EVA heat-conducting adhesive film material for photovoltaic and preparation method thereof

Abstract

The application discloses a kind of EVA heat-conducting adhesive film materials for photovoltaic and preparation method thereof.The EVA heat-conducting adhesive film materials for photovoltaic includes, by weight parts, EVA resin 100 parts, composite heat-conducting agent 10-20 parts, coupling agent 0.3-2 parts;The composite heat-conducting agent includes boron nitride nanosheet and short carbon fiber with three-dimensional space network structure.The application first constructs main heat-conducting network system using short carbon fiber, then boron nitride nanosheet is injected into main heat-conducting cavity using vacuum assisted layered perfusion method, forming heat-conducting adhesive film material with double heat-conducting material interpenetration, finally the EVA heat-conducting adhesive film for photovoltaic is prepared by adopting multistage stretching extrusion molding, the heat-conducting adhesive film prepared by the preparation process has excellent heat conductivity and insulation, and the peel strength of adhesive film and glass substrate is improved, with good adhesive strength, higher thermal stability and good mechanical properties.

Description

Technical Field

[0001] This invention belongs to the field of photovoltaic EVA film technology, specifically relating to a photovoltaic EVA thermally conductive adhesive film material and its preparation method. Background Technology

[0002] Solar cells generate a significant amount of heat during photovoltaic power generation, which is the primary reason for their elevated temperature. Studies show that for every 1°C increase in solar cell temperature, their photoelectric conversion efficiency decreases at a rate of 0.4–0.6%, highlighting the crucial impact of temperature on the cell. Secondly, excessively high temperatures within the solar cell also significantly affect the stability of the EVA film, making it prone to thermal aging and oxidation. Therefore, excessively high temperatures within the solar cell not only drastically reduce the cell's photoelectric conversion efficiency but also shorten the lifespan of the solar module. Thus, effectively dissipating excess heat from the solar cell module and reducing its temperature is key to improving the lifespan of photovoltaic cells.

[0003] Currently, most EVA films use a single thermally conductive material. However, the heat generated by solar cells is mainly concentrated in the middle layer. Since the cells are very thin, very little heat is lost from the edges. Most heat is dissipated through the upper and lower modules. Therefore, a single thermally conductive material cannot completely dissipate all the heat generated during photovoltaic cell operation. Furthermore, adding a single thermally conductive material may cause agglomeration within the EVA film, resulting in excessively low volume resistivity. Additionally, a single filler often fails to form thermal conductive pathways, severely impacting the heat dissipation capacity of the photovoltaic cell.

[0004] Existing EVA thermally conductive films suffer from poor thermal stability, and prolonged exposure to sunlight can cause aging and yellowing. For example, Chinese invention patent application number 201711480286.8 discloses a cross-linked EVA thermally conductive encapsulating film and its preparation method, which mainly improves thermal conductivity by shortening the lamination time and increasing the degree of cross-linking. Chinese invention patent application number 201410382044.5 discloses a method for preparing an EVA thermally conductive composite film for photovoltaic encapsulation, the main purpose of which is to obtain an encapsulating film with good adhesion and impact resistance. Chinese invention patent application number 201310285225.1 discloses a method for preparing an EVA thermally conductive composite film for filled solar cell encapsulation, which improves the thermal conductivity of the film by adding thermally conductive materials during the preparation process, but this method may reduce the light transmittance of the film, affecting photovoltaic efficiency. Summary of the Invention To address the aforementioned shortcomings, the present invention aims to provide a photovoltaic EVA thermally conductive film material and its preparation method, thereby solving the problems of poor thermal conductivity, high thermal resistance of modules, low insulation, poor heat dissipation, low volume resistivity, and poor thermal stability of existing EVA film thermally conductive materials.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A photovoltaic EVA thermally conductive film material, by weight, comprises: 100 parts of EVA resin, 10-20 parts of composite thermal conductive agent, and 0.3-2 parts of coupling agent; wherein the composite thermal conductive agent comprises boron nitride nanosheets and short carbon fibers with a three-dimensional spatial network structure.

[0006] Preferably, the mass ratio of boron nitride nanosheets to short carbon fibers is 1:5 to 5:1.

[0007] Preferably, the coupling agent is at least one of vinyltriethoxysilane and 3-propenoxytrimethoxysilane.

[0008] Preferably, the above-mentioned thermally conductive adhesive film material further includes additives, which include 0.2-3 parts of crosslinking agent, 0.2-2 parts of co-crosslinking agent, 0.5-4 parts of deacidifying agent, 0.1-0.5 parts of ultraviolet absorber, 0.1-0.4 parts of antioxidant, and 8-14 parts of curing agent.

[0009] Preferably, the crosslinking agent is at least one of dicumyl peroxide and tert-amyl peroxide-2-ethylhexyl carbonate.

[0010] Preferably, the crosslinking agent is at least one of triallyl isocyanurate and ethylene glycol diacrylate.

[0011] Preferably, the ultraviolet absorber is at least one of 2-hydroxy-4-n-octyloxybenzophenone and resorcinol monobenzoate.

[0012] Preferably, the deacidifying agent is at least one of sodium hydroxide and magnesium oxide; the curing agent is an organic acid anhydride curing agent.

[0013] Preferably, the antioxidant is at least one of β-(3,5-di-tert-butyl,4-hydroxyphenyl)propionate and tris(2,4-di-tert-butylphenyl) phosphite.

[0014] This invention also provides a method for preparing EVA thermally conductive adhesive film material for photovoltaic applications, comprising the following steps: (1) Short carbon fibers are woven into a three-dimensional spatial mesh structure to obtain a three-dimensional spatial mesh carbon fiber; (2) Mix EVA resin, three-dimensional spatial network carbon fiber, coupling agent and solvent evenly, and then add additives to the mixture. Use self-templating method to form a dominant thermal network system of separated carbon fiber and additives on the surface of EVA resin matrix. (3) After uniformly mixing boron nitride nanosheets with isopropanol, add the mixture obtained in step (2); then place it in a vacuum oven to degas, repeatedly evacuate until no more bubbles emerge, and then cure to obtain the composite material; (4) The composite material is melt-blended and extruded in a twin-screw extruder using a multi-stage stretch extrusion molding method. The melt-extruded material is then cast, embossed, cooled, and wound up to obtain the photovoltaic EVA thermal conductive adhesive film material.

[0015] The self-templating method, as the name suggests, involves the material used as a template ultimately becoming part of the mixture. Therefore, this method has the advantage of not requiring additional template removal. In step (2) of this invention, the self-templating method refers to not introducing a third phase during the preparation of the dominant thermal network cavity. Instead, it directly utilizes the interface between EVA resin particles as a template to construct the separation structure of the filler. This allows the additives to be mainly located on the surface of the EVA resin, achieving sufficient contact between the short carbon fibers and the additives, and forming a thermally conductive mesh cavity. The advantage of the self-templating method is that no support is placed inside the hollow short carbon fiber mesh, which, compared to completely dispersed fillers, can form a 3D network cavity.

[0016] Directly mixing boron nitride nanosheets and the like will cause boron nitride to accumulate in the entire cavity. However, in step (3) of this invention, the dissolved EVA resin is used as a layer of separators, and boron nitride nanosheets are added by vacuum-assisted layered injection method to build a secondary thermal conductive system in the thermal conductive cavity, and finally form a thermal conductive film material with interpenetrating dual thermal conductive materials, thereby improving the thermal conductivity of the material.

[0017] The beneficial effects of this invention are: This invention selects boron nitride nanosheets and short carbon fibers as thermally conductive filler materials. To achieve superior thermal conductivity, short carbon fibers with a three-dimensional spatial network structure are used to construct the primary thermal network cavity. Then, boron nitride nanosheets are injected into the primary thermal cavity using a vacuum-assisted layered infusion method, constructing a secondary thermally conductive system within the primary thermal cavity to form a composite thermally conductive material with interpenetrating dual thermally conductive materials. Finally, a multi-stage stretching and extrusion molding process is used to prepare a photovoltaic EVA thermally conductive film. The thermally conductive film prepared by this process has excellent thermal conductivity and insulation properties, while also improving the peel strength between the film and the glass substrate, exhibiting good adhesion strength, high thermal stability, and excellent mechanical properties. Detailed Implementation

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

[0019] In this invention, unless otherwise specified, all processes that can realize this invention are known to those skilled in the art based on existing technology. For example, weaving short carbon fibers into carbon fibers with a three-dimensional spatial network structure can be carried out using conventional process flow: determining the weaving structure - carbon fiber pretreatment - weaving equipment preparation - carbon fiber weaving - curing treatment; the self-templating method can be carried out by mixing carbon fibers, additives and EVA resin, drying and then hot pressing molding, etc.

[0020] Example 1 The photovoltaic EVA thermally conductive adhesive film material of this embodiment comprises, by weight, 100 parts EVA resin, 10 parts composite thermal conductive agent, 0.2 parts crosslinking agent, 0.2 parts co-crosslinking agent, 0.3 parts coupling agent, 0.5 parts deacidifying agent, 0.1 parts ultraviolet absorber, 0.1 parts antioxidant, 8 parts curing agent, 3 parts isopropanol, and 5 parts solvent. The composite thermal conductive agent comprises boron nitride nanosheets and short carbon fibers with a three-dimensional network structure in a mass ratio of 1:5. The crosslinking agent is dicumyl peroxide, and the co-crosslinking agent is triallyl isocyanurate. The coupling agent is vinyltriethoxysilane, the ultraviolet absorber is 2-hydroxy-4-n-octyloxybenzophenone, the antioxidant is β-(3,5-di-tert-butyl,4-hydroxyphenyl)propionate octadecyl alcohol ester, the deacidifying agent is MgO, the curing agent is phthalic anhydride, and the solvent is DMF.

[0021] The method for preparing photovoltaic EVA thermally conductive adhesive film material in this embodiment includes the following steps: (1) The short carbon fibers are impregnated in concentrated nitric acid for surface modification to enhance tensile strength and prevent agglomeration with EVA resin in subsequent processes; (2) The modified short carbon fibers are woven into a three-dimensional spatial mesh carbon fiber using conventional carbon fiber weaving technology, that is, the four sides are mesh and the middle is hollow, so as to provide a heat-conducting cavity for subsequent fillers. (3) Mix EVA resin, coupling agent and solvent, and stir magnetically until no bubbles are generated. The heating temperature during the mixing process is 90℃, and the heating time is 4h. (4) Add the woven short carbon fibers and additives to the mixing system of step (3) and stir evenly. After drying, hot press to form a dominant thermal network system on the surface of the EVA resin matrix, separating the carbon fibers and additives. (5) After uniformly mixing boron nitride nanosheets with isopropanol, add the mixture obtained in step (4); then place it in a vacuum oven to degas, repeatedly evacuate until no more bubbles emerge, and then cure to obtain the composite material; (6) The composite material is melt-blended and extruded in a twin-screw extruder using a multi-stage stretch extrusion molding method. The melt-extruded material is then cast, embossed, cooled, and wound up to obtain EVA thermally conductive adhesive film material for photovoltaic applications. The twin-screw extruder is set to a speed of 120 r / min, and there are four temperature ranges from the feed inlet to the extruder die head, which are set to 85℃, 175℃, 180℃, and 190℃ respectively.

[0022] Comparative Example 1 The material composition of this comparative example is the same as that of Example 1, the only difference being that only boron nitride nanosheets are added as the thermal conductive agent. The preparation process is as follows: (1) Mix EVA resin, coupling agent, additive and solvent, and stir magnetically until no bubbles are generated. The heating temperature during the mixing process is 90℃ and heated for 4 hours. (2) After uniformly mixing boron nitride nanosheets with isopropanol, add the mixture obtained in step (1); then place it in a vacuum oven to degas, repeatedly evacuate until no more bubbles emerge, and then cure to obtain the composite material; (3) The composite material is melt-blended and extruded in a twin-screw extruder using a multi-stage stretch extrusion molding method. The melt-extruded material is then cast, embossed, cooled, and wound up to obtain EVA thermally conductive adhesive film material for photovoltaic applications. The twin-screw extruder is set to a speed of 120 r / min, and there are four temperature ranges from the feed inlet to the extruder head, which are set to 85℃, 175℃, 180℃, and 190℃ respectively.

[0023] Comparative Example 2 The material composition of this comparative example is the same as that of Example 1, the only difference being that only short carbon fibers are added as the thermal conductive agent. Its preparation process is as follows: (1) Surface modification is carried out by impregnating short carbon fibers with concentrated nitric acid; (2) The modified short carbon fibers are woven into a three-dimensional spatial mesh carbon fiber using conventional carbon fiber weaving technology; (3) Mix EVA resin, coupling agent and solvent, and stir magnetically until no bubbles are generated. The heating temperature during the mixing process is 90℃, and the heating time is 4h. (4) Add the woven short carbon fibers and additives to the mixing system of step (3) and stir evenly. After drying, hot press to form a dominant thermal network system on the surface of the EVA resin matrix, separating the carbon fibers and additives. (5) The composite material from step (4) is melt-blended and extruded in a twin-screw extruder using a multi-stage stretch extrusion molding method. The melt-extruded material is then cast, embossed, cooled, and wound up to obtain EVA thermally conductive adhesive film material for photovoltaic applications. The twin-screw extruder is set to a speed of 120 r / min, and there are four temperature ranges from the feed inlet to the extruder head, which are set to 85℃, 175℃, 180℃, and 190℃ respectively.

[0024] Example 2 The photovoltaic EVA thermally conductive film material of this embodiment comprises, by weight, 100 parts EVA resin, 15 parts composite thermal conductive agent, 1.2 parts crosslinking agent, 0.8 parts co-crosslinking agent, 1 part coupling agent, 2 parts deacidifying agent, 0.3 parts ultraviolet absorber, 0.3 parts antioxidant, 11 parts curing agent, 6 parts isopropanol, and 8 parts polar solvent. The composite thermal conductive agent comprises boron nitride nanosheets and short carbon fibers with a three-dimensional network structure in a mass ratio of 5:1. The crosslinking agent is dicumyl peroxide, and the co-crosslinking agent is triallyl isocyanurate. The coupling agent is vinyltriethoxysilane, the ultraviolet absorber is 2-hydroxy-4-n-octyloxybenzophenone, the antioxidant is β-(3,5-di-tert-butyl,4-hydroxyphenyl)propionate octadecyl alcohol ester, the deacidifying agent is MgO, the curing agent is phthalic anhydride, and the solvent is DMF.

[0025] The preparation method of the EVA thermally conductive adhesive film material is the same as in Example 1.

[0026] Comparative Example 3 The material composition of this comparative example is the same as that of Example 2, the only difference being that no thermal conductive agent is added. Its preparation process is as follows: (1) Mix EVA resin, coupling agent, additive and solvent, and stir magnetically until no bubbles are generated. The heating temperature during the mixing process is 90℃, and the mixture is heated for 4 hours to obtain the composite material. (2) The composite material is melt-blended and extruded in a twin-screw extruder using a multi-stage stretch extrusion molding method. The melt-extruded material is then cast, embossed, cooled, and wound up to obtain EVA thermally conductive adhesive film material for photovoltaic applications. The twin-screw extruder is set to a speed of 120 r / min, and there are four temperature ranges from the feed inlet to the extruder head, which are set to 85℃, 175℃, 180℃, and 190℃ respectively.

[0027] Example 3 The photovoltaic EVA thermally conductive adhesive film material of this embodiment includes, by weight, 100 parts of EVA resin, 16 parts of composite thermally conductive agent, 1.2 parts of crosslinking agent, 1 part of co-crosslinking agent, 1.2 parts of coupling agent, 2.5 parts of deacidifying agent, 0.4 parts of ultraviolet absorber, 0.2 parts of antioxidant, 12 parts of curing agent, 6 parts of isopropanol, and 8 parts of polar solvent.

[0028] The composite thermal conductive agent comprises boron nitride nanosheets in a mass ratio of 5:1 and short carbon fibers with a three-dimensional spatial network structure. The crosslinking agent is tert-amyl peroxide-2-ethylhexyl carbonate, and the co-crosslinking agent is ethylene glycol diacrylate. The coupling agent is vinyltriethoxysilane, the ultraviolet absorber is 2-hydroxy-4-n-octyloxybenzophenone, the antioxidant is β-(3,5-di-tert-butyl,4-hydroxyphenyl)propionate octadecyl alcohol ester, the acid remover is MgO, the curing agent is phthalic anhydride, and the solvent is DMF.

[0029] The preparation method of the EVA thermally conductive adhesive film material is the same as in Example 1.

[0030] Comparative Example 4 The material composition and proportions of this comparative example are the same as those of Example 3. The only difference is that the primary thermal network system and the secondary thermally conductive filler system were not constructed in the preparation process of this comparative example. That is, the two thermally conductive agents were directly compounded and mixed with additives to prepare the photovoltaic film. The preparation process is as follows: (1) Mix EVA resin, boron nitride nanosheets, short carbon fibers, coupling agent, additives and solvent, and stir magnetically until no bubbles are generated. The heating temperature during the mixing process is 90℃, and the mixture is heated for 4 hours to obtain the composite material. (2) The composite material is melt-blended and extruded in a twin-screw extruder using a multi-stage stretch extrusion molding method. The melt-extruded material is then cast, embossed, cooled, and wound up to obtain EVA thermally conductive adhesive film material for photovoltaic applications. The twin-screw extruder is set to a speed of 120 r / min, and there are four temperature ranges from the feed inlet to the extruder head, which are set to 85℃, 175℃, 180℃, and 190℃ respectively.

[0031] Example 4 The photovoltaic EVA thermally conductive adhesive film material of this embodiment includes, by weight, 100 parts of EVA resin, 18 parts of composite thermally conductive agent, 1.5 parts of crosslinking agent, 1.5 parts of co-crosslinking agent, 1 part of coupling agent, 4 parts of deacidifying agent, 0.5 parts of ultraviolet absorber, 0.4 parts of antioxidant, 12 parts of curing agent, 8 parts of isopropanol, and 10 parts of polar solvent.

[0032] The composite thermal conductive agent comprises boron nitride nanosheets in a mass ratio of 1:1 and short carbon fibers with a three-dimensional spatial network structure. The crosslinking agent is tert-amyl peroxide-2-ethylhexyl carbonate, and the co-crosslinking agent is ethylene glycol diacrylate. The coupling agent is vinyltriethoxysilane, the ultraviolet absorber is 2-hydroxy-4-n-octyloxybenzophenone, the antioxidant is β-(3,5-di-tert-butyl,4-hydroxyphenyl)propionate octadecyl alcohol ester, the acid remover is MgO, the curing agent is phthalic anhydride, and the solvent is DMF.

[0033] The preparation method of the EVA thermally conductive adhesive film material is the same as in Example 1.

[0034] Example 5 The photovoltaic EVA thermally conductive adhesive film material of this embodiment includes, by weight, 100 parts of EVA resin, 20 parts of composite thermally conductive agent, 1.2 parts of crosslinking agent, 2 parts of co-crosslinking agent, 1.5 parts of coupling agent, 3 parts of deacidifying agent, 0.5 parts of ultraviolet absorber, 0.4 parts of antioxidant, 12 parts of curing agent, 6 parts of isopropanol, and 8 parts of polar solvent.

[0035] The composite thermal conductive agent comprises boron nitride nanosheets in a mass ratio of 1:2 and short carbon fibers with a three-dimensional spatial network structure. The crosslinking agent is tert-amyl peroxide-2-ethylhexyl carbonate, and the co-crosslinking agent is ethylene glycol diacrylate. The coupling agent is vinyltriethoxysilane, the ultraviolet absorber is 2-hydroxy-4-n-octyloxybenzophenone, the antioxidant is β-(3,5-di-tert-butyl,4-hydroxyphenyl)propionate octadecyl alcohol ester, the acid remover is MgO, the curing agent is phthalic anhydride, and the solvent is DMF.

[0036] The preparation method of the EVA thermally conductive adhesive film material is the same as in Example 1.

[0037] Performance testing Volume resistivity: The volume resistivity was tested according to GB / T 1410-2006 "Test methods for volume resistivity and surface resistivity of solid insulating materials".

[0038] Peel strength: Tested according to the national standard GB / T 2790-1665 "Adhesives 180° Peel Strength Test Method" to test the peel strength between EVA film and glass.

[0039] Tensile strength: The tensile strength was tested according to GB / T 1040-2006 "Determination of tensile properties of plastics".

[0040] Thermal conductivity: Tested using the laser pulse method according to ISO 22007 standard, and calculated using the following formula: k = α × ρ × C Where k is the thermal conductivity of the sample, W / (m·K), and α is the thermal diffusivity of the sample, m 2 / s, ρ - sample density, g / cm³ 3 C - Specific heat capacity of sample, J / (kg·K).

[0041] The performance test results of the EVA thermally conductive adhesive film materials prepared in the above embodiments and comparative examples are as follows:

[0042] As can be seen from the table above, the EVA thermally conductive adhesive film material prepared by this invention has excellent thermal conductivity and insulation, high peel strength between the adhesive film and the glass substrate, and good mechanical properties.

[0043] Comparing Example 1 with Comparative Examples 1 and 2, it can be seen that the combination of the primary thermal system and the secondary thermal system makes it easier to achieve a synergistic effect and form a thermal network path, which is much greater than the heat dissipation of a single thermal material. This greatly increases the thermal conductivity of the EVA film. Due to the use of a dual thermal system, the corresponding volume resistivity is also improved, thus increasing the insulation of the photovoltaic module.

[0044] Comparing Comparative Example 3 with Example 2, it was found that the thermal conductivity of the film without the addition of thermal conductive agent was greatly reduced.

[0045] Compared with Example 3, Comparative Example 4, and compared with directly compounding the two thermally conductive agents, the present invention forms a thermally conductive adhesive film with interpenetrating dual thermally conductive materials by constructing a primary thermal network system and a secondary thermally conductive filler system. The resulting thermally conductive adhesive film has excellent thermal conductivity and insulation, while improving the peel strength between the adhesive film and the glass substrate, and has good adhesion strength and high thermal stability.

[0046] In summary, this invention first utilizes short carbon fibers to construct a dominant thermal network system, then uses a vacuum-assisted layered infusion method to inject boron nitride nanosheets into the dominant thermal cavity to form a thermally conductive adhesive film material with interpenetrating dual thermally conductive materials. Finally, a photovoltaic EVA thermally conductive adhesive film is prepared by multi-stage stretching and extrusion molding. The thermally conductive adhesive film prepared by this process has excellent thermal conductivity and insulation properties, while improving the peel strength between the adhesive film and the glass substrate, exhibiting good adhesion strength and high thermal stability, and also contributing to the improvement of mechanical properties.

[0047] It should be noted that all the above embodiments belong to the same inventive concept, and the descriptions of each embodiment have different focuses. Where the description in a particular embodiment is not detailed, please refer to the description in other embodiments.

[0048] The embodiments described above are merely illustrative of implementation methods of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A photovoltaic EVA thermally conductive adhesive film material, characterized in that, By weight, the material comprises: 100 parts EVA resin, 10-20 parts composite thermal conductive agent, and 0.3-2 parts coupling agent; the composite thermal conductive agent comprises boron nitride nanosheets and short carbon fibers with a three-dimensional spatial network structure; the photovoltaic EVA thermal conductive adhesive film material further comprises additives, including 0.2-3 parts crosslinking agent, 0.2-2 parts co-crosslinking agent, 0.5-4 parts acid remover, 0.1-0.5 parts ultraviolet absorber, 0.1-0.4 parts antioxidant, and 8-14 parts curing agent; The preparation method of the photovoltaic EVA thermally conductive adhesive film material includes the following steps: (1) Short carbon fibers are woven into a three-dimensional spatial mesh structure to obtain a three-dimensional spatial mesh carbon fiber; (2) Mix EVA resin, three-dimensional spatial network carbon fiber, coupling agent and solvent evenly, and then add additives to the mixture. Use self-templating method to form a dominant thermal network system of separated carbon fiber and additives on the surface of EVA resin matrix. (3) After uniformly mixing boron nitride nanosheets with isopropanol, add the mixture obtained in step (2); then place it in a vacuum oven to degas, repeatedly pump air until no more bubbles emerge, and obtain the composite material after curing; (4) The composite material is melt-blended and extruded in a twin-screw extruder using a multi-stage stretch extrusion molding method. The melt-extruded material is then cast, embossed, cooled, and wound up to obtain the photovoltaic EVA thermal conductive adhesive film material.

2. The photovoltaic EVA thermally conductive adhesive film material according to claim 1, characterized in that, The mass ratio of boron nitride nanosheets to short carbon fibers is 1:5 to 5:

1.

3. The photovoltaic EVA thermally conductive adhesive film material according to claim 1, characterized in that, The coupling agent is at least one of vinyltriethoxysilane and 3-propenoxytrimethoxysilane.

4. The photovoltaic EVA thermally conductive adhesive film material according to claim 1, characterized in that, The crosslinking agent is at least one of dicumyl peroxide and tert-amyl peroxide-2-ethylhexyl carbonate.

5. The photovoltaic EVA thermally conductive adhesive film material according to claim 1, characterized in that, The crosslinking agent is at least one of triallyl isocyanurate and ethylene glycol diacrylate.

6. The photovoltaic EVA thermally conductive adhesive film material according to claim 1, characterized in that, The ultraviolet absorber is at least one of 2-hydroxy-4-n-octyloxybenzophenone and resorcinol monobenzoate.

7. The photovoltaic EVA thermally conductive adhesive film material according to claim 4, characterized in that, The deacidifying agent is at least one of sodium hydroxide and magnesium oxide; the curing agent is an organic acid anhydride curing agent.

8. The photovoltaic EVA thermally conductive adhesive film material according to claim 4, characterized in that, The antioxidant is at least one of β-(3,5-di-tert-butyl,4-hydroxyphenyl)propionate octadecyl alcohol ester and tris(2,4-di-tert-butylphenyl) phosphite.

9. The method for preparing photovoltaic EVA thermally conductive adhesive film material according to any one of claims 1 to 8, characterized in that, Includes the following steps: (1) Short carbon fibers are woven into a three-dimensional spatial mesh structure to obtain a three-dimensional spatial mesh carbon fiber; (2) Mix EVA resin, three-dimensional spatial network carbon fiber, coupling agent and solvent evenly, and then add additives to the mixture. Use self-templating method to form a dominant thermal network system of separated carbon fiber and additives on the surface of EVA resin matrix. (3) After uniformly mixing boron nitride nanosheets with isopropanol, add the mixture obtained in step (2); then place it in a vacuum oven to degas, repeatedly pump air until no more bubbles emerge, and obtain the composite material after curing; (4) The composite material is melt-blended and extruded in a twin-screw extruder using a multi-stage stretch extrusion molding method. The melt-extruded material is then cast, embossed, cooled, and wound up to obtain the photovoltaic EVA thermal conductive adhesive film material.

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