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

Abstract

To provide a light-emitting element with low drive voltage and good reliability.SOLUTION: Provided is a light-emitting element that has an electron injection layer between a cathode and a light-emitting layer. The electron injection layer is a mixed film of a metal and an organic compound having a function of interacting with the metal in tridentate or quadridentate. A metal atom and the organic compound form a SOMO (Single Occupied Molecular Orbital).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] One embodiment of the present invention relates to a light-emitting element having a novel electron-injection layer, or to a display device, an electronic device, and a lighting device each having the light-emitting element.

[0002] Note that one embodiment of the present invention is not limited to the above technical field. The technical field of one embodiment of the invention disclosed in this specification relates to an object, a method, or a manufacturing method. Alternatively, one embodiment of the present invention relates to a process, a machine, a manufacture, or a composition of matter. Therefore, more specifically, examples of the technical field of one embodiment of the present invention disclosed in this specification include a semiconductor device, a display device, a liquid crystal display device, a light-emitting device, a lighting device, a power storage device, a memory device, a driving method thereof, or a manufacturing method thereof. [Background technology]

[0003] In recent years, research and development of light-emitting elements that utilize electroluminescence (EL) has been actively conducted. The basic structure of these light-emitting elements is a layer (EL layer) containing a light-emitting substance sandwiched between a pair of electrodes. By applying a voltage between the electrodes of this element, light can be emitted from the light-emitting substance.

[0004] Since the above-mentioned light-emitting element is a self-luminous type, a display device using the light-emitting element has advantages such as excellent visibility, no need for a backlight, low power consumption, etc. Furthermore, the display device can be manufactured to be thin and lightweight, and has high response speed, etc.

[0005] In general, an electron injection layer is provided between the cathode and the light-emitting layer in an EL element to reduce the driving voltage. In order to reduce the electron injection barrier between the cathode and the EL layer, the electron injection layer uses a metal with a small work function, such as an alkali metal or alkaline earth metal, typified by lithium (Li) or calcium (Ca), or a compound of these metals (e.g., Patent Document 1). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2001-102175 A Summary of the Invention [Problem to be solved by the invention]

[0007] Metals and their compounds with small work functions are highly reactive with oxygen and water and are difficult to handle. In addition, when such metals or metal compounds are used in light-emitting devices, they may be affected by oxygen and water, resulting in a decrease in the light-emitting efficiency of the light-emitting device, an increase in the driving voltage, or a decrease in reliability. Therefore, there is a demand for the development of an electron injection layer that is less susceptible to the effects of oxygen and water and has a small electron injection barrier between the cathode and the EL layer.

[0008] In view of the above-described problems, an object of one embodiment of the present invention is to provide a light-emitting element with low driving voltage. Alternatively, an object of one embodiment of the present invention is to provide a light-emitting element with high moisture resistance. Alternatively, an object of one embodiment of the present invention is to provide a light-emitting element with high oxygen resistance. Alternatively, an object of one embodiment of the present invention is to provide a light-emitting element with reduced power consumption. Alternatively, an object of one embodiment of the present invention is to provide a light-emitting element with high reliability. Alternatively, an object of one embodiment of the present invention is to provide a novel light-emitting element. Alternatively, an object of one embodiment of the present invention is to provide a novel semiconductor device. Alternatively, an object of one embodiment of the present invention is to provide an organic compound that can be used for a light-emitting element with high moisture resistance.

[0009] Another object of one embodiment of the present invention is to provide an electronic device or a lighting device which uses the light-emitting element and has high moisture resistance.Another object of one embodiment of the present invention is to provide a light-emitting device which uses the light-emitting element and has reduced power consumption.Another object of one embodiment of the present invention is to provide a light-emitting device which uses the light-emitting element and has a long lifetime.

[0010] Note that the description of the above problems does not preclude the existence of other problems. Note that one embodiment of the present invention does not necessarily have to solve all of these problems. Problems other than the above are obvious from the description of the specification, etc., and problems other than the above can be extracted from the description of the specification, etc. [Means for solving the problem]

[0011] As described above, there is a demand for the development of a light-emitting element that has high moisture resistance and high electron injection properties, and therefore a demand for the development of a light-emitting element that does not use a metal with a small work function.

[0012] Therefore, one embodiment of the present invention is a light-emitting element that has a light-emitting layer between an anode and a cathode and a first layer between the light-emitting layer and the cathode, the first layer has a first organic compound and a metal, the metal belongs to any of Groups 3 to 13 in the periodic table, the first organic compound has a substituted or unsubstituted heteroaromatic ring having 1 to 30 carbon atoms, the heteroaromatic ring contains nitrogen, the first organic compound has a function of interacting with the metal at a tridentate or tetradentate site on the nitrogen, and the first organic compound and the metal form a SOMO (Single Occupied Molecular Orbital).

[0013] Another embodiment of the present invention is a light-emitting element that includes a first light-emitting unit and a second light-emitting unit between an anode and a cathode, and a first layer between the first light-emitting unit and the second light-emitting unit. The first layer includes a first organic compound and a metal, the metal belonging to any of Groups 3 to 13 in the periodic table, the first organic compound includes a substituted or unsubstituted heteroaromatic ring having 1 to 30 carbon atoms, the heteroaromatic ring includes nitrogen, the first organic compound has a function of interacting with the metal at a tridentate or tetradentate site on the nitrogen, and the first organic compound and the metal form a SOMO.

[0014] In the above structure, the first organic compound is preferably an organic compound represented by general formula (G0).

[0015] [ka]

[0016] In general formula (G0), A 1 , A 2 and A 3 each independently represents a substituted or unsubstituted heteroaromatic ring having 1 to 30 carbon atoms; A 1 , A 2 and A 3 may form a condensed ring with each other.

[0017] In the above structure, the first organic compound is preferably an organic compound represented by general formula (G1).

[0018] [ka]

[0019] In general formula (G1), X 1 ~X 6 each independently represents carbon (C) or nitrogen (N), and carbon has a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 7 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 25 carbon atoms, or a substituted or unsubstituted heteroaromatic hydrocarbon group having 3 to 30 carbon atoms; R 1 ~R 4 each independently represents hydrogen, an alkyl group having 1 to 4 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 7 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 25 carbon atoms, or a substituted or unsubstituted heteroaromatic hydrocarbon group having 3 to 30 carbon atoms; Ar represents hydrogen, an alkyl group having 1 to 4 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 7 carbon atoms, an aromatic hydrocarbon group having 6 to 60 carbon atoms, or a heteroaromatic hydrocarbon group having 2 to 60 carbon atoms.

[0020] In the above structure, the first organic compound is preferably an organic compound represented by general formula (G2).

[0021] [ka]

[0022] In general formula (G2), X 1 and X 2 each independently represents carbon (C) or nitrogen (N), and carbon has a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 7 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 25 carbon atoms, or a substituted or unsubstituted heteroaromatic hydrocarbon group having 3 to 30 carbon atoms; R 1 ~R 8 each independently represents hydrogen, an alkyl group having 1 to 4 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 7 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 25 carbon atoms, or a substituted or unsubstituted heteroaromatic hydrocarbon group having 3 to 30 carbon atoms; Ar represents hydrogen, an alkyl group having 1 to 4 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 7 carbon atoms, an aromatic hydrocarbon group having 6 to 60 carbon atoms, or a heteroaromatic hydrocarbon group having 2 to 60 carbon atoms.

[0023] In the above structure, the first organic compound is preferably an organic compound represented by any one of general formulas (G3-1) to (G3-3).

[0024] [ka]

[0025] In general formulae (G3-1) to (G3-3), R 1 ~R 8each independently represents hydrogen, an alkyl group having 1 to 4 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 7 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 25 carbon atoms, or a substituted or unsubstituted heteroaromatic hydrocarbon group having 3 to 30 carbon atoms; Ar represents hydrogen, an alkyl group having 1 to 4 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 7 carbon atoms, an aromatic hydrocarbon group having 6 to 60 carbon atoms, or a heteroaromatic hydrocarbon group having 2 to 60 carbon atoms.

[0026] In the above structure, the first organic compound is preferably an organic compound represented by any one of general formulas (G4-1) to (G4-3).

[0027] [ka]

[0028] In general formulae (G4-1) to (G4-3), Ar represents hydrogen, an alkyl group having 1 to 4 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 7 carbon atoms, an aromatic hydrocarbon group having 2 to 60 carbon atoms, or a heteroaromatic hydrocarbon group having 2 to 60 carbon atoms.

[0029] In the above structure, the first organic compound is preferably an organic compound represented by any one of the following structural formulas (100) to (103).

[0030] [ka]

[0031] In the above structure, the work function of the metal is preferably 4.0 eV or more and 5.3 eV or less.

[0032] In the above structure, the first organic compound preferably has a LUMO (Lowest Unoccupied Molecular Orbital) level of −3.6 eV or more and −2.3 eV or less.

[0033] In the above configuration, the metal is preferably a transition metal, more preferably a metal belonging to any of Groups 5, 7, 9, or 11, more preferably a transition metal belonging to Group 11, and even more preferably Ag or Cu.

[0034] In the above structure, the heteroaromatic ring preferably has a substituted or unsubstituted electron-deficient heteroaromatic ring, and more preferably has any one of a pyridine ring, a diazine ring, and a triazine ring.

[0035] In the above structure, it is preferable that a second layer is further provided between the cathode and the first layer, and the second layer contains a second organic compound having an electron-deficient heteroaromatic ring.

[0036] In the above structure, the LUMO level of the second organic compound is preferably lower than the energy level of the SOMO.

[0037] In the above structure, the first layer is preferably a light-emitting element containing no alkali metal or alkaline earth metal.

[0038] In the above structure, it is preferable that a molar ratio of the metal to the first organic compound in the first layer is 0.2 or more and 0.8 or less.

[0039] In the above configuration, it is preferable that the cathode contains the same metal as the first layer.

[0040] Another embodiment of the present invention is an organic compound represented by structural formulas (200) to (203).

[0041] [ka]

[0042] Another embodiment of the present invention is an electronic device having a display device having any of the above configurations and at least one of a housing or a touch sensor. Another embodiment of the present invention is a lighting device having a light-emitting element having any of the above configurations and at least one of a housing or a touch sensor. Another embodiment of the present invention includes not only a light-emitting device having a light-emitting element, but also an electric device having a light-emitting device. Therefore, the light-emitting device in this specification refers to an image display device or a light source (including a lighting device). Another embodiment of the present invention is a display module in which a connector, for example, an FPC (Flexible Printed Circuit) or a TCP (Tape Carrier Package) is attached to a light-emitting element, a display module in which a printed wiring board is provided at the end of a TCP, or a display module in which an IC (Integrated Circuit) is directly mounted on a light-emitting element by a COG (Chip On Glass) method. Effect of the Invention

[0043] According to one embodiment of the present invention, a light-emitting element having a low driving voltage can be provided. According to another embodiment of the present invention, a light-emitting element having high moisture resistance can be provided. According to another embodiment of the present invention, a light-emitting element having high oxygen resistance can be provided. According to another embodiment of the present invention, a light-emitting element with reduced power consumption can be provided. According to another embodiment of the present invention, a light-emitting element with high reliability can be provided. According to another embodiment of the present invention, a novel light-emitting element can be provided. According to another embodiment of the present invention, a novel semiconductor device can be provided. According to another embodiment of the present invention, an organic compound that can be used for a light-emitting element having high moisture resistance can be provided.

[0044] According to one embodiment of the present invention, an electronic device and a lighting device having high moisture resistance using the light-emitting element can be provided. According to one embodiment of the present invention, a light-emitting device using the light-emitting element and having reduced power consumption can be provided. According to one embodiment of the present invention, a light-emitting device using the light-emitting element and having a long lifetime can be provided.

[0045] Note that the description of these effects does not preclude the existence of other effects. Note that one embodiment of the present invention does not necessarily have all of these effects. Note that effects other than these are self-evident from the description in the specification, drawings, claims, etc., and it is possible to extract effects other than these from the description in the specification, drawings, claims, etc. [Brief description of the drawings]

[0046] [Figure 1] 1A and 1B are a cross-sectional schematic diagram illustrating a light-emitting element of one embodiment of the present invention and a diagram illustrating the correlation between energy levels of an electron-injection layer. [Diagram 2] 1 is a schematic cross-sectional view illustrating a light-emitting element of one embodiment of the present invention. [Diagram 3] 1 is a schematic cross-sectional view illustrating a light-emitting element of one embodiment of the present invention. [Figure 4] 1 is a schematic cross-sectional view illustrating a light-emitting element of one embodiment of the present invention. [Diagram 5] 1A and 1B are a top view and a cross-sectional schematic diagram illustrating a display device of one embodiment of the present invention. [Figure 6] 1A and 1B are schematic cross-sectional views illustrating a display device according to one embodiment of the present invention. [Figure 7] 1A and 1B are schematic cross-sectional views illustrating a display device according to one embodiment of the present invention. [Figure 8] 1A to 1C illustrate electronic devices of one embodiment of the present invention. [Figure 9] 1A to 1C illustrate electronic devices of one embodiment of the present invention. [Figure 10] 1A to 1C illustrate electronic devices of one embodiment of the present invention. [Figure 11] 1A to 1C are diagrams illustrating a lighting device according to one embodiment of the present invention. [Figure 12] FIG. 13 is a graph showing current efficiency vs. luminance characteristics of a light-emitting element in the embodiment. [Figure 13] FIG. 13 is a graph showing current-voltage characteristics of a light-emitting element in the embodiment. [Figure 14] FIG. 13 is a graph showing external quantum efficiency vs. luminance characteristics of a light-emitting element according to an embodiment. [Figure 15] FIG. 2 is a graph showing electroluminescence spectra of light-emitting elements according to an embodiment of the present invention. [Figure 16] 13A to 13C are diagrams illustrating the results of a reliability test of a light-emitting element in the examples. [Figure 17] FIG. 13 is a graph showing current efficiency vs. luminance characteristics of a light-emitting element in the embodiment. [Figure 18] FIG. 13 is a graph showing current-voltage characteristics of a light-emitting element in the embodiment. [Figure 19] FIG. 13 is a graph showing external quantum efficiency vs. luminance characteristics of a light-emitting element according to an embodiment. [Figure 20] FIG. 2 is a graph showing electroluminescence spectra of light-emitting elements according to an embodiment of the present invention. [Figure 21] 13A to 13C are diagrams illustrating the results of a reliability test of a light-emitting element in the examples. [Figure 22] FIG. 13 is a graph showing current efficiency vs. luminance characteristics of a light-emitting element in the embodiment. [Figure 23] FIG. 13 is a graph showing current-voltage characteristics of a light-emitting element in the embodiment. [Figure 24] FIG. 13 is a graph showing external quantum efficiency vs. luminance characteristics of a light-emitting element according to an embodiment. [Diagram 25] FIG. 2 is a graph showing electroluminescence spectra of light-emitting elements according to an embodiment of the present invention. [Figure 26] FIG. 2 is a diagram illustrating an NMR spectrum of a compound according to an embodiment. [Figure 27] FIG. 2 is a diagram illustrating an NMR spectrum of a compound according to an embodiment. [Figure 28] FIG. 2 is a diagram illustrating an NMR spectrum of a compound according to an embodiment. [Figure 29] FIG. 2 is a diagram illustrating an NMR spectrum of a compound according to an embodiment. [Diagram 30] FIG. 2 is a diagram illustrating an NMR spectrum of a compound according to an embodiment. [Diagram 31] 1 is a schematic cross-sectional view illustrating a light-emitting element of one embodiment of the present invention. [Diagram 32] FIG. 13 is a graph showing current efficiency vs. luminance characteristics of a light-emitting element in the embodiment. [Diagram 33] FIG. 13 is a graph showing current-voltage characteristics of a light-emitting element in the embodiment. [Diagram 34] FIG. 13 is a graph showing power efficiency vs. luminance characteristics of a light-emitting element in the embodiment. [Diagram 35] FIG. 13 is a graph showing external quantum efficiency vs. luminance characteristics of a light-emitting element according to an embodiment. [Diagram 36] FIG. 2 is a graph showing electroluminescence spectra of light-emitting elements according to an embodiment of the present invention. [Figure 37] FIG. 13 is a graph showing current efficiency vs. luminance characteristics of a light-emitting element in the embodiment. [Figure 38] FIG. 13 is a graph showing current-voltage characteristics of a light-emitting element in the embodiment. [Figure 39] FIG. 13 is a graph showing power efficiency vs. luminance characteristics of a light-emitting element in the embodiment. [Diagram 40] FIG. 13 is a graph showing external quantum efficiency vs. luminance characteristics of a light-emitting element according to an embodiment. [Diagram 41] FIG. 2 is a graph showing electroluminescence spectra of light-emitting elements according to an embodiment of the present invention. [Diagram 42] FIG. 13 is a graph showing current efficiency vs. luminance characteristics of a light-emitting element in the embodiment. [Diagram 43] FIG. 13 is a graph showing current-voltage characteristics of a light-emitting element in the embodiment. [Diagram 44] FIG. 13 is a graph showing power efficiency vs. luminance characteristics of a light-emitting element in the embodiment. [Diagram 45] FIG. 13 is a graph showing external quantum efficiency vs. luminance characteristics of a light-emitting element according to an embodiment. [Figure 46] FIG. 2 is a graph showing electroluminescence spectra of light-emitting elements according to an embodiment of the present invention. [Figure 47] FIG. 13 is a graph showing current efficiency vs. luminance characteristics of a light-emitting element in the embodiment. [Figure 48] FIG. 13 is a graph showing current-voltage characteristics of a light-emitting element in the embodiment. [Figure 49] FIG. 13 is a graph showing power efficiency vs. luminance characteristics of a light-emitting element in the embodiment. [Figure 50] FIG. 13 is a graph showing external quantum efficiency vs. luminance characteristics of a light-emitting element according to an embodiment. [Figure 51] FIG. 2 is a graph showing electroluminescence spectra of light-emitting elements according to an embodiment of the present invention. [Figure 52] 13A to 13C are diagrams illustrating the results of a reliability test of a light-emitting element in the examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0047] Hereinafter, the embodiment 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 various changes can be made in the form and details without departing from the spirit and scope of the present invention. Therefore, the present invention should not be interpreted as being limited to the description of the embodiment shown below.

[0048] In addition, for ease of understanding, the position, size, range, etc. of each component shown in the drawings, etc. may not represent the actual position, size, range, etc. Therefore, the disclosed invention is not necessarily limited to the position, size, range, etc. disclosed in the drawings, etc.

[0049] In addition, in this specification, ordinal numbers such as first, second, etc. are used for convenience and may not indicate the order of steps or stacking. Therefore, for example, "first" can be appropriately replaced with "second" or "third" to explain. In addition, the ordinal numbers described in this specification may not match the ordinal numbers used to specify one embodiment of the present invention.

[0050] In addition, in this specification and the like, when describing the configuration of the invention using drawings, the same reference numerals are used in common between different drawings.

[0051] In addition, in this specification and the like, the term "film" and the term "layer" can be interchanged. For example, the term "conductive layer" may be changed to the term "conductive film." Or, for example, the term "insulating film" may be changed to the term "insulating layer."

[0052] (Embodiment 1) In this embodiment, a light-emitting element of one embodiment of the present invention will be described below with reference to FIG.

[0053] <Configuration example 1 of light-emitting element> FIG. 1A is a schematic cross-sectional view of a light-emitting element 150 of one embodiment of the present invention.

[0054] The light-emitting element 150 has a pair of electrodes (electrode 101 and electrode 102) and an EL layer 100 provided between the pair of electrodes. The EL layer 100 has at least a light-emitting layer 140 and an electron injection layer 130.

[0055] The EL layer 100 shown in FIG. 1A includes functional layers such as a hole injection layer 111, a hole transport layer 112, and an electron transport layer 118 in addition to the light emitting layer 140 and the electron injection layer .

[0056] In the present embodiment, the electrode 101 of the pair of electrodes is described as an anode and the electrode 102 as a cathode, but the configuration of the light-emitting element 150 is not limited to this. That is, the electrode 101 may be the cathode and the electrode 102 may be the anode, and the layers between the electrodes may be stacked in the reverse order. That is, the order of stacking from the anode side may be the hole injection layer 111, the hole transport layer 112, the light-emitting layer 140, the electron transport layer 118, and the electron injection layer 130.

[0057] Note that the configuration of the EL layer 100 is not limited to the configuration shown in FIG. 1(A), and includes at least the light-emitting layer 140 and the electron injection layer 130, and may or may not include the hole injection layer 111, the hole transport layer 112, and the electron transport layer 118.

[0058] In addition, the EL layer between the pair of electrodes may have a layer according to a required function, and is not limited thereto. That is, the EL layer between the pair of electrodes may have a layer having a function of reducing the hole or electron injection barrier, improving the hole or electron transportability, inhibiting the hole or electron transportability, suppressing the quenching phenomenon caused by the electrodes, or the like.

[0059] Moreover, the light-emitting layer 140 preferably contains a host material and a guest material (light-emitting material).

[0060] As the host material, it is preferable to use either one or both of a material having a function of transporting holes (hole transport property) (hole transport material) and a material having a function of transporting electrons (electron transport property) (electron transport material), and a material having both hole transport property and electron transport property may be used.

[0061] In addition, when the host material is a combination of an electron transporting material and a hole transporting material (mixed host), the carrier balance can be easily controlled by the mixing ratio. Specifically, the electron transporting material:hole transporting material is preferably in the range of 1:9 to 9:1 (weight ratio). In addition, since the carrier balance can be easily controlled by having this configuration, the carrier recombination region can also be easily controlled.

[0062] In addition, a light-emitting compound may be used as the guest material, and the light-emitting compound is preferably a substance capable of emitting fluorescence (hereinafter also referred to as a fluorescent compound) or a substance capable of emitting phosphorescence (hereinafter also referred to as a phosphorescent compound).

[0063] In order to reduce the driving voltage of the light-emitting element, it is necessary to reduce the electron injection barrier between the light-emitting layer 140 and the electrode 102. Therefore, it is preferable to provide the electron injection layer 130 between the light-emitting layer 140 and the electrode 102. In conventional light-emitting elements, a metal material having an alkali metal or an alkaline earth metal with a small work function is used for the electron injection layer 130. However, since a metal material having a small work function is highly reactive with oxygen and water, when a reaction with oxygen or water occurs in the light-emitting element, the electron injection property decreases, which may cause a decrease in the light-emitting efficiency, an increase in the driving voltage, a decrease in the element life, and the occurrence of shrink (a non-light-emitting region at the end of the light-emitting part), and may lead to a decrease in the characteristics and reliability of the light-emitting element. In other words, a metal material having a small work function may be a factor in element deterioration. Therefore, in order to suppress a decrease in the characteristics and reliability of the light-emitting element, it is preferable that the light-emitting element does not have an alkali metal or an alkaline earth metal.

[0064] On the other hand, although a metal with a large work function has low reactivity with oxygen and water, when used in the electron injection layer 130, the electron injection barrier between the light-emitting layer 140 and the electrode 102 becomes large, which may result in a problem that the driving voltage of the light-emitting element becomes high or the light-emitting efficiency decreases.

[0065] Here, the inventors have found that a SOMO is formed by interaction between a metal and an organic compound having a function of interacting with the metal at a tridentate or tetradentate state, and that a composite material of an organic compound and a metal that forms the SOMO is used in the electron injection layer, thereby reducing the barrier for electron injection from the cathode to the light-emitting layer and providing a light-emitting element with excellent moisture resistance. In other words, the inventors have found that the electron injection layer 130 can be produced without using an alkali metal or an alkaline earth metal.

[0066] Therefore, a light-emitting element according to one embodiment of the present invention is a light-emitting element in which a composite material of a metal and an organic compound having a function of interacting with a metal at a tridentate or tetradentate structure is used for an electron-injection layer.

[0067] The organic compound and the metal interact with each other to form a SOMO. The SOMO is an orbital derived from an unpaired electron of the metal, but is also distributed on the orbital of the organic compound. This shows that the electron orbital of the metal and the electron orbital of the organic compound interact with each other. In order to efficiently interact with the organic compound and the metal, the organic compound preferably has many interacting atoms. An organic compound having many interacting atoms is likely to interact with the metal, and therefore, a SOMO can be easily formed by mixing the organic compound with the metal. For this reason, the organic compound used in the light-emitting element of one embodiment of the present invention preferably has a function of interacting with the metal at a tridentate or tetradentate. In addition, when a SOMO is formed with an organic compound having many interacting atoms and a metal, the SOMO level is likely to be high, and the electron injection characteristics from the cathode to the light-emitting layer are improved. In addition, the organic compound also interacts with a metal having a high work function to form a SOMO. For this reason, the organic compound used in the light-emitting element of one embodiment of the present invention preferably has a function of interacting with the metal at a tridentate or tetradentate.

[0068] Examples of the atom that interacts with the metal include a heteroatom having an unshared electron pair in an organic compound. Examples include oxygen (O), nitrogen (N), sulfur (S), and phosphorus (P), and nitrogen is preferable. Nitrogen has high electronegativity and therefore easily interacts with metals. In addition, the organic compound having a tridentate or tetradentate function that interacts with metals and is used in the light-emitting element of one embodiment of the present invention is preferably used for an electron injection layer and therefore preferably has electron transport properties. For this reason, the organic compound is preferably an organic compound in which conjugation extends throughout the molecule. Here, nitrogen can form a conjugated bond in an organic compound, and therefore, by using nitrogen in a molecule, particularly in a heteroaromatic ring, an organic compound with high carrier transport properties can be obtained. Therefore, the interacting atom is preferably nitrogen, and more preferably nitrogen is contained in a heteroaromatic ring in an organic compound. With this structure, an organic compound that has an ability to interact with metals and has excellent carrier transport properties can be obtained. In addition, it is more preferable that the heteroaromatic ring is an even-numbered ring such as a 6-membered ring or an 8-membered ring. With this structure, the unshared electron pair on the nitrogen is not involved in conjugation and is therefore more likely to interact with the metal.

[0069] In order to form a SOMO by the interaction of an organic compound having a function of interacting with a metal at a tridentate or tetradentate with the metal, it is preferable that the total number of electrons of the organic compound and the metal is odd. Therefore, when the number of electrons of the organic compound is even, it is preferable that the metal is in an odd group in the periodic table. Also, when the number of electrons of the organic compound is odd, it is preferable that the metal is in an even group in the periodic table.

[0070] As the compound having a function of interacting with a metal at a tridentate or tetradentate site, an organic compound having an electron transport function is preferable, and an organic compound functioning as an electron acceptor for the metal is also preferable.

[0071] In addition, the organic compound used in one embodiment of the present invention has a high ability to interact with the metal because it interacts with the metal at a tridentate or tetradentate position. Therefore, not only transition metals in groups 3 to 11, but also metals in groups 12 and 13 having closed d orbitals can be used in one embodiment of the present invention. In addition, metals such as gold (Au) and cobalt (Co) having a very large work function can also be used preferably.

[0072] Metals having a large work function such as metals belonging to Groups 3 to 13 have low reactivity with water and oxygen, and therefore, when used in a light-emitting element, deterioration of the element caused by water and oxygen, which is a concern when a metal having a low work function is used, is less likely to occur. Specifically, the work function of the metal is preferably 4.0 eV to 5.3 eV, more preferably 4.2 eV to 5.0 eV, even more preferably 4.5 eV to 5.0 eV, and even more preferably 4.7 eV to 5.0 eV. With this structure, one embodiment of the present invention can provide a light-emitting element having excellent moisture resistance and oxygen resistance.

[0073] 1B is a schematic diagram of an electron-injection layer 130 in a light-emitting element of one embodiment of the present invention. The electron-injection layer 130 includes a compound 131 and a metal 132. The compound 131 has a function of interacting with the metal 132 at a tridentate or tetradentate site.

[0074] 1C shows an energy diagram of the electron-injection layer 130 in the light-emitting element of one embodiment of the present invention. When the metal 132 and the compound 131 are mixed, the compound 131 interacts with atoms of the metal 132 to form a SOMO. In this case, the HOMO (Highest Occupied Molecular Orbital) level formed by the interaction of the compound 131 with atoms of the metal 132 is preferably similar to the HOMO level of the original compound 131. When an organic compound having a function of transporting electrons is used for the compound 131, the HOMO level of the compound 131 is low, and holes are unlikely to be injected into the compound 131. Therefore, when the HOMO level formed by the interaction of the compound 131 with the metal 132 is similar to the HOMO level of the original compound 131, a hole-injection barrier between the electron-injection layer 130 and the electrode 102 becomes large, so that holes are unlikely to escape from the electron-injection layer 130 to the electrode 102, which is preferable because the carrier balance in the light-emitting element can be improved. In this specification and the like, HOMO refers to the molecular orbital filled with electrons that has the highest energy.

[0075] Since the SOMO is an orbital having only one electron, when a voltage is applied to the light-emitting element 150, the electrons in the SOMO become carriers in the light-emitting element and are transported to the electron transport layer 118 and the light-emitting layer 140. In addition, electrons can be easily injected from the electrode 102 into the electron injection layer 130, and furthermore, electrons can be easily injected from the electron injection layer 130 into the light-emitting layer 140 through the electron transport layer 118. That is, since the electron injection layer 130 has a combination of materials that form a SOMO, electrons can be easily injected from the electrode 102 into the light-emitting layer 140. In addition, it is preferable that the SOMO level is lower than the LUMO level of the compound 131. Therefore, it is preferable that the LUMO level of the compound 131 is higher. Specifically, it is preferable that the LUMO level of the compound 131 is -3.6 eV or more and -2.3 eV or less. When an organic compound having such a LUMO level is mixed with a metal, the SOMO level formed by the interaction becomes a level suitable for electron injection, so that the barrier for electron injection from the electrode 102 to the light-emitting layer 140 can be reduced.

[0076] The HOMO and LUMO levels of organic compounds are generally estimated by CV (cyclic voltammetry), photoelectron spectroscopy, optical absorption spectroscopy, inverse photoelectron spectroscopy, etc. When comparing values ​​between different compounds, it is preferable to use values ​​estimated by the same measurement.

[0077] Here, the above-mentioned metal preferably belongs to any one of Groups 3, 5, 7, 9, 11, and 13. These odd-numbered metals have one electron (unpaired electron) in the outermost orbital, and therefore are particularly preferred because they easily form a SOMO with compound 131.

[0078] <Estimation of SOMO levels in the interaction between metal 132 and compound 131 by quantum chemical calculation> In the light-emitting element of one embodiment of the present invention, compound 131 and metal 132 form a SOMO. When the SOMO level is extremely low, the compound is inappropriate for an electron-injection layer. Thus, the SOMO level formed when compound 131 interacts with a metal atom was estimated by quantum chemical calculation. The results are shown in Table 1. Note that examples of organic compounds having a function of interacting with a metal at a tridentate or tetradentate include 4',4''''-(1,4-phenylene)bis(2,2':6',2"-terpyridine) (abbreviation: tPy2P), 4',4''''-(9,10-anthryl)bis(2,2':6',2"-terpyridine) (abbreviation: tPy2A), and 2,2'-(pyridine-2,6-diyl)bis(4-phenylbenzo[h]quinazoline). ) (abbreviation: 2,6(P-Bqn)2Py), 2,2'-(2,2'-bipyridine-6,6'-diyl)bis(4-phenylbenzo[h]quinazoline) (abbreviation: 6,6'(P-Bqn)2BPy), 2,4,6-tris(2-pyridyl)-1,3,5-triazine (abbreviation: 2Py3Tzn), and 2,4,6-tris(5-phenylpyrimidin-2-yl)-1,3,5-triazine (abbreviation: PPm3Tzn) were used.

[0079] [ka]

[0080] [Table 1]

[0081] In addition, the LUMO levels of the organic compounds in Table 1 were calculated by cyclic voltammetry (CV) measurements.

[0082] The measurement device used was an electrochemical analyzer (BAS Corporation, model number: ALS model 600A or 600C). The solution used in the CV measurement was prepared by dissolving tetra-n-butylammonium perchlorate (n-Bu4NClO4) (Tokyo Chemical Industry Co., Ltd., catalog number: T0836) as a supporting electrolyte in dehydrated dimethylformamide (DMF) (Aldrich Corporation, 99.8%, catalog number: 22705-6) to a concentration of 100 mmol / L, and further dissolving the measurement target to a concentration of 2 mmol / L. The working electrode was a platinum electrode (BAS Corporation, PTE platinum electrode), the auxiliary electrode was a platinum electrode (BAS Corporation, Pt counter electrode for VC-3 (5 cm)), and the reference electrode was an Ag / Ag electrode. + An electrode (manufactured by BAS Co., Ltd., RE7 non-aqueous solvent reference electrode) was used. The measurements were performed at room temperature (20 to 25° C.). The scan speed during CV measurement was standardized to 0.1 V / sec, and the oxidation potential Ea [V] and reduction potential Ec [V] relative to the reference electrode were measured. Ea was the midpoint potential of the oxidation-reduction wave, and Ec was the midpoint potential of the reduction-oxidation wave. Here, since the potential energy of the reference electrode used in this example relative to the vacuum level is known to be −4.94 [eV], the HOMO level and the LUMO level can be calculated from the formulas HOMO level [eV] = −4.94-Ea and LUMO level [eV] = −4.94-Ec, respectively.

[0083] Gaussian09 was used as the quantum chemical calculation program. The calculations were performed using a high-performance computer (ICE X, manufactured by SGI). First, the most stable structures in the ground state of the organic compound alone, the ground state of the metal alone, and the ground state of the composite material of the organic compound and the metal were calculated using density functional theory (DFT). 6-311G(d,p) and LanL2DZ were used as basis functions, and B3LYP was used as the functional. Next, the stabilization energy was calculated from the difference between the total energy of the composite material of the organic compound and the sum of the total energy of the organic compound alone and the total energy of the metal alone. In other words, (stabilization energy) = (total energy of the composite material of the organic compound and the metal) - (total energy of the organic compound alone) - (total energy of the metal alone). The total energy of DFT is expressed as the sum of the potential energy, the electrostatic energy between electrons, the kinetic energy of electrons, and the exchange-correlation energy, which includes all the complex interactions between electrons. In DFT, the exchange-correlation interaction is approximated by a functional (a function of a function) of a single-electron potential expressed in terms of electron density, so calculations are highly accurate.

[0084] Table 1 shows the calculation results of the SOMO levels formed by each organic compound and each metal for the 7th group transition metal manganese (Mn), the 9th group transition metal cobalt (Co), the 11th group transition metal copper (Cu), silver (Ag), and gold (Au), and the 13th group metal aluminum (Al) and indium (In). In addition, the SOMO levels formed by each organic compound and lithium (Li), which is widely used as an electron injection layer material, were also calculated. As a result of the calculation, it was obtained that in the combinations of organic compounds and metals shown in Table 1, the organic compound and the metal interact and stabilize near the nitrogen in the heteroaromatic ring of the organic compound, and the stabilization energy shows a negative value. In other words, when these organic compounds and metals are mixed, the energy is more stable when the organic compound and the metal interact with each other than when they do not interact. In this way, a stable composite material is obtained by interacting with an organic compound that has the function of interacting with a metal at a tridentate or tetradentate and a metal. In addition, from Table 1, the SOMO level formed by the organic compound having the function of interacting with the metal at a tridentate or tetradentate and each metal was roughly equivalent to the SOMO level formed by each organic compound and Li. Therefore, it was found that the composite material of the organic compound having the function of interacting with the metal at a tridentate or tetradentate and the metal has high electron injection properties. In particular, the composite material using Cu, Ag, Au, which are elements of Group 11, and Co, which is an element of Group 9, showed a high SOMO level, and it was found that the composite material of the organic compound having the function of interacting with the metal at a tridentate or tetradentate and a metal belonging to Group 9 or Group 11 has high electron injection properties.

[0085] In addition, Table 1 suggests that the SOMO level formed by an organic compound having a function of interacting with a metal at a tridentate or tetradentate site and each metal is influenced by the LUMO level of the organic compound rather than the work function of each metal. Therefore, by using an organic compound with a high LUMO level, a composite material of an organic compound and a metal having a high SOMO level and excellent electron injection properties can be prepared. As described above, the LUMO level of the organic compound is preferably -3.6 eV or more and -2.3 eV or less.

[0086] On the other hand, in consideration of the manufacturing process of the light-emitting element, the EL layer of the light-emitting element, particularly the electron injection layer and the cathode, are generally formed by the vacuum deposition method. In this case, it is preferable to use a material that can be easily vacuum-deposited, that is, a material with a low melting point, boiling point, and sublimation point, and it is preferable to use a material that has a low temperature at which the vapor pressure is generated during vacuum deposition. Here, since the melting points of the 11th and 13th group elements are lower than those of the 7th and 9th groups, they can be suitably used for vacuum deposition. In particular, since the melting points of the 11th and 13th group elements such as Ag and Al are low, it is preferable to use the vacuum deposition method, since the metal atoms and the organic compounds can be easily mixed.

[0087] Ag, Cu, Au, Al, and In can also be used as cathode materials. Using the same material for the electron injection layer 130 and the electrode 102 is preferable because it allows the light-emitting device to be easily manufactured. Using the same material for the electron injection layer 130 and the electrode 102 can increase the adhesion between the electron injection layer 130 and the electrode 102, thereby improving the reliability of the light-emitting device. In addition, the manufacturing cost of the light-emitting device can be reduced.

[0088] In addition, in the light-emitting element of one embodiment of the present invention, a metal with a high work function can be used for the electron-injection layer 130. Therefore, a metal having a work function equal to or higher than the work function of the metal contained in the electrode 102 can be used for the electron-injection layer 130. Even when a metal with a high work function is used in the light-emitting element of one embodiment of the present invention, the electron-injection barrier between the electrode 102 and the electron-injection layer 130 can be reduced, and thus the driving voltage can be reduced.

[0089] In addition, when compound 131 interacts with metal 132, it is preferable that metal 132 be an electron donor and compound 131 be an electron acceptor. In this case, compound 131 preferably has a plurality of electron-deficient heteroaromatic rings. In such a configuration, compound 131 is likely to receive electrons, and therefore is likely to form SOMO when interacting with metal 132 atoms. In addition, a compound having an electron-deficient heteroaromatic ring has good electron transport properties, and therefore is preferable as compound 131 when used in an electron injection layer, since it can reduce the driving voltage of a light-emitting element.

[0090] The electron-deficient heteroaromatic ring is preferably a nitrogen-containing heteroaromatic ring, and more preferably has at least one of a pyridine ring, a diazine ring (pyrimidine ring, pyrazine ring, pyridazine ring), and a triazine ring. These rings have excellent electrochemical stability, and therefore can provide a light-emitting element with good reliability. In addition, they have excellent electron transport properties, and therefore can provide a light-emitting element with reduced driving voltage. The compound having the electron-deficient heteroaromatic ring may be a metal complex.

[0091] In addition, when an organic compound is used as the compound 131, the number of carbon atoms is preferably 25 or more and 100 or less. By using such a carbon number, an organic compound with excellent sublimation properties can be obtained, so that thermal decomposition of the organic compound can be suppressed in vacuum deposition, and good material usage efficiency can be obtained. Furthermore, the glass transition point (Tg) is preferably 100° C. or more. By using an organic compound having such a Tg in the EL layer, a light-emitting element with excellent heat resistance can be obtained.

[0092] In addition, the organic compound used in this calculation has N, a coordination atom, on a heterocycle, and further has conjugated double bonds arranged in the order of NCCN via multiple heterocycles. This is because, when the organic compound has such a binding site, it is possible to form a chelate ring when compound 131 interacts with metal 132 (compound 131 interacts with metal 132 to form a ring structure). The combination of compound 131 and metal 132 that can form a chelate ring is preferable because it is easy to interact with each other and to form SOMO.

[0093] Therefore, an organic compound having a function of interacting with a metal at a tridentate or tetradentate structure, which can be suitably used in a light-emitting element according to one embodiment of the present invention, has a structure represented by the following general formula (G0).

[0094] [ka]

[0095] In general formula (G0), A 1 , A 2 and A 3 each independently represents a substituted or unsubstituted heteroaromatic ring having 1 to 30 carbon atoms; A 1 , A 2 and A 3 may form a condensed ring with each other.

[0096] The organic compound represented by the general formula (G0) has a conjugated double bond in which N on a heteroaromatic ring is arranged in the order of NCCN, and has a function of interacting with a metal in a tridentate or higher state. As described above, an organic compound having such a structure is likely to form a SOMO when mixed with a metal, and therefore can be suitably used for the light-emitting element of one embodiment of the present invention.

[0097] In addition, in the above general formula (G0), A 1 , A 2 and A 3 Examples of the substituted or unsubstituted heteroaromatic ring having 1 to 30 carbon atoms represented by the formula (I) include a pyridine ring, a diazine ring (pyrimidine ring, pyrazine ring, pyridazine ring), a triazine ring, a quinoline ring, a quinoxaline ring, a quinazoline ring, a benzoquinazoline ring, a phenanthroline ring, an azafluoranthene ring, an imidazole ring, an oxazole ring, and an oxadiazole ring. Specific examples include the heteroaromatic rings represented by the following formulas (A-1) to (A-16). However, A 1 , A 2 and A 3 The substituted or unsubstituted heteroaromatic ring having 1 to 30 carbon atoms represented by the following formula is not limited to these. 1, A 2 and A 3 may form a condensed ring. For example, A 1 and A 2 may be bonded to each other to form a phenanthroline ring.

[0098] [ka]

[0099] Further, an organic compound having a function of interacting with a metal at a tridentate or tetradentate structure, which can be suitably used in a light-emitting element according to one embodiment of the present invention, has a structure represented by the following general formula (G1).

[0100] [ka]

[0101] In general formula (G1), X 1 ~X 6 each independently represents carbon (C) or nitrogen (N), and carbon has a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 7 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 25 carbon atoms, or a substituted or unsubstituted heteroaromatic hydrocarbon group having 3 to 30 carbon atoms; R 1 ~R 4 each independently represents hydrogen, an alkyl group having 1 to 4 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 7 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 25 carbon atoms, or a substituted or unsubstituted heteroaromatic hydrocarbon group having 3 to 30 carbon atoms; Ar represents hydrogen, an alkyl group having 1 to 4 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 7 carbon atoms, an aromatic hydrocarbon group having 6 to 60 carbon atoms, or a heteroaromatic hydrocarbon group having 2 to 60 carbon atoms.

[0102] It is more preferable that an organic compound having a function of interacting with a metal at a tridentate or tetradentate position, such as an organic compound represented by general formula (G1), has at least one of a pyridine ring, a diazine ring (pyrimidine ring, pyrazine ring, pyridazine ring), and a triazine ring. These rings have excellent electrochemical stability, so that a light-emitting element with good reliability can be provided. In addition, because they have excellent electron transport properties, a light-emitting element with reduced driving voltage can be provided.

[0103] Further, an organic compound having a function of interacting with a metal at a tridentate or tetradentate structure, which can be suitably used in a light-emitting element according to one embodiment of the present invention, has a structure represented by the following general formula (G2).

[0104] [ka]

[0105] In general formula (G2), X 1 and X 2 each independently represents carbon (C) or nitrogen (N), and carbon has a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 7 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 25 carbon atoms, or a substituted or unsubstituted heteroaromatic hydrocarbon group having 3 to 30 carbon atoms; R 1 ~R 8 each independently represents hydrogen, an alkyl group having 1 to 4 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 7 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 25 carbon atoms, or a substituted or unsubstituted heteroaromatic hydrocarbon group having 3 to 30 carbon atoms; Ar represents hydrogen, an alkyl group having 1 to 4 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 7 carbon atoms, an aromatic hydrocarbon group having 6 to 60 carbon atoms, or a heteroaromatic hydrocarbon group having 3 to 60 carbon atoms.

[0106] Organic compounds with a pyridine skeleton tend to have a high LUMO level. Therefore, when an organic compound with a pyridine skeleton such as that represented by general formula (G2) is mixed with a metal, a composite material with a high SOMO level can be produced. In other words, by mixing an organic compound with a pyridine ring and the ability to interact with a metal at a tridentate or tetradentate with a metal, a composite material with high electron injection properties can be produced.

[0107] Further, an organic compound having a function of interacting with a metal at a tridentate or tetradentate structure, which can be suitably used in a light-emitting element according to one embodiment of the present invention, is represented by any one of the following general formulas (G3-1) to (G3-3).

[0108] [ka]

[0109] In general formulae (G3-1) to (G3-3), R 1 ~R 8 each independently represents hydrogen, an alkyl group having 1 to 4 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 7 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 25 carbon atoms, or a substituted or unsubstituted heteroaromatic hydrocarbon group having 3 to 30 carbon atoms; Ar represents hydrogen, an alkyl group having 1 to 4 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 7 carbon atoms, an aromatic hydrocarbon group having 6 to 60 carbon atoms, or a heteroaromatic hydrocarbon group having 2 to 60 carbon atoms.

[0110] Further, an organic compound having a function of interacting with a metal at a tridentate or tetradentate structure, which can be suitably used in a light-emitting element according to one embodiment of the present invention, is represented by any one of the following general formulas (G4-1) to (G4-3).

[0111] [ka]

[0112] In general formulae (G4-1) to (G4-3), Ar represents hydrogen, an alkyl group having 1 to 4 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 7 carbon atoms, an aromatic hydrocarbon group having 2 to 60 carbon atoms, or a heteroaromatic hydrocarbon group having 2 to 60 carbon atoms.

[0113] <Examples of Substituents> In general formulae (G0) to (G3), R 1 ~R 8 Examples of the substituent represented by the formula (I) or the substituent carried by C include hydrogen, an alkyl group having 1 to 4 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 7 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 25 carbon atoms, or a substituted or unsubstituted heteroaromatic hydrocarbon group having 3 to 30 carbon atoms. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, and an n-hexyl group. Examples of the cycloalkyl group include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group. Specific examples of the aryl group include a phenyl group, a naphthyl group, a biphenyl group, a fluorenyl group, and a spirofluorenyl group. More specifically, examples of the groups represented by the following structural formulas (R-1) to (R-56) include groups. In addition, R 1 ~R 8 The substituent represented by the following formula (I) or the substituent carried by C is not limited thereto.

[0114] [ka]

[0115] In the general formulas (G0) to (G3), Ar represents hydrogen, an alkyl group having 1 to 4 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 7 carbon atoms, an aromatic hydrocarbon group having 6 to 60 carbon atoms, or a heteroaromatic hydrocarbon group having 3 to 60 carbon atoms. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, and an n-hexyl group. Examples of the cycloalkyl group include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group. Specific examples of the aryl group include a phenyl group, a naphthyl group, a biphenyl group, a fluorenyl group, and a spirofluorenyl group. More specific examples include groups represented by the following structural formulas (Ar-1) to (Ar-48). The group represented by Ar is not limited to these, and may have a substituent.

[0116] [ka]

[0117] <Specific examples of compounds> Specific examples of the compounds represented by the general formulae (G0) to (G3) include organic compounds represented by the following structural formulae (100) to (111) and structural formulae (200) to (211). The organic compounds represented by the general formulae (G0) to (G3) are not limited to the following examples.

[0118] [ka]

[0119] [ka]

[0120] Moreover, the molar ratio of the metal 132 to the compound 131 is preferably 0.1 or more and 10 or less, more preferably 0.2 or more and 2 or less, and even more preferably 0.2 or more and 0.8 or less. By mixing the metal 132 and the compound 131 at such a ratio, a light-emitting element having good electron injection properties can be provided. If the molar ratio of the metal 132 to the compound 131 is too small compared to the above ratio, the amount of the compound 131 that interacts with the metal 132 to form SOMO is small, so that the electron injection properties may be reduced. If the molar ratio of the metal 132 to the compound 131 is too large compared to the above ratio, the transmittance of the electron injection layer 130 is reduced, so that the luminous efficiency of the light-emitting element may be reduced.

[0121] In addition, the LUMO level of the organic compound contained in the electron transport layer 118 is preferably lower than the SOMO level formed in the electron injection layer 130. With this configuration, the electron injection barrier between the electron injection layer 130 and the electron transport layer 118 is reduced, so that the driving voltage can be reduced. In addition, since the organic compound contained in the electron transport layer 118 is required to have electron transport properties, it is preferable that the organic compound has an electron-deficient heteroaromatic ring.

[0122] Moreover, the thickness of the electron injection layer 130 is preferably 3 nm or more, and more preferably 5 nm or more. With this configuration, the metal 132 and the compound 131 can function well as a composite material in which they are mixed. Moreover, the thickness of the electron injection layer 130 is preferably 50 nm or less, more preferably 20 nm or less, and even more preferably 10 nm or less. With this configuration, the influence of light absorption by the electron injection layer 130 can be reduced, and a light-emitting element exhibiting high luminous efficiency can be provided.

[0123] <Light-emitting element configuration example 2> Next, an example of a configuration different from that of the light-emitting element 150 shown in FIG. 1 will be described below with reference to FIG.

[0124] Fig. 2(A) is a schematic cross-sectional view showing a light-emitting device according to one embodiment of the present invention. Note that in Fig. 2(A), the same hatch patterns are used for parts having the same functions as those shown in Fig. 1, and the reference symbols may be omitted. The same reference symbols are used for parts having the same functions, and detailed descriptions thereof may be omitted.

[0125] The light-emitting element 152 has a pair of electrodes (electrode 101 and electrode 102) and an EL layer 100 provided between the pair of electrodes. The EL layer 100 has at least a light-emitting layer 140 and an electron injection layer 130. The EL layer 100 further has a buffer layer 127. The buffer layer 127 is provided between the electron injection layer 130 and the electrode 102.

[0126] The EL layer 100 shown in FIG. 2A includes functional layers such as a hole injection layer 111, a hole transport layer 112, and an electron transport layer 118 in addition to the light emitting layer 140.

[0127] In one embodiment of the present invention, a composite material of the above-described compound 131 and a metal 132 is used for the electron-injection layer 130, and a compound 133 having an electron-deficient heteroaromatic ring is used for the buffer layer 127. The electron-deficient heteroaromatic ring has excellent electron-transport properties, and therefore the driving voltage of the light-emitting element can be reduced.

[0128] By sandwiching the buffer layer 127 between the electron injection layer 130 and the electrode 102, it is possible to reduce the electron injection barrier between the electrode 102 and the electron injection layer 130, which is preferable. In addition, the thickness of the buffer layer 127 is preferably 1 nm or more and 20 nm or less. With this structure, it is possible to reduce the electron injection barrier while maintaining high electron transport properties.

[0129] In addition, the LUMO level of the compound 133 is preferably lower than the SOMO level formed in the electron injection layer 130. By adopting such a structure, the electron injection barrier between the electron injection layer 130 and the electrode 102 can be reduced, which is preferable.

[0130] <Configuration example 3 of light-emitting element> In addition, a configuration example different from the light-emitting element 150 shown in FIG. 1A and the light-emitting element 152 shown in FIG. 2A will be described below with reference to FIG. 2B.

[0131] Fig. 2(B) is a schematic cross-sectional view showing a light-emitting element of one embodiment of the present invention. Note that in Fig. 2(B), the same hatch patterns are used for parts having the same functions as those shown in Fig. 1, and the reference symbols may be omitted. The same reference symbols are used for parts having the same functions, and detailed descriptions thereof may be omitted.

[0132] The light-emitting element 154 has a pair of electrodes (electrode 101 and electrode 102) and an EL layer 100 provided between the pair of electrodes. The EL layer 100 has at least a light-emitting layer 140 and an electron injection layer 130. The EL layer 100 further has a charge generation layer 129. The charge generation layer 129 is provided between the electron injection layer 130 and the electrode 102.

[0133] 2B includes functional layers such as a hole injection layer 111, a hole transport layer 112, and an electron transport layer 118 in addition to the light emitting layer 140. In addition, the EL layer 100 shown in FIG.

[0134] By providing the charge generation layer 129 between the electrode 102 and the electron injection layer 130 as shown in Figure 2 (B), the probability that the electron injection layer 130 will come into contact with oxygen or moisture is reduced, which is expected to further improve the moisture resistance and oxidation resistance of the light-emitting element.

[0135] The charge generating layer 129 may be a structure in which an electron accepting material is added to a hole transporting material, or a structure in which an electron donating material is added to an electron transporting material. In addition, both of these structures may be laminated, but a structure in which an electron accepting material is added to a hole transporting material is preferable because it improves moisture resistance and reduces the number of laminated layers.

[0136] As described above, when the charge generation layer 129 has a structure including a hole transport material and an electron accepting material, if a metal material having an alkali metal or an alkaline earth with a small work function is used for the electron injection layer 130, the electron accepting material of the charge generation layer 129 extracts electrons from the material used for the electron injection layer 130, and a depletion layer is generated near the interface between the charge generation layer 129 and the electron injection layer 130. This may result in an increase in the driving voltage. In order to suppress the generation of the depletion layer, it is necessary to provide a layer having a function of transferring electrons between the electron injection layer 130 and the charge generation layer 129.

[0137] On the other hand, in a light-emitting element of one embodiment of the present invention, by using a composite material of a transition metal and an organic compound having a function of interacting with a metal in a tridentate or tetradentate manner for the electron-injection layer 130, the charge-generation layer 129 can be provided without generating the above-mentioned depletion layer, and therefore a light-emitting element with a small number of stacked layers and a low driving voltage can be manufactured.

[0138] Furthermore, the thickness of the charge generation layer 129 is not particularly limited and can be adjusted appropriately. For example, by adjusting the thickness of the film from the light emitting layer 140 to the electrode 102, the light emitted from the light emitting layer 140 can be efficiently extracted to the outside of the light emitting element. In other words, by adjusting the thickness of the charge generation layer 129, the light extraction efficiency can be improved.

[0139] In addition, the charge generation layer 129 and the electrode 102 are preferably in contact with each other. With this structure, an electron injection barrier between the electrode 102 and the EL layer 100 can be reduced, and therefore the driving voltage of the light-emitting element can be reduced. Furthermore, it is more preferable that the charge generation layer 129 and the electron injection layer 130 are in contact with each other. In one embodiment of the present invention, even when the charge generation layer 129 and the electron injection layer 130 are in contact with each other, a light-emitting element with a low driving voltage can be manufactured. Therefore, with this structure, the number of stacked layers of the EL layer 100 can be reduced.

[0140] In addition, a transition metal oxide can be preferably used as the electron-accepting material of the charge generation layer 129. 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, and silver oxide. In particular, molybdenum oxide is preferable because it is stable in the air, has low hygroscopicity, and is inexpensive. By using the transition metal oxide, an electron injection barrier between the electrode 102 and the charge generation layer 129 can be reduced, which is preferable. Therefore, one embodiment of the present invention is a light-emitting element in which the electron injection layer 130 contains a transition metal element and the charge generation layer 129 contains a transition metal element. Note that the electron-accepting material of the charge generation layer 129 is not limited to the above-mentioned compounds.

[0141] In addition, an organic compound containing any one of a pyrrole skeleton, a thiophene skeleton, a furan skeleton, and an aromatic amine skeleton is preferably used as the hole-transporting material of the charge generation layer 129. Since the organic compound having such a skeleton has high hole-transporting properties, the driving voltage of the light-emitting element can be reduced by using it for the charge generation layer 129. The hole-transporting material of the charge generation layer 129 is not limited to the above-mentioned compounds.

[0142] The composite material of the compound 131 having a function of interacting with the metal 132 at a tridentate or tetradentate bond can be used in a thin-film solar cell. More specifically, it can be suitably used as an electron injection layer of a thin-film solar cell.

[0143] <Components of light-emitting element> Next, the components of the light-emitting device shown in FIGS. 1 and 2 will be described in detail below.

[0144] ≪Electron injection layer≫ The electron injection layer 130 is a layer containing a substance with high electron injection properties, and a composite material of the above-mentioned metal and an organic compound having a function of interacting with the metal at a tridentate or tetradentate can be suitably used. As the organic compound having a function of interacting with the metal at a tridentate or tetradentate, an organic compound represented by any of the general formulae (G0) to (G4-3) can be used, and specifically, an organic compound represented by any of the structural formulae (100) to (111) and (200) to (211) can be used. In particular, heterocyclic compounds having a diazine (pyrimidine or pyrazine) skeleton and a triazine skeleton are preferred because they have high electron transport properties and contribute to reducing the driving voltage. In addition, an organic compound having a function of interacting with the metal at a tridentate or tetradentate can be used in an amount of 1×10 -6 cm 2 It is preferable that the electron mobility of the electron-injecting layer 130 be 1 / Vs or more. Note that any substance other than the above may be used for the electron-injecting layer 130 as long as it has a higher electron-transporting property than a hole-transporting property.

[0145] <Hole injection layer> The hole injection layer 111 and the charge generation layer 129 have a function of promoting hole injection by reducing the hole injection barrier from one of the pair of electrodes (electrode 101 or electrode 102), and are formed of, for example, a transition metal oxide, a phthalocyanine derivative, or an aromatic amine. Examples of transition metal oxides include molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, and manganese oxide. Examples of phthalocyanine derivatives include phthalocyanine and metal phthalocyanine. Examples of aromatic amines include benzidine derivatives and phenylenediamine derivatives. Polymer compounds such as polythiophene and polyaniline can also be used, and a representative example is poly(ethylenedioxythiophene) / poly(styrenesulfonic acid), which is a self-doped polythiophene.

[0146] The hole injection layer 111 and the charge generation layer 129 may be formed of a layer having a composite material of a hole transporting material and a material exhibiting electron accepting properties. Alternatively, a stack of a layer containing a material exhibiting electron accepting properties and a layer containing a hole transporting material may be used. Charge can be exchanged between these materials in a stationary state or in the presence of an electric field. Examples of materials exhibiting electron accepting properties include organic acceptors such as quinodimethane derivatives, chloranil derivatives, and hexaazatriphenylene derivatives. Specifically, compounds having an electron-withdrawing group (especially a halogen group such as a fluoro group or a cyano group) such as 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation: F4-TCNQ), chloranil, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviation: HAT-CN), 1,3,4,5,7,8-hexafluorotetracyano-naphthoquinodimethane (abbreviation: F6-TCNNQ) can be mentioned. In particular, a compound in which an electron-withdrawing group is bonded to a condensed aromatic ring having a plurality of heteroatoms, such as HAT-CN, is thermally stable and preferable. Radialene derivatives having an electron-withdrawing group (especially a halogen group such as a fluoro group or a cyano group) [3] are preferred because they have a very high electron-accepting property. Specific examples include α,α',α''-1,2,3-cyclopropane triylidene tris[4-cyano-2,3,5,6-tetrafluorobenzeneacetonitrile], α,α',α''-1,2,3-cyclopropane triylidene tris[2,6-dichloro-3,5-difluoro-4-(trifluoromethyl)benzeneacetonitrile], and α,α',α''-1,2,3-cyclopropane triylidene tris[2,3,4,5,6-pentafluorobenzeneacetonitrile]. Transition metal oxides, for example, oxides of metals from Group 4 to Group 8, can also be used. Specific examples include vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide, and rhenium oxide. Among these, molybdenum oxide is preferred because it is stable in the air, has low hygroscopicity, and is easy to handle.

[0147] As the hole transporting material, a material having a higher hole transporting property than that of electrons can be used. -6 cm 2 It is preferable that the hole transport material has a hole mobility of 100 / Vs or more. Specifically, the aromatic amine, carbazole derivative, aromatic hydrocarbon, stilbene derivative, etc., which are listed as examples of hole transport materials that can be used in the light emitting layer 140, can be used, and it is particularly preferable that the hole transport material has a heteroaromatic skeleton having 1 to 20 carbon atoms and containing two or more. In particular, a nitrogen-containing heterocyclic five-membered skeleton is preferable. The hole transport material may be a polymer compound.

[0148] Other examples of hole transport materials include aromatic hydrocarbons, such as 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), and 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, and the like. In addition, pentacene, coronene, etc. can also be used. -6 cm 2It is more preferable to use an aromatic hydrocarbon having a hole mobility of 1 / Vs or more and having 14 to 42 carbon atoms.

[0149] The aromatic hydrocarbon may have a vinyl skeleton. Examples of aromatic hydrocarbons having a vinyl group include 4,4'-bis(2,2-diphenylvinyl)biphenyl (abbreviation: DPVBi) and 9,10-bis[4-(2,2-diphenylvinyl)phenyl]anthracene (abbreviation: DPVPA).

[0150] In addition, 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(dibenzothiophene-4-yl)benzene (abbreviation: DBT3P-II), 2,8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)furan] Thiophene compounds such as 4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviation: DBTFLP-III), 4-[3-(triphenylen-2-yl)phenyl]dibenzothiophene (abbreviation: mDBTPTp-II), furan compounds, fluorene compounds, triphenylene compounds, and phenanthrene compounds can be used. Among the above-mentioned compounds, compounds having a pyrrole skeleton, a furan skeleton, a thiophene skeleton, or an aromatic amine skeleton are preferred because they are stable and reliable. In addition, compounds having such skeletons have high hole transport properties and contribute to reducing the driving voltage.

[0151] <Hole transport layer> The hole transport layer 112 is a layer containing a hole transporting material, and can use the materials exemplified as the material of the hole injection layer 111. The hole transport layer 112 has a function of transporting holes injected from the hole injection layer 111 to the light emitting layer 140.

[0152] In this case, it is preferable to use a hole transporting material having a HOMO level between the LUMO level of the acceptor material of the hole injection layer 111 and the HOMO level of the material of the light emitting layer 140 for the hole transporting layer 112. The hole transporting layer 112 may be a single layer or may be a laminate of two or more layers. In this case, it is preferable to laminate the hole transporting layer materials so that the HOMO levels are lower in order from the hole injection layer 111 side to the light emitting layer 140. When the hole transporting layer 112 is laminated in two or more layers, in order to smoothly transport holes, the difference in the HOMO levels of each hole transporting material is preferably 0 eV or more and 0.5 eV or less, more preferably 0 eV or more and 0.3 eV or less, and more preferably 0 eV or more and 0.2 eV or less.

[0153] Examples of materials having a hole transporting property include 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB), 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), 4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP), 4-phenyl-3'-(9-phenylfluoren-9-yl)triphenylamine (abbreviated as mBPAFLP), 4-phenyl-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviated as PCBA1BP), 4,4'-diphenyl-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviated as PCBBi1BP), 4-(1-naphthyl)-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviated as PCBBi1BP), Aromatic amines such as 4,4'-di(1-naphthyl)-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBANB), 9,9-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]fluoren-2-amine (abbreviation: PCBAF), and N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]spiro-9,9'-bifluoren-2-amine (abbreviation: PCBASF) Compounds with a carbazole skeleton, such as 1,3-bis(N-carbazolyl)benzene (abbreviation: mCP), 4,4'-di(N-carbazolyl)biphenyl (abbreviation: CBP), 3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviation: CzTP), and 3,3'-bis(9-phenyl-9H-carbazole) (abbreviation: PCCP), and compounds with a carbazole skeleton, such as 4,4',4''-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation: DBT3P-II), 2,Examples of the compounds include compounds having a thiophene skeleton such as 8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene (abbreviation: DBTFLP-III) and 4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviation: DBTFLP-IV), and compounds having a furan skeleton such as 4,4',4''-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation: DBF3P-II) and 4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran (abbreviation: mmDBFFLBi-II). Among the above, compounds having an aromatic amine skeleton and compounds having a carbazole skeleton are preferable because they have good reliability, high hole transportability, and contribute to reducing the driving voltage. In addition to the hole transporting materials described above, hole transporting materials may be selected from various substances.

[0154] Furthermore, examples of the material having a high hole transporting property include 3-[4-(1-naphthyl)-phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPN), 3-[4-(9-phenanthryl)-phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPPn), 4-phenyl-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4'-di(1-naphthyl)-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBNBB), 4-phenyl Diphenyl-(9-phenyl-9H-carbazol-3-yl)amine (abbreviation: PCA1BP), 3,3'-bis(9-phenyl-9H-carbazole) (abbreviation: PCCP), N-[4-(9H-carbazol-9-yl)phenyl]-N-(4-phenyl)phenylaniline (abbreviation: YGA1BP), 1,3,5-tri(dibenzothiophen-4-yl)-benzene (abbreviation: DBT3P-II), 4,4',4''-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation: DBF3P-II), 4-phenyl-4'-(9 -phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP), 4-[3-(triphenylen-2-yl)phenyl]dibenzothiophene (abbreviation: mDBTPTp-II), 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), Compounds with aromatic amine skeletons such as 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'-bifluoren-2-yl)-N-phenylamino]biphenyl (abbreviation: BSPB), 3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA1), 3,Examples include 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), etc. In addition, carbazole compounds such as 4,4'-di(N-carbazolyl)biphenyl (abbreviation: CBP) and 1,3,5-tris[4-(N-carbazolyl)phenyl]benzene (abbreviation: TCPB), amine compounds, dibenzothiophene compounds, dibenzofuran compounds, fluorene compounds, triphenylene compounds, phenanthrene compounds, etc. can be used. The substances listed here are mainly 1×10, -6 cm 2 However, other substances may be used as long as they have a higher hole transporting property than electron transporting property.

[0155] The compounds usable for the hole transport layer may be used for the hole injection layer, and may also be suitably used as hole transport materials for the charge generation layer 129.

[0156] <Light-emitting layer> The light-emitting layer 140 includes a light-emitting material that has a function of emitting at least one of purple, blue, blue-green, green, yellow-green, yellow, orange, and red light. In addition to the light-emitting material, the light-emitting layer 140 includes one or both of an electron-transporting material and a hole-transporting material as a host material.

[0157] As the light-emitting material, a light-emitting substance capable of converting singlet excitation energy into light emission or a light-emitting substance capable of converting triplet excitation energy into light emission can be used.

[0158] Examples of luminescent substances capable of converting singlet excitation energy into luminescence include substances that emit fluorescence (fluorescent compounds). Fluorescent compounds are not particularly limited, but are preferably anthracene derivatives, tetracene derivatives, chrysene derivatives, phenanthrene derivatives, pyrene derivatives, perylene derivatives, stilbene derivatives, acridone derivatives, coumarin derivatives, phenoxazine derivatives, and phenothiazine derivatives, and for example, the following substances can be used.

[0159] 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: 1,6FLPAPrn), N,N'-bis[4-(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'-diphenyl-N,N'-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-3,8-dicyclohexylpyrene-1,6-diamine (abbreviation: ch-1,6FLPAPrn), N,N'-(pyrene-1,6- diyl)bis[(6,N-diphenylbenzo[b]naphtho[1,2-d]furan)-8-amine] (abbreviation: 1,6BnfAPrn-03), 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-carbazol-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-diyldi-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-carbazol-3-amine (abbreviation: 2PCAPPA), N-[4-(9,10-diphenyl-2-anthryl)phenyl]-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviation: 2DPAPPA), N,N,N',N',N'',N'',N'''',N'''-octaphenyldibenzo[g,p]chrysene-2,7,10,15-tetraamine (abbreviation: DBC1), Coumarin 3 0, N-(9,10-diphenyl-2-anthryl)-N,9-diphenyl-9H-carbazol-3-amine (abbreviation: 2PCAPA), N-[9,10-bis(1,1'-biphenyl-2-yl)-2-anthryl]-N,9-diphenyl-9H-carbazol-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-carbazol-9-yl)phenyl]-N-phenylanthracen-2-amine (abbreviation: 2YGABPhA), N,N,9-triphenylanthracen-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]ethyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCJTI), lysine-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]indeno[1,2,3-cd:1',2',3'-lm]perylene, and the like.

[0160] In addition, examples of luminescent substances capable of converting triplet excitation energy into luminescence include substances that emit phosphorescence (phosphorescent compounds). Examples of phosphorescent compounds include organometallic complexes or metal complexes of iridium, rhodium, or platinum. Examples of platinum complexes and organic iridium complexes having porphyrin ligands include organic iridium complexes, and among these, organic iridium complexes, such as iridium orthometal complexes, are preferred. Examples of orthometalated ligands include 4H-triazole ligands, 1H-triazole ligands, imidazole ligands, pyridine ligands, pyrimidine ligands, pyrazine ligands, and isoquinoline ligands. In this case, the phosphorescent compound has an absorption band of triplet MLCT (Metal to Ligand Charge Transfer) transition.

[0161] An example of a substance having a blue or green emission peak is tris{2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazol-3-yl-κN 2 ]phenyl-κC}iridium(III) (abbreviation: Ir(mpptz-dmp)3), tris(5-methyl-3,4-diphenyl-4H-1,2,4-triazolato)iridium(III) (abbreviation: Ir(Mptz)3), tris[4-(3-biphenyl)-5-isopropyl-3-phenyl-4H-1,2,4-triazolato]iridium(III) (abbreviation: Ir(iPr iridium(III) (abbreviation: Ir(iPr5btz)3), and other organometallic iridium complexes with a 4H-triazole skeleton, such as tris[3-(5-biphenyl)-5-isopropyl-4-phenyl-4H-1,2,4-triazolato]iridium(III) (abbreviation: Ir(iPr5btz)3). organometallic iridium complexes with 1H-triazole skeletons, such as tris(1-methyl-5-phenyl-3-propyl-1H-1,2,4-triazolato)iridium(III) (abbreviation: Ir(Prptz1-Me)3), 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), and organometallic iridium complexes with imidazole skeletons, such as 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’ ] Organometallic iridium complexes having a phenylpyridine derivative having an electron-withdrawing group as a ligand, such as iridium(III) acetylacetonate (abbreviation: FIr(acac)). Among the above, organometallic iridium complexes having a nitrogen-containing five-membered heterocyclic skeleton, such as a 4H-triazole skeleton, a 1H-triazole skeleton, and an imidazole skeleton, are particularly preferred because they have high triplet excitation energy and are excellent in reliability and luminous efficiency.

[0162] Examples of substances having a green or yellow emission peak 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[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(tBuppm)2(acac)), ... Organometallic compounds with pyrimidine skeletons such as Ir(mpmppm)2(acac)), (acetylacetonato)bis{4,6-dimethyl-2-[6-(2,6-dimethylphenyl)-4-pyrimidinyl-κN3]phenyl-κC}iridium(III) (abbreviation: Ir(dmppm-dmp)2(acac)), and (acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III) (abbreviation: Ir(dppm)2(acac)). Iridium complexes, organometallic iridium complexes with pyrazine skeletons such as (acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazinate)iridium(III) (abbreviation: Ir(mppr-Me)2(acac)) and (acetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazinate)iridium(III) (abbreviation: Ir(mppr-iPr)2(acac)), and tris(2-phenylpyrazinate-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’ Organometallic iridium complexes with pyridine skeletons such as iridium(III) acetylacetonate (abbreviation: Ir(pq)2(acac)) and 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’ Examples of such complexes include organometallic iridium complexes such as iridium(III) acetylacetonate (abbreviated as Ir(bt)2(acac)) and rare earth metal complexes such as tris(acetylacetonato)(monophenanthroline)terbium(III) (abbreviated as Tb(acac)3(Phen)). Among the above, organometallic iridium complexes having a pyrimidine skeleton are particularly preferred because of their outstanding reliability and luminous efficiency.

[0163] Examples of substances having a yellow or red emission peak include those 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)), and bis[4,6-di(naphthalen-1-yl)pyrimidinato](dipivaloylmethanato)iridium(III) (abbreviation: Ir(d1npm)2(dpm)). and organometallic iridium complexes with pyrazine skeletons 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)), and (acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III) (abbreviation: Ir(Fdpq)2(acac)). 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 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin platinum(II) (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)). Among the above, organometallic iridium complexes having a pyrimidine skeleton are particularly preferred because they are remarkably excellent in reliability and luminous efficiency. Furthermore, an organometallic iridium complex having a pyrazine skeleton can emit red light with good chromaticity.

[0164] In addition to phosphorescent compounds, materials capable of converting triplet excitation energy into light emission include thermally activated delayed fluorescence (TADF) materials. Therefore, the part described as phosphorescent compound may be read as thermally activated delayed fluorescence compound. Thermally activated delayed fluorescence compounds are materials that have a small difference between the singlet excitation energy level and the triplet excitation energy level and have the function of converting triplet excitation energy into singlet excitation energy by reverse intersystem crossing. Therefore, it is possible to upconvert the triplet excitation state to the singlet excitation state (reverse intersystem crossing) with a small amount of thermal energy, and it is possible to efficiently exhibit light emission (fluorescence) from the singlet excitation state. Conditions for efficiently obtaining thermally activated delayed fluorescence include a difference between the singlet excitation energy level and the triplet excitation energy level that is preferably greater than 0 eV and less than 0.3 eV, more preferably greater than 0 eV and less than 0.2 eV, and even more preferably greater than 0 eV and less than 0.1 eV.

[0165] When the thermally activated delayed fluorescent compound is composed of one type of material, for example, the following material can be used.

[0166] First, there are fullerene and its derivatives, acridine derivatives such as proflavine, eosin, etc. Also, there are metal-containing porphyrins including magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), palladium (Pd), etc. Examples of the metal-containing porphyrin 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)), and octaethylporphyrin-platinum chloride complex (PtCl2OEP).

[0167] In addition, heterocyclic compounds having a π-electron rich heteroaromatic skeleton and a π-electron deficient heteroaromatic skeleton can also be used as the thermally activated delayed fluorescent compound composed of one kind of material. 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-phenoxazin-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[acridin-9,9'-anthracene]-10'-one (abbreviation: ACRSA), etc. The heterocyclic compound has a π-electron-rich heteroaromatic skeleton and a π-electron-deficient heteroaromatic skeleton, and therefore has high electron transport properties and hole transport properties, making it preferable. Among the π-electron-deficient heteroaromatic skeletons, diazine skeletons (pyrimidine skeleton, pyrazine skeleton, pyridazine skeleton) or triazine skeletons are preferred because they are stable and reliable. Among the π-electron-rich heteroaromatic skeletons, acridine skeleton, phenoxazine skeleton, phenothiazine skeleton, furan skeleton, thiophene skeleton, and pyrrole skeleton are stable and reliable, so it is preferred to have one or more selected from these skeletons. As the pyrrole skeleton, indole skeleton, carbazole skeleton, and 9-phenyl-3,3'-bi-9H-carbazole skeleton are particularly preferred.In addition, a substance in which a π-electron-rich heteroaromatic skeleton and a π-electron-deficient heteroaromatic skeleton are directly bonded is particularly preferable because the donor property of the π-electron-rich heteroaromatic skeleton and the acceptor property of the π-electron-deficient heteroaromatic skeleton are both strong, and the difference between the singlet excitation energy level and the triplet excitation energy level is small.

[0168] In addition, the material exhibiting thermally activated delayed fluorescence may be a material that can generate a singlet excited state from a triplet excited state by reverse intersystem crossing on its own, or may be composed of multiple materials that form an excited complex (also called an exciplex).

[0169] As the host material used in the light-emitting layer 140, a hole-transporting material and an electron-transporting material can be used.

[0170] Materials that can be used as the host material of the light-emitting layer are not particularly limited, and examples thereof include tris(8-quinolinolato)aluminum(III) (abbreviation: Alq3), 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: B Alq), 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), and other metal complexes; 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD), and other metal complexes; 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-carbazo 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), and 4,4'-bis[N-(spiro-9,9'-bifluoren-2-yl)-N-phenylamino]biphenyl (abbreviation: BSPB).Further, examples of condensed polycyclic aromatic compounds include anthracene derivatives, phenanthrene derivatives, pyrene derivatives, chrysene derivatives, and dibenzo[g,p]chrysene derivatives. Specific examples of such compounds include 9,10-diphenylanthracene (abbreviation: DPAnth), N,N-diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine (abbreviation: CzA1PA), 4-(10-phenyl-9-anthryl)triphenylamine (abbreviation: DPhPA), YGAPA, PCAPA, N,9-diphenyl-N-{4-[4-(10-phenyl-9-anthryl)phenyl]phenyl}-9H-carbazol-3-amine (abbreviation: PCAPBA), 2PCAPA, 6,12-dimethoxy-5,11-diphenylchrysene, DBC1, 9-[4-(10-phenyl -9-anthracenyl)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), 1,3,5-tri(1-pyrenyl)benzene (abbreviation: TPB3), etc. can be mentioned. Among these and various substances, one or more substances having a larger energy gap than the energy gap of the above-mentioned light-emitting material may be selected and used. In addition, when the light-emitting material is a phosphorescent compound, a substance having a larger triplet excitation energy than the triplet excitation energy of the light-emitting material may be selected as the host material.

[0171] In addition, when a plurality of materials are used as the host material of the light-emitting layer, it is preferable to use two kinds of compounds that form an exciplex in combination. In this case, various carrier transport materials can be appropriately used, but it is particularly preferable to combine an electron transport material and a hole transport material in order to efficiently form an exciplex.

[0172] This is because, when an electron transporting material and a hole transporting material are combined to form a host material that forms an exciplex, the carrier balance of holes and electrons in the light-emitting layer can be easily optimized by adjusting the mixing ratio of the electron transporting material and the hole transporting material. By optimizing the carrier balance of holes and electrons in the light-emitting layer, it is possible to suppress bias in the region where recombination of electrons and holes occurs in the light-emitting layer. By suppressing bias in the region where recombination occurs, it is possible to improve the reliability of the light-emitting element.

[0173] As the electron transport material, metal complexes having zinc or aluminum, and π-electron-deficient heteroaromatic compounds such as nitrogen-containing heteroaromatic compounds can be used. Specifically, metal complexes such as 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), and bis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ) can be used. 4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD), 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviation: TAZ), 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), 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), and other heterocyclic compounds with an azole skeleton, such as 2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTPDBq-II), 2-[3'-(dibenzo 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), 6-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 6mDBTPDBq-II), 4,6-bis[3-(phenanthren-9-yl)phenyl]pyrimidine (abbreviation: 4,6mPnP2Pm), 4,6-bis[3-(4-dibenzothienyl)phenyl] Heterocyclic compounds having a diazine skeleton, such as pyrimidine (abbreviation: 4,6mDBTP2Pm-II), 4,6-bis[3-(9H-carbazol-9-yl)phenyl]pyrimidine (abbreviation: 4,6mCzP2Pm), and 4-{3-[3'-(9H-carbazol-9-yl)]biphenyl-3-yl}benzofuro[3,2-d]pyrimidine (abbreviation: 4mCzBPBfpm) and heterocyclic compounds having a triazine skeleton such as 2-{4-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: PCCzPTzn), 2,4,6-tris[3'-(pyridin-3-yl)biphenyl-3-yl]-1,3,5-triazine (abbreviation: TmPPPyTz), and 2,4,6-tris(2-pyridyl)-1,3,5-triazine (abbreviation: 2Py3Tz), and heterocyclic compounds having a pyridine skeleton such as 3,5-bis[3-(9H-carbazol-9-yl)phenyl]pyridine (abbreviation: 35DCzPPy), and 1,3,5-tri[3-(3-pyridyl)phenyl]benzene (abbreviation: TmPyPB). Among the above, heterocyclic compounds having a diazine skeleton and a triazine skeleton and heterocyclic compounds having a pyridine skeleton are preferable because of their high reliability. In particular, heterocyclic compounds having a diazine (pyrimidine or pyrazine) skeleton and a triazine skeleton have high electron transport properties and contribute to reducing the driving voltage.

[0174] As the hole transport material, π-electron-rich heteroaromatic compounds (e.g., carbazole derivatives and indole derivatives) or aromatic amines can be suitably used. Specifically, 2-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]spiro-9,9'-bifluorene (abbreviation: PCASF), 4,4',4''-tris[N-(1-naphthyl)-N-phenylamino]triphenylamine (abbreviation: 1-TNATA), 2,7-bis[N-(4-diphenylaminophenyl)-N-phenylamino]-spiro-9,9'-bifluorene (abbreviation: DPA2SF), N,N'-bis(9-phenylcarbazol-3-yl)-N,N'-diphenylbenzene -1,3-diamine (abbreviation: PCA2B), N-(9,9-dimethyl-2-diphenylamino-9H-fluoren-7-yl)diphenylamine (abbreviation: DPNF), N,N',N''-triphenyl-N,N',N''-tris(9-phenylcarbazol-3-yl)benzene-1,3,5-triamine (abbreviation: PCA3B), 2-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]spiro-9,9'-bifluorene (abbreviation: PCASF), 2-[N-(4-diphenylaminophenyl N,N'-bis[4-(carbazol-9-yl)phenyl]-N,N'-diphenyl-9,9-dimethylfluorene-2,7-diamine (abbreviation: YGA2F), 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB), N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (abbreviation: TPD), 4,4'-bis[N-(4 -diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation: DPAB), 4,4'-bis[N-(spiro-9,9'-bifluoren-2-yl)-N-phenylamino]biphenyl (abbreviation: BSPB), 4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP), 4-phenyl-3'-(9-phenylfluoren-9-yl)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), 3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA1), 3-[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzDPA1), 3,6-bis[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzDPA1), N,N'-bis{4-[bis(3-methylphenyl)amino]phenyl}-N,N'-diphenyl-(1,1'-biphenyl)-4,4'-diamine (abbreviation: DNTPD), 3,6-bis[N-(4-diphenylaminophenyl)-N-(1-naphthyl)amino]-9-phenylcarbazole (abbreviation: PCzTPN2), 3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA2), 4-phenyl-4'-(9-phenyl-9H-carbazole 4,4'-diphenyl-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), 3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)a N-(4-biphenyl)-N-(9,9-dimethyl-9H-fluoren-2-yl)-9-phenyl-9H-carbazol-3-amine (abbreviation: PCBAF), N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]spiro-9,9'-bifluoren-2-amine (abbreviation: PCBASF), N-(4-biphenyl)-N-(9,9-dimethyl-9H-fluoren-2-yl)-9-phenyl-9H-carbazol-3-amine (abbreviation: PCBiF), N-(1,Compounds with aromatic amine skeletons such as 1'-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: PCBBiF), compounds with carbazole skeletons such as 1,3-bis(N-carbazolyl)benzene (abbreviation: mCP), 4,4'-di(N-carbazolyl)biphenyl (abbreviation: CBP), 3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviation: CzTP), and 9-phenyl-9H-3-(9-phenyl-9H-carbazol-3-yl)carbazole (abbreviation: PCCP), and compounds with 4,4',4''-(benzene-1,3,5-triyl)tri(dibenzyl)carbazole (abbreviation: PCCP) Examples of the compounds include compounds having a thiophene skeleton such as 2,8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene (abbreviation: DBTFLP-III), and 4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviation: DBTFLP-IV), and compounds having a furan skeleton such as 4,4',4''-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation: DBF3P-II), and 4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran (abbreviation: mmDBFFLBi-II). Among the above, compounds having an aromatic amine skeleton and compounds having a carbazole skeleton are preferable because they have good reliability, high hole transport properties, and contribute to reducing the driving voltage.

[0175] The combination of host materials that form an exciplex is not limited to the above-mentioned compounds, and any combination that can transport carriers and form an exciplex may be used as long as the emission of the exciplex overlaps with the absorption band on the longest wavelength side in the absorption spectrum of the light-emitting material (absorption corresponding to the transition from the singlet ground state to the singlet excited state of the light-emitting material). Other materials may also be used.

[0176] Furthermore, a thermally activated delayed fluorescent material may be used as the host material for the light-emitting layer.

[0177] In addition, the electron transport material used in the light-emitting layer can be the same as the electron transport material used in the electron injection layer, which can simplify the fabrication of the light-emitting device and reduce the manufacturing cost of the light-emitting device.

[0178] <Electron transport layer and buffer layer> The electron transport layer 118 and the buffer layer 127 are layers containing a substance with high electron transport properties. Examples of organic compounds that can be used for the electron transport layer 118 and the buffer layer 127 include metal complexes having a quinoline ligand, a benzoquinoline ligand, an oxazole ligand, or a thiazole ligand, oxadiazole derivatives, triazole derivatives, phenanthroline derivatives, pyridine derivatives, and bipyridine derivatives. In addition, organic compounds having a function of interacting with a metal at a tridentate or tetradentate site, which are exemplified as compounds that can be used for the electron injection layer 130, can also be used.

[0179] Specific examples of the metal complexes having the above-mentioned quinoline ligand, benzoquinoline ligand, oxazole ligand, or thiazole ligand, oxadiazole derivatives, triazole derivatives, phenanthroline derivatives, pyridine derivatives, and bipyridine derivatives include metal complexes such as Alq3, Almq3, BeBq2, BAlq, bis(8-quinolinolato)zinc(II) (abbreviation: Znq), bis[2-(2-benzoxazolyl)phenolato]zinc(II) (abbreviation: ZnPBO), and bis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ). In addition, 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), 3-(4 '-tert-butylphenyl)-4-phenyl-5-(4''-biphenylyl)-1,2,4-triazole (abbreviation: TAZ), 3-(4-tert-butylphenyl)-4-(4-ethylphenyl)-5-(4-biphenylyl)-1,2,4-triazole (abbreviation: p-EtTAZ), 4,4'-bis(5-methylbenzoxazol-2-yl)stilbene (abbreviation: BzOS), 2,2',2''- Heterocyclic compounds with an azole skeleton, such as (1,3,5-benzenetriyl)tris(1-phenyl-1H-benzimidazole) (abbreviation: TPBI) and 2-[3-(dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzimidazole (abbreviation: mDBTBIm-II), and 2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBT PDBq-II), 2-[3'-(dibenzothiophene-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), 4,6-bis[3-(phenanthren-9-yl)phenyl]pyrimidine (abbreviation: 4,6mPnP2Pm), Heterocyclic compounds with diazine skeletons such as 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 4-{3-[3'-(9H-carbazol-9-yl)]biphenyl-3-yl}benzofuro[3,2-d]pyrimidine (abbreviation: 4mCzBPBfpm) and 2-{4 -[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: PCCzPTzn), 2,4,6-tris[3'-(pyridin-3-yl)biphenyl-3-yl]-1,3,5-triazine (abbreviation: TmPPPyTz), 2,4,6-tris(2-pyridyl)-1,3,5-triazine (abbreviation: 2Py3Tz) and other triazine skeletons 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), bathocuproine (abbreviation: BCP), and 2,9-bis(naphthalene-2-yl)-4,7-diphenyl-1,10-phenanthroline (abbreviation: NBPhen). Among the above, heterocyclic compounds having a diazine skeleton and a triazine skeleton and heterocyclic compounds having a pyridine skeleton are preferred because of their good reliability. In particular, heterocyclic compounds having a diazine (pyrimidine or pyrazine) skeleton and a triazine skeleton have high electron transport properties and contribute to reducing the driving voltage. The substances described here are mainly 1×10, -6 cm 2The electron-injecting layer 130 may be formed using any other substance than those mentioned above as long as it has a higher electron-transporting property than a hole-transporting property.

[0180] In addition, the electron transport layer 118 and the buffer layer 127 may each be a single layer, or may be a stack of two or more layers made of the above-mentioned substances.

[0181] 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 140. This layer is made by adding a small amount of a substance with high electron trapping properties to a material with high electron transport properties as described above, and it is possible to adjust the carrier balance by suppressing the movement of electron carriers. This type of configuration is highly effective in suppressing problems (e.g., a decrease in device life) that occur due to electrons penetrating the light-emitting layer.

[0182] In addition, the electron transport material used in the electron transport layer may be the same as the electron transport material used in the electron injection layer. In addition, the electron transport material used in the electron transport layer may be the same as the electron transport material used in the light emitting layer. In this way, the light emitting device can be easily manufactured, and the manufacturing cost of the light emitting device can be reduced.

[0183] The above-mentioned hole injection layer, hole transport layer, light emitting layer, electron transport layer, and electron injection layer can be formed by a deposition method (including a vacuum deposition method), an ink jet method, a coating method, gravure printing, etc. In addition to the above-mentioned materials, the above-mentioned hole injection layer, hole transport layer, light emitting layer, electron transport layer, and electron injection layer may use inorganic compounds such as quantum dots or polymer compounds (oligomers, dendrimers, polymers, etc.).

[0184] As the quantum dots, colloidal quantum dots, alloy quantum dots, core-shell quantum dots, core quantum dots, etc. may be used. Quantum dots containing element groups of groups 2 and 16, 13 and 15, 13 and 17, 11 and 17, or 14 and 15 may be used. Quantum dots containing elements such as cadmium (Cd), selenium (Se), zinc (Zn), sulfur (S), phosphorus (P), indium (In), tellurium (Te), lead (Pb), gallium (Ga), arsenic (As), and aluminum (Al) may be used.

[0185] Examples of liquid media that can be used in the wet process include 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 N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO).

[0186] Examples of polymer compounds that can be used in the light-emitting layer include polyphenylenevinylene (PPV) derivatives such as poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (abbreviation: MEH-PPV) and poly(2,5-dioctyl-1,4-phenylenevinylene), poly(9,9-di-n-octylfluorenyl-2,7-diyl) (abbreviation: PF8), poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(benzo[2,1,3]thiadiazole-4,8-diyl)] (abbreviation: F8BT), poly Examples of suitable polyfluorene derivatives include poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(2,2'-bithiophene-5,5'-diyl)] (abbreviation: F8T2), poly[(9,9-dioctyl-2,7-divinylenefluorenylene)-alt-(9,10-anthracene)], and poly[(9,9-dihexylfluorene-2,7-diyl)-alt-(2,5-dimethyl-1,4-phenylene)]; polyalkylthiophene (PAT) derivatives such as poly(3-hexylthiophene) (abbreviation: P3HT); and polyphenylene derivatives. Furthermore, these polymer compounds, poly(N-vinylcarbazole) (abbreviation: PVK), poly(2-vinylnaphthalene), poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (abbreviation: PTAA), etc. may be doped with a light-emitting low molecular weight compound and used in the light-emitting layer. As the light-emitting low molecular weight compound, the fluorescent compounds listed above can be used.

[0187] The electrode 101 and the electrode 102 function as an anode or a cathode of a light-emitting element. The electrode 101 and the electrode 102 can be formed using a metal, an alloy, a conductive compound, or a mixture or stack of these materials.

[0188] One of the electrode 101 and the electrode 102 is preferably formed of a conductive material having a function of reflecting light. Examples of the conductive material include aluminum (Al) and 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. Furthermore, aluminum is abundant in the earth's crust and is inexpensive, so that the manufacturing cost of the light-emitting element can be reduced by using aluminum. Furthermore, silver (Ag) has a high light reflectance and can be suitably used as an electrode material. Furthermore, Ag is a transition metal of group 11. When Ag is used as the cathode of a light-emitting element using Ag in an electron injection layer, which is one embodiment of the present invention, the adhesion between the electrode and the electron injection layer is improved, which is preferable. Alternatively, 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, and an alloy containing silver and ytterbium. In addition, transition metals such as tungsten, chromium (Cr), molybdenum (Mo), copper, and titanium can be used.

[0189] Furthermore, light emitted from the light-emitting layer is extracted through one or both of the electrodes 101 and 102. Therefore, at least one of the electrodes 101 and 102 is preferably made of a conductive material that has a light-transmitting function. 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 Examples include conductive materials with a resistance of Ω·cm or less.

[0190] The electrodes 101 and 102 may be made of a conductive material that has both a light transmitting and light reflecting function. The conductive material has a visible light reflectance of 20% to 80%, preferably 40% to 70%, and a resistivity of 1×10 -2 Examples of the conductive material include a material having a resistivity of Ω·cm or less. For example, the conductive material can be formed by using one or more conductive metals, alloys, conductive compounds, etc. Specifically, for example, metal oxides such as indium tin oxide (hereinafter, ITO), indium tin oxide containing silicon or silicon oxide (abbreviated as ITSO), indium oxide-zinc oxide, indium oxide-tin oxide containing titanium, indium-titanium oxide, indium oxide containing tungsten oxide and zinc oxide, etc. can be used. In addition, a metal thin film having a thickness of about 1 nm or more and 30 nm or less that transmits light 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.

[0191] In this specification and the like, the material having a function of transmitting light may be any material that has a function of transmitting visible light and has electrical conductivity, and includes, for example, oxide conductors such as ITO as described above, as well as oxide semiconductors and organic conductors containing organic substances. Examples of organic conductors containing organic substances include composite materials obtained by mixing an organic compound with an electron donor, and composite materials obtained by mixing an organic compound with an electron acceptor. Inorganic carbon-based materials such as graphene may also be used. The resistivity of the material is preferably 1×10 5 Ω cm or less, more preferably 1×10 4 Ω·cm or less.

[0192] Alternatively, one or both of the electrode 101 and the electrode 102 may be formed by stacking a plurality of the above materials.

[0193] In addition, in order to improve the light extraction efficiency, a material having a higher refractive index than an electrode having a function of transmitting light may be formed in contact with the electrode. Such a material may be a material having a function of transmitting visible light, and may be a material having or not having electrical conductivity. For example, in addition to the oxide conductor as described above, an oxide semiconductor and an organic material may be mentioned. As the organic material, for example, the materials exemplified in the light-emitting layer, the hole injection layer, the hole transport layer, the electron transport layer, or the electron injection layer may be mentioned. In addition, an inorganic carbon-based material or a metal thin film having a thickness of several nm to several tens of nm may be used, and a plurality of layers may be stacked.

[0194] When the electrode 101 or the electrode 102 functions as a cathode, it is preferable that the electrode 101 or the electrode 102 is made of a material having a small work function (3.8 eV or less).

[0195] 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).

[0196] The electrodes 101 and 102 may be a laminate of a conductive material having a light reflecting function and a conductive material having a light transmitting function. In that case, the electrodes 101 and 102 are preferable because they can have a function of adjusting the optical distance so that light of a desired wavelength from each light emitting layer can be resonated and the light of the desired wavelength can be intensified.

[0197] The electrodes 101 and 102 can be formed by any suitable method, such as sputtering, vapor deposition, printing, coating, MBE (Molecular Beam Epitaxy), CVD, pulsed laser deposition, or ALD (Atomic Layer Deposition).

[0198] <Substrate> The light-emitting element according to one embodiment of the present invention may be fabricated over a substrate made of glass, plastic, or the like. The order of fabrication on the substrate may be from the electrode 101 side or from the electrode 102 side.

[0199] As a substrate on which the light-emitting element according to one embodiment of the present invention can be formed, for example, glass, quartz, or plastic can be used. A flexible substrate may also be used. A flexible substrate is a substrate that can be bent (flexible), and examples of the flexible substrate include a plastic substrate made of polycarbonate or polyarylate. A film, an inorganic deposition film, or the like can also be used. Any other substrate may be used as long as it functions as a support in the manufacturing process of the light-emitting element and the optical element. Alternatively, any substrate may be used as long as it has a function of protecting the light-emitting element and the optical element.

[0200] For example, in the present specification and the like, a light-emitting element can be formed using various substrates. The type of substrate is not particularly limited. Examples of the substrate include a semiconductor substrate (e.g., a single crystal substrate or a silicon substrate), an SOI substrate, a glass substrate, a quartz substrate, a plastic substrate, a metal substrate, a stainless steel substrate, a substrate having stainless steel foil, a tungsten substrate, a substrate having tungsten foil, a flexible substrate, a laminated film, cellulose nanofiber (CNF) or paper containing a fibrous material, or a base film. Examples of glass substrates include barium borosilicate glass, aluminoborosilicate glass, or soda lime glass. Examples of flexible substrates, laminated films, base films, and the like include the following. For example, there are plastics represented by polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), and polytetrafluoroethylene (PTFE). Alternatively, there are resins such as acrylic. Alternatively, there are polypropylene, polyester, polyvinyl fluoride, or polyvinyl chloride. Alternatively, for example, there may be polyamide, polyimide, aramid, epoxy, an inorganic vapor deposition film, or paper.

[0201] Alternatively, a flexible substrate may be used as the substrate, and the light-emitting element may be formed directly on the flexible substrate. Alternatively, a peeling layer may be provided between the substrate and the light-emitting element. The peeling layer can be used to separate the light-emitting element from the substrate after a part or all of the light-emitting element is completed thereon, and transfer it to another substrate. In this case, the light-emitting element can be transferred to a substrate having poor heat resistance or a flexible substrate. For the above-mentioned peeling layer, for example, a laminated structure of inorganic films such as a tungsten film and a silicon oxide film, or a configuration in which a resin film such as polyimide is formed on a substrate, can be used.

[0202] 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 the light-emitting element may be disposed on the other substrate. In addition to the above-mentioned substrates, examples of the substrate onto which the light-emitting element may be transferred include a cellophane substrate, a stone substrate, a wood substrate, a cloth substrate (including natural fibers (silk, cotton, hemp), synthetic fibers (nylon, polyurethane, polyester), or regenerated fibers (acetate, cupra, rayon, regenerated polyester), etc.), a leather substrate, or a rubber substrate. By using these substrates, a light-emitting element that is not easily broken, has high heat resistance, is lightweight, or is thin.

[0203] Also, for example, a field effect transistor (FET) may be formed on the above-mentioned substrate, and the light emitting element 150 may be fabricated on an electrode electrically connected to the FET. This makes it possible to fabricate an active matrix display device in which the driving of the light emitting element is controlled by the FET.

[0204] The structure described in this embodiment mode can be used in appropriate combination with other embodiment modes.

[0205] (Embodiment 2) In this embodiment, a light-emitting element having a different structure from that of the light-emitting element shown in Embodiment 1 and a light-emitting mechanism of the light-emitting element will be described below with reference to Fig. 3. Note that in Fig. 3, the same hatch pattern may be used for parts having the same functions as those shown in Fig. 1(A), and the reference numerals may be omitted. Also, the same reference numerals may be used for parts having the same functions, and detailed description thereof may be omitted.

[0206] <Configuration Example 4 of Light-Emitting Element> FIG. 3 is a schematic cross-sectional view of the light emitting element 250a and the light emitting element 250b.

[0207] The light-emitting element 250a and the light-emitting element 250b have an electrode 101, an electrode 102, an electrode 103, and an electrode 104 over a substrate 200. At least a light-emitting unit 106, a light-emitting unit 108, and an electron injection layer 130 are provided between the electrode 101 and the electrode 102, between the electrode 102 and the electrode 103, and between the electrode 102 and the electrode 104. A charge generation layer 115 is provided between the light-emitting unit 106 and the light-emitting unit 108. The light-emitting unit 106 and the light-emitting unit 108 may have the same structure or different structures.

[0208] Charge generation layer 115 sandwiched between light-emitting unit 106 and light-emitting unit 108 may be any layer that injects electrons into one light-emitting unit and injects holes into the other light-emitting unit when a voltage is applied between electrode 101 and electrode 102. For example, in FIG. 1, when a voltage is applied so that the potential of electrode 102 is higher than the potential of electrode 101, charge generation layer 115 injects electrons into light-emitting unit 106 and injects holes into light-emitting unit 108.

[0209] The light-emitting unit 106 includes, for example, a hole injection layer 111, a hole transport layer 112, a light-emitting layer 140, and an electron transport layer 113. The light-emitting unit 108 includes, for example, a hole injection layer 116, a hole transport layer 117, a light-emitting layer 170, an electron transport layer 118, and an electron injection layer 119.

[0210] 3, the electron injection layer 130 is preferably adjacent to the electron transport layer 113 and provided between the light-emitting unit 108 and the electron transport layer 113. Also, as shown in FIG 3, the charge generation layer 115 is preferably adjacent to the electron injection layer 130 and provided between the electron injection layer 130 and the light-emitting unit 108. With this configuration, electrons can be efficiently transported to the light-emitting unit 106.

[0211] In the present embodiment, the electrodes 101, 103, and 104 are described as an anode, and the electrode 102 is described as a cathode. However, the configuration of the light-emitting element 250a and the light-emitting element 250b is not limited to this. That is, the electrodes 101, 103, and 104 may be the cathode, and the electrode 102 may be the anode, and the layers between the electrodes may be stacked in the reverse order. That is, the light-emitting unit 106 may be stacked in the order of the hole injection layer 111, the hole transport layer 112, the light-emitting layer 140, the electron transport layer 113, and the electron injection layer 130 from the anode side, and the light-emitting unit 108 may be stacked in the order of the hole injection layer 116, the hole transport layer 117, the light-emitting layer 170, the electron transport layer 118, and the electron injection layer 119 from the anode side.

[0212] In addition, the configuration of the light-emitting element 250a and the light-emitting element 250b is not limited to the configuration shown in FIG. 3, and each of the light-emitting elements 250a and 250b has at least the light-emitting layer 140, the light-emitting layer 170, the charge generation layer 115, and the electron injection layer 130, and may or may not have the hole injection layer 111, the hole injection layer 116, the hole transport layer 112, the hole transport layer 117, the electron transport layer 113, the electron transport layer 118, and the electron injection layer 119.

[0213] In addition, a layer corresponding to the function may be formed between the pair of electrodes, and is not limited thereto. That is, a layer having a function of reducing the hole or electron injection barrier, improving the hole or electron transportability, inhibiting the hole or electron transportability, suppressing the quenching phenomenon caused by the electrodes, or the like may be formed between the pair of electrodes.

[0214] In addition, when the anode side surface of the light-emitting unit is in contact with the charge generation layer 115, as in the case of the light-emitting unit 108, the charge generation layer 115 may also serve as the hole injection layer of the light-emitting unit 108, and therefore, it may not be necessary to provide a hole injection layer for the light-emitting unit.

[0215] Although a light-emitting element having two light-emitting units has been described in Fig. 3, a light-emitting element having three or more light-emitting units stacked thereon may be used. As shown in the light-emitting element 250a and the light-emitting element 250b, by disposing a plurality of light-emitting units between a pair of electrodes and separating them with a charge generating layer, a light-emitting element that can emit light with high luminance while keeping the current density low and has a long life can be realized. In addition, a light-emitting element with low power consumption can be realized.

[0216] In the light-emitting element 250a, the electrodes 101, 103, and 104 have a function of reflecting visible light, and the electrode 102 has a function of transmitting visible light. In the light-emitting element 250b, the electrodes 101, 103, and 104 have a function of transmitting visible light, and the electrode 102 has a function of reflecting visible light.

[0217] Therefore, light emitted by the light-emitting element 250a is emitted to the outside through the electrode 102, and light emitted by the light-emitting element 250b is emitted to the outside through the electrodes 101, 103, and 104. However, one embodiment of the present invention is not limited thereto, and the light-emitting element may be one that extracts light both above and below the substrate 200 on which the light-emitting element is formed.

[0218] The electrode 101 includes a conductive layer 101a and a conductive layer 101b on and in contact with the conductive layer 101a. The electrode 103 includes a conductive layer 103a and a conductive layer 103b on and in contact with the conductive layer 103a. The electrode 104 includes a conductive layer 104a and a conductive layer 104b on and in contact with the conductive layer 104a.

[0219] The conductive layer 101b, the conductive layer 103b, and the conductive layer 104b have a function of transmitting visible light. In the light-emitting element 250a, the conductive layer 101a, the conductive layer 103a, and the conductive layer 104a have a function of reflecting visible light. In the light-emitting element 250b, the conductive layer 101a, the conductive layer 103a, and the conductive layer 104a have a function of transmitting visible light.

[0220] A light-emitting element 250a shown in FIG. 3A and a light-emitting element 250b shown in FIG. 3B each have a partition wall 145 between a region 222B sandwiched between the electrodes 101 and 102, a region 222G sandwiched between the electrodes 102 and 103, and a region 222R sandwiched between the electrodes 102 and 104. The partition wall 145 has insulating properties. The partition wall 145 covers ends of the electrodes 101, 103, and 104 and has openings overlapping the electrodes. By providing the partition wall 145, the electrodes on the substrate 200 in each region can be separated into island shapes.

[0221] In FIG. 3, the hole injection layer 111, the hole injection layer 116, the hole transport layer 112, the hole transport layer 117, the light-emitting layer 140, the light-emitting layer 170, the electron transport layer 113, the electron transport layer 118, the electron injection layer 119, the charge generation layer 115, and the electrode 102 are illustrated as being provided in common to each region without being separated from each other, but may be provided separately from each other in each region.

[0222] In the light-emitting element 250a and the light-emitting element 250b according to one embodiment of the present invention, a voltage is applied between a pair of electrodes (electrodes 101 and 102) in the region 222B, between a pair of electrodes (electrodes 102 and 103) in the region 222G, and between a pair of electrodes (electrodes 102 and 104) in the region 222R, whereby electrons are injected from the cathode into the electron injection layer 119 and holes are injected from the anode into the hole injection layer 111, causing a current to flow. Also, electrons are injected from the charge generation layer 115 into the electron injection layer 130, and holes are injected from the charge generation layer 115 into the hole injection layer 116. Then, the injected carriers (electrons and holes) are recombined to form excitons. When carriers (electrons and holes) recombine in the light-emitting layers 140 and 170 containing the light-emitting material to form excitons, the light-emitting material contained in the light-emitting layers 140 and 170 enters an excited state, and light is emitted from the light-emitting material.

[0223] Light-emitting layer 140 and light-emitting layer 170 preferably contain one or more light-emitting materials selected from the group consisting of purple, blue, blue-green, green, yellow-green, yellow, yellow-orange, orange, and red light-emitting materials.

[0224] The light-emitting layer 140 and the light-emitting layer 170 may have a two-layer laminated structure. By using two types of light-emitting materials, a first compound and a second compound, each of which has a function of exhibiting different colors, in the two light-emitting layers, it is possible to simultaneously obtain multiple lights. In particular, it is preferable to select the light-emitting material used in each light-emitting layer so that the light emitted by the light-emitting layer 140 and the light-emitting layer 170 is white or a color close to white.

[0225] Furthermore, the light-emitting layer 140 and the light-emitting layer 170 may have a configuration in which three or more layers are laminated, and may include a layer that does not have a light-emitting material.

[0226] Furthermore, the light emitting element 250a and the light emitting element 250b have a substrate 220 on which the optical elements 224B, 224G, and 224R are provided, respectively, in the direction in which the light emitted from the region 222B, the region 222G, and the region 222R is extracted. The light emitted from each region is emitted to the outside of the light emitting element through each optical element. That is, the light emitted from the region 222B is emitted through the optical element 224B, the light emitted from the region 222G is emitted through the optical element 224G, and the light emitted from the region 222R is emitted through the optical element 224R.

[0227] In addition, optical element 224B, optical element 224G, and optical element 224R have a function of selectively transmitting light of a specific color from the incident light. For example, the light emitted from region 222B via optical element 224B is blue light, the light emitted from region 222G via optical element 224G is green light, and the light emitted from region 222R via optical element 224R is red light.

[0228] In Fig. 3(A) and Fig. 3(B), the light emitted from each region through each optical element is shown by a dashed arrow as blue (B), green (G), and red (R) light. The light-emitting element 250a shown in Fig. 3(A) is a top-emission type light-emitting element, and the light-emitting element 250b shown in Fig. 3(B) is a bottom-emission type light-emitting element.

[0229] In addition, a light-shielding layer 223 is provided between each optical element. The light-shielding layer 223 has a function of blocking light emitted from an adjacent region. Note that a configuration may be adopted in which the light-shielding layer 223 is not provided. Also, a configuration may be adopted in which one or more of the optical element 224B, the optical element 224G, and the optical element 224R are not provided. By adopting a configuration in which the optical element 224B, the optical element 224G, and the optical element 224R are not provided, it is possible to increase the extraction efficiency of light emitted from the light-emitting element.

[0230] The charge generation layer 115 can be formed from a material in which an electron acceptor is added to a hole transporting material, or a material in which an electron donor is added to an electron transporting material.

[0231] Here, in order to reduce the driving voltage of the light-emitting element, it is preferable to reduce the electron injection barrier from the charge generation layer 115 to the electron transport layer 113 and smoothly inject and transport electrons generated in the charge generation layer 115 into the electron transport layer 113. Therefore, it is preferable to provide the electron injection layer 130 between the charge generation layer 115 and the electron transport layer 113. Since the electron injection layer 119 and the electron injection layer 130 are required to have high electron injection properties, an alkali metal such as lithium (Li) or cesium (Cs) or a compound thereof, or an alkaline earth metal such as calcium (Ca) or a compound thereof is used for the electron injection layer. However, when such metals and compounds are used in the electron injection layer 130, for example, when a voltage is applied between the electrodes 103 and 102 to pass a current through the region 222G as shown in Fig. 4, a current may also pass through the regions 222B and 222R adjacent to the region 222G via the electron injection layer 130 and the electron transport layer 113, causing light emission not only from the region 222G but also from the adjacent regions 222B and 222R, a phenomenon known as crosstalk. In Fig. 4, the currents flowing through the regions 222G, 222R, and 222B are indicated by solid arrows.

[0232] When crosstalk occurs in a light-emitting element, light is emitted not only from the desired region (e.g., region 222G) but also from other regions (e.g., regions 222B and 222R), which may result in a decrease in the color purity of the light emitted by light-emitting element 250a and light-emitting element 250b or a decrease in the light-emitting intensity.

[0233] One of the reasons for the crosstalk is that the alkali metal, alkaline earth metal, or compound thereof used in the electron injection layer 130 sandwiched between the charge generation layer 115 and the electron transport layer 113 diffuses into the electron transport layer 113, improving the conductivity of the electron transport layer 113 (particularly the conductivity in the direction perpendicular to the voltage application direction). When a metal with a small atomic number such as Li or Ca or a compound thereof is used in the electron injection layer 130, the metal with a small atomic number is likely to diffuse into the electron transport layer 113. Therefore, in order to suppress the crosstalk, it is preferable that the electron injection layer 130 does not contain an alkali metal or an alkaline earth metal. On the other hand, when the electron injection layer 130 does not contain an alkali metal, an alkaline earth metal, or a compound thereof, the electron injection barrier from the charge generation layer 115 to the electron transport layer 113 becomes high, making it difficult to inject electrons into the electron transport layer 113, which may increase the driving voltage of the light-emitting device or reduce the luminous efficiency.

[0234] Therefore, in order to reduce the driving voltage of the light-emitting device, improve the light-emitting efficiency, and suppress crosstalk, it is preferable to use a metal that has excellent electron injection properties and is difficult to diffuse in an organic compound when mixed with the organic compound for the electron injection layer 130. As the metal that is difficult to diffuse for use in the electron injection layer 130, a metal with a large atomic radius is preferable. Also, a metal with a large atomic weight is preferable.

[0235] Here, a light-emitting element according to one embodiment of the present invention includes a composite material of a metal and an organic compound having a function of interacting with a metal at a tridentate or tetradentate position. As the metal, a metal that belongs to Groups 3 to 13 and has a large atomic weight or atomic radius can be preferably used. Therefore, one embodiment of the present invention can provide a light-emitting element with reduced crosstalk.

[0236] In particular, transition metals have a large atomic weight and are less likely to diffuse in organic compounds, making it possible to provide a light-emitting element in which crosstalk is suppressed.

[0237] The light-emitting units 106 and 108 and the charge generating layer 115 can be formed by a deposition method (including a vacuum deposition method), an inkjet method, a coating method, gravure printing, or the like.

[0238] Note that the structure described in this embodiment mode can be used in appropriate combination with structures described in other embodiment modes.

[0239] (Embodiment 3) In this embodiment mode, a light-emitting device using the light-emitting elements described in Embodiment Modes 1 and 2 will be described with reference to FIGS. 5(A) and 5(B).

[0240] Fig. 5(A) is a top view showing a light-emitting device, and Fig. 5(B) is a cross-sectional view taken along lines AB and CD in Fig. 5(A). This light-emitting device includes a driver circuit section (source side driver circuit) 601, a pixel section 602, and a driver circuit section (gate side driver circuit) 603, all of which are shown by dotted lines to control the light emission of the light-emitting element. In addition, 604 is a sealing substrate, 625 is a desiccant, and 605 is a sealant, and the inside surrounded by the sealant 605 is a space 607.

[0241] The lead wiring 608 is a wiring for transmitting signals input to the source side driver circuit 601 and the gate side driver circuit 603, and receives a video signal, a clock signal, a start signal, a reset signal, and the like from an FPC (flexible printed circuit) 609 serving as an external input terminal. Although only an FPC is shown here, a printed wiring board (PWB: Printed Wiring Board) may be attached to this FPC. In this specification, the light emitting device includes not only the light emitting device itself, but also a light emitting device to which an FPC or PWB is attached.

[0242] Next, the cross-sectional structure of the light-emitting device will be described with reference to Fig. 5(B). A driver circuit section and a pixel section are formed on an element substrate 610, and here, a source side driver circuit 601, which is the driver circuit section, and one pixel in the pixel section 602 are shown.

[0243] The source side driver circuit 601 is formed as a CMOS circuit combining an n-channel TFT 623 and a p-channel TFT 624. The driver circuit may be formed of various CMOS circuits, PMOS circuits, and NMOS circuits. In this embodiment, a driver integrated type in which the driver circuit is formed on the substrate is shown, but this is not necessarily required, and the driver circuit may be formed externally instead of on the substrate.

[0244] The pixel section 602 is formed of pixels including a switching TFT 611, a current control TFT 612, and a first electrode 613 electrically connected to the drain of the TFT 612. An insulator 614 is formed so as to cover an end of the first electrode 613. The insulator 614 can be formed by using a positive type photosensitive resin film.

[0245] In order to improve the coverage of the film formed on the insulator 614, a surface having a curvature is formed at the upper or lower end 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 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. In addition, either a negative type photosensitive material or a positive type photosensitive material can be used as the insulator 614.

[0246] An EL layer 616 and a second electrode 617 are formed on the first electrode 613. Here, it is desirable to use a material with a large work function as the material used for the first electrode 613 that functions as an anode. For example, in addition to a single layer film such as an ITO film, an indium tin oxide film containing silicon, an indium oxide film containing 2 wt% to 20 wt% zinc oxide, a titanium nitride film, a chromium film, a tungsten film, a Zn film, or a Pt film, a laminated film of a film mainly composed of titanium nitride and aluminum, or 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 a laminated structure provides low resistance as wiring, good ohmic contact, and can further function as an anode.

[0247] The EL layer 616 is formed by various methods such as a deposition method using a deposition mask, an inkjet method, a spin coating method, etc. The material constituting the EL layer 616 may be a low molecular weight compound or a high molecular weight compound (including an oligomer and a dendrimer).

[0248] Furthermore, the second electrode 617 formed on the EL layer 616 and functioning as a cathode is preferably made of a material having a small work function (such as Al, Mg, Li, Ca, or an alloy or compound thereof (MgAg, MgIn, AlLi, etc.)). When the second electrode 617 is to transmit light generated in the EL layer 616, the second electrode 617 is preferably made of a laminate of a thin metal thin film and a transparent conductive film (ITO, indium oxide containing 2 wt% to 20 wt% zinc oxide, indium tin oxide containing silicon, zinc oxide (ZnO), etc.).

[0249] 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 is preferably a light-emitting element having the structure of Embodiments 1 and 2. Note that a plurality of light-emitting elements are formed in the pixel portion, but the light-emitting device in this embodiment may include both light-emitting elements having the structures described in Embodiments 1 and 2 and light-emitting elements having other structures.

[0250] Furthermore, by bonding the sealing substrate 604 to the element substrate 610 with a sealant 605, a structure is formed in which a light emitting element 618 is provided in a space 607 surrounded by the element substrate 610, the sealing substrate 604, and the sealant 605. The space 607 is filled with a filler, which may be an inert gas (nitrogen, argon, etc.), a resin, a drying agent, or both.

[0251] It is preferable to use epoxy resin or glass frit for the sealing material 605. It is also preferable that these materials are as moisture and oxygen impermeable as possible. In addition to a glass substrate or a quartz substrate, the sealing substrate 604 can be a plastic substrate made of FRP (Fiber Reinforced Plastics), PVF (Polyvinyl Fluoride), polyester, acrylic, or the like.

[0252] In the above manner, a light-emitting device using the light-emitting element described in Embodiment 1 and Embodiment 2 can be obtained.

[0253] <Light-emitting device configuration example 1> FIG. 6 shows, as an example of a display device, a light emitting device in which a light emitting element that emits white light and a colored layer (color filter) are formed.

[0254] Figure 6(A) illustrates a substrate 1001, a base insulating film 1002, a gate insulating film 1003, gate electrodes 1006, 1007, 1008, a first interlayer insulating film 1020, a second interlayer insulating film 1021, a peripheral portion 1042, a pixel portion 1040, a driving circuit portion 1041, first electrodes 1024W, 1024R, 1024G, 1024B of the light-emitting element, a partition wall 1026, an EL layer 1028, a second electrode 1029 of the light-emitting element, a sealing substrate 1031, a sealant 1032, a red pixel 1044R, a green pixel 1044G, a blue pixel 1044B, and a white pixel 1044W.

[0255] In addition, in Fig. 6(A) and Fig. 6(B), colored layers (red colored layer 1034R, green colored layer 1034G, blue colored layer 1034B) are provided on a transparent base material 1033. A black layer (black matrix) 1035 may also be provided. The transparent base material 1033 provided with the colored layers and the black layer is aligned and fixed to the substrate 1001. The colored layers and the black layer are covered with an overcoat layer 1036. In Fig. 6(A), there is light that does not pass through the colored layers and goes out, and light that passes through the colored layers of each color and goes out. The light that does not pass through the colored layers is white, and the light that passes through the colored layers is red, blue, and green, so an image can be expressed by four color pixels.

[0256] 6B shows an example in which a red colored layer 1034R, a green colored layer 1034G, and a blue colored layer 1034B are formed between the gate insulating film 1003 and the first interlayer insulating film 1020. As shown in FIG. 6B, the colored layers may be provided between the substrate 1001 and the sealing substrate 1031.

[0257] Furthermore, the light-emitting device described above has a structure (bottom emission structure) in which light is extracted to the substrate 1001 side on which the TFT is formed, but it may also be a light-emitting device with a structure (top emission structure) in which light is extracted to the sealing substrate 1031 side.

[0258] <Configuration Example 2 of Light Emitting Device> 7A and 7B show cross-sectional views of a top-emission type light-emitting device. In this case, a substrate that does not transmit light can be used as the substrate 1001. The steps up to the fabrication of a connection electrode that connects the TFT and the anode of the light-emitting element are performed in the same manner as in 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 also play a role in planarization. The third interlayer insulating film 1037 can be formed using the same material as the second interlayer insulating film 1021, as well as various other materials.

[0259] The lower electrode 1025W, the lower electrode 1025R, the lower electrode 1025G, and the lower electrode 1025B of the light-emitting element are anodes here, but may be cathodes. In addition, in the case of a top-emission type light-emitting device as shown in FIG. 7(A) and (B), the lower electrode 1025W, the lower electrode 1025R, the lower electrode 1025G, and the lower electrode 1025B are preferably reflective electrodes. Note that the second electrode 1029 preferably has a function of reflecting light and a function of transmitting light. In addition, it is preferable to apply a microcavity structure between the second electrode 1029 and the lower electrode 1025W, the lower electrode 1025R, the lower electrode 1025G, and the lower electrode 1025B to amplify light of a specific wavelength. The EL layer 1028 has a structure as described in the first and second embodiments, and has an element structure that can emit white light.

[0260] 6(A), 6(B), 7(A) and (B), the configuration of the EL layer that can emit white light can be realized by using multiple light-emitting layers, multiple light-emitting units, etc. Note that the configuration for obtaining white light emission is not limited to these.

[0261] In the top emission structure as shown in Figures 7(A) and (B), sealing can be performed with a sealing substrate 1031 provided with colored layers (red colored layer 1034R, green colored layer 1034G, blue colored layer 1034B). The sealing substrate 1031 may be provided with a black layer (black matrix) 1035 so as to be located between pixels. The colored layers (red colored layer 1034R, green colored layer 1034G, blue colored layer 1034B) and the black layer (black matrix) may be covered with an overcoat layer. Note that a light-transmitting substrate is used as the sealing substrate 1031.

[0262] In addition, while Fig. 7(A) shows a configuration in which a full-color display is performed using three colors, red, green, and blue, as shown in Fig. 7(B), a full-color display may be performed using four colors, red, green, blue, and white. The configuration in which a full-color display is performed is not limited to this. For example, a full-color display may be performed using four colors, red, green, blue, and yellow.

[0263] A light-emitting element according to one embodiment of the present invention uses a fluorescent material as a guest material. The fluorescent material has a sharper spectrum than a phosphorescent material, and therefore light emission with high color purity can be obtained. Therefore, by using the light-emitting element in the light-emitting device described in this embodiment, a light-emitting device with high color reproducibility can be obtained.

[0264] In the above manner, a light-emitting device using the light-emitting element described in Embodiment 1 and Embodiment 2 can be obtained.

[0265] Note that this embodiment mode can be appropriately combined with other embodiment modes.

[0266] (Embodiment 4) In this embodiment, an electronic device and a display device according to one embodiment of the present invention will be described.

[0267] According to one embodiment of the present invention, highly reliable electronic devices and display devices having a flat surface and high emission efficiency can be manufactured. According to one embodiment of the present invention, highly reliable electronic devices and display devices having a curved surface and high emission efficiency can be manufactured. Light emission with high color purity can be obtained from the light-emitting element of one embodiment of the present invention. Therefore, by using the light-emitting element in the light-emitting device described in this embodiment, electronic devices and display devices with high color reproducibility can be obtained.

[0268] Examples of electronic devices include television sets, desktop or notebook personal computers, computer monitors, digital cameras, digital video cameras, digital photo frames, mobile phones, portable game machines, personal digital assistants, audio playback devices, and large game machines such as pachinko machines.

[0269] A portable information terminal 900 shown in FIGS. 8A and 8B includes a housing 901, a housing 902, a display portion 903, a hinge portion 905, and the like.

[0270] Housings 901 and 902 are connected by a hinge portion 905. The mobile information terminal 900 can be unfolded from a folded state (FIG. 8(A)) as shown in FIG. 8(B). This allows for excellent portability when carried around, and excellent visibility due to the large display area when in use.

[0271] A portable information terminal 900 has a flexible display unit 903 that spans a housing 901 and a housing 902 that are connected by a hinge unit 905 .

[0272] A light-emitting device manufactured according to one embodiment of the present invention can be used for the display portion 903. In this way, a highly reliable portable information terminal can be manufactured.

[0273] The display unit 903 can display at least one of document information, still images, and moving images, etc. When document information is displayed on the display unit, the portable information terminal 900 can be used as an electronic book terminal.

[0274] When the mobile information terminal 900 is unfolded, the display portion 903 is held in a state in which the radius of curvature is large. For example, the display portion 903 is held including a curved portion with a radius of curvature of 1 mm to 50 mm, preferably 5 mm to 30 mm. In part of the display portion 903, pixels are continuously arranged from the housing 901 to the housing 902, and a curved display can be performed.

[0275] The display unit 903 functions as a touch panel and can be operated with a finger, a stylus, or the like.

[0276] The display unit 903 is preferably configured as a single flexible display. This allows continuous display without interruption between the housing 901 and the housing 902. Note that each of the housing 901 and the housing 902 may be provided with a display.

[0277] It is preferable that the hinge section 905 has a locking mechanism so that the angle between the housing 901 and the housing 902 does not become larger than a predetermined angle when the mobile information terminal 900 is unfolded. For example, the angle at which the lock is applied (the housing does not open any further) is preferably equal to or greater than 90 degrees and less than 180 degrees, and typically can be 90 degrees, 120 degrees, 135 degrees, 150 degrees, or 175 degrees. This can improve the convenience, safety, and reliability of the mobile information terminal 900.

[0278] If the hinge section 905 has a locking mechanism, excessive force is not applied to the display section 903, and damage to the display section 903 can be prevented. Therefore, a highly reliable portable information terminal can be realized.

[0279] The housing 901 and the housing 902 may each include a power button, an operation button, an external connection port, a speaker, a microphone, and the like.

[0280] Either the housing 901 or the housing 902 is provided with a wireless communication module, and data can be transmitted and received via a computer network such as the Internet, a LAN (Local Area Network), or Wi-Fi (registered trademark).

[0281] A portable information terminal 910 shown in FIG. 8C includes a housing 911, a display portion 912, operation buttons 913, an external connection port 914, a speaker 915, a microphone 916, a camera 917, and the like.

[0282] A light-emitting device manufactured according to one embodiment of the present invention can be used for the display portion 912. This enables portable information terminals to be manufactured with high yield.

[0283] The mobile information terminal 910 has a touch sensor on a display unit 912. Any operation, such as making a call or inputting characters, can be performed by touching the display unit 912 with a finger, a stylus, or the like.

[0284] In addition, by operating the operation button 913, it is possible to turn the power on and off, and to switch the type of image displayed on the display unit 912. For example, it is possible to switch from a mail creation screen to a main menu screen.

[0285] Furthermore, by providing a detection device such as a gyro sensor or an acceleration sensor inside the mobile information terminal 910, the orientation (portrait or landscape) of the mobile information terminal 910 can be determined and the orientation of the screen display on the display unit 912 can be automatically switched. The orientation of the screen display can also be switched by touching the display unit 912, by operating the operation button 913, or by voice input using the microphone 916.

[0286] The mobile information terminal 910 has one or more functions selected from, for example, a telephone, a notebook, or an information viewing device. Specifically, it can be used as a smartphone. The mobile information terminal 910 can execute various applications such as mobile phone, e-mail, text viewing and creation, music playback, video playback, Internet communication, and games.

[0287] 8D includes a housing 921, a display portion 922, an operation button 923, a shutter button 924, and the like.

[0288] A light-emitting device manufactured according to one embodiment of the present invention can be used for the display portion 922. In this way, a highly reliable camera can be manufactured.

[0289] Here, camera 920 is configured such that lens 926 can be detached from housing 921 and replaced, but lens 926 and housing 921 may be integrated.

[0290] The camera 920 can capture still images or moving images by pressing a shutter button 924. The display unit 922 also has a function as a touch panel, and an image can also be captured by touching the display unit 922.

[0291] The camera 920 may be equipped with a strobe device, a viewfinder, and the like, or these may be incorporated into the housing 921.

[0292] FIG. 9(A) is a schematic diagram showing an example of a cleaning robot.

[0293] The cleaning robot 5100 has a display 5101 arranged on the top surface, a plurality of cameras 5102 arranged on the side surface, a brush 5103, and an operation button 5104. Although not shown, the bottom surface of the cleaning robot 5100 is provided with tires, a suction port, and the like. The cleaning robot 5100 also has various sensors such as an infrared sensor, an ultrasonic sensor, an acceleration sensor, a piezoelectric sensor, an optical sensor, and a gyro sensor. The cleaning robot 5100 also has wireless communication means.

[0294] The cleaning robot 5100 can move by itself, detect dirt 5120, and suck up the dirt from a suction port provided on the bottom surface.

[0295] 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, steps, etc. Furthermore, when an object that may become entangled in the brush 5103, such as a wire, is detected by image analysis, the rotation of the brush 5103 can be stopped.

[0296] The remaining battery level, the amount of sucked up dirt, etc. can be displayed on the display 5101. The route traveled by the cleaning robot 5100 may be displayed on the display 5101. The display 5101 may be a touch panel, and an operation button 5104 may be provided on the display 5101.

[0297] The cleaning robot 5100 can communicate with a portable electronic device 5140 such as a smartphone. Images captured by the camera 5102 can be displayed on the portable electronic device 5140. Therefore, the owner of the cleaning robot 5100 can know the state of the room even when he or she is away from home. Also, the display on the display 5101 can be confirmed on a portable electronic device such as a smartphone.

[0298] The light-emitting device according to one embodiment of the present invention can be used for the display 5101 .

[0299] The robot 2100 shown in FIG. 9(B) includes a computing device 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 movement mechanism 2108.

[0300] The microphone 2102 has a function of detecting the user's voice, environmental sounds, etc. 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.

[0301] The display 2105 has a function of displaying various information. The robot 2100 can display information desired by the user on the display 2105. The display 2105 may be equipped with a touch panel. The display 2105 may also be a removable information terminal, and by installing it in a fixed position on the robot 2100, charging and data transfer are possible.

[0302] The upper camera 2103 and the lower camera 2106 have a function of capturing images of the surroundings of the robot 2100. In addition, the obstacle sensor 2107 can detect the presence or absence of an obstacle in the direction of travel 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.

[0303] The light-emitting device according to one embodiment of the present invention can be used for the display 2105 .

[0304] 9C 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 ray), a microphone 5008, a second display unit 5002, a support unit 5012, and earphones 5013.

[0305] The light-emitting device of one embodiment of the present invention can be used for the display portion 5001 and the second display portion 5002 .

[0306] 10A and 10B 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. 10A shows the portable information terminal 5150 in an unfolded state. Fig. 10B shows the portable information terminal 5150 in a folded state. Although the portable information terminal 5150 has a large display area 5152, it is compact and highly portable when folded.

[0307] Display area 5152 can be folded in half by bending portion 5153. Bending portion 5153 is composed of an expandable member and a number of support members. When folding the display area, the expandable member stretches and bending portion 5153 has a radius of curvature of 2 mm or more, preferably 5 mm or more.

[0308] Note that the display region 5152 may be a touch panel (input / output device) equipped with a touch sensor (input device). The light-emitting device of one embodiment of the present invention can be used for the display region 5152.

[0309] This embodiment mode can be combined with other embodiment modes as appropriate.

[0310] (Embodiment 5) In this embodiment, an example in which a light-emitting element of one embodiment of the present invention is applied to various lighting devices will be described with reference to Fig. 11. By using a light-emitting element of one embodiment of the present invention, a lighting device with high emission efficiency and high reliability can be manufactured.

[0311] By manufacturing the light-emitting element of one embodiment of the present invention over a flexible substrate, electronic devices and lighting devices each having a light-emitting region with a curved surface can be realized.

[0312] Furthermore, a light-emitting device to which a light-emitting element of one embodiment of the present invention is applied can also be used for lighting in an automobile; for example, lighting can be provided on a windshield, a ceiling, or the like.

[0313] FIG. 11 shows an example in which a light-emitting element is used as an indoor lighting device 8501. Since the light-emitting element can be made large, a large-area lighting device can also be formed. In addition, by using a housing having a curved surface, a lighting device 8502 in which the light-emitting region has a curved surface can also be formed. The light-emitting element shown in this embodiment mode is a thin film, and the housing has a high degree of freedom in design. Therefore, lighting devices with various designs can be formed. Furthermore, a large-sized lighting device 8503 may be provided on a wall surface in a room. A touch sensor may be provided in the lighting devices 8501, 8502, and 8503 to turn the power on or off.

[0314] Furthermore, by using a light-emitting element on the front surface side of a table, the lighting device 8504 can function as a table. Note that by using a light-emitting element in part of other furniture, the lighting device can function as furniture.

[0315] In the above manner, a lighting device and an electronic device can be obtained by applying the light-emitting device of one embodiment of the present invention. Note that the light-emitting device of one embodiment of the present invention is not limited to the one described in this embodiment, and can be applied to lighting devices and electronic devices in various fields.

[0316] The structure described in this embodiment mode can be used in appropriate combination with structures described in other embodiment modes. EXAMPLES

[0317] In this example, examples of fabricating light-emitting elements 2 to 5 and a comparative light-emitting element 1, which are light-emitting elements according to one embodiment of the present invention, are described. FIG. 1A shows a schematic cross-sectional view of the light-emitting element fabricated in this example, and Tables 2 and 3 show details of the element structure. Chemical formulas of organic compounds used in this example are shown below. Note that the structures and abbreviations of other compounds can be referred to in the above embodiment 1.

[0318] [ka]

[0319] [Table 2]

[0320] [Table 3]

[0321] <Fabrication of light-emitting element> A method for manufacturing the light-emitting elements manufactured in this example is described below. Comparative light-emitting element 1 is a light-emitting element that uses LiF, which is a Li compound that is generally used in an electron-injection layer, and light-emitting elements 2 to 5 are light-emitting elements that are one embodiment of the present invention and use a composite material of an organic compound and a metal that has a function of interacting with a metal at a tridentate or tetradentate position in an electron-injection layer.

[0322] <Preparation of comparative light-emitting element 1> An ITSO film was formed on a glass substrate as an electrode 101 to a thickness of 110 nm. The electrode area of ​​the electrode 101 was 4 mm 2 (2mm x 2mm).

[0323] Next, as the hole injection layer 111, DBT3P-II and molybdenum oxide (MoO3) were co-deposited on the electrode 101 in a weight ratio (DBT3P-II:MoO3) of 1:0.5 to a thickness of 25 nm.

[0324] Next, PCBBiF was deposited on the hole injection layer 111 as the hole transport layer 112 to a thickness of 20 nm.

[0325] Next, 2mDBTBPDBq-II, PCBBiF, and Ir(dmdppr-dmp)2(dpm) were co-deposited on the hole transport layer 112 to form the light emitting layer 140, with a weight ratio (2mDBTBPDBq-II: PCBBiF: Ir(dmdppr-dmp)2(dpm)) of 0.75:0.25:0.08 and a thickness of 40 nm. In the light emitting layer 140, 2mDBTBPDBq-II and PCBBiF are host materials, and Ir(dmdppr-dmp)2(dpm) is a guest material (phosphorescent compound).

[0326] Next, 2mDBTBPDBq-II was deposited on the light-emitting layer 140 as the electron transport layer 118(1) to a thickness of 20 nm.

[0327] Next, NBPhen was evaporated onto electron transport layer 118(1) to form electron transport layer 118(2) to a thickness of 15 nm.

[0328] Lithium fluoride (LiF) was deposited on the electron transport layer 118(2) as the electron injection layer 130 to a thickness of 1 nm.

[0329] Next, on the electron injection layer 130, aluminum (Al) was formed as the electrode 102 to a thickness of 200 nm.

[0330] Next, without sealing, the resultant was heat-treated in air at 80° C. for 1 hour. Through the above steps, comparative light-emitting element 1 was obtained.

[0331] <Fabrication of Light-Emitting Devices 2 to 5> Light-emitting elements 2 to 5 were fabricated in the same manner as for the comparative light-emitting element 1, except for the step of forming the electron injection layer 130.

[0332] <Fabrication of Light-emitting Device 2> On the electron transport layer 118(2), an electron injection layer 130 was formed by co-deposition of tPy2P and Ag at a weight ratio (tPy2P:Ag) of 1:0.3 to a thickness of 5 nm.

[0333] <Fabrication of Light-emitting Device 3> On the electron transport layer 118(2), an electron injection layer 130 was formed by co-deposition of 2Py3Tzn and Cu at a weight ratio (2Py3Tzn:Cu) of 1:0.3 and a thickness of 5 nm.

[0334] <Fabrication of Light-emitting Device 4> On the electron transport layer 118(2), an electron injection layer 130 was formed by co-deposition of Pm3Tzn and Cu at a weight ratio (Pm3Tzn:Cu) of 1:0.3 and a thickness of 5 nm.

[0335] <Fabrication of Light-emitting Device 5> On the electron transport layer 118(2), tPy2P and Co were co-deposited as the electron injection layer 130 in a weight ratio (tPy2P:Co) of 1:0.2 to a thickness of 5 nm.

[0336] <Characteristics of light-emitting element> Next, the element characteristics of the comparative light-emitting element 1 and the light-emitting elements 2 to 5 prepared above were measured. A color luminance meter (BM-5A, manufactured by Topcon Corporation) was used to measure the luminance and CIE chromaticity, and a multichannel spectrometer (PMA-11, manufactured by Hamamatsu Photonics KK) was used to measure the electroluminescence spectrum.

[0337] The current efficiency-luminance characteristics of the comparative light-emitting element 1 and the light-emitting elements 2 to 5 thus fabricated are shown in FIG. 12, the current-voltage characteristics are shown in FIG. 13, and the external quantum efficiency-luminance characteristics are shown in FIG. 14. Note that the measurement of each light-emitting element was performed at room temperature (atmosphere maintained at 23° C.). In addition, each light-emitting element was supplied with a current of 2.5 mA / cm 2 The electroluminescence spectrum when a current was passed at a current density of 1000 nm is shown in Fig. 15. The measurement was carried out at room temperature.

[0338] Also, 1000cd / m 2 Table 4 shows the element characteristics of the comparative light-emitting element 1 and the light-emitting elements 2 to 5 in the vicinity.

[0339] [Table 4]

[0340] 14 and Table 4, the comparative light-emitting element 1 and the light-emitting element 2 to the light-emitting element 5 all exhibited high emission efficiency with an external quantum efficiency of more than 25%. Furthermore, the light-emitting element 2 to the light-emitting element 5, which are one embodiment of the present invention, exhibited high efficiency equivalent to that of the comparative light-emitting element 1 which uses LiF, which is a material generally used for an electron-injection layer.

[0341] 13 and Table 4, the comparative light-emitting element 1 and the light-emitting element 2 to the light-emitting element 5 exhibited favorable current-voltage characteristics. The light-emitting element 2 to the light-emitting element 5 exhibited current-voltage characteristics equivalent to that of the comparative light-emitting element 1. It was found that a composite material of a transition metal with a large work function (4.5 eV or more), such as Cu, Ag, or Co, and an organic compound having a function of interacting with the metal in a tridentate or tetradentate manner has an extremely favorable electron injection property equivalent to that of LiF, which is a material generally used for an electron-injection layer.

[0342] 15, the comparative light-emitting element 1 and the light-emitting element 2 to the light-emitting element 5 all exhibited red light emission with peak wavelengths of around 619 nm and full widths at half maximum of around 58 nm in the electroluminescence spectra. The obtained electroluminescence spectra revealed that the light emission was from the guest material Ir(dmdppr-dmp)2(dpm).

[0343] <Constant current driving test results for light emitting elements> Next, a constant current driving test at 1.0 mA was performed on the comparative light-emitting element 1 and the light-emitting element 2 to the light-emitting element 5 in the air atmosphere. The results are shown in FIG. 16. As described above, the comparative light-emitting element 1 and the light-emitting element 2 to the light-emitting element 5 were not sealed. As can be seen from FIG. 16, the light-emitting element 2 to the light-emitting element 5 had better reliability in the air atmosphere than the comparative light-emitting element 1. The comparative light-emitting element 1 uses a material having a metal with a small work function for the electron injection layer. Metals with a small work function are highly reactive with water and may cause moisture to enter the light-emitting element. Therefore, when the light-emitting element 1 is driven in the air atmosphere, the reliability is reduced due to the influence of moisture. On the other hand, the light-emitting element according to one embodiment of the present invention can use a metal with a large work function that is less reactive with water for the electron injection layer. Therefore, the light-emitting element according to one embodiment of the present invention is unlikely to allow moisture to enter the light-emitting element, and a light-emitting element with high reliability can be realized even when driven in the air atmosphere. Furthermore, the light-emitting element 3 to the light-emitting element 5 exhibit excellent reliability. From this, a light-emitting element with excellent reliability can be realized by using a metal with a work function of 4.7 eV or more, such as Cu or Co. EXAMPLES

[0344] In this example, examples of fabricating light-emitting elements 7 to 10, which are light-emitting elements according to one embodiment of the present invention, and a comparative light-emitting element 6 are described. A schematic cross-sectional view of the light-emitting elements fabricated in this example is shown in FIG. 1A, and details of the element structures are shown in Tables 5 and 6. Note that the structures and abbreviations of the organic compounds used in this example may be referred to in the above-described Embodiment 1 and Example 1.

[0345] [Table 5]

[0346] [Table 6]

[0347] <Fabrication of light-emitting element> A method for manufacturing the light-emitting elements manufactured in this example is described below. Comparative light-emitting element 6 is a light-emitting element in which an electron-injection layer is not formed and an electrode is in contact with an electron-transport layer, and light-emitting elements 7 to 10 are light-emitting elements, which are one embodiment of the present invention, in which an electron-injection layer includes a composite material of an organic compound and a metal that has a function of interacting with a metal at a tridentate or tetradentate interface.

[0348] <Preparation of Comparative Light-Emitting Element 6> Comparative light-emitting element 6 was fabricated in the same manner as comparative light-emitting element 1, except for the step of forming the electron injection layer 130 .

[0349] The electron injection layer 130 of the comparative light-emitting element 6 was not formed, and instead, Al was evaporated to a thickness of 200 nm as the electrode 102 on the electron transport layer 118. That is, in the comparative light-emitting element 6, the electrode 102 and the electron transport layer 118 are in contact with each other.

[0350] <Fabrication of Light-emitting Elements 7 to 10> The light-emitting elements 7 to 10 were fabricated in the same manner as the comparative light-emitting element 1, except for the step of forming the electron injection layer 130.

[0351] <Fabrication of Light-Emitting Element 7> On the electron transport layer 118(2), as the electron injection layer 130 of the light emitting element 7, tPy2P and Au were co-deposited at a weight ratio (tPy2P:Au) of 1:0.6 to a thickness of 5 nm.

[0352] <Preparation of Light-Emitting Element 8> On the electron transport layer 118(2), as the electron injection layer 130 of the light emitting element 8, 2Py3Tzn and Ag were co-deposited at a weight ratio (2Py3Tzn:Ag) of 1:0.5 to a thickness of 5 nm.

[0353] <Preparation of Light-Emitting Element 9> On the electron transport layer 118(2), as the electron injection layer 130 of the light emitting element 9, tPy2P and Cu were co-deposited at a weight ratio (tPy2P:Cu) of 1:0.2 to a thickness of 5 nm.

[0354] <Fabrication of Light-Emitting Element 10> On the electron transport layer 118(2), as the electron injection layer 130 of the light emitting element 10, 2Py3Tzn and Co were co-deposited at a weight ratio (2Py3Tzn:Co) of 1:0.3 to a thickness of 5 nm.

[0355] <Characteristics of light-emitting element> Next, the element characteristics of the comparative light-emitting element 6 and the light-emitting elements 7 to 10 prepared as above were measured. The measurement was performed in the same manner as in Example 1.

[0356] The current efficiency-luminance characteristics of the comparative light-emitting element 6 and the light-emitting elements 7 to 10 thus fabricated are shown in FIG. 17, the current-voltage characteristics are shown in FIG. 18, and the external quantum efficiency-luminance characteristics are shown in FIG. 19. Note that the measurement of each light-emitting element was performed at room temperature (atmosphere maintained at 23° C.). In addition, each light-emitting element was supplied with a current of 2.5 mA / cm 2 The electroluminescence spectrum when a current was passed at a current density of 1000 nm is shown in Fig. 20. The measurement was carried out at room temperature.

[0357] Also, 1000cd / m 2 Table 7 shows the element characteristics of the comparative light-emitting element 6 and the light-emitting elements 7 to 10 in the vicinity.

[0358] [Table 7]

[0359] As shown in FIG. 19 and Table 7, it was found that the light-emitting elements 7 to 10 had higher external quantum efficiency than the comparative light-emitting element 6. In particular, the light-emitting elements 9 and 10 had high external quantum efficiency of more than 25%. Furthermore, as shown in FIG. 18, the light-emitting elements 7 to 10 had better current-voltage characteristics than the comparative light-emitting element 6. In particular, the light-emitting element 9 had excellent current-voltage characteristics. These results show that the light-emitting elements 7 to 10 have better electron injection characteristics than the comparative light-emitting element 6.

[0360] In the comparative light-emitting element 6, the electrode and the electron-transport layer are in contact with each other, and in the light-emitting elements 7 to 10, a metal having a higher work function than Al used in the electrode is used in the electron-injection layer. Thus, in terms of the work function of the metal, the comparative light-emitting element 6 is expected to have better electron injection characteristics than the light-emitting elements 7 to 10. However, as described above, the light-emitting elements 7 to 10 have better electron injection characteristics than the comparative light-emitting element 6. Thus, in the light-emitting element of one embodiment of the present invention, a composite material of an organic compound and a metal having a function of interacting with a metal at a tridentate or tetradentate is used in the electron-injection layer, so that a SOMO of the composite material is formed in the electron-injection layer. Therefore, even if a metal having a work function higher than the work function of the electrode material is used in the electron-injection layer, good electron injection characteristics can be obtained.

[0361] 20, the comparative light-emitting element 6 and the light-emitting elements 7 to 10 all exhibited red light emission with peak wavelengths of around 619 nm and full widths at half maximum of around 58 nm in the electroluminescence spectra. The obtained electroluminescence spectra revealed that the light emission was from the guest material Ir(dmdppr-dmp)2(dpm).

[0362] <Constant current driving test results for light emitting elements> Next, a constant current drive test at 1.0 mA was performed on the comparative light-emitting element 6 and the light-emitting elements 7 to 10 in an air atmosphere. The results are shown in FIG. 21. Note that the comparative light-emitting element 6 and the light-emitting elements 7 to 10 were not sealed. FIG. 21 shows that the light-emitting elements 7 to 10 have better reliability than the comparative light-emitting element 6. Here, FIGS. 18 and 19 show that the electron injection characteristics of the comparative light-emitting element 6 are inferior to those of the light-emitting elements 7 to 10, and the carrier balance of the comparative light-emitting element 6 is poor, which adversely affects the reliability. On the other hand, the light-emitting element that is one embodiment of the present invention has good electron injection characteristics and therefore good carrier balance in each light-emitting element, and therefore a light-emitting element with high reliability can be realized. EXAMPLES

[0363] In this example, examples of fabricating light-emitting elements 12 to 15, which are light-emitting elements according to one embodiment of the present invention, and comparative light-emitting element 11 are shown. FIG. 1A shows a schematic cross-sectional view of the light-emitting element fabricated in this example, and Tables 8 and 9 show details of the element structure. Chemical formulas of organic compounds used in this example are shown below. Note that the structures and abbreviations of other compounds can be found in the previous examples and Embodiment 1.

[0364] [ka]

[0365] [Table 8]

[0366] [Table 9]

[0367] <Fabrication of light-emitting element> A method for manufacturing the light-emitting elements manufactured in this example is described below. Comparative light-emitting element 11 is a light-emitting element that uses LiF, which is a Li compound that is generally used in the electron-injection layer, and light-emitting elements 12 to 15 are light-emitting elements that are one embodiment of the present invention and use a composite material of an organic compound and a metal that has a function of interacting with a metal at a tridentate or tetradentate position in the electron-injection layer.

[0368] <Preparation of Comparative Light-Emitting Element 11> An ITSO film was formed on a glass substrate as an electrode 101 to a thickness of 70 nm. The electrode area of ​​the electrode 101 was 4 mm 2 (2mm x 2mm).

[0369] Next, as the hole injection layer 111, DBT3P-II and molybdenum oxide (MoO3) were co-deposited on the electrode 101 in a weight ratio (DBT3P-II:MoO3) of 1:0.5 and to a thickness of 40 nm.

[0370] Next, PCCP was deposited on the hole injection layer 111 as a hole transport layer 112 to a thickness of 20 nm.

[0371] Next, 9-[3-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]-9'-phenyl-2,3'-bi-9H-carbazole (abbreviation: mPCCzPTzn-02), PCCP and GD270 (manufactured by Jilin OLED Co., Ltd.) were co-deposited on the hole transport layer 112 as the light emitting layer 140 in a weight ratio (mPCCzPTzn:PCCP:GD270) of 0.5:0.5:0.1 and a thickness of 40 nm. In the light emitting layer 140, mPCCzPTzn and PCCP are host materials, and GD270 is a guest material (phosphorescent compound).

[0372] Next, mPCCzPTzn-02 was deposited on the light-emitting layer 140 as the electron transport layer 118(1) to a thickness of 10 nm.

[0373] Next, NBPhen was evaporated onto electron transport layer 118(1) to form electron transport layer 118(2) to a thickness of 15 nm.

[0374] On the electron transport layer 118(2), LiF was deposited to a thickness of 1 nm as the electron injection layer 130.

[0375] Next, on the electron injection layer 130, aluminum (Al) was formed as the electrode 102 to a thickness of 200 nm.

[0376] Next, without sealing, the resultant was heat-treated in air at 80° C. for 1 hour. Through the above steps, comparative light-emitting element 11 was obtained.

[0377] <Fabrication of Light-emitting Elements 12 to 15> Light-emitting elements 12 to 15 were fabricated in the same manner as for the comparative light-emitting element 11, except for the steps of forming the electron transport layer 118(2) and the electron injection layer 130.

[0378] <Fabrication of Light-Emitting Element 12> On the electron transport layer 118(1), NBPhen was evaporated to a thickness of 15 nm as the electron transport layer 118(2). Next, on the electron transport layer 118(2), tPy2P and Ag were co-evaporated to a thickness of 5 nm as the electron injection layer 130 in a weight ratio (tPy2P:Ag) of 1:0.3.

[0379] <Fabrication of Light-Emitting Element 13> On the electron transport layer 118(1), NBPhen was evaporated to a thickness of 10 nm as the electron transport layer 118(2). Next, on the electron transport layer 118(2), NBPhen and Ag were co-evaporated to a thickness of 5 nm in a weight ratio (NBPhen:Ag) of 1:0.3 as the electron injection layer 130, and tPy2P and Au were co-evaporated thereon in a weight ratio (tPy2P:Au) of 1:0.6 as the electron injection layer 130.

[0380] <Fabrication of Light-Emitting Element 14> On the electron transport layer 118(1), NBPhen was evaporated to a thickness of 15 nm as the electron transport layer 118(2). Next, on the electron transport layer 118(2), 2Py3Tzn and Cu were co-evaporated to a thickness of 5 nm as the electron injection layer 130 in a weight ratio (2Py3Tzn:Cu) of 1:0.3.

[0381] <Fabrication of Light-Emitting Element 15> On the electron transport layer 118(1), NBPhen was evaporated to a thickness of 10 nm as the electron transport layer 118(2). Next, on the electron transport layer 118(2), NBPhen and Cu were co-evaporated to a thickness of 5 nm in a weight ratio (NBPhen:Cu) of 1:0.2 as the electron injection layer 130, and 2Py3Tzn and Co were co-evaporated thereon in a weight ratio (2Py3Tzn:Co) of 1:0.2 as the electron injection layer 130.

[0382] <Characteristics of light-emitting element> Next, the element characteristics of the comparative light-emitting element 11 and the light-emitting elements 12 to 15 prepared as above were measured. The measurement was performed in the same manner as in Example 1.

[0383] The current efficiency-luminance characteristics of the fabricated comparative light-emitting element 11 and light-emitting elements 12 to 15 are shown in FIG. 22, the current-voltage characteristics are shown in FIG. 23, and the external quantum efficiency-luminance characteristics are shown in FIG. 24. Note that the measurement of each light-emitting element was performed at room temperature (atmosphere maintained at 23° C.). In addition, each light-emitting element was supplied with a current of 2.5 mA / cm 2 The electroluminescence spectrum when a current was passed at a current density of 1000 nm is shown in Fig. 25. The measurement was carried out at room temperature.

[0384] Also, 1000cd / m 2 Table 10 shows the element characteristics of the comparative light-emitting element 11 and the light-emitting elements 12 to 15 in the vicinity.

[0385] [Table 10]

[0386] 24 and Table 10, it was found that the comparative light-emitting element 11 and the light-emitting element 12 to the light-emitting element 15 had equivalent external quantum efficiency. Moreover, the external quantum efficiency of the light-emitting element 12 to the light-emitting element 14 was a high value exceeding 20%. Moreover, as shown in FIG. 23 and Table 10, the comparative light-emitting element 11 and the light-emitting element 12 to the light-emitting element 15 had equivalent current-voltage characteristics. These results show that the light-emitting element 12 to the light-emitting element 15 have the same electron injection property as the comparative light-emitting element 11, which uses LiF that is generally used for the electron injection layer.

[0387] 25, the comparative light-emitting element 11 and the light-emitting elements 12 to 15 all exhibited green light emission with peak wavelengths of around 520 nm and full widths at half maximum of around 63 nm in the electroluminescence spectra. The obtained electroluminescence spectra revealed that the light was emitted from the guest material GD270.

[0388] <Evaluation of Reliability of Light-Emitting Device> Next, a constant temperature and humidity storage test was performed on the comparative light-emitting element 11 and the light-emitting elements 12 to 15. Since each light-emitting element was not sealed, the cathode and the EL layer were exposed to the atmosphere of the test environment. In general, when moisture penetrates into a light-emitting element, dark spots (non-light-emitting regions inside the light-emitting part) and shrinks (non-light-emitting regions at the ends of the light-emitting part) occur, adversely affecting the reliability of the light-emitting element. Therefore, the reliability of the light-emitting element against moisture can be evaluated by performing a constant temperature and humidity storage test.

[0389] The comparative light-emitting element 11 and the light-emitting elements 12 to 15 were left in a thermostatic chamber maintained at a constant temperature of 40° C. and humidity of 90% for 350 hours, and then the light-emitting state of each light-emitting element was examined.

[0390] The luminescence state was evaluated by estimating the ratio of the luminescent area before and after the constant temperature and humidity storage test. The results are shown in Table 11.

[0391] [Table 11]

[0392] In Table 11, the light-emitting area ratio (%)=light-emitting area after constant temperature and humidity storage test / light-emitting area before constant temperature and humidity test×100. Table 11 shows that the comparative light-emitting element 11, which uses LiF, an alkali metal compound, in the electron-injection layer, deteriorated due to the storage test and did not emit light. On the other hand, the light-emitting elements 12 to 15, which are light-emitting elements of one embodiment of the present invention, have a larger light-emitting area ratio than the comparative light-emitting element 11. That is, the light-emitting element of one embodiment of the present invention was shown to have better moisture resistance than a light-emitting element in which a material having a small work function, such as an alkali metal, is used in the electron-injection layer. This is because a material having a small work function is highly reactive with water and moisture penetrates into the light-emitting element. On the other hand, the light-emitting element of one embodiment of the present invention can use a metal having a large work function that is poorly reactive with water, and therefore moisture is less likely to penetrate into the light-emitting element. Therefore, a light-emitting element with high moisture resistance can be realized.

[0393] As described above, the light-emitting element according to one embodiment of the present invention has excellent electron injection properties, and therefore has low driving voltage and high light-emitting efficiency. In addition, the light-emitting element has excellent moisture resistance because a material with a high work function can be used. The structure described in this embodiment can be used in appropriate combination with other embodiments and embodiments. EXAMPLES

[0394] In this example, examples of organic compounds that can be used for a light-emitting element according to one embodiment of the present invention and synthesis examples thereof will be described.

[0395] <Synthesis of 4'-[4-(10-phenyl-9-anthryl)phenyl]-2,2':6',2''-terpyridine (abbreviation: PAtPy) (structural formula (200))> In a 100 mL three-neck flask, 1.0 g (2.6 mmol) of 4'-(4-bromophenyl)-2,2':6',2''-terpyridine, 0.86 g (2.9 mmol) of 10-phenyl-9-anthrylboronic acid, 0.85 g (8.0 mmol) of sodium carbonate, 20 mL of toluene, 5 mL of ethanol, and 5 mL of water were added. This mixture was degassed while stirring under reduced pressure, and then the atmosphere in the flask was replaced with nitrogen. To this mixture, 65 mg (56 μmol) of tetrakis(triphenylphosphine)palladium(0) was added, and the mixture was refluxed at 100°C for 8 hours under a nitrogen stream. After stirring, the reaction mixture was cooled to room temperature, and the precipitated solid was collected by suction filtration. The chloroform solution of the obtained solid was washed with water, saturated sodium bicarbonate, and saturated saline, and dried over magnesium sulfate. The mixture of the chloroform solution and magnesium sulfate was gravity filtered, and the filtrate was concentrated to obtain a solid. The obtained solid was suspended in methanol and irradiated with ultrasonic waves, and the solid was collected by suction filtration. Furthermore, when recrystallized with toluene, the target pale red powder was obtained in an amount of 1.2 g and a yield of 81%. The synthesis scheme is shown in the following formula (a-1).

[0396] [ka]

[0397] The resulting pale red powder (1.2 g) was purified by train sublimation. The sublimation purification was performed by heating PAtPy at 290°C under conditions of a pressure of 4.5 Pa and an argon flow rate of 10 mL / min. After sublimation purification, 0.55 g of pale red powder of PAtPy was obtained, with a recovery rate of 47%.

[0398] The pale red powder obtained above was analyzed by nuclear magnetic resonance spectroscopy ( 1 The analytical results are shown below.

[0399] 1 H-NMR (CDCl3,300MHz): δ=7.34-7.40(m, 6H), 7.49-7.79(m, 11H), 7.91(dt, J=1.5Hz, 7.2Hz, 2H), 8.16(d, J=7.8Hz, 2H), 8.72-8.78(m, 4H), 8.93(s, 2H).

[0400] In addition, the pale red powder obtained 1 The H NMR charts are shown in Figures 26(A) and (B). Figure 26(B) is an enlarged view of the range from 7.0 ppm to 9.5 ppm in Figure 26(A). The measurement results showed that the target compound, PAtPy, was obtained. EXAMPLES

[0401] In this example, examples of organic compounds that can be used for a light-emitting element according to one embodiment of the present invention and synthesis examples thereof will be described.

[0402] <Synthesis of 2-[4'-(2,2':6',2''-terpyridin-4'-yl)biphenyl-4-yl]benzoxazole (abbreviation: BOxtPy) (structural formula (201))> In a 100 mL three-neck flask, 1.0 g (2.6 mmol) of 4'-(4-bromophenyl)-2,2':6',2''-terpyridine, 0.68 g (2.9 mmol) of 4-(benzoxazol-2-yl)phenylboronic acid, 0.62 g (5.8 mmol) of sodium carbonate, 20 mL of toluene, 5 mL of ethanol, and 3 mL of water were added. The mixture was degassed while stirring under reduced pressure, and then the atmosphere in the flask was replaced with nitrogen. To this mixture, 63 mg (55 μmol) of tetrakis(triphenylphosphine)palladium(0) was added, and the mixture was refluxed at 100°C for 5 hours under a nitrogen stream. After refluxing, the reaction mixture was cooled to room temperature, and the precipitated solid was collected by suction filtration. The chloroform solution of the obtained solid was washed with water, saturated sodium bicarbonate, and saturated saline, and dried over magnesium sulfate. The mixture of the obtained chloroform solution and magnesium sulfate was gravity filtered, and the filtrate was concentrated to obtain a solid. The obtained solid was recrystallized from toluene to obtain 1.0 g of the target pale red powder in a yield of 78%. The synthesis scheme is shown in the following formula (b-1).

[0403] [ka]

[0404] The resulting BOxtPy powder (1.0 g) was purified by train sublimation. The purification was performed by heating BOxtPy at 280°C under conditions of a pressure of 4.4 Pa and an argon flow rate of 10 mL / min. After the purification, 0.64 g of pale red BOxtPy powder was obtained with a recovery rate of 63%.

[0405] The pale red powder obtained above was analyzed by nuclear magnetic resonance spectroscopy ( 1 The analytical results are shown below.

[0406] 1H-NMR (CDCl3,300MHz): δ=7.32-7.41(m, 4H), 7.59-7.65(m, 1H), 7.78-7.93(m, 7H), 8.05(d, J=8.4Hz, 2H), 8.37(d, J=7.8Hz, 2H), 8.70(d, J=7.8Hz, 2H), 8.75-8.77(m, 2H), 8.81(s, 2H).

[0407] In addition, the pale red powder obtained 1 The H NMR charts are shown in Figures 27(A) and (B). Figure 27(B) is an enlarged view of the range from 7.0 ppm to 9.0 ppm in Figure 27(A). The measurement results showed that the target product, BOxtPy, was obtained. EXAMPLES

[0408] In this example, examples of organic compounds that can be used for a light-emitting element according to one embodiment of the present invention and synthesis examples thereof will be described.

[0409] Synthesis of 4'-{4-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]phenyl}-2,2':6',2''-terpyridine (abbreviation: O11tPy) (structural formula (202)) In a 100 mL three-neck flask, 1.0 g (2.6 mmol) of 4'-(4-bromophenyl)-2,2':6',2''-terpyridine, 0.73 g (2.7 mmol) of 4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenylboronic acid, 0.71 g (6.7 mmol) of sodium carbonate, 20 mL of toluene, 5 mL of ethanol, and 3 mL of water were added. The mixture was degassed by stirring under reduced pressure, and the atmosphere in the flask was replaced with nitrogen. To this mixture, 68 mg (59 μmol) of tetrakis(triphenylphosphine)palladium(0) was added. The mixture was refluxed at 100°C for 9 hours under a nitrogen stream. After stirring, the mixture was cooled to room temperature, and the precipitated solid was filtered by suction. The chloroform solution of the obtained solid was washed with water, a saturated aqueous solution of sodium bicarbonate, and saturated saline, and dried with magnesium sulfate. The mixture was gravity filtered, and the filtrate was concentrated to obtain a solid. The solid obtained was washed with methanol and then recrystallized with toluene / hexane to obtain 0.72 g of the target white powder in a yield of 51%. The synthesis scheme is shown in the following formula (c-1).

[0410] [ka]

[0411] The obtained O11tPy powder (0.71 g) was purified by train sublimation. The sublimation purification was performed by heating O11tPy at 270°C under conditions of a pressure of 4.0 Pa and an argon flow rate of 10 mL / min. After the sublimation purification, 0.29 g of white powder of O11tPy was obtained with a recovery rate of 41%.

[0412] The white powder obtained above was analyzed by nuclear magnetic resonance spectroscopy ( 1 The analytical results are shown below.

[0413] 1H-NMR (CDCl3,300MHz): δ=7.35-7.39(m, 2H), 7.52-7.58(m, 3H), 7.79-7.93(m, 6H), 8.04(d, J=8.4Hz, 2H), 8.16-8.19(m, 2H), 8.24(d, J=8.4Hz, 2H), 8.69(d, J=7.8Hz, 2H), 8.74-8.76(m, 2H), 8.80(s, 2H).

[0414] In addition, the obtained white powder 1 The H NMR charts are shown in Figures 28(A) and (B). Figure 28(B) is an enlarged view of the range from 7.0 ppm to 9.0 ppm in Figure 28(A). The measurement results showed that the target product, O11tPy, was obtained. EXAMPLES

[0415] In this example, examples of organic compounds that can be used for a light-emitting element according to one embodiment of the present invention and synthesis examples thereof will be described.

[0416] Synthesis of 9,9'-[5-(2,2':6',2''-terpyridin-4'-yl)-1,3-phenylene]bis(9H-carbazole) (abbreviation: Cz2PtPy) (Structural formula (203) In a 100 mL three-neck flask, 0.94 g (3.0 mmol) of 4'-bromo-2,2':6',2''-terpyridine, 1.4 g (3.2 mmol) of 3,5-bis(9H-carbazol-9-yl)phenylboronic acid, 0.86 g (6.2 mmol) of sodium carbonate, 30 mL of toluene, 5 mL of ethanol, and 3 mL of water were added. The mixture was degassed by stirring under reduced pressure, and the atmosphere in the flask was replaced with nitrogen. To this mixture, 72 mg (62 μmol) of tetrakis(triphenylphosphine)palladium(0) was added. The mixture was stirred at 80°C for 7 hours under a nitrogen stream. After stirring, the aqueous layer of the mixture was extracted with toluene, and the extracted solution and the organic layer were combined, washed with a saturated aqueous solution of sodium bicarbonate and saturated saline, and dried with magnesium sulfate. The mixture was gravity filtered, and the filtrate was concentrated to obtain a solid. The obtained solid was washed with methanol and then recrystallized with toluene to obtain 1.1 g of the target white powder in a yield of 55%. The synthesis scheme is shown in the following formula (d-1).

[0417] [ka]

[0418] The obtained Cz2PtPy powder (0.83 g) was purified by train sublimation. The sublimation purification was performed by heating Cz2PtPy at 290°C under conditions of a pressure of 3.2 Pa and an argon flow rate of 5.0 mL / min. After the sublimation purification, 0.71 g of white powder of Cz2PtPy was obtained with a recovery rate of 86%.

[0419] The white powder obtained above was analyzed by nuclear magnetic resonance spectroscopy ( 1 The analytical results are shown below.

[0420] 1 H-NMR (CDCl3,300MHz): δ=7.31-7.37(m, 6H), 7.47(dt, J=0.9Hz, 7.2Hz, 4H), 7.59(d, J=8.1Hz, 4H), 7.85-7.92(m, 3H), 8.17-8.22(m, 6H), 8.66-8.69(m, 4H), 8.82(s, 2H).

[0421] In addition, the obtained white powder 1 The H NMR charts are shown in Figures 29(A) and (B). Figure 29(B) is an enlarged view of the range from 7.0 ppm to 9.0 ppm in Figure 29(A). The measurement results showed that the target compound, Cz2PtPy, was obtained. EXAMPLES

[0422] In this example, examples of organic compounds that can be used for a light-emitting element according to one embodiment of the present invention and synthesis examples thereof will be described.

[0423] Synthesis of 2,4,6-tris(5-phenyl-2-pyrimidin-2-yl)-1,3,5-triazine (abbreviation: PPm3Tzn) (Structural formula (105) Into a 50 mL two-neck flask were added 0.80 g (4.0 mmol) of 5-phenylpyrimidine-2-carboximidamide, 1.4 g (7.7 mmol) of 2-cyano-5-phenylpyridine, 2 mL of diglyme, and 1 mL of 1,2,3,4-tetrahydronaphthalene. This mixture was stirred under a nitrogen stream at 180°C for 29 hours and at 200°C for 100 hours. After stirring, the mixture was cooled to room temperature and washed with ethyl acetate, yielding 0.82 g of brown powder. The synthesis scheme is shown in the following formula (e-1). In addition, before the sublimation purification described below, 1 When H-NMR was measured, the proton ratio was PPm3Tzn:5-phenylpyrimidine-2-carboximidamide = 1:1.7, and it was found that the brown powder was a mixture of the target product and the raw material. In addition, no signal derived from 2-cyano-5-phenylpyridine was observed.

[0424] [ka]

[0425] 0.79 g of the obtained brown powder was purified by train sublimation. The sublimation purification was performed by heating at 310°C under conditions of a pressure of 3.7 Pa and an argon flow rate of 15 mL / min. After the sublimation purification, 0.19 g of light brown powder of 2,4,6-tris(5-phenyl-2-pyrimidin-2-yl)-1,3,5-triazine was obtained. 1 When H-NMR was measured, the signal derived from 5-phenylpyrimidine-2-carboximidamide disappeared, indicating that the target product can be easily purified by sublimation purification.

[0426] The light brown powder obtained above was analyzed by nuclear magnetic resonance spectroscopy ( 1 The analytical results are shown below.

[0427] 1 H-NMR (CDCl3,300MHz): δ=7.52-7.63(m, 9H), 7.73(dd, J=1.5Hz, 7.8Hz, 6H), 9.35(s, 6H).

[0428] In addition, the obtained light brown powder 1 The H NMR charts are shown in Figures 30(A) and (B). Figure 30(B) is an enlarged view of the range from 7.0 ppm to 9.5 ppm in Figure 30(A). The measurement results showed that the target compound, PPm3Tzn, was obtained. EXAMPLES

[0429] As light-emitting elements according to one embodiment of the present invention, examples of fabrication of light-emitting elements 16 to 21 and comparative light-emitting elements 33 and 34, which are examples of a tandem element described later, are shown below. FIG. 31 shows a schematic cross-sectional view of the light-emitting elements fabricated in this example, and Tables 12 to 14 show details of the element structures, respectively. Chemical formulas of organic compounds used in this example are shown below. Note that the structures and abbreviations of other compounds may be referred to in the previous Examples and Embodiment 1. Note that the light-emitting elements 16 to 21 are examples of light-emitting elements in which a composite material of an organic compound and a metal having a function of interacting with a metal at a tridentate or tetradentate is used in an electron-injection layer (electron-injection layer 114 in FIG. 31) in contact with a charge-generation layer (charge-generation layer 115 in FIG. 31) between EL layers in an element (also referred to as a tandem element) in which a plurality of EL layers are connected in series between a pair of electrodes via a charge-generation layer.

[0430] [ka]

[0431] [Table 12]

[0432] [Table 13]

[0433] [Table 14]

[0434] <Fabrication of light-emitting element 16> An ITSO film was formed on a glass substrate as an electrode 101 to a thickness of 110 nm. The electrode area was 4 mm 2 (2mm x 2mm).

[0435] Next, as the hole injection layer 111, DBT3P-II and MoO3 were co-deposited on the electrode 101 in a weight ratio (DBT3P-II:MoO3) of 1:0.5 to a thickness of 25 nm.

[0436] Next, PCBBiF was deposited on the hole injection layer 111 as the hole transport layer 112 to a thickness of 20 nm.

[0437] Next, 2mDBTBPDBq-II, PCBBiF, and Ir(dmdppr-dmp)2(dpm) were co-deposited on the hole transport layer 112 to form the light emitting layer 170, with a weight ratio (2mDBTBPDBq-II: PCBBiF: Ir(dmdppr-dmp)2(dpm)) of 0.75:0.25:0.08 and a thickness of 40 nm. In the light emitting layer 170, 2mDBTBPDBq-II and PCBBiF are host materials, and Ir(dmdppr-dmp)2(dpm) is a guest material (phosphorescent compound).

[0438] Next, 2mDBTBPDBq-II was deposited to a thickness of 10 nm as the electron transport layer 113(1) on the light-emitting layer 170. Subsequently, NBPhen was deposited to a thickness of 15 nm as the electron transport layer 113(2).

[0439] On the electron transport layer 113(2), 2,2'-(pyridine-2,6-diyl)bis(4-phenylbenzo[h]quinazoline) (abbreviation: 2,6(P-Bqn)2Py) and Cu were co-deposited as the electron injection layer 114 in a weight ratio (2,6(P-Bqn)2Py:Cu) of 1:0.2 to a thickness of 5 nm.

[0440] Next, as the charge generation layer 115, DBT3P-II and MoO3 were co-deposited on the electron injection layer 114 in a weight ratio (DBT3P-II:MoO3) of 1:0.5 to a thickness of 80 nm.

[0441] Next, PCBBiF was deposited on the charge generating layer 115 as a hole transport layer 119 to a thickness of 20 nm.

[0442] Next, on the hole transport layer 119, 2mDBTBPDBq-II, PCBBiF, and Ir(dmdppr-dmp)2(dpm) were co-deposited as the light-emitting layer 140 in a weight ratio (2mDBTBPDBq-II:PCBBiF:Ir(dmdppr-dmp)2(dpm)) of 0.75:0.25:0.08 to a thickness of 40 nm.

[0443] Next, 2mDBTBPDBq-II was deposited to a thickness of 25 nm as electron transport layer 118(1) on light-emitting layer 140. Subsequently, NBPhen was deposited to a thickness of 10 nm as electron transport layer 118(2) on electron transport layer 118(1).

[0444] On the electron transport layer 118(2), NBPhen and Cu were co-deposited as the electron injection layer 130 in a weight ratio (NBPhen:Cu) of 1:0.2 to a thickness of 5 nm.

[0445] Next, Al was evaporated onto the electron injection layer 130 as the electrode 102 to a thickness of 200 nm.

[0446] Next, in a glove box with a nitrogen atmosphere, a glass substrate for sealing was fixed to the glass substrate on which the organic material was formed using a sealant for organic EL, thereby sealing the light-emitting element 16. Specifically, the sealant was applied to the periphery of the organic material formed on the glass substrate, the glass substrate and the glass substrate for sealing were attached to each other, and ultraviolet light having a wavelength of 365 nm was applied at 6 J / cm. 2 The light-emitting element 16 was obtained by the above steps.

[0447] <Fabrication of Light-emitting Elements 17 to 21, Comparative Light-emitting Elements 33, and Comparative Light-emitting Elements 34> Light-emitting elements 17 to 21, comparative light-emitting element 33, and comparative light-emitting element 34 were fabricated in a manner similar to that of the above-described light-emitting element 16. Details of the element structures are as shown in Tables 12 to 14, and therefore details of the fabrication methods are omitted.

[0448] <Measurement of each light-emitting element> The element characteristics of the fabricated light-emitting elements 16 to 21, the comparative light-emitting element 33, and the comparative light-emitting element 34 were measured. A color luminance meter (BM-5A, manufactured by Topcon Corporation) was used to measure the luminance and CIE chromaticity, and a multichannel spectrometer (PMA-11, manufactured by Hamamatsu Photonics KK) was used to measure the electroluminescence spectrum.

[0449] The current efficiency-luminance characteristics of the fabricated light-emitting elements 16 to 21, comparative light-emitting element 33, and comparative light-emitting element 34 are shown in FIG 32, their current-voltage characteristics in FIG 33, their power efficiency-luminance characteristics in FIG 34, and their external quantum efficiency-luminance characteristics in FIG 35. Note that each light-emitting element was measured at room temperature (atmosphere maintained at 23°C). 2 The electroluminescence spectrum when a current was passed at a current density of 1000 s is shown in Fig. 36. The measurement was carried out at room temperature.

[0450] Also, 1000cd / m 2 Table 15 shows the element characteristics of the light-emitting elements 16 to 21, the comparative light-emitting element 33, and the comparative light-emitting element 34 in the vicinity.

[0451] [Table 15]

[0452] As shown in Figure 36, the peak wavelengths of the electroluminescence spectra of light-emitting element 16 to light-emitting element 21, comparative light-emitting element 33, and comparative light-emitting element 34 are all around 620 nm, and it was found that light-emitting element 16 to light-emitting element 21, comparative light-emitting element 33, and comparative light-emitting element 34 exhibit light emission originating from Ir(dmdppr-dmp)2(dpm), which is the guest material contained in each light-emitting element.

[0453] 35 and Table 15, all of the light-emitting elements 16 to 21 exhibited very high luminous efficiency, with an external quantum efficiency exceeding 50%, which was equivalent to that of the comparative light-emitting element 33. Furthermore, as shown in FIGS. 32 and 34, the light-emitting elements exhibited high current efficiency and high power efficiency. On the other hand, the comparative light-emitting element 34 had a low external quantum efficiency of 27.2%, and did not achieve sufficient efficiency as a tandem element. These results show that the light-emitting elements 16 to 21 have electron injection properties equivalent to that of the comparative light-emitting element 33, which uses Li2O, a Li compound that is generally used in the electron injection layer in contact with the charge generation layer between the EL layers.

[0454] 33 and Table 15, the light-emitting elements 16 to 21 had lower driving voltages and better current-voltage characteristics than the comparative light-emitting elements 33 and 34. It was also found that the comparative light-emitting element 34 had a very high driving voltage and had a problem with the electron injection property from the charge generation layer. These results show that the light-emitting elements 16 to 21 have better electron injection properties than the comparative light-emitting element 33, which uses Li2O, a Li compound that is generally used in the electron injection layer in contact with the charge generation layer between the EL layers. Thus, it was found that a composite material of a metal and an organic compound having a function of interacting with a metal at a tridentate or tetradentate position exhibits good driving voltage characteristics even when used as an electron injection layer in contact with the charge generation layer between the EL layers in a tandem element.

[0455] <Constant current driving test results for light emitting elements> Next, a constant current drive test at 1.0 mA was performed on the light-emitting element 18, the light-emitting element 19, the comparative light-emitting element 33, and the comparative light-emitting element 34 at room temperature. The results are shown in FIG. 52. As can be seen from FIG. 52, it was found that the light-emitting element 18 and the light-emitting element 19 have better reliability than the comparative light-emitting element 33 and the comparative light-emitting element 34. These results show that the light-emitting element 18 and the light-emitting element 19 have better reliability than the comparative light-emitting element 33, which uses Li2O, a Li compound that is generally used in the electron injection layer in contact with the charge generation layer, and the comparative light-emitting element 34, which does not have an electron injection layer in contact with the charge generation layer. Thus, a composite material of an organic compound and a metal having a function of interacting with a metal at a tridentate or tetradentate position can be used as an electron injection layer in contact with the charge generation layer between EL layers in a tandem element to realize a light-emitting element with excellent reliability.

[0456] As described above, the light-emitting element according to one embodiment of the present invention has excellent electron injection properties and therefore has low driving voltage and high light-emitting efficiency. In addition, the light-emitting element has excellent moisture resistance and high reliability because a material with a high work function can be used. The structure described in this embodiment can be used in appropriate combination with other embodiments and embodiments. EXAMPLES

[0457] As light-emitting elements according to one embodiment of the present invention, examples of fabrication of light-emitting elements 22 to 25 are described below. A schematic cross-sectional view of the light-emitting elements fabricated in this example is shown in FIG. 1, and details of the element structures are shown in Table 16. Note that the structures and abbreviations of other compounds may be referred to in the previous Examples and Embodiment 1. Note that light-emitting elements 22 to 25 are light-emitting elements that use In, a metal belonging to Group 13, as a metal used in a composite material of an organic compound having a function of interacting with a metal at a tridentate or tetradentate position and a metal. [Table 16]

[0458] <Fabrication of light-emitting element 22> The light-emitting element 22 was fabricated in the same manner as the comparative light-emitting element 1, except for the step of forming the electron injection layer 130.

[0459] As the electron injection layer 130 of the light emitting element 22, tPy2P and In were co-deposited on the electron transport layer 118(2) to a weight ratio (tPy2P:In) of 1:0.4 and a thickness of 5 nm.

[0460] <Fabrication of light-emitting element 23> The light-emitting element 23 was fabricated in the same manner as the comparative light-emitting element 1, except for the steps of forming the electron transport layer 118(2) and the electron injection layer 130.

[0461] As the electron transport layer 118(2) of the light-emitting element 23, NBPhen was deposited on the electron transport layer 118(1) to a thickness of 10 nm.

[0462] Next, as the electron injection layer 130(1), NBPhen and Ag were co-deposited on the electron transport layer 118(2) in a weight ratio (NBPhen:Ag) of 1:0.3 and a thickness of 5 nm. Subsequently, as the electron injection layer 130(2), 2Py3Tzn and In were co-deposited on the electron injection layer 130(1) in a weight ratio (2Py3Tzn:In) of 1:0.6 and a thickness of 5 nm.

[0463] <Fabrication of light-emitting element 24 and light-emitting element 25> The light-emitting elements 24 and 25 were fabricated in the same manner as the light-emitting element 23, except for the step of forming the electron injection layer 130(2).

[0464] <Fabrication of Light-Emitting Element 24> As the electron injection layer 130(2) of the light emitting element 24, 2,6(P-Bqn)2Py and In were co-deposited on the electron transport layer 130(1) to a weight ratio (2,6(P-Bqn)2Py:In) of 1:0.3 and a thickness of 5 nm.

[0465] <Fabrication of Light-Emitting Element 25> As the electron injection layer 130(2) of the light emitting element 25, 2,6(NP-PPm)2Py and In were co-deposited on the electron transport layer 130(1) to a weight ratio (2,6(NP-PPm)2Py:In) of 1:0.3 and a thickness of 5 nm.

[0466] In addition, for the light-emitting elements 22 to 25, the cathodes were prepared in the same manner as for the comparative light-emitting element 1, and then the elements were heat-treated in the air at 80° C. for 1 hour without sealing.

[0467] <Measurement of each light-emitting element> The element characteristics of the fabricated light-emitting elements 22 to 25 were measured. A color luminance meter (BM-5A, manufactured by Topcon Corporation) was used to measure the luminance and CIE chromaticity, and a multichannel spectrometer (PMA-11, manufactured by Hamamatsu Photonics KK) was used to measure the electroluminescence spectrum.

[0468] The current efficiency-luminance characteristics of the fabricated light-emitting elements 22 to 25 are shown in FIG. 37, the current-voltage characteristics in FIG. 38, the power efficiency-luminance characteristics in FIG. 39, and the external quantum efficiency-luminance characteristics in FIG. 40. Note that each light-emitting element was measured at room temperature (atmosphere maintained at 23° C.). In addition, each light-emitting element was supplied with a current of 2.5 mA / cm 2 The electroluminescence spectrum when a current was passed at a current density of 1000 nm is shown in Fig. 41. The measurement was carried out at room temperature.

[0469] Also, 1000cd / m 2 Table 17 shows the element characteristics of the light-emitting elements 22 to 25 in the vicinity.

[0470] [Table 17]

[0471] As shown in Figure 41, the peak wavelengths of the electroluminescence spectra of light-emitting elements 22 to 25 are all around 615 nm, and it was found that light-emitting elements 22 to 25 exhibit light emission originating from Ir(dmdppr-dmp)2(dpm), which is the guest material possessed by each light-emitting element.

[0472] 40 and Table 17, all of the light-emitting elements 22 to 25 exhibited extremely high luminous efficiency with an external quantum efficiency exceeding 25%. As shown in Fig. 37 and Fig. 39, the light-emitting elements exhibited high current efficiency and high power efficiency. Thus, it was found that In is suitable as a metal for use in a composite material of a metal and an organic compound having a function of interacting with a metal at a tridentate or tetradentate state.

[0473] 38, the light-emitting elements 22 to 25 exhibited favorable current-voltage characteristics. Thus, it was found that In is suitable as a metal for use in a composite material of a metal and an organic compound having a function of interacting with a metal in a tridentate or tetradentate manner.

[0474] As described above, the light-emitting element according to one embodiment of the present invention has excellent electron injection properties, and therefore has low driving voltage and high light-emitting efficiency. In addition, the light-emitting element has excellent moisture resistance because a material with a high work function can be used. The structure described in this embodiment can be used in appropriate combination with other embodiments and embodiments. EXAMPLES

[0475] Fabrication examples of light-emitting elements 26 to 28, which are examples of light-emitting elements according to one embodiment of the present invention, are shown below. A schematic cross-sectional view of the light-emitting element fabricated in this example is shown in FIG. 1, and details of the element structure are shown in Table 18. Chemical formulas of organic compounds used in this example are shown below. For structures and abbreviations of other compounds, the previous Examples and Embodiment 1 may be referred to. Note that the light-emitting elements 26 to 28 are examples of light-emitting elements using an organic compound having a triazine skeleton or a bipyridine skeleton as an organic compound used in a composite material of an organic compound having a function of interacting with a metal at a tridentate or tetradentate site and a metal. Note that in this example, a composite material of an organic compound having a function of interacting with a metal at a tridentate site and a metal is used for the electron-injection layer 130.

[0476] [ka]

[0477] [Table 18]

[0478] <Fabrication of Light-emitting Elements 26 to 28> Light-emitting elements 26 to 28 were fabricated in the same manner as for the comparative light-emitting element 1, except for the step of forming the electron injection layer 130.

[0479] As the electron injection layer 130 of the light-emitting element 26, PPm3Tzn and Cu were co-deposited on the electron transport layer 118(2) so that the weight ratio (PPm3Tzn:Cu) was 1:0.2 and the thickness was 5 nm. PPm3Tzn is an example of an organic compound having a triazine skeleton. PPm3Tzn can also be said to be an organic compound having a pyrimidine skeleton.

[0480] As the electron injection layer 130 of the light-emitting element 27, 2,2'-(2,2'-bipyridine-6,6'-diyl)bis(4-phenylbenzo[h]quinazoline) (abbreviation: 6,6'(P-Bqn)2BPy) and Ag were co-deposited on the electron transport layer 118(2) in a weight ratio (6,6'(P-Bqn)2BPy:Ag) of 1:0.3 and a thickness of 5 nm. Note that 6,6'(P-Bqn)2BPy is an example of an organic compound having a bipyridine skeleton. It can also be said that 6,6'(P-Bqn)2BPy is an organic compound having a quinazoline skeleton.

[0481] As the electron injection layer 130 of the light emitting element 28, 6,6'(P-Bqn)2BPy) and Cu were co-deposited on the electron transport layer 118(2) in a weight ratio (6,6'(P-Bqn)2BPy:Cu) of 1:0.3 to a thickness of 5 nm.

[0482] In addition, for the light-emitting elements 26 to 28, the cathodes were prepared in the same manner as for the comparative light-emitting element 1, and then the elements were heat-treated in the air at 80° C. for 1 hour without sealing.

[0483] <Measurement of each light-emitting element> The device characteristics of the fabricated light-emitting elements 26 to 28 were measured. A color luminance meter (BM-5A, manufactured by Topcon Corporation) was used to measure the luminance and CIE chromaticity, and a multichannel spectrometer (PMA-11, manufactured by Hamamatsu Photonics KK) was used to measure the electroluminescence spectrum.

[0484] The current efficiency-luminance characteristics of the fabricated light-emitting elements 26 to 28 are shown in FIG. 42, the current-voltage characteristics in FIG. 43, the power efficiency-luminance characteristics in FIG. 44, and the external quantum efficiency-luminance characteristics in FIG. 45. Note that each light-emitting element was measured at room temperature (atmosphere maintained at 23° C.). In addition, each light-emitting element was supplied with a current of 2.5 mA / cm 2 The electroluminescence spectrum when a current was passed at a current density of 1000 nm is shown in Fig. 46. The measurement was carried out at room temperature.

[0485] Also, 1000cd / m 2 Table 19 shows the element characteristics of the light-emitting elements 26 to 28 in the vicinity.

[0486] [Table 19]

[0487] As shown in Figure 46, the peak wavelengths of the electroluminescence spectra of light-emitting elements 26 to 28 are all around 618 nm, and it was found that light-emitting elements 26 to 28 exhibit light emission derived from Ir(dmdppr-dmp)2(dpm), which is the guest material possessed by each light-emitting element.

[0488] 45 and Table 19, all of the light-emitting elements 26 to 28 showed very high luminous efficiency with an external quantum efficiency of more than 29%. As shown in FIG. 42 and FIG. 44, the light-emitting elements showed high current efficiency and high power efficiency. Thus, it was found that an organic compound having a triazine skeleton (or a pyrimidine skeleton) or a bipyridine skeleton (or a quinazoline skeleton) is suitable as an organic compound used for a composite material of an organic compound having a function of interacting with a metal at a tridentate or tetradentate position and a metal.

[0489] 43, the light-emitting elements 26 to 28 showed favorable current-voltage characteristics. Therefore, it was found that an organic compound having a triazine skeleton (or a pyrimidine skeleton) or a bipyridine skeleton (or a quinazoline skeleton) is suitable as an organic compound used for a composite material of an organic compound having a function of interacting with a metal at a tridentate or tetradentate site and a metal.

[0490] As described above, the light-emitting element according to one embodiment of the present invention has excellent electron injection properties, and therefore has low driving voltage and high light-emitting efficiency. In addition, the light-emitting element has excellent moisture resistance because a material with a high work function can be used. The structure described in this embodiment can be used in appropriate combination with other embodiments and embodiments. EXAMPLES

[0491] Fabrication examples of light-emitting elements 29 to 32, which are examples of light-emitting elements according to one embodiment of the present invention, are shown below. A schematic cross-sectional view of the light-emitting elements fabricated in this example is shown in FIG. 1, and details of the element structure are shown in Table 20. Chemical formulas of organic compounds used in this example are shown below. For structures and abbreviations of other compounds, the previous Examples and Embodiment 1 may be referred to. Note that the light-emitting elements 29 to 32 are examples of light-emitting elements using an organic compound having a pyridine skeleton as an organic compound used in a composite material of an organic compound having a function of interacting with a metal at a tridentate or tetradentate site and a metal. Note that in this example, a composite material of an organic compound having a function of interacting with a metal at a tridentate site and a metal is used for the electron-injection layer 130.

[0492] [Table 20]

[0493] <Fabrication of Light-emitting Elements 29 to 32> Light-emitting elements 29 to 32 were fabricated in the same manner as for the comparative light-emitting element 1, except for the step of forming the electron injection layer 130.

[0494] As the electron injection layer 130 of the light-emitting element 29, 2,6(P-Bqn)2Py and Ag were co-deposited on the electron transport layer 118(2) in a weight ratio (2,6(P-Bqn)2Py:Ag) of 1:0.3 and a thickness of 5 nm. Note that 2,6(P-Bqn)2Py is an example of an organic compound having a pyridine skeleton. It can also be said that 2,6(P-Bqn)2Py is an organic compound having a quinazoline skeleton.

[0495] As the electron injection layer 130 of the light emitting element 30, 2,6(P-Bqn)2Py and Cu were co-deposited on the electron transport layer 118(2) in a weight ratio (2,6(P-Bqn)2Py:Cu) of 1:0.2 to a thickness of 5 nm.

[0496] As the electron injection layer 130 of the light-emitting element 31, 2,6'(NP-PPm)2Py and Ag were co-deposited on the electron transport layer 118(2) in a weight ratio (2,6'(NP-PPm)2Py:Ag) of 1:0.3 and a thickness of 5 nm. Note that 2,6'(NP-PPm)2Py is an example of an organic compound having a pyridine skeleton. It can also be said that 2,6'(NP-PPm)2Py is an organic compound having a pyrimidine skeleton.

[0497] In addition, for the light-emitting elements 29 to 32, the cathodes were prepared in the same manner as for the comparative light-emitting element 1, and then the elements were heat-treated in the air at 80° C. for 1 hour without sealing.

[0498] <Measurement of each light-emitting element> The device characteristics of the fabricated light-emitting elements 29 to 32 were measured. A color luminance meter (BM-5A, manufactured by Topcon Corporation) was used to measure the luminance and CIE chromaticity, and a multichannel spectrometer (PMA-11, manufactured by Hamamatsu Photonics KK) was used to measure the electroluminescence spectrum.

[0499] The current efficiency-luminance characteristics of the fabricated light-emitting elements 29 to 32 are shown in FIG. 47, the current-voltage characteristics in FIG. 48, the power efficiency-luminance characteristics in FIG. 49, and the external quantum efficiency-luminance characteristics in FIG. 50. Note that each light-emitting element was measured at room temperature (atmosphere maintained at 23° C.). 2The electroluminescence spectrum when a current was passed at a current density of 1000 nm is shown in Fig. 51. The measurement was carried out at room temperature.

[0500] Also, 1000cd / m 2 Table 21 shows the element characteristics of the light-emitting elements 29 to 32 in the vicinity.

[0501] [Table 21]

[0502] As shown in Figure 51, the peak wavelengths of the electroluminescence spectra of light-emitting elements 29 to 32 are all around 618 nm, and it was found that light-emitting elements 29 to 32 exhibit light emission originating from Ir(dmdppr-dmp)2(dpm), which is the guest material possessed by each light-emitting element.

[0503] 50 and Table 21, all of the light-emitting elements 29 to 32 showed very high luminous efficiency with an external quantum efficiency of more than 28%. As shown in FIG. 47 and FIG. 49, the light-emitting elements showed high current efficiency and high power efficiency. Thus, it was found that an organic compound having a pyridine skeleton (pyrimidine skeleton, or quinazoline skeleton) is suitable as an organic compound used for a composite material of an organic compound having a function of interacting with a metal at a tridentate or tetradentate position and a metal.

[0504] 48, the light-emitting elements 29 to 32 exhibited favorable current-voltage characteristics. Therefore, it was found that an organic compound having a triazine skeleton (or a pyrimidine skeleton) or a bipyridine skeleton (or a quinazoline skeleton) is suitable as an organic compound used for a composite material of an organic compound having a function of interacting with a metal at a tridentate or tetradentate site and a metal.

[0505] As described above, the light-emitting element according to one embodiment of the present invention has excellent electron injection properties, and therefore has low driving voltage and high light-emitting efficiency. In addition, the light-emitting element has excellent moisture resistance because a material with a high work function can be used. The structure described in this embodiment can be used in appropriate combination with other embodiments and embodiments. [Explanation of symbols]

[0506] 100: EL layer, 101: electrode, 101a: conductive layer, 101b: conductive layer, 102: electrode, 103: electrode, 103a: conductive layer, 103b: conductive layer, 104: electrode, 104a: conductive layer, 104b: conductive layer, 106: light-emitting unit, 108: light-emitting unit, 110: EL layer, 111: hole injection layer, 112: hole transport layer, 113: electron transport layer, 115: charge generation layer, 116: hole injection layer, 117: hole transport layer, 118: electron transport layer, 119: electron injection layer, 127: buffer layer, 129: charge generation layer, 130: electron injection layer, 131: compound, 132: metal, 133 : Compound, 140: Light-emitting layer, 145: Partition wall, 150: Light-emitting element, 152: Light-emitting element, 154: Light-emitting element, 170: Light-emitting layer, 200: Substrate, 220: Substrate, 222B: Region, 222G: Region, 222R: Region, 223: Light-shielding layer, 224B: Optical element, 224G: Optical element, 224R: Optical element, 250a: Light-emitting element, 250b: Light-emitting element, 601: Source side driving circuit, 602: Pixel portion, 603: Gate side driving circuit, 604: Sealing substrate, 605: Sealing material, 607: Space, 608: Wiring, 610: Element substrate, 611: Switching TFT, 612: Current control TFT for a display device, 613: electrode, 614: insulator, 616: EL layer, 617: electrode, 618: light emitting element, 623: n-channel TFT, 624: p-channel TFT, 900: portable information terminal, 901: housing, 902: housing, 903: display unit, 905: hinge unit, 910: portable information terminal, 911: housing, 912: display unit, 913: operation button, 914: external connection port, 915: speaker, 916: microphone, 917: camera, 920: camera, 921: housing, 922: display unit, 923: operation button, 924: shutter button, 926: lens, 1001: substrate, 1002: Undercoat insulating film, 1003: Gate insulating film, 1006: Gate electrode, 1007: Gate electrode, 1008: Gate electrode, 1020: Interlayer insulating film, 1021: Interlayer insulating film, 1022: Electrode, 1024B: Electrode, 1024G: Electrode, 1024R: Electrode, 1024W: Electrode, 1025B: Lower electrode, 1025G: Lower electrode, 1025R: Lower electrode, 1025W: Lower electrode, 1026: Partition wall, 1028: EL layer, 1029: Electrode, 1031: Sealing substrate, 1032: Sealing material, 1033: Base material, 1034B: Colored layer, 1034G: Colored layer, 1034R: Colored layer,1036: overcoat layer, 1037: interlayer insulating film, 1040: pixel section, 1041: driving circuit section, 1042: peripheral section, 2100: robot, 2101: illuminance sensor, 2102: microphone, 2103: upper camera, 2104: speaker, 2105: display, 2106: lower camera, 2107: obstacle sensor, 2108: moving mechanism, 2110: computing device, 5000: housing, 5001: display section, 5002: display section, 5003: speaker, 5004: LED lamp, 5005: operation key, 5006: connection terminal, 5007: sensor, 5008: microphone, 5012: support part, 5013: earphone, 5100: cleaning robot, 5101: display, 5102: camera, 5103: brush, 5104: operation button, 5120: dust, 5140: portable electronic device, 5150: mobile information terminal, 5151: housing, 5152: display area, 5153: bending part, 8501: lighting device, 8502: lighting device, 8503: lighting device, 8504: lighting device,

Claims

1. A light-emitting layer is disposed between an anode and a cathode, a first layer between the light-emitting layer and the cathode; a second layer between the first layer and the cathode; the first layer comprises a first organic compound and a metal; The metal belongs to any one of Groups 3 to 13 in the periodic table, the first organic compound has a substituted or unsubstituted heteroaromatic ring having 1 to 30 carbon atoms, the heteroaromatic ring contains nitrogen; the first organic compound has a function of interacting with the metal at a tridentate or tetradentate site on the nitrogen; a sum of the number of electrons of the first organic compound and the number of electrons of the metal is an odd number, The second layer includes a second organic compound having an electron-deficient heteroaromatic ring.

2. In claim 1, The light-emitting device has a first layer free of alkali metals and alkaline earth metals.

3. The light emitting device according to claim 1 or 2, At least one of a color filter or a transistor; A light emitting device having the above structure.

4. A light emitting device according to claim 3; At least one of a housing or a display unit; An electronic device having the

5. The light emitting device according to claim 1 or 2, A lighting device having a housing.

Images