Photovoltaic encapsulation film, its preparation method and photovoltaic module

Abstract

This application relates to the technical field of encapsulation materials for photovoltaic modules, and particularly relates to a photovoltaic encapsulation film, a preparation method thereof, and a photovoltaic module. The photovoltaic encapsulation film comprises a water-blocking layer film, a water-absorbing layer film, and an EVA layer film which are sequentially stacked; the water-blocking layer film comprises the following raw materials: EVA resin, crosslinking agent, first co-crosslinking agent, coupling agent, light stabilizer, and modified acid-resistant agent; the water-absorbing layer film comprises the following raw materials: ion adsorbent, hydrophilic auxiliary agent, and second co-crosslinking agent; the EVA layer film comprises the following raw materials: EVA resin, crosslinking agent, first co-crosslinking agent, coupling agent, and light stabilizer. In this application, the ion adsorbent can adsorb sodium ions to improve the anti-PID effect, and the hydrophilic auxiliary agent highly absorbs water to reduce the influence of water vapor on the battery chip and also provides an environment for the ion adsorbent to adsorb ions; the modified acid-resistant agent in the water-blocking layer film has a good dispersion effect in the EVA resin, thereby improving the acid resistance effect.

Description

Technical Field

[0001] The present application relates to the technical field of encapsulation materials for photovoltaic modules, and particularly to a photovoltaic encapsulation film, a preparation method thereof, and a photovoltaic module. Background Art

[0002] Photovoltaic modules are the main equipment for solar photovoltaic power generation. When sunlight shines on the photovoltaic module, it will generate current and output the current through relevant equipment. Structurally, it includes a tempered glass panel, an EVA (ethylene-vinyl acetate copolymer) film, a crystalline silicon cell, an EVA film, and a backsheet (TPT board) in sequence. With the continuous development of photovoltaic module technology and some problems found in use, that is, there is a risk of potential potential-induced degradation (PID) of photovoltaic modules under negative bias, that is, in a humid environment, due to the current leakage caused by voltage differences, which in turn causes the performance of the module to decline.

[0003] The PID phenomenon of photovoltaic modules is, on the one hand, restricted by the migration of Na + ions in the module glass and film to the cell, which damages the anti-reflection layer / passivation layer. Moreover, when in an acidic or high-humidity environment, the migration of Na + ions will be accelerated; on the other hand, it is restricted by the corrosion of the free acetic acid generated by the hydrolysis of the EVA film on the cell paste. Generally, an ion scavenger is added to improve the problem of Na + ion migration; a modified anti-acid agent is added to neutralize acetic acid and reduce the corrosion of the acidic medium on the paste.

[0004] However, the adsorption effect of the ion scavenger has a great relationship with its dispersion, concentration, and water vapor. In a humid and hot environment of the cell, the migration rate of Na + ions will be accelerated, making it difficult for the ion scavenger to fully achieve the effect of adsorbing ions. And there is also a dispersion problem of the inorganic anti-acid agent in the EVA film, which is easy to agglomerate, resulting in a poor anti-acid effect, thus affecting the long-term stability of the cell.

[0005] It should be noted that the above content is not necessarily prior art and does not limit the scope of patent protection of the present application. Summary of the Invention

[0006] The embodiments of the present application provide a photovoltaic encapsulation film, a preparation method thereof, and a photovoltaic module to solve or alleviate one or more of the above technical problems.

[0007] In a first aspect, the embodiments of the present application provide a photovoltaic encapsulation film, including a water-blocking layer film, a water-absorbing layer film, and an EVA layer film that are sequentially stacked;

[0008] The water-blocking layer film comprises the following raw materials in parts by weight: 90-100 parts of EVA resin, 0.4-0.8 parts of crosslinking agent, 0.6-1.0 parts of first co-crosslinking agent, 0.1-0.5 parts of coupling agent, 0.01-0.15 parts of light stabilizer, and 0.1-0.3 parts of modified anti-acid agent;

[0009] The water-absorbing layer film comprises the following raw materials in parts by weight: 5-20 parts of ion adsorbent, 25-50 parts of hydrophilic auxiliary agent, and 30-40 parts of second co-crosslinking agent;

[0010] The EVA layer film comprises the following raw materials in parts by weight: 90-100 parts of EVA resin, 0.4-0.8 parts of crosslinking agent, 0.6-1.0 parts of first co-crosslinking agent, 0.1-0.5 parts of coupling agent, and 0.01-0.15 parts of light stabilizer.

[0011] Optionally, the hydrophilic auxiliary agent includes one of hydrophilic monomers and hydrophilic polymers.

[0012] Optionally, the hydrophilic monomer includes one or more of 2-hydroxyethyl methacrylate, 1-vinyl-2-pyrrolidone NVP, dimethylaminoethyl methacrylate, and polyvinylpyrrolidone.

[0013] Optionally, the hydrophilic auxiliary agent includes a hydrophilic polymer obtained by polymerizing one or more of 2-hydroxyethyl methacrylate, 1-vinyl-2-pyrrolidone NVP, dimethylaminoethyl methacrylate, and polyvinylpyrrolidone;

[0014] The number-average molecular weight of the hydrophilic polymer is 2000-10000.

[0015] Optionally, the carbodiimide coupling agent is obtained by the catalytic action of an isocyanate coupling agent under an organophosphorus catalyst.

[0016] Optionally, the ion adsorbent includes one or both of silicon dioxide and zirconium phosphate.

[0017] Optionally, the modified anti-acid agent includes one or both of modified magnesium hydroxide or modified magnesium oxide;

[0018] Among them, the modified magnesium hydroxide is magnesium hydroxide modified by a carbodiimide coupling agent; the modified magnesium oxide is magnesium oxide modified by a carbodiimide coupling agent.

[0019] Optionally, the crosslinking agent includes one or both of tert-butyl peroxy-2-ethylhexyl carbonate TAEC and tert-butyl peroxy-2-ethylhexyl carbonate TBEC.

[0020] Optionally, the first co-crosslinking agent includes one or more of TAIC, dipropylene glycol diacrylate, propoxylated glycerol triacrylate, pentaerythritol triacrylate, ethoxylated trimethylolpropane triacrylate, 1,6-hexanediol diacrylate, and pentaerythritol tetraacrylate.

[0021] Optionally, the coupling agent includes one or more of 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, and vinyltriethoxysilane.

[0022] Optionally, the second co-crosslinking agent includes one or more of ethoxylated trimethylolpropane triacrylate, polyethylene glycol diacrylate, dipropylene glycol diacrylate, propoxylated glycerol triacrylate, pentaerythritol triacrylate, ethoxylated trimethylolpropane triacrylate, 1,6-hexanediol diacrylate, and pentaerythritol tetraacrylate, etc.

[0023] Optionally, the thickness ratio of the water-blocking layer film, the water-absorbing layer film, and the EVA layer film is (10~15):(1~2):(30~35).

[0024] In a second aspect, an embodiment of the present application provides a method for preparing a photovoltaic encapsulation film, including the following steps:

[0025] By weight, 90~100 parts of EVA resin are added to a mixing tank, and then 0.4~0.8 parts of a crosslinking agent, 0.6~1.0 parts of a first co-crosslinking agent, 0.1~0.5 parts of a coupling agent, and 0.01~0.15 parts of a light stabilizer are mixed evenly and added to the mixing tank. After heat preservation treatment, 0.1~0.3 parts of a modified acid-resistant agent are added, and after standing, it is extruded to obtain a water-blocking layer film;

[0026] By weight, 25~50 parts of a hydrophilic auxiliary agent and 30~40 parts of a second co-crosslinking agent are mixed evenly to obtain a mixed solution. Then, 5~20 parts of an ion adsorbent are added to the mixed solution and stirred. After adjusting the viscosity, a pre-water-absorbing layer film is obtained. Then, the pre-water-absorbing layer film is roll-coated on the surface of the water-blocking layer film and cured to obtain a water-absorbing layer film;

[0027] By weight, 90~100 parts of EVA resin are added to a mixing tank, and then 0.4~0.8 parts of a crosslinking agent, 0.6~1.0 parts of a first co-crosslinking agent, 0.1~0.5 parts of a coupling agent, and 0.01~0.15 parts of a light stabilizer are mixed evenly and added to the mixing tank. After heat preservation treatment, it is extruded to obtain an EVA layer film;

[0028] The EVA layer film is placed on the surface of the water-absorbing layer film and compounded through an embossing roller to obtain a photovoltaic encapsulation film.

[0029] Optionally, the curing treatment includes one of EB irradiation, UV curing, or thermal curing.

[0030] In a third aspect, an embodiment of the present application provides a photovoltaic module, which includes:

[0031] Solar cells;

[0032] The photovoltaic encapsulation film as described above, or the photovoltaic encapsulation film prepared by the method as described above;

[0033] The photovoltaic encapsulation film is used to encapsulate the solar cells.

[0034] The embodiments of the present application adopting the above technical solutions may include the following advantages:

[0035] When Na + ions migrate, the ion adsorbent in the water-absorbing layer film can adsorb Na + ions, improving the anti-PID effect. The hydrophilic assistant can highly absorb water, reducing the impact of water vapor on the solar cells. At the same time, it also provides an environment for the ion adsorbent to adsorb ions, effectively reducing the performance degradation of the solar cells. In addition, the modified anti-acid agent in the water-blocking layer film has a good dispersion effect in the EVA resin and is not prone to agglomeration, thereby improving the anti-acid effect. The combined action of the water-absorbing layer film and the water-blocking layer film effectively maintains the long-term stability and photoelectric conversion efficiency of the solar cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In the drawings, unless otherwise specified, the same reference numerals throughout the several views denote the same or similar parts or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings only depict some embodiments disclosed in the present application and should not be regarded as limiting the scope of the present application.

[0037] Figure 1 is a schematic structural diagram of the photovoltaic encapsulation film provided by the embodiment of the present application.

[0038] Figure 2 is a schematic diagram of the sea-island structure of the water-absorbing layer film provided by the embodiment of the present application.

[0039] Figure 3 is a corrosion-resistant EL diagram of the photovoltaic encapsulation film provided by Embodiment 1 of the present application.

[0040] Figure 4 is a corrosion-resistant EL diagram of the photovoltaic encapsulation film provided by Comparative Example 1 of the present application.

[0041] Figure 5 is a PID test EL diagram of the photovoltaic encapsulation film provided by Embodiment 1 of the present application.

[0042] Figure 6 It is the EL diagram of the PID test of the photovoltaic encapsulation film provided in Embodiment 2 of the present application.

[0043] Figure 7 It is the EL diagram of the PID test of the photovoltaic encapsulation film provided in Embodiment 3 of the present application.

[0044] Figure 8 It is the EL diagram of the PID test of the photovoltaic encapsulation film provided in Embodiment 4 of the present application.

[0045] Figure 9 It is the EL diagram of the PID test of the photovoltaic encapsulation film provided in Embodiment 5 of the present application.

[0046] Figure 10 It is the EL diagram of the PID test of the photovoltaic encapsulation film provided in Embodiment 6 of the present application.

[0047] Figure 11 It is the EL diagram of the PID test of the photovoltaic encapsulation film provided in Embodiment 7 of the present application.

[0048] Figure 12 It is the EL diagram of the PID test of the photovoltaic encapsulation film provided in Comparative Example 1 of the present application.

[0049] Figure 13 It is the EL diagram of the PID test of the photovoltaic encapsulation film provided in Comparative Example 2 of the present application.

[0050] Figure 14 It is the EL diagram of the PID test of the photovoltaic encapsulation film provided in Comparative Example 3 of the present application.

[0051] Figure 15 It is the EL diagram of the PID test of the photovoltaic encapsulation film provided in Comparative Example 4 of the present application.

[0052] Explanation of reference numerals:

[0053] 1. Water-blocking layer film; 2. Water-absorbing layer film; 3. EVA layer film; 4. Ion adsorbent; 5. Hydrophilic auxiliary agent. Detailed Description of the Embodiment

[0054] The embodiments of the present application will be described in detail below. The examples of the embodiments are shown in the accompanying drawings. In the drawings, for clarity, the dimensions of layers, regions, and elements, as well as their relative dimensions, may be exaggerated. Where the same or similar reference numerals throughout indicate the same or similar elements or elements having the same or similar functions. The embodiments described below by referring to the accompanying drawings are exemplary and are only used to explain the present application and should not be construed as a limitation of the present application. It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments may be combined with each other.

[0055] It should be understood that when an element or layer is referred to as "on", "adjacent to", "connected to", or "coupled to" another element or layer, it can be directly on, adjacent to, connected, or coupled to the other element or layer, or there may be intervening elements or layers. In contrast, when an element is referred to as "directly on", "directly adjacent to", "directly connected to", or "directly coupled to" another element or layer, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers, and / or parts, these elements, components, regions, layers, and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, or part from another element, component, region, layer, or part. Thus, without departing from the teachings of the present disclosure, the first element, component, region, layer, or part discussed below may be referred to as the second element, component, region, layer, or part. And when discussing the second element, component, region, layer, or part, it does not mean that there must be a first element, component, region, layer, or part in the present application disclosure.

[0056] In this application, unless otherwise clearly specified and defined, the terms "install", "connect", "join", "fix", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements or the interaction relationship between two elements, unless otherwise clearly defined. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0057] It should be noted that the terms "first", "second", etc. in the specification, claims, and above-mentioned drawings of this application are used to distinguish similar objects, and do not necessarily have to be used to describe a specific order or sequence. It should be understood that such terms can be interchanged under appropriate circumstances so that the embodiments of this application described here can be implemented in an order other than those illustrated or described here. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products, or devices.

[0058] In this application, when it comes to numerical intervals (i.e., numerical ranges), unless otherwise specified, the distribution of the selectable numerical values within the numerical interval is considered continuous, and includes the two numerical endpoints (i.e., the minimum value and the maximum value) of the numerical interval, as well as each numerical value between these two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to the integers within the numerical interval, it includes the two endpoint integers of the numerical range, as well as each integer between the two endpoints, which is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be combined. In other words, unless otherwise specified, the numerical ranges disclosed in this application should be understood to include any and all sub-ranges subsumed therein. The "numerical value" in this numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. The "numerical interval" allows for a broad inclusion of quantitative intervals such as percentage intervals, ratio intervals, ratio value intervals, etc.

[0059] The following provides the term explanations of this application.

[0060] TAEC: tert-butyl peroxy-2-ethylhexyl carbonate;

[0061] TBEC: tert-butyl peroxy-2-ethylhexyl carbonate;

[0062] GPTA: glycerol triacrylate propoxylate;

[0063] TAIC: triallyl isocyanurate;

[0064] Light stabilizer 770: bis(2,2,6,6-tetramethylpiperidin-4-yl) sebacate;

[0065] Light stabilizer 292: bis(1,2,2,6,6-pentamethylpiperidin-4-yl) sebacate;

[0066] EB: electron beam irradiation.

[0067] Next, exemplary embodiments according to this application will be described in more detail with reference to the accompanying drawings. It should be noted that these exemplary embodiments can be implemented in many different forms and should not be construed as being limited only to the embodiments set forth herein.

[0068] An embodiment of the present application provides a photovoltaic encapsulation film. The photovoltaic encapsulation film may include a water-blocking layer film, a water-absorbing layer film, and an EVA layer film that are sequentially stacked; the water-blocking layer film includes the following raw materials in parts by weight: 90-100 parts of EVA resin, 0.4-0.8 parts of crosslinking agent, 0.6-1.0 parts of first co-crosslinking agent, 0.1-0.5 parts of coupling agent, 0.01-0.15 parts of light stabilizer, and 0.1-0.3 parts of modified acid-resistant agent; the water-absorbing layer film includes the following raw materials in parts by weight: 5-20 parts of ion adsorbent, 25-50 parts of hydrophilic auxiliary agent, and 30-40 parts of second co-crosslinking agent; the EVA layer film includes the following raw materials in parts by weight: 90-100 parts of EVA resin, 0.4-0.8 parts of crosslinking agent, 0.6-1.0 parts of first co-crosslinking agent, 0.1-0.5 parts of coupling agent, and 0.01-0.15 parts of light stabilizer.

[0069] In the embodiment of the present application, as Figure 2 shown, the water-absorbing layer film all forms a sea-island structure, wherein, the island component in the water-absorbing layer film is the ion adsorbent 4, and the sea component is the hydrophilic auxiliary agent 5. The water-blocking layer film contacts the battery chip, and the EVA layer film contacts the glass. When Na + ions migrate towards the battery chip under the action of an electric field, the island component which is the ion adsorbent can adsorb Na + ions, improving the anti-PID effect, while the sea component which is the hydrophilic auxiliary agent can highly absorb water, reducing the influence of water vapor on the battery chip. At the same time, it also provides an environment for the ion adsorbent to adsorb ions, effectively reducing the performance degradation of the battery chip; in addition, the modified acid-resistant agent in the water-blocking layer film can improve its dispersion effect in the EVA film, reduce agglomeration, and thus improve the acid-resistant effect; the water-absorbing layer film and the water-blocking layer film work together to effectively maintain the long-term stability and efficiency of the battery chip.

[0070] It should be noted that Na + ions generally come from the glass and the EVA film. Especially in a humid and hot environment, Na + ions will migrate into the battery chip through the action of an electric field, thereby damaging the antireflection layer and the passivation layer, and reducing the battery efficiency and stability. In the embodiment of the present application, the water-absorbing layer film is between the EVA layer film and the water-blocking layer film, which can effectively absorb water and provide an environment for the ion adsorbent to capture Na + ions, reducing the influence of Na + ions on the battery chip, and also blocking the influence of water vapor on the battery chip.

[0071] In some embodiments, the light stabilizer includes one or both of light stabilizer 292 and light stabilizer 770.

[0072] In the embodiments of the present application, the light stabilizer can absorb ultraviolet rays, reduce the damage of ultraviolet rays to the EVA resin, and also inhibit the generation of free radicals, thereby reducing the oxidation and degradation rate of the EVA resin; in addition, it also improves the weather resistance of the resin, maintains the mechanical properties and appearance of the resin, and reduces the phenomena of yellow edges and embrittlement.

[0073] In an alternative embodiment, the hydrophilic aid includes one of a hydrophilic monomer and a hydrophilic polymer.

[0074] In the embodiments of the present application, one of the hydrophilic monomer and the hydrophilic polymer, as a hydrophilic aid in the water-absorbing layer film, absorbs water vapor and blocks the influence of water vapor on the battery cell. At the same time, by absorbing water vapor, it provides an environment for the ion adsorbent to capture Na + ions; while selecting a mixture of the two hydrophilic monomer and hydrophilic polymer as the hydrophilic aid, the two can act synergistically with each other, which can enhance the water absorption effect and enable the film to maintain better performance in a humid environment.

[0075] In an alternative embodiment, the hydrophilic monomer includes one or more of 2-hydroxyethyl methacrylate, 1-vinyl-2-pyrrolidone NVP, dimethylaminoethyl methacrylate, and polyvinylpyrrolidone.

[0076] In the embodiments of the present application, the above-mentioned hydrophilic monomers can interact with water molecules through hydrogen bonds in the water-absorbing layer film to form a hydration layer and adsorb water, thereby effectively blocking the influence of water vapor on the battery cell.

[0077] In an alternative embodiment, the hydrophilic aid includes a hydrophilic polymer obtained by polymerizing one or two of 2-hydroxyethyl methacrylate, 1-vinyl-2-pyrrolidone NVP, dimethylaminoethyl methacrylate, and polyvinylpyrrolidone; the number-average molecular weight of the hydrophilic polymer is 2000 to 10000.

[0078] In the embodiments of the present application, when the number-average molecular weight is lower than 2000, the hydrophilic polymer will be too short to form a stable three-dimensional network; when the number-average molecular weight is higher than 10000, the hydrophilic polymer will have poor fluidity, restricting the entry of water. Therefore, the hydrophilic polymer with a number-average molecular weight in the range of 2000 to 10000 enables the hydrophilic polymer to form a three-dimensional network structure when absorbing water, better capture and retain water, form a hydration layer, and block the influence of water vapor on the battery cell. Moreover, the hydrophilic polymer interacts with water molecules to form a larger hydrophilic surface area, further improving the overall water absorption performance.

[0079] In an alternative embodiment, the ion adsorbent includes one or two of silica and zirconium phosphate. Further, the particle size of the silica is 10 nm to 10 μm.

[0080] In the embodiments of the present application, the surface of silica contains hydroxyl groups, which can adsorb sodium ions through electrostatic attraction; and silica is porous, providing a large specific surface area, enabling sodium ions to effectively enter and be captured. The structure of zirconium phosphate contains phosphate groups (PO4³⁻), which can bind to sodium ions through ion exchange; zirconium phosphate also has good complexing ability and can form stable complexes with sodium ions, enhancing its capture effect. Further, the particle size of silica is 10 nm to 10 μm. The smaller particle size of silica can provide a larger specific surface area, increasing the contact opportunity with sodium ions and helping to improve the adsorption efficiency. In addition, the smaller particle size of silica has a more abundant pore structure, enabling sodium ions to more easily enter its interior and enhancing the capture ability. When the particle size of silica is greater than 10 μm, the fluidity of silica is poor and it is difficult to disperse uniformly, thus reducing the capture efficiency of sodium ions.

[0081] In an alternative embodiment, the modified antacid includes one or both of modified magnesium hydroxide or modified magnesium oxide; wherein, the modified magnesium hydroxide is magnesium hydroxide modified by a carbodiimide coupling agent; the modified magnesium oxide is magnesium oxide modified by a carbodiimide coupling agent. Further, the particle size of magnesium dioxide is 50 nm to 5 μm, and the coating rate of the modified magnesium dioxide is 5% to 20%.

[0082] In the embodiments of the present application, the surface of magnesium hydroxide or magnesium oxide is modified by a carbodiimide coupling agent, which can reduce the agglomeration of magnesium hydroxide or magnesium oxide, improve its dispersion performance, and at the same time reduce the dosage of magnesium hydroxide or magnesium oxide, reducing the impact of magnesium hydroxide or magnesium oxide on the light transmittance of the glue film. The carbodiimide coupling agent has a highly unsaturated structure, which can not only react with the moisture infiltrated in the humid and hot environment to generate urea, reducing the water vapor permeation, but also easily react with the carboxylic acid generated by the hydrolysis of EVA to generate stable acylurea, thereby improving the hydrolysis stability of the EVA resin and maintaining the long-term stability of the battery chip in the humid and hot environment.

[0083] In an optional embodiment, the carbodiimide coupling agent is obtained by an isocyanate coupling agent under the catalysis of an organic phosphorus catalyst, and the isocyanate coupling agent includes 3-isocyanate propyl triethoxysilane and 3-isocyanate propyl trimethoxysilane. The ratio of the amount of the reactants of 3-isocyanate propyl triethoxysilane and 3-isocyanate propyl trimethoxysilane is 1:1, and the carbodiimide coupling agent is obtained by catalysis of an organic phosphorus catalyst under a temperature of 100°C. The ratio of the amount of the reactants of 3-isocyanate propyl triethoxysilane and 3-isocyanate propyl trimethoxysilane is 1:1, which can balance the reaction rates of the two isocyanate groups while maintaining the stability of the two during the reaction process, so that the preparation of the carbodiimide coupling agent has a higher conversion efficiency. Isocyanate coupling agent is used as raw material, and isocyanate coupling agent is both a coupling agent and a water barrier agent. On the one hand, it can play the role of a coupling agent to treat the surface of magnesium hydroxide or magnesium oxide, and on the other hand, it can react with acid and water to reduce water vapor transmission.

[0084] In an optional embodiment, the cross-linking agent includes one or both of tert-butyl peroxy-2-ethylhexanoate (TAEC) and tert-butyl peroxy-2-ethylhexyl carbonate (TBEC).

[0085] In the embodiments of the present application, the cross-linking agent can enhance the heat resistance of the film, making it less likely to deform or degrade in a high temperature environment, thereby improving its thermal stability; the cross-linking agent can form a network structure between the polymers through cross-linking, thereby enhancing the strength and toughness of the film, and improving its tear and compression resistance. The cross-linking agent can also improve the corrosion resistance of the water-blocking layer film and the EVA layer film. In addition, the cross-linking agent can improve the physical properties of the water-blocking layer film and the EVA layer film, such as improving transparency, reducing gas permeability, etc., thereby improving its performance in photovoltaic module packaging.

[0086] In an optional embodiment, the first auxiliary cross-linking agent includes one or more of TAIC, tripropylene glycol diacrylate, propoxylated glycerol triacrylate, pentaerythritol triacrylate, ethoxylated trimethylolpropane triacrylate, 1,6-hexanediol diacrylate and pentaerythritol tetraacrylate.

[0087] In the embodiment of the present application, the first co-crosslinking agent is added to the water-blocking layer film, which can improve the crosslinking degree of the water-blocking layer film, improve the overall strength and durability of the water-blocking layer, and also improve the water resistance, thermal stability, corrosion resistance and mechanical properties of the water-blocking layer film.

[0088] In an optional embodiment, the coupling agent includes one or more of 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane and vinyltriethoxysilane.

[0089] In the embodiments of the present application, the above coupling agent can improve the compatibility between the EVA resin and other additives, and can improve the water penetration resistance of the EVA film, reducing the influence of moisture on the film properties. In addition, the coupling agent added to the water barrier film and the EVA layer film can also form covalent bonds with the EVA matrix, enhancing the adhesion of the film to the substrate (such as glass, metal, etc.) and improving the interfacial bonding strength.

[0090] In an alternative embodiment, the second co-crosslinking agent includes one or more of ethoxylated trimethylolpropane triacrylate, polyethylene glycol diacrylate, dipropylene glycol diacrylate, propoxylated glycerol triacrylate, pentaerythritol triacrylate, ethoxylated trimethylolpropane triacrylate, 1,6-hexanediol diacrylate, and pentaerythritol tetraacrylate, etc.

[0091] In the embodiments of the present application, the second co-crosslinking agent chemically crosslinks with the hydrophilic additive to form a more stable three-dimensional network structure, effectively improving the hydrolysis resistance and anti-aging performance of the water absorption layer film, and extending the service life of the photovoltaic module. The second co-crosslinking agent increases the crosslinking density of the water absorption layer film, thereby enhancing the mechanical properties and stability of the water absorption layer film, ensuring that the water absorption layer film will not undergo excessive swelling or degradation due to water vapor or environmental stress during use. In addition, the second co-crosslinking agent can also improve the thermal stability and heat resistance of the water absorption layer film, ensuring that the photovoltaic encapsulation film can still effectively block water vapor, maintain structural integrity, and provide an environment for ion adsorption under high-temperature conditions, thereby enhancing the protection performance of the entire photovoltaic encapsulation film.

[0092] In an alternative embodiment, the thickness ratio of the water barrier film, the water absorption layer film, and the EVA layer film is (10~15):(1~2):(30~35). For example, the thickness ratio of the water barrier film, the water absorption layer film, and the EVA layer film is 10:1:30 and 15:2:35.

[0093] The embodiments of the present application can also provide a method for preparing a photovoltaic encapsulation film,

[0094] The preparation method includes the following steps:

[0095] By weight, 90~100 parts of EVA resin are added to a mixing tank, and then 0.4~0.8 parts of crosslinking agent, 0.6~1.0 parts of the first co-crosslinking agent, 0.1~0.5 parts of coupling agent, and 0.01~0.15 parts of light stabilizer are mixed evenly and added to the mixing tank. After heat preservation treatment, 0.1~0.3 parts of modified anti-acid agent are added, and after standing, it is extruded to obtain the water barrier film;

[0096] By weight, 25 to 50 parts of a hydrophilic auxiliary agent and 30 to 40 parts of a second co-crosslinking agent are mixed evenly to obtain a mixed solution. Then, 5 to 20 parts of an ion adsorbent are added to the mixed solution and stirred. After adjusting the viscosity, a pre-absorbent layer film is obtained. The pre-absorbent layer film is then roll-coated on the surface of the water-blocking layer film, and after curing treatment, an absorbent layer film is obtained;

[0097] By weight, 90 to 100 parts of an EVA resin are added to a mixing tank. Then, 0.4 to 0.8 parts of a crosslinking agent, 0.6 to 1.0 parts of a first co-crosslinking agent, 0.1 to 0.5 parts of a coupling agent, and 0.01 to 0.15 parts of a light stabilizer are mixed evenly and added to the mixing tank. After heating and heat preservation treatment and standing, it is extruded to obtain an EVA layer film;

[0098] The EVA layer film is placed on the surface of the absorbent layer film, and a photovoltaic encapsulation film is obtained by compounding with an embossing roller.

[0099] In an alternative embodiment, the curing treatment includes one of EB irradiation, UV curing, or thermal curing.

[0100] In the embodiment of the present application, after the pre-absorbent layer film is treated by the above curing method, it can further attract Na+ ions to reduce the migration rate and provide an adsorption environment for the ion adsorbent. Moreover, during the preparation of the absorbent layer film, the ion adsorbent is added to the hydrophilic auxiliary agent, and the hydrophilic auxiliary agent can fully wet and disperse the ion adsorbent, improving the problem of uneven dispersion of the ion adsorbent, and thus improving the adsorption effect of the ion adsorbent on Na + ions.

[0101] The following specific examples further illustrate the present application in detail, but should not be construed as a limitation of the present application. Without departing from the spirit and essence of the present application, any modification or replacement of the methods, steps, or conditions of the present application belongs to the scope of the present application.

[0102]

Example 1

[0103] As Figure 1 shown, a specific structure of a photovoltaic encapsulation film includes a water-blocking layer film 1, an absorbent layer film 2, and an EVA layer film 3 stacked in sequence, wherein the water-blocking layer film 1 contacts the battery cell, and the EVA layer film 3 contacts the glass.

[0104] A specific preparation process of a photovoltaic encapsulation film includes the following steps:

[0105] S1: By weight, 98 parts of EVA resin are added to a mixing tank, and then 0.6 part of crosslinking agent tert-butyl peroxy-2-ethylhexyl carbonate (TAEC), 0.4 part of the first co-crosslinking agent TAIC, 0.4 part of the first co-crosslinking agent ethoxylated trimethylolpropane triacrylate, 0.3 part of coupling agent 3-methacryloxypropyltriethoxysilane, and 0.1 part of light stabilizer 770 are mixed evenly to form a liquid additive. Then the liquid additive is sprayed onto the EVA resin particles, and then heated and insulated at a temperature of 50°C for 2 hours for absorption. After that, 0.2 part of modified anti-acid agent is added and mixed for 2 hours. Finally, the temperature of the discharging module is set to 75°C and the temperature of the die orifice is set to 95°C for casting, and a water-blocking layer film is extruded; wherein, the modified anti-acid agent is modified magnesium oxide, and the modified magnesium oxide is magnesium oxide coated with carbodiimide coupling agent (the particle size of magnesium oxide is 0.5 μm, the coating rate is 5%, and the granulation concentration is 5%); the carbodiimide coupling agent is prepared by catalyzing isocyanate coupling agent (3-isocyanatopropyltriethoxysilane and 3-isocyanatopropyltrimethoxysilane) at a temperature of 100°C through an organophosphorus catalyst.

[0106] S2: By weight, 20 parts of ion adsorbent silica (particle size of 50 nm) are added to 50 parts of hydrophilic additive, and then 30 parts of the second co-crosslinking agent pentaerythritol tetraacrylate are added to obtain a pre-absorbent layer film with a viscosity of 1500 mPa·s. The pre-absorbent layer film is applied to the surface of the water-blocking layer film by a doctor blade method, and the pre-absorbent layer film is cured by EB electron beam irradiation (irradiation voltage is 0.2 eV, irradiation penetration depth, irradiation dose is 40 kGy) to obtain an absorbent layer film; wherein, the hydrophilic additive includes 25 parts of 2-hydroxyethyl methacrylate and 25 parts of 1-vinyl-2-pyrrolidone (NVP).

[0107] S3: By weight, 98 parts of EVA resin are added to a mixing tank, and then 0.6 part of crosslinking agent tert-butyl peroxy-2-ethylhexyl carbonate (TAEC), 0.4 part of the first co-crosslinking agent TAIC, 0.4 part of the first co-crosslinking agent ethoxylated trimethylolpropane triacrylate, 0.3 part of coupling agent 3-methacryloxypropyltriethoxysilane, and 0.1 part of light stabilizer 770 are mixed evenly to form a liquid additive. Then the liquid additive is sprayed onto the EVA resin particles, and then heated and insulated at a temperature of 50°C for 4 hours for absorption and then left standing. Finally, the temperature of the discharging module is set to 75°C and the temperature of the die orifice is set to 95°C for casting, and an EVA layer film is extruded.

[0108] S4: The EVA layer film is placed on the surface of the absorbent layer film, and a three-layer photovoltaic encapsulation film is obtained by laminating with an embossing roller, and the thickness ratio of the water-blocking layer film, the absorbent layer film, and the EVA layer film is 10:2:33.

[0109]

Example 2

Example 3

[0110] The difference from Example 1 is that in Examples 2-3, the types and dosages of various raw materials are different. The specific components of the photovoltaic encapsulation film in Examples 1-3 are shown in Table 1.

[0111] Table 1 Formulation of the photovoltaic encapsulation film in Examples 1-3

[0112]

[0113]

Example 4

Example 7

[0114] The difference from Example 1 is that in Example 4, the hydrophilic aid used is a hydrophilic monomer, which includes 25 parts of dimethylaminoethyl methacrylate and 25 parts of 2-hydroxyethyl methacrylate.

[0115] The difference from Example 1 is that in Example 5, the hydrophilic aid used includes 20 parts of 2-hydroxyethyl methacrylate (number average molecular weight is 2000) and 5 parts of polyvinylpyrrolidone (number average molecular weight is 10000).

[0116] The difference from Example 1 is that in Example 6, the ion adsorbent used is zirconium phosphate.

[0117] The difference from Example 1 is that in Example 7, the modified acid-resistant agent used is modified magnesium hydroxide.

[0118]

Comparative Example 1

[0119] The specific preparation process of a photovoltaic encapsulation film includes the following steps:

[0120] By weight, 98 parts of EVA resin are added to a mixing tank, and then 0.6 part of the crosslinking agent tert-butyl peroxy-2-ethylhexyl carbonate (TAEC), 0.4 part of the first co-crosslinking agent TAIC, 0.4 part of the first co-crosslinking agent ethoxylated trimethylolpropane triacrylate, 0.3 part of the coupling agent 3-methacryloxypropyltriethoxysilane, and 0.1 part of the light stabilizer 770 are mixed uniformly to form a liquid additive. Then the liquid additive is sprayed onto the EVA resin particles, followed by heat preservation absorption at 50°C for 4 hours and then standing. Finally, the temperature of the extrusion die module is set to 75°C and the temperature of the die orifice is set to 95°C for casting, and an EVA layer film of 400 g is extruded.

[0121]

Comparative Example 2

[0122] The difference from Example 1 is that in Comparative Example 2, there is no water-absorbing layer film.

[0123]

Comparative Example 3

[0124] The difference from Example 1 is that the water absorption layer film of Comparative Example 3 is replaced by an EVA adsorption layer;

[0125] The preparation method of the EVA adsorption layer is as follows:

[0126] By weight, 98 parts of EVA resin are added to the mixing tank, and then 0.6 parts of the crosslinking agent tert-butyl peroxy-2-ethylhexyl carbonate (TAEC), 0.4 parts of the first co-crosslinking agent TAIC, 0.4 parts of the first co-crosslinking agent ethoxylated trimethylolpropane triacrylate, 0.3 parts of the coupling agent 3-methacryloxypropyltriethoxysilane, and 0.1 part of the light stabilizer 770 are mixed evenly to form a liquid additive. Then the liquid additive is sprayed onto the EVA resin particles, and then heated and kept warm at 50°C for 2 h. After that, 0.2 parts of the anti-polarization masterbatch silica masterbatch (masterbatch content 5%, particle size 50 nm) are added and mixed for 2 h and left to stand. Finally, the temperature of the extrusion die module is set at 75°C and the temperature of the die orifice is set at 95°C for casting, and the EVA adsorption layer is extruded.

[0127]

Comparative Example 4

[0128] The difference from Example 1 is that the anti-acid agent in the water-blocking layer film of Comparative Example 4 is not modified.

[0129] Next, the photovoltaic encapsulation films provided in Examples 1-7 and Comparative Examples 1-4 of the present application are used to encapsulate the battery chips, and then the performance of the encapsulated battery chips is tested:

[0130] Corrosion test: A laminate is made according to the stack of glass / film / battery chip-TOPCon / film / backplane, and the lamination conditions are 145°C for 15 min; the laminate is further laminated with a heat transfer tape at 145°C for 5 min. After cooling and standing in an environment with a temperature of 23°C ± 2°C and a relative humidity of 50% ± 10% for more than 4 h; the laminate is placed in a PCT box for testing, and the test conditions are: test temperature 121°C, humidity RH100%. It is taken out after 24 h and 48 h, and EL photography is performed.

[0131] Component reliability: A component is made according to the stack of glass / EVA film / TOPCon battery / EVA film / glass, and the lamination conditions are 145°C for 15 min; after lamination, it is cooled and framed. The component is pre-treated by exposure to 5.5 KW / h, and then PID96 test is carried out under the conditions of: test temperature 85°C, humidity RH85%, negative bias -1500 V. It is taken out after 96 h, kept at a constant temperature and left to stand for 6 h, and EL photography and power test are performed to obtain the open circuit voltage Voc, fill factor FF, and short circuit current density Jsc of the corresponding battery device, and the test results are shown in Table 2.

[0132] Table 2 Performance test results of photovoltaic encapsulation films in Examples 1-7 and Comparative Examples 1-4 for encapsulating solar cells

[0133]

[0134]

[0135] As can be seen from Table 2, compared with Comparative Examples 1-4, the output power attenuation of the solar cells in Examples 1-7 is very small, while the output power attenuation of the solar cells in Comparative Examples 1-4 is relatively serious, indicating that the three-layer stacked photovoltaic encapsulation film in this application can better maintain the long-term stability and efficiency of the solar cells in a humid and hot environment.

[0136] Combined with Figures 3 - 4 , Examples 1 and Comparative Example 1, it can be seen that in Comparative Example 1, no modified anti-acid agent was added, and the corrosion of the solar cells was relatively serious, making it difficult to maintain stable electrical conductivity, resulting in relatively serious output power attenuation of the solar cells.

[0137] Combined with Figures 5 - 15 , Examples 1-7 and Comparative Examples 1-4, it can be seen that Figures 5 - 11 it can be clearly seen that after the PID96 test, the solar cells became darker to a small extent, that is, the attenuation of the solar cells was small, while Figures 12 - 15 it can be clearly seen that the solar cells became darker to a large extent, that is, the attenuation of the solar cells was relatively serious. The single-layer EVA film used in Comparative Example 1 has a minimal effect on reducing PID, so the output function attenuation is relatively serious. The encapsulation film in Comparative Example 2 has no water-absorbing film. Although the modified anti-acid agent in the water-blocking film can improve acid resistance and partially water-blocking performance, its contribution to reducing PID is limited, and the encapsulation film is still greatly affected by water vapor, and there is no ion adsorbent to adsorb the migrated sodium ions, resulting in relatively large output power attenuation of the solar cells. In Comparative Example 3, no hydrophilic auxiliary agent was added to the EVA adsorption layer, and an ion adsorbent was directly added. Then, in a humid and hot environment, the migration speed of sodium ions is relatively fast, and under the influence of more water vapor, the adsorption effect of the ion adsorbent on sodium ions is not ideal, resulting in relatively large output power attenuation of the solar cells; while in Examples 1-7, the hydrophilic auxiliary agent and the ion adsorbent act together to form a water-absorbing film with a sea-island structure. The island component in the water-absorbing film is the ion adsorbent, and the sea component is the hydrophilic auxiliary agent. When Na + ions migrate towards the solar cells under the action of an electric field, the island component, which is the ion adsorbent, can adsorb Na +Ions can improve the anti-PID effect. The hydrophilic auxiliary agent highly absorbs water, reducing the impact of water vapor on the battery cells. At the same time, it also provides an environment for the ion adsorbent to adsorb ions, effectively reducing the performance degradation of the battery cells. In Comparative Example 4, the acid-resistant agent was not modified, resulting in poor dispersion performance in the EVA resin, easy agglomeration, and relatively poor acid-resistant effect. However, the acid-resistant agents in Examples 1-7 were modified with carbodiimide coupling agent. Carbodiimide coupling agent can not only react with the water infiltrated in the humid and hot environment to generate urea, reducing the water vapor permeation, but also easily react with the carboxylic acid generated by the hydrolysis of EVA resin to form stable acylurea. While improving the dispersion performance of the acid-resistant agent, it also improves the water-blocking performance, enhances the anti-PID effect, and thus improves the hydrolysis stability of the photovoltaic encapsulation film.

[0138] An embodiment of the present application can also provide a photovoltaic module (not shown), which includes a battery cell and the photovoltaic encapsulation film as described above, and the photovoltaic encapsulation film is used to encapsulate the battery cell.

[0139] It should be noted that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present application. The orientation terms "inner" and "outer" refer to the inside and outside relative to the contour of each component itself. For example, if the device in the drawing is inverted, the device described as "above other devices or structures" or "on other devices or structures" will be positioned as "below other devices or structures" or "under other devices or structures" afterwards. Thus, the exemplary term "above..." can include both the orientation of "above..." and "below...". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the corresponding explanations for the relative spatial descriptions used here will be made.

[0140] It should also be noted that the "one embodiment", "another embodiment", "embodiment", etc. mentioned in the present application refer to the specific features, structures or characteristics described in combination with this embodiment being included in at least one embodiment generally described in the present application. The same expression appearing in multiple places in the specification does not necessarily refer to the same embodiment. Further, when describing a specific feature, structure or characteristic in combination with any embodiment, it is intended that the implementation of such feature, structure or characteristic in combination with other embodiments also falls within the scope of the present application.

[0141] In the above embodiments, the descriptions of the respective embodiments each have their own emphasis. For parts not described in detail in a certain embodiment, reference may be made to the relevant descriptions of other embodiments.

[0142] It should also be noted that the above are only the preferred embodiments of the present application, and do not limit the patent protection scope of the present application. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present application, or directly or indirectly applied in other related technical fields, shall equally be included in the patent protection scope of the present application.

Claims

1. A photovoltaic encapsulation film, characterized in that, It includes a water-blocking layer film, a water-absorbing layer film, and an EVA layer film that are stacked in sequence; The water-blocking layer film comprises raw materials in the following parts by weight: 90-100 parts of EVA resin, 0.4-0.8 parts of cross-linking agent, 0.6-1.0 parts of first co-cross-linking agent, 0.1-0.5 parts of coupling agent, 0.01-0.15 parts of light stabilizer, and 0.1-0.3 parts of modified anti-acid agent; The water-absorbing layer film comprises raw materials in the following parts by weight: 5-20 parts of ion adsorbent, 25-50 parts of hydrophilic auxiliary agent, and 30-40 parts of second co-cross-linking agent; The EVA layer film comprises raw materials in the following parts by weight: 90-100 parts of EVA resin, 0.4-0.8 parts of cross-linking agent, 0.6-1.0 parts of first co-cross-linking agent, 0.1-0.5 parts of coupling agent, and 0.01-0.15 parts of light stabilizer; Among them, the hydrophilic auxiliary agent includes one of hydrophilic monomers and hydrophilic polymers; The hydrophilic monomer includes one or more of 2-hydroxyethyl methacrylate, 1-vinyl-2-pyrrolidone NVP, and dimethylaminoethyl methacrylate; The hydrophilic polymer is a hydrophilic polymer obtained by polymerizing one or more of 2-hydroxyethyl methacrylate, 1-vinyl-2-pyrrolidone NVP, and dimethylaminoethyl methacrylate; the number-average molecular weight of the hydrophilic polymer is 2000-10000; The modified anti-acid agent includes one or two of modified magnesium hydroxide or modified magnesium oxide; Among them, the modified magnesium hydroxide is magnesium hydroxide modified by carbodiimide coupling agent; the modified magnesium oxide is magnesium oxide modified by carbodiimide coupling agent.

2. The photovoltaic encapsulation film according to claim 1, wherein The carbodiimide coupling agent is obtained by the catalytic action of an isocyanate coupling agent under an organophosphorus catalyst.

3. The photovoltaic encapsulation film according to claim 1, wherein The ion adsorbent includes one or two of silica and zirconium phosphate.

4. The photovoltaic encapsulation film according to claim 1, wherein The cross-linking agent includes one or two of tert-butyl peroxy-2-ethylhexyl carbonate TAEC and tert-butyl peroxy-2-ethylhexyl carbonate TBEC.

5. The photovoltaic encapsulation film according to claim 1, wherein The first co-cross-linking agent includes one or more of TAIC, dipropylene glycol diacrylate, propoxylated glycerol triacrylate, pentaerythritol triacrylate, ethoxylated trimethylolpropane triacrylate, 1,6-hexanediol diacrylate, and pentaerythritol tetraacrylate.

6. The photovoltaic encapsulation film according to claim 1, wherein The coupling agent includes one or more of 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, and vinyltriethoxysilane.

7. The photovoltaic encapsulation film according to claim 1, wherein The second co-crosslinking agent includes one or more of ethoxylated trimethylolpropane triacrylate, polyethylene glycol diacrylate, dipropylene glycol diacrylate, propoxylated glycerol triacrylate, pentaerythritol triacrylate, ethoxylated trimethylolpropane triacrylate, 1,6-hexanediol diacrylate, and pentaerythritol tetraacrylate.

8. A method for preparing the photovoltaic encapsulation adhesive film according to any one of claims 1-7, characterized in that, It includes the following steps: By weight, 90-100 parts of EVA resin are added to a mixing tank, and then 0.4-0.8 parts of crosslinking agent, 0.6-1.0 parts of the first co-crosslinking agent, 0.1-0.5 parts of coupling agent, and 0.01-0.15 parts of light stabilizer are mixed evenly and added to the mixing tank. After heating and heat preservation treatment, 0.1-0.3 parts of modified anti-acid agent are added, and after standing, it is extruded to obtain a water-blocking layer film. By weight, 25-50 parts of hydrophilic auxiliary agent and 30-40 parts of the second co-crosslinking agent are mixed evenly to obtain a mixed solution. Then, 5-20 parts of ion adsorbent are added to the mixed solution and stirred. After adjusting the viscosity, a pre-absorbent layer film is obtained. Then, the pre-absorbent layer film is roll-coated on the surface of the water-blocking layer film, and after curing treatment, an absorbent layer film is obtained. By weight, 90-100 parts of EVA resin are added to a mixing tank, and then 0.4-0.8 parts of crosslinking agent, 0.6-1.0 parts of the first co-crosslinking agent, 0.1-0.5 parts of coupling agent, and 0.01-0.15 parts of light stabilizer are mixed evenly and added to the mixing tank. After heating and heat preservation treatment, it is extruded to obtain an EVA layer film. The EVA layer film is placed on the surface of the absorbent layer film, and a photovoltaic encapsulation film is obtained by compounding through an embossing roller.

9. The method for preparing a photovoltaic encapsulation film according to claim 8, wherein The curing treatment includes one of EB irradiation, UV curing, or thermal curing.

10. A photovoltaic module, characterized in that, It includes: Solar cells; The photovoltaic encapsulation film according to any one of claims 1 to 7, or the photovoltaic encapsulation film prepared by the method for preparing a photovoltaic encapsulation film according to claim 8 or 9; The photovoltaic encapsulation film is used for encapsulating the solar cells.

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