EME-X adhesive film for insulating high-thermal-conductivity photovoltaic module and preparation method thereof

Abstract

The preparation method comprises the following steps: dissolving EVA (Ethylene Vinyl Acetate) and EVA-g-MAH (Ethylene Vinyl Acetate-g-Maleic Anhydride) in xylene, enabling molecules of the EVA and the EVA-g-MAH to be cross-linked, adding stripped hydroxylated boron nitride BNNs-OH into a solution, and enabling hydroxyl on the BNNs-OH to be subjected to chemical reaction with a maleic anhydride functional group; finally, the solution is poured into the surface of a film coating machine for circular blade coating and drying, and the layer-by-layer stacked high-thermal-conductivity EME-X adhesive film can be obtained. According to the invention, molecular crosslinking between polymers and chemical reaction between the polymers and the heat-conducting filler are utilized, and the high-heat-conductivity EME-X adhesive film with BNNs-OH stacked layers is directly obtained through circular blade coating; the process does not need complex equipment, is simple to operate, and can realize large-scale production and large-area application of the composite adhesive film; the EME-X adhesive film has excellent thermal conductivity, reflectivity and emissivity, and can be applied to a photovoltaic module.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermally conductive photovoltaic encapsulation films, and specifically relates to an EME-X adhesive film for an insulating and highly thermally conductive photovoltaic assembly and a preparation method thereof; it also relates to a preparation method for an insulating and highly thermally conductive photovoltaic assembly. Background Art

[0002] Photovoltaic power generation is a major renewable energy source, characterized by its widespread availability, cleanness, and sustainability. PV modules primarily operate under high solar radiation, and their power generation performance is closely linked to changes in the external environment. The operating temperature of solar modules is a key factor influencing their performance. Rising temperatures negatively impact solar cells, reducing their photoelectric conversion efficiency. This not only affects the efficiency of PV modules but also negatively impacts their safety and lifespan.

[0003] To address this issue, the industry has adopted various solutions to lower the operating temperature of photovoltaic modules. These include liquid cooling, air cooling, phase change materials, hygroscopic hydrogels, and heat dissipation fins. However, these cooling methods may require additional energy to operate the heat dissipation device, resulting in complex structures and cumbersome processes, which can affect the normal operation of the photovoltaic module. Alternatively, they may completely replace the original natural heat dissipation from the back with other structures, thereby improving the overall quality of the module and hindering practical production and application. Furthermore, these solutions do not address the low thermal conductivity of the photovoltaic module itself, which causes the heat generated by the photovoltaic cells to accumulate continuously, affecting the normal operation of the module. Therefore, the key to solving this problem is to quickly dissipate the accumulated heat within the photovoltaic module.

[0004] Generally speaking, a photovoltaic module typically consists of a cover sheet, an upper layer of EVA film, photovoltaic cells, a lower layer of EVA film, and a backsheet. However, conventional EVA has low thermal conductivity, making it difficult to quickly dissipate the heat generated by the cells during operation, resulting in the photovoltaic cells being exposed to a constant high temperature. Although many researchers have introduced high-thermal-conductivity fillers into the EVA matrix to improve its thermal conductivity, these fillers have poor compatibility and dispersibility in EVA, which in turn affects the thermal conductivity and mechanical properties of the module. Therefore, a solution to improve this problem is urgently needed. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing an EME-X adhesive film for an insulating and highly thermally conductive photovoltaic module, thereby solving the problem of poor thermal conductivity of conventional EVA adhesive films.

[0006] The present invention also aims to provide an EME-X adhesive film for insulating and highly thermally conductive photovoltaic modules.

[0007] The present invention also aims to provide a method for preparing an insulating and highly thermally conductive photovoltaic module.

[0008] The first technical solution adopted by the present invention is a method for preparing an EVA film for insulating and highly thermally conductive photovoltaic modules, and the specific steps are as follows: Step 1: Add isopropyl alcohol, distilled water, hexagonal boron nitride, potassium hydroxide and sodium hydroxide to a high-power cell crusher, crush, centrifuge and dry to prepare hydroxylated boron nitride BNNs-OH; Step 2: Dissolve ethylene-vinyl acetate copolymer (EVA) and maleic anhydride-grafted ethylene-vinyl acetate copolymer (EVA-g-MAH) in xylene solvent at the same time, and stir them uniformly in a water bath at 80°C to obtain an EME solution. Add the hydroxylated boron nitride (BNNs-OH) obtained in step 1 to the mixed solution, heat and stir, and obtain an EME-X dispersion. Step 3: Place the release paper flat on the surface of the scraper, pour the EME-X dispersion evenly onto the surface of the release paper and scrape it at a constant speed. Heat to volatilize the xylene. After it is completely dry, continue to pour the dispersion and scrape 3-8 layers in a cycle to obtain the EME-X film for insulating and highly thermally conductive photovoltaic modules.

[0009] The present invention is also characterized in that: The mass ratio of hexagonal boron nitride, potassium hydroxide, sodium hydroxide, distilled water and isopropyl alcohol in step 1 is 1-5:1.5-7.5:1.5-7.5:50-250:50-250.

[0010] The crushing time in step 1 is 8-16 h.

[0011] In step 2, the mass ratio of the hydroxylated boron nitride BNNs-OH, maleic anhydride grafted ethylene-vinyl acetate copolymer EVA-g-MAH and ethylene-vinyl acetate copolymer EVA is 10-50:1-10:40-89.

[0012] In step 3, the scraper height is 2 mm, the heating temperature is 50° C., and the scraping rate is 80 mm / s.

[0013] Hydroxylated boron nitride BNNs-OH, maleic anhydride grafted ethylene-vinyl acetate copolymer EVA-g-MAH, and ethylene-vinyl acetate copolymer EVA are added to a xylene solution, stirred and heated to 80°C. After EVA and EVA-g-MAH are completely dissolved, the premix is placed in a vacuum box for defoaming treatment.

[0014] The second technical solution employed by the present invention is an EME-X film for insulating and highly thermally conductive photovoltaic modules, produced using the aforementioned preparation method. The EME-X film has a thermal conductivity of 2.87-7.49 W / m·K, a reflectivity of 72.7%-94.1% in the solar wavelength range, an emissivity of 89.3%-95.8% in the mid-infrared, a volume resistivity of 94.2-337.3 TΩ·cm, a shear strength of 2.77-4.72 MPa, an elongation at break of 62.3%-792.76%, and a breaking strength of 4.15-15.34 MPa.

[0015] The third technical solution adopted by the present invention is a method for preparing an insulated and highly thermally conductive photovoltaic module, and the specific steps are as follows: Step 1: Select the photovoltaic cell and check whether it is in good contact with a multimeter to eliminate the risk of short circuit or open circuit; Step 2: From top to bottom, stack the photovoltaic glass, ethylene-vinyl acetate copolymer (EVA), photovoltaic cells, EME-X film, and photovoltaic glass in this order to form a photovoltaic module. Step 3: Place the laminated photovoltaic modules in a vacuum chamber at 120°C for 15-30 minutes, and take them out after the vacuum chamber temperature drops to room temperature. Step 4: Conduct voltage and current tests on the laminated photovoltaic modules to inspect product quality.

[0016] Preparation mechanism of the present invention: (1) In step 1 of the present invention, the raw material is crushed, and the van der Waals force of the original boron nitride is destroyed by strong shear force, so that it becomes thin sheets, and the B-N bond is destroyed, and the B-OH bond is obtained in an alkaline environment; thereby, lamellar hydroxylated boron nitride BNNs-OH is obtained.

[0017] (2) The modified hydroxylated boron nitride sheet is introduced into the formula of the present invention. The shear force generated during the flow delay period during the coating process causes the BNNs-OH to be arranged in a horizontal manner in the matrix, which is conducive to the formation of a three-dimensional heat conduction network path; the dissolved EVA-g-MAH molecular chain can be well entangled with the EVA molecular chain, and the maleic anhydride group on its molecular chain can chemically react with the hydroxyl group of BNNs-OH, thereby improving the compatibility of the filler in the system and reducing the thermal resistance of the filler-polymer interface; (3) The thermal conductive filler hydroxylated boron nitride BNNs-OH is connected to the polymer through a covalent bond, which is conducive to the dispersion of the filler, prevents the accumulation of the filler, and thus eliminates the stress defect points formed by the accumulation of the filler; the carboxyl group produced by the reaction of BNNs-OH with maleic anhydride can form a hydrogen bond with the hydroxyl group on the surface of the photovoltaic glass, thereby increasing its shear stress; this solution solves the current problem of poor compatibility between thermal conductive fillers and EVA, and ensures the mechanical properties and long-term stability of the thermal conductive EVA-based composite material; (4) The stacked layers of BNNs-OH in the composite EME-X film obtained by the present invention are beneficial to improving the reflectivity of the composite material (2.5-25 μm), have good light stability, are beneficial to delaying the aging of the film, and ensure the stability of the component during long-term use; (5) The EME-X adhesive film of the present invention has good resistivity, thereby preventing hidden dangers such as short circuits and short circuits in photovoltaic modules, thereby ensuring their safety.

[0018] (6) The thermally conductive filler BNNs-OH in the EME-X film of the present invention is stacked layer by layer in the polymer. The thermal conductivity of the composite film is 2.87-7.49 W / m·K, the reflectivity in the solar band is 72.7%-94.1%, and the emissivity in the mid-infrared is 89.3%-95.8%.

[0019] The beneficial effects of the present invention are as follows: the method for preparing the EME-X adhesive film for insulating and highly thermally conductive photovoltaic modules of the present invention utilizes molecular cross-linking between polymers and chemical reactions between polymers and thermally conductive fillers, and a high thermal conductivity EME-X photovoltaic encapsulation film with stacked layers of BNNs-OH can be directly obtained through simple cyclic scraping; the operation does not require complex equipment and is simple to operate, and can realize large-scale production and large-area application of the composite adhesive film; the material has excellent thermal conductivity, reflectivity, and emissivity, and can be applied to photovoltaic modules, aiming to quickly transfer the heat generated by photovoltaic cells to the outside world through heat transfer, radiation, etc.; the material has excellent shear force and volume resistance, aiming to ensure the stability and safety of the modules in practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The present invention provides cross-sectional SEM images of Example 2, Example 3, Example 4, Example 5, Example 6, and Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, and Comparative Example 5; FIG2 (a) shows the backsheet temperature curves of the novel photovoltaic module according to Example 4 of the present invention and a commercial photovoltaic module under irradiation by an indoor solar simulator; FIG2( b ) is a real-time power generation voltage curve of the novel photovoltaic module according to Example 4 of the present invention and a commercial photovoltaic module under irradiation of an indoor solar simulator; FIG3 (a) is a graph showing the current density-voltage (JV) characteristic curves of the novel photovoltaic module according to Example 4 of the present invention and a commercial photovoltaic module under irradiation of an indoor solar simulator, and the results of testing the novel photovoltaic module and the conventional commercial module using a solar cell testing system under an indoor solar simulator before and after operation for one hour; FIG3 (b) shows the fill factor (FF) and maximum power generation (P) of the novel photovoltaic module of Example 4 of the present invention and a commercial photovoltaic module tested using a solar cell testing system under an indoor solar simulator before and after operation for 1 hour. max ) Histogram; Figure 4 Example 4 provided for the present invention is a physical picture of a new photovoltaic module and a commercial photovoltaic module placed in an outdoor environment, a backplane temperature curve, and a real-time power generation voltage curve. DETAILED DESCRIPTION

[0021] The technical solutions and preparation methods of the present invention will be described clearly and comprehensively below. The embodiments described below are part of the present invention, but not all embodiments.

[0022] Example 1 The present invention describes a method for preparing an insulating, highly thermally conductive EME-X adhesive film for photovoltaic modules. Ethylene-vinyl acetate copolymer and maleic anhydride-grafted ethylene-vinyl acetate copolymer are dissolved in a xylene solution to crosslink their molecular chains. Exfoliated hydroxylated boron nitride (BNNs-OH) is then added to the solution, allowing the hydroxyl groups on the BNNs-OH to react with the maleic anhydride functional groups. Finally, the solution is poured onto a coating machine, blade-coated, and dried to produce a highly thermally conductive adhesive film with layers of thermally conductive fillers. The resulting thermally conductive, insulating EME-30 adhesive film has a thermal conductivity of 5.93 W / m·K, allowing it to quickly dissipate heat generated by photovoltaic cells through thermal conduction. Its reflectivity in the solar wavelength range is 92.3%, preventing the backsheet from absorbing sunlight reflected from the ground, thereby preventing secondary heating of the module. Its emissivity in the mid-infrared range reaches 95.2%, exceeding terrestrial blackbody radiation, allowing the surface material to transfer heat through thermal radiation. Furthermore, the composite material exhibits excellent mechanical properties and volume resistivity, providing excellent safety, stability, and operational reliability.

[0023] In the present invention, hexagonal boron nitride is abbreviated as h-BN, boron nitride sheets are abbreviated as BNNs, hydroxylated boron nitride is abbreviated as BNNs-OH, ethylene-vinyl acetate copolymer is abbreviated as EVA, maleic anhydride grafted ethylene-vinyl acetate copolymer is abbreviated as EVA-g-MAH, sodium hydroxide is abbreviated as NaOH, potassium hydroxide is abbreviated as KOH, isopropyl alcohol is abbreviated as IPA, the mixture of EVA and EVA-g-MAH is abbreviated as EME, and the mixture of BNNs-OH and EME is abbreviated as EME-X, where X indicates the mass fraction of BNNs-OH in the system.

[0024] In the present invention, unless otherwise specified, percentages (%) are percentages relative to the solute composition and are irrelevant to the mass of the solvent xylene.

[0025] The method for preparing the EME-X adhesive film for insulating and highly thermally conductive photovoltaic modules of the present invention comprises the following steps: S1. Preparation of hydroxylated boron nitride sheets (BNNs-OH) 20 g of h-BN, 30 g of NaOH, and 30 g of KOH were added to a mixed solution of 1000 mL of distilled water and 1000 mL of IPA. The mixture was then placed in a high-power cell disruptor (1200 W) for exfoliation and modification. The supernatant was collected, centrifuged, and dried to obtain a monolayer of BNNs-OH. S2, preparing BNNs-OH dispersion; Xylene is selected as a dispersion liquid of BNNs-OH, and 10%-50% of BNNs-OH is ultrasonically dispersed in a xylene solution to obtain a BNNs-OH dispersion liquid; S3, preparing EME-X dispersion; Dissolve 40-89% EVA and 1-10% EVA-g-MAH in xylene solvent, and stir at a constant speed in a water bath at 80°C to obtain an EME solution. Add the dispersion obtained in step S2 to the EME solution, heat and stir, and obtain an EME-X dispersion. S4, preparing EME-X encapsulation film; Place the release paper evenly on the surface of the doctor blade coater, pour the dispersion obtained in step S3 evenly onto the surface of the release paper, control the distance and speed between the doctor blade and the release paper, apply the dispersion at a constant speed, heat to volatilize the xylene, and after it is completely dried, repeat the process of applying 3-8 layers of dispersion to obtain the EME-X encapsulation film. Wherein, X is the content of BNNs-OH, ranging from 10% to 50%.

[0026] The EME-X adhesive film for insulating and highly thermally conductive photovoltaic modules of the present invention has a thermal conductivity of 2.87-7.49 W / m·K, a reflectivity of 72.7%-94.1% in the solar wavelength band, an emissivity of 89.3%-95.8% in the mid-infrared, a volume resistivity of 94.2-337.3 TΩ·cm, a shear strength of 2.77-4.72 MPa, an elongation at break of 62.3%-792.76%, and a breaking strength of 4.15-15.34 MPa.

[0027] Example 2 S1. Dissolve 85% EVA and 5% EVA-g-MAH in xylene solvent and stir at a constant speed in a water bath at 80°C. Then, add 10% BNNs-OH dispersion and heat with stirring to obtain EME-10 dispersion. S2. Place the release paper evenly on the surface of the doctor blade coater, pour the dispersion obtained in step S1 evenly onto the surface of the release paper, and apply it at a constant speed. Heat to volatilize the xylene. After it is completely dry, continue the doctor blade coating cycle for 5 times to obtain the EME-10 film. S3. After testing, the thermal conductivity of the thermally conductive insulating EME-10 film prepared in Example 1 is 2.87 W / m·K, the reflectivity in the solar band is 72.7%, the emissivity in the mid-infrared is 89.3%, the volume resistivity is 337.3 TΩ·cm, the shear strength is 4.72 MPa, the elongation at break is 792.76%, and the breaking strength is 15.34 MPa.

[0028] Example 3 S1. Dissolve 75% EVA and 5% EVA-g-MAH in xylene solvent and stir at a constant speed in a water bath at 80°C. Then, add 20% BNNs-OH dispersion and heat with stirring to obtain EME-20 dispersion. S2. Place the release paper evenly on the surface of the doctor blade coater, pour the dispersion obtained in step S1 evenly onto the surface of the release paper, and apply it at a constant speed. Heat to volatilize the xylene. After it is completely dry, continue the doctor blade coating cycle for 5 times to obtain the EME-20 film. S3. After testing, the thermal conductivity of the thermally conductive insulating EME-20 adhesive film prepared in Example 2 is 4.65 W / m·K, the reflectivity in the solar band is 84.4%, the emissivity in the mid-infrared is 91.3%, the volume resistivity is 277.4 TΩ·cm, the shear strength is 411 MPa, the elongation at break is 616.3%, and the breaking strength is 11.43 MPa.

[0029] Example 4 S1. Dissolve 65% EVA and 5% EVA-g-MAH in xylene solvent and stir them uniformly in a water bath at 80°C. Then, add 30% BNNs-OH dispersion and heat with stirring to obtain EME-30 dispersion. S2. Place the release paper evenly on the surface of the doctor blade coater, pour the dispersion obtained in step S1 evenly onto the surface of the release paper, and apply it at a constant speed. Heat to volatilize the xylene. After it is completely dry, continue the doctor blade coating cycle for 5 times to obtain the EME-30 film. S3. After testing, the thermal conductivity of the thermally conductive insulating EME-30 film prepared in Example 3 is 5.93 W / m·K, the reflectivity in the solar band is 92.3%, the emissivity in the mid-infrared is 95.2%, the volume resistivity is 235.3 TΩ·cm, the shear strength is 4.01 MPa, the elongation at break is 547.6%, and the breaking strength is 9.72 MPa.

[0030] Example 5 S1. Dissolve 55% EVA and 5% EVA-g-MAH in xylene solvent and stir them uniformly in a water bath at 80°C. Then, add 40% BNNs-OH dispersion and heat with stirring to obtain EME-40 dispersion. S2. Place the release paper evenly on the surface of the doctor blade coater, pour the dispersion obtained in step S1 evenly onto the surface of the release paper, and apply it at a constant speed. Heat to volatilize the xylene. After it is completely dry, continue the doctor blade coating cycle for 5 times to obtain the EME-40 film. S3. After testing, the thermal conductivity of the thermally conductive insulating EME-40 adhesive film prepared in Example 4 is 6.8 W / m·K, the reflectivity in the solar band is 94.1%, the emissivity in the mid-infrared is 95.8%, the volume resistivity is 144.3 TΩ·cm, the shear strength is 2.77 MPa, the elongation at break is 373.1%, and the breaking strength is 7.3 MPa.

[0031] Example 6 S1. Dissolve 45% EVA and 5% EVA-g-MAH in xylene solvent and stir them uniformly in a water bath at 80°C. Then, add 50% BNNs-OH dispersion and heat with stirring to obtain EME-50 dispersion. S2. Place the release paper evenly on the surface of the doctor blade coater, pour the dispersion obtained in step S1 evenly onto the surface of the release paper, and apply it at a constant speed. Heat to volatilize the xylene. After it is completely dry, continue the doctor blade coating cycle for 5 times to obtain the EME-50 film. S3. After testing, the thermal conductivity of the thermally conductive insulating EME-50 film prepared in Example 5 is 7.49 W / m·K, the reflectivity in the solar band is 88.7%, the emissivity in the mid-infrared is 94.7%, the volume resistivity is 94.2 TΩ·cm, the shear strength is 0.93 MPa, the elongation at break is 62.3%, and the breaking strength is 4.15 MPa.

[0032] Comparative Example 1 S1. Dissolve 90% EVA in xylene solvent and stir uniformly in a water bath at 80°C; then add 10% BNNs-OH dispersion, heat and stir to obtain EVA-10 dispersion; S2. Place the release paper evenly on the surface of the doctor blade coater, pour the dispersion obtained in step S1 evenly onto the surface of the release paper, and apply it at a constant speed. Heat to volatilize the xylene. After it is completely dry, continue the doctor blade coating cycle for 5 times to obtain an EVA-10 encapsulating film. S3. After testing, the thermal conductivity of the thermally conductive insulating EVA-10 film prepared in Comparative Example 1 is 2.36 W / m·K, the reflectivity in the solar band is 68.7%, the emissivity in the mid-infrared is 87.7%, the volume resistivity is 293.9 TΩ·cm, the shear strength is 4.21 MPa, the elongation at break is 693.7%, and the breaking strength is 12.8 MPa.

[0033] Comparative Example 2 S1. Dissolve 80% EVA in xylene solvent and stir uniformly in a water bath at 80°C; then add 20% BNNs-OH dispersion, heat and stir to obtain EVA-20 dispersion; S2. Place the release paper evenly on the surface of the doctor blade coater, pour the dispersion obtained in step S1 evenly onto the surface of the release paper, and apply it at a constant speed. Heat to volatilize the xylene. After it is completely dry, continue the doctor blade coating cycle for 5 times to obtain the EVA-20 encapsulation film. S3. After testing, the thermal conductivity of the thermally conductive insulating EVA-20 film prepared in Comparative Example 2 is 3.76 W / m·K, the reflectivity in the solar band is 79.4%, the emissivity in the mid-infrared is 88.6%, the volume resistivity is 183.3 TΩ·cm, the shear strength is 3.94 MPa, the elongation at break is 580.9%, and the breaking strength is 9.85 MPa.

[0034] Comparative Example 3 S1. Dissolve 70% EVA in xylene solvent and stir uniformly in a water bath at 80°C; then add 30% BNNs-OH dispersion, heat and stir to obtain EVA-30 dispersion; S2. Place the release paper evenly on the surface of the doctor blade coater, pour the dispersion obtained in step S1 evenly onto the surface of the release paper, and apply it at a constant speed. Heat to volatilize the xylene. After it is completely dry, continue the doctor blade coating cycle for 5 times to obtain the EVA-30 encapsulation film. S3. After testing, the thermal conductivity of the thermally conductive insulating EVA-30 film prepared in Comparative Example 3 is 4.92 W / m·K, the reflectivity in the solar light band is 87.3%, the emissivity in the mid-infrared is 93.4%, the volume resistivity is 117.7 TΩ·cm, the shear strength is 3.55 MPa, the elongation at break is 480.0%, and the breaking strength is 8.1 MPa.

[0035] Comparative Example 4 S1. Dissolve 60% EVA in xylene solvent and stir uniformly in a water bath at 80°C; then add 40% BNNs-OH dispersion, heat and stir to obtain EVA-40 dispersion; S2. Place the release paper evenly on the surface of the doctor blade coater, pour the dispersion obtained in step S1 evenly onto the surface of the release paper, and apply it at a constant speed. Heat to volatilize the xylene. After it is completely dry, continue the doctor blade coating cycle for 5 times to obtain the EVA-40 encapsulation film. S3. After testing, the thermal conductivity of the thermally conductive insulating EVA-40 film prepared in Comparative Example 4 is 6.73 W / m·K, the reflectivity in the solar band is 90.1%, the emissivity in the mid-infrared is 94.4%, the volume resistivity is 101.6 TΩ·cm, the shear strength is 1.82 MPa, the elongation at break is 346.34%, and the breaking strength is 5.29 MPa.

[0036] Comparative Example 5 S1. Dissolve 50% EVA in xylene solvent and stir uniformly in a water bath at 80°C; then add 50% BNNs-OH dispersion, heat and stir to obtain EVA-50 dispersion; S2. Place the release paper evenly on the surface of the doctor blade coater, pour the dispersion obtained in step S1 evenly onto the surface of the release paper, and apply it at a constant speed. Heat to volatilize the xylene. After it is completely dry, continue the doctor blade coating cycle for 5 times to obtain the EVA-50 encapsulation film. S3. After testing, the thermal conductivity of the thermally conductive insulating EVA-50 encapsulating film prepared in Comparative Example 5 was 7.30 W / m·K, the reflectivity in the solar band was 83.4%, the emissivity in the mid-infrared was 92.8%, the volume resistivity was 90.3 TΩ·cm, the shear strength was 0.78 MPa, the elongation at break was 20.26%, and the breaking strength was 1.64 MPa. It is worth noting that the film-forming property of the EVA-50 encapsulating film was poor, and some cracks appeared on the surface. The test items involved in the present invention are: thermal conductivity λ; reflectivity R, infrared emissivity E, volume resistivity ρ, shear strength σ, elongation at break e, and breaking strength σc.

[0037] The test results are summarized in the following table: Table 1 Test results of the embodiments and comparative examples:

[0038] The present invention dissolves EVA and EVA-g-MAH in xylene, entangles their molecular chains, and then introduces BNNs-OH. The chemical reaction between the hydroxyl groups on the BNNs-OH and the anhydride groups on the EVA-g-MAH enhances the compatibility between the thermally conductive filler and the polymer. A comparative example uses EVA dissolved in xylene alone without the addition of EVA-g-MAH. The EME-X series encapsulation films prepared in this embodiment exhibit higher thermal conductivity, reflectivity, infrared emissivity, volume resistivity, shear strength, elongation at break, and fracture strength than those of the EVA-X series. These films exhibit improved heat transfer and thermal radiation properties, allowing the temperature inside the module to be transferred to the outside more quickly. Furthermore, EME-X exhibits superior mechanical properties and volume resistivity, ensuring greater stability and safety when applied to photovoltaic modules.

[0039] See also Figure 1 From the cross-sectional SEM images of Examples 1, 2, 3, 4, and 5 of the present invention and Comparative Examples 1, 2, 3, 4, and 5, it can be found that after the introduction of EVA-g-MAH, BNNs-OH has better dispersion in the polymer and no obvious particle aggregation occurs, thereby preventing the filler from aggregating and forming stress defect points; the layered and evenly dispersed BNNs-OH can provide a continuous heat conduction path; As shown in Table 1, considering the thermal conductivity, reflectivity, infrared emissivity, volume resistivity, shear strength, elongation at break, and breaking strength of the composite film, the EME-30 film prepared in Example 4 of the present invention was selected as the best example sample, and vacuum lamination was performed to prepare a novel photovoltaic module. 2 (a) - 2 (b), the present invention uses the EME-30 adhesive film prepared in Example 4 to replace the traditional photovoltaic backsheet EVA adhesive film, and prepares a new photovoltaic module by vacuum hot pressing. 2 ) using thermocouples and multimeters to measure real-time backsheet temperature and power generation voltage, and compared them with those of traditional commercial photovoltaic modules. The experimental results show that the prepared new photovoltaic module backsheet can reduce the temperature by an average of 3.23°C and increase the real-time power generation voltage by an average of 9.8mV. 3 (a) - 3 (b), the new photovoltaic module of Example 4 and the traditional commercial module were used in an indoor solar simulator (1000 W / m 2 ) under the condition of , the solar cell test system was used to test the current density-voltage (JV) characteristics before and after 1 hour of operation; the test results showed that the power generation efficiency of the new photovoltaic module using Example 4 only decreased by 1.52% after 1 hour of operation, while the traditional photovoltaic module decreased by 2.34% after 1 hour of operation; in addition, compared with the traditional photovoltaic module, the fill factor (FF) and maximum power generation power (P max ) have all improved; See Figure 4 The new photovoltaic module of Example 4 of the present invention and commercial photovoltaic modules were placed in an outdoor environment (the test location was Shaanxi University of Science and Technology, Xi'an, Shaanxi, China, on October 14, 2023, with an outdoor temperature of about 23°C). The front panel temperature, back panel temperature and real-time power generation voltage of the two groups of photovoltaic modules were respectively tested using an infrared camera, a thermocouple and a multimeter. The experimental results show that the new photovoltaic module prepared using the EME-30 film of Example 4 can reduce the temperature by an average of 3.12°C and increase the average voltage by 3.01 mV.

[0040] The preparation process of the present invention is simple to operate and suitable for large-scale production. The preparation of EME-X adhesive film has very broad application prospects and is of great significance in improving photovoltaic power generation efficiency, energy conservation and emission reduction, etc.

[0041] The above content is only for explaining the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing EME-X adhesive film for insulating and highly thermally conductive photovoltaic modules, characterized in that: The specific steps are as follows: Step 1: Add isopropyl alcohol, distilled water, hexagonal boron nitride, potassium hydroxide and sodium hydroxide to a high-power cell crusher, crush, centrifuge and dry to prepare hydroxylated boron nitride BNNs-OH; Step 2: Dissolve ethylene-vinyl acetate copolymer (EVA) and maleic anhydride-grafted ethylene-vinyl acetate copolymer (EVA-g-MAH) in xylene solvent at the same time, and stir them uniformly in a water bath at 80°C to obtain an EME solution. Add the hydroxylated boron nitride (BNNs-OH) obtained in step 1 to the mixed solution, heat and stir, and obtain an EME-X dispersion. Step 3: Place the release paper flat on the surface of the scraper, pour the EME-X dispersion evenly onto the surface of the release paper and scrape it at a constant speed. Heat to volatilize the xylene. After it is completely dry, continue to pour the dispersion and scrape 3-8 layers in a cycle to obtain the EME-X film for insulating and highly thermally conductive photovoltaic modules.

2. The method for preparing the EME-X adhesive film for insulating and highly thermally conductive photovoltaic modules according to claim 1, characterized in that: The mass ratio of hexagonal boron nitride, potassium hydroxide, sodium hydroxide, distilled water and isopropyl alcohol in step 1 is 1-5:1.5-7.5:1.5-7.5:50-250:50-250.

3. The method for preparing the EME-X adhesive film for insulating and highly thermally conductive photovoltaic modules according to claim 1, characterized in that: The crushing time in step 1 is 8-16 h.

4. The method for preparing the EME-X adhesive film for insulating and highly thermally conductive photovoltaic modules according to claim 1, characterized in that: In step 2, the mass ratio of the hydroxylated boron nitride BNNs-OH, maleic anhydride grafted ethylene-vinyl acetate copolymer EVA-g-MAH and ethylene-vinyl acetate copolymer EVA is 10-50:1-50:40-89.

5. The method for preparing the EME-X adhesive film for insulating and highly thermally conductive photovoltaic modules according to claim 1, characterized in that: In step 3, the scraper height is 2 mm, the heating temperature is 50° C., and the scraping rate is 80 mm / s.

6. The method for preparing the EME-X adhesive film for insulating and highly thermally conductive photovoltaic modules according to claim 1, characterized in that: Hydroxylated boron nitride BNNs-OH, maleic anhydride grafted ethylene-vinyl acetate copolymer EVA-g-MAH, and ethylene-vinyl acetate copolymer EVA are added to a xylene solution, stirred and heated to 80°C. After EVA and EVA-g-MAH are completely dissolved, the premix is placed in a vacuum box for defoaming treatment.

7. EME-X film for insulating and highly thermally conductive photovoltaic modules, characterized by: The invention is prepared by the preparation method of the EME-X adhesive film for insulating and highly thermally conductive photovoltaic modules according to any one of claims 1 to 6.

8. A method for preparing an insulating and highly thermally conductive photovoltaic module, characterized in that: The specific steps are as follows: Step 1: Select the photovoltaic cell and check whether it is in good contact with a multimeter to eliminate the risk of short circuit or open circuit; Step 2: From top to bottom, stack the photovoltaic glass, ethylene-vinyl acetate copolymer (EVA), photovoltaic cells, EME-X film, and photovoltaic glass in this order to form a photovoltaic module. Step 3: Place the laminated photovoltaic modules in a vacuum chamber at 120°C for 15-30 minutes, and take them out after the vacuum chamber temperature drops to room temperature. Step 4: Conduct voltage and current tests on the laminated photovoltaic modules to inspect product quality.

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