Photovoltaic backboard and preparation method thereof, and photovoltaic module

Abstract

The invention relates to the field of photovoltaic technology, in particular to a photovoltaic backboard, a preparation method thereof and a photovoltaic module. The photovoltaic backboard comprises a base material layer, a structural layer, a reflecting layer and an inner coating, the base material layer is provided with a bearing surface, the bearing surface is provided with a plurality of battery areas and light reflecting areas, and the light reflecting areas are arranged around the battery areas; the structural layer is located on the reflective area, the structural layer is provided with a plurality of raised structures which are arranged in a directional mode, and the included angle between the arrangement direction of the raised structures and the edge of the reflective area is an acute angle; the reflecting layer covers the structural layer; and the inner coating layer is positioned on the battery region. The photovoltaic backboard provided by the invention is high in energy utilization rate, effectively improves the durability and reliability of the photovoltaic backboard, and facilitates the improvement of the power generation efficiency and the service life of a photovoltaic module.

Description

Technical Field

[0001] The present application relates to the field of photovoltaic technology, and in particular to a photovoltaic backplane and a preparation method thereof, and a photovoltaic module. Background Art

[0002] As energy shortages, rising global temperatures and environmental degradation become more prominent, solar energy as a green renewable energy source has received more and more attention. Photovoltaic modules are devices that convert renewable solar energy into electrical energy.

[0003] In photovoltaic modules, the power generation of the cell is an important indicator to measure the performance of photovoltaic modules, which directly reflects the efficiency of photovoltaic modules in utilizing light energy. Specifically, high power generation is conducive to reducing the cost of photovoltaic module manufacturing. Under the condition that the power generation of photovoltaic modules is the same, the higher the power generation of the cell, the smaller the size of the photovoltaic module, and the corresponding weight of the photovoltaic module is also lower.

[0004] The photovoltaic backplane is set on the back of the cell to protect the cell from corrosion by water vapor, oxygen and ultraviolet rays. However, traditional photovoltaic backplanes have difficulty in improving both the efficiency of light energy utilization and the reliability of the structure, which affects the power generation and service life of the cell. Summary of the invention

[0005] Based on this, it is necessary to provide a photovoltaic backplane and a preparation method thereof, and a photovoltaic module to solve the problem that traditional photovoltaic backplanes are difficult to balance in improving light energy utilization efficiency and improving structural reliability.

[0006] The above-mentioned purpose of the present application is achieved through the following technical solutions:

[0007] In a first aspect of the present application, a photovoltaic backsheet is provided, comprising a substrate layer, a structural layer, a reflective layer and an inner coating layer;

[0008] The substrate layer has a bearing surface, the bearing surface is provided with a plurality of battery areas and a reflective area, and the reflective area is arranged around the battery area;

[0009] The structural layer is located on the reflective area, and the structural layer has a plurality of convex structures arranged in a direction, and the angle between the arrangement direction of the convex structures and the edge of the reflective area is an acute angle;

[0010] The reflective layer covers the structural layer;

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

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

[0013] In some embodiments, the protrusion structure is a sawtooth structure, the top angle of the sawtooth structure is 90° to 150°, and the height is 5 μm to 30 μm.

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

[0015] In some embodiments, the base 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 layer includes one or more of a fluorocarbon resin and an 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, and the weather-resistant layer is located on a surface of the substrate layer away from the supporting 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 weather-resistant layer has a thickness of 5 μm to 30 μm.

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

[0025] In a second aspect of the present application, a method for preparing a photovoltaic backsheet is provided, comprising the following steps:

[0026] Providing a substrate layer, wherein the substrate layer has a bearing surface, the bearing surface is provided with a plurality of battery areas and a reflective area, and the reflective area is arranged around the battery area;

[0027] An inner coating is formed on the battery area, and a structural layer and a reflective layer are sequentially formed on the reflective area, wherein the structural layer has a plurality of convex structures arranged in a direction, and an angle between the arrangement direction of the convex structures 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: using acrylic resin to coat the reflective area to form a liquid film, etching the liquid film to form a plurality of protruding structures by embossing or rolling, and solidifying to obtain the structural layer; and forming a reflective layer on the structural layer by evaporation.

[0029] In a third aspect of the present application, a photovoltaic module is provided, comprising the photovoltaic backsheet as described above, or comprising a photovoltaic backsheet manufactured using the method for manufacturing the photovoltaic backsheet as described above.

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

[0031] The photovoltaic backplane provided by the present application includes a substrate layer, a structural layer, a reflective layer and an inner coating. The bearing surface of the substrate layer is provided with a plurality of battery areas and reflective areas, and the reflective area is arranged around the battery area. The inner coating is located in the battery area, and is used to bond the battery cells, improve the adhesion between the battery cells and the battery area, and improve the structural stability of the photovoltaic module. The structural layer is located in the reflective area, and it has a plurality of convex structures arranged in a direction, and the arrangement direction of the convex structure and the edge of the reflective area form an angle of 0°~90°. With the reflective layer covering the structural layer, the light incident to the reflective area can be reflected to the battery area in a directionally manner, and the reflection direction is controllable, which effectively improves the utilization rate of light energy, thereby facilitating the increase of the power generation power of the battery cell. In addition, the photovoltaic backplane provided by the present application adopts an integrated design, and the metal film strip that enhances the reflection effect can be not additionally coated, which is conducive to simplifying the module structure, reducing the lamination thickness and module weight, reducing the risk of hidden cracks in the battery cell, and avoiding the yellowing and cracking of the metal film strip, etc., so that the durability and reliability of the photovoltaic backplane are greatly improved, thereby extending the service life of the photovoltaic module. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present application and to more completely understand the present application and its beneficial effects, the following is a brief introduction to the drawings required for the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application, and those skilled in the art can obtain other drawings based on these drawings without creative work.

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

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

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

[0036] Figure 4Schematic diagram of the process of preparing photovoltaic backsheets in some embodiments.

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

[0038] In order to facilitate the understanding of the present application, the present application is further described in detail below in conjunction with specific embodiments. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present application more thorough and comprehensive.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

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

[0041] When a numerical range is disclosed in this application, the above range is considered to be continuous and includes the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed in this application should be understood to include any and all subranges included therein.

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

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

[0044] The temperature parameters in this application, unless otherwise specified, are allowed to be either constant temperature treatment or to vary within a certain temperature range. It should be understood that the constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument. Fluctuations within the range of ±5°C, ±4°C, ±3°C, ±2°C, and ±1°C are allowed.

[0045] In the present application, room temperature refers to indoor temperature, normal temperature or general temperature. Generally speaking, the range of room temperature can be any one of the following temperature intervals: 23°C ± 2°C, 25°C ± 5°C or 20°C ± 5°C.

[0046] At present, photovoltaic backplanes generally include a weather-resistant layer, a substrate layer, and an inner coating layer stacked in sequence. In order to improve the utilization of the cell spacing and string spacing in photovoltaic modules, a high-reflection coating is usually provided between the substrate layer and the inner coating layer. The high-reflection coating can be set to black or white as required, and its distribution position corresponds to the cell spacing and string spacing, and is generally called a grid backplane. This grid backplane can perform secondary reflection on the light incident on the gap between the cells, thereby improving the utilization of light by the cells, thereby increasing the power generation of the photovoltaic module. However, the grid backplane is based on diffuse reflection of the high-reflection coating, the reflection direction is uncontrollable, the reflection efficiency is insufficient, the utilization rate of light is low, and the power enhancement effect of the photovoltaic module is not good.

[0047] In addition to the above-mentioned grid backplane, some photovoltaic modules will install metal film tapes at the gaps between cells to improve the utilization rate of incident light. The traditional metal film tape includes an adhesive layer, a substrate layer, a structural layer and a reflective layer stacked in sequence. The structural layer has a serrated structure, which can reflect the incident light at the gap between the cells to the cells. The utilization rate of light is higher than that of the grid backplane, which makes the power of photovoltaic modules better. However, when the metal film tape is applied to the gap between the cells, the lamination thickness of the photovoltaic module is thicker, resulting in an increased risk of hidden cracks in the cells, affecting the reliability of the photovoltaic module. In addition, the adhesive layer of the metal film tape uses EVA film, which is generally 60μm~90μm thick. It is exposed to sunlight for a long time, has a high yellowing value, and has the risk of cracking and failure.

[0048] Based on this, the first aspect of the present application provides a photovoltaic backplane, which aims to increase the probability of the photovoltaic backplane reflecting light incident on the gap between battery cells onto the battery cells, while improving the structural reliability of the photovoltaic backplane.

[0049] In some embodiments, Figure 1 As shown, the photovoltaic backsheet includes a substrate layer 10, a structural layer 20, a reflective layer 30 and an inner coating 40. The substrate layer 10 has two surfaces opposite to 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 bearing surface of the substrate layer 10 is provided with a plurality of battery areas 11 and a reflective area 12, and the reflective area 12 is arranged around the battery area 11. Among them, the structural layer 20 is located on the reflective area 12, and the structural layer 20 has a plurality of convex structures arranged in a direction, and the angle between the arrangement direction of the convex structure and the edge of the reflective area 12 is 0°~90°; the reflective layer 30 covers the structural layer 20; and the inner coating layer 40 is located on the battery area 11.

[0051] The photovoltaic backplane provided in the present application includes a substrate layer 10, a structural layer 20, a reflective layer 30 and an inner coating 40. The bearing surface of the substrate layer 10 is provided with a plurality of battery areas 11 and reflective areas 12, and the reflective area 12 is arranged around the battery area 11. The inner coating 40 is located in the battery area 11, and is used to bond the battery cells, improve the adhesion between the battery cells and the battery area 11, and improve the structural stability of the photovoltaic module. The structural layer 20 is located in the reflective area 12, and has a plurality of convex structures arranged in a direction. The arrangement direction of the convex structure and the edge of the reflective area 12 form an angle of 0° to 90°. In conjunction with the reflective layer 30 covering the structural layer 20, the light incident to the reflective area 12 can be reflected to the battery area 11 in a directionally controlled manner. The reflection direction is controllable, which effectively improves the utilization rate of light energy, thereby facilitating the increase of the power generation power of the battery cell. In addition, the photovoltaic backplane provided in the present application adopts an integrated design and does not require the additional metal film tape to enhance the reflective effect. This is conducive to simplifying the module structure, reducing the lamination thickness and module weight, reducing the risk of hidden cracks in the battery cells, and avoiding problems such as yellowing and cracking of the metal film tape, thereby greatly improving the durability and reliability of the photovoltaic backplane, thereby extending the service life of the photovoltaic module.

[0052] In some embodiments, Figure 2 As shown, on the supporting surface of the substrate layer 10, multiple battery areas 11 are distributed in a grid shape, and the distance between two adjacent battery areas 11 is 2mm~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, Figure 3 As shown, the direction formed by the edge of the reflective area 12 is the first direction A, the protruding structures in the structural layer 20 are arranged in a direction along the second direction B, and the angle between the arrangement direction of the protruding structures 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 structures can be directionally controlled according to the structural design and light receiving 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 structures 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, and the light at the reflective area 12 is fully utilized, which is conducive to increasing the power generation power of the battery cell.

[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°, that is, 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 probability that the protruding structure will directionally reflect the light incident on the reflective area 12 to the battery area 11 is further increased, the utilization rate of the light in the reflective area 12 is significantly improved, and the power generation efficiency of the battery cell is particularly significant.

[0057] In some embodiments, Figure 1 As shown, the protrusion structure is a sawtooth structure, and the sawtooth structure has a vertex angle on the side away from the substrate layer 10, the vertex angle of the sawtooth structure is 90° to 150°, and the height is 5μm to 30μm. Figure 3 As shown, the sawtooth structure is arranged in a directional manner on the reflective area 12 along the second direction B, the solid line in the reflective area 12 is the bottom edge of the sawtooth structure, and the dotted line in the reflective area 12 is the top edge of the sawtooth structure, which is also where its vertex angle is located. As an example, the vertex angle of the sawtooth structure includes but is not limited to 90°, 100°, 110°, 120°, 130°, 140°, 150°, 160° or 170°, and can further be 112°~120°; the height of the sawtooth structure includes but is not limited to 5μm, 8μm, 10μm, 12μm, 15μm, 18μm, 20μm, 22μm, 25μm, 28μm or 30μm, and can further be 5μm~15μm.

[0058] Therefore, the raised structure is a sawtooth structure having two inclined reflective surfaces. By controlling the top angle and height of the sawtooth structure, the size and number of the sawteeth 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 the light in the reflective area 12 is higher.

[0059] In some embodiments, the matrix resin of the structural layer 20 includes 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 can be one or more of polymethyl methacrylate (PMMA, also known as acrylic), polyethyl methacrylate (PEMA), polyacrylic acid (PAA), polymethyl acrylate (PMA), polybutyl acrylate (PBA), polyhydroxyethyl acrylate (PHEMA) and polyglycidyl methacrylate (PGMA).

[0060] Selecting acrylic resin as the base resin of the structural layer 20 has the following three advantages:

[0061] (1) Acrylic resin has good fluidity, flexibility and processability, is not easy to break during the molding process, and is suitable for molding processes such as embossing or rolling, thereby achieving the preparation of high-precision convex 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) The light transmittance of acrylic resin is very high, usually 90% to 92%, and even close to 94%, which can ensure that the light transmittance of the structural layer 20 reaches more than 90%. When part of the light is not reflected by the reflective layer 30 but passes through the reflective layer 30, the light can continue to pass through the structural layer 20 and be incident on the supporting surface of the substrate layer 10, and then be reflected to the battery area 11 by diffuse reflection, thereby maximizing the utilization rate of the light in the reflective area 12 and significantly improving the power generation of the battery cell.

[0064] In the present application, the structural layer 20 may also include functional additives dispersed in the matrix resin, such as one or more of anti-UV agents, dispersants, leveling agents and defoaming agents. Those skilled in the art may make adjustments based on the performance requirements and preparation process of the structural layer 20, and the present application does not make 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 oxide (eg, Al 2 O 3 ).

[0066] Aluminum (Al) is a light, low-cost, high-reflectivity metal material, and its reflectivity in the visible light range can reach almost 100%. The use of evaporation coating or magnetron coating technology can further improve its reflectivity, thereby making the reflective effect of the reflective layer 30 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 bus bar, thereby reducing the risk of leakage or short circuit.

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

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

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

[0071] In the present application, the substrate layer 10 may also include inorganic fillers and functional additives dispersed in the matrix resin. Among them, the inorganic filler in the substrate layer 10 may be one or more of titanium dioxide, montmorillonite, zinc oxide, aluminum oxide and silicon dioxide, which can enhance the toughness and mechanical properties of the substrate layer 10, and at the same time improve the diffuse reflection effect of the substrate layer 10, so that the light incident on the substrate layer 10 is reflected to the battery area 11 for the second time. The functional additive in the substrate layer 10 may be one or more of an anti-ultraviolet agent, a dispersant, a leveling agent and a defoaming agent, and those skilled in the art may adjust it according to the performance requirements and preparation process of the substrate layer 10, and this application does not make any special restrictions on this.

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

[0073] In this way, the substrate layer 10 can have good mechanical strength, and the lamination thickness of the photovoltaic module can be reduced as much as possible, thereby reducing the risk of hidden cracks in the cell during the lamination process.

[0074] In some embodiments, the base resin of the inner coating 40 includes one or more of a fluorocarbon resin and an 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 acrylate (PMA), polybutyl acrylate (PBA), polyhydroxyethyl acrylate (PHEMA), and polyglycidyl methacrylate (PGMA).

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

[0076] In the present application, the inner coating 40 may also include auxiliary resins, inorganic fillers and functional additives dispersed in the base 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, and the functional additives in the inner coating 40 may be one or more of thickeners, coupling agents, dispersants, leveling agents and defoaming agents. Those skilled in the art may make adjustments based on the performance requirements and preparation process of the inner coating 40, and the present application does not make any special restrictions 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 smaller than the total thickness of the structural layer 20 and the reflective layer 30. After the cell is bonded to the photovoltaic backplane through the inner coating 40, the total thickness of the inner coating 40 and the cell is also lower than the total thickness of the structural layer 20 and the reflective layer 30. This is more conducive to the cell absorbing the light reflected from the reflective layer 30, thereby improving the power generation efficiency of the cell.

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

[0080] Thus, the thickness of the inner coating 40 can be reduced while ensuring good bonding performance, thereby increasing the absorption of reflected light by the cell and significantly improving the light utilization rate in the reflective area 12 .

[0081] In some embodiments, the photovoltaic backsheet further includes a weather-resistant layer 50, which is located on the surface of the substrate layer 10 away from the bearing surface, that is, the weather-resistant layer 50 is located on the non-bearing surface of the substrate layer 10. Thus, by providing the weather-resistant layer 50, the substrate layer 10 can be protected from the erosion of oxygen and ultraviolet rays, thereby improving the durability and structural stability of the photovoltaic backsheet.

[0082] In some embodiments, the base 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 base 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 acrylate (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 the present application, the weather-resistant layer 50 may also include auxiliary resins, inorganic fillers and functional additives dispersed in the base 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 additive in the weather-resistant layer 50 may be one or more of matting powder (such as ultrafine silica, talcum powder, aluminum stearate, calcium stearate, white carbon black after organic surface treatment, etc.), dispersant, leveling agent and defoaming agent. Those skilled in the art may make adjustments according to the performance requirements and preparation process of the weather-resistant layer 50, and the present application does not make any special restrictions on this.

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

[0085] Thus, the thickness of the weather-resistant layer 50 can be reduced as much as possible while ensuring that the weather-resistant layer 50 has good weather-resistant performance, thereby preventing the lamination thickness of the photovoltaic module from being too high and causing hidden cracks in the cell.

[0086] In a second aspect of the present application, a method for preparing a photovoltaic backsheet is provided, which is used to prepare the above-mentioned photovoltaic backsheet.

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

[0088] S100: providing a substrate layer, wherein the substrate layer has a bearing surface, the bearing surface is provided with a plurality of battery areas and a reflective area, and the reflective area is arranged around the battery area;

[0089] S200: forming an inner coating layer on the battery area, and sequentially forming a structural layer and a reflective layer on the reflective area, wherein the structural layer has a plurality of convex structures arranged in a direction, and an angle between the arrangement direction of the convex structures and the edge of the reflective area is an acute angle.

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

[0091] In the present application, a suitable polymer film layer can be selected as the substrate layer, and the substrate layer can also be prepared by mixing, high-temperature melting and extrusion molding. For the bearing surface of the substrate layer, the number, size, arrangement of the battery areas and the distance between two adjacent battery areas, those skilled in the art can make adaptive adjustments according to the size of the battery cell and the performance requirements of the photovoltaic module, and this application does not make any special restrictions on this.

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

[0093] In some specific examples, the raw material of the weather-resistant layer is a liquid resin system containing PET. The weather-resistant layer and the substrate layer can be prepared by co-extrusion molding. At this time, 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 backplane are improved.

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

[0095] In some specific examples, the raw material of the weather-resistant layer is 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 composited by glue bonding, and the glue can be one or more of ethylene-vinyl acetate copolymer (EVA), polyolefin elastomer (POE) and polyvinyl butyral (PVB).

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

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

[0098] In some embodiments, sequentially forming a structural layer and a reflective layer on the reflective area includes the following steps:

[0099] S210: coating the reflective area with acrylic resin to form a liquid film, etching the liquid film to form a plurality of protruding structures by an embossing method or a roller pressing method, and curing to obtain a structural layer;

[0100] S220: forming a reflective layer on the structural layer by an evaporation method.

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

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

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

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

[0105] In a third aspect of the present application, a photovoltaic module is provided, which includes the photovoltaic backsheet mentioned above, or includes a photovoltaic backsheet manufactured using the method for manufacturing the photovoltaic backsheet mentioned above.

[0106] The photovoltaic module provided in this application has the advantages of high light energy utilization, high power generation and high structural reliability. It can be applied to distributed photovoltaic scenes such as color steel tile roofs, photovoltaic tiles or photovoltaic curtain walls, photovoltaic building integration (Building Integrated Photovoltaic, BIPV) and other scenes requiring photoelectric conversion.

[0107] In some embodiments, a photovoltaic module includes a photovoltaic backsheet, a cell, a packaging film, and a photovoltaic cover. The cell is located on the inner coating of the photovoltaic backsheet, and a plurality of cells are electrically connected to form a cell string; the packaging film covers the surface of the cell string, and the photovoltaic cover covers the surface of the packaging film away from the cell string.

[0108] In some embodiments, the cell includes one or more of a silicon solar cell, a compound solar cell, and an organic solar cell. Among them, the crystalline silicon solar cell includes one or more of an emitter and back passivated cell (PassivatedEmitter and Rear Solar Cell, referred to as PERC cell), a tunnel oxide passivated contact solar cell (TunnelOxide Passivated Contact Solar Cell, referred to as TOPCon cell), an intrinsic thin film heterojunction cell (Heterojunction with Intrinsic Thin-film Solar Cell, referred to as HJT cell or HIT cell), and an interdigitated back contact cell (Interdigitated Back Contact Solar Cell, referred to as IBC cell). Compound solar cells include perovskite solar cells (referred to as PSC cells), copper indium gallium selenide solar cells (referred to as CIGS cells), cadmium telluride solar cells (referred to as CdTe cells), and gallium arsenide solar cells (referred to as AsGa cells).

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

[0110] In some embodiments, a plurality of battery cells are electrically connected via conductive tapes to form a battery string, and the plurality of 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 is further described in conjunction with specific embodiments and comparative examples. The raw materials involved in the following specific embodiments and comparative examples, unless otherwise specified, can all be commercially available, the instruments used, unless otherwise specified, can all be commercially available, and the processes involved, unless otherwise specified, are all routinely selected by those skilled in the art.

[0113] Example 1

[0114] The photovoltaic backsheet of this embodiment is prepared by the following method:

[0115] (1) Providing a substrate layer: A 280 μm thick PET film is selected as the substrate layer. The substrate layer includes a bearing surface and a non-bearing surface that are arranged opposite to each other. A battery area and a reflective area are provided on the bearing surface.

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

[0117] (3) Preparation of 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 a microstructure 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 top 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 90 nm thick Al layer is formed 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; a fluorocarbon resin is coated on the surface of the battery area and cured to obtain an inner coating with a thickness of 10 μm; the mask in the reflective area is then removed to obtain a photovoltaic backplane.

[0120] Embodiment 2-8

[0121] The preparation methods of the photovoltaic backsheets of Examples 2-8 are basically the same as the preparation method of the photovoltaic backsheet of Example 1, and the specific differences are as follows:

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

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

[0124] Embodiment 4: The top angle of the sawtooth structure is 90°.

[0125] Embodiment 5: The top angle of the sawtooth structure is 150°.

[0126] Embodiment 6: The height of the sawtooth structure is 10 μm.

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

[0128] Embodiment 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 back panel of Comparative Example 1 adopts a traditional grid back panel.

[0131] The photovoltaic back sheet comprises a weather-resistant layer, a substrate layer, a high-reflective coating and an inner coating, wherein the weather-resistant layer, the substrate layer and the inner coating are the same as those in Example 1; the high-reflective coating is a white high-reflective coating and is disposed on the reflective area of ​​the bearing surface of the substrate layer.

[0132] Comparative Example 2

[0133] The photovoltaic backsheet of Comparative Example 2 introduces a metal film tape.

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

[0135] Test Case

[0136] The photovoltaic backsheets prepared in Examples 1 to 8 and Comparative Examples 1 to 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-shielding ability of a material. Optical density has no dimension and is a logarithmic value. Usually, the optical density of an aluminum-coated film is 1 to 3 (i.e., the light transmittance is 10% to 0.1%). The larger the value, the thicker the aluminum coating. The optical density can be calculated using the following formula: OD = log (1 / trans), where trans represents the transmittance, which can be measured in accordance with ASTM D1003 "Test Method for Light Transmittance and Haze of Transparent Plastics".

[0138] (2) Reflectivity: Refer to CQC 3308-2013 "Technical Specifications for Certification of Backsheets for Photovoltaic Module Packaging".

[0139] (3) Weathering test: refer to GB / T 2423.3 "High and low temperature and humidity test methods".

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

[0141] (5) Lamination reliability: The photovoltaic backplane, 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 hidden cracks in the solar cells is calculated based on the number of hidden cracks in the photovoltaic module.

[0142] Table 1. Test results of photovoltaic backsheet

[0143]

[0144] As can be seen from Table 1, in the photovoltaic backsheets of Examples 1 to 8, the optical density (OD) of the reflective area is >3, indicating that the thickness of the reflective layer (aluminum layer) in the reflective area is relatively high, the light transmittance is below 0.1%, and the reflection effect is excellent. Compared with the diffuse reflection of Comparative Example 1, Examples 1 to 8 significantly improve the reflectivity of the reflective area through directional reflection of the structural layer and the reflective layer, and the photovoltaic backsheet has a high utilization rate of light energy, which is beneficial to improve the reflection power of the battery cell. Thanks to the protection of the emission layer and the weather-resistant layer, the photovoltaic backsheets of Examples 1 to 8 have no bubbles or cracks in appearance after 2000 hours of high and low temperature and humidity. After the UV test, there is no crack in the external light, no stratification, and a low yellowing index. It has high weather resistance and high UV resistance, thereby reducing the impact on the reflection effect. At the same time, after the photovoltaic backsheets of Examples 1 to 8 are assembled to obtain photovoltaic modules, the probability of hidden cracks in the battery cell can be stably controlled to be below 5%, and the lamination reliability is high.

[0145] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described 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 above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of protection of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the scope of protection of the present application. Therefore, the scope of protection of the present application shall be subject to the attached claims.

Claims

1. A photovoltaic backsheet, characterized in that: It includes a substrate layer, a structural layer, a reflective layer and an inner coating layer; The substrate layer has a bearing surface, the bearing surface is provided with a plurality of battery areas and a reflective area, and the reflective area is arranged around the battery area; The structural layer is located on the reflective area, and the structural layer has a plurality of convex structures arranged in a direction, and the angle between the arrangement direction of the convex structures and the edge of the reflective area is an acute angle; The reflective layer covers the structural layer; The inner coating is located on the battery region.

2. The photovoltaic backsheet according to claim 1, characterized in that: The angle between the arrangement direction of the protruding structures and the edge of the reflective area is 30° to 60°.

3. The photovoltaic backsheet according to claim 2, characterized in that: The protrusion structure is a sawtooth structure, the top angle of the sawtooth structure is 90° to 150°, and the height is 5 μm to 30 μm.

4. The photovoltaic backsheet according to claim 3, characterized in that: The matrix resin of the structural layer includes acrylic resin, and the light transmittance of the structural layer is ≥90%.

5. The photovoltaic backsheet according to any one of claims 1 to 4, characterized in that: One or more of the following conditions are met: (1) The base resin of the substrate layer includes polyethylene terephthalate; (2) The thickness of the substrate layer is 180 μm to 350 μm; (3) The material of the reflective layer includes one or more of aluminum and aluminum oxide; (4) The thickness of the reflective layer is 30 nm to 100 nm; (5) The base resin of the inner coating layer includes one or more of fluorocarbon resin and acrylic resin; (6) The thickness ratio of the inner coating layer to the structural layer is 1:(1-2).

6. The photovoltaic backsheet according to any one of claims 1 to 4, characterized in that: The photovoltaic backsheet further includes a weather-resistant layer, which is located on a 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 5 μm to 30 μm.

7. The photovoltaic backsheet according to any one of claims 1 to 4, characterized in that: The distance between two adjacent battery areas is 2 mm to 4 mm.

8. A method for preparing a photovoltaic backsheet, characterized in that: The following steps are involved: Providing a substrate layer, wherein the substrate layer has a bearing surface, the bearing surface is provided with a plurality of battery areas and a reflective area, and the reflective area is arranged around the battery area; An inner coating is formed on the battery area, and a structural layer and a reflective layer are sequentially formed on the reflective area, wherein the structural layer has a plurality of convex structures arranged in a direction, and an angle between the arrangement direction of the convex structures and the edge of the reflective area is an acute angle.

9. The method for preparing a photovoltaic back sheet according to claim 8, characterized in that: Sequentially forming a structural layer and a reflective layer on the reflective area comprises the following steps: Using acrylic resin to coat the reflective area to form a liquid film, etching the liquid film to form a plurality of protruding structures by an embossing method or a roller pressing method, and curing to obtain the structural layer; A reflective layer is formed on the structural layer by an evaporation method.

10. A photovoltaic module, characterized in that: The invention comprises a photovoltaic back sheet as claimed in any one of claims 1 to 7, or comprises a photovoltaic back sheet made by the method for making a photovoltaic back sheet as claimed in claim 8 or 9.

Images