A solar cell front panel and its fabrication method

Abstract

A solar cell front panel and its fabrication method are disclosed, comprising an outer weather-resistant film and an inner supporting base film, which are bonded together by an adhesive layer. The supporting base film includes a substrate layer, with an online coating layer on each of its two surfaces, and a barrier layer sputtered onto the outer side of the online coating layer. The substrate layer includes an inner film and an outer film. Multiple equally spaced, parallel inner prism structures with isosceles trapezoidal cross-sections are formed on the inner film. A refractive layer is formed on the outer side of the inner prism structures. The cavity between the outer film and the refractive layer is filled with the outer prism structures, and the outer film and the refractive layer are connected together by the outer prism structures. The weather-resistant film on the outer side of the front panel of this application provides reinforcement and weather resistance, while the inner supporting base film provides support and protection, as well as stronger barrier properties. The substrate layer of the supporting base film improves sunlight utilization by setting a refractive layer between the inner and outer prism structures.

Description

Technical Field

[0001] This application belongs to the field of solar cell technology, and in particular relates to a solar cell front panel and its preparation method. Background Technology

[0002] A typical solar photovoltaic (PV) module consists of a front panel, solar cells, encapsulation materials, and a backsheet. PV modules are typically used in outdoor environments, where they must withstand wind, sun, rain, dust, and abrasion. Therefore, the performance requirements for the front panel, the light-receiving surface, are very high, requiring high light transmittance, water resistance, UV resistance, and a certain level of mechanical strength.

[0003] CN 115179631 A discloses an encapsulation material and a photovoltaic module. The encapsulation material includes a fluoroplastic film and a water-blocking film, connected by a weather-resistant pressure-sensitive adhesive layer. A wear-resistant water-blocking layer is provided on the surface of the fluoroplastic film away from the water-blocking film. The fluoroplastic film undergoes low-pressure, low-temperature plasma surface treatment. The weather-resistant pressure-sensitive adhesive layer comprises acrylate pressure-sensitive adhesive, a combination of liquid ultraviolet absorbers, and a combination of solid ultraviolet absorbers. The fluoroplastic film used in the prior art front panel encapsulation material has high water permeability, poor wear resistance, low surface energy, and is prone to delamination and dust adsorption. After a period of outdoor use, this poses risks such as decreased module power generation and delamination. To avoid the water absorption and wear resistance problems of the fluoroplastic film, the prior art adds an additional water-blocking film. However, the weather resistance of the water-blocking film is weaker than that of the fluoroplastic film; the water-blocking film becomes brittle and cracks before the fluoroplastic film, and this does not fundamentally solve the defects of the fluoroplastic film. Summary of the Invention

[0004] The technical problem to be solved by this application is to provide a solar cell front panel and a method for its fabrication, so as to reduce or avoid the problems mentioned above.

[0005] To address the aforementioned technical problems, this application proposes a solar cell front panel, comprising an outer weather-resistant film and an inner supporting base film, which are bonded together by an adhesive layer. The supporting base film includes a substrate layer, with an online coating layer on each of its two surfaces. A barrier layer is sputtered onto the outer side of the online coating layer. The substrate layer includes an inner film facing the solar cell and an outer film away from the solar cell. Multiple equally spaced, parallel inner prism structures with isosceles trapezoidal cross-sections are formed on the inner film. A refractive layer is formed on the outer side of the inner prism structures by vacuum sputtering. The cavity between the outer film and the refractive layer is filled with the outer prism structure, and the outer film and the refractive layer are connected together by the outer prism structure.

[0006] Preferably, the refractive indices of both the inner and outer prism structures are less than the refractive index of the refractive layer.

[0007] Preferably, the refractive layer is composed of Nb2O5 with a refractive index of 2.01 to 2.48.

[0008] Preferably, the barrier layer is made of silicon dioxide and has a thickness of 200 nm.

[0009] 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 base coat, and then curing it through online coating; the mass ratio of each component of the online coating layer (22) is 100:(10-15):(20-30):(10-15):(5-10).

[0010] Preferably, the length of the lower base of the isosceles trapezoid of the cross-section of the inner prism structure is 20-30 μm, the lower base angle is 30-60 degrees, the height is 25-50 μm, and the minimum gap between adjacent inner prism structures is 50-100 μm.

[0011] Preferably, the inner and outer membranes are made of PET of the same thickness with a visible light transmittance greater than 85%.

[0012] In addition, this application also proposes a method for preparing the aforementioned solar cell front panel, including a step of preparing a supporting base film and a step of bonding the supporting base film and the weather-resistant film; wherein, the step of preparing the supporting base film includes: using PET chips as raw materials for preparing PET films, 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 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 on the surface of the film, and then sputtering a barrier layer composed of silicon dioxide on the outside of the online coating layer, thereby obtaining an inner layer film and an outer layer film with an online coating layer and a barrier layer for later use; in the case where the inner layer film does not form an online coating layer On one side of the barrier layer, multiple parallel inner prism structures with isosceles trapezoidal cross-sections are cured to form an inner prism structure with equal intervals. A refractive layer is formed on the inner prism structure by vacuum sputtering. UV-curable acrylic resin is filled into the recessed cavity outside the refractive layer, and an outer film away from the solar cell is bonded to the outside of the refractive layer and the filled UV-curable acrylic resin. The side of the outer film that does not form the online coating layer and the barrier layer is bonded to the refractive layer. UV light is irradiated through the barrier layer side of the outer film to cure the filled UV-curable acrylic resin to form the outer prism structure. While the outer prism structure is curing, the outer film and the refractive layer are connected together through the outer prism structure to obtain the base film.

[0013] Preferably, the bonding step of the supporting base film and the weather-resistant film includes: bonding one side of the outer layer of the supporting base film to the weather-resistant film as a whole through an adhesive layer, wherein the weather-resistant film is composed of a PVDF film with PVDF as the main component.

[0014] Preferably, the thickness of the weather-resistant film is 20-30 μm.

[0015] The weather-resistant film on the outer side of the front panel of this application has the functions of reinforcement and weather resistance, while the inner supporting base film provides support and protection functions and stronger barrier properties. The substrate layer of the supporting base film improves the utilization rate of sunlight by setting a refractive layer between the inner prism structure and the outer prism structure. Attached Figure Description

[0016] The accompanying drawings are intended only to illustrate and explain this application and do not limit the scope of this application.

[0017] Figure 1 The diagram shown is a cross-sectional schematic of the front panel of a solar cell according to a specific embodiment of this application.

[0018] Figure 2 The diagram shown is a schematic representation of a specific structure of a support base film for a solar cell front panel according to a specific embodiment of this application.

[0019] Figure 3 The diagram shown is a structural schematic of a support base film for a solar cell front panel according to another specific embodiment of this application.

[0020] Figure 4 The diagram shown is an exploded perspective view of a substrate layer for a support base film that can be used in the front panel of a solar cell according to yet another specific embodiment of this application. Detailed Implementation

[0021] 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.

[0022] like Figure 1 As shown, this application proposes a solar cell front panel, including an outer weather-resistant film 100 and an inner supporting base film 200, which are bonded together by an adhesive layer 300. In one specific embodiment, the total thickness of the front panel is approximately 125-240 μm; the thickness of the weather-resistant film 100 is approximately 20-30 μm; the thickness of the supporting base film 200 is approximately 100-200 μm; and the thickness of the adhesive layer 300 is approximately 5-10 μm.

[0023] The main functions of the weather-resistant film 100 on the outermost side of the front panel are reinforcement, weather resistance, UV resistance, moisture protection, low dielectric constant, and high breakdown voltage. Preferably, a PVDF film with a thickness of 20-30μm can be used as the weather-resistant film 100. For example, a commercially available PVDF film with a thickness of 20-30μm can be used, or PVDF raw material particles with a mass content of greater than or equal to 90% can be used, with the addition of ultraviolet absorbers, wear-resistant fillers, etc., and formed by melt co-extrusion and biaxial stretching.

[0024] The support base film 200 is adjacent to the circuit side of the solar panel. In addition to providing stronger support and protection, it also needs to provide stronger barrier properties to protect the internal circuitry.

[0025] The adhesive layer 300 can be made of conventional EVA adhesive or UV-cured adhesive.

[0026] The supporting base film 200 can be made of PET film with a visible light transmittance greater than 85%, and can be a single-layer or multi-layer structure formed by biaxial stretching. PET film provides 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 front panel, typically requiring a barrier property of 10. -3 g / m2 • Day-level. The common approach to enhancing barrier properties is to increase material thickness, which increases material cost, weight per unit area, and reduces flexibility. Excessive thickness also leads to slippage and leakage when the edges of the substrate are bent. Current domestic encapsulation technologies struggle to achieve the required barrier properties. Even in Japan, with its advanced encapsulation technology, flexible solar cells have not yet reached mass production levels, resulting in high costs for commercially available flexible solar cells. Furthermore, their actual lifespan is slightly shorter than that of crystalline silicon solar cells due to limitations in the encapsulation process.

[0027] In view of this, Figure 2 In one specific embodiment of the supporting base film 200 shown, the supporting base film 200 includes a substrate layer 21, and each of the two sides of the substrate layer 21 has an in-line coating layer 22. A barrier layer 23 is sputtered to the outer side of the in-line coating layer 22. The thickness of the substrate layer 21 is preferably 100-200 μm, for example, it can be made of a single-layer 188 μm biaxially oriented PET film, or it can be made of a multilayer film composite (this will be described in further detail below). The barrier layer 23 is preferably made of silicon dioxide; its thickness is 200 nm.

[0028] By setting the barrier layer 23, the barrier properties of the substrate layer 21 can be improved without increasing the thickness of the substrate layer 21, thus improving the adaptability of flexible solar cells. In order to improve the surface smoothness and enhance the adhesion of the barrier layer 23, it is preferable to perform an online coating process on both sides of the substrate layer 21 before sputtering to form the barrier layer 23, forming an online coating layer 22 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 21 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 22 can be applied to the thick sheet before or during the stretching of the polyester film constituting the substrate layer 21. 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 22.

[0031] In one specific embodiment, the online coating layer 22 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 22 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 single-layer 188μm biaxially oriented PET film. Then, a barrier layer composed of silicon dioxide was sputtered onto the outside of the online coating layer.

[0034]

[0035]

[0036] As a comparison, a 200 nm thick barrier layer of silicon dioxide was directly sputtered onto each of the two surfaces of a single 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.

[0037] Furthermore, such as Figure 3 As described above, this application proposes another specific embodiment of a support base film that can be used in the front panel of the solar cell of this application, and... Figure 2 Similar to the illustrated embodiment, the support base film 200 in this embodiment also includes a substrate layer 21. Each of the two surfaces of the substrate layer 21 has an online coating layer 22, and a barrier layer 23 is sputtered onto the outer side of the online coating layer 22. Similar to... Figure 2 The difference between this embodiment and the previous one is that the substrate layer 21 is a multilayer thin film composite structure, while the remaining online coating layer 22 and barrier layer 23 can have the same structure and composition as in the previous embodiment. The following is a detailed description of the substrate layer 21 of the multilayer composite structure in this embodiment.

[0038] like Figure 3-4As shown, the substrate layer 21 of this embodiment includes an inner layer film 1 facing the solar cell (not shown) and an outer layer film 2 away from the solar cell. The inner layer film 1 has a plurality of parallel inner prism structures 3 with equal intervals and isosceles trapezoidal cross sections. A refractive layer 4 is formed on the outside of the inner prism structure 3 by vacuum sputtering. The cavity between the outer layer film 2 and the refractive layer 4 is filled with an outer prism structure 5. The outer layer film 2 and the refractive layer 4 are connected as one unit through the outer prism structure 5.

[0039] The inner film 1 and the outer film 2 can be made of PET with a visible light transmittance greater than 85%. The double-layer PET film can provide excellent insulation, water resistance, mechanical properties, and dimensional stability. Two nested prismatic structures are formed between the inner film 1 and the outer film 2, and the two prismatic structures are separated by a sputtered refractive layer 4, which elongates the channel between the two prismatic structures and enhances water resistance and airtightness.

[0040] In one specific embodiment, the refractive indices of both the inner prism structure 3 and the outer prism structure 5 are lower than that of the refractive layer 4. For example, the refractive layer 4 can be composed of Nb₂O₅ with a refractive index of 2.01–2.48. The outer prism structure 5 can be made of UV-curable acrylic resin, with a preferred refractive index of 1.4–1.6 (a small amount of high-refractive-index microparticles can be added as needed to adjust the overall refractive index, such as 1%–5% lead fluoride nanoparticles). The inner prism structure 3 can be made of the same material as the outer prism structure 5, that is, it can be made of UV-curable acrylic resin, with a preferred refractive index of 1.4–1.6 (again, a small amount of high-refractive-index microparticles can be added as needed to adjust the overall refractive index, such as 1%–5% lead fluoride nanoparticles).

[0041] As mentioned earlier, since flexible solar cells can be integrated into windows, roofs, exterior walls, or interior walls, their orientation is fixed and cannot be adjusted once installed. Therefore, the efficiency of flexible solar cells is greatly affected by the direction of sunlight. Generally speaking, direct sunlight has the highest efficiency, but the duration is very short, and the direction of sunlight is tilted for a large part of the time. In this application, the substrate layer 21 is provided and formed with an inner prism structure and an outer prism structure, with a refractive layer between them. When light shines at an angle on the trapezoidal side of the prism structure, due to the difference in the angle of illumination and refractive index, the light entering the inner prism structure will converge towards the center of the prism structure. This allows the tilt angle of the light to be deflected to a certain extent towards a direction as perpendicular as possible to the solar cell, thereby improving the utilization rate of sunlight. In addition, for flexible solar cells laid on roofs, the prism structure with the stripes pointing north and south is more efficient, which can improve the utilization rate of east and west-facing light in the morning and evening. For flexible solar cells laid on vertical walls, the prism structure with the stripes pointing east and west is more efficient, which can improve the utilization rate of light that shines on the wall at an angle from the top during the strongest midday sunlight.

[0042] Regarding the principle of light-gathering using a prism structure, the inventors drew inspiration from the prism film technology used in backlight panels of liquid crystal displays (LCDs). Since the applicant's field has involved years of research and development in LCDs, the inventors were able to gain inspiration from the vastly different field of LCDs. However, this inspiration should not be considered obvious to those skilled in the art of solar cells, as the two fields differ significantly. For example, in LCDs, light refraction only requires refraction from air into the prism; the refractive index difference between air and the prism is substantial, thus eliminating the need for an additional refractive layer. However, in the solar cell field of this application, issues such as sealing and waterproofing must be considered, making it impossible to contain air in the substrate layer 21. Therefore, when applying a prism structure to solar cells, where there is no significant difference in refractive index between material layers, applying the prism film technology from LCD backlight panels to solar cells cannot directly achieve the light-gathering effect.

[0043] Furthermore, since the substrate layer 21 in the field of solar cells needs to be airtight, in the absence of air, it is necessary to consider using different interface materials to form a single unit, while also taking into account manufacturing costs. While using two prism structures with different refractive indices is feasible, considering light transmittance, it is difficult to find two materials with similar light transmittance but significantly different refractive indices. Moreover, significant differences in processing technology between two materials with significantly different properties can lead to substantial cost drawbacks, and the compatibility with specialized equipment must also be considered, making this impractical in real-world applications.

[0044] Therefore, the two-layer prism structure in this application can be made of materials with the same or similar properties. For example, it can be prepared using UV-cured acrylic resin commonly used in prism films for liquid crystal display backplanes. The processing technology for the two-layer prism structure is the same, and it can be formed using the same UV curing equipment. Moreover, the light transmittance and refractive index of the two layers are the same or similar, making it easy to select materials with a suitable refractive index range to prepare the refractive layer. In addition, it should be emphasized that since solar cells need to maintain a relatively high light transmittance, it is difficult to change the refractive index of the bulk material by adding a high-refractive-index material to the two-layer prism structure. This is because the increased difference between the refractive index of the added high-refractive-index material and the refractive index of the bulk material will cause refractive index mismatch defects, leading to a decrease in the light transmittance of the material.

[0045] In another improved embodiment, the inner prism structure 3 can be made of UV-curable acrylic resin with added UV-excited phosphor, preferably with a refractive index of 1.6-1.7 (a small amount of high-refractive-index microparticles can be added as needed to adjust the overall refractive index, such as 1%-5% lead fluoride nanoparticles). Preferably, the mass percentage of the UV-excited phosphor in the inner prism structure 3 is 3%-5%. In this embodiment, adding an appropriate amount of commercially available UV-excited phosphor can spectrally modulate the UV light focused into the inner prism structure, converting harmful UV light into longer-wavelength visible light, thereby achieving effective UV radiation protection and improved light utilization efficiency.

[0046] It should be noted that commonly used UV-excited phosphors on the market typically emit red light and are generally one or a mixture of silicate, aluminate, nitride, and fluoride phosphor materials. This application preferably uses UV-excited phosphor materials made of fluoride phosphors. The advantage is that the refractive index of fluoride phosphor materials is slightly higher than that of UV-curable acrylic resins. Therefore, with a small addition of 3%-5% (by mass), the light transmittance of the original prism structure prepared by UV-curable acrylic resin can be maintained. If the refractive index of the phosphor material differs significantly from that of the bulk material, the light transmittance in the visible light range will be weakened, which is detrimental to the light conversion of the solar cell. Furthermore, a small amount of high-refractive-index microparticles can be added as needed to adjust the overall refractive index, for example, adding 1%-5% (by mass) of lead fluoride nanoparticles.

[0047] This improved embodiment, by adding ultraviolet-excited phosphor to the inner prism structure 3, can further convert the ultraviolet light in the converged light into long-wavelength visible light usable by the solar panel, based on the light convergence of the prism structure. This can further improve light utilization and reduce the damage of ultraviolet light to the solar panel. Of course, adding ultraviolet-excited phosphor will reduce the overall light transmittance of the substrate layer 21. Therefore, it is not recommended to add ultraviolet-excited phosphor to the outer prism structure 5 as well. Since the ultraviolet-excited phosphor added to the inner prism structure 3 can convert the converged light, it can offset the impact on light transmittance to some extent. Therefore, this improved embodiment is a compromise solution, achieving a higher solar energy utilization rate at a lower cost, while effectively preventing ultraviolet light damage to the solar panel.

[0048] The method for fabricating the front panel of the solar cell of this application will be further described in detail below with reference to the accompanying drawings. As mentioned above, the front panel of the solar cell of this application includes an outer weather-resistant film 100 and an inner supporting base film 200, which are bonded together by an adhesive layer 300. The supporting base film 200 includes a substrate layer 21, and each of the two sides of the substrate layer 21 has an online coating layer 22. A barrier layer 23 is sputtered on the outer side of the online coating layer 22. The substrate layer 21 includes an inner layer film 1 facing the solar cell and an outer layer film 2 away from the solar cell. The inner layer film 1 has a plurality of equally spaced parallel inner prism structures 3 with an isosceles trapezoidal cross section. A refractive layer 4 is formed on the outer side of the inner prism structure 3 by vacuum sputtering. The cavity between the outer layer film 2 and the refractive layer 4 is filled with an outer prism structure 5, and the outer layer film 2 and the refractive layer 4 are connected together by the outer prism structure 5. To save costs and reduce the number of processes, the preparation method of this application uses PET films of the same thickness as the inner film 1 and the outer film 2.

[0049] Furthermore, the preparation method of this application includes a step of preparing a supporting base film 200, and a step of bonding the supporting base film 200 and the weather-resistant film 100. The step of preparing the supporting base film 200 includes:

[0050] First, PET chips are used as the raw material for preparing PET film. A single-layer sheet is obtained through melt extrusion, preheated, and then longitudinally stretched 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 using a coating machine. Then, the film is transversely stretched, shaped, cooled, and wound up, thereby forming an online coating layer 22 on the film surface. A barrier layer 23 composed of silicon dioxide is then sputtered to form on the outer side of the online coating layer 22, thus obtaining an inner layer film 1 and an outer layer film 2 with the online coating layer 22 and the barrier layer 23 for later use. The thickness of the inner layer film 1 and the outer layer film 2 is preferably 40-60 μm, and the visible light transmittance is 85%-95%.

[0051] Then, on the side of the inner film 1 where the online coating layer 22 and the barrier layer 23 are not formed, a plurality of equally spaced parallel inner prism structures 3 with isosceles trapezoidal cross-sections are cured to form. For example, a roller with a pattern matching the shape of the inner prism structure can be used. UV-curable acrylic resin is applied to the roller, and the inner film 1 is pressed and rolled along the roller surface, while the UV-curable acrylic resin is pressed onto the inner film 1 according to the shape of the inner prism structure. Then, the UV-curable acrylic resin is cured by irradiating with UV light, thereby forming the inner prism structure 3 of the desired shape on the inner film 1. The refractive index of the formed inner prism structure 3 is 1.4-1.6. Alternatively, in another embodiment, UV-curable acrylic resin with added UV-excited phosphor can be used to form the inner prism structure 3 using the same process, with a refractive index of 1.6-1.7. The length of the lower base of the isosceles trapezoidal cross section of the formed inner prism structure 3 is 20-30 μm, the lower base angle is 30-60 degrees, the height is 25-50 μm, and the minimum gap between adjacent inner prism structures 3 is 50-100 μm.

[0052] Subsequently, a refractive layer 4 is formed on the inner prism structure 3 by vacuum sputtering. For example, a layer of Nb₂O₅ with a thickness of 0.5-2 μm and a refractive index of 2.01-2.48 can be formed on the inner prism structure 3 by vacuum sputtering. Since the thickness of the formed refractive layer 4 is relatively very thin, Figure 4 The refractive layer 4 is not shown in the image. Figure 3The refractive layer 4 in the image has also been magnified for easier understanding. It should be noted that the refractive layer 4 primarily provides interface refraction, ensuring light transmittance while also providing a certain degree of isolation. Furthermore, because the inner prism structure 3 protrudes from the surface of the inner film 1 during sputtering, the thickness of the refractive layer 4 formed on the surface of the inner prism structure 3 is slightly thicker, while the refractive layer 4 formed on the surface of the inner film 1 located between the inner prism structures 3 is slightly thinner. This refractive layer 4 on the surface of the inner film 1 does not contribute to light convergence; it primarily serves an isolation function, and its 0.5-2 μm thickness does not affect light transmittance.

[0053] Next, UV-curable acrylic resin is filled into the recessed cavity on the outer side of the refractive layer 4. An outer film 2, located away from the solar cell, is then bonded to the outer side of the refractive layer 4 and the filled UV-curable acrylic resin. The side of the outer film 2 without the online coating layer 22 and the barrier layer 23 is bonded to the refractive layer 4. Preferably, while filling the recessed cavity on the outer side of the refractive layer 4 with UV-curable acrylic resin, the resin outside the top of the refractive layer 4 is scraped off with a scraper, making the filled UV-curable acrylic resin flush with the top of the refractive layer 4. This eliminates gaps and ensures a stronger bond between the bonded layers. Because the refractive layer 4 is relatively thin, the thickness of the filled UV-curable acrylic resin is almost equal to the thickness of the inner prism structure 3.

[0054] Then, ultraviolet light is irradiated through one side of the barrier layer 23 of the outer film 2 to cure the filled ultraviolet light curing acrylic resin to form the outer prism structure 5. While the outer prism structure 5 is curing, the outer film 2 and the refractive layer 4 are connected together through the outer prism structure 5 to obtain the support base film 200.

[0055] The bonding steps of the supporting base film 200 and the weather-resistant film 100 include: bonding one side of the outer layer 2 of the supporting base film 200 to the weather-resistant film 100 as a single unit via an adhesive layer 300. The weather-resistant film 100 can be composed of a PVDF film with PVDF as the main component. This PVDF film can be a commercially available PVDF film with a thickness of 20-30 μm, or it can be formed by melt co-extrusion and biaxial stretching of PVDF raw material particles with a mass content of ≥90%, adding ultraviolet absorbers, wear-resistant fillers, etc.

[0056] Examples 6-11

[0057] The substrate layer for the support base film used in the front panel of a solar cell is prepared according to the parameters in the table below.

[0058]

[0059]

[0060] Comparative Examples 12-14

[0061] Comparative Examples 12-14 used a single-layer PET film as the substrate layer, with the following parameters.

[0062] Comparative Example 12 Comparative Example 13 Comparative Example 14 Thickness μm 100 150 200 Visible light transmittance 85％ 90％ 95％

[0063] The parameter performance of each embodiment is compared as follows.

[0064]

[0065]

[0066]

[0067] As can be seen from the performance parameter comparison of the above embodiments, the insulation, light transmittance, mechanical properties, ultraviolet light blocking properties, and dimensional stability of the substrate layer used for the front panel of solar cells in this application are significantly improved, while the ultraviolet light transmittance of the improved example with added phosphor is significantly reduced.

[0068] 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.

[0069] 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 solar cell front sheet comprising an outer weather resistant film (100) and an inner support base film (200) which are bonded together by an adhesive layer (300); characterized in that, The support base film (200) comprises a base material layer (21), both sides of the base material layer (21) are provided with an in-line coating layer (22), and an outer side of the in-line coating layer (22) is provided with a barrier layer (23) formed by sputtering; the base material layer (21) comprises an inner layer film (1) facing one side of the solar cell piece and an outer layer film (2) away from the other side of the solar cell piece, the inner layer film (1) is provided with a plurality of inner layer prism structures (3) in equal intervals and parallel arrangement, the cross section of the inner layer prism structure (3) is isosceles trapezoidal, an outer side of the inner layer prism structure (3) is provided with a refractive layer (4) formed by vacuum sputtering, the outer layer film (2) and the refractive layer (4) are connected into an integrated whole through the outer layer prism structure (5) filled in a recessed cavity between the outer layer film (2) and the refractive layer (4); the refractive index of the inner layer prism structure (3) and the outer layer prism structure (5) is less than the refractive index of the refractive layer (4).

2. The front sheet of claim 1, wherein, The refractive layer (4) is composed of Nb2O5 with a refractive index of 2.01-2.

48.

3. The front sheet of claim 1, wherein The barrier layer (23) is composed of silicon dioxide; the thickness is 200 nm.

4. The front sheet of claim 1, wherein, The in-line coating layer (22) is formed by uniformly mixing acrylic resin, silicon dioxide nanoparticles with a particle size of 5-10 nm, 1,4-dioxane, polyethylene oxide and ethylene-vinyl acetate copolymer into a primer liquid and then forming by in-line coating and curing; the mass ratio of each component of the in-line coating layer (22) is that the acrylic resin: the silicon dioxide nanoparticles: the 1,4-dioxane: the polyethylene oxide: the ethylene-vinyl acetate copolymer is 100: (10-15): (20-30): (10-15): (5-10).

5. The front sheet of claim 1, wherein, The length of the lower base of the isosceles trapezoidal cross section of the inner layer prism structure (3) is 20-30 μm, the lower base angle is 30-60 degrees, the height is 25-50 μm, and the minimum gap between adjacent inner layer prism structures (3) is 50-100 μm.

6. The front sheet of claim 1, wherein, The inner layer film (1) and the outer layer film (2) are made of PET with a visible light transmittance of more than 85% and the same thickness.

7. A method of producing a solar cell front sheet as claimed in any one of claims 1 to 6, comprising a step of producing a support base film (200), and a step of bonding the support base film (200) and the weather-resistant film (100); wherein, The preparation steps of the support base film (200) comprise: PET chips are used as raw materials for preparing PET films, a single-layer thick sheet is obtained by melt extrusion, the film is stretched longitudinally after preheating, each component of the in-line coating layer is coated on one side of the film by an in-line coating machine, then the film is stretched transversely, and the in-line coating layer (22) is formed on the surface of the film after shaping, cooling and winding; then a barrier layer (23) composed of silicon dioxide is formed on the outer side of the in-line coating layer (22) by sputtering, thereby obtaining the inner layer film (1) and the outer layer film (2) with the in-line coating layer (22) and the barrier layer (23) for standby use; A plurality of inner layer prism structures (3) in equal intervals and parallel arrangement with isosceles trapezoidal cross sections are formed on the side of the inner layer film (1) without the in-line coating layer (22) and the barrier layer (23); A refractive layer (4) is formed on the inner layer prism structure (3) by vacuum sputtering; The recessed cavity outside the refractive layer (4) is filled with ultraviolet light curing acrylic resin, and a layer of outer film (2) is attached to the outside of the refractive layer (4) and the filled ultraviolet light curing acrylic resin, away from the side of the solar cell piece; wherein the outer film (2) is not formed in the side of the line coating layer (22) and the barrier layer (23) to be attached to the refractive layer (4); The filled ultraviolet light curing acrylic resin is cured to form an outer layer prism structure (5) by irradiating ultraviolet light through the side of the barrier layer (23) of the outer film (2), and at the same time, the outer layer prism structure (5) is cured, the outer film (2) and the refractive layer (4) are connected as a whole through the outer layer prism structure (5), thereby obtaining the prepared base film (200).

8. The method of claim 7, wherein, The adhesion step of supporting the base film (200) and the weather-resistant film (100) includes: one side of the outer film (2) of the supporting base film (200) is adhered to the weather-resistant film (100) through the adhesive layer (300), wherein the weather-resistant film (100) is composed of a PVDF film with PVDF as the main body.

9. The method of claim 7, wherein, The thickness of the weather-resistant film (100) is 20-30 μm.

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