Photoelectric conversion element and photoelectric conversion device

Abstract

The present invention addresses the problem of providing a photoelectric conversion element that exhibits an improved photoelectric conversion efficiency. In order to solve this problem, the present invention is a photoelectric conversion element that has a first electrode, a second electrode, and a photoelectric conversion layer disposed between the first electrode and the second electrode and comprising a crystal having a perovskite structure, wherein the photoelectric conversion element characteristically has, between the photoelectric conversion layer and the first electrode, a hole transport layer that contains a compound having a prescribed structure.

Description

Photoelectric conversion element and photoelectric conversion device

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

[0002] In order to solve the problems 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 hydropower. Among these, interest is growing in solar cells that directly convert sunlight into electrical energy. Here, a solar cell refers to a cell that generates current and voltage by utilizing the photovoltaic effect, in which light energy from sunlight is absorbed and electrons and holes are generated.

[0003] Currently, n-p 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 solar power generation. However, these require high-temperature processing steps and the materials themselves are expensive, resulting in high costs per unit of power. Furthermore, there are also supply issues due to the limited 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 in a so-called roll-to-roll method, which is expected to reduce costs. However, further improvements in power generation efficiency and durability are desired for the practical application of organic solar cells. Development of hole transport materials for use in hole transport layers is underway with the aim of improving the photoelectric conversion efficiency by enhancing the function of selectively transporting holes. For example, Patent Document 1 and Non-Patent Document 1 describe that photoelectric conversion efficiency can be improved by providing a hole transport layer containing a compound having a specific structure. Furthermore, perovskite solar cells having crystals with a perovskite structure as a photoelectric conversion layer have excellent photoelectric conversion properties, and therefore are being particularly developed for the practical application of organic solar cells.

[0005] International Publication No. 2022 / 153962

[0006] J. Kumar, et al, RSC Adv. , 2013, 3, 15626

[0007] According to the investigations of the present inventors, in a photoelectric conversion element having a photoelectric conversion layer containing a crystal of a perovskite structure, a photoelectric conversion element using the compounds described in Patent Document 1 and Non-Patent Document 1 in a hole transport layer had insufficient photoelectric conversion efficiency.

[0008] Therefore, an object of the present invention is to provide a photoelectric conversion element having improved photoelectric conversion efficiency by using a compound having a specific structure in a hole transport layer, and a photoelectric conversion device having improved photoelectric conversion efficiency by using a compound having a specific structure in a hole transport layer.

[0009] The above object can be achieved by the present invention, which provides a photoelectric conversion element having a first electrode, a second electrode, and a photoelectric conversion layer containing a crystal of a perovskite structure and disposed between the first electrode and the second electrode, characterized in that the photoelectric conversion element further comprises a hole transport layer between the photoelectric conversion layer and the first electrode, the hole transport layer containing a compound represented by the following formula (1): (In formula (1), R １ and R ２ each represents a linear or branched alkyl group having 1 to 6 carbon atoms, and R ３ ~R ２２each independently represent a hydrogen atom, a trimethylsilyl group, a linear or branched alkyl group of 1 to 20 carbon atoms which may have a substituent, a linear or branched alkenyl group of 2 to 20 carbon atoms which may have a substituent, a cycloalkyl group of 3 to 10 carbon atoms which may have a substituent, an alkoxy group of 1 to 20 carbon atoms which may have a substituent, a cycloalkoxy group of 3 to 10 carbon atoms which may have a substituent, an alkylthio group of 1 to 18 carbon atoms which may have a substituent, an amino group having an alkyl group of 1 to 20 carbon atoms which may have a substituent, an aromatic hydrocarbon group of 6 to 36 carbon atoms which may have a substituent, or a heterocyclic group of 5 to 36 ring atoms which may have a substituent. The substituents that each functional group may have are a halogeno group, a linear or branched alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkylthio group having 1 to 18 carbon atoms, an amino group having an alkyl group having 1 to 20 carbon atoms, an aromatic hydrocarbon group having 6 to 36 carbon atoms, or a heterocyclic group having 5 to 36 ring atoms.) The present invention also provides a photoelectric conversion device having the above photoelectric conversion element.

[0010] According to the present invention, it is possible to provide a photoelectric conversion element and a photoelectric conversion device with improved photoelectric conversion efficiency.

[0011] Fig. 1 is an example of a schematic cross-sectional view in the thickness direction of one embodiment of the photoelectric conversion element of the present invention. Fig. 2 is another example of a schematic cross-sectional view in the thickness direction of one embodiment of the photoelectric conversion element of the present invention. Fig. 3 is a perspective view schematically showing one embodiment of a moving body including the photoelectric conversion element of the present invention. Fig. 4 is a perspective view schematically showing one embodiment of a building material including the photoelectric conversion element of the present invention.

[0012] One embodiment relates to a photoelectric conversion element, which has a first electrode, a second electrode, and a photoelectric conversion layer containing a crystal of a perovskite structure and disposed between the first electrode and the second electrode, and further has a hole transport layer between the photoelectric conversion layer and the first electrode, the hole transport layer containing a compound represented by the following formula (1): In formula (1), R １ and R ２each represents a linear or branched alkyl group having 1 to 6 carbon atoms, and R ３ ~R ２２ each independently represent a hydrogen atom, a trimethylsilyl group, a linear or branched alkyl group of 1 to 20 carbon atoms which may have a substituent, a linear or branched alkenyl group of 2 to 20 carbon atoms which may have a substituent, a cycloalkyl group of 3 to 10 carbon atoms which may have a substituent, an alkoxy group of 1 to 20 carbon atoms which may have a substituent, a cycloalkoxy group of 3 to 10 carbon atoms which may have a substituent, an alkylthio group of 1 to 18 carbon atoms which may have a substituent, an amino group having an alkyl group of 1 to 20 carbon atoms which may have a substituent, an aromatic hydrocarbon group of 6 to 36 carbon atoms which may have a substituent, or a heterocyclic group of 5 to 36 ring atoms which may have a substituent. The substituent that each functional group may have is a halogeno group, a linear or branched alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkylthio group having 1 to 18 carbon atoms, an amino group having an alkyl group having 1 to 20 carbon atoms, an aromatic hydrocarbon group having 6 to 36 carbon atoms, or a heterocyclic group having 5 to 36 ring atoms.

[0013] As a result of investigations, the present inventors have found that a photoelectric conversion element having improved photoelectric conversion efficiency can be obtained by providing a hole transport layer containing a compound represented by formula (1) between the photoelectric conversion layer and the first electrode. Although the details of why a photoelectric conversion element having improved photoelectric conversion efficiency can be obtained in the present invention are not clear, the following is thought to be the reason.

[0014] The compound represented by formula (1) has a structure characterized by the following (A) and (B): (A) Nitrogen atoms are directly bonded to the carbon atoms at positions 2 and 7 of the fluorene skeleton; and (B) the α-carbon atom of the malonic acid ester is bonded to the carbon atom at position 9 of the fluorene skeleton via a carbon-carbon double bond.

[0015] DFT calculations suggest that the structure having the characteristic (A) allows the electron distribution of the highest occupied molecular orbital (HOMO) to spread throughout the molecule, which is thought to improve the hole transport ability in the hole transport layer.

[0016] Furthermore, DFT calculations suggest that the structure of feature (B) increases the molecular dipole moment and provides high polarity. The use of such a highly polar hole transport compound in the hole transport layer is thought to improve the interaction between the hole transport layer and the photoelectric conversion layer, thereby improving the efficiency with which holes generated in the photoelectric conversion layer move to the hole transport layer. As explained by the above mechanism, features (A) and (B) synergistically interact to achieve the effects of the present invention.

[0017] In the formula (1), R ３ ~R ２２ are each preferably independently a hydrogen atom, a linear or branched alkyl group having 1 to 20 carbon atoms which may have a substituent, an alkoxy group having 1 to 20 carbon atoms which may have a substituent, or an amino group having an alkyl group having 1 to 20 carbon atoms which may have a substituent, and R ５ , R １０ , R １５ , R ２０ is more preferably an alkoxy group having 1 to 20 carbon atoms, each of which may have a substituent. By having such a substituent, the photoelectric conversion efficiency is improved.

[0018] Specific examples of the compound represented by formula (1) are listed below (exemplary compounds 1-1 to 1-12), but the present invention is not limited to these.

[0019]

[0020] 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 those skilled in the art without departing from the spirit of the present invention are also included in the scope of the present invention.

[0021] 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 and intricate structure together with other layers. 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.

[0022] 1 is a cross-sectional view schematically illustrating the configuration of one embodiment of the photoelectric conversion element of the present invention. The photoelectric conversion element has a second electrode 3, an electron transport layer 4, a photoelectric conversion layer 5, a hole transport layer 6, and a first electrode 7 on a substrate 2. One of the first electrode 7 and the second electrode 3 is a positive electrode and the other is a negative electrode, and current can be extracted by connecting the first electrode 7 and the second electrode 3 to an external circuit.

[0023] 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 through the first electrode 7 and the hole transport layer 6, and generates electrons or holes. That is, the photoelectric conversion layer 5 generates a current between the first electrode 7 and the second electrode 3. The electron transport layer 4 is a layer disposed between the photoelectric conversion layer 5 and the two electrodes 3 and 7, and may not be formed in some cases. A structure in which multiple electron transport layers 4 and photoelectric conversion layers 5 are stacked may also be called a tandem structure. Alternatively, as shown in FIG. 2 , a photoelectric conversion element may be fabricated on the substrate 2 in the following order: the first electrode 7, the hole transport layer 6, the photoelectric conversion layer 5, the electron transport layer 4, and the second electrode 3. The photoelectric conversion element of the present invention and each of the components constituting the photoelectric conversion element will be described below.

[0024] [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 hole transport layer is provided between the photoelectric conversion layer and the first electrode. Furthermore, in order to improve the photoelectric conversion efficiency, the photoelectric conversion elements may be stacked in a tandem configuration. The photoelectric conversion elements to be stacked are not limited to a specific type of photoelectric conversion element, and may include perovskite solar cells that use perovskite crystals in the photoelectric conversion layer, silicon solar cells, CIGS solar cells, and the like.

[0025] Methods for forming each layer of the photoelectric conversion element of the present invention include coating methods and vapor deposition methods. Examples of coating methods 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 involves preparing a coating solution for each layer described below, applying the solution in the desired layer order, and drying the solution. A desired method can be selected from these film formation methods depending on the layer. Each layer will be described below.

[0026] [Substrate] The photoelectric conversion element 1 of the present invention may include a substrate 2, for example, a transparent glass substrate such as soda lime glass or alkali-free glass, a ceramic substrate, or a transparent plastic substrate. In Fig. 1, when light is taken in from the first electrode 7 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.

[0027] [Electrodes] There are no particular limitations on the materials for the first electrode 7 and the second electrode 3, and conventionally known materials can be used. For example, metals such as gold, silver, titanium, and copper, sodium, sodium-potassium alloy, lithium, magnesium, carbon, aluminum, magnesium-silver mixture, magnesium-indium mixture, aluminum-lithium alloy, and Al / Al ２ O ３ Examples of transparent electrode materials include CuI, ITO (indium tin oxide), and SnO ２Examples of the conductive transparent material include AZO (aluminum zinc oxide), IZO (indium zinc oxide), GZO (gallium zinc oxide), FTO (fluorine-doped tin oxide), and ATO (antimony-doped tin oxide), as well as conductive transparent polymers. These materials may be used alone or in combination of two or more. The first electrode 7 and the second electrode 3 are configured such that at least one electrode on the light incident side is a transparent electrode, and the other electrode may be a transparent electrode or may double as a reflective layer formed of a light-reflective material, or may be a transparent electrode with a reflective layer on the side opposite the light incident side. When the first electrode 7 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.

[0028] [Photoelectric Conversion Layer] The photoelectric conversion layer 5 has a crystal with a perovskite structure. The crystal with a perovskite structure used in the present invention is preferably represented by the following formula [2]: ABX ３ [2]

[0029] In the above formula [2], 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. ｐ N ｍ H ｎ (where p, m, and n are all positive integers) Specific examples include methylammonium and formamidium.

[0030] The inorganic atom is not particularly limited, but lithium, cesium, sodium, potassium, and rubidium are preferred. These organic molecules or inorganic atoms may be used alone or in combination of two or more.

[0031] If the constituent cation A is too large to fit within a three-dimensional perovskite structure crystal, the resulting crystal may be a two-dimensional perovskite structure crystal, a 2.5-dimensional perovskite structure crystal having both two-dimensional and three-dimensional properties, a bilayer crystal of three-dimensional and two-dimensional perovskite structures, or a mixed three-dimensional and two-dimensional perovskite structure crystal, all of which function as a photoelectric conversion layer. A bilayer crystal of three-dimensional and two-dimensional perovskite structures refers to a crystal in which three-dimensional and two-dimensional perovskite structure crystals are stacked as independent, separate layers. A mixed three-dimensional and two-dimensional perovskite structure crystal refers to a crystal with a structure in which both regions or domains of two-dimensional or 2.5-dimensional layered and three-dimensional perovskite structure crystals are mixed.

[0032] The crystal having a two-dimensional perovskite structure or the crystal having a 2.5-dimensional perovskite structure is preferably represented by the following formulas [3] to [5]: R' ２ A ｎ－１ B ｎ X ３ｎ＋１ [3] R''A ｎ－１ B ｎ X ３ｎ＋１ [4] R'''A ｎ B ｎ X ３ｎ＋１ [5] In the formulas [3] to [5], [3] forms an RP (Ruddlesden-Popper) type perovskite structure, [4] forms a DJ (Dion-Jacobson) type perovskite structure, and [5] forms an ACI (Alternating cations in the interlayer) type perovskite structure.

[0033] R', R'', and R''' in the formulas [3] to [5] are large cations that cannot fit into a three-dimensional perovskite structure. For example, in organic molecules, p N m H n(p, m, and n are all positive integers). A may or may not have a substituent, and specific examples thereof include ethylammonium, propylammonium, n-butylammonium, n-hexylammonium, n-octylammonium, 1,6-hexanediammonium, isobutylammonium, 3-(nonafluoro-tert-butyloxy)propylammonium, 1,3-propanediammonium, 1,5-pentamethylenediamine, 1,8-octyldiammonium, 2,2-(ethylenedioxy)bis(ethylammonium), 5-aminovaleric acid, 4-tert-butylammonium, N,N'-dimethylethylene-1,2-diammonium, 2,2,3,3,3-pentafluoropropylammonium, guanidium, propylammonium, propargylammonium, alkylammonium, cyclohexylmethylammonium, 4-(aminomethyl)piperidinium, piperidinium, pyrrolidinium, cyclohexylammonium, 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-phenylenedimethaneammonium, 3-phenyl-2-propene-1-ammonium, phenylbutylammonium, 4-tert-butyl - benzylammonium, 3- (aminomethyl) piperidinium, 4- (aminomethyl) piperidinium is preferred.

[0034] B in the formulas [2] to [5] is a metal atom, and examples thereof include 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.

[0035] X in the formulas [2] to [5] is a halogen atom, such as chlorine, bromine, or iodine. These halogen atoms may be used alone or in combination of two or more. Among these, halogen atoms are preferred because the inclusion of halogen in the structure makes the perovskite structure crystal more soluble in organic solvents, enabling application to inexpensive printing methods, etc. Furthermore, iodine is more preferred because it narrows the energy band gap of the perovskite structure crystal.

[0036] Specifically, 3D perovskite, 2D perovskite, and mixed 3D / 2D perovskite are MAPbI ３ and FAPbCl ３ , FAPbI ３ , 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 ０．０５ FA ０．８８ MA ０．０７ PbI ２．５６ Br ０．４４ , (FAPbI ３ ) ０．９５ (MAPbBr ３ ) ０．０５ , (FAPbI ３ ) ０．８５ (MAPbBr ３ ) ０．１５ , CsPbI ３ , CsPbBr３ 、Cs ｘ (MA) １－ｘ PbI ３ 、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 、(PEA) ２ (MA) ２ Pb ３ I １０ 、(PTA) ２ (MA) ４ Pb ５ I １６ 、(PEA) ２ (MA) ４ Pb ５ I １６ 、(ThMA) ２ (MA) ２ Pb ３ I １０ 、(3BBA) ２ (MA) ２ Pb ３ I １０ 、(ThMA) ２ (FA) ４ Pb ５ I １６ 、(4FPEA) ２ (FA ０．３ MA ０．７ ) ４ Pb ５ I １６ 、(PDMA)FA ２ Pb ３ I １０ 、(3AMPY)(MA) ３Pb ４ I １３ 、(PDMA)MA ５ Pb ６ I １９ 、(PDMA)MA ３ Pb ４ I １３ 、(TTDMA)MA ３ Pb ４ I １３ 、(TTDMA)MA ４ Pb ５ I １６ 、 (BA ０．９ PEA ０．１ ) ２ MA ４ Pb ５ I １６ 、 (BA ０．９ PEA ０．１ ) ２ MA ３ Pb ４ I １３ 、(4FFEA) ２ MA ３ Pb ４ I １３ 、(4FFEA) ２ MA ４ Pb ５ I １６ (BA) ２ MA ２ Pb ３ I １０ 、(BA) ２ MA ３ Pb ４ I １３ 、(TEA) ２ MA ２ Pb ３ I １０ 、(BA) ２ MA ４ Pb ５ I １６ 、(BA) ２ MA ３ Pb ４ I １３In the above specific examples, "MA" represents methylammonium, "FA" represents formamidinium, "PEA" represents phenethylammonium, "PTA" represents phenyltriethylammonium, "ThMA" represents 2-thiophenemethylammonium, "3BBA" represents 3-bromobenzylammonium, "3AMPY" represents 3-(aminomethyl)pyridine, "PDMA" represents 1,4-phenylenedimethaneammonium, "TTDMA" represents thieno[3,2-b]thiophene-2.5-diyldimethaneammonium, "4FPEA" represents 4-fluorophenethylammonium, "BA" represents butylammonium, and "TEA" represents 2-thiophenethylammonium.

[0037] The perovskite crystal 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 or X at the face center. Although the details are not clear, it is presumed that the presence of such a structure allows the orientation of the octahedra in the crystal lattice to be easily changed, thereby increasing the mobility of electrons in the perovskite crystal and improving the photoelectric conversion efficiency of the photoelectric conversion element.

[0038] The organic-inorganic perovskite compound used in the present invention is preferably a crystalline semiconductor. A crystalline semiconductor refers to a semiconductor from which a scattering peak can be detected by measuring an X-ray scattering intensity distribution. When the organic-inorganic perovskite compound is a crystalline semiconductor, the mobility of electrons in the organic-inorganic perovskite compound increases, improving the photoelectric conversion efficiency of the photoelectric conversion element.

[0039] The thickness of the photoelectric conversion layer according to the present invention is preferably 5 nm or more and 2000 nm or less. A thickness of 5 nm or more allows sufficient absorption of light, and a thickness of 2000 nm or less allows generated charges to be transported to each electrode. A more preferred lower limit is 50 nm, a more preferred upper limit is 1200 nm, an even more preferred lower limit is 100 nm, and an even more preferred upper limit is 1000 nm.

[0040] 1 and 2 , the present invention includes a hole transport layer 6 between the photoelectric conversion layer 5 and the first electrode 7. As described above, the hole transport layer 6 contains the compound represented by formula (1). A dopant (oxidizing agent) or a basic compound may be added to the hole transport layer 6 for the purpose of improving the photoelectric conversion efficiency.

[0041] The thickness of the hole transport layer according to the present invention is preferably 10 nm or more and 1000 nm or less. If the thickness is 10 nm or more, holes can be sufficiently transported to the electrode, and if the thickness is 1000 nm or less, resistance during hole transport is unlikely to occur, resulting in high photoelectric conversion efficiency. The lower limit of the thickness of the hole transport layer is more preferably 50 nm, and the upper limit is more preferably 500 nm.

[0042] 1 and 2 , in the photoelectric conversion element of the present invention, 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, perylene derivatives, 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.

[0043] The thickness of the electron transport layer 4 is preferably 1 nm or more at a lower limit and 2000 nm or more at a upper limit. A thickness of 1 nm or more ensures sufficient hole blocking, while a thickness of 2000 nm or less reduces resistance during electron transport, resulting in high photoelectric conversion efficiency. The thickness of the electron transport layer 4 is more preferably 3 nm or more at a lower limit and 1000 nm or more at a higher limit, and even more preferably 5 nm or more at a higher limit and 500 nm or more at a lower limit and 1000 nm or more at a higher limit.

[0044] <Application Examples> Application examples relate to photoelectric conversion devices, mobile objects, and building materials. [Photoelectric Conversion Device] The photoelectric conversion device of the present invention includes the photoelectric conversion element of the present invention. A photoelectric conversion device can be configured by using multiple photoelectric conversion elements of the present invention. When multiple photoelectric conversion elements are connected, the photoelectric conversion device can also be called a photoelectric conversion cell or a photoelectric conversion module. The photoelectric conversion element may be stacked with elements having different absorption wavelengths to increase the output voltage. The photoelectric conversion device may also include 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. Examples include secondary batteries using lithium ions, all-solid-state batteries, and electric double layer capacitors.

[0045] [Mobile object] FIG. 3 is a perspective view schematically illustrating one embodiment of a mobile object equipped with a photoelectric conversion element of the present invention. The mobile object 30 includes a 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 disposed in a position on the vehicle 32 where it can receive external light. If the mobile object 30 is an automobile, the photoelectric conversion element 31 may be disposed on the roof. The electrical energy obtained by the photoelectric conversion element 31 may power the mobile object 30 or may power other electrical equipment. Electrical energy generated from the power of the mobile object 30 may be used to power the photoelectric conversion element 31. If the mobile object 30 is an automobile, frictional energy generated by braking may be converted into electrical energy and used to control the photoelectric conversion element 31.

[0046] The mobile body 30 may be, for example, an automobile, a ship, an airplane, or a drone. The configuration of the body 32 of the mobile body 30 is not particularly limited, but it is preferably made of a high-strength material.

[0047] 4 is a perspective view schematically showing one embodiment of a building material including a 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 a 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 exterior coverings 44a and 44b.

[0048] 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 the photoelectric conversion element 41 is used on a roof or the like, the temperature of the photoelectric conversion element 41 may rise due to sunlight, which may result in a decrease in photoelectric conversion efficiency. The use of the heat dissipation member 43 can reduce the decrease in photoelectric conversion efficiency. Examples of the heat dissipation member 43 include a metal, an alloy, a liquid metal, and a liquid resin.

[0049] The building material 40 of the present invention may also have exterior coatings 44a and 44b. The exterior coatings 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 coating material, and a material with low light absorption and high heat insulation properties is preferred.

[0050] 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.

[0051] Synthesis of Exemplary Compound (1-2) Exemplary Compound (1-2) was synthesized by the following method. 2,7-Dibromo-9-fluorenone (3.38 g, manufactured by Tokyo Chemical Industry Co., Ltd.), 4,4'-dimethoxydiphenylamine (5.04 g, manufactured by Tokyo Chemical Industry Co., Ltd.), palladium acetate (89.8 mg, manufactured by Tokyo Chemical Industry Co., Ltd.), 1,1'-bis(diphenylphosphino)ferrocene (332.6 mg, manufactured by Tokyo Chemical Industry Co., Ltd.), cesium carbonate (9.77 g, manufactured by Tokyo Chemical Industry Co., Ltd.), and toluene (300 mL) were placed in a reaction vessel and stirred under reflux for 18 hours under a nitrogen atmosphere. The reaction solution was returned to room temperature, filtered under reduced pressure, and washed with toluene. The filtrate was concentrated and purified by silica gel column chromatography (developing solvent: toluene) to obtain an intermediate represented by the following formula (A) as a purple powder (yield: 44%).

[0052] Subsequently, the intermediate (1.27 g), diethyl malonate (1.60 g, manufactured by Tokyo Chemical Industry Co., Ltd.), tetrahydrofuran (30 mL), and pyridine (5 mL) were added to a reaction vessel, cooled to 0°C with ice water, and titanium tetrachloride (3.79 g, manufactured by Tokyo Chemical Industry Co., Ltd.) was added dropwise. After the addition, the mixture was returned to room temperature and stirred for 18 hours. After the reaction was completed, water and ethyl acetate were added and the mixture was separated. The organic layer was washed with water and saturated saline and concentrated. The obtained crude product was purified by silica gel column chromatography (developing solvent: ethyl acetate / heptane = 1 / 3) to obtain exemplary compound (1-2) as a purple powder (yield 71%).

[0053] <Production of Photoelectric Conversion Element> (Example 1) [Formation of Electron Transport Layer] A glass substrate with an ITO film was cleaned, and a tin (II) oxide coating solution adjusted to a concentration of 3% by mass was applied thereon by spin coating, followed by heating at 150°C for 30 minutes to form a thin-film electron transport layer having a thickness of 15 nm.

[0054] [Formation of Photoelectric Conversion Layer] 22.4 mg of lead 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, 389.72 mg of cesium iodide was dissolved in 1000 μL of dimethyl sulfoxide, and the mixture was stirred for 1 hour (Solution 2). Then, Solution 2 (40 μL) 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, resulting in the formation of Cs ０．０５ (FA ０．８３ MA ０．１７ ) ０．９５ Pb(I ０．９５ Br ０．０５ ) ３ A photoelectric conversion layer having a thickness of 500 nm was formed.

[0055] [Formation of Hole Transport Layer] 0.15 g of the exemplary compound (1-2) was dissolved in 2.2 g of chlorobenzene to prepare hole transport layer coating solution 1. This coating solution was spin-coated on the photoelectric conversion layer to form a hole transport layer with a thickness of 200 nm.

[0056] [Formation of First Electrode] A first electrode having a thickness of 80 nm and an area of ​​0.09 cm was formed on the hole transport layer. ２ A gold electrode was formed by vacuum deposition to obtain a photoelectric conversion element.

[0057] Example 2 A photoelectric conversion element is obtained in the same manner as in Example 1, except that in the preparation of the hole transport layer coating solution 1, the exemplary compound (1-2) is changed to the compound represented by the exemplary compound (1-3).

[0058] Example 3 A photoelectric conversion element is obtained in the same manner as in Example 1, except that in the preparation of the hole transport layer coating solution 1, the exemplary compound (1-2) is changed to the compound represented by the exemplary compound (1-5).

[0059] Comparative Example 1 A photoelectric conversion element was obtained in the same manner as in Example 1, except that in the preparation of the hole transport layer coating solution 1, the exemplary compound (1-2) was changed to the compound represented by the formula (A).

[0060] Comparative Example 2 A photoelectric conversion element is obtained in the same manner as in Example 1, except that in the preparation of the hole transport layer coating solution 1, the exemplary compound (1-2) is changed to a compound represented by the following formula (B).

[0061] Example 4 Formation of Electron Transport Layer A glass substrate with an ITO film was cleaned, and a tin (II) oxide coating solution adjusted to a concentration of 3% by mass was applied thereon by spin coating, followed by heating at 150°C for 30 minutes to form a thin-film electron transport layer having a thickness of 15 nm.

[0062] [Formation of Photoelectric Conversion Layer] 22.4 mg of lead 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, 389.72 mg of cesium iodide was dissolved in 1000 μL of dimethyl sulfoxide, and the mixture was stirred for 1 hour (Solution 2). Then, Solution 2 (40 μL) 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, resulting in the formation of Cs ０．０５ (FA ０．８３ MA ０．１７ ) ０．９５ Pb(I ０．９５ Br ０．０５ ) ３ A photoelectric conversion layer having a thickness of 500 nm was formed.

[0063] [Formation of Hole Transport Layer] 0.15 g of exemplary compound (1-2) was dissolved in 2.2 g of chlorobenzene. 36 μL of an acetonitrile solution obtained by dissolving 0.2 g of lithium-bis(trifluoromethanesulfonyl)imide in 0.3 g of acetonitrile and 36 μL of t-butylpyridine were added to this chlorobenzene solution and mixed. Furthermore, 58 μL of an 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 added to prepare hole transport layer coating solution 2. This coating solution was spin-coated on the photoelectric conversion layer to form a hole transport layer with a thickness of 200 nm.

[0064] [Formation of First Electrode] A first electrode having a thickness of 80 nm and an area of ​​0.09 cm was formed on the hole transport layer. ２ A gold electrode was formed by vacuum deposition to obtain a photoelectric conversion element.

[0065] <Evaluation> (Evaluation of photoelectric conversion efficiency) A power supply (manufactured by Keithley, Model 236) was connected between the electrodes of the photoelectric conversion element obtained in Example 1, and an intensity of 100 mW / cm ２ The photoelectric conversion efficiency was evaluated by irradiating the cells with a constant amount of light using a solar simulator (manufactured by Yamashita Denso Co., Ltd.) and measuring the generated current and voltage. The same evaluation was also carried out for Examples 2 to 4 and Comparative Examples 1 and 2. The results are shown in Tables 1 and 2.

[0066]

[0067]

[0068] The present invention is not limited to the above-described embodiments, and various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, the following claims are appended to apprise the public of the scope of the present invention.

[0069] This application claims priority based on Japanese Patent Application No. 2024-002687, filed January 11, 2024, the entire contents of which are incorporated herein by reference.

[0070] REFERENCE SIGNS LIST 1 Photoelectric conversion element 2 Substrate 3 Second electrode 4 Electron transport layer 5 Photoelectric conversion layer 6 Hole transport layer 7 First electrode

Claims

1. A photoelectric conversion element having a first electrode, a second electrode, and a photoelectric conversion layer containing a perovskite-structured crystal disposed between the first electrode and the second electrode, wherein a hole transport layer containing a compound represented by the following formula (1) is provided between the photoelectric conversion layer and the first electrode. (In formula (1), R １ and R ２ each represent a linear or branched alkyl group having 1 to 6 carbon atoms, and R ３ to R ２２ each independently represent a hydrogen atom, a trimethylsilyl group, a linear or branched alkyl group having 1 to 20 carbon atoms which may have a substituent, a linear or branched alkenyl group having 2 to 20 carbon atoms which may have a substituent, a cycloalkyl group having 3 to 10 carbon atoms which may have a substituent, an alkoxy group having 1 to 20 carbon atoms which may have a substituent, a cycloalkoxy group having 3 to 10 carbon atoms which may have a substituent, an alkylthio group having 1 to 18 carbon atoms which may have a substituent, an amino group having an alkyl group having 1 to 20 carbon atoms which may have a substituent, an aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent, or a heterocyclic group having 5 to 36 ring-forming atoms which may have a substituent. The substituent that each functional group may have is a halogeno group, a linear or branched alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkylthio group having 1 to 18 carbon atoms, an amino group having an alkyl group having 1 to 20 carbon atoms, an aromatic hydrocarbon group having 6 to 36 carbon atoms, or a heterocyclic group having 5 to 36 ring-forming atoms.) 2. In the formula (1), R ３ ~R ２２ are each independently a hydrogen atom, a linear or branched alkyl group having 1 to 20 carbon atoms which may have a substituent, an alkoxy group having 1 to 20 carbon atoms which may have a substituent, or an amino group having an alkyl group having 1 to 20 carbon atoms which may have a substituent. The photoelectric conversion element according to claim 1.

3. In the formula (1), R ５ , R １０ , R １５ , R ２０ is each an alkoxy group having 1 to 20 carbon atoms which may each have a substituent, the photoelectric conversion element according to claim 1 or 2.

4. A photoelectric conversion device having the photoelectric conversion element according to any one of claims 1 to 3.

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