Photovoltaic encapsulant film for BC battery and preparation method thereof

Abstract

The application discloses a kind of photovoltaic encapsulation adhesive film for BC battery and preparation method thereof, belong to photovoltaic encapsulation material technical field.The encapsulation adhesive film includes three layers structure: high adhesion heat-conducting upper layer with glass contact, high adhesion heat-conducting lower layer with battery piece contact and intermediate high elastic layer.Silane modified transparent silicon powder with particle size of 0.5~1.5 μm and rod-shaped SiC with diameter of 0.5~10 μm and length of 5~100 μm are added as heat-conducting fillers in high adhesion heat-conducting upper and lower layers;heterocyclic co-crosslinking agent is used in intermediate high elastic layer, the co-crosslinking agent is heterocyclic compound with more than six members, and at least contains 2 reactive functional groups, which can effectively reduce the crosslinking density of intermediate layer, improve elasticity, and alleviate the problem of broken pieces and hidden cracks during lamination.The encapsulation adhesive film has good heat-conducting performance and elasticity, and is suitable for the encapsulation of BC battery, improving the reliability and service life of photovoltaic module.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic encapsulation materials, specifically to a photovoltaic encapsulation film for BC batteries and its preparation method. Background Technology

[0002] With the rapid development of the photovoltaic industry, the encapsulation technology of photovoltaic modules is also constantly being innovated and improved. As a key material for photovoltaic modules, the performance of the encapsulating film directly affects the reliability, service life, and power generation efficiency of the module. Especially in the application of BC (Back Contact) cell technology, the increase in module size and cell light-receiving area leads to an increase in short-circuit current and operating temperature, which places higher demands on the thermal conductivity, light transmittance, and adhesion performance of the encapsulating film.

[0003] Currently, photovoltaic encapsulation films mainly include EVA (ethylene-vinyl acetate copolymer) films and POE (polyolefin elastomer) films. EVA films are widely used due to their good light transmittance and low cost, but they have low thermal conductivity and are easily affected by factors such as light, heat, oxygen, and moisture, leading to aging, debonding, and failure.

[0004] Although POE films have good aging resistance, their market share is small due to the cost of POE particles. Furthermore, POE encapsulation often involves various process problems such as additive precipitation, slippage, and bubbles during lamination. Currently, its compatibility with BC batteries still needs further optimization.

[0005] EPE encapsulation film has become a popular choice in recent years. It combines the stability of EVA manufacturing process with the excellent weather resistance of POE, while also balancing the price difference between EVA and POE particles. It is currently the most cost-effective encapsulation film and the first choice for BC battery manufacturers.

[0006] With the development of BC battery technology, the thickness of battery cells is becoming increasingly thinner, leading to problems such as cell breakage and microcracks. Furthermore, since both the positive and negative electrodes of BC batteries are located on the back, higher demands are placed on the buffering and heat dissipation performance of the encapsulating film. Existing encapsulating films struggle to simultaneously achieve high thermal conductivity, high light transmittance, and excellent adhesion, particularly when applying BC battery technology, presenting the following issues:

[0007] 1. The thermal conductivity of existing encapsulation films is insufficient, making it difficult to effectively dissipate the heat generated during the operation of BC cells, which increases the risk of hot spots and affects the reliability and power generation efficiency of the modules;

[0008] 2. The addition of thermally conductive fillers often reduces the light transmittance of the encapsulating film, affecting the power generation efficiency of the module;

[0009] 3. Insufficient interlayer bonding strength of the multilayer encapsulation film can easily lead to interlayer delamination, affecting the long-term reliability of the component.

[0010] Therefore, it is of great significance to develop a photovoltaic encapsulating film for BC cells that can simultaneously possess high thermal conductivity, high light transmittance, and excellent adhesion properties to meet the needs of BC cell technology development. Summary of the Invention

[0011] To address the challenge of simultaneously achieving high thermal conductivity, high light transmittance, and excellent adhesion in existing photovoltaic encapsulation films, and to improve the reliability and power generation efficiency of BC battery modules, this invention provides a photovoltaic encapsulation film for BC batteries and its preparation method.

[0012] The technical solution adopted by this invention to solve its technical problem is:

[0013] A photovoltaic encapsulation film for BC batteries, the encapsulation film comprising a three-layer structure, namely a high-viscosity thermally conductive upper layer in contact with glass, a high-viscosity thermally conductive lower layer in contact with the battery cell, and a high-elasticity layer in between the two layers, wherein the high-viscosity thermally conductive upper layer and the high-viscosity thermally conductive lower layer are each provided with a first thermally conductive filler and a second thermally conductive filler, the first thermally conductive filler being silane-modified transparent silicon micropowder.

[0014] Furthermore, the thickness of the high-viscosity thermally conductive upper layer and the high-viscosity thermally conductive lower layer is 0.1 to 1 mm, and the thickness of the intermediate high-elasticity layer is 0.05 to 0.5 mm.

[0015] Furthermore, the silane-modified transparent silicon micropowder has a particle size of 0.5–1.5 μm, and the second thermally conductive filler is rod-shaped SiC with a diameter of 0.5–10 μm and a length of 5–100 μm.

[0016] Furthermore, the intermediate high-elasticity layer uses a heterocyclic crosslinking agent, which is a heterocyclic compound with six or more members and contains at least two reactive functional groups. The heteroatoms on the heterocyclic compound include silicon, nitrogen, oxygen, and sulfur, and the reactive functional groups include unsaturated double bonds, carboxyl groups, hydroxyl groups, amino groups, and nitro groups.

[0017] Furthermore, the heterocyclic co-crosslinking agent includes one or more of the following: tetramethyltetravinylcyclotetrasiloxane (8-membered heterocyclic compound), 2,5-divinyltetrahydro-2H-pyran (6-membered heterocyclic compound), and (2R,3S,6R,7S)-2,7-diallyloxetane-3,6-diol (8-membered heterocyclic compound).

[0018] Furthermore, the first thermally conductive filler, silane-modified transparent silica micropowder, is prepared by the following method:

[0019] 1) Using alcohol as a solvent, the silica was initially ground for 10 minutes to form a slurry, which promoted uniform dispersion;

[0020] 2) Prepare an aqueous solution with pH 4-5 and an alcoholic solution of silane coupling agent. The mass ratio of silane to silicon dioxide is 1:10. During the grinding process, the aqueous solution with pH 4-5 is continuously added to acidify the surface of silicon dioxide. At the same time, the alcoholic solution of silane coupling agent is added dropwise at a constant rate. The grinding speed is 1500 r / min. After the alcoholic solution of silane coupling agent is added, the acidified silicon dioxide is washed with pure water and dried at low temperature to obtain silane-modified transparent silicon micropowder.

[0021] Furthermore, in step 1), the particle size of the silica is 0.5–1.5 μm.

[0022] In step 2), the volume ratio of silane to alcohol is 1:2, the drying temperature is controlled at 40–60°C, and the volatile matter content is tested at 120°C for 10 minutes and controlled to be below 0.2%. The specific surface area of ​​the silane-modified transparent silica powder is controlled at 50–150 m². 2 / g.

[0023] Furthermore, both the high-viscosity thermally conductive upper layer and the high-viscosity thermally conductive lower layer comprise 90-98% matrix resin and 2-10% silane-modified transparent silica powder, wherein the matrix resin is EVA.

[0024] It also contains the following components, added in amounts based on the total mass of the matrix resin and silane-modified transparent silica powder:

[0025] Rod-shaped SiC, with a mass percentage of 0.5-2%;

[0026] Crosslinking agent: 0.5-1% by mass;

[0027] Crosslinking agent: 0.4-1% by weight

[0028] Light stabilizer, 0.1-0.3% by mass;

[0029] Antioxidant, 0.1-0.3% by mass;

[0030] Silane coupling agent, with a mass percentage of 0.2-0.5%.

[0031] Furthermore, the matrix resin of the high-elasticity layer is selected from POE, with a mass percentage of 100%, and also contains the following components, the amount of which is based on the POE matrix resin:

[0032] Crosslinking agent: 0.5-1.5% by mass;

[0033] Heterocyclic crosslinking agent, with a mass percentage of 0.5-2%;

[0034] Light stabilizer, 0.1-0.3% by mass;

[0035] Antioxidant, 0.1-0.3% by mass;

[0036] Silane coupling agent, with a mass percentage of 0.1-0.5%.

[0037] A method for preparing a photovoltaic encapsulating film for BC batteries, the method comprising the following steps:

[0038] 1) The first thermally conductive filler, silane-modified transparent silica powder, the second thermally conductive filler, rod-shaped SiC, and the matrix resin, EVA, are weighed according to the formula ratio and extruded and granulated at 120°C using a twin-screw granulator to obtain a uniformly dispersed thermally conductive masterbatch.

[0039] 2) Add the thermally conductive masterbatch, light stabilizer, antioxidant, crosslinking agent, co-crosslinking agent, and silane coupling agent prepared in step 1) to a mixer according to the formula ratio and mix evenly to obtain high-viscosity thermally conductive upper layer and high-viscosity thermally conductive lower layer materials for later use.

[0040] 3) Add POE, multi-cyclic adhesive, crosslinking agent, silane coupling agent, antioxidant, and light stabilizer to the mixer according to the formula ratio and mix evenly to obtain the intermediate high-elasticity layer material for later use.

[0041] 4) Add the materials obtained in steps 2) and 3) to the two barrels of the co-extrusion equipment, and after casting, cooling and winding, obtain the photovoltaic encapsulation film for BC batteries.

[0042] The beneficial effects of this invention are as follows:

[0043] 1. Employing a three-layer structure design, this invention effectively solves the problems of increased size and poor heat conduction in existing encapsulation films when applying BC battery technology by optimizing the material formulation and structural composition of each layer. Compared with existing technologies, the encapsulation film of this invention can better adapt to the increased short-circuit current and operating temperature caused by the increased size of BC battery modules and the increased light-receiving area of ​​the cells, reducing the risk of hot spots and improving the reliability and power generation efficiency of the modules.

[0044] 2. The high-viscosity, thermally conductive upper and lower layers use EVA as the matrix resin, with silane-modified transparent silica powder and rod-shaped SiC added as thermally conductive fillers, forming a dense thermally conductive network that significantly improves thermal conductivity while maintaining high light transmittance. Furthermore, the siloxanes on the silane-modified transparent silica powder, after specific processing, can condense with hydroxyl groups on the glass to form chemical bonds, enhancing adhesion to the glass while maintaining light transmittance.

[0045] 3. The intermediate high-elasticity layer uses POE as the matrix resin and adds a multi-component heterocyclic crosslinking agent with multiple reactive functional groups. This multi-component heterocyclic crosslinking agent has a large molecular volume and large steric hindrance, making it less likely to participate in the crosslinking reaction. This results in relatively fewer crosslinking sites, lower crosslinking density, reduced material rigidity, and improved flexibility and elasticity. This design is particularly suitable for addressing the trend of increasingly thinner solar cells, effectively relieving stress, reducing issues such as cell breakage and microcracks, and meeting the demands of emerging technologies.

[0046] This invention significantly improves the overall performance and durability of the encapsulating film through a three-layer structure design and material optimization. Detailed Implementation

[0047] The technical solution of the present invention will now be clearly and completely described with reference to specific embodiments. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0048] According to one aspect of this application, a photovoltaic encapsulating film for BC batteries is provided. The encapsulating film comprises a three-layer structure: a high-viscosity thermally conductive upper layer in contact with glass, a high-viscosity thermally conductive lower layer in contact with the battery cell, and a high-elasticity layer in between the two layers. The thicknesses of the high-viscosity thermally conductive upper and lower layers are 0.1–1 mm, and the thickness of the intermediate high-elasticity layer is 0.05–0.5 mm.

[0049] Both the high-viscosity thermally conductive upper and lower layers contain a first thermally conductive filler of silane-modified transparent silica powder and a second thermally conductive filler of rod-shaped SiC. The silane-modified transparent silica powder has a particle size of 0.5–1.5 μm, and the SiC has a diameter of 0.5–10 μm and a length of 5–100 μm. The intermediate high-elasticity layer uses a heterocyclic co-crosslinking agent, which is a heterocyclic compound with six or more members and contains at least two reactive functional groups. The heteroatoms on the heterocyclic compound include, but are not limited to, silicon, nitrogen, oxygen, and sulfur. The reactive functional groups include, but are not limited to, unsaturated double bonds, carboxyl groups (-COOH), hydroxyl groups (-OH), amino groups (-NH2), and nitro groups (-NO2). The high-viscosity thermally conductive upper and lower layers use EVA as the matrix resin, and add silane-modified transparent silica powder and rod-shaped SiC as thermally conductive fillers to form a dense thermally conductive network, which significantly improves thermal conductivity while maintaining high light transmittance.

[0050] The preparation method of the first thermally conductive filler, silane-modified transparent silica micropowder, in this application is as follows:

[0051] 1) Using alcohol as a solvent, silica with a particle size of 0.5-1.5 μm was initially ground for 10 minutes to form a slurry, which promoted uniform dispersion;

[0052] 2) Prepare an aqueous solution with pH 4-5 and an alcoholic solution of silane coupling agent. The mass ratio of silane to silica is 1:10. During the grinding process, the aqueous solution with pH 4-5 is continuously added to acidify the silica surface. Simultaneously, the alcoholic solution of silane coupling agent is added dropwise at a constant rate. The grinding speed is 1500 r / min. After the alcoholic solution of silane coupling agent is added, the acidified silica is washed with pure water and dried at low temperature to obtain silane-modified transparent silica micropowder. The volume ratio of silane to alcohol is 1:2. The drying temperature is controlled at 40-60℃. The volatile matter is tested at 120℃ for 10 min and controlled to be within 0.2%. The specific surface area of ​​the silane-modified transparent silica micropowder is controlled at 50-150 m². 2 / g.

[0053] The siloxane on the silane-modified transparent silica micropowder, after being processed by a specific process, can condense with the hydroxyl groups on the glass to form chemical bonds, thereby improving the adhesion to the glass while maintaining light transmittance.

[0054] In some embodiments, both the high-viscosity thermally conductive upper layer and the high-viscosity thermally conductive lower layer comprise 90-98% matrix resin and 2-10% silane-modified transparent silica powder, wherein the matrix resin is EVA, and further comprises the following components, the amounts of which are based on the total mass of the matrix resin and the silane-modified transparent silica powder:

[0055] Rod-shaped SiC, with a mass percentage of 0.5-2%;

[0056] Crosslinking agent: 0.5-1% by mass;

[0057] Crosslinking agent: 0.4-1% by mass;

[0058] Light stabilizer, 0.1-0.3% by mass;

[0059] Antioxidant, 0.1-0.3% by mass;

[0060] Silane coupling agent, with a mass percentage of 0.2-0.5%.

[0061] The matrix resin of the high-elasticity layer is POE, with a mass percentage of 100%, and also contains the following components, the amount of which is based on the POE matrix resin:

[0062] Heterocyclic adhesive additives, with a mass percentage of 0.5% to 1.5%;

[0063] Crosslinking agent: 0.5-2% by mass;

[0064] Light stabilizer, 0.1-0.3% by mass;

[0065] Antioxidant, 0.1-0.3% by mass;

[0066] Silane coupling agent, with a mass percentage of 0.1-0.5%.

[0067] In some embodiments, the heterocyclic co-crosslinking agent includes, but is not limited to, one or more of the following: the eight-membered heterocyclic compound tetramethyltetravinylcyclotetrasiloxane, the six-membered heterocyclic compound 2,5-divinyltetrahydro-2H-pyran, and the eight-membered heterocyclic compound (2R,3S,6R,7S)-2,7-diallyloxetane-3,6-diol.

[0068] The crosslinking agent is a peroxide-based crosslinking agent, including but not limited to one or more of 2-ethylhexyl carbonate tert-amyl peroxide, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, and tert-butyl peroxide.

[0069] The co-crosslinking agent includes, but is not limited to, one or more of triallyl isocyanurate, pentaerythritol tetraacrylate ethoxylate, trimethylallyl isocyanate, and pentaerythritol tetraacrylate propoxylate.

[0070] The light stabilizers include, but are not limited to, one or more of bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, bis(2,2,6,6-tetramethylpiperidinyl) sebacate, and hexadecyl 3,5-di-tert-butyl-4-hydroxybenzoate.

[0071] The antioxidants include, but are not limited to, one or more of octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].

[0072] The silane coupling agent includes, but is not limited to, one or more of vinyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and γ-glycidoxypropyltrimethoxysilane.

[0073] In some embodiments, the method for preparing a photovoltaic encapsulating film for BC batteries includes the following steps:

[0074] 1) The first thermally conductive filler, silane-modified transparent silica powder, the second thermally conductive filler, rod-shaped SiC, and the matrix resin, EVA, are weighed according to the formula ratio and extruded and granulated at 120°C using a twin-screw granulator to obtain a uniformly dispersed thermally conductive masterbatch.

[0075] 2) Add the thermally conductive masterbatch, light stabilizer, antioxidant, crosslinking agent, co-crosslinking agent, and silane coupling agent prepared in step 1) to a mixer according to the formula ratio and mix evenly to obtain high-viscosity thermally conductive upper layer and high-viscosity thermally conductive lower layer materials for later use.

[0076] 3) Add POE, multi-cyclic adhesive, crosslinking agent, silane coupling agent, antioxidant, and light stabilizer to the mixer according to the formula ratio and mix evenly to obtain the intermediate high-elasticity layer material for later use.

[0077] 4) Add the materials obtained in steps 2) and 3) to the two barrels of the co-extrusion equipment, and after casting, cooling and winding, obtain the photovoltaic encapsulation film for BC batteries.

[0078] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0079] Example 1

[0080] A photovoltaic encapsulating film for BC batteries comprises a three-layer structure: a high-viscosity thermally conductive upper layer in contact with glass, a high-viscosity thermally conductive lower layer in contact with the battery cell, and a high-elasticity layer in between. The thicknesses of the high-viscosity thermally conductive upper and lower layers are 0.15 mm, and the thickness of the intermediate high-elasticity layer is 0.3 mm.

[0081] The high-viscosity, thermally conductive upper and lower layers contain a first thermally conductive filler, silane-modified transparent silicon micropowder, and a second thermally conductive material, rod-shaped SiC. The silane-modified transparent silicon micropowder has a particle size of 0.5 μm, and the SiC has a diameter of 0.5 μm and a length of 12 μm. The intermediate high-elasticity layer uses an eight-membered heterocyclic co-crosslinking agent, tetramethyltetravinylcyclotetrasiloxane. The preparation method of the first thermally conductive filler, silane-modified transparent silicon micropowder, is as follows:

[0082] 1) Grind the silica with a particle size of 0.5μm. First, use alcohol as a solvent to grind the silica for 10 minutes to make a slurry, so as to promote uniform dispersion;

[0083] 2) Prepare an aqueous solution with pH 4-5 and an alcoholic solution of silane coupling agent. The volume ratio of silane to alcohol is 1:2, and the ratio of silane to silica is 1:10. During the grinding process, continuously add the pH 4-5 aqueous solution to acidify the silica surface. Simultaneously, add the alcoholic solution of silane coupling agent dropwise at a constant rate. Grind at 1500 rpm. After the alcoholic solution of silane coupling agent is added, wash the acidified silica with pure water and dry it at a low temperature (controlled at 50℃). Test the volatile matter at 120℃ for 10 minutes, controlling it to be below 0.2%. The specific surface area of ​​the modified silica powder is controlled at 75 m². 2 / g.

[0084] Both the high-viscosity thermally conductive upper and lower layers use Sirbon V2825 EVA as their base resin, accounting for 96% by weight. The high-viscosity thermally conductive layer also contains the following components:

[0085] Silane-modified transparent silica micropowder, with a mass percentage of 3%, is produced by Xuancheng Jingrui New Materials Co., Ltd., under the brand name Jinghe, model VK-SP500, with a particle size of 0.5μm.

[0086] Rod-shaped SiC, with a mass percentage of 1%, is produced by Forsmann Technology Co., Ltd. The SiC has a diameter of 0.5 μm and a length of 12 μm.

[0087] Crosslinking agent: 0.5% by mass, specifically 2-ethylhexyl tert-amyl carbonate peroxide produced by Wuhan Chengfeng Chemical Co., Ltd. in Hubei Province;

[0088] Crosslinking agent: 0.6% by mass, specifically triallyl isocyanurate produced by Anhui Xiangyun Rubber & Plastics Co., Ltd.;

[0089] The light stabilizer, at a mass percentage of 0.1%, is specifically bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate produced by Suzhou Qihang Biotechnology Co., Ltd.

[0090] Antioxidant, with a mass percentage of 0.2%, specifically β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-octadecyl alcohol ester produced by Nantong Runfeng Petrochemical Co., Ltd.;

[0091] The silane coupling agent, with a mass percentage of 0.3%, specifically is vinyltrimethoxysilane produced by Hangzhou Jessica Chemical Co., Ltd.

[0092] The matrix resin of the high-elasticity layer is selected from Dow POE, PV 8669 and PV 8660 in a mass percentage of 60% and 40%, respectively, and also contains the following components:

[0093] Heterocyclic adhesive additive, 1% by weight, specifically 0.5% methyltetravinylcyclotetrasiloxane from Shandong Yuanjin New Material Co., Ltd., and 0.5% 2,5-divinyltetrahydro-2H-pyran from Shanghai Jizhi Biochemical Technology Co., Ltd.

[0094] Crosslinking agent: 0.8% by mass, specifically 2-ethylhexyl carbonate tert-amyl peroxide produced by Wuhan Chengfeng Chemical Co., Ltd. in Hubei Province;

[0095] The light stabilizer, at a mass percentage of 0.1%, is specifically bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate produced by Suzhou Qihang Biotechnology Co., Ltd.

[0096] Antioxidant, with a mass percentage of 0.2%, specifically β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-octadecyl alcohol ester produced by Nantong Runfeng Petrochemical Co., Ltd.;

[0097] The silane coupling agent, with a mass percentage of 0.2%, is specifically vinyltrimethoxysilane produced by Hangzhou Jessica Chemical Co., Ltd.

[0098] The method for preparing the encapsulating film includes the following steps:

[0099] 1) The first thermally conductive filler, silane-modified transparent silica powder, the second thermally conductive filler, rod-shaped SiC, and the matrix resin EVA are weighed in a mass ratio of 10:3.3:86.7 using a batch weigher and extruded and granulated at 120°C using a twin-screw granulator to obtain a uniformly dispersed thermally conductive masterbatch.

[0100] 2) Add the thermally conductive masterbatch, light stabilizer, antioxidant, crosslinking agent, co-crosslinking agent and silane coupling agent prepared in step 1) to the mixer according to the formula ratio and mix evenly. The thermally conductive masterbatch is added at a ratio of 3% and the EVA matrix resin is 97%. The high-viscosity thermally conductive upper layer and high-viscosity thermally conductive lower layer are prepared for use.

[0101] 3) Add POE, multi-cyclic adhesive, crosslinking agent, silane coupling agent, antioxidant, and light stabilizer to the mixer according to the formula ratio and mix evenly to obtain the intermediate high-elasticity layer material for later use.

[0102] 4) Add the materials obtained in steps 2) and 3) to the two barrels of the co-extrusion equipment, and after casting, cooling and winding, obtain the photovoltaic encapsulation film for BC batteries.

[0103] Example 2

[0104] The difference from Example 1 lies in the addition ratio of the first and second thermally conductive fillers in the high-viscosity thermally conductive layer:

[0105] Silane-modified transparent silica powder, 5% by mass;

[0106] Rod-shaped SiC, 1.5% by mass, Example 3

[0107] The difference from Example 1 lies in the thickness of each layer: the thickness of the high-viscosity thermally conductive upper layer and the high-viscosity thermally conductive lower layer is 0.25 mm, and the thickness of the middle high-elasticity layer is 0.1 mm.

[0108] Example 4

[0109] The difference from Example 1 lies in the size of the thermally conductive filler: the particle size of the silane-modified transparent silicon micropowder is 1 μm, specifically produced by Qinghe County Chaotai Metal Materials Co., Ltd., model XWJ-50601, with a particle size of 1 micrometer, a SiC diameter of 1.5 μm, and a length of 18 μm.

[0110] Comparative Example 1

[0111] The difference from Implementation List 1 is that no silane-modified transparent silica powder and rod-shaped SiC were added, and the EVA mass percentage was 100%.

[0112] Performance testing:

[0113] Lamination method: Lamination set temperature: 148℃, vacuum time: 6min, lamination time: 10min. After lamination, the following tests were performed: peel strength, light transmittance, component power and modulus.

[0114] Samples were prepared and tested according to the peel strength test method and transmittance test method provided in GB / T 29848-2018.

[0115] The power degradation of the photovoltaic (PV) module was tested according to the test method for potential induced degradation detection as specified in IEC TS 62804-1:2025.

[0116] The component operating temperature shall be measured in accordance with the measurement method for the nominal operating temperature of the component as specified in IEC 61215-2016;

[0117] Samples were prepared and tested in accordance with the modulus test method specified in IEC 62788-1-1.

[0118] Table 1

[0119]

[0120] As shown in Table 1, the film with added silane-modified transparent silicon micropowder exhibits significantly stronger adhesion to glass than the control film without it. The addition of the first and second thermally conductive fillers has little impact on the film's light transmittance, maintaining a high initial power output for the module, with almost no loss compared to the control film. Furthermore, the operating temperature of the modules shows varying degrees of decrease compared to the control film. Higher levels of the first and second thermally conductive fillers, or a thicker high-viscosity thermally conductive layer, result in better thermal conductivity and lower module operating temperatures. Additionally, larger particle sizes of the silane-modified transparent silicon micropowder and longer SiC lengths contribute to better thermal conductivity and lower module operating temperatures. Compared to the control film using conventional crosslinking agents, the film using heterocyclic crosslinking agents has a lower modulus and is softer, effectively mitigating lamination stress.

[0121] In summary, the photovoltaic encapsulating film for BC cells described in this invention not only solves the problems of increased size and poor heat conduction in existing encapsulating films when applying BC cell technology, but also maintains high light transmittance. The application of silane modification further enhances adhesion to glass, improving module reliability and power generation efficiency. The intermediate high-elasticity layer uses a multi-component heterocyclic crosslinking agent, reducing crosslinking density and improving the material's flexibility and elasticity. This effectively alleviates problems such as breakage and microcracks caused by high stress during module lamination, aligning with the development trend of ultra-thin crystalline silicon solar cells.

[0122] It should be noted that Examples 1, 2, 3, and 4 are all types of photovoltaic encapsulation films for BC batteries.

[0123] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A photovoltaic encapsulating film for BC batteries, characterized in that: The encapsulation film comprises a three-layer structure, namely a high-viscosity thermally conductive upper layer in contact with the glass, a high-viscosity thermally conductive lower layer in contact with the battery cell, and a high-elasticity layer in between the two layers. Both the high-viscosity thermally conductive upper layer and the high-viscosity thermally conductive lower layer contain a first thermally conductive filler and a second thermally conductive filler. The first thermally conductive filler is silane-modified transparent silicon micropowder. The silane-modified transparent silica powder has a particle size of 0.5~1.5μm, and the second thermally conductive filler is rod-shaped SiC with a diameter of 0.5~10μm and a length of 5~100μm; The intermediate high-elasticity layer uses a heterocyclic crosslinking agent, which is a heterocyclic compound with six or more members and contains at least two reactive functional groups. The heteroatoms on the heterocyclic compound include silicon, nitrogen, oxygen, and sulfur, and the reactive functional groups include unsaturated double bonds, carboxyl groups, hydroxyl groups, amino groups, and nitro groups. Both the high-viscosity thermally conductive upper layer and the high-viscosity thermally conductive lower layer comprise 90-98% matrix resin and 2-10% silane-modified transparent silica powder, wherein the matrix resin is EVA. It also contains the following components, added in amounts based on the total mass of the matrix resin and silane-modified transparent silica powder: Rod-shaped SiC, with a mass percentage of 0.5-2%; Crosslinking agent: 0.5-1% by mass; Crosslinking agent: 0.4-1% by weight Light stabilizer, 0.1-0.3% by weight; Antioxidant, 0.1-0.3% by weight; Silane coupling agent, with a mass percentage of 0.2-0.5%; The matrix resin of the high-elasticity layer is POE, with a mass percentage of 100%, and also contains the following components, the amount of which is based on the POE matrix resin: Crosslinking agent: 0.5~1.5% by mass; Heterocyclic crosslinking agent, with a mass percentage of 0.5-2%; Light stabilizer, 0.1-0.3% by weight; Antioxidant, 0.1-0.3% by weight; Silane coupling agent, with a mass percentage of 0.1-0.5%.

2. The photovoltaic encapsulating film for BC batteries according to claim 1, characterized in that: The thickness of the high-viscosity thermally conductive upper layer and the high-viscosity thermally conductive lower layer is 0.1~1mm, and the thickness of the intermediate high-elasticity layer is 0.05~0.5mm.

3. The photovoltaic encapsulating film for BC batteries according to claim 1, characterized in that: The heterocyclic co-crosslinking agent includes one or more of the following: tetramethyltetravinylcyclotetrasiloxane (eight-membered heterocyclic compound), 2,5-divinyltetrahydro-2H-pyran (six-membered heterocyclic compound), and (2R,3S,6R,7S)-2,7-diallyloxetane-3,6-diol (eight-membered heterocyclic compound).

4. The photovoltaic encapsulating film for BC batteries according to claim 1, characterized in that, The first thermally conductive filler, silane-modified transparent silica micropowder, is prepared by the following method: 1) Using alcohol as a solvent, silica is initially ground into a slurry to promote uniform dispersion; 2) Prepare an aqueous solution with pH 4-5 and an alcoholic solution of silane coupling agent. During the grinding process, continuously add the aqueous solution with pH 4-5 to acidify the surface of silica. At the same time, add the alcoholic solution of silane coupling agent dropwise at the same rate. After the alcoholic solution of silane coupling agent is added, wash the acidified silica with pure water and dry it at low temperature to obtain silane-modified transparent silica micropowder.

5. The photovoltaic encapsulating film for BC batteries according to claim 4, characterized in that: In step 1), the particle size of the silica is 0.5~1.5μm. In step 2), the volume ratio of silane to alcohol is 1:2~3, the mass ratio of silane coupling agent to silica is 1:10~15, and the specific surface area of ​​the silane-modified transparent silica powder is controlled at 50~150 m². 2 / g.

6. The method for preparing a photovoltaic encapsulating film for BC batteries as described in claim 1, characterized in that: The preparation method includes the following steps: 1) The first thermally conductive filler, silane-modified transparent silica powder, the second thermally conductive filler, rod-shaped SiC, and the matrix resin, EVA, are weighed according to the formula ratio and extruded and granulated at 120°C using a twin-screw granulator to obtain a uniformly dispersed thermally conductive masterbatch. 2) Add the thermally conductive masterbatch, light stabilizer, antioxidant, crosslinking agent, co-crosslinking agent, and silane coupling agent prepared in step 1) to a mixer according to the formula ratio and mix evenly to obtain high-viscosity thermally conductive upper layer and high-viscosity thermally conductive lower layer materials for later use. 3) Add POE, multi-cyclic adhesive, crosslinking agent, silane coupling agent, antioxidant, and light stabilizer to the mixer according to the formula ratio and mix evenly to obtain the intermediate high-elasticity layer material for later use. 4) Add the materials obtained in steps 2) and 3) to the two barrels of the co-extrusion equipment, and after casting, cooling and winding, obtain the photovoltaic encapsulation film for BC batteries.

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