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

Abstract

To provide a light-emitting element with high light extraction efficiency.SOLUTION: A light-emitting element has a light-emitting layer between a pair of electrodes. A low refractive index layer containing an organic compound and an inorganic compound is provided between the light-emitting layer and an anode or between the light-emitting layer and a cathode. A low refractive index layer has a refractive index of 1.80 or less at a wavelength of light extracted from the light-emitting layer.SELECTED DRAWING: Figure 35

Description

Technical Field

[0001] One aspect of the present invention relates to a novel light-emitting element. Alternatively, it relates to a light-emitting element having a low refractive index layer between a pair of electrodes. Alternatively, it relates to a light-emitting device, an electronic device, and a lighting device having the light-emitting element.

[0002] Note that one aspect of the present invention is not limited to the above technical field. One aspect of the present invention relates to an article, a method, or a manufacturing method. Alternatively, the present invention relates to a process, a machine, a manufacture, or a composition of matter. In particular, one aspect of the present invention relates to a semiconductor device, a light-emitting device, a display device, a lighting device, a light-emitting element, and a method for manufacturing them.

Background Art

[0003] The practical application of a light-emitting element (organic EL element) using electroluminescence (EL) using an organic compound has been progressing. The basic configuration of the light-emitting element is such that a semiconductor layer containing an organic compound is sandwiched between a pair of electrodes.

[0004] Such a light-emitting element has various advantages such as being lightweight, flexible, highly designable, and capable of a coating process, and thus research and development are being actively promoted. In particular, since the light-emitting element is self-luminous, when used as a pixel of a display, it has advantages such as high visibility and no need for a backlight, and is suitable as a flat panel display element.

[0005] In such a light-emitting element, an organic semiconductor layer is mainly formed by thinning an organic compound, and since the organic compound and the layer structure have a great influence on the light-emitting element, the selection of the organic compound and the layer structure is important. Furthermore, in a light-emitting element, a structure with high light extraction efficiency is important.

[0006] Various methods have been proposed to improve the light extraction efficiency of organic EL elements. For example, in Patent Document 1, the light extraction efficiency is improved by creating an uneven shape on part of the electrode or the EL layer. Also, in Patent Document 2, the light extraction efficiency is improved by providing a low refractive index layer and a high refractive index layer outside the electrode.

[0007] Also, one of the problems that often occur in organic EL elements is the low light extraction efficiency. In particular, the attenuation due to reflection caused by the difference in refractive index is a major factor in reducing the efficiency of the element. To reduce this influence, a configuration has been proposed in which a layer made of a low refractive index material is formed inside the EL layer (see, for example, Non-Patent Document 1).

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] In a light-emitting element, as a method for improving the light extraction efficiency as described above, a method of providing a low refractive index layer in the light-emitting element is known. However, many of the materials that can be used for the low refractive index layer have low carrier transport properties. When a low refractive index layer is provided between a pair of electrodes, there is a problem that the carrier transport property of the light-emitting element is inhibited. Also, when a low refractive index layer is provided outside the electrode, there is a problem that the manufacturing process becomes complicated. Therefore, there is a need to develop a layer structure that can be easily manufactured and can improve the light extraction efficiency.

[0010] In view of the above problems, an aspect of the present invention aims to provide a light-emitting element with high light extraction efficiency. Or, in an aspect of the present invention, it is an object to provide a light-emitting element including a low refractive index layer. Or, in an aspect of the present invention, it is an object to provide a light-emitting element with a low driving voltage. Or, in an aspect of the present invention, it is an object to provide a light-emitting element with reduced power consumption. Or, in an aspect of the present invention, it is an object to provide a highly reliable light-emitting element. Or, in an aspect of the present invention, it is an object to provide a light-emitting element with high luminous efficiency. Or, in an aspect of the present invention, it is an object to provide a novel light-emitting element. Or, an aspect of the present invention aims to provide a novel electronic device. Or, an aspect of the present invention aims to provide a novel lighting device.

[0011] Note that the description of the above problems does not prevent the existence of other problems. Note that an aspect of the present invention does not necessarily need to solve all of these problems. Other problems than those described above will be obvious from the description in the specification and the like, and it is possible to extract other problems than those described above from the description in the specification and the like.

Means for Solving the Problems

[0012] An aspect of the present invention is a light-emitting element having a first electrode, a second electrode, a light-emitting layer, and an organic layer, having a light-emitting layer and a first layer between the first electrode and the second electrode, the second electrode being provided between the first electrode and the organic layer, the organic layer being provided in contact with the second electrode, the first electrode having a function of reflecting light, the second electrode having a function of reflecting light and a function of transmitting light, light emission with a peak wavelength λ being obtained from the light-emitting layer, the first layer being provided in a region where the optical distance from the interface of the light-emitting layer on the first electrode side is within λ / 2 or in a region where the optical distance from the interface of the light-emitting layer on the second electrode side is within λ / 2, and the refractive index of the first layer being 1.80 or less.

[0013] Another aspect of the present invention is a light-emitting element having a first electrode, a second electrode, a light-emitting layer, and an organic layer. The light-emitting layer and a first layer are provided between the first electrode and the second electrode. The second electrode is provided between the first electrode and the organic layer. The organic layer is provided in contact with the second electrode. The first electrode has a function of reflecting light. The second electrode has a function of reflecting light and a function of transmitting light. Light emission with a peak wavelength λ is obtained from the light-emitting layer. The first layer is provided in a region where the optical distance from the interface of the light-emitting layer on the first electrode side is within λ / 2 or in a region where the optical distance from the interface of the light-emitting layer on the second electrode side is within λ / 2. The first layer contains a first organic compound, and the refractive index of the first organic compound is 1.80 or less.

[0014] Another aspect of the present invention is a light-emitting element having a first electrode, a second electrode, a third electrode, a light-emitting layer, and an organic layer. The light-emitting layer and a first layer are provided between the first electrode and the second electrode. The second electrode is provided between the first electrode and the organic layer. The organic layer is provided in contact with the second electrode. The first electrode and the third electrode are in contact with each other. The first electrode has a function of reflecting light. The second electrode has a function of reflecting light and a function of transmitting light. Light emission with a peak wavelength λ is obtained from the light-emitting layer. The first layer is provided in a region where the optical distance from the interface of the light-emitting layer on the first electrode side is within λ / 2 or in a region where the optical distance from the interface of the light-emitting layer on the second electrode side is within λ / 2. The optical distance from either the interface of the light-emitting layer on the first electrode side or the interface of the light-emitting layer on the second electrode side to the third electrode is in the range of λ / 4 ± 50 nm. The optical distance from either the interface of the light-emitting layer on the first electrode side or the interface of the light-emitting layer on the second electrode side to the first electrode is in the range of 3λ / 4 ± 50 nm. The refractive index of the first layer is 1.80 or less.

[0015] Another aspect of the present invention is a light-emitting device having a first electrode, a second electrode, a third electrode, a light-emitting layer, and an organic layer. The light-emitting layer and a first layer are provided between the first electrode and the second electrode. The second electrode is provided between the first electrode and the organic layer. The organic layer is provided in contact with the second electrode. The first electrode and the third electrode are in contact with each other. The first electrode has a function of reflecting light. The second electrode has a function of reflecting light and a function of transmitting light. Light emission with a peak wavelength λ is obtained from the light-emitting layer. The first layer is provided in a region where the optical distance from the interface of the light-emitting layer on the first electrode side is within λ / 2 or in a region where the optical distance from the interface of the light-emitting layer on the second electrode side is within λ / 2. The optical distance from either the interface of the light-emitting layer on the first electrode side or the interface of the light-emitting layer on the second electrode side to the third electrode is in the range of λ / 4 ± 50 nm. The optical distance from either the interface of the light-emitting layer on the first electrode side or the interface of the light-emitting layer on the second electrode side to the first electrode is in the range of 3λ / 4 ± 50 nm. The first layer has a first organic compound, and the refractive index of the first organic compound is 1.80 or less.

[0016] In the above configuration, it is preferable that the film thickness of the first layer is 5 nm or more.

[0017] Also, in the above configuration, it is preferable that the first electrode is an anode and the second electrode is a cathode.

[0018] Also, in the above configuration, it is preferable that the refractive index of the first layer is lower than the refractive index of the third electrode.

[0019] Also, in the above configuration, it is preferable that the third electrode has light transmissibility.

[0020] Also, in the above configuration, it is preferable that the first organic compound has electron-donating properties.

[0021] Also, in the above configuration, it is preferable that the refractive index of the first layer is lower than the refractive index of the light-emitting layer.

[0022] Another aspect of the present invention is a light-emitting device having an anode, a cathode, and an EL layer, wherein the EL layer is located between the anode and the cathode, the EL layer has an organic compound and an inorganic compound, and at least a part of the inorganic compound exists in a microcrystalline state.

[0023] Alternatively, in another aspect of the present invention, in the above configuration, the EL layer has a light-emitting layer, and the inorganic compound existing in a microcrystalline state is a light-emitting device existing between the light-emitting layer and the cathode.

[0024] Alternatively, in another aspect of the present invention, in the above configuration, the EL layer has an electron transport layer, the electron transport layer is located between the light-emitting layer and the cathode, and the inorganic compound existing in a microcrystalline state is a light-emitting device existing in the electron transport layer.

[0025] Alternatively, in another aspect of the present invention, in the above configuration, the compound existing in a microcrystalline state is a light-emitting device in contact with the cathode.

[0026] Alternatively, in another aspect of the present invention, there is provided a light-emitting device having an anode, a cathode, and an EL layer, wherein the EL layer is located between the anode and the cathode, the EL layer has a light-emitting layer, and the EL layer has a low refractive index layer containing an organic compound and an inorganic compound between the light-emitting layer and the cathode.

[0027] Alternatively, in another aspect of the present invention, in the above configuration, the inorganic compound is a fluoride of an alkali metal or a fluoride of an alkaline earth metal.

[0028] Alternatively, in another aspect of the present invention, in the above configuration, the refractive index of the low refractive index layer is 1.70 or less at the wavelength of the light extracted from the light-emitting layer.

[0029] Alternatively, in another aspect of the present invention, in the above configuration, the EL layer further has an electron transport layer, the electron transport layer is located between the light-emitting layer and the cathode, and at least a part of the low refractive index layer serves as the electron transport layer.

[0030] Alternatively, another aspect of the present invention is a light-emitting device in the above configuration, wherein the low refractive index layer is an electron transport layer.

[0031] Alternatively, another aspect of the present invention is a light-emitting device in the above configuration, wherein the EL layer has a second low refractive index layer between the light-emitting layer and the anode.

[0032] Alternatively, another aspect of the present invention is a light-emitting device in the above configuration, wherein the EL layer has a low refractive index layer containing a first substance, a second substance, and a third substance between the light-emitting layer and the anode, the first substance is a compound containing fluorine, the second substance is an organic compound having hole-transporting properties, and the third substance is a substance that exhibits electron-accepting properties with respect to the second substance.

[0033] Alternatively, another aspect of the present invention is a light-emitting device in the above configuration, wherein the first substance is a fluoride of an alkali metal, a fluoride of an alkaline earth metal, or a fluorinated alkyl.

[0034] Alternatively, another aspect of the present invention is a light-emitting device in the above configuration, wherein the first substance is a fluoride of an alkaline earth metal.

[0035] Alternatively, another aspect of the present invention is a light-emitting device in the above configuration, wherein the first substance is any one of lithium fluoride, calcium fluoride, and magnesium fluoride.

[0036] Alternatively, another aspect of the present invention is a light-emitting device in the above configuration, wherein the third substance is any one or more of a transition metal oxide, an oxide of a metal belonging to Groups 4 to 8 in the periodic table, and an organic compound having an electron-withdrawing group.

[0037] Alternatively, in another aspect of the present invention, in the above configuration, the third substance is one or more selected from titanium oxide, vanadium oxide, tantalum oxide, molybdenum oxide, tungsten oxide, rhenium oxide, ruthenium oxide, chromium oxide, zirconium oxide, hafnium oxide, silver oxide, 7,7,8,8 - tetracyano - 2,3,5,6 - tetrafluoroquinodimethane, chloranil, 2,3,6,7,10,11 - hexacyano - 1,4,5,8,9,12 - hexaazatriphenylene, 1,3,4,5,7,8 - hexafluorotetracyano - naphthoquinodimethane, α,α’,α’’ - 1,2,3 - cyclopropanetriylidene tris[4 - cyano - 2,3,5,6 - tetrafluorobenzeneacetonitrile], and the light - emitting element is such.

[0038] Alternatively, in another aspect of the present invention, in the above configuration, the third substance is molybdenum oxide, and the light - emitting element is such.

[0039] Alternatively, in another aspect of the present invention, in the above configuration, the second substance is a π - electron - excessive heteroaromatic compound or an aromatic amine compound, and the light - emitting element is such.

[0040] Alternatively, in another aspect of the present invention, in the above configuration, the HOMO level of the second substance is - 5.7 eV or more, and the light - emitting element is such.

[0041] Alternatively, in another aspect of the present invention, in the above configuration, the HOMO level of the second substance is - 5.5 eV or more, and the light - emitting element is such.

[0042] Alternatively, in another aspect of the present invention, in the above configuration, the refractive index of the low - refractive - index layer is 1.70 or less, and the light - emitting element is such.

[0043] Alternatively, in another aspect of the present invention, in the above configuration, the EL layer has a hole - transporting layer between the light - emitting layer and the low - refractive - index layer, and the hole - transporting layer contains an organic compound having hole - transporting properties, and the light - emitting element is such.

[0044] Alternatively, in another aspect of the present invention, in the above configuration, the EL layer has a hole injection layer in contact with the anode, the hole injection layer includes a first hole injection layer and a second hole injection layer, the first hole injection layer is located between the second hole injection layer and the anode, the first hole injection layer is a low refractive index layer, the second hole injection layer has a fourth substance and a fifth substance, the fourth substance is an organic compound having hole transporting properties, and the fifth substance is a substance showing acceptor properties to the fourth substance, which is a light-emitting element.

[0045] Alternatively, in another aspect of the present invention, in the above configuration, it is a light-emitting element in which the fifth substance and the third substance are the same.

[0046] Alternatively, in another aspect of the present invention, it has an anode, a cathode, and an EL layer, the EL layer is located between the anode and the cathode, the EL layer has an organic compound and an inorganic compound, the inorganic compound is a fluoride of an alkali metal or a fluoride of an alkaline earth metal, and when the EL layer is analyzed by energy-dispersive X-ray analysis, it is a light-emitting element in which there is a portion where the number of fluorine atoms is larger than the number of nitrogen atoms.

[0047] Alternatively, in another aspect of the present invention, in the above configuration, it is a light-emitting element in which the number of fluorine atoms is three times or more the number of nitrogen atoms.

[0048] Alternatively, in another aspect of the present invention, in the above configuration, the EL layer has a light-emitting layer, and a portion where the number of fluorine atoms is larger than the number of nitrogen atoms exists between the light-emitting layer and the cathode, which is a light-emitting element.

[0049] Alternatively, in another aspect of the present invention, in the above configuration, the EL layer further has an electron transport layer, the electron transport layer is located between the light-emitting layer and the cathode, and a portion where the number of fluorine atoms is larger than the number of nitrogen atoms exists in the electron transport layer, which is a light-emitting element.

[0050] Alternatively, another aspect of the present invention is a light-emitting device having an anode, a cathode, and an EL layer. The EL layer is located between the anode and the cathode. The EL layer has a light-emitting layer and an electron transport layer. The electron transport layer is located between the light-emitting layer and the cathode. The electron transport layer contains an organic compound and an inorganic compound. The inorganic compound is a fluoride of an alkali metal or a fluoride of an alkaline earth metal. The concentration of the inorganic compound in the electron transport layer is 50 vol% or more.

[0051] Alternatively, another aspect of the present invention is a light-emitting device in the above configuration, wherein the concentration of the inorganic compound in the electron transport layer is 50 vol% or more and less than 95 vol%.

[0052] Alternatively, another aspect of the present invention is a light-emitting device in the above configuration, wherein the organic compound is an organic compound having electron transporting properties.

[0053] Alternatively, another aspect of the present invention is a light-emitting device in the above configuration, wherein the organic compound is a π-electron deficient heteroaromatic.

[0054] Alternatively, another aspect of the present invention is a light-emitting device in the above configuration, wherein the organic compound is an organic compound having a bipyridine skeleton.

[0055] Alternatively, another aspect of the present invention is a light-emitting device in the above configuration, wherein the organic compound is an organic compound having a phenanthroline skeleton.

[0056] Alternatively, another aspect of the present invention is a light-emitting device in the above configuration, wherein the organic compound is 2,9-bis(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline.

[0057] Alternatively, another aspect of the present invention is a light-emitting device in the above configuration, wherein the inorganic compound is any one of lithium fluoride, calcium fluoride, and magnesium fluoride.

[0058] Alternatively, another aspect of the present invention is an electronic device including the above light-emitting element, a sensor, an operation button, a speaker, or a microphone.

[0059] Alternatively, another aspect of the present invention is a light-emitting device including the above light-emitting element, a transistor, or a substrate.

[0060] Alternatively, another aspect of the present invention is a lighting device including the above light-emitting element and a housing.

[0061] Alternatively, another aspect of the present invention is a material including a crystallized alkali metal salt or a crystallized alkaline earth metal salt and an organic compound.

[0062] Alternatively, another aspect of the present invention is a material including a crystallized alkali metal fluoride or a crystallized alkaline earth metal fluoride and an organic compound.

[0063] Alternatively, another aspect of the present invention is a material in which the organic compound in the material having the above configuration is an organic compound having a bipyridine skeleton.

[0064] Alternatively, another aspect of the present invention is a material in which the organic compound in the material having the above configuration is an organic compound having a phenanthroline skeleton.

[0065] Alternatively, another aspect of the present invention is a material in which the organic compound in the material having the above configuration is 2,9-bis(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline.

[0066] Alternatively, another aspect of the present invention is a material in which the crystallized alkali metal fluoride or the crystallized alkaline earth metal fluoride in the material having the above configuration is any one of lithium fluoride, calcium fluoride, and magnesium fluoride.

[0067] Alternatively, another aspect of the present invention is a material for a light-emitting element including the above material.

[0068] Alternatively, another aspect of the present invention is a film containing the above material.

[0069] Alternatively, another aspect of the present invention is a light-emitting element having a layer made of the above material.

[0070] Furthermore, another aspect of the present invention is an electronic device having at least one of the light-emitting element configured as described above and a housing or a touch sensor. Another aspect of the present invention is a lighting device having at least one of the light-emitting element configured as described above and a housing, a connection terminal, or a protective cover. Also, one aspect of the present invention includes not only a light-emitting device having a light-emitting element but also an electronic device having the light-emitting device. Therefore, the light-emitting device in this specification refers to an image display device or a light source (including a lighting device). Also, a display module in which a connector, for example, an FPC (Flexible Printed Circuit) or a TCP (Tape Carrier Package), is attached to the light-emitting element, a display module in which a printed wiring board is provided at the tip of the TCP, or a display module in which an IC (integrated circuit) is directly mounted on the light-emitting element by a COG (Chip On Glass) method is also one aspect of the present invention.

Advantages of the Invention

[0071] One aspect of the present invention can provide a light-emitting element with high light extraction efficiency. Alternatively, one aspect of the present invention can provide a light-emitting element including a low refractive index layer. Alternatively, one aspect of the present invention can provide a light-emitting element with a low driving voltage. Alternatively, one aspect of the present invention can provide a light-emitting element with reduced power consumption. Alternatively, one aspect of the present invention can provide a highly reliable light-emitting element. Also, one aspect of the present invention can provide a light-emitting element with high luminous efficiency. Alternatively, one aspect of the present invention can provide a novel light-emitting element. Alternatively, one aspect of the present invention can provide a novel electronic device. Alternatively, one aspect of the present invention can provide a novel lighting device.

[0072] Note that the description of these effects does not preclude the existence of other effects. Note that one aspect of the present invention does not necessarily have to have all of these effects. Note that other effects are obvious from the descriptions in the specification, drawings, claims, etc., and it is possible to extract these other effects from the descriptions in the specification, drawings, claims, etc.

Brief Description of the Drawings

[0073]

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Embodiments for Carrying Out the Invention

[0074] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and its form and details can be variously changed without departing from the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited to the description of the embodiments shown below.

[0075] Note that the positions, sizes, ranges, etc. of the respective components shown in the drawings and the like may not represent the actual positions, sizes, ranges, etc. for the sake of simplicity of understanding. For this reason, the disclosed invention is not necessarily limited to the positions, sizes, ranges, etc. disclosed in the drawings and the like.

[0076] Also, in this specification and the like, ordinal numbers such as first, second, etc. are used for convenience and may not indicate the process order or the stacking order. Therefore, for example, "the first" can be appropriately replaced with "the second" or "the third" and so on for explanation. Also, the ordinal numbers described in this specification and the like may not match the ordinal numbers used to specify an aspect of the present invention.

[0077] Also, in this specification and the like, when explaining the configuration of the invention using drawings, reference numerals indicating the same thing may be commonly used among different drawings.

[0078] Also, in this specification and the like, the term "film" and the term "layer" can be interchanged with each other. For example, the term "conductive layer" may be changed to the term "conductive film" in some cases. Or, for example, the term "insulating film" may be changed to the term "insulating layer" in some cases.

[0079] Also, the refractive index n includes n Ordinary which is the refractive index of the ordinary ray, n Extra-ordinary which is the refractive index of the extraordinary ray, and n average which is the average value of the two. When simply described as "refractive index" in this specification, if anisotropy analysis is not performed, it may be read as n average, and if anisotropy analysis is performed, it may be read as n Ordinary. Also, anisotropy is represented by the difference between n Ordinary and n Extra-ordinary. Note that n average is the value obtained by dividing the sum of twice the value of n Ordinary and the value of n Extra-ordinary by 3.

[0080] Note that in this specification and the like, room temperature refers to a temperature in the range of 0°C or higher and 40°C or lower.

[0081] (Embodiment 1) In this embodiment, a light-emitting element of one aspect of the present invention will be described below with reference to FIG. 1.

[0082] Figure 1(A) is a schematic cross-sectional view of a light-emitting element 150 according to an aspect of the present invention.

[0083] The light-emitting element 150 has a pair of electrodes (electrode 101 and electrode 102), and has an EL layer 100 provided between the pair of electrodes. The EL layer 100 has at least a light-emitting layer 130 and a low-refractive-index layer 160. Further, it has a cap layer 145 in contact with the electrode 102 and on the side opposite to the EL layer.

[0084] In FIG. 1(A), the low-refractive-index layer 160 is provided between the light-emitting layer 130 and the electrode 101, but the configuration of the light-emitting element 150 is not limited thereto. As in the light-emitting element 152 shown in FIG. 1(B), the low-refractive-index layer 160 may be provided between the light-emitting layer 130 and the electrode 102.

[0085] The refractive index of the low-refractive-index layer 160 is preferably 1.80 or less, more preferably 1.75 or less, and still more preferably 1.70 or less.

[0086] Also, as in the light-emitting element 154 shown in FIG. 2(A), the EL layer 100 has 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, and it is preferable that at least one of the hole injection layer 111, the hole transport layer 112, the electron transport layer 118, and the electron injection layer 119 also has the characteristics of the low-refractive-index layer 160. FIG. 2(A) shows a configuration in which the hole injection layer 111 also has the characteristics of the low-refractive-index layer 160, and FIG. 2(B) shows a configuration in which the electron injection layer 119 also has the characteristics of the low-refractive-index layer 160.

[0087] In the present embodiment, the electrode 101 is described as an electrode having a function of reflecting light, and the electrode 102 is described as an electrode having a function of reflecting light and a function of transmitting light, but the configuration of the light-emitting element 150 is not limited thereto. That is, the electrode 101 may be an electrode having a function of reflecting light and a function of transmitting light, and the electrode 102 may be an electrode having a function of reflecting light.

[0088] Also, in this embodiment, among the pair of electrodes, electrode 101 is described as the anode and electrode 102 as the cathode. However, the structure of the light-emitting element 150 is not limited to this. That is, electrode 101 may be the cathode and electrode 102 may be the anode, and the lamination of each layer between the electrodes may be in the reverse order. That is, from the anode side, the hole injection layer 111, the hole transport layer 112, the light-emitting layer 130, the electron transport layer 118, and the electron injection layer 119 may be laminated in this order.

[0089] Also, in this embodiment, the directions of the arrows shown in FIGS. 1(A), (B) and FIGS. 2(A), (B), that is, the side of electrode 102 (cathode) is described as the light extraction side. However, the structure of the light-emitting element 150 is not limited to this. That is, the light extraction side may be the side of electrode 101 (anode), or light may be extracted from both electrodes 101 and 102. When the light extraction side is electrode 101, it is preferable to form a cap layer 145 in contact with electrode 101 on the side opposite to the EL layer. When light is extracted from both electrodes 101 and 102, it is preferable to form cap layers 145 in contact with electrodes 101 and 102, respectively.

[0090] Note that the structure of the EL layer 100 is not limited to the structure shown in FIG. 1(A), and it may have at least a light-emitting layer 130, and the hole injection layer 111, the hole transport layer 112, the electron transport layer 118, and the electron injection layer 119 may or may not be included respectively. Also, the EL layer 100 may have a structure having a functional layer having functions such as reducing the injection barrier of holes or electrons, improving the transport property of holes or electrons, inhibiting the transport property of holes or electrons, suppressing the quenching phenomenon by the electrode, and suppressing the exciton diffusion. Note that each functional layer may be a single layer or a structure in which a plurality of layers are laminated.

[0091] ≪Microcavity Structure≫ In addition, in the light-emitting element which is one aspect of the present invention, electrode 101 has a function of reflecting light, and electrode 102 has a function of reflecting light and a function of transmitting light. Therefore, by forming electrode 101, electrode 102, and EL layer 100 into a microcavity structure, the light emitted from light-emitting layer 130 included in EL layer 100 can be resonated between both electrodes, and the light emitted from electrode 102 can be enhanced.

[0092] Specifically, it is preferable to adjust the distance between electrode 101 and electrode 102 to be in the vicinity of mλ / 2 (where m is a natural number) with respect to the peak wavelength λ of the light obtained from light-emitting layer 130. Also, it is preferable that the distance between the electrodes is in the range of ±50 nm from the ideal distance (mλ / 2), and more preferably in the range of ±20 nm. By adopting such a configuration, the effect of the microcavity can be obtained efficiently.

[0093] In addition, in order to amplify the desired light (peak wavelength: λ) obtained from light-emitting layer 130, the optical distance from electrode 101 to the region (light-emitting region) where the desired light of the light-emitting layer can be obtained and the optical distance from electrode 102 to the region (light-emitting region) where the desired light of light-emitting layer 130 can be obtained are each preferably adjusted to be in the vicinity of (2m'-1)λ / 4 (where m' is a natural number). Also, it is preferable that the optical distance is in the range of ±50 nm from the ideal distance (2m'-1)λ / 4, and more preferably in the range of ±20 nm. By adopting such a configuration, the effect of the microcavity can be obtained efficiently. In this specification, the light-emitting region refers to the recombination region of holes and electrons in light-emitting layer 130. FIG. 1(A) shows a case where the light-emitting region exists near the center of light-emitting layer 130.

[0094] By performing such optical adjustment, the spectrum of specific monochromatic light obtained from light-emitting layer 130 can be narrowed, and light emission with good color purity can be obtained.

[0095] In order to efficiently obtain light emission from the above-described light-emitting element 150, it is preferable that the light extraction efficiency of the light-emitting element 150 is good. Here, it is known that the light extraction efficiency is improved by providing a low refractive index layer between the layer having a function of reflecting light and the EL layer. However, many of the materials that can be used for the low refractive index layer have low conductivity, and when used in the EL layer, the conductivity may be inhibited. Therefore, it was provided on the side opposite to the EL layer with respect to the electrode 101. In this configuration, there were problems such as the number of manufacturing steps becoming complicated and the manufacturing cost increasing.

[0096] Here, the inventors of the present invention have a light-emitting layer 130 and a low refractive index layer 160 between a pair of electrodes (electrode 101 and electrode 102). When the peak wavelength of the light emission obtained from the light-emitting layer 130 is λ, as shown in FIG. 2, the low refractive index layer 160 is provided in a region where the optical distance from the light-emitting layer 130 is 0 nm or more and λ / 2 or less, and a cap layer 145 is provided in contact with the electrode 102 on the light extraction side. As a result, it has been found that a light-emitting element with improved light extraction efficiency can be provided with a simple manufacturing process.

[0097] By providing the low refractive index layer 160 in a region where the optical distance from the light-emitting layer 130 is 0 nm or more and λ / 2 or less, it is possible to efficiently obtain the light extraction effect due to the microcavity structure and the light extraction effect due to the introduction of the low refractive index layer 160, which is preferable. Further, by providing the low refractive index layer 160 in the EL layer 100, it is possible to suppress the attenuation of light due to the evanescent mode that occurs in the vicinity of the electrode 101, the electrode 102, or the electrode 103 described later. Further, with this configuration, the film thickness of the EL layer 100 does not increase, so the driving voltage can be reduced. Further, with this configuration, the optical distance from the light-emitting layer to the electrode 101 having a function of reflecting light from the light-emitting layer can be reduced, so the loss due to the waveguide mode of the light obtained from the light-emitting layer can be suppressed. More preferably, the low refractive index layer 160 is provided at an optical distance of λ / 4 or less from the light-emitting layer 130.

[0098] Also, as shown in Fig. 2(A), it is preferable that the low refractive index layer 160 is provided between the anode and the light-emitting layer 130, and the optical distance between the anode-side interface of the light-emitting layer 130 and the light-emitting layer 130-side interface of the low refractive index layer 160 is 0 nm or more and within λ / 2. More preferably, the optical distance is 0 nm or more and within λ / 4. With this configuration, optical design (design of the film thicknesses of the respective layers of the EL layer 100) can be facilitated.

[0099] Also, as in the light-emitting element 156 shown in Fig. 2(B), it is preferable that the low refractive index layer 160 is provided between the cathode and the light-emitting layer 130, and the optical distance between the cathode-side interface of the light-emitting layer 130 and the light-emitting layer 130-side interface of the low refractive index layer 160 is 0 nm or more and within λ / 2. More preferably, the optical distance is 0 nm or more and within λ / 4. With this configuration, optical design can be facilitated.

[0100] Also, it is preferable that the refractive index of the low refractive index layer 160 is 1.80 or less. More preferably, it is 1.75 or less, and even more preferably, it is 1.70 or less. With this configuration, a light-emitting element with high light extraction efficiency can be provided.

[0101] Also, it is preferable that the refractive index of the low refractive index layer 160 is lower than the refractive index of the light-emitting layer 130. With this configuration, attenuation due to the waveguide mode can be suppressed, and thus the light extraction efficiency can be improved.

[0102] Also, it is preferable that at least one of the hole injection layer 111, the hole transport layer 112, the electron transport layer 118, and the electron injection layer 119 has a low refractive index. That is, in the light-emitting element according to one aspect of the present invention, it is preferable that at least one of the hole injection layer 111, the hole transport layer 112, the electron transport layer 118, and the electron injection layer 119 also functions as the low refractive index layer 160. With this configuration, the low refractive index layer 160 can be introduced into the EL layer 100 while maintaining the number of manufacturing steps of the conventional light-emitting element, and thus a light-emitting element with high light extraction efficiency can be easily provided.

[0103] In addition, when at least one of the hole injection layer 111, the hole transport layer 112, the electron transport layer 118, and the electron injection layer 119 also functions as the low refractive index layer 160, the film thickness of the layer having the function of the low refractive index layer 160 is preferably 5 nm or more. With this configuration, a layer having the function of the low refractive index layer can be formed while maintaining the function of the original layer (hole injection property in the case of the hole injection layer 111).

[0104] In addition, the light extraction efficiency can be improved by providing a cap layer 145 on the side opposite to the EL layer 100 in contact with the electrode on the light extraction side. In the light emitting element 150, by providing the cap layer 145 so as to be in contact with the electrode 102, the refractive index difference at the interface between the electrode 102 and the air can be reduced, and thus the light extraction efficiency can be improved. The film thickness is preferably 5 nm or more and 120 nm or less. More preferably, it is 30 nm or more and 90 nm or less. With this configuration, a cap layer 145 with good film quality can be obtained. In addition, it is preferable to use a conductive material, such as ITO, for the cap layer. Since an electrode having functions of reflecting light and transmitting light, such as the electrode 102, needs to have a thin film thickness, the film quality may become insufficient and the conductivity may deteriorate. Here, by using a conductive material for the cap layer 145, the light extraction efficiency can be improved while ensuring conductivity and improving the yield of manufacturing the light emitting element. In addition, an organic compound can be preferably used for the cap layer 145. In particular, an organic compound having little absorption in the visible light region can be preferably used. In addition, since the organic compound used for the EL layer 100 can be used as the cap layer 145, the cap layer 145 can be formed in the film forming apparatus or film forming chamber in which the EL layer 100 is formed, and thus the cap layer 145 can be easily formed.

[0105] Also, it is preferable to introduce an electrode 103 so as to be in contact with the electrode 101 and the EL layer 100 as in the light-emitting element 158 shown in FIG. 3. The electrode 101 has a function of reflecting light, and in some cases, materials such as Ag and Cu whose surfaces are liable to react are used for this function. Therefore, the surface may be deteriorated by being exposed to the atmosphere during or after the manufacturing process of the electrode 101. By manufacturing the electrode 103 on the electrode 101, such deterioration can be suppressed. Here, the electrode 103 is preferably a transparent electrode, and more preferably contains indium (In) and tin (Sn). For example, ITO or ITSO described later can be preferably used. In addition, it is also preferable to employ titanium oxide as an electrode having a high refractive index.

[0106] In the light-emitting element according to one aspect of the present invention, a low-refractive-index layer is provided between the light-emitting layer 130 and the third electrode 103. Here, when the refractive index of the third electrode is higher than the refractive index of the layer in contact with the third electrode (the hole injection layer 111 in FIG. 3), when the light emitted from the light-emitting layer is reflected at the interface of the layer in contact with the third electrode, it becomes a fixed-end reflection, and thus the phase of the reflected light is shifted by π compared to the phase of the light emitted from the light-emitting layer. Therefore, in order to form a microcavity structure between the electrodes 103 and 102 and improve the light extraction efficiency, the optical distance between the light-emitting layer 130 and the electrode 103 is preferably in the range of λ / 4 ± 50 nm. By adopting such a configuration, the light emitted from the light-emitting layer and the light reflected by the electrode 103 can be enhanced. Also, the optical distance between the light-emitting layer 130 and the electrode 103 is preferably in the range of ± 50 nm from the ideal film thickness (λ / 4), and more preferably in the range of ± 20 nm. By adopting such a configuration, the effect of the microcavity can be obtained efficiently.

[0107] Therefore, when the hole injection layer 111 in contact with the third electrode 103 also serves as the function of the low-refractive-index layer 160, it is preferable because the effect of the microcavity can be obtained efficiently by adjusting the optical path length. Further, by adopting such a configuration, the attenuation of light emission due to the evanescent mode can also be suppressed, which is preferable.

[0108] In addition, the light emitted from the light-emitting layer 130 and transmitted through the electrode 103 is reflected by the electrode 101. In order to form a microcavity structure between the electrode 103 and the electrode 102 to improve the light extraction efficiency, it is preferable that the optical distance (d) between the light-emitting layer 130 and the electrode 103 is in the range of ±50 nm from the value satisfying the following formula.

[0109]

Equation

[0110] In addition, in the light-emitting device according to one aspect of the present invention, it is preferable that the hole injection layer 111 also functions as the low refractive index layer 160. That is, the hole injection layer 111 preferably has a low refractive index (refractive index of 1.80 or less) and has hole injection properties. In order to obtain hole injection characteristics in the hole injection layer 111, a substance having electron accepting properties and an organic compound having electron donating properties are mixed. The thin film having such a configuration has a small change in hole injection properties due to a change in film thickness. That is, by changing the film thickness of the hole injection layer 111, it is possible to easily perform optical adjustment between the electrodes 101 and 103 and the light-emitting layer while maintaining the carrier balance of the EL layer.

[0111] Also, by using an organic compound with a low refractive index for the hole injection layer 111, even when using a substance with a high electron-accepting property and a high refractive index, a layer with hole injection characteristics and a low refractive index can be formed. Further, by using an organic compound with a low refractive index for the hole injection layer 111, the light extraction efficiency can be improved even when materials with a low refractive index are not used for the light-emitting layer and the layers around the light-emitting layer (light-emitting layer 130, hole transport layer 112, and electron transport layer 118), which particularly greatly affect the characteristics of the light-emitting device. That is, the range of selection of organic compounds that can be used for the light-emitting layer and the layers around the light-emitting layer can be widened. That is, by reducing the refractive index of the hole injection layer 111 or using an organic compound with a low refractive index for the hole injection layer 111, the light extraction efficiency and the effect of the microcavity can be improved while maintaining the characteristics of the EL layer.

[0112] Here, the mixing ratio of the above-described organic compound having an electron-donating property and the substance having an electron-accepting property is preferably such that the volume ratio of the substance having an electron-accepting property is 0.01 or more and 0.3 or less with respect to the organic compound. With this configuration, even when using a substance with a high refractive index for the substance having an electron-accepting property, a hole injection layer 111 with a low refractive index can be formed by using an organic compound with a low refractive index for the organic compound.

[0113] Also, the refractive index of the organic compound having an electron-donating property is preferably 1.80 or less. More preferably, it is 1.75 or less, and still more preferably, it is 1.70 or less. With this configuration, a hole injection layer 111 with a low refractive index can be formed.

[0114] <Organic compound having a low refractive index and carrier transport property>

[0115] Carrier (electron or hole) transport property is required for the layers included in the EL layer (hole injection layer 111, hole transport layer 112, electron transport layer 118, and electron injection layer 119). Here, in the light-emitting device according to one aspect of the present invention, an organic compound having a low refractive index and carrier transport property is preferably used for the low refractive index layer.

[0116] The refractive index of a polymer is represented by the Lorentz-Lorentz equation (Equation (2)) shown below.

[0117]

Equation

[0118] By transforming Equation (2), Equation (3) is obtained.

[0119]

Equation

[0120] In Equations (2) and (3), n is the refractive index, α is the polarizability, N is the number of molecules per unit volume, ρ is the density, N A is Avogadro's number, M is the molecular weight, V0 is the molar volume, and [R] represents the atomic refraction.

[0121] To decrease the refractive index n from Equation (3), it is sufficient to decrease φ. To decrease φ from Equation (2), it is sufficient to decrease the atomic refraction [R]. That is, to decrease the refractive index n, an organic compound with a small atomic refraction [R] may be selected.

[0122] Since the above equations are for polymers, when applied to low-molecular-weight compounds, it is expected that there will be some deviation in the calculated values. However, since the general trend is considered to be the same, it is preferable to select an organic compound with a small atomic refraction [R] as the organic compound used for the low refractive index layer. Furthermore, an organic compound having a π-conjugated system in the molecule has good carrier transport properties. Since carrier transport properties are required for the low refractive index layer, it is more preferable that the organic compound used for the low refractive index layer is an organic compound having a small atomic refraction [R] and a π-conjugated system in the molecule.

[0123] The atomic refraction [R] is a substituent containing fluorine such as a fluoro group or a trifluoromethyl group, a cyclohexyl group, or a bond via an aromatic ring with sp 3It tends to be small when it has a structure in which the conjugation between aromatic rings is broken, typified by hybrid orbitals. Therefore, as the organic compound used for the low refractive index layer, an organic compound having the above-described substituent or bond is preferable.

[0124] As the organic compound used for the low refractive index layer, an organic compound having an aromatic amine skeleton, a pyrrole skeleton, a fluorene skeleton, or an aromatic ring having a bulky substituent such as a methyl group, a t-butyl group, or an isopropyl group can also be preferably used. The organic compound has a π-conjugated system in the molecule and tends to have a lower refractive index.

[0125] <Material> Next, details of the components of the light-emitting element according to one embodiment of the present invention will be described below.

[0126] ≪Light-emitting layer≫ As shown in FIG. 1(C), the light-emitting layer 130 preferably has at least a host material 131 and further has a guest material 132. The host material 131 may have an organic compound 131_1 and an organic compound 131_2. In the light-emitting layer 130, the host material 131 is present in the largest amount by weight, and the guest material 132 is dispersed in the host material 131. When the guest material 132 is a fluorescent compound, the S1 level of the host material 131 (organic compound 131_1 and organic compound 131_2) of the light-emitting layer 130 is preferably higher than the S1 level of the guest material (guest material 132) of the light-emitting layer 130. When the guest material 132 is a phosphorescent compound, the T1 level of the host material 131 (organic compound 131_1 and organic compound 131_2) of the light-emitting layer 130 is preferably higher than the T1 level of the guest material (guest material 132) of the light-emitting layer 130.

[0127] The organic compound 131_1 preferably has a heteroaromatic skeleton having 1 to 20 carbon atoms containing two or more nitrogens. A compound having a pyrimidine skeleton and a triazine skeleton is preferable. As the organic compound 131_1, a material having higher electron transportability than holes (electron transport material) can be used, 1×10 -6 cm 2It is preferably a material having an electron mobility of 1 / Vs or more.

[0128] Specifically, for example, heterocyclic compounds having a diazine skeleton such as 4,6-bis[3-(phenanthren-9-yl)phenyl]pyrimidine (abbreviation: 4,6mPnP2Pm), 4,6-bis[3-(4-dibenzothienyl)phenyl]pyrimidine (abbreviation: 4,6mDBTP2Pm-II), 4,6-bis[3-(9H-carbazol-9-yl)phenyl]pyrimidine (abbreviation: 4,6mCzP2Pm), and 2-{4-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: PCCzPTzn), 2-{3-[3-(benzo[b]naphtho[1,2-d]furan-8-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mBnfBPTzn), 2,4,6-tris(biphenyl-3-yl)-1,3,5-triazine (abbreviation: T2T), 2,4,6-tris[3'-(pyridin-3-yl)-biphenyl-3-yl]-1,3,5-triazine (abbreviation: TmPPPyTz), 9-[4-(3,5-diphenyl-1H-1,2,4-triazol-1-yl)]phenyl-9H-carbazole (abbreviation: CzTAZ(1H)) and other heterocyclic compounds having a triazine skeleton, a pyrimidine skeleton, or a triazole skeleton are stable and have good reliability and are preferable. Further, the heterocyclic compound having such a skeleton has high electron transport properties and also contributes to reducing the driving voltage. The substances described herein mainly have an electron mobility of 1×10 -6 cm 2 / Vs or more. Note that any substance other than the above may be used as long as it has higher electron transport properties than holes.

[0129] In addition, as the organic compound 131_1, compounds such as pyridine derivatives, pyrazine derivatives, pyridazine derivatives, bipyridine derivatives, quinoxaline derivatives, dibenzoquinoxaline derivatives, phenanthroline derivatives, and purine derivatives can also be preferably used. When such an organic compound has 1×10 -6 cm 2It is preferably a material having an electron mobility of Vs or more.

[0130] Specifically, for example, heterocyclic compounds having a pyridine skeleton such as bathophenanthroline (abbreviation: BPhen), 2,9-bis(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline (abbreviation: NBPhen), bathocuproine (abbreviation: BCP), etc., and 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’-(9H-carbazol-9-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mCzBPDBq), 2-[4-(3,6-diphenyl-9H-carbazol-9-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2CzPDBq-III), 7-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 7mDBTPDBq-II), and 6-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 6mDBTPDBq-II), 2-[3-(3,9’-bi-9H-carbazol-9-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2mCzCzPDBq), etc., heteroaromatic ring compounds having a pyrazine skeleton, and heterocyclic compounds having a pyridine skeleton such as 3,5-bis[3-(9H-carbazol-9-yl)phenyl]pyridine (abbreviation: 35DCzPPy), 1,3,5-tri[3-(3-pyridyl)phenyl]benzene (abbreviation: TmPyPB) can also be used. In addition, polymer compounds such as poly(2,5-pyridinediyl) (abbreviation: PPy), poly[(9,9-dihexylfluorene-2,7-diyl)-co-(pyridine-3,5-diyl)] (abbreviation: PF-Py), poly[(9,9-dioctylfluorene-2,7-diyl)-co-(2,2’-bipyridine-6,6’-diyl)] (abbreviation: PF-BPy) can also be used. Note that as long as it is a substance with higher electron transportability than holes, substances other than the above can be used.

[0131] As the organic compound 131_2, it preferably has a heteroaromatic skeleton with 1 to 20 carbon atoms containing two or more nitrogens. In particular, a nitrogen-containing hetero five-membered ring skeleton is preferred. For example, an imidazole skeleton, a triazole skeleton, and a tetrazole skeleton can be mentioned. Also, as the organic compound 131_2, a material with higher hole transportability than electrons (hole transporting material) can be used, and it is preferably a material having a hole mobility of 1×10 -6 cm 2 / Vs or more. Further, the hole transporting material may be a polymer compound.

[0132] Specifically, for example, 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviation: TAZ), 9-[4-(4,5-diphenyl-4H-1,2,4-triazol-3-yl)phenyl]-9H-carbazole (abbreviation: CzTAZ1), 2,2’,2’’-(1,3,5-benzenetriyl)tris(1-phenyl-1H-benzimidazole) (abbreviation: TPBI), 2-[3-(dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzimidazole (abbreviation: mDBTBIm-II), etc. can be used.

[0133] As the organic compound 131_2, compounds having other nitrogen-containing hetero five-membered ring skeletons or tertiary amine skeletons can also be preferably used. Specifically, a pyrrole skeleton or an aromatic amine skeleton can be mentioned. For example, indole derivatives, carbazole derivatives, triarylamine derivatives, etc. can be mentioned. Also, as the organic compound 131_2, a material with higher hole transportability than electrons (hole transporting material) can be used, and it is preferably a material having a hole mobility of 1×10 -6 cm 2 / Vs or more. Further, the hole transporting material may be a polymer compound.

[0134] As these materials with high hole-transporting properties, specifically, as aromatic amine compounds, N,N'-di(p-tolyl)-N,N'-diphenyl-p-phenylenediamine (abbreviation: DTDPPA), 4,4'-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation: DPAB), N,N'-bis{4-[bis(3-methylphenyl)amino]phenyl}-N,N'-diphenyl-(1,1'-biphenyl)-4,4'-diamine (abbreviation: DNTPD), 1,3,5-tris[N-(4-diphenylaminophenyl)-N-phenylamino]benzene (abbreviation: DPA3B), etc. can be mentioned.

[0135] Also, as carbazole derivatives, specifically, 3-[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzDPA1), 3,6-bis[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzDPA2), 3,6-bis[N-(4-diphenylaminophenyl)-N-(1-naphthyl)amino]-9-phenylcarbazole (abbreviation: PCzTPN2), 3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA1), 3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA2), 3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole (abbreviation: PCzPCN1), 4,4'-bis(9-carbazolyl)-2,2'-dimethyl-biphenyl (abbreviation: dmCBP), etc. can be mentioned.

[0136] In addition, as the carbazole derivative, 4,4'-di(N-carbazolyl)biphenyl (abbreviation: CBP), 1,3,5-tris[4-(N-carbazolyl)phenyl]benzene (abbreviation: TCPB), 9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: CzPA), 7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenz[c,g]carbazole (abbreviation: cgDBCzPA), 1,4-bis[4-(N-carbazolyl)phenyl]-2,3,5,6-tetraphenylbenzene, etc. can also be used.

[0137] In addition, N,N-diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole-3-amine (abbreviation: CzA1PA), 4-(10-phenyl-9-anthryl)triphenylamine (abbreviation: DPhPA), 4-(9H-carbazol-9-yl)-4'-(10-phenyl-9-anthryl)triphenylamine (abbreviation: YGAPA), N,9-diphenyl-N-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole-3-amine (abbreviation: PCAPA), N,9-diphenyl-N-{4-[4-(10-phenyl-9-anthryl)phenyl]phenyl}-9H-carbazole-3-amine (abbreviation: PCAPBA), N,9-diphenyl-N-(9,10-diphenyl-2-anthryl)-9H-carbazole-3-amine (abbreviation: 2PCAPA), 9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: PCzPA), 3,6-diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: DPCzPA), N,N,N',N',N'',N'',N''',N''' -octaphenyldibenz[g,p]chrysene-2,7,10,15-tetraamine (abbreviation: DBC1), etc. can also be used.

[0138] In addition, high molecular compounds such as poly(N-vinylcarbazole) (abbreviation: PVK), poly(4-vinyltriphenylamine) (abbreviation: PVTPA), poly[N-(4-{N’-[4-(4-diphenylamino)phenyl]phenyl-N’-phenylamino}phenyl)methacrylamide] (abbreviation: PTPDMA), and poly[N,N’-bis(4-butylphenyl)-N,N’-bis(phenyl)benzidine] (abbreviation: Poly-TPD) can also be used.

[0139] Furthermore, examples of materials with high hole-transporting properties include 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB or α-NPD), N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (abbreviation: TPD), 4,4',4''-tris(carbazol-9-yl)triphenylamine (abbreviation: TCTA), 4,4',4''-tris[N-(1-naphthyl)-N-phenylamino]triphenylamine (abbreviation: 1'-TNATA), 4,4',4''-tris(N,N-diphenylamino)triphenylamine (abbreviation: TDATA), 4,4',4''-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine (abbreviation: MTDATA), 4,4'-bis[N-(spiro-9,9'-bifluorene-2-yl)-N-phenylamino]biphenyl (abbreviation: BSPB), 4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP), 4-phenyl-3'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: mBPAFLP), N-(9,9-dimethyl-9H-fluoren-2-yl)-N-{9,9-dimethyl-2-[N'-phenyl-N'-(9,9-dimethyl-9H-fluoren-2-yl)amino]-9H-fluoren-7-yl}phenylamine (abbreviation: DFLADFL), N-(9,9-dimethyl-2-diphenylamino-9H-fluoren-7-yl)diphenylamine (abbreviation: DPNF), 2-[N-(4-diphenylaminophenyl)-N-phenylamino]spiro-9,9'-bifluorene (abbreviation: DPASF), 4-phenyl-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4'-diphenyl-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBBi1BP), 4-(1-naphthyl)-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBANB), 4,4'-Di(1-naphthyl)-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBNBB), 4-phenyldiphenyl-(9-phenyl-9H-carbazol-3-yl)amine (abbreviation: PCA1BP), N,N'-bis(9-phenylcarbazol-3-yl)-N,N'-diphenylbenzene-1,3-diamine (abbreviation: PCA2B), N,N',N''-triphenyl-N,N',N''-tris(9-phenylcarbazol-3-yl)benzene-1,3,5-triamine (abbreviation: PCA3B), N-(4-biphenyl)-N-(9,9-dimethyl-9H-fluoren-2-yl)-9-phenyl-9H-carbazol-3-amine (abbreviation: PCBiF), N-(1,1'-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: PCBBiF), 9,9-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]fluorene-2-amine (abbreviation: PCBAF), N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]spiro-9,9'-bifluorene-2-amine (abbreviation: PCBASF), 2-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]spiro-9,9'-bifluorene (abbreviation: PCASF), 2,7-bis[N-(4-diphenylaminophenyl)-N-phenylamino]spiro-9,9'-bifluorene (abbreviation: DPA2SF), N-[4-(9H-carbazol-9-yl)phenyl]-N-(4-phenyl)phenylaniline (abbreviation: YGA1BP), N,N'-bis[4-(carbazol-9-yl)phenyl]-N,N'-diphenyl-9,9-dimethylfluorene-2,7-diamine (abbreviation: YGA2F) and other aromatic amine compounds can be used. Also, 3-[4-(1-naphthyl)phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPN), 3-[4-(9-phenanthryl)phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPPn), 3,3'-bis(9-phenyl-9H-carbazole) (abbreviation: PCCP), 1,3-bis(N-carbazolyl)benzene (abbreviation: mCP), 3,6-bis(3,Aminocompounds, carbazole compounds, etc., such as (5-diphenylphenyl)-9-phenylcarbazole (abbreviation: CzTP), 3,6-di(9H-carbazol-9-yl)-9-phenyl-9H-carbazole (abbreviation: PhCzGI), 2,8-di(9H-carbazol-9-yl)dibenzothiophene (abbreviation: Cz2DBT), can be used. Among the above-described compounds, compounds having a pyrrole skeleton and an aromatic amine skeleton are preferable because they are stable and have good reliability. Further, the compounds having such a skeleton have high hole transportability and contribute to a reduction in driving voltage.,

[0140] In addition, in the light-emitting layer 130, the guest material 132 is not particularly limited. As the fluorescent compound, anthracene derivatives, tetracene derivatives, chrysene derivatives, phenanthrene derivatives, pyrene derivatives, perylene derivatives, stilbene derivatives, acridone derivatives, coumarin derivatives, phenoxazine derivatives, phenothiazine derivatives, etc. are preferable, and for example, the following substances can be used.

[0141] Specifically, 5,6-bis[4-(10-phenyl-9-anthryl)phenyl]-2,2'-bipyridine (abbreviation: PAP2BPy), 5,6-bis[4'-(10-phenyl-9-anthryl)biphenyl-4-yl]-2,2'-bipyridine (abbreviation: PAPP2BPy), N,N'-diphenyl-N,N'-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine (abbreviation: 1,6FLPAPrn), N,N'-bis(3-methylphenyl)-N,N'-bis[3-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine (abbreviation: 1,6mMemFLPAPrn), N,N'-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-N,N'-bis(4-tert-butylphenyl)pyrene-1,6-diamine (abbreviation: 1,6tBu-FLPAPrn), N,N'-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-N,N'-diphenyl-3,8-dicyclohexylpyrene-1,6-diamine (abbreviation: ch-1,6FLPAPrn), N,N'-bis[4-(9H-carbazol-9-yl)phenyl]-N,N'-diphenylstilbene-4,4'-diamine (abbreviation: YGA2S), 4-(9H-carbazol-9-yl)-4'-(10-phenyl-9-anthryl)triphenylamine (abbreviation: YGAPA), 4-(9H-carbazol-9-yl)-4'-(9,10-diphenyl-2-anthryl)triphenylamine (abbreviation: 2YGAPPA), N,9-diphenyl-N-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole-3-amine (abbreviation: PCAPA), perylene, 2,5,8,11-tetra(tert-butyl)perylene (abbreviation: TBP), 4-(10-phenyl-9-anthryl)-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBAPA), N,N''-(2-tert-butylanthracene-9,10-diyl-di-4,1-phenylene)bis[N,N',N'-triphenyl-1,4-phenylenediamine] (abbreviation: DPABPA), N,9-diphenyl-N-[4-(9,10-diphenyl-2-anthryl)phenyl]-9H-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’’’-octaphenyldibenz[g,p]chrysene-2,7,10,15-tetraamine (abbreviation: DBC1), Coumarin 30, N-(9,10-diphenyl-2-anthryl)-N,9-diphenyl-9H-carbazole-3-amine (abbreviation: 2PCAPA), N-[9,10-bis(1,1’-biphenyl-2-yl)-2-anthryl]-N,9-diphenyl-9H-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-(9H-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), Rubrene, 2,8-di-tert-butyl-5,11-bis(4-tert-butylphenyl)-6,12-diphenyltetracene (abbreviation: TBRb), Nile Red, 5,12-bis(1,1’-biphenyl-4-yl)-6,11-diphenyltetracene (abbreviation: BPT), 2-(2-{2-[4-(dimethylamino)phenyl]ethenyl}-6-methyl-4H-pyran-4-ylidene)propanedinitrile (abbreviation: DCM1), 2-{2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCM2), N,N,N’,N’-tetrakis(4-methylphenyl)tetracene-5,11-diamine (abbreviation: p-mPhTD), 7,14-diphenyl-N,N,N’,N’-tetrakis(4-methylphenyl)acenaphtho[1,2-a]fluoranthene-3,10-diamine (abbreviation: p-mPhAFD), 2-{2-isopropyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCJTI), 2-{2-tert-butyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCJTB), 2-(2,6-bis{2-[4-(dimethylamino)phenyl]ethenyl}-4H-pyran-4-ylidene)propanedinitrile (abbreviation: BisDCM), 2-{2,6-bis[2-(8-methoxy-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: BisDCJTM), 5,10,15,20-tetraphenylbisbenzo[5,6]inden[1,2,3-cd:1’,2’,3’-lm]perylene, and the like.

[0142] Examples of the guest material 132 (phosphorescent compound) include iridium, rhodium, or platinum-based organometallic complexes, or metal complexes. Among them, organoiridium complexes, such as iridium orthometal complexes, are preferred. Examples of the ligand for orthometalation include 4H-triazole ligand, 1H-triazole ligand, imidazole ligand, pyridine ligand, pyrimidine ligand, pyrazine ligand, or isoquinoline ligand. Examples of the metal complex include platinum complexes having a porphyrin ligand.

[0143] Examples of the substance having an emission peak in blue or green include, for example, tris{2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazol-3-yl-κN 2Phenyl-κC iridium(III) (abbreviation: Ir(mpptz-dmp)3), tris(5-methyl-3,4-diphenyl-4H-1,2,4-triazolato)iridium(III) (abbreviation: Ir(Mptz)3), tris[4-(3-biphenyl)-5-isopropyl-3-phenyl-4H-1,2,4-triazolato]iridium(III) (abbreviation: Ir(iPrptz-3b)3), tris[3-(5-biphenyl)-5-isopropyl-4-phenyl-4H-1,2,4-triazolato]iridium(III) (abbreviation: Ir(iPr5btz)3), and other organometallic iridium complexes having a 4H-triazole skeleton, tris[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-triazolato]iridium(III) (abbreviation: Ir(Mptz1-mp)3), tris(1-methyl-5-phenyl-3-propyl-1H-1,2,4-triazolato)iridium(III) (abbreviation: Ir(Prptz1-Me)3), and other organometallic iridium complexes having a 1H-triazole skeleton, fac-tris[1-(2,6-diisopropylphenyl)-2-phenyl-1H-imidazole]iridium(III) (abbreviation: Ir(iPrpmi)3), tris[3-(2,6-dimethylphenyl)-7-methylimidazo[1,2-f]phenanthridinato]iridium(III) (abbreviation: Ir(dmpimpt-Me)3), tris{2-[1-(4-cyano-2,6-diisobutylphenyl)-1H-benzimidazol-2-yl-κN 3 Phenyl-κC iridium(III) (abbreviation: Ir(pbi-diBuCNp)3) and other organometallic iridium complexes having an imidazole skeleton, bis[2-(4’,6’-difluorophenyl)pyridinato-N,C 2’ Iridium(III) tetrakis(1-pyrazolyl)borate (abbreviation: FIr6), bis[2-(4’,6’-difluorophenyl)pyridinato-N,C 2’ Iridium(III) picolinate (abbreviation: FIrpic), bis{2-[3’,5’-bis(trifluoromethyl)phenyl]pyridinato-N,C 2’Iridium(III) picolinate (abbreviation: Ir(CF3ppy)2(pic)), bis[2-(4’,6’-difluorophenyl)pyridinato-N,C 2’ Examples of the organometallic iridium complex having a phenylpyridine derivative having an electron-withdrawing group such as iridium(III) acetylacetonate (abbreviation: FIr(acac)) as a ligand. Among those described above, the organometallic iridium complex having a nitrogen-containing five-membered heterocyclic skeleton such as 4H-triazole skeleton, 1H-triazole skeleton and imidazole skeleton has high triplet excitation energy and is also excellent in reliability and luminescence efficiency, and thus is particularly preferable.

[0144] In addition, examples of the substance having a luminescence peak in green or yellow include tris(4-methyl-6-phenylpyrimidinato)iridium(III) (abbreviation: Ir(mppm)3), tris(4-t-butyl-6-phenylpyrimidinato)iridium(III) (abbreviation: Ir(tBuppm)3), (acetylacetonato)bis(6-methyl-4-phenylpyrimidinato)iridium(III) (abbreviation: Ir(mppm)2(acac)), (acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidinato)iridium(III) (abbreviation: Ir(tBuppm)2(acac)), (acetylacetonato)bis[4-(2-norbornyl)-6-phenylpyrimidinato]iridium(III) (abbreviation: Ir(nbppm)2(acac)), (acetylacetonato)bis[5-methyl-6-(2-methylphenyl)-4-phenylpyrimidinato]iridium(III) (abbreviation: Ir(mpmppm)2(acac)), (acetylacetonato)bis{4,6-dimethyl-2-[6-(2,6-dimethylphenyl)-4-pyrimidinyl-κN 3Phenyl-κC iridium(III) (abbreviation: Ir(dmppm-dmp)2(acac)), organometallic iridium complexes having a pyrimidine skeleton such as bis(4,6-diphenylpyrimidinato)(acetylacetonato)iridium(III) (abbreviation: Ir(dppm)2(acac)), or organometallic iridium complexes having a pyrazine skeleton such as bis(3,5-dimethyl-2-phenylpyrazinato)(acetylacetonato)iridium(III) (abbreviation: Ir(mppr-Me)2(acac)), bis(5-isopropyl-3-methyl-2-phenylpyrazinato)(acetylacetonato)iridium(III) (abbreviation: Ir(mppr-iPr)2(acac)), or tris(2-phenylpyridinato-N,C 2’ )iridium(III) (abbreviation: Ir(ppy)3), bis(2-phenylpyridinato-N,C 2’ )iridium(III) acetylacetonate (abbreviation: Ir(ppy)2(acac)), bis(benzo[h]quinolinato)iridium(III) acetylacetonate (abbreviation: Ir(bzq)2(acac)), tris(benzo[h]quinolinato)iridium(III) (abbreviation: Ir(bzq)3), tris(2-phenylquinolinato-N,C 2’ )iridium(III) (abbreviation: Ir(pq)3), bis(2-phenylquinolinato-N,C 2’ )iridium(III) acetylacetonate (abbreviation: Ir(pq)2(acac)), or organometallic iridium complexes having a pyridine skeleton such as bis(2,4-diphenyl-1,3-oxazolato-N,C 2’ )iridium(III) acetylacetonate (abbreviation: Ir(dpo)2(acac)), bis{2-[4’-(perfluorophenyl)phenyl]pyridinato-N,C 2’}iridium(III) acetylacetonate (abbreviation: Ir(p-PF-ph)2(acac)), bis(2-phenylbenzothiazolato-N,C 2’In addition to organometallic iridium complexes such as iridium(III) acetylacetonate (abbreviation: Ir(bt)2(acac)), rare earth metal complexes such as tris(acetylacetonato)(monophenanthroline)terbium(III) (abbreviation: Tb(acac)3(Phen)) are also included. Among those described above, organometallic iridium complexes having a pyrimidine skeleton are particularly preferred because they are remarkably excellent in reliability and luminous efficiency.

[0145] In addition, examples of substances having a yellow or red emission peak include organometallic iridium complexes having a pyrimidine skeleton such as (diisobutyrylmethanato)bis[4,6-bis(3-methylphenyl)pyrimidinato]iridium(III) (abbreviation: Ir(5mdppm)2(dibm)), bis[4,6-bis(3-methylphenyl)pyrimidinato](dipivaloylmethanato)iridium(III) (abbreviation: Ir(5mdppm)2(dpm)), bis[4,6-di(naphthalen-1-yl)pyrimidinato](dipivaloylmethanato)iridium(III) (abbreviation: Ir(d1npm)2(dpm)), organometallic iridium complexes having a pyrazine skeleton such as (acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III) (abbreviation: Ir(tppr)2(acac)), bis(2,3,5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III) (abbreviation: Ir(tppr)2(dpm)), (acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III) (abbreviation: Ir(Fdpq)2(acac)), tris(1-phenylisoquinolinato-N,C 2’ )iridium(III) (abbreviation: Ir(piq)3), bis(1-phenylisoquinolinato-N,C 2’)In addition to organometallic iridium complexes having a pyridine skeleton such as iridium(III) acetylacetonate (abbreviation: Ir(piq)2(acac)), platinum complexes such as platinum(II) 2,3,7,8,12,13,17,18 - octaethyl - 21H,23H - porphyrin (abbreviation: PtOEP), and rare - earth metal complexes such as tris(1,3 - diphenyl - 1,3 - propanedionato)(monophenanthroline)europium(III) (abbreviation: Eu(DBM)3(Phen)) and tris[1 - (2 - thenoyl)-3,3,3 - trifluoroacetonato](monophenanthroline)europium(III) (abbreviation: Eu(TTA)3(Phen)) can be mentioned. Among those described above, organometallic iridium complexes having a pyrimidine skeleton are particularly preferable because they are remarkably excellent in reliability and luminescence efficiency. Also, organometallic iridium complexes having a pyrazine skeleton can obtain red luminescence with good chromaticity.

[0146] As the light - emitting material contained in the light - emitting layer 130, any material that can convert triplet excitation energy into light emission is preferable. As materials that can convert triplet excitation energy into light emission, in addition to phosphorescent compounds, thermally activated delayed fluorescence (TADF) materials can be mentioned. Therefore, regarding the part described as a phosphorescent compound, it may be read as a thermally activated delayed fluorescence material. A thermally activated delayed fluorescence material is a material in which the energy difference between the triplet excitation energy level and the singlet excitation energy level is small and has a function of converting energy from the triplet excited state to the singlet excited state by reverse intersystem crossing. Therefore, up - conversion (reverse intersystem crossing) from the triplet excited state to the singlet excited state is possible with a small amount of thermal energy, and light emission (fluorescence) from the singlet excited state can be efficiently exhibited. Also, as conditions for efficiently obtaining thermally activated delayed fluorescence, the energy difference between the triplet excitation energy level and the singlet excitation energy level is preferably greater than 0 eV and 0.2 eV or less, more preferably greater than 0 eV and 0.1 eV or less.

[0147] When the thermally activated delayed fluorescence material is composed of one type of material, for example, the following materials can be used.

[0148] First, examples include fullerenes and their derivatives, acridine derivatives such as proflavine, and eosin. Also included are metal-containing porphyrins containing magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), or palladium (Pd), etc. Examples of the 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)), etioporphyrin-tin fluoride complex (SnF2(Etio I)), octaethylporphyrin-platinum chloride complex (PtCl2OEP), and the like.

[0149] In addition, as a thermally activated delayed fluorescence material composed of a single type of material, a heterocyclic compound having a π-electron-rich heteroaromatic ring and a π-electron-deficient heteroaromatic ring can also be used. Specifically, 2-(biphenyl-4-yl)-4,6-bis(12-phenylindolo[2,3-a]carbazol-11-yl)-1,3,5-triazine (abbreviation: PIC-TRZ), 2-{4-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: PCCzPTzn), 2-[4-(10H-phenoxazine-10-yl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviation: PXZ-TRZ), 3-[4-(5-phenyl-5,10-dihydrophenazin-10-yl)phenyl]-4,5-diphenyl-1,2,4-triazole (abbreviation: PPZ-3TPT), 3-(9,9-dimethyl-9H-acridin-10-yl)-9H-xanthen-9-one (abbreviation: ACRXTN), bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone (abbreviation: DMAC-DPS), 10-phenyl-10H,10’H-spiro[acridine-9,9’-anthracene]-10’-one (abbreviation: ACRSA), etc. can be mentioned. Since the heterocyclic compound has a π-electron-rich heteroaromatic ring and a π-electron-deficient heteroaromatic ring, it has high electron transportability and hole transportability, which is preferable. Among them, among the skeletons having a π-electron-deficient heteroaromatic ring, a diazine skeleton (pyrimidine skeleton, pyrazine skeleton, pyridazine skeleton), or a triazine skeleton is preferable because it is stable and has good reliability. Also, among the skeletons having a π-electron-rich heteroaromatic ring, an acridine skeleton, a phenoxazine skeleton, a thiophene skeleton, a furan skeleton, and a pyrrole skeleton are preferable because they are stable and have good reliability, and it is preferable to have any one or more selected from among these skeletons. In addition, as the pyrrole skeleton, an indole skeleton, a carbazole skeleton, and a 3-(9-phenyl-9H-carbazol-3-yl)-9H-carbazole skeleton are particularly preferable.In addition, a substance in which a π-electron rich heteroaromatic ring and a π-electron deficient heteroaromatic ring are directly bonded is particularly preferable because both the donor property of the π-electron rich heteroaromatic ring and the acceptor property of the π-electron deficient heteroaromatic ring are strong, and the difference between the energy level of the singlet excited state and the energy level of the triplet excited state becomes small.

[0150] Further, in the light emitting layer 130, it may have materials other than the host material 131 and the guest material 132.

[0151] The materials that can be used for the light emitting layer 130 are not particularly limited. For example, condensed polycyclic aromatic compounds such as anthracene derivatives, phenanthrene derivatives, pyrene derivatives, chrysene derivatives, and dibenzo[g,p]chrysene derivatives can be mentioned. Specifically, 9,10-diphenylanthracene (abbreviation: DPAnth), 6,12-dimethoxy-5,11-diphenylchrysene, 9,10-bis(3,5-diphenylphenyl)anthracene (abbreviation: DPPA), 9,10-di(2-naphthyl)anthracene (abbreviation: DNA), 2-tert-butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA), 9,9'-bianthryl (abbreviation: BANT), 9,9'-(stilbene-3,3'-diyl)diphenanthrene (abbreviation: DPNS), 9,9'-(stilbene-4,4'-diyl)diphenanthrene (abbreviation: DPNS2), 1,3,5-tri(1-pyrenyl)benzene (abbreviation: TPB3), etc. can be mentioned. Further, from these and known substances, a substance having a singlet excitation energy level or a triplet excitation energy level higher than the excitation energy level of the guest material 132 may be selected and used alone or in combination of two or more.

[0152] In addition, for example, a compound having a heteroaromatic skeleton such as an oxadiazole derivative can be used in the light-emitting layer 130. Specifically, for example, 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene (abbreviation: OXD-7), 9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole (abbreviation: CO11), 4,4'-bis(5-methylbenzoxazol-2-yl)stilbene (abbreviation: BzOS) and other heterocyclic compounds can be mentioned.

[0153] In addition, a metal complex having a heterocyclic ring (for example, a zinc and aluminum-based metal complex) can be used in the light-emitting layer 130. For example, metal complexes having a quinoline ligand, a benzoquinoline ligand, an oxazole ligand, or a thiazole ligand can be mentioned. Specifically, for example, tris(8-quinolinolato)aluminum(III) (abbreviation: Alq), tris(4-methyl-8-quinolinolato)aluminum(III) (abbreviation: Almq3), bis(10-hydroxybenzo[h]quinolinato)beryllium(II) (abbreviation: BeBq2), bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III) (abbreviation: BAlq), bis(8-quinolinolato)zinc(II) (abbreviation: Znq) and other metal complexes having a quinoline skeleton or a benzoquinoline skeleton can be mentioned. In addition, other metal complexes having an oxazole-based or thiazole-based ligand such as bis[2-(2-benzoxazolyl)phenolato]zinc(II) (abbreviation: ZnPBO), bis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ) can also be used.

[0154] Note that the light-emitting layer 130 can also be composed of two or more layers. For example, when the first light-emitting layer and the second light-emitting layer are stacked in order from the hole-transporting layer side to form the light-emitting layer 130, a substance having hole-transporting properties can be used as the host material of the first light-emitting layer, and a substance having electron-transporting properties can be used as the host material of the second light-emitting layer. Also, the light-emitting materials of the first light-emitting layer and the second light-emitting layer may be the same material or different materials, and may be materials having a function of emitting light of the same color or materials having a function of emitting light of different colors. By using light-emitting materials having functions of emitting light of different colors in the two light-emitting layers, a plurality of emissions can be obtained simultaneously. In particular, it is preferable to select the light-emitting materials used in each light-emitting layer so that white light is obtained by the emissions presented by the two light-emitting layers.

[0155] Note that the light-emitting layer 130 can be formed by methods such as vapor deposition (including vacuum vapor deposition), inkjet method, coating method, gravure printing, etc. Also, in addition to the materials described above, it may contain inorganic compounds such as quantum dots or polymer compounds (oligomers, dendrimers, polymers, etc.).

[0156] <<Hole injection layer>> The positive hole injection layer 111 has a function of promoting hole injection by reducing the hole injection barrier from one of a pair of electrodes (electrode 101 or electrode 102), and is formed of, for example, an electron-donating transition metal oxide, a phthalocyanine derivative, an aromatic amine, a heteropoly acid, or the like. Examples of the transition metal oxide include titanium oxide, vanadium oxide, tantalum oxide, molybdenum oxide, tungsten oxide, rhenium oxide, ruthenium oxide, chromium oxide, zirconium oxide, hafnium oxide, silver oxide, etc. The transition metal oxide is excellent in electron-accepting property and is preferable because it can be easily formed into a film by a vacuum evaporation method or a wet method. Examples of the phthalocyanine derivative include phthalocyanine and metal phthalocyanine. Examples of the aromatic amine include benzidine derivatives and phenylenediamine derivatives. Polymer compounds such as polythiophene and polyaniline can also be used, and for example, poly(ethylenedioxythiophene) / poly(styrenesulfonic acid), which is self-doped polythiophene, is a typical example. Examples of the heteropoly acid include phosphomolybdic acid, phosphotungstic acid, silicomolybdic acid, silicotungstic acid, etc. The heteropoly acid and the polymer compound are preferable because they can be easily formed into a film by a wet method.

[0157] As the positive hole injection layer 111, it is preferable to use a layer having a composite material of a hole transporting material having a substituent, a skeleton or a chemical bond with a small atomic refraction [R] as described above and a material exhibiting the above-described electron accepting property. By adopting such a configuration, it is possible to form a layer having hole injection / transport properties and a low refractive index. As the organic material having an electron accepting property, 7,7,8,8-tetracyanoquinodimethane (abbreviation: TCNQ), 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation: F4-TCNQ), 1,3,4,5,7,8-hexafluorocyano-naphthoquinodimethane (abbreviation: F6TCNNQ) can be preferably used. Further, a laminate of a layer containing a material exhibiting an electron accepting property and a layer containing a hole transporting material may be used. Charge transfer is possible between these materials in a steady state or in the presence of an electric field. As the organic material having an electron accepting property, in addition to the above-described TCNQ, F4TCNQ, and F6TCNNQ, organic acceptors such as quinodimethane derivatives, chloranil derivatives, and hexaazatriphenylene derivatives can be mentioned. Specifically, compounds having an electron-withdrawing group (halogen group or cyano group) such as chloranil, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviation: HAT-CN) can be mentioned. Further, [3]radialene derivatives having an electron-withdrawing group are preferable because of their very high electron accepting property. Specifically, α,α’,α’’-1,2,3-cyclopropanetriylidene tris[4-cyano-2,3,5,6-tetrafluorobenzeneacetonitrile], α,α’,α’’-1,2,3-cyclopropanetriylidene tris[2,6-dichloro-3,5-difluoro-4-(trifluoromethyl)benzeneacetonitrile], α,α’,α’’-1,2,3-cyclopropanetriylidene tris[2,3,4,5,6-pentafluorobenzeneacetonitrile] and the like can also be mentioned. Further, substances containing oxygen and transition metals such as titanium, vanadium, tantalum, molybdenum, tungsten, rhenium, ruthenium, chromium, zirconium, hafnium, silver and the like can be used.Specifically, they are titanium oxide, vanadium oxide, tantalum oxide, molybdenum oxide, tungsten oxide, rhenium oxide, ruthenium oxide, chromium oxide, zirconium oxide, hafnium oxide, silver oxide, phosphomolybdic acid, molybdenum bronzes, tungsten bronzes, etc. Among them, molybdenum oxide is preferable because it is stable in the atmosphere, has low hygroscopicity, and is easy to handle.

[0158] In addition, as described above, the hole-transporting material with a low refractive index used for the hole injection layer 111 is an organic compound having a structure that cuts the conjugation between aromatic rings typified by sp 3 bonding, or an organic compound having an aromatic ring with a bulky substituent can be preferably used. However, on the other hand, such compounds tend to be poor in carrier transportability and have been unsuitable for conventional hole injection layers. On the other hand, a simple substance of a substance containing a transition metal and oxygen as described above has a very high effect of enhancing hole injection properties, but has a problem of high refractive index. However, when a substance containing a transition metal and oxygen as described above is used for the hole injection layer 111 in combination with a hole-transporting material having a low refractive index as a material showing electron-accepting properties, it has been found that the hole injection properties and transportability can be ensured while keeping the refractive index of the hole injection layer 111 low. That is, this configuration can cancel out the demerits of both and exhibit only the merits. This is considered to be because the electron-accepting property of the substance containing a transition metal oxide is high and the hole injection property can be ensured by adding a small amount.

[0159] As the hole-transporting material, a material with higher hole transportability than electrons can be used, and 1×10 -6 cm 2It is preferably a material having a hole mobility of 0 / Vs or more. Further, as described above, the hole transporting material preferably has a refractive index of 1 or more and 1.75 or less, more preferably 1 or more and 1.73 or less, and even more preferably 1 or more and 1.70 or less. Specifically, aromatic amines, carbazole derivatives, aromatic hydrocarbons, stilbene derivatives, etc. mentioned as hole transporting materials that can be used in the light emitting layer 130 can be used, but it is particularly preferable to have a heteroaromatic skeleton having 1 to 20 carbon atoms containing two or more nitrogens. In particular, a nitrogen-containing hetero five-membered ring skeleton is preferable. Further, the hole transporting material may be a polymer compound.

[0160] In addition, other hole transporting materials include aromatic hydrocarbons, for example, 2-tert-butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA), 2-tert-butyl-9,10-di(1-naphthyl)anthracene, 9,10-bis(3,5-diphenylphenyl)anthracene (abbreviation: DPPA), 2-tert-butyl-9,10-bis(4-phenylphenyl)anthracene (abbreviation: t-BuDBA), 9,10-di(2-naphthyl)anthracene (abbreviation: DNA), 9,10-diphenylanthracene (abbreviation: DPAnth), 2-tert-butylanthracene (abbreviation: t-BuAnth), 9,10-bis(4-methyl-1-naphthyl)anthracene (abbreviation: DMNA), 2-tert-butyl-9,10-bis[2-(1-naphthyl)phenyl]anthracene, 9,10-bis[2-(1-naphthyl)phenyl]anthracene, 2,3,6,7-tetramethyl-9,10-di(1-naphthyl)anthracene, 2,3,6,7-tetramethyl-9,10-di(2-naphthyl)anthracene, 9,9'-bianthryl, 10,10'-diphenyl-9,9'-bianthryl, 10,10'-bis(2-phenylphenyl)-9,9'-bianthryl, 10,10'-bis[(2,3,4,5,6-pentaphenyl)phenyl]-9,9'-bianthryl, anthracene, tetracene, rubrene, perylene, 2,5,8,11-tetra(tert-butyl)perylene, etc. can be mentioned. In addition, pentacene, coronene, etc. can also be used. Thus, 1×10 -6cm 2 It is more preferable to use an aromatic hydrocarbon having a hole mobility of 1 cm2 / Vs or more and having 14 to 42 carbon atoms.

[0161] The aromatic hydrocarbon may have a vinyl skeleton. Examples of the aromatic hydrocarbon having a vinyl group include 4,4'-bis(2,2-diphenylvinyl)biphenyl (abbreviation: DPVBi), 9,10-bis[4-(2,2-diphenylvinyl)phenyl]anthracene (abbreviation: DPVPA), and the like.

[0162] In addition, thiophene compounds, furan compounds, fluorene compounds, triphenylene compounds, phenanthrene compounds, etc. such as 4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran (abbreviation: mmDBFFLBi-II), 4,4',4''-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation: DBF3P-II), 1,3,5-tri(dibenzothiophen-4-yl)-benzene (abbreviation: DBT3P-II), 2,8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene (abbreviation: DBTFLP-III), 4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviation: DBTFLP-IV), 4-[3-(triphenylene-2-yl)phenyl]dibenzothiophene (abbreviation: mDBTPTp-II) can be used. Among the above-described compounds, compounds having a pyrrole skeleton, a furan skeleton, a thiophene skeleton, or an aromatic amine skeleton are preferable because they are stable and have good reliability. In addition, compounds having such a skeleton have high hole transport properties and contribute to reducing the driving voltage.

[0163] <<Hole Transport Layer>> The hole transport layer 112 is a layer containing a hole transporting material, and the hole transporting materials exemplified as the material of the hole injection layer 111 can be used. Since the hole transport layer 112 has a function of transporting the holes injected into the hole injection layer 111 to the light emitting layer 130, it preferably has a HOMO (Highest Occupied Molecular Orbital) level that is the same as or close to the HOMO level of the hole injection layer 111.

[0164] Also, it is preferably a substance having a hole mobility of 1×10 -6 cm 2 / Vs or more. However, as long as it is a substance with higher hole transportability than electrons, substances other than these may be used. Note that the layer containing a substance with high hole transportability may be not only a single layer, but also two or more layers of the layers made of the above substances laminated.

[0165] <<Electron transport layer>> The electron transport layer 118 has a function of transporting the electrons injected from the other of the pair of electrodes (electrode 101 or electrode 102) through the electron injection layer 119 to the light emitting layer 130. As the electron transporting material, a material with higher electron transportability than holes can be used, and it is preferably a material having an electron mobility of 1×10 -6 cm 2 / Vs or more. As the compound (material having electron transportability) that easily receives electrons, π-electron deficient heteroaromatics such as nitrogen-containing heteroaromatic compounds and metal complexes can be used. Specifically, the pyridine derivatives, bipyridine derivatives, pyrimidine derivatives, triazine derivatives, quinoxaline derivatives, dibenzoquinoxaline derivatives, phenanthroline derivatives, triazole derivatives, benzimidazole derivatives, oxadiazole derivatives, etc. mentioned as the electron transporting materials that can be used in the light emitting layer 130 can be cited, but it is preferable to have a heteroaromatic skeleton having 1 to 20 carbon atoms containing two or more nitrogens. In particular, it is preferably a compound having a pyrimidine skeleton and a triazine skeleton. Also, 1×10 -6 cm 2It is preferably a substance having an electron mobility of Vs or more. Note that, as long as it is a substance having higher electron transportability than holes, substances other than the above may be used as the electron transport layer. Further, the electron transport layer 118 may be not only a single layer but also two or more layers of layers made of the above substances stacked.

[0166] In addition, metal complexes having a heterocyclic ring can be mentioned. For example, metal complexes having a quinoline ligand, a benzoquinoline ligand, an oxazole ligand, or a thiazole ligand can be mentioned. Specifically, for example, tris(8-quinolinolato)aluminum(III) (abbreviation: Alq), tris(4-methyl-8-quinolinolato)aluminum(III) (abbreviation: Almq3), bis(10-hydroxybenzo[h]quinolinato)beryllium(II) (abbreviation: BeBq2), bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III) (abbreviation: BAlq), bis(8-quinolinolato)zinc(II) (abbreviation: Znq), etc., metal complexes having a quinoline skeleton or a benzoquinoline skeleton can be mentioned. In addition, other metal complexes having an oxazole-based or thiazole-based ligand such as bis[2-(2-benzoxazolyl)phenolato]zinc(II) (abbreviation: ZnPBO) and bis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ) can also be used.

[0167] In addition, a layer for controlling the movement of electron carriers may be provided between the electron transport layer 118 and the light-emitting layer 130. This is a layer in which a small amount of a substance having high electron trapping property is added to a material having high electron transportability as described above, and by suppressing the movement of electron carriers, it becomes possible to adjust the carrier balance. Such a configuration has a great effect in suppressing problems (for example, a decrease in element life) that occur when the electron transportability of the electron transport material is significantly higher than the hole transportability of the hole transport material.

[0168] ≪Electron injection layer≫ The electron injection layer 119 has a function of promoting electron injection by reducing the electron injection barrier from the electrode 102. For example, group 1 metals, group 2 metals, or their oxides, halides, carbonates, etc. can be used. Also, a composite material of the electron transporting material shown above and a material exhibiting electron donating properties can be used. Examples of materials exhibiting electron donating properties include group 1 metals, group 2 metals, or their oxides. Specifically, lithium fluoride (LiF), sodium fluoride (NaF), cesium fluoride (CsF), calcium fluoride (CaF2), lithium oxide (LiO x ) and other alkali metals, alkaline earth metals, or their compounds can be used. Also, rare earth metal compounds such as erbium fluoride (ErF3) can be used. Also, electrides may be used for the electron injection layer 119. Examples of such electrides include substances obtained by adding electrons at a high concentration to a mixed oxide of calcium and aluminum. Also, substances that can be used in the electron transport layer 118 may be used for the electron injection layer 119.

[0169] Also, a composite material formed by mixing an organic compound and an electron donor may be used for the electron injection layer 119. Such a composite material is excellent in electron injection properties and electron transport properties because electrons are generated in the organic compound by the electron donor. In this case, the organic compound is preferably a material excellent in transporting the generated electrons. Specifically, for example, substances constituting the above-described electron transport layer 118 (such as metal complexes and heteroaromatic compounds) can be used. Any material that exhibits electron donating properties with respect to the organic compound can be used as the electron donor. Specifically, alkali metals, alkaline earth metals, and rare earth metals are preferable, and examples include lithium, sodium, cesium, magnesium, calcium, erbium, ytterbium, etc. Also, alkali metal oxides and alkaline earth metal oxides are preferable, and examples include lithium oxide, calcium oxide, barium oxide, etc. Also, Lewis bases such as magnesium oxide can be used. Also, organic compounds such as tetrathiafulvalene (abbreviation: TTF) can be used.

[0170] Note that the above-described light-emitting layer, hole injection layer, hole transport layer, electron transport layer, and electron injection layer can each be formed by methods such as vapor deposition (including vacuum vapor deposition), inkjet printing, coating, gravure printing, etc. Further, in addition to the above-described materials, inorganic compounds such as quantum dots and polymer compounds (oligomers, dendrimers, polymers, etc.) may be used for the above-described light-emitting layer, hole injection layer, hole transport layer, electron transport layer, and electron injection layer.

[0171] ≪Quantum Dots≫ Quantum dots are semiconductor nanocrystals with sizes ranging from several nm to several tens of nm, and are composed of about 1×10 3 atoms to 1×10 6 atoms. Since quantum dots exhibit energy shifts depending on their size, even quantum dots composed of the same substance have different emission wavelengths depending on their size. Therefore, the emission wavelength can be easily changed by changing the size of the quantum dots used.

[0172] In addition, since quantum dots have a narrow peak width in their emission spectrum, light emission with good color purity can be obtained. Furthermore, the theoretical internal quantum efficiency of quantum dots is said to be approximately 100%, which is much higher than 25% of organic compounds that exhibit fluorescence emission and is equivalent to that of organic compounds that exhibit phosphorescence emission. Therefore, by using quantum dots as a light-emitting material, a light-emitting device with high luminous efficiency can be obtained. Moreover, since quantum dots, which are inorganic materials, are also excellent in their inherent stability, a light-emitting device that is preferable from the perspective of lifespan can be obtained.

[0173] Examples of materials constituting quantum dots include group 14 elements, group 15 elements, group 16 elements, compounds composed of a plurality of group 14 elements, compounds of elements belonging to groups 4 to 14 and group 16 elements, compounds of group 2 elements and group 16 elements, compounds of group 13 elements and group 15 elements, compounds of group 13 elements and group 17 elements, compounds of group 14 elements and group 15 elements, compounds of group 11 elements and group 17 elements, iron oxides, titanium oxides, chalcogenide spinels, semiconductor clusters, and the like.

[0174] Specifically, cadmium selenide, cadmium sulfide, cadmium telluride, zinc selenide, zinc oxide, zinc sulfide, zinc telluride, mercury sulfide, mercury selenide, mercury telluride, indium arsenide, indium phosphide, gallium arsenide, gallium phosphide, indium nitride, gallium nitride, indium antimonide, gallium antimonide, aluminum phosphide, aluminum arsenide, aluminum antimonide, lead selenide, lead telluride, lead sulfide, indium selenide, indium telluride, indium sulfide, gallium selenide, arsenic sulfide, arsenic selenide, arsenic telluride, antimony sulfide, antimony selenide, antimony telluride, bismuth sulfide, bismuth selenide, bismuth telluride, silicon, silicon carbide, germanium, tin, selenium, tellurium, boron, carbon, phosphorus, boron nitride, boron phosphide, boron arsenide, aluminum nitride, aluminum sulfide, barium sulfide, barium selenide, barium telluride, calcium sulfide, calcium selenide, calcium telluride, beryllium sulfide, beryllium selenide, beryllium telluride, magnesium sulfide, magnesium selenide, germanium sulfide, germanium selenide, germanium telluride, tin sulfide, tin selenide, tin telluride, lead oxide, copper fluoride, copper chloride, copper bromide, copper iodide, copper oxide, copper selenide, nickel oxide, cobalt oxide, cobalt sulfide, iron oxide, iron sulfide, manganese oxide, molybdenum sulfide, vanadium oxide, tungsten oxide, tantalum oxide, titanium oxide, zirconium oxide, silicon nitride, germanium nitride, aluminum oxide, barium titanate, a compound of selenium, zinc, and cadmium, a compound of indium, arsenic, and phosphorus, a compound of cadmium, selenium, and sulfur, a compound of cadmium, selenium, and tellurium, a compound of indium, gallium, and arsenic, a compound of indium, gallium, and selenium, a compound of indium, selenium, and sulfur, a compound of copper, indium, and sulfur, and combinations thereof, etc. can be mentioned, but not limited thereto. Also, so-called alloy-type quantum dots whose composition is represented by an arbitrary ratio may be used. For example, alloy-type quantum dots of cadmium, selenium, and sulfur can change the emission wavelength by changing the content ratio of the elements, so it is one of the effective means to obtain blue light emission.

[0175] As the structure of quantum dots, there are core type, core-shell type, core-multi-shell type, etc., and any of them can be used. However, by forming a shell with another inorganic material having a wider bandgap covering the core, the influence of defects and dangling bonds existing on the nanocrystal surface can be reduced. As a result, it is preferable to use core-shell type or core-multi-shell type quantum dots because the quantum efficiency of light emission is greatly improved. Examples of the shell material include zinc sulfide and zinc oxide.

[0176] In addition, since quantum dots have a high proportion of surface atoms, they are highly reactive and prone to aggregation. Therefore, it is preferable that a protective agent is attached to or a protecting group is provided on the surface of the quantum dots. By attaching the protective agent or providing the protecting group, aggregation can be prevented and the solubility in a solvent can be increased. It is also possible to reduce the reactivity and improve the electrical stability. Examples of the protective agent (or protecting group) include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, and polyoxyethylene oleyl ether; trialkylphosphines such as tripropylphosphine, tributylphosphine, trihexylphosphine, and trioctylphosphine; polyoxyethylene alkylphenyl ethers such as polyoxyethylene n-octylphenyl ether and polyoxyethylene n-nonylphenyl ether; tertiary amines such as tri(n-hexyl)amine, tri(n-octyl)amine, and tri(n-decyl)amine; organophosphorus compounds such as tripropylphosphine oxide, tributylphosphine oxide, trihexylphosphine oxide, trioctylphosphine oxide, and tridecylphosphine oxide; polyethylene glycol diesters such as polyethylene glycol dilaurate and polyethylene glycol distearate; organic nitrogen compounds such as nitrogen-containing aromatic compounds such as pyridine, lutidine, collidine, and quinoline; aminoalkanes such as hexylamine, octylamine, decylamine, dodecylamine, tetradecylamine, hexadecylamine, and octadecylamine; dialkyl sulfides such as dibutyl sulfide; dialkyl sulfoxides such as dimethyl sulfoxide and dibutyl sulfoxide; organic sulfur compounds such as sulfur-containing aromatic compounds such as thiophene; higher fatty acids such as palmitic acid, stearic acid, and oleic acid; alcohols; sorbitan fatty acid esters; fatty acid-modified polyesters; tertiary amine-modified polyurethanes; and polyethyleneimines, etc.

[0177] Since the bandgap of quantum dots increases as their size decreases, their size is appropriately adjusted so that light of a desired wavelength can be obtained. As the size of the crystal decreases, the emission of the quantum dots shifts towards the blue side, i.e., towards the high-energy side. Therefore, by changing the size of the quantum dots, the emission wavelength can be adjusted over the wavelength regions of the spectra in the ultraviolet, visible, and infrared regions. The size (diameter) of the quantum dots is usually preferably in the range of 0.5 nm to 20 nm, more preferably 1 nm to 10 nm. Note that the narrower the size distribution of the quantum dots, the narrower the emission spectrum and the better the color purity of the emission can be obtained. Also, the shape of the quantum dots is not particularly limited and may be spherical, rod-shaped, disk-shaped, or other shapes. Note that quantum rods, which are rod-shaped quantum dots, have the function of exhibiting light with directivity. Therefore, by using quantum rods as the light-emitting material, a light-emitting device with better external quantum efficiency can be obtained.

[0178] By the way, in many cases in organic EL devices, the light-emitting material is dispersed in the host material to suppress concentration quenching of the light-emitting material and thereby increase the light-emitting efficiency. The host material needs to be a material having a singlet excitation energy level or a triplet excitation energy level higher than that of the light-emitting material. In particular, when a blue phosphorescent material is used as the light-emitting material, a host material having a triplet excitation energy level higher than that and excellent in terms of lifetime is required, and its development is extremely difficult. Here, since quantum dots can maintain the light-emitting efficiency even when forming a light-emitting layer only with quantum dots without using a host material, a preferable light-emitting device can be obtained also from the viewpoint of lifetime in this regard. When forming a light-emitting layer only with quantum dots, the quantum dots preferably have a core-shell structure (including a core-multishell structure).

[0179] When a quantum dot is used as the light-emitting material of the light-emitting layer, the film thickness of the light-emitting layer is 3 nm to 100 nm, preferably 10 nm to 100 nm, and the content of the quantum dot in the light-emitting layer is 1 to 100% by volume. However, it is preferable to form the light-emitting layer only with quantum dots. When forming a light-emitting layer in which the quantum dots are dispersed in a host as a light-emitting material, the quantum dots are dispersed in the host material, or the host material and the quantum dots are dissolved or dispersed in an appropriate liquid medium and formed by a wet process (spin coating method, casting method, die coating method, blade coating method, roll coating method, inkjet method, printing method, spray coating method, curtain coating method, Langmuir-Blodgett method, etc.). For a light-emitting layer using a phosphorescent light-emitting material, in addition to the above wet process, a vacuum evaporation method can also be preferably used.

[0180] As the liquid medium used in the wet process, for example, ketones such as methyl ethyl ketone and cyclohexanone, fatty acid esters such as ethyl acetate, halogenated hydrocarbons such as dichlorobenzene, aromatic hydrocarbons such as toluene, xylene, mesitylene, and cyclohexylbenzene, aliphatic hydrocarbons such as cyclohexane, decalin, and dodecane, and organic solvents such as dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) can be used.

[0181] ≪A pair of electrodes≫ The electrode 101 and the electrode 102 have functions as an anode or a cathode of the light-emitting element. The electrode 101 and the electrode 102 can be formed using metals, alloys, conductive compounds, and mixtures or laminates thereof.

[0182] Preferably, one of the electrode 101 or the electrode 102 is formed of a conductive material having a function of reflecting light. Examples of the conductive material include aluminum (Al) or an alloy containing Al. Examples of the alloy containing Al include an alloy containing Al and L (L represents one or more of titanium (Ti), neodymium (Nd), nickel (Ni), and lanthanum (La)), such as an alloy containing Al and Ti, or an alloy containing Al, Ni, and La. Aluminum has a low resistance value and a high light reflectance. In addition, since aluminum is abundant in the earth's crust and inexpensive, the manufacturing cost of the light-emitting element can be reduced by using aluminum. Further, silver (Ag) or an alloy containing Ag and N (N represents 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 the alloy containing silver include an alloy containing silver, palladium, and copper, an alloy containing silver and copper, an alloy containing silver and magnesium, an alloy containing silver and nickel, an alloy containing silver and gold, an alloy containing silver and ytterbium, and the like. In addition, transition metals such as W, chromium (Cr), molybdenum (Mo), Cu, and Ti can be used.

[0183] In addition, the light emitted from the light-emitting layer is extracted through one or both of the electrode 101 and the electrode 102. Therefore, preferably, at least one of the electrode 101 or the electrode 102 is formed of a conductive material having a function of transmitting light. The conductive material has a visible light transmittance of 40% or more and 100% or less, preferably 60% or more and 100% or less, and a resistivity of 1×10 -2 Ω·cm or less.

[0184] In addition, the electrodes 101 and 102 may be formed of a conductive material having a function of transmitting light and a function of reflecting light. As the conductive material, the reflectance of visible light is 20% or more and 80% or less, preferably 40% or more and 70% or less, and its resistivity is 1×10 -2 Ω·cm or less. For example, it can be formed by using one or more of a conductive metal, alloy, conductive compound, etc. Specifically, for example, indium tin oxide (Indium Tin Oxide, hereinafter referred to as ITO), indium tin oxide containing silicon or silicon oxide (abbreviation: ITSO), indium zinc oxide, indium tin oxide containing titanium, indium titanate, and metal oxides such as indium oxide containing tungsten oxide and zinc oxide can be used. Also, a metal thin film having a degree of transmitting light (preferably having a thickness of 1 nm or more and 30 nm or less) can be used. As the metal, for example, Ag, or an alloy such as Ag and Al, Ag and Mg, Ag and Au, Ag and Yb, etc. can be used.

[0185] In the present specification, etc., the material having a function of transmitting light may be a material having a function of transmitting visible light and having conductivity. For example, in addition to the oxide conductor typified by ITO as described above, it includes an oxide semiconductor or an organic conductor containing an organic substance. Examples of the organic conductor containing an organic substance include a composite material formed by mixing an organic compound and an electron donor, and a composite material formed by mixing an organic compound and an electron acceptor. Also, an inorganic carbon-based material such as graphene may be used. Also, the resistivity of the material is preferably 1×10 5 Ω·cm or less, more preferably 1×10 4 Ω·cm or less.

[0186] Also, one or both of the electrodes 101 and 102 may be formed by laminating a plurality of the above materials.

[0187] In addition, in order to improve the light extraction efficiency, a material having a higher refractive index than that of the electrode may be formed in contact with an electrode having a function of transmitting light. Such a material may be any material having a function of transmitting visible light, and may or may not be a conductive material. For example, in addition to the above-described oxide conductors, oxide semiconductors and organic substances can be mentioned. Examples of the organic substance include the materials exemplified for the light emitting layer, the hole injection layer, the hole transport layer, the electron transport layer, or the electron injection layer. Further, inorganic carbon-based materials and metal thin films through which light can pass can also be used, and a plurality of layers having a thickness of several nm to several tens of nm may be laminated.

[0188] When the electrode 101 or the electrode 102 has a function as a cathode, it preferably has a material having a small work function (3.8 eV or less). For example, elements belonging to Group 1 or Group 2 of the periodic table (alkali metals such as lithium, sodium, and cesium, alkaline earth metals such as calcium and strontium, magnesium, etc.), alloys containing these elements (for example, Ag and Mg, Al and Li), rare earth metals such as europium (Eu) and Yb, alloys containing these rare earth metals, aluminum, alloys containing silver, etc. can be used.

[0189] When the electrode 101 or the electrode 102 is used as an anode, it is preferable to use a material having a large work function (4.0 eV or more).

[0190] The electrodes 101 and 102 may be a laminate of a conductive material having a function of reflecting light and a conductive material having a function of transmitting light. In that case, the electrodes 101 and 102 are preferable because they can have a function of adjusting the optical distance so as to resonate light having a desired wavelength from each light emitting layer and enhance the light having the desired wavelength.

[0191] As the film forming method of the electrodes 101 and 102, a sputtering method, an evaporation method, a printing method, a coating method, an MBE (Molecular Beam Epitaxy) method, a CVD method, a pulsed laser deposition method, an ALD (Atomic Layer Deposition) method, etc. can be appropriately used.

[0192] <<Substrate>> In addition, the light-emitting element according to one aspect of the present invention may be manufactured on a substrate made of glass, plastic, or the like. As for the order of manufacturing on the substrate, it may be laminated in order from the electrode 101 side or in order from the electrode 102 side.

[0193] Note that, as the substrate on which the light-emitting element according to one aspect of the present invention can be formed, for example, glass, quartz, plastic, or the like can be used. A flexible substrate may also be used. A flexible substrate is a substrate that can be bent (flexible), and examples thereof include plastic substrates made of polycarbonate and polyarylate. In addition, a film, an inorganic vapor deposition film, or the like can also be used. Note that, as long as it functions as a support in the manufacturing process of the light-emitting element and the optical element, other materials may be used. Alternatively, as long as it has a function of protecting the light-emitting element and the optical element, it may be used.

[0194] For example, in the present invention and the like, light-emitting elements can be formed using various substrates. The type of the substrate is not particularly limited. As an example of the substrate, a semiconductor substrate (e.g., a single-crystalline substrate or a silicon substrate), an SOI substrate, a glass substrate, a quartz substrate, a plastic substrate, a metal substrate, a stainless steel substrate, a substrate having a stainless steel foil, a tungsten substrate, a substrate having a tungsten foil, a flexible substrate, a laminated film, paper containing a fibrous material, or a base film, etc. are available. As an example of the glass substrate, there are barium borosilicate glass, aluminoborosilicate glass, or soda lime glass, etc. Examples of the flexible substrate, the laminated film, the base film, etc. include the following. For example, there are plastics typified by polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), and polytetrafluoroethylene (PTFE). Or, as an example, there are resins such as acrylic. Or, as an example, there are polypropylene, polyester, polyvinyl fluoride, or polyvinyl chloride, etc. Or, as an example, there are polyamide, polyimide, aramid, epoxy, an inorganic vapor deposition film, or papers, etc.

[0195] Further, as the substrate, a flexible substrate may be used, and a light-emitting element may be directly formed on the flexible substrate. Or, a release layer may be provided between the substrate and the light-emitting element. The release layer can be used to separate from the substrate after partially or completely completing the light-emitting element thereon and transfer it to another substrate. At that time, the light-emitting element can also be transferred to a substrate with poor heat resistance or a flexible substrate. Note that, for the above-mentioned release layer, for example, a configuration of a laminated structure of inorganic films of a tungsten film and a silicon oxide film, a configuration in which a resin film such as polyimide is formed on the substrate, etc. can be used.

[0196] That is, a light-emitting element may be formed using a certain substrate, and then the light-emitting element may be transferred to another substrate and disposed on the other substrate. As an example of the substrate to which the light-emitting element is transferred, in addition to the substrates described above, there are cellophane substrates, stone substrates, wood substrates, cloth substrates (including natural fibers (silk, cotton, linen), synthetic fibers (nylon, polyurethane, polyester), or recycled fibers (acetate, cupra, rayon, recycled polyester), etc.), leather substrates, or rubber substrates. By using these substrates, a light-emitting element that is difficult to break, a light-emitting element with high heat resistance, a light-emitting element with reduced weight, or a light-emitting element with reduced thickness can be obtained.

[0197] Further, for example, a field-effect transistor (FET) may be formed on the above-described substrate, and a light-emitting element 150 may be fabricated on an electrode electrically connected to the FET. Thereby, an active matrix type display device that controls the driving of the light-emitting element 150 by the FET can be fabricated.

[0198] The components of a solar cell, which is an example of an electronic device according to an aspect of the present invention, will be described below.

[0199] The materials that can be used for the above-described light-emitting element can be applied to the solar cell. The hole-transporting material and the electron-transporting material described above can be used for the carrier transport layer of the solar cell, and the hole-transporting material and the electron-transporting material described above, the light-emitting material, silicon, and perovskite crystals represented by CH3NH3PbI3 can be used for the photoactive layer. Also, regarding the substrate and the electrode, the materials that can be used for the above-described light-emitting element can be applied.

[0200] As described above, the configurations shown in the present embodiment can be used in appropriate combination with other embodiments.

[0201] (Embodiment 2) FIG. 35(A) shows a light-emitting element according to an aspect of the present invention. The light-emitting element according to an aspect of the present invention has an anode 310, a cathode 311, and an EL layer 312 containing an organic compound sandwiched therebetween.

[0202] The EL layer 312 has a light-emitting layer 314 and a first layer 313. The light-emitting layer 314 is a layer responsible for the light-emitting function in the light-emitting element, and the light-emitting element mainly obtains light emission from the light-emitting layer 314. Further, the first layer 313 is a layer containing an organic compound and an inorganic compound.

[0203] The organic compound in the first layer 313 is preferably an organic compound having electron-transporting properties, and the inorganic compound is preferably a layer containing a fluoride of an alkali metal or a fluoride of an alkaline earth metal.

[0204] Here, the refractive index of an organic compound having good carrier-transporting properties used in an organic electronic device is about 1.7. Since the refractive index of a fluoride of an alkali metal or a fluoride of an alkaline earth metal is about 1.35, the first layer 313 containing an organic compound and a fluoride of an alkali metal or a fluoride of an alkaline earth metal can be a layer having a lower refractive index compared to a layer using a material used in a normal light-emitting element.

[0205] FIG. 36 is a graph showing the refractive index of a mixed film composed of BPhen and lithium fluoride. In this graph, the horizontal axis represents the concentration of BPhen. The rightmost plot represents the refractive index of BPhen itself, and the leftmost plot represents the refractive index of lithium fluoride itself. From FIG. 36, although there are differences at each wavelength, since the refractive index of the film changes according to the content ratio of lithium fluoride and BPhen, it can be seen that the first layer 313 containing a fluoride of an alkali metal or a fluoride of an alkaline earth metal as described above is a layer having a lower refractive index compared to a layer using a material used in a normal light-emitting element.

[0206] Thus, according to one aspect of the present invention, it becomes possible to provide a layer with a low refractive index between the light-emitting layer and the cathode. By providing a layer with a low refractive index inside the light-emitting element, as described in Non-Patent Document 1, the luminous efficiency of the light-emitting element can be improved. The reason for the efficiency improvement is considered to be due to the suppression of the thin-film mode and the surface plasmon polariton mode. Therefore, by providing the first layer 313 with a low refractive index inside the light-emitting element as in one aspect of the present invention, the light-emitting element of one aspect of the present invention can be a light-emitting element with good luminous efficiency.

[0207] In addition, if the content of the fluoride of an alkali metal or the fluoride of an alkaline earth metal in the first layer 313 is greater than 0 vol%, the refractive index of the first layer 313 becomes lower compared to the case where it is composed only of an organic compound, so the light-emitting element has improved luminous efficiency. And as described above, since the refractive index decreases as the content of the fluoride in the first layer 313 increases, the luminous efficiency of the light-emitting element improves. However, as a result of the study by the present inventors, it was found that when the lithium fluoride content exceeds 95 vol%, the efficiency decreases significantly (see Fig. 37). For this reason, the content of the fluoride of an alkali metal or the fluoride of an alkaline earth metal in the first layer 313 is preferably less than 95 vol%.

[0208] Also, it was found that in a light-emitting element where the content of the fluoride of an alkali metal or the fluoride of an alkaline earth metal in the first layer 313 is 0 vol% or more and less than 50 vol%, the current amount at the same voltage tends to decrease as the content of the fluoride increases (see Fig. 38). That is, in this concentration range, the driving voltage of the light-emitting element increases. However, surprisingly, as a result of the study by the present inventor, it was found that when the fluoride content exceeds 50 vol%, the current amount at the same voltage tends to increase as the fluoride content increases. As a result, since the driving voltage also decreases in the region where the fluoride content is 50 vol% or more, the content of the fluoride of an alkali metal or the fluoride of an alkaline earth metal in the first layer 313 is preferably 50 vol% or more.

[0209] As will be described later, the content of 50 vol% of this lithium fluoride is the concentration at which the fluoride of an alkali metal or the fluoride of an alkaline earth metal starts to crystallize in the first layer 313. That is, the decrease in the driving voltage accompanying this increase in the current amount is considered to be related to the increase in the content of the fluoride of an alkali metal or the fluoride of an alkaline earth metal in the first layer 313 and the crystallization. It is also known that the fluoride of an alkali metal or the fluoride of an alkaline earth metal contained in the first layer 313 at a content of 50 vol% or more exists in a microcrystalline state in the layer.

[0210] From the above, in one aspect of the present invention, the content of the fluoride of an alkali metal or the fluoride of an alkaline earth metal in the first layer 313 is preferably 50 vol% or more and less than 95 vol%. Note that 60 vol% or more and 80 vol% or less is more preferable for the driving voltage to be better, and since the characteristics are best at 75 vol%, it is even more preferable to be 70 vol% or more and 80 vol% or less.

[0211] As described above, in one aspect of the present invention, the content of the fluoride of an alkali metal or the fluoride of an alkaline earth metal in the first layer 313 is preferably 50 vol% or more. However, conventionally, in the materials used as the electron injection layer and the electron transport layer, a configuration in which a large amount of the fluoride of an alkali metal or the fluoride of an alkaline earth metal is contained as in one aspect of the present invention has not been studied. This is presumably because the fluoride of an alkali metal or the fluoride of an alkaline earth metal is inherently insulating, so the deterioration of the characteristics was considered inevitable. In fact, the deterioration of the driving voltage as expected in the region where the content of the fluoride is less than 50 vol% is also considered to be a major inhibiting factor. However, in such a situation, one aspect of the present invention is very epoch-making in that the driving voltage characteristics are conversely improved in the region of 50 vol% or more, realizing a light-emitting element with good driving voltage and improved efficiency by providing a layer with a low refractive index.

[0212] Note that the organic compound used for the first layer 313 is preferably an organic compound having electron transporting properties, and the first layer 313 is preferably provided between the light emitting layer 314 and the cathode 311. Further, the first layer 313 can function as part of an electron transport layer. In particular, a first layer containing an electron transporting organic compound and a fluoride of an alkali metal or a fluoride of an alkaline earth metal and having a fluoride content of 50 vol% or more contains microcrystals of the fluoride and has high electron transporting properties. Therefore, using such a first layer 313 as part or all of the electron transport layer is a preferable configuration because a decrease in driving voltage can be expected. Further, since the first layer 313 exhibits good characteristics even when in direct contact with the cathode 311, it can also serve as an electron injection layer. By the first layer 313 also serving as an electron transport layer, the number of layers constituting the light emitting device can be reduced, and this configuration is advantageous in terms of cost.

[0213] Further, the organic compound having electron transporting properties is preferably a π-electron deficient heteroaromatic compound, and among them, an organic compound having a bipyridine skeleton such as a phenanthroline skeleton is preferable. Specifically, bathophenanthroline (abbreviation: BPhen) and 2,9-bis(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline (abbreviation: NBPhen) are preferable, and NBPhen, which exhibits a particularly high glass transition point (Tg) and high heat resistance, is suitable.

[0214] Here, FIG. 39 shows the results of analysis by energy dispersive X-ray spectroscopy (EDX) using a scanning transmission electron microscope (HD-2700) manufactured by Hitachi High-Technologies Corporation for the portion corresponding to the first layer 313 in the light emitting device having the configuration of one embodiment of the present invention. In the EDX measurement, an electron beam is irradiated onto each point in the analysis target region of the sample, and the energy and the number of occurrences of characteristic X-rays of the sample generated thereby are measured to obtain an EDX spectrum corresponding to each point. In the present embodiment, elements were identified from the peak energies of the EDX spectra of each point, and the element concentration ratios were calculated from the peak intensity ratios using the software attached to the HD-2700.

[0215] The first layer 313 in the light-emitting element used as a sample is a film containing BPhen represented by the following structural formula and lithium fluoride, and the content of lithium fluoride was set to 75 vol%.

[0216]

Chemical formula

[0217] Table 11 shows the abundance ratio of each atom calculated from the spectral peak in FIG. 39.

[0218]

Table 11

[0219] From FIG. 39 and Table 11, it is clear that the number of fluorine atoms in this layer is much larger than the number of nitrogen atoms, and it was detected more than three times the intensity of nitrogen. Also, the inclusion of lithium fluoride in this film can be confirmed by TOF-SIMS, TEM-EELS, XPS, etc. The film and the light-emitting element of one aspect of the present invention show characteristic measurement results by the above-described analysis. Although there are substances containing a large amount of fluorine as some organic compounds, since it can be confirmed by TOF-SIMS, TEM-EELS, XPS even in the presence of such organic compounds, it is possible to distinguish from the results of the present invention.

[0220] Subsequently, the results of performing selected area electron diffraction analysis on a light-emitting element of one aspect of the present invention are shown. The figure shown in FIG. 40 is a cross-sectional transmission electron microscope (TEM) photograph of a light-emitting element of one aspect of the present invention, and the four circles shown in the figure are the locations where the selected area electron diffraction analysis was performed. The cross-sectional transmission electron microscope (TEM) observation and the selected area electron diffraction analysis were performed using an H-9000NAR manufactured by Hitachi High-Technologies Corporation.

[0221] The results of the selected area electron diffraction analysis of each measurement location are shown below in Fig. 40, corresponding to the photos with the same reference signs in the TEM photo above Fig. 40. The first layer 313 is a layer composed of BPhen and lithium fluoride, and a sample with a lithium fluoride content of 75 vol% was used in the first layer 313.

[0222] From the upper figure of Fig. 40, it can be seen that the measurement locations containing the first layer 313 are *1 and *2, and *3 and *4 are measurement locations that do not contain the first layer 313. However, particulate bright spots in the ring-shaped pattern were only observed at *1 and *2 in the lower figure. This pattern suggests that there are crystals with different orientations in the layer. Note that they do not exist at *3 and *4, and a halo pattern indicating amorphous and spots derived from aluminum used for the cathode appeared. Thus, it was found that the first layer 313 is highly likely to contain microcrystals.

[0223] Also, the same analysis was performed on a light-emitting device using calcium fluoride instead of lithium fluoride. The first layer 313 in the TEM photo above Fig. 41 is a layer composed of BPhen and calcium fluoride, and the calcium fluoride content in the first layer 313 is 75 vol%. Also, the three circles shown in the TEM photo are the locations where the selected area electron diffraction analysis was performed.

[0224] From the upper figure of Fig. 41, it can be seen that the measurement locations containing the first layer 313 are *1 and *2, and *3 is a measurement location that does not contain the first layer 313. However, particulate bright spots were only observed at *1 and *2 in the lower figure in the ring-shaped pattern. This pattern suggests that there are crystals with different orientations in the layer. Note that they do not exist at *3, and only a halo pattern indicating amorphous appeared. Thus, it was found that the first layer 313 is highly likely to contain microcrystals.

[0225] Subsequently, when this sample was observed by high-magnification TEM, lattice fringes were confirmed (Fig. 42). In Fig. 42, lattice fringes indicating crystallization were confirmed at a size of about 10 nm. Also, the orientation of the lines of the lattice fringes was random. From this result, it can be seen that in the first layer 313 composed of BPhen and calcium fluoride, microcrystals with random crystal orientations are formed.

[0226] Here, the results of performing the attenuated total reflection (ATR) method in Fourier transform infrared spectroscopy (FT-IR) on the mixed film of BPhen and lithium fluoride are shown in Figs. 43(A) to (C). The FT-IR measurement was performed using a Nicolet iS50 Analytical manufactured by Thermo Fisher Scientific. As the measurement sample, a vapor deposition film formed to about 50 nm on a quartz substrate was adopted.

[0227] In this measurement, a mixed film of BPhen and lithium fluoride was measured, and a plurality of samples of films with different mixing ratios were used. Fig. 43(B) shows the range from 1300 cm -1 to 1700 cm -1 in Fig. 43(A), and Fig. 43(C) is a graph showing an enlarged view of the range from 400 cm -1 to 800 cm -1 . The absorption in the range from 1400 cm -1 to 1700 cm -1 is mainly the absorption derived from BPhen, and the absorption in the range from 500 cm -1 to 700 cm -1 having a peak at 650 cm -1 is mainly the absorption derived from the vibration of lithium fluoride.

[0228] The absorption derived from BPhen in the range from 1400 cm -1 to 1700 cm -1 tended to increase as the content rate of BPhen increased. On the other hand, the absorption in the range from 500 cm -1 to 700 cm -1The absorption derived from lithium fluoride hardly changed until the lithium fluoride content reached about 50 vol%, and tended to increase when it exceeded that level.

[0229] Figure 44 shows the result of plotting the relationship between the BPhen ratio and the absorbance at 1491 cm -1 and 644 cm -1 From Figure 44, the absorption derived from BPhen having a peak at 1491 cm -1 increases as the BPhen concentration increases, while the absorption intensity having a peak at 644 cm -1 does not increase at low lithium fluoride concentrations and becomes more clearly evident that it begins to increase from around 50 vol%. The IR absorption of lithium fluoride having a peak at 644 cm -1 is due to the longitudinal optical lattice vibration of the lithium fluoride crystal, so it was found that lithium fluoride begins to crystallize when the content exceeds 50 vol%, and the amount of crystallized parts increases as the concentration increases.

[0230] That is, considering together with the results of the above-mentioned selected area electron diffraction analysis, it can be said that the first layer 313 with a lithium fluoride content of 50 vol% or more is a layer having lithium fluoride microcrystals. Also, from these results and the results of Figure 38 (when the lithium fluoride content is increased, the current decreases and the driving voltage increases, but when it exceeds 50 vol%, the current turns to increase and the driving voltage decreases), it is considered that the driving voltage of the light-emitting element decreases with the crystallization of the first layer 313.

[0231] Thus, a light-emitting element having the first layer 313 containing an organic compound and a fluoride of an alkali metal or a fluoride of an alkaline earth metal can obtain a light-emitting element with a low driving voltage because the first layer 313 contains microcrystals of a fluoride of an alkali metal or a fluoride of an alkaline earth metal which is an inorganic compound.

[0232] In addition, salts of alkali metals or alkaline earth metals such as fluorides of alkali metals or fluorides of alkaline earth metals are inexpensive, and thus, a light-emitting device using an electron transport layer containing more than half of them can be an inexpensive light-emitting device, which is advantageous in terms of cost.

[0233] Note that an important point of the present invention is that even if the first layer 313 as described above is installed in the device, it can be formed without significantly affecting the characteristics of the light-emitting device.

[0234] Normally, a low refractive index, high carrier transportability, and reliability when used in a light-emitting device are in a trade-off relationship. This is because the carrier transportability and reliability in organic compounds are largely derived from the presence of unsaturated bonds, and organic compounds having many unsaturated bonds tend to have a high refractive index.

[0235] The refractive index of a certain material is represented by the square root of (με / μ o ε o ε), where μ is the magnetic permeability of the material, ε is the dielectric constant of the material, μ0 is the magnetic permeability of vacuum, and ε0 is the dielectric constant of vacuum. The larger the non-dielectric constant, the easier it is for the refractive index to increase. In organic compounds, substances with many unsaturated bonds tend to have a large dielectric constant because the movement of charges within the molecule is easier, and as a result, the presence of unsaturated bonds becomes a factor that increases the refractive index.

[0236] Here, organic compounds exhibiting high carrier transportability are unsaturated hydrocarbons having a wide π-conjugated system, and it is known that organic compounds that can provide high reliability when used as materials for light-emitting devices are unsaturated hydrocarbons having a rigid structure due to unsaturated bonds and having a high Tg. Therefore, if an organic compound with fewer unsaturated bonds is selected to form a layer with a small refractive index, it is likely to cause an increase in the driving voltage due to poor carrier transportability of the organic compound and a decrease in reliability due to the lack of a rigid structure. Therefore, it has been very difficult to form a layer with a small refractive index in a light-emitting device using organic materials without strongly sacrificing the device characteristics.

[0237] In one aspect of the present invention, an organic compound containing a fluoride of an alkali metal and a fluoride of an alkaline earth metal at a high content that has not been conventionally used is utilized as the first layer 313. As a result, effects such as improved luminous efficiency, reduced driving voltage, and low-cost fabrication can be obtained.

[0238] Subsequently, the materials that can be used for the first layer 313 will be specifically described. As described above, the first layer 313 is a layer containing an organic compound and an inorganic compound.

[0239] The inorganic compound is a salt of an alkali metal or a salt of an alkaline earth metal, preferably a fluoride of an alkali metal or a fluoride of an alkaline earth metal. As the fluoride of an alkali metal, lithium fluoride is preferable. As the fluoride of an alkaline earth metal, calcium fluoride or magnesium fluoride is preferable.

[0240] As the organic compound, an organic compound having electron transporting properties, particularly an organic compound having an electron mobility of 10 -6 cm 2 / Vs or more is preferable. Also, it is preferably a π-electron deficient heteroaromatic compound. Examples of materials having electron transporting properties include the above-described metal complexes and heterocyclic compounds having an azole skeleton, a diazine skeleton, or a pyridine skeleton. Among them, BPhen and NBPhen having a bipyridine skeleton such as a phenanthroline skeleton are preferable, and particularly NBPhen is suitable.

[0241] As described above, in the light-emitting device of one aspect of the present invention, the refractive index of the first layer 313 can be made to decrease more than the refractive index of the surrounding materials, and in a light-emitting device in which the concentration of the fluoride of the alkali metal or alkaline earth metal is greater than 0 vol% and less than 95 vol%, the luminous efficiency of the light-emitting device can be improved. Further, the first layer 313 containing 50 vol% or more of a salt of an alkali metal or an alkaline earth metal can be made into a light-emitting device with an improved driving voltage.

[0242] <Configuration Example of Light-Emitting Element> FIG. 35(B) is a diagram showing a light-emitting element according to an aspect of the present invention. The light-emitting element according to an aspect of the present invention has an anode 401, a cathode 402, and an EL layer 403. The EL layer 403 has a light-emitting layer 413 and a first layer. In FIG. 35(B), the case where the above-mentioned first layer is an electron transport layer is illustrated.

[0243] In FIG. 35(B), the case where the electron transport layer is composed of two layers, a first electron transport layer 414-1 and a second electron transport layer 414-2, is illustrated. The first layer 313 in FIG. 35(A) corresponds to the second electron transport layer 414-2. The first electron transport layer 414-1 is an electron transport layer that does not contain a fluoride of an alkali metal or a fluoride of an alkaline earth metal.

[0244] The EL layer 403 may also have a hole injection layer 411, a hole transport layer 412, an electron injection layer 415, and the like.

[0245] In FIG. 35(B), the configuration of a light-emitting element including a hole injection layer 411, a hole transport layer 412, a light-emitting layer 413, a first electron transport layer 414-1, a second electron transport layer 414-2, and an electron injection layer 415 in this order from the anode 401 side is illustrated. However, the light-emitting element according to an aspect of the present invention may have a structure having other functional layers, or may have a structure that does not have any one or a plurality of layers other than the second electron transport layer 414-2 and the light-emitting layer 413. Note that, as the anode 401, the cathode 402, the hole injection layer 411, the hole transport layer 412, the light-emitting layer 413, the first electron transport layer 414-1, and the electron injection layer 415, the materials exemplified in Embodiment 1 can be used.

[0246] Note that the above configuration can be appropriately combined with other embodiments or other configurations in this embodiment.

[0247] (Embodiment 3) In this embodiment, a configuration in which a low-refractive-index layer is also provided between the light-emitting layer 314 and the anode 310 will be described with reference to FIG. 45. Note that the configuration between the light-emitting layer 314 and the cathode 311 is the same as that in Embodiment 2, and thus the description thereof is omitted. Refer to the description of Embodiment 2. In this embodiment, among the EL layers 312, a second layer 315, which is a low-refractive-index layer, is provided between the anode and the light-emitting layer, and a first layer 313, which is a low-refractive-index layer, is provided between the light-emitting layer and the cathode, whereby a light-emitting element with further improved luminous efficiency can be provided.

[0248] In this embodiment, as shown in FIG. 45, in addition to the first layer 313, which is a low-refractive-index layer, a second layer 315, which is a low-refractive-index layer, is provided between the light-emitting layer 314 and the anode 310. The second layer 315 is a layer containing a first substance, which is a fluorine-containing substance, a second substance, which is a hole-transporting organic compound, and a third substance, which exhibits electron-accepting properties with respect to the second substance. The second layer 315 can be a low-refractive-index layer by containing the first substance containing fluorine.

[0249] Further, since the second layer 315 contains the second substance, which is a hole-transporting organic compound, and the third substance, which exhibits electron-accepting properties with respect to the second substance, the second layer 315 is a layer excellent in hole injection properties and hole transport properties from the electrode.

[0250] The presence of the first substance does not have a great influence on the hole injection properties and hole transport properties brought about by the interaction between the second substance and the third substance. Therefore, the reduction in refractive index by the first substance and the hole injection properties and transport properties of the second layer 315 can be made compatible. Thus, the second layer 315, which is a layer excellent in hole injection properties and hole transport properties, can function as a hole injection layer in contact with the anode.

[0251] Note that depending on the HOMO level of the organic compound selected as the second substance, the driving voltage of the second layer 315 may increase as compared with the film not containing the first substance. In such a case, the influence can be reduced by forming a third layer composed only of the second substance and the third substance and not containing the first substance in contact with the cathode-side surface of the second layer 315. In this case, the second substance and the third substance used for the third layer may be the same as or different from the second substance and the third substance used for the second layer 315.

[0252] Also, since good characteristics can be obtained by the film constituting the second layer 315 having a spin density of 1.0×10 18 spins / cm 3 or more, the spin density of the second layer 315 is preferably 1.0×10 18 spins / cm 3 or more. The spin density can be measured by the ESR method and increases or decreases depending on the content and type of the first to third substances.

[0253] The first substance containing fluorine is preferably an alkali metal fluoride, an alkaline earth metal fluoride, or an alkyl fluoride. In particular, it is preferably any one of lithium fluoride, magnesium fluoride, and calcium fluoride.

[0254] Further, the third substance is preferably any one or more of a transition metal oxide, an oxide of a metal belonging to Groups 4 to 8 in the periodic table, and an organic compound having an electron-withdrawing group. Specifically, examples thereof include titanium oxide, vanadium oxide, tantalum oxide, molybdenum oxide, tungsten oxide, rhenium oxide, ruthenium oxide, chromium oxide, zirconium oxide, hafnium oxide, silver oxide, 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane, chloranil, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene, 1,3,4,5,7,8-hexafluorotetracyano-naphthoquinodimethane, α,α’,α’’-1,2,3-cyclopropanetriylidene tris[4-cyano-2,3,5,6-tetrafluorobenzeneacetonitrile], and the like. Among these, molybdenum oxide is particularly preferable because it has excellent electron-accepting properties and high stability.

[0255] As the second substance which is an organic compound having hole-transporting properties, the substances listed as organic compounds having hole-transporting properties in Embodiment 1 can be used, but it is preferably a π-electron-excessive heteroaromatic compound or an aromatic amine compound. In particular, when the HOMO level is -5.7 eV or higher, more preferably -5.5 eV, a light-emitting device having no increase in driving voltage and better characteristics can be obtained.

[0256] Although the refractive index of the second layer 315 can be changed depending on the content of the first substance, it is preferable that the refractive index of the second layer 315 is 1.70 or less because the effect of improving the light-emitting efficiency is high. It is one of the features of this configuration that even if the content of the first substance in the second layer 315 is larger than that of the second substance or the first substance, it does not significantly affect the characteristics of the light-emitting device, and the refractive index of the layer can be greatly decreased.

[0257] In addition, when the second layer 315 is in contact with the light-emitting layer 314, it may be quenched. Therefore, it is preferable that a hole-transporting layer exists between the second layer 315 and the light-emitting layer 314.

[0258] Also, the second layer 315 is preferably disposed within a range of an optical distance of approximately 1 / 4λ from the interface on the anode side of the light-emitting layer. On the other hand, the interface between the second layer 315 and the anode is preferably disposed so as to be approximately 1 / 4λ from the center of the light-emitting layer.

[0259] The light-emitting device having such a configuration can be a very efficient light-emitting device due to the effects of the first layer 313 and the second layer 315, which are low-refractive-index layers present on the anode side and the cathode side.

[0260] (Embodiment 4) In this embodiment, a light-emitting device having a configuration different from that of the light-emitting device shown in Embodiment 1 and the light-emitting mechanism of the light-emitting device will be described below with reference to FIGS. 4 and 5. In FIGS. 4 and 5, portions having the same functions as those denoted by the reference numerals shown in FIG. 1(A) may be given the same hatching patterns and the reference numerals may be omitted. Also, portions having the same functions may be denoted by the same reference numerals, and detailed descriptions thereof may be omitted.

[0261] <Example configuration 1 of the light-emitting device> FIG. 4(A) is a schematic cross-sectional view of a light-emitting device 250.

[0262] The light-emitting device 250 shown in FIG. 4(A) has a plurality of light-emitting units (light-emitting unit 106 and light-emitting unit 108 in FIG. 4(A)) between a pair of electrodes (electrode 101 and electrode 102). In the light-emitting device 250, although it will be described below assuming that the electrode 101 functions as the anode and the electrode 102 functions as the cathode, the configuration of the light-emitting device 250 may be reversed.

[0263] Also, in the light-emitting device 250 shown in FIG. 4(A), the light-emitting unit 106 and the light-emitting unit 108 are stacked, and a charge generation layer 115 is provided between the light-emitting unit 106 and the light-emitting unit 108. Note that the light-emitting unit 106 and the light-emitting unit 108 may have the same configuration or different configurations.

[0264] Further, the light-emitting element 250 includes a light-emitting layer 120 and a light-emitting layer 170. The light-emitting unit 106 further includes a hole injection layer 111, a hole transport layer 112, an electron transport layer 113, and an electron injection layer 114 in addition to the light-emitting layer 170. The light-emitting unit 108 further includes a hole injection layer 116, a hole transport layer 117, an electron transport layer 118, and an electron injection layer 119 in addition to the light-emitting layer 120.

[0265] The charge generation layer 115 may be configured such that an acceptor material, which is an electron acceptor, is added to a hole-transporting material, or a donor material, which is an electron donor, is added to an electron-transporting material. Further, both of these configurations may be laminated.

[0266] When the charge generation layer 115 contains a composite material of an organic compound and an acceptor material, the composite material may be the same as the composite material used for the hole injection layer 111 shown in Embodiment 1. As the organic compound, various compounds such as aromatic amine compounds, carbazole compounds, aromatic hydrocarbons, and polymer compounds (oligomers, dendrimers, polymers, etc.) can be used. Note that, as the organic compound, it is preferable to apply a substance having a hole mobility of 1×10 -6 cm 2 / Vs or more. However, any other substance may be used as long as it has higher hole transportability than electrons. Since the composite material of the organic compound and the acceptor material is excellent in carrier injection property and carrier transport property, low-voltage driving and low-current driving can be realized. When the anode-side surface of the light-emitting unit is in contact with the charge generation layer 115, the charge generation layer 115 can also serve as the hole injection layer or the hole transport layer of the light-emitting unit. Therefore, the light-emitting unit may be configured not to have a hole injection layer or a hole transport layer. Alternatively, when the cathode-side surface of the light-emitting unit is in contact with the charge generation layer 115, the charge generation layer 115 can also serve as the electron injection layer or the electron transport layer of the light-emitting unit. Therefore, the light-emitting unit may be configured not to have an electron injection layer or an electron transport layer.

[0267] Note that the charge generation layer 115 may be formed as a laminated structure combining a layer containing a composite material of an organic compound and an acceptor material and a layer composed of other materials. For example, it may be formed by combining a layer containing a composite material of an organic compound and an acceptor material and a layer containing one compound selected from electron-donating substances and a compound having high electron transportability. Further, it 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 film.

[0268] Note that the charge generation layer 115 sandwiched between the light-emitting unit 106 and the light-emitting unit 108 may be any layer that injects electrons into one light-emitting unit and holes into the other light-emitting unit when a voltage is applied between the electrodes 101 and 102. For example, in FIG. 4(A), 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 holes into the light-emitting unit 108.

[0269] Note that from the viewpoint of light extraction efficiency, the charge generation layer 115 preferably has translucency with respect to visible light (specifically, the transmittance of visible light with respect to the charge generation layer 115 is 40% or more). Further, the charge generation layer 115 can function even with a conductivity lower than that of a pair of electrodes (electrodes 101 and 102).

[0270] By forming the charge generation layer 115 using the materials described above, an increase in the driving voltage when the light-emitting layer is laminated can be suppressed.

[0271] Further, in FIG. 4(A), a light-emitting element having two light-emitting units has been described, but the same can be similarly applied to a light-emitting element in which three or more light-emitting units are laminated. As shown in the light-emitting element 250, by arranging a plurality of light-emitting units between a pair of electrodes partitioned by a charge generation layer, high-brightness light emission can be enabled while keeping the current density low, and a light-emitting element with a longer lifespan can be realized. Further, a light-emitting element with low power consumption can be realized.

[0272] In addition, in each of the above configurations, the emission colors exhibited by the guest materials used in the light-emitting units 106 and 108 may be the same as or different from each other. When there are guest materials having the function of emitting light of the same color in the light-emitting unit 106 and the light-emitting unit 108, the light-emitting element 250 preferably becomes a light-emitting element that exhibits high emission luminance at a low current value. Also, when there are guest materials having the function of emitting light of different colors in the light-emitting unit 106 and the light-emitting unit 108, the light-emitting element 250 preferably becomes a light-emitting element that exhibits multi-color emission. In this case, by using a plurality of light-emitting materials having different emission wavelengths in either or both of the light-emitting layer 120 and the light-emitting layer 170, the emission spectrum exhibited by the light-emitting element 250 becomes light in which emissions having different emission peaks are synthesized, and thus becomes an emission spectrum having at least two maximum values.

[0273] The above configuration is also suitable for obtaining white light emission. By making the lights of the light-emitting layer 120 and the light-emitting layer 170 be in a complementary color relationship with each other, white light emission can be obtained. In particular, it is preferable to select a guest material so as to obtain white light emission with high color rendering properties, or emission having at least red, green, and blue.

[0274] Also, in the case of a light-emitting element in which three or more light-emitting units are stacked, the emission colors exhibited by the guest materials used in each light-emitting unit may be the same as or different from each other. When there are a plurality of light-emitting units that exhibit emission of the same color, the emission colors exhibited by these plurality of light-emitting units can obtain high emission luminance at a low current value as compared with other colors. Such a configuration can be suitably used for adjusting the emission color. In particular, it is suitable when guest materials having different emission efficiencies and exhibiting different emission colors are used. For example, in the case of having three layers of light-emitting units, by having two layers of light-emitting units having a fluorescent material of the same color and one layer of a light-emitting unit having a phosphorescent material exhibiting an emission color different from that of the fluorescent material, the emission intensities of fluorescent emission and phosphorescent emission can be adjusted. That is, the intensity of the emission color can be adjusted according to the number of light-emitting units.

[0275] In the case of a light-emitting device having two such fluorescence-emitting units and one phosphorescence-emitting unit, it is preferable that the light-emitting device contains two light-emitting units including a blue fluorescent material and one light-emitting unit including a yellow phosphorescent material, or a light-emitting device having two light-emitting units including a blue fluorescent material and one light-emitting layer unit including a red phosphorescent material and a green phosphorescent material, or a light-emitting device having two light-emitting units including a blue fluorescent material and one light-emitting layer unit including a red phosphorescent material, a yellow phosphorescent material, and a green phosphorescent material, because white light emission can be efficiently obtained.

[0276] Further, at least one of the light-emitting layer 120 or the light-emitting layer 170 may be further divided into layers, and different light-emitting materials may be contained in each of the divided layers. That is, at least one of the light-emitting layer 120 or the light-emitting layer 170 can also be composed of two or more layers. For example, when the first light-emitting layer and the second light-emitting layer are laminated in order from the hole transport layer side to form a light-emitting layer, a material having hole transport properties is used as the host material of the first light-emitting layer, and a material having electron transport properties is used as the host material of the second light-emitting layer. In this case, the light-emitting materials of the first light-emitting layer and the second light-emitting layer may be the same material or different materials, and may be materials having a function of emitting light of the same color or materials having a function of emitting light of different colors. With a configuration having a plurality of light-emitting materials having functions of emitting light of different colors, it is also possible to obtain white light emission with high color rendering properties composed of the three primary colors or four or more light-emitting colors.

[0277] Note that by applying the configuration shown in Embodiment 1 to at least one of the plurality of units, a light-emitting device with good light extraction efficiency can be provided. Specifically, it is preferable that the region from 0 nm to λ / 2 or less from the light-emitting layer 170 has a low refractive index. In FIG. 4, it is particularly preferable that the hole injection layer 111 also serves as a low refractive index layer.

[0278] Further, as shown in FIG. 4(B), the light-emitting layer 120 included in the light-emitting unit 108 has a guest material 121 and a host material 122. Note that the guest material 121 will be described below as a fluorescent material.

[0279] ≪Light emission mechanism of light-emitting layer 120≫ The light emission mechanism of the light-emitting layer 120 will be described below.

[0280] Excitons are generated by the recombination of electrons and holes injected from a pair of electrodes (electrode 101 and electrode 102) or a charge generation layer in the light-emitting layer 120. Since the host material 122 exists in a large amount compared to the guest material 121, the generation of excitons forms an excited state of the host material 122 almost. Note that an exciton is a pair of carriers (electrons and holes).

[0281] When the excited state of the formed host material 122 is a singlet excited state, singlet excitation energy transfers from the S1 level of the host material 122 to the S1 level of the guest material 121, and a singlet excited state of the guest material 121 is formed.

[0282] Since the guest material 121 is a fluorescent material, when a singlet excited state is formed in the guest material 121, the guest material 121 emits light promptly. At this time, in order to obtain high luminous efficiency, it is preferable that the fluorescence quantum yield of the guest material 121 is high. Note that the same applies when carriers recombine in the guest material 121 and the generated excited state is a singlet excited state.

[0283] Next, the case where a triplet excited state of the host material 122 is formed by the recombination of carriers will be described. The correlation of the energy levels of the host material 122 and the guest material 121 in this case is shown in Fig. 4(C). Also, the notations and symbols in Fig. 4(C) are as follows. Note that since it is preferable that the T1 level of the host material 122 is lower than the T1 level of the guest material 121, this case is illustrated in Fig. 4(C), but the T1 level of the host material 122 may be higher than the T1 level of the guest material 121.

[0284] ·Guest(121): Guest material 121 (fluorescent material) ·Host(122): Host material 122 ·SFG : S1 level of guest material 121 (fluorescent material) ·T FG : T1 level of guest material 121 (fluorescent material) ·S FH : S1 level of host material 122 ·T FH : T1 level of host material 122 ·Energy: Energy

[0285] As shown in Fig. 4(C), by triplet-triplet annihilation (TTA), triplet excitons generated by carrier recombination interact with each other, transfer excitation energy to each other, and exchange spin angular momentum. As a result, a reaction occurs in which singlet excitons with the energy of the S1 level (S FH ) of host material 122 are formed (see TTA in Fig. 4(C)). The singlet excitation energy of host material 122 undergoes energy transfer from S FH to the S1 level (S FG ) of guest material 121 with lower energy (see route E1 in Fig. 4(C)), forming a singlet excited state of guest material 121, and guest material 121 emits light (Emission).

[0286] Note that when the density of triplet excitons in the light-emitting layer 120 is sufficiently high (for example, 1×10 12 cm -3 or higher), the deactivation of single triplet excitons can be ignored, and only the reaction of two neighboring triplet excitons can be considered.

[0287] Also, when carriers recombine in guest material 121 to form a triplet excited state, the triplet excited state of guest material 121 undergoes thermal deactivation, making it difficult to utilize for light emission. However, when the T1 level (T FH ) of host material 122 is lower than the T1 level (T FG ) of guest material 121, the triplet excitation energy of guest material 121 is at the T1 level (T FG) to the T1 level (T of the host material 122 FH ) It is possible to transfer energy (see Route E2 in Fig. 4(C)), and then it is used for TTA.

[0288] That is, the host material 122 preferably has a function of converting triplet excitation energy into singlet excitation energy by TTA. By doing so, a part of the triplet excitation energy generated in the light-emitting layer 120 is converted into singlet excitation energy by TTA in the host material 122, and the singlet excitation energy is transferred to the guest material 121, so that it can be extracted as fluorescence emission. For that purpose, the S1 level (S of the host material 122 FH ) is preferably higher than the S1 level (S of the guest material 121 FG ). Also, the T1 level (T of the host material 122 FH ) is preferably lower than the T1 level (T of the guest material 121 FG ).

[0289] In particular, when the T1 level (T of the guest material 121 FG ) is lower than the T1 level (T of the host material 122 FH ), the weight ratio of the guest material 121 to the host material 122 is preferably lower. Specifically, when the host material 122 is set to 1, the weight ratio of the guest material 121 is preferably greater than 0 and 0.05 or less. By doing so, the probability of carrier recombination in the guest material 121 can be reduced. Also, the probability of energy transfer from the T1 level (T of the host material 122 FH ) to the T1 level (T of the guest material 121 FG ) can be reduced.

[0290] Note that the host material 122 may be composed of a single compound or may be composed of a plurality of compounds.

[0291] When the light-emitting units 106 and 108 have guest materials with different emission colors, it is preferable to configure the emission from the light-emitting layer 120 to have a peak on the shorter wavelength side than the emission from the light-emitting layer 170. A light-emitting device using a material with a high triplet excitation energy level tends to have rapid luminance degradation. Therefore, by using TTA in the light-emitting layer that exhibits short-wavelength emission, a light-emitting device with small luminance degradation can be provided.

[0292] <Configuration Example 2 of Light-Emitting Device> FIG. 5(A) is a schematic cross-sectional view of the light-emitting device 252.

[0293] Similar to the light-emitting device 250 shown above, the light-emitting device 252 shown in FIG. 5(A) has a plurality of light-emitting units (light-emitting unit 106 and light-emitting unit 110 in FIG. 5(A)) between a pair of electrodes (electrode 101 and electrode 102). At least one light-emitting unit has a configuration similar to that of the EL layer 100. Note that the light-emitting unit 106 and the light-emitting unit 110 may have the same configuration or different configurations.

[0294] In the light-emitting device 252 shown in FIG. 5(A), the light-emitting unit 106 and the light-emitting unit 110 are stacked, and a charge generation layer 115 is provided between the light-emitting unit 106 and the light-emitting unit 110. For example, it is preferable to use the EL layer 100 for the light-emitting unit 106.

[0295] The light-emitting device 252 also has a light-emitting layer 140 and a light-emitting layer 170. In addition to the light-emitting layer 170, the light-emitting unit 106 has a hole injection layer 111, a hole transport layer 112, an electron transport layer 113, and an electron injection layer 114. In addition to the light-emitting layer 140, the light-emitting unit 110 has a hole injection layer 116, a hole transport layer 117, an electron transport layer 118, and an electron injection layer 119.

[0296] Among the plurality of units, by applying the configuration shown in Embodiment 1 to at least one unit, a light-emitting element with good light extraction efficiency can be provided. Specifically, it is preferable to have a low refractive index in the region from 0 nm to λ / 2 or less from the light-emitting layer 170. In FIG. 5, it is particularly preferable that the hole injection layer 111 also serves as the low refractive index layer.

[0297] The light-emitting layer 140 included in the light-emitting unit 110 has a guest material 141 and a host material 142, as shown in FIG. 5(B). The host material 142 has an organic compound 142_1 and an organic compound 142_2. Hereinafter, the guest material 141 included in the light-emitting layer 140 is described as a phosphorescent material.

[0298] ≪Light-emitting mechanism of the light-emitting layer 140≫ Next, the light-emitting mechanism of the light-emitting layer 140 is described below.

[0299] The organic compound 142_1 and the organic compound 142_2 included in the light-emitting layer 140 form an exciplex.

[0300] The combination of the organic compound 142_1 and the organic compound 142_2 may be any combination that can form an exciplex with each other, but it is more preferable that one is a compound having hole-transporting properties and the other is a compound having electron-transporting properties.

[0301] The energy level correlation among the organic compound 142_1, the organic compound 142_2, and the guest material 141 in the light-emitting layer 140 is shown in FIG. 5(C). The notations and symbols in FIG. 5(C) are as follows. ·Guest(141): Guest material 141 (phosphorescent material) ·Host(142_1): Organic compound 142_1 (host material) ·Host(142_2): Organic compound 142_2 (host material) ·T PG : T1 level of the guest material 141 (phosphorescent material) ·S PH1: S1 level of organic compound 142_1 (host material) ·T PH1 : T1 level of organic compound 142_1 (host material) ·S PH2 : S1 level of organic compound 142_2 (host material) ·T PH2 : T1 level of organic compound 142_2 (host material) ·S PE : S1 level of the exciplex ·T PE : T1 level of the exciplex ·Energy: Energy

[0302] Organic compound 142_1 and organic compound 142_2 form an exciplex, and the S1 level (S PE ) and T1 level (T PE ) of the exciplex are adjacent energies to each other (see Route E3 in Fig. 5(C)).

[0303] Organic compound 142_1 and organic compound 142_2 quickly form an exciplex by one receiving holes and the other receiving electrons. Alternatively, when one is in an excited state, it quickly interacts with the other to form an exciplex. Therefore, most of the excitons in the light-emitting layer 140 exist as an exciplex. Since the excitation energy levels (S PE or T PE ) of the exciplex are lower than the S1 levels (S PH1 and S PH2 ) of the host materials (organic compound 142_1 and organic compound 142_2) forming the exciplex, it is possible to form an excited state of the host material 142 with a lower excitation energy. As a result, the driving voltage of the light-emitting element can be lowered.

[0304] Then, the energies of both (S PE ) and (T PE ) of the exciplex are transferred to the T1 level of the guest material 141 (phosphorescent material) (see Routes E4 and E5 in Fig. 5(C)), and light emission (Emission) is obtained.

[0305] Note that the T1 level (T PE ) of the exciplex is preferably higher than the T1 level (T PG ) of the guest material 141. By doing so, the singlet excitation energy and triplet excitation energy of the generated exciplex can be transferred from the S1 level (S PE ) and T1 level (T PE ) of the exciplex to the T1 level (T PG ) of the guest material 141.

[0306] In addition, in order to efficiently transfer the excitation energy from the exciplex to the guest material 141, the T1 level (T PE ) of the exciplex is preferably equal to or lower than the T1 levels (T PH1 and T PH2 ) of each organic compound (organic compound 142_1 and organic compound 142_2) that forms the exciplex. This makes it less likely for the triplet excitation energy of the exciplex to be quenched by each organic compound (organic compound 142_1 and organic compound 142_2), and energy transfer from the exciplex to the guest material 141 occurs efficiently.

[0307] In addition, for organic compound 142_1 and organic compound 142_2 to efficiently form an exciplex, it is preferable that the HOMO level of one of organic compound 142_1 and organic compound 142_2 is higher than that of the other, and the LUMO level of one is higher than that of the other. For example, when organic compound 142_1 has hole-transporting properties and organic compound 142_2 has electron-transporting properties, it is preferable that the HOMO level of organic compound 142_1 is higher than the HOMO level of organic compound 142_2, and it is preferable that the LUMO level of organic compound 142_1 is higher than the LUMO level of organic compound 142_2. Alternatively, when organic compound 142_2 has hole-transporting properties and organic compound 142_1 has electron-transporting properties, it is preferable that the HOMO level of organic compound 142_2 is higher than the HOMO level of organic compound 142_1, and it is preferable that the LUMO level of organic compound 142_2 is higher than the LUMO level of organic compound 142_1. Specifically, the energy difference between the HOMO level of organic compound 142_1 and the HOMO level of organic compound 142_2 is preferably 0.05 eV or more, more preferably 0.1 eV or more, and even more preferably 0.2 eV or more. Also, the energy difference between the LUMO level of organic compound 142_1 and the LUMO level of organic compound 142_2 is preferably 0.05 eV or more, more preferably 0.1 eV or more, and even more preferably 0.2 eV or more.

[0308] In addition, when the combination of organic compound 142_1 and organic compound 142_2 is a combination of a compound having hole-transporting properties and a compound having electron-transporting properties, it becomes possible to easily control the carrier balance depending on the mixing ratio. Specifically, the range of hole-transporting compound : electron-transporting compound = 1:9 to 9:1 (weight ratio) is preferable. Also, by having this configuration, since the carrier balance can be easily controlled, the control of the carrier recombination region can also be easily performed.

[0309] By configuring the light-emitting layer 140 as described above, it becomes possible to efficiently obtain light emission from the guest material 141 (phosphorescent material) of the light-emitting layer 140.

[0310] In addition, the process of routes E3 to E5 shown above may be referred to as ExTET (Exciplex-Triplet Energy Transfer) in this specification and the like. In other words, in the light-emitting layer 140, there is donation of excitation energy from the exciplex to the guest material 141. In this case, it is not always necessary that the reverse intersystem crossing efficiency from T PE to S PE is high, nor is it necessary that the luminescence quantum yield from S PE is high. Therefore, a wide range of materials can be selected.

[0311] Also, it is preferable that the light emission from the light-emitting layer 170 has a peak of light emission on the shorter wavelength side than the light emission from the light-emitting layer 140. A light-emitting element using a phosphorescent material that exhibits short-wavelength light emission tends to have rapid luminance degradation. Therefore, by making the short-wavelength light emission fluorescent light emission, a light-emitting element with little luminance degradation can be provided.

[0312] <Examples of materials that can be used in the light-emitting layer> Next, materials that can be used in the light-emitting layer 120, the light-emitting layer 140, and the light-emitting layer 170 will be described below.

[0313] ≪Materials that can be used in the light-emitting layer 120≫ In the light-emitting layer 120, the host material 122 is present in the largest amount by weight ratio, and the guest material 121 (fluorescent material) is dispersed in the host material 122. It is preferable that the S1 level of the host material 122 is higher than the S1 level of the guest material 121 (fluorescent material), and the T1 level of the host material 122 is lower than the T1 level of the guest material 121 (fluorescent material).

[0314] In the light-emitting layer 120, the guest material 121 is not particularly limited, but anthracene derivatives, tetracene derivatives, chrysene derivatives, phenanthrene derivatives, pyrene derivatives, perylene derivatives, stilbene derivatives, acridone derivatives, coumarin derivatives, phenoxazine derivatives, phenothiazine derivatives, etc. are preferable, and the fluorescent compounds shown in Embodiment 1 can be preferably used.

[0315] In addition, in the light-emitting layer 120, the materials that can be used for the host material 122 are not particularly limited. For example, metal complexes such as tris(8-quinolinolato)aluminum(III) (abbreviation: Alq), tris(4-methyl-8-quinolinolato)aluminum(III) (abbreviation: Almq3), bis(10-hydroxybenzo[h]quinolinato)beryllium(II) (abbreviation: BeBq2), bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III) (abbreviation: BAlq), bis(8-quinolinolato)zinc(II) (abbreviation: Znq), bis[2-(2-benzoxazolyl)phenolato]zinc(II) (abbreviation: ZnPBO), bis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ); heterocyclic compounds such as 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene (abbreviation: OXD-7), 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviation: TAZ), 2,2’,2’’-(1,3,5-benzenetriyl)tris(1-phenyl-1H-benzimidazole) (abbreviation: TPBI), bathocuproine (abbreviation: BCP), 9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole (abbreviation: CO11); and aromatic amine compounds such as 4,4’-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB or α-NPD), N,N’-bis(3-methylphenyl)-N,N’-diphenyl-[1,1’-biphenyl]-4,4’-diamine (abbreviation: TPD), 4,4’-bis[N-(spiro-9,9’-bifluoren-2-yl)-N-phenylamino]biphenyl (abbreviation: BSPB).In addition, condensed polycyclic aromatic compounds such as anthracene derivatives, phenanthrene derivatives, pyrene derivatives, chrysene derivatives, dibenzo[g,p]chrysene derivatives, etc. can be mentioned. Specifically, 9,10-diphenylanthracene (abbreviation: DPAnth), N,N-diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole-3-amine (abbreviation: CzA1PA), 4-(10-phenyl-9-anthryl)triphenylamine (abbreviation: DPhPA), 4-(9H-carbazol-9-yl)-4'-(10-phenyl-9-anthryl)triphenylamine (abbreviation: YGAPA), N,9-diphenyl-N-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole-3-amine (abbreviation: PCAPA), N,9-diphenyl-N-{4-[4-(10-phenyl-9-anthryl)phenyl]phenyl}-9H-carbazole-3-amine (abbreviation: PCAPBA), N,9-diphenyl-N-(9,10-diphenyl-2-anthryl)-9H-carbazole-3-amine (abbreviation: 2PCAPA), 6,12-dimethoxy-5,11-diphenylchrysene, N,N,N',N',N'',N'',N''',N'''-octaphenyldibenzo[g,p]chrysene-2,7,10,15-tetraamine (abbreviation: DBC1), 9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: CzPA), 3,6-diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: DPCzPA), 9,10-bis(3,5-diphenylphenyl)anthracene (abbreviation: DPPA), 9,10-di(2-naphthyl)anthracene (abbreviation: DNA), 2-tert-butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA), 9,9'-bianthryl (abbreviation: BANT), 9,9'-(stilbene-3,3'-diyl)diphenanthrene (abbreviation: DPNS), 9,9'-(stilbene-4,4'-diyl)diphenanthrene (abbreviation: DPNS2), 3,3',3''-(benzene-1,3,5-triyl)tripyrene (abbreviation: TPB3), etc. can be listed.In addition, one or more substances having an energy gap larger than the energy gap of the guest material 121 may be selected and used from among these and known substances.

[0316] Note that the light-emitting layer 120 can also be composed of two or more layers. For example, when the first light-emitting layer and the second light-emitting layer are laminated in order from the hole-transporting layer side to form the light-emitting layer 120, a substance having hole-transporting properties is used as the host material of the first light-emitting layer, and a substance having electron-transporting properties is used as the host material of the second light-emitting layer, etc.

[0317] In addition, in the light-emitting layer 120, the host material 122 may be composed of one kind of compound or may be composed of a plurality of compounds. Alternatively, in the light-emitting layer 120, materials other than the host material 122 and the guest material 121 may be included.

[0318] ≪Materials that can be used for the light-emitting layer 140≫ In the light-emitting layer 140, the host material 142 is present in the largest amount by weight, and the guest material 141 (phosphorescent material) is dispersed in the host material 142. The T1 level of the host material 142 (organic compound 142_1 and organic compound 142_2) of the light-emitting layer 140 is preferably higher than the T1 level of the guest material 141.

[0319] Examples of the organic compound 142_1 include zinc and aluminum-based metal complexes, oxadiazole derivatives, triazole derivatives, benzimidazole derivatives, quinoxaline derivatives, dibenzoquinoxaline derivatives, dibenzothiophene derivatives, dibenzofuran derivatives, pyrimidine derivatives, triazine derivatives, pyridine derivatives, bipyridine derivatives, phenanthroline derivatives, etc. Other examples include aromatic amines and carbazole derivatives. Specifically, the electron-transporting material and the hole-transporting material shown in Embodiment 1 can be used.

[0320] As the organic compound 142_2, a combination capable of forming an exciplex with the organic compound 142_1 is preferable. Specifically, the electron transporting material and the hole transporting material shown in Embodiment 1 can be used. In this case, it is preferable to select the organic compound 142_1, the organic compound 142_2, and the guest material 141 (phosphorescent material) so that the emission peak of the exciplex formed by the organic compound 142_1 and the organic compound 142_2 overlaps with the absorption band of the triplet MLCT (Metal to Ligand Charge Transfer) transition of the guest material 141 (phosphorescent material), more specifically, the absorption band on the longest wavelength side. Thereby, a light-emitting element with a dramatically improved luminous efficiency can be obtained. However, when a thermally activated delayed fluorescence material is used instead of the phosphorescent material, the absorption band on the longest wavelength side is preferably a singlet absorption band.

[0321] Examples of the guest material 141 (phosphorescent material) include iridium, rhodium, or platinum-based organometallic complexes, or metal complexes. Among them, an organic iridium complex, for example, an iridium-based orthometal complex is preferable. Examples of the ligand for orthometalation include 4H-triazole ligand, 1H-triazole ligand, imidazole ligand, pyridine ligand, pyrimidine ligand, pyrazine ligand, or isoquinoline ligand. Examples of the metal complex include a platinum complex having a porphyrin ligand. Specifically, the materials exemplified as the guest material 132 shown in Embodiment 1 can be used.

[0322] The light-emitting material contained in the light-emitting layer 140 may be any material that can convert triplet excitation energy into light emission. Examples of the material that can convert triplet excitation energy into light emission include thermally activated delayed fluorescence materials in addition to phosphorescent materials. Therefore, the part described as the phosphorescent material may be read as a thermally activated delayed fluorescence material.

[0323] In addition, the material showing thermally activated delayed fluorescence may be a material that can generate a singlet excited state from a triplet excited state by reverse intersystem crossing alone, or may be composed of a plurality of materials that form an exciplex (also referred to as an exciplex or Exciplex).

[0324] When the thermally activated delayed fluorescence material is composed of one type of material, specifically, the thermally activated delayed fluorescence material shown in Embodiment 1 can be used.

[0325] In addition, when using a thermally activated delayed fluorescence material as a host material, it is preferable to use a combination of two types of compounds that form an exciplex. In this case, it is particularly preferable to use a compound that easily receives electrons and a compound that easily receives holes, which is the combination that forms the exciplex shown above.

[0326] ≪Materials that can be used for the light-emitting layer 170≫ As the material that can be used for the light-emitting layer 170, the material that can be used for the light-emitting layer shown in Embodiment 1 may be incorporated, and by doing so, a light-emitting device with high luminous efficiency can be fabricated.

[0327] In addition, there is no limitation on the emission color of the light-emitting materials included in the light-emitting layer 120, the light-emitting layer 140, and the light-emitting layer 170, and they may be the same or different from each other. Since the light emitted from each is mixed and extracted outside the device, for example, when the emission colors of both are complementary to each other, the light-emitting device can give white light. Considering the reliability of the light-emitting device, it is preferable that the 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.

[0328] Note that the light-emitting unit 106, the light-emitting unit 108, the light-emitting unit 110, and the charge generation layer 115 can be formed by methods such as vapor deposition (including vacuum vapor deposition), inkjet method, coating method, gravure printing, etc.

[0329] As described above, the configuration shown in this embodiment can be used in appropriate combination with the configurations shown in other embodiments.

[0330] (Embodiment 5) FIG. 6(A) is a top view showing a light-emitting device, and FIG. 6(B) is a cross-sectional view obtained by cutting FIG. 6(A) along A-B and C-D. This light-emitting device includes a drive circuit section (source-side drive circuit) 601, a pixel section 602, and a drive circuit section (gate-side drive circuit) 603, which are indicated by dotted lines, for controlling the light emission of the light-emitting element. Further, 604 is a sealing substrate, 625 is a drying material, and 605 is a sealing material. The inside surrounded by the sealing material 605 is a space 607.

[0331] Note that the routing wiring 608 is a wiring for transmitting signals input to the source-side drive circuit 601 and the gate-side drive circuit 603, and receives a video signal, a clock signal, a start signal, a reset signal, etc. from an FPC (Flexible Printed Circuit) 609 that serves as an external input terminal. Note that only the FPC is shown here, but a printed wiring board (PWB) may be attached to this FPC. The light-emitting device in this specification includes not only the light-emitting device main body but also a state in which an FPC or a PWB is attached thereto.

[0332] Next, the cross-sectional structure of the above-described light-emitting device will be described with reference to FIG. 6(B). A drive circuit section and a pixel section are formed on the element substrate 610. Here, one pixel in the source-side drive circuit 601, which is a drive circuit section, and the pixel section 602 is shown.

[0333] Note that the source-side drive circuit 601 is formed of a CMOS circuit in which an n-channel type TFT 623 and a p-channel type TFT 624 are combined. Further, the drive circuit may be formed of various CMOS circuits, PMOS circuits, and NMOS circuits. In this embodiment, a driver integrated type in which the drive circuit is formed on the substrate is shown, but this is not necessarily required, and the drive circuit can be formed outside the substrate instead of on the substrate.

[0334] Further, the pixel portion 602 is formed by pixels each including a switching TFT 611, a current control TFT 612, and a first electrode 613 electrically connected to the drain thereof. An insulator 614 is formed so as to cover an end portion of the first electrode 613. The insulator 614 can be formed by using a positive photosensitive resin film.

[0335] In addition, in order to improve the covering property of the film formed on the insulator 614, a surface having a curvature is formed at the upper end portion or the lower end portion of the insulator 614. For example, when photosensitive acrylic is used as the material of the insulator 614, it is preferable to provide a curved surface only at the upper end portion of the insulator 614. The radius of curvature of the curved surface is preferably 0.2 μm or more and 0.3 μm or less. Further, as the insulator 614, either a negative photosensitive material or a positive photosensitive material can be used.

[0336] An EL layer 616 and a second electrode 617 are respectively formed on the first electrode 613. Here, as the material used for the first electrode 613 that functions as an anode, it is desirable to use a material having a large work function. For example, in addition to single-layer films such as an ITO film, an indium tin oxide film containing silicon, an indium oxide film containing 2 wt% or more and 20 wt% or less of zinc oxide, a titanium nitride film, a chromium film, a tungsten film, a Zn film, and a Pt film, a laminate of a film mainly composed of titanium nitride and aluminum, a three-layer structure of a titanium nitride film, a film mainly composed of aluminum, and a titanium nitride film can be used. Note that when a laminated structure is used, the resistance as a wiring is low, good ohmic contact can be achieved, and it can further function as an anode.

[0337] Further, the EL layer 616 is formed by various methods such as a vapor deposition method using a vapor deposition mask, an inkjet method, and a spin coating method. As the material constituting the EL layer 616, a low molecular compound or a high molecular compound (including an oligomer and a dendrimer) may be used.

[0338] Furthermore, as the material used for the second electrode 617 formed on the EL layer 616 and functioning as a cathode, it is preferable to use a material with a small work function (Al, Mg, Li, Ca, or their alloys or compounds, MgAg, MgIn, AlLi, etc.). When the light generated in the EL layer 616 is to be transmitted through the second electrode 617, it is good to use a laminate of a thin metal film with a reduced film thickness and a transparent conductive film (ITO, indium oxide containing 2 wt% or more and 20 wt% or less of zinc oxide, indium tin oxide containing silicon, zinc oxide (ZnO), etc.) as the second electrode 617.

[0339] Note that a light-emitting element 618 is formed by the first electrode 613, the EL layer 616, and the second electrode 617. The light-emitting element 618 preferably has the configuration of the light-emitting element according to Embodiment 1 to Embodiment 4. Note that although a plurality of light-emitting elements are formed in the pixel portion, in the light-emitting device according to the present embodiment, both a light-emitting element having the configuration described in Embodiment 1 to Embodiment 4 and a light-emitting element having other configurations may be included.

[0340] Furthermore, by bonding the sealing substrate 604 to the element substrate 610 with the sealing material 605, a structure is formed in which the light-emitting element 618 is provided in the space 607 surrounded by the element substrate 610, the sealing substrate 604, and the sealing material 605. Note that the space 607 is filled with a filling material, and in addition to the case where an inert gas (nitrogen, argon, etc.) is filled, it may be filled with a resin or a drying material or both.

[0341] Note that it is preferable to use an epoxy-based resin or glass frit for the sealing material 605. Also, these materials are desirably materials that hardly transmit moisture and oxygen. In addition to a glass substrate or a quartz substrate, a plastic substrate made of FRP (Fiber Reinforced Plastics), PVF (polyvinyl fluoride), polyester, acrylic, or the like can be used as the material for the sealing substrate 604.

[0342] As described above, a light-emitting device using the light-emitting elements described in Embodiment 1 and Embodiment 2 can be obtained.

[0343] <Configuration Example 1 of Light-Emitting Device> FIG. 7 shows an example of a light-emitting device in which a light-emitting element that exhibits white light emission is formed and a coloring layer (color filter) is formed.

[0344] FIG. 7(A) shows a substrate 1001, an underlying insulating film 1002, a gate insulating film 1003, gate electrodes 1006, 1007, 1008, a first interlayer insulating film 1020, a second interlayer insulating film 1021, a peripheral portion 1042, a pixel portion 1040, a drive circuit portion 1041, first electrodes 1024W, 1024R, 1024G, 1024B of the light-emitting element, a partition 1026, an EL layer 1028, a second electrode 1029 of the light-emitting element, a sealing substrate 1031, a sealing material 1032, etc.

[0345] Further, FIGS. 7(A) and 7(B) show that a coloring layer (a red coloring layer 1034R, a green coloring layer 1034G, and a blue coloring layer 1034B) is provided on a transparent base material 1033. A black layer (black matrix) 1035 may be further provided. The transparent base material 1033 provided with the coloring layer and the black layer is aligned and fixed to the substrate 1001. Note that the coloring layer and the black layer are covered with an overcoat layer 1036. In FIG. 7(A), there are a light-emitting layer in which light does not pass through the coloring layer and exits to the outside, and a light-emitting layer in which light passes through the coloring layers of each color and exits to the outside. Since the light that does not pass through the coloring layer is white, and the light that passes through the coloring layer is red, blue, or green, an image can be expressed with four-color pixels.

[0346] FIG. 7(B) shows an example in which a red coloring layer 1034R, a green coloring layer 1034G, and a blue coloring layer 1034B are formed between the gate insulating film 1003 and the first interlayer insulating film 1020. As shown in FIG. 7(B), the coloring layer may be provided between the substrate 1001 and the sealing substrate 1031.

[0347] In addition, in the light-emitting device described above, a light-emitting device having a structure that extracts light from the side of the substrate 1001 on which the TFT is formed (bottom emission type) is used, but a light-emitting device having a structure that extracts light from the side of the sealing substrate 1031 (top emission type) may also be used.

[0348] <Example Configuration 2 of Light-Emitting Device> A cross-sectional view of a top emission type light-emitting device is shown in FIG. 8. In this case, a substrate that does not transmit light can be used as the substrate 1001. Until a connection electrode connecting the TFT and the anode of the light-emitting element is fabricated, it is formed in the same manner as the bottom emission type light-emitting device. Thereafter, a third interlayer insulating film 1037 is formed to cover the electrode 1022. This insulating film may serve as a planarization film. The third interlayer insulating film 1037 can be formed using various materials in addition to the same material as the second interlayer insulating film 1021.

[0349] The first lower electrodes 1025W, 1025R, 1025G, and 1025B of the light-emitting element are anodes here, but they may be cathodes. Further, in the case of a top emission type light-emitting device as shown in FIG. 8, the lower electrodes 1025W, 1025R, 1025G, and 1025B are preferably reflective electrodes. Note that the second electrode 1029 preferably has a function of reflecting light and a function of transmitting light. Further, it preferably has a function of applying a microcavity structure between the second electrode 1029 and the lower electrodes 1025W, 1025R, 1025G, and 1025B to amplify light of a specific wavelength. The configuration of the EL layer 1028 is the same as the configuration described in Embodiment 2, and an element structure capable of obtaining white light emission is adopted.

[0350] In FIGS. 7(A), 7(B), and 8, as the configuration of the EL layer capable of obtaining white light emission, it may be realized by using a plurality of light-emitting layers, using a plurality of light-emitting units, or the like. Note that the configuration for obtaining white light emission is not limited to these.

[0351] In a top emission structure as shown in Fig. 8, sealing can be performed with a sealing substrate 1031 provided with coloring layers (red coloring layer 1034R, green coloring layer 1034G, blue coloring layer 1034B). A black layer (black matrix) 1035 may be provided on the sealing substrate 1031 so as to be located between pixels. The coloring layers (red coloring layer 1034R, green coloring layer 1034G, blue coloring layer 1034B) and the black layer (black matrix) may be covered with an overcoat layer. Note that a substrate having translucency is used for the sealing substrate 1031.

[0352] Also, here, an example of full-color display using four colors of red, green, blue, and white is shown, but it is not particularly limited, and full-color display may be performed using three colors of red, green, and blue. Further, full-color display may be performed using four colors of red, green, blue, and yellow.

[0353] So far, the active matrix type light-emitting device has been described. Hereinafter, the passive matrix type light-emitting device will be described. Fig. 46 shows a passive matrix type light-emitting device manufactured by applying the present invention. Note that Fig. 46(A) is a perspective view showing the light-emitting device, and Fig. 46(B) is a cross-sectional view obtained by cutting Fig. 46(A) along X-Y. In Fig. 46, an EL layer 955 is provided between an electrode 952 and an electrode 956 on a substrate 951. The end portion of the electrode 952 is covered with an insulating layer 953. Then, a partition layer 954 is provided on the insulating layer 953. The side walls of the partition layer 954 have an inclination such that the distance between one side wall and the other side wall becomes narrower as it approaches the substrate surface. That is, the cross-section of the partition layer 954 in the short side direction is trapezoidal, and the bottom side (the side facing the same direction as the surface direction of the insulating layer 953 and in contact with the insulating layer 953) is shorter than the upper side (the side facing the same direction as the surface direction of the insulating layer 953 and not in contact with the insulating layer 953). By providing the partition layer 954 in this way, it is possible to prevent defects in the light-emitting element caused by static electricity or the like. Also, in the passive matrix type light-emitting device, the light-emitting elements described in Embodiments 1 to 4 are used, and a light-emitting device with low power consumption can be obtained.

[0354] As described above, the light-emitting device can control each of a large number of minute light-emitting elements arranged in a matrix, and thus is a light-emitting device that can be suitably used as a display device for expressing an image.

[0355] Note that this embodiment can be appropriately combined with other embodiments.

[0356] (Embodiment 6) In this embodiment, an electronic device according to one aspect of the present invention will be described.

[0357] Since one aspect of the present invention is a light-emitting element using an organic EL, by using the light-emitting element according to one aspect of the present invention, an electronic device having a flat surface, good luminous efficiency, and high reliability can be manufactured. Further, according to one aspect of the present invention, an electronic device having a curved surface, good luminous efficiency, and high reliability can be manufactured. Further, according to one aspect of the present invention, an electronic device having flexibility, good luminous efficiency, and high reliability can be manufactured.

[0358] Examples of the electronic device include a television device, a desktop or notebook personal computer, a monitor for a computer, a digital camera, a digital video camera, a digital photo frame, a mobile phone, a portable game machine, a portable information terminal, an audio reproduction device, and a large game machine such as a pachinko machine.

[0359] In addition, the light-emitting device according to one aspect of the present invention can achieve high visibility regardless of the intensity of external light. Therefore, it can be suitably used for portable electronic devices, wearable electronic devices (wearable devices), and electronic book terminals.

[0360] The portable information terminal 900 shown in FIGS. 9(A) and 9(B) includes a housing 901, a housing 902, a display unit 903, a hinge unit 905, and the like.

[0361] The housing 901 and the housing 902 are connected by a hinge portion 905. The portable information terminal 900 can be unfolded as shown in FIG. 9(B) from the folded state (FIG. 9(A)). Thereby, it has excellent portability when carried, and excellent visibility due to a large display area when used.

[0362] The portable information terminal 900 is provided with a flexible display unit 903 across the housing 901 and the housing 902 connected by the hinge portion 905.

[0363] The light-emitting device manufactured using one aspect of the present invention can be used for the display unit 903. Thereby, a portable information terminal can be manufactured with a high yield.

[0364] The display unit 903 can display at least one of document information, still images, moving images, and the like. When document information is displayed on the display unit, the portable information terminal 900 can be used as an e-book terminal.

[0365] When the portable information terminal 900 is unfolded, the display unit 903 is held in a largely curved form. For example, the display unit 903 is held including a portion curved with a curvature radius of 1 mm or more and 50 mm or less, preferably 5 mm or more and 30 mm or less. A part of the display unit 903 has pixels continuously arranged from the housing 901 to the housing 902 and can perform a curved surface display.

[0366] The display unit 903 functions as a touch panel and can be operated by a finger, a stylus, or the like.

[0367] The display unit 903 is preferably composed of one flexible display. Thereby, a continuous display without interruption between the housing 901 and the housing 902 can be performed. Note that a configuration in which a display is provided for each of the housing 901 and the housing 902 may also be adopted.

[0368] When the portable information terminal 900 is unfolded, the hinge portion 905 preferably has a locking mechanism so that the angle between the housing 901 and the housing 902 does not become larger than a predetermined angle. For example, the angle at which locking is applied (it cannot be opened further) is preferably 90 degrees or more and less than 180 degrees, and typically can be 90 degrees, 120 degrees, 135 degrees, 150 degrees, or 175 degrees, etc. Thereby, the convenience, safety, and reliability of the portable information terminal 900 can be enhanced.

[0369] When the hinge portion 905 has a locking mechanism, it is possible to prevent the display portion 903 from being damaged without applying an excessive force to the display portion 903. Therefore, a highly reliable portable information terminal can be realized.

[0370] The housing 901 and the housing 902 may have a power button, operation buttons, an external connection port, a speaker, a microphone, etc.

[0371] A wireless communication module is provided in either one of the housing 901 or the housing 902, and it is possible to transmit and receive data via a computer network such as the Internet, a LAN (Local Area Network), or Wi-Fi (registered trademark) (Wireless Fidelity).

[0372] The portable information terminal 910 shown in FIG. 9(C) has a housing 911, a display portion 912, operation buttons 913, an external connection port 914, a speaker 915, a microphone 916, a camera 917, etc.

[0373] The light-emitting device manufactured using one aspect of the present invention can be used for the display portion 912. Thereby, a portable information terminal can be manufactured with a high yield.

[0374] The portable information terminal 910 is provided with a touch sensor on the display portion 912. Any operation such as making a call or inputting characters can be performed by touching the display portion 912 with a finger or a stylus.

[0375] Also, by operating the operation button 913, it is possible to turn the power on and off and switch the type of image displayed on the display unit 912. For example, it is possible to switch from the mail creation screen to the main menu screen.

[0376] Further, by providing a detection device such as a gyro sensor or an acceleration sensor inside the portable information terminal 910, the orientation (portrait or landscape) of the portable information terminal 910 can be determined, and the screen display orientation of the display unit 912 can be automatically switched. Also, the switching of the screen display orientation can be performed by touching the display unit 912, operating the operation button 913, or voice input using the microphone 916.

[0377] The portable information terminal 910 has one or more functions selected from, for example, a telephone, a notebook, or an information browsing device. Specifically, it can be used as a smartphone. The portable information terminal 910 can execute various applications such as mobile phone, email, text browsing and creation, music playback, video playback, Internet communication, and games.

[0378] The camera 920 shown in FIG. 9(D) has a housing 921, a display unit 922, an operation button 923, a shutter button 924, etc. A detachable lens 926 is attached to the camera 920.

[0379] The light-emitting device manufactured using one aspect of the present invention can be used for the display unit 922. Thereby, a camera can be manufactured with a high yield.

[0380] Here, the camera 920 is configured such that the lens 926 can be removed from the housing 921 and replaced, but the lens 926 and the housing 921 may be integrated.

[0381] The camera 920 can capture still images or videos by pressing the shutter button 924. Also, the display unit 922 has a function as a touch panel, and it is also possible to capture images by touching the display unit 922.

[0382] Note that the camera 920 can be separately equipped with a strobe device, a viewfinder, etc. Or, these may be incorporated in the housing 921.

[0383] Figs. 10(A) to (E) are diagrams showing electronic devices. These electronic devices include a housing 9000, a display unit 9001, a speaker 9003, operation keys 9005 (including a power switch or an operation switch), connection terminals 9006, a sensor 9007 (having a function of measuring force, displacement, position, speed, acceleration, angular velocity, rotation speed, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, inclination, vibration, odor or infrared rays), a microphone 9008, etc.

[0384] The light-emitting device manufactured using one aspect of the present invention can be suitably used for the display unit 9001. Thereby, an electronic device can be manufactured with a high yield.

[0385] The electronic devices shown in Figs. 10(A) to (E) can have various functions. For example, a function of displaying various information (such as still images, videos, text images, etc.) on the display unit, a touch panel function, a function of displaying a calendar, date or time, etc., a function of controlling processing by various software (programs), a wireless communication function, a function of connecting to various computer networks using the wireless communication function, a function of transmitting or receiving various data using the wireless communication function, a function of reading out a program or data recorded on a recording medium and displaying it on the display unit, etc. Note that the functions of the electronic devices shown in Figs. 10(A) to (E) are not limited to these, and they may have other functions.

[0386] FIG. 10(A) is a perspective view showing a wristwatch-type portable information terminal 9200, and FIG. 10(B) is a perspective view showing a wristwatch-type portable information terminal 9201.

[0387] The portable information terminal 9200 shown in FIG. 10(A) can execute various applications such as mobile phone, e-mail, text viewing and creation, music playback, Internet communication, and computer games. Further, the display unit 9001 is provided with a curved display surface, and the display can be performed along the curved display surface. In addition, the portable information terminal 9200 can execute short-range wireless communication conforming to a communication standard. For example, it can communicate hands-free by communicating with a wireless headset. Further, the portable information terminal 9200 has a connection terminal 9006 and can directly exchange data with other information terminals via a connector. Charging can also be performed via the connection terminal 9006. Note that the charging operation may be performed by wireless power supply without using the connection terminal 9006.

[0388] Unlike the portable information terminal shown in FIG. 10(A), the display surface of the display unit 9001 of the portable information terminal 9201 shown in FIG. 10(B) is not curved. Further, the outer shape of the display unit of the portable information terminal 9201 is non-rectangular (circular in FIG. 10(B)).

[0389] FIGS. 10(C) to (E) are perspective views showing a foldable portable information terminal 9202. Note that FIG. 10(C) is a perspective view of the portable information terminal 9202 in an unfolded state, FIG. 10(D) is a perspective view of the portable information terminal 9202 in a state changing from one of the unfolded state or the folded state to the other, and FIG. 10(E) is a perspective view of the portable information terminal 9202 in a folded state.

[0390] The portable information terminal 9202 has excellent portability when folded, and when unfolded, it has excellent display listability due to a seamless and wide display area. The display unit 9001 of the portable information terminal 9202 is supported by three housings 9000 connected by a hinge 9055. By bending between the two housings 9000 via the hinge 9055, the portable information terminal 9202 can be reversibly deformed from the unfolded state to the folded state. For example, the portable information terminal 9202 can be bent with a radius of curvature of 1 mm or more and 150 mm or less.

[0391] This embodiment can be appropriately combined with other embodiments.

[0392] (Embodiment 7) In this embodiment, an example of applying the light-emitting element of one aspect of the present invention to various lighting devices will be described with reference to FIGS. 11 and 12. By using the light-emitting element which is one aspect of the present invention, a lighting device with good luminous efficiency and high reliability can be manufactured.

[0393] By fabricating the light-emitting element of one aspect of the present invention on a flexible substrate, an electronic device and a lighting device having a light-emitting region with a curved surface can be realized.

[0394] In addition, the light-emitting device to which the light-emitting element of one aspect of the present invention is applied can also be applied to vehicle lighting. For example, lighting can also be installed on the front glass, ceiling, etc.

[0395] FIG. 11(A) shows a perspective view of one side of the multifunctional terminal 3500, and FIG. 11(B) shows a perspective view of the other side of the multifunctional terminal 3500. The multifunctional terminal 3500 has a display unit 3504, a camera 3506, lighting 3508, etc. incorporated in a housing 3502. The light-emitting device of one aspect of the present invention can be used for the lighting 3508.

[0396] The illumination 3508 functions as a surface light source by using the light-emitting device according to an aspect of the present invention. Therefore, unlike a point light source typified by an LED, light emission with less directivity can be obtained. For example, when the illumination 3508 and the camera 3506 are used in combination, the illumination 3508 can be turned on or blinked and imaged by the camera 3506. Since the illumination 3508 has a function as a surface light source, a photograph as if taken under natural light can be taken.

[0397] Note that the multifunctional terminal 3500 shown in FIGS. 11(A) and 11(B) can have various functions in the same manner as the electronic devices shown in FIGS. 10(A) to 10(C).

[0398] Also, inside the housing 3502, a speaker, a sensor (including those having a function of measuring force, displacement, position, speed, acceleration, angular velocity, rotation speed, distance, light, liquid, magnetism, temperature, chemical substance, voice, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, gradient, vibration, odor or infrared rays), a microphone, etc. can be provided. Further, by providing a detection device having a sensor for detecting inclination such as a gyro or an acceleration sensor inside the multifunctional terminal 3500, the orientation (vertical or horizontal) of the multifunctional terminal 3500 can be determined and the screen display of the display unit 3504 can be automatically switched.

[0399] The display unit 3504 can also function as an image sensor. For example, by touching the display unit 3504 with a palm or a finger and imaging a palm print, a fingerprint, etc., personal authentication can be performed. Also, if a backlight that emits near-infrared light or a sensing light source that emits near-infrared light is used for the display unit 3504, finger veins, palm veins, etc. can also be imaged. Note that the light-emitting device according to an aspect of the present invention may be applied to the display unit 3054.

[0400] FIG. 11(C) shows a perspective view of a security light 3600. The light 3600 has an illumination 3608 on the outside of the housing 3602, and a speaker 3610 etc. are incorporated in the housing 3602. The light-emitting element according to an aspect of the present invention can be used for the illumination 3608.

[0401] As the light 3600, for example, it can emit light by gripping, holding, or retaining the illumination 3608. Also, inside the housing 3602, there may be provided an electronic circuit capable of controlling the light emission method from the light 3600. As the electronic circuit, for example, it may be a circuit capable of emitting light once or intermittently a plurality of times, or a circuit capable of adjusting the light amount of light emission by controlling the current value of light emission. Also, a circuit may be incorporated such that a loud alarm sound is output from the speaker 3610 simultaneously with the light emission of the illumination 3608.

[0402] Since the light 3600 can emit light in all directions, for example, it can intimidate with light or light and sound toward a thug or the like. Also, the light 3600 may have a photographing function by including a camera such as a digital still camera.

[0403] FIG. 12 shows an example in which the light-emitting element is used as an indoor lighting device 8501. Since the light-emitting element can also be made larger in area, a large-area lighting device can also be formed. In addition, by using a housing having a curved surface, a lighting device 8502 having a curved light-emitting area can also be formed. The light-emitting element shown in this embodiment is in a thin film shape, and the degree of freedom in the design of the housing is high. Therefore, lighting devices with various elaborate designs can be formed. Furthermore, a large lighting device 8503 may be provided on the wall surface of the room. Also, a touch sensor may be provided in the lighting devices 8501, 8502, 8503 to turn the power on or off.

[0404] Also, by using the light-emitting element on the surface side of the table, a lighting device 8504 having a function as a table can be obtained. In addition, by using the light-emitting element in a part of other furniture, a lighting device having a function as furniture can be obtained.

[0405] As described above, a lighting device and an electronic device can be obtained by applying the light-emitting device according to one aspect of the present invention. Note that the applicable lighting devices and electronic devices are not limited to those shown in this embodiment, and can be applied to electronic devices in any field.

[0406] In addition, the configurations shown in this embodiment can be used in appropriate combination with the configurations shown in other embodiments.

[0407] (Embodiment 8) In this embodiment, an example in which the light-emitting element described in Embodiments 1 to 4 is used as a lighting device will be described with reference to FIG. 47. FIG. 47(B) is a top view of the lighting device, and FIG. 47(A) is a cross-sectional view taken along the line e-f in FIG. 47(B).

[0408] In the lighting device in this embodiment, an anode 4401 is formed on a translucent substrate 4400 that is a support. The anode 4401 corresponds to the electrodes 101, 103 or the anode 401 in Embodiments 1 to 4. When extracting light from the anode 4401 side, the anode 4401 is formed of a translucent material.

[0409] A pad 4412 for supplying a voltage to the cathode 4404 is formed on the substrate 4400.

[0410] An EL layer 4403 is formed on the anode 4401. The EL layer 4403 corresponds to the configuration of the EL layer, the light-emitting units 106, 108, 110, and the configuration of the light-emitting units in Embodiments 1 to 4. For these configurations, refer to the corresponding descriptions.

[0411] The cathode 4404 is formed to cover the EL layer 4403. The cathode 4404 corresponds to the electrode 102 or the cathode 402 in Embodiments 1 to 4. When extracting light from the anode 4401 side, the cathode 4404 is formed of a material with high reflectivity. The cathode 4404 is connected to the pad 4412 to supply a voltage.

[0412] The lighting device shown in this embodiment has a light-emitting element having an anode 4401, an EL layer 4403, and a cathode 4404. Since the light-emitting element has high luminous efficiency, the lighting device in this embodiment can be a lighting device with low power consumption.

[0413] A substrate 4400 on which a light-emitting element having the above configuration is formed and a sealing substrate 4407 are fixed and sealed using sealing materials 4405 and 4406, thereby completing the lighting device. Either of the sealing materials 4405 and 4406 may be used. Further, a desiccant can be mixed into the inner sealing material 4406 (not shown in FIG. 47(B)), whereby moisture can be adsorbed, leading to an improvement in reliability.

[0414] Also, by extending a part of the pad 4412 and the anode 4401 outside the sealing materials 4405 and 4406, an external input terminal can be formed. Further, an IC chip 4420 or the like on which a converter or the like is mounted may be provided thereon.

[0415] As described above, the lighting device described in this embodiment uses the light-emitting element described in Embodiments 1 to 4 for the EL element and can be a light-emitting device with low power consumption.

[0416] (Embodiment 9) In this embodiment, an example of an electronic device including a part of the light-emitting element described in Embodiments 1 to 4 will be described. The light-emitting element described in Embodiments 1 to 4 is a light-emitting element having good luminous efficiency and driving voltage. As a result, the electronic device described in this embodiment can be an electronic device with low power consumption.

[0417] As electronic devices to which the above light-emitting element is applied, for example, there are a television set (also referred to as a TV or a television receiver), a monitor for a computer, a digital camera, a digital video camera, a digital photo frame, a mobile phone (also referred to as a cellular phone or a mobile phone device), a portable game machine, a portable information terminal, an audio reproduction device, a large game machine such as a pachinko machine, and the like. Specific examples of these electronic devices are shown below.

[0418] FIG. 48(A) shows an example of a television set. In the television set, a display unit 7103 is incorporated in a housing 7101. Here, a configuration in which the housing 7101 is supported by a stand 7105 is shown. The display unit 7103 can display an image, and the display unit 7103 is configured by arranging any one of the light-emitting elements described in Embodiments 1 to 4 in a matrix.

[0419] The operation of the television set can be performed by an operation switch provided in the housing 7101 or a separate remote control operation unit 7110. By the operation keys 7109 provided in the remote control operation unit 7110, operations such as changing channels and adjusting the volume can be performed, and the image displayed on the display unit 7103 can be operated. Further, the remote control operation unit 7110 may be configured to be provided with a display unit 7107 for displaying information output from the remote control operation unit 7110.

[0420] Note that the television set has a configuration including a receiver, a modem, and the like. The receiver can receive general television broadcasts, and further, by connecting to a communication network by wire or wirelessly via a modem, one-way (from the sender to the receiver) or two-way (between the sender and the receiver, or between the receivers) information communication can also be performed.

[0421] Figure 48(B1) shows a computer, which includes a main body 7201, a housing 7202, a display unit 7203, a keyboard 7204, an external connection port 7205, a pointing device 7206, etc. Note that this computer is manufactured by arranging the light-emitting elements described in Embodiments 1 to 4 in a matrix and using them for the display unit 7203. The computer in Figure 48(B1) may be in the form shown in Figure 48(B2). In the computer of Figure 48(B2), a second display unit 7210 is provided instead of the keyboard 7204 and the pointing device 7206. The second display unit 7210 is a touch panel type, and input can be performed by operating the input display shown on the second display unit 7210 with a finger or a dedicated pen. In addition, the second display unit 7210 can display not only input displays but also other images. Also, the display unit 7203 may also be a touch panel. By connecting the two screens with a hinge, it is possible to prevent troubles such as damaging or breaking the screens during storage or transportation.

[0422] Figure 48(C) shows an example of a mobile terminal. The mobile terminal includes, in addition to a display unit 7402 incorporated in a housing 7401, operation buttons 7403, an external connection port 7404, a speaker 7405, a microphone 7406, etc. Note that the mobile terminal has a display unit 7402 manufactured by arranging the light-emitting elements described in Embodiments 1 to 4 in a matrix.

[0423] The mobile terminal shown in Figure 48(C) can also be configured such that information can be input by touching the display unit 7402 with a finger or the like. In this case, operations such as making a call or creating an email can be performed by touching the display unit 7402 with a finger or the like.

[0424] The screen of the display unit 7402 mainly has three modes. The first is a display mode mainly for displaying images, the second is an input mode mainly for inputting information such as characters, and the third is a display + input mode in which the two modes of the display mode and the input mode are mixed.

[0425] For example, when making a phone call or creating an email, the display unit 7402 can be set to a character input mode mainly for character input, and an input operation on the characters displayed on the screen can be performed. In this case, it is preferable to display a keyboard or number buttons on most of the screen of the display unit 7402.

[0426] In addition, by providing a detection device having sensors such as a gyro and an acceleration sensor inside the mobile terminal to detect the inclination, the orientation (portrait or landscape) of the mobile terminal can be determined, and the screen display of the display unit 7402 can be automatically switched.

[0427] Also, the switching of the screen mode is performed by touching the display unit 7402 or operating the operation button 7403 of the housing 7401. It can also be switched according to the type of image displayed on the display unit 7402. For example, if the image signal displayed on the display unit is video data, it is switched to the display mode, and if it is text data, it is switched to the input mode.

[0428] In addition, in the input mode, the signal detected by the optical sensor of the display unit 7402 is detected, and when there is no input by touch operation on the display unit 7402 for a certain period, the screen mode may be controlled to be switched from the input mode to the display mode.

[0429] The display unit 7402 can also function as an image sensor. For example, by touching the display unit 7402 with a palm or finger and imaging palm prints, fingerprints, etc., personal authentication can be performed. Also, if a backlight that emits near-infrared light or a sensing light source that emits near-infrared light is used for the display unit, finger veins, palm veins, etc. can also be imaged.

[0430] Note that the configurations shown in this embodiment can be used by appropriately combining the configurations shown in Embodiments 1 to 4.

[0431] As described above, the scope of application of the light-emitting device including the light-emitting element according to any one of Embodiments 1 to 4 is extremely wide, and this light-emitting device can be applied to electronic devices in all fields. By using the light-emitting element according to any one of Embodiments 1 to 4, an electronic device with low power consumption can be obtained.

[0432] FIG. 49(A) is a schematic diagram showing an example of a cleaning robot.

[0433] The cleaning robot 5100 has a display 5101 disposed on the upper surface, a plurality of cameras 5102 disposed on the side surface, a brush 5103, and operation buttons 5104. Although not shown, the lower surface of the cleaning robot 5100 is provided with tires, a suction port, and the like. The cleaning robot 5100 is further provided with various sensors such as an infrared sensor, an ultrasonic sensor, an acceleration sensor, a piezo sensor, an optical sensor, and a gyro sensor. In addition, the cleaning robot 5100 is provided with wireless communication means.

[0434] The cleaning robot 5100 can travel automatically, detect dust 5120, and suck the dust from the suction port provided on the lower surface.

[0435] In addition, the cleaning robot 5100 can analyze the image captured by the camera 5102 and determine the presence or absence of obstacles such as walls, furniture, or steps. Further, when an object likely to be entangled with the brush 5103 such as wiring is detected by image analysis, the rotation of the brush 5103 can be stopped.

[0436] The display 5101 can display the remaining amount of the battery, the amount of sucked dust, and the like. The path traveled by the cleaning robot 5100 may be displayed on the display 5101. Further, the display 5101 may be a touch panel, and the operation buttons 5104 may be provided on the display 5101.

[0437] The cleaning robot 5100 can communicate with a mobile electronic device 5140 such as a smartphone. Images captured by the camera 5102 can be displayed on the mobile electronic device 5140. Therefore, the owner of the cleaning robot 5100 can know the state of the room even when away from home. Also, the display on the display 5101 can be confirmed on a mobile electronic device such as a smartphone.

[0438] The light-emitting device according to one aspect of the present invention can be used for the display 5101.

[0439] The robot 2100 shown in Fig. 49(B) includes an arithmetic unit 2110, an illuminance sensor 2101, a microphone 2102, an upper camera 2103, a speaker 2104, a display 2105, a lower camera 2106, an obstacle sensor 2107, and a moving mechanism 2108.

[0440] The microphone 2102 has a function of detecting the user's voice and environmental sounds, etc. Also, the speaker 2104 has a function of emitting sound. The robot 2100 can communicate with the user using the microphone 2102 and the speaker 2104.

[0441] The display 2105 has a function of displaying various information. The robot 2100 can display the information desired by the user on the display 2105. The display 2105 may be equipped with a touch panel. Also, the display 2105 may be a removable information terminal, and by installing it in a fixed position of the robot 2100, charging and data transfer are made possible.

[0442] The upper camera 2103 and the lower camera 2106 have the function of imaging the surroundings of the robot 2100. Also, the obstacle sensor 2107 can detect the presence or absence of obstacles in the traveling direction when the robot 2100 moves forward using the moving mechanism 2108. The robot 2100 can recognize the surrounding environment and move safely using the upper camera 2103, the lower camera 2106, and the obstacle sensor 2107.

[0443] The light-emitting device according to one aspect of the present invention can be used for the display 2105.

[0444] FIG. 49(C) is a diagram showing an example of a goggle-type display. The goggle-type display includes, for example, a housing 5000, a display unit 5001, a speaker 5003, an LED lamp 5004, a connection terminal 5006, a sensor 5007 (including a function of measuring force, displacement, position, speed, acceleration, angular velocity, rotation speed, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, gradient, vibration, odor, or infrared rays), a microphone 5008, a second display unit 5002, a support unit 5012, earphones 5013, and the like.

[0445] The light-emitting device according to one aspect of the present invention can be used for the display unit 5001 and the second display unit 5002.

[0446] FIG. 50 is an example in which the light-emitting element described in any one of Embodiments 1 to 4 is used in an electric stand which is a lighting device. The electric stand shown in FIG. 50 has a housing 2001 and a light source 2002, and as the light source 2002, the lighting device described in Embodiment 8 may be used.

[0447] FIG. 51 shows an example in which the light-emitting element described in any one of Embodiments 1 to 4 is used as an indoor lighting device 3001. Since the light-emitting element described in any one of Embodiments 1 to 4 is a light-emitting element with high luminous efficiency, it can be made into a lighting device with low power consumption. Also, since the light-emitting element described in any one of Embodiments 1 to 4 can be made into a large area, it can be used as a large-area lighting device. Further, since the light-emitting element described in any one of Embodiments 1 to 4 is thin, it can be used as a thin lighting device.

[0448] The light-emitting element described in any one of Embodiments 1 to 4 can also be mounted on the windshield or dashboard of an automobile. FIG. 52 shows one aspect of using the light-emitting element described in any one of Embodiments 1 to 4 on the windshield or dashboard of an automobile. Display areas 5200 to 5203 are displays provided using the light-emitting element described in any one of Embodiments 1 to 4.

[0449] Display area 5200 and display area 5201 are display devices equipped with the light-emitting element described in any one of Embodiments 1 to 4 provided on the windshield of an automobile. The light-emitting element described in any one of Embodiments 1 to 4 can be made into a so-called see-through display device where the opposite side can be seen through by forming the anode and cathode with light-transmissive electrodes. For a see-through display, even if it is installed on the windshield of an automobile, it can be installed without obstructing the view. When providing a transistor or the like for driving, it is preferable to use a light-transmissive transistor such as an organic transistor made of an organic semiconductor material or a transistor using an oxide semiconductor.

[0450] The display area 5202 is a display device equipped with the light-emitting element described in any one of Embodiments 1 to 4 provided in the pillar portion. By projecting the video from the imaging means provided on the vehicle body in the display area 5202, the visual field blocked by the pillar can be complemented. Similarly, the display area 5203 provided in the dashboard portion can complement the visual field blocked by the vehicle body by projecting the video from the imaging means provided outside the vehicle, thereby making up for the blind spot and enhancing safety. By projecting the video so as to complement the invisible part, safety confirmation can be performed more naturally and without a sense of discomfort.

[0451] The display area 5203 can also provide various other information such as navigation information, speedometer, tachometer, driving distance, fuel, gear state, air conditioner settings, etc. The display can appropriately change the display items and layout according to the user's preference. Note that this information can also be provided in the display areas 5200 to 5202. In addition, the display areas 5200 to 5203 can also be used as lighting devices.

[0452] Also, FIGS. 53(A) and (B) show a foldable portable information terminal 5150. The foldable portable information terminal 5150 has a housing 5151, a display area 5152, and a bending portion 5153. FIG. 53(A) shows the portable information terminal 5150 in the unfolded state. FIG. 53(B) shows the portable information terminal in the folded state. Despite having a large display area 5152, the portable information terminal 5150 is compact and highly portable when folded.

[0453] The display area 5152 can be folded in half by the bending portion 5153. The bending portion 5153 is composed of an extensible member and a plurality of support members. When folding, the extensible member extends. The bending portion 5153 is folded with a radius of curvature of 2 mm or more, preferably 3 mm or more.

[0454] Note that the display area 5152 may be a touch panel (input / output device) equipped with a touch sensor (input device). The light-emitting device according to one aspect of the present invention can be used for the display area 5152.

[0455] In addition, FIGS. 54(A) to (C) show a foldable portable information terminal 9310. FIG. 54(A) shows the portable information terminal 9310 in an unfolded state. FIG. 54(B) shows the portable information terminal 9310 in a state midway between changing from the unfolded state or the folded state to the other. FIG. 54(C) shows the portable information terminal 9310 in a folded state. The portable information terminal 9310 has excellent portability in the folded state, and in the unfolded state, it has excellent display listability due to a seamless and wide display area.

[0456] The display panel 9311 is supported by three housings 9315 connected by a hinge 9313. Note that the display panel 9311 may be a touch panel (input / output device) equipped with a touch sensor (input device). Further, the display panel 9311 can be reversibly deformed from the unfolded state to the folded state of the portable information terminal 9310 by bending between the two housings 9315 via the hinge 9313. The light-emitting device according to one aspect of the present invention can be used for the display panel 9311. The display area 9312 in the display panel 9311 is a display area located on the side surface of the portable information terminal 9310 in the folded state. Information icons, shortcuts of frequently used apps or programs, etc. can be displayed in the display area 9312, and information can be confirmed and apps can be started smoothly.

Example

[0457] In this example, an example of manufacturing a light-emitting element according to one aspect of the present invention and the characteristics of the light-emitting element will be described. In addition, the refractive index of the organic compound used for the hole injection layer and the refractive index of the hole injection layer will be described. A cross-sectional view of the element structure manufactured in this example is shown in FIG. 3. Further, the details of the element structure are shown in Table 1. In addition, the structures and abbreviations of the compounds used are shown below.

[0458] [Chemical]

[0459] [Table 1]

[0460] [Table 2]

[0461] [Table 3]

[0462] [Measurement of Refractive Index] The refractive indices of the organic compounds used in the hole injection layer 111 of Light Emitting Elements 1 to 4 and Comparative Light Emitting Elements 5 to 16 and the hole injection layer 111 were measured. The refractive index was measured at room temperature using a rotating compensator type multi-incidence angle spectroscopic ellipsometer (M-2000U) manufactured by J.A. Woolam Co., Ltd. The measurement sample was fabricated by vacuum evaporation on a quartz substrate. n Ordinary and n Extra-ordinary were measured, and n average was calculated.

[0463] The results of measuring the refractive index of each film for light with a wavelength of 532 nm are shown in Fig. 13. From Fig. 13, it was found that TAPC used in Light Emitting Elements 1 to 4 and Comparative Light Emitting Elements 9 to 12 is an organic compound with a very low refractive index with n Ordinary being 1.70 or less. It was found that DBT3P-II used in Comparative Light Emitting Elements 5 to 8 and Comparative Light Emitting Elements 13 to 16 has a high refractive index with n Ordinary exceeding 1.80.

[0464] In addition, since the hole injection layer 111 is required to have hole injection properties, it preferably contains an electron-donating material. The hole injection layer 111 of each light-emitting element using MoO3 with a high refractive index as the electron-donating material is expected to have a high refractive index. However, as shown in Fig. 13, it was found that the refractive index of the film obtained by adding MoO3, which is the hole injection layer 111 of each light-emitting element, to each organic compound increased slightly compared to the refractive index of each organic compound. That is, it was found that by using the refractive index of the organic compound for the hole injection layer 111, a hole injection layer 111 with a low refractive index can be obtained even when a material with a high refractive index is used for the electron-donating material.

[0465] In addition, as shown in Fig. 13, it was found that the difference between n Ordinary and Extra-ordinary of the hole injection layer 111 of each light-emitting element is smaller than that of the film of each organic compound. That is, it was found that the mixed film of MoO3, which is an electron-donating material, and the organic compound has a reduced anisotropy compared to the organic compound film.

[0466] <Fabrication of Light-Emitting Element> ≪Fabrication of Light-Emitting Elements 1 to 4≫ An electrode 101 was formed by sequentially forming an alloy of silver, palladium, and copper (Ag-Pd-Cu, also referred to as APC) as the first anode (1) and an ITSO film as the second anode (2) on the substrate 200 to thicknesses of 100 nm and 110 nm, respectively. The ITSO film has a function of transmitting light, and the APC film is a conductive film having a function of reflecting light and a function of transmitting light. The electrode area of the electrode 101 was 4 mm 2 (2 mm × 2 mm). The refractive index (n Ordinary) of the ITSO film at 532 nm light is 2.07.

[0467] Next, on the first electrode 101(2), as the hole injection layer 111, 1,1-bis-(4-bis(4-methyl-phenyl)-amino-phenyl)-cyclohexane (abbreviation: TAPC) and MoO3 were co-evaporated such that the weight ratio (TAPC:MoO3) was 2:0.5 and the thickness was x1 nm. Note that the value of x1 varies depending on each light-emitting element, and the value of x1 for each light-emitting element is the value shown in Table 3.

[0468] Next, on the hole injection layer 111, as the hole transport layer 112, PCCP was deposited to a thickness of 20 nm.

[0469] Next, on the hole transport layer 112, as the first light-emitting layer 130(1), 4,6mCzP2Pm, PCCP, and Ir(ppy)3 were co-evaporated such that the weight ratio was (4,6mCzP2Pm:PCCP:Ir(ppy)3) = 0.5:0.5:0.1 and the thickness was 20 nm. Subsequently, as the second light-emitting layer 130(2), they were co-evaporated such that the weight ratio (4,6mCzP2Pm:PCCP:Ir(ppy)3) = 0.8:0.2:0.1 and the thickness was 20 nm. Note that in the first light-emitting layer 130(1) and the second light-emitting layer 130(2), Ir(ppy)3 is a guest material that exhibits phosphorescent emission.

[0470] Next, on the second light-emitting layer 130(2), as the first electron transport layer 118(1), 4,6mCzP2Pm was deposited to a thickness of 20 nm. Subsequently, on the first electron transport layer 118(1), as the second electron transport layer 118(2), NBPhen was deposited to a film thickness of 15 nm.

[0471] Next, on the second electron transport layer 118(2), as the electron injection layer 119, lithium fluoride (LiF) was deposited to a thickness of 1 nm.

[0472] Next, on the electron injection layer 119, as the first electrode 102(1), aluminum (Al) was formed to a thickness of 1 nm. Subsequently, on the first electrode 102(1), as the second electrode 102(2), Ag was deposited to a film thickness of 24 nm.

[0473] Next, DBT3P-II was deposited as the cap layer 145 on the second electrode 102(2) to a film thickness of 70 nm.

[0474] Next, in a glove box under a nitrogen atmosphere, a glass substrate for sealing using a sealing material for organic EL was fixed to the glass substrate on which the organic material was formed, thereby sealing the light-emitting elements 1 to 4. Specifically, the sealing material was applied around the organic material on the glass substrate on which the organic material was formed, and the substrate was bonded to the glass substrate for sealing, and ultraviolet light with a wavelength of 365 nm was irradiated at 6 J / cm 2 and heat-treated at 80 °C for 1 hour. The light-emitting elements 1 to 4 were obtained through the above steps.

[0475] ≪Fabrication of Comparative Light-Emitting Elements 5 to 8≫ The fabrication processes of the comparative light-emitting elements 5 to 8 differed only in the fabrication process of the hole injection layer 111 from the fabrication processes of the light-emitting elements 1 to 4, and the other processes were performed in the same manner as those of the light-emitting elements 1 to 4.

[0476] On the electrode 101, DBT3P-II and MoO3 were co-evaporated as the hole injection layer 111 such that the weight ratio (DBT3P-II:MoO3) was 2:0.5 and the thickness was x1 nm. Note that the value of x1 differed depending on each light-emitting element, and the value of x1 for each light-emitting element was the value shown in Table 3.

[0477] ≪Fabrication of Comparative Light-Emitting Elements 9 to 12≫ The fabrication processes of the comparative light-emitting elements 9 to 12 differed only in the fabrication process of the cap layer 145 from the fabrication processes of the light-emitting elements 1 to 4, and the other processes were performed in the same manner as those of the light-emitting elements 1 to 4.

[0478] The comparative light-emitting elements 9 to 12 did not form the cap layer 145. That is, after forming the electrode 102(2), sealing was performed to obtain the comparative light-emitting elements 9 to 12.

[0479] <<Fabrication of Comparative Light-Emitting Elements 13 to 16>> The fabrication processes of Comparative Light-Emitting Elements 13 to 16 were different only in the fabrication processes of the above Comparative Light-Emitting Elements 5 to 8 and the fabrication process of the cap layer 145, and the other processes were carried out in the same manner as those of Comparative Light-Emitting Elements 5 to 8.

[0480] For Comparative Light-Emitting Elements 13 to 16, the cap layer 145 was not formed. That is, after forming the electrode 102(2), sealing was performed to obtain Comparative Light-Emitting Elements 13 to 16.

[0481] Note that Light-Emitting Elements 1 to 4 and Comparative Light-Emitting Elements 5 to 16 are top-emission type light-emitting elements, and the light extraction side is the electrode 102 side.

[0482] <Characteristics of Light-Emitting Elements> Next, the characteristics of the fabricated Light-Emitting Elements 1 to 4 and Comparative Light-Emitting Elements 5 to 16 were measured. For the measurement of luminance and CIE chromaticity, a color luminance meter (Topcon Corporation, BM-5A) was used, and for the measurement of the electroluminescence spectrum, a multi-channel spectroscope (Hamamatsu Photonics K.K., PMA-11) was used. Note that the measurement of each light-emitting element was performed at room temperature (an atmosphere maintained at 23°C).

[0483] Among the fabricated light-emitting elements, the current efficiency-luminance characteristics of Light-Emitting Element 1, Comparative Light-Emitting Element 5, Comparative Light-Emitting Element 9, and Comparative Light-Emitting Element 13 are shown in FIG. 14. Also, the current density-voltage characteristics are shown in FIG. 15. Further, the external quantum efficiency-luminance characteristics are shown in FIG. 16. Note that, as described above, as the organic compound of the hole injection layer 111, TAPC with a low refractive index was used for Light-Emitting Element 1 and Comparative Light-Emitting Element 9, and DBT3P-II was used for Comparative Light-Emitting Element 5 and Comparative Light-Emitting Element 13, respectively. Also, Light-Emitting Element 1 and Comparative Light-Emitting Element 5 are light-emitting elements having the cap layer 145, and Comparative Light-Emitting Element 9 and Comparative Light-Emitting Element 13 are light-emitting elements not having the cap layer 145. The parts other than the organic compound used for the hole injection layer 111 and the presence or absence of the cap layer 145 have the same element structure.

[0484] As shown in Fig. 15, it was found that the light-emitting element 1, the comparative light-emitting element 5, the comparative light-emitting element 9, and the comparative light-emitting element 13 have the same current density-voltage characteristics. Therefore, it was found that even when an organic compound with a low refractive index is used for the hole injection layer 111, it has good hole injection characteristics.

[0485] Also, from Figs. 14 and 16, it was found that the light-emitting element 1, the comparative light-emitting element 5, the comparative light-emitting element 9, and the comparative light-emitting element 13 have a high current efficiency exceeding 100 cd / A and a high external quantum efficiency exceeding 20%. Also, when comparing the light-emitting element 1 and the comparative light-emitting element 9, the light-emitting element 1 has better current efficiency and external quantum efficiency. The light-emitting element 1 has the cap layer 145, while the comparative light-emitting element 9 does not have the cap layer 145. Therefore, the light-emitting element 1 with good light extraction efficiency has better current efficiency and external quantum efficiency. The same applies to the relationship between the comparative light-emitting element 5 and the comparative light-emitting element 13.

[0486] Also, the emission spectra of the light-emitting element 1, the comparative light-emitting element 5, the comparative light-emitting element 9, and the comparative light-emitting element 13 when a current is passed at a current density of 25 mA / cm 2 are shown in Fig. 17. As shown in Fig. 17, the emission spectra of the light-emitting element 1, the comparative light-emitting element 5, the comparative light-emitting element 9, and the comparative light-emitting element 13 each have a peak near 530 nm, 538 nm, 548 nm, and 556 nm, and it was found that they are derived from the emission of Ir(ppy)3, which is the guest material contained in the light-emitting layer 130.

[0487] Also, Table 4 shows the element characteristics of the light-emitting elements 1 to 4 and the comparative light-emitting elements 5 to 16 near 1000 cd / m 2 .

[0488]

Table 4

[0489] The above results show that the light-emitting elements 1 to 4 and the comparative light-emitting elements 5 to 16 fabricated in this example exhibit good driving voltages and luminous efficiencies regardless of the structure of the hole-injection layer 111. Furthermore, it is clear that the light-emitting elements 1 to 4 and the comparative light-emitting elements 5 to 8, which have the cap layer 145, have better efficiency than the comparative light-emitting elements 9 to 16.

[0490] Furthermore, it is believed that the guest material Ir(ppy)3 emits light in each of the light-emitting elements 1 to 4 and the comparative light-emitting elements 5 to 16. Therefore, the peak wavelength of the light emitted from the light-emitting elements 1 to 4 and the comparative light-emitting elements 5 to 16 is believed to be approximately 530 nm to 580 nm, as shown in FIG. 17 . Here, in the light-emitting elements 1 to 4 and the comparative light-emitting elements 9 to 12, the optical distance between the low-refractive-index hole injection layer 111 and the light-emitting layer 130 is λ / 2 or less of the peak wavelength. Furthermore, the optical distance from the anode (electrode 101) side or the cathode (electrode 102) side of the light-emitting layer 130 to the electrode 101(2) is λ / 4±50 nm or less, and the optical distance from the anode (electrode 101) side or the cathode (electrode 102) side of the light-emitting layer 130 to the electrode 101(2) is 3λ / 4±50 nm or less.

[0491] <Relationship between Refractive Index of Hole Injection Layer 111 and External Quantum Efficiency> FIG. 18 shows the 1000 cd / m 2 18 shows the relationship between the external quantum efficiency in the vicinity of the peak wavelength of light emitted from each light-emitting element and the peak wavelength of light emitted from each light-emitting element. In FIG. 18, the data for the "TAPC" curve were obtained from the values of comparative light-emitting elements 9 to 12, and the data for the "DBT3P-II" curve were obtained from the values of comparative light-emitting elements 13 to 16.

[0492] 19 shows the luminance distribution of the light-emitting elements 1 to 4 and the comparative light-emitting elements 5 to 8 at 1000 cd / m 2Shows the relationship between the external quantum efficiency in the vicinity and the emission peak wavelength obtained from each light-emitting element. In Fig. 19, the values of light-emitting elements 1 to 4 are used for the data of the "TAPC" curve, and the values of comparative light-emitting elements 5 to 8 are used for the data of the "DBT3P-II" curve, respectively.

[0493] From Figs. 18 and 19, it can be seen that in the range of the film thickness of the hole injection layer 111 fabricated in this example, the relationship between the external quantum efficiency and the peak wavelength is such that as the peak wavelength increases, the external quantum efficiency tends to decrease. In the light-emitting element without the cap layer 145, in Fig. 18, the data of the "TAPC" curve and the data of the "DBT3P-II" curve overlap, indicating almost the same efficiency regardless of the refractive index of the hole injection layer 111. On the other hand, from Fig. 19, it can be seen that in the light-emitting element with the cap layer 145, the data of the "TAPC" curve shows better efficiency than the data of the "DBT3P-II" curve. That is, it was found that in the light-emitting element with the cap layer 145, the luminous efficiency can be improved by using a hole injection layer with a low refractive index.

[0494] Therefore, it was found that the efficiency can be improved by using a hole injection layer 111 and a cap layer 145 with a low refractive index in the top emission type light-emitting element.

Example

[0495] In this example, as a light-emitting element according to an aspect of the present invention, an example of fabricating a light-emitting element different from that in Example 1 and the characteristics of the light-emitting element will be described. The details of the element structure are shown in Table 5. The structures and abbreviations of the compounds used are shown below. For other organic compounds, reference may be made to Example 1 above.

[0496]

Chemical formula

[0497]

Table 5

[0498] ≪Fabrication of Light-Emitting Element 17≫ Electrode 101 was formed by sequentially forming an APC film and an ITSO film on substrate 200 to thicknesses of 100 nm and 85 nm, respectively.

[0499] Next, on electrode 101, as hole injection layer 111, PCPPn and MoO3 were co-evaporated such that the weight ratio (PCPPn:MoO3) was 2:0.5 and the thickness was 20 nm.

[0500] Next, on hole injection layer 111, as hole transport layer 112, PCPPn was evaporated to a thickness of 30 nm.

[0501] Next, on hole transport layer 112, as light-emitting layer 130, cgDBCzPA and N,N’-(pyrene-1,6-diyl)bis[(6,N-diphenylbenzo[b]naphtho[1,2-d]furan)-8-amine] (abbreviation: 1,6BnfAPrn-03) were co-evaporated such that the weight ratio was (cgDBCzPA:1,6BnfAPrn-03)=1:0.03 and the thickness was 25 nm. In light-emitting layer 130, 1,6BnfAPrn-03 is a guest material that exhibits blue fluorescence emission.

[0502] Next, on light-emitting layer 130, as the first electron transport layer 118(1), cgDBCzPA was evaporated to a thickness of 5 nm. Subsequently, on the first electron transport layer 118(1), as the second electron transport layer 118(2), BPhen was evaporated to a film thickness of 5 nm.

[0503] Next, on the second electron transport layer 118(2), as electron injection layer 119, BPhen and LiF were co-evaporated such that the weight ratio was (BPhen:LiF)=8:1 and the thickness was 15 nm. It is known that a film formed by co-evaporating a fluoride and an organic compound has a lower refractive index than a single organic compound film. Therefore, in light-emitting element 17, electron injection layer 119 functions as both an electron injection layer and a low refractive index layer.

[0504] Next, as the electrode 102, Ag and Mg were formed on the electron injection layer 119 such that the weight ratio was (Ag:Mg) = 1:0.017 and the thickness was 25 nm.

[0505] Next, as the cap layer 145, DBT3P-II was deposited on the electrode 102 to a film thickness of 70 nm.

[0506] Next, in a glove box under a nitrogen atmosphere, the light-emitting element 17 was sealed by fixing a glass substrate for sealing using an organic EL sealing material to the glass substrate on which the organic material was formed. Specifically, the sealing material was applied around the organic material on the glass substrate on which the organic material was formed, and the substrate was bonded to the glass substrate for sealing, and ultraviolet light with a wavelength of 365 nm was irradiated at 6 J / cm 2 and heat-treated at 80°C for 1 hour. The light-emitting element 17 was obtained through the above steps.

[0507] ≪Fabrication of Comparative Light-Emitting Element 18≫ The fabrication process of the comparative light-emitting element 18 differed only in the fabrication processes of the electron transport layer 118(2) and the electron injection layer 119 from the fabrication process of the above light-emitting element 17, and the other processes were performed in the same manner as those for the light-emitting element 17.

[0508] As the electron transport layer 118(2) of the comparative light-emitting element 18, 15 nm of BPhen was deposited. Subsequently, as the electron injection layer 119, 1 nm of LiF was deposited.

[0509] <Characteristics of the Light-Emitting Element> Next, the characteristics of the fabricated light-emitting element 17 and the comparative light-emitting element 18 were measured. The measurement was performed in the same manner as in Example 1.

[0510] The current efficiency-luminance characteristics of the light-emitting element 17 and the comparative light-emitting element 18 are shown in FIG. 20. Also, the current density-voltage characteristics are shown in FIG. 21. Further, the external quantum efficiency-luminance characteristics are shown in FIG. 22.

[0511] Also, the element characteristics of the light-emitting element 17 and the comparative light-emitting element 18 in the vicinity of 1000 cd / m 2 are shown in Table 6.

[0512]

Table 6

[0513] From FIG. 21 and Table 6, it was found that the light-emitting element 17 and the comparative light-emitting element 18 have equivalent current density-voltage characteristics.

[0514] Also, from FIGS. 20, 22 and Table 6, it was found that the light-emitting element 17 and the comparative light-emitting element 18 have good current efficiency and external quantum efficiency. Further, it was found that the light-emitting element 17 having the mixed film of BPhen and LiF which is a low refractive index layer has better current efficiency and external quantum efficiency than the comparative light-emitting element 18 which does not have the mixed film, that is, does not have a low refractive index layer. Therefore, in the light-emitting element having the cap layer 145, the luminous efficiency can be improved by using the electron injection layer 119 having a low refractive index.

[0515] Also, the emission spectra of the light-emitting element 17 and the comparative light-emitting element 18 when a current was passed at a current density of 2.5 mA / cm 2 are shown in FIG. 23. As shown in FIG. 23, the emission spectra of the light-emitting element 17 and the comparative light-emitting element 18 have a peak near 457 nm, and it was found that this is due to the emission of 1,6BnfAPrn-03 which is the guest material contained in the light-emitting layer 130. Here, in the light-emitting element 17, the optical distance between the electron injection layer 119 which is a low refractive index layer and the light-emitting layer 130 is λ / 2 or less of the peak wavelength. Further, the optical distance from the light-emitting layer 130 to the electrode 101(2) is λ / 4 or less, and the optical distance from the light-emitting layer 130 to the electrode 101(1) is 3λ / 4 or less.

Example

[0516] In this example, a production example of a light-emitting element and a comparative light-emitting element according to an aspect of the present invention different from the previous example and the characteristics of the light-emitting element will be described. The cross-sectional view of the element structure fabricated in this example is the same as that of FIG. 3. The details of the element structure are shown in Table 7. For the structure of the compounds used, reference may be made to the previous examples and embodiments.

[0517]

Table 7

[0518] ≪Fabrication of Light-Emitting Element 19≫ The electrode 101 was formed by sequentially depositing an APC film and an ITSO film on the substrate 200 to thicknesses of 100 nm and 85 nm, respectively.

[0519] Next, on the electrode 101, calcium fluoride (CaF2), TAPC, and MoO3 were co-evaporated as the hole injection layer 111 such that the weight ratio (CaF2:TAPC:MoO3) was 3:1:0.5 and the thickness was 35 nm. The hole injection layer 111 functions as a low refractive index layer. Subsequently, PCPPn and MoO3 were co-evaporated such that the weight ratio (PCPPn:MoO3) was 2:0.5 and the thickness was 5 nm.

[0520] Next, PCPPn was deposited as the hole transport layer 112 on the hole injection layer 111 to a thickness of 10 nm.

[0521] Next, cgDBCzPA and 1,6BnfAPrn-03 were co-evaporated as the light-emitting layer 130 on the hole transport layer 112 such that the weight ratio (cgDBCzPA:1,6BnfAPrn-03) = 1:0.03 and the thickness was 25 nm. In the light-emitting layer 130, 1,6BnfAPrn-03 is a guest material that exhibits blue fluorescence emission.

[0522] Next, NBPhen was deposited as the electron transport layer 118 on the light-emitting layer 130 to a thickness of 5 nm.

[0523] Next, BPhen and LiF were co-evaporated as the electron injection layer 119 on the electron transport layer 118 such that the weight ratio (BPhen:LiF) was 8:1 and the thickness was 30 nm. The electron injection layer 119 functions as a low refractive index layer.

[0524] Next, on the electron injection layer 119, as the electrode 102, Ag and magnesium (Mg) were formed such that the weight ratio was (Ag:Mg) = 1:0.017 and the thickness was 15 nm.

[0525] Next, on the electrode 102, DBT3P-II was vapor-deposited as the cap layer 145 to a film thickness of 70 nm.

[0526] Next, in a glove box under a nitrogen atmosphere, the light-emitting element 19 was sealed by fixing a glass substrate for sealing using an organic EL sealing material to the glass substrate on which the organic material was formed. Specifically, the sealing material was applied around the organic material on the glass substrate on which the organic material was formed, and the substrate was bonded to the glass substrate for sealing, and ultraviolet light with a wavelength of 365 nm was irradiated at 6 J / cm 2 and heat-treated at 80 °C for 1 hour. The light-emitting element 19 was obtained through the above steps.

[0527] ≪Fabrication of Comparative Light-Emitting Element 20≫ As a comparison with the light-emitting element 19, a comparative light-emitting element 20 was fabricated. In the comparative light-emitting element 20, the hole injection layer 111 and the electron injection layer 119 do not function as low refractive index layers.

[0528] On the substrate 200, the electrode 101 was formed by sequentially forming the APC and ITSO films to thicknesses of 100 nm and 85 nm, respectively.

[0529] Next, on the electrode 101, as the hole injection layer 111, PCPPn and MoO3 were co-vapor-deposited such that the weight ratio (PCPPn:MoO3) was 2:1 and the thickness was 35 nm.

[0530] Next, on the hole injection layer 111, as the hole transport layer 112, PCPPn was vapor-deposited to a thickness of 10 nm.

[0531] Next, as the light-emitting layer 130 on the hole transport layer 112, cgDBCzPA and 1,6BnfAPrn-03 were co-evaporated such that the weight ratio was (cgDBCzPA:1,6BnfAPrn-03) = 1:0.03 and the thickness was 25 nm.

[0532] Next, on the light-emitting layer 130, as the electron transport layer 118, NBPhen was deposited to a thickness of 25 nm.

[0533] Next, on the electron transport layer 118, as the electron injection layer 119, LiF was deposited to a thickness of 1 nm. Subsequently, on the electron injection layer 119, as the electrode 102, Ag and magnesium (Mg) were formed such that the weight ratio was (Ag:Mg) = 1:0.017 and the thickness was 15 nm.

[0534] Next, on the electrode 102, as the cap layer 145, DBT3P-II was deposited to a film thickness of 70 nm.

[0535] Next, in a glove box under a nitrogen atmosphere, a glass substrate for encapsulation using an organic EL encapsulant was fixed to the glass substrate on which the organic material was formed, thereby encapsulating the comparative light-emitting element 20. Specifically, the encapsulant was applied around the organic material on the glass substrate on which the organic material was formed, and the substrate was bonded to the glass substrate for encapsulation, and ultraviolet light with a wavelength of 365 nm was irradiated at 6 J / cm 2 and heat-treated at 80 °C for 1 hour. Through the above steps, the comparative light-emitting element 20 was obtained.

[0536] <Characteristics of the light-emitting element> Next, the characteristics of the above-prepared light-emitting element 19 and comparative light-emitting element 20 were measured. For the measurement of luminance and CIE chromaticity, a spectro-radiance meter (manufactured by Topcon Corporation, SR-UL1R) was used, and for the measurement of the electroluminescence spectrum, a multi-channel spectrometer (manufactured by Hamamatsu Photonics K.K., PMA-11) was used. The measurement of each light-emitting element was performed at room temperature (an atmosphere maintained at 23 °C).

[0537] The current efficiency-luminance characteristics of the light-emitting element 19 and the comparative light-emitting element 20 are shown in FIG. 24. The external quantum efficiency-luminance characteristics are shown in FIG. 25.

[0538] In addition, Table 8 shows the device characteristics of the light-emitting element 19 and the comparative light-emitting element 20 near 1000 cd / m 2 2.

[0539]

Table 8

[0540] Further, from FIGS. 24, 25, and Table 8, it was found that the light-emitting element 19 and the comparative light-emitting element 20 have good current efficiency and external quantum efficiency. Also, it was found that the light-emitting element 19 having the low refractive index layer has better current efficiency and external quantum efficiency than the comparative light-emitting element 20 not having the low refractive index layer. Therefore, in the light-emitting element having the cap layer 145, the light-emitting efficiency can be improved by using the low refractive index layer.

[0541] In addition, the emission spectra of the light-emitting element 19 and the comparative light-emitting element 20 when a current was passed at a current density of 2.5 mA / cm 2 2 are shown in FIG. 26. As shown in FIG. 26, the emission spectra of the light-emitting element 19 and the comparative light-emitting element 20 have a peak near 457 nm, and it was found that this is due to the emission of 1,6BnfAPrn-03, which is the guest material contained in the light-emitting layer 130. From FIGS. 26 and 8, the emission spectra of the light-emitting element 19 and the comparative light-emitting element 20 are almost the same and have almost the same chromaticity.

Example

[0542] In this example, an example of manufacturing a light-emitting element according to an aspect of the present invention different from the previous example and the characteristics of the light-emitting element will be described. The cross-sectional view of the device structure fabricated in this example is the same as that in FIG. 3. The details of the device structure are shown in Table 9. In addition, the structures and abbreviations of the compounds used are shown below. For other organic compounds, reference may be made to the previous examples and embodiments.

[0543] [Chemical formula]

[0544] [Table 9]

[0545] [Fabrication of Light-Emitting Element 21] The electrode 101 was formed by sequentially forming an APC film and an ITSO film on the substrate 200 to thicknesses of 100 nm and 85 nm, respectively.

[0546] Next, as the hole injection layer 111 on the electrode 101, calcium fluoride (CaF2), TAPC, and MoO3 were co-evaporated so that the weight ratio (CaF2:TAPC:MoO3) was 3:1:0.5 and the thickness was 30 nm. The hole injection layer 111 functions as a low refractive index layer. Subsequently, PCPPn and MoO3 were co-evaporated so that the weight ratio (PCPPn:MoO3) was 2:0.5 and the thickness was 5 nm.

[0547] Next, as the hole transport layer 112 on the hole injection layer 111, PCPPn was evaporated to a thickness of 10 nm.

[0548] Next, as the light-emitting layer 130 on the hole transport layer 112, cgDBCzPA and 3,10-bis[N-(dibenzofuran-3-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviation: 3,10FrA2Nbf(IV)-02) were co-evaporated so that the weight ratio (cgDBCzPA:3,10FrA2Nbf(IV)-02) = 1:0.01 and the thickness was 25 nm. In the light-emitting layer 130, 3,10FrA2Nbf(IV)-02 is a guest material that exhibits blue fluorescence emission.

[0549] Next, as the electron transport layer 118 on the light-emitting layer 130, NBPhen was evaporated to a thickness of 5 nm.

[0550] Next, on the electron transport layer 118, as the electron injection layer 119, BPhen and LiF were co-evaporated such that the weight ratio was (BPhen:LiF) = 8:1 and the thickness was 25 nm. The electron injection layer 119 functions as a low refractive index layer.

[0551] Next, on the electron injection layer 119, as the electrode 102, Ag and magnesium (Mg) were formed such that the weight ratio was (Ag:Mg) = 1:0.017 and the thickness was 15 nm.

[0552] Next, on the electrode 102, DBT3P-II was deposited as the cap layer 145 to a film thickness of 70 nm.

[0553] Next, in a glove box under a nitrogen atmosphere, the light-emitting element 21 was sealed by fixing a glass substrate for sealing using an organic EL sealing material to the glass substrate on which the organic material was formed. Specifically, the sealing material was applied around the organic material on the glass substrate on which the organic material was formed, and the substrate was bonded to the glass substrate for sealing, and ultraviolet light with a wavelength of 365 nm was irradiated at 6 J / cm 2 and heat-treated at 80°C for 1 hour. The light-emitting element 21 was obtained through the above steps.

[0554] <Characteristics of the light-emitting element> Next, the characteristics of the above-prepared light-emitting element 21 were measured. For the measurement of luminance and CIE chromaticity, a spectro-radiance meter (manufactured by Topcon Corporation, SR-UL1R) was used, and for the measurement of the electroluminescence spectrum, a multi-channel spectrometer (manufactured by Hamamatsu Photonics K.K., PMA-11) was used. The measurement of the light-emitting element was performed at room temperature (an atmosphere maintained at 23°C).

[0555] The current efficiency-luminance characteristics of the light-emitting element 21 are shown in FIG. 27, the current density-voltage characteristics are shown in FIG. 28, and the external quantum efficiency-luminance characteristics are shown in FIG. 29.

[0556] Also, the element characteristics in the vicinity of 1000 cd / m 2 of the light-emitting element 21 are shown in Table 10.

[0557]

Table 10

[0558] In addition, the emission spectrum when a current is passed through the light-emitting element 21 at a current density of 2.5 mA / cm 2 is shown in FIG. 30. As shown in FIG. 30, the emission spectrum of the light-emitting element 21 has a peak at 452 nm and a full width at half maximum of 22 nm. Therefore, it was found that the peak was derived from the fluorescence emission of 3,10FrA2Nbf(IV)-02, which is the guest material contained in the light-emitting layer 130.

[0559] In addition, from FIGS. 27, 29 and Table 10, it was found that the light-emitting element 21 has very good current efficiency and external quantum efficiency. The light-emitting element 21 is a fluorescence light-emitting element, and although it emits light in a region with low visibility, it has a very high efficiency with a current efficiency of approximately 7.5 cd / A. Therefore, in the light-emitting element having the cap layer 145, the light-emitting efficiency can be improved by using a low refractive index layer. The optical distance from the light-emitting layer 130 to the electrode 101(2) is λ / 4 or less, and the optical distance from the light-emitting layer 130 to the electrode 101(1) is 3λ / 4 or less. (Reference Example)

[0560] In this reference example, the synthesis method of 3,10FrA2Nbf(IV)-02 used for the light-emitting element 21 will be described.

[0561] <Step 1: Synthesis of 3,7-bis(4-chloro-2-fluorophenyl)-2,6-dimethoxynaphthalene> Into a 500 mL three-necked flask, 11 g (24 mmol) of 3,7-diiodo-2,6-dimethoxynaphthalene, 14 g (78 mmol) of 4-chloro-2-fluorophenylboronic acid, 22 g (0.16 mol) of potassium carbonate, and 0.74 g (2.4 mmol) of tris(2-methylphenyl)phosphine were added. 120 mL of toluene was added to this mixture. The mixture was degassed by stirring under reduced pressure. 0.11 g (0.49 mmol) of palladium(II) acetate was added to this mixture, and it was stirred at 110 °C for 50.5 hours under a nitrogen stream.

[0562] After stirring, toluene was added to this mixture, and it was suction filtered through Florisil (Wako Pure Chemical Industries, Ltd., catalog number: 540-00135), Celite (Wako Pure Chemical Industries, Ltd., catalog number: 531-16855), and alumina to obtain a filtrate. The filtrate was concentrated to obtain a solid.

[0563] The obtained solid was purified by silica gel column chromatography (developing solvent: toluene:hexane = 1:1). The obtained solid was recrystallized from ethyl acetate to obtain 5.7 g of a white solid with a yield of 53%. The synthesis scheme of Step 1 is shown below.

[0564]

Chemical formula

[0565] The 1 1H NMR data of the obtained solid are shown in Figure 31, and the numerical data are shown below. 1 1H NMR (CDCl3, 300 MHz): δ = 3.88 (s, 6H), 7.18 - 7.24 (m, 6H), 7.37 (t, J1 = 7.2 Hz, 2H), 7.65 (s, 2H).

[0566] <Step 2: Synthesis of 3,7-bis(4-chloro-2-fluorophenyl)-2,6-dihydroxynaphthalene> 5.7 g (13 mmol) of 3,7-bis(4-chloro-2-fluorophenyl)-2,6-dimethoxynaphthalene was placed in a 200 mL three-necked flask, and the inside of the flask was purged with nitrogen. 32 mL of dichloromethane was added to this flask. 28 mL (28 mmol) of boron tribromide (approx. 1.0 mol / L dichloromethane solution) and 20 mL of dichloromethane were added dropwise to this solution. After the addition was complete, the solution was stirred at room temperature.

[0567] After stirring, approximately 20 mL of water was added to this solution under ice-cooling, and the mixture was stirred. After stirring, the organic layer and the aqueous layer were separated, and the aqueous layer was extracted with dichloromethane and ethyl acetate. The extraction solution and the organic layer were combined and washed with saturated brine and saturated aqueous sodium hydrogen carbonate solution. Magnesium sulfate was added to the organic layer to adsorb moisture, and after drying, the mixture was filtered naturally. The resulting filtrate was concentrated to obtain 5.4 g of a white solid. The synthesis scheme for Step 2 is shown below.

[0568]

Chemical formula

[0569] The 1 1H NMR data of the obtained solid are shown in Figure 32, and the numerical data are shown below. 1 1H NMR (DMSO-d6, 300 MHz): δ = 7.20 (s, 2H), 7.37 (dd, J1 = 8.4 Hz, J2 = 1.8 Hz, 2H), 7.46 - 7.52 (m, 4H), 7.59 (s, 2H), 9.71 (s, 2H).

[0570] <Step 3: Synthesis of 3,10-dichloronaphtho[2,3-b;6,7-b']bisbenzofuran> 5.4 g (13 mmol) of 3,7-bis(4-chloro-2-fluorophenyl)-2,6-dihydroxynaphthalene and 7.1 g (52 mmol) of potassium carbonate were placed in a 200 mL three-necked flask. 130 mL of N-methyl-2-pyrrolidone was added to this mixture, and the mixture was degassed by stirring under reduced pressure. After degassing, the mixture was stirred at 120 °C for 7 hours under a nitrogen stream. After stirring, water was added to the mixture, and the precipitated solid was collected by filtration. This solid was washed with water and ethanol. Ethanol was added to the obtained solid, and after heating and stirring, filtration was performed to obtain a solid. Ethyl acetate was added to the obtained solid, and after heating and stirring, filtration was performed to obtain 4.5 g of a pale yellow solid with a yield of 92%. The synthesis scheme of Step 3 is shown below.

[0571]

Chemical formula

[0572] For the obtained solid 1 The 1H NMR data are shown in Figure 33, and the numerical data are shown below. 1 1H NMR (1,1,2,2-Tetrachloroethane-D2, 300 MHz): δ = 7.44 (dd, J1 = 8.1 Hz, J2 = 1.5 Hz, 2H), 7.65 (d, J1 = 1.8 Hz, 2H), 8.05 (d, J1 = 8.4 Hz, 2H), 8.14 (s, 2H), 8.52 (s, 2H).

[0573] <Step 4: Synthesis of 3,10-bis[N-(dibenzofuran-3-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviation: 3,10FrA2Nbf(IV)-02)> 1.2 g (3.0 mmol) of 3,10-dichloronaphtho[2,3-b;6,7-b']bisbenzofuran, 2.0 g (7.7 mmol) of N-(d...

Claims

1. having a light-emitting layer and a first layer between an anode and a cathode, wherein the light-emitting layer is positioned between the anode and the first layer, wherein the first layer is positioned between the light-emitting layer and the cathode, wherein the first layer has an organic compound and an inorganic compound, wherein the organic compound is an organic compound having electron transporting properties, wherein the inorganic compound is either a fluoride of an alkali metal or a fluoride of an alkaline earth metal, wherein the content of the inorganic compound in the first layer is 50 vol% or more and 95 vol% or less, wherein at least a part of the inorganic compound exists in a microcrystalline state, wherein the inorganic compound existing in the microcrystalline state is in contact with the cathode in a light-emitting device (however, excluding the combination where the organic compound is BeBq2 below and the inorganic compound is LiF, and the combination where the organic compound is MC-1 below and the inorganic compound is LiF). 【Chemical 1】

2. having a light-emitting layer and a first layer between an anode and a cathode, wherein the light-emitting layer is positioned between the anode and the first layer, wherein the first layer is positioned between the light-emitting layer and the cathode, wherein the first layer has an organic compound and an inorganic compound, wherein the organic compound is a π-electron deficient heteroaromatic compound, wherein the inorganic compound is either a fluoride of an alkali metal or a fluoride of an alkaline earth metal, wherein the content of the inorganic compound in the first layer is 50 vol% or more and 95 vol% or less, wherein at least a part of the inorganic compound exists in a microcrystalline state, wherein the inorganic compound existing in the microcrystalline state is in contact with the cathode in a light-emitting device (however, excluding the combination where the organic compound is BeBq2 below and the inorganic compound is LiF, and the combination where the organic compound is MC-1 below and the inorganic compound is LiF). [Chemical 2]

3. Having a light-emitting layer and a first layer between an anode and a cathode, wherein the light-emitting layer is positioned between the anode and the first layer, wherein the first layer is positioned between the light-emitting layer and the cathode, wherein the first layer has an organic compound and an inorganic compound, wherein the organic compound is an organic compound having electron transporting properties, wherein the inorganic compound is either a fluoride of an alkali metal or a fluoride of an alkaline earth metal, wherein the content of the inorganic compound in the first layer is 60 vol% or more and 95 vol% or less, At least a part of the inorganic compound exists in a microcrystalline state, wherein the inorganic compound existing in the microcrystalline state is a light-emitting element in contact with the cathode (however, excluding the combination where the organic compound is the following MC-1 and the inorganic compound is LiF). [Chemical 3]

4. A light-emitting device having a light-emitting layer and a first layer between an anode and a cathode, wherein the light-emitting layer is located between the anode and the first layer, the first layer is located between the light-emitting layer and the cathode, the first layer has an organic compound and an inorganic compound, the organic compound is a π-electron deficient heteroaromatic compound, the inorganic compound is either a fluoride of an alkali metal or a fluoride of an alkaline earth metal, the content of the inorganic compound in the first layer is 60 vol% or more and 95 vol% or less, at least a part of the inorganic compound exists in a microcrystalline state, wherein the inorganic compound existing in the microcrystalline state is a light-emitting element in contact with the cathode (however, excluding the combination where the organic compound is the following MC-1 and the inorganic compound is LiF). 【Chemical 4】

5. In any one of Claims 1 to 4, a light-emitting device wherein the inorganic compound is any one of lithium fluoride, calcium fluoride, and magnesium fluoride.

6. An electronic device having the light-emitting device according to any one of Claims 1 to 5, and a sensor, an operation button, a speaker, or a microphone.

7. A light-emitting device having the light-emitting device according to any one of Claims 1 to 5, and a transistor or a substrate.

8. A lighting device having the light-emitting device according to any one of Claims 1 to 5, and a housing.

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