Photoelectric conversion element, photoelectric conversion device, and method for manufacturing a photoelectric conversion element

Abstract

To provide a photoelectric conversion element that is mass-producible, suppresses shunt lique caused by defects such as irregularities and gaps in the perovskite crystal, suppresses the increase in series resistance, and has high photoelectric conversion efficiency. [Solution] A photoelectric conversion element comprising a first electrode, a second electrode, a photoelectric conversion layer containing a perovskite structure crystal disposed between the first electrode and the second electrode, and an insulating resin layer on the surface of the perovskite structure crystal and in the gaps between the perovskite structure crystal, wherein the insulating resin layer is formed on the parts of the perovskite structure surface with large irregularities, and the insulating resin layer contains polyvinyl butyral or polymethyl methacrylate as the insulating resin, and if the insulating resin layer contains polymethyl methacrylate, the thickness of the insulating resin layer is 5 nm or more and 10 nm or less.

Description

[Technical Field]

[0001] The present invention relates to a photoelectric conversion element, a photoelectric conversion device, and a method for manufacturing 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 is 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 photovoltaic power generation. However, these have the problem of high cost per unit of power due to the need for high-temperature processing and the high price of the material itself. Furthermore, there are supply issues from the perspective of silicon resources.

[0004] On the other hand, solar cells using organic materials (hereinafter referred to as "organic solar cells") do not require high-temperature processing and can be produced using a so-called roll-to-roll method on sheet substrates, which is expected to reduce costs. In particular, perovskite solar cells, which have a perovskite structure crystal (hereinafter also called "perovskite crystal") as the photoelectric conversion layer, have excellent photoelectric conversion characteristics and are therefore being developed towards the practical application of solar cells.

[0005] Various methods have been proposed for forming these perovskite crystal films. While spin coating is frequently used in research-level studies, in studies aimed at mass production, die coating and blade coating, which are more suitable for mass production, are often used due to considerations such as connectivity with preceding and succeeding processes, the size of the area that can be coated at once, and applicability to roll-to-roll methods.

[0006] On the other hand, perovskite crystals are difficult to manufacture, resulting in various defects, both large and small, including molecular-level defects and defects in the coating. These defects lead to a decrease in the carrier transport capacity between the upper and lower layers, i.e., a decrease in photoelectric conversion efficiency and accelerated degradation of perovskite solar cells in terms of durability. Therefore, research into suppressing and repairing defects is being actively conducted.

[0007] Patent Document 1 describes detecting through-hole defects in a semiconductor layer using a transmitted light image irradiated from the transparent member side of the substrate, and preventing electrical short circuits by ejecting insulating material into the through-hole defects using an inkjet printer. Non-Patent Document 1 describes increasing conversion efficiency by suppressing shunt liquefaction by including polymethyl methacrylate (PMMA) as a leak prevention layer on top of the perovskite. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2010-267940 [Non-patent literature]

[0009] [Non-Patent Document 1] F. Wang,et al,J.Phys.Chem.C,2017,121,1562 [Overview of the Initiative] [Problems that the invention aims to solve]

[0010] According to the inventors' studies, the photoelectric conversion elements described in Patent Document 1 and Non-Patent Document 1 presented challenges in achieving further improvements in conversion efficiency while maintaining the suppression of shunt lique.

[0011] Therefore, an object of the present invention is to provide a photoelectric conversion element that is mass-producible, achieves both suppression of shunt lique caused by defects such as irregularities and gaps in the perovskite crystal and suppression of an increase in series resistance, and has high photoelectric conversion efficiency. Another object of the present invention is to provide a method for manufacturing a photoelectric conversion element that is mass-producible, achieves both suppression of shunt lique caused by defects such as irregularities and gaps in the perovskite crystal and suppression of an increase in series resistance, and has high photoelectric conversion efficiency. [Means for solving the problem]

[0012] The above objective is achieved by the present invention as follows. That is, the present invention is First electrode and The second electrode and A photoelectric conversion layer comprising a perovskite crystal is disposed between the first electrode and the second electrode, An insulating resin layer is provided on the surface of the perovskite crystal and in the gaps between the perovskite crystals. It has, The insulating resin layer is formed on the parts of the perovskite structure where the surface irregularities are large. The insulating resin layer contains polyvinyl butyral or polymethyl methacrylate as the insulating resin. The photoelectric conversion element is characterized in that, when the insulating resin layer contains polymethyl methacrylate, the thickness of the insulating resin layer is 5 nm or more and 10 nm or less. Furthermore, the present invention is a photoelectric conversion device having the above-mentioned photoelectric conversion element. Furthermore, the present invention is A process of forming the first electrode and the second electrode, The process involves forming a photoelectric conversion layer containing a perovskite crystal between the first electrode and the second electrode, The process involves forming an insulating resin layer on the surface of the perovskite crystal and in the gaps between the perovskite crystals. Includes, The insulating resin layer is formed on the parts of the perovskite structure where the surface irregularities are large. The insulating resin layer contains polyvinyl butyral or polymethyl methacrylate as the insulating resin. A method for manufacturing a photoelectric conversion element, characterized in that, when the insulating resin layer contains polymethyl methacrylate, the thickness of the insulating resin layer is 5 nm or more and 10 nm or less. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a photoelectric conversion element with improved leakage resistance and conversion efficiency. [Brief explanation of the drawing]

[0014] [Figure 1] This is a schematic cross-sectional view of one embodiment of the photoelectric conversion element of the present invention. [Figure 2] This is a schematic cross-sectional view of one embodiment of the photoelectric conversion element of the present invention. [Figure 3] This is an SEM image of the photoelectric conversion layer of one embodiment of the photoelectric conversion element of the present invention. [Figure 4] This is a normalized integrated power spectrum obtained by frequency analysis of a SEM image of the photoelectric conversion layer of one embodiment of the photoelectric conversion element of the present invention. [Figure 5] This is a normalized integrated power spectrum obtained by frequency analysis of an optical microscope image of the photoelectric conversion layer of one embodiment of the photoelectric conversion element of the present invention. [Modes for carrying out the invention]

[0015] The present invention will be described in detail below with reference to preferred embodiments. The photoelectric conversion element of the present invention comprises a first electrode, a second electrode, and a photoelectric conversion layer containing a perovskite crystal disposed between the first electrode and the second electrode, wherein an insulating resin layer is disposed on the surface and in the gaps between the perovskite crystals, and the insulating resin layer is formed in the areas where the surface irregularities of the perovskite structure are large.

[0016] As a result of their investigation, the inventors found that having the above-mentioned photoelectric conversion layer results in a photoelectric conversion element with excellent leakage resistance and conversion efficiency. Although the details of why a highly stable photoelectric conversion element can be obtained in the present invention are not yet clear, it is thought to be as follows.

[0017] Various methods have been proposed for forming perovskite crystal films. To create photoelectric conversion elements with excellent leakage resistance and conversion efficiency, it is necessary to form high-quality perovskite crystals free from molecular-level defects and coating defects. The wet coating method is a suitable film deposition method that is easily applicable to roll-to-roll systems.

[0018] For high-quality perovskite crystals to form using the wet-coat method, a fast drying rate of the coating film is crucial. If the drying rate is slow, the solute concentration in the coating film will be lower compared to a faster drying rate, reducing the frequency of new crystal nucleation and leading to a dominant crystal growth state and larger grain size.

[0019] Perovskite crystal layers formed under such conditions have large surface irregularities, and in severe cases, gaps between grain boundaries occur. In the spin-coating method, which is being actively studied at the research level, a poor solvent method is used as the drying method for the coating film. Although the substrate size is small, a high drying rate can be achieved across the entire surface within that small area, resulting in a high-quality perovskite crystal layer with small surface irregularities and few gaps between grain boundaries (pinhole defects).

[0020] However, for film formation methods suitable for mass production, such as die coating and blade coating, drying methods include spraying dry gas (such as dry air or dry nitrogen) onto the coating with an air knife, volatilizing the solvent by reducing pressure, heating the substrate, and combinations of these methods.

[0021] This drying method makes it difficult to dry a large area uniformly and quickly without uneven drying rates. As a result, uneven drying rates lead to perovskite crystal inconsistencies, resulting in a mixture of high-quality perovskite crystals with small surface irregularities and few grain boundary gaps (pinhole defects), similar to spin-coated films, and low-quality crystals with large surface irregularities and grain boundary gaps.

[0022] Because the unevenness in drying rate is continuous, the quality of the crystal also changes continuously, rather than being a discontinuous anomaly such as defects caused by dust. In areas with large surface irregularities and many defects, shunt liquefaction increases, leading to a decrease in conversion efficiency. In such areas, the decrease in conversion efficiency can be suppressed by laminating an insulating layer to inhibit shunt liquefaction.

[0023] On the other hand, in regions where a high-quality perovskite layer is formed, there are no shunt liques. If an insulating layer is formed in such areas, the conversion efficiency will decrease due to an increase in series resistance. In other words, it is possible to improve the conversion efficiency by changing the thickness of the insulating layer in accordance with the continuously changing quality of the perovskite crystal.

[0024] Furthermore, to suppress shunt liquefaction, the conversion efficiency can be further improved by using an insulating layer containing charge-transporting particles and an insulating resin. When a layer of charge-transporting particles and an insulating resin is formed on a poor-quality perovskite crystal, the charge-transporting particles and the insulating resin exist independently. As a result, the insulating resin preferentially penetrates the sides of the irregularities and gaps in the perovskite crystal, thereby suppressing the recombination of electrons and holes that occurs there.

[0025] At the same time, the presence of charge-transporting material as particles on the perovskite crystal is thought to maintain charge transport efficiency from the perovskite crystal to the first electrode without the insulating resin hindering charge transport. As described above, the effects of the present invention can be achieved by forming the insulating resin in the areas of the perovskite structure where the surface irregularities are large.

[0026] The present invention will be described in detail below with reference to preferred embodiments. The present invention is not limited to the following embodiments, and the scope of the present invention also includes modifications, improvements, etc., to the following embodiments based on the ordinary knowledge of those skilled in the art, without departing from the spirit of the invention.

[0027] 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, interwoven structures 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 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.

[0028] <First Embodiment> The first embodiment relates to a photoelectric conversion element. The photoelectric conversion element of the present invention is First electrode and The second electrode and A photoelectric conversion layer comprising a perovskite crystal is disposed between the first electrode and the second electrode, An insulating resin layer is provided on the surface of the perovskite crystal and in the gaps between the perovskite crystals. It has, The insulating resin layer is formed on the parts of the perovskite structure where the surface irregularities are large. The insulating resin layer contains polyvinyl butyral or polymethyl methacrylate as the insulating resin. The insulating resin layer is characterized in that, if it contains polymethyl methacrylate, the thickness of the insulating resin layer is 5 nm or more and 10 nm or less. The following explains each item.

[0029] Figure 1 is a schematic cross-sectional view showing the configuration of one embodiment of the photoelectric conversion element of the present invention. The photoelectric conversion element 10 has a second electrode 2, an electron transport layer 3, a photoelectric conversion layer 4 containing a perovskite structure crystal, an insulating resin layer 5 laminated on the areas of the photoelectric conversion layer 4 with large surface irregularities, a charge transport layer 6, and a first electrode 7 on a substrate 1. The first electrode 7 and the second electrode 2 are an anode and a cathode, respectively, and current can be extracted by connecting the first electrode 7 and the second electrode 2 with an external circuit.

[0030] The photoelectric conversion layer 4 is excited by light incident through the substrate 1, the second electrode 2, and the electron transport layer 3, or the first electrode 7, generating electrons or holes. That is, the photoelectric conversion layer 4 generates an electric current between the first electrode 7 and the second electrode 2. The electron transport layer 3 is a layer placed between the photoelectric conversion layer 4 and the two electrodes (second electrode 2, first electrode 7), and may not be formed in some cases. Multiple electron transport layers 3 and photoelectric conversion layers 4 may be stacked. Such a configuration can also be called a tandem structure. Each component will be described below. Also, as shown in Figure 2, the insulating resin layer 5 may be a layer containing charge-transporting particles 8.

[0031] [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. Volume resistivity is 10 8 It is necessary that the density is Ω·cm or greater. In the present invention, it is preferable that the glass transition temperature of the insulating resin is less than 100°C.

[0032] Suitable solvents for insulating resins include alcohol-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents. Alcohol-based solvents and aromatic hydrocarbon-based solvents are considered particularly preferred.

[0033] In this embodiment, 2-propanol is used as the solvent for the insulating resin. Specifically, polyvinyl butyral is dissolved in 2-propanol by stirring for 24 hours to prepare the resin solution.

[0034] [Insulating resin containing charge-transporting particles] In the formation of an insulating resin containing charge-transporting particles, the charge-transporting particles and the insulating resin exist independently, and the insulating resin preferentially penetrates the sides of the irregularities and gaps in the perovskite crystal. This suppresses the recombination of electrons and holes.

[0035] [Charge transporting particles] In the present invention, it is preferable that the coating solution for the insulating resin layer contains charge-transporting particles. The inclusion of charge-transporting particles allows for the smooth flow of 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 value be less than or equal to nm.

[0036] Within the above range, 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 insulating resin layer can be determined as the volume-average particle size from the particle size distribution obtained by scanning electron microscopy (SEM) image imaging.

[0037] Specific examples of charge-transporting particles include phthalocyanine pigments, azo pigments, lake pigments, quinacridone pigments, dioxazine pigments, perylene pigments, and isoindolinone pigments.

[0038] In the present invention, it is preferable that the charge-transporting particles are particles containing a cyclic conjugated compound in which a plurality of pyrrole rings are conjugated together. By forming the cyclic conjugated compound, in which a plurality of pyrrole rings are covalently bonded, into charge-transporting particles, high charge transport ability is achieved.

[0039] In the present invention, the charge-transporting particles preferably contain a phthalocyanine compound, more preferably have a structure represented by the following formula (Pc-2), and even more preferably contain a hydroxygallium phthalocyanine compound. 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.) The structure of the charge-transporting particles and other chemical substances of the present invention can be confirmed by nuclear magnetic resonance (NMR) spectroscopy.

[0040] 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]

[0041] [Photoelectric conversion element] The photoelectric conversion element of the present invention is characterized by comprising a photoelectric conversion layer containing a perovskite structure crystal, and an insulating resin layer formed according to the crystal state of the perovskite structure, or an insulating resin layer having charge transport particles and an insulating resin. The photoelectric conversion element may also have a first electrode, a second electrode, a photoelectric conversion layer containing a perovskite structure crystal disposed between the first electrode and the second electrode, and a charge transport layer between the photoelectric conversion layer and the first electrode.

[0042] Furthermore, to improve photoelectric conversion efficiency, a tandem type with stacked photoelectric conversion elements may be used. The type of photoelectric conversion element to be stacked is not limited to perovskite solar cells that use perovskite crystals as the photoelectric conversion layer, but also includes silicon solar cells, CIGS solar cells, and other types of photoelectric conversion elements.

[0043] Methods for forming the photoelectric conversion layer and charge transport layer of the photoelectric conversion element of the present invention include coating methods and vapor deposition methods. Examples of coating methods include immersion coating, spin coating, spray coating, inkjet coating, meniscus coating, screen coating, roll coating, die coating, blade coating, curtain coating, and wire bar coating. These film formation methods can be selected according to the requirements of each layer.

[0044] The following explains each layer. [Base material] The photoelectric conversion element 10 of the present invention comprises a substrate 1, which can be made of, for example, a transparent glass substrate such as soda-lime glass or alkali-free glass, a ceramic substrate, or a transparent plastic substrate. Examples of transparent plastic substrates include PET film and polyimide film. When light is taken in from the first electrode 7 side, the substrate 1 can be made of an opaque material, and when light is taken in from the second electrode 2 side, the substrate 1 is made of a transparent material.

[0045] 〔electrode〕 The photoelectric conversion element of the present invention has a first electrode and a second electrode. The materials of the first electrode 7 and the second electrode 2 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, and Al / LiF mixtures.

[0046] 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 types.

[0047] The first electrode 7 and the second electrode 2 may have at least one electrode on the light incidence side that is transparent, while the other electrode may be transparent or also serve as a reflective layer made of a light-reflective material, or it may be a transparent electrode with a reflective layer on the side opposite to the light incidence side. When the first electrode 7 is on the light incidence side, the second electrode 2 may be a transparent electrode and the substrate 1 may be a reflective layer. The electrodes may also be patterned electrodes.

[0048] [Charge transport layer] The thickness of the charge transport layer is preferably 1 nm to 1000 nm, and more preferably 5 nm to 500 nm. The material of the charge transport layer is not particularly limited, and examples 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 at the membrane interface, and Spiro-OMeTAD, PTAA, and phthalocyanine compounds are preferred.

[0049] Furthermore, the 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.

[0050] [Photoelectric conversion layer] The photoelectric conversion element of the present invention has a photoelectric conversion layer containing a perovskite structure crystal, which is disposed between a first electrode and a second electrode. The photoelectric conversion layer 4 has a perovskite structure crystal. The perovskite structure crystal used in the present invention is preferably represented by the following general formula [1]. ABX3[1] In the above general formula [1], A is a monovalent cation of an organic molecule or metal atom, B is a divalent metal cation, and X is a monovalent halide anion.

[0051] As A in the above general formula [1], for example, in organic molecules, C p N m H n It is preferable that the formula be expressed as (where p, m, and n are all positive integers). Specifically, examples include methylammonium and formamidium.

[0052] Furthermore, while the metal atoms are not particularly limited, 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.

[0053] When the cation of A that constitutes is too large to fit within the crystal of the three-dimensional perovskite structure, crystals of a two-dimensional perovskite structure, crystals of a 2.5-dimensional perovskite structure having both two-dimensional and three-dimensional properties, two-layer crystals of three-dimensional and two-dimensional perovskite structures, or crystals of a mixed three-dimensional·two-dimensional perovskite structure are formed, and all of them function as a photoelectric conversion layer.

[0054] The two-layer crystal of three-dimensional and two-dimensional perovskite refers to a crystal in which crystals of three-dimensional and two-dimensional perovskite structures are stacked as independent and separate layers, and the mixed three-dimensional·two-dimensional perovskite indicates a crystal having a structure in which both regions or domains of two-dimensional or 2.5-dimensional layered and three-dimensional perovskite structures are mixed.

[0055] 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]

[0056] Each of the above general formulas forms a perovskite structure of the [2] RP (Ruddlesden-Popper) type, [3] DJ (Dion-Jacobson) type, and [4] ACI (Alternating cations in the interlayer) type.

[0057] 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, cyclohex Silammonium, 4-fluorophenethylammonium, 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.

[0058] 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.

[0059] 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.

[0060] 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 (PEA)2(MA)2Pb3I 10 (PTA)2(MA)4Pb5I 16 (PEA)2(MA)4Pb5I 16 (ThMA)2(MA)2Pb3I 10 (3BBA)2(MA)2Pb3I 10 (ThMA)2(FA)4Pb5I 16 (4FPEA)2(FA 0.3 MA 0.7 )4Pb5I 16 (PDMA)FA2Pb3I 10 (3AMPY)(MA)3Pb4I 13 (PDMA)MA5Pb6I 19 (PDMA)MA3Pb4I 13 (TTDMA)MA3Pb4I 13 (TTDMA)MA4Pb5I 16 (BA) 0.9 PEA 0.1 2MA4Pb5I 16 (BA) 0.9 PEA 0.1 2MA3Pb4I 13 (4FPEA)2MA3Pb4I 13 (4FPEA)2MA4Pb5I 16 (BA)2MA2Pb3I 10, (BA)2MA3Pb4I 13 , (TEA)2MA2Pb3I 10 , (BA)2MA4Pb5I 16 , (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 less or excessive, and the combination of x1 to x5 may be changed according to the purpose. The combination of x1 to x5 is, for example, as shown in Table 1. A 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.

[0061]

Table 1

[0062] 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-diyl dimethaneammonium, "4FPEA" represents 4-fluorophenethylammonium, "BA" represents butylammonium, and "TEA" represents 2-thiophenethylammonium.

[0063] 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.

[0064] The organic-inorganic perovskite compound used in this invention 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. Furthermore, the photoelectric conversion layer according to the present invention may also contain materials other than the organic-inorganic perovskite crystal, as long as it does not impair photoelectric conversion efficiency or charge transport properties.

[0065] The thickness of the photoelectric conversion layer according to the present invention is preferably 5 nm or more and 2000 nm or less. If the thickness is 5 nm or more, light can be 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.

[0066] In the present invention, 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.

[0067] In the present invention, the size of the perovskite crystal in the photoelectric conversion layer is preferably 1 μm or more. Here, the crystal size means the major axis of the largest perovskite crystal observed. When the perovskite crystal is large, the uneven shape on the perovskite surface is likely to occur, and the arithmetic mean roughness increases. The arithmetic mean roughness Ra is preferably 10 nm or more and 200 nm or less. When the arithmetic mean roughness Ra is 10 nm or more, the recombination suppression effect of the insulating resin is more likely to be exhibited.

[0068] Further, when the arithmetic mean roughness Ra becomes larger than 200 nm, the charge transporting particles are likely to penetrate to the second electrode side of the photoelectric conversion layer, and the recombination suppression effect may decrease. Ra is more preferably 20 nm or more and 180 nm or less, and even more preferably 40 nm or more and 150 nm or less. In the production method of the mass-producible photoelectric conversion layer, the perovskite crystal is likely to become large and the arithmetic mean roughness is likely to become large for the reasons described above.

[0069] 〔Insulating resin layer〕 The photoelectric conversion device of the present invention has an insulating resin layer on the surface of the crystal of the perovskite structure and in the gaps between the crystals of the perovskite structure. And depending on the state of the perovskite crystal, an insulating resin layer is disposed on the surface of the photoelectric conversion layer, and the insulating resin layer is formed in a portion where the unevenness on the surface of the perovskite structure is large. The insulating resin layer may also be formed of charge transporting particles and an insulating resin. In the photoelectric conversion device of the present invention, it is preferable that the insulating resin is disposed between the crystals of the perovskite structure in the photoelectric conversion layer. Each item such as charge transporting particles and insulating resin is as described above.

[0070] In the present invention, the insulating resin layer contains charge transporting particles that are P-type semiconductors and an insulating resin, and the volume of the charge transporting particles in the insulating resin layer is preferably 5 times or more and 30 times or less with respect to the volume of the insulating resin in the insulating resin layer. The insulating resin has a volume resistivity of 10 8 Ω·cm or more.

[0071] The thickness of the insulating resin 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 thicker the insulating resin 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. Furthermore, a thinner insulating resin layer can suppress the decrease in current and power generation due to the charge transport layer acting as a resistor.

[0072] The photoelectric conversion element of the present invention comprises an insulating resin material containing polyvinyl butyral or polymethyl methacrylate. When the insulating resin material contains polymethyl methacrylate, the thickness of the insulating resin layer is 5 nm to 10 nm. When the insulating resin layer contains polyvinyl butyral, it is preferable that the thickness of the insulating resin layer is 50 nm to 200 nm.

[0073] In the photoelectric conversion element of the present invention, the insulating resin layer preferably contains charge-transporting particles, and the coverage rate of the insulating resin layer is preferably 20% or less. By doing so, the photoelectric conversion element of the present invention can more effectively suppress shunt lique caused by defects such as irregularities and gaps in the perovskite crystal and suppress the increase in series resistance, thereby increasing the photoelectric conversion efficiency.

[0074] The insulating resin layer can be formed by preparing a coating solution for an insulating resin layer containing the above-mentioned materials and solvents, forming this coating film on the photoelectric conversion layer, and drying it. 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.

[0075] [Charge transport layer] Examples of materials for the 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.

[0076] Furthermore, the 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.

[0077] [Electron transport layer] In the photoelectric conversion element of the present invention, an electron transport layer 3 may be placed between the second electrode 2 and the photoelectric conversion layer 4, as shown in Figure 1. The material of the electron transport layer 3 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, and more specifically, cyano group-containing polyphenylene vinylene, boron-containing polymers, vasocuproin, vasophenanthrene, 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, and zinc sulfide. In particular, tin oxide may be obtained by reacting tin(2) chloride, tin(4) chloride, tin(2) chloride dihydrate, or tin(4) chloride pentahydrate.

[0078] The preferred thickness of the electron transport layer 3 is 1 nm at the lower limit and 2000 nm at the upper limit. If the thickness of the electron transport layer 3 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.

[0079] [Controlling the particle size of charge-transporting particles] The particle size of charge-transporting particles can be changed by dispersing the insulating resin coating solution 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 insulating resin coating solution to a centrifuge.

[0080] <Second Embodiment> The second embodiment relates to a method for manufacturing a photoelectric conversion element. The method for manufacturing the photoelectric conversion element of the present invention is as follows: A process of forming the first electrode and the second electrode, The process involves forming a photoelectric conversion layer containing a perovskite crystal between the first electrode and the second electrode, The process involves forming an insulating resin layer on the surface of the perovskite crystal and in the gaps between the perovskite crystals. Includes, The insulating resin layer is formed on the parts of the perovskite structure where the surface irregularities are large. The insulating resin layer contains polyvinyl butyral or polymethyl methacrylate as the insulating resin. The insulating resin layer is characterized in that, if it contains polymethyl methacrylate, the thickness of the insulating resin layer is 5 nm or more and 10 nm or less. The following explains each item. Note that some items described in the first embodiment may be omitted from this explanation.

[0081] [Process for forming the photoelectric conversion layer] The present invention relates to a method for manufacturing a photoelectric conversion element, which includes the step of forming a photoelectric conversion layer containing a perovskite crystal between a first electrode and a second electrode. The step of forming the photoelectric conversion layer is characterized by using a large-area film formation method. The large-area film formation method can be classified into a coating method and a vapor deposition method.

[0082] 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.

[0083] The coating method involves preparing the coating solution for each layer, as described later, applying it to the desired substrate or layer, and then drying it. Processes for forming the photoelectric conversion layer include immersion coating, spin coating, spray coating, inkjet 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 fabricated, such as thickness control and orientation control.

[0084] The process described above is merely an example, and any coating method that is an improved version of these general-purpose coating methods may also be used. Furthermore, the process may be used alone or in combination with other coating methods. Among these, from the viewpoint of high mass productivity, 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.

[0085] Immersion coating is a method of coating a substrate by immersing it in paint and then lifting it out. Spin coating is a method of coating a substrate by dropping paint onto it and rotating it to form a uniform coating film using centrifugal force.

[0086] Spray coating is a method of forming a coating film by spraying paint onto the surface of a substrate. Inkjet coating is a method of uniformly forming a coating film by dropping paint onto the surface of a substrate drop by drop.

[0087] Screen coating is a method of application that uses a screen mesh made of synthetic or metal fibers. The paint passes through the mesh and is applied to the substrate.

[0088] Roll coating is a coating method that uses one or more rollers to obtain an optimal coated 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 coated surface uniform on deformable films such as films using rolls, as exemplified by the roll-to-roll method.

[0089] Gravure coating is a method of applying paint by adhering it 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.

[0090] 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 pushing paint through a slit with a certain width at a uniform flow rate in the width direction, transferring the paint directly onto the substrate without forming any liquid pools. Bar coating is a method of forming a uniform coating film by dropping paint onto a substrate and passing it through bars that have grooves formed between them.

[0091] The next step is to dry the wet film of the photoelectric conversion layer coating obtained in the photoelectric conversion layer deposition step, thereby generating a perovskite crystal film. In addition to the general drying of the wet film, the process of generating the perovskite crystal film also involves generating nuclei for the perovskite crystal and growing them.

[0092] If drying is slow, the wet film may move during drying, making it easier for unevenness to occur in the film, and if there are too few nuclei in the perovskite crystals, gaps are more likely to form between the perovskite crystals. Therefore, a fast drying rate is preferable.

[0093] On the other hand, if drying is too fast, many perovskite crystal nuclei are formed, resulting in smaller individual perovskite crystals. Smaller perovskite crystals mean more interfaces, which can lead to increased interfacial resistance, reduced photoelectric conversion efficiency, and decreased durability due to the movement of raw material ions across the interfaces. Therefore, it is preferable that the drying rate in the process of forming the perovskite crystal film is within an appropriate range.

[0094] Examples of processes 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 generating perovskite crystals. Because the good solvent is replaced immediately, many perovskite crystal nuclei are generated.

[0095] Therefore, film defects are less likely to form, 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 a wet film by blowing gas onto it. Since the decomposition of perovskite crystals is accelerated by moisture, it is preferable that the gas blown on is a low-moisture gas. Examples of gases to be blown on include nitrogen gas and dry air. The gas may also be heated in advance to blow hot air.

[0096] The reduced pressure method involves creating a reduced pressure in the space where the wet film is located, thereby promoting the evaporation of the solvent within the wet film and drying it. The rapid heating method involves heating the wet film to accelerate drying. Heating methods include direct heating by bringing a heat source into contact with the substrate, and indirect heating using methods such as infrared radiation.

[0097] In the process of forming 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 the present invention, the photoelectric conversion layer may be deposited by depositing the perovskite crystal raw material all at once, or by depositing the raw material in multiple stages.

[0098] 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.

[0099] [Process for evaluating the photoelectric conversion layer] The method for manufacturing the photoelectric conversion element of the present invention preferably includes a step of evaluating the photoelectric conversion layer, which involves evaluating a perovskite crystal structure and determining a region for forming an insulating resin layer based on the evaluation results. Preferably, after the step of forming the photoelectric conversion layer, the step of evaluating the photoelectric conversion layer is performed, and the step of forming an insulating resin layer (described later) in the region is performed.

[0100] In the process of depositing the photoelectric conversion layer, variations in drying rate result in differences in the grain size, surface roughness, and density of gaps in the grain boundaries of the perovskite crystals. The relationship between drying rate and crystal growth mechanism can be considered as follows, based on the LaMer model: In regions with slow drying rates, crystal nuclei are formed when the precursor concentration in the coating film exceeds the critical concentration.

[0101] The formation of crystal nuclei reduces the precursor concentration, and the precursor concentration in the coating film is maintained in a region above saturation but below critical concentration. As a result, the formation of new crystal nuclei is unlikely, and crystal growth becomes dominant. Consequently, individual perovskite crystals become large and uniform in size. In this case, the density of crystal grain boundary gaps increases, leading to the formation of shuntia.

[0102] For such areas, it is possible to improve photoelectric conversion efficiency by forming an insulating resin film to prevent shunt liquefaction. On the other hand, in regions with a fast drying rate, when the precursor concentration of the coating film exceeds the critical concentration, crystal nuclei begin to form, and the precursor concentration decreases, but it does not fall below the critical concentration, so new crystal nucleation and crystal growth occur in parallel.

[0103] As a result, the size of individual perovskite crystals is relatively small and non-uniform. In this case, since there are no gaps at the grain boundaries, shunt lique does not occur, and therefore, the deposition of an insulating resin is unnecessary. Conversely, if an insulating resin is deposited in such areas, the series resistance increases, resulting in a decrease in photoelectric efficiency compared to those without the deposition.

[0104] Based on the mechanism described above, it was found that the probability of shuntia formation correlates with the distribution of perovskite crystal sizes. Therefore, by measuring the size distribution of perovskite crystals, it is possible to determine the region where insulating resin should be deposited. The size of perovskite crystals can be observed using a scanning electron microscope (SEM) or an optical microscope.

[0105] Because the magnification and resolution differ, the crystal size distribution profile will vary depending on the observation method. However, the difference in crystal size distribution profile due to differences in drying speed can be confirmed with each observation method. Therefore, by appropriately setting the threshold for each observation method, it is possible to extract the region where insulating resin should be deposited regardless of the method used. In the case of optical microscopes, it is not necessary to create a vacuum in the observation system, making it easy to implement in mass production equipment such as roll-to-roll systems.

[0106] Figures 3(a) and 3(b) show SEM images after the deposition of the photoelectric conversion layer (magnification 5000x, resolution 20nm / pixel, pixel count 1280×1026). Figure 3(a) shows an SEM image of an area with a relatively slow drying rate, and Figure 3(b) shows an SEM image of an area with a relatively fast drying rate.

[0107] The crystal size distribution was analyzed for each photograph using ImageJ, an image processing software developed by the National Institutes of Health (NIH), in the following manner: A region consisting of a power of two pixels was selected from the target image, an FFT (Fast Fourier Transform) was performed, and the normalized integral power spectrum was obtained from the power values ​​of the resulting two-dimensional power spectrum.

[0108] The normalized integral power spectrum can be obtained by exponentially transforming the 256-level values ​​back to their original power values, integrating the power values ​​on a circle centered at the origin, and then normalizing the spectrum by dividing by the sum of the power values ​​other than the DC component (center value).

[0109] Figure 4 shows the normalized integrated power spectra obtained by frequency analysis of the SEM images in Figures 3(a) and 3(b). In the case of slow drying in the SEM image (Figure 3(a)), there is a peak value (main frequency) around 0.0003 to 0.0004, but in the case of fast drying in the SEM image (Figure 3(b)), there is no peak value (main frequency).

[0110] In other words, in the case of high-speed drying, there is no main crystal size, and it can be confirmed that the crystal size is non-uniform compared to low-speed drying. Next, the same sample was photographed with an optical microscope (Evident, model number DSX-1000), and the normalized power spectrum was determined in the same way, as shown in Figures 5(a) and 5(b).

[0111] The optical microscope image was taken at a magnification of 4990x, with a resolution of 43.5 nm / pixel and a pixel count of 12000 x 1200. The normalized integrated power spectrum differs from that of the SEM image, but differences in the spectra of slow drying and fast drying can be observed, with a stronger peak appearing in the slow drying case.

[0112] Figure 5 shows the profile normalized by the peak value Imax of the spectrum (Imax is set to 1). In the embodiments described below, the process of forming an insulating resin layer, as described later, was performed in the region where the ratio Iave / Imax, which is the average Iave of the normalized integral power values ​​below a spatial frequency of 0.0002, was 0.92 or less.

[0113] [Process for forming an insulating resin layer] The present invention provides a method for manufacturing a photoelectric conversion element, which includes the step of forming an insulating resin layer on the surface of a perovskite crystal and in the gaps between the perovskite crystals, and it is preferable to control the film thickness according to the state of the photoelectric conversion layer. Film formation is not required in areas of the perovskite crystal that are free of defects. The film formation method can be the same as the method for forming the photoelectric conversion layer, but in the case of vapor deposition, a mask cover can be used to ensure that areas are not film-formed.

[0114] Suitable coating methods include those that allow for regional color separation. For example, screen printing, print transfer, inkjet, and spray methods can be used. Inkjet and spray methods are more preferable because they easily reflect the coating area determined from the evaluation results of the perovskite crystal.

[0115] The following methods can be mentioned in detail. For example, one method involves placing charge-transporting particles on the surface of the photoelectric conversion layer and then applying a resin solution containing dissolved insulating resin; another method involves applying a resin solution containing dissolved insulating resin to the surface of the photoelectric conversion layer and then placing charge-transporting particles; and a third method involves applying a solution in which charge-transporting particles are dispersed in a resin solution containing dissolved insulating resin to the surface of the photoelectric conversion layer.

[0116] [Steps for forming the first electrode and steps for forming the second electrode] The present invention relates to a method for manufacturing a photoelectric conversion element, which includes the steps of forming a first electrode and a second electrode. In the steps of forming the first electrode and forming the second electrode, an appropriate method can be selected depending on 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.

[0117] When manufacturing solar cells, 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.

[0118] [Modularization Process] The method for manufacturing the photoelectric conversion element of the present invention may include a modularization step of encapsulating the element up to the electrodes. Examples of encapsulation methods include encapsulation with resin or encapsulation with film. Examples of materials used for encapsulation 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 sealed elements may be given a hairline finish.

[0119] [others] The present invention relates to a method for manufacturing a photoelectric conversion element in which an insulating resin layer is formed on a portion of the perovskite structure where the surface irregularities are large, and the insulating resin layer contains polyvinyl butyral or polymethyl methacrylate as the insulating resin, and when the insulating resin layer contains polymethyl methacrylate, the thickness of the insulating resin layer is 5 nm or more and 10 nm or less. Details of these are as described in the first embodiment.

[0120] <Application Examples> An example of the application of this invention is a photoelectric conversion device. [Photoelectric converter] The photoelectric conversion device of the present invention has a photoelectric conversion element of the present invention. A photoelectric conversion device can be constructed by using multiple photoelectric conversion elements of the present invention. When multiple photoelectric conversion elements are connected together, such a photoelectric conversion device can also be called a photoelectric conversion cell or a photoelectric conversion module. Photoelectric conversion elements with different absorption wavelengths may be stacked to increase the output voltage.

[0121] Furthermore, the photoelectric conversion device comprises the photoelectric conversion element of the present invention and an inverter. The inverter may be a converter that converts direct current to alternating current. The photoelectric conversion device may also 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, and electric double-layer capacitors. 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. [Examples]

[0122] The present invention will be described in more detail below using examples and comparative examples. The present invention is not limited in any way by the following examples, unless it exceeds the gist of the invention. In the following descriptions of examples, "parts" refers to mass unless otherwise specified.

[0123] <Preparation of Particle 1> Process (1) Under a nitrogen flow atmosphere, 5.46 parts of orthophthalonitrile and 45 parts of α-chloronaphthalene were added to the reaction vessel, and the mixture was heated to a temperature of 30°C, which was then maintained. Next, 3.75 parts of gallium trichloride were added at this temperature (30°C). The water concentration of the mixture at the time of addition was 150 ppm. The temperature was then raised to 200°C.

[0124] Next, the reaction was carried out at 200°C for 4.5 hours under a nitrogen flow atmosphere, then cooled, and the product was filtered when the temperature reached 150°C. The obtained filtrate was dispersed and washed with N,N-dimethylformamide at 140°C for 2 hours, and then filtered. The obtained filtrate was washed with methanol and dried to obtain chlorogallium phthalocyanine particles in 71% yield.

[0125] Process (2) 4.65 parts of the chlorogallium phthalocyanine particles were dissolved in 139.5 parts of concentrated sulfuric acid at 10°C, and the mixture was added dropwise to 620 parts of ice water under stirring to reprecipitate. The mixture was then filtered under reduced pressure using a filter press. A No. 5C filter (manufactured by Advantec Co., Ltd.) was used for this process. The resulting wet cake (filtrate) was dispersed and washed with 2% ammonia water for 30 minutes, and then filtered using a filter press.

[0126] Next, the obtained wet cake (filtrate) was dispersed and washed with deionized water, and then filtered three times using a filter press. Finally, freeze-drying was performed to obtain hydroxygallium phthalocyanine particles (hydrated hydroxygallium phthalocyanine particles) with a solid content of 23% by mass in yield of 71%. These hydroxygallium phthalocyanine particles were dried using a hyper-dry dryer (product name: HD-06R, frequency (oscillation frequency): 2455MHz ± 15MHz, manufactured by Nippon Biocon) to obtain hydroxygallium phthalocyanine (OHGaPc) particles (crystals) with a moisture content of 1.0% by mass or less.

[0127] Process (3) Five parts of the hydroxygallium phthalocyanine particles were mixed with five parts of N-methylformamide solvent. This mixture was dispersed for six hours using a sand mill (TSG-1 / 4G-4U, manufactured by Igarashi Machinery Manufacturing Co., Ltd. (now AIMEX), with a disc diameter of 70 mm and five discs) containing five glass beads, and then filtered and dried to obtain particle 1.

[0128] <Preparation of resin solution 1> 1.0 g of polyvinyl butyral (product name: BM-2, manufactured by Sekisui Chemical Co., Ltd., glass transition temperature 71°C) was dissolved in 19 g of 2-propanol with stirring for 24 hours to obtain resin solution 1.

[0129] <Preparation of resin solution 2> 1.0 g of polymethyl methacrylate (PMMA, manufactured by Sigma-Aldrich, glass transition temperature 100°C) was dissolved in 19 g of 2-propanol with stirring for 24 hours to obtain resin solution 2.

[0130] (Example 1) [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 as a thin film with a thickness of 16 nm.

[0131] [Formation and evaluation of the photoelectric conversion layer] A coating solution for the photoelectric conversion layer 1 was prepared by dissolving 11.525 g of lead iodide, 3.975 g of methylammonium iodide, and 0.68 g of methylammonium chloride in 13.97 g of N,N-dimethylformamide and 4.935 g of dimethyl sulfoxide, and stirring for 1 hour. This coating solution was applied to the electron transport layer, which had been heated to a substrate temperature of 56°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 150°C for 10 minutes to form a black photoelectric conversion layer made of MAPbI3, with a width of 30 mm and a length of 100 mm.

[0132] The gas quenching conditions were as follows: dry air at room temperature (24°C) was used, the air velocity at the air knife nozzle was 50 m / s, and the distance from the air knife tip to the substrate was 15 mm. Subsequently, the surface of the photoelectric conversion layer was observed at 1 mm intervals using an optical microscope, and the region to be deposited with the insulating layer was extracted using the image analysis described above. At this time, the area percentage for which the insulating layer was deposited was 5%.

[0133] [Formation of an insulating resin layer] Resin solution 2 was spray-coated onto the areas extracted during the evaluation of the photoelectric conversion layer, and a 5 nm thick insulating resin layer was formed by drying.

[0134] [Formation of a charge transport layer] 0.15 g of Spiro-OMeTAD, used as the material for the charge transport layer, was dissolved in 2.2 g of chlorobenzene. To this chlorobenzene solution, 36 μL of an acetonitrile solution obtained by dissolving 0.2 g of lithium bis(trifluoromethanesulfonyl)imide in 0.3 g of acetonitrile and 60 μL of 4-tert-butylpyridine (TBP) were added and mixed. Furthermore, 58 μL of an acetonitrile solution obtained by dissolving 0.11 g of [tris(2-(1H-pyrazole-1-yl)-4-tert-butylpyridine)cobalt(3)tris(bis(trifluoromethylsulfonyl)imide)] in 0.3 g of acetonitrile was added and mixed to prepare a coating solution for the charge transport layer. This was applied by spin coating onto a photoelectric conversion layer with a partially formed insulating resin layer to form a 100 nm thick charge transport layer.

[0135] [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.

[0136] (Example 2) In forming the photoelectric conversion layer, the air velocity was changed to 40 m / s for film deposition. Subsequently, using light microscopy observation and image analysis, the area to which the insulating resin layer was deposited was extracted, and the area proportion for which the insulating resin layer was deposited was 10%. Otherwise, a photoelectric conversion element was obtained in the same manner as in Example 1.

[0137] (Example 3) In forming the photoelectric conversion layer, the air velocity was changed to 30 m / s for film deposition. Subsequently, using light microscopy observation and image analysis, the area to which the insulating resin layer was deposited was extracted, and the area proportion for which the insulating resin layer was deposited was 15%. The photoelectric conversion element was obtained in the same manner as in Example 1.

[0138] (Example 4) A photoelectric conversion element was obtained in the same manner as in Example 1, except that the insulating resin layer to be deposited on the photoelectric conversion layer contained the charge-transporting particles described below. 0.1 g of the charge-transporting particles 1 and 0.01 g of a calixarene compound (Japanese Patent Publication No. 2003-207913) were mixed with 10.6 g of 2-propanol, and 11 g of beads (zirconia beads, Treceram® zirconia beads, 0.3 mm) were enclosed in this mixture and dispersed in a paint shaker (manufactured by Toyo Seiki) for 7 hours. Then, 0.2 g of resin solution 1 was added, and dispersion in a paint shaker was repeated for 6 hours to prepare a coating solution for the insulating resin layer containing charge-transporting particles. This coating solution was applied by spray coating and dried to form a charge transport layer with a thickness of 150 nm.

[0139] (Example 5) In forming the photoelectric conversion layer, the air velocity was changed to 40 m / s for film deposition. Subsequently, using light microscopy observation and image analysis, the area to which the insulating resin layer was deposited was extracted, and the area proportion for which the insulating resin layer was deposited was 10%. Otherwise, a photoelectric conversion element was obtained in the same manner as in Example 4.

[0140] (Example 6) In forming the photoelectric conversion layer, the air velocity was changed to 30 m / s for film deposition. Subsequently, using light microscopy observation and image analysis, the area to which the insulating resin layer was deposited was extracted, and the area proportion for which the insulating resin layer was deposited was 15%. Otherwise, a photoelectric conversion element was obtained in the same manner as in Example 4.

[0141] (Example 7) A photoelectric conversion element was obtained in the same manner as in Example 1, except that the film thickness of the insulating resin layer was changed to 7 nm.

[0142] (Example 8) A photoelectric conversion element was obtained in the same manner as in Example 1, except that the film thickness of the insulating resin layer was changed to 7 nm.

[0143] (Comparative Example 1) A photoelectric conversion element was obtained in the same manner as in Example 1, except that an insulating resin layer was not formed.

[0144] (Comparative Example 2) In forming the photoelectric conversion layer, spin coating was used instead of die coating. Subsequent evaluation by optical microscopy revealed that no region suitable for forming an insulating resin layer was identified, so the insulating resin layer was not formed. Otherwise, a photoelectric conversion element was obtained in the same manner as in Example 1.

[0145] (Comparative Example 3) A photoelectric conversion element was obtained in the same manner as in Example 1, except that the thickness of the insulating resin layer was set to 2 nm.

[0146] (Comparative Example 4) A photoelectric conversion element was obtained in the same manner as in Example 1, except that the thickness of the insulating resin layer was set to 15 nm. Table 2 shows some of the manufacturing conditions for the photoelectric conversion elements produced in Examples 1-8 and Comparative Examples 1-4. The die-coating method for coating the photoelectric conversion layer was deemed suitable for mass production.

[0147] [Table 2]

[0148] [evaluation] The following evaluations were performed on the photoelectric conversion elements obtained in each example and each comparative example. (Evaluation of the element) In Example 1, a power supply (KEITHLEY, Model 236) was connected between the electrodes of the photoelectric conversion element, with an intensity of 100 mW / cm². 2The photoelectric conversion efficiency (PCE) was evaluated by irradiating a constant amount of light using a solar simulator (manufactured by Yamashita Densou Co., Ltd.) and measuring the generated current and voltage. The series resistance was approximately calculated by reciprocal of the slope near Voc of the obtained current-voltage curve, and the shunt resistance was approximately calculated by reciprocal of the slope near Jsc of the obtained current-voltage curve. Leakage resistance can be evaluated from the values ​​of the series resistance and the shunt resistance. The photoelectric conversion efficiency was determined for Examples 2 to 8 and Comparative Examples 1 to 4 in the same manner as Example 1. The PCE values, shunt resistance values, and series resistance values ​​in Table 2 are shown as relative values ​​with the result of Example 2 set to 1. The results are shown in Table 3.

[0149] (Evaluation of the photoelectric conversion layer) The photoelectric conversion layer was evaluated by taking images with an optical microscope (Evident, model DSX-1000) after film deposition and drying of the photoelectric conversion layer. The optical microscope image magnification was 4990x, the resolution was 43.5nm / pixel, and the number of pixels was 12000×1200. Images were taken at 1mm pitch, and the normalized power spectrum was determined for each image as described above. Regions where the ratio Iave / Imax of the average normalized integral power value Iave to the peak value Imax for spatial frequencies of 0.0002 or less was 0.92 or less were judged as NG. The percentage of the region judged as NG relative to the evaluated region was then calculated as the NG region percentage. The results are shown in Table 3. In this invention, the NG region can be considered as the region covered by the insulating resin layer, and the NG region percentage can be considered as the coverage rate of the insulating resin layer.

[0150] [Table 3]

[0151] In Examples 1 to 8, by forming an insulating resin layer in accordance with the crystal state of the perovskite in the photoelectric conversion layer, a decrease in shunt resistance and an increase in series resistance were suppressed, resulting in an improvement in photoelectric conversion efficiency.

[0152] This embodiment includes the following configurations and methods. (Composition 1) First electrode and The second electrode and A photoelectric conversion layer comprising a perovskite crystal is disposed between the first electrode and the second electrode, An insulating resin layer is provided on the surface of the perovskite crystal and in the gaps between the perovskite crystals. It has, The insulating resin layer is formed on the parts of the perovskite structure where the surface irregularities are large. The insulating resin layer contains polyvinyl butyral or polymethyl methacrylate as the insulating resin. A photoelectric conversion element characterized in that, when the insulating resin layer contains polymethyl methacrylate, the thickness of the insulating resin layer is 5 nm or more and 10 nm or less. (Configuration 2) The photoelectric conversion element according to configuration 1, wherein the insulating resin layer contains charge-transporting particles. (Composition 3) The photoelectric conversion element according to configuration 1 or 2, wherein the coverage rate of the insulating resin layer is 20% or less. (Composition 4) The photoelectric conversion element according to configuration 2, wherein the charge-transporting particle has a cyclic conjugated compound in which a plurality of pyrrole rings are conjugated together. (Composition 5) The photoelectric conversion element according to configuration 2 or 4, wherein the charge-transporting particles include a phthalocyanine compound. (Composition 6) The photoelectric conversion element according to configuration 2, 4, or 5, wherein the charge-transporting particle has a hydroxygallium phthalocyanine compound. (Composition 7) A photoelectric conversion element according to any one of configurations 1 to 6, wherein the glass transition temperature of the insulating resin is less than 100°C. (Composition 8) The photoelectric conversion element according to any one of configurations 1 to 7, wherein the insulating resin layer contains polyvinyl butyral, and the thickness of the insulating resin layer is 50 nm or more and 200 nm or less. (Composition 9) A photoelectric conversion device having a photoelectric conversion element described in any one of configurations 1 to 8. (Method 1) A process of forming the first electrode and the second electrode, The process involves forming a photoelectric conversion layer containing a perovskite crystal between the first electrode and the second electrode, The process involves forming an insulating resin layer on the surface of the perovskite crystal and in the gaps between the perovskite crystals. Includes, The insulating resin layer is formed on the parts of the perovskite structure where the surface irregularities are large. The insulating resin layer contains polyvinyl butyral or polymethyl methacrylate as the insulating resin. A method for manufacturing a photoelectric conversion element, characterized in that, when the insulating resin layer contains polymethyl methacrylate, the thickness of the insulating resin layer is 5 nm or more and 10 nm or less. (Method 2) The process includes evaluating the crystal structure of the perovskite and determining the region where the insulating resin layer is formed based on the evaluation results, and evaluating the photoelectric conversion layer. A method for manufacturing a photoelectric conversion element according to Method 1, comprising the steps of forming the photoelectric conversion layer, evaluating the photoelectric conversion layer, and forming the insulating resin layer in the region. [Explanation of Symbols]

[0153] 1 Base material 2 Second electrode 3 Electron transport layer 4. Photoelectric conversion layer containing perovskite structure crystals 5. Insulating resin layer 6 Charge transport layer 7 First electrode 8 Charge transporting particles 10 Photoelectric conversion element

Claims

1. First electrode and The second electrode and A photoelectric conversion layer comprising a perovskite crystal is disposed between the first electrode and the second electrode, An insulating resin layer is provided on the surface of the perovskite crystal and in the gaps between the perovskite crystals. It has, The insulating resin layer is formed on the parts of the perovskite structure where the surface irregularities are large. The insulating resin layer contains polyvinyl butyral or polymethyl methacrylate as the insulating resin. A photoelectric conversion element characterized in that, when the insulating resin layer contains polymethyl methacrylate, the thickness of the insulating resin layer is 5 nm or more and 10 nm or less.

2. The photoelectric conversion element according to claim 1, wherein the insulating resin layer includes charge-transporting particles.

3. The photoelectric conversion element according to claim 1, wherein the coverage rate of the insulating resin layer is 20% or less.

4. The photoelectric conversion element according to claim 2, wherein the charge-transporting particle has a cyclic conjugated compound in which a plurality of pyrrole rings are conjugated together.

5. The photoelectric conversion element according to claim 2, wherein the charge-transporting particles include a phthalocyanine compound.

6. The photoelectric conversion element according to claim 2, wherein the charge-transporting particle has a hydroxygallium phthalocyanine compound.

7. The photoelectric conversion element according to claim 1, wherein the glass transition temperature of the insulating resin is less than 100°C.

8. The photoelectric conversion element according to claim 1, wherein, if the insulating resin layer contains polyvinyl butyral, the thickness of the insulating resin layer is 50 nm or more and 200 nm or less.

9. A photoelectric conversion device having a photoelectric conversion element according to any one of claims 1 to 8.

10. A process of forming the first electrode and the second electrode, The process involves forming a photoelectric conversion layer containing a perovskite crystal between the first electrode and the second electrode, The process involves forming an insulating resin layer on the surface of the perovskite crystal and in the gaps between the perovskite crystals. Includes, The insulating resin layer is formed on the parts of the perovskite structure where the surface irregularities are large. The insulating resin layer contains polyvinyl butyral or polymethyl methacrylate as the insulating resin. A method for manufacturing a photoelectric conversion element, characterized in that, when the insulating resin layer contains polymethyl methacrylate, the thickness of the insulating resin layer is 5 nm or more and 10 nm or less.

11. The process includes evaluating the crystal structure of the perovskite and determining the region where the insulating resin layer is formed based on the evaluation results, and evaluating the photoelectric conversion layer. A method for manufacturing a photoelectric conversion element according to claim 10, comprising the steps of forming the photoelectric conversion layer, evaluating the photoelectric conversion layer, and forming the insulating resin layer in the region.

Images