Photoelectric conversion elements and photoelectric conversion devices

Abstract

The present invention addresses the problem of providing a photoelectric conversion element exhibiting improved photoelectric conversion efficiency. To solve the aforementioned problem, the present invention provides a photoelectric conversion element having a first electrode, a second electrode, and a photoelectric conversion layer disposed between the first electrode and the second electrode and containing a crystal with a perovskite structure. The photoelectric conversion element is characterized by having a hole transport layer containing a compound with a specific structure between the photoelectric conversion layer and the first electrode.

Description

Technical Field

[0001] This invention relates to a photoelectric conversion element and a photoelectric conversion device. Background Technology

[0002] To address the problems associated with the depletion of fossil fuels and the environmental problems caused by their use, research has been actively conducted on renewable and clean alternative energy sources such as solar, wind, and hydropower. Among these, solar cells, which directly convert sunlight into electricity, are receiving increasing attention. Here, a solar cell refers to a battery that uses the photovoltaic effect—absorbing light energy from sunlight and generating electrons and holes—to produce current and voltage.

[0003] Currently, NP-diode-based silicon (Si) monocrystalline solar cells with a light-to-energy conversion efficiency greater than 20% are well-known and are practically used in solar power generation. However, these require high-temperature processing steps, and the materials themselves are expensive, leading to a high cost per unit of electricity. Furthermore, these also face supply issues due to silicon resource availability.

[0004] In contrast, solar cells using organic materials (hereinafter referred to as "organic solar cells") do not require high-temperature processing steps and can be manufactured using a so-called roll-to-roll method with sheet-like substrates, thereby reducing costs. However, for the practical application of such organic solar cells, further improvements in power generation efficiency and durability are desired. To enhance the selective hole transport function and improve photoelectric conversion efficiency, hole transport materials for hole transport layers have been developed. For example, Patent Document 1 and Non-Patent Document 1 describe improving photoelectric conversion efficiency by setting a hole transport layer containing a compound with a specific structure. Furthermore, perovskite-type solar cells with perovskite-structured crystals as photoelectric conversion layers exhibit high photoelectric conversion performance; therefore, they have been specifically developed for the practical application of organic solar cells.

[0005] Reference List

[0006] Patent documents

[0007] Patent Document 1: International Publication No. WO2022 / 153962

[0008] Non-patent literature

[0009] Non-patent literature 1: J. Kumar et al., RSC Adv., 2013, 3, 15626 Summary of the Invention

[0010] The problem the invention aims to solve

[0011] According to the inventors' research, in photoelectric conversion elements comprising a photoelectric conversion layer containing a crystal having a perovskite structure, and in photoelectric conversion elements wherein a compound disclosed in Patent Document 1 and Non-Patent Document 1 is used in the hole transport layer, the photoelectric conversion efficiency is insufficient.

[0012] Therefore, the present invention aims to provide a photoelectric conversion element with improved photoelectric conversion efficiency by using a compound with a specific structure in the hole transport layer. Furthermore, the present invention aims to provide a photoelectric conversion device with improved photoelectric conversion efficiency by using a compound with a specific structure in the hole transport layer.

[0013] Solution for solving the problem

[0014] These aspects are achieved by the present invention as shown below. In other words, the present invention is a photoelectric conversion element comprising a first electrode, a second electrode, and a photoelectric conversion layer containing a crystal having a perovskite structure, the photoelectric conversion layer being disposed between the first electrode and the second electrode, wherein a hole transport layer containing a compound represented by the following formula (1) is disposed between the photoelectric conversion layer and the first electrode.

[0015] [Chemistry 1]

[0016]

[0017] (In equation (1), R) 1 and R 2 Each represents a straight-chain or branched alkyl group having 1 to 6 carbon atoms, and R 3 To R 22 Each of the following independently represents a hydrogen atom, a trimethylsilyl group, a straight-chain or branched alkyl group having 1 to 20 carbon atoms and optionally having substituents, a straight-chain or branched alkenyl group having 2 to 20 carbon atoms and optionally having substituents, a cycloalkyl group having 3 to 10 carbon atoms and optionally having substituents, an alkoxy group having 1 to 20 carbon atoms and optionally having substituents, a cycloalkoxy group having 3 to 10 carbon atoms and optionally having substituents, an alkylthio group having 1 to 18 carbon atoms and optionally having substituents, or a group having 1 to 20 carbon atoms and optionally having substituents. The functional group may be an amino group with a substituent alkyl group, an aromatic hydrocarbon group having 6 to 36 carbon atoms and optionally having a substituent, or a heterocyclic group having 5 to 36 cyclic atoms and optionally having a substituent; and each functional group may optionally have a substituent that is a halogen group, a straight-chain or branched alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkathio group having 1 to 18 carbon atoms, an amino group with a 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 cyclic atoms.

[0018] Furthermore, the present invention is a photoelectric conversion device including the above-mentioned photoelectric conversion element.

[0019] The effects of the invention

[0020] According to the present invention, photoelectric conversion elements and photoelectric conversion devices with improved photoelectric conversion efficiency can be provided. Attached Figure Description

[0021] [ Figure 1 [Illustration 1] is an example of a cross-sectional schematic diagram of a photoelectric conversion element in the thickness direction according to an embodiment of the present invention.

[0022] [ Figure 2 [This is another example of a cross-sectional schematic diagram of a photoelectric conversion element in the thickness direction according to an embodiment of the present invention.]

[0023] [ Figure 3 [This is a perspective view schematically illustrating one embodiment of a moving body including a photoelectric conversion element according to the present invention.]

[0024] [ Figure 4 [This is a perspective view schematically illustrating one embodiment of a building material including a photoelectric conversion element according to the invention.] Detailed Implementation

[0025] <Implementation Plan>

[0026] One implementation involves a photoelectric conversion element.

[0027] The photoelectric conversion element according to the present invention is a photoelectric conversion element comprising a first electrode, a second electrode, and a photoelectric conversion layer containing a crystal having a perovskite structure, the photoelectric conversion layer being disposed between the first electrode and the second electrode, wherein a hole transport layer containing a compound represented by the following formula (1) is disposed between the photoelectric conversion layer and the first electrode:

[0028] [Chemistry 2]

[0029]

[0030] In equation (1), R 1 and R 2 Each represents a straight-chain or branched alkyl group having 1 to 6 carbon atoms, R 3 To R 22Each of the following can independently represent a hydrogen atom, a trimethylsilyl group, a straight-chain or branched alkyl group having 1 to 20 carbon atoms and optionally having a substituent, a straight-chain or branched alkenyl group having 2 to 20 carbon atoms and optionally having a substituent, a cycloalkyl group having 3 to 10 carbon atoms and optionally having a substituent, an alkoxy group having 1 to 20 carbon atoms and optionally having a substituent, a cycloalkoxy group having 3 to 10 carbon atoms and optionally having a substituent, an alkylthio group having 1 to 18 carbon atoms and optionally having a substituent, an amino group having an alkyl group having 1 to 20 carbon atoms and optionally having a substituent, an aromatic hydrocarbon group having 6 to 36 carbon atoms and optionally having a substituent, or a heterocyclic group having 5 to 36 cyclic atoms and optionally having a substituent. Each functional group may optionally have substituents that are halogen groups, straight-chain or branched alkyl groups having 1 to 20 carbon atoms, alkoxy groups having 1 to 20 carbon atoms, alkylthio groups having 1 to 18 carbon atoms, amino groups having 1 to 20 carbon atoms, aromatic hydrocarbon groups having 6 to 36 carbon atoms, or heterocyclic groups having 5 to 36 cyclic atoms.

[0031] As a result of the research, the inventors discovered that by distributing a hole transport layer containing a compound represented by formula (1) between the photoelectric conversion layer and the first electrode, a photoelectric conversion element with improved photoelectric conversion efficiency is obtained. While the reasons for obtaining a photoelectric conversion element with improved photoelectric conversion efficiency are not explained in detail in this invention, the following reasons can be considered.

[0032] The compound represented by formula (1) has a structure containing the following features (A) and (B).

[0033] (A) The nitrogen atom is directly bonded to the carbon atoms at the 2- and 7-positions of the fluorene skeleton.

[0034] (B) The α-carbon atom of the malonate is bonded to the carbon atom at position 9 of the fluorene skeleton via a carbon-carbon double bond.

[0035] DFT calculations show that when this structure is included in a compound, the electron distribution of the highest occupied molecular orbital (HOMO) diffuses throughout the molecule through the structure with characteristic (A). It is believed that the electron distribution of the HOMO diffused throughout the molecule leads to an enhancement of hole transport capability in the hole transport layer.

[0036] DFT calculations also show that when such a structure is included in the compound, the structure with characteristic (B) increases the dipole moment of the molecule, resulting in its high polarity. Considering the use of such a highly polar hole-transporting compound in the hole transport layer, the interaction between the hole transport layer and the photoelectric conversion layer is improved, thus increasing the migration efficiency of holes generated in the photoelectric conversion layer to the hole transport layer.

[0037] Similar to the mechanism described above, the effects of the present invention can be achieved through the synergistic effect caused by features (A) and (B).

[0038] In equation (1), preferably, R 3 To R 22 Each of the following independently represents a hydrogen atom, a straight-chain or branched alkyl group having 1 to 20 carbon atoms and optionally having a substituent, an alkoxy group having 1 to 20 carbon atoms and optionally having a substituent, or an amino group having 1 to 20 carbon atoms and optionally having a substituent, more preferably, R 5 R 10 R 15 and R 20 Each of these groups independently represents an alkoxy group having 1 to 20 or fewer carbon atoms and optionally having substituents. When such substituents are present, the photoelectric conversion efficiency is improved.

[0039] In the following text, specific examples of compounds represented by formula (1) will be shown (example compounds 1-1 to 1-12), but the invention is not limited to these.

[0040] [Chemistry 3]

[0041]

[0042] [Chemistry 4]

[0043]

[0044] [Chemistry 5]

[0045]

[0046] [Chemistry 6]

[0047]

[0048] [Chemistry 7]

[0049]

[0050] [Chemistry 8]

[0051]

[0052] [Chemistry 9]

[0053]

[0054] [Chemistry 10]

[0055]

[0056] [Chemistry 11]

[0057]

[0058] [Chemistry 12]

[0059]

[0060] [Chemistry 13]

[0061]

[0062] [Chemistry 14]

[0063]

[0064] The invention will now be described in detail with reference to suitable embodiments. The invention is not limited to the embodiments shown below, but encompasses those obtained by suitably changing or modifying the embodiments shown below based on the general knowledge of those skilled in the art without departing from the spirit of the invention.

[0065] In this specification, "layer" refers not only to a layer with clear boundaries and a flat, thin film-like structure, but also to a layer with a gradient concentration of elements that gradually changes, and a layer that can form complex structures with other layers. Elemental analysis of a layer can be performed, for example, by performing TOF-SIMS / FE-TEM / EDS line analysis on a cross-section of the photoelectric conversion element and verifying the elemental distribution of specific elements.

[0066] Figure 1 This is a schematic cross-sectional view illustrating the configuration of a photoelectric conversion element according to an embodiment of the present invention. The substrate 2 includes a second electrode 3, an electron transport layer 4, a photoelectric conversion layer 5, a hole transport layer 6, and a first electrode 7. One of the first electrode 7 and the second electrode 3 is a positive electrode, and the other is a negative electrode. Current can be extracted by connecting the first electrode 7 and the second electrode 3 to an external circuit.

[0067] The photoelectric conversion layer 5 is excited by light entering 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, generating 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 either of the two electrodes 3 and 7, and in some cases, it is not required. On the other hand, multiple electron transport layers 4 and multiple photoelectric conversion layers 5 can be formed in a stack. This form can also be called a series structure. Figure 2 As shown, the photoelectric conversion element can be fabricated by sequentially forming a first electrode 7, a hole transport layer 6, a photoelectric conversion layer 5, an electron transport layer 4, and a second electrode 3 on a substrate 2.

[0068] The photoelectric conversion element according to the present invention and the components included in the photoelectric conversion element will be described below.

[0069] [Photoelectric conversion element]

[0070] The photoelectric conversion element according to the present invention comprises a first electrode, a second electrode, and a photoelectric conversion layer containing a crystal having a perovskite structure, wherein the photoelectric conversion layer is disposed between the first and second electrodes, and a hole transport layer is disposed between the photoelectric conversion layer and the first electrode. To improve photoelectric conversion efficiency, the photoelectric conversion elements can be stacked in series. The stacked photoelectric conversion elements are not limited to any particular type of photoelectric conversion element, such as perovskite solar cells, silicon solar cells, and CIGS solar cells whose photoelectric conversion layer contains a perovskite crystal.

[0071] Examples of methods for forming layers in a photoelectric conversion element according to the present invention include coating methods and deposition methods. Examples of coating methods include dip coating, spin coating, spray coating, inkjet coating, meniscus coating, screen coating, roll coating, die coating, doctor blade coating, curtain coating, and wire rod coating. Coating methods involve preparing a coating solution for the layers described below, applying the coating solution in a desired layer sequence, and then drying. A desired method can be selected from these film-forming methods depending on the specific layers.

[0072] The layers will be described below.

[0073] [Substrate]

[0074] The photoelectric conversion element 1 according to the present invention may include a substrate 2, and examples of substrates include transparent glass substrates made of soda-lime glass or alkali-free glass, ceramic substrates, and transparent plastic substrates. When light comes from... Figure 1 When light enters from the first electrode 7 side, an opaque material can be used in the substrate 2. When light enters from the second electrode 3 side, the substrate 2 is formed of a transparent material.

[0075] [electrode]

[0076] There are no particular limitations on the materials of the first electrode 7 and the second electrode 3; conventionally known materials can be used. Examples include metals such as gold, silver, titanium, copper, sodium, sodium-potassium alloys, lithium, magnesium, carbon, aluminum, magnesium-silver mixtures, magnesium-indium mixtures, aluminum-lithium alloys, Al / Al2O3 mixtures, and Al / LiF mixtures. Examples of materials for transparent electrodes include conductive transparent materials such as CuI, ITO (indium tin oxide), SnO2, AZO (zinc aluminum oxide), IZO (zinc indium oxide), GZO (zinc gallium oxide), FTO (fluorine-doped tin oxide), and ATO (antimony-doped tin oxide), as well as conductive transparent polymers. These materials can be used alone or in combination of two or more of them. For the first electrode 7 and the second electrode 3, at least one electrode on the light-incident side is a transparent electrode, while the other can be a transparent electrode, an electrode used as a reflective layer formed of a reflective material, or a transparent electrode that includes a reflective layer on the side opposite to the light-incident side. When the first electrode 7 is disposed on the light-incident side, the second electrode 3 can be a transparent electrode, and the substrate 2 can be a reflective layer. Transparent electrodes can be patterned electrodes.

[0077] [Photoelectric conversion layer]

[0078] The photoelectric conversion layer 5 contains a crystal with a perovskite structure. The perovskite structure crystal used in this invention is preferably represented by the following formula [2].

[0079] ABX3[2]

[0080] In the above formula [2], A represents a monovalent cation of an organic molecule or metal atom, B represents a divalent metal cation, and X represents a monovalent halide anion.

[0081] In the above formula [2], A is preferably, for example, made from C. p N m H n (where p, m, and n are all positive integers) represents an organic molecule. Specifically, examples of A include methylammonium and formamidinium.

[0082] The preferred inorganic atoms are lithium, cesium, sodium, potassium, and rubidium, although there are no particular limitations. These organic molecules or inorganic atoms can be used alone or in combination of two or more of them.

[0083] When the cation containing A is too large to fit within a three-dimensional perovskite crystal, such cations form crystals with a two-dimensional perovskite structure, crystals with a 2.5-dimensional perovskite structure possessing properties derived from both two-dimensional and three-dimensional perovskite structures, two-layer crystals with both three-dimensional and two-dimensional perovskite structures, or crystals with a mixed structure of three-dimensional and two-dimensional perovskite structures. All of these function as photoelectric conversion layers. A two-layer crystal with both three-dimensional and two-dimensional perovskite structures refers to a crystal in which crystals with three-dimensional and two-dimensional perovskite structures are stacked as independent and separate layers. A crystal with a mixed structure of three-dimensional and two-dimensional perovskite structures refers to a crystal with a structure comprising a mixture of regions or domains of crystals with both two-dimensional or 2.5-dimensional layered perovskite structures and three-dimensional perovskite structures.

[0084] Preferably, a crystal having a two-dimensional perovskite structure or a crystal having a 2.5-dimensional perovskite structure is represented by the following formulas [3] to [5].

[0085] R'2A n-1 B n X 3 n+1 [3]

[0086] R''A n-1 B n X 3 n+1 [4]

[0087] R'''A n B n X 3 n+1 [5]

[0088] Formulas [3] to [5] respectively form RP (Ruddlesden-Popper) type perovskite structure, DJ (Dion-Jacobson) type perovskite structure and ACI (alternating cations in the interlayer) type perovskite structure.

[0089] In equations [3] to [5], R', R'', and R''' each represent a cation that is too large for a three-dimensional perovskite structure, and, for example, in an organic molecule, R', R'', and R''' are preferably composed of C p N m H n(where p, m, and n are all positive integers) represents A. A can be unsubstituted or substituted; specifically, A is preferably 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, guanidinium, propylammonium, propargylammonium, alkylammonium, cyclohexylmethylammonium, 4-(aminomethyl)piperidinium, piperidinium, pyrrolidineammonium, cyclohexylammonium, 4-fluorophenylethylammonium, 4-fluorophenyl Ethylammonium, trifluoromethylbenzylammonium, pentafluorobenzylammonium, pentafluorophenylethylammonium, 4-methoxyphenylammonium, imidazolium, pyridinium, 3-thiophenemethylammonium, 2-thiopheneethylammonium, 2-thiopheneformamidinium, 2-thiophenemethylammonium, 1-naphthylmethylammonium, 2-naphthylmethylammonium, phenethylammonium, phenylammonium, benzylammonium, 2,5-thiophene dimethylammonium, phenylpropylammonium, 1,4-phenylenedimethanammonium, 3-phenyl-2-propen-1-ammonium, phenylbutylammonium, 4-tert-butylbenzylammonium, 3-(aminomethyl)piperidinium or 4-(aminomethyl)piperidinium.

[0090] In formulas [2] to [5], B represents a metal atom, examples of which 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 of them.

[0091] In formulas [2] to [5], X represents a halogen atom, and examples include chlorine, bromine, and iodine. These halogen atoms can be used alone or in combination of two or more of them. Halogen atoms are preferred because the presence of halogens in the structure may cause crystals having the above-described perovskite structure to be soluble in organic solvents and to be applicable to inexpensive printing methods, etc. Furthermore, iodine is more preferred because crystals having a perovskite structure have a narrower band gap.

[0092] Specifically, three-dimensional perovskites, two-dimensional perovskites, and mixed three-dimensional and two-dimensional perovskites are preferably MAPbI3, FAPbCl3, FAPbI3, or MAPbI x Br 3-x MAPbI x Cl 3-x Cs 0.05 (MA 0.17 FA 0.83 ) 0.95 Pb(I0.83 Br 0.17 )3、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 、CsPbI3、CsPbBr3、Cs x (MA) 1-x PbI3、Cs x (FA) 1-x PbI3、MA x (FA) 1-x PbI3、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 、(4 FPEA)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 ,(THAT0.9 PEA 0.1 )2MA4Pb5I 16 、(BA 0.9 PEA 0.1 )2MA3Pb4I 13 (4FPEA)2MA3Pb4I 13 (4FPEA)2MA4Pb5I 16 (BA)2MA2Pb3I 10 (BA)2MA3Pb4I 13 (TEA)2MA2Pb3I 10 (BA)2MA4Pb5I 16 、and (BA)2MA3Pb4I 13 In the specific examples above, "MA" represents methylammonium, "FA" represents formamidinium, "PEA" represents phenylethylammonium, "PTA" represents phenyltriethylammonium, "ThMA" represents 2-thiophenemethylammonium, "3BBA" represents 3-bromobenzylammonium, "3AMPY" represents 3-(aminomethyl)pyridine, "PDMA" represents 1,4-phenylenediamine, "TTDMA" represents thieno[3,2-b]thiophene-2,5-dimethylammonium, "4FPEA" represents 4-fluorophenylethylammonium, "BA" represents butylammonium, and "TEA" represents 2-thiopheneethylammonium.

[0093] Crystals with the above-described perovskite structure preferably have a cubic crystal system, wherein the metal atom B is body-centered, the organic molecule A is disposed at the vertices, and the halogen atom or X is face-centered. Although the details are unclear, it is inferred that when a crystal has this structure, the orientation of the octahedrons in the lattice can be easily changed, which increases the electron mobility in the perovskite crystal and improves the photoelectric conversion efficiency of the photoelectric conversion device.

[0094] The organic-inorganic perovskite compound used in this invention is preferably a crystalline semiconductor. A crystalline semiconductor is one whose scattering peaks can be detected by measuring the X-ray scattering intensity distribution. When the organic-inorganic perovskite compound is a crystalline semiconductor, the electron mobility in the organic-inorganic perovskite compound increases, and the photoelectric conversion efficiency of the photoelectric conversion element is improved.

[0095] The thickness of the photoelectric conversion layer according to the present invention is preferably 5 nm or more to 2000 nm or less. If the photoelectric conversion layer has a thickness of 5 nm or more, the photoelectric conversion layer can sufficiently absorb light. If the photoelectric conversion layer has a thickness of 2000 nm or less, the generated charge can be transferred to each electrode. More preferably, the lower limit is 50 nm, and more preferably, the upper limit is 1200 nm. Even more preferably, the lower limit is 100 nm, and even more preferably, the upper limit is 1000 nm.

[0096] [Hollow transport layer]

[0097] In this invention, the hole transport layer 6 is disposed between the photoelectric conversion layer 5 and the first electrode 7, such as... Figure 1 and 2 As shown. As described above, the hole transport layer 6 contains a compound represented by formula (1).

[0098] To improve photoelectric conversion efficiency, dopants (oxidants) or basic compounds can be added.

[0099] The hole transport layer according to the present invention preferably has a thickness of 10 nm or more to 1000 nm or less. If the hole transport layer has a thickness of 10 nm or more, it can sufficiently transport holes to the electrode. If the hole transport layer has a thickness of 1000 nm or less, it is unlikely to act as a resistor in hole transport, thus increasing the photoelectric conversion efficiency. A more preferred lower limit for the thickness of the hole transport layer is 50 nm, and a more preferred upper limit is 500 nm.

[0100] [Electron transport layer]

[0101] In the photoelectric conversion element according to the present invention, such as Figure 1 and Figure 2 As shown, an electron transport layer 4 can be disposed between the second electrode 3 and the photoelectric conversion layer 5.

[0102] Examples of materials used for electron transport layer 4 include, but are not limited to, N-type conductive polymers, N-type low-molecular-weight organic semiconductors, N-type metal oxides, N-type metal sulfides, alkali metal halides, alkali metals, and surfactants. Specifically, examples include cyano-containing polyphenylene vinylene, boron-containing polymers, copper bath, phenanthroline, aluminum hydroxyquinoline, oxadiazole compounds, benzimidazole compounds, naphthalenetetracarboxylic acid compounds, perylene derivatives, phosphine oxide compounds, phosphine sulfide compounds, fluorinated phthalocyanines, titanium dioxide, zinc oxide, indium oxide, tin oxide, gallium oxide, tin sulfide, indium sulfide, and zinc sulfide.

[0103] The preferred lower limit for the thickness of the electron transport layer 4 is 1 nm, and the preferred upper limit is 2000 nm. If the electron transport layer has a thickness of 1 nm or more, it can effectively block holes. If the electron transport layer has a thickness of less than 2000 nm, it is unlikely to act as a resistor in electron transport, thus increasing the photoelectric conversion efficiency. A more preferred lower limit for the thickness of the electron transport layer 4 is 3 nm, and a more preferred upper limit is 1000 nm. Even more preferred is a lower limit of 5 nm, and even more preferred is an upper limit of 500 nm.

[0104] <Application Example>

[0105] Applications include photoelectric conversion devices, mobile bodies, and building materials.

[0106] Photoelectric conversion device

[0107] The photoelectric conversion device according to the present invention includes a photoelectric conversion element according to the present invention. The photoelectric conversion device can be formed using multiple photoelectric conversion elements according to the present invention. When multiple photoelectric conversion elements are connected, the photoelectric conversion device can also be called a photoelectric conversion unit or a photoelectric conversion module. To increase the output voltage, photoelectric conversion elements with different absorption wavelengths can be stacked. The photoelectric conversion device includes a photoelectric conversion element according to the present invention and an inverter. The inverter can be a converter that converts DC to AC. The photoelectric conversion device may include an energy storage unit connected to the photoelectric conversion element. There are no limitations on the energy storage unit, as long as it can store electricity. Examples include secondary batteries using lithium ions, all-solid-state batteries, and double-layer capacitors.

[0108] [Moving Object]

[0109] Figure 3 This is a perspective view schematically illustrating one embodiment of a mobile body including a photoelectric conversion element according to the invention. The mobile body 30 includes a photoelectric conversion element 31 according to the invention and a body 32 including the photoelectric conversion element 31. The photoelectric conversion element 31 is disposed at a position such that the photoelectric conversion element 31 can receive light from outside the body 32. If the mobile body 30 is a vehicle, the photoelectric conversion element 31 may be disposed on its roof. The electrical energy obtained through the photoelectric conversion element 31 can be used as the power source for the mobile body 30, or as the power source for other electrical devices. The electrical energy generated by the power source of the mobile body 30 can be used as the power source for the photoelectric conversion element 31. If the mobile body 30 is a vehicle, the frictional energy generated by braking can be converted into electrical energy, which can be used to control the photoelectric conversion element 31.

[0110] The mobile body 30 may be, for example, a vehicle, a ship, an airplane, or a drone. The body 32 of the mobile body 30 may be formed of any material, but is preferably formed of a high-strength material.

[0111] [Building Materials]

[0112] Figure 4 This is a perspective view schematically illustrating one embodiment of a building material including a photoelectric conversion element according to the invention. Building material 40 may be the roof of a building. Building material 40 according to this embodiment includes a photoelectric conversion element 41 according to the invention, a protective member 42 protecting the photoelectric conversion element 41, a heat dissipation member 43, and exterior finishes 44a and 44b.

[0113] The building material 40 according to the invention may include a heat dissipation member 43 having a higher thermal conductivity than the photoelectric conversion element 41. If the photoelectric conversion element 41 is used as a roof, etc., in some cases, the temperature of the photoelectric conversion element 41 may rise due to sunlight, which may reduce the photoelectric conversion efficiency. The use of the heat dissipation member 43 can suppress the reduction in photoelectric conversion efficiency. Examples of heat dissipation members 43 include metals, alloys, liquid metals, and liquid resins.

[0114] The building material 40 according to the invention may include exterior trim 44a and 44b. Exterior trim 44a may have a different color than exterior trim 44b, or it may have the same color as exterior trim 44b. Exterior trim 44a and 44b may be formed from the same component, or they may be formed from different components. As exterior trim components, paint and transparent substrates may be used. Those with low light absorption and high heat-shielding properties are preferred.

[0115] [Example]

[0116] The invention will be described in more detail below by way of examples and comparative examples. The invention is not limited to the following examples without departing from its spirit. It should be noted that in the following examples, "parts" are based on mass unless otherwise specified.

[0117] <Synthesis of Example Compounds (1-2)>

[0118] Example compounds (1-2) were synthesized using the following methods.

[0119] 2,7-Dibromo-9-fluorenone (3.38 g, purchased from Tokyo Chemical Industry Co., Ltd.), 4,4'-dimethoxydiphenylamine (5.04 g, purchased from Tokyo Chemical Industry Co., Ltd.), palladium acetate (89.8 mg, purchased from Tokyo Chemical Industry Co., Ltd.), 1,1'-bis(diphenylphosphino)ferrocene (332.6 mg, purchased from Tokyo Chemical Industry Co., Ltd.), cesium carbonate (9.77 g, purchased from Tokyo Chemical Industry Co., Ltd.), and toluene (300 mL) were placed in a reactor and stirred under reflux for 18 hours under a nitrogen atmosphere. The reaction solution was allowed to stand at room temperature, then filtered under reduced pressure and washed with toluene. The filtrate was concentrated and purified by silica gel column chromatography (developing solvent: toluene) to give the intermediate product represented by formula (A) as a purple powder (yield: 44%).

[0120] [Chemistry 15]

[0121]

[0122] Subsequently, the intermediate product (1.27 g), diethyl malonate (1.60 g, purchased from Tokyo Chemical Industry Co., Ltd.), tetrahydrofuran (30 mL), and pyridine (5 mL) were placed in a reactor and cooled to 0°C with ice water. Then, titanium tetrachloride (3.79 g, purchased from Tokyo Chemical Industry Co., Ltd.) was added dropwise. After addition, the reaction solution was allowed to stand at room temperature and stirred for 18 hours. After the reaction was complete, water and ethyl acetate were added for liquid separation. The organic layer was washed with water and saturated brine and concentrated. The resulting crude product was purified by silica gel column chromatography (developing solvent: ethyl acetate / heptane = 1 / 3) to give example compounds (1-2) as purple powder (yield: 71%).

[0123] Manufacturing of Photoelectric Conversion Components

[0124] (Example 1)

[0125] [Formation of the electron transport layer]

[0126] A glass substrate with an ITO film was washed, and a tin(II) oxide coating solution with a concentration adjusted to 3% by mass was applied to it by spin coating. The workpiece was then heated at 150°C for 30 minutes to form an electron transport layer in the form of a thin film with a thickness of 15 nm.

[0127] [Formation of the photoelectric conversion layer]

[0128] 22.4 mg lead bromide, 172 mg formamidinium iodide, and 576 mg lead iodide were dissolved in 600 μL of N,N-dimethylformamide and 160 μL of dimethyl sulfoxide, and then stirred for 1 hour (solution 1). Further, 389.72 mg cesium iodide was dissolved in 1000 μL of dimethyl sulfoxide, and then stirred for 1 hour (solution 2). Subsequently, solution 2 (40 μL) was added to solution 1 to prepare the coating solution for the photoelectric conversion layer. The coating solution was applied to the electron transport layer by spin coating to form a Cs... 0.05 (FA 0.83 MA 0.17 ) 0.95 Pb(I 0.95 Br 0.05 )3 A photoelectric conversion layer with a thickness of 500nm is formed.

[0129] [Formation of the hole transport layer]

[0130] 0.15 g of example compounds (1-2) were dissolved in 2.2 g of chlorobenzene to prepare coating solution 1 for the hole transport layer. The coating solution was spin-coated onto the photoelectric conversion layer to form a hole transport layer with a thickness of 200 nm.

[0131] [Formation of the first electrode]

[0132] A hole transport layer with a thickness of 80 nm and an area of ​​0.09 cm² was formed on the hole transport layer using vacuum deposition. 2 Gold electrodes are used to obtain photoelectric conversion elements.

[0133] (Example 2)

[0134] Except that when preparing the coating liquid 1 for the hole transport layer, the example compound (1-2) was replaced with the compound represented by example compound (1-3), the photoelectric conversion element was obtained in the same manner as in Example 1.

[0135] (Example 3)

[0136] Except that when preparing the coating liquid 1 for the hole transport layer, the example compounds (1-2) were replaced with compounds represented by example compounds (1-5), the photoelectric conversion element was obtained in the same manner as in Example 1.

[0137] (Comparative Example 1)

[0138] Except that when preparing the coating liquid 1 for the hole transport layer, the example compounds (1-2) were replaced with compounds represented by formula (A), the photoelectric conversion element was obtained in the same manner as in Example 1.

[0139] (Comparative Example 2)

[0140] Except that when preparing the coating liquid 1 for the hole transport layer, the example compounds (1-2) were replaced with compounds represented by the following formula (B), the photoelectric conversion element was obtained in the same manner as in Example 1.

[0141] [Chemistry 16]

[0142]

[0143] (Example 4)

[0144] [Formation of the electron transport layer]

[0145] A glass substrate with an ITO film was washed, and a tin(II) oxide coating solution with a concentration adjusted to 3% by mass was applied to it by spin coating. The workpiece was then heated at 150°C for 30 minutes to form an electron transport layer in the form of a thin film with a thickness of 15 nm.

[0146] [Formation of the photoelectric conversion layer]

[0147] 22.4 mg lead bromide, 172 mg formamidinium iodide, and 576 mg lead iodide were dissolved in 600 μL of N,N-dimethylformamide and 160 μL of dimethyl sulfoxide, and then stirred for 1 hour (solution 1). Further, 389.72 mg cesium iodide was dissolved in 1000 μL of dimethyl sulfoxide, and then stirred for 1 hour (solution 2). Subsequently, solution 2 (40 μL) was added to solution 1 to prepare the coating solution for the photoelectric conversion layer. The coating solution was spin-coated onto the electron transport layer to form a Cs... 0.05 (FA 0.83 MA 0.17 ) 0.95 Pb(I 0.95 Br 0.05 )3 A photoelectric conversion layer with a thickness of 500nm is formed.

[0148] [Formation of the hole transport layer]

[0149] 0.15 g of example compounds (1-2) were 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 tert-butylpyridine were added to and mixed with the resulting chlorobenzene solution. 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(trifluoromethanesulfonyl)imide)] in 0.3 g of acetonitrile was mixed in to prepare coating solution 2 for the hole transport layer. The coating solution was spin-coated onto the photoelectric conversion layer to form a charge transport layer with a thickness of 200 nm.

[0150] [Formation of the first electrode]

[0151] A hole transport layer with a thickness of 80 nm and an area of ​​0.09 cm² was formed on the hole transport layer using vacuum deposition. 2 Gold electrodes are used to obtain photoelectric conversion elements.

[0152] <Evaluation>

[0153] (Evaluation of photoelectric conversion efficiency)

[0154] A power supply (purchased from Keithley Instruments, Inc., 236 Model) was connected between the electrodes of the photoelectric conversion element obtained in Example 1. A power intensity of 100 mW / cm was used. 2 The solar simulator (purchased from Yamashita Denso Corporation) illuminates the photoelectric conversion element with certain light and measures the resulting current and voltage to evaluate the photoelectric conversion efficiency.

[0155] Examples 2 through 4 and Comparative Examples 1 and 2 were evaluated similarly. The results are shown in Tables 1 and 2.

[0156] [Table 1]

[0157]

[0158] [Table 2]

[0159]

[0160] This invention is not limited to the embodiments described above, and various changes and modifications can be made without departing from the spirit and scope of the invention. Therefore, the claims are appended to disclose the scope of the invention.

[0161] This application claims priority to Japanese Patent Application No. 2024-002687, filed on January 11, 2024, the entire contents of which are incorporated herein by reference.

[0162] List of reference numerals

[0163] 1. Photoelectric conversion element

[0164] 2 substrate

[0165] 3 Second electrode

[0166] 4. Electron transport layer

[0167] 5 Photoelectric conversion layer

[0168] 6 Hole transport layer

[0169] 7 First Electrode

Claims

1. A photoelectric conversion element comprising a first electrode, a second electrode, and a photoelectric conversion layer comprising a crystal having a perovskite structure, the photoelectric conversion layer being disposed between the first electrode and the second electrode. in, A hole transport layer containing a compound represented by the following formula (1) is disposed between the photoelectric conversion layer and the first electrode: In equation (1), R 1 and R 2 Each represents a straight-chain or branched alkyl group having 1 to 6 carbon atoms, and R 3 To R 22 Each of the following independently represents a hydrogen atom, a trimethylsilyl group, a straight-chain or branched alkyl group having 1 to 20 carbon atoms and optionally having substituents, a straight-chain or branched alkenyl group having 2 to 20 carbon atoms and optionally having substituents, a cycloalkyl group having 3 to 10 carbon atoms and optionally having substituents, an alkoxy group having 1 to 20 carbon atoms and optionally having substituents, a cycloalkoxy group having 3 to 10 carbon atoms and optionally having substituents, an alkylthio group having 1 to 18 carbon atoms and optionally having substituents, or a group having 1 to 20 carbon atoms and optionally having substituents. The alkyl group having a substituent, an amino group having a substituent, an aromatic hydrocarbon group having a carbon number of 6 to 36 and optionally having a substituent, or a heterocyclic group having a cyclic atom number of 5 to 36 and optionally having a substituent; and each functional group optionally having a substituent is a halogen group, a straight-chain or branched alkyl group having a carbon number of 1 to 20, an alkoxy group having a carbon number of 1 to 20, an alkylthio group having a carbon number of 1 to 18, an amino group having a carbon number of 1 to 20, an aromatic hydrocarbon group having a carbon number of 6 to 36, or a heterocyclic group having a cyclic atom number of 5 to 36.

2. The photoelectric conversion element according to claim 1, wherein in formula (1), R 3 To R 22 Each of the following independently represents a hydrogen atom, a straight-chain or branched alkyl group having 1 to 20 carbon atoms and optionally having a substituent, an alkoxy group having 1 to 20 carbon atoms and optionally having a substituent, or an amino group having 1 to 20 carbon atoms and optionally having a substituent.

3. The photoelectric conversion element according to claim 1 or 2, wherein in formula (1), R 5 R 10 R 15 and R 20 Each represents an alkoxy group having 1 to 20 or fewer carbon atoms and optionally having substituents.

4. A photoelectric conversion device comprising a photoelectric conversion element according to any one of claims 1 to 3.

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