Photoelectric conversion element and photoelectric conversion device

Abstract

To provide a photoelectric conversion element and a photoelectric conversion device that achieve open-circuit voltage and durability at high level.SOLUTION: A photoelectric conversion element has a first electrode, a second electrode, and a photoelectric conversion layer arranged between the first electrode and the second electrode and including a crystal of a perovskite structure. The photoelectric conversion element has, between the photoelectric conversion layer and the first electrode, a charge transport layer including an annular conjugated compound in which a plurality of pyrrole rings are conjugated and bonded and which is a crystal of a compound having an axial ligand, and resin having a Lewis basic functional group.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a photoelectric conversion element and a photoelectric conversion device. [Background technology]

[0002] In order to solve the problem of fossil energy depletion and the global environmental problems caused by the use of fossil energy, active research is being conducted on renewable and clean alternative energy sources such as solar energy, wind power, and hydroelectric power. Among them, interest in solar cells that directly convert sunlight into electrical energy is increasing. Here, a solar cell refers to a cell that generates a current and voltage by utilizing the photovoltaic effect in which light energy from sunlight is absorbed and electrons and holes are generated.

[0003] Currently, np diode type silicon (Si) single crystal-based solar cells with a light energy conversion efficiency of over 20% are widely known and are actually used for photovoltaic power generation. However, these require high-temperature processing and the materials themselves are expensive, so they have the problem of high cost per unit of power. In addition, there are problems with supply in terms of silicon resources.

[0004] On the other hand, solar cells using organic materials (hereinafter referred to as "organic solar cells") do not require high-temperature processing and can be produced using a sheet-like substrate by the so-called roll-to-roll method, which is expected to reduce costs. However, further improvements in conversion efficiency and durability are required for the practical use of organic solar cells. In particular, perovskite solar cells, which have crystals with a perovskite structure as a photoelectric conversion layer, have excellent photoelectric conversion properties, so development is being promoted for the practical use of solar cells.

[0005] For example, Patent Document 1 describes a technique for improving conversion efficiency and durability by mixing an insulating polymer and a hole transport material in the hole transport layer (hereinafter also referred to as the "charge transport layer") to suppress peeling from the anode. Non-Patent Document 1 describes a technique for improving conversion efficiency by mixing copper phthalocyanine and a conductive polymer in the hole transport layer. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2018-170382 A [Non-patent literature]

[0007] [Non-Patent Document 1] Q. Hu,et al,Sol.RRL,2019,3,1800264 Summary of the Invention [Problem to be solved by the invention]

[0008] According to the study by the present inventors, there is a problem in achieving both high open circuit voltage (Voc) and high durability in the photoelectric conversion elements of Patent Document 1 and Non-Patent Document 1. Therefore, an object of the present invention is to provide a photoelectric conversion element and a photoelectric conversion device which achieve both high open circuit voltage and high durability. [Means for solving the problem]

[0009] The above object can be achieved by the present invention as described below. That is, the photoelectric conversion element of the present invention is a photoelectric conversion element having a first electrode, a second electrode, and a photoelectric conversion layer containing a crystal of a perovskite structure, which is disposed between the first electrode and the second electrode, The present invention is characterized in that a charge transport layer is provided between the photoelectric conversion layer and the first electrode, the charge transport layer including a crystal of a compound having an axial ligand, the compound being a cyclic conjugated compound formed by conjugating bonds between a plurality of pyrrole rings, and a resin having a Lewis basic functional group. Effect of the Invention

[0010] According to the present invention, it is possible to provide a photoelectric conversion element which has both high open circuit voltage and high durability. [Brief description of the drawings]

[0011] [Figure 1] 1 is an example of a schematic cross-sectional view in a thickness direction of one embodiment of a photoelectric conversion element of the present invention. [Diagram 2] FIG. 2 is another example of a schematic cross-sectional view in a thickness direction of an embodiment of a photoelectric conversion element of the present invention. [Diagram 3] 1 is an X-ray diffraction spectrum using CuKα radiation of a crystal of a cyclic conjugated compound of the present invention in which a plurality of pyrrole rings are conjugated and which has an axial ligand. [Figure 4] 1 is a perspective view showing a schematic diagram of an embodiment of a moving body including a photoelectric conversion element of the present invention; [Diagram 5] FIG. 1 is a perspective view showing a schematic diagram of one embodiment of a building material including a photoelectric conversion element of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The photoelectric conversion element of the present invention is a photoelectric conversion element having a first electrode, a second electrode, and a photoelectric conversion layer containing a crystal of a perovskite structure disposed between the first electrode and the second electrode, and has a charge transport layer between the photoelectric conversion layer and the first electrode, the charge transport layer containing a crystal of a compound having an axial ligand, the compound being a cyclic conjugated compound formed by conjugating bonds between a plurality of pyrrole rings, and a resin having a Lewis basic functional group.

[0013] As a result of investigations, the present inventors have found that the inclusion of the charge transport layer results in a photoelectric conversion element having a high open circuit voltage and excellent durability. Although the details of why a photoelectric conversion element having a high open circuit voltage and excellent durability can be obtained in the present invention are not clear, it is believed to be for the following reason.

[0014] Cyclic conjugated compounds, which are formed by covalently bonding multiple pyrrole rings, have a planar structure in which the π-electron conjugated system extends throughout the molecule. When these cyclic conjugated compounds are formed into films as charge transport materials, they exhibit high hole transport properties. In addition, these cyclic conjugated compounds can form complexes with various elements at the center of the ring, and can also take axial ligands that are positioned above and below the plane of the cyclic conjugated compound.

[0015] A photoelectric conversion element exhibiting high hole transport ability can be fabricated by forming a film of, for example, a crystal of a phthalocyanine compound having an axial ligand between the photoelectric conversion layer and the electrode as a cyclic conjugated compound in which multiple pyrrole rings are covalently bonded. In this case, the use of a crystal of a phthalocyanine compound having an axial ligand was more advantageous in terms of durability than the use of a crystal of a phthalocyanine compound having no axial ligand. The reason for this is considered to be as follows. In perovskite solar cells, there is a phenomenon in which water molecules from the outside and ions and molecules constituting the photoelectric conversion element migrate to other layers, destroying the structure of the photoelectric conversion element. In contrast, it is speculated that the reason for this is that the migrated water molecules, ions, molecules, etc. are trapped in the space inside the phthalocyanine crystal having an axial ligand, thereby suppressing the progress of migration. In the case of a crystal of a phthalocyanine having no axial ligand, it is difficult to be trapped in the space due to the stacked planar structure. However, in the case of phthalocyanine crystals having axial ligands, the crystal structure is composed of repeated structures in which the axial ligands protrude from a planar structure, and it is thought that trapping occurs easily in the space.

[0016] However, when phthalocyanine crystals with axial ligands were used, a decrease in the open-circuit voltage of the photoelectric conversion element was observed compared to phthalocyanine crystals without axial ligands. The reason for this is thought to be as follows. In phthalocyanines with axial ligands, the axial ligands protrude from the planar structure, resulting in a large moment of biased charge. It is speculated that when the photoelectric conversion element is irradiated with light and a voltage is generated, the large bias in charge acts to cancel out the generated voltage. Thus, there were challenges in achieving a photoelectric conversion element that had a high open-circuit voltage and the durability to maintain that open-circuit voltage.

[0017] In the present invention, it was found that by using a phthalocyanine crystal having an axial ligand, which is a cyclic conjugated compound formed by covalently bonding multiple pyrrole rings, and a resin having a Lewis basic functional group, both high open circuit voltage and durability can be achieved. This is thought to be because the Lewis basic functional group acts electronically on the phthalocyanine crystal having an axial ligand, thereby reducing the large moment of the phthalocyanine crystal having an axial ligand. It is speculated that a photoelectric conversion element that combines durability and high voltage can be achieved by optimizing the moment while keeping the crystal structure that is effective for durability intact.

[0018] The cyclic conjugated compound of the present invention, which is formed by covalently bonding multiple pyrrole rings, has a central element for having an axial ligand. The central element may be various elements, but Ga, Ti, V, Al, In, Fe, and Mn are preferred because they have high charge transport ability. It is more preferred that the cyclic conjugated compound has at least one central element selected from the group consisting of Ga, Ti, V, Al, In, Fe, and Mn. Among them, Ga is more preferred from the viewpoint of electronic interaction with a resin having a Lewis basic functional group.

[0019] The type of axial ligand may be a halogen atom, an alkyl group, an aryl group, a carboxy group, an alkoxy group, a hydroxyl group, a cyano group, an amino group, an oxygen atom, etc. Among them, OH, Cl, and O are preferred from the viewpoint of electronic interaction with a resin having a Lewis basic functional group, and it is preferred that the axial ligand is at least one selected from the group consisting of OH, Cl, and O.

[0020] The crystal of the cyclic conjugated compound of the present invention, which is formed by conjugating multiple pyrrole rings, has a large moment and high charge transport ability because it has an axial ligand. A large moment is generated by having an axial ligand on one side of the planar structure. When there are two axial ligands, when two are coordinated from one side of the planar structure, or when there are different ligands on both sides of the planar structure, a moment is generated, which interacts with the Lewis basic functional group, thereby achieving the effect of the present invention. It is preferable that the cyclic conjugated compound has one axial ligand, since it is easy to interact with the Lewis basic functional group.

[0021] The cyclic conjugated compound of the present invention, which is formed by conjugating a plurality of pyrrole rings, is crystalline. In the present invention, it can be confirmed by the X-ray diffraction spectrum described below that the planar structure of the cyclic conjugated compound formed by conjugating a plurality of pyrrole rings has a crystal structure regularly arranged in at least two directions. It is considered that this crystallinity makes it easier to trap water molecules and ions, and exerts an effect on durability. This can be confirmed by the half-width of the peak in the X-ray diffraction spectrum using CuKα rays for this compound. The smaller the half-width, the larger the crystallites and the stronger the crystallinity. In the present invention, it is sufficient that the half-width of the maximum peak (first peak) and the next largest peak (second peak) in the range of 2θ of 5° to 30° in the X-ray diffraction spectrum are both 1.00° or less. For example, when there is a large peak in the range of 2θ of 5° to 10°, it is considered that there are many crystals stacked in the direction in which the planar structures of the cyclic conjugated compound formed by conjugating a plurality of pyrrole rings overlap. In addition, when there is a large peak in the range of 2θ from 25° to 30°, it is considered that there are many crystals in which the planar structure of the cyclic conjugated compound formed by conjugating multiple pyrrole rings is stacked in the horizontal direction. For example, in FIG. 3, the Bragg angle showing the first peak is 2θ=7.5°, the half width=0.30°, and the Bragg angle showing the second peak is 2θ=28.3°, the half width=0.35°, and this is a crystalline compound of the present invention.

[0022] Specifically, the compound is packed into a Boro-Silicate capillary (length 70 nm, wall thickness 0.01 mm, inner diameter 0.7 mm) (manufactured by W. Muller), and X-ray diffraction measurement is performed under the following conditions. Measuring equipment used: Rigaku Corporation, X-ray diffraction device RINT-TTRII X-ray tube:Cu X-ray wavelength: Kα1 Tube voltage: 50KV Tube current: 300mA Scan method: 2θ-θ scan Scan speed: 4.0° / min Sampling interval: 0.02° Start angle 2θ: 5.0° Stop angle 2θ: 30.0° Goniometer: Rotor horizontal goniometer (TTR-2) Attachment: Capillary rotating sample stage Filter: None Detector: Scintillation counter Incident Monochrome: Use Slit: Variable slit (parallel beam) Counter monochromator: Not used Divergence slit: open Divergence vertical limit slit: 10.00mm Scattering slit: open Receiving slit: open

[0023] The data obtained is then subjected to appropriate processing such as smoothing, background removal, and Kα2 removal, and then fitted with a profile function to obtain an X-ray diffraction spectrum. Specifically, the integrated powder X-ray analysis software PDXL is used, manual processing is selected in data processing, and an X-ray diffraction spectrum is obtained under the following conditions. Smoothing: B-spline smoothing, x-threshold 1.50 Background subtraction: Sonneveld-Visser method, peak threshold 1.00, intensity threshold 10.00 Kα2 removal: intensity ratio 0.4970 Peak search: Second derivative method, σ cut value 6.00 Profile fitting: Split Pearson VII function (fitted to measured data)

[0024] The cyclic conjugated compound having a plurality of pyrrole rings covalently bonded thereto is preferably a porphyrin compound or a phthalocyanine compound, more preferably a phthalocyanine compound, from the viewpoint of the extent of the π-electron cloud that serves as the starting point of the interaction. In particular, a hydroxygallium phthalocyanine compound is preferable from the viewpoint of the interaction with a resin having a Lewis basic functional group.

[0025] Specific examples of the porphyrin compound of the present invention are given below. [ka] R1~R 12 each independently represents an organic group containing a hydrogen atom, an aromatic group which may have a substituent, or an aliphatic group which may have a substituent.

[0026] R1~R 12Specifically, each of R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R15, R16, R17, R18, R19, R20, R21, R22, R23, R24, R25, R26, R27, R28, R29, R30, R31, R32, R33, R34, R35, R36, R37, R38, R39, R40, R41, R42, R43, R44, R45, R46, R47, R48, R49 ... X represents a metal atom, and specifically, Ga, Ti, V, Al, In, Fe, and Mn are preferable. Y is preferably a halogen atom, an alkyl group, an aryl group, a carboxy group, an alkoxy group, a hydroxyl group, a cyano group, an amino group, or an oxygen atom. n is 1 or 2. When n is 2, it is preferable that each Y is different.

[0027] Specific examples of the phthalocyanine compound of the present invention are given below. [ka] R 13 ~R 28Each independently represents an organic group containing a hydrogen atom, an aromatic group which may have a substituent, or an aliphatic group which may have a substituent, and specifically, a hydrogen atom, a methyl group, an ethyl group, a propyl group, a isopropyl group, a butyl group, a octyloxy group, a butoxy group, a halogen atom, a phenyl group, a phenoxy group, a carboxyphenyl group, a benzenesulfonic acid group, a hydroxyphenyl group, a dihydroxyphenyl group, a trihydroxyphenyl group, a methoxyphenyl group, a dimethoxyphenyl group, a trimethoxyphenyl group, a methylphenyl group, a dimethylphenyl group, a trimethylphenyl group, a pyridyl group, an aminophenyl group, a sodium sulfonate base, a 4-cumylphenoxy group, a sulfonic acid group, a phenylthio group, a tert-butyl group, a hydroxy group, a carbonyl group, a methoxy group, an amino group, a sulfo group, and an aldehyde group are preferable. Depending on the type and number of these, the crystallinity is weakened and the state approaches an amorphous state, or solubility in a solvent can be provided. For example, a branched alkyl molecule such as a tert-butyl group can be attached to each benzene ring (for example, R 15 , R 19 , R 23 , R 27 ) in total, the crystallinity tends to be low and the solubility tends to be high. X represents a metal atom, specifically Ga, Ti, V, Al, In, Fe, and Mn are preferable. Y is preferably a halogen atom, an alkyl group, an aryl group, a carboxy group, an alkoxy group, a hydroxyl group, a cyano group, an amino group, or an oxygen atom. n is 1 or 2. When n is 2, it is preferable that each Y is different.

[0028] The charge transport layer of the present invention contains a resin having a Lewis basic functional group. Specific examples of the Lewis basic functional group include a hydroxyl group, a halogen, a sulfo group, an amino group, a carbonyl group, an ester group, an ether group, a carboxyl group, an aldehyde group, a methoxy group, an amide group, a sulfide group, a cyano group, a thienyl group, a pyridyl group, a furyl group, a pyrazolyl group, an imidazolyl group, an oxazolyl group, and a thiazolyl group. Among them, a hydroxyl group, a carbonyl group, an ether group, an amino group, an ester group, a pyridyl group, and a thienyl group are preferred from the viewpoint of electronic interaction with a cyclic conjugated compound formed by conjugating a plurality of pyrrole rings. In particular, it is more preferable that the resin having a Lewis basic functional group has at least one functional group selected from the group consisting of a hydroxy group, a carbonyl group, an ether group, an amino group, an ester group, a pyridyl group, and a thienyl group, and it is even more preferable that the resin has at least two functional groups selected from the group consisting of a hydroxy group, a carbonyl group, an ether group, an amino group, an ester group, a pyridyl group, and a thienyl group. Different functional groups may be contained in one resin, or two resins having different functional groups may be mixed. It is preferable that the Lewis basic functional group is contained in the repeating structure of the resin. In the present invention, the structure of the chemical substance can be determined by, for example, analysis using nuclear magnetic resonance (NMR) or X-ray photoelectron spectroscopy (XPS).

[0029] From the viewpoint of interacting with a cyclic conjugated compound formed by conjugating a plurality of pyrrole rings, and forming a film, the weight average molecular weight of the resin is preferably 10,000 or more.

[0030] Specific examples of the resin having a Lewis basic functional group that can be preferably used in the present invention are given below. Specific examples of such polyvinyl butyral, poly(4-vinylpyridine), poly(vinyl chloride), poly(vinylidene fluoride), polyacrylonitrile, poly(vinylidene fluoride-co-hexafluoropropylene), poly(acrylonitrile-co-butadiene), poly(styrene-co-acrylonitrile), polychloroprene, poly(4-chlorostyrene), polymethyl methacrylate, polyvinyl acetate, polyethyleneimine, polyvinyl alcohol, polyacrylic acid, poly(sodium 4-styrenesulfonate), poly(allylamine hydrochloride), sodium polyacrylate, poly(4-styrenesulfonic acid), poly(N-isopropylacrylamide), poly(2-ethyl-2-oxazoline), poly(ethylene-alt-maleic anhydride), poly(2-acrylamido-2-methyl-1-propanesulfonic acid), potassium poly(vinyl sulfate), and polyanetholsulfonic acid. sodium salt, poly(2-dimethylamino)ethyl methacrylate) methyl chloride quaternary salt, poly(methyl vinyl ether), poly(2-propyl acrylic acid), polyvinylpyrrolidone, polypropylene glycol, poly(propylene carbonate), polyvinyl acetate, poly(tetrahydrofuran), nylon-6, poly(ethylene-co-vinyl acetate), poly(propylene glycol) bis(2-aminopropyl ether), poly(bisphenol A carbonate), poly(1,4-butylene adipate), poly(4-vinylphenol), poly(propylene glycol) monobutyl ether, poly Preferred are poly(glycidyl methacrylate), polybutyl acrylate, poly(ethylene succinate), poly(propylene glycol) methacrylate, nylon 11, nylon 12, poly(2-ethylhexyl acrylate), poly(bisphenol A carbonate), poly(propylene glycol) bis(2-aminopropyl ether), polyetherimide, poly(vinyl formal), poly(vinyl methyl ketone), poly(3-hexylthiophene-2,5-diyl), polyaniline, and a composite of poly(3,4-ethylenedioxythiophene) and polystyrene sulfonate (PEDOT:PSS).Among these, polyvinyl butyral, polymethyl methacrylate, poly(3-hexylthiophene-2,5-diyl), polyaniline, polyvinyl acetate, polyvinyl alcohol, polyacrylic acid, poly(2-propylacrylic acid), polybutyl acrylate, and poly(4-vinylpyridine) are particularly preferred from the viewpoint of electronic interaction.

[0031] From the viewpoint of open circuit voltage and durability due to electronic interaction between a cyclic conjugated compound formed by covalently bonding multiple pyrrole rings and a resin having a Lewis basic functional group, the content of the resin having a Lewis basic functional group in the charge transport layer is preferably 5% by mass or more and 50% by mass or less, more preferably 7% by mass or more and 20% by mass or less, based on the content of the cyclic conjugated compound in the charge transport layer. In the present invention, the mass ratio of chemical substances can be determined, for example, by nuclear magnetic resonance (NMR).

[0032] In the present invention, the glass transition temperature of the resin having a Lewis basic functional group is preferably 95° C. or less. Within this range, the cyclic conjugated compound formed by covalently bonding multiple pyrrole rings and the resin having a Lewis basic functional group are easily in close contact with each other, and are more likely to electronically interact with each other. The glass transition temperature can be determined by a differential scanning calorimeter (DSC).

[0033] The present invention is effective due to the presence of a charge transport layer between the photoelectric conversion layer and the first electrode. Even if another hole transport layer or insulating layer is sandwiched between the charge transport layer and the photoelectric conversion layer, the effects of durability and high open circuit voltage can be obtained because molecules are trapped in the charge transport layer. In order to obtain the effect of durability by suppressing the decomposition and migration of the components of the photoelectric conversion layer, it is most effective to provide a charge transport layer next to the photoelectric conversion layer. Specific examples of the hole transport layer or insulating layer that may be interposed between the charge transport layer and the charge generating layer of the present invention include sodium chloride, sodium iodide, potassium iodide, rubidium iodide, cesium acetate, copper bromide (1), copper iodide (1), nickel chloride (2), zinc iodide, germanium dioxide, aluminum acetylacetonate, europium (3) acetylacetonate, 1,8-diaminooctane dihydroiodide, 1,4-butanediamine dihydroiodide, hexylamine hydrobromide, n-octylamine hydrobromide, 2-phenylethylammonium iodide, ethylenediamine Preferred examples include hydroiodide, sodium fluoride, cesium chloride, methylammonium chloride, lead thiocyanate (2), lead acetate (2), potassium chloride, niobium fluoride (5), choline chloride, L-α-phosphatidylcholine, fullerene, PCBM [(6-6)-phenyl C61 methyl butyrate], iodopentafluorobenzene, F4TCNQ, thiophene, pyridine, pentafluorobenzyl bromide, (3-mercaptopropyl)trimethoxysilane, thiourea, benzylamine, hexamethylenetetramine, N-(3-aminopropyl)-2-pyrrolidinone, theophylline, caffeine, 2-aminoethanesulfonamide hydrochloride, tri-n-octylphosphine oxide, graphene oxide, poly(3-hexylthiophene-2,5-diyl), poly(4-vinylpyridine), polyethylene oxide, polyvinylpyrrolidone, and poly(methyl methacrylate).Among these, sodium chloride, potassium iodide, rubidium iodide, cesium acetate, nickel(2) chloride, aluminum acetylacetonate, n-octylamine hydrobromide, 2-phenylethylammonium iodide, sodium fluoride, cesium chloride, methylammonium chloride, potassium chloride, niobium(5) fluoride, thiophene, pyridine, trimethoxysilane, thiourea, benzylamine, theophylline, poly(4-vinylpyridine), and poly(methyl methacrylate) are particularly preferred.

[0034] When the charge transport layer is formed by a coating method, the coating liquid for the charge transport layer can be prepared by dispersing the crystals of a cyclic conjugated compound in which a plurality of pyrrole rings are covalently bonded in a solvent having a resin having a Lewis basic functional group by various known methods. By coating this coating liquid, a layer can be formed that has the crystals of a cyclic conjugated compound in which a plurality of pyrrole rings are covalently bonded and the resin having a Lewis basic functional group. Examples of the solvent to be used include alcohol-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents. Among these solvents, alcohol-based solvents or aromatic hydrocarbon-based solvents are preferred.

[0035] The thickness of the charge transport layer is preferably from 1 nm to 1000 nm, more preferably from 5 nm to 500 nm, and particularly preferably from 10 nm to 200 nm.

[0036] As explained above, the respective components exert a synergistic effect on each other, thereby making it possible to achieve the effects of the present invention.

[0037] The present invention will be described in detail below with reference to preferred embodiments. The present invention is not limited to the following embodiments, and any modifications or improvements to the following embodiments based on the ordinary knowledge of a person skilled in the art without departing from the spirit of the present invention are also included in the scope of the present invention.

[0038] In this specification, the term "layer" refers not only to a layer having a clear boundary or a flat thin-film layer, but also to a layer having a concentration gradient in which the contained elements gradually change, or to a layer that can form a complex structure together with other layers. Furthermore, elemental analysis of a layer can be performed, for example, by performing TOF-SIMS / FE-TEM / EDS line analysis measurement of a cross section of a photoelectric conversion element to confirm the element distribution of a specific element.

[0039] 1 is a cross-sectional view showing a schematic configuration of one embodiment of the photoelectric conversion element of the present invention. A second electrode 3, an electron transport layer 4, a photoelectric conversion layer 5, a charge transport layer 6, a second charge transport layer 7, and a first electrode 8 are provided on a substrate 2. A current can be extracted by connecting the first electrode 8 and the second electrode 3 with an external circuit.

[0040] The photoelectric conversion layer 5 is excited by light incident through the substrate 2, the second electrode 3, and the electron transport layer 4, or the first electrode 8, the second charge transport layer 7, and the charge transport layer 6, and generates electrons and holes. That is, the photoelectric conversion layer 5 generates a current between the first electrode 8 and the second electrode 3. The electron transport layer 4 is a layer disposed between the photoelectric conversion layer 5 and the second electrode 3, and may not be formed in some cases. The second charge transport layer 7 is a layer disposed between the charge transport layer 6 and the first electrode 8, and may not be formed in some cases. A form in which a plurality of electron transport layers 4 and photoelectric conversion layers 5 are stacked may be used. Such a form may also be called a tandem structure.

[0041] The position of the substrate 2 in Fig. 2 is different from that in Fig. 1. The first electrode 8, the second charge transport layer 7, the charge transport layer 6, the photoelectric conversion layer 5, the electron transport layer 4, and the second electrode 3 are formed in this order on the substrate 2. Thus, even if the position of the substrate 2 is different, the effect of the present invention is achieved. Each component will be described below.

[0042] [Photoelectric conversion element] The photoelectric conversion element of the present invention is a photoelectric conversion element having a first electrode, a second electrode, and a photoelectric conversion layer containing a crystal of a perovskite structure disposed between the first electrode and the second electrode, characterized in that a charge transport layer is provided between the photoelectric conversion layer and the first electrode, the charge transport layer containing a crystal of a compound having an axial ligand, which is a cyclic conjugated compound formed by conjugating a plurality of pyrrole rings, and a resin having a Lewis basic functional group. In addition, in order to improve the photoelectric conversion efficiency, the photoelectric conversion elements may be stacked in a tandem type. The photoelectric conversion elements to be stacked are not limited to the type of photoelectric conversion element, and may include a perovskite solar cell using a crystal of a perovskite structure in the photoelectric conversion layer, a silicon solar cell, a CIGS solar cell, etc.

[0043] Examples of the method for forming the photoelectric conversion layer and each layer including the charge transport layer and each electrode of the photoelectric conversion element of the present invention include a coating method and a deposition method. Examples of the coating method include dip coating, spin coating, spray coating, inkjet coating, meniscus coating, screen coating, roll coating, die coating, blade coating, curtain coating, and wire bar coating. The coating method is a method in which the coating liquid for each layer described later is prepared, coated in the desired layer order, and dried. A desired method can be selected from these film formation methods according to each layer and each electrode. Each layer will be described below.

[0044] 〔substrate〕 The photoelectric conversion element 1 of the present invention may include a substrate 2, examples of which include a transparent glass substrate such as soda-lime glass or alkali-free glass, a ceramic substrate, a transparent plastic substrate, etc. When light is taken in from the first electrode 8 side, an opaque material can be used for the substrate 2, and when light is taken in from the second electrode 3 side, the substrate 2 is made of a transparent material.

[0045] 〔electrode〕 The material of the first electrode 8 and the second electrode 3 is not particularly limited, and a conventionally known material can be used. For example, metals such as gold, silver, titanium, and copper, sodium, sodium-potassium alloy, lithium, carbon nanotubes, magnesium, carbon, aluminum, magnesium-silver mixture, magnesium-indium mixture, aluminum-lithium alloy, Al / Al2O3 mixture, and Al / LiF mixture can be mentioned. Examples of transparent electrode materials include conductive transparent materials such as CuI, ITO (indium tin oxide), SnO2, AZO (aluminum zinc oxide), IZO (indium zinc oxide), GZO (gallium zinc oxide), FTO (fluorine-doped tin oxide), and ATO (antimony-doped tin oxide), and conductive transparent polymers. These materials may be used alone, or two or more kinds may be used in combination. At least one of the electrodes on the light incident side of the first electrode 8 and the second electrode 3 is a transparent electrode, and the other may be a transparent electrode or a transparent electrode that also serves as a reflective layer formed of a light-reflective material, and may be a transparent electrode provided with a reflective layer on the opposite side to the light incident side. When the first electrode 8 is on the light incident side, the second electrode 3 may be a transparent electrode and the substrate 2 may be a reflective layer. The transparent electrode may be a patterned electrode.

[0046] [Photoelectric Conversion Layer] The photoelectric conversion layer 5 has a crystal having a perovskite structure. The crystal having a perovskite structure used in the present invention is preferably represented by the following general formula [1]. ABX3[1] In the above general formula [1], A is a monovalent cation of an organic molecule or a metal atom, B is a divalent metal cation, and X is a monovalent halide anion. In the general formula [1], A is preferably represented by, for example, CpNqHr (where p, q, and r are all positive integers) in the case of an organic molecule. Specific examples include methylammonium and formamidium. The metal atom is not particularly limited, but lithium, cesium, sodium, potassium, and rubidium are preferred. These organic molecules or metal atoms may be used alone or in combination of two or more.

[0047] When the constituent A cations are too large to fit within the 3D perovskite crystal, they form 2D perovskite crystals, 2.5D perovskite crystals with both 2D and 3D properties, bilayer crystals of 3D and 2D perovskite structures, or mixed 3D and 2D perovskite crystals, all of which function as photoelectric conversion layers. A bilayer crystal of 3D and 2D perovskite refers to a crystal in which 3D and 2D perovskite crystals are stacked as independent, separate layers, while a mixed 3D and 2D perovskite refers to a crystal with a structure in which both regions or domains of 2D or 2.5D layered and 3D perovskite crystals are mixed.

[0048] The crystals having a two-dimensional perovskite or 2.5-dimensional perovskite structure are preferably represented by the following general formulas [2] to [4], where n is a positive integer. R'2A n-1 B n X 3n+1 [2] R''A n-1 B n X 3n+1 [3] R'''A n B n X 3n+1 [4] In the above general formulas, [2] forms an RP (Ruddlesden-Popper) type perovskite structure, [3] forms a DJ (Dion-Jacobson) type perovskite structure, and [4] forms an ACI (Alternating cations in the interlayer) type perovskite structure.

[0049] R', R'', and R''' in the above general formulas [2] to [4] are organic molecules or metal cations which may have a substituent, and specific examples thereof include ethylammonium, propylammonium, n-butylammonium, n-hexylammonium, n-octylammonium, 1,6-hexadiammonium, isobutylammonium, 3-(nonafluoro-tert-butyloxy)propylamine, 1,3-propanediammonium, 1,5-pentamethylenediamine, octyldiammonium, 2,2-(ethylenedioxy)bis(ethylammonium), 5-aminovaleric acid, 4-tert-butylammonium, N,N'-dimethylethylene-1,2-diammonium, 2,2,3,3,3-pentafluoropropylammonium, guanidinium, propylammonium, propargylamine, alkylammonium, cyclohexylmethylammonium, 4-(aminomethyl)piperidinium, piperidinium, pyrrolidinium, cyclohexylmethylammonium, 4-(aminomethyl)piperidinium, piperidinium, pyrrolidinium, cyclohexylmethylammonium, 4-aminomethyl)piperidin ... Cylammonium, 4-fluorophenethylammonium, 4-fluorophenethylammonium, trifluoromethylbenzylammonium, pentafluorobenzylammonium, pentafluorophenylethylammonium, 4-methoxyphenethylammonium, imidazolium, pyridinium, 3-thiophenemethylammonium, 2-thiopheneethylammonium, 2-thiopheneformamidium, 2-thiophenemethylammonium, 1-naphthylmethylammonium, 2-naphthylmethylammonium, phenethylammonium, phenylammonium, benzylammonium, 2,5-thiophenedimethylammonium, phenylpropylammonium, 1,4-phenylenedimethanamine, 3-phenyl-2-propene-1-ammonium, phenylbutylammonium, 4-tert-butyl-benzylammonium, 3-(aminomethyl)piperidinium, 4-(aminomethyl)piperidinium are preferred.

[0050] In the above formulas [1] to [4], B is a metal atom, such as lead, tin, bismuth, zinc, titanium, antimony, nickel, iron, cobalt, silver, copper, gallium, germanium, magnesium, calcium, indium, aluminum, manganese, chromium, molybdenum, and europium. Among these, lead, tin, and bismuth are preferred from the viewpoint of electron orbital overlap. These metal atoms may be used alone or in combination of two or more.

[0051] X in the above formulas [1] to [4] is a halogen atom, such as chlorine, bromine, and iodine. These halogen atoms may be used alone or in combination of two or more. Among them, halogen atoms are preferred because the perovskite crystals are easily soluble in organic solvents by containing halogen in the structure, making it possible to apply the perovskite crystals to inexpensive printing methods and the like. Furthermore, iodine is more preferred because the energy band gap of the perovskite crystals is narrowed.

[0052] Specifically, 3D perovskites, 2D perovskites, and mixed 3D / 2D perovskites are MAPbI3 and FAPbCl 3、 FAPbI3, MAPbI x Br 3-x、 MAPbI x Cl 3-x、 Cs 0.05 (MA 0.17 FA 0.83 ) 0.95 Pb(I 0.83 Br 0.17 )3, {Cs x1 (FA x2 MA 1-x2 ) 1-x1} x3 Pb(I x4 Br 1-x4 ) x5 , Cs 0.05 FA 0.88 MA 0.07 PbI 2.56 Br 0.44 , (FAPbI3) 0.95 (MAPbBr3) 0.05 , (FAPbI3) 0.85(MAPbBr3) 0.15 、CsPbI 3、 CsPbBr 3、 Cs x (MA) 1-x PbI3,Cs x (FA) 1-x PbI 3, MA x (FA) 1-x PbI 3, MA 0.17 FA 0.83 Pb(I 0.83 Br 0.17 ) 3, Cs 0.15 FA 0.85 PbI 2.55 Br 0.45 、Cs 0.05 FA 0.88 MA 0.07 PbI 2.56 Br 0.44 、Cs 0.15 FA 0.85 PbI 2.55 Br 0.45、 (AND)2(MA)2Pb3I 10 ,(PTA)2(MA)4Pb5I 16 ,(AND)2(MA)4Pb5I 16 ,(ThMA)2(MA)2Pb3I 10, (3BBA)2(MA)2Pb3I 10, (ThMA)2(FA)4Pb5I 16, (4FPEA)2(FA 0.3 MA 0.7 )4Pb5I 16 ,(PDMA)FA2Pb3I 10, (3AMPY)(MA)3Pb4I 13 ,(PDMA)MA5Pb6I 19 ,(PDMA)MA3Pb4I 13 ,(TTDMA)MA3Pb4I 13 ,(TTDMA)MA4Pb5I 16 ,(THAT 0.9 AND 0.1 )2MA4Pb5I 16 ,(THAT 0.9 AND 0.1 )2MA3Pb4I 13 、(4FPEA)2MA3Pb4I13 , (4FPEA)2MA4Pb5I 16 , (BA)2MA2Pb3I 10 , (BA)2MA3Pb4I 13 , (TEA)2MA2Pb3I 10 , (BA)2MA4Pb5I 16 , (BA)2MA3Pb4I 13、 CsSnBr3, CsSnI3, FA 0.75 MA 0.25 Sn 0.95 Ge 0.05 I3, FAMASnGeI3, FASnBr3, FASnI3, MA2Sn3I8, MASnBr3, MASnGeI3, and MASnI3 are preferred.

[0053] Depending on the purpose, the A site, B site, or X site in the above general formula may be adjusted to be under- or over-adjusted, and the combination of x1 to x5 may be changed depending on the purpose. Combinations of x1 to x5 are, for example, as shown in Table 1. Particularly preferred ranges are 0.03≦x1≦0.10, 0.80≦x2≦0.96, 0.95≦x3≦1.05, 0.80≦x4≦0.96, and 2.95≦x5≦3.05. MACl may be included as a material for forming perovskite crystals. [Table 1]

[0054] In the above specific examples, "MA" stands for methylammonium, "FA" stands for formamidinium, "PEA" stands for phenethylammonium, "PTA" stands for phenyltriethylammonium, "ThMA" stands for 2-thiophenemethylammonium, "3BBA" stands for 3-bromobenzylammonium, "3AMPY" stands for 3-(aminomethyl)pyridine, "PDMA" stands for 1,4-phenylenedimethaneammonium, "TTDMA" stands for thieno[3,2-b]thiophene-2,5-diyldimethaneammonium, "4FPEA" stands for 4-fluorophenethylammonium, "BA" stands for butylammonium, and "TEA" stands for 2-thiophenethylammonium.

[0055] The crystal with the perovskite structure preferably has a cubic structure in which a metal atom B is located at the body center, an organic molecule A at each vertex, and a halogen atom X at the face center. Although the details are not clear, it is presumed that the presence of such a structure makes it easy to change the orientation of the octahedron in the crystal lattice, thereby increasing the mobility of electrons in the crystal with the perovskite structure and improving the photoelectric conversion efficiency of the photoelectric conversion element.

[0056] The perovskite crystal used in the present invention is preferably a crystalline semiconductor. The crystalline semiconductor means a semiconductor in which the scattering peak can be detected by measuring the X-ray scattering intensity distribution. By using the perovskite crystal as a crystalline semiconductor, the mobility of electrons in the perovskite crystal is increased, and the photoelectric conversion efficiency of the photoelectric conversion element is improved.

[0057] The thickness of the photoelectric conversion layer according to the present invention is preferably 5 nm or more and 2000 nm or less. If the thickness is 5 nm or more, light can be sufficiently absorbed, and if the thickness is 2000 nm or less, the generated charge can be transported to each electrode. The more preferred lower limit is 50 nm, the more preferred upper limit is 1200 nm, the even more preferred lower limit is 100 nm, and the even more preferred upper limit is 1000 nm.

[0058] [Hole transport layer (second charge transport layer)] In the present invention, it is preferable to have a second charge transport layer between the first electrode and the charge transport layer from the viewpoint of film compatibility. The material of the second charge transport layer 7 is not particularly limited, and examples thereof include spirofluorene compounds, triphenylamine compounds, chrysene compounds, pyrene compounds, phthalocyanine compounds, carbazole compounds, fluorene compounds, phenylcyclohexane compounds, benzidine compounds, phenoxazine compounds, phenylenediamine compounds, thiocyanate compounds, and thiophene compounds. In particular, from the viewpoint of compatibility with the film interface, it is preferable that the compound has an aromatic ring, and Spiro-OMeTA, PTAA, and phthalocyanine compounds are preferred.

[0059] The second charge transport layer may have a dopant as an additive to improve the charge transport ability. Examples of materials that can be used as a dopant include lithium compounds such as bis(trifluoromethanesulfonyl)imide lithium, cobalt compounds such as [tris(2-(1H-pyrazol-1-yl)-4-tert-butylpyridine)cobalt(3)tris(bis(trifluoromethylsulfonyl)imide)], boron compounds such as tetrakis(pentafluorophenyl)borate, molybdenum compounds such as tris[1-(methoxycarbonyl)-2-(trifluoromethyl)-ethane-1,2-dithiolene]molybdenum, organic compounds having a tetracyanoquinodimethane skeleton such as 2,3,4,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane, and organic compounds having a pyridine skeleton such as 4-tert-butylpyridine.

[0060] [Electron transport layer] In the photoelectric conversion element of the present invention, as shown in FIGS. 1 and 2, an electron transport layer 4 may be disposed between the second electrode 3 and the photoelectric conversion layer 5. The material of the electron transport layer 4 is not particularly limited, and examples thereof include N-type conductive polymers, N-type low-molecular-weight organic semiconductors, N-type metal oxides, N-type metal sulfides, alkali metal halides, alkali metals, surfactants, and the like. Specific examples thereof include cyano group-containing polyphenylene vinylene, boron-containing polymers, bathocuproine, bathophenanthrene, hydroxyquinolinatoaluminum, oxadiazole compounds, benzimidazole compounds, naphthalene tetracarboxylic acid compounds, fullerene compounds, perylene compounds, phosphine oxide compounds, phosphine sulfide compounds, fluoro group-containing phthalocyanines, titanium oxide, zinc oxide, indium oxide, tin oxide, gallium oxide, tin sulfide, indium sulfide, and zinc sulfide.

[0061] The thickness of the electron transport layer 4 is preferably 1 nm at the lower limit and 2000 nm at the upper limit. If the thickness is 1 nm or more, holes can be blocked sufficiently, and if the thickness is 2000 nm or less, the layer is unlikely to become a resistance during electron transport, and the photoelectric conversion efficiency is increased. The more preferable lower limit of the thickness is 3 nm, the more preferable upper limit is 1000 nm, the even more preferable lower limit is 5 nm, and the even more preferable upper limit is 500 nm.

[0062] <Application Examples> Application examples of the present invention are photoelectric conversion devices, moving bodies, building materials, etc. The following will explain the application examples.

[0063] [Photoelectric conversion device] The photoelectric conversion device of the present invention has the photoelectric conversion element of the present invention. A photoelectric conversion device can be configured by using a plurality of photoelectric conversion elements of the present invention. When a plurality of photoelectric conversion elements are connected, such a photoelectric conversion device can also be called a photoelectric conversion cell or a photoelectric conversion module. The photoelectric conversion element may be a stack of elements having different absorption wavelengths in order to increase the output voltage. The photoelectric conversion device may have the photoelectric conversion element of the present invention and an inverter. The inverter may be a converter that converts direct current to alternating current. The photoelectric conversion device may have a storage unit connected to the photoelectric conversion element. The storage unit is not limited as long as it can store electricity. For example, a secondary battery using lithium ions, an all-solid-state battery, and an electric double layer capacitor can be mentioned. In order to impart a function such as maintaining or increasing the amount of incident light, a surface layer that is resistant to water and dirt, or a function of collecting or guiding light may be added.

[0064] [Mobile object] The moving body of the present invention has the photoelectric conversion element of the present invention. FIG. 4 is a perspective view showing an embodiment of a moving body equipped with the photoelectric conversion element of the present invention. The moving body 30 has the photoelectric conversion element 31 of the present invention and a vehicle 32 equipped with the photoelectric conversion element 31. The photoelectric conversion element 31 is arranged at a position where it can receive external light from the vehicle 32. If the moving body 30 is an automobile, it may be arranged on the roof. The electric energy obtained by the photoelectric conversion element 31 may be used as the power of the moving body 30 or as the power of other electric devices. The electric energy generated from the power of the moving body 30 may be used to power the photoelectric conversion element 31. If the moving body 30 is an automobile, frictional energy generated by braking may be converted into electric energy and used to control the photoelectric conversion element 31. The moving body 30 may be, for example, an automobile, a motorcycle, a railroad vehicle, a ship, an artificial satellite, an airplane, or a flying object including a drone. The configuration of the body 32 of the moving body 30 is not particularly limited, but it is preferable that the body 32 be made of a high-strength material.

[0065] [Building materials] The building material of the present invention has the photoelectric conversion element of the present invention. Fig. 5 is a perspective view showing an embodiment of a building material including the photoelectric conversion element of the present invention. The building material 40 may be the roof of a building. The building material 40 of this embodiment has the photoelectric conversion element 41 of the present invention, a protective member 42 that protects the photoelectric conversion element 41, a heat dissipation member 43, and exteriors 44a and 44b.

[0066] The building material 40 of the present invention may have a heat dissipation member 43 having a higher thermal conductivity than the photoelectric conversion element 41. When used on a roof or the like, the temperature of the photoelectric conversion element 41 may increase due to sunlight, and the photoelectric conversion efficiency may decrease. The use of the heat dissipation member 43 can reduce the decrease in photoelectric conversion efficiency. Examples of the heat dissipation member 43 include metal, alloy, liquid metal, and liquid resin.

[0067] Furthermore, the building material 40 of the present invention may have exteriors 44a and 44b. The exteriors 44a and 44b may emit different colors or may be the same. 44a and 44b may be made of the same material or different materials. Paint or a transparent substrate may be used as the exterior. A material with low light absorption and high heat insulation is preferable.

[0068] 〔others〕 In addition to the above application examples, other application examples include the following: Portable devices, such as calculators, sensors, and small solar panels. Wearable devices, such as eyeglass-type terminals, wristwatch-type terminals, and portable medical equipment. Sheet structures supported by multiple frames, such as tents, vinyl greenhouses, and truck beds. Fixed structures, such as road panels, floating panels, building materials that take advantage of the flexibility of the substrate, wall-type building materials, glass-type building materials, and mega solar panels.

[0069] [About the manufacturing method of photoelectric conversion element] A method for producing a photoelectric conversion element of the present invention includes the steps of forming a first electrode, forming a second electrode, forming a photoelectric conversion layer containing crystals with a perovskite structure between the first electrode and the second electrode, and forming a charge transport layer between the photoelectric conversion layer and the first electrode. Each step of the manufacturing method will be described below.

[0070] (Step of forming a first electrode and step of forming a second electrode) In the step of forming the first electrode and the step of forming the second electrode, an appropriate method can be selected according to the material of the first electrode and the material of the second electrode, respectively. Examples of such methods include, but are not limited to, sputtering vacuum deposition, CVD (vapor phase deposition), and SPD (spray pyrolysis deposition). The materials of the first electrode and the second electrode are as described above. When either or both of the first electrode and the second electrode are transparent electrodes, the thickness of the transparent electrode is preferably 0.03 μm or more and 3 μm or less. When manufacturing a solar cell, cutting may be performed between each process to form a circuit. Examples of cutting include mechanical patterning and laser patterning.

[0071] (Modularization process) The element having the electrodes formed thereon may be sealed. Examples of the sealing method include sealing with a resin or sealing with a film. Examples of the material used for sealing include silazane, silicone rubber, a resin having a siloxane skeleton, and glass. In addition, from the viewpoint of preventing adhesion between elements that occurs when the elements are wound in a roll-to-roll system, the surfaces of the encapsulated elements may be subjected to a hairline treatment.

[0072] (Step of forming photoelectric conversion layer) The step of forming the photoelectric conversion layer may include a step of applying a liquid containing the material of the photoelectric conversion layer described above. Examples of the application method include spin coating, blade coating, slit die coating, screen printing, bar coater, casting, printing transfer, immersion and pulling, inkjet, spraying, and vacuum deposition. Among these, a method is appropriately selected according to the characteristics of the photoelectric conversion layer to be produced, such as thickness control and orientation control.

[0073] In order to remove the solvent or dispersion medium from the liquid containing the applied photoelectric conversion layer material, annealing may be performed under reduced pressure or in an inert atmosphere (nitrogen or argon atmosphere). The temperature of the annealing is preferably 40° C. or higher and 300° C. or lower, and more preferably 50° C. or higher and 150° C. or lower. Note that annealing is preferable because it may increase the contact area at the interface between the stacked layers by allowing the materials constituting each layer to penetrate into each other, thereby increasing the short-circuit current.

[0074] (Step of forming charge transport layer) The step of forming the charge transport layer is preferably a method of applying a liquid containing the material of the charge transport layer. Examples of the application method include spin coating, blade coating, slit die coating, screen printing, bar coater, casting, printing transfer, immersion and pulling, inkjet, spraying, and vacuum deposition. Examples of the step of forming the charge transport layer include the following.

[0075] The methods include a method of arranging crystals of a compound having an axial ligand, which is a cyclic conjugated compound formed by conjugating a plurality of pyrrole rings, and then applying a resin having a Lewis basic functional group; a method of applying a resin solution in which a resin having a Lewis basic functional group is dissolved, and then arranging crystals of a compound having an axial ligand, which is a cyclic conjugated compound formed by conjugating a plurality of pyrrole rings, and then applying a solution in which crystals of a compound having an axial ligand, which is a cyclic conjugated compound formed by conjugating a plurality of pyrrole rings, and then applying an axial ligand crystal dispersion to a resin solution in which a resin having a Lewis basic functional group is dissolved. EXAMPLES

[0076] The present invention will be described in more detail below using examples and comparative examples. The present invention is not limited to the following examples without departing from the gist of the present invention. In the following description of the examples, "parts" are by mass unless otherwise specified.

[0077] Example 1 [Formation of Electron Transport Layer] A glass substrate with ITO was cleaned, and tin(II) oxide adjusted to 3% by mass was applied thereon by spin coating. The substrate was then heated at 150° C. for 30 minutes to form a thin-film electron transport layer having a thickness of 15 nm.

[0078] [Formation of photoelectric conversion layer] 22.4 mg of methylammonium bromide, 172 mg of formamidium iodide, and 576 mg of lead iodide were dissolved in 600 μL of N,N-dimethylformamide and 160 μL of dimethyl sulfoxide, and the mixture was stirred for 1 hour (solution 1). Furthermore, 389.7 mg of cesium iodide was dissolved in 1000 μL of dimethyl sulfoxide, and the mixture was stirred for 1 hour (solution 2). After that, 40 μL of the dissolved cesium iodide solution (solution 2) was added to solution 1 to prepare a coating solution for the photoelectric conversion layer. This coating solution was spin-coated on the electron transport layer to obtain Cs 0.05 (FA 0.83 MA 0.17 ) 0.96 Pb(I 0.95 Br 0.05 A photoelectric conversion layer having a thickness of 400 nm was formed from the photoelectric conversion layer 3.

[0079] [Formation of Charge Transport Layer] Preparation of particle 1 Process (1) In a nitrogen flow atmosphere, 5.46 parts of orthophthalonitrile and 45 parts of α-chloronaphthalene were put into a reaction vessel, and then heated to a temperature of 30° C. and maintained at this temperature. Next, 3.75 parts of gallium trichloride were put in at this temperature (30° C.). The water concentration of the mixed liquid at the time of putting in was 150 ppm. Then, the temperature was raised to 200° C. Next, under a nitrogen flow atmosphere, the reaction was carried out at a temperature of 200° C. for 4.5 hours, and then cooled. When the temperature reached 150° C., the product was filtered. The obtained filtrate was dispersed and washed using N,N-dimethylformamide at a temperature of 140° C. for 2 hours, and then filtered. The obtained filtrate was washed with methanol and then dried to obtain chlorogallium phthalocyanine particles with a yield of 71% by mass.

[0080] Process (2) 4.65 parts of the chlorogallium phthalocyanine particles were dissolved in 139.5 parts of concentrated sulfuric acid at a temperature of 10°C, dropped into 620 parts of ice water under stirring to reprecipitate, and filtered under reduced pressure using a filter press. No. 5C (manufactured by Advantec Co., Ltd.) was used as the filter. The obtained wet cake (filtrate) was dispersed and washed with 2% ammonia water for 30 minutes, and then filtered using a filter press. Next, the obtained wet cake (filtrate) was dispersed and washed with ion-exchanged water, and then filtration using a filter press was repeated three times. Finally, freeze-drying was performed to obtain hydroxygallium phthalocyanine particles (hydrated hydroxygallium phthalocyanine particles) with a solid content of 23% by mass at a yield of 71% by mass. The hydroxygallium phthalocyanine particles were dried using a hyper-dry dryer (trade name: HD-06R, frequency (oscillation frequency): 2455MHz±15MHz, manufactured by Japan Biocon Co., Ltd.) to obtain hydroxygallium phthalocyanine particles with a water content of 1.0% by mass or less.

[0081] Process (3) Five parts of the hydroxygallium phthalocyanine particles were mixed with five parts of dimethylformamide, and the mixture was dispersed for six hours using a sand mill (TSG-1 / 4G-4U, manufactured by Igarashi Machinery Manufacturing Co., Ltd. (now Imex), disk diameter 70 mm, number of disks 5) containing five parts of glass beads, filtered, and dried to obtain Particle 1.

[0082] <X-ray diffraction measurement of particle 1> The measurements were performed according to the method described above. The half-widths of the first and second peaks were 1.0° or less.

[0083] Preparation of resin solution 1 1.0 g of polyvinyl butyral (product name: BM-2, manufactured by Sekisui Chemical Co., Ltd., glass transition temperature 71° C.) was dissolved in 19 g of 2-propanol with stirring for 24 hours to obtain resin solution 1. 0.1g of the particles 1 and 0.01g of a calixarene compound (JP Patent Publication 2003-207913) were mixed with 10.6g of 2-propanol, 11g of zirconia beads were encapsulated in this mixture, and dispersion was performed for 6 hours using a paint shaker (manufactured by Toyo Seiki Co., Ltd.). Then, 0.2g of resin solution 1 was added, and dispersion was performed again for 6 hours using a paint shaker to prepare a coating liquid for a charge transport layer. The coating liquid for the charge transport layer was spin-coated on the photoelectric conversion layer to form a charge transport layer having a thickness of 180nm.

[0084] [Formation of the second charge transport layer] 0.15 g of Spiro-OMeTAD as the second charge transport layer was dissolved in 2.2 g of chlorobenzene. 36 μL of acetonitrile solution obtained by dissolving 0.2 g of bis(trifluoromethanesulfonyl)imide lithium in 0.3 g of acetonitrile and 60 μL of t-butylpyridine (TBP) were added to this chlorobenzene solution and mixed. Furthermore, 58 μL of acetonitrile solution obtained by dissolving 0.11 g of [tris(2-(1H-pyrazol-1-yl)-4-tert-butylpyridine)cobalt(III) tris(bis(trifluoromethylsulfonyl)imide)] in 0.3 g of acetonitrile was mixed to prepare a coating solution for the second charge transport layer. This was applied by spin coating on the charge transport layer to form a second charge transport layer with a thickness of 200 nm.

[0085] [Formation of the first electrode] On the second charge transport layer, a layer having a thickness of 80 nm and an area of ​​0.09 cm 2 A gold electrode was formed by vacuum deposition to obtain a photoelectric conversion element.

[0086] [Analysis of compound amounts] The electrode surface of the photoelectric conversion element was peeled off to expose the charge transport layer surface. This charge transport layer surface was wiped with a cotton swab soaked in a solvent, dissolved in heavy water sulfuric acid, and 1H-NMR measurement (apparatus: AVANCE3-500, manufactured by BRUKER) was performed. In addition, the peeled off charge transport layer components were subjected to mass and structure analysis by elemental analysis such as GPC, MALDI-TOF-MS, IR, gas chromatography, XPS, and EDX to confirm the presence of compounds. The phthalocyanine was recovered from the charge transport layer of the photoelectric conversion element and subjected to XRD measurement according to the above-mentioned method, and it was confirmed that the half-width of the first peak and the second peak was 1.0° or less. The film thickness was confirmed by cutting the photoelectric conversion element, fixing it to an inclined sample stage, and then observing the cross-section with a SEM (apparatus: Carl Zeiss, SmartSEM).

[0087] Example 2 The preparation was carried out in the same manner as in Example 1, except that the cyclic conjugated compound formed by conjugating a plurality of pyrrole rings was changed to titanyl phthalocyanine.

[0088] Example 3 The preparation was carried out in the same manner as in Example 1, except that the cyclic conjugated compound formed by conjugating a plurality of pyrrole rings was changed to chlorogallium phthalocyanine.

[0089] Example 4 The photoelectric conversion layer is formed in the same manner as in Example 1. Then, a solution in which 2.49 mg of 2-phenethylethylamine hydroiodide is dissolved in 1 mL of 2-propanol is spin-coated onto the photoelectric conversion layer to form a layer having a thickness of 20 nm. Then, a charge transport layer, a second charge transport layer, and a first electrode are formed in the same manner as in Example 1.

[0090] Example 5 The preparation was carried out in the same manner as in Example 1, except that the second charge transport layer was not formed.

[0091] Example 6 The charge transport layer coating solution was prepared in the same manner as in Example 1, except that 0.2 g of particles 1 was used.

[0092] Example 7 The charge transport layer coating solution was prepared in the same manner as in Example 1, except that 0.14 g of resin solution 1 was used.

[0093] Example 8 The charge transport layer coating solution was prepared in the same manner as in Example 1, except that 0.40 g of resin solution 1 was used.

[0094] Example 9 In preparing the coating solution for the charge transport layer, the resin having a Lewis basic functional group was changed to poly(3-hexylthiophene-2,5-diyl) P3HT (weight average molecular weight 50,000 to 100,000, manufactured by Sigma-Aldrich), the solvent used was changed from 2-propanol to monochlorobenzene to prepare a resin solution, and 1 g of the resin solution was used when preparing the coating solution for the charge transport layer. Except for this, the coating solution for the charge transport layer was prepared in the same manner as in Example 1.

[0095] Example 10 In preparing the coating solution for the charge transport layer, the resin having a Lewis basic functional group was changed to poly(3-hexylthiophene-2,5-diyl) P3HT (weight average molecular weight 50,000 to 100,000, manufactured by Sigma-Aldrich), the solvent used was changed from 2-propanol to monochlorobenzene to prepare a resin solution, and 2 g of the resin solution was used when preparing the coating solution for the charge transport layer. Except for this, the coating solution for the charge transport layer was prepared in the same manner as in Example 1.

[0096] Example 11 In preparing the coating solution for the charge transport layer, the resin having a Lewis basic functional group was changed to poly(3-hexylthiophene-2,5-diyl) P3HT (weight average molecular weight 50,000 to 100,000, manufactured by Sigma-Aldrich), the solvent used was changed from 2-propanol to monochlorobenzene to prepare the resin solution, and 0.24 g of the resin solution was used when preparing the coating solution for the charge transport layer. Except for this, the coating solution for the charge transport layer was prepared in the same manner as in Example 1.

[0097] Example 12 The coating solution for the charge transport layer was prepared in the same manner as in Example 1, except that the resin having a Lewis basic functional group was changed to polyaniline (weight average molecular weight 65,000, manufactured by Sigma-Aldrich), and the solvent used was changed from 2-propanol to N-methyl-2-pyrrolidone to prepare the resin solution.

[0098] Example 13 In preparing the coating solution for the charge transport layer, the resin having a Lewis basic functional group was changed to polymethyl methacrylate resin PMMA (manufactured by Sigma-Aldrich, glass transition temperature 70°C), and the solvent used was changed from 2-propanol to monochlorobenzene to prepare the resin solution. Except for this, the coating solution was prepared in the same manner as in Example 1.

[0099] Example 14 The coating solution for the charge transport layer was prepared in the same manner as in Example 1, except that the resin having a Lewis basic functional group was changed to poly(4-vinylpyridine) (weight average molecular weight 60,000, manufactured by Sigma-Aldrich, glass transition temperature 137°C).

[0100] Example 15 In preparing the coating solution for the charge transport layer, the resin having a Lewis basic functional group was changed to polyacrylonitrile (weight average molecular weight 150,000, manufactured by Sigma-Aldrich, glass transition temperature 85°C), and the solvent used was changed from 2-propanol to dimethylformamide to prepare the resin solution. Except for this, the coating solution for the charge transport layer was prepared in the same manner as in Example 1.

[0101] (Example 16) The preparation was carried out in the same manner as in Example 1, except that the cyclic conjugated compound formed by conjugating a plurality of pyrrole rings was changed to 5,10,15,20-tetraphenyl-21H,23H-porphine iron chloride.

[0102] (Example 17) The preparation was carried out in the same manner as in Example 1, except that the cyclic conjugated compound formed by conjugating a plurality of pyrrole rings was changed to vanadyl phthalocyanine.

[0103] (Example 18) The preparation was carried out in the same manner as in Example 1, except that the cyclic conjugated compound formed by conjugating a plurality of pyrrole rings was changed to chloroindium phthalocyanine.

[0104] (Example 19) The preparation was carried out in the same manner as in Example 1, except that the cyclic conjugated compound formed by conjugating a plurality of pyrrole rings was changed to chloroaluminum phthalocyanine.

[0105] (Example 20) The preparation was carried out in the same manner as in Example 1, except that the cyclic conjugated compound formed by conjugating a plurality of pyrrole rings was changed to 5,10,15,20-tetraphenyl-21H,23H-porphine manganese chloride.

[0106] Example 21 The coating solution for the charge transport layer was prepared in the same manner as in Example 1, except that the resin having a Lewis basic functional group was changed to polymethyl methacrylate resin (PMMA, manufactured by Sigma-Aldrich, glass transition temperature 100°C), and the solvent used was changed from 2-propanol to monochlorobenzene to prepare the resin solution.

[0107] Example 22 The coating solution for the charge transport layer was prepared in the same manner as in Example 1, except that the resin having a Lewis basic functional group was changed to a polyvinyl acetal resin (product name: BX-1, manufactured by Sekisui Chemical Co., Ltd., glass transition temperature 95°C).

[0108] (Example 23) In preparing the coating solution for the charge transport layer, the resin having a Lewis basic functional group was changed to a polyvinyl acetal resin (product name: KS-10, manufactured by Sekisui Chemical Co., Ltd., glass transition temperature: 105°C), and the solvent used was changed from 2-propanol to ethanol to prepare the resin solution. Except for this, the coating solution was prepared in the same manner as in Example 1.

[0109] Comparative Example 1 Resin solution 1 was prepared in the same manner as in Example 1, except that a resin having a Lewis basic functional group was not used.

[0110] Comparative Example 2 The preparation was carried out in the same manner as in Comparative Example 1, except that the cyclic conjugated compound formed by conjugating a plurality of pyrrole rings was changed to copper phthalocyanine.

[0111] Comparative Example 3 The same procedure as in Example 1 was repeated except that the cyclic conjugated compound formed by conjugating multiple pyrrole rings was changed to 2,9,16,23-tetra-tert-butyl-29H,31H-chloroaluminum phthalocyanine, and chloroform was used instead of 2-propanol in the preparation of the coating liquid for the charge transport layer.

[0112] Comparative Example 4 The coating solution for the charge transport layer was prepared in the same manner as in Example 1, except that the resin was changed to poly(9,9-dioctylfluorenyl-2,7-diyl) (weight average molecular weight 50,000 to 150,000, manufactured by Sigma-Aldrich) and the solvent was changed from 2-propanol to xylene.

[0113] Comparative Example 5 The preparation was carried out in the same manner as in Example 1, except that the cyclic conjugated compound formed by conjugating a plurality of pyrrole rings was changed to copper phthalocyanine.

[0114] Comparative Example 6 The preparation was carried out in the same manner as in Example 1, except that the cyclic conjugated compound formed by conjugating a plurality of pyrrole rings was changed to zinc phthalocyanine.

[0115] Comparative Example 7 The charge transport layer coating solution was prepared in the same manner as in Example 1, except that the particles 1 were changed to Spiro-OMeTAD, the resin having a Lewis basic functional group was changed to polymethyl methacrylate resin (PMMA, manufactured by Sigma-Aldrich, glass transition temperature 100°C), and the solvent used was changed from 2-propanol to monochlorobenzene to prepare the resin solution.

[0116] [evaluation] (Open circuit voltage evaluation) A power supply (KEITHLEY, Model 236) was connected between the electrodes of the photoelectric conversion element of Example 1, and the intensity was 100 mW / cm 2 A constant amount of light was irradiated using a solar simulator (manufactured by Yamashita Denso Co., Ltd.) and the generated current and voltage were measured to evaluate the open circuit voltage. The results are shown in Table 3. Examples 2 to 23 and Comparative Examples 1 to 7 were also evaluated in the same manner as in Example 1 to evaluate the open circuit voltage. The results are shown in Table 3.

[0117] (Durability evaluation) The durability of the photoelectric conversion element of Example 1 was evaluated by continuously irradiating it with 10,000 Lx of light from a white LED and measuring the open circuit voltage after 30 days. It was evaluated as the maintenance rate of the open circuit voltage after 30 days relative to the initial open circuit voltage. The results are shown in Table 3. Examples 2 to 23 and Comparative Examples 1 to 7 were also evaluated in the same manner as Example 1, and the durability was evaluated as the maintenance rate of the open circuit voltage after 30 days relative to the initial open circuit voltage. The results are shown in Table 3.

[0118] (Evaluation of X-ray diffraction measurements) As a result of X-ray diffraction measurement of a cyclic conjugated compound, if the half width of the maximum peak and the second largest peak are both 1.0° or less, it is rated as A, and if it does not satisfy this condition, it is rated as B. In the present invention, in the case of A, it is determined that the cyclic conjugated compound is crystalline, and in the case of B, it is determined that the cyclic conjugated compound is not crystalline. The results are shown in Table 3.

[0119] [Table 2]

[0120] [Table 3]

[0121] The disclosure of this embodiment includes the following configuration. [Configuration 1] A photoelectric conversion element having a first electrode, a second electrode, and a photoelectric conversion layer including a crystal having a perovskite structure and disposed between the first electrode and the second electrode, a charge transport layer between the photoelectric conversion layer and the first electrode, the charge transport layer including a crystal of a compound having an axial ligand, the compound being a cyclic conjugated compound formed by conjugating a plurality of pyrrole rings, and a resin having a Lewis basic functional group. [Configuration 2] The photoelectric conversion element according to configuration 1, further comprising a second charge transport layer between the first electrode and the charge transport layer. [Configuration 3] The photoelectric conversion element according to any one of configurations 1 and 2, wherein the resin having a Lewis basic functional group has at least one functional group selected from the group consisting of a hydroxyl group, a carbonyl group, an ether group, an amino group, an ester group, a pyridyl group, and a thienyl group. [Configuration 4] 4. The photoelectric conversion element according to claim 3, wherein the resin having a Lewis basic functional group has at least two functional groups selected from the group consisting of a hydroxy group, a carbonyl group, an ether group, an amino group, an ester group, a pyridyl group, and a thienyl group. [Configuration 5] The photoelectric conversion element according to any one of configurations 1 to 4, wherein the content of the resin having a Lewis basic functional group in the charge transport layer is 5% by mass to 50% by mass with respect to the content of the cyclic conjugated compound in the charge transport layer. [Configuration 6] The photoelectric conversion element according to configuration 5, wherein the content of the resin having a Lewis basic functional group in the charge transport layer is 7% by mass or more and 20% by mass or less with respect to the content of the cyclic conjugated compound in the charge transport layer. [Configuration 7] 7. The photoelectric conversion element according to any one of configurations 1 to 6, wherein the cyclic conjugated compound has at least one central element selected from the group consisting of Ga, Ti, V, Al, In, Fe, and Mn. [Configuration 8] 8. The photoelectric conversion element according to any one of configurations 1 to 7, wherein the cyclic conjugated compound has one axial ligand. [Configuration 9] The photoelectric conversion element according to any one of configurations 1 to 8, wherein the axial ligand is at least one selected from the group consisting of OH, Cl and O. [Configuration 10] 10. The photoelectric conversion element according to any one of configurations 1 to 9, wherein the cyclic conjugated compound is a phthalocyanine compound. [Configuration 11] 11. The photoelectric conversion element according to configuration 10, wherein the phthalocyanine compound is a hydroxygallium phthalocyanine compound. [Configuration 12] 12. The photoelectric conversion element according to any one of configurations 1 to 11, wherein the resin having a Lewis basic functional group has a glass transition temperature of 95° C. or lower. [Configuration 13] A photoelectric conversion device comprising the photoelectric conversion element according to any one of configurations 1 to 12. [Explanation of symbols]

[0122] 1 Photoelectric conversion element 2. Board 3 Second electrode 4 Electron transport layer 5 Photoelectric conversion layer 6 Charge transport layer 7 Second Charge Transport Layer 8 First electrode 30 Mobile 31, 41 Photoelectric conversion element 32 Aircraft 40 Building materials 42 Protective materials 43 Heat dissipation materials 44a, 44b Exterior

Claims

1. A photoelectric conversion element having a first electrode, a second electrode, and a photoelectric conversion layer including a crystal having a perovskite structure and disposed between the first electrode and the second electrode, a charge transport layer between the photoelectric conversion layer and the first electrode, the charge transport layer including a crystal of a compound having an axial ligand, the compound being a cyclic conjugated compound formed by conjugating a plurality of pyrrole rings, and a resin having a Lewis basic functional group.

2. The photoelectric conversion element according to claim 1 , further comprising a second charge transport layer between the first electrode and the charge transport layer.

3. 2. The photoelectric conversion element according to claim 1, wherein the resin having a Lewis basic functional group has at least one functional group selected from the group consisting of a hydroxy group, a carbonyl group, an ether group, an amino group, an ester group, a pyridyl group, and a thienyl group.

4. 4. The photoelectric conversion element according to claim 3, wherein the resin having a Lewis basic functional group has at least two functional groups selected from the group consisting of a hydroxy group, a carbonyl group, an ether group, an amino group, an ester group, a pyridyl group, and a thienyl group.

5. 2. The photoelectric conversion element according to claim 1, wherein the content of the resin having a Lewis basic functional group in the charge transport layer is 5% by mass to 50% by mass with respect to the content of the cyclic conjugated compound in the charge transport layer.

6. 6. The photoelectric conversion element according to claim 5, wherein the content of the resin having a Lewis basic functional group in the charge transport layer is 7% by mass to 20% by mass with respect to the content of the cyclic conjugated compound in the charge transport layer.

7. 2. The photoelectric conversion element according to claim 1, wherein the cyclic conjugated compound has at least one central element selected from the group consisting of Ga, Ti, V, Al, In, Fe, and Mn.

8. The photoelectric conversion element according to claim 1 , wherein the cyclic conjugated compound has one axial ligand.

9. The photoelectric conversion element according to claim 1 , wherein the axial ligand is at least one selected from the group consisting of OH, Cl and O.

10. The photoelectric conversion element according to claim 1 , wherein the cyclic conjugated compound is a phthalocyanine compound.

11. The photoelectric conversion element according to claim 10 , wherein the phthalocyanine compound is a hydroxygallium phthalocyanine compound.

12. 2. The photoelectric conversion element according to claim 1, wherein the resin having a Lewis basic functional group has a glass transition temperature of 95[deg.] C. or lower.

13. A photoelectric conversion device comprising the photoelectric conversion element according to any one of claims 1 to 12.

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