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

Abstract

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

Description

[Technical field]

[0001] One embodiment of the present invention is a light-emitting element, or a display device, an electronic device, and a lighting device each having the light-emitting element. Regarding the lighting device.

[0002] Note that one embodiment of the present invention is not limited to the above technical fields. The technical field of one aspect of the present invention relates to an article, a method, or a manufacturing method. is a process, machine, manufacture, or composition of matter. Therefore, the technical field of one embodiment of the present invention disclosed in the present specification more specifically relates to Examples of the semiconductor device include a semiconductor device, a display device, a liquid crystal display device, a light-emitting device, a lighting device, a power storage device, a memory device, etc. Examples include devices, methods for driving them, and methods for manufacturing them. . [Background technology]

[0003] In recent years, electroluminescence (EL) The basic structure of these light-emitting devices is as follows: The device has a structure in which a layer containing a light-emitting substance (EL layer) is sandwiched between a pair of electrodes. By applying a voltage between them, light is emitted from the luminescent material.

[0004] Since the above-mentioned light-emitting element is a self-luminous type, a display device using the light-emitting element has excellent visibility and backlighting. It has the advantage of not requiring a light source and consuming little power. It also has the advantage of having a high response speed.

[0005] An EL device that uses an organic compound as a light-emitting substance and has the light-emitting organic compound between a pair of electrodes In the case of a light-emitting element having a layer (for example, an organic EL element), a voltage is applied between a pair of electrodes. As a result, electrons are injected from the cathode and holes are injected from the anode into the light-emitting EL layer. The injected electrons and holes are then recombined to produce light-emitting The organic compound is excited, and light can be emitted from the excited luminescent organic compound. do.

[0006] The types of excited states that organic compounds can form include singlet excited states (S * ) and triplet excitation Status(T * ) in which the emission from the singlet excited state is fluorescent and the emission from the triplet excited state is phosphorescent. The statistical generation ratio of these in a light-emitting element is S * :T * = Therefore, compared to a light-emitting element using a compound that emits fluorescence (a fluorescent compound), Light-emitting elements that use compounds that emit phosphorescence (phosphorescent compounds) have higher luminous efficiency. Therefore, it is possible to convert the energy of the triplet excited state into light emission. 2. Description of the Related Art In recent years, light-emitting devices using phosphorescent compounds have been actively developed.

[0007] Among light-emitting elements using phosphorescent compounds, particularly light-emitting elements that emit blue light, It is difficult to develop stable compounds with high triplet excitation energy levels, so they are not yet in practical use. Therefore, efforts are being made to develop light-emitting devices that use more stable fluorescent compounds. Methods to improve the luminous efficiency of light-emitting devices using fluorescent compounds (fluorescent light-emitting devices) are being explored. It has been done.

[0008] One example is thermally activated delayed fluorescence (TDE). Light-emitting devices using TADF (Transparent Anode Fluorescence) materials are known. In thermally activated delayed fluorescent materials, the triplet excited state is converted to the singlet excited state by reverse intersystem crossing. The singlet excited state is converted into light emission.

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

[0010] [Patent Document 1] JP 2014-45179 A [Non-patent literature]

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

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

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

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

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

[0016] As described above, in a light-emitting element that exhibits fluorescence, triplet excitation energy is efficiently converted into light emission. Therefore, the development of a method for converting energy between materials used in the light-emitting layer is required. It is necessary to improve dynamic efficiency.

[0017] Therefore, one embodiment of the present invention is a light-emitting layer between a pair of electrodes, the light-emitting layer containing a first organic compound. a first organic compound, a second organic compound, and a third organic compound, The singlet excited energy of the second organic compound is converted into light emission. The difference between the energy of the first organic compound and the triplet excitation energy of the second organic compound is 0 eV or more and 0.2 eV or less. V or less, and the third organic compound has a function of converting the singlet excitation energy into light emission. The light emitting layer emits light emitted by the third organic compound, forming a light emitting element.

[0018] In another embodiment of the present invention, a light-emitting layer is provided between a pair of electrodes. a first organic compound, a second organic compound, and a third organic compound, The second organic compound has a function of converting the excitation energy into light emission, and the second organic compound has a π-electron-rich skeleton and The third organic compound has a π-electron deficient skeleton and functions to convert singlet excitation energy into light emission. and the light emitting layer emits light emitted by a third organic compound. be.

[0019] In another embodiment of the present invention, a light-emitting layer is provided between a pair of electrodes. a first organic compound, a second organic compound, and a third organic compound, The first organic compound can form an exciplex with the first organic compound, and the first organic compound can form a triplet excited exciplex with the first organic compound. The second organic compound has a function of converting the singlet excitation energy of the second organic compound into light emission. The difference between the triplet excited energy level of the first organic compound and the triplet excited energy level of the second organic compound is 0 eV or more and 0.2 eV or less. The third organic compound has a function of converting the singlet excitation energy into light emission. The light emitted from the light-emitting layer is a light-emitting element having light emitted from the third organic compound.

[0020] Another embodiment of the present invention is a light-emitting element having a light-emitting layer between a pair of electrodes, the light-emitting layer including a first organic compound. a first organic compound, a second organic compound, and a third organic compound, The first organic compound can form an exciplex with the organic compound, and the first organic compound can emit triplet excited energy. The second organic compound has a π-electron rich skeleton and a π-electron deficient skeleton. the third organic compound has a function of converting singlet excitation energy into luminescence; The light emitting layer emits light from the third organic compound, forming a light emitting element.

[0021] In the above-mentioned structure, the first organic compound provides excitation energy to the third organic compound. It is preferable that the function be

[0022] In the above structure, the exciplex has a function of donating excitation energy to the third organic compound. It is preferable that the function be

[0023] In the above structure, the π-electron-rich skeleton and the π-electron-deficient skeleton are preferably directly bonded to each other. It is.

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

[0025] In the above structure, the first organic compound is Ru, Rh, Pd, Os, Ir, or It is preferable to have Pt.

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

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

[0028] In the above structure, the emission spectrum of the exciplex is determined based on the absorption spectrum of the third organic compound. It is preferable that the absorption band has a region overlapping with the absorption band on the longest wavelength side of the spectrum.

[0029] In the above-mentioned configuration, the first organic compound has a luminescence quantum yield of 0% or more and 40% or less at room temperature. It is preferred to have a high yield.

[0030] In the above structure, it is preferable that the third organic compound exhibits fluorescence.

[0031] Another embodiment of the present invention is a light-emitting element having any of the above structures, and a color filter or a transistor. and at least one of a first transistor and a second transistor. The electronic device has the display device and at least one of a housing and a touch sensor. Another embodiment of the present invention is a display device including a light-emitting element having any of the above structures and at least one housing or a touch sensor. Another embodiment of the present invention is a lighting device having a light-emitting element. The term "light emitting device" includes not only optical devices but also electronic devices having light emitting devices. The light-emitting device in this specification refers to an image display device or a light source (including a lighting device). Connectors for optical elements, such as FPC (Flexible Printed Circuit) t), TCP (Tape Carrier Package) mounted display module A display module with a printed wiring board at the end of the TCP, or a light-emitting element with C Display with IC (integrated circuit) directly mounted using OG (Chip On Glass) method The module may also be included in the light emitting device. Effect of the Invention

[0032] According to one embodiment of the present invention, a light-emitting element with high emission efficiency can be provided. According to one embodiment of the present invention, a light-emitting element with low driving voltage can be provided. According to one embodiment of the present invention, a light-emitting element with high reliability can be provided. According to one embodiment of the present invention, a light-emitting element with reduced power consumption can be provided. According to one embodiment of the present invention, a light-emitting element with high color purity can be provided. According to one embodiment of the present invention, a novel light-emitting element can be provided. Therefore, a novel light-emitting device can be provided. It is possible to provide new electronic devices.

[0033] Note that the description of these effects does not preclude the existence of other effects. It is not necessary to have all of these effects. Effects other than these are described in the specification. The disclosure of the specification, drawings, claims, etc. is self-evident, and the disclosure of the specification, drawings, claims, etc. is self-evident. From this, it is possible to extract other effects. [Brief description of the drawings]

[0034] [Figure 1] 1A and 1B are schematic cross-sectional views of a light-emitting element of one embodiment of the present invention and a diagram illustrating the correlation between energy levels of a light-emitting layer. [Diagram 2] 1A and 1B are diagrams illustrating the correlation between energy levels of a light-emitting layer of a light-emitting element according to one embodiment of the present invention. [Diagram 3] 1A and 1B are diagrams illustrating the correlation between energy levels of a light-emitting layer of a light-emitting element according to one embodiment of the present invention. [Figure 4] 1A and 1B are diagrams illustrating the correlation between energy levels of a light-emitting layer of a light-emitting element according to one embodiment of the present invention. [Diagram 5] 1 is a schematic cross-sectional view of a light-emitting element according to one embodiment of the present invention. [Figure 6] 1A and 1B are a top view and a cross-sectional schematic diagram illustrating a display device of one embodiment of the present invention. [Figure 7] 1A and 1B are schematic cross-sectional views illustrating a display device according to one embodiment of the present invention. [Figure 8] 1A and 1B are schematic cross-sectional views illustrating a display device according to one embodiment of the present invention. [Figure 9] 1A to 1C illustrate electronic devices of one embodiment of the present invention. [Figure 10] 1A to 1C illustrate electronic devices of one embodiment of the present invention. [Figure 11] 1A to 1C illustrate electronic devices of one embodiment of the present invention. [Figure 12] 1A to 1C are diagrams illustrating a lighting device according to one embodiment of the present invention. [Figure 13] FIG. 13 is a graph showing current efficiency vs. luminance characteristics of a light-emitting element in the embodiment. [Figure 14] FIG. 13 is a graph showing current-voltage characteristics of a light-emitting element in the embodiment. [Figure 15] FIG. 13 is a graph showing external quantum efficiency vs. luminance characteristics of a light-emitting element according to an embodiment. [Figure 16] 1A and 1B are diagrams illustrating emission spectra of light-emitting elements in accordance with an embodiment. [Figure 17] FIG. 13 is a diagram illustrating the results of time-resolved luminescence measurement in the examples. [Figure 18] FIG. 4 is a diagram illustrating the relationship between an emission spectrum and an absorption spectrum in the example. [Figure 19] FIG. 11 is a diagram illustrating transient fluorescence characteristics in the embodiment. [Figure 20] FIG. 2 is a diagram illustrating an emission spectrum of a compound according to an example. [Figure 21]FIG. 2 is a diagram illustrating an emission spectrum of a compound according to an example. [Figure 22] 13A to 13C are diagrams illustrating the results of a reliability test of a light-emitting element in the examples. [Diagram 23] FIG. 13 is a graph showing current efficiency vs. luminance characteristics of a light-emitting element in the embodiment. [Figure 24] FIG. 13 is a graph showing current-voltage characteristics of a light-emitting element in the embodiment. [Diagram 25] FIG. 13 is a graph showing external quantum efficiency vs. luminance characteristics of a light-emitting element according to an embodiment. [Figure 26] 1A and 1B are diagrams illustrating emission spectra of light-emitting elements in accordance with an embodiment. [Figure 27] FIG. 13 is a diagram illustrating the results of time-resolved luminescence measurement in the examples. [Figure 28] 13A to 13C are diagrams illustrating the results of a reliability test of a light-emitting element in the examples. [Figure 29] FIG. 13 is a graph showing current efficiency vs. luminance characteristics of a light-emitting element in the embodiment. [Diagram 30] FIG. 13 is a graph showing current-voltage characteristics of a light-emitting element in the embodiment. [Diagram 31] FIG. 13 is a graph showing external quantum efficiency vs. luminance characteristics of a light-emitting element according to an embodiment. [Diagram 32] 1A and 1B are diagrams illustrating emission spectra of light-emitting elements in accordance with an embodiment. [Diagram 33] FIG. 13 is a diagram illustrating the results of time-resolved luminescence measurement in the examples. [Diagram 34] FIG. 13 is a diagram illustrating the results of time-resolved luminescence measurement in the examples. [Diagram 35] FIG. 2 is a diagram illustrating an emission spectrum of a compound according to an example. [Diagram 36] 13A to 13C are diagrams illustrating the results of a reliability test of a light-emitting element in the examples. [Figure 37] FIG. 13 is a graph showing current efficiency vs. luminance characteristics of a light-emitting element in the embodiment. [Figure 38] FIG. 13 is a graph showing current-voltage characteristics of a light-emitting element in the embodiment. [Figure 39] FIG. 13 is a graph showing external quantum efficiency vs. luminance characteristics of a light-emitting element according to an embodiment. [Diagram 40]1A and 1B are diagrams illustrating emission spectra of light-emitting elements in accordance with an embodiment. [Diagram 41] FIG. 13 is a diagram illustrating the results of time-resolved luminescence measurement in the examples. [Diagram 42] FIG. 2 is a diagram illustrating an emission spectrum of a compound according to an example. [Diagram 43] 13A to 13C are diagrams illustrating the results of a reliability test of a light-emitting element in the examples. [Diagram 44] FIG. 13 is a graph showing current efficiency vs. luminance characteristics of a light-emitting element in the embodiment. [Diagram 45] FIG. 13 is a graph showing current-voltage characteristics of a light-emitting element in the embodiment. [Diagram 46] FIG. 13 is a graph showing external quantum efficiency vs. luminance characteristics of a light-emitting element according to an embodiment. [Figure 47] 1A and 1B are diagrams illustrating emission spectra of light-emitting elements in accordance with an embodiment. [Figure 48] 1A and 1B are diagrams illustrating emission spectra of light-emitting elements in accordance with an embodiment. [Figure 49] FIG. 13 is a diagram illustrating the results of time-resolved luminescence measurement in the examples. [Figure 50] FIG. 4 is a diagram illustrating the relationship between an emission spectrum and an absorption spectrum in the example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] Hereinafter, the embodiment of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the above description, and the embodiments and details thereof are not limited to those described above without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited to the following embodiments and examples. The present invention should not be construed as being limited to the contents of the examples.

[0036] In addition, the position, size, range, etc. of each component shown in the drawings are not necessarily shown in order to facilitate understanding. The actual position, size, range, etc. may not be shown. The present invention is not necessarily limited to the position, size, range, etc. disclosed in the drawings, etc.

[0037] In addition, in this specification, ordinal numbers such as 1st, 2nd, etc. are used for convenience. In some cases, the order of steps or layers may not be indicated. For example, "first" may be replaced with "second" or " " can be appropriately replaced with "the third" etc. The ordinal numbers used to identify an aspect of the present invention may not match those used in the present invention. be.

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

[0039] In addition, in this specification and the like, the terms "film" and "layer" are interchangeable. For example, the term "conductive layer" can be changed to the term "conductive film." Alternatively, for example, the term "insulating film" may be changed to "insulating layer." It may be possible to change the term to:

[0040] In the present specification and the like, the singlet excited state (S * ) is a single charge with excitation energy The S1 level is the lowest singlet excited energy level. , the lowest excited energy level of the singlet state (S1 state). term excited state (T * ) is a triplet state with an excited energy. The lowest triplet excited energy level is the lowest triplet excited state (T1 In this specification and the like, the term "singlet excited state" refers to the excited energy level of the Even when written as states and singlet excited energy levels, the S1 state and S1 level The triplet excited state and triplet excited energy level are also used. Even in this case, it may refer to a T1 state and a T1 level.

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

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

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

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

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

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

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

[0048] The EL layer 100 shown in FIG. 1A includes a hole injection layer 111, a hole injection layer 112, a light emitting layer 130, and a cathode. It has functional layers such as a hole transport layer 112 , an electron transport layer 118 , and an electron injection layer 119 .

[0049] In this embodiment, of the pair of electrodes, electrode 101 is an anode, and electrode 1 Although the description will be given assuming that 02 is a cathode, the configuration of the light-emitting element 150 is not limited to this. The electrode 101 is a cathode, the electrode 102 is an anode, and the layers between the electrodes are stacked in the reverse order. That is, from the anode side, the hole injection layer 111, the hole transport layer 112, and the light emitting layer 113 may be arranged in that order. The light-emitting layer 130, the electron transport layer 118, and the electron injection layer 119 may be laminated in this order. .

[0050] The configuration of the EL layer 100 is not limited to the configuration shown in FIG. 1(A). At least one selected from the group consisting of a hole transport layer 112, an electron transport layer 118, and an electron injection layer 119. Alternatively, the EL layer 100 may be a hole or electron injector. Reduce the barrier, improve the transportability of holes or electrons, or inhibit the transportability of holes or electrons. or suppressing the quenching phenomenon caused by the electrode. Each functional layer may be a single layer or a laminate of multiple layers. It may be composed of

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

[0052] In one embodiment of the present invention, the light-emitting device 150 has a fluorescent compound in the light-emitting layer 130. The fluorescent light-emitting element has good reliability and has an emission spectrum similar to that of phosphorescence. Since the color tends to be sharper than that of light-emitting elements, it is possible to obtain light-emitting elements with high color purity. However, in the case of organic EL devices, the generation ratio of singlet excitons and triplet excitons (hereafter referred to as exciton The probability of singlet exciton generation is 1:3 due to statistical probability. In a fluorescent light-emitting device that uses luminescence, only 25% of the generated excitons can contribute to luminescence. Therefore, in order to increase the efficiency of fluorescent light-emitting devices, it is important to make triplet excitons contribute to light emission. It is essential.

[0053] Here, the present inventors have used an organic compound capable of converting triplet excitation energy into light emission in the light-emitting layer. The difference between the singlet excitation energy and the triplet excitation energy is 0 eV or more and 0.2 eV or less. By using organic compounds and organic compounds that exhibit fluorescent emission, triplet excitation can be efficiently achieved. It is possible to make the electrons contribute to the fluorescent emission, i.e., it is possible to obtain a highly efficient fluorescent element. In addition, we found that the difference between the singlet excitation energy and the triplet excitation energy is 0 eV or more. Organic compounds with an electron-rich and electron-deficient structure in one molecule have an electron-poor structure and an electron-rich and electron-deficient structure in one molecule. The compound may be an organic compound having the above structure.

[0054] In addition, the difference between the singlet excitation energy and the triplet excitation energy is 0 eV or more and 0.2 eV or less. Examples of organic compounds that can achieve this include thermally activated delayed fluorescence (TADF) materials. Activated delayed fluorescence materials are materials in which the difference between the S1 and T1 levels is small and triple-phase fluorescence occurs due to reverse intersystem crossing. The function of converting energy from first excitation energy to singlet excitation energy Therefore, the triplet excitation energy can be converted to a single state by a small amount of thermal energy. It is possible to upconvert to singlet excited energy (reverse intersystem crossing), and efficiently convert singlet excited states It is possible to generate an excited state by two substances. The exciplex (also called exciplex or exciplex) is a nucleon that consists of the S1 and T1 levels. The difference between the triplet excitation energy and the singlet excitation energy is extremely small, making it possible to convert the triplet excitation energy into singlet excitation energy. The compound has a function as a thermally activated delayed fluorescent material.

[0055] In addition, organic compounds that have a π-electron rich skeleton and a π-electron deficient skeleton in one molecule are known to be bipolar. Since it has good carrier (electron and hole) transport properties, it can be used for light-emitting devices. This improves the carrier balance and reduces the driving voltage. In addition, the organic compound may have TADF properties. In this case, It is preferable that the π-electron-deficient skeleton and the π-electron-deficient skeleton are directly bonded. This increases the efficiency, making it possible to obtain TADF materials with good luminous efficiency.

[0056] In addition, TADF materials are organic compounds that have a π-electron rich skeleton and a π-electron deficient skeleton in one molecule. Therefore, as described above, TADF materials have good carrier transport properties and are effective as light-emitting elements. By using it as a light-emitting element, the carrier balance can be improved. The driving voltage can be reduced.

[0057] The above-mentioned organic compound having a function of converting triplet excitation energy into light emission. Examples of such compounds include compounds that can emit phosphorescence (hereinafter, also referred to as phosphorescent compounds). In this specification, the term "phosphorescent compound" refers to a compound that emits light in a temperature range of from a low temperature (e.g., 77 K) to room temperature. (i.e., 77K or higher and 313K or lower) Phosphorescent compounds are compounds that do not efficiently convert triplet excitation energy into light. In order to convert the phosphorescent compound, it is preferable to have a heavy atom. The spin-orbit interaction (interaction between the spin angular momentum of the electron and the orbital angular momentum) Transitions between the ground state and the triplet excited state are allowed. The transition probability between the triplet excited state and the triplet excited state is increased, so the efficiency and In addition, the triplet excitation energy of the phosphorescent compound can be increased. -level to the singlet excited energy level of a fluorescent compound by the Förster mechanism Energy transfer is also permitted. To achieve this, the phosphorescent compound must have a large spin-orbit coupling. It is preferable that the alloy contains a metal element having a low molecular weight, specifically, a transition metal element, and particularly, a platinum group element ( Ruthenium (Ru), Rhodium (Rh), Palladium (Pd), Osmium (Os), It is preferable that the metal oxide has iridium (Ir) or platinum (Pt), among which iridium is preferably used. By having the above structure, the transition probability for the direct transition between the singlet ground state and the triplet excited state can be increased. In addition, it is preferable that the triplet excitation energy can be converted into light emission. Materials having this capability include the above-mentioned TADF materials.

[0058] FIG. 1(B) is a schematic cross-sectional view showing an example of the light-emitting layer 130 shown in FIG. The light-emitting layer 130 shown in FIG. 1B contains compounds 131, 132, and 133. In one embodiment of the present invention, compound 131 is capable of converting triplet excitation energy into luminescence. Compound 132 is preferably a TADF material. Compound 133 is , a guest material that exhibits fluorescent emission.

[0059] <Emitting layer configuration example 1> FIG. 1C illustrates one example of the correlation of energy levels in a light-emitting layer in a light-emitting element of one embodiment of the present invention. In this configuration example, a phosphorescent compound is used as the compound 131.

[0060] In addition, the compounds 131, 132, and 133 in the light-emitting layer 130 The correlation between the energy levels is shown in Figure 1(C). The notations and symbols in Figure 1(C) are as follows: As shown below. ·Comp(131): Compound 131 ·Comp(132): Compound 132 ·Guest(133): Compound 133 T C1 :T1 level of compound 131 ·S C2 : S1 level of compound 132 T C2 :T1 level of compound 132 ·S G : S1 level of compound 133 T G :T1 level of compound 133

[0061] In Figure 1(C), compound 131 or compound 132 accepts holes and electrons. Here, compound 131 is a phosphorescent compound, so it forms a singlet state and a triplet state. Intersystem crossing between the singlet state and the 132 singlet excited energy is therefore Both the triplet excitation energy and the triplet excitation energy can be rapidly transferred to compound 131 (Figure 1). 1(C) Root A1). In this case, S C2 ≧T C1 , T C2 ≧T C1 It is preferable that The light-emitting layer 130 is formed by mixing compounds 131, 132, and 133. However, it is preferable that the mixture ratio of compound 131 and compound 132 is higher than that of compound 132. Specifically, the weight ratio of Compound 131:Compound 132 is preferably from 1:9 to 3:7. This configuration allows compound 131 to be excited efficiently. Since 31 is a phosphorescent compound, it can efficiently utilize the triplet excitation energy of compound 131. The singlet excitation energy of compound 133 can be converted to the singlet excitation energy of compound 133 (Figure 1(C) Route A 2) Here, as shown in Figure 1(C), S C2 ≧T C1 ≧S G If so, the singlet excited This is preferable because the energy is efficiently transferred to the guest material, compound 133. C 2 ≧ T C1 ≧S G When the triplet excitation energy is converted to singlet excitation energy efficiently, This is favorable for migration to the guest material, compound 133.

[0062] Also, T C1 From T G When triplet excited energy transfer occurs to is inactivated (Fig. 1(C) Route A3). Therefore, the energy transfer of Route A3 The less the better. To inhibit route A3, the more the concentration of compounds 131 and 132 is increased. The weight ratio of the total amount to the compound 133 is preferably low, and specifically, The weight ratio of compound 133 to the total amount of compound 131 and compound 132 is preferably It is 0.001 or more and 0.05 or less, and more preferably 0.001 or more and 0.01 or less. .

[0063] In addition, when the direct recombination process of carriers becomes dominant in compound 133, compound 13 In 3, a large number of triplet excitons are generated, and the emission efficiency is reduced due to thermal deactivation. Therefore, route A is preferred over the direct recombination of carriers in compound 133. The higher the ratio of the energy transfer process via 2, the higher the probability of generating the triplet excited state of compound 133. This is preferable because it is possible to reduce the rate of oxidation and suppress thermal deactivation. The weight ratio of the total amount of Compound 131 and Compound 132 to Compound 133 is It is preferable that the ratio is low, specifically, the ratio of compound 131 to the total amount of compound 132. The weight ratio of the substance 133 is preferably 0.001 or more and 0.05 or less, more preferably 0. Greater than or equal to .001 and less than or equal to 0.01.

[0064] In addition, in the light-emitting element of one embodiment of the present invention, Compound 132 has a function of exhibiting thermally activated delayed fluorescence ( In other words, compound 132 has the ability to upconvert triplet excitation energy. It has the function of converting it into singlet excitation energy by the reaction (Figure 1(C) Route A 4) The singlet excitation energy of compound 132 is rapidly transferred to compound 133. (Fig. 1(C) Route A5). At this time, S C2 ≧S G It is preferable that:

[0065] In addition, route A1 can occur even if reverse intersystem crossing represented by route A4 does not occur. The energy transfer represented by route A1 occurs with reverse intersystem crossing represented by route A4. It can happen even if it doesn't occur.

[0066] As described above, in the light-emitting element of one embodiment of the present invention, the route A1 and the route A2 in FIG. The triplet excitation energy is transferred to the guest material, compound 133, via the pathway shown in Figure 1. There is a route to compound 133 via route A4 and route A5 in (C). The existence of a pathway for the transfer of doublet excitation energy to a fluorescent compound allows the emission of a fluorescent light-emitting element. The light efficiency can be improved. In addition, the triplet excitation energy is transferred to the fluorescent compound. The presence of multiple paths can further increase the luminous efficiency.

[0067] By configuring the light-emitting layer 130 as described above, light emitted from the fluorescent compound in the light-emitting layer 130 can be efficiently emitted. You can get it at a good rate.

[0068] Also, T G It is preferable that the wavelength is 2.0 eV or less. By adopting this configuration, the light emission with good reliability can be achieved. The element can be obtained.

[0069] In the above configuration, it is not necessary to use a material with a high luminescence quantum yield as the phosphorescent compound. This makes it easier to design materials, and the range of material options is broadened. At room temperature or normal temperature, it may be 0% or more and 50% or less, and 0% or more and 40% or less It may be 0% or more and 25% or less, or it may be 0% or more and 10% or less. The compound may have a heavy atom, and may be present in an amount of 0% or more and 1% or less. The heavy atom is preferably Ru, Rh, Pd, Os, Ir, Pt, etc. .

[0070] <Emitting layer configuration example 2> FIG. 2B shows the energy levels in the light-emitting layer 130 of the light-emitting element 150 of one embodiment of the present invention. In this configuration example, a phosphorescent compound is used as compound 131, and This shows the case where compound 132 forms an exciplex.

[0071] The combination of Compound 131 and Compound 132 is a combination capable of forming an exciplex. However, one of the compounds may be a compound having a hole transporting property and the other a compound having an electron transporting property. In this case, it is more preferable that the compound is a donor-acceptor type exciplex. This makes it easier to form the compound 131, which allows for efficient formation of the exciplex. The combination with compound 132 is a compound having hole transport properties and a compound having electron transport properties. In the case of a combination of these, the carrier balance can be easily controlled by the mixture ratio. Specifically, the compound having hole transporting property: the compound having electron transporting property=1 The weight ratio is preferably in the range of 9:9 to 9:1. Since the rear balance can be controlled, the carrier recombination region can be easily controlled. It is possible.

[0072] The formation of the exciplex can be seen, for example, in the emission spectrum of compound 131 and the emission spectrum of compound 132. The emission spectra of the mixed films were compared to those of the mixed films. The emission spectrum is shifted to longer wavelengths than the emission spectrum of each compound (or This can be confirmed by observing the phenomenon of a new peak on the side of the Transient photoluminescence (PL) of compound 131, transient PL of compound 132, and The transient PL lifetime of the mixed film was compared with that of the mixed film. Transients that have a longer life than the PL lifetime or have a larger proportion of delayed components. This can be confirmed by observing the difference in response. It may be read as electroluminescence (EL). That is, Compound 131 The transient EL of the compound 132 and the mixed film of these were compared, and the transient response By observing the difference, the formation of the exciplex can also be confirmed.

[0073] In addition, the combination of compounds 131 and 132 is an example of a combination of materials that efficiently form an exciplex. One of the HOMOs (Highest Occupied Molecule) of the substance 132 r Orbital (also called the highest occupied molecular orbital) level is higher than the HOMO level of the other LUMO (Lowest Unoccupied Molecular Orbita) It is preferable that the LUMO level of the 1st or 2nd LUMO is higher than the LUMO level of the other LUMO. The energy difference between the HOMO level of compound 131 and the HOMO level of compound 132 is preferably It is preferably 0.1 eV or more, more preferably 0.2 eV or more, and further preferably The LUMO level of compound 131 and the LUMO level of compound 132 are 0.3 eV or more. The energy difference between the level is preferably 0.1 eV or more, and more preferably 0.2 eV or more. The correlation between the energy levels is preferably 0.3 eV or more, and more preferably 0.3 eV or more. By doing so, the carriers injected from the pair of electrodes (electrodes 101 and 102) The holes and electrons are easily injected into the compound 131 and the compound 132, respectively. In addition, the HOMO level of compound 131 is equal to or greater than the HOMO level of compound 132. Alternatively, the LUMO level of compound 131 may be equivalent to the LUMO level of compound 132.

[0074] The LUMO and HOMO levels of the compounds were determined by cyclic voltammetry (C V) Derived from the electrochemical properties (reduction potential and oxidation potential) of the compound measured by the measurement It is possible.

[0075] For example, when compound 131 has a hole transporting property and compound 132 has an electron transporting property, As shown in the energy band diagram in Figure 2(A), the HOMO level of compound 131 is The HOMO level of compound 131 is preferably higher than the HOMO level of compound 32, and the LUMO level of compound 131 is preferably higher than the HOMO level of compound 13. It is preferable that the LUMO level of the 2-nuclear molecule is higher than that of the 2-nuclear molecule. The carriers injected from the pair of electrodes (electrodes 101 and 102) are holes and This is preferable because electrons can be easily injected into compound 131 and compound 132, respectively.

[0076] In FIG. 2(A), Comp(131) represents compound 131, and Comp(1 32) represents compound 132, ΔE C1 are the LUMO and HOMO levels of compound 131 and represents the energy difference, ΔE C2 is the energy between the LUMO and HOMO levels of compound 132. represents the energy difference, and ΔE E is the LUMO level of compound 132 and the HOMO level of compound 131. are the notation and symbol representing the energy difference between

[0077] In addition, the exciplex formed by compound 131 and compound 132 has a HOMO and compound 132 becomes an exciplex having a LUMO molecular orbital. The excitation energy of the exciplex is the LUMO level of compound 132 and the HOMO level of compound 131. Energy difference between the levels (ΔE E ) and the LUMO and HOMO levels of compound 131 are Energy difference between the levels (ΔE C1 ) and the relationship between the LUMO and HOMO levels of compound 132 Energy difference (ΔE C2 ) is smaller than that of Compound 131 and Compound 132. By forming an exciplex at , it is possible to form an excited state at a lower excitation energy. In addition, since the excitation energy is lower, the exciplex has a stable excited state. It can be formed.

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

[0079] In the light-emitting element of one embodiment of the present invention shown in this configuration example, the compound contained in the light-emitting layer 130 Compound 131 and compound 132 form an exciplex. The S1 level of the exciplex (S E ) and exciplexes T1 level (T E) are adjacent energy levels (Figure 2(B) Route A See 6).

[0080] The exciplexes formed by the above process can emit light or transfer the excitation energy to other materials. When an electron goes to the ground state by losing excitation energy, such as by donating it to a nucleon, it forms an exciplex. The two substances that were once separated will once again behave as separate substances.

[0081] Excitation energy levels of exciplexes (S E and T E ) is a compound that forms an exciplex. The S1 levels (S C1 and S C2 ) is lower, It is possible to form an excited state with lower excitation energy. This allows the luminescent element The driving voltage of the element 150 can be reduced.

[0082] The S1 level of the exciplex (S E ) and T1 level (T E ) are adjacent energy levels Therefore, the exciplex has the function of exhibiting thermally activated delayed fluorescence. It has the function of converting energy into singlet excitation energy by upconversion. Therefore, a part of the triplet excitation energy generated in the light-emitting layer 130 is absorbed by the exciplex. To do this, the S1 level (S E ) and T1 standard Place(T E The energy difference between the two is preferably greater than 0 eV and less than 0.2 eV, more preferably The electron energy is preferably greater than 0 eV or less than 0.1 eV. To do this, the T1 level of the exciplex (T E ) are each compound that forms an exciplex (compound 131 and and compound 132) T1 level (T C1 and T C2 ) is preferable. The triplet excitation energy of the exciplexes by compounds 131 and 132 was quenched by The exciplex efficiently converts triplet excitation energy into singlet excitation energy. Reverse intersystem crossing to the energy occurs.

[0083] In addition, the singlet excited energy level of the exciplex (S E ) is a light-emitting material, compound 133 The singlet excited energy level (S G ) is preferable. By assuming a correlation between the positions, the singlet excitation energy of the generated exciplex is Excitation energy level (S E ) to the singlet excited energy level (S G )Hehe Energy can be transferred.

[0084] In this case, the correlation between the energy levels of compounds 131 and 132 is limited to that shown in FIG. 2(B). That is, the singlet excited energy level (S C1 ) is a compound The singlet excited energy level of 132 (S C2 ) may be higher or lower. The triplet excited energy level of 131 (T C1 ) is the triplet excitation energy of compound 132 Level (T C2 ) may be higher or lower.

[0085] In one embodiment of the present invention, a phosphorescent compound is added to one of the compounds forming the exciplex. Because of this, intersystem crossing between the singlet and triplet states is permitted. It is possible to form an exciplex that can undergo a transition from an excited state to a singlet ground state. In this case, the triplet excited energy level of the exciplex (T E ) is one of the light-emitting materials, compound 133. Singlet excited energy level (S G ) is preferable. By correlating the triplet excitation energy of the generated exciplex, Energy Level (T E ) to the singlet excited energy level (S G ) to Energy In addition, the S1 level (S E ) and T1 level (T E )teeth, Because the energy levels are adjacent to each other, the emission spectrum clearly shows fluorescence and phosphorescence. In some cases, it may be difficult to distinguish between fluorescence and phosphorescence. It may be possible to distinguish.

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

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

[0088] In addition, when the direct recombination process of carriers becomes dominant in compound 133, compound 13 In 3, a large number of triplet excitons are generated, and the emission efficiency is reduced due to thermal deactivation. Therefore, rather than a direct recombination process of carriers in compound 133, the exciplex The higher the ratio of the energy transfer process via the formation process of 1, the greater the reaction rate. The probability of generating the triplet excited state of compound 133 can be reduced, and thermal deactivation can be suppressed. For this reason, the total amount of Compound 131 and Compound 132 and the amount of Compound 133 should be The weight ratio of the compound 133 to the compound 133 is preferably low. The weight ratio of compound 133 to the total amount of compound 131 and compound 132 is preferably 0.001 It is preferably from 0.001 to 0.01.

[0089] Also, T G It is preferable that the wavelength is 2.0 eV or less. By adopting this configuration, the light emission with good reliability can be achieved. The element can be obtained.

[0090] Note that compound 131 has an electron transporting property, and compound 132 has a hole transporting property. In this case, the HOMO level of compound 132 may be higher than the HOMO level of compound 131. It is preferable that the LUMO level of compound 132 is higher than the LUMO level of compound 131. It is preferable that

[0091] In addition, the weight ratio of compound 131 to compound 132 is low. It is preferred that the weight ratio of compound 131 to compound 132 is preferably 0.0 The ratio is 1 or more and 0.5 or less, and more preferably 0.05 or more and 0.3 or less.

[0092] As described above, all of the energy transfer processes in routes A6 and A7 described above occur efficiently. For example, both the singlet excitation energy and the triplet excitation energy generated in the light-emitting layer 130 can be efficiently used. Since the energy of the singlet excited state of compound 133 is efficiently converted into the energy of the singlet excited state of compound 133, the light-emitting element 150 It becomes possible to emit light with high luminous efficiency.

[0093] In the light-emitting element according to one embodiment of the present invention, compound 132 has a π-electron-deficient skeleton. This is preferable. By adopting this structure, the LUMO level of the compound 132 is lowered, and the excited complex This is ideal for body shaping.

[0094] In the light-emitting element according to one embodiment of the present invention, compound 132 has a π-electron-rich skeleton. This is preferable. By adopting this structure, the HOMO level of the compound 132 is increased, and the excited complex This is ideal for body shaping.

[0095] In addition, in the light-emitting element of one embodiment of the present invention, Compound 132 has a function of exhibiting thermally activated delayed fluorescence ( Therefore, in compound 132, which does not form an exciplex, As shown in the previous example of the light-emitting layer configuration, triplet excitation energy is converted into The compound has the function of converting the excited energy into singlet energy (Figure 2(B) Route A9). The singlet excitation energy of 132 can be rapidly transferred to compound 133. (Figure 2(B) Route A 10 ). At this time, S C2 ≧S G It is preferable that:

[0096] As described above, in the light-emitting element of one embodiment of the present invention, the route A6 and the route A7 in FIG. The triplet excitation energy is transferred to the guest material, compound 133, via the pathway shown in Figure 2. (B) Route A9 and Route A 10 There is a pathway to compound 133 via As in the previous example of the light-emitting layer configuration, there is a path through which triplet excitation energy transfers to the fluorescent compound. The presence of the triplet excitation energy can increase the luminous efficiency of the fluorescent light emitting device. The existence of multiple pathways for the transfer of ions to fluorescent compounds further increases the luminescence efficiency. can be done.

[0097] The above-mentioned processes of routes A6 and A7 are referred to as ExSET (ExcSET) in this specification. iplex-Singlet Energy Transfer) or ExEF (Ex This is sometimes called ciplex-Enhanced Fluorescence. In other words, the light-emitting layer 130 is formed by providing excitation energy from an exciplex to a fluorescent compound. do.

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

[0099] <Emitting layer configuration example 3> FIG. 3 is an example of the correlation of energy levels in a light-emitting layer in a light-emitting element according to one embodiment of the present invention. In this configuration example, a TADF material is used for compound 131. The notations and symbols in FIG. 3 are the same as those shown in FIG. 1(C). ·S C1 : S1 level of compound 131

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

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

[0102] Also, TC1 From T G When triplet excitation energy transfer occurs to (Fig. 3 Route A 14 ) Therefore, root A 14 There is little energy transfer Route A is preferable. 14 In order to suppress the energy transfer of T C1 and T G With A larger energy difference is preferable. To achieve this, T G is preferably 2.0 eV or less. By using such a structure, a light-emitting element having high luminous efficiency and high reliability can be obtained. .

[0103] In addition, as shown in the previous example of the light-emitting layer configuration, compound 132 is a TADF material, so A mechanism for converting doublet excitation energy into singlet excitation energy by upconversion (Fig. 3 Route A 15 The singlet excitation energy of compound 132 is This can be easily transferred to compound 133 (Figure 3, Route A). 16 ). At this time, S C2 ≧S G It is preferable that:

[0104] As in the previous example of the structure of the light-emitting layer, in the light-emitting element of one embodiment of the present invention, route A in FIG. 11 No To Route A 13 Through this, the triplet excitation energy is transferred to the guest material, compound 133. Route A in Figure 3 15 and Route A 16 The route to compound 133 via In addition, there exists a pathway for triplet excitation energy to be transferred to a fluorescent compound. The triplet excitation energy of the fluorescent compound is The existence of multiple paths for light to travel to the target region can further increase the light emission efficiency.

[0105] In addition, Route A 11 is root A 15 This can occur even if reverse intersystem crossing, represented by In other words, Route A 11 The energy transfer represented by route A 15 Reverse intersystem crossing, expressed as This may or may not occur.

[0106] <Emitting layer configuration example 4> FIG. 4A shows a case where four kinds of materials are used for the light-emitting layer 130. In the light-emitting layer 130, compound 131, compound 132, compound 133, and compound 134 are In one embodiment of the present invention, compound 131 converts triplet excitation energy into luminescence. Compound 132 is preferably a TADF material. Compound 3 is a guest material that exhibits fluorescent emission. Compound 134 also forms an exciplex with compound 132. They are organic compounds that make up the body.

[0107] In addition, the compounds 131, 132, and 133 in the light-emitting layer 130 are The energy level correlation of the substance 134 is shown in FIG. 4(B). The symbols and notations are as follows, and the other symbols and notations are the same as those shown in FIG. 2(B). Same here. ·S C3 : S1 level of compound 134 T C3 :T1 level of compound 134

[0108] In the light-emitting element of one embodiment of the present invention shown in this configuration example, the compound contained in the light-emitting layer 130 Compound 132 forms an exciplex with compound 134. The S1 level of the exciplex (S E ) and exciplexes T1 level (T E ) are adjacent energy levels (Figure 4(B) Route A 17 reference).

[0109] The exciplexes formed by the above process lose their excitation energy, as described above. The two substances that formed the exciplex then behave as if they were separate substances again.

[0110] Excitation energy levels of exciplexes (S E and T E ) is a compound that forms an exciplex. The S1 levels (S C2 and S C3 ) is lower, It is possible to form an excited state with lower excitation energy. This allows the luminescent element The driving voltage of the element 150 can be reduced.

[0111] Here, since compound 131 is a phosphorescent compound, the intersystem between the singlet state and the triplet state is Crossover is allowed. Therefore, the singlet excitation energy and triplet excitation energy of the exciplex are Both the energy and the cations are rapidly transferred to compound 131 (Route A). 18 ). At this time, T E ≧T C1 In addition, the triplet excitation energy of compound 131 can be efficiently converted to The singlet excitation energy of compound 133 can be converted directly into the singlet excitation energy of compound 133 (Route A). 19 ).child As shown in FIG. 4(B), T E ≧T C1 ≧S G Then, the excitation energy of compound 131 is The energy is efficiently transferred to the guest material, compound 133, as singlet excitation energy. Therefore, it is preferable.

[0112] In this case, the combination of Compound 132 and Compound 134 can form an exciplex. Any possible combination is acceptable, but one of them is a compound having hole transport properties and the other is an electron It is more preferable that the compound has a transport property. In this case, the compound is a donor-acceptor type. This makes it easier to form an exciplex, and the exciplex can be formed efficiently. The combination of Compound 132 and Compound 134 is a compound having hole transport properties and a compound having electron transport properties. When a compound that can be used in combination with a carrier is used, the carrier balance can be easily controlled by changing the mixture ratio. Specifically, a compound having a hole transporting property and a compound having an electron transporting property can be The compound ratio is preferably in the range of 1:9 to 9:1 (weight ratio). Since the carrier balance can be easily controlled, the carrier recombination region can also be controlled. It can be done easily.

[0113] In addition, the combination of compounds 132 and 133 is an example of a combination of materials that efficiently forms an exciplex. One HOMO level of the compound 134 is higher than the other HOMO level, and one LUMO level It is preferable that the HOMO level of compound 132 is higher than the LUMO level of the other compound. The energy difference between the level and the HOMO level of compound 134 is preferably 0.1 eV or more. More preferably, it is 0.2 eV or more, and even more preferably, it is 0.3 eV or more. The energy difference between the LUMO level of compound 132 and the LUMO level of compound 134 is preferably or 0.1 eV or more, more preferably 0.2 eV or more, and further preferably By making the energy level correlation in this way, Carriers, ie, holes and electrons, injected from the electrode 101 and the electrode 102 are transferred to compound 13. Compound 132 and Compound 134 are suitable for injection. The HOMO level of compound 134 is equal to the HOMO level of compound 134, or the LUMO level of compound 132 is equal to the HOMO level of compound 134. The LUMO level of the compound 134 may be equivalent to that of the compound 134.

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

[0115] In the light-emitting element according to one embodiment of the present invention, compound 132 has a π-electron-deficient skeleton. This is preferable. By adopting this structure, the LUMO level of the compound 132 is lowered, and the excited complex This is ideal for body shaping.

[0116] In the light-emitting element according to one embodiment of the present invention, compound 132 has a π-electron-rich skeleton. This is preferable. By adopting this structure, the HOMO level of the compound 132 is increased, and the excited complex This is ideal for body shaping.

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

[0118] As in the above-described example of the structure of the light-emitting layer, in the light-emitting element of one embodiment of the present invention, the route A in FIG. 17 Route A 19 The triplet excitation energy is transferred to the guest material, compound 133. The route to travel and route A in Fig. 4(B) 21 and Route A 22 Transferred to compound 133 via There are also pathways through which triplet excitation energy can be transferred to fluorescent compounds. The triplet excitation energy is The existence of multiple pathways for transport to fluorescent compounds can further increase the luminescence efficiency. do.

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

[0120] Also, T G It is preferable that the wavelength is 2.0 eV or less. By adopting this configuration, the light emission with good reliability can be achieved. The element can be obtained.

[0121] <Energy transfer mechanism> Here, we will explain the factors that govern the energy transfer process between molecules. The mechanisms of electron transfer are the Förster mechanism (dipole-dipole interaction) and the Dexter mechanism. Two mechanisms have been proposed: the first excited state (electron exchange interaction) and the second excited state (electron exchange interaction). Regarding the transfer of excitation energy from a material to a second material in the ground state, The energy transfer process between the molecules of the material in 2 is explained. The same is true in the case of

[0122] <Förster mechanism> In the Förster mechanism, the energy transfer does not require direct contact between molecules. Energy transfer occurs through the resonance phenomenon of the dipole vibration of a material and a second material. The first material transfers energy to the second material through the resonance phenomenon of the excitation current, and the first material The first material is in the ground state, and the second material in the ground state is in the excited state. The rate constant of the mechanism, k h*→g is shown in Equation (1).

[0123]

number

[0124] In formula (1), ν represents the frequency, and f' h(ν) is the normalized value of the first material The emission spectrum (or the fluorescence spectrum when discussing energy transfer from a singlet excited state) , and phosphorescence spectrum when discussing energy transfer from triplet excited states), and ε g ( ν) represents the molar extinction coefficient of the second material, N represents Avogadro's number, and n represents the refractive index of the medium. represents the refractive index, R represents the intermolecular distance between the first and second materials, and τ represents the measured excitation represents the lifetime of the state (fluorescence lifetime or phosphorescence lifetime), c represents the speed of light, and φ represents the luminescence quantum yield ( When discussing energy transfer from a singlet excited state, the fluorescence quantum yield is used. When discussing energy transfer from a triplet excited state, the fluorescence quantum yield is used. When discussing energy transfer, it stands for phosphorescence quantum yield, and K 2 is the first material and the second material is a coefficient (0 to 4) that represents the orientation of the transition dipole moment of the The match is K 2 =2 / 3.

[0125] <Dexter System> In the Dexter mechanism, the first and second materials overlap at a certain contact distance. Through the exchange of electrons from the first material in an excited state with those from the second material in the ground state, Energy transfer occurs. The rate constant for the Dexter mechanism is k h*→g is shown in formula (2). vinegar.

[0126]

number

[0127] In formula (2), h is the Planck constant, and K is a constant with the dimension of energy. where ν is the frequency and f' is the h (ν) is the normalized emission spectrum of the first material (When discussing energy transfer from a singlet excited state, the fluorescence spectrum and the triplet excited state are used.) When discussing energy transfer from the nucleophilic state, it represents the phosphorescence spectrum, and ε' g (ν) is the second represents the normalized absorption spectrum of the material, L represents the effective molecular radius, and R represents the first It represents the intermolecular distance between a material and a second material.

[0128] Here, the energy transfer efficiency from the first material to the second material, φ ET is expressed as formula (3). It will be done. r We discuss the emission process of the first material (energy transfer from the singlet excited state). The rate constants are expressed as follows: fluorescence in the case of a compound that is a triplet excited state, and phosphorescence in the case of a compound that is a triplet excited state. S, k n represents the rate constant of non-radiative processes (thermal deactivation and intersystem crossing) in the second material, and τ is the actual represents the lifetime of the excited state of the first material that is measured.

[0129]

number

[0130] From equation (3), the energy transfer efficiency φ ET To increase the rate of energy transfer, Degree constant k h*→g By increasing the other competing rate constants k r +k n (=1 / τ) is relatively It turns out that the smaller it is, the better.

[0131] <Concept for improving energy transfer> First, consider the energy transfer via the Förster mechanism. Substituting equation (1) into equation (3), Therefore, in the case of the Förster mechanism, the energy Energy transfer efficiency φ ETdoes not depend on the lifetime τ of the excited state of the first material. Movement efficiency φ ET is the emission quantum yield φ (when considering energy transfer from a singlet excited state) is the fluorescence quantum yield, and when discussing energy transfer from the triplet excited state, is the phosphorescence quantum yield) It can be said that higher is better.

[0132] In addition, the emission spectrum of the first material (when discussing energy transfer from a singlet excited state) When discussing energy transfer from triplet excited states, we use the fluorescence spectrum. the absorption spectrum of the first material (corresponding to the transition from the singlet ground state to the singlet excited state) It is preferable that the molar absorption coefficient of the second material is high. This means that the emission spectrum of the first material is preferably the longest wavelength of the second material. This means that the absorption band that appears on the side of the singlet ground state of the second material overlaps with that of the Since direct transition from the triplet excited state to the triplet excited state is forbidden, The molar extinction coefficient for the state is negligible. There is no energy transfer process from the excited state of the first material to the triplet excited state of the second material. Therefore, only the energy transfer process to the singlet excited state of the second material needs to be considered.

[0133] Next, consider the energy transfer via the Dexter mechanism. According to equation (2), the rate constant is k h*→g To increase the emission spectrum of the first material (energy from the singlet excited state), When discussing energy transfer, consider the fluorescence spectrum, and when discussing energy transfer from triplet excited states. in the case of phosphorescence spectrum) and the absorption spectrum of the second material (singlet ground state to singlet excited state) It can be seen that it is better to have a larger overlap with the absorption corresponding to the transition to the The efficiency of energy transfer is optimized by matching the emission spectrum of the first material with the longest wavelength of the second material. This is achieved by overlapping with the absorption band appearing on the long side.

[0134] In addition, by substituting formula (2) into formula (3), the energy transfer in the Dexter mechanism is Efficiency φ ET It can be seen that depends on τ. The Dexter mechanism is an energy mechanism based on electron exchange. Since this is a quantum transfer process, the singlet excited state of the first material is converted to the singlet excited state of the second material. Similarly, the energy transfer from the triplet excited state of the first material to the triplet excited state of the second material Energy transfer to the state also occurs.

[0135] Similar to the energy transfer from the first material to the second material, the fluorescent compound is generated from the exciplex. The energy transfer process to the compound is also possible via both the Förster mechanism and the Dexter mechanism. Energy transfer occurs via the mechanism:

[0136] In the light-emitting element of one embodiment of the present invention, the second material is a fluorescent compound. It is preferred that the efficiency of energy transfer to the triplet excited state of the material is low. It is preferred that the efficiency of energy transfer from the material to the second material based on the Dexter mechanism is low. The efficiency of energy transfer from the first material to the second material based on the Förster mechanism is high. It is preferable.

[0137] As already mentioned, the efficiency of energy transfer in the Förster mechanism is On the other hand, the efficiency of energy transfer in the Dexter mechanism does not depend on the lifetime τ of the excited state of the material. depends on the excitation lifetime τ of the first material and reduces the efficiency of energy transfer in the Dexter mechanism. In order to reduce the excitation wavelength, it is preferable that the excitation lifetime τ of the first material is short.

[0138] In view of this, one embodiment of the present invention uses an exciplex or a TADF material as a first material, One of the compounds that forms the exciplex has the function of converting triplet excitation energy into luminescence. According to the configuration of one aspect of the present invention, the triplet excited state of the exciplex (first material) is converted to a singlet excited state. Promotes reverse intersystem crossing to the excited state, and increases the excited state lifetime of the triplet excited state of the exciplex (first material) It is possible to shorten τ. In addition, the triplet excited state of the exciplex (first material) can be converted to a singlet The transition to the ground state is promoted, and the excited lifetime τ of the triplet excited state of the exciplex (first material) is As a result, the triplet excited state of the exciplex (first material) emits fluorescent light. Efficiency of energy transfer to the triplet excited state of a compound (second material) via the Dexter mechanism Therefore, in one embodiment of the present invention, a light-emitting element with high emission efficiency can be provided. It is possible.

[0139] In addition, the fluorescence lifetime of the thermally activated delayed fluorescence component of the emission from the exciplex is short. Specifically, it is preferable that the period is 10 ns or more and 50 μs or less, and more preferably 10 It is preferably from ns to 20 μs, and more preferably from 10 ns to 10 μs.

[0140] The rate constant of the Förster mechanism is inversely proportional to the sixth power of the distance between the first material and the second material. The rate constant of the Dexter mechanism is inversely proportional to the exponential function of the distance between the first and second materials. Therefore, when the distance between the two molecules is approximately 1 nm or less, the Dexter mechanism becomes dominant, and Above 1 nm, the Förster mechanism is dominant. In order to reduce the efficiency of energy transfer, the distance between the first material and the second material is increased. Specifically, it is preferable that the thickness is 0.7 nm or more, and more preferably 0.9 nm or more. m or more, and more preferably 1 nm or more. In addition, the Förster mechanism occurs efficiently. To this end, the distance between the first material and the second material is preferably 5 nm or less.

[0141] Thus, in one embodiment of the present invention, the fluorescent compound, compound 133, is a 2-carbon It is preferable that the compound 133 has at least two of the above alkyl groups. It is preferable that the alkyl group has at least two branched alkyl groups each having 3 to 10 carbon atoms. Alternatively, compound 133 has at least two cyclic hydrocarbon groups having 3 to 10 carbon atoms. or more, or at least two or more bridged cyclic hydrocarbon groups having 3 to 10 carbon atoms. Furthermore, compound 133 has a condensed aromatic hydrocarbon having 3 to 12 carbon atoms. It is preferable to do so.

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

[0143] <Light-emitting layer> The materials that can be used for the light-emitting layer 130 are described below.

[0144] Compound 132 is, for example, a TADF material. It is preferable that the energy difference between the potential and the potential is small. Specifically, it is preferable that the energy difference between the potential and the potential is larger than 0 eV and smaller than 0.2 eV. Below.

[0145] Compound 132 has a skeleton having a hole transporting property and a skeleton having an electron transporting property. Alternatively, compound 132 may be a compound having a π-electron rich backbone or an aromatic amine backbone and It is preferable that the π-electron-deficient skeleton is provided. In this way, the donor-accessor structure is formed in the molecule. In addition, the donor and activator functions in the compound 132 molecule are easily formed. The structure is such that the electron-transporting skeleton and the hole-transporting skeleton are both strong. Alternatively, it is preferable that the structure has a π-electron-rich skeleton or an aromatic structure. It is preferable that the aromatic amine skeleton and the π-electron deficient skeleton are directly bonded to each other. By strengthening both the donor and acceptor properties of , the HOMO of compound 132 is split. The overlap between the region where the molecular orbitals are distributed and the region where the molecular orbitals in the LUMO are distributed is reduced. The singlet and triplet excited energy levels of compound 132 can be calculated. It is possible to reduce the energy difference between the triplet excited states of compound 132 and This allows the energy levels to be kept at high energies.

[0146] When the thermally activated delayed fluorescent material is composed of one kind of material, for example, the following material is used: It is possible.

[0147] First, fullerene and its derivatives, acridine derivatives such as proflavine, and eosin are listed. In addition, magnesium (Mg), zinc (Zn), cadmium (Cd), tin (S n), platinum (Pt), indium (In), or palladium (Pd) Examples of the metal-containing porphyrin include protoporphyrin. Porphyrin-tin fluoride complex (SnF2(Proto IX)), mesoporphyrin-fluoride Tin complex (SnF2(Meso IX)), hematoporphyrin-tin fluoride complex (Sn F2 (Hemato IX)), coproporphyrin tetramethyl ester-tin fluoride Complex (SnF2(Copro III-4Me)), Octaethylporphyrin-fluoride Tin complex (SnF2(OEP)), etioporphyrin-tin fluoride complex (SnF2(E tio I)), octaethylporphyrin-platinum chloride complex (PtCl2OEP), etc. Can be obtained.

[0148] [ka]

[0149] In addition, as a thermally activated delayed fluorescent material composed of one kind of material, a π-electron-rich skeleton and Heterocyclic compounds having a π-electron deficient skeleton can also be used. 4,6-bis(12-phenylindolo[2,3-a]carbazole) -11-yl)-1,3,5-triazine (abbreviation: PIC-TRZ), 2-{4-[3- (N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl] {phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: PCCzPTzn), 2-[4-(10H-phenoxazin-10-yl)phenyl]-4,6-diphenyl- 1,3,5-Triazine (abbreviation: PXZ-TRZ), 3-[4-(5-phenyl-5,1 0-Dihydrophenazin-10-yl)phenyl]-4,5-diphenyl-1,2,4- Triazole (abbreviation: PPZ-3TPT), 3-(9,9-dimethyl-9H-acridine -10-yl)-9H-xanthen-9-one (abbreviation: ACRXTN), bis[4-(9 ,9-Dimethyl-9,10-dihydroacridine)phenyl]sulfone (abbreviation: DMAC -DPS), 10-phenyl-10H,10'H-spiro[acridine-9,9'-an 4-(9'-phenyl-3,3'-biphenyl)-10'-one (abbreviation: ACRSA), -9H-carbazol-9-yl)benzofuro[3,2-d]pyrimidine (abbreviation: 4PC CzBfpm), 4-[4-(9'-phenyl-3,3'-bi-9H-carbazole-9 -yl)phenyl]benzofuro[3,2-d]pyrimidine (abbreviation: 4PCCzPBfpm ), 9-[3-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl] -9'-phenyl-2,3'-bi-9H-carbazole (abbreviation: mPCCzPTzn-0 2) and the like. Since the heterocyclic compound has a π-electron rich skeleton and a π-electron deficient skeleton, Therefore, the electron transport property and the hole transport property are high, and thus it is preferable. Diazine skeleton (pyrimidine skeleton, pyrazine skeleton, pyridazine skeleton), and triazine skeleton The triazine skeleton is preferred because it is stable and reliable. In particular, the benzofuropyrimidine skeleton is preferred. , benzothienopyrimidine skeleton, benzofuropyrazine skeleton, benzothienopyrazine skeleton It is preferred because it has high acceptor properties and good reliability. In addition, among the π-electron-rich skeletons, Acridine skeleton, phenoxazine skeleton, phenothiazine skeleton, furan skeleton, thiophene skeleton Since the pyrrole skeleton and the pyrrole skeleton are stable and reliable, It is preferable that the furan skeleton is a dibenzofuran skeleton, and the thiophene skeleton is As the pyrrole skeleton, a dibenzothiophene skeleton is preferable. Dole skeleton, carbazole skeleton, bicarbazole skeleton, 3-(9-phenyl-9H-carbazole Particularly preferred is a π-electron-rich skeleton. In the case of a substance in which the π-electron-rich skeleton is directly bonded to the π-electron-deficient skeleton, the donor properties of the π-electron-rich skeleton and the π-electron-deficient skeleton are The acceptor properties of both are strong, and the difference between the levels of the singlet excited state and the triplet excited state is small. In addition, an aromatic ring having an electron-withdrawing group such as a cyano group bonded thereto is preferably a π-electron-conducting ring. It may also be used as a molecule-deficient backbone.

[0150] [ka]

[0151] Next, as for compound 131, as described above, it is possible to convert triplet excitation energy into luminescence. As an organic compound having such a function, a phosphorescent material or Examples of the material include thermally activated delayed fluorescent materials.

[0152] The phosphorescent compound may be an organometallic complex of iridium, rhodium, or platinum, or In addition, platinum complexes with porphyrin ligands and organic iridium complexes complexes, among which organic iridium complexes such as iridium orthometal complexes are mentioned. The orthometalating ligand is preferably a 4H-triazole ligand, a 1H-triazole ligand, or a 2H-triazole ligand. Azole ligands, imidazole ligands, pyridine ligands, pyrimidine ligands, pyrazine ligands In this case, compound 131 (phosphorescent compound) is triplet MLCT (Metal to Ligand Charge Tran) sfer) transition absorption band.

[0153] Examples of substances having a blue or green emission peak include tris{2-[5-(2 -methylphenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazo 3-yl-κN 2 ]phenyl-κC}iridium(III) (abbreviation: Ir(mpp tz-dmp)3), tris(5-methyl-3,4-diphenyl-4H-1,2,4-trimethyl riazolate)iridium(III) (abbreviation: Ir(Mptz)3), tris[4-(3- Biphenyl)-5-isopropyl-3-phenyl-4H-1,2,4-triazolato]i Iridium(III) (abbreviation: Ir(iPrptz-3b)3), tris[3-(5-biphenyl] (phenyl)-5-isopropyl-4-phenyl-4H-1,2,4-triazolato]irid Ir(III) (abbreviation: Ir(iPr5btz)3), a 4H-triazole skeleton and organometallic iridium complexes having tris[3-methyl-1-(2-methylphenyl) -5-phenyl-1H-1,2,4-triazolato]iridium(III) (abbreviation: Ir (Mptz1-mp)3), tris(1-methyl-5-phenyl-3-propyl-1H- 1,2,4-Triazolate)iridium(III) (abbreviation: Ir(Prptz1-Me) 3) and fac-triazole-based organometallic iridium complexes. S[1-(2,6-diisopropylphenyl)-2-phenyl-1H-imidazole] Iridium(III) (abbreviation: Ir(iPrpmi)3), tris[3-(2,6-dimethyl phenyl)-7-methylimidazo[1,2-f]phenanthridinato]iridium(I II) Imidazole skeleton-containing compounds such as Ir(dmpimpt-Me)3 Organic metal iridium complexes and bis[2-(4',6'-difluorophenyl)pyridinato N,C 2’]Iridium(III) tetrakis(1-pyrazolyl)borate (abbreviation: FI r6), Bis[2-(4',6'-difluorophenyl)pyridinato-N,C 2’ ]Ili Dium(III) picolinate (abbreviation: FIrpic), bis{2-[3',5'-bis (Trifluoromethyl)phenyl]pyridinato-N,C 2’}Iridium(III) pico Ir(CF3ppy)2(pic) (fluorophenyl)pyridinato-N,C 2’ ]Iridium(III) acetylacetonate (abbreviation: FIr(acac)) Among the above, 4H-triazole is an organometallic iridium complex. Nitrogen-containing five-membered heterocyclic skeletons such as 1H-triazole skeleton and imidazole skeleton The organometallic iridium complex has high triplet excitation energy and is highly reliable and has excellent luminescence efficiency. It is particularly preferred because it is also excellent in

[0154] In addition, examples of substances having a green or yellow emission peak include tris(4-methylphenyl) Ir(mppm)3, Tris(4-t-butyl-6-phenylpyrimidinato)iridium(III) (abbreviation: I r(tBuppm)3), (acetylacetonato)bis(6-methyl-4-phenylpyridine Iridium(III) (abbreviation: Ir(mppm)2(acac)), (acetylacetonate ruacetonato)bis(6-tert-butyl-4-phenylpyrimidinato)iridium( III) (abbreviation: Ir(tBuppm)2(acac)), (acetylacetonato)bis [4-(2-norbornyl)-6-phenylpyrimidinato]iridium(III) (abbreviation Ir(nbppm)2(acac)), (acetylacetonato)bis[5-methyl-6 -(2-methylphenyl)-4-phenylpyrimidinato]iridium(III) (abbreviation: Ir(mpmppm)2(acac)), (acetylacetonato)bis{4,6-dimethyl 2-[6-(2,6-dimethylphenyl)-4-pyrimidinyl-κN 3 ]Phenyl- {κC}iridium(III) (abbreviation: Ir(dmppm-dmp)2(acac)), ( Acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III)( Abbreviation: Ir(dppm)2(acac) (acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazine) Iridium(III) (abbreviation: Ir(mppr-Me)2(acac)), (acetylacetonate arylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazinate)irid Pyrazine skeleton such as Ir(III) (abbreviation: Ir(mppr-iPr)2(acac)) Organometallic iridium complexes and tris(2-phenylpyridinato-N,C 2’ ) Iridium(III) (abbreviation: Ir(ppy)3), bis(2-phenylpyridinato-N ,C 2’ ) Iridium(III) acetylacetonate (abbreviation: Ir(ppy)2(ac ac)), bis(benzo[h]quinolinato)iridium(III) acetylacetonate (abbreviation: Ir(bzq)2(acac)), tris(benzo[h]quinolinato)iridium Ir(III) (abbreviation: Ir(bzq)3), tris(2-phenylquinolinato-N,C 2 ’ ) Iridium(III) (abbreviation: Ir(pq)3), bis(2-phenylquinolinato- N,C 2’ ) Iridium(III) acetylacetonate (abbreviation: Ir(pq)2(ac Organometallic iridium complexes with pyridine skeletons such as bis(2,4-difluorophenyl) and Venyl-1,3-oxazolato-N,C 2’ ) Iridium(III) acetylacetoner Ir(dpo)2(acac)), bis{2-[4'-(perfluorophenyl (phenyl)pyridinato-N,C 2’}Iridium(III) acetylacetonate ( Abbreviation: Ir(p-PF-ph)2(acac)), bis(2-phenylbenzothiazol -N,C 2’ ) Iridium(III) acetylacetonate (abbreviation: Ir(bt)2(a In addition to organometallic iridium complexes such as tris(acetylacetonato)(monophenyl) Anthroline) terbium(III) (abbreviation: Tb(acac)3(Phen)) Among the above, the organometallic iridium complexes having a pyrimidine skeleton are Dium complexes are particularly preferred because they are remarkably excellent in reliability and luminous efficiency.

[0155] Examples of substances having a yellow or red emission peak include diisobutyryl Methanato)bis[4,6-bis(3-methylphenyl)pyrimidinato]iridium(II I) (abbreviation: Ir(5mdppm)2(dibm)), bis[4,6-bis(3-methyl phenyl)pyrimidinato](dipivaloylmethanato)iridium(III) (abbreviation: Ir (5mdppm)2(dpm)), bis[4,6-di(naphthalene-1-yl)pyrimidinyl] Nato](dipivaloylmethanato)iridium(III) (abbreviation: Ir(d1npm)2( Organometallic iridium complexes with pyrimidine skeletons such as (acetylacetamide) Iridium(III) r(tppr)2(acac)), bis(2,3,5-triphenylpyrazine)(dipyridine) Valoylmethanato)iridium(III) (abbreviation: Ir(tppr)2(dpm)), ( Acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]i Ir(Fdpq)2(acac) and other pyrazine-based compounds Organometallic iridium complexes and tris(1-phenylisoquinolinato-N,C 2’ ) Iridium(III) (abbreviation: Ir(piq)3), bis(1-phenylisoquinolinato -N,C 2’ ) Iridium(III) acetylacetonate (abbreviation: Ir(piq)2( In addition to organometallic iridium complexes with pyridine skeletons such as acac), 2,3,7, 8,12,13,17,18-Octaethyl-21H,23H-porphyrin platinum(II) ) (abbreviation: PtOEP) and tris(1,3-diphenyl-1,3-propanediol). (Eu(DB))(monophenanthroline)europium(III) M) 3(Phen)), tris[1-(2-thenoyl)-3,3,3-trifluoroacetate [Tonato](monophenanthroline)europium(III) (abbreviation: Eu(TTA)3( Among the above, rare earth metal complexes such as pyrimidine skeletons are Organometallic iridium complexes having the above structure are particularly preferred because they are extremely reliable and have excellent luminous efficiency. In addition, organometallic iridium complexes with pyrazine skeletons can emit red light with good chromaticity. can be done.

[0156] In addition, the material that can be used as compound 131 is the above-mentioned thermally activated delayed fluorescence. Optical materials are included.

[0157] In addition, the compound 133 in the light-emitting layer 130 is preferably a fluorescent compound. The compound is not particularly limited, but may be an anthracene derivative, a tetracene derivative, or a chrysene derivative. Derivatives, phenanthrene derivatives, pyrene derivatives, perylene derivatives, stilbene derivatives, Cridone derivatives, coumarin derivatives, phenoxazine derivatives, phenoxazine derivatives, Thiazine derivatives and the like are preferred.

[0158] Specifically, 5,6-bis[4-(10-phenyl-9-anthryl)phenyl]-2 ,2'-bipyridine (abbreviation: PAP2BPy), 5,6-bis[4'-(10-phenyl -9-anthryl)biphenyl-4-yl]-2,2'-bipyridine (abbreviation: PAPP2 BPy), N,N'-diphenyl-N,N'-bis[4-(9-phenyl-9H-fluoro 1,6-Pyrene-9-yl)phenyl]pyrene-1,6-diamine (abbreviation: 1,6FLPAPrn) , N,N'-bis(3-methylphenyl)-N,N'-bis[3-(9-phenyl-9H -fluoren-9-yl)phenyl]pyrene-1,6-diamine (abbreviation: 1,6mMem FLPAPrn), N,N'-bis[4-(9-phenyl-9H-fluoren-9-yl )phenyl]-N,N'-bis(4-tert-butylphenyl)pyrene-1,6-diazo 1,6tBu-FLPAPrn, N,N'-diphenyl-N,N'-bis(1,6tBu-FLPAPrn) [4-(9-phenyl-9H-fluoren-9-yl)phenyl]-3,8-dicyclohexyl Xylpyrene-1,6-diamine (abbreviation: ch-1,6FLPAPrn), N,N'-biphenyl S[4-(9H-carbazol-9-yl)phenyl]-N,N'-diphenylstilbe YGA2S, 4-(9H-carbazol-9-yl) -4'-(10-phenyl-9-anthryl)triphenylamine (abbreviation: YGAPA) , 4-(9H-carbazol-9-yl)-4'-(9,10-diphenyl-2-anthracene N,9-diphenyl-N-[4- (10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine (abbreviation Name: PCAPA), Perylene, 2,5,8,11-tetra(tert-butyl)perylene (abbreviation: TBP), 4-(10-phenyl-9-anthryl)-4'-(9-phenyl- 9H-Carbazol-3-yl)triphenylamine (abbreviation: PCBAPA), N,N' '-(2-tert-butylanthracene-9,10-diyldi-4,1-phenylene) Bis[N,N',N'-triphenyl-1,4-phenylenediamine] (abbreviation: DPAB PA), N,9-diphenyl-N-[4-(9,10-diphenyl-2-anthryl)phenyl] phenyl]-9H-carbazol-3-amine (abbreviation: 2PCAPPA), N-[4-(9 ,10-diphenyl-2-anthryl)phenyl]-N,N',N'-triphenyl-1 ,4-Phenylenediamine (abbreviation: 2DPAPPA), N,N,N',N',N'',N '',N''',N'''-Octaphenyldibenzo[g,p]chrysene-2,7,10 ,15-Tetraamine (abbreviation: DBC1), Coumarin 30, N-(9,10-diphenyl -2-anthryl)-N,9-diphenyl-9H-carbazol-3-amine (abbreviation: 2 PCAPA), N-[9,10-bis(1,1'-biphenyl-2-yl)-2-anthracene aryl]-N,9-diphenyl-9H-carbazol-3-amine (abbreviation: 2PCABPh A), N-(9,10-diphenyl-2-anthryl)-N,N',N'-triphenyl -1,4-phenylenediamine (abbreviation: 2DPAPA), N-[9,10-bis(1,1 '-biphenyl-2-yl)-2-anthryl]-N,N',N'-triphenyl-1, 4-Phenylenediamine (abbreviation: 2DPABPhA), 9,10-bis(1,1'-biphenyl) phenyl-2-yl)-N-[4-(9H-carbazol-9-yl)phenyl]-N- Phenylanthracene-2-amine (abbreviation: 2YGABPhA), N,N,9-triphenyl Dianthracene-9-amine (abbreviation: DPhAPhA), Coumarin 6, Coumarin 545T , N,N'-diphenylquinacridone (abbreviation: DPQd), rubrene, 2,8-di-te rt-Butyl-5,11-bis(4-tert-butylphenyl)-6,12-diphenyl Tetrathracene (abbreviation: TBRb), Nile Red, 5,12-bis(1,1'-biphenyl) 2-(2-(2-phenyl-4-yl)-6,11-diphenyltetracene (abbreviation: BPT), [4-(Dimethylamino)phenyl]ethenyl}-6-methyl-4H-pyran-4-yl 2-(2-methyl-6-[2-(2,3-dimethylphenyl)propanedinitrile (abbreviation: DCM1), ,6,7-Tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl ]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCM2), N,N,N ',N'-Tetrakis(4-methylphenyl)tetracene-5,11-diamine (abbreviation: p-mPhTD), 7,14-diphenyl-N,N,N',N'-tetrakis(4-methyl phenyl)acenaphtho[1,2-a]fluoranthene-3,10-diamine (abbreviation: p -mPhAFD), 2-{2-isopropyl-6-[2-(1,1,7,7-tetramethyl 2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl )Ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCJTI) , 2-{2-tert-butyl-6-[2-(1,1,7,7-tetramethyl-2,3, 6,7-Tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl] -4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCJTB), 2-(2, 6-Bis{2-[4-(dimethylamino)phenyl]ethenyl}-4H-pyran-4-yl 2-{2,6-bis[2-(8- Methoxy-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H -benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}p Dopanedinitrile (abbreviation: BisDCJTM), 5,10,15,20-tetraphenyl Bisbenzo[5,6]indeno[1,2,3-cd:1',2',3'-lm]perylene , etc.

[0159] In addition, when compound 131 and compound 132 form an exciplex, the exciplex formed is The emission peak of the compound 133, which is the luminescent material, is at the longest wavelength (lowest energy) absorption peak. It is preferable to select compounds 131, 132, and 133 so that they overlap with the band. This makes it possible to provide a light emitting device with significantly improved luminous efficiency.

[0160] The light-emitting layer 130 may be composed of two or more layers. When the light-emitting layer 130 is formed by laminating the first light-emitting layer and the second light-emitting layer in this order from the hole transport layer side, A substance having a hole transporting property is used as a host material for the first light-emitting layer, and a substance having a hole transporting property is used as a host material for the second light-emitting layer. For example, a substance having an electron transport property is used as the insulating film.

[0161] As shown in FIG. 4, in the light-emitting layer 130, the compound 131, the compound 132, and The compound 132 may contain a material other than the compound 133 (compound 134). It is preferable to form an exciplex with compound 134. The HOMO level of one of the compounds 134 is the highest among the materials in the light-emitting layer 130. The other LUMO level is the lowest LUMO level of the material in the light-emitting layer 130. That is, it is preferable that the HOMO level of one of the compounds 132 and 134 is The HOMO level of the other compound is higher than that of compound 131, and the LUMO level of the other compound is higher than that of compound 132. It is preferred that the LUMO level of the compound is lower than the LUMO level of the other compound and the LUMO level of compound 131. This structure suppresses the reaction of compound 132 and compound 131 to form an exciplex. It is possible.

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

[0163] As the hole transporting material, a material having a higher hole transporting property than an electron transporting property can be used. ×10 -6 cm 2It is preferable that the material has a hole mobility of 1 / Vs or more. The hole transporting material may be an aromatic amine, a carbazole derivative, or the like. The material may be a polymer.

[0164] As examples of materials with high hole transport properties, aromatic amine compounds include N,N' -Di(p-tolyl)-N,N'-diphenyl-p-phenylenediamine (abbreviation: DTDP PA), 4,4'-bis[N-(4-diphenylaminophenyl)-N-phenylamino ]biphenyl (abbreviation: DPAB), N,N'-bis{4-[bis(3-methylphenyl) Amino]phenyl}-N,N'-diphenyl-(1,1'-biphenyl)-4,4'-di Amine (abbreviation: DNTPD), 1,3,5-tris[N-(4-diphenylaminophenyl Examples include]-N-phenylamino]benzene (abbreviation: DPA3B).

[0165] Specific examples of carbazole derivatives include 3-[N-(4-diphenylamino phenyl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzDPA1 ), 3,6-bis[N-(4-diphenylaminophenyl)-N-phenylamino]-9 -Phenylcarbazole (abbreviation: PCzDPA2), 3,6-bis[N-(4-diphenyl [N-(1-naphthyl)amino]-9-phenylcarbazole (abbreviation :PCzTPN2), 3-[N-(9-phenylcarbazol-3-yl)-N-phenyl 3,6-bis[N- (9-Phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazol PCzPCA2, 3-[N-(1-naphthyl)-N-(9-phenylcarbazone] carbazol-3-yl)amino]-9-phenylcarbazole (abbreviation: PCzPCN1) etc. can be mentioned.

[0166] Another example of a carbazole derivative is 4,4'-di(N-carbazolyl)biphene. Nyl (abbreviation: CBP), 1,3,5-tris[4-(N-carbazolyl)phenyl]benzoyl Zene (abbreviation: TCPB), 1,4-bis[4-(N-carbazolyl)phenyl]-2,3 , 5,6-tetraphenylbenzene, etc. can be used.

[0167] As a material with high hole transport properties, for example, 4,4'-bis[N-(1-naphthyl )-N-phenylamino]biphenyl (abbreviation: NPB or α-NPD) and N,N'-biphenyl S(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4 '-Diamine (abbreviation: TPD), 4,4',4''-tris(carbazol-9-yl) Triphenylamine (abbreviation: TCTA), 4,4',4''-tris[N-(1-naphthalene 1'-TNATA, 4,4'-N-phenylamino]triphenylamine ,4''-Tris(N,N-diphenylamino)triphenylamine (abbreviation: TDATA ), 4,4',4''-tris[N-(3-methylphenyl)-N-phenylamino] Triphenylamine (abbreviation: m-MTDATA), 4,4'-bis[N-(spiro-9,9 '-Bifluoren-2-yl)-N-phenylamino]biphenyl (abbreviation: BSPB), 4-Phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation :BPAFLP), 4-phenyl-3'-(9-phenylfluoren-9-yl)trifluoroacetate mBPAFLP, N-(9,9-dimethyl-9H-fluorene- 2-yl)-N-{9,9-dimethyl-2-[N'-phenyl-N'-(9,9-dimethyl (amino)-9H-fluoren-7-yl}phenyl DFLADFL, N-(9,9-dimethyl-2-diphenylamino-9H -fluoren-7-yl)diphenylamine (abbreviation: DPNF), 2-[N-(4-difluorophenyl) (N-phenylaminophenyl)-N-phenylamino]spiro-9,9'-bifluorene (abbreviation :DPASF), 4-phenyl-4'-(9-phenyl-9H-carbazol-3-yl ) Triphenylamine (abbreviation: PCBA1BP), 4,4'-diphenyl-4''-(9 -phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBBi1 BP), 4-(1-naphthyl)-4'-(9-phenyl-9H-carbazol-3-yl ) Triphenylamine (abbreviation: PCBANB), 4,4'-di(1-naphthyl)-4'' -(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCB NBB), 4-phenyldiphenyl-(9-phenyl-9H-carbazol-3-yl) Amine (abbreviation: PCA1BP), N,N'-bis(9-phenylcarbazol-3-yl) )-N,N'-diphenylbenzene-1,3-diamine (abbreviation: PCA2B), N,N' ,N''-Triphenyl-N,N',N''-tris(9-phenylcarbazole-3- N-(4-biphenylyl)benzene-1,3,5-triamine (abbreviation: PCA3B) )-N-(9,9-dimethyl-9H-fluoren-2-yl)-9-phenyl-9H-carbazone PCBiF, N-(1,1'-biphenyl-4-yl) )-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9- Dimethyl-9H-fluoren-2-amine (abbreviation: PCBBiF), 9,9-dimethyl- N-Phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl] Fluorene-2-amine (abbreviation: PCBAF), N-phenyl-N-[4-(9-phenyl 9,9'-bifluorene-2-yl-9H-carbazol-3-ylphenyl Amine (abbreviation: PCBASF), 2-[N-(9-phenylcarbazol-3-yl)- N-phenylamino]spiro-9,9'-bifluorene (abbreviation: PCASF), 2,7- Bis[N-(4-diphenylaminophenyl)-N-phenylamino]-spiro-9,9 '-Bifluorene (abbreviation: DPA2SF), N-[4-(9H-carbazol-9-yl )phenyl]-N-(4-phenyl)phenylaniline (abbreviation: YGA1BP), N,N '-Bis[4-(carbazol-9-yl)phenyl]-N,N'-diphenyl-9,9 -Dimethylfluorene-2,7-diamine (abbreviation: YGA2F) and other aromatic amine compounds Also usable are 3-[4-(1-naphthyl)-phenyl]-9-phenyl. PCPN, 3-[4-(9-phenanthryl)- phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPPn), 3,3'-bis( 9-phenyl-9H-carbazole) (abbreviation: PCCP), 1,3-bis(N-carbazo mCP, 3,6-bis(3,5-diphenylphenyl)-9- Phenylcarbazole (abbreviation: CzTP), 4-{3-[3-(9-phenyl-9H- mmDBFFLBi -II), 4,4',4''-(benzene-1,3,5-triyl)tri(dibenzofuran) DBF3P-II, 1,3,5-tri(dibenzothiophene-4-yl) -Benzene (abbreviation: DBT3P-II), 2,8-diphenyl-4-[4-(9-phenyl [Dibenzothiophene (abbreviation: DBTFLP)] -III), 4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6 -Phenyldibenzothiophene (abbreviation: DBTFLP-IV), 4-[3-(triphenyl (2-phenyl)dibenzothiophene (abbreviation: mDBTPTp-II) Mine compounds, carbazole compounds, thiophene compounds, furan compounds, fluorene compounds , triphenylene compounds, phenanthrene compounds, etc. can be used. The substance is mainly 1×10 -6 cm 2 A material that has a hole mobility of 1000V or more. Any other substance may be used as long as it has a higher hole transporting property than electron transporting property.

[0168] As the electron transport material, a material having a higher electron transporting property than a hole transporting property can be used. 10 -6 cm 2 It is preferable that the material has an electron mobility of .beta. / Vs or more. Compounds that are easy to remove (materials with electron transport properties) include nitrogen-containing heteroaromatic compounds. Examples of suitable π-electron deficient heteroaromatic compounds and metal complexes include quinolinol, ... Phosphorus, benzoquinoline, oxazole, or thiazole ligands In addition, oxadiazole derivatives, triazole derivatives, fluorine derivatives, etc. Phenolic acid derivatives, pyridine derivatives, bipyridine derivatives, pyrimidine derivatives, benzo Examples of the derivatives include furopyrimidine derivatives and benzothienopyrimidine derivatives. Any other material that has a higher electron transporting capacity than holes may be used as the electron transport layer. That's fine.

[0169] A specific example of the electron transport material is tris(8-quinolinolato)aluminum (III ) (abbreviation: Alq), tris(4-methyl-8-quinolinolato)aluminum(III) (abbreviation: Almq3), bis(10-hydroxybenzo[h]quinolinato)beryllium ( II) (abbreviation: BeBq2), bis(2-methyl-8-quinolinolato)(4-phenylphenyl) (Enolato)aluminum(III)(abbreviation: BAlq), bis(8-quinolinolato)zinc (II) (abbreviation: Znq), etc., metal complexes having a quinoline or benzoquinoline skeleton In addition, bis[2-(2-benzoxazolyl)phenolato]zinc(I I) (abbreviation: ZnPBO), bis[2-(2-benzothiazolyl)phenolato]zinc (I I) Metal complexes with oxazole and thiazole ligands such as ZnBTZ In addition to metal complexes, 2-(4-biphenylyl)-5 -(4-tert-Butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD) and 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazo OXD-7), 9-[4-(5-phenyl-1,3, 4-Oxadiazol-2-yl)phenyl]-9H-carbazole (abbreviation: CO11) , 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)- 1,2,4-Triazole (abbreviation: TAZ), 2,2',2''-(1,3,5-benzene (1-phenyl-1H-benzimidazole) (abbreviation: TPBI), 2-[3-(dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzo Imidazole (abbreviation: mDBTBIm-II), bathophenanthroline (abbreviation: BPhe n), Bathocuproine (abbreviation: BCP), 2,9-bis(naphthalene-2-yl)-4 ,7-Diphenyl-1,10-phenanthroline (abbreviation: NBPhen) and other heterocyclization Compounds such as 2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]ky Noxalin (abbreviation: 2mDBTPDBq-II), 2-[3'-(dibenzothiophene- 4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBT BPDBq-II), 2-[3'-(9H-carbazol-9-yl)biphenyl-3- yl]dibenzo[f,h]quinoxaline (abbreviation: 2mCzBPDBq), 2-[4-(3 ,6-diphenyl-9H-carbazol-9-yl)phenyl]dibenzo[f,h]quino Xaline (abbreviation: 2CzPDBq-III), 7-[3-(dibenzothiophene-4-yl) 7mDBTPDBq-II 6-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxalate 6mDBTPDBq-II, 4,6-bis[3-(phenanthrene-9-yl) 4,6-bis[3-(4-phenyl)pyrimidine (abbreviation: 4,6mPnP2Pm), Dibenzothienyl)phenyl]pyrimidine (abbreviation: 4,6mDBTP2Pm-II), 4 ,6-Bis[3-(9H-carbazol-9-yl)phenyl]pyrimidine (abbreviation: 4, Heterocyclic compounds with diazine skeletons such as 6mCzP2Pm, and PCCzPTzn Heterocyclic compounds with triazine skeletons such as 3,5-bis[3-(9H-carbazole- 9-yl)phenyl]pyridine (abbreviation: 35DCzPPy), 1,3,5-tri[3-( 3-pyridyl)phenyl]benzene (abbreviation: TmPyPB) Heterocyclic compound, 4,4'-bis(5-methylbenzoxazol-2-yl)stilbene Heteroaromatic compounds such as poly(2,5 -pyridinediyl) (abbreviation: PPy), poly[(9,9-dihexylfluorene-2,7 -diyl)-co-(pyridine-3,5-diyl)] (abbreviation: PF-Py), poly[(9 ,9-Dioctylfluorene-2,7-diyl)-co-(2,2'-bipyridine-6, 6'-diyl)] (abbreviation: PF-BPy) can also be used. The substances mentioned here are mainly 1×10 -6 cm 2 / Vs or higher. Note that any substance other than those mentioned above may be used as long as it has a higher electron transporting property than a hole transporting property. do not have.

[0170] In addition, when compound 134 and compound 132 form an exciplex, the resulting exciplex is The emission peak of the compound 131 was determined so as to overlap with the absorption band of the compound 131 on the longest wavelength side (lowest energy side). In particular, it is preferable to select Compound 131, Compound 132, and Compound 134. As a result, a light-emitting element with significantly improved luminous efficiency can be obtained.

[0171] The electrode 101 and the electrode 102 have a function of injecting holes and electrons into the light-emitting layer 130. The electrodes 101 and 102 are made of metals, alloys, conductive compounds, and mixtures or laminates thereof. The metal can be aluminum (Al) as a typical example. , and other transition metals such as silver (Ag), tungsten, chromium, molybdenum, copper, and titanium. , alkali metals such as lithium (Li) and cesium, calcium, magnesium (Mg) Group 2 metals such as ytterbium (Yb) can be used as transition metals. A rare earth metal may be used. As the alloy, an alloy containing the above metals may be used. Examples of the conductive compound include MgAg and AlLi. Indium tin oxide (ITO), silicon or silicon oxide Including indium tin oxide (abbreviation: ITSO), indium zinc oxide (Indium Z inc Oxide), tungsten and zinc-containing indium oxide, etc. As the conductive compound, an inorganic carbon-based material such as graphene may be used. As described above, electrodes 101 and 10 are formed by stacking multiple layers of these materials. 2 or both may be formed.

[0172] The light emitted from the light-emitting layer 130 is emitted from one or both of the electrodes 101 and 102. Therefore, at least one of the electrodes 101 and 102 is visible. The conductive material has a function of transmitting light. The transmittance is 40% or more and 100% or less, preferably 60% or more and 100% or less, and the resistance Resistance is 1×10 -2 Materials with a conductivity of Ω cm or less are also suitable. The electrode is made of a conductive material having a function of transmitting light and a function of reflecting light. The conductive material has a visible light reflectance of 20% or more and 80% or less, preferably 4 0% to 70% and its resistivity is 1×10 -2 Conductive materials with a resistance of Ω·cm or less When a material with low optical transparency, such as a metal or alloy, is used for the electrode that extracts light, The electrode 10 is formed with a thickness that is thick enough to transmit visible light (for example, 1 nm to 10 nm). Either or both of the electrode 101 and the electrode 102 may be formed.

[0173] In this specification and the like, the electrode having a function of transmitting light includes an electrode having a function of transmitting visible light. Any material having both the function and electrical conductivity may be used, and examples thereof include ITO as mentioned above. In addition to the oxide conductor layer, an oxide semiconductor layer or an organic conductor layer containing an organic material is included. The organic conductive layer containing an organic substance may be, for example, a layer containing an organic compound and an electron donor. A layer including a composite material obtained by mixing an organic compound and an electron acceptor. 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.

[0174] The electrode 101 and the electrode 102 may be formed by a sputtering method, a vapor deposition method, a printing method, or the like. Coating method, MBE (Molecular Beam Epitaxy) method, CVD method, Pulse Laser deposition method, ALD (Atomic Layer Deposition) method, etc. It can be used as appropriate.

[0175] <Hole injection layer> The hole injection layer 111 is configured to inject holes from one of the pair of electrodes (electrode 101 or electrode 102). It has the function of promoting hole injection by reducing the injection barrier. It is formed by phthalocyanine derivatives or aromatic amines. Transition metal oxides and Examples include molybdenum oxide, vanadium oxide, ruthenium oxide, and tungsten oxide. , manganese oxide, etc. Phthalocyanine derivatives include phthalocyanine, Examples of aromatic amines include benzidine derivatives and phenyl Diamine derivatives, etc. Polymer compounds such as polythiophene and polyaniline It is also possible to use self-doped polythiophenes such as poly(ethylenediaminetetraacetate). Representative examples include poly(oxythiophene) / poly(styrenesulfonic acid).

[0176] The hole injection layer 111 is made of a compound of a hole transporting material and a material that has an electron accepting property. Alternatively, a layer containing a material exhibiting electron accepting properties and a layer containing a positive electrode may be used. A stack of layers containing hole transporting materials may also be used. It is possible to give and receive electric charges in the presence of a magnetic field. Materials that exhibit electron-accepting properties include quinodimethane. Organic acceptors such as aryl, chloranil, and hexaazatriphenylene derivatives Specifically, 7,7,8,8-tetracyano-2,3,5,6- Tetrafluoroquinodimethane (abbreviation: F4-TCNQ), chloranil, 2,3,6,7, 10,11-Hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviation Name: HAT-CN), 1,3,4,5,7,8-Hexafluorotetracyano-naphthyl Electron-withdrawing groups such as fluoro groups, e.g., dimethylmethane (abbreviation: F6-TCNNQ) In particular, compounds having multiple groups such as HAT-CN can be mentioned. Compounds in which an electron-withdrawing group is bonded to a condensed aromatic ring having multiple atomic atoms are thermally stable. It is also preferable that the aryl group has an electron-withdrawing group (particularly a halogen group such as a fluoro group or a cyano group). [3] Radialene derivatives are preferred because they have a very high electron-accepting property. Specifically, α,α' ,α''-1,2,3-cyclopropanetriylidenetris[4-cyano-2,3,5, 6-Tetrafluorobenzeneacetonitrile], α,α',α''-1,2,3-cyclo Propane triylidene tris[2,6-dichloro-3,5-difluoro-4-(trifluoro (O-methyl)benzeneacetonitrile], α,α',α''-1,2,3-cyclopropane Tris[2,3,4,5,6-pentafluorobenzeneacetonitrile] In addition, transition metal oxides, for example, oxides of metals in Groups 4 to 8, are used. Specifically, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, , molybdenum oxide, tungsten oxide, manganese oxide, rhenium oxide, etc. Molybdenum oxide is preferred because it is stable in the air, has low hygroscopicity, and is easy to handle.

[0177] As the hole transporting material, a material having a higher hole transporting property than an electron transporting property can be used. ×10 -6 cm 2 It is preferable that the material has a hole mobility of 1 / Vs or more. The aromatic amines and the like listed as hole transporting materials that can be used in the light emitting layer 130 are Carbazole derivatives can be used. Aromatic hydrocarbons and stilbene derivatives can also be used. The hole transporting material may be a polymer compound.

[0178] Examples of aromatic hydrocarbons include 2-tert-butyl-9,10-di(2-naphthyl) 2-tert-butyl-9,10-di(1 -naphthyl)anthracene, 9,10-bis(3,5-diphenylphenyl)anthracene DPPA, 2-tert-butyl-9,10-bis(4-phenylphenyl) )anthracene (abbreviation: t-BuDBA), 9,10-di(2-naphthyl)anthracene (Abbreviation: DNA), 9,10-diphenylanthracene (Abbreviation: DPAnth), 2-t ert-Butylanthracene (abbreviation: t-BuAnth), 9,10-bis(4-methyl -1-naphthyl)anthracene (abbreviation: DMNA), 2-tert-butyl-9,10- Bis[2-(1-naphthyl)phenyl]anthracene, 9,10-bis[2-(1-naphthyl)phenyl]anthracene 2,3,6,7-tetramethyl-9,10-di(1-nathyl)phenyl]anthracene 2,3,6,7-tetramethyl-9,10-di(2-naphthyl)anthracene Anthracene, 9,9'-bianthryl, 10,10'-diphenyl-9,9'-bianthryl tolyl, 10,10'-bis(2-phenylphenyl)-9,9'-bianthryl, 10 ,10'-Bis[(2,3,4,5,6-pentaphenyl)phenyl]-9,9'-bis Anthracene, anthracene, tetracene, rubrene, perylene, 2,5,8,11-tetra (tert-butyl)perylene, etc. In addition, pentacene, coronene, etc. can also be used. Thus, 1×10 -6 cm 2 / Vs or more It is more preferable to use aromatic hydrocarbons having 14 or more carbon atoms and 42 or less carbon atoms.

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

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

[0181] <Hole transport layer> The hole transport layer 112 is a layer containing a hole transporting material. The hole transport layer 112 is formed by injecting the hole into the hole injection layer 111. Since it has a function of transporting holes to the light-emitting layer 130, it has a HOMO level similar to that of the hole injection layer 111. It is preferable that the HOMO level of each of the aryl groups is the same as or close to the HOMO level of each of the aryl groups.

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

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

[0184] As the electron transport material, the materials exemplified as the material of Compound 134 can be used. Also, 1×10 -6 cm 2 It is preferable that the material has an electron mobility of .beta. / Vs or more. The electron transport layer 118 may be a single layer or a laminate of two or more layers made of the above-mentioned materials. You may do so.

[0185] In addition, a layer for controlling the movement of electron carriers is provided between the electron transport layer 118 and the light emitting layer 130. The layer for controlling the movement of electron carriers may be made of a material having high electron transport properties as described above. A small amount of a substance with high electron trapping properties is added to the layer, which suppresses the movement of electron carriers. This makes it possible to adjust the carrier balance. To prevent problems caused by electrons penetrating through layers (such as reduced device life) It has a great effect.

[0186] ≪Electron injection layer≫ The electron injection layer 119 promotes electron injection by reducing the electron injection barrier from the electrode 102. For example, Group 1 metals, Group 2 metals, or their oxides and halides In addition, the above-mentioned electron transporting material and the corresponding electron A composite material of a material exhibiting electron donating properties can also be used. Examples of the metal include Group 1 metals, Group 2 metals, and oxides thereof. Lithium fluoride (LiF), sodium fluoride (NaF), and cesium fluoride (CsF ), calcium fluoride (CaF2), lithium oxide (LiO x ) and other alkaline gold Metals, alkaline earth metals, or compounds thereof can be used. A rare earth metal compound such as fluorine (ErF3) can be used. An electride may be used for 119. The electride may be, for example, calcium. Examples include a material in which electrons are highly concentrated in a mixed oxide of aluminum and ruthenium. The injection layer 119 may be made of a material that can be used in the electron transport layer 118 .

[0187] In addition, the electron injection layer 119 is made of a composite material obtained by mixing an organic compound and an electron donor. Such composite materials may be made by adding electrons to an organic compound via an electron donor. In this case, the organic compound is It is preferable that the material has excellent transport properties for the generated electrons. Specifically, for example, the above-mentioned The material constituting the electron transport layer 118 (metal complex, heteroaromatic compound, etc.) can be used. The electron donor may be any substance that exhibits electron donating properties to organic compounds. For the metal, alkali metals, alkaline earth metals and rare earth metals are preferred, and lithium, cesium, Magnesium, calcium, erbium, ytterbium, etc. Preferred are lithium metal oxides and alkaline earth metal oxides, and lithium oxide and calcium oxide are preferred. , barium oxide, etc. Also, Lewis bases such as magnesium oxide are used. It is also possible to use organic compounds such as tetrathiafulvalene (TTF). It is also possible.

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

[0189] The quantum dots are classified into colloidal quantum dots, alloy quantum dots, and core-shell quantum dots. In addition, a group 2 and a group 16, a group 13 and a group 14, and a core type quantum dot may be used. Contains element groups 15, 13 and 17, 11 and 17, or 14 and 15 Quantum dots may also be used. Alternatively, cadmium (Cd), selenium (Se), zinc (Zn ), sulfur (S), phosphorus (P), indium (In), tellurium (Te), lead (Pb), gallium (Ga), Quantum dots containing elements such as Ga, Arsenic, and Aluminum are used. It's fine.

[0190] Examples of liquid media used in wet processes include methyl ethyl ketone, cyclohexane, etc. Ketones such as xanone, fatty acid esters such as ethyl acetate, halogens such as dichlorobenzene Hydrocarbons, aromatics such as toluene, xylene, mesitylene, and cyclohexylbenzene Hydrocarbons, aliphatic hydrocarbons such as cyclohexane, decalin, and dodecane, dimethylformamide, etc. Organic solvents such as dichloromethane (DMF) and dimethyl sulfoxide (DMSO) can be used. Cut.

[0191] Examples of polymer compounds that can be used in the light-emitting layer include poly[2-methoxy]phenylene. [MeH] -PPV), polyphenylenes such as poly(2,5-dioctyl-1,4-phenylenevinylene), 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 Name: F8BT), poly[(9,9-di-n-octylfluorenyl-2,7-diyl)- alt-(2,2'-bithiophene-5,5'-diyl)] (abbreviation: F8T2), poly[ (9,9-dioctyl-2,7-divinylenefluorenylene)-alt-(9,10-a poly[(9,9-dihexylfluorene-2,7-diyl)-alt- (2,5-dimethyl-1,4-phenylene)] and other polyfluorene derivatives, poly(3- Polyalkylthiophenes such as polyalkylthiophene (P3HT) PAT) derivatives, polyphenylene derivatives, etc. , PVK, poly(2-vinylnaphthalene), poly[bis(4-phenyl)(2,4,6- A polymer compound such as PTAA (trimethylphenyl)amine, a luminescent compound The light-emitting layer may be doped with the above-mentioned light-emitting compounds. Things can be used.

[0192] In one embodiment of the present invention, a benzofuropyrimidine skeleton or a benzothienopyrimidine skeleton is an organic compound having a triplet excitation energy, an organic compound capable of converting triplet excitation energy into luminescence, and a fluorescent compound having a Three types of organic compounds that emit light are mixed and used in the light-emitting layer 130. For example, a polymer compound having a benzofuropyrimidine skeleton or The compound has a benzothienopyrimidine skeleton and a substituent that can convert triplet excitation energy into luminescence. A polymer compound having a substituent that exhibits fluorescent light may be used as the light-emitting layer 130. In addition, the benzofuropyrimidine skeleton or the benzothienopyrimidine skeleton and the triplet excited state A polymer compound having a substituent capable of converting energy into light emission and a low molecular weight compound exhibiting fluorescent light emission. The light-emitting layer 130 may be fabricated by mixing the polymer compound. The utilization efficiency can be improved, and the manufacturing cost can be reduced.

[0193] <Substrate> In addition, the light-emitting element according to one embodiment of the present invention is provided on a substrate made of glass, plastic, or the like. Regarding the order of fabrication on the substrate, the layers may be stacked in order from the electrode 101 side. They may be laminated in order from the pole 102 side.

[0194] The substrate on which the light-emitting element according to one embodiment of the present invention can be formed is, for example, glass or quartz. A flexible substrate may be used. The substrate is a flexible substrate, such as polycarbonate. Examples of the substrate include plastic substrates made of polyacrylate and polyarylate. In the process of manufacturing the light-emitting element, a film formed by vapor deposition may be used. Any other material may be used as long as it functions as a light-emitting element. Anything that has a function will suffice.

[0195] For example, in this specification, a light emitting element can be formed using various substrates. The type of the substrate is not particularly limited. An example of the substrate is a semiconductor substrate (e.g., a single crystal crystal substrate or silicon substrate), SOI substrate, glass substrate, quartz substrate, plastic substrate, gold Metallic substrate, stainless steel substrate, substrate with stainless steel foil, tungsten Tungsten substrate, substrate with tungsten foil, flexible substrate, laminated film, fiber These include cellulose nanofibers (CNFs), papers, and base films that contain such materials. Examples of glass substrates include barium borosilicate glass, aluminoborosilicate glass, and Soda lime glass, etc. Flexible substrates, laminated films, base films, etc. Examples of such materials include polyethylene terephthalate (PET), Polyethylene naphthalate (PEN), polyethersulfone (PES), polytetrafluoroethylene Examples of plastics include fluoroethylene (PTFE). Resins such as acrylic, etc., or polypropylene, polyester, etc. Examples include polyvinyl fluoride or polyvinyl chloride. Alternatively, an example is polyamide. , polyimide, aramid, epoxy, inorganic vapor deposition film, or paper.

[0196] In addition, a flexible substrate may be used as the substrate, and the light emitting element may be formed directly on the flexible substrate. Alternatively, a release layer may be provided between the substrate and the light-emitting element. After a part or all of a chip is completed, it is separated from the board and used to transfer it to another board. In this case, the light-emitting element can be transferred onto a substrate having poor heat resistance or a flexible substrate. The above-mentioned peeling layer has a laminated structure of inorganic films, for example, a tungsten film and a silicon oxide film. or a structure in which a resin film such as polyimide is formed on a substrate.

[0197] That is, a light emitting element is formed using a certain substrate, and then the light emitting element is transferred to another substrate. The light emitting element may be disposed on another substrate. In addition to the above mentioned substrates, cellophane substrates, stone substrates, wood substrates, fabric substrates (natural fibers (silk, cotton, Hemp), synthetic fibers (nylon, polyurethane, polyester) or regenerated fibers (acetate (including cellulose, cupra, rayon, recycled polyester, etc.), leather substrate, rubber substrate, etc. By using these substrates, light-emitting elements that are not easily broken and have high heat resistance can be produced. The light emitting element may be a small light emitting element, a light emitting element that is lighter in weight, or a light emitting element that is thinner.

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

[0199] The structure shown in this embodiment mode can be used in appropriate combination with other embodiment modes. Cut.

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

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

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

[0203] In addition, in the light-emitting element 250 shown in FIG. The light-emitting unit 106 and the light-emitting unit 108 are laminated together, and a charge generating layer 1 is provided between the light-emitting unit 106 and the light-emitting unit 108. The light-emitting units 106 and 108 have different configurations. For example, the light-emitting unit 108 may have the same structure as the EL layer 100. This is preferable.

[0204] The light emitting element 250 includes a light emitting layer 120 and a light emitting layer 170. In addition to the light-emitting layer 120, the knit 106 includes a hole injection layer 111, a hole transport layer 112, an electron transport The light-emitting unit 108 also includes an emissive layer 170. In addition to the above, a hole injection layer 116, a hole transport layer 117, an electron transport layer 118, and an electron injection layer 11 Has 9.

[0205] The light-emitting element 250 is provided in any of the layers of the light-emitting unit 106 and the light-emitting unit 108. It is sufficient that the organic compound according to one embodiment of the present invention is contained. The electron transport layer 113 or the electron transport layer 118 is preferable as the light emitting layer. The optical layer 120 or the light-emitting layer 170 .

[0206] The charge generating layer 115 is formed by adding an acceptor material, which is an electron acceptor, to a hole transporting material. Even if the structure is such that the electron transport material is a material having a donor property, the structure may be such that the donor property is added to the electron transport material. In addition, both of these configurations may be laminated.

[0207] When the charge generating layer 115 contains a composite material of an organic compound and an acceptor substance, As the composite material, the composite material which can be used for the hole-injection layer 111 shown in Embodiment 1 is used. The organic compounds include aromatic amine compounds, carbazole compounds, aromatic carbon compounds, etc. Various compounds such as hydrogen and polymer compounds (oligomers, dendrimers, polymers, etc.) are used. As an organic compound, a hole mobility of 1×10 -6 cm 2 / Vs However, it is preferable to use a material having a higher hole transporting property than an electron transporting property. Other materials may be used as long as they are compatible with the organic compound and the acceptor material. The material has excellent carrier injection and transport properties, enabling low-voltage and low-current operation. In addition, the anode side surface of the light-emitting unit is in contact with the charge generating layer 115. In this case, the charge generating layer 115 also serves as a hole injection layer or a hole transport layer for the light emitting unit. Therefore, the light-emitting unit does not need to have a hole injection layer or a hole transport layer. Alternatively, when the cathode side surface of the light-emitting unit is in contact with the charge generating layer 115, The charge generating layer 115 also serves as an electron injection layer or an electron transport layer for the light emitting unit. Therefore, the light-emitting unit does not have an electron injection layer or an electron transport layer. is also good.

[0208] The charge generating layer 115 may be a layer including a composite material of an organic compound and an acceptor substance. For example, the organic EL element may be formed as a laminated structure in which layers made of the organic material are combined. A layer including a composite material of a compound and an acceptor material, and a layer including a compound selected from an electron donor material. The compound may be combined with a compound having a high electron transporting property to form a layer. A layer including a composite material of an organic compound and an acceptor substance and a layer including a transparent conductive film are combined. It may be formed by combining the above.

[0209] The charge generating layer 115 sandwiched between the light emitting unit 106 and the light emitting unit 108 is When a voltage is applied between the electrode 101 and the electrode 102, electrons are injected into one of the light-emitting units, It is sufficient if the electrode 1 injects holes into the other light-emitting unit. When a voltage is applied so that the potential of electrode 01 is higher than the potential of electrode 102, a charge is generated. Layer 115 injects electrons into light-emitting unit 106 and holes into light-emitting unit 108. .

[0210] From the viewpoint of light extraction efficiency, the charge generating layer 115 is required to be transparent to visible light (specifically, It is preferable that the charge generating layer 115 has a visible light transmittance of 40% or more. In addition, the charge generating layer 115 has a lower electrical conductivity than the pair of electrodes (the electrodes 101 and 102). But it still works.

[0211] When the charge generating layer 115 is formed using the above-mentioned material, the light emitting layer is laminated. In this case, the increase in the driving voltage can be suppressed.

[0212] In addition, in FIG. 5, a light emitting element having two light emitting units has been described. The same can be applied to a light-emitting element in which two or more light-emitting units are stacked. As shown in the light-emitting element 250, a plurality of light-emitting units are separated by a charge generating layer between a pair of electrodes. By arranging the LEDs in this way, it is possible to achieve high brightness light emission while keeping the current density low, and also to achieve a long life. In addition, a light-emitting element with low power consumption can be realized.

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

[0214] The above-mentioned structure is also suitable for obtaining white light emission. By making the lights complementary to each other, white light can be obtained. The design is such that the resulting white light has a high light emission, or at least light emission having red, green and blue colors. It is preferable to select a material that is

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

[0216] In addition, in the case of a light-emitting element having three or more stacked light-emitting units, the The emission colors of the guest materials may be the same or different. In the case where a plurality of light-emitting units that emit light are included, the emission colors of the plurality of light-emitting units are as follows: Compared to other colors, it is possible to obtain high luminance with a small current value. The composition can be suitably used to adjust the luminous color. This is suitable when using a guest material that exhibits a luminescent color. For example, In this case, two layers of light-emitting units having fluorescent materials of the same color are used, and one layer of a light-emitting material having a different color from the fluorescent material is used. By forming a light-emitting unit having a phosphorescent material that exhibits fluorescence and phosphorescence in a single layer, the intensity of the fluorescence and phosphorescence can be enhanced. In other words, the light emission intensity of each color can be adjusted by changing the number of light-emitting units. It is possible.

[0217] In the case of a light-emitting device having two layers of such fluorescent light-emitting units and one layer of a phosphorescent light-emitting unit, The light-emitting layer includes two layers of light-emitting units containing color fluorescent materials and one layer of light-emitting unit containing yellow phosphorescent materials. The light-emitting element has two layers of light-emitting units including a blue fluorescent material, and a red phosphorescent material and a green phosphorescent material. A light-emitting element having one layer of a light-emitting unit containing a blue fluorescent material or two layers of light-emitting units containing a blue fluorescent material. and a light-emitting element having one layer of a light-emitting unit including a red phosphorescent material, a yellow phosphorescent material, and a green phosphorescent material. This is preferable because white light can be efficiently emitted.

[0218] In addition, at least one of the light-emitting layer 120 and the light-emitting layer 170 is further divided into layers, Each of the divided layers may contain a different light-emitting material. Alternatively, at least one of the light-emitting layers 170 may be composed of two or more layers. For example, the first light-emitting layer and the second light-emitting layer can be laminated in this order from the hole transport layer side to form the light-emitting layer. In this case, a material having a hole transporting property is used as the host material of the first light-emitting layer, and a material having a hole transporting property is used as the host material of the second light-emitting layer. In this case, a material having an electron transporting property is used as the host material. The light-emitting material in the light-emitting layer and the second light-emitting layer may be the same or different. Even if a material has a function of emitting light of the same color, it is preferable that the material has a function of emitting light of different colors. The material may be a material having the following function: By using a material with a structure that has three primary colors or four or more colors, it is possible to obtain white light with high color rendering. It is also possible.

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

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

[0221] FIG. 6(A) is a top view showing a light-emitting device, and FIG. 6(B) is a cross-sectional view of FIG. 6(A) along lines AB and CD. This light emitting device is a cross-sectional view of a light emitting element. The illustrated driving circuit section (source side driving circuit) 601, pixel section 602, and driving circuit section (gate side The driver circuit 603 is a sealing substrate 604, a desiccant 625, and a shielding material 605. The inside surrounded by the sealing material 605 is a space 607 .

[0222] The lead wiring 608 is connected to the source side driver circuit 601 and the gate side driver circuit 603. The wiring is for transmitting the signals to be input, and the FPC (flexible printed circuit board) is the external input terminal. Video signal, clock signal, start signal, reset signal, etc. from the 609 Although only the FPC is shown here, the FPC has a printed wiring board. Even if a printed wiring board (PWB) is installed, The light emitting device in this specification includes not only the light emitting device itself but also an FPC or This includes the state where the PWB is installed.

[0223] Next, a cross-sectional structure of the light emitting device will be described with reference to FIG. A driving circuit section and a pixel section are formed on the source side driving circuit section. A circuit 601 and one pixel in a pixel portion 602 are shown.

[0224] The source side driver circuit 601 includes an n-channel TFT 623 and a p-channel TFT 624. The driver circuit is a combination of various CMOS circuits, It may be formed of a MOS circuit or an NMOS circuit. This shows a driver integrated type with a driver circuit formed on the board, but this is not necessarily required. Alternatively, it may be formed externally.

[0225] The pixel section 602 includes a switching TFT 611, a current control TFT 612 and its drain. The pixel includes a first electrode 613 electrically connected to the input. An insulator 614 is formed so as to cover the end of the electrode 613. The insulating layer can be formed by using a photosensitive resin film having a mold.

[0226] In order to improve the coverage of the film formed on the insulator 614, the insulator 614 is The upper end or the lower end is formed to have a curved surface. For example, When photosensitive acrylic is used as the material, it is possible to make only the upper end of the insulator 614 curved. The radius of curvature of the curved surface is preferably 0.2 μm or more and 0.3 μm or less. The border 614 may be either a negative or positive photosensitive material.

[0227] An EL layer 616 and a second electrode 617 are formed on the first electrode 613. Here, the material used for the first electrode 613 functioning as an anode is a material having a work function of It is desirable to use a material with a large capacitance. For example, an ITO film or an indium tin oxide film containing silicon. Indium tin oxide film, indium oxide film containing 2wt% to 20wt% zinc oxide, nitride In addition to single-layer films such as titanium film, chromium film, tungsten film, Zn film, and Pt film, titanium nitride film and Lamination with a film mainly composed of aluminum, titanium nitride film and a film mainly composed of aluminum A three-layer structure of a titanium nitride film and a silicon nitride film can be used. The resistance of the anode is low, good ohmic contact can be achieved, and the anode can function as well. This can be done.

[0228] The EL layer 616 is formed by deposition using a deposition mask, inkjet printing, or spin coating. The EL layer 616 can be formed by various methods such as the above. The polymer may be a polymer compound (including an oligomer or a dendrimer).

[0229] Furthermore, a material for a second electrode 617 formed on the EL layer 616 and functioning as a cathode As the material, materials with a small work function (Al, Mg, Li, Ca, or alloys or compounds of these) It is preferable to use a material such as MgAg, MgIn, or AlLi. In the case where the generated light is transmitted through the second electrode 617, a thin film is used as the second electrode 617. A thin metal film and a transparent conductive film (ITO, containing 2wt% to 20wt% zinc oxide) Indium oxide, silicon-containing indium tin oxide, zinc oxide (ZnO, etc.) It is better to use layers.

[0230] The first electrode 613, the EL layer 616, and the second electrode 617 form a light-emitting element 618. The light emitting element 618 is a light emitting element having the configurations of the first and second embodiments. It is preferable that the pixel portion is formed with a plurality of light emitting elements. In the light emitting device of the embodiment, a light emitting device having the configuration described in the first and second embodiments is The light-emitting element may include both a light-emitting element and a light-emitting element having other configurations.

[0231] Furthermore, the sealing substrate 604 is bonded to the element substrate 610 with a sealant 605, A light emitting element is disposed in a space 607 surrounded by a child substrate 610, a sealing substrate 604, and a sealant 605. 618. The space 607 is filled with a filler. In addition to inert gas (nitrogen, argon, etc.) being filled, resin, desiccant or its Sometimes it is filled with both.

[0232] It is preferable to use epoxy resin or glass frit for the sealing material 605. It is desirable that these materials are as impermeable to moisture and oxygen as possible. Materials used for the sealing substrate 604 include glass substrates, quartz substrates, and FRP (Fiber Reinforced Plastics). reinforced plastics), PVF (polyvinyl fluoride), polyester A plastic substrate made of, for example, polyester or acrylic can be used.

[0233] As described above, a light emitting device using the light emitting elements described in the first and second embodiments can be obtained.

[0234] <Light-emitting device configuration example 1> FIG. 7 shows an example of a light-emitting device in which a light-emitting element that emits white light is formed and a color layer (color filter) is formed. An example of a light emitting device in which a GaN-GaN filter is formed is shown.

[0235] FIG. 7A shows a substrate 1001, an insulating base film 1002, a gate insulating film 1003, and a gate electrode. 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, and a first electrode 102 of a light-emitting element. 4W, 1024R, 1024G, 1024B, partition wall 1026, EL layer 1028, light-emitting element The second electrode 1029, the sealing substrate 1031, the sealant 1032, the red pixel 1044R, the green Shown are color pixels 1044G, blue pixels 1044B, white pixels 1044W, etc.

[0236] In addition, in FIG. 7(A), the colored layers (red colored layer 1034R, green colored layer 1034G, blue A colored layer (1034B) is provided on the transparent substrate 1033. A transparent substrate 1 having a colored layer and a black layer may be further provided. The colored layer and the black layer are fixed to the substrate 1001. It is covered with a bar coat layer 1036. In FIG. 7(A), light passes through the colored layer. There are two types of light-emitting layers: one that emits light directly to the outside without passing through the other, and one that transmits light through the colored layers of each color to the outside. The light that does not pass through the colored layer becomes white, and the light that passes through the colored layer becomes red, blue, and green, so a four-color image is produced. It is possible to express images using only natural materials.

[0237] In FIG. 7B, a red colored layer 1034R, a green colored layer 1034G, and a blue colored layer 103 An example in which 4B is formed between the gate insulating film 1003 and the first interlayer insulating film 1020 is shown. As shown in FIG. 7B, the colored layer may be provided between the substrate 1001 and the sealing substrate 1031. stomach.

[0238] In the light emitting device described above, the light is taken in toward the substrate 1001 on which the TFT is formed. The light emitting device has a bottom emission structure, but the light is taken in from the sealing substrate 1031 side. The light emitting device may have a top emission structure.

[0239] <Configuration Example 2 of Light Emitting Device> Cross-sectional views of a top-emission type light-emitting device are shown in Figures 8(A) and 8(B). The plate 1001 can be a light-opaque substrate. The process is the same as that of a bottom emission type light emitting device until the connection electrodes are formed. Thereafter, a third interlayer insulating film 1037 is formed to cover the electrode 1022. This insulating film is planarized. The third interlayer insulating film 1037 may have the same function as the second interlayer insulating film 1021. In addition to the above materials, various other materials can be used.

[0240] The lower electrode 1025W, the lower electrode 1025R, the lower electrode 1025G, and the lower electrode 1 Here, 025B is an anode, but it may be a cathode. In the case of a top emission type light emitting device such as the above, the lower electrode 1025W, the lower electrode It is preferable that the lower electrode 1025R, the lower electrode 1025G, and the lower electrode 1025B are reflective electrodes. It is preferable that the second electrode 1029 has a function of reflecting light and a function of transmitting light. In addition, the second electrode 1029, the lower electrode 1025W, the lower electrode 1025R, and the lower electrode 1 A microcavity structure is applied between the lower electrode 1025B and the lower electrode 1025G to detect light of a specific wavelength. The EL layer 1028 has a structure similar to that of the first embodiment and the second embodiment. The device has a configuration as described in embodiment 2, and has an element structure capable of obtaining white light emission.

[0241] In FIG. 7(A), FIG. 7(B), FIG. 8(A) and FIG. 8(B), the EL layer from which white light is obtained The configuration may be such that a plurality of light-emitting layers are used, or a plurality of light-emitting units are used. However, the configuration for obtaining white light emission is not limited to these.

[0242] In the top emission structure shown in FIG. 8(A) and (B), a colored layer (red colored layer 103 4R, a green colored layer 1034G, and a blue colored layer 1034B) are provided on the sealing substrate 1031. The sealing substrate 1031 is provided with black insulating film 1032 disposed between the pixels. A layer (black matrix) 1035 may be provided. A color layer (red color layer 1034R , green colored layer 1034G, blue colored layer 1034B) and black layer (black matrix The sealing substrate 1031 may be covered with an overcoat layer. A substrate is used.

[0243] In addition, in FIG. 8(A), a full-color display using three colors, red, green, and blue, is shown. As shown in B), a full-color display may be performed using four colors: red, green, blue, and white. The full-color display configuration is not limited to these. For example, four colors of red, green, blue, and yellow may be used. A full color display may be performed.

[0244] A light-emitting element according to one embodiment of the present invention uses a fluorescent material as a guest material. Compared to other materials, the spectrum is sharper, so light with high color purity can be obtained. Therefore, by using the light-emitting element in the light-emitting device shown in this embodiment, color reproducibility can be improved. Therefore, a light emitting device with high light emission efficiency can be obtained.

[0245] As described above, a light emitting device using the light emitting elements described in the first and second embodiments can be obtained.

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

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

[0248] According to one embodiment of the present invention, a highly reliable electronic device and display having a flat surface and high light emission efficiency can be provided. According to one embodiment of the present invention, a reliable display device having a curved surface and high luminous efficiency can be manufactured. The light-emitting element of one embodiment of the present invention has high color purity. Therefore, when the light-emitting element is used in the light-emitting device described in this embodiment, By this, it is possible to obtain electronic devices and display devices with high color reproducibility.

[0249] Examples of electronic devices include television sets, desktop or notebook PCs, etc. Computers, monitors for computers, digital cameras, digital video cameras Cameras, digital photo frames, mobile phones, portable game consoles, personal digital assistants, audio playback Examples of such devices include large gaming machines such as pachinko machines.

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

[0251] The housing 901 and the housing 902 are connected by a hinge portion 905. The mobile information terminal 900 includes: It can be unfolded from the folded state (FIG. 9(A)) to the state shown in FIG. 9(B). This makes it highly portable when you carry it around, and when you use it, the large display area makes it easy to see. Excellent recognition.

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

[0253] A light-emitting device manufactured according to one embodiment of the present invention can be used for the display portion 903. This makes it possible to manufacture a highly reliable portable information terminal.

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

[0255] When the portable information terminal 900 is unfolded, the display portion 903 is held in a gently curved state. For example, the radius of curvature is 1 mm or more and 50 mm or less, preferably 5 mm or more and 30 mm or less. The display unit 903 is supported by the housing 901 and the other parts of the display unit 903. Pixels are arranged continuously across the body 902, enabling curved surface display.

[0256] The display unit 903 functions as a touch panel and can be operated by a finger, a stylus, etc. can.

[0257] It is preferable that the display unit 903 is composed of one flexible display. This makes it possible to perform continuous display without interruption between the housing 901 and the housing 902. In addition, a display may be provided in each of the housings 901 and 902. You may do so.

[0258] The hinge portion 905 is a portion that connects the housing 901 and the housing 902 when the mobile information terminal 900 is unfolded. It is preferable to have a locking mechanism to prevent the angle from becoming larger than a predetermined angle. For example, the angle at which the door will lock (will not open any further) must be greater than 90 degrees and less than 180 degrees. Typically, the angle is 90 degrees, 120 degrees, 135 degrees, 150 degrees, or 17 degrees. 5 degrees, etc. This improves the convenience, safety, and Reliability can be improved.

[0259] If the hinge portion 905 has a locking mechanism, the display portion 903 can be opened without applying excessive force. Therefore, it is possible to prevent the display unit 903 from being damaged. It can be achieved.

[0260] The housing 901 and the housing 902 are provided with a power button, an operation button, an external connection port, a speaker, a microphone, and the like. It may have an inch or the like.

[0261] A wireless communication module is provided in either the housing 901 or the housing 902. Internet, LAN (Local Area Network), Wi-Fi (registered trademark ) and the like.

[0262] A portable information terminal 910 shown in FIG. 9C includes a housing 911, a display unit 912, and an operation button 913. , an external connection port 914, a speaker 915, a microphone 916, a camera 917, etc.

[0263] A light-emitting device manufactured according to one embodiment of the present invention can be used for the display portion 912. This makes it possible to manufacture portable information terminals with a high yield.

[0264] The mobile information terminal 910 has a touch sensor on the display unit 912. All operations, such as inputting characters, can be performed by touching the display 912 with a finger or a stylus. It can be done.

[0265] In addition, the operation button 913 is operated to turn the power on and off, and to display on the display unit 912. For example, you can change the type of image displayed on the main screen from the email composition screen. You can switch to the menu screen.

[0266] In addition, a detection device such as a gyro sensor or an acceleration sensor is provided inside the portable information terminal 910. By providing the above, the orientation of the mobile information terminal 910 (vertical or horizontal) can be determined and the screen of the display unit 912 can be adjusted. The display orientation can be switched automatically. The screen orientation can also be switched by The input is made by touching the display unit 912, by operating the operation button 913, or by inputting voice using the microphone 916. It can also be performed by using force or the like.

[0267] The mobile information terminal 910 is, for example, one or more devices selected from a telephone, a notebook, an information viewing device, etc. Or it has multiple functions. Specifically, it can be used as a smartphone. The information terminal 910 is, for example, a mobile phone, an e-mail, a document viewing and creation, a music playback, a video It can run various applications such as playback, internet communication, and games. do.

[0268] The camera 920 shown in FIG. 9(D) includes a housing 921, a display unit 922, an operation button 923, and a shutter. The camera 920 also has a detachable lens 926. It is attached.

[0269] The light-emitting device manufactured according to one embodiment of the present invention can be used for the display portion 922. This makes it possible to manufacture a highly reliable camera.

[0270] Here, the camera 920 and the lens 926 can be removed from the housing 921 and replaced. However, the lens 926 and the housing 921 may be integrated together.

[0271] The camera 920 captures still or moving images by pressing the shutter button 924. In addition, the display unit 922 has a function as a touch panel. It is also possible to capture an image by touching the

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

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

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

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

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

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

[0278] The cleaning robot 5100 can communicate with a portable electronic device 5140 such as a smartphone. The images captured by the camera 5102 can be displayed on the portable electronic device 5140. Therefore, the owner of the Cleaning Robot 5100 can check the state of the room even when he / she is away from home. In addition, the display on the display 5101 can be displayed on a mobile electronic device such as a smartphone. You can also check at 5140.

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

[0280] The robot 2100 shown in FIG. 10(B) includes a computing device 2110, an illuminance sensor 2101, A microphone 2102, an upper camera 2103, a speaker 2104, a display 2105, It is equipped with a lower camera 2106, an obstacle sensor 2107, and a movement mechanism 2108.

[0281] The microphone 2102 has a function of detecting the user's voice and environmental sounds. The speaker 2104 has a function of emitting sound. The user can communicate with the computer using the computer 2102 and the speaker 2104. It is possible.

[0282] The display 2105 has a function of displaying various information. It is possible for the user to display desired information on the display 2105. The display 2105 may be equipped with a touch panel. The information terminal may be a terminal that can be used for charging and discharging the battery. and enables data transfer.

[0283] The upper camera 2103 and the lower camera 2106 are used to capture images of the surroundings of the robot 2100. The obstacle sensor 2107 detects the obstacles of the robot 210 using the moving mechanism 2108. When the robot 21 moves forward, it can sense the presence or absence of obstacles in its path. 00 uses an upper camera 2103, a lower camera 2106, and an obstacle sensor 2107. It is possible for the robot to recognize its surrounding environment and move around safely.

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

[0285] FIG. 10C is a diagram showing an example of a goggle-type display. For example, the device includes a housing 5000, a display unit 5001, a speaker 5003, and an LED lamp 5004. , operation keys 5005 (including a power switch or an operation switch), a connection terminal 5006, Sensor 5007 (force, displacement, position, velocity, acceleration, angular velocity, rotation speed, distance, light, liquid, magnetism, Temperature, chemicals, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, gradient (including functions for measuring temperature, vibration, smell, or infrared rays), microphone 5008, It has a second display unit 5002, a support unit 5012, earphones 5013, and the like.

[0286] 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. can.

[0287] 11(A) and (B) show a foldable mobile information terminal 5150. The foldable mobile information terminal 5150 includes a housing 5151, a display area 5152, and a bending portion 515. 11(A) shows the portable information terminal 5150 in an unfolded state. FIG. 5B) shows the portable information terminal 5150 in a folded state. The portable information terminal 5150 is large. Although it has a large display area 5152, it can be folded up to be compact and highly portable.

[0288] The display area 5152 can be folded in half by the bend 5153. 3 is composed of an expandable member and multiple support members, and when folding, the expandable The member is stretched, and the bent portion 5153 has a radius of curvature of 2 mm or more, preferably 5 mm or more. It can be folded.

[0289] The display area 5152 is a touch panel (input / output) equipped with a touch sensor (input device). The light-emitting device according to one embodiment of the present invention can be used in the display region 5152. Cut.

[0290] This embodiment mode can be combined with other embodiment modes as appropriate.

[0291] (Embodiment 5) In this embodiment, an example in which the light-emitting element of one embodiment of the present invention is applied to various lighting devices will be described. The light-emitting element according to one embodiment of the present invention is used to improve the light-emitting efficiency. Thus, a highly reliable lighting device can be manufactured.

[0292] The light-emitting element of one embodiment of the present invention can be fabricated over a flexible substrate to have a curved surface. It is possible to realize electronic devices and lighting devices having a light-emitting region.

[0293] In addition, a light-emitting device using a light-emitting element according to one embodiment of the present invention can be used for automobile lighting. For example, lighting can be installed on the windshield, ceiling, etc.

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

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

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

[0297] The structure described in this embodiment may be used in appropriate combination with structures described in other embodiments. There can be. EXAMPLES

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

[0299] [ka]

[0300] [Table 1]

[0301] <Fabrication of light-emitting element> A method for manufacturing the light-emitting element manufactured in this embodiment will be described below.

[0302] <Fabrication of light-emitting element 1> An ITSO film was formed on a glass substrate as an electrode 101 to a thickness of 70 nm. The electrode area of ​​the electrode 101 is 4 mm 2 (2mm x 2mm).

[0303] Next, a hole injection layer 111 made of DBT3P-II and molybdenum oxide was formed on the electrode 101. (MoO3) and the weight ratio (DBT3P-II:MoO3) was 1:0.5. The deposition was carried out to a thickness of 40 nm.

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

[0305] Next, a light-emitting layer 130 was formed on the hole transport layer 112 by depositing 4PCCzBfpm and tris[2 -(1H-pyrazol-1-yl-κN 2)phenyl-κC]iridium(III)(abbreviation Name: Ir(ppz)3) and 10-(2-benzothiazolyl)-2,3,6,7-tetramethylphenyl Hydro-1,1,7,7-tetramethyl-1H,5H,11H-[1]benzopyrano[6 ,7,8-ij]quinolizin-11-one (abbreviation: coumarin545T) and The ratio (4PCCzBfpm:Ir(ppz)3:coumarin545T) was 0.8: The layers were co-deposited at a ratio of 0.2:0.005 to a thickness of 30 nm. In 130, coumarin545T is the fluorescent compound, Ir(ppz)3 is a phosphorescent compound.

[0306] Next, on the light-emitting layer 130, 4,6mCzP2Pm was deposited to a thickness of 2 Then, NBPhen was evaporated in order to a thickness of 10 nm. On the electron transport layer 118, LiF was deposited to a thickness of 1 nm as the electron injection layer 119. It was evaporated.

[0307] Next, on the electron injection layer 119, aluminum (Al) was deposited to a thickness of 20 It was formed so that the thickness was 0 nm.

[0308] Next, in a glove box with a nitrogen atmosphere, a glass substrate for sealing is The EL sealant is used to fix the organic material to the glass substrate, forming a light-emitting element 1. Specifically, a sealant was applied to the periphery of the organic material formed on the glass substrate, and the The glass substrate and the sealing glass substrate are bonded together, and ultraviolet light with a wavelength of 365 nm is applied for 6 hours. J / cm 2 The light-emitting element 1 was obtained by irradiating the light with light and then heat-treating it for 1 hour at 80° C.

[0309] <Preparation of comparative light-emitting element 2> The comparative light-emitting element 2 is different from the light-emitting element 1 described above only in the process of forming the light-emitting layer 130. The other steps were the same as those for the light-emitting element 1.

[0310] The light-emitting layer 130 of the comparative light-emitting element 2 was made of 4PCCzBfpm, Ir(ppz)3, and The weight ratio (4PCCzBfpm:Ir(ppz)3) was 0.8:0.2, and The difference between the comparative light-emitting element 2 and the light-emitting element 1 is that the fluorescent The difference is the presence or absence of a reactive compound, but the rest of the structures are similar.

[0311] <Fabrication of light-emitting element 3> The light-emitting element 3 differs from the light-emitting element 1 described above only in the process of forming the light-emitting layer 130. The steps were the same as those for the light-emitting element 1.

[0312] The light-emitting layer 130 of the light-emitting element 3 is 4-[4-(9'-phenyl-3,3'-bi-9H -carbazol-9-yl)phenyl]benzofuro[3,2-d]pyrimidine (abbreviation: 4 PCCzPBfpm), Ir(ppz)3, and coumarin545T in weight ratio (4PCCzPBfpm:Ir(ppz)3:coumarin545T) is 0.8:0 They were co-evaporated in a ratio of 0.2:0.005 to a thickness of 30 nm.

[0313] <Preparation of comparative light-emitting element 4> The comparative light-emitting element 4 is different from the light-emitting element 3 described above only in the process of forming the light-emitting layer 130. The other steps were the same as those for the light-emitting element 3.

[0314] The light-emitting layer 130 of the comparative light-emitting element 4 was made of 4PCCzPBfpm, Ir(ppz)3, and , so that the weight ratio (4PCCzPBfpm:Ir(ppz)3) is 0.8:0.2 The difference between the comparative light-emitting element 4 and the light-emitting element 3 is The difference is whether or not a fluorescent compound is present; otherwise, the structures are the same.

[0315] <Preparation of Comparative Light-Emitting Element 5> The comparative light-emitting element 5 is the same as the light-emitting element 1 described above except that the steps of forming the light-emitting layer 130 and the electron transport layer 11 are the same. The only difference was the formation process of 8, and the other processes were the same as those of the light-emitting element 1.

[0316] The light-emitting layer 130 of the comparative light-emitting element 5 was made of 4,4'-bis(9-carbazolyl)biphenyl. CBP, Ir(ppz)3, and coumarin545T were mixed in a weight ratio of ( CBP:Ir(ppz)3:coumarin545T) is 0.8:0.2:0.005 The light-emitting element 5 and the light-emitting element 6 were co-deposited to a thickness of 30 nm. The difference from 1 is the host material. Comparative light-emitting element 5 uses CBP, which is not a TADF material, as the host material. It is used as a coating material.

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

[0318] <Characteristics of light-emitting element> Next, the characteristics of the fabricated light-emitting elements 1 and 3 and the comparative light-emitting elements 2, 4, and 5 were measured. A color luminance meter (Topcon, BM-5A) was used to measure the luminance and CIE chromaticity. A multichannel spectrometer (Hamamatsu Photonics, PMA-11) was used to measure the optical spectrum. was used.

[0319] Current efficiency of the light-emitting element 1, the light-emitting element 3, the comparative light-emitting element 2, the comparative light-emitting element 4, and the comparative light-emitting element 5 The efficiency-luminance characteristics are shown in Fig. 13, the current-voltage characteristics in Fig. 14, and the external quantum efficiency-luminance characteristics in Fig. 15. The light-emitting element 1, the light-emitting element 3, the comparative light-emitting element 2, the comparative light-emitting element 4, and and comparative light-emitting element 5, 2.5 mA / cm 2 The electric field generated when a current is passed through the The optical spectrum is shown in Figure 16. The measurements of each light-emitting element were performed at room temperature (in an atmosphere maintained at 23°C). ) was used.

[0320] Also, 1000cd / m 2 Light-emitting element 1, light-emitting element 3, and comparative light-emitting element 2 in the vicinity Table 2 shows the element characteristics of the comparative light-emitting element 4 and the comparative light-emitting element 5.

[0321] [Table 2]

[0322] As shown in FIG. 16, the electroluminescence spectra of the light-emitting element 1, the light-emitting element 3, and the comparative light-emitting element 5 are The peak wavelength is 509 nm, and the fluorescent compound coumarin545T is responsible for this. In this manner, the light-emitting element 1 and the light-emitting element according to one embodiment of the present invention were The light-emitting element No. 3 has a peak wavelength in the electroluminescence spectrum that is shorter than that of the comparative light-emitting element No. 2 and the comparative light-emitting element No. 4. Therefore, in one embodiment of the present invention, the full width at half maximum is small and light emission with high color purity can be obtained. Such a light-emitting element is suitable for use in a display device.

[0323] In addition, as shown in FIG. 13, FIG. 15 and Table 2, the light-emitting elements 1 and 3 have high luminous efficiency. The efficiency (current efficiency, power efficiency, and external quantum efficiency) of the photoelectron beam is shown in Fig. 1. The probability of generating singlet excitons by recombination of injected carriers (holes and electrons) is Since the maximum efficiency is 25%, the external quantum efficiency when the light extraction efficiency to the outside is 25% is The maximum is 6.25%. The light-emitting elements 1 and 3 are fluorescent light-emitting elements. Nevertheless, the external quantum efficiency is higher than 6.25%. In the light-emitting element 1 and the light-emitting element 3 according to the above aspect, in addition to the emission originating from singlet excitons, The heavy atom effect of the phosphorescent compound Ir(ppz)3 and the TADF material This is because triplet excitons can be made to contribute to fluorescence emission by reverse intersystem crossing, which occurs in the nucleon.

[0324] Furthermore, the luminous efficiency of the light-emitting element 1 and the light-emitting element 3 is higher than that of the comparative light-emitting element 5. The light-emitting layer 130 of the comparative light-emitting element 5 is made of CBP, which is not a TADF material. Therefore, the comparative light-emitting element 5 converts triplet excitons into singlet excitons due to reverse intersystem crossing in the TADF material. On the other hand, the light-emitting elements 1 and 3 of one embodiment of the present invention do not have a function of converting light into light. The optical layer 130 includes a TADF material. Therefore, the light-emitting element 1 and the light-emitting element 3 have reverse intersystem crossing. This allows triplet excitons to be converted into singlet excitons, achieving high luminous efficiency. can be done.

[0325] <Time-resolved luminescence measurement> Next, time-resolved luminescence measurements were performed on the light-emitting element 1, the light-emitting element 3, the comparative light-emitting element 2, and the comparative light-emitting element 4. The determination was made.

[0326] The measurements were performed using a picosecond fluorescence lifetime measurement system (Hamamatsu Photonics). In order to measure the lifetime of the fluorescent light emitted from the light-emitting element, a rectangular pulse voltage is applied to the light-emitting element, The decaying light emission from the voltage drop was measured in time resolution using a streak camera. The pulse voltage is applied at a frequency of 10 Hz, and the S The data obtained was of a high / N ratio. The measurements were performed at room temperature (300K), and the luminance of the light-emitting element was 100 0 cd / m 2 Apply a pulse voltage of around 3V to 4V so that the Interval: 100μsec, negative bias voltage: -5V (when element drive is OFF), measurement time range The measurement results are shown in FIG. 17. In FIG. 17, is the emission intensity when carriers are constantly being injected (when the pulse voltage is ON). The intensity is shown as a normalized value, and the horizontal axis indicates the time elapsed from the fall of the pulse voltage.

[0327] As shown in FIG. 17, the light-emitting element 1 and the light-emitting element 3 are superior to the comparative light-emitting element 2 and the comparative light-emitting element 3 in terms of the light-emitting element composition. The decay rate of the luminescence is faster than that of molecule 4. This is because the excitation energy is rapidly converted into luminescence. This means that the exciton density is high (a large amount of Even when a current of 100 kV is flowing, light can be efficiently emitted. As shown in FIGS. 13 and 15, the light-emitting element 1 and the light-emitting element 3 have little roll-off. In addition, the high brightness range is 15000cd / m 2 The external quantum efficiency in the vicinity of 8. 0%, comparative light-emitting element 2 7.3%, light-emitting element 3 4.8%, and comparative light-emitting element 4 4. That is, the efficiency of the light-emitting element 1 was higher than that of the comparative light-emitting element 2, and the efficiency of the light-emitting element 3 was The efficiency was higher than that of the comparative light-emitting element 4. Thus, the small roll-off is an advantage of the present invention. This is one of the features of the light-emitting element of one embodiment.

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

[0329] and the LUMO level was -2.84 eV. Also, the HOMO level of 4PCCzPBfpm was -5.64 eV and the LUMO level was -3.01 eV.

[0330] As described above, the LUMO levels of 4PCCzBfpm and 4PCCzPBfpm are lower than the LUMO level of Ir (ppz)3, and the HOMO level of Ir(ppz)3 is higher than the HOMO levels of 4PCCz Bfpm and 4PCCzPBfpm. Therefore, when the compound is used in the light-emitting layer as in Light-Emitting Element 1 and Light-Emitting Element 3, electrons and holes, which are carriers injected from a pair of electrodes, can efficiently combine with 4PCCzBfpm and 4PCCzPBfpm ​​​Ir(ppz)3 is injected into 4PCCzBfpm and 4PCCzPBfpm, respectively. Therefore, the light-emitting element 1 and the light-emitting element The element 3 can be said to be a light-emitting element that uses ExEF.

[0331] In addition, the exciplex formed by 4PCCzBfpm and Ir(ppz)3 is 4PCCzB It becomes an exciplex with a LUMO level at fpm and a HOMO level at Ir(ppz)3. In addition, the energy between the LUMO level of 4PCCzBfpm and the HOMO level of Ir(ppz)3 is The energy difference is 2.55 eV. This value is the same as the emission spectrum of the comparative light-emitting element 2 shown in FIG. This roughly matches the emission energy (2.42 eV) calculated from the peak wavelength of the quark. From this, it can be seen that the emission spectrum of the comparative light-emitting element 2 is pz)3. The exciplex is an electron with a level of S1. Since the difference between the S1 and T1 levels is small, the emission energy is It can be considered as the energy (2.42 eV).

[0332] Similarly, the exciplex formed by 4PCCzPBfpm and Ir(ppz)3 is 4PCC An exciplex with a LUMO level at zPBfpm and a HOMO level at Ir(ppz)3 In addition, the LUMO level of 4PCCzPBfpm and the HOMO level of Ir(ppz)3 are The energy difference between the light-emitting element 1 and the light-emitting element 2 is 2.38 eV. Approximately consistent with the emission energy (2.30 eV) calculated from the peak wavelength of the emission spectrum From this, it can be seen that the emission spectrum of the comparative light-emitting element 4 is It can be said that the emission is based on an exciplex formed by Ir(ppz)3. The exciplex has a small difference between the S1 level and the T1 level, so the emission energy can be regarded as the energy of the S1 level and the T1 level (2.30 eV) of the exciplex.

[0333] <Relationship between the emission spectrum of the exciplex and the absorption spectrum of the guest material> Further, FIG. 18 shows the results of measuring the absorption spectrum of a toluene solution of coumarin545T. Also, in accordance with FIG. 18, the emission spectra of the exciplexes exhibited by comparative light-emitting element 2 and comparative light-emitting element 4 are shown. For the measurement of the absorption spectrum, an ultraviolet-visible spectrophotometer (manufactured by JASCO Corporation, model V550) was used, and the measurement was performed at room temperature (in an atmosphere maintained at 23 °C).

[0334] As shown in FIG. 18, there is a region where the absorption spectrum of coumarin545T overlaps with the emission spectra of the exciplexes exhibited by comparative light-emitting element 2 and comparative light-emitting element 4. Therefore, it is possible to efficiently transfer excitation energy from the exciplexes formed by 4PCCzBfpm and Ir(ppz)3 and the exciplexes formed by 4PCCzPBfpm and Ir(ppz)3 to coumarin5 45T, which is a fluorescent compound. Also, thereby, it is possible to provide a light-emitting element that exhibits emission having a peak wavelength shorter than the peak wavelength of the electroluminescence spectrum of the exciplex, like the electroluminescence spectra of light-emitting element 1 and light-emitting element 3 shown in FIG. 16.

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

[0336] In addition, the absorption and emission spectra were used to estimate the T1 level of Ir(ppz)3. A dichloromethane solution of Ir(ppz)3 was prepared and placed in a quartz cell. The absorption spectrum was measured using a UV-Vis spectrophotometer (Japan The spectrum of the measured sample was obtained using a quartz cell and The absorption spectrum of the solvent was subtracted. The measurement was performed at room temperature (atmosphere kept at 23°C). Ta.

[0337] From the above absorption spectrum data, the absorption edge is calculated, and the transition energy assuming a direct transition is calculated. As a result of estimating, the transition energy of Ir(ppz)3 was calculated to be 3.27 eV. Since r(ppz)3 is a phosphorescent compound, the lowest energy absorption edge is the triplet excitation. Therefore, the T1 level of Ir(ppz)3 is The absorption edge is calculated to be 3.27 eV.

[0338] From the above measurement results, the T1 level (2.58 eV) of 4PCCzBfpm and 4PCCz The T1 level of PBfpm (2.46 eV) is the same as the T1 level of Ir(ppz)3 (3.27 eV ) and the T1 level of 4PCCzBfpm (2.58 eV) and 4PCCzPBfpm The T1 level (2.46 eV) of 4PCCzBfpm and Ir(ppz)3 is The T1 level (2.42 eV) of the complex and the structure of 4PCCzPBfpm and Ir(ppz)3. This is higher than the T1 level (2.30 eV) of the resulting exciplex. Ir(ppz)3 and 4PCCzPBfpm and Ir(ppz)3 exciplexes The triplet excitation energies are 4PCCzBfpm, 4PCCzPBfpm and Ir(pp z)3. Therefore, the triplet excited energy of the exciplex is not quenched by The energy is converted to singlet excitation energy by reverse intersystem crossing, which is converted to luminescence. Alternatively, energy can be transferred to a fluorescent compound.

[0339] In addition, when we attempted to measure the emission spectrum of Ir(ppz)3 at room temperature, In Non-Patent Document 1, the luminescence quantum yield of Ir(ppz)3 was It is reported that the solubility of Ir(ppz)3 at room temperature is less than 1%. It can be seen that the material does not emit light. In other words, the compound has a low luminescence quantum yield of less than 1%. Even in the case where an organic EL element is used, a light-emitting element having high luminous efficiency can be obtained.

[0340] <Transient fluorescence properties of host materials> Here, 4PCCzBfpm and 4PCCzPBf used in the light-emitting elements 1 and 3 To confirm that pm is a TADF material, we measured the transient fluorescence properties by time-resolved luminescence measurements. Measurements were taken.

[0341] Time-resolved luminescence measurements were performed using bis[2-(diphenylphosphino)phenyl] Weight ratio of ether oxide (abbreviation: DPEPO) and 4PCCzPBfpm (DPEP O:4PCCzPBfpm) is 0.8:0.2 and the thickness is 50 nm. The co-evaporated thin film samples and the weight ratio of DPEPO to 4PCCzBfpm (DPE PO:4PCCzBfpm) is 0.8:0.2 and the thickness is 50 nm. The measurements were carried out using a thin film sample co-evaporated as shown below.

[0342] The measurements were performed using a picosecond fluorescence lifetime measurement system (Hamamatsu Photonics). To measure the lifetime of the fluorescence emitted by the thin film, the thin film was irradiated with a pulsed laser. The decaying emission was then time-resolved and measured using a streak camera. A nitrogen gas laser with a wavelength of 337 nm was used, and a 500 ps pulse laser was used at a frequency of 10 Hz. By irradiating a thin film with light and accumulating the data measured repeatedly, data with a high S / N ratio can be obtained. The measurements were carried out at room temperature (an atmosphere maintained at 23°C).

[0343] The measured transient fluorescence characteristics of 4PCCzBfpm are shown in Figure 19 (A) and (B). FIG. 19(A) shows the measurement results of the luminescence components with short luminescence lifetimes, and FIG. 19(B) shows the The results are from measurements of luminescence components with long luminescence lifetimes. The transient fluorescence characteristics of 4PCCzPBfpm are particularly Although not shown, measurements were performed in the same manner as for 4PCCzBfpm, and the following calculations were performed.

[0344] In addition, the attenuation curves shown in Figures 19(A) and 19(B) were fitted using the following formula (4). We conducted a training session.

[0345]

number

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

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

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

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

[0350] In addition to the usual measurement of the emission spectrum, the emission spectrum was measured using a We also measured the time-resolved emission spectrum focusing on the long emission. Because the measurement was performed at low temperature (10K), the main emission component, In addition to fluorescence, some phosphorescence was also observed. In the optical spectrum measurement, phosphorescence was mainly observed.

[0351] From the results of the above measured emission spectrum, the fluorescence of the emission spectrum of 4PCCzBfpm The wavelengths of the shortest wavelength peaks (including shoulders) of the luminescent and phosphorescent components are 45 The fluorescence components of the emission spectrum of 4PCCzPBfpm were The wavelengths of the shortest wavelength peaks (including shoulders) of the luminescence and phosphorescence components are 480 nm and 505 nm.

[0352] Therefore, 4PCCzBfpm calculated from the wavelength of the above peak (including the shoulder) The S1 level is 2.72 eV and the T1 level is 2.58 eV. The energy difference was calculated to be 0.14 eV. The S1 level of 4PCCzPBfpm is 2 The energy difference between the S1 and T1 levels is: It was calculated to be 0.12 eV.

[0353] In addition, from the results of the above measured emission spectrum, the emission spectrum of 4PCCzBfpm The wavelengths of the fluorescent and phosphorescent components on the short wavelength side are 435 nm and 46 4 nm. In addition, the fluorescence and phosphorescence components of the emission spectrum of 4PCCzPBfpm The wavelengths at the beginning of the short wavelength side of the spectrum were 458 nm and 491 nm, respectively. The wavelength at the beginning of the short wavelength side of the emission spectrum is the tangent of the spectrum. A tangent line was drawn at the wavelength where the slope had a maximum value, and the wavelength at the intersection of the tangent line and the horizontal axis was determined as the wavelength.

[0354] The S1 level of 4PCCzBfpm calculated from the rising wavelength as above is 2.85 The energy difference between the S1 and T1 levels is 0.1 eV, the T1 level is 2.67 eV, and the S1 level is 0.1 eV. The S1 level of 4PCCzPBfpm was calculated to be 2.71 eV, and the T1 level The energy difference between the S1 and T1 levels is calculated to be 0.18 eV. It was.

[0355] As described above, the wavelength of the peak (including the shoulder) on the shortest wavelength side of the emission spectrum and 4PCCzPBfpm and 4PCCzBfpm calculated at the rising wavelength on the short wavelength side The energy difference between the S1 level and the T1 level is greater than 0 eV and less than 0.2 eV. Therefore, 4PCCzPBfpm and 4PCCzBfpm In both cases, triplet excitation energy is converted to singlet excitation energy by reverse intersystem crossing. It has a function of exhibiting thermally activated delayed fluorescence.

[0356] <Reliability of light-emitting elements> FIG. 22 shows a light-emitting element 1, a comparative light-emitting element 2, a light-emitting element 3, a comparative light-emitting element 4, and a comparative light-emitting element 5. 22 shows the results of a constant current drive test at 0.5 mA. Light-emitting element 3 has better reliability than comparative light-emitting element 4. The difference between the light-emitting element 1 and the comparative light-emitting element 2 and the light-emitting element 3 and the comparative light-emitting element 4 were The difference between the light-emitting element 1 and the light-emitting element 4 is whether or not they contain a fluorescent compound. The light emitted from the fluorescent compound was observed from the element 3, and the light-emitting elements 2 and 4 were observed from the exciton complex. Thus, light emission from the body is obtained. It was found that the reliability of obtaining light emission from the light-emitting element 1 and the light-emitting element 2 was higher. It was found that the device 3 had better reliability than the comparative light-emitting device 5. Host Material By using a host material with TADF properties, a highly reliable light-emitting element can be produced. can be obtained. EXAMPLES

[0357] In this example, a manufacturing example of a light-emitting element according to one embodiment of the present invention and a comparative light-emitting element will be described. The structure of the light-emitting element manufactured in this example is the same as that shown in Figure 1(A). The details of the element structure are shown in Table 3. The structures and abbreviations of the compounds used are shown below. The structures and abbreviations of other compounds are shown in the actual examples. Please refer to Example 1 and the above embodiments.

[0358] [ka]

[0359] [Table 3]

[0360] <Fabrication of light-emitting element> A method for manufacturing the light-emitting element manufactured in this embodiment will be described below.

[0361] <Fabrication of light-emitting element 6> An ITSO film was formed on a glass substrate as an electrode 101 to a thickness of 70 nm. The electrode area of ​​the electrode 101 is 4 mm 2 (2mm x 2mm).

[0362] Next, a hole injection layer 111 made of DBT3P-II and molybdenum oxide was formed on the electrode 101. (MoO3) and the weight ratio (DBT3P-II:MoO3) was 1:0.5. The deposition was carried out to a thickness of 45 nm.

[0363] Next, a hole transport layer 112 was formed on the hole injection layer 111 by depositing PCBBi1BP to a thickness of 20 The deposition was carried out so as to give a thickness of nm.

[0364] Next, a light-emitting layer 130 containing 4PCCzBfpm and GD270 was formed on the hole transport layer 112. (manufactured by Jilin OLED Co., Ltd.) and 2,8-di-tert-butyl-5,11-bis(4-ter t-Butylphenyl)-6,12-diphenyltetracene (abbreviation: TBRb) and The ratio (4PCCzBfpm:GD270:TBRb) is 0.8:0.2:0.01. The light-emitting layer 130 was formed by co-evaporation to a thickness of 40 nm. 0 is a phosphorescent compound and TBRb is a fluorescent compound.

[0365] Next, on the light-emitting layer 130, 4,6mCzP2Pm was deposited to a thickness of 2 Then, NBPhen was evaporated in order to a thickness of 10 nm. On the electron transport layer 118, LiF was deposited to a thickness of 1 nm as the electron injection layer 119. It was evaporated.

[0366] Next, on the electron injection layer 119, aluminum (Al) was deposited to a thickness of 20 It was formed so that the thickness was 0 nm.

[0367] Next, in a glove box with a nitrogen atmosphere, a glass substrate for sealing is The EL sealant is used to fix the organic material to the glass substrate, forming a light-emitting element 6. Specifically, a sealant was applied to the periphery of the organic material formed on the glass substrate, and the The glass substrate and the sealing glass substrate are bonded together, and ultraviolet light with a wavelength of 365 nm is applied for 6 hours. J / cm 2 The light-emitting element 6 was obtained by the above steps.

[0368] <Preparation of Comparative Light-Emitting Element 7> The comparative light-emitting element 7 differs from the light-emitting element 6 described above only in the process of forming the light-emitting layer 130. The other steps were the same as those for the light-emitting element 6.

[0369] The light-emitting layer 130 of the comparative light-emitting element 7 was made of 4PCCzBfpm and GD270 by weight. The ratio (4PCCzBfpm:GD270) is 0.8:0.2, and the thickness is 40 The light-emitting layer 130 of the light-emitting element 6 was co-deposited to have a thickness of about 100 nm. The light-emitting layer 130 does not contain the fluorescent compound TBRb.

[0370] <Preparation of Comparative Light-Emitting Element 8> An ITSO film was formed on a glass substrate as an electrode 101 to a thickness of 70 nm. The electrode area of ​​the electrode 101 is 4 mm 2 (2mm x 2mm).

[0371] Next, a hole injection layer 111 made of DBT3P-II and molybdenum oxide was formed on the electrode 101. (MoO3) and the weight ratio (DBT3P-II:MoO3) was 1:0.5. The deposition was carried out to a thickness of 45 nm.

[0372] Next, mCzFLP was deposited to a thickness of 20 nm on the hole injection layer 111 as the hole transport layer 112. The vapor deposition was carried out so that

[0373] Next, on the hole transport layer 112, a light emitting layer 130 containing CBP, GD270, and TBRb The weight ratio (CBP:GD270:TBRb) was 0.8:0.2:0.01. The light-emitting layers of the light-emitting element 6 and the comparative light-emitting element 8 were co-deposited to a thickness of 30 nm. The difference between the light-emitting element 130 and the light-emitting element 130 is the host material. The optical element 8 uses CBP, which is not a TADF material.

[0374] Next, bathocuproin (abbreviation: BCP) was deposited on the light-emitting layer 130 as the electron transport layer 118. ) to a thickness of 10 nm, and NBPhen to a thickness of 15 nm. Next, LiF was deposited to a thickness of 1 nm on the electron transport layer 118 as the electron injection layer 119. The vapor deposition was carried out so that

[0375] Next, on the electron injection layer 119, aluminum (Al) was deposited to a thickness of 20 It was formed so that the thickness was 0 nm.

[0376] Next, in a glove box with a nitrogen atmosphere, a glass substrate for sealing is By using an EL sealant to fix the organic material to a glass substrate, a comparative light-emitting element was Specifically, a sealant was applied around the organic material formed on the glass substrate. The glass substrate and a glass substrate for sealing are bonded together, and ultraviolet light having a wavelength of 365 nm is applied to the glass substrate. 6J / cm 2The light-emitting element 8 was then irradiated with light and heat-treated at 80° C. for 1 hour. obtained.

[0377] <Preparation of Comparative Light-Emitting Element 9> The comparative light-emitting element 9 has the same structure as the comparative light-emitting element 8 described above, except that the structure of the light-emitting layer 130 and the electron transport layer 118 are the same as those of the comparative light-emitting element 8 described above. The only difference was the synthesis process, and the other steps were the same as those for the comparative light-emitting element 8.

[0378] The light-emitting layer 130 of the comparative light-emitting element 9 was made of bis[2-(diphenylphosphino)phenyl ] ether oxide (abbreviation: DPEPO), 4PCCzBfpm, and TBRb, The weight ratio (DPEPO:4PCCzBfpm:TBRb) was 0.8:0.2:0.01. The layer was co-deposited so as to have a thickness of 30 nm. In comparison with the light-emitting layer 130 of the comparative light-emitting device 9, the light-emitting layer 130 of the comparative light-emitting device 9 has a phosphorescent Contains no compounds.

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

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

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

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

[0383] [Table 4]

[0384] As shown in FIG. 26, the emission spectra of the light-emitting element 6, the comparative light-emitting element 8, and the comparative light-emitting element 9 are The peak wavelengths are 565 nm, 562 nm, and 561 nm, respectively, and the full width at half maximum is The light-emitting element 6 and the comparative light-emitting element 7 emitted yellow light at wavelengths of 72 nm, 67 nm, and 69 nm, respectively. The light emitted by the light-emitting element 8 and the comparative light-emitting element 9 is derived from the fluorescent compound TBRb. The emission spectrum of the comparative light-emitting element 7 has a peak wavelength of 528 nm. The comparative light-emitting element 7 emitted green light with a full width at half maximum of 76 nm. The emission is due to GD270. The emission spectrum peak wavelength full width at half maximum is smaller than that of comparative light emitting element 7, and the emission has high color purity. Therefore, the light-emitting element of one embodiment of the present invention is suitable for a display device.

[0385] As shown in FIG. 23 and FIG. 25 and Table 4, the external quantum efficiency of the light-emitting element 6 was Although it is an optical element, its external quantum efficiency is lower than the maximum value of 6.25% for a fluorescent light-emitting element. This is because the light-emitting element 6 according to one embodiment of the present invention exhibits high efficiency due to the singlet excitation. In addition to the emission from the nucleon, the phosphorescent compound GD270 is also capable of emitting triplet light. This is because the doublet excitons can contribute to the fluorescence emission. The 4PCCzBfpm contained in the optical element 6 is a TADF material. The triplet excitons can be made to contribute to the fluorescence emission by the reverse intersystem crossing that occurs, and this leads to a high luminescence efficiency. This is because it is possible to improve the rate.

[0386] Furthermore, the luminous efficiency of the light-emitting element 6 is higher than that of the comparative light-emitting element 8. The light-emitting layer 130 in this example is made of CBP, not TADF material. The function of molecule 8 is the conversion of triplet excitons to singlet excitons by reverse intersystem crossing in TADF materials. On the other hand, the light-emitting element 6 according to one embodiment of the present invention does not include a TADF material in the light-emitting layer 130. Therefore, the light-emitting device 6 can achieve triplet emission by utilizing the reverse intersystem crossing of the TADF material. It is possible to convert doublet excitons into singlet excitons, and the luminous efficiency is higher than that of comparative light-emitting element 8. It can be achieved.

[0387] Furthermore, the luminous efficiency of the light-emitting element 6 is higher than that of the comparative light-emitting element 9. The light-emitting layer 130 contains a TADF material but does not contain a phosphorescent compound. Therefore, in the comparative light-emitting element 9, triplet excitons are allowed to contribute to fluorescent emission via a phosphorescent compound. On the other hand, in the light-emitting element 6 according to one embodiment of the present invention, the light-emitting layer 130 is made of a TADF material. In addition to the TADF material, the light-emitting element 6 also contains a phosphorescent compound. In addition to the high efficiency effect of inter-electrode crossing, triplet excitons contribute to fluorescence emission via phosphorescent compounds. Thus, higher luminous efficiency than that of the comparative light-emitting element 9 can be achieved.

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

[0389] As shown in FIG. 27, the light-emitting element 6 has a faster light-emission decay rate than the comparative light-emitting element 7. This means that the excitation energy is rapidly converted into light emission. Even when the exciton density is high (when a large amount of current is flowing) in the light-emitting layer, Therefore, as shown in Figs. 23 and 25, The element 6 has a small roll-off. In addition, the light-emitting element 6 has a higher luminous efficiency than the comparative light-emitting element 7. The light-emitting layer 130 of the light-emitting element 6 is the same as that of the comparative light-emitting element 7 except that the light-emitting layer contains a fluorescent compound, TBRb As shown in Figure 27, the addition of a fluorescent compound increases the amount of light emitted. It can be seen that the decay rate is improved. Therefore, the deactivation of excitons is suppressed, and the light-emitting element 6 It can be said that the luminous efficiency of the comparative light-emitting element 7 is improved.

[0390] <Reliability of light-emitting elements> FIG. 28 shows the results of the light-emitting element 6, the comparative light-emitting element 7, and the comparative light-emitting element 8 at a constant current drive of 2.0 mA. 28 shows the results of a dynamic test. It can be seen from FIG. 28 that the light-emitting element 6 has better reliability than the comparative light-emitting element 7. The difference between the light-emitting element 6 and the comparative light-emitting element 7 is the presence or absence of a fluorescent compound. As described above, the light-emitting element 6 emits light from a fluorescent compound, and the comparative light-emitting element 7 emits light from a phosphorescent compound. Thus, light emission is obtained from a fluorescent compound, as in the light-emitting element of one embodiment of the present invention. It was found that the reliability of obtaining light emission from the light-emitting element 6 was higher than that of the light-emitting element 6. It was found that the light-emitting element had better reliability than Light-emitting element 8. By using a host material having such a property, a light-emitting element having high reliability can be obtained. do. EXAMPLES

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

[0392] [ka]

[0393] [Table 5]

[0394] <Fabrication of light-emitting element> A method for manufacturing the light-emitting element manufactured in this embodiment will be described below.

[0395] <Fabrication of light-emitting element 10> An ITSO film was formed on a glass substrate as an electrode 101 to a thickness of 70 nm. The electrode area of ​​the electrode 101 is 4 mm 2 (2mm x 2mm).

[0396] Next, a hole injection layer 111 made of DBT3P-II and molybdenum oxide was formed on the electrode 101. (MoO3) and the weight ratio (DBT3P-II:MoO3) was 1:0.5. The deposition was carried out to a thickness of 45 nm.

[0397] Next, a hole transport layer 112 was formed on the hole injection layer 111 by depositing PCBBi1BP to a thickness of 20 The deposition was carried out so as to give a thickness of nm.

[0398] Next, a light-emitting layer 130 consisting of PCCzPTzn and GD270( Jilin OLED Co., Ltd.) and TBRb in a weight ratio of (PCCzPTzn:GD270:TBR b) was co-evaporated to a thickness of 40 nm with a ratio of 0.8:0.2:0.01. In the light-emitting layer 130, GD270 is a phosphorescent compound and TBRb is a fluorescent compound. It is a mixture.

[0399] Next, on the light-emitting layer 130, as the electron transport layer 118, PCCzPTzn was deposited to a thickness of 20 nm. Then, the thickness of NBPhen was 10 nm. On the electron transport layer 118, LiF was evaporated to a thickness of 1 nm as the electron injection layer 119. did.

[0400] Next, on the electron injection layer 119, aluminum (Al) was deposited to a thickness of 20 It was formed so that the thickness was 0 nm.

[0401] Next, in a glove box with a nitrogen atmosphere, a glass substrate for sealing is The EL sealant is used to fix the organic material to the glass substrate, forming a light-emitting element 1. Specifically, a sealant was applied around the organic material formed on the glass substrate, The glass substrate and a sealing glass substrate are attached to each other, and ultraviolet light with a wavelength of 365 nm is applied. 6J / cm 2 The light-emitting element 10 was obtained by the above steps. Ta.

[0402] <Preparation of Comparative Light-Emitting Element 11> The comparative light-emitting element 11 differs from the previously described light-emitting element 10 only in the process of forming the light-emitting layer 130. The other steps were the same as those for the light emitting element 10.

[0403] The light-emitting layer 130 of the comparative light-emitting element 11 was made of PCCzPTzn and GD270 by weight. The ratio (PCCzPTzn:GD270) is 0.8:0.2, and the thickness is 40 In comparison with the light-emitting layer 130 of the light-emitting element 10, the comparative light-emitting element 1 The light-emitting layer 130 of No. 1 does not contain the fluorescent compound TBRb.

[0404] <Preparation of Comparative Light-Emitting Element 12> The comparative light-emitting element 12 is the same as the light-emitting element 10 described above, except that the hole transport layer 112 and the light-emitting layer 130 are the same. Only the formation process was different, and the other processes were the same as those for the light emitting element 10.

[0405] The hole transport layer 112 of the comparative light emitting element 12 was formed by depositing PCCP on the hole injection layer 111 to a thickness of 2 The deposition was carried out so that the thickness was 0 nm.

[0406] Next, as the light emitting layer 130, PCCzPTzn and TBRb were mixed in a weight ratio of (PCCzP Co-evaporation was performed so that the ratio of Tzn:TBRb was 1:0.01 and the thickness was 30 nm. In comparison with the light-emitting layer 130 of the light-emitting element 10, the light-emitting layer 130 of the comparative light-emitting element 12 does not contain the phosphorescent compound GD270.

[0407] <Characteristics of light-emitting element> Next, the light-emitting element 10, the comparative light-emitting element 11, the comparative light-emitting element 12, and the above-mentioned ratio The characteristics of the comparative light emitting element 8 were measured. The measurement method was the same as in Example 1.

[0408] Current efficiency of the light-emitting element 10, the comparative light-emitting element 11, the comparative light-emitting element 12, and the comparative light-emitting element 8 - The luminance characteristics are shown in Fig. 29, the current-voltage characteristics in Fig. 30, and the external quantum efficiency-luminance characteristics in Fig. 31. The light-emitting element 10, the comparative light-emitting element 11, the comparative light-emitting element 12, and the comparative light-emitting element 13 are also shown. 2.5mA / cm for element 8, respectively 2 Electroluminescence spectrum when a current is applied at a current density of The results are shown in Figure 32. The measurements of each light-emitting element were carried out at room temperature (an atmosphere maintained at 23°C). .

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

[0410] [Table 6]

[0411] As shown in FIG. 32, the emission spectra of the light-emitting element 10, the comparative light-emitting element 8, and the comparative light-emitting element 12 are The spectra have peak wavelengths of 566 nm, 562 nm, and 560 nm, respectively, and full width at half maximum The light-emitting element 10 emitted yellow light at about 74 nm, 67 nm, and 69 nm, respectively. The light emitted by the comparative light-emitting element 8 and the comparative light-emitting element 12 is due to the fluorescent compound TBRb. The emission spectrum of the comparative light-emitting element 11 has a peak wavelength of 533 nm. The comparative light-emitting element 11 exhibited green light emission with a full width at half maximum of 78 nm. The luminescence emitted from the luminescent element according to one embodiment of the present invention is luminescence derived from GD270. The element 10 has a smaller full width at half maximum of the peak wavelength of the emission spectrum than the comparative light-emitting element 11, and has a higher color purity. Therefore, the light-emitting element of one embodiment of the present invention can be used in a display device. It is suitable for.

[0412] As shown in FIG. 29, FIG. 31, and Table 6, the light-emitting element 10 is a fluorescent light-emitting element. Nevertheless, the external quantum efficiency is higher than 6.25%. In the light-emitting device 10 according to the embodiment of the present invention, in addition to the emission due to singlet excitons, phosphorescence The contribution of triplet excitons to fluorescence emission via the compound GD270 In addition, as will be described later, the PCCzPTz contained in the light emitting device 10 n is the TADF material. Therefore, triplet excitation occurs due to reverse intersystem crossing originating from the TADF material. Since the electrons can be made to contribute to fluorescent emission, the luminous efficiency can be improved.

[0413] Furthermore, the luminous efficiency of the light-emitting element 10 is higher than that of the comparative light-emitting element 8. The light-emitting layer 130 of No. 8 is made of CBP, not TADF material. Device 8 has a function of converting triplet excitons to singlet excitons by reverse intersystem crossing using TADF materials. On the other hand, the light-emitting element 10 according to one embodiment of the present invention has a TADF material in the light-emitting layer 130. Therefore, the light-emitting device 10 utilizes the reverse intersystem crossing of the TADF material. This allows triplet excitons to be converted into singlet excitons, and the light-emitting element has a higher luminescence than the comparative light-emitting element 8. Efficiency can be achieved.

[0414] Furthermore, the luminous efficiency of the light-emitting element 10 is higher than that of the comparative light-emitting element 12. The light-emitting layer 130 of the semiconductor device 12 contains a TADF material but does not contain a phosphorescent compound. Therefore, in the comparative light-emitting element 12, triplet excitons contribute to fluorescent emission via a phosphorescent compound. On the other hand, in the light-emitting element 10 according to one embodiment of the present invention, the light-emitting layer 130 has a T In addition to the ADF material, the light emitting device 10 contains a phosphorescent compound. In addition to the high efficiency effect due to the reverse intersystem crossing resulting from the luminescence of triplet excitons via phosphorescent compounds, It is possible to contribute to light emission and realize a higher luminous efficiency than that of the comparative light-emitting element 12. can.

[0415] <Time-resolved luminescence measurement> Next, time-resolved luminescence measurements were performed on the light-emitting element 10 and the comparative light-emitting element 11. The results are shown in FIG. The measurement method is the same as that shown in the previous example.

[0416] As shown in FIG. 33, the light-emitting element 10 has a faster light-emission decay rate than the comparative light-emitting element 11. This means that the excitation energy is rapidly converted into light emission. Therefore, in the light-emitting layer, the exciton density was high (a large amount of current was flowing). Therefore, as shown in Figs. 29 and 31, The light-emitting element 10 has less roll-off. Also, the light-emitting element 10 has a higher luminance than the comparative light-emitting element 11. The light emitting layer 130 of the light emitting element 10 has a higher light efficiency than the light emitting layer 130 of the comparative light emitting element 11. The compound TBRb is added. Therefore, the decay rate of the luminescence is improved. It can be said that the light emitting element 10 has improved luminous efficiency compared to the comparative light emitting element 11.

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

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

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

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

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

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

[0423] In addition, from Figure 35, the short-wavelength fluorescence and phosphorescence components of the emission spectrum of PCCzPTzn The wavelengths of the longer side rising were 450 nm and 477 nm, respectively. The wavelength at the beginning of the spectrum on the short wavelength side is the slope of the tangent line in the spectrum. A tangent line was drawn at the wavelength having the maximum value, and the wavelength at the intersection of the tangent line and the horizontal axis was determined as the wavelength.

[0424] The S1 level of PCCzPTzn calculated from the rising wavelength as above is 2.76e V, the T1 level is 2.60 eV, and the energy difference between the S1 level and the T1 level is 0.16 It was calculated to be eV.

[0425] As described above, the wavelength of the peak (including the shoulder) on the shortest wavelength side of the emission spectrum and The energy between the S1 and T1 levels of PCCzPTzn calculated at the rising wavelength on the short wavelength side The energy differences were all very small, greater than 0 eV and less than 0.2 eV. Therefore, PCCzPTzn converts triplet excitation energy to singlet excitation energy by reverse intersystem crossing. It has the function of converting photovoltaic energy into photovoltaic energy and exhibiting thermally activated delayed fluorescence.

[0426] <Reliability of light-emitting elements> FIG. 36 shows the light-emitting element 10, the comparative light-emitting element 11, the comparative light-emitting element 12, and the comparative light-emitting element 8. 36 shows the results of a constant current driving test at 0 mA. As described above, the light-emitting device 10 has a fluorescent property. The comparative light-emitting element 11 emits light from a phosphorescent compound. Therefore, light emission from a fluorescent compound, as in the case of the light-emitting element of one embodiment of the present invention, is more reliable. In addition, the light-emitting element 10 had better reliability than the comparative light-emitting element 12. As described above, the light-emitting device 10 is made of a TADF material and a phosphorescent compound. The triplet excitation energy can be transferred to a fluorescent compound via the The optical element 12 transfers triplet excitation energy to the fluorescent compound only through the TADF material. Therefore, as in the light-emitting element of one embodiment of the present invention, It was found that multiple pathways for transferring doublet excitation energy are more reliable. In addition, it was found that the light-emitting element 10 had better reliability than the comparative light-emitting element 8. By using a host material with TADF properties, it is possible to achieve high reliability. A light emitting element having such a configuration can be obtained.

[0427] As described above, according to one embodiment of the present invention, a light-emitting element having high emission efficiency and good reliability can be provided. According to one embodiment of the present invention, a light-emitting element with low driving voltage and low power consumption can be provided. It can be provided. EXAMPLES

[0428] In this example, a manufacturing example of a light-emitting element according to one embodiment of the present invention and a comparative light-emitting element will be described. The structure of the light-emitting element manufactured in this example is the same as that shown in Figure 1 (A). The details of the element structure are shown in Table 7. In addition, the structures and abbreviations of the compounds used may be referred to in the above Examples and Embodiments.

[0429] [Table 7]

[0430] <Fabrication of light-emitting element> A method for manufacturing the light-emitting element manufactured in this embodiment will be described below.

[0431] <Preparation of light-emitting element 13> An ITSO film was formed on a glass substrate as an electrode 101 to a thickness of 70 nm. The electrode area of ​​the electrode 101 is 4 mm 2 (2mm x 2mm).

[0432] Next, a hole injection layer 111 made of DBT3P-II and molybdenum oxide was formed on the electrode 101. (MoO3) and the weight ratio (DBT3P-II:MoO3) was 1:0.5. The deposition was carried out to a thickness of 45 nm.

[0433] Next, mCzFLP was deposited to a thickness of 20 nm on the hole injection layer 111 as the hole transport layer 112. The vapor deposition was carried out so that

[0434] Next, mPCCzPTzn-02 and GD 270 (manufactured by Jilin OLED Co., Ltd.) and TBRb in a weight ratio (mPCCzPTzn-02:G D270:TBRb) is 0.8:0.2:0.01, and the thickness is 40 nm. In the light-emitting layer 130, GD270 was a phosphorescent compound, and T BRb is a fluorescent compound.

[0435] Next, mPCCzPTzn-02 was deposited to a thickness of 100 nm on the light-emitting layer 130 as the electron transport layer 118. They were then evaporated in sequence to a thickness of 20 nm, and NBPhen to a thickness of 10 nm. Next, LiF was deposited on the electron transport layer 118 to form the electron injection layer 119 to a thickness of 1 nm. The vapor was evaporated.

[0436] Next, on the electron injection layer 119, aluminum (Al) was deposited to a thickness of 20 It was formed so that the thickness was 0 nm.

[0437] Next, in a glove box with a nitrogen atmosphere, a glass substrate for sealing is The EL sealant is used to fix the organic material to the glass substrate, forming a light-emitting element 1. Specifically, a sealant was applied around the organic material formed on the glass substrate, The glass substrate and a glass substrate for sealing were attached to each other, and ultraviolet light with a wavelength of 365 nm was applied. 6J / cm 2 The light-emitting element 13 was obtained by the above steps. Ta.

[0438] <Preparation of Comparative Light-Emitting Element 14> The comparative light-emitting element 14 differs from the previously described light-emitting element 13 only in the formation process of the light-emitting layer 130. The other steps were the same as those for the light-emitting element 13.

[0439] The light-emitting layer 130 of the comparative light-emitting element 14 was made of mPCCzPTzn-02, GD270, and , so that the weight ratio (mPCCzPTzn-02:GD270) was 0.8:0.2, The thickness of the light-emitting layer 130 of the light-emitting element 13 is 40 nm. The light-emitting layer 130 of the comparative light-emitting element 14 does not contain TBRb, which is a fluorescent compound.

[0440] <Preparation of Comparative Light-Emitting Element 15> The comparative light-emitting element 15 is the same as the light-emitting element 13 described above, except that the hole transport layer 112 and the light-emitting layer 130 are the same. Only the formation process was different, and the other processes were the same as those for the light emitting element 13.

[0441] The hole transport layer 112 of the comparative light-emitting element 15 was formed by depositing PCCP on the hole injection layer 111 to a thickness of 2. The deposition was carried out so that the thickness was 0 nm.

[0442] Next, as the light-emitting layer 130, mPCCzPTzn-02 and TBRb were mixed in a weight ratio (m The ratio of PCCzPTzn-02:TBRb was 1:0.01 and the thickness was 30 nm. In comparison with the light-emitting layer 130 of the light-emitting element 13, the comparative light-emitting element 15 The light-emitting layer 130 does not contain the phosphorescent compound GD270.

[0443] <Characteristics of light-emitting element> Next, the light-emitting element 13, the comparative light-emitting element 14, the comparative light-emitting element 15, and the above-mentioned ratio The characteristics of the comparative light emitting element 8 were measured. The measurement method was the same as in Example 1.

[0444] Current of the light-emitting element 13, the comparative light-emitting element 14, the comparative light-emitting element 15, and the comparative light-emitting element 8 The efficiency-luminance characteristics are shown in Fig. 37, the current-voltage characteristics in Fig. 38, and the external quantum efficiency-luminance characteristics in Fig. 3 9, respectively. In addition, the light-emitting element 13, the comparative light-emitting element 14, the comparative light-emitting element 15, and the The comparative light-emitting element 8 described above had a current of 2.5 mA / cm 2 The electric field when a current is passed with a current density of The emission spectrum is shown in Figure 40. The measurements of each light-emitting element were performed at room temperature (in an atmosphere maintained at 23°C). I went there with a feeling of excitement.

[0445] Also, 1000cd / m 2 The light-emitting element 13, the comparative light-emitting element 14, and the comparative light-emitting element The element characteristics of the optical element 15 are shown in Table 8.

[0446] [Table 8]

[0447] As shown in FIG. 40, the emission spectra of the light-emitting element 13, the comparative light-emitting element 8, and the comparative light-emitting element 15 are The spectra have peak wavelengths of 564 nm, 562 nm, and 562 nm, respectively, and full width at half maximum The light-emitting element 13 emitted yellow light at about 72 nm, 67 nm, and 69 nm, respectively. The light emitted by the comparative light-emitting element 8 and the comparative light-emitting element 15 is due to the fluorescent compound TBRb. The emission spectrum of the comparative light-emitting element 14 has a peak wavelength of 527 nm. m and emitted green light with a full width at half maximum of 73 nm. The luminescence emitted is luminescence derived from GD270. The element 13 has a smaller full width at half maximum of the peak wavelength of the emission spectrum than the comparative light-emitting element 14, and Therefore, the light-emitting element of one embodiment of the present invention can be used in a display device. It is suitable for placement.

[0448] As shown in FIG. 37, FIG. 39 and Table 8, the light-emitting element 13 is a fluorescent light-emitting element. Nevertheless, the external quantum efficiency is higher than 6.25%. In the light-emitting device 13 according to the embodiment of the present invention, in addition to the emission due to singlet excitons, phosphorescence The contribution of triplet excitons to fluorescence emission via the compound GD270 In addition, as described later, the mPCCzPT Zn-02 is a TADF material. Therefore, the triplet is generated by reverse intersystem crossing derived from the TADF material. Since the doublet excitons can be made to contribute to the fluorescent emission, the luminous efficiency can be improved. .

[0449] Furthermore, the luminous efficiency of the light-emitting element 13 is higher than that of the comparative light-emitting element 8. The light-emitting layer 130 of No. 8 is made of CBP, not TADF material. Device 8 has a function of converting triplet excitons to singlet excitons by reverse intersystem crossing using TADF materials. On the other hand, the light-emitting element 13 according to one embodiment of the present invention has a light-emitting layer 130 made of a TADF material. Therefore, the light-emitting element 13 utilizes the reverse intersystem crossing of the TADF material. This allows triplet excitons to be converted into singlet excitons, and the light-emitting element has a higher luminescence than the comparative light-emitting element 8. Efficiency can be achieved.

[0450] Furthermore, the luminous efficiency of the light-emitting element 13 is higher than that of the comparative light-emitting element 15. The light-emitting layer 130 of the semiconductor device 15 contains a TADF material but does not contain a phosphorescent compound. Therefore, in the comparative light-emitting element 15, triplet excitons contribute to fluorescent emission via a phosphorescent compound. On the other hand, the light-emitting element 13 according to one embodiment of the present invention is made of a TADF material and Therefore, triplet excitons can be converted to fluorescent light via the phosphorescent compound. Therefore, a higher luminous efficiency than that of the comparative light-emitting element 15 can be achieved.

[0451] <Time-resolved luminescence measurement> Next, to confirm that mPCCzPTzn-02 is a TADF material, we performed time-resolved Luminescence measurement was carried out. The results are shown in Figure 41. The measurement method was the same as that shown in the previous example. In addition, a light-emitting element 16 having the element structure shown in Table 9 below was used for the measurement.

[0452] [Table 9]

[0453] As shown in Fig. 41, a plurality of light-emitting components having different fluorescence lifetimes were observed from the light-emitting element 16 In addition to the initial fluorescence component with a short emission lifetime, a delayed fluorescence component with a long emission lifetime was observed . Therefore, it can be said that mPCCzPTzn-02 is a TADF material. On the other hand, from Fig. 41 The ratio of the delayed fluorescence component to all the light-emitting components (fast light-emitting component + delayed fluorescence component) is about 10% and the ratio that is converted into light after the triplet excitons are converted into singlet excitons is calculated to be about 4% . Therefore, mPCCzPTzn-02 has TADF properties, but its luminescence efficiency cannot be said to be high. However, as described above, in the light-emitting element 13, a very high efficiency exceeding 2 7% is obtained. Therefore, the TADF material used in the light-emitting element of one aspect of the present invention only needs to have TADF properties, and the luminescence efficiency of the TADF material may be low .

[0454] <Measurement of S1 level and T1 level> Next, in order to calculate the S1 level and T1 level of mPCCzPTzn-02, the emission spectrum of mPCCzPTzn-02 at low temperature (10 K) was measured. The measurement method is the same as the method shown in Example 1. The measurement results are shown in Fig. 42

[0455] From Fig. 42, the wavelengths of the peaks (including shoulders) on the shortest wavelength side of the fluorescence component and the phosphorescence component of the emission spectrum of mPCCzPTzn-02 are 471 nm and 496 nm respectively .

[0456] Therefore, the S1 level of mPCCzPTzn -02 calculated from the wavelengths of the above peaks (including shoulders) is 2.63 eV, the T1 level is 2.50 eV, and the energy difference between the S1 level and the T1 level is calculated to be 0.13 eV​

[0457] As described above, at the wavelength of the shortest wavelength peak (including the shoulder) of the emission spectrum, The calculated energy difference between the S1 and T1 levels of mPCCzPTzn-02 is The value was very small, greater than 0 eV and less than 0.2 eV. zPTzn-02 converts triplet excitation energy to singlet excitation energy by reverse intersystem crossing. It has the function of converting the fluorescein into a fluorine-containing compound and has the function of exhibiting thermally activated delayed fluorescence.

[0458] <Reliability of light-emitting elements> FIG. 43 shows the light-emitting element 13, the comparative light-emitting element 14, the comparative light-emitting element 15, and the comparative light-emitting element 8. 43 shows the results of a constant current driving test at 0 mA. As described above, the light-emitting device 13 is a fluorescent material. The comparative light-emitting element 14 emits light from a phosphorescent compound. Therefore, light emission from a fluorescent compound, as in the case of the light-emitting element of one embodiment of the present invention, is more reliable. In addition, the light-emitting element 13 had better reliability than the comparative light-emitting element 15. As described above, the light-emitting element 13 is made of a TADF material and a phosphorescent compound. The triplet excitation energy can be transferred to a fluorescent compound via the The optical element 15 can convert triplet excitation energy into fluorescent compounds only through the TADF material. Therefore, in the light-emitting element of one embodiment of the present invention, It has been found that the reliability of the transfer of triplet excitation energy to a substance is improved when there are multiple pathways. In addition, it was found that the light-emitting element 13 had better reliability than the comparative light-emitting element 8. By using a host material with TADF properties, high reliability was achieved. A light emitting element having the above structure can be obtained.

[0459] As described above, according to one embodiment of the present invention, a light-emitting element having high emission efficiency and good reliability can be provided. According to one embodiment of the present invention, a light-emitting element with low driving voltage and low power consumption can be provided. It can be provided. EXAMPLES

[0460] In this example, a manufacturing example of a light-emitting element according to one embodiment of the present invention and a comparative light-emitting element will be described. The structure of the light-emitting element fabricated in this example is the same as that shown in Figure 1(A). The details of the element structure are shown in Table 10. The structures and abbreviations of the compounds used may be found in the above examples and embodiments.

[0461] [Table 10]

[0462] <Fabrication of light-emitting element> A method for manufacturing the light-emitting element manufactured in this embodiment will be described below.

[0463] <Preparation of light-emitting element 17> An ITSO film was formed on a glass substrate as an electrode 101 to a thickness of 70 nm. The electrode area of ​​the electrode 101 is 4 mm 2 (2mm x 2mm).

[0464] Next, a hole injection layer 111 made of DBT3P-II and molybdenum oxide was formed on the electrode 101. (MoO3) and the weight ratio (DBT3P-II:MoO3) was 1:0.5. The deposition was carried out to a thickness of 45 nm.

[0465] Next, mCzFLP was deposited to a thickness of 20 nm on the hole injection layer 111 as the hole transport layer 112. The vapor deposition was carried out so that

[0466] Next, mPCCzPTzn-02 and PC CP, GD270, and TBRb were mixed in a weight ratio of (mPCCzPTzn-02:PCCP: GD270:TBRb) is 0.5:0.5:0.1:0.01, and the thickness is In the light-emitting layer 130, TBRb was a fluorescent compound. be.

[0467] Next, mPCCzPTzn-02 was deposited to a thickness of 100 nm on the light-emitting layer 130 as the electron transport layer 118. They were then evaporated in sequence to a thickness of 20 nm, and NBPhen to a thickness of 10 nm. Next, LiF was deposited on the electron transport layer 118 to form an electron injection layer 119 with a thickness of 1 nm. The vapor was evaporated.

[0468] Next, on the electron injection layer 119, aluminum (Al) was deposited to a thickness of 20 It was formed so that the thickness was 0 nm.

[0469] Next, in a glove box with a nitrogen atmosphere, a glass substrate for sealing is The EL sealant is used to fix the organic material to the glass substrate, forming a light-emitting element 1. Specifically, a sealant was applied around the organic material formed on the glass substrate, The glass substrate and a sealing glass substrate are attached to each other, and ultraviolet light with a wavelength of 365 nm is applied. 6J / cm 2 The light-emitting element 17 was obtained by the above steps. Ta.

[0470] <Preparation of Comparative Light-Emitting Element 18> The comparative light-emitting element 18 is different from the previously described light-emitting element 17 only in the process of forming the light-emitting layer 130. The other steps were the same as those for the light-emitting element 17.

[0471] The light-emitting layer 130 of the comparative light-emitting element 18 was made of mPCCzPTzn-02, PCCP, and GD270 was added at a weight ratio (mPCCzPTzn-02:PCCP:GD270) of 0.5:0. The mixture was co-evaporated to a thickness of 40 nm in a ratio of 0.5:0.1. Light-emitting element 17 In comparison with the light-emitting layer 130 of the comparative light-emitting device 18, the light-emitting layer 130 of the comparative light-emitting device 18 contains a fluorescent compound. TBRb is not included.

[0472] <Characteristics of light-emitting element> Next, the characteristics of the light-emitting element 17, the comparative light-emitting element 18, and the light-emitting element 13 prepared above were measured. The measurement method was the same as in Example 1.

[0473] FIG. 44 shows the current efficiency vs. luminance characteristics of the light-emitting element 17, the comparative light-emitting element 18, and the light-emitting element 13. The current-voltage characteristics are shown in FIG. 45, and the external quantum efficiency-luminance characteristics are shown in FIG. The light-emitting element 17, the comparative light-emitting element 18, and the light-emitting element 13 were each 2.5 mA / cm 2 Electricity The electroluminescence spectrum when a current was applied at a current density is shown in FIG. was carried out at room temperature (atmosphere maintained at 23°C).

[0474] Also, 1000cd / m 2 Element characteristics of the light-emitting element 17 and the comparative light-emitting element 18 in the vicinity is shown in Table 11.

[0475] [Table 11]

[0476] As shown in Fig. 47, the electroluminescence spectra of the light-emitting element 17 and the light-emitting element 13 have peaks at wavelengths of 559 nm and 564 nm, respectively, and full widths at half maximum of about 71 nm and 72 nm, indicating yellow emission. Therefore, the emission exhibited by the light-emitting element 17 and the light-emitting element 13 is emission derived from the fluorescent compound TBRb. Also, the electroluminescence spectrum of the comparative light-emitting element 18 showed green emission with a peak wavelength of 524 nm and a full width at half maximum of 72 nm. Therefore, the emission exhibited by the comparative light-emitting element 18 is emission derived from the phosphorescent compound GD270.

[0477] Also, as shown in Figs. 44 and 46 and Table 11, the light-emitting element 17, the comparative light-emitting element 18, and the light-emitting element 13 exhibit very high luminous efficiencies (current efficiency, power efficiency, and external quantum efficiency). Also, despite the light-emitting element 17 being a fluorescent light-emitting element, a very high efficiency exceeding 6.25% in external quantum efficiency has been obtained. This is due to emission derived not only from singlet excitons generated by the recombination of carriers (holes and electrons), but also from triplet excitons, indicating that excitation energy is transferred from the phosphorescent compound GD270 to the fluorescent compound TBRb. In addition, as described above, mPCCzPTzn-02 contained in the light-emitting element 17 is a TADF material. Therefore, the reverse intersystem crossing derived from the TADF material can contribute triplet excitons to fluorescence emission, thereby improving the luminous efficiency.

[0478] <CV measurement results> Next, the HOMO level and the LUMO level were calculated by cyclic voltammetry (CV) measurement of the electrochemical characteristics (oxidation reaction characteristics and reduction reaction characteristics) of the above compounds. The measurement ​​​​​​​​​​​​ The determination method was the same as in Example 1 described above.

[0479] From the CV measurement, the HOMO level of mPCCzPTzn-02 is -5.69 eV, and the LUMO level is The HOMO level of PCCP is -3.00 eV, the HOMO level of PCCP is -5.63 eV, and the LUMO level is -1. It was 96 eV.

[0480] Therefore, mPCCzPTzn-02 has a higher HOMO level and a lower LUMO level than PCCP. Therefore, mPCCzPTzn-02 and PCCP have the excited states in the emission layer. This is a combination that forms a complex.

[0481] In addition, the emission spectrum of the exciplex formed from mPCCzPTzn-02 and PCCP The S1 and T1 levels calculated from the peak wavelength are 2.45 eV. Since the T1 level of is 2.44 eV (calculated from the absorption edge of the chloroform solution), The excitation energy of can be transferred to GD270.

[0482] <Investigation of exciplex formation> To investigate whether mPCCzPTzn-02 and PCCP form an exciplex, The light-emitting element 19 shown in FIG. 12 and the light-emitting element 16 described above were fabricated. The emission spectrum of mPCCzPTzn-02 and mPCCzPTzn-02 and PCC The emission spectra of the P mixed films were compared.

[0483] [Table 12]

[0484] <EL spectrum> 2.5 mA / cm for the light emitting element 16 and the light emitting element 19 2 The EL spectrum obtained when a current of The spectrum is shown in FIG. 48. From FIG. 48, it is seen that mPCCzPTzn-02 is emitted from the light-emitting element 16. Here, light emission from the light-emitting element 19 is stronger than that from the light-emitting element 16. Light emission having a peak on the long wavelength side is obtained. The emission energy (2.45 eV) calculated from the peak wavelength is mPCCzPTzn-0 This roughly corresponds to the difference between the LUMO level of 2 and the HOMO level of PCCP (2.63 eV). Therefore, it can be said that mPCCzPTzn-02 and PCCP form an exciplex.

[0485] <Time-resolved luminescence measurement> Furthermore, time-resolved luminescence measurements were performed on the light-emitting elements 16 and 19. The results are shown in FIG. As shown in FIG. 49, the proportion of delayed fluorescent components is larger in the light-emitting element 19 than in the light-emitting element 16. In addition, the light-emitting element 19 contains a light-emitting component with a longer life than the light-emitting element 16. In other words, the transient response characteristics of the light-emitting element 16 and the light-emitting element 19 are different. Therefore, it can be said that mPCCzPTzn-02 and PCCP form an exciplex. .

[0486] <Relationship between the emission spectrum of exciplexes and the absorption spectrum of guest materials> Figure 50 shows the absorption spectrum of TBRb in a toluene solution. FIG. 50 also shows the emission spectrum of the comparative light-emitting element 18. The experiment was carried out in the same manner as in the example shown in .

[0487] As shown in FIG. 50, the absorption spectrum of TBRb and the emission spectrum of the comparative light-emitting element 18 are Therefore, the mPCCzPTzn-02 and PCCP The excitation energy is efficiently transferred from the corresponding exciplex to the fluorescent compound TBRb via GD270. It is possible to donate energy to TBRb via the phosphorescent compound GD270. The triplet excitation energy is contributed to the fluorescence emission by the energy transfer. In addition, when mPCCzPTzn-02, which does not form an exciplex, is excited, Since mPCCzPTzn-02 has TADF properties, triplet excitons can be generated by reverse intersystem crossing. In the light-emitting layer 130, singlet excitons are generated from the TADF material. Exciton generation and its transfer to the fluorescent compound TBRb via the phosphorescent compound GD270 The triplet excitation energy transfer occurs, and the light-emitting element 17 exhibits extremely high luminous efficiency. can be obtained.

[0488] <Reliability of light-emitting elements> Constant current driving test at 2.0 mA for the light-emitting element 17, the comparative light-emitting element 18, and the light-emitting element 13 The time it takes for the luminance to decrease by 40% (LT 60 ) are shown in Table 13.

[0489] [Table 13]

[0490] From Table 13, it can be seen that the light-emitting element 17, the comparative light-emitting element 18, and the light-emitting element 13 have good reliability. It was also found that the light-emitting element 17 had better reliability than the comparative light-emitting element 18. In addition, it was found that the light-emitting element 17 had a higher LT than the light-emitting element 13. 60 was good. Therefore, by using a TADF material as the host material and using an exciplex, it is possible to achieve high reliability. A light emitting element can be obtained. [Explanation of symbols]

[0491] 100 EL layer 101 Electrode 102 electrode 106 Light Emitting Unit 108 Light Emitting Unit 111 Hole injection layer 112 Hole transport layer 113 Electron transport layer 114 Electron injection layer 115 Charge generation layer 116 Hole injection layer 117 Hole transport layer 118 Electron transport layer 119 Electron injection layer 120 Light-emitting layer 130 Light-emitting layer 131 compounds 132 compounds 133 Compound 134 compounds 150 Light emitting element 170 Light-emitting layer 250 Light emitting element 601 Source side driver circuit 602 Pixel section 603 Gate side drive circuit 604 Sealing substrate 605 Sealing material 607 Space 608 Wiring 609 FPC 610 Element Substrate 611 Switching TFT 612 Current Control TFT 613 Electrode 614 Insulation 616 EL layer 617 Electrode 618 Light-emitting element 623 n-channel TFT 624 p-channel TFT 625 Dry material 900 Mobile Information Terminal 901 Case 902 Case 903 Display section 905 Hinge part 910 Mobile Information Terminal 911 Case 912 Display section 913 Operation button 914 External connection port 915 Speaker 916 Mike 917 Camera 920 Camera 921 Case 922 Display section 923 Operation button 924 Shutter button 926 Lens 1001 Board 1002 Undercoat insulating film 1003 Gate insulating film 1006 Gate electrode 1007 Gate electrode 1008 Gate electrode 1020 Interlayer insulating film 1021 Interlayer insulating film 1022 Electrode 1024B Electrode 1024G electrode 1024R electrode 1024W electrode 1025B Lower electrode 1025G bottom electrode 1025R lower electrode 1025W bottom electrode 1026 Bulkhead 1028 EL layer 1029 Electrode 1031 Sealing substrate 1032 Sealing material 1033 Base material 1034B Colored layer 1034G colored layer 1034R colored layer 1035 black layer 1036 overcoat layer 1037 Interlayer insulating film 1040 Pixel section 1041 Drive circuit section 1042 Periphery 1044B Blue pixel 1044G green pixels 1044R Red pixel 1044W white pixels 2100 Robot 2101 Illuminance sensor 2102 Microphone 2103 Upper Camera 2104 Speaker 2105 Display 2106 Lower Camera 2107 Obstacle Sensor 2108 Moving mechanism 2110 Arithmetic equipment 5000 cabinet 5001 Display section 5002 Display section 5003 Speaker 5004 LED Lamp 5005 Operation key 5006 Connection terminal 5007 Sensor 5008 Microphone 5012 Support part 5013 Earphones 5100 Cleaning robot 5101 Display 5102 Camera 5103 Brush 5104 Operation button 5120 Garbage 5140 Portable electronic devices 5150 Portable Information Terminal 5151 Case 5152 Display area 5153 Bend 8501 Lighting equipment 8502 Lighting equipment 8503 Lighting equipment 8504 Lighting equipment

Claims

1. A light-emitting layer is disposed between a pair of electrodes, the light-emitting layer includes a first organic compound, a second organic compound, a third organic compound, and a fourth organic compound; the first organic compound has a function of converting triplet excitation energy into luminescence, a difference between an S1 level of the second organic compound and a T1 level of the second organic compound is 0 eV or more and 0.2 eV or less; the third organic compound is an organic compound that forms an exciplex with the second organic compound, The fourth organic compound is a light-emitting element having a function of converting singlet excitation energy into light emission.

2. A light-emitting layer is disposed between a pair of electrodes, the light-emitting layer includes a first organic compound, a second organic compound, a third organic compound, and a fourth organic compound; the first organic compound has a function of converting triplet excitation energy into luminescence, the second organic compound has a π-electron rich skeleton and a π-electron deficient skeleton, the third organic compound is an organic compound that forms an exciplex with the second organic compound, The fourth organic compound is a light-emitting element having a function of converting singlet excitation energy into light emission.

3. In claim 1 or 2, The exciplex has a function of donating excitation energy to the first organic compound.

4. In any one of claims 1 to 3, The first organic compound comprises Ru, Rh, Pd, Os, Ir, or Pt.

5. In any one of claims 1 to 4, The first organic compound is a light-emitting element having a function of exhibiting phosphorescence.

6. In any one of claims 1 to 5, The first organic compound has a light emitting quantum yield of 0% or more and 40% or less at room temperature.

7. In any one of claims 1 to 6, The fourth organic compound is a light-emitting element that exhibits fluorescence.

8. In any one of claims 1 to 7, A light-emitting element that emits light originating from the fourth organic compound.

9. A light emitting element according to any one of claims 1 to 8, At least one of a color filter or a transistor; A display device having the above configuration.

10. A display device according to claim 9 ; At least one of a housing or a touch sensor; An electronic device having the

11. A light emitting element according to any one of claims 1 to 8, At least one of a housing or a touch sensor; A lighting device having the above structure.

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