Organic thin film, organic electroluminescent element, display device, lighting device, organic thin film solar cell, and organic thin film transistor

Abstract

The present invention addresses the problem of providing an organic thin film which uses an organic material having high electron affinity as a hole injection material and which can improve the driving stability of an organic device, the organic thin film as a solution being a hole-injectable organic thin film containing two or more organic acceptor materials having different electron affinity, the present invention relates to a film comprising a first layer comprising an organic acceptor material having a relatively small electron affinity, and a second layer laminated on the first layer and comprising an organic acceptor material having a relatively large electron affinity, the electron affinity of the organic acceptor material having a relatively small electron affinity is smaller than the electron affinity of the organic acceptor material having a relatively large electron affinity, and the first layer is disposed on the anode side for use.

Description

Technical Field

[0001] The present invention relates to an organic thin film, an organic electroluminescent element, a display device, a lighting device, an organic thin film solar cell and an organic thin film transistor. Background Art

[0002] In organic devices such as organic electroluminescence (EL) elements, organic thin-film solar cells, and organic thin-film transistors, charge exchange is required between electrodes and organic thin films, so people are actively studying hole injection materials and electron injection materials used between electrodes and organic thin films.

[0003] In order to inject electrons into an organic thin film, an electron injection material is required that can make the work function of the cathode equivalent to the electron affinity (EA) of the organic thin film. Alkali metals have been widely used in the past, but organic materials are also being developed (Non-Patent Document 1).

[0004] On the other hand, regarding hole injection materials, both inorganic materials and organic materials have been developed (Non-patent Document 1). It is reported that as inorganic materials, materials with large work functions such as molybdenum oxide or nickel oxide are suitable for hole injection materials. In addition, as organic materials, it has been reported that materials with large electron affinity represented by 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene hexacarbonitrile (HAT-CN) are suitable for hole injection materials. Due to the large electron affinity, electrons can be extracted from the highest occupied molecular orbital (HOMO) of the organic material, thereby generating holes.

[0005] The HAT-CN is widely used as a hole injection material for organic electroluminescence devices (OLEDs). As other materials with large electron affinity, tetracyanonaphtho-quinodimethane (TNAP), 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquino dimethane (F4TCNQ) and hexafluorotetracyanonaphthoquino dimethane (F6TCNNQ) have been reported. The electron affinity of these materials is greater than that of HAT-CN, and they are considered to be suitable for use as hole injection materials.

[0006] Prior art literature

[0007] Non-patent literature

[0008] Non-patent document 1: Karsten Walzer, Chemical Reviews, 107, 2007, p1233-1271

[0009] Non-patent document 2: Xiaozhi Cero, Japanese Journal of Applied Physics (JJ Appl. Phys.), 53, 2014, p042102

[0010] Non-patent document 3: Jeong-Hwan Lee, ACS Applied Materials & Interfaces, 9, 2017, p3277 Summary of the invention

[0011] Problems to be solved by the invention

[0012] However, there is no report of an organic device with excellent stability using materials with high electron affinity (TNAP, F4TCNQ, F6TCNNQ, etc.) other than HAT-CN. Here, if materials with high electron affinity can be used, electrons can be extracted from various organic materials with high ionization potential (IP), and it can be expected to achieve low voltage in organic EL devices, improve power generation efficiency in organic thin film solar cells, and improve mobility in p-type organic thin film transistors.

[0013] Therefore, an object of the present invention is to provide an organic thin film which uses an organic material having a high electron affinity as a hole injection material and which can improve the driving stability of an organic device.

[0014] Another object of the present invention is to provide an organic electroluminescent element, a display device, a lighting device, an organic thin film solar cell, and an organic thin film transistor using such an organic thin film and having excellent driving stability.

[0015] Means for solving problems

[0016] The inventors of the present application have discovered that by using two or more organic acceptor materials with different electron affinities for a hole injection layer, configuring the organic acceptor material with relatively small electron affinity among the two or more organic acceptor materials on the anode side, and stacking a material with relatively large electron affinity on the organic acceptor material with relatively small electron affinity, a hole injection layer with high hole injection properties and excellent driving stability can be achieved, thereby solving the above-mentioned problems.

[0017] That is, the main structures of the organic thin film, organic electroluminescent element, display device, lighting device, organic thin film solar cell, and organic thin film transistor of the present invention that solve the above-mentioned problems are as follows.

[0018] [1] An organic thin film having hole-injecting properties comprising two or more organic acceptor materials having different electron affinities, characterized in that it comprises:

[0019] A first layer comprising an organic acceptor material having a relatively low electron affinity; and

[0020] The second layer, stacked on the first layer, comprises an organic acceptor material having a relatively large electron affinity,

[0021] The electron affinity of the organic acceptor material with relatively small electron affinity is smaller than the electron affinity of the organic acceptor material with relatively large electron affinity,

[0022] The first layer is configured for use on the anode side.

[0023] [2] The organic thin film as described in [1], wherein the electron affinity of the organic acceptor material with relatively small electron affinity is less than 4.5 eV,

[0024] The electron affinity of the organic acceptor material having relatively large electron affinity is 4.5 eV or more.

[0025] [3] The organic thin film according to [1] or [2], wherein the second layer is a film formed by mixing the organic acceptor material having a relatively high electron affinity with other organic materials.

[0026] [4] The organic thin film according to any one of [1] to [3], wherein the organic acceptor material is a cyano-containing compound or a fluorine-containing compound.

[0027] [5] The organic thin film according to any one of [1] to [4], wherein the organic acceptor material is a compound containing a 2-methylenepropanedinitrile group.

[0028] [6] An organic thin film as described in any one of [1] to [3], wherein the organic acceptor material with relatively low electron affinity is any one of the following materials: fluorine-containing compounds, aromatic hydrocarbons, phosphoric acid, and materials constituting a self-assembled monolayer.

[0029] [7] The organic thin film according to any one of [1] to [3], wherein the electron affinity of the organic acceptor material having a relatively small electron affinity is greater than or equal to 0.35 eV and less than 4.5 eV.

[0030] [8] An organic electroluminescent element comprising, in order, a cathode, a light-emitting layer, and an anode, characterized in that:

[0031] An organic thin film as described in any one of [1] to [7] is included between the anode and the light-emitting layer,

[0032] The first layer of the organic thin film is arranged on the anode side.

[0033] [9] The organic electroluminescent element according to [8], wherein the average thickness of the organic thin film is 2 nm to 100 nm.

[0034]

[10] A display device comprising the organic electroluminescent element according to [8] or [9].

[0035]

[11] A lighting device comprising the organic electroluminescent element described in [8] or [9].

[0036]

[12] An organic thin film solar cell, comprising the organic thin film described in any one of [1] to [7].

[0037]

[13] An organic thin film transistor, comprising the organic thin film according to any one of [1] to [7].

[0038] Effects of the Invention

[0039] According to the present invention, an organic thin film capable of improving the driving stability of an organic device can be provided.

[0040] Furthermore, according to the present invention, an organic electroluminescent element, a display device, a lighting device, an organic thin film solar cell, and an organic thin film transistor using such an organic thin film and having excellent driving stability can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a schematic diagram showing an example of the structure of the organic EL element of the present invention.

[0042] Figure 2 The diagrams are schematic diagrams showing two structural examples of the hole injection layer of the organic EL device of the present invention.

[0043] Figure 3 It is an explanatory diagram showing energy levels in organic EL elements of Examples and Comparative Examples.

[0044] Figure 4 : This is the reverse electron spectrum of each organic acceptor material used in Examples and Comparative Examples.

[0045] Figure 5 It is an explanatory diagram showing the relationship between the structural example of the hole injection layer and its electron affinity.

[0046] Figure 6 This is a graph showing the relationship between the applied voltage and the current density of the organic EL elements of Examples 1 to 4.

[0047] Figure 7 This is a graph showing the relationship between the applied voltage and the current density of the organic EL elements of Comparative Examples 1 to 7.

[0048] Figure 8 This is a graph showing the relationship between the applied voltage and the current density of the organic EL elements of Examples 5 to 8 and Comparative Examples 8 to 9.

[0049] Fig. 9 This is a graph showing the correlation between the measured values ​​and the calculated values ​​of the electron affinities of various organic materials. DETAILED DESCRIPTION

[0050] Hereinafter, the organic thin film, the organic electroluminescent element, the display device, the lighting device, the organic thin film solar cell, and the organic thin film transistor of the present invention will be described in detail based on the embodiments thereof.

[0051] <Organic thin film>

[0052] The organic thin film of the present embodiment is a hole-injecting organic thin film comprising two or more organic acceptor materials having different electron affinities. Furthermore, the organic thin film of the present embodiment is characterized in that it comprises a first layer and a second layer, the first layer comprising an organic acceptor material having a relatively small electron affinity, the second layer being stacked on the first layer and comprising an organic acceptor material having a relatively large electron affinity, the electron affinity of the organic acceptor material having a relatively small electron affinity being smaller than the electron affinity of the organic acceptor material having a relatively large electron affinity, and the first layer being arranged on the anode side for use.

[0053] In addition, as a method for measuring electron affinity, there are two measurement methods: low-energy inverse photoemission spectroscopy (LEIPS) or a method of measuring ionization energy and optical band gap and subtracting them. However, the value measured using the optical band gap is about 0.5 eV larger than the value measured using LEIPS, and the magnitude of the electron affinity depends on the measurement method. Therefore, in this specification, the electron affinity (EA) of the organic acceptor material is a calculated value, which is a value calculated using molecular orbital calculation [density functional theory (Density Functional Theory), B3LYP, basis function: 6-31G (d)].

[0054] Organic acceptor materials can extract electrons from adjacent molecules or atoms. The greater the electron affinity (EA), the easier it is to extract electrons. When an organic acceptor material with a large electron affinity is formed on the anode, the amount of electron migration from the anode to the organic acceptor material increases, and the film composed of the organic acceptor material has a strong negative charge. This state of strong negative charge is not a stable state. Therefore, when an organic acceptor material with a large electron affinity is formed on the anode of an organic device, the driving stability of the organic device will decrease.

[0055] In this regard, in the organic thin film of this embodiment, the first layer disposed on the anode side contains an organic acceptor material with a relatively small electron affinity, and the second layer stacked on the first layer contains an organic acceptor material with a relatively large electron affinity. By providing the first layer containing an organic acceptor material with a relatively small electron affinity on the anode side, the amount of electron migration from the anode side can be reduced, and the first layer can be suppressed from being negatively charged and made close to neutral, thereby improving the stability of the first layer and improving the driving stability of the organic device using the organic thin film.

[0056] In addition, by providing a second layer containing an organic acceptor material with relatively large electron affinity on the first layer (the cathode side of the first layer), the second layer draws electrons from the cathode side (for example, in an organic EL element, a hole transport layer, etc.), thereby achieving low voltage in the organic EL element, improving power generation efficiency in organic thin-film solar cells, and improving mobility in p-type organic thin-film transistors.

[0057] The organic film of this embodiment is a hole-injecting organic film containing two or more organic acceptor materials with different electron affinities, and the types of organic acceptor materials contained may be two or more. In addition, the organic film of this embodiment has hole-injecting properties, that is, it has the property of injecting holes sent from the anode side into the layer adjacent to the cathode side.

[0058] The organic thin film of this embodiment includes: a first layer including an organic acceptor material with a relatively small electron affinity; and a second layer stacked on the first layer and including an organic acceptor material with a relatively large electron affinity, and may further include other layers in addition to the first layer and the second layer. Here, the electron affinity of the organic acceptor material with a relatively small electron affinity used in the first layer is smaller than the electron affinity of the organic acceptor material with a relatively large electron affinity used in the second layer.

[0059] In addition, as described above, by providing a first layer containing an organic acceptor material with relatively small electron affinity on the anode side, the amount of electron migration from the anode side is reduced and the negative charge of the first layer is suppressed. Therefore, the organic film of this embodiment is characterized in that the first layer of the organic film is configured on the anode side for use.

[0060] The electron affinity of the organic acceptor material with relatively small electron affinity is preferably less than 4.5 eV. When the electron affinity of the organic acceptor material with relatively small electron affinity used for the first layer is less than 4.5 eV, the amount of electron migration from the anode side is further reduced, and the first layer is further suppressed from being negatively charged, making it closer to neutrality, thereby further improving the stability of the first layer and further improving the driving stability of the organic device using the organic film. In addition, the lower limit of the electron affinity of the organic acceptor material with relatively small electron affinity is not particularly limited, but in one embodiment, it is greater than 0.35 eV, and in another embodiment, it is greater than 1.0 eV. In addition, the electron affinity of the organic acceptor material with relatively small electron affinity is preferably greater than 0.35 eV and less than 4.5 eV.

[0061] In addition, the electron affinity of the organic acceptor material with relatively large electron affinity is preferably 4.5 eV or more, more preferably 4.8 eV or more, and preferably 7.0 eV or less. When the electron affinity of the organic acceptor material with relatively large electron affinity used in the second layer is 4.5 eV or more, the second layer is more likely to extract electrons from the cathode side (for example, in an organic EL element, a hole transport layer, etc.), which can further reduce the voltage in the organic EL element, further improve the power generation efficiency in an organic thin film solar cell, and further improve the mobility in a p-type organic thin film transistor.

[0062] The second layer may be a film composed of the organic acceptor material having relatively high electron affinity, but is preferably a film in which the organic acceptor material having relatively high electron affinity is mixed with other organic materials. Here, other materials include donor materials, and the materials used in the hole transport layer of the organic EL element described later can be used as the donor material.

[0063] In addition, when the second layer is a film formed by mixing an organic acceptor material with relatively large electron affinity with other organic materials, the ratio of the organic acceptor material to the other organic materials is preferably 5.0:95.0 to 50.0:50.0 in terms of mass ratio (organic acceptor material: other organic materials).

[0064] As the organic acceptor material, various hole-injecting organic materials can be used, but in one embodiment, cyano compounds and fluorine-containing compounds are preferred, and compounds containing 2-methylenemalononitrile groups are more preferred. When the organic acceptor material is a cyano compound or a fluorine-containing compound, the hole injection property of the organic film is improved. In addition, when the organic acceptor material is a compound containing 2-methylenemalononitrile groups, the hole injection property of the organic film is further improved. Among them, the 2-methylenemalononitrile group is a group [=C(CN)2] with a structure formed by bonding two cyano groups to one of the carbons constituting the carbon-carbon double bond, also known as dicyanomethylene.

[0065] Examples of the cyano group-containing compound include 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (HAT-CN), tetracyanonaphthoquinone dimethane (TNAP), 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinone dimethane (F4TCNQ), hexafluorotetracyanonaphthoquinone dimethane (F6TCNNQ), and hexacyano-trimethylene-cyclopropane (CN6-CP).

[0066] Examples of the fluorine-containing compound include 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), hexafluorotetracyanonaphthoquinodimethane (F6TCNNQ), and 1,2,3,4,5,6,7,8-octafluoro-9,10-bis[4-(trifluoromethyl)phenyl]anthracene.

[0067] In addition, examples of the compound containing a 2-methylenemalononitrile group include tetracyanonaphthoquinone dimethane (TNAP), 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinone dimethane (F4TCNQ), hexafluorotetracyanonaphthoquinone dimethane (F6TCNNQ), and hexacyano-trimethylene-cyclopropane (CN6-CP).

[0068] The organic acceptor material with relatively large electron affinity used in the second layer is preferably a compound containing 2-methylenemalononitrile. The electron affinity (EA) of the compound containing 2-methylenemalononitrile is particularly large, and the second layer is more likely to extract electrons from the cathode side (for example, in an organic EL element, a hole transport layer, etc.), which can further reduce the voltage in the organic EL element, further improve the power generation efficiency in the organic thin film solar cell, and further improve the mobility in the p-type organic thin film transistor.

[0069] In addition, in one embodiment, the organic acceptor material with relatively low electron affinity used in the first layer is preferably any one of fluorine-containing compounds, aromatic hydrocarbons, phosphoric acid or materials constituting self-assembled monolayers. These materials further reduce the amount of electron migration from the anode side, further suppress the first layer from being negatively charged, and make it closer to neutrality, thereby further improving the stability of the first layer and further improving the driving stability of organic devices using organic thin films. Here, as fluorine-containing compounds, there are 1,2,3,4,5,6,7,8-octafluoro-9,10-bis[4-(trifluoromethyl)phenyl]anthracene (BCF3Ph-F8-Ant) and the like; as aromatic hydrocarbons, there are 2-(9,9'-spirobifluorene-2-yl)-9,9'-spirobifluorene (BSBF) and the like; as phosphoric acid, there are 4-fluorobenzyl phosphonic acid (FP-ly-POA) and the like; and as materials constituting self-assembled monolayers, there are 4-fluorobenzyl phosphonic acid (FP-ly-POA) and the like.

[0070] <Organic electroluminescent element>

[0071] The organic electroluminescent element of this embodiment has a cathode, a light-emitting layer and an anode in order, and the organic thin film is provided between the anode and the light-emitting layer. In addition, the organic EL electroluminescent element of this embodiment is characterized in that the first layer of the organic thin film is arranged on the anode side.

[0072] In the organic EL element of this embodiment, since the first layer of the organic thin film is arranged on the anode side, the electron migration amount from the anode side is reduced, and the negative charge of the first layer is suppressed to be close to neutrality, thereby improving the stability of the first layer and improving the driving stability of the organic EL element.

[0073] In addition, in the organic EL element of this embodiment, since the second layer of the organic thin film is arranged on the first layer (the cathode side of the first layer), the second layer can achieve low voltage by extracting electrons from the cathode side (such as the hole transport layer, the light-emitting layer, etc.).

[0074] In the organic EL element of this embodiment, the average thickness of the organic film is preferably 2nm to 100nm, more preferably 5nm to 100nm. When the average thickness of the organic film is 2nm to 100nm, the driving stability of the organic EL device can be further improved, and the driving voltage can be further reduced.

[0075] Here, the average thickness of the organic thin film can be measured by a stylus step profiler or a spectroscopic ellipsometer (SE).

[0076] Next, the organic EL element of this embodiment will be described in detail with reference to examples.

[0077] Figure 1 This is a schematic cross-sectional view for explaining an example of the organic EL element according to this embodiment. Figure 1 The organic EL element 1 shown has a light-emitting layer 6 between an anode 3 and a cathode 9 , and further has an organic thin film of this embodiment as a hole injection layer 4 between the anode 3 and the light-emitting layer 6 .

[0078] More specifically, Figure 1 The organic EL element 1 shown has a stacked structure in which an anode 3, a hole injection layer (organic film) 4, a hole transport layer 5, a light-emitting layer 6, an electron transport layer 7, an electron injection layer 8, and a cathode 9 are sequentially formed on a substrate 2, wherein the hole injection layer (organic film) 4 has a first layer 4-1 on the anode 3 side and a second layer 4-2 on the hole transport layer 5 side.

[0079] exist Figure 1In the organic EL element 1 shown, holes are injected from the anode 3 and electrons are injected from the cathode 9, and the respective charges reach the light-emitting layer 6 via the transport layers 5 and 7 and are recombined, thereby generating light. Figure 1 The organic EL element 1 shown may be a top emission type element that extracts light on the side opposite to the substrate 2 , or may be a bottom emission type element that extracts light on the substrate 2 side.

[0080] (Substrate)

[0081] Examples of the material of the substrate 2 include resin materials, glass materials, etc. As the material of the substrate 2, only one kind may be used, or two or more kinds may be used in combination.

[0082] Examples of the resin material used for the substrate 2 include polyethylene terephthalate, polyethylene naphthalate, cycloolefin polymer, polyamide, polyethersulfone, polymethyl methacrylate, polycarbonate, polyarylate, etc. When a resin material is used as the material for the substrate 2, an organic EL element 1 having excellent flexibility can be obtained, which is preferred.

[0083] On the other hand, examples of the glass material used for the substrate 2 include quartz glass, soda glass, and the like.

[0084] When the organic EL element 1 is a bottom emission type element, a transparent substrate is used as a material of the substrate 2 .

[0085] On the other hand, when the organic EL element 1 is a top emission type element, not only a transparent substrate but also an opaque substrate can be used as the material of the substrate 2. Examples of the opaque substrate include a substrate made of a ceramic material such as alumina, a substrate having an oxide film (insulating film) formed on the surface of a metal plate such as stainless steel, and a substrate made of a resin material.

[0086] The average thickness of the substrate 2 can be determined according to the material of the substrate 2, and is preferably 0.1 mm to 30 mm, and more preferably 0.1 mm to 10 mm. In addition, the average thickness of the substrate 2 can be measured by a digital multimeter or a vernier caliper.

[0087] (electrode)

[0088] In the organic EL element 1 of the present embodiment, a known conductive material can be used as the anode 3 and the cathode 9 as appropriate, but in order to extract light, it is preferred that at least one of them is transparent. Examples of known transparent conductive materials include ITO (tin-doped indium oxide), ATO (antimony-doped indium oxide), IZO (indium-doped zinc oxide), AZO (aluminum-doped zinc oxide), and FTO (fluorine-doped indium oxide).

[0089] On the other hand, examples of the opaque conductive material include calcium, magnesium, aluminum, barium, tin, indium, copper, silver, ytterbium, and alloys thereof.

[0090] Among these opaque conductive materials, ITO, IZO, and FTO are preferred as the anode 3 .

[0091] On the other hand, among these opaque conductive materials, Al and AgMg alloys are preferred as the cathode 9 .

[0092] The average thickness of the anode 3 is not particularly limited, but is preferably 10 nm to 500 nm, more preferably 70 nm to 200 nm. In addition, the average thickness of the anode 3 can be measured by a stylus step profiler or an ellipsometer.

[0093] The average thickness of the cathode 9 is not particularly limited, but is preferably 10 nm to 1000 nm, more preferably 30 nm to 150 nm. In addition, even when a non-transmissive material is used, for example, by setting the average thickness to about 10 nm to 30 nm, it can be used as a top-emitting and transparent cathode 9. In addition, the average thickness of the cathode 9 can be measured by a quartz crystal oscillation film thickness meter during film formation.

[0094] (Hole Injection Layer)

[0095] The hole injection layer 4 may have the same structure as the above-mentioned organic thin film, that is, a first layer 4-1 including an organic acceptor material with relatively small electron affinity and a second layer 4-2 including an organic acceptor material with relatively large electron affinity stacked on the first layer 4-1, wherein the first layer 4-1 is arranged on the side of the anode 3. With this structure, a hole injection layer 4 with improved hole injectability and stability can be formed.

[0096] In the organic EL element 1 of this embodiment, it is preferred that two organic acceptor materials are stacked to form the hole injection layer 4, but the hole injection layer 4 may have various structures. Figure 2 As shown in A, a first layer 4-1 including an organic acceptor material with relatively small electron affinity (organic acceptor material 1) and a second layer 4-2 including an organic acceptor material with relatively large electron affinity (organic acceptor material 2) can be stacked and used as the hole injection layer 4, or Figure 2 As shown in B, a layer (second layer 4-2) of a mixed organic acceptor material (organic acceptor material 2) having a relatively large electron affinity and a donor material is stacked on a single film (first layer 4-1) of an organic acceptor material (organic acceptor material 1) having a relatively small electron affinity and used as a hole injection layer 4.

[0097] Here, as the donor material mixed in the organic acceptor material, the material of the hole transport layer 5 described later can be applied. In addition, if the second layer 4-2 contains an organic acceptor material and a donor material, the ratio of the organic acceptor material to the donor material is preferably 5.0:95.0 to 50.0:50.0 in terms of mass ratio (organic acceptor material: donor material).

[0098] The form of the hole injection layer of the organic EL element of the present invention is not limited to this, and other structures may be adopted.

[0099] The average thickness of the hole injection layer 4 is not particularly limited, but is preferably 1 nm to 1000 nm, more preferably 2 nm to 100 nm, further preferably 5 nm to 100 nm, and particularly preferably 5 nm to 50 nm. In addition, the average film thickness of the first layer 4-1 and the second layer 4-2 are each independently preferably in the range of 1 nm to 50 nm.

[0100] The average thickness of the hole injection layer 4 (the first layer 4 - 1 and the second layer 4 - 2 ) can be measured, for example, by a stylus step profiler or a spectroscopic ellipsometer.

[0101] (Hole Transport Layer)

[0102] As the material of the hole transport layer 5 , any compound (donor material) that can be generally used as a material for a hole transport layer can be used, and various p-type high molecular materials and various p-type low molecular materials can be used alone or in combination.

[0103] As the p-type polymer material (organic polymer), for example, polyarylamine, fluorene-arylamine copolymer, fluorene-bithiophene copolymer, poly(N-vinylcarbazole), polyvinylpyrene, polyvinylanthracene, polythiophene, polyalkylthiophene, polyhexylthiophene, poly(p-phenylene vinylene), polythiophene vinylene (ポリチレンビレン), pyrene formaldehyde resin, ethylcarbazole formaldehyde resin or their derivatives, etc. In addition, these polymer materials can also be used as a mixture with other compounds. As an example, as a mixture containing polythiophene, poly(3,4-ethylenedioxythiophene / styrenesulfonic acid) (PEDOT / PSS) and the like are included.

[0104] Examples of the p-type low molecular weight material include aromatic cycloalkane compounds such as 1,1-bis(4-di-p-triaminophenyl)cyclohexane, 1,1'-bis(4-di-p-tolylaminophenyl)-4-phenyl-cyclohexane, 4,4',4"-trimethyltriphenylamine, N,N,N',N'-tetraphenyl-1,1'-biphenyl-4,4'-diamine, N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD1), N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD2), and N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD1). -bis(4-methoxyphenyl)-1,1'-biphenyl-4,4'-diamine (TPD2), N,N,N',N'-tetrakis(4-methoxyphenyl)-1,1'-biphenyl-4,4'-diamine (TPD3), N,N'-di(1-naphthyl)-N,N'-diphenylamino-1,1'-biphenyl-4,4'-diamine (TPD4), N,N'-di(1-naphthyl)-N,N'-diphenylamino-1,1'-biphenyl-4,4'-diamine (TPD5), N,N'-di(1-naphthyl)-N,N'-diphenylamino-1,1'-biphenyl-4,4'-diamine (TPD6), N,N'-di(1-naphthyl)-N,N'-diphenylamino-1,1'-biphenyl-4,4'-diamine (TPD7), N,N'-di(1-naphthyl)-N,N'-diphenylamino-1,1'-biphenyl-4,4'-diamine (TPD8), N,N'-di(1-naphthyl)-N,N'-diphenylamino-1,1'-biphenyl-4,4'-diamine (TPD9), N,N'-di(1-naphthyl)-N,N'-diphenylamino-1,1'-biphenyl-4,4'-diamine (TPD10), N,N'-di(1-naphthyl)-N,N'-diphenylamino-1,1'-biphenyl-4,4'-diamine (TPD11), N,N'-di(1-naphthyl)-N,N'-diphenylamino-1,1'-biphenyl-4,4'-diamine (TPD12), N,N'-di(1-naphthyl)- -di(l-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine, α-NPD), 4,4'-bis[N-phenyl-N-[4'-diphenylamino-1,1'-biphenyl-4-yl]amino]-1,1'-biphenyl, TPTE), tris(4-carbazolyl-9-ylphenyl)amine, TcTa Aromatic amine compounds, such as N,N,N',N'-tetraphenyl-p-phenylenediamine, N,N,N',N'-tetra(p-phenyl)-p-phenylenediamine, N,N,N',N'-tetra(meta-tolyl)meta-phenylenediamine (PDA), and other phenylenediamine compounds, carbazole compounds such as carbazole, N-isopropylcarbazole, and N-phenylcarbazole, stilbene compounds such as stilbene and 4-di-p-tolylaminostilbene, oxazole compounds such as OxZ, triphenylmethane, 4,4',4”-tris(N-3-methylphenyl-N-phenylamino)triphenylamine (m-MTDATA) and other triphenylmethane compounds, 1-phenyl-3-(p-dimethylaminophenyl)pyrazoline and other pyrazoline compounds, benzylene (cyclohexa diene) compounds, triazole compounds such as triazole, imidazole compounds such as imidazole, 1,3,4-oxadiazole, 2,5-bis(4-dimethylaminophenyl)-1,3,4-oxadiazole and other oxadiazole compounds, anthracene compounds such as anthracene and 9-(4-diethylaminophenyl)anthracene, fluorenone, 2,4,7-trinitro-9-fluorenone, 2,7-bis(2-hydroxy-3-(2-chlorophenylcarbamoyl)-1-naphthylazo)fluorenone (2,7-Bis(2-hydroxy-3-(2-chlorophenylcarbamoyl)-1-naphthylazo)fluorenone s(2-hydroxy-3-(2-chlorophenylcarbamoyl)-1-naphthylazo)fluorenone) and other fluorenone compounds, polyaniline and other aniline compounds, silane compounds, 1,4-dithio-3,6-diphenyl-pyrrole-(3,4-c)pyrrolopyrrole and other pyrrole compounds, fluorene and other fluorene compounds, porphyrin, metal tetraphenylporphyrin Porphyrin compounds such as phenothiophene, quinacridone compounds such as quinacridone, metal or metal-free phthalocyanine compounds such as phthalocyanine, copper phthalocyanine, tetra(tert-butyl) copper phthalocyanine, and iron phthalocyanine, metal or metal-free naphthalocyanine compounds such as copper naphthalocyanine, vanadium naphthalocyanine, and gallium monochloronaphthalocyanine, N,N'-di(naphthalene-1-yl)-N,N'-diphenyl-benzidine, N,N,N',N'-tetraphenylbenzidine, and the like, and one or more of them can be used. Among them, aromatic amine compounds such as TcTa, α-NPD, and TPTE are particularly preferred. ,

[0105] The average thickness of the hole transport layer 5 is not particularly limited, but is preferably 5 nm to 150 nm, and more preferably 10 nm to 100 nm.

[0106] The average thickness of the hole transport layer 5 can be measured, for example, by a stylus step profiler or a spectroscopic ellipsometer.

[0107] (Luminous layer)

[0108] In the organic EL element 1 of this embodiment, the material forming the light emitting layer 6 may be a low molecular weight compound or a high molecular weight compound, or a mixture of these. In the present invention, the so-called low molecular weight material refers to a material that is not a high molecular weight material (polymer), and does not necessarily refer to an organic compound with a low molecular weight.

[0109] In addition, in the light-emitting layer 6, in addition to materials generally called light-emitting materials, donor materials, electron transport materials, etc. can also be mixed and used. Here, as donor materials, the materials used in the hole transport layer 5 mentioned above can be listed, and as electron transport materials, the materials used in the electron transport layer 7 described later can be listed.

[0110] Examples of the polymer material forming the light-emitting layer 6 include: for example, trans-polyacetylene, cis-polyacetylene, poly(di-phenylacetylene) (Poly(di-Phenylacetylene, PDPA), poly(alkylphenylacetylene) (Poly(alkylPhenylacetylene, PAPA) and other polyacetylene compounds; poly(para-phenylenevinylene, PPV), poly(2,5-dialkoxy-para-phenylenevinylene, RO-PPV), cyano-substituted poly(para-phenylenevinylene, PPV), poly(2,5-dialkoxy-para-phenylenevinylene, RO-PPV ... Poly(p-phenylenevinylene) compounds such as poly(cyano-substitution-poly(para-phenylenevinylene), CN-PPV), poly(2-dimethyloctylsilyl-para-phenylenevinylene), DMOS-PPV, poly(2-methoxy, 5-(2'-ethylhexoxy)-para-phenylenevinylene), MEH-PPV, etc. ; poly(3-alkylthiophene) (PAT), poly(oxypropylene) triol (POPT) and other polythiophene compounds; poly(9,9-dialkylfluorene) (PDAF), poly(dioctylfluorene-alt-benzothiadiazole) (F8BT), α,ω-bis[N,N'-di(methylphenyl)aminophenyl]-poly[9,9-bis(2-ethylhexyl)fluorene-2,7-diyl] Polyfluorene compounds such as (α,ω-bis[N,N'-di(methylphenyl)aminophenyl]-poly[9,9-bis(2-ethylhexyl)fluorene-2,7-diyl], PF2 / 6am4), poly(9,9-dioctyl-2,7-dienylidenefluorenyl-alternate-copoly(anthracene-9,10-diyl); poly(para-phenylene) (PPP), poly(1,5-dialkoxy-para-phenylene) (poly(l,5-dialkoxy-para-phenylene), RO-PPP) and the like;Polycarbazole compounds such as poly(N-vinylcarbazole) (PVK); polysilane compounds such as poly(methylphenylsilane) (PMPS), poly(naphthylphenylsilane) (PNPS), and poly(biphenylylphenylsilane) (PBPS); and boron compound polymer materials described in Japanese Patent Laid-Open No. 2011-184430 and Japanese Patent Laid-Open No. 2012-151148. ;

[0111] Examples of low molecular weight materials for forming the light emitting layer 6 include a tricoordinate iridium complex having 2,2'-bipyridine-4,4'-dicarboxylic acid as a ligand, fac-Tris(2-phenylpyridine)iridium(III), fac-Tris(3-methyl-2-phenylpyridine-N,C2'-)iridium(III), 8-hydroxyquinoline aluminum (Alq3), tris(4-methyl-8-hydroxyquinoline)aluminum(III) tris(4-methyl-8-quinolinolate), Almq3), 8-hydroxyquinoline zinc (Znq2), (1,10-phenanthroline)-tris-(4,4,4-trifluoro-1-(2-thienyl)-butane-1,3-dione) europium (III) (Eu(TTA)3(phen)), 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin platinum (II) and other metal complexes; benzene compounds such as distyrylbenzene (DSB) and diaminodistyrylbenzene (DADSB); naphthalene compounds such as naphthalene and Nile red (nilered); phenanthrene compounds such as phenanthrene; (chrysene), 6-nitro wait perylene compounds, such as perylene and N,N'-bis(2,5-di-t-butylphenyl)-3,4,9,10-perylene-di-carboxyimide (BPPC); coronene compounds such as coronene; anthracene compounds such as anthracene and bis-phenylenedithracene; pyrene compounds such as pyrene; 4-(di-cyanomethylene)-2-methyl-6-(para-dimethylaminophenylenediyl)-4H-pyran (4-(di-cyanomethylene)-2-methyl-6-(para-dimethylaminophenylenediyl)-4H-pyran ostyryl)-4H-pyran, DCM) and other pyran compounds; acridine and other acridine compounds; stilbene and other stilbene compounds; carbazole compounds such as 4,4'-bis[9-dicarbazolyl]-2,2'-biphenyl (4,4'-bis[9-dicarbazolyl]-2,2'-biphenyl, CBP) and 4,4'-bis(9-ethyl-3-carbazovinylene)-1,1'-biphenyl (4,4'-bis(9-ethyl-3-carbazovinylene)-1,1'-biphenyl, BCzVBi); thiophene compounds such as 2,5-dibenzoxazolthiophene; benzoxazoles such as benzoxazole compounds; benzimidazole compounds such as benzimidazole; benzothiazole compounds such as 2,2'-(p-phenylenedivinylene)-bisbenzothiazole; butadiene compounds such as bisphenylvinyl (1,4-diphenyl-1,3-butadiene) and tetraphenylbutadiene; naphthalene dicarboximide compounds such as naphthalene dicarboximide; coumarin compounds such as coumarin; perinone compounds such as perylene; oxadiazole compounds such as oxadiazole, aldazines compounds, 1,2,3,4,5-pentaphenyl-1,3-cyclopentadiene (PP CP) and other cyclopentadiene compounds; quinacridone compounds such as quinacridone and quinacridone red; pyridine compounds such as pyrrolopyridine and thiadiazolopyridine; triazine compounds such as 2,4-diphenyl-6-bis(12-phenylindolo[2,3-a]carbazol-11-yl)-1,3,5-triazine (DIC-TRZ); spiro compounds such as 2,2',7,7'-tetraphenyl-9,9'-spirobifluorene, and metal or metal-free phthalocyanine compounds such as phthalocyanine (H2Pc) and copper phthalocyanine;As well as boron compound materials described in Japanese Patent Laid-Open No. 2009-155325 and Japanese Patent No. 5660371, one or more of them can be used. In addition, quantum dots or perovskite materials can also be used as the light-emitting layer. ;

[0112] The average thickness of the light-emitting layer 6 is not particularly limited, but is preferably 10 nm to 150 nm, and more preferably 20 nm to 100 nm.

[0113] The average thickness of the light-emitting layer 6 can be measured by a stylus-type step profiler, or by a quartz crystal oscillator-type film thickness meter when the light-emitting layer 6 is formed.

[0114] (Electron Transport Layer)

[0115] As the material of the electron transport layer 7, a wide range of known materials (electron transport materials) that can transport electrons can be used, and specifically, phosphorus oxide derivatives such as phenyl-dipyrene phosphine oxide (POPy2); pyridine derivatives such as tri-1,3,5-(3'-(pyridin-3")-yl)phenyl)benzene (TmPhPyB); quinoline derivatives such as 2-(3-(9-carbazolyl)phenyl)quinoline (mCQ); pyrimidine derivatives such as 2-phenyl-4,6-bis(3,5-dipyridylphenyl)pyrimidine (BPyPPM); pyrazine derivatives; bathophenanthroline (bathophenanthroline, BPhen) and other phenanthroline derivatives; 2,4-bis(4-biphenyl)-6-(4'-(2-pyridyl)-4-biphenyl)-[1,3,5]triazine (MPT), 2,4,6-tris(m-pyridin-3-yl-phenyl)triazine (TmPPyTz), 2,4-diphenyl-6-bis(12-phenylindole[2,3-a]carbazole-11-yl)-1,3,5-triazine (DIC-TRZ) and other triazine derivatives; 3-phenyl-4-(1'-naphthyl)-5-phenyl-1,2,4-triazole (TAZ) and other triazole derivatives; oxazole derivatives; 2-(4-biphenyl)-5- Oxadiazole derivatives such as (4-tert-butylphenyl-1,3,4-oxadiazole) (PBD); imidazole derivatives such as 2,2',2"-(1,3,5-benzenetriyl)-tri(1-phenyl-1-H-benzimidazole) (TPBI); aromatic tetracarboxylic anhydrides such as naphthalene and perylene; various metal complexes represented by bis[2-(2-hydroxyphenyl)benzothiazole]zinc (Zn(BTZ)2) and tris(8-hydroxyquinoline)aluminum (Alq3); 2,5-bis(6'-(2',2"-bipyridine)-1,1-dimethyl-3,4-diphenylsilanol (2,5-bis(6'-(2',2" -bipyridyl))-1,1-dimethyl-3,4-diphenylsilole, PyPySPyPy) and other silole derivatives represented by organic silane derivatives; Japanese Patent Publication No. 2013-239691, International Publication No. 2014 / 133141, Japanese Patent Publication No. 2016-172728, Japanese Patent Publication No. 2016-199507 and Japanese Patent Publication No. 2016-199508, etc., one or more of these substances can be used.

[0116] The average thickness of the electron transport layer 7 is not particularly limited, but is preferably 10 nm to 150 nm, and more preferably 20 nm to 100 nm.

[0117] The average thickness of the electron transport layer 7 can be measured by a stylus step profiler or an ellipsometer.

[0118] (Electron Injection Layer)

[0119] The material for the electron injection layer 8 is selected from the viewpoints of the work function of the cathode 9 and the lowest unoccupied molecular orbital (LUMO) energy level of the electron transport layer 7. In the case where the electron transport layer 7 is not provided, the material for the light-emitting layer 6 is selected in consideration of the LUMO energy level. The material for the electron injection layer 8 can be either an organic compound or an inorganic compound. In the case where the electron injection layer 8 is composed of an inorganic compound, for example, in addition to alkali metals and alkaline earth metals, lithium fluoride, sodium fluoride, potassium fluoride, cesium fluoride, cesium carbonate, etc. can also be used. In addition, in the case where the electron injection layer 8 is composed of an organic compound, for example, 8-quinolinolato-lithium (Liq), a hexahydropyrimidopyrimidine compound having a structure represented by the following general formula (1), or a compound having a structure represented by the following general formula (2) can be used.

[0120] [Chemical formula 1]

[0121]

[0122] (In general formula (1), R 1 represents an aromatic hydrocarbon group, an aromatic heterocyclic group, an aryl alkylene group, a divalent to tetravalent chain or cyclic hydrocarbon group which may have a substituent, or a group formed by combining two or more of these groups, or a group formed by combining one or more of these groups with a nitrogen atom. 1 is an integer from 1 to 4. )

[0123] [Chemical formula 2]

[0124]

[0125] (In general formula (2), X 1 , X 2 are the same or different and represent a nitrogen atom, an oxygen atom, a sulfur atom or a divalent linking group which may have a substituent. L represents a direct bond or a p-valent linking group. 2 represents a number of 0 or 1, and p represents a number from 1 to 4. q represents a number of 0 or 1, and when p is 1, q is 0. 2 To R 4 The same or different, represents a monovalent substituent. 1 To m 3 The same or different, representing a number from 0 to 3. 2 To R 4 Can be used with X 1 and X 2 bond to form a ring structure. When multiple R2 When multiple R 2 can be bonded to form a ring structure. In addition, when there are multiple R 3 When multiple R 3 They can also be bonded to form a ring structure. 4 When multiple R 4 They can also be bonded to form a ring structure.)

[0126] In the above general formula (1), R 1 It represents an aromatic hydrocarbon group, an aromatic heterocyclic group, an aryl alkylene group, a divalent to tetravalent chain or cyclic hydrocarbon group which may have a substituent, or a group formed by combining two or more of these groups, or a group formed by combining one or more of these groups with a nitrogen atom.

[0127] As the aromatic hydrocarbon group or aromatic heterocyclic group, a group having 3 to 30 carbon atoms is preferred, a group having 4 to 24 carbon atoms is more preferred, and a group having 5 to 20 carbon atoms is further preferred.

[0128] As the aromatic hydrocarbon group, there can be listed a group formed by removing 1 to 4 hydrogen atoms from any aromatic ring of the following compounds, including: compounds consisting of only one aromatic ring such as benzene; compounds in which multiple aromatic rings are directly bonded between one carbon atom such as biphenyl and diphenylbenzene; and condensed-ring aromatic hydrocarbon compounds such as naphthalene, anthracene, phenanthrene, and pyrene.

[0129] Examples of the aromatic heterocyclic group include groups formed by removing 1 to 4 hydrogen atoms from any aromatic heterocyclic ring of the following compounds: compounds consisting of only one aromatic heterocyclic ring, such as thiophene, furan, pyrrole, oxazole, oxadiazole, thiazole, thiadiazole, imidazole, pyridine, pyrimidine, pyrazine, triazine, etc.; compounds in which these compounds consisting of only one aromatic heterocyclic ring are directly bonded to each other via one carbon atom (such as bipyridine); and condensed-ring heteroaromatic compounds such as quinoline, quinoxaline, benzothiophene, benzothiazole, benzimidazole, benzoxazole, indole, carbazole, dibenzofuran, dibenzothiophene, acridine, and phenanthroline.

[0130] Examples of the arylalkylene group include groups in which the above-mentioned aromatic hydrocarbon groups and an alkylene group having 1 to 3 carbon atoms are combined.

[0131] The divalent to tetravalent chain or cyclic hydrocarbon group is preferably a hydrocarbon group having 1 to 12 carbon atoms, more preferably a hydrocarbon group having 1 to 6 carbon atoms, and further preferably a hydrocarbon group having 1 to 4 carbon atoms. The chain hydrocarbon group may be linear or branched.

[0132] In addition, R 1The group may be a group formed by combining two or more of the above-mentioned aromatic hydrocarbon groups, aromatic heterocyclic groups, aryl alkylene groups, and divalent to tetravalent chain hydrocarbon groups.

[0133] In addition, R 1 The group may be a group formed by combining one or more of the above aromatic hydrocarbon groups, aromatic heterocyclic groups, aryl alkylene groups, and divalent to tetravalent chain hydrocarbon groups with a nitrogen atom. Examples of such a group include a group formed by removing 1 to 4 hydrogen atoms from trialkylamines such as trimethylamine or triphenylamine.

[0134] The aromatic hydrocarbon group, aromatic heterocyclic group or arylalkylene group may have one or two or more monovalent substituents.

[0135] Examples of the monovalent substituent include: a fluorine atom; a halogenated alkyl group such as a fluoromethyl group, a difluoromethyl group, and a trifluoromethyl group; a linear or branched alkyl group having 1 to 20 carbon atoms such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, and a tert-butyl group; a cyclic alkyl group having 5 to 7 carbon atoms such as a cyclopentyl group, a cyclohexyl group, and a cycloheptyl group; a linear or branched alkoxy group having 1 to 20 carbon atoms such as a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, an isobutoxy group, a tert-butoxy group, a pentyloxy group, a hexyloxy group, a heptyloxy group, and an octyloxy group; a nitro group; a cyano group; an alkylamino group having an alkyl group having 1 to 10 carbon atoms such as a methylamino group, an ethylamino group, a dimethylamino group, and a diethylamino group; a pyrrolidino group; group), cyclic amine groups such as piperidinyl and morpholinyl; diarylamine groups such as diphenylamine and carbazolyl; acyl groups such as acetyl, propionyl and butyryl; alkenyl groups having 2 to 30 carbon atoms such as styryl; aryl groups having 5 to 20 carbon atoms (specific examples of aryl groups are the same as the above-mentioned aromatic hydrocarbon groups) which may be substituted with halogen atoms such as fluorine atoms or alkyl groups, alkoxy groups, amine groups having 1 to 20 carbon atoms; heterocyclic groups having 4 to 40 carbon atoms and containing at least one of nitrogen atoms, sulfur atoms and oxygen atoms (heterocyclic groups may consist of only one or more heterocyclic groups); It may be composed of a ring, a compound composed of only one aromatic heterocyclic ring, a compound formed by directly bonding multiple rings between one carbon atom, or a fused heterocyclic group. Specific examples of heterocyclic groups include: thiophene ring, furan ring, pyrrole ring, benzothiophene ring, benzofuran ring, indole ring, dibenzothiophene ring, dibenzofuran ring, carbazole ring, thiazole ring, benzothiazole ring, oxazole ring, benzoxazole ring, imidazole ring, benzimidazole ring, pyridine ring, pyrimidine ring, pyrazine ring, pyridazine ring, triazine ring, quinoline ring, isoquinoline ring, quinoxaline ring, benzothiadiazole ring, phenanthridine ring and other specific examples of aromatic heterocyclic groups. ); ester group, thioether group, etc. These groups may be substituted by halogen atoms or heteroelements, alkyl groups, aromatic rings, etc.

[0136] In the above general formula (1), n1 It is an integer of 1 to 4, but is preferably 2 or 3.

[0137] The compound represented by the general formula (1) can be synthesized using a halide having iodine, bromine, chlorine or fluorine and hexahydropyrimidopyrimidine as raw materials by Ullmann coupling reaction, Buchwald-Hartwig amination reaction or nucleophilic substitution reaction.

[0138] In the above general formula (2), X 1 , X 2 The same or different means a nitrogen atom, an oxygen atom, a sulfur atom or a divalent linking group which may have a substituent.

[0139] Examples of the divalent linking group include a divalent hydrocarbon group and a group in which a part of carbon atoms in the hydrocarbon group is substituted with a heteroatom selected from the group consisting of a nitrogen atom, an oxygen atom and a sulfur atom.

[0140] The hydrocarbon group is preferably a hydrocarbon group having 1 to 6 carbon atoms, and more preferably a hydrocarbon group having 1, 2 or 6 carbon atoms.

[0141] The hydrocarbon group may be linear, branched, cyclic, or a combination thereof.

[0142] The divalent hydrocarbon group may be an alkylene group which is a saturated hydrocarbon group, or an unsaturated hydrocarbon group such as an alkenylene group or an alkynylene group.

[0143] In the above general formula (2), L represents a direct bond or a p-valent linking group. In addition, only when p is 2, L is a direct bond.

[0144] Examples of the p-valent linking group include nitrogen atoms, oxygen atoms, sulfur atoms and carbon atoms, as well as hydrocarbon groups or groups obtained by removing p hydrogen atoms from a group obtained by replacing a portion of the carbon atoms of a hydrocarbon group with a heteroatom selected from nitrogen atoms, oxygen atoms and sulfur atoms.

[0145] When the p-valent linking group has a carbon atom, the linking group preferably has 1 to 30 carbon atoms, and more preferably has 1 to 20 carbon atoms.

[0146] The hydrocarbon group may be linear, branched, cyclic, or a combination thereof.

[0147] The hydrocarbon group may be any of a saturated hydrocarbon group, an unsaturated hydrocarbon group, and an aromatic hydrocarbon group.

[0148] Examples of the aromatic hydrocarbon group include groups other than hydrogen atoms in aromatic compounds such as a benzene ring, a naphthalene ring, an anthracene ring, a tetracene ring, a pentacene ring, a triphenylene ring, a pyrene ring, a fluorene ring, and an indene ring.

[0149] In the above general formula (2), R 2 To R 4 are the same or different and represent a monovalent substituent. 1 To m 3 Same or different, represents a number from 0 to 3.

[0150] Examples of the monovalent substituent include: a fluorine atom; a halogenated alkyl group such as a fluoromethyl group, a difluoromethyl group, and a trifluoromethyl group; a linear or branched alkyl group having 1 to 20 carbon atoms such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, and a tert-butyl group; a cyclic alkyl group having 5 to 7 carbon atoms such as a cyclopentyl group, a cyclohexyl group, and a cycloheptyl group; a linear or branched alkoxy group having 1 to 20 carbon atoms such as a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, an isobutoxy group, a tert-butoxy group, a pentyloxy group, a hexyloxy group, a heptyloxy group, and an octyloxy group; a nitro group; a cyano group; an alkylamino group having an alkyl group having 1 to 10 carbon atoms such as a methylamino group, an ethylamino group, a dimethylamino group, and a diethylamino group; a pyrrolidino group; group), cyclic amino groups such as piperidinyl and morpholinyl; diarylamino groups such as diphenylamino and carbazolyl; acyl groups such as acetyl, propionyl and butyryl; alkenyl groups having 2 to 30 carbon atoms such as styryl; aryl groups having 5 to 20 carbon atoms (specific examples of aryl groups are the same as the above-mentioned aromatic hydrocarbon groups) which may be substituted with halogen atoms such as fluorine atoms or alkyl groups, alkoxy groups, amine groups having 1 to 20 carbon atoms; heterocyclic groups having 4 to 40 carbon atoms and containing at least one of nitrogen atoms, sulfur atoms and oxygen atoms which may be substituted with halogen atoms such as fluorine atoms or alkyl groups, alkoxy groups, amine groups having 1 to 20 carbon atoms (heterocyclic groups may consist of only one It may be composed of a ring, or a compound composed of only one aromatic heterocyclic ring, or a compound formed by directly bonding multiple rings between one carbon atom, or a fused heterocyclic group. Specific examples of heterocyclic groups include: thiophene ring, furan ring, pyrrole ring, benzothiophene ring, benzofuran ring, indole ring, dibenzothiophene ring, dibenzofuran ring, carbazole ring, thiazole ring, benzothiazole ring, oxazole ring, benzoxazole ring, imidazole ring, benzimidazole ring, pyridine ring, pyrimidine ring, pyrazine ring, pyridazine ring, triazine ring, quinoline ring, isoquinoline ring, quinoxaline ring, benzothiadiazole ring, phenanthridine ring and other specific examples of aromatic heterocyclic groups. ); ester group, thioether group, etc. These groups may be substituted by halogen atoms or heteroelements, alkyl groups, aromatic rings, etc.

[0151] p in the above general formula (2) represents a number of 1 to 4, and is preferably a number of 1 to 3.

[0152] In addition, n in the above general formula (2) 2It represents a number of 0 or 1, but preferably 0.

[0153] The average thickness of the electron injection layer 8 can be from 1 nm to several μm, but from the viewpoint of an organic EL element that can be driven at a low voltage, it is preferably from 1 nm to 1000 nm, and more preferably from 2 nm to 100 nm. The average thickness of the electron injection layer 8 can be measured by a stylus step profiler or an ellipsometer.

[0154] (Formation method)

[0155] Figure 1 The organic EL element 1 shown can be manufactured by sequentially forming an anode 3, a hole injection layer 4, a hole transport layer 5, a light-emitting layer 6, an electron transport layer 7, an electron injection layer 8, and a cathode 9 on a substrate 2. The formation method of each layer of the anode 3, the hole injection layer 4, the hole transport layer 5, the light-emitting layer 6, the electron transport layer 7, the electron injection layer 8, and the cathode 9 is not particularly limited, and can be formed by appropriately using various formation methods known in the past according to the characteristics of the materials used in each layer. As a method for forming each layer, chemical vapor deposition (CVD) such as plasma CVD, thermal CVD, and laser CVD as a gas phase film formation method; dry plating methods such as vacuum evaporation, sputtering, and ion plating; thermal spraying; and wet plating methods such as electrolytic plating, immersion plating, and electroless plating as a liquid phase film formation method; and printing techniques such as sol-gel method, MOD method, spray pyrolysis method, scraper method using a microparticle dispersion, spin coating method, inkjet method, and screen printing method can be used. These methods are preferably selected according to the characteristics of the materials of each layer, and the manufacturing methods of each layer may also be different.

[0156] The organic EL element 1 of this embodiment can change the emission color by appropriately selecting the material of the light-emitting layer 6, and can also obtain a desired emission color by using a color filter, etc. Therefore, the organic EL element of the present invention can be applied to display devices or lighting devices.

[0157] (Other examples)

[0158] The organic EL element of the present invention is not limited to the organic EL element described in the above embodiment.

[0159] Specifically, in the above embodiment, the organic EL element 1 with a forward structure in which the anode 3 is arranged between the substrate 2 and the light-emitting layer 6 is described as an example, but the organic EL element of the present invention can also be an organic EL element with a reverse structure in which the cathode is arranged between the substrate and the light-emitting layer.

[0160] In the organic EL device of the present invention, the hole transport layer, the electron transport layer, and the electron injection layer may be formed as necessary, or may not be provided.

[0161] In addition, each layer of the anode, hole injection layer, hole transport layer, light emitting layer, electron transport layer, electron injection layer, and cathode may be formed of one layer or two or more layers.

[0162] In addition, the organic EL element of the present invention may also have other layers between each layer of the anode, hole injection layer, hole transport layer, light-emitting layer, electron transport layer, electron injection layer, and cathode. Specifically, for reasons such as further improving the characteristics of the organic EL element, an electron blocking layer may also be provided as required.

[0163] <Display device>

[0164] The display device of the present invention is characterized in that it has the above-mentioned organic electroluminescent element. Since the display device of the present invention has the above-mentioned organic EL element with low driving voltage and excellent driving stability, the driving voltage is low and the driving stability is excellent. In addition to the above-mentioned organic electroluminescent element, the display device of the present invention may also include other components commonly used in display devices.

[0165] <Lighting device>

[0166] The lighting device of the present invention is characterized by having the above-mentioned organic electroluminescent element. Since the lighting device of the present invention has the above-mentioned organic EL element with low driving voltage and excellent driving stability, the driving voltage is low and the driving stability is excellent. In addition to the above-mentioned organic electroluminescent element, the lighting device of the present invention may also include other components commonly used in lighting devices.

[0167] <Organic thin-film solar cells, organic thin-film transistors>

[0168] The present invention is not limited to the above-mentioned embodiments. The organic thin film of the present invention can be used in devices such as organic thin film solar cells and organic thin film transistors.

[0169] The organic thin film solar cell of the present invention includes an organic thin film. For example, when the organic thin film is used in the hole injection layer of the organic thin film solar cell, holes are easily injected, so the hole transmission speed is fast and a higher power generation efficiency can be obtained. Therefore, it is preferred as an organic thin film solar cell or a photoelectric conversion element.

[0170] In addition, the organic thin film transistor of the present invention includes an organic thin film. For example, by providing the above-mentioned organic thin film on an electrode, the mobility can be improved.

[0171] Example

[0172] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples.

[0173] In order to prove the effectiveness of the present invention, an organic EL element was selected as an organic device. A plurality of organic EL elements that depend on a hole injection layer were driven by a constant current, and the stability of the hole injection layer can be evaluated by measuring the brightness change. The embodiments and comparative examples shown here relate to an organic EL element, but the organic film of the present invention can also be used for an organic thin film solar cell or an organic thin film transistor using an organic material.

[0174] The layer structure of the organic EL element 1 is as follows: Figure 1 As shown, the organic EL element is composed of an anode 3, a hole injection layer 4, a hole transport layer 5, a light emitting layer 6, an electron transport layer 7, an electron injection layer 8, and a cathode 9. The characteristics of the organic EL element depending on the hole injection layer 4 were evaluated.

[0175] <Materials used in the hole transport layer 5 , the light emitting layer 6 , the electron transport layer 7 , and the electron injection layer 8 >

[0176] In this embodiment, an excimer complex composed of a donor material and other materials is used as a main component of the light-emitting layer 6 . Furthermore, the donor material is used for the hole transport layer 5 , and other materials are used for the electron transport layer 7 .

[0177] Specifically, Ir(mppy) 3 was used as the light-emitting material, DIC-TRZ was used as the other material used for the formation of the exciplex (electron transport layer 7 ), and Py-hpp 2 was used as the electron injection layer 8 .

[0178] Here, the migration of electrons from the donor material (material used in the hole transport layer 5) to the hole injection layer 4 is closely related to the hole injection characteristics. Therefore, when discussing the hole injection layer 4, the selection of the donor material becomes important. In the past, it was reported that efficient hole injection can be performed between N,N'-diphenyl-N,N'-bis(1-naphthyl)-1,1'-biphenyl-4,4'-diamine (α-NPD), which is a common donor material and has an ionization potential (IP) of about 5.4 eV, and HAT-CN, which is widely used as a hole injection layer material (Yong-Ki Kim, Applied.Physics.Letters., 94, 2009, p063305).

[0179] In this embodiment, in order to discuss the device application of materials with large electron affinity (EA), tris(4-carbazol-9-ylphenyl)amine (TcTa) with an ionization potential (IP) of about 5.7 eV is selected as a donor material that cannot efficiently inject holes from HAT-CN.

[0180] like Figure 3As shown, in the organic EL element 1 of the present embodiment, since there is no energy barrier, the influence of the hole injection layer 4 on the characteristics of the organic EL element 1 can be accurately studied.

[0181] In addition, in this embodiment, the following two types of organic EL elements are produced, namely, Figure 2 When the stacked organic acceptor material shown in A is used as the hole injection layer 4, Figure 2 In the case shown in B, a mixed layer of an organic acceptor material and a donor material is stacked on a single film of an organic acceptor material and used as the hole injection layer 4 .

[0182] <About the organic acceptor material used in the hole injection layer 4>

[0183] In the present embodiment, three types of cyano group-containing compounds, namely, HAT-CN, TNAP, and F6TCNNQ, are mainly used as the organic acceptor material used in the hole injection layer 4 .

[0184] In addition, F16CuPc was used as an organic acceptor material other than the cyano compound.

[0185] The structure of the material used in the hole injection layer 4 is as follows.

[0186] [Chemical formula 3]

[0187]

[0188] In recent years, it has been reported that the size of the electron affinity (EA) of organic acceptor materials depends largely on the charged state of the organic acceptor materials, and when negatively charged, the electron affinity decreases (David Kiefer, Nature Materials, 18, 2019, p149-155). Therefore, molecular orbital calculations [density functional theory, B3LYP, basis function: 6-31G (d)] were used to study the correlation of the electron affinity (EA) of the three materials HAT-CN, TNAP and F6TCNNQ. The results are shown in Table 1.

[0189]

Table 1

[0190] EA (calculated value, eV)* EA (measured value, eV) HAT-CN 4.4 4.3 TNAP 4.7 4.7 F6T 5.0 5.0

[0191] *Molecular orbital calculations [Density functional theory, B3LYP, basis function: 6-31G(d)]

[0192] As shown in Table 1, it can be seen that the electron affinity (EA) varies according to the material. Among the three materials, HAT-CN has the smallest electron affinity (EA) and F6TCNNQ has the largest electron affinity (EA).

[0193] also, Figure 4 2 shows the results of measuring the electron affinity of each material using low-energy inverse photoemission spectroscopy (LEIPS).

[0194] Depend on Figure 4 It can be seen from A that when a 1 nm thick HAT-CN film is formed on ITO, the electron affinity (EA) is about 3.8 eV, but by setting the thickness of HAT-CN to 5 nm, the electron affinity (EA) increases to 4.3 eV.

[0195] In addition, from Figure 4 It can be seen from Figure B that for TNAP, when a 1 nm film is formed on ITO, the electron affinity (EA) is 3.8 eV, and when the thickness is set to 5 nm, the electron affinity (EA) is 4.7 eV. In addition, it can be seen that the electron affinity (EA) is also 4.7 eV when a 5 nm HAT-CN film is formed on ITO and a 1 nm TNAP film is formed thereon.

[0196] In addition, from Figure 4 It can be seen from C that for F6TCNNQ, the electron affinity (EA) is 4.2 eV when a 1 nm film is formed on ITO, and the electron affinity (EA) is 5.0 eV when a 5 nm HAT-CN film is formed on ITO and a 1 nm F6TCNNQ film is formed thereon.

[0197] The above results are schematically shown in Figure 5. When an ultra-thin film is formed on the substrate in this way, due to the charge migration from the substrate, the organic acceptor material is negatively charged, and the electron affinity (EA) becomes smaller. In contrast, the electron affinity (EA) of the organic acceptor material at a position far away from the substrate is large. In addition, it can be seen that there is a strong correlation between the electron affinity (EA) of the neutral state measured by LEIPS and the electron affinity (EA) estimated by molecular orbital calculation. Therefore, in this embodiment, four materials are used to make an organic EL element, but it is believed that the material group with a large electron affinity (EA) calculated by molecular orbital calculation, such as CN6-CP represented by the following structural formula (EA calculated value: 5.4eV, JingLi, Material Horizons, 6, 2019, p107-114) or TECTFCNBN (EA calculated value: 5.3eV, Zhenhua Ci, Organic Electronics, 95, 2021, P106197) is also suitable for the present invention.

[0198] [Chemical formula 4]

[0199]

[0200] <Examples 1 to 8 and Comparative Examples 1 to 9>

[0201] A commercially available transparent glass substrate having an electrode (anode 3) composed of ITO having a thickness of 100 nm was prepared as the substrate 2. On the anode 3 of the substrate 2, a hole injection layer 4 (first layer 4-1, second layer 4-2), a hole transport layer 5, a light emitting layer 6, an electron transport layer 7, an electron injection layer 8 and a cathode 9 were sequentially stacked.

[0202] Table 2 shows the structures of the hole injection layer 4 (first layer 4 - 1 , second layer 4 - 2 ) and the hole transport layer 5 .

[0203] In addition, as a public layer,

[0204] On the hole transport layer 5, Ir(mppy)3, TcTa and DIC-TRZ were co-evaporated as the light-emitting layer 6 [Ir(mppy)3:TcTa:DIC-TRZ (mass ratio) = 0.05:0.475:0.475, thickness 30 nm],

[0205] As the electron transport layer 7, a DIC-TRZ film (thickness 40 nm) was formed.

[0206] As the electron injection layer 8, Py-hpp2 and DIC-TRZ were co-evaporated [Py-hpp2:DIC-TRZ (mass ratio) = 0.4:0.6, thickness 5 nm],

[0207] As the cathode 9, Al (thickness: 100 nm) was laminated and sealed using glass and UV curing resin.

[0208] The structures of materials used in the hole transport layer 5 , the light emitting layer 6 , the electron transport layer 7 , and the electron injection layer 8 are as follows.

[0209] [Chemical formula 5]

[0210]

[0211] In addition, the above-mentioned Py-hpp2 was synthesized according to the method described in T. Sasaki, m. Hasegawa, K. Inagaki, H. Ito, K. Suzuki, T. Oono, K. Morii, T. Shimizu and H. Fukagawa, Nature Communications, 12, pp. 2706.1, DOI: 10.1038 / s41467-021-23067-2.

[0212] For the organic EL elements of Examples 1 to 8 and Comparative Examples 1 to 9 obtained in this way, voltage was applied using a "2400 Source Meter" manufactured by Keithley, and the brightness was measured using an "LS-100" manufactured by Konica Minolta. The relationship between the applied voltage and the brightness was studied, and further, the relationship between the applied voltage and the current density was studied.

[0213] Figures 6 to 8 The current density-voltage characteristics of a plurality of organic EL elements depending on the hole injection layer are shown.

[0214] Table 2 shows the structures of the hole injection layer 4 and the hole transport layer 5 of Examples 1 to 8 and Comparative Examples 1 to 9 and the characteristics of the organic EL element 1 produced using the same. As can be seen from the results shown in the figure and the table, the flow of current depends largely on the hole injection layer 4.

[0215]

Table 2

[0216]

[0217] Observing the results of Comparative Examples 1, 2, and 3, it can be seen that even with the same thickness of the hole injection layer, the hole injection property in the organic EL element depends largely on the electron affinity (EA) of the material. It can be seen that the current density value when compared under the same applied voltage increases in the order of HAT-CN, TNAP, and F6TCNNQ. The greater the electron affinity (EA) of the organic acceptor material used in the hole injection layer, the easier it is to extract electrons from TcTa as a donor material.

[0218] Next, attention is paid to the driving stability of Comparative Examples 1, 2, and 3. It is reported that the driving stability of an organic EL element using Ir(mPPy)3 as a light-emitting material is increased from an initial luminance of 10000 cd / m 2 The luminance half-life during continuous driving is about 300 hours (Tsubasa Sasaki, Nature Communications, 12, 2021, p2706). However, it can be seen that the luminance half-life of the organic EL elements of Comparative Examples 1, 2, and 3 is less than 100 hours, and the driving stability is poor.

[0219] Next, we focus on the results of Example 1 in which a hole injection layer is formed by stacking 5 nm of HAT-CN and 1 nm of F6TCNNQ. Compared with Comparative Example 3 using the same 1 nm of F6TCNNQ, by inserting 5 nm of HAT-CN, it can be confirmed that a higher current density is obtained and hole injection is improved. In addition, the brightness half-life, which is an indicator of driving stability, is 550 hours, and by inserting 5 nm of HAT-CN, a leap of more than 5 times in life is confirmed.

[0220] In addition, for Example 3 in which a hole injection layer is formed by stacking 5 nm of HAT-CN and 1 nm of TNAP, the same results as those of Example 1 were obtained. Compared with Comparative Example 2 using the same 1 nm of TNAP, by inserting 5 nm of HAT-CN, it was confirmed that a higher current density was obtained and the hole injection property was improved. In addition, the brightness half-life, which is an indicator of driving stability, was also confirmed to be about 10 times longer by inserting 5 nm of HAT-CN.

[0221] This shows that a hole injection layer can be formed by forming a film of an organic acceptor material with high electron affinity (EA) on HAT-CN, which is an organic acceptor material with relatively low electron affinity (EA), thereby forming a hole injection layer with excellent hole injection property and driving stability.

[0222] The reason why a hole injection layer using such a plurality of organic acceptor materials is associated with formation of a hole injection layer having excellent hole injection property and driving stability is described below.

[0223] Organic acceptor materials can extract electrons from adjacent molecules or atoms. The greater the electron affinity (EA), the easier it is to extract electrons. Therefore, for the three materials used this time, F6TCNNQ or TNAP is greater than HAT-CN in terms of the ease of attracting electrons. When these organic acceptor materials are formed into films on a substrate, the amount of electron migration from the substrate to the organic acceptor material is greater in F6TCNNQ or TNAP than in HAT-CN, suggesting that F6TCNNQ or TNAP is more negatively charged than HAT-CN. Moreover, this strongly negatively charged state is not a stable state. In the organic EL elements of Comparative Examples 2 and 3, even if holes can be injected relatively, there is a possibility of lack of driving stability.

[0224] In contrast, in Examples 1 and 3 in which HAT-CN is inserted, F6TCNNQ or TNAP is less likely to undergo electron migration from the substrate and can exist in a neutral state without being negatively charged, so that it can contact with the donor material in a state of high electron affinity (EA) and can be driven at a low voltage. In addition, it is believed that the negatively charged state on ITO is unstable, and by existing in a neutral state on HAT-CN, an organic EL element with excellent driving stability can be realized.

[0225] In addition, since the characteristics and life of the organic EL element of Comparative Example 7 are significantly worse than those of Example 1, it can be seen that the order of stacking the organic acceptor material with low electron affinity on the anode and stacking the material with high electron affinity on the organic acceptor material with low electron affinity is important.

[0226] In addition, although the driving voltage of the organic EL element of Example 4 in which F16CuPc was inserted between ITO and F6TCNNQ was higher than that of Comparative Example 3, the driving stability of the organic EL element of Example 4 was excellent, and the results suggesting the assumption related to the driving stability were obtained.

[0227] Next, another embodiment of the present invention is described. Figure 2 Characteristics of the organic EL element of the hole injection layer 4 of B.

[0228] Compared with the organic EL element of Comparative Example 8 having a hole injection layer 4 in which F6TCNNQ is doped in TcTa, the organic EL element of Example 5 in which HAT-CN is inserted between the hole injection layer 4 and the anode 3 has good performance in terms of driving voltage and life. In addition, compared with the organic EL element of Comparative Example 9 having a hole injection layer 4 in which TANP is doped in TcTa, the organic EL element of Example 7 in which HAT-CN is inserted between the hole injection layer 4 and the anode 3 has good performance in terms of driving voltage and life.

[0229] Therefore, even in the case of using a hole injection layer 4 obtained by doping an organic acceptor material in a donor material, it has been found that stacking an organic acceptor material with a small electron affinity on the anode 3 and stacking a layer containing a material with a large electron affinity on the organic acceptor material with a small electron affinity are also effective for reducing the driving voltage and extending the life. In this case, it can be said that a system in which an organic acceptor material (HAT-CN) with a small electron affinity is doped in other organic materials is formed on the anode 3, which is also an embodiment of the present invention.

[0230] <Study of organic acceptor materials with relatively low electron affinity used in the first layer>

[0231] As organic acceptor materials with relatively low electron affinity used in the first layer, various materials (BCF3Ph-F8-Ant, BSBF, FP-ly-POA) were studied. The structures of BCF3Ph-F8-Ant (1,2,3,4,5,6,7,8-octafluoro-9,10-bis[4-(trifluoromethyl)phenyl]anthracene), BSBF (2-(9,9'-spirobifluorene-2-yl)-9,9'-spirobifluorene), and FP-ly-POA (4-fluorobenzylphosphonic acid) are shown below.

[0232] [Chemical formula 6]

[0233]

[0234] Fig. 9 The correlation between the measured and calculated electron affinities of a plurality of organic materials (a1 to a7, b1 to b4) is shown. Fig. 9 The data shown can be used to obtain the following relationship:

[0235] Measured electron affinity = 0.92 × calculated electron affinity + 0.52

[0236] According to this formula, for BCF3Ph-F8-Ant, BSBF and FP-ly-POA, the electron affinities were estimated from the calculated values ​​of the electron affinities.

[0237] The electron affinity of each material is shown in Table 3.

[0238]

Table 3

[0239]

[0240]

[0241] <Examples 9 to 11>

[0242] In the same manner as in Examples 1 to 8, organic EL devices of Examples 9 to 11 were produced by trial using BCF3Ph-F8-Ant and BSBF as the first layer.

[0243] In addition, regarding 4-fluorobenzylphosphoric acid (FP-ly-POA), a material constituting a self-assembled monolayer, a 0.012 mass % ethanol solution was prepared, the ethanol solution was sprayed onto the substrate, and after spin coating at 3500rpm and 45s, it was heated at 105°C for half an hour in a nitrogen atmosphere. Then, after washing the substrate with ethanol, it was dried at 80°C for another half an hour in a nitrogen atmosphere to prepare a self-assembled monolayer of FP-ly-POA, and F6TCNNQ was vapor-deposited on the self-assembled monolayer of FP-ly-POA to form a hole injection layer. Except for this, the organic EL element was prepared in the same manner as in Examples 1 to 8.

[0244] For the organic EL elements of Examples 9 to 11 thus obtained, the relationship between the applied voltage and the luminance, and the relationship between the applied voltage and the current density were studied in the same manner as in Examples 1 to 8. The obtained characteristics are summarized in Table 4. In addition, for comparison, the results of Comparative Example 3 are also recorded in Table 4.

[0245]

Table 4

[0246]

[0247] As shown in Table 4, by inserting the material for the first layer between ITO and F6TCNNQ, the organic EL elements of Examples 9 to 11 can be driven at a lower voltage than that of Comparative Example 3. In addition, almost all of the organic EL elements confirmed higher driving stability than that of Comparative Example 3.

[0248] BCF3Ph-F8-Ant is a fluorine-containing compound, BSBF is an aromatic hydrocarbon, and FP-ly-POA is phosphoric acid and is a material constituting a self-assembled monomolecular film, and therefore it can be shown that these materials are suitable for the first layer.

[0249] Industrial Applicability

[0250] The organic thin film of the present invention can be used for organic EL elements, display devices, lighting devices, organic thin film solar cells, organic thin film transistors, and the like.

[0251] Description of Reference Numerals

[0252] 1: Organic EL element;

[0253] 2: Substrate;

[0254] 3: anode;

[0255] 4: Hole injection layer (organic film);

[0256] 4-1: First floor;

[0257] 4-2: Second floor;

[0258] 5: hole transport layer;

[0259] 6: luminescent layer;

[0260] 7: electron transport layer;

[0261] 8: electron injection layer;

[0262] 9: cathode.

Claims

1. An organic thin film, which is a hole-injecting organic thin film comprising two or more organic acceptor materials having different electron affinities, characterized in that: have: A first layer comprising an organic acceptor material having a relatively low electron affinity; and The second layer, stacked on the first layer, comprises an organic acceptor material having a relatively large electron affinity, The electron affinity of the organic acceptor material with relatively small electron affinity is smaller than the electron affinity of the organic acceptor material with relatively large electron affinity, The first layer is configured for use on the anode side.

2. The organic thin film according to claim 1, wherein The electron affinity of the organic acceptor material with relatively small electron affinity is less than 4.5 eV, The electron affinity of the organic acceptor material having relatively large electron affinity is 4.5 eV or more.

3. The organic thin film according to claim 1, wherein The second layer is a film in which the organic acceptor material having relatively high electron affinity is mixed with other organic materials.

4. The organic thin film according to claim 1, wherein The organic acceptor material is a cyano compound or a fluorine compound.

5. The organic thin film according to claim 1, wherein The organic acceptor material is a compound containing a 2-methylenemalononitrile group.

6. The organic thin film according to claim 1, wherein The organic acceptor material with relatively small electron affinity is any one of the following materials: a fluorine-containing compound, an aromatic hydrocarbon, phosphoric acid, and a material constituting a self-assembled monomolecular film.

7. The organic thin film according to claim 1, wherein The electron affinity of the organic acceptor material having relatively small electron affinity is greater than or equal to 0.35 eV and less than 4.5 eV.

8. An organic electroluminescent element, which is an organic electroluminescent element comprising a cathode, a light-emitting layer and an anode in sequence, characterized in that: An organic thin film according to any one of claims 1 to 7 is provided between the anode and the light-emitting layer, The first layer of the organic thin film is arranged on the anode side.

9. The organic electroluminescent element according to claim 8, wherein The average thickness of the organic thin film is 2 nm to 100 nm.

10. A display device, characterized in that: An organic electroluminescent device according to claim 8.

11. A lighting device, characterized in that: An organic electroluminescent device according to claim 8.

12. An organic thin film solar cell, characterized in that: An organic film comprising the organic film according to any one of claims 1 to 7.

13. An organic thin film transistor, characterized in that: An organic film comprising the organic film according to any one of claims 1 to 7.

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