Solar cell integral backboard and preparation method thereof

Abstract

The invention discloses a solar cell overall backboard and a preparation method thereof, and relates to the field of solar cells, the solar cell overall backboard comprises a weather-proof layer, a base material layer and a bottom layer which are sequentially arranged from top to bottom, and the weather-proof layer is prepared from 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 an auxiliary agent; through the design of a multi-layer composite structure, collaborative optimization of weather resistance, mechanical strength and photoelectric performance is achieved, the weather-resistant layer adopts a PEI / PET rigid-flexible composite matrix and is combined with an organic-inorganic hybrid barrier constructed by modified montmorillonite, the ultraviolet resistance, damp-heat resistance and permeation resistance are remarkably improved, material degradation caused by environmental stress is effectively inhibited, and the service life of the weather-resistant layer is prolonged. And a long-acting and reliable protection solution is provided for a photovoltaic system.

Description

Technical Field

[0001] The present invention relates to the field of solar cells, and particularly to an overall backsheet for a solar cell and a preparation method thereof. Background Art

[0002] A solar cell is a device that directly converts solar energy into electrical energy through the photovoltaic effect of semiconductor materials and is an important component of a clean energy system. Currently, the mainstream commercial products are mainly crystalline silicon cells, and their typical structure includes cell wafers, upper and lower encapsulation films (such as EVA or POE), a glass cover plate, and a backsheet. The cell wafers form a circuit through series / parallel connection. The encapsulation film is responsible for bonding each layer and providing buffer protection. The glass cover plate serves as a front light-transmitting protective layer, while the backsheet serves as a back encapsulation barrier, undertaking the core functions of isolating moisture, resisting environmental erosion, maintaining electrical insulation, and structural stability. Its performance directly affects the output efficiency and full-life cycle reliability of the module.

[0003] As an integrated system of a multi-layer composite material, the backsheet of a solar cell needs to simultaneously meet the following core requirements: weather resistance protection: long-term resistance to extreme environments such as ultraviolet (280 - 400 nm band) irradiation, high and low temperature cycling (-40°C to 85°C), and humidity (above 85% RH), to avoid yellowing, embrittlement, and delamination of materials; mechanical properties: having puncture resistance, tensile strength, and dimensional stability to cope with physical impacts such as wind and snow loads and transportation vibrations; barrier properties: inhibiting the penetration of moisture (water vapor transmission rate < 1.5 g / (m²·day)) and oxygen to prevent electrode corrosion and PID effects; optical properties: reducing light reflection loss and maintaining the stability of the photoelectric conversion efficiency of the module.

[0004] The current mainstream backsheets usually adopt a "sandwich" structure design, which includes a weather-resistant layer, an intermediate adhesive layer (such as polyurethane glue), and an insulating layer (such as PET or fluorine-containing film) from the outside to the inside. Among them, the weather-resistant layer, as the first barrier facing the environment, is particularly crucial in material selection: polyester (such as PET): low cost and high mechanical strength, but poor ultraviolet aging resistance (molecular chain breakage leads to yellowing after long-term exposure) and weak humidity resistance (ester bonds are easily hydrolyzed and degraded), and the service life is usually less than 10 years; fluorine-containing polymers (such as PVDF, PVF): excellent weather resistance and chemical inertness are achieved by virtue of the high bond energy of the C-F bond, but the processing temperature is high (melting temperature > 200°C), the interfacial adhesion is poor (surface activation treatment is required), and the raw material cost is 3 - 5 times that of PET; modified composite materials: by adding functional fillers such as nano-montmorillonite and silica in a polymer matrix (such as polyimide), an attempt is made to balance weather resistance and mechanical properties, but physical blending easily leads to filler agglomeration and stress concentration, reducing the material homogeneity.

[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)~(1:19), and the addition amount of other additives is 6~10wt% 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 tried to optimize the backplane structure through multi-layer co-extrusion, in-situ polymerization and other technologies, such as developing fluorine-polyester composite films or introducing inorganic nanosheets to improve barrier properties, but it still faces technical bottlenecks such as mismatch in thermal expansion coefficients between layers and weak interface bonding. Therefore, building a backplane material system that integrates intrinsic weather resistance, high barrier, and strong interface bonding has become a technical difficulty that needs to be broken through in the field of photovoltaic packaging. Summary of the invention

[0007] In order to address the deficiencies in the prior art, 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 solution:

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

[0010] Preferably, 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 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; Activation and amination of montmorillonite: Montmorillonite is treated with sulfuric acid solution to remove the interlayer metal cations (such as Na⁺) through proton exchange, expand the interlayer spacing, and expose the surface silanol groups. Subsequently, KH550 silane coupling agent is added, and the silanol (-Si-OH) generated by its hydrolysis undergoes a condensation reaction with the surface hydroxyl groups of montmorillonite to form stable Si-O-Si bonds, and at the same time introduce amino groups (-NH2) at the end. This process realizes the opening of the interlayer structure of montmorillonite and the surface amino functionalization, providing active sites for subsequent grafting.

[0011] Preferably, in step (1), the concentration of the sulfuric acid solution is 0.1 - 0.8 mol / L, and the dosage ratio of montmorillonite to the sulfuric acid solution is 10 g: 300 - 500 mL; the specific adjustment of the system pH is to adjust the system pH to 4.5 - 5.5 with acetic acid; the dosage ratio of the activated montmorillonite, KH550 and the ethanol aqueous solution is 10 g: 1 - 3.5 mL: 100 - 150 mL; the volume ratio of ethanol to water in the ethanol aqueous solution is 3 - 5: 1.

[0012] Preferably, in step (1), the mechanical stirring condition is mechanical stirring at 60 - 80 °C for 4 - 8 h; the stirring reaction condition is stirring reaction at 70 - 80 °C for 6 - 10 h.

[0013] (2) Add the aminated montmorillonite and 3-allylsalicylaldehyde into absolute ethanol, stir and react while controlling the system pH, and centrifuge and wash the product to obtain the grafted montmorillonite; Schiff base grafted with allylsalicylaldehyde: The surface amino groups (-NH2) of the aminated montmorillonite and the aldehyde groups (-CHO) of 3-allylsalicylaldehyde undergo a condensation reaction under weak acidic conditions to form imine bonds (C=N), while retaining the allyl double bond (C=C). This step anchors the photo-responsive salicylaldehyde structure on the surface of montmorillonite through dynamic covalent chemistry and introduces allyl functional groups that can further react to form grafted montmorillonite with photosensitive properties. The reaction process is as follows:

[0014] Preferably, in step (2), the dosage ratio of the aminated montmorillonite, 3-allylsalicylaldehyde and absolute ethanol is 10 g: 2.4 - 3.6 g: 100 - 150 mL.

[0015] Preferably, in step (2), stir and react at 60 - 70 °C for 6 - 8 h, and control the system pH to 6 - 7 with glacial acetic acid during the reaction.

[0016] (3) Add the grafted montmorillonite and 1,1,3,3-tetramethyldisiloxane into toluene, then add Karstedt catalyst and BHT inhibitor, and carry out a stepwise temperature-raising reaction under a nitrogen atmosphere. Centrifuge, wash and dry the product to obtain the modified montmorillonite.

[0017] Constructing a silicone oxygen network by hydrosilylation: The allyl double bond (C=C) grafted on montmorillonite reacts with the silicon-hydrogen bond (Si-H) of 1,1,3,3-tetramethyldisiloxane under the catalysis of platinum to form a Si-C covalent bond. Meanwhile, the BHT inhibitor inhibits the side reactions initiated by free radicals. The stepwise temperature-rising strategy preferentially promotes the main reaction of C=C and Si-H and inhibits the side reactions of residual amino or imine bonds, ultimately constructing a crosslinked silicone oxygen network on the surface of montmorillonite, endowing the material with thermal stability and hydrophobicity.

[0018] Preferably, in step (3), the dosage ratio of the 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; the concentration of the Karstedt catalyst is 5 wt%.

[0019] Preferably, in step (3), the temperature-rising reaction conditions are stirring and reacting for 2 - 5 h at 50 - 70 °C and stirring and reacting for 7 - 10 h at 70 - 90 °C.

[0020] Preferably, the raw material of the substrate layer is a PET sheet.

[0021] Preferably, the preparation method of the raw material of the bottom layer is: blending 50 - 60 parts of homopolypropylene, 50 - 60 parts of linear low-density polyethylene, and 5 - 10 parts of maleic anhydride-grafted polyethylene, granulating by blending, drying, and then injection molding into sheets.

[0022] Preferably, the melt index of the homopolypropylene under the conditions of 230 °C and 2.16 kg is 5 - 12 g / 10 min.

[0023] Preferably, the melt index of the linear low-density polyethylene under the conditions of 190 °C and 2.16 kg is 0.6 - 2 g / 10 min.

[0024] Preferably, the melt index of the maleic anhydride-grafted polyethylene under the conditions of 190 °C and 2.16 kg is 0.1 - 0.5 g / 10 min.

[0025] 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; Preferably, the preparation method of the raw material of the weather-resistant layer is: blending the raw materials, granulating by blending, drying, and then injection molding into sheets.

[0026] The auxiliary agent is one or more of a dispersant, a leveling agent, and an antifoaming agent.

[0027] The present invention also claims to protect a method for preparing the overall backsheet of the solar cell, comprising the following steps: feeding the weather-resistant layer, the substrate layer, and the bottom layer raw materials into a backsheet co-extrusion production line, extruding through a die to obtain a sheet-shaped melt, and obtaining the overall backsheet of the solar cell after cooling and shaping, winding or cutting.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. The present invention provides an overall backsheet for a solar cell, and the performance of the backsheet of the solar cell is optimized through a multi-layer composite structure: the weather-resistant layer is based on PEI and PET to form a protection system that combines rigidity and flexibility. Due to its intrinsic high temperature resistance and ultraviolet resistance, PEI effectively resists thermal-oxidative aging and ultraviolet irradiation in the long-term outdoor environment; PET provides mechanical support through the regular arrangement of molecular chains to inhibit the 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 ultraviolet resistance, high temperature resistance, and impermeability. The additive system optimizes the processing fluidity, ensures the surface of the weather-resistant layer is dense and flat, reduces light scattering loss, and thus maintains the stability of the photoelectric conversion efficiency of the photovoltaic module.

[0030] 2. The present invention provides a modified montmorillonite, which combines acid activation and expansion with silane coupling agent grafting to increase the density of active sites between layers and surface reaction activity; allylsalicylaldehyde introduced by Schiff base reaction forms an imine bond (C=N) through the condensation of amino group and aldehyde group, and its adjacent hydroxyl group and imine nitrogen atom construct a rigid six-membered ring through intramolecular hydrogen bonding. This cyclic conjugated structure can broaden the ultraviolet absorption spectrum range, convert ultraviolet light energy into low-energy thermal energy through the π-electron delocalization effect, and at the same time, the hydrogen bond network inhibits the generation of excited-state free radicals, blocking the photooxidation chain reaction from the source. The organosilicon segments (Si-O / Si-C bonds) introduced by hydrosilylation not only inhibit thermal-oxidative aging through a high thermal stability skeleton and a hydrophobic crosslinked network, but also its flexible siloxane segments can reduce the surface energy, improve the dispersion of montmorillonite sheets in the matrix, reduce aggregation and enhance the interfacial binding force. This multi-scale modification transforms montmorillonite from a traditional filler into a functional carrier, realizing mechanical enhancement, environmental adaptability regulation, and long-term durability improvement in the backsheet, providing guarantee for long-term stable service under complex working conditions such as extreme humidity, heat, and alternating temperature differences. Specific Embodiments

[0031] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the following further elaborates on the present invention in conjunction with embodiments. Of course, the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0032] Unless otherwise specified, the chemical reagents and materials in the present invention are purchased through market channels or synthesized from raw materials purchased through market channels.

[0033] The Karstedt catalyst was purchased from Shanghai Macklin Biochemical Co., Ltd.; The BHT inhibitor was purchased from Nanjing Pasteur Chemical Co., Ltd.; PEI is polyetherimide and was purchased from SABIC, with the grade of Ultem2310 - 1000; PET was purchased from DuPont in the United States, with the model of FC51; The homopolypropylene is Sanren F850EA (On - spec.) from Shanghai Petrochemical; The linear low - density polyethylene has the model of TAISOX 2410; The maleic anhydride - type polyethylene grafted product has the grade of ADMERTM AT2235E.

[0034] A preparation method of an overall backplane for a solar cell, comprising the following steps: (1) Disperse 10 g of montmorillonite into 300 - 500 mL of 0.1 - 0.8 mol / L sulfuric acid solution, mechanically stir 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 into 100 - 150 mL of an ethanol - water 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 - functionalized montmorillonite; (2) Add 10 g of amino - functionalized montmorillonite and 2.4 - 3.6 g of 3 - allylsalicylaldehyde to 100 - 150 mL of absolute ethanol, stir and react at 60 - 70 °C for 6 - 8 h, and control the pH of the system to 6 - 7 with glacial acetic acid during the process, centrifuge and wash the product to obtain grafted montmorillonite; (3) Add 10 g of grafted montmorillonite and 3.6 - 7.2 g of 1,1,3,3 - tetramethyldisiloxane to 100 - 150 mL of toluene, then add 0.1 - 0.5 mL of 5 wt% Karstedt catalyst and 0.01 - 0.1 g of BHT inhibitor, stir and react at 50 - 70 °C for 2 - 5 h and at 70 - 90 °C for 7 - 10 h under a nitrogen atmosphere, centrifuge, wash and dry the product to obtain modified montmorillonite; (4) Blend 10 - 30 parts of PEI, 60 - 85 parts of PET, 3 - 12 parts of modified montmorillonite, and 1 - 5 parts of additives, granulate them, dry, and then injection - mold into sheets to obtain the raw material for the weather - resistant layer; Blend 50 - 60 parts of homopolypropylene, 50 - 60 parts of linear low - density polyethylene, and 5 - 10 parts of maleic anhydride - based polyethylene graft copolymer, granulate them, dry, and then injection - mold into sheets to obtain the raw material for the bottom layer; Transport the weather - resistant layer, substrate layer, and raw material for the bottom layer to the back - sheet co - extrusion production line, extrude through a die to obtain a sheet - shaped melt, and then obtain the overall back - sheet of the solar cell after cooling, shaping, winding or cutting.

[0035] The additive is one or more of a dispersant, a leveling agent, and an antifoaming agent.

[0036] 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.

[0037] The following is a further description of the present invention through specific examples. Example 1

[0038] A preparation method of an overall back - sheet of a solar cell includes the following steps: (1) Disperse 10 g of montmorillonite into 500 mL of 0.5 mol / L sulfuric acid solution, mechanically stir 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 into 150 mL of ethanol - aqueous solution (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 - modified montmorillonite; (2) Add 10 g of amino - modified montmorillonite and 3.6 g of 3 - allylsalicylaldehyde to 150 mL of absolute ethanol, stir and react at 70 °C for 6 h, and control the pH of the system to 6.5 with glacial acetic acid during the process, centrifuge and wash the product to obtain grafted montmorillonite; (3) Add 10 g of grafted montmorillonite and 7.2 g of 1,1,3,3 - tetramethyldisiloxane to 150 mL of toluene, then add 0.5 mL of 5 wt% Karstedt catalyst and 0.1 g of BHT inhibitor, stir and react at 70 °C for 2 h and at 90 °C for 7 h under a nitrogen atmosphere, centrifuge, wash, and dry the product to obtain modified montmorillonite; (4) Blend 300 g of PEI, 850 g of PET, 120 g of modified montmorillonite, and 50 g of additives, granulate the mixture, dry it, and then injection mold it into sheets to obtain the raw material for the weather-resistant layer. Blend 600 g of homopolypropylene, 500 g of linear low-density polyethylene, and 80 g of maleic anhydride-grafted polyethylene, granulate the mixture, dry it, and then injection mold it into sheets to obtain the raw material for the bottom layer. Feed the weather-resistant layer, the substrate layer, and the raw material for the bottom layer into the co-extrusion production line for the backsheet, extrude the sheet-like melt through a die, and obtain the overall backsheet of the solar cell after cooling and shaping and winding.

[0039] The additives are obtained by mixing Disperbyk 760W (a dispersant), BYK-346 (a leveling agent), and BYK-028 (an antifoaming agent) in a weight ratio of 2:1:1.

[0040] 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

[0041] A method for preparing an overall backsheet of a solar cell, comprising the following steps: (1) Disperse 10 g of montmorillonite in 500 mL of 0.5 mol / L sulfuric acid solution, mechanically stir 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 aqueous solution (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-functionalized montmorillonite. (2) Add 10 g of amino-functionalized montmorillonite and 3.2 g of 3-allylsalicylaldehyde to 150 mL of absolute ethanol, stir and react at 65 °C for 7 h, and control the pH of the system to 6.5 with glacial acetic acid during the reaction. Centrifuge and wash the product to obtain grafted montmorillonite. (3) Add 10 g of grafted montmorillonite and 6.0 g of 1,1,3,3-tetramethyldisiloxane to 150 mL of toluene, then add 0.4 mL of 5 wt% Karstedt catalyst and 0.06 g of BHT inhibitor, stir and react under a nitrogen atmosphere at 64 °C for 3 h and at 84 °C for 8 h. Centrifuge, wash, and dry the product to obtain modified montmorillonite. (4) Blend 240 g of PEI, 800 g of PET, 90 g of modified montmorillonite, and 40 g of additives, granulate the mixture, dry it, and then injection mold it into sheets to obtain the raw material for the weather-resistant layer. Blend 600 g of homopolypropylene, 500 g of linear low-density polyethylene, and 80 g of maleic anhydride-grafted polyethylene, granulate the mixture, dry it, and then injection mold it into sheets to obtain the raw material for the bottom layer. Feed the weather-resistant layer, the substrate layer, and the raw material for the bottom layer into the co-extrusion production line for the backsheet, extrude the sheet-like melt through a die, and obtain the overall backsheet of the solar cell after cooling and shaping and winding.

[0042] The auxiliary agent is obtained by mixing dispersant Disperbyk 760W, leveling agent BYK-346, and defoaming agent BYK-028 in a weight ratio of 2:1:1.

[0043] 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

[0044] A preparation method of an overall backplane for a solar cell includes the following steps: (1) Dispersing 10 g of montmorillonite into 500 mL of 0.5 mol / L sulfuric acid solution, mechanically stirring at 70 °C for 6 h, filtering and washing to obtain activated montmorillonite; dispersing 10 g of activated montmorillonite and 2 mL of KH550 into 150 mL of an ethanol aqueous solution (volume ratio of ethanol to water is 4:1), adjusting the pH of the system to 5.0 with acetic acid, stirring and reacting at 75 °C for 8 h, centrifuging, washing, and drying the product to obtain amino-functionalized montmorillonite; (2) Adding 10 g of amino-functionalized montmorillonite and 2.8 g of 3-allylsalicylaldehyde to 150 mL of absolute ethanol, stirring and reacting at 65 °C for 7 h, controlling the pH of the system to 6.5 with glacial acetic acid during the process, centrifuging and washing the product to obtain grafted montmorillonite; (3) Adding 10 g of grafted montmorillonite and 4.8 g of 1,1,3,3-tetramethyldisiloxane to 150 mL of toluene, then adding 0.3 mL of 5 wt% Karstedt catalyst and 0.04 g of BHT inhibitor, stirring and reacting at 55 °C for 4 h and at 75 °C for 9 h under a nitrogen atmosphere, centrifuging, washing, and drying the product to obtain modified montmorillonite; (4) Blending 150 g of PEI, 700 g of PET, 60 g of modified montmorillonite, and 30 g of auxiliary agent, granulating and drying, and then injection molding into sheets to obtain the raw material for the weather-resistant layer; blending 600 g of homopolypropylene, 500 g of linear low-density polyethylene, and 80 g of maleic anhydride-grafted polyethylene, granulating and drying, and then injection molding into sheets to obtain the raw material for the bottom layer; conveying the raw materials for the weather-resistant layer, substrate layer, and bottom layer to a backplane co-extrusion production line, extruding through a die to obtain a sheet-shaped melt, and obtaining the overall backplane for the solar cell after cooling, shaping, and winding.

[0045] The auxiliary agent is obtained by mixing dispersant Disperbyk 760W, leveling agent BYK-346, and defoaming agent BYK-028 in a weight ratio of 2:1:1.

[0046] 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

[0047] A preparation method of an overall backplane for a solar cell, comprising the following steps: (1) Dispersing 10 g of montmorillonite into 500 mL of 0.5 mol / L sulfuric acid solution, mechanically stirring at 70 °C for 6 h, filtering and washing to obtain activated montmorillonite; dispersing 10 g of activated montmorillonite and 1 mL of KH550 into 150 mL of an ethanol aqueous solution (volume ratio of ethanol to water is 4:1), adjusting the pH of the system to 5.0 with acetic acid, stirring and reacting at 70 °C for 10 h, centrifuging, washing and drying the product to obtain amino-functionalized montmorillonite; (2) Adding 10 g of amino-functionalized montmorillonite and 2.4 g of 3-allylsalicylaldehyde to 150 mL of absolute ethanol, stirring and reacting at 60 °C for 8 h, controlling the pH of the system to 6.5 with glacial acetic acid during the process, centrifuging and washing the product to obtain grafted montmorillonite; (3) Adding 10 g of grafted montmorillonite and 3.6 g of 1,1,3,3-tetramethyldisiloxane to 150 mL of toluene, then adding 0.1 mL of 5 wt% Karstedt catalyst and 0.01 g of BHT inhibitor, stirring and reacting at 50 °C for 5 h and at 70 °C for 10 h under a nitrogen atmosphere, centrifuging, washing and drying the product to obtain modified montmorillonite; (4) Blending 100 g of PEI, 600 g of PET, 30 g of modified montmorillonite and 10 g of an auxiliary agent, granulating and drying, and injection molding into sheets to obtain a raw material for the weather-resistant layer; blending 600 g of homopolypropylene, 500 g of linear low-density polyethylene and 80 g of maleic anhydride-grafted polyethylene, granulating and drying, and injection molding into sheets to obtain a raw material for the bottom layer; conveying the weather-resistant layer, the substrate layer and the raw material for the bottom layer to a backplane co-extrusion production line, extruding through a die to obtain a sheet-like melt, and obtaining the overall backplane for the solar cell after cooling, shaping and winding.

[0048] The auxiliary agent is obtained by mixing a dispersant Disperbyk 760W, a leveling agent BYK-346 and an antifoaming agent BYK-028 in a weight ratio of 2:1:1.

[0049] 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.

[0050] Comparative Example 1

[0051] A preparation method of an overall backplane for a solar cell, comprising the following steps: (1) Disperse 10 g of montmorillonite into 500 mL of 0.5 mol / L sulfuric acid solution, mechanically stir 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 into 150 mL of ethanol aqueous solution (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-functionalized montmorillonite; (2) Add 10 g of amino-functionalized montmorillonite and 3.6 g of 3-allylsalicylaldehyde to 150 mL of absolute ethanol, stir and react at 70 °C for 6 h, and control the pH of the system to 6.5 with glacial acetic acid during the process. Centrifuge and wash the product to obtain grafted montmorillonite; (3) Blend 300 g of PEI, 850 g of PET, 120 g of grafted montmorillonite and 50 g of additives, granulate and dry, then injection mold into sheets to obtain the raw material for the weather-resistant layer; blend 600 g of homopolypropylene, 500 g of linear low-density polyethylene and 80 g of maleic anhydride-grafted polyethylene, granulate and dry, then injection mold into sheets to obtain the raw material for the bottom layer; convey the weather-resistant layer, the substrate layer and the raw material for the bottom layer to the co-extrusion production line of the backsheet, extrude through a die to obtain a sheet-like melt, and obtain the overall backsheet of the solar cell after cooling, shaping and winding.

[0052] The additives are obtained by mixing dispersant Disperbyk 760W, leveling agent BYK-346 and defoaming agent BYK-028 in a weight ratio of 2:1:1.

[0053] 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.

[0054] Comparative Example 2

[0055] A preparation method of an overall backsheet of a solar cell, comprising the following steps: (1) Disperse 10 g of montmorillonite into 500 mL of 0.5 mol / L sulfuric acid solution, mechanically stir 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 into 150 mL of ethanol aqueous solution (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-functionalized montmorillonite; (2) Blend 300 g of PEI, 850 g of PET, 120 g of aminated montmorillonite, and 50 g of additives, granulate them, dry them, and then injection mold them into sheets to obtain the raw material for the weather-resistant layer; blend 600 g of homopolypropylene, 500 g of linear low-density polyethylene, and 80 g of maleic anhydride-grafted polyethylene, granulate them, dry them, and then injection mold them into sheets to obtain the raw material for the bottom layer; convey the weather-resistant layer, the substrate layer, and the raw material for the bottom layer to the co-extrusion production line for the backsheet, extrude them through a die to obtain a sheet-shaped melt, and after cooling and shaping and winding, obtain the overall backsheet of the solar cell.

[0056] The additives are obtained by mixing dispersant Disperbyk 760W, leveling agent BYK-346, and defoamer BYK-028 in a weight ratio of 2:1:1.

[0057] 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.

[0058] Conduct performance tests on the weather-resistant layers prepared in Examples 1 to 4 and Comparative Examples 1 to 2. Use a universal tensile testing machine with a load of 5 kN to measure the mechanical properties. Refer to GB / T 1040.3-2006 "Determination of Tensile Properties of Plastics - Part 3: Test Conditions for Films and Sheets" to test the tensile strength and elongation at break, and conduct an aging test in a xenon lamp weather resistance aging test chamber. Place the specimen in the test chamber, set the aging temperature to 55 °C, the humidity to 70%, the irradiation intensity to 280 w / m 2 , the distance to 20 cm, simulate the light environment to accelerate aging, the simulated aging time is 30 days, and test the tensile strength and elongation at break after aging; refer to ASTM E313 to test the yellowness of the weather-resistant layer at 110 °C for 72 h; after placing the weather-resistant layer material products of each example in hot air at 85 °C for 96 hours of artificial accelerated aging, measure the heat aging resistance by the retention rate of the tensile strength. The larger the value, the better the heat aging resistance; refer to GB / T 26253-2010 "Determination of Water Vapor Transmission Rate of Plastic Films and Sheets - Infrared Detector Method" to test its water vapor transmission rate. The specific data are shown in Table 1.

[0059] Table 1 Performance Test Results of Weather-Resistant Layer Products

[0060] As mentioned above, only the specific preferred embodiments of the present invention are described, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and all should be covered by the protection scope of the present invention.

Claims

1. An overall backplane of a solar cell, 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 by weight: 10-30 parts of PEI, 60-85 parts of PET, 3-12 parts of modified montmorillonite, and 1-5 parts of auxiliary agent.

2. The overall backplane of the solar cell according to claim 1, characterized in that, 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 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 aminated montmorillonite and 3-allyl salicylaldehyde to anhydrous ethanol, stirring the reaction and controlling the pH of the system, centrifuging and washing the product to obtain grafted montmorillonite; (3) Grafted montmorillonite and 1,1,3,3-tetramethyldisiloxane are added to toluene, and then Karstedt catalyst and BHT inhibitor are added. The temperature is increased stepwise under a nitrogen atmosphere. The product is centrifuged, washed, and dried to obtain modified montmorillonite.

3. The overall backplane of the solar cell according to claim 2, 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 to 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; the volume ratio of ethanol to water in the ethanol aqueous solution is 3-5:

1.

4. The overall backplane of the solar cell according to claim 2, wherein, 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.

5. The overall backplane of the solar cell according to claim 2, 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.

6. The overall backplane of the solar cell according to claim 2, wherein, In step (2), the reaction is stirred at 60-70° C. for 6-8 hours, during which the pH value of the system is controlled to 6-7 with glacial acetic acid.

7. The overall backplane of the solar cell according to claim 2, wherein 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; the concentration of Karstedt catalyst is 5 wt%.

8. The overall backplane of the solar cell according to claim 2, 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.

9. The overall backplane of the solar cell according to claim 1, characterized in that, 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. The preparation method of the weather-resistant layer raw material is: blending and granulating the raw materials, drying them, and injection molding them into sheets.

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

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