A grid-free HJT cell encapsulating film, its preparation method, and a photovoltaic module thereof.

Abstract

This invention relates to the field of solar cell technology, and more particularly to an encapsulating film for grid-free HJT cells, its preparation method, and a photovoltaic module. The invention provides an encapsulating film for grid-free HJT cells that exhibits excellent low flowability by precisely pre-crosslinking the film near the cell side or a specific area of ​​the film. This characteristic effectively solves the technical problem of overflow due to excessive film flowability during low-temperature lamination, which hinders the formation of a good connection between the solder wire and the cell, thus significantly avoiding the defect of localized darkening of the EL in the module and improving production yield. Simultaneously, this encapsulating film integrates ultraviolet light conversion functionality, converting harmful ultraviolet light into usable visible light, which not only slows down the power decay of the module but also increases the initial power.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, and in particular to an encapsulating film for gridless HJT cells, its preparation method, and a photovoltaic module. Background Technology

[0002] Heterojunction with Intrinsic Thin-layer (HJT) cells are inherently susceptible to damage from ultraviolet (UV) light, leading to significant power degradation after UV radiation. Currently, HJT cells are typically encapsulated using encapsulating films with UV blocking capabilities. However, this encapsulation method results in lower initial power output for HJT cell modules, making them unable to compete with Topcon cell modules. Therefore, the application of UV conversion film technology to HJT cells has begun to attract attention.

[0003] High-junction (HJT) cells cannot be fabricated into strings using traditional welding methods due to their inability to withstand high temperatures. Furthermore, the high silver content in the main busbar of HJT cells makes welded HJT cells less competitive in price compared to Topcon cells. Therefore, the current mainstream research and development direction for HJT cells is to develop busbar-less HJT cells using low-temperature welding methods to achieve alloy bonding between the welding wire and the HJT cell during photovoltaic lamination. Low-temperature welding technology requires encapsulating films with extremely low fluidity. Commonly used encapsulating films have high fluidity, which can seep between the welding wire and the HJT cell during lamination, preventing proper bonding and leading to localized darkening of the electroluminescence (EL) area in the HJT cell. Therefore, these encapsulating films are not ideal for encapsulating busbar-less HJT cells.

[0004] Therefore, an encapsulating film with both ultraviolet light conversion and low flowability is needed to meet the performance and encapsulation requirements of gridless HJT cells. Summary of the Invention

[0005] This invention provides an encapsulating film for grid-free HJT cells, a method for preparing the same, and a photovoltaic module, to solve the aforementioned technical problems existing in the encapsulating films for grid-free HJT cells.

[0006] According to a first aspect of the present invention, the present invention provides an encapsulating film for a gridless HJT battery, comprising a low-flow film 1 and a first ultraviolet conversion film 2 stacked together, wherein the pre-crosslinking degree of the low-flow film 1 is 30%-60%.

[0007] According to the encapsulating film of the present invention, the low-flow film 1 comprises a base resin by weight, the base resin comprising a resin containing GMA groups, the resin containing GMA groups accounting for 5-40% of the total mass of the base resin; the GMA groups accounting for 0.1% to 30% of the weight of the resin containing GMA groups.

[0008] Preferably, the matrix resin is selected from one or more of the following: GMA-grafted ethylene vinyl acetate copolymer, GMA-grafted ethylene-α-olefin copolymer, ethylene-acrylate-glycidyl methacrylate copolymer, ethylene-glycidyl methacrylate copolymer, or ethylene-vinyl acetate-glycidyl methacrylate copolymer. Preferably, the melt index of the matrix resin is 2~15 g / 10 min; Preferably, the low-flow adhesive film 1 further includes one or more of the following: matrix processing aid, UV blocking agent, and matrix crosslinking agent.

[0009] According to the encapsulating film of the present invention, the low-flow film 1 further includes a tackifier, wherein the tackifier accounts for 0.5%-5.5% of the weight of the low-flow film 1, preferably 1%-3%.

[0010] According to the encapsulating film of the present invention, the tackifying agent is epoxidized polybutadiene liquid rubber, and the viscosity of the epoxidized polybutadiene liquid rubber at 25°C is 100-20000 mPa·s, preferably 1000-6000 mPa·s.

[0011] According to the encapsulating film of the present invention, the first ultraviolet light conversion film 2 comprises the following components: a first resin, a first processing aid, a first crosslinking agent, and a first ultraviolet light conversion material; Preferably, based on 100 parts by weight of the first resin, the first ultraviolet conversion film 2 includes 0.5-2 parts of the first processing aid, 0.5-2 parts of the first crosslinking agent, and 0.05-1 parts of the first ultraviolet conversion material.

[0012] According to the encapsulation film of the present invention, the thickness of the low-flow adhesive film 1 is 80-170 micrometers, and the thickness of the first ultraviolet light conversion adhesive film 2 is 200-400 micrometers; preferably, the thickness ratio of the first ultraviolet light conversion adhesive film to the low-flow adhesive film is (1.5-4):1.

[0013] According to a second aspect of the present invention, the present invention also provides a method for preparing the above-described encapsulating film, comprising the following steps: After the low-flow adhesive film 1 is cast and extruded, it is pre-crosslinked to make the pre-crosslinking degree of the low-flow adhesive film 1 30%-60%, and then it is laminated with the first ultraviolet light conversion adhesive film 2. Alternatively, after co-extruding the low-flow adhesive film 1 and the first ultraviolet conversion adhesive film 2, the low-flow adhesive film 1 is pre-crosslinked to achieve a pre-crosslinking degree of 30%-60%.

[0014] According to a third aspect of the present invention, the present invention also provides an encapsulating film for a gridless HJT battery, the encapsulating film comprising a second ultraviolet light conversion film 4, wherein the pre-crosslinking degree of the second ultraviolet light conversion film 4 at the position corresponding to the welding wire of the gridless HJT battery is 30%-60%.

[0015] According to the encapsulating film of the present invention, the second ultraviolet conversion film is coated with a radiation-cured coating at a position having a pre-crosslinking degree.

[0016] According to the encapsulating film of the present invention, along the thickness direction, the second ultraviolet light conversion film includes a first film portion and a second film portion. When the first film portion is laid, it is close to the side of the gridless HJT cell, and when the second film portion is laid, it is away from the side of the gridless HJT cell. The pre-crosslinking degree of the first film portion at the position corresponding to the welding wire of the gridless HJT cell is 30%-60%. Preferably, the thickness of the first adhesive film portion is 80-170 micrometers; preferably, the pre-crosslinking degree of the first adhesive film portion at the position corresponding to the non-welding wire of the gridless HJT battery is <10%; preferably, the pre-crosslinking degree of the second adhesive film portion is <10%.

[0017] According to the encapsulation film of the present invention, the encapsulation film includes two or more ultraviolet light conversion films, and the two or more ultraviolet light conversion films further include a third ultraviolet light conversion film. The third ultraviolet light conversion film is stacked with the second ultraviolet light conversion film. When the second ultraviolet light conversion film is laid, it is close to the side of the gridless HJT cell, and the third ultraviolet light conversion film is located on the side of the second ultraviolet light conversion film away from the gridless HJT cell. Preferably, the pre-crosslinking degree of the second UV conversion adhesive film at the position corresponding to the gridless HJT battery welding wire is 40%-55%; preferably, the pre-crosslinking degree of the third UV conversion adhesive film is <10%, and more preferably ≤5%. Preferably, the second ultraviolet conversion film comprises the following components: a second resin, a second crosslinking agent, and a second ultraviolet conversion material; preferably, the melt index of the second resin is 5-40 g / 10 min, the second resin includes a resin containing GMA groups, the resin containing GMA groups accounts for 5-40% of the total amount of the second resin; the weight content of the GMA groups in the resin containing GMA groups is 0.1%~30%; the second crosslinking agent is an acrylate crosslinking agent.

[0018] Preferably, the second ultraviolet light conversion material is 0.05 to 1% of the weight of the second resin.

[0019] Preferably, the third ultraviolet light conversion film comprises the following components: a third resin, a third co-crosslinking agent, and a third ultraviolet light conversion material; preferably, the melt index of the third resin is 20-30 g / 10 min; the third co-crosslinking agent is an allyl-based co-crosslinking agent; Preferably, the second ultraviolet light conversion material is any one or a mixture of at least two of rare earth inorganic compounds, silicon quantum dots, GaAs quantum dots, CdS quantum dots, CdSe quantum dots, CdTe quantum dots, ZnS quantum dots, ZnSe quantum dots, ZnTe quantum dots, or perovskite quantum dots; the third ultraviolet light conversion material is any one or a mixture of at least two of organic fluorescent pigments, rare earth organic complexes, rare earth inorganic compounds, benzotriazole compounds, silicon quantum dots, GaAs quantum dots, CdS quantum dots, CdSe quantum dots, CdTe quantum dots, ZnS quantum dots, ZnSe quantum dots, ZnTe quantum dots, or perovskite quantum dots.

[0020] According to a fourth aspect of the present invention, the present invention also provides a method for preparing the above-described encapsulating film, comprising the following steps: First, the encapsulating film is cast and extruded, and then a pre-crosslinking process is used to pre-crosslink the encapsulating film so that the pre-crosslinking degree at the position corresponding to the second ultraviolet light conversion film 4 and the welding wire of the gridless HJT battery is 30%-60%. Preferably, the pre-crosslinking process includes any one of UV irradiation crosslinking, thermosetting crosslinking, and electron beam curing crosslinking; Preferably, the pre-crosslinking process is electron beam curing crosslinking; more preferably, the radiation energy of the electron beam curing crosslinking is 135-300keV, the irradiation dose is 50-200kGy, and the distance between the electron beam irradiation device and the encapsulating film is 10-55mm. Preferably, when the encapsulating film is pre-crosslinked using a pre-crosslinking process, a baffle arranged in HJT grid lines is provided above the encapsulating film.

[0021] According to a fifth aspect of the present invention, the present invention also provides a photovoltaic module, comprising a glass cover, a front encapsulation film, a grid-less HJT cell, a back encapsulation film, and a back cover, wherein the front encapsulation film and / or the back encapsulation film are the aforementioned encapsulation films; and the back cover is a glass cover or a backplate.

[0022] This invention provides an encapsulating film for grid-free HJT cells. By precisely pre-crosslinking the film or a specific area of ​​the film near the cell side, it achieves excellent low flowability. This feature effectively solves the technical problem of excessive film flowability causing overflow during low-temperature lamination, which hinders the bonding wire from forming a good connection with the cell. This significantly avoids the defect of localized darkening of the photoluminescence (EL) in the module and improves production yield. Simultaneously, this encapsulating film integrates ultraviolet light conversion, converting harmful ultraviolet light into usable visible light. This not only slows down the power degradation of the module but also increases the initial power. While ensuring low flowability, this invention maintains high adhesion strength to the cell and other materials, successfully resolving the contradiction between the three key requirements of low flowability, high adhesion, and UV degradation resistance in grid-free HJT cell encapsulation, ensuring the high performance and long-term reliability of photovoltaic modules. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the structure of an encapsulating film for a gridless HJT battery provided in a first embodiment of the present invention.

[0025] Figure 2 This is a schematic diagram of the structure of an encapsulating film for a gridless HJT battery provided in a second embodiment of the present invention.

[0026] Figure 3 This is a schematic diagram of the structure of an encapsulating film for a gridless HJT battery in a third embodiment of the present invention.

[0027] Figure 4 This is a top view of the encapsulation film for a gridless HJT battery provided in a fourth embodiment of the present invention.

[0028] Figure 5 This is a schematic diagram of the structure of an encapsulating film for a gridless HJT battery in a fifth embodiment of the present invention.

[0029] Figure 6 This is a schematic diagram of the structure of an encapsulating film for a gridless HJT battery in a sixth embodiment of the present invention.

[0030] Figure label: 1: Low flowability adhesive film; 2: First UV conversion adhesive film; 3: UV conversion coating; 4: Second UV conversion adhesive film; 41: First adhesive film portion; 42: Second adhesive film portion; 401: Pre-crosslinked region; 402: Non-pre-crosslinked region; 5: Third UV conversion adhesive film. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0032] As analyzed in the background section, the encapsulating films in the prior art generally have high fluidity, which can seep into the space between the welding wire and the HJT cell during the lamination process, causing the welding wire and the HJT cell to fail to connect, resulting in local darkening of the HJT cell's EL. To solve this problem, the present invention provides an encapsulating film for gridless HJT cells, its preparation method, and a photovoltaic module.

[0033] In a first typical embodiment of the present invention, the present invention provides an encapsulating film for gridless HJT batteries, such as... Figure 1 As shown, it includes a low-flow adhesive film 1 and a first ultraviolet light conversion adhesive film 2 stacked together, and the pre-crosslinking degree of the low-flow adhesive film 1 is 30%-60%.

[0034] Specifically, the first ultraviolet conversion adhesive film 2 and the low-flow adhesive film 1 can be laminated together by means of bonding or by means of co-extrusion molding. Optionally, the pre-crosslinking degree of the low-flow adhesive film 1 can be 30%, 35%, 40%, 45%, 50%, 55%, or 60%, etc., or other values ​​within the above range, which are not limited here.

[0035] In the above-described scheme, the encapsulating film for a gridless HJT battery of the present invention includes a low-flow encapsulating film 1 and a first ultraviolet light conversion encapsulating film 2 stacked together. During layup, the low-flow encapsulating film 1 is close to the gridless HJT battery side, and the first ultraviolet light conversion encapsulating film 2 is away from the gridless HJT battery side. By limiting the pre-crosslinking degree of the low-flow encapsulating film 1 to 30%-60%, the low flowability of the encapsulating film close to the gridless HJT battery side can be achieved, so that the encapsulating film will not seep into the space between the solder wire and the HJT battery during the lamination process, avoiding the situation where the solder wire and the HJT battery cannot be connected. It also enables the low-flow encapsulating film 1 to have high adhesive performance, achieving a firm bond between the encapsulating film and the HJT battery, improving encapsulation stability, and avoiding the phenomenon of delamination between the encapsulating film and the gridless HJT battery during aging. When the pre-crosslinking degree of the low-flow encapsulant film 1 is less than 30%, its flowability is too high. During lamination, the encapsulant film may seep between the welding wire and the HJT cell. When the pre-crosslinking degree of the low-flow encapsulant film 1 is greater than 60%, it will result in fewer reactive groups during relamination, thus reducing the adhesion of the encapsulant film. Furthermore, by combining the first ultraviolet light conversion encapsulant film 2 with the low-flow encapsulant film 1, the low flowability and adhesion performance of the encapsulant film and the encapsulant film on the side of the gridless HJT cell are ensured, while also enabling the encapsulant film to have ultraviolet light conversion function, effectively preventing the power degradation of the HJT cell assembled with this encapsulant film.

[0036] In some specific embodiments of the present invention, the low-flow adhesive film 1 comprises a matrix resin by weight parts.

[0037] The base resin is a vinyl polymer, and types commonly used in the encapsulation film industry can be used, including but not limited to polyethylene, or copolymers of ethylene and α-olefins, or copolymers of ethylene with one or more of vinyl acetate, acrylic acid, acrylates, methacrylic acid, methacrylates, maleic anhydride, and glycidyl methacrylate. Preferably, the α-olefin is one or more of propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, and 1-decene. These types of vinyl polymers have better encapsulation performance and better compatibility with the epoxidized polybutadiene liquid rubber used as a tackifier, resulting in a better synergistic effect when used together.

[0038] Depending on the specific application environment of the encapsulating film, the aforementioned low-flow encapsulating film 1 may further include one or more of the following: matrix processing aids, UV cut-off agents, and matrix co-crosslinking agents, to further improve the corresponding performance aspects of the encapsulating film. The specific types and amounts of matrix processing aids can be referenced from existing technologies. In some embodiments of this application, the matrix processing aids include any one or a combination of at least two of the following: crosslinking agents, silane coupling agents, light stabilizers, or inorganic powders. The aforementioned crosslinking agents, matrix co-crosslinking agents, UV cut-off agents, silane coupling agents, light stabilizers, and inorganic powders can all be selected from existing technologies.

[0039] Adding a crosslinking agent helps to increase the crosslinking rate of the crosslinked encapsulating film; adding a silane coupling agent helps to improve the interfacial interaction between the co-crosslinking agent and the matrix resin, thereby improving the mechanical properties of the crosslinked encapsulating film. Furthermore, preferred additives help to improve their synergistic effect with adjacent UV conversion films, thereby improving the performance of the encapsulating film.

[0040] In one embodiment of this application, the preferred crosslinking agent is selected from any one or more of the following: tert-butyl peroxycarbonate, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, 1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, tert-butyl peroxycarbonate-2-ethylhexyl ester, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-pentylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-pentylperoxy)cyclohexane, 2,2-bis(tert-butylperoxy)butane, tert-pentyl peroxycarbonate, and tert-butyl peroxide-3,3,5-trimethylhexanoate.

[0041] In one embodiment of this application, the preferred matrix co-crosslinking agent is selected from pentaerythritol triacrylate, pentaerythritol tetraacrylate, pentaerythritol tetraacrylate ethoxylated, pentaerythritol tetraacrylate propionate ethoxylated, trimethylolpropane triacrylate, trimethylolpropane triacrylate ethoxylated, trimethylolpropane triacrylate propionate ethoxylated, glycerol triacrylate propionate ethoxylated, trimethylolpropane trimethacrylate, trimethylolpropane trimethacrylate ethoxylated, triethylene glycol dimethacrylate, diethylene glycol dimethacrylate. Acrylic ester, ethylene glycol dimethacrylate, polyethylene glycol (200) diacrylate, polyethylene glycol (400) diacrylate, polyethylene glycol (600) diacrylate, polyethylene glycol (200) dimethacrylate, polyethylene glycol (400) dimethacrylate, polyethylene glycol (600) dimethacrylate, ethoxylated bisphenol A diacrylate, ethoxylated bisphenol A dimethacrylate, 1,3-butanediol diacrylate, 1,4-butanediol diacrylate, neopentyl glycol diacrylate, any one or more of these.

[0042] In one embodiment of this application, the preferred UV cutoff agent is selected from benzotriazole UV cutoff agents.

[0043] In one embodiment of this application, the preferred silane coupling agent is selected from any one or more of vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, 3-(2,3-epoxypropoxy)propyltrimethoxysilane, methacrylate silane, and vinyltriisopropoxysilane.

[0044] In one embodiment of this application, the preferred light stabilizer is selected from any one or more of bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, bis(1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate, poly(4-hydroxy-2,2,6,6-tetramethyl-1-piperidinol) ester, 2-hydroxy-4-n-octoxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-2′-carboxybenzophenone, and 2,4-dihydroxybenzophenone.

[0045] In some specific embodiments of the present invention, the low-flow film 1 comprises 0.5-2 parts of matrix processing aid, 0.1-1 parts of UV cutoff agent and 0.5-2 parts of matrix crosslinking agent, based on 100 parts by weight of matrix resin.

[0046] In some specific embodiments of the present invention, the matrix processing aid comprises 0.25-1 parts by weight of silane coupling agent and 0.25-1 parts by weight of crosslinking agent.

[0047] In some specific embodiments of the present invention, the matrix resin includes a tackifying resin; preferably, the tackifying resin is a resin containing GMA (glycidyl methacrylate) groups, and the resin containing GMA groups accounts for 5-40% of the total mass of the matrix resin. The GMA groups account for 0.1% to 30% of the weight of the resin containing GMA groups, preferably 20-30%.

[0048] Optionally, the resin containing GMA groups can be a GMA-grafted ethylene vinyl acetate copolymer, a GMA-grafted ethylene-α-olefin copolymer, an ethylene-acrylate-glycidyl methacrylate copolymer, an ethylene-glycidyl methacrylate copolymer, or an ethylene-vinyl acetate-glycidyl methacrylate copolymer.

[0049] In the above scheme, by limiting the matrix resin to include a tackifying resin, the adhesive properties of the low-flow adhesive film 1 can be further improved. In some specific embodiments of the present invention, the tackifying agent of the low-flow adhesive film 1 accounts for 0.5%-5.5% by weight of the low-flow adhesive film 1, preferably 1%-3%; and / or, the tackifying agent can be epoxidized polybutadiene liquid rubber, wherein the epoxidized polybutadiene liquid rubber has a viscosity of 100-20000 mPa·s at 25°C, preferably 1000-6000 mPa·s.

[0050] Preferably, the number-average molecular weight (Mn) of the epoxidized polybutadiene liquid rubber is 2000–10000, and the molecular weight distribution index (D) is 1.01–2.5. Polybutadiene liquid rubber generally has a molecular weight of less than 10,000 and is a flowing liquid at room temperature, offering significant advantages over solid rubber during processing. The molecular weight and microstructure of the rubber have a significant impact on product performance. During polymerization, 1,3-butadiene monomers produce three main microstructures: cis-1,4, trans-1,4, and 1,2-vinyl structures. Among these, a higher content of the 1,4-structure, especially the cis-1,4-structure, results in better molecular chain flexibility, lower viscosity, and lower glass transition temperature. The 1,2-vinyl structure helps improve the product's resistance to wet slip and heat-induced oxidation.

[0051] Applying the technical solution of this application, this application selects an epoxidized polybutadiene liquid rubber with a specific content of epoxy bonds and carbon-carbon double bonds, and with a specific ratio of cis-1,4-polybutadiene segments, trans-1,4-polybutadiene segments, and 1,2-structure polybutadiene segments, as well as a specific range of number-average molecular weight, viscosity, and molecular weight distribution, as a tackifier. This results in the tackifier provided by this application possessing not only excellent anti-slip and heat resistance, but also excellent permeability and flexibility, while exhibiting high polarity and excellent compatibility with polar substances. Therefore, when added to a resin composition, it can form a highly polar encapsulating film with vinyl polymers, which firmly bonds to the transparent oxide film and grid lines on the surface of the heterojunction battery, effectively meeting the encapsulation requirements of heterojunction batteries.

[0052] In the above scheme, by limiting the low-flow adhesive film 1 to also include a tackifier, the bonding performance of the low-flow adhesive film 1 can be further improved, and the amount of tackifier can be further limited to a reasonable range, so as to ensure the bonding performance of the low-flow adhesive film 1 without affecting the peel performance of the encapsulation film.

[0053] In some specific embodiments of the present invention, the first ultraviolet light conversion film 2 includes the following components: a first resin, a first processing aid, a first crosslinking agent, and a first ultraviolet light conversion material.

[0054] Preferably, the first resin can be EVA resin, POE resin, EAA resin, EEA resin or EMA resin, etc., and preferably, the first resin is EVA resin.

[0055] Preferably, the first processing aid includes any one or a combination of at least two of the following: a crosslinking agent, a silane coupling agent, a light stabilizer, or an inorganic powder.

[0056] Preferably, the first co-crosslinking agent can be an allyl co-crosslinking agent, such as triallyl isocyanurate or triallyl cyanurate.

[0057] Preferably, the first ultraviolet light conversion material is any one or a mixture of at least two of the following: organic fluorescent pigment, rare earth organic complex, rare earth inorganic compound, benzotriazole compound, silicon quantum dot, GaAs quantum dot, CdS quantum dot, CdSe quantum dot, CdTe quantum dot, ZnS quantum dot, ZnSe quantum dot, ZnTe quantum dot, or perovskite quantum dot.

[0058] In some specific embodiments of the present invention, based on 100 parts by weight of the first resin, the first ultraviolet light conversion film 2 includes 0.5-2 parts of the first processing aid, 0.5-2 parts of the first crosslinking agent and 0.05-1 parts of the first ultraviolet light conversion material.

[0059] In some specific embodiments of the present invention, the first processing aid comprises 0.25-1 parts by weight of silane coupling agent and 0.25-1 parts by weight of crosslinking agent.

[0060] In some specific embodiments of the present invention, the thickness of the low-flow adhesive film 1 is 80-170 micrometers, and the thickness of the first ultraviolet light conversion adhesive film 2 is 200-400 micrometers.

[0061] In the above scheme, by limiting the thickness of the low-flow encapsulant film 1 and the first ultraviolet light conversion encapsulant film 2 to a reasonable range, the overall structure of the assembled photovoltaic module is not affected while ensuring that the encapsulant film has excellent adhesion performance, low flow on the battery side and ultraviolet light conversion function.

[0062] In some specific embodiments of the present invention, the thickness ratio of the first ultraviolet conversion film 2 to the low flowability film 1 is (1.5~4):1.

[0063] In the above scheme, by limiting the thickness ratio of the low-flow encapsulant film 1 and the first ultraviolet light conversion encapsulant film 2 to a reasonable range, the low-flow encapsulant film 1 and the first ultraviolet light conversion encapsulant film 2 can play a better synergistic effect. While ensuring that the encapsulating film has excellent adhesion performance, low flow on the battery side and ultraviolet light conversion function, it does not affect the overall structure of the assembled photovoltaic module.

[0064] In a second typical embodiment of the present invention, the present invention provides a method for preparing the above-mentioned encapsulating film, comprising the following steps: After the low-flow adhesive film 1 is cast and extruded, it is pre-crosslinked to make the pre-crosslinking degree of the low-flow adhesive film 1 30%-60%, and then it is laminated with the first ultraviolet light conversion adhesive film 2. Alternatively, after co-extruding the low-flow adhesive film 1 and the first ultraviolet conversion adhesive film 2, the low-flow adhesive film 1 is pre-crosslinked to achieve a pre-crosslinking degree of 30%-60%.

[0065] Optionally, the pre-crosslinking treatment may include any one of UV irradiation crosslinking, thermosetting crosslinking, and electron beam curing crosslinking.

[0066] In the above scheme, by pre-crosslinking the low-flow adhesive film 1 after casting and extrusion and then bonding it with the first UV conversion adhesive film 2, or by co-extruding the low-flow adhesive film 1 and the first UV conversion adhesive film 2 and then pre-crosslinking the low-flow adhesive film 1 separately, the pre-crosslinking of the low-flow adhesive film 1 can be achieved, ensuring the low flowability of the low-flow adhesive film 1, while avoiding the pre-crosslinking treatment of the first UV conversion adhesive film 2. This effectively prevents the loss of UV conversion material in the first UV conversion adhesive film 2 due to the pre-crosslinking process, and ensures the UV conversion function of the encapsulation film.

[0067] In some specific embodiments of the present invention, such as Figure 2 As shown, a UV conversion coating 3 is coated onto the pre-crosslinked low-flow adhesive film 1, and then it is bonded to the first UV conversion adhesive film 2.

[0068] Preferably, the ultraviolet conversion coating 3 comprises the following components: 40-80 parts of UV resin; 10-30 parts of diluent monomer; 0-5 parts of photoinitiator or thermal initiator; 1-20 parts of ultraviolet conversion material; and 1-5 parts of additives.

[0069] Preferably, the UV resin has an elongation of ≥100%; preferably, the UV resin is selected from any one or more of polyurethane acrylate, polyester acrylate, and pure acrylate; preferably, the polyurethane acrylate is selected from any one or more of CN8881NS, CN8887NS, CN8888NS, CN9001 NS, CN9021, CN966J75 NS, 6148J-75, DR-U299, and DR-U384; preferably, the polyester acrylate is selected from any one or more of CN704, CN710, CN3108 NS, and DR-E524; preferably, the pure acrylate is selected from any one or more of 6584N-1, DR-A845, and DR-A822.

[0070] Preferably, the diluent monomer is an organic compound containing a C=C double bond, preferably the molecular weight of the diluent monomer is 100 to 1000, and preferably the diluent monomer is selected from any one or more of (meth)acrylates and vinyl ethers.

[0071] Preferably, the photoinitiator is an ultraviolet photoinitiator, and more preferably, the ultraviolet photoinitiator is selected from any one or more of photoinitiator TPO, photoinitiator 184, photoinitiator 1173, and photoinitiator TPO-L.

[0072] The thermal initiator is a peroxide-based crosslinking agent or an aziridine-based crosslinking agent, preferably an aziridine-based crosslinking agent.

[0073] The preferred additives are selected from any one or more of dispersants, defoamers, and leveling agents. Preferably, the dispersant is selected from any one or more of anionic dispersants and polymeric dispersants. Preferably, the defoamer is selected from any one or more of acrylate defoamers and silicone defoamers. Preferably, the leveling agent is selected from any one or more of acrylate leveling agents and fluorocarbon leveling agents.

[0074] The ultraviolet light conversion material in the ultraviolet light conversion coating 3 is any one or a mixture of at least two of the following: organic fluorescent pigments, rare earth organic complexes, rare earth inorganic compounds, benzotriazole compounds, silicon quantum dots, GaAs quantum dots, CdS quantum dots, CdSe quantum dots, CdTe quantum dots, ZnS quantum dots, ZnSe quantum dots, ZnTe quantum dots, or perovskite quantum dots.

[0075] In the above scheme, a UV conversion coating 3 is coated onto the low-flowability adhesive film 1 after pre-crosslinking treatment. The UV conversion coating 3 can reduce the amount of UV conversion additives used in the adhesive film. In addition, the UV conversion coating 3 has UV conversion function, which can further improve the UV conversion function of the encapsulation film. Furthermore, the composition of the UV conversion coating 3 is further defined so that it can play a better synergistic role with the first UV conversion adhesive film 2, and better improve the UV conversion function of the entire encapsulation film.

[0076] In a third typical embodiment of the present invention, the present invention also provides an encapsulating film for gridless HJT batteries, such as... Figure 3 As shown, the encapsulating film includes a second ultraviolet light conversion film 4, and the pre-crosslinking degree of the second ultraviolet light conversion film 4 at the position corresponding to the welding wire of the gridless HJT battery is 30%-60%.

[0077] Optionally, the pre-crosslinking degree at the position corresponding to the gridless HJT battery welding wire of the second ultraviolet conversion film 4 can be 30%, 35%, 40%, 45%, 50%, 55% or 60%, etc., or other values ​​within the above range, which are not limited here.

[0078] In the above scheme, the encapsulating film includes a second ultraviolet light conversion film 4, which has an ultraviolet light conversion function. At the same time, the pre-crosslinking degree of the second ultraviolet light conversion film 4 at the position corresponding to the welding wire of the gridless HJT cell is limited to 30%-60%. This can achieve low flowability of the encapsulating film near the welding wire position on the gridless HJT cell side, so that the encapsulating film will not seep into the gap between the welding wire and the HJT cell during the lamination process, avoiding the situation where the welding wire and the HJT cell cannot be connected. It can also make the encapsulating film have high adhesion performance at the welding wire position, which can achieve a firm bond between the encapsulating film and the HJT cell, improve the encapsulation stability, and avoid the phenomenon of delamination between the encapsulating film and the gridless HJT cell during aging. When the pre-crosslinking degree of the second UV conversion film 4 at the position corresponding to the welding wire of the gridless HJT cell is less than 30%, the fluidity is too high. During the lamination process, the encapsulation film may seep into the space between the welding wire and the HJT cell. When the pre-crosslinking degree of the second UV conversion film 4 at the position corresponding to the welding wire of the gridless HJT cell is greater than 60%, it will result in fewer reactive groups during relamination, thereby reducing the adhesion of the encapsulation film.

[0079] Specifically, the second ultraviolet light conversion film 4 may not be pre-crosslinked at the position corresponding to the non-welding wire of the gridless HJT battery, or it may be pre-crosslinked with a pre-crosslinking degree of <10% to reduce the damage to the ultraviolet light conversion material in the second ultraviolet light conversion film 4 caused by excessive pre-crosslinking.

[0080] like Figure 4 As shown, the second UV conversion film 4 is not pre-crosslinked at the positions corresponding to the non-welding wires of the gridless HJT cell. Thus, the second UV conversion film 4 has pre-crosslinked regions 401 and non-pre-crosslinked regions 402 formed on it. The pre-crosslinked regions 401 correspond to the welding wire positions of the gridless HJT cell, and the non-pre-crosslinked regions 402 correspond to the non-welding wire positions of the gridless HJT cell. The pre-crosslinked regions 401 and non-pre-crosslinked regions 402 are arranged at intervals along the length or width direction of the second UV conversion film 4.

[0081] In some specific embodiments of the present invention, the second ultraviolet conversion film 4 is coated with a radiation-cured coating at a position having a pre-crosslinking degree.

[0082] In the above scheme, by coating the second ultraviolet light conversion film 4 with a radiation-cured coating at the pre-crosslinked position, the damage to the light conversion material in the second ultraviolet light conversion film 4 by the pretreatment process (such as electron beam radiation) can be avoided, thus ensuring the ultraviolet light conversion function of the encapsulation film.

[0083] In some specific embodiments of the present invention, the second ultraviolet light conversion film 4 includes the following components: a second resin, a second processing aid, a second crosslinking agent, and a second ultraviolet light conversion material.

[0084] Preferably, the melt index of the second resin is 5-40 g / 10 min. Optionally, the second resin can be EVA resin, POE resin, EAA resin, EEA resin, or EMA resin, etc., preferably, the second resin is EVA resin.

[0085] Preferably, the second processing aid includes any one or a combination of at least two of the following: a crosslinking agent, a silane coupling agent, a light stabilizer, or an inorganic powder.

[0086] Preferably, the second crosslinking agent is an acrylate crosslinking agent. The acrylate crosslinking agent can be any one or a mixture of at least two of trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate, and ethoxylated pentaerythritol tetraacrylate. The second ultraviolet light conversion material is any one or a mixture of at least two of rare earth inorganic compounds, silicon quantum dots, GaAs quantum dots, CdS quantum dots, CdSe quantum dots, CdTe quantum dots, ZnS quantum dots, ZnSe quantum dots, ZnTe quantum dots, or perovskite quantum dots.

[0087] In the above scheme, by limiting the components of the second UV-conversion film 4 and the amounts of each component, the second UV-conversion film 4 can have better adhesion properties and good pre-crosslinking processing properties, thereby achieving an ideal degree of pre-crosslinking and thus realizing the low flowability of the second UV-conversion film 4. Furthermore, by using a low melt index second resin in the above scheme, combined with an acrylate-based co-crosslinking agent, the pre-crosslinking speed of the second UV-conversion film 4 can be relatively faster, thereby achieving the goal of a high degree of pre-crosslinking.

[0088] In some specific embodiments of the present invention, the second ultraviolet conversion film 4, based on 100 parts by weight of the second resin, comprises the following components: 0.5-2 parts of the second processing aid, 0.05-3 parts of the second crosslinking agent, and 0.05-1 parts of the second ultraviolet conversion material; preferably, the melt index of the second resin is 20-40 g / 10 min.

[0089] In some specific embodiments of the present invention, the second processing aid comprises 0.25-1 parts by weight of silane coupling agent and 0.25-1 parts by weight of crosslinking agent.

[0090] In some specific embodiments of the present invention, the second ultraviolet light conversion material is 0.05 to 1% of the weight of the second resin.

[0091] In the above scheme, by limiting the amount of the second ultraviolet light conversion material within a reasonable range, it is beneficial to realize the ultraviolet light conversion function, while not affecting the transparency and low flow performance of the encapsulation film.

[0092] In some specific embodiments of the present invention, the second resin includes a tackifying resin; preferably, the tackifying resin is a resin containing GMA groups, and the resin containing GMA groups accounts for 5-40% of the total mass of the matrix resin. The GMA groups account for 0.1% to 30% of the weight of the resin containing GMA groups, preferably 20-30%.

[0093] Optionally, the resin containing GMA groups can be a GMA-grafted ethylene-vinyl acetate copolymer, a GMA-grafted ethylene-α-olefin copolymer, an ethylene-acrylate-glycidyl methacrylate copolymer, an ethylene-glycidyl methacrylate copolymer, or an ethylene-vinyl acetate-glycidyl methacrylate copolymer.

[0094] In the above scheme, by limiting the second resin to include a tackifying resin, the adhesion performance of the second ultraviolet light conversion film 4 can be further improved.

[0095] In some specific embodiments of the present invention, the second ultraviolet conversion film 4 further includes a tackifier, the tackifier accounting for 0.5%-5% of the weight of the second ultraviolet conversion film 4, preferably 1%-3%; and / or, the tackifier of the second ultraviolet conversion film 4 is epoxidized polybutadiene liquid rubber, the viscosity of the epoxidized polybutadiene liquid rubber at 25°C is 100-20000 mPa·s, preferably 1000-6000 mPa·s.

[0096] In the above scheme, by limiting the second ultraviolet light conversion adhesive film 4 to also include an adhesion promoter, the adhesion performance of the second ultraviolet light conversion adhesive film 4 can be further improved, and the amount of adhesion promoter can be further limited to a reasonable range. While ensuring the adhesion performance of the second ultraviolet light conversion adhesive film 4, the peel performance of the encapsulation film is not affected.

[0097] The encapsulation film of the present invention may include one layer of ultraviolet light conversion film, or two or more layers of ultraviolet light conversion film.

[0098] In some specific embodiments of the present invention, the encapsulating film of the present invention may include a layer of ultraviolet light conversion film. For example... Figure 5 As shown, along the thickness direction, the second ultraviolet light conversion film 4 includes a first film portion 41 and a second film portion 42. When the first film portion 41 is laid, it is close to the side of the gridless HJT cell, and when the second film portion 42 is laid, it is away from the side of the gridless HJT cell. The pre-crosslinking degree at the position of the first film portion 41 corresponding to the welding wire of the gridless HJT cell is 30%-60%. Preferably, the thickness of the first film portion 41 is 80-170 micrometers.

[0099] In the above scheme, by pre-crosslinking the first encapsulant film portion 41 near the gridless HJT cell side, the pre-crosslinking degree of the first encapsulant film portion 41 at the position corresponding to the gridless HJT cell welding wire is 30%-60%. The encapsulant film, through the second ultraviolet light conversion encapsulant film 4, can not only realize the ultraviolet light conversion function of the encapsulant film, but also achieve low flowability of the encapsulant film near the welding wire position on the gridless HJT cell side. This prevents the encapsulant film from seeping into the gap between the welding wire and the HJT cell during the lamination process, avoiding the situation where the welding wire and the HJT cell cannot be connected. It also makes the encapsulant film have high adhesion performance at the welding wire position, which can achieve a firm bond between the encapsulant film and the HJT cell, improve the encapsulation stability, and avoid the phenomenon of delamination between the encapsulant film and the gridless HJT cell during aging.

[0100] Furthermore, the first adhesive film portion 41 can be pre-crosslinked at the position corresponding to the non-welding wire of the gridless HJT battery, or it can be left untreated.

[0101] In some specific embodiments of the present invention, in order to improve the bonding performance between the first adhesive film portion 41 and the non-welding wire of the gridless HJT battery, and at the same time reduce the damage to the ultraviolet light conversion material in the second ultraviolet light conversion adhesive film 4 caused by excessive pre-crosslinking treatment, the pre-crosslinking degree between the first adhesive film portion 41 and the non-welding wire of the gridless HJT battery is <10% (preferably ≤5%).

[0102] Furthermore, the second adhesive film portion 42 may or may not undergo pre-crosslinking treatment.

[0103] In some specific embodiments of the present invention, in order to improve the adhesion performance between the second ultraviolet light conversion film 4 and the glass cover plate or back cover plate, and at the same time reduce the damage to the ultraviolet light conversion material in the second ultraviolet light conversion film 4 caused by excessive pre-crosslinking treatment, the second film portion 42 can be pre-crosslinked, and the pre-crosslinking degree of the second film portion 42 is ensured to be <10% (preferably ≤5%).

[0104] The encapsulating film of this invention may include two or more layers of ultraviolet (UV) conversion films. The design of multiple layers of UV conversion films can minimize or avoid damage to the light conversion material in the UV conversion films caused by pre-crosslinking treatment. The two or more layers of UV conversion films can be joined by lamination or by co-extrusion molding.

[0105] In some specific embodiments of the present invention, the encapsulating film comprises two layers of ultraviolet light conversion film, such as... Figure 6 As shown, the encapsulating film also includes a third ultraviolet light conversion film 5, which is stacked with the second ultraviolet light conversion film 4. When the second ultraviolet light conversion film 4 is laid, it is close to the side of the gridless HJT cell, and the third ultraviolet light conversion film 5 is located on the side of the second ultraviolet light conversion film 4 away from the gridless HJT cell.

[0106] In the above scheme, the encapsulation film of the present invention includes two layers of ultraviolet light conversion film. The second ultraviolet light conversion film 4 can be used to bond with the gridless HJT cell, and the third ultraviolet light conversion film 5 can be used to bond with the glass cover or the back cover.

[0107] In some specific embodiments of the present invention, the pre-crosslinking degree at the position corresponding to the gridless HJT battery welding wire of the second ultraviolet conversion adhesive film 4 is 40%-55%.

[0108] In the above scheme, by further limiting the pre-crosslinking degree of the second ultraviolet light conversion adhesive film 4 to 40%-55% at the position corresponding to the gridless HJT battery welding wire, the low flowability and adhesion performance of the battery-side adhesive film of the encapsulation film can be achieved more effectively, and the encapsulation performance of the encapsulation film can be better realized.

[0109] In some specific embodiments of the present invention, the pre-crosslinking degree of the third ultraviolet light conversion film 5 is <10%, preferably ≤5%.

[0110] In the above scheme, by limiting the pre-crosslinking degree of the third UV conversion film 5 on the side away from the gridless HJT cell to a reasonable range, the adhesion performance of the encapsulation film on the side away from the gridless HJT cell can be improved more effectively, and the encapsulation performance of the encapsulation film can be better achieved. At the same time, it can also reduce the damage to the UV conversion material in the third UV conversion film 5 caused by excessive pre-crosslinking treatment.

[0111] In some specific embodiments of the present invention, the second ultraviolet light conversion film 4 comprises the following components: a second resin, a second crosslinking agent, and a second ultraviolet light conversion material; preferably, the melt index of the second resin is ≤15g / 10min, the second resin comprises a resin containing GMA groups, the resin containing GMA groups accounts for 20-40% of the total amount of the second resin; the GMA groups account for 0.1% to 30% of the weight content of the resin containing GMA groups.

[0112] In some specific embodiments of the present invention, the second ultraviolet conversion film 4 comprises the following components based on 100 parts by weight of the second resin: 0.05-3 parts of the second crosslinking agent and 0.05-1 parts of the second ultraviolet conversion material; preferably, the melt index of the second resin is 5-15 g / 10 min.

[0113] In some specific embodiments of the present invention, the third ultraviolet light conversion film 5 comprises the following components: a third resin, a third co-crosslinking agent, and a third ultraviolet light conversion material; preferably, the melt index of the third resin is 20-30 g / 10 min; the third co-crosslinking agent is an allyl co-crosslinking agent.

[0114] Optionally, the third resin can be EVA resin, POE resin, EAA resin, EEA resin, or EMA resin, etc. The allyl crosslinking agent can be triallyl isocyanurate or triallyl cyanurate, etc. The third ultraviolet light conversion material is any one or a mixture of at least two of the following: organic fluorescent pigments, rare earth organic complexes, rare earth inorganic compounds, benzotriazole compounds, silicon quantum dots, GaAs quantum dots, CdS quantum dots, CdSe quantum dots, CdTe quantum dots, ZnS quantum dots, ZnSe quantum dots, ZnTe quantum dots, or perovskite quantum dots.

[0115] In the above scheme, by limiting the components of the third UV-conversion film 5 and the amounts of each component, the third UV-conversion film 5 can have better adhesion performance and good pre-crosslinking processing performance, thereby achieving an ideal degree of pre-crosslinking and ensuring the adhesion performance between the third UV-conversion film 5 and the glass cover plate or back cover plate. Furthermore, by using a conventional melt index third resin in the above scheme, combined with an allyl-based co-crosslinking agent, the pre-crosslinking speed of the third UV-conversion film 5 can be slowed down, thus achieving the goal of a low degree of pre-crosslinking.

[0116] In a fourth typical embodiment of the present invention, the present invention also provides a method for preparing the above-mentioned encapsulating film, comprising the following steps: First, the encapsulating film is cast and extruded, and then a pre-crosslinking process is used to pre-crosslink the encapsulating film so that the pre-crosslinking degree at the position corresponding to the second ultraviolet light conversion film 4 and the gridless HJT battery welding wire is 30%-60%.

[0117] In some specific embodiments of the present invention, the pre-crosslinking process includes any one of UV irradiation crosslinking, thermosetting crosslinking, and electron beam curing crosslinking.

[0118] Preferably, the pre-crosslinking process is electron beam curing crosslinking; more preferably, the radiation energy of electron beam curing crosslinking is 135-300 keV, the irradiation dose is 50-200 kGy, and the distance between the electron beam irradiation equipment and the encapsulating film is 10-55 mm. More preferably, the radiation energy of electron beam curing crosslinking is 200-300 keV.

[0119] In the above scheme, the pre-crosslinking treatment of the encapsulating film can be effectively achieved by selecting a suitable pre-crosslinking process. Further selecting electron beam curing crosslinking as the pre-crosslinking process, and rationally selecting the radiation energy, irradiation dose, and distance between the electron beam irradiation equipment and the encapsulating film, can better achieve the target degree of pre-crosslinking.

[0120] In some specific embodiments of the present invention, when the encapsulating film is pre-crosslinked using a pre-crosslinking process, a baffle arranged in HJT grid lines is provided above the encapsulating film.

[0121] In the above scheme, when the encapsulation film is pre-crosslinked using a pre-crosslinking process, by setting a baffle arranged according to the HJT grid lines above the encapsulation film, the encapsulation film can avoid the pre-crosslinking treatment of the positions corresponding to the HJT grid lines, and only the positions corresponding to the HJT battery welding wires are pre-crosslinked.

[0122] In a fifth typical embodiment of the present invention, the present invention also provides a photovoltaic module, including a glass cover plate, a front encapsulation film, a gridless HJT cell, a back encapsulation film, and a back cover plate, wherein the front encapsulation film and / or the back encapsulation film are the encapsulation films in the first typical embodiment of the present invention or the third typical embodiment of the present invention; the back cover plate is a glass cover plate or a back plate.

[0123] In the above solution, the encapsulating film of the present invention is used for encapsulation between the glass cover plate, the gridless HJT battery cell and the back cover plate. The encapsulating film has low flowability, high adhesion performance and ultraviolet light conversion function. During the lamination process, the encapsulating film will not seep into the space between the welding wire and the HJT battery, avoiding the situation where the welding wire and the HJT battery cannot be connected. It can achieve a firm bond between the components, improve the encapsulation stability, and effectively avoid the power decay of the HJT battery.

[0124] The beneficial effects of the present invention will be described below with reference to specific embodiments and comparative examples.

[0125] Example 1 This embodiment provides an encapsulating film for gridless HJT batteries, such as... Figure 1 As shown, the film includes a low-flow adhesive film 1 and a first ultraviolet conversion adhesive film 2 stacked together. The pre-crosslinking degree of the low-flow adhesive film 1 is 45%. The thickness of the low-flow adhesive film 1 is 80 micrometers, and the thickness of the first ultraviolet conversion adhesive film 2 is 200 micrometers. The thickness ratio of the first ultraviolet conversion adhesive film 2 to the low-flow adhesive film 1 is 2.5:1.

[0126] The base resin of the low-flow film 1 consists of 70 parts by weight of EVA with a melt index of 15 g / 10 min, 30 parts by weight of ethylene-acrylate-glycidyl methacrylate copolymer with a melt index of 7 g / 10 min and a GMA content of 3.5%; the low-flow film 1 also contains 1 part of a matrix processing aid (composed of 0.5 parts by weight of silane coupling agent γ-methacryloyloxypropyltrimethoxysilane and 0.5 parts by weight of crosslinking agent dicumyl peroxide), 0.5 parts by weight of benzotriazole UV cutoff agent 2-(2'-hydroxy-5'-methylphenyl)benzotriazole and 1 part by weight of matrix co-crosslinking agent allyl acrylate.

[0127] The first UV conversion film 2 is composed of 100 parts by weight of EVA with a melt index of 30 g / 10 min, 1 part of processing aid (composed of 0.5 parts by weight of silane coupling agent γ-methacryloyloxypropyltrimethoxysilane and 0.5 parts by weight of crosslinking agent dicumyl peroxide), 0.8 parts of benzotriazole compound and 1 part by weight of co-crosslinking agent triallyl cyanurate.

[0128] The preparation method of the encapsulating film for gridless HJT cells is as follows: After the low-flow adhesive film 1 is cast and extruded, it is pre-crosslinked to make the pre-crosslinking degree of the low-flow adhesive film 1 45%, and then it is laminated with the first ultraviolet light conversion adhesive film 2.

[0129] Examples 2-5 This embodiment provides an encapsulation film for gridless HJT batteries. The difference from Embodiment 1 is that the pre-crosslinking degree of the low flow film 1 is 30%, 40%, 50% and 60%, respectively.

[0130] Examples 6-11 This embodiment provides an encapsulation film for gridless HJT batteries. The difference from Embodiment 1 is that in the low-flow film 1, the GMA content in the ethylene-acrylate-glycidyl methacrylate copolymer is 0.1%, 7%, 10%, 20%, 25%, and 30%, respectively, and the melt index is 7g / 10min, 7g / 10min, 3g / 10min, 7g / 10min, 15g / 10min, and 30g / 10min, respectively.

[0131] Example 12 This embodiment provides an encapsulation film for gridless HJT batteries. The difference from Embodiment 1 is that in the low flow film 1, the matrix resin is composed of 100 parts by weight of EVA with a melt index of 15 g / 10 min, and contains 0.5 parts by weight of epoxidized polybutadiene liquid rubber.

[0132] Examples 13-18 This embodiment provides an encapsulation film for gridless HJT batteries. The difference from Embodiment 1 is that the low-flow film 1 further includes a tackifier, which is epoxidized polybutadiene liquid rubber with a viscosity of 3000 mPa·s at 25°C. The tackifier in the low-flow film 1 is present in weight proportions of 0.5 parts, 1 part, 2.1 parts, 3.2 parts, 4.3 parts, and 5.3 parts, respectively.

[0133] Example 19 This embodiment provides an encapsulating film for a gridless HJT battery. The difference from Embodiment 15 is that the low-flow film 1 has a thickness of 80 micrometers, and the first ultraviolet conversion film 2 has a thickness of 240 micrometers. The thickness ratio of the first ultraviolet conversion film 2 to the low-flow film 1 is 3:1.

[0134] Example 20 This embodiment provides an encapsulating film for a gridless HJT battery. The difference from Embodiment 19 is that the low-flow film 1 has a thickness of 150 micrometers, and the first ultraviolet conversion film 2 has a thickness of 225 micrometers. The thickness ratio of the first ultraviolet conversion film 2 to the low-flow film 1 is 1.5:1.

[0135] Example 21 This embodiment provides an encapsulating film for a gridless HJT battery. The difference from Embodiment 19 is that the low-flow film 1 has a thickness of 170 micrometers, and the first ultraviolet conversion film 2 has a thickness of 400 micrometers. The thickness ratio of the first ultraviolet conversion film 2 to the low-flow film 1 is 2.35:1.

[0136] Example 22 This embodiment provides an encapsulating film for a gridless HJT battery. The difference from Embodiment 19 is that the low-flow film 1 has a thickness of 100 micrometers, and the first ultraviolet conversion film 2 has a thickness of 400 micrometers. The thickness ratio of the first ultraviolet conversion film 2 to the low-flow film 1 is 4:1.

[0137] Example 23 This embodiment provides an encapsulating film for gridless HJT batteries, which differs from Embodiment 19 in that the preparation method of the encapsulating film for gridless HJT batteries is as follows: After co-extruding the low-flow adhesive film 1 and the first ultraviolet conversion adhesive film 2, the low-flow adhesive film 1 is pre-crosslinked to make the pre-crosslinking degree of the low-flow adhesive film 1 45%.

[0138] Comparative Examples 1-2 This comparative example provides an encapsulating film for gridless HJT batteries. The difference from Example 1 is that the pre-crosslinking degree of the low-flow film 1 is 25% and 65%, respectively.

[0139] Example 24 This embodiment provides an encapsulating film for gridless HJT batteries, the structure of which is as follows: Figure 3 As shown, the encapsulating film includes a second ultraviolet conversion film 4. The second ultraviolet conversion film 4 is composed of a matrix resin consisting of 100 parts by weight of EVA with a melt index of 30 g / 10 min, 0.5 parts by weight of epoxidized polybutadiene liquid rubber, and 1 part by weight of processing aid (composed of 0.5 parts by weight of silane coupling agent γ-methacryloyloxypropyltrimethoxysilane and 0.5 parts by weight of crosslinking agent dicumyl peroxide), 0.8 parts of silicon quantum dots, and 1 part by weight of co-crosslinking agent trimethylolpropane triacrylate.

[0140] like Figure 5 As shown, along the thickness direction, the second ultraviolet light conversion film 4 includes a first film portion 41 and a second film portion 42. When the first film portion 41 is laid, it is close to the side of the gridless HJT cell, and when the second film portion 42 is laid, it is away from the side of the gridless HJT cell.

[0141] The pre-crosslinking degree at the position corresponding to the gridless HJT battery welding wire of the first adhesive film 41 is 45%, the thickness of the first adhesive film 41 is 80 micrometers, and the thickness of the second adhesive film 42 is 200 micrometers.

[0142] The preparation method of the encapsulating film is as follows: First, the encapsulating film is cast and extruded, and then a pre-crosslinking process is used to pre-crosslink the encapsulating film so that the pre-crosslinking degree at the position corresponding to the second ultraviolet light conversion film 4 and the welding wire of the gridless HJT battery is 45%; the pre-crosslinking process is electron beam curing crosslinking; the radiation energy of electron beam curing crosslinking is 150keV, the irradiation dose is 160kGy, and the distance between the electron beam irradiation equipment and the encapsulating film is 10mm; when the encapsulating film is pre-crosslinked, a baffle arranged according to the HJT grid lines is set above the encapsulating film.

[0143] Examples 25-28 This embodiment provides an encapsulating film for gridless HJT batteries. The difference from Embodiment 24 is that the pre-crosslinking degree at the positions of the first film portion 41 and the corresponding positions of the gridless HJT battery welding wires is 30%, 40%, 50%, and 60%, respectively. The corresponding irradiation doses are 130 kGy, 150 kGy, 180 kGy, and 200 kGy, respectively.

[0144] Examples 29-32 This embodiment provides an encapsulation film for gridless HJT batteries. The difference from embodiment 24 is that the pre-crosslinking degree of the first film portion 41 at the position corresponding to the non-welding wire of the gridless HJT battery is 1%, 5%, 9% and 10%.

[0145] Examples 33-36 This embodiment provides an encapsulation film for gridless HJT batteries, which differs from Embodiment 29 in that the pre-crosslinking degree of the second film portion 42 is 1%, 5%, 9% and 10%.

[0146] Example 37 This embodiment provides an encapsulating film for gridless HJT batteries. The difference from embodiment 24 is that the second ultraviolet conversion film 4 is coated with a radiation-cured coating at the pre-crosslinked position. The radiation-cured coating is composed of 84 parts CN8881 NS, 7 parts isobornyl acrylate, 7 parts neopentyl glycol diacrylate, 1 part BYK-110 and 1 part BYK-1790.

[0147] Comparative Examples 3-4 This comparative example provides an encapsulation film for a gridless HJT battery. The difference from Example 24 is that the pre-crosslinking degree of the first film portion 41 at the position corresponding to the gridless HJT battery welding wire is 25% and 65%, respectively.

[0148] Example 38 This embodiment provides an encapsulating film for gridless HJT batteries, the structure of which is as follows: Figure 6As shown, the encapsulating film includes a second ultraviolet (UV) conversion film 4 and a third UV conversion film 5. The third UV conversion film 5 is stacked with the second UV conversion film 4. When the second UV conversion film 4 is laid, it is closer to the side of the gridless HJT cell, and the third UV conversion film 5 is located on the side of the second UV conversion film 4 away from the gridless HJT cell. The thicknesses of the second UV conversion film 4 and the third UV conversion film 5 are 80 micrometers and 200 micrometers, respectively. The pre-crosslinking degree at the position of the second UV conversion film 4 corresponding to the gridless HJT cell bonding wire is 50%.

[0149] The second ultraviolet light conversion film 4 comprises the following components: 100 parts by weight of a second resin, 1 part by weight of a second co-crosslinking agent, and 0.05 parts by weight of a second ultraviolet light conversion material. The second resin is composed of 70 parts by weight of EVA with a melt index of 15 g / 10 min, 30 parts by weight of ethylene-acrylate-glycidyl methacrylate copolymer with a melt index of 7 g / 10 min and 3.5% GMA content. The second co-crosslinking agent is trimethylolpropane triacrylate, and the second ultraviolet light conversion material is silicon quantum dots.

[0150] The third ultraviolet conversion film 5 comprises the following components: 100 parts by weight of third resin, 0.8 parts by weight of third co-crosslinking agent and 1 part by weight of third ultraviolet conversion material, wherein the third resin is EVA with a melt index of 25 g / 10 min, the third co-crosslinking agent is triallyl cyanurate, and the third ultraviolet conversion material is a benzotriazole compound.

[0151] The preparation method of the encapsulating film is as follows: First, the encapsulating film is cast and extruded, and then a pre-crosslinking process is used to pre-crosslink the encapsulating film so that the pre-crosslinking degree at the position corresponding to the second ultraviolet light conversion film 4 and the welding wire of the gridless HJT battery is 45%; the pre-crosslinking process is electron beam curing crosslinking; the radiation energy of electron beam curing crosslinking is 135keV, the irradiation dose is 160kGy, and the distance between the electron beam irradiation equipment and the encapsulating film is 10mm; when the encapsulating film is pre-crosslinked, a baffle arranged according to the HJT grid lines is set above the encapsulating film.

[0152] Examples 39-42 This embodiment provides an encapsulation film for gridless HJT batteries. The difference from embodiment 38 is that the pre-crosslinking degree of the second ultraviolet conversion film 4 at the position corresponding to the gridless HJT battery welding wire is 30%, 40%, 55%, and 60%.

[0153] Examples 43-46 This embodiment provides an encapsulating film for gridless HJT batteries. The difference from embodiment 38 is that the pre-crosslinking degree of the third ultraviolet conversion film 5 is 1%, 5%, 9% and 10%.

[0154] The encapsulating films of the above embodiments and comparative examples were subjected to performance tests, and the test methods are as follows: (1) EL: The encapsulating films obtained in the above examples and comparative examples are assembled into photovoltaic modules according to the structure of glass / encapsulating film / cell / encapsulating film / glass, and the appearance of the modules is tested and statistically analyzed by an electron light emission detection device (EL).

[0155] (2) Power: The test method refers to the standard IEC61215 "Ground-mounted crystalline silicon photovoltaic modules - design qualification and type approval". Sample size: 0BB bifacial HJT cells, 16 half-cell module; test conditions: AM 1.5, irradiance 1000W / m2, +25℃, 50%RH.

[0156] (3) Peel strength: The test was conducted in the following order: glass, conventional adhesive film, battery cell, test adhesive film, and conventional backsheet. The first side of the encapsulating film was in contact with the battery, and the second side of the encapsulating film was in contact with the glass. HJT structure battery cells were selected. The cells were laminated and cured at 150℃ for 18 minutes. Three replicates were required for each test sample. The test method was in accordance with standard GB / T2790 "Test method for 180° peel strength of adhesives, flexible materials versus rigid materials". Sample size: 300mm*300mm; tensile speed: 100mm / min.

[0157] (4) Yellowing index before and after aging test: The upper and lower surfaces of the film were laminated with the glass layer to obtain the pre-pressed component, and UV120 aging test was carried out in a multi-times UV aging chamber (power 142W, temperature 70℃). The yellowing index (ΔYI) of the pre-pressed component before and after aging test was determined according to the national standard GB 2409 "Test method for yellow index of plastic".

[0158] (5) The TC test method and requirements are as follows: Refer to IEC 61215 10.11: The module temperature is cycled between -40℃±2℃ and +85℃±2℃. At each extreme temperature, the module shall remain stable for at least 30 minutes. The difference is that the number of cycles with the module being supplied with an amount equal to ±2% of the maximum power point current under standard test conditions is increased from 200 to 400, and the current is maintained only when the module temperature exceeds 25℃.

[0159] The test results are shown in Tables 1-3 below.

[0160] Table 1 Lamination appearance performance and initial EL TC400 after EL Component power / W Peel strength with HJT battery (N / cm) Multiple UV 120kWh yellowing ΔYI Example 1 The appearance of the laminate and the EL were both normal. Localized EL dimming 71.3 25 4.5 Example 2 The appearance of the laminate and the EL were both normal. Localized EL dimming 71.4 40 4.3 Example 3 The appearance of the laminate and the EL were both normal. Localized EL dimming 71.3 35 4.3 Example 4 The appearance of the laminate and the EL were both normal. EL no abnormalities 71.2 20 4.5 Example 5 The appearance of the laminate and the EL were both normal. EL no abnormalities 71.2 18 4.7 Example 6 The appearance of the laminate and the EL were both normal. Localized EL dimming 71.3 16 4.5 Example 7 The appearance of the laminate and the EL were both normal. Localized EL dimming 71.3 25 4.5 Example 8 The appearance of the laminate and the EL were both normal. Localized EL dimming 71.3 25 4.5 Example 9 The appearance of the laminate and the EL were both normal. EL no abnormalities 71.3 30 4.5 Example 10 The appearance of the laminate and the EL were both normal. EL no abnormalities 71.3 35 4.5 Example 11 The appearance of the laminate and the EL were both normal. EL no abnormalities 71.3 40 4.5 Example 12 The appearance of the laminate and the EL were both normal. Localized EL dimming 71.3 18 4.5 Example 13 The appearance of the laminate and the EL were both normal. EL no abnormalities 71.3 26 4.5 Example 14 The appearance of the laminate and the EL were both normal. EL no abnormalities 71.3 30 4.5 Example 15 The appearance of the laminate and the EL were both normal. EL no abnormalities 71.3 32 4.5 Example 16 The appearance of the laminate and the EL were both normal. EL no abnormalities 71.3 35 4.5 Example 17 The appearance of the laminate and the EL were both normal. EL no abnormalities 71.3 38 4.5 Example 18 The appearance of the laminate and the EL were both normal. EL no abnormalities 71.3 40 4.5 Example 19 The appearance of the laminate and the EL were both normal. EL no abnormalities 71.6 32 4.5 Example 20 The appearance of the laminate and the EL were both normal. EL no abnormalities 71.3 32 4.6 Example 21 The appearance of the laminate and the EL were both normal. EL no abnormalities 72 32 4.4 Example 22 The appearance of the laminate and the EL were both normal. EL no abnormalities 72.2 30 4.4 Example 23 The appearance of the laminate and the EL were both normal. EL no abnormalities 71 28 4.7 Comparative Example 1 The laminated appearance is normal, but some areas of the HJT battery have darkened EL (electrode density). EL dark areas expanded 69.5 22 4.3 Comparative Example 2 The laminated appearance shows signs of unmelted adhesive film, with some areas of unmelted adhesive film resulting in localized darkening of the EL (electrode photometer) of the HJT battery. EL dark areas expanded 69.3 14 4.1 Table 2 Lamination appearance performance and initial EL TC400 after EL Component power Peel strength with HJT battery (N / cm) Peel strength from glass (N / cm) Multiple UV 120kWh yellowing ΔYI Example 24 The appearance of the laminate and the EL were both normal. EL no abnormalities 70.3 22 75 4.4 Example 25 The appearance of the laminate and the EL were both normal. EL no abnormalities 70.6 35 90 4.1 Example 26 The appearance of the laminate and the EL were both normal. EL no abnormalities 70.4 30 80 4.2 Example 27 The appearance of the laminate and the EL were both normal. EL no abnormalities 70.1 20 70 4.5 Example 28 The appearance of the laminate and the EL were both normal. EL no abnormalities 69.9 18 60 4.5 Example 29 The appearance of the laminate and the EL were both normal. EL no abnormalities 70.3 25 100 4.2 Example 30 The appearance of the laminate and the EL were both normal. EL no abnormalities 70.3 24 90 4.3 Example 31 The appearance of the laminate and the EL were both normal. EL no abnormalities 70.2 20 70 4.4 Example 32 The appearance of the laminate and the EL were both normal. EL no abnormalities 70.2 18 61 4.5 Example 33 The appearance of the laminate and the EL were both normal. EL no abnormalities 70.3 22 80 4.1 Example 34 The appearance of the laminate and the EL were both normal. EL no abnormalities 70.3 22 72 4.2 Example 35 The appearance of the laminate and the EL were both normal. EL no abnormalities 70.2 22 65 4.4 Example 36 The appearance of the laminate and the EL were both normal. EL no abnormalities 70.2 22 60 4.5 Example 37 The appearance of the laminate and the EL were both normal. EL no abnormalities 72.0 20 80 4.1 Comparative Example 3 The laminated appearance is normal, but some areas of the HJT battery have darkened EL (electrode density). EL dark areas expanded 68.5 22 110 4.3 Comparative Example 4 The laminated appearance shows signs of unmelted adhesive film, with some areas of unmelted adhesive film resulting in localized darkening of the EL (electrode photometer) of the HJT battery. EL dark areas expanded 68.3 14 55 4.1 Table 3 Lamination appearance performance and initial EL TC400 after EL Component power Peel strength with HJT battery (N / cm) Peel strength from glass (N / cm) Multiple UV 120kWh yellowing ΔYI Example 38 The appearance of the laminate and the EL were both normal. EL no abnormalities 71.3 22 95 4.4 Example 39 The appearance of the laminate and the EL were both normal. EL no abnormalities 71.6 35 105 4.1 Example 40 The appearance of the laminate and the EL were both normal. EL no abnormalities 71.4 30 100 4.2 Example 41 The appearance of the laminate and the EL were both normal. EL no abnormalities 71.1 20 85 4.5 Example 42 The appearance of the laminate and the EL were both normal. EL no abnormalities 70.9 18 75 4.5 Example 43 The appearance of the laminate and the EL were both normal. EL no abnormalities 71.3 22 100 4.1 Example 44 The appearance of the laminate and the EL were both normal. EL no abnormalities 71.3 22 92 4.2 Example 45 The appearance of the laminate and the EL were both normal. EL no abnormalities 70.2 22 65 4.4 Example 46 The appearance of the laminate and the EL were both normal. EL no abnormalities 70.2 22 60 4.5 As can be seen from the experimental data in Tables 1 to 3, this invention effectively solves the core process challenge in gridless HJT battery packaging by precisely controlling the pre-crosslinking degree of the encapsulant film or a specific area of ​​the encapsulant film near the battery side within the range of 30% to 60%. When the pre-crosslinking degree is below 30% (as in Comparative Examples 1 and 3), the encapsulant film has excessive fluidity, resulting in EL darkening defects after lamination; while when the pre-crosslinking degree is above 60% (as in Comparative Examples 2 and 4), the encapsulant film cannot fully melt due to excessive crosslinking, resulting in a significant reduction in peel strength and module power. All samples from successful embodiments are within this critical range, effectively avoiding the EL darkening problem, exhibiting excellent peel strength and higher initial power, and maintaining a low yellowing index (ΔYI) after UV aging testing.

[0161] 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 type of encapsulating film for gridless HJT batteries, characterized in that, It includes a low-flow adhesive film (1) and a first ultraviolet light conversion adhesive film (2) stacked together, wherein the pre-crosslinking degree of the low-flow adhesive film (1) is 30%-60%.

2. The encapsulating film according to claim 1, characterized in that, By weight, the low-flow adhesive film (1) comprises a base resin, the base resin comprising a resin containing GMA groups, wherein the resin containing GMA groups accounts for 5-40% of the total mass of the base resin; and the GMA groups account for 0.1% to 30% of the weight of the resin containing GMA groups. Preferably, the matrix resin is selected from one or more of the following: GMA-grafted ethylene vinyl acetate copolymer, GMA-grafted ethylene-α-olefin copolymer, ethylene-acrylate-glycidyl methacrylate copolymer, ethylene-glycidyl methacrylate copolymer, or ethylene-vinyl acetate-glycidyl methacrylate copolymer. Preferably, the melt index of the matrix resin is 2~15 g / 10 min; Preferably, the low-flow adhesive film (1) further includes one or more of the following: matrix processing aid, UV cutoff agent, and matrix crosslinking agent.

3. The encapsulating film according to claim 2, characterized in that, The low-flow adhesive film (1) further includes a tackifier, wherein the tackifier accounts for 0.5%-5.5% of the weight of the low-flow adhesive film (1), preferably 1%-3%; And / or, the tackifier is epoxidized polybutadiene liquid rubber, wherein the viscosity of the epoxidized polybutadiene liquid rubber at 25°C is 100-20000 mPa·s, preferably 1000-6000 mPa·s.

4. The encapsulating film according to claim 1, characterized in that, The first ultraviolet light conversion film (2) comprises the following components: a first resin, a first processing aid, a first crosslinking agent, and a first ultraviolet light conversion material; Preferably, based on 100 parts by weight of the first resin, the first ultraviolet conversion film (2) includes 0.5-2 parts of the first processing aid, 0.5-2 parts of the first crosslinking agent, and 0.05-1 parts of the first ultraviolet conversion material.

5. The encapsulating film according to claim 1, characterized in that, The thickness of the low-flow adhesive film (1) is 80-170 micrometers, and the thickness of the first ultraviolet light conversion adhesive film (2) is 200-400 micrometers; preferably, the thickness ratio of the first ultraviolet light conversion adhesive film to the low-flow adhesive film is (1.5-4):

1.

6. The method for preparing the encapsulating film according to any one of claims 1-5, characterized in that, Includes the following steps: After the low flowability adhesive film (1) is cast and extruded, it is pre-crosslinked to make the pre-crosslinking degree of the low flowability adhesive film (1) 30%-60%, and then it is bonded to the first ultraviolet light conversion adhesive film (2). Alternatively, after co-extruding the low-flow adhesive film (1) and the first ultraviolet conversion adhesive film (2), the low-flow adhesive film (1) is pre-crosslinked so that the pre-crosslinking degree of the low-flow adhesive film (1) is 30%-60%.

7. An encapsulating film for gridless HJT batteries, characterized in that, The encapsulation film includes a second ultraviolet light conversion film (4), and the pre-crosslinking degree of the second ultraviolet light conversion film (4) at the position corresponding to the welding wire of the gridless HJT battery is 30%-60%.

8. The encapsulating film according to claim 7, characterized in that, The second ultraviolet conversion film (4) is coated with a radiation-cured coating at a position with a pre-crosslinking degree.

9. The encapsulating film according to claim 7 or 8, characterized in that, Along the thickness direction, the second ultraviolet light conversion film (4) includes a first film portion (41) and a second film portion (42). When the first film portion (41) is laid, it is close to the side of the gridless HJT cell, and when the second film portion (42) is laid, it is away from the side of the gridless HJT cell. The pre-crosslinking degree at the position of the first film portion (41) corresponding to the welding wire of the gridless HJT cell is 30%-60%. Preferably, the thickness of the first adhesive film portion (41) is 80-170 micrometers; preferably, the pre-crosslinking degree of the first adhesive film portion (41) at the position corresponding to the non-welding wire of the gridless HJT battery is <10%; preferably, the pre-crosslinking degree of the second adhesive film portion (42) is <10%.

10. The encapsulating film according to claim 7, characterized in that, The encapsulation film includes two or more layers of ultraviolet light conversion film, and the two or more layers of ultraviolet light conversion film also include a third ultraviolet light conversion film (5). The third ultraviolet light conversion film (5) is stacked with the second ultraviolet light conversion film (4). When the second ultraviolet light conversion film (4) is laid, it is close to the side of the gridless HJT cell. The third ultraviolet light conversion film (5) is located on the side of the second ultraviolet light conversion film (4) away from the gridless HJT cell. Preferably, the pre-crosslinking degree of the second ultraviolet conversion film (4) at the position corresponding to the gridless HJT battery welding wire is 40%-55%; preferably, the pre-crosslinking degree of the third ultraviolet conversion film (5) is <10%, and more preferably ≤5%; Preferably, the second ultraviolet conversion film (4) comprises the following components: a second resin, a second crosslinking agent, and a second ultraviolet conversion material; preferably, the melt index of the second resin is 5-40 g / 10 min, the second resin includes a resin containing GMA groups, the resin containing GMA groups accounts for 5-40% of the total amount of the second resin; the weight content of the GMA groups in the resin containing GMA groups is 0.1%~30%; the second crosslinking agent is an acrylate crosslinking agent; Preferably, the second ultraviolet light conversion material is 0.05~1% of the weight of the second resin; Preferably, the third ultraviolet light conversion film (5) comprises the following components: a third resin, a third co-crosslinking agent, and a third ultraviolet light conversion material; preferably, the melt index of the third resin is 20-30 g / 10 min; the third co-crosslinking agent is an allyl co-crosslinking agent; Preferably, the second ultraviolet light conversion material is any one or a mixture of at least two of rare earth inorganic compounds, silicon quantum dots, GaAs quantum dots, CdS quantum dots, CdSe quantum dots, CdTe quantum dots, ZnS quantum dots, ZnSe quantum dots, ZnTe quantum dots, or perovskite quantum dots; the third ultraviolet light conversion material is any one or a mixture of at least two of organic fluorescent pigments, rare earth organic complexes, rare earth inorganic compounds, benzotriazole compounds, silicon quantum dots, GaAs quantum dots, CdS quantum dots, CdSe quantum dots, CdTe quantum dots, ZnS quantum dots, ZnSe quantum dots, ZnTe quantum dots, or perovskite quantum dots.

11. The method for preparing the encapsulating film according to any one of claims 7-10, characterized in that, Includes the following steps: First, the encapsulating film is cast and extruded, and then a pre-crosslinking process is used to pre-crosslink the encapsulating film so that the pre-crosslinking degree at the position corresponding to the second ultraviolet light conversion film (4) and the welding wire of the gridless HJT battery is 30%-60%; Preferably, the pre-crosslinking process includes any one of UV irradiation crosslinking, thermosetting crosslinking, and electron beam curing crosslinking; Preferably, the pre-crosslinking process is electron beam curing crosslinking; more preferably, the radiation energy of the electron beam curing crosslinking is 135-300keV, the irradiation dose is 50-200kGy, and the distance between the electron beam irradiation device and the encapsulating film is 10-55mm. Preferably, when the encapsulating film is pre-crosslinked using a pre-crosslinking process, a baffle arranged in HJT grid lines is provided above the encapsulating film.

12. A photovoltaic module, characterized in that, It includes a glass cover, a front encapsulation film, a gridless HJT battery cell, a back encapsulation film, and a back cover, wherein the front encapsulation film and / or the back encapsulation film are any one of the encapsulation films according to claims 1-5 or 7-10; and the back cover is a glass cover or a back plate.

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