A high-barrier weather-resistant solar cell backsheet and a preparation method thereof

Abstract

A kind of high-barrier weather-resistant solar cell backboard, including the base film close to the back of solar cell piece and weather-resistant film located at the outside of base film, weather-resistant film and base film are bonded by adhesive layer and are integrated;The weather-resistant film includes a PVDF film, a plurality of equidistant parallel arranged sawtooth stripes with isosceles triangle cross section are formed on the two side surfaces of the PVDF film, the surface of sawtooth stripe on the side facing solar cell piece is formed with a layer of white protective layer by vacuum sputtering, the surface of sawtooth stripe on the side away from solar cell piece is formed with a layer of black protective layer by vacuum sputtering;The side of the PVDF film with white protective layer is bonded with a layer of heat-conducting metal film.The weather-resistant film of the application can increase the contact area with adhesive by setting sawtooth stripe, thereby increasing the overall adhesion of weather-resistant film, avoid the problem that weather-resistant film is easy to delaminate, simultaneously still have excellent heat-conducting performance and self-cleaning ability, base film also has excellent barrier property.

Description

Technical Field

[0001] This application relates to the field of solar cell technology, particularly to the field of solar cell backsheet technology, and especially to a high-barrier, weather-resistant solar cell backsheet and its preparation method. Background Technology

[0002] CN 101582458 B discloses a solar cell backsheet, comprising a weather-resistant layer, a first adhesive layer, a structural reinforcement layer, a second adhesive layer, and an adhesive reflective layer sequentially bonded together. The weather-resistant layer is an inorganically modified polyvinylidene fluoride alloy layer, and the adhesive reflective layer is a white polyethylene layer. The background section of this prior art also mentions that a common backsheet structure is a TPT structure, where T typically refers to polyvinyl fluoride (PVF) film and P typically refers to polyethylene terephthalate (PET) film, i.e., a PVF / PET / PVF structure. The main function of PVF film is weather resistance, but it is expensive and has low surface energy, making it prone to delamination.

[0003] CN 103563096 A discloses a backsheet for a solar cell module, comprising a polyester film layer and a fluorine coating applied to at least one surface of the polyester film layer. The backsheet is formed on the upper surface of the polyester film layer and includes a polyethylene film layer attached to the ethylene vinyl acetate (EVA) plate of the solar cell module. This prior art also mentions that the adhesion of the existing fluorine-containing film is poor, resulting in insufficient adhesion between the weather-resistant fluorine-containing film covering the backsheet and the substrate, or even the EVA plate of the solar cell module. Therefore, even though the fluorine-containing film has excellent weather resistance, its weak adhesion leads to poor barrier properties and poor moisture resistance. This prior art uses an outer fluorine coating to reduce costs and improve adhesion; however, the coating contains relatively few effective weather-resistant components, and because it is located on the outermost side of the backsheet, it is difficult to resist wind and sand erosion for extended periods, and the coating is prone to peeling off. In addition, in order to reduce costs and improve adhesion, the existing technology also emphasizes that the coating should not be too thick. Therefore, the weather resistance at the same thickness will obviously be weaker than that of fluorinated films. If better protection is to be achieved, the coating thickness can only be increased. However, a thicker coating will reduce the ability to withstand changes in thermal stress on the backing plate. Under alternating hot and cold conditions, the coating is more likely to peel off.

[0004] In addition to requiring a thicker fluorine-containing coating, the backsheets of the aforementioned prior art also need to use a white polyethylene film layer on the inside. Although this enhances adhesion, the increased thickness makes it difficult to apply to flexible solar cells where greater flexibility is required. Furthermore, the barrier properties of the backsheets in the aforementioned prior art are also insufficient. Summary of the Invention

[0005] The technical problem to be solved by this application is to provide a high-barrier, weather-resistant solar cell backsheet and its preparation method, so as to reduce or avoid the problems mentioned above.

[0006] To address the aforementioned technical problems, this application proposes a high-barrier, weather-resistant solar cell backsheet, comprising a base film near the back of the solar cell and a weather-resistant film located outside the base film, wherein the weather-resistant film and the base film are bonded together by an adhesive layer; the weather-resistant film comprises a PVDF film, wherein multiple equally spaced parallel serrated stripes with an isosceles triangular cross-section are formed on both sides of the PVDF film; a white protective layer is formed on the surface of the serrated stripes facing the solar cell by vacuum sputtering, and a black protective layer is formed on the surface of the serrated stripes away from the solar cell by vacuum sputtering; a thermally conductive metal film is bonded to the side of the PVDF film with the white protective layer.

[0007] Preferably, the base of the isosceles triangle of the sawtooth stripe has a length of 5-10 μm, a vertex angle of 45-135 degrees, a height of 5-10 μm, and a minimum gap between adjacent sawtooth stripes of 0-5 μm.

[0008] Preferably, the maximum thickness of the PVDF film is 20-30 μm.

[0009] Preferably, the white protective layer is made of titanium dioxide; the black protective layer is made of silicon carbide.

[0010] Preferably, the thicknesses of the white protective layer and the black protective layer are 1-3 μm, respectively.

[0011] Preferably, the serrated stripes on both sides of the PVDF film are arranged perpendicularly to each other; the angle between the length direction of the serrated stripes and the four rectangular sides of the PVDF film is 45 degrees.

[0012] Preferably, the base film includes a substrate layer, and each of the two sides of the substrate layer has an online coating layer, and a barrier layer is sputtered to form the outer side of the online coating layer.

[0013] Preferably, the barrier layer is made of silicon dioxide and has a thickness of 200 nm.

[0014] Preferably, the online coating layer is formed by uniformly mixing acrylic resin, silica nanoparticles with a particle size of 5-10 nm, 1,4-dioxane, polyethylene oxide, and ethylene-vinyl acetate copolymer into a primer, and then curing it through online coating; the mass ratio of each component of the online coating layer is 100:(10~15):(20~30):(10~15):(5~10).

[0015] Preferably, the total thickness of the back sheet is 170-332 μm; the thickness of the base film is 120-250 μm; the thickness of the weather-resistant film is 45-72 μm; and the thickness of the adhesive layer is 5-10 μm.

[0016] This application also proposes a method for preparing a high-barrier, weather-resistant solar cell backsheet. The high-barrier, weather-resistant solar cell backsheet includes a base film near the back of the solar cell and a weather-resistant film located outside the base film. The weather-resistant film and the base film are bonded together by an adhesive layer. The base film includes a substrate layer, and each of the two sides of the substrate layer has an online coating layer. A barrier layer is sputtered to form the outer side of the online coating layer. The method is characterized by including a base film preparation step, a weather-resistant film preparation step, and a bonding step between the base film and the weather-resistant film. The base film preparation step includes: using PET chips as raw material for preparing PET film, obtaining a single-layer thick sheet through melt extrusion, preheating and then longitudinally stretching it into a film, and after longitudinal stretching, using a coating machine to online coat one side of the film with the components constituting the online coating layer. The mixture is then stretched laterally, shaped, cooled, and wound up to form an online coating layer on the film surface. A barrier layer is then sputtered on the outside of the online coating layer to obtain a base film with an online coating layer and a barrier layer. The preparation steps of the weather-resistant film include: providing a PVDF film; forming multiple equally spaced parallel serrated stripes with isosceles triangle cross-sections on both sides of the PVDF film by hot pressing; forming a white protective layer on one side of the serrated stripes by vacuum sputtering and a black protective layer on the other side of the serrated stripes by vacuum sputtering; bonding a thermally conductive metal film to the side with the white protective layer to obtain the weather-resistant film; the bonding steps of the base film and the weather-resistant film include: bonding one side of the thermally conductive metal film of the weather-resistant film to the base film as a single unit through an adhesive layer.

[0017] The weather-resistant film of the high-barrier weather-resistant solar cell backsheet of this application can increase the contact area with the adhesive through the set serrated stripes, thereby increasing the overall adhesion of the weather-resistant film and avoiding the problem of easy delamination of the weather-resistant film. At the same time, it also has excellent thermal conductivity and self-cleaning ability, and the base film also has excellent barrier properties. Attached Figure Description

[0018] The accompanying drawings are intended only to illustrate and explain this application and do not limit the scope of this application.

[0019] Figure 1 The diagram shown is a cross-sectional schematic of a high-barrier, weather-resistant solar cell backsheet according to a specific embodiment of this application.

[0020] Figure 2The diagram shown is a schematic representation of the base film of a high-barrier, weather-resistant solar cell backsheet according to a specific embodiment of this application.

[0021] Figure 3 The diagram shown is a cross-sectional schematic of a weather-resistant film that can be used in the backsheet of a high-barrier weather-resistant solar cell according to a specific embodiment of this application.

[0022] Figure 4 The diagram shown is a structural schematic of a weather-resistant film that can be used in the backsheet of a high-barrier weather-resistant solar cell according to another specific embodiment of this application. Detailed Implementation

[0023] To provide a clearer understanding of the technical features, objectives, and effects of this application, specific embodiments are now described with reference to the accompanying drawings. Identical components are denoted by the same reference numerals.

[0024] like Figure 1 As shown, this application proposes a high-barrier, weather-resistant solar cell backsheet, comprising a base film 100 near the back of the solar cell (not shown) and a weather-resistant film 200 located on the outer side of the base film 100. The weather-resistant film 200 and the base film 100 are bonded together by an adhesive layer 300. In a specific embodiment, the total thickness of the backsheet is approximately 170-332 μm; the thickness of the base film 100 is approximately 120-250 μm; the thickness of the weather-resistant film 200 is approximately 45-72 μm; and the thickness of the adhesive layer 300 is approximately 5-10 μm. The adhesive layer 300 can be made of conventional EVA adhesive or UV-curable adhesive.

[0025] The weather-resistant film on the outer side of a solar cell backsheet provides excellent resistance to environmental corrosion, while the base film on the inner side possesses good insulation and mechanical properties. In the prior art backsheets cited in the background section, the base film only serves a simple supporting function; the reflection of transmitted light and heat transfer require other coatings, which involve complex processes and unstable coating structures, making them prone to aging and delamination under prolonged heating.

[0026] In one specific embodiment of this application, the base film 100 can be made of PET film, which can be a single-layer or multi-layer structure formed by biaxial stretching. PET film can provide excellent insulation, water resistance, mechanical properties, and dimensional stability. However, for solar cells, especially for mainstream CI(G)S flexible solar cells, the process characteristics require stronger barrier properties to protect the internal circuitry, thus placing high demands on the backsheet, typically requiring a barrier property of 10. -3g / m²·day level. The common approach to enhancing barrier properties is to increase the thickness of the material, which increases the material cost, increases the unit weight, and reduces the material's flexibility. Excessively thick material can also cause slippage and leakage when the edges of the sheet are bent.

[0027] In view of this, Figure 2 In one specific embodiment of the base film 100 shown, the base film 100 includes a substrate layer 101, with an in-line coating layer 102 on each of its two side surfaces. A barrier layer 103 is sputtered onto the outer side of the in-line coating layer 102. The thickness of the substrate layer 101 is approximately 120-250 μm, and it can be made of, for example, a 188 μm biaxially oriented PET film. The barrier layer 103 is preferably made of silicon dioxide and has a thickness of 200 nm.

[0028] By setting the barrier layer 103, the barrier properties of the substrate layer 101 can be improved without increasing the thickness of the substrate layer 101, thus improving the adaptability of flexible solar cells. In order to improve surface smoothness and enhance the adhesion of the barrier layer 103, it is preferable to perform an online coating process on both sides of the substrate layer 101 before sputtering to form the barrier layer 103, forming an online coating layer 102 with a preferred thickness of 0.1-0.3 μm on each side.

[0029] Online coating allows chemicals to be applied directly to the substrate layer 101 during the production process using an online coating machine. Online coating can be formed directly in the later stages of the substrate layer production process without the need to re-unroll the roll material. The coating is uniform, fast, efficient, and low-cost.

[0030] In one specific embodiment, the primer liquid constituting the online coating layer 102 can be applied to the thick sheet before or during the stretching of the polyester film constituting the substrate layer 101. Then, as the thick sheet is stretched into a film of the required thickness, the primer liquid coated on its surface becomes thinner as it is stretched, and is cured together with the high temperature during the stretching process to form the online coating layer 102.

[0031] In one specific embodiment, the online coating layer 102 is formed by uniformly mixing acrylic resin, silica nanoparticles with a particle size of 5-10 nm, 1,4-dioxane, polyethylene oxide, and ethylene-vinyl acetate copolymer into a primer, and then curing it through online coating.

[0032] Specifically, the mass ratio of each component in the online coating layer 102 is as follows: acrylic resin: silica nanoparticles: 1,4-dioxane: polyethylene oxide: ethylene-vinyl acetate copolymer = 100:(10~15):(20~30):(10~15):(5~10). The ethylene-vinyl acetate copolymer can be Evaflex 550 from Mitsui Chemicals, Inc. of Japan, containing 14% vinyl acetate polymer by mass.

[0033] According to the raw material weight ratio in the table below, online coating layers were prepared on both sides of a 188μm biaxially oriented PET film, and then a barrier layer composed of silicon dioxide was sputtered on the outside of the online coating layer.

[0034]

[0035] In comparison, a 200 nm thick barrier layer of silicon dioxide was directly sputtered onto each of the two surfaces of a 188 μm biaxially oriented PET film as a comparative example. Measurements showed that the 180-degree peel strength (N / 25 mm) of the barrier layers in Examples 1-5 was increased by 34.5%, 36.2%, 35.1%, 34.8%, and 36.1% respectively compared to the comparative examples.

[0036] Furthermore, regarding the weather-resistant film 200, the fluorinated films used in the prior art as weather-resistant films are expensive and suffer from problems such as low surface energy, insufficient adhesion, and easy delamination. Therefore, this application proposes a weather-resistant film 200 for the high-barrier weather-resistant solar cell backsheet of this application, such as... Figure 3 As shown, the weather-resistant film 200 includes a PVDF film 201. Multiple equally spaced parallel sawtooth stripes 211 with an isosceles triangle cross section are formed on both sides of the PVDF film 201. A white protective layer 212 is formed on the surface of the sawtooth stripes 211 facing the solar cell by vacuum sputtering, and a black protective layer 213 is formed on the surface of the sawtooth stripes 211 away from the solar cell by vacuum sputtering.

[0037] The PVDF membrane 201 contains PVDF with a mass content of ≥90%. To improve its performance, ultraviolet absorbers, wear-resistant fillers, etc., can be added. Preferably, the serrated stripes 211 formed on both sides of the PVDF membrane 201 are identical. The dimensions of the weather-resistant membrane 200 shown in the figure have been enlarged for easier observation and understanding; the actual serrated stripes 211 are relatively small, with only barely perceptible textures on the surface. In one specific embodiment, the maximum thickness of the PVDF membrane 201 is 20-30 μm.

[0038] Existing PVDF weather-resistant films suffer from low surface energy and insufficient adhesion, leading to a tendency to delaminate. To overcome this problem, this application forms serrated stripes 211 on the surface of the PVDF film 201. The serrated stripes 211 increase the contact area with the adhesive 203 (which will be described in more detail later). For example, when the apex angle of the isosceles trapezoid of the serrated stripes 211 is 60 degrees, the serrated stripes 211 can double the surface area, thereby increasing the overall adhesion of the PVDF film 201 and preventing the weather-resistant film from easily delaminating.

[0039] It should be noted that improving the overall adhesion of the weather-resistant film 200 actually only requires setting serrated stripes 211 on the inner side of the PVDF film 201. However, since the stripes are very small and difficult to observe, the inventors chose to form the same serrated stripes 211 on both sides of the PVDF film 201 simultaneously for ease of assembly, so that film coating can be performed on both sides, thus increasing the applicability of the weather-resistant film 200. The inventors believed that the serrated stripes 211 originally located on the outer side did not seem to have any function. However, in actual laying experiments, it was found that if the scale of the serrated stripes 211 formed on the surface of the PVDF film 201 is smaller than a certain range, it can play a self-cleaning role, reducing the adhesion of dust to the surface of the weather-resistant film 200, and rainwater can easily wash away the attached dust. For example, in a specific embodiment, the isosceles triangle of the serrated stripes 211 preferably has a base length of 5-10 μm, a vertex angle of 45-135 degrees, a height of 5-10 μm, and a minimum gap between adjacent serrated stripes 211 of 0-5 μm. Forming identical serrated stripes 211 on both sides of the PVDF film 201 not only reduces manufacturing costs, but also allows for better adhesion on the inner side and excellent dust resistance on the outer side by selecting serrated stripes 211 within this size range. Furthermore, the serrated stripes 211 on the outer side further increase the surface area, thereby increasing the heat dissipation area and improving the overall heat dissipation performance of the weather-resistant film.

[0040] Furthermore, to improve the adhesion of the PVDF film 201 and prevent delamination, this application selects the angle between the length direction of the serrated stripes 211 and the four rectangular sides of the weather-resistant film to be 45 degrees, such as... Figure 4As shown. Generally, solar panels are designed in a rectangular shape with four perpendicular sides. If the length direction of the sawtooth stripes 211 is perpendicular to one pair of rectangular sides of the weather-resistant film 200, then the other pair of rectangular sides will be parallel to the length direction of the sawtooth stripes 211. Since the stiffness of the sawtooth stripes 211 is different in the length and width directions, their expansion rates are also different, which can cause one pair of rectangular sides of the weather-resistant film 200 to warp and delaminate. In this application, the direction of the sawtooth stripes 211 is turned at a 45-degree angle to the four rectangular sides. The proportion of stiffness differences in different directions caused by the sawtooth stripes 211 spreading to the four rectangular sides will tend to be averaged, thus avoiding the delamination problem of the weather-resistant film 200 caused by the sawtooth stripes 211, and further improving the structural performance of the weather-resistant film 200.

[0041] Furthermore, if the same serrated stripes 211 are formed on both sides, and the serrated stripes 211 on both sides are oriented in the same direction (i.e., their length directions are parallel), the different thermal expansion rates on both sides will concentrate in the same direction, potentially leading to stress concentration and delamination. To avoid delamination caused by the serrated stripes 211 on both sides being oriented in the same direction, this application proposes a special design where the serrated stripes 211 on both sides of the PVDF film 201 are arranged perpendicularly to each other, thereby avoiding the problem of stress bias in one direction causing delamination.

[0042] Furthermore, to avoid the problem that the excessively thick backsheets of existing technologies are difficult to apply to flexible solar cells with higher flexibility requirements, this application forms a white protective layer 212 and a black protective layer 213 on the PVDF film with a serrated stripe structure via vacuum sputtering. Since the bonding strength of the sputtered layer formed by vacuum sputtering is much greater than that of adhesive bonding, a very thin protective layer can achieve the protective function. For example, the white protective layer 212 can be made of titanium dioxide; the black protective layer 213 can be made of silicon carbide. Preferably, the thicknesses of the white protective layer 212 and the black protective layer 213 are 1-3 μm, respectively.

[0043] The white protective layer 212 provides excellent light reflection, reflecting as much light transmitted from the front of the solar cell back to the solar cell as possible, thus improving light conversion efficiency. Furthermore, since the white protective layer 212 is integrally sputtered onto the surface of the serrated stripes 211, an additional white polyethylene film layer is unnecessary, simplifying the structure of the weather-resistant film 200 and reducing the film thickness.

[0044] The black protective layer 213 is also a very thin sputtered layer, which can be used to improve wear resistance and enhance the weather-resistant film 200's ability to resist wind and sand erosion. In addition, the black protective layer 213 has better thermal radiation capabilities, facilitating the rapid dissipation of heat absorbed by the backsheet to reduce the temperature of the solar cell module. Simultaneously, the sputtering method improves adhesion while reducing additional film layers, thus lowering thickness and cost.

[0045] Furthermore, to further improve the heat dissipation capacity of the backplate, this application adheres a thermally conductive metal film 202 to one side of the PVDF film 201 with the white protective layer 212. For example, the thermally conductive metal film 202 can be bonded to the PVDF film 201 as a single unit using a suitable adhesive 203. Through the thermally conductive metal film 202, the heat absorbed by the backplate can be conducted to the PVDF film 201, and the heat can be efficiently radiated away through the increased surface area of ​​the serrated stripes on the outer side. In a specific embodiment, the thermally conductive metal film 202 can be made of aluminum foil with a thickness of 8-16 μm, and the adhesive 203 can be commercially available EVA adhesive or acrylic adhesive with a maximum thickness of 15-20 μm.

[0046] Examples 6-11

[0047] The weather-resistant film for solar cell backsheets was prepared according to the parameters in the table below.

[0048]

[0049] In Examples 6-8, the angle between the serrated stripes and the rectangular sides of the weather-resistant film is 45 degrees. In Examples 9-11, the angle between the serrated stripes and the rectangular sides of the weather-resistant film is 0 / 90 degrees, that is, the angle between the serrated stripes and one pair of rectangular sides is 0 degrees, and the angle with the other pair of rectangular sides is 90 degrees. The white protective layer is composed of titanium dioxide; the black protective layer is composed of silicon carbide.

[0050] Comparative Examples 1-6

[0051] Comparative Examples 1-6 used PVDF films without serrated stripes, and bonded thermally conductive metal films as weather-resistant films, with the following parameters. In Examples 6-11 and Comparative Examples 1-6, EVA adhesive was used, and aluminum foil was used as the thermally conductive metal film.

[0052]

[0053] The weather-resistant films of Examples 6-11 and Comparative Examples 1-6 were respectively bonded to the surface of a 188μm PET base film, and the parameter performance of each example of the weather-resistant film was measured and compared as follows.

[0054]

[0055] As can be seen from the performance parameter comparison of the above embodiments, the weather-resistant film for solar cell backsheets of this application, even with serrated stripes, can significantly improve adhesion performance and avoid delamination, has excellent thermal conductivity, increases the contact angle of the outer surface, improves self-cleaning ability, and has excellent dust resistance.

[0056] The preparation method of the high-barrier weather-resistant solar cell backsheet of this application is further described in detail below with reference to the accompanying drawings. As mentioned above, the high-barrier weather-resistant solar cell backsheet of this application includes a base film 100 near the back of the solar cell and a weather-resistant film 200 located outside the base film 100. The weather-resistant film 200 and the base film 100 are bonded together by an adhesive layer 300. The weather-resistant film 200 includes a PVDF film 201. Multiple equally spaced parallel serrated stripes 211 with an isosceles triangle cross-section are formed on both sides of the PVDF film 201. A white protective layer 212 is formed on the surface of the serrated stripes 211 facing the solar cell by vacuum sputtering, and a black protective layer 213 is formed on the surface of the serrated stripes 211 away from the solar cell by vacuum sputtering. A thermally conductive metal film 202 is bonded to the side of the PVDF film 201 with the white protective layer 212.

[0057] The preparation method of this application includes a step of preparing a weather-resistant film 200, and a step of bonding a base film 100 and a weather-resistant film 200. The preparation step of the weather-resistant film 200 includes:

[0058] First, a PVDF membrane 201 is provided. This PVDF membrane 201 can be a commercially available PVDF membrane with a thickness of 20-30μm, or it can be formed by melt co-extrusion and biaxial stretching of PVDF raw material particles with a mass content of ≥90%, with the addition of ultraviolet absorbers, wear-resistant fillers, etc.

[0059] Then, a plurality of equally spaced, parallel serrated stripes 211 with isosceles triangular cross-sections are formed on both sides of the PVDF film 201 by hot pressing. For example, two rollers with patterns matching the shape of the serrated stripes, positioned vertically opposite each other, can be used. The heated PVDF film 201 is passed between the two rollers, and then the PVDF film 201 is air-cooled or water-cooled to obtain the cured serrated stripes 211 on the PVDF film 201. The length directions of the patterns matching the shape of the serrated stripes on the surfaces of the two vertically opposite rollers are perpendicular to each other, thus forming mutually perpendicular serrated stripes 211 on both sides of the PVDF film 201. For example, if the pattern direction on the surfaces of the two rollers forms a 45-degree angle with the direction of travel of the PVDF film 201, serrated stripes 11 forming a 45-degree angle with the four rectangular sides of the weather-resistant film 200 can be formed.

[0060] Subsequently, a white protective layer 212 is formed on one side of the serrated stripe 211 by vacuum sputtering, and a black protective layer 213 is formed on the other side of the serrated stripe 211 by vacuum sputtering. For example, a layer of titanium dioxide with a thickness of 1-3 μm can be formed on one side of the serrated stripe 211 by vacuum sputtering to form the white protective layer 212; and a layer of silicon carbide with a thickness of 1-3 μm can be formed on the other side of the serrated stripe 211 by vacuum sputtering to form the black protective layer 213. Since the thickness of the formed protective layer is relatively very thin, Figure 4 The protective layer is not shown in the image, and at the same time, Figure 3 The protective layers 212 and 213 in the image have also been enlarged for easier understanding.

[0061] Finally, a thermally conductive metal film 202 is adhered to the side with the white protective layer 212 to form the weather-resistant film 200. For example, a layer of acrylic adhesive with a thickness of 15-20 μm can be coated on the side with the white protective layer 212, the surface can be smoothed, and then an 8-16 μm layer of aluminum foil can be adhered as the thermally conductive metal film 202 to prepare the weather-resistant film 200.

[0062] The bonding steps of the base film 100 and the weather-resistant film 200 include: bonding the base film 100 to the weather-resistant film 200 together via the adhesive layer 300. The base film 100 can be made of PET film, which can be a single-layer or multi-layer structure formed by biaxial stretching. In a preferred embodiment, the base film 100 includes a substrate layer 101, and each of the two sides of the substrate layer 101 has an online coating layer 102, and a barrier layer 103 is sputtered to the outer side of the online coating layer 102.

[0063] Therefore, the preparation method of this application may further include a preparation step of the base film 100, including:

[0064] Using PET chips as raw material for preparing PET film, a single-layer thick sheet is obtained by melt extrusion. After preheating, it is stretched longitudinally into a film. After longitudinal stretching, a mixture of components constituting the online coating layer of this application is online coated on one side of the film by a coating machine. Then, it is stretched laterally, shaped, cooled, and wound up to form an online coating layer 102 on the film surface. Then, a barrier layer 103 composed of silicon dioxide is sputtered to form on the outside of the online coating layer 102, thereby obtaining a base film 100 with the online coating layer 102 and the barrier layer 103.

[0065] Those skilled in the art should understand that although this application is described by way of multiple embodiments, not every embodiment contains only one independent technical solution. This description is merely for clarity, and those skilled in the art should understand the specification as a whole and consider the technical solutions involved in each embodiment as being able to be combined with each other to form different embodiments to understand the scope of protection of this application.

[0066] The above description is merely an illustrative embodiment of this application and is not intended to limit the scope of this application. Any equivalent changes, modifications, and combinations made by those skilled in the art without departing from the concept and principles of this application shall fall within the scope of protection of this application.

Claims

1. A high-barrier, weather-resistant solar cell backsheet, comprising a base film (100) near the back of the solar cell and a weather-resistant film (200) located outside the base film (100), wherein the weather-resistant film (200) and the base film (100) are bonded together by an adhesive layer (300); characterized in that, The weather-resistant film (200) includes a PVDF film (201). Multiple equally spaced parallel serrated stripes (211) with isosceles triangle cross sections are formed on both sides of the PVDF film (201). The serrated stripes (211) on both sides of the PVDF film (201) are perpendicular to each other. The angle between the length direction of the serrated stripes (211) and the four rectangular sides of the PVDF film (201) is 45 degrees. A white protective layer (212) is formed on the surface of the serrated stripes (211) facing the solar cell by vacuum sputtering, and a black protective layer (213) is formed on the surface of the serrated stripes (211) away from the solar cell by vacuum sputtering. A thermally conductive metal film (202) is bonded to the side of the PVDF film (201) with the white protective layer (212).

2. The backplate as described in claim 1, characterized in that, The isosceles triangle of the sawtooth stripe (211) has a base length of 5-10 μm, a vertex angle of 45-135 degrees, a height of 5-10 μm, and a minimum gap between adjacent sawtooth stripes (211) of 0-5 μm.

3. The backplate as described in claim 1, characterized in that, The maximum thickness of the PVDF membrane (201) is 20-30 μm.

4. The backplate as described in claim 1, characterized in that, The white protective layer (212) is made of titanium dioxide; the black protective layer (213) is made of silicon carbide.

5. The backplate as described in claim 1, characterized in that, The thicknesses of the white protective layer (212) and the black protective layer (213) are 1-3 μm, respectively.

6. The backplate as described in claim 1, characterized in that, The base film (100) includes a substrate layer (101), and each of the two sides of the substrate layer (101) has an online coating layer (102). A barrier layer (103) is sputtered to the outside of the online coating layer (102); the barrier layer (103) is made of silicon dioxide.

7. The backplate as described in claim 6, characterized in that, The thickness of the barrier layer (103) is 200 nm.

8. The backplate as described in claim 6, characterized in that, The online coating layer (102) is formed by uniformly mixing acrylic resin, silica nanoparticles with a particle size of 5-10 nm, 1,4-dioxane, polyethylene oxide, and ethylene-vinyl acetate copolymer into a base coat, and then curing it through online coating. The mass ratio of each component of the online coating layer (102) is 100: (10~15): (20~30): (10~15): (5~10).

9. A method for preparing a high-barrier weather-resistant solar cell backsheet, wherein the high-barrier weather-resistant solar cell backsheet comprises a base film (100) near the back of the solar cell and a weather-resistant film (200) located outside the base film (100), the weather-resistant film (200) and the base film (100) are bonded together by an adhesive layer (300); the base film (100) comprises a substrate layer (101), each of the two sides of the substrate layer (101) has an online coating layer (102), and a barrier layer (103) is sputtered to the outside of the online coating layer (102); characterized in that, The preparation method includes the following steps: preparation of a base film (100), preparation of a weather-resistant film (200), and bonding of the base film (100) and the weather-resistant film (200); wherein, the preparation of the base film (100) includes: using PET chips as raw material for preparing PET film, obtaining a single-layer thick sheet by melt extrusion, preheating and then longitudinally stretching it into a film, and after longitudinal stretching, using a coating machine to online coat a mixture of components constituting the online coating layer on one side of the film, then stretching it laterally, shaping, cooling, and winding it up, thereby forming an online coating layer (102) on the surface of the film, and then sputtering a barrier layer (103) on the outside of the online coating layer (102), thereby obtaining a base film (100) with an online coating layer (102) and a barrier layer (103); the preparation of the weather-resistant film (200) includes: providing a PVDF film (201); and hot pressing the PVDF film into the film. Multiple equally spaced parallel sawtooth stripes (211) with isosceles triangle cross sections are formed on both sides of the PVDF film (201); the sawtooth stripes (211) on both sides of the PVDF film (201) are arranged perpendicularly to each other; the angle between the length direction of the sawtooth stripes (211) and the four rectangular sides of the PVDF film (201) is 45 degrees; a white protective layer (212) is formed on one side of the sawtooth stripes (211) by vacuum sputtering, and a black protective layer (213) is formed on the other side of the sawtooth stripes (211) by vacuum sputtering; a thermally conductive metal film (202) is bonded to the side with the white protective layer (212) to obtain the weather-resistant film (200); the bonding step of the base film (100) and the weather-resistant film (200) includes: bonding one side of the thermally conductive metal film (202) of the weather-resistant film (200) to the base film (100) as a whole through the adhesive layer (300).

Images