Photoelectric conversion element and method for manufacturing the same

Abstract

The present invention reduces the dark current ratio. The photoelectric conversion element (10) includes: an anode (16); a cathode (12); an active layer (14) disposed between the anode and the cathode; and at least one electron transport layer (13) disposed between the active layer and the cathode, the electron transport layer comprising an insulating material and a semiconductor material, and the difference between the work function of the electron transport layer and the work function of the cathode is greater than 0.88 eV. In addition, in the photoelectric conversion element, the active layer comprises a p-type semiconductor material and an n-type semiconductor material, and the work function Wf1 of the electron transport layer and the energy level (LUMO) of the LUMO of the n-type semiconductor material satisfy the following formula (2): |LUMO|-Wf1≥0.06 eV (2).

Description

Technical Field

[0001] The present invention relates to a photoelectric conversion element and a method for manufacturing the same. Background Art

[0002] Photoelectric conversion elements are extremely useful devices from the perspectives of, for example, saving energy and reducing carbon dioxide emissions, and have attracted attention.

[0003] A photoelectric conversion element is an element having at least a pair of electrodes consisting of an anode and a cathode, and an active layer disposed between the pair of electrodes. In a photoelectric conversion element, one of the electrodes is made of a transparent or translucent material, and light is incident on the active layer from the transparent or translucent electrode side. The energy (hν) of the light incident on the active layer generates charges (holes and electrons) in the active layer, and the generated holes move to the anode, and the electrons move to the cathode.

[0004] Then, the charges reaching the anode and the cathode are extracted to the outside of the element.

[0005] Photoelectric conversion elements are used, for example, as light detection elements. Photoelectric conversion elements used as light detection elements are used in a state where voltage is applied, and light incident on the element is converted and detected in the form of current. However, even when light is not incident, a weak current flows through the photoelectric conversion element. This current is known as dark current and is the main reason for reducing the accuracy of light detection. Generally, the dark current varies depending on the voltage applied to the photoelectric conversion element.

[0006] Since the voltage applied to the photoelectric conversion element varies depending on the type of device on which the element is mounted, the dark current varies depending on the device on which the element is mounted. From the perspective of versatility, it is preferable that the dark current does not vary depending on the device mounted.

[0007] It is known that there is a structure in which a single-layer electron transport layer is used for the purpose of improving the photoelectric conversion efficiency and other characteristics in a photoelectric conversion element. The single-layer electron transport layer contains zinc oxide and PFN (poly[(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-alternate-2,7-(9,9-dioctyl)fluorene]) or PEI (polyethyleneimine) (see non-patent documents 1 and 2).

[0008] Prior art literature

[0009] Non-patent literature

[0010] Non-patent document 1: Solar Energy Materials & Solar Cells 141 (2015) 248-259

[0011] Non-patent document 2: Organic Electronics 38 (2016) 150-157 Summary of the invention

[0012] Problems to be solved by the invention

[0013] However, in the photoelectric conversion elements disclosed in the above-mentioned Non-Patent Documents 1 and 2, the variation in dark current caused by the variation in voltage applied to the photoelectric conversion element is not sufficiently reduced.

[0014] Means for solving problems

[0015] The present inventors have conducted intensive studies to solve the above problems and have found that if the work function of the electron transport layer and the work function of the cathode satisfy a predetermined relationship, the variation of the dark current caused by the variation of the voltage applied to the photoelectric conversion element can be reduced, thereby completing the present invention.

[0016] That is, the present invention provides the following [1] to

[20] .

[0017] [1] A photoelectric conversion element comprising: an anode; a cathode; an active layer disposed between the anode and the cathode; and at least one electron transport layer disposed between the active layer and the cathode.

[0018] One of the at least one electron transport layer includes an insulating material and a semiconductor material, and a work function (Wf1) of the layer and a work function (Wf2) of the cathode satisfy the following formula (1).

[0019] Wf2-Wf1≥0.88eV (1)

[0020] [2] The photoelectric conversion element according to [1], wherein

[0021] The active layer comprises p-type semiconductor material and n-type semiconductor material.

[0022] The work function (Wf1) of the electron transport layer and the LUMO energy level (LUMO) of the n-type semiconductor material satisfy the following formula (2).

[0023] |LUMO|-Wf1≥0.06eV (2)

[0024] [3] The photoelectric conversion element according to [1] or [2], wherein the n-type semiconductor material is a fullerene derivative.

[0025] [4] The photoelectric conversion element according to [3], wherein the fullerene derivative is C60PCBM.

[0026] [5] A photoelectric conversion element as described in any one of [1] to [4], wherein the work function (Wf3) of the insulating material, the work function (Wf1) of the electron transport layer and the work function (Wf4) of the semiconductor material satisfy the following equations (3) and (4).

[0027] Wf3>Wf1 (3)

[0028] Wf3<Wf4 (4)

[0029] [6] The photoelectric conversion element according to any one of [1] to [5], wherein the semiconductor material is one or more oxide semiconductor materials selected from the group consisting of ZnO, AZO, and GZO.

[0030] [7] The photoelectric conversion element according to any one of [1] to [6], wherein the insulating material is a polymer having an amino group or an alkoxy group.

[0031] [8] The photoelectric conversion element according to [7], wherein the insulating material is ethoxylated polyethyleneimine.

[0032] [9] The photoelectric conversion element as described in any one of [1] to [8], wherein the electron transport layer is a layer obtained by drying and curing a coating film, the coating film comprising the insulating material, the semiconductor material and a solvent with a boiling point of 68° C. or higher.

[0033]

[10] The photoelectric conversion element according to [9], wherein the solvent includes an alcohol solvent having a pKa of 15.5 or more.

[0034]

[11] The photoelectric conversion element according to

[10] , wherein the alcohol solvent includes one or more alcohol solvents selected from the group consisting of ethanol, 2-propanol, and 3-pentanol.

[0035]

[12] The photoelectric conversion element according to any one of [1] to

[11] , wherein the photoelectric conversion element is a light detection element.

[0036]

[13] An image sensor comprising the photoelectric conversion element described in

[12] .

[0037]

[14] A fingerprint recognition device comprising the photoelectric conversion element described in

[12] .

[0038]

[15] A method for manufacturing a photoelectric conversion element, which is the method for manufacturing a photoelectric conversion element according to [1], comprising the following steps:

[0039] The electron transport layer is formed by applying a coating liquid containing the insulating material, the semiconductor material and a solvent having a boiling point of 68° C. or higher to form a coating film, and then drying and curing the coating film.

[0040]

[16] The method for manufacturing a photoelectric conversion element according to

[15] , wherein the semiconductor material is one or more oxide semiconductor materials selected from the group consisting of ZnO, AZO and GZO.

[0041]

[17] The method for producing a photoelectric conversion element according to

[15] or

[16] , wherein the insulating material is a polymer having an amino group or an alkoxy group.

[0042]

[18] The method for producing a photoelectric conversion element according to

[17] , wherein the insulating material is ethoxylated polyethyleneimine.

[0043]

[19] The method for producing a photoelectric conversion element according to any one of

[15] to

[18] , wherein the solvent comprises an alcohol solvent having a pKa of 15.5 or more.

[0044]

[20] The method for producing a photoelectric conversion element according to

[19] , wherein the alcohol solvent comprises one or more alcohol solvents selected from the group consisting of ethanol, 2-propanol, and 3-pentanol.

[0045] Effects of the Invention

[0046] According to the photoelectric conversion element of the present invention, it is possible to reduce the variation of dark current caused by the variation of voltage applied to the photoelectric conversion element. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a diagram schematically showing a configuration example of a photoelectric conversion element.

[0048] Figure 2 It is a diagram schematically showing a configuration example of an image detection unit.

[0049] Figure 3 It is a diagram schematically showing a configuration example of a fingerprint detection unit. DETAILED DESCRIPTION

[0050] Hereinafter, the photoelectric conversion element of the embodiment of the present invention will be described with reference to the accompanying drawings. It should be noted that the accompanying drawings are only schematically shown to the extent that the invention can be understood, the shape, size and configuration of the constituent elements. The present invention is not limited to the following description, and each constituent element can be appropriately changed within the scope of the gist of the present invention. In addition, the structure of the embodiment of the present invention is not necessarily limited to the configuration shown in the accompanying drawings for manufacture or use.

[0051] 1. Photoelectric conversion element

[0052] The photoelectric conversion element of this embodiment includes: an anode; a cathode; an active layer arranged between the anode and the cathode; and at least one electron transport layer arranged between the active layer and the cathode, one of the at least one electron transport layer includes an insulating material and a semiconductor material, and the work function (Wf1) of the layer and the work function (Wf2) of the cathode satisfy the following formula.

[0053] Wf2-Wf1≥0.88eV

[0054] Here, possible configuration examples of the photoelectric conversion element of this embodiment will be described. Figure 1 It is a diagram schematically showing a configuration example of a photoelectric conversion element according to this embodiment.

[0055] like Figure 1 As shown, the photoelectric conversion element 10 of this embodiment is provided on a supporting substrate 11, for example. The photoelectric conversion element 10 includes: a cathode 12 provided in contact with the supporting substrate 11; an electron transport layer 13 provided in contact with the cathode 12; an active layer 14 provided in contact with the electron transport layer 13; a hole transport layer 15 provided in contact with the active layer 14; and an anode 16 provided in contact with the hole transport layer 15.

[0056] This configuration example further includes a sealing substrate 17 provided so as to be in contact with the anode 16 .

[0057] Hereinafter, parameters, components, and a manufacturing method related to the photoelectric conversion element of this embodiment will be described in more detail.

[0058] (Substrate)

[0059] Photoelectric conversion elements are usually formed on a substrate. Electrodes including a cathode and an anode are usually formed on the substrate. The material of the substrate is not particularly limited as long as it is a material that does not undergo chemical changes when forming a layer, especially a layer containing an organic compound. Examples of the material of the substrate include glass, plastic, polymer film, and silicon. When the substrate is opaque, it is preferred that the electrode on the opposite side of the electrode arranged on the opaque substrate side (i.e., the electrode on the side away from the substrate) is a transparent or translucent electrode. In addition, as a substrate, a substrate having an electrode (cathode or anode) described later or a layer structure capable of forming an electrode by further processes such as a patterning process can be used.

[0060] (electrode)

[0061] As the material of the transparent or translucent electrode, for example, a conductive metal oxide film and a translucent metal film can be cited. Specifically, conductive materials such as indium oxide, zinc oxide, tin oxide and indium tin oxide (ITO), indium zinc oxide (IZO), NESA, gold, platinum, silver, and copper as their composites can be cited. As the material of the transparent or translucent electrode, ITO, IZO, and tin oxide are preferred. In addition, as the electrode, a transparent conductive film using organic compounds such as polyaniline and its derivatives, polythiophene and its derivatives as the material can be adopted. The transparent or translucent electrode can be an anode or a cathode.

[0062] If one electrode is transparent or translucent, the other electrode can be an electrode with low light transmittance. As materials for electrodes with low light transmittance, metals and conductive polymers can be cited, for example. Specific examples of materials for electrodes with low light transmittance include metals such as lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, barium, aluminum, scandium, vanadium, zinc, yttrium, indium, cerium, samarium, europium, terbium, ytterbium, and alloys of two or more of these metals; or alloys of one or more of these metals with one or more of the metals selected from the group consisting of gold, silver, platinum, copper, manganese, titanium, cobalt, nickel, tungsten, and tin; graphite, graphite intercalation compounds, polyaniline and its derivatives, polythiophene and its derivatives. As alloys, magnesium-silver alloys, magnesium-indium alloys, magnesium-aluminum alloys, indium-silver alloys, lithium-aluminum alloys, lithium-magnesium alloys, lithium-indium alloys, and calcium-aluminum alloys can be cited.

[0063] In the photoelectric conversion element of the present embodiment, the work function (Wf1) of the electron transport layer and the work function (Wf2) of the cathode satisfy the following formula (1).

[0064] Wf2-Wf1≥0.88eV (1)

[0065] The material of the cathode can be selected in consideration of the work function of the cathode and the work function of the electron transport layer.

[0066] Examples of the cathode material of the present embodiment include ITO (work function: 5.1 eV), Au (work function: 5.2 eV), and Ag (work function: 4.9 eV).

[0067] As the cathode material, ITO is preferred from the viewpoint of light transmittance.

[0068] From the perspective of reducing the change in dark current caused by the change in voltage applied to the photoelectric conversion element, the work function of the electron transport layer (Wf1) and the work function of the cathode (Wf2) preferably satisfy the following formula (1-1), more preferably satisfy the following formula (1-2), and even more preferably satisfy the following formula (1-3).

[0069] Wf2-Wf1≥0.90eV (1-1)

[0070] Wf2-Wf1≥0.93eV (1-2)

[0071] Wf2-Wf1≥0.95eV (1-3)

[0072] In addition, the work function (Wf1) of the electron transport layer and the work function (Wf2) of the cathode preferably satisfy the following formula (1-4), and more preferably satisfy the following formula (1-5).

[0073] Wf2-Wf1≤10eV (1-4)

[0074] Wf2-Wf1≤5eV (1-5)

[0075] The work function of the cathode can be measured using, for example, a Kelvin probe apparatus (for example, FAC-2, manufactured by Riken Keiki Co., Ltd.).

[0076] As the method for forming the electrode, any suitable method known in the art can be used. As the method for forming the electrode, for example, vacuum evaporation, sputtering, ion plating and plating can be cited. The method for forming the electrode may include further steps such as a step of patterning the layer formed by the above method and a step of performing surface treatment.

[0077] (Middle layer)

[0078] like Figure 1 As shown, the photoelectric conversion element may include an additional intermediate layer such as a charge transport layer (electron transport layer, hole transport layer, electron injection layer, hole injection layer) as a further component for improving characteristics such as increasing photoelectric conversion efficiency and reducing dark current.

[0079] As the material used for such an intermediate layer, any suitable material known in the art can be used. Examples of the material for the intermediate layer include halides and oxides of alkali metals or alkaline earth metals such as lithium fluoride.

[0080] Examples of the material used for the intermediate layer include fine particles of inorganic semiconductor materials such as titanium oxide, and a mixture of PEDOT (poly(3,4-ethylenedioxythiophene)) and PSS (poly(4-styrenesulfonate)) (PEDOT:PSS).

[0081] like Figure 1 As shown, the photoelectric conversion element may include a hole transport layer between the anode and the active layer. The hole transport layer has a function of transporting holes from the active layer to the electrode.

[0082] The hole transport layer may be a single layer or may be stacked with two or more layers. The hole transport layer disposed in contact with the anode is sometimes specifically referred to as a hole injection layer. The hole transport layer (hole injection layer) disposed in contact with the anode has the function of promoting the injection of holes into the anode. The hole transport layer (hole injection layer) may be in contact with the active layer.

[0083] The hole transport layer contains a hole transport material. Examples of the hole transport material include polythiophene and its derivatives, aromatic amine compounds, polymer compounds containing a structural unit having an aromatic amine residue, CuSCN, CuI, NiO, and molybdenum oxide (MoO3).

[0084] The photoelectric conversion element of this embodiment may have an electron transport layer between the cathode and the active layer. The electron transport layer has the function of transporting electrons from the active layer to the cathode. The electron transport layer may be in contact with the cathode. The electron transport layer may also be in contact with the active layer. The electron transport layer may be a single layer or may be stacked with two or more layers. In the case where the electron transport layer is two or more layers, as long as at least one electron transport layer is an electron transport layer that satisfies the conditions described. It should be noted that the electron transport layer disposed in contact with the cathode is sometimes particularly referred to as an electron injection layer.

[0085] The electron transport layer of this embodiment includes an insulating material and a semiconductor material, which will be described in detail below.

[0086] (1) Insulating materials

[0087] The work function (Wf3) of the insulating material of this embodiment, the work function (Wf1) of the electron transport layer, and the work function (Wf4) of the semiconductor material may satisfy the following formula (3) and the following formula (4).

[0088] Wf3>Wf1 (3)

[0089] Wf3<Wf4 (4)

[0090] The insulating material or semiconductor material that can be included in the electron transport layer can be selected so as to satisfy this condition.

[0091] Examples of the insulating material that may be included in the electron transport layer of this embodiment include a compound having an alkylene structure, polyvinyl pyrrolidone (PVP), polymethyl methacrylate resin (PMMA), and poly(4-vinylphenol) (P-4VP).

[0092] As the insulating material, a polymer having an amino group or an alkoxy group is preferable.

[0093] Examples of compounds having an alkylene structure include polyalkyleneimines and their derivatives. Examples of polyalkyleneimines and their derivatives include polymers obtained by polymerizing one or more of alkyleneimines having 2 to 8 carbon atoms, particularly alkyleneimines having 2 to 4 carbon atoms, such as ethyleneimine, propyleneimine, butyleneimine, dimethylethyleneimine, pentyleneimine, hexyleneimine, heptyleneimine, and octyleneimine by conventional methods, and polymers chemically modified by reacting these polymers with various compounds.

[0094] As polyalkylene imine and its derivatives, ethoxylated polyethylene imine (PEIE, work function: 4.1 eV) is preferably used because it can effectively improve the work function of the electron transport layer. It is a modified product containing polyethylene imine (PEI) and polyalkylene imine as the main chain and ethylene oxide added to the nitrogen atom in the main chain.

[0095] (2) Semiconductor materials

[0096] Examples of semiconductor materials that can be included in the electron transport layer of this embodiment include metal compounds and semimetals.

[0097] Examples of the metal compound include metal oxides, metal hydroxides, and metal alkoxides. The metal oxide preferably contains a divalent or higher valent metal, and more preferably contains zinc or titanium.

[0098] Examples of metal oxides include zinc oxide (ZnO, work function: 4.5 eV), aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO), titanium oxide, and niobium oxide. Metal oxides containing zinc are preferred, and from the perspective of ease of availability and ease of processing, one or more oxide semiconductor materials selected from the group consisting of ZnO, AZO, and GZO are more preferred.

[0099] Examples of the metal hydroxide include zinc hydroxide, titanium hydroxide, and niobium hydroxide. As the metal hydroxide, a metal hydroxide containing zinc or titanium is preferred, and titanium hydroxide is preferred among them.

[0100] Examples of metal alkoxides include metal methoxides, metal ethoxides, metal propoxides, metal isopropoxides, metal n-butoxides, metal sec-butoxides, metal isobutoxides, and metal tert-butoxides. Metal alkoxides containing titanium are preferred, and titanium (IV) isopropoxide is particularly preferred.

[0101] As examples of semimetals, Si, Ge, As, Sb, and Te can be cited.

[0102] The semiconductor material that can be included in the electron transport layer of the present embodiment is preferably nanoparticles having a particle size of 0.1 nm to 100 nm, for example, from the viewpoint of improving the characteristics of the photoelectric conversion element and facilitating production.

[0103] The weight ratio of the insulating material to the semiconductor material contained in the electron transport layer is generally insulating material:semiconductor material=1:10 to 1:5000, preferably insulating material:semiconductor material=1:50 to 1:2500.

[0104] The intermediate layer is preferably formed by a coating method such as a slit coating method, a blade coating method, a spin coating method, a micro gravure coating method, a gravure printing method, a bar coating method, or an inkjet printing method.

[0105] (Active layer)

[0106] The photoelectric conversion element of this embodiment is an organic photoelectric conversion element having at least one active layer containing an organic material. The active layer contains an organic material, and the organic material contains a polymer compound.

[0107] The active layer of this embodiment preferably has a bulk heterojunction structure including a p-type semiconductor material (electron donating compound) and an n-type semiconductor material (electron accepting compound).

[0108] In this embodiment, the work function (Wf1) of the electron transport layer described above and the energy level (LUMO) of the LUMO of the n-type semiconductor material contained in the active layer preferably satisfy the following formula (2-1), more preferably satisfy the following formula (2-2), and further preferably satisfy the following formula (2-3). Here, "|LUMO|" refers to the absolute value of LUMO.

[0109] |LUMO|-Wf1≥0.1 (2-1)

[0110] |LUMO|-Wf1≥0.2 (2-2)

[0111] |LUMO|-Wf1≥0.25 (2-3)

[0112] In addition, the work function (Wf1) of the electron transport layer and the LUMO energy level (LUMO) of the n-type semiconductor material included in the active layer preferably satisfy the following formula (2-4), and more preferably satisfy the following formula (2-5).

[0113] |LUMO|-Wf1≤1.0 (2-4)

[0114] |LUMO|-Wf1≤0.5 (2-5)

[0115] The preferred p-type semiconductor material and n-type semiconductor material are described in detail below, and the p-type semiconductor material and n-type semiconductor material can be relatively determined based on the HOMO or LUMO energy levels of the selected p-type semiconductor material and n-type semiconductor material.

[0116] The determination of the energy levels of HOMO and LUMO of the semiconductor material (p-type semiconductor material and n-type semiconductor material) of the present embodiment can be carried out according to the method known from the literature, etc., using an existing known measuring device. Specifically, a cyclic voltammetry measuring device (e.g., electrochemical analyzer 600B, manufactured by BAS) can be used for determination.

[0117] The thickness of the active layer is usually 1 nm to 100 μm. In particular, the thickness of the active layer of a photoelectric conversion element used as a light detection element is preferably 500 nm to 1000 nm.

[0118] According to the photoelectric conversion element of this embodiment, by having the above-described configuration, the dark current ratio can be further reduced.

[0119] The dark current ratio can be measured using any suitable measuring device known in the art. An example of the measuring device is a semiconductor parameter analyzer (B1500A, manufactured by Agilent Technologies).

[0120] The dark current ratio is the ratio of the dark current obtained when a higher voltage is applied to the photoelectric conversion element to the dark current obtained when a lower voltage is applied (dark current (when high voltage is applied) / dark current (when low voltage is applied)).

[0121] 2. Method for manufacturing photoelectric conversion element

[0122] The method for producing the photoelectric conversion element of the present embodiment is not particularly limited. The photoelectric conversion element can be produced by a formation method suitable for the material selected when forming each component.

[0123] The manufacturing method of the photoelectric conversion element of the present embodiment is a manufacturing method of the following photoelectric conversion element, which includes an anode; a cathode; an active layer arranged between the anode and the cathode; and at least one electron transport layer arranged between the active layer and the cathode, one of the at least one electron transport layer includes an insulating material and a semiconductor material, and the work function (Wf1) of the layer and the work function (Wf2) of the cathode satisfy the following formula (1), and the manufacturing method includes the following steps: applying a coating liquid including an insulating material, a semiconductor material and a solvent with a boiling point of 68°C or above to form a coating film, and curing the coating film by drying it to form an electron transport layer.

[0124] Wf2-Wf1≥0.88eV (1)

[0125] (1) Electron transport layer formation process

[0126] The electron transport layer of this embodiment can be formed by a coating method using a coating liquid for forming an electron transport layer (hereinafter sometimes referred to as ink). It should be noted that other intermediate layers such as a hole transport layer can also be formed in the same manner.

[0127] Hereinafter, the step (i) and the step (ii) which may be included in the step of forming the electron transport layer which is the main component of the photoelectric conversion element of the present embodiment will be described.

[0128] (Process (i))

[0129] Step (i) is a step of applying a coating liquid containing an insulating material, a semiconductor material, and a solvent having a boiling point of 68° C. or higher to form a coating film.

[0130] The coating object of the coating liquid for forming the electron transport layer varies according to the layer structure and layer formation order of the photoelectric conversion element to be manufactured. For example, in the case where the photoelectric conversion element has a layer structure of substrate / anode / hole transport layer / active layer / electron transport layer / cathode and is a reverse lamination structure formed from the cathode side, the coating object of the coating liquid for forming the electron transport layer is the cathode, the substrate formed with the cathode, or other electron transport layers. In addition, for example, in the case where the photoelectric conversion element is a forward lamination structure formed from the anode side, the coating object of the coating liquid for forming the electron transport layer is the active layer or other electron transport layers.

[0131] As a method of applying the electron transport layer-forming coating liquid onto the object on which the electron transport layer is to be formed, any appropriate coating method can be used.

[0132] As the coating method, slit coating, blade coating, spin coating, micro gravure coating, gravure printing, rod coating, inkjet printing, nozzle coating or capillary coating is preferred, spin coating, capillary coating or rod coating is more preferred, and spin coating is further preferred.

[0133] The electron transport layer-forming coating liquid may be a solution, or may be a dispersion such as a dispersion, an emulsion (emulsion), or a suspension (suspension).

[0134] The electron transport layer-forming coating liquid may contain only one solvent or may be a mixed solvent containing two or more solvents.

[0135] Examples of the solvent having a boiling point of 68° C. or higher that may be contained in the electron transport layer coating liquid include water, alcohols, ketones, and hydrocarbons.

[0136] Specific examples of the alcohol include ethanol, 1-propanol, 2-propanol, 2-butanol, 2-pentanol, 3-pentanol, ethylene glycol, propylene glycol, butoxyethanol, and methoxybutanol.

[0137] Specific examples of ketones include acetone, methyl ethyl ketone, methyl isobutyl ketone, 2-heptanone, and cyclohexanone.

[0138] Specific examples of the hydrocarbon include n-pentane, cyclohexane, n-hexane, benzene, toluene, xylene, tetralin, chlorobenzene, and o-dichlorobenzene.

[0139] The solvent preferably contains an alcohol solvent having a pKa (-logKa, where Ka is an acid dissociation constant) of 15.5 or more in order to further increase the work function of the electron transport layer.

[0140] As such an alcohol solvent, an alcohol solvent having a carbon number of 2 or more can be cited, more specifically, ethanol (boiling point: 78.4°C, pKa: 15.9), 2-propanol (boiling point: 82.6°C, pKa: 16.5) and 3-pentanol (boiling point: 116°C, pKa: 18.2) can be cited. That is, the coating solution for forming the electron transport layer preferably contains one or more alcohol solvents selected from the group consisting of ethanol, 2-propanol and 3-pentanol. By using such an alcohol solvent, the work function of the electron transport layer can be made greater than the work function assumed by the work function of the selected insulating material and semiconductor material, and the work function of the electron transport layer of the existing two-layer structure such as ZnO / PEIE.

[0141] In addition, if the above-mentioned solvent is used, the photoelectric conversion element can be manufactured even without using toxic solvents such as methoxyethanol, which has been used as a solvent for PEIE in the past. Furthermore, even after the active layer is formed, the formation process can be carried out regardless of the stacking order (forward stacking or reverse stacking), so the manufacture of the photoelectric conversion element can be carried out more simply and efficiently.

[0142] When the weight of materials other than the solvent that may be contained in the electron transport layer is defined as 1, the amount of the solvent in the electron transport layer-forming coating liquid is preferably 1 to 10,000 weight, more preferably 10 to 1,000 weight.

[0143] (Step (ii))

[0144] Step (ii) is a step of drying the coating film to solidify it, thereby forming an electron transport layer.

[0145] As a method for curing the coating film by drying it, in other words, as a method for forming an electron transport layer by removing the solvent from the coating film and curing it, any suitable method can be used. Examples of drying methods include direct heating using a hot plate, hot air drying, infrared heating drying, flash lamp annealing drying, and reduced pressure drying.

[0146] (2) Active layer formation process

[0147] The active layer of this embodiment can be formed by a coating method using a coating liquid (ink) for forming an active layer, similarly to the formation process of the electron transport layer described above. Therefore, detailed descriptions of common terms and processes may be omitted.

[0148] The active layer as the main component of the photoelectric conversion element of this embodiment preferably has a bulk heterojunction structure. Therefore, the active layer having a bulk heterojunction structure can be formed by a coating method using a coating solution containing a p-type semiconductor material, an n-type semiconductor material and a solvent.

[0149] In the manufacturing method of the photoelectric conversion element of this embodiment, the step of forming the active layer is the following step: applying a coating liquid containing a p-type semiconductor material, an n-type semiconductor material and a solvent to form a coating film, and drying the coating film to solidify it to form the active layer.

[0150] Hereinafter, the step (i) and the step (ii) which may be included in the step of forming the active layer of the photoelectric conversion element of this embodiment will be described.

[0151] (Process (i))

[0152] Step (i) is a step of applying a coating liquid containing a p-type semiconductor material, an n-type semiconductor material, and a solvent to form a coating film.

[0153] As a method of applying the active layer forming coating liquid onto the coating object on which the active layer is to be formed, any appropriate coating method described above can be used.

[0154] The coating object of the coating liquid for forming the active layer varies depending on the layer structure of the photoelectric conversion element to be manufactured and the order of layer formation. For example, in the case where the photoelectric conversion element has a layer structure of substrate / anode / hole transport layer / active layer / electron transport layer / cathode and is a reverse stacking structure formed from the cathode side, the coating object of the coating liquid for forming the active layer is the electron transport layer. In addition, for example, in the case where the photoelectric conversion element is a forward stacking structure formed from the anode side, the coating object of the coating liquid for forming the active layer is the hole transport layer.

[0155] (Step (ii))

[0156] Step (ii) is a step of forming an active layer by drying the applied film to solidify it.

[0157] As a method for removing the solvent from the coating film, in other words, as a method for removing the solvent from the coating film to form a cured film, any appropriate method described above can be used.

[0158] The process of forming the active layer may include other steps in addition to the above-mentioned steps (i) and (ii) without impairing the object and effect of the present invention.

[0159] The method for producing a photoelectric conversion element may be a method for producing a photoelectric conversion element including two or more active layers. In this case, the steps (i) and (ii) may be repeated two or more times.

[0160] The coating liquid for forming the active layer that can be used may be a solution, or a dispersion liquid such as a dispersion liquid, an emulsion, or a suspension liquid. The coating liquid for forming the active layer contains a p-type semiconductor material, an n-type semiconductor material, and a first solvent, and may further contain a second solvent as required. The components of the coating liquid for forming the active layer of this embodiment are described below.

[0161] Here, terms commonly used in the description of this embodiment are described.

[0162] A "polymer compound" refers to a polymer having a molecular weight distribution and a polystyrene-equivalent number average molecular weight of 1×10 3 Above 1×10 8 The following polymers: The total amount of the structural units contained in the polymer compound is 100 mol%.

[0163] The term "structural unit" refers to a unit existing at least one unit in a polymer compound.

[0164] The "hydrogen atom" may be a protium atom or a deuterium atom.

[0165] The "halogen atom" includes a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.

[0166] The term “having or not having a substituent” includes two aspects: the case where all hydrogen atoms constituting the compound or group are unsubstituted, and the case where part or all of one or more hydrogen atoms are substituted with a substituent.

[0167] Unless otherwise specified, "alkyl" may be any of linear, branched, and cyclic. The number of carbon atoms in a linear alkyl group, excluding the number of carbon atoms in a substituent, is usually 1 to 50, preferably 1 to 30, and more preferably 1 to 20. The number of carbon atoms in a branched or cyclic alkyl group, excluding the number of carbon atoms in a substituent, is usually 3 to 50, preferably 3 to 30, and more preferably 4 to 20.

[0168] The alkyl group may or may not have a substituent. As specific examples of the alkyl group, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, 2-ethylbutyl, n-hexyl, cyclohexyl, n-heptyl, cyclohexylmethyl, cyclohexylethyl, n-octyl, 2-ethylhexyl, 3-n-propylheptyl, adamantyl, n-decyl, 3,7-dimethyloctyl, 2-ethyloctyl, 2-n-hexyldecyl, n-dodecyl, tetradecyl, hexadecyl, octadecyl, eicosyl, etc. can be cited. As examples of alkyl groups with substituents, trifluoromethyl, pentafluoroethyl, perfluorobutyl, perfluorohexyl, perfluorooctyl, 3-phenylpropyl, 3-(4-methylphenyl)propyl, 3-(3,5-di-n-hexylphenyl)propyl and 6-ethoxyhexyl can be cited.

[0169] The "aryl group" refers to an atomic group remaining after removing one hydrogen atom directly bonded to a carbon atom constituting a ring from an aromatic hydrocarbon which may have a substituent.

[0170] The aryl group may or may not have a substituent. Specific examples of the aryl group include phenyl, 1-naphthyl, 2-naphthyl, 1-anthryl, 2-anthryl, 9-anthryl, 1-pyrenyl, 2-pyrenyl, 4-pyrenyl, 2-fluorenyl, 3-fluorenyl, 4-fluorenyl, 2-phenylphenyl, 3-phenylphenyl, 4-phenylphenyl, and groups in which these groups further have a substituent such as an alkyl group, an alkoxy group, an aryl group, or a fluorine atom.

[0171] The "alkoxy group" may be any of linear, branched, and cyclic. The number of carbon atoms in a linear alkoxy group is usually 1 to 40, preferably 1 to 10, excluding the number of carbon atoms in the substituent. The number of carbon atoms in a branched or cyclic alkoxy group is usually 3 to 40, preferably 4 to 10, excluding the number of carbon atoms in the substituent.

[0172] The alkoxy group may be substituted. Specific examples of the alkoxy group include methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, tert-butoxy, n-pentyloxy, n-hexyloxy, cyclohexyloxy, n-heptyloxy, n-octyloxy, 2-ethylhexyloxy, n-nonyloxy, n-decyloxy, 3,7-dimethyloctyloxy and lauryloxy.

[0173] The carbon number of the "aryloxy group" is usually 6 to 60, preferably 6 to 48, not including the carbon number of the substituent.

[0174] The aryloxy group may be substituted. Specific examples of the aryloxy group include phenoxy, 1-naphthyloxy, 2-naphthyloxy, 1-anthryloxy, 9-anthryloxy, 1-pyreneoxy, and groups in which these groups further have a substituent such as an alkyl group, an alkoxy group, or a fluorine atom.

[0175] The "alkylthio group" may be any of linear, branched, and cyclic. The number of carbon atoms of a linear alkylthio group excluding the number of carbon atoms of the substituent is usually 1 to 40, preferably 1 to 10. The number of carbon atoms of a branched or cyclic alkylthio group excluding the number of carbon atoms of the substituent is usually 3 to 40, preferably 4 to 10.

[0176] The alkylthio group may be substituted. Specific examples of the alkylthio group include methylthio, ethylthio, propylthio, isopropylthio, butylthio, isobutylthio, tert-butylthio, pentylthio, hexylthio, cyclohexylthio, heptylthio, octylthio, 2-ethylhexylthio, nonylthio, decylthio, 3,7-dimethyloctylthio, laurylthio and trifluoromethylthio.

[0177] The "arylthio group" has generally 6 to 60 carbon atoms, preferably 6 to 48 carbon atoms, not including the carbon atoms of the substituent.

[0178] The arylthio group may have a substituent. Examples of the arylthio group include a phenylthio group, a C1-C12 alkoxyphenylthio group (the term "C1-C12" means that the group immediately following it has 1 to 12 carbon atoms. The same applies to the following), a C1-C12 alkylphenylthio group, a 1-naphthylthio group, a 2-naphthylthio group, and a pentafluorophenylthio group.

[0179] "P-valent heterocyclic group" (P represents an integer greater than 1) refers to an atomic group remaining after removing P hydrogen atoms directly bonded to carbon atoms or heteroatoms constituting the ring from a heterocyclic compound which may or may not have a substituent. Among the P-valent heterocyclic groups, "P-valent aromatic heterocyclic group" is preferred. "P-valent aromatic heterocyclic group" refers to an atomic group remaining after removing P hydrogen atoms directly bonded to carbon atoms or heteroatoms constituting the ring from an aromatic heterocyclic compound which may or may not have a substituent.

[0180] Examples of the substituent which the heterocyclic compound may have include a halogen atom, an alkyl group, an aryl group, an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, a monovalent heterocyclic group, a substituted amino group, an acyl group, an imide residue, an amide group, an imide group, a substituted oxycarbonyl group, an alkenyl group, an alkynyl group, a cyano group, and a nitro group.

[0181] The aromatic heterocyclic compound includes not only compounds in which the heterocyclic ring itself exhibits aromaticity, but also compounds in which an aromatic ring is further fused to a heterocyclic ring that does not exhibit aromaticity.

[0182] Among the aromatic heterocyclic compounds, specific examples of compounds in which the heterocycle itself exhibits aromaticity include oxadiazole, thiadiazole, thiazole, oxazole, thiophene, pyrrole, phosphole, furan, pyridine, pyrazine, pyrimidine, triazine, pyridazine, quinoline, isoquinoline, carbazole and dibenzophosphole.

[0183] Specific examples of the aromatic heterocyclic compound in which an aromatic ring is fused to a heterocyclic ring that does not exhibit aromaticity include phenoxazine, phenothiazine, dibenzoborole, dibenzosilole, and benzopyran.

[0184] The monovalent heterocyclic group has usually 2 to 60 carbon atoms, preferably 4 to 20 carbon atoms, excluding the carbon atoms of the substituent.

[0185] The monovalent heterocyclic group may or may not have a substituent. Specific examples of the monovalent heterocyclic group include thienyl, pyrrolyl, furyl, pyridyl, piperidyl, quinolyl, isoquinolyl, pyrimidyl, triazinyl, and groups in which these groups have a substituent such as an alkyl group or an alkoxy group.

[0186] "Substituted amino group" refers to an amino group having a substituent. Examples of substituents that the amino group may have include an alkyl group, an aryl group, and a monovalent heterocyclic group. As the substituent, an alkyl group, an aryl group, or a monovalent heterocyclic group is preferred. The number of carbon atoms in the substituted amino group is usually 2 to 30.

[0187] Examples of the substituted amino group include dialkylamino groups such as dimethylamino and diethylamino groups, and diarylamino groups such as diphenylamino groups, bis(4-methylphenyl)amino groups, bis(4-tert-butylphenyl)amino groups, and bis(3,5-di-tert-butylphenyl)amino groups.

[0188] The carbon number of the "acyl group" is usually about 2 to 20, preferably 2 to 18. Specific examples of the acyl group include acetyl, propionyl, butyryl, isobutyryl, pivaloyl, benzoyl, trifluoroacetyl and pentafluorobenzoyl.

[0189] "Imine residue" refers to an atomic group remaining after removing a hydrogen atom directly bonded to a carbon atom or a nitrogen atom constituting a carbon-nitrogen double bond from an imine compound. "Imine compound" refers to an organic compound having a carbon-nitrogen double bond in a molecule. Examples of imine compounds include aldimine, ketimines, and compounds in which the hydrogen atom bonded to the nitrogen atom constituting a carbon-nitrogen double bond in aldimine is substituted with an alkyl group or the like.

[0190] The imine residue generally has about 2 to 20 carbon atoms, and preferably has 2 to 18 carbon atoms. Examples of the imine residue include groups represented by the following formulae.

[0191] [Chemistry 1]

[0192]

[0193] The "amide group" refers to an atomic group remaining after removing one hydrogen atom bonded to a nitrogen atom from an amide. The number of carbon atoms in the amide group is usually 1 to 20, preferably 1 to 18.

[0194] Specific examples of the amide group include formamide, acetamide, propionamide, butyramide, benzamide, trifluoroacetamide, pentafluorobenzamide, diformamide, diacetamide, dipropionamide, dibutyramide, dibenzamide, bis(trifluoroacetamide) and bis(pentafluorobenzamide).

[0195] The "acylimido group" refers to an atomic group remaining after removing one hydrogen atom bonded to a nitrogen atom from an imide. The number of carbon atoms in the acylimido group is usually 4 to 20. Specific examples of the acylimido group include groups represented by the following formulae.

[0196] [Chemistry 2]

[0197]

[0198] The "substituted oxycarbonyl group" refers to a group represented by R'-O-(C=O)-.

[0199] Here, R' represents an alkyl group, an aralkyl group or a monovalent heterocyclic group.

[0200] The substituted oxycarbonyl group has usually 2 to 60 carbon atoms, preferably 2 to 48 carbon atoms.

[0201] Specific examples of the substituted oxycarbonyl group include methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, isopropoxycarbonyl, butoxycarbonyl, isobutoxycarbonyl, tert-butoxycarbonyl, pentyloxycarbonyl, hexyloxycarbonyl, cyclohexyloxycarbonyl, heptyloxycarbonyl, octyloxycarbonyl, 2-ethylhexyloxycarbonyl, nonyloxycarbonyl, decyloxycarbonyl, 3,7-dimethyloctyloxycarbonyl, dodecyloxycarbonyl, trifluoromethoxycarbonyl, pentafluoroethoxycarbonyl, perfluorobutoxycarbonyl, perfluorohexyloxycarbonyl, perfluorooctyloxycarbonyl, phenoxycarbonyl, naphthoxycarbonyl and pyridyloxycarbonyl.

[0202] The "alkenyl group" may be any of linear, branched, and cyclic. The number of carbon atoms of a linear alkenyl group is usually 2 to 30, preferably 3 to 20, excluding the number of carbon atoms of the substituent. The number of carbon atoms of a branched or cyclic alkenyl group is usually 3 to 30, preferably 4 to 20, excluding the number of carbon atoms of the substituent.

[0203] The alkenyl group may or may not have a substituent. Specific examples of the alkenyl group include vinyl, 1-propenyl, 2-propenyl, 2-butenyl, 3-butenyl, 3-pentenyl, 4-pentenyl, 1-hexenyl, 5-hexenyl, 7-octenyl, and groups in which these groups further have a substituent such as an alkyl group or an alkoxy group.

[0204] The "alkynyl group" may be any of linear, branched, and cyclic. The number of carbon atoms of a linear alkynyl group, excluding the number of carbon atoms of the substituent, is usually 2 to 20, preferably 3 to 20. The number of carbon atoms of a branched or cyclic alkynyl group, excluding the number of carbon atoms of the substituent, is usually 4 to 30, preferably 4 to 20.

[0205] The alkynyl group may or may not have a substituent. Specific examples of the alkynyl group include ethynyl, 1-propynyl, 2-propynyl, 2-butynyl, 3-butynyl, 3-pentynyl, 4-pentynyl, 1-hexynyl, 5-hexynyl, and groups in which these groups further have a substituent such as an alkyl group or an alkoxy group.

[0206] (p-type semiconductor material)

[0207] The p-type semiconductor material that can be included in the active layer of the photoelectric conversion element of the present embodiment is preferably a polymer compound having a predetermined weight average molecular weight in terms of polystyrene.

[0208] Here, the polystyrene-equivalent weight average molecular weight refers to a weight average molecular weight calculated using a standard sample of polystyrene by gel permeation chromatography (GPC).

[0209] Regarding the polystyrene-equivalent weight average molecular weight of the p-type semiconductor material as a polymer compound, particularly from the perspective of reducing the dark current ratio, it is preferably from 40,000 to 200,000, more preferably from 40,000 to 150,000, and particularly from the perspective of improving solubility in solvents, it is further preferably from 45,000 to 150,000.

[0210] As the p-type semiconductor material of this embodiment, for example, polyvinylcarbazole and its derivatives, polysilane and its derivatives, polysiloxane derivatives containing an aromatic amine structure in the side chain or the main chain, polyaniline and its derivatives, polythiophene and its derivatives, polypyrrole and its derivatives, polyphenylene vinylene and its derivatives, polythiophenylene vinylene and its derivatives, polyfluorene and its derivatives, and the like can be cited.

[0211] The p-type semiconductor material is preferably a polymer compound including a structural unit represented by the following formula (I) and / or a structural unit represented by the following formula (II).

[0212] [Chemistry 3]

[0213]

[0214] In formula (I), Z represents a group represented by any one of the following formulae (Z-1) to (Z-7). 1 and Ar 2 represents a trivalent aromatic heterocyclic group which may be the same or different.

[0215] [Chemistry 4]

[0216] -Ar 3 - (II)

[0217] In formula (II), Ar 3 It represents a divalent aromatic heterocyclic group.

[0218] [Chemistry 5]

[0219]

[0220] In formulas (Z-1) to (Z-7), R represents a hydrogen atom, a halogen atom, an amino group, an alkyl group, an aryl group, an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, a monovalent heterocyclic group, a substituted amino group, an acyl group, an imide residue, an amide group, an imide group, a substituted oxycarbonyl group, an alkenyl group, an alkynyl group, a cyano group, or a nitro group. In each of formulas (Z-1) to (Z-7), when there are two Rs, they may be the same or different from each other.

[0221] The structural unit represented by formula (I) is preferably a structural unit represented by the following formula (I-1).

[0222] [Chemistry 6]

[0223]

[0224] In the formula (I-1), Z has the same meaning as described above.

[0225] Z is preferably a group represented by any one of formula (Z-4) to formula (Z-7).

[0226] Examples of the structural unit represented by formula (I-1) include structural units represented by the following formulae (501) to (505).

[0227] [Chemistry 7]

[0228]

[0229] In the above formulae (501) to (505), R has the same meaning as above. When there are two Rs, the two Rs may be the same as or different from each other.

[0230] Among the structural units represented by the above formulae (501) to (505), the structural unit represented by the following formula is preferred.

[0231] [Chemistry 8]

[0232]

[0233] In the formula, R has the same meaning as above, and two Rs may be the same as or different from each other.

[0234] Ar 3 The divalent aromatic heterocyclic group represented by is usually 2 to 60 carbon atoms, preferably 4 to 60 carbon atoms, and more preferably 4 to 20 carbon atoms. 3 The divalent aromatic heterocyclic group represented by may have a substituent. 3 Examples of substituents that the divalent aromatic heterocyclic group represented may have include a halogen atom, an amino group, an alkyl group, an aryl group, an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, a monovalent heterocyclic group, a substituted amino group, an acyl group, an imide residue, an amide group, an imide group, a substituted oxycarbonyl group, an alkenyl group, an alkynyl group, a cyano group, and a nitro group.

[0235] As Ar 3 Examples of the divalent aromatic heterocyclic group represented by include groups represented by the following formulae (101) to (185).

[0236] [Chemistry 9]

[0237]

[0238] [Chemistry 10]

[0239]

[0240] [Chemistry 11]

[0241]

[0242] [Chemistry 12]

[0243]

[0244] In formulae (101) to (185), R has the same meaning as above. When there are two or more R, the two or more R may be the same as or different from each other.

[0245] As the structural unit represented by the above formula (II), structural units represented by the following formulas (II-1) to (II-6) are preferred.

[0246] [Chemistry 13]

[0247]

[0248] In formula (II-1) to formula (II-6), X 1 and X 2 Each independently represents an oxygen atom or a sulfur atom, and R has the same meaning as above. When there are two or more R, the two or more R may be the same as or different from each other.

[0249] From the viewpoint of the availability of the raw material compounds, X in Formula (II-1) to Formula (II-6) 1 and X 2 Preferably, they are all sulfur atoms.

[0250] The P-type semiconductor material is preferably a polymer compound including a structural unit having a thiophene skeleton.

[0251] The polymer compound used as the P-type semiconductor material may contain two or more structural units of the formula (I), or may contain two or more structural units of the formula (II).

[0252] In order to improve solubility in a solvent, the polymer compound as a P-type semiconductor material may contain a structural unit represented by the following formula (III).

[0253] [Chemistry 14]

[0254] -Ar 4 - (III)

[0255] In formula (III), Ar 4 It represents an arylene group.

[0256] Ar 4 The arylene group represented here refers to the atomic group remaining after removing two hydrogen atoms from an aromatic hydrocarbon with or without a substituent. Aromatic hydrocarbons also include compounds having condensed rings, and compounds in which two or more selected from the group consisting of independent benzene rings and condensed rings are bonded directly or via a divalent group such as vinylene.

[0257] Examples of the substituent which the aromatic hydrocarbon may have include the same substituents as exemplified as the substituent which the heterocyclic compound may have.

[0258] The carbon number of the part excluding the substituent in the arylene group is usually 6 to 60, preferably 6 to 20. The carbon number of the arylene group including the substituent is usually 6 to 100.

[0259] Examples of arylene groups include phenylene groups (for example, formulas 1 to 3 below), naphthalene diyl groups (for example, formulas 4 to 13 below), anthracene diyl groups (for example, formulas 14 to 19 below), biphenyl diyl groups (for example, formulas 20 to 25 below), terphenyl diyl groups (for example, formulas 26 to 28 below), condensed ring compound groups (for example, formulas 29 to 35 below), fluorene diyl groups (for example, formulas 36 to 38 below), and benzofluorene diyl groups (for example, formulas 39 to 46 below).

[0260] [Chemistry 15]

[0261]

[0262] [Chemistry 16]

[0263]

[0264] [Chemistry 17]

[0265]

[0266] [Chemistry 18]

[0267]

[0268] [Chemistry 19]

[0269]

[0270] [Chemistry 20]

[0271]

[0272] [Chemistry 21]

[0273]

[0274] [Chemistry 22]

[0275]

[0276] In Formulae 1 to 46, R as a substituent has the same meaning as above. Two or more R may be the same as or different from each other.

[0277] The structural unit constituting the polymer compound serving as a p-type semiconductor material may be a structural unit formed by combining and linking two or more structural units selected from the structural unit represented by formula (I), the structural unit represented by formula (II) and the structural unit represented by formula (III).

[0278] In the case where a polymer compound serving as a p-type semiconductor material contains a structural unit represented by formula (I) and / or a structural unit represented by formula (II), the total amount of the structural unit represented by formula (I) and the structural unit represented by formula (II) is generally 20 to 100 mol % in the total structural units (100 mol %) contained in the polymer compound, and is preferably 40 to 100 mol %, and more preferably 50 to 100 mol % in order to improve the charge transport properties of the p-type semiconductor material.

[0279] Specific examples of the polymer compound as the p-type semiconductor material include polymer compounds represented by the following formulae P-1 to P-6.

[0280] [Chemistry 23]

[0281]

[0282] [Chemistry 24]

[0283]

[0284] The active layer forming coating liquid of the present embodiment may contain only one kind of p-type semiconductor material, or may contain two or more kinds of p-type semiconductor materials in combination at any ratio.

[0285] (n-type semiconductor material)

[0286] The n-type semiconductor material (electron accepting compound) that can be included in the active layer of this embodiment can be selected in consideration of the work function of the electron transport layer so that the difference between the work function of the electron transport layer and the LUMO energy level of the n-type semiconductor material described above is 0.06 eV or more.

[0287] The n-type semiconductor material may be a low molecular compound or a high molecular compound.

[0288] Examples of n-type semiconductor materials that are low molecular weight compounds include oxadiazole derivatives, anthraquinone dimethane and its derivatives, benzoquinone and its derivatives, naphthoquinone and its derivatives, anthraquinone and its derivatives, tetracyanoanthraquinone dimethane and its derivatives, fluorenone derivatives, diphenyl dicyanoethylene and its derivatives, diphenoquinone derivatives, metal complexes of 8-hydroxyquinoline and its derivatives, C 60 Fullerenes such as fullerene and their derivatives, and phenanthrene derivatives such as bathocuproin.

[0289] Examples of n-type semiconductor materials that are polymer compounds include polyvinylcarbazole and its derivatives, polysilane and its derivatives, polysiloxane derivatives having an aromatic amine structure in the side chain or the main chain, polyaniline and its derivatives, polythiophene and its derivatives, polypyrrole and its derivatives, polyphenylene vinylene and its derivatives, polythiophenylene vinylene and its derivatives, polyquinoline and its derivatives, polyquinoxaline and its derivatives, and polyfluorene and its derivatives.

[0290] As the n-type semiconductor material, at least one selected from fullerene and fullerene derivatives is preferred, and a fullerene derivative is more preferred.

[0291] As an example of fullerene, C 60 Fullerene, C 70 Fullerene, C 76 Fullerene, C 78 Fullerene and C 84 Fullerene. Examples of fullerene derivatives include derivatives of these fullerenes. Fullerene derivatives refer to compounds in which at least a part of fullerene is modified.

[0292] Examples of the fullerene derivative include compounds represented by the following formula (N-1) to formula (N-4).

[0293] [Chemistry 25]

[0294]

[0295] In formula (N-1) to formula (N-4), R a represents an alkyl group, an aryl group, a monovalent heterocyclic group or a group having an ester structure. a They may be the same as or different from each other.

[0296] R b represents an alkyl group or an aryl group. b They may be the same as or different from each other.

[0297] As R a Examples of the group having an ester structure include a group represented by the following formula (19).

[0298] [Chemistry 26]

[0299]

[0300] In formula (19), u1 represents an integer of 1 to 6. u2 represents an integer of 0 to 6. R c represents an alkyl group, an aryl group or a monovalent heterocyclic group.

[0301] As C60 Examples of fullerene derivatives include the following compounds.

[0302] [Chemistry 27]

[0303]

[0304] Examples of C70 fullerene derivatives include the following compounds.

[0305] [Chemistry 28]

[0306]

[0307] Specific examples of fullerene derivatives include [6,6]-phenyl-C61 butyric acid methyl ester (C60PCBM, [6,6]-Phenyl C61 butyric acid methyl ester), [6,6]-phenyl-C71 butyric acid methyl ester (C70PCBM, [6,6]-Phenyl C71 butyric acid methyl ester), [6,6]-phenyl-C85 butyric acid methyl ester (C84PCBM, [6,6]-Phenyl C85 butyric acid methyl ester) and [6,6]-thienyl-C61 butyric acid methyl ester.

[0308] The active layer forming coating liquid of the present embodiment may contain only one type of n-type semiconductor material, or may contain two or more types of n-type semiconductor materials in combination at any ratio.

[0309] (First solvent)

[0310] The solvent may be selected in consideration of its solubility in the selected p-type semiconductor material and n-type semiconductor material and its characteristics (boiling point, etc.) corresponding to the drying conditions when forming the active layer.

[0311] The first solvent as the main solvent (good solvent) is an aromatic hydrocarbon (hereinafter referred to as aromatic hydrocarbon) which may have a substituent (eg, an alkyl group or a halogen atom). The first solvent is preferably selected in consideration of the solubility of the selected p-type semiconductor material and n-type semiconductor material.

[0312] Examples of such aromatic hydrocarbons include toluene, xylenes (e.g., o-xylene, m-xylene, p-xylene), trimethylbenzenes (e.g., mesitylene, 1,2,4-trimethylbenzene (pseudocumene)), butylbenzenes (e.g., n-butylbenzene, sec-butylbenzene, tert-butylbenzene), methylnaphthalene (e.g., 1-methylnaphthalene), tetralin, indane, chlorobenzene, and dichlorobenzene (o-dichlorobenzene).

[0313] The first solvent may be composed of only one type of aromatic hydrocarbon or may be composed of two or more types of aromatic hydrocarbons. The first solvent is preferably composed of only one type of aromatic hydrocarbon.

[0314] The first solvent preferably contains one or more selected from the group consisting of toluene, o-xylene, m-xylene, p-xylene, mesitylene, pseudocumene, n-butylbenzene, sec-butylbenzene, tert-butylbenzene, methylnaphthalene, tetralin, indane, chlorobenzene and o-dichlorobenzene, and more preferably contains o-xylene, pseudocumene, tetralin, chlorobenzene or o-dichlorobenzene.

[0315] (Second solvent)

[0316] The second solvent (poor solvent) is a solvent selected from the viewpoint of improving the solubility of the n-type semiconductor material. Examples of the second solvent include ketone solvents such as acetone, methyl ethyl ketone, cyclohexanone, acetophenone, and propiophenone; and ester solvents such as ethyl acetate, butyl acetate, phenyl acetate, ethyl cellosolve acetate, methyl benzoate, butyl benzoate, and benzyl benzoate.

[0317] The second solvent is preferably acetophenone, propiophenone or benzyl benzoate.

[0318] (Combination of the first solvent and the second solvent)

[0319] Examples of the combination of the first solvent and the second solvent include the combinations shown in Table 1 below.

[0320] [Table 1]

[0321] (Table 1)

[0322] No. 1 solvent Second solvent o-Xylene Acetophenone Pseudocumene Benzyl benzoate Tetralin Phenylpropiotone Pseudocumene Phenylpropiotone

[0323] (Weight ratio of the first solvent to the second solvent)

[0324] From the viewpoint of further improving the solubility of the p-type semiconductor material and the n-type semiconductor material, the weight ratio of the first solvent to the second solvent (first solvent / second solvent) is preferably in the range of 85 / 15 to 97 / 3.

[0325] (Total weight percentage of the first solvent and the second solvent in the active layer forming coating liquid)

[0326] When the total weight of the coating liquid for forming an active layer is 100 weight %, from the perspective of further improving the solubility of the p-type semiconductor material and the n-type semiconductor material, the total weight of the first solvent and the second solvent contained in the coating liquid for forming an active layer of this embodiment is preferably 90 weight % or more, more preferably 92 weight % or more, and further preferably 95 weight % or more, and from the perspective of easily forming a layer of a certain thickness or more by increasing the concentration of the p-type semiconductor material and the n-type semiconductor material in the coating liquid for forming an active layer, it is preferably 99 weight % or less, more preferably 98 weight % or less, and further preferably 97.5 weight % or less.

[0327] (Optional solvent)

[0328] The coating liquid for forming an active layer of the present embodiment may also contain an optional solvent other than the first solvent and the second solvent. When the total weight of all solvents contained in the coating liquid for forming an active layer is assumed to be 100 wt %, the content of the optional solvent is preferably 5 wt % or less, more preferably 3 wt % or less, and further preferably 1 wt % or less. As the optional solvent, a solvent having a higher boiling point than the second solvent is preferred.

[0329] (Optional Ingredients)

[0330] The coating liquid for forming an active layer of the present embodiment may contain, in addition to the first solvent, the second solvent, the p-type semiconductor material and the n-type semiconductor material, optional components such as ultraviolet absorbers, antioxidants, sensitizers for enhancing the function of generating charges by utilizing the absorbed light, and light stabilizers for increasing stability against ultraviolet rays, within the limit not impairing the purpose and effect of the present invention.

[0331] (Concentrations of p-type semiconductor material and n-type semiconductor material in active layer forming coating solution)

[0332] The total concentration of the p-type semiconductor material and the n-type semiconductor material in the coating solution for forming the active layer of the present embodiment is preferably 0.01 wt% to 20 wt%, more preferably 0.01 wt% to 10 wt%, further preferably 0.01 wt% to 5 wt%, and particularly preferably 0.1 wt% to 5 wt%. In the coating solution for forming the active layer, the p-type semiconductor material and the n-type semiconductor material may be dissolved or dispersed. The p-type semiconductor material and the n-type semiconductor material are preferably at least partially dissolved, and more preferably completely dissolved.

[0333] (Preparation of coating solution for forming active layer)

[0334] The coating liquid for forming the active layer of this embodiment can be prepared by a known method. For example, it can be prepared by the following methods: a method of mixing a first solvent and a second solvent to prepare a mixed solvent, and adding a p-type semiconductor material and an n-type semiconductor material to the obtained mixed solvent; a method of adding a p-type semiconductor material to the first solvent, adding an n-type semiconductor material to the second solvent, and then mixing the first solvent and the second solvent to which the materials are added; and the like.

[0335] The first solvent, the second solvent, the p-type semiconductor material, and the n-type semiconductor material may be heated to a temperature not higher than the boiling point of the solvent and mixed.

[0336] After the first solvent and the second solvent are mixed with the p-type semiconductor material and the n-type semiconductor material, the resulting mixture can be filtered using a filter, and the resulting filtrate can be used as ink. As the filter, for example, a filter made of a fluororesin such as polytetrafluoroethylene (PTFE) can be used.

[0337] (Application of photoelectric conversion element)

[0338] The photoelectric conversion element of this embodiment can generate a photoelectromotive force between electrodes by irradiating light, and can operate as a solar cell. In addition, a plurality of solar cells can be integrated to form a thin-film solar cell module.

[0339] In addition, the photoelectric conversion element of this embodiment can flow photocurrent by irradiating light from the transparent or translucent electrode side when a voltage is applied between the electrodes, and can work as a light detection element (photosensor). In addition, it can also be used as an image sensor by integrating multiple photosensors.

[0340] (Application examples of photoelectric conversion elements)

[0341] The photoelectric conversion element according to the embodiment of the present invention described above can be suitably applied to detection units provided in various electronic devices such as workstations, personal computers, portable information terminals, entry and exit management systems, digital cameras, and medical equipment.

[0342] The photoelectric conversion element (light detection element) of the present invention can be appropriately applied to image detection units (image sensors) for solid-state imaging devices such as X-ray imaging devices and CMOS image sensors, detection units for detecting specific features of certain biological bodies such as fingerprint detection units, face detection units, vein detection units and iris detection units, and detection units of optical biosensors such as pulse oximeters, etc., which are possessed by the electronic devices exemplified above.

[0343] Hereinafter, configuration examples of an image detection unit for a solid-state imaging device and a fingerprint detection unit for a biometric information authentication device (fingerprint recognition device) among detection units of a photoelectric conversion element according to an embodiment of the present invention to which the present invention can be suitably applied will be described with reference to the drawings.

[0344] (Image Detection Unit)

[0345] Figure 2 It is a diagram schematically showing a configuration example of an image detection section for a solid-state imaging device.

[0346] The image detection unit 1 includes: a CMOS transistor substrate 20; an interlayer insulating film 30 arranged in a manner covering the CMOS transistor substrate 20; a photoelectric conversion element 10 of an embodiment of the present invention arranged on the interlayer insulating film 30; an interlayer wiring portion 32 arranged in a manner penetrating the interlayer insulating film 30 and electrically connecting the CMOS transistor substrate 20 and the photoelectric conversion element 10; a sealing layer 40 arranged in a manner covering the photoelectric conversion element 10; and a color filter 50 arranged on the sealing layer 40.

[0347] The CMOS transistor substrate 20 has any suitable configuration known in the art in accordance with the design.

[0348] The CMOS transistor substrate 20 includes transistors, capacitors, and the like formed within the thickness of the substrate, and includes functional elements such as CMOS transistor circuits (MOS transistor circuits) for realizing various functions.

[0349] Examples of the functional element include a floating diffusion element, a reset transistor, an output transistor, and a selection transistor.

[0350] By using such functional elements, wirings, etc., a signal reading circuit and the like are manufactured on the CMOS transistor substrate 20 .

[0351] The interlayer insulating film 30 may be made of any suitable insulating material known in the art, such as silicon oxide, insulating resin, etc. The interlayer wiring portion 32 may be made of any suitable conductive material (wiring material) known in the art, such as copper, tungsten, etc. The interlayer wiring portion 32 may be, for example, an in-hole wiring formed simultaneously with the formation of the wiring layer, or may be an embedded plug formed separately from the wiring layer.

[0352] The sealing layer 40 may be made of any suitable material known in the art as long as it can prevent or suppress the penetration of harmful substances such as oxygen and water that may deteriorate the function of the photoelectric conversion element 10. The sealing layer 40 may also be made of the sealing substrate 17 described above.

[0353] As the color filter 50, for example, a primary color filter made of any suitable material known in the art and corresponding to the design of the image detection unit 1 can be used. In addition, as the color filter 50, a complementary color filter that can be thinner than the primary color filter can also be used. As the complementary color filter, for example, a color filter composed of three colors (yellow, cyan, magenta), three colors (yellow, cyan, transparent), three colors (yellow, transparent, magenta) and a combination of three colors (transparent, cyan, magenta) can be used. They can be configured in any suitable configuration corresponding to the design of the photoelectric conversion element 10 and the CMOS transistor substrate 20, provided that they can generate color image data.

[0354] The light received by the photoelectric conversion element 10 through the color filter 50 is converted into an electrical signal according to the amount of received light by the photoelectric conversion element 10 and output to the outside of the photoelectric conversion element 10 through the electrode in the form of a received light signal, that is, an electrical signal corresponding to the object.

[0355] Next, the received light signal output from the photoelectric conversion element 10 is input to the CMOS transistor substrate 20 via the interlayer wiring portion 32, is read by a signal reading circuit manufactured on the CMOS transistor substrate 20, and is processed by any other suitable existing known functional portion not shown, thereby generating image information based on the photographed object.

[0356] (Fingerprint detection unit)

[0357] Figure 3 FIG. 1 is a diagram schematically showing a configuration example of a fingerprint detection unit integrally configured with a display device.

[0358] The display device 2 of the portable information terminal includes a fingerprint detection unit 100 including the photoelectric conversion element 10 according to the embodiment of the present invention as a main component, and a display panel unit 200 provided on the fingerprint detection unit 100 and displaying a predetermined image.

[0359] In this configuration example, the fingerprint detection unit 100 is provided in a region substantially coinciding with the display region 200 a of the display panel unit 200 . In other words, the display panel unit 200 is integrally stacked above the fingerprint detection unit 100 .

[0360] When fingerprint detection is performed only in a partial area of ​​the display area 200 a , the fingerprint detection unit 100 may be provided only corresponding to the partial area.

[0361] The fingerprint detection unit 100 includes the photoelectric conversion element 10 of the embodiment of the present invention as a functional unit that performs substantial functions. The fingerprint detection unit 100 may include any suitable existing known components such as a protection film (not shown), a supporting substrate, a sealing substrate, a sealing component, a barrier film, a bandpass filter, and an infrared cut-off film in a manner corresponding to a design that can obtain desired characteristics. The fingerprint detection unit 100 may also adopt the configuration of the image detection unit described above.

[0362] The photoelectric conversion element 10 may be included in the display region 200a in any manner. For example, two or more photoelectric conversion elements 10 may be arranged in a matrix.

[0363] As described above, the photoelectric conversion element 10 is provided on the supporting substrate 11 or the sealing substrate, and electrodes (anodes or cathodes) are provided on the supporting substrate 11 in a matrix form, for example.

[0364] The light received by the photoelectric conversion element 10 is converted into an electrical signal corresponding to the amount of received light by the photoelectric conversion element 10 and output to the outside of the photoelectric conversion element 10 via the electrode in the form of a received light signal, that is, an electrical signal corresponding to the photographed fingerprint.

[0365] In this configuration example, the display panel unit 200 is configured as an organic electroluminescent display panel (organic EL display panel) including a touch sensor panel. Instead of the organic EL display panel, the display panel unit 200 may be configured as a display panel having any suitable existing known configuration, such as a liquid crystal display panel including a light source such as a backlight.

[0366] The display panel unit 200 is provided on the fingerprint detection unit 100 described above. The display panel unit 200 includes an organic electroluminescent element (organic EL element) 220 as a functional unit that performs substantial functions. The display panel unit 200 may further include any suitable existing known components such as a glass substrate (support substrate 210 or sealing substrate 240), a sealing component, a barrier film, a polarizing plate such as a circular polarizing plate, and a touch sensor panel 230 in a manner corresponding to the desired characteristics.

[0367] In the configuration example described above, the organic EL element 220 is used as a light source for pixels in the display region 200 a and is also used as a light source for fingerprint imaging in the fingerprint detection unit 100 .

[0368] Here, the operation of the fingerprint detection unit 100 will be briefly described.

[0369] When performing fingerprint recognition, the fingerprint detection unit 100 detects the fingerprint using the light emitted from the organic EL element 220 of the display panel unit 200. Specifically, the light emitted from the organic EL element 220 passes through the components existing between the organic EL element 220 and the photoelectric conversion element 10 of the fingerprint detection unit 100, and is reflected by the skin (finger surface) of the fingertip of the finger placed in contact with the surface of the display panel unit 200 in the display area 200a. At least a portion of the light reflected from the finger surface passes through the components existing therebetween and is received by the photoelectric conversion element 10, and is converted into an electrical signal corresponding to the amount of light received by the photoelectric conversion element 10. Then, the converted electrical signal constitutes image information related to the fingerprint on the finger surface.

[0370] The portable information terminal including the display device 2 compares the obtained image information with fingerprint data for fingerprint recognition recorded in advance through any suitable procedure known in the art to perform fingerprint recognition.

[0371] Example

[0372] Hereinafter, examples will be described in order to explain the present invention in further detail. However, the present invention is not limited to the following examples.

[0373] <Example 1> Production and evaluation of photoelectric conversion element

[0374] (Manufacturing of photoelectric conversion elements)

[0375] An ITO thin film (cathode) was formed on a glass substrate by sputtering to a thickness of 150 nm. The surface of the glass substrate was subjected to ozone UV treatment.

[0376] Next, with respect to 10 g of 3-pentanol, 0.1 g of a 1 wt% polyethyleneimine ethoxylate (PEIE) aqueous solution (manufactured by Aldrich, trade name polyethyleneimine, 80% ethoxylated solution, weight average molecular weight 110,000) and 1 g of a solution containing 10 wt% zinc oxide / isopropyl alcohol dispersion (manufactured by TAYCA, product name: HTD-711Z) were mixed to prepare a coating solution for forming an electron transport layer.

[0377] The obtained coating liquid for forming an electron transport layer was applied onto the ITO thin film of the glass substrate treated with ozone UV by spin coating to form a coating film.

[0378] The glass substrate with the coating film formed thereon was heated at 120° C. for 10 minutes using a hot plate to cure the formed coating film, thereby forming an electron transport layer on the ITO thin film serving as the cathode. The thickness of the obtained electron transport layer was 50 nm.

[0379] The weight ratio (p / n ratio) of the polymer compound P-1 represented by the following formula as a p-type semiconductor material and the weight ratio (p / n ratio) of C60PCBM (manufactured by Frontier Carbon, trade name: E100) as an n-type semiconductor material is 1 / 1.75. The obtained mixture is added to a mixed solvent of o-xylene and acetophenone (o-xylene / acetophenone=95 / 5 (weight ratio)) so that the content of the p-type semiconductor material is 2% by weight relative to the mixed solvent, and stirred at 60°C for 10 hours to dissolve it, thereby obtaining a coating solution for forming an active layer.

[0380] [Chemistry 29]

[0381]

[0382] The obtained coating liquid for forming an active layer was applied to the electron transport layer formed on the glass substrate by spin coating to form a coating film. The obtained coating film was dried by heating it for 10 minutes on a hot plate heated to 100° C., thereby forming an active layer. The thickness of the obtained active layer was 550 nm.

[0383] Molybdenum oxide (MoO 3 ) was evaporated to a thickness of about 30 nm on the obtained active layer using a resistance heating evaporation device, thereby forming a hole transport layer.

[0384] A silver (Ag) layer was deposited on the obtained hole transport layer to a thickness of about 80 nm to form an anode, thereby manufacturing a photoelectric conversion element (light detection element).

[0385] A UV curing agent is applied onto a sealing substrate (glass substrate), and after the substrate and the glass substrate are bonded together so that the UV curing agent surrounds the obtained photoelectric conversion element, the photoelectric conversion element is sealed by irradiating the substrate with UV light.

[0386] The planar shape of the obtained photoelectric conversion element when viewed in the thickness direction was a square of 2 mm×2 mm.

[0387] (Evaluation of Photoelectric Conversion Element)

[0388] The manufactured photoelectric conversion element and related parameters were measured and calculated as described below. The results are shown in Table 2 below.

[0389] (1) Evaluation of dark current ratio

[0390] The dark current ratio of the manufactured photoelectric conversion element was evaluated. Here, the dark current ratio refers to the ratio of the dark current obtained when a voltage of 10 V is applied to the dark current obtained when a voltage of 2 V is applied (dark current (10 V) / dark current (2 V)).

[0391] The dark current was measured using a semiconductor parameter analyzer (B1500A, manufactured by Agilent Technologies) when a reverse bias voltage of 10 V and 2 V was applied. The dark current ratio was calculated based on the obtained dark current values.

[0392] (2) Determination of the LUMO energy level of n-type semiconductor materials

[0393] The energy level of LUMO of the n-type semiconductor material C60PCBM included in the active layer was estimated by cyclic voltammetry (CV).

[0394] The CV measurement was performed under the same conditions as the method described in Advanced Materials, Vol. 18, 2006, pp. 789 to 794. The equipment and materials used were as follows.

[0395] CV measurement device: BAS electrochemical analyzer 600B

[0396] Supporting electrolyte: dehydrated acetonitrile solution containing 0.1 M tetrabutylammonium hexafluorophosphate (TBAPF6, manufactured by Aldrich)

[0397] Working electrode: platinum foil / n-type semiconductor material (dropping solution dissolved in chloroform)

[0398] Counter electrode: Platinum foil

[0399] Reference electrode: Ag / AgCl electrode

[0400] Standard potential: Ferrocene

[0401] As a result, the energy level of LUMO of C60PCBM is -4.3 eV.

[0402] (3) Determination of the work function (WF) of the electron transport layer

[0403] The coating liquid for forming the electron transport layer was applied to the glass substrate, and the coating liquid was heated at 120°C for 10 minutes using a hot plate. The obtained electron transport layer was measured using a Kelvin probe device to determine the work function of the electron transport layer. The Kelvin probe device used was FAC-2 from Riken Keiki Co., Ltd. Gold (WF: 5.1 eV) was used as a calibration reference sample. The work function of the electron transport layer was 3.77 eV.

[0404] (4) Determination of cathode work function (WF)

[0405] An ITO film (cathode) was formed on a glass substrate with a thickness of 150 nm, and the formed ITO film was measured using a Kelvin probe device to determine the work function of the cathode. The Kelvin probe device used was FAC-2 from Riken Keiki Co., Ltd. Gold (WF: 5.1 eV) was used as a calibration reference sample. The work function of the cathode was 4.80 eV.

[0406] (5) Calculation of ΔWF and ΔE

[0407] Based on the obtained LUMO energy level (LUMO) of C60PCBM (n-type semiconductor material included in the active layer), the work function of the electron transport layer (Wf1) and the work function of the cathode (Wf2), ΔWF and ΔE were calculated by the following formulae.

[0408] ΔWF=Wf2-Wf1

[0409] ΔE=|LUMO|-Wf1

[0410] <Example 2>

[0411] A photoelectric conversion element was produced and evaluated in the same manner as in Example 1 except that 2-propanol was used instead of 3-pentanol used as a solvent in the electron transport layer-forming coating liquid.

[0412] <Example 3>

[0413] A photoelectric conversion element was produced and evaluated in the same manner as in Example 1 except that ethanol was used instead of 3-pentanol used as a solvent in the electron transport layer-forming coating liquid.

[0414] <Comparative Example 1>

[0415] (Manufacturing of photoelectric conversion elements)

[0416] An ITO thin film (cathode) was formed on a glass substrate by sputtering to a thickness of 150 nm. The surface of the glass substrate was subjected to ozone UV treatment.

[0417] With respect to 10 g of water, 0.1 g of a 1 wt % aqueous solution of polyethyleneimine ethoxylate (PEIE) (manufactured by Aldrich, trade name polyethyleneimine, 80% ethoxylated solution, weight average molecular weight 110,000) was mixed, and a photoelectric conversion element was manufactured and evaluated in the same manner as in Example 1 except that the coating liquid for forming an electron transport layer was used.

[0418] <Comparative Example 2>

[0419] A photoelectric conversion element was produced and evaluated in the same manner as in Example 1 except that a 10 wt % zinc oxide / isopropyl alcohol dispersion (manufactured by TAYCA, product name: HTD-711Z) was diluted 10 times with 3-pentanol and the diluted electron transport layer-forming coating liquid was used.

[0420] <Comparative Example 3>

[0421] A 10 wt % zinc oxide / isopropyl alcohol dispersion (manufactured by TAYCA, product name: HTD-711Z) was diluted 10 times with 3-pentanol, and the diluted solution was used as a coating solution for forming the first electron transport layer and applied by spin coating onto the ITO thin film of the glass substrate subjected to ozone UV treatment.

[0422] The glass substrate coated with the coating liquid for forming the first electron transport layer was heated at 120° C. for 10 minutes using a hot plate to form the first electron transport layer on the ITO thin film serving as the cathode.

[0423] Next, a 1 wt% aqueous solution of polyethyleneimine ethoxylate (PEIE) (manufactured by Aldrich, trade name polyethyleneimine, 80% ethoxylated solution, weight average molecular weight 110000) was diluted 100 times with 2-methoxyethanol, and the diluted solution was used as a coating solution for forming the second electron transport layer, and was applied to the first electron transport layer by spin coating. The second electron transport layer was formed on the first electron transport layer by heating at 120° C. for 10 minutes using a hot plate. In this way, the electron transport layer of Comparative Example 3 has a two-layer structure in which the first electron transport layer and the second electron transport layer are stacked.

[0424] Thereafter, a photoelectric conversion element was produced in the same manner as in Example 1 and evaluated.

[0425] <Comparative Example 4>

[0426] A photoelectric conversion element was produced and evaluated in the same manner as in Example 1 except that methanol was used instead of 3-pentanol used as a solvent in the electron transport layer-forming coating liquid.

[0427] [Table 2]

[0428] (Table 2)

[0429]

[0430] As can be seen from the above-mentioned embodiments and comparative examples, in the photoelectric conversion elements of embodiments 1 to 3 in which a single-layer electron transport layer including ZnO as a semiconductor material and PEIE as an insulating material is formed using a specified solvent, the work function of the electron transport layer can be significantly increased compared to comparative examples 1 to 4 that do not satisfy the above-mentioned conditions. In particular, the work function can be increased compared to comparative example 3 having an existing two-layer structure of ZnO / PEIE and comparative example 4 having a single-layer structure including ZnO and PEIE but using methanol as a solvent.

[0431] It was thus confirmed that the difference ΔWf between the work function of the electron transport layer and the work function of the cathode can be increased, and can be greater than the LUMO energy level of the n-type semiconductor material contained in the active layer, so the difference ΔE between the work function of the electron transport layer and the LUMO energy level of the n-type semiconductor material can be further increased. As a result, it was confirmed that the dark current ratio can be further reduced.

[0432] As described above, the photoelectric conversion element of the present invention has little variation in dark current even when the voltage applied to the photoelectric conversion element varies, and can therefore be flexibly applied to various applications requiring different operating voltages without making special design changes.

[0433] Explanation of symbols

[0434] 1 Image detection unit

[0435] 2 Display device

[0436] 10 Photoelectric conversion element

[0437] 11. 210 Support base plate

[0438] 12 Cathode

[0439] 13 Electron transport layer

[0440] 14 Active layer

[0441] 15. Hole transport layer

[0442] 16 Anode

[0443] 17. 240 sealing substrate

[0444] 20 CMOS transistor substrate

[0445] 30 interlayer insulation film

[0446] 32 Interlayer wiring section

[0447] 40 Sealing layer

[0448] 50 Color Filters

[0449] 100 Fingerprint detection unit

[0450] 200 Display panel unit

[0451] 200a Display area

[0452] 220 Organic EL elements

[0453] 230 Touch sensor panel

Claims

1. A photoelectric conversion element comprising: an anode; a cathode; an active layer disposed between the anode and the cathode; and at least one electron transport layer disposed between the active layer and the cathode, One of the at least one electron transport layer comprises an insulating material and a semiconductor material, and a work function Wf1 of the layer and a work function Wf2 of the cathode satisfy the following formula (1): The active layer comprises a p-type semiconductor material and an n-type semiconductor material, The work function Wf1 of the electron transport layer and the energy level LUMO of the LUMO of the n-type semiconductor material satisfy the following formula (2): Wf2-Wf1≥0.88eV (1) |LUMO|-Wf1≥0.06eV (2).

2. The photoelectric conversion element according to claim 1, wherein The n-type semiconductor material is a fullerene derivative.

3. The photoelectric conversion element according to claim 2, wherein: The fullerene derivative is C60PCBM.

4. The photoelectric conversion element according to claim 1, wherein The work function Wf3 of the insulating material, the work function Wf1 of the electron transport layer, and the work function Wf4 of the semiconductor material in the electron transport layer satisfy the following equations (3) and (4), Wf3>Wf1 (3) Wf3<Wf4 (4).

5. The photoelectric conversion element according to claim 1, wherein The semiconductor material is one or more oxide semiconductor materials selected from the group consisting of ZnO, AZO and GZO.

6. The photoelectric conversion element according to claim 1, wherein The insulating material is a polymer having an amino group or an alkoxy group.

7. The photoelectric conversion element according to claim 6, wherein: The insulating material is ethoxylated polyethyleneimine.

8. The photoelectric conversion element according to claim 1, wherein The electron transport layer is a layer obtained by drying and curing a coating film containing the insulating material, the semiconductor material, and a solvent having a boiling point of 68° C. or higher.

9. The photoelectric conversion element according to claim 8, wherein The solvent includes an alcohol solvent having a pKa of 15.5 or more.

10. The photoelectric conversion element according to claim 9, wherein The alcohol solvent includes one or more alcohol solvents selected from the group consisting of ethanol, 2-propanol, and 3-pentanol.

11. The photoelectric conversion element according to claim 1, wherein The photoelectric conversion element is a light detection element. 12 . An image sensor comprising the photoelectric conversion element according to claim 11 .

13. A fingerprint recognition device comprising the photoelectric conversion element according to claim 11.

14. A method for manufacturing a photoelectric conversion element, which is the method for manufacturing a photoelectric conversion element according to claim 1, comprising the following steps: The electron transport layer is formed by applying a coating liquid including the insulating material, the semiconductor material and a solvent having a boiling point of 68° C. or higher to form a coating film, and drying and curing the coating film.

15. The method for manufacturing a photoelectric conversion element according to claim 14, wherein: The semiconductor material is one or more oxide semiconductor materials selected from the group consisting of ZnO, AZO and GZO.

16. The method for manufacturing a photoelectric conversion element according to claim 14 or 15, wherein: The insulating material is a polymer having an amino group or an alkoxy group.

17. The method for manufacturing a photoelectric conversion element according to claim 16, wherein: The insulating material is ethoxylated polyethyleneimine.

18. The method for manufacturing a photoelectric conversion element according to claim 14 or 15, wherein: The solvent includes an alcohol solvent having a pKa of 15.5 or more.

19. The method for manufacturing a photoelectric conversion element according to claim 18, wherein: The alcohol solvent includes one or more alcohol solvents selected from the group consisting of ethanol, 2-propanol, and 3-pentanol.

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