet excited state of the host material, further improving the luminous efficiency of the light-emitting element and improving the reliability.

[0017] Therefore, an object of one embodiment of the present invention is to provide a light-emitting element capable of obtaining multiple luminous colors from one EL layer. An object of one embodiment of the present invention is to provide a light-emitting element with high luminous efficiency. In addition, an object of one embodiment of the present invention is to provide a light-emitting element with high reliability. In addition, an object of one embodiment of the present invention is to provide a light-emitting element with reduced power consumption. In addition, an object of one embodiment of the present invention is to provide a novel light-emitting element. In addition, an object of one embodiment of the present invention is to provide a novel light-emitting device. In addition, an object of one embodiment of the present invention is to provide a novel display device.

[0018] Note that the description of the above-mentioned purpose does not prevent the existence of other purposes. One embodiment of the present invention does not necessarily need to achieve all of the above-mentioned purposes. In addition, purposes other than the above-mentioned purpose can be known and derived from the description of the specification, etc. Solutions to technical problems

[0019] As described above, it is necessary to develop a method that can efficiently convert triplet excitation energy into luminescence in a fluorescent light-emitting element. To this end, it is necessary to improve the energy transfer efficiency between materials used in the light-emitting layer. To this end, it is necessary to suppress the transfer of triplet excitation energy based on the Dexter mechanism between energy donors and energy acceptors.

[0020] Therefore, one embodiment of the present invention is a light-emitting element, which includes a light-emitting layer between a pair of electrodes. The light-emitting layer includes a first material having a function of converting triplet excitation energy into light-emitting and a second material having a function of converting singlet excitation energy into light-emitting. The second material includes a luminophore and five or more protective groups. The luminophore is a fused aromatic ring or a fused heteroaromatic ring. The five or more protective groups independently have any one of an alkyl group having a carbon number of 1 or more and a carbon number of 10 or less, a substituted or unsubstituted cycloalkyl group having a carbon number of 3 or more and a carbon number of 10 or less, and a trialkylsilyl group having a carbon number of 3 or more and a carbon number of 12 or less. The light-emitting element obtains light emission from both the first material and the second material.

[0021] In the above structure, it is preferred that at least four of the five or more protecting groups are independently any one of an alkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, and a trialkylsilyl group having 3 to 12 carbon atoms.

[0022] In addition, another embodiment of the present invention is a light-emitting element, which includes a light-emitting layer between a pair of electrodes. The light-emitting layer includes a first material having a function of converting triplet excitation energy into light-emitting and a second material having a function of converting singlet excitation energy into light-emitting. The second material includes 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 independently have any one of an alkyl group having a carbon number of 3 or more and a carbon number of 10 or less, a substituted or unsubstituted cycloalkyl group having a carbon number of 3 or more and a carbon number of 10 or less, and a trialkylsilyl group having a carbon number of 3 or more and a carbon number of 12 or less. The light-emitting element obtains light emission from both the first material and the second material.

[0023] In addition, another embodiment of the present invention is a light-emitting element, which includes a light-emitting layer between a pair of electrodes. The light-emitting layer includes a first material having a function of converting triplet excitation energy into light emission and a second material having a function of converting singlet excitation energy into light emission. The second material includes a light emitter and two or more diarylamino groups. The light emitter is a fused aromatic ring or a fused heteroaromatic ring. The fused aromatic ring or the fused heteroaromatic ring is bonded to two or more diarylamino groups, and the two or more diarylamino groups independently have at least one protecting group. The protecting groups independently have any one of an alkyl group having a carbon number of 3 or more and a carbon number of 10 or less, a substituted or unsubstituted cycloalkyl group having a carbon number of 3 or more and a carbon number of 10 or less, and a trialkylsilyl group having a carbon number of 3 or more and a carbon number of 12 or less. The light-emitting element obtains light emission from both the first material and the second material.

[0024] In addition, another embodiment of the present invention is a light-emitting element, which includes a light-emitting layer between a pair of electrodes. The light-emitting layer includes a first material having a function of converting triplet excitation energy into light emission and a second material having a function of converting singlet excitation energy into light emission. The second material includes a light emitter and two or more diarylamino groups. The light emitter is a fused aromatic ring or a fused heteroaromatic ring. The fused aromatic ring or the fused heteroaromatic ring is bonded to two or more diarylamino groups, and the two or more diarylamino groups independently have at least two protecting groups. The protecting groups independently have any one of an alkyl group having a carbon number of 3 or more and a carbon number of 10 or less, a substituted or unsubstituted cycloalkyl group having a carbon number of 3 or more and a carbon number of 10 or less, and a trialkylsilyl group having a carbon number of 3 or more and a carbon number of 12 or less. The light-emitting element obtains light emission from both the first material and the second material.

[0025] In the above structure, the diarylamino group is preferably a diphenylamino group.

[0026] In addition, in the above structure, the alkyl group is preferably a branched alkyl group.

[0027] In addition, another embodiment of the present invention is a light-emitting element, which includes a light-emitting layer between a pair of electrodes. The light-emitting layer includes a first material having a function of converting triplet excitation energy into light emission and a second material having a function of converting singlet excitation energy into light emission. The second material includes a luminophore and a plurality of protective groups. The luminophore is a fused aromatic ring or a fused heteroaromatic ring. At least one of the atoms constituting the plurality of protective groups is located directly on one face of the fused aromatic ring or the fused heteroaromatic ring. At least one of the atoms constituting the plurality of protective groups is located directly on another face of the fused aromatic ring or the fused heteroaromatic ring. The light-emitting element obtains light emission from both the first material and the second material.

[0028] In addition, another embodiment of the present invention is a light-emitting element, which includes a light-emitting layer between a pair of electrodes. The light-emitting layer includes a first material having a function of converting triplet excitation energy into light emission and a second material having a function of converting singlet excitation energy into light emission. The second material includes a light emitter and two or more diphenylamino groups. The light emitter is a fused aromatic ring or a fused heteroaromatic ring. The fused aromatic ring or the fused heteroaromatic ring is bonded to two or more diphenylamino groups, and the phenyl groups in the two or more diphenylamino groups independently have protecting groups at the 3rd and 5th positions. The protecting groups independently have any one of an alkyl group having a carbon number of 3 or more and a carbon number of 10 or less, a substituted or unsubstituted cycloalkyl group having a carbon number of 3 or more and a carbon number of 10 or less, and a trialkylsilyl group having a carbon number of 3 or more and a carbon number of 12 or less. The light-emitting element obtains light emission from both the first material and the second material.

[0029] In addition, in the above structure, the alkyl group is preferably a branched alkyl group.

[0030] In addition, in the above structure, the branched alkyl group preferably contains a quaternary carbon.

[0031] In the above structure, the fused aromatic ring or fused heteroaromatic ring preferably includes naphthalene, anthracene, fluorene, At least one of chrysene, triphenylene, pyrene, tetracene, perylene, coumarin, quinacridone and naphthobisbenzofuran.

[0032] In the above structure, preferably, the first material includes a first organic compound and a second organic compound, and the first organic compound and the second organic compound form an exciplex. More preferably, the first organic compound emits phosphorescent light.

[0033] In the above structure, the peak wavelength of the emission spectrum of the first material is preferably closer to the shorter wavelength side than the peak wavelength of the emission spectrum of the second material.

[0034] In addition, in the above structure, the first material is preferably a compound that emits phosphorescence or delayed fluorescence.

[0035] In the above structure, the emission spectrum of the first material preferably overlaps with the absorption band on the longest wavelength side of the absorption spectrum of the second material.

[0036] In the above structure, the concentration of the second material in the light emitting layer is preferably 0.01 wt % or more and 2 wt % or less.

[0037] In addition, another embodiment of the present invention is a display device including a light-emitting element of each structure described above, and at least one of a color filter and a transistor. In addition, another embodiment of the present invention is an electronic device including the above-mentioned display device, and at least one of a housing and a touch sensor. In addition, another embodiment of the present invention is a lighting device including a light-emitting element of each structure described above, and at least one of a housing and a touch sensor. In addition, one embodiment of the present invention is that its scope includes not only a light-emitting device having a light-emitting element but also an electronic device having a light-emitting device. Therefore, the light-emitting device in this specification refers to an image display device or a light source (including a lighting device). In addition, the light-emitting device sometimes also includes the following modules: a display module in which a connector such as an FPC (Flexible Printed Circuit) or a TCP (Tape Carrier Package) is installed in the light-emitting element; a display module in which a printed circuit board is provided at the end of the TCP; or a display module in which an IC (integrated circuit) is directly mounted on the light-emitting element by a COG (Chip On Glass) method. Effects of the Invention

[0038] According to one embodiment of the present invention, a light-emitting element capable of obtaining multiple luminous colors from one EL layer can be provided. According to one embodiment of the present invention, a light-emitting element with high luminous efficiency can be provided. In addition, according to one embodiment of the present invention, a light-emitting element with high reliability can be provided. In addition, according to one embodiment of the present invention, a light-emitting element with reduced power consumption can be provided. In addition, according to one embodiment of the present invention, a novel light-emitting element can be provided. In addition, according to one embodiment of the present invention, a novel light-emitting device can be provided. In addition, according to one embodiment of the present invention, a novel display device can be provided.

[0039] Note that the description of these effects does not prevent the existence of other effects. In addition, one mode of the present invention does not necessarily need to have all of the above effects. In addition, effects other than the above effects can be known and derived from the description of the specification, drawings, claims, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] [ Figure 1A ] is a schematic cross-sectional view of a light-emitting element according to one embodiment of the present invention. [ Figure 1B] is a schematic cross-sectional view of a light-emitting layer of a light-emitting element according to one embodiment of the present invention. [ Figure 1C ] is a diagram illustrating the energy level correlation of the light-emitting layer of a light-emitting device according to one embodiment of the present invention. [ Figure 2A ] is a schematic diagram of existing guest materials. [ Figure 2B ] is a schematic diagram of a guest material for a light-emitting element according to one embodiment of the present invention. [ Figure 3A ] is a structural formula of a guest material used in a light-emitting element according to one embodiment of the present invention. [ Figure 3B ] is a ball-and-stick diagram of the guest material used in the light-emitting element of one embodiment of the present invention. [ Figure 4A ] is a schematic cross-sectional view of a light-emitting layer of a light-emitting element according to one embodiment of the present invention. [ Figure 4B ]to[ Figure 4D ] is a diagram illustrating the energy level correlation of a light-emitting layer of a light-emitting device according to one embodiment of the present invention. [ Figure 5A ] is a schematic cross-sectional view of a light-emitting layer of a light-emitting element according to one embodiment of the present invention. [ Figure 5B ]and[ Figure 5C ] is a diagram illustrating the energy level correlation of a light-emitting layer of a light-emitting device according to one embodiment of the present invention. [ Fig. 6A ] is a schematic cross-sectional view of a light-emitting layer of a light-emitting element according to one embodiment of the present invention. [ Figure 6B ]and[ Figure 6C ] is a diagram illustrating the energy level correlation of a light-emitting layer of a light-emitting device according to one embodiment of the present invention. [ Figure 7 ] is a cross-sectional schematic diagram illustrating a light-emitting element of one embodiment of the present invention. [ Fig. 8A ] is a top view of a display device for explaining one embodiment of the present invention. [ Figure 8B ] is a cross-sectional schematic diagram illustrating a display device according to one embodiment of the present invention. [ Fig.9A ]and[ Fig. 9B ] is a cross-sectional schematic diagram illustrating a display device according to one embodiment of the present invention. [ Fig. 10A ]and[ Fig. 10B ] is a cross-sectional schematic diagram illustrating a display device according to one embodiment of the present invention. [ Fig.11A ]to[ Fig.11D ] is a three-dimensional diagram of a display module for illustrating one embodiment of the present invention. [ Fig. 12A ]to[ Fig. 12C ] is a diagram of an electronic device illustrating one embodiment of the present invention. [ Fig.13A ]and[ Fig. 13B ] is a stereoscopic diagram of a display device for illustrating one embodiment of the present invention. [ Fig.14 ] is a diagram of a lighting device for illustrating one embodiment of the present invention. [ Fig.15 ] is a diagram illustrating the external quantum efficiency-luminance characteristics of the light-emitting element according to the embodiment. [ Fig.16 ] is a diagram illustrating the electroemission spectrum of the light-emitting element according to the embodiment and the absorption and emission spectra of the compound. [ Fig.17 ] is a diagram illustrating the reliability test results of the light emitting element according to the embodiment. [ Fig.18 ] is a diagram illustrating the external quantum efficiency-luminance characteristics of the light-emitting element according to the embodiment. [ Fig.19 ] is a diagram illustrating the electroemission spectrum of the light-emitting element according to the embodiment and the absorption and emission spectra of the compound. [ Fig. 20 ] is a diagram illustrating the electroemission spectrum of the light-emitting element according to the embodiment and the absorption and emission spectra of the compound. [ Fig.21 ] is a diagram illustrating the reliability test results of the light emitting element according to the embodiment. [ Fig. 22 ] is a diagram illustrating the external quantum efficiency-luminance characteristics of the light-emitting element according to the embodiment. [ Fig.23 ] is a diagram illustrating the electroemission spectrum of the light-emitting element according to the embodiment and the absorption and emission spectra of the compound. [ Fig.24 ] is a diagram illustrating the reliability test results of the light emitting element according to the embodiment. [ Fig.25A ]and[ Fig.25B ] is a diagram illustrating the NMR spectrum of the compound according to Reference Example. [ Fig.26 ] is a diagram illustrating the NMR spectrum of the compound according to Reference Example. [ Fig.27A ]and[ Fig.27B ] is a diagram illustrating the NMR spectrum of the compound according to Reference Example. [ Fig.28 ] is a diagram illustrating the NMR spectrum of the compound according to Reference Example. [ Fig.29 ] is a diagram illustrating the external quantum efficiency-luminance characteristics of the light-emitting element according to the embodiment. [ Fig.30] is a diagram illustrating the electroemission spectrum of the light-emitting element according to the embodiment and the absorption and emission spectra of the compound. [ Fig.31 ] is a diagram illustrating the results of a light emitting lifetime test of a light emitting element according to an embodiment. [ Fig.32 ] is a diagram illustrating the reliability test results of the light emitting element according to the embodiment. [ Fig.33 ] is a diagram illustrating the external quantum efficiency-luminance characteristics of the light-emitting element according to the embodiment. [ Fig.34 ] is a diagram illustrating the electroemission spectrum of the light-emitting element according to the embodiment and the absorption and emission spectra of the compound. [ Fig.35 ] is a diagram illustrating the external quantum efficiency-luminance characteristics of the light-emitting element according to the embodiment. [ Fig.36 ] is a diagram illustrating the electroemission spectrum of the light-emitting element according to the embodiment and the absorption and emission spectra of the compound. [ Fig.37 ] is a diagram illustrating the electroemission spectrum of the light-emitting element according to the embodiment and the absorption and emission spectra of the compound. [ Fig.38A ]and[ Fig.38B ] is a diagram illustrating the NMR spectrum of the compound according to Reference Example. [ Fig.39 ] is a diagram illustrating the NMR spectrum of the compound according to Reference Example. [ Fig.40A ]and[ Fig.40B ] is a diagram illustrating the NMR spectrum of the compound according to Reference Example. [ Fig.41A ]and[ Fig.41B ] is a diagram illustrating the NMR spectrum of the compound according to Reference Example. [ Fig.42 ] is a diagram illustrating the NMR spectrum of the compound according to Reference Example. [ Fig.43 ] is a diagram illustrating the results of a light emitting lifetime test of a light emitting element according to an embodiment. Modes for Carrying Out the Invention

[0041] Hereinafter, the embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that the present invention is not limited to the following description, and its mode and details can be transformed into various forms without departing from the purpose and scope of the present invention. Therefore, the present invention should not be interpreted as being limited to the contents recorded in the embodiments shown below.

[0042] In addition, for ease of understanding, the position, size, range, etc. of each structure shown in the drawings and the like may not represent its actual position, size, range, etc. Therefore, the disclosed invention is not necessarily limited to the position, size, range, etc. disclosed in the drawings and the like.

[0043] In addition, in this specification, for easy understanding, ordinal numbers such as first and second are added, but they do not sometimes indicate the order of processes or the order of stacking. Therefore, for example, "first" can be appropriately replaced with "second" or "third" for description. In addition, the ordinal numbers recorded in this specification and the like are sometimes inconsistent with the ordinal numbers used to specify one embodiment of the present invention.

[0044] Note that in this specification and the like, when describing the configuration of the invention using drawings, reference numerals may be used in common to indicate the same components in different drawings.

[0045] In addition, in this specification, "film" and "layer" may be interchanged. For example, "conductive layer" may be replaced by "conductive film". Also, "insulating film" may be replaced by "insulating layer".

[0046] In this specification, the singlet excited state (S * ) refers to a singlet state with excitation energy. In addition, the S1 energy level is the lowest energy level of the singlet excitation energy level, which refers to the excitation energy level of the lowest singlet excitation state (S1 state). In addition, the triplet excitation state (T * ) refers to a triplet state with excitation energy. In addition, the T1 energy level is the lowest energy level of the triplet excitation energy level, and it refers to the excitation energy level of the lowest triplet excitation state (T1 state). In addition, in this specification, although sometimes only "singlet excited state" and "singlet excitation energy level" are recorded, sometimes they represent the S1 state and S1 energy level respectively. In addition, even when "triplet excited state" and "triplet excitation energy level" are recorded, sometimes they represent the T1 state and T1 energy level respectively.

[0047] In addition, in this specification, etc., a fluorescent material refers to a compound that emits light in the visible light region when returning from a singlet excited state to a ground state. A phosphorescent material refers to a compound that emits light in the visible light region at room temperature when returning from a triplet excited state to a ground state. In other words, a phosphorescent material refers to one of the compounds that can convert triplet excitation energy into visible light.

[0048] Note that in this specification and the like, room temperature refers to a temperature within a range of 0° C. or higher and 40° C. or lower.

[0049] In addition, in this specification, etc., the wavelength region of blue refers to the wavelength region of more than 400nm and less than 490nm, and the blue luminescence has at least one emission spectrum peak in this wavelength region. In addition, the wavelength region of green refers to the wavelength region of more than 490nm and less than 580nm, and the green luminescence has at least one emission spectrum peak in this wavelength region. In addition, the wavelength region of red refers to the wavelength region of more than 580nm and less than 680nm, and the red luminescence has at least one emission spectrum peak in this wavelength region. In addition, even when two emission spectra have emission spectrum peaks respectively in the same wavelength region, when the peak wavelengths are different, sometimes the luminescent colors of the two emission spectra are regarded as different. Note that the emission spectrum peak is a maximum value, or includes a shoulder peak.

[0050] (Implementation Method 1) In this embodiment, refer to Figures 1A to 6C A light-emitting element according to one embodiment of the present invention will be described.

[0051] <Structural Example of Light Emitting Element> First, we will refer to Figures 1A to 1C The structure of a light-emitting element according to one embodiment of the present invention will be described.

[0052] Figure 1A It is a schematic cross-sectional view of a light emitting element 150 according to one embodiment of the present invention.

[0053] The light-emitting element 150 includes a pair of electrodes (electrode 101 and electrode 102 ) and includes an EL layer 100 provided between the pair of electrodes. The EL layer 100 includes at least a light-emitting layer 130 .

[0054] in addition, Figure 1A The EL layer 100 shown includes functional layers such as a hole injection layer 111 , a hole transport layer 112 , an electron transport layer 118 , and an electron injection layer 119 in addition to the light-emitting layer 130 .

[0055] Note that although the electrode 101 of a pair of electrodes is described as an anode and the electrode 102 is described as a cathode in this embodiment, the structure of the light-emitting element 150 is not limited to this. That is, the electrode 101 may be used as a cathode, the electrode 102 may be used as an anode, and the 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 stacked in order from the anode side.

[0056] Note that the structure of the EL layer 100 is not limited to Figure 1AThe structure shown may include at least one selected from the group consisting of the hole injection layer 111, the hole transport layer 112, the electron transport layer 118, and the electron injection layer 119. Alternatively, the EL layer 100 may include a functional layer having the following functions: a functional layer capable of reducing the injection barrier of holes or electrons; a functional layer capable of improving the transportability of holes or electrons; a functional layer capable of hindering the transportability of holes or electrons; or a functional layer capable of suppressing the quenching phenomenon caused by the electrode. The functional layer may be a single layer or a stack of multiple layers.

[0057] <Light Emission Mechanism of Light Emitting Element> The light emission mechanism of the light emitting layer 130 is described below.

[0058] In the light-emitting element 150 of one embodiment of the present invention, by applying voltage between a pair of electrodes (electrode 101 and electrode 102), electrons and holes are injected from the cathode and anode into the EL layer 100, respectively, so that current flows. Among the excitons generated by the recombination of carriers (electrons and holes), the statistical probability of the ratio of singlet excitons to triplet excitons (hereinafter referred to as the exciton generation probability) is 1:3. Therefore, the ratio of singlet excitons is 25%, and the ratio of triplet excitons is 75%. Therefore, in order to improve the luminous efficiency of the light-emitting element, it is important to make the triplet exciton contribute to luminescence. Therefore, as the light-emitting layer 130, it is preferred to use a material having the function of converting triplet excitation energy into luminescence.

[0059] As a material having the function of converting triplet excitation energy into luminescence, a compound capable of emitting phosphorescence (hereinafter referred to as a phosphorescent material) can be cited. In this specification, etc., a phosphorescent material refers to a compound that emits phosphorescence without emitting fluorescence at any temperature in a temperature range of 77K or above and below room temperature (i.e., 77K or above and 313K or below). The phosphorescent material preferably contains a metal element with a large spin-orbit interaction, specifically, preferably contains a transition metal element, particularly preferably contains a platinum group element (ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir) or platinum (Pt)), and particularly preferably contains iridium. Iridium can increase the transition probability of the direct transition between the singlet ground state and the triplet excited state, so it is preferred.

[0060] In addition, as a material having the function of converting triplet excitation energy into luminescence, TADF material can be cited. TADF material refers to a material in which the difference between the S1 energy level and the T1 energy level is small and the triplet excitation energy can be converted into singlet excitation energy by anti-intersystem crossing. Therefore, it is possible to up-convert the triplet excitation energy into singlet excitation energy (anti-intersystem crossing) using tiny thermal energy and efficiently generate a singlet excited state. The exciplex (Exciplex) formed by two substances in an excited state has the function of a TADF material that converts triplet excitation energy into singlet excitation energy because the difference between the S1 energy level and the T1 energy level is extremely small.

[0061] As an indicator of the T1 level, a phosphorescence spectrum observed at a low temperature (e.g., 10 K) can be used. For TADF materials, it is preferred that a tangent line is drawn at the tail of the short wavelength side of the fluorescence spectrum at room temperature or low temperature, and the energy of the wavelength of the extrapolated line is set as the S1 level, and a tangent line is drawn at the tail of the short wavelength side of the phosphorescence spectrum, and the energy of the wavelength of the extrapolated line is set as the T1 level, and the difference between S1 and T1 is 0.2 eV or less.

[0062] In addition, as a material having the function of converting triplet excitation energy into luminescence, a nanostructure of a transition metal compound having a perovskite structure can be cited. Metal halide perovskite nanostructures are particularly preferred. As the nanostructure, nanoparticles and nanorods are preferred.

[0063] Figure 1B 1 is a schematic cross-sectional view of a light-emitting layer 130 of a light-emitting element according to one embodiment of the present invention. In one embodiment of the present invention, the light-emitting layer 130 includes a compound 131 and a compound 132. The compound 131 has a function of converting triplet excitation energy into light emission, and the compound 132 has a function of converting singlet excitation energy into light emission. It is preferred to use a fluorescent material as the compound 132 in order to obtain a light-emitting element with high reliability. Here, in the light-emitting layer 130, the compound 131 is used as an energy donor, and the compound 132 is used as an energy acceptor. That is, in Figure 1C In the embodiment of the present invention, the host material is used as an energy donor and the guest material is used as an energy acceptor. In addition, in the light-emitting element of one embodiment of the present invention, the compound 131 has the function of converting triplet excitation energy into luminescence as described above, and thus luminescence from the compound 131 as an energy donor and luminescence from the compound 132 as an energy acceptor can be obtained from the light-emitting layer 130. In this specification, a light-emitting element in which the energy donor has the function of converting triplet excitation energy into luminescence and a fluorescent material is used as an energy acceptor as described above is sometimes referred to as a triplet photosensor.

[0064] <Structural Example 1 of Light Emitting Layer> Figure 1CAn example of energy level correlation in a light-emitting layer of a light-emitting element according to one embodiment of the present invention is shown. In this structural example, a case where a TADF material is used as Compound 131 is shown.

[0065] in addition, Figure 1C The energy level correlation between the compound 131 and the compound 132 in the light-emitting layer 130 is shown. Figure 1C The symbols and signs in are as follows. Host (131): Compound 131 Guest(132): Compound 132 ·T C1 :T1 energy level of compound 131 ·S C1 :S1 energy level of compound 131 ·S G :S1 energy level of compound 132 ·T G :T1 energy level of compound 132

[0066] Here, we focus on the triplet excitation energy of compound 131 generated by current excitation. Compound 131 has TADF characteristics. Therefore, compound 131 has the function of converting triplet excitation energy into singlet excitation energy by upconversion ( Figure 1C Path A 1 The singlet excitation energy of compound 131 can be transferred to compound 132 ( Figure 1C Path A 2 ). In this case, it is preferred to satisfy S C1 ≥S G Here, path A 2 The process competes with the luminescence process of compound 131 (transfer from the S1 energy level to the ground state of compound 131). That is, the singlet excitation energy possessed by compound 131 is converted into the luminescence of compound 131 and the luminescence of compound 132. Therefore, the light-emitting element of one embodiment of the present invention can obtain both luminescence from compound 131 and luminescence from compound 132. Note that the singlet excitation energy of compound 131 generated by current excitation is also converted into the luminescence of compound 131 and compound 132.

[0067] Note that, specifically, it is preferable to draw a tangent line at the tail of the fluorescence spectrum of Compound 131 on the short wavelength side, and set the energy of the wavelength of the extrapolated line to S C1 , the energy of the wavelength at the absorption end of the absorption spectrum of compound 132 is set as S G , then satisfy S C1 ≥S GIn addition, the emission spectrum of compound 131 preferably overlaps with the absorption band on the longest wavelength side of the absorption spectrum of compound 132.

[0068] The triplet excitation generated in compound 131 can be obtained through the above-mentioned pathway A 1 and Path A 2 The triplet excitation energy is efficiently converted into fluorescent light by transferring to the S1 level of compound 132 as the guest material, and compound 132 emits light. 2 In the embodiment of the present invention, Compound 131 is used as an energy donor and Compound 132 is used as an energy acceptor. In the light-emitting element of one embodiment of the present invention, Compound 131 is used as an energy donor and also as a light-emitting material.

[0069] In order to use compound 131 as an energy donor and also as a luminescent material, it is preferred that the concentration of compound 132 relative to compound 131 be set to 0.01 wt% or more and 2 wt% or less. By adopting this structure, the excitation energy of compound 131 can be efficiently converted into the luminescence of compound 131 and the luminescence of compound 132, thereby obtaining a highly efficient multicolor light-emitting element. In addition, by adjusting the concentrations of compound 131 and compound 132, the luminescent color can be adjusted.

[0070] In addition, if Figure 1C As shown, the S1 energy level of compound 131 is higher than the S1 energy level of compound 132. Therefore, the emission spectrum from compound 131 is closer to the short wavelength side than that of compound 132. More specifically, the peak wavelength of the emission spectrum of compound 131 is closer to the short wavelength side than the peak wavelength of the emission spectrum of compound 132. By adopting this structure, energy transfer from compound 131 to compound 132 can be efficiently performed, thereby obtaining a multicolor light-emitting element with high luminous efficiency.

[0071] Here, in the light-emitting layer 130, the compound 131 and the compound 132 are mixed together. Therefore, the path A may occur. 1 With path A 2 The process in which the triplet excitation energy of compound 131 is converted into the triplet excitation energy of compound 132 by competition ( Figure 1C Path A 3 ). Since compound 132 is a fluorescent material, the triplet excitation energy of compound 132 does not contribute to luminescence. That is, when path A occurs 3 The energy transfer from T C1 to T G Energy transfer (path A 3 ), it is possible that the energy is not directly transferred but once it is above the T of compound 132 GThe triplet excited state becomes T through internal conversion. G However, this process is omitted in the figure. The undesirable thermal inactivation process in the following description, i.e. to T G The deactivation process is the same.

[0072] As the energy transfer mechanism between molecules, the Forster mechanism (dipole-dipole interaction) and the Dexter mechanism (electron exchange interaction) are known. Since the compound 132 as the energy acceptor is a fluorescent material, in the path A 3 The Dexter mechanism is dominant in the energy transfer. Generally speaking, the Dexter mechanism occurs significantly when the distance between compound 131 as an energy donor and compound 132 as an energy acceptor is less than 1 nm. Therefore, in order to inhibit path A 3 It is important to make the distance between the host material and the guest material, that is, the distance between the energy donor and the energy acceptor, long.

[0073] Since the direct transition from the singlet ground state to the triplet excited state in compound 132 is a forbidden transition, the singlet excited level (S C1 ) to the triplet excited level (T G ) is unlikely to be the main energy transfer process and is therefore not shown in the diagram.

[0074] Figure 1C T G Most of them are derived from the energy level of the luminophore in the energy acceptor. Therefore, in more detail, in order to suppress path A 3 It is important to make the distance between the energy donor and the luminophore included in the energy acceptor long.

[0075] The present inventors have found that the above-mentioned decrease in luminous efficiency can be suppressed by using, as an energy acceptor, a fluorescent material having a protecting group for increasing the distance from the energy donor.

[0076] <Concept of fluorescent material having a protective group> Figure 2A A schematic diagram showing a case where a fluorescent material having no protective group, which is a general fluorescent material, is dispersed in a host material as a guest material. Figure 2B A schematic diagram showing a case where a fluorescent material having a protective group is dispersed in a host material as a guest material in a light-emitting element of one embodiment of the present invention. The host material can be referred to as an energy donor and the guest material can be referred to as an energy acceptor. Here, the protective group has the function of lengthening the distance between the luminophore and the host material. Figure 2A In the embodiment, the guest material 301 has a light emitting body 310. On the other hand, in Figure 2BIn the embodiment, the guest material 302 includes a luminophore 310 and a protective group 320. Figure 2A and Figure 2B In FIG. 3 , the guest material 301 and the guest material 302 are surrounded by the host material 330. Figure 2A In the embodiment, since the distance between the luminescent body and the host material is short, energy transfer based on the Förster mechanism may occur as energy transfer from the host material 330 to the guest material 301 ( Figure 2A and Figure 2B Path A in 4 ) and energy transfer based on the Dexter mechanism ( Figure 2A and Figure 2B Path A in 5 ). When energy transfer of triplet excitation energy from the host material to the guest material occurs based on the Dexter mechanism to generate a triplet excited state of the guest material, when the guest material is a fluorescent material, non-radiative deactivation of the triplet excitation energy occurs, which may be one of the causes of decreased luminous efficiency.

[0077] On the other hand, Figure 2B In the embodiment, the guest material 302 has a protective group 320. Therefore, the distance between the luminescent body 310 and the host material 330 can be made long. Therefore, the energy transfer based on the Dexter mechanism (path A) can be suppressed. 5 ).

[0078] Here, in order to make the guest material 302 emit light, the guest material 302 needs to receive energy from the host material 330 based on the Foster mechanism because the Dexter mechanism is suppressed. That is, it is preferable to efficiently utilize the energy transfer based on the Foster mechanism while suppressing the energy transfer based on the Dexter mechanism. It is known that the energy transfer based on the Foster mechanism is also affected by the distance between the host material and the guest material. Generally speaking, when the distance between the host material 330 and the guest material 302 is less than 1nm, the Dexter mechanism is dominant, and when it is greater than 1nm and less than 10nm, the Foster mechanism is dominant. Generally speaking, when the distance between the host material 330 and the guest material 302 is greater than 10nm, energy transfer is not easy to occur. Here, the distance between the host material 330 and the guest material 302 can be replaced by the distance between the host material 330 and the luminescent body 310.

[0079] Therefore, the protecting group 320 is preferably diffused within a range of 1 nm to 10 nm from the luminescent body 310. More preferably, it is diffused within a range of 1 nm to 5 nm from the luminescent body 310. By adopting this structure, energy transfer based on the Foster mechanism can be efficiently utilized while suppressing energy transfer based on the Dexter mechanism from the host material 330 to the guest material 302. Therefore, a light-emitting element with high luminous efficiency can be manufactured.

[0080] In a light-emitting element of one embodiment of the present invention, a guest material having a protective group in the luminophore is used for the light-emitting layer. Energy transfer based on the Foster mechanism can be efficiently utilized while suppressing energy transfer based on the Dexter mechanism, so a light-emitting element with high luminous efficiency can be obtained as a light-emitting element of one embodiment of the present invention. In addition, by using a material having the function of converting triplet excitation energy into luminescence as a host material, a fluorescent light-emitting element having a high luminous efficiency equal to that of a phosphorescent light-emitting element can be manufactured. In addition, since the luminous efficiency is improved by using a fluorescent material with high stability, a light-emitting element with high reliability can be manufactured. In addition, by obtaining luminescence from a material having the function of converting triplet excitation energy into luminescence used as a host material, a multicolor light-emitting element that usually requires stacking of luminescent layers can be obtained using only one luminescent layer.

[0081] Here, the luminophore refers to an atomic group (skeleton) that is the cause of luminescence in a fluorescent material. The luminophore generally has a π bond, preferably contains an aromatic ring, and preferably has a fused aromatic ring or a fused heteroaromatic ring. In addition, as another way, it can be considered that the luminophore refers to an atomic group (skeleton) of an aromatic ring containing a transition dipole vector on a ring plane. In addition, when a fluorescent material has a plurality of fused aromatic rings or fused heteroaromatic rings, sometimes the skeleton with the lowest S1 energy level in the plurality of fused aromatic rings or fused heteroaromatic rings is regarded as the luminophore of the fluorescent material. In addition, sometimes the skeleton with an absorption end on the longest wavelength side in the plurality of fused aromatic rings or fused heteroaromatic rings is regarded as the luminophore of the fluorescent material. In addition, sometimes the luminophore of the fluorescent material can be predicted based on the shape of the emission spectrum of each of the plurality of fused aromatic rings or fused heteroaromatic rings.

[0082] Examples of the condensed aromatic ring or condensed heteroaromatic ring include a phenanthrene skeleton, a stilbene skeleton, an acridone skeleton, a phenoxazine skeleton, a phenothiazine skeleton, and the like. In particular, a naphthalene skeleton, an anthracene skeleton, a fluorene skeleton, A fluorescent material having 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 preferable because the fluorescence quantum yield is high.

[0083] In addition, the substituent used as a protecting group needs to have a triplet excitation energy level higher than the T1 energy level of the luminophore and the host material. Therefore, it is preferred to use a saturated hydrocarbon group. This is because the triplet excitation energy level of the substituent without a π bond is high. In addition, the carrier (electron or hole) transport function of the substituent without a π bond is low. Therefore, the saturated hydrocarbon group can hardly affect the excited state or carrier transport of the host material and make the distance between the luminophore and the host material long. In addition, in an organic compound containing a substituent without a π bond and a substituent with π conjugation at the same time, in many cases, the frontier orbital {HOMO (Highest Occupied Molecular Orbital, also known as the highest occupied molecular orbital) and LUMO (Lowest Unoccupied Molecular Orbital, also known as the lowest empty molecular orbital)} exists on the side of the substituent with π conjugation, especially, the luminophore has many cases of frontier orbitals. As described later, for energy transfer based on the Dexter mechanism, the overlap of the HOMO of the energy donor and the energy acceptor and the overlap of the LUMO are very important. Therefore, by using a saturated hydrocarbon group as a protecting group, the distance between the frontier orbital of a host material as an energy donor and the frontier orbital of a guest material as an energy acceptor can be made long, thereby suppressing energy transfer based on the Dexter mechanism.

[0084] As a specific example of the protecting group, an alkyl group having a carbon number of 1 or more and 10 or less can be cited. Since the distance between the luminophore and the host material needs to be long, the protecting group is preferably a bulky substituent. Therefore, an alkyl group having a carbon number of 3 or more and 10 or less, a substituted or unsubstituted cycloalkyl group having a carbon number of 3 or more and 10 or less, or a trialkylsilyl group having a carbon number of 3 or more and 12 or less can be applied. In particular, the alkyl group is preferably a bulky branched alkyl group. In addition, the substituent is a bulky substituent when it contains a quaternary carbon, so it is particularly preferred.

[0085] In addition, it is preferred to have five or more protective groups for one luminophore. By adopting this structure, the entire luminophore can be covered with protective groups, so the distance between the host material and the luminophore can be appropriately adjusted. Figure 2B , but it is more preferred that the protecting group is not directly bonded to the luminophore. For example, the protecting group may be bonded to the luminophore via a divalent or higher substituent such as an arylene group or an amino group. By bonding the protecting group to the luminophore via the substituent, the distance between the luminophore and the host material can be effectively increased. Therefore, when the luminophore and the protecting group are not directly bonded, by having four or more protecting groups relative to one luminophore, the energy transfer based on the Dexter mechanism can be effectively suppressed.

[0086] In addition, the divalent or higher substituent that bonds the luminophore to the protective group is preferably a substituent having π conjugation. By adopting this structure, the luminescent color, HOMO energy level, glass transition point and other physical properties of the guest material can be adjusted. In addition, the protective group is preferably configured in a manner that is located at the outermost side when the molecular structure is observed with the luminophore as the center.

[0087] <Examples of Fluorescent Materials Having Protective Groups and Molecular Structures> Here, the structure of the fluorescent material N,N'-[(2-tert-butylanthracene)-9,10-diyl]-N,N'-bis(3,5-di-tert-butylphenyl)amine (abbreviated as 2tBu-mmtBuDPhA2Anth) which can be used in a light-emitting element of one embodiment of the present invention and is represented by the following structural formula (102) is shown. In 2tBu-mmtBuDPhA2Anth, the anthracene ring is a luminescent body, and the tert-butyl group (tBu group) is used as a protecting group.

[0088] [Chemical formula 1]

[0089] exist Figure 3B In the figure, the 2tBu-mmtBuDPhA2Anth is represented by a ball-and-stick model. Figure 3B In the figure, it is shown that Figure 3A The situation when looking at 2tBu-mmtBuDPhA2Anth in the direction of the arrow (horizontal to the anthracene ring surface). Figure 3B The shaded portion of represents the portion directly above the anthracene ring surface as the luminescent body, and it can be confirmed that the portion directly above has a region overlapping with the tBu group as the protecting group. Figure 3B In the figure, the atom indicated by arrow (a) is the carbon atom of the tBu group overlapping with the shaded portion, and the atom indicated by arrow (b) is the hydrogen atom of the tBu group overlapping with the shaded portion. That is, in 2tBu-mmtBuDPhA2Anth, the atoms constituting the protecting group are located directly on one face of the luminophore surface, and the atoms constituting the protecting group are also located directly on one face of the luminophore surface. By adopting this structure, even when the guest material is dispersed in the host material, the distance between the anthracene ring as the luminophore and the host material can be made long in the plane direction and the vertical direction of the anthracene ring, thereby suppressing the energy transfer based on the Dexter mechanism.

[0090] For example, in the case where the migration related to energy transfer is the migration between HOMO and LUMO, for the energy transfer based on the Dexter mechanism, the overlap of the HOMO of the host material and the guest material and the overlap of the LUMO of the host material and the guest material are important. When the HOMO and LUMO of these two materials overlap, the Dexter mechanism occurs significantly. Therefore, in order to suppress the Dexter mechanism, it is important to suppress the overlap of the HOMO and LUMO of the two materials. That is, it is important to make the distance between the skeleton related to the excited state and the host material long. Here, in the fluorescent material, HOMO and LUMO mostly have a luminophore. For example, when the HOMO and LUMO of the guest material diffuse to the top and bottom of the luminophore surface (the top and bottom of the anthracene ring in 2tBu-mmtBuDPhA2Anth), it is important in the molecular structure that the top and bottom of the luminophore surface are covered by a protective group.

[0091] In addition, in a fused aromatic ring or fused heteroaromatic ring such as a pyrene ring or anthracene ring used as a light emitter, a transition dipole vector exists on the ring plane. Figure 3B In the embodiment, 2tBu-mmtBuDPhA2Anth preferably has a region overlapping with the tBu group as a protecting group on the surface where the transition dipole vector exists, that is, directly on the surface of the anthracene ring. Specifically, the plurality of protecting groups ( Figure 3A and Figure 3B At least one of the atoms of the tBu group in the fused aromatic ring or fused heteroaromatic ring ( Figure 3A and Figure 3B The tBu group is located directly on one face of the anthracene ring in the anthracene ring, and at least one of the atoms constituting the plurality of protecting groups is located directly on another face of the fused aromatic ring or the fused heteroaromatic ring. By adopting this structure, even when the guest material is dispersed in the host material, the distance between the luminophore and the host material can be long, so that the energy transfer based on the Dexter mechanism can be suppressed. In addition, it is preferred that the tBu group is configured in a manner that covers the luminophore such as the anthracene ring.

[0092] <Structural Example 2 of Light Emitting Layer> Figure 4C An example of energy level correlation in the light-emitting layer 130 of the light-emitting element 150 according to one embodiment of the present invention is shown. Figure 4A The light-emitting layer 130 shown includes compound 131, compound 132, and compound 133. In one embodiment of the present invention, compound 132 is preferably a fluorescent material. In addition, in this structural example, compound 131 and compound 133 are a combination that forms an exciplex.

[0093] As a combination of compound 131 and compound 133, as long as it is a combination that can form an exciplex, it is preferred that one of them is a compound having a function of transporting holes (hole transport properties), and the other is a compound having a function of transporting electrons (electron transport properties). In this case, it is easy to form a donor-acceptor type exciplex, and the exciplex can be efficiently formed. In addition, when the combination of compound 131 and compound 133 is a combination of a compound having hole transport properties and a compound having electron transport properties, the balance of carriers can be easily controlled by adjusting their mixing ratio. Specifically, the compound having hole transport properties: the compound having electron transport properties is preferably in the range of 1:9 to 9:1 (weight ratio). In addition, by having this structure, the balance of carriers can be easily controlled, thereby easily controlling the carrier recombination region.

[0094] In addition, as a combination of host materials that efficiently form an exciplex, it is preferred that the HOMO energy level of one of Compound 131 and Compound 133 is higher than the HOMO energy level of the other, and the LUMO energy level of one of them is higher than the LUMO energy level of the other. In addition, the HOMO energy level of Compound 131 may be equal to the HOMO energy level of Compound 133, or the LUMO energy level of Compound 131 may be equal to the LUMO energy level of Compound 133.

[0095] Note that the LUMO energy level and the HOMO energy level of a compound can be obtained from the electrochemical properties (reduction potential and oxidation potential) of the compound measured by cyclic voltammetry (CV) measurement.

[0096] For example, when compound 131 has hole transport properties and compound 133 has electron transport properties, as Figure 4B As shown in the energy band diagram, it is preferred that the HOMO energy level of compound 131 is higher than the HOMO energy level of compound 133, and the LUMO energy level of compound 131 is higher than the LUMO energy level of compound 133. Due to this energy level correlation, holes and electrons as carriers injected from a pair of electrodes (electrode 101 and electrode 102) are easily injected into compound 131 and compound 133, respectively, so it is preferred.

[0097] In addition, Figure 4B In the formula, Comp(131) represents compound 131, Comp(133) represents compound 133, and ΔE C1 represents the energy difference between the LUMO level and the HOMO level of compound 131, ΔE C3 represents the energy difference between the LUMO level and the HOMO level of compound 133, and ΔE EIt represents the energy difference between the LUMO level of compound 133 and the HOMO level of compound 131.

[0098] In addition, the exciplex formed by Compound 131 and Compound 133 has a HOMO molecular orbital in Compound 131 and a LUMO molecular orbital in Compound 133. In addition, the excitation energy of the exciplex is approximately equivalent to the energy difference (ΔE) between the LUMO energy level of Compound 133 and the HOMO energy level of Compound 131. E ), and is smaller than the energy difference between the LUMO and HOMO levels of compound 131 (ΔE C1 ) and the energy difference between the LUMO and HOMO levels of compound 133 (ΔE C3 ). Therefore, by forming an exciplex from Compound 131 and Compound 133, an excited state can be formed with a lower excitation energy. In addition, the exciplex can form a stable excited state due to its lower excitation energy.

[0099] Figure 4C The energy level correlation of compound 131, compound 132 and compound 133 in the light-emitting layer 130 is shown as follows: Figure 4C Marks and symbols in. ·Comp(131): Compound 131 ·Comp(133): Compound 133 Guest(132): Compound 132 ·S C1 :S1 energy level of compound 131 ·T C1 :T1 energy level of compound 131 ·S C3 :S1 energy level of compound 133 ·T C3 :S1 energy level of compound 133 ·S G :S1 energy level of compound 132 ·T G :T1 energy level of compound 132 ·S E : S1 energy level of the exciplex ·T E : T1 energy level of the exciplex

[0100] In the light-emitting element of one embodiment of the present invention, the compound 131 and the compound 133 contained in the light-emitting layer 130 form an exciplex. The S1 level (S E ) and the T1 energy level (T E ) become adjacent energy levels (refer to Figure 4C Path A in 6 ).

[0101] The excited energy level of the exciplex (S E and T E ) than the S1 level (S C1 and S C3 ) is low, so an excited state can be formed with a lower excitation energy. As a result, the driving voltage of the light-emitting element 150 can be reduced.

[0102] Because the S1 energy level (S E ) and T1 level (T E ) are adjacent energy levels, so they are prone to antisystem crossing and have TADF characteristics. Therefore, the exciplex has the function of converting triplet excitation energy into singlet excitation energy by upconversion ( Figure 4C Path A 7 ). The singlet excitation energy of the exciplex can be rapidly transferred to compound 132 ( Figure 4C Path A 8 ). In this case, it is preferred to satisfy S E ≥S G On path A 8 In the embodiment, the exciplex is used as an energy donor and compound 132 is used as an energy acceptor. Specifically, it is preferred to draw a tangent line at the tail of the fluorescence spectrum of the exciplex on the short wavelength side and set the energy of the wavelength of the extrapolated line as S E , the energy of the wavelength at the absorption end of the absorption spectrum of compound 132 is set as S G , then satisfy S E ≥S G Here, path A 8 The process of exciplexes competes with the process of luminescence of the exciplexes (transfer of the exciplexes from the S1 energy level to the ground state or transfer of the exciplexes from the T1 energy level to the ground state). In other words, the singlet and triplet excitation energy of the exciplexes is converted into luminescence of the exciplexes and luminescence of compound 132. Therefore, the light-emitting element of one embodiment of the present invention can obtain luminescence from the exciplexes and luminescence from compound 132.

[0103] In order to use the exciplex as an energy donor and also as a luminescent material, the concentration of compound 132 relative to the total amount of compound 131 and compound 133 is preferably set to 0.01wt% or more and 2wt% or less. By adopting this structure, the excitation energy of the exciplex can be efficiently converted into the luminescence of the exciplex and the luminescence of compound 132, thereby obtaining a highly efficient multicolor light-emitting element. In addition, by adjusting the concentrations of compound 131, compound 132 and compound 133, the luminescent color can be adjusted.

[0104] Note that, specifically, it is preferable to draw a tangent line at the tail of the fluorescence spectrum of the exciplex on the short wavelength side, and set the energy of the wavelength of the extrapolated line to S. E , the energy of the wavelength at the absorption end of the absorption spectrum of compound 132 is set as S G , then satisfy S E ≥S G In addition, the emission spectrum of the exciplex preferably overlaps with the absorption band on the longest wavelength side of the absorption spectrum of Compound 132.

[0105] In order to enhance the TADF properties of the exciplex, it is preferred that the T1 level of compounds 131 and 133, i.e., T C1 and T C3 T E As an indicator, it is preferred that the emission peak wavelengths on the shortest wavelength side of the phosphorescence spectra of Compound 131 and Compound 133 are both below the maximum emission peak wavelength of the exciplex. Alternatively, it is preferred that a tangent line is drawn at the tail of the short wavelength side of the fluorescence spectrum of the exciplex, and the energy of the wavelength of the extrapolated line is set as S E , a tangent line was drawn at the tail of the short wavelength side of the phosphorescence spectra of compound 131 and compound 133, and the energy of the wavelength of the extrapolated line was set as the T of each compound. C1 and T C3 , in this case, S is preferred E -T C1 ≤0.2eV and S E -T C3 ≦≤0.2eV.

[0106] The triplet excitation energy generated in the light-emitting layer 130 can be transmitted through the above-mentioned path A. 6 and energy transfer from the S1 level of the exciplex to the S1 level of the guest material (path A 8 ), thereby making the guest material emit light. Therefore, by using the material that forms the combination of exciplexes for the light-emitting layer 130, the light-emitting efficiency of the fluorescent light-emitting element can be improved.

[0107] Here, in the light-emitting element of one embodiment of the present invention, a guest material whose light emitter has a protecting group is used as compound 132. By adopting this structure, as described above, the reaction of the light emitter via path A can be suppressed. 9 The energy transfer based on the Dexter mechanism can be expressed, and the deactivation of triplet excitation energy can be suppressed. Therefore, a fluorescent light-emitting element with high luminous efficiency can be obtained.

[0108] In this specification, the above-mentioned path A may be referred to as 6 To A 8 This process is called ExSET (Exciplex-Singlet Energy Transfer) or ExEF (Exciplex-Enhanced Fluorescence). In other words, in the light-emitting layer 130, the excitation energy is supplied from the exciplex to the fluorescent material.

[0109] <Structural Example 3 of Light Emitting Layer> In this structural example, a case where a phosphorescent material is used as the compound 133 of the light-emitting element using the ExEF is described. That is, a case where a phosphorescent material is used for one of the compounds forming an exciplex is described.

[0110] In this structural example, a compound containing a heavy atom is used as one of the compounds for forming an exciplex. Therefore, intersystem crossing between a singlet excited state and a triplet excited state is promoted. Therefore, an exciplex capable of transitioning from a triplet excited state to a singlet ground state (i.e., capable of exhibiting phosphorescence) can be formed. At this time, unlike a general exciplex, the triplet excited energy level (T E ) is the energy level of the energy donor, so T E The singlet excitation energy level (S G Specifically, it is preferred that a tangent line be drawn at the tail of the emission spectrum of the exciplex using heavy atoms on the short wavelength side, and the energy of the wavelength of the extrapolated line be set to T E , the energy of the wavelength at the absorption end of the absorption spectrum of compound 132 is set as S G , then satisfies T E ≥S G .

[0111] In the case of such energy level correlation, the triplet excitation energy of the generated exciplex can be increased from the triplet excitation energy level (T E ) to the singlet excited level (S G ) for energy transfer. Note that the S1 energy level (S E ) and T1 level (TE ) are adjacent to each other, so it is sometimes difficult to clearly distinguish fluorescence and phosphorescence in the emission spectrum. In this case, fluorescence and phosphorescence can sometimes be distinguished based on the emission lifetime.

[0112] The phosphorescent material used in the above structure preferably contains heavy atoms such as Ir, Pt, Os, Ru, Pd, etc. That is, the energy transfer from the triplet excitation energy level of the exciplex to the singlet excitation energy level of the guest material is allowed transition. In the energy transfer from the exciplex composed of the above phosphorescent material or the above phosphorescent material to the guest material, 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 allowed transition, so it is preferred. Therefore, it is possible not to go through Figure 4C Path A in 7 The triple excitation energy of the exciplex is transferred through path A 8 The process of transferring to the S1 level (S G ). That is, you can only go through path A 6 and Path A 8 The triplet excitation energy and singlet excitation energy are transferred to the S1 energy level of the guest material. 8 In this case, the exciplex is used as the energy donor and compound 132 is used as the energy acceptor. 8 The process competes with the luminescence process of the exciplex (transfer of the exciplex from the S1 energy level or the T1 energy level to the ground state). That is, the singlet excitation energy or triplet excitation energy possessed by the exciplex is converted into the luminescence of compound 131 and the luminescence of compound 132. Therefore, a light-emitting element of one embodiment of the present invention can obtain luminescence from compound 131 and luminescence from compound 132. In addition, in this structural example, by adjusting the concentration of compound 133 in the light-emitting layer 130, luminescence from compound 133 can also be obtained.

[0113] In order to use compound 133 and the exciplex as an energy donor and also as a luminescent material, it is preferred that the concentration of compound 132 relative to the total amount of compound 131 and compound 133 be set to 0.01wt% or more and 2wt% or less. By adopting this structure, the excitation energy of compound 133 and the exciplex can be efficiently converted into the luminescence of compound 133, the luminescence of the exciplex and the luminescence of compound 132, thereby obtaining a highly efficient multicolor light-emitting element. In addition, by adjusting the concentrations of compound 131, compound 132 and compound 133, the luminescent color can be adjusted.

[0114] Here, in the light-emitting element of one embodiment of the present invention, a guest material whose light emitter has a protecting group is used as compound 132. By adopting this structure, as described above, the reaction of the light emitter via path A can be suppressed.9 The energy transfer based on the Dexter mechanism can be expressed, and the deactivation of triplet excitation energy can be suppressed. Therefore, a fluorescent light-emitting element with high luminous efficiency can be obtained.

[0115] <Structural Example 4 of Light Emitting Layer> In this structural example, using Figure 4D The case where a material having TADF characteristics is used as Compound 133 of the light-emitting element utilizing ExEF described above is described below.

[0116] Since compound 133 is a TADF material, compound 133 that does not form an exciplex has the function of converting triplet excitation energy into singlet excitation energy by upconversion ( Figure 4D Path A 10 The singlet excitation energy of compound 133 can be rapidly transferred to compound 132 ( Figure 4D Path A 11 ). In this case, preferably S C3 ≥S G .

[0117] As in the above-mentioned example of the structure of the light-emitting layer, in a light-emitting element of one embodiment of the present invention, there is a triplet excitation energy Figure 4D Path A in 6 To Path A 8 The path of transfer to compound 132 as the guest material and the triplet excitation energy through Figure 4D Path A in 10 and Path A 11 The triplet excitation energy can be transferred to the fluorescent material through multiple pathways, so the luminescence efficiency can be further improved. 8 In the pathway A, the exciplex is used as the energy donor and compound 132 is used as the energy acceptor. 11 In this case, compound 133 is used as an energy donor and compound 132 is used as an energy acceptor. 11 The process of luminescence of compound 133 (transfer of compound 133 from S1 level to ground state) competes. That is, the singlet excitation energy of compound 133 is converted into the luminescence of compound 133 and the luminescence of compound 132. Therefore, the light-emitting element of one embodiment of the present invention can obtain luminescence from compound 133 and luminescence from compound 132. In addition, as described above, path A 8The process of the exciplex competes with the process of luminescence of the exciplex (transfer of the exciplex from the S1 energy level to the ground state). In other words, the singlet excitation energy of the exciplex is converted into the luminescence of the exciplex and the luminescence of compound 132. Therefore, the light-emitting element of one embodiment of the present invention can obtain luminescence from the exciplex and luminescence from compound 132.

[0118] In order to use compound 133 and the exciplex as an energy donor and also as a luminescent material, it is preferred that the concentration of compound 132 relative to the total amount of compound 131 and compound 133 be set to 0.01wt% or more and 2wt% or less. By adopting this structure, the excitation energy of compound 133 and the exciplex can be efficiently converted into the luminescence of compound 133, the luminescence of the exciplex and the luminescence of compound 132, thereby obtaining a highly efficient multicolor light-emitting element. In addition, by adjusting the concentrations of compound 131, compound 132 and compound 133, the luminescent color can be adjusted.

[0119] In this structural example, the exciplex and compound 133 were used as energy donors, and compound 132 was used as an energy acceptor.

[0120] <Structural Example 5 of Light Emitting Layer> Figure 5A The case where four types of materials are used for the light emitting layer 130 is shown. Figure 5A The light-emitting layer 130 in the embodiment includes compound 131, compound 132, compound 133 and compound 134. In one embodiment of the present invention, compound 133 has the function of converting triplet excitation energy into light emission. In this structural example, the description is based on the premise that compound 133 is a phosphorescent material. Compound 132 is a guest material that exhibits fluorescent light emission. In addition, compound 131 is an organic compound that forms an exciplex with compound 134.

[0121] in addition, Figure 5B The energy level correlation of compound 131, compound 132, compound 133, and compound 134 in the light-emitting layer 130 is shown as follows: Figure 5B The marks and symbols in Figure 4C The markings and symbols shown are the same. ·Comp(134): Compound 134 ·S C4 :S1 energy level of compound 134 ·T C4 :T1 energy level of compound 134

[0122] In the light-emitting element of one embodiment of the present invention shown 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 ) and the T1 energy level (T E ) become adjacent energy levels (refer to Figure 5B Path A in 12 ).

[0123] The exciplex generated through the above process is as described above, and when the excitation energy is lost, the two substances forming the exciplex are used again as the original two substances.

[0124] The excited energy level of the exciplex (S E and T E ) than the S1 energy level (S C1 and S C4 ) is low, so an excited state can be formed with a lower excitation energy. As a result, the driving voltage of the light-emitting element 150 can be reduced.

[0125] Here, when compound 133 is a phosphorescent material, intersystem crossing between singlet and triplet states is allowed. Therefore, both the singlet excitation energy and triplet excitation energy of the exciplex can be quickly transferred to compound 133 (path A). 13 ). Here, it is preferred to satisfy T E ≥T C3 In addition, the triplet excitation energy of compound 133 can be efficiently converted into the singlet excitation energy of compound 132 (path A). 14 ). Here, Figure 5B As shown, at T E ≥T C3 ≥S G In the case of , the excitation energy of compound 133 is efficiently transferred to compound 132 as a guest material as singlet excitation energy, so it is preferred. Specifically, it is preferred to draw a tangent line at the tail of the short wavelength side of the phosphorescence spectrum of compound 133, and set the energy of the wavelength of the extrapolated line as T C3 , the energy of the wavelength at the absorption end of the absorption spectrum of compound 132 is set as S G , then satisfies T C3 ≥S G In addition, the peak wavelength of the emission spectrum of compound 133 preferably overlaps with the absorption band on the longest wavelength side of the absorption spectrum of compound 132. 14 In this case, compound 133 is used as an energy donor and compound 132 is used as an energy acceptor. 14The process of emitting light from compound 133 (transfer from the T1 level to the ground state of compound 133) competes. In other words, the triplet excitation energy of compound 133 is converted into the luminescence of compound 133 and the luminescence of compound 132. Therefore, the light-emitting element of one embodiment of the present invention can obtain luminescence from compound 133 and luminescence from compound 132.

[0126] In this case, the combination of Compound 131 and Compound 134 may be any combination as long as they can form an exciplex, and preferably one of them is a compound having a hole-transporting property and the other is a compound having an electron-transporting property.

[0127] In order to use compound 133 as an energy donor and also as a luminescent material, the concentration of compound 132 relative to the total amount of compound 131, compound 133 and compound 134 is preferably set to 0.01wt% or more and 2wt% or less. By adopting this structure, the excitation energy of compound 133 can be efficiently converted into the luminescence of compound 133 and the luminescence of compound 132, thereby obtaining a highly efficient multicolor light-emitting element. In addition, by adjusting the concentrations of compound 131, compound 132, compound 133 and compound 134, the luminescent color can be adjusted.

[0128] In addition, as a combination of materials that efficiently form an exciplex, it is preferred that the HOMO level of one of Compound 131 and Compound 134 is higher than the HOMO level of the other, and the LUMO level of one of Compound 131 and Compound 134 is higher than the LUMO level of the other.

[0129] In addition, the energy level correlation between compound 131 and compound 134 is not limited to Figure 5B That is, the singlet excitation level (S C1 ) can be higher than the singlet excitation level (S C4 ) can also be lower than the singlet excitation level (S C4 In addition, the triplet excitation level (T C1 ) can be higher than the triplet excitation level (T C4 ) can also be lower than the triplet excitation level (T C4 ).

[0130] In the light-emitting element of one embodiment of the present invention, Compound 131 preferably has a π-electron-deficient skeleton. With this structure, the LUMO level of Compound 131 becomes low, which is suitable for the formation of an exciplex.

[0131] In the light-emitting element of one embodiment of the present invention, Compound 131 preferably has a π-electron-rich skeleton. With such a structure, the HOMO level of Compound 131 becomes high, which is suitable for the formation of an exciplex.

[0132] Here, in the light-emitting element of one embodiment of the present invention, a guest material whose light emitter has a protecting group is used as compound 132. By adopting this structure, as described above, the reaction of the light emitter via path A can be suppressed. 15 The energy transfer based on the Dexter mechanism can be expressed, and the deactivation of triplet excitation energy can be suppressed. Therefore, a fluorescent light-emitting element with high luminous efficiency can be obtained.

[0133] Note that in this specification, the above-mentioned path A may be referred to as 12 and A 13 The process is called ExTET (Exciplex-Triplet Energy Transfer). In other words, in the light-emitting layer 130, the excitation energy is supplied from the exciplex to the compound 133. Therefore, it can be said that the present structural example is a structure in which a fluorescent material having a protective group is mixed into a light-emitting layer that can use ExTET.

[0134] <Structural Example 6 of Light Emitting Layer> In this structural example, a case where a material having TADF characteristics is used for the compound 134 described in the structural example 5 of the above-mentioned light-emitting layer is described.

[0135] Figure 5C The case where four types of materials are used for the light emitting layer 130 is shown. Figure 5C The light-emitting layer 130 in the embodiment includes compound 131, compound 132, compound 133 and compound 134. In one embodiment of the present invention, compound 133 has the function of converting triplet excitation energy into light emission. Compound 132 is a guest material exhibiting fluorescent light emission. In addition, compound 131 is an organic compound that forms an exciplex with compound 134.

[0136] Here, since compound 134 is a TADF material, compound 134 that does not form an exciplex has a function of converting triplet excitation energy into singlet excitation energy by up-conversion ( Figure 5C Path A 16 The singlet excitation energy of compound 134 can be rapidly transferred to compound 132 ( Figure 5C Path A 17 ). In this case, it is preferred to satisfy S C4 ≥S G Here, path A 17The process of emitting light from compound 134 (transfer from the S1 energy level to the ground state of compound 134) competes. That is, the singlet excitation energy of compound 134 is converted into the luminescence of compound 134 and the luminescence of compound 132. Therefore, the light-emitting element of one embodiment of the present invention can obtain luminescence from compound 134 and luminescence from compound 132. In addition, as shown in structural example 5 of the light-emitting layer, the triplet excitation energy of compound 133 can be efficiently converted into the singlet excitation energy of compound 132 (path A). 14 ), luminescence from compound 133 can also be obtained.

[0137] In order to use compound 133 and compound 134 as energy donors and also as luminescent materials, it is preferred that the concentration of compound 132 relative to the total amount of compound 131, compound 133 and compound 134 be set to 0.01wt% or more and 2wt% or less. By adopting this structure, the excitation energy of compound 133 and compound 134 can be efficiently converted into the luminescence of compound 133, the luminescence of compound 134 and the luminescence of compound 132, thereby obtaining a highly efficient multicolor light-emitting element. In addition, by adjusting the concentrations of compound 131, compound 132, compound 133 and compound 134, the luminescent color can be adjusted.

[0138] Specifically, it is preferred that a tangent line be drawn at the tail of the fluorescence spectrum of compound 134 on the short wavelength side, and the energy of the wavelength of the extrapolated line be set as S C4 , the energy of the wavelength at the absorption end of the absorption spectrum of compound 132 is set as S G , then satisfy S C4 ≥S G In addition, the emission spectrum of compound 134 preferably overlaps with the absorption band on the longest wavelength side of the absorption spectrum of compound 132.

[0139] As in the above-mentioned example of the structure of the light-emitting layer, in a light-emitting element of one embodiment of the present invention, there is a triplet excitation energy Figure 5C Path A in 12 To Path A 14 The path of transfer to compound 132 as the guest material and the triplet excitation energy through Figure 5C Path A in 16 and Path A 17 The triplet excitation energy can be transferred to the fluorescent material through multiple pathways, so the luminescence efficiency can be further improved. 14 In the reaction, compound 133 was used as an energy donor and compound 132 was used as an energy acceptor. 17In this reaction, compound 134 was used as the energy donor and compound 132 was used as the energy acceptor.

[0140] As described above, the light-emitting element of one embodiment of the present invention can obtain multicolor light emission according to the energy transfer path. In addition, by adjusting the concentration of compound 132, compound 133, and compound 134 in the light-emitting layer 130, the light emission color can be adjusted. That is, by adjusting the concentration of compound 132, compound 133, and compound 134 in the light-emitting layer 130, the light emission intensity from compound 132, the light emission intensity from compound 133, and the light emission intensity from the exciplex can be adjusted.

[0141] <Structural Example 7 of Light Emitting Layer> Figure 6B An example of energy level correlation in the light-emitting layer 130 of the light-emitting element 150 according to one embodiment of the present invention is shown. Fig. 6A The light-emitting layer 130 in the embodiment includes compound 131, compound 132 and compound 133. In one embodiment of the present invention, compound 132 is a guest material having a protective group. Compound 133 has the function of converting triplet excitation energy into light emission. In this structural example, the description is based on the premise that compound 133 is a phosphorescent material.

[0142] Figure 6B and the following Figure 6C The symbols and signs in are as follows. ·Comp(131): Compound 131 ·Comp(133): Compound 133 Guest(132): Compound 132 ·S C1 :S1 energy level of compound 131 ·T C1 :T1 energy level of compound 131 ·T C3 :T1 energy level of compound 133 ·T G :T1 energy level of compound 132 ·S G :S1 energy level of compound 132

[0143] In the light-emitting element of one embodiment of the present invention, since carrier recombination mainly occurs in the compound 131 included in the light-emitting layer 130, singlet excitons and triplet excitons are generated. Since the compound 133 here is a phosphorescent material, by selecting a compound that satisfies T C3 ≤T C1 The material with a relationship of can transfer the singlet excitation energy and triplet excitation energy generated in compound 131 to the T of compound 133.C3 energy level( Figure 6B Path A in 18 ). Note that some of the carriers may recombine in compound 133.

[0144] Note that the phosphorescent material used in the above structure preferably contains heavy atoms such as Ir, Pt, Os, Ru, and Pd. When the phosphorescent material is used as the phosphorescent material of compound 133, the energy transfer from the triplet excitation level of the energy donor to the singlet excitation level of the guest material (energy acceptor) is preferred as a transition allowed. Therefore, the triplet excitation energy of compound 133 can be transferred via path A. 19 The process of transferring to the S1 level (S G ). On path A 19 In this case, compound 133 is used as an energy donor and compound 132 is used as an energy acceptor. C3 ≥S G In the case of , the excitation energy of compound 133 is efficiently transferred to the singlet excited state of compound 132 as the guest material, so it is preferred. Here, path A 19 The process of emitting light from compound 133 (transfer from the T1 level to the ground state of compound 133) competes. In other words, the triplet excitation energy of compound 133 is converted into the luminescence of compound 133 and the luminescence of compound 132. Therefore, the light-emitting element of one embodiment of the present invention can obtain luminescence from compound 133 and luminescence from compound 132.

[0145] In order to use compound 133 as an energy donor and also as a luminescent material, it is preferred that the concentration of compound 132 relative to the total amount of compound 131 and compound 133 be set to 0.01wt% or more and 2wt% or less. By adopting this structure, the excitation energy of compound 133 can be efficiently converted into the luminescence of compound 133 and the luminescence of compound 132, thereby obtaining a highly efficient multicolor light-emitting element. In addition, by adjusting the concentrations of compound 131, compound 132, and compound 133, the luminescent color can be adjusted.

[0146] Specifically, it is preferred that a tangent line be drawn at the tail of the short-wavelength side of the phosphorescence spectrum of compound 133, and the energy of the wavelength of the extrapolated line be set as T C3 , the energy of the wavelength at the absorption end of the absorption spectrum of compound 132 is set as S G , then satisfies T C3 ≥S G In addition, the emission spectrum of compound 133 preferably overlaps with the absorption band on the longest wavelength side of the absorption spectrum of compound 132.

[0147] Here, in the light-emitting element of one embodiment of the present invention, a guest material whose light emitter has a protecting group is used as compound 132. By adopting this structure, as described above, the reaction of the light emitter via path A can be suppressed. 20 The energy transfer based on the Dexter mechanism can be expressed, and the deactivation of triplet excitation energy can be suppressed. Therefore, a fluorescent light-emitting element with high luminous efficiency can be obtained.

[0148] <Structural Example 8 of Light Emitting Layer> Figure 6C An example of energy level correlation in the light-emitting layer 130 of the light-emitting element 150 according to one embodiment of the present invention is shown. Figure 6C The light-emitting layer 130 includes compound 131, compound 132 and compound 133. In one embodiment of the present invention, compound 132 is a guest material having a protective group. In addition, compound 133 has a function of converting triplet excitation energy into light emission. In this structural example, the description is based on the premise that compound 133 is a compound having TADF characteristics.

[0149] The following is Figure 6C The marks and symbols in Figure 6B The markings and symbols shown are the same. ·S C3 :S1 energy level of compound 133

[0150] In the light-emitting element of one embodiment of the present invention, since recombination of carriers mainly occurs in the compound 131 included in the light-emitting layer 130, singlet excitons and triplet excitons are generated. C3 ≤S C1 and T C3 ≤T C1 The singlet excitation energy and triplet excitation energy generated in compound 131 can be transferred to the S of compound 133. C3 Energy level and T C3 energy level( Figure 6C Path A in 21 ). Note that some of the carriers may recombine in compound 133.

[0151] Here, since compound 133 is a TADF material, compound 133 has a function of converting triplet excitation energy into singlet excitation energy by up-conversion ( Figure 6C Path A 22 In addition, the singlet excitation energy of compound 133 can be rapidly transferred to compound 132 ( Figure 6C Path A 23 ). In this case, it is preferred to satisfy S C3 ≥S G Here, path A23 The process of emitting light from compound 133 (transfer from the S1 level to the ground state of compound 133) competes. In other words, the singlet excitation energy of compound 133 is converted into the luminescence of compound 133 and the luminescence of compound 132. Therefore, the light-emitting element of one embodiment of the present invention can obtain luminescence from compound 133 and luminescence from compound 132.

[0152] In order to use compound 133 as an energy donor and also as a luminescent material, it is preferred that the concentration of compound 132 relative to the total amount of compound 131 and compound 133 be set to 0.01wt% or more and 2wt% or less. By adopting this structure, the excitation energy of compound 133 can be efficiently converted into the luminescence of compound 133 and the luminescence of compound 132, thereby obtaining a highly efficient multicolor light-emitting element. In addition, by adjusting the concentrations of compound 131, compound 132, and compound 133, the luminescent color can be adjusted.

[0153] Specifically, it is preferred that a tangent line be drawn at the tail of the fluorescence spectrum of compound 133 on the short wavelength side, and the energy of the wavelength of the extrapolated line be set as S C3 , the energy of the wavelength at the absorption end of the absorption spectrum of compound 132 is set as S G , then satisfy S C3 ≥S G In addition, the emission spectrum of compound 133 preferably overlaps with the absorption band on the longest wavelength side of the absorption spectrum of compound 132. 21 To Path A 23 The process can convert the triplet excitation energy in the light-emitting layer 130 into the fluorescent light of the compound 132. 23 In this reaction, compound 133 was used as the energy donor and compound 132 was used as the energy acceptor.

[0154] Here, in the light-emitting element of one embodiment of the present invention, a guest material whose light emitter has a protecting group is used as compound 132. By adopting this structure, as described above, the reaction of the light emitter via path A can be suppressed. 24 The energy transfer based on the Dexter mechanism can be expressed, and the deactivation of triplet excitation energy can be suppressed. Therefore, a fluorescent light-emitting element with high luminous efficiency can be obtained.

[0155] <Energy transfer mechanism> The Foster mechanism and the Dexter mechanism are described below. Although the energy transfer process between molecules of the first material and the second material is described here in relation to the supply of excitation energy from the first material in an excited state to the second material in a ground state, the same is true when either of the above is an exciplex.

[0156] Foster Mechanism In the Förster mechanism, direct contact between molecules is not required for energy transfer, and energy transfer occurs through the resonance phenomenon of dipole oscillation between the first material and the second material. Through the resonance phenomenon of dipole oscillation, the first material supplies energy to the second material, the excited state of the first material becomes the ground state, and the ground state of the second material becomes the excited state. In addition, the rate constant k of the Förster mechanism is shown in equation (1): h*→g .

[0157] [Formula 1]

[0158] In formula (1), ν represents the oscillation number, f' h (ν) represents the normalized emission spectrum of the first material (fluorescence spectrum when discussing energy transfer from a singlet excited state, phosphorescence spectrum when discussing energy transfer from a triplet excited state), ε g (ν) represents the molar absorption coefficient of the second material, N represents the Avogadro number, n represents the refractive index of the medium, R represents the molecular distance between the first material and the second material, τ represents the lifetime of the excited state measured (fluorescence lifetime or phosphorescence lifetime), c represents the speed of light, φ represents the luminescence quantum yield (fluorescence quantum yield when discussing energy transfer from a singlet excited state, and phosphorescence quantum yield when discussing energy transfer from a triplet excited state), K 2 A coefficient (0 to 4) representing the orientation of the transition dipole moment of the first material and the second material. In addition, in the random orientation, K 2 =2 / 3.

[0159] Dexter Mechanism In the Dexter mechanism, the first material and the second material are close to the contact effective distance that causes the overlap of orbits, and energy transfer occurs by exchanging the electrons of the first material in the excited state and the electrons of the second material in the ground state. In addition, the rate constant k of the Dexter mechanism is shown in equation (2): h*→g .

[0160] [Formula 2]

[0161] In equation (2), h represents Planck's constant, K represents a constant with energy dimension, ν represents the oscillation number, and f' h (ν) represents the normalized emission spectrum of the first material (fluorescence spectrum when discussing energy transfer from a singlet excited state, phosphorescence spectrum when discussing energy transfer from a triplet excited state), ε' g (ν) represents the normalized absorption spectrum of the second material, L represents the effective molecular radius, and R represents the molecular distance between the first material and the second material.

[0162] Here, the energy transfer efficiency from the first material to the second material is φ ET It is expressed as formula (3). r represents the rate constant of the light emission process of the first material (fluorescence when discussing energy transfer from a singlet excited state, phosphorescence when discussing energy transfer from a triplet excited state), k n represents the rate constant of the non-luminescent process (thermal deactivation or intersystem crossing) of the second material, and τ represents the measured lifetime of the excited state of the first material.

[0163] [Formula 3]

[0164] From equation (3), we can see that in order to improve the energy transfer efficiency φ ET , which can increase the rate constant k of energy transfer h*→g To make other competition rate constants k r +k n (=1 / τ) becomes relatively smaller.

[0165] Concepts for enhancing energy transfer First, consider the energy transfer based on the Förster mechanism. By substituting equation (1) into equation (3), τ can be eliminated. Therefore, in the Förster mechanism, the energy transfer efficiency φ ET It does not depend on the lifetime τ of the excited state of the first material. In addition, when the luminescence quantum yield φ is high, it can be said that the energy transfer efficiency φ ET Higher.

[0166] In addition, the overlap between the emission spectrum of the first material and the absorption spectrum of the second material (equivalent to the absorption of the transition from the singlet ground state to the singlet excited state) is preferably large. Furthermore, the molar absorptivity of the second material is preferably high. This means that the emission spectrum of the first material overlaps with the absorption band present on the longest wavelength side of the second material. Note that since the direct transition from the singlet ground state to the triplet excited state in the second material is prohibited, the molar absorptivity in the triplet excited state in the second material is so small that it can be ignored. As a result, the energy transfer process from the excited state of the first material to the triplet excited state of the second material based on the Förster mechanism can be ignored, and only the energy transfer process to the singlet excited state of the second material needs to be considered.

[0167] In addition, according to formula (1), the energy transfer rate based on the Foster mechanism is inversely proportional to the sixth power of the molecular distance R between the first material and the second material. As described above, when R is less than 1 nm, the energy transfer based on the Dexter mechanism is dominant. Therefore, in order to suppress the energy transfer based on the Dexter mechanism while increasing the energy transfer rate based on the Foster mechanism, the molecular distance is preferably greater than 1 nm and less than 10 nm. Therefore, the above-mentioned protecting group is required to be not too large, and the number of carbon atoms constituting the protecting group is preferably greater than 3 and less than 10.

[0168] Next, consider the energy transfer based on the Dexter mechanism. From equation (2), we can see that in order to increase the rate constant k h*→g The overlap between the emission spectrum of the first material (fluorescence spectrum when discussing energy transfer from a singlet excited state, phosphorescence spectrum when discussing energy transfer from a triplet excited state) and the absorption spectrum of the second material (equivalent to the absorption of the transition from a singlet ground state to a singlet excited state) is preferably large. Therefore, the energy transfer efficiency can be optimized by overlapping the emission spectrum of the first material with the absorption band on the longest wavelength side of the second material.

[0169] In addition, when equation (2) is substituted into equation (3), it can be seen that the energy transfer efficiency φ in the Dexter mechanism is ET Depends on τ. Since the Dexter mechanism is an energy transfer process based on electron exchange, energy transfer from the triplet excited state of the first material to the triplet excited state of the second material also occurs in addition to energy transfer from the singlet excited state of the first material to the singlet excited state of the second material.

[0170] In the light-emitting element of one embodiment of the present invention, the second material is a fluorescent material, so the energy transfer efficiency to the triplet excited state of the second material is preferably low. In other words, 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.

[0171] As described above, the energy transfer efficiency based on the Förster mechanism does not depend on the lifetime τ of the excited state of the first material. On the other hand, the energy transfer efficiency based on the Dexter mechanism depends on the excitation lifetime τ of the first material. In order to reduce the energy transfer efficiency based on the Dexter mechanism, the excitation lifetime τ of the first material is preferably short.

[0172] 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 have the function of converting triplet excitation energy into luminescence. The energy transfer efficiency of the Förster mechanism depends on the luminescence quantum yield of the energy donor. Therefore, the first material that can convert the energy of the triplet excited state into luminescence, such as a phosphorescent material, an exciplex or a TADF material, can utilize the Förster mechanism to transfer its excitation energy to the second material. On the other hand, through the structure of one embodiment of the present invention, the antisystem crossing from the triplet excited state to the singlet excited state of the first material (exciplex or TADF material) can be promoted, and the excitation lifetime τ of the triplet excited state of the first material can be shortened. In addition, the transition from the triplet excited state to the singlet ground state of the first material (phosphorescent material or an exciplex using a phosphorescent material) can be promoted, and the excitation lifetime τ of the triplet excited state of the first material can be shortened. As a result, the energy transfer efficiency based on the Dexter mechanism from the triplet excited state of the first material to the triplet excited state of the fluorescent material (second material) can be reduced.

[0173] In a light-emitting element of one embodiment of the present invention, as described above, a fluorescent material having a protective group is used as the second material. Therefore, the molecular distance between the first material and the second material can be made large. Therefore, in a light-emitting element of one embodiment of the present invention, by using a material having a function of converting triplet excitation energy into luminescence for the first material and using a fluorescent material having a protective group for the second material, the energy transfer efficiency based on the Dexter mechanism can be reduced. As a result, the non-radiative deactivation of the triplet excitation energy in the light-emitting layer 130 can be suppressed, thereby providing a light-emitting element with high luminous efficiency.

[0174] <Materials> Next, components of a light-emitting element according to one embodiment of the present invention are described.

[0175] Luminous Layer The materials that can be used for the light-emitting layer 130 are described below. In the light-emitting layer of the light-emitting element of one embodiment of the present invention, an energy acceptor having the function of converting triplet excitation energy into light emission and an energy donor whose light emitter has a protective group are used. As materials having the function of converting triplet excitation energy into light emission, TADF characteristic materials and phosphorescent materials can be cited.

[0176] Examples of the luminescent material of compound 132 used as an energy acceptor include a phenanthrene skeleton, a stilbene skeleton, an acridone skeleton, a phenoxazine skeleton, a phenothiazine skeleton, and the like. In particular, a naphthalene skeleton, an anthracene skeleton, a fluorene skeleton, Fluorescent materials having a chrysene skeleton, a triphenylene skeleton, a tetracene skeleton, a pyrene skeleton, a perylene skeleton, a coumarin skeleton, a quinacridone skeleton, or a naphthobisbenzofuran skeleton are preferred because they have high fluorescence quantum yields.

[0177] 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 alkyl group having 3 to 10 carbon atoms, or a trialkylsilyl group having 3 to 12 carbon atoms.

[0178] Examples of the alkyl group having 1 to 10 carbon atoms include methyl, ethyl, propyl, pentyl, and hexyl groups, and particularly preferred are branched alkyl groups having 3 to 10 carbon atoms described below. Note that the alkyl group is not limited thereto.

[0179] As the cycloalkyl group having 3 or more and 10 or less carbon atoms, cyclopropyl, cyclobutyl, cyclohexyl, norbornyl, adamantyl, etc. can be cited. The cycloalkyl group is not limited thereto. In addition, when the cycloalkyl group has a substituent, as the substituent, alkyl groups having 1 to 7 carbon atoms such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, and hexyl, cycloalkyl groups having 5 to 7 carbon atoms such as cyclopentyl, cyclohexyl, cycloheptyl, and 8,9,10-trinorbornyl, and aryl groups having 6 to 12 carbon atoms such as phenyl, naphthyl, biphenyl, etc. can be cited.

[0180] Examples of the branched alkyl group having 3 to 10 carbon atoms include isopropyl, sec-butyl, isobutyl, tert-butyl, isopentyl, sec-pentyl, tert-pentyl, neopentyl, isohexyl, 3-methylpentyl, 2-methylpentyl, 2-ethylbutyl, 1,2-dimethylbutyl, and 2,3-dimethylbutyl. The branched alkyl group is not limited thereto.

[0181] Examples of the trialkylsilyl group having 3 to 12 carbon atoms include a trimethylsilyl group, a triethylsilyl group, a tert-butyldimethylsilyl group, etc. The trialkylsilyl group is not limited thereto.

[0182] In addition, as the molecular structure of the energy acceptor, it is preferred that the luminophore is bonded to two or more diarylamino groups and each aryl group possessed by the diarylamino group has at least one protecting group. More preferably, at least two protecting groups are bonded to each aryl group. This is because: the more the number of protecting groups, the greater the effect of suppressing energy transfer based on the Dexter mechanism when the guest material is used in the light-emitting layer. In order to suppress the increase in molecular weight and maintain sublimation, the diarylamino group is preferably a diphenylamino group.

[0183] By bonding two or more amino groups to a light emitter, a fluorescent material with a high quantum yield can be obtained while adjusting the luminescent color. In addition, the amino group is preferably bonded to a symmetrical position relative to the light emitter. By adopting this structure, a fluorescent material with a high quantum yield can be realized.

[0184] In addition, the protecting group may be bonded to the luminophore via the aryl group possessed by the diarylamine, rather than directly bonding the protecting group to the luminophore. By adopting this structure, the protecting group can be arranged in a manner covering the luminophore, so the distance between the host material and the luminophore can be made long from all directions, which is preferred. In addition, when the protecting group is not directly bonded to the luminophore, it is preferred to bond four or more protecting groups to one luminophore.

[0185] In addition, if Figure 3A and Figure 3B As shown, it is preferred that at least one of the atoms constituting the plurality of protecting groups is located directly on the luminophore, that is, directly on one face of the fused aromatic ring or the fused heteroaromatic ring, and at least one of the atoms constituting the plurality of protecting groups is located directly on another face of the fused aromatic ring or the fused heteroaromatic ring. As a specific method, the following structure can be cited. That is, the fused aromatic ring or the fused heteroaromatic ring of the luminophore is bonded to two or more diphenylamino groups, and the phenyl groups in the two or more diphenylamino groups each independently have protecting groups at the 3-position and the 5-position.

[0186] By adopting such a structure, Figure 3A and Figure 3B As shown, the configuration in which the protecting group at the 3-position or 5-position on the phenyl group is located directly on the condensed aromatic ring or condensed heteroaromatic ring of the luminophore can be realized. As a result, the upper and lower surfaces of the condensed aromatic ring or the condensed heteroaromatic ring can be efficiently covered, and the energy transfer based on the Dexter mechanism can be suppressed.

[0187] As the energy acceptor material, for example, an organic compound represented by the following general formula (G1) or (G2) can be used.

[0188] [Chemical formula 2]

[0189] In the general formulae (G1) and (G2), A represents a substituted or unsubstituted fused aromatic ring having 10 to 30 carbon atoms or a substituted or unsubstituted fused heteroaromatic ring having 10 to 30 carbon atoms, Ar 1 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 any one of a branched alkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, and a trialkylsilyl group having 3 to 12 carbon atoms. 1 To R 10Each independently represents any one of hydrogen, an alkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, and a trialkylsilyl group having 3 to 12 carbon atoms.

[0190] As the aromatic hydrocarbon group having 6 to 13 carbon atoms, phenyl, biphenyl, naphthyl, fluorenyl, etc. can be cited. Note that the aromatic hydrocarbon group is not limited thereto. In addition, when the aromatic hydrocarbon group has a substituent, as the substituent, alkyl groups having 1 to 7 carbon atoms such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, hexyl, cycloalkyl groups having 5 to 7 carbon atoms such as cyclopentyl, cyclohexyl, cycloheptyl, 8,9,10-tribornyl, phenyl, naphthyl, biphenyl, etc., aryl groups having 6 to 12 carbon atoms, etc. can be cited.

[0191] In the general formula (G1), a substituted or unsubstituted fused aromatic ring having 10 to 30 carbon atoms or a substituted or unsubstituted fused heteroaromatic ring having 10 to 30 carbon atoms represents the above-mentioned luminophore, and the above-mentioned skeleton can be used. In the general formulas (G1) and (G2), X 1 To X 12 Represents a protecting group.

[0192] In the general formula (G2), the protecting group is bonded to the quinacridone skeleton which is the luminophore via the arylene group. By adopting this structure, the protecting group can be configured in a manner covering the luminophore, so that the energy transfer based on the Dexter mechanism can be suppressed. In addition, it is also possible to have a protecting group directly bonded to the luminophore.

[0193] As the energy acceptor material, an organic compound represented by the following general formula (G3) or (G4) can be used.

[0194] [Chemical formula 3]

[0195] In the general formulae (G3) and (G4), A represents a substituted or unsubstituted fused aromatic ring having 10 to 30 carbon atoms or a substituted or unsubstituted fused heteroaromatic ring having 10 to 30 carbon atoms, and X 1 To X 12 each independently represents any one of a branched alkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, and a trialkylsilyl group having 3 to 12 carbon atoms,

[0196] The protecting group is preferably bonded to the luminophore through a phenylene group. By adopting this structure, the protecting group can be configured in a manner that covers the luminophore, so the energy transfer based on the Dexter mechanism can be suppressed. In addition, when the luminophore and the protecting group are bonded through 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 position. By adopting this structure, the luminophore can be efficiently covered, so the energy transfer based on the Dexter mechanism can be suppressed. As an example of an organic compound represented by general formula (G3), the above-mentioned 2tBu-mmtBuDPhA2Anth can be cited. That is, in one embodiment of the present invention, general formula (G3) is a particularly preferred example.

[0197] As the energy acceptor material, an organic compound represented by the following general formula (G5) can be used.

[0198] [Chemical formula 4]

[0199] In the general formula (G5), X 1 To X 8 each independently represents any one of a branched alkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, and a trialkylsilyl group having 3 to 12 carbon atoms, and R 11 To R 18 Each independently represents any one of hydrogen, a branched 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 12 carbon atoms, and a substituted or unsubstituted aryl group having 6 to 25 carbon atoms.

[0200] As the aryl group having a carbon number of 6 or more and 25 or less, for example, phenyl, naphthyl, biphenyl, fluorenyl, spirofluorenyl, etc. can be cited. Note that the aryl group having a carbon number of 6 or more and 25 or less is not limited thereto. In addition, when the aryl group has a substituent, as the substituent, an alkyl group having a carbon number of 1 or more and 10 or less, a branched alkyl group having a carbon number of 3 or more and 10 or less, a substituted or unsubstituted cycloalkyl group having a carbon number of 3 or more and 10 or less, and a trialkylsilyl group having a carbon number of 3 or more and 12 or less can be cited.

[0201] Anthracene compounds have high luminescence quantum yields and their luminophores have a small area, so the protective groups can efficiently cover the upper and lower surfaces of the anthracene. An example of an organic compound represented by the general formula (G5) is the above-mentioned 2tBu-mmtBuDPhA2Anth.

[0202] Examples of compounds listed in general formulae (G1) to (G5) are shown below by structural formulae (102) to (105) and (200) to (284). Note that the compounds listed in general formulae (G1) to (G5) are not limited thereto. In addition, the compounds represented by structural formulae (102) to (105) and (200) to (284) can be appropriately used as guest materials of a light-emitting element of one embodiment of the present invention. Note that the guest material is not limited thereto.

[0203] [Chemical formula 5]

[0204] [Chemical formula 6]

[0205] [Chemical formula 7]

[0206] [Chemical formula 8]

[0207] [Chemical formula 9]

[0208] [Chemical formula 10]

[0209] [Chemical formula 11]

[0210] [Chemical formula 12]

[0211] [Chemical formula 13]

[0212] [Chemical formula 14]

[0213] [Chemical formula 15]

[0214] [Chemical formula 16]

[0215] [Chemical formula 17]

[0216] [Chemical formula 18]

[0217] [Chemical formula 19]

[0218] [Chemical formula 20]

[0219] [Chemical formula 21]

[0220] [Chemical formula 22]

[0221] [Chemical formula 23]

[0222] [Chemical formula 24]

[0223] [Chemical formula 25]

[0224] [Chemical formula 26]

[0225] Structural formulas (100) and (101) represent examples of materials that can be preferably used as a guest material in a light-emitting element of one embodiment of the present invention. Note that the guest material is not limited to these.

[0226] [Chemical formula 27]

[0227] When compound 133 is used as an energy donor, for example, a TADF material may be used. Preferably, the energy difference between the S1 energy level and the T1 energy level of compound 133 is small, specifically, greater than 0 eV and less than 0.2 eV.

[0228] Compound 133 preferably includes a skeleton having hole transport properties and a skeleton having electron transport properties. Alternatively, compound 133 preferably has a π-electron-rich skeleton or an aromatic amine skeleton and has a π-electron-deficient skeleton. It is thus easy to form a donor-acceptor type excited state in the molecule. Furthermore, it is preferred that a structure in which a skeleton having electron transport properties is directly bonded to a skeleton having hole transport properties is included in a manner that simultaneously enhances donor properties and acceptor properties in the molecule of compound 133. Alternatively, it is preferred that a structure in which a π-electron-rich skeleton or an aromatic amine skeleton is directly bonded to a π-electron-deficient skeleton is included. By simultaneously enhancing donor properties and acceptor properties in the molecule, the region where the molecular orbital distribution of HOMO overlaps with the region where the molecular orbital distribution of LUMO overlaps can be reduced in compound 133, and the energy difference between the singlet excitation energy level and the triplet excitation energy level of compound 133 can be reduced. In addition, the triplet excitation energy level of compound 133 can be kept high.

[0229] When the TADF material is composed of one material, for example, the following materials can be used.

[0230] First, fullerene or its derivatives, acridine derivatives such as protoflavin, eosin, etc. can be cited. In addition, metal-containing porphyrins containing magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In) or palladium (Pd) can be cited. As the metal-containing porphyrin, for example, protoporphyrin-tin fluoride complex (SnF 2 (Proto IX)), mesoporphyrin-tin fluoride complex (SnF 2 (Meso IX)), hematoporphyrin-tin fluoride complex (SnF 2 (Hemato IX)), coproporphyrin tetramethyl ester-tin fluoride complex (SnF 2 (Copro III-4Me)), octaethylporphyrin-tin fluoride complex (SnF 2 (OEP)), protoporphyrin-tin fluoride complex (SnF 2 (Etio I)), octaethylporphyrin-platinum chloride complex (PtCl 2 OEP) etc.

[0231] [Chemical formula 28]

[0232] In addition, as a TADF material composed of a single material, heterocyclic compounds having a π-electron-rich skeleton and a π-electron-deficient skeleton can also be used. Specifically, 2-(biphenyl-4-yl)-4,6-bis(12-phenylindolo[2,3-a]carbazole-11-yl)-1,3,5-triazine (abbreviated as: PIC-TRZ), 2-{4-[3-(N-phenyl-9H-carbazole-3-yl)-9H-carbazole-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviated as: PCCzPTzn), 2 -[4-(10H-phenoxazine-10-yl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviated as PXZ-TRZ), 3-[4-(5-phenyl-5,10-dihydrophenazine-10-yl)phenyl]-4,5-diphenyl-1,2,4-triazole (abbreviated as PPZ-3TPT), 3-(9,9-dimethyl-9H-acridin-10-yl)-9H-xanthene-9 -ketone (abbreviation: ACRXTN), bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone (abbreviation: DMAC-DPS), 10-phenyl-10H,10'H-spiro[acridine-9,9'-anthracen]-10'-one (abbreviation: ACRSA), 4-(9'-phenyl-3,3'-bi-9H-carbazole-9-yl)benzofurano[3,2-d]pyrimidine (abbreviation: :4PCCzBfpm), 4-[4-(9'-phenyl-3,3'-bi-9H-carbazole-9-yl)phenyl]benzofurano[3,2-d]pyrimidine (abbreviation: 4PCCzPBfpm), 9-[3-(4,6-diphenyl-1,3,5-triazine-2-yl)phenyl]-9'-phenyl-2,3'-bi-9H-carbazole (abbreviation: mPCCzPTzn-02), etc. This heterocyclic compound has a π-electron-rich heteroaromatic ring and a π-electron-deficient heteroaromatic ring, so it has high electron transport and hole transport properties, so it is preferred. In particular, among the skeletons with π-electron-deficient heteroaromatic rings, the pyridine skeleton, the diazine skeleton (pyrimidine skeleton, pyrazine skeleton, pyridazine skeleton) and the triazine skeleton are stable and have good reliability, so they are preferred. In particular, the benzofuran pyrimidine skeleton, the benzothiophene pyrimidine skeleton, the benzofuran pyrazine skeleton, and the benzothiophene pyrazine skeleton have high acceptor properties and good reliability, so they are preferred. In addition, among the skeletons having π-electron-rich heteroaromatic rings, the acridine skeleton, the phenoxazine skeleton, the phenothiazine skeleton, the furan skeleton, the thiophene skeleton, and the pyrrole skeleton are stable and have good reliability, so it is preferred to have at least one of the above skeletons. In addition, as the furan skeleton, a dibenzofuran skeleton is preferably used, and as the thiophene skeleton, a dibenzothiophene skeleton is preferably used. As the pyrrole skeleton, an indole skeleton, a carbazole skeleton, a bicarbazole skeleton, and a 3-(9-phenyl-9H-carbazole-3-yl)-9H-carbazole skeleton are particularly preferably used.In addition, in a substance in which a π-electron-rich heteroaromatic ring and a π-electron-deficient heteroaromatic ring are directly bonded, the donor property of the π-electron-rich heteroaromatic ring and the acceptor property of the π-electron-deficient heteroaromatic ring are both strong, and the difference in energy level between the singlet excited state and the triplet excited state becomes small, so it is particularly preferred. In addition, an aromatic ring bonded with an electron-withdrawing group such as a cyano group can also be used instead of a π-electron-deficient heteroaromatic ring.

[0233] [Chemical formula 29]

[0234] When compound 133 does not have the function of converting triplet excitation energy into luminescence, as a combination of compound 131 and compound 133 or a combination of compound 131 and compound 134, it is preferred that the combination forms an exciplex with each other, but there is no particular limitation. Preferably, one has the function of transmitting electrons and the other has the function of transmitting holes. As compound 131, in addition to zinc and aluminum metal complexes, oxadiazole derivatives, triazole derivatives, benzimidazole derivatives, quinoxaline derivatives, dibenzoquinoxaline derivatives, dibenzothiophene derivatives, dibenzofuran derivatives, pyrimidine derivatives, triazine derivatives, pyridine derivatives, bipyridine derivatives, phenanthroline derivatives, etc. can also be cited. As other examples, aromatic amines or carbazole derivatives can be cited.

[0235] In addition, for example, the following hole transporting materials and electron transporting materials can be used.

[0236] As the hole transport material, a material having a hole transport property higher than an electron transport property can be used, and preferably a material having a 1×10 -6 cm 2 / Vs or higher. Specifically, aromatic amines, carbazole derivatives, aromatic hydrocarbons, stilbene derivatives, etc. can be used. The hole transport material may also be a polymer compound.

[0237] As materials with high hole transport properties, for example, as aromatic amine compounds, there can be mentioned N,N'-di(p-tolyl)-N,N'-diphenyl-p-phenylenediamine (abbreviation: DTDPPA), 4,4'-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation: DPAB), N,N'-bis{4-[bis(3-methylphenyl)amino]phenyl}-N,N'-diphenyl-(1,1'-biphenyl)-4,4'-diamine (abbreviation: DNTPD), 1,3,5-tris[N-(4-diphenylaminophenyl)-N-phenylamino]benzene (abbreviation: DPA3B), etc.

[0238] In addition, specific examples of carbazole derivatives include 3-[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole (abbreviated as PCzDPA1), 3,6-bis[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole (abbreviated as PCzDPA2), 3,6-bis[N-(4-diphenylaminophenyl)-N-(1-naphthyl)amino]-9-phenylcarbazole (abbreviated as PCzDPA3), : PCzTPN2), 3-[N-(9-phenylcarbazole-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviated as: PCzPCA1), 3,6-bis[N-(9-phenylcarbazole-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviated as: PCzPCA2), 3-[N-(1-naphthyl)-N-(9-phenylcarbazole-3-yl)amino]-9-phenylcarbazole (abbreviated as: PCzPCN1), etc.

[0239] In addition, examples of carbazole derivatives 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-anthracenyl)phenyl]-9H-carbazole (abbreviation: CzPA), and 1,4-bis[4-(N-carbazolyl)phenyl]-2,3,5,6-tetraphenylbenzene.

[0240] Examples of the aromatic hydrocarbons 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'-bianthracene, 10,10'-diphenyl-9,9'-bianthracene, 10,10'-bis(2-phenylphenyl)-9,9'-bianthracene, 10,10'-bis[(2,3,4,5,6-pentaphenyl)phenyl]-9,9'-bianthracene, anthracene, tetracene, rubrene, perylene, 2,5,8,11-tetra(tert-butyl)perylene, and the like. In addition, pentacene, coronene, and the like can also be used. Thus, it is more preferable to use a 1×10 -6 cm 2 / Vs or more and an aromatic hydrocarbon having 14 to 42 carbon atoms.

[0241] Note that the aromatic hydrocarbon may also have a vinyl skeleton. Examples of the aromatic hydrocarbon having 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).

[0242] In addition, polymer compounds such as poly(N-vinylcarbazole) (abbreviation: PVK), poly(4-vinyltriphenylamine) (abbreviation: PVTPA), poly[N-(4-{N'-[4-(4-diphenylamino)phenyl]phenyl-N'-phenylamino}phenyl)methacrylamide] (abbreviation: PTPDMA), and poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine] (abbreviation: Poly-TPD) can also be used.

[0243] In addition, as a material with high hole transport properties, for example, 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviated as: NPB or α-NPD), N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (abbreviated as: TPD), 4,4',4"-tri(carbazol-9-yl)triphenylamine (abbreviated as: TCTA), 4,4',4"-tri[N-(1-naphthyl)-N-phenylamino]triphenylamine (abbreviated as: 1'-TNATA), 4,4',4"-tri(N,N-diphenylamino)triphenylamine (abbreviated as: TDATA), 4,4',4"-tri[N-(3-methylphenyl)-N-phenylamino]triphenylamine amine (abbreviation: MTDATA), 4,4'-bis[N-(spiro-9,9'-difluoren-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)biphenylamine triphenylamine (abbreviation: PCBAB), 4-(1-naphthyl)-4'-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBNBB), 4-phenyl-4'-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: DPNF), 2-[N-(4-diphenylaminophenyl)-N-phenylamino]spiro-9,9'-difluorene (abbreviation: DPASF), 4-phenyl-4'-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4'-diphenyl-4"-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBBi1BP), 4-(1-naphthyl)-4'-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBANB), 4,4'-di(1-naphthyl)-4"-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBNBB), 4-phenyl-4'-(9-phenyl-9H -carbazole-3-yl)amine (abbreviation: PCA1BP), N,N'-bis(9-phenylcarbazole-3-yl)-N,N'-diphenylbenzene-1,3-diamine (abbreviation: PCA2B), N,N',N"-triphenyl-N,N',N"-tri(9-phenylcarbazole-3-yl)benzene-1,3,5-triamine (abbreviation: PCA3B), N-(4-biphenyl)-N-(9,9-dimethyl-9H-fluoren-2-yl)-9-phenyl-9H-carbazole-3-amine (abbreviation: PCBiF), N-(1,1'-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazole-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'-difluoren-2-amine (abbreviation: PCBASF), 2-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]spiro-9,9'-difluoren-2-amine (abbreviation: PCASF), 2,7 -Bis[N-(4-diphenylaminophenyl)-N-phenylamino]spiro-9,9'-difluorene (abbreviation: DPA2SF), N-[4-(9H-carbazole-9-yl)phenyl]-N-(4-phenyl)phenylaniline (abbreviation: YGA1BP), N,N'-bis[4-(carbazole-9-yl)phenyl]-N,N'-diphenyl-9,9-dimethylfluorene-2,7-diamine (abbreviation: YGA2F) and other aromatic amine compounds. In addition, 3-[4-(1-naphthyl)-phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPN), 3-[4-(9-phenanthrenyl)-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)tris(dibenzofuran) (abbreviation: abbreviation: DBF3P-II), 1,3,5-tris(dibenzothiophene-4-yl)benzene (abbreviation: DBT3P-II), 2,8-diphenyl-4-[4-(9-phenyl-9H-fluorene-9-yl)phenyl]dibenzothiophene (abbreviation: DBTFLP-III), 4-[4-(9-phenyl-9H-fluorene-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviation: DBTFLP-IV), 4-[3-(triphenylene-2-yl)phenyl]dibenzothiophene (abbreviation: mDBTPTp-II) and other amine compounds, carbazole compounds, thiophene compounds, furan compounds, fluorene compounds, triphenylene compounds, phenanthrene compounds, etc. The substances described here are mainly those with a hole mobility of 1×10, -6 cm 2 However, any substance other than the above substances may be used as long as the substance has a higher hole-transporting property than an electron-transporting property.

[0244] As the electron transport material, a material having a higher electron transport property than a hole transport property can be used, and preferably a material having a 1×10 -6 cm 2 / Vs or more of the electron mobility. As the material that easily receives electrons (material with electron transport properties), π-electron-deficient heteroaromatic compounds or metal complexes such as nitrogen-containing heteroaromatic compounds can be used. As specific examples, metal complexes including quinoline ligands, benzoquinoline ligands, oxazole ligands or thiazole ligands, oxadiazole derivatives, triazole derivatives, phenanthroline derivatives, pyridine derivatives, bipyridine derivatives, pyrimidine derivatives, etc. can be cited.

[0245] For example, a metal complex having a quinoline skeleton or a benzoquinoline skeleton such as tris(8-hydroxyquinoline)aluminum(III) (abbreviated as Alq), tris(4-methyl-8-hydroxyquinoline)aluminum(III) (abbreviated as Almq) or the like can be used. 3 ), bis(10-hydroxybenzo[h]quinolinolato)beryllium(II) (abbreviated as: BeBq 2), bis(2-methyl-8-hydroxyquinoline)(4-phenylphenol)aluminum(III) (abbreviated as BAlq), bis(8-hydroxyquinoline)zinc(II) (abbreviated as Znq), etc. In addition, metal complexes having oxazolyl or thiazole ligands such as bis[2-(2-benzoxazolyl)phenol]zinc(II) (abbreviated as ZnPBO) and bis[2-(2-benzothiazolyl)phenol]zinc(II) (abbreviated as ZnBTZ) can also be used.In addition to the metal complex, 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazole-2-yl]benzene (abbreviation: OXD-7), 9-[4-(5-phenyl-1,3,4-oxadiazole-2-yl)phenyl]-9H-carbazole (abbreviation: CO11), 3-(4-biphenyl)-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-(dibenzothiophene-4-yl)-1,3,4-oxadiazole-2-yl]phenyl]-9H-carbazole (abbreviation: CO11), phenyl]-1-phenyl-1H-benzimidazole (abbreviated as: mDBTBIm-II), bathophenanthroline (abbreviated as: BPhen), 2,9-bis(naphthalene-2-yl)-4,7-diphenyl-1,10-phenanthroline (abbreviated as: NBPhen), bathocuproin (abbreviated as: BCP) and other heterocyclic compounds; 2-[3-(dibenzothiophene-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviated as: 2mDBTPDBq-II), 2-[3'-(dibenzothiophene-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviated as: 2mDBTBPDBq-II), 2-[3'-(9H-carbazole-9-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviated as: 2mC zBPDBq), 2-[4-(3,6-diphenyl-9H-carbazole-9-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviated as: 2CzPDBq-III), 7-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviated as: 7mDBTPDBq-II), 6-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviated as: 6mDBTPDBq-II), 4,6-bis[3-(phenanthrene-9-yl)phenyl]pyrimidine (abbreviated as: 4,6mPnP2Pm), 4,6-bis[3-(4-dibenzothiophene)phenyl]pyrimidine (abbreviated as: 4,6mDBTP2Pm-II), 4,6-bis[3-(9H -carbazole-9-yl)phenyl]pyrimidine (abbreviation: 4,6mCzP2Pm) and other heterocyclic compounds having a diazine skeleton; 2-{4-[3-(N-phenyl-9H-carbazole-3-yl)-9H-carbazole-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: PCCzPTzn) and other heterocyclic compounds having a triazine skeleton; 3,5-bis[3-(9H-carbazole-9-yl)phenyl]pyridine (abbreviation: 35DCzPPy), 1,3,5-tris[3-(3-pyridyl)phenyl]benzene (abbreviation: TmPyPB) and other heterocyclic compounds having a pyridine skeleton; 4,4'-bis(5-methylbenzoxazolyl-2-yl)stilbene (abbreviation: BzOs) and other heteroaromatic compounds.In addition, polymer compounds such as poly(2,5-pyridinediyl) (abbreviated as PPy), poly[(9,9-dihexylfluorene-2,7-diyl)-co-(pyridine-3,5-diyl)] (abbreviated as PF-Py), and poly[(9,9-dioctylfluorene-2,7-diyl)-co-(2,2'-bipyridine-6,6'-diyl)] (abbreviated as PF-BPy) can also be used. The substances described here mainly have an electron mobility of 1×10. -6 cm 2 Note that any substance other than the above substances may be used as long as it has a higher electron-transporting property than a hole-transporting property.

[0246] Compound 133 or compound 134 is preferably a material that can form an exciplex with compound 131. Specifically, hole transport materials and electron transport materials as shown above can be used. At this time, compound 131 and compound 133 or compound 131 and compound 134 are selected in such a way that the emission peak of the exciplex formed by compound 131 and compound 133 or compound 131 and compound 134 overlaps with the absorption band on the longest wavelength side (low energy side) of compound 132 (fluorescent material). Thus, a light-emitting element with significantly improved luminous efficiency can be achieved.

[0247] As compound 133, a phosphorescent material can be used. As a phosphorescent material, iridium, rhodium, platinum-type organic metal complexes or metal complexes can be cited. In addition, platinum complexes or organic iridium complexes with porphyrin ligands can be cited, and in particular, for example, organic iridium complexes such as ortho-metal complexes of iridium can be preferably used. As ortho-metallated ligands, 4H-triazole ligands, 1H-triazole ligands, imidazole ligands, pyridine ligands, pyrimidine ligands, pyrazine ligands or isoquinoline ligands can be cited. At this time, compound 133 (phosphorescent material) has an absorption band of triple MLCT (charge transfer from metal to ligand: Metal to Ligand Charge Transfer) transition. In addition, it is preferred to select compound 133 and compound 132 (fluorescent material) in a manner that the luminescence peak of compound 133 overlaps with the absorption band on the longest wavelength side (low energy side) of compound 132 (fluorescent material). Thus, a light-emitting element with significantly improved luminous efficiency can be achieved. In addition, even if 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 it only needs to be able to emit light at room temperature when forming an exciplex. In this case, for example, Ir(ppz) 3 etc. are used as phosphorescent materials.

[0248] Examples of substances having a blue or green emission peak include tris{2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazol-3-yl-κN 2 ]phenyl-κC}iridium(III) (abbreviation: Ir(mpptz-dmp) 3 ), tris(5-methyl-3,4-diphenyl-4H-1,2,4-triazole)iridium(III) (abbreviated as: Ir(Mptz) 3 ), tris[4-(3-biphenyl)-5-isopropyl-3-phenyl-4H-1,2,4-triazole]iridium(III) (abbreviated as: Ir(iPrptz-3b) 3 ), tris[3-(5-biphenyl)-5-isopropyl-4-phenyl-4H-1,2,4-triazole]iridium(III) (abbreviated as: Ir(iPr5btz) 3 ) and other organic metal iridium complexes with a 4H-triazole skeleton; tris[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-triazole]iridium(III) (abbreviated as: Ir(Mptz1-mp) 3 ), tris(1-methyl-5-phenyl-3-propyl-1H-1,2,4-triazole)iridium(III) (abbreviated as: Ir(Prptz1-Me) 3 ) and other organometallic iridium complexes with a 1H-triazole skeleton; fac-tris[1-(2,6-diisopropylphenyl)-2-phenyl-1H-imidazole]iridium(III) (abbreviated as: Ir(iPrpmi) 3 ), tris[3-(2,6-dimethylphenyl)-7-methylimidazo[1,2-f]phenanthridinato]iridium(III) (abbreviated as: Ir(dmpimpt-Me) 3 ) and other organometallic iridium complexes with an imidazole skeleton; and bis[2-(4',6'-difluorophenyl)pyridinium-N,C 2 '] iridium (III) tetrakis (1-pyrazolyl) borate (abbreviated as Fir6), bis [2-(4',6'-difluorophenyl) pyridinium-N,C 2 '] iridium (III) picolinate (abbreviated as Firpic), bis{2-[3',5'-bis(trifluoromethyl)phenyl]pyridinium-N,C 2 '}Iridium(III) picolinate (abbreviated as: Ir(CF 3 ppy) 2 (pic)), bis[2-(4',6'-difluorophenyl)pyridinium-N,C 2'] Iridium (III) acetylacetone (abbreviated as Fir (acac)) and other organic metal iridium complexes with phenylpyridine derivatives having electron-withdrawing groups as ligands. Among the above materials, organic metal iridium complexes having nitrogen-containing five-membered heterocyclic skeletons such as 4H-triazole skeleton, 1H-triazole skeleton and imidazole skeleton are particularly preferred because of their high triplet excitation energy, high reliability and high luminous efficiency.

[0249] Examples of substances having a green or yellow emission peak include tris(4-methyl-6-phenylpyrimidine)iridium(III) (abbreviation: Ir(mppm) 3 ), tri(4-tert-butyl-6-phenylpyrimidine)iridium(III) (abbreviated as: Ir(tBuppm) 3 ), (acetylacetonate)bis(6-methyl-4-phenylpyrimidine)iridium(III) (abbreviated as: Ir(mppm) 2 (acac)), (acetylacetonate)bis(6-tert-butyl-4-phenylpyrimidine)iridium(III) (abbreviated as: Ir(tBuppm) 2 (acac)), (acetylacetonato)bis[4-(2-norbornyl)-6-phenylpyrimidine]iridium(III) (abbreviation: Ir(nbppm) 2 (acac)), (acetylacetonato)bis[5-methyl-6-(2-methylphenyl)-4-phenylpyrimidine]iridium(III) (abbreviation: Ir(mpmppm) 2 (acac)), (acetylacetonato)bis{(4,6-dimethyl-2-[6-(2,6-dimethylphenyl)-4-pyrimidinyl-κN 3 ]phenyl-κC}iridium(III) (abbreviation: Ir(dmppm-dmp) 2 (acac)), (acetylacetonate)bis(4,6-diphenylpyrimidine)iridium(III) (abbreviated as: Ir(dppm) 2 (acac)) and other organometallic iridium complexes with pyrimidine skeletons; (acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazine)iridium(III) (abbreviated as: Ir(mppr-Me) 2 (acac)), (acetylacetonate)bis(5-isopropyl-3-methyl-2-phenylpyrazine)iridium(III) (abbreviated as: Ir(mppr-iPr) 2 (acac)) and other organometallic iridium complexes with pyrazine skeletons; tris(2-phenylpyridine-N,C 2 ') Iridium (III) (abbreviation: Ir(ppy) 3 ), bis(2-phenylpyridinium-N,C 2 ') Iridium(III) acetylacetonate (abbreviated as: Ir(ppy) 2(acac)), bis(benzo[h]quinoline)iridium(III)acetylacetonate (abbreviated as: Ir(bzq) 2 (acac)), tris(benzo[h]quinoline)iridium(III) (abbreviation: Ir(bzq) 3 ), tris(2-phenylquinoline-N,C 2′ )Iridium(III) (Abbreviation: Ir(pq) 3 ), bis(2-phenylquinoline-N,C 2 ') Iridium(III) acetylacetonate (abbreviated as: Ir(pq) 2 (acac)) and other organic metal iridium complexes with pyridine skeletons; bis(2,4-diphenyl-1,3-oxazole-N,C 2 ') Iridium(III) acetylacetonate (abbreviated as: Ir(dpo) 2 (acac)), bis{2-[4'-(perfluorophenyl)phenyl]pyridine-N,C 2 '}Iridium(III) acetylacetonate (abbreviated as: Ir(p-PF-ph) 2 (acac)), bis(2-phenylbenzothiazole-N,C 2 ') Iridium(III) acetylacetonate (abbreviated as: Ir(bt) 2 (acac)) and other organometallic iridium complexes; tris(acetylacetonate)(monophenanthroline)terbium(III) (abbreviated as: Tb(acac) 3 Among the above materials, organic metal iridium complexes having a pyrimidine skeleton are particularly preferred because of their very high reliability and luminous efficiency.

[0250] In addition, examples of substances having a yellow or red emission peak include (diisobutyrylmethane)bis[4,6-bis(3-methylphenyl)pyrimidinyl]iridium(III) (abbreviation: Ir(5mdppm) 2 (dibm)), bis[4,6-bis(3-methylphenyl)pyrimidinyl](dipivaloylmethanyl)iridium(III) (abbreviated as: Ir(5mdppm) 2 (dpm)), bis[4,6-di(naphthalene-1-yl)pyrimidinyl](dipivaloylmethano)iridium(III) (abbreviated as: Ir(d1npm) 2 (dpm)) and other organic metal iridium complexes with pyrimidine skeletons; (acetylacetonato)bis(2,3,5-triphenylpyrazine)iridium(III) (abbreviated as: Ir(tppr) 2 (acac)), bis(2,3,5-triphenylpyrazine)(dipivaloylmethano)iridium(III) (abbreviated as: Ir(tppr) 2(dpm)), (acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxaline]iridium(III) (abbreviated as: Ir(Fdpq) 2 (acac)) and other organic metal iridium complexes with pyrazine skeletons; tris(1-phenylisoquinoline-N,C 2’ )Iridium(III) (Abbreviation: Ir(piq) 3 ), bis(1-phenylisoquinoline-N,C 2’ )iridium(III) acetylacetonate (abbreviated as: Ir(piq) 2 (acac)) and other organometallic iridium complexes with a pyridine skeleton; platinum complexes such as 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin platinum (II) (abbreviated as PtOEP); and tris(1,3-diphenyl-1,3-propanedione)(monophanate)europium(III) (abbreviated as Eu(DBM) 3 (Phen)), tris[1-(2-thenoyl)-3,3,3-trifluoroacetone](monophanate) europium(III) (abbreviated as: Eu(TTA) 3 Among the above substances, organic metal iridium complexes with a pyrimidine skeleton are particularly preferred because they also have very high reliability and luminous efficiency. In addition, organic metal iridium complexes with a pyrazine skeleton can obtain red luminescence with good chromaticity.

[0251] In addition, as a material that can be used as the energy donor, a metal halide perovskite material can be mentioned. The metal halide perovskite material can be represented by any one of the following general formulas (g1) to (g3).

[0252] (SA)MX 3 :(g1) (LA) 2 (SA) n-1 M n X 3n+1 :(g2) (PA)(SA) n-1 M n X3 n+1 :(g3)

[0253] In the above general formula, M represents a divalent metal ion, and X represents a halogen ion.

[0254] Specifically, as the divalent metal ion, a divalent cation such as lead or tin is used.

[0255] Specifically, as the halogen ion, anions such as chlorine, bromine, iodine, and fluorine are used.

[0256] In addition, although n represents an integer of 1 to 10, when n is greater than 10 in the general formula (g2) or the general formula (g3), its properties are similar to those of the metal halide perovskite material represented by the general formula (g1).

[0257] In addition, LA indicates that the 30 -NH 3 + Represents ammonium ion.

[0258] In the general formula R 30 -NH 3 + In the ammonium ion represented by 30 The group is any one of an alkyl group, an aryl group and a heteroaryl group having 2 to 20 carbon atoms; or a group composed of an alkyl group, an aryl group or a heteroaryl group having 2 to 20 carbon atoms and an alkylene group, a vinylene group, an arylene group and a heteroarylene group having 1 to 12 carbon atoms. In the case of the latter, multiple alkylene groups, arylene groups and heteroarylene groups may be linked together, or multiple groups of the same type may be used. When multiple alkylene groups, vinylene groups, arylene groups and heteroarylene groups are linked together, the total number of alkylene groups, vinylene groups, arylene groups and heteroarylene groups is preferably 35 or less.

[0259] SA represents a monovalent metal ion or R 31 -NH 3 + Represents and R 31 It represents an ammonium ion of an alkyl group having 1 to 6 carbon atoms.

[0260] PA stands for NH 3 + -R 32 -NH 3 + NH 3 + -R 33 -R 34 -R 35 -NH 3 + Or a part or all of the branched polyethyleneimine containing ammonium cations, the valence of the part is +2. The charges in the general formula are almost balanced.

[0261] Here, the charge of the metal halide perovskite material does not necessarily need to be strictly balanced in all parts of the material according to the above general formula, as long as the neutrality of the material as a whole is maintained. Sometimes other ions such as freed ammonium ions, freed halogen ions, impurity ions, etc. exist locally in the material, and sometimes they neutralize the charge. In addition, sometimes the surface of a particle or a film, a crystal grain boundary, etc., is not kept neutral locally, and it is not necessarily necessary to keep all parts neutral.

[0262] As (LA) in the general formula (g2), for example, substances represented by the following general formulae (a-1) to (a-11) and (b-1) to (b-6) can be used.

[0263] [Chemical formula 30]

[0264] [Chemical formula 31]

[0265] (PA) in the general formula (g3) above typically represents a substance represented by any one of the following general formulas (c-1), (c-2) and (d) and a part or all of a branched polyethyleneimine containing an ammonium cation, and has a +2 charge. These polymers sometimes neutralize charges in a plurality of unit lattices, or sometimes each charge included in two different polymer molecules neutralizes a charge in one unit lattice.

[0266] [Chemical formula 32]

[0267] [Chemical formula 33]

[0268] However, in the above general formula, R 20 represents an alkyl group having 2 to 18 carbon atoms, R 21 , R 22 and R 23 represents hydrogen or an alkyl group having 1 to 18 carbon atoms, R 24 The following structural formula and general formula (R 24 -1) to (R 24 -14). 25 and R 26 Each of them independently represents hydrogen or an alkyl group having 1 to 6 carbon atoms. X represents a combination of monomer units A and monomer units B represented by any one of the above (d-1) to (d-6), and has a structure including monomer units A and monomer units B, the number of monomer units A is u, and the number of monomer units B is v. Note that there is no restriction on the arrangement order of monomer units A and B. m and l are each independently an integer from 0 to 12, and t is an integer from 1 to 18. u is an integer from 0 to 17, v is an integer from 1 to 18, and u+v is an integer from 1 to 18.

[0269] [Chemical formula 34]

[0270] Note that these descriptions are merely examples, and substances that can be used for (LA) and (PA) are not limited to these.

[0271] In the case of (SA)MX represented by the general formula (g1) 3 In the three-dimensional structure of the metal halide perovskite material, a regular octahedral structure having a metal atom M at the center and halogen atoms at six vertices is three-dimensionally arranged in a manner that the halogen atoms at each vertex are used in common to form a skeleton. The regular octahedral structural unit having a halogen atom at each vertex is called a perovskite unit. As a structure, there are: a zero-dimensional structure in which the above-mentioned perovskite unit exists alone; a linear structure in which the perovskite unit is one-dimensionally connected by the halogen atoms at the vertices; a thin sheet structure in which the perovskite unit is two-dimensionally connected; a structure in which the perovskite unit is three-dimensionally connected. In addition, there is: a complex two-dimensional structure formed by stacking a plurality of thin sheet structures in which the perovskite unit is two-dimensionally connected. In addition, there are more complex structures. In terms of definition, all these structures including the perovskite unit are collectively referred to as metal halide perovskite materials.

[0272] The light-emitting layer 130 may also be formed of a plurality of layers of two or more. For example, when the light-emitting layer 130 is formed by stacking a first light-emitting layer and a second light-emitting layer in sequence from the hole transport layer side, a substance having a hole transport property may be used as a main material of the first light-emitting layer, and a substance having an electron transport property may be used as a main material of the second light-emitting layer.

[0273] In addition, the light-emitting layer 130 may also contain a material other than compound 131, compound 132, compound 133, and compound 134 (compound 135). In this case, in order to allow compound 131 and compound 133 (or compound 134) to efficiently form an exciplex, it is preferred that the HOMO energy level of one of compound 131 and compound 133 (or compound 134) is the highest among the materials in the light-emitting layer 130, and the LUMO energy level of the other of compound 131 and compound 132 is the lowest among the materials in the light-emitting layer 130. By adopting such an energy level correlation, the reaction of compound 131 and compound 135 to form an exciplex can be suppressed.

[0274] For example, when compound 131 has a hole transport property and compound 133 (or compound 134) has an electron transport property, it is preferred that the HOMO energy level of compound 131 is higher than the HOMO energy level of compound 133 and the HOMO energy level of compound 135, and the LUMO energy level of compound 133 is lower than the LUMO energy level of compound 131 and the LUMO energy level of compound 135. In this case, the LUMO energy level of compound 135 may be higher or lower than the LUMO energy level of compound 131. In addition, the HOMO energy level of compound 135 may be higher or lower than the HOMO energy level of compound 133.

[0275] Although the material (compound 135) that can be used for the light-emitting layer 130 is not particularly limited, examples thereof include tris(8-hydroxyquinoline)aluminum(III) (abbreviated as Alq), tris(4-methyl-8-hydroxyquinoline)aluminum(III) (abbreviated as Almq), 3 ), bis(10-hydroxybenzo[h]quinolinolato)beryllium(II) (abbreviated as: BeBq 2 ), bis(2-methyl-8-hydroxyquinoline)(4-phenylphenol)aluminum(III) (abbreviated as BAlq), bis(8-hydroxyquinoline)zinc(II) (abbreviated as Znq), bis[2-(2-benzoxazolyl)phenol]zinc(II) (abbreviated as ZnPBO), bis[2-(2-benzothiazolyl)phenol]zinc(II) (abbreviated as ZnBTZ), etc.; 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviated as PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazole-2-yl]benzene (abbreviated as OXD-7), 3-(4-biphenyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviated as TAZ), 2,2',2"-(1,3 Heterocyclic compounds such as 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviated as NPB or α-NPD), N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (abbreviated as TPD), 4,4'-bis[N-(spiro-9,9'-difluorene-2-yl)-N-phenylamino]biphenyl (abbreviated as BSPB) and the like. In addition, anthracene derivatives, phenanthrene derivatives, pyrene derivatives, Derivatives, dibenzo[g,p] Condensed polycyclic aromatic compounds such as derivatives. Specifically, 9,10-diphenylanthracene (abbreviation: DPAnth), N,N-diphenyl-9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole-3-amine (abbreviation: CzA1PA), 4-(10-phenyl-9-anthracenyl)triphenylamine (abbreviation: DPhPA), 4-(9H-carbazole-9-yl)-4'-(10-phenyl-9-anthracenyl)triphenylamine (abbreviation: YGAPA), N,9-diphenyl-N -[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole-3-amine (abbreviated as: PCAPA), N,9-diphenyl-N-{4-[4-(10-phenyl-9-anthracenyl)phenyl]phenyl}-9H-carbazole-3-amine (abbreviated as: PCAPBA), N,9-diphenyl-N-(9,10-diphenyl-2-anthracenyl)-9H-carbazole-3-amine (abbreviated as: 2PCAPA), 6,12-dimethoxy-5,11-diphenyl N,N,N',N',N",N",N"',N"'-octaphenyldibenzo[g,p] -2,7,10,15-tetramine (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'-anthracene (abbreviation: BANT), 9,9'-(stilbene-3,3'-diyl)phenanthrene (abbreviation: DPNS), 9,9'-(stilbene-4,4'-diyl)phenanthrene (abbreviation: DPNS2) and 3,3',3"-(benzene-1,3,5-triyl)tripyrene (abbreviation: TPB3), etc. From these substances and known substances, one or more substances having an energy gap larger than the energy gap of the above-mentioned compounds 131 and 132 can be selected.

[0276] A pair of electrodes The electrode 101 and the electrode 102 have the function of injecting holes and electrons into the light-emitting layer 130. The electrode 101 and the electrode 102 can be formed using metals, alloys, conductive compounds, and mixtures or laminates thereof. A typical example of a metal is aluminum (Al). In addition, transition metals such as silver (Ag), tungsten, chromium, molybdenum, copper, and titanium; alkali metals such as lithium (Li) or cesium; and Group 2 metals such as calcium or magnesium (Mg) can be used. As a transition metal, a rare earth metal such as ytterbium (Yb) can also be used. As an alloy, an alloy including the above-mentioned metals can be used, for example, MgAg, AlLi, etc. can be mentioned. As a conductive compound, for example, metal oxides such as indium tin oxide (hereinafter referred to as ITO), indium tin oxide containing silicon or silicon oxide (abbreviated as: ITSO), indium zinc oxide (Indium Zinc Oxide), and indium oxide containing tungsten and zinc can be mentioned. Inorganic carbon materials such as graphene can also be used as conductive compounds. As described above, one or both of the electrode 101 and the electrode 102 may be formed by laminating a plurality of these materials.

[0277] In addition, the light emitting layer 130 is extracted through one or both of the electrode 101 and the electrode 102. Therefore, at least one of the electrode 101 and the electrode 102 has the function of transmitting visible light. As the conductive material having the light transmitting function, a material having a visible light transmittance of 40% or more and 100% or less, preferably 60% or more and 100% or less, and a resistivity of 1×10 -2 The electrode on the light extraction side may also be formed of a conductive material having a light-transmitting function and a light-reflecting function. Examples of the conductive material include a material having a visible light reflectance of 20% to 80%, preferably 40% to 70%, and a resistivity of 1×10 -2 When a material with low light transmittance such as a metal or alloy is used for an electrode for extracting light, one or both of the electrodes 101 and 102 may be formed with a thickness that allows visible light to pass therethrough (for example, a thickness of 1 nm to 10 nm).

[0278] Note that in this specification, as the electrode having the function of transmitting light, a material having the function of transmitting visible light and having conductivity may be used, for example, an oxide conductor layer represented by ITO (Indium Tin Oxide), an oxide semiconductor layer, or an organic conductor layer containing organic matter. As the organic conductor layer containing organic matter, for example, a layer containing a composite material formed by mixing an organic compound and an electron donor (donor), a layer containing a composite material formed by mixing an organic compound and an electron acceptor (acceptor), etc. can be cited. In addition, the resistivity of the transparent conductive layer is preferably 1×10 5 Ω·cm or less, more preferably 1×10 4 Ω·cm or less.

[0279] In addition, as a film forming method of the electrode 101 and the electrode 102, a sputtering method, a vapor deposition method, a printing method, a coating method, an MBE (Molecular Beam Epitaxy) method, a CVD method, a pulsed laser deposition method, an ALD (Atomic Layer Deposition) method, or the like can be applied.

[0280] Hole injection layer The hole injection layer 111 has the function of lowering the injection barrier of holes from one of the pair of electrodes (electrode 101 or electrode 102) to promote hole injection, and is formed using, for example, transition metal oxides, phthalocyanine derivatives or aromatic amines. Examples of transition metal oxides include molybdenum oxides, vanadium oxides, ruthenium oxides, tungsten oxides, manganese oxides, etc. Examples of phthalocyanine derivatives include phthalocyanine or metal phthalocyanines. Examples of aromatic amines include benzidine derivatives or phenylenediamine derivatives. Polymer compounds such as polythiophene or polyaniline may also be used, typically: poly(ethyldioxythiophene) / poly(styrene sulfonic acid) as self-doped polythiophene.

[0281] As the hole injection layer 111, a layer having a composite material composed of a hole transport material and a material having the property of receiving electrons from the hole transport material can be used. Alternatively, a stack of a layer containing a material having the property of receiving electrons and a layer containing a hole transport material can be used. In a steady state or in the presence of an electric field, charge transfer can be performed between these materials. As materials having the property of receiving electrons, organic acceptors such as quinone dimethane derivatives, tetrachlorobenzoquinone derivatives, and hexaazatriphenylene derivatives can be cited. Specifically, 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviated as: F 4Compounds having electron-withdrawing groups (especially halogen groups such as fluorine groups and cyano groups) such as chloranil, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviated as HAT-CN), and 1,3,4,5,7,8-hexafluorotetracyano-naphthoquinodimethane (abbreviated as F6-TCNNQ). In particular, compounds such as HAT-CN in which electron-withdrawing groups are bonded to fused aromatic rings having multiple heteroatoms are thermally stable and therefore are preferred. In addition, [3] ylidene derivatives containing electron-withdrawing groups (especially halogen groups such as fluorine groups and cyano groups) are particularly preferred because of their very high electron-accepting properties. Specifically, α, α', α"-1,2,3-cycloalkyltriylidene tris[4-cyano-2,3,5,6-tetrafluorophenylacetonitrile], α, α', α"-1,2,3-cyclopropyltriylidene tris[2,6-dichloro-3,5-difluoro-4-(trifluoromethyl)phenylacetonitrile], α, α', α"-1,2,3-cycloalkyltriylidene tris[2,3,4,5,6-pentafluorophenylacetonitrile], etc. can be mentioned. In addition, transition metal oxides, such as oxides of metals of Groups 4 to 8, can be used. Specifically, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide, rhenium oxide, etc. can be used. Molybdenum oxide is particularly preferably used because it is stable even in the atmosphere, has low hygroscopicity, and is easy to handle.

[0282] As the hole transport material, a material having a hole transport property higher than an electron transport property can be used, and preferably a material having a 1×10 -6 cm 2 / Vs or higher. Specifically, aromatic amines and carbazole derivatives mentioned as hole transporting materials that can be used for the light-emitting layer 130 can be used. In addition, aromatic hydrocarbons and stilbene derivatives can also be used. The hole transporting material can also be a polymer compound.

[0283] Examples of the aromatic hydrocarbons 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'-bianthracene, 10,10'-diphenyl-9,9'-bianthracene, 10,10'-bis(2-phenylphenyl)-9,9'-bianthracene, 10,10'-bis[(2,3,4,5,6-pentaphenyl)phenyl]-9,9'-bianthracene, anthracene, tetracene, rubrene, perylene, 2,5,8,11-tetra(tert-butyl)perylene, and the like. In addition, pentacene, coronene, and the like can also be used. Thus, it is more preferable to use a 1×10 -6 cm 2 / Vs or more and an aromatic hydrocarbon having 14 to 42 carbon atoms.

[0284] Note that the aromatic hydrocarbon may also have a vinyl skeleton. Examples of the aromatic hydrocarbon having 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).

[0285] In addition, polymer compounds such as poly(N-vinylcarbazole) (abbreviation: PVK), poly(4-vinyltriphenylamine) (abbreviation: PVTPA), poly[N-(4-{N'-[4-(4-diphenylamino)phenyl]phenyl-N'-phenylamino}phenyl)methacrylamide] (abbreviation: PTPDMA), and poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine] (abbreviation: Poly-TPD) can also be used.

[0286] Hole transport layer The hole transport layer 112 is a layer containing a hole transport material, and the materials exemplified as the materials for the hole injection layer 111 can be used. The hole transport layer 112 has a function of transporting holes injected into the hole injection layer 111 to the light emitting layer 130, and therefore preferably has a HOMO level that is the same as or close to the HOMO level of the hole injection layer 111.

[0287] As the hole transport material, the materials listed as examples of the material for the hole injection layer 111 can be used. In addition, it is preferable to use a material having a 1×10 -6 cm 2 / Vs or more. However, as long as the hole transport property is higher than the electron transport property, a substance other than the above substances can be used. In addition, the layer including the substance with high hole transport property is not limited to a single layer, and two or more layers composed of the above substances can be stacked.

[0288] Electron Transport Layer The electron transport layer 118 has a function of transporting electrons injected from the other of the pair of electrodes (electrode 101 or electrode 102) through the electron injection layer 119 to the light-emitting layer 130. As the electron transport material, a material having a higher electron transport property than a hole transport property can be used, and preferably a material having a 1×10 -6 cm 2 / Vs or more. As a compound that easily accepts electrons (a material with electron transport properties), a π-electron-deficient heteroaromatic compound such as a nitrogen-containing heteroaromatic compound or a metal complex can be used. Specifically, metal complexes including quinoline ligands, benzoquinoline ligands, oxazole ligands or thiazole ligands that can be used as electron transport materials for the light-emitting layer 130 can be cited. In addition, oxadiazole derivatives, triazole derivatives, phenanthroline derivatives, pyridine derivatives, bipyridine derivatives, pyrimidine derivatives, etc. can be cited. In addition, it is preferably a material with 1×10 -6 cm 2 / Vs or higher. However, as the electron transport layer, as long as the electron transport property is higher than the hole transport property, substances other than the above can be used. In addition, the electron transport layer 118 is not limited to a single layer, and two or more layers composed of the above substances can be stacked.

[0289] In addition, a layer for controlling the movement of electron carriers may be provided between the electron transport layer 118 and the light emitting layer 130. The layer for controlling the movement of electron carriers is a layer in which a small amount of a substance with high electron capture property is added to the material with high electron transport property, and the balance of the carriers can be adjusted by suppressing the movement of the electron carriers. This structure has a great effect on suppressing the problems caused by the passage of electrons through the light emitting layer (such as the reduction of the life of the element).

[0290] 《Electron injection layer》 The electron injection layer 119 has the function of lowering the injection barrier of electrons from the electrode 102 and promoting electron injection. For example, a Group 1 metal, a Group 2 metal, or their oxides, halides, carbonates, etc. can be used. In addition, a composite material of the above-mentioned electron transport material and a material having the property of supplying electrons to the electron transport material can also be used. As materials having electron-donating properties, Group 1 metals, Group 2 metals, or their oxides, etc. can be cited. Specifically, lithium fluoride (LiF), sodium fluoride (NaF), cesium fluoride (CsF), calcium fluoride (CaF 2 ) and lithium oxide (LiO x ) or other alkali metals, alkaline earth metals, or compounds of these metals. In addition, erbium fluoride (ErF 3 ) and other rare earth metal compounds. In addition, an electron salt may be used for the electron injection layer 119. As the electron salt, for example, a substance in which electrons are added to a mixed oxide of calcium and aluminum at a high concentration may be cited. In addition, a substance that can be used for the electron transport layer 118 may be used for the electron injection layer 119.

[0291] In addition, a composite material formed by mixing an organic compound with an electron donor (donor) can also be used for the electron injection layer 119. This composite material has excellent electron injection and electron transport properties because electrons are generated in the organic compound by the electron donor. In this case, the organic compound is preferably a material with excellent performance in transporting the generated electrons. Specifically, for example, the substances (metal complexes, heteroaromatic compounds, etc.) constituting the electron transport layer 118 as described above can be used. As an electron donor, any substance that exhibits electron donating properties to organic compounds can be used. Specifically, alkali metals, alkaline earth metals and rare earth metals are preferably used, and lithium, cesium, magnesium, calcium, erbium, ytterbium, etc. can be mentioned. In addition, alkali metal oxides or alkaline earth metal oxides are preferably used, and lithium oxide, calcium oxide, barium oxide, etc. can be mentioned. In addition, Lewis bases such as magnesium oxide can also be used. In addition, organic compounds such as tetrathiafulvalene (abbreviated as: TTF) can also be used.

[0292] In addition, the above-mentioned light-emitting layer, hole injection layer, hole transport layer, electron transport layer and electron injection layer can be formed by evaporation (including vacuum evaporation), inkjet, coating, nozzle printing, gravure printing and other methods. In addition, as the above-mentioned light-emitting layer, hole injection layer, hole transport layer, electron transport layer and electron injection layer, in addition to the above-mentioned materials, inorganic compounds such as quantum dots or high molecular compounds (oligomers, dendrimers, polymers, etc.) can also be used.

[0293] As quantum dots, colloidal quantum dots, alloy quantum dots, core-shell quantum dots, core-type quantum dots, etc. can be used. In addition, quantum dots containing element groups of Group 2 and Group 16, Group 13 and Group 15, Group 13 and Group 17, Group 11 and Group 17, or Group 14 and Group 15 can also be used. Alternatively, quantum dots containing elements such as cadmium (Cd), selenium (Se), zinc (Zn), sulfur (S), phosphorus (P), indium (In), tellurium (Te), lead (Pb), gallium (Ga), arsenic (As), and aluminum (Al) can be used.

[0294] As the liquid medium used for the wet method, for example, ketones such as methyl ethyl ketone and cyclohexanone; fatty acid esters such as ethyl acetate; halogenated aromatic hydrocarbons such as dichlorobenzene; aromatic hydrocarbons such as toluene, xylene, mesitylene, cyclohexylbenzene; aliphatic hydrocarbons such as cyclohexane, decalin, dodecane; and organic solvents such as dimethylformamide (DMF) and dimethyl sulfoxide (DMSO).

[0295] Examples of the polymer compound that can be used for the light-emitting layer include polyphenylene vinylene (PPV) derivatives such as poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene vinylene] (abbreviation: MEH-PPV) and poly(2,5-dioctyl-1,4-phenylene vinylene); polyfluorene derivatives such as poly(9,9-di-n-octylfluorenyl-2,7-diyl) (abbreviation: PF8), poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(benzo[2,1,3]thiadiazole-4,8-diyl)] (abbreviation: F8BT), poly[(9 , 9-dioctylfluorenyl-2,7-diyl)-alt-(2,2'-bithiophene-5,5'-diyl)] (abbreviated as F8T2), poly[(9,9-dioctyl-2,7-divinylenefluorenyl)-alt-(9,10-anthracene)], poly[(9,9-dihexylfluorenyl-2,7-diyl)-alt-(2,5-dimethyl-1,4-phenylene)], etc.; polyalkylthiophene (PAT) derivatives such as poly(3-hexylthiophene-2,5-diyl) (abbreviated as P3HT), polyphenylene derivatives, etc. In addition, the above-mentioned polymer compounds, PVK, poly(2-vinylnaphthalene), poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (abbreviated as PTAA) and other polymer compounds can also be doped with a light-emitting compound and used in the light-emitting layer. As the light-emitting compound, the light-emitting compounds exemplified above can be used.

[0296] Substrate The light-emitting element of one embodiment of the present invention can be manufactured over a substrate made of glass, plastic, etc. The order of stacking layers on the substrate may be stacked sequentially from the electrode 101 side or from the electrode 102 side.

[0297] In addition, as a substrate capable of forming a light-emitting element of one embodiment of the present invention, for example, glass, quartz or plastic can be used. Alternatively, a flexible substrate can also be used. A flexible substrate is a substrate that can be bent, such as a plastic substrate made of polycarbonate or polyarylate. In addition, a film, an inorganic vapor-deposited film, etc. can be used. Note that other materials can be used as long as they serve as a support in the manufacturing process of the light-emitting element and the optical element. Alternatively, any material can be used as long as it has the function of protecting the light-emitting element and the optical element.

[0298] For example, in this specification, etc., various substrates can be used to form a light-emitting element. There is no particular restriction on the type of substrate. As examples of the substrate, for example, a semiconductor substrate (for example, a single crystal substrate or a silicon substrate), an SOI substrate, a glass substrate, a quartz substrate, a plastic substrate, a metal substrate, a stainless steel substrate, a substrate with a stainless steel foil, a tungsten substrate, a substrate with a tungsten foil, a flexible substrate, a laminated film, a cellulose nanofiber (CNF) containing a fibrous material, paper or a substrate film, etc. can be used. As examples of glass substrates, there are barium borosilicate glass, aluminoborosilicate glass, soda-lime glass, etc. As flexible substrates, laminated films, substrate films, etc., the following examples can be cited. For example, plastics represented by polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyether sulfone (PES), and polytetrafluoroethylene (PTFE) can be cited. Or, as an example, resins such as acrylic resins can be cited. Or, as an example, polypropylene, polyester, polyvinyl fluoride or polyvinyl chloride can be cited. Alternatively, polyamide, polyimide, aramid, epoxy resin, inorganic vapor-deposited film, paper, etc. can be cited as examples.

[0299] In addition, a flexible substrate may be used as a substrate, and a light-emitting element may be directly formed on the flexible substrate. Alternatively, a peeling layer may be provided between the substrate and the light-emitting element. The peeling layer may be used when a part or all of the light-emitting element is manufactured on the peeling layer, and then it is separated from the substrate and transferred to another substrate. In this case, the light-emitting element may also be transferred to a substrate with low heat resistance or a flexible substrate. In addition, as the above-mentioned peeling layer, for example, a laminated structure of an inorganic film of a tungsten film and a silicon oxide film or a structure in which a resin film such as polyimide is formed on a substrate may be used.

[0300] That is, a light-emitting element can also be formed using one substrate, and then the light-emitting element can be transferred to another substrate. As examples of substrates to which the light-emitting element is transferred, in addition to the above-mentioned substrates, there can be cited cellophane substrates, stone substrates, wood substrates, cloth substrates (including natural fibers (silk, cotton, linen), synthetic fibers (nylon, polyurethane, polyester) or regenerated fibers (acetate, cuprammonium fiber, rayon, regenerated polyester), etc.), leather substrates, rubber substrates, etc. By using these substrates, it is possible to manufacture light-emitting elements that are not easily damaged, light-emitting elements with high heat resistance, light-emitting elements that are lightweight, or light-emitting elements that are thin.

[0301] Alternatively, a field effect transistor (FET) may be formed over the substrate, and the light emitting element 150 may be formed on an electrode electrically connected to the FET. Thus, an active matrix display device in which driving of the light emitting element is controlled by the FET can be manufactured.

[0302] The structure described in this embodiment mode can be used in combination with the structures described in other embodiment modes as appropriate.

[0303] (Implementation Method 2) In this embodiment, an example of a method for synthesizing an organic compound applicable to a light-emitting element of one embodiment of the present invention is described by taking organic compounds represented by general formulae (G1) and (G2) as examples.

[0304] <Method for synthesizing the organic compound represented by the general formula (G1)> The organic compound represented by the general formula (G1) can be synthesized by a synthesis method utilizing various reactions. For example, it can be synthesized by the following synthesis schemes (S-1) and (S-2). By coupling compound 1, arylamine (compound 2) and arylamine (compound 3), a diamine compound (compound 4) is obtained.

[0305] Then, by coupling the diamine compound (Compound 4), the aryl halide (Compound 5), and the aryl halide (Compound 6), the organic compound represented by the above-mentioned general formula (G1) can be obtained.

[0306] [Chemical formula 35]

[0307] [Chemical formula 36]

[0308] Note that in the above synthesis schemes (S-1) and (S-2), A represents a substituted or unsubstituted fused aromatic ring having 10 to 30 carbon atoms or a substituted or unsubstituted fused heteroaromatic ring having 10 to 30 carbon atoms, Ar 1 To Ar4 Each independently represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 13 carbon atoms, X 1 To X 8 Each independently represents any one of an alkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, and a trialkylsilyl group having 3 to 12 carbon atoms. Examples of the condensed aromatic ring or condensed heteroaromatic ring include Phenanthrene, stilbene, acridone, phenoxazine, phenothiazine, etc. Particularly preferred are anthracene, pyrene, coumarin, quinacridone, perylene, tetracene, and naphthobisbenzofuran.

[0309] Note that in the above-mentioned synthesis schemes (S-1) and (S-2), when the Buchwald-Hartwig reaction using a palladium catalyst is performed, X 10 To X 13 Represents halogen or triflate, and as halogen, preferably iodine, bromine or chlorine. In the above reaction, palladium compounds such as bis(dibenzylideneacetone) palladium (0), palladium acetate (II), tri(tert-butyl) phosphine, tri(n-hexyl) phosphine, tricyclohexyl phosphine, di(1-adamantane)-n-butyl phosphine and 2-dicyclohexylphosphino-2', 6'-dimethoxy-1, 1'-biphenyl etc. can be used. In addition, in the above reaction, inorganic bases such as organic bases such as sodium tert-butoxide, potassium carbonate, cesium carbonate, sodium carbonate etc. can be used. As solvent, toluene, xylene, mesitylene, benzene, tetrahydrofuran, dioxane etc. can be used. Note that the reagents that can be used for the above reaction are not limited to the above reagents.

[0310] The reactions carried out in the above-mentioned synthesis schemes (S-1) and (S-2) are not limited to the Buchwald-Hartwig reaction, and the Ueda-Kosugi-Stille coupling reaction using an organic tin compound, a coupling reaction using a Grignard reagent, an Ullmann reaction using copper or a copper compound, etc. can also be used.

[0311] In the above-mentioned synthesis scheme (S-1), when compound 2 and compound 3 have different structures, it is preferred to react compound 1 with compound 2 to form a coupled product, and then react the obtained coupled product with compound 3. Note that, when compound 1 is reacted with compound 2 and compound 3 one by one, compound 1 is preferably a dihalide, and X 10 and X 11 Preference is given to using different halogens and carrying out the amination reaction selectively one by one.

[0312] Furthermore, in the above synthesis scheme (S-2), when compound 5 and compound 6 have different structures, it is preferred to react compound 4 with compound 5 to form a coupled product, and then react the obtained coupled product with compound 6.

[0313] (Implementation 3) In this embodiment, refer to Figure 7 A light-emitting element having a structure different from that of the light-emitting element described in Embodiment 1 will be described. Figure 7 In the Figure 1A Parts with the same functions as the reference numerals shown in the figure are shaded the same, and the reference numerals are sometimes omitted. Figure 1A Components with the same functions are denoted by the same reference numerals, and detailed description thereof may be omitted.

[0314] <Structural Example 2 of Light Emitting Element> Figure 7 is a schematic cross-sectional view of the light emitting element 250 . Figure 7 The light emitting element 250 shown has a plurality of light emitting units (light emitting unit 106 and light emitting unit 108) between a pair of electrodes (electrode 101 and electrode 102). One of the plurality of light emitting units preferably has Figure 1A The EL layer 100 has the same structure as shown. That is, Figure 1A The light emitting element 150 shown preferably has one light emitting unit, while the light emitting element 250 preferably has a plurality of light emitting units. Note that in the light emitting element 250, although the electrode 101 is an anode and the electrode 102 is a cathode, the structure of the light emitting element 250 may be the opposite.

[0315] exist Figure 7 In the light-emitting element 250 shown, the light-emitting unit 106 and the light-emitting unit 108 are stacked, and the charge generation layer 115 is provided between the light-emitting unit 106 and the light-emitting unit 108. In addition, the light-emitting unit 106 and the light-emitting unit 108 may have the same structure or different structures. For example, the light-emitting unit 108 preferably has the same structure as the EL layer 100.

[0316] The light emitting element 250 includes a light emitting layer 120 and a light emitting layer 170. The light emitting unit 106 includes a hole injection layer 111, a hole transport layer 112, an electron transport layer 113, and an electron injection layer 114 in addition to the light emitting layer 120. The light emitting unit 108 includes a hole injection layer 116, a hole transport layer 117, an electron transport layer 118, and an electron injection layer 119 in addition to the light emitting layer 170.

[0317] In the light-emitting element 250, any one of the light-emitting unit 106 and the light-emitting unit 108 may contain the compound according to one embodiment of the present invention. Note that the light-emitting layer 120 or the light-emitting layer 170 is preferably the layer containing the compound.

[0318] The charge generation layer 115 may have a structure in which an acceptor substance serving as an electron acceptor is added to a hole transport material, or a structure in which a donor substance serving as an electron donor is added to an electron transport material. Alternatively, these two structures may be stacked.

[0319] When the charge generation layer 115 includes a composite material composed 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 as the composite material. As the organic compound, various compounds such as aromatic amine compounds, carbazole compounds, aromatic hydrocarbons, and high molecular weight compounds (oligomers, dendrimers, polymers, etc.) can be used. In addition, as the organic compound, it is preferred to use an organic compound having a hole mobility of 1×10 -6 cm 2 / Vs or above. However, as long as the hole transport property is higher than the electron transport property, substances other than these can be used. Because the composite material composed of organic compounds and acceptor substances has good carrier injection and carrier transport properties, low voltage driving and low current driving can be achieved. Note that when the surface on the anode side of the light-emitting unit contacts the charge generation layer 115, the charge generation layer 115 can also have the function of the hole injection layer or hole transport layer of the light-emitting unit, so the hole injection layer or hole transport layer may not be provided in the light-emitting unit. Alternatively, when the surface on the cathode side of the light-emitting unit contacts the charge generation layer 115, the charge generation layer 115 can also have the function of the electron injection layer or electron transport layer of the light-emitting unit, so the electron injection layer or electron transport layer may not be provided in the light-emitting unit.

[0320] Note that the charge generation layer 115 may also be a stacked structure in which a layer of a composite material including an organic compound and an acceptor substance is combined with a layer composed of other materials. For example, a structure in which a layer of a composite material including an organic compound and an acceptor substance is combined with a layer including a compound selected from electron-donating substances and a compound with high electron transport properties may be combined. In addition, a structure in which a layer of a composite material including an organic compound and an acceptor substance is combined with a layer including a transparent conductive film may be combined.

[0321] The charge generation layer 115 sandwiched between the light-emitting unit 106 and the light-emitting unit 108 may have a structure that injects electrons into one light-emitting unit and injects holes into the other light-emitting unit when a voltage is applied between the electrode 101 and the electrode 102. Figure 7In the embodiment, when a voltage is applied so that the potential of the electrode 101 is higher than the potential of the electrode 102 , the charge generation layer 115 injects electrons into the light-emitting unit 106 and injects holes into the light-emitting unit 108 .

[0322] From the viewpoint of light extraction efficiency, the charge generation layer 115 preferably has visible light transmittance (specifically, visible light transmittance is 40% or more). The charge generation layer 115 functions even if its conductivity is lower than that of the pair of electrodes (electrode 101 and electrode 102).

[0323] By forming the charge generation layer 115 using the above-mentioned material, an increase in driving voltage when a light-emitting layer is stacked can be suppressed.

[0324] Although in Figure 7 , a light-emitting element having two light-emitting units is described, but the same structure can be applied to a light-emitting element having three or more light-emitting units stacked. As shown in light-emitting element 250, by arranging a plurality of light-emitting units between a pair of electrodes in a manner separated by a charge generation layer, a light-emitting element can be realized that can emit light with high brightness while maintaining a low current density and has a longer life. In addition, a light-emitting element with low power consumption can also be realized.

[0325] In addition, in each of the above structures, the luminescent colors of the guest materials used for the light-emitting unit 106 and the light-emitting unit 108 may be the same or different. When the light-emitting unit 106 and the light-emitting unit 108 include guest materials having the function of emitting light of the same color, the light-emitting element 250 becomes a light-emitting element that exhibits high luminous brightness at a lower current value, so it is preferred. In addition, when the light-emitting unit 106 and the light-emitting unit 108 include guest materials having the function of emitting light of different colors from each other, the light-emitting element 250 emits light of multiple colors, so it is preferred. At this time, when multiple light-emitting materials with different luminescent wavelengths are used for one or both of the light-emitting layer 120 and the light-emitting layer 170, light with different luminescent peaks is synthesized, so the emission spectrum of the light-emitting element 250 has at least two maximum values.

[0326] The above structure is suitable for obtaining white light emission. White light emission can be obtained by making the light of the light emitting layer 120 and the light emitting layer 170 complementary colors. It is particularly preferred to select the guest material in a manner that realizes white light emission with high color rendering index or light emission having at least red, green, and blue.

[0327] It is preferable that the structure of the light-emitting layer 130 described in Embodiment 1 is used for one or both of the light-emitting layer 120 and the light-emitting layer 170. By adopting this structure, a light-emitting element with good light-emitting efficiency and reliability can be obtained. The guest material included in the light-emitting layer 130 is a fluorescent material. Therefore, by using the structure of the light-emitting layer 130 described in Embodiment 1 for one or both of the light-emitting layer 120 and the light-emitting layer 170, a light-emitting element with high efficiency and high reliability can be obtained.

[0328] In addition, in a light-emitting element having three or more stacked light-emitting units, the light-emitting colors of the guest materials used for each light-emitting unit may be the same or different. In the case where the light-emitting element includes a plurality of light-emitting units emitting light of the same color, these plurality of light-emitting units can obtain a light-emitting color with a high light-emitting brightness at a current value lower than that of other colors. This structure is suitable for adjusting the light-emitting color. It is particularly preferred for use in the case of using guest materials with different luminous efficiencies and exhibiting different light-emitting colors. For example, in the case where three light-emitting units are provided, by providing two light-emitting units including a fluorescent material exhibiting the same light-emitting color and a light-emitting unit including a phosphorescent material exhibiting a light-emitting color different from that of the fluorescent material, the light-emitting intensity of the fluorescent light and the phosphorescent light can be adjusted. In other words, the intensity of the light-emitting color can be adjusted according to the number of light-emitting units.

[0329] In the case of using the above-mentioned light-emitting element including two fluorescent light-emitting units and one phosphorescent light-emitting unit, it is preferred to use the following light-emitting elements because white light emission can be efficiently obtained: a light-emitting element including two light-emitting units including a blue fluorescent material and one light-emitting unit including a yellow phosphorescent material; a light-emitting element including two light-emitting units including a blue fluorescent material and one light-emitting unit including a red phosphorescent material and a green phosphorescent material; or a light-emitting element including two light-emitting units including a blue fluorescent material and one light-emitting unit including a red phosphorescent material, a yellow phosphorescent material, and a green phosphorescent material. In this way, the light-emitting element of one embodiment of the present invention and the phosphorescent light-emitting unit can be appropriately combined.

[0330] In addition, at least one of the light-emitting layer 120 and the light-emitting layer 170 may be further divided into layers and each layer may contain a different light-emitting material. That is, at least one of the light-emitting layer 120 and the light-emitting layer 170 may also be formed by a plurality of layers of two or more. For example, in the case where the light-emitting layer is formed by stacking the first light-emitting layer and the second light-emitting layer in sequence from the hole transport layer side, a material having a hole transport property may be used as the main material of the first light-emitting layer, and a material having an electron transport property may be used as the main material of the second light-emitting layer. In this case, the light-emitting materials contained in the first light-emitting layer and the second light-emitting layer may also be the same or different materials. In addition, the light-emitting materials contained in the first light-emitting layer and the second light-emitting layer may be materials having the function of emitting light of the same color, or materials having the function of emitting light of different colors. By adopting a structure of multiple light-emitting materials having the function of emitting light of different colors from each other, white light with high color rendering properties composed of three primary colors or four or more light-emitting colors can also be obtained.

[0331] This embodiment mode can be combined with other embodiment modes as appropriate.

[0332] (Implementation 4) In this embodiment, refer to Fig. 8A and Figure 8B A light-emitting device using the light-emitting element described in Embodiment Modes 1 and 3 will be described.

[0333] Fig. 8A is a top view showing a light emitting device, Figure 8B is along Fig. 8A AB and CD cut cross-sectional view in FIG. The light-emitting device includes a driving circuit portion (source side driving circuit) 601 for controlling the light emission of the light-emitting element, a pixel portion 602, and a driving circuit portion (gate side driving circuit) 603 indicated by a dotted line. In addition, reference numeral 604 is a sealing substrate, reference numeral 625 is a desiccant, reference numeral 605 is a sealant, and the inside surrounded by the sealant 605 is a space 607.

[0334] In addition, the guide wiring 608 is a wiring for transmitting signals input to the source side driving circuit 601 and the gate side driving circuit 603, and receives a video signal, a clock signal, a start signal, a reset signal, etc. from an FPC (flexible printed circuit) 609 used as an external input terminal. In addition, although only the FPC is shown here, the FPC may also be installed with a printed wiring board (PWB). The light-emitting device in this specification includes not only the light-emitting device body, but also a light-emitting device installed with an FPC or a PWB.

[0335] Next, refer to Figure 8BThe cross-sectional structure of the light emitting device is described below. A driver circuit portion and a pixel portion are formed over an element substrate 610 , and a source-side driver circuit 601 as the driver circuit portion and one pixel in the pixel portion 602 are shown here.

[0336] In addition, in the source side driving circuit 601, a CMOS circuit combining an n-channel TFT 623 and a p-channel TFT 624 is formed. In addition, the driving circuit can also be formed using various CMOS circuits, PMOS circuits, or NMOS circuits. In addition, in this embodiment, although a driver-integrated type in which the driving circuit is formed on the substrate is shown, this structure does not necessarily have to be adopted, and the driving circuit can also be formed outside instead of being formed on the substrate.

[0337] The pixel portion 602 is formed of a pixel including a switching TFT 611, a current control TFT 612, and a first electrode 613 electrically connected to the drain of the current control TFT 612. An insulator 614 is formed to cover the end of the first electrode 613. The insulator 614 can be formed using a positive photosensitive resin film.

[0338] In order to increase the coverage of the film formed on the insulator 614, the upper end or the lower end of the insulator 614 is formed into a curved surface having a curvature. For example, when a photosensitive acrylic resin is used as the material of the insulator 614, it is preferred that only the upper end of the insulator 614 has a curved surface. The curvature radius of the curved surface is preferably not less than 0.2 μm and not more than 0.3 μm. In addition, as the insulator 614, a negative photosensitive material or a positive photosensitive material can be used.

[0339] An EL layer 616 and a second electrode 617 are formed on the first electrode 613. Here, as a material of the first electrode 613 used as an anode, a material having a large work function is preferably used. For example, in addition to a single-layer film such as an ITO film, an indium tin oxide film containing silicon, an indium oxide film containing 2 wt% or more and 20 wt% or less of zinc oxide, a titanium nitride film, a chromium film, a tungsten film, a Zn film, or a Pt film, a stacked film composed of a titanium nitride film and a film containing aluminum as a main component, and a three-layer stacked film composed of a titanium nitride film, a film containing aluminum as a main component, and a titanium nitride film can be used. Note that when a stacked structure is used, wiring resistance is also low, good ohmic contact can be obtained, and it can be used as an anode.

[0340] The EL layer 616 is formed by various methods such as vapor deposition using a vapor deposition mask, inkjet, and spin coating. As a material constituting the EL layer 616, a low molecular compound or a high molecular compound (including an oligomer and a dendrimer) may be used.

[0341] In addition, as a material of the second electrode 617 formed on the EL layer 616 and serving as a cathode, a material having a small work function (such as Al, Mg, Li, Ca, or alloys and compounds thereof, MgAg, MgIn, AlLi, etc.) is preferably used. Note that when light generated in the EL layer 616 is transmitted through the second electrode 617, a stacked layer composed of a metal thin film with a reduced thickness and a transparent conductive film (such as ITO, indium oxide containing 2 wt% or more and 20 wt% or less of zinc oxide, indium tin oxide containing silicon, zinc oxide (ZnO), etc.) is preferably used as the second electrode 617.

[0342] In addition, a light-emitting element 618 is formed by a first electrode 613, an EL layer 616, and a second electrode 617. The light-emitting element 618 preferably has a structure described in Embodiment Mode 1 or Embodiment Mode 2. In addition, the pixel portion includes a plurality of light-emitting elements, and the light-emitting device of this embodiment mode may include both a light-emitting element having the structure described in Embodiment Mode 1 or Embodiment Mode 2 and a light-emitting element having another structure.

[0343] Furthermore, by bonding the sealing substrate 604 and the element substrate 610 together using the sealant 605, a light emitting element 618 is provided in a space 607 surrounded by the element substrate 610, the sealing substrate 604, and the sealant 605. In addition, the space 607 is filled with a filler, and in addition to being filled with an inert gas (nitrogen, argon, etc.), it is sometimes filled with a resin or a dry material, or both a resin and a dry material.

[0344] As the sealant 605, epoxy resin or glass powder is preferably used. In addition, these materials are preferably materials that do not allow moisture and oxygen to pass through as much as possible. In addition, as a material for sealing the substrate 604, in addition to a glass substrate and a quartz substrate, a plastic substrate composed of FRP (Fiber Reinforced Plastics), PVF (polyvinyl fluoride), polyester or acrylic resin can also be used.

[0345] By the above method, a light-emitting device using the light-emitting element described in Embodiment Modes 1 and 3 can be obtained.

[0346] <Structural Example 1 of Light Emitting Device> exist Fig.9A and Fig. 9B In the embodiment of the present invention, a light-emitting device including a light-emitting element that emits white light and a coloring layer (color filter) is shown as an example of the light-emitting device.

[0347] Fig.9AShown are a substrate 1001, a base insulating film 1002, a gate insulating film 1003, gate electrodes 1006, 1007, 1008, a first interlayer insulating film 1020, a second interlayer insulating film 1021, a peripheral portion 1042, a pixel portion 1040, a driving circuit portion 1041, first electrodes 1024W, 1024R, 1024G, 1024B of the light-emitting element, a partition wall 1026, an EL layer 1028, a second electrode 1029 of the light-emitting element, a sealing substrate 1031, a sealant 1032, a red pixel 1044R, a green pixel 1044G, a blue pixel 1044B, a white pixel 1044W, etc.

[0348] In addition, Fig.9A and Fig. 9B In the embodiment, the coloring layers (red coloring layer 1034R, green coloring layer 1034G, blue coloring layer 1034B) are provided on the transparent substrate 1033. In addition, a black layer (black matrix) 1035 may be provided. The transparent substrate 1033 provided with the coloring layers and the black layer is aligned and fixed on the substrate 1001. In addition, the coloring layers and the black layer are covered by the covering layer 1036. In addition, Fig.9A It shows that light does not pass through the coloring layer but passes through the external luminescent layer, and light passes through the coloring layers of each color and passes through the external luminescent layer. The light that does not pass through the coloring layer becomes white light and the light that passes through the coloring layer becomes red light, blue light, and green light, so that images can be displayed with pixels of four colors.

[0349] Fig. 9B An example is shown in which a red coloring layer 1034R, a green coloring layer 1034G, and a blue coloring layer 1034B are formed between the gate insulating film 1003 and the first interlayer insulating film 1020. Fig. 9B As shown, a coloring layer may be provided between the substrate 1001 and the sealing substrate 1031.

[0350] Although the light-emitting device described above has a structure in which light is emitted from the substrate 1001 side on which a TFT is formed (bottom emission type), a light-emitting device in which light is emitted from the sealing substrate 1031 side (top emission type) may also be used.

[0351] <Structural Example 2 of Light Emitting Device> Fig. 10A and Fig. 10B1001 is a cross-sectional view of a top-emitting light-emitting device. In this case, a substrate that does not allow light to pass through can be used as the substrate 1001. The process until the connection electrode for connecting the TFT and the anode of the light-emitting element is manufactured is performed in the same manner as the bottom-emitting light-emitting device. Then, a third interlayer insulating film 1037 is formed in a manner covering the electrode 1022. The insulating film may also have a planarization function. The third interlayer insulating film 1037 may be formed using the same material as the second interlayer insulating film 1021 or various other materials.

[0352] Although the lower electrodes 1025W, 1025R, 1025G, and 1025B of the light-emitting element are all anodes here, they may also be cathodes. Fig. 10A and Fig. 10B In the top emission type light-emitting device shown, the lower electrode 1025W, the lower electrode 1025R, the lower electrode 1025G, and the lower electrode 1025B are preferably reflective electrodes. In addition, the second electrode 1029 preferably has a function of emitting light and a function of transmitting light. In addition, a microcavity structure is preferably used between the second electrode 1029 and the lower electrodes 1025W, the lower electrode 1025R, the lower electrode 1025G, and the lower electrode 1025B to amplify light of a specific wavelength. The structure of the EL layer 1028 is the same as that described in Embodiment Modes 1 and 3, and an element structure capable of obtaining white light emission is used.

[0353] exist Fig.9A and Fig. 9B and Fig. 10A and Fig. 10B In the embodiment of the present invention, a structure of an EL layer capable of obtaining white light emission may be realized by using a plurality of light-emitting layers or a plurality of light-emitting units. Note that the structure for obtaining white light emission is not limited to this.

[0354] In adopting Fig. 10A and Fig. 10B In the case of the top emission structure shown, a sealing substrate 1031 provided with a coloring layer (red coloring layer 1034R, green coloring layer 1034G, blue coloring layer 1034B) can be used for sealing. A black layer (black matrix) 1030 located between pixels can be provided on the sealing substrate 1031. The coloring layer (red coloring layer 1034R, green coloring layer 1034G, blue coloring layer 1034B) and the black layer (black matrix) 1035 can also be covered by a cover layer. In addition, a light-transmitting substrate is used as the sealing substrate 1031.

[0355] In addition, although Fig. 10A The structure of full-color display using three colors of red, green and blue is shown in FIG. Fig. 10BAs shown, full-color display can also be performed in four colors of red, green, blue, and white. In addition, the structure for performing full-color display is not limited to these structures. For example, full-color display can also be performed in four colors of red, green, blue, and yellow.

[0356] The light-emitting element according to one embodiment of the present invention uses a fluorescent material as a guest material. Since the fluorescent material has a sharper spectrum than the phosphorescent material, light with high color purity can be obtained. Therefore, by using the light-emitting element in the light-emitting device shown in this embodiment, a light-emitting device with high color reproducibility can be obtained.

[0357] By the above method, a light-emitting device using the light-emitting element described in Embodiment Modes 1 and 3 can be obtained.

[0358] In addition, this embodiment mode can be combined with other embodiment modes as appropriate.

[0359] (Implementation method 5) In this embodiment, an electronic device and a display device which are one embodiment of the present invention are described.

[0360] According to one embodiment of the present invention, an electronic device and a display device having a flat surface, high luminous efficiency and high reliability can be manufactured. According to one embodiment of the present invention, an electronic device and a display device having a curved surface, high luminous efficiency and high reliability can be manufactured. As described above, a light-emitting element with high color reproducibility can be obtained.

[0361] Examples of the electronic equipment include television sets; desktop or notebook personal computers; displays for computers, etc.; digital cameras; digital video cameras; digital photo frames; mobile phones; portable game consoles; portable information terminals; sound reproduction devices; and large-scale game machines such as pinball machines.

[0362] Fig.11A and Fig. 11B The illustrated portable information terminal 900 includes a housing 901 , a housing 902 , a display portion 903 , a hinge portion 905 , and the like.

[0363] The housing 901 and the housing 902 are connected together by a hinge portion 905. The portable information terminal 900 can be opened from a folded state ( Fig.11A ) is converted into Fig. 11B As a result, the portability is good when carrying, and the visibility is high when using due to the large display area.

[0364] The portable information terminal 900 is provided with a flexible display portion 903 across a housing 901 and a housing 902 connected by a hinge portion 905 .

[0365] The light-emitting device manufactured using one embodiment of the present invention can be used for the display portion 903. Thus, a highly reliable portable information terminal can be manufactured.

[0366] The display portion 903 can display at least one of document information, static images, dynamic images, etc. When the document information is displayed on the display portion, the portable information terminal 900 can be used as an electronic book reader.

[0367] When the portable information terminal 900 is unfolded, the display portion 903 is maintained in a state with a large curvature radius. For example, the display portion 903 may be maintained in a manner including a portion curved with a curvature radius of 1 mm to 50 mm, preferably 5 mm to 30 mm. A portion of the display portion 903 is continuously provided with pixels across the housing 901 and the housing 902, thereby enabling curved display.

[0368] The display portion 903 is used as a touch panel and can be operated with a finger, a stylus pen, or the like.

[0369] The display unit 903 is preferably formed of a flexible display, so that a continuous display can be performed across the housing 901 and the housing 902. In addition, the housing 901 and the housing 902 can also be provided with displays respectively.

[0370] In order to prevent the angle formed by the housing 901 and the housing 902 from exceeding a predetermined angle when the portable information terminal 900 is unfolded, the hinge portion 905 preferably has a locking mechanism. For example, the locking angle (at which the portable information terminal 900 cannot be further opened) is preferably greater than 90° and less than 180°, and typically can be 90°, 120°, 135°, 150°, or 175°, etc. Thus, the convenience, safety, and reliability of the portable information terminal 900 can be improved.

[0371] When the hinge portion 905 has the above-described locking mechanism, it is possible to suppress application of an excessive force to the display portion 903, thereby preventing damage to the display portion 903. Thus, a highly reliable portable information terminal can be realized.

[0372] Housing 901 and housing 902 may also include a power button, operation buttons, an external connection port, a speaker, a microphone, and the like.

[0373] Either the housing 901 or the housing 902 may be provided with a wireless communication module, and data may be sent and received via a computer network such as the Internet, a LAN (Local Area Network), or Wireless Fidelity (Wi-Fi: registered trademark).

[0374] Fig. 11CThe illustrated portable information terminal 910 includes a housing 911 , a display portion 912 , operation buttons 913 , an external connection port 914 , a speaker 915 , a microphone 916 , a camera 917 , and the like.

[0375] The light-emitting device manufactured by one embodiment of the present invention can be used for the display portion 912. Thus, the portable information terminal can be manufactured with a high yield.

[0376] The portable information terminal 910 includes a touch sensor in the display portion 912. By touching the display portion 912 with a finger or a stylus pen, various operations such as making a call and inputting text can be performed.

[0377] Furthermore, by operating the operation button 913, it is possible to turn the power on and off or switch the type of image displayed on the display portion 912. For example, the e-mail composition screen can be switched to the main menu screen.

[0378] In addition, by providing a detection device such as a gyro sensor or an acceleration sensor inside the portable information terminal 910, the direction (vertical or horizontal) of the portable information terminal 910 can be determined, and the screen display direction of the display unit 912 can be automatically switched. In addition, the screen display direction can also be switched by touching the display unit 912, operating the operation button 913, or inputting a sound using the microphone 916.

[0379] The portable information terminal 910 has one or more functions selected from a telephone, a notebook, and an information reading device, for example. Specifically, the portable information terminal 910 can be used as a smart phone. The portable information terminal 910 can execute various applications such as mobile phone, e-mail, article reading and editing, music playing, animation playing, network communication, computer games, etc.

[0380] Fig.11D The camera 920 shown includes a housing 921 , a display portion 922 , operation buttons 923 , a shutter button 924 , etc. In addition, the camera 920 is equipped with a detachable lens 926 .

[0381] The light-emitting device manufactured by one embodiment of the present invention can be used for the display portion 922. Thus, a highly reliable camera can be manufactured.

[0382] Here, although the camera 920 has a structure in which the lens 926 can be detached from the housing 921 and replaced, the lens 926 and the housing 921 may be formed integrally.

[0383] The camera 920 can capture a still image or a moving image by pressing the shutter button 924. Alternatively, the display portion 922 may have a touch panel function, and the image may be captured by touching the display portion 922.

[0384] In addition, the camera 920 may further include a flash device and a viewfinder that are separately installed. In addition, these components may also be assembled in the housing 921.

[0385] Fig. 12A Schematic diagram showing an example of a sweeping robot.

[0386] The cleaning robot 5100 includes a display 5101 on the top surface and a plurality of cameras 5102, a brush 5103 and an operation button 5104 on the side. Although not shown, the bottom surface of the cleaning robot 5100 is provided with tires and a suction port, etc. In addition, the cleaning robot 5100 also includes various sensors such as an infrared sensor, an ultrasonic sensor, an acceleration sensor, a piezoelectric sensor, an optical sensor, and a gyroscope sensor. In addition, the cleaning robot 5100 includes a wireless communication unit.

[0387] The sweeping robot 5100 can walk automatically, detect garbage 5120, and suck the garbage from the suction port on the bottom.

[0388] In addition, the cleaning robot 5100 can determine the presence or absence of obstacles such as walls, furniture, or steps by analyzing the image captured by the camera 5102. In addition, when objects such as wiring that may be wrapped around the brush 5103 are detected through image analysis, the rotation of the brush 5103 can be stopped.

[0389] The remaining battery power and the amount of attracted garbage can be displayed on the display 5101. In addition, the walking path of the cleaning robot 5100 can also be displayed on the display 5101. In addition, the display 5101 can be a touch panel, and the operation button 5104 can be displayed on the display 5101.

[0390] The cleaning robot 5100 can communicate with a portable electronic device 5140 such as a smartphone. The image captured by the camera 5102 can be displayed on the portable electronic device 5140. Therefore, the owner of the cleaning robot 5100 can also know the situation of the room when going out. In addition, the display content of the display 5101 can be confirmed using a portable electronic device 5140 such as a smartphone.

[0391] The light-emitting device of one embodiment of the present invention can be used for the display 5101.

[0392] Fig. 12BThe robot 2100 shown includes a computing device 2110 , an illumination 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 .

[0393] The microphone 2102 has a function of detecting the user's voice and surrounding sounds, etc. In addition, the speaker 2104 has a function of emitting sound. The robot 2100 can communicate with the user using the microphone 2102 and the speaker 2104.

[0394] The display 2105 has a function of displaying various information. The robot 2100 can display the information desired by the user on the display 2105. The display 2105 can be equipped with a touch panel. The display 2105 can be a detachable information terminal, and by setting the information terminal at a predetermined position of the robot 2100, charging and data transmission and reception can be performed.

[0395] The upper camera 2103 and the lower camera 2106 have the function of photographing the surrounding environment of the robot 2100. In addition, the obstacle sensor 2107 can detect the presence or absence of obstacles in front of the robot 2100 when the robot 2100 moves using the moving mechanism 2108. The robot 2100 can recognize the surrounding environment using the upper camera 2103, the lower camera 2106, and the obstacle sensor 2107 and move safely.

[0396] The light-emitting device of one embodiment of the present invention can be used for the display 2105 .

[0397] Fig. 12C 5 is a diagram showing an example of a goggle-type display. The goggle-type display includes, for example, a housing 5000, a display unit 5001, a speaker 5003, an LED lamp 5004, an operation key 5005 (including a power switch or an operation switch), a connection terminal 5006, a sensor 5007 (which has a function of measuring the following factors: force, displacement, position, speed, acceleration, angular velocity, rotation speed, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current, voltage, electricity, radiation, flow, humidity, inclination, vibration, smell or infrared), a microphone 5008, a second display unit 5002, a support unit 5012, an earphone 5013, etc.

[0398] The light-emitting device of one embodiment of the present invention can be used for the display portion 5001 and the second display portion 5002 .

[0399] Fig.13A and Fig. 13BA foldable portable information terminal 5150 is shown. The foldable portable information terminal 5150 includes a housing 5151, a display area 5152, and a bending portion 5153. Fig.13A The portable information terminal 5150 is shown in the unfolded state. Fig. 13B The portable information terminal 5150 is shown in a folded state. Although the portable information terminal 5150 has a large display area 5152, by folding the portable information terminal 5150, the portable information terminal 5150 becomes small and has good portability.

[0400] The display area 5152 can be folded in half by the curved portion 5153. The curved portion 5153 is composed of a retractable member and a plurality of supporting members, and when folded, the retractable member is stretched so that the curved portion 5153 has a curvature radius of 2 mm or more, preferably 5 mm or more.

[0401] The display area 5152 may be a touch panel (input / output device) on which a touch sensor (input device) is mounted. The light-emitting device of one embodiment of the present invention can be used for the display area 5152 .

[0402] This embodiment mode can be combined with other embodiment modes as appropriate.

[0403] (Implementation method 6) In this embodiment, refer to Fig.14 Examples of cases where the light-emitting element of one embodiment of the present invention is applied to various lighting devices will be described. By using the light-emitting element of one embodiment of the present invention, a lighting device with high light emission efficiency and reliability can be manufactured.

[0404] By forming the light-emitting element of one embodiment of the present invention on a flexible substrate, an electronic device or a lighting device having a light-emitting region on a curved surface can be realized.

[0405] Furthermore, a light-emitting device to which the light-emitting element of one embodiment of the present invention is applied can also be applied to lighting for an automobile provided on a windshield, a ceiling, or the like.

[0406] Fig.14This is an example of using a light-emitting element for an indoor lighting device 8501. In addition, since the light-emitting element can be large-area, a large-area lighting device can also be formed. In addition, a lighting device 8502 in which the light-emitting area has a curved surface can be formed by using a shell having a curved surface. The light-emitting element shown in this embodiment is in the form of a thin film, so the design freedom of the shell is high. Therefore, a lighting device that can correspond to various designs can be formed. In addition, a large lighting device 8503 can also be provided on the wall of the room. In addition, a touch sensor can also be provided in the lighting device 8501, the lighting device 8502, and the lighting device 8503 to start or turn off the power.

[0407] In addition, by using the light-emitting element on the surface side of the table, a lighting device 8504 having the function of a table can be provided. In addition, by using the light-emitting element on a part of other furniture, a lighting device having the function of furniture can be provided.

[0408] As described above, by applying the light-emitting element of one embodiment of the present invention, a lighting device and an electronic device can be obtained. Note that the present invention is not limited to the lighting device and the electronic device described in this embodiment, but can be applied to lighting devices and electronic devices in various fields.

[0409] The structure described in this embodiment mode can be used in combination with the structures described in other embodiment modes as appropriate. [Example 1]

[0410] In this embodiment, a light-emitting element according to one embodiment of the present invention and a comparative light-emitting element are described as well as the characteristics of the light-emitting element. Figure 1A Likewise, the details of the element structure are shown in Table 1. In addition, the structures and abbreviations of the compounds used are shown below.

[0411] [Chemical formula 37]

[0412] [Table 1]

[0413] <Manufacturing of Light Emitting Element> A method for manufacturing the light-emitting element manufactured in this embodiment is described below.

[0414] 《Manufacturing of Comparative Light Emitting Element 1》 As the electrode 101, an ITSO film with a thickness of 70 nm was formed on a glass substrate. Note that the electrode area of ​​the electrode 101 is 4 mm 2 (2mm×2mm).

[0415] Next, DBT3P-II and molybdenum oxide (MoO) were deposited on the electrode 101 as a hole injection layer 111. 3 ) by weight ratio (DBT3P-II:MoO 3 ) was co-evaporated in a manner of 1:0.5 and a thickness of 40 nm.

[0416] Next, PCCP was deposited on the hole injection layer 111 to a thickness of 20 nm as the hole transport layer 112 .

[0417] Next, as the light-emitting layer 130, 4,6mCzP2Pm and Ir(Mptz1-mp) were deposited on the hole transport layer 112. 3 By weight ratio (4,6mCzP2Pm:Ir(Mptz1-mp) 3 ) is co-evaporated in a manner of 0.8:0.2 and a thickness of 40 nm. In the light-emitting layer 130, Ir(Mptz1-mp) 3 It is a phosphorescent material containing Ir, 4,6mCzP2Pm and Ir(Mptz1-mp) 3 It is a combination that forms an exciplex.

[0418] Next, 4,6mCzP2Pm and NBPhen were sequentially deposited to a thickness of 20 nm on the light emitting layer 130 as the electron transport layer 118 and to a thickness of 10 nm. Next, LiF was deposited to a thickness of 1 nm on the electron transport layer 118 as the electron injection layer 119 .

[0419] Next, aluminum (Al) was formed to a thickness of 200 nm on the electron injection layer 119 as the electrode 102 .

[0420] Next, in a glove box with a nitrogen atmosphere, a sealing glass substrate was fixed to a glass substrate on which an organic material was formed using an organic EL sealing agent, thereby sealing the comparative light-emitting element 1. Specifically, the sealing agent was applied to the periphery of the organic material formed on the glass substrate, and the glass substrate and the sealing glass substrate were bonded together, and the sealing agent was applied at 6 J / cm 2 Ultraviolet light with a wavelength of 365 nm was irradiated, and a heat treatment was performed at 80° C. for 1 hour. Comparative light-emitting element 1 was obtained through the above steps.

[0421] 《Manufacturing of Light Emitting Element 2》 The light-emitting element 2 is different from the comparative light-emitting element 1 in the structure of the light-emitting layer 130, and the other steps are the same as the manufacturing method of the comparative light-emitting element 1. The details of the element structure are described in Table 1, so the details of the manufacturing method are omitted. Note that in the light-emitting layer 130 of the light-emitting element 2, 2-tert-butyl-N,N,N',N'-tetrakis(4-tert-butylphenyl)-9,10-anthracenediamine (abbreviated as: 2tBu-ptBuDPhA2Anth), which is an organic compound represented by the structural formula (100), is a guest material having a protective group around the light-emitting body.

[0422] <Characteristics of Light Emitting Element> Next, the characteristics of the comparative light-emitting element 1 and the light-emitting element 2 manufactured as described above were measured. A colorimeter (BM-5A manufactured by Topcon Technohouse) was used for the measurement of brightness and CIE chromaticity. A multi-channel spectrum analyzer (PMA-11 manufactured by Hamamatsu Photonics Co., Ltd.) was used for the measurement of electroemission spectrum.

[0423] Fig.15 The external quantum efficiency-luminance characteristics of the comparative light-emitting element 1 and the light-emitting element 2 are shown. Fig.16 The values ​​are shown at 2.5 mA / cm 2 Electroluminescence spectra of light-emitting element 1 and light-emitting element 2 were compared when a current of a current density of was passed through the light-emitting element. In addition, the measurement of each light-emitting element was performed at room temperature (an atmosphere maintained at 23°C). Note that Fig.16 Also shown are the absorption and emission spectra of a toluene solution of 2tBu-ptBuDPhA2Anth, which is a guest material of the light-emitting element 2.

[0424] Note that the absorption and emission spectra of 2tBu-ptBuDPhA2Anth in the toluene solution were measured using an ultraviolet-visible spectrophotometer (V550 model manufactured by JASCO Corporation). Fig.16 The emission spectrum and absorption spectrum shown are obtained by subtracting the spectra measured by placing only toluene in a quartz cell from the spectra of the toluene solution of 2tBu-ptBuDPhA2Anth.

[0425] In addition, Table 2 shows that 1000 cd / m 2 The device characteristics of the light-emitting element 1 and the light-emitting element 2 are compared nearby.

[0426] [Table 2]

[0427] like Fig.16As shown, the peak wavelength of the emission spectrum of the comparative light-emitting element 1 is 502nm and the half width is 91nm. This is consistent with the results obtained from 4,6mCzP2Pm and Ir(Mptz1-mp) 3 The emission spectra obtained are different, which shows that the light emitted from the comparative light-emitting element 1 is emitted by 4,6mCzP2Pm and Ir(Mptz1-mp). 3 The emission spectrum of the light emitting element 2 has a peak wavelength of 524 nm and a half width of 67 nm. The emission spectrum of the light emitting element 2 is mainly green light emitted from 2tBu-ptBuDPhA2Anth, but Fig.16 As shown, the emission spectrum of light-emitting element 2 is different from the emission spectrum of 2tBu-ptBuDPhA2Anth.

[0428] Here, the emission spectrum of the light emitting element 2 includes light emission different from 2tBu-ptBuDPhA2Anth in the range of about 440nm to about 470nm. The light emitting element 2 includes 4,6mCzP2Pm and Ir(Mptz1-mp) as materials exhibiting light emission. 3 The excited complex and 2tBu-ptBuDPhA2Anth as the guest material. Fig.16 It can be seen that the emission from around 440nm to around 470nm is also included in 4,6mCzP2Pm and Ir(Mptz1-mp) 3 Therefore, according to the above records and Fig.16 It can be seen that light emission from both the exciplex and the guest material is obtained from the light emitting element 2. As described above, multicolor light emission can be obtained from the light emitting element of one embodiment of the present invention. Figure 4C As shown, the excitation energy of the exciplex can contribute to the luminescence of the exciplex and the luminescence of the guest material.

[0429] Although the light emitting element 2 emits light from the fluorescent material, Fig.15 As shown in Table 2, it has a very high luminous efficiency, that is, an external quantum efficiency of more than 25%. Based on this result, it can be said that in the light-emitting element of one embodiment of the present invention, a fluorescent material having a protective group around the light-emitting body is used, so that the non-radiative deactivation of triplet excitons is suppressed, and both singlet excitation energy and triplet excitation energy are efficiently converted into luminescence of the fluorescent material and the exciplex.

[0430] Here, the maximum generation probability of singlet excitons generated due to the recombination of carriers (holes and electrons) injected from a pair of electrodes is 25%. Therefore, when the light extraction efficiency to the outside is 30%, the maximum external quantum efficiency of the fluorescent light-emitting element is 7.5%. However, in the light-emitting element 2, an external quantum efficiency higher than 7.5% is obtained. This is because, in addition to the light emission of singlet excitons generated due to the recombination of carriers (holes and electrons) injected from a pair of electrodes, light emission due to energy transfer from triplet excitons or light emission of singlet excitons generated from triplet excitons through reverse intersystem crossing in exciplexes is obtained from the fluorescent material. That is to say, the light-emitting element 2 is a light-emitting element that utilizes ExEF.

[0431] <CV measurement results> Next, cyclic voltammetry (CV) was used to measure the electrochemical properties (oxidation reaction properties and reduction reaction properties) of 4,6mCzP2Pm and Ir(Mptz1-mp) for the light-emitting layers of the respective light-emitting elements. The measurement method and calculation method are shown below. 3 The electrochemical properties (oxidation reaction properties and reduction reaction properties) of 4,6mCzP2Pm and Ir(Mptz1-mp) for the light-emitting layers of the respective light-emitting elements were measured using cyclic voltammetry (CV). The measurement method and calculation method are shown below.

[0432] As the measurement device, an electrochemical analyzer (manufactured by BAS Inc., model: ALS model 600A or 600C) was used. In the solution during CV measurement, dehydrated dimethylformamide (DMF) (manufactured by Aldrich Co., Ltd., 99.8%, catalog number: 22705-6) was used as the solvent, tetra-n-butylammonium perchlorate (n-Bu 4 NClO 4 )(manufactured by Tokyo Chemical Industry Co., Ltd., catalog number: T0836) was dissolved at a concentration of 100 mmol / L, and the measurement object was dissolved at a concentration of 2 mmol / L for preparation. In addition, a platinum electrode (manufactured by BAS Inc., PTE platinum electrode) was used as the working electrode, a platinum electrode (manufactured by BAS Inc., Pt counter electrode for VC-3 (5 cm)) was used as the auxiliary electrode, and Ag / Ag +Electrode (manufactured by BAS Co., Ltd., RE7 non-aqueous reference electrode). In addition, the measurement was performed at room temperature (20°C to 25°C). In addition, the scanning speed during CV measurement was unified to 0.1V / sec, and the oxidation potential Ea[V] and reduction potential Ec[V] relative to the reference electrode were measured. Ea is the middle potential of the oxidation-reduction wave, and Ec is the middle potential of the reduction-oxidation wave. Here, since it is known that the potential energy of the reference electrode used in this embodiment relative to the vacuum energy level is -4.94[eV], the HOMO energy level and LUMO energy level can be calculated according to the formula of HOMO energy level [eV] = -4.94-Ea, LUMO energy level [eV] = -4.94-Ec.

[0433] As a result of CV measurement, the oxidation potential of 4,6mCzP2Pm was 0.95 V and the reduction potential was -2.06 V. In addition, the HOMO energy level of 4,6mCzP2Pm calculated from CV measurement was -5.89 eV and the LUMO energy level was -2.88 eV. In addition, Ir(Mptz1-mp) 3 The oxidation potential of Ir is 0.49 V and the reduction potential is -3.17 V. In addition, Ir(Mptz1-mp) calculated from CV measurement 3 The HOMO energy level is -5.39 eV and the LUMO energy level is -1.77 eV.

[0434] As mentioned above, the LUMO level of 4,6mCzP2Pm is lower than that of Ir(Mptz1-mp) 3 LUMO energy level of Ir(Mptz1-mp) 3 The HOMO level of 4,6mCzP2Pm is higher than that of 4,6mCzP2Pm. Therefore, when the compound is used in the light-emitting layer, electrons and holes can be efficiently injected into 4,6mCzP2Pm and Ir(Mptz1-mp) respectively. 3 , making 4,6mCzP2Pm and Ir(Mptz1-mp) 3 Forming an exciplex.

[0435] In addition, by Fig.16 It is known that the absorption band on the longest wavelength side of the absorption spectrum of 2tBu-ptBuDPhA2Anth overlaps with the emission spectrum of the exciplex. Therefore, the light emitting element 2 can receive the excitation energy of the exciplex and emit light.

[0436] Note that by Fig.16 It can be seen that compared with the emission spectrum obtained from 2tBu-ptBuDPhA2Anth, the emission spectra from 4,6mCzP2Pm and Ir(Mptz1-mp) 3The emission spectrum obtained by the exciplex has a peak on the short wavelength side. Therefore, the excitation energy of the exciplex can be efficiently transferred to 2tBu-ptBuDPhA2Anth. Therefore, a multicolor light-emitting element with high luminous efficiency can be manufactured by one embodiment of the present invention.

[0437] <Reliability test of light-emitting components> Next, a driving test was performed on the comparative light emitting element 1 and the light emitting element 2 at a constant current of 2.0 mA. Fig.17 The results are shown in Figure 2. Fig.17 It can be seen that the light-emitting element 2 including the fluorescent material in the light-emitting layer has high reliability compared to the comparative light-emitting element 1. This means that by adding the fluorescent material, the excitation energy in the light-emitting layer can be efficiently converted into light emission. Because the light emission speed of the fluorescent material is fast, the excited molecules in the light-emitting layer can quickly return to the ground state after transferring the excitation energy to the fluorescent material. Therefore, by adding the fluorescent material, the occurrence of molecular degradation and quenching factors that may cause brightness degradation can be suppressed. When a general fluorescent material is used in a triplet photosensor, the triplet excitons in the light-emitting layer are deactivated, making it difficult to manufacture a light-emitting element with high luminous efficiency and high reliability. However, in a light-emitting element of one embodiment of the present invention, a fluorescent material having a protective group around the light-emitting body is used to suppress the deactivation of triplet excitons. Thus, a light-emitting element with high efficiency and high reliability can be manufactured.

[0438] As described above, according to the light-emitting element of one embodiment of the present invention, a multicolor light-emitting element having high efficiency and high reliability can be provided. [Example 2]

[0439] In this embodiment, a light-emitting element of one embodiment of the present invention different from the above-described embodiment and a manufacturing example of a comparative light-emitting element and characteristics of the light-emitting element are described. Figure 1A Likewise. Table 3 shows the details of the element structure. In addition, the structures and abbreviations of the compounds used are shown below. Note that for other organic compounds, reference can be made to the above Examples and the above Embodiments.

[0440] [Chemical formula 38]

[0441] [Table 3]

[0442] <Manufacturing of Light Emitting Element> A method for manufacturing the light-emitting element manufactured in this embodiment is described below.

[0443] 《Manufacturing of Comparative Light Emitting Element 3》 As the electrode 101, an ITSO film with a thickness of 70 nm was formed on a glass substrate. Note that the electrode area of ​​the electrode 101 is 4 mm 2 (2mm×2mm).

[0444] Next, DBT3P-II and molybdenum oxide (MoO) were deposited on the electrode 101 as a hole injection layer 111. 3 ) by weight ratio (DBT3P-II:MoO 3 ) was co-evaporated in a manner of 1:0.5 and a thickness of 40 nm.

[0445] Next, PCCP was deposited on the hole injection layer 111 to a thickness of 20 nm as the hole transport layer 112 .

[0446] Next, as the light-emitting layer 130 (1), 4,6mCzP2Pm, PCCP, and Firpic were co-evaporated in a weight ratio (4,6mCzP2Pm: PCCP: Firpic) of 0.5:0.5:0.1 and a thickness of 20 nm on the hole transport layer 112. Next, as the light-emitting layer 130 (2), 4,6mCzP2Pm, PCCP, and Firpic were co-evaporated in a weight ratio (4,6mCzP2Pm: PCCP: Firpic) of 0.8:0.2:0.1 and a thickness of 20 nm on the light-emitting layer 130 (1).

[0447] Next, 4,6mCzP2Pm and NBPhen were sequentially deposited to a thickness of 20 nm on the light emitting layer 130 as the electron transport layer 118 and to a thickness of 10 nm. Next, LiF was deposited to a thickness of 1 nm on the electron transport layer 118 as the electron injection layer 119 .

[0448] Next, aluminum (Al) was formed to a thickness of 200 nm on the electron injection layer 119 as the electrode 102 .

[0449] Next, in a glove box with a nitrogen atmosphere, a sealing glass substrate was fixed to a glass substrate on which an organic material was formed using an organic EL sealing agent, thereby sealing the comparative light-emitting element 3. Specifically, the sealing agent was applied around the organic material formed on the glass substrate, and the glass substrate and the sealing glass substrate were bonded together, and the sealing agent was applied at 6 J / cm 2 Ultraviolet light with a wavelength of 365 nm was irradiated, and a heat treatment was performed at 80° C. for 1 hour. Comparative light-emitting element 3 was obtained through the above steps.

[0450] 《Manufacturing of Light-Emitting Element 4, Comparative Light-Emitting Element 5 and Light-Emitting Element 6》 The manufacturing process of the light-emitting element 4 is different from that of the comparative light-emitting element 3 in the light-emitting layer 130, and the manufacturing processes of the comparative light-emitting elements 5 and 6 are different from that of the comparative light-emitting element 3 in the hole transport layer 112 and the light-emitting layer 130, and the other processes are the same as the manufacturing method of the comparative light-emitting element 3. The details of the element structure are described in Table 3, so the details of the manufacturing method are omitted.

[0451] Comparative light-emitting element 3 and comparative light-emitting element 5 do not include a fluorescent material in the light-emitting layer 130, but light-emitting element 4 and light-emitting element 6 include a fluorescent material having a protective group. In addition, in this embodiment, 4,6mCzP2Pm and PCCP are a combination that forms an exciplex, and Firpic and Ir (Fppy-iPr) 3 It is a phosphorescent material containing Ir. Therefore, in the light-emitting element 4 and the light-emitting element 6, the exciplex or the phosphorescent material is used as an energy donor, so these light-emitting elements are light-emitting elements that can convert triplet excitation energy into fluorescent light. In addition, it can be said that the light-emitting layer of the light-emitting element 4 and the light-emitting element 6 is a light-emitting layer formed by adding a fluorescent material to the light-emitting layer that can utilize ExTET.

[0452] <Characteristics of Light Emitting Element> Next, the device characteristics of the comparative light-emitting element 3, the comparative light-emitting element 4, the comparative light-emitting element 5, and the light-emitting element 6 manufactured as described above were measured. Note that the measurement method is the same as that of Example 1.

[0453] Fig.18 The external quantum efficiency-luminance characteristics of the comparative light-emitting element 3, the light-emitting element 4, the comparative light-emitting element 5, and the light-emitting element 6 are shown. Fig.19 The values ​​are shown at 2.5 mA / cm 2 The electroluminescence spectra of light emitting element 3 and light emitting element 4 when a current of a current density of 1000 Å is passed through the light emitting element 3 and the light emitting element 4 are compared. Fig. 20 The values ​​are shown at 2.5 mA / cm 2 Electroluminescence spectra when a current of a current density of 200 Å was passed through the comparative light-emitting element 5 and the light-emitting element 6. In addition, the measurement of each light-emitting element was performed at room temperature (an atmosphere maintained at 23° C.). Note that Fig.19 and Fig. 20 Also shown are emission and absorption spectra of a toluene solution of 2tBu-ptBuDPhA2Anth which is a guest material of Light-Emitting Element 4 and Light-Emitting Element 6.

[0454] In addition, Table 4 shows that 1000 cd / m 2 Element characteristics of the comparative light emitting element 3, the light emitting element 4, the comparative light emitting element 5, and the light emitting element 6 in the vicinity.

[0455] [Table 4]

[0456] like Fig.19 As shown in FIG. 1 , the peak wavelengths of the emission spectrum of the comparative light-emitting element 3 are 473 nm and 501 nm, and the half width is 72 nm. This is the emission from Firpic. In addition, the peak wavelength of the emission spectrum of the light-emitting element 4 is 527 nm, and the half width is 69 nm. The emission spectrum of the light-emitting element 4 is mainly green light from 2tBu-ptBuDPhA2Anth, but as shown in FIG. Fig.19 As shown in FIG. 1 , the emission spectrum of light-emitting element 4 is different from the emission spectrum of 2tBu-ptBuDPhA2Anth. As with light-emitting element 2 shown in Example 1, it can be seen that the emission spectrum obtained from light-emitting element 4 includes the emission of Firpic as an energy donor in addition to the emission of 2tBu-ptBuDPhA2Anth. Therefore, multicolor emission can be obtained from the light-emitting element of one embodiment of the present invention. In addition, as Figure 5B As shown, the excitation energy of Firpic as an iridium complex can contribute to the luminescence of Firpic and the luminescence of the guest material.

[0457] like Fig. 20 As shown, the peak wavelengths of the emission spectrum of the comparative light-emitting element 5 are 482nm and 507nm, and the half width is 65nm. This is due to the fact that Ir(Fppy-iPr) 3 In addition, the peak wavelength of the emission spectrum of light-emitting element 6 is 524nm and the half width is 68nm. The emission spectrum of light-emitting element 6 is mainly derived from the green light of 2tBu-ptBuDPhA2Anth, but Fig. 20 As shown in FIG. 1 , the emission spectrum of light-emitting element 6 is different from the emission spectrum of 2tBu-ptBuDPhA2Anth. As with light-emitting element 2 shown in Example 1, it can be seen that the emission spectrum obtained from light-emitting element 6 contains Ir(Fppy-iPr) as an energy donor in addition to the emission of 2tBu-ptBuDPhA2Anth. 3 Therefore, multi-color luminescence can be obtained from the light-emitting element of one embodiment of the present invention. Figure 5B As shown, Ir(Fppy-iPr) 3 The excitation energy can help Ir(Fppy-iPr) 3 luminescence and the luminescence of the guest material.

[0458] In addition, although the light emitting elements 4 and 6 emit light from the fluorescent material, Fig.18As shown in Table 4, it has a high luminous efficiency, that is, an external quantum efficiency exceeding 20%. According to this result, it can be said that in the light-emitting element of one embodiment of the present invention, the non-radiative deactivation of triplet excitons is suppressed and efficiently converted into light emission. Thus, it can be understood that by using a guest material having a protecting group for the light-emitting layer, the energy transfer based on the Dexter mechanism of triplet excitation energy from the host material to the guest material and the non-radiative deactivation of triplet excitation energy can be suppressed.

[0459] <CV measurement results> Next, cyclic voltammetry (CV) was used to measure the electrochemical properties (oxidation reaction properties and reduction reaction properties) of 4,6mCzP2Pm and PCCP used for the light-emitting layer of each light-emitting element. The measurement was the same as the method shown in Example 1.

[0460] As described above, the HOMO level of 4,6mCzP2Pm calculated from the CV measurement was -5.89 eV, and the LUMO level was -2.88 eV. Similarly, the HOMO level of PCCP was -5.63 eV, and the LUMO level was -1.96 eV.

[0461] As described above, the LUMO level of 4,6mCzP2Pm is lower than the LUMO level of PCCP, while the HOMO level of PCCP is higher than the HOMO level of 4,6mCzP2Pm. Thus, when these compounds are used for the light-emitting layer, electrons and holes can be efficiently injected into 4,6mCzP2Pm and PCCP, respectively, such that 4,6mCzP2Pm and PCCP form an exciplex. The emission spectrum of Comparative Light-Emitting Element 3 shows luminescence from Firpic, and the emission spectrum of Comparative Light-Emitting Element 5 shows luminescence from Ir(Fppy-iPr) 3 of. That is, the excitation energy is supplied from 4,6mCzP2Pm and PCCP to Firpic or Ir(Fppy-iPr) 3 . Thus, it can be said that Comparative Light-Emitting Element 3 and Comparative Light-Emitting Element 5 are light-emitting elements using ExTET. Light-Emitting Element 4 can be regarded as a light-emitting element obtained by adding a fluorescent material having a protecting group to Comparative Light-Emitting Element 3, and Light-Emitting Element 6 can be regarded as a light-emitting element obtained by adding a fluorescent material having a protecting group to Comparative Light-Emitting Element 5. Thus, it can be said that Light-Emitting Element 4 and Light-Emitting Element 6 are light-emitting elements obtained by adding a fluorescent material having a protecting group to a light-emitting element using ExTET.

[0462] In addition, from Fig.19 it can be seen that the absorption band on the longest wavelength side of the absorption spectrum of 2tBu-ptBuDPhA2Anth overlaps with the emission spectrum of Firpic. Thus, Light-Emitting Element 4 can receive the excitation energy of the above-mentioned Firpic and emit light. Similarly, from Fig. 20It can be seen that the absorption band on the longest wavelength side of the absorption spectrum of 2tBu-ptBuDPhA2Anth is similar to Ir(Fppy-iPr) 3 Thus, the light emitting element 4 can receive the above-mentioned Ir(Fppy-iPr) 3 The excitation energy emits light.

[0463] <Reliability test of light-emitting components> Next, a driving test was performed on the comparative light emitting element 3, the comparative light emitting element 4, the comparative light emitting element 5, and the light emitting element 6 at a constant current of 2.0 mA. Fig.21 The results are shown in Figure 2. Fig.21 It can be seen that the light-emitting elements 4 and 6 containing the fluorescent material in the light-emitting layer have higher reliability than the comparative light-emitting elements 3 and 5. As described in Example 1, this means that the excitation energy in the light-emitting layer can be efficiently converted into light emission by adding the fluorescent material. Therefore, in the light-emitting element of one embodiment of the present invention, by using the fluorescent material having a protective group in the triplet photosensor, a light-emitting element with high efficiency and high reliability can be manufactured.

[0464] As described above, the light-emitting element of one embodiment of the present invention can use an exciplex or a phosphorescent material as a host material. Alternatively, a structure in which a fluorescent material is added to a light-emitting layer that can utilize ExTET can be used. [Example 3]

[0465] In this embodiment, a light-emitting element of one embodiment of the present invention different from the above-described embodiment and a manufacturing example of a comparative light-emitting element and characteristics of the light-emitting element are described. Figure 1A Likewise. Table 5 shows the details of the element structure. In addition, the structures and abbreviations of the compounds used are shown below. Note that for other organic compounds, reference can be made to the above Examples and the above Embodiments.

[0466] [Chemical formula 39]

[0467] [Table 5]

[0468] 《Manufacturing of Comparative Light Emitting Element 7》 As the electrode 101, an ITSO film with a thickness of 70 nm was formed on a glass substrate. Note that the electrode area of ​​the electrode 101 is 4 mm 2 (2mm×2mm).

[0469] Next, DBT3P-II and molybdenum oxide (MoO) were deposited on the electrode 101 as a hole injection layer 111. 3 ) by weight ratio (DBT3P-II:MoO 3 ) was co-evaporated in a manner of 1:0.5 and a thickness of 40 nm.

[0470] Next, mCzFLP was deposited on the hole injection layer 111 to a thickness of 20 nm as the hole transport layer 112 .

[0471] Next, as the light-emitting layer 130, 4,6mCzP2Pm and 4-(9'-phenyl-3,3'-bi-9H-carbazole-9-yl)benzofurano[3,2-d]pyrimidine (abbreviated as: 4PCCzBfpm) were co-evaporated at a weight ratio (4,6mCzP2Pm:4PCCzBfpm) of 0.8:0.2 and a thickness of 40 nm on the hole transport layer 112. 4PCCzBfpm is a TADF material, and the comparative light-emitting element 7 obtained light emission derived from 4PCCzBfpm.

[0472] Next, 4,6mCzP2Pm and NBPhen were sequentially deposited to a thickness of 20 nm on the light emitting layer 130 as the electron transport layer 118 and to a thickness of 10 nm. Next, LiF was deposited to a thickness of 1 nm on the electron transport layer 118 as the electron injection layer 119 .

[0473] Next, aluminum (Al) was formed to a thickness of 200 nm on the electron injection layer 119 as the electrode 102 .

[0474] Next, in a glove box with a nitrogen atmosphere, a sealing glass substrate was fixed to a glass substrate on which an organic material was formed using an organic EL sealing agent, thereby sealing the comparative light-emitting element 7. Specifically, the sealing agent was applied around the organic material formed on the glass substrate, and the glass substrate and the sealing glass substrate were bonded together, and the sealing agent was heated at 6 J / cm 2 The ultraviolet light having a wavelength of 365 nm was irradiated, and a heat treatment was performed at 80° C. for 1 hour. Through the above steps, a comparative light-emitting element 7 was obtained.

[0475] 《Comparison of the manufacturing of light-emitting element 8 and light-emitting element 9》 The only difference between the comparative light-emitting element 8 and the light-emitting element 9 and the comparative light-emitting element 7 is the structure of the light-emitting layer 130, and the other processes are the same as the manufacturing method of the comparative light-emitting element 7. The details of the element structure are described in Table 5, so the details of the manufacturing method are omitted. Note that in the light-emitting layer 130 of the light-emitting element 9, Firpic is a phosphorescent material containing Ir and is used as an energy donor. In addition, 2,6-di-tert-butyl-N,N,N',N'-tetrakis(3,5-di-tert-butylphenyl)-9,10-anthracenediamine (abbreviated as: 2,6tBu-mmtBuDPhA2Anth), which is an organic compound represented by structural formula (103), is a guest material having a protective group around the light-emitting body.

[0476] <Characteristics of Light Emitting Element> Next, the characteristics of the comparative light-emitting element 7, the comparative light-emitting element 8, and the light-emitting element 9 manufactured as described above were measured. Note that the measurement method is the same as that of Example 1.

[0477] Fig. 22 The external quantum efficiency-luminance characteristics of the comparative light-emitting element 7, the comparative light-emitting element 8, and the light-emitting element 9 are shown. Fig.23 The values ​​are shown at 2.5 mA / cm 2 Electroluminescence spectra when a current of a current density of 1000 Å is passed through Comparative Light Emitting Element 7, Comparative Light Emitting Element 8, and Light Emitting Element 9. The measurements of each light emitting element were performed at room temperature (an atmosphere maintained at 23° C.). Fig.23 Also shown are the emission and absorption spectra of a toluene solution of 2,6tBu-mmtBuDPhA2Anth, which is a guest material of light-emitting element 9. The emission and absorption spectra of a toluene solution of 2,6tBu-mmtBuDPhA2Anth were measured in the same manner as in Example 1.

[0478] In addition, Table 6 shows that 1000 cd / m 2 Element characteristics of the comparative light-emitting element 7, the comparative light-emitting element 8, and the light-emitting element 9 in the vicinity.

[0479] [Table 6]

[0480] like Fig.23As shown, the peak wavelength of the emission spectrum of comparative light-emitting element 7 is 488nm, and the half width is 92nm. This is the light emission from 4PCCzBfpm. In addition, the peak wavelengths of the emission spectrum of comparative light-emitting element 8 are 471nm and 501nm, and the half width is 75nm. The emission spectrum of comparative light-emitting element 8 is the light emission from Firpic. The peak wavelength of the emission spectrum of light-emitting element 9 is 511nm, and the half width is 69nm. This is the green light emission from 2,6tBu-mmtBuDPhA2Anth, but as shown in FIG. Fig.23 As shown, the emission spectrum of light-emitting element 9 is different from the emission spectrum of 2,6tBu-mmtBuDPhA2Anth. It can be seen that the emission spectrum obtained from light-emitting element 9 includes the emission of Firpic as an energy donor in addition to the emission of 2,6tBu-mmtBuDPhA2Anth. Therefore, multi-color emission can be obtained from a light-emitting element of one embodiment of the present invention.

[0481] In addition, although the light emitting element 9 emits light from the fluorescent material, Fig. 22 As shown in Table 6, it has high luminous efficiency, that is, an external quantum efficiency of more than 15%. According to this result, it can be said that in the light-emitting element of one embodiment of the present invention, the non-radiative deactivation of triplet excitons is suppressed and efficiently converted into luminescence. It can be seen that by using a guest material having a protective group in the light-emitting layer, the energy transfer based on the Dexter mechanism of triplet excitation energy from the host material to the guest material and the non-radiative deactivation of triplet excitation energy can be suppressed.

[0482] As mentioned above, 4PCCzBfpm is a TADF material and Firpic is a phosphorescent material. Fig.23 It can be seen that the absorption band on the longest wavelength side of the absorption spectrum of 2,6tBu-mmtBuDPhA2Anth overlaps with the emission spectrum of 4PCCzBfpm and the emission spectrum of Firpic. Therefore, the light emitting element 9 can receive the excitation energy of the above 4PCCzBfpm and / or Firpic and emit light.

[0483] <Testing the Fluorescence Lifetime of Light Emitting Elements> Next, the fluorescence lifetime of the comparative light-emitting element 7, the comparative light-emitting element 8 and the light-emitting element 9 was tested. In the test, a picosecond fluorescence lifetime measurement system (manufactured by Hamamatsu Photonics Co., Ltd., Japan) was used. In this test, a rectangular pulse voltage was applied to the light-emitting element, and a streak camera was used to perform time-resolved measurement of the luminescence that decayed after the voltage dropped. The pulse voltage was applied at a frequency of 10 Hz, and data with a high S / N ratio was obtained by accumulating the data of repeated measurements. In addition, the test was carried out under the following conditions: at room temperature (300K), the brightness of the light-emitting element became 1000 cd / m 2A pulse voltage of about 3V to 4V was applied in a near manner, the pulse time width was 100 μsec, the negative bias voltage was -5V (when the device drive was OFF), and the measurement time range was 20 μsec. Fig.43 The test results are shown. Note that Fig.43 In the graph, the vertical axis represents the normalized intensity of the emission intensity in the state where carriers are continuously injected (when the pulse voltage is ON). In addition, the horizontal axis represents the elapsed time after the pulse voltage drops.

[0484] When using the exponential function Fig.43 When fitting the decay curve shown, it can be seen that the comparative light-emitting element 7 exhibits light emission including an instantaneous fluorescence component of less than 0.2 μs and a delayed fluorescence component of about 11 μs, wherein the ratio of the instantaneous fluorescence component is about 30%. Light emission originating from 4PCCzBfpm was observed from the comparative light-emitting element 7. Therefore, it can be seen that 4PCCzBfpm is a TADF material.

[0485] It can also be seen that the comparative light emitting element 8 emits light including a light emitting component of about 1 μs, and the light emitting element 9 emits light including a fluorescent component of less than 0.4 μs. Fig.43 It can be seen that no delayed fluorescence component of more than 10 μs was observed in comparative light-emitting element 8, but phosphorescence was observed. In addition, light emission faster than comparative light-emitting element 8 was observed from light-emitting element 9. This shows that fluorescence was observed from light-emitting element 9, and excitation energy was efficiently converted into light emission.

[0486] <Reliability test of light-emitting components> Next, a driving test was performed on the comparative light emitting element 8 and the light emitting element 9 at a constant current of 2.0 mA. Fig.24 The results are shown in Figure 2. Fig.24 It can be seen that the light-emitting element 9 including the fluorescent material in the light-emitting layer has higher reliability than the comparative light-emitting element 8. As described in Example 1, this means that the excitation energy in the light-emitting layer can be efficiently converted into light emission by adding the fluorescent material. Therefore, in the light-emitting element of one embodiment of the present invention, by using the fluorescent material having a protective group in the triplet photosensor, a light-emitting element with high efficiency and high reliability can be manufactured. [Example 4]

[0487] In this embodiment, a light-emitting element according to one embodiment of the present invention and a comparative light-emitting element are described as well as the characteristics of the light-emitting element. Figure 1A Likewise. Table 7 shows the details of the element structure. In addition, the structures and abbreviations of the compounds used are shown below. Note that for other organic compounds, reference can be made to the above Examples and the above Embodiments.

[0488] [Chemical formula 40]

[0489] [Table 7]

[0490] 《Comparative Manufacturing of Light-Emitting Element 10 and Light-Emitting Element 11》 The only difference between the comparative light-emitting element 10 and the light-emitting element 11 and the comparative light-emitting element 8 is the structure of the light-emitting layer 130, and the other steps are the same as the manufacturing method of the comparative light-emitting element 8. The details of the element structure are described in Table 7, so the details of the manufacturing method are omitted. Note that in the light-emitting layer 130 of the comparative light-emitting element 10 and the light-emitting element 11, 8-(dibenzothiophene-4-yl)-4-phenyl-2-(9'-phenyl-3,3'-bi-9H-carbazole-9-yl)-[1]benzofurano[3,2-d]pyrimidine (abbreviation: 4Ph-8DBt-2PCCzBfpm) is a TADF material. In the light-emitting layer 130 of the light-emitting element 11, 2,6-diphenyl-N,N,N',N'-tetrakis(3,5-di-tert-butylphenyl)-9,10-anthracene diamine (abbreviation: 2,6Ph-mmtBuDPhA2Anth) is a guest material having a protective group around the light-emitting body. Figure 6C A light-emitting element according to one embodiment of the present invention is shown.

[0491] 〈Characteristics of Light Emitting Elements〉 Next, the characteristics of the comparative light-emitting element 10 and the light-emitting element 11 manufactured as described above were measured. The measurement method was the same as that of Example 1.

[0492] Fig.29 The external quantum efficiency-luminance characteristics of the light emitting element 11 are shown. Fig.30 The values ​​are shown at 2.5 mA / cm 2 The electroluminescence spectra when a current of a current density of 200 Å was passed through the light-emitting element 10 and the light-emitting element 11 were compared. In addition, the measurement of each light-emitting element was performed at room temperature (an atmosphere maintained at 23° C.). Fig.30 Also shown are the emission and absorption spectra of a toluene solution of 2,6Ph-mmtBuDPhA2Anth, which is a guest material of the light emitting element 11. The emission and absorption spectra of the toluene solution of 2,6Ph-mmtBuDPhA2Anth are measured in the same manner as in Example 1.

[0493] In addition, Table 8 shows that 1000 cd / m 2 The device characteristics of the light emitting element 10 and the light emitting element 11 are shown in the figure.

[0494] [Table 8]

[0495] like Fig.30 As shown in FIG. 1 , the peak wavelength of the emission spectrum of comparative light-emitting element 10 is 516 nm and the half width is 93 nm. This is the emission from 4Ph-8DBt-2PCCzBfpm. The peak wavelength of the emission spectrum of comparative light-emitting element 11 is 540 nm and the half width is 71 nm. This includes green emission from 2,6Ph-mmtBuDPhA2Anth, but as shown in FIG. Fig.30 As shown, the emission spectrum of the light-emitting element 11 is different from the emission spectrum of 2,6Ph-mmtBuDPhA2Anth. It can be seen that the emission spectrum obtained from the light-emitting element 11 includes the emission of 4Ph-8DBt-2PCCzBfpm as an energy donor in addition to the emission of 2,6Ph-mmtBuDPhA2Anth. Therefore, multi-color emission can be obtained from a light-emitting element of one embodiment of the present invention.

[0496] In addition, although the light emitting element 11 emits light from the fluorescent material, Fig.29 As shown in Table 8, it has high luminous efficiency, that is, has an external quantum efficiency with a maximum value exceeding 15%. According to this result, it can be said that in the light-emitting element of one embodiment of the present invention, the non-radiative deactivation of triplet excitons is suppressed and efficiently converted into luminescence. It can be seen that by using a guest material having a protective group in the light-emitting layer, the energy transfer based on the Dexter mechanism of triplet excitation energy from the host material to the guest material and the non-radiative deactivation of triplet excitation energy can be suppressed.

[0497] As mentioned above, 4Ph-8DBt-2PCCzBfpm is a TADF material. Fig.30 It can be seen that the absorption band on the longest wavelength side of the absorption spectrum of 2,6Ph-mmtBuDPhA2Anth overlaps with the emission spectrum of 4Ph-8DBt-2PCCzBfpm. Therefore, it can be seen that in the light-emitting element 11, 2,6Ph-mmtBuDPhA2Anth can receive the excitation energy of 4Ph-8DBt-2PCCzBfpm and emit light.

[0498] <Testing of fluorescence lifetime of light-emitting element> Next, the fluorescence lifetime of the light-emitting element 10 is tested for comparison. In the test, a picosecond fluorescence lifetime measurement system (manufactured by Hamamatsu Photonics Co., Ltd., Japan) is used. In this test, a rectangular pulse voltage is applied to the light-emitting element, and a streak camera is used to perform time-resolved measurement of the luminescence that decays after the voltage drops. The pulse voltage is applied at a frequency of 10 Hz, and data with a high S / N ratio is obtained by accumulating the data of repeated measurements. In addition, the test is carried out under the following conditions: at room temperature (300K), the brightness of the light-emitting element becomes 1000 cd / m 2 A pulse voltage of about 3V to 4V was applied in a near manner, the pulse time width was 100 μsec, the negative bias voltage was -5V (when the device drive was OFF), and the measurement time range was 200 μsec. Fig.31 The test results are shown. Note that Fig.31 In the graph, the vertical axis represents the normalized intensity of the emission intensity in the state where carriers are continuously injected (when the pulse voltage is ON). In addition, the horizontal axis represents the elapsed time after the pulse voltage drops.

[0499] When using the exponential function Fig.31 When the decay curve shown is fitted, it can be seen that the comparative light-emitting element 10 exhibits light emission including an instantaneous fluorescence component of less than 0.4 μs and a delayed fluorescence component of about 89 μs. Light emission derived from 4Ph-8DBt-2PCCzBfpm is observed from the comparative light-emitting element 10. Therefore, it can be seen that 4Ph-8DBt-2PCCzBfpm is a TADF material.

[0500] <Reliability test of light-emitting components> Next, a driving test was performed on the comparative light emitting element 10 and the light emitting element 11 at a constant current of 2.0 mA. Fig.32 The results are shown in Figure 2. Fig.32 It can be seen that the light-emitting element 11 including the fluorescent material in the light-emitting layer has higher reliability than the comparative light-emitting element 10. As described in Example 1, this means that the excitation energy in the light-emitting layer can be efficiently converted into light emission by adding the fluorescent material. Therefore, in the light-emitting element of one embodiment of the present invention, by using the fluorescent material having a protective group in the triplet photosensor, a light-emitting element with high efficiency and high reliability can be manufactured. [Example 5]

[0501] In this embodiment, a light-emitting element according to one embodiment of the present invention and a comparative light-emitting element are described as well as the characteristics of the light-emitting element. Figure 1A Likewise. Table 9 shows the details of the element structure. In addition, the structures and abbreviations of the compounds used are shown below. Note that for other organic compounds, reference can be made to the above Examples and the above Embodiments.

[0502] [Chemical formula 41]

[0503] [Table 9]

[0504] 《Comparison of the manufacturing of light-emitting element 12 and light-emitting element 13》 The difference between the comparative light-emitting element 12 and the comparative light-emitting element 8 is only the structure of the thickness of the light-emitting layer 130 and the electron transport layer 118 (2), and the other processes are the same as the manufacturing method of the comparative light-emitting element 8. In addition, the difference between the comparative light-emitting element 13 and the comparative light-emitting element 8 is only the structure of the light-emitting layer 130, and the other processes are the same as the manufacturing method of the comparative light-emitting element 8. The details of the element structure are recorded in Table 9, so the details of the manufacturing method are omitted. Note that in the light-emitting layer 130 of the comparative light-emitting element 12 and the light-emitting element 13, 2,4,6-tris(9H-carbazole-9-yl)-3,5-bis(3,6-diphenylcarbazole-9-yl)benzonitrile (abbreviation: 3C2zDPhCzBN) is a TADF material. This is recorded in non-patent document 1. In addition, in the light-emitting layer 130 of the light-emitting element 13, 2,6Ph-mmtBuDPhA2Anth is a guest material having a protecting group around the light-emitting body. The light-emitting element 13 is Figure 6C A light-emitting element according to one embodiment of the present invention is shown.

[0505] <Characteristics of Light Emitting Element> Next, the characteristics of the comparative light-emitting element 12 and the light-emitting element 13 manufactured as described above were measured. The measurement method was the same as that of Example 1.

[0506] Fig.33 The external quantum efficiency-luminance characteristics of the comparative light-emitting element 12 and the light-emitting element 13 are shown. Fig.34 The values ​​are shown at 2.5 mA / cm 2 The electroluminescence spectra when a current of a current density of 200 Å was passed through the light-emitting element 12 and the light-emitting element 13 were compared. In addition, the measurement of each light-emitting element was performed at room temperature (an atmosphere maintained at 23° C.). Fig.34 Also shown are the emission and absorption spectra of a toluene solution of 2,6Ph-mmtBuDPhA2Anth which is a guest material of the light-emitting element 13.

[0507] In addition, Table 10 shows that 1000 cd / m 2 The device characteristics of the light emitting element 12 and the light emitting element 13 are compared nearby.

[0508] [Table 10]

[0509] like Fig.34 As shown in FIG. 1 , the peak wavelength of the emission spectrum of the comparative light-emitting element 12 is 506 nm and the half width is 81 nm. This is the light emission from 3C2zDPhCzBN. The peak wavelength of the emission spectrum of the light-emitting element 13 is 540 nm and the half width is 73 nm. This includes green light emission from 2,6Ph-mmtBuDPhA2Anth, but as shown in FIG. Fig.34 As shown, the emission spectrum of the light-emitting element 13 is different from the emission spectrum of 2,6Ph-mmtBuDPhA2Anth. It is known that the emission spectrum obtained from the light-emitting element 13 includes the emission of 3C2zDPhCzBN as an energy donor in addition to the emission of 2,6Ph-mmtBuDPhA2Anth. Therefore, multi-color emission can be obtained from a light-emitting element of one embodiment of the present invention.

[0510] In addition, although the light emitting element 13 emits light from the fluorescent material, Fig.33 As shown in Table 10, it has high luminous efficiency, that is, it has an external quantum efficiency whose maximum value exceeds 20%. Based on the present results, it can be said that in a light-emitting element of one embodiment of the present invention, the non-radiative deactivation of triplet excitons is suppressed and efficiently converted into luminescence. It can be seen that by using a guest material having a protective group for the light-emitting layer, the energy transfer based on the Dexter mechanism of the triplet excitation energy from the host material to the guest material and the non-radiative deactivation of the triplet excitation energy can be suppressed. In addition, it can be seen that the light-emitting element 13 has a high luminous efficiency compared with the comparative light-emitting element 12 having only TADF material as the light-emitting material.

[0511] As mentioned above, 3C2zDPhCzBN is a TADF material. Fig.34 It can be seen that the absorption band on the longest wavelength side of the absorption spectrum of 2,6Ph-mmtBuDPhA2Anth overlaps with the emission spectrum of 3C2zDPhCzBN. This shows that in the light emitting element 13, 2,6Ph-mmtBuDPhA2Anth can receive the excitation energy of 3C2zDPhCzBN and emit light. [Example 6]

[0512] In this embodiment, a light-emitting element according to one embodiment of the present invention and a comparative light-emitting element are described as well as the characteristics of the light-emitting element. Figure 1A Likewise. Table 11 shows the details of the element structure. In addition, the structures and abbreviations of the compounds used are shown below. Note that for other organic compounds, reference can be made to the above Examples and the above Embodiments.

[0513] [Chemical formula 42]

[0514] [Table 11]

[0515] 《Manufacturing of Comparative Light-Emitting Element 14, Comparative Light-Emitting Element 15, and Light-Emitting Element 16》 The only difference between the comparative light-emitting element 14, the comparative light-emitting element 15 and the light-emitting element 16 and the comparative light-emitting element 8 is the structure of the light-emitting layer 130, and the other processes are the same as the manufacturing method of the comparative light-emitting element 8. The details of the element structure are described in Table 11, so the details of the manufacturing method are omitted. Note that in the light-emitting layer 130 of the comparative light-emitting element 14, the comparative light-emitting element 15 and the light-emitting element 16, 3C2zDPhCzBN is a TADF material. In addition, in the comparative light-emitting element 15, N,N′-diphenylquinacridone (abbreviated as: DPQd) is a fluorescent material having no protective group around the light-emitting body. In the light-emitting layer 130 of the light-emitting element 16, 1,3,8,10-tetra-tert-butyl-7,14-bis(3,5-di-tert-butylphenyl)-5,12-dihydroquinolino[2,3-b]acridine-7,14-dione (abbreviation: Oct-tBuDPQd) is a guest material having a protective group around the light-emitting body. The light-emitting element 16 is Figure 6C A light-emitting element according to one embodiment of the present invention is shown.

[0516] <Characteristics of Light Emitting Element> Next, the characteristics of the comparative light-emitting element 14, the comparative light-emitting element 15, and the light-emitting element 16 manufactured as described above were measured. The measurement method was the same as that of Example 1.

[0517] Fig.35 The external quantum efficiency-luminance characteristics of the comparative light-emitting element 14, the comparative light-emitting element 15, and the light-emitting element 16 are shown. Fig.36 The values ​​are shown at 2.5 mA / cm 2 The electroluminescence spectra when a current density of 1000 Å is passed through the light emitting element 14 and the light emitting element 16 are compared. Fig.37 The values ​​are shown at 2.5 mA / cm 2 Electroluminescence spectra when a current of a current density of 1000 Å is passed through the comparative light-emitting element 14 and the comparative light-emitting element 15. In addition, the measurement of each light-emitting element was performed at room temperature (an atmosphere maintained at 23° C.). Fig.36 The absorption and emission spectra of a toluene solution of Oct-tBuDPQd, which is a guest material of the light-emitting element 16, are also shown. Fig.37 Also shown are absorption and emission spectra of a toluene solution of DPQd which is a guest material of the comparative light-emitting element 15 .

[0518] In addition, Table 12 shows that 1000 cd / m 2 Element characteristics of the comparative light emitting element 14, the comparative light emitting element 15, and the light emitting element 16 in the vicinity.

[0519] [Table 12]

[0520] like Fig.36 and Fig.37 As shown in FIG. 1 , the peak wavelength of the emission spectrum of the comparative light-emitting element 14 is 506 nm and the half width is 81 nm. This is the light emission from 3C2zDPhCzBN. In addition, the peak wavelength of the emission spectrum of the light-emitting element 16 is 524 nm and the half width is 33 nm. This includes green light emission from Oct-tBuDPQd, but as shown in FIG. Fig.36 As shown in FIG. 1 , the emission spectrum of light-emitting element 16 is different from that of Oct-tBuDPQd. It is known that the emission spectrum obtained from light-emitting element 16 contains the emission of 3C2zDPhCzBN as an energy donor in addition to the emission of Oct-tBuDPQd. Therefore, multicolor emission can be obtained from a light-emitting element of one embodiment of the present invention. In addition, the peak wavelength of the emission spectrum of comparison light-emitting element 15 is 526nm and the half width is 26nm. This is green emission from DPQd, but as shown in FIG. Fig.37 As shown, the emission spectrum of the comparative light-emitting element 15 is different from the emission spectrum of DPQd. It is known that the emission spectrum obtained from the comparative light-emitting element 15 includes the emission of 3C2zDPhCzBN as an energy donor in addition to the emission of DPQd.

[0521] In addition, although the light emitting element 16 emits light from the fluorescent material, Fig.35 As shown in Table 12, it has a high luminous efficiency, that is, an external quantum efficiency whose maximum value exceeds 20%. Based on this result, it can be said that in a light-emitting element of one embodiment of the present invention, the non-radiative deactivation of triplet excitons is suppressed and efficiently converted into luminescence. In addition, the result that the external quantum efficiency of light-emitting element 16 is higher than that of the comparative light-emitting element 15 is shown. The fluorescent material used for the light-emitting layer in the comparative light-emitting element 15 is different from that of the light-emitting element 16. From this result, it can be seen that by using a fluorescent material having a protecting group, a light-emitting element with a high luminous efficiency can be obtained compared with the case of using a fluorescent material without a protecting group. This is because the deactivation of the triplet excitons in the light-emitting layer based on the Dexter mechanism is suppressed.

[0522] (Reference Example 1) In this reference example, a method for synthesizing the fluorescent material having a protecting group used in Examples 1 and 2, namely, 2tBu-ptBuDPhA2Anth, is described.

[0523] 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 tert-butoxide, and 60 mg (0.15 mmol) of 2-dicyclohexylphosphino-2',6'-dimethoxy-1,1'-biphenyl (abbreviated as: SPhos) were placed in a 200 mL three-necked flask, and the air in the flask was replaced with nitrogen. 35 mL of xylene was added to the mixture, and the mixture was degassed under reduced pressure, and 40 mg (70 μmol) of bis(dibenzylideneacetone)palladium (0) was added to the mixture, and then the mixture was stirred at 170° C. for 4 hours under a nitrogen stream.

[0524] After stirring, 400 mL of toluene was added to the obtained mixture, and then the mixture was filtered through magnesium silicate (Wako Pure Chemical Industries, Ltd., Japan, catalog number: 066-05265), diatomaceous earth (Wako Pure Chemical Industries, Ltd., Japan, catalog number: 537-02305), and alumina to obtain a filtrate. The obtained filtrate was concentrated to obtain a brown solid.

[0525] The solid was purified by silica gel column chromatography (developing solvent: hexane: toluene = 9:1) to obtain a yellow solid of the target. The yellow solid was recrystallized using toluene, hexane and ethanol to obtain 1.5 g of the target yellow solid in a yield of 61%. The following is a synthesis scheme (A-1).

[0526] [Chemical formula 43]

[0527] 1.5 g of the obtained yellow solid was purified by sublimation by gradient sublimation. The yellow solid was heated at 315° C. for 15 hours under a pressure of 4.5 Pa for sublimation purification. After sublimation purification, 1.3 g of the target yellow solid was obtained at a recovery rate of 89%.

[0528] In addition, the utilization of the yellow solid obtained by this synthesis is shown below: 1 H NMR measurement results. In addition, Fig.25A and Fig.25B , Fig.26 Show 1 H NMR spectrum. Fig.25B yes Fig.25A A zoomed in graph of the 6.5ppm to 9.0ppm range. Fig.26 yes Fig.25A This is an enlarged view of the range of 0.5ppm to 2.0ppm. From this result, it can be seen that the target 2tBu-ptBuDPhA2Anth was obtained.

[0529] 1 H NMR (CDCl 3 ,300MHz):σ=8.20-8.13(m,2H), 8.12(d,J=8.8Hz,1H), 8.05(d,J=2.0Hz,1H), 7.42(dd,J=9.3Hz,2.0Hz, 1H), 7.32-7.26 (m, 2H), 7.20 (d, J = 8.8Hz, 8H), 7.04 (dd, J = 8.8Hz, 2.4Hz, 8H), 1.26 (s, 36H), 1.18 (s, 9H).

[0530] (Reference Example 2) In this reference example, a method for synthesizing the fluorescent material having a protective group used in Example 3, namely, 2,6tBu-mmtBuDPhA2Anth, is described.

[0531] 1.1 g (2.5 mmol) of 2,6-di-tert-butylanthracene, 2.3 g (5.8 mmol) of bis(3,5-tert-butylphenyl)amine, 1.1 g (11 mmol) of sodium tert-butoxide, and 60 mg (0.15 mmol) of 2-dicyclohexylphosphino-2',6'-dimethoxy-1,1'-biphenyl (abbreviated as: SPhos) were placed in a 200 mL three-necked flask, and the air in the flask was replaced with nitrogen. 25 mL of xylene was added to the mixture, and the mixture was degassed under reduced pressure, and 40 mg (70 μmol) of bis(dibenzylideneacetone)palladium (0) was added to the mixture, and then the mixture was stirred at 150° C. for 6 hours under a nitrogen stream.

[0532] After stirring, 400 mL of toluene was added to the obtained mixture, and then suction filtration was performed through magnesium silicate, diatomaceous earth, and alumina to obtain a filtrate. The obtained filtrate was concentrated to obtain a brown solid.

[0533] The solid was purified by silica gel column chromatography (developing solvent: hexane: toluene = 9:1) to obtain a yellow solid of the target. The yellow solid was recrystallized using hexane and methanol to obtain 0.45 g of the target yellow solid at a yield of 17%. The synthesis scheme (B-1) of step 1 is shown below.

[0534] [Chemical formula 44]

[0535] 0.45 g of the obtained yellow solid was purified by sublimation by gradient sublimation. The yellow solid was heated at 275° C. for 15 hours under a pressure of 5.0 Pa for sublimation purification. After sublimation purification, 0.37 g of the target yellow solid was obtained at a recovery rate of 82%.

[0536] In addition, the following shows the utilization of the yellow solid obtained by the above step 1: 1 H NMR measurement results. In addition, Fig.27A and Fig.27B , Fig.28 Show 1 H NMR spectrum. Fig.27B yes Fig.28 A zoomed in graph of the 6.5ppm to 9.0ppm range. Fig.28 yes Fig.27A This is an enlarged view of the range of 0.5ppm to 2.0ppm. From this result, it can be seen that 2,6tBu-mmtBuDPhA2Anth was obtained.

[0537] 1 H NMR (CDCl 3 , 300MHz): σ=8.11(d,J=9.3Hz,2H), 7.92(d,J=1.5Hz,1H), 7.34(dd,J=9.3Hz,2.0Hz,2H), 6.96-6.95(m,8H), 6.91-6.90(m,4H), 1.13-1.12(m,90H).

[0538] (Reference Example 3) In this reference example, a method for synthesizing the fluorescent material having a protective group used in Example 4, namely, 2,6Ph-mmtBuDPhA2Anth, is described.

[0539] <Step 1: Synthesis of 2,6Ph-mmtBuDPhA2Anth> 1.8 g (3.6 mmol) of 9,10-dibromo-2,6-diphenylanthracene, 2.8 g (7.2 mmol) of bis(3,5-tert-butylphenyl)amine, 1.4 g (15 mmol) of sodium tert-butoxide, and 60 mg (0.15 mmol) of SPhos were placed in a 200 mL three-necked flask, and the air in the flask was replaced with nitrogen. 36 mL of xylene was added to the mixture, and the mixture was degassed under reduced pressure. Then, 40 mg (70 μmol) of bis(dibenzylideneacetone)palladium(0) was added to the mixture, and the mixture was stirred at 150°C for 3 hours under a nitrogen stream. After stirring, 400 mL of toluene was added to the obtained mixture, and then the mixture was filtered through magnesium silicate, diatomaceous earth, and alumina to obtain a filtrate. The obtained filtrate was concentrated to obtain a brown solid. The solid was purified by silica gel column chromatography (developing solvent: hexane: toluene = 9:1) to obtain a yellow solid. The obtained yellow solid was recrystallized from ethyl acetate and ethanol to obtain 0.61 g of the target compound as a yellow solid at a yield of 15%. The synthesis scheme (C-1) of step 1 is shown below.

[0540] [Chemical formula 45]

[0541] 0.61 g of the obtained yellow solid was purified by sublimation by gradient sublimation. The yellow solid was heated at 280° C. for 15 hours under a pressure of 3.8 Pa for sublimation purification. After sublimation purification, 0.56 g of the target yellow solid was obtained at a recovery rate of 91%.

[0542] In addition, the following shows the utilization of the yellow solid obtained by the above step 1: 1 H NMR measurement results. In addition, Fig.38A and Fig.38B , Fig.39 Show 1 H NMR spectrum. Fig.38B yes Fig.38A A zoomed in graph of the 6.5ppm to 9.0ppm range. Fig.39 yes Fig.38A This is an enlarged view of the range of 0.5ppm to 2.0ppm. From this result, it can be seen that 2,6Ph-mmtBuDPhA2Anth was obtained.

[0543] 1 H NMR (CDCl 3 ,300MHz): σ=8.35(d,J=1.5Hz,2H), 8.24(d,J=8.8Hz,2H), 7.60(dd,J=1.5Hz,8.8Hz,2H), 7.43-7.40(m,4H), 7.35-7.24(m,6H), 7.03-7.02(m,8H), 6.97-6.96(m,4H), 1.16(s,72H).

[0544] (Reference Example 4) In this reference example, the synthesis method of the TADF material used in Example 4, namely 4Ph-8DBt-2PCCzBfpm, is described.

[0545] <Step 1: Synthesis of 2,8-dichloro-4-phenyl[1]benzofurano[3,2-d]pyrimidine> First, 10 g (37 mmol) of 2,4,8-trichloro[1]benzofurano[3,2-d]pyrimidine, 4.5 g (371 mmol) of phenylboronic acid, 37 g of 2M potassium carbonate aqueous solution, 180 mL of toluene and 18 mL of ethanol were placed in a 500 mL three-necked flask, degassed, and the air in the flask was replaced with nitrogen. 1.3 g (1.8 mmol) of bis(triphenylphosphine)palladium(II) dichloride was added to the mixture and stirred at 80°C for 16 hours. After the specified time, the obtained reaction mixture was concentrated, water was added and filtered. The obtained filter residue was washed with ethanol to obtain a solid. The solid was dissolved in toluene and filtered by sequentially stacking diatomaceous earth, alumina, and diatomaceous earth as a filter agent. The obtained filtrate was concentrated to obtain 11 g of the target white solid with a yield of 91%. The synthesis scheme (D-1) of step 1 is shown below.

[0546] [Chemical formula 46]

[0547] <Step 2: Synthesis of 8-chloro-4-phenyl-2-(9'-phenyl-3,3'-bi-9H-carbazole-9-yl)-[1]benzofurano[3,2-d]pyrimidine> Next, 5.0 g (16 mmol) of 2,8-dichloro-4-phenyl[1]benzofurano[3,2-d]pyrimidine obtained in step 1, 6.5 g (16 mmol) of 9-phenyl-3,3'-bi-9H-carbazole, 3.1 g (32 mmol) of sodium tert-butoxide and 150 mL of xylene were placed in a 300 mL three-necked flask, and the air in the flask was replaced with nitrogen. 224 mg (0.64 mmol) of di-tert-butyl(1-methyl-2,2-diphenylcyclopropyl)phosphine (abbreviated as: cBRIDP) and 58 mg (0.16 mmol) of allylpalladium(II) chloride dimer were added thereto, and stirred at 90°C for 7 hours. Water was added to the obtained reaction mixture, and the aqueous layer was extracted with toluene. The obtained extract solution and the organic layer were combined, washed with saturated brine, and anhydrous magnesium sulfate was added to the organic layer for drying. The obtained mixture was gravity filtered, and the filtrate was concentrated to obtain a solid. The solid was purified by silica gel column chromatography. A mixed solvent of toluene:hexane = 1:1 was used as a developing solvent. The obtained fraction was concentrated to obtain 5.5 g of the target yellow solid at a yield of 50%. The synthesis scheme (D-2) of step 2 is shown below.

[0548] [Chemical formula 47]

[0549] <Step 3: Synthesis of 8-(dibenzothiophene-4-yl)-4-phenyl-2-(9'-phenyl-3,3'-bi-9H-carbazole-9-yl)-[1]benzofurano[3,2-d]pyrimidine (abbreviation: 4Ph-8DBt-2PCCzBfpm)> Next, 2.25 g (3.3 mmol) of 8-chloro-4-phenyl-2-(9'-phenyl-3,3'-bi-9H-carbazole-9-yl)-[1]benzofurano[3,2-d]pyrimidine obtained in the above step 2, 0.82 g (3.6 mmol) of 4-dibenzothiopheneboronic acid, 1.5 g (9.8 mmol) of cesium fluoride and 35 mL of xylene were placed in a three-necked flask, and the air in the flask was replaced with nitrogen. The temperature of the mixture was raised to 60° C., 60 mg (0.065 mmol) of tris(dibenzylideneacetone)dipalladium(0) and 77 mg (0.2 mmol) of 2'-(dicyclohexylphosphino)acetophenone vinyl ketal were added ther...

Claims

1. A light emitting element, comprising: a first electrode; A light-emitting layer on the first electrode, the light-emitting layer comprising a first material configured to emit delayed fluorescence and a second material configured to convert singlet excitation energy into light emission; and a second electrode on the light-emitting layer, Wherein, the second material comprises a luminophore and five or more protecting groups, Wherein, the luminophore comprises a fused aromatic ring or a fused heteroaromatic ring, wherein the five or more protecting groups independently include any one of an alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, and a trialkylsilyl group having 3 to 12 carbon atoms, The emission spectrum of the first material and the absorption bands on the longest wavelength side of the absorption spectrum of the second material overlap with each other.

2. A light emitting element, comprising: a first electrode; A light-emitting layer on the first electrode, the light-emitting layer comprising a first material configured to emit delayed fluorescence and a second material configured to convert singlet excitation energy into light emission; and a second electrode on the light-emitting layer, Wherein, the second material comprises a luminophore and five or more protecting groups, The luminophore comprises a fused aromatic ring having 10 to 30 carbon atoms or a fused heteroaromatic ring having 10 to 30 carbon atoms. wherein the five or more protecting groups independently include any one of an alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, and a trialkylsilyl group having 3 to 12 carbon atoms, The emission spectrum of the first material and the absorption band of the second material on the longest wavelength side overlap each other. Among them, at least four of the five or more protecting groups are independently any one of an alkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, and a trialkylsilyl group having 3 to 12 carbon atoms.

3. A light emitting element, comprising: a first electrode; A light-emitting layer on the first electrode, the light-emitting layer comprising a first material configured to emit delayed fluorescence and a second material configured to convert singlet excitation energy into light emission; and a second electrode on the light-emitting layer, Wherein, the second material comprises a luminophore and at least four protecting groups, Wherein, the luminophore comprises a fused aromatic ring or a fused heteroaromatic ring, wherein the at least four protecting groups are not directly bonded to one of the fused aromatic ring and the fused heteroaromatic ring, wherein the at least four protecting groups independently include any one of an alkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, and a trialkylsilyl group having 3 to 12 carbon atoms, The emission spectrum of the first material and the absorption bands on the longest wavelength side of the absorption spectrum of the second material overlap with each other.

4. A light emitting element, comprising: a first electrode; a light-emitting layer on the first electrode, the light-emitting layer comprising a first material configured to emit delayed fluorescence and a second material configured to convert singlet excitation energy into light emission; as well as a second electrode on the light-emitting layer, Wherein, the second material comprises a luminophore and a plurality of protecting groups, wherein the luminophore is one of a fused aromatic ring and a fused heteroaromatic ring, wherein at least one of the atoms of the plurality of protecting groups is located directly on one surface of the luminescent body, and at least one of the atoms of the plurality of protecting groups is located directly on another surface of the luminescent body, The emission spectrum of the first material and the absorption bands on the longest wavelength side of the absorption spectrum of the second material overlap with each other.

5. A light emitting element, comprising: a first electrode; A light-emitting layer on the first electrode, the light-emitting layer comprising a first material configured to emit delayed fluorescence and a second material configured to convert singlet excitation energy into light emission; and a second electrode on the light-emitting layer, Wherein, the second material comprises a luminescent body and two or more diphenylamino groups, Wherein, the luminophore is a fused aromatic ring or a fused heteroaromatic ring, wherein the luminophore is bonded to the two or more diphenylamino groups, wherein the phenyl groups in the two or more diphenylamino groups each independently contain a protecting group at the 3-position and the 5-position, wherein the protecting groups independently include any one of an alkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, and a trialkylsilyl group having 3 to 12 carbon atoms, The emission spectrum of the first material and the absorption bands on the longest wavelength side of the absorption spectrum of the second material overlap with each other.

6. A light emitting element, comprising: a first electrode; A light-emitting layer on the first electrode, the light-emitting layer comprising a first material configured to emit delayed fluorescence and a second material configured to convert singlet excitation energy into light emission; and a second electrode on the light-emitting layer, Wherein, the second material comprises a luminophore and five or more protecting groups, Wherein, the luminophore comprises a fused aromatic ring or a fused heteroaromatic ring, wherein the five or more protecting groups independently include any one of an alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, and a trialkylsilyl group having 3 to 12 carbon atoms, The emission spectrum of the first material and the absorption band of the second material on the longest wavelength side overlap each other. The excitation energy level difference between the lowest singlet excited state and the lowest triplet excited state of the first material is less than 0.2 eV.

7. A light emitting element, comprising: a first electrode; A light-emitting layer on the first electrode, the light-emitting layer comprising a first material configured to emit delayed fluorescence and a second material configured to convert singlet excitation energy into light emission; and a second electrode on the light-emitting layer, Wherein, the second material comprises a luminophore and five or more protecting groups, Wherein, the luminophore comprises a fused aromatic ring or a fused heteroaromatic ring, wherein the five or more protecting groups independently include any one of an alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, and a trialkylsilyl group having 3 to 12 carbon atoms, The emission spectrum of the first material and the absorption band of the second material on the longest wavelength side overlap each other. The five or more protecting groups are arranged at a distance of more than 1 nm and less than 10 nm from the luminescent body.

8. A light emitting element, comprising: a first electrode; A light-emitting layer on the first electrode, the light-emitting layer comprising a first material configured to emit delayed fluorescence and a second material configured to convert singlet excitation energy into light emission; and a second electrode on the light-emitting layer, Wherein, the second material comprises a luminophore and at least four protecting groups, Wherein, the luminophore comprises a fused aromatic ring or a fused heteroaromatic ring, wherein the at least four protecting groups are not directly bonded to one of the fused aromatic ring and the fused heteroaromatic ring, wherein the at least four protecting groups independently include any one of an alkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, and a trialkylsilyl group having 3 to 12 carbon atoms, The emission spectrum of the first material and the absorption band of the second material on the longest wavelength side overlap each other. The alkyl group having 3 or more and 10 or less carbon atoms is a branched alkyl group.

9. A light emitting element, comprising: a first electrode; A light-emitting layer on the first electrode, the light-emitting layer comprising a first material configured to emit delayed fluorescence and a second material configured to convert singlet excitation energy into light emission; and a second electrode on the light-emitting layer, Wherein, the second material comprises a luminophore and five or more protecting groups, Wherein, the luminophore comprises a fused aromatic ring or a fused heteroaromatic ring, wherein the five or more protecting groups independently include any one of an alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, and a trialkylsilyl group having 3 to 12 carbon atoms, The emission spectrum of the first material and the absorption band of the second material on the longest wavelength side overlap each other. Wherein, the fused aromatic ring or fused heteroaromatic ring comprises naphthalene, anthracene, fluorene, Any of triphenylene, tetracene, pyrene, perylene, coumarin, quinacridone and naphthobisbenzofuran.

10. A light emitting element, comprising: a first electrode; A light-emitting layer on the first electrode, the light-emitting layer comprising a first material configured to emit delayed fluorescence and a second material configured to convert singlet excitation energy into light emission; and a second electrode on the light-emitting layer, Wherein, the second material comprises a luminophore and five or more protecting groups, Wherein, the luminophore comprises a fused aromatic ring or a fused heteroaromatic ring, wherein the five or more protecting groups independently include any one of an alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, and a trialkylsilyl group having 3 to 12 carbon atoms, The emission spectrum of the first material and the absorption band of the second material on the longest wavelength side overlap each other. The concentration of the second material in the light-emitting layer is greater than or equal to 0.01 wt % and less than or equal to 2 wt %.

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