Method for manufacturing solar cell, method for manufacturing solar cell module, solar cell, and solar cell module

Abstract

The present invention provides: a method for manufacturing a solar cell, with which it is possible to improve durability and conversion efficiency; a method for manufacturing a solar cell module; a solar cell; and a solar cell module.　A method for manufacturing a solar cell 10 includes: a step for forming an electron transport layer 3 on a first electrode 2; a step for forming a light absorption layer 4 of a perovskite compound on the electron transport layer 3; a step for forming a hole transport layer 5 on the light absorption layer 4; and a step for forming a second electrode 6 on the hole transport layer 5. The step for forming the hole transport layer 5 and / or the step for forming the electron transport layer 3 includes a buffer layer formation step for forming a buffer layer 31, 51 between the hole transport layer 5 and the light absorption layer 4 and / or between the electron transport layer 3 and the light absorption layer 4. In the buffer layer formation step, a solution which contains a polyamino acid that is obtained by polymerizing an amino acid having a charged side chain of a reactive functional group is added.

Description

Manufacturing method of solar cell, manufacturing method of solar cell module, solar cell and solar cell module

[0001] The present disclosure relates to solar cells and solar modules having a light absorption layer made of a perovskite compound, and methods for manufacturing the same.

[0002] BACKGROUND ART Solar cells have been disclosed in which a specific organic compound is used in a charge transport layer between an electrode and a light absorbing layer having a perovskite crystal structure.

[0003] For example, Patent Document 1 discloses a perovskite film layer that can effectively improve the efficiency of a perovskite light-emitting device, which is composed of one layer of discontinuous and irregularly distributed perovskite crystal particles and a low-refractive-index organic insulating layer embedded between the perovskite crystal particles, and which includes a charge transport layer that bonds to or reacts with the organic insulating layer and includes a multilayer thin film modified with an amino acid-based organic substance or a polyamine-based organic substance.

[0004] Special Publication No. 2021-504901

[0005] However, the amino acid-based organic compounds and polyamine-based organic compounds disclosed in Patent Document 1 were insufficient to exhibit and maintain stable performance as a charge transport layer. That is, in the case of amino acid-based organic compounds, amino groups are used during the formation of the charge transport layer, making it impossible to increase the amine accumulation required for stable performance as a charge transport layer. Furthermore, although amino acids are bonded to each other using functional groups possessed by amino acids, the bonds are made on an amino acid basis, preventing the penetration of water molecules into the light absorption layer and making it difficult to achieve sufficient density as a thin film structure. In the case of polyamine-based organic compounds, although the density of the charge transport layer itself is improved by the polymer, the polymer is composed of allylamine units, and therefore does not take into account the amine accumulation required for stable performance as a charge transport layer.

[0006] Therefore, the present disclosure provides a solar cell and a solar cell module that can improve the durability of the charge transport layer and exhibit stable performance.

[0007] A method for manufacturing a solar cell according to one aspect of the present disclosure includes the steps of forming an electron transport layer on a first electrode, forming a light absorbing layer of a perovskite compound on the electron transport layer, forming a hole transport layer on the light absorbing layer, and forming a second electrode on the hole transport layer, or the method includes the steps of forming a hole transport layer on a second electrode, forming a light absorbing layer of a perovskite compound on the hole transport layer, forming an electron transport layer on the light absorbing layer, and forming a first electrode on the electron transport layer, wherein the step of forming the hole transport layer and / or the step of forming the electron transport layer includes a buffer layer formation step of forming a buffer layer between the hole transport layer and the light absorbing layer and / or between the electron transport layer and the light absorbing layer, and the buffer layer formation step is characterized by adding a solution containing a polyamino acid obtained by polymerizing an amino acid having a charged side chain of a reactive functional group.

[0008] A method for manufacturing a solar cell according to one aspect of the present disclosure includes the steps of forming an electron transport layer on a first electrode, forming a light absorbing layer of a perovskite compound on the electron transport layer, forming a hole transport layer on the light absorbing layer, and forming a second electrode on the hole transport layer, or the method includes the steps of forming a hole transport layer on a second electrode, forming a light absorbing layer of a perovskite compound on the hole transport layer, forming an electron transport layer on the light absorbing layer, and forming a first electrode on the electron transport layer, wherein the step of forming the hole transport layer and / or the step of forming the electron transport layer is characterized by adding a solution containing a polyamino acid obtained by polymerizing an amino acid having a charged side chain of a reactive functional group.

[0009] A method for manufacturing a solar cell module according to one aspect of the present disclosure is characterized in that solar cells manufactured by a method for manufacturing a solar cell are integrated and modularized.

[0010] A solar cell according to one aspect of the present disclosure has a charge transport layer made of a hole transport layer or an electron transport layer between an electrode and a light absorption layer of a perovskite compound, and is characterized in that it contains an organic compound having a polymerized structure of at least an amino acid having a charged side chain of a reactive functional group, (1) as a buffer layer between the light absorption layer and the charge transport layer, or (2) as a composition of the charge transport layer.

[0011] A solar cell module according to one aspect of the present disclosure is characterized in that solar cells are integrated and modularized.

[0012] According to the present disclosure, it is possible to improve the durability of solar cells.

[0013] FIG. 1(a) is a schematic cross-sectional view of a solar cell according to a first embodiment of the present invention, FIG. 1(b) is a schematic cross-sectional view of a solar cell according to a second embodiment of the present invention, FIG. 1(c) is a schematic cross-sectional view of a solar cell according to a third embodiment of the present invention, FIG. 1(d) is a schematic cross-sectional view of a solar cell according to a fourth embodiment of the present invention, FIG. 1(e) is a schematic cross-sectional view of a solar cell according to a fifth embodiment of the present invention, FIG. 1(f) is a schematic cross-sectional view of a solar cell according to a sixth embodiment of the present invention, FIG. 1(g) is a schematic cross-sectional view of a solar cell according to a seventh embodiment of the present invention, and FIG. 1(h) is a schematic cross-sectional view of a solar cell according to an eighth embodiment of the present invention. FIG. 2(a) is a schematic cross-sectional view of a solar cell according to a ninth embodiment of the present invention, FIG. 2(b) is a schematic cross-sectional view of a solar cell according to a tenth embodiment of the present invention, FIG. 2(c) is a schematic cross-sectional view of a solar cell according to an eleventh embodiment of the present invention, FIG. 2(d) is a schematic cross-sectional view of a solar cell according to a twelfth embodiment of the present invention, FIG. 2(e) is a schematic cross-sectional view of a solar cell according to a thirteenth embodiment of the present invention, FIG. 2(f) is a schematic cross-sectional view of a solar cell according to a fourteenth embodiment of the present invention, FIG. 2(g) is a schematic cross-sectional view of a solar cell according to a fifteenth embodiment of the present invention, and FIG. 2(h) is a schematic cross-sectional view of a solar cell according to a sixteenth embodiment of the present invention. FIG. 3 is a schematic cross-sectional view of a solar cell module including solar cells according to the present embodiment. FIG. 4 is a schematic cross-sectional view of a solar cell module including solar cells according to the present embodiment (Variation 1). FIG. 5 is a schematic cross-sectional view of a solar cell module including solar cells according to the present embodiment (Variation 2). FIG. 6 is a diagram in which the schematic cross-sectional view of one solar cell included in the solar cell module shown in FIG. 3 and an equivalent circuit of the solar cell are superimposed. FIG. 7 is an equivalent circuit of the solar cell module.

[0014] Preferred embodiments of the present disclosure will be described in detail below with reference to the drawings. Note that the embodiments described below do not unnecessarily limit the content of the present disclosure as defined in the claims, and not all of the configurations described in the embodiments are necessarily essential to the solution of the present disclosure. Furthermore, for illustrative purposes, the light incident side is referred to as the lower side and the side opposite the light incident side as the upper side. However, this is for convenience and does not relate to the installation direction or recommended installation direction. The above-mentioned terms can be reversed as long as there is no contradiction. In other words, the present disclosure is valid even if the light incident side and the side opposite the light incident side are reversed as long as there is no contradiction. Furthermore, in a monofacial solar cell, the light incident side refers to the side from which light enters the solar cell. However, in a bifacial solar cell, it is sufficient to consider either side as the light incident side. Furthermore, if at least one side is considered as the light incident side, the solar cell can be considered to fall within the technical scope of the present disclosure as long as it has the configuration of the present disclosure. In other words, even if one side does not have the configuration of the present disclosure when considered as the light-receiving side, it can be considered to fall within the technical scope of the present disclosure as long as the other side has the configuration of the present disclosure when considered as the light-receiving side. In the following description, unless otherwise specified, the same components are generally designated by the same reference numerals, and their names and functions are also the same. Therefore, in such cases, detailed descriptions thereof will not be repeated.

[0015] 1. Solar Cell <First Embodiment> Fig. 1(a) is a schematic cross-sectional view of a solar cell 10 according to this embodiment. As shown in Fig. 1(a), the solar cell 10 according to this embodiment includes a base 1. The solar cell 10 also includes a first electrode 2, an electron transport layer 3 formed on the first electrode 1, a light absorbing layer 4 formed on the electron transport layer 3, a hole transport layer 5 formed on the light absorbing layer 4 with a buffer layer 51 interposed therebetween, and a second electrode 6 formed on the hole transport layer 5. The first electrode 2 is in contact with the electron transport layer 3, the electron transport layer 3 is in contact with the light absorbing layer 4, the light absorbing layer 4 is in contact with the hole transport layer 5 with the buffer layer 51 interposed therebetween, and the hole transport layer 5 is in contact with the second electrode 6. Each component will be described in detail below. In the present embodiment, the first electrode 2 is in contact with the electron transport layer 3, the electron transport layer 3 is in contact with the light absorbing layer 4, the light absorbing layer 4 is in contact with the hole transport layer 5 via the buffer layer 51, and the hole transport layer 5 is in contact with the second electrode 6. However, this does not exclude the case where they are not in contact with each other and another layer is interposed between them.

[0016] [Base] The base 1 is the base of the solar cell 10 and is the same as or includes the substrate or base material. In this embodiment, the base 1 is made of a transparent material. However, the side of the solar cell 10 opposite the base may be made of a transparent material, or both sides may be made of a transparent material. The base 1 is preferably a transparent base. The base 1 is disposed on the light-receiving side of the solar cell 10 (also referred to as the light-receiving side, including the portion where light is incident, as in the present disclosure). The base 1 is connected to the first electrode 2. Note that "connected" means being in direct physical contact. Furthermore, "transparent" or "light-transmitting" means transmitting light, but does not exclude materials that reflect or absorb even a small amount of light. It is sufficient for a material to be disposed on the light-receiving side of the solar cell 10 and transmit light appropriately. This can be considered synonymous with being disposed on the light-receiving side of the solar cell 10. Therefore, being disposed at least on the light-receiving side of the solar cell 10 can be considered transparent. That is, the transparent substrate means a substrate provided on the light-receiving surface side of the solar cell 10 .

[0017] The material of the base 1 can be, for example, plastic such as PET or polyimide, or glass. By using a flexible base 1, the solar cell 10 itself can be made flexible.

[0018] When the material of the base 1 is a transparent resin such as an organic film, the solar cell 10 may have a barrier layer (not shown) on the base 1. This can prevent moisture and the like from penetrating into the light absorbing layer 4. The barrier layer may be provided, for example, between the base 1 and the first electrode 2.

[0019] The thickness of the substrate 1 may be about 50 μm to 5000 μm.

[0020] [First Electrode] The first electrode 2 is a conductive member. For example, a transparent conductive film is used. The first electrode 2 is a conductive film on the light-receiving surface side of the solar cell 10. Examples of materials constituting the first electrode 2 include transparent conductive materials (particularly, transparent conductive oxides (TCO)) and non-transparent conductive materials. Examples of transparent conductive materials include indium tin oxide (ITO), tin oxide (SnO ２Examples of suitable conductive materials include fluorine-doped tin oxide (FTO), aluminum-doped zinc oxide (AZO), indium zinc oxide (IZO), and gallium-doped zinc oxide (GZO). The film may be formed by a known method. For example, sputtering, CVD, or vapor deposition may be used. The film thickness of the first electrode 2 may be, for example, 30 nm to 1000 nm. A transparent conductive material refers to a material that, even if its physical properties are non-transparent at a certain thickness, can become transparent depending on the thickness of the material, and therefore can be used as a conductive film on the light-receiving surface side of the solar cell 10. Note that the term "layer" or "film" does not specify thickness or width, and includes patterned or island-shaped structures and structures with portions of different thicknesses. Preferably, the layer or film has a substantially constant thickness. Unless otherwise specified, the terms "approximately" and "approximately" mean that variations within the range of manufacturing error are permitted, and preferably, variations of plus or minus 15% of the numerical value are permitted. In this disclosure, unless otherwise specified, thickness, width, etc. are confirmed by cross-sectional observation. For example, SEM observation is performed by observing a single 400 nm-wide cross-sectional SEM image. It is sufficient to confirm the thickness, width, etc. within that range; it is not necessary to confirm all cross sections. In other words, a "substantially constant thickness" can be defined as a thickness that is within a range of plus or minus 15% of the average thickness in a single 400 nm-wide cross-sectional SEM image. Note that the transparent conductive film does not necessarily have to be transparent. In other words, even if there is a transparent portion in the solar cell 10, the photoelectric conversion function is ensured, and the conductive film does not necessarily have to be transparent.

[0021] The first electrode 2 is provided on the substrate 1 and connected to the electron transport layer 3 .

[0022] [Electron Transport Layer] The electron transport layer 3 has a function of transporting electrons generated in the light absorbing layer 4. Here, for example, it transports electrons generated in the light absorbing layer 4 to the first electrode 2. Furthermore, it is preferable that the electron transport layer 3 has a function of blocking holes generated in the light absorbing layer 4. The electron transport layer 3 naturally has this function as long as it is disposed between the first electrode 2 and the light absorbing layer 4 of the solar cell 10, and there is no need to confirm this function as long as the solar cell 10 functions when disposed between the first electrode 2 and the light absorbing layer 4. The electron transport layer 3 preferably contains a material that easily transports electrons generated in the light absorbing layer 4 to the first electrode 2. Note that a hole blocking layer may be used instead of the electron transport layer.

[0023] The electron transport layer 3 may be made of, for example, tin oxide, titanium oxide, zinc oxide, or the like. The layer thickness may be, for example, 10 nm to 200 nm, but is not limited thereto. The layer may be formed by a known method. For example, a sputtering method, a die coating method, a screen printing method, or the like may be used.

[0024] [Light-Absorbing Layer] The light-absorbing layer 4 is a layer that absorbs light and generates electrons and holes. The light-absorbing layer 4 preferably contains a perovskite compound. The thickness of the light-absorbing layer 4 is preferably 500 nm or more and 2 μm or less, and more preferably 400 nm or more and 600 nm or less. It is self-evident that the light-absorbing layer 4 absorbs light and generates electrons and holes as long as the solar cell functions as a solar cell, and no confirmation is required. As long as a material having a light-absorbing function is included, the light-absorbing layer 4 can be considered to absorb light and generate electrons and holes.

[0025] The perovskite compound contained in the light absorbing layer 4 has the general formula: ABX ３It is preferable that the light absorbing layer is composed of a compound (perovskite compound) represented by the formula (1). However, while the composition ratio of each element is preferably 1:1:3, it is not necessarily 1:1:3. The content of each element may be varied as appropriate, and each constituent element does not necessarily have to be of a single type. As long as the light absorbing layer has a photoelectric conversion function, there is a degree of freedom in the configuration as described above. In general formula (1), A is an organic molecule (including an organic group or an organic cation), an inorganic atom or molecule (including an inorganic group or an inorganic cation), or a combination thereof; B is a metal atom or molecule (including a metal cation); and X is a halogen atom or molecule or a chalcogen atom or molecule (including a halogen anion or a chalcogen anion). In general formula (1), the three Xs may be the same or different from each other.

[0026] When contained in a light absorbing layer, a perovskite compound can absorb light and convert it into electricity, and this fact should be taken into consideration. That is, a perovskite compound can be confirmed by, for example, detecting organic molecules, metal atoms, and halogen atoms. Furthermore, a perovskite compound can be confirmed by detecting elements corresponding to A, B, and X, as long as the light absorbing layer has a photoelectric conversion function. For example, molecules containing carbon, nitrogen, and hydrogen are suitable as organic molecules, and therefore, carbon, nitrogen, hydrogen, a metal element, and a halogen element or chalcogen element can be detected. Alternatively, a perovskite compound can be confirmed by detecting A, B, and X, for example, by detecting inorganic atoms, a metal atom, and a halogen atom. Furthermore, a perovskite compound can be confirmed by detecting elements corresponding to A, B, and X, as long as the light absorbing layer has a photoelectric conversion function. For example, cesium or rubidium is suitable as the inorganic atom, and therefore, cesium or rubidium, a metal element, and a halogen or chalcogen can be detected. Furthermore, it is not necessary to confirm that the light absorbing layer 4 is a perovskite compound, since it is a natural consequence that the light absorbing layer 4 must have a crystalline structure in order to have a photoelectric conversion function. The light absorbing layer 4 may also contain compounds other than perovskite compounds.

[0027] The light-absorbing layer 4 may contain an organic-inorganic hybrid compound. An organic-inorganic hybrid compound refers to a compound containing an inorganic material and an organic material. Solar cells using perovskite compounds, which are organic-inorganic hybrid compounds, are also called organic-inorganic hybrid solar cells. "Organic" typically refers to a material composed of multiple carbon atoms. Note that graphite, graphene, carbon nanowires, carbon nanofibers, carbon nanotubes, and carbon materials such as carbon and carbon black that function as electrodes are not considered organic. In other words, organic refers to materials that contain multiple carbon atoms as one of their constituent elements, excluding carbon materials such as graphite. "Inorganic" refers to materials that are not organic. In other words, organic-inorganic hybrid compounds include materials that contain multiple carbon atoms as one of their constituent elements, and materials that do not contain multiple carbon atoms as constituent elements, such as metal atoms, halogen atoms, or chalcogen atoms.

[0028] In general formula (1), examples of the organic molecule represented by A include alkylamine, alkylammonium, and nitrogen-containing heterocyclic compounds. In the perovskite compound (1), the organic molecule represented by A may be only one type of organic molecule, or may be two or more types of organic molecules.

[0029] Examples of alkylamines include methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, dipentylamine, dihexylamine, trimethylamine, triethylamine, tripropylamine, tributylamine, tripentylamine, trihexylamine, ethylmethylamine, methylpropylamine, butylmethylamine, methylpentylamine, hexylmethylamine, ethylpropylamine, and ethylbutylamine.

[0030] Alkylammonium is an ionized product of the above-mentioned alkylamine. Examples of alkylammonium include methylammonium (CH３ NH ３ ), ethylammonium, propylammonium, butylammonium, pentylammonium, hexylammonium, dimethylammonium, diethylammonium, dipropylammonium, dibutylammonium, dipentylammonium, dihexylammonium, trimethylammonium, triethylammonium, tripropylammonium, tributylammonium, tripentylammonium, trihexylammonium, ethylmethylammonium, methylpropylammonium, butylmethylammonium, methylpentylammonium, hexylmethylammonium, ethylpropylammonium, and ethylbutylammonium.

[0031] Examples of the nitrogen-containing heterocyclic compound include imidazole, azole, pyrrole, aziridine, azirine, azetidine, azeto, azole, imidazoline, and carbazole. The nitrogen-containing heterocyclic compound may be an ionized compound. As the nitrogen-containing heterocyclic compound that is an ionized compound, it is preferable to use phenethylammonium.

[0032] In general formula (1), the organic molecule represented by A is preferably methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, methylammonium, ethylammonium, propylammonium, butylammonium, pentylammonium, hexylammonium, or phenethylammonium, more preferably methylamine, ethylamine, propylamine, methylammonium, ethylammonium, or propylammonium, and even more preferably methylammonium.

[0033] In general formula (1), examples of the metal atom represented by B include lead, tin, zinc, titanium, antimony, bismuth, nickel, iron, cobalt, silver, copper, gallium, germanium, magnesium, calcium, indium, aluminum, manganese, chromium, molybdenum, and europium. In the perovskite compound, the metal atom represented by B may be only one type of metal atom, or may be two or more types of metal atoms. From the viewpoint of improving the light absorption properties and charge generation properties of the perovskite compound, the metal atom represented by B is preferably a lead atom.

[0034] In general formula (1), examples of the halogen atom represented by X include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. In the perovskite compound, the halogen atom represented by X may be one type of halogen atom or two or more types of halogen atoms. From the viewpoint of narrowing the energy band gap of the perovskite compound, the halogen atom represented by X is preferably an iodine atom. Specifically, of the three Xs, it is preferable that at least one X represents an iodine atom, and it is more preferable that all three Xs represent iodine atoms.

[0035] The perovskite compound may be a compound represented by the general formula "CH ３ NH ３ PbX ３ (wherein X represents a halogen atom)) is preferably used, and ３ NH ３ PbI ３ It is more preferable to use a perovskite compound represented by the general formula "CH ３ NH ３ PbX ３ " (particularly, compounds represented by CH ３ NH ３ PbI ３ By using the above-mentioned cations, conduction electrons and holes can be generated more efficiently in the perovskite compound, and as a result, the conversion efficiency of the solar cell 10 can be further improved.

[0036] The perovskite layer contains a perovskite material having an energy level of the valence band maximum (VBM) in the range of −5.1 eV to −5.7 eV and an energy level of the conduction band minimum (CBM) in the range of −3.5 eV to −4.0 eV. Such a perovskite layer can be suitably used in the solar cell 10 according to the present embodiment. Here, the energy levels of the valence band maximum and the conduction band minimum are negative because the vacuum level is set to 0 and energy levels below this vacuum level are expressed as negative values. However, in actual measurements, electron affinity and ionization energy are measured. Therefore, the absolute value of the difference between the vacuum level and the energy level of the bottom of the conduction band can be rephrased as the electron affinity (or its absolute value), and the absolute value of the difference between the vacuum level and the energy level of the top of the valence band can be rephrased as the ionization potential (or its absolute value). Here, the energy level of the bottom of the conduction band and the energy level of the top of the valence band are generally expressed as deep and shallow to indicate whether they are high or low. When referring to the energy level of the bottom of the conduction band or the energy level of the top of the valence band, "deep" means "the corresponding electron affinity or ionization energy is large or far from the vacuum level," while when referring to the energy level of the bottom of the conduction band or the energy level of the top of the valence band, "shallow" means "the corresponding electron affinity or ionization energy is small or close to the vacuum level."

[0037] [Hole Transport Layer] The hole transport layer 5 has a function of transporting holes generated in the light absorbing layer 4. Here, for example, the hole transport layer 5 transports holes to the second electrode 6. Furthermore, it is preferable that the hole transport layer 5 has a function of blocking electrons generated in the light absorbing layer 4. The hole transport layer 5 naturally has a hole transport function as long as it is disposed between the light absorbing layer 4 and the second electrode 6 of the solar cell 10, and as long as it is disposed on the hole transport side and the solar cell 10 has a photoelectric conversion function, it is not necessary to confirm the hole transport function. In other words, the hole transport layer 5 means one that is disposed on the hole transport side of the light absorbing layer 4.

[0038] The hole transport layer 5 may be formed of a material selected from the group consisting of PTAA (Poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine]), poly-TPD (Poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)-benzidine], N,N'-bis( Polymer organic materials such as spiro-OMeTAD (N ２ , N ２ , N ２ ', N ２ ', N ７ , N ７ , N ７ ', N ７ '-octakis(4-methoxyphenyl)-9,9'-spirobi[9H-fluorene]-2,2',7,7'-tetraamine), 5-AVAI (5-Aminopentanoic Acid Hydroiodide Homopiperidinic Acid Hydroiodide), 5-aminopentanoic acid hydroiodide, 3-apy (3-aminopyridine), 3-aminopyridine, MeO-2PACz ([2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid), 2PACz ([2-(9H-carbazol-9-yl)ethyl]phosphonic acid), and other low molecular weight organic materials can be used. The hole transport layer 5 can be formed by coating and drying a solution of the compound dissolved in a solvent. A polyamino acid for forming the buffer layer 51 described later may be added to this solution. The thickness of the hole transport layer 5 may be, for example, 40 nm to 600 nm.

[0039]

[0040] In this embodiment, the hole transport layer 5 is provided between the light absorbing layer 4 and the hole transport layer 5 via a buffer layer 51. The buffer layer 51 is made of a polyamino acid obtained by polymerizing amino acids having a charged side chain of a reactive functional group. As shown below, the buffer layer 51 is formed by polymerizing an amino acid having a charged side chain of a reactive functional group from a monomer. During polymerization, the polyamino acid consumes a pair of an amino group and a carboxyl group, resulting in a state in which the polyamino acid has a peptide bond equal to the number of polymerization units, and a reactive functional group equal to the number of polymerization units remains.

[0041]

[0042] In this case, the hole transport layer 5 is formed by applying a polyamino acid that already has a polymer structure to the buffer layer 51 in contact with the light absorbing layer 4. This results in a dense structure, preventing the formation of gaps that allow water molecules and the like to penetrate into the light absorbing layer 4 and improving durability. In addition, the reactive functional groups provided on the charged side chains of the monomers provide additional performance. For example, when the reactive functional group is an amino group, amine accumulation, particularly accumulation of primary amine amino groups, is high. It is already understood that high amine accumulation increases photoelectric conversion efficiency, and when this is a primary amine amino group, the photoelectric conversion efficiency is further increased. Furthermore, when the reactive functional group is a carboxyl group or a hydroxyl group, these carboxyl groups or hydroxyl groups react with the hole transport layer 5 and the light absorbing layer 4, thereby increasing the adhesion of the buffer layer 51 to the hole transport layer 5 and the light absorbing layer 4.

[0043] Examples of polyamino acids used in this buffer layer 51, which are obtained by polymerizing amino acids having charged side chains with reactive functional groups, include polyamino acids whose monomers are amino acids having polar, uncharged side chains such as asparagine, cysteine, glutamine, serine, and threonine; polyamino acids whose monomers are basic amino acids having charged side chains such as arginine, histidine, and lysine; polyamino acids whose monomers are acidic amino acids having charged side chains such as aspartic acid and glutamic acid; polyamino acids whose monomers are aliphatic amino acids having hydrophobic side chains such as glycine, alanine, isoleucine, leucine, methionine, and valine; polyamino acids whose monomers are aromatic amino acids having hydrophobic side chains such as phenylalanine, tryptophan, and tyrosine; and polyamino acids whose monomers are other amino acids such as proline.

[0044]

[0045] The molecular weight of this polyamino acid is 100,000 or less, preferably 1,000 to 100,000, and more preferably 2,000 to 5,000. Furthermore, the degree of polymerization can be any value as long as it is 2 or greater, and it may be a polymer with a degree of polymerization of up to about 500. It may also be an oligomer with a degree of polymerization of up to about 20. Furthermore, these polyamino acids may be a combination of multiple amino acid monomers with different reactive functional group-containing charged side chains, different degrees of polymerization, or different molecular weights.

[0046] Among these polyamino acids, when polyarginine and polylysine are used in particular, the layer can be made dense due to the polymer structure, and since they have amino groups as charged side chains, the accumulation of amines, particularly the accumulation of amino groups which are primary amines, is high, and as a result, the photoelectric conversion efficiency between the light absorbing layer 4 and the second electrode 6 can be increased.

[0047] In the buffer layer 51 containing this polyamino acid, or in the hole transport layer 5, buffer layer 31, and electron transport layer 3 containing this polyamino acid as described below, the structure of the polyamino acid and the amino acid can be distinguished by combining the following analytical methods, for example. Extraction of the analysis area: A specific layer is separated from the solar cell 10 by cutting, peeling, or other methods. If the separated solid (powder) can be analyzed, the excess components are dissolved in a solvent and removed, and then the subsequent analysis is performed. Amino group detection method: The amount of free residues is quantified by color reaction, fluorescence reaction, or other methods with a test reagent. Distinguishing between polymer-derived and monomer-derived amino acids: The presence or absence of polymeric moieties is confirmed using FT-IR, HPLC, LC / MS, NMR, etc., and the polymer is hydrolyzed and then separated and analyzed by chromatography, allowing for identification of the amino acid type.

[0048] [Second Electrode] The second electrode 6 is conductive and may be a counter electrode on the non-light-receiving side of the solar cell 10 or on the side opposite the light-receiving side, or may be a transparent electrode that is light-transmitting like the first electrode 1. When the second electrode 6 is used as a counter electrode, it is preferable that the second electrode 6 has a light-reflecting function. In this case, the second electrode 6 preferably contains a metal or alloy containing at least one selected from the group consisting of Au, Ag, Cu, and Al. The film thickness of the second electrode 6 may be, for example, 50 nm to 300 nm. Note that the second electrode 6 does not necessarily need to have a light-reflecting function. When the second electrode 6 is used as a transparent electrode, the same material as the first electrode 1 described above may be used.

[0049] The second electrode 6 is connected to the hole transport layer 5 .

[0050] As described above, the solar cell 10 according to the first embodiment includes the first electrode 2, the electron transport layer 3 formed on the first electrode 1, the light absorbing layer 4 formed on the electron transport layer 3, the hole transport layer 5 formed on the light absorbing layer 4, and the second electrode 6 formed on the hole transport layer 5, with the hole transport layer 5 being provided on the light absorbing layer 4 via a buffer layer 51. This makes the buffer layer 51 dense at the boundary between the light absorbing layer 4 and the hole transport layer 5, preventing the formation of gaps that allow water molecules and the like to penetrate into the light absorbing layer 4 and improving the durability between the light absorbing layer 4 and the hole transport layer 5. Furthermore, depending on the polyamino acid used, the buffer layer 51 can improve the photoelectric conversion rate of the light absorbing layer 4 and increase the adhesion between the light absorbing layer 4 and the hole transport layer 5, thereby improving performance.

[0051] <Second embodiment> Figure 1(b) is a cross-sectional view of a solar cell 10 according to a second embodiment. The solar cell 10 according to the second embodiment differs from the solar cell 10 according to the first embodiment shown in Figure 1(a) in the configuration of the hole transport layer 5. That is, in the solar cell 10 according to the second embodiment, the hole transport layer 5 does not constitute the buffer layer 51, and the polyamino acid that constitutes the buffer layer 51 is included in the entire hole transport layer 5 to constitute the hole transport layer 5.

[0052] In the solar cell 10 according to the second embodiment, the inclusion of the polyamino acid makes it possible to make the entire hole transport layer 5 dense, and the reactive functional groups provided on the charged side chains of the polyamino acid can improve the photoelectric conversion efficiency of the light absorbing layer 4 and improve the adhesion between the light absorbing layer 4 and the hole transport layer 5.

[0053] <Third Embodiment> Figure 1(c) is a cross-sectional view of a solar cell 10 according to a third embodiment. The solar cell 10 according to the third embodiment has a so-called reverse junction planar structure, and is similar to the solar cell 10 according to the first embodiment shown in Figure 1(a) above, except for the reverse junction planar structure. The solar cell 10 includes a second electrode 6 provided on a base 1, a hole transport layer 5 provided on the second electrode 6, a light absorbing layer 4 provided on the hole transport layer 5 via a buffer layer 51, an electron transport layer 3 provided on the light absorbing layer 4, and a first electrode 2 provided on the electron transport layer 3. Identical components are designated by the same reference numerals, and descriptions thereof will be omitted.

[0054] <Fourth Embodiment> Figure 1(d) is a cross-sectional view of a solar cell 10 according to a fourth embodiment. The solar cell 10 according to the fourth embodiment has a so-called reverse junction planar structure, and is similar to the solar cell 10 according to the second embodiment shown in Figure 1(b) above, except for the reverse junction planar structure. The solar cell 10 includes a second electrode 6 provided on a base 1, a hole transport layer 5 provided on the second electrode 6, a light absorbing layer 4 provided on the hole transport layer 5, an electron transport layer 3 provided on the light absorbing layer 4, and a first electrode 2 provided on the electron transport layer 3. Identical components are designated by the same reference numerals, and descriptions thereof will be omitted.

[0055] Fifth Embodiment Fig. 1(e) is a cross-sectional view of a solar cell 10 according to a fifth embodiment. The solar cell 10 according to the fifth embodiment is similar in configuration to the solar cell 10 according to the first embodiment shown in Fig. 1(a) except for the configurations of the electron transport layer 3 and the hole transport layer 5. Here, only the differences will be described, and the same components will be denoted by the same reference numerals and description thereof will be omitted. In the solar cell 10 according to the fifth embodiment, the electron transport layer 3, which is the other charge transport layer different from the hole transport layer 5, has a buffer layer 31 and is in contact with the light absorbing layer 4 via this buffer layer 31. On the other hand, the hole transport layer 5 does not have a buffer layer 51.

[0056] The configuration of the electron transport layer 3 is the same as that of the electron transport layer 3 of the solar cell 10 according to the first embodiment shown in Fig. 1(a). However, the electron transport layer 3 of the solar cell 10 according to the fifth embodiment has a buffer layer 31, and is in contact with the light absorbing layer 4 via this buffer layer 31. This buffer layer 31, like the buffer layer 51 of the hole transport layer 5 of the solar cell 10 according to the first embodiment, is made of a polyamino acid obtained by polymerizing an amino acid having a charged side chain of a reactive functional group.

[0057] The hole transport layer 5 does not have a buffer layer 51 , and the hole transport layer 5 is provided in contact with the light absorption layer 4 .

[0058] In the solar cell 10 according to the fifth embodiment, the inclusion of polyamino acid makes the buffer layer 31 at the boundary between the light absorbing layer 4 and the electron transport layer 3 dense, preventing the formation of gaps that allow water molecules and the like to penetrate into the light absorbing layer 4 and increasing the durability between the light absorbing layer 4 and the electron transport layer 3. Furthermore, depending on the polyamino acid used, the buffer layer 31 can improve the photoelectric conversion rate of the light absorbing layer 4 and increase the adhesion between the light absorbing layer 4 and the electron transport layer 3, thereby improving performance.

[0059] <Sixth embodiment> Figure 1(f) is a cross-sectional view of a solar cell 10 according to a sixth embodiment. The solar cell 10 according to the sixth embodiment differs from the solar cell 10 according to the fifth embodiment shown in Figure 1(e) in the configuration of the electron transport layer 3. That is, in the solar cell 10 according to the sixth embodiment, the electron transport layer 3 does not constitute the buffer layer 31, and the polyamino acid that constituted the buffer layer 31 is contained in the entire electron transport layer 3 to constitute the electron transport layer 3.

[0060] In the solar cell 10 according to the sixth embodiment, the inclusion of the polyamino acid makes it possible to make the entire hole transport layer 5 dense, and the reactive functional groups provided on the charged side chains of the polyamino acid can improve the photoelectric conversion efficiency of the light absorbing layer 4 and improve the adhesion between the light absorbing layer 4 and the hole transport layer 5.

[0061] Seventh Embodiment Figure 1(g) is a cross-sectional view of a solar cell 10 according to a seventh embodiment. The solar cell 10 according to the seventh embodiment has a so-called reverse junction planar structure, and is similar to the solar cell 10 according to the fifth embodiment shown in Figure 1(e) above, except for the reverse junction planar structure. The solar cell 10 includes a second electrode 6 provided on a base 1, a hole transport layer 5 provided on the second electrode 6, a light absorbing layer 4 provided on the hole transport layer 5, an electron transport layer 3 provided on the light absorbing layer 4, and a first electrode 2 provided on the electron transport layer 3. Identical components are designated by the same reference numerals, and descriptions thereof will be omitted.

[0062] Eighth Embodiment Figure 1(h) is a cross-sectional view of a solar cell 10 according to an eighth embodiment. The solar cell 10 according to the eighth embodiment has a so-called reverse junction planar structure, and is similar to the solar cell 10 according to the fifth embodiment shown in Figure 1(e) above, except for the reverse junction planar structure. The solar cell 10 includes a second electrode 6 provided on a base 1, a hole transport layer 5 provided on the second electrode 6, a light absorbing layer 4 provided on the hole transport layer 5, an electron transport layer 3 provided on the light absorbing layer 4, and a first electrode 2 provided on the electron transport layer 3. Identical components are designated by the same reference numerals, and descriptions thereof will be omitted.

[0063] <Ninth embodiment> Fig. 2(a) is a cross-sectional view of a solar cell 10 according to a ninth embodiment. The solar cell 10 according to the ninth embodiment is similar to the solar cell 10 according to the first embodiment shown in Fig. 1(a) except for the configuration of the electron transport layer 3. Here, only the differences will be described, and the same components will be denoted by the same reference numerals and description thereof will be omitted. In the solar cell 10 according to the ninth embodiment, the electron transport layer 3 is configured by including a polyamino acid in the electron transport layer 3, similar to the electron transport layer 3 shown in Fig. 1(f).

[0064] <Tenth Embodiment> Fig. 2(b) is a cross-sectional view of a solar cell 10 according to a tenth embodiment. The solar cell 10 according to the tenth embodiment is similar in configuration to the solar cell 10 according to the second embodiment shown in Fig. 1(b) except for the configuration of the electron transport layer 3. Here, only the differences will be described, and the same components will be denoted by the same reference numerals and description thereof will be omitted. In the solar cell 10 according to the tenth embodiment, the electron transport layer 3 has a buffer layer 31, similar to the electron transport layer 3 shown in Fig. 1(e), and is in contact with the light absorbing layer 4 via this buffer layer 31.

[0065] Eleventh Embodiment Fig. 2(c) is a cross-sectional view of a solar cell 10 according to an eleventh embodiment. The solar cell 10 according to the eleventh embodiment has a so-called reverse junction planar structure, and is similar to the solar cell 10 according to the ninth embodiment shown in Fig. 2(a) described above, except for the reverse junction planar structure. The same components are denoted by the same reference numerals, and descriptions thereof will be omitted.

[0066] <Twelfth embodiment> Figure 2(d) is a cross-sectional view of a solar cell 10 according to a twelfth embodiment. The solar cell 10 according to the twelfth embodiment has a so-called reverse junction planar structure, and other than the reverse junction planar structure, it is the same as the solar cell 10 according to the tenth embodiment shown in Figure 2(b) described above. The same components are given the same reference numerals and descriptions thereof will be omitted.

[0067] <Thirteenth embodiment> Figure 2(e) is a cross-sectional view of a solar cell 10 according to a thirteenth embodiment. The solar cell 10 according to the thirteenth embodiment is similar in configuration to the solar cell 10 according to the ninth embodiment shown in Figure 2(a) except for the configuration of the electron transport layer 3. Here, only the differences will be described, and the same components will be denoted by the same reference numerals and description thereof will be omitted. In the solar cell 10 according to the thirteenth embodiment, the electron transport layer 3 has a buffer layer 31, similar to the electron transport layer 3 shown in Figure 1(e), and is in contact with the light absorbing layer 4 via this buffer layer 31.

[0068] <Fourteenth embodiment> Figure 2(f) is a cross-sectional view of a solar cell 10 according to a fourteenth embodiment. The solar cell 10 according to the fourteenth embodiment is similar to the solar cell 10 according to the tenth embodiment shown in Figure 2(b) except for the configuration of the electron transport layer 3. Here, only the differences will be described, and the same components will be denoted by the same reference numerals and description thereof will be omitted. In the solar cell 10 according to the fourteenth embodiment, the electron transport layer 3 is configured by including a polyamino acid throughout the entire electron transport layer 3, similar to the electron transport layer 3 shown in Figure 1(f).

[0069] <Fifteenth embodiment> Figure 2(g) is a cross-sectional view of a solar cell 10 according to a fifteenth embodiment. The solar cell 10 according to the fifteenth embodiment has a so-called reverse junction planar structure, and is similar to the solar cell 10 according to the thirteenth embodiment shown in Figure 2(e) above, except for the reverse junction planar structure. The same components are given the same reference numerals, and descriptions thereof will be omitted.

[0070] <Sixteenth embodiment> Figure 2(h) is a cross-sectional view of a solar cell 10 according to a sixteenth embodiment. The solar cell 10 according to the sixteenth embodiment has a so-called reverse junction planar structure, and is similar to the solar cell 10 according to the tenth embodiment shown in Figure 2(f) above, except for the reverse junction planar structure. The same components are given the same reference numerals, and descriptions thereof will be omitted.

[0071] 2. Method for Manufacturing Solar Cell A method for manufacturing each of the solar cells 10 described above will be described using the solar cell 10 shown in the first embodiment in FIG. 1(a) as an example.

[0072] The method for manufacturing the solar cell 10 includes the steps of forming an electron transport layer 3 on a first electrode 2, forming a light absorbing layer 4 of a perovskite compound on the electron transport layer 3, forming a hole transport layer 5 on the light absorbing layer 4 via a buffer layer 51, and forming a second electrode 6 on the hole transport layer 5.

[0073] The first electrode 2 is formed on the substrate 1 by sputtering, vacuum deposition, or the like. The electron transport layer 3 formed on this first electrode 2 is formed by applying a coating liquid containing dissolved constituent materials of the electron transport layer 3 onto the first electrode 2, and then heating and drying to evaporate the solvent from the coating liquid, thereby forming a film. At this time, the method for applying the coating liquid is not limited to spin coating, dip coating, inkjet printing, screen printing, slit die coating, or the like, and any suitable coating method can be selected. The light absorbing layer 4 formed on the electron transport layer 3 is also formed by applying a coating liquid containing dissolved constituent materials of the light absorbing layer 4 onto the electron transport layer 3, and then heating and drying to evaporate the solvent from the coating liquid, similar to the electron transport layer 3, thereby forming a film. At this time, the coating method is also not limited to the above, and any suitable coating method can be selected. Next, the hole transport layer 5 is formed on the light absorbing layer 4. In this process, a solution dissolving the polyamino acid that constitutes the buffer layer 51 is first applied to the light absorbing layer 4, and the solution is heated and dried to evaporate the solvent from the coating solution, forming the buffer layer 51. Thereafter, a coating solution dissolving the constituent materials of the hole transport layer 5 is applied to the buffer layer 51, and the solution is heated and dried to evaporate the solvent from the coating solution, forming the hole transport layer 5. Then, the second electrode 6 is formed on the hole transport layer 5 by sputtering, vacuum deposition, or the like, thereby forming the solar cell 10. The above is an example of forming the solar cell 10 of the first embodiment, and the components are basically formed in the order in which they are stacked on the base 1.

[0074] 1(b), in the case where only the hole transport layer 5 is provided without providing the buffer layer 51, the polyamino acid constituting the buffer layer 51 is mixed and dissolved in a coating liquid in which the constituent materials of the hole transport layer 5 are dissolved, and the solution is applied to the light absorbing layer 4 and heated and dried to evaporate the solvent of the coating liquid, thereby forming the hole transport layer 5. The same applies to the case where an electron transport layer 3 having a buffer layer 31 and an electron transport layer 3 without a buffer layer 31 are formed. In the case where an electron transport layer 3 having a buffer layer 31 is formed, a solution in which the polyamino acid constituting the buffer layer 31 is dissolved is applied to the light absorbing layer 4 and heated and dried to evaporate the solvent of the coating liquid, thereby forming the buffer layer 31. Thereafter, a coating liquid in which the constituent materials of the electron transport layer 3 are dissolved is applied to the buffer layer 31, and the coating liquid is heated and dried to evaporate the solvent of the coating liquid, thereby forming the electron transport layer 3. When forming the electron transport layer 3 without the buffer layer 31, the polyamino acid that constitutes the buffer layer 31 is mixed and dissolved in a coating liquid in which the constituent materials of the electron transport layer 3 are dissolved, and this is applied onto the light absorbing layer 4 and heated and dried to remove the solvent from the coating liquid, thereby forming the electron transport layer 3. When manufacturing the solar cell 10 of the second embodiment to the solar cell 10 of the sixteenth embodiment, they can also be manufactured through the steps in the same manner as above.

[0075] 3. Solar Cell Module and Method for Manufacturing Solar Cell Module Figure 3 is a schematic cross-sectional view of a solar cell module 100 (series-connected solar cell) including solar cell 10 according to the present embodiment. As shown in Figure 3, solar cell module 100 according to the present embodiment is produced by integrating solar cell 10 described above. As described above, by forming buffer layers 31, 51 containing polyamino acid in solar cell 10, and by forming electron transport layer 3 and hole transport layer 5 containing polyamino acid, it is possible to improve the durability and conversion efficiency of solar cell 10.

[0076] 3 , the solar cell module 100 according to the present embodiment includes a base 1, a first electrode 2 provided on the base 1, an electron transport layer 3 provided on the first electrode 2, a light absorbing layer 4 provided on the electron transport layer 3, a hole transport layer 5 provided on the light absorbing layer 4, a second electrode 6 provided on the hole transport layer 5, a second barrier layer 72 provided on the second electrode 6, and a back surface substrate 74 provided on the second barrier layer 72, with a buffer layer 51 provided between the light absorbing layer 4 and the hole transport layer 5. The solar cell module 100 shown in FIG. 3 is a solar cell module 100 in which the base 1 is transparent glass.

[0077] 4 and 5 are schematic cross-sectional views of a solar cell module 110 including a solar cell 10 (variations 1 and 2) according to the present embodiment, in which the base 1 is a transparent resin such as an organic film. As shown in FIGS. 4 and 5 , the solar cell module 110 according to the present embodiment includes a base 1, a first barrier layer 71 provided on the base 1, a first electrode 2 provided on the first barrier layer 71, an electron transport layer 3 provided on the first electrode 2, a light absorbing layer 4 provided on the electron transport layer 3, a hole transport layer 5 provided on the light absorbing layer 4, a second electrode 6 provided on the hole transport layer 5, a second barrier layer 72 provided on the second electrode 6, a third barrier layer 73 provided on the second barrier layer 72, and a back substrate 74 provided on the third barrier layer 73. A buffer layer 51 is provided between the light absorbing layer 4 and the hole transport layer 5. The first barrier layer 71 is a layer made of a material with high gas barrier properties. The second barrier layer 72 is a dense inorganic material layer, and the third barrier layer 73 is a layer made of a material with high gas barrier properties.

[0078] 4 and 5, the second barrier layer 72 is provided so as to cover the side portions of the hole transport layer 5 and the second electrode 6, and also so as to cover the upper portion of the second electrode 6. The second barrier layer 72 covers the upper surface and side surfaces of each of the solar cell cells 10.

[0079] 3, 4, and 5, the hole transport layer 5 covers the top and side of the light absorption layer 4. The second electrode 6 covers the top and one side of the hole transport layer 5. The second electrode 6 extends from the top to the side of the hole transport layer 5 and is connected to the top of the first electrode 2 of an adjacent solar cell 10, and in this way, the adjacent solar cell 10 is connected in series.

[0080] The solar cell modules 100, 110 of the present embodiment include a plurality of solar cells 10-10, a first terminal 81, and a second terminal 82, and the plurality of solar cells 10-10 are connected in series. Of the plurality of solar cells 10-10 connected in series, the solar cell 10 at one end is connected to the first terminal 81, and the solar cell 10 at the other end is connected to the second terminal 82. There is no particular limitation on the number of solar cells 10-10 connected in series, as long as there is a plurality.

[0081] The base 1 is the substrate of the solar cell modules 100, 110. The base 1 may be a transparent glass substrate as shown in Fig. 3, or a transparent organic film as shown in Figs. 4 and 5. This allows light to enter the interior of the solar cell 10. When the base 1 is a flexible organic film, the solar cell module 110 becomes a flexible solar cell module.

[0082] Specific examples of the material for the organic film that will become the substrate 1 include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), polyetherimide (PEI), polyamideimide (PAI), and polyethylene naphthalate (PEN), but other resins can also be used as long as they satisfy the requirements. The thickness of the organic film that will become the substrate 1 is preferably 50 μm to 100 μm.

[0083] When the base 1 is a transparent organic film, a first barrier layer 71 may be provided on one of the +Y-direction major surfaces of the base 1, as shown in FIGS. 4 and 5 . The first barrier layer 71 is a layer made of a material with high gas barrier properties. This prevents internal deterioration of the solar cell 10 due to moisture and oxygen in the air. The first barrier layer 71 is also a layer made of an insulating material. This prevents leakage current. The thickness of the first barrier layer 71 can be several tens of nanometers to 100 nanometers. This allows the first barrier layer 71 to have light-transmitting properties. Furthermore, the solar cell 10 and the solar cell module 110 can have flexibility. Specific examples of materials for the first barrier layer 71 include silicon oxide and aluminum oxide. As long as the first barrier layer 71 has gas barrier properties, insulating properties, and light-transmitting properties, other oxides and insulators can also be used as the material for the first barrier layer 71. Typical methods for forming the first barrier layer 71 include sputtering and vacuum deposition.

[0084] The first electrode 2 is provided on the substrate 1 (on the first barrier layer 71 in the examples shown in FIGS. 4 and 5 ) and extracts a current generated by the photovoltaic power of the solar cell 10. The first electrode 2 is made of a conductive transparent material such as aluminum-doped zinc oxide (AZO), indium zinc oxide (IZO), gallium-doped zinc oxide (GZO), fluorine-doped tin oxide (FTO), or indium tin oxide (ITO). The sheet resistance of the first electrode 2 is preferably 10 Ω / sq or less, and the light transmittance of the first electrode 2 is preferably 30% or more. Examples of methods for forming the first electrode 2 include sputtering and vacuum deposition.

[0085] When a plurality of solar cells 10 are provided on the base 1, the first electrode 2 formed on the base 1 is divided for each solar cell 10. For example, the solar cell modules 100, 110 shown in FIGS. 3, 4, and 5 include five solar cells 10, and therefore the first electrode 2 is divided, and five first electrodes 2 are formed. The groove O separating two adjacent first electrodes 2 may be filled with a light absorbing layer 4 or the like. The first electrode 2 spans two adjacent solar cells 10, 10. That is, as shown in FIGS. 3, 4, and 5, an electron transport layer 3 is formed on one first electrode 2, and a light absorbing layer 4 is formed on the other first electrode.

[0086] A first terminal 81 of the solar cell module 100, 110 is provided on the light-receiving surface side of the base 1, and a portion of the first terminal 81 penetrates the base 1 (the first barrier layer 71 in the example shown in FIGS. 4 and 5 ) and is in contact with or electrically connected to the first electrode 2 at one end of the series-connected solar cell 10. This first terminal 81 can be used to extract the current generated by the photovoltaic power of the solar cell module 100, 110. An example of a material for the first terminal 81 is a SnZn-based solder paste. Other conductive pastes and materials for the second electrode 6 can also be used as long as they meet the requirements.

[0087] After the first electrode 2 is formed on the transparent substrate 1, a cut (L1) is made in the first electrode 2 by laser scribing in order to separate and form the solar cell 10 on the substrate 1. The wavelength of the laser used is preferably in the infrared region. The cut (L1) is made in the first electrode 2, and the first electrode 2 having the cut is formed. No cut is made in the substrate 1 (first barrier layer 71 in the example shown in Figures 4 and 5). For example, a perovskite compound can be formed on the substrate 1 and the first electrode 2 in which the cut (L1) has been made by laser scribing, to form the light absorbing layer 4.

[0088] Examples of organic solvents (contained in the coating liquid) used in the coating method for forming the light-absorbing layer 4 include aromatic hydrocarbons such as toluene, xylene, mesitylene, tetralin, diphenylmethane, dimethoxybenzene, and dichlorobenzene; halogenated hydrocarbons such as dichloromethane, dichloroethane, and tetrachloropropane; ethers such as tetrahydrofuran (THF), dioxane, dibenzyl ether, dimethoxymethyl ether, and 1,2-dimethoxyethane; ketones such as methyl ethyl ketone, cyclohexanone, acetophenone, and isophorone; esters such as methyl benzoate, ethyl acetate, and butyl acetate; sulfur-containing solvents such as diphenyl sulfide; fluorine-based solvents such as hexafluoroisopropanol; aprotic polar solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide; alcohols such as methanol, ethanol, and isopropanol; and glyme-based solvents such as ethylene glycol and diethylene glycol monomethyl ether. These can be used alone or as a mixed solvent. These solvents may contain water. Among these solvents, non-halogen organic solvents are preferably used from the viewpoint of consideration for the global environment.

[0089] After the light absorbing layer 4 is formed, a cut (L2) is made in a part of the light absorbing layer 4 by laser scribing in order to connect the first electrode 2 of one of two adjacent solar cell cells 10 to the hole transport layer 5 and second electrode 6 of the other solar cell 10. The wavelength of the laser used is preferably in the visible light region. For example, the light absorbing layer 4 is formed by making the cut (L2) in the light absorbing layer 4. This laser scribing removes the light absorbing layer 4, but does not remove the first electrode 2 (first barrier layer 71 in the example shown in FIGS. 4 and 5 ).

[0090] Thereafter, the hole transport layer 5 is formed, and the second electrode 6 is formed.

[0091] The second electrode 6 is provided on the hole transport layer 5 and serves to extract the current generated by the photovoltaic power of the light absorbing layer 4 of the solar cell 10. The second electrode 6 is, for example, a metal film having a work function of 5 eV or more. When the second electrode 6 is made of a metal having a deep work function (5 eV or more), a bending of the band structure occurs at the interface between the light absorbing layer 4 and the second electrode 6, which allows for a smooth flow of electrons. The film thickness of the second electrode 6 is preferably 50 nm to 150 nm. The light absorbing layer 4 or the second electrode 6 can be formed by, for example, a sputtering film formation method or a vacuum deposition method.

[0092] After the second electrode 6 is formed, a cut (L3) is made in a part of the hole transport layer 5 and the second electrode 6 by laser scribing in order to form a series connection circuit of adjacent solar cell 10 on the base 1. Furthermore, in order to make the second barrier layer 72 function as a varistor, a cut (L3) may be made in the electron transport layer 3, the light absorption layer 4, the hole transport layer 5, and the second electrode 6. The wavelength of the laser used is preferably in the ultraviolet region. For example, the cut (L3) is made in the hole transport layer 5 and the second electrode 6, and the hole transport layer 5 and the second electrode 6 are formed. Furthermore, a cut for forming a varistor can be made. If the part with the cut (L3) functions as a varistor, the cut can be omitted.

[0093] The second barrier layer 72 is a dense inorganic material layer and is provided so as to cover the side portions of the light absorbing layer 4. The second barrier layer 72 can also be provided so as to cover the entire periphery of the light absorbing layer 4. The second barrier layer 72 can also be provided so as to cover the upper surface of the second electrode 6. This second barrier layer 72 can prevent moisture (such as water vapor) from penetrating the light absorbing layer 4, thereby preventing deterioration of the solar cell 10. Furthermore, because the second barrier layer 72 is a dense inorganic material layer, it is possible to prevent the barrier function of the second barrier layer 72 from being reduced by ultraviolet rays, temperature changes, and the like. Furthermore, the barrier properties against water vapor can also be improved by completely coating the light absorbing layer 4 with the second barrier layer 72, the first electrode 2, the base 1, and the like.

[0094] The second barrier layer 72 may also be made of a material that exhibits varistor characteristics. The second barrier layer 72 can be provided so as to be connected to the first electrode 2 and the second electrode 6, so that the second barrier layer 72 and the light absorbing layer 4 are connected in parallel. The varistor characteristics are voltage-current characteristics (current non-linearity) in which current suddenly begins to flow at a certain constant voltage. There are no particular restrictions on the material that exhibits varistor characteristics, as long as it is a material that can be used in a varistor element.

[0095] The thickness of the second barrier layer 72 can be, for example, 30 nm or more and 100 nm or less. The second barrier layer 72 is formed on the second electrode 6 after laser scribing. The second barrier layer 72 can be formed to fill the notch (L3). This allows the periphery and upper surface of the light absorbing layer 4 to be covered with the second barrier layer 72. The second barrier layer 72 can be formed to fill the notch. This allows the second barrier layer 72 to be connected to the first electrode 2 and the second electrode 6 so that the second barrier layer 72 and the light absorbing layer 4 are connected in parallel.

[0096] By connecting a part of the second barrier layer 72 in parallel to the light absorbing layer 4 as a varistor element structure, it is possible to realize a solar cell 10 that is integrally provided with a bypass diode (varistor of the second barrier layer 72). This makes it possible to prevent a decrease in power generation efficiency due to shadows on the solar cell module 110 at low cost.

[0097] The second barrier layer 72 may contain, for example, zinc oxide (ZnO) as a main material, and may contain, as additive materials, silicon oxide, aluminum oxide, titanium oxide, etc. The varistor characteristics (I=KVα, K: element-specific constant, α: voltage nonlinearity coefficient) of the second barrier layer 72 between the first electrode 2 and the second electrode 6 are preferably α=20 to 60, with a bending voltage of 2 V or higher.

[0098] The rear surface substrate 74 is a substrate disposed on the non-light-receiving surface side, and the light absorbing layer 4 is located between the substrate 1 and the rear surface substrate 74. The rear surface substrate 74 may be the substrate of the solar cell modules 100 and 110. The rear surface substrate 74 may be a glass substrate, a transparent organic film, or an opaque organic film.

[0099] When the rear substrate 74 is an organic film, a third barrier layer 73 may be provided on one of the main surfaces of the rear substrate 74, as shown in Figures 4 and 5. The third barrier layer 73 is a layer made of a material with high gas barrier properties. This makes it possible to prevent deterioration inside the solar cell 10 due to moisture, oxygen, and the like in the air. The third barrier layer 73 is also a layer made of an insulating material. This makes it possible to suppress the flow of leakage current. The film thickness of the third barrier layer 73 can be several tens of nanometers to 100 nanometers. Specific examples of materials for the third barrier layer 73 include silicon oxide and aluminum oxide.

[0100] A second terminal 82 of the solar cell module 100, 110 is formed on the organic film that serves as the rear substrate 74, and a portion of the second terminal 82 penetrates the organic film (rear substrate 74) (the third barrier layer 73 in the example shown in FIGS. 4 and 5 ) and is in contact with the second electrode 6 at the other end of the series-connected solar cell 10 or is connected via the second barrier layer 72. The first terminal 81 and the second terminal 82 can be used to extract current generated by photovoltaic power of the solar cell module 100, 110. An example of a material for the second terminal 82 is a SnZn-based solder paste. Other conductive pastes and materials for the second electrode 6 can also be used as long as they meet the requirements.

[0101] After forming the second barrier layer 72 on the second electrode 6 (and further forming a third barrier layer 73 on the second barrier layer 72), a back substrate 74 on which a second terminal 82 has been formed is attached to the second barrier layer 72 (third barrier layer 73) via a laminate sheet, followed by heat lamination to complete the solar cell module 100, 110 in which multiple solar cell cells 10 are connected in series. The laminate sheet sandwiched between the second barrier layer 72 and the back substrate 74 (third barrier layer 73) is perforated at the location where the second terminal 82 will be located. This ensures good connection between the second terminal 82 and the second barrier layer 72 during lamination. This forms a varistor between the second electrode 6 and the second terminal 82. Because a high voltage is applied between the second electrode 6 and the second terminal 82 during power generation, the varistor characteristics do not impede current extraction. Alternatively, the second electrode 6 and the second terminal 82 may be in contact with each other.

[0102] The laminate sheet may be a general laminate material, and is preferably a resin film that has a lamination temperature of 130° C. or less and is highly waterproof.

[0103] Fig. 6 is a diagram in which a schematic cross-sectional view of one solar cell 10 included in the solar cell module 100 shown in Fig. 3 is superimposed on an equivalent circuit of the solar cell 10, and Fig. 7 is an equivalent circuit of the solar cell module 100. As shown in Figs. 6 and 7, the electron transport layer 3, the light absorption layer 4, and the hole transport layer 5 can be represented by a current source 92 and a diode 93. In addition, the varistor 91 is connected to the first electrode 2 and the second electrode 6 so as to be connected in parallel with the light absorption layer 4.

[0104] 4. Uses of Solar Cells and Solar Cell Modules The solar cell 10 and solar cell modules 100, 110 constructed in this manner can be used in a wide variety of applications. In particular, when the substrate 1 is a flexible organic film, the solar cell module 110 becomes a flexible solar cell module, making it possible to apply it to curved surfaces. Moreover, it can be made lighter than when the substrate 1 is made of glass. Furthermore, the configuration of the electron transport layer 3, buffer layer 31, hole transport layer 5, and buffer layer 51, which contain polyamino acids, provides high durability and is therefore suitable for outdoor use.

[0105] As for applications, the material can be applied to the body surfaces and interiors of various transport vehicles such as trains, automobiles, ships, and aircraft, and used as part of the power used by these various transport vehicles. It can also be applied to the housing surfaces of various electrical appliances that require power, and used as part of the power used by these electrical appliances. Furthermore, it can be applied to the surfaces of various outdoor structures such as buildings, apartment buildings, warehouses, houses, viaducts, bridges, control towers, signs, and other structures, and the obtained power can be used within these structures or transmitted to be used elsewhere. Of course, it can also be used as a solar power generation system (mega solar).

[0106] Although the embodiments and examples of the present disclosure have been described in detail above, it will be readily apparent to those skilled in the art that many modifications are possible without substantially departing from the novel features and effects of the present disclosure. Therefore, all such modifications are intended to be included within the scope of the present disclosure.

[0107] For example, a term described at least once in the specification or drawings together with a different term having a broader or equivalent meaning can be replaced with that different term anywhere in the specification or drawings. Furthermore, the configurations and operations of the solar cell, the method for manufacturing the solar cell, and the solar cell module are not limited to those described in the embodiments and examples of the present disclosure, and various modifications are possible.

[0108] This application claims priority from Japanese Patent Application No. 2024-151889, filed on September 4, 2024, the entire contents of which are incorporated herein by reference. [Additional Notes] (Aspect 1) A method for manufacturing a solar cell, comprising: forming an electron transport layer on a first electrode; forming a light absorption layer of a perovskite compound on the electron transport layer; forming a hole transport layer on the light absorption layer; and forming a second electrode on the hole transport layer; or forming a hole transport layer on a second electrode; forming a light absorption layer of a perovskite compound on the hole transport layer; forming an electron transport layer on the light absorption layer; and forming a first electrode on the electron transport layer; wherein the step of forming the hole transport layer and / or the step of forming the electron transport layer comprises a buffer layer formation step of forming a buffer layer between the hole transport layer and the light absorption layer and / or between the electron transport layer and the light absorption layer, and the buffer layer formation step is characterized in that the buffer layer formation step includes adding a solution containing a polyamino acid obtained by polymerizing an amino acid having a charged side chain of a reactive functional group. (Aspect 2) A method for manufacturing a solar cell, comprising the steps of: forming an electron transport layer on a first electrode; forming a light-absorbing layer of a perovskite compound on the electron transport layer; forming a hole transport layer on the light-absorbing layer; and forming a second electrode on the hole transport layer; or the steps of: forming a hole transport layer on a second electrode; forming a light-absorbing layer of a perovskite compound on the hole transport layer; forming an electron transport layer on the light-absorbing layer; and forming a first electrode on the electron transport layer, wherein the step of forming the hole transport layer and / or the step of forming the electron transport layer includes adding a solution containing a polyamino acid obtained by polymerizing an amino acid having a charged side chain of a reactive functional group. (Aspect 3) The method for manufacturing a solar cell according to Aspect 1 or 2, wherein the polyamino acid is a polymer having a molecular weight of 1,000 to 100,000. (Aspect 4) The method for manufacturing a solar cell according to Aspect 1 or 2, wherein the polyamino acid is a polymer having a molecular weight of 2,000 to 5,000.(Aspect 5) The method for producing a solar cell according to any one of Aspects 1 to 4, wherein the polyamino acid is polyarginine or polylysine. (Aspect 6) A method for producing a solar cell module, comprising integrating and modularizing solar cells produced by the method for producing a solar cell according to any one of Aspects 1 to 5. (Aspect 7) A solar cell having a charge transport layer consisting of a hole transport layer or an electron transport layer between an electrode and a light absorption layer of a perovskite compound, the solar cell comprising: (1) an organic compound having a polymerized structure of an amino acid having at least a reactive functional group as a buffer layer between the light absorption layer and the charge transport layer; or (2) an organic compound contained in the charge transport layer. (Aspect 8) The solar cell according to Aspect 7, wherein the amino acid in the organic compound is an amino acid having a basic charged side chain. (Aspect 9) The solar cell according to Aspect 7 or 8, wherein the organic compound is a polymer having a molecular weight of 1,000 to 100,000. (Aspect 10) The solar cell according to Aspect 7 or 8, wherein the organic compound is a polymer having a molecular weight of 2,000 to 5,000. (Aspect 11) The solar cell according to any one of Aspects 7 to 10, wherein the organic compound is polyarginine or polylysine. (Aspect 12) The solar cell according to any one of Aspects 7 to 11, wherein the charge transport layer is a hole transport layer. (Aspect 13) A solar cell module comprising an integrated modularization of solar cells according to any one of Aspects 7 to 12. (Aspect 14) A transport device comprising the solar cell according to any one of Aspects 7 to 12. (Aspect 15) An electrical appliance comprising the solar cell according to any one of Aspects 7 to 12. (Aspect 16) A structure comprising the solar cell according to any one of Aspects 7 to 12.

[0109] REFERENCE SIGNS LIST 1 Substrate 2 First electrode 3 Electron transport layer (charge transport layer) 31 Buffer layer 31 4 Light absorption layer 5 Hole transport layer (charge transport layer) 51 Buffer layer 51 6 Second electrode 10 Solar cell 100 Solar cell module 110 Solar cell module

Claims

1. A method for manufacturing a solar cell, comprising the steps of: forming an electron transport layer on a first electrode; forming a light absorption layer of a perovskite compound on the electron transport layer; forming a hole transport layer on the light absorption layer; and forming a second electrode on the hole transport layer; or the steps of forming a hole transport layer on a second electrode; forming a light absorption layer of a perovskite compound on the hole transport layer; forming an electron transport layer on the light absorption layer; and forming a first electrode on the electron transport layer, wherein the step of forming the hole transport layer and / or the step of forming the electron transport layer comprises a buffer layer formation step of forming a buffer layer between the hole transport layer and the light absorption layer and / or between the electron transport layer and the light absorption layer, wherein the buffer layer formation step comprises adding a solution containing a polyamino acid obtained by polymerizing an amino acid having a charged side chain of a reactive functional group.

2. A method for manufacturing a solar cell, comprising the steps of: forming an electron transport layer on a first electrode; forming a light absorption layer of a perovskite compound on the electron transport layer; forming a hole transport layer on the light absorption layer; and forming a second electrode on the hole transport layer; or forming a hole transport layer on a second electrode; forming a light absorption layer of a perovskite compound on the hole transport layer; forming an electron transport layer on the light absorption layer; and forming a first electrode on the electron transport layer, wherein the step of forming the hole transport layer and / or the step of forming the electron transport layer comprises adding a solution containing a polyamino acid obtained by polymerizing an amino acid having a charged side chain of a reactive functional group.

3. The method for producing a solar cell according to claim 1 or 2, wherein the polyamino acid is a polymer with a molecular weight of 1,000 to 100,000.

4. The method for producing a solar cell according to claim 1 or 2, wherein the polyamino acid is a polymer having a molecular weight of 2,000 to 5,000.

5. The method for producing a solar cell according to any one of claims 1 to 4, wherein the polyamino acid is polyarginine or polylysine.

6. A method for manufacturing a solar cell module, comprising integrating solar cells manufactured by the method for manufacturing a solar cell according to any one of claims 1 to 5, and modularizing the solar cells.

7. A solar cell having a charge transport layer consisting of a hole transport layer or an electron transport layer between an electrode and a light-absorbing layer of a perovskite compound, characterized in that (1) as a buffer layer between the light-absorbing layer and the charge transport layer, or (2) as a composition of the charge transport layer, an organic compound having a polymer structure of amino acids having charged side chains of reactive functional groups.

8. The solar cell according to claim 7, wherein the amino acid of the organic compound is an amino acid having a basic charged side chain.

9. The solar cell according to claim 7 or 8, wherein the organic compound is a polymer having a molecular weight of 1,000 to 100,000.

10. The solar cell according to claim 7 or 8, wherein the organic compound is a polymer having a molecular weight of 2,000 to 5,000.

11. The solar cell according to any one of claims 7 to 10, wherein the organic compound is polyarginine or polylysine.

12. The solar cell according to any one of claims 7 to 11, wherein the charge transport layer is a hole transport layer.

13. A solar cell module comprising the solar cell according to any one of claims 7 to 12 integrated and modularized.

14. A transport device comprising the solar cell according to any one of claims 7 to 12.

15. An electrical appliance comprising a solar cell according to any one of claims 7 to 12.

16. A structure comprising a solar cell according to any one of claims 7 to 12.

Images