A solar cell integral back sheet and its preparation method

Abstract

The present invention discloses a solar cell integral backsheet and a preparation method thereof, relating to the field of solar cells. The solar cell integral backsheet comprises a weather-resistant layer, a substrate layer, and a bottom layer, arranged sequentially from top to bottom. The weather-resistant layer is made of the following components, by weight: 10-30 parts of PEI, 60-85 parts of PET, 3-12 parts of modified montmorillonite, and 1-5 parts of an additive. The present invention achieves synergistic optimization of weather resistance, mechanical strength, and photoelectric performance through a multi-layer composite structure design. The weather-resistant layer adopts a PEI / PET rigid-flexible composite matrix, combined with an organic-inorganic hybrid barrier constructed of modified montmorillonite, significantly improving UV resistance, moisture and heat resistance, and penetration resistance, effectively suppressing material degradation caused by environmental stress, and providing a long-lasting and reliable protection solution for photovoltaic systems.

Description

Technical Field

[0001] The present invention relates to the field of solar cells, and in particular to an integral solar cell backplane and a preparation method thereof. Background Art

[0002] Solar cells are devices that convert sunlight directly into electricity through the photovoltaic effect of semiconductor materials and are a crucial component of clean energy systems. Currently, mainstream commercial products are based on crystalline silicon cells, whose typical structure includes a cell, upper and lower encapsulation films (such as EVA or POE), a glass cover, and a backsheet. Cells are connected in series or parallel to form a circuit. The encapsulation films bond the layers together and provide buffering protection. The glass cover acts as a light-transmitting protective layer on the front, while the backsheet acts as a back-encapsulation barrier, fulfilling the core functions of isolating moisture, resisting environmental corrosion, maintaining electrical insulation, and maintaining structural stability. Their performance directly impacts the module's output efficiency and lifetime reliability.

[0003] As an integrated system of multi-layer composite materials, solar cell backsheets must simultaneously meet the following core requirements: Weather resistance: long-term protection against extreme environments such as UV radiation (280-400 nm band), high and low temperature cycles (-40°C to 85°C), and humidity and heat (above 85% RH) to prevent material yellowing, embrittlement, and delamination; Mechanical properties: puncture resistance, tensile strength, and dimensional stability to cope with physical shocks such as wind and snow loads and transportation vibrations; Barrier properties: inhibiting water vapor (water vapor permeability <1.5 g / (m²·day)) and oxygen permeation to prevent electrode corrosion and PID effects; Optical properties: reducing light reflection loss to maintain stable module photoelectric conversion efficiency.

[0004] Current mainstream backsheets typically utilize a "sandwich" structure, consisting of a weather-resistant layer, an intermediate adhesive layer (such as polyurethane adhesive), and an insulating layer (such as PET or fluorinated film). The weather-resistant layer, as the first barrier to the environment, requires particularly critical material selection: Polyesters (such as PET) are low-cost and mechanically strong, but exhibit poor UV aging resistance (yellowing due to molecular chain breakage after long-term exposure) and poor resistance to moisture and heat (ester bonds are susceptible to hydrolysis and degradation), with a lifespan typically less than 10 years. Fluoropolymers (such as PVDF and PVF) offer excellent weather resistance and chemical inertness thanks to the high bond energy of the C-H bonds. However, these materials require high processing temperatures (melting temperature > 200°C), poor interfacial adhesion (surface activation treatment is required), and raw material costs are 3-5 times that of PET. Modified composites attempt to balance weather resistance and mechanical properties by adding functional fillers such as nano-montmorillonite and silica to a polymer matrix (such as polyimide). However, physical blending can easily lead to filler agglomeration, stress concentration, and reduced material uniformity.

[0005] CN116948547A discloses a novel white reinforced photovoltaic backplane base film, a preparation method, and its application in photovoltaic cells. The photovoltaic backplane base film includes a weather-resistant layer, an insulating layer, and an adhesive layer from the outside to the inside. The weather-resistant layer is prepared from the following raw materials: PET, modified montmorillonite, and other additives. The mass ratio of modified montmorillonite to PET is (1:99) to (1:19), and the amount of other additives added is 6 to 10 wt% of the total mass of the weather-resistant layer; the insulating layer is PET loaded with modified montmorillonite; and the adhesive layer is a composite material of PET and EVA.

[0006] In recent years, the industry has attempted to optimize backsheet structures through multi-layer co-extrusion and in-situ polymerization techniques, such as developing fluoropolyester composite films or introducing inorganic nanosheets to enhance barrier properties. However, these efforts continue to face technical bottlenecks, such as interlayer thermal expansion coefficient mismatch and weak interfacial bonding. Therefore, constructing a backsheet material system that integrates intrinsic weather resistance, high barrier properties, and strong interfacial bonding has become a technical challenge urgently needed to be overcome in the photovoltaic packaging field. Summary of the Invention

[0007] In order to address the shortcomings of the existing technology, the purpose of the present invention is to provide an integral solar cell backplane and a preparation method thereof. Through a multi-layer composite structure design, the coordinated optimization of weather resistance, mechanical strength and photoelectric performance is achieved. The weather-resistant layer adopts a PEI / PET rigid-flexible composite matrix, combined with an organic-inorganic hybrid barrier constructed with modified montmorillonite, which significantly improves the anti-ultraviolet, anti-humidity and anti-penetration properties, effectively inhibits material degradation caused by environmental stress, and provides a long-term and reliable protection solution for photovoltaic systems.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A solar cell integral backsheet comprises a weather-resistant layer, a substrate layer, and a bottom layer arranged in sequence from top to bottom; the weather-resistant layer is made of the following components by weight: 10-30 parts of PEI, 60-85 parts of PET, 3-12 parts of modified montmorillonite, and 1-5 parts of an additive.

[0010] Preferably, the preparation method of the modified montmorillonite comprises the following steps:

[0011] (1) Dispersing montmorillonite in sulfuric acid solution, mechanically stirring, filtering, and washing to obtain activated montmorillonite; dispersing activated montmorillonite and KH550 in ethanol aqueous solution, adjusting the pH of the system, stirring the reaction, centrifuging, washing, and drying the product to obtain amination montmorillonite;

[0012] Montmorillonite activation and amination: Montmorillonite is treated with sulfuric acid solution to remove interlayer metal cations (such as Na⁺) through proton exchange, expanding the interlayer spacing and exposing surface silanol groups. Subsequently, KH550 silane coupling agent is added. The hydrolysis-generated silanols (-Si-OH) react with the surface hydroxyls of the montmorillonite to form stable Si-O-Si bonds and introduce amino groups (-NH₂) at the termini. This process opens up the interlayer structure of the montmorillonite and functionalizes the surface amino groups, providing active sites for subsequent grafting.

[0013] Preferably, in step (1), the concentration of the sulfuric acid solution is 0.1-0.8 mol / L, the dosage ratio of montmorillonite and sulfuric acid solution is 10 g:300-500 mL; the pH of the system is adjusted to 4.5-5.5 using acetic acid; the dosage ratio of activated montmorillonite, KH550 and ethanol aqueous solution is 10 g:1-3.5 mL:100-150 mL; and the volume ratio of ethanol to water in the ethanol aqueous solution is 3-5:1.

[0014] Preferably, in step (1), the mechanical stirring condition is 60-80° C. for 4-8 h; and the stirring reaction condition is 70-80° C. for 6-10 h.

[0015] (2) adding amination-modified montmorillonite and 3-allyl salicylaldehyde to anhydrous ethanol, stirring the reaction while controlling the pH of the system, centrifuging and washing the product to obtain grafted montmorillonite;

[0016] Schiff base grafting of allyl salicylaldehyde: The surface amino groups (-NH2) of the aminated montmorillonite react with the aldehyde group (-CHO) of 3-allyl salicylaldehyde under weakly acidic conditions to form an imine bond (C=N) while retaining the allyl double bond (C=C). This step anchors the photoresponsive salicylaldehyde structure to the montmorillonite surface through dynamic covalent chemistry and introduces further reactive allyl functional groups, forming a grafted montmorillonite with photosensitivity. The reaction process is as follows:

[0017]

[0018] Preferably, in step (2), the usage ratio of amination montmorillonite, 3-allyl salicylaldehyde, and anhydrous ethanol is 10 g: 2.4-3.6 g: 100-150 mL.

[0019] Preferably, in step (2), the reaction is stirred at 60-70° C. for 6-8 hours, during which the pH of the system is controlled to 6-7 with glacial acetic acid.

[0020] (3) Grafted montmorillonite and 1,1,3,3-tetramethyldisiloxane were added to toluene, and then Karstedt catalyst and BHT inhibitor were added. The temperature was increased stepwise under a nitrogen atmosphere. The product was centrifuged, washed, and dried to obtain modified montmorillonite.

[0021] Hydrosilylation to build a siloxane network: Allyl double bonds (C=C) of the grafted montmorillonite react with the Si-H bonds (Si-H) of 1,1,3,3-tetramethyldisiloxane under platinum catalysis to form Si-C covalent bonds. Meanwhile, a BHT inhibitor suppresses side reactions initiated by free radicals. A step-by-step temperature increase strategy prioritizes the primary reaction between C=C and Si-H, suppressing side reactions with residual amino or imine bonds. Ultimately, a cross-linked siloxane network is constructed on the montmorillonite surface, imparting thermal stability and hydrophobicity to the material.

[0022] Preferably, in step (3), the usage ratio of grafted montmorillonite, 1,1,3,3-tetramethyldisiloxane, toluene, Karstedt catalyst, and BHT inhibitor is 10 g: 3.6-7.2 g: 100-150 mL: 0.1-0.5 mL: 0.01-0.1 g; and the concentration of Karstedt catalyst is 5 wt%.

[0023] Preferably, in step (3), the temperature-raising reaction conditions are: stirring the reaction at 50-70°C for 2-5 hours, and stirring the reaction at 70-90°C for 7-10 hours.

[0024] Preferably, the substrate layer raw material is PET sheet.

[0025] Preferably, the bottom layer raw material is prepared by blending 50-60 parts of homopolypropylene, 50-60 parts of linear low-density polyethylene, and 5-10 parts of maleic anhydride polyethylene graft, granulating the mixture, drying the mixture, and injection molding the mixture into sheets.

[0026] Preferably, the homopolypropylene has a melt index of 5 to 12 g / 10 min at 230° C. and 2.16 kg.

[0027] Preferably, the linear low-density polyethylene has a melt index of 0.6-2 g / 10 min at 190° C. and 2.16 kg.

[0028] Preferably, the maleic anhydride polyethylene graft has a melt index of 0.1-0.5 g / 10 min at 190° C. and 2.16 kg.

[0029] The thickness of the weather-resistant layer is 10-50 μm, the thickness of the substrate layer is 100-300 μm, and the thickness of the bottom layer is 10-100 μm;

[0030] Preferably, the method for preparing the weather-resistant layer raw materials is: blending the raw materials into granules, drying the granules, and injection molding the granules into sheets.

[0031] The auxiliary agent is one or more of a dispersant, a leveling agent, and a defoaming agent.

[0032] The present invention also claims protection for a method for preparing the integral back panel of the solar cell, comprising the following steps: transporting the weather-resistant layer, substrate layer, and bottom layer raw materials to a back panel co-extrusion production line, extruding through a mold to obtain a sheet-like melt, and then cooling, shaping, winding or cutting to obtain the integral back panel of the solar cell.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. The present invention provides an integral solar cell backplane, which achieves performance optimization through a multi-layer composite structure: the weather-resistant layer uses PEI and PET as a matrix to form a rigid and flexible protection system. PEI, with its inherent high-temperature resistance and UV resistance, effectively resists thermal oxidative aging and UV radiation in long-term outdoor environments; PET provides mechanical support through the regular arrangement of molecular chains, inhibiting deformation of the substrate. The introduction of modified montmorillonite constructs an organic-inorganic hybrid structure through chemical modification, and its nanosheets form a dense physical barrier in the matrix, synergistically improving UV resistance, high-temperature resistance, and anti-permeability. The additive system optimizes processing fluidity, ensures a dense and smooth surface of the weather-resistant layer, reduces light scattering losses, and thus maintains the stability of the photoelectric conversion efficiency of the photovoltaic module.

[0035] 2. This invention provides a modified montmorillonite clay that combines acid-activated layer expansion with silane coupling agent grafting to increase the density of interlayer active sites and surface reactivity. Allyl salicylaldehyde introduced by a Schiff base reaction condenses with the aldehyde group via amino groups to form an imine bond (C=N). Its ortho-hydroxyl group and the imine nitrogen atom form a rigid six-membered ring via intramolecular hydrogen bonding. This cyclic conjugated structure broadens the UV absorption spectrum and converts UV light energy into low-energy thermal energy through π-electron delocalization. Simultaneously, the hydrogen bonding network inhibits the generation of excited-state free radicals, blocking the photooxidative chain reaction at its source. The organosilicon segments (Si-O / Si-C bonds) introduced by hydrosilylation not only inhibit thermal oxidative aging through their highly thermally stable backbone and hydrophobic crosslinking network, but also their flexible siloxane segments reduce surface energy, improving the dispersion of the montmorillonite flakes in the matrix, reducing agglomeration, and enhancing interfacial bonding. This multi-scale modification transforms montmorillonite from a traditional filler into a functional carrier, achieving mechanical enhancement, environmental adaptability regulation and long-term durability improvement in the backplane at the same time, providing guarantee for long-term stable service under complex working conditions such as extreme humidity and heat, and alternating temperature differences. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the embodiments. Of course, the specific embodiments described here are only used to explain the present invention and are not used to limit the present invention.

[0037] Unless otherwise specified, the chemical reagents and materials in the present invention are purchased from commercial sources or synthesized from commercially purchased raw materials.

[0038] Karstedt catalyst was purchased from Shanghai MacLean Biochemical Technology Co., Ltd.;

[0039] BHT inhibitor was purchased from Nanjing Pasteur Chemical Co., Ltd.;

[0040] PEI is polyetherimide, purchased from SABIC, brand Ultem2310-1000;

[0041] PET was purchased from DuPont, USA, model FC51;

[0042] Homopolymer polypropylene was Sanren F850EA (On-spec.) from Shanghai Petrochemical;

[0043] The linear low-density polyethylene model is TAISOX 2410;

[0044] The brand of maleic anhydride polyethylene grafted compound is ADMER™ AT2235E.

[0045] A method for preparing an integral solar cell backsheet comprises the following steps:

[0046] (1) Disperse 10 g of montmorillonite in 300-500 mL of 0.1-0.8 mol / L sulfuric acid solution, stir mechanically at 60-80 °C for 4-8 h, filter and wash to obtain activated montmorillonite; disperse 10 g of activated montmorillonite and 1-3.5 mL of KH550 in 100-150 mL of ethanol aqueous solution (the volume ratio of ethanol to water is 3-5:1), adjust the pH of the system to 4.5-5.5 with acetic acid, stir and react at 70-80 °C for 6-10 h, centrifuge, wash and dry the product to obtain amino montmorillonite;

[0047] (2) Add 10 g of amination-modified montmorillonite and 2.4-3.6 g of 3-allyl salicylaldehyde to 100-150 mL of anhydrous ethanol, stir and react at 60-70 °C for 6-8 h, during which the pH of the system is controlled to 6-7 with glacial acetic acid. Centrifuge and wash the product to obtain grafted montmorillonite.

[0048] (3) 10 g of grafted montmorillonite and 3.6-7.2 g of 1,1,3,3-tetramethyldisiloxane were added to 100-150 mL of toluene, and then 0.1-0.5 mL of 5 wt% Karstedt catalyst and 0.01-0.1 g of BHT inhibitor were added. The mixture was stirred at 50-70 °C in a nitrogen atmosphere for 2-5 h and at 70-90 °C for 7-10 h. The product was centrifuged, washed, and dried to obtain modified montmorillonite.

[0049] (4) 10-30 parts of PEI, 60-85 parts of PET, 3-12 parts of modified montmorillonite and 1-5 parts of auxiliary agent are blended and granulated, dried and injection-molded into sheets to obtain weather-resistant layer raw materials; 50-60 parts of homopolypropylene, 50-60 parts of linear low-density polyethylene and 5-10 parts of maleic anhydride polyethylene graft are blended and granulated, dried and injection-molded into sheets to obtain bottom layer raw materials; the weather-resistant layer, substrate layer and bottom layer raw materials are transported to the backplane co-extrusion production line, extruded through a mold to obtain a sheet melt, and after cooling, shaping, winding or cutting, the integrated solar cell backplane is obtained.

[0050] The auxiliary agent is one or more of a dispersant, a leveling agent, and a defoaming agent.

[0051] The thickness of the weather-resistant layer is 10-50 μm, the thickness of the base material layer is 100-300 μm, and the thickness of the bottom layer is 10-100 μm.

[0052] The present invention will be further described below with reference to specific examples. Example 1

[0053] A method for preparing an integral solar cell backsheet comprises the following steps:

[0054] (1) Disperse 10 g of montmorillonite in 500 mL of 0.5 mol / L sulfuric acid solution, stir mechanically at 70 °C for 6 h, filter and wash to obtain activated montmorillonite; disperse 10 g of activated montmorillonite and 3.5 mL of KH550 in 150 mL of ethanol-water solution (the volume ratio of ethanol to water is 4:1), adjust the pH of the system to 5.0 with acetic acid, stir and react at 80 °C for 6 h, centrifuge, wash and dry the product to obtain amino montmorillonite;

[0055] (2) 10 g of amination-modified montmorillonite and 3.6 g of 3-allyl salicylaldehyde were added to 150 mL of anhydrous ethanol and stirred at 70 °C for 6 h. During this period, the pH of the system was controlled to 6.5 with glacial acetic acid. The product was centrifuged and washed to obtain grafted montmorillonite.

[0056] (3) 10 g of grafted montmorillonite and 7.2 g of 1,1,3,3-tetramethyldisiloxane were added to 150 mL of toluene, and then 0.5 mL of 5 wt% Karstedt catalyst and 0.1 g of BHT inhibitor were added. The mixture was stirred at 70 °C for 2 h and at 90 °C for 7 h under a nitrogen atmosphere. The product was centrifuged, washed, and dried to obtain modified montmorillonite.

[0057] (4) 300 g of PEI, 850 g of PET, 120 g of modified montmorillonite, and 50 g of an auxiliary agent are blended and granulated, dried, and injection-molded into sheets to obtain a weather-resistant layer raw material; 600 g of homopolymer polypropylene, 500 g of linear low-density polyethylene, and 80 g of maleic anhydride polyethylene graft are blended and granulated, dried, and injection-molded into sheets to obtain a bottom layer raw material; the weather-resistant layer, substrate layer, and bottom layer raw material are transported to a backplane co-extrusion production line, extruded through a mold to obtain a sheet melt, and after cooling, shaping, and winding, the integrated solar cell backplane is obtained.

[0058] The auxiliary agent is obtained by mixing a dispersant Digo 760W, a leveling agent BYK-346, and a defoaming agent BYK-028 in a weight ratio of 2:1:1.

[0059] The thickness of the weather-resistant layer is 30 μm, the thickness of the substrate layer is 200 μm, and the thickness of the bottom layer is 50 μm. Example 2

[0060] A method for preparing an integral solar cell backsheet comprises the following steps:

[0061] (1) Disperse 10 g of montmorillonite in 500 mL of 0.5 mol / L sulfuric acid solution, stir mechanically at 70 °C for 6 h, filter and wash to obtain activated montmorillonite; disperse 10 g of activated montmorillonite and 3.0 mL of KH550 in 150 mL of ethanol-water solution (the volume ratio of ethanol to water is 4:1), adjust the pH of the system to 5.0 with acetic acid, stir and react at 75 °C for 8 h, centrifuge, wash and dry the product to obtain amino montmorillonite;

[0062] (2) 10 g of amination-modified montmorillonite and 3.2 g of 3-allyl salicylaldehyde were added to 150 mL of anhydrous ethanol and stirred at 65 °C for 7 h. During this period, the pH of the system was controlled to 6.5 with glacial acetic acid. The product was centrifuged and washed to obtain grafted montmorillonite.

[0063] (3) 10 g of grafted montmorillonite and 6.0 g of 1,1,3,3-tetramethyldisiloxane were added to 150 mL of toluene, and then 0.4 mL of 5 wt% Karstedt catalyst and 0.06 g of BHT inhibitor were added. The mixture was stirred at 64 °C for 3 h and at 84 °C for 8 h under a nitrogen atmosphere. The product was centrifuged, washed, and dried to obtain modified montmorillonite.

[0064] (4) 240 g of PEI, 800 g of PET, 90 g of modified montmorillonite, and 40 g of an auxiliary agent are blended and granulated, dried, and injection-molded into sheets to obtain a weather-resistant layer raw material; 600 g of homopolypropylene, 500 g of linear low-density polyethylene, and 80 g of maleic anhydride polyethylene graft are blended and granulated, dried, and injection-molded into sheets to obtain a bottom layer raw material; the weather-resistant layer, substrate layer, and bottom layer raw material are transported to a backplane co-extrusion production line, extruded through a mold to obtain a sheet melt, and after cooling, shaping, and winding, the integrated solar cell backplane is obtained.

[0065] The auxiliary agent is obtained by mixing a dispersant Digo 760W, a leveling agent BYK-346, and a defoaming agent BYK-028 in a weight ratio of 2:1:1.

[0066] The thickness of the weather-resistant layer is 30 μm, the thickness of the substrate layer is 200 μm, and the thickness of the bottom layer is 50 μm. Example 3

[0067] A method for preparing an integral solar cell backsheet comprises the following steps:

[0068] (1) Disperse 10 g of montmorillonite in 500 mL of 0.5 mol / L sulfuric acid solution, stir mechanically at 70 °C for 6 h, filter and wash to obtain activated montmorillonite; disperse 10 g of activated montmorillonite and 2 mL of KH550 in 150 mL of ethanol-water solution (the volume ratio of ethanol to water is 4:1), adjust the pH of the system to 5.0 with acetic acid, stir and react at 75 °C for 8 h, centrifuge, wash and dry the product to obtain amino montmorillonite;

[0069] (2) 10 g of amination-modified montmorillonite and 2.8 g of 3-allyl salicylaldehyde were added to 150 mL of anhydrous ethanol and stirred at 65 °C for 7 h. During this period, the pH of the system was controlled to 6.5 with glacial acetic acid. The product was centrifuged and washed to obtain grafted montmorillonite.

[0070] (3) 10 g of grafted montmorillonite and 4.8 g of 1,1,3,3-tetramethyldisiloxane were added to 150 mL of toluene, and then 0.3 mL of 5 wt% Karstedt catalyst and 0.04 g of BHT inhibitor were added. The mixture was stirred at 55 °C for 4 h and at 75 °C for 9 h under a nitrogen atmosphere. The product was centrifuged, washed, and dried to obtain modified montmorillonite.

[0071] (4) 150 g of PEI, 700 g of PET, 60 g of modified montmorillonite, and 30 g of an auxiliary agent are blended and granulated, dried, and injection-molded into sheets to obtain a weather-resistant layer raw material; 600 g of homopolypropylene, 500 g of linear low-density polyethylene, and 80 g of maleic anhydride polyethylene graft are blended and granulated, dried, and injection-molded into sheets to obtain a bottom layer raw material; the weather-resistant layer, substrate layer, and bottom layer raw material are transported to a backplane co-extrusion production line, extruded through a mold to obtain a sheet melt, and cooled, shaped, and rolled to obtain the integral solar cell backplane.

[0072] The auxiliary agent is obtained by mixing a dispersant Digo 760W, a leveling agent BYK-346, and a defoaming agent BYK-028 in a weight ratio of 2:1:1.

[0073] The thickness of the weather-resistant layer is 30 μm, the thickness of the substrate layer is 200 μm, and the thickness of the bottom layer is 50 μm. Example 4

[0074] A method for preparing an integral solar cell backsheet comprises the following steps:

[0075] (1) Disperse 10 g of montmorillonite in 500 mL of 0.5 mol / L sulfuric acid solution, stir mechanically at 70 °C for 6 h, filter and wash to obtain activated montmorillonite; disperse 10 g of activated montmorillonite and 1 mL of KH550 in 150 mL of ethanol-water solution (the volume ratio of ethanol to water is 4:1), adjust the pH of the system to 5.0 with acetic acid, stir and react at 70 °C for 10 h, centrifuge, wash and dry the product to obtain amino montmorillonite;

[0076] (2) 10 g of amination-modified montmorillonite and 2.4 g of 3-allyl salicylaldehyde were added to 150 mL of anhydrous ethanol and stirred at 60 °C for 8 h. During this period, the pH of the system was controlled to 6.5 with glacial acetic acid. The product was centrifuged and washed to obtain grafted montmorillonite.

[0077] (3) 10 g of grafted montmorillonite and 3.6 g of 1,1,3,3-tetramethyldisiloxane were added to 150 mL of toluene, and then 0.1 mL of 5 wt% Karstedt catalyst and 0.01 g of BHT inhibitor were added. The mixture was stirred at 50 °C for 5 h and at 70 °C for 10 h under a nitrogen atmosphere. The product was centrifuged, washed, and dried to obtain modified montmorillonite.

[0078] (4) 100 g of PEI, 600 g of PET, 30 g of modified montmorillonite, and 10 g of an auxiliary agent are blended and granulated, dried, and injection-molded into sheets to obtain a weather-resistant layer raw material; 600 g of homopolypropylene, 500 g of linear low-density polyethylene, and 80 g of maleic anhydride polyethylene graft are blended and granulated, dried, and injection-molded into sheets to obtain a bottom layer raw material; the weather-resistant layer, substrate layer, and bottom layer raw material are transported to a backplane co-extrusion production line, extruded through a mold to obtain a sheet melt, and cooled, shaped, and rolled to obtain the integral solar cell backplane.

[0079] The auxiliary agent is obtained by mixing a dispersant Digo 760W, a leveling agent BYK-346, and a defoaming agent BYK-028 in a weight ratio of 2:1:1.

[0080] The thickness of the weather-resistant layer is 30 μm, the thickness of the substrate layer is 200 μm, and the thickness of the bottom layer is 50 μm.

[0081] Comparative Example 1

[0082] A method for preparing an integral solar cell backsheet comprises the following steps:

[0083] (1) Disperse 10 g of montmorillonite in 500 mL of 0.5 mol / L sulfuric acid solution, stir mechanically at 70 °C for 6 h, filter and wash to obtain activated montmorillonite; disperse 10 g of activated montmorillonite and 3.5 mL of KH550 in 150 mL of ethanol-water solution (the volume ratio of ethanol to water is 4:1), adjust the pH of the system to 5.0 with acetic acid, stir and react at 80 °C for 6 h, centrifuge, wash and dry the product to obtain amino montmorillonite;

[0084] (2) 10 g of amination-modified montmorillonite and 3.6 g of 3-allyl salicylaldehyde were added to 150 mL of anhydrous ethanol and stirred at 70 °C for 6 h. During this period, the pH of the system was controlled to 6.5 with glacial acetic acid. The product was centrifuged and washed to obtain grafted montmorillonite.

[0085] (3) 300 g of PEI, 850 g of PET, 120 g of grafted montmorillonite, and 50 g of an auxiliary agent are blended and granulated, dried, and injection-molded into sheets to obtain a weather-resistant layer raw material; 600 g of homopolypropylene, 500 g of linear low-density polyethylene, and 80 g of maleic anhydride polyethylene graft are blended and granulated, dried, and injection-molded into sheets to obtain a bottom layer raw material; the weather-resistant layer, substrate layer, and bottom layer raw material are transported to a backplane co-extrusion production line, extruded through a mold to obtain a sheet melt, and after cooling, shaping, and winding, the integrated solar cell backplane is obtained.

[0086] The auxiliary agent is obtained by mixing a dispersant Digo 760W, a leveling agent BYK-346, and a defoaming agent BYK-028 in a weight ratio of 2:1:1.

[0087] The thickness of the weather-resistant layer is 30 μm, the thickness of the substrate layer is 200 μm, and the thickness of the bottom layer is 50 μm.

[0088] Comparative Example 2

[0089] A method for preparing an integral solar cell backsheet comprises the following steps:

[0090] (1) Disperse 10 g of montmorillonite in 500 mL of 0.5 mol / L sulfuric acid solution, stir mechanically at 70 °C for 6 h, filter and wash to obtain activated montmorillonite; disperse 10 g of activated montmorillonite and 3.5 mL of KH550 in 150 mL of ethanol-water solution (the volume ratio of ethanol to water is 4:1), adjust the pH of the system to 5.0 with acetic acid, stir and react at 80 °C for 6 h, centrifuge, wash and dry the product to obtain amino montmorillonite;

[0091] (2) 300 g of PEI, 850 g of PET, 120 g of amino-modified montmorillonite, and 50 g of an auxiliary agent are blended and granulated, dried, and injection-molded into sheets to obtain a weather-resistant layer raw material; 600 g of homopolymer polypropylene, 500 g of linear low-density polyethylene, and 80 g of maleic anhydride polyethylene graft are blended and granulated, dried, and injection-molded into sheets to obtain a bottom layer raw material; the weather-resistant layer, substrate layer, and bottom layer raw material are transported to a backplane co-extrusion production line, extruded through a mold to obtain a sheet melt, and cooled, shaped, and rolled to obtain the integral solar cell backplane.

[0092] The auxiliary agent is obtained by mixing a dispersant Digo 760W, a leveling agent BYK-346, and a defoaming agent BYK-028 in a weight ratio of 2:1:1.

[0093] The thickness of the weather-resistant layer is 30 μm, the thickness of the substrate layer is 200 μm, and the thickness of the bottom layer is 50 μm.

[0094] The weather-resistant layers prepared in Examples 1 to 4 and Comparative Examples 1 to 2 were subjected to performance tests. Mechanical properties were measured using a universal tensile testing machine with a load of 5 kN. The tensile strength and elongation at break were measured in accordance with GB / T 1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets". An aging test was also conducted in a xenon lamp weathering test chamber. The samples were placed in the test chamber and the aging temperature was set at 55°C, the humidity was 70%, and the irradiation intensity was 280 w / m 2The samples were subjected to accelerated aging at a distance of 20 cm in a simulated light environment for 30 days. The tensile strength and elongation at break were then tested after aging. Yellowing of the weathering layer was tested at 110°C for 72 hours according to ASTM E313. After 96 hours of artificial accelerated aging in hot air at 85°C, the heat aging resistance of each weathering layer material was measured by the retention of tensile strength; a higher value indicates better heat aging resistance. Water vapor transmission rate (WVT) was also tested according to GB / T 26253-2010, "Plastic Film and Sheeting—Determination of Water Vapor Transmission Rate—Infrared Detector Method." Specific data are shown in Table 1.

[0095] Table 1 Performance test results of weather-resistant layer products

[0096]

[0097] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A solar cell backsheet, comprising a weather-resistant layer, a substrate layer, and a bottom layer arranged in sequence from top to bottom; characterized in that: The weather-resistant layer is made of the following components in parts by weight: 10-30 parts of PEI, 60-85 parts of PET, 3-12 parts of modified montmorillonite, and 1-5 parts of additives; The preparation method of the modified montmorillonite comprises the following steps: (1) dispersing montmorillonite in a sulfuric acid solution, mechanically stirring, filtering, and washing to obtain activated montmorillonite, dispersing the activated montmorillonite and KH550 in an ethanol aqueous solution, adjusting the pH of the system, stirring the reaction, centrifuging, washing, and drying the product to obtain an amination montmorillonite; (2) adding amination-modified montmorillonite and 3-allyl salicylaldehyde to anhydrous ethanol, stirring the reaction while controlling the pH of the system, centrifuging and washing the product to obtain grafted montmorillonite; (3) Grafted montmorillonite and 1,1,3,3-tetramethyldisiloxane were added to toluene, and then Karstedt catalyst and BHT inhibitor were added. The temperature was increased stepwise under a nitrogen atmosphere. The product was centrifuged, washed, and dried to obtain modified montmorillonite.

2. The solar cell integral back sheet according to claim 1, characterized in that: In step (1), the concentration of the sulfuric acid solution is 0.1-0.8 mol / L, the dosage ratio of montmorillonite and sulfuric acid solution is 10 g: 300-500 mL; the pH of the system is adjusted to 4.5-5.5 with acetic acid; the dosage ratio of activated montmorillonite, KH550 and ethanol aqueous solution is 10 g: 1-3.5 mL: 100-150 mL; and the volume ratio of ethanol to water in the ethanol aqueous solution is 3-5:

1.

3. The solar cell integral back sheet according to claim 1, characterized in that: In step (1), the mechanical stirring condition is mechanical stirring at 60-80° C. for 4-8 h; and the stirring reaction condition is stirring reaction at 70-80° C. for 6-10 h.

4. The solar cell integral back sheet according to claim 1, characterized in that: In step (2), the usage ratio of amination montmorillonite, 3-allyl salicylaldehyde and anhydrous ethanol is 10 g: 2.4-3.6 g: 100-150 mL.

5. The solar cell integral back sheet according to claim 1, characterized in that: In step (2), the reaction is stirred at 60-70° C. for 6-8 h, during which the pH of the system is controlled to 6-7 with glacial acetic acid.

6. The solar cell integral back sheet according to claim 1, characterized in that: In step (3), the usage ratio of grafted montmorillonite, 1,1,3,3-tetramethyldisiloxane, toluene, Karstedt catalyst, and BHT inhibitor is 10 g: 3.6-7.2 g: 100-150 mL: 0.1-0.5 mL: 0.01-0.1 g; and the concentration of Karstedt catalyst is 5 wt%.

7. The solar cell integral back sheet according to claim 1, characterized in that: In step (3), the temperature reaction conditions are: stirring the reaction at 50-70°C for 2-5 hours, and stirring the reaction at 70-90°C for 7-10 hours.

8. The solar cell integral back sheet according to claim 1, characterized in that: The thickness of the weather-resistant layer is 10-50 μm, the thickness of the base material layer is 100-300 μm, and the thickness of the bottom layer is 10-100 μm. The preparation method of the weather-resistant layer raw materials is: blending and granulating the raw materials, drying them, and injection molding them into sheets.

9. A method for preparing the integral solar cell back sheet according to any one of claims 1 to 8, characterized in that: The method comprises the following steps: transporting the weather-resistant layer, the substrate layer and the bottom layer raw materials to the backboard co-extrusion production line, extruding through a mold to obtain a sheet-like melt, and obtaining the solar cell integral backboard after cooling, shaping, winding or cutting.

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