Photovoltaic cell gap reflective composite film and preparation method thereof

Abstract

The present invention discloses a photovoltaic cell interstitial reflective composite film and its preparation method. The film comprises a base layer, an adhesive layer formed on one surface of the base layer, a microstructure layer formed on the other surface of the base layer, and a reflective layer formed on the surface of the microstructure layer. The film also comprises a UV light conversion layer formed on the surface of the reflective layer. By forming the UV light conversion layer on the surface of the reflective layer, the UV wavelength in the reflected light can be converted into usable visible light, thereby improving the conversion efficiency of the entire photovoltaic cell.

Description

Technical Field

[0001] The invention belongs to the field of composite materials and relates to a reflective composite film, in particular to a photovoltaic cell gap reflective composite film and a preparation method thereof. Background Art

[0002] Photovoltaic modules (i.e., photovoltaic cells) are composed of high-efficiency crystalline silicon solar cells, ultra-clear glass, EVA, a transparent backsheet, and a frame. They feature a long service life and strong resistance to mechanical stress and external forces. During use, a single solar cell has a low output voltage and is susceptible to environmental influences, which can cause electrodes to detach. Therefore, several single cells are sealed together in series or parallel to form a solar cell module. For safety reasons, photovoltaic modules maintain a certain gap (defined as the inter-cell spacing or string spacing) between cells and between strings. For example, a conventional 72P double-glass module has a cell spacing of 1.8mm and a string spacing of 1.9mm. The inter-cell / string spacing area accounts for approximately 2.8% of the total module area; therefore, light that falls between the cell spacing or string spacing of the module is largely unused.

[0003] Currently, patents have disclosed reflective films for gaps, comprising an adhesive layer, a substrate layer, a prism layer, and a reflective layer stacked in sequence from bottom to top. These reflective films are long strips that can be adjusted to the spacing between cells, thereby improving the utilization of light passing through the cell spacing or string spacing. However, solar cells primarily absorb visible light and are unable to effectively utilize UV ​​light. Chinese invention patent application number 202210463340.2 discloses a UV light conversion packaging material, its preparation method, and its application. The UV light conversion packaging material of this invention comprises the following components, by weight: 100 parts of a base material, 0.005-1 part of a UV light conversion agent, 0.1-1 part of a light stabilizer, and 0.1-1 part of an antioxidant. The UV light conversion agent is any one of, or a mixture of at least two of, an organic fluorescent pigment, a rare earth organic complex, a rare earth inorganic compound, CdSe quantum dots, or perovskite quantum dots. This UV light conversion packaging material can convert light below 380nm into visible light above 380nm, allowing it to pass through, increasing the efficiency of the cell assembly and providing long-term weather resistance. While this UV light conversion packaging material has good UV light conversion efficiency, its poor adhesion to metals limits its use in reflective layers in the cell / string gap area. Summary of the Invention

[0004] In view of the above-mentioned defects, the present invention provides a photovoltaic cell gap reflective composite film, which has good metal adhesion and insulation properties while ensuring light conversion efficiency.

[0005] In order to achieve the above-mentioned objectives, the present invention provides a photovoltaic cell gap reflective composite film, which includes a base layer, an adhesive layer formed on any surface of the base layer, a microstructure layer formed on the other surface of the base layer, and a reflective layer formed on the surface of the microstructure layer. It also includes a UV light conversion layer formed on the surface of the reflective layer.

[0006] Optimally, the material of the base layer is poly(meth)acrylate, polyethylene terephthalate, polyethylene naphthalate, polyethersulfone, polyurethane, polycarbonate, polyvinyl chloride, syndiotactic polystyrene or cycloolefin copolymer, the bonding layer is ethylene-vinyl acetate polymer, acrylic acid or acrylate, the microstructure layer is poly(meth)acrylate, and the material of the reflective layer is aluminum.

[0007] Optimally, the UV light conversion layer comprises the following raw material components in parts by weight:

[0008]

[0009] The matrix polymer is a mixture of polyvinyl butyral and silane-grafted ethylene polymer, the mass content of polyvinyl butyral in the matrix polymer is 10-40%, and the mass content of the silane-grafted ethylene polymer is 60-90%.

[0010] Furthermore, the viscosity of the terminal vinyl siloxane is 100-200 mPa.s.

[0011] Furthermore, the chemical formula of the UV light conversion agent is Eu2A x B 4-x C, wherein A is 2-thenoyltrifluoroacetone, B is pyridine-2,6-dicarboxylic acid, and C is 4,4'-(butane-1,4-di(oxy))bis(pyridine-2,6-dicarboxylic acid), and the value of x ranges from 0.5 to 2.

[0012] Furthermore, the light stabilizer is a mixture of one or more selected from bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidinyl)decanedioate, bis(2,2,6,6-tetramethyl-4-piperidinyl)decanedioate and poly(4-hydroxy-2,2,6,6-tetramethyl-1-piperidinethanol) ester, or a mixture of one or more selected from light stabilizer UV-531, light stabilizer UV-P, light stabilizer 770 and light stabilizer 944.

[0013] Furthermore, the antioxidant is a mixture of one or more selected from the group consisting of antioxidant 1010, antioxidant 1076, antioxidant 168 and antioxidant B215.

[0014] Furthermore, the silane coupling agent is a mixture of one or more selected from vinyltriethoxysilane, (3-(isomethacryloyloxy)propyltrimethoxysilane, vinyltrimethoxysilane, vinyltri(β-methoxyethoxy)silane, γ-glycidyloxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane and 3-ureapropyltrimethoxysilane.

[0015] Another object of the present invention is to provide a method for preparing the above-mentioned UV light conversion layer, comprising the following steps: mixing a matrix polymer, a terminal vinyl siloxane, a UV light conversion agent, a light stabilizer, an antioxidant and a silane coupling agent in a formulated amount to obtain a mixture, then adding the mixture to an extruder, melt-plasticizing, and extruding to form a film.

[0016] The photovoltaic cell gap reflective composite film of the present invention forms a UV light conversion layer on the surface of the reflective layer, thereby converting the UV band in the reflected light into usable visible light, thereby improving the conversion efficiency of the entire photovoltaic cell. In addition, by using a specific base polymer in combination with terminal vinyl siloxane, etc., it is possible to ensure that the components are mixed evenly, so that the polymer can interact with the metal surface and further cross-link the polymer, thereby improving the bonding performance to the metal while enhancing the strength and insulation performance of the UV light conversion layer, and facilitating a reduction in the amount of light stabilizer used. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic structural diagram of the reflective composite film in the gap between photovoltaic cells of the present invention. DETAILED DESCRIPTION

[0018] The photovoltaic cell interstitial reflective composite film of the present invention comprises a base layer 20, an adhesive layer 10 formed on either surface of the base layer 20, a microstructured layer 30 formed on another surface of the base layer 20, and a reflective layer 40 formed on the surface of the microstructured layer 30. The film also includes a UV light conversion layer 50 formed on the surface of the reflective layer 40. The base layer 20 is made of poly(meth)acrylate, polyethylene terephthalate, polyethylene naphthalate, polyethersulfone, polyurethane, polycarbonate, polyvinyl chloride, syndiotactic polystyrene, or cycloolefin copolymer, and has a thickness of 50 to 200 μm; poly(meth)acrylate is preferred. The adhesive layer 10 is formed on either surface of the base layer 20 using conventional methods (such as coating or screen printing). It is made of ethylene-vinyl acetate polymer, acrylic acid, or acrylic ester (preferably ethylene-vinyl acetate polymer), and has a thickness of 50 to 100 μm. The microstructured layer 30 is formed on the other surface of the substrate layer 20, such that the microstructured layer 30 and the adhesive layer 10 are located on opposite surfaces of the substrate layer 20 (typically made of poly(meth)acrylate and having a thickness of 20-50 μm). The microstructured layer 30 is composed of a plurality of parallel and continuously arranged triangular prism structures. Each triangular prism structure forms an angle of 18-22° with the long side of the substrate layer 20 (the substrate layer 20 is a thin layer, and its long side is approximately considered the long side). In this embodiment, the microstructured layer 30 is formed using conventional methods, such as rolling with a corresponding structure roller. The reflective layer 40 is formed on the surface of the microstructured layer 30 using conventional methods, such as coating or deposition. It is made of aluminum and has a thickness of 300-800 angstroms. The UV light conversion layer 50 is formed on the surface of the reflective layer 40 and has a thickness of typically 100-600 μm. By forming a UV light conversion layer on the surface of the reflective layer, the UV band in the reflected light can be converted into usable visible light, thereby improving the conversion efficiency of the entire photovoltaic cell; in addition, by using a specific base polymer in combination with terminal vinyl siloxane, etc., it is possible to ensure that the various components are mixed evenly, so that the polymer can interact with the metal surface and further cross-link the polymer, thereby improving the bonding performance to the metal while improving the strength and insulation performance of the UV light conversion layer, and helping to reduce the amount of light stabilizer used.

[0019] The UV light conversion layer 50 comprises the following raw material components by weight: 100 parts of a base polymer; 5-10 parts of a vinyl-terminated siloxane; 0.01-0.5 parts of a UV light converter; 0.01-0.05 parts of a light stabilizer; 0.05-0.5 parts of an antioxidant; and 0.05-0.2 parts of a silane coupling agent. The base polymer is a mixture of polyvinyl butyral and a silane-grafted ethylene polymer, with the polyvinyl butyral content in the base polymer being 10-40% by weight and the silane-grafted ethylene polymer content being 60-90% by weight. By combining the specific base polymer with the vinyl-terminated siloxane, the polymer can interact with the metal surface while ensuring uniform mixing of the components, further crosslinking the polymer. This improves adhesion to the metal, enhances the strength and insulation properties of the UV light conversion layer, and reduces the amount of light stabilizer used.

[0020] The viscosity of the terminal vinyl siloxane is 100-200 mPa.s. When the viscosity of the terminal vinyl siloxane is too high, it is not conducive to mixing with other components. When the viscosity of the terminal vinyl siloxane is too low, it is easy to remain in the equipment during the film forming process, affecting the product performance. The chemical formula of the UV light conversion agent is Eu2A x B 4-x C, wherein A is 2-thenoyltrifluoroacetone, B is pyridine-2,6-dicarboxylic acid, and C is 4,4'-(butane-1,4-di(oxy))bis(pyridine-2,6-dicarboxylic acid), wherein the value of x ranges from 0.5 to 2 (note: in the following embodiments and comparative examples, products with the value of x being 1 are used); and the above-mentioned silane coupling agent is a mixture of one or more selected from vinyltriethoxysilane, (3-(isomethacryloyloxy)propyltrimethoxysilane, vinyltrimethoxysilane, vinyltri(β-methoxyethoxy)silane, γ-glycidyloxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane and 3-ureapropyltrimethoxysilane; the UV light conversion agent of this structure is selected to enable the coordination center Eu to be sufficiently connected with the -OH silane The coupling agent, matrix resin, etc. interact with each other, thereby facilitating improved UV light conversion efficiency. The light stabilizer can be a conventional one, such as a mixture of one or more selected from bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl)decanedioate, bis(2,2,6,6-tetramethyl-4-piperidyl)decanedioate, and poly(4-hydroxy-2,2,6,6-tetramethyl-1-piperidinylethanol) succinate, or a mixture of one or more selected from light stabilizer UV-531, light stabilizer UV-P, light stabilizer 770, and light stabilizer 944. The antioxidant can be a conventional one, such as a mixture of one or more selected from antioxidant 1010, antioxidant 1076, antioxidant 168, and antioxidant B215.

[0021] The method for preparing the UV light conversion layer for the photovoltaic cell gap reflective unit comprises the following steps: mixing a matrix polymer, terminal vinyl siloxane, a UV light conversion agent, a light stabilizer, an antioxidant, and a silane coupling agent in a formulated amount to obtain a mixture; then adding the mixture to an extruder, melt-plasticizing, and extruding to form a film.

[0022] In order to enable those skilled in the art to better understand the present invention, the following will provide a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained under the premise of equivalent changes and modifications made by ordinary technicians in this field should fall within the scope of protection of the present invention.

[0023] Example 1

[0024] like Figure 1The photovoltaic cell interstitial reflective composite film shown includes a base layer 20, an adhesive layer 10 formed on either surface of the base layer 20, a microstructured layer 30 formed on another surface of the base layer 20, and a reflective layer 40 formed on the surface of the microstructured layer 30. It also includes a UV light conversion layer 50 formed on the surface of the reflective layer 40 (prepared using conventional methods). The base layer 20 is made of poly(meth)acrylate, polyethylene terephthalate, polyethylene naphthalate, polyethersulfone, polyurethane, polycarbonate, polyvinyl chloride, syndiotactic polystyrene, or cycloolefin copolymer, and has a thickness of 50 to 200 μm; poly(meth)acrylate is preferred. The adhesive layer 10 is formed on either surface of the base layer 20 using conventional methods (such as coating or screen printing). It is made of ethylene-vinyl acetate polymer, acrylic acid, or acrylic ester (preferably ethylene-vinyl acetate polymer), and has a thickness of 50 to 100 μm. The microstructured layer 30 is formed on the other surface of the substrate layer 20, such that the microstructured layer 30 and the adhesive layer 10 are located on opposite surfaces of the substrate layer 20 (typically made of poly(meth)acrylate and having a thickness of 20-50 μm). The microstructured layer 30 is composed of a plurality of parallel and continuously arranged triangular prism structures, each of which forms an angle of 5-10° with the long side of the substrate layer 20 (the substrate layer 20 is a thin layer, and its long side is approximately considered the long side). In this embodiment, the microstructured layer 30 is formed using conventional methods, such as rolling with a corresponding structure roller. The reflective layer 40 is formed on the surface of the microstructured layer 30 using conventional methods, such as coating or deposition. It is made of aluminum and has a thickness of 300-800 angstroms. The UV light conversion layer 50 is formed on the surface of the reflective layer 40 and is typically 100-600 μm thick. By forming a UV light conversion layer on the surface of the reflective layer, the UV band in the reflected light can be converted into usable visible light, thereby improving the conversion efficiency of the entire photovoltaic cell (compared to photovoltaic cells without UV light conversion layers, the photoelectric conversion efficiency of the product of this embodiment is increased by at least 1% when applied to photovoltaic cells).

[0025] Examples 2-6, Comparative Examples 1-7

[0026] Examples 2-6 and Comparative Examples 1-7 respectively provide a UV light conversion layer for a photovoltaic cell gap reflective unit, and the raw material components thereof are shown in Table 1 (unit: g).

[0027] Table 1. Raw material usage of UV light conversion layer for photovoltaic cell gap reflective unit in Examples 2-6 and Comparative Examples 1-7

[0028]

[0029]

[0030] Note: The base polymer is a mixture of polyvinyl butyral and a silane-grafted ethylene polymer. In Examples 2-4, the masses of polyvinyl butyral (Merck) and the silane-grafted ethylene polymer (4244Q) are 40 g and 60 g, respectively; in Example 5, the masses of polyvinyl butyral (Merck) and the silane-grafted ethylene polymer (4244Q) are 10 g and 90 g, respectively; in Example 6, the masses of polyvinyl butyral (Merck) and the silane-grafted ethylene polymer (4244Q) are 25 g and 75 g, respectively; in Comparative Example 1, the base polymer is polyvinyl butyral, and in Comparative Example 2, the base polymer is a silane-grafted ethylene polymer. Terminal vinyl siloxane (i.e., terminal vinyl polydimethylsiloxane, Handafei; the viscosity in Examples 1-5 is 100-200 mPa.s, the viscosity in Comparative Example 3 is 20 mPa.s, and the viscosity in Comparative Example 4 is 500 mPa.s). The light stabilizer is bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidinyl)decanediol. The antioxidant is antioxidant 1010. The silane coupling agent is vinyltriethoxysilane, while Comparative Example 5 uses silane coupling agent KH550.

[0031] The preparation method of the UV light conversion layer for the above-mentioned photovoltaic cell gap reflective unit is: mixing the matrix polymer, terminal vinyl siloxane, UV light conversion agent, light stabilizer, antioxidant and silane coupling agent in a formulated amount to obtain a mixture, and then adding the mixture to a conventional extruder, melt-plasticizing, and extruding to form a film (conventional process parameters).

[0032] The products in each of the above examples were tested for adhesion, insulation, and light conversion performance, with the results listed in Table 2. Adhesion was tested using the following method: Using the aluminum plate / UV light conversion layer (0.05 mm thick) / aluminum plate (0.2 mm thick) structure, the UV light conversion layer was pre-heat-pressed onto the aluminum plate surface at 150°C for 5 minutes. Another aluminum plate and the pre-laminated aluminum plate with the UV light conversion layer were then placed in a hot press at 150°C for 10 seconds at a pressure of 0.5 MPa. Peel strength testing was performed according to GB / T 2791-1995. Insulation testing was performed according to GB / T 1410-1989. Light conversion performance was tested according to GB / T 2410-2008 (measurement of transmittance in the UV range of 280-380 nm).

[0033] Table 2 Performance test table of products in Examples 2-6 and Comparative Examples 1-7

[0034] Peel strength (N / cm) Resistivity (Ω·cm) Light transmittance (280~380nm) Example 2 45.2 <![CDATA[6.5×10 15 ]]> 7.2 Example 3 48.5 <![CDATA[7.4×10 15 ]]> 9.2 Example 4 46.3 <![CDATA[6.8×10 15 ]]> 9.0 Example 5 40.1 <![CDATA[8.9×10 15 ]]> 10.2 Example 6 41.2 <![CDATA[8.0×10 15 ]]> 9.8 Comparative Example 1 34.5 <![CDATA[1.5×10 15 ]]> 11.5 Comparative Example 2 46.0 <![CDATA[6.8×10 15 ]]> 12.0 Comparative Example 3 20.2 <![CDATA[6.0×10 15 ]]> 15.2 Comparative Example 4 - - - Comparative Example 5 38.1 <![CDATA[5.2×10 15 ]]> 7.5 Comparative Example 6 40.2 <![CDATA[1.0×10 16 ]]> 19.0 Comparative Example 7 25.6 <![CDATA[2.5×10 15 ]]> 8.2

[0035] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. At the same time, the above description should be clear and implementable to those with ordinary knowledge in the relevant technical field. Therefore, other equivalent changes or modifications that do not depart from the concepts disclosed in the present invention should be included in the scope of protection of the present invention.

Claims

1. A photovoltaic cell gap reflective composite film, comprising a base layer (20), an adhesive layer (10) formed on any surface of the base layer (20), a microstructure layer (30) formed on the other surface of the base layer (20), and a reflective layer (40) formed on the surface of the microstructure layer (30), characterized in that: It also includes a UV light conversion layer (50) formed on the surface of the reflective layer (40); The UV light conversion layer (50) comprises the following raw material components in parts by weight: 100 parts of base polymer; 5-10 parts of terminal vinyl siloxane; 0.01~0.5 parts of UV light conversion agent; Light stabilizer 0.01~0.05 parts; 0.05~0.5 parts of antioxidant; Silane coupling agent 0.05~0.2 parts; The matrix polymer is a mixture of polyvinyl butyral and silane-grafted ethylene polymer 4244Q, wherein the mass content of polyvinyl butyral in the matrix polymer is 10-40%, and the mass content of the silane-grafted ethylene polymer is 60-90%. The viscosity of the terminal vinyl siloxane is 100-200 mPa.s, and the silane coupling agent is a mixture of one or more selected from vinyl triethoxy silane, vinyl trimethoxy silane and vinyl tri(β-methoxyethoxy) silane.

2. The photovoltaic cell gap reflective composite film according to claim 1, characterized in that: The material of the base layer (20) is poly(meth)acrylate, polyethylene terephthalate, polyethylene naphthalate, polyethersulfone, polyurethane, polycarbonate, polyvinyl chloride, syndiotactic polystyrene or cycloolefin copolymer, the bonding layer is ethylene-vinyl acetate polymer, the microstructure layer is poly(meth)acrylate, and the material of the reflective layer is aluminum.

3. The photovoltaic cell gap reflective composite film according to claim 1, characterized in that: The chemical formula of the UV light converter is Eu2A x B 4-x C, wherein A is 2-thenoyltrifluoroacetone, B is pyridine-2,6-dicarboxylic acid, and C is 4,4'-(butane-1,4-di(oxy))bis(pyridine-2,6-dicarboxylic acid), and the value of x ranges from 0.5 to 2.

4. The photovoltaic cell gap reflective composite film according to claim 1, characterized in that: The light stabilizer is a mixture of one or more selected from bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidinyl)decanedioate, bis(2,2,6,6-tetramethyl-4-piperidinyl)decanedioate and poly(4-hydroxy-2,2,6,6-tetramethyl-1-piperidinethanol) ester, or a mixture of one or more selected from light stabilizer UV-531, light stabilizer UV-P, light stabilizer 770 and light stabilizer 944.

5. The photovoltaic cell gap reflective composite film according to claim 1, characterized in that: The antioxidant is a mixture of one or more selected from the group consisting of antioxidant 1010, antioxidant 1076, antioxidant 168 and antioxidant B215.

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