JP2021190520A - Photoelectric conversion element - Google Patents

Abstract

To provide a photoelectric conversion element with excellent photoelectric conversion efficiency, in which dark current can be suppressed.SOLUTION: A photoelectric conversion element includes an anode, a photoelectric conversion unit including at least two photoelectric conversion layers that are continuous, and a cathode. The photoelectric conversion unit includes at least two kinds of photoelectric conversion layers selected from a photoelectric conversion layer (PEL1) including a semiconductor particle (A1) whose surface is processed with a hole-transporting ligand, a photoelectric conversion layer (PEL2) including a semiconductor particle (A2) whose surface is processed with an electron-transporting ligand, a photoelectric conversion layer (PEL3) including a semiconductor particle (A3) whose surface is processed with both the hole-transporting ligand and the electron-transporting ligand, and a photoelectric conversion layer (PEL4) including a mixture of the semiconductor particle (A1) and the semiconductor particle (A2).SELECTED DRAWING: None

Description

The present invention relates to a photoelectric conversion element.

Photoelectric conversion elements that convert light energy into electrical energy are used in solar cells, photosensors, copiers, and the like. Of these, optical sensors that use near-infrared light as light energy are attracting attention for their use in night vision, ranging, security, semiconductor wafer inspection, and the like.

By the way, in recent years, it has been reported that semiconductor particles (quantum dots) such as PbS are used as materials for photoelectric conversion such as photoelectric conversion elements and solar cells. For example, Non-Patent Document 1 reports that by substituting ethanedithiol for oleic acid around the semiconductor particles of PbSe, the semiconductor particles are brought closer to each other and the electrical conductivity is improved. Further, Patent Document 1 describes ultrafine particles in which a plurality of ultrafine particles such as CdS are bonded by a molecular chain such as benzenedithiol, and can be used for various purposes such as optical materials and electronic materials. It has been disclosed. Patent Document 2 discloses that by substituting oleic acid around the semiconductor particles of PbSe with 2-aminoethane-1-thiol or the like, the semiconductor particles are closer to each other and a high photocurrent value can be obtained. There is. In Patent Document 3, the energy level of PbS quantum dots is controlled by using a halide salt of benzenethiol, benzenedithiol, 3-mercaptopropionic acid, ethylenediamine, tetrabutylammonium, etc. as a ligand instead of oleic acid. It is suggested that the characteristics of the photoelectric conversion element can be improved.

Japanese Unexamined Patent Publication No. 7-60109 International Publication No. 2014/105353 Special Table 2017-516320 Gazette

J. M. Luther et al., "Structure, Optical, and Electrical Properties of Self-Assembled Films of PbSe Nanocrystals Treated with 1,2,2-Ethanethi

However, in the above invention, it is necessary to further improve the photoelectric conversion ability. Further, in light detection applications, the dark current that causes noise cannot be sufficiently suppressed, which has been a problem. Therefore, an object to be solved by the present invention is to provide a photoelectric conversion element capable of excellent photoelectric conversion efficiency and suppression of dark current.

The present inventors have reached the present invention as a result of repeated diligent studies to solve the above problems.
That is, the present invention
A semiconductor particle having a photoelectric conversion unit having an anode, at least two continuous photoelectric conversion layers, and a cathode, wherein the photoelectric conversion unit is surface-treated with a hole transporting ligand. A photoelectric conversion layer (PEL1) containing (A1), a photoelectric conversion layer (PEL2) containing semiconductor particles (A2) surface-treated with an electron-transporting ligand, and a surface of both a hole-transporting ligand and an electron-transporting ligand. At least selected from the group consisting of a photoelectric conversion layer (PEL3) containing the processed semiconductor particles (A3) and a photoelectric conversion layer (PEL4) containing a mixture of the semiconductor particles (A1) and the semiconductor particles (A2). The present invention relates to a photoelectric conversion element having two types of photoelectric conversion layers.

The present invention also relates to the photoelectric conversion element having a photoelectric conversion layer in which at least one selected from the group consisting of the semiconductor particles (A1), (A2) and (A3) contains a compound semiconductor.

Further, in the present invention, the photoelectric conversion unit has (PEL1) / (PEL2), (PEL1) / (PEL3), (PEL3) / (PEL2), (PEL1) / (PEL3) / (from the anode side. The present invention relates to the above-mentioned photoelectric conversion element arranged in the order of PEL2), (PEL1) / (PEL4), (PEL4) / (PEL2), or (PEL1) / (PEL4) / (PEL2).

The present invention also relates to the photoelectric conversion element in which the energy level of the highest occupied orbital (HOMO) of the hole transporting ligand is 0.2 eV or more larger than the energy level of HOMO of the electron transporting ligand.

The present invention also relates to the photoelectric conversion element in which the energy level of the lowest empty orbit (LUMO) of the hole transporting ligand is 0.2 eV or more larger than the energy level of LUMO of the electron transporting ligand.

The present invention also relates to the photoelectric conversion element in which at least one selected from the group consisting of the semiconductor particles (A1), (A2) and (A3) can absorb an electromagnetic wave having a wavelength of 700 to 2500 nm.

Further, the present invention, the semiconductor particles (A1), (A2) and at least one member selected from the group consisting of (A3) is, PbS, photoelectric comprising at least one selected from the group consisting of PbSe and Ag ₂ S The present invention relates to the photoelectric conversion element having a conversion layer.

According to the present invention, it is possible to obtain a photoelectric conversion element capable of excellent photoelectric conversion efficiency and suppressing dark current.

Hereinafter, embodiments of the present invention will be described.
<Photoelectric conversion material>
The photoelectric conversion material used for the photoelectric conversion layer is a semiconductor particle (A1) surface-treated with a hole-transporting ligand, a semiconductor particle (A2) surface-treated with an electron-transporting ligand, or a hole-transporting property. It is characterized by containing any of semiconductor particles (A3) surface-treated with both a ligand and an electron-transporting ligand. Examples of the semiconductor particles in the semiconductor particles (A1), (A2) or (A3) include the semiconductor particles described below, and these may be the same or different. However, the semiconductor particles (A1) and (A2) exclude the case where they are semiconductor particles (A3).

<Semiconductor particles>
The semiconductor particles referred to in the present specification refer to particles made of semiconductors having an average particle size of 0.5 nm to 100 nm. From the viewpoint of improving stability and photoelectric conversion efficiency, the average particle size of the semiconductor particles is preferably 1 nm or more, more preferably 1.5 nm or more, still more preferably 2 nm or more, and improve film forming property and photoelectric conversion efficiency. From the viewpoint of allowing the particles to grow, it is preferably 20 nm or less, more preferably 10 nm or less. The particle size of the semiconductor particles in the present specification is a numerical value measured by observation with a transmission electron microscope.

The semiconductor particles preferably contain compound semiconductors. The compound semiconductor consists of a group consisting of group 1 element, group 2 element, group 10 element, group 11 element, group 12 element, group 13 element, group 14 element, group 15 element, group 16 element and group 17 element. It is preferably a semiconductor composed of a compound containing at least two or more selected elements. It is preferable that the semiconductor particles can absorb electromagnetic waves having a wavelength of 700 to 2500 nm.

An electromagnetic wave having a wavelength of 700 to 2500 nm is generally called near-infrared light (also referred to as near-infrared light), and in order for a semiconductor particle to absorb an electromagnetic wave having a wavelength of 700 to 2500 nm, the semiconductor particle has an electromagnetic wave having a wavelength of 700 to 2500 nm. It preferably contains a compound semiconductor that can be absorbed. Examples of the compound semiconductor capable of absorbing electromagnetic waves having a wavelength of 700 to 2500 nm include compound semiconductors having a perovskite crystal structure and metal chalcogenides (for example, oxides, sulfides, selenes, and tellurides). Specific examples of the compound semiconductor having a perovskite crystal structure include CH ₃ NH ₃ PbF ₃ , CH ₃ NH ₃ PbCl ₃ , CH ₃ NH ₃ PbBr ₃ , CH ₃ NH ₃ PbI ₃ , CsPbF ₃ , CsPbCl ₃ , and CsPbBr. ₃ , CsPbI ₃ , RbPbF ₃ , RbPbCl ₃ , RbPbBr ₃ , RbPbI ₃ , KPbF ₃ , KPbCl ₃ , KPbBr ₃ , KPbI _{3 and the} like. Specific examples of the metal chalcogenide include PbS, PbSe, PbTe, CdS, CdSe, CdTe, Sb ₂ S ₃ , Bi ₂ S ₃ , Ag ₂ S, Ag ₂ Se, Ag ₂ Te, Au ₂ S, and so on. Au ₂ Se, Au ₂ Te, Cu ₂ S, Cu ₂ Se, Cu ₂ Te, Fe ₂ S, Fe ₂ Se, Fe ₂ Te, In ₂ S ₃ , SnS, SnSe, SnTe, CuInS ₂ , CuInSe ₂ , CuInTe ₂ , EuS, EuSe, EuTe and the like can be mentioned. Among these, PbS, PbSe, Ag ₂ S is preferred.

<Ligand>
The ligand is used for surface treatment of semiconductor particles and covers at least a part of the surface of the semiconductor particles.

[Hole-transporting ligand]
The hole-transporting ligand consists of an adsorption site on the surface of semiconductor particles and a hole-transporting site having a hole-transporting function. The adsorption site and the hole transporting site do not have to be completely separated. For example, a part of the hole transporting site may be an adsorption site.

Examples of the adsorption site include a carboxyl group (-COOH), an amino group (-NH ₂ ), a phosphino group (-PH ₂ ), a sulfanyl group (-SH) and the like as monovalent groups, and examples thereof include a sulfanyl group (-SH). Examples of the divalent group include a carbonyl group (> (C = O)) and the like, and examples of the trivalent group include a phosphoroso group (> (P = O) −).

Examples of the hole-transporting moiety include a moiety (partial structure, residue) having a structure composed of a known hole-transporting compound used as an organic electroluminescent element material and a derivative thereof, and the hole transporting moiety is not particularly limited. Tertiary aromatic amines, thiophene oligomers, thiophene polymers, pyrrole oligomers, pyrrole polymers, phenylene vinylene oligomers, phenylene vinylene polymers, vinyl carbazole oligomers, vinyl carbazole polymers, fluorene oligomers, fluorene polymers, phenylene ethine oligomers, phenylene ethine polymers, phenylene oligomers. , Phenylene polymer, acetylene oligomer, acetylene polymer, phthalocyanine, phthalocyanine derivative, porphyrin and other compounds and residues obtained by removing one or more hydrogen atoms from the derivative. The residues of the compounds shown below can also function as hole-transporting sites.

Further, as a preferable structure of the hole transporting ligand, those represented by the following general formula (1), general formula (2) or general formula (3) can be mentioned.

[In the general formula (1), X ¹ may have a hydrogen atom, an aliphatic hydrocarbon group which may have a substituent, an aromatic ring group which may have a substituent, or a substituent. It is an acyl group, and R ^{1 to} R ⁸ each independently have a hydrogen atom, an aliphatic hydrocarbon group which may have a substituent, an aromatic ring group which may have a substituent, and a substituent. It may have an alkoxy group which may have a substituent, an aryloxy group which may have a substituent, an acyl group which may have a substituent, an amino group which may have a substituent, and a substituent (which may have a substituent (which may be used). Poly) It is an organosiloxane group, a carboxyl group or a sulfanyl group, and ^{at least one of X 1} and R ^{1 to} R ⁸ is a group having a carboxyl group or a group having a sulfanyl group. ]

[In the general formula (2), R ^{11 to} R ²⁵ are independently hydrogen atom, an aliphatic hydrocarbon group which may have a substituent, an aromatic ring group which may have a substituent, and a substituent. An alkoxy group which may have a group, an aryloxy group which may have a substituent, an acyl group which may have a substituent, a (poly) organosiloxane group which may have a substituent, and a nitro group. , Amino group, carboxyl group or sulfanyl group which may have a substituent ^{, and at least one of R 11 to} R ²⁵ is a group having a carboxyl group or a group having a sulfanyl group. ]

[In the general formula (3), X ² is a hydrogen atom, an aliphatic hydrocarbon group which may have a substituent, an aromatic ring group which may have a substituent (excluding a phenyl group), or a substituent. It is an acyl group which may have a group, and R ^{26 to} R ³⁵ are independently hydrogen atoms, an aliphatic hydrocarbon which may have a substituent, and an aromatic ring which may have a substituent. A group, an alkoxy group which may have a substituent, an aryloxy group which may have a substituent, a (poly) organosiloxane group which may have a substituent, and an amino group which may have a substituent. , An acyl group, a carboxyl group or a sulfanyl group which may have a substituent ^{, and at least one of X 2} and R ^{26 to} R ³⁵ is a group having a carboxyl group or a sulfanyl group. ]

Hereinafter, the groups in the above general formulas (1) to (3) will be described.
The aliphatic hydrocarbon group is a monovalent residue in which one hydrogen atom is formally removed from the aliphatic hydrocarbon, and examples thereof include saturated aliphatic hydrocarbon groups and unsaturated aliphatic hydrocarbon groups. Examples of the saturated aliphatic hydrocarbon group include an alkyl group and a cycloalkyl group. Examples of the unsaturated aliphatic hydrocarbon group include an alkenyl group, an alkynyl group, a cycloarikenyl group and the like. The aliphatic hydrocarbon group may be linear, branched or cyclic. Specific examples of the aliphatic hydrocarbon group include a linear alkyl group such as a methyl group, an ethyl group, a hexyl group, a dodecyl group and an eicosyl group; a branched alkyl group such as a 2-ethylhexyl group; a cyclohexyl group and a 3-cyclohexylpropyl group. Cycloalkyl groups such as ethenyl groups, alkenyl groups such as dodecene groups; alkynyl groups such as propa-2-in-1- group and propargyl group. The aliphatic hydrocarbon group preferably has 1 to 30 carbon atoms.

Aromatic ring groups are monovalent residues in which one hydrogen atom is formally removed from an aromatic ring, and examples thereof include aromatic hydrocarbon groups and aromatic heterocyclic groups. Examples of the aromatic hydrocarbon group include an aryl group which is an aromatic hydrocarbon group selected from the group consisting of a monocyclic ring, a fused ring and a ring assembly. Specific examples of the aryl group include monovalent residues in which one hydrogen atom is formally removed from aromatic hydrocarbons such as benzene, naphthalene, pyrene, biphenyl, and terphenyl. The aryl group preferably has 6 to 30 carbon atoms. An aromatic heterocyclic group is a monovalent residue obtained by formally removing one hydrogen atom from an aromatic heterocycle. Specific examples of the aromatic heterocyclic group include pyridine, pyrimidine, pyridazine, pyrazine, quinoline, furan, pyrrol, thiophene, imidazole, pyrazole, oxazole, thiazole, indol, benzimidazole, benzofuran, purine, acrydin, phenothiazine and the like. Examples include monovalent residues in which one hydrogen atom is formally removed from the group heterocycle. The aromatic heterocyclic group preferably has 2 to 30 carbon atoms.

The alkoxy group is a functional group to which an alkyl group is bonded via an ether bond, and examples of the alkyl group include the above-mentioned alkyl group.

The aryloxy group is a functional group to which an aryl group is bonded via an ether bond, and examples of the aryl group include the above-mentioned aryl group.

The acyl group is a functional group to which an alkyl group or an aryl group is bonded via a carbonyl group, and examples of the alkyl group and the aryl group include the above-mentioned alkyl group and the aryl group.

The (poly) organosiloxane group is a residue obtained by formally removing one hydrogen atom from the organosiloxane. Examples of the organosiloxane include pentamethyldisiloxane, heptaethyltrisiloxane, undecamethyltetrasiloxane, trimethylsiloxydimethylsilanol, 1,1,3,3-tetramethyl-1,3-dihydroxydisiloxane or 1,1. , 3,3,5,5-hexamethyl-1,5-dihydroxytrisiloxane and the like. The number of repeating units of the siloxane bond in the (poly) organosiloxane group is preferably 1 to 4.

Further, the aliphatic hydrocarbon group, aromatic ring group, alkoxy group, aryloxy group, acyl group, amino group and (poly) organosiloxane group in the general formulas (1) to (3) further have a substituent. May be.

The group having a carboxyl group or a sulfanyl group is an alkyl group, an aryl group, an alkoxy group, an aryloxy group, an amino group, which has a carboxyl group or a sulfanyl group as a substituent in addition to the carboxyl group and the sulfanyl group. ) Monovalent organic residues such as an organosiloxane group or an acyl group can be mentioned.

Examples of the alkyl group having a carboxyl group or the aryl group having a carboxyl group include, for example, a 2-carbosixylethyl group, a 2,2-dicarboxyethyl group, a 2-carbosixylethenyl group, and a 2-cyano-. Examples thereof include 2-carbosixylethenyl group, 2-trifluoromethyl-2-carbosixylethenyl group, 2-fluoro-2-carbosixylethenyl group and the like.

Examples of the alkyl group having a sulfanyl group, the aryl group having a sulfanyl group, or the acyl group having a sulfanyl group include [(3-sulfanylpropanoyl) oxy] ethyl group and [(2-sulfanylacetyl) oxy] ethyl group. , 4- (Sulfanylmethyl) phenyl group, [(3-sulfanylpropanol) oxy] propyl group, 3-sulfanyl [(3-sulfanylpropanoyl) oxy] ethyl group, or {[(2-sulfanylethoxy) propanoyl] Oxy} ethyl group and the like can be mentioned.

Specific examples of the ligands represented by the general formulas (1) to (3) are shown below, but the present invention is not limited thereto. In the following structural formula, when cis-type and trans-type geometric isomers are present, they may be cis-type, trans-type, or a mixture of cis-type and trans-type isomers. May be good. The same applies to the thin-anti geometric isomerism.

[Electron-transporting ligand]
The electron-transporting ligand consists of an adsorption site on the surface of semiconductor particles and an electron-transporting site having an electron-transporting function. The adsorption site and the electron transporting site do not have to be completely separated. For example, a part of the electron transporting site may be an adsorption site. Examples of the adsorption site include the same adsorption sites as those described in the section on hole transporting ligands. In addition, a 2,2'-bipyridine skeleton, an 8-quinolinol skeleton, or the like can also be used as an adsorption site.

The hole-transporting site and the electron-transporting site described above contain the same structure, because they can be both an electron-transporting site and a hole-transporting site. Whether the ligand behaves as hole-transporting or electron-transporting depends on the relative highest occupied orbital (HOMO) energy level and lowest empty orbital (LUMO) of the hole-transporting ligand and the electron-transporting ligand. It is determined by the energy level relationship and the relationship between the HOMO energy level and the LUMO energy level relative to other compounds used in the electric field light emitting element, and further, even with a specific structure, electron attraction. The energy level of HOMO and the energy level of LUMO change due to the presence of an electron-donating substituent. Organic residues obtained by removing one or more hydrogen atoms from the compounds and derivatives thereof shown below can function as electron-transporting sites, but the electron-transporting sites are not limited thereto.

<photoelectric conversion element>
The photoelectric conversion element of the present invention has a photoelectric conversion layer between a pair of electrodes. The photoelectric conversion layer contributes to charge separation and has a function of transporting electrons and holes generated by absorption of electromagnetic waves (mainly light) toward electrodes in opposite directions, respectively. The photoelectric conversion layer used in the present invention has a function of transporting electrons and holes. The conversion layer comprises the photoelectric conversion material of the present invention. Further, in the photoelectric conversion element of the present invention, a known configuration of the photoelectric conversion element can be applied.

For the photoelectric conversion element, various shapes of element structures have been proposed depending on the energy matching between the electrode and the semiconductor particles and the method of manufacturing the photoelectric conversion layer made of the semiconductor particles for the purpose of improving the photoelectric conversion efficiency. For example, a photoelectric conversion element having the known configuration shown below can be manufactured.

1. 1. Schottky type photoelectric conversion element A photoelectric conversion element that obtains photovoltaic power by using a Schottky barrier formed at the interface between an electron-donating (p-type) or electron-accepting (n-type) semiconductor particle and an electrode. .. For example, when a p-type photoelectric conversion layer is used, a Schottky barrier is formed at the interface between the pair of electrodes and the electrode having the smaller internal work function, and charge separation occurs at the interface to perform photoelectric conversion. ..

2. 2. Bilayer heterojunction photoelectric conversion element Electron-donating (p-type) and electron-accepting (n-type) semiconductor particles and other semiconductor materials are individually formed between a pair of electrodes, and light charges are applied to the pn junction interface. It is a photoelectric conversion element that causes separation and obtains a photocurrent.

3. 3. Bulk heterojunction type photoelectric conversion element An organic semiconductor layer is formed by mixing electron-donating (p-type) and electron-accepting (n-type) semiconductor particles and other semiconductor materials at an arbitrary ratio between a pair of electrodes. At this time, the p-type and n-type materials may be uniformly dispersed or non-uniform. Since photocharge separation occurs at the interface formed by each p-type material and n-type material, it is possible to form a wider pn junction than the bilayer heterojunction type.

<photoelectric conversion unit>
The photoelectric conversion unit includes a photoelectric conversion layer (PEL1) containing semiconductor particles (A1) surface-treated with a hole-transporting ligand, and a photoelectric conversion layer containing semiconductor particles (A2) surface-treated with an electron-transporting ligand. (PEL2), a photoelectric conversion layer (PEL3) containing semiconductor particles (A3) surface-treated with both hole-transporting ligands and electron-transporting ligands, and semiconductor particles (A1) and semiconductor particles (A2). It has at least two types of photoelectric conversion layers selected from the group consisting of a photoelectric conversion layer (PEL4) containing a mixture, and the at least two types of photoelectric conversion layers are continuously arranged. However, the photoelectric conversion layer (PEL1) and (PEL2) are excluded from the case of the photoelectric conversion layer (PEL4).

From the anode side, the photoelectric conversion unit performs (PEL1) / (PEL2), (PEL1) / (PEL3), (PEL3) / (PEL2), (PEL1) / (PEL3) / (PEL2), (PEL1) / ( When arranged in the order of PEL4), (PEL4) / (PEL2), or (PEL1) / (PEL4) / (PEL2), the anode side has excellent hole transport property when relatively viewed inside the photoelectric conversion unit. The cathode side is preferable because it has excellent electron transportability.

The photoelectric conversion layer (PEL3) containing the semiconductor particles (A3) surface-treated with both the hole-transporting ligand and the electron-transporting ligand has a mass ratio of the hole-transporting ligand to the electron-transporting ligand of 10:90. It is preferably in the range of ~ 90:10.

The mass ratio of the semiconductor particles (A1) to the semiconductor particles (A2) in the photoelectric conversion layer (PEL4) containing a mixture of the semiconductor particles (A1) and the semiconductor particles (A2) is 10:90 to 90:10. It is preferably in the range.

The energy level of HOMO of the hole transporting ligand is preferably -6.5 eV or more and -4.6 eV or less. The LUMO energy level of the electron transporting ligand is preferably −4.5 eV or more and −2.5 eV or less.

Further, it is preferable that the energy level of HOMO of the hole transporting ligand is 0.2 eV or more larger than the energy level of HOMO of the electron transporting ligand. Further, it is preferable that the energy level of LUMO of the hole transporting ligand is 0.2 eV or more larger than the energy level of LUMO of the electron transporting ligand.

Further, when the semiconductor particles are semiconductor particles surface-treated with a plurality of hole-transporting ligands and / or electron-transporting ligands, the combination of the hole-transporting ligand and the electron-transporting ligand to be considered is There are multiple. In such a case, it is preferable that many of the plurality of combinations satisfy the above-mentioned preferable energy level conditions, and it is particularly preferable that all the combinations satisfy the conditions.

When the HOMO energy and / or LUMO energy of the hole-transporting ligand and the electron-transporting ligand satisfy the above conditions, the transport of electrons and holes in the photoelectric conversion element and the electrons and holes from the semiconductor particles are satisfied. It is preferable because it can be taken out excellently and a high-performance photoelectric conversion element can be obtained.

The photoelectric conversion layer is coated and printed with a composition for forming a photoelectric conversion layer in which semiconductor particles (A1), (A2), a mixture of (A1) and (A2), or (A3) is dispersed in a solvent. Can be formed with.

As the solvent used in the composition for forming the photoelectric conversion layer, various conventionally known solvents can be used and are not particularly limited, but for example, toluene, o-xylene, m-xylene, p-xylene, methicylene, cyclocarbonate, and the like. Aromatic hydrocarbons such as tetraline; Halogenized aromatic hydrocarbons such as chlorobenzene, dichlorobenzene, trichlorobenzene; 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, anisole, phenetol, 2-methoxytoluene, 3-methoxy Aromatic ethers such as toluene, 4-methoxytoluene, 2,3-dimethylanisole, 2,4-dimethylanisole; phenyl acetate, phenyl propionate, methyl benzoate, ethyl benzoate, propyl benzoate, n-butyl benzoate Aromatic esters such as: Hydrocarbons having an alicyclic such as cyclohexanone and cyclooctanone; Aromatic ketones such as methylethylketone and dibutylketone; Alcohols having an alicyclic such as methylethylketone, cyclohexanol and cyclooctanol; Fats such as butanol and hexanol Group alcohols; aliphatic ethers such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol-1-monomethyl ether acetate (PGMEA); aliphatic esters such as ethyl acetate, n-butyl acetate, ethyl lactate, n-butyl lactate. N-hexane, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, 2,3-dimethylbutane, n-heptane, n-decane, 2,2,4-trimethylpentane, cyclohexane, methylcyclohexane , Aromatic hydrocarbons such as mineral spirits; etc., and may be used alone or in combination of two or more.

A known photoelectric conversion material other than semiconductor particles, for example, an organic photoelectric conversion material or a known additive may be added to the composition for forming a photoelectric conversion layer as long as the object of the present invention is not impaired. The known additive is not particularly limited, and examples thereof include a defoaming agent, a leveling agent, and a thickener.

As a method for obtaining a photoelectric conversion layer from a composition for forming a photoelectric conversion layer, a known wet film forming method, for example, a coating method, an inkjet method, a dip coating method, a die coating method, a spray coating method, a spin coating method, or a roll coater method is used. , Wet pickling method, screen printing method, flexographic printing, screen printing method, LB method and the like.

<Electrode>
It is preferable that at least one of the pair of electrodes constituting the photoelectric conversion element transmits light. Specific examples include conductive metal oxides such as tin oxide, zinc oxide, indium oxide, and indium tin oxide (ITO), or gold, silver, platinum, chromium, nickel, lithium, indium, aluminum, calcium, and magnesium. And the like, and examples thereof include a mixture or a laminate of these metals and a conductive metal oxide.

The electrode is generally flat, but may be corrugated, pyramidal, comb-shaped or the like in order to improve energy conversion efficiency. As a method for forming these electrodes, a general electrode forming method can be used, and a PVD method such as a vacuum vapor deposition method, a sputtering method, and an ion plating method, a CVD method, a chemical reaction method (sol-gel method, etc.), and casting can be used. Examples thereof include a method, a spray coating method, an inkjet method, and a spin coating method.

The photoelectric conversion element may include a layer other than the photoelectric conversion layer between the pair of electrodes, and has a hole injection layer, a hole transport layer, an electron transport layer, and / or an electron injection layer. May be good.

<Hole injection layer>
For the hole injection layer, a hole injection material that exhibits an excellent hole injection effect on the photoelectric conversion layer and can form a hole injection layer having excellent adhesion to the anode interface and thin film formation is used. .. Further, when such a material is laminated in multiple layers and a material having a high hole injection effect and a material having a high hole transport effect are laminated in multiple layers, the materials used for each are referred to as a hole injection material and a hole transport material. Sometimes. These hole injection materials and hole transport materials need to have a large hole mobility and a small ionization energy of usually 5.5 eV or less. As such a hole injection layer, a material that transports holes to the light emitting layer with a lower electric field strength is preferable, and further ^{, when an electric field with a hole mobility of, for example, 10 4} to 10 ⁶ V / cm is applied, at least. It is preferably 10 ^-6 cm ² / V · sec. The hole injecting material and the hole transporting material are not particularly limited as long as they have the above-mentioned preferable properties, and are conventionally used as a hole charge transporting material in a photoconductive material or an organic EL element. Any known material used for the hole injection layer can be selected and used.

Examples of such hole injecting materials and hole transporting materials include carbazole derivatives, polyarylalkane derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted carcon derivatives, styrylanthracene derivatives, fluorene derivatives, hydrazone derivatives, and stylben derivatives. , Silazan derivatives, aromatic tertiary amine compounds, styrylamine compounds, aromatic dimethyridin compounds, porphyrin compounds, phthalocyanine compounds, oligothiophene derivatives, polythiophene derivatives, polypyrrole derivatives, polyparaphenylene vinylene derivatives and the like. ..

Further, as materials that can be used for the hole injection layer, molybdenum oxide (MоOx), vanadium oxide (VO _X ), ruthenium oxide (RuO _X ), copper oxide (CuO _X ), tungsten oxide (WO _X ), and iridium oxide (Iridium oxide) IrO _X) inorganic oxides and their doped body such may be mentioned.

In order to form the hole injection layer, the above-mentioned compound is thinned by a known method such as a vacuum deposition method, a spin coating method, a casting method, or a Langmuir-Brojet method (LB method). The film thickness of the hole injection layer is not particularly limited, but is usually 5 nm to 5 μm.

<Electron injection layer>
For the electron injection layer, an electron injection material that exhibits an excellent electron injection effect on the photoelectric conversion layer and can form an electron injection layer having excellent adhesion to the cathode interface and thin film forming property is used. Further, when such a material is laminated in multiple layers and a material having a high electron injection effect and a material having a high electron transport effect are laminated in multiple layers, the materials used for each may be referred to as an electron injection material and an electron transport material. Examples of such electron-injected materials include metal complex compounds, nitrogen-containing five-membered ring derivatives, fluorenone derivatives, anthraquinodimethane derivatives, diphenoquinone derivatives, thiopyrandioxide derivatives, perylenetetracarboxylic acid derivatives, fleolenilidenemethane. Examples thereof include derivatives, anthron derivatives, silol derivatives, triarylphosphin oxide derivatives, polyquinolin and its derivatives, polyquinoxalin and its derivatives, polyfluorene and its derivatives, calcium acetylacetonate, sodium acetate and the like. Inorganic / organic composite materials in which a metal such as cesium is doped with vasophenanthroline (Proceedings of the Society of Polymer Science, Vol. 50, No. 4, p. 660, published in 2001) and the 50th Joint Lecture on Applied Physics. Proceedings of the lecture, No. BCP, TPP, T5MPyTZ, etc. described on page 3, 1402, published in 2003 are also given as examples of electron injection materials, but they can form a thin film necessary for device fabrication, inject electrons from the cathode, and transport electrons. As long as it is a material, it is not particularly limited to these.

Further, as the material that can be used for the electron injection layer, inorganic oxides such as zinc oxide (ZnOx) and titanium oxide (TiOx) and their doped materials, as well as lithium fluoride (LiF) and cesium fluoride (CsF). Alkali metal fluorides such as are also mentioned.

The photoelectric conversion element may include other constituent members in addition to the layers constituting the photoelectric conversion element. For example, an optical film (filter) that does not transmit ultraviolet rays may be provided. Since ultraviolet rays have high energy, they contribute to deterioration of materials constituting the photoelectric conversion element. By blocking this ultraviolet ray, the life of the device can be extended.

A protective film may be provided for the purpose of protecting the photoelectric conversion layer from an external impact. The protective film is, for example, a polymer film such as styrene resin, epoxy resin, acrylic resin, polyurethane, polyimide, polyvinyl alcohol, polyvinylidene fluoride, polyethylene polyvinyl alcohol copolymer, or an inorganic oxide film such as silicon oxide, silicon nitride, or aluminum oxide. It can be composed of a nitride film, a metal plate such as aluminum or a metal foil, or a laminated film thereof. As the material of these protective films, only one kind may be used, or two or more kinds may be used.

It is generally said that semiconductor particles are deteriorated by moisture and oxygen in the air. A barrier membrane may be provided to prevent this. For example, metals or inorganic oxides are preferable, and Ti, Al, Mg, Zr, silicon oxide, aluminum oxide, silicon oxide, aluminum oxide, magnesium oxide, zinc oxide, indium oxide, tin oxide, yttrium oxide, boron oxide, etc. Calcium oxide and the like can be mentioned. There is no particular order in which these various functional films are laminated, and a functional film having these functions may be used.

Hereinafter, the present invention will be specifically described based on examples. Unless otherwise specified, "part" means "part by mass" and "%" means "% by mass". Unless otherwise specified, all measurements were performed at 25 ° C.

<Preparation of semiconductor particles PbS-0>
First, as a sulfur source solution, 0.40 part of elemental sulfur and 6.0 parts of oleylamine were heated to 120 ° C. in a nitrogen atmosphere in a reaction vessel to form a uniform solution, and then cooled to 25 ° C. Next, as a lead source solution, 0.32 parts of lead chloride and 6.0 parts of oleylamine were heated to 120 ° C. in another reaction vessel under a nitrogen atmosphere. Then, after preparing the lead source solution at 40 ° C., 1.8 parts of the above sulfur source solution was added at once. After reacting for 30 seconds, the container was immersed in an ice bath and rapidly cooled, and then diluted with 13 parts of hexane. After centrifuging (4000 rpm, 5 minutes) to remove unreacted raw materials, add 12 parts of a mixed solution of butanol: methanol = 2: 1 (volume ratio) to precipitate the semiconductor particles and centrifuge (4000 rpm). 5 minutes) to recover the semiconductor particles. Then, 24 parts of a mixed solution consisting of hexane: oleic acid = 1: 2 (volume ratio) was added, and the mixture was stirred for 30 minutes, centrifuged, and the supernatant was recovered. Semiconductor particle sedimentation, redispersion, and impurity sedimentation are repeated twice, and finally the semiconductor particles are precipitated and vacuum dried, and then adjusted to a solid content concentration of 5% using n-octane to obtain semiconductor particles PbS-0. (Average particle size 3.5 nm).

<Semiconductor particle PbSe-0 synthesis>
As a lead source solution, 0.22 parts of lead oxide, 0.73 parts of oleic acid, and 10 parts of 1-octadecene were heated to 150 ° C. in a reaction vessel under a nitrogen atmosphere. Then, a mixture consisting of 2.5 parts of 1M trioctylphosphine-selenium solution and 0.028 parts of diphenylphosphine was quickly added, the reaction solution was heated to 180 ° C., kept at 160 ° C., and reacted for 2 minutes. , The reaction solution was quenched. After diluting with 10 parts of hexane, it was precipitated with acetone. The precipitate was washed with acetone 5 times and vacuum dried to obtain semiconductor particles PbSe-0 (average particle size 2.7 nm).

<Semiconductor particle Ag ₂ S-0 synthesis>
0.04 parts of silver oleate, 8 parts of octanethiol, and 4 parts of dodecylamine were heated in a reaction vessel at 200 ° C. for 0.5 hours in an Ar atmosphere. After allowing this solution to cool to room temperature, 40 parts of absolute ethanol was added. The obtained mixture was centrifuged and vacuum dried to obtain semiconductor particles Ag ₂ S-0 (average particle size 2.5 nm).

<Semiconductor particles PbS-1>
Semiconductor particles PbS-0 were prepared in a toluene solution having a solid content concentration of 1%. After mixing 1 part of the prepared solution and 1 part of a 5% toluene solution of the hole transporting ligand (1) shown in Table 1, the mixture was stirred for 12 hours. Purification was performed by the reprecipitation method using toluene and ethanol. The precipitate was vacuum dried to prepare semiconductor particles PbS-1 as a 10% by mass solution of toluene.

<Semiconductor particles PbS-2 to 8>
Similar to the semiconductor particles PbS-1 except that the hole transporting ligand (1) was changed to the hole transporting ligands (2) to (6) and the electron transporting ligands (7) and (8) shown in Table 1, respectively. PbS-2 to 8 were prepared respectively.

<Semiconductor particles PbS-9>
PbS-9 was prepared in the same manner as the semiconductor particles PbS-1 except that the surface treatment agent was changed to benzenethiol.

<Semiconductor particles (A3) PbS-10-19>
With the semiconductor particles PbS-1, except that the hole-transporting ligand (1) and the electron-transporting ligand (7) shown in Table 1 were mixed and used at mass ratios of 9: 1, 1: 1, and 1: 9, respectively. PbS-10 to 12 were prepared in the same manner. Semiconductor particles PbS-1 except that the hole-transporting ligand (2) and the electron-transporting ligand (8) also shown in Table 1 were mixed and used at mass ratios of 9: 1, 1: 1, and 1: 9, respectively. PbS-13 to 15 were prepared in the same manner as above. Similarly, the same as that of the semiconductor particles PbS-1 except that the hole-transporting ligands (3) to (6) and the electron-transporting ligands (7) shown in Table 1 were mixed and used at a mass ratio of 1: 1. PbS-16 to 19 were prepared respectively.

<Semiconductor particle mixed material PbS-20 to 29>
The prepared PbS-1 and PbS-7 were mixed at a mass ratio of 9: 1, 1: 1 and 1: 9, respectively, to prepare PbS-20 to 22 respectively. The similarly prepared PbS-2 and PbS-8 were mixed at a mass ratio of 9: 1, 1: 1, and 1: 9, respectively, to prepare PbS-23 to 25, respectively. PbS-3 to 6 prepared in the same manner and PbS-7 were mixed at a mass ratio of 1: 1 to prepare PbS-26 to 29, respectively.

<Semiconductor particles PbSe-1>
Semiconductor particles PbSe-0 were prepared in a toluene solution having a solid content concentration of 1%. After mixing 1 part of the prepared solution and 1 part of a 5% toluene solution of the hole transporting ligand (1) shown in Table 1, the mixture was stirred for 12 hours. Purification was performed by the reprecipitation method using toluene and ethanol. The precipitate was vacuum dried to prepare semiconductor particles PbSe-1 as a 10% by mass solution of toluene.

<Semiconductor particles PbSe-2 to 8>
Similar to the semiconductor particles PbSe-1 except that the hole transporting ligand (1) was changed to the hole transporting ligands (2) to (6) and the electron transporting ligands (7) and (8) shown in Table 1, respectively. PbSe-2 to 8 were prepared respectively.

<Semiconductor particles (A3) PbSe-10-19>
Similar to semiconductor particles PbSe-1 except that the hole-transporting ligand (1) and the electron-transporting ligand (7) shown in Table 1 are mixed and used at mass ratios of 9: 1, 1: 1, and 1: 9, respectively. To prepare PbSe-10-12. The semiconductor particles PbSe-1 are used except that the hole-transporting ligand (2) and the electron-transporting ligand (8) also shown in Table 1 are mixed and used at mass ratios of 9: 1, 1: 1, and 1: 9, respectively. PbSe-13 to 15 were prepared in the same manner. Similarly, PbSe is the same as that of the semiconductor particles PbSe-1, except that the hole-transporting ligands (3) to (6) and the electron-transporting ligands (7) shown in Table 1 are mixed and used at a mass ratio of 1: 1. -16 to 19 were prepared.

<Semiconductor particle mixed material PbSe-20 to 29>
The prepared PbSe-1 and PbSe-7 were mixed at a mass ratio of 9: 1, 1: 1, and 1: 9, respectively, to prepare PbSe-20 to 22. The similarly prepared PbSe-2 and PbSe-8 were mixed at a mass ratio of 9: 1, 1: 1, and 1: 9, respectively, to prepare PbSe-23 to 25. PbSe-3 to 6 prepared in the same manner and PbSe-7 were mixed at a mass ratio of 1: 1 to prepare PbSe-26 to 29.

<Semiconductor particles Ag ₂ S-1>
Was prepared semiconductor particles Ag ₂ S-0 to a solid concentration of 1% toluene solution. After mixing 1 part of the prepared solution and 1 part of a 5% toluene solution of the hole transporting ligand (1) shown in Table 1, the mixture was stirred for 12 hours. Purification was performed by the reprecipitation method using toluene and ethanol. _{The precipitate was vacuum dried to prepare semiconductor particles Ag 2} S-1 as a 10% by mass solution of toluene.

<Semiconductor particles Ag ₂ S-2 to 8>
_{Semiconductor particles Ag 2} S-1 except that the hole-transporting ligand (1) was changed to the hole-transporting ligands (2) to (6) and the electron-transporting ligands (7) and (8) shown in Table 1, respectively. Ag ₂ S-2 to 8 were prepared in the same manner as above.

<Semiconductor particles (A3) Ag ₂ S-10-19>
_{Semiconductor particles Ag 2} S-1 except that the hole-transporting ligand (1) and the electron-transporting ligand (7) shown in Table 1 are mixed and used at mass ratios of 9: 1, 1: 1, and 1: 9, respectively. It was prepared Ag ₂ S-10 to 12 in the same manner as. _{Semiconductor particles Ag 2} S- except that the hole-transporting ligand (2) and the electron-transporting ligand (8) also shown in Table 1 are mixed and used at mass ratios of 9: 1, 1: 1, and 1: 9, respectively. It was prepared Ag ₂ S-13 to 15 in the same manner as 1. _{Similarly, the same as the semiconductor particles Ag 2} S-1 except that the hole transporting ligands (3) to (6) and the electron transporting ligands (7) shown in Table 1 are mixed and used at a mass ratio of 1: 1. Ag ₂ S-16-19 was prepared.

<Semiconductor particle mixed material Ag ₂ S-20-29>
The prepared Ag ₂ S-1 and Ag ₂ S-7 were mixed at a mass ratio of 9: 1, 1: 1 and 1: 9, respectively, _{to prepare Ag 2} S-20 to 22. The similarly prepared Ag ₂ S-2 and Ag ₂ S-8 were mixed at a mass ratio of 9: 1, 1: 1 and 1: 9, respectively, _{to prepare Ag 2} S-23 to 25. _{Ag 2} S-3 to 6 prepared in the same manner _{and Ag 2} S-7 were mixed at a mass ratio of 1: 1 _{to prepare Ag 2} S-26 to 29.

<Measurement of HOMO energy level and LUMO energy level of ligand>
The energy levels of HOMO and LUMO of the hole-transporting ligand and the electron-transporting ligand were measured by the following evaluation methods.

(HOMO energy level)
The energy level of HOMO was measured using a photoelectron yield spectroscope PYS-202 (manufactured by Sumitomo Heavy Industries Mechatronics). A conductive carbon double-sided tape (nonwoven fabric base material, manufactured by Nissin EM) was attached onto a glass substrate with ITO (indium tin oxide), and a ligand powder to be evaluated was attached thereto to prepare a sample. The surface of the ITO was grounded, and the ligand powder to be evaluated on the carbon double-sided tape was irradiated with probe light for measurement. Measuring range: 4.0 to 7.0 (eV), measurement interval: 0.1 (eV), measured and atmosphere: in vacuum (10 ^-2 (Pa) base).

(LUMO energy level)
The LUMO energy level was calculated from the HOMO value and the bandgap value measured by the above method by estimating the bandgap from the absorption edge of the absorption spectrum. The absorption spectrum was ^{adjusted to a concentration of 10-5} (mol / L) using toluene, and measured using a quartz cell having an optical path length of 1 cm. Table 1 shows the measured values of the HOMO energy level and the LUMO energy level of the hole-transporting ligand and the electron-transporting ligand used.

Using the semiconductor particles and the mixture prepared above as a photoelectric conversion material, a photoelectric conversion element was prepared and evaluated as follows. Table 2 summarizes the photoelectric conversion layer configuration of the manufactured device, the details of the materials used, and the evaluation results.

(Manufacturing of photoelectric conversion element)
Hereinafter, the fabrication of a photoelectric conversion element having an element area of 2 mm × 2 mm used for the evaluation of the present invention will be described. First, on a glass plate with an ITO electrode that has been processed with an etching pattern, PEDOT / PSS (poly (3,4-ethylenedioxy) -2,5-thiophene / polystyrene sulfonic acid, CLEVIOUS (registered trademark) PVP CH8000 manufactured by Heraeus) ) Was applied by a spin coating method and dried at 110 ° C. for 20 minutes to obtain a hole injection layer having a thickness of 35 nm. On the hole injection layer, the material of the first layer (PEL1), (PEL3) or (PEL4) of the photoelectric conversion layer in Table 2 was applied by a spin coating method to form a layer having a thickness of 100 nm. Next, the material of the second layer (PEL2), (PEL3) or (PEL4) of the photoelectric conversion layer in Table 2 was applied by a spin coating method to form a layer having a thickness of 100 nm. When the third layer (PEL2) was provided, it was similarly coated by a spin coating method to form a layer having a thickness of 100 nm. Further, a ZnO dispersion liquid N-10 manufactured by Avantama was formed by spin coating on the laminated photoelectric conversion layer to form an electron injection layer having a thickness of 50 nm. Next, aluminum (hereinafter referred to as Al) having a thickness of 200 nm was vapor-filmed on the electron injection layer in a mask pattern to form an electrode, and a photoelectric conversion element was obtained. The vapor deposition was ^{carried out in a vacuum of 10 -4} Pa under the condition that the temperature was not controlled such as heating and cooling of the substrate.

(Evaluation of photoelectric conversion element)
The IV curve of the obtained device was measured by the method shown below.
The IV curve is obtained by using an IV characteristic measuring device (PECK2400-N, manufactured by Pexel Technologies Co., Ltd.) with a scanning speed of 0.1 V / sec (0.01 Vstep), a waiting time of 50 msec after voltage setting, and measurement integration. The measurement was performed under the conditions of a time of 50 msec, a start voltage of −0.5 V, and an end voltage of 1.1 V. The IV curve was measured in a light-shielded state and a light irradiation state. Xenon lamp White light is used as a light source (PEC-L01 manufactured by Pexel Technologies Co., Ltd.), and the light irradiation area is 0.0363 cm ² ( ^{100 mW / cm 2) equivalent to sunlight (AM1.5).} It was carried out under a mask of 2 mm square). Short-circuit current density is the current density of the applied voltage of 0V I-V curve of the light irradiation state ^{_{I L (mA / cm 2)}} , and, in current at applied voltage -0.5V than I-V curve of the light-shielding state A certain dark current density _ID (μA / cm ² ) is shown in Table 2. As I _L is high, also the lower the I _D, it can be said to be satisfactory. In Table 2, the "HOMO difference" represents | the energy level of HOMO of the hole transporting ligand-the energy level of HOMO of the electron transporting ligand |, and the "LUMO difference" means | hole. Represents the LUMO energy level of the transportable ligand-the LUMO energy level of the electron transportable ligand |.

The photoelectric conversion elements (Examples 1 to 50) of the present invention all showed a _{higher short-circuit current density IL} and a lower dark current density _{ID than the elements of Comparative Examples 1 and 2.} That is, it was clarified that the noise was higher than that of the comparative example in sensitivity and photoelectric conversion ability, and lower than that of the comparative example. Since the photoelectric conversion material of the present invention consists of two or more types of semiconductor particles surface-treated with either a hole-transporting ligand or an electron-transporting ligand, excitons generated by light absorption are efficiently dissociated. It is considered that the photoelectric conversion ability is high by being transported. Further, it is considered that by having at least two continuous photoelectric conversion layers made of different photoelectric conversion materials, the bilayer heterojunction type is formed between the photoelectric conversion layers, so that the rectification characteristics are enhanced and the dark current density is suppressed.

Claims (7)

A semiconductor particle having a photoelectric conversion unit having an anode, at least two continuous photoelectric conversion layers, and a cathode, wherein the photoelectric conversion unit is surface-treated with a hole transporting ligand. A photoelectric conversion layer (PEL1) containing (A1), a photoelectric conversion layer (PEL2) containing semiconductor particles (A2) surface-treated with an electron-transporting ligand, and a surface of both a hole-transporting ligand and an electron-transporting ligand. At least selected from the group consisting of a photoelectric conversion layer (PEL3) containing the processed semiconductor particles (A3) and a photoelectric conversion layer (PEL4) containing a mixture of the semiconductor particles (A1) and the semiconductor particles (A2). A photoelectric conversion element having two types of photoelectric conversion layers. The photoelectric conversion element according to claim 1, wherein at least one selected from the group consisting of the semiconductor particles (A1), (A2) and (A3) has a photoelectric conversion layer containing a compound semiconductor. From the anode side, the photoelectric conversion unit performs (PEL1) / (PEL2), (PEL1) / (PEL3), (PEL3) / (PEL2), (PEL1) / (PEL3) / (PEL2), (PEL1). The photoelectric conversion element according to claim 1 or 2, which is arranged in the order of / (PEL4), (PEL4) / (PEL2), or (PEL1) / (PEL4) / (PEL2). The third to one of claims, wherein the energy level of the highest occupied orbital (HOMO) of the hole transporting ligand is 0.2 eV or more larger than the energy level of the HOMO of the electron transporting ligand. Photoelectric conversion element. The photoelectric of any one of claims 1 to 4, wherein the energy level of the lowest empty orbital (LUMO) of the hole-transporting ligand is 0.2 eV or more larger than the energy level of LUMO of the electron-transporting ligand. Conversion element. The photoelectric conversion element according to any one of claims 1 to 5, wherein at least one selected from the group consisting of the semiconductor particles (A1), (A2) and (A3) can absorb an electromagnetic wave having a wavelength of 700 to 2500 nm. Said semiconductor particles (A1), at least one member selected from the group consisting of (A2) and (A3) is, PbS, claim having a photoelectric conversion layer comprising at least one selected from the group consisting of PbSe and Ag ₂ S The photoelectric conversion element according to any one of 1 to 6.