Photoelectric conversion element

Abstract

The present invention provides a photoelectric conversion element in which the deterioration of an organic compound and electrodes over time due to water vapor is suppressed. Provided is a photoelectric conversion element (1) characterized by comprising a first electrode (7), a photoelectric conversion layer (6), a second electrode (4), and a substrate (2), and by having a porous layer (3) between the substrate (2) and the second electrode (4), wherein the porous layer (3) has a refractive index of 1.18-1.28 at a wavelength of 550 nm, and has a thickness of 70 nm or more.

Description

Photoelectric conversion element

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

[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 by utilizing the photovoltaic effect, which generates electrons and holes.

[0003] Currently, n-p diode type silicon (Si) single-crystal based solar cells with a light energy conversion efficiency 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 electricity. 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 a sheet-shaped substrate, thus enabling cost reduction in production. 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 due to 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 is made of a material of the general formula (1): R - [M(OR １ ) ｙ (O-) ｘ－ｙ ] ｎ A solar cell is described that contains an organometallic oxide having a structure represented by -R.

[0007] Patent Application No. 2020-522127

[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.

[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.

[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.

[0012] This is a schematic cross-sectional view of one embodiment of the photoelectric conversion element of the present disclosure. This is a schematic cross-sectional view of one embodiment of the photoelectric conversion element of the present disclosure. This is a schematic cross-sectional view of one embodiment of the photoelectric conversion element of the present disclosure. This is a schematic cross-sectional view of one embodiment of the photoelectric conversion element of the present disclosure.

[0013] The present disclosure will be described in detail below with reference to preferred embodiments. The present 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 conducting TOF-SIMS / FE-TEM / EDS radiation analysis on a cross-section of the photoelectric element to confirm the elemental distribution of specific elements. Analysis of each layer may also be performed by peeling off the completed photoelectric 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. Each layer will be described below.

[0021] [Substrate] The photoelectric conversion element of this disclosure includes a substrate, which is made of a base material such as transparent glass (e.g., soda-lime glass, alkali-free glass), ceramic, or transparent plastic, or may include these base materials. Examples of transparent plastics include PET film and polyimide film. When light is taken in from the first electrode side, an opaque material can be used for the substrate, 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 FIG. 1, the photoelectric conversion element 1 of the present disclosure includes a substrate 2, a porous layer 3, and a second electrode 4. Further, as shown in FIG. 4, a laminate 9 may be formed between the substrate 2 and the porous layer 3. By forming the laminate 9 between the substrate 2 and the porous layer 3, an antireflection effect can be obtained, and the light capture efficiency can be improved. The laminate is preferably formed by laminating a plurality of layers containing materials having different refractive indices. In particular, the laminate preferably 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.

[0023] The film thickness of the porous layer of the present 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 film thickness is less than 0.07 μm, the water retention amount will be insufficient. Also, if it exceeds 5 μm, it is difficult to fabricate the porous layer. Considering the productivity of fabricating the porous layer, it is preferably not more than 300 nm. As shown in FIG. 4, when forming the laminate 9 between the substrate 2 and the porous layer 3, in addition to the water vapor absorption, the film thickness can be appropriately designed in consideration of the antireflection performance.

[0024] The porous layer contains pores, and the average pore diameter of the pores is preferably 3 nm or more and 50 nm or less in the value obtained by measuring the pore size distribution by the nitrogen gas adsorption method.

[0025] The amount of pores contained in the porous layer can be determined as the pore volume by the nitrogen gas adsorption method. The pore volume is preferably 0.1 cm ３ / g or more and 1.0 cm ３ / g or less. If the pore volume is 0.1 cm ３ / g or more, an amount of water sufficient to provide an antifogging property can be ensured in the porous layer. If the pore volume is 1.0 cm ３ / g or less, sufficient scratch resistance can be obtained without reducing the hardness of the skeleton. A more preferable pore volume is 0.3 cm ３ / g or more and 0.6 cm ３ / g or less.

[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] (Particles) 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 large, so the water coagulation effect cannot be obtained and the moisture absorption amount becomes small, which is undesirable.

[0032] Here, the average particle diameter of chain-like solid particles, which are particles 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 average Ferret diameter of each particle can be measured by particle measurement, and the average value can be calculated. If the chain-like solid particles are dispersed in a solvent solution, the average particle diameters of the short and long axes can be determined by measurement using 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. ２ These may be chain-like solid particles of organic resins such as fluorine or silicon. Preferably, the content of chain-like solid particles in the porous layer of this disclosure is 40% by volume or more and 60% by volume or less.

[0034] The material that makes up the hollow particles is preferably one with a low refractive index, such as SiO ２ MgF ２ Examples include metal oxides such as fluorine and silicon, or organic resins, but SiO is easy to manufacture the particles of. ２ This is preferable.

[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. A material with a low refractive index is preferred for the hollow particles, such as SiO₂. ２ MgF ２ Examples include fluorine, silicon, and organic resins, but SiO is easy to manufacture as a particle. ２This is more preferable. With hollow particles, multiple layers of particles aligned parallel to the substrate surface are stacked, and voids are formed between the particles, making it possible to absorb moisture.

[0037] The average particle diameter of the hollow particles is preferably between 15 nm and 100 nm, more 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 the 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 the silanealkoxy hydrolysis condensate, 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, which 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 or lower. If the silanealkoxy hydrolysis condensate is subjected to temperatures below 5°C, the hydrolysis 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 silanes 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] [Electrodes] The photoelectric conversion element of this disclosure 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. For example, 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 / Al ２ O ３ Examples include mixtures, Al / LiF mixtures, etc. Examples of transparent electrode materials include CuI, ITO (indium tin oxide), and SnO. ２ Examples include conductive transparent materials such as 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, and 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. When the first electrode is on the light incidence side, the second electrode may be a transparent electrode and the substrate may be a reflective layer. The electrodes may also be patterned electrodes.

[0043] [Process for forming the first electrode and the second electrode] The photoelectric conversion element of this disclosure is formed by a process for forming a first electrode and a process for forming a second electrode. In the process for forming the first electrode and the process for 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. If 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 of this disclosure includes a photoelectric conversion layer, and the photoelectric conversion layer is not limited to any layer capable of photoelectric conversion, such as perovskite type, silicon type, CIGS type, etc., and these may be combined and stacked. In particular, the photoelectric conversion element preferably includes a perovskite type photoelectric conversion layer containing a perovskite structure crystal.

[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. The stacked photoelectric conversion elements can be of any type, including a perovskite type using a perovskite crystal as the photoelectric conversion layer, a silicon type, a CIGS type, etc., and are not limited to the type of photoelectric conversion element.

[0047] The perovskite crystal structure is preferably represented by the following general formula [1]: ABX ３ [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. For example, in an organic molecule, A in the above general formula [1] is C ｐ N ｍ H ｎ It is preferable that the formula be represented by (p, m, and n are all positive integers). Specifically, examples include methylammonium and formamidium. The metal atom is not particularly limited, but lithium, cesium, sodium, potassium, and rubidium are preferred. These organic molecules or metal atoms may be used individually, or two or more may be used in combination.

[0048] If the constituent cation A is too large to fit within a three-dimensional perovskite crystal, it forms a two-dimensional perovskite crystal, a 2.5-dimensional perovskite crystal possessing properties of both two and three dimensions, a two-layer crystal of three-dimensional and two-dimensional perovskite structures, or a mixed three-dimensional / two-dimensional perovskite crystal, all of which function as photoelectric conversion layers. A two-layer crystal of three-dimensional and two-dimensional perovskite refers to a crystal in which three-dimensional and two-dimensional perovskite crystals are stacked as independent, separate layers, while a mixed three-dimensional / two-dimensional perovskite refers to a crystal in which regions or domains of both two-dimensional or 2.5-dimensional layered and three-dimensional perovskite crystals are mixed.

[0049] Crystals of two-dimensional perovskite or 2.5-dimensional perovskite structures are preferably represented by the following general formulas [2] to [4]. In the following general formulas, n is a positive integer. R' ２ A 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 for [2], the DJ (Dion-Jacobson) type for [3], and the ACI (Alternating Cautions in the Interlayer) type for [4].

[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, isobutylammonium, 3-(nonafluoro-tert-butyloxy)propylamine, 1,3-propanediammonium, 1,5-pentamethylenediamine, octyldiammonium, 2,2-(ethylenedioxy)bis(ethylammonium), 5-aminovaleric acid, 4-tert-butylammonium, N,N'-dimethylethylene-1,2-diammonium, 2,2,3,3,3-pentafluoropropylammonium, guanidium, propylammonium, propargylamine, alkylammonium, cyclohexylmethylammonium, 4-(aminomethyl)piperidinium, piperidinium, pyrrolidinium, cyclohexylammonium, 4- Luorophenethylammonium, 4-fluorophenethylammonium, trifluoromethylbenzylammonium, pentafluorobenzylammonium, pentafluorophenylethylammonium, 4-methoxyphenethylammonium, imidazolium, pyridinium, 3-thiophenemethylammonium, 2-thiophenethylammonium, 2-thiophenformamidium, 2-thiophenemethylammonium, 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, and examples 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 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 classified as MAPbI ３ ya FAPbCl ３ , FAPbi ３ MAPbI ｘ Br ３－ｘ MAPbI ｘ Cl ３－ｘ , Cs ０．０５ (MA ０．１７ FA ０．８３ ) ０．９５ Pb(I ０．８３ Br ０．１７ ) ３ , {Cs 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 (FAPbI ３ ) ０．９５ (MAPbBr３ ) ０．０５ 、(FAPbI ３ ) ０．８５ (MAPbBr ３ ) ０．１５ 、CsPbI ３ 、CsPbBr ３ 、Cs ｘ (MA) １－ｘ PbI ３ 、Csx(FA) １－ｘ PbI ３ 、MA ｘ (FA) １－ｘ PbI ３ 、MA ０．１７ FA ０．８３ Pb(I ０．８３ Br ０．１７ ) ３ 、Cs ０．１５ FA ０．８５ PbI ２．５５ Br ０．４５ 、Cs ０．０５ FA ０．８８ MA ０．０７ PbI ２．５６ Br ０．４４ 、Cs ０．１５ FA ０．８５ PbI ２．５５ Br ０．４５ 、(PEA) ２ (MA) ２ Pb ３ I １０ 、(PTA) ２ (MA) ４ Pb ５ I １６ 、(PEA) ２ (MA) ４ Pb ５ I １６ 、(ThMA) ２ (MA) ２ Pb ３ I １０ 、(3BBA) ２ (MA) ２ Pb ３ I １０ 、(ThMA) ２ (FA) ４ Pb ５ I １６ 、(pF-PEA) ２ (FA ０．３ MA ０．７ )４ Pb ５ I １６ 、(PDMA)FA ２ Pb ３ I １０ 、(3AMPY)(MA) ３ Pb ４ I １３ 、(PDMA)MA ５ Pb ６ I １９ 、(PDMA)MA ３ Pb ４ I １３ 、(TTDMA)MA ３ Pb ４ I １３ 、(TTDMA)MA ４ Pb ５ I １６ 、(BA ０．９ PEA ０．１ ) ２ MA ４ Pb ５ I １６ 、(BA ０．９ PEA ０．１ ) ２ MA ３ Pb ４ I １３ 、(4FPEA) ２ MA ３ Pb ４ I １３ 、(4FPEA) ２ MA ４ Pb ５ I １６ (BA) ２ MA ２ Pb ３ I １０ 、(BA) ２ MA ３ Pb ４ I １３ 、(TEA) ２ MA ２ Pb ３ I １０ 、(BA) ２ MA ４ Pb ５ I １６ 、(BA) ２ MA ３ Pb ４ I １３ 、CsSnBr ３ 、CsSnI３ FA ０．７５ MA ０．２５ Sn ０．９５ Ge ０．０５ I ３ , FAMASnGeI ３ FASnBr ３ FASnI ３ MA ２ Sn ３ I ８ ,MASnBr ３ ,MASnGeI ３ , MASnI ３ This is preferable. 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 too much, and the combinations of x1 to x5 may be changed depending on the purpose. Examples of combinations of x1 to x5 are shown in Table 1. Particularly preferred ranges are 0.03 ≤ x1 ≤ 0.10, 0.80 ≤ x2 ≤ 0.96, 0.95 ≤ x3 ≤ 1.05, 0.80 ≤ x4 ≤ 0.96, and 2.95 ≤ x5 ≤ 3.05. MACL may also be included as the material for forming the perovskite crystal.

[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-phenylenedimethaneammonium, "TTDMA" represents thieno[3,2-b]thiophene-2,5-diyldimethaneammonium, "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 arranged at the body center, organic molecules A are arranged at each vertex, and halogen atoms X are arranged at the face centers. Although the details are not clear, it is presumed that having such a structure allows the orientation of the octahedra in 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 compound used in this disclosure is preferably a crystalline semiconductor. A crystalline semiconductor is a semiconductor in which the X-ray scattering intensity distribution can be measured and a scattering peak can be detected. The crystalline nature of the organic-inorganic perovskite compound increases the electron mobility within the compound, thereby improving the photoelectric conversion efficiency of the photoelectric conversion element.

[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 10 nm to 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 20 nm to 180 nm, and even more preferably 40 nm to 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. Examples of 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. These are selected appropriately according to the characteristics of the photoelectric conversion layer to be manufactured, such as thickness control and orientation control. The above-described process is merely an example, and improved versions of these general-purpose coating methods are also acceptable. Furthermore, each process may be used individually or in combination with other coating methods. Among these, from the viewpoint of high mass productivity, it is preferable to have at least 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 width called a slot die, and forming 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 dropped onto the substrate between the substrate and a 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 width, and transferring the paint directly onto the substrate without forming a liquid reservoir. Bar coating is a method of forming a uniform coating film by passing paint dropped onto the substrate between bars with grooves formed after application. One method of creating a film is to dry the applied, undried film (wet film). If 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 drying the general wet film, but also creating nuclei for perovskite crystals and growing them.If drying is slow, the wet film is likely to move during drying, leading to unevenness in the film, and if there are too few perovskite crystal nuclei, spaces are likely to form between the perovskite crystals. Therefore, a fast drying rate is preferable. On the other hand, if drying is too fast, too many perovskite crystal nuclei are generated, resulting in smaller individual perovskite crystals. Smaller perovskite crystals mean more interfaces, which can lead to increased interfacial resistance, decreased photoelectric conversion efficiency, and reduced durability due to the movement of raw material ions across the interfaces. Therefore, it is preferable that the drying rate in 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, etc.

[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. ２The 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 with 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 charge transport particles and 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 times or more and 30 times or less 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 the photoelectric conversion element of this 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] It is preferable that the paint for the charge transport layer contains charge-transporting particles. By including charge-transporting particles, it becomes possible to smoothly transport the charge generated in the photoelectric conversion layer. The average particle size of the charge-transporting 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 scanning electron microscopy (SEM) image imaging. 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 a structure represented 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. (In the above formula (Pc-2), M is H ２ (This represents a metal atom with a ligand, or a metal atom without a ligand.)

[0079] The chemical substances such as charge-transporting particles described herein can be identified by nuclear magnetic resonance (NMR) spectroscopy. In particular, M in the above formula (Pc-2) is H ２ When this is the case, the above equation (Pc-2) is given by the following equation (Pc-1).

[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 closer contact, 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 compatibility of the charge transport layer film, 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, it is preferable that the material has an aromatic ring from the viewpoint of compatibility of the film 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 the present 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 of 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 phthalocyanine, titanium dioxide, zinc oxide, indium oxide, tin oxide, gallium oxide, tin sulfide, indium sulfide, zinc sulfide, etc. In particular, tin oxide may be reacted with 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 may be, for example, a film. Examples of materials for the sealing member include silazane, silicone rubber, resin 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 conversion element will be described. A photoelectric converter can be configured by using multiple photoelectric conversion elements of this disclosure. When multiple photoelectric conversion elements are connected, such a photoelectric converter 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 converter also has a photoelectric conversion element of this disclosure and an inverter. The inverter may be a converter that converts DC to AC. The photoelectric converter may have a power storage unit connected to the photoelectric conversion element. The power storage unit is not limited as long as it 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 Methods] 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 (J.A. Wollam EC-400) to measure the film formed on the substrate. Alternatively, the film thickness can be measured by cutting a photoelectric conversion element and performing cross-sectional observation using a SEM. After cutting the photoelectric conversion element and fixing it on 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 and 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 example, the arithmetic mean roughness Ra was calculated by image analysis of an image obtained using an atomic force microscope AFM / SPM (Oxford Instruments MFP-3D Origin) in AM-FM mode. The measurement conditions were as follows: a cantilever: OMCL-AC-160TS (Olympus Corporation) was used, and a range of 90 μm × 90 μm 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 256.

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

[0095] [Moisture Absorption] Using an automatic vapor adsorption measuring 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.

[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 an IPA dispersion of chain-like solid particles (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 1-propoxy-2-propanol dispersion of chain-like solid particles (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 mass% phosphinic acid (10 equivalents relative to TEOS) as catalyst water, and mixing and stirring in a 20°C water bath for 60 minutes. 32.8 g of binder solution 1, containing components necessary for binder formation equivalent to 0.5 mass% in oxide terms, was added to 251.3 g of a 1-propoxy-2-propanol dispersion of chain-like solid particles. Subsequently, 174.5 g of 1-propoxy-2-propanol and 546.5 g of ethyl lactate were added to adjust the solid content concentration of the chain-like solid particles to 4.3 mass% in oxide terms, and the mixture was stirred for 60 minutes to obtain a 1-propoxy-2-propanol:ethyl lactate ratio of 40:60. This was prepared 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, the solution was heated to form a porous layer with a width of 30 mm, a length of 100 mm, and a thickness of 300 nm.

[0100] [Formation of ITO on a porous layer substrate] The substrate with the porous layer attached 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 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 electron transport layer] Two square ITO-coated glass substrates, each 100 mm on a side, were cleaned. A 5-fold diluted tin(II) oxide colloidal solution (15% water dispersion, manufactured by Alfa Aesar) was then applied to them by spin coating. Finally, the substrates were heated at 150°C for 30 minutes to form an electron transport layer on a thin film with a thickness of 16 nm.

[0102] [Formation of Photoelectric Conversion Layer] 8.245 g of lead iodide, 2.843 g of methylammonium iodide, and 0.362 g of methylammonium chloride were dissolved in 6.10 g of N,N-dimethylformamide and 7.45 g of N-methyl-2-pyrrolidone, and the mixture was stirred for 1 hour to prepare coating solution 1 for the photoelectric conversion layer. 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 MAPbI ３ A black photoelectric conversion layer was formed, having 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 25 mm square substrates were cut from the ITO-coated glass substrate on which the photoelectric conversion layer was formed. For each of the obtained 25 mm square substrates, a thickness of 80 nm and an area of ​​0.09 cm² was formed. 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 the 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 in the preparation of porous solution 1, the IPA dispersion of chain-like solid particles was changed to a hollow silica slurry IPA dispersion (Thru-Ria 1110 manufactured by JGC Catalysts & Chemicals Co., Ltd., average Ferret diameter 50 nm, solid content concentration 20.5 mass%) to prepare the porous solution.

[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 a 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) A photoelectric conversion element was obtained in the same manner as in Example 1, except that in the preparation of porous solution 1, the IPA dispersion of chain-like solid particles was changed to 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 (J.A. Wollam EC-400) on films formed on a substrate.

[0114] [Porosity] The porosity was evaluated by calculating the ratio of the refractive index of the film-forming material (1.46 in the case of silica) to the refractive index of air based on the refractive index measurement results.

[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] [Judgment] A: Effective in improving durability (0.90 or higher), B: Somewhat effective in improving durability (0.65 or higher and less than 0.90), C: Some effect on durability (0.40 or higher and less than 0.65), D: Insufficient effect on durability (less than 0.40)

[0117] In Examples 1 to 3, increasing the thickness of the porous layer increased the amount of moisture absorbed, resulting in improved durability. The results of Example 7 showed that the effect could be obtained without limiting the substrate to glass. On the other hand, the results of Comparative Examples 1 and 2 show that the effect is insufficient when the thickness of the porous layer is absent or thin. The results of Comparative Example 3 show that when the porosity is low, the amount of moisture absorbed decreases, resulting in an insufficient effect.

[0118] (Example 8) Tantalum pentoxide (OA-100, Canon Optron Inc.) and alumina (Al, Canon Optron Inc.) were placed on a flat glass substrate (S-BSL7, manufactured by Ohara Corporation, nd=1.52). ２ O ３ ) Substrate heating temperature: 250°C, Vacuum level during film formation after oxygen introduction: 7 × 10 －３ An 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 prepared in the same manner as in Example 2, except that silicon dioxide (SiO2E type, manufactured by Canon Optron Inc.) and a mixed film of tantalum pentoxide and titanium dioxide (OA-600, manufactured by Canon Optron Inc.) 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 at wavelengths of 380 nm to 780 nm was measured using a reflectance measuring instrument (USPM-RU, manufactured by Olympus Corporation), and the average reflectance at wavelengths of 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] 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 the 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] This disclosure is not limited to the embodiments described above, and various modifications and alterations are possible without departing from the spirit and scope of this disclosure. Accordingly, the following claims are attached to make the scope of this disclosure public.

[0125] This application claims priority based on Japanese Patent Application No. 2024-187558, filed on October 24, 2024, and all of its contents are incorporated herein by reference.

[0126] 1. Photoelectric conversion element 2. Substrate 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. 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.

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 or 2, characterized in that the porous layer contains a plurality of particles and has voids between the particles.

4. The photoelectric conversion element according to any one of claims 1 to 3, characterized in that the porous layer contains particles made of a plurality of silicon dioxide.

5. The photoelectric conversion element according to claim 3 or 4, characterized in that the contact points between the 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 any one of claims 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.

8. The photoelectric conversion element according to claim 7, characterized in that the laminate comprises 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 any one of claims 1 to 8, characterized in that the substrate includes a base material selected from the group consisting of glass, PET film, and polyimide film.

10. A photoelectric conversion element according to any one of claims 1 to 9, 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 12 or 13, wherein the phthalocyanine compound is a hydroxygallium phthalocyanine compound.

15. The photoelectric conversion element according to any one of claims 11 to 14, wherein the glass transition temperature of the insulating resin is less than 100°C.

16. The photoelectric conversion element according to any one of claims 11 to 15, wherein the insulating resin is polyvinyl acetal resin or polyvinyl butyral resin.

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