Method for manufacturing solar cells and solar cells

Abstract

Provided are a method for manufacturing a solar cell that can fill every corner of voids in a porous layer with a light-absorbing material that forms a perovskite compound, and a solar cell in which every corner of voids in a porous layer is filled with a light-absorbing material that forms a perovskite compound. [Solution] A method for manufacturing a solar cell having a light-absorbing material in the voids of a porous layer, comprising: a first supply step S31 in which a prior solution containing an organic compound that can bond with the porous surface of the voids of the porous layer is supplied to the voids of the porous layer; a first drying step in which the prior solution supplied in the first supply step S31 is dried; a second supply step S32 in which a precursor solution containing a light-absorbing material that forms a perovskite compound is supplied; and a second drying step in which the precursor solution supplied in the second supply step S32 is dried.

Description

[Technical Field]

[0001] This disclosure relates to a method for manufacturing a solar cell having a light-absorbing material in the voids of a porous layer, and to a solar cell in which a substrate, a transparent conductive layer, a hole-blocking layer, and a porous layer are sequentially laminated. [Background technology]

[0002] In recent years, perovskite solar cells, which use light-absorbing materials that form perovskite compounds as photoelectric conversion materials, have attracted attention because they can achieve photoelectric conversion efficiencies comparable to silicon-based solar cells. In addition to planar structures in which flat films are sequentially stacked, photoelectric conversion elements using light-absorbing materials that form perovskite compounds are known to use porous structures, and among these structures, the forward structure type (forward type) is known.

[0003] Among porous structures, sequential structures are common, and Patent Document 1 discloses a mesoscopic solar cell based on a perovskite-type light-absorbing material in which a base (1), a hole-blocking layer (2), a mesoporous nanocrystalline layer (3), an insulating spacer layer (4), and a mesoporous hole-collecting layer (5) are sequentially stacked, as well as a method for manufacturing the same. Note that the terms and symbols used are those in Patent Document 1.

[0004] The mesoporous nanocrystalline layer (3), mesoporous insulating spacer layer (4), and mesoporous pore collection layer (5) of the mesoscopic solar cell (collectively referred to as a porous laminated structure) are filled with a perovskite-type semiconductor material, with the mesoporous nanocrystalline layer (3) serving as a light-absorbing layer.

[0005] In the manufacturing of the light-absorbing layer, the method for forming the perovskite compound on a porous laminated structure (before the perovskite compound is formed on the porous surface of the voids) involves dropping a precursor solution containing a light-absorbing material for forming the perovskite compound into the porous laminated structure, allowing it to permeate, and then drying it to form a crystallized film.

[0006] The ease of penetration of the precursor solution is related to the wettability of the porous surface of the voids with the precursor solution, and is influenced not only by the composition of the precursor solution and the film-forming conditions of the porous laminated structure, but also by external environments such as the humidity and temperature when the precursor solution is penetrated, and the storage conditions of the substrate on which the porous laminated structure is laminated before the precursor solution is penetrated.

[0007] Therefore, when the precursor solution penetrates the voids, it may not spread throughout the entire porous laminate structure, resulting in uneven filling. Since uneven filling can cause variations and deterioration in performance, there has been a need for a manufacturing method for filling every corner of the porous laminate structure with the precursor solution, as well as a solar cell constructed in which every corner of the porous laminate structure is filled with the precursor solution and a manufacturing method thereof. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 6267790 Summary of the Invention [Problem to be solved by the invention]

[0009] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a method for manufacturing a solar cell that can fill every corner of the voids in a porous layer with a light-absorbing material that forms a perovskite compound, and a solar cell in which every corner of the voids in a porous layer is filled with a light-absorbing material that forms a perovskite compound. [Means for solving the problem]

[0010] To achieve the above-mentioned objective, the present disclosure is a method for manufacturing a solar cell having a light-absorbing material in the voids of a porous layer, characterized by sequentially performing: a first supply step of supplying a prior solution containing an organic compound that can bond with the porous surface of the voids of the porous layer; a first drying step of drying the prior solution supplied in the first supply step; a second supply step of supplying a precursor solution containing a light-absorbing material that forms a perovskite compound; and a second drying step of drying the precursor solution supplied in the second supply step.

[0011] According to the above configuration, the porous surface of the voids in the porous layer is coated with an organic compound that can increase the affinity between the precursor solution and the porous surface of the voids in the porous layer, thereby improving the wettability of the porous surface of the voids in the porous layer. Then, a precursor solution containing a light-absorbing material that forms a perovskite compound is supplied to the voids. This improves the permeability of the precursor solution, allowing the light-absorbing material to fill every corner of the voids in the organic compound. As a result, a perovskite nanocrystalline structure can be formed in every corner of the voids in the porous layer.

[0012] The use of organic compounds improves the wettability of the porous surface within the voids of the porous layer, thereby reducing the unfilled areas of the precursor solution inside the porous layer. This improves the efficiency of carrier extraction from the power generation layer and enhances performance. Furthermore, the improved wettability of the porous surface within the voids of the porous layer by the organic compounds shortens the time required to fill every corner of the voids in the porous layer with the precursor solution.

[0013] It is also conceivable to fill the voids with a mixed solution, which is prepared by pre-mixing a precursor solution containing an organic compound capable of bonding with the porous surface of the voids with a precursor solution containing a light-absorbing material that forms a perovskite compound. In this case, in order for the mixed solution to reach every corner of the porous voids, it is necessary to mix a considerable amount of the organic compound into the mixed solution.

[0014] However, since the organic compound itself does not contribute to improving the power generation efficiency of the light absorbing layer, it is desirable that the amount of organic compound contained in the light absorbing layer be small.

[0015] According to the manufacturing method of the present disclosure, first, only the necessary amount of organic compound is coated on the porous surface of the porous void portion, and then the light-absorbing material is filled in. This allows the amount of organic compound present in the light-absorbing layer to be reduced, thereby improving efficiency.

[0016] In addition, the fact that the precursor solution reaches every corner of the porous voids means that the area in which the precursor solution reaches is greater than in conventional manufacturing methods, and the existence of areas in which the precursor solution has not reached sufficiently does not fall outside the scope of the objectives of the present disclosure.

[0017] In order to achieve the above-mentioned object, the solar cell according to the present disclosure is a solar cell constructed by sequentially stacking a substrate, a transparent conductive layer, a hole blocking layer, and a porous layer, wherein the porous layer contains a light-absorbing material that forms a perovskite compound in the voids of the porous layer and an organic compound, and the organic compound constitutes a light-absorbing layer that is unevenly distributed in positions close to the porous surface of the voids.

[0018] Note that "distributed close to the porous surface of the voids" typically means, but is not limited to, a position in contact with the porous surface of the voids. In other words, the region in which elements contained in the target are detected has a certain width depending on the size and shape of the target, and the concentration of the element contained in the target does not necessarily peak at a position in contact with the porous surface of the voids. At the very least, it is sufficient that the concentration near the porous surface of the voids is higher than that near the center of the voids. However, it is desirable that the concentration peak be near the surface within a range of width approximately equal to the size of the organic compound.

[0019] In the present disclosure, the organic compound may be bonded to the porous surface of the void portion.

[0020] In this disclosure, the organic compound may be characterized by having a reactive functional group.

[0021] Examples of organic compounds having reactive functional groups include amino groups, carboxyl groups, hydroxyl groups, phosphoryl groups, thiol groups, sulfo groups, halogen groups, isocyanate groups, isothiocyanate groups, silane groups, and epoxy groups.

[0022] In this disclosure, the organic compound may be characterized by being a halide salt of an organic ammonium cation.

[0023] Examples of organic ammonium cation halide salts include MAI (Methylamine Hydroiodide), MABr, MACl, DMAI (Dimethylammonium Iodide), DMABr, DMACl, PEAI (Phenethylamine Hydroiodide), PEABr, F-PEAI, F-PEABr, F-PEACl, MeO-PEAI, MeO-PEABr, MeO-PEACl, 3-Aminopropionic Acid Hydroiodide, and 5-Aminopentanoic Acid Hydroiodide.

[0024] In this disclosure, the organic compound may be characterized by being a halide salt of an organicamidinium cation.

[0025] Preferred examples of organic amidinium cation halide salts include FAI (Formamidine Hydroiodide), FABr, FACl, Acetamidinium Iodide, Acetamidinium Bromide, and Acetamidinium Chloride.

[0026] In this disclosure, the organic compound may be characterized by containing a heterocycle or a benzene ring in its structure.

[0027] Preferred examples of organic compounds containing a heterocycle or a benzene ring in their structure include pyrrole, pyrroline, imidazole, pyridine, pyrazine, piperidine, thiophene, thiazole, indole, quinoline, carbazole, and derivatives thereof having a substituent.

[0028] In this disclosure, the porous layer may be characterized by being composed of metal oxide particles.

[0029] In this disclosure, the porous layer may be characterized by comprising a porous electron transport layer, a porous insulating layer, and a porous conductive layer. [Brief explanation of the drawings]

[0030] [Figure 1] Figure 1 is a schematic cross-sectional view of the solar cell relating to this disclosure. [Figure 2] Figure 2 is a flowchart of the method for manufacturing a solar cell according to this disclosure. [Figure 3] Figure 3 is an SEM image of the porous layer after it has been formed using the manufacturing method shown in Figure 2. [Figure 4] Figure 4 is an SEM image after the light-absorbing layer has been formed using the manufacturing method shown in Figure 2. [Figure 5] Figure 5 is an SEM image of the case where the light-absorbing layer was formed without performing the first supply step in the manufacturing method shown in Figure 2. [Figure 6] Figure 6 is an SEM image of the case where the light-absorbing layer was formed without performing the first supply step in the manufacturing method shown in Figure 2. DETAILED DESCRIPTION OF THE INVENTION

[0031] Preferred embodiments of the present disclosure will be described in detail below with reference to the drawings. 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 following embodiments are necessarily essential to the solutions of the present disclosure. Furthermore, for illustrative purposes, the light-receiving side of the solar cell will be referred to as the lower side and the side opposite the light-receiving side as the upper side. However, this is for convenience and does not affect the installation orientation or recommended installation orientation. The present disclosure can be applied even if the top and bottom are reversed as long as there is no contradiction. In other words, the present disclosure is valid even if the light-receiving side and the side opposite the light-receiving side are reversed as long as there is no contradiction. In the following description, as a general rule, unless otherwise specified, identical components are assigned the same reference numerals, and their names and functions are also the same. Therefore, in such cases, detailed descriptions thereof will not be repeated.

[0032] [Solar Cells] FIG. 1 is a schematic cross-sectional view of a solar cell 1 according to this embodiment. The solar cell 1 is configured by sequentially stacking a flat layer 2, which includes a transparent conductive layer 22 and a hole blocking layer 23 stacked on a substrate 21, and a porous layer 3, which includes a porous electron transport layer 31, a porous insulating layer 32, and a porous conductive layer 33. A light-absorbing material that forms a perovskite compound and an organic compound coexist on the porous surface of voids 34 of the porous layer 3, with the organic compound being unevenly distributed at the interface between the voids 34 and the light-absorbing material. In the solar cell 1, the transparent conductive layer 22 serves as the negative electrode, the porous layer 3 serves as the light-absorbing layer 4, and the porous conductive layer 33 serves as the positive electrode.

[0033] Note that "layer" or "film" preferably refers to a member having an approximately constant film thickness, but is not limited thereto, and may have portions with different thicknesses, or may be patterned or island-like. Furthermore, unless otherwise specified, "approximately" or "approximately" refers to the range of manufacturing error, and indicates that a variation of plus or minus 15% of the numerical value is preferentially allowed.

[0034] Furthermore, "porous" is also referred to as porous or mesoporous, and includes both. However, it is preferable that "porous" be mesoporous. Regarding mesoporous, priority is given to determining the term. Furthermore, "porous" means that at least a light-absorbing material can be contained in the voids 34 (which can be variously expressed as gaps, holes, or holes). In this disclosure, unless otherwise contradictory, "voids in a porous layer" means "a region where the material constituting the porous layer is not present in a region where the material constituting the porous layer is generally distributed in a dispersed or continuous manner."

[0035] The porous layer 3 has voids 34 inside, and these voids 34 are connected to each other. For example, when a precursor solution is dropped into the porous layer 3, it penetrates into the interior of the porous layer 3. For example, the precursor solution is filled into the voids 34 of the porous electron transport layer 31, the porous insulating layer 32, and the porous conductive layer 33.

[0036] Each part of the solar cell 1 will be described in detail below. [Base material] The substrate 21 may be hard and highly rigid, or may be flexible and less rigid. The substrate 21 may be, for example, flat, sheet, or cylindrical. To use the substrate 21 as a light-receiving surface, the substrate 21 is made of a transparent material such as glass or a heat-resistant resin. Examples of glass include soda-lime glass and alkali-free glass. Examples of heat-resistant resins include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), polyetherimide (PEI), polytetrafluoroethylene (PTFE), polyamideimide (PAI), and polyethylene naphthalate (PEN). In cases where light is not irradiated through the substrate 21, the substrate 21 may be opaque.

[0037] [Transparent conductive layer (negative electrode)] The transparent conductive layer 22 serving as the negative electrode is a layer having electrical conductivity. The transparent conductive layer 22 is laminated on the substrate 21 by a known film formation method such as a sputtering film formation method or a chemical vapor deposition method (CVD method).

[0038] The transparent conductive layer 22 may be made of a carbon material containing, for example, tin-doped indium oxide (ITO), fluorine-doped tin oxide (FTO), or aluminum-doped zinc oxide (AZO).

[0039] The thickness of the transparent conductive layer 22 is not particularly limited and can be any thickness that allows it to exhibit the desired properties (e.g., electron transportability and transparency).

[0040] [Hole Block Layer] The hole blocking layer 23 transports electrons generated in the light absorbing layer 4 to the transparent conductive layer 22, which serves as the negative electrode. The hole blocking layer 23 inhibits holes generated in the light absorbing layer 4 from migrating to the transparent conductive layer 22. The hole blocking layer 23 is preferably a dense electron transport layer. As long as the solar cell 1 functions as a solar cell, it is self-evident that an electron transport layer located on the electron transport side of the light absorbing layer 4 or on the electron transport side of the light absorbing layer 4 has the function of transporting electrons, and no confirmation is required. In other words, as long as the solar cell 1 functions as a solar cell, a layer located on the electron transport side of the light absorbing layer 4 or on the electron transport side of the light absorbing layer 4 is referred to as an electron transport layer. The electron transport side can be rephrased as the negative electrode side of the photoelectric conversion element.

[0041] The hole blocking layer 23 is mainly composed of an electron transport material. Examples of the electron transport material include metal oxides (N-type metal oxides) such as titanium oxide, zinc oxide, indium oxide, tin oxide, aluminum oxide, and gallium oxide, and metal sulfides (N-type metal sulfides) such as tin sulfide, indium sulfide, and zinc sulfide. Components contained in the hole blocking layer 23 other than the electron transport material include an organic binder resin and a plasticizer.

[0042] In the manufacturing method according to the present disclosure, when the preceding solution or precursor solution is dropped onto the porous layer 3, the preceding solution or precursor solution penetrates the porous electron transport layer 31, but hardly penetrates the hole blocking layer 23. Therefore, providing the hole blocking layer 23 can prevent contact between the light absorbing layer 4 and the transparent conductive layer 22. The hole blocking layer 23 preferably contains, for example, dense titanium oxide. Note that the term "dense material" is also referred to as "compact" or "compacted material," and includes these terms. A dense material refers to a material that, when observed in cross section, is free of a light absorbing material (perovskite compound in this embodiment, hereinafter referred to as "perovskite compound") on one side (e.g., the lower side) in the thickness direction of the dense material. In other words, even if a perovskite compound is present on the upper side of the dense material, it is possible to ensure that it does not penetrate to the lower side of the dense material. Furthermore, a dense material preferably has extremely small voids. Preferably, a dense material refers to a material in which the maximum void width is less than 5 nm. More preferably, dense refers to a material that does not contain a perovskite compound in the voids 34 or does not have any areas where the perovskite compound is present continuously throughout the thickness of the dense material. That is, a dense material is defined as a material that can be observed by SEM or EDX to have no areas where the perovskite compound is present throughout the layer thickness. In this disclosure, unless otherwise specified, SEM observations can be performed by observing a 400 nm wide cross-sectional SEM (or EDX) image and confirming this. For example, if a 400 nm wide cross-sectional SEM or EDX observation shows no areas where the perovskite compound is present throughout the layer thickness, the layer can be said to be dense.

[0043] [Porous electron transport layer] The porous electron transport layer 31 is a layer that transports electrons generated in the light absorption layer 4 to the transparent conductive layer 22, which is the negative electrode. Preferably, the porous electron transport layer 31 also functions as a hole-blocking layer that suppresses the movement of holes generated in the light absorption layer 4 to the transparent conductive layer 22. It is self-evident that as long as the solar cell 1 functions as a solar cell, the electron transport layer located on the electron transport side of the light absorption layer 4 or on the electron transport side of the light absorption layer 4 has the function of transporting electrons, and no confirmation is required. In other words, as long as the solar cell 1 functions as a solar cell, the layer located on the electron transport side of the light absorption layer 4 or on the electron transport side of the light absorption layer 4 is called the electron transport layer. The electron transport side can be rephrased as the negative electrode side of the photoelectric conversion element.

[0044] The porous electron transport layer 31 is composed mainly of an electron transport material. Examples of electron transport materials include metal oxides (N-type metal oxides) such as titanium oxide, zinc oxide, indium oxide, tin oxide, aluminum oxide, and gallium oxide; and metal sulfides (N-type metal sulfides) such as tin sulfide, indium sulfide, and zinc sulfide. Other components that the porous electron transport layer 31 may contain include organic binder resins and plasticizers. Preferably, the porous electron transport layer 31 is composed of metal oxide particles.

[0045] Examples of the structure of the porous electron transport layer 31 include a structure in which multiple electron transport material particles are bonded together by an organic binder resin, and a structure in which multiple electron transport material particles are molded or sintered.

[0046] [Porous insulating layer] As shown in Figure 1, a porous insulating layer 32 is provided between the porous electron transport layer 31 and the porous conductive layer 33. By providing the porous insulating layer 32, contact between the porous electron transport layer 31 and the porous conductive layer 33 can be prevented, thereby suppressing the generation of leakage current. By adding the porous insulating layer 32, the distance between the transparent conductive layer 22 and the hole block layer 23 and the porous conductive layer 33 can be increased, suppressing physical contact between the materials on both sides, and preventing the recombination of electrons and holes generated in the light absorption layer 4.

[0047] The porous insulating layer 32 is primarily composed of an insulating material or a high-resistance semiconductor material. Examples of insulating materials or high-resistance semiconductor materials include metal oxides containing titanium oxide, zirconium dioxide, and aluminum oxide, and oxides containing silicon dioxide. Components other than the insulating material and high-resistance semiconductor material that the porous insulating layer 32 may contain include an organic binder resin and a plasticizer. Preferably, the porous insulating layer 32 is composed of metal oxide particles.

[0048] Examples of the structure of the porous insulating layer 32 include a structure in which multiple insulating material particles or high-resistance semiconductor material particles are bonded together by an organic binder resin, and a structure in which multiple insulating material particles or high-resistance semiconductor material particles are molded or sintered.

[0049] [Porous conductive layer] The porous conductive layer 33, acting as the positive electrode, is a layer that transports holes generated in the light-absorbing layer 4. Preferably, the porous conductive layer 33 also functions as an electron-blocking layer for electrons generated in the light-absorbing layer 4.

[0050] The porous conductive layer 33 is mainly composed of a hole transport material. Examples of the hole transport material include metal oxides (P-type metal oxides) such as molybdenum oxide, vanadium oxide, tungsten oxide, nickel oxide, copper oxide, and tin oxide; metal sulfides (P-type metal sulfides) such as molybdenum sulfide, tungsten sulfide, copper sulfide, and tin sulfide; copper compounds such as fluoro-group-containing phosphonic acid, carbonyl-group-containing phosphonic acid, CuSCN, and CuI; and carbon-containing materials such as optionally surface-modified carbon nanotubes and graphene.

[0051] Components other than the hole transport material that may be contained in the porous conductive layer 33 include an organic binder resin and a plasticizer. The porous conductive layer 33 may be composed of only the hole transport material without containing an organic binder resin, a plasticizer, etc. Preferably, the porous conductive layer 33 is composed of metal oxide particles.

[0052] The porous conductive layer 33 may have a structure in which a plurality of hole transport material particles are bound by an organic binder resin, or a structure in which a plurality of hole transport material particles are molded or sintered, for example.

[0053] The thickness of the porous conductive layer 33 is not particularly limited and can be any thickness that allows it to exhibit the desired properties (e.g., hole transport).

[0054] [Light absorbing layer] The light absorbing layer 4 is a layer that can absorb incident light and generate electrons and holes. The electrons generated in the light absorbing layer 4 move to the porous electron transport layer 31, and the holes move to the porous conductive layer 33.

[0055] The light-absorbing layer 4 can be configured such that an organic compound is bonded to the porous surface of the voids 34 of the porous layer 3, which consists of a porous electron transport layer 31, a porous insulating layer 32, and a porous conductive layer 33, and a light-absorbing material that forms a perovskite compound is bonded to the organic compound. It should be noted that the light-absorbing layer 4 absorbs light and generates electrons and holes, as long as the solar cell 1 functions as a solar cell, this is self-evident and does not require verification. As long as a material with light-absorbing function is included, it can be assumed that the light-absorbing layer 4 absorbs light and generates electrons and holes.

[0056] The organic compound may be an organic compound having a reactive functional group, a halide salt of an organic ammonium cation, a halide salt of an organic amidinium cation, or an organic compound containing a heterocycle or a benzene ring in its structure.

[0057] Preferred examples of organic compounds having a reactive functional group include an amino group, a carboxyl group, a hydroxyl group, a phosphoryl group, a thiol group, a sulfo group, a halogen group, an isocyanate group, an isothiocyanate group, a silane group, and an epoxy group.

[0058] Examples of organic ammonium cation halide salts include MAI (Methylamine Hydroiodide), MABr, MACl, DMAI (Dimethylammonium Iodide), DMABr, DMACl, PEAI (Phenethylamine Hydroiodide), PEABr, F-PEAI, F-PEABr, F-PEACl, MeO-PEAI, MeO-PEABr, MeO-PEACl, 3-Aminopropionic Acid Hydroiodide, and 5-Aminopentanoic Acid Hydroiodide.

[0059] Preferred examples of organic amidinium cation halide salts include FAI (Formamidine Hydroiodide), FABr, FACl, Acetamidinium Iodide, Acetamidinium Bromide, and Acetamidinium Chloride.

[0060] Preferred examples of organic compounds containing a heterocycle or a benzene ring in their structure include pyrrole, pyrroline, imidazole, pyridine, pyrazine, piperidine, thiophene, thiazole, indole, quinoline, carbazole, and derivatives thereof having a substituent.

[0061] The light-absorbing material that forms the perovskite compound is composed of a compound represented by the general formula: ABX3 (1). However, although the composition ratio of each element is preferably 1:1:3, it is not necessarily 1:1:3, the content ratio of each element may be varied as appropriate, and each constituent element does not necessarily have to be of one type; as long as the light-absorbing layer 4 has a photoelectric conversion function, the light-absorbing material that forms the perovskite compound contained in the light-absorbing layer 4 exhibits this photoelectric conversion function, and therefore it is reasonable to consider that the function is exhibited even if there is a degree of freedom in the composition as explained above regarding the composition ratio and the types of constituent elements.

[0062] In general formula (1), A is an organic molecule (containing an organic group or an organic cation, as is the case in this disclosure) or an inorganic atom or molecule (containing an inorganic group or an inorganic cation, as is the case in this disclosure) or a combination thereof; B is a metal atom or molecule (containing a metal cation, as is the case in this disclosure); and X is a halogen atom or molecule or a chalcogen atom or molecule (containing a halogen anion or a chalcogen anion, as is the case in this disclosure).

[0063] In general formula (1), the three X's may be the same or different from each other. As long as the photoelectric conversion element has a photoelectric conversion function, the light-absorbing material that forms the perovskite compound contained in the light-absorbing layer 4 is exhibiting a photoelectric conversion function, and this should be taken into consideration. That is, if it can be confirmed that the light-absorbing material that forms the perovskite compound has A, B, and X, it is reasonable to consider it as a light-absorbing material that forms a perovskite compound that exhibits a photoelectric conversion function. For example, it is sufficient to know that it has organic molecules, metal atoms, and halogen atoms.

[0064] Furthermore, whether a material is a light-absorbing material that forms a perovskite compound can be confirmed by detecting elements corresponding to A, B, and X, as long as the photoelectric conversion element has a photoelectric conversion function. For example, organic molecules containing carbon, nitrogen, and hydrogen are preferred, and therefore, it is sufficient if carbon, nitrogen, hydrogen, metallic elements, and halogens or chalcogens are detected. Alternatively, whether a material is a light-absorbing material that forms a perovskite compound can be confirmed if it contains A, B, and X, for example, if it is found to contain inorganic atoms, metallic atoms, and halogen atoms.

[0065] Furthermore, as long as the photoelectric conversion element has a photoelectric conversion function, the light-absorbing material can be confirmed as forming a perovskite compound by detecting elements corresponding to A, B, and X. For example, cesium or rubidium is suitable as the inorganic atom, and therefore, it is sufficient to detect cesium or rubidium, a metal element, and a halogen or chalcogen. Furthermore, as long as the photoelectric conversion element has a photoelectric conversion function, it is a natural consequence that the material has a crystalline structure, and therefore it is not necessary to confirm that the material has a crystalline structure to be forming a perovskite compound. This does not exclude the light-absorbing layer 4 from containing light-absorbing materials other than those that form a perovskite compound.

[0066] The method for preparing the precursor solution containing the light-absorbing material that forms the perovskite compound is not particularly limited, but for example, it can be prepared by mixing the AX solution and the BX2 solution.

[0067] Below, based on Figure 2, the manufacturing method of the solar cell 1 will be described, first by explaining the process of forming the flat layer 2 and the porous layer 3, and then by explaining the process of forming the light-absorbing layer 4.

[0068] [Substrate drying process] In manufacturing the solar cell 1, the substrate 21 is first heated at a temperature of approximately 150°C for about 1 hour, which causes the moisture contained in the substrate 21 to evaporate. After the substrate 21 has been dried in this way and cooled to room temperature, the following steps are performed.

[0069] [Flattening layer forming step] In the flat layer formation step S10, a transparent conductive layer formation step S11 is performed to form a transparent conductive layer 22 on the substrate 21. Then, a hole block layer formation step S12 is performed to form a hole block layer 23 on the transparent conductive layer 22. During the flat layer formation step S10, mask patterning in the film formation step and insulation decomposition treatment by laser scribing after flat film formation are also performed as appropriate to form the cell pattern necessary for module formation by cellization and cell integration. Once the flat layer 2 is formed in this way, the porous layer 3 formation step is then performed.

[0070] [Porous layer forming step] In the porous layer formation step S20, a porous electron transport layer formation step S21 is performed to form a porous electron transport layer 31 on the flat layer 2. Then, a porous insulating layer formation step S22 is performed to form a porous insulating layer 32 on the porous electron transport layer 31. Furthermore, a porous conductive layer formation step S23 is performed to form a porous conductive layer 33 on the porous insulating layer 32.

[0071] In the porous electron transport layer forming step S21, the porous insulating layer forming step S22, and the porous conductive layer forming step S23, the porous electron transport layer 31, the porous insulating layer 32, and the porous conductive layer 33 are formed by coating and forming a film using a known method such as screen printing, spin coating, or bar coating.

[0072] As shown in FIG. 3, when the cross section of the porous layer 3 was observed by energy dispersive X-ray spectroscopy (SEM-EDX), it was confirmed that there were many voids in the porous layer 3.

[0073] After the porous layer 3 is formed in this manner, the light absorbing layer forming step S30 of forming the light absorbing layer 4 is carried out.

[0074] [Light-absorbing layer forming step] In the light absorbing layer forming step S30, a first supplying step S31 is carried out to supply, to the voids 34 of the porous layer 3, a preceding solution containing an organic compound capable of bonding to the porous surfaces of the voids 34.

[0075] In the first supplying step S31, a precursor solution having a predetermined concentration, for example, 0.1 to 5 mg / ml, is dropped onto the porous conductive layer 33 side of the porous layer 3 by spin coating or a dispenser.

[0076] After the preceding solution is dropped from the porous conductive layer 33 side of the porous layer 3 in the first supplying step S31, a first drying step is performed to dry the preceding solution. In the first drying step, the porous layer 3 onto which the preceding solution has been dropped is heated at a temperature of about 100°C for about 10 minutes. Note that the drying time does not depend much on the material. As a result, the solvent contained in the preceding solution volatilizes, and the organic compound is bonded to the porous surface of the voids 34.

[0077] When the first drying step completes the drying of the porous layer 3 onto which the preceding solution has been dropped, the porous layer 3 is allowed to cool to room temperature, and then a second supplying step S32 is carried out in which a precursor solution containing a light-absorbing material that forms a perovskite compound is dropped onto the porous layer 3.

[0078] In the second supplying step S32, a precursor solution of a predetermined concentration is dropped by spin coating, a dispenser, or the like from the porous conductive layer 33 side of the porous layer 3. At this time, the precursor solution fills every corner of the voids 34 with the organic compound bound to the porous surfaces of the voids 34.

[0079] After the precursor solution is dripped onto the porous layer 3 from the porous conductive layer 33 side in the second supply step S32, the porous layer 3 is held in solvent vapor for a certain period of time to distribute the precursor solution throughout the porous layer 3, and then a second drying step is performed to dry the precursor solution. In the second drying step, the porous layer 3 onto which the precursor solution has been dripped is dried by heating at 50 to 100°C, preferably at approximately 50°C, to grow crystals and form a film. Note that the drying time must be optimally controlled depending on the evaporation rate of the solvent, the crystallization rate of the film material, and the amount of liquid supplied. As a result, the solvent contained in the precursor solution evaporates, and a perovskite compound of the light-absorbing material is formed in the voids 34, forming the light-absorbing layer 4 (S33).

[0080] As shown in Figure 4, when the cross-section of the porous layer 3 was observed using energy-dispersive X-ray spectroscopy (SEM-EDX), it was confirmed that the voids in the porous layer 3 were filled with a light-absorbing material that forms a perovskite compound throughout the entire area of ​​the observation target.

[0081] In the manufacturing method according to the present disclosure, a preceding solution containing an organic compound material is dropped onto the porous layer 3 prior to dropping the precursor solution. After dropping the preceding solution, a heat treatment is performed to evaporate the solvent in the preceding solution, thereby coating the porous surfaces of the voids 34 with the organic compound. By surface treating the porous surfaces of the voids 34 with a thin molecular layer before dropping the precursor solution, the permeability of the precursor solution is improved. Then, by dropping the precursor solution into the voids 34, the precursor solution can fill every corner of the porous surfaces of the voids 34 coated with the organic compound material. The thin molecular layer is preferably a self-assembled monolayer (SAM).

[0082] On the other hand, as shown in Figures 5 and 6, even when a precursor solution containing a light-absorbing material that forms a perovskite compound is dropped into the porous layer of a linear solar cell without performing the first supply step S31, it was confirmed that there are regions in the voids 34 where the light-absorbing material does not sufficiently penetrate.

[0083] (Addendum) [Aspect 1] A method for manufacturing a solar cell having a light-absorbing material in voids of a porous layer, comprising: a first supplying step of supplying a precursor solution containing an organic compound capable of bonding to the porous surface of the voids of the porous layer into the voids of the porous layer; a first drying step of drying the preceding solution supplied in the first supplying step; A second supply step involves supplying a precursor solution containing a light-absorbing material that forms a perovskite compound, and a second drying step of drying the precursor solution supplied in the second supplying step. [Aspect 2] A solar cell constructed by sequentially stacking a substrate, a transparent conductive layer, a hole blocking layer, and a porous layer, The porous layer contains a light-absorbing material that forms a perovskite compound in the voids of the porous layer, and an organic compound that coexists with the porous layer, and the organic compound constitutes a light-absorbing layer that is unevenly distributed in positions close to the porous surface of the voids. [Aspect 3] 3. The solar cell according to aspect 2, wherein the organic compound is bonded to the porous surface of the void portion. [Aspect 4] 4. The solar cell according to aspect 2 or 3, wherein the organic compound has a reactive functional group. [Aspect 5] 4. The solar cell according to aspect 2 or 3, wherein the organic compound is a halide salt of an organic ammonium cation. [Aspect 6] 4. The solar cell according to aspect 2 or 3, wherein the organic compound is a halide salt of an organic amidinium cation. [Aspect 7] 4. The solar cell according to aspect 2 or 3, wherein the organic compound contains a heterocycle or a benzene ring in its structure. [Aspect 8] 8. The solar cell according to claim 2, wherein the porous layer is made of metal oxide particles. [Aspect 9] 9. The solar cell according to any one of aspects 2 to 8, wherein the porous layer is composed of a porous electron transport layer, a porous insulating layer, and a porous conductive layer.

[0084] The configurations disclosed in any of the embodiments described above can be applied in combination with the configurations disclosed in other embodiments, insofar as they do not conflict with each other. Furthermore, the embodiments disclosed herein are illustrative and not limited to those disclosed herein, and can be modified as appropriate without departing from the purpose of this disclosure. [Explanation of symbols]

[0085] 1: Solar cell 2: Flat layer 3: Porous layer 4: Light absorbing layer 21: Base material 22: Transparent conductive layer 23: Hole blocking layer 31: Porous electron transport layer 32: Porous insulating layer 33: Porous conductive layer 34:Void part S10: Flat layer formation process S11: Transparent conductive layer formation process S12: Hole blocking layer forming step S20: Porous layer formation process S21: Porous electron transport layer formation process S22: Porous insulating layer forming process S23: Porous conductive layer formation process S30: Light absorption layer forming process S31: First supply process S32:Second supply process

Claims

1. A method for manufacturing a solar cell having a light-absorbing material in voids of a porous layer, comprising: a first supplying step of supplying a precursor solution containing an organic compound capable of bonding to the porous surface of the voids of the porous layer into the voids of the porous layer; a first drying step of drying the preceding solution supplied in the first supplying step; A second supply step involves supplying a precursor solution containing a light-absorbing material that forms a perovskite compound, and a second drying step of drying the precursor solution supplied in the second supplying step.

2. A solar cell constructed by sequentially stacking a substrate, a transparent conductive layer, a hole blocking layer, and a porous layer, The porous layer contains a light-absorbing material that forms a perovskite compound in the voids of the porous layer, and an organic compound that coexists with the porous layer, and the organic compound constitutes a light-absorbing layer that is unevenly distributed in positions close to the porous surface of the voids.

3. The solar cell according to claim 2, characterized in that the organic compound is bonded to the porous surface of the void.

4. 3. The solar cell according to claim 2, wherein the organic compound has a reactive functional group.

5. 3. The solar cell according to claim 2, wherein the organic compound is a halide salt of an organic ammonium cation.

6. 3. The solar cell according to claim 2, wherein the organic compound is a halide salt of an organic amidinium cation.

7. 3. The solar cell according to claim 2, wherein the organic compound contains a heterocycle or a benzene ring in its structure.

8. 3. The solar cell according to claim 2, wherein the porous layer is made of metal oxide particles.

9. 3. The solar cell according to claim 2, wherein the porous layer comprises a porous electron transport layer, a porous insulating layer, and a porous conductive layer.

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