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

Abstract

The present application has a title of "Light-emitting element, light-emitting device, electronic device, and lighting device". A light-emitting element with high emission efficiency is provided in a light-emitting element including a fluorescent material. A light-emitting element with a high ratio of delayed fluorescence components derived from TTA in light-emitting components is provided. A novel light-emitting device with high emission efficiency and low power consumption is provided. A light-emitting element includes an anode, a cathode, and an EL layer. The EL layer includes a light-emitting layer containing a host material and an electron transport layer containing a first material in contact with the light-emitting layer. The LUMO level of the first material is lower than the LUMO level of the host material. The ratio of delayed fluorescence components derived from TTA is more than 10% of light emitted by the EL layer. The ratio of delayed fluorescence components derived from TTA is more than 15% of light emitted.

Description

Technical Field

[0001] One aspect of the present invention relates to light-emitting elements, display modules, lighting modules, display devices, light-emitting devices, electronic devices, and lighting devices. However, another aspect of the present invention is not limited to the aforementioned technical fields. The technical field of one aspect of the invention disclosed in this specification relates to an object, method, or manufacturing method. Furthermore, one aspect of the present invention relates to a process, machine, manufacture, or composition of matter. Specifically, examples of the technical field of one aspect of the present invention disclosed in this specification include: semiconductor devices, display devices, liquid crystal display devices, light-emitting devices, lighting devices, energy storage devices, storage devices, imaging devices, driving methods for these devices, and manufacturing methods for these devices. Background Technology

[0002] In recent years, there has been active research and development on light-emitting elements utilizing electroluminescence (EL). The basic structure of these light-emitting elements consists of a layer containing luminescent material (EL layer) sandwiched between a pair of electrodes. By applying a voltage between the electrodes of this element, light emission from the luminescent material can be obtained.

[0003] Because the aforementioned light-emitting element is a self-emissive element, the display device using this element has the following advantages: good visibility; no need for a backlight; and low power consumption. Furthermore, the display device also has the following advantages: it can be manufactured to be thin and light; and it has a fast response time.

[0004] When using a light-emitting element (e.g., an organic EL element) that uses an organic material as the luminescent material and has an EL layer containing the luminescent organic material disposed between a pair of electrodes, current flows through it by applying a voltage between the pair of electrodes, where electrons and holes are injected from the cathode and anode into the luminescent EL layer, respectively. Furthermore, the injected electrons recombine with the holes, exciting the luminescent organic material, thereby allowing light to be emitted from the excited luminescent organic material.

[0005] As types of excited states formed by organic materials, there are singlet excited states (S... * ) and triple excited state (T * Emission from a singlet excited state is called fluorescence, and emission from a triplet excited state is called phosphorescence. Additionally, in this light-emitting element, S... ＊ :T ＊The statistical production ratio is 1:3. Therefore, light-emitting elements using phosphorescent materials can achieve higher luminous efficiency than those using fluorescent materials. Consequently, in recent years, there has been active development of light-emitting elements using phosphorescent materials capable of converting triplet excited states into luminescence.

[0006] In light-emitting elements using phosphorescent materials, the development of stable materials with high triplet excitation energy levels is challenging, thus preventing the practical application of blue-emitting light-emitting elements. Therefore, research is underway to develop blue-emitting light-emitting elements using more stable fluorescent materials, and methods to improve the luminous efficiency of light-emitting elements using fluorescent materials are being explored.

[0007] As a mechanism for converting a portion of a triplet excited state into light emission, triplet-triplet annihilation (TTA) is known. TTA refers to the generation of a singlet exciton when two triplet excitons are adjacent to each other, through the transfer of excitation energy and the exchange of spin angular momentum.

[0008] Anthracene compounds are known as TTA-generating compounds. Non-Patent Literature 1 reports that by using anthracene compounds as the host material of a light-emitting element, a high external quantum efficiency exceeding 10% can be achieved in a blue light-emitting element. It has also been reported that the delayed fluorescence component induced by TTA in anthracene compounds accounts for approximately 10% of the luminescent component of the light-emitting element.

[0009] Furthermore, tetraphenyl compounds are known to have a high proportion of delayed fluorescence components induced by TTA. Non-Patent Literature 2 reports that the proportion of delayed fluorescence components induced by TTA in tetraphenyl compounds is higher than that in anthracene compounds.

[0010] Furthermore, when TTA occurs, luminescence with a longer lifetime than that obtained when TTA does not occur (delayed fluorescence) is produced. This delayed fluorescence can be confirmed by observing the decay of luminescence after continuous carrier injection is stopped at a certain point in time. In this case, the shape of the delayed fluorescence spectrum is consistent with the shape of the luminescence spectrum when carriers are continuously injected.

[0011] [References] [Non-patent literature] [Non-Patent Literature 1] Tsunenori Suzuki and six others, Japanese Journal of Applied Physics, Vol. 53, 052102 (2014) [Non-patent literature 2] DY Kondakov and three others, Journal of Applied Physics, Vol. 106, 124510 (2009). Summary of the Invention

[0012] In light-emitting elements containing fluorescent materials, to improve luminescence efficiency, it is crucial to convert the energy of triplet excitons (which do not contribute to luminescence) into the energy of luminescent singlet excitons and to improve this conversion efficiency. In other words, it is important to convert the energy of triplet excitons into the energy of singlet excitons via TTA (transient photoluminescence transfer). Therefore, increasing the proportion of delayed fluorescence components derived from TTA in the luminescent composition of the light-emitting element is particularly important. This is because a high proportion of delayed fluorescence components derived from TTA implies a high generation rate of luminescent singlet excitons.

[0013] Therefore, one objective of this invention is to provide a light-emitting element comprising a fluorescent material and exhibiting high luminous efficiency. Another objective of this invention is to provide a light-emitting element with a high proportion of delayed fluorescence components derived from TTA in its luminescent composition. Furthermore, one objective of this invention is to provide a novel light-emitting device that exhibits high luminous efficiency and reduced power consumption. Finally, one objective of this invention is to provide a novel display device.

[0014] Note that the description of the above objectives does not preclude the existence of other objectives. Furthermore, one aspect of the present invention does not need to address all of the above objectives. Other objectives are obvious from the description in the specification, etc., and can be extracted from said description.

[0015] One embodiment of the light-emitting element of the present invention includes: an anode, a cathode, and an EL layer sandwiched between the anode and the cathode. The EL layer includes a light-emitting layer and an electron transport layer in contact with the light-emitting layer. The light-emitting layer comprises a host material. The electron transport layer comprises a first material. The LUMO energy level of the first material is lower than that of the host material. The proportion of delayed fluorescence component originating from triplet-triplet annihilation is more than 10% of the total light emitted by the EL layer.

[0016] Alternatively, another embodiment of the light-emitting element of the present invention includes: an anode, a cathode, and an EL layer sandwiched between the anode and the cathode. The EL layer includes a light-emitting layer and an electron transport layer in contact with the light-emitting layer. The light-emitting layer comprises a host material. The electron transport layer comprises a first material. The LUMO energy level of the first material is at least 0.05 eV lower than the LUMO energy level of the host material. The proportion of delayed fluorescence component originating from triplet-triplet annihilation is at least 10% of the total light emitted by the EL layer.

[0017] In another embodiment of the present invention, the proportion of delayed fluorescence component originating from triplet-triplet annihilation may be 15% or more of the total light emitted by the EL layer. Furthermore, the first material may be a substance comprising a fused heterocyclic aromatic ring skeleton having a diazine or triazine skeleton. Alternatively, the first material may be a substance having a pyrazine or pyrimidine skeleton. Additionally, the triplet excitation energy of the first material may be 0.2 eV or more greater than the triplet excitation energy of the material with the highest triplet excitation energy contained in the luminescent layer.

[0018] Additionally, one aspect of the present invention includes a hole transport layer in contact with the light-emitting layer. The hole transport layer comprises a second material. The LUMO energy level of the second material is higher than the LUMO energy level of the host material. Alternatively, the light-emitting element of one aspect of the present invention may also include a hole transport layer in contact with the light-emitting layer, the hole transport layer comprising a second material, the triplet excitation energy of the second material being 0.2 eV or higher than the triplet excitation energy of the material with the highest triplet excitation energy contained in the light-emitting layer.

[0019] Alternatively, in another embodiment of the present invention, the luminescent layer may further comprise a luminescent element containing a fluorescent material. Alternatively, in another embodiment of the present invention, the luminescent element may have a triplet excitation energy of the fluorescent material that is greater than the triplet excitation energy of the host material. Alternatively, in another embodiment of the present invention, the luminescent element may have a LUMO energy level of the fluorescent material that is equal to or greater than the LUMO energy level of the host material. Alternatively, in another embodiment of the present invention, the luminescent layer may emit blue light.

[0020] Additionally, one aspect of the present invention is a light-emitting device comprising a light-emitting element, a transistor, or a substrate. Furthermore, another aspect of the present invention can also be an electronic device that includes, in addition to a light-emitting device, a sensor, an operation button, a speaker, or a microphone. Moreover, another aspect of the present invention can also be a lighting device that includes, in addition to a light-emitting device, a frame.

[0021] According to one aspect of the present invention, a light-emitting element comprising a fluorescent material and exhibiting high luminous efficiency can be provided. Additionally, according to one aspect of the present invention, a light-emitting element with a high proportion of delayed fluorescence components derived from TTA in the luminescent composition can be provided. According to one aspect of the present invention, a novel light-emitting device exhibiting high luminous efficiency and reduced power consumption can be provided. Furthermore, according to one aspect of the present invention, a novel display device can be provided.

[0022] Note that the description of these effects does not preclude the existence of other effects. One aspect of the invention does not necessarily require all of the aforementioned effects. Other effects are obvious from the description, drawings, claims, etc., and can be extracted from the description itself. Attached Figure Description

[0023] Figures 1A to 1C This is a cross-sectional schematic diagram of a light-emitting element and a related schematic diagram of the energy level, illustrating one aspect of the present invention; Figure 2 This is a diagram illustrating the potential barrier and the composite region; Figures 3A to 3C It is a diagram illustrating the composition of the transition dipole moment; Figure 4A and Figure 4B This is a schematic diagram illustrating the method for measuring molecular orientation; Figure 5 This is a cross-sectional schematic diagram of a light-emitting element according to one embodiment of the present invention; Figure 6A and Figure 6B This is a cross-sectional schematic diagram of a light-emitting element according to one embodiment of the present invention; Figure 7A and Figure 7B This is a cross-sectional schematic diagram of a light-emitting element and a related schematic diagram of the energy level, illustrating one aspect of the present invention; Figure 8A and Figure 8B This is a cross-sectional schematic diagram of a light-emitting element and a related schematic diagram of the energy level, illustrating one aspect of the present invention; Figure 9A and Figure 9B This is a block diagram and circuit diagram illustrating one aspect of the present invention for a display device; Figure 10A and Figure 10B This is a perspective view illustrating an example of a touch panel according to one aspect of the present invention; Figures 11A to 11C This is a cross-sectional view illustrating an example of a display device and touch sensor according to one aspect of the present invention; Figure 12A and Figure 12B This is a cross-sectional view illustrating an example of a touch panel according to one aspect of the present invention; Figure 13A and Figure 13B This is a block diagram and timing diagram of a touch sensor according to one aspect of the present invention; Figure 14 This is a circuit diagram of a touch sensor according to one aspect of the present invention; Figure 15 This is a perspective view illustrating one aspect of the present invention; Figures 16A to 16G This is a diagram illustrating an electronic device according to one aspect of the present invention; Figure 17 This is a diagram illustrating one aspect of a lighting device according to the present invention; Figure 18 This is a diagram illustrating the light-emitting element; Figure 19 It is the ratio of delayed fluorescence components of light-emitting elements 1 to 8 relative to the LUMO energy level; Figure 20 It is the external quantum efficiency of light-emitting elements 1 to 8 relative to the ratio of delayed fluorescence components; Figure 21 This is a graph showing the current density-brightness characteristics of the light-emitting element 4-2; Figure 22 This is a diagram showing the voltage-brightness characteristics of the light-emitting element 4-2; Figure 23 This is a graph showing the brightness-current efficiency characteristics of the light-emitting element 4-2; Figure 24 This is a diagram showing the voltage-current characteristics of the light-emitting element 4-2; Figure 25 This is a graph showing the brightness-external quantum efficiency characteristics of the light-emitting element 4-2; Figure 26 This is a diagram showing the emission spectrum of the light-emitting element 4-2; Figure 27 This is a graph showing the decay curve of the instantaneous fluorescence characteristics of the light-emitting element 4-2; Figure 28 This is a diagram illustrating the reliability of the light-emitting element 4-2; Figure 29 The angle-dependent characteristics and calculation results of the light-emitting element 9 are shown. Detailed Implementation

[0024] The embodiments of the present invention will now be described. However, those skilled in the art will readily understand that the methods and details disclosed herein can be transformed into various forms without departing from the spirit and scope of the invention. Therefore, the present invention should not be construed as being limited to the contents described in these embodiments.

[0025] Furthermore, in each of the accompanying drawings described in this specification, the dimensions or thicknesses of the anode, EL layer, intermediate layer, cathode, etc., are sometimes exaggerated for ease of explanation. Therefore, the dimensions of each component are not limited to those shown in the drawings, nor are they limited to the relative sizes between the components.

[0026] Note that in this specification and other documents, ordinal numbers such as "first," "second," and "third" are used for convenience, but they do not indicate the order of processes or hierarchical relationships. Therefore, for example, "first" can be appropriately replaced with "second" or "third," etc., for explanation. Furthermore, sometimes the ordinal numbers described in this specification and other documents do not need to be the same as the ordinal numbers used to specify one aspect of the present invention.

[0027] Furthermore, in the configuration of the present invention described in this specification and other documents, the same symbol is used across different drawings to denote the same part or parts having the same function, and repeated descriptions are omitted. Additionally, sometimes the same shading line is used for parts having the same function, without specifically adding additional reference numerals to indicate that part.

[0028] In this specification, color is defined by three elements: hue (equivalent to the wavelength of monochromatic light), chroma (color intensity, i.e., the degree to which it differs from white), and lightness (brightness, i.e., the intensity of light). In this specification, color may also be defined by any one or any two of these three elements. In this specification, the difference in color between two lights refers to a difference in at least one of the three elements, and also includes differences in the shape of the spectra of the two lights or the distribution of the relative intensities of the peaks in the spectra.

[0029] In addition, depending on the situation or state, the "film" and "layer" can be interchanged. For example, sometimes the "conductive layer" can be replaced with the "conductive film". Or, sometimes the "insulating film" can be replaced with the "insulating layer".

[0030] Furthermore, in this specification, etc., the singlet excited state (S ＊ A singlet excited state (S1) refers to a singlet excited state with an excitation energy. The excited state with the lowest energy among the singlet excited states is called the lowest singlet excited state. Furthermore, a singlet excited energy level refers to an energy level of a singlet excited state. The lowest excitation energy level among the singlet excited energy levels is called the lowest singlet excited (S1) energy level. In addition, even when simply expressed as "singlet excited state" or "singlet excited state energy level," it sometimes refers to the lowest singlet excited state or the S1 energy level, respectively.

[0031] Furthermore, in this specification, etc., the triplet excited state (T ＊ A triplet excited state (T1) refers to a triplet excited state with an excitation energy. The excited state with the lowest energy among the triplet excited states is called the lowest triplet excited state. Additionally, a triplet excited energy level refers to an energy level of a triplet excited state. The lowest excitation energy level among the triplet excited energy levels is called the lowest triplet excited (T1) energy level. Furthermore, in this specification, even when simply expressed as "triple excited state" or "triple excited state energy level," it may sometimes refer to the lowest triplet excited state or the T1 energy level, respectively.

[0032] In this specification, fluorescent materials refer to materials that emit light in the visible light region when returning from a singlet excited state to the ground state. Phosphorescent materials refer to materials that emit light in the visible light region at room temperature when returning from a triplet excited state to the ground state. In other words, phosphorescent materials are materials capable of converting triplet excitation energy into visible light.

[0033] Note that in this instruction manual, etc., "room temperature" refers to a temperature in the range of 0°C to 40°C.

[0034] In this specification, the blue wavelength region refers to the wavelength region above 400 nm and below 550 nm, and blue emission refers to emission with at least one emission spectral peak in the wavelength region.

[0035] Implementation Method 1 <Example of a light-emitting element structure> First, the following will refer to Figures 1A to 1C The structure of a light-emitting element according to one aspect of the present invention is described.

[0036] Figure 1A This is a cross-sectional schematic diagram of a light-emitting element 150 according to one embodiment of the present invention.

[0037] The light-emitting element 150 includes an EL layer 100 disposed between a pair of electrodes (electrode 101 and electrode 102). The EL layer 100 includes at least a light-emitting layer 130. Note that although this embodiment is described with electrode 101 as the anode and electrode 102 as the cathode, the light-emitting element 150 may also have the opposite structure.

[0038] Figure 1A The EL layer 100 shown includes functional layers in addition to the light-emitting layer 130. The functional layers include a hole injection layer 111, a hole transport layer 112, an electron transport layer 118, and an electron injection layer 119. Note that the structure of the EL layer 100 is not limited to... Figure 1A The structure shown may include at least one selected from hole injection layer 111, hole transport layer 112, electron transport layer 118, and electron injection layer 119. Alternatively, the EL layer 100 may also include a functional layer that can reduce the injection barrier of holes or electrons; improve the transport of holes or electrons; hinder the transport of holes or electrons; or suppress quenching caused by electrodes, etc.

[0039] Figure 1B It is shown Figure 1A A cross-sectional schematic diagram of an example of the light-emitting layer 130 shown. Figure 1B The light-emitting layer 130 shown includes at least a host material 131 and a guest material 132.

[0040] In other words, the host material 131 preferably has the function of converting triple excitation energy into single excitation energy using TTA. Thus, a portion of the triple excitation energy generated in the light-emitting layer 130 is converted into single excitation energy using the TTA in the host material 131. This allows the single excitation energy generated by the TTA to be transferred to the guest material 132 and extracted as fluorescence. Therefore, the lowest single excitation energy level (S1 level) of the host material 131 is preferably higher than the S1 level of the guest material 132. Furthermore, the lowest triple excitation energy level (T1 level) of the host material 131 is preferably lower than the T1 level of the guest material 132.

[0041] Note that the host material 131 may consist of a single compound or multiple compounds. As the guest material 132, a luminescent organic material may be used; preferably, a material capable of emitting fluorescence (hereinafter also referred to as a fluorescent material) is used. The structure of the fluorescent material used as the guest material 132 will be described in the following description. Note that the guest material 132 may also be referred to as a fluorescent material.

[0042] <Light-emitting mechanism of light-emitting elements> First, the light-emitting mechanism of the light-emitting element 150 will be explained below.

[0043] In one embodiment of the light-emitting element 150 of the present invention, electrons and holes are injected into the EL layer 100 from the cathode and anode, respectively, by applying a voltage between a pair of electrodes (electrode 101 and electrode 102), thereby allowing current to flow. The injected electrons and holes recombine to form excitons. Among the excitons generated by the recombination of charge carriers (electrons and holes), the statistical probability of the ratio of singlet excitons to triplet excitons (hereinafter referred to as the exciton generation probability) is 1:3. Here, the generation probability of singlet excitons is 25%.

[0044] An exciton is a pair of charge carriers (electrons and holes). Because excitons have excitation energy, the material that generates excitons is in an excited state.

[0045] In addition, singlet excitons are generated in the EL layer 100 through the following two processes, thereby obtaining luminescence from the guest material 132. (α) Direct generation process (β) TTA process.

[0046] <<(α) Direct Generation Process>> The following describes the situation where carriers (electrons or holes) recombine to form singlet excitons in the light-emitting layer 130 contained in the EL layer 100.

[0047] When carrier recombination occurs in the host material 131, an excited state (singleton or triplet excited state) is formed in the host material 131 due to exciton generation. When the excited state of the host material 131 is a singleton excited state, the singleton excitation energy migrates from the S1 level of the host material 131 to the S1 level of the guest material 132, thereby forming a singleton excited state in the guest material 132. Note that the case where the excited state of the host material 131 is a triplet excited state will be explained in the subsequent (β)TTA process.

[0048] Furthermore, when carrier recombination occurs in the guest material 132, excited states (single or triple excited states) of the guest material 132 are formed due to the generation of excitons.

[0049] When the excited state of the formed guest material 132 is a singlet excited state, luminescence from the singlet excited state of the guest material 132 can be obtained. In this case, in order to obtain high luminescence efficiency, the fluorescence quantum yield of the guest material 132 is preferably high.

[0050] On the other hand, when the excited state of guest material 132 is a triplet excited state, since guest material 132 is a fluorescent material, the triplet excited state of guest material 132 does not contribute to luminescence due to thermal deactivation. However, when the T1 energy level of host material 131 is lower than the T1 energy level of guest material 132, the triplet excitation energy of guest material 132 migrates from the T1 energy level of guest material 132 to the T1 energy level of host material 131, which exists in greater quantities than guest material 132. In this case, the triplet excitation energy can be converted to a singlet excitation energy through the subsequent (β)TTA process. Therefore, in order to increase the probability of TTA, it is important to make the T1 energy level of host material 131 lower than the T1 energy level of guest material 132.

[0051] When the T1 energy level of the host material 131 is higher than that of the guest material 132, and the weight ratio of the guest material 132 to the host material 131 is lower, the probability of carrier recombination in the guest material 132 can be reduced. Furthermore, the probability of energy transfer from the T1 energy level of the host material 131 to the T1 energy level of the guest material 132 can also be reduced. Specifically, it is preferable that the weight ratio of the guest material 132 to the host material 131 is greater than 0 and less than 0.05.

[0052] <<(β)TTA process>> Next, we will explain the case where a singlet exciton is formed by the recombination of triplet excitons in the luminescent layer 130.

[0053] This section explains the situation where the T1 energy level of the host material 131 is lower than the T1 energy level of the guest material 132. Figure 1C This is a schematic diagram illustrating the energy level relationships at this point. Note that... Figure 1C The descriptions and symbols are as follows. Additionally, the T1 energy level of the host material 131 may be higher than the T1 energy level of the guest material 132. •Host (131): Main material 131 •Guest (132): Guest material 132 (fluorescent material) ·S FH S1 level of main material 131 ·T FH T1 energy level of main material 131 ·S FG S1 energy level of guest material 132 (fluorescent material) ·T FG : The T1 energy level of guest material 132 (fluorescent material).

[0054] In the host material 131, carrier recombination leads to the formation of excited states of the host material 131 due to exciton generation. At this time, when the generated exciton is a triplet exciton, the following reaction may occur: the two generated triplet excitons approach each other, and one of them is converted to the S1 energy level of the host material 131 (S... FH singlet excitons with energy of ) (refer to) Figure 1C The reaction is shown in general formula (G1) or (G2) below, and the number of triplet excitons decreases with the generation of singlet excitons.

[0055] .

[0056] The general formula (G1) is the following reaction: In the host material 131, two triplet excitons with a total spin quantum number of 0 ( 3 H ＊ ) form exciton pairs with a total spin quantum number of 0. 1 (HH) ＊ ), through higher-order singlet excitons excited by electronic or vibrational means ( 1 H ＊＊ Generate singlet excitons ( 1 H ＊ Furthermore, the general formula (G2) is the following reaction: in the host material 131, two triplet excitons with a total spin quantum number of 1 (atomic unit) 3 H ＊ ) form exciton pairs with a total spin quantum number of 1. 3 (HH) ＊ ), through higher-order triplet excitons excited by electronic or vibrational means ( 3 H ＊＊ Generate triplet excitons ( 3 H ＊In general formulas (G1) and (G2), H represents the ground state of the host material 131.

[0057] In general formulas (G1) and (G2), the number of triplet exciton pairs with a total spin quantum number of 1 (atomic unit) is three times that of triplet exciton pairs with a total spin quantum number of 0. That is, among excitons generated from two triplet excitons, the ratio of singlet excitons to triplet excitons regenerated according to statistical probability is 1:3. Furthermore, the density of triplet excitons in the luminescent layer 130 is very high (e.g., 1 × 10⁻⁶). 12 cm -3 In the above case, it is not necessary to consider the thermal deactivation of a triplet exciton; only the reaction between two closely spaced triplet excitons needs to be considered.

[0058] Therefore, based on one reaction of general formula (G1) and three reactions of general formula (G2), from eight triple excitons ( 3 H * A singlet exciton is generated in ) 1 H * ) and three higher-order triplet excitons excited electronically or vibrationally ( 3 H ** ).

[0059] .

[0060] The higher-order triplet excitons generated in general formula (G3) are excited electronically or vibrationally. 3 H ** It becomes a triple exciton due to rapid relaxation. 3 H * ), and then repeatedly induces the reaction of general formula (G3) with other triple excitons. Thus, in general formula (G3), considering all triple excitons ( 3 H * ) becomes a single exciton ( 1 H * In the case of five triple excitons ( 3 H * A singlet exciton is generated in ) 1 H * (General formula (G4)).

[0061] .

[0062] On the other hand, singlet excitons are directly generated through recombination of charge carriers injected from a pair of electrodes. 1 H * ) and triple exciton ( 3 H * The statistically significant proportion of () is 1H * : 3 H * =1:3. In other words, the probability of directly generating a singlet exciton through recombination of charge carriers injected from a pair of electrodes is 25%.

[0063] Therefore, by combining singlet excitons directly generated through recombination of charge carriers injected from a pair of electrodes with those generated through TTA, 8 singlet excitons (the sum of singlet and triplet excitons) can be generated from the 20 excitons directly generated through recombination of charge carriers injected from a pair of electrodes. That is, by utilizing TTA, the probability of singlet exciton generation can be increased from the current 25% to a maximum of 40% (=8 / 20).

[0064] .

[0065] In the singlet excited state of the host material 131 formed by the singlet exciton generated through the above process, the energy rises from the S1 energy level (S... FH ) migrates to the S1 energy level of the guest material 132, which has a lower energy level (S FG ) (reference Figure 1C Route A). Thus, the guest material 132, which becomes a singlet excited state, emits fluorescence.

[0066] Furthermore, when a triplet excited state is formed in the guest material 132 due to exciton generation from carrier recombination, the T1 energy level (T1) of the host material 131... FH The T1 energy level (T1) is lower than that of the guest material 132. FG In the case of T, FG The triple excitation energy does not deactivate, allowing its energy to migrate to T. FH (Reference Figure 1C Route B), and is used in TTA.

[0067] Additionally, at the T1 energy level (T1) of the guest material 132 FG The energy level is lower than the T1 level of the host material 131 (T FH In the case of [specific conditions], the preferred guest material 132 has a lower weight percentage than the host material 131. Specifically, the preferred weight ratio of guest material 132 to host material 131 is greater than 0 and less than 0.05. This reduces the probability of carrier recombination in the guest material 132. Furthermore, it reduces the probability of carrier recombination from the T1 energy level (T1) of the host material 131. FH ) to the T1 energy level of the guest material 132 (T FG The probability of energy transfer occurring.

[0068] As described above, by means of TTA, the triplet exciton formed in the luminescent layer 130 is transformed into a singlet exciton, thereby enabling efficient luminescence from the guest material 132.

[0069] <Probability of TTA Occurrence> As mentioned above, the luminous efficiency of a light-emitting element can be improved by utilizing TTA to increase the probability of singlet exciton generation. However, to obtain high luminous efficiency, it is important to increase the probability of TTA generation (also known as TTA efficiency). In other words, it is important to increase the proportion of delayed fluorescence component utilizing TTA in the light emitted by the light-emitting element.

[0070] As mentioned above, the TTA process can increase the generation probability of singlet excitons. Combined with the 25% of singlet excitons generated by the direct recombination of charge carriers injected from a pair of electrodes, the generation probability of singlet excitons can be increased to a maximum of 40%. In other words, the proportion of delayed fluorescence component originating from TTA in the light emitted by the light-emitting element can be increased to (40%-25%) / 40% = 37.5%.

[0071] <Increased luminescence efficiency due to the increased delayed fluorescence component> For example, in a blue-light-emitting element that contains a commonly used anthracene compound as the main material, the proportion of delayed fluorescence component originating from TTA in the emission is approximately 10%. Note that in this specification, delayed fluorescence refers to fluorescence that continues to emit light for 1 × 10⁻¹⁰ even after the continuous injection of charge carriers into the light-emitting layer has ceased. -6 The emission intensity is greater than 0.01 times the emission intensity when charge carriers are continuously injected.

[0072] In blue light-emitting elements, to improve the luminous efficiency of the element, it is necessary to increase the proportion of delayed fluorescence components originating from TTA in the light emission.

[0073] As described above, the TTA process is the process by which triplet excitons formed during the recombination process of charge carriers in the light-emitting layer 130 form singlet excitons. However, there is a problem: when the triplet excitons formed during the recombination process of charge carriers are deactivated due to other processes, they do not contribute to the formation of singlet excitons, resulting in a reduction in the delayed fluorescence component originating from TTA in the light emitted by the light-emitting element.

[0074] There are several reasons that can cause the triplet excitons to become inactive, one of which is the effect of charge carrier electrons in the luminescent layer 130. When the triplet excitons formed in the luminescent layer 130 interact with charge carrier electrons, they can sometimes become inactive.

[0075] Therefore, in a light-emitting element according to one aspect of the present invention, the deactivation of triplet excitons is reduced by appropriately adjusting the density of charge carrier electrons in the light-emitting layer 130. Since the charge carrier electrons in the light-emitting layer 130 are mainly supplied by the electron transport layer 118, it is only necessary to appropriately adjust the migration of charge carrier electrons from the electron transport layer 118 to the light-emitting layer 130. Therefore, it is sufficient to create a potential barrier between the LUMO energy level of the material used in the electron transport layer 118 and the LUMO energy level of the host material 131 contained in the light-emitting layer 130.

[0076] In a light-emitting element according to one aspect of the present invention, a barrier to suppress the migration of charge carrier electrons can be formed by making the LUMO energy level of the material used in the electron transport layer 118 lower than the LUMO energy level of the host material 131 contained in the light-emitting layer 130. When the migration of charge carrier electrons to the light-emitting layer 130 is suppressed, the recombination region of charge carriers in the light-emitting layer 130 extends towards the electron transport layer 118. In the recombination region, the density of triplet excitons and charge carrier electrons is reduced, thereby reducing the probability of triplet exciton deactivation. Of course, the decrease in triplet exciton density may also reduce the possibility of TTA itself. However, the inventors have found that, in fact, the suppression effect of triplet exciton deactivation caused by the decrease in electron density is greater than the adverse effects caused by the decrease in triplet exciton density, and the above structure is more prone to TTA.

[0077] Figure 2 This diagram shows energy levels when the LUMO level of the material used in electron transport layer 118 is higher or lower than the LUMO level of the host material 131 contained in light-emitting layer 130. Figure 2 It is known that when an energy barrier is formed between the electron transport layer 118 (ETL) and the light-emitting layer 130 (EmL), the recombination region extends towards the electron transport layer 118 (ETL), reducing the density of triplet excitons and electrons, thus decreasing the probability of triplet exciton quenching. This reduced probability of quenching increases the number of singlet excitons formed from triplet excitons through the TTA process, thereby increasing the delayed fluorescence component originating from TTA in the light emitted by the light-emitting element. Therefore, the luminous efficiency of the light-emitting element can be improved through one aspect of the present invention.

[0078] For example, by means of the present invention, the proportion of delayed fluorescence component originating from TTA in the light emitted by the light-emitting element can be 10% or more. Furthermore, by using a material with a deeper LUMO energy level in the electron transport layer 118, the proportion of delayed fluorescence component originating from TTA in the light emitted by the light-emitting element can be 15% or more. To achieve the above effects, it is preferable that there is a suitable potential barrier between the LUMO energy level of the material used in the electron transport layer 118 and the LUMO energy level of the host material 131 used in the light-emitting layer 130, and preferably the energy difference is 0.05 eV or more.

[0079] Here, when the LUMO level of the material used in the electron transport layer 118 is too deep, carrier electrons are less likely to migrate from the electron transport layer 118 to the light-emitting layer 130, affecting the carrier balance in the light-emitting layer 130, which may lead to a decrease in the luminous efficiency of the light-emitting element. Conversely, in order to appropriately suppress the migration of carrier electrons from the electron transport layer 118 to the light-emitting layer 130, the aforementioned barrier needs to be sufficiently large. Therefore, it is preferable that the difference between the LUMO level of the material used in the electron transport layer 118 and the LUMO level of the host material 131 contained in the light-emitting layer 130 is 0.05 eV or more and 0.3 eV or less.

[0080] Furthermore, as described above, the light-emitting element of one embodiment of the present invention can appropriately suppress carrier electron migration from the electron transport layer 118 to the light-emitting layer 130. Therefore, in the light-emitting layer 130, when the guest material 132, which is less abundant than the host material 131, traps carrier electrons, electron migration is less likely to occur in the light-emitting layer 130, thus preventing an unnecessary increase in the driving voltage. In view of the above, it is preferable that the LUMO energy level of the guest material is higher than that of the host material.

[0081] In light-emitting elements that emit delayed fluorescence, the delayed fluorescence is caused not only by TTA but also by thermally activated delayed fluorescence resulting from anti-intersystem crossing from a triplet excited state to a singlet excited state. To efficiently generate anti-intersystem crossing, the energy difference between the S1 and T1 levels is preferably less than 0.2 eV. In other words, when the energy difference between the S1 and T1 levels is greater than 0.2 eV, anti-intersystem crossing is less likely to occur. Therefore, to efficiently generate TTA, in compounds that generate TTA, the energy difference between the lowest excited singlet level and the lowest excited triplet level is preferably greater than 0.2 eV, more preferably greater than 0.5 eV.

[0082] The lowest excited singlet level can be observed from the absorption spectrum of an organic compound transitioning from its ground state to the lowest excited singlet state. Alternatively, the lowest excited singlet level can be estimated from the peak wavelength of the fluorescence emission spectrum of the organic compound. Furthermore, the lowest excited triplet level can be observed from the absorption spectrum of an organic compound transitioning from its ground state to the lowest excited triplet state; however, since this transition is forbidden, it is sometimes difficult to observe. In this case, the lowest excited triplet level can also be estimated from the peak wavelength of the phosphorescence emission spectrum of the organic compound. Therefore, the energy conversion difference between the peak wavelength of the fluorescence emission spectrum and the peak wavelength of the phosphorescence emission spectrum in the organic compound is preferably greater than 0.2 eV, more preferably 0.5 eV or greater.

[0083] <Hole transport layer and improvement of luminescence efficiency> The above describes the relationship between the material contained in the electron transport layer 118 and the luminous efficiency. Next, the relationship between the material contained in the hole transport layer 112 and the luminous efficiency will be explained.

[0084] Preferably, the LUMO energy level of the material contained in the hole transport layer 112 is higher than that of the host material 131. When the LUMO energy level of the material contained in the hole transport layer 112 is equal to that of the host material 131, the charge carrier electrons reaching the luminescent layer 130 will not remain in the luminescent layer 130 but will migrate to the hole transport layer 112. In this case, carrier recombination also occurs in the hole transport layer 112, which leads to a decrease in the recombination efficiency of the charge carriers in the luminescent layer 130. Unless the energy of the excitons generated in the hole transport layer 112 can be transferred to the luminescent material in the luminescent layer 130, the luminescence efficiency will decrease.

[0085] Therefore, it is preferable that the LUMO energy level of the material contained in the hole transport layer 112 is higher than that of the host material 131. Furthermore, it is more preferable that the LUMO energy level of the material contained in the hole transport layer 112 is 0.3 eV or higher than that of the host material 131. This effectively suppresses the migration of charge carrier electrons from the light-emitting layer 130 to the hole transport layer 112.

[0086] Suppressing the transfer of triplet excitation energy The following describes a method for suppressing the transfer of triplet excitation energy generated in the light-emitting layer 130 to the outside of the light-emitting layer 130 and keeping it in the light-emitting layer 130.

[0087] When the triplet excitation energy generated by the emissive layer 130 is transferred to the outside, the probability of TTA in the emissive layer 130 decreases. Therefore, by suppressing the transfer of triplet excitation energy, the high probability of TTA in the emissive layer can be maintained, thereby maintaining the high luminous efficiency of the light-emitting element.

[0088] First, in order to suppress the transfer of triplet excitation energy from the light-emitting layer 130 to the hole transport layer 112, it is preferable that the T1 energy level of the material contained in the hole transport layer 112 is higher than the T1 energy level of the host material 131 contained in the light-emitting layer 130. More preferably, the T1 energy level of the material contained in the hole transport layer 112 is 0.2 eV or higher than the T1 energy level of the host material 131 contained in the light-emitting layer 130.

[0089] Similarly, in order to suppress the transfer of triplet excitation energy from the light-emitting layer 130 to the electron transport layer 118, it is preferable that the T1 energy level of the material contained in the electron transport layer 118 is higher than the T1 energy level of the host material 131 contained in the light-emitting layer 130. More preferably, the T1 energy level of the material contained in the electron transport layer 118 is 0.2 eV or higher than the T1 energy level of the host material 131 contained in the light-emitting layer 130.

[0090] By suppressing the transfer of triplet excitation energy and keeping it in the light-emitting layer 130, the triplet excitation energy is not easily lost except for TTA. This maintains the high occurrence probability of TTA in the light-emitting layer 130, thereby maintaining the high luminous efficiency of the light-emitting element.

[0091] <Determination of delayed fluorescence components> An example of a method for evaluating the delayed fluorescence component in the emission from the luminescent layer is illustrated.

[0092] When the luminescent layer is continuously injected with charge carriers, the emission from the luminescent layer has an intensity that includes delayed fluorescence and other components. The emission intensity associated with delayed fluorescence reaches its maximum value when charge carriers are injected into the luminescent layer for a sufficiently long time. Therefore, the proportion of delayed fluorescence in the emission refers to the value under the condition that the luminescent layer is continuously injected with charge carriers.

[0093] The proportion of delayed fluorescence in luminescence can be evaluated by stopping carrier injection into the luminescent layer and measuring the gradually decaying luminescence. The lifetime from the cessation of carrier injection to luminescence quenching is a few μs, while the lifetime of typical fluorescence is a few ns. Therefore, delayed fluorescence can be evaluated by measuring the component that quenches within a few μs.

[0094] An exponential decay curve can be obtained by observing the decay of luminescence using a streak camera within a few μs after carrier injection into the luminescent layer. The luminescence at the moment carrier injection into the luminescent layer stops includes delayed fluorescence and other components, but after a few ns, only delayed fluorescence remains. By fitting an exponential function to this decay curve, a decay curve formula with time as a parameter can be obtained.

[0095] By substituting the time 0s into the decay curve formula, the intensity of the delayed fluorescence component at the point where carrier injection stops can be estimated. Since carriers are continuously injected into the luminescent layer immediately after the injection stops, the estimated intensity of the delayed fluorescence component is the intensity of the delayed fluorescence component under the condition of continuous carrier injection. From the luminescence intensity of the luminescent layer under the condition of continuous carrier injection and the intensity of the obtained delayed fluorescence component, the proportion of the delayed fluorescence component in the luminescence can be calculated.

[0096] Furthermore, the delayed fluorescence component in the emission of the luminescent layer may include not only delayed fluorescence originating from the TTA process involving intermolecular interactions, but also thermally activated delayed fluorescence (TADF) arising from energy transfer from the triplet excitation level to the singlet excitation level of a molecule. However, TADF only occurs under conditions where reverse energy transfer from the triplet excitation level to the singlet excitation level is possible. TADF only occurs when the energy levels of the two excitations are close and their band gap is below approximately 0.2 eV, and only a few molecules used in the luminescent layer meet this condition. Therefore, except when the luminescent layer uses molecules with a small band gap, TADF need not be considered. Thus, it can be assumed that the delayed fluorescence component in the emission emitted by this luminescent layer is essentially all delayed fluorescence originating from the TTA process.

[0097] For specific measurement methods, please refer to the examples.

[0098] Molecular orientation and light extraction efficiency In organic electron luminescence (EL), charge carriers are supplied to the luminescent layer and recombine within it, resulting in luminescence generated by the guest material contained within the luminescent layer. However, this luminescence is sometimes not isotropic; that is, the luminescence intensity is angle-dependent. The luminescence is perpendicular to the transition dipole moment of the guest material. Therefore, the orientation of the transition dipole moment affects the angle dependence of the luminescence. Since the orientation of the transition dipole moment of organic molecules is influenced by the molecular orientation of the organic molecules, the molecular orientation of the guest molecules sometimes results in anisotropic luminescence from the guest material.

[0099] The light-emitting layer comprises multiple molecules, with guest materials dispersed within the host material. Under certain manufacturing conditions, the guest molecules in the host material are not randomly oriented but rather oriented along a specific direction; that is, the molecular orientation of the guest molecules is biased towards one side. Therefore, when the guest material in the light-emitting layer has an orientation that facilitates light extraction to the outside of the light-emitting element, the light extraction efficiency of the light-emitting element becomes higher. Specifically, it is preferable that the guest molecules are oriented with their transition dipole moments parallel to the substrate surface.

[0100] When evaluating molecular orientation, it is difficult to directly observe how the transition dipole moments of molecules, especially guest materials, in the luminescent layer of an actual light-emitting element are oriented. Therefore, the following method was devised: p-polarized emission components are extracted by linearly polarizing the emission extracted from the luminescent layer, and the angle dependence of the integrated intensity of the obtained p-polarized emission spectrum across wavelengths from the visible to the near-infrared region (440 nm to 956 nm) is measured. The molecular orientation of the luminescent material within the luminescent layer is then derived by analyzing the results through calculation (simulation). The method for deriving molecular orientation is explained below.

[0101] Here, we will explain the state of random orientation of guest molecules within host molecules. When guest molecules are randomly oriented within host molecules, the sum of the transition dipole moments of all molecules has equal components in the mutually orthogonal x, y, and z directions. For example, in the case of layers existing on planes extending in the x and y directions, when the molecules in the layers are isotropically oriented, the components parallel to the layers have two dimensions and account for two-thirds (67%) of the total transition dipole moments, while the components perpendicular to the layers account for one-third (33%) of the total.

[0102] Next, the measurement will be explained. When measuring the luminescence intensity of the luminescent layer using the measuring device, the light is incident on and passes through a Glan-Taylor polarizer before it is incident on the detector. This allows the detector to measure only the polarization component in a specific direction.

[0103] Here, the luminescent transition dipole moment is determined by... Figures 3A to 3C The three components shown determine the polarization: A) component 181, which is the transition dipole moment in the direction parallel to the detector's observation direction 180, parallel to the emitting layer 130; B) component 182, which is the transition dipole moment in the direction perpendicular to the detector's observation direction 180, parallel to the emitting layer 130; and C) component 183, which is the transition dipole moment in the direction perpendicular to the emitting layer 130. Since component B cannot pass through the Glan-Taylor polarizer between the detector and the emitting layer 130, component B is not detected by the detector. In other words, p-polarization composed of components A and C is observed in this measurement.

[0104] Next, in order to evaluate the angle dependence of light emission, the detector 185 is set to the initial position in the direction perpendicular to the light emission layer 130, and the light emission layer 130 is gradually tilted. Figure 4A Indicates the initial state. Figure 4BThe diagram shows the state in which the luminescent layer 130 is tilted (tilt angle θ). Since the detector 185 is positioned in the front direction of the luminescent layer 130 in the initial state (tilt angle 0°), the emission originating from component C is not observed, but component A is observed. By increasing the tilt angle of the luminescent layer 130, the detector 185 can observe not only component A but also component C corresponding to the tilt angle. Therefore, the angle dependence of the emission can be evaluated.

[0105] Here, because the component of light emitted perpendicular to the light-emitting layer 130 has a very low intensity compared to the component parallel to the light-emitting layer 130, it is difficult to evaluate the C component under these conditions. Therefore, the thickness of each layer of the light-emitting element is pre-adjusted, and optical interference is used to reduce the light intensity of the component parallel to the light-emitting layer 130. That is, the light emitted from the front direction of the light-emitting element includes the component directly emitted from the light-emitting layer 130 and the component emitted after being reflected from the electrode by light generated in the light-emitting layer 130. By adjusting the thickness of each layer of the light-emitting element, the phases of these two components are reversed and cancel each other out. This weakens the A component and facilitates the observation of the C component.

[0106] The angle dependence of emission from the luminescent layer can be measured using the method described above. The shape of the graph obtained by plotting the measurement results with the tilt angle from the initial state of the luminescent layer 130 as the horizontal axis and the integrated intensity of the normalized emission spectrum as the vertical axis varies according to the ratio of A to C components in the emission. Here, the shapes of each graph corresponding to the change in the ratio of A to C components in the emission can be obtained through calculation (simulation). Therefore, the ratio of A to C components in the emission can be obtained by fitting the shape of the graph obtained from the measurement results to the calculated graph. Since the orientation of the transition dipole moment is an inherent property of the molecule (here, the guest material), information related to the orientation of the guest material can be obtained from the ratio of A to C components.

[0107] An A component exceeding 67% means that more of the transition dipole moment is parallel to the emissive layer. Simply put, an A component of 100% means a completely horizontal orientation. Since light is emitted from a direction perpendicular to the transition dipole moment, the closer the transition dipole moment is to being parallel to the emissive layer, the higher the light extraction efficiency. That is, the closer the A component is to 100%, the higher the luminous efficiency of the device.

[0108] Furthermore, through the above-described measurements and observations of the light emitted from the light-emitting element according to one aspect of the present invention, it can be seen that the guest material is not randomly oriented but has a specific orientation state, and the transition dipole moment deviates significantly from the vertical direction of the light-emitting layer. When the transition dipole moment deviates from the vertical direction of the light-emitting layer, the light emission in the vertical direction of the light-emitting layer becomes stronger. Therefore, it can be concluded that the high luminous efficiency of the light-emitting element according to one aspect of the present invention is related to the orientation state of the guest material.

[0109] In addition, detailed information on the measurement and calculation can be found in the description of the embodiments.

[0110] <Material> Next, the constituent elements of a light-emitting element according to one aspect of the present invention will be described.

[0111] Luminescent Layer In the luminescent layer 130, the weight ratio of the host material 131 is at least higher than that of the guest material 132, and the guest material 132 (fluorescent material) is dispersed in the host material 131. In the luminescent layer 130, an organic compound with a high proportion of delayed fluorescence components originating from triplet-triplet annihilation (TTA) in the emitted light is preferably used as the material suitable for use in the host material 131. Specifically, an organic compound with a TTA-derived delayed fluorescence component proportion of 20% or more is preferably used. Furthermore, in the luminescent layer 130, the host material 131 can be composed of one compound or multiple compounds.

[0112] In addition, there are no particular restrictions on the guest material 132 in the light-emitting layer 130, but it is preferable to use anthracene derivatives, tetraphenyl derivatives, chrysene derivatives, phenanthrene derivatives, pyrene derivatives, perylene derivatives, stilbene derivatives, acridinone derivatives, coumarin derivatives, phenoxazine derivatives, phenothiazine derivatives, etc., for example, the following materials can be used.

[0113] Specifically, examples include: 5,6-bis[4-(10-phenyl-9-anthrayl)phenyl]-2,2'-bipyridine (abbreviated as: PAP2BPy), 5,6-bis[4'-(10-phenyl-9-anthrayl)biphenyl-4-yl]-2,2'-bipyridine (abbreviated as: PAPP2BPy), N,N'-diphenyl-N,N'-bis[4-(9-phenyl-9H-fluorene-9-yl)phenyl]pyrene-1,6-diamine (abbreviated as: 1,6FLPAPrn), N,N'-bis(3-methylphenyl)-N,N'-bis[3-(9-phenyl-9H-fluorene-9-yl)phenyl]pyrene-1,6-diamine (abbreviated as: 1,6mMemFLPAPrn), N,N'-bis[4 ... and N,N'-bis[4-(9-phenyl-9H-fluorene-9-yl)phenyl]pyrene-1,6-diamine (abbreviated as: 1,6mMemFLPAPrn). [H-Carbazole-9-yl)phenyl]-N,N'-Diphenylstilbene-4,4'-diamine (abbreviation: YGA2S), 4-(9H-carbazole-9-yl)-4'-(10-phenyl-9-anthrayl)triphenylamine (abbreviation: YGAPA), 4-(9H-carbazole-9-yl)-4'-(9,10-diphenyl-2-anthrayl)triphenylamine (abbreviation: 2YGAPPA), N,9-diphenyl-N-[4-(10-phenyl-9-anthrayl)phenyl]-9H-carbazole-3-amine (abbreviation: PCAPA), perylene, 2,5,8,11-tetra(tert-butyl)perylene (abbreviation: TBP), 4-(10-phenyl-9-anthrayl)-4'-(9-phenyl-9H-carbazole-3-yl)triphenyl Amines (abbreviated as: PCPAPA), N,N''-(2-tert-butylanthracene-9,10-diylbis-4,1-phenylene)bis[N,N',N'-triphenyl-1,4-phenylenediamine] (abbreviated as: DPABPA), N,9-diphenyl-N-[4-(9,10-diphenyl-2-anthrayl)phenyl]-9H-carbazole-3-amine (abbreviated as: 2PCAPPA), N-[4-(9,10-diphenyl-2-anthrayl)phenyl]-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviated as: 2DPAPPA), N,N,N',N',N'',N'',N''',N'''-octaphenyldibenzo[g,p] chrysene-2,7,10,1 5-Tetraamine (abbreviated as: DBC1), Coumarin 30, N-(9,10-diphenyl-2-anthrayl)-N,9-diphenyl-9H-carbazole-3-amine (abbreviated as: 2PCAPA), N-[9,10-bis(1,1'-biphenyl-2-yl)-2-anthrayl]-N,9-diphenyl-9H-carbazole-3-amine (abbreviated as: 2PCABPhA), N-(9,10-diphenyl-2-anthrayl)-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviated as: 2DPAPA), N-[9,10-bis(1,1'-biphenyl-2-yl)-2-anthrayl]-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviated as: 2DPABPhA), 9,10-bis(1,1'-Biphenyl-2-yl)-N-[4-(9H-carbazol-9-yl)phenyl]-N-phenylanthracene-2-amine (abbreviation: 2YGABPhA), N,N,9-triphenylanthracene-9-amine (abbreviation: DPhAPhA), coumarin 6, coumarin 545T, N,N'-diphenylquinacridone (abbreviation: DPQd), rubrene, 5,12-bis(1,1'-biphenyl-4-yl)-6,11-diphenyltetraphenyl (abbreviation: BPT), 2-(2-{2-[4-(dimethylamino)phenyl]vinyl}-6-methyl) 2-{2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinazin-9-yl)vinyl]-4H-pyran-4-yl}malonium (DCM1), N,N,N',N'-tetra(4-methylphenyl)tetraphenyl-5,11-diamine (p-mPhTD), 7,14-diphenyl-N,N,N',N'-tetra(4-methylphenyl)acenaphthene[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]quinazin-9-yl)vinyl]-4H-pyran-4-yl}malonium (abbreviation: DCJTI), 2-{2-tert-butyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinazin-9-yl)vinyl]-4H-pyran-4-yl}malonium (abbreviation: DCJT) B), 2-(2,6-bis{2-[4-(dimethylamino)phenyl]vinyl}-4H-pyran-4-ylidene)malonitrile (abbreviated as BisDCM), 2-{2,6-bis[2-(8-methoxy-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinazin-9-yl)vinyl]-4H-pyran-4-ylidene}malonitrile (abbreviated as BisDCJTM), 5,10,15,20-tetraphenylbisbenzo[5,6]indo[1,2,3-cd:1',2',3'-lm]perylene, etc.

[0114] Alternatively, the light-emitting layer 130 may also include materials other than the host material 131 and the object material 132.

[0115] While there are no particular restrictions on the materials that can be used for the light-emitting layer 130, examples include: tris(8-hydroxyquinoline)aluminum(III) (abbreviated: Alq), tris(4-methyl-8-hydroxyquinoline)aluminum(III) (abbreviated: Almq3), bis(10-hydroxybenzo[h]quinoline)beryllium(II) (abbreviated: BeBq2), bis(2-methyl-8-hydroxyquinoline)(4-phenylphenol)aluminum(III) (abbreviated: BAlq), and bis... (8-Hydroxyquinoline)zinc(II) (abbreviated as Znq), bis[2-(2-benzoxazolyl)phenol]zinc(II) (abbreviated as ZnPBO), bis[2-(2-benzothiazolyl)phenol]zinc(II) (abbreviated as ZnBTZ) and other metal complexes; 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviated as PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazole- 2-[[2-yl]benzene (abbreviation: OXD-7), 3-(4-biphenyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviation: TAZ), 2,2',2''-(1,3,5-phenyltriyl)tris(1-phenyl-1H-benzimidazole) (abbreviation: TPBI), BPhen, BCP, 9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)benzene] Heterocyclic compounds such as [1,1'-carbazole](CO11); aromatic amine compounds such as 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB), N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (TPD), and 4,4'-bis[N-(spiro-9,9'-difluorene-2-yl)-N-phenylamino]biphenyl (BSPB). Additionally, condensed polycyclic aromatic compounds such as anthracene derivatives, phenanthrene derivatives, pyrene derivatives, chrysene derivatives, and dibenzo[g,p]chrysene derivatives can be cited.Specifically, examples include 9,10-diphenylanthracene (DPAnth), N,N-diphenyl-9-[4-(10-phenyl-9-anthrayl)phenyl]-9H-carbazole-3-amine (CzA1PA), 4-(10-phenyl-9-anthrayl)triphenylamine (DPhPA), 4-(9H-carbazole-9-yl)-4'-(10-phenyl-9-anthrayl)triphenylamine (YGAPA), and N,9-diphenyl-N-[4-(10H-carbazole-9-yl)-4'-(10H-anthrayl)triphenylamine (YGAPA). 2,9-diphenyl-N-{4-[4-(10-phenyl-9-anthryl)phenyl]phenyl}-9H-carbazole-3-amine (abbreviated as PCAPA), N,9-diphenyl-N-(9,10-diphenyl-2-anthryl)-9H-carbazole-3-amine (abbreviated as 2PCAPA), 6,12-dimethoxy-5,11-diphenylamine, N,N,N',N',N '',N'',N''',N'''-octaphenyldibenzo[g,p] chrysene-2,7,10,15-tetramine (abbreviation: DBC1), 9-[4-(10-phenyl-9-anthrayl)phenyl]-9H-carbazole (abbreviation: CzPA), 3,6-diphenyl-9-[4-(10-phenyl-9-anthrayl)phenyl]-9H-carbazole (abbreviation: DPCzPA), 9,10-bis(3,5-diphenylphenyl)anthracene (abbreviation: Examples of such substances include DPPA, 9,10-bis(2-naphthyl)anthracene (abbreviated as DNA), 2-tert-butyl-9,10-bis(2-naphthyl)anthracene (abbreviated as t-BuDNA), 9,9'-bianthracite (abbreviated as BANT), 9,9'-(stilbene-3,3'-diyl)phenanthrene (abbreviated as DPNS), 9,9'-(diphenylethylene-4,4'-diyl)phenanthrene (abbreviated as DPNS2), and 1,3,5-tris(1-pyrene)benzene (abbreviated as TPB3). Furthermore, one or more substances with a band gap larger than that of the aforementioned guest material 132 can be selected from these substances and known substances.

[0116] The light-emitting layer 130 may also be formed from two or more layers. For example, when the light-emitting layer 130 is formed by sequentially stacking a first light-emitting layer and a second light-emitting layer from the hole transport layer side, a material with hole transport properties can be used as the host material of the first light-emitting layer, and a material with electron transport properties can be used as the host material of the second light-emitting layer. In addition, the light-emitting layer 130 may include a first region containing a host material and a guest material, and a second region containing the host material.

[0117] Below, on Figure 1A The details of the other constituent elements of the light-emitting element 150 shown will be explained.

[0118] A pair of electrodes Electrodes 101 and 102 function to inject holes and electrons into the light-emitting layer 130. Electrodes 101 and 102 can be formed using metals, alloys, conductive compounds, and mixtures or stacks thereof. Typical examples of metals are aluminum; in addition, transition metals such as silver, tungsten, chromium, molybdenum, copper, and titanium can be used; alkali metals such as lithium or cesium; and Group 2 metals such as calcium or magnesium. Rare earth metals such as ytterbium (Yb) can also be used as transition metals. Alloys including the aforementioned metals can be used, for example, MgAg alloys and AlLi alloys. Conductive compounds include metal oxides such as indium tin oxide. Inorganic carbon materials such as graphene can also be used as conductive compounds. As described above, one or both of these materials can be formed by stacking multiple layers of these materials.

[0119] Additionally, one or both of the light-emitting electrodes 101 and 102 obtained from the light-emitting layer 130 are extracted. Therefore, at least one of the electrodes 101 and 102 has the function of allowing visible light to pass through. When a material with low light transmittance, such as a metal or alloy, is used for the light-extracting electrode, one or both of the electrodes 101 and 102 can be formed with a thickness sufficient to allow visible light to pass through (e.g., a thickness of 1 nm to 10 nm).

[0120] Hole Injection Layer The hole injection layer 111 has the function of lowering the injection barrier of holes from one of the pair of electrodes (electrode 101 or electrode 102) to promote hole injection, and is formed, for example, using transition metal oxides, phthalocyanine derivatives, or aromatic amines. Examples of transition metal oxides include molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, and manganese oxide. Examples of phthalocyanine derivatives include phthalocyanine or metal phthalocyanine. Examples of aromatic amines include benzidine derivatives or phenylenediamine derivatives. Polymer compounds such as polythiophene or polyaniline can also be used, typically poly(ethylene dioxythiophene) / poly(styrene sulfonic acid) as self-doped polythiophene.

[0121] As the hole injection layer 111, a layer comprising a composite material consisting of a hole-transporting material and a material having the property of receiving electrons from the hole-transporting material can be used. Alternatively, a stack of a layer containing a material having electron-receiving properties and a layer containing a hole-transporting material can be used. Charge transfer and acceptance can occur between these materials in a stationary state or in the presence of an electric field. Examples of materials having electron-receiving properties include organic acceptors such as quinone dimethane derivatives, tetrachlorobenzoquinone derivatives, and hexaazatriphenylene derivatives. Specifically, compounds with electron-withdrawing groups (halogen or cyano groups) such as 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinone dimethane (abbreviated: F4-TCNQ), chloroquinone, and 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviated: HAT-CN) can also be used. Transition metal oxides, such as oxides of group 4 to group 8 metals, can also be used. Specifically, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide, rhenium oxide, etc., can be used. Molybdenum oxide is particularly preferred because it is stable in the atmosphere, has low hygroscopicity, and is easy to handle.

[0122] As a hole transport material, materials with higher hole transport properties than electron transport properties can be used, preferably having a hole transport property of 1×10⁻⁶. -6 cm 2 Materials with hole mobility of / Vs or higher can be used. Specifically, aromatic amines, carbazole derivatives, aromatic hydrocarbons, stilbene derivatives, etc., can be used. The aforementioned hole transport materials can also be polymer compounds.

[0123] Examples of aromatic amine compounds that are highly hole-transporting materials include N,N'-bis(p-tolyl)-N,N'-diphenyl-p-phenylenediamine (DTDPPA), 4,4'-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (DPAB), N,N'-bis{4-[bis(3-methylphenyl)amino]phenyl}-N,N'-diphenyl-(1,1'-biphenyl)-4,4'-diamine (DNTPD), and 1,3,5-tris[N-(4-diphenylaminophenyl)-N-phenylamino]benzene (DPA3B).

[0124] Specific examples of carbazole derivatives are 3-[N-(9-phenylcarbazole-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviated as PCzPCA1), 3,6-bis[N-(9-phenylcarbazole-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviated as PCzPCA2), 3-[N-(1-naphthyl)-N-(9-phenylcarbazole-3-yl)amino]-9-phenylcarbazole (abbreviated as PCzPCN1), and 3-[4-(9-phenanthyl)-phenyl]-9-phenyl-9H-carbazole (abbreviated as PCPPn).

[0125] Other examples of carbazole derivatives include 4,4'-bis(N-carbazolyl)biphenyl (CBP), 1,3,5-tris[4-(N-carbazolyl)phenyl]benzene (TCPB), 9-[4-(10-phenyl-9-anthrayl)phenyl]-9H-carbazole (CzPA), and 1,4-bis[4-(N-carbazolyl)phenyl]-2,3,5,6-tetraphenylbenzene.

[0126] Examples of aromatic hydrocarbons include 2-tert-butyl-9,10-bis(2-naphthyl)anthracene (t-BuDNA), 2-tert-butyl-9,10-bis(1-naphthyl)anthracene, 9,10-bis(3,5-diphenylphenyl)anthracene (DPPA), 2-tert-butyl-9,10-bis(4-phenylphenyl)anthracene (t-BuDBA), 9,10-bis(2-naphthyl)anthracene (DNA), 9,10-diphenylanthracene (DPAnth), 2-tert-butylanthracene (t-BuAnth), 9,10-bis(4-methyl-1-naphthyl)anthracene (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-bis(1-naphthyl)anthracene, 2,3,6,7-tetramethyl-9,10-bis(2-naphthyl)anthracene, 9,9'-bianthracene, 10,10'-diphenyl-9,9'-bianthracene, 10,10'-bis(2-phenylphenyl)-9,9'-bianthracene, 10,10'-bis[(2,3,4,5,6-pentaphenyl)phenyl]-9,9'-bianthracene, anthracene, tetraphenylene, rubrogene, perylene, 2,5,8,11-tetra(tert-butyl)perylene, etc. Other examples are pentaphenylene and halophenylene. Thus, it is more preferable to have 1×10 -6 cm 2 Aromatic hydrocarbons with a hole mobility of / Vs or higher and a carbon number of 14 to 42.

[0127] Note that aromatic hydrocarbons can also have a vinyl skeleton. Examples of aromatic hydrocarbons with a vinyl skeleton are 4,4'-bis(2,2-diphenylvinyl)biphenyl (abbreviated as DVBBi) and 9,10-bis[4-(2,2-diphenylvinyl)phenyl]anthracene (abbreviated as DPVPA), etc.

[0128] Other examples include polymers such as poly(N-vinylcarbazole) (PVK), poly(4-vinyltriphenylamine) (PVTPA), poly[N-(4-{N'-[4-(4-diphenylamino)phenyl]phenyl-N'-phenylamino}phenyl)methacrylamide] (PTPDMA), and poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine] (Poly-TPD).

[0129] Hole transport layer Hole transport layer 112 is a layer containing a hole transport material, and the material exemplified as that used in hole injection layer 111 can be used. Hole transport layer 112 has the function of transporting holes injected into hole injection layer 111 to light-emitting layer 130, so it is preferable to have a HOMO level that is the same as or close to the highest occupied molecular orbital (HOMO) level of hole injection layer 111.

[0130] In addition to the materials exemplified as the material of the hole injection layer 111, the following substances with high hole transportability can also be used as the aforementioned hole transport material: aromatic amine compounds such as 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviated as NPB), N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (abbreviated as TPD), 4,4',4”-tris(N,N-diphenylamino)triphenylamine (abbreviated as TDATA), 4,4',4”-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine (abbreviated as MTDATA), 4,4'-bis[N-(spiro-9,9'-difluorene-2-yl)-N-phenylamino]biphenyl (abbreviated as BSPB), 4-phenyl-4'-(9-phenylfluorene-9-yl)triphenylamine (abbreviated as BPAFLP), etc. The material described here is primarily of 1×10 -6 cm 2 Materials with a hole mobility of / Vs or higher. However, any material whose hole transport is higher than its electron transport can be used, except for those described above. Furthermore, the layer including the material with high hole transport is not limited to a single layer, but can also be a layer composed of two or more layers of the above-mentioned materials.

[0131] Furthermore, the hole transport material contained in the hole transport layer 112 preferably has a higher LUMO energy level and a lower excitation triplet energy (T1) level than the host material 131 of the light-emitting layer. When the material contained in the hole transport layer 112 is equal to the LUMO energy level of the host material 131, the charge carrier electrons reaching the light-emitting layer 130 will not remain in the light-emitting layer 130 but will migrate to the hole transport layer 112. As a result, exciton recombination in the light-emitting layer 130 decreases, leading to a decrease in luminous efficiency. In addition, when the energy level is equal to the lower excitation triplet energy (T1) level of the host material 131, the triplet excitons generated in the light-emitting layer 130 will not undergo TTA in the light-emitting layer 130, and the triplet energy will diffuse into the hole transport layer 112, resulting in a decrease in luminous efficiency.

[0132] For example, 3-[4-(9-phenanthyl)-phenyl]-9-phenyl-9H-carbazole (abbreviated as PCPPn) is preferably used as the hole transport material contained in the hole transport layer 112. PCPPn has a suitablely high LUMO energy level and a minimum excited triplet energy (T1) level, and can appropriately... Suppressing the diffusion of charge carrier electrons from the light-emitting layer 130 to the hole transport layer 112 can increase the probability of TTA occurrence in the light-emitting layer 130, thereby improving the luminous efficiency of the light-emitting element.

[0133] Electron Transport Layer The electron transport layer 118 functions to transport electrons injected from one of the two electrodes (electrode 101 or electrode 102) through the electron injection layer 119 to the light-emitting layer 130. As the electron transport material, a material with higher electron transport than hole transport can be used, preferably having a electron transport capacity of 1×10⁻⁶. -6 cm 2 Materials with electron mobilities of / Vs or higher. Specifically, examples include metal complexes of quinoline ligands, benzoquinoline ligands, oxazole or thiazole ligands, oxadiazole derivatives, triazole derivatives, phenanthroline derivatives, pyridine derivatives, bipyridine derivatives, and pyrimidine derivatives.

[0134] Metal complexes containing quinoline or benzoquinoline skeletons include tris(8-hydroxyquinoline)aluminum(III) (abbreviated: Alq), tris(4-methyl-8-hydroxyquinoline)aluminum(III) (abbreviated: Almq3), bis(10-hydroxybenzo[h]quinoline)beryllium(II) (abbreviated: BeBq2), and bis(2-methyl-8-hydroxyquinoline)(4-phenylphenol)aluminum(III) (abbreviated: BAlq). In addition, metal complexes with oxazole or thiazole ligands, such as bis[2-(2-hydroxyphenyl)benzoxazole]zinc(II) (abbreviated: Zn(BOX)2) and bis[2-(2-hydroxyphenyl)benzothiazole]zinc(II) (abbreviated: Zn(BTZ)2), can also be used. Besides metal complexes, the following can also be used: 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazole-2-yl]benzene (abbreviation: OXD-7), 3-(4-biphenyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviation: TAZ), phenanthrene-2-ylbenzene (abbreviation: BPhen), benzoyl peroxide (abbreviation: BCP), etc. The substances described here are mainly those with a concentration of 1×10⁻⁶. -6 cm 2 Materials with an electron mobility of / Vs or higher. Furthermore, the electron transport layer 118 is not limited to a single layer, but may also consist of two or more layers composed of the aforementioned materials.

[0135] In particular, 2,2'-(pyridine-2,6-diyl)bis(4,6-diphenylpyrimidine) (abbreviated as: 2,6(P2Pm)2Py), 2,9-bis(naphthyl-2-yl)-4,7-diphenyl-1,10-phenanthroline (abbreviated as: NBPhen), and 2,2'-(pyridine-2,6-diyl)bis(4-phenylbenzo[h]quinazoline) (abbreviated as: 2,6(P-Bqn)2Py) are preferred as electron transport materials with deep LUMO.

[0136] Furthermore, as a deep electron transport material with high LUMO, substances containing a fused heterocyclic ring skeleton with a diazine or triazine skeleton in their molecular structure are preferred. Additionally, substances containing a pyrazine or pyrimidine skeleton in their molecular structure are also preferred.

[0137] Preferably, the LUMO energy level of the material used in the electron transport layer 118 is deeper than the LUMO energy level of the host material 131 contained in the light-emitting layer 130, thereby forming a barrier that suppresses the migration of charge carrier electrons. This barrier suppresses the migration of charge carrier electrons to the light-emitting layer 130, causing the charge carrier recombination region in the light-emitting layer 130 to extend towards the electron transport layer 118. In the recombination region, the density of triplet excitons and charge carrier electrons is reduced, thereby reducing the deactivation of excitons generated by injecting charge carrier electrons into triplet excitons.

[0138] Additionally, a layer for controlling the movement of electron carriers can be provided between the electron transport layer 118 and the light-emitting layer 130. This layer is a layer in which a small amount of a substance with high electron trapping properties is added to the aforementioned material with high electron transport properties, and this layer can regulate the balance of charge carriers by suppressing the migration of electron carriers. This structure is very effective in suppressing problems that occur when electrons pass through the light-emitting layer (e.g., reduced device lifetime).

[0139] Electron Injection Layer The electron injection layer 119 has the function of lowering the injection barrier of electrons from the electrode 102 and promoting electron injection. For example, it can use group 1 metals, group 2 metals or their oxides, halides, carbonates, etc. Alternatively, it can be a composite material of the aforementioned electron transport materials and materials having the property of supplying electrons to electron transport materials. Examples of materials with electron-donating properties include group 1 metals, group 2 metals or their oxides.

[0140] Furthermore, the aforementioned light-emitting layer, hole injection layer, hole transport layer, electron transport layer, and electron injection layer can all be formed by methods such as vapor deposition (including vacuum vapor deposition), inkjet printing, coating, and gravure printing. In addition to the materials mentioned above, inorganic compounds or polymeric compounds (oligomers, dendritic polymers, polymers) can also be used as the aforementioned light-emitting layer, hole injection layer, hole transport layer, electron transport layer, and electron injection layer.

[0141] Substrate Light-emitting element 150 is manufactured on a substrate made of glass, plastic, etc. The order in which the elements are stacked on the substrate can be either from the electrode 101 side or from the electrode 102 side.

[0142] Additionally, the substrate for forming the light-emitting element 150 can be made of materials such as glass, quartz, or plastic. Alternatively, a flexible substrate can be used. A flexible substrate is a flexible substrate that can be bent, such as a plastic substrate made of polycarbonate or polyarylate. Thin films, inorganic thin films formed by vapor deposition, etc., can also be used. Note that other materials can be used as long as they serve as a support in the manufacturing process of the light-emitting element and optical element. Alternatively, other materials can be used as long as they have the function of protecting the light-emitting element and optical element.

[0143] For example, various substrates can be used to form the light-emitting element 150. There are no particular limitations on the type of substrate. Examples of substrates include semiconductor substrates (e.g., single-crystal substrates or silicon substrates), SOI substrates, glass substrates, quartz substrates, plastic substrates, metal substrates, stainless steel substrates, substrates with stainless steel foil, tungsten substrates, substrates with tungsten foil, flexible substrates, laminated films, paper or substrate films containing fibrous materials, etc. Examples of glass substrates include barium borosilicate glass substrates, aluminum borosilicate glass substrates, and soda-lime glass substrates. Examples of flexible substrates, laminated films, substrate films, etc., include plastic substrates represented by polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), and polytetrafluoroethylene (PTFE). As an example, resins such as acrylic resins can be used. Alternatively, examples include polypropylene, polyester, polyvinyl fluoride, or polyvinyl chloride. Alternatively, examples could include polyamides, polyimides, aromatic polyamides, epoxy resins, inorganic vapor-deposited films, and paper.

[0144] Alternatively, a flexible substrate can be used as the substrate, and the light-emitting element can be formed directly on the flexible substrate. Alternatively, a release layer can be provided between the substrate and the light-emitting element. A release layer can be used when part or all of the light-emitting element is fabricated on the release layer, and then it is separated from the substrate and transferred to another substrate. In this case, the light-emitting element can also be transferred to a substrate with low heat resistance or a flexible substrate. Furthermore, as the aforementioned release layer, for example, a stacked structure of inorganic films such as tungsten film and silicon oxide film can be used, or a resin film such as polyimide can be formed on the substrate.

[0145] In other words, a light-emitting element can be formed on one substrate and then transferred to another substrate. Examples of substrates for transferring the light-emitting element, besides those mentioned above, include cellophane substrates, stone substrates, wood substrates, cloth substrates (including natural fibers (silk, cotton, hemp), synthetic fibers (nylon, polyurethane, polyester) or recycled fibers (acetate fiber, cupro fiber, rayon, recycled polyester), leather substrates, and rubber substrates. By using these substrates, it is possible to manufacture highly durable light-emitting elements, highly heat-resistant light-emitting elements, lightweight light-emitting elements, or thin light-emitting elements.

[0146] For example, a field-effect transistor (FET) can be formed on the aforementioned substrate, and a light-emitting element 150 can be formed on an electrode electrically connected to the FET. This allows the fabrication of an active matrix display device in which the driving of the light-emitting element 150 is controlled by the FET.

[0147] Furthermore, one aspect of the present invention will be described in this embodiment. Another aspect of the present invention will be described in other embodiments. However, the present invention is not limited to this. For example, although an example is shown in one aspect of the present invention where the proportion of delayed fluorescence component originating from TTA in the light emitted by the EL layer is 10% or more and the energy level of the LUMO of the material contained in the electron transport layer is lower than the energy level of the LUMO of the host material contained in the emitting layer, the present invention is not limited to this. Depending on the circumstances, in one aspect of the present invention, for example, the proportion of delayed fluorescence component in the light emitted by the EL layer may not be 10% or more. Alternatively, the energy level of the LUMO of the material contained in the electron transport layer may be higher than the energy level of the LUMO of the host material. Furthermore, although an example is shown in one aspect of the present invention where the energy level of the LUMO of the material contained in the electron transport layer is 0.05 eV or more lower than the energy level of the LUMO of the host material contained in the emitting layer, the present invention is not limited to this. Depending on the circumstances or conditions, in one aspect of the invention, for example, the energy level of the LUMO of the material contained in the electron transport layer may not be more than 0.05 eV lower than the energy level of the LUMO of the host material contained in the light-emitting layer.

[0148] The structure shown in this embodiment can be appropriately combined with the structures shown in other embodiments.

[0149] Implementation Method 2 Below, refer to Figures 5 to 7B An example of the structure of a light-emitting element according to one aspect of the present invention, as described in Embodiment 1, will be explained.

[0150] <Example 1 of the structure of a light-emitting element> Below, refer to Figure 5 An example of the structure of a light-emitting element according to one aspect of the present invention will be described. Figure 5 This is a cross-sectional view illustrating a light-emitting element according to one embodiment of the present invention.

[0151] Figure 5The light-emitting element 250 shown is a bottom-emitting (bottom-emitting) type light-emitting element that extracts light to one side of the substrate 200. Note that one aspect of the present invention is not limited to this; it may also be a top-emitting (top-emitting) type light-emitting element or a double-emitting (double-emitting) type light-emitting element that extracts the light emitted by the light-emitting element to both sides above and below the substrate 200 on the opposite side of the substrate 200 where the light-emitting element is formed.

[0152] The light-emitting element 250 includes electrodes 101 and 102 on the substrate 200. Light-emitting layers 123B, 123G, and 123R are disposed between electrodes 101 and 102. In addition, hole injection layer 111, hole transport layer 112, electron transport layer 118, and electron injection layer 119 are also disposed.

[0153] When both light-emitting elements 260a and 260b have a bottom-emitting structure, electrode 101 preferably has the function of transmitting light, and electrode 102 preferably has the function of reflecting light.

[0154] exist Figure 5 In the substrate 200, partition walls 140 are provided between regions 221B, 221G, and 221R, which are sandwiched between electrodes 101 and 102. The partition walls 140 are insulating. The partition walls 140 cover the ends of the electrodes 101 and have openings that overlap with the electrodes. By utilizing the partition walls 140, the electrodes 101 on the substrate 200 in each region can be divided into island-like structures.

[0155] Furthermore, the light-emitting layers 123B, 123G, and 123R preferably contain light-emitting materials that emit different colors. For example, when the light-emitting layers 123B, 123G, and 123R respectively contain light-emitting materials capable of emitting blue, green, and red light, the light-emitting element 250 can be used in a display device capable of full-color display. The film thickness of each light-emitting layer can be the same or different.

[0156] Furthermore, as shown in Embodiment 1, the LUMO energy level of the material used in the electron transport layer 118 is lower than the LUMO energy level of the host material contained in the light-emitting layer 123B. This allows for the fabrication of a light-emitting element in which the proportion of delayed fluorescence component in the light emitted by the light-emitting layer 123B is relatively high.

[0157] In addition, any one or more of the light-emitting layers 123B, 123G, and 123R can be stacked in two or more layers.

[0158] <Example 2 of the structure of a light-emitting element> Next, refer to Figure 6A and Figure 6BExplanation and Figure 5 Examples of different light-emitting element structures are shown.

[0159] Figure 6A and Figure 6B This is a cross-sectional view illustrating a light-emitting element according to one embodiment of the present invention. Figure 6A and Figure 6B In China, the use of Figure 5 The same shading line indicates that it has the same Figure 5 Parts with the same function are sometimes indicated by the same reference numerals, and sometimes their detailed descriptions are omitted.

[0160] Figure 6A and Figure 6B This is an example of a series-connected light-emitting element with a charge-generating layer 115 stacked between a pair of electrode layers. Figure 6A The light-emitting element 252 shown has a top-emission (top-emitting) structure that extracts light in a direction opposite to that of the substrate 200, and Figure 6B The light-emitting element 254 shown has a bottom-emitting (bottom-emitting) structure that extracts light to one side of the substrate 200. Note that one aspect of the invention is not limited to this structure, and it may also have a double-emitting (double-emitting) structure that extracts the light emitted by the light-emitting element to both above and below the substrate 200 on which the light-emitting element is formed.

[0161] Light-emitting elements 252 and 254 include electrodes 101, 102, 103, and 104 on the substrate 200. Furthermore, a light-emitting layer 160, a charge-generating layer 115, and a light-emitting layer 170 are disposed between electrodes 101 and 102, between electrodes 102 and 103, and between electrodes 102 and 104. Additionally, a hole injection layer 111, a hole transport layer 112, an electron transport layer 113, an electron injection layer 114, a hole injection layer 116, a hole transport layer 117, an electron transport layer 118, and an electron injection layer 119 are also included.

[0162] Additionally, electrode 101 includes a conductive layer 101a and a conductive layer 101b on and in contact with the conductive layer 101a. Furthermore, electrode 103 includes a conductive layer 103a and a conductive layer 103b on and in contact with the conductive layer 103a. Electrode 104 includes a conductive layer 104a and a conductive layer 104b on and in contact with the conductive layer 104a.

[0163] Figure 6A The light-emitting element 252 shown and Figure 6BThe light-emitting element 254 shown includes partition walls 140 between regions 222B held by electrodes 101 and 102, 222G held by electrodes 102 and 103, and 222R held by electrodes 102 and 104. The partition walls 140 are insulating. The partition walls 140 cover the ends of electrodes 101, 103, and 104 and include openings overlapping with these electrodes. By utilizing the partition walls 140, the electrodes on the substrate 200 in each region can be divided into island-like structures.

[0164] Light-emitting elements 252 and 254 have substrates 220 on which optical elements 224B, 224G, and 224R are respectively disposed in the direction in which light emitted from regions 222B, 222G, and 222R is extracted. Light emitted from each region passes through each optical element and exits to the outside of the light-emitting element. That is, light emitted from region 222B passes through optical element 224B and exits, light emitted from region 222G passes through optical element 224G and exits, and light emitted from region 222R passes through optical element 224R and exits.

[0165] Optical elements 224B, 224G, and 224R have the function of selectively transmitting incident light of a specific color. For example, light emitted from region 222B becomes blue light when it passes through optical element 224B, light emitted from region 222G becomes green light when it passes through optical element 224G, and light emitted from region 222R becomes red light when it passes through optical element 224R.

[0166] exist Figure 6A and Figure 6B The dashed arrows schematically illustrate the blue (B), green (G), and red (R) light emitted from each region through the optical elements.

[0167] A light-shielding layer 223 is included between each optical element. The light-shielding layer 223 has the function of blocking light emitted from adjacent areas. Alternatively, a structure without the light-shielding layer 223 may also be used.

[0168] Micro Cavity Furthermore, the light-emitting elements 252 and 254 have microcavity structures.

[0169] Light emitted from light-emitting layers 160 and 170 is resonant between a pair of electrodes (e.g., electrodes 101 and 102). Furthermore, in light-emitting elements 252 and 254, by adjusting the thickness of the conductive layers (conductive layers 101b, 103b, and 104b) in each region, the desired wavelength of light emitted from light-emitting layers 160 and 170 can be enhanced. Additionally, the thickness of at least one of the hole injection layer 111 and hole transport layer 112 can be different in each region to enhance the wavelength of light emitted from light-emitting layers 160 and 170.

[0170] For example, when the refractive index of the conductive material in electrodes 101 to 104 that has the function of reflecting light is less than the refractive index of the light-emitting layer 160 or 170, the optical distance between electrodes 101 and 102 is taken as m. B λ B / 2 (m) B λ represents a natural number. B The thickness of the conductive layer 101b in electrode 101 is adjusted in a manner that indicates the wavelength of the light enhanced in region 222B. Similarly, the optical distance between electrode 103 and electrode 102 is m. G λ G / 2 (m) G λ represents a natural number. G The thickness of the conductive layer 103b in electrode 103 is adjusted in a manner that indicates the wavelength of the light enhanced in region 222G. Furthermore, the optical distance between electrode 104 and electrode 102 is m. R λ R / 2 (m) R λ represents a natural number. R The thickness of the conductive layer 104b in the electrode 104 is adjusted in a manner that indicates the wavelength of the light enhanced in region 222R.

[0171] As described above, by adjusting the optical distance between a pair of electrodes in each region using a microcavity structure, light scattering and absorption near each electrode can be suppressed, thereby achieving high light extraction efficiency. Furthermore, in the above structure, conductive layers 101b, 103b, and 104b preferably have light-transmitting capabilities. The materials of conductive layers 101b, 103b, and 104b can be the same or different. Conductive layers 101b, 103b, and 104b can also each have two or more stacked layers.

[0172] because Figure 6AThe light-emitting element 252 shown has a top-surface emitting structure, so the conductive layer 101a of electrode 101, the conductive layer 103a of electrode 103, and the conductive layer 104a of electrode 104 preferably have the function of reflecting light. In addition, electrode 102 preferably has the function of transmitting light and reflecting light.

[0173] In addition, due to Figure 6B The light-emitting element 254 shown has a bottom-emitting structure, so the conductive layer 101a of electrode 101, the conductive layer 103a of electrode 103, and the conductive layer 104a of electrode 104 preferably have the functions of transmitting light and reflecting light. In addition, electrode 102 preferably has the function of reflecting light.

[0174] In light-emitting elements 252 and 254, conductive layers 101a, 103a, or 104a can be made of the same material or different materials. When conductive layers 101a, 103a, and 104a are made of the same material, the manufacturing cost of light-emitting elements 252 and 254 can be reduced. Alternatively, conductive layers 101a, 103a, and 104a can each be two or more layers stacked together.

[0175] Furthermore, as shown in Embodiment 1, the LUMO energy level of the material used in the electron transport layer 113 is lower than the LUMO energy level of the host material contained in the light-emitting layer 170. Additionally, the LUMO energy level of the material used in the electron transport layer 118 is lower than the LUMO energy level of the host material contained in the light-emitting layer 160. Therefore, a light-emitting element with a high proportion of delayed fluorescence component in the light emitted by the light-emitting layer can be manufactured.

[0176] For example, light-emitting layer 160 and light-emitting layer 170 may each have a two-layer structure, such as light-emitting layer 170a and light-emitting layer 170b. By using two light-emitting materials (a first compound and a second compound) that emit different colors as the two light-emitting layers, multiple light emission methods can be obtained simultaneously. In particular, it is preferable to select the light-emitting materials for each light-emitting layer so that white light emission can be obtained by combining the light emitted by light-emitting layer 160 and light-emitting layer 170.

[0177] The light-emitting layer 160 or the light-emitting layer 170 may also have a structure with three or more layers stacked, and may also include a layer without light-emitting material.

[0178] The structure shown in this embodiment can be appropriately combined with the structures shown in other embodiments.

[0179] Implementation Method 3 In this embodiment, refer to Figures 7A to 8BThe light-emitting element with a structure different from that shown in Embodiments 1 and 2, and the light-emitting mechanism of the light-emitting element, will be explained.

[0180] <Example 1 of the structure of a light-emitting element> Figure 7A This is a cross-sectional schematic diagram of the light-emitting element 450.

[0181] Figure 7A The light-emitting element 450 shown has multiple light-emitting units between a pair of electrodes (electrode 401 and electrode 402). Figure 7A (Light-emitting units 441 and 442 in the text). One light-emitting unit has the same characteristics as... Figure 1A The EL layer 100 shown has the same structure. That is to say, Figure 1A The light-emitting element 150 shown includes a light-emitting unit, and the light-emitting element 450 includes multiple light-emitting units. Note that in the following description of the light-emitting element 450, electrode 401 is used as the anode and electrode 402 is used as the cathode, but the functions in the light-emitting element 450 can also be interchanged.

[0182] In addition, Figure 7A In the light-emitting element 450 shown, light-emitting units 441 and 442 are stacked, and a charge-generating layer 445 is disposed between the light-emitting units 441 and 442. Furthermore, the light-emitting units 441 and 442 may have the same structure or different structures. For example, preferably, [the structure is...]. Figure 1A The EL layer 100 shown is used for the light-emitting unit 441.

[0183] That is, the light-emitting element 450 includes a light-emitting layer 420 and a light-emitting layer 430. In addition to the light-emitting layer 420, the light-emitting unit 441 also includes a hole injection layer 411, a hole transport layer 412, an electron transport layer 413, and an electron injection layer 414. Furthermore, in addition to the light-emitting layer 430, the light-emitting unit 442 also includes a hole injection layer 416, a hole transport layer 417, an electron transport layer 418, and an electron injection layer 419.

[0184] The charge generation layer 445 comprises a composite material consisting of an organic compound and an acceptor substance. As this composite material, a composite material suitable for use in the hole injection layer 111 shown in Embodiment 1 can be used. As the organic compound, various compounds such as aromatic amine compounds, carbazole compounds, aromatic hydrocarbons, and polymers (oligomers, dendritic polymers, polymers, etc.) can be used. Furthermore, it is preferable to use a compound with a hole mobility of 1 × 10⁻⁶. -6 cm 2Organic compounds with a density of / Vs or higher. However, any material other than these can be used as long as its hole transport capability is higher than its electron transport capability. Because composite materials composed of organic compounds and acceptor substances have good carrier injection and carrier transport capabilities, low-voltage and low-current driving can be achieved. Note that, as shown in the light-emitting unit 442, when the surface of the anode side of the light-emitting unit is in contact with the charge generation layer 445, the charge generation layer 445 can also function as a hole injection layer or a hole transport layer of the light-emitting unit. Therefore, a hole injection layer or a hole transport layer may not be provided in this light-emitting unit.

[0185] Note that the charge-generating layer 445 may also have a laminated structure combining a layer comprising a composite material consisting of an organic compound and an acceptor substance with a layer composed of other materials. For example, it may also have a structure combining a layer comprising a composite material consisting of an organic compound and an acceptor substance with a layer comprising a compound selected from substances having electron-donating properties and a compound having high electron transport properties. Alternatively, it may have a structure combining a layer comprising a composite material consisting of an organic compound and an acceptor substance with a transparent conductive film.

[0186] The charge generation layer 445 provided between the light-emitting units 441 and 442 can have any structure, as long as it can inject electrons into the light-emitting unit on one side and holes into the light-emitting unit on the other side when a voltage is applied to the electrodes 401 and 402. For example, in Figure 7A When a voltage is applied in such a way that the potential of electrode 401 is higher than that of electrode 402, the charge generation layer 445 injects electrons into light-emitting unit 441 and holes into light-emitting unit 442.

[0187] Although Figure 7A The description refers to a light-emitting element with two light-emitting units, but the same principle can be applied to light-emitting elements with three or more light-emitting units stacked together. As shown in light-emitting element 450, by arranging multiple light-emitting units between a pair of electrodes and separating them by a charge-generating layer, a light-emitting element can achieve high brightness emission while maintaining low current density and a longer lifespan. Additionally, a light-emitting element with low power consumption can be provided.

[0188] Furthermore, the light-emitting layer 420 comprises a host material 421 and a guest material 422. Additionally, the light-emitting layer 430 comprises a host material 431 and a guest material 432. The host material 431 comprises organic compound 431_1 and organic compound 431_2.

[0189] Furthermore, in this embodiment, the light-emitting layer 420 has a similar structure to... Figure 1AThe light-emitting layer 130 shown has the same structure. That is, the host material 421 and guest material 422 of the light-emitting layer 420 are equivalent to the host material 131 and guest material 132 of the light-emitting layer 130, respectively. Furthermore, the following description addresses the case where the guest material 432 of the light-emitting layer 430 is a phosphorescent material. Note that electrodes 401, 402, hole injection layers 411 and 416, hole transport layers 412 and 417, electron transport layers 413 and 418, electron injection layers 414 and 419 are equivalent to electrodes 101, 102, 111, 112, 118, and 119 shown in Embodiment 1, respectively. Therefore, detailed descriptions are omitted in this embodiment.

[0190] Furthermore, as shown in Embodiment 1, the LUMO energy level of the material used in the electron transport layer 413 is lower than the LUMO energy level of the host material contained in the light-emitting layer 420. Additionally, the LUMO energy level of the material used in the electron transport layer 418 is lower than the LUMO energy level of the host material contained in the light-emitting layer 430. Therefore, a light-emitting element with a high proportion of delayed fluorescence component in the light emitted by the light-emitting layer can be manufactured.

[0191] The luminescence mechanism of luminescent layer 420 The luminescence mechanism of luminescent layer 420 and Figure 1A The light-emitting mechanism of the light-emitting layer 130 shown is the same.

[0192] The luminescence mechanism of luminescent layer 430 The light-emitting mechanism of the light-emitting layer 430 will be explained below.

[0193] The organic compounds 431_1 and 431_2 in the light-emitting layer 430 form an excitocomplex. Here, organic compound 431_1 is used as the main material and organic compound 431_2 is used as an auxiliary material for explanation.

[0194] Although the combination of organic compounds 431_1 and 431_2 can be any combination that can form an excitocomplex in the light-emitting layer 444, a combination in which one organic compound is a hole-transporting material and the other organic compound is an electron-transporting material is preferred.

[0195] Figure 7B The energy level relationships between organic compounds 431_1 and 431_2 in the luminescent layer 430 and the guest material 432 are shown. Additionally, Figure 7B The records and symbols in the text represent the following: Host (431_1): Organic compound 431_1 (host material); Assist (431_2): Organic compound 431_2 (auxiliary material); Guest (432): Guest material 432 (phosphorescent material); Exciplex: Excitocomplex S PH The lowest energy level of the singlet excited state of organic compound 431_1; T PH The lowest energy level of the triplet excited state of organic compound 431_1; T PG The lowest energy level of the triplet excited state of guest material 432 (phosphorescent material); S E The lowest energy level of the singlet excited state of the excitocomplex; and T E : The lowest energy level of the triplet excited state of the excitocomplex.

[0196] The lowest energy level (S) of the singlet excited state of the excitocomplex formed by organic compounds 431_1 and 431_2 E The lowest energy level (T) of the triplet excited state of the excitokinetic complex. E ) Approaching each other (refer to) Figure 7B Route C).

[0197] By using the S of the excitocomplex E and T E The energy of both parties is transferred to the lowest energy level of the triplet excited state of the guest material 432 (phosphorescent material), resulting in luminescence (see reference). Figure 7B Route D).

[0198] Note that, in this specification and other documents, the processes described above for Route C and Route D may be referred to as exciplex-triplet energy transfer (ExTET).

[0199] Furthermore, when one of the organic compounds 431_1 and 431_2 receives a hole and the other an electron, they rapidly form an exciton complex when they approach each other. Alternatively, when one compound is in an excited state, it rapidly interacts with the other compound to form an exciton complex. Therefore, most of the excitons in the luminescent layer 430 exist as exciton complexes. Because the band gap of the exciton complex is narrower than that of organic compounds 431_1 and 431_2, the driving voltage can be reduced when exciton complexes are formed due to hole and electron recombination.

[0200] When the luminescent layer 430 has the above structure, the luminescence of the guest material 432 (phosphorescent material) from the luminescent layer 430 can be obtained efficiently.

[0201] Preferably, the emission peak from the light-emitting layer 420 has a shorter wavelength side than the emission peak from the light-emitting layer 430. Light-emitting elements using phosphorescent materials that emit light at short wavelengths tend to experience rapid brightness degradation. Therefore, using fluorescence to emit light at short wavelengths provides a light-emitting element with less brightness degradation.

[0202] Furthermore, by having the light-emitting layers 420 and 430 emit light of different wavelengths, a multi-color light-emitting element can be realized. In this case, the emission spectrum of the light-emitting element is formed by the synthesis of light with different emission peaks, and therefore the emission spectrum has at least two peaks.

[0203] Furthermore, the above structure is suitable for obtaining white light emission. White light emission can be obtained by making the light from the light-emitting layer 420 and the light from the light-emitting layer 430 complementary colors.

[0204] Alternatively, by using multiple luminescent materials with different emission wavelengths on one or both of the luminescent layers 420 and 430, it is also possible to obtain white light with high color rendering composed of three primary colors or four or more emission colors. In this case, one or both of the luminescent layers 420 and 430 can also be divided into layers, and each of the divided layers can contain different luminescent materials.

[0205] <Examples of materials that can be used in light-emitting layers> The materials that can be used in the light-emitting layer 420 and the light-emitting layer 430 will be described below.

[0206] Materials that can be used in the luminescent layer 420 As a material that can be used in the light-emitting layer 420, the material that can be used in the light-emitting layer 130 as shown in Embodiment 1 above can be referred to.

[0207] Materials that can be used in the luminescent layer 430 In the luminescent layer 430, the organic compound 431_1 (the host material) has the largest weight ratio, and the guest material 432 (the phosphorescent material) is dispersed in the organic compound 431_1 (the host material).

[0208] Examples of organic compounds 431_1 (host materials) include zinc or aluminum metal complexes, oxadiazole derivatives, triazole derivatives, benzimidazole derivatives, quinoxaline derivatives, dibenzoquinoxaline derivatives, dibenzothiophene derivatives, dibenzofuran derivatives, pyrimidine derivatives, triazine derivatives, pyridine derivatives, bipyridine derivatives, phenanthroline derivatives, etc. Other examples are aromatic amines or carbazole derivatives, etc.

[0209] Examples of guest materials 432 (phosphorescent materials) include iridium, rhodium, and platinum-based organometallic complexes or metal complexes, with organoiridium complexes, such as iridium-based ortho-metal complexes, being preferred. Examples of ortho-metallized ligands include 4H-triazole ligands, 1H-triazole ligands, imidazole ligands, pyridine ligands, pyrazine ligands, or isoquinoline ligands. Examples of metal complexes include platinum complexes with porphyrin ligands.

[0210] As organic compound 431_2 (auxiliary material), a substance capable of forming an excimer complex with organic compound 431_1 is used. In this case, organic compound 431_1, organic compound 431_2, and guest material 432 (phosphorescent material) are preferably selected such that the emission peak of the excimer complex overlaps with the absorption band of the triple MLCT (Metal to Ligand Charge Transfer) transition of guest material 432 (phosphorescent material) (specifically, the absorption band on the longest wavelength side). This allows for the realization of a light-emitting element with significantly improved luminescence efficiency. Note that when a thermally activated delayed fluorescence material is used instead of a phosphorescent material, the absorption band on the longest wavelength side is preferably a singlet absorption band.

[0211] As the luminescent material included in the luminescent layer 430, any material can be used, as long as it is capable of converting the triplet excited state energy into luminescence. Besides phosphorescent materials, thermally activated delayed fluorescence (TADF) materials can also be cited as materials capable of converting this triplet excited state energy into luminescence. Therefore, the description of "phosphorescent material" can be regarded as a description of "thermally activated delayed fluorescence material." Note that a thermally activated delayed fluorescence material refers to a material that can efficiently exhibit luminescence (fluorescence) from the singlet excited state by up-converting the triplet excited state into a singlet excited state (anti-intersystem crossing) with a small amount of thermal energy. Conditions for efficiently obtaining thermally activated delayed fluorescence include, for example, the energy difference between the triplet excited state energy level and the singlet excited state energy level being greater than 0 eV and less than 0.2 eV, preferably greater than 0 eV and less than 0.1 eV.

[0212] In addition, materials exhibiting thermally activated delayed fluorescence can be either materials that generate singlet excited states from triplet excited states through antisystem crossing alone, or materials that combine to form exciplexes (also known as exciplexes).

[0213] Furthermore, there are no restrictions on the emission colors of the light-emitting materials contained in the light-emitting layer 420 and the light-emitting materials contained in the light-emitting layer 430; they can be the same or different. The emission from each material is mixed and extracted to the outside of the element, so that, for example, when the two emission colors are in a complementary relationship, the light-emitting element can emit white light. When considering the reliability of the light-emitting element, the emission peak wavelength of the light-emitting material contained in the light-emitting layer 420 is preferably shorter than that of the light-emitting material contained in the light-emitting layer 430.

[0214] <Example 2 of the structure of a light-emitting element> The following is for reference Figure 8A and Figure 8B to and Figure 7A and Figure 7B The different structural examples of the light-emitting elements shown are illustrated.

[0215] Figure 8A This is a cross-sectional schematic diagram of the light-emitting element 452.

[0216] Figure 8A The light-emitting element 452 shown has an EL layer 400 sandwiched between a pair of electrodes (electrode 401 and electrode 402). Note that in the light-emitting element 452, electrode 401 is used as the anode and electrode 402 is used as the cathode.

[0217] Furthermore, the EL layer 400 includes a light-emitting layer 420 and a light-emitting layer 430. In addition to the light-emitting layers 420 and 430, the EL layer 400 in the light-emitting element 452 also includes a hole injection layer 411, a hole transport layer 412, an electron transport layer 418, and an electron injection layer 419. However, the above-described stacked structure is only an example, and the structure of the EL layer 400 in the light-emitting element 452 is not limited to this. For example, the stacking order of the above-described layers in the EL layer 400 can be changed. Alternatively, functional layers other than the above-described layers can be provided in the EL layer 400. These functional layers can, for example, have functions such as injecting charge carriers (electrons or holes), transporting charge carriers, suppressing charge carriers, or generating charge carriers.

[0218] Furthermore, the luminescent layer 420 comprises a host material 421 and a guest material 422. Additionally, the luminescent layer 430 comprises a host material 431 and a guest material 432. The host material 431 comprises organic compounds 431_1 and 431_2. The following description addresses the case where the guest material 422 is a fluorescent material and the guest material 432 is a phosphorescent material.

[0219] <Emission mechanism of luminescent layer 420> The luminescence mechanism of luminescent layer 420 and Figure 1A The light-emitting mechanism of the light-emitting layer 130 shown is the same.

[0220] <Emission mechanism of luminescent layer 430> The luminescence mechanism of luminescent layer 430 and Figure 7A The light-emitting mechanism of the light-emitting layer 430 shown is the same.

[0221] <Light emission mechanism of light-emitting layer 420 and light-emitting layer 430> The above describes the light-emitting mechanism of each of the light-emitting layers 420 and 430. As shown in the light-emitting element 452, when the light-emitting layers 420 and 430 are in contact with each other, even if energy transfer (especially triple excitation level energy transfer) occurs at the interface between the light-emitting layers 420 and 430 from the excitocomplex to the host material 421 of the light-emitting layer 420, the triple excitation energy can be converted into light emission in the light-emitting layer 420.

[0222] The T1 energy level of the host material 421 of the luminescent layer 420 is preferably lower than the T1 energy levels of the organic compounds 431_1 and 431_2 in the luminescent layer 430. In the luminescent layer 420, the S1 energy level of the host material 421 is preferably higher than the S1 energy level of the guest material 422 (fluorescent material), while the T1 energy level of the host material 421 is lower than the T1 energy level of the guest material 422 (fluorescent material).

[0223] Specifically, Figure 8B The energy level relationships are shown when TTA is used in the emitting layer 420 and ExTET is used in the emitting layer 430. Figure 8B The records and symbols in the text represent the following: Fluorescence EML (420): Fluorescent layer (emissive layer 420); Phosphorescence EML (430): Phosphorescent layer (emissive layer 430); S FH The lowest energy level of the singlet excited state of the host material 421; T FH The lowest energy level of the triplet excited state of the host material 421; S FG The lowest energy level of the singlet excited state of guest material 422 (fluorescent material); T FG The lowest energy level of the triplet excited state of guest material 422 (fluorescent material); S PHThe lowest energy level of the singlet excited state of the host material (organic compound 431_1); T PH The lowest energy level of the triplet excited state of the host material (organic compound 431_1); T PG The lowest energy level of the triplet excited state of guest material 432 (phosphorescent material); S E The lowest energy level of the singlet excited state of the excitocomplex; and T E : The lowest energy level of the triplet excited state of the excitocomplex.

[0224] like Figure 8B As shown, the exciton complex is only in an excited state, therefore exciton diffusion between exciton complexes is not easily achieved. The excitation energy level (S) of the exciton complex... E T E The excitation energy level (S) of the organic compound 431_1 (i.e., the host material of the phosphorescent material) in the luminescent layer 430 is higher than that of the organic compound 431_1. PH T PH The energy diffusion distance of the excitons from the exciton complex to organic compound 431_1 is low, thus preventing energy diffusion from the exciton complex to organic compound 431_2. In other words, the exciton diffusion distance of the excitons in the phosphorescent layer (emitting layer 430) is short, thus maintaining the luminescence efficiency of the phosphorescent layer (emitting layer 430). Even if a portion of the triplet excitation energy of the exciton complex in the phosphorescent layer (emitting layer 430) diffuses into the fluorescent layer (emitting layer 420) at the interface between the fluorescent layer (emitting layer 420) and the phosphorescent layer (emitting layer 430), the triplet excitation energy of the fluorescent layer (emitting layer 420) caused by this diffusion is converted into luminescence using TTA, thus reducing energy loss.

[0225] As described above, in the light-emitting element 452, by utilizing ExTET in the light-emitting layer 430 and TTA in the light-emitting layer 420 to reduce energy loss, a light-emitting element with high luminous efficiency can be realized. Furthermore, as shown in the light-emitting element 452, when a structure is adopted in which the light-emitting layer 420 and the light-emitting layer 430 are in contact with each other, the number of layers in the EL layer 400 can be reduced while minimizing the aforementioned energy loss. Therefore, a light-emitting element with low manufacturing cost can be realized.

[0226] Alternatively, a structure can be adopted in which the emitting layer 420 does not necessarily contact the emitting layer 430. In this case, energy transfer (especially triplet energy transfer) utilizing the Dexter mechanism from the excited state of the organic compound 431_1, organic compound 431_2, or guest material 432 (phosphorescent material) generated in the emitting layer 430 to the host material 421 or guest material 422 (fluorescent material) in the emitting layer 420 can be prevented. Therefore, the layer disposed between the emitting layer 420 and the emitting layer 430 only needs to have a thickness of about a few nm.

[0227] The layer disposed between the light-emitting layer 420 and the light-emitting layer 430 may contain a single material or a hole-transporting material and an electron-transporting material. When the layer contains only a single material, a bipolar material may also be used. Here, a bipolar material refers to a material whose electron-hole mobility ratio is less than 100. Hole-transporting materials or electron-transporting materials may also be used. Alternatively, at least one of them may be formed using the same material as the host material (organic compound 431_1 or organic compound 431_2) of the light-emitting layer 430. This makes the fabrication of the light-emitting element easier and reduces the driving voltage. Furthermore, a hole-transporting material and an electron-transporting material may be used to form an exciton complex, which can effectively suppress exciton diffusion. Specifically, energy transfer from the excited state of the host material (organic compound 431_1 or organic compound 431_2) or guest material 432 (phosphorescent material) of the light-emitting layer 430 to the host material 421 or guest material 422 (fluorescent material) of the light-emitting layer 420 can be prevented.

[0228] In the light-emitting element 452, the recombination region of charge carriers preferably has a certain degree of distribution. Therefore, the light-emitting layer 420 or 430 preferably has appropriate charge carrier trapping properties; in particular, the guest material 432 (phosphorescent material) in the light-emitting layer 430 preferably has electron trapping properties. Furthermore, the guest material 422 (fluorescent material) included in the light-emitting layer 420 preferably has hole trapping properties.

[0229] Furthermore, a preferred structure is one in which the peak value of the emission from the light-emitting layer 420 is closer to the shorter wavelength side compared to the peak value of the emission from the light-emitting layer 430. Light-emitting elements using phosphorescent materials that emit light at short wavelengths tend to experience rapid brightness degradation. Therefore, by employing fluorescence emission as the short wavelength emission, a light-emitting element with minimal brightness degradation can be provided.

[0230] Furthermore, by having the light-emitting layers 420 and 430 emit light of different wavelengths, a multicolor light-emitting element can be realized. In this case, since light with different emission peaks is synthesized, the emission spectrum becomes an emission spectrum with at least two peaks.

[0231] Furthermore, the above structure is suitable for obtaining white light emission. By making the light emitted by the light-emitting layer 420 and the light-emitting layer 430 complementary colors, white light emission can be obtained.

[0232] Furthermore, by using multiple luminescent materials with different emission wavelengths in the luminescent layer 420, it is also possible to obtain white light with high color rendering composed of three primary colors or four or more emission colors. In this case, the luminescent layer 420 can also be further divided into layers, with each of the divided layers containing a different luminescent material.

[0233] Materials that can be used in light-emitting layers The materials that can be used in the light-emitting layer 420 and the light-emitting layer 430 are described below.

[0234] Materials that can be used in the luminescent layer 420 In the luminescent layer 420, the host material 421 has the largest weight ratio, and the guest material 422 (fluorescent material) is dispersed in the host material 421. Preferably, the S1 energy level of the host material 421 is higher than the S1 energy level of the guest material 422 (fluorescent material), and the T1 energy level of the host material 421 is lower than the T1 energy level of the guest material 422 (fluorescent material).

[0235] Materials that can be used in the luminescent layer 430 In the luminescent layer 430, the host material (organic compound 431_1 or organic compound 431_2) has the largest weight ratio, and the guest material 432 (phosphorescent material) is dispersed in the host material (organic compound 431_1 and organic compound 431_2). Preferably, the T1 energy level of the host material (organic compound 431_1 and organic compound 431_2) of the luminescent layer 430 is higher than the T1 energy level of the guest material 422 (fluorescent material) of the luminescent layer 420.

[0236] As the host material (organic compound 431_1 and organic compound 431_2) and guest material 432 (phosphorescent material), it can be used as... Figure 7A and Figure 7B The light-emitting element 450 in the diagram is described.

[0237] In addition, the light-emitting layer 420 and the light-emitting layer 430 can be formed by methods such as vapor deposition (including vacuum vapor deposition), inkjet printing, coating, and gravure printing.

[0238] The structure shown in this embodiment can be implemented by appropriately combining it with the structures shown in other embodiments.

[0239] Implementation Method 4 In this embodiment, refer to Figure 9A and Figure 9BThe description includes a display device with a light-emitting element according to one aspect of the present invention.

[0240] Notice, Figure 9A This is a block diagram illustrating one aspect of the display device of the present invention. Figure 9B This is a circuit diagram illustrating the pixel circuitry included in a display device according to one aspect of the present invention.

[0241] <Explanation of the display device> Figure 9A The display device shown includes: a region having pixels with display elements (hereinafter referred to as pixel section 802); a circuit section (hereinafter referred to as driving circuit section 804) disposed outside the pixel section 802 and having circuitry for driving the pixels; a circuitry having the function of a protection element (hereinafter referred to as protection circuitry 806); and a terminal section 807. Alternatively, the protection circuitry 806 may be omitted.

[0242] Part or all of the drive circuit section 804 is preferably formed on the same substrate as the pixel section 802. This reduces the number of components or terminals. When part or all of the drive circuit section 804 is not formed on the same substrate as the pixel section 802, part or all of the drive circuit section 804 can be mounted by COG or TAB (Tape Automated Bonding).

[0243] The pixel unit 802 includes a circuit (hereinafter referred to as pixel circuit 801) for driving a plurality of display elements arranged in X rows (X is a natural number of 2 or more) and Y columns (Y is a natural number of 2 or more). The driving circuit unit 804 includes a circuit (hereinafter referred to as scan line driving circuit 804a) for outputting a signal (scan signal) for selecting pixels and a circuit (hereinafter referred to as signal line driving circuit 804b) for supplying signals (data signals) for driving the display elements for driving pixels.

[0244] The scan line drive circuit 804a includes a shift register, etc. The scan line drive circuit 804a receives signals for driving the shift register via terminal 807 and outputs signals. For example, the scan line drive circuit 804a receives a start pulse signal, a clock signal, etc., and outputs a pulse signal. The scan line drive circuit 804a has the function of controlling the potential of the wiring supplied with scan signals (hereinafter referred to as scan lines GL_1 to GL_X). Alternatively, multiple scan line drive circuits 804a can be provided, and scan lines GL_1 to GL_X can be controlled by each of the multiple scan line drive circuits 804a. Alternatively, the scan line drive circuit 804a can have the function of supplying an initialization signal. However, it is not limited to this; the scan line drive circuit 804a can also supply other signals.

[0245] The signal line driver circuit 804b includes a shift register, etc. The signal line driver circuit 804b receives signals (image signals) via terminal 807 to drive the shift register and from which data signals are derived. The signal line driver circuit 804b has the function of generating data signals to be written to the pixel circuit 801 based on the image signals. Furthermore, the signal line driver circuit 804b has the function of controlling the output of data signals in response to pulse signals generated by inputs such as start pulse signals and clock signals. Additionally, the signal line driver circuit 804b has the function of controlling the potential of the wiring (hereinafter referred to as data lines DL_1 to DL_Y) to which data signals are supplied. Alternatively, the signal line driver circuit 804b can supply initialization signals. However, it is not limited to this; the signal line driver circuit 804b can supply other signals.

[0246] The signal line drive circuit 804b can be configured using, for example, multiple analog switches. By sequentially turning on the multiple analog switches, the signal line drive circuit 804b can output a signal obtained by time-dividing the image signal as a data signal. Furthermore, the signal line drive circuit 804b may also include a shift register, etc.

[0247] A pulse signal from one of the multiple scan lines GL, which are supplied with scan signals, and a data signal from one of the multiple data lines DL, which are supplied with data signals, are input to each of the multiple pixel circuits 801. Furthermore, each of the multiple pixel circuits 801 controls the writing and holding of data signals via a scan line driving circuit 804a. For example, for the pixel circuit 801 in the m-th row and n-th column, a pulse signal is input to the pixel circuit 801 in the m-th row and n-th column via the scan line GL_m (where m is a natural number less than or equal to X) from the scan line driving circuit 804a, and a data signal is input from the signal line driving circuit 804b via the data line DL_n (where n is a natural number less than or equal to Y) according to the potential of the scan line GL_m.

[0248] Figure 9A The protection circuit 806 shown is connected, for example, to the scan line GL, which is the wiring between the scan line drive circuit 804a and the pixel circuit 801. Alternatively, the protection circuit 806 is connected to the data line DL, which is the wiring between the signal line drive circuit 804b and the pixel circuit 801. Alternatively, the protection circuit 806 may be connected to the wiring between the scan line drive circuit 804a and the terminal portion 807. Alternatively, the protection circuit 806 may be connected to the wiring between the signal line drive circuit 804b and the terminal portion 807. Furthermore, the terminal portion 807 refers to the portion provided with terminals for inputting power, control signals, and image signals to the display device from external circuitry.

[0249] The protection circuit 806 is a circuit that enables conduction between the connected wiring and other wiring when a potential outside a certain range is supplied to the wiring connected to it.

[0250] like Figure 9A As shown, by providing protection circuits 806 to the pixel section 802 and the driving circuit section 804 respectively, the display device's tolerance to overcurrent caused by ESD (Electro Static Discharge) and the like can be improved. However, the structure of the protection circuit 806 is not limited to this. For example, a structure in which the scan line driving circuit 804a is connected to the protection circuit 806 or a structure in which the signal line driving circuit 804b is connected to the protection circuit 806 can also be used. Alternatively, a structure in which the terminal section 807 is connected to the protection circuit 806 can also be used.

[0251] In addition, although Figure 9A The illustration shows an example of a drive circuit section 804 formed by a scan line drive circuit 804a and a signal line drive circuit 804b, but it is not limited to this. For example, it is also possible to form only the scan line drive circuit 804a and mount a separately prepared substrate on which the signal line drive circuit is formed (e.g., a drive circuit substrate formed of a single crystal semiconductor film or a polycrystalline semiconductor film).

[0252] <Structure Examples of Pixel Circuits> Figure 9A The multiple pixel circuits 801 shown can, for example, employ... Figure 9B The structure shown.

[0253] Figure 9B The pixel circuit 801 shown includes transistors 852 and 854, capacitor 862, and light-emitting element 872.

[0254] One of the source and drain electrodes of transistor 852 is electrically connected to the wiring (data line DL_n) to which the data signal is supplied. Furthermore, the gate electrode of transistor 852 is electrically connected to the wiring (scan line GL_m) to which the gate signal is supplied.

[0255] Transistor 852 has the function of controlling the writing of data signals.

[0256] One of the electrodes of capacitor 862 is electrically connected to the wiring supplied with the potential (hereinafter referred to as the potential supply line VL_a), and the other is electrically connected to the other of the source and drain electrodes of transistor 852.

[0257] Capacitor 862 functions as a storage capacitor for storing the data that has been written to it.

[0258] One of the source and drain electrodes of transistor 854 is electrically connected to the potential supply line VL_a. Furthermore, the gate electrode of transistor 854 is electrically connected to the other of the source and drain electrodes of transistor 852.

[0259] One of the anode and cathode of the light-emitting element 872 is electrically connected to the potential supply line VL_b, and the other is electrically connected to the other of the source and drain electrodes of the transistor 854.

[0260] As the light-emitting element 872, the light-emitting elements shown in Embodiments 1 to 3 can be used.

[0261] In addition, one of the potential supply lines VL_a and VL_b is given a high power supply potential VDD, and the other is given a low power supply potential VSS.

[0262] For example, in having Figure 9B In the display device with pixel circuit 801, through Figure 9A The scan line drive circuit 804a shown sequentially selects the pixel circuits 801 of each row and turns on the transistor 852 to write the data signal.

[0263] When transistor 852 is turned off, the pixel circuit 801, on which data is being written, remains in a held state. Furthermore, the amount of current flowing between the source and drain electrodes of transistor 854 is controlled according to the potential of the written data signal, and the light-emitting element 872 emits light with a brightness corresponding to the amount of current flowing through it. By performing the above steps line by line, an image can be displayed.

[0264] In addition, the light-emitting element of one aspect of the present invention can be applied to an active matrix method that includes active elements in the pixels of a display device or a passive matrix method that does not include active elements in the pixels of a display device.

[0265] In active matrix designs, various active elements (non-linear elements) besides transistors can be used as active elements. For example, MIM (Metal-Insulator-Metal) or TFD (Thin Film Diode) diodes can also be used. Because these elements require fewer manufacturing steps, manufacturing costs can be reduced or yields can be increased. Furthermore, due to their small size, the aperture ratio can be increased, thereby enabling low power consumption or high brightness.

[0266] In addition to the active matrix method, a passive matrix type that does not use active elements (non-linear elements) can also be used. Since no active elements (non-linear elements) are used, there are fewer manufacturing steps, thereby reducing manufacturing costs or increasing yield. Furthermore, since no active elements (non-linear elements) are used, the aperture ratio can be increased, enabling lower power consumption or higher brightness.

[0267] The structure shown in this embodiment can be implemented by appropriately combining it with the structures shown in other embodiments.

[0268] Implementation Method 5 In this embodiment, refer to Figures 10A to 14 The description includes a display device with a light-emitting element according to one aspect of the present invention, and an electronic device on which an input device is mounted.

[0269] <Instructions for the Touch Panel 1> Note that in this embodiment, a touch panel 2000 combining a display device and an input device will be described as an example of an electronic device. Additionally, a case using a touch sensor will be described as an example of an input device.

[0270] Figure 10A and Figure 10B This is a perspective view of the Touch Panel 2000. Additionally, in... Figure 10A and Figure 10B For clarity, the typical components of a touch panel 2000 are shown below.

[0271] Touch panel 2000 includes display device 2501 and touch sensor 2595 (see reference). Figure 10B Furthermore, the touch panel 2000 includes substrates 2510, 2570, and 2590. Additionally, substrates 2510, 2570, and 2590 are all flexible. Note that any one or all of substrates 2510, 2570, and 2590 may not be flexible.

[0272] Display device 2501 includes a plurality of pixels on substrate 2510 and a plurality of wirings 2511 capable of supplying signals to the pixels. The plurality of wirings 2511 are guided on the outer periphery of substrate 2510, a portion of which forms a terminal 2519. Terminal 2519 is electrically connected to FPC 2509 (1).

[0273] The substrate 2590 includes a touch sensor 2595 and a plurality of wirings 2598 electrically connected to the touch sensor 2595. The plurality of wirings 2598 are guided on the outer periphery of the substrate 2590, a portion of which forms a terminal. This terminal is electrically connected to FPC 2509 (2). Additionally, for clarity, in Figure 10B The electrodes and wiring of the touch sensor 2595, which are disposed on the back side of the substrate 2590 (the side opposite to the substrate 2510), are shown in solid lines in the middle.

[0274] As a touch sensor 2595, a capacitive touch sensor can be used, for example. Examples of capacitive touch sensors include surface capacitive and projected capacitive types.

[0275] As a projection-type capacitive sensor, it is mainly divided into self-capacitance type and mutual capacitance type, depending on the driving method. When using the mutual capacitance type, multiple points can be detected simultaneously, so it is the preferred method.

[0276] Notice, Figure 10B The touch sensor 2595 shown adopts the structure of a projection capacitive touch sensor.

[0277] In addition, the touch sensor 2595 can be used with various sensors that can detect the proximity or contact of objects such as fingers.

[0278] The projection-type capacitive touch sensor 2595 includes electrodes 2591 and 2592. Electrode 2591 is electrically connected to any one of a plurality of wirings 2598, while electrode 2592 is electrically connected to any other one of the plurality of wirings 2598.

[0279] like Figure 10A and Figure 10B As shown, electrode 2592 has the shape of multiple quadrilaterals arranged in one direction, with one corner of one quadrilateral connected to another corner of another quadrilateral.

[0280] Electrode 2591 is quadrilateral and is arranged in a direction that intersects the direction in which electrode 2592 extends.

[0281] Wiring 2594 is electrically connected to two electrodes 2591 that sandwich electrode 2592. In this case, the area of ​​the intersection between electrode 2592 and wiring 2594 is preferably as small as possible. This reduces the area of ​​regions without electrodes, thereby reducing transmittance deviation. Consequently, the brightness deviation of light transmitted through touch sensor 2595 can be reduced.

[0282] Note that the shapes of electrodes 2591 and 2592 are not limited to this and can have various shapes. For example, a structure can also be adopted in which multiple electrodes 2591 are arranged with as few gaps as possible between them, and multiple electrodes 2592 are spaced apart by an insulating layer to form areas that do not overlap with the electrodes 2591. In this case, it is preferable to provide a virtual electrode that is electrically insulated from these electrodes between two adjacent electrodes 2592, because the area of ​​regions with different transmittance can be reduced.

[0283] <Explanation of the display device> Next, refer to Figure 11A This section describes the detailed contents of display device 2501. Figure 11A It is along Figure 10B The cross-sectional view of the portion indicated by the dashed lines X1-X2 in the figure.

[0284] The display device 2501 includes a plurality of pixels configured in a matrix. Each pixel includes a display element and pixel circuitry for driving the display element.

[0285] The following description illustrates an example of using a light-emitting element that emits white light for a display element, but the display element is not limited to this. For example, EL elements emitting different colors of light can be included in a manner that allows adjacent pixels to emit different light.

[0286] For example, substrates 2510 and 2570 can be used with a water vapor transmission rate of [missing information]. The following are preferred The following are flexible materials. Alternatively, it is preferable to use a material whose thermal expansion coefficients are approximately the same as those of substrate 2510 and substrate 2570. For example, the linear expansion coefficient of the above-mentioned material is preferably 1 × 10⁻⁶. -3 / K or less, preferably 5×10 -5 Below / K, further preferably 1×10 -5 / K or below.

[0287] Note that substrate 2510 is a stacked structure, including an insulating layer 2510a to prevent impurities from diffusing into the light-emitting element, a flexible substrate 2510b, and an adhesive layer 2510c to bond the insulating layer 2510a and the flexible substrate 2510b. Additionally, substrate 2570 is a stacked structure, including an insulating layer 2570a to prevent impurities from diffusing into the light-emitting element, a flexible substrate 2570b, and an adhesive layer 2570c to bond the insulating layer 2570a and the flexible substrate 2570b.

[0288] Adhesive layers 2510c and 2570c can be made of, for example, polyester, polyolefin, polyamide (nylon, aramid, etc.), polyimide, polycarbonate or acrylic resin, polyurethane, epoxy resin. Alternatively, resins with siloxane bonds, such as silicone, can also be used.

[0289] Furthermore, a sealing layer 2560 is included between substrate 2510 and substrate 2570. The sealing layer 2560 preferably has a refractive index higher than that of air. Additionally, as... Figure 11A As shown, when light is extracted from one side of the sealing layer 2560, the sealing layer 2560 can also serve as an optical bonding layer.

[0290] Additionally, a sealant can be formed on the outer periphery of the sealing layer 2560. Using this sealant, a light-emitting element 2550R can be disposed in the area surrounded by the substrate 2510, substrate 2570, sealing layer 2560, and sealant. Furthermore, an inert gas (nitrogen or argon, etc.) can be used instead of the sealing layer 2560. A desiccant can be placed within this inactive gas to absorb moisture. Alternatively, ultraviolet-curable or thermosetting resins can be used, such as PVC (polyvinyl chloride) resins, acrylic resins, polyimide resins, epoxy resins, silicone resins, PVB (polyvinyl butyral) resins, or EVA (ethylene vinyl acetate) resins. As the aforementioned sealant, epoxy resins or glass powder are preferred, for example. Furthermore, as the material used for the sealant, a material that does not allow moisture or oxygen to permeate is preferred.

[0291] Additionally, the display device 2501 includes a pixel 2502R. Furthermore, the pixel 2502R includes a light-emitting module 2580R.

[0292] Pixel 2502R includes a light-emitting element 2550R and a transistor 2502t that can supply power to the light-emitting element 2550R. Note that the transistor 2502t is used as part of the pixel circuit. Furthermore, the light-emitting module 2580R includes the light-emitting element 2550R and a color layer 2567R.

[0293] The light-emitting element 2550R includes a lower electrode, an upper electrode, and an EL layer between the lower electrode and the upper electrode. For example, the light-emitting elements shown in Embodiments 1 to 4 can be used as the light-emitting element 2550R.

[0294] Alternatively, a microcavity structure can be used between the lower and upper electrodes to enhance the intensity of light at a specific wavelength.

[0295] In addition, when the sealing layer 2560 is disposed on the light extraction side, the sealing layer 2560 contacts the light-emitting element 2550R and the coloring layer 2567R.

[0296] The coloring layer 2567R is located in the area overlapping with the light-emitting element 2550R. As a result, a portion of the light emitted from the light-emitting element 2550R passes through the coloring layer 2567R and is emitted to the outside of the light-emitting module 2580R as shown by the arrow in the figure.

[0297] The display device 2501 includes a light-shielding layer 2567BM on the side that extracts light. The light-shielding layer 2567BM is arranged to surround the color layer 2567R.

[0298] The color layer 2567R only needs to have the function of allowing light in a specific wavelength range to pass through. For example, a color filter that allows light in the red wavelength range to pass through, a color filter that allows light in the green wavelength range to pass through, a color filter that allows light in the blue wavelength range to pass through, and a color filter that allows light in the yellow wavelength range to pass through can be used. Each color filter can be formed by printing, inkjet printing, etching using photolithography, etc., using various materials.

[0299] Furthermore, an insulating layer 2521 is provided in the display device 2501. The insulating layer 2521 covers the transistor 2502t. In addition, the insulating layer 2521 has the function of flattening the unevenness caused by pixel circuits. Furthermore, the insulating layer 2521 can suppress impurity diffusion. As a result, the reliability reduction of transistors such as 2502t due to impurity diffusion can be suppressed.

[0300] Furthermore, a light-emitting element 2550R is formed on an insulating layer 2521. Additionally, a partition wall 2528 is provided such that it overlaps with the end of the lower electrode included in the light-emitting element 2550R. Furthermore, spacers controlling the spacing between the substrate 2510 and the substrate 2570 can be formed on the partition wall 2528.

[0301] The scan line driving circuit 2503g(1) includes a transistor 2503t and a capacitor 2503c. The driving circuit and the pixel circuit can be formed on the same substrate in the same process.

[0302] Additionally, a signal-supplying wiring 2511 is provided on the substrate 2510. Furthermore, a terminal 2519 is provided on the wiring 2511. The FPC2509(1) is electrically connected to the terminal 2519. Furthermore, the FPC2509(1) has the function of supplying video signals, clock signals, start signals, reset signals, etc. Additionally, a printed circuit board (PWB) can also be mounted on the FPC2509(1).

[0303] In the display device 2501, transistors of various structures can be used. Figure 11A This illustration demonstrates the use of a bottom-gate transistor, but the invention is not limited to this example; other examples may be used. Figure 11BThe top-gate transistor shown is suitable for display device 2501.

[0304] Furthermore, there are no particular restrictions on the polarity of transistors 2502t and 2503t. N-channel and P-channel transistors, or either N-channel or P-channel transistors, can be used for these transistors. Additionally, there are no particular restrictions on the crystallinity of the semiconductor film used for transistors 2502t and 2503t. For example, amorphous semiconductor films and crystalline semiconductor films can be used. Furthermore, as the semiconductor material, Group 13 semiconductors (e.g., gallium-containing semiconductors), Group 14 semiconductors (e.g., silicon-containing semiconductors), compound semiconductors (including oxide semiconductors), organic semiconductors, etc., can be used. Using an oxide semiconductor with a bandgap of 2 eV or more, preferably 2.5 eV or more, and more preferably 3 eV or more, for any one or both of transistors 2502t and 2503t is preferred because it reduces the off-state current of the transistors. Examples of oxide semiconductors include In-Ga oxides and In-M-Zn oxides (where M represents aluminum (Al), gallium (Ga), yttrium (Y), zirconium (Zr), lanthanum (La), cerium (Ce), tin (Sn), hafnium (Hf), or neodymium (Nd)).

[0305] <Explanation of Touch Sensor> Next, refer to Figure 11C This section provides detailed information about the touch sensor 2595. Figure 11C Equivalent to along Figure 10B The cross-sectional view of the portion indicated by the dashed lines X3-X4 in the figure.

[0306] The touch sensor 2595 includes: electrodes 2591 and 2592 arranged in an interleaved shape on a substrate 2590; an insulating layer 2593 covering the electrodes 2591 and 2592; and wiring 2594 that electrically connects adjacent electrodes 2591.

[0307] Electrodes 2591 and 2592 are formed using a transparent conductive material. Transparent conductive materials can be indium oxide, indium tin oxide, indium zinc oxide, zinc oxide, gallium-added zinc oxide, or other conductive oxides. Alternatively, a graphene-containing film can be used. For example, a graphene-containing film can be formed by reducing a graphene oxide-containing film. The reduction method can include heating.

[0308] Electrodes 2591 and 2592 are formed by, for example, by sputtering a transparent conductive material onto a substrate 2590, and then removing unwanted portions by various patterning techniques such as photolithography.

[0309] In addition, as materials used for the insulating layer 2593, in addition to resins such as acrylic resin, epoxy resin, and silicone resins with siloxane bonds, inorganic insulating materials such as silicon oxide, silicon oxynitride, and aluminum oxide can also be used.

[0310] Furthermore, the opening reaching electrode 2591 is provided in insulating layer 2593, and wiring 2594 is electrically connected to adjacent electrode 2591. Since the aperture ratio of the touch panel can be increased, a light-transmitting conductive material can be used for wiring 2594. Additionally, since resistance can be reduced, a material with higher conductivity than electrode 2591 and electrode 2592 can be used for wiring 2594.

[0311] Electrodes 2592 extend in one direction, and multiple electrodes 2592 are arranged in a stripe pattern. In addition, wiring 2594 is arranged to intersect with electrodes 2592.

[0312] A pair of electrodes 2591 are provided, sandwiched between an electrode 2592. Additionally, wiring 2594 electrically connects the pair of electrodes 2591.

[0313] In addition, the multiple electrodes 2591 do not necessarily have to be arranged in a direction orthogonal to one electrode 2592, and can also be arranged to form an angle greater than 0° and less than 90°.

[0314] In addition, a wiring 2598 is electrically connected to an electrode 2591 or an electrode 2592. Furthermore, a portion of the wiring 2598 is used as a terminal. The wiring 2598 can be made of, for example, metallic materials such as aluminum, gold, platinum, silver, nickel, titanium, tungsten, chromium, molybdenum, iron, cobalt, copper, or palladium, or alloys containing such metallic materials.

[0315] In addition, by providing an insulating layer covering the insulating layer 2593 and the wiring 2594, the touch sensor 2595 can be protected.

[0316] In addition, the connection layer 2599 is electrically connected to the wiring 2598 and the FPC 2509 (2).

[0317] As the connecting layer 2599, anisotropic conductive film (ACF) or anisotropic conductive paste (ACP) can be used.

[0318] <Instructions regarding the touch panel 2> Next, refer to Figure 12A This section details the Touch Panel 2000. Figure 12A Equivalent to along Figure 10A The cross-sectional view of the portion indicated by the dashed lines X5-X6 in the figure.

[0319] exist Figure 12A In the touch panel 2000 shown, Figure 11A The described display device 2501 and Figure 11C The touch sensor 2595 described is attached together.

[0320] in addition, Figure 12A The touch panel 2000 shown, in addition to Figure 11A and Figure 11C In addition to the structure described, it also includes adhesive layer 2597 and anti-reflective layer 2567p.

[0321] The adhesive layer 2597 is provided in contact with the wiring 2594. Note that the adhesive layer 2597 adheres the substrate 2590 to the substrate 2570 such that the touch sensor 2595 overlaps the display device 2501. Furthermore, the adhesive layer 2597 preferably has light transmittance. Additionally, as the adhesive layer 2597, a thermosetting resin or a UV-curable resin can be used. For example, acrylic resins, urethane resins, epoxy resins, or silicone resins can be used.

[0322] The anti-reflective layer 2567p is located in the area overlapping with the pixel. For example, a circular polarizer can be used as the anti-reflective layer 2567p.

[0323] Next, refer to Figure 12B to and Figure 12A The different structures of the touch panels shown are explained.

[0324] Figure 12B This is a cross-sectional view of the touch panel 2001. Figure 12B The touch panel 2001 shown is Figure 12A The difference between the touch panel 2000 shown is the position of the touch sensor 2595 relative to the display device 2501. The different parts will be described in detail here, while the description of the touch panel 2000 can be used as a reference for the other identical parts.

[0325] The color layer 2567R is located below the light-emitting element 2550R. Furthermore, Figure 12B The light-emitting element 2550R shown emits light toward the side where the transistor 2502t is disposed. Thus, a portion of the light emitted by the light-emitting element 2550R passes through the coloring layer 2567R, and... Figure 12B The arrow in the image indicates that the light is emitted to the outside of the 2580R light-emitting module.

[0326] In addition, a touch sensor 2595 is disposed on one side of the substrate 2510 of the display device 2501.

[0327] The adhesive layer 2597 is located between the substrate 2510 and the substrate 2590, and attaches the display device 2501 and the touch sensor 2595 together.

[0328] like Figure 12A and Figure 12B As shown, light is emitted from the light-emitting element onto one or both sides of the top and bottom surfaces of the substrate.

[0329] <Explanation of the Touch Panel Driver Method> Next, refer to Figure 13A and Figure 13B An example of a touch panel driving method is provided.

[0330] Figure 13A This is a block diagram illustrating the structure of a mutual capacitance touch sensor. Figure 13A The diagram shows a pulse voltage output circuit 2601 and a current detection circuit 2602. Additionally, in... Figure 13A In the diagram, six wirings X1 to X6 represent the electrode 2621 to which a pulse voltage is applied, and six wirings Y1 to Y6 represent the electrode 2622 to which a change in current is detected. Furthermore, Figure 13A The capacitor 2603 is shown as formed by overlapping electrodes 2621 and 2622. Note that the functions of electrodes 2621 and 2622 can be interchanged.

[0331] The pulse voltage output circuit 2601 is used to sequentially apply pulse voltages to the wiring from X1 to X6. By applying pulse voltages to the wiring from X1 to X6, an electric field is generated between electrodes 2621 and 2622 that form capacitor 2603. For example, when the electric field between the electrodes is blocked, a change (mutual capacitance) occurs in capacitor 2603. This change can be used to detect the approach or contact of a detected object.

[0332] The current detection circuit 2602 is used to detect changes in current in the wiring Y1 to Y6 caused by changes in the mutual capacitance of capacitor 2603. When no object is approaching or making contact, the detected current value in wiring Y1 to Y6 remains unchanged. On the other hand, when the mutual capacitance decreases due to the approach or contact of an object being detected, a decrease in the current value is detected. Alternatively, an integrating circuit or similar device can be used for current detection.

[0333] then, Figure 13B Show Figure 13A The diagram shows the timing of the input / output waveforms in a mutual capacitance touch sensor. Figure 13B In this process, the detection of objects in each row and column is performed during a frame. Additionally, in... Figure 13BThe diagram shows the periods during which no object was detected (not touched) and the periods during which an object was detected (touched). Furthermore, Figure 13B The waveforms of the voltage values ​​corresponding to the current values ​​detected for wiring Y1 to Y6 are shown.

[0334] A pulse voltage is sequentially applied to the wiring from X1 to X6, and the waveforms of the wiring from Y1 to Y6 change accordingly. When no object is near or in contact with the device, the waveforms of Y1 to Y6 change in the same way as the voltage changes of the wiring from X1 to X6. On the other hand, when an object is near or in contact with the device, the current value decreases, and therefore the waveform of the corresponding voltage value also changes.

[0335] Thus, by detecting changes in mutual capacitance, the proximity or contact of the object being tested can be detected.

[0336] <Explanation of Sensor Circuit> Additionally, as a touch sensor, Figure 13A Although the structure shown is a passive matrix touch sensor with only capacitor 2603 provided at the intersection of the wiring, an active matrix touch sensor including transistors and capacitors can also be used. Figure 14 An example of the sensor circuitry included in an active matrix touch sensor is shown.

[0337] Figure 14 The sensor circuit shown includes capacitor 2603, transistor 2611, transistor 2612 and transistor 2613.

[0338] A signal G2 is applied to the gate of transistor 2613. A voltage VRES is applied to one of the source and drain of transistor 2613, and the other of the source and drain of transistor 2613 is electrically connected to one electrode of capacitor 2603 and the gate of transistor 2611. One of the source and drain of transistor 2611 is electrically connected to one of the source and drain of transistor 2612, and a voltage VSS is applied to the other of the source and drain of transistor 2611. A signal G1 is applied to the gate of transistor 2612, and the other of the source and drain of transistor 2612 is electrically connected to wiring ML. A voltage VSS is applied to the other electrode of capacitor 2603.

[0339] Next, for Figure 14 The operation of the sensor circuit will be explained. First, by applying a potential as signal G2 to turn on transistor 2613, a potential corresponding to voltage VRES is applied to node n, which is connected to the gate of transistor 2611. Next, by applying a potential as signal G2 to turn off transistor 2613, the potential of node n is maintained.

[0340] Then, as the detected object, such as a finger, approaches or touches it, the mutual capacitance of capacitor 2603 changes, and the potential of node n changes with it due to VRES.

[0341] During readout, a potential is applied as signal G1 to turn on transistor 2612. The current flowing through transistor 2611, i.e., the current flowing through wiring ML, varies according to the potential of node n. By detecting this current, the proximity or contact of the object being detected can be determined.

[0342] In transistors 2611, 2612, and 2613, an oxide semiconductor layer is preferably used as the semiconductor layer in which the channel region is formed. In particular, by using such a transistor in transistor 2613, the potential of node n can be maintained for a long period of time, thereby reducing the frequency of resupplying VRES to node n (refresh operation).

[0343] The structure shown in this embodiment can be implemented by appropriately combining it with the structures shown in other embodiments.

[0344] Implementation Method 6 In this embodiment, refer to Figures 15 to 16G A display module and an electronic device incorporating a light-emitting element according to one aspect of the present invention will be described.

[0345] <Explanation of the display module> Figure 15 The display module 8000 shown includes a touch sensor 8004 connected to FPC 8003, a display device 8006 connected to FPC 8005, a frame 8009, a printed circuit board 8010, and a battery 8011, located between the upper cover 8001 and the lower cover 8002.

[0346] For example, the light-emitting element of one aspect of the present invention can be used in a display device 8006.

[0347] The upper cover 8001 and the lower cover 8002 can be appropriately changed in shape or size according to the size of the touch sensor 8004 and the display device 8006.

[0348] The touch sensor 8004 can be a resistive film touch sensor or a capacitive touch sensor, and can be formed to overlap with the display device 8006. Alternatively, the opposing substrate (sealed substrate) of the display device 8006 can also function as a touch sensor. Furthermore, an optical touch sensor can be formed by providing a light sensor within each pixel of the display device 8006.

[0349] In addition to protecting the display device 8006, the frame 8009 also serves as electromagnetic shielding to block electromagnetic waves generated by the operation of the printed circuit board 8010. Furthermore, the frame 8009 can also function as a heat sink.

[0350] The printed circuit board 8010 includes a power supply circuit and a signal processing circuit for outputting video and clock signals. The power supply to the power supply circuit can be either an external commercial power supply or a separately installed battery 8011. When using a commercial power supply, the battery 8011 can be omitted.

[0351] In addition, components such as polarizers, phase difference plates, and prism sheets can be added to the display module 8000.

[0352] <Explanation of Electronic Devices> Figures 16A to 16G This diagram illustrates electronic devices. These electronic devices may include a housing 9000, a display unit 9001, a speaker 9003, operation keys 9005 (including a power switch or operation switch), connection terminals 9006, a sensor 9007 (which has the function of measuring factors such as force, displacement, position, velocity, acceleration, angular velocity, rotational speed, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, tilt, vibration, odor, or infrared radiation), a microphone 9008, etc.

[0353] Figures 16A to 16G The electronic device shown can have various functions. For example, it can have the following functions: displaying various information (still images, moving images, text images, etc.) on a display unit; touch sensor functionality; displaying calendars, dates, or times; controlling processing using various software (programs); wireless communication functionality; connecting to various computer networks using wireless communication functionality; sending or receiving various data using wireless communication functionality; reading programs or data stored in a storage medium and displaying them on the display unit; etc. Note that... Figures 16A to 16G The electronic device shown may have functions not limited to those described above, but may possess a variety of functions. Furthermore, although in Figures 16A to 16G Although not illustrated, the electronic device may include multiple display units. Furthermore, a camera or similar device may be incorporated into the electronic device to provide the following functions: the ability to capture still images; the ability to capture moving images; the ability to store captured images in a storage medium (external storage medium or storage medium built into the camera); the ability to display captured images on a display unit; and so on.

[0354] The following is a detailed explanation. Figures 16A to 16G The electronic device shown.

[0355] Figure 16A This is a perspective view showing a portable information terminal 9100. The display unit 9001 included in the portable information terminal 9100 is flexible. Therefore, the display unit 9001 can be assembled along the curved surface of the curved frame 9000. In addition, the display unit 9001 is equipped with a touch sensor, and can be operated by touching the screen with a finger or stylus. For example, an application can be launched by touching an icon displayed on the display unit 9001.

[0356] Figure 16B This is a perspective view showing a portable information terminal 9101. The portable information terminal 9101 has one or more functions, such as a telephone, an electronic notebook, and an information reading device. Specifically, it can be used as a smartphone. Note that the speaker 9003, connection terminal 9006, sensor 9007, etc., are not shown in the portable information terminal 9101, but can be provided with... Figure 16A The portable information terminal 9100 shown is in the same location. Furthermore, the portable information terminal 9101 can display text and image information on multiple surfaces. For example, three operation buttons 9050 (also called operation icons or simply icons) can be displayed on one surface of the display unit 9001. Additionally, information 9051, represented by a dashed rectangle, can be displayed on another surface of the display unit 9001. Furthermore, as examples of information 9051, there may be displays of notifications for received emails, SNS (Social Networking Services), phone calls, etc.; the subject of the email or SNS message; the sender's name; the date; the time; battery level; antenna reception strength, etc. Alternatively, operation buttons 9050 can be displayed instead of information 9051 in the same location where information 9051 is displayed.

[0357] Figure 16C This is a perspective view showing a portable information terminal 9102. The portable information terminal 9102 has the function of displaying information on three or more surfaces of the display unit 9001. Here, examples are shown where information 9052, information 9053, and information 9054 are displayed on different surfaces. For example, the user of the portable information terminal 9102 can check its display (in this case, information 9053) while the portable information terminal 9102 is placed in an upper pocket. Specifically, the phone number or name of the caller is displayed in a position that allows the user to view this information from above the portable information terminal 9102. The user can check this display without taking the portable information terminal 9102 out of their pocket, thereby determining whether to answer the call.

[0358] Figure 16D This is a perspective view showing a watch-type portable information terminal 9200. The portable information terminal 9200 can execute various applications such as mobile phone use, email, article reading and editing, music playback, internet communication, and computer games. Furthermore, the display surface of the display unit 9001 is curved, allowing images to be displayed on the curved surface. Additionally, the portable information terminal 9200 can perform short-range communication according to communication standards. For example, hands-free calling can be performed by communicating with a wireless headset using the portable information terminal 9200. Furthermore, the portable information terminal 9200 includes a connection terminal 9006, allowing direct data exchange with other information terminals via a connector. Charging can also be performed via the connection terminal 9006. Moreover, charging can also be performed wirelessly without using the connection terminal 9006.

[0359] Figures 16E to 16G This is a perspective view showing the foldable portable information terminal 9201. Additionally, Figure 16E This is a perspective view of the 9201 portable information terminal in its unfolded state. Figure 16F This is a perspective view of the portable information terminal 9201 in its unfolded and folded states. Figure 16G This is a perspective view of the portable information terminal 9201 in its folded state. The portable information terminal 9201 offers good portability in its folded state. When the portable information terminal 9201 is unfolded, its seamless, large display area provides excellent visibility. The display unit 9001 included in the portable information terminal 9201 is supported by three frames 9000 connected by hinges 9055. By bending the portable information terminal 9201 between two frames 9000 using the hinges 9055, it can be reversibly changed from its unfolded state to a folded state. For example, the portable information terminal 9201 can be bent with a radius of curvature of 1 mm or more and 150 mm or less.

[0360] The electronic device shown in this embodiment includes a display unit for displaying certain information. Note that the light-emitting element according to one aspect of the present invention can also be applied to an electronic device that does not include a display unit. Furthermore, although this embodiment shows a structure in which the display unit of the electronic device has a flexible structure that allows display on a bent display surface or a structure that allows the display unit to be folded, it is not limited to this; a structure that does not have flexibility and displays on a flat surface can also be used.

[0361] The structure shown in this embodiment can be used in appropriate combinations with the structures shown in other embodiments.

[0362] Implementation Method 7 In this embodiment, refer to Figure 17This describes an example of a lighting device that incorporates a light-emitting element according to one aspect of the present invention.

[0363] Figure 17 This is an example of using a light-emitting element in an indoor lighting device 8501. Furthermore, because the light-emitting element can be made large-area, large-area lighting devices can also be formed. Additionally, a lighting device 8502 with a curved light-emitting area can be formed by using a frame with a curved surface. The light-emitting element shown in this embodiment is thin-film, so there is a high degree of freedom in the design of the frame. Therefore, lighting devices that can accommodate various designs can be formed. Furthermore, a large lighting device 8503 can also be installed on an indoor wall. Touch sensors can also be provided in lighting devices 8501, 8502, and 8503 to turn the power on or off.

[0364] Additionally, by using the light-emitting element on one side of the table surface, a lighting device 8504 that functions as a table can be provided. Furthermore, by using the light-emitting element as part of other furniture, a lighting device that functions as furniture can be provided.

[0365] As described above, a wide variety of lighting devices that utilize light-emitting elements can be obtained. Furthermore, such lighting devices are included in one embodiment of the present invention.

[0366] Furthermore, the structure shown in this embodiment can be implemented by appropriately combining it with the structures shown in other embodiments.

[0367] Example 1 In this embodiment, eight types of light-emitting elements with different structures were fabricated. These eight types of light-emitting elements include: four types using different materials for the electron transport layer; and four types that differ from the aforementioned four types only in the material used for the hole transport layer. Additionally, refer to... Figure 18 The manufacture of light-emitting elements 1 to 8 will be described below. The chemical formulas of the materials used in this embodiment are shown below.

[0368] [Chemistry 1] .

[0369] Manufacturing of Light-Emitting Elements 1 to 8 First, an indium tin oxide (ITO) film containing silicon oxide is deposited on a glass substrate 900 by sputtering, thereby forming a first electrode 901, which is used as the anode. Furthermore, the first electrode has a thickness of 70 nm and an area of ​​2 mm × 2 mm.

[0370] Next, as a pretreatment for forming light-emitting elements on substrate 900, the substrate surface is washed with water, calcined at 200°C for 1 hour, and then subjected to UV ozone treatment for 370 seconds.

[0371] Then, the substrate is placed inside and depressurized to 1×10⁻⁶. -4 The substrate 900 is subjected to vacuum calcination at 170°C for 30 minutes in a vacuum evaporation apparatus at approximately Pa, and then cooled for approximately 30 minutes in a heating chamber within the apparatus.

[0372] Next, the substrate 900 is fixed to a support disposed in a vacuum evaporation apparatus with the surface of the substrate on which the first electrode 901 is formed facing downwards. In this embodiment, a hole injection layer 911, a hole transport layer 912, a light-emitting layer 913, an electron transport layer 914, and an electron injection layer 915, which are included in the EL layer 902, are sequentially formed by vacuum evaporation.

[0373] The vacuum device was depressurized to 1×10⁻⁶. -4 Following Pa, in the case of light-emitting elements 1 to 4, 3-[4-(9-phenanthyl)-phenyl]-9-phenyl-9H-carbazole (abbreviated as PCPPn) and molybdenum oxide are co-deposited at a weight ratio of PCPPn:molybdenum oxide = 4:2, forming a hole injection layer 911 on the first electrode 901. The film thickness is 10 nm. Additionally, as light-emitting elements 5 to 8, 9-phenyl-3-[4-(10-phenyl-9-anthrayl)phenyl]-9H-carbazole (abbreviated as PCzPA) and molybdenum oxide are deposited by co-depositing at a weight ratio of PCzPA:molybdenum oxide = 4:2, forming a hole injection layer 911 on the first electrode 901. The film thickness is set to 10 nm. Co-depositation refers to a deposition method in which multiple different substances are simultaneously evaporated from different evaporation sources.

[0374] Next, in the case of light-emitting elements 1 to 4, a hole transport layer 912 is formed by evaporating a 30 nm thick layer of PCPPn onto the hole injection layer 911. In the case of light-emitting elements 5 to 8, a hole transport layer 912 is formed by evaporating a 30 nm thick layer of PCzPA onto the hole injection layer 911.

[0375] Next, a light-emitting layer 913 was formed on the hole transport layer 912 by co-evaporation of 7-[4-(10-phenyl-9-anthrayl)phenyl]-7H-dibenzo[c,g]carbazole (abbreviated as cgDBCzPA) and N,N'-bis(3-methylphenyl)-N,N'-bis[3-(9-phenyl-9H-fluorene-9-yl)phenyl]-pyrene-1,6-diamine (abbreviated as 1,6mMemFLPAPrn). The film thickness was set to 25 nm.

[0376] Next, in the case of light-emitting elements 1 and 5, an electron transport layer 914 is formed by depositing red phenanthroline (BPhen) with a thickness of 25 nm on the light-emitting layer 913 by vapor deposition. In the case of light-emitting elements 2 and 6, an electron transport layer 914 is formed by depositing 2,2'-(pyridin-2,6-diyl)bis(4,6-diphenylpyrimidine) (2,6(P2Pm)2Py) with a thickness of 25 nm on the light-emitting layer 913 by vapor deposition. In the case of light-emitting elements 3 and 7, an electron transport layer 914 is formed by depositing 2,9-bis(naphthyl)-4,7-diphenyl-1,10-phenanthroline (NBPhen) with a thickness of 25 nm on the light-emitting layer 913 by vapor deposition. In the case of light-emitting elements 4 and 8, an electron transport layer 914 is formed by depositing 2,2'-(pyridine-2,6-diyl)bis(4-phenylbenzo[h]quinazoline) (abbreviated as: 2,6(P-Bqn)2Py) on the light-emitting layer 913 with a thickness of 25 nm by vapor deposition.

[0377] Furthermore, an electron injection layer 915 is formed by depositing lithium fluoride on the electron transport layer 914 with a thickness of 1 nm by vapor deposition.

[0378] Finally, aluminum is deposited on the electron injection layer 915 with a thickness of 200 nm by vapor deposition to form the second electrode 903, which serves as the cathode. This manufactures light-emitting elements 1 to 8. Furthermore, the vapor deposition is performed using a resistance heating method throughout the entire vapor deposition process described above.

[0379] Table 1 shows the element structures of light-emitting elements 1 to 8 obtained through the above steps.

[0380] [Table 1] .

[0381] In addition, the manufactured light-emitting elements 1 to 8 were sealed in a glove box under a nitrogen atmosphere without being exposed to the atmosphere (a sealant was applied around the elements, and UV treatment and heat treatment at 80°C for 1 hour were performed during sealing). Furthermore, four of each light-emitting element were manufactured for the purpose of conducting the following measurements.

[0382] Characteristics of light-emitting elements 1 to 8 Four of each of the manufactured light-emitting elements 1 to 8 were measured using a picosecond fluorescence lifetime measurement system (manufactured by Hamamatsu Photonics Co., Ltd., Japan). To measure the lifetime of fluorescence emission in the light-emitting elements, a rectangular pulse voltage was applied to the elements, and a streak camera was used to perform time-resolved measurements of the decaying emission after the voltage drop. The pulse voltage was applied at a frequency of 10 Hz. Data with a high signal-to-noise ratio (S / N) was obtained by accumulating the data from repeated measurements. The measurements were performed under the following conditions: room temperature (300 K); pulse voltage of approximately 3 V; pulse duration of 100 μsec; negative bias of -5 V; and measurement time range of 50 μsec.

[0383] The decay curve of instantaneous fluorescence was obtained by fitting the formula (f1) with the measured value.

[0384] .

[0385] In formula (f1), L represents the normalized luminous intensity, and t represents the elapsed time.

[0386] The fitted decay curves can be obtained by measurement with n=1 and 2. Furthermore, it is known that light-emitting elements 1 to 8 contain not only fluorescent components but also delayed fluorescence components. The delayed fluorescence component refers to the fluorescence emission measured after the pulse voltage is turned off, i.e., after carrier injection into the light-emitting layer is stopped. The measurement of the delayed fluorescence component indicates that triplet-triplet annihilation (TTA) has occurred in the EL layer of the light-emitting element. The delayed fluorescence component ratio refers to the ratio of the fluorescence emission intensity of the light-emitting element when the pulse voltage is supplied to the fluorescence emission intensity of the light-emitting element after the pulse voltage is turned off; that is, the ratio of the fluorescence emission intensity of the light-emitting element when carrier injection into the light-emitting layer is continuous to the fluorescence emission intensity of the light-emitting element after carrier injection stops. Table 2 below shows the delayed fluorescence component ratios of light-emitting elements 1 to 8.

[0387] Furthermore, the luminescence characteristics of light-emitting elements 1 to 8 were measured, and the external quantum efficiency was determined. The external quantum efficiency of each light-emitting element was obtained by rotating the substrate from -80 degrees to 80 degrees, measuring the viewing angle dependence of the luminescence, and taking into account the light distribution characteristics of electroluminescence. The results are shown in Table 2 below. The measurements were performed at room temperature (in an atmosphere maintained at 25°C).

[0388] [Table 2] .

[0389] In addition, Table 3 shows the LUMO energy levels of the materials used in the electron transport layers of light-emitting elements 1 to 8. The LUMO energy levels were estimated by cyclic voltammetry determination of each material in N,N-dimethylformamide (DMF) solvent.

[0390] [Table 3] .

[0391] Figure 19 The table shows the percentage (%) of delayed fluorescence components at the LUMO energy levels (eV) of the materials used for the electron transport layers of light-emitting elements 1 to 8 (shown in Table 3). Figure 19 In the diagram, the same notation is used to represent the light-emitting elements 1 to 4 of the hole transport layer using PCPPn, and the same notation is used to represent the light-emitting elements 5 to 8 of the hole transport layer using PCzPA.

[0392] The results show that although the ratios of the materials used for the hole transport layer have different values, there is a tendency for the material used for the electron transport layer to have a higher LUMO energy level and a higher delayed fluorescence ratio. That is, the delayed fluorescence ratio of the luminescent element using 2,6(P-Bqn)2Py with the largest LUMO energy level (-2.92 eV) is greater than that of the luminescent element with the same structure except for the electron transport layer.

[0393] in addition, Figure 20 The relationship between the delayed fluorescence component ratio (%) of light-emitting elements 1 to 8 and the external quantum efficiency (%) is shown.

[0394] The results show that the higher the percentage of delayed fluorescence components (%), the higher the external quantum efficiency (%).

[0395] Here, the fluorescence intensity during the direct generation process is expressed as I. P The fluorescence intensity of delayed fluorescence originating from TTA is expressed as I. D The following formula (f2) represents the ratio of delayed fluorescence components (X).

[0396] .

[0397] Furthermore, according to the definition of external quantum efficiency (EQE), when I D When I = 0 (X = 0), the singlet exciton generation rate (α) is 0.25. However, when I... D As α increases, EQE and I also increase accordingly.P +I D It is directly proportional. Therefore, the following formula (f3) can be derived.

[0398] .

[0399] Because X is synonymous with Figure 20 The x-axis, so as Figure 20 As shown, the relationships between the delayed fluorescence ratio (%) and external quantum efficiency (%) in light-emitting elements 1 to 4 using PCPPn as the hole transport layer, and between the delayed fluorescence ratio (%) and external quantum efficiency (%) in light-emitting elements 5 to 8 using PCzPA as the hole transport layer, can both be applied to the above formula (f3). This indicates that there is a correlation between the delayed fluorescence ratio (%) and the external quantum efficiency (%).

[0400] In addition, the characteristics of light-emitting element 4-2, which has the same element structure as the light-emitting element 4 shown in Table 1, were measured. Figure 21 The current density-luminance characteristics of the light-emitting element 4-2 are shown. Figure 22 The voltage-brightness characteristics are shown. Figure 23 The brightness-current efficiency characteristics are shown. Figure 24 The voltage-current characteristics are shown. Figure 25 The brightness-external quantum efficiency characteristics are shown. Here, Figure 25 The external quantum efficiency of the light-emitting element shown is a value obtained by the method described above: the viewing angle dependence of the light emission was determined by rotating the substrate from -80 degrees to 80 degrees and taking into account the light distribution characteristics of EL emission. Figures 21 to 24 The characteristic values ​​of the light-emitting element shown were determined based on the front brightness using a BM-5A colorimeter (manufactured by Topcon Technohouse).

[0401] Additionally, Table 4 shows 1000 cd / m 2 The main initial characteristic values ​​of the nearby light-emitting element 4-2.

[0402] [Table 4] .

[0403] in addition, Figure 26 It shows 12.5 mA / cm 2 The current density determines the emission spectrum when current flows through the light-emitting element 4-2. For example... Figure 26 As shown, the emission spectrum of the light-emitting element 4-2 has a peak near 464 nm, which may originate from 1,6mMemFLPAPrn used as a guest material (dopant) in the light-emitting layer of the light-emitting element 4-2.

[0404] in addition, Figure 27 This is a decay curve showing the instantaneous fluorescence characteristics of the light-emitting element 4-2. Additionally, in Figure 27 In the diagram, the vertical axis represents the normalized intensity of the luminescence under conditions of continuous carrier injection (when a pulse voltage is supplied), and the horizontal axis represents the elapsed time after the pulse voltage decreases. Furthermore, using the aforementioned formula (f1)... Figure 27 The decay curves shown were fitted, and the percentage of delayed fluorescence components (%) was found to be 21.5%.

[0405] Next, a reliability test was conducted on the light-emitting element 4-2. Figure 28 The results of the reliability test are shown. Figure 28 In the graph, the vertical axis represents the normalized luminance (%) when the initial luminance is 100%, while the horizontal axis represents the drive time (h) of the component. Additionally, in reliability testing, the initial luminance was 5000 cd / m². 2 Under the condition of fixed current density, drive the light-emitting element 4-2.

[0406] As a result, the light-emitting element 4-2 of one embodiment of the present invention has high reliability.

[0407] Example 2 In this embodiment, the orientation of the molecular transition dipole moments related to the light emitted by the light-emitting layer of the light-emitting element is derived. Specifically, the orientation of the molecular transition dipole moments is derived by measuring the angle dependence of the spectral intensity of the p-polarized component of the emitted light and analyzing the results through calculation (simulation). The chemical formulas of materials used in this embodiment that are not described in Example 1 are shown below.

[0408] [Chemistry 2] .

[0409] Manufacturing of Light Emitting Element 9 First, use Figure 18 The fabrication of the light-emitting element 9, which is the object of measurement, will be described. First, indium tin oxide (ITO) containing silicon oxide is deposited on a glass substrate 900 by sputtering, thereby forming a first electrode 901, which is used as the anode. Note that the thickness of the first electrode is 70 nm, and the electrode area is 2 mm × 2 mm.

[0410] Next, as a pretreatment for forming light-emitting elements on substrate 900, the substrate surface is washed with water and calcined at 200°C for 1 hour, followed by UV ozone treatment for 370 seconds.

[0411] Then, the substrate is placed inside and depressurized to 1×10⁻⁶. -4The substrate 900 is placed in a vacuum evaporation apparatus at approximately Pa and then calcined at 170°C for 30 minutes in the heating chamber of the apparatus, followed by cooling for approximately 30 minutes.

[0412] Next, the substrate 900 is fixed to a support provided in a vacuum evaporation apparatus with the surface of the substrate on which the first electrode 901 is formed facing downwards. In this embodiment, the case in which the hole injection layer 911, hole transport layer 912, light emission layer 913, electron transport layer 914 and electron injection layer 915, which are included in the EL layer 902, are sequentially formed by vacuum evaporation.

[0413] Reduce the pressure inside the vacuum device to 1×10⁻⁶. -4 Following Pa, a hole injection layer 911 is formed on the first electrode 901 by co-evaporation deposition of 1,3,5-tris(dibenzothiophene-4-yl)benzene (abbreviated as DBT3P-II) and molybdenum oxide in a weight ratio of DBT3P-II:molybdenum oxide = 2:1. Its thickness is set to 10 nm. Furthermore, co-evaporation refers to a deposition method in which multiple different substances are simultaneously evaporated from different evaporation sources.

[0414] Next, a hole transport layer 912 is formed by depositing BPAFLP on the hole injection layer 911 with a thickness of 30 nm by vapor deposition.

[0415] Next, 7-[4-(10-phenyl-9-anthrayl)phenyl]-7H-dibenzo[c,g]carbazole (abbreviated as cgDBCzPA) and N,N'-bis(3-methylphenyl)-N,N'-bis[3-(9-phenyl-9H-fluorene-9-yl)phenyl]pyrene-1,6-diamine (abbreviated as 1,6mMemFLPAPrn) were co-deposited on the hole transport layer 912 in a weight ratio of cgDBCzPA:1,6mMemFLPAPrn = 1:0.03 to form the light-emitting layer 913. The film thickness is 15 nm.

[0416] Next, a 20 nm thick 7-[4-(10-phenyl-9-anthrayl)phenyl]-7H-dibenzo[c,g]carbazole (abbreviated as cgDBCzPA) is formed on the light-emitting layer 913, and a 15 nm thick 2,9-bis(naphthyl-2-yl)-4,7-diphenyl-1,10-phenanthroline (abbreviated as NBPhen) is deposited on it to form the electron transport layer 914.

[0417] Furthermore, lithium oxide is deposited on the electron transport layer 914 with a thickness of 0.1 nm by vapor deposition, followed by the deposition of copper phthalocyanine (CuPc) with a thickness of 2 nm by vapor deposition, and the electron injection layer 915 is formed by co-deposition of DBT3P-II and molybdenum oxide with a thickness of 60 nm by a weight ratio of 1,3,5-tris(dibenzothiophene-4-yl)-benzene (abbreviated as DBT3P-II):molybdenum oxide = 2:1.

[0418] Finally, aluminum is deposited on the electron injection layer 915 with a thickness of 200 nm by vapor deposition to form the second electrode 903, which serves as the cathode. This manufactures the light-emitting element 9. Furthermore, the entire vapor deposition process described above is performed using a resistance heating method.

[0419] The thickness of each layer of the light-emitting element 9 is determined in a way that minimizes the brightness of the emitted light from the front. This allows for a relative increase in brightness derived from the transition dipole moment with components in the direction perpendicular to the light-emitting layer 913, making it easier to evaluate the light emission.

[0420] Polarization Measurement Next, the measurement will be explained. A multi-channel spectrometer (PMA-12, manufactured by Hamamatsu Photonics Co., Ltd., Japan) was used as the detector. A polarizer manufactured by Edmund Optics Co., Ltd. was placed in the optical path from the light-emitting element 9 to the detector, so that only the polarization component parallel to the observation direction reaches the detector. The light passing through the polarizer was detected by the PMA-12 (multi-channel spectrometer: manufactured by Hamamatsu Photonics Co., Ltd., Japan) to obtain the emission spectrum. At this time, with the front side of the light-emitting surface of the substrate as 0 degrees, the substrate was rotated from 0 degrees to 80 degrees and the emission spectrum of each degree was measured, thereby plotting the integrated intensity of the spectrum.

[0421] Computation (Simulation) Next, the calculations will be explained. The calculations were performed using the setfos organic device simulator manufactured by CYBERNET SYSTEMS, Japan. The stacked structure and film thickness of the element, the refractive index n and extinction coefficient k of each layer, the emission position, and the emission spectrum were set as parameters, and the orientation degree of the transition dipole moment of the luminescent molecules was used as a variable parameter for fitting (parameter a described below). Furthermore, the emission position was assumed to be near the interface between the hole transport layer and the luminescent layer. The film thickness of each layer was determined based on the value of the quartz crystal oscillator (detector) of the vapor deposition machine used during sample fabrication, and the refractive index n and extinction coefficient k were determined based on the analysis results of the spectral ellipsometry of each thin film. The emission spectrum was measured using the photoluminescence (PL) method for thin films.

[0422] The parameter representing the orientation degree of the transition dipole moment is defined as 'a'. That is, 'a' represents the ratio of the perpendicular component to the total component perpendicular to the emitting layer and the component parallel to the emitting layer in the transition dipole moment. 'a' = 1 indicates that the transition dipole moment exists only in the state perpendicular to the emitting layer, and 'a' = 0 indicates that the transition dipole moment exists only in the state parallel to the emitting layer. When the molecular orientation is isotropic, the transition dipole moment has equal components in the perpendicular x, y, and z directions, respectively; therefore, 'a' = 0.33.

[0423] Fitting Measurement Results to Calculations (Simulations) Figure 29 The measured plots and calculation results of the angle-dependent characteristics are shown, where a = 0 (transition dipole moment is completely horizontal), a = 0.16, a = 0.33 (transition dipole moment is randomly oriented), and a = 1 (transition dipole moment is completely perpendicular). By comparing the measured plots and calculation results of the angle-dependent characteristics, it can be seen that 84% of the components of the transition dipole moment are parallel to the luminescent layer, and 16% are perpendicular (a = 0.16). The calculated result is very close to the measured plot. Therefore, it can be inferred that 84% of the components of the transition dipole moments of the luminescent molecules contained in the luminescent layer 913 of the luminescent element 9 are parallel to the luminescent layer 913, and most transition dipole moments are oriented in a state deviating from the perpendicular direction of the luminescent layer.

[0424] The above results show that the luminescent molecules contained in the luminescent layer are not randomly oriented but have a strong orientation. This strong orientation of the luminescent molecules may be the reason why the luminescent element of one aspect of the present invention has a high luminous efficiency. Therefore, in the luminescent element of one aspect of the present invention, when the transition dipole moment of the luminescent material (in this embodiment, the guest material) is divided into components parallel to and perpendicular to the luminescent layer, the ratio of the parallel components is preferably 80% or more and 100% or less.

[0425] This application is based on Japanese Patent Application No. 2015-234485, filed with the Japan Patent Office on December 1, 2015, and Japanese Patent Application No. 2016-051071, filed with the Japan Patent Office on March 15, 2016, the entire contents of which are incorporated herein by reference.

[0426] Symbol Explanation 100: Electrode layer; 101: Electrode; 101a: Conductive layer; 101b: Conductive layer; 102: Electrode; 103: Electrode; 103a: Conductive layer; 103b: Conductive layer; 104: Electrode; 104a: Conductive layer; 104b: Conductive layer; 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; 123B: Light-emitting layer; 123G: Light-emitting layer; 123R: Light-emitting layer; 130: Light-emitting layer; 131: Host material; 132: Guest material; 140: Separator; 150: Light-emitting element; 160: Emitting layer; 170: Emitting layer; 170b: Emitting layer; 180: Detector observation direction; 181: Composition of transition dipole moment; 182: Composition of transition dipole moment; 183: Composition of transition dipole moment; 185: Detector; 200: Substrate; 220: Substrate; 221B: Region; 221G: Region; 221R: Region; 222B: Region; 222G: Region; 222R: Region; 223: Light-shielding layer; 224B: Optical element; 224G: Optical element; 224R: Optical element; 250: Emitting element; 252: Emitting element; 254: Emitting element; 400: EL layer; 401: Electrode; 402: Electrode; 411: Hole injection layer; 412: Hole transport layer; 413: Electron transport layer; 414: Electron injection layer; 416: Hole injection layer; 417: Hole transport layer; 418: Electron transport layer; 419: Electron injection layer; 420: Light-emitting layer; 421: Host material; 422: Guest material; 430: Light-emitting layer; 431: Host material; 431_1 Organic compound; 431_2 Organic compound; 432: Guest material; 441: Light-emitting unit; 442: Light-emitting unit; 445: Charge generation layer; 450: Light-emitting element; 452: Light-emitting element; 801: Pixel circuit; 802: Pixel section; 804: Driving circuit section; 804a: Scan line driving circuit; 804b: Signal line driving circuit; 806: Protection circuit; 807: Terminal section; 852: Transistor; 854: Transistor; 862: Capacitor element; 872: Light-emitting element; 900: Substrate; 901: First electrode; 902: EL layer; 903: Second electrode; 911: Hole injection layer; 912: Hole transport layer; 913: Light-emitting layer; 914: Electron transport layer; 915: Electron injection layer; 2000: Touch panel; 2001: Touch panel; 2501: Display device; 2502R: Pixel;2502t: Transistor; 2503c: Capacitor; 2503g: Scan line drive circuit; 2503t: Transistor; 2509: FPC; 2510: Substrate; 2510a: Insulating layer; 2510b: Flexible substrate; 2510c: Adhesive layer; 2511: Wiring; 2519: Terminal; 2521: Insulating layer; 2528: Separator; 2550R: Light-emitting element; 2560: Sealing layer; 2567BM: Light-shielding layer; 2567p: Anti-reflective layer; 2567R: Coloring layer; 2570: Substrate; 2570a: Insulating layer; 2570b: Flexible substrate; 2570c: Adhesive layer; 2580R: Light-emitting module; 2590: Substrate; 2591: Electrode; 2592: Electrode; 2593: Insulating layer; 2594: Wiring; 2595: Touch sensor; 2597: Adhesive layer; 2598: Wiring; 2599: Adhesive layer; 2601: Pulse voltage output circuit; 2602: Current output circuit; 2603: Capacitor; 2611: Transistor; 2612: Transistor; 2613: Transistor; 2621: Electrode; 2622: Electrode; 8000: Display module; 8001: Top cover; 8002: Bottom cover; 8003: FPC; 8004: Touch sensor; 8005: FPC; 8006: Display device; 8009: Frame; 8010: Printed substrate; 8011: Battery; 8501: Illumination device; 8502: Illumination device; 8503: Illumination device; 8504: Lighting device; 9000: Frame; 9001: Display unit; 9003: Speaker; 9005: Operation key; 9006: Connection terminal; 9007: Sensor; 9008: Microphone; 9050: Operation button; 9051: Information; 9052: Information; 9053: Information; 9054: Information; 9055: Hinge; 9100: Portable information terminal; 9101: Portable information terminal; 9102: Portable information terminal; 9200: Portable information terminal; 9201: Portable information terminal.

Claims

1. A light-emitting element, comprising: anode; cathode; as well as The charge generation layer between the anode and the cathode; The first EL layer between the anode and the charge generation layer; The second EL layer between the charge generation layer and the cathode. The first EL layer includes a first light-emitting layer and a first electron transport layer in contact with the first light-emitting layer. The first light-emitting layer comprises a first host material. The first electron transport layer comprises a first material. The LUMO energy level of the first material is lower than that of the first host material. The difference between the triplet excitation energy and the singlet excitation energy of the first host material is greater than 0.2 eV. Furthermore, the second EL layer comprises a second main material and a second auxiliary material.

2. A light-emitting element, comprising: anode; cathode; as well as The charge generation layer between the anode and the cathode; The first EL layer between the anode and the charge generation layer; The second EL layer between the charge generation layer and the cathode. The first EL layer includes a first light-emitting layer, a first electron transport layer in contact with the first light-emitting layer, and a hole injection layer. The first light-emitting layer comprises a first host material. The first electron transport layer comprises a first material. The hole injection layer contains a substance with halogen groups. The LUMO energy level of the first material is lower than that of the first host material. The difference between the triplet excitation energy and the singlet excitation energy of the first host material is greater than 0.2 eV. Furthermore, the second EL layer comprises a second main material and a second auxiliary material.

3. A light-emitting element, comprising: First electrode; Second electrode; First luminescent layer; Second light-emitting layer; Electron transport layer; as well as Charge generation layer, The first light-emitting layer is located between the first electrode and the electron transport layer. The electron transport layer is located between the first light-emitting layer and the charge-generating layer. The charge generation layer is located between the electron transport layer and the second light-emitting layer. The second light-emitting layer is located between the charge-generating layer and the second electrode. The electron transport layer is configured to be in contact with the first light-emitting layer. The first light-emitting layer comprises a third organic compound and a fluorescent material. The electron transport layer comprises a first material. The second light-emitting layer comprises a first organic compound, a second organic compound, and a phosphorescent material. The energy difference between the S1 and T1 energy levels of the third organic compound is greater than 0.2 eV. The third organic compound is a compound having an anthracene skeleton. The fluorescent material is a compound that emits blue light. Furthermore, the LUMO energy level of the first material is lower than that of the third organic compound.

4. A light-emitting element, comprising: First electrode; Second electrode; First luminescent layer; Second light-emitting layer; Electron transport layer; as well as Charge generation layer, The first light-emitting layer is located between the first electrode and the electron transport layer. The electron transport layer is located between the first light-emitting layer and the charge-generating layer. The charge generation layer is located between the electron transport layer and the second light-emitting layer. The second light-emitting layer is located between the charge-generating layer and the second electrode. The electron transport layer is configured to be in contact with the first light-emitting layer. The first light-emitting layer comprises a third organic compound and a fluorescent material. The electron transport layer comprises a first material. The second light-emitting layer comprises a first organic compound, a second organic compound, and a phosphorescent material. The S1 energy level of the third organic compound is higher than that of the fluorescent material. The T1 energy level of the third organic compound is lower than that of the fluorescent material. The energy difference between the S1 and T1 energy levels of the third organic compound is greater than 0.2 eV. The third organic compound is a compound having an anthracene skeleton. The fluorescent material is a compound that emits blue light. Furthermore, the LUMO energy level of the first material is lower than that of the third organic compound.

5. A light-emitting element, comprising: First electrode; Second electrode; First luminescent layer; Second light-emitting layer; Electron transport layer; as well as Charge generation layer, The first light-emitting layer is located between the first electrode and the electron transport layer. The electron transport layer is located between the first light-emitting layer and the charge-generating layer. The charge generation layer is located between the electron transport layer and the second light-emitting layer. The second light-emitting layer is located between the charge-generating layer and the second electrode. The electron transport layer is configured to be in contact with the first light-emitting layer. The first light-emitting layer comprises a third organic compound and a fluorescent material. The electron transport layer comprises a first material. The second light-emitting layer comprises a first organic compound, a second organic compound, and a phosphorescent material. The energy difference between the S1 and T1 energy levels of the third organic compound is greater than 0.2 eV. The third organic compound is a compound having an anthracene skeleton. The fluorescent material is a compound that emits blue light. The LUMO energy level of the fluorescent material is higher than that of the third organic compound. Furthermore, the LUMO energy level of the first material is lower than that of the third organic compound.

6. A light-emitting element, comprising: First electrode; Second electrode; First luminescent layer; Second light-emitting layer; Electron transport layer; as well as Charge generation layer, The first light-emitting layer is located between the first electrode and the electron transport layer. The electron transport layer is located between the first light-emitting layer and the charge-generating layer. The charge generation layer is located between the electron transport layer and the second light-emitting layer. The second light-emitting layer is located between the charge-generating layer and the second electrode. The electron transport layer is configured to be in contact with the first light-emitting layer. The first light-emitting layer comprises a third organic compound and a fluorescent material. The electron transport layer comprises a first material. The second light-emitting layer comprises a first organic compound, a second organic compound, and a phosphorescent material. The S1 energy level of the third organic compound is higher than that of the fluorescent material. The T1 energy level of the third organic compound is lower than that of the fluorescent material. The energy difference between the S1 and T1 energy levels of the third organic compound is greater than 0.2 eV. The third organic compound is a compound having an anthracene skeleton. The fluorescent material is a compound that emits blue light. The LUMO energy level of the fluorescent material is higher than that of the third organic compound. Furthermore, the LUMO energy level of the first material is lower than that of the third organic compound.

7. The light-emitting element according to any one of claims 3 to 6, in, Compared to the emission from the second emitting layer, the emission from the first emitting layer has an emission peak on the shorter wavelength side.

8. The light-emitting element according to any one of claims 3 to 6, in, The first organic compound and the second organic compound are a combination that forms an excitocomplex.

9. The light-emitting element according to any one of claims 3 to 6, in, The first organic compound is at least one of the following: oxadiazole derivative, triazole derivative, benzimidazole derivative, quinoxaline derivative, dibenzoquinoxaline derivative, dibenzothiophene derivative, dibenzofuran derivative, pyrimidine derivative, triazine derivative, pyridine derivative, bipyridine derivative, phenanthrene-rhein derivative, aromatic amine, and carbazole derivative.

10. The light-emitting element according to any one of claims 3 to 6, in, The phosphorescent material is any one of an iridium complex, a rhodium complex, and a platinum complex.

11. A light-emitting element, comprising: First electrode; Second electrode; Emissive layer; as well as Electron transport layer The light-emitting layer is located between the first electrode and the electron transport layer. The electron transport layer is located between the light-emitting layer and the second electrode. Between the first electrode and the light-emitting layer, there is a layer comprising a compound having at least one of a halogen group and a cyano group. The light-emitting layer comprises a host material and a fluorescent material. The electron transport layer comprises a first material. The S1 energy level of the host material is higher than that of the fluorescent material. The T1 energy level of the host material is lower than that of the fluorescent material. The energy difference between the S1 and T1 energy levels of the host material is greater than 0.2 eV. The LUMO energy level of the fluorescent material is higher than that of the host material. Furthermore, the LUMO energy level of the first material is lower than that of the host material.

12. A light-emitting element, comprising: First electrode; Second electrode; Emissive layer; as well as Electron transport layer The light-emitting layer is located between the first electrode and the electron transport layer. The electron transport layer is located between the light-emitting layer and the second electrode. Between the first electrode and the light-emitting layer, there is a layer containing receptors. The light-emitting layer comprises a host material and a fluorescent material. The electron transport layer comprises a first material. The S1 energy level of the host material is higher than that of the fluorescent material. The T1 energy level of the host material is lower than that of the fluorescent material. The energy difference between the S1 and T1 energy levels of the host material is greater than 0.2 eV. The LUMO energy level of the fluorescent material is higher than that of the host material. Furthermore, the LUMO energy level of the first material is lower than that of the host material.

13. A light-emitting element, comprising: First electrode; Second electrode; Emissive layer; as well as Electron transport layer The light-emitting layer is located between the first electrode and the electron transport layer. The electron transport layer is located between the light-emitting layer and the second electrode. Between the first electrode and the light-emitting layer, there is a layer comprising a compound having at least one of a halogen group and a cyano group. The light-emitting layer comprises a host material and a fluorescent material. The electron transport layer comprises a first material. The S1 energy level of the host material is higher than that of the fluorescent material. The T1 energy level of the host material is lower than that of the fluorescent material. The energy difference between the S1 and T1 energy levels of the host material is greater than 0.2 eV. The LUMO energy level of the fluorescent material is higher than that of the host material. Furthermore, the LUMO energy level of the first material is more than 0.05 eV lower than the LUMO energy level of the host material.

14. A light-emitting element, comprising: First electrode; Second electrode; Emissive layer; as well as Electron transport layer The light-emitting layer is located between the first electrode and the electron transport layer. The electron transport layer is located between the light-emitting layer and the second electrode. Between the first electrode and the light-emitting layer, there is a layer containing receptors. The light-emitting layer comprises a host material and a fluorescent material. The electron transport layer comprises a first material. The S1 energy level of the host material is higher than that of the fluorescent material. The T1 energy level of the host material is lower than that of the fluorescent material. The energy difference between the S1 and T1 energy levels of the host material is greater than 0.2 eV. The LUMO energy level of the fluorescent material is higher than that of the host material. Furthermore, the LUMO energy level of the first material is more than 0.05 eV lower than the LUMO energy level of the host material.

15. The light-emitting element according to any one of claims 11 to 14, in, The light-emitting layer emits blue light.

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