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

Abstract

The present invention provides a light-emitting device comprising a first organic compound, a second organic compound, and a guest material. The LUMO level of the first organic compound is lower than that of the second organic compound. The HOMO level of the first organic compound is lower than that of the second organic compound. The LUMO level of the guest material is higher than that of the first organic compound. The HOMO level of the guest material is higher than that of the second organic compound. The energy difference between the LUMO level and the HOMO level of the guest material is greater than the energy difference between the LUMO level of the first organic compound and the HOMO level of the second organic compound. The guest material can convert triplet excitation energy into light emission. The first organic compound and the second organic compound are combined to form an excited complex.

Description

Technology Field

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

[0002] Furthermore, one embodiment of the present invention is not limited to the technical field described above. The technical field of one embodiment of the invention disclosed in this specification, etc., relates to an article, a method, or a method of production. One embodiment of the present invention relates to a process, a machine, a product, or a composition of matter. Specifically, examples of the technical field of one embodiment of the present invention disclosed in this specification include a semiconductor device, a display device, a liquid crystal display device, a light-emitting device, a lighting device, a capacitor device, a memory device, a method of driving any of these, and a method of manufacturing any of these. Background Technology

[0003] In recent years, research and development on light-emitting devices using EL (electroluminescence) have been widely conducted. Such light-emitting devices have a basic structure in which a layer containing a light-emitting material (EL layer) is provided between a pair of electrodes. Light emission from the light-emitting material can be obtained by applying a voltage between the electrodes of this device.

[0004] Since this light-emitting element is self-emissive, a display device using this light-emitting element has advantages such as high visibility, the elimination of the need for a backlight, and low power consumption. In addition, the display device can be formed to be thin and lightweight and can have a fast response speed.

[0005] In the case of a light-emitting device (e.g., an organic EL device) in which an EL layer comprises an organic material as a light-emitting material and the EL layer is provided between a pair of electrodes, when a voltage is applied between the pair of electrodes, electrons from the cathode and holes from the anode are injected into the EL layer that has light emission properties, and current flows. As the injected electrons and holes recombine, the light-emitting organic material becomes excited, and light emission is obtained.

[0006] The excited state formed by organic materials is a singlet excited state (S * ) or triplet excited state (T * ...can be ). Luminescence from a singlet excited state is called fluorescence, and luminescence from a triplet excited state is called phosphorescence. The statistical generation rate of the excited state in the above-mentioned light-emitting device is S * :T * It is thought that the ratio is 1:3. In other words, light-emitting devices formed using phosphorescent materials have higher luminous efficiency than light-emitting devices formed using fluorescent materials. Therefore, in recent years, light-emitting devices formed using phosphorescent materials capable of converting a triplet excited state into light emission have been actively developed (see, for example, Patent Document 1).

[0007] The energy required to excite an organic material depends on the energy difference between the LUMO and HOMO levels of the organic material. This energy difference is approximately equivalent to the singlet excitation energy. In light-emitting devices containing phosphorescent organic materials, the triplet excitation energy is converted into luminescence energy. Therefore, when the energy difference between the singlet and triplet excited states of the organic material is large, the energy required to excite the organic material is higher than the luminescence energy by an amount equivalent to the energy difference. The difference between the energy required to excite the organic material and the luminescence energy affects the device characteristics of the light-emitting device: an increase in the driving voltage of the light-emitting device. Research and development of technologies to reduce this increase in driving voltage is being conducted (see Patent Document 2).

[0008] Among light-emitting devices formed using phosphorescent materials, those emitting blue light, in particular, have not yet reached practical application because it is difficult to develop stable compounds with high triplet excitation energy levels. Therefore, there is a need for the development of stable phosphorescent materials with high luminous efficiency and phosphorescent light-emitting devices that are both highly efficient and reliable. Prior art literature

[0009] Japanese Published Patent Application No. 2010-182699 Japanese Published Patent Application No. 2012-212879 The problem to be solved

[0010] Iridium complexes are known as phosphorescent materials with high luminescence efficiency. Iridium complexes with high luminescence energy include iridium complexes containing a pyridine backbone or a nitrogen-containing five-membered complex skeleton as a ligand. Pyridine backbones and nitrogen-containing five-membered complex skeletons have high triplet excitation energies but low electron acceptability. Therefore, iridium complexes having these backbones as ligands have high HOMO and LUMO levels, making it easy to inject hole carriers, while it is difficult to inject electron carriers. Consequently, development of iridium complexes having backbones with high electron acceptability as ligands is being pursued.

[0011] On the other hand, the HOMO and LUMO levels of an iridium complex having a ligand with a high electron acceptability are low, making it easy to inject electron carriers, while it is difficult to inject hole carriers. Therefore, there are cases where excitation by direct recombination of carriers is difficult, and efficient light emission of the light-emitting device may be hindered.

[0012] In the above context, an object of one embodiment of the present invention is to provide a light-emitting element comprising a phosphorescent material and having high luminous efficiency. Another object of one embodiment of the present invention is to provide a light-emitting element with reduced power consumption. Another object of one embodiment of the present invention is to provide a light-emitting element with high reliability. Another object of one embodiment of the present invention is to provide a novel light-emitting element. Another object of one embodiment of the present invention is to provide a novel light-emitting device. Another object of one embodiment of the present invention is to provide a novel display device. means of solving the problem

[0013] Furthermore, the description of the aforementioned purpose does not prevent the existence of other purposes. In one embodiment of the present invention, it is not necessary to solve all of these purposes. Other purposes may become apparent and derivable from the description in the specification, etc.

[0014] One embodiment of the present invention is a light-emitting device in which an excited composite capable of efficiently exciting a phosphorescent material is formed.

[0015] Accordingly, one embodiment of the present invention is a light-emitting device comprising a first organic compound, a second organic compound, and a guest material. The LUMO level of the first organic compound is lower than that of the second organic compound. The HOMO level of the first organic compound is lower than that of the second organic compound. The LUMO level of the guest material is lower than that of the first organic compound. The energy difference between the LUMO level and the HOMO level of the guest material is greater than the energy difference between the LUMO level of the first organic compound and the HOMO level of the second organic compound. The guest material has the function of converting triplet excitation energy into light emission. The first organic compound and the second organic compound are combined to form an excited complex.

[0016] Another embodiment of the present invention is a light-emitting device comprising a first organic compound, a second organic compound, and a guest material. The LUMO level of the first organic compound is lower than that of the second organic compound. The HOMO level of the first organic compound is lower than that of the second organic compound. The LUMO level of the guest material is lower than that of the first organic compound. The energy difference between the LUMO level and the HOMO level of the guest material is greater than the energy difference between the LUMO level of the first organic compound and the HOMO level of the second organic compound. The guest material has the function of converting triplet excitation energy into light emission. The first organic compound and the second organic compound form an excited complex by combining. The energy difference between the LUMO level of the guest material and the HOMO level of the second organic compound is greater than the transition energy calculated from the absorption end of the absorption spectrum of the guest material.

[0017] Another embodiment of the present invention is a light-emitting device comprising a first organic compound, a second organic compound, and a guest material. The LUMO level of the first organic compound is lower than that of the second organic compound. The HOMO level of the first organic compound is lower than that of the second organic compound. The LUMO level of the guest material is lower than that of the first organic compound. The energy difference between the LUMO level and the HOMO level of the guest material is greater than the energy difference between the LUMO level of the first organic compound and the HOMO level of the second organic compound. The guest material has the function of converting triplet excitation energy into light emission. The first organic compound and the second organic compound are combined to form an excited complex. The energy difference between the LUMO level of the guest material and the HOMO level of the second organic compound is greater than the light emission energy of the guest material.

[0018] In each of the above structures, it is desirable that the energy difference between the LUMO level of the guest material and the HOMO level of the guest material is at least 0.4 eV greater than the transition energy calculated from the absorption spectrum terminal of the guest material's absorption spectrum.

[0019] In each of the above structures, it is desirable that the energy difference between the LUMO level of the guest material and the HOMO level of the guest material is greater than 0.4 eV than the luminescence energy of the guest material.

[0020] In each of the above structures, it is desirable for the excited complex to transfer the excitation energy to the guest material. Additionally, it is desirable for the emission spectrum of the excited complex to have a region that overlaps with the absorption band on the longest wavelength side of the absorption spectrum of the guest material.

[0021] In each of the above structures, it is preferable that the guest material includes iridium.

[0022] In each of the above structures, it is preferable that the first organic compound has a function of transporting electrons, and it is preferable that the second organic compound has a function of transporting holes. It is preferable that the first organic compound comprises a π-electron-deficient complex aromatic ring framework, and the second organic compound comprises at least one of a π-electron-excess complex aromatic ring framework and an aromatic amine framework.

[0023] Another embodiment of the present invention is a display device comprising a light-emitting element having any of the structures described above, and a color filter, a real, or a transistor. Another embodiment of the present invention is an electronic device comprising the display device described above and a housing or a touch sensor. Another embodiment of the present invention is a lighting device comprising a light-emitting element having any of the structures described above and a housing or a touch sensor. The scope of an embodiment of the present invention includes not only a light-emitting device comprising a light-emitting element but also an electronic device comprising a light-emitting device. In this specification, a light-emitting device refers to an image display device and a light source (e.g., a lighting device). A light-emitting device may be included in a module in which a connector such as an FPC (flexible printed circuit) or TCP (tape carrier package) is connected to the light-emitting device, a module in which a printed circuit board is provided at the end of the TCP, or a module in which an IC (integrated circuit) is directly mounted on the light-emitting element by a COG (chip on glass) method. Effects of the invention

[0024] According to one embodiment of the present invention, a light-emitting element comprising a phosphorescent material and having high luminous efficiency is provided. According to one embodiment of the present invention, a light-emitting element with low power consumption is provided. According to one embodiment of the present invention, a light-emitting element with high reliability is provided. According to one embodiment of the present invention, a novel light-emitting element is provided. According to one embodiment of the present invention, a novel light-emitting device is provided. According to one embodiment of the present invention, a novel display device is provided.

[0025] Furthermore, the description of these effects does not preclude the existence of other effects. One embodiment of the present invention is not necessarily required to have all the effects described above. Other effects may become apparent and can be derived from the description in the specification, drawings, and claims, etc. Brief explanation of the drawing

[0026] Figures 1 (A) and (B) are schematic cross-sectional views of a light-emitting element of one embodiment of the present invention. Figures 2 (A) and (B) show the correlation of energy bands and energy levels of a light-emitting layer of a light-emitting element of one embodiment of the present invention. Figures 3 (A) and (B) are each schematic cross-sectional views of a light-emitting element of one embodiment of the present invention, and Figure 3 (C) shows a correlation of energy bands. Figures 4 (A) and (B) are each schematic cross-sectional views of a light-emitting element of one embodiment of the present invention, and Figure 4 (C) shows the correlation of energy bands. Figures 5 (A) and (B) are schematic cross-sectional views of a light-emitting element of one embodiment of the present invention. Figures 6 (A) and (B) are schematic cross-sectional views of a light-emitting element of one embodiment of the present invention. FIG. 7 (A) to (C) are schematic cross-sectional views illustrating a method for fabricating a light-emitting element of one embodiment of the present invention. FIG. 8 (A) to (C) are cross-sectional schematic diagrams illustrating a method for fabricating a light-emitting element of one embodiment of the present invention. FIG. 9 (A) and (B) are a top view and a cross-sectional schematic view illustrating a display device of one embodiment of the present invention. Figures 10 (A) and (B) are cross-sectional schematic diagrams illustrating a display device of one embodiment of the present invention. FIG. 11 is a schematic cross-sectional view illustrating a display device of one embodiment of the present invention. Figures 12 (A) and (B) are cross-sectional schematic diagrams illustrating a display device of one embodiment of the present invention. Figures 13 (A) and (B) are cross-sectional schematic diagrams illustrating a display device of one embodiment of the present invention. FIG. 14 is a schematic cross-sectional view illustrating a display device of one embodiment of the present invention. Figures 15 (A) and (B) are cross-sectional schematic diagrams illustrating a display device of one embodiment of the present invention. FIG. 16 is a schematic cross-sectional view illustrating a display device of one embodiment of the present invention. Figures 17 (A) and (B) are cross-sectional schematic diagrams illustrating a display device of one embodiment of the present invention. Figures 18 (A) and (B) are a block diagram and a circuit diagram illustrating a display device of one embodiment of the present invention. Figures 19 (A) and (B) are circuit diagrams illustrating pixel circuits of a display device of one embodiment of the present invention. Figures 20 (A) and (B) are circuit diagrams illustrating pixel circuits of a display device of one embodiment of the present invention. FIG. 21 (A) and (B) are perspective views illustrating examples of a touch panel of one embodiment of the present invention. FIG. 22 (A) to (C) are cross-sectional views illustrating examples of a display device and a touch sensor of one embodiment of the present invention. Figures 23 (A) and (B) are cross-sectional views illustrating examples of a touch panel of one embodiment of the present invention. FIG. 24 (A) and (B) are a block diagram and timing chart of a touch sensor of one embodiment of the present invention. FIG. 25 is a circuit diagram of a touch sensor of one embodiment of the present invention. FIG. 26 is a perspective view illustrating a display module of one form of the present invention. Figures 27 (A) to (G) illustrate an electronic device of one embodiment of the present invention. Figures 28 (A) to (D) illustrate an electronic device of one embodiment of the present invention. Figures 29 (A) and (B) are perspective views illustrating a display device of one embodiment of the present invention. FIG. 30 (A) to (C) is a perspective view and a cross-sectional view illustrating a light-emitting device of one embodiment of the present invention. Figures 31 (A) to (D) are cross-sectional views illustrating a light-emitting device of one embodiment of the present invention. FIG. 32 (A) and (B) illustrate an electronic device of one embodiment of the present invention, and FIG. 32 (C) illustrates a lighting device of one embodiment of the present invention. FIG. 33 illustrates a lighting device of one form of the present invention. FIG. 34 is a schematic cross-sectional view illustrating a light-emitting element of an embodiment. FIG. 35 is a graph showing the emission spectrum of the host material of the example. FIG. 36 is a graph showing the absorption spectrum and emission spectrum of the guest material of the example. FIG. 37 is a graph showing the phosphorescence spectrum of the host material of the example. FIG. 38 is a graph showing the luminance-current density characteristics of the light-emitting element of the example. FIG. 39 is a graph showing the luminance-voltage characteristics of the light-emitting element of the embodiment. FIG. 40 is a graph showing the current efficiency-luminance characteristics of the light-emitting element of the example. FIG. 41 is a graph showing the external quantum efficiency-luminance characteristics of the light-emitting device of the example. FIG. 42 is a graph showing the electroluminescence spectrum of the light-emitting element of the embodiment. FIG. 43 is a graph showing the reliability test results of the light-emitting element of the embodiment. Figure 44 shows the correlation of the energy bands of the example. FIG. 45 shows the angular distribution of light from the light-emitting element of the embodiment. FIG. 46 is a graph showing the luminance-current density characteristics of the light-emitting element of the example. FIG. 47 is a graph showing the luminance-voltage characteristics of the light-emitting element of the example. FIG. 48 is a graph showing the current efficiency-luminance characteristics of the light-emitting element of the example. FIG. 49 is a graph showing the external quantum efficiency-luminance characteristics of the light-emitting device of the example. FIG. 50 is a graph showing the electroluminescence spectrum of the light-emitting element of the embodiment. FIG. 51 is a graph showing the absorption spectrum and emission spectrum of the guest material of the example. FIG. 52 is a graph showing the absorption spectrum and emission spectrum of the guest material of the example. FIG. 53 shows the reliability test results of the light-emitting element of the embodiment. FIG. 54 is a graph showing the luminance-current density characteristics of the light-emitting element of the example. FIG. 55 is a graph showing the luminance-voltage characteristics of the light-emitting element of the example. Figure 56 is a graph showing the current efficiency-luminance characteristics of the light-emitting element of the example. FIG. 57 is a graph showing the external quantum efficiency-luminance characteristics of the light-emitting element of the example. FIG. 58 is a graph showing the electroluminescence spectrum of the light-emitting element of the embodiment. FIG. 59 shows the reliability test results of the light-emitting element of the embodiment. FIG. 60 is a graph showing the luminance-current density characteristics of the light-emitting element of the example. FIG. 61 is a graph showing the luminance-voltage characteristics of the light-emitting element of the embodiment. FIG. 62 is a graph showing the current efficiency-luminance characteristics of the light-emitting element of the example. FIG. 63 is a graph showing the external quantum efficiency-luminance characteristics of the light-emitting device of the example. FIG. 64 is a graph showing the electroluminescence spectrum of the light-emitting element of the embodiment. Figures 65 (A) and (B) are graphs showing the emission spectra of the host material of the example. FIG. 66 is a graph showing the luminance-current density characteristics of the light-emitting element of the example. FIG. 67 is a graph showing the luminance-voltage characteristics of the light-emitting element of the example. FIG. 68 is a graph showing the current efficiency-luminance characteristics of the light-emitting element of the example. FIG. 69 is a graph showing the external quantum efficiency-luminance characteristics of the light-emitting device of the example. FIG. 70 is a graph showing the electroluminescence spectrum of the light-emitting element of the embodiment. FIG. 71 is a graph showing the absorption spectrum and emission spectrum of the guest material of the example. FIG. 72 is a graph showing the absorption spectrum and emission spectrum of the guest material of the example. FIG. 73 is a graph showing the phosphorescent emission spectrum of the host material of the example. FIG. 74 is a graph showing the phosphorescent emission spectrum of the host material of the example. FIG. 75 is a graph showing the phosphorescent emission spectrum of the host material of the example. FIG. 76 is a graph showing the phosphorescent emission spectrum of the host material of the example. FIG. 77 is a graph showing the luminance-current density characteristics of the light-emitting element of the example. FIG. 78 is a graph showing the luminance-voltage characteristics of the light-emitting element of the example. FIG. 79 is a graph showing the current efficiency-luminance characteristics of the light-emitting element of the example. FIG. 80 is a graph showing the external quantum efficiency-luminance characteristics of the light-emitting device of the example. FIG. 81 is a graph showing the electroluminescence spectrum of the light-emitting element of the embodiment. FIG. 82 is a graph showing the absorption spectrum and emission spectrum of the guest material of the example. FIG. 83 is a graph showing the reliability test results of the light-emitting element of the embodiment. Specific details for implementing the invention

[0027] Embodiments of the present invention will be described below with reference to the drawings. However, the present invention is not limited to the description below, and it is readily understood that various changes to its form and details can be made without departing from the purpose and scope of the present invention. Accordingly, the present invention is not to be interpreted as being limited to the contents of the embodiments below.

[0028] In addition, the location, size, or scope of each structure depicted in drawings, etc., may not be accurately represented for the sake of simplification. Therefore, the disclosed invention is not necessarily limited to the location, size, or scope, etc., disclosed in the drawings, etc.

[0029] In addition, ordinal numbers such as "first" and "second" in this specification are used for convenience and do not indicate the order of steps or the stacking order. Therefore, for example, it is possible to explain the process by appropriately replacing "first" with "second" or "third." Furthermore, ordinal numbers in this specification are not necessarily the same as those specifying an embodiment of the present invention.

[0030] In describing the form of the present invention with reference to the drawings in this specification and the like, the same components of different drawings may be commonly indicated by the same reference numeral.

[0031] In this specification and other contexts, the terms "film" and "layer" may be interchanged depending on the case or situation. For example, the term "conductive layer" may be replaced with the term "conductive film." Additionally, the term "insulating film" may be replaced with the term "insulating layer."

[0032] In the present specification, etc., a single claim excited state (S * ) refers to a singlet state possessing excitation energy. The lowest level of singlet excitation energy (S1 level) refers to the excitation energy level at the lowest singlet excited state. The triplet excited state (T *) refers to a triplet state having excitation energy. The lowest level of triplet excitation energy levels (T1 level) refers to the excitation energy level in the lowest triplet excitation state. Additionally, in this specification and others, a singlet excitation state or a singlet excitation energy level may refer to the lowest singlet excitation state or the S1 level. A triplet excitation state or a triplet excitation energy level may refer to the lowest triplet excitation state or the T1 level.

[0033] In this specification and others, a fluorescent material refers to a material that emits light in the visible light region when relaxed from a singlet excited state to a ground state. A phosphorescent material refers to a material that emits light in the visible light region at room temperature when relaxed from a triplet excited state to a ground state. That is, a phosphorescent material refers to a material capable of converting triplet excitation energy into visible light.

[0034] The phosphorescent emission energy or triplet excitation energy can be obtained from the wavelength of the phosphorescent emission peak (including shoulder) on the shortest wavelength side of the phosphorescent emission. Additionally, phosphorescent emission can be observed by time-resolved photoluminescence in a low-temperature (e.g., 10K) environment. The emission energy of the thermally activated delayed fluorescence can be obtained from the wavelength of the emission peak (including shoulder) on the shortest wavelength side of the thermally activated delayed fluorescence.

[0035] In addition, in this specification, "room temperature" refers to a temperature of 0°C or higher and 40°C or lower.

[0036] In the present specification, etc., the wavelength range of blue refers to a wavelength range of 400 nm or more and less than 500 nm, and blue light has at least one peak in the range of the emission spectrum. The wavelength range of green refers to a wavelength range of 500 nm or more and less than 580 nm, and green light has at least one peak in the range of the emission spectrum. The wavelength range of red refers to a wavelength range of 580 nm or more and less than or equal to 680 nm, and red light has at least one peak in the range of the emission spectrum.

[0037] (Embodiment 1)

[0038] In this embodiment, a light-emitting element of one form of the present invention will be described below with reference to (A) and (B) of FIG. 1 and (A) and (B) of FIG. 2.

[0039] <Example of structure of a light-emitting element>

[0040] First, the structure of a light-emitting element of one embodiment of the present invention will be explained with reference to (A) and (B) of FIG. 1.

[0041] Figure 1 (A) is a schematic cross-sectional view of a light-emitting element (152) of one form of the present invention.

[0042] The light-emitting element (152) includes a pair of electrodes (electrode (101) and electrode (102)) and an EL layer (100) between the pair of electrodes. The EL layer (100) includes at least a light-emitting layer (140).

[0043] The EL layer (100) shown in (A) of FIG. 1 includes, in addition to the light-emitting layer (140), functional layers such as a hole injection layer (111), a hole transport layer (112), an electron transport layer (118), and an electron injection layer (119).

[0044] In this embodiment, the description assumes that the electrode (101) and the electrode (102) of a pair of electrodes function as an anode and a cathode, respectively, but the structure of the light-emitting element (152) is not limited thereto. That is, the electrode (101) may be a cathode, the electrode (102) may be an anode, and the stacking order of the layers between the electrodes may be reversed. In other words, the hole injection layer (111), hole transport layer (112), light-emitting layer (140), electron transport layer (118), and electron injection layer (119) may be stacked in this order on the anode side.

[0045] The structure of the EL layer (100) is not limited to the structure shown in (A) of FIG. 1, and may adopt a structure including at least one layer selected from a hole injection layer (111), a hole transport layer (112), an electron transport layer (118), and an electron injection layer (119). Alternatively, the EL layer (100) may include a functional layer capable of, for example, reducing the barrier to hole or electron injection, improving the transportability of holes or electrons, inhibiting the transportability of holes or electrons, or suppressing the quenching phenomenon caused by the electrode. In addition, each of the functional layers may be a single layer or a stack.

[0046] FIG. 1 (B) is a schematic cross-sectional view illustrating an example of the light-emitting layer (140) of FIG. 1 (A). The light-emitting layer (140) of FIG. 1 (B) includes a host material (141) and a guest material (142). The host material (141) includes an organic compound (141_1) and an organic compound (141_2).

[0047] The guest material (142) may be a luminescent organic material, and it is preferable that the luminescent organic material be a substance capable of emitting phosphorescence (hereinafter also referred to as a phosphorescent material). A structure using a phosphorescent material as the guest material (142) will be described below. The guest material (142) may be referred to as a phosphorescent material.

[0048] Light-emitting mechanism of a light-emitting element

[0049] Next, the light-emitting mechanism of the light-emitting layer (140) will be explained below.

[0050] The organic compounds (141_1) and (141_2) included in the host material (141) in the light-emitting layer (140) form an excited complex.

[0051] A combination of organic compound (141_1) and organic compound (141_2) is suitable if it can form an excited complex, but it is preferable that one is a compound having a hole transport function (hole transportability) and the other is a compound having an electron transport function (electron transportability). In this case, since it is easy to form a donor-acceptor excited complex, efficient formation of the excited complex is possible.

[0052] The combination of organic compound (141_1) and organic compound (141_2) is preferably as follows: one has a lower HOMO (highest occupied molecular orbital) level and LUMO (lowest unoccupied molecular orbital) level than the other.

[0053] For example, as shown in the energy band diagram of (A) in FIG. 2, when the organic compound (141_1) has electron transport and the organic compound (141_2) has hole transport, it is preferable that the HOMO level of the organic compound (141_1) is lower than the HOMO level of the organic compound (141_2), and the LUMO level of the organic compound (141_1) is lower than the LUMO level of the organic compound (141_2).

[0054] At this time, the excited complex formed by the organic compound (141_1) and the organic compound (141_2) is the energy difference (ΔE) between the LUMO level of the organic compound (141_1) and the HOMO level of the organic compound (141_2). ExIt has an excitation energy approximately equivalent to ). This energy difference is desirable because it facilitates the injection of electron carriers and hole carriers from a pair of electrodes (electrode (101) and electrode (102)) into the organic compound (141_1) and the organic compound (141_2).

[0055] The difference between the HOMO level of the organic compound (141_1) and the HOMO level of the organic compound (141_2) is preferably 0.1 eV or more, and more preferably 0.2 eV or more. Likewise, the difference between the LUMO level of the organic compound (141_1) and the LUMO level of the organic compound (141_2) is preferably 0.1 eV or more, and more preferably 0.2 eV or more.

[0056] Also, in (A) of FIG. 2, Host (141_1) represents an organic compound (141_1), Host (141_2) represents an organic compound (141_2), Guest (142) represents a guest material (142), and ΔE Ex θ represents the energy difference between the LUMO level of the organic compound (141_1) and the HOMO level of the organic compound (141_2), and ΔE B represents the energy difference between the LUMO level of the guest material (142) and the HOMO level of the organic compound (141_2), and ΔE G represents the energy difference between the LUMO level and the HOMO level of the guest material (142).

[0057] The shorter the emission wavelength of the guest material (142), the higher the emission energy; therefore, the energy difference (ΔE) between the LUMO level and the HOMO level of the guest material (142) G) is better the larger it is. However, since it is desirable for the excitation energy of the light-emitting element (152) to be as small as possible to reduce the driving voltage, the excitation energy of the excited complex formed by the organic compound (141_1) and the organic compound (141_2) is better the smaller it is. Accordingly, the energy difference (ΔE) between the LUMO level of the organic compound (141_1) and the HOMO level of the organic compound (141_2) Ex It is desirable for ) to be small.

[0058] Since the guest material (142) is a phosphorescent light-emitting material, it has the function of converting triplet excitation energy into light emission. Additionally, the energy is more stable in the triplet excited state than in the singlet excited state. Therefore, the guest material (142) has an energy difference (ΔE) between the LUMO level and the HOMO level of the guest material (142). G It can emit light with less energy than ). The energy difference (ΔE) between the LUMO level and the HOMO level of the guest material (142). G ) is the energy difference (ΔE) between the LUMO level of the organic compound (141_1) and the HOMO level of the organic compound (141_2). Ex Even when greater than ), the luminescence energy (ΔE) of the guest material (142) Em ) or transition energy (ΔE) calculated from the absorption spectrum group abs ) is ΔE Ex The inventors of the present invention have discovered that if ΔE of the guest material (142) is less than or equal to ΔE, it is possible to transfer excitation energy from the excited complex formed by the organic compound (141_1) and the organic compound (141_2) to the guest material (142) and to obtain luminescence from the guest material (142). G The luminescence energy (ΔE) of the guest material (142) Em ) or transition energy (ΔE) calculated from the absorption spectrum group abs If ΔE is greater than ) in order to directly induce electric excitation of the guest material (142), GSince high electrical energy equivalent to is required, the driving voltage of the light-emitting element increases. However, in one embodiment of the present invention, ΔE Ex (ΔE G Since the excited composite is electrically excited by electrical energy equivalent to (less than ΔE) and light emission from the guest material (142) can be obtained through energy transfer from the excited composite, high-efficiency light emission from the guest material (142) can be obtained at a low driving voltage. That is, one embodiment of the present invention is, ΔE G The luminescence energy (ΔE) of the guest material (142) Em ) or transition energy (ΔE) calculated from the absorption spectrum abs It is particularly useful when it is significantly larger than ) (for example, when the guest material is a blue emitting material).

[0059] Additionally, when the guest material (142) contains a heavy metal, the inter-term crossing between the singlet state and the triplet state is promoted by spin-orbit interaction (interaction between the momentum of the electron's spin angle and the orbital angle momentum), and the transition between the singlet ground state and the triplet excited state of the guest material (142) is not prohibited. Therefore, the luminescence efficiency and absorption probability regarding the transition between the singlet ground state and the triplet excited state of the guest material (142) can be increased. Accordingly, it is preferable for the guest material (142) to contain a metal element with large spin-orbit interaction, particularly a platinum group element (ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), or platinum (Pt)). In particular, iridium is preferred because it can increase the absorption probability regarding the direct transition between the singlet ground state and the triplet excited state.

[0060] In addition, since it is desirable for the LUMO level of the guest material (142) to be low so that the guest material (142) can have stability and high reliability, it is desirable for the ligand coordinating to the heavy metal atom of the guest material (142) to have a low LUMO level and high electron acceptability.

[0061] Such guest materials are likely to have molecular structures with low LUMO levels and high electron acceptability. When the guest material (142) has a molecular structure with high electron acceptability, the LUMO level of the guest material (142) may be lower than that of the organic compound (141_1). Also, ΔE G ΔE Ex In the case where it is larger, the HOMO level of the guest material (142) is lower than the HOMO level of the organic compound (141_2). Also, the energy difference between the HOMO level of the guest material (142) and the HOMO level of the organic compound (141_2) is greater than the energy difference between the LUMO level of the guest material (142) and the LUMO level of the organic compound (141_1).

[0062] Here, when the LUMO level of the guest material (142) is lower than that of the organic compound (141_1) and the HOMO level of the guest material (142) is lower than that of the organic compound (141_2), among the carriers (holes and electrons) injected from a pair of electrodes (electrode (101) and electrode (102)), the electrons injected from the cathode and the holes injected from the anode are easily injected into the guest material (142) and the organic compound (141_2) of the light-emitting layer (140), respectively. Therefore, among the materials of the light-emitting layer (140), when the guest material (142) has the lowest LUMO level and the organic compound (141_2) has the highest HOMO level, there is a possibility that the organic compound (141_2) and the guest material (142) will form an excited complex. In particular, the energy difference (ΔE) between the HOMO level of the organic compound (141_2) and the LUMO level of the guest material (142). B) is the luminescence energy (ΔE) of the guest material Em When it becomes smaller than ), the formation of an excited complex formed of an organic compound (141_2) and a guest material (142) becomes dominant. In this case, it becomes difficult to form an excited complex with the guest material (142) alone, and thus the luminous efficiency of the light-emitting device is reduced.

[0063] This reaction can be expressed by Equation (G1) or Equation (G2).

[0064] D + +G - →(D·G) * (G1)

[0065] D+G * →(D·G) * (G2)

[0066] Formula (G1) is in which the organic compound (141_2) and guest material (142) receive holes (D + ) Guest material (142) receives electrons (G - ), receiving the main attack (D + ), and receiving electrons (G - ) exhibiting a reaction, and the organic compound (141_2) and guest material (142) are excited complex ((D·G) * Forms ). Formula (G2) is the guest material (142) in the excited state (G * By ) interacting with the ground state organic compound (141_2)(D), the organic compound (141_2) and the guest material (142) form an excited complex ((D·G) * ) forms a complex ((D·G) excited by an organic compound (141_2) and a guest material (142) * By forming ) the excited state (G) of the guest material (142) alone * It becomes difficult for ) to form.

[0067] The excited complex formed by the organic compound (141_2) and the guest material (142) has an energy difference (ΔE) between the HOMO level of the organic compound (141_2) and the LUMO level of the guest material (142). B It has an excitation energy approximately equivalent to ). The energy difference (ΔE) between the HOMO level of the organic compound (141_2) and the LUMO level of the guest material (142) B ) is the luminescence energy (ΔE) of the guest material (142) Em ) or the transition energy (ΔE) calculated from the absorption spectrum group of the guest material (142) abs The inventors have discovered that when ΔE is greater than ) the reaction for the formation of an excited complex by the organic compound (141_2) and the guest material (142) can be suppressed, thereby increasing the luminescence efficiency of the guest material (142). abs is ΔE B Because it is smaller, the guest material (142) is more likely to receive excitation energy. Rather than forming an excited complex with the organic compound (141_2), the guest material (142) can receive excitation energy and become excited, which can result in a low-energy, stable excited state.

[0068] As described above, the energy difference (ΔE) between the LUMO level and the HOMO level of the guest material (142) G ) is the energy difference (ΔE) between the LUMO level of the organic compound (141_1) and the HOMO level of the organic compound (141_2). Ex Even in cases where it is greater than ), the transition energy (ΔE) calculated from the absorption end of the guest material (142) G_abs ) is ΔE Ex If the above, excitation energy is efficiently transferred from the excited complex formed by the organic compound (141_1) and the organic compound (141_2) to the guest material (142). As a result, a light-emitting device with high luminous efficiency and low driving voltage can be obtained, which is a feature of one embodiment of the present invention. At this time, Equation ΔEG_abs ≤ΔE Ex <ΔE G (ΔE G_abs is ΔE Ex Less than or equal to and ΔE Ex is ΔE G It satisfies (less than). Therefore, a mechanism of one form of the present invention satisfies ΔE abs ΔE G It is suitable for cases smaller than ΔE. In other words, a mechanism of one form of the present invention is ΔE G ΔE abs It is suitable for cases where it is larger. Specifically, the energy difference (ΔE) between the LUMO level and the HOMO level of the guest material (142). G ) is the transition energy (ΔE) calculated from the absorption spectrum terminal of the guest material (142) G_abs It is desirable that it be at least 0.4 eV greater than ). The luminescence energy of the guest material (142) is ΔE G_abs Since it is less than or equal to the energy difference (ΔE) between the LUMO level and the HOMO level of the guest material (142) G ) is the luminescence energy (ΔE) of the guest material (142). Em It is desirable that it be at least 0.4 eV greater than ). In addition, the luminescence energy (ΔE Em ) can be derived from the peak wavelength (including the maximum value or shoulder peak) on the shortest wavelength side of the emission spectrum.

[0069] When the LUMO level of the guest material (142) is lower than that of the organic compound (141_1), as described above, ΔE abs ≤ΔE B (ΔE abs is ΔE B (less than or equal to) or ΔE Em ≤ΔE B (ΔE Em is ΔE B The following) is desirable. Therefore, ΔE abs ≤ΔE B <ΔE Ex <ΔE G (ΔE abs is ΔE B Below, ΔEB is ΔE Ex Less than, and ΔE Ex is ΔE G Less than) or ΔE Em ≤ΔE B <ΔE Ex <ΔE G (ΔE Em is ΔE B Below, ΔE B is ΔE Ex under , and ΔE Ex is ΔE G Less than) is a desirable condition, and this is an important discovery in one embodiment of the present invention.

[0070] In addition, the shorter the emission wavelength of the guest material (142) and the emission energy (ΔE Em As ) increases, the energy difference (ΔE) between the LUMO level and the HOMO level of the guest material (142) G ) increases, and therefore, a large amount of energy is required to electrically excite the guest material. However, in one embodiment of the present invention, the transition energy (ΔE) calculated from the absorption spectrum terminal of the guest material (142) abs ) is ΔE Ex When less than or equal to, ΔE G ΔE much smaller than Ex The guest material (142) can be excited with an energy of a certain degree, thereby reducing the power consumption of the light-emitting device. Accordingly, the effect of the mechanism of one form of the present invention is the transition energy (ΔE) calculated from the absorption spectrum terminal of the guest material (142). G_abs The energy difference (ΔE) between the LUMO level and the HOMO level of the guest material (142) G It is evident when the energy difference of ) is large (especially when the guest material is a blue emitting material).

[0071] Transition energy (ΔE) calculated from the absorption spectrum of the guest material (142) G_absAs ) decreases, the luminescence energy of the guest material (142) also decreases. In this case, it is difficult to obtain luminescence requiring high energy, such as blue luminescence. That is, ΔE abs and ΔE G If the difference is excessively large, it becomes difficult to obtain high-energy luminescence, such as blue luminescence.

[0072] For this reason, the energy difference (ΔE) between the LUMO level and the HOMO level of the guest material (142) G ) is the transition energy (ΔE) calculated from the absorption spectrum terminal of the guest material (142) G_abs It is preferable that the luminescence energy (ΔE) of the guest material (142) be greater than 0.4 eV to 0.8 eV, more preferably 0.5 eV to 0.8 eV. Em ) is ΔE abs Since it is less than or equal to the energy difference (ΔE) between the LUMO level and the HOMO level of the guest material (142) G ) is the luminescence energy (ΔE) of the guest material (142). Em It is desirable that it be 0.4 eV to 0.8 eV larger than ), more preferably 0.5 eV to 0.8 eV larger.

[0073] The difference between the LUMO level of the guest material (142) and the LUMO level of the organic compound (141_1) is preferably 0.05 eV or more and 0.4 eV or less. The reason for this is that a suitable electron trap produces the effect of a long lifespan for the light-emitting device, while if the LUMO level of the guest material is excessively low, the aforementioned ΔE B This is because the difference in HOMO levels between the guest material (142) and the organic compound (141_2) is preferably 0.05 eV or more, more preferably 0.1 eV or more, and even more preferably 0.2 eV or more. This is because hole carriers are easily injected into the organic compound (141_2) due to the correlation of these energy levels.

[0074] The energy difference (ΔE) between the LUMO level of the organic compound (141_1) and the HOMO level of the organic compound (141_2). Ex Since ) is smaller than the energy difference between the LUMO and HOMO levels of the organic compound (141_1) and smaller than the energy difference between the LUMO and HOMO levels of the organic compound (141_2), the formation of an excited complex by the organic compound (141_1) and the organic compound (141_2) is energetically more stable than the formation of an excited state by the organic compound (141_1) alone or by the organic compound (141_2) alone. Additionally, the energy difference (ΔE) between the LUMO and HOMO levels of the guest material (142) G ) is the energy difference (ΔE) between the LUMO level of the organic compound (141_1) and the HOMO level of the organic compound (141_2). Ex Because it is larger than ), the formation of excited complexes by organic compounds (141_1) and organic compounds (141_2) as excited states formed by the recombination of carriers (holes and electrons) injected into the light-emitting layer (140) is energetically more stable. Therefore, most of the excited states generated in the light-emitting layer (140) exist as excited complexes formed by organic compounds (141_1) and organic compounds (141_2). Accordingly, a structure of one embodiment of the present invention facilitates the transfer of excitation energy from the excited complexes to the guest material (142), thereby lowering the driving voltage of the light-emitting element and increasing the luminous efficiency.

[0075] Additionally, the HOMO level of the guest material (142) may be higher or lower than the HOMO level of the organic compound (141_1).

[0076] Additionally, the guest material (142) functions as an electron trap in the light-emitting layer (140) because its LUMO level is lower than the LUMO level of the organic compound (141_1). This is desirable because the carrier balance in the light-emitting layer can be easily controlled and a long lifespan effect is obtained due to the guest material (142) functioning as an electron trap.

[0077] When the combination of the organic compound (141_1) and the organic compound (141_2) is a combination of a compound having hole transport and a compound having electron transport, the carrier balance can be easily controlled according to the mixing ratio. Specifically, it is preferable that the weight ratio of the compound having hole transport to the compound having electron transport is within the range of 1:9 to 9:1. With this structure, the carrier balance can be easily controlled, and the carrier recombination region can also be easily controlled.

[0078] The excited complex formed by the organic compound (141_1) and the organic compound (141_2) has a HOMO in one organic compound and a LUMO in the other organic compound, so the overlap between the HOMO and the LUMO is very small. That is, in the excited complex, the difference between the singlet excitation energy level and the triplet excitation energy level is small. Therefore, the difference between the triplet excitation energy level and the singlet excitation energy level of the excited complex formed by the organic compound (141_1) and the organic compound (141_2) is preferably greater than 0 eV and less than or equal to 0.2 eV, and more preferably greater than 0 eV and less than or equal to 0.1 eV.

[0079] FIG. 2 (B) illustrates the correlation of energy levels of an organic compound (141_1), an organic compound (141_2), and a guest material (142) in a light-emitting layer (140). The terms and symbols in FIG. 2 (B) are explained below.

[0080] Host(141_1): Host material(organic compound(141_1));

[0081] Host(141_2): Host material(organic compound(141_2));

[0082] Guest(142): Guest material(142)(phosphorescent material);

[0083] Exciplex: Excited complex (organic compound (141_1) and organic compound (141_2))

[0084] S PH1 : S1 level of the host material (organic compound (141_1));

[0085] T PH1 : T1 level of the host material (organic compound (141_1));

[0086] S PH2 : S1 level of the host material (organic compound (141_2));

[0087] T PH2 : T1 level of the host material (organic compound (141_2));

[0088] S PG : S1 level of guest material (142) (phosphorescent material);

[0089] T PG : T1 level of guest material (142) (phosphorescent material);

[0090] S PE : S1 level of the excited complex; and

[0091] T PE : T1 level of the excited complex.

[0092] In one embodiment of the light-emitting device of the present invention, organic compounds (141_1 and 141_2) included in the light-emitting layer (140) form an excited complex. The lowest singlet excitation energy level (S) of the excited complex. PE ) and the lowest triplet excitation energy level (T) of the excited complex PE ) are adjacent to each other (see root E7 in (B) of Fig. 2).

[0093] An excited complex is an excited state formed by two types of materials. In photoexcitation, an excited complex is formed by the interaction between one material in an excited state and the other material in a ground state. The two types of materials that formed the excited complex return to the ground state by the emission of light and act as the original two types of materials. In electroexcitation, when one material becomes excited, the one material immediately interacts with the other material to form an excited complex. Alternatively, one material receives a hole and the other material receives an electron, immediately forming an excited complex. In this case, since the excited complex can be formed without either material forming an excited state on its own, most of the excitons in the light-emitting layer (140) can exist as the excited complex. The excitation energy level (S) of the excited complex E or T E ) is the S1 level (S) of the host material (organic compound (141_1) and organic compound (141_2)) forming the excited complex. PH1 and S PH2 Because it is lower than ), the excited state of the host material (141) can be formed with a lower excitation energy. This allows the driving voltage of the light-emitting element (152) to be reduced.

[0094] And the S of the excited complex PE and T PE Both sides of the energy level of the lowest triplet excited state of the guest material (142) (phosphorescent material) (T PG When moved to ), luminescence is obtained (see E8 and E9 in (B) of Fig. 2).

[0095] Also, the T1 level (T PE ) is the T1 level (T of guest material (142) PG It is desirable that it be higher than ). In this way, the singlet excitation energy and triplet excitation energy of the formed excited complex are the S1 level (S) of the excited complex. PE ) and T1 level (TPE The T1 level (T) of the guest material (142) from ) PG It can be moved to ).

[0096] If the light-emitting layer (140) has the structure described above, light emission from the guest material (142) (phosphorescent material) of the light-emitting layer (140) can be efficiently obtained.

[0097] The above-described process through roots E7, E8, and E9 is sometimes referred to as ExTET (exciplex-triplet energy transfer) in this specification and other sources. In other words, in the light-emitting layer (140), excitation energy is transferred from the excited composite to the guest material (142). In this case, T PE From S PE The cross-terminal efficiency of the row does not necessarily need to be high, and S PE Since the emission quantum yield from it does not necessarily have to be high, materials can be selected from a wide range of options.

[0098] In addition, the above-described reaction can be represented by Equation (G3) to Equation (G5).

[0099] D + +A - →(D·A) * (G3)

[0100] (D·A) * +G→D+A+G * (G4)

[0101] G * →G+h ν (G5)

[0102] In formula (G3), one of the organic compound (141_1) and the organic compound (141_2) receives a hole (D + ) By the other side receiving the electron (A - ), organic compound (141_1) and organic compound (141_2) are excited complex ((D·A) * ) forms. In Equation (G4), the excited complex ((D·A) *As energy is transferred from ) to the guest material (142)(G), the excited state (G) of the guest material (142) * ) is generated. Then, as indicated by Equation (G5), the guest material (142) in the excited state emits light (h ν ).

[0103] In addition, in order to efficiently transfer the excitation energy from the guest material (142) to the excited complex, the T1 level (T PE It is preferable that the T1 level of the organic compounds (organic compound (141_1) and organic compound (141_2)) in the host material forming the excited complex is lower than the T1 level of the organic compounds. This makes it difficult for the triplet excitation energy of the excited complex to be quenched by the organic compounds, thereby allowing for efficient energy transfer to the guest material (142).

[0104] When the organic compound (141_2) contains a framework with strong donor properties, holes injected into the light-emitting layer (140) become easier to be injected into and transported by the organic compound (141_2). When the organic compound (141_1) contains a framework with strong acceptor properties, electrons injected into the light-emitting layer (140) become easier to be injected into and transported by the organic compound (141_1). Accordingly, the organic compound (141_1) and the organic compound (141_2) easily form an excited complex.

[0105] If the light-emitting layer (140) has the structure described above, light emission from the guest material (142) of the light-emitting layer (140) can be efficiently obtained.

[0106] Energy transport device

[0107] Next, the factors controlling the process of intermolecular energy transfer between the host material (141) and the guest material (142) will be described. Two mechanisms for intermolecular energy transfer have been proposed: the Foerster mechanism (dipole-dipole interaction) and the Dexter mechanism (electron exchange interaction). Here, the process of intermolecular energy transfer between the host material (141) and the guest material (142) will be described, but the same can be applied when the host material (141) is an excited complex.

[0108] Förster apparatus

[0109] In the Foerster mechanism, direct intermolecular contact is not required for energy transfer, and energy is transferred through the resonance phenomenon of dipole oscillations between the host material (141) and the guest material (142). Due to the resonance phenomenon of dipole oscillations, the host material (141) provides energy to the guest material (142), causing the excited host material (141) to become the ground state and the ground guest material (142) to become the excited state. Additionally, the rate constant of the Foerster mechanism k h *→ g It is expressed by equation (1).

[0110] [Equation 1]

[0111]

[0112] In Equation (1), ν represents the frequency, and f' h (ν) represents the normalized emission spectrum of the host material (141) (fluorescence spectrum in the energy shift from the singlet excited state, phosphorescence spectrum in the energy shift from the triplet excited state), and ε g (ν) represents the molar absorption coefficient of the guest material (142), and N represents Avogadro's number, and n represents the refractive index of the medium, and Rrepresents the intermolecular distance between the host material (141) and the guest material (142), and τ represents the lifetime of the excited state being measured (fluorescent lifetime or phosphorescent lifetime), c represents the speed of light, and φ represents the emission quantum yield (fluorescence quantum yield in the energy shift from the singlet excited state, and phosphorescence quantum yield in the energy shift from the triplet excited state), K 2 represents the coefficient (0 to 4) of the orientation of the transition dipole moment between the host material (141) and the guest material (142). Also, in the case of random orientation, K 2 is 2 / 3.

[0113] Dexter Device

[0114] In the Dexter mechanism, the host material (141) and the guest material (142) are close to an effective contact distance where their orbits overlap, and energy transfer occurs as the excited host material (141) and the ground-state guest material (142) exchange electrons. Additionally, the rate constant of the Dexter mechanism k h *→ g It is expressed by equation (2).

[0115] [Equation 2]

[0116]

[0117] In equation (2), h represents Planck's constant, and K represents a constant with energy dimensions, and ν represents frequency, f ' h (ν) represents the normalized emission spectrum of the host material (141) (fluorescence spectrum at energy shift from the singlet excited state, and phosphorescence spectrum at energy shift from the triplet excited state), and ε' g (ν) represents the normalized absorption spectrum of the guest material (142), and Lrepresents the effective molecular radius, and R It represents the intermolecular distance between the host material (141) and the guest material (142).

[0118] Here, the efficiency of energy transfer from the host material (141) to the guest material (142) (energy transfer efficiency φ) ET ) is expressed by Equation (3). In this equation k r The host material (141) represents the rate constant of the luminescence process (fluorescence in the energy transfer from the singlet excited state, and phosphorescence in the energy transfer from the triplet excited state), and k n represents the rate constant of the non-luminescent process (thermal deactivation or inter-term crossover) of the host material (141), and τ represents the lifetime of the excited state of the host material (141) being measured.

[0119] [Equation 3]

[0120]

[0121] According to Equation (3), the rate constant of energy transfer k h *→ g By making large, other competing speed constants k r + k n By making the energy transfer efficiency φ relatively small (=1 / τ), ET It can be seen that it can increase.

[0122] <<Concept to facilitate energy transfer>>

[0123] In energy transfer by the Foerster mechanism, high energy transfer efficiency φ ETThis is obtained when the quantum yield φ (fluorescence quantum yield when discussing energy transfer from a singlet excited state, and phosphorescence quantum yield when discussing energy transfer from a triplet excited state) is high. Additionally, it is desirable that the emission spectrum of the host material (141) (fluorescence spectrum when discussing energy transfer from a singlet excited state) overlaps significantly with the absorption spectrum of the guest material (142) (absorption corresponding to the transition from a singlet ground state to a triplet excited state). It is also desirable that the molar absorption coefficient of the guest material (142) is high. This means that the emission spectrum of the host material (141) overlaps with the absorption band on the longest wavelength side of the guest material (142).

[0124] In energy transfer by the Dexter mechanism, the rate constant k h*→g In order to increase the energy transfer efficiency, it is desirable that the emission spectrum of the host material (141) (fluorescence spectrum when discussing energy transfer from a singlet excited state, and phosphorescence spectrum when discussing energy transfer from a triplet excited state) overlap significantly with the absorption spectrum of the guest material (142) (absorption corresponding to the transfer from a singlet ground state to a triplet excited state). Accordingly, the energy transfer efficiency can be optimized by overlapping the emission spectrum of the host material (141) with the absorption band on the longest wavelength side of the guest material (142).

[0125] In a manner similar to the energy transfer from the host material (141) to the guest material (142), energy transfer by both the Foerster mechanism and the Dexter mechanism also occurs during the energy transfer process from the excited complex to the guest material (142).

[0126] Accordingly, one embodiment of the present invention provides a light-emitting device comprising an organic compound (141_1) and an organic compound (141_2) as a host material (141), which are a combination forming an excited complex that functions as an energy donor capable of efficiently transferring energy to a guest material (142). The excitation energy for forming the excited complex by the organic compound (141_1) and the organic compound (141_2) can be lower than the excitation energy of the organic compound (141_1) in the excited state and lower than the excitation energy of the organic compound (141_2) in the excited state. Thus, the driving voltage of the light-emitting device (152) can be reduced. Additionally, in order to facilitate energy transfer from the singlet excitation energy level of the excited complex to the triplet excitation energy level of the guest material (142) that functions as an energy acceptor, it is preferable that the absorption band of the guest material (142) at the longest wavelength side (low energy side) overlaps with the emission spectrum of the excited complex. Therefore, the efficiency of generating a triplet excited state of the guest material (142) can be increased. The excited complex generated in the light-emitting layer (140) has the characteristic that the singlet excited energy level approaches the triplet excited energy level. Therefore, by overlapping the absorption band of the guest material (142) at the longest wavelength side (lowest energy side) with the emission spectrum of the excited complex, the energy transfer from the triplet excited energy level of the excited complex to the triplet excited energy level of the guest material (142) can be facilitated.

[0127] Ingredients

[0128] Next, the components of a light-emitting element of one embodiment of the present invention will be described in detail below.

[0129] <<Luminous Layer>>

[0130] In the light-emitting layer (140), the host material (141) is present in the largest weight ratio, and the guest material (142) (phosphorescent material) is dispersed within the host material (141). It is preferable that the T1 level of the host material (141) (organic compound (141_1) and organic compound (141_2)) in the light-emitting layer (140) is higher than the T1 level of the guest material (guest material (142)) in the light-emitting layer (140).

[0131] As an organic compound (141_1), a material having the characteristic of transporting electrons more than holes can be used, and the electron mobility is 1×10 -6 cm 2 A material having / Vs or higher is preferred. For example, a compound containing a π-electron-deficient complex aromatic ring skeleton, such as a nitrogen-containing complex aromatic compound, a metal complex, or a zinc-based metal complex or an aluminum-based metal complex can be used as a material that readily accepts electrons (a material having electron transport properties). Specific examples include a metal complex having a quinoline ligand, a benzoquinoline ligand, an oxazole ligand, or a thiazole ligand, which can be described as an electron transport material that can be used in an organic compound (141_1), and oxadiazole derivatives, triazole derivatives, benzimidazole derivatives, quinoxaline derivatives, dibenzoquinoxaline derivatives, phenanthroline derivatives, pyridine derivatives, bipyridine derivatives, pyrimidine derivatives, and triazine derivatives, which can be cited as electron transport materials that can be used in an organic compound (141_1).

[0132] Specific examples include tris(8-quinolinolenate)aluminum(III) (abbreviated: Alq), tris(4-methyl-8-quinolinolenate)aluminum(III) (abbreviated: Almq3), and bis(10-hydroxybenzo[ hMetal complexes having a quinoline or benzoquinoline backbone, such as ]quinolinato)beryllium(II) (abbreviated: BeBq2), bis(2-methyl-8-quinolinoleato)(4-phenylphenolato)aluminum(III) (abbreviated: BAlq), and bis(8-quinolinoleato)zinc(II) (abbreviated: Znq), are included. Alternatively, metal complexes having oxazole or thiazole ligands, such as bis[2-(2-benzoxazolyl)phenolate]zinc(II) (abbreviated: ZnPBO) or bis[2-(2-benzothiazolyl)phenolate]zinc(II) (abbreviated: ZnBTZ), may be used. In addition to these metal complexes, any of the following may be used: 2-(4-biphenylyl)-5-(4- tert -butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD), 1,3-bis[5-( p - tert -butylphenyl)-1,3,4-oxadiazole-2-yl]benzene (abbreviation: OXD-7), 9-[4-(5-phenyl-1,3,4-oxadiazole-2-yl)phenyl]-9 H -Carbazole (abbreviation: CO11), 3-(biphenyl-4-yl)-4-phenyl-5-(4- tert -butylphenyl)-1,2,4-triazole (abbreviation: TAZ), 9-[4-(4,5-diphenyl-4 H -1,2,4-triazole-3-yl)phenyl]-9 H -Carbazole (abbreviation: CzTAZ1), 2,2',2''-(1,3,5-benzenetriyl)tris(1-phenyl-1 H 2-Benzimidazole)(abbreviation: TPBI), 2-[3-(dibenzothiophen-4-yl)phenyl]-1-phenyl-1 H - Homocyclic compounds such as benzimidazole (abbreviation: mDBTBIm-II), vasophenanthroline (abbreviation: BPhen), and vasocuproin (abbreviation: BCP); 2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[ f , h ]quinoxaline (abbreviation: 2mDBTPDBq-II), 2-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[ f , h]quinoxaline (abbreviation: 2mDBTBPDBq-II), 2-[3'-(9 H -carbazole-9-yl)biphenyl-3-yl]dibenzo[ f , h ]quinoxaline (abbreviation: 2mCzBPDBq), 2-[4-(3,6-diphenyl-9 H -carbazole-9-yl)phenyl]dibenzo[ f , h ]quinoxaline (abbreviation: 2CzPDBq-III), 7-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[ f , h ]quinoxaline (abbreviation: 7mDBTPDBq-II), 6-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[ f , h ]quinoxaline (abbreviation: 6mDBTPDBq-II), 2-[3-(3,9'-bi-9 H -carbazole-9-yl)phenyl]dibenzo[ f , h ]quinoxaline (abbreviated: 2mCzCzPDBq), 4,6-bis[3-(phenanthren-9-yl)phenyl]pyrimidine (abbreviated: 4,6mPnP2Pm), 4,6-bis[3-(4-dibenzothienyl)phenyl]pyrimidine (abbreviated: 4,6mDBTP2Pm-II), and 4,6-bis[3-(9 H Heterocyclic compounds having a diazine backbone such as -carbazole-9-yl)phenyl]pyrimidine (abbreviation: 4,6mCzP2Pm); 2-{4-[3-( N -phenyl-9 H -Carbazol-3-day)-9 H Heterocyclic compounds having a triazine backbone such as -carbazole-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviated: PCCzPTzn); 3,5-bis[3-(9 HA heterocyclic compound having a pyridine backbone such as -carbazole-9-yl)phenyl]pyridine (abbreviated: 35DCzPPy); and a heteroaromatic compound such as 4,4'-bis(5-methylbenzoxazole-2-yl)stilbene (abbreviated: BzOs). Among the heterocyclic compounds, a heterocyclic compound having a triazine backbone, a diazine backbone (pyrimidine, pyrazine, pyridazine), or a pyridine backbone is preferably used because it is highly reliable and stable. In addition, the heterocyclic compound having the above backbone has high electron transportability and contributes to the reduction of the driving voltage. Alternatively, polymeric compounds such as poly(2,5-pyridinediyl) (abbreviated: PPy), poly[(9,9-dihexylfluorene-2,7-diyl)-co-(pyridine-3,5-diyl)] (abbreviated: PF-Py), or poly[(9,9-dioctylfluorene-2,7-diyl)-co-(2,2'-bipyridine-6,6'-diyl)] (abbreviated: PF-BPy) may be used. The materials described herein mainly have an electron mobility of 1×10⁻⁶ -6 cm 2 It is a material with / Vs or higher. Additionally, other materials may be used as long as electron transport is higher than hole transport.

[0133] As the organic compound (141_2), it is preferable to use a material capable of forming an excited complex together with the organic compound (141_1). Specifically, the organic compound (141_2) preferably includes a highly donorable framework, such as a π-electron-excess complex aromatic ring framework or an aromatic amine framework. Examples of compounds having a π-electron-excess complex aromatic ring framework include complex aromatic compounds such as dibenzothiophene derivatives, dibenzofuran derivatives, and carbazole derivatives. In this case, it is preferable to select the organic compound (141_1), the organic compound (141_2), and the guest material (142) (phosphorescent material) such that the emission peak of the excited complex formed by the organic compound (141_1) and the organic compound (141_2) overlaps with the absorption band, specifically the absorption band on the longest wavelength side of the triplet MLCT (metal to ligand charge transfer) transition of the guest material (142) (phosphorescent material). This makes it possible to provide a light-emitting device with significantly improved luminous efficiency. Furthermore, when a thermally activated delayed fluorescent material is used instead of a phosphorescent material, it is desirable that the absorption band on the longest wavelength side becomes a singlet absorption band.

[0134] As an organic compound (141_2), a material having hole transport properties as described below can be used.

[0135] As hole transport materials, materials having the characteristic of transporting more holes than electrons can be used, and the hole mobility is 1×10 -6 cm 2 A material with a value of / Vs or higher is preferred. Specifically, aromatic amines, carbazole derivatives, aromatic hydrocarbons, or stilbene derivatives may be used. In addition, the hole transport material may be a polymer compound.

[0136] Examples of materials with high hole transport include N , N '-die( p -Tolil)-N , N -diphenyl- p -phenylenediamine (abbreviation: DTDPPA), 4,4'-bis[ N -(4-diphenylaminophenyl)- N -phenylamino]biphenyl (abbreviation: DPAB), N , N -bis{4-[bis(3-methylphenyl)amino]phenyl}- N , N '-diphenyl-(1,1'-biphenyl)-4,4'-diamine (abbreviated: DNTPD), and 1,3,5-tris[ N -(4-diphenylaminophenyl)- N -Phenylamino]benzene (abbreviation: DPA3B), etc.

[0137] Specific examples of carbazole derivatives include 3-[ N -(4-diphenylaminophenyl)- N -phenylamino]-9-phenylcarbazole (abbreviation: PCzDPA1), 3,6-bis[ N -(4-diphenylaminophenyl)- N -phenylamino]-9-phenylcarbazole (abbreviation: PCzDPA2), 3,6-bis[ N -(4-diphenylaminophenyl)- N -(1-naphthyl)amino]-9-phenylcarbazole (abbreviated: PCzTPN2), 3-[ N -(9-phenylcarbazole-3-yl)- N -phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA1), 3,6-bis[ N -(9-phenylcarbazole-3-yl)- N -phenylamino]-9-phenylcarbazole (abbreviated: PCzPCA2), and 3-[ N -(1-Naphthyl)- N Examples include -(9-phenylcarbazole-3-yl)amino]-9-phenylcarbazole (abbreviated: PCzPCN1).

[0138] Other examples of carbazole derivatives include 4,4'-di( N -Carbazolyl)biphenyl (abbreviated: CBP), 1,3,5-tris[4-( N-carbazolyl)phenyl]benzene (abbreviation: TCPB), 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9 H -carbazole (abbreviation: CzPA), and 1,4-bis[4-( N Examples include -carbazolyl)phenyl]-2,3,5,6-tetraphenylbenzene, etc.

[0139] Examples of aromatic hydrocarbons include 2- tert -Butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA), 2- tert -Butyl-9,10-di(1-naphthyl)anthracene, 9,10-bis(3,5-diphenylphenyl)anthracene (abbreviation: DPPA), 2- tert -Butyl-9,10-bis(4-phenylphenyl)anthracene (abbreviation: t-BuDBA), 9,10-di(2-naphthyl)anthracene (abbreviation: DNA), 9,10-diphenylanthracene (abbreviation: DPAnth), 2- tert -Butylanthracene (abbreviation: t-BuAnth), 9,10-bis(4-methyl-1-naphthyl)anthracene (abbreviation: DMNA), 2- tert -butyl-9,10-bis[2-(1-naphthyl)phenyl]anthracene, 9,10-bis[2-(1-naphthyl)phenyl]anthracene, 2,3,6,7-tetramethyl-9,10-di(1-naphthyl)anthracene, 2,3,6,7-tetramethyl-9,10-di(2-naphthyl)anthracene, 9,9'-bianthrile, 10,10'-diphenyl-9,9'-bianthrile, 10,10'-bis(2-phenylphenyl)-9,9'-bianthrile, 10,10'-bis[(2,3,4,5,6-pentaphenyl)phenyl]-9,9'-bianthrile, anthracene, tetracene, rubrene, perylene, and 2,5,8,11-tetra( tert -Butyl perylene, etc. Other examples include pentacene and coronene. Hole mobility is 1×10⁻⁶ -6 cm 2 Aromatic hydrocarbons having a carbon number of 14 to 42 and a Vs of or greater are particularly preferred.

[0140] Aromatic hydrocarbons may have a vinyl backbone. Examples of aromatic hydrocarbons having a vinyl group include 4,4'-bis(2,2-diphenylvinyl)biphenyl (abbreviated: DPVBi) and 9,10-bis[4-(2,2-diphenylvinyl)phenyl]anthracene (abbreviated: DPVPA).

[0141] Another example is poly( N -Vinylcarbazole)(abbreviation: PVK), poly(4-vinyltriphenylamine)(abbreviation: PVTPA), poly[ N -(4-{ N '-[4-(4-diphenylamino)phenyl]phenyl- N '-phenylamino}phenyl)methacrylamide](abbreviated: PTPDMA), and poly[ N , N -bis(4-butylphenyl)- N , N It is a polymer compound such as [-bis(phenyl)benzidine] (abbreviated: Poly-TPD).

[0142] Examples of materials with high hole transport include 4,4'-bis[ N -(1-Naphthyl)- N -phenylamino]biphenyl (abbreviated: NPB or α-NPD), N , N -bis(3-methylphenyl)- N , N '-diphenyl-[1,1'-biphenyl]-4,4'-diamine (abbreviation: TPD), 4,4',4''-tris(carbazole-9-yl)triphenylamine (abbreviation: TCTA), 4,4',4''-tris[ N -(1-Naphthyl)- N -phenylamino]triphenylamine (abbreviation: 1'-TNATA), 4,4',4''-tris( N , N -Diphenylamino)triphenylamine (abbreviation: TDATA), 4,4',4''-tris[ N -(3-methylphenyl)- N -phenylamino]triphenylamine (abbreviation: MTDATA), 4,4'-bis[ N -(Spyro-9,9'-bifluorene-2-yl)- N―phenylamino]biphenyl (abbreviation: BSPB), 4-phenyl-4'-(9-phenylfluorene-9-yl)triphenylamine (abbreviation: BPAFLP), 4-phenyl-3'-(9-phenylfluorene-9-yl)triphenylamine (abbreviation: mBPAFLP), N -(9,9-dimethyl-9 H -Fluoren-2-il)- N -{9,9-dimethyl-2-[ N '-phenyl- N -(9,9-dimethyl-9 H -fluorene-2-yl)amino]-9 H -fluorene-7-yl}phenylamine (abbreviated: DFLADFL), N -(9,9-dimethyl-2-diphenylamino-9 H -Fluorene-7-yl)diphenylamine (abbreviation: DPNF), 2-[ N -(4-diphenylaminophenyl)- N -phenylamino]spiro-9,9'-bifluorene (abbreviation: DPASF), 4-phenyl-4'-(9-phenyl-9 H -Carbazole-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4'-diphenyl-4''-(9-phenyl-9 H -Carbazole-3-yl)triphenylamine (abbreviation: PCBBi1BP), 4-(1-naphthyl)-4'-(9-phenyl-9 H -Carbazole-3-yl)triphenylamine (abbreviation: PCBANB), 4,4'-di(1-naphthyl)-4''-(9-phenyl-9 H -Carbazole-3-yl)triphenylamine (abbreviation: PCBNBB), 4-phenyldiphenyl-(9-phenyl-9 H -Carbazole-3-yl)amine (abbreviation: PCA1BP), N , N -bis(9-phenylcarbazole-3-yl)- N , N -Diphenylbenzene-1,3-diamine (abbreviation: PCA2B), N , N ', N ''-triphenyl- N , N ', N''-Tris(9-phenylcarbazole-3-yl)benzene-1,3,5-triamine (abbreviation: PCA3B), N -(4-biphenyl)- N -(9,9-dimethyl-9 H -fluorene-2-yl)-9-phenyl-9 H -Carbazole-3-amine (abbreviation: PCBiF), N -(1,1'-biphenyl-4-yl)- N -[4-(9-phenyl-9 H -carbazole-3-yl)phenyl]-9,9-dimethyl-9 H -Fluorene-2-amine (abbreviation: PCBBiF), 9,9-dimethyl- N -phenyl- N -[4-(9-phenyl-9 H -carbazole-3-yl)phenyl]fluorene-2-amine (abbreviated: PCBAF), N -phenyl- N -[4-(9-phenyl-9 H -carbazole-3-yl)phenyl]spiro-9,9'-bifluorene-2-amine (abbreviated: PCBASF), 2-[ N -(9-phenylcarbazole-3-yl)- N -phenylamino]spiro-9,9'-bifluorene (abbreviation: PCASF), 2,7-bis[ N -(4-diphenylaminophenyl)- N -phenylamino]-spiro-9,9'-bifluorene (abbreviation: DPA2SF), N -[4-(9 H -carbazole-9-yl)phenyl]- N -(4-phenyl)phenylaniline (abbreviation: YGA1BP), and N , N '-bis[4-(carbazole-9-yl)phenyl]- N , N There are aromatic amine compounds such as -diphenyl-9,9-dimethylfluorene-2,7-diamine (abbreviated: YGA2F). Other examples include 3-[4-(1-naphthyl)-phenyl]-9-phenyl-9 H -Carbazole (abbreviation: PCPN), 3-[4-(9-phenanthryl)-phenyl]-9-phenyl-9 H -Carbazole (abbreviation: PCPPn), 3,3'-bis(9-phenyl-9)H -Carbazole)(abbreviation: PCCP), 1,3-bis( N -carbazolyl)benzene (abbreviation: mCP), 3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviation: CzTP), 3,6-di(9 H -carbazole-9-yl)-9-phenyl-9 H -Carbazol (abbreviation: PhCzGI), 2,8-di(9 H -carbazole-9-yl)-dibenzothiophen (abbreviation: Cz2DBT), 4-{3-[3-(9-phenyl-9 H -fluorene-9-yl)phenyl]phenyl}dibenzofuran (abbreviation: mmDBFFLBi-II), 4,4',4''-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation: DBF3P-II), 1,3,5-tri(dibenzothiophen-4-yl)-benzene (abbreviation: DBT3P-II), 2,8-diphenyl-4-[4-(9-phenyl-9 H -fluorene-9-yl)phenyl]dibenzothiophene (abbreviation: DBTFLP-III), 4-[4-(9-phenyl-9 H There are amine compounds such as fluorene-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviated: DBTFLP-IV) and 4-[3-(triphenylene-2-yl)phenyl]dibenzothiophene (abbreviated: mDBTPTp-II), carbazole compounds, thiophene compounds, furan compounds, fluorene compounds, triphenylene compounds, and phenanthrene compounds. Among the compounds described above, compounds containing a pyrrole backbone, a furan backbone, a thiophene backbone, or an aromatic amine backbone are preferred because they have high stability and reliability. In addition, compounds having the above backbones have high hole transport and contribute to the reduction of the driving voltage.

[0143] As the guest material (142) (phosphorescent material), an iridium-based, rhodium-based, or platinum-based organometallic complex or metal complex may be used, and an organoiridium complex, such as an iridium-based ortho-metallated complex, is particularly preferred. As for the ortho-metallated ligand, 4 H - Triazole ligand, 1 HExamples include triazole ligands, imidazole ligands, pyridine ligands, pyrimidine ligands, pyrazine ligands, and isoquinoline ligands. Examples of metal complexes include platinum complexes having porphyrin ligands.

[0144] It is preferable that the organic compound (141_1), the organic compound (141_2), and the guest material (142) (phosphorescent material) be selected such that the LUMO level of the guest material (142) (phosphorescent material) is lower than that of the organic compound (141_1) and the HOMO level of the guest material (142) is lower than that of the organic compound (141_2). With this structure, a light-emitting device with high luminous efficiency and low driving voltage can be obtained.

[0145] Examples of substances having emission peaks in the blue or green wavelength range include tris{2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)-4 H -1,2,4-triazole-3-yl-κ N 2]phenyl-κ C}Iridium(III) (abbreviation: Ir(mpptz-dmp)3), tris(5-methyl-3,4-diphenyl-4 H -1,2,4-triazoleate)iridium(III)(abbreviation: Ir(Mptz)3), tris[4-(3-biphenyl)-5-isopropyl-3-phenyl-4 H -1,2,4-triazoleto]iridium(III) (abbreviated: Ir(iPrptz-3b)3), and tris[3-(5-biphenyl)-5-isopropyl-4-phenyl-4 H 4 of -1,2,4-triazoleate]iridium(III) (abbreviated: Ir(iPr5btz)3) etc. H -Organometallic iridium complex having a triazole backbone; tris[3-methyl-1-(2-methylphenyl)-5-phenyl-1 H -1,2,4-triazoleto]iridium(III) (abbreviated: Ir(Mptz1-mp)3) and tris(1-methyl-5-phenyl-3-propyl-1 H-1,2,4-triazoleate)iridium(III) (abbreviation: Ir(Prptz1-Me)3) etc. 1 H -Organometallic iridium complex having a triazole backbone; fac -tris[1-(2,6-diisopropylphenyl)-2-phenyl-1 H -imidazole]iridium(III) (abbreviation: Ir(iPrpmi)3) and tris[3-(2,6-dimethylphenyl)-7-methylimidazo[1,2- f Organometallic iridium complexes having an imidazole backbone such as ]phenantridinato]iridium(III) (abbreviated: Ir(dmpimpt-Me)3); and bis[2-(4',6'-difluorophenyl)pyridinato- N , C 2' ]Iridium(III)tetrakis(1-pyrazolyl)borate (abbreviated: FIr6), bis[2-(4',6'-difluorophenyl)pyridinate- N , C 2' ]Iridium(III)picolinate (abbreviated: FIrpic), bis{2-[3',5'-bis(trifluoromethyl)phenyl]pyridinate- N , C 2'}Iridium(III)picolinate (abbreviated: Ir(CF3ppy)2(pic)), and bis[2-(4',6'-difluorophenyl)pyridinate- N , C 2' Organometallic iridium complexes are included, wherein a phenylpyridine derivative having an electron-withdrawing group such as iridium(III) acetylacetonate (abbreviated: FIr(acac)) is used as a ligand. Among the materials described above, 4 H -Triazole backbone, 1 H Organometallic iridium complexes containing nitrogen-containing five-membered heterocyclic skeletons, such as triazole skeletons or imidazole skeletons, are particularly desirable due to their high triplet excitation energy, reliability, and luminescence efficiency.

[0146] Examples of substances having emission peaks in the green or yellow wavelength range include tris(4-methyl-6-phenylpyrimidineto)iridium(III) (abbreviated: Ir(mppm)3), tris(4- t -butyl-6-phenylpyrimidinato)iridium(III)(abbreviation: Ir(tBuppm)3), (acetylacetonato)bis(6-methyl-4-phenylpyrimidinato)iridium(III)(abbreviation: Ir(mppm)2(acac)), (acetylacetonato)bis(6- tert -butyl-4-phenylpyrimidinato)iridium(III)(abbreviated: Ir(tBuppm)2(acac)), (acetylacetonato)bis[4-(2-norbonyl)-6-phenylpyrimidinato]iridium(III)(abbreviated: Ir(nbppm)2(acac)), (acetylacetonato)bis[5-methyl-6-(2-methylphenyl)-4-phenylpyrimidinato]iridium(III)(abbreviated: Ir(mpmppm)2(acac)), (acetylacetonato)bis{4,6-dimethyl-2-[6-(2,6-dimethylphenyl)-4-pyrimidinyl-κ N 3]phenyl-κ C Organometallic iridium complexes having a pyrimidine backbone such as iridium(III) (abbreviated: Ir(dmppm-dmp)2(acac)) and (acetylacetonato)bis(4,6-diphenylpyrimidineto)iridium(III) (abbreviated: Ir(dppm)2(acac)); organometallic iridium complexes having a pyrazine backbone such as (acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazineto)iridium(III) (abbreviated: Ir(mppr-Me)2(acac)) and (acetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazineto)iridium(III) (abbreviated: Ir(mppr-iPr)2(acac)); tris(2-phenylpyridineto- N , C 2' )Iridium(III) (abbreviation: Ir(ppy)3), bis(2-phenylpyridineto- N , C 2' )Iridium(III)acetylacetonate (abbreviation: Ir(ppy)2(acac)), bis(benzo[ h]quinolinate)iridium(III)acetylacetonate (abbreviation: Ir(bzq)2(acac)), tris(benzo[ h ]quinolinato)iridium(III) (abbreviation: Ir(bzq)3), tris(2-phenylquinolinato- N , C 2' )iridium(III) (abbreviated: Ir(pq)3), and bis(2-phenylquinolinate- N , C 2' Organometallic iridium complexes having a pyridine backbone such as )iridium(III) acetylacetonate (abbreviated: Ir(pq)2(acac)); bis(2,4-diphenyl-1,3-oxazolato- N , C 2' )Iridium(III)acetylacetonate (abbreviation: Ir(dpo)2(acac)), bis{2-[4'-(perfluorophenyl)phenyl]pyridinate- N , C 2'}Iridium(III)acetylacetonate (abbreviated: Ir(p-PF-ph)2(acac)), and bis(2-phenylbenzothiazolate- N , C 2' Organometallic iridium complexes such as iridium(III) acetylacetonate (abbreviated: Ir(bt)2(acac)); and rare earth metal complexes such as tris(acetylacetonate)(monophenanthrolin)terbium(III) (abbreviated: Tb(acac)3(Phen)) are included. Among the materials described above, an organometallic iridium complex having a pyrimidine backbone is particularly preferred because it has remarkably high reliability and luminescence efficiency.

[0147] Examples of materials having emission peaks in the yellow or red wavelength range include organometallic iridium complexes having a pyrimidine backbone, such as (diisobutylmetaneto)bis[4,6-bis(3-methylphenyl)pyrimidineto]iridium(III) (abbreviated: Ir(5mdppm)2(dibm)), bis[4,6-bis(3-methylphenyl)pyrimidineto](dipivaloylmetaneto)iridium(III) (abbreviated: Ir(5mdppm)2(dpm)), and bis[4,6-di(naphthalene-1-yl)pyrimidineto](dipivaloylmetaneto)iridium(III) (abbreviated: Ir(d1npm)2(dpm)); Organometallic iridium complexes having a pyrazine backbone such as (acetylacetonato)bis(2,3,5-triphenylpyrazineto)iridium(III) (abbreviated: Ir(tppr)2(acac)), bis(2,3,5-triphenylpyrazineto)(dipivaloylmetaneto)iridium(III) (abbreviated: Ir(tppr)2(dpm)), and (acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III) (abbreviated: Ir(Fdpq)2(acac)); tris(1-phenylisoquinolinato- N , C 2' )Iridium(III) (abbreviated: Ir(piq)3) and bis(1-phenylisoquinolinate- N , C 2' Organometallic iridium complexes having a pyridine backbone, such as iridium(III) acetylacetonate (abbreviated: Ir(piq)2(acac)); 2,3,7,8,12,13,17,18-octaethyl-21 H ,23 HPlatinum complexes such as porphyrin platinum(II) (abbreviated: PtOEP); and rare earth metal complexes such as tris(1,3-diphenyl-1,3-propanedioto)(monophenanthrolin)europium(III) (abbreviated: Eu(DBM)3(Phen)) and tris[1-(2-tenoyl)-3,3,3-trifluoroacetonato](monophenanthrolin)europium(III) (abbreviated: Eu(TTA)3(Phen)) are included. Among the materials described above, organometallic iridium complexes having a pyrimidine backbone are particularly preferred because they exhibit remarkably high reliability and luminescence efficiency. Additionally, organometallic iridium complexes having a pyrazine backbone can provide red luminescence with good color intensity.

[0148] The above-described organometallic iridium complex having a pyrimidine backbone or a pyrazine backbone is suitable for one embodiment of the present invention because it has a ligand with high electron acceptability and is prone to having a low LUMO level. Likewise, a compound having an electron-withdrawing group, such as a halogen group (e.g., a fluoro group) or a cyano group (e.g., an iridium complex), is suitable because it is prone to having a low LUMO level.

[0149] As for the light-emitting material included in the light-emitting layer (140), any material can be used as long as it is a material capable of converting triplet excitation energy into light emission. Examples of materials capable of converting triplet excitation energy into light emission include, in addition to phosphorescent materials, thermally activated delayed fluorescence (TADF) materials. Therefore, in the description, "phosphorescent material" may be replaced with "thermally activated delayed fluorescence material." Furthermore, a thermally activated delayed fluorescence material is a material that has a small difference between the triplet excitation energy level and the singlet excitation energy level and has the function of converting triplet excitation energy into singlet excitation energy through inverse term crossing. Therefore, the TADF material can upconvert the triplet excited state to the singlet excited state using a small amount of thermal energy (i.e., inverse term crossing is possible), and can efficiently exhibit light emission (fluorescence) from the singlet excited state. TADF is efficiently obtained under conditions where the energy difference between the triplet excitation energy level and the singlet excitation energy level is preferably greater than 0 eV and less than or equal to 0.2 eV, and more preferably greater than 0 eV and less than or equal to 0.1 eV.

[0150] If the heat-activated delayed fluorescent material is composed of a type of material, for example, any of the following materials may be used.

[0151] First, fullerenes, their derivatives, acridin derivatives such as proflavins, and eosin can be cited. Additionally, metal-containing porphyrins such as porphyrins containing magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), or palladium (Pd) can be cited. Examples of metal-containing porphyrins include protoporphyrin-tin fluoride complex (SnF2(Proto IX)), mesoporphyrin-tin fluoride complex (SnF2(Meso IX)), hematoporphyrin-tin fluoride complex (SnF2(Hemato IX)), coproporphyrin tetramethyl ester-tin fluoride complex (SnF2(Copro III-4Me)), octaethylporphyrin-tin fluoride complex (SnF2(OEP)), ethioporphyrin-tin fluoride complex (SnF2(Etio I)), and octaethylporphyrin-platinum chloride complex (PtCl2(OEP)).

[0152] As a thermally activated delayed fluorescent material composed of a single type of material, a complex ring compound comprising a π-electron-excess complex aromatic ring and a π-electron-deficient complex aromatic ring may also be used. Specifically, 2-(biphenyl-4-yl)-4,6-bis(12-phenylindolo[2,3- a ]carbazole-11-yl)-1,3,5-triazine (abbreviation: PIC-TRZ), 2-{4-[3-( N -phenyl-9 H -Carbazol-3-day)-9 H -carbazole-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: PCCzPTzn), 2-[4-(10 H -Phenoxazine-10-yl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviation: PXZ-TRZ), 3-[4-(5-phenyl-5,10-dihydrophenazine-10-yl)phenyl]-4,5-diphenyl-1,2,4-triazole (abbreviation: PPZ-3TPT), 3-(9,9-dimethyl-9 H -Acridin-10-day)-9 H- Xanthen-9-one (abbreviation: ACRXTN), bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone (abbreviation: DMAC-DPS), or 10-phenyl-10 H ,10' H -Spiro[acridine-9,9'-anthracene]-10'-one (abbreviated: ACRSA) may be used. The above-mentioned complex ring compound is preferred because it possesses π-electron-excessive complex aromatic rings and π-electron-deficient complex aromatic rings with high electron and hole transport. Among the frameworks having π-electron-deficient complex aromatic rings, diazine frameworks (pyrimidine framework, pyrazine framework, or pyridazine framework) and triazine frameworks are particularly preferred due to their high stability and reliability. Among the frameworks having π-electron-excessive complex aromatic rings, acridine framework, phenoxazine framework, thiophene framework, furan framework, and pyrrole framework are preferred because they exhibit high stability and reliability; therefore, it is desirable to include one or more of these frameworks. As a pyrrole framework, an indole framework, a carbazole framework, or 3-(9-phenyl-9) H -Carbazol-3-day)-9 H - A carbazole backbone is particularly desirable. In addition, a material in which a π-electron-excess complex aromatic ring is directly bonded to a π-electron-deficient complex aromatic ring is particularly desirable because both the donor nature of the π-electron-excess complex aromatic ring and the acceptor nature of the π-electron-deficient complex aromatic ring are high, and the difference between the singlet excitation energy level and the triplet excitation energy level is small.

[0153] The light-emitting layer (140) may have a structure in which two or more layers are stacked. For example, when the light-emitting layer (140) is formed by stacking the first light-emitting layer and the second light-emitting layer in this order on the side of the hole transport layer, the first light-emitting layer is formed using a material having hole transport properties as a host material, and the second light-emitting layer is formed using a material having electron transport properties as a host material. The light-emitting material included in the first light-emitting layer may be the same as or different from the light-emitting material included in the second light-emitting layer. In addition, these materials may have the function of emitting light of the same color, or they may have the function of emitting light of a different color. By using two types of light-emitting materials having the function of emitting light of a different color in the two light-emitting layers, light of multiple light-emitting colors can be obtained simultaneously. It is particularly desirable to select the light-emitting material of the light-emitting layer so that white light can be obtained by combining the light emission from the two light-emitting layers.

[0154] The light-emitting layer (140) may include materials other than the host material (141) and the guest material (142).

[0155] Additionally, the light-emitting layer (140) can be formed by a deposition method (including vacuum deposition), an inkjet method, a coating method, or gravure printing, etc. In addition to the materials described above, inorganic compounds such as quantum dots or polymer compounds (e.g., oligomers, dendrimers, and polymers) may also be used.

[0156] <<Hole Injection Layer>>

[0157] The hole injection layer (111) is formed using, for example, a transition metal oxide, a phthalocyanine derivative, or an aromatic amine to reduce the barrier to hole injection from one of the pair of electrodes (electrode (101) or electrode (102)) in order to promote hole injection. Examples of transition metal oxides include molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, or manganese oxide. Examples of phthalocyanine derivatives include phthalocyanine or metal phthalocyanine. Examples of aromatic amines include benzidine derivatives or phenylenediamine derivatives. Polymeric compounds such as polythiophene or polyaniline may also be used, and a representative example is poly(ethylenedioxythiophene) / poly(styrenesulfonic acid), which is a self-doped polythiophene.

[0158] As a hole injection layer (111), a layer comprising a composite material of a hole transport material and a material having the property of receiving electrons from the hole transport material may be used. Alternatively, a stack of a layer comprising a material having electron accepting properties and a layer comprising a hole transport material may be used. In a steady state or in the presence of an electric field, charges may be transferred between these materials. Examples of materials having electron accepting properties include organic acceptors such as quinodimethane derivatives, chloranyl derivatives, and hexa-azatriphenylene derivatives. Specific examples include compounds having electron-withdrawing groups (halogen groups or cyano groups), such as 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviated: F4-TCNQ), chloranyl, or 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviated: HAT-CN). Alternatively, transition metal oxides, such as oxides of metals from Group 4 to Group 8, may be used. Specifically, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide, or rhenium oxide may be used. In particular, molybdenum oxide is preferred because it is stable in the atmosphere, has low hygroscopicity, and is easy to handle.

[0159] As hole transport materials, materials having the characteristic of transporting more holes than electrons can be used, and the hole mobility is 1×10 -6 cm 2 A material with a value greater than / Vs is preferred. Specifically, any of the aromatic amines, carbazole derivatives, aromatic hydrocarbons, and stilbene derivatives described as examples of hole transport materials that can be used in the light-emitting layer (140) may be used. Additionally, the hole transport material may be a polymer compound.

[0160] <<Precision Transport Layer>>

[0161] The hole transport layer (112) is a layer containing a hole transport material and can be formed using any of the hole transport materials exemplified as the material of the hole injection layer (111). In order for the hole transport layer (112) to have the function of transporting holes injected into the hole injection layer (111) to the light-emitting layer (140), it is preferable that the HOMO level of the hole transport layer (112) is equal to or close to the HOMO level of the hole injection layer (111).

[0162] As a hole transport material, the hole mobility is 1×10 -6 cm 2 It is preferable to use a material with a value of / Vs or higher. Additionally, any material other than the material described above may be used as long as its hole transportability is higher than its electron transportability. The layer containing the material with high hole transportability is not limited to a single layer, and two or more layers containing the material described above may be stacked.

[0163] Electron Transport Layer

[0164] The electron transport layer (118) has the function of transporting electrons injected from the other of a pair of electrodes (electrode (101) or electrode (102)) to the light-emitting layer (140) through the electron injection layer (119). A material having the characteristic of transporting electrons more than holes can be used as an electron transport material, and has an electron mobility of 1×10 -6 cm 2It is preferable that the material be of a value greater than or equal to / Vs. As a compound that readily accepts electrons (a material having electron transport properties), examples may be used, such as π-electron-deficient complexes like nitrogen-containing complex aromatic compounds or metal complexes. Specifically, metal complexes having the quinoline ligand, benzoquinoline ligand, oxazole ligand, or thiazole ligand described above may be used as electron transport materials for use in the light-emitting layer (140). In addition, oxadiazole derivatives, triazole derivatives, benzimidazole derivatives, quinoxaline derivatives, dibenzoquinoxaline derivatives, phenanthroline derivatives, pyridine derivatives, bipyridine derivatives, pyrimidine derivatives, and triazine derivatives may be used. The electron mobility is 1×10 -6 cm 2 A material with a value of / Vs or higher is preferred. In addition to these materials, any material having the characteristic of transporting electrons more than holes may be used in the electron transport layer. The electron transport layer (118) is not limited to a single layer and may include a stack of two or more layers including the materials described above.

[0165] A layer that controls the movement of electron carriers may be provided between the electron transport layer (118) and the light-emitting layer (140). This layer is formed by adding a small amount of a material with high electron trapping properties to the aforementioned material with high electron transport properties, and this layer can control the carrier balance by suppressing the movement of electron carriers. This structure is very effective in preventing problems (such as a decrease in device lifespan) that occur when electrons pass through the light-emitting layer.

[0166] <<Electron Injection Layer>>

[0167] The electron injection layer (119) has the function of reducing the barrier to electron injection from the electrode (102) to promote electron injection, and may be formed, for example, using a Group 1 metal or a Group 2 metal, or an oxide, halide, or carbonate of either of these metals. Alternatively, a composite material may be used that includes an electron transport material (described above) and a material having the property of donating electrons to the electron transport material. Examples of materials having electron-donating properties include Group 1 metals, Group 2 metals, or oxides of any of these metals. Specifically, lithium fluoride (LiF), sodium fluoride (NaF), cesium fluoride (CsF), calcium fluoride (CaF2), or lithium oxide (LiO2). x Alkali metals, alkaline earth metals, or compounds thereof such as ) may be used. Alternatively, rare earth metal compounds such as erbium fluoride (ErF3) may be used. An electride may be used in the electron injection layer (119). Examples of this electride include a material in which electrons are added to calcium oxide-aluminum oxide at a high concentration. The electron injection layer (119) may be formed using a material that can be used in the electron transport layer (118).

[0168] In the electron injection layer (119), a composite material comprising an organic compound and an electron donor (donor) may be used. Since electrons are generated from the organic compound by the electron donor, such a composite material has excellent electron injection and electron transport properties. In this case, it is desirable that the organic compound be a material with excellent transport of the generated electrons. Specifically, for example, a material forming the electron transport layer (118) described above (e.g., a metal complex and a complex aromatic compound) may be used. As an electron donor, a material exhibiting electron-donating properties with respect to the organic compound may be used. Specifically, alkali metals, alkaline earth metals, and rare earth metals are preferred, and examples include lithium, sodium, cesium, magnesium, calcium, erbium, and ytterbium. Additionally, alkali metal oxides or alkaline earth metal oxides are preferred, and examples include lithium oxide, calcium oxide, and barium oxide. Lewis bases such as magnesium oxide may also be used. Organic compounds such as tetrathiafulvalene (abbreviated as TTF) may also be used.

[0169] In addition, each of the above-described light-emitting layer, hole injection layer, hole transport layer, electron transport layer, and electron injection layer can be formed by deposition methods (including vacuum deposition), inkjet methods, coating methods, or gravure printing methods. In addition to the materials described above, inorganic compounds such as quantum dots or polymer compounds (e.g., oligomers, dendrimers, and polymers) may be used for the light-emitting layer, hole injection layer, hole transport layer, electron transport layer, and electron injection layer.

[0170] Quantum dots may be, for example, colloidal quantum dots, alloy quantum dots, core-shell quantum dots, or core quantum dots. Quantum dots containing elements belonging to Group 2 and Group 16, elements belonging to Group 13 and Group 15, elements belonging to Group 13 and Group 17, elements belonging to Group 11 and Group 17, or elements belonging to Group 14 and Group 15 may be used. Alternatively, quantum dots containing elements such as cadmium (Cd), selenium (Se), zinc (Zn), sulfur (S), phosphorus (P), indium (In), tellurium (Te), lead (Pb), gallium (Ga), arsenic (As), or aluminum (Al) may be used.

[0171] A pair of electrodes

[0172] The electrodes (101 and 102) function as the anode and cathode of each light-emitting element. The electrodes (101 and 102) can be formed using a metal, an alloy, or a conductive compound, or a mixture thereof, or a laminate, etc.

[0173] It is preferable that one of the electrode (101) and the electrode (102) be formed using a conductive material having a light-reflecting function. Examples of conductive materials include aluminum (Al) and alloys containing Al. Examples of alloys containing Al include alloys containing Al and Ti and alloys containing Al, Ni, and La, etc., Al and L ( L ...includes alloys containing one or more of titanium (Ti), neodymium (Nd), nickel (Ni), and lanthanum (La). Aluminum has low resistance and high light reflectivity. Since aluminum is abundant in the Earth's crust and inexpensive, using aluminum can reduce the manufacturing cost of light-emitting devices. Or, Ag, or silver (Ag) and N ( NAlloys of silver (representing one or more of yttrium (Y), Nd, magnesium (Mg), ytterbium (Yb), Al, Ti, gallium (Ga), zinc (Zn), indium (In), tungsten (W), manganese (Mn), tin (Sn), iron (Fe), Ni, copper (Cu), palladium (Pd), iridium (Ir), or gold (Au)) may be used. Examples of alloys containing silver include alloys containing silver, palladium, and copper; alloys containing silver and copper; alloys containing silver and magnesium; alloys containing silver and nickel; alloys containing silver and gold; and alloys containing silver and ytterbium. In addition, transition metals such as tungsten, chromium (Cr), molybdenum (Mo), copper, or titanium may be used.

[0174] Light emitted from the light-emitting layer is extracted through the electrode (101) and / or electrode (102). Therefore, it is preferable that at least one of the electrode (101) and the electrode (102) be formed using a conductive material having the function of transmitting light. As for the conductive material, the visible light transmittance is 40% or more and 100% or less, preferably 60% or more and 100% or less, and the resistivity is 1×10⁻⁶ -2 Conductive materials with a conductivity of Ω·cm or less can be used.

[0175] Each of the electrode (101) and the electrode (102) may be formed using a conductive material having the function of transmitting light and the function of reflecting light. As for the conductive material, the visible light reflectance is 20% or more and 80% or less, preferably 40% or more and 70% or less, and the resistivity is 1×10 -2A conductive material having a conductivity of Ω·cm or less may be used. For example, one or more types of conductive metals and alloys, and conductive compounds may be used. Specifically, metal oxides such as indium tin oxide (hereinafter referred to as ITO), indium tin oxide containing silicon or silicon oxide (ITSO), indium zinc oxide, indium tin oxide containing titanium, indium titanium oxide, or indium oxide containing tungsten oxide and zinc oxide may be used. A metal thin film with a thickness that transmits light (preferably a thickness of 1 nm or more and 30 nm or less) may also be used. As the metal, Ag, an alloy of Ag and Al, an alloy of Ag and Mg, an alloy of Ag and Au, or an alloy of Ag and ytterbium (Yb) may be used.

[0176] In this specification and others, as a material that transmits light, a material that transmits visible light and possesses conductivity is used. Examples of such materials include, in addition to oxide conductors represented by the ITO described above, oxide semiconductors and organic conductors comprising organic materials. Examples of organic conductors comprising organic materials include composite materials formed by mixing an organic compound with an electron donor (donor material) and composite materials formed by mixing an organic compound with an electron acceptor (acceptor material). Alternatively, inorganic carbon-based materials such as graphene may be used. The resistivity of the material is preferably 1×10⁻⁶. 5 Ω·cm or less, more preferably 1×10⁻⁶ 4 It is less than Ω·cm.

[0177] Alternatively, the electrode (101) and / or electrode (102) may be formed by stacking two or more of these materials.

[0178] To increase light extraction efficiency, a material with a higher refractive index than the electrode having a light-transmitting function may be formed to come into contact with said electrode. Such a material may be electrically conductive or non-conductive as long as it has the function of transmitting visible light. In addition to the oxide conductors described above, oxide semiconductors and organic materials may be cited as examples of materials. Examples of organic materials include materials for the light-emitting layer, hole injection layer, hole transport layer, electron transport layer, and electron injection layer. Alternatively, inorganic carbon-based materials or metal thin films capable of transmitting light may be used. Alternatively, a stack having a thickness of several nanometers to tens of nanometers may be used.

[0179] When the electrode (101) or electrode (102) functions as a cathode, it is preferable that the electrode comprises a material having a low work function (3.8 eV or less). Examples include elements belonging to Group 1 or Group 2 of the periodic table of elements (e.g., alkali metals such as lithium, sodium, or cesium, alkaline earth metals such as calcium or strontium, or magnesium), alloys containing any of these elements (e.g., Ag-Mg or Al-Li), rare earth metals such as europium (Eu) or Yb, alloys containing any of these rare earth metals, and alloys containing aluminum and silver.

[0180] When using electrode (101) or electrode (102) as an anode, it is preferable to use a material with a high work function (4.0 eV or higher).

[0181] The electrode (101) and the electrode (102) may be a laminate of a conductive material having a light-reflecting function and a conductive material having a light-transmitting function. In that case, it is preferable that the electrode (101) and the electrode (102) have a function of adjusting the optical path length to resonate and enhance the light of a desired wavelength emitted from each light-emitting layer.

[0182] As a method for forming the electrode (101) and electrode (102), sputtering, deposition, printing, coating, MBE (molecular beam epitaxy), CVD, pulsed laser deposition, or ALD (atomic layer deposition) can be appropriately used.

[0183] <<Circuit Board>>

[0184] One embodiment of the light-emitting element of the present invention may be formed on a substrate such as glass or plastic. As a method of stacking on the substrate, the layers may be stacked sequentially from the electrode (101) side or stacked sequentially from the electrode (102) side.

[0185] A substrate capable of forming a light-emitting element of one embodiment of the present invention may be, for example, glass, quartz, or plastic. Alternatively, a flexible substrate may be used. A flexible substrate refers to a bendable substrate, such as a plastic substrate made of polycarbonate or polyarylate, for example. Alternatively, a film or an inorganic deposition film may be used. Other materials may be used as long as the substrate functions as a support in the fabrication process of the light-emitting element or optical element, or has the function of protecting the light-emitting element or optical element.

[0186] In the present specification and the like, the light-emitting element may be formed using any of various substrates, for example. There are no specific 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 containing stainless steel foil, tungsten substrates, substrates containing tungsten foil, flexible substrates, bonding films, and paper containing fibrous materials, and substrate films. Examples of glass substrates include barium borosilicate glass substrates, aluminoborosilicate glass substrates, and soda-lime glass substrates. Examples of flexible substrates, bonding films, and substrate films include plastic substrates represented by polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyether sulfone (PES), and polytetrafluoroethylene (PTFE). Other examples include resins such as acrylic. In addition, examples include polypropylene, polyester, polyfluorinated vinyl, and polyvinyl chloride. Other examples include polyamide, polyimide, aramid, epoxy, inorganic deposited films, and paper.

[0187] Alternatively, a flexible substrate may be used as the substrate to directly provide the light-emitting element to the flexible substrate. Alternatively, a separation layer may be provided between the substrate and the light-emitting element. The separation layer can be used to separate part or all of the light-emitting element formed on the separation layer from the substrate and transfer it to another substrate. In this case, the light-emitting element may be transferred to a substrate with low heat resistance or a flexible substrate. For the separation layer described above, a structure may be used in which, for example, an inorganic film comprising a tungsten film and a silicon oxide film is laminated, or a resin film such as polyimide is formed on the substrate.

[0188] In other words, after forming a light-emitting element using a substrate, the light-emitting element may be transferred to another substrate. Examples of substrates for transferring the light-emitting element include, in addition to the substrates described above, cellophane substrates, stone substrates, wood substrates, cloth substrates (including natural fibers (e.g., silk, cotton, or linen), synthetic fibers (e.g., nylon, polyurethane, or polyester), recycled fibers (e.g., acetate, cupro, rayon, or recycled polyester), etc.), leather substrates, and rubber substrates. By using such substrates, it is possible to form a light-emitting element that is highly durable, highly heat-resistant, lightweight, or thin.

[0189] The light-emitting element (152) may be formed on an electrode electrically connected to a field-effect transistor (FET) formed on, for example, any substrate described above. Accordingly, an active matrix display device can be manufactured in which the FET controls the driving of the light-emitting element (152).

[0190] In this embodiment, one form of the present invention has been described. In other embodiments, other forms of the present invention are described. However, one form of the present invention is not limited thereto. That is, since various forms of the present invention are described in this embodiment and other embodiments, one form of the present invention is not limited to a specific embodiment. Although an example of using one form of the present invention in a light-emitting element has been described, one form of the present invention is not limited thereto. For example, depending on the situation or conditions, one form of the present invention does not necessarily need to be used in a light-emitting element. One form of the present invention includes a first organic compound, a second organic compound, and a guest material capable of converting triplet excitation energy into light emission, and illustrates an example in which the LUMO level of the first organic compound is lower than that of the second organic compound and the HOMO level of the first organic compound is lower than that of the second organic compound, but is not limited thereto. Depending on the situation or conditions, in one form of the present invention, for example, the LUMO level of the first organic compound does not necessarily need to be lower than that of the second organic compound. Alternatively, the HOMO level of the first organic compound does not necessarily have to be lower than that of the second organic compound. One embodiment of the present invention illustrates an example in which the first organic compound and the second organic compound form an excited complex, but is not limited thereto. Depending on the circumstances or conditions, in one embodiment of the present invention, for example, the first organic compound and the second organic compound do not necessarily have to form an excited complex. One embodiment of the present invention illustrates an example in which the LUMO level of the guest material is higher than that of the first organic compound and the HOMO level of the guest material is lower than that of the second organic compound, but is not limited thereto. Depending on the circumstances or conditions, in one embodiment of the present invention, for example, the LUMO level of the guest material does not necessarily have to be higher than that of the first organic compound. Alternatively, the HOMO level of the guest material does not necessarily have to be lower than that of the second organic compound.

[0191] The structure described in this embodiment may be used in appropriate combination with any of the structures described in other embodiments.

[0192] (Embodiment 2)

[0193] In this embodiment, a light-emitting element having a structure different from that described in Embodiment 1, and a light-emitting mechanism of said light-emitting element, will be described below with reference to FIGS. 3 (A) to (C) and FIGS. 4 (A) to (C). In FIGS. 3 (A) to (C) and FIGS. 4 (A) to (C), parts having a function similar to FIG. 1 (A) are indicated by a hatch pattern similar to FIG. 1 (A) and may not be specifically indicated by a symbol. In addition, common symbols are used for parts having a similar function, and detailed descriptions of such parts may be omitted.

[0194] <Structure Example 1 of a Light-Emitting Element>

[0195] Figure 3 (A) is a schematic cross-sectional view of a light-emitting element (250).

[0196] The light-emitting element (250) illustrated in FIG. 3 (A) includes a plurality of light-emitting units (light-emitting unit (106) and light-emitting unit (108) in FIG. 3 (A)) between a pair of electrodes (electrode (101) and electrode (102)). It is preferable that one of the light-emitting units has a structure similar to the EL layer (100) illustrated in FIG. 1 (A) and (B). That is, the light-emitting element (152) in FIG. 1 (A) and (B) includes one light-emitting unit, while the light-emitting element (250) includes a plurality of light-emitting units. Furthermore, in the following description of the light-emitting element (250), the electrode (101) functions as an anode and the electrode (102) functions as a cathode, but these functions may be interchanged in the light-emitting element (250).

[0197] In the light-emitting element (250) shown in (A) of FIG. 3, a light-emitting unit (106) and a light-emitting unit (108) are stacked, and a charge generating layer (115) is provided between the light-emitting unit (106) and the light-emitting unit (108). Additionally, the light-emitting unit (106) and the light-emitting unit (108) may have the same structure or different structures. For example, it is preferable that the EL layer (100) shown in (A) and (B) of FIG. 1 be used in the light-emitting unit (108).

[0198] The light-emitting element (250) includes a light-emitting layer (120) and a light-emitting layer (170). The light-emitting unit (106) includes, in addition to the light-emitting layer (120), a hole injection layer (111), a hole transport layer (112), an electron transport layer (113), and an electron injection layer (114). The light-emitting unit (108) includes, in addition to the light-emitting layer (170), a hole injection layer (116), a hole transport layer (117), an electron transport layer (118), and an electron injection layer (119).

[0199] The charge generation layer (115) may have a structure in which an acceptor material, which is an electron acceptor, is added to a hole transport material, or a structure in which a donor material, which is an electron donor, is added to an electron transport material. Alternatively, both of these structures may be stacked.

[0200] When the charge generation layer (115) comprises a composite material of an organic compound and an acceptor material, the composite material may be a composite material that can be used for the hole injection layer (111) described in Embodiment 1. As the organic compound, various compounds such as aromatic amine compounds, carbazole compounds, aromatic hydrocarbons, and polymer compounds (oligomers, dendrimers, or polymers, etc.) may be used. As the organic compound, a hole mobility of 1×10 -6 cm 2It is preferable to use an organic compound with a value of / Vs or higher. Additionally, any other material may be used as long as the transportability of holes is higher than that of electrons. Since the composite material of the organic compound and the acceptor material has excellent carrier injection and carrier transportability, low-voltage driving or low-current driving can be realized. Furthermore, when the surface of the light-emitting unit on the anode side, such as the light-emitting unit (108), comes into contact with the charge generation layer (115), the charge generation layer (115) can also function as a hole injection layer or a hole transport layer of the light-emitting unit; therefore, the light-emitting unit does not necessarily need to include a hole injection layer or a hole transport layer.

[0201] The charge generation layer (115) may have a stacked structure comprising a layer containing a composite material of an organic compound and an acceptor material and a layer containing other materials. For example, the charge generation layer (115) may be formed by combining a layer containing a composite material of an organic compound and an acceptor material, and a layer containing one selected from electron-donating materials and a compound with high electron transportability. Additionally, the charge generation layer (115) may be formed by combining a layer containing a composite material of an organic compound and an acceptor material and a layer containing a transparent conductive material.

[0202] Additionally, the charge generation layer (115) provided between the light-emitting unit (106) and the light-emitting unit (108) may have any structure as long as it is capable of injecting electrons into one light-emitting unit and injecting holes into the other light-emitting unit when a voltage is applied between the electrode (101) and the electrode (102). For example, in (A) of FIG. 3, when a voltage is applied such that the potential of the electrode (101) is higher than the potential of the electrode (102), the charge generation layer (115) injects electrons into the light-emitting unit (106) and injects holes into the light-emitting unit (108).

[0203] In addition, from the perspective of light extraction efficiency, it is desirable for the charge generating layer (115) to have visible light transmittance (specifically, a visible light transmittance of 40% or more). The charge generating layer (115) functions even if its conductivity is lower than that of a pair of electrodes (electrode (101) and electrode (102)).

[0204] If the charge generation layer (115) is formed using any of the materials described above, the increase in the driving voltage generated by the stacking of the light-emitting layer can be suppressed.

[0205] A light-emitting device having two light-emitting units is described with reference to (A) of FIG. 3, but the same structure can be applied to a light-emitting device in which three or more light-emitting units are stacked. As a light-emitting device (250), if a plurality of light-emitting units are separated by a charge-generating layer between a pair of electrodes, light can be emitted with high brightness while maintaining a low current density, and a light-emitting device with a long lifespan can be provided. A light-emitting device with low power consumption can be provided.

[0206] By applying the structure described in Embodiment 1 to at least one of a plurality of units, a light-emitting element with high light-emitting efficiency can be provided.

[0207] The light-emitting layer (170) of the light-emitting unit (108) has the same structure as the light-emitting layer (140) described in embodiment 1, and in this case, it is preferable that the light-emitting element (250) has high light-emitting efficiency.

[0208] The light-emitting layer (120) included in the light-emitting unit (106) comprises a host material (121) and a guest material (122) as shown in (B) of FIG. 3. Additionally, the guest material (122) is described below as a fluorescent material.

[0209] <<Light-emitting mechanism of the light-emitting layer (120)>>

[0210] The light-emitting mechanism of the light-emitting layer (120) is described below.

[0211] Excitons are formed by recombining electrons and holes injected from a charge generation layer or a pair of electrodes (electrode (101) and electrode (102)) in the light-emitting layer (120). Since the amount of host material (121) is greater than that of guest material (122), the host material (121) becomes excited by the generation of excitons.

[0212] Furthermore, the term "exciton" refers to a carrier (electron and hole) pair. Because excitons possess energy, the material from which they are generated becomes excited.

[0213] When the excited state of the formed host material (121) is a singlet excited state, the singlet excited energy moves from the S1 level of the host material (121) to the S1 level of the guest material (122) to form a singlet excited state of the guest material (122).

[0214] Since the guest material (122) is a fluorescent material, when a singlet excited state is formed in the guest material (122), the guest material (122) emits light immediately. In this case, to obtain high luminescence efficiency, it is desirable for the fluorescence quantum yield of the guest material (122) to be high. The same applies when a singlet excited state is formed by recombining carriers in the guest material (122).

[0215] Next, the case in which carrier recombination forms a triplet excited state of the host material (121) is described. The correlation of the energy levels of the host material (121) and the guest material (122) in this case is shown in FIG. 3 (C). The terms and symbols in FIG. 3 (C) represent the following. Additionally, since it is preferable that the T1 level of the host material (121) is lower than the T1 level of the guest material (122), FIG. 3 (C) represents this preferred case. However, the T1 level of the host material (121) may be higher than the T1 level of the guest material (122).

[0216] Host(121): Host material(121);

[0217] Guest(122): Guest material(122)(fluorescent material);

[0218] S FH : S1 level of host material (121);

[0219] T FH : T1 level of host material (121);

[0220] S FG : S1 level of guest material (122) (fluorescent material); and

[0221] T FG : T1 level of guest material (122) (fluorescent material).

[0222] As illustrated in (C) of FIG. 3, triplet-triplet annihilation (TTA) occurs, that is, triplet excitons formed by carrier recombination interact, excitation energy is transferred and spin angular momentum is exchanged; consequently, triplet excitons reach the S1 level (S1) of the host material (121). FH A reaction occurs in which it is converted into a singlet exciton having the energy of (see TTA in (C) of FIG. 3). The singlet excitation energy of the host material (121) is S FH From, S FH S1 level (S FG Move to (see root E1 of (C) in Fig. 3), and a singlet excited state of the guest material (122) is formed, causing the guest material (122) to emit light.

[0223] In addition, when the density of triplet excitons in the light-emitting layer (120) is sufficiently high (e.g., 1×10⁻⁶ -12 cm -3 (Above), only the reactions of two triplet excitons close to each other can be considered, whereas the inactivation of a triplet exciton group can be ignored.

[0224] When the triplet excited state of the guest material (122) is formed by carrier recombination, the triplet excited state of the guest material (122) is thermally deactivated and difficult to use for light emission. However, the T1 level (T FH ) is the T1 level (T of guest material (122) FG If lower than ), the triplet excitation energy of the guest material (122) is the T1 level (T FG The T1 level (T) of the host material (121) from ) FH It can be moved to (see Route E2 in (C) of Fig. 3), and is used in TTA.

[0225] In other words, it is desirable for the host material (121) to have the function of converting triplet excitation energy into singlet excitation energy through the generation of TTA, and thus the triplet excitation energy generated in the light-emitting layer (120) can be partially converted into singlet excitation energy by TTA in the host material (121). The singlet excitation energy can be transferred to the guest material (122) and extracted as fluorescence. To achieve this, the S1 level (S FH ) is the S1 level (S of guest material (122) FG It is desirable that it be higher than ). Also, the T1 level (T FH ) is the T1 level (T of guest material (122) FG It is desirable that it be lower than ).

[0226] In addition, in particular, the T1 level (T FG ) is the T1 level (T FHWhen lower than ), it is preferable that the weight ratio of the guest material (122) to the host material (121) be low. Specifically, it is preferable that the weight ratio of the guest material (122) to the host material (121) be greater than 0 and less than or equal to 0.05, in which case the possibility of carrier recombination of the guest material (122) can be reduced. In addition, the T1 level (T FH The T1 level (T) of the guest material (122) from ) FG The possibility of energy transfer to ) can be reduced.

[0227] Additionally, the host material (121) may be composed of a single compound or may be composed of multiple compounds.

[0228] Additionally, in each of the structures described above, the emission color of the guest material used in the light-emitting unit (106) and the light-emitting unit (108) may be the same or different. When the same guest material emitting light of the same color is used in the light-emitting unit (106) and the light-emitting unit (108), it is desirable for the light-emitting element (250) to exhibit high luminous brightness with a small current value. When a guest material emitting light of a different color is used in the light-emitting unit (106) and the light-emitting unit (108), it is desirable for the light-emitting element (250) to exhibit multi-color light emission. In this case, if multiple light-emitting materials with different emission wavelengths are used in one or both of the light-emitting layer (120) and the light-emitting layer (170), light with different emission peaks is combined with the light from the light-emitting element (250). That is, the emission spectrum of the light-emitting element (250) has at least two maximum values.

[0229] The above structure is also suitable for obtaining white light emission. White light emission can be obtained when the light-emitting layer (120) and the light-emitting layer (170) emit light of complementary colors. It is particularly desirable to select guest materials so as to obtain white light emission with high color rendering or at least red, green, and blue light emission.

[0230] One or both of the light-emitting layer (120) and the light-emitting layer (170) may be divided into layers, and each divided layer may include a different light-emitting material. That is, one or both of the light-emitting layer (120) and the light-emitting layer (170) may include two or more layers. For example, when a light-emitting layer is formed by stacking a first light-emitting layer and a second light-emitting layer in this order from the hole transport layer side, the first light-emitting layer is formed using a material having hole transport properties as a host material, and the second light-emitting layer is formed using a material having electron transport properties as a host material. In this case, the light-emitting material included in the first light-emitting layer may be the same as or different from the light-emitting material included in the second light-emitting layer. In addition, the material may have the function of emitting light of the same color or light of a different color. White light with high color rendering, formed with three primary colors or four or more colors, can be obtained by using a plurality of light-emitting materials that emit light of a different color.

[0231] When the light-emitting unit (106) and the light-emitting unit (108) include guest materials of different colors, it is preferable that the light emitted from the light-emitting layer (120) has a peak on the shorter wavelength side than the light emitted from the light-emitting layer (170). The brightness of a light-emitting device using a material with a high triplet excitation energy level tends to degrade quickly, and TTA is used in a light-emitting layer that emits short wavelength light so as to provide a light-emitting device with less brightness degradation.

[0232] <Structure Example of a Light-Emitting Element 2>

[0233] Next, other structural examples different from the light-emitting elements shown in FIGS. 3 (A) to (C) are described below with reference to FIGS. 4 (A) to (C).

[0234] Figure 4 (A) is a schematic cross-sectional view of a light-emitting element (252).

[0235] In the light-emitting element (252) shown in (A) of FIG. 4, the EL layer (110) is located between a pair of electrodes (electrode (101) and electrode (102)). In the following description of the light-emitting element (252), electrode (101) functions as an anode and electrode (102) functions as a cathode, but these functions may be interchanged in the light-emitting element (252).

[0236] The EL layer (110) includes a light-emitting layer (180). The light-emitting layer (180) includes a light-emitting layer (120) and a light-emitting layer (170). The EL layer (110) also includes a hole injection layer (111), a hole transport layer (112), an electron transport layer (118), and an electron injection layer (119), but since this stacked structure is an example, the structure of the EL layer (110) of the light-emitting device (252) is not limited thereto. For example, the stacking order of these layers of the EL layer (110) may be changed, or other functional layers may be provided in the EL layer (110). The functional layer may have, for example, a function to reduce a hole injection barrier or an electron injection barrier, a function to improve hole transportability or electron transportability, a function to suppress the transport of holes or electrons, or a function to generate holes or electrons.

[0237] As illustrated in FIG. 4 (B), the light-emitting layer (120) comprises a host material (121) and a guest material (122). The light-emitting layer (170) comprises a host material (171) and a guest material (172). The host material (171) comprises an organic compound (171_1) and an organic compound (171_2). Additionally, as described below, the guest material (122) is a fluorescent material and the guest material (172) is a phosphorescent material.

[0238] <<Light-emitting mechanism of the light-emitting layer (180)>>

[0239] The light-emitting mechanism of the light-emitting layer (120) is the same as that of the light-emitting layer (120) shown in (A) to (C) of FIG. 3. The light-emitting mechanism of the light-emitting layer (170) is the same as that of the light-emitting layer (140) of Embodiment 1. In other words, the host material (171), organic compound (171_1), organic compound (171_2), and guest material (172) are the same as the host material (141), guest material (142), organic compound (141_1), and organic compound (141_2).

[0240] When the light-emitting layer (120) and the light-emitting layer (170) are in contact with each other, such as in the light-emitting element (252), even if energy is transferred from the excited composite to the host material (121) of the light-emitting layer (120) at the interface between the light-emitting layer (120) and the light-emitting layer (170) (especially if energy of the triplet excitation level is transferred), the triplet excitation energy can be converted into light emission in the light-emitting layer (120).

[0241] It is preferable that the T1 level of the host material (121) of the light-emitting layer (120) is lower than the T1 level of the organic compound (171_1) and organic compound (171_2) of the light-emitting layer (170). In the light-emitting layer (120), it is preferable that the S1 level of the host material (121) is higher than the S1 level of the guest material (122) (fluorescent material), while it is preferable that the T1 level of the host material (121) is lower than the T1 level of the guest material (122) (fluorescent material).

[0242] Fig. 4(C) shows the correlation of energy levels when TTA is used in the light-emitting layer (120) and ExTET is used in the light-emitting layer (170). The terms and symbols in Fig. 4(C) represent the following:

[0243] Fluorescence EML (120): Emitting layer (120) (fluorescent emitting layer);

[0244] Phosphorescence EML (170): Emissive layer (170) (phosphorescent emissive layer);

[0245] Host(121): Host material(121);

[0246] Guest(122): Guest material(122)(fluorescent material);

[0247] Host(171_1): Host material(organic compound(171_1));

[0248] Guest(172): Guest material(172)(phosphorescent material);

[0249] Exciplex: Excited complex (organic compound (171_1) and organic compound (171_2))

[0250] S FH : S1 level of host material (121);

[0251] T FH : T1 level of host material (121);

[0252] S FG : S1 level of guest material (122) (fluorescent material);

[0253] T FG : T1 level of guest material (122) (fluorescent material);

[0254] S PH : S1 level of organic compound (171_1) (host material);

[0255] T PH : T1 level of organic compound (171_1) (host material);

[0256] T PG : T1 level of guest material (172) (phosphorescent material);

[0257] S E : S1 level of the excited complex; and

[0258] T E : T1 level of the excited complex

[0259] As shown in (C) of Fig. 4, since excited complexes exist only in the excited state, diffusion of excitons between excited complexes is difficult to occur. In addition, the excitation energy level (S) of the excited complex E and TE ) is the excitation energy level (S) of the organic compound (171_1) (host material of the phosphorescent material) of the light-emitting layer (170). PH and T PH Because it is lower than ), energy diffusion from the excited complex to the organic compound (171_1) does not occur. That is, since the exciton diffusion distance of the excited complex in the phosphorescent light-emitting layer (light-emitting layer (170)) is short, the luminescence efficiency of the phosphorescent light-emitting layer (light-emitting layer (170)) can be maintained. In addition, even if some of the triplet excitation energy of the excited complex of the phosphorescent light-emitting layer (light-emitting layer (170)) diffuses to the fluorescent light-emitting layer (light-emitting layer (120)) through the interface between the fluorescent light-emitting layer (light-emitting layer (120)) and the phosphorescent light-emitting layer (light-emitting layer (170)), energy loss can be reduced because the triplet excitation energy of the fluorescent light-emitting layer (light-emitting layer (120)) generated by diffusion is converted into light emission through TTA.

[0260] As described above, the light-emitting element (252) can have high luminous efficiency because energy loss is reduced since ExTET is used in the light-emitting layer (170) and TTA is used in the light-emitting layer (120). When the light-emitting layer (120) and the light-emitting layer (170) are in contact with each other, as in the light-emitting element (252), the number of EL layers (110) can be reduced in addition to energy loss. Therefore, a light-emitting element with low manufacturing costs can be obtained.

[0261] Additionally, the light-emitting layer (120) and the light-emitting layer (170) do not necessarily need to be in contact with each other. In this case, it is possible to prevent energy transfer (particularly triplet energy transfer) by the Dexter mechanism from the excited state organic compound (171_1) and organic compound (171_2) or the excited state guest material (172) (phosphorescent material) generated in the light-emitting layer (170) to the host material (121) or guest material (122) (fluorescent material) in the light-emitting layer (120). Accordingly, the thickness of the layer provided between the light-emitting layer (120) and the light-emitting layer (170) needs to be several nm, and in particular, it is preferable that the thickness be between 1 nm and 5 nm, and in this case, an increase in the driving voltage can be suppressed.

[0262] The layer provided between the light-emitting layer (120) and the light-emitting layer (170) may include a single material, or may include both a hole transport material and an electron transport material. In the case of a single material, a bipolar material may be used. Here, a bipolar material refers to a material in which the ratio of electron mobility to hole mobility is 100 or less. Alternatively, a hole transport material or an electron transport material may be used. At least one of the materials included in the layer may be the same as the host material of the light-emitting layer (170) (organic compound (171_1) or organic compound (171_2)). This facilitates the manufacture of the light-emitting device and reduces the driving voltage. In addition, the hole transport material and the electron transport material may form an excited composite, thereby effectively preventing the diffusion of excitons. Specifically, it is possible to prevent energy transfer from an excited state host material (organic compound (171_1) or organic compound (171_2)) or an excited state guest material (172) (phosphorescent material) of the light-emitting layer (170) to a host material (121) or guest material (122) (fluorescent material) in the light-emitting layer (120).

[0263] In the light-emitting element (252), the light-emitting layer (120) and the light-emitting layer (170) are described as being located on the side of the hole transport layer (112) and the side of the electron transport layer (118), respectively, but the light-emitting element of one embodiment of the present invention is not limited to this structure. For example, the light-emitting layer (120) and the light-emitting layer (170) may be located on the side of the electron transport layer (118) and the side of the hole transport layer (112), respectively.

[0264] In addition, in the light-emitting element (252), it is desirable that the carrier recombination region be distributed to a certain extent. Accordingly, it is desirable that the light-emitting layer (120) or the light-emitting layer (170) have suitable carrier trapping properties. It is particularly desirable that the guest material (172) (phosphorescent material) of the light-emitting layer (170) have electron trapping properties. Accordingly, it is desirable that the light-emitting layer (170) have the structure of the light-emitting layer (140) in Embodiment 1.

[0265] In addition, it is preferable that the light emitted from the light-emitting layer (120) has a peak on the shorter wavelength side than the light emitted from the light-emitting layer (170). A light-emitting device using a phosphorescent material that emits short-wavelength light tends to experience rapid brightness degradation. In this regard, by using fluorescence for short-wavelength light emission, a light-emitting device with low brightness degradation can be provided.

[0266] Additionally, the light-emitting layer (120) and the light-emitting layer (170) can be made into a multi-color light-emitting element by emitting light of different wavelengths. In this case, the light emission spectrum has at least two peaks because it is formed by combining light having different light emission peaks.

[0267] The above-described structure is suitable for obtaining white light emission. When the light-emitting layer (120) and the light-emitting layer (170) emit light of a complementary color, white light emission can be obtained.

[0268] Additionally, by using a plurality of light-emitting materials that emit light of different wavelengths in one or both of the light-emitting layer (120) and the light-emitting layer (170), high color rendering white light emission consisting of three primary colors or four or more colors can be obtained. In this case, the light-emitting layer (120) may be divided into layers, and each of the divided layers may include a light-emitting material different from that of the other layers.

[0269] <Materials usable in the light-emitting layer>

[0270] Next, materials that can be used for the light-emitting layer (120) and the light-emitting layer (170) will be described.

[0271] <<Materials that can be used for the light-emitting layer (120)>>

[0272] In the light-emitting layer (120), the host material (121) is present in the largest weight ratio, and the guest material (122) (fluorescent material) is dispersed within the host material (121). It is preferable that the S1 level of the host material (121) is higher than the S1 level of the guest material (122) (fluorescent material), while it is preferable that the T1 level of the host material (121) is lower than the T1 level of the guest material (122) (fluorescent material).

[0273] In the light-emitting layer (120), the guest material (122) is not particularly limited but is preferably an anthracene derivative, tetracene derivative, chrysene derivative, phenanthrene derivative, pyrene derivative, perylene derivative, stilbene derivative, acridone derivative, coumarin derivative, phenoxazine derivative, or phenothiazine derivative, and any of the following materials may be used, for example.

[0274] Examples include 5,6-bis[4-(10-phenyl-9-anthryl)phenyl]-2,2'-bipyridine (abbreviated: PAP2BPy), 5,6-bis[4'-(10-phenyl-9-anthryl)biphenyl-4-yl]-2,2'-bipyridine (abbreviated: PAPP2BPy), N , N -diphenyl- N , N'-bis[4-(9-phenyl-9 H -fluorene-9-yl)phenyl]pyrene-1,6-diamine (abbreviation: 1,6FLPAPrn), N , N -bis(3-methylphenyl)- N , N '-bis[3-(9-phenyl-9 H -Fluorene-9-yl)phenyl]pyrene-1,6-diamine (abbreviation: 1,6mMemFLPAPrn), N , N '-bis[4-(9-phenyl-9 H -fluorene-9-yl)phenyl]- N , N '-bis(4- tert -Butylphenyl)pyrene-1,6-diamine (abbreviation: 1,6tBu-FLPAPrn), N , N -diphenyl- N , N '-bis[4-(9-phenyl-9 H -fluorene-9-yl)phenyl]-3,8-dicyclohexylpyrene-1,6-diamine (abbreviation: ch-1,6FLPAPrn), N , N '-bis[4-(9 H -carbazole-9-yl)phenyl]- N , N '-Diphenylstilbene-4,4'-diamine (abbreviation: YGA2S), 4-(9 H -carbazole-9-yl)-4'-(10-phenyl-9-anthryl)triphenylamine (abbreviation: YGAPA), 4-(9 H -carbazole-9-yl)-4'-(9,10-diphenyl-2-anthryl)triphenylamine (abbreviated: 2YGAPPA), N ,9-diphenyl- N -[4-(10-phenyl-9-antryl)phenyl]-9 H -Carbazole-3-amine (abbreviation: PCAPA), perylene, 2,5,8,11-tetra( tert -Butyl)perylene (abbreviation: TBP), 4-(10-phenyl-9-anthryl)-4'-(9-phenyl-9 H -Carbazole-3-yl)triphenylamine (abbreviation: PCBAPA), N , N ''-(2- tert -butylanthracene-9,10-diyldi-4,1-phenylene)bis[ N , N ', N [-triphenyl-1,4-phenylenediamine](abbreviated: DPABPA), N ,9-diphenyl- N -[4-(9,10-diphenyl-2-anthryl)phenyl]-9 H -Carbazole-3-amine (abbreviation: 2PCAPPA), N -[4-(9,10-diphenyl-2-anthryl)phenyl]- N , N ', N -triphenyl-1,4-phenylenediamine (abbreviation: 2DPAPPA), N , N , N ', N ', N '', N '', N ''', N '''-Octaphenyldibenzo[ g , p ]Chrysene-2,7,10,15-tetraamine (abbreviation: DBC1), coumarin 30, N -(9,10-diphenyl-2-anthryl)- N ,9-diphenyl-9 H -Carbazole-3-amine (abbreviation: 2PCAPA), N -[9,10-bis(1,1'-biphenyl-2-yl)-2-anthryl]- N ,9-diphenyl-9 H -Carbazole-3-amine (abbreviation: 2PCABPhA), N -(9,10-diphenyl-2-anthryl)- N , N ', N -triphenyl-1,4-phenylenediamine (abbreviation: 2DPAPA), N -[9,10-bis(1,1'-biphenyl-2-yl)-2-anthryl]- N , N ', N '-triphenyl-1,4-phenylenediamine (abbreviation: 2DPABPhA), 9,10-bis(1,1'-biphenyl-2-yl)- N -[4-(9 H-carbazole-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), Lubren, 2,8-di- tert -butyl-5,11-bis(4- tert -butylphenyl)-6,12-diphenyltetracene (abbreviation: TBRb), nyled, 5,12-bis(1,1'-biphenyl-4-yl)-6,11-diphenyltetracene (abbreviation: BPT), 2-(2-{2-[4-(dimethylamino)phenyl]ethenyl}-6-methyl-4 H -pyran-4-ylidene)propanedynitrile (abbreviation: DCM1), 2-{2-methyl-6-[2-(2,3,6,7-tetrahydro-1 H ,5 H -Benzo[ ij ]quinolizine-9-yl)ethenyl]-4 H -Pyran-4-Ilidene}Propaindynitrile (abbreviation: DCM2), N , N , N ', N -tetrakis(4-methylphenyl)tetracene-5,11-diamine (abbreviation: p-mPhTD), 7,14-diphenyl- N , N , N ', N '-tetrakis(4-methylphenyl)acenaphtho[1,2- a ]Fluoranthen-3,10-diamine (abbreviation: p-mPhAFD), 2-{2-isopropyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1 H ,5 H -Benzo[ ij ]quinolizine-9-yl)ethenyl]-4 H -Pyran-4-Ilidene}Propaganda Dynitrile (abbreviated: DCJTI), 2-{2- tert -butyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1 H ,5H -Benzo[ ij ]quinolizine-9-yl)ethenyl]-4 H -pyran-4-ylidene}propanedynitrile (abbreviation: DCJTB), 2-(2,6-bis{2-[4-(dimethylamino)phenyl]ethenyl}-4 H -Pyran-4-Ilidene)propanedynitrile (abbreviation: BisDCM), 2-{2,6-bis[2-(8-methoxy-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1 H ,5 H -Benzo[ ij ]quinolizine-9-yl)ethenyl]-4 H -pyran-4-ylidene}propanedynitrile (abbreviated: BisDCJTM), and 5,10,15,20-tetraphenylbisbenzo[5,6]deno[1,2,3- CD :1',2',3'- lm ] contains perylene.

[0275] There are no particular limitations on the materials that can be used as the host material (121) in the light-emitting layer (120), but for example, any of the following materials may be used: tris(8-quinolinoleto)aluminum(III) (abbreviated: Alq), tris(4-methyl-8-quinolinoleto)aluminum(III) (abbreviated: Almq3), bis(10-hydroxybenzo[ h Metal complexes such as ]quinolinato)beryllium(II) (abbreviated: BeBq2), bis(2-methyl-8-quinolinoleato)(4-phenylphenolate)aluminum(III) (abbreviated: BAlq), bis(8-quinolinoleato)zinc(II) (abbreviated: Znq), bis[2-(2-benzoxazolyl)phenolate]zinc(II) (abbreviated: ZnPBO), and bis[2-(2-benzothiazolyl)phenolate]zinc(II) (abbreviated: ZnBTZ); 2-(4-biphenylyl)-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-biphenylyl)-4-phenyl-5-(4- tert-butylphenyl)-1,2,4-triazole (abbreviation: TAZ), 2,2',2"-(1,3,5-benzenetriyl)-tris(1-phenyl-1 H -benzimidazole) (abbreviated: TPBI), vasofenanthroline (abbreviated: BPhen), vasocuproin (abbreviated: BCP), and 9-[4-(5-phenyl-1,3,4-oxadiazole-2-yl)phenyl]-9 H - Complex cyclic compounds such as carbazole (abbreviation: CO11); and 4,4'-bis[ N -(1-Naphthyl)- N -phenylamino]biphenyl (abbreviated: NPB or α-NPD), N , N -bis(3-methylphenyl)- N , N '-diphenyl-[1,1'-biphenyl]-4,4'-diamine (abbreviated: TPD), and 4,4'-bis[ N -(Spyro-9,9'-bifluorene-2-yl)- N Aromatic amine compounds such as -phenylamino]biphenyl (abbreviated: BSPB). Also, anthracene derivatives, phenanthrene derivatives, pyrene derivatives, chrysene derivatives, and dibenzo[ g , p Examples include condensation polycyclic aromatic compounds such as chrysene derivatives, and specific examples include 9,10-diphenylanthracene (abbreviated: DPAnth), N , N -diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9 H -Carbazole-3-amine (abbreviation: CzA1PA), 4-(10-phenyl-9-anthryl)triphenylamine (abbreviation: DPhPA), 4-(9 H -carbazole-9-yl)-4'-(10-phenyl-9-anthryl)triphenylamine (abbreviation: YGAPA), N ,9-diphenyl- N -[4-(10-phenyl-9-antryl)phenyl]-9 H -Carbazole-3-amine (abbreviation: PCAPA), N ,9-diphenyl- N -{4-[4-(10-phenyl-9-antryl)phenyl]phenyl}-9 H-Carbazol-3-amine (abbreviation: PCAPBA), N ,9-diphenyl- N -(9,10-diphenyl-2-anthryl)-9H-carbazole-3-amine (abbreviation: 2PCAPA), 6,12-dimethoxy-5,11-diphenylchrycene, N , N , N ', N ', N ", N ", N ''', N '''-Octaphenyldibenzo[ g , p ]Chrysene-2,7,10,15-tetramine (abbreviation: DBC1), 9-[4-(10-phenyl-9-antryl)phenyl]-9 H -Carbazole (abbreviation: CzPA), 3,6-diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9 H -Carbazole (abbreviation: DPCzPA), 9,10-Bis(3,5-Diphenylphenyl)anthracene (abbreviation: DPPA), 9,10-Di(2-Naphthyl)anthracene (abbreviation: DNA), 2- tert Examples include butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA), 9,9'-bianthrile (abbreviation: BANT), 9,9'-(stilbene-3,3'-diyl)diphenanthrene (abbreviation: DPNS), 9,9'-(stilbene-4,4'-diyl)diphenanthrene (abbreviation: DPNS2), and 3,3',3"-(benzene-1,3,5-triyl)tripyrene (abbreviation: TPB3). Among these and known materials, it is preferable to select one or more materials having a wider energy gap than the guest material (122) described above.

[0276] The light-emitting layer (120) may have a structure in which two or more layers are stacked. For example, when the light-emitting layer (120) is formed by stacking the first light-emitting layer and the second light-emitting layer in this order on the hole transport layer side, the first light-emitting layer is formed by using a material having hole transport properties as a host material, and the second light-emitting layer is formed by using a material having electron transport properties as a host material.

[0277] In the light-emitting layer (120), the host material (121) may be composed of a type of compound or a plurality of compounds. The light-emitting layer (120) may include materials other than the host material (121) and the guest material (122).

[0278] <<Materials that can be used for the light-emitting layer (170)>>

[0279] As a material that can be used for the light-emitting layer (170), a material that can be used for the light-emitting layer (140) of Embodiment 1 may be used. By using a material that can be used for the light-emitting layer (140) as the material for the light-emitting layer (170), the light-emitting efficiency of the light-emitting element can be increased.

[0280] There is no limitation on the light emission color of the light-emitting material included in the light-emitting layer (120) and the light-emitting layer (170), and it may be the same or different. Since the light emission from the light-emitting material is mixed and extracted outside the device, for example, if the light emission color is a complementary color, the light-emitting device can emit white light. Considering the reliability of the light-emitting device, it is preferable that the light emission peak wavelength of the light-emitting material included in the light-emitting layer (120) is shorter than that of the light-emitting material included in the light-emitting layer (170).

[0281] Additionally, the light-emitting unit (106), the light-emitting unit (108), and the charge-generating layer (115) can be formed by a deposition method (including vacuum deposition), an inkjet method, a coating method, or gravure printing, etc.

[0282] The structure described in this embodiment may be used in appropriate combination with any of the structures described in other embodiments.

[0283] (Embodiment 3)

[0284] In this embodiment, examples of light-emitting elements having a structure different from that described in Embodiments 1 and 2 are described below with reference to FIGS. 5 (A) and (B), FIGS. 6 (A) and (B), FIGS. 7 (A) to (C), and FIGS. 8 (A) to (C).

[0285] <Structure Example 1 of a Light-Emitting Element>

[0286] FIGS. 5 (A) and (B) are cross-sectional views illustrating a light-emitting element according to one embodiment of the present invention. In FIGS. 5 (A) and (B), parts having a function similar to that of FIG. 1 (A) are indicated by a hatch pattern similar to that of FIG. 1 (A) and may not be specifically indicated by a symbol. Additionally, common symbols are used for parts having similar functions, and detailed descriptions of such parts may be omitted.

[0287] The light-emitting elements (260a and 260b) of FIG. 5 (A) and (B) may have a bottom emission structure in which light is extracted through the substrate (200), or a top emission structure in which light emitted from the light-emitting element is extracted in a direction opposite to that of the substrate (200). However, one embodiment of the present invention is not limited to this structure, and may use a light-emitting element having a dual emission structure in which light emitted from the light-emitting element is extracted in both the upper and lower directions of the substrate (200).

[0288] If each of the light-emitting elements (260a and 260b) has a bottom emission structure, it is preferable that the electrode (101) has a function of transmitting light and the electrode (102) has a function of reflecting light. Alternatively, if each of the light-emitting elements (260a and 260b) has a top emission structure, it is preferable that the electrode (101) has a function of reflecting light and the electrode (102) has a function of transmitting light.

[0289] Each of the light-emitting elements (260a and 260b) includes an electrode (101) and an electrode (102) on a substrate (200). Between the electrodes (101 and 102), a light-emitting layer (123B), a light-emitting layer (123G), and a light-emitting layer (123R) are provided. A hole injection layer (111), a hole transport layer (112), an electron transport layer (118), and an electron injection layer (119) are also provided.

[0290] The light-emitting element (260b) includes a conductive layer (101a), a conductive layer (101b) above the conductive layer (101a), and a conductive layer (101c) below the conductive layer (101a) as part of the electrode (101). In other words, the light-emitting element (260b) includes an electrode (101) having a structure in which the conductive layer (101a) is sandwiched between the conductive layer (101b) and the conductive layer (101c).

[0291] In the light-emitting element (260b), the conductive layer (101b) and the conductive layer (101c) may be formed of different materials or may be formed of the same material. It is preferable that the electrode (101) has a structure in which the electrode (101) is fitted between layers formed of the same conductive material, so that patterning by etching in the process of forming the electrode (101) can be easily performed.

[0292] Additionally, the light-emitting element (260b) may include either the conductive layer (101b) or the conductive layer (101c).

[0293] For each of the conductive layers (101a, 101b, and 101c) included in the electrode (101), the structure and material of the electrode (101 or 102) described in Embodiment 1 may be used.

[0294] In FIG. 5 (A) and (B), a partition (145) is provided between the region (221B), region (221G), and region (221R) sandwiched between the electrode (101) and the electrode (102). The partition (145) has insulating properties. The partition (145) covers the end of the electrode (101) and has an opening that overlaps with the electrode. By the partition (145), the electrode (101) provided on the substrate (200) in the region can be divided into an island shape.

[0295] Additionally, the light-emitting layer (123B) and the light-emitting layer (123G) may overlap each other in the area overlapping with the partition wall (145). The light-emitting layer (123G) and the light-emitting layer (123R) may overlap each other in the area overlapping with the partition wall (145). The light-emitting layer (123R) and the light-emitting layer (123B) may overlap each other in the area overlapping with the partition wall (145).

[0296] The partition (145) is insulating and is formed using inorganic or organic materials. Examples of inorganic materials include silicon oxide, silicon nitride, silicon nitride, silicon nitride, aluminum oxide, and aluminum nitride. Examples of organic materials include photosensitive resin materials such as acrylic resin and polyimide resin.

[0297] In addition, a silicon oxynitride film refers to a film in which the proportion of oxygen is higher than the proportion of nitrogen. It is preferable that the silicon oxynitride film contains oxygen, nitrogen, silicon, and hydrogen in the ranges of 55 atomic% to 65 atomic%, 1 atomic% to 20 atomic%, 25 atomic% to 35 atomic%, and 0.1 atomic% to 10 atomic%, respectively. A silicon nitride film refers to a film in which the proportion of nitrogen is higher than the proportion of oxygen. It is preferable that the silicon nitride film contains nitrogen, oxygen, silicon, and hydrogen in the ranges of 55 atomic% to 65 atomic%, 1 atomic% to 20 atomic%, 25 atomic% to 35 atomic%, and 0.1 atomic% to 10 atomic%, respectively.

[0298] It is preferable that the light-emitting layers (123R, 123G, and 123B) contain a light-emitting material having the function of emitting light of different colors. For example, if the light-emitting layer (123R) contains a light-emitting material having the function of displaying red, the region (221R) emits red light. If the light-emitting layer (123G) contains a light-emitting material having the function of displaying green, the region (221G) emits green light. If the light-emitting layer (123B) contains a light-emitting material having the function of displaying blue, the region (221B) emits blue light. By using a light-emitting element (260a or 260b) having such a structure in a pixel of a display device, a full-color display device can be manufactured. The thicknesses of the light-emitting layers may be the same or different.

[0299] It is preferable that one or more of the light-emitting layers (123B, 123G, and 123R) have a structure similar to the structure of the light-emitting layer (140) described in Embodiment 1. In that case, a light-emitting device with high light-emitting efficiency can be manufactured.

[0300] One or more of the light-emitting layers (123B, 123G, and 123R) may include two or more stacked layers.

[0301] As described above, if at least one light-emitting layer comprises the light-emitting layer described in Embodiment 1 and Embodiment 2, and a light-emitting element (260a or 260b) comprising the light-emitting layer is used in a pixel of a display device, a display device with high light-emitting efficiency can be manufactured. By doing so, the power consumption of the display device comprising the light-emitting element (260a or 260b) can be reduced.

[0302] By providing an optical element (e.g., a color filter, a polarizer, and an anti-reflective film) on the light extraction side of the electrode from which light is extracted, the color purity of each of the light-emitting elements (260a and 260b) can be improved. Accordingly, the color purity of a display device including the light-emitting elements (260a or 260b) can be improved. Alternatively, the reflection of external light by each of the light-emitting elements (260a and 260b) can be reduced. Therefore, the contrast ratio of a display device including the light-emitting elements (260a or 260b) can be improved.

[0303] For other components of the light-emitting elements (260a and 260b), reference may be made to the components of the light-emitting elements of Embodiment 1 and Embodiment 2.

[0304] <Structure Example of a Light-Emitting Element 2>

[0305] Next, an example of a structure of a light-emitting element different from the light-emitting element shown in (A) and (B) of FIGS. 5 will be described below with reference to (A) and (B) of FIGS. 6.

[0306] FIGS. 6 (A) and (B) are cross-sectional views of a light-emitting element according to one embodiment of the present invention. In FIGS. 6 (A) and (B), parts having a function similar to the parts of FIGS. 5 (A) and (B) are indicated by a hatch pattern as in FIGS. 5 (A) and (B) and may not be specifically indicated by a symbol. In addition, common symbols are used for parts having a similar function, and detailed descriptions of such parts are not repeated.

[0307] FIGS. 6 (A) and (B) illustrate an example of a structure of a light-emitting element comprising a light-emitting layer between a pair of electrodes. The light-emitting element (262a) shown in FIG. 6 (A) has a top emission structure in which light is extracted in a direction opposite to the substrate (200), and the light-emitting element (262b) shown in FIG. 6 (B) has a bottom emission structure in which light is extracted toward the substrate (200). However, one embodiment of the present invention is not limited to these structures and may have a dual emission structure in which light emitted from the light-emitting element is extracted in both upward and downward directions relative to the substrate (200) on which the light-emitting element is formed.

[0308] Each of the light-emitting elements (262a and 262b) comprises an electrode (101), an electrode (102), an electrode (103), and an electrode (104) on a substrate (200). Between the electrode (101) and the electrode (102), between the electrode (102) and the electrode (103), and between the electrode (102) and the electrode (104), at least a light-emitting layer (170), a light-emitting layer (190), and a charge-generating layer (115) are provided. 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 further provided.

[0309] The electrode (101) includes a conductive layer (101a) and a conductive layer (101b) that is on the conductive layer (101a) and in contact with the conductive layer (101a). The electrode (103) includes a conductive layer (103a) and a conductive layer (103b) that is on the conductive layer (103a) and in contact with the conductive layer (103a). The electrode (104) includes a conductive layer (104a) and a conductive layer (104b) that is on the conductive layer (104a) and in contact with the conductive layer (104a).

[0310] Each of the light-emitting element (262a) shown in FIG. 6 (A) and the light-emitting element (262b) shown in FIG. 6 (B) includes a partition (145) between the region (222B) sandwiched between electrode (101) and electrode (102), the region (222G) sandwiched between electrode (102) and electrode (103), and the region (222R) sandwiched between electrode (102) and electrode (104). The partition (145) has insulating properties. The partition (145) covers the ends of the electrodes (101, 103, and 104) and has an opening that overlaps with the electrodes. By the partition (145), the electrodes provided on the substrate (200) in the region can be separated into an island shape.

[0311] The charge generation layer (115) can be formed from a material obtained by adding an electron acceptor to a hole transport material, or from a material obtained by adding an electron donor to an electron transport material. Additionally, if the conductivity of the charge generation layer (115) is as high as the conductivity of a pair of electrodes, carriers generated in the charge generation layer (115) may move to an adjacent pixel and light emission may occur in the pixel. To prevent such false light emission from an adjacent pixel, it is preferable to form the charge generation layer (115) with a material having a conductivity lower than that of a pair of electrodes.

[0312] Each of the light-emitting elements (262a and 262b) comprises a substrate (220) provided with an optical element (224B), an optical element (224G), and an optical element (224R) in a direction from which light emitted from region (222B), light emitted from region (222G), and light emitted from region (222R) is extracted. Light emitted from each region is emitted outside the light-emitting element through each optical element. In other words, light from region (222B), light from region (222G), and light from region (222R) are each emitted through the optical element (224B), the optical element (224G), and the optical element (224R).

[0313] Each of the optical elements (224B, 224G, and 224R) has the function of selectively transmitting light of a specific color from incident light. For example, the light emitted from region (222B) through the optical element (224B) is blue light, the light emitted from region (222G) through the optical element (224G) is green light, and the light emitted from region (222R) through the optical element (224R) is red light.

[0314] For example, the optical elements (224R, 224G, and 224B) may use a coloring layer (also called a color filter), a bandpass filter, or a multilayer filter. Alternatively, a color conversion element may be used as the optical element. A color conversion element is an optical element that converts incident light into light having a longer wavelength than the incident light. Quantum dot elements may be suitably used as the color conversion element. By using a quantum dot type, the color reproduction of the display device can be improved.

[0315] One or more optical elements may be laminated on each optical element (224R, 224G, and 224B). Other optical elements may include, for example, a circular polarizer or an anti-reflective film. If a circular polarizer is provided on the side from which light emitted from the light-emitting element of the display device is extracted, the phenomenon in which light entering from outside the display device is reflected inside the display device and returned to the outside can be prevented. The anti-reflective film can weaken external light reflected to the surface of the display device. As a result, the light emitted from the display device can be observed clearly.

[0316] In addition, in Figures 6 (A) and (B), blue light (B), green light (G), and red light (R) emitted from the region through the optical element are schematically represented by dashed arrows.

[0317] A light-blocking layer (223) is provided between the optical elements. The light-blocking layer (223) has the function of blocking light emitted from adjacent regions. Additionally, a structure without a light-blocking layer (223) may be adopted.

[0318] The light-blocking layer (223) has the function of reducing the reflection of external light. The light-blocking layer (223) has the function of preventing light emitted from adjacent light-emitting elements from mixing. As the light-blocking layer (223), a metal, a resin containing a black pigment, carbon black, a metal oxide, or a composite oxide containing a solid solution of multiple metal oxides may be used.

[0319] Additionally, the optical element (224B) and the optical element (224G) may overlap each other in the area overlapping with the light-blocking layer (223). Additionally, the optical element (224G) and the optical element (224R) may overlap each other in the area overlapping with the light-blocking layer (223). Additionally, the optical element (224R) and the optical element (224B) may overlap each other in the area overlapping with the light-blocking layer (223).

[0320] For the substrate (200) and the substrate (220) on which the optical element is provided, reference can be made to Embodiment 1.

[0321] In addition, the light-emitting elements (262a and 262b) have a microcavity structure.

[0322] Microcavity Structure

[0323] Light emitted from the light-emitting layer (170) and the light-emitting layer (190) resonates between a pair of electrodes (e.g., electrode (101) and electrode (102)). The light-emitting layer (170) and the light-emitting layer (190) are formed at a position where light of a desired wavelength among the emitted light is enhanced. For example, by adjusting the length of the light path from the reflection area of ​​electrode (101) to the light-emitting area of ​​the light-emitting layer (170) and the length of the light path from the reflection area of ​​electrode (102) to the light-emitting area of ​​the light-emitting layer (170), light of a desired wavelength among the light emitted from the light-emitting layer (170) can be enhanced. By adjusting the length of the light path from the reflection area of ​​electrode (101) to the light-emitting area of ​​the light-emitting layer (190) and the length of the light path from the reflection area of ​​electrode (102) to the light-emitting area of ​​the light-emitting layer (190), light of a desired wavelength among the light emitted from the light-emitting layer (190) can be enhanced. In the case of a light-emitting device in which a plurality of light-emitting layers (here, light-emitting layers (170 and 190)) are stacked, it is desirable that the length of the light path of the light-emitting layers (170 and 190) be optimized.

[0324] By adjusting the thickness of the conductive layer (conductive layer (101b), conductive layer (103b), and conductive layer (104b)) in each region of each of the light-emitting elements (262a and 262b), light of a desired wavelength among the light emitted from the light-emitting layers (170 and 190) can be enhanced. Additionally, the light emitted from the light-emitting layers (170 and 190) may be enhanced by making the thickness of at least one of the hole injection layer (111) and the hole transport layer (112) different between regions.

[0325] For example, if the refractive index of the conductive material having the function of reflecting light of the electrodes (101 to 104) is lower than the refractive index of the light-emitting layer (170 or 190), the thickness of the conductive layer (101b) of the electrode (101) is adjusted so that the length of the light path between the electrode (101) and the electrode (102) m B λ B / 2( m Bis a natural number and λ B (is the wavelength of light enhanced in region (222B). Likewise, the thickness of the conductive layer (103b) of the electrode (103) is adjusted so that the length of the optical path between the electrode (103) and the electrode (102) m G λ G / 2( m G is a natural number and λ G (is the wavelength of light enhanced in region (222G). In addition, the thickness of the conductive layer (104b) of the electrode (104) is adjusted so that the length of the optical path between the electrode (104) and the electrode (102) m R λ R / 2( m R is a natural number and λ R Make it so that it becomes the wavelength of light that is enhanced in the region (222R).

[0326] If it is difficult to accurately determine the reflection region of the electrodes (101 to 104), the length of the light path to increase the intensity of light emitted from the light-emitting layer (170 or 190) may be derived by assuming that a predetermined region of the electrodes (101 to 104) is a reflection region. If it is difficult to accurately determine the light-emitting region of the light-emitting layer (170 and 190), the length of the light path to increase the intensity of light emitted from the light-emitting layer (170 and 190) may be derived by assuming that a predetermined region of the light-emitting layer (170 and 190) is a light-emitting region.

[0327] As described above, by means of a microcavity structure that adjusts the length of the optical path between a pair of electrodes in each region, scattering and absorption of light near the electrodes can be suppressed, and accordingly, the light extraction efficiency is increased.

[0328] In the structure described above, it is preferable that the conductive layers (101b, 103b, and 104b) have a function of transmitting light. The materials of the conductive layers (101b, 103b, and 104b) may be the same or different. It is preferable to use the same material for the conductive layers (101b, 103b, and 104b) so that patterning by etching during the formation process of the electrodes (101, 103, and 104) can be easily performed. Each of the conductive layers (101b, 103b, and 104b) may have a stacked structure of two or more layers.

[0329] Since the light-emitting element (262a) illustrated in Fig. 6 (A) has a top emission structure, it is preferable that the conductive layer (101a), the conductive layer (103a), and the conductive layer (104a) have a function of reflecting light. Additionally, it is preferable that the electrode (102) has a function of transmitting light and a function of reflecting light.

[0330] Since the light-emitting element (262b) illustrated in (B) of FIG. 6 has a bottom emission structure, it is preferable that the conductive layer (101a), the conductive layer (103a), and the conductive layer (104a) have the function of transmitting light and reflecting light. Additionally, it is preferable that the electrode (102) has the function of reflecting light.

[0331] In each of the light-emitting elements (262a and 262b), the conductive layers (101a, 103a, and 104a) may be formed of different materials or the same material. If the conductive layers (101a, 103a, and 104a) are formed of the same material, the manufacturing cost of the light-emitting elements (262a and 262b) can be reduced. Additionally, each of the conductive layers (101a, 103a, and 104a) may have a stacked structure including two or more layers.

[0332] It is preferable that at least one of the structures described in Embodiment 1 and Embodiment 2 be used in at least one of the light-emitting layer (170) and the light-emitting layer (190) included in the light-emitting element (262a and 262b). In this way, the light-emitting efficiency of the light-emitting element can be increased.

[0333] Either or both of the light-emitting layers (170 and 190) may have a stacked structure consisting of two layers, for example, light-emitting layers (190a and 190b). Multiple colors can be emitted by two light-emitting layers each comprising two types of light-emitting materials (a first compound and a second compound) that emit light of different colors. It is particularly desirable to select the light-emitting materials of the light-emitting layers so that white light can be obtained by combining the light emitted from the light-emitting layers (170 and 190).

[0334] Either or both of the light-emitting layers (170 and 190) may have a stacked structure consisting of three or more layers, or may include a layer that does not contain a light-emitting material.

[0335] In the manner described above, by using a light-emitting element (262a or 262b) comprising a light-emitting layer having at least one of the structures described in Embodiment 1 and Embodiment 2 in a pixel of a display device, a display device with high light-emitting efficiency can be manufactured. Accordingly, power consumption of the display device including the light-emitting element (262a or 262b) can be reduced.

[0336] For other components of the light-emitting elements (262a and 262b), reference may be made to the light-emitting elements (260a or 260b), or to the components of the light-emitting elements of Embodiment 1 and Embodiment 2.

[0337] Method for fabricating light-emitting devices

[0338] Next, a method for manufacturing a light-emitting element according to one embodiment of the present invention will be described below with reference to FIGS. 7 (A) to (C) and FIGS. 8 (A) to (C). Here, a method for manufacturing a light-emitting element (262a) illustrated in FIG. 6 (A) will be described.

[0339] Figures 7 (A) to (C) and Figures 8 (A) to (C) are cross-sectional views illustrating a method for manufacturing a light-emitting element according to one embodiment of the present invention.

[0340] The method for manufacturing the light-emitting element (262a) described below includes steps 1 to 7.

[0341] <<Stage 1>>

[0342] In the first step, electrodes of the light-emitting element (specifically, a conductive layer (101a) of electrode (101), a conductive layer (103a) of electrode (103), and a conductive layer (104a) of electrode (104)) are formed on a substrate (200) (see (A) of FIG. 7).

[0343] In this embodiment, a conductive layer having a light-reflecting function is formed on a substrate (200) and processed into a desired shape to form a conductive layer (101a, 103a, and 104a). As the conductive layer having a light-reflecting function, an alloy film of silver, palladium, and copper (also called an Ag-Pd-Cu film or APC) is used. It is preferable to form the conductive layer (101a, 103a, and 104a) through the step of processing the same conductive layer, as this can reduce manufacturing costs.

[0344] In addition, prior to the first step, a plurality of transistors may be formed on the substrate (200). The plurality of transistors may be electrically connected to the conductive layers (101a, 103a, and 104a).

[0345] <<Stage 2>>

[0346] In the second step, a transparent conductive layer (101b) having a light-transmitting function is formed on the conductive layer (101a) of the electrode (101), a transparent conductive layer (103b) having a light-transmitting function is formed on the conductive layer (103a) of the electrode (103), and a transparent conductive layer (104b) having a light-transmitting function is formed on the conductive layer (104a) of the electrode (104) (see (B) of FIG. 7).

[0347] In this embodiment, electrodes (101), electrode (103), and electrode (104) are formed by forming conductive layers (101b, 103b, and 104b) that each have a function of transmitting light on conductive layers (101a, 103a, and 104a) that each have a function of reflecting light. ITSO films are used as the conductive layers (101b, 103b, and 104b).

[0348] The conductive layers (101b, 103b, and 104b) having the function of transmitting light may be formed in multiple steps. If the conductive layers (101b, 103b, and 104b) having the function of transmitting light are formed in multiple steps, they can be formed with a thickness that enables a suitable microcavity structure to be realized in each region.

[0349] <<Stage 3>>

[0350] In the third step, a partition (145) covering the ends of the electrodes of the light-emitting element is formed (see (C) in FIG. 7).

[0351] The partition wall (145) includes an opening that overlaps with the electrode. The conductive film exposed by the opening functions as the anode of the light-emitting element. In this embodiment, a polyimide-based resin is used as the partition wall (145).

[0352] In the first to third steps, various film formation methods and microfabrication techniques can be employed because there is no possibility of damaging the EL layer (a layer containing an organic compound). In this embodiment, a reflective conductive layer is formed by a sputtering method, a pattern is formed on the conductive layer by a lithography method, and then the conductive layer is processed into an island shape by a dry etching method or a wet etching method to form the conductive layer (101a) of the electrode (101), the conductive layer (103a) of the electrode (103), and the conductive layer (104a) of the electrode (104). Then, a transparent conductive film is formed by a sputtering method, a pattern is formed on the transparent conductive film by a lithography method, and then the transparent conductive film is processed into an island shape by a wet etching method to form the electrodes (101, 103, and 104).

[0353] <<Stage 4>>

[0354] In the fourth step, a hole injection layer (111), a hole transport layer (112), a light-emitting layer (190), an electron transport layer (113), an electron injection layer (114), and a charge generation layer (115) are formed (see (A) in FIG. 8).

[0355] The hole injection layer (111) can be formed by co-depositing a material containing a hole transport material and an acceptor material. Additionally, the co-depositing method is a deposition method in which a plurality of different materials are simultaneously evaporated from different evaporation sources. The hole transport layer (112) can be formed by depositing a hole transport material.

[0356] The light-emitting layer (190) can be formed by depositing a guest material that emits light of at least one color selected from purple, blue, cyan, green, yellow-green, yellow, orange, and red. As the guest material, a fluorescent or phosphorescent organic material may be used. It is preferable to adopt the structure of the light-emitting layer described in Embodiment 1 or Embodiment 2. The light-emitting layer (190) may have a two-layer structure. In this case, it is preferable that each of the two light-emitting layers contains a light-emitting material that emits light of a different color.

[0357] The electron transport layer (113) can be formed by depositing a material with high electron transportability. The electron injection layer (114) can be formed by depositing a material with high electron injectionability.

[0358] The charge generation layer (115) can be formed by depositing a material obtained by adding an electron acceptor to a hole transport material, or a material obtained by adding an electron donor to an electron transport material.

[0359] <<Step 5>>

[0360] In the fifth step, a hole injection layer (116), a hole transport layer (117), a light-emitting layer (170), an electron transport layer (118), an electron injection layer (119), and an electrode (102) are formed (see (B) of FIG. 8).

[0361] The hole injection layer (116) can be formed by using a material and method similar to that of the hole injection layer (111). The hole transport layer (117) can be formed by using a material and method similar to that of the hole transport layer (112).

[0362] The light-emitting layer (170) can be formed by depositing a guest material that emits light of at least one color selected from purple, blue, cyan, green, yellow-green, yellow, orange, and red. As the guest material, a fluorescent or phosphorescent organic compound may be used. It is preferable to adopt the structure of the light-emitting layer described in Embodiment 1. In addition, it is preferable that at least one of the light-emitting layer (170) and the light-emitting layer (190) has the structure of the light-emitting layer described in Embodiment 1 or Embodiment 2. It is preferable that the light-emitting layers (170 and 190) include a light-emitting organic compound that exhibits light of a different color.

[0363] The electron transport layer (118) can be formed by using a material and method similar to that of the electron transport layer (113). The electron injection layer (119) can be formed by using a material and method similar to that of the electron injection layer (114).

[0364] The electrode (102) can be formed by laminating a reflective conductive film and a transparent conductive film. The electrode (102) may have a single-layer structure or a laminated structure.

[0365] Through the process described above, a light-emitting element including regions (222B), (222G), and (222R), respectively, is formed on the electrode (101), electrode (103), and electrode (104) on the substrate (200).

[0366] <<Step 6>>

[0367] In the sixth step, a light-blocking layer (223), an optical element (224B), an optical element (224G), and an optical element (224R) are formed on the substrate (220) (see (C) of FIG. 8).

[0368] As a light-blocking layer (223), a resin film containing black pigment is formed in a desired area. Then, an optical element (224B), an optical element (224G), and an optical element (224R) are formed on the substrate (220) and the light-blocking layer (223). As for the optical element (224B), a resin film containing blue pigment is formed in a desired area. As for the optical element (224G), a resin film containing green pigment is formed in a desired area. As for the optical element (224R), a resin film containing red pigment is formed in a desired area.

[0369] <<Step 7>>

[0370] In the seventh step, a light-emitting element formed on a substrate (200) is bonded to a light-blocking layer (223), an optical element (224B), an optical element (224G), and an optical element (224R) formed on a substrate (220), and sealed using a sealant (not shown).

[0371] A light-emitting element (262a) illustrated in (A) of FIG. 6 can be formed through the process described above.

[0372] The structure described in this embodiment may be used in appropriate combination with any of the structures described in other embodiments.

[0373] (Embodiment 4)

[0374] In this embodiment, a display device according to one form of the present invention will be described below with reference to FIGS. 9 (A) and (B), FIGS. 10 (A) and (B), FIGS. 11, FIGS. 12 (A) and (B), FIGS. 13 (A) and (B), FIGS. 14, FIGS. 15 (A) and (B), FIGS. 16, and FIGS. 17 (A) and (B).

[0375] <Example of Display Device Structure 1>

[0376] FIG. 9 (A) is a top view illustrating a display device (600), and FIG. 9 (B) is a cross-sectional view taken along dotted lines AB and CD of FIG. 9 (A). The display device (600) includes a driving circuit section (signal line driving circuit section (601) and scan line driving circuit section (603)) and a pixel section (602). Additionally, the signal line driving circuit section (601), the scan line driving circuit section (603), and the pixel section (602) have the function of controlling light emission from a light-emitting element.

[0377] Additionally, the display device (600) includes a device substrate (610), a sealing substrate (604), a real part (605), a region (607) surrounded by the real part (605), lead wiring (608), and an FPC (609).

[0378] Additionally, the lead wiring (608) is wiring for transmitting signals input to the signal line driving circuit (601) and the scan line driving circuit (603), and is wiring for receiving video signals, clock signals, start signals, and reset signals from the FPC (609) which functions as an external input terminal. Although only the FPC (609) is shown here, the FPC (609) may be provided with a printed wiring board (PWB).

[0379] As a signal line driving circuit (601), a CMOS circuit is formed by combining an n-channel transistor (623) and a p-channel transistor (624). Various types of circuits, such as CMOS circuits, PMOS circuits, or NMOS circuits, can be used as the signal line driving circuit (601) or the scan line driving circuit (603). In the display device of this embodiment, the driver and the pixel formed with the driving circuit are formed on the same surface of the substrate, but the driving circuit does not necessarily have to be formed on the substrate and can be formed outside the substrate.

[0380] The pixel portion (602) includes a switching transistor (611), a current control transistor (612), and a lower electrode (613) electrically connected to the drain of the current control transistor (612). Additionally, a partition (614) is formed to cover the end of the lower electrode (613). For example, a positive-type photosensitive acrylic resin film may be used as the partition (614).

[0381] In order to obtain good coverage, the partition wall (614) is formed to have a curved surface with curvature at its upper or lower portion. For example, when positive-type photosensitive acrylic is used as the material for the partition wall (614), it is preferable that only the upper portion of the partition wall (614) has a curved surface with curvature (radius of curvature 0.2 μm to 3 μm). As for the partition wall (614), a negative-type photosensitive resin or a positive-type photosensitive resin may be used.

[0382] In addition, there are no specific limitations on the structure of each transistor (transistors (611, 612, 623, and 624)). For example, staggered transistors may be used. In addition, there are no specific limitations on the polarity of these transistors. For example, n-channel and p-channel transistors may be used for these transistors, or either an n-channel transistor or a p-channel transistor may be used. In addition, there are no specific limitations on the crystallinity of the semiconductor film used for these transistors. For example, an amorphous semiconductor film or a crystalline semiconductor film may be used. Examples of semiconductor materials include group 14 semiconductors (e.g., semiconductors including silicon), compound semiconductors (including oxide semiconductors), and organic semiconductors. For example, it is preferable to use an oxide semiconductor for the transistor having an energy gap of 2 eV or more, preferably 2.5 eV or more, and more preferably 3 eV or more, thereby reducing the off-state current of the transistor. Examples of oxide semiconductors include In-Ga oxide and In-M-Zn oxide (where M is aluminum (Al), gallium (Ga), yttrium (Y), zirconium (Zr), lanthanum (La), cerium (Ce), tin (Sn), hafnium (Hf), or neodymium (Nd).

[0383] An EL layer (616) and an upper electrode (617) are formed on the lower electrode (613). Here, the lower electrode (613) functions as an anode, and the upper electrode (617) functions as a cathode.

[0384] Additionally, the EL layer (616) is formed by various methods such as deposition using a deposition mask, inkjet method, or spin coating method. Other materials included in the EL layer (616) may include low molecular weight compounds or high molecular weight compounds (including oligomers or dendrimers).

[0385] Additionally, the light-emitting element (618) is formed by a lower electrode (613), an EL layer (616), and an upper electrode (617). It is preferable that the light-emitting element (618) has any of the structures described in embodiments 1 to 3. When the pixel portion includes a plurality of light-emitting elements, the pixel portion may include both any of the light-emitting elements described in embodiments 1 to 3 and light-emitting elements having a different structure.

[0386] Additionally, when the sealing substrate (604) and the device substrate (610) are joined together with the actual material (605), a light-emitting element (618) is provided in the region (607) surrounded by the device substrate (610), the sealing substrate (604), and the actual material (605). The region (607) is filled with a filler. The region (607) may be filled with an inert gas (such as nitrogen or argon), or with a UV-curing resin or a heat-curing resin that can be used in the actual material (605). For example, PVC (polyvinyl chloride) resin, acrylic resin, polyimide resin, epoxy resin, silicone resin, PVB (polyvinyl butyral) resin, or EVA (ethylene vinyl acetate) resin may be used. It is preferable to provide a concave portion in the sealing substrate and provide a desiccant in the concave portion so that deterioration due to the influence of moisture can be suppressed.

[0387] An optical element (621) is provided under a sealing substrate (604) so ​​as to overlap with a light-emitting element (618). A light-blocking layer (622) is provided under the sealing substrate (604). The structure of the optical element (621) and the light-blocking layer (622) can be the same as that of the optical element and the light-blocking layer of Embodiment 3, respectively.

[0388] In practice (605), it is preferable to use an epoxy resin or glass frit. It is desirable that such materials do not allow moisture or oxygen to pass through as much as possible. As for the sealing substrate (604), a glass substrate, a quartz substrate, or a plastic substrate formed of FRP (fiber reinforced plastic), PVF (poly(vinyl fluoride)), polyester, or acrylic, etc., may be used.

[0389] As described above, a display device including any light-emitting element and optical element described in embodiments 1 to 3 can be obtained.

[0390] <Example of Display Device Structure 2>

[0391] Next, other examples of display devices will be described with reference to FIGS. 10 (A) and (B) and FIG. 11. Additionally, FIGS. 10 (A) and (B) and FIG. 11 are each cross-sectional views of a display device according to one embodiment of the present invention.

[0392] Figure 10 (A) illustrates a substrate (1001), a lower insulating film (1002), a gate insulating film (1003), gate electrodes (1006, 1007, and 1008), a first interlayer insulating film (1020), a second interlayer insulating film (1021), a peripheral portion (1042), a pixel portion (1040), a driving circuit portion (1041), lower electrodes of a light-emitting element (1024R, 1024G, and 1024B), a partition (1025), an EL layer (1028), an upper electrode of a light-emitting element (1026), a sealing layer (1029), a sealing substrate (1031), and an actual material (1032).

[0393] In FIG. 10 (A), as an example of an optical element, a colored layer (a red colored layer (1034R), a green colored layer (1034G), and a blue colored layer (1034B)) is provided on a transparent substrate (1033). Additionally, a light-blocking layer (1035) may be provided. The transparent substrate (1033) provided with the colored layer and the light-blocking layer is fixed to the substrate (1001) by positioning. Additionally, the colored layer and the light-blocking layer are covered with an overcoat layer (1036). In the structure of FIG. 10 (A), since red light, green light, and blue light pass through the colored layer, an image can be displayed using three-color pixels.

[0394] FIG. 10 (B) illustrates an example of an optical element in which a colored layer (a red colored layer (1034R), a green colored layer (1034G), and a blue colored layer (1034B)) is provided between a gate insulating film (1003) and a first interlayer insulating film (1020). As in this structure, the colored layer may be provided between a substrate (1001) and a sealing substrate (1031).

[0395] FIG. 11 illustrates an example of an optical element in which a colored layer (a red colored layer (1034R), a green colored layer (1034G), and a blue colored layer (1034B)) is provided between a first interlayer insulating film (1020) and a second interlayer insulating film (1021). As in this structure, the colored layer may be provided between a substrate (1001) and a sealing substrate (1031).

[0396] The above-described display device has a structure (bottom emission structure) for extracting light from the side of the substrate (1001) on which the transistor is formed, but may also have a structure (top emission structure) for extracting light from the side of the sealed substrate (1031).

[0397] <Example of Display Device Structure 3>

[0398] Each of (A) and (B) of FIG. 12 is an example of a cross-sectional view of a display device having a top emission structure. Also, each of (A) and (B) of FIG. 12 is a cross-sectional view illustrating a display device according to one embodiment of the present invention, and the driving circuit part (1041) and peripheral part (1042), etc., illustrated in FIG. 10 (A) and (B) and FIG. 11 are not illustrated.

[0399] In this case, a substrate that does not transmit light may be used as the substrate (1001). The process up to the step of forming a connection electrode that connects the anode of the transistor and the light-emitting element is performed in the same way as a display device having a bottom emission structure. Then, a third interlayer insulating film (1037) is formed to cover the electrode (1022). This insulating film may have a flattening function. The third interlayer insulating film (1037) may be formed using a material similar to the second interlayer insulating film, or may be formed using any of various other materials.

[0400] Here, each of the lower electrodes (1024R, 1024G, and 1024B) of the light-emitting element functions as an anode, but may also function as a cathode. Additionally, in the case of a display device having a top emission structure as shown in (A) and (B) of FIG. 12, it is preferable that the lower electrodes (1024R, 1024G, and 1024B) have a function of reflecting light. An upper electrode (1026) is provided on the EL layer (1028). It is preferable that the upper electrode (1026) has a function of reflecting light and a function of transmitting light, and it is preferable to use a microcavity structure between the upper electrode (1026) and the lower electrodes (1024R, 1024G, and 1024B) to increase the intensity of light of a specific wavelength.

[0401] In the case of a top emission structure as illustrated in (A) of FIG. 12, sealing can be performed using a sealing substrate (1031) provided with a colored layer (a red colored layer (1034R), a green colored layer (1034G), and a blue colored layer (1034B)). The sealing substrate (1031) may also be provided with a light-blocking layer (1035) located between pixels. Additionally, a transparent substrate is preferably used as the sealing substrate (1031).

[0402] FIG. 12 (A) illustrates a structure providing light-emitting elements and coloring layers for the light-emitting elements, but the structure is not limited thereto. For example, as shown in FIG. 12 (B), a structure may be adopted that includes a red coloring layer (1034R) and a blue coloring layer (1034B) and does not include a green coloring layer, thereby enabling full-color display in three colors: red, green, and blue. The structure illustrated in FIG. 12 (A), which provides coloring layers to the light-emitting elements, is effective in suppressing external light reflection. Meanwhile, the structure illustrated in FIG. 12 (B), which provides a red coloring layer and a blue coloring layer to the light-emitting elements and does not have a green coloring layer, is effective in reducing power consumption because there is less energy loss of light emitted from the green light-emitting element.

[0403] <Example of Display Device Structure 4>

[0404] Although a display device including three colors (red, green, and blue) of subpixels has been described above, the number of colors of the subpixels may be four (red, green, blue, and yellow, or red, green, blue, and white). Figures 13 (A) and (B), Figure 14, and Figures 15 (A) and (B) illustrate the structures of display devices each including a lower electrode (1024R, 1024G, 1024B, and 1024Y). Figures 13 (A) and (B) and Figure 14 each illustrate a display device having a structure (bottom emission structure) for extracting light from a substrate (1001) on which a transistor is formed, and Figures 15 (A) and (B) each illustrate a display device having a structure (top emission structure) for extracting light from a sealed substrate (1031).

[0405] FIG. 13 (A) illustrates an example of a display device in which optical elements (coloring layer (1034R), coloring layer (1034G), coloring layer (1034B), and coloring layer (1034Y)) are provided on a transparent substrate (1033). FIG. 13 (B) illustrates an example of a display device in which optical elements (coloring layer (1034R), coloring layer (1034G), and coloring layer (1034B)) are provided between a gate insulating film (1003) and a first interlayer insulating film (1020). FIG. 14 illustrates an example of a display device in which optical elements (coloring layer (1034R), coloring layer (1034G), coloring layer (1034B), and coloring layer (1034Y)) are provided between a first interlayer insulating film (1020) and a second interlayer insulating film (1021).

[0406] The colored layer (1034R) transmits red light, the colored layer (1034G) transmits green light, and the colored layer (1034B) transmits blue light. The colored layer (1034Y) transmits yellow light or transmits light of a plurality of colors selected from blue, green, yellow, and red. If the colored layer (1034Y) can transmit light of a plurality of colors selected from blue, green, yellow, and red, the light emitted from the colored layer (1034Y) may be white light. Since the light-emitting element that transmits yellow or white light has high luminous efficiency, the power consumption of the display device including the colored layer (1034Y) can be reduced.

[0407] In the top emission display device illustrated in (A) and (B) of FIG. 15, it is preferable that the light-emitting element including the lower electrode (1024Y) has a microcavity structure between the upper electrode (1026) and the lower electrodes (1024R, 1024G, 1024B, and 1024Y), as in the display device illustrated in (A) of FIG. 12. In the display device illustrated in (A) of FIG. 15, sealing can be performed with a sealing substrate (1031) provided with a coloring layer (red coloring layer (1034R), green coloring layer (1034G), blue coloring layer (1034B), and yellow coloring layer (1034Y)).

[0408] The light emitted through the microcavity and the yellow colored layer (1034Y) has a emission spectrum in the yellow region. Since yellow is a color with high visual sensitivity, the light-emitting element emitting yellow light has high luminous efficiency. Therefore, the display device of (A) in FIG. 15 can reduce power consumption.

[0409] FIG. 15 (A) illustrates a structure providing light-emitting elements and coloring layers for the light-emitting elements, but the structure is not limited thereto. For example, as shown in FIG. 15 (B), a structure may be adopted that includes a red coloring layer (1034R), a green coloring layer (1034G), and a blue coloring layer (1034B) and does not include a yellow coloring layer, thereby enabling full-color display in four colors: red, green, blue, and yellow, or red, green, blue, and white. The structure illustrated in FIG. 15 (A), which provides coloring layers to the light-emitting elements, is effective in suppressing external light reflection. Meanwhile, the structure illustrated in FIG. 15 (B), which provides a red coloring layer, a green coloring layer, and a blue coloring layer to the light-emitting elements and does not have a yellow coloring layer, is effective in reducing power consumption because there is less energy loss of light emitted from the yellow or white light-emitting elements.

[0410] <Structure Example 5 of a Display Device>

[0411] Next, another embodiment of the display device of the present invention will be described with reference to FIG. 16. FIG. 16 is a cross-sectional view taken along the dotted line AB and the dotted line CD of FIG. 9 (A). In addition, parts in FIG. 16 that have a function similar to that of FIG. 9 (B) are given the same reference numerals as FIG. 9 (B), and a detailed description of such parts is omitted.

[0412] The display device (600) of FIG. 16 includes a sealing layer (607a), a sealing layer (607b), and a sealing layer (607c) in a region (607) surrounded by an element substrate (610), a sealing substrate (604), and an actual material (605). One or more of the sealing layers (607a), sealing layer (607b), and sealing layer (607c) may use a resin such as a PVC (polyvinyl chloride) resin, an acrylic resin, a polyimide resin, an epoxy resin, a silicone resin, a PVB (polyvinyl butyral) resin, or an EVA (ethylene vinyl acetate) resin. Alternatively, inorganic materials such as silicon oxide, silicon nitride oxide, silicon nitride oxide, silicon nitride, aluminum oxide, or aluminum nitride may be used. Forming the sealing layers (607a, 607b, and 607c) is desirable because it prevents the deterioration of the light-emitting element (618) due to impurities such as water. When forming sealing layers (607a, 607b, and 607c), it is not necessary to provide the actual (605).

[0413] Alternatively, one or two of the sealing layers (607a, 607b, and 607c) may be provided, or four or more sealing layers may be formed. If the sealing layer has a multilayer structure, it can effectively prevent impurities such as water from outside the display device (600) from entering the light-emitting element (618) inside the display device. If the sealing layer has a multilayer structure, it is preferable to laminate a resin and an inorganic material.

[0414] <Structure Example 6 of a Display Device>

[0415] Each of the display devices of Structure Examples 1 to 4 of the present embodiment has a structure including an optical element, but one form of the present invention does not necessarily have to include an optical element.

[0416] Each of (A) and (B) of FIG. 17 illustrates a display device (top emission display device) having a structure for extracting light from the side of a sealed substrate (1031). FIG. 17 (A) illustrates an example of a display device including a light-emitting layer (1028R), a light-emitting layer (1028G), and a light-emitting layer (1028B). FIG. 17 (B) illustrates an example of a display device including a light-emitting layer (1028R), a light-emitting layer (1028G), a light-emitting layer (1028B), and a light-emitting layer (1028Y).

[0417] The light-emitting layer (1028R) has the function of emitting red light, the light-emitting layer (1028G) has the function of emitting green light, and the light-emitting layer (1028B) has the function of emitting blue light. The light-emitting layer (1028Y) has the function of emitting yellow light, or has the function of emitting light of a plurality of colors selected from blue, green, and red. The light-emitting layer (1028Y) may also emit white light. Since the light-emitting element emitting yellow or white light has high luminous efficiency, the power consumption of the display device including the light-emitting layer (1028Y) can be reduced.

[0418] Each display device of (A) and (B) of FIG. 17 does not necessarily need to include a coloring layer that functions as an optical element, because an EL layer that displays different colors of light is included in the subpixel.

[0419] In the sealing layer (1029), a resin such as a PVC (polyvinyl chloride) resin, an acrylic resin, a polyimide resin, an epoxy resin, a silicone resin, a PVB (polyvinyl butyral) resin, or an EVA (ethylene vinyl acetate) resin may be used. Alternatively, an inorganic material such as silicon oxide, silicon nitride oxide, silicon nitride oxide, silicon nitride, aluminum oxide, or aluminum nitride may be used. Forming the sealing layer (1029) is desirable because it prevents the deterioration of the light-emitting element caused by impurities such as water.

[0420] Alternatively, the sealing layer (1029) may have a single layer or two-layer structure, or four or more sealing layers may be formed as the sealing layer (1029). When the sealing layer has a multi-layer structure, it can effectively prevent impurities such as water from outside the display device from entering the display device. When the sealing layer has a multi-layer structure, it is preferable to laminate resin and inorganic materials.

[0421] Additionally, the sealing substrate (1031) has the function of protecting the light-emitting element. Therefore, a flexible substrate or film can be used for the sealing substrate (1031).

[0422] The structure described in this embodiment may be appropriately combined with any of the other structures of this embodiment and other embodiments.

[0423] (Embodiment 5)

[0424] In this embodiment, a display device including a light-emitting element according to one form of the present invention will be described with reference to (A) and (B) of FIG. 18, (A) and (B) of FIG. 19, and (A) and (B) of FIG. 20.

[0425] FIG. 18 (A) is a block diagram illustrating a display device according to one embodiment of the present invention, and FIG. 18 (B) is a circuit diagram illustrating a pixel circuit of a display device according to one embodiment of the present invention.

[0426] <Description of the display device>

[0427] The display device illustrated in (A) of FIG. 18 includes a region containing pixels of a display element (hereinafter, this region is referred to as a pixel section (802)), a circuit section provided outside the pixel section (802) and including a circuit for driving the pixels (hereinafter, this section is referred to as a driving circuit section (804)), a circuit having a function of protecting the element (hereinafter, this circuit is referred to as a protection circuit (806)), and a terminal section (807). Additionally, it is not necessary to provide a protection circuit (806).

[0428] It is preferable to form part or all of the driving circuit (804) on the substrate on which the pixel (802) is formed, as this can reduce the number of components and terminals. If part or all of the driving circuit (804) is not formed on the substrate on which the pixel (802) is formed, part or all of the driving circuit (804) can be mounted by COG or TAB (tape automated bonding).

[0429] The pixel section (802) is, X line( X is a natural number greater than or equal to 2) Y heat( Y It includes a plurality of circuits for driving display elements arranged in a manner that is a natural number greater than or equal to 2 (hereinafter, these circuits are referred to as pixel circuits (801)). The driving circuit section (804) includes driving circuits such as a circuit for supplying a signal (scan signal) to select a pixel (hereinafter, this circuit is referred to as a scan line driving circuit (804a)) and a circuit for supplying a signal (data signal) to drive a display element of a pixel (hereinafter, this circuit is referred to as a signal line driving circuit (804b)).

[0430] The scan line driving circuit (804a) includes a shift register, etc. Through the terminal portion (807), the scan line driving circuit (804a) receives a signal to drive the shift register and outputs a signal. For example, the scan line driving circuit (804a) receives a start pulse signal or a clock signal, etc., and outputs a pulse signal. The scan line driving circuit (804a) includes wires that receive a scan signal (hereinafter, these wires are scan lines (GL_1 to GL_ X It has the function of controlling the potential of the (referred to as ). In addition, it has the function of controlling the scan lines (GL_1 to GL_ X In order to control ) individually, a plurality of scan line driving circuits (804a) may be provided. Alternatively, the scan line driving circuit (804a) has the function of supplying an initialization signal. Not limited thereto, the scan line driving circuit (804a) may supply other signals.

[0431] The signal line driving circuit (804b) includes a shift register, etc. The signal line driving circuit (804b) receives not only a signal for driving the shift register through the terminal portion (807), but also a signal (video signal) that serves as the basis for the data signal. The signal line driving circuit (804b) has the function of generating a data signal based on the video signal to be recorded in the pixel circuit (801). In addition, the signal line driving circuit (804b) has the function of controlling the output of the data signal according to a pulse signal generated by an input such as a start pulse signal or a clock signal. In addition, the signal line driving circuit (804b) includes wires that receive the data signal (hereinafter, these wires are data lines (DL_1 to DL_ Y It has the function of controlling the potential of (referred to as ). Alternatively, the signal line driving circuit (804b) has the function of supplying an initialization signal. Not limited to this, the signal line driving circuit (804b) may supply other signals.

[0432] The signal line driving circuit (804b) includes, for example, a plurality of analog switches. The signal line driving circuit (804b) can output a signal obtained by time-dividing a video signal as a data signal by sequentially turning on a plurality of analog switches. The signal line driving circuit (804b) may include a shift register, etc.

[0433] A pulse signal and a data signal are input to each of the plurality of pixel circuits (801) through one of the plurality of scan lines (GL) receiving a scan signal and one of the plurality of data lines (DL) receiving a data signal. The recording and maintenance of the data signal in each of the plurality of pixel circuits (801) is controlled by a scan line driving circuit (804a). For example, m line n tenth ( m silver X It is a natural number less than or equal to, and n silver Y In the pixel circuit (801) of the natural number below), the scan line (GL_ m A pulse signal is input from the scan line driving circuit (804a) through ), and the scan line (GL_ m Depending on the potential of ), the data line (DL_ n A data signal is input from the signal line driving circuit (804b) through ).

[0434] The protection circuit (806) shown in (A) of FIG. 18 is connected, for example, to a scan line (GL) between a scan line driving circuit (804a) and a pixel circuit (801). Alternatively, the protection circuit (806) is connected to a data line (DL) between a signal line driving circuit (804b) and a pixel circuit (801). Alternatively, the protection circuit (806) may be connected to wiring between a scan line driving circuit (804a) and a terminal section (807). Alternatively, the protection circuit (806) may be connected to wiring between a signal line driving circuit (804b) and a terminal section (807). Additionally, the terminal section (807) refers to a part having terminals for inputting power, control signals, and video signals from an external circuit to a display device.

[0435] The protection circuit (806) is a circuit that electrically connects the wiring connected to the protection circuit to another wiring when a potential outside a specific range is applied to the wiring connected to the protection circuit.

[0436] As illustrated in FIG. 18 (A), by providing a protection circuit (806) to the pixel section (802) and the driving circuit section (804), the resistance of the display device to overcurrent caused by ESD (electrostatic discharge), etc., can be improved. Furthermore, the configuration of the protection circuit (806) is not limited thereto, and, for example, a configuration in which the protection circuit (806) is connected to the scan line driving circuit (804a) or a configuration in which the protection circuit (806) is connected to the signal line driving circuit (804b) may be adopted. Alternatively, the protection circuit (806) may be connected to the terminal section (807).

[0437] Although the driving circuit section (804) in FIG. 18 (A) is shown as an example including a scan line driving circuit (804a) and a signal line driving circuit (804b), the structure is not limited thereto. For example, only the scan line driving circuit (804a) may be formed, or a separately prepared substrate on which the signal line driving circuit is formed (for example, a driving circuit substrate formed of a single-crystal semiconductor film or a polycrystalline semiconductor film) may be mounted.

[0438] <Example of Pixel Circuit Structure>

[0439] Each of the plurality of pixel circuits (801) in (A) of FIG. 18 may have a structure as illustrated in (B) of FIG. 18, for example.

[0440] The pixel circuit (801) illustrated in (B) of FIG. 18 includes transistors (852 and 854), capacitive elements (862), and light-emitting elements (872).

[0441] One of the source electrode and drain electrode of the transistor (852) is a wire (data line (DL_) that receives a data signal. n The gate electrode of the transistor (852) is electrically connected to the wiring (scan line (GL_)) that receives the gate signal. m It is electrically connected to ))

[0442] The transistor (852) has the function of controlling whether to record a data signal.

[0443] One of the pair of electrodes of the capacitive element (862) is electrically connected to a wire to which potential is supplied (hereinafter referred to as the potential supply line (VL_a)), and the other is electrically connected to the other of the source electrode and drain electrode of the transistor (852).

[0444] The capacitance element (862) functions as a holding capacity for storing recorded data.

[0445] One of the source electrode and drain electrode of the transistor (854) is electrically connected to the potential supply line (VL_a). Additionally, the gate electrode of the transistor (854) is electrically connected to the other of the source electrode and drain electrode of the transistor (852).

[0446] 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 electrode and drain electrode of the transistor (854).

[0447] As the light-emitting element (872), any of the light-emitting elements described in embodiments 1 to 3 may be used.

[0448] In addition, a high power potential (VDD) is supplied to one of the potential supply lines (VL_a) and (VL_b), and a low power potential (VSS) is supplied to the other.

[0449] In a display device including the pixel circuit (801) of (B) of FIG. 18, for example, by sequentially selecting the pixel circuit (801) for each row by the scan line driving circuit (804a) of (A) of FIG. 18, the transistor (852) is turned on and a data signal is recorded.

[0450] When the transistor (852) is turned off, the pixel circuit (801) on which data is recorded remains in a maintained state. Additionally, the amount of current flowing between the source electrode and the drain electrode of the transistor (854) is controlled according to the potential of the recorded data signal. The light-emitting element (872) emits light with a brightness corresponding to the amount of current flowing. By performing this operation sequentially for each row, an image is displayed.

[0451] Alternatively, the pixel circuit may have a function to compensate for variations such as the threshold voltage of the transistor. Figures 19 (A) and (B) and Figures 20 (A) and (B) illustrate examples of pixel circuits.

[0452] The pixel circuit illustrated in (A) of FIG. 19 includes six transistors (transistors (303_1 to 303_6)), a capacitance element (304), and a light-emitting element (305). The pixel circuit illustrated in (A) of FIG. 19 is electrically connected to wiring (301_1 to 301_5) and wiring (302_1 and 302_2). Additionally, for the transistors (303_1 to 303_6), for example, p-channel transistors may be used.

[0453] The pixel circuit shown in FIG. 19 (B) has a configuration in which a transistor (303_7) is added to the pixel circuit shown in FIG. 19 (A). The pixel circuit shown in FIG. 19 (B) is electrically connected to the wiring (301_6 and 301_7). The wiring (301_5 and 301_6) may be electrically connected to each other. Additionally, for example, a p-channel transistor may be used as the transistor (303_7).

[0454] The pixel circuit shown in FIG. 20 (A) includes six transistors (transistors (308_1 to 308_6)), a capacitance element (304), and a light-emitting element (305). The pixel circuit shown in FIG. 20 (A) is electrically connected to wiring (306_1 to 306_3) and wiring (307_1 to 307_3). The wiring (306_1 and 306_3) may be electrically connected to each other. Additionally, for the transistors (308_1 to 308_6), for example, p-channel transistors may be used.

[0455] The pixel circuit illustrated in FIG. 20 (B) includes two transistors (transistors (309_1 and 309_2)), two capacitance elements (capacitance elements (304_1 and 304_2)), and a light-emitting element (305). The pixel circuit illustrated in FIG. 20 (B) is electrically connected to wiring (311_1 to 311_3) and wiring (312_1 and 312_2). By configuring the pixel circuit illustrated in FIG. 20 (B), the pixel circuit can be driven by a voltage input current driving method (also called CVCC). Additionally, for example, p-channel transistors can be used as the transistors (309_1 and 309_2).

[0456] A light-emitting element according to one embodiment of the present invention can be used in an active matrix method in which an active element is included in the pixel of a display device, or in a passive matrix method in which an active element is not included in the pixel of a display device.

[0457] In the active matrix method, various active (non-linear) devices, not just transistors, can be used as active (non-linear) devices. For example, metal insulator metal (MIM) or thin film diode (TFD) can be used. Since these devices can be formed with a small number of fabrication steps, manufacturing costs can be reduced or yield can be improved. Alternatively, because the size of these devices is small, the aperture ratio can be improved, which allows for reduced power consumption and the achievement of high brightness.

[0458] In addition to the active matrix method, a passive matrix method that does not use active components (non-linear components) may also be used. Since active components (non-linear components) are not used, the number of manufacturing steps is reduced, which can lower manufacturing costs or improve yield. Alternatively, because active components (non-linear components) are not used, the aperture ratio can be improved, which, for example, can reduce power consumption or achieve high brightness.

[0459] The structure described in this embodiment may be used in appropriate combination with the structure described in any other embodiment.

[0460] (Embodiment 6)

[0461] In this embodiment, a display device including a light-emitting element according to one embodiment of the present invention and an electronic device provided with an input device to the display device will be described with reference to FIG. 21 (A) and (B), FIG. 22 (A) to (C), FIG. 23 (A) and (B), FIG. 24 (A) and (B), and FIG. 25.

[0462] <Touch Panel Explanation 1>

[0463] In this embodiment, a touch panel (2000) including a display device and an input device is described as an example of an electronic device. Additionally, an example including a touch sensor as an input device is described.

[0464] Figures 21 (A) and (B) are perspective views of a touch panel (2000). Additionally, for simplification, Figures 21 (A) and (B) show only the main components of the touch panel (2000).

[0465] The touch panel (2000) includes a display device (2501) and a touch sensor (2595) (see (B) of FIG. 21). Additionally, the touch panel (2000) includes a substrate (2510), a substrate (2570), and a substrate (2590). Each of the substrate (2510), the substrate (2570), and the substrate (2590) is flexible. Additionally, one or all of the substrates (2510, 2570, and 2590) may not be flexible.

[0466] A display device (2501) includes a plurality of pixels on a substrate (2510) and a plurality of wires (2511) that supply signals to the pixels. The plurality of wires (2511) are led to the outer periphery of the substrate (2510), and a portion of the plurality of wires (2511) forms a terminal (2519). The terminal (2519) is electrically connected to an FPC (2509(1)). The plurality of wires (2511) can supply signals from a signal line driving circuit (2503s(1)) to the plurality of pixels.

[0467] The substrate (2590) includes a touch sensor (2595) and a plurality of wires (2598) electrically connected to the touch sensor (2595). The plurality of wires (2598) are led to the outer periphery of the substrate (2590), and a portion of the plurality of wires (2598) forms a terminal. The terminal is electrically connected to the FPC (2509(2)). Additionally, in (B) of FIG. 21, for clarity, the electrodes and wiring of the touch sensor (2595) provided on the rear side (the side facing the substrate (2510)) of the substrate (2590) are shown as solid lines.

[0468] A capacitive touch sensor can be used as the touch sensor (2595). Examples of capacitive touch sensors include surface-type capacitive touch sensors and projected-type capacitive touch sensors.

[0469] Examples of projected capacitive touch sensors include magnetic capacitive touch sensors and mutual capacitive touch sensors, which differ mainly in their driving methods. Using the mutual capacitive type is desirable because it allows for the simultaneous detection of multiple points.

[0470] Additionally, the touch sensor (2595) shown in (B) of FIG. 21 is an example using a projected capacitive touch sensor.

[0471] Additionally, as the touch sensor (2595), various sensors capable of detecting proximity or contact of a detection target, such as a finger, can be used.

[0472] The projected capacitive touch sensor (2595) includes an electrode (2591) and an electrode (2592). The electrode (2591) is electrically connected to any one of the plurality of wires (2598), and the electrode (2592) is electrically connected to any other of the plurality of wires (2598).

[0473] Each of the electrodes (2592) has a shape in which a plurality of quadrilaterals are arranged in one direction, with one corner of one quadrilateral connected to one corner of another quadrilateral, as shown in (A) and (B) of FIG. 21.

[0474] Each of the electrodes (2591) has a quadrilateral shape and is arranged in a direction that intersects with the direction in which the electrode (2592) extends.

[0475] The wiring (2594) electrically connects two electrodes (2591) located between the electrode (2592). It is desirable that the area where the electrode (2592) and the wiring (2594) intersect be as small as possible. With this structure, the area of ​​the region where no electrode is provided can be reduced, thereby reducing the variation in transmittance. As a result, the variation in brightness of light passing through the touch sensor (2595) can be reduced.

[0476] In addition, the shapes of the electrode (2591) and the electrode (2592) are not limited to this and can be any of various shapes. For example, a structure may be adopted in which a plurality of electrodes (2591) are arranged so that the gap between the electrodes (2591) is as small as possible, and an electrode (2592) is provided spaced apart from the electrode (2591) with an insulating layer interposed therebetween so that an area not overlapping with the electrode (2591) is formed. In this case, it is preferable to provide a dummy electrode that is electrically insulated from these electrodes between two adjacent electrodes (2592) so that the area of ​​the region with different transmittance can be reduced.

[0477] <Description of Display Device>

[0478] Next, the display device (2501) will be described in detail with reference to (A) of FIG. 22. (A) of FIG. 22 corresponds to a cross-sectional view taken along the dotted line X1-X2 of (B) of FIG. 21.

[0479] The display device (2501) includes a plurality of pixels arranged in a matrix. Each of the pixels includes a display element and a pixel circuit that drives the display element.

[0480] In the following description, examples are described in which a light-emitting element emitting white light is used as a display element, but the display element is not limited to such an element. For example, a light-emitting element emitting different colors of light may be included so that light of different colors can be emitted from adjacent pixels.

[0481] The substrate (2510) and the substrate (2570) have, for example, a moisture permeability of 1×10 -5 g·m -2 ·day -1 Below, preferably 1×10 -6 g·m -2 ·day -1A flexible material having the following properties may be preferably used. Alternatively, it is preferable to use materials for the substrate (2510) and the substrate (2570) that have substantially the same coefficient of thermal expansion. For example, the coefficient of linear expansion of the material is preferably 1×10⁻⁶. -3 / K or less, and more preferably 5×10 -5 / K or less, and more preferably 1×10 -5 / K is less than

[0482] Additionally, the substrate (2510) is a laminate comprising an insulating layer (2510a) that prevents the diffusion of impurities into a light-emitting element, a flexible substrate (2510b), and an adhesive layer (2510c) that bonds the insulating layer (2510a) and the flexible substrate (2510b) together. The substrate (2570) is a laminate comprising an insulating layer (2570a) that prevents the diffusion of impurities into a light-emitting element, a flexible substrate (2570b), and an adhesive layer (2570c) that bonds the insulating layer (2570a) and the flexible substrate (2570b) together.

[0483] For example, the adhesive layer (2510c) and the adhesive layer (2570c) may use polyester, polyolefin, polyamide (e.g. nylon, aramid), polyimide, polycarbonate, or acrylic resin, polyurethane, or epoxy resin. Alternatively, a material comprising a resin having siloxane bonds, such as silicone, may be used.

[0484] A sealing layer (2560) is provided between the substrate (2510) and the substrate (2570). It is preferable that the sealing layer (2560) have a refractive index higher than that of the atmosphere. As shown in (A) of FIG. 22, when light is extracted toward the sealing layer (2560), the sealing layer (2560) can also function as an optical adhesive layer.

[0485] A sealant may be formed on the outer periphery of the sealing layer (2560). By using the sealant, a light-emitting element (2550R) can be provided in the area surrounded by the substrate (2510), the substrate (2570), the sealing layer (2560), and the sealant. Additionally, an inert gas (such as nitrogen and argon) may be used instead of the sealing layer (2560). A desiccant may be provided within the inert gas to adsorb moisture, etc. A resin such as acrylic resin or epoxy resin may be used. It is preferable to use an epoxy-based resin or glass frit as the sealant. As the material used for the sealant, it is preferable to use a material that does not allow moisture and oxygen to pass through.

[0486] The display device (2501) includes a pixel (2502R). The pixel (2502R) includes a light-emitting module (2580R).

[0487] The pixel (2502R) includes a light-emitting element (2550R) and a transistor (2502t) capable of supplying power to the light-emitting element (2550R). Additionally, the transistor (2502t) functions as part of the pixel circuit. The light-emitting module (2580R) includes a light-emitting element (2550R) and a coloring layer (2567R).

[0488] The light-emitting element (2550R) includes a lower electrode, an upper electrode, and an EL layer between the lower electrode and the upper electrode. Any of the light-emitting elements described in embodiments 1 to 3 may be used as the light-emitting element (2550R).

[0489] A microcavity structure may be adopted between the lower electrode and the upper electrode to increase the intensity of light of a specific wavelength.

[0490] When the sealing layer (2560) is provided on the light extraction side, the sealing layer (2560) is in contact with the light-emitting element (2550R) and the coloring layer (2567R).

[0491] The coloring layer (2567R) is located in an area that overlaps with the light-emitting element (2550R). Accordingly, some 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 indicated by the arrow in the drawing.

[0492] The display device (2501) includes a light-blocking layer (2567BM) on the light extraction side. The light-blocking layer (2567BM) is provided to surround a colored layer (2567R).

[0493] The colored layer (2567R) is a colored layer that has the function of transmitting light in a specific wavelength range. For example, a color filter that transmits light in a red wavelength range, a color filter that transmits light in a green wavelength range, a color filter that transmits light in a blue wavelength range, or a color filter that transmits light in a yellow wavelength range may be used. Each color filter can be formed by printing, inkjet, or etching using photolithography technology, using any of various materials.

[0494] An insulating layer (2521) is provided in the display device (2501). The insulating layer (2521) covers the transistor (2502t). Additionally, the insulating layer (2521) has the function of covering irregularities caused by the pixel circuit. The insulating layer (2521) may also have the function of suppressing the diffusion of impurities. By doing so, it is possible to prevent the reliability of the transistor (2502t), etc., from being degraded due to the diffusion of impurities.

[0495] A light-emitting element (2550R) is formed on an insulating layer (2521). A partition (2528) is provided to overlap with the end of the lower electrode of the light-emitting element (2550R). Additionally, a spacer for controlling the gap between the substrate (2510) and the substrate (2570) may be formed on the partition (2528).

[0496] The scan line driving circuit (2503g(1)) includes a transistor (2503t) and a capacitive element (2503c). Additionally, the driving circuit can be formed on the same substrate in the same process as the pixel circuit.

[0497] Wiring (2511) capable of supplying signals is provided on the substrate (2510). A terminal (2519) is provided on the wiring (2511). An FPC (2509(1)) is electrically connected to the terminal (2519). The FPC (2509(1)) has the function of supplying a video signal, a clock signal, a start signal, or a reset signal. Additionally, a PWB may be provided on the FPC (2509(1)).

[0498] Additionally, any transistor of any of the various structures may be used in the display device (2501). Figure 22 (A) illustrates an example using a bottom gate transistor, but the present invention is not limited to this example, and a top gate transistor may be used in the display device (2501) as shown in Figure 22 (B).

[0499] In addition, there are no specific limitations regarding the polarity of the transistor (2502t) and the transistor (2503t). For example, n-channel and p-channel transistors may be used for these transistors, and either an n-channel transistor or a p-channel transistor may be used. In addition, there are no specific limitations regarding the crystallinity of the semiconductor film used for the transistors (2502t and 2503t). For example, an amorphous semiconductor film or a crystalline semiconductor film may be used. Examples of semiconductor materials include group 14 semiconductors (e.g., semiconductors including silicon), compound semiconductors (including oxide semiconductors), and organic semiconductors. It is preferable to use an oxide semiconductor with an energy gap of 2 eV or more, preferably 2.5 eV or more, more preferably 3 eV or more, for one or both of the transistors (2502t and 2503t), thereby reducing the off-state current of the transistor. Examples of oxide semiconductors include In-Ga oxide and In-M-Zn oxide (where M represents Al, Ga, Y, Zr, La, Ce, Sn, Hf, or Nd).

[0500] <Explanation of Touch Sensors>

[0501] Next, the touch sensor (2595) will be described in detail with reference to (C) of FIG. 22. (C) of FIG. 22 corresponds to a cross-sectional view taken along the dotted line X3-X4 of (B) of FIG. 21.

[0502] The touch sensor (2595) includes electrodes (2591) and electrodes (2592) provided in a staggered pattern on a substrate (2590), an insulating layer (2593) covering electrodes (2591) and electrodes (2592), and wiring (2594) electrically connecting adjacent electrodes (2591) to each other.

[0503] The electrodes (2591) and (2592) are formed using a transparent conductive material. As the transparent conductive material, conductive oxides such as indium oxide, indium tin oxide, indium zinc oxide, zinc oxide, or gallium-added zinc oxide may be used. Additionally, a film containing graphene may be used. A film containing graphene may be formed, for example, by reducing a film containing graphene oxide. As a reduction method, methods such as heating may be employed.

[0504] The electrodes (2591) and (2592) can be formed, for example, by depositing a transparent conductive material on a substrate (2590) by a sputtering method and then removing unnecessary parts by any of various pattern forming techniques such as photolithography.

[0505] Examples of materials for the insulating layer (2593) include resins such as acrylic resin or epoxy resin, resins having siloxane bonds, and inorganic insulating materials such as silicon oxide, silicon nitride oxide, or aluminum oxide.

[0506] An opening reaching the electrode (2591) is formed in the insulating layer (2593), and the wiring (2594) electrically connects the adjacent electrodes (2591). A transparent conductive material can increase the opening ratio of the touch panel, so it can be suitably used as the wiring (2594). In addition, since electrical resistance can be reduced, a material having higher conductivity than that of the electrodes (2591 and 2592) can be suitably used for the wiring (2594).

[0507] One electrode (2592) extends in one direction, and multiple electrodes (2592) are provided in a stripe shape. Wiring (2594) intersects the electrode (2592).

[0508] Adjacent electrodes (2591) are provided with one electrode (2592) interposed between them. Wiring (2594) electrically connects the adjacent electrodes (2591).

[0509] Additionally, the plurality of electrodes (2591) do not necessarily have to be arranged in a direction orthogonal to one electrode (2592), and may be arranged to intersect one electrode (2592) at an angle greater than 0 degrees and less than 90 degrees.

[0510] The wiring (2598) is electrically connected to one of the electrodes (2591 and 2592). A portion of the wiring (2598) functions as a terminal. For the wiring (2598), a metal material such as aluminum, gold, platinum, silver, nickel, titanium, tungsten, chromium, molybdenum, iron, cobalt, copper, or palladium, or an alloy material containing any of these metal materials may be used.

[0511] Additionally, an insulating layer covering the insulating layer (2593) and wiring (2594) may be provided to protect the touch sensor (2595).

[0512] The wiring (2598) and the FPC (2509(2)) are electrically connected by a connection layer (2599).

[0513] Any of the following can be used as the connection layer (2599): anisotropic conductive film (ACF) or anisotropic conductive paste (ACP).

[0514] <Touch Panel Explanation 2>

[0515] Next, the touch panel (2000) will be described in detail with reference to (A) of FIG. 23. (A) of FIG. 23 corresponds to a cross-sectional view taken along the dotted line X5-X6 of (A) of FIG. 21.

[0516] In the touch panel (2000) illustrated in (A) of FIG. 23, the display device (2501) described with reference to (A) of FIG. 22 and the touch sensor (2595) described with reference to (C) of FIG. 22 are joined together.

[0517] The touch panel (2000) illustrated in (A) of FIG. 23 includes an adhesive layer (2597) and an anti-reflective layer (2567p) in addition to the components described with reference to (A) and (C) of FIG. 22.

[0518] The adhesive layer (2597) is provided in contact with the wiring (2594). Additionally, the substrate (2590) is bonded to the substrate (2570) by the adhesive layer (2597), so that the touch sensor (2595) overlaps with the display device (2501). It is preferable that the adhesive layer (2597) be transparent. A thermosetting resin or a UV-curing resin may be used for the adhesive layer (2597). For example, an acrylic resin, a urethane-based resin, an epoxy-based resin, or a siloxane-based resin may be used.

[0519] The anti-reflection layer (2567p) is placed in an area that overlaps with the pixel. As the anti-reflection layer (2567p), for example, a circular polarizer can be used.

[0520] Next, a touch panel having a structure different from the structure shown in (A) of FIG. 23 will be described with reference to (B) of FIG. 23.

[0521] FIG. 23 (B) is a cross-sectional view of a touch panel (2001). The touch panel (2001) shown in FIG. 23 (B) has a different position of the touch sensor (2595) relative to the display device (2501) than the touch panel (2000) shown in FIG. 23 (A). The differences will be described in detail below, and for other similar parts, refer to the description of the touch panel (2000) described above.

[0522] The coloring layer (2567R) is placed in an area that overlaps with the light-emitting element (2550R). The light-emitting element (2550R) shown in (B) of FIG. 23 emits light toward the side where the transistor (2502t) is provided. Accordingly, some 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 indicated by the arrow in (B) of FIG. 23.

[0523] A touch sensor (2595) is provided on the substrate (2510) side of the display device (2501).

[0524] An adhesive layer (2597) is provided between the substrate (2510) and the substrate (2590) and bonds the touch sensor (2595) to the display device (2501).

[0525] As illustrated in (A) or (B) of FIG. 23, light may be emitted from the light-emitting element through one or both of the substrate (2510) and the substrate (2570).

[0526] <Explanation of how to operate the touch panel>

[0527] Next, an example of a method for driving a touch panel will be explained with reference to (A) and (B) of FIG. 24.

[0528] FIG. 24 (A) is a block diagram illustrating the structure of a mutual capacitive touch sensor. FIG. 24 (A) illustrates a pulse voltage output circuit (2601) and a current detection circuit (2602). Additionally, in FIG. 24 (A), six wires (X1 to X6) represent electrodes (2621) to which pulse voltage is applied, and six wires (Y1 to Y6) represent electrodes (2622) that detect changes in current. FIG. 24 (A) also illustrates capacitive elements (2603) formed in the overlapping regions of the electrodes (2621 and 2622). Additionally, the functions of the electrodes (2621 and 2622) are interchangeable.

[0529] The pulse voltage output circuit (2601) is a circuit for sequentially applying pulse voltages to the wires (X1 to X6). When pulse voltages are applied to the wires (X1 to X6), an electric field is generated between the electrodes (2621 and 2622) of the capacitive element (2603). When the electric field between these electrodes is shielded, a change occurs, for example, in the capacitive element (2603) (mutual capacitance). By utilizing this change, proximity or contact of a detection target can be detected.

[0530] The current detection circuit (2602) is a circuit for detecting a change in current flowing through wiring (Y1 to Y6) caused by a change in mutual capacitance in the capacitance element (2603). If there is no proximity or contact with the detection target, a change in the current value in the wiring (Y1 to Y6) is not detected, but if the mutual capacitance decreases due to proximity or contact with the detection target, a decrease in the current value is detected. Additionally, an integration circuit or the like is used for detecting the current value.

[0531] FIG. 24 (B) is a timing chart showing the input / output waveforms of the mutual capacitive touch sensor illustrated in FIG. 24 (A). In FIG. 24 (B), detection of the detection target is performed in all matrices during a 1-frame period. FIG. 24 (B) shows the period during which the detection target is not detected (non-touch) and the period during which the detection target is detected (touch). In FIG. 24 (B), the current values ​​of the detected wiring (Y1 to Y6) are shown as waveforms of voltage values.

[0532] Pulse voltages are sequentially applied to the wires (X1 to X6), and the waveforms of the wires (Y1 to Y6) change according to these pulse voltages. When there is no proximity or contact with the detection target, the waveforms of the wires (Y1 to Y6) change according to the change in voltage of the wires (X1 to X6). In the part where the detection target is in proximity or contact, the waveform of the voltage value changes because the current value decreases.

[0533] In this way, by detecting changes in mutual capacity, proximity or contact of the detection target can be detected.

[0534] <Explanation of Sensor Circuit>

[0535] FIG. 24 (A) illustrates a passive matrix type touch sensor that provides only a capacitive element (2603) at the intersection of the wires as a touch sensor, but an active matrix type touch sensor including a transistor and a capacitive element may also be used. FIG. 25 illustrates an example of a sensor circuit included in an active matrix type touch sensor.

[0536] The sensor circuit of FIG. 25 includes a capacitive element (2603) and transistors (2611, 2612, and 2613).

[0537] A signal (G2) is input to the gate of the transistor (2613). A voltage (VRES) is applied to one of the source and drain of the transistor (2613), and the gate of the transistor (2611) and one electrode of the capacitive element (2603) are electrically connected to the other of the source and drain of the transistor (2613). One of the source and drain of the transistor (2611) is electrically connected to one of the source and drain of the transistor (2612), and a voltage (VSS) is applied to the other of the source and drain of the transistor (2611). A signal (G1) is input to the gate of the transistor (2612), and a wire (ML) is electrically connected to the other of the source and drain of the transistor (2612). A voltage (VSS) is applied to the other electrode of the capacitive element (2603).

[0538] Next, the operation of the sensor circuit of FIG. 25 will be described. First, a potential that turns on the transistor (2613) is supplied as a signal (G2), so that a potential corresponding to the voltage (VRES) is applied to the node (n) connected to the gate of the transistor (2611). Then, a potential that turns off the transistor (2613) is applied as a signal (G2), so that the potential of the node (n) is maintained.

[0539] And, as the mutual capacitance of the capacitance element (2603) changes due to proximity or contact with a detection target such as a finger, the potential of the node (n) changes from VRES.

[0540] In the reading operation, a potential that turns on the transistor (2612) is supplied as a signal (G1). Depending on the potential of the node (n), the current flowing through the transistor (2611), that is, the current flowing through the wiring (ML), changes. By detecting this current, proximity or contact of the detection target can be detected.

[0541] For each of the transistors (2611, 2612, and 2613), it is preferable to use an oxide semiconductor layer as the semiconductor layer in which the channel region is formed. In particular, using such a transistor as the transistor (2613) is desirable because the potential of the node (n) can be maintained for a long time and the frequency of the operation (refresh operation) of supplying VRES to the node (n) again can be reduced.

[0542] The structure described in this embodiment may be used in appropriate combination with any of the structures described in other embodiments.

[0543] (Embodiment 7)

[0544] In this embodiment, a display module and an electronic device including a light-emitting element according to one embodiment of the present invention will be described with reference to FIGS. 26, FIGS. 27 (A) to (G), FIGS. 28 (A) to (D), and FIGS. 29 (A) and (B).

[0545] <Display Module>

[0546] In the display module (8000) of FIG. 26, between the upper cover (8001) and the lower cover (8002), a touch sensor (8004) connected to an FPC (8003), a display device (8006) connected to an FPC (8005), a frame (8009), a printed circuit board (8010), and a battery (8011) are provided.

[0547] A light-emitting element according to one embodiment of the present invention can be used, for example, in a display device (8006).

[0548] The shape and size of the upper cover (8001) and the lower cover (8002) can be appropriately changed according to the size of the touch sensor (8004) and the display device (8006).

[0549] The touch sensor (8004) may be a resistive touch sensor or a capacitive touch sensor, and may be formed in overlap with the display device (8006). The opposing substrate (sealed substrate) of the display device (8006) may have a touch sensor function. A photosensor may be provided at each pixel of the display device (8006) so that an optical touch sensor is obtained.

[0550] The frame (8009) protects the display device (8006) and also functions as an electromagnetic shield to block electromagnetic waves generated by the operation of the printed circuit board (8010). The frame (8009) may also function as a radiator plate.

[0551] The printed circuit board (8010) has a power circuit and a signal processing circuit for outputting a video signal and a clock signal. As a power source to supply power to the power circuit, an external commercial power source or a separately provided battery (8011) may be used. The battery (8011) may be omitted if a commercial power source is used.

[0552] In the display module (8000), additional components such as a polarizing plate, a phase difference plate, or a prism sheet may be provided.

[0553] Electronic devices

[0554] Figures 27 (A) through (G) illustrate an electronic device. The electronic device may include a housing (9000), a display unit (9001), a speaker (9003), an operation key (9005) (including a power switch or an operation switch), a connection terminal (9006), a sensor (9007) (a sensor having the function of measuring or detecting force, displacement, position, velocity, acceleration, angular velocity, rotational speed, distance, light, liquid, magnetism, temperature, chemical substances, sound, time, longitude, electric field, current, voltage, power, radiation, flow rate, humidity, tilt, vibration, odor, or infrared radiation), and a microphone (9008). Additionally, the sensor (9007) may have the function of measuring biometric information, such as a pulse sensor and a fingerprint sensor.

[0555] The electronic device illustrated in FIGS. 27 (A) to (G) may have various functions, such as a function to display various data (still images, video, text images, etc.) on a display unit, a touch sensor function, a function to display a calendar, date, time, etc., a function to control processing with various software (programs), a wireless communication function, a function to connect to various computer networks via a wireless communication function, a function to transmit and receive various data via a wireless communication function, and a function to read programs or data stored in a storage medium and display programs or data on a display unit. In addition, the functions that may be provided to the electronic device illustrated in FIGS. 27 (A) to (G) are not limited to those described above, and the electronic device may have various functions. Although not illustrated in FIGS. 27 (A) to (G), the electronic device may include a plurality of display units. The electronic device may have a camera, etc., and may have a function to capture still images, a function to capture video, a function to store captured images in a storage medium (an external storage medium or a storage medium included in the camera), or a function to display captured images on a display unit.

[0556] The electronic devices illustrated in (A) to (G) of FIG. 27 will be described in detail below.

[0557] FIG. 27 (A) is a perspective view of a portable information terminal (9100). The display unit (9001) of the portable information terminal (9100) is flexible. Therefore, the display unit (9001) can be provided along the curved surface of the curved housing (9000). In addition, the display unit (9001) includes a touch sensor, and operation can be performed by touching the screen with a finger or a stylus. For example, an application can be launched by touching an icon displayed on the display unit (9001).

[0558] FIG. 27 (B) is a perspective view of a portable information terminal (9101). The portable information terminal (9101) functions as one or more of, for example, a telephone, a notebook, and an information viewing system. Specifically, the portable information terminal can be used as a smartphone. Additionally, a speaker (9003), a connection terminal (9006), and a sensor (9007), which are not shown in FIG. 27 (B), can be placed in the portable information terminal (9101) as in the portable information terminal (9100) shown in FIG. 27 (A). The portable information terminal (9101) can display text and image information on its 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 the other surface of the display unit (9001). Examples of information (9051) include an indication of receiving emails, social networking service (SNS) messages, and phone calls; the subject and sender of emails and SNS messages; the date; the time; the remaining battery level; and the reception strength of the antenna. At the location where the information (9051) is displayed, an operation button (9050), etc., may be displayed instead of the information (9051).

[0559] Figure 27 (C) is a perspective view of a portable information terminal (9102). The portable information terminal (9102) has the function of displaying information on three or more surfaces of a display unit (9001). Here, information (9052), information (9053), and information (9054) are displayed on different surfaces. For example, a user of the portable information terminal (9102) can view the display (here, information (9053)) while the portable information terminal (9102) is placed in the chest pocket of their clothing. Specifically, the phone number or name of the caller of an incoming call is displayed in a position visible from above the portable information terminal (9102). Thus, the user can view the display and decide whether to answer the call without taking the portable information terminal (9102) out of the pocket.

[0560] Figure 27 (D) is a perspective view of a wristwatch-type portable information terminal (9200). The portable information terminal (9200) can execute various applications such as mobile phone, email, viewing and editing text, music playback, internet communication, and computer games. The display surface of the display unit (9001) is curved, and an image can be displayed on the curved display surface. The portable information terminal (9200) may adopt short-range wireless communication, which is a communication method according to existing communication standards. In that case, for example, mutual communication between the portable information terminal (9200) and a headset capable of wireless communication can be performed, enabling hands-free calling. The portable information terminal (9200) includes a connection terminal (9006) and can directly transmit data to another information terminal or directly receive data from another information terminal through the connector. Charging is possible through the connection terminal (9006). Additionally, charging operation may be performed by wireless power supply without using the connection terminal (9006).

[0561] Figures 27 (E), (F), and (G) are perspective views of a foldable portable information terminal (9201). Figure 27 (E) is a perspective view showing the portable information terminal (9201) in an unfolded state. Figure 27 (F) is a perspective view showing the portable information terminal (9201) in an unfolded state or in a folded state. Figure 27 (G) is a perspective view showing the portable information terminal (9201) in a folded state. The portable information terminal (9201) is very easy to carry when folded. When the portable information terminal (9201) is unfolded, the visibility of the large, seamless display area is high. The display portion (9001) of the portable information terminal (9201) is supported by three housings (9000) connected by a hinge (9055). By using a hinge (9055) to fold the portable information terminal (9201) at the connection between two housings (9000), the portable information terminal (9201) can be reversibly deformed from an 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.

[0562] Examples of electronic devices include television devices (also called televisions or television receivers), monitors such as computers, cameras such as digital cameras or digital video cameras, digital photo frames, mobile phones (also called mobile phones or mobile phone devices), goggle-type displays (head-mounted displays), portable game consoles, portable information terminals, audio playback devices, and large game machines such as pachinko machines.

[0563] Figure 28 (A) illustrates an example of a television device. In the television device (9300), a display unit (9001) is provided in the housing (9000). Here, the housing (9000) is supported by a stand (9301).

[0564] The television device (9300) illustrated in (A) of FIG. 28 may be operated by an operating switch of the housing (9000) or by a separate remote control (9311). The display unit (9001) may include a touch sensor. The television device (9300) may be operated by touching the display unit (9001) with a finger or the like. The remote control (9311) may be provided with a display unit for displaying data output from the remote control (9311). By means of the operating keys or touch panel of the remote control (9311), the channel or volume may be controlled, and the image displayed on the display unit (9001) may be controlled.

[0565] A television device (9300) is provided with a receiver or a modem, etc. General television broadcasts can be received via the receiver. By connecting the television device to a communication network via a wired or wireless connection through a modem, unidirectional (from sender to receiver) or bidirectional (between sender and receiver or between receivers) data communication can be performed.

[0566] An electronic device or lighting device according to one embodiment of the present invention has flexibility, so it can be provided along the curved surface of the inner / outer wall of a house or building, or the curved surface of the interior / exterior of a car.

[0567] Figure 28 (B) is an exterior view of a vehicle (9700). Figure 28 (C) illustrates the driver's seat of the vehicle (9700). The vehicle (9700) includes a vehicle body (9701), wheels (9702), a dashboard (9703), and lights (9704), etc. A display device or light-emitting device according to one embodiment of the present invention may be used in a display section of the vehicle (9700). For example, a display device or light-emitting device according to one embodiment of the present invention may be used in a display section (9710 to 9715) shown in Figure 28 (C).

[0568] Each of the display unit (9710) and the display unit (9711) is a display device provided on the windshield of a vehicle. A display device or light-emitting device, etc., according to one embodiment of the present invention, can be made into a see-through display device in which the opposite side is visible by using a transparent conductive material for its electrodes and wiring. Such a see-through display unit (9710 or 9711) does not obstruct the driver's field of vision while driving the vehicle (9700). Therefore, a display device or light-emitting device, etc., according to one embodiment of the present invention can be provided on the windshield of a vehicle (9700). In addition, when providing a transistor, etc., for driving the display device or light-emitting device, etc., it is preferable to use a transparent transistor, such as an organic transistor using an organic semiconductor material or a transistor using an oxide semiconductor.

[0569] The display unit (9712) is a display device provided on the pillar portion. For example, by displaying an image acquired by an imaging means provided on the vehicle body on the display unit (9712), the view obscured by the pillar portion can be supplemented. The display unit (9713) is a display device provided on the dashboard. For example, by displaying an image acquired by an imaging means provided on the vehicle body on the display unit (9713), the view obscured by the dashboard can be supplemented. That is, by displaying an image acquired by an imaging means provided on the exterior of the vehicle, blind spots can be eliminated and safety can be enhanced. By displaying an image that supplements the parts the driver cannot see, the driver can check safety more easily and comfortably.

[0570] Fig. 28 (D) illustrates the interior of a vehicle using bench seats in the driver's seat and passenger seat. The display unit (9721) is a display device provided in the door portion. For example, by displaying an image acquired by an imaging means provided in the vehicle body on the display unit (9721), the view obscured by the door can be supplemented. The display unit (9722) is a display device provided in the steering wheel. The display unit (9723) is a display device provided in the center of the seat surface of the bench seat. Additionally, by providing the display device to the seat surface or the backrest, and by using the heat generated by this display device as a heat source, the display device can be used as a seat heater.

[0571] The display unit (9714), display unit (9715), and display unit (9722) can provide various types of information, such as navigation data, speedometer, tachometer, driving distance, fuel meter, gear shift indicator, and air conditioner settings. The items or layout of the display unit can be freely changed by the user as appropriate. The above-mentioned information may also be displayed on the display units (9710 to 9713, 9721, and 9723). The display units (9710 to 9715 and 9721 to 9723) may also be used as lighting devices. The display units (9710 to 9715 and 9721 to 9723) may also be used as heating devices.

[0572] In addition, an electronic device according to one embodiment of the present invention may include a secondary battery. It is preferable that the secondary battery be chargeable by non-contact power transmission.

[0573] Examples of secondary batteries include lithium-ion secondary batteries such as lithium polymer batteries (lithium-ion polymer batteries) using gel electrolytes, lithium-ion batteries, nickel-hydrogen batteries, nickel-cadmium batteries, organic radical batteries, lead-acid batteries, air secondary batteries, nickel-zinc batteries, and silver-zinc batteries.

[0574] An electronic device according to one embodiment of the present invention may include an antenna. When a signal is received by the antenna, the electronic device may display an image or data, etc. on a display unit. If the electronic device includes a secondary battery, the antenna may be used for non-contact power transmission.

[0575] The display device (9500) illustrated in (A) and (B) of FIG. 29 includes a plurality of display panels (9501), a shaft (9511), and a bearing (9512). Each of the plurality of display panels (9501) includes a display area (9502) and a light-transmitting area (9503).

[0576] Each of the multiple display panels (9501) is flexible. Two adjacent display panels (9501) are provided to partially overlap each other. For example, the light-transmitting regions (9503) of two adjacent display panels (9501) can be overlapped. A display device having a large screen can be obtained by using multiple display panels (9501). This display device has high versatility because the display panels (9501) can be rolled up depending on the application.

[0577] In addition, in (A) and (B) of FIG. 29, the display areas (9502) of adjacent display panels (9501) are separated from each other, but this structure is not limited thereto, and for example, the display areas (9502) of adjacent display panels (9501) may be overlapped without gaps to obtain a continuous display area (9502).

[0578] Each of the electronic devices described in this embodiment includes a display unit for displaying some type of data. Additionally, a light-emitting element according to one embodiment of the present invention may be used in electronic devices that do not have a display unit. Although the electronic device described in this embodiment has been exemplified as having a structure in which the display unit is flexible and can display on a curved display surface, or a structure in which the display unit of the electronic device is foldable, the structure is not limited thereto, and a structure in which the display unit of the electronic device is not flexible and displays on a flat surface may also be adopted.

[0579] The structure described in this embodiment may be used in appropriate combination with the structure described in any other embodiment.

[0580] (Embodiment 8)

[0581] In this embodiment, a light-emitting device including a light-emitting element according to one embodiment of the present invention will be described with reference to FIGS. 30 (A) to (C) and FIGS. 31 (A) to (D).

[0582] FIG. 30 (A) is a perspective view of a light-emitting device (3000) shown in the present embodiment, and FIG. 30 (B) is a cross-sectional view taken along the dashed line EF of FIG. 30 (A). In addition, in FIG. 30 (A), some of the components are indicated by dashed lines to avoid complexity in the drawing.

[0583] The light-emitting device (3000) illustrated in (A) and (B) of FIG. 30 includes a substrate (3001), a light-emitting element (3005) on the substrate (3001), a first sealing area (3007) provided on the outer circumference of the light-emitting element (3005), and a second sealing area (3009) provided on the outer circumference of the first sealing area (3007).

[0584] Light is emitted from the light-emitting element (3005) through one or both of the substrate (3001) and the substrate (3003). Figures (A) and (B) of FIG. 30 illustrate a structure in which light is emitted downward (towards the substrate (3001)) from the light-emitting element (3005).

[0585] As illustrated in FIG. 30 (A) and (B), the light-emitting device (3000) has a double sealing structure in which a light-emitting element (3005) is surrounded by a first sealing region (3007) and a second sealing region (3009). By means of the double sealing structure, it is preferable to suppress the entry of impurities (e.g., water and oxygen, etc.) into the light-emitting element (3005) from the outside. Furthermore, it is not necessary to provide both the first sealing region (3007) and the second sealing region (3009). For example, it is acceptable to provide only the first sealing region (3007).

[0586] Additionally, in (B) of FIG. 30, each of the first sealing region (3007) and the second sealing region (3009) is provided in contact with the substrate (3001) and the substrate (3003). However, the structure is not limited to this, and, for example, one or both of the first sealing region (3007) and the second sealing region (3009) may be provided in contact with an insulating film or a conductive film provided on the substrate (3001). Alternatively, one or both of the first sealing region (3007) and the second sealing region (3009) may be provided in contact with an insulating film or a conductive film provided on the substrate (3003).

[0587] The substrate (3001) and the substrate (3003) may each have a structure similar to the substrate (200) and the substrate (220) described in the above-described embodiment. The light-emitting element (3005) may have a structure similar to any of the light-emitting elements described in the above-described embodiment.

[0588] In the first sealing area (3007), a material containing glass (e.g., glass frit and glass ribbon) may be used. In the second sealing area (3009), a material containing resin may be used. By using a material containing glass in the first sealing area (3007), productivity and sealing performance can be improved. Additionally, by using a material containing resin in the second sealing area (3009), impact resistance and heat resistance can be improved. However, the materials used in the first sealing area (3007) and the second sealing area (3009) are not limited to these, and the first sealing area (3007) may be formed using a material containing resin, and the second sealing area (3009) may be formed using a material containing glass.

[0589] The glass frit may contain, for example, magnesium oxide, calcium oxide, strontium oxide, barium oxide, cesium oxide, sodium oxide, potassium oxide, boron oxide, vanadium oxide, zinc oxide, tellurium oxide, aluminum oxide, silicon dioxide, lead oxide, tin oxide, phosphorus oxide, ruthenium oxide, rhodium oxide, iron oxide, copper oxide, manganese oxide, molybdenum oxide, niobium oxide, titanium oxide, tungsten oxide, bismuth oxide, zirconium oxide, lithium oxide, antimony oxide, lead borate glass, tin phosphate glass, vanadate glass, or borosilicate glass. It is preferable for the glass frit to contain at least one type of transition metal to absorb infrared light.

[0590] As for the glass frit described above, for example, a frit paste is applied to a substrate, and heat treatment or laser light irradiation is performed. The frit paste contains the glass frit and a resin (also called a binder) diluted with an organic solvent. Additionally, an absorbent that absorbs light of the wavelength of the laser light may be added to the glass frit. For example, it is preferable to use an Nd:YAG laser or a semiconductor laser as the laser. The shape of the laser light may be circular or square.

[0591] As a material containing the resin described above, for example, polyester, polyolefin, polyamide (e.g., nylon, aramid), polyimide, polycarbonate, acrylic resin, polyurethane, or epoxy resin may be used. Alternatively, a material containing a resin having siloxane bonds, such as silicone, may be used.

[0592] In addition, when a glass-containing material is used in one or both of the first sealing area (3007) and the second sealing area (3009), it is preferable that the glass-containing material has a thermal expansion rate close to that of the substrate (3001). By the structure described above, cracks can be suppressed in the glass-containing material or the substrate (3001) due to thermal stress.

[0593] For example, if a material containing glass is used in the first sealing area (3007) and a material containing resin is used in the second sealing area (3009), the following advantageous effects can be obtained.

[0594] The second sealing area (3009) is provided closer to the outer periphery of the light-emitting device (3000) than the first sealing area (3007). In the light-emitting device (3000), deformation caused by external force, etc. increases as it moves toward the outer periphery. Therefore, the outer periphery of the light-emitting device (3000), where greater deformation occurs, i.e., the second sealing area (3009), is sealed using a material containing resin, and the first sealing area (3007), which is provided inward from the second sealing area (3009), is sealed using a material containing glass, so that even if deformation occurs due to external force, the light-emitting device (3000) is less likely to be damaged.

[0595] Additionally, as shown in (B) of FIG. 30, the first region (3011) corresponds to an area surrounded by a substrate (3001), a substrate (3003), a first sealing region (3007), and a second sealing region (3009). The second region (3013) corresponds to an area surrounded by a substrate (3001), a substrate (3003), a light-emitting element (3005), and a first sealing region (3007).

[0596] It is preferable that the first region (3011) and the second region (3013) be filled with an inert gas, for example, a noble gas or nitrogen gas. Alternatively, it is preferable that the first region (3011) and the second region (3013) be filled with a resin, such as an acrylic resin or an epoxy resin. Furthermore, for the first region (3011) and the second region (3013), a reduced pressure state is preferable to an atmospheric pressure state.

[0597] Figure 30 (C) illustrates a modified example of the structure of Figure 30 (B). Figure 30 (C) is a cross-sectional view illustrating a modified example of a light-emitting device (3000).

[0598] Fig. 30 (C) illustrates a structure for providing a desiccant (3018) to a recess provided in a part of the substrate (3003). The other components are the same as the structure shown in Fig. 30 (B).

[0599] As a desiccant (3018), a substance that adsorbs moisture, etc. by chemical adsorption or a substance that adsorbs moisture, etc. by physical adsorption may be used. Examples of substances that can be used as a desiccant (3018) include alkali metal oxides, alkaline earth metal oxides (e.g., calcium oxide and barium oxide), sulfates, metal halides, perchlorates, zeolites, and silica gel.

[0600] Next, a modified example of the light-emitting device (3000) shown in (B) of FIG. 30 will be described with reference to (A) to (D) of FIG. 31. Additionally, (A) to (D) of FIG. 31 are cross-sectional views showing a modified example of the light-emitting device (3000) shown in (B) of FIG. 30.

[0601] In each of the light-emitting devices illustrated in (A) to (D) of FIG. 31, the second sealing region (3009) is not provided, and only the first sealing region (3007) is provided. Additionally, in each of the light-emitting devices illustrated in (A) to (D) of FIG. 31, a region (3014) is provided instead of the second region (3013) illustrated in (B) of FIG. 30.

[0602] In the region (3014), for example, polyester, polyolefin, polyamide (e.g., nylon, aramid), polyimide, polycarbonate, acrylic resin, polyurethane, or epoxy resin may be used. Alternatively, a material including a resin having siloxane bonds, such as silicone, may be used.

[0603] If the material described above is used in the region (3014), a so-called solid sealing light-emitting device can be obtained.

[0604] In the light-emitting device shown in (B) of Fig. 31, a substrate (3015) is provided on the side of the substrate (3001) of the light-emitting device shown in (A) of Fig. 31.

[0605] As shown in (B) of FIG. 31, the substrate (3015) has irregularities. By providing the substrate (3015) having irregularities to the side from which light emitted from the light-emitting element (3005) is extracted, the extraction efficiency of light from the light-emitting element (3005) can be improved. In addition, instead of the structure having irregularities shown in (B) of FIG. 31, a substrate having a function as a diffuser may be provided.

[0606] In the light-emitting device shown in (C) of FIG. 31, unlike the light-emitting device shown in (A) of FIG. 31 where light is extracted through the substrate (3001) side, light is extracted through the substrate (3003) side.

[0607] The light-emitting device shown in (C) of FIG. 31 includes a substrate (3015) on the substrate (3003) side. The other components are the same as those of the light-emitting device shown in (B) of FIG. 31.

[0608] In the light-emitting device shown in (D) of FIG. 31, the substrate (3003) and substrate (3015) included in the light-emitting device shown in (C) of FIG. 31 are not provided, and a substrate (3016) is provided.

[0609] The substrate (3016) includes a first irregularity located close to the light-emitting element (3005) and a second irregularity located away from the light-emitting element (3005). The light extraction efficiency from the light-emitting element (3005) can be further improved by the structure shown in (D) of FIG. 31.

[0610] Therefore, by using the structure described in the present embodiment, a light-emitting device can be provided in which the degradation of the light-emitting element due to impurities such as moisture and oxygen is suppressed. Alternatively, a light-emitting device with high light extraction efficiency can be obtained by the structure described in the present embodiment.

[0611] In addition, the structure described in this embodiment may be appropriately combined with the structure described in any other embodiment.

[0612] (Embodiment 9)

[0613] In this embodiment, examples of using a light-emitting element according to one form of the present invention in various lighting devices and electronic devices will be described with reference to FIGS. 32 (A) to (C) and FIG. 33.

[0614] By using a light-emitting element according to one embodiment of the present invention fabricated on a flexible substrate, an electronic device or lighting device having a light-emitting region with a curved surface can be obtained.

[0615] In addition, a light-emitting device applying one embodiment of the present invention can also be applied to lighting of automobiles, examples of which include lighting for dashboards, windshields, and ceilings.

[0616] FIG. 32 (A) is a perspective view showing one side of a multifunctional terminal (3500), and FIG. 32 (B) is a perspective view showing another side of a multifunctional terminal (3500). The housing (3502) of the multifunctional terminal (3500) is provided with a display unit (3504), a camera (3506), and a light (3508), etc. A light-emitting device according to one embodiment of the present invention can be used for the light (3508).

[0617] A light source (3508) including a light-emitting device according to one embodiment of the present invention functions as a surface light source. Therefore, unlike a point light source represented by an LED, the light source (3508) can provide light with low directionality. For example, if the light source (3508) and the camera (3506) are used in combination, the camera (3506) can take an image by using the lighting or flashing of the light source (3508). Since the light source (3508) functions as a surface light source, it is possible to take a picture that looks like it was taken under natural light.

[0618] In addition, the multifunctional terminal (3500) shown in (A) and (B) of FIG. 32 may have various functions, such as the electronic device shown in (A) to (G) of FIG. 27.

[0619] The housing (3502) may include a speaker, a sensor (a sensor having the function of measuring force, displacement, position, speed, acceleration, angular velocity, rotational speed, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, longitude, electric field, current, voltage, power, radiation, flow rate, humidity, tilt, vibration, odor, or infrared), and a microphone, etc. If a detection device including a sensor that detects tilt, such as a gyroscope or an accelerometer, is provided inside the multifunction terminal (3500), the orientation of the multifunction terminal (3500) (whether the multifunction terminal is placed horizontally to become a landscape mode or vertically to become a portrait mode) can be determined and the screen display of the display unit (3504) can be automatically switched.

[0620] The display unit (3504) may function as an image sensor. For example, personal authentication can be performed by capturing an image such as a palm or fingerprint when the display unit (3504) is touched by a palm or finger. Additionally, an image such as finger veins or palm veins can be captured by providing a backlight or a sensing light source that emits near-infrared light to the display unit (3504). Furthermore, a light-emitting device according to one embodiment of the present invention may be used in the display unit (3504).

[0621] Figure 32 (C) is a perspective view of a security light (3600). The security light (3600) includes a light source (3608) on the outside of a housing (3602), and the housing (3602) is provided with a speaker (3610), etc. A light-emitting device according to one embodiment of the present invention can be used for the light source (3608).

[0622] The security light (3600) emits light, for example, when the light (3608) is grasped or held. The housing (3602) may be provided with an electronic circuit capable of controlling the method of light emission from the security light (3600). The electronic circuit may be a circuit capable of enabling light emission once or intermittently multiple times, or a circuit capable of adjusting the amount of light emission by controlling the current value of the light emission. A circuit may also be provided that enables a loud sound alarm to be output from the speaker (3610) simultaneously with the light emission from the light (3608).

[0623] Since the security light (3600) can emit light in various directions, it can scare away the light or the light and sound. Additionally, the security light (3600) may have a photo-taking function including a camera such as a digital still camera.

[0624] FIG. 33 illustrates an example of using the light-emitting element in an indoor lighting device (8501). Since the light-emitting element can be made larger in area, a large-area lighting device may be formed. Additionally, by using a housing having a curved surface, a lighting device (8502) having a curved light-emitting area may be formed. Since the light-emitting element described in this embodiment is in the form of a thin film, it is possible to design the housing more freely. Therefore, the lighting device can be designed in various sophisticated forms. Additionally, a large lighting device (8503) may be provided on the wall of a room. A touch sensor may be provided on the lighting device (8501, 8502, and 8503) to control the power on / off of the lighting device.

[0625] Additionally, if the light-emitting element is used on the table surface side, a lighting device (8504) having the function of a table can be obtained. If the light-emitting element is used as part of other furniture, a lighting device having the function of that furniture can be obtained.

[0626] As described above, a lighting device and an electronic device can be obtained by applying a light-emitting device according to one embodiment of the present invention. Furthermore, the light-emitting device is not limited to the lighting device and electronic device described in this embodiment, but can be used in lighting devices and electronic devices in various fields.

[0627] The structure described in this embodiment may be used in appropriate combination with any structure described in other embodiments.

[0628] (Example 1)

[0629] In this embodiment, an example of fabrication of a light-emitting element (light-emitting element 1 and light-emitting element 2) according to one embodiment of the present invention is described. FIG. 34 is a schematic cross-sectional view of a light-emitting element fabricated in this embodiment. The detailed structure of the element is shown in Table 1. The structure and abbreviation of the compound used herein are shown below.

[0630] [Chemical Formula 1]

[0631]

[0632] [Table 1]

[0633]

[0634] Fabrication of light-emitting devices

[0635] <<Fabrication of Light-Emitting Element 1>>

[0636] As an electrode (101), an ITSO film was formed on a substrate (200) to a thickness of 70 nm. The electrode area of ​​the electrode (101) is 4 mm 2 It was set to (2mm×2mm).

[0637] On the electrode (101), as a hole injection layer (111), 4,4',4"-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviated: DBT3P-II) and molybdenum oxide (MoO3) were deposited by co-deposition in a weight ratio of DBT3P-II:MoO3 = 1:0.5 to a thickness of 60 nm.

[0638] On the hole injection layer (111), 4-phenyl-4'-(9-phenylfluorene-9-yl)triphenylamine (abbreviated as BPAFLP) was deposited by deposition to a thickness of 20 nm as a hole transport layer (112).

[0639] Next, as a light-emitting layer (160) on the hole transport layer (112), 2-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[ f , h ]Quinoxaline (abbreviation: 2mDBTBPDBq-II), N -(1,1'-biphenyl-4-yl)- N -[4-(9-phenyl-9 H -carbazole-3-yl)phenyl]-9,9-dimethyl-9 H Fluorene-2-amine (abbreviated: PCBBiF) and bis(2,3,5-triphenylpyrazineto)(dipivaloylmetaneto)iridium(Ш) (abbreviated: Ir(tppr)2(dpm)) are deposited by co-deposition in a weight ratio of 2mDBTBPDBq-II:PCBBiF:Ir(tppr)2(dpm) = 0.7:0.3:0.05 to form a layer (160(1)) with a thickness of 20 nm, and subsequently, 2mDBTBPDBq-II, PCBBiF, and Ir(tppr)2(dpm) are deposited by co-deposition in a weight ratio of 2mDBTBPDBq-II:PCBBiF:Ir(tppr)2(dpm) = 0.8:0.2:0.05 to form a layer (160(2)) with a thickness of 20 nm. Deposited by. Also, in the light-emitting layer (160), 2mDBTBPDBq-II corresponds to the first organic compound, PCBBiF corresponds to the second organic compound, and Ir(tppr)2(dpm) corresponds to the guest material (phosphorescent material).

[0640] As an electron transport layer (118) on the light-emitting layer (160), 2mDBTBPDBq-II was deposited by deposition as a layer (118(1)) with a thickness of 20 nm, and vasophenanthroline (abbreviated as BPhen) was deposited sequentially as a layer (118(2)) with a thickness of 15 nm. Then, on the electron transport layer (118), lithium fluoride (LiF) was deposited by deposition as an electron injection layer (119) with a thickness of 1 nm.

[0641] On the electron injection layer (119), aluminum (Al) was deposited as an electrode (102) to a thickness of 200 nm.

[0642] Next, the light-emitting element 1 was sealed by fixing the substrate (220) to the substrate (200) on which the organic material was deposited using a sealant for an organic EL device within a glove box containing a nitrogen atmosphere. Specifically, the sealant was applied to the substrate (220), and the substrate (220) was bonded to the substrate (200) on which the organic material was deposited. Then, ultraviolet light with a wavelength of 365 nm was applied at 6 J / cm² 2 After irradiating, heat treatment was performed at 80°C for 1 hour. Through the above process, a light-emitting element 1 was obtained.

[0643] <<Fabrication of Light-Emitting Element 2>>

[0644] A light-emitting element 2 was fabricated in a manner similar to light-emitting element 1, except for the step of forming an electron transport layer (118) with a material different from that of light-emitting element 1.

[0645] Specifically, as an electron transport layer (118) of the light-emitting element 2, 2mDBTBPDBq-II was deposited by deposition as a layer (118(1)) with a thickness of 20 nm, and 2,9-bis(naphthalene-2-yl)-4,7-diphenyl-1,10-phenanthroline (abbreviated as NBPhen) was sequentially deposited as a layer (118(2)) with a thickness of 15 nm.

[0646] <Emission Spectrum of Host Material>

[0647] In the light-emitting device, 2mDBTBPDBq-II and PCBBiF were used as host materials (first organic compound and second organic compound). Figure 35 shows the measurement results of the emission spectra of a thin film of 2mDBTBPDBq-II alone, a thin film of PCBBiF alone, and a mixed thin film of 2mDBTBPDBq-II and PCBBiF.

[0648] To measure the emission spectrum, thin film samples were formed on a quartz substrate by vacuum deposition. The emission spectrum was measured at room temperature (in an atmosphere maintained at 23°C) using a PL-EL measuring device (manufactured by Hamamatsu Photonics KK). The thickness of each thin film was 50 nm. The mixing ratio of the two types of compounds (first organic compound: second organic compound) in the mixed thin film was 0.8:0.2.

[0649] As shown in Fig. 35, the emission spectrum of the mixed thin film of 2mDBTBPDBq-II and PCBBiF differs from the emission spectra of 2mDBTBPDBq-II alone and PCBBiF alone. As will be explained later, the LUMO level of 2mDBTBPDBq-II is lower than the LUMO level of PCBBiF, and the HOMO level of PCBBiF is higher than the HOMO level of 2mDBTBPDBq-II. The mixed thin film of 2mDBTBPDBq-II and PCBBiF emits light having energy equivalent to the energy difference between the LUMO level of 2mDBTBPDBq-II and the HOMO level of PCBBiF. Furthermore, the emission from the mixed thin film has a longer wavelength (lower energy) than the emission from 2mDBTBPDBq-II alone and PCBBiF alone. For this reason, the luminescence from the mixed thin film can be attributed to the excited complex formed by these compounds. That is, 2mDBTBPDBq-II and PCBBiF are organic compounds that form an excited complex when combined with each other. By using 2mDBTBPDBq-II and PCBBiF as host materials, a light-emitting device using ExTET can be fabricated.

[0650] Absorption Spectrum and Emission Spectrum of Guest Material

[0651] Figure 36 shows the measurement results of the absorption spectrum and emission spectrum of Ir(tppr)2(dpm), a guest material of the light-emitting device.

[0652] To measure the absorption spectrum, a dichloromethane solution containing a guest material (Ir(tppr)2(dpm)) was prepared, and a quartz cell was used. The absorption spectrum was measured using a UV-visible spectrophotometer (V-550, manufactured by JASCO Corporation). The absorption spectrum of the quartz cell was then subtracted from the measured absorption spectrum. Additionally, the emission spectrum of the solution was measured using a PL-EL measuring device (manufactured by Hamamatsu Photonics KK). The measurements were performed at room temperature (in an atmosphere maintained at 23°C).

[0653] As shown in Fig. 36, the lowest energy side (longest wavelength side) of the absorption spectrum of Ir(tppr)2(dpm) is around 580 nm. The absorption band was calculated from the absorption spectrum data, and the transition energy was estimated assuming a direct transition, yielding the following results: the absorption band of Ir(tppr)2(dpm) is 596 nm, and the transition energy of Ir(tppr)2(dpm) is 2.08 eV.

[0654] This result indicates that the absorption band on the lowest energy side (longest wavelength side) of the absorption spectrum of Ir(tppr)2(dpm) has a region that overlaps with the emission of the excited complex formed by 2mDBTBPDBq-II and PCBBiF (emission spectrum shown in Fig. 35). Therefore, in light-emitting device 1 and light-emitting device 2, which respectively include 2mDBTBPDBq-II and PCBBiF as host materials, the excitation energy can be effectively transferred to the guest material.

[0655] As described above, light-emitting element 1 and light-emitting element 2 are light-emitting elements that each form an excited complex by combining host materials of 2mDBTBPDBq-II (first organic compound) and PCBBiF (second organic compound).

[0656] Phosphorescent emission spectrum of host material

[0657] Figure 37 shows the measurement results of the triplet excitation energy levels of the first organic compound (2mDBTBPDBq-II) and the second organic compound (PCBBiF) used as host materials.

[0658] To measure the triplet excitation energy level, phosphorescence from a thin film of the compound was measured. This measurement was performed at a measurement temperature of 10 K using a PL microscope LabRAM HR-PL (manufactured by HORIBA, Ltd.), a He-Cd laser (325 nm) as the excitation light, and a CCD detector. The triplet excitation energy level was calculated from the peak at the shortest wavelength side of the phosphorescence spectrum obtained from the above measurement.

[0659] As shown in Fig. 37, the peak wavelengths at the shortest wavelength side of the phosphorescent emission spectra of the first organic compound (2mDBTBPDBq-II) and the second organic compound (PCBBiF) were 515 nm and 509 nm, respectively. Accordingly, the triplet excitation energy levels of the first organic compound and the second organic compound derived from this result were 2.41 eV and 2.44 eV, respectively.

[0660] The peak wavelength on the shortest wavelength side of the phosphorescent emission spectra of 2mDBTBPDBq-II and PCBBiF is shorter than the peak wavelength on the shortest wavelength side of the emission spectrum of the excited complex formed by 2mDBTBPDBq-II and PCBBiF, as shown in FIG. 35. The excited complex is characterized by a small energy difference between the singlet excitation energy level and the triplet excitation energy level; thus, the triplet excitation energy level of the excited complex can be derived from the peak wavelength on the shortest wavelength side of the emission spectrum. Accordingly, the triplet excitation energy levels of the first organic compound (2mDBTBPDBq-II) and the second organic compound (PCBBiF) are higher than the triplet excitation energy level of the excited complex.

[0661] In addition, the triplet excitation energy levels of 2mDBTBPDBq-II and PCBBiF are higher than the transition energy of 2.08 eV of the ...

Claims

Claim 1 As a light-emitting device, the light-emitting layer has a metal complex having a platinum group element, a first organic compound, and a second organic compound, wherein the LUMO level of the first organic compound is lower than the LUMO level of the second organic compound, the HOMO level of the first organic compound is lower than the HOMO level of the second organic compound, the LUMO level of the metal complex having a platinum group element is lower than the LUMO level of the first organic compound, the energy difference between the LUMO level and the HOMO level of the metal complex having a platinum group element is greater than the energy difference between the LUMO level of the first organic compound and the HOMO level of the second organic compound, the first organic compound and the second organic compound are a combination forming an excited complex, the first organic compound is a heterocyclic compound having any one of a triazine backbone, a pyrimidine backbone, a pyridazine backbone, and a pyridine backbone, and the second organic compound is A light-emitting device that is a compound having any one of a pyrrole backbone, a furan backbone, a thiophene backbone, and an aromatic amine backbone. Claim 2 As a light-emitting element, the light-emitting layer has a metal complex having a platinum group element, a first organic compound, and a second organic compound; the LUMO level of the first organic compound is lower than the LUMO level of the second organic compound, the HOMO level of the first organic compound is lower than the HOMO level of the second organic compound, the LUMO level of the metal complex having a platinum group element is lower than the LUMO level of the first organic compound, the energy difference between the LUMO level and the HOMO level of the metal complex having a platinum group element is greater than the energy difference between the LUMO level of the first organic compound and the HOMO level of the second organic compound, the first organic compound and the second organic compound are a combination forming an excited complex, and the first organic compound is an oxadiazole derivative, a triazole derivative, a benzimidazole derivative, a phenanthroline derivative, a pyridine derivative, a bipyridine derivative, A light-emitting device, wherein the second organic compound is a compound having a pyrrole backbone, a furan backbone, a thiophene backbone, and an aromatic amine backbone, and is either a pyrimidine derivative or a triazine derivative. Claim 3 As a light-emitting element, the light-emitting layer has a metal complex having a platinum group element, a first organic compound, and a second organic compound; the LUMO level of the first organic compound is lower than the LUMO level of the second organic compound, the HOMO level of the first organic compound is lower than the HOMO level of the second organic compound, the LUMO level of the metal complex having a platinum group element is lower than the LUMO level of the first organic compound, the energy difference between the LUMO level and the HOMO level of the metal complex having a platinum group element is greater than the energy difference between the LUMO level of the first organic compound and the HOMO level of the second organic compound, the first organic compound and the second organic compound are a combination forming an excited complex, and the energy difference between the LUMO level of the metal complex having a platinum group element and the HOMO level of the second organic compound in the absorption spectrum of the metal complex having a platinum group element A light-emitting device having a transition energy greater than that produced from an absorption unit, wherein the first organic compound is a heterocyclic compound having any one of a triazine backbone, a pyrimidine backbone, a pyridazine backbone, and a pyridine backbone, and the second organic compound is a compound having any one of a pyrrole backbone, a furan backbone, a thiophene backbone, and an aromatic amine backbone. Claim 4 As a light-emitting element, the light-emitting layer has a metal complex having a platinum group element, a first organic compound, and a second organic compound; the LUMO level of the first organic compound is lower than the LUMO level of the second organic compound, the HOMO level of the first organic compound is lower than the HOMO level of the second organic compound, the LUMO level of the metal complex having a platinum group element is lower than the LUMO level of the first organic compound, the energy difference between the LUMO level and the HOMO level of the metal complex having a platinum group element is greater than the energy difference between the LUMO level of the first organic compound and the HOMO level of the second organic compound, the first organic compound and the second organic compound are a combination forming an excited complex, and the energy difference between the LUMO level of the metal complex having a platinum group element and the HOMO level of the second organic compound in the absorption spectrum of the metal complex having a platinum group element A light-emitting device having a transition energy greater than that produced from an absorption unit, wherein the first organic compound is any one of an oxadiazole derivative, a triazole derivative, a benzimidazole derivative, a phenanthroline derivative, a pyridine derivative, a bipyridine derivative, a pyrimidine derivative, and a triazine derivative, and the second organic compound is a compound having any one of a pyrrole backbone, a furan backbone, a thiophene backbone, and an aromatic amine backbone. Claim 5 As a light-emitting element, the light-emitting layer comprises a metal complex having a platinum group element, a first organic compound, and a second organic compound; the LUMO level of the first organic compound is lower than the LUMO level of the second organic compound, the HOMO level of the first organic compound is lower than the HOMO level of the second organic compound, the LUMO level of the metal complex having a platinum group element is lower than the LUMO level of the first organic compound, the energy difference between the LUMO level and the HOMO level of the metal complex having a platinum group element is greater than the energy difference between the LUMO level of the first organic compound and the HOMO level of the second organic compound, the first organic compound and the second organic compound are a combination forming an excited complex, and the energy difference between the LUMO level of the metal complex having a platinum group element and the HOMO level of the second organic compound is the energy of the light emission exhibited by the metal complex having a platinum group element. A light-emitting device, wherein the first organic compound is a heterocyclic compound having any one of a triazine backbone, a pyrimidine backbone, a pyridazine backbone, and a pyridine backbone, and the second organic compound is a compound having any one of a pyrrole backbone, a furan backbone, a thiophene backbone, and an aromatic amine backbone. Claim 6 As a light-emitting element, the light-emitting layer comprises a metal complex having a platinum group element, a first organic compound, and a second organic compound; the LUMO level of the first organic compound is lower than the LUMO level of the second organic compound, the HOMO level of the first organic compound is lower than the HOMO level of the second organic compound, the LUMO level of the metal complex having a platinum group element is lower than the LUMO level of the first organic compound, the energy difference between the LUMO level and the HOMO level of the metal complex having a platinum group element is greater than the energy difference between the LUMO level of the first organic compound and the HOMO level of the second organic compound, the first organic compound and the second organic compound are a combination forming an excited complex, and the energy difference between the LUMO level of the metal complex having a platinum group element and the HOMO level of the second organic compound is the energy of the light emission exhibited by the metal complex having a platinum group element. A light-emitting device, wherein the first organic compound is any one of an oxadiazole derivative, a triazole derivative, a benzimidazole derivative, a phenanthroline derivative, a pyridine derivative, a bipyridine derivative, a pyrimidine derivative, and a triazine derivative, and the second organic compound is a compound having any one of a pyrrole backbone, a furan backbone, a thiophene backbone, and an aromatic amine backbone. Claim 7 A light-emitting device according to any one of claims 1 to 6, wherein the energy difference between the LUMO level and the HOMO level of the metal complex having the platinum group element is at least 0.4 eV greater than the transition energy calculated from the absorption terminal in the absorption spectrum of the metal complex having the platinum group element. Claim 8 A light-emitting device according to any one of claims 1 to 6, wherein the energy difference between the LUMO level and the HOMO level of the metal complex having the platinum group element is at least 0.4 eV greater than the energy of the luminescence exhibited by the metal complex having the platinum group element. Claim 9 A light-emitting device according to any one of claims 1 to 6, wherein the light emission spectrum exhibited by the excited complex has a region that overlaps with the absorption band on the longest wavelength side of the absorption spectrum of the metal complex having the platinum group element. Claim 10 A light-emitting element according to any one of claims 1 to 6, wherein the metal complex having the platinum group element has ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), or platinum (Pt). Claim 11 A display device having a light-emitting element described in any one of claims 1 to 6, a color filter, an actual, or a transistor. Claim 12 An electronic device having a display device as described in claim 11 and a housing or touch sensor. Claim 13 A lighting device having a light-emitting element described in any one of claims 1 to 6, and a housing or a touch sensor.

Images