Photovoltaic backsheet and its preparation method, photovoltaic module

Abstract

This application relates to the field of photovoltaic technology, and in particular to a photovoltaic backsheet and its preparation method, as well as a photovoltaic module. The photovoltaic backsheet includes a substrate layer, a structural layer, a reflective layer, and an inner coating layer. The substrate layer has a bearing surface, which is provided with multiple cell areas and reflective areas, the reflective areas surrounding the cell areas. The structural layer is located above the reflective areas and has multiple oriented protrusions, the angle between the arrangement direction of the protrusions and the edge of the reflective areas being an acute angle. The reflective layer covers the structural layer. The inner coating layer is located above the cell areas. The photovoltaic backsheet provided by this application has high energy utilization and effectively improves the durability and reliability of the photovoltaic backsheet, which is beneficial to improving the power generation efficiency and service life of the photovoltaic module.

Description

Technical Field

[0001] This application relates to the field of photovoltaic technology, and in particular to a photovoltaic backsheet and its preparation method, and a photovoltaic module. Background Technology

[0002] With the increasing prominence of problems such as energy shortages, rising global temperatures, and worsening environmental degradation, solar energy, as a green and renewable energy source, has received growing attention. A photovoltaic (PV) module is a device that converts renewable solar energy into electrical energy.

[0003] In photovoltaic (PV) modules, the power output of the solar cells is a crucial indicator of the module's performance, directly reflecting its efficiency in utilizing solar energy. Specifically, higher power output helps reduce manufacturing costs. Given the same power output, higher cell power output results in a smaller module size and consequently, a lighter weight.

[0004] Photovoltaic backsheets are installed on the back of solar cells to protect them from moisture, oxygen, and ultraviolet radiation. However, traditional photovoltaic backsheets struggle to balance improving light energy utilization efficiency and structural reliability, thus affecting the power generation and lifespan of the solar cells. Summary of the Invention

[0005] Therefore, it is necessary to provide a photovoltaic backsheet and its preparation method, as well as a photovoltaic module, to solve the problem that traditional photovoltaic backsheets cannot simultaneously improve light energy utilization efficiency and structural reliability.

[0006] The above-mentioned objective of this application is achieved through the following technical solution:

[0007] In a first aspect, this application provides a photovoltaic backsheet, comprising a substrate layer, a structural layer, a reflective layer, and an inner coating layer;

[0008] The substrate layer has a bearing surface, and the bearing surface is provided with multiple battery areas and reflective areas, with the reflective areas surrounding the battery areas;

[0009] The structural layer is located above the reflective area, and the structural layer has multiple oriented protrusions, the angle between the orientation of the protrusions and the edge of the reflective area being an acute angle.

[0010] The reflective layer covers the structural layer;

[0011] The inner coating is located above the battery region.

[0012] In some embodiments, the angle between the arrangement direction of the protrusions and the edge of the reflective area is 30° to 60°.

[0013] In some embodiments, the protrusion structure is a serrated structure, with an apex angle of 90°~150° and a height of 5μm~30μm.

[0014] In some embodiments, the matrix resin of the structural layer includes acrylic resin, and the light transmittance of the structural layer is ≥90%.

[0015] In some embodiments, the matrix resin of the substrate layer includes polyethylene terephthalate.

[0016] In some embodiments, the thickness of the substrate layer is 180 μm to 350 μm.

[0017] In some embodiments, the material of the reflective layer includes one or more of aluminum and aluminum oxide.

[0018] In some embodiments, the thickness of the reflective layer is 30 nm to 100 nm.

[0019] In some embodiments, the base resin of the inner coating includes one or more of fluorocarbon resin and acrylic resin.

[0020] In some embodiments, the thickness ratio of the inner coating layer to the structural layer is 1:(1~2).

[0021] In some embodiments, the photovoltaic backsheet further includes a weather-resistant layer located on the surface of the substrate layer away from the bearing surface.

[0022] In some embodiments, the base resin of the weather-resistant layer includes one or more of acrylic resin, fluorocarbon resin, and polyethylene terephthalate.

[0023] In some embodiments, the thickness of the weather-resistant layer is 5 μm to 30 μm.

[0024] In some embodiments, the distance between two adjacent battery regions is 2mm to 4mm.

[0025] A second aspect of this application provides a method for preparing a photovoltaic backsheet, comprising the following steps:

[0026] A substrate layer is provided, the substrate layer having a bearing surface, the bearing surface having a plurality of battery areas and reflective areas, the reflective areas being arranged around the battery areas;

[0027] An inner coating is formed on the battery area, and a structural layer and a reflective layer are formed sequentially on the reflective area. The structural layer has multiple oriented protrusions, and the angle between the orientation of the protrusions and the edge of the reflective area is an acute angle.

[0028] In some embodiments, a structural layer and a reflective layer are sequentially formed on the reflective area, comprising the following steps: coating the reflective area with acrylic resin to form a liquid film, etching the liquid film to form a plurality of the raised structures by an imprinting method or a roll pressing method, and curing to obtain the structural layer; and forming a reflective layer on the structural layer by a vapor deposition method.

[0029] In a third aspect, this application provides a photovoltaic module, including the photovoltaic backsheet as described above, or including a photovoltaic backsheet prepared using the photovoltaic backsheet preparation method described above.

[0030] This application has at least the following beneficial effects:

[0031] The photovoltaic backsheet provided in this application includes a substrate layer, a structural layer, a reflective layer, and an inner coating layer. The substrate layer has multiple cell areas and a reflective area on its bearing surface, with the reflective area surrounding the cell areas. The inner coating layer is located in the cell areas and is used to bond the cells, improving the adhesion between the cells and the cell areas and enhancing the structural stability of the photovoltaic module. The structural layer is located in the reflective area and has multiple oriented protrusions. The orientation of these protrusions forms an angle of 0° to 90° with the edge of the reflective area. Combined with the reflective layer covering the structural layer, it can directionally reflect light incident on the reflective area back to the cell areas. The reflection direction is controllable, effectively improving the utilization rate of light energy, thereby increasing the power generation of the cells. Furthermore, the photovoltaic backsheet provided in this application adopts an integrated design, eliminating the need for additional metal film strips to enhance reflection. This simplifies the module structure, reduces lamination thickness and module weight, lowers the risk of microcracks in the cells, and avoids problems such as yellowing and cracking of the metal film strip. This significantly improves the durability and reliability of the photovoltaic backsheet, thereby extending the lifespan of the photovoltaic module. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of this application and to more completely understand this application and its beneficial effects, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a structural schematic diagram of the cross-section of a photovoltaic backsheet in some embodiments;

[0034] Figure 2 This is a schematic diagram of the structure of the bearing surface of the substrate layer in some embodiments;

[0035] Figure 3 This is a schematic diagram of the protrusion structure in some embodiments;

[0036] Figure 4This is a schematic flowchart of the photovoltaic backsheet fabrication method in some embodiments.

[0037] Reference numerals: 10, substrate layer; 11, battery area; 12, reflective area; 20, structural layer; 30, reflective layer; 40, inner coating layer; 50, weather-resistant layer; A, first direction; B, second direction. Detailed Implementation

[0038] To facilitate understanding of this application, the following detailed description is provided in conjunction with specific embodiments. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0040] In this application, "and / or" means any and all combinations of one or more of the related listed items. "At least one" means one or more, such as one, two, or more. "Multiple" or "several" means at least two, such as two, three, etc., and "multi-layered" means at least two layers, such as two, three, etc., unless otherwise expressly and specifically defined. In the description of this application, "several" means at least one, such as one, two, etc., unless otherwise expressly and specifically defined.

[0041] When a numerical range is disclosed in this application, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed in this application should be understood to include any and all subranges to which they are included.

[0042] Unless otherwise specified, all steps in this application may be performed sequentially or randomly. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0043] In this application, "above" or "below" includes the number itself. For example, "below 1" includes 1.

[0044] Unless otherwise specified, the temperature parameters in this application are permitted to be either constant-temperature treatment or variations within a certain temperature range. It should be understood that the constant-temperature treatment allows temperature fluctuations within the precision range of the instrument control, such as ±5℃, ±4℃, ±3℃, ±2℃, or ±1℃.

[0045] In this application, room temperature refers to indoor temperature, normal temperature, or general temperature. Generally, room temperature can be any of the following temperature ranges: 23℃±2℃, 25℃±5℃, or 20℃±5℃.

[0046] Currently, photovoltaic backsheets generally consist of a weather-resistant layer, a substrate layer, and an inner coating layer stacked sequentially. To improve the utilization rate of cell spacing and string spacing in photovoltaic modules, a high-reflectivity coating is usually placed between the substrate layer and the inner coating layer. This high-reflectivity coating can be black or white as needed, and its distribution corresponds to the cell spacing and string spacing; it is generally called a grid backsheet. This grid backsheet can perform secondary reflection on light incident on the gaps between cells, improving the cell's light utilization rate and thus increasing the power generation of the photovoltaic module. However, the grid backsheet relies on diffuse reflection based on the high-reflectivity coating, resulting in uncontrollable reflection direction, insufficient reflection efficiency, low light utilization, and poor power increase effect of the photovoltaic module.

[0047] In addition to the aforementioned grid backsheet, some photovoltaic (PV) modules incorporate metal film strips between the cells to improve the utilization of incident light. Traditional metal film strips consist of an adhesive layer, a substrate layer, a structural layer, and a reflective layer, stacked sequentially. The structural layer has a serrated structure, which reflects incident light from the cell gaps back onto the cells, resulting in higher light utilization than a grid backsheet and improved power output. However, applying the metal film strip to the cell gaps increases the lamination thickness of the PV module, raising the risk of microcracks in the cells and impacting the module's reliability. Furthermore, the adhesive layer of the metal film strip uses EVA film, typically 60μm~90μm thick, which, under prolonged sunlight exposure, exhibits high yellowing values ​​and poses a risk of cracking and failure.

[0048] Based on this, the first aspect of this application provides a photovoltaic backsheet, which aims to increase the probability that the photovoltaic backsheet reflects light incident on the gap between the solar cells back onto the solar cells, while improving the structural reliability of the photovoltaic backsheet.

[0049] In some embodiments, such as Figure 1 As shown, the photovoltaic backsheet includes a substrate layer 10, a structural layer 20, a reflective layer 30, and an inner coating layer 40. The substrate layer 10 has two surfaces opposite each other in its thickness direction, one of which is a bearing surface and the other surface away from the bearing surface is a non-bearing surface.

[0050] like Figure 2 As shown, the substrate layer 10 has multiple battery areas 11 and reflective areas 12 on its bearing surface, with the reflective areas 12 surrounding the battery areas 11. A structural layer 20 is located above the reflective areas 12, and the structural layer 20 has multiple oriented protrusions. The angle between the orientation of the protrusions and the edge of the reflective areas 12 is 0° to 90°. A reflective layer 30 covers the structural layer 20, and an inner coating layer 40 is located above the battery areas 11.

[0051] The photovoltaic backsheet provided in this application includes a substrate layer 10, a structural layer 20, a reflective layer 30, and an inner coating layer 40. The substrate layer 10 has multiple cell areas 11 and reflective areas 12 on its bearing surface, with the reflective areas 12 surrounding the cell areas 11. The inner coating layer 40 is located in the cell areas 11 and is used to bond the cells, improving the adhesion between the cells and the cell areas 11 and enhancing the structural stability of the photovoltaic module. The structural layer 20 is located in the reflective areas 12 and has multiple oriented protrusions. The orientation of the protrusions forms an angle of 0° to 90° with the edge of the reflective areas 12. Together with the reflective layer 30 covering the structural layer 20, it can directionally reflect light incident on the reflective areas 12 back to the cell areas 11. The reflection direction is controllable, effectively improving the utilization rate of light energy, thereby increasing the power generation of the cells. Furthermore, the photovoltaic backsheet provided in this application adopts an integrated design, which eliminates the need for additional metal film strips to enhance the reflection effect. This simplifies the module structure, reduces the lamination thickness and module weight, lowers the risk of microcracks in the cells, and avoids problems such as yellowing and cracking of the metal film strip. This greatly improves the durability and reliability of the photovoltaic backsheet, thereby extending the service life of the photovoltaic module.

[0052] In some embodiments, such as Figure 2 As shown, on the bearing surface of the substrate layer 10, multiple battery areas 11 are distributed in a grid pattern, and the distance between two adjacent battery areas 11 is 2mm to 4mm, including but not limited to 2mm, 2.2mm, 2.5mm, 2.8mm, 3mm, 3.2mm, 3.5mm, 3.8mm or 4mm.

[0053] In some embodiments, such as Figure 3 As shown, the direction formed by the edge of the reflective area 12 is denoted as the first direction A. The protrusions in the structural layer 20 are oriented along the second direction B. The angle between the arrangement direction of the protrusions and the edge of the reflective area 12 is α. Then, 0° < α < 90°, including but not limited to: 5°, 10°, 20°, 30°, 40°, 50°, 60°, 70°, 80° or 85°.

[0054] Therefore, the arrangement direction of the protruding structure can be directionally controlled according to the structural design and light reception requirements of the photovoltaic module, so that the light incident on the reflective area 12 is directionally reflected to the battery area 11. At the same time, since the angle between the arrangement direction of the protruding structure and the edge of the reflective area 12 is an acute angle, the phenomenon that the reflected light cannot be reflected to the battery area 11 due to the reflective surface of the protruding structure being perpendicular to the edge of the reflective area 12 can be avoided, making full use of the light at the reflective area 12, which is conducive to increasing the power generation of the battery cells.

[0055] In some embodiments, the angle between the arrangement direction of the protruding structures and the edge of the reflective area 12 is 30° to 60°, i.e., 30°≤α≤60°, including but not limited to: 30°, 35°, 40°, 45°, 50°, 55° or 60°. Further, the angle between the arrangement direction of the protruding structures and the edge of the reflective area 12 is 45°.

[0056] As a result, the protruding structure further increases the probability of directional reflection of light incident on the reflective area 12 to the battery area 11, significantly improving the utilization rate of light at the reflective area 12, and making the power generation of the battery cell particularly significant.

[0057] In some embodiments, such as Figure 1 As shown, the protruding structure is a serrated structure, with a apex angle on the side of the serrated structure away from the substrate layer 10. The apex angle of the serrated structure is 90°~150°, and the height is 5μm~30μm. Figure 3 As shown, the serrated structure is oriented along the second direction B on the reflective area 12. The solid line within the reflective area 12 represents the bottom edge of the serrated structure, and the dashed line within the reflective area 12 represents the top edge of the serrated structure, which is also where its apex is located. As an example, the apex angle of the serrated structure includes, but is not limited to, 90°, 100°, 110°, 120°, 130°, 140°, 150°, 160°, or 170°, and can be further selected as 112°~120°; the height of the serrated structure includes, but is not limited to, 5μm, 8μm, 10μm, 12μm, 15μm, 18μm, 20μm, 22μm, 25μm, 28μm, or 30μm, and can be further selected as 5μm~15μm.

[0058] Therefore, the protruding structure is a sawtooth structure with two inclined reflective surfaces. By controlling the apex angle and height of the sawtooth structure, the size and number of sawtooths in the reflective area 12 can be adjusted to ensure that the sawtooth structure has a better reflective effect, thereby further increasing the probability that the light incident on the reflective area 12 is reflected to the battery area 11, and the utilization rate of light in the reflective area 12 is higher.

[0059] In some embodiments, the matrix resin of the structural layer 20 includes an acrylic resin, and the light transmittance of the structural layer 20 is ≥90%, including but not limited to: 90%, 91%, 92%, 93%, or 95%. As an example, in the matrix resin of the structural layer 20, the acrylic resin may be one or more of polymethyl methacrylate (PMMA, also known as acrylic), polyethyl methacrylate (PEMA), polyacrylic acid (PAA), polymethyl methacrylate (PMA), polybutyl acrylate (PBA), polyhydroxyethyl acrylate (PHEMA), and polyglycidyl methacrylate (PGMA).

[0060] Using acrylic resin as the matrix resin for structural layer 20 has the following three advantages:

[0061] (1) Acrylic resin has good fluidity, flexibility and processability, and is not easy to break during the molding process. It is suitable for molding processes such as embossing or roll forming, so as to achieve the preparation of high-precision raised structures.

[0062] (2) Acrylic resin has excellent weather resistance and UV resistance, and can maintain good stability and aesthetics during the long-term operation of photovoltaic modules, avoiding yellowing or cracking.

[0063] (3) Acrylic resin has a very high light transmittance, usually 90%~92%, and can even approach 94%, which can ensure that the light transmittance of the structural layer 20 reaches more than 90%. When some light is not reflected by the reflective layer 30, but passes through the reflective layer 30, this light can continue to pass through the structural layer 20 and be incident on the bearing surface of the substrate layer 10, and then be reflected a second time to the battery area 11 through diffuse reflection, thereby maximizing the utilization rate of light in the reflective area 12 and significantly improving the power generation of the battery cell.

[0064] In this application, the structural layer 20 may also include one or more functional additives dispersed in the matrix resin, such as UV stabilizers, dispersants, leveling agents and defoamers. Those skilled in the art can make adjustments according to the performance requirements and preparation process of the structural layer 20, and this application does not impose any special limitations on this.

[0065] In some embodiments, the material of the reflective layer 30 includes one or more of aluminum (Al) and aluminum oxides (such as Al2O3).

[0066] Aluminum (Al) is a lightweight, inexpensive, and highly reflective metallic material. Its reflectivity can reach almost 100% in the visible light range. By using evaporation coating or magnetron coating processes, its reflectivity can be further improved, making the reflective layer 30 reflect even better.

[0067] In some embodiments, there is a certain distance between the edge of the reflective layer 30 and the edge of the reflective area 12 to prevent the reflective layer 30 from contacting the busbar and reduce the risk of leakage or short circuit.

[0068] In some embodiments, the thickness of the reflective layer 30 is 30nm to 100nm, including but not limited to: 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm or 100nm.

[0069] In some embodiments, the matrix resin of the substrate layer 10 includes polyethylene terephthalate (PET).

[0070] PET has a light transmittance that is slightly lower than that of acrylic resin, usually around 90%. It has good insulation, heat resistance and mechanical properties, and can withstand high mechanical stress. This ensures that the substrate layer 10 has higher strength and toughness, thereby improving the structural stability of the photovoltaic backsheet.

[0071] In this application, the substrate layer 10 may further include inorganic fillers and functional additives dispersed in the matrix resin. The inorganic fillers in the substrate layer 10 may be one or more of titanium dioxide, montmorillonite, zinc oxide, alumina, and silica, which can enhance the toughness and mechanical properties of the substrate layer 10, and also improve the diffuse reflection effect of the substrate layer 10, causing light incident on the substrate layer 10 to be reflected a second time to the battery region 11. The functional additives in the substrate layer 10 may be one or more of UV stabilizers, dispersants, leveling agents, and defoamers. Those skilled in the art can adjust these additives according to the performance requirements and preparation process of the substrate layer 10; this application does not impose any special limitations on this.

[0072] In some embodiments, the thickness of the substrate layer 10 is 180μm to 350μm, including but not limited to 180μm, 190μm, 200μm, 210μm, 220μm, 230μm, 240μm, 250μm, 260μm, 270μm, 280μm, 290μm, 300μm, 310μm, 320μm, 330μm, 340μm or 350μm.

[0073] This allows the substrate layer 10 to have good mechanical strength and minimizes the lamination thickness of the photovoltaic module, thereby reducing the risk of microcracks in the cells during the lamination process.

[0074] In some embodiments, the base resin of the inner coating 40 includes one or more of fluorocarbon resin and acrylic resin. As an example, in the base resin of the inner coating 40, the fluorocarbon resin may be one or more of polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), and fluoroethylene-vinyl ether copolymer (FEVE), and the acrylic resin may be one or more of polymethyl methacrylate (PMMA, also known as acrylic), polyethyl methacrylate (PEMA), polyacrylic acid (PAA), polymethyl methacrylate (PMA), polybutyl acrylate (PBA), polyhydroxyethyl acrylate (PHEMA), and polyglycidyl methacrylate (PGMA).

[0075] Fluorocarbon resin has excellent weather resistance, chemical resistance and UV stability, while acrylic resin has high light transmittance, flexibility, weather resistance and UV resistance. Using fluorocarbon resin or acrylic resin as the base resin for the inner coating 40 can ensure that the inner coating 40 has high weather resistance and prevent it from yellowing, cracking and other adverse phenomena under long-term UV radiation.

[0076] In this application, the inner coating 40 may further include auxiliary resin, inorganic filler, and functional additives dispersed in the matrix resin. The auxiliary resin in the inner coating 40 may be one or more of polyester resin and epoxy resin. The inorganic filler in the inner coating 40 may be one or more of silica, mica powder, wollastonite, calcium carbonate, and diatomaceous earth. The functional additives in the inner coating 40 may be one or more of tackifiers, coupling agents, dispersants, leveling agents, and defoamers. Those skilled in the art can make adjustments according to the performance requirements and preparation process of the inner coating 40, and this application does not impose any special limitations on this.

[0077] In some embodiments, the thickness ratio of the inner coating layer 40 to the structural layer 20 is 1:(1~2), including but not limited to 1:1, 1:1.2, 1:1.4, 1:1.6, 1:1.8 or 1:2.

[0078] Therefore, the thickness of the inner coating 40 is significantly less than the total thickness of the structural layer 20 and the reflective layer 30. After the solar cell is bonded to the photovoltaic backsheet through the inner coating 40, the total thickness of the inner coating 40 and the solar cell is also lower than the total thickness of the structural layer 20 and the reflective layer 30. This makes it more conducive for the solar cell to absorb the light reflected from the reflective layer 30, thereby improving the power generation of the solar cell.

[0079] In some embodiments, the thickness of the inner coating 40 is 5μm to 20μm, including but not limited to 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm or 20μm.

[0080] Therefore, while ensuring that the inner coating 40 has good adhesion properties, its thickness can be reduced, thereby improving the absorption of reflected light by the cell and significantly improving the light utilization rate at the reflective area 12.

[0081] In some embodiments, the photovoltaic backsheet further includes a weathering layer 50, which is located on the surface of the substrate layer 10 away from the load-bearing surface, i.e., the weathering layer 50 is located on the non-load-bearing surface of the substrate layer 10. Thus, the weathering layer 50 protects the substrate layer 10 from oxygen and ultraviolet radiation, thereby improving the durability and structural stability of the photovoltaic backsheet.

[0082] In some embodiments, the matrix resin of the weather-resistant layer 50 includes one or more of acrylic resin, fluorocarbon resin, and polyethylene terephthalate (PET). As an example, in the matrix resin of the weather-resistant layer 50, the acrylic resin may be one or more of polymethyl methacrylate (PMMA, also known as acrylic), polyethyl methacrylate (PEMA), polyacrylic acid (PAA), polymethyl methacrylate (PMA), polybutyl acrylate (PBA), polyhydroxyethyl acrylate (PHEMA), and polyglycidyl methacrylate (PGMA), and the fluorocarbon resin may be one or more of polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), and fluoroethylene-vinyl ether copolymer (FEVE).

[0083] In this application, the weather-resistant layer 50 may further include auxiliary resin, inorganic filler, and functional additives dispersed in the matrix resin. As an example, the auxiliary resin in the weather-resistant layer 50 may be one or more of polyester resin and epoxy resin; the inorganic filler in the weather-resistant layer 50 may be one or more of silica, mica powder, wollastonite, calcium carbonate, and diatomaceous earth; and the functional additives in the weather-resistant layer 50 may be one or more of matting agents (such as ultrafine silica, talc, aluminum stearate, calcium stearate, organically surface-treated silica, etc.), dispersants, leveling agents, and defoamers. Those skilled in the art can adjust these components according to the performance requirements and preparation process of the weather-resistant layer 50, and this application does not impose any special limitations on them.

[0084] In some embodiments, the thickness of the weather-resistant layer 50 is 5μm to 30μm, including but not limited to 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, 22μm, 25μm, 28μm or 30μm.

[0085] Therefore, while ensuring that the weather-resistant layer 50 has good weather resistance, its thickness can be reduced as much as possible to prevent the photovoltaic module from having excessive lamination thickness, which could cause microcracks in the cells.

[0086] In a second aspect, this application provides a method for preparing a photovoltaic backsheet, used to prepare the aforementioned photovoltaic backsheet.

[0087] In some embodiments, such as Figure 4 As shown, the method for preparing a photovoltaic backsheet includes the following steps:

[0088] S100: Provides a substrate layer with a bearing surface. The bearing surface is provided with multiple battery areas and reflective areas, and the reflective areas are arranged around the battery areas.

[0089] S200: An inner coating is formed on the battery area, and a structural layer and a reflective layer are formed sequentially on the reflective area. The structural layer has multiple oriented protrusions, and the angle between the orientation of the protrusions and the edge of the reflective area is an acute angle.

[0090] Understandably, Figure 4 At least some of the steps in the process may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but may be executed at different times. The execution order of these steps or stages is not necessarily sequential, but may be executed in turn or alternately with other steps or at least some of the steps or stages in other steps.

[0091] In this application, a suitable polymer film layer can be selected as the substrate layer, or the substrate layer can be prepared by mixing, high-temperature melting, and extrusion molding. Regarding the bearing surface of the substrate layer, the number, size, arrangement of the battery regions, and the distance between two adjacent battery regions, those skilled in the art can make adaptive adjustments according to the size of the battery cells and the performance requirements of the photovoltaic module; this application does not impose any special limitations in this regard.

[0092] In some embodiments, the method for preparing a photovoltaic backsheet further includes the step of forming a weather-resistant layer on the non-load-bearing surface of the substrate layer. The weather-resistant layer preparation step can be performed before or after step S200, and this application does not impose any special restrictions on this.

[0093] In some specific examples, the weather-resistant layer is made from a liquid resin system containing PET. The weather-resistant layer and the substrate layer can be prepared by co-extrusion molding. In this case, the material of the substrate layer is basically the same as that of the weather-resistant layer and also has good weather resistance. The durability and reliability of the photovoltaic backsheet are improved.

[0094] In some specific examples, the raw material for the weather-resistant layer is a liquid resin system containing matrix resins such as acrylic resin, fluorocarbon resin, and PET. The weather-resistant layer can be prepared by coating: the liquid resin system is coated on the non-load-bearing surface of the substrate layer, and the weather-resistant layer is formed after curing.

[0095] In some specific examples, the weather-resistant layer is made of fluorocarbon resin film (also known as fluorine film), such as PVF film (also known as T film) or PVDF film (also known as K film). The weather-resistant layer and the substrate layer can be bonded together using an adhesive bonding method. The adhesive can be one or more of ethylene-vinyl acetate copolymer (EVA), polyolefin elastomer (POE) and polyvinyl butyral (PVB).

[0096] In this application, there is no strict order restriction on the preparation of the inner coating layer and the structural layer and reflective layer in step S200. In some specific examples, the inner coating layer can be formed on the battery area first, and then the structural layer and reflective layer can be formed sequentially on the reflective area. In other specific examples, the structural layer and reflective layer can be formed sequentially on the reflective area first, and then the inner coating layer can be formed on the battery area.

[0097] In some embodiments, forming an inner coating on the battery area includes the following steps: protecting the reflective area with a mask, forming the inner coating on the battery area using a coating method, and removing the mask from the reflective area.

[0098] In some embodiments, a structural layer and a reflective layer are sequentially formed on the reflective area, including the following steps:

[0099] S210: Acrylic resin is coated on the reflective area to form a liquid film. Multiple raised structures are formed by etching the liquid film through imprinting or rolling, and then cured to obtain a structural layer.

[0100] S220: A reflective layer is formed on the structural layer by vapor deposition.

[0101] In some embodiments, before step S210, a step of protecting the battery area with a mask is included; and after step S220, a step of removing the mask on the battery area is included.

[0102] In some embodiments, in step S210, after forming the liquid film, an imprint plate with microstructures is used to imprint on the liquid film, or a roller with microstructures is used to roll on the liquid film to etch and form a plurality of raised structures, wherein the microstructures on the imprint plate and the microstructures on the roller correspond to the raised structures.

[0103] In some embodiments, in step S210, the curing method of the structural layer is ultraviolet (UV) curing.

[0104] In some embodiments, in step S220, the reflective layer is prepared by vapor deposition. The longer the vapor deposition time, the greater the thickness of the reflective layer. The thickness of the reflective layer can be controlled by adjusting the vapor deposition time. In addition, the density and surface roughness of the reflective layer can be improved by adjusting parameters such as vapor deposition temperature, vapor deposition power, and vapor deposition pressure, thereby enhancing its reflectivity to light.

[0105] In a third aspect, this application provides a photovoltaic module comprising the aforementioned photovoltaic backsheet, or comprising a photovoltaic backsheet prepared using the aforementioned photovoltaic backsheet preparation method.

[0106] The photovoltaic modules provided in this application have the advantages of high light energy utilization, high power generation and high structural reliability. They can be applied to distributed photovoltaic scenarios such as building integrated photovoltaic (BIPV) such as color steel tile roofs, photovoltaic tiles or photovoltaic curtain walls, as well as other scenarios that require photoelectric conversion.

[0107] In some embodiments, a photovoltaic module includes a photovoltaic backsheet, solar cells, an encapsulating film, and a photovoltaic cover plate. The solar cells are located on the inner coating of the photovoltaic backsheet, and multiple solar cells are electrically connected to form a cell string. The encapsulating film covers the surface of the cell string, and the photovoltaic cover plate covers the surface of the encapsulating film facing away from the cell string.

[0108] In some embodiments, the solar cell includes one or more of silicon solar cells, compound solar cells, and organic solar cells. Crystalline silicon solar cells include one or more of the following: Passivated Emitter and Rear Solar Cell (PERC), Tunnel Oxide Passivated Contact Solar Cell (TOPCon), Heterojunction with Intrinsic Thin-film Solar Cell (HJT or HIT), and Interdigitated Back Contact Solar Cell (IBC). Compound solar cells include perovskite solar cells (PSC), copper indium gallium selenide (CIGS), cadmium telluride (CdTe), and gallium arsenide (AsGa).

[0109] In some embodiments, the solar cell may further include a tandem cell, which includes a bottom cell and a top cell, and the bottom cell and top cell may be one or more of the silicon solar cells, compound solar cells and organic solar cells described above.

[0110] In some embodiments, multiple battery cells are electrically connected to form a battery string, and the multiple battery strings are electrically connected in series and / or in parallel.

[0111] In some embodiments, the photovoltaic cover plate may be a glass cover plate or a plastic cover plate with high light transmittance.

[0112] The following description is further illustrated with specific embodiments and comparative examples. Unless otherwise specified, the raw materials involved in the following specific embodiments and comparative examples are all commercially available. Unless otherwise specified, the instruments used are all commercially available. Unless otherwise specified, the processes involved are conventionally selected by those skilled in the art.

[0113] Example 1

[0114] The photovoltaic backsheet in this embodiment is prepared using the following method:

[0115] (1) Provide a substrate layer: 280μm thick PET film is selected as the substrate layer. The substrate layer includes a carrier surface and a non-carrier surface arranged opposite to each other. The carrier surface is provided with a battery area and a reflective area.

[0116] (2) Preparation of weather-resistant layer: A 25μm thick T film is selected as the weather-resistant layer and bonded to the non-load-bearing surface of the substrate layer through an EVA adhesive layer.

[0117] (3) Preparation of the structural layer: A mask is set on the battery area on the bearing surface of the substrate layer; acrylic resin is coated on the surface of the reflective area to form a liquid film; a roller with microstructures is used for rolling to etch the liquid film to form a sawtooth structure, and a stable structural layer is formed by UV curing. The apex angle of the sawtooth structure is 120°, the height is 12μm, and the angle between the arrangement direction of the sawtooth structure and the edge of the reflective area is 45°.

[0118] (4) Preparation of reflective layer: A 90nm thick Al layer is deposited on the structural layer by vacuum evaporation as a reflective layer, and then the mask of the battery area is removed.

[0119] (5) Preparation of inner coating: A mask is set in the reflective area; fluorocarbon resin is coated on the surface of the battery area and cured to obtain an inner coating with a thickness of 10 μm; then the mask in the reflective area is removed to obtain a photovoltaic backsheet.

[0120] Examples 2-8

[0121] The preparation methods of the photovoltaic backsheets in Examples 2-8 are basically the same as those in Example 1, with the following specific differences:

[0122] Example 2: The angle between the arrangement direction of the sawtooth structure and the edge of the reflective area is 30°.

[0123] Example 3: The angle between the arrangement direction of the sawtooth structure and the edge of the reflective area is 60°.

[0124] Example 4: The apex angle of the sawtooth structure is 90°.

[0125] Example 5: The apex angle of the sawtooth structure is 150°.

[0126] Example 6: The height of the serrated structure is 10 μm.

[0127] Example 7: The height of the serrated structure is 15 μm.

[0128] Example 8: The thickness of the weather-resistant layer is 20 μm, and the thickness of the inner coating layer is 20 μm.

[0129] Comparative Example 1

[0130] The photovoltaic backsheet in Comparative Example 1 uses a traditional grid backsheet.

[0131] The photovoltaic backsheet includes a weather-resistant layer, a substrate layer, a high-reflectivity coating, and an inner coating. The weather-resistant layer, substrate layer, and inner coating are the same as in Example 1; the high-reflectivity coating is a white high-reflectivity coating and is applied to the reflective area of ​​the substrate layer's bearing surface.

[0132] Comparative Example 2

[0133] Comparative Example 2's photovoltaic backsheet incorporates a metal film strip.

[0134] The photovoltaic backsheet comprises a weather-resistant layer, a substrate layer, and a metal film strip. The weather-resistant layer and substrate layer are the same as in Example 1. The metal film strip is attached to the reflective area of ​​the substrate layer's bearing surface and includes an EVA adhesive layer, a base film, a structural layer, and a reflective layer. The base film is a 230μm thick PET film, and the structural and reflective layers are the same as in Example 1.

[0135] Test case

[0136] The photovoltaic backsheets prepared in Examples 1-8 and Comparative Examples 1-2 were tested, and the test results are shown in Table 1. The specific test methods and test standards are as follows:

[0137] (1) Optical Density (OD): Characterizes the light-blocking ability of a material. Optical density has no dimensionless unit and is a logarithmic value. Typically, the optical density value of aluminized film is 1~3 (i.e., the light transmittance is 10%~0.1%), and the higher the value, the thicker the aluminized layer. Optical density can be calculated using the following formula: OD=log(1 / trans), where trans represents the light transmittance, which can be measured with reference to ASTM D1003 "Test Method for Light Transmittance and Haze of Transparent Plastics".

[0138] (2) Reflectivity: Refer to CQC 3308-2013 "Technical Specification for Certification of Backsheet for Photovoltaic Module Encapsulation".

[0139] (3) Weathering test: Refer to GB / T 2423.3 "High and low temperature damp heat test method".

[0140] (4) UV test: Refer to GB / T 31034 "Insulating backsheet for crystalline silicon solar cell modules".

[0141] (5) Lamination reliability: The photovoltaic backsheet, multiple solar cells, encapsulation film and photovoltaic cover are assembled and then laminated under a pressure of 0.1MPa~0.15MPa to obtain a photovoltaic module. The probability of microcracks in the solar cells is calculated based on the number of solar cells with microcracks in the photovoltaic module.

[0142] Table 1. Test results of photovoltaic backsheet

[0143]

[0144] As shown in Table 1, in the photovoltaic backsheets of Examples 1-8, the optical density (OD) of the reflective area is >3, indicating that the reflective layer (aluminum layer) in the reflective area has a high thickness and the light transmittance is below 0.1%, resulting in excellent reflection effect. Compared with the diffuse reflection of Comparative Example 1, Examples 1-8 achieve directional reflection through the structural layer and reflective layer, significantly improving the reflectivity of the reflective area. This results in high utilization of light energy by the photovoltaic backsheet, which is beneficial for improving the reflective power of the solar cells. Thanks to the protection of the emitting layer and weather-resistant layer, the photovoltaic backsheets of Examples 1-8 show no bubbles or cracks after 2000 hours of high and low temperature humid heat. After UV testing, they show no cracks, no delamination, and a low yellowing index, exhibiting high weather resistance and high UV resistance, thus reducing the impact on the reflection effect. Furthermore, after assembling the photovoltaic backsheets of Examples 1-8 into photovoltaic modules, the probability of microcracks in the solar cells can be stably controlled below 5%, demonstrating high lamination reliability.

[0145] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0146] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of protection of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these modifications and improvements all fall within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the appended claims.

Claims

1. A photovoltaic module, characterized in that, The photovoltaic module includes a photovoltaic backsheet and solar cells. The photovoltaic backsheet includes a substrate layer, a structural layer, a reflective layer, and an inner coating layer. The substrate layer has a bearing surface, and the bearing surface is provided with multiple battery areas and reflective areas, with the reflective areas surrounding the battery areas; The structural layer is located above the reflective area. The structural layer has multiple oriented protrusions, the angle between the arrangement direction of the protrusions and the edge of the reflective area is acute, and the angle between the arrangement direction of the protrusions and the edge of the reflective area is 30° to 60°. The protrusions are serrated, the apex angle of the serrations is 90° to 150°, and the height is 5μm to 30μm. The matrix resin of the structural layer includes acrylic resin, and the light transmittance of the structural layer is ≥90%. The reflective layer covers the structural layer; The inner coating is located above the battery region; The solar cells are located on the inner coating of the photovoltaic backsheet; The thickness ratio of the inner coating layer to the structural layer is 1:(1-2), the total thickness of the inner coating layer and the battery cell is lower than the total thickness of the structural layer and the reflective layer, the thickness of the inner coating layer is 5μm-20μm, and the base resin of the inner coating layer includes one or more of fluorocarbon resin and acrylic resin.

2. The photovoltaic module as described in claim 1, characterized in that, The protrusion structure is a serrated structure, and the height of the serrated structure is 10μm to 15μm.

3. The photovoltaic module as described in claim 1, characterized in that, The matrix resin of the structural layer includes one or more of polymethyl methacrylate, polyethyl methacrylate, polyacrylic acid, polymethyl methacrylate, polybutyl methacrylate, polyhydroxyethyl methacrylate, and polyglycidyl methacrylate.

4. The photovoltaic module as described in any one of claims 1 to 3, characterized in that, One or more of the following conditions must be met: (1) The matrix resin of the substrate layer includes polyethylene terephthalate; (2) The thickness of the substrate layer is 180μm to 350μm; (3) The material of the reflective layer includes one or more of aluminum and aluminum oxide; (4) The thickness of the reflective layer is 30nm to 100nm.

5. The photovoltaic module as described in any one of claims 1 to 3, characterized in that, The photovoltaic backsheet further includes a weather-resistant layer, which is located on the surface of the substrate layer away from the bearing surface, and the weather-resistant layer satisfies one or more of the following conditions: (1) The base resin of the weather-resistant layer includes one or more of acrylic resin, fluorocarbon resin and polyethylene terephthalate; (2) The thickness of the weather-resistant layer is 5μm to 30μm.

6. The photovoltaic module as described in any one of claims 1 to 3, characterized in that, The distance between two adjacent battery areas is 2mm to 4mm.

7. The photovoltaic module as described in any one of claims 1 to 3, characterized in that, The photovoltaic module includes an encapsulating film and a photovoltaic cover plate. Multiple solar cells are electrically connected to form a cell string. The encapsulating film covers the surface of the cell string, and the photovoltaic cover plate covers the surface of the encapsulating film opposite to the surface of the cell string.

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