Perovskite solar cell encapsulant and perovskite solar cell

Abstract

This perovskite solar cell encapsulant comprises, in a surface layer, a sheet formed from a composition containing an ethylene / unsaturated carboxylic acid copolymer (A) or an ionomer (A1) of an ethylene / unsaturated carboxylic acid copolymer, said composition containing 5% by mass or more of a constituent unit derived from an unsaturated carboxylic acid and having a melting point of 90°C or less, wherein the adhesive strength of the composition to a glass plate by a specified method 1 is 2.0 N / 15 mm or more.

Description

Perovskite solar cell encapsulant and perovskite solar cell

[0001] The present invention relates to a perovskite solar cell encapsulant and a perovskite solar cell.

[0002] In recent years, as environmental concerns have grown, solar power generation has been attracting attention as a clean energy source. Solar power generation directly converts solar energy into electrical energy using semiconductors (solar cell elements) such as silicon cells. The solar cell elements used here are thin and prone to cracking, and some of them lose their functionality when directly exposed to the outside air. For this reason, the solar cell elements are sandwiched between encapsulants to protect them and prevent the intrusion of foreign matter and moisture. Furthermore, transparency is required for the encapsulant to efficiently transmit sunlight to the solar cell elements. Examples of technologies related to solar cell encapsulants include those described in Patent Documents 1 to 3.

[0003] Patent Document 1 describes a multilayer sheet for solar cell encapsulant having an excellent balance of transparency, adhesiveness, moisture resistance, and insulating properties, and the multilayer sheet for solar cell encapsulant comprises a resin layer (A) containing an ethylene-unsaturated carboxylic acid copolymer or an ionomer thereof as a main component, and an adhesive layer (B) provided on one or both surfaces of the resin layer (A), the adhesive layer (B) comprising an epoxy group-containing ethylene copolymer (B1), an ethylene-polar monomer copolymer, and an ethylene-polar monomer copolymer having a density of 920 kg / m ３ The document describes a multilayer sheet for a solar cell encapsulant, which contains at least one ethylene-based copolymer (B2) selected from the following ethylene-α-olefin copolymers (excluding the epoxy group-containing ethylene-based copolymer (B1)):

[0004] Patent Document 2 aims to provide a resin composition for a solar cell encapsulant that can provide a solar cell encapsulant having an excellent balance of transparency and creep resistance. The resin composition is used to form a solar cell encapsulant, and contains an ionomer (A) of an ethylene-unsaturated carboxylic acid copolymer and an epoxy group-containing ethylene copolymer (B), and the ionomer (A) of the ethylene-unsaturated carboxylic acid copolymer contains two or more types of metal ions.

[0005] Patent Document 3 describes a solar cell having an objective of providing a solar cell with improved durability, the solar cell comprising a support member, a photoelectric conversion element, a water vapor concentration adjuster, and a sealing member, the photoelectric conversion element and the water vapor concentration adjuster being sealed by the support member and the sealing member, and the photoelectric conversion element containing a perovskite compound.

[0006] International Publication No. 2017 / 057217 International Publication No. 2021 / 039397 Japanese Patent Application Laid-Open No. 2023-101351

[0007] The present invention provides a perovskite solar cell encapsulant that has an improved balance of low-temperature adhesion, transparency, moisture resistance, and insulation properties.

[0008] The inventors have discovered that by providing a surface layer with a sheet using an ethylene-unsaturated carboxylic acid copolymer or an ionomer of an ethylene-unsaturated carboxylic acid copolymer, in which the content of structural units derived from unsaturated carboxylic acid and the melting point are within specific numerical ranges, and by setting the adhesive strength to a glass plate within specific numerical ranges, it is possible to obtain a perovskite solar cell encapsulant with an improved performance balance between low-temperature adhesion, transparency, moisture resistance, and insulation.

[0009] The present invention provides the following perovskite solar cell encapsulant and perovskite solar cell.

[0010] [1] A perovskite solar cell encapsulant having, as a surface layer, a sheet made of a composition including an ethylene-unsaturated carboxylic acid copolymer (A) or an ionomer (A1) of the ethylene-unsaturated carboxylic acid copolymer, the content of which is 5% by mass or more of a structural unit derived from an unsaturated carboxylic acid and the melting point of which is 90°C or less, wherein the adhesive strength of the composition to a glass plate is 2.0 N / 15 mm or more, as measured by the following (Method 1): (Method 1) A 120 mm x 75 mm x 0.2 mm sheet made of the composition is obtained. The sheet is then laminated on the tin side of a 120 mm x 75 mm x 3.9 mm glass plate, and the sheet is vacuum-laminated at 80°C for 3 minutes using a vacuum laminator, followed by pressing at 80°C and 0.1 MPa (gauge pressure) for 5 minutes to adhere the sheet to the tin side of the glass plate. The sheet is then peeled from the glass plate at a peel angle of 180°C and a pulling rate of 100 mm / min, and the maximum stress when this is calculated is the adhesive strength (N / 15 mm) to the glass plate. [2] The perovskite solar cell encapsulant according to [1], wherein the content of the ethylene-unsaturated carboxylic acid copolymer (A) or the ionomer (A1) of the ethylene-unsaturated carboxylic acid copolymer in the composition is 80 mass% or more relative to the total mass of the composition. [3] The perovskite solar cell encapsulant according to [1] or [2], wherein the ethylene-unsaturated carboxylic acid copolymer (A) comprises at least one selected from the group consisting of an ethylene-α,β-unsaturated carboxylic acid copolymer and an ethylene-α,β-unsaturated carboxylic acid-α,β-unsaturated carboxylic acid ester copolymer. [4] The perovskite solar cell encapsulant according to [3], wherein the α,β-unsaturated carboxylic acid ester of the ethylene-α,β-unsaturated carboxylic acid-α,β-unsaturated carboxylic acid ester copolymer comprises isobutyl (meth)acrylate. [5] The perovskite solar cell encapsulant according to any one of [1] to [4] above, wherein the ethylene-unsaturated carboxylic acid copolymer of the ionomer (A1) of the ethylene-unsaturated carboxylic acid copolymer comprises at least one selected from the group consisting of an ethylene-α,β-unsaturated carboxylic acid copolymer and an ethylene-α,β-unsaturated carboxylic acid-α,β-unsaturated carboxylic acid ester copolymer.[6] The perovskite solar cell encapsulant according to [5] above, wherein the α,β-unsaturated carboxylic acid ester of the ethylene / α,β-unsaturated carboxylic acid / α,β-unsaturated carboxylic acid ester copolymer includes isobutyl (meth)acrylate. [7] The perovskite solar cell encapsulant according to any one of [1] to [6] above, which consists of the sheet. [8] The perovskite solar cell encapsulant according to any one of [1] to [6] above, which is a multilayer laminate comprising an intermediate layer on the inner side of the surface layer. [9] A perovskite solar cell comprising a photoelectric conversion element containing a perovskite compound and the perovskite solar cell encapsulant according to any one of [1] to [8] above.

[0011] According to the present invention, it is possible to provide a perovskite solar cell encapsulant having an improved balance of low-temperature adhesion, transparency, moisture resistance, and insulating properties.

[0012] The above-mentioned objects, as well as other objects, features and advantages, will become more apparent from the preferred embodiments described below and the accompanying drawings.

[0013] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments.

[0014] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all drawings, similar components are designated by common reference numerals, and descriptions thereof will be omitted where appropriate. Furthermore, the drawings are schematic diagrams and do not necessarily correspond to actual dimensional ratios. In this specification, "A to B" indicating a numerical range means A or more and B or less, unless otherwise specified. In this specification, "(meth)acrylic" means acrylic, methacrylic, or both acrylic and methacrylic.

[0015] 1. Perovskite Solar Cell Encapsulant The perovskite solar cell encapsulant of this embodiment is a perovskite solar cell encapsulant comprising, as a surface layer, a sheet made of a composition including an ethylene-unsaturated carboxylic acid copolymer (A) or an ionomer (A1) of the ethylene-unsaturated carboxylic acid copolymer, the content of which is 5% by mass or more of structural units derived from an unsaturated carboxylic acid and the melting point of which is 90°C or less, wherein the adhesive strength of the composition to a glass plate measured by the following (Method 1) is 2.0 N / 15 mm or more. The content of structural units derived from an unsaturated carboxylic acid is the value when all structural units in the ethylene-unsaturated carboxylic acid copolymer (A) or the ionomer (A1) of the ethylene-unsaturated carboxylic acid copolymer in the composition are taken as 100% by mass.

[0016] (Method 1) A 120 mm x 75 mm x 0.2 mm sheet composed of the above composition is obtained. Next, the sheet is laminated on the tin side of a 120 mm x 75 mm x 3.9 mm glass plate, and after vacuum-holding for 3 minutes at a heating temperature of 80 ° C. using a vacuum laminator, the sheet is pressed at a heating temperature of 80 ° C. and 0.1 MPa (gauge pressure) for 5 minutes to adhere the sheet to the tin side of the glass plate. Next, the sheet is peeled from the glass plate at a peel angle of 180 ° C. and a pulling rate of 100 mm / min. The maximum stress when peeled is calculated as the adhesive strength (N / 15 mm) to the glass plate.

[0017] According to the perovskite solar cell encapsulant of this embodiment, a sheet using an ethylene-unsaturated carboxylic acid copolymer or an ionomer of an ethylene-unsaturated carboxylic acid copolymer is provided as a surface layer, and the content of structural units derived from unsaturated carboxylic acid and the melting point thereof are set within specific numerical ranges. By setting the adhesive strength to a glass plate within specific numerical ranges, it is possible to improve the performance balance of low-temperature adhesion, transparency, moisture resistance, and insulation.

[0018] From the viewpoint of further improving the performance balance of low-temperature adhesion, transparency, moisture resistance, and insulating properties, the adhesive strength of the perovskite solar cell encapsulant of this embodiment is preferably 2.3 N / 15 mm or more, more preferably 2.5 N / 15 mm or more, even more preferably 2.8 N / 15 mm or more, and even more preferably 3.0 N / 15 mm or more. The upper limit of the adhesive strength is not particularly limited, and may be, for example, 50.0 N / 15 mm or less, 40.0 N / 15 mm or less, 30.0 N / 15 mm or less, 20.0 N / 15 mm or less, or 10.0 N / 15 mm or less. Furthermore, from the viewpoint of achieving an even better balance of low-temperature adhesion, transparency, moisture resistance, and insulating properties, the adhesive strength of the perovskite solar cell encapsulant of this embodiment is preferably 2.3 N / 15 mm or more and 50.0 N / 15 mm or less, more preferably 2.3 N / 15 mm or more and 40.0 N / 15 mm or less, even more preferably 2.5 N / 15 mm or more and 30.0 N / 15 mm or less, even more preferably 2.8 N / 15 mm or more and 20.0 N / 15 mm or less, and even more preferably 3.0 N / 15 mm or more and 10.0 N / 15 mm or less.

[0019] The adhesive strength of the perovskite solar cell encapsulant of this embodiment to a glass plate after 1000 hours by the following (Method 2) is preferably 9.0 N / 15 mm or more, more preferably 10.0 N / 15 mm or more, even more preferably 12.0 N / 15 mm or more, still more preferably 13.0 N / 15 mm or more, even more preferably 14.0 N / 15 mm or more, and still more preferably 15.0 N / 15 mm or more, from the viewpoint of further improving the performance balance of low-temperature adhesion, transparency, moisture resistance, and insulation. The upper limit of the adhesive strength after 1000 hours is not particularly limited, but may be, for example, 100.0 N / 15 mm or less, 90.0 N / 15 mm or less, 80.0 N / 15 mm or less, 70.0 N / 15 mm or less, 60.0 N / 15 mm or less, 50.0 N / 15 mm or less, 40.0 N / 15 mm or less, or 30.0 N / 15 mm or less. Furthermore, from the viewpoint of further improving the performance balance of low-temperature adhesion, transparency, moisture resistance, and insulating properties, the adhesive strength after 1,000 hours of use of the perovskite solar cell encapsulant of this embodiment is preferably 9.0 N / 15 mm or more and 100.0 N / 15 mm or less, more preferably 10.0 N / 15 mm or more and 90.0 N / 15 mm or less, even more preferably 10.0 N / 15 mm or more and 80.0 N / 15 mm or less, still more preferably 12.0 N / 15 mm or more and 70.0 N / 15 mm or less, even more preferably 12.0 N / 15 mm or more and 60.0 N / 15 mm or less, still more preferably 13.0 N / 15 mm or more and 50.0 N / 15 mm or less, still more preferably 14.0 N / 15 mm or more and 40.0 N / 15 mm or less, and still more preferably 15.0 N / 15 mm or more and 30.0 N / 15 mm or less.

[0020] (Method 2) A 120 mm x 75 mm x 0.2 mm sheet composed of the above composition is obtained. Next, the sheet is laminated on the tin side of a 120 mm x 75 mm x 3.9 mm glass plate, and after 3 minutes of vacuum holding at a heating temperature of 80 ° C. in a vacuum laminator, the sheet is pressed at a heating temperature of 80 ° C. and 0.1 MPa (gauge pressure) for 5 minutes to adhere the sheet to the tin side of the glass plate. Then, the sheet and the glass plate are stored for 1000 hours under conditions of 85 ° C. and 90% RH. Next, the sheet is peeled from the glass plate at a peel angle of 180 ° C. and a pulling rate of 100 mm / min. The maximum stress when peeled off is calculated as the adhesive strength (N / 15 mm) to the glass plate after 1000 hours.

[0021] The perovskite solar cell encapsulant of this embodiment may comprise a sheet as a surface layer, the sheet comprising a composition including an ethylene-unsaturated carboxylic acid copolymer (A) or an ionomer (A1) of the ethylene-unsaturated carboxylic acid copolymer, the composition having a content of structural units derived from an unsaturated carboxylic acid of 5% by mass or more and a melting point of 90°C or less. Alternatively, the perovskite solar cell encapsulant of this embodiment may comprise an intermediate layer inside the surface layer. Of these, the perovskite solar cell encapsulant of this embodiment is preferably comprised of a sheet, from the viewpoint of further improving the performance balance of low-temperature adhesion, transparency, moisture resistance, insulation, and production efficiency. Furthermore, from the viewpoint of further improving the performance balance of low-temperature adhesion, transparency, moisture resistance, and insulation, the perovskite solar cell encapsulant of this embodiment is preferably a multilayer laminate comprising an intermediate layer inside the surface layer, and more preferably a multilayer laminate having a three-layer or greater structure including an intermediate layer and surface layers provided on both sides of the intermediate layer. The term "the perovskite solar cell encapsulant of this embodiment is comprised of a sheet" refers to the perovskite solar cell encapsulant being a single layer.

[0022] The thickness of the perovskite solar cell encapsulant of the present embodiment is preferably 1 μm or more and 2000 μm or less, more preferably 10 μm or more and 1000 μm or less, even more preferably 50 μm or more and 500 μm or less, and still more preferably 100 μm or more and 300 μm or less, from the viewpoint of further improving the performance balance of low-temperature adhesion, transparency, moisture resistance, and insulation.

[0023] When the perovskite solar cell encapsulant of the present embodiment is a multilayer laminate including an intermediate layer on the inner side of a surface layer, the ratio (a / b) of the thickness (a) of the intermediate layer to the thickness (b) of the surface layer is preferably 1 / 1 or more and 10 / 1 or less, more preferably 2 / 1 or more and 6 / 1 or less, from the viewpoint of further improving the performance balance of transparency, adhesion, moisture resistance, insulation, flexibility, heat resistance, and processability. Furthermore, when the perovskite solar cell encapsulant of the present embodiment is a multilayer laminate having a three-layer or greater structure including an intermediate layer and surface layers provided on both sides thereof, the ratio (a / b) of the thickness (a) of one of the intermediate layers constituting the multilayer laminate to the thickness (b) of one of the surface layers is preferably 1 / 1 or more and 10 / 1 or less, more preferably 2 / 1 or more and 6 / 1 or less, from the viewpoint of further improving the performance balance of transparency, adhesion, moisture resistance, insulation, flexibility, heat resistance, and processability. Note that the thicknesses of the two surface layers may be different as long as the thickness ratio is as described above.

[0024] The total light transmittance of the perovskite solar cell encapsulant of this embodiment, measured in accordance with JIS K7136:2000, is preferably 70% or more, more preferably 75% or more, even more preferably 80% or more, and even more preferably 85% or more, from the viewpoint of further improving the performance balance between transparency and the power generation efficiency of the solar cell. The upper limit of the total light transmittance is not particularly limited, and may be, for example, 100% or less, 98% or less, 95% or less, or 93% or less. Furthermore, the total light transmittance of the perovskite solar cell encapsulant of this embodiment is preferably 70% or more and 100% or less, more preferably 75% or more and 98% or less, even more preferably 80% or more and 95% or less, and even more preferably 85% or more and 93% or less.

[0025] The haze of the perovskite solar cell encapsulant of this embodiment, measured in accordance with JIS K7136:2000, is preferably 40% or less, more preferably 30% or less, even more preferably 20% or less, and even more preferably 10% or less, from the viewpoint of further improving the performance balance between transparency and the power generation efficiency of the solar cell. The lower limit of the haze is not particularly limited, and may be, for example, 0% or more, 1% or more, 3% or more, or 5% or more. Furthermore, the haze of the perovskite solar cell encapsulant of this embodiment is preferably 0% or more and 40% or less, more preferably 1% or more and 30% or less, even more preferably 3% or more and 20% or less, and even more preferably 5% or more and 10% or less.

[0026] The moisture permeability of the perovskite solar cell encapsulant of this embodiment, measured by the cup method (based on JIS Z0208:1976, measurement atmosphere: 40°C x 90% RH), is preferably 15 g / (m), from the viewpoint of further improving the performance balance between moisture permeability resistance and long-term reliability. ２ 24h) or less, more preferably 13g / (m ２ 24h) or less, more preferably 10g / (m ２ 24h) or less, more preferably 8g / (m ２ The lower limit of the moisture permeability is not particularly limited, but is, for example, 0.01 g / (m ２ 24h) or more, and ２ 24h) or more, and may be 0.5g / (m ２ 24h) or more, and may be 1.0 g / (m ２ The moisture permeability of the perovskite solar cell encapsulant of this embodiment may be preferably 0.01 g / (m 2 ) or more, from the viewpoint of further improving the performance balance between moisture permeability resistance and long-term reliability. ２ ・24h) or more 15g / (m ２ 24h) or less, more preferably 0.1g / (m ２ ・24h) or more 13g / (m ２ 24h) or less, more preferably 0.5g / (m ２ ・24h) or more 10g / (m ２24h) or less, more preferably 1.0 g / (m ２ ・24h) or more 8g / (m ２ ・24h) or less.

[0027] The volume resistivity of the perovskite solar cell encapsulant of this embodiment, measured in accordance with JIS C2139:2008, is preferably 1.00 × 10, from the viewpoint of further improving the performance balance between insulation properties and long-term reliability. １０ Ω cm or more, more preferably 1.00 × 10 １２ Ω cm or more, more preferably 1.00 × 10 １５ Ω cm or more, more preferably 1.00 × 10 １７ The upper limit of the specific volume resistivity is not particularly limited, but is, for example, 1.00×10 ２０ Ω cm or less, and may be 1.00 × 10 １９ Ω cm or less, and may be 1.00 × 10 １８ Ω cm or less, and may be 5.00 × 10 １７ Furthermore, the volume resistivity of the perovskite solar cell encapsulant of this embodiment is preferably 1.00×10 Ω·cm or less, from the viewpoint of further improving the performance balance between insulation properties and long-term reliability. １０ Ω・cm or more 1.00×10 ２０ Ω cm or less, more preferably 1.00 × 10 １２ Ω・cm or more 1.00×10 １９ Ω cm or less, more preferably 1.00 × 10 １５ Ω・cm or more 1.00×10 １８ Ω cm or less, more preferably 1.00 × 10 １７ Ω・cm or more 5.00×10 １７ It is Ω·cm or less.

[0028] <Surface Layer> The surface layer of the perovskite solar cell encapsulant of this embodiment is a sheet made of a composition containing an ethylene-unsaturated carboxylic acid copolymer (A) or an ionomer of an ethylene-unsaturated carboxylic acid copolymer (A1), which has a content of structural units derived from an unsaturated carboxylic acid of 5 mass% or more and a melting point of 90°C or less.

[0029] In the ethylene-unsaturated carboxylic acid copolymer (A) or the ionomer (A1) of the ethylene-unsaturated carboxylic acid copolymer, from the viewpoint of further improving the performance balance of transparency, flexibility, adhesiveness, heat resistance, and mechanical strength, the content of structural units derived from ethylene is preferably 65% ​​by mass or more and 95% by mass or less, more preferably 70% by mass or more and 95% by mass or less, even more preferably 75% by mass or more and 94% by mass or less, and still more preferably 80% by mass or more and 93% by mass or less, when all structural units in the ethylene-unsaturated carboxylic acid copolymer (A) or the ionomer (A1) of the ethylene-unsaturated carboxylic acid copolymer are taken as 100% by mass. Furthermore, in the ethylene-unsaturated carboxylic acid copolymer (A) or the ionomer (A1) of the ethylene-unsaturated carboxylic acid copolymer, from the viewpoint of further improving the performance balance of transparency, flexibility, adhesiveness, heat resistance, and mechanical strength, the content of structural units derived from unsaturated carboxylic acids is preferably 5% by mass or more and 35% by mass or less, more preferably 5% by mass or more and 30% by mass or less, even more preferably 6% by mass or more and 25% by mass or less, even more preferably 7% by mass or more and 20% by mass or less, and still more preferably 8% by mass or more and 15% by mass or less, when all structural units in the ethylene-unsaturated carboxylic acid copolymer (A) or the ionomer (A1) of the ethylene-unsaturated carboxylic acid copolymer are taken as 100% by mass.

[0030] The melting point of the ethylene-unsaturated carboxylic acid copolymer (A) or the ionomer (A1) of the ethylene-unsaturated carboxylic acid copolymer is preferably 89°C or lower, more preferably 88°C or lower, and even more preferably 87°C or lower, from the viewpoint of further improving the performance balance of transparency, flexibility, adhesiveness, heat resistance, and mechanical strength. The lower limit of the melting point is not particularly limited, and may be, for example, 60°C or higher, 65°C or higher, 70°C or higher, or 75°C or higher. Furthermore, from the viewpoint of further improving the performance balance of transparency, flexibility, adhesiveness, heat resistance, and mechanical strength, the melting point of the ethylene-unsaturated carboxylic acid copolymer (A) or the ionomer (A1) of the ethylene-unsaturated carboxylic acid copolymer of this embodiment is preferably 60°C or higher and 90°C or lower, more preferably 65°C or higher and 89°C or lower, even more preferably 70°C or higher and 88°C or lower, and even more preferably 75°C or higher and 87°C or lower.

[0031] The ethylene-unsaturated carboxylic acid copolymer (A) and the ionomer (A1) of the ethylene-unsaturated carboxylic acid copolymer in the perovskite solar cell encapsulant of this embodiment preferably comprise at least one selected from the group consisting of an ethylene-α,β-unsaturated carboxylic acid copolymer and an ethylene-α,β-unsaturated carboxylic acid-α,β-unsaturated carboxylic acid ester copolymer, from the viewpoint of further improving the balance of low-temperature adhesion, transparency, moisture resistance, and insulating properties. Furthermore, when the perovskite solar cell encapsulant of this embodiment comprises an ethylene-unsaturated carboxylic acid copolymer (A), the ethylene-unsaturated carboxylic acid copolymer (A) more preferably comprises an ethylene-α,β-unsaturated carboxylic acid-α,β-unsaturated carboxylic acid ester copolymer.

[0032] Examples of the α,β-unsaturated carboxylic acid in the ethylene / α,β-unsaturated carboxylic acid copolymer or the ethylene / α,β-unsaturated carboxylic acid / α,β-unsaturated carboxylic acid ester copolymer include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, maleic anhydride, itaconic anhydride, monomethyl maleate, and monoethyl maleate. Among these, from the viewpoint of further improving the productivity and hygiene of the ethylene / unsaturated carboxylic acid copolymer (A) or the ionomer (A1) of the ethylene / unsaturated carboxylic acid copolymer, and the performance balance of the low-temperature adhesion, transparency, moisture resistance, and insulating properties of the perovskite solar cell encapsulant, preferably the copolymer contains at least one selected from acrylic acid and methacrylic acid, more preferably methacrylic acid, and even more preferably methacrylic acid. Note that these unsaturated carboxylic acids may be used alone or in combination of two or more.

[0033] Examples of the type of ester in the ethylene / α,β-unsaturated carboxylic acid copolymer or the ethylene / α,β-unsaturated carboxylic acid / α,β-unsaturated carboxylic acid ester copolymer include methyl ester, ethyl ester, n-propyl ester, isopropyl ester, n-butyl ester, isobutyl ester, 2-ethylhexyl ester, etc. Among these, isobutyl ester is preferred from the viewpoint of further improving the productivity and hygiene of the ethylene / unsaturated carboxylic acid copolymer (A) or the ionomer (A1) of the ethylene / unsaturated carboxylic acid copolymer, and the performance balance of the low-temperature adhesion, transparency, moisture resistance, and insulating properties of the perovskite solar cell encapsulant.

[0034] In the ethylene-unsaturated carboxylic acid copolymer (A) or the ionomer (A1) of the ethylene-unsaturated carboxylic acid copolymer in the perovskite solar cell encapsulant of this embodiment, the α,β-unsaturated carboxylic acid ester of the ethylene-α,β-unsaturated carboxylic acid-α,β-unsaturated carboxylic acid ester copolymer preferably contains isobutyl (meth)acrylate, and more preferably contains isobutyl acrylate, from the viewpoint of further improving the productivity and sanitation of the ethylene-unsaturated carboxylic acid copolymer (A) or the ionomer (A1) of the ethylene-unsaturated carboxylic acid copolymer, and the performance balance of the low-temperature adhesion, transparency, moisture resistance, and insulating properties of the perovskite solar cell encapsulant.

[0035] When the perovskite solar cell encapsulant of the present embodiment contains the ionomer (A1) of an ethylene-unsaturated carboxylic acid copolymer, examples of the ion source in the ionomer include alkali metals such as lithium and sodium; and polyvalent metals such as calcium, magnesium, zinc, and aluminum.

[0036] The ionomer used has a degree of neutralization of, for example, 80% or less. When the degree of neutralization is within the above range, a perovskite solar cell encapsulant having excellent transparency and high-temperature storage stability can be obtained. From the viewpoints of the transparency, adhesiveness, and processability of the perovskite solar cell encapsulant, the degree of neutralization of the ionomer (A1) is preferably 70% or less, more preferably 60% or less, even more preferably 55% or less, even more preferably 50% or less, even more preferably 45% or less, and even more preferably 40% or less. The lower limit of the degree of neutralization is not particularly limited, but may be, for example, 1% or more, preferably 2% or more, more preferably 3% or more, even more preferably 4% or more, and even more preferably 5% or more. From the viewpoints of transparency, adhesion, and processability of the perovskite solar cell encapsulant, the degree of neutralization of the ionomer (A1) is preferably 1% or more and 70% or less, more preferably 2% or more and 60% or less, even more preferably 2% or more and 55% or less, even more preferably 3% or more and 50% or less, even more preferably 4% or more and 45% or less, and even more preferably 5% or more and 40% or less.

[0037] The ethylene-unsaturated carboxylic acid copolymer (A) can be obtained by radical copolymerization of each polymerization component under high temperature and high pressure, and the ionomer (A1) of the ethylene-unsaturated carboxylic acid copolymer can be obtained by reacting the ethylene-unsaturated carboxylic acid copolymer (A) with a metal compound.

[0038] From the viewpoint of further improving processability and mechanical properties, the ethylene-unsaturated carboxylic acid copolymer (A) or the ionomer (A1) of the ethylene-unsaturated carboxylic acid copolymer preferably has a melt flow rate (JIS K7210:1999) at 190°C under a load of 2160 g of 0.1 g / 10 min or more and 150 g / 10 min or less, more preferably 0.1 g / 10 min or more and 50 g / 10 min or less.

[0039] The content of the ethylene-unsaturated carboxylic acid copolymer (A) or the ionomer (A1) of the ethylene-unsaturated carboxylic acid copolymer in the composition constituting the surface layer of the perovskite solar cell encapsulant of this embodiment is preferably 80% by mass or more, and more preferably 90% by mass or more, based on 100% by mass of the entire composition, from the viewpoint of further improving the performance balance of low-temperature adhesion, transparency, moisture resistance, and insulating properties.

[0040] The composition constituting the surface layer of the perovskite solar cell encapsulant of this embodiment can contain various additives within the scope of the present invention. Examples of such additives include crosslinking agents, crosslinking aids, silane coupling agents, ultraviolet absorbers, light stabilizers, and antioxidants.

[0041] As the crosslinking agent, an organic peroxide having a decomposition temperature of 1 hour half-life of, for example, 90 to 180° C., preferably 100 to 150° C. is preferably used. From the viewpoint of further improving the performance balance of low-temperature adhesion, moisture resistance, and mechanical properties, the organic peroxide in the composition constituting the surface layer of the perovskite solar cell encapsulant of this embodiment is preferably t-butylperoxyisopropyl carbonate, t-butylperoxyacetate, t-butylperoxybenzoate, dicumyl peroxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, di-t-butyl peroxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexyne-3, 1,1-bis(t-butylperoxy)hexane ... The perovskite solar cell encapsulant of the present embodiment contains one or more crosslinkers selected from the group consisting of 2,5-dimethylhexyl-2,5-bisperoxybenzoate, t-butyl hydroperoxide, p-menthane hydroperoxide, benzoyl peroxide, p-chlorobenzoyl peroxide, t-butylperoxyisobutyrate, hydroxyheptyl peroxide, and dicyclohexanone peroxide. The content of the crosslinker in the composition constituting the surface layer of the perovskite solar cell encapsulant of the present embodiment is preferably 0.1 parts by mass or more and 5 parts by mass or less, more preferably 0.5 parts by mass or more and 3 parts by mass or less, per 100 parts by mass of the ethylene-unsaturated carboxylic acid copolymer (A) or the ionomer of the ethylene-unsaturated carboxylic acid copolymer (A1), from the viewpoint of further improving the performance balance of low-temperature adhesion, moisture permeation resistance, and mechanical properties.

[0042] The cross-linking aid in the composition constituting the surface layer of the perovskite solar cell encapsulant of this embodiment preferably contains at least one polyunsaturated compound selected from the group consisting of polyallyl compounds and poly(meth)acryloxy compounds, and more preferably one or more selected from the group consisting of polyallyl compounds, poly(meth)acryloxy compounds, and divinylbenzene, from the viewpoint of further improving the performance balance of low-temperature adhesion, moisture resistance, and mechanical properties. The polyallyl compound of this embodiment preferably contains one or more selected from the group consisting of triallyl isocyanurate, triallyl cyanurate, diallyl phthalate, diallyl fumarate, and diallyl maleate. The poly(meth)acryloxy compound of this embodiment preferably contains at least one selected from the group consisting of ethylene glycol diacrylate, ethylene glycol dimethacrylate, and trimethylolpropane trimethacrylate. The content of the cross-linking aid in the composition constituting the surface layer of the perovskite solar cell encapsulant of this embodiment is preferably 0.1 parts by mass or more and 5 parts by mass or less, more preferably 0.5 parts by mass or more and 3 parts by mass or less, relative to 100 parts by mass of the ethylene-unsaturated carboxylic acid copolymer (A) or the ionomer of the ethylene-unsaturated carboxylic acid copolymer (A1), from the viewpoint of further improving the performance balance of low-temperature adhesion, moisture resistance, and mechanical properties.

[0043] From the viewpoint of further improving the performance balance of low-temperature adhesion, moisture resistance, and mechanical properties, the silane coupling agent in the composition constituting the surface layer of the perovskite solar cell encapsulant of this embodiment preferably contains a silane coupling agent having a vinyl group, an amino group, or an epoxy group, and a hydrolyzable group such as an alkoxy group, and more preferably vinyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-acryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, The compound includes one or more selected from the group consisting of N-(aminoethyl)3-aminopropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, N-2-(aminoethyl)3-aminopropyltrimethoxysilane, N-2-(aminoethyl)3-aminopropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, and N-phenyl-3-aminopropyltriethoxysilane. Among these, from the viewpoint of further improving the performance balance of low-temperature adhesion, moisture resistance, and mechanical properties, the silane coupling agent in the composition of the present embodiment preferably includes one or more types selected from the group consisting of silane coupling agents having an amino group, silane coupling agents having a dimethoxy group, and silane coupling agents having a trimethoxy group, more preferably includes one or more types selected from the group consisting of silane coupling agents having an amino group and silane coupling agents having a dimethoxy group, and even more preferably includes a silane coupling agent having an amino group and a dimethoxy group.

[0044] Examples of the silane coupling agent having an amino group and a dimethoxy group according to this embodiment include N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminomethyl)-3-aminopropylmethyldimethoxysilane, and the like.

[0045] From the viewpoint of further improving the performance balance of low-temperature adhesion, moisture resistance, and mechanical properties, the content of the silane coupling agent in the composition constituting the surface layer of the perovskite solar cell encapsulant of this embodiment is preferably from 0.01 to 5 parts by mass, more preferably from 0.02 to 4 parts by mass, even more preferably from 0.03 to 3 parts by mass, even more preferably from 0.04 to 2 parts by mass, even more preferably from 0.05 to 1.5 parts by mass, even more preferably from 0.06 to 1.0 parts by mass, even more preferably from 0.07 to 0.9 parts by mass, even more preferably from 0.08 to 0.8 parts by mass, even more preferably from 0.09 to 0.7 parts by mass, and even more preferably from 0.10 to 0.6 parts by mass, relative to 100 parts by mass of the ethylene-unsaturated carboxylic acid copolymer (A) or the ionomer (A1) of the ethylene-unsaturated carboxylic acid copolymer.

[0046] From the viewpoint of further improving the performance balance of low-temperature adhesion, moisture resistance, and mechanical properties, the content of the silane coupling agent having an amino group and a dimethoxy group in the composition of this embodiment is preferably 30% by mass or more and 100% by mass or less, more preferably 50% by mass or more and 100% by mass or less, and even more preferably 70% by mass or more and 100% by mass or less, when the total amount of the silane coupling agent in the composition of this embodiment is taken as 100% by mass.

[0047] Furthermore, in order to prevent deterioration of the perovskite solar cell encapsulant due to ultraviolet rays, it is preferable to include an ultraviolet absorber, a light stabilizer, an antioxidant, and the like in the composition that constitutes the surface layer of the perovskite solar cell encapsulant of this embodiment.

[0048] Examples of the ultraviolet absorber include benzophenone-based ultraviolet absorbers such as 2-hydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-2-carboxybenzophenone, and 2-hydroxy-4-n-octoxybenzophenone; 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol, 2-(2'-hydroxy-3',5'-di-t-butylphenyl)benzotriazole, 2-[2-hydroxy-3,5-b Examples of usable ultraviolet absorbers include benzotriazole-based ultraviolet absorbers such as [2-(2'-hydroxy-5-methylphenyl)benzotriazole]-2H-benzotriazole, 2-(2'-hydroxy-5-t-octylphenyl)benzotriazole, and fatty acid ester-based ultraviolet absorbers such as phenyl salicylate, p-octylphenyl salicylate, and methanetetrayltetramethanol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].

[0049] Examples of the light stabilizer that can be used include hindered amine-based light stabilizers such as bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate. Examples of the antioxidant that can be used include hindered phenol-based antioxidants such as 2-[4,6-bis([1,1'-biphenyl]-4-yl)-1,3,5-triazin-2-yl]-5-[(2-ethylhexyl)oxy]phenol, and phosphite-based antioxidants. The content of each of the antioxidant, light stabilizer, and UV absorber is preferably 0.01 to 5 parts by mass, more preferably 0.1 to 3 parts by mass, per 100 parts by mass of the ethylene-unsaturated carboxylic acid copolymer (A) or the ionomer (A1) of the ethylene-unsaturated carboxylic acid copolymer.

[0050] Furthermore, in addition to the additives described above, the composition constituting the surface layer of the perovskite solar cell encapsulant of this embodiment can contain additives such as colorants, light diffusing agents, and flame retardants, as necessary. Examples of colorants include pigments, inorganic compounds, and dyes, and examples of white colorants in particular include titanium oxide, zinc oxide, and calcium carbonate. When a perovskite solar cell encapsulant containing these additives is used as an encapsulant on the light-receiving side of a solar cell element, transparency may be impaired. However, it is suitable for use as an encapsulant on the side opposite the light-receiving side of a solar cell element.

[0051] Examples of the light diffusing agent include inorganic spherical substances such as glass beads, silica beads, silicon alkoxide beads, hollow glass beads, etc. Examples of organic spherical substances include acrylic or vinylbenzene plastic beads, etc.

[0052] Examples of the flame retardant include halogen-based flame retardants such as bromides, phosphorus-based flame retardants, silicone-based flame retardants, and metal hydrates such as magnesium hydroxide and aluminum hydroxide.

[0053] <Intermediate Layer> The intermediate layer of the perovskite solar cell encapsulant of this embodiment preferably contains, as a main component, one or more selected from the group consisting of an ethylene-unsaturated carboxylic acid copolymer or an ionomer thereof, and an ethylene-α-olefin copolymer. Here, "main component" means that the intermediate layer contains 60 mass % or more of the one or more selected from the group consisting of an ethylene-unsaturated carboxylic acid copolymer or an ionomer thereof, and an ethylene-α-olefin copolymer.

[0054] In the ethylene-unsaturated carboxylic acid copolymer or its ionomer, from the viewpoint of further improving the performance balance of transparency, flexibility, adhesiveness, heat resistance, and mechanical strength, the content of structural units derived from ethylene is preferably from 65 to 95% by mass, more preferably from 75 to 92% by mass, when all structural units in the ethylene-unsaturated carboxylic acid copolymer or its ionomer are taken as 100% by mass. Furthermore, in the ethylene-unsaturated carboxylic acid copolymer or its ionomer, from the viewpoint of further improving the performance balance of transparency, flexibility, adhesiveness, heat resistance, and mechanical strength, the content of structural units derived from unsaturated carboxylic acid is preferably from 5 to 35% by mass, more preferably from 8 to 25% by mass, when all structural units in the ethylene-unsaturated carboxylic acid copolymer or its ionomer are taken as 100% by mass.

[0055] Examples of the unsaturated carboxylic acid in the ethylene-unsaturated carboxylic acid copolymer include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, maleic anhydride, itaconic anhydride, monomethyl maleate, and monoethyl maleate. Among these, from the viewpoints of productivity and hygiene of the ethylene-unsaturated carboxylic acid copolymer, at least one selected from acrylic acid and methacrylic acid is preferred. These unsaturated carboxylic acids may be used alone or in combination of two or more.

[0056] From the viewpoint of improving the flexibility of the perovskite solar cell encapsulant of this embodiment, the ethylene-unsaturated carboxylic acid copolymer may contain structural units derived from other copolymerizable monomers in an amount of preferably 0% by mass to 30% by mass, more preferably 0% by mass to 25% by mass, relative to 100% by mass of the total of the ethylene and unsaturated carboxylic acid copolymer. Examples of the other copolymerizable monomers include unsaturated esters, for example, vinyl esters such as vinyl acetate and vinyl propionate; and (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, isobutyl (meth)acrylate, n-butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate.

[0057] In this embodiment, an ionomer thereof can be used instead of the ethylene-unsaturated carboxylic acid copolymer. The intermediate layer constituting the perovskite solar cell encapsulant of this embodiment contains an ionomer of an ethylene-unsaturated carboxylic acid copolymer as a main component, thereby further improving the moisture resistance of the perovskite solar cell encapsulant of this embodiment. Examples of ion sources for the ionomer include alkali metals such as lithium and sodium; and polyvalent metals such as calcium, magnesium, zinc, and aluminum.

[0058] The ionomer used has a degree of neutralization of, for example, 80% or less. A degree of neutralization within the above range allows for the production of a perovskite solar cell encapsulant having excellent transparency and high-temperature storage stability. From the viewpoints of the transparency, adhesiveness, and processability of the perovskite solar cell encapsulant, the degree of neutralization of the ionomer is preferably 70% or less, more preferably 60% or less, even more preferably 55% or less, even more preferably 50% or less, even more preferably 45% or less, and even more preferably 40% or less. The lower limit of the degree of neutralization is not particularly limited, but may be, for example, 1% or more, preferably 2% or more, more preferably 3% or more, even more preferably 4% or more, and even more preferably 5% or more. Furthermore, from the viewpoints of the transparency, adhesiveness, and processability of the perovskite solar cell encapsulant, the degree of neutralization of the ionomer is preferably 1% or more and 70% or less, more preferably 2% or more and 60% or less, even more preferably 2% or more and 55% or less, even more preferably 3% or more and 50% or less, even more preferably 4% or more and 45% or less, and even more preferably 5% or more and 40% or less.

[0059] The ethylene-unsaturated carboxylic acid copolymer can be obtained by radical copolymerization of the respective polymerization components under high temperature and pressure, and the ionomer can be obtained by reacting such a copolymer with a metal compound.

[0060] From the viewpoint of achieving a further improved balance of performance among transparency, flexibility, adhesiveness, heat resistance, and mechanical strength, the ethylene / α-olefin copolymer preferably comprises a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms, more preferably a copolymer of ethylene and an α-olefin having 3 to 15 carbon atoms, even more preferably a copolymer of ethylene and an α-olefin having 3 to 10 carbon atoms, and even more preferably a copolymer of ethylene and an α-olefin having 3 to 8 carbon atoms.

[0061] The α-olefin having 3 to 20 carbon atoms preferably includes one or more selected from the group consisting of linear α-olefins such as propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nanodecene, and 1-eicosene; and branched α-olefins such as 3-methyl-1-butene, 3-methyl-1-pentene, 4-methyl-1-pentene, 2-ethyl-1-hexene, and 2,2,4-trimethyl-1-pentene.

[0062] Specifically, the ethylene / α-olefin copolymer preferably includes one or more selected from the group consisting of an ethylene / propylene copolymer, an ethylene / 1-butene copolymer, an ethylene / 4-methyl-1-pentene copolymer, an ethylene / 1-hexene copolymer, and an ethylene / 1-octene copolymer.

[0063] From the viewpoint of further improving the performance balance of transparency, flexibility, adhesiveness, heat resistance, bleed resistance, and mechanical strength, the content of structural units derived from ethylene in the ethylene-α-olefin copolymer is preferably 50 mol% to 95 mol%, more preferably 60 mol% to 90 mol%, and even more preferably 70 mol% to 85 mol%, when all structural units in the ethylene-α-olefin copolymer are taken as 100% by mass. Furthermore, from the viewpoint of further improving the performance balance of transparency, flexibility, adhesiveness, heat resistance, bleed resistance, and mechanical strength, the content of structural units derived from α-olefin in the ethylene-α-olefin copolymer is preferably 5 mol% to 50 mol%, more preferably 10 mol% to 40 mol%, and even more preferably 15 mol% to 30 mol%, when all structural units in the ethylene-α-olefin copolymer are taken as 100% by mass.

[0064] The density of the ethylene-α-olefin copolymer, measured in accordance with JIS K7112, is preferably 850 kg / m from the viewpoint of further improving the performance balance of transparency, flexibility, adhesiveness, heat resistance, bleeding resistance, and mechanical strength. ３ More than 920kg / m ３ or less, more preferably 860 kg / m ３ More than 920kg / m ３ More preferably, 870 kg / m or less ３ More than 910kg / m ３ The following is the result.

[0065] Such ethylene / α-olefin copolymers can be produced by, for example, a slurry polymerization method, a solution polymerization method, a bulk polymerization method, a gas phase polymerization method, or the like using a metallocene catalyst.

[0066] From the viewpoint of further improving processability and mechanical properties, the one or more selected from the group consisting of ethylene-unsaturated carboxylic acid copolymers or ionomers thereof, and ethylene-α-olefin copolymers preferably have a melt flow rate (JIS K7210:1999) at 190°C under a load of 2160 g of 0.1 g / 10 min or more and 150 g / 10 min or less, more preferably 0.1 g / 10 min or more and 50 g / 10 min or less.

[0067] In the intermediate layer constituting the perovskite solar cell encapsulant of the present embodiment, the content of one or more selected from the group consisting of ethylene-unsaturated carboxylic acid copolymers or ionomers thereof, and ethylene-α-olefin copolymers is preferably 80% by mass or more, and more preferably 90% by mass or more, when the entire intermediate layer is taken as 100% by mass, from the viewpoint of further improving the performance balance of low-temperature adhesion, transparency, moisture resistance, and insulating properties.

[0068] The intermediate layer constituting the perovskite solar cell encapsulant of this embodiment can contain various additives within the scope of the present invention. Examples of such additives include crosslinking agents, crosslinking aids, silane coupling agents, ultraviolet absorbers, light stabilizers, and antioxidants.

[0069] As the crosslinking agent, an organic peroxide having a decomposition temperature of 1 hour half-life of typically 90 to 180° C., preferably 100 to 150° C., is preferably used. From the viewpoint of further improving the performance balance of low-temperature adhesion, moisture resistance, and mechanical properties, the organic peroxide in the intermediate layer constituting the perovskite solar cell encapsulant of this embodiment is preferably t-butylperoxyisopropyl carbonate, t-butylperoxyacetate, t-butylperoxybenzoate, dicumyl peroxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, di-t-butyl peroxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexyne-3, 1,1-bis(t-butyl The perovskite solar cell encapsulant of the present embodiment contains one or more crosslinkers selected from the group consisting of ethylene-unsaturated carboxylic acid copolymers or ionomers thereof, and ethylene-α-olefin copolymers, in order to further improve the performance balance of low-temperature adhesion, moisture permeation resistance, and mechanical properties. The content of the crosslinker in the intermediate layer constituting the perovskite solar cell encapsulant of the present embodiment is preferably 0.1 parts by mass or more and 5 parts by mass or more, more preferably 0.5 parts by mass or more and 3 parts by mass or less, based on 100 parts by mass of the one or more crosslinkers selected from the group consisting of ethylene-unsaturated carboxylic acid copolymers or ionomers thereof, and ethylene-α-olefin copolymers.

[0070] The cross-linking aid in the intermediate layer constituting the perovskite solar cell encapsulant of this embodiment preferably contains at least one polyunsaturated compound selected from the group consisting of polyallyl compounds and poly(meth)acryloxy compounds, from the viewpoint of further improving the performance balance of low-temperature adhesion, moisture resistance, and mechanical properties, and more preferably contains one or more compounds selected from the group consisting of polyallyl compounds, poly(meth)acryloxy compounds, and divinylbenzene. The polyallyl compound of this embodiment preferably contains one or more compounds selected from the group consisting of triallyl isocyanurate, triallyl cyanurate, diallyl phthalate, diallyl fumarate, and diallyl maleate. The poly(meth)acryloxy compound of this embodiment preferably contains at least one compound selected from the group consisting of ethylene glycol diacrylate, ethylene glycol dimethacrylate, and trimethylolpropane trimethacrylate. From the viewpoint of achieving a further improvement in the performance balance of low-temperature adhesion, moisture resistance, and mechanical properties, the content of the cross-linking aid in the intermediate layer constituting the perovskite solar cell encapsulant of the present embodiment is preferably 0.1 parts by mass or more and 5 parts by mass or less, more preferably 0.5 parts by mass or more and 3 parts by mass or less, relative to 100 parts by mass of the content of one or more selected from the group consisting of ethylene-unsaturated carboxylic acid copolymer or its ionomer, and ethylene-α-olefin copolymer.

[0071] Examples of the silane coupling agent in the intermediate layer constituting the perovskite solar cell encapsulant of this embodiment include silane coupling agents having a vinyl group, an amino group, or an epoxy group and a hydrolyzable group such as an alkoxy group, etc. Among these, vinyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-acryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, N-2-(aminoethyl)3-aminopropyltrimethoxysilane, N-2-(aminoethyl)3-aminopropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, and N-phenyl-3-aminopropyltriethoxysilane are mentioned. From the viewpoint of achieving a further improvement in the performance balance of low-temperature adhesion, moisture resistance, and mechanical properties, the content of the silane coupling agent in the intermediate layer constituting the perovskite solar cell encapsulant of the present embodiment is preferably 0.01 parts by mass or more and 5 parts by mass or less, more preferably 0.02 parts by mass or more and 3 parts by mass or less, relative to 100 parts by mass of the content of one or more selected from the group consisting of ethylene-unsaturated carboxylic acid copolymer or its ionomer, and ethylene-α-olefin copolymer.

[0072] Furthermore, in order to prevent deterioration of the perovskite solar cell encapsulant due to ultraviolet rays, it is preferable to incorporate an ultraviolet absorber, a light stabilizer, an antioxidant, and the like into the intermediate layer that constitutes the perovskite solar cell encapsulant of this embodiment.

[0073] Examples of the ultraviolet absorber include benzophenone-based ultraviolet absorbers such as 2-hydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-2-carboxybenzophenone, and 2-hydroxy-4-n-octoxybenzophenone; benzotriazole-based ultraviolet absorbers such as 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol, 2-(2'-hydroxy-3',5'-di-t-butylphenyl)benzotriazole, 2-(2'-hydroxy-5-methylphenyl)benzotriazole, and 2-(2'-hydroxy-5-t-octylphenyl)benzotriazole; and salicylate-based ultraviolet absorbers such as phenyl salicylate and p-octylphenyl salicylate.

[0074] As the light stabilizer, a hindered amine light stabilizer or the like is used. As the antioxidant, various hindered phenol antioxidants, phosphite antioxidants, etc. are used. The content of the antioxidant, light stabilizer, and ultraviolet absorber is preferably 0.01 parts by mass or more and 5 parts by mass or less, more preferably 0.1 parts by mass or more and 3 parts by mass or less, respectively, relative to 100 parts by mass of the content of one or more selected from the group consisting of ethylene-unsaturated carboxylic acid copolymer or its ionomer, and ethylene-α-olefin copolymer.

[0075] Furthermore, in addition to the additives described above, the intermediate layer constituting the perovskite solar cell encapsulant of this embodiment can contain additives such as colorants, light diffusing agents, and flame retardants, as needed. Examples of colorants include pigments, inorganic compounds, and dyes, and examples of white colorants in particular include titanium oxide, zinc oxide, and calcium carbonate. When a perovskite solar cell encapsulant containing these additives is used as an encapsulant on the light-receiving side of a solar cell element, transparency may be impaired. However, it is suitable for use as an encapsulant on the side opposite the light-receiving side of a solar cell element.

[0076] Examples of the light diffusing agent include inorganic spherical substances such as glass beads, silica beads, silicon alkoxide beads, hollow glass beads, etc. Examples of organic spherical substances include acrylic or vinylbenzene plastic beads, etc.

[0077] Examples of the flame retardant include halogen-based flame retardants such as bromides, phosphorus-based flame retardants, silicone-based flame retardants, and metal hydrates such as magnesium hydroxide and aluminum hydroxide.

[0078] <Method for Manufacturing Perovskite Solar Cell Encapsulant> The method for manufacturing the perovskite solar cell encapsulant of this embodiment is not particularly limited, and a conventionally known manufacturing method can be used. Examples of methods for manufacturing the perovskite solar cell encapsulant of this embodiment include press molding, extrusion molding, T-die molding, injection molding, compression molding, cast molding, calendar molding, and inflation molding. Among these, extrusion molding is preferred. That is, the perovskite solar cell encapsulant of this embodiment can be obtained, for example, by a manufacturing method including a step of extruding a composition that constitutes the surface layer of the perovskite solar cell encapsulant of this embodiment into a sheet shape. The processing temperature in the extrusion step is not particularly limited, but is preferably less than 220°C, more preferably less than 200°C, from the viewpoint of suppressing the curing reaction.

[0079] 1 is a cross-sectional view schematically showing an example of the structure of a perovskite solar cell 1 according to an embodiment of the present invention. The perovskite solar cell 1 of this embodiment preferably comprises a photoelectric conversion element 3 containing a perovskite compound, and a perovskite solar cell encapsulant 5 of this embodiment. The perovskite solar cell 1 of this embodiment can be produced by encapsulating the photoelectric conversion element 3 with the perovskite solar cell encapsulant 5 of this embodiment.

[0080] The photoelectric conversion element 3 contains a perovskite compound. The perovskite compound is preferably represented by the composition formula ABX ３ where A is a monovalent cation, B is a divalent cation, and X is a monovalent anion.

[0081] In the perovskite compound of this embodiment, A preferably includes at least one selected from the group consisting of organic cations and alkali metal cations.

[0082] In the perovskite compound of this embodiment, the organic cation is preferably a methylammonium cation (CH ３ NH ３ ＋ ), formamidinium cation (HC(NH ２ ) ２ ＋ ), ethylammonium cation (CH ３ CH ２ NH ３ ＋ ) and guanidinium cation (CH ６ N ３ ＋ ) and includes one or more selected from the group consisting of

[0083] In the perovskite compound of this embodiment, the alkali metal cation is preferably a potassium cation (K ＋ ), cesium cation (Cs ＋ ) and rubidium cation (Rb ＋ ) and includes one or more selected from the group consisting of

[0084] In the perovskite compound of this embodiment, the divalent cation B is preferably a lead cation (Pb ２＋ ) and tin cations (Sn ２＋ ) and at least one selected from the group consisting of

[0085] In the perovskite compound of this embodiment, the monovalent anion X preferably includes a halogen anion.

[0086] In the perovskite compound of this embodiment, each of the A, B, and X sites may be occupied by multiple types of ions.

[0087] In the perovskite solar cell 1 of this embodiment, the multiple photoelectric conversion elements 3 are preferably electrically connected in series via interconnectors 6 .

[0088] As shown in Figure 2, the perovskite solar cell 1 of this embodiment may further include a substrate 2. Examples of the substrate 2 that constitutes the perovskite solar cell 1 include substrates made of glass, acrylic resin, polycarbonate, polyester, fluorine-containing resin, etc. The perovskite solar cell encapsulant 5 of this embodiment exhibits good adhesion to these substrates 2.

[0089] As shown in Figure 2, the perovskite solar cell 1 of this embodiment may further include a back sheet 4. The back sheet 4 may be, for example, a single-layer or multi-layer sheet of metal or various thermoplastic resin films, and examples of the back sheet 4 include single-layer or multi-layer sheets of metals such as tin, aluminum, and stainless steel; inorganic materials such as glass; polyester, inorganic-deposited polyester, fluorine-containing resin, and polyolefin. The perovskite solar cell encapsulant 5 of this embodiment exhibits good adhesion to these back sheets 4.

[0090] Various types of perovskite solar cells 1 can be exemplified. Examples include a configuration in which the photoelectric conversion element 3 is sandwiched between perovskite solar cell encapsulant 5 on both sides, such as a configuration of perovskite solar cell encapsulant 5 / photoelectric conversion element 3 / perovskite solar cell encapsulant 5, or a configuration of substrate 2 / perovskite solar cell encapsulant 5 / photoelectric conversion element 3 / perovskite solar cell encapsulant 5 / backsheet 4, a configuration in which the photoelectric conversion element 3 is pre-formed on the surface of a substrate 2 such as glass, and then configured as substrate 2 / photoelectric conversion element 3 / perovskite solar cell encapsulant 5 / backsheet 4, and a configuration in which the perovskite solar cell encapsulant 5 and backsheet 4 are formed on the photoelectric conversion element 3 formed on the inner peripheral surface of the substrate 2, for example, a configuration in which the photoelectric conversion element is formed on a fluororesin sheet by sputtering or the like, and then the perovskite solar cell encapsulant 5 and backsheet 4 are formed on top of the photoelectric conversion element 3.

[0091] The method for manufacturing the perovskite solar cell 1 of this embodiment is not particularly limited, and examples thereof include the following method. First, a plurality of photoelectric conversion elements 3 electrically connected using interconnectors 6 are sandwiched between perovskite solar cell encapsulating materials 5, and these perovskite solar cell encapsulating materials 5 are further sandwiched between a substrate 2 and a backsheet 4 to produce a laminate. Next, the laminate is heated and pressurized to bond the respective members together, thereby obtaining the perovskite solar cell 1.

[0092] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various other configurations may be adopted. Furthermore, the present invention is not limited to the above-described embodiments, and modifications and improvements within the scope of achieving the object of the present invention are included in the present invention.

[0093] The present embodiment will be described in detail below with reference to examples, etc. However, the present embodiment is not limited to the descriptions of these examples.

[0094] [Materials] The following components were used.

[0095] <Ethylene-Unsaturated Carboxylic Acid Copolymer and Ionomer of Ethylene-Unsaturated Carboxylic Acid Copolymer> Copolymer 1: Ethylene-Methacrylic Acid-Isobutyl Acrylate Copolymer (Ethylene Content: 80% by Mass, Methacrylic Acid Content: 10% by Mass, Isobutyl Acrylate Content: 10% by Mass, Melting Point: 86°C) Copolymer 2: Ethylene-Methacrylic Acid-Isobutyl Acrylate Copolymer (Ethylene Content: 75% by Mass, Methacrylic Acid Content: 8% by Mass, Isobutyl Acrylate Content: 17% by Mass, Melting Point: 80°C) Copolymer 3: Ethylene-Methacrylic Acid Copolymer (Ethylene Content: 85% by Mass, Methacrylic Acid Content: 15% by Mass, Melting Point: 93°C)

[0096] <Weather-resistant agent masterbatch> Weather-resistant agent masterbatch 1: 94.2 parts by mass of ionomer of ethylene-methacrylic acid copolymer (ethylene content: 85% by mass, methacrylic acid content: 15% by mass, metal ion: zinc ion, degree of neutralization: 23%), 3.0 parts by mass of 2-[2-hydroxy-3,5-bis(α,α-dimethylbenzyl)phenyl]-2H-benzotriazole (manufactured by BASF Japan Ltd., Tinuvin 234), 2-[4,6-bis([1,1'-biphenyl]-4-yl)-1,3,5-triazin-2-yl]-5- Weathering agent master batch 1 was obtained by pre-mixing 0.6 parts by mass of [(2-ethylhexyl)oxy]phenol (manufactured by BASF Japan Ltd., TINUVIN 1600), 1.9 parts by mass of bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate (manufactured by BASF Japan Ltd., TINUVIN 770DF), and 0.3 parts by mass of methanetetrayltetramethanol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (manufactured by BASF Japan Ltd., Ir1010).

[0097] <Silane Coupling Agent> Silane Coupling Agent 1: N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., KBM-602)

[0098] [Examples 1 to 4 and Comparative Examples 1 and 2] Using a resin composition obtained by dry-blending each material in the compounding ratio (unit: parts by mass) shown in Table 1, a film was formed using a T-die molding machine at a processing temperature of 140°C to produce a sheet of each example having a length of 120 mm, a width of 75 mm, and a thickness of 0.2 mm.

[0099] <Evaluation Method> (1) Adhesion Evaluation Using a vacuum laminator (double vacuum chamber laminator manufactured by NPC Corporation, LM-50x50S), the sheet of each example was laminated on the tin side of a glass sheet measuring 120 mm length x 75 mm width x 3.9 mm thickness, and then vacuum-held at a heating temperature of 80 ° C for 3 minutes. After that, the sheet was pressed at a heating temperature of 80 ° C and 0.1 MPa (gauge pressure) for 5 minutes to adhere the sheet to the tin side of the glass plate. The laminate was then left to stand in the air and slowly cooled by natural cooling. A 15 mm wide slit was made in the sheet portion of the completed laminate to prepare a test specimen, which was then placed in a tensile tester. Next, the sheet was peeled from the glass plate at a peel angle of 180 ° C and a tensile speed of 100 mm / min, and the maximum stress was determined as the adhesive strength (initial) (unit: N / 15 mm) to the glass plate. The laminate was also stored for 1000 hours under conditions of 85 ° C and 90% RH. After storage, a 15 mm wide slit was made in the sheet portion of the laminate to prepare a test specimen, which was then placed in a tensile tester. The sheet was then peeled away from the glass plate at a peel angle of 180°C and a pulling rate of 100 mm / min, and the maximum stress was determined as the adhesive strength to the glass plate (after 1000 hours) (unit: N / 15 mm). The results are shown in Table 1.

[0100] (2) Transparency Evaluation A laminate was prepared by laminating 3.2 mm thick glass / each example sheet / 3.2 mm thick glass in this order in the same manner as in the adhesiveness evaluation in (1), and the total light transmittance (unit: %) and haze (cloudiness, unit: %) of the laminate were measured in accordance with JIS K7136:2000 using a haze meter manufactured by Suga Test Instruments Co., Ltd. The results are shown in Table 1.

[0101] (3) Moisture Permeability Evaluation The moisture permeability (unit: g / (m)) of the sheet obtained by the cup method (JIS Z0208:1976 compliant, measurement atmosphere: 40°C x 90% RH) was measured. ２ The results are shown in Table 1.

[0102] (4) Volume Resistivity The volume resistivity (unit: Ω cm) of the obtained sheet was measured in accordance with JIS C2139: 2008. The results are shown in Table 1.

[0103]

[0104] The sheets of Examples 1 to 4 had an excellent balance of low-temperature adhesion, transparency, moisture resistance, and insulating properties. In contrast, the sheets of Comparative Examples 1 and 2 had an inferior balance of low-temperature adhesion, transparency, moisture resistance, and insulating properties.

[0105] This application claims priority based on Japanese Patent Application No. 2024-055597, filed March 29, 2024, the disclosure of which is incorporated herein by reference in its entirety.

[0106] REFERENCE SIGNS LIST 1 Perovskite solar cell 2 Substrate 3 Photoelectric conversion element 4 Back sheet 5 Perovskite solar cell encapsulant 6 Interconnector

Claims

1. A perovskite solar cell encapsulant having, as a surface layer, a sheet made of a composition including an ethylene-unsaturated carboxylic acid copolymer (A) or an ionomer (A1) of the ethylene-unsaturated carboxylic acid copolymer, the content of structural units derived from an unsaturated carboxylic acid being 5% by mass or more and the melting point being 90°C or less, wherein the adhesive strength of the composition to a glass plate is 2.0 N / 15 mm or more, as determined by the following (Method 1): (Method 1) A 120 mm x 75 mm x 0.2 mm sheet made of the composition is obtained. The sheet is then laminated on the tin side of a 120 mm x 75 mm x 3.9 mm glass plate, and the sheet is heated in a vacuum laminator at 80°C for 3 minutes, followed by pressing at 80°C and 0.1 MPa (gauge pressure) for 5 minutes to adhere the sheet to the tin side of the glass plate. Next, the sheet is peeled away from the glass plate at a peel angle of 180° C. and a pulling rate of 100 mm / min, and the maximum stress when the sheet is peeled away from the glass plate is calculated as the adhesive strength (N / 15 mm) to the glass plate.

2. The perovskite solar cell encapsulant according to claim 1, wherein the content of the ethylene-unsaturated carboxylic acid copolymer (A) or the ionomer (A1) of the ethylene-unsaturated carboxylic acid copolymer in the composition is 80 mass% or more relative to the total mass of the composition.

3. The perovskite solar cell encapsulant according to claim 1 or 2, wherein the ethylene-unsaturated carboxylic acid copolymer (A) comprises at least one selected from the group consisting of an ethylene-α,β-unsaturated carboxylic acid copolymer and an ethylene-α,β-unsaturated carboxylic acid-α,β-unsaturated carboxylic acid ester copolymer.

4. The perovskite solar cell encapsulant according to claim 3, wherein the α,β-unsaturated carboxylic acid ester of the ethylene / α,β-unsaturated carboxylic acid / α,β-unsaturated carboxylic acid ester copolymer contains isobutyl (meth)acrylate.

5. The perovskite solar cell encapsulant according to any one of claims 1 to 4, wherein the ethylene-unsaturated carboxylic acid copolymer of the ionomer (A1) of ethylene-unsaturated carboxylic acid copolymer comprises at least one selected from the group consisting of an ethylene-α,β-unsaturated carboxylic acid copolymer and an ethylene-α,β-unsaturated carboxylic acid-α,β-unsaturated carboxylic acid ester copolymer.

6. The perovskite solar cell encapsulant according to claim 5, wherein the α,β-unsaturated carboxylic acid ester of the ethylene / α,β-unsaturated carboxylic acid / α,β-unsaturated carboxylic acid ester copolymer contains isobutyl (meth)acrylate.

7. The perovskite solar cell encapsulant according to any one of claims 1 to 6, which comprises the sheet.

8. The perovskite solar cell encapsulant according to any one of claims 1 to 6, which is a multilayer laminate having an intermediate layer on the inside of the surface layer.

9. A perovskite solar cell comprising a photoelectric conversion element containing a perovskite compound and the perovskite solar cell encapsulant according to any one of claims 1 to 8.

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