Waterproof sheets for solar cells and solar cells with waterproof sheets

Abstract

To provide a waterproof sheet for solar cells that can suppress the migration of plasticizers added to the waterproof sheet to the adhesive layer and solar cells, and a highly reliable solar cell equipped with such a waterproof sheet. [Solution] The waterproof sheet for solar cells according to the present invention is a flexible waterproof sheet for solar cells provided between a sheet-type solar cell and a frame, comprising a waterproof layer made of a soft polyvinyl chloride resin containing a plasticizer, and a shielding layer laminated on the waterproof layer and containing metal, wherein the shielding layer is positioned on the sheet-type solar cell side of the waterproof layer.

Description

Technical Field

[0001] The present invention relates to a waterproof sheet for a solar cell and a solar cell with a waterproof sheet.

Background Art

[0002] As a method of installing a solar cell on a structure such as a roof of a building, a method of laying a solar cell integrated waterproof sheet material is known.

[0003] For example, Patent Document 1 discloses a waterproof sheet in which a base material sheet layer, an intermediate resin layer, and a surface resin layer are sequentially laminated. Further, Patent Document 1 discloses a solar cell integrated waterproof sheet material in which a thin film amorphous solar cell is embedded in the intermediate resin layer.

[0004] Such a solar cell integrated waterproof sheet material can be constructed in the same manner as an ordinary waterproof sheet. Therefore, a solar cell can be installed while imparting waterproofness to the structure without performing large-scale installation work.

[0005] Further, Patent Document 2 discloses a solar cell layer with a waterproof sheet formed by bonding, via an adhesive layer, a laminated body in which a waterproof sheet and two layers of sealing materials and two layers of protective layers are provided so as to sandwich a film-like solar cell cell. Polyvinyl chloride is used as a constituent material of the waterproof sheet. Polyvinyl chloride imparts excellent waterproofness to the waterproof sheet. Further, by adding a predetermined amount of a plasticizer to polyvinyl chloride, the mechanical properties and flexibility of the waterproof sheet can be enhanced.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

[0007] However, in solar cell layers with waterproof sheets, over time, plasticizers added to the waterproof sheet may migrate to the adhesive layer and laminate. These migrated plasticizers can cause deterioration of the adhesive layer and a decrease in the performance of the solar cells.

[0008] The object of the present invention is to provide a waterproof sheet for solar cells that can suppress the migration of plasticizers added to the waterproof sheet to the adhesive layer and solar cells, and a highly reliable solar cell equipped with such a waterproof sheet. [Means for solving the problem]

[0009] These objectives are achieved by the present invention as described in (1) to (11) below. (1) A flexible waterproof sheet for solar cells, provided between a sheet-type solar cell and a building structure, A waterproof layer composed of a flexible polyvinyl chloride resin containing a plasticizer, A shielding layer containing metal is laminated on the aforementioned waterproof layer, Equipped with, A waterproof sheet for solar cells, characterized in that the shielding layer is positioned on the sheet-type solar cell side of the waterproof layer.

[0010] (2) The shielding layer is a foil made of the metal, as described in (1) above, for a waterproof sheet for solar cells.

[0011] (3) The waterproof sheet for solar cells as described in (2) above, wherein the foil body is composed of an element, alloy, or compound containing Al, Cu, Cr, Ti, Zn, Fe, or Si.

[0012] (4) The shielding layer comprises a resin film and a metal film formed on the resin film, as described in (1) above.

[0013] (5) The waterproof sheet for solar cells according to (4) above, wherein the metal film is composed of a single substance, an alloy or a compound containing Al, Cu, Cr, Ti or Si.

[0014] (6) The waterproof sheet for solar cells according to (4) or (5) above, wherein the thickness of the metal film is 3 nm or more and 500 nm or less.

[0015] (7) The waterproof sheet for solar cells according to (1) above, wherein the thickness of the shielding layer is 1 μm or more and 500 μm or less.

[0016] (8) The waterproof sheet for solar cells according to (1) above, wherein the thickness of the waterproof layer is 0.1 mm or more and 5 mm or less.

[0017] (9) The waterproof sheet for solar cells according to any one of (1) to (8) above, comprising an interlayer adhesive layer for adhering the waterproof layer and the shielding layer.

[0018] (10) The waterproof sheet for solar cells according to any one of (1) to (9) above, wherein the specular glossiness (60° / 60°) measured by the method specified in JIS Z 8741:1997 on the surface of the shielding layer is 50% or more and 900% or less.

[0019] (11) A solar cell with a waterproof sheet, comprising the waterproof sheet for solar cells according to any one of (1) to (10) above, the sheet-type solar cell, characterized by comprising. [Advantages of the Invention]

[0020] According to the present invention, a waterproof sheet for solar cells capable of suppressing the migration of the plasticizer added to the waterproof sheet to the adhesive layer or the solar cell can be obtained.

[0021] Further, according to the present invention, a highly reliable solar cell with a waterproof sheet including the above waterproof sheet for solar cells can be obtained. [Brief Description of the Drawings]

[0022] [Figure 1] It is an exploded cross-sectional view showing a solar cell with a waterproof sheet according to an embodiment installed on a body. [Figure 2] It is a detailed view of the sheet-type solar cell shown in FIG. 1. [Figure 3] It is a cross-sectional view showing a configuration example of a solar cell with a waterproof sheet in which a plurality of laminates (laminates including a photoelectric conversion layer) are embedded in a sealing material. [Figure 4] It is a cross-sectional view showing a configuration example when the shielding layer of FIG. 1 is a composite. [Figure 5] It is a cross-sectional view showing a configuration example when the waterproof sheet for a solar cell of FIG. 1 includes an interlayer adhesive layer.

Mode for Carrying Out the Invention

[0023] Hereinafter, the waterproof sheet for a solar cell and the solar cell with a waterproof sheet according to the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

[0024] 1. Solar cell with a waterproof sheet The solar cell with a waterproof sheet according to the embodiment is used for installing a solar cell on a body such as the roof of a building.

[0025] FIG. 1 is an exploded cross-sectional view showing a solar cell 1 with a waterproof sheet according to an embodiment installed on a body 100. In FIG. 1, X-axis, Y-axis, and Z-axis are set as three axes orthogonal to each other, and each axis is indicated by an arrow. Also, the base end side of the arrow is referred to as the minus side of each axis, and the tip side is referred to as the plus side of each axis. Further, the Z-axis plus side is also referred to as "up", and the Z-axis minus side is also referred to as "down". In each figure, for the sake of illustration, the dimensional ratios of each part are made different from the actual ones.

[0026] The structure 100 shown in Figure 1 includes a flat roof floor 110. The upper surface of the floor 110 extends along the XY plane. A plate-shaped insulation material 120 is laid on the upper surface of the floor 110. A sheet-shaped insulating layer 130 is laid on the upper surface of the insulation material 120. A sheet-shaped existing waterproof layer 140 is laid on the upper surface of the insulating layer 130.

[0027] The insulation material 120 provides thermal insulation to the floor 110. Examples of constituent materials for the insulation material 120 include expanded polystyrene, polyurethane foam, polyisocyanurate foam, and phenolic foam. The insulation material 120 may be provided as needed and may be omitted.

[0028] The insulating layer 130 prevents direct contact between the heat insulation material 120 and the existing waterproofing layer 140, thereby suppressing deterioration and alteration of the heat insulation material 120 and the existing waterproofing layer 140. Examples of constituent materials for the insulating layer 130 include resin materials, metal materials, oxide materials, etc. The constituent materials for the insulating layer 130 may also be a composite material of two or more of these types. The insulating layer 130 may be provided as needed and may be omitted.

[0029] The existing waterproof layer 140 is a watertight layer formed by various waterproofing treatments. Examples of waterproofing treatments include sheet waterproofing, urethane waterproofing, asphalt waterproofing, and FRP waterproofing. Of these, the existing waterproof layer 140 formed by sheet waterproofing is mainly composed of resin materials such as vinyl chloride resin, ethylene vinyl acetate resin, and thermoplastic elastomer, and is preferably mainly composed of vinyl chloride resin.

[0030] Furthermore, any additional material, such as a concrete overlay layer, may be provided on the existing waterproofing layer 140. Also, the existing waterproofing layer 140 may be provided only as needed and may be omitted.

[0031] A solar cell with a waterproof sheet 1 is laid on the upper surface of the existing waterproof layer 140. Installation can be done by welding such as heat welding or solvent welding, or by bonding with an adhesive. The solar cell with a waterproof sheet 1 shown in Figure 1 comprises a waterproof sheet 2 for solar cells, a sheet-type solar cell 3, and an inter-sheet adhesive layer 4, and these are integrated into a laminate. The solar cell with a waterproof sheet 1 is positioned so that the waterproof sheet 2 for solar cells is located between the sheet-type solar cell 3 and the existing waterproof layer 140. By laying such a solar cell with a waterproof sheet 1 on the upper surface of the existing waterproof layer 140 (on the structure 100), waterproofing of the floor 110 and insulation material 120, and installation of the sheet-type solar cell 3 can be performed simultaneously. In the following explanation, it is assumed that light is irradiated from the top to the bottom of Figure 1, and that the sheet-type solar cell 3 receives the light and generates electricity.

[0032] Examples of sheet-type solar cells 3 include perovskite solar cells, thin-film silicon solar cells, CIGS solar cells, dye-sensitized solar cells, organic semiconductor solar cells, multi-junction solar cells, and quantum dot solar cells. The waterproof sheet 2 for solar cells comprises a waterproof layer 21 and a shielding layer 22, and is flexible.

[0033] The waterproof layer 21 shown in Figure 1 is located on the upper surface of the existing waterproof layer 140. The waterproof layer 21 is made of a flexible polyvinyl chloride resin containing a plasticizer. Such a waterproof layer 21 has good flexibility, mechanical properties, and waterproofing properties. Therefore, it is possible to realize a waterproof sheet 2 for solar cells that has excellent shape conformability and can provide good waterproofing treatment to the structure 100.

[0034] The shielding layer 22 shown in Figure 1 is located on the upper surface of the waterproof layer 21. The shielding layer 22 contains metal. Such a shielding layer 22 has good shielding properties due to the metal. Therefore, when the plasticizer contained in the waterproof layer 21 tries to migrate towards the inter-sheet adhesive layer 4 and the sheet-type solar cell 3 over time, the shielding layer 22 suppresses this migration. This suppresses the deterioration of the inter-sheet adhesive layer 4 and the degradation of the characteristics of the sheet-type solar cell 3 that occur due to the migration of plasticizer.

[0035] The inter-sheet adhesive layer 4 shown in Figure 1 is provided between the waterproof sheet 2 for the solar cell and the sheet-type solar cell 3, and adheres them together.

[0036] 1.1. Sheet-type solar cells The sheet-type solar cell 3 shown in Figure 1 is, as an example, a perovskite solar cell. Because perovskite solar cells are manufactured at a lower temperature than other solar cells, organic materials can be used as constituent materials. This makes it possible to realize a flexible and lightweight sheet-type solar cell 3.

[0037] Figure 2 is a detailed view of the sheet-type solar cell 3 shown in Figure 1. The sheet-type solar cell 3 shown in Figure 2 comprises a photoelectric conversion layer 31, a back electrode 32, a front electrode 33, a substrate 34, a sealing material 35, a back protective layer 36, and a front protective layer 37.

[0038] The photoelectric conversion layer 31 has the function of absorbing light, generating electric charge, and separating the generated charge. The photoelectric conversion layer 31 includes, for example, a perovskite compound represented by the compositional formula ABX3. A is a monovalent cation such as alkali metal cations and organic cations. B is a divalent cation such as lead cations and tin cations. X is a monovalent anion such as halogen anions.

[0039] The thickness of the photoelectric conversion layer 31 is preferably 50 nm to 10 μm. The thickness of the photoelectric conversion layer 31 can be determined by observing a magnified cross-section of the sheet-type solar cell 3 and averaging the thickness of 10 or more points on the photoelectric conversion layer 31.

[0040] The back electrode 32 is a current collector that collects the charge separated by the photoelectric conversion layer 31. The material of the back electrode 32 is not particularly limited as long as it is conductive, but examples include gold, platinum, silver, copper, aluminum, etc., in their elemental form or alloy, graphene, etc. The back electrode 32 may also be translucent. In this case, the material of the back electrode 32 may be a translucent and conductive material as described later.

[0041] The thickness of the back electrode 32 is preferably 1 nm to 1000 nm, and more preferably 5 nm to 500 nm. By setting the thickness of the back electrode 32 within the above range, the resistivity of the back electrode 32 can be sufficiently reduced, and the efficiency of forming the back electrode 32 can be improved.

[0042] The surface electrode 33 is a current collector that collects the charge separated in the photoelectric conversion layer 31. The constituent material of the surface electrode 33 is not particularly limited as long as it is a transparent and conductive material, but examples of oxides include ITO (Indium Tin Oxide), FTO (F-doped Tin Oxide), ATO (Antimony Tin Oxide), IZO (Indium Zinc Oxide), In2O3, SnO2, Sb-containing SnO2, and Al-containing ZnO.

[0043] The thickness of the surface electrode 33 is preferably 1 nm to 1000 nm, and more preferably 10 nm to 500 nm. By setting the thickness of the surface electrode 33 within the above range, the resistivity of the surface electrode 33 can be sufficiently reduced, and the efficiency of forming the surface electrode 33 can be improved.

[0044] The thicknesses of the back electrode 32 and the front electrode 33 are determined by observing a magnified cross-section of the sheet-type solar cell 3 and averaging the thicknesses of at least 10 points on each of the back electrode 32 and the front electrode 33.

[0045] The substrate 34 transmits light incident from above and increases the mechanical strength of the sheet-type solar cell 3. The constituent material of the substrate 34 is not particularly limited as long as it is a light-transmitting and insulating material, but examples include polyethylene terephthalate, polyethylene naphthalate, polystyrene, polypropylene, polyamide, acrylic resin, polyimide, etc.

[0046] The thickness of the substrate 34 is preferably 5 μm to 500 μm, more preferably 10 μm to 300 μm, and even more preferably 20 μm to 200 μm. If the thickness of the substrate 34 is within the above range, it is possible to achieve both the mechanical strength and flexibility of the sheet-type solar cell 3. If the thickness of the substrate 34 falls below the lower limit, the mechanical strength of the sheet-type solar cell 3 may be insufficient. On the other hand, if the thickness of the substrate 34 exceeds the upper limit, the flexibility of the sheet-type solar cell 3 may decrease. The base material 34 may be provided as needed, but may be omitted.

[0047] The sealing material 35 is filled between the back protective layer 36 and the front protective layer 37, encapsulating the laminate of the photoelectric conversion layer 31, back electrode 32, front electrode 33, and substrate 34. This suppresses the intrusion of moisture, oxygen, etc., and protects the photoelectric conversion layer 31 from them. In particular, in the example shown in Figure 2, the sealing material 35 surrounds the top, bottom, and sides of the laminate. This minimizes the entry routes for moisture, oxygen, etc., and significantly enhances the durability of the sheet-type solar cell 3. Furthermore, a single layer of sealing material 35 may contain multiple of the above-mentioned laminates.

[0048] Figure 3 is a cross-sectional view showing an example of the configuration of a solar cell 1 with a waterproof sheet, in which multiple laminates (laminated structures including a photoelectric conversion layer 31) are embedded in a sealing material 35.

[0049] In the waterproof solar cell 1 shown in Figure 3, multiple laminates may be arranged at predetermined intervals along the XY plane, and these laminates may be embedded in a single layer of sealing material 35. With such a configuration, it is possible to realize a waterproof solar cell 1 that is sufficiently large while increasing the degree of freedom in the size of the laminates. In other words, it is possible to realize a larger waterproof solar cell 1 that is more efficient to install while optimizing the manufacturing efficiency and conversion efficiency of the laminates.

[0050] Furthermore, the sealing material 35 may be made up of two or more layers. For example, the sealing material 35 may be formed by placing the above-mentioned laminate between two layers of films made of the constituent materials of the sealing material 35, and sealing the laminate with the films.

[0051] Examples of constituent materials for the sealing material 35 include ultraviolet-curable resins such as acrylic resin, urethane resin, vinyl ester resin, and alkyd resin; thermosetting resins such as epoxy resin, polyester resin, urethane resin, silicone resin, and ethylene vinyl acetate (EVA); and thermoplastic resins such as polyvinyl butyral (PVB), polyisobutylene (PIB), polyolefin, polystyrene, ionomer resin, and isobutylene-based elastomer.

[0052] Of these, silicone resin, ethylene vinyl acetate, or polyolefin is preferably used.

[0053] Silicone resins and ethylene vinyl acetate are preferred in terms of flexibility, moldability, and adhesiveness.

[0054] As the polyolefin, for example, an ethylene-based copolymer containing an ethylene monomer is preferably used. Ethylene-based copolymers have low water vapor permeability and good insulation properties under wet conditions. For this reason, they are useful as constituent materials for the sealing material 35. Examples of ethylene-based copolymers include ethylene-methyl acrylate copolymer, ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, and ethylene-α-olefin copolymer.

[0055] The back protective layer 36 protects the photoelectric conversion layer 31 and other components from moisture, oxygen, external pressure, etc. Examples of materials that make up the back protective layer 36 include polyethylene resin, polypropylene resin, cyclic polyolefin resin, AS (acrylonitrile-styrene) resin, ABS (acrylonitrile-butadiene-styrene) resin, polyvinyl chloride resin, fluororesin, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, phenolic resin, polyacrylic resin, polyamide resins such as various types of nylon, polyimide resin, polyamide-imide resin, polyurethane resin, cellulose resin, silicone resin, and polycarbonate resin.

[0056] Of these, a fluororesin is preferably used as the constituent material of the back surface protective layer 36. Fluorine resins have excellent heat resistance and weather resistance. Therefore, they can effectively protect the photoelectric conversion layer 31 from heat and light. Examples of fluororesins include polytetrafluoroethylene (PTFE), 4-fluoroethylene-perchloroalkoxy copolymer (PFA), 4-fluoroethylene-6-fluoropropylene copolymer (FEP), 2-ethylene-4-fluoroethylene copolymer (ETFE), poly-3-fluoroethylene chloride (PCTFE), polyvinylidene fluoride (PVDF), and polyvinyl fluoride (PVF).

[0057] Furthermore, the back surface protective layer 36 may be surface-treated on at least one side as needed. This surface treatment is performed, for example, to improve the adhesion between the back surface protective layer 36 and the sealing material 35. Examples of surface treatments include corona treatment, plasma treatment, ultraviolet irradiation treatment, and electron beam irradiation treatment.

[0058] The surface protective layer 37 protects the photoelectric conversion layer 31 and other components from moisture, oxygen, external pressure, etc. The constituent material of the surface protective layer 37 is the same resin as that used for the constituent material of the back surface protective layer 36.

[0059] Of these, a fluororesin is preferably used as the constituent material of the surface protective layer 37. Fluorine resins have excellent heat resistance and weather resistance. Therefore, they can effectively protect the photoelectric conversion layer 31 from heat and light.

[0060] Furthermore, the surface protection layer 37 may be subjected to surface treatment on at least one of its surfaces, if necessary. This surface treatment is performed, for example, to improve the adhesion between the surface protection layer 37 and the sealing material 35. Examples of surface treatments include corona treatment, plasma treatment, ultraviolet irradiation treatment, electron beam irradiation treatment, and the like.

[0061] 1.2. Waterproof sheet for solar panels The waterproof sheet 2 for solar cells comprises a waterproof layer 21 and a shielding layer 22, and is flexible.

[0062] 1.2.1. Waterproof layer The waterproof layer 21 is made of a flexible polyvinyl chloride resin containing a plasticizer. Such a waterproof layer 21 has good flexibility, mechanical properties, and waterproofness.

[0063] The flexible polyvinyl chloride resin contained in the waterproof layer 21 is a polyvinyl chloride resin that has been softened by the addition of a plasticizer.

[0064] Vinyl chloride resins are polymers containing vinyl chloride, i.e., oligomers, prepolymers, or polymers. Specifically, vinyl chloride resins include monomeric polymers of vinyl chloride, copolymers with other monomers, or mixtures of two or more of these.

[0065] In the case of copolymers, the proportion of vinyl chloride is preferably set to 50% by mass or more, more preferably 70% by mass or more. Examples of monomers copolymerized with vinyl chloride include olefins such as ethylene and propylene; halogenated olefins such as allyl chloride, vinylidene chloride, vinyl fluoride, and trifluoroethylene chloride; vinyl carboxylate esters such as vinyl acetate and vinyl propionate; vinyl ethers such as isobutyl vinyl ether and cetyl vinyl ether; allyl ethers such as allyl-3-chloro-2-oxypropyl ether and allyl glycidyl ether; unsaturated carboxylic acids such as acrylic acid, maleic acid, itaconic acid, 2-hydroxyethyl acrylate, methyl methacrylate, monomethyl maleate, diethyl maleate, and maleic anhydride, their esters, or acid anhydrides; unsaturated nitriles such as acrylonitrile and methacrylonitrile; acrylamides such as acrylamide, N-methylolacrylamide, acrylamide-2-methylpropanesulfonic acid, and (meth)acrylamidopropyltrimethylammonium chloride; and allylamines or their derivatives such as allylamine benzoate and diallyldimethylammonium chloride.

[0066] The vinyl chloride resin preferably uses polyvinyl chloride as its main material. "Main material" means that the content is more than 50% by mass, preferably 70% by mass or more. By using polyvinyl chloride as the main material, a waterproof layer 21 with particularly good flexibility, waterproofing, and durability can be obtained.

[0067] The average degree of polymerization of the vinyl chloride resin is preferably 300 to 1800, and more preferably 600 to 1500. This results in a waterproof layer 21 that is relatively flexible and has excellent shape conformability.

[0068] The average degree of polymerization is calculated on a standard polystyrene basis using gel permeation chromatography (GPC).

[0069] Examples of plasticizers added to the waterproof layer 21 include phthalate ester plasticizers, phosphate ester plasticizers, adipic acid ester plasticizers, sebatic acid ester plasticizers, etc., and one or a mixture of two or more of these is used.

[0070] Examples of phthalate ester plasticizers include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), dihexyl phthalate (DHP), di-2-ethylhexyl phthalate (DOP), diisodecyl phthalate (DIDP), butyl benzyl phthalate (BBP), diisononyl phthalate (DINP), and dinonyl phthalate (DNP).

[0071] Examples of phosphate ester plasticizers include tricresyl phosphate (TCP) and trixylylene phosphate (TXP).

[0072] Examples of adipic acid ester plasticizers include dioctyl adipate (DOA) and diisodecyl adipate (DIDA).

[0073] Examples of sebatic acid ester plasticizers include dibutyl sebacate (DBS) and dioctyl sebacate (DOS).

[0074] The plasticizer added to the waterproof layer 21 may be a plasticizer that is compatible with vinyl chloride resin and is solid at room temperature. The plasticizer that is solid at room temperature is preferably a copolymer containing carbon monoxide and ethylene, more preferably an ethylene-unsaturated ester-carbon monoxide copolymer, and even more preferably an ethylene-methyl acrylate-carbon monoxide copolymer, an ethylene-vinyl acetate-carbon monoxide copolymer, or an ethylene-methyl methacrylate-carbon monoxide copolymer.

[0075] Furthermore, specific examples of plasticizers that are solid at room temperature include Elbaroy® 741, Elbaroy 742, Elbaroy H441, Elbaroy HP661, Elbaroy HP662, Elbaroy HP4051, Elbaroy AS, and Elbaroy AM (all manufactured by Mitsui Dow Polychemical Co., Ltd.).

[0076] The plasticizer content in the waterproof layer 21 is preferably 15 parts by mass or more, more preferably 20 parts by mass or more and 100 parts by mass or less, per 100 parts by mass of vinyl chloride resin. By setting the plasticizer content within the above range, a waterproof layer 21 with particularly excellent shape conformability can be obtained.

[0077] Methods for measuring the plasticizer content in the waterproof layer 21 include, for example, gas chromatography-mass spectrometry, liquid chromatography-mass spectrometry, and attenuated total reflection-fourier transform infrared spectroscopy (ATR-FTIR), which are appropriately selected depending on the constituent materials of the waterproof layer 21. If necessary, the sample of the waterproof layer 21 to be measured for plasticizer content may be pre-treated. An example of pre-treatment is contacting the sample with an organic solvent to dissolve the plasticizer.

[0078] The thickness of the waterproof layer 21 is not particularly limited, but is preferably 0.1 mm to 5 mm, more preferably 0.3 mm to 3 mm, and even more preferably 0.5 mm to 2 mm. This makes it possible to achieve both waterproofness and durability and shape conformability of the waterproof layer 21.

[0079] Furthermore, the waterproof layer 21 may consist of a single layer, or it may have a multilayer structure in which two or more layers are laminated in the thickness direction. A fiber layer may be used in the multilayer structure. The fiber layer is composed of a sheet containing fibers or the like. The multilayer structure may also have a structure in which this fiber layer is sandwiched between two polyvinyl chloride resin sheets.

[0080] Examples of the fiber layer include woven fabrics and nonwoven fabrics, and nets formed by creating multiple grids with warp and weft threads. Examples of fibers included in the fiber layer include resin fibers, glass fibers, and carbon fibers. By having such a fiber layer, the mechanical strength of the waterproof layer 21, such as tear strength and tensile strength, and durability, such as resistance to repeated fatigue, can be improved.

[0081] 1.2.2. Shielding layer The shielding layer 22 contains a metal. Such a shielding layer 22 has good shielding properties derived from the metal. Therefore, the shielding layer 22 suppresses the migration of plasticizer from the waterproof layer 21 to the inter-sheet adhesive layer 4 and the sheet-type solar cell 3. This suppresses the deterioration of the inter-sheet adhesive layer 4 and the degradation of the characteristics of the sheet-type solar cell 3 that occur due to the migration of plasticizer.

[0082] Furthermore, the shielding layer 22 containing metal has excellent light reflectivity. Therefore, light transmitted through the sheet-type solar cell 3 can be reflected by the shielding layer 22. This allows the reflected light to be re-incidentated into the sheet-type solar cell 3, thereby increasing the photoelectric conversion efficiency in the photoelectric conversion layer 31.

[0083] Furthermore, the shielding layer 22 containing metal has superior light resistance, heat resistance, water vapor shielding, and oxygen shielding properties compared to a shielding layer 22 composed of non-metallic materials, such as organic materials. Therefore, the waterproof layer 21 can be protected from light, heat, moisture, and oxygen over a long period. As a result, a waterproof sheet 2 for solar cells can be realized that maintains waterproofing over a long period while also maintaining the above-mentioned effects.

[0084] Furthermore, the shielding layer 22 containing metal has excellent thermal conductivity. For example, if the sheet-type solar cell 3 generates heat due to light reception, the shielding layer 22 can diffuse that heat in the in-plane direction. This contributes to heat dissipation of the sheet-type solar cell 3 and suppresses the decrease in photoelectric conversion efficiency of the photoelectric conversion layer 31 that occurs with rising temperature.

[0085] The metallic elements contained in the shielding layer 22 are not particularly limited, but examples include Al, Au, Ag, Cu, Co, Ni, Pd, Pt, Ti, Sn, Ru, Fe, Cr, Mo, Ta, Nb, Mg, W, etc. In this specification, metallic elements also include elements known as metalloids. Examples of metalloids include Si, Ge, Sb, etc. Furthermore, the shielding layer 22 may contain these metallic elements in their elemental form, or alloys or compounds containing these metallic elements. Examples of compounds include oxides, nitrides, carbides, sulfides, and borides.

[0086] The metal content in the shielding layer 22 is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and even more preferably 1.0% by mass or more. This allows the shielding layer 22 to fully exhibit the above-mentioned effects, particularly the suppression of plasticizer migration and light reflectivity. On the other hand, the upper limit of the metal content in the shielding layer 22 is not particularly limited and may be 100% by mass or less than 100% by mass. In the latter case, the degree of freedom in the manufacturing method is increased, and for example, a resin film containing metal can be used as the shielding layer 22.

[0087] The metal content in the shielding layer 22 is the sum of the metal element content obtained by elemental analysis of the shielding layer 22. Examples of elemental analysis methods include ICP emission spectroscopy (ICP-AES) and energy-dispersive X-ray spectroscopy (EDS). In addition, the shielding layer 22 may be isolated prior to elemental analysis.

[0088] The form of the shielding layer 22 may be, for example, a foil made of metal. In this case, the metal content in the shielding layer 22 can be particularly increased. As a result, a shielding layer 22 with particularly good properties such as suppression of plasticizer migration, light reflectivity, light resistance, heat resistance, water vapor shielding, oxygen shielding, and thermal conductivity can be obtained.

[0089] The foil is preferably composed of elements containing Al, Cu, Cr, Ti, Zn, Fe, or Si, alloys containing these elements, or compounds containing these elements. These exhibit excellent light reflectivity, light resistance, heat resistance, and thermal conductivity. From the viewpoint of light reflectivity and thermal conductivity, it is preferable that the foil contains metallic elements other than those belonging to the metalloid class.

[0090] As the alloy containing Fe, stainless steel (SUS) is preferably used. Stainless steel has particularly good weather resistance. Examples of stainless steel include ferritic stainless steel, austenitic stainless steel, and martensitic stainless steel. Of these, austenitic stainless steel, which has even better weather resistance, is preferably used.

[0091] The form of the shielding layer 22 may be, for example, a composite having a resin film and a metal film provided on its surface. Furthermore, layers with any desired function may be added to this composite.

[0092] Figure 4 is a cross-sectional view showing an example of a configuration when the shielding layer 22 in Figure 1 is a composite. The shielding layer 22 shown in Figure 4 has a base resin film 222 and a metal film 224 provided on its upper surface. With this configuration, it is possible to realize a shielding layer 22 that can be handled as a single film while suppressing the metal content in the shielding layer 22. This makes it possible to reduce the cost and improve the handling of the shielding layer 22 while maintaining various properties derived from the metal.

[0093] The constituent materials of the resin film 222 are not particularly limited, but include various resin materials such as low-density polyethylene (LDPE), high-density polyethylene (HDPE), polyolefins such as polypropylene, polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyamides such as nylon, acrylic resins, and polyvinylidene chloride. In this specification, low-density polyethylene refers to a material with a density of 0.94 g / cm³. 3 The following refers to polyethylene, and high-density polyethylene has a density of 0.94 g / cm³. 3 This refers to ultra-high-grade polyethylene. Furthermore, polyolefins, polyesters, or polyamides are particularly preferred as this resin material.

[0094] The metal film 224 is preferably composed of elements containing Al, Cu, Cr, Ti, or Si, alloys containing these elements, or compounds containing these elements. These exhibit excellent light reflectivity, light resistance, heat resistance, and thermal conductivity. From the viewpoint of light reflectivity and thermal conductivity, it is preferable that the metal film 224 contains metal elements other than those belonging to the metalloid class.

[0095] Methods for forming the metal film 224 include, for example, vapor phase deposition methods such as sputtering and vacuum deposition, liquid phase deposition methods such as coating, inkjet, immersion, and spraying, and plating methods such as electrolytic plating and electroless plating. Alternatively, the metal film 224 may be formed using a lamination method in which the aforementioned foil body is attached to the resin film 222.

[0096] The thickness of the shielding layer 22 is not particularly limited, but is preferably 1 μm to 500 μm, more preferably 3 μm to 150 μm, and even more preferably 5 μm to 70 μm. If the thickness of the shielding layer 22 is within the above range, sufficient suppression of plasticizer migration and light reflectivity can be ensured. In addition, good flexibility of the waterproof sheet 2 for solar cells can be ensured. Furthermore, if the thickness of the shielding layer 22 is within the above range, the shielding layer 22 can be treated as a single film, thereby increasing the flexibility of the manufacturing method for the waterproof sheet 2 for solar cells.

[0097] The thickness of the shielding layer 22 is determined by observing a magnified cross-section of the sheet-type solar cell 3 and averaging the thickness of 10 or more points on the shielding layer 22. Furthermore, if the shielding layer 22 is a composite as shown in Figure 4, the total thickness of the shielding layer 22 is the sum of the thickness of the resin film 222 and the thickness of the metal film 224.

[0098] When the form of the shielding layer 22 is the composite described above, the thickness of the metal film 224 is preferably 3 nm to 500 nm, and more preferably 10 nm to 100 nm. This makes it possible to realize a waterproof sheet 2 for solar cells that can maintain various properties derived from metal while sufficiently reducing the amount of metal used and lowering costs.

[0099] The thickness of the metal film 224 can be determined by observing a magnified cross-section of the sheet-type solar cell 3 and averaging the thickness of 10 or more points on the metal film 224.

[0100] 1.2.3.Interlayer adhesive layer Figure 5 is a cross-sectional view showing an example configuration in which the waterproof sheet 2 for solar cells in Figure 1 is equipped with an interlayer adhesive layer 23.

[0101] The interlayer adhesive layer 23 shown in Figure 5 is provided between the waterproof layer 21 and the shielding layer 22, and adheres them together. This allows the waterproof sheet 2 for solar cells to be manufactured by bonding the waterproof layer 21 and the shielding layer 22 together after they have been manufactured separately. As a result, the degree of freedom in the manufacturing method is increased, and the degree of freedom in selecting the constituent materials of each layer is also increased.

[0102] Examples of materials that make up the interlayer adhesive layer 23 include ethylene-based copolymers such as ethylene-methyl acrylate copolymer, ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, and ethylene-α-olefin copolymer, as well as polyolefins, polyamides, polyurethanes, acrylic resins, and synthetic rubbers.

[0103] Furthermore, the interlayer adhesive layer 23 may be composed of a solidified hot-melt adhesive. Hot-melt adhesives are easy to handle because they bond the adherends by heating and melting, followed by cooling and solidification.

[0104] The interlayer adhesive layer 23 may be provided as needed, and may be omitted if, for example, the waterproof layer 21 and the shielding layer 22 can be directly joined.

[0105] The thickness of the interlayer adhesive layer 23 is not particularly limited, but is preferably 0.1 μm to 30 μm, more preferably 0.5 μm to 10 μm, and even more preferably 1 μm to 5 μm. If the thickness of the interlayer adhesive layer 23 is within the above range, it is possible to prevent the waterproof film 2 for solar cells from becoming thicker, and thus prevent a decrease in handling ease.

[0106] The thickness of the interlayer adhesive layer 23 is determined by observing a magnified cross-section of the sheet-type solar cell 3 and averaging the thickness of 10 or more points on the interlayer adhesive layer 23.

[0107] 1.2.4. Characteristics of waterproof sheets for solar cells Next, we will explain the various characteristics of the waterproof sheet 2 for solar cells.

[0108] 1.2.4.1. Flexibility The waterproof sheet 2 for solar cells is flexible. Flexibility refers to a degree of bending rigidity that allows it to be easily bent by hand.

[0109] The flexibility of the waterproof sheet 2 for solar cells can be evaluated by its flexural modulus. The flexural modulus of the waterproof sheet 2 for solar cells is preferably 800 MPa to 4000 MPa, more preferably 1000 MPa to 3500 MPa, and even more preferably 1500 MPa to 3000 MPa. If the flexural modulus is within the above range, a waterproof sheet 2 for solar cells can be obtained that has sufficient bending rigidity to be easily bent by hand, although this may vary slightly depending on the thickness, and that also has excellent shape conformability. Such a waterproof sheet 2 for solar cells has good workability for installation on the construction surface. Furthermore, by using such a waterproof sheet 2 for solar cells, a solar cell 1 with a waterproof sheet that has good workability for installation on the construction surface can be obtained.

[0110] The flexural modulus of the waterproof sheet 2 for solar cells is measured using a strip-shaped test specimen in accordance with the method specified in JIS K 7171:2016. The size of the test specimen is, for example, 80 mm × 10 mm. The test speed is 2 mm / min.

[0111] 1.2.4.2. Mirror Gloss The waterproof sheet 2 for solar cells preferably has a specular gloss of 50% to 900% (60° / 60°) and more preferably 100% to 700% (60° / 60°) when the specular gloss of the surface of the shielding layer 22 is measured by the following method.

[0112] The waterproof sheet 2 for solar cells, having such specular gloss, exhibits particularly good light reflectivity and allows for a large amount of specularly reflected light. Therefore, by optimally designing the thickness of the sheet-type solar cell 3, the spacing between photoelectric conversion layers 31, and the thickness of the inter-sheet adhesive layer 4, the probability of light transmitted through the sheet-type solar cell 3 being reflected by the waterproof sheet 2 and re-incidentated to the photoelectric conversion layer 31 increases. Furthermore, since a certain amount of light that is scattered rather than specularly reflected can also be secured, the probability of light being re-incidentated to the photoelectric conversion layer 31 even if it is not positioned optimally for specular reflection increases. As a result, the overall photoelectric conversion efficiency of the sheet-type solar cell 3 can be increased.

[0113] Furthermore, if the specular gloss (60° / 60°) falls below the lower limit, the specular reflection component decreases, and when light transmitted through the sheet-type solar cell 3 is reflected toward the photoelectric conversion layer 31, there is a risk that the amount of light from the specular reflection component may not be sufficient. On the other hand, if the specular gloss (60° / 60°) exceeds the upper limit, the amount of light from the scattered component decreases, and the overall photoelectric conversion efficiency of the sheet-type solar cell 3 decreases.

[0114] The specular gloss (60° / 60°) of the waterproof sheet 2 for solar cells is measured in accordance with the specular gloss measurement method specified in JIS Z 8741:1997. For example, a gloss meter is used for the measurement.

[0115] 1.2.4.3. Surface roughness The waterproof sheet 2 for solar cells has an arithmetic mean height Ra of 0.01 μm to 30.0 μm, more preferably 0.05 μm to 20.0 μm, even more preferably 0.10 μm to 10.0 μm, and particularly preferably 0.20 μm to 5.0 μm, when the arithmetic mean height Ra of the surface of the shielding layer 22 is measured by the following method. If the arithmetic mean height Ra of the surface of the shielding layer 22 is within the above range, the probability of light transmitted through the sheet-type solar cell 3 being reflected again by the waterproof sheet 2 for solar cells and incident on the photoelectric conversion layer 31 is increased by optimally designing the thickness of the sheet-type solar cell 3, the spacing between photoelectric conversion layers 31, the thickness of the inter-sheet adhesive layer 4, etc. Furthermore, since a certain amount of light for the scattered component rather than specular reflection can be secured, the probability of light being incident again on the photoelectric conversion layer 31 that is outside the position suitable for the specular reflection component is also increased. As a result, the photoelectric conversion efficiency of the entire sheet-type solar cell 3 can be increased.

[0116] The arithmetic mean height Ra of the surface of the waterproof sheet 2 for solar cells is the arithmetic mean roughness Ra of the contour curve as defined in JIS B 0601:2001, and is measured, for example, using a laser microscope.

[0117] 1.3. Inter-sheet adhesive layer The inter-sheet adhesive layer 4 adheres the waterproof sheet 2 for solar cells and the sheet-type solar cell 3.

[0118] Examples of constituent materials for the inter-sheet adhesive layer 4 include ethylene-based copolymers such as ethylene-methyl acrylate copolymer, ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, and ethylene-α-olefin copolymer, as well as polyolefins, polyamides, polyurethanes, acrylic resins, and synthetic rubbers.

[0119] Furthermore, the inter-sheet adhesive layer 4 may be composed of a solidified hot-melt adhesive. Hot-melt adhesives are easy to handle because they bond the adherends by heating and melting, then cooling and solidifying.

[0120] The inter-sheet adhesive layer 4 may be provided as needed, and may be omitted if, for example, the waterproof sheet 2 for solar cells and the sheet-type solar cell 3 can be directly joined together.

[0121] The thickness of the inter-sheet adhesive layer 4 is not particularly limited, but is preferably 10 μm to 1000 μm, more preferably 50 μm to 800 μm, and even more preferably 100 μm to 300 μm. If the thickness of the inter-sheet adhesive layer 4 is within the above range, sufficient adhesive strength can be ensured, and the flexibility of the solar cell 1 with the waterproof sheet can be sufficiently ensured.

[0122] The thickness of the inter-sheet adhesive layer 4 can be determined by observing a magnified cross-section of the sheet-type solar cell 3 and averaging the thickness of the inter-sheet adhesive layer 4 at 10 or more locations.

[0123] 1.4. Characteristics of solar cells with waterproof sheets The thickness of the waterproof sheet-covered solar cell 1 is not particularly limited, but is preferably 0.8 mm to 5.0 mm, more preferably 1.2 mm to 4.0 mm, and even more preferably 1.5 mm to 3.0 mm. If the thickness of the waterproof sheet-covered solar cell 1 is within the above range, a waterproof sheet-covered solar cell 1 can be obtained that has bending rigidity such that it can be easily bent by hand and has excellent shape conformability. Such a waterproof sheet-covered solar cell 1 has good workability for laying on the construction surface.

[0124] 4. Effects of the above embodiment The waterproof sheet 2 for solar cells according to the above embodiment is provided between the sheet-type solar cell 3 and the building structure 100 and is flexible. This waterproof sheet 2 for solar cells comprises a waterproof layer 21 and a shielding layer 22. The waterproof layer 21 is made of a flexible polyvinyl chloride resin containing a plasticizer. The shielding layer 22 is laminated on the waterproof layer 21 and contains metal. The waterproof sheet 2 for solar cells is used such that the shielding layer 22 is located on the sheet-type solar cell 3 side of the waterproof layer 21.

[0125] With this configuration, it is possible to realize a waterproof sheet 2 for solar cells that can suppress the migration of plasticizers contained in the waterproof layer 21 to, for example, the sheet-type solar cell 3 or the inter-sheet adhesive layer 4 used to bond it. This makes it possible to suppress the deterioration of the characteristics of the sheet-type solar cell 3 and the degradation of the inter-sheet adhesive layer 4 that occur due to the migration of plasticizers.

[0126] In the waterproof sheet 2 for solar cells according to the above embodiment, the shielding layer 22 may be a foil made of metal.

[0127] With this configuration, the metal content in the shielding layer 22 can be particularly increased. As a result, a shielding layer 22 with particularly good properties such as suppression of plasticizer migration, light reflectivity, light resistance, heat resistance, water vapor shielding, oxygen shielding, and thermal conductivity can be obtained.

[0128] In the waterproof sheet 2 for solar cells according to the above embodiment, the foil body is preferably composed of an element, alloy, or compound containing Al, Cu, Cr, Ti, Zn, Fe, or Si.

[0129] With this configuration, a shielding layer 22 with excellent light reflectivity, light resistance, heat resistance, and thermal conductivity can be obtained.

[0130] In the waterproof sheet 2 for solar cells according to the above embodiment, the shielding layer 22 may have a resin film 222 and a metal film 224 formed on the resin film 222.

[0131] This configuration makes it possible to create a shielding layer 22 that can be handled as a standalone film while keeping the metal content of the shielding layer 22 low. This makes it possible to reduce the cost and improve the handling of the shielding layer 22 while maintaining various properties derived from the metal.

[0132] In the waterproof sheet 2 for solar cells according to the above embodiment, the metal film is preferably composed of an element, alloy, or compound containing Al, Cu, Cr, Ti, or Si.

[0133] With this configuration, a shielding layer 22 with excellent light reflectivity, light resistance, heat resistance, and thermal conductivity can be obtained.

[0134] In the waterproof sheet 2 for solar cells according to the above embodiment, the thickness of the metal film is preferably 3 nm or more and 500 nm or less.

[0135] This configuration makes it possible to create a waterproof sheet 2 for solar cells that can maintain various properties derived from metal while significantly reducing the amount of metal used and lowering costs.

[0136] In the waterproof sheet 2 for solar cells according to the above embodiment, the thickness of the shielding layer 22 is preferably 1 μm or more and 500 μm or less.

[0137] This configuration ensures sufficient suppression of plasticizer migration and reliable light reflectivity. Furthermore, it ensures good flexibility for the solar cell waterproof sheet 2. Additionally, if the thickness of the shielding layer 22 is within the specified range, the shielding layer 22 can be treated as a standalone film, thereby increasing the flexibility of the manufacturing method for the solar cell waterproof sheet 2.

[0138] In the waterproof sheet 2 for solar cells according to the above embodiment, the thickness of the waterproof layer 21 is preferably 0.1 mm or more and 5 mm or less.

[0139] With this configuration, it is possible to achieve both waterproofness and durability of the waterproof layer 21 and shape conformability.

[0140] The waterproof sheet 2 for solar cells according to the above embodiment may include an interlayer adhesive layer 23 that bonds the waterproof layer 21 and the shielding layer 22.

[0141] With this configuration, the waterproof sheet 2 for solar cells can be manufactured by separately manufacturing the waterproof layer 21 and the shielding layer 22 and then bonding them together. As a result, the degree of freedom in the manufacturing method can be increased, and the degree of freedom in selecting the constituent materials of each layer can also be increased.

[0142] In the waterproof sheet 2 for solar cells according to the above embodiment, it is preferable that the specular gloss (60° / 60°) of the surface of the shielding layer 22, measured by the method specified in JIS Z 8741:1997, is 50% or more and 900% or less.

[0143] This configuration provides a waterproof sheet 2 for solar cells that exhibits particularly good light reflectivity and has a large amount of specularly reflected light. By optimizing the thickness of the sheet-type solar cell 3, the spacing between photoelectric conversion layers 31, and the thickness of the inter-sheet adhesive layer 4, the probability of light transmitted through the sheet-type solar cell 3 being reflected by the waterproof sheet 2 and re-incidentated to the photoelectric conversion layer 31 increases. Furthermore, since a certain amount of light that is scattered rather than specularly reflected can be secured, the probability of light being re-incidentated to the photoelectric conversion layer 31 that is not in a position suitable for specular reflection also increases. As a result, the overall photoelectric conversion efficiency of the sheet-type solar cell 3 can be increased.

[0144] The solar cell 1 with a waterproof sheet according to the above embodiment comprises a waterproof sheet 2 for solar cells according to the above embodiment and a sheet-type solar cell 3.

[0145] With this configuration, a waterproof sheet-equipped solar cell 1 can be obtained that, when laid on the structure 100, simultaneously provides waterproofing and allows for the installation of sheet-type solar cells 3.

[0146] The waterproof sheet for solar cells and solar cells with waterproof sheets according to the present invention have been described above, but the present invention is not limited to these.

[0147] For example, in the waterproof sheet for solar cells and the solar cell with the waterproof sheet according to the present invention, each component of the above embodiment may be replaced with any component that can perform a similar function, or any component may be added to the above embodiment. [Examples]

[0148] Next, specific embodiments of the present invention will be described. 5. Fabrication of waterproof sheet for solar cells Waterproof sheets for solar cells were fabricated according to each example and comparative example, having the configuration shown in Table 1. The raw materials used to fabricate the waterproof sheets for solar cells are as follows. The numbers in parentheses represent the thickness.

[0149] Shielding layer: Al foil (12μm) SUS foil (30μm) : Al vapor-deposited film 1 (Al layer 50nm, PET film 12μm) : Al vapor-deposited film 2 (Al layer 30nm, OPP film 40μm) : Cu vapor-deposited film (Cu layer 100nm, PET film 20μm) Silica vapor-deposited film (silica layer 20nm, nylon film 15μm) : Al laminate film (Al layer 12μm, PET film 50μm) SUS laminate film (SUS layer 20μm, PET film 15μm) Interlayer bonding layer: Hot melt adhesive (HM adhesive, 20 μm) : Ethylene-vinyl acetate copolymer (EVA, 40 μm) Waterproofing layer: Flexible polyvinyl chloride resin sheet (PVC sheet, 0.9mm)

[0150] The above-mentioned flexible polyvinyl chloride resin sheet contains 60 parts by mass of di-2-ethylhexyl phthalate (DOP) as a plasticizer per 100 parts by mass of polyvinyl chloride with an average degree of polymerization of 700.

[0151] Furthermore, the flexural modulus of the fabricated waterproof sheets for solar cells was within the range of 1500 MPa to 3000 MPa.

[0152] Furthermore, the specular gloss (60° / 60°) of the fabricated waterproof sheet for solar cells was measured. The measurement results are shown in Table 1.

[0153] 6. Evaluation of waterproof sheets for solar cells The following evaluations were performed on the waterproof sheets for solar cells in each example and comparative example.

[0154] 6.1. Contact migration of plasticizers First, test specimens of the waterproof sheet for solar cells were prepared for each example and comparative example. The size of the test specimens for the waterproof sheet for solar cells was 10 cm in length and 10 cm in width. Next, the weight (initial weight) of the prepared test specimens was measured.

[0155] Next, test specimens were prepared by stacking test pieces of the waterproof sheets for solar cells from each example and comparative example with an ethylene-vinyl acetate copolymer film used to form the inter-sheet adhesive layer. The size of the ethylene-vinyl acetate copolymer film was 10 cm in length, 10 cm in width, and 300 μm in thickness.

[0156] Next, two test specimens of waterproof solar cell sheets were stacked on top of each other, and then two ethylene-vinyl acetate copolymer films were placed on top of them, sandwiching them between the sheets. If the waterproof solar cell sheet test specimens had a shielding layer, the orientation of the test specimens was set so that the shielding layer and the ethylene-vinyl acetate copolymer films were in contact.

[0157] Next, the prepared test specimen was sandwiched between two glass plates, and a 100g weight was placed on top. In this state, it was left in a constant temperature and humidity chamber at 25°C and 60% relative humidity for 50 days.

[0158] After 50 days, the test specimens were removed, and their weight (post-test weight) was measured again. The percentage change in the weight of the test specimens was then calculated using the following formula. Weight change rate of the test specimen (%) = {(Weight after test / Initial weight) - 1} × 100

[0159] Next, the contact migration properties of the plasticizer in each test specimen were evaluated based on the calculated weight change rate of the test specimens according to the following evaluation criteria.

[0160] A: The weight change rate of the test specimen is less than 4%. B: The weight change rate of the test specimen is 4% or more and less than 10%. C: The weight change rate of the test specimen is 10% or more.

[0161] 6.2. Photoelectric conversion efficiency of solar cells with waterproof sheeting First, a solar cell with a waterproof sheet was fabricated using the waterproof sheet for each example and comparative example, along with the following components.

[0162] • Sheet-type solar cells: Perovskite solar cells (525 μm) • Inter-sheet adhesive layer: Ethylene-vinyl acetate copolymer film (300 μm)

[0163] Next, the photoelectric conversion efficiency of the fabricated waterproof solar cell was measured using the following method.

[0164] First, using a solar simulator, a xenon lamp filtered through an AM1.5 filter was used to generate 1000W / m² of power from a xenon lamp attached to a waterproof sheet. 2 The sample was irradiated with simulated sunlight. Then, the current-voltage characteristics were measured using an IV tester.

[0165] Next, the photoelectric conversion efficiency was calculated from the obtained current-voltage characteristics. The calculated result is referred to as "Photoelectric conversion efficiency (conversion efficiency η1) [%] of a solar cell with a waterproof sheet".

[0166] On the other hand, the photoelectric conversion efficiency of a sheet-type solar cell without a waterproof sheet attached was also calculated using the same method as above. The calculation result is referred to as "Photoelectric conversion efficiency of sheet-type solar cell (conversion efficiency η2) [%]".

[0167] Next, the conversion efficiency η1 - conversion efficiency η2 was calculated. This calculated value will be positive if the waterproof sheet for the solar cell contributes to improving the photoelectric conversion efficiency, and negative if it does not, thus serving as an evaluation index for the waterproof sheet for the solar cell. This calculated value was evaluated against the following evaluation criteria.

[0168] A: The calculated value of conversion efficiency η1 - conversion efficiency η2 is +0.3% or higher. B: The calculated value of conversion efficiency η1 - conversion efficiency η2 is greater than 0% and less than 0.3%. C: The calculated value of conversion efficiency η1 - conversion efficiency η2 is 0% or less.

[0169] 6.3. Discussion The results of the above evaluation are shown in Table 1.

[0170] [Table 1]

[0171] As shown in Table 1, the weight change rate of the test specimens was sufficiently suppressed in the waterproof sheets for solar cells of each embodiment. Therefore, it was confirmed that the migration of plasticizers could be sufficiently suppressed in the waterproof sheets for solar cells of each embodiment.

[0172] Furthermore, in each example of the solar cell with a waterproof sheet, the calculated value of conversion efficiency η1 - conversion efficiency η2 was found to be greater than 0%. This result suggests that the waterproof sheet for the solar cell may have contributed to the improvement of photoelectric conversion efficiency. [Explanation of Symbols]

[0173] 1. Solar panel with waterproof sheet 2. Waterproof sheet for solar cells 3 Sheet-type solar cells 4. Inter-sheet adhesive layer 21 Waterproof layer 22 Shielding layer 23 Interlayer adhesive layer 31 Photoelectric conversion layer 32 Backside electrodes 33 Surface electrode 34 Base material 35 Sealing material 36. Back protective layer 37 Surface protective layer 100 skeleton 110 Floor section 120 Insulation 130 Insulating layer 140 Existing waterproofing layer 222 Resin film 224 Metal film

Claims

1. A flexible waterproof sheet for solar cells, provided between a sheet-type solar cell and a building structure, A waterproof layer composed of a flexible polyvinyl chloride resin containing a plasticizer, A shielding layer containing metal is laminated on the aforementioned waterproof layer, Equipped with, A waterproof sheet for solar cells, characterized in that the shielding layer is positioned on the sheet-type solar cell side of the waterproof layer.

2. The waterproof sheet for solar cells according to claim 1, wherein the shielding layer is a foil made of the metal.

3. The waterproof sheet for solar cells according to claim 2, wherein the foil body is composed of an element, alloy, or compound containing Al, Cu, Cr, Ti, Zn, Fe, or Si.

4. The aforementioned shielding layer is resin film and The metal film formed on the aforementioned resin film, A waterproof sheet for solar cells according to claim 1, having the following features.

5. The waterproof sheet for solar cells according to claim 4, wherein the metal film is composed of an element, alloy, or compound containing Al, Cu, Cr, Ti, or Si.

6. The waterproof sheet for solar cells according to claim 4, wherein the thickness of the metal film is 3 nm or more and 500 nm or less.

7. The waterproof sheet for solar cells according to claim 1, wherein the thickness of the shielding layer is 1 μm or more and 500 μm or less.

8. The waterproof sheet for solar cells according to claim 1, wherein the thickness of the waterproof layer is 0.1 mm or more and 5 mm or less.

9. The waterproof sheet for solar cells according to claim 1, further comprising an interlayer adhesive layer for bonding the waterproof layer and the shielding layer.

10. The waterproof sheet for solar cells according to claim 1, wherein the specular gloss (60° / 60°) of the surface of the shielding layer, measured by the method specified in JIS Z 8741:1997, is 50% or more and 900% or less.

11. A waterproof sheet for solar cells according to any one of claims 1 to 10, The aforementioned sheet-type solar cell, A solar cell with a waterproof sheet, characterized by having the following features.

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