Flexible solar cell and method for installing flexible solar cell

Abstract

The purpose of the present invention is to provide: a flexible solar cell that exhibits high dew proofness and makes it possible to prevent leakage of current during installation; and a method for installing said flexible solar cell. The present invention is a flexible solar cell characterized by including: a power generation unit (1) that has a light-receiving surface; a metal layer (4) that is disposed parallel to a surface facing the light-receiving surface of the power generation unit (1) and covers the entirety of the power generation unit (1); and an insulating layer (5) that covers at least the lower surface of the metal layer (4). The flexible solar cell is also characterized in that: at least one through-hole is included along a direction penetrating the insulating layer (5); the through-hole has a protective layer (7) on the inner surface thereof; and the metal layer (4) and the protective layer (7) are disposed with an insulating portion (10) therebetween.

Description

Flexible solar cells and methods for installing flexible solar cells

[0001] The present invention relates to a flexible solar cell and a method for installing a flexible solar cell.

[0002] There is a demand for sheet-type solar cells (flexible solar cells), which are thinner and lighter than conventional panel-type solar cells, to be used as solar cell modules installed outdoors. Flexible solar cells have the advantage of reducing costs such as transportation due to their thinness and light weight. Conventional technology regarding the installation structure of flexible solar cells has been proposed, for example, to attach and fix them to waterproof sheets etc. via double-sided tape provided on the back of the solar cell module (see Patent Document 1, etc.).

[0003] Japanese Patent Publication No. 2006-269610

[0004] While flexible solar cells have the significant advantages of being lightweight and flexible, their lightness and flexibility also make them susceptible to damage from wind. Furthermore, flexible solar cells installed outdoors require high resistance to condensation. To address this, a metal layer is laminated on the back of the flexible solar cell to enhance condensation resistance, and metal-reinforced through-holes (such as grommets) are provided to allow the flexible solar cell to be fixed to stakes without damage. However, those installed outdoors for extended periods require even higher resistance to condensation than usual. Additionally, in flexible solar cells with grommets, current can flow from the stake to the ground through the grommets, resulting in a problem where the desired solar cell output cannot be obtained.

[0005] Figure 3 is a schematic cross-sectional view illustrating an example of an installation method for a flexible solar cell having a metal layer on its back surface and through-holes formed therein. The flexible solar cell in Figure 3 has a power generation unit 1 consisting of electrodes, a photoelectric conversion unit, a counter electrode, etc., and the entire power generation unit 1 is sealed with a sealing material 2, with a front sheet 3 placed on the light-receiving surface of the power generation unit 1. Furthermore, a metal layer 4 covering the entire power generation unit 1 is arranged parallel to the light-receiving surface on the surface facing the light-receiving surface of the power generation unit 1. In addition, an insulating layer 5 exists so as to cover the lower surface of the metal layer 4, and through-holes are formed in a manner that penetrates the front sheet 3, the sealing material 2, and the insulating layer 5. A protective layer 7 is formed on the inner surface of the through-holes, and the metal layer 4 and the protective layer 7 are in direct contact. Such a flexible solar cell is installed on the installation surface 6 by a fixing member 8. In the flexible solar cell installation method shown in Figure 3, current (leakage current) flows sequentially from the power generation unit 1 through the sealing material 2, insulating layer 5, metal layer 4, protective layer 7, and fixing member 8 to the installation surface 6, which presents a problem in that the desired output of the solar cell cannot be obtained.

[0006] The present invention aims to provide a flexible solar cell and a method for installing a flexible solar cell that have high condensation resistance and can prevent current leakage during installation.

[0007] The present invention includes the following disclosures 1 to 8. The present invention will be described in detail below. Disclosure 1 is a flexible solar cell comprising: a power generation unit having a light-receiving surface; a metal layer arranged parallel to the surface facing the light-receiving surface of the power generation unit and covering the entire power generation unit; and an insulating layer covering at least the lower surface of the metal layer, wherein the insulating layer has at least one through-hole in a direction penetrating it, the through-hole has a protective layer on its inner surface, and the metal layer and the protective layer are arranged via the insulating unit. Disclosure 2 is the flexible solar cell according to Disclosure 1, characterized in that the minimum distance between the metal layer and the protective layer is 0.4 mm or more and 100 mm or less. Disclosure 3 is the flexible solar cell according to Disclosure 1 or 2, characterized in that the entire metal layer is covered with an insulating layer. Disclosure 4 is the flexible solar cell according to any one of Disclosures 1 to 3, characterized in that the ratio of the area of ​​the power generation unit to the area of ​​the metal layer in a plan view is 80% or more and 98% or less. Disclosure 5 is a flexible solar cell according to any one of Disclosures 1 to 4, characterized in that the dielectric constant of the insulating portion is 2.0 or more and 10 or less. Disclosure 6 is a flexible solar cell according to any one of Disclosures 1 to 5, characterized in that the distance from the end of the metal layer to the end of the power generation portion in a plan view is 10 mm or more. Disclosure 7 is a flexible solar cell according to any one of Disclosures 1 to 6, characterized in that the ratio of the thickness of the metal layer to the thickness of the insulating portion is 3% or more and 20% or less. Disclosure 8 is a method for installing a flexible solar cell, characterized in that the flexible solar cell according to any one of Disclosures 1 to 7 is fixed to an installation surface.

[0008] The flexible solar cell of the present invention will be described with reference to the drawings. Figure 1 is a schematic cross-sectional view showing an example of an installation method using the flexible solar cell of the present invention. The flexible solar cell in Figure 1 has a power generation unit 1 consisting of electrodes, a photoelectric conversion unit, a counter electrode, etc., and the entire power generation unit 1 is sealed with a sealing material 2, with a front sheet 3 placed on the light-receiving surface of the power generation unit 1. Furthermore, a metal layer 4 covering the entire power generation unit 1 is placed on the surface facing the light-receiving surface of the power generation unit 1, parallel to the light-receiving surface. In addition, an insulating layer 5 exists so as to cover at least the lower surface of the metal layer 4, and through holes are formed in a manner that penetrates the front sheet 3, the sealing material 2, and the insulating layer 5, and a protective layer 7 is formed on the inner surface of the through holes. Such a flexible solar cell is installed on the installation surface 6 by a fixing member 8. In the installation method using the flexible solar cell of the present invention shown in Figure 1, the current that flows sequentially from the power generation unit 1 to the sealing material 2, insulating layer 5, and metal layer 4 is interrupted by the insulating portion 10 of the insulating layer 5, thereby preventing current leakage to the installation surface 6. This prevents current leakage during installation and makes it possible to obtain the desired output of the solar cell. In addition, the presence of the metal layer 4 provides high condensation resistance even when installed outdoors. Figure 2 is a schematic cross-sectional view that further clarifies the configuration of the power generation unit 1 (the installation surface 6, protective layer 7, and fixing member 8 are omitted). The power generation unit 1 has an electrode 12, a photoelectric conversion unit 13, and a counter electrode 14, and on the surface of the power generation unit 1 facing the light-receiving surface, a metal layer 4 covering the entire power generation unit 1 is arranged parallel to the light-receiving surface. Here, a sealing material 2 and an insulating layer 5 are interposed between the counter electrode 14 and the metal layer 4. Note that the metal layer 4 is not a component of the power generation unit 1 like the electrode 12 or the counter electrode 14.

[0009] The flexible solar cell of the present invention has a power generation section having a light-receiving surface. Here, the light-receiving surface side refers to the side of the flexible solar cell to which light is incident, and the installation surface side refers to the side opposite to the light-receiving surface, that is, the side facing the installation surface when the flexible solar cell is installed. The power generation section is the part that converts sunlight into electricity and is composed of electrodes, counter electrodes, a photoelectric conversion section, an electron transport layer, a hole transport layer, etc., and has at least electrodes, a photoelectric conversion section, and a counter electrode. In this specification, "layer" means not only layers with clear boundaries, but also layers with a concentration gradient in which the contained elements change gradually. Elemental analysis of a layer can be performed, for example, by performing FE-TEM / EDS line analysis of the cross-section of the solar cell to confirm the elemental distribution of specific elements. Furthermore, in this specification, "layer" means not only flat, thin-film layers, but also layers that can form a complex, interwoven structure together with other layers. In this specification, "upper" refers to the direction of the light-incident surface side in the thickness direction of the solar cell, and "lower" refers to the opposite direction, that is, the direction of the installation surface side.

[0010] The materials for the electrodes and counter electrodes are not particularly limited and include, for example, FTO (fluorine-doped tin oxide), ITO (tin-doped indium oxide), AZO (aluminum zinc oxide), IZO (indium zinc oxide), GZO (gallium zinc oxide), sodium, sodium-potassium alloy, lithium, magnesium, aluminum, magnesium-silver mixture, magnesium-indium mixture, aluminum-lithium alloy, Al / Al ２ O ３ Examples include mixtures, Al / LiF mixtures, etc. Also, gold, silver, titanium, molybdenum, tantalum, tungsten, carbon, nickel, chromium, stainless steel (alloys of Fe, Cr, Ni, etc.) are also examples, and these are particularly preferred to be used as counter electrode materials. The electrode and counter electrode materials described above may be used individually, or two or more may be used in combination.

[0011] The thickness of the electrode and counter electrode is not particularly limited, but a preferred lower limit is 10 nm and a preferred upper limit is 1000 nm. If the thickness is 10 nm or more, the electrode can function while suppressing resistance. If the thickness is 1000 nm or less, the light transmittance can be further improved. A more preferred lower limit for the thickness of the electrode and counter electrode is 50 nm and a more preferred upper limit is 500 nm. The electrode and counter electrode may have exposed portions for electrical connection. Alternatively, another conductor (e.g., conductive tape material) electrically connected to the electrode and counter electrode may be provided and exposed.

[0012] The photoelectric conversion material constituting the above-mentioned photoelectric conversion unit only needs to be able to convert sunlight into electricity, and may be an inorganic semiconductor such as conventional silicon, or an organic-inorganic hybrid semiconductor such as an organic-inorganic perovskite compound. In particular, it is preferable that the above-mentioned photoelectric conversion unit, i.e., the power generation unit, contains an organic-inorganic perovskite compound because it allows for a thin and lightweight solar cell.

[0013] The above organic-inorganic perovskite compound is represented by the general formula AMX (where A is an organic base compound and / or alkali metal, M is a lead or tin atom, and X is a halogen atom). By using the above organic-inorganic perovskite compound in the photoelectric conversion layer, the photoelectric conversion efficiency of the solar cell can be improved.

[0014] The above A is an organic base compound and / or alkali metal. Specifically, the above organic base compounds include, for example, methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, dipentylamine, dihexylamine, trimethylamine, triethylamine, tripropylamine, tributylamine, tripentylamine, trihexylamine, ethylmethylamine, methylpropylamine, butylmethylamine, methylpentylamine, hexylmethylamine, ethylpropylamine, ethylbutylamine, formamidine, acetamidine, guanidine, imidazole, azole, pyrrole, aziridine, azirine, azetidine, azeto, azole, imidazoline, carbazole and their ions (for example, methylammonium (CH4) ３ NH ３ Examples include ) and phenethylammonium. Among these, methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, formamidine, acetamidine and their ions and phenethylammonium are preferred, and methylamine, ethylamine, propylamine, formamidine and their ions are more preferred. Examples of the alkali metals mentioned above include lithium, sodium, potassium, rubidium, cesium, etc.

[0015] The above M is a metal atom, which is either lead or tin. These metal atoms may be used individually or in combination of two or more. In particular, it is preferable that M contains lead because it can further increase the photoelectric conversion efficiency.

[0016] The above X is a halogen atom, and examples of halogen atoms include chlorine, bromine, iodine, sulfur, and selenium. These halogen atoms may be used individually or in combination of two or more. By including a halogen in the structure, the above organic-inorganic perovskite compound becomes soluble in organic solvents, making it possible to apply it to inexpensive printing methods and the like. In particular, X is preferably iodine because it narrows the energy band gap of the above organic-inorganic perovskite compound.

[0017] The above organic-inorganic perovskite compound preferably has a cubic crystal structure in which a metal atom M is located at the body center, an organic base compound or alkali metal A is located at each vertex, and a halogen atom X is located at the face center. Although the details are not clear, it is presumed that having the above structure allows the orientation of the octahedra in the crystal lattice to change easily, thereby increasing the electron mobility in the organic-inorganic perovskite compound and improving the photoelectric conversion efficiency of the solar cell.

[0018] The above organic-inorganic perovskite compound is preferably a crystalline semiconductor. A crystalline semiconductor is a semiconductor in which the X-ray scattering intensity distribution can be measured and a scattering peak can be detected. The crystalline nature of the organic-inorganic perovskite compound increases the electron mobility within it, thereby improving the photoelectric conversion efficiency of the solar cell.

[0019] Furthermore, the degree of crystallinity can also be evaluated as an indicator of crystallization. The degree of crystallinity can be determined by separating the scattering peaks originating from the crystalline portion and the halos originating from the amorphous portion, detected by X-ray scattering intensity distribution measurement, by fitting them together, calculating the integral of each intensity, and then calculating the ratio of the crystalline portion to the whole. The preferred lower limit for the degree of crystallinity of the above organic-inorganic perovskite compound is 30%. When the degree of crystallinity is 30% or higher, the electron mobility in the above organic-inorganic perovskite compound increases, improving the photoelectric conversion efficiency of the solar cell. A more preferred lower limit for the degree of crystallinity is 50%, and an even more preferred lower limit is 70%. In addition, methods for increasing the degree of crystallinity of the above organic-inorganic perovskite compound include, for example, thermal annealing, irradiation with high-intensity light such as lasers, and plasma irradiation.

[0020] The photoelectric conversion layer may further contain an organic semiconductor or an inorganic semiconductor in addition to the organic-inorganic perovskite compound, as long as the effects of the present invention are not impaired. The organic semiconductor or inorganic semiconductor mentioned herein may function as a hole transport layer or an electron transport layer. Examples of the organic semiconductor include compounds having a thiophene skeleton such as poly(3-alkylthiophene). Other examples include conductive polymers having a polyparaphenylene vinylene skeleton, a polyvinylcarbazole skeleton, a polyaniline skeleton, a polyacetylene skeleton, and the like. Further examples include compounds having a porphyrin skeleton such as a phthalocyanine skeleton, a naphthalocyanine skeleton, a pentacene skeleton, a benzoporphyrin skeleton, a spirobifluorene skeleton, and the like, as well as carbon-containing materials such as optionally surface-modified carbon nanotubes, graphene, and fullerenes.

[0021] Examples of the inorganic semiconductor include titanium oxide, zinc oxide, indium oxide, tin oxide, gallium oxide, tin sulfide, indium sulfide, zinc sulfide, CuSCN, Cu ２ O, CuI, MoO ３ , V ２ O ５ , WO ３ , MoS ２ , MoSe ２ , Cu ２ S, and the like.

[0022] When the photoelectric conversion layer contains the organic-inorganic perovskite compound and the organic semiconductor or the inorganic semiconductor, it may be a laminate obtained by laminating a thin-film organic semiconductor or inorganic semiconductor portion and a thin-film organic-inorganic perovskite compound portion, or may be a composite film obtained by compositing an organic semiconductor or inorganic semiconductor portion and an organic-inorganic perovskite compound portion. A laminate is preferable from the viewpoint of simple production process, and a composite film is preferable from the viewpoint that the charge separation efficiency in the organic semiconductor or the inorganic semiconductor can be improved.

[0023] The thickness of the above photoelectric conversion layer has a preferred lower limit of 5 nm and a preferred upper limit of 5000 nm. If the thickness is 5 nm or more, sufficient light can be absorbed, and the photoelectric conversion efficiency will be increased. If the thickness is 5000 nm or less, the occurrence of regions where charge separation is not possible can be suppressed, which leads to an improvement in photoelectric conversion efficiency. A more preferred lower limit for the above thickness is 10 nm, a more preferred upper limit is 1000 nm, an even more preferred lower limit is 20 nm, and an even more preferred upper limit is 500 nm.

[0024] When the photoelectric conversion layer is a composite film formed by combining an organic semiconductor or inorganic semiconductor portion with an organic-inorganic perovskite compound portion, the preferred lower limit of the thickness of the composite film is 30 nm, and the preferred upper limit is 3000 nm. If the thickness is 30 nm or more, sufficient light can be absorbed, and the photoelectric conversion efficiency will be high. If the thickness is 3000 nm or less, the charge can reach the electrodes more easily, and the photoelectric conversion efficiency will be high. A more preferred lower limit of the thickness is 40 nm, a more preferred upper limit is 2000 nm, an even more preferred lower limit is 50 nm, and an even more preferred upper limit is 1000 nm.

[0025] The method for forming the above-mentioned photoelectric conversion layer is not particularly limited and includes methods such as vacuum deposition, sputtering, vapor deposition (CVD), electrochemical deposition, and printing. In particular, by employing the printing method, solar cells that can exhibit high photoelectric conversion efficiency can be easily formed over a large area. Examples of printing methods include spin coating and casting, and methods using the printing method include roll-to-roll.

[0026] The above-mentioned power generation unit may have an electron transport layer between the electrode acting as the cathode or the counter electrode and the photoelectric conversion layer. The material of the electron transport layer is not particularly limited and includes, for example, N-type conductive polymers, N-type low molecular weight organic semiconductors, N-type metal oxides, N-type metal sulfides, alkali metal halides, alkali metals, surfactants, etc. Specifically, examples include cyano group-containing polyphenylene vinylene, boron-containing polymers, vasocuproin, vasophenanthrene, hydroxyquinolinatoaluminum, oxadiazole compounds, benzimidazole compounds, naphthalenetetracarboxylic acid compounds, perylene derivatives, phosphine oxide compounds, phosphine sulfide compounds, fluoro group-containing phthalocyanines, titanium dioxide, zinc oxide, indium oxide, tin oxide, gallium oxide, tin sulfide, indium sulfide, zinc sulfide, etc.

[0027] The electron transport layer described above may consist only of a thin-film electron transport layer, but it is preferable to include a porous electron transport layer. In particular, when the photoelectric conversion layer is a composite film formed by combining an organic semiconductor or inorganic semiconductor portion with an organic-inorganic perovskite compound portion, a more complex composite film (a more intricately interwoven structure) can be obtained, and the photoelectric conversion efficiency is higher, so it is preferable that the composite film is fabricated on a porous electron transport layer.

[0028] The preferred lower limit for the thickness of the electron transport layer is 1 nm, and the preferred upper limit is 2000 nm. If the thickness is 1 nm or more, holes can be sufficiently blocked. If the thickness is 2000 nm or less, it will not be a resistance during electron transport, and the photoelectric conversion efficiency will be high. A more preferred lower limit for the thickness of the electron transport layer is 3 nm, a more preferred upper limit is 1000 nm, an even more preferred lower limit is 5 nm, and an even more preferred upper limit is 500 nm.

[0029] The above-mentioned power generation unit may have a hole transport layer between the electrode that acts as the anode or the counter electrode and the photoelectric conversion layer. The material of the hole transport layer is not particularly limited, and the hole transport layer may be made of an organic material. Examples of materials for the hole transport layer include P-type conductive polymers, P-type low molecular weight organic semiconductors, P-type metal oxides, P-type metal sulfides, surfactants, etc. Specifically, examples include compounds having a thiophene skeleton such as poly(3-alkylthiophene). Also, examples include conductive polymers having a triphenylamine skeleton, poly(p-phenylenevinylene) skeleton, polyvinylcarbazole skeleton, polyaniline skeleton, polyacetylene skeleton, etc. Furthermore, examples include compounds having phthalocyanine skeletons, naphthalocyanine skeletons, pentacene skeletons, porphyrin skeletons such as benzoporphyrin skeletons, spirobifluorene skeletons, molybdenum sulfide, tungsten sulfide, copper sulfide, tin sulfide, fluoro group-containing phosphonic acids, carbonyl group-containing phosphonic acids, copper compounds such as CuSCN and CuI, etc.

[0030] The above-mentioned power generation unit may be formed on a substrate. Examples of the substrate include resin films made of polyimide or polyester-based heat-resistant polymers, metal foils, thin glass sheets, etc. In particular, from the viewpoint of flexibility and transparency, the substrate is preferably made of polyethylene terephthalate, polyethylene, polypropylene, polyethylene naphthalate, polymethyl methacrylate, polystyrene, or polycarbonate.

[0031] The above-mentioned substrate is preferably 30 μm or more and 200 μm or less in thickness. Having the substrate thickness within this range makes it difficult for the flame-retardant portion to wrap around the sides of the substrate and come into contact with the power generation portion, even when the substrate is in contact with the flame-retardant portion described later, and also increases flexibility. From the viewpoint of making it difficult for the power generation portion to reach the flame-retardant portion, the substrate thickness is more preferably 50 μm or more, and even more preferably 70 μm or more. From the viewpoint of further increasing flexibility, the substrate thickness is more preferably 150 μm or less, and even more preferably 100 μm or less.

[0032] The flexible solar cell of the present invention preferably has a sealing material. Preferably, the sealing material has a structure that covers the entire power generation section when viewed from the light-receiving surface side and the installation surface side. By covering both sides of the power generation section with the sealing material, deterioration of the power generation section due to components in the atmosphere can be suppressed. Preferably, the sealing material covers 105% or more of the upper and lower surfaces of the power generation section, and more preferably 110% or more. Note that the sealing material does not necessarily have to be in direct contact with the power generation section.

[0033] The sealing material that forms the main component of the above sealing material only needs to be able to seal the power generation section. Specific examples of the above sealing material include thermosetting resins, thermoplastic resins, or inorganic materials. Examples of thermosetting resins or thermoplastic resins include epoxy resins, acrylic resins, silicone resins, phenolic resins, melamine resins, and urea resins. Other examples include butyl rubber, polyester, polyurethane, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyvinyl alcohol, polyvinyl acetate, ABS resin, polybutadiene, polyamide, polycarbonate, polyimide, polyisobutylene, and polyisoprene. In particular, when the power generation section contains an organic-inorganic perovskite compound in the photoelectric conversion section, the durability of the power generation section over time can be further enhanced, therefore, polybutadiene, polyisobutylene, polyisoprene, and butyl rubber, which are resins having at least one skeleton selected from the group consisting of polybutadiene, polyisobutylene, and polyisoprene, are preferred.

[0034] The above-mentioned encapsulant may contain a crosslinking agent. By including a crosslinking agent in the encapsulant, the water expansion rate can be easily adjusted to the above range. Examples of the above-mentioned crosslinking agent include quinone oximes, bisphenols, and alkylphenol resins.

[0035] The flexible solar cell of the present invention may optionally include a front sheet at the uppermost position on the light-receiving surface side. The front sheet functions to suppress light reflection and improve the drainage performance of the solar cell surface by forming patterns such as irregularities and arcs on its surface. For example, when a front sheet having a convex arc with a vertex at the center of the solar cell is provided, a drainage gradient from the center to the edge of the solar cell can be formed; when a front sheet having a concave arc with a lowest point at the center of the solar cell is provided, a water collecting portion extending from the edge toward the center of the solar cell can be provided. By providing such a drainage gradient or water collecting portion, accumulation of dirt and the like can be concentrated at a specific location. In addition, designability can be improved by randomly forming irregularities on the front sheet.

[0036] The material of the front sheet is not particularly limited as long as it has transparency, and examples thereof include fluorine-containing resins, vinyl chloride-based resins, polyethylene-based resins, and polycarbonate-based resins. Specific examples include polycarbonate, polyvinyl chloride, tetrafluoroethylene resin, polyvinylidene fluoride, and polychlorotrifluoroethylene. Among these, fluorine-containing resins are preferred because of their excellent weather resistance.

[0037] The thickness of the front sheet is not particularly limited, but from the viewpoint of balancing light transmittance and the functionality of the front sheet, the thickness is preferably 25 µm or more, more preferably 50 µm or more, and preferably 1000 µm or less, more preferably 300 µm or less.

[0038] The flexible solar cell of the present invention has a metal layer that is arranged parallel to the surface opposite to the light-receiving surface of the power generation unit and covers the entire power generation unit. The expression "covers the entire power generation unit" as used herein means that when the power generation unit and the metal layer are viewed from the lower surface (when viewed from the bottom), the metal layer is arranged so as to cover the entire power generation unit. The metal layer may be in the form of a metal foil or a thin metal film.

[0039] Examples of the material for the metal layer include aluminum, cobalt, chromium, molybdenum, tungsten, gold, silver, copper, magnesium, nickel, titanium, and stainless steel. Two or more of these may also be used in combination. Among these, aluminum and cobalt are preferable, and aluminum is more preferable, because they have high dew resistance and improve the photoelectric conversion efficiency of flexible solar cells.

[0040] The thickness of the metal layer is not particularly limited, but from the viewpoint of balancing flexibility and the functionality of dew resistance, it is preferably 10 µm or more, more preferably 30 µm or more, preferably 500 µm or less, and more preferably 100 µm or less. In particular, it is preferable that the thickness is as thin as a film, not as thick as a substrate.

[0041] In the flexible solar cell of the present invention, the distance from the end of the metal layer to the end of the power generation unit in plan view is preferably 5 mm or more, and more preferably 10 mm or more. This can suppress the intrusion of water vapor from the end of the metal layer. The distance from the end of the metal layer to the end of the power generation unit is more preferably 20 mm or more, and even more preferably 25 mm or more. Although there is no particular limitation on the upper limit, 100 mm or less is preferable. The distance from the end of the metal layer to the end of the power generation unit in plan view means the length in the parallel direction from the end of the metal layer to the end of the power generation unit when viewed in plan, and refers to the length "A" in the case of FIG. 1. Further, it is preferable that the ratio of the area of the power generation unit to the area of the metal layer in plan view is 80% or more and 98% or less.

[0042] The flexible solar cell of the present invention has an insulating layer that covers at least the lower surface of the metal layer. The insulating layer is not particularly limited as long as it covers at least the lower surface of the metal layer, but it is preferable that the entire metal layer is covered with the insulating layer as shown in FIG. 1. In particular, it is preferable that the side surfaces of the metal layer are covered with the insulating layer. Further, it is preferable that the upper surface of the metal layer is covered with the insulating layer. In such a case, since the insulating layer and the sealing layer are interposed between the electrode of the power generation unit and the metal layer, the occurrence of leakage current can be more suitably prevented.

[0043] The material for the insulating layer is not particularly limited as long as it is an insulating material, and examples include insulating resins. Examples of insulating resins include polyethylene, polypropylene, polystyrene, polyvinyl chloride, polycarbonate, polyamide, fluorine-containing resin, polyethylene terephthalate, polyphenylene sulfide, polyetheretherketone, polysulfone, polyetherimide, polyvinylidene fluoride, polyimide, silicone, acrylic resin, ABS resin, epoxy resin, phenolic resin (Bakelite), polyurethane, and cyano resin. Among these, polyimide, silicone, and polyethylene terephthalate are more preferred because they have excellent heat resistance and mechanical strength. The insulating part and the sealing material may be made of the same material. If the same material is used, the production process is simplified and it can be manufactured at a low cost. On the other hand, if different materials are used, a material with higher insulating properties than the sealing material can be selected, so leakage current can be suppressed more effectively.

[0044] The thickness of the insulating layer is not particularly limited, but from the viewpoint of balancing flexibility and insulating functionality, it is preferably 180 μm or more, more preferably 600 μm or more, preferably 3000 μm or less, and more preferably 2000 μm or less.

[0045] The flexible solar cell of the present invention has at least one through-hole in a direction that penetrates the insulating layer. The through-hole is for mounting to an installation surface via a fixing member or the like. In addition to the insulating layer, the through-hole may also penetrate the front sheet and sealing material, as shown in Figure 1.

[0046] The diameter of the through-hole is not particularly limited, but is preferably 5 mm or more, more preferably 10 mm or more, preferably 50 mm or less, and more preferably 30 mm or less. The shape of the through-hole can be, for example, a circle or a polygon such as a square, but is preferably circular.

[0047] The through-hole has a protective layer on its inner surface. The protective layer serves to reinforce the through-hole. The material of the protective layer is not particularly limited, but is preferably a metal. For example, known materials such as iron, aluminum alloy, stainless steel, nickel alloy, and copper alloy can be used.

[0048] The thickness of the protective layer is not particularly limited, but is preferably 0.1 mm or more, more preferably 1 mm or more, preferably 10 mm or less, and more preferably 5 mm or less.

[0049] In the flexible solar cell of the present invention, the metal layer and the protective layer are arranged with an insulating portion in between. In the present invention, the insulating portion prevents current flowing from the power generation unit from leaking to the installation surface by blocking the current flowing from the power generation unit at the insulating portion. The insulating portion is not particularly limited as long as it is installed between the metal layer and the protective layer, but it is preferable that the insulating layer is interposed between the metal layer and the protective layer to form an insulating portion, as shown in Figure 1. Furthermore, it is preferable that the protective layer is in direct contact with the front sheet.

[0050] The same material as the insulating layer can be used for the insulating portion. The dielectric constant of the insulating portion is preferably 1.0 or more and 15 or less, and more preferably 2.0 or more and 10 or less. The dielectric constant is even more preferably 3.0 or more, and even more preferably 8.0 or less. The dielectric constant can be measured using an impedance analyzer.

[0051] The thickness of the insulating portion is not particularly limited, but from the viewpoint of insulating properties, it is preferably 100 μm or more, more preferably 180 μm or more, preferably 1000 μm or less, and more preferably 700 μm or less. The ratio of the thickness of the metal layer to the thickness of the insulating portion is preferably 3% or more and 20% or less. This prevents current leakage to the installation surface. The ratio of the thickness is more preferably 4% or more, more preferably 18% or less, and even more preferably 9% or less.

[0052] In the flexible solar cell of the present invention, it is preferable that the minimum distance between the metal layer and the protective layer is 0.4 mm or more and 100 mm or less. The minimum distance represents the length of the insulating portion in the planar direction (parallel direction), and being within this range prevents current leakage to the installation surface. The minimum distance is more preferably 1 mm or more, even more preferably 12 mm or more, even more preferably 80 mm or less, and even more preferably 50 mm or less. Note that "minimum distance between the metal layer and the protective layer" represents "minimum width in the parallel direction of the insulating portion".

[0053] In the flexible solar cell of the present invention, it is preferable that the minimum distance between the electrodes of the power generation section and the metal layer is 50 μm or more and 5000 μm or less. The above minimum distance represents the length in the thickness direction (vertical direction) of the metal layer, and being within the above range prevents current leakage to the installation surface. The above minimum distance is more preferably 100 mm or more, even more preferably 150 mm or more, even more preferably 1000 mm or less, and even more preferably 500 mm or less. Note that the "minimum distance between the electrodes of the power generation section and the metal layer" is the length shown as "B" in Figure 2.

[0054] In the flexible solar cell of the present invention, it is preferable that the resistance between the electrodes of the power generation section and the metal layer is 10 kΩ or more and 10,000 kΩ or less. By keeping it within this range, the overall thickness can be reduced and current leakage to the installation surface can be prevented. It is preferable that the above resistance value is 100 kΩ or more and 1,000 kΩ or less. Note that the above electrodes refer to the electrodes installed in the power generation section that are closer to the metal layer.

[0055] The flexible solar cell of the present invention may have a backsheet at the bottom of the mounting surface. The backsheet plays a role in improving the weather resistance of the solar cell by preventing the intrusion of substances that cannot be prevented by the sealing layer alone, such as moisture. Examples of materials for the backsheet include polyethylene terephthalate.

[0056] The thickness of the backsheet is not particularly limited, but from the viewpoint of balancing flexibility and the functionality of the backsheet, it is preferably 50 μm or more, more preferably 100 μm or more, preferably 1000 μm or less, and most preferably 500 μm or less.

[0057] The method for manufacturing the flexible solar cell of the present invention is not particularly limited, but it is preferable to first laminate an insulating material onto a metal layer to create an insulating sheet in which the entire surface of the metal layer is covered with an insulating layer, then laminate a power generation unit between a sheet (sheet A) having a sealing material and, if necessary, a front sheet and a sheet (sheet B) having a sealing material and the insulating sheet, and further form through holes having a protective layer.

[0058] One example of the lamination method described above is the roll-to-roll method. By using the roll-to-roll method, large-area solar cells can be manufactured continuously.

[0059] A method for installing a flexible solar cell, characterized by fixing the flexible solar cell to an installation surface, is also part of the present invention. The method of fixing to the installation surface is not particularly limited, but examples include inserting a fixing member into a through hole and fixing it. Examples of the fixing member include fixing to the installation surface using a stake, bolt, screw, pin, etc.

[0060] The material of the fixing member described above should have sufficient rigidity to fix the flexible solar cell and be able to undergo plastic deformation. Examples include metals such as steel, aluminum alloy, stainless steel, nickel alloy, and copper alloy; hard plastics such as polyvinyl chloride, polycarbonate, acrylic, polypropylene, ABS resin, AS resin, and PPS resin; rubber; ceramics; or composite materials thereof.

[0061] According to the present invention, it is possible to provide a flexible solar cell and a method for installing a flexible solar cell that have high condensation resistance and can prevent current leakage during installation.

[0062] This is a schematic cross-sectional diagram illustrating an example of an installation method using the flexible solar cell of the present invention. This is a schematic cross-sectional diagram illustrating an example of a flexible solar cell of the present invention. This is a schematic cross-sectional diagram illustrating an example of an installation method using a flexible solar cell having through holes.

[0063] The present invention will be described in more detail below with reference to specific embodiments, but the present invention is not limited to these embodiments.

[0064] (Example 1) (1) A polyethylene terephthalate (PET) film with a thickness of 100 μm was prepared as the manufacturing substrate layer for a flexible solar cell. An ITO film with a thickness of 200 nm was formed on the block layer as an electrode by sputtering. A thin-film electron transport layer with a thickness of 20 nm was formed on the formed electrode by sputtering. Furthermore, a titanium dioxide paste containing titanium dioxide was applied to the thin-film electron transport layer by spin coating and then dried to form a porous electron transport layer with a thickness of 100 nm. Next, lead iodide was dissolved as a metal halide compound in a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) to prepare a 1 M solution, which was then formed on the porous electron transport layer by spin coating. Furthermore, methylammonium iodide was dissolved in 2-propanol as an amine compound to prepare an 8% by weight solution. This solution is applied to the lead iodide mentioned above by spin coating, and annealed at 150°C for 10 minutes to form a 700 nm thick organic inorganic perovskite compound, CH ３ NH ３ PbI ３ A photoelectric conversion layer containing [a specific substance] was formed. Next, a chlorobenzene solution containing 2% by weight of Spiro-OMETAD (Merck) was applied to the photoelectric conversion layer by spin coating and then dried to form a hole transport layer with a thickness of 80 nm. Subsequently, a 100 nm thick Al film was formed on the photoelectric conversion layer by sputtering to serve as a counter electrode, and a power generation unit consisting of an electrode, electron transport layer, photoelectric conversion layer, hole transport layer, and counter electrode was obtained on a block layer.

[0065] Next, a PET sheet with a thickness of 50 μm was prepared as the front sheet. Then, a encapsulant made of polyisobutylene was applied to the front sheet to a thickness of 70 μm to obtain sheet A. On the other hand, an insulating sheet was prepared in which a 30 μm thick aluminum foil (metal layer) was completely covered with PET (dielectric constant: 3.0), and a encapsulant made of polyisobutylene was applied to it to a thickness of 70 μm to obtain sheet B. After that, the encapsulant of sheet A and the encapsulant of sheet B were placed opposite each other, and a power generation unit was placed between sheet A and sheet B and laminated to obtain a laminate. Then, holes were formed in the four corners of the obtained laminate using a 1 cm diameter eyelet punch, penetrating the front sheet, encapsulant, and insulating layer, and through holes were formed by eyelet processing (protective layer, stainless steel), thereby obtaining a flexible solar cell. The resulting flexible solar cell had a configuration in which a metal layer and a protective layer were arranged with an insulating layer (PET) in between, as shown in Figure 1. The minimum distance between the metal layer and the protective layer was 30 mm, the distance from the edge of the metal layer to the edge of the power generation section in a plan view was 30 mm, and the ratio of the thickness of the metal layer to the thickness of the insulating layer was 4%. The minimum distance from the electrode (counter electrode) of the power generation section to the metal layer was 200 μm.

[0066] (2) Installation of flexible solar cells A stake was inserted into the through hole of the obtained flexible solar cell and installed on the grass surface. Since the flexible solar cell obtained in Example 1 has a metal layer, it can exhibit high dew-proof properties even when installed in a place such as a grass surface.

[0067] (Examples 2-6) For Examples 2-4 and 6, flexible solar cells were obtained in the same manner as in Example 1, except that the "minimum distance between the metal layer and the protective layer," "distance from the edge of the metal layer to the edge of the power generation section in a plan view," "minimum distance from the electrodes of the power generation section to the metal layer," and "ratio of the thickness of the metal layer to the thickness of the insulating section" were changed to those shown in Table 1. For Example 5, a flexible solar cell was obtained in the same manner as in Example 1, except that the insulating section was changed from "PET (dielectric constant: 3.0)" to "phenol resin (dielectric constant: 5.0)." Stakes were inserted into the through holes of the obtained flexible solar cells and installed on a grass surface. It was confirmed that the flexible solar cells obtained in Examples 2-6 also exhibit high dew prevention even when installed on a grass surface, due to the presence of a metal layer.

[0068] (Examples 7-10) For Examples 7-10, flexible solar cells were obtained in the same manner as in Example 1, except that the "minimum distance between the metal layer and the protective layer," "distance from the edge of the metal layer to the edge of the power generation section in a plan view," "minimum distance from the electrode of the power generation section to the metal layer," and "ratio of the thickness of the metal layer to the thickness of the insulating section" were changed to those shown in Table 1. In Example 9, the insulating section was changed from "PET (dielectric constant: 3.0)" to "fluororesin (dielectric constant: 18.0)."

[0069] (Comparative Example 1) A flexible solar cell was obtained in the same manner as in Example 1, except that the metal layer and the protective layer were in direct contact as shown in Figure 3.

[0070] <Evaluation> The flexible solar cells obtained in the examples and comparative examples were evaluated as follows.

[0071] (1) Evaluation of Leakage Current Leakage current was measured using a clamp ammeter for leakage current. The measured values ​​are shown in Table 1. A measured value of 0A was evaluated as "○", a measured value exceeding 0A but 0.1A or less was evaluated as "△", and a measured value exceeding 0.1A was evaluated as "×". A leakage current of 0A is below the measurement limit and indicates that no current leakage is occurring.

[0072]

[0073] 1. Power generation unit 2. Sealing material 3. Front sheet 4. Metal layer 5. Insulating layer 6. Mounting surface 7. Protective layer 8. Fixing member 10. Insulating part 12. Electrode 13. Photoelectric conversion unit 14. Counter electrode

Claims

1. A flexible solar cell comprising: a power generation unit having a light-receiving surface; a metal layer arranged parallel to the surface facing the light-receiving surface of the power generation unit and covering the entire power generation unit; and an insulating layer covering at least the lower surface of the metal layer, wherein the insulating layer has at least one through-hole in a direction penetrating it, the through-hole has a protective layer on its inner surface, and the metal layer and the protective layer are arranged with the insulating unit in between.

2. The flexible solar cell according to claim 1, characterized in that the minimum distance between the metal layer and the protective layer is 0.4 mm or more and 100 mm or less.

3. The flexible solar cell according to claim 1 or 2, characterized in that the entire metal layer is covered with an insulating layer.

4. The flexible solar cell according to any one of claims 1 to 3, characterized in that the ratio of the area of ​​the power generation section to the area of ​​the metal layer in a plan view is 80% or more and 98% or less.

5. The flexible solar cell according to any one of claims 1 to 4, characterized in that the insulating portion has a dielectric constant of 2.0 or more and 10 or less.

6. The flexible solar cell according to any one of claims 1 to 5, characterized in that the distance from the end of the metal layer to the end of the power generation section in a plan view is 10 mm or more.

7. The flexible solar cell according to any one of claims 1 to 6, characterized in that the ratio of the thickness of the metal layer to the thickness of the insulating portion is 3% or more and 20% or less.

8. A method for installing a flexible solar cell, characterized by fixing the flexible solar cell described in any one of claims 1 to 7 to an installation surface.

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