Composite encapsulant, method of making the same, and photovoltaic module

Abstract

A composite encapsulant film, its preparation method, and a photovoltaic module are disclosed. The composite encapsulant film includes a main region, a transition region, and a peripheral region. The transition region is connected to the main region and disposed at the outer periphery of the main layer. The peripheral region is connected to the transition region and disposed at the outer periphery of the transition region. The visible light transmittance of the main region is a1, the visible light transmittance of the transition region is a2, and the visible light transmittance of the peripheral region is a3, satisfying a1 > a2 > a3 ≥ 90%. This composite encapsulant film has a U-shaped partitioning pattern. The main region has the highest transmittance and is the core high-transmittance bearing area of ​​the composite encapsulant film. The transition region is used to achieve a smooth transition between performance and transmittance, avoiding interface stress concentration and light scattering. The peripheral region, as the outermost layer, is used to protect the main region and the transition region. The transmittance of the peripheral region is greater than or equal to 90%, avoiding dragging down the overall transmittance performance of the composite encapsulant film. This composite encapsulant film achieves good overall transmittance performance while satisfying the protection effect on the main region.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic technology, specifically to a composite encapsulant film, its preparation method, and a photovoltaic module. Background Technology

[0002] To meet the diverse encapsulation requirements of crystalline silicon photovoltaic modules, which require high water resistance and anti-aging properties at the edges and high flow and adhesion in the middle, existing composite films have undergone structural or formulation improvements around EVA / POE-based films. However, the visible light transmittance of existing composite films is generally below 85%, and incident light is excessively absorbed or reflected at the composite film, directly reducing the output power of the photovoltaic module. Summary of the Invention

[0003] The purpose of this invention is to provide a composite film, its preparation method, and a photovoltaic module, thereby solving the problem of excessively low visible light transmittance of the composite film.

[0004] To achieve the objectives of this invention, the following technical solution is provided: In a first aspect, the present invention provides a composite adhesive film for use in photovoltaic modules, comprising: Main area; A transition zone, connected to the main body area and located at the outer peripheral edge of the main body layer; The peripheral area is connected to the transition area and is located at the outer periphery of the transition area; Wherein, the visible light transmittance of the main area is a1, the visible light transmittance of the transition area is a2, and the visible light transmittance of the peripheral area is a3, satisfying: a1>a2>a3≥90%.

[0005] In one implementation, a1≥93%, a1-a2≤3%, and a2-a3≤3%.

[0006] In one embodiment, the thickness of the composite film is 0.3 mm to 0.4 mm; and / or, The main body region accounts for 85%-90% of the area of ​​the composite film; and / or, The width of the transition zone is 2mm-3mm; and / or, The width of the outer perimeter is 10mm-20mm.

[0007] In one embodiment, the main body area includes a first main material, and the peripheral area includes a second main material; the vinyl acetate content in the first main material is 28%-30%; and the vinyl acetate content in the second main material is 20%-22%.

[0008] In one embodiment, the composite film includes a light transmittance enhancer, wherein the particle size of the light transmittance enhancer is 30nm-50nm; The light transmittance enhancer includes one or more of zirconium oxide, aluminum oxide, titanium dioxide, and zinc oxide.

[0009] In one embodiment, the water vapor permeability of the peripheral zone is less than or equal to 0.5 g / (m²). 2 d); The peripheral region includes a water-blocking additive, which includes one or more of thermoplastic polyurethane, polyisobutylene, organosilicon, and ethylene-octene copolymer. The water-blocking additive accounts for 25%-30% of the mass of the outer perimeter area.

[0010] In one embodiment, the main body region further includes a light-transmitting synergist, which includes one or more of polyethylene glycol monomethyl ether, benzotriazole, phenyl methacrylate, silicone resin, and sorbitol.

[0011] In a second aspect, the present invention provides a method for preparing a composite adhesive film, the method being used to prepare the composite adhesive film described in any one of the various embodiments of the first aspect, the method comprising: A first slurry, a second slurry, and a third slurry are provided, wherein the first slurry is used to form a main region, the second slurry is used to form a transition region, and the third slurry is used to form a peripheral region; The composite film is obtained by co-extruding the first slurry, the second slurry, and the third slurry using a three-screw extruder.

[0012] In one embodiment, the first slurry and the third slurry are mixed in a certain proportion to form the second slurry.

[0013] Thirdly, the present invention provides a photovoltaic module, including a solar cell, a composite film and a backsheet, wherein the solar cell, the composite film and the backsheet are sequentially laminated, wherein the composite film is any one of the composite films described in any one of the embodiments of the first aspect, or a composite film obtained by using the preparation method of the composite film described in any one of the embodiments of the second aspect.

[0014] The composite film of this invention is divided into a U-shaped section. The main area has the highest light transmittance and is the core area bearing the high light transmittance of the composite film. The visible light transmittance of the transition area is between that of the main area and the outer area, which is used to achieve a smooth transition in performance and light transmittance, avoiding interface stress concentration and light scattering. The outer area surrounds the transition area and the main area. As the outermost area, the outer area is used to protect the main area and the transition area. The light transmittance of the outer area is the lowest, but still greater than or equal to 90%, so as not to drag down the overall light transmittance performance of the composite film. Therefore, the composite film of this invention has good overall light transmittance performance while satisfying the protection effect of the main area. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0016] Figure 1 This is a top view of a composite film according to one embodiment; Figure 2 This is a flowchart of the preparation process of a composite film according to one embodiment.

[0017] Explanation of reference numerals in the attached figures: 10 - Main area, 20 - Transition area, 30 - Outer area. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] It should be noted that when a component is said to be "fixed" to another component, it can be directly on the other component or it can be in a middle component. When a component is said to be "connected" to another component, it can be directly connected to the other component or it may be in a middle component.

[0020] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0021] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0022] Please refer to Figure 1This invention provides a composite encapsulant film for photovoltaic modules. The composite encapsulant film includes a main region 10, a transition region 20, and a peripheral region 30. The transition region 20 is connected to the main region 10 and disposed at the outer peripheral edge of the main layer. The peripheral region 30 is connected to the transition region 20 and disposed at the outer peripheral edge of the transition region 20. The visible light transmittance of the main region 10 is a1, the visible light transmittance of the transition region 20 is a2, and the visible light transmittance of the peripheral region 30 is a3, satisfying the condition: a1 > a2 > a3 ≥ 90%.

[0023] Optionally, the main area 10 can be a rectangle, triangle, circle, polygon, etc., without restriction.

[0024] Optionally, the width of the transition zone 20 is the same everywhere, and the width of the outer zone 30 is the same everywhere.

[0025] Optionally, a3 can be 90%, 91%, 92%, 93%, etc., without restriction. Furthermore, the visible light transmittance should exhibit a gradual, step-like decrease from the main area 10 to the outer area 30.

[0026] Optionally, the composite adhesive film should have a uniform thickness throughout. Uneven thickness, especially in areas that are too thin, can accelerate aging, reduce adhesion, weaken puncture resistance, and make the film more susceptible to puncture by solder ribbons, potentially causing electrical short circuits. Optionally, the thickness uniformity error of the composite adhesive film should be ≤0.02mm.

[0027] Optionally, the melt flow index of the main body region 10 is 15g / 10min-20g / 10min, and the peel strength between the main body region 10 and the glass / cell is ≥180N / cm, so as to ensure the high fluidity and high adhesion of the main body region 10, and enable the main body region 10 to fully fill the gaps between the cells.

[0028] The composite film of the present invention is divided into a U-shaped partition. The main body region 10 has the highest light transmittance and is the core bearing area for high light transmittance of the composite film. The visible light transmittance of the transition region 20 is between that of the main body region 10 and the outer region 30, which is used to achieve a smooth transition in performance and light transmittance, and avoid interface stress concentration and light scattering. The outer region 30 surrounds the transition region 20 and the main body region 10. As the outermost region, the outer region 30 is used to protect the main body region 10 and the transition region 20. The light transmittance of the outer region 30 is the lowest but still greater than or equal to 90%, so as not to drag down the overall light transmittance performance of the composite film. Therefore, the composite film of the present invention has good overall light transmittance performance while satisfying the protection effect of the main body region 10.

[0029] In one implementation, a1≥93%, a1-a2≤3%, and a2-a3≤3%.

[0030] Optionally, a1 can be 93%, 94%, 95%, 96%, 97%, 98%, etc., without restriction. a1-a2 can be 3%, 2%, 1%, 0.5%, etc., without restriction. a2-a3 can be 3%, 2%, 1%, 0.5%, etc., without restriction.

[0031] Large differences in visible light transmittance are usually accompanied by poor material compatibility. If the outer region 30 has poor bonding with the main region 10 and the transition region 20 due to a low-transmittance formulation (such as a high-water-resistant filler), the interface may become a preferential penetration channel for water vapor and corrosive substances, accelerating the grid line corrosion of the solar cell. Excessive differences in visible light transmittance also mean that the optimal lamination conditions are mismatched, which may cause some areas to be over-crosslinked (become brittle) while other areas are under-crosslinked (insufficient adhesion).

[0032] In one embodiment, the thickness of the composite film is 0.3mm-0.4mm. Optionally, the thickness of the composite film is 0.3mm, 0.31mm, 0.32mm, 0.33mm, 0.34mm, 0.35mm, 0.36mm, 0.37mm, 0.38mm, 0.39mm, 0.4mm, etc., and is not limited.

[0033] When the composite encapsulant film is too thin, the microcrack rate of the solar cells increases significantly after module encapsulation. Simultaneously, the passivation and protection provided by the composite encapsulant film for the solar cells are weakened. An excessively thin composite encapsulant film is prone to insufficient filling at the edges after module lamination, leading to bubbles and delamination. An excessively thick composite encapsulant film has greater fluidity during lamination, and the shrinkage stress during curing can cause the solar cells to shift, deviating from their intended position. Furthermore, the thicker the composite encapsulant film, the stronger its interference with light transmission and absorption, resulting in a decrease in the optical efficiency of the photovoltaic module. A composite encapsulant film of suitable thickness can achieve both protection of the solar cells and without affecting the optical efficiency of the photovoltaic module.

[0034] In one embodiment, the main body region 10 accounts for 85%-90% of the area of ​​the composite film. Optionally, the area percentage of the main body region 10 in the composite film can be 85%, 86%, 87%, 88%, 89%, 90%, etc., without limitation. A too small area percentage of the main body region 10 directly limits effective light reception, leading to a reduction in the output power of the photovoltaic module. A too large area percentage of the main body region 10 may prevent the transition region 20 and the peripheral region 30 from fully realizing their functions, affecting the long-term use of the composite film. Therefore, limiting the area percentage of the main body region 10 can balance high power and long-term reliability.

[0035] In one embodiment, the width of the transition zone 20 is 2mm-3mm. Optionally, the width of the transition zone 20 can be 2mm, 2.1mm, 2.2mm, 2.3mm, 2.4mm, 2.5mm, 2.6mm, 2.7mm, 2.8mm, 2.9mm, 3mm, etc., without limitation. If the transition zone 20 is too narrow, it cannot effectively buffer stress, and stress concentration is likely to occur at the junction of the main body zone 10 and the outer perimeter zone 30, leading to lamination cracking or delamination. If the transition zone 20 is too wide, it will lead to improper stress transmission, which may cause stress concentration between the main body zone 10 and the outer perimeter zone 30 during lamination, increasing the risk of delamination. Limiting the width of the transition zone 20 ensures stress buffering and achieves a smooth performance transition.

[0036] In one embodiment, the width of the outer perimeter region 30 is 10mm-20mm. Optionally, the width of the outer perimeter region 30 is 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 17mm, 18mm, 19mm, 20mm, etc., and is not limited.

[0037] Optionally, the edge width accuracy error of the outer area 30 is ≤0.5mm, which is used to adapt to the accuracy requirements of photovoltaic module mounting and improve the encapsulation qualification rate.

[0038] An excessively narrow outer region 30 can lead to edge encapsulation failure, failing to provide reliable mechanical support and sealing. This can easily cause bubbles and delamination, increasing the risk of external moisture corrosion and resulting in photovoltaic module power degradation or failure. An excessively wide outer region 30 increases costs and encroaches on the area of ​​the main body region 10, reducing the overall power of the photovoltaic module. Limiting the width of the outer region 30 saves costs while ensuring the reliability of the photovoltaic module's edges and maintaining the overall power of the photovoltaic module.

[0039] In one embodiment, the main body area 10 includes a first main material, and the peripheral area 30 includes a second main material; the vinyl acetate content in the first main material is 28%-30%; and the vinyl acetate content in the second main material is 20%-22%.

[0040] Optionally, both the first and second main materials are ethylene-vinyl acetate copolymers (EVA). As the core substrates for photovoltaic module encapsulation, the first and second main materials have good adhesion and flowability.

[0041] Optionally, the vinyl acetate content in the first main material can be 28%, 28.5%, 29%, 29.5%, 30%, etc.; the vinyl acetate content in the second main material can be 20%, 20.5%, 21%, 21.5%, 22%, etc., without restriction.

[0042] The vinyl acetate (VA) content determines the performance of the composite film. A high VA content in the first main material leads to increased polarity and reduced crystallinity, thereby directly improving the transparency of the main body region 10 and its adhesion strength to the glass and backsheet, ensuring efficient light delivery to the solar cells. A low VA content in the second main material reduces the probability of decomposition and acetic acid production under photothermal effects. Simultaneously, the low VA content material forms a highly weather-resistant protective layer, preventing corrosion of the solar cells and extending the lifespan of the outer region 30.

[0043] In one embodiment, the composite film includes a light transmittance enhancer with a particle size of 30nm-50nm.

[0044] Light transmittance enhancers can improve the light transmittance of composite films and reduce light scattering. They can adjust the equivalent refractive index of the composite film to a level between that of glass and the solar cell, creating a refractive index gradient. This significantly reduces interfacial reflection caused by abrupt changes in refractive index, allowing more light to enter the cell. Uniformly dispersed nano-light transmittance enhancers can disrupt microcrystalline or macromolecular agglomerates that may form within the film, making the composite film medium more optically uniform. This suppresses light scattering by the composite film itself, ensuring that light reaches the solar cell surface efficiently along a direct path.

[0045] Optionally, the particle size of the light transmittance enhancer can be 30nm, 35nm, 40nm, 45nm, 50nm, etc., without limitation. Excessively large particle size of the light transmittance enhancer can lead to fogging and decreased transparency of the composite film. Conversely, excessively small particle size can result in severe loss of short-wavelength light and easy particle aggregation. Limiting the particle size of the light transmittance enhancer minimizes scattering loss while improving its dispersibility.

[0046] In one embodiment, the light transmittance enhancer includes one or more of zirconium oxide, aluminum oxide, titanium dioxide, and zinc oxide. Specifically, zirconium oxide can maximize light transmittance through refractive index matching. Zirconia can be used to adjust the interfacial refractive index difference between the composite film and the glass or solar cell, thereby significantly reducing interfacial light reflection loss. Aluminum oxide can improve light transmittance by constructing a single uniform layer.

[0047] In one specific embodiment, the light transmittance enhancer of the present invention is a composite of nano-zirconia and nano-alumina in a mass ratio of 1:1.

[0048] In one embodiment, the water vapor transmission rate of the outer zone 30 is less than or equal to 0.5 g / (m²). 2 d). Optionally, the water vapor permeability of the outer 30° zone is 0.1 g / (m²). 2 d) 0.2g / (m 2 d) 0.3g / (m2 d) 0.4g / (m 2 d), 0.5g / (m 2 d) etc., are not restricted.

[0049] In one embodiment, the peripheral region 30 includes a water-blocking additive, which includes one or more of thermoplastic polyurethane, polyisobutylene, silicone, and ethylene-octene copolymer.

[0050] Thermoplastic polyurethane possesses abrasion resistance and puncture resistance, making it an excellent impact-resistant and moisture-proof barrier. Polyisobutylene has extremely low water vapor permeability, as low as 0.15 g / (m²). 2 d) is a key material for constructing water-blocking barriers. Organosilicon has high weather resistance and excellent anti-PID properties, and is highly efficient in processing.

[0051] Ethylene-octene copolymer (POE) has a molecular chain composed entirely of carbon and hydrogen atoms, containing no ester groups. Therefore, its structure is highly stable and it will not undergo hydrolysis in water, avoiding performance degradation due to its own degradation. Furthermore, POE's non-polar nature makes it difficult to form hydrogen bonds with water molecules (polar molecules), effectively blocking the intrusion of external moisture. POE is also impermeable to sodium ions, effectively preventing sodium ion migration and thus improving its resistance to potential-induced degradation (PID).

[0052] In one embodiment, the water-blocking additive accounts for 25%-30% of the mass of the outer perimeter region 30. Optionally, the mass percentage of the water-blocking additive in the outer perimeter region 30 can be 25%, 26%, 27%, 28%, 29%, 30%, etc., without limitation. Insufficient water-blocking additive will directly lead to insufficient moisture barrier capacity of the outer perimeter region 30, resulting in compromised long-term reliability. Excessive water-blocking additive will damage the polymer structure of the outer perimeter region 30, reducing its adhesion to the glass and frame, directly increasing the risk of delamination. Therefore, the amount of water-blocking additive added needs to be limited.

[0053] In one embodiment, the main body region 10 further includes a light-transmitting synergist, which includes one or more of polyethylene glycol monomethyl ether, benzotriazole, phenyl methacrylate, silicone resin, and sorbitol.

[0054] Specifically, the light transmittance synergist includes polyethylene glycol monomethyl ether (mPEG-2000) with a molecular weight of 2000. mPEG-2000 can more effectively capture free radicals generated during aging, delaying the yellowing of the composite film under long-term UV exposure. By delaying degradation, it ensures that the composite film maintains its high light transmittance for a longer period throughout its entire lifespan. The melting point and viscosity characteristics of mPEG within this molecular weight range allow it to be well-matched with the processing temperature (approximately 100℃-130℃) of commonly used photovoltaic encapsulation resins such as EVA and POE, facilitating blending. The light transmittance synergist also solves the agglomeration problem of light transmittance enhancers, optimizes the surface smoothness of the composite film, and synergistically improves light transmittance.

[0055] Specifically, benzotriazole is a UV down-conversion additive that converts UV photons in the 250nm-400nm wavelength range into blue light. It transforms harmful UV light (280nm-380nm) into blue light (400nm-450nm), which has higher battery susceptibility, thereby increasing initial power and reducing light-induced degradation (UVID). Sorbitol refines the crystal structure of polymers such as EVA, reducing light scattering and improving overall transmittance. Organosilicon resins and phenyl methacrylate, as light diffusing agents, possess excellent heat resistance and dispersibility, improving the uniformity of light distribution and increasing the probability of the battery receiving light, thus enhancing light utilization.

[0056] In one embodiment, the composite film of the present invention retains a light transmittance of ≥90% and an elongation at break of ≥85% after xenon lamp accelerated aging for 600 hours.

[0057] The composite film of this invention has a sheet-like structure, comprising a main body region 10, a transition region 20, and a peripheral region 30. All three regions have the same thickness, with no thickness difference, thus avoiding issues related to frame assembly accuracy and interface light scattering. The main body region 10 is located in the middle area, and its core functions are high flowability, high adhesion, and high light transmittance. It is the core area supporting the high light transmittance of the film. The transition region 20 is located between the main body region 10 and the peripheral region 30, achieving a smooth transition in performance and light transmittance, avoiding interface stress concentration and light scattering. The peripheral region 30 is U-shaped, wrapping around the main body region 10 and the transition region 20. Its core functions are high water resistance, anti-aging, and anti-PID, while ensuring a visible light transmittance of ≥90%, thus avoiding dragging down the overall light transmittance performance.

[0058] Please refer to Figure 2 This invention provides a method for preparing a composite adhesive film. The method is used to prepare the composite adhesive film described in any of the foregoing embodiments. The preparation method includes: Step S10: Provide a first slurry, a second slurry, and a third slurry, wherein the first slurry is used to form the main body region, the second slurry is used to form the transition region, and the third slurry is used to form the peripheral region; Step S20: Using a three-screw extruder, co-extrude the first slurry, the second slurry, and the third slurry to obtain a composite film.

[0059] Optionally, in step S10, the first slurry specifically includes a first main material (100 parts), a crosslinking agent (0.5-1 parts), a silane coupling agent (0.3-0.5 parts), a light transmittance enhancer (0.2-0.3 parts), a light stabilizer (0.01-0.1 parts), an antioxidant (0.1-0.3 parts), and a light transmittance synergist (0.01-0.05 parts). Specifically, the crosslinking agent can be trimethylolpropane triacrylate (TBEC), which is a clean crosslinking agent with high crosslinking efficiency and no harmful byproducts. The silane coupling agent can specifically be 3-aminopropyltriethoxysilane (KH-550), which is used to improve the interfacial adhesion between the composite film, the battery cell, and the backsheet. The light stabilizer can specifically be poly(4-hydroxy-2,2,6,6-tetramethyl-1-piperidinol) ester (UV-622), used to improve the long-term resistance of the composite film to ultraviolet aging. The antioxidant is specifically pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid], also known as antioxidant 1010. The antioxidant effectively terminates the oxidation chain reaction by capturing free radicals, thus significantly delaying the material aging of the composite film.

[0060] Optionally, in step S10, the third slurry specifically includes the second main material (70-75 parts), water-blocking additive (25-30 parts), compatibilizer (3-5 parts), crosslinking agent (0.5-1 part), silane coupling agent (0.3-1 part), silicone oil (0.2-0.5 parts), light stabilizer (0.1-0.2 parts), antioxidant (0.1-0.5 parts), and light transmittance enhancer (0.1-0.2 parts). Specifically, the water-blocking additive is ethylene-octene copolymer; the compatibilizer is maleic anhydride-grafted EVA (EVA-g-MAH), which is used to improve the compatibility of EVA and POE and prevent phase separation; the crosslinking agent is TBEC; the silane coupling agent of the third slurry is γ-(2,3-epoxypropoxy)propyltrimethoxysilane, i.e., KH-560; the silicone oil is low-viscosity transparent grade methyl silicone oil; the antioxidants include tris(2,4-di-tert-butylphenyl) phosphite (i.e., antioxidant 169) and antioxidant 1010, with the mass ratio of antioxidant 1010 to antioxidant 168 being 1:1; and the light stabilizer is UV-622.

[0061] Optionally, the amount of POE in the second slurry is controlled at 25%-30%, and the compatibility problem is solved by using EVA-g-MAH compatibilizer. While ensuring high water resistance at the edges, the raw material cost is significantly reduced, balancing performance and economy.

[0062] Optionally, in step S10, the first, second, and third slurries also require corresponding pretreatment: the light transmittance enhancer and / or silicone oil and / or light transmittance synergist are premixed with 2 parts of EVA, ultrasonically dispersed for 5 minutes, and then the corresponding components of each slurry are added to a high-speed mixer to obtain the first, second, and third slurries. The addition of the ultrasonic dispersion pretreatment step can solve the problem of agglomeration of the light transmittance enhancer.

[0063] Optionally, step S20 specifically includes: gradient co-extrusion plasticizing, casting (extruding the melt into a flat die to form a thin and wide molten sheet, which is then cast onto a specially designed cooling roller for rapid cooling and shaping), cooling and cutting, inspection and winding, etc. The cooling and cutting can specifically be a combination of air cooling and water cooling processes. Furthermore, the temperature of the feeding section, plasticizing section, and homogenizing section of the three-screw extruder gradually increases, while the temperature of the die head section is lower than that of the homogenizing section. The screw speed of the three-screw extruder is 150 r / min-300 r / min. Step S20 can be modified from existing composite film production lines to achieve mass production.

[0064] The three-screw extruder is used for gradient co-extrusion to achieve synchronous extrusion and seamless fusion of materials in the main body zone, transition zone and edge zone, avoiding the defects of splicing process; through the composite cooling process of air cooling and water cooling and precise temperature control casting, the composite film is guaranteed to be free of deformation and defects, and light scattering is reduced.

[0065] In one embodiment, the first slurry and the third slurry are mixed in a certain proportion to form the second slurry. Specifically, the first slurry and the third slurry are mixed in a 1:1 mass ratio to obtain the second slurry.

[0066] The present invention provides a photovoltaic module, comprising a solar cell, a composite encapsulant film, and a backsheet, wherein the solar cell, the composite encapsulant film, and the backsheet are sequentially laminated, wherein the composite encapsulant film is any one of the composite encapsulant films described in any of the foregoing embodiments, or a composite encapsulant film obtained by using the preparation method of the composite encapsulant film described in any one of the foregoing embodiments.

[0067] Optionally, the backsheet serves as a protective layer for the module, specifically a three-layer TPT (polyvinyl fluoride composite film) structure: the outer layer is a T film, with a polyvinyl fluoride (PVF) thickness of up to 37μm, providing UV aging resistance, corrosion resistance, and mechanical protection. The middle layer is a P layer, with a polyester film (BOPET) thickness of up to 250μm, serving as a moisture barrier, electrical insulation, and dimensional stability. The inner PVF film layer undergoes surface treatment to enhance adhesion to the composite film. The white backsheet scatters incident light, improving light absorption efficiency, while its high infrared emissivity reduces the operating temperature of the photovoltaic module.

[0068] Optionally, the solar cells achieve photoelectric conversion through PN junctions, passivation layers, and metallization structures, while the backsheet provides physical and environmental protection. The composite film ensures the long-term stable operation of the photovoltaic module through functions such as bonding and sealing, and light transmission buffering. The three work together to form the core structure of a high-efficiency and durable photovoltaic module.

[0069] The technical solution of the present invention will be described in detail below through specific embodiments.

[0070] Example 1 This embodiment provides a composite film with a main area accounting for 85% of the total area, a peripheral area with a width of 15mm, a transition area with a width of 2mm, and a thickness of 0.35mm. The visible light transmittance a1 of the main area is 95%, the visible light transmittance a2 of the transition area is 94%, and the visible light transmittance a3 of the peripheral area is 93%.

[0071] The method for preparing the composite film in this embodiment is as follows: a first slurry, a second slurry, and a third slurry are provided. The specific composition of the first slurry is as follows: 100 parts of the first main material (the content of vinyl acetate in the first main material is 28%), 0.6 parts of crosslinking agent (TBEC), 0.4 parts of silane coupling agent (KH-550), 0.2 parts of light transmission enhancer (a composite of nano-zirconia and nano-alumina with a mass ratio of 1:1 and a particle size of 30nm-50nm), 0.08 parts of light stabilizer (UV-622), 0.15 parts of antioxidant (antioxidant 1010), and 0.04 parts of light transmission synergist (mPEG-2000).

[0072] The specific composition of the third slurry is as follows: 72 parts of the second main material (the content of vinyl acetate in the second main material is 20%), 28 parts of water-blocking additive (POE), 4 parts of compatibilizer (EVA-g-MAH), 0.7 parts of crosslinking agent (TBEC), 0.5 parts of silane coupling agent (KH-560), 0.25 parts of low viscosity transparent grade methyl silicone oil, 0.12 parts of light transmission enhancer (a composite of nano-zirconia and nano-alumina, with a mass ratio of 1:1 and a particle size of 40nm), 0.12 parts of light stabilizer (UV-622), and 0.25 parts of antioxidant (antioxidant 1010 + antioxidant 168, with a mass ratio of 1:1).

[0073] The second slurry is formed by mixing the first and third slurries in a mass ratio of 1:1.

[0074] The first, second, and third slurries require corresponding pretreatment: the light transmittance enhancer and / or silicone oil and / or light transmittance synergist are premixed with 2 parts of EVA, ultrasonically dispersed at 300W for 5 minutes, and then the corresponding components of each slurry are added to a high-speed mixer at a mixing temperature of 85℃, a mixing speed of 350r / min, and a mixing time of 18 minutes to obtain the first, second, and third slurries.

[0075] A composite film is obtained by co-extruding the first, second, and third slurries using a three-screw extruder. The process includes: gradient co-extrusion plasticizing, with the temperatures of the three-screw extruder's feed section at 115℃, the plasticizing section at 135℃, the homogenizing section at 145℃, and the die head section at 140℃, and the screw speed at 220 r / min. The first, second, and third slurries are added to the three feed ports respectively, with precise control of the extrusion amount; casting molding, with the casting roller temperature at 55℃, the pressure at 0.4 MPa, and the speed at 10 m / min, followed by matte finishing; cooling and cutting, first air cooling to 85℃, then water cooling to room temperature, and cutting the outer area to a width of 15 mm without burrs; and inspection and winding, after passing the performance test, winding at a speed of 12 m / min to obtain the composite film.

[0076] Example 2 The difference between this embodiment and Embodiment 1 is that the area of ​​the main body region accounts for 90%, the width of the outer perimeter region is 10mm, and the thickness of the composite film is 0.3mm. The visible light transmittance a1 of the main body region is 95%, the visible light transmittance a2 of the transition region is 92%, and the visible light transmittance a3 of the outer perimeter region is 91%.

[0077] The specific composition of the first slurry in this embodiment is as follows: 100 parts of the first main material (the content of vinyl acetate in the first main material is 30%), 0.5 parts of crosslinking agent (TBEC), 0.3 parts of silane coupling agent (KH-550), 0.2 parts of light transmission enhancer (a composite of nano-zirconia and nano-alumina in a mass ratio of 1:1 with a particle size of 30nm), 0.05 parts of light stabilizer (UV-622), 0.1 parts of antioxidant (antioxidant 1010), and 0.03 parts of light transmission synergist (mPEG-2000).

[0078] The specific composition of the third slurry is as follows: 75 parts of the second main material (the content of vinyl acetate in the second main material is 22%), 25 parts of water-blocking additive (POE), 3 parts of compatibilizer (EVA-g-MAH), 0.6 parts of crosslinking agent (TBEC), 0.4 parts of silane coupling agent (KH-560), 0.2 parts of low viscosity transparent grade methyl silicone oil, 0.1 parts of light transmission enhancer (a composite of nano-zirconia and nano-alumina, with a mass ratio of 1:1 and a particle size of 40nm), 0.1 parts of light stabilizer (UV-622), and 0.2 parts of antioxidant (antioxidant 1010 + antioxidant 168, with a mass ratio of 1:1).

[0079] The first, second, and third slurries require corresponding pretreatment: the light transmittance enhancer and / or silicone oil and / or light transmittance synergist are premixed with 2 parts of EVA, ultrasonically dispersed at 300W for 5 minutes, and then the corresponding components of each slurry are added to a high-speed mixer at a mixing temperature of 80℃, a mixing speed of 300r / min, and a mixing time of 15 minutes to obtain the first, second, and third slurries.

[0080] A composite film is obtained by co-extruding the first, second, and third slurries using a three-screw extruder. The process includes: gradient co-extrusion plasticizing, with the temperatures of the three-screw extruder's feed section at 110℃, the plasticizing section at 130℃, the homogenizing section at 140℃, and the die head section at 135℃, and the screw speed at 200 r / min. The first, second, and third slurries are added to the three feed ports respectively, with precise control of the extrusion amount; casting molding, with the casting roller temperature at 50℃, the pressure at 0.3 MPa, and the speed at 8 m / min, followed by matte finishing; cooling and cutting, first air cooling to 80℃, then water cooling to room temperature, and cutting the outer area to a width of 10 mm without burrs; and inspection and winding, after passing the performance test, winding at a speed of 10 m / min to obtain the composite film.

[0081] Example 3 The difference between this embodiment and Embodiment 1 is that the area ratio of the main body region is 88%, the width of the outer perimeter region is 20mm, the width of the transition region is 3mm, and the thickness of the composite film is 0.3mm. The visible light transmittance a1 of the main body region is 94%, the visible light transmittance a2 of the transition region is 93%, and the visible light transmittance a3 of the outer perimeter region is 90%.

[0082] The specific composition of the first slurry in this embodiment is as follows: 100 parts of the first main material (the content of vinyl acetate in the first main material is 29%), 0.7 parts of crosslinking agent (TBEC), 0.5 parts of silane coupling agent (KH-550), 0.25 parts of light transmission enhancer (a composite of nano-zirconia and nano-alumina in a mass ratio of 1:1 with a particle size of 50nm), 0.01 parts of light stabilizer (UV-622), 0.2 parts of antioxidant (antioxidant 1010), and 0.05 parts of light transmission synergist (mPEG-2000).

[0083] The specific composition of the third slurry is as follows: 70 parts of the second main material (the content of vinyl acetate in the second main material is 21%), 30 parts of water-blocking additive (POE), 5 parts of compatibilizer (EVA-g-MAH), 0.86 parts of crosslinking agent (TBEC), 0.6 parts of silane coupling agent (KH-560), 0.3 parts of low viscosity transparent grade methyl silicone oil, 0.15 parts of light transmission enhancer (a composite of nano-zirconia and nano-alumina, with a mass ratio of 1:1 and a particle size of 50nm), 0.15 parts of light stabilizer (UV-622), and 0.3 parts of antioxidant (antioxidant 1010 + antioxidant 168, with a mass ratio of 1:1).

[0084] The first, second, and third slurries require pretreatment: the light transmittance enhancer and / or silicone oil and / or light transmittance synergist are premixed with 2 parts of EVA, ultrasonically dispersed at 300W for 5 minutes, and then the corresponding components of each slurry are added to a high-speed mixer at a mixing temperature of 90℃, a mixing speed of 400r / min, and a mixing time of 20 minutes to obtain the first, second, and third slurries.

[0085] A composite film is obtained by co-extruding the first, second, and third slurries using a three-screw extruder. The process includes: gradient co-extrusion plasticizing, with the temperatures of the three-screw extruder's feed section at 120℃, the plasticizing section at 140℃, the homogenizing section at 150℃, and the die head section at 145℃, and the screw speed at 250 r / min. The first, second, and third slurries are added to the three feed ports respectively, with precise control of the extrusion amount; casting molding, with the casting roller temperature at 60℃, the pressure at 0.5 MPa, and the speed at 12 m / min, followed by matte finishing; cooling and cutting, first air cooling to 90℃, then water cooling to room temperature, and cutting the outer area to a width of 20 mm without burrs; and inspection and winding, after passing the performance test, winding at a speed of 15 m / min to obtain the composite film.

[0086] The relevant properties of the composite films in Examples 1-3 were tested, and the results showed that: the overall visible light transmittance of the composite film in Example 1 was 93.5%, the ultraviolet light transmittance was 88.6%, the intermediate melt index was 17.8 g / 10 min, the glass peel strength was 185 N / cm, and the edge water vapor transmittance was 0.42 g / (m²). 2 d) The transmittance remained at 90.5% after 600 hours of xenon lamp aging, and the cost was reduced by 35% compared to pure POE film. The composite film of Example 2 had an overall visible light transmittance of 93.1%, an ultraviolet light transmittance of 88.3%, an intermediate melt index of 19.2 g / 10 min, a glass peel strength of 182 N / cm, and an edge moisture transmittance of 0.48 g / (m²). 2 d) The transmittance remained at 90.1% after 600 hours of xenon lamp aging, and the cost was reduced by 38% compared to pure POE film. The composite film of Example 3 had an overall visible light transmittance of 94.5%, an ultraviolet light transmittance of 89.2%, an intermediate melt index of 16.5 g / 10 min, a glass peel strength of 188 N / cm, and an edge moisture transmittance of 0.39 g / (m²). 2 d) The light transmittance retention rate after 600 hours of xenon lamp aging is 91.2%, and the cost is reduced by 32% compared to pure POE film.

[0087] The composite film of this invention, by adding a highly efficient light transmittance enhancer and a light transmittance synergist of nano-zirconia / alumina compound to the slurry, forms a low light scattering structure, thereby increasing the overall visible light transmittance of the composite film to over 93% (up to 94.5%) and the ultraviolet light transmittance to ≥88%, an improvement of more than 8 percentage points compared to existing technologies. The composite film exhibits uniform overall light transmittance, resulting in a 1.5%-2.5% increase in photovoltaic module power generation efficiency compared to existing films, demonstrating significant economic benefits. The water vapor transmittance in the outer region is less than or equal to 0.5 g / (m²). 2 d) It is far superior to pure EVA film, meeting the standards for PID resistance and anti-aging performance; while ensuring high water resistance, the visible light transmittance of the edge area is greater than or equal to 90%, effectively resolving the contradiction that high water resistance inevitably reduces transmittance; by setting compatibilizers, gradient compatible transition zones, and a three-screw co-extrusion process, seamless connection of the three regions is achieved, completely avoiding delamination and warping. After 600 hours of accelerated aging under xenon lamps, the transmittance of the composite film remains ≥90%, the elongation at break remains ≥85%, with no yellowing or defects, and the service life of the photovoltaic module can reach 25 years. The composite film of the present invention adopts a blending system with EVA as the main component and POE as the auxiliary component (25%-30%), which significantly reduces the raw material cost. Moreover, it relies on the existing EVA film production line for modification, only adding an ultrasonic dispersion step, reducing equipment investment by more than 60%, and the production efficiency is on par with the existing EVA film (≥500m / day). The cost is 30%-40% lower than that of pure POE film and 15%-20% lower than that of existing loop-shaped film, approaching the cost of pure EVA film, which enables the composite film of the present invention to be industrialized and mass-produced.

[0088] In the description of the embodiments of the present invention, it should be noted that the orientation or positional relationship of the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and other indicators are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0089] The above description discloses only one preferred embodiment of the present invention, and should not be construed as limiting the scope of the present invention. Those skilled in the art will understand that all or part of the processes of the above embodiments can be implemented, and equivalent changes made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A composite adhesive film for use in photovoltaic modules, characterized in that, include: Main area; A transition zone, connected to the main body area and located at the outer peripheral edge of the main body layer; The peripheral area is connected to the transition area and is located at the outer periphery of the transition area; Wherein, the visible light transmittance of the main area is a1, the visible light transmittance of the transition area is a2, and the visible light transmittance of the peripheral area is a3, satisfying: a1>a2>a3≥90%.

2. The composite film according to claim 1, characterized in that, a1≥93%, a1-a2≤3%, a2-a3≤3%.

3. The composite film according to claim 1, characterized in that, The thickness of the composite film is 0.3mm-0.4mm; and / or, The main body region accounts for 85%-90% of the area of ​​the composite film; and / or, The width of the transition zone is 2mm-3mm; and / or, The width of the outer perimeter is 10mm-20mm.

4. The composite film according to any one of claims 1 to 3, characterized in that, The main body area includes a first main material, and the peripheral area includes a second main material; the vinyl acetate content in the first main material is 28%-30%; the vinyl acetate content in the second main material is 20%-22%.

5. The composite film according to claim 4, characterized in that, The composite film includes a light transmittance enhancer, and the particle size of the light transmittance enhancer is 30nm-50nm; The light transmittance enhancer includes one or more of zirconium oxide, aluminum oxide, titanium dioxide, and zinc oxide.

6. The composite film according to claim 4, characterized in that, The water vapor transmission rate of the outer perimeter zone is less than or equal to 0.5 g / (m²). 2 d); The peripheral region includes a water-blocking additive, which includes one or more of thermoplastic polyurethane, polyisobutylene, organosilicon, and ethylene-octene copolymer. The water-blocking additive accounts for 25%-30% of the mass of the outer perimeter area.

7. The composite film according to claim 4, characterized in that, The main body area also includes a light-transmitting synergist, which includes one or more of polyethylene glycol monomethyl ether, benzotriazole, phenyl methacrylate, organosilicon resin, and sorbitol.

8. A method for preparing a composite adhesive film, characterized in that, The method for preparing the composite adhesive film is used to prepare the composite adhesive film as described in any one of claims 1-7, and the method includes: A first slurry, a second slurry, and a third slurry are provided, wherein the first slurry is used to form a main region, the second slurry is used to form a transition region, and the third slurry is used to form a peripheral region; The composite film is obtained by co-extruding the first slurry, the second slurry, and the third slurry using a three-screw extruder.

9. The method for preparing the composite film according to claim 8, characterized in that, The first slurry and the third slurry are mixed in proportion to form the second slurry.

10. A photovoltaic module, characterized in that, The device includes a battery cell, a composite film, and a backsheet, wherein the battery cell, the composite film, and the backsheet are sequentially laminated together, wherein the composite film is the composite film as described in any one of claims 1-7, or a composite film obtained using the preparation method of the composite film as described in claim 8 or 9.

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