Photoelectric conversion element

Abstract

To provide a photoelectric conversion element that suppresses the aging degradation of organic compounds and electrodes due to water vapor. [Solution] A photoelectric conversion element is provided, comprising a first electrode, a photoelectric conversion layer, a second electrode, and a substrate, wherein a porous layer is provided between the substrate and the second electrode, and the porous layer has a refractive index of 1.18 or more and 1.28 or less at a wavelength of 550 nm, and a thickness of 70 nm or more.

Description

[Technical Field]

[0001] This disclosure relates to a photoelectric conversion element. [Background technology]

[0002] In order to address the depletion of fossil fuels and the environmental problems caused by their use, research is actively being conducted on renewable and clean alternative energy sources such as solar, wind, and hydroelectric power. Among these, there is growing interest in solar cells, which directly convert sunlight into electrical energy. Here, a solar cell refers to a battery that absorbs light energy from sunlight and generates current-voltage using the photovoltaic effect, which generates electrons and holes.

[0003] Currently, np diode type silicon (Si) single-crystal based solar cells with light energy conversion efficiencies exceeding 20% ​​are widely known and actually used in solar power generation. However, these require high-temperature processing in their manufacture, and the material itself is expensive, resulting in high costs per unit of power. Furthermore, supply becomes difficult if silicon resources are insufficient.

[0004] On the other hand, solar cells using organic materials (hereinafter referred to as "organic solar cells") do not require high-temperature processing steps in their manufacture. Furthermore, solar cells using organic materials can be produced using a so-called roll-to-roll method on sheet-shaped substrates, which is expected to reduce production costs. Among solar cells using organic materials, perovskite-type solar cells, which have a perovskite structure crystal (hereinafter also called "perovskite crystal") as the photoelectric conversion layer, are being developed for practical use because of their excellent photoelectric conversion characteristics.

[0005] A typical organic solar cell has a photoelectric conversion element structure comprising a first electrode, a photoelectric conversion layer, a second electrode, and a substrate.

[0006] In such photoelectric conversion elements, the photoelectric conversion layer is covered and sealed with a resin-based encapsulant. For example, Patent Document 1 describes a solar cell having a first substrate, a first electrode, an organic photoelectric conversion unit, a second electrode, and a second substrate, wherein a water vapor barrier layer is provided between the first substrate and the second substrate, and the water vapor barrier layer contains an organometallic oxide having a structure represented by general formula 1): R-[M(OR1)y(O-)xy]nR. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Patent Application No. 2020-522127 [Overview of the project] [Problems that the invention aims to solve]

[0008] Organic solar cells are generally considered to have lower durability than inorganic solar cells. This is due to degradation caused by water vapor entering from the atmosphere. The resin materials used as encapsulants in organic solar cells cannot completely block water vapor permeation, leading to significant degradation of the organic compounds and electrodes over time, drastically reducing their durability. To address these issues, the development of improvement technologies is highly desirable.

[0009] Therefore, the object of this disclosure is to provide a photoelectric conversion element that suppresses the aging degradation of organic compounds and electrodes due to water vapor. [Means for solving the problem]

[0010] The above objectives are achieved by the present disclosure below. Specifically, the present disclosure provides a photoelectric conversion element comprising a first electrode, a photoelectric conversion layer, a second electrode, and a substrate, wherein a porous layer is provided between the substrate and the second electrode, and the porous layer is characterized in that the refractive index at a wavelength of 550 nm is 1.18 or more and 1.28 or less, and the thickness is 70 nm or more. [Effects of the Invention]

[0011] According to this disclosure, it is possible to provide a photoelectric conversion element that suppresses the aging degradation of organic compounds and electrodes due to water vapor. [Brief explanation of the drawing]

[0012] [Figure 1] This is a schematic cross-sectional view of one embodiment of the photoelectric conversion element of the present disclosure. [Figure 2] This is a schematic cross-sectional view of one embodiment of the photoelectric conversion element of the present disclosure. [Figure 3] This is a schematic cross-sectional view of one embodiment of the photoelectric conversion element of the present disclosure. [Figure 4] This is a schematic cross-sectional view of one embodiment of the photoelectric conversion element of the present disclosure. [Modes for carrying out the invention]

[0013] The present disclosure will be described in detail below with reference to preferred embodiments. This disclosure relates to a photoelectric conversion element comprising a first electrode, a photoelectric conversion layer, a second electrode, and a substrate, wherein a porous layer is provided between the substrate and the second electrode, and the porous layer has a refractive index of 1.18 or more and 1.28 or less at a wavelength of 550 nm, and a thickness of 70 nm or more.

[0014] The inventors have found, through their research, that a photoelectric conversion element characterized by having a porous layer that satisfies certain requirements between the substrate and the second electrode suppresses the aging degradation of organic compounds and electrodes due to water vapor. The reason for this is thought to be as follows.

[0015] By having a porous layer that meets certain requirements between the substrate and the second electrode, water vapor is absorbed by the porous layer, preventing moisture from directly reaching the organic compound or electrode, thereby suppressing the progression of degradation.

[0016] As described above, the effects of this disclosure can be achieved by having a porous layer that satisfies certain requirements between the substrate and the second electrode.

[0017] The present invention will be described in detail below with reference to preferred embodiments. The present invention is not limited to the embodiments described below, and the scope of the present invention also includes modifications, improvements, etc., to the embodiments described below, based on the ordinary knowledge of those skilled in the art, without departing from the spirit of the present invention.

[0018] In this specification, "layer" refers not only to layers with clear boundaries or flat, thin films, but also to layers with gradually changing elemental concentrations and layers that can form complex structures together with other layers. Elemental analysis of layers can be performed, for example, by TOF-SIMS / FE-TEM / EDS line analysis of the cross-section of the photoelectric conversion element to confirm the elemental distribution of specific elements. Analysis of each layer may also be performed by peeling off the completed photoelectric conversion element, exposing the layer to be analyzed, and then measuring it.

[0019] Figure 1 is a schematic cross-sectional view showing the configuration of one embodiment of the photoelectric conversion element of the present disclosure. The photoelectric conversion element 1 has a porous layer 3, a second electrode 4, a photoelectric conversion layer 6, and a first electrode 7 on a substrate 2. One of the first electrode 7 and the second electrode 4 is the anode and the other is the cathode, and current can be extracted by connecting the first electrode 7 and the second electrode 4 with an external circuit.

[0020] The photoelectric conversion layer 6 is excited by light incident through the substrate 2 and the second electrode 4 or the first electrode 7, generating electrons or holes. That is, the photoelectric conversion layer 6 generates an electric current between the first electrode 7 and the second electrode 4. If necessary, an electron transport layer 5 may be placed between the photoelectric conversion layer 6 and the two electrodes (second electrode 4, first electrode 7), as shown in Figure 2. Multiple electron transport layers 5 and photoelectric conversion layers 6 may be stacked. Such a configuration can also be called a tandem structure. Each component will be described below. Alternatively, as shown in Figure 3, a porous layer 3 may be present on the substrate 2, and the second electrode 4, electron transport layer 5, photoelectric conversion layer 6, first electrode 7, and charge transport layer 8 may be provided in this order. The following explains each layer.

[0021] 〔substrate〕 The photoelectric conversion element of this disclosure includes a substrate, which may be made of a base material such as transparent glass (e.g., soda-lime glass, alkali-free glass), ceramic, or transparent plastic, or may include such base materials. Examples of transparent plastics include PET film and polyimide film. When light is taken in from the first electrode side, the substrate can be made of an opaque material, and when light is taken in from the second electrode side, the substrate is made of a transparent material.

[0022] [Porous layer] As shown in Figure 1, the photoelectric conversion element 1 of this disclosure includes a substrate 2, a porous layer 3, and a second electrode 4. Furthermore, as shown in Figure 4, a laminate 9 may be formed between the substrate 2 and the porous layer 3. By forming a laminate 9 between the substrate 2 and the porous layer 3, an anti-reflective effect is obtained and the light capture efficiency is improved. The laminate is preferably made up of multiple layers containing materials with different refractive indices. In particular, the laminate is preferably made up of a layer containing a material selected from the group consisting of zirconium oxide, titanium oxide, tantalum oxide, niobium oxide, and hafnium oxide, and a layer containing a material selected from the group consisting of alumina, silicon oxide, and magnesium fluoride.

[0023] The thickness of the porous layer in this disclosure is 70 nm or more. There is no particular upper limit, but it is preferably 5 μm or less, and more preferably 300 nm or less. If the thickness is less than 0.07 μm, the amount of moisture retained will be insufficient. Also, if it exceeds 5 μm, it becomes difficult to manufacture the porous layer. Considering the productivity of manufacturing the porous layer, it is preferable that it does not exceed 300 nm. As shown in Figure 4, when forming a laminate 9 between the substrate 2 and the porous layer 3, the thickness can be appropriately designed considering not only water vapor absorption but also anti-reflective performance.

[0024] The porous layer contains voids, and the average pore size of the voids is preferably between 3 nm and 50 nm, as determined by pore distribution measurement using nitrogen gas adsorption.

[0025] The amount of pores contained in the porous layer can be determined as pore volume by nitrogen gas adsorption. The pore volume is 0.1 cm³. 3 / g or more 1.0cm 3 It is preferable that the pore volume is 0.1 cm³ or less. 3 A pore volume of 1.0 cm³ or more ensures a sufficient amount of water in the porous layer to provide anti-fogging properties. 3 If the density is less than / g, sufficient scratch resistance can be obtained without a decrease in the hardness of the skeleton. A more preferable pore volume is 0.3 cm³. 3 / g or more 0.6cm 3 It is less than / g.

[0026] Methods for forming a porous layer include depositing the material under vacuum and forming it by wet deposition.

[0027] The porous layer only needs to be able to adsorb and retain moisture, and inorganic porous materials or organic porous materials can be used. However, inorganic porous materials composed of metal oxides are preferred due to their high film strength and the fact that they do not swell when absorbing water. Examples of metal oxides include silicon dioxide, zirconium dioxide, and titanium dioxide.

[0028] Methods for forming a porous layer from a metal oxide include wet deposition of a metal oxide precursor, such as silicon oxide, using a sol-gel method, or wet deposition from a dispersion of metal oxide particles. Wet deposition from a dispersion of metal oxide particles is particularly preferred because the pores are easily connected, and the average pore size and porosity can be kept constant. In this case, it is preferable to use a dispersion containing silicon oxide, which is easy to produce and has relatively high stability.

[0029] (particle) The porous layer can be formed by including particles, and it is particularly preferable that it be formed by including metal oxide particles.

[0030] The particles can be solid particles or hollow particles. If they are solid particles, they can further be solid particles linked together in a chain (chain-like solid particles).

[0031] When using chain-like solid particles, the average particle diameter of the chain-like solid particles is preferably 10 nm to 50 nm for the short axis and 60 nm to 200 nm for the long axis. If the short axis is smaller than 10 nm or the long axis is smaller than 60 nm, the voids between the chain-like solid particles become small, and sufficient moisture absorption cannot be obtained. If the short axis exceeds 50 nm or the long axis exceeds 200 nm, the voids between the chain-like solid particles become larger, resulting in a lack of water flocculation effect and a reduced moisture absorption rate, which is undesirable.

[0032] Here, the average particle diameter of a chain-like solid particle, which is a particle in which solid particles are linked together in a chain, is the average Ferret diameter. This average Ferret diameter can be measured by image processing of images observed using a transmission electron microscope. Commercial image processing software such as image Pro PLUS (manufactured by Media Cybernetics, Inc.) can be used for image processing. In a predetermined image area, the contrast can be adjusted as needed, the average Ferret diameter of each particle can be measured by particle measurement, and the average value can be calculated. If the solution consists of chain-like solid particles dispersed in a solvent, the average particle diameter along the short and long axes can be determined by dynamic light scattering.

[0033] As the chain-like solid particles, metal oxides such as silicon dioxide, magnesium fluoride, fluorine, and silicon, or organic resin particles can be used. Alternatively, the chain-like solid particles may be made of silicon dioxide, magnesium fluoride (MgF2), fluorine, or organic resins such as silicon. The content of chain-like solid particles in the porous layer of this disclosure is preferably 40% by volume or more and 60% by volume or less.

[0034] The material constituting the hollow particles is preferably one with a low refractive index, and examples include metal oxides such as SiO2, MgF2, fluorine, and silicon, or organic resins, but SiO2 is more preferred because it is easy to manufacture the particles.

[0035] Hollow particles have pores inside. Furthermore, hollow particles that have a shell surrounding the outside of the pores may also be used. Because the outside of the pores is covered by a shell, the amount of moisture absorbed is inferior to that of solid particles, but the voids between the hollow particles can be utilized.

[0036] The pores can be single-pore or multi-pore, and can be selected as appropriate. The material constituting the hollow particles is preferably one with a low refractive index, such as SiO2, MgF2, fluorine, silicon, or organic resins, but SiO2 is more preferred because it is easy to manufacture. The hollow particles allow for moisture absorption by stacking multiple layers of particles aligned parallel to the substrate surface, creating voids between the particles.

[0037] The average particle diameter of the hollow particles should be between 15 nm and 100 nm, preferably between 15 nm and 60 nm. If the average particle diameter of the hollow particles is less than 15 nm, it is difficult to stably produce the core particles. If it exceeds 100 nm, the gaps between the particles become large, so the water coagulation effect is not obtained, resulting in a small amount of moisture absorption, which is undesirable.

[0038] (binder) In a porous layer, particles can be bound together with a binder. The binder can, for example, form siloxane bonds at the contact points between particles. The binder may be prepared by mixing a solution containing the necessary components for forming a binder made of a silanealkoxy hydrolysis condensate with a solution in which the particles are dispersed in a solvent, or by coating a solution in which the particles are dispersed in a solvent, aligning the particles, and then coating the surface with a solution containing the necessary components for forming the binder.

[0039] A solution containing the components necessary to form a binder can be obtained by stirring and reacting alkoxysilane with water to hydrolyze the alkoxysilane and produce a silanealkoxy hydrolysis condensate. Since alkoxysilane, a precursor of silanealkoxy hydrolysis condensates, is immiscible with water, when alkoxysilane and water are mixed, the reaction initially results in a two-layer separation. As the reaction progresses, the alkoxide is converted to silanol, increasing the number of hydrophilic groups. This causes the hydrolysate of alkoxysilane to dissolve in the aqueous layer, eliminating the two-layer separation and resulting in a homogeneous mixture. The amount of water mixed with the alkoxysilane is preferably 5 to 20 equivalents relative to the alkoxysilane. An acid or base may be added as a catalyst to promote hydrolysis. As a catalyst, it is preferable to use a catalyst containing an acid or base such as sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, or ammonia at a concentration of 1% by mass or less. The temperature of the solution, in which alkoxysilane and water are uniformly mixed, is preferably between 5°C and 30°C. If the temperature is below 5°C, the hydrolysis of the silanealkoxy hydrolysis condensate takes too long, resulting in poor productivity. If the temperature exceeds 30°C, the condensation reaction proceeds too quickly, causing the silanealkoxy hydrolysis condensate to grow excessively and increasing scattering, which is undesirable.

[0040] The progress of the hydrolysis and condensation reactions of silanealkoxy hydrolysis condensates can be evaluated by the average particle size. It is preferable that the silanealkoxy hydrolysis condensate has an average particle size of 8 nm to 30 nm, as measured by dynamic light scattering of a solution containing the components necessary for forming the binder. It is even more preferable that the silanealkoxy hydrolysis condensate has an average particle size of 8 nm to 15 nm.

[0041] As precursors for forming the components necessary for forming the binder, methyl-modified trifunctional silanes such as methyltriethoxysilane and methyltrimethoxysilane, or tetrafunctional silanes such as tetraethoxysilane, may be used, or a mixture of the above trifunctional and tetrafunctional silanes may be used. Increasing the number of silanol groups increases the probability of siloxane bond formation at the particle contact points, thereby increasing the strength of the anti-reflective coating, so it is particularly preferable to use tetrafunctional silanes.

[0042] 〔electrode〕 The photoelectric conversion element disclosed herein has a first electrode and a second electrode. The materials of the first electrode and the second electrode are not particularly limited, and conventionally known materials can be used. Examples include metals such as gold, silver, titanium, and copper; sodium, sodium-potassium alloys; lithium, magnesium, carbon, carbon nanotubes; aluminum, magnesium-silver mixtures; magnesium-indium mixtures; aluminum-lithium alloys; Al / Al2O3 mixtures; Al / LiF mixtures; and so on. 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 (antimond-doped tin oxide), as well as conductive transparent polymers. These materials may be used individually or in combination of two or more. The first electrode and the second electrode may have at least one electrode on the light incidence side as a transparent electrode, while the other electrode may be a transparent electrode or a reflective layer formed of a light-reflective material, or a transparent electrode with a reflective layer on the side opposite to the light incidence side. If the first electrode is on the light incidence side, the second electrode may be a transparent electrode and the substrate may be the reflective layer. The electrodes may also be patterned electrodes.

[0043] [Process for forming the first electrode and the formation of the second electrode] The photoelectric conversion element of this disclosure is formed by a step of forming a first electrode and a 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 deposition), and SPD (spray pyrolysis deposition). The materials of the first electrode and the second electrode are as described above. When either the first electrode or the second electrode, or both, are transparent electrodes, the thickness of the transparent electrode is preferably 0.03 μm or more and 3 μm or less.

[0044] When manufacturing photoelectric conversion elements, it is common practice to perform cutting processes between each stage of the manufacturing process to form circuits. Examples of cutting processes include mechanical patterning and laser patterning.

[0045] [Photoelectric conversion layer] The photoelectric conversion element disclosed herein includes a photoelectric conversion layer, and the photoelectric conversion layer is not limited to perovskite type, silicon type, CIGS type, or any other layer capable of photoelectric conversion, and these may be combined and stacked. In particular, the photoelectric conversion element preferably includes a perovskite-type photoelectric conversion layer containing a perovskite crystal structure.

[0046] When a photoelectric conversion layer containing a perovskite crystal is included, the photoelectric conversion element has a first electrode and a second electrode, with the photoelectric conversion layer containing the perovskite crystal disposed between the first electrode and the second electrode, and a charge transport layer may be further provided between the photoelectric conversion layer and the first electrode. Furthermore, to improve the photoelectric conversion efficiency, a tandem type in which photoelectric conversion elements are stacked may be used. In addition to the perovskite type using a perovskite crystal as the photoelectric conversion layer, silicon type, CIGS type, etc. can be used as the stacked photoelectric conversion elements, and the type of photoelectric conversion element is not limited to this.

[0047] Crystals with a perovskite structure are 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. As A in the above general formula [1], for example, in the case of an organic molecule, C p N m H n (where p, m, and n are all positive integers) is preferably represented. Specifically, methylammonium and formamidinium can be mentioned. The metal atom is not particularly limited, but lithium, cesium, sodium, potassium, and rubidium are preferable. These organic molecules or metal atoms may be used alone or in combination of two or more.

[0048] When the cation of A constituting it is too large to fit within the crystal of the three-dimensional perovskite structure, a crystal of a two-dimensional perovskite structure, a crystal of a 2.5-dimensional perovskite structure having both two-dimensional and three-dimensional properties, a two-layer crystal of a three-dimensional and two-dimensional perovskite structure, or a crystal of a mixed three-dimensional·two-dimensional perovskite structure is formed, and all of them function as a photoelectric conversion layer. The two-layer crystal of a three-dimensional and two-dimensional perovskite refers to a crystal in which crystals of a three-dimensional and two-dimensional perovskite structure are stacked as independent separate layers, and the mixed three-dimensional·two-dimensional perovskite indicates a crystal having a structure in which both regions or domains of a two-dimensional or 2.5-dimensional layered and three-dimensional perovskite structure are mixed.

[0049] The two-dimensional perovskite or the crystal of the 2.5-dimensional perovskite structure is preferably represented by the following general formulas [2] to [4]. N represented by the following general formula 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]

[0050] The above general formulas form perovskite structures of the RP (Ruddlesden-Popper) type (2), the DJ (Dion-Jacobson) type (3), and the ACI (Alternating cations in the interlayer) type (4), respectively.

[0051] In the above general formulas [2] to [4], R', R'', and R''' are cations of organic molecules or metals that may have substituents, specifically ethylammonium, propylammonium, n-butylammonium, n-hexylammonium, n-octylammonium, 1,6-hexadiammonium, iso-butylammonium, 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, guanidium, propylammonium, propargylamine, alkylammonium, cyclohexylmethylammonium, 4-(aminomethyl)piperidinium, piperidinium, pyrrolidinium, cyclohexylammonium, 4- Luorophenethylammonium, 4-fluorophenethylammonium, trifluoromethylbenzylammonium, pentafluorobenzylammonium, pentafluorophenylethylammonium, 4-methoxyphenethylammonium, imidazolium, pyridinium, 3-thiophenmethylammonium, 2-thiophenethylammonium, 2-thiophenformamidium, 2-thiophenmethylammonium, 1-naphthylmethylammonium, 2-naphthylmethylammonium, phenethylammonium, phenylammonium, benzylammonium, 2,5-thiophendimethylammonium, phenylpropylammonium, 1,4-phenylenedimethaneamine, 3-phenyl-2-propene-1-ammonium, phenylbutylammonium, 4-tert-butylbenzylammonium, 3-(aminomethyl)piperidinium, and 4-(aminomethyl)piperidinium are preferred.

[0052] In the general formulas [1] to [4] above, 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 individually or in combination of two or more.

[0053] In the general formulas [1] to [4] above, X is a halogen atom, such as chlorine, bromine, or iodine. These halogen atoms may be used individually or in combination of two or more. Among these, halogen atoms are preferred because the inclusion of a halogen in the structure makes the perovskite crystal more soluble in organic solvents, enabling its application to inexpensive printing methods and the like. Furthermore, iodine is more preferred because it narrows the energy band gap of the perovskite crystal.

[0054] Specifically, 3D perovskites, 2D perovskites, and mixed 3D-2D perovskites are MAPbI3, FAPbCl3, FAPbI3, and 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 、CsPbI3、CsPbBr3、Cs x (MA) 1-x PbI3、Csx(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 、(pF-AND)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)2MA3Pb4I 13 、(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, MASnI3 are preferred. Depending on the purpose, the A-site, B-site or X-site in the above general formula may be adjusted to be too little or excessive, and the combination of x1 to x5 may be changed according to the purpose. The combination of x1 to x5 is as shown in Table 1 for example. The particularly preferred range is 0.03 ≤ x1 ≤ 0.10, 0.80 ≤ x2 ≤ 0.96, 0.95 ≤ x3 ≤ 1.05, 0.80 ≤ x4 ≤ 0.96, 2.95 ≤ x5 ≤ 3.05. Note that MACl may be included as a material for forming perovskite crystals.

Table 1

[0055] In 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-phenylenedimethanammonium, "TTDMA" represents thieno[3,2-b]thiophene-2,5-diyl dimethanammonium, "4FPEA" represents 4-fluorophenethylammonium, "BA" represents butylammonium, and "TEA" represents 2-thiophenethylammonium.

[0056] The perovskite crystal described above preferably has a cubic crystal structure in which a metal atom B is located at the body center, organic molecules A are located at each vertex, and halogen atoms X are located at the face centers. Although the details are not clear, it is presumed that having such a structure allows the orientation of octahedra within the crystal lattice to change easily, thereby increasing the electron mobility in the perovskite crystal and improving the photoelectric conversion efficiency of the photoelectric conversion element.

[0057] The organic-inorganic perovskite compounds used in this disclosure are preferably crystalline semiconductors. A crystalline semiconductor is a semiconductor in which the X-ray scattering intensity distribution can be measured and a scattering peak can be detected. When the organic-inorganic perovskite compound is a crystalline semiconductor, the electron mobility in the organic-inorganic perovskite compound is increased, and the photoelectric conversion efficiency of the photoelectric conversion element is improved.

[0058] Furthermore, the photoelectric conversion layer relating to this disclosure may include materials other than crystals with an organic-inorganic perovskite structure.

[0059] The thickness of the photoelectric conversion layer according to this disclosure is preferably 5 nm or more and 2000 nm or less. If the thickness is 5 nm or more, light can be absorbed sufficiently, and if it is 2000 nm or less, the generated charge can be transported to each electrode. A more preferable lower limit is 50 nm or more, a more preferable upper limit is 1200 nm, an even more preferable lower limit is 100 nm, and an even more preferable upper limit is 1000 nm.

[0060] In this disclosure, it is preferable that the photoelectric conversion layer has voids. In mass-producible methods for manufacturing photoelectric conversion layers, voids tend to occur for the reasons mentioned above. Furthermore, the presence of voids in the photoelectric conversion layer makes it easier for the charge-transporting particles to penetrate to the second electrode side of the photoelectric conversion layer, which can reduce the recombination suppression effect.

[0061] In this disclosure, the size of the perovskite crystals in the photoelectric conversion layer is preferably 1 μm or larger. Here, the crystal size refers to the longest axis of the largest perovskite crystal observed. Larger perovskite crystals tend to create uneven surfaces, resulting in a larger arithmetic mean roughness. The arithmetic mean roughness Ra is preferably between 10 nm and 200 nm. An arithmetic mean roughness Ra of 10 nm or more makes it easier for the recombination suppression effect of the insulating resin to manifest. Furthermore, if the arithmetic mean roughness Ra is greater than 200 nm, the charge-transporting particles tend to penetrate to the second electrode side of the photoelectric conversion layer, which can reduce the recombination suppression effect. Ra is more preferably between 20 nm and 180 nm, and even more preferably between 40 nm and 150 nm. In a mass-producible method for manufacturing a photoelectric conversion layer, for the reasons mentioned above, the perovskite crystals tend to be large, and the arithmetic mean roughness tends to be large.

[0062] [Formation of the photoelectric conversion layer] The photoelectric conversion layer of the photoelectric conversion element of the present disclosure can be formed using a large-area film deposition method. Large-area film deposition methods can be classified into vapor deposition methods and coating methods. Vapor deposition is a method of forming a film by volatilizing solid raw materials and then solidifying them again on the surface of a substrate. Vapor deposition methods include physical vapor deposition (PVD) and chemical vapor deposition (CVD). Examples of PVD methods include co-evaporation, pulsed laser deposition (PLD), electron beam heating deposition, and molecular beam epitaxy. Examples of CVD methods include thermal CVD, plasma CVD, and atomic layer deposition.

[0063] The coating method involves preparing coating solutions for each layer, which will be explained in detail later, applying the coating solutions onto the desired substrate or layer, and then drying the coating film to form a film. Methods for applying the coating solution include immersion coating, spin coating, spray coating, inkjet coating, meniscus coating, screen coating, roll coating, gravure coating, die coating, blade coating, curtain coating, and bar coating. From these, the appropriate method is selected according to the characteristics of the photoelectric conversion layer to be manufactured, such as thickness control and orientation control. The above-mentioned process is merely an example, and improved coating methods based on these general-purpose coating methods may also be used. Furthermore, the process may be used individually or in combination with other coating methods. Among these, from the viewpoint of high mass production capability, it is preferable to have one of the following processes: die coating, blade coating, spray coating, inkjet coating, gravure coating, or screen coating, and it is even more preferable to have die coating.

[0064] Immersion coating is a method of coating by immersing the substrate in paint and then lifting it out. Spin coating is a method of forming a uniform coating film by dropping paint onto the substrate and rotating it using centrifugal force. Spray coating is a method of forming a coating film by spraying paint onto the surface of the substrate. Inkjet coating is a method of forming a uniform coating film by dropping paint onto the surface of the substrate drop by drop. Screen coating is a method of coating using a screen mesh made of synthetic or metal fibers. The paint passes through the mesh of the screen and is applied to the substrate. Roll coating is a coating method that uses one or more rollers to obtain an optimal coating surface. Roll coating has a wide range of applications and includes various methods such as controlling the amount of paint on the roller beforehand using die coating or blade coating and then applying it to the substrate, controlling the gap of the paint passing through the roller to make the coating film uniform, and making the coating surface uniform using a roll on a deformable film such as a film, as represented by the roll-to-roll method. Gravure coating is a method of coating by adhering paint to a gravure roll with an uneven surface and then transferring it to the substrate. Die coating is a method of forming a coating film by extruding paint at a uniform flow rate in the width direction through a slit with a certain width called a slot die, and creating a liquid reservoir called a bead between the substrate and the slit. Blade coating is a method of forming a uniform coating film by passing paint, which has been dropped onto the substrate, between the substrate and the blade. Curtain coating is a method of forming a coating film by extruding paint at a uniform flow rate in the width direction through a slit with a certain width, and transferring the paint directly onto the substrate without creating a liquid reservoir. Bar coating is a method of forming a uniform coating film by passing paint, which has been dropped onto the substrate, between bars with grooves formed after application. One method for creating a film is to dry the applied, undried film (wet film). When the photoelectric conversion layer contains perovskite crystals, a perovskite crystal film can be created by drying the wet film after applying the coating solution. The process of creating a perovskite crystal film involves not only the general drying of a wet film, but also the creation and growth of perovskite crystal nuclei. If drying is slow, the wet film is likely to move during drying, resulting in unevenness in the film, and if there are too few perovskite crystal nuclei, gaps are likely to form between the perovskite crystals. Therefore, a fast drying speed is preferable. On the other hand, if drying is too fast, too many perovskite crystal nuclei are created, resulting in smaller individual perovskite crystals. Smaller perovskite crystals mean more perovskite crystal interfaces, which can lead to increased interfacial resistance, decreased photoelectric conversion efficiency, and reduced durability due to the movement of perovskite crystal raw material ions across the interfaces. Therefore, it is preferable that the drying rate during perovskite crystal film formation is within an appropriate range.

[0065] Examples of methods for producing perovskite crystal films include the poor solvent method, gas quenching method, reduced pressure method, rapid heating method, and air drying. The poor solvent method involves applying a poor solvent to a wet film obtained by a coating method to immediately replace the good solvent in the paint for the photoelectric conversion layer, thereby producing perovskite crystals. Because the good solvent is immediately replaced, many perovskite crystal nuclei are formed. Therefore, film defects are less likely to form, the roughness tends to be small, and individual crystals tend to be small. The gas quenching method is a method of producing perovskite crystals by accelerating the drying of the wet film by blowing gas onto it. Since the decomposition of perovskite crystals is accelerated by moisture, it is preferable to use a gas with low moisture content. Examples of gases to be blown include nitrogen gas and dry air. The gas may also be heated beforehand to produce hot air. The reduced pressure method is a method of drying the wet film by reducing the pressure in the space where the wet film is located, thereby accelerating the volatilization of the solvent in the wet film. Rapid heating is a method of accelerating the drying of a wet film by heating it. Heating methods include direct heating by bringing a heat source into contact with the substrate, and indirect heating using infrared radiation or the like.

[0066] In the deposition of the photoelectric conversion layer of a photoelectric conversion element, the deposition area of ​​the photoelectric conversion layer is 5 cm². 2 Preferably, it should be 20 cm or more. 2 The above is even more preferable. The larger the film deposition area of ​​the photoelectric conversion layer, the better the mass productivity. Also, the larger the film deposition area, the easier it is for uneven shapes and voids to occur in the photoelectric conversion layer, and the more easily the recombination suppression effect of the insulating resin is exhibited. In this disclosure, the photoelectric conversion layer may be deposited by depositing the raw materials all at once, or by depositing the raw materials in multiple stages.

[0067] To completely remove the solvent or dispersion medium from the liquid containing the 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 treatment is preferably 40°C to 300°C, and more preferably 50°C to 150°C. Annealing is preferable because it can increase the contact area at the interface between the stacked layers, as the materials constituting each layer penetrate each other, thereby increasing the short-circuit current.

[0068] [Charge transport layer] In the photoelectric conversion element of this disclosure, a charge transport layer is disposed between the photoelectric conversion layer and the first electrode, and the charge transport layer is formed on the surface of the photoelectric conversion layer from charge transport particles and an insulating resin. In the photoelectric conversion element of this disclosure, it is preferable that the insulating resin is disposed between the perovskite crystals of the photoelectric conversion layer. The details of each item, such as the charge transport particles and the insulating resin, are as described above.

[0069] In this disclosure, the charge transport layer contains charge transport particles which are P-type semiconductors and an insulating resin, and it is preferable that the volume of the charge transport particles in the charge transport layer is 5 to 30 times the volume of the insulating resin in the charge transport layer. The insulating resin has a volume resistivity of 10 8 It is greater than or equal to Ω·cm.

[0070] The thickness of the charge transport layer is preferably 1 nm to 1000 nm, more preferably 5 nm to 500 nm, even more preferably 10 nm to 200 nm, and particularly preferably 50 nm to 200 nm. The larger the thickness of the charge transport layer, the greater the concealment effect of the voids generated in the photoelectric conversion layer, and an improvement in conversion efficiency can be expected when the photoelectric conversion layer is fabricated by a large-area film deposition method. In addition, a smaller thickness of the charge transport layer can suppress the decrease in current and power generation due to the charge transport layer acting as a resistor.

[0071] [Formation of charge transport layer] As an example of a method for forming a charge transport layer in a photoelectric conversion element according to the present disclosure, a method is given in which a coating solution for the charge transport layer is applied to the surface of the photoelectric conversion layer and then dried. Examples of solvents used in the coating solution 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.

[0072] Methods for applying coatings for the charge transport layer include immersion coating, spin coating, spray coating, inkjet coating, meniscus coating, screen coating, roll coating, gravure coating, die coating, blade coating, curtain coating, bar coating, etc. Among these, from the viewpoint of high mass production capability, one of the following methods is preferred: die coating, blade coating, spray coating, inkjet coating, gravure coating, or screen coating, with die coating being even more preferred. The coating solution may be applied in combination with other coating methods.

[0073] There are no particular limitations on the method for drying the paint for the charge transport layer, but examples include heating, blowing gas, and reducing pressure. Among these, drying by heating is preferred from the viewpoint of simplicity.

[0074] When the photoelectric conversion layer contains perovskite crystals, the charge transport layer is preferably formed by applying a resin solution containing dissolved insulating resin. This allows the insulating resin to preferentially penetrate the gaps between the perovskite crystal grains.

[0075] Furthermore, the following are examples of methods for forming the charge transport layer: a method of applying a resin solution obtained by dissolving an insulating resin after arranging charge transport particles on the surface of the photoelectric conversion layer; a method of applying a resin solution obtained by dissolving an insulating resin on the surface of the photoelectric conversion layer and then arranging charge transport particles; or a method of applying a solution obtained by dispersing charge transport particles in a resin solution obtained by dissolving an insulating resin to the surface of the photoelectric conversion layer.

[0076] [Charge transporting particles] The paint for the charge transport layer preferably contains charge transport particles. The inclusion of charge transport particles allows for the smooth flow of charge generated in the photoelectric conversion layer. The average particle size of the charge transport particles is 1.0 × 10⁻⁶. 1 nm or more 3.0×10 2 It is preferable that the size is less than or equal to nm. Within the above range, if the photoelectric conversion layer contains perovskite crystals, the penetration of charge-transporting particles into the perovskite crystal grains can be suppressed, and the uniformity of the film can be maintained, thereby suppressing the loss of charge transport. The particle size of the charge-transporting particles contained in the charge transport layer can be determined as the volume-average particle size from the particle size distribution obtained by image imaging using a scanning electron microscope (SEM). Furthermore, specific examples of materials for charge-transporting particles include phthalocyanine pigments, azo pigments, lake pigments, quinacridone pigments, dioxazine pigments, perylene pigments, and isoindolinone pigments.

[0077] In this disclosure, it is preferable that the charge-transporting particles are particles containing a cyclic conjugated compound in which multiple pyrrole rings are conjugated together. By forming a cyclic conjugated compound in which multiple pyrrole rings are covalently bonded together as charge-transporting particles, the charge-transporting layer exhibits high charge-transporting ability.

[0078] In this disclosure, the charge-transporting particles are preferably particles containing a phthalocyanine compound, and more preferably particles having the structure shown by the following formula (Pc-2). Among the particles containing a phthalocyanine compound, hydroxygallium phthalocyanine compounds are even more preferred. These charge-transporting particles can transport the charge generated in the photoelectric conversion layer more efficiently. [ka] (In the above formula (Pc-2), M represents H2, a ligand-containing metal atom, or a ligand-free metal atom.)

[0079] The chemical substances, such as charge-transporting particles, described herein can be identified by nuclear magnetic resonance (NMR) spectroscopy. In particular, when M in the above equation (Pc-2) is H2, the above equation (Pc-2) is expressed as the following equation (Pc-1). [ka]

[0080] The particle size of the charge-transporting particles can be changed by dispersing the coating solution for the charge-transporting layer in a paint shaker, and the particle size can be reduced by increasing the dispersion time. Furthermore, the particle size can be reduced even further by subjecting the coating solution for the charge-transporting layer to a centrifuge.

[0081] [Insulating resin] The coating for the charge transport layer preferably contains an insulating resin. Specific examples of insulating resins include polyacetal resin, acrylic resin, polyarylate resin, polycarbonate resin, polyvinyl acetate resin, polyester resin, polyamide resin, polyurethane resin, and polystyrene resin. Among these, polyvinyl acetal resin or polyvinyl butyral resin is preferred. This insulating resin allows for close contact with the charge transport material (charge transport particles), enabling the formation of a more effective charge distribution.

[0082] In this disclosure, the glass transition temperature of the insulating resin is preferably less than 100°C, and more preferably 95°C or lower. Within this range, it is possible to make close contact with the charge transport material (charge transport particles) and form a more effective charge distribution. The glass transition temperature can be determined by differential scanning calorimeter (DSC). In this disclosure, the molecular weight of the insulating resin is preferably 10,000 or more. In this disclosure, it is preferable that the charge transport layer contains an aromatic ring compound having a hydroxyl group, which is different from the charge transport material (charge transport particles) and the insulating resin. By having an aromatic ring compound having a hydroxyl group, the charge transport material (charge transport particles) and the insulating resin can come into contact more easily, and a more effective charge distribution can be formed.

[0083] In this disclosure, the photoelectric conversion element may have a second charge transport layer between the first electrode and the charge transport layer. Having a second charge transport layer may facilitate the transfer of carriers to the electrode.

[0084] [Second charge transport layer] In this disclosure, from the viewpoint of the compatibility of the charge transport layer films, a second charge transport layer that does not contain charge transport particles may be further provided between the charge transport layer and the first electrode. Examples of materials for the second charge transport layer 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, materials having an aromatic ring are preferred from the viewpoint of compatibility at the membrane interface, and Spiro-OMeTAD, PTAA, and phthalocyanine compounds are preferred.

[0085] Furthermore, the second charge transport layer may contain dopants as additives to improve its charge transport capability. Examples of substances that can be used as dopants include lithium compounds such as bis(trifluoromethanesulfonyl)imide lithium, cobalt compounds such as [tris(2-(1H-pyrazole-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.

[0086] [Electron transport layer] In the photoelectric conversion element of this disclosure, an electron transport layer 5 may be placed between the second electrode 4 and the photoelectric conversion layer 6, as shown in Figure 2. The material for the electron transport layer is not particularly limited and includes, for example, 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, etc. Specifically, examples include cyano group-containing polyphenylene vinylene, boron-containing polymers, bathocuproine, bathophenanthroline, hydroxyquinolinatoaluminum, oxadiazole compounds, benzimidazole compounds, naphthalenetetracarboxylic acid compounds, fullerene compounds, perylene derivatives, phosphine oxide compounds, phosphine sulfide compounds, fluoro group-containing phthalocyanines, titanium dioxide, zinc oxide, indium oxide, tin oxide, gallium oxide, tin sulfide, indium sulfide, zinc sulfide, etc. In particular, tin oxide may be obtained by reacting tin(2) chloride, tin(4) chloride, tin(2) chloride dihydrate, or tin(4) chloride pentahydrate.

[0087] The preferred thickness of the electron transport layer 5 is 1 nm at the lower limit and 2000 nm at the upper limit. If the thickness of the electron transport layer 5 is 1 nm or more, holes can be sufficiently blocked, and if it is 2000 nm or less, it will not be a resistance during electron transport, and the photoelectric conversion efficiency will be high. A more preferred lower limit for the thickness is 3 nm, a more preferred upper limit is 1000 nm, an even more preferred lower limit is 5 nm, and an even more preferred upper limit is 500 nm.

[0088] [Laminate] As mentioned above, the photoelectric conversion element of this disclosure may have a laminate in which a high refractive index layer and a medium refractive index layer, etc., are formed as a single or multiple layers between a porous layer and a substrate in order to provide an anti-reflective function. Examples of the high refractive index layer and medium refractive index layer include zirconium oxide, titanium oxide, tantalum oxide, niobium oxide, hafnium oxide, alumina, silica, magnesium fluoride, etc. These materials can be deposited on a substrate by vapor deposition, sputtering, etc. Preferably, the laminate includes a layer containing any material selected from the group consisting of zirconium oxide, titanium oxide, tantalum oxide, niobium oxide, and hafnium oxide, and a layer containing a material selected from the group consisting of alumina, silicon oxide, and magnesium fluoride.

[0089] [Sealing member] The photoelectric conversion element of this disclosure may further include a sealing member for sealing the element. The sealing member can be, for example, in the form of a film. Examples of materials for the sealing member include silazane, silicone rubber, resins having a siloxane skeleton, and glass. Furthermore, from the viewpoint of suppressing adhesion between elements that occurs when winding in a roll-to-roll manner, the surface of the sealing member may be given a hairline finish.

[0090] [Application Examples] Examples of applications of this disclosure include photoelectric converters, mobile devices, and building materials. A photoelectric converter having a photoelectric converter element will be described. A photoelectric conversion device can be constructed by using multiple photoelectric conversion elements of the present disclosure. When multiple photoelectric conversion elements are connected, such a photoelectric conversion device can also be called a photoelectric conversion cell or a photoelectric conversion module. Photoelectric conversion elements may be stacked to increase the output voltage by stacking photoelectric conversion elements with different absorption wavelengths. The photoelectric conversion device also includes the photoelectric conversion elements of the present disclosure and an inverter. The inverter may be a converter that converts DC to AC. The photoelectric conversion device may have a power storage unit connected to the photoelectric conversion elements. The power storage unit is not limited to anything that can store electricity. Examples include secondary batteries using lithium ions, all-solid-state batteries, electric double-layer capacitors, etc. To provide functions such as maintaining or increasing the amount of incident light, a surface that is resistant to water and dirt, or a function to collect or guide light may be added.

[0091] [Measurement method] Examples of each measurement method are described below.

[0092] [Film thickness and refractive index measurement] The average film thickness of porous layers and laminates used as substrates for porous layers can be measured using spectroscopic ellipsometry (JAWoollam EC-400) to determine the thickness and refractive index of the film formed on the substrate. Alternatively, the photoelectric conversion element can be cut and measured by performing cross-sectional observation using a scanning electron microscope (SEM). After cutting the photoelectric conversion element and fixing it to an inclined sample stage, cross-sectional observation can be performed using an SEM (device: Carl Zeiss GmbH, SmartSEM). During observation, other layers can be distinguished by differences in the contrast of the observed image or by compositional analysis using the SEM-EDX function.

[0093] [Measurement of arithmetic mean roughness Ra] The arithmetic mean roughness Ra of the photoelectric conversion layer is the surface roughness on the first electrode side. Measurement methods include measuring the photoelectric conversion layer after removing the first electrode and charge transport layer from the photoelectric conversion element using AFM / SPM, and calculating it from a cross-sectional image of the photoelectric conversion element. In the following examples, the arithmetic mean roughness Ra was calculated by image analysis of height images obtained in AM-FM mode using an atomic force microscope (AFM / SPM) (Oxford Instruments MFP-3D Origin). The measurement conditions were as follows: a cantilever (OMCL-AC-160TS, Olympus Corporation) was used, and a 90 μm × 90 μm area was measured at a scanning frequency of 1 Hz. The number of X data points was 256, and the number of Y data points was also 256.

[0094] [Reflectance] Using a reflectance meter (USPM-RU manufactured by Olympus Corporation), the absolute reflectance from wavelengths of 380 nm to 780 nm can be measured, and the average reflectance from wavelengths of 400 nm to 700 nm can be calculated.

[0095] [Moisture absorption] Using an automatic vapor adsorption measurement device (BELSORP18, manufactured by Nippon Bell Co., Ltd.), the amount of moisture absorbed can be measured when the relative humidity is changed from 60%RH to 98%RH. The amount of moisture absorbed at 90%RH can be evaluated. [Examples]

[0096] The present disclosure will be described in more detail below using examples and comparative examples. The present disclosure is not limited in any way by the following examples unless it exceeds the gist of the disclosure. In the following examples, "parts" refers to a mass basis unless otherwise specified.

[0097] (Example 1) <Preparation of porous solution 1> A portion of the solvent in a chain-like solid particle IPA dispersion (IPA-ST-UP®, manufactured by Nissan Chemical Industries, Ltd., particle size 40-100 nm; dynamic light scattering method, solid content concentration 15% by mass) was replaced from 2-propanol to 1-propoxy-2-propanol (manufactured by Sigma) by evaporation. This yielded a chain-like solid particle 1-propoxy-2-propanol dispersion (solid content concentration 17% by mass). The solvent ratio was 2-propanol:1-propoxy-2-propanol = 7.5:92.5.

[0098] Binder solution 1 was prepared by adding 18.5 g of tetraethoxysilane (TEOS, manufactured by Tokyo Chemical Industry Co., Ltd.) and 16.0 g of 0.1% by mass phosphinic acid (10 equivalents relative to TEOS) as catalyst water, and mixing and stirring in a 20°C water bath for 60 minutes. To 251.3 g of a 1-propoxy-2-propanol dispersion of chain-like solid particles, 32.8 g of binder solution 1, which contains components necessary for binder formation equivalent to 0.5% by mass in terms of oxides, was added. Subsequently, to adjust the solid content concentration of the chain-like solid particles to 4.3% by mass in terms of oxides, 174.5 g of 1-propoxy-2-propanol and 546.5 g of ethyl lactate were added, and the mixture was stirred for 60 minutes to obtain a 1-propoxy-2-propanol:ethyl lactate ratio of 40:60. This was designated as porous solution 1.

[0099] [Formation of a porous layer on a substrate] Porous solution 1 was applied to a glass substrate (S-BSL7, manufactured by Ohara Corporation, nd=1.52) using a die coat with a 30 mm wide die head. After drying at room temperature and finally heating, a porous layer with a width of 30 mm, a length of 100 mm, and a thickness of 300 nm was formed.

[0100] [Formation of ITO on a porous layer substrate] A substrate with a porous layer is placed in a vacuum chamber, and the inside of the chamber is kept under high vacuum (starting vacuum level: 10 -6 (Below Tor). Next, the substrate was set to 300°C, and during that time, the vacuum level inside the chamber was set to 10 -4 The temperature was maintained below Torr. The target material, ITO, was heated and evaporated at 2000°C using electron beam deposition (EBM). During this process, a small amount of oxygen gas was introduced to compensate for oxygen deficiency and improve the crystallinity of the film (gas flow rate: 5 sccm). The ITO deposition rate was controlled to 0.5 angstroms per second, and the film thickness was set to 100 nm. After film deposition, the ITO-coated glass substrate was fabricated by annealing at 400°C for 20 minutes to improve the conductivity and optical properties of the ITO.

[0101] [Formation of the electron transport layer] Two 100mm square ITO-coated glass substrates were cleaned, and a 5-fold diluted tin(II) oxide colloidal solution (15% water dispersion, manufactured by Alfa Aesar) was applied to them by spin coating. The substrates were then heated at 150°C for 30 minutes to form an electron transport layer on a 16nm thick thin film.

[0102] [Formation of the photoelectric conversion layer] A coating solution 1 for the photoelectric conversion layer was prepared by dissolving 8.245 g of lead iodide, 2.843 g of methylammonium iodide, and 0.362 g of methylammonium chloride in 6.10 g of N,N-dimethylformamide and 7.45 g of N-methyl-2-pyrrolidone, and stirring for 1 hour. This coating solution was applied to the electron transport layer, which had been heated to 55°C, using a die coat with a 30 mm wide die head. The mixture was then dried by a gas quenching method and finally heated to form a black photoelectric conversion layer made of MAPbI3, with a width of 30 mm, a length of 100 mm, a thickness of 600 nm, and an arithmetic mean roughness Ra of 125 nm.

[0103] [Formation of the first electrode] Three 25mm square substrates were cut from the ITO-coated glass substrate on which the photoelectric conversion layer was formed. Each of the resulting 25mm square substrates had a thickness of 80nm and an area of ​​0.09cm². 2 Ten gold electrodes were formed by vacuum deposition to obtain a photoelectric conversion element.

[0104] (Example 2) A photoelectric conversion element was obtained in the same manner as in Example 1, except that the thickness of the porous layer on the substrate was changed to 110 nm.

[0105] (Example 3) A photoelectric conversion element was obtained in the same manner as in Example 1, except that the thickness of the porous layer on the substrate was changed to 70 nm.

[0106] (Example 4) A photoelectric conversion element was obtained in the same manner as in Example 1, except that the porous solution 1 was prepared without adding binder solution 1.

[0107] (Example 5) A photoelectric conversion element was obtained in the same manner as in Example 1, except that the amount of binder solution 1 added was changed from 0.5% by mass to 0.8% by mass when preparing the porous solution 1.

[0108] (Example 6) A photoelectric conversion element was obtained in the same manner as in Example 1, except that the porous solution 1 was prepared by changing the chain-like solid particle IPA dispersion to a hollow silica slurry IPA dispersion (JGC Catalysts & Chemicals, Ltd., Thru-Ria 1110, average Ferret diameter 50 nm, solid content concentration 20.5 mass%).

[0109] (Example 7) A photoelectric conversion element was obtained in the same manner as in Example 1, except that the glass substrate was changed to a PET film when forming the porous layer on the substrate.

[0110] (Comparative Example 1) A photoelectric conversion element was obtained without forming a porous layer.

[0111] (Comparative Example 2) A photoelectric conversion element was obtained in the same manner as in Example 1, except that the thickness of the porous layer on the substrate was changed to 60 nm.

[0112] (Comparative Example 3) In preparing porous solution 1, a photoelectric conversion element was obtained in the same manner as in Example 1, except that the IPA dispersion of chain-like solid particles was replaced with a solid silica slurry PGME dispersion (PGM-ST®, manufactured by Nissan Chemical Industries, Ltd., particle size 10-15 nm; dynamic light scattering method, solid content concentration 30% by mass) to prepare the porous solution.

[0113] [evaluation] [Film thickness and refractive index measurement] Film thickness and refractive index were measured using spectroscopic ellipsometry (JAWoollam EC-400) on films formed on a substrate.

[0114] [Porosity] Based on the refractive index measurement results, the ratio of the refractive index of the film-forming material (1.46 in the case of silica) to the refractive index of air was calculated and evaluated.

[0115] [Moisture absorption] The amount of moisture absorbed was measured using an automatic vapor adsorption measuring device (BELSORP18, manufactured by Nippon Bell Co., Ltd.) when the relative humidity was changed from 60%RH to 98%RH. The amount of moisture absorbed by the porous layer substrate at 90%RH was evaluated.

[0116] 〔judgement〕 A: Effective in improving durability (0.90 or higher), B: Somewhat effective in improving durability (0.65 or higher but less than 0.90), C: Some effect on durability (0.40 or higher but less than 0.65), D: Insufficient effect on durability (less than 0.40)

[0117] [Table 2] In Examples 1-3, increasing the thickness of the porous layer increased moisture absorption and improved durability. The results of Example 7 showed that the effect was not limited to glass substrates. On the other hand, the results of Comparative Examples 1-2 indicate that the effect is insufficient when the porous layer is absent or thin. The results of Comparative Example 3 show that when the porosity is low, moisture absorption decreases, resulting in an insufficient effect.

[0118] (Example 8) Tantalum pentoxide (OA-100, Canon Optron Co., Ltd.) and alumina (Al2O3, Canon Optron Co., Ltd.) were deposited on a flat glass substrate (S-BSL7, manufactured by Ohara Corporation, nd=1.52) at a substrate heating temperature of 250°C, with a vacuum of 7 × 10⁻¹⁰ during film formation after oxygen introduction. -3An optical component was fabricated using the same method as in Example 2, except that the film was deposited under the conditions of Pa and a deposition rate of 0.6 nm / second to achieve the film configuration shown in Table 3.

[0119] (Example 9) An optical component was fabricated in the same manner as in Example 2, except that silicon dioxide (SiO2E type, manufactured by Canon Optron Corporation) and a mixed film of tantalum pentoxide and titanium dioxide (OA-600, manufactured by Canon Optron Corporation) were deposited on a PET film to form the film configuration shown in Table 3.

[0120] (Comparative Example 4) The evaluation was performed under the conditions of Comparative Example 1.

[0121] [evaluation] [Reflectance] The absolute reflectance was measured at wavelengths from 380 nm to 780 nm using a reflectance meter (USPM-RU, manufactured by Olympus Corporation), and the average reflectance value for wavelengths from 400 nm to 700 nm was calculated.

[0122] [Moisture absorption] The amount of moisture absorbed was measured using an automatic vapor adsorption measuring device (BELSORP18, manufactured by Nippon Bell Co., Ltd.) when the relative humidity was changed from 60%RH to 98%RH. The amount of moisture absorbed by the porous layer substrate at 90%RH was evaluated.

[0123] [Table 3] In Example 8, by providing a laminate between the substrate and the porous layer, the reflectivity was reduced, and the effect of capturing more light while maintaining moisture absorption was obtained. From the results of Example 9, the effect was obtained without limiting the substrate to glass. In the absence of a laminate between the porous layer, as in Comparative Example 4, there is no effect of suppressing light reflection.

[0124] Embodiments of this disclosure include the following configurations. (Composition 1) The device comprises a first electrode, a photoelectric conversion layer, a second electrode, and a substrate. A porous layer is provided between the substrate and the second electrode. The photoelectric conversion element is characterized in that the porous layer has a refractive index of 1.18 or more and 1.28 or less at a wavelength of 550 nm, and a thickness of 70 nm or more. (Configuration 2) The photoelectric conversion element according to claim 1, characterized in that the thickness of the porous layer is 300 nm or less. (Composition 3) The photoelectric conversion element according to configuration 1 or 2, characterized in that the porous layer contains a plurality of particles and has voids between the particles. (Composition 4) The photoelectric conversion element according to any one of configurations 1 to 3, characterized in that the porous layer contains particles made of a plurality of silicon dioxide. (Composition 5) The photoelectric conversion element according to configuration 3 or 4, characterized in that the contact points between the particles are bonded together with a binder. (Composition 6) The photoelectric conversion element according to configuration 5, characterized in that the binder contains a siloxane bond. (Composition 7) A photoelectric conversion element according to any one of configurations 1 to 6, characterized in that it has a laminate in which a plurality of layers containing materials with different refractive indices are stacked between the substrate and the porous layer. (Composition 8) The photoelectric conversion element according to configuration 6, characterized in that the laminate includes a layer containing a material selected from the group consisting of zirconium oxide, titanium oxide, tantalum oxide, niobium oxide, and hafnium oxide, and a layer containing a material selected from the group consisting of alumina, silicon oxide, and magnesium fluoride. (Composition 9) The photoelectric conversion element according to any one of configurations 1 to 8, characterized in that the substrate includes a base material selected from the group consisting of glass, PET film, and polyimide film. (Composition 10) A photoelectric conversion element according to any one of configurations 1 to 9, characterized in that it has a charge transport layer on the surface of a photoelectric conversion layer. (Composition 11) The photoelectric conversion element according to configuration 9, characterized in that the charge transport layer contains charge transport particles and an insulating resin. (Composition 12) The photoelectric conversion element according to configuration 11, wherein the charge-transporting particle has a cyclic conjugated compound in which a plurality of pyrrole rings are conjugated together. (Composition 13) The photoelectric conversion element according to configuration 12, wherein the cyclic conjugated compound is a phthalocyanine compound. (Composition 14) The photoelectric conversion element according to configuration 12 or 13, wherein the phthalocyanine compound is a hydroxygallium phthalocyanine compound. (Composition 15) A photoelectric conversion element according to any one of the configurations 11 to 14, wherein the glass transition temperature of the insulating resin is less than 100°C. (Composition 16) The photoelectric conversion element according to any one of the configurations 11 to 15, wherein the insulating resin is polyvinyl acetal resin or polyvinyl butyral resin. [Explanation of Symbols]

[0125] 1. Photoelectric conversion element 2 circuit boards 3. Porous layer 4 Second electrode 5 Electron transport layer 6. Photoelectric conversion layer 7 First electrode 8 Charge transport layer 9 Laminate

Claims

1. The device comprises a first electrode, a photoelectric conversion layer, a second electrode, and a substrate. A porous layer is provided between the substrate and the second electrode. The photoelectric conversion element is characterized in that the porous layer has a refractive index of 1.18 or more and 1.28 or less at a wavelength of 550 nm, and a thickness of 70 nm or more.

2. The photoelectric conversion element according to claim 1, characterized in that the thickness of the porous layer is 300 nm or less.

3. The photoelectric conversion element according to claim 1, characterized in that the porous layer contains a plurality of particles and has voids between the particles.

4. The photoelectric conversion element according to claim 1, characterized in that the porous layer contains particles made of a plurality of silicon dioxide particles.

5. The photoelectric conversion element according to claim 3, characterized in that the contact points between the aforementioned particles are bonded together with a binder.

6. The photoelectric conversion element according to claim 5, characterized in that the binder contains a siloxane bond.

7. The photoelectric conversion element according to claim 1, characterized in that it has a laminate in which a plurality of layers containing materials with different refractive indices are stacked between the substrate and the porous layer.

8. The photoelectric conversion element according to claim 7, characterized in that the laminate includes a layer containing any material selected from the group consisting of zirconium oxide, titanium oxide, tantalum oxide, niobium oxide, and hafnium oxide, and a layer containing a material selected from the group consisting of alumina, silicon oxide, and magnesium fluoride.

9. The photoelectric conversion element according to claim 1, characterized in that the substrate includes a base material selected from the group consisting of glass, PET film, and polyimide film.

10. The photoelectric conversion element according to claim 1, characterized in that it has a charge transport layer on the surface of the photoelectric conversion layer.

11. The photoelectric conversion element according to claim 10, characterized in that the charge transport layer contains charge transport particles and an insulating resin.

12. The photoelectric conversion element according to claim 11, wherein the charge transporting particle has a cyclic conjugated compound in which a plurality of pyrrole rings are conjugated together.

13. The photoelectric conversion element according to claim 12, wherein the cyclic conjugated compound is a phthalocyanine compound.

14. The photoelectric conversion element according to claim 13, wherein the phthalocyanine compound is a hydroxygallium phthalocyanine compound.

15. The photoelectric conversion element according to claim 11, wherein the glass transition temperature of the insulating resin is less than 100°C.

16. The photoelectric conversion element according to claim 11, wherein the insulating resin is polyvinyl acetal resin or polyvinyl butyral resin.

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