Thermally conductive composite packaging film and photovoltaic module

Abstract

The present invention relates to the technical field of solar encapsulation films, and provides a heat-conductive composite encapsulation film and a photovoltaic module. The heat-conductive composite encapsulation film is a composite encapsulation film after pre-crosslinking treatment, comprising a phase-change heat storage adhesive layer in contact with a solar cell sheet, a nano silver wire layer, and a heat-conductive adhesive layer in contact with a photovoltaic back plate or a front plate; the phase-change heat storage adhesive layer comprises a first resin and a phase-change heat storage material, the phase-change heat storage material is a paraffin microcapsule, and the addition amount thereof is 20-30% of the mass of the first resin; the heat-conductive adhesive layer comprises a second resin and a heat-conductive material, and the addition amount of the heat-conductive material is 10%-30% of the mass of the second resin; the first resin and the second resin are both EVA resins. The heat-conductive composite encapsulation film can effectively avoid the problems of reduced insulation and wet leakage performance and delamination caused by existing adhesive films in photovoltaic modules, and the heat storage and rapid heat conduction performance are effectively improved, and efficient cooling can be achieved, thereby improving the power generation and reliability of photovoltaic modules.

Description

Technical Field

[0001] The invention relates to the technical field of solar packaging adhesive films, and in particular to a heat-conductive composite packaging adhesive film and a photovoltaic module. Background Art

[0002] In recent years, in order to meet the market demand for reducing the levelized cost of electricity (LCOE), various new photovoltaic technologies that can reduce costs have emerged. Among them, increasing the light-receiving area of ​​the cell and increasing the size of the cell and photovoltaic module are important ways to reduce the levelized cost of electricity in recent years. Therefore, there are 182-type cells and photovoltaic modules, 210-type cells and photovoltaic modules on the market, and these two types are gradually replacing 166-type cells and photovoltaic modules, and will become the mainstream types in the future market. However, with the increase in the size of the cell and photovoltaic module, the short-circuit current of the photovoltaic module increases, and the temperature of the photovoltaic module during operation continues to rise, which will lead to an increase in the hot spot temperature of the photovoltaic module, an increase in the risk of hot spots, and a decrease in the reliability of the photovoltaic module. In winter, the surface temperature of the photovoltaic module often reaches above 60°C when it is working; in summer, the surface temperature of the photovoltaic module often reaches above 80°C when it is working. The higher the operating temperature of the PV module, not only will the risk of hot spots be higher, but the power generation will also be lower; for example, the temperature coefficient of PERC PV modules is -0.35% / ℃, and the temperature coefficient of TOPCON PV modules is -0.3% / ℃.

[0003] In order to solve the above problems, the industry has adopted various innovative methods to reduce the working temperature of photovoltaic modules, reduce the risk of hot spots, and increase the power generation of photovoltaic modules. Thermally conductive encapsulation film is one of the innovative solutions. However, although many film manufacturers have developed various types of thermally conductive encapsulation films to improve the thermal conductivity of the film to reduce the working temperature of photovoltaic modules; however, these thermally conductive encapsulation films all have certain problems.

[0004] For example, patents with publication numbers CN113308206B and CN109337612B disclose the technology of directly adding inorganic powder thermal conductors to resin to form adhesive films. This technology can improve the thermal conductivity of the adhesive film. After the adhesive film is directly in contact with the battery cell and bonded, it can reduce the temperature on the battery cell when the photovoltaic module is working. However, the amount of inorganic powder thermal conductor added to the adhesive film must reach a certain value in the polymer resin so that the thermal conductive particles dispersed in the polymer resin can contact each other to form an effective thermal conductive network, thereby greatly improving the thermal conductivity of the adhesive film. Generally, the higher the amount of the inorganic powder thermal conductor added, the more perfect the thermal conductive network formed; therefore, the amount of the inorganic powder thermal conductor added generally needs to reach more than 10% of the resin mass ratio to initially form a partial thermal conductive network. When the amount of inorganic powder thermal conductor added is high, the volume resistivity of the film will drop significantly, which will lead to poor insulation between the film and the cell, and then significantly reduce the insulation of the photovoltaic module, and significantly reduce the wet leakage performance, resulting in reduced reliability of the photovoltaic module. Moreover, the thermal conductivity and cooling effect of the film with inorganic powder thermal conductor added needs to be improved.

[0005] For example, the patent with publication number CN207250535U discloses a white solar cell film: it is a composite film composed of a high-transmittance EVA film layer in contact with the cell, a white EVA film layer, and a thermally conductive EVA film layer in contact with the photovoltaic back panel or photovoltaic front panel. Although this composite film can improve its volume resistivity to a certain extent and improve the insulation between the composite film and the cell. However, on the one hand, the volume resistivity and insulation of this composite film need to be further improved; on the other hand, since the high-transmittance EVA film layer in contact with the cell has no thermal conductivity, even if a thermally conductive EVA film layer is provided, the thermal conductivity of this composite film cannot be greatly improved. Therefore, this composite film cannot quickly remove the heat from the cell, which results in a small decrease in the temperature of the cell when the photovoltaic module is working, and the cooling effect is not obvious.

[0006] In addition, the patent with publication number CN112812694B discloses a heat-insulating packaging film, which includes a heat-conducting film layer contacting the battery cell, an intermediate heat-insulating layer, and a phase-change energy storage layer contacting the photovoltaic backplane; its phase-change energy storage layer is obtained by directly adding the phase-change material paraffin to the third film main resin (such as ethylene-vinyl acetate copolymer resin). However, the heat-conducting and cooling effects of this heat-insulating packaging film also need to be further improved. Moreover, due to the poor compatibility of paraffin and ethylene-vinyl acetate copolymer resin, after the solid paraffin is converted into liquid paraffin during the heat absorption process, the liquid paraffin will penetrate from the ethylene-vinyl acetate copolymer resin and reach the interface between the resin and the photovoltaic backplane (such as photovoltaic glass), destroying the chemical bond between the resin and the photovoltaic backplane, thereby causing the packaging film and the photovoltaic backplane to delaminate, causing water vapor to easily enter the interior of the photovoltaic module from the delaminated area, corroding the battery cell and the welding strip, and then reducing the reliability and power generation of the photovoltaic module. Summary of the invention

[0007] The purpose of the present invention is to provide a thermally conductive composite encapsulation film and a photovoltaic module in view of the deficiencies in the prior art, so as to effectively avoid the problems of reduced insulation and moisture leakage performance and delamination caused by the existing films in photovoltaic modules, and the heat storage and rapid thermal conductivity of the composite film are effectively improved, which can achieve efficient cooling, thereby improving the power generation and reliability of the photovoltaic module.

[0008] Based on this, the present invention discloses a heat-conductive composite encapsulation adhesive film, which is a composite encapsulation adhesive film that has been pre-crosslinked, and includes a phase change heat storage adhesive layer that contacts a solar cell sheet, a nano silver wire layer, and a heat-conductive adhesive layer that contacts a photovoltaic back sheet or a photovoltaic front sheet, which are sequentially stacked;

[0009] The phase-change heat storage adhesive layer includes a first resin and a phase-change heat storage material dispersed in the first resin, wherein the phase-change heat storage material is paraffin microcapsules, and the addition amount of the paraffin microcapsules is 20-30% of the mass of the first resin;

[0010] The thermally conductive adhesive layer includes a second resin and a thermally conductive material dispersed in the second resin, and the amount of the thermally conductive material added is 10%-30% of the mass of the second resin;

[0011] Wherein, the first resin and the second resin are both ethylene-vinyl acetate copolymer.

[0012] Preferably, the thickness of the phase change heat storage glue layer is 0.3-0.4 mm.

[0013] Further preferably, the phase change melting point of the paraffin microcapsule is in the range of 35-40°C, the thermal enthalpy value is greater than 160KJ / KG, and the heat resistance temperature is greater than 200°C.

[0014] In the thermally conductive composite encapsulation film of the present invention, the phase change heat storage material - paraffin microcapsules used in the phase change heat storage adhesive layer can quickly and efficiently absorb and transfer the heat on the battery cells when the photovoltaic module is working, so that the battery cells can be cooled quickly and efficiently, effectively reducing the risk of hot spots in the photovoltaic module, and thus effectively increasing the power generation of the photovoltaic module.

[0015] Furthermore, on snowy or frosty days, its phase change heat storage material - paraffin microcapsules can release the heat absorbed by the photovoltaic modules when they are working during the day, thereby reducing the duration and probability of the photovoltaic modules being covered by snow or frost at night, and increasing the power generation of the photovoltaic modules.

[0016] Moreover, its phase change heat storage material - paraffin microcapsule, after undergoing a phase change from solid paraffin to liquid paraffin, is constrained by the outer microcapsule shell, and the liquid paraffin is difficult to seep out of the microcapsule shell. Therefore, it can effectively avoid the delamination problem between the composite encapsulation film and the battery cell, thereby improving the reliability of photovoltaic modules.

[0017] In addition, since its phase change heat storage material - paraffin microcapsule is an organic material with a high volume resistivity, it will maintain a high volume resistivity of the phase change heat storage adhesive layer, thereby further avoiding the deterioration of the insulation between the composite packaging adhesive film and the battery cell, further improving the wet leakage and insulation performance of the photovoltaic module, and further improving the reliability of the photovoltaic module.

[0018] Preferably, the diameter of the nano-silver wires used in the nano-silver wire layer is 50-70 nm and the length is 20-30 um.

[0019] Further preferably, the thickness of the silver nanowire layer is 150-250 nm.

[0020] Among them, silver has a relatively high thermal conductivity coefficient, which can reach above 420W / mK. Therefore, the thermal conductivity of its nano-silver wire layer is very high, and it can quickly and efficiently transfer the heat transferred from the phase change heat storage glue layer to the thermal conductive glue layer, thereby achieving efficient cooling and effectively increasing the power generation of photovoltaic modules.

[0021] Especially when a certain cell on a photovoltaic module has hidden cracks or is blocked, or a certain string of cells is blocked, the cell or the string of cells is very likely to have a hot spot risk, and the temperature will rise sharply; at this time, the phase change heat storage glue layer at the corresponding position will quickly absorb the heat of the cell under the hot spot, and quickly transfer the heat to the nano silver wire at the corresponding position. The nano silver wire, relying on its own thermal conductivity advantage, quickly transfers the heat laterally to the entire nano silver wire layer, thereby greatly improving the heat conduction efficiency, quickly cooling the cell under the hot spot, and quickly and efficiently reducing the risk of diode thermal breakdown and photovoltaic module burning caused by the hot spot for the cell or the string of cells, further improving the reliability and power generation of photovoltaic modules.

[0022] Moreover, although the conductivity of the nano silver wire layer is particularly outstanding, since the thermally conductive composite packaging film of the present invention arranges the nano silver wire layer between the phase change heat storage adhesive layer and the thermally conductive adhesive layer, the thermally conductive composite packaging film can not only improve the efficient cooling effect on the battery cell, but also enable it to have a higher volume resistivity, so that its wet leakage and insulation properties can better meet the performance requirements, thereby improving the power generation and reliability of the photovoltaic module at the same time.

[0023] Preferably, the thermally conductive material comprises inorganic thermally conductive particles and vinyltrimethoxysilane coated on the outer layer of the inorganic thermally conductive particles, and the added amount of vinyltrimethoxysilane is 1.5-3% of the mass of the thermally conductive material.

[0024] Among the thermally conductive materials used in the thermally conductive adhesive layer, the vinyltrimethoxysilane coated on the outer layer of the inorganic thermally conductive particles can promote their compatibility with the EVA resin, improve their dispersibility in the EVA resin, and ensure their thermal conductive effect.

[0025] Further preferably, the inorganic thermally conductive particles are one or more of aluminum nitride, boron nitride and silicon carbide.

[0026] More preferably, the thickness of the thermal conductive adhesive layer is 0.1-0.2 mm; and the particle size range of the thermal conductive material is 0.1-10 um.

[0027] In the thermally conductive composite packaging adhesive film of the present invention, the thermally conductive adhesive layer can quickly transfer the heat transferred from the nano silver wire layer to the photovoltaic back panel or photovoltaic front panel (such as glass), and then quickly transfer and radiate the heat to the external air environment through the photovoltaic back panel or photovoltaic front panel.

[0028] Preferably, the pre-crosslinking degree of the composite packaging film is controlled at 15-25%.

[0029] Preferably, the phase-change heat storage adhesive layer and the heat conductive adhesive layer are both added with additives accounting for 2-3% of the mass of the ethylene-vinyl acetate copolymer of the respective layers.

[0030] Further preferably, the auxiliary agent includes 0.6% of tert-butyl peroxy-2-ethylhexyl carbonate, 0.5% of triallyl isocyanurate, 0.5% of ethoxylated trimethylolpropane triacrylate, 0.3% of γ-methacryloxypropyltrimethoxysilane, 0.15% of bis(2,2,6,6-tetramethylpiperidinyl)sebacate and 0.05% of triethylene glycol bis[β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate] in terms of the mass percentage of the ethylene-vinyl acetate copolymer in each layer.

[0031] Among them, the thermally conductive composite encapsulation film has undergone pre-crosslinking treatment, which can make the phase change heat storage adhesive layer and the thermal conductive adhesive layer have a certain degree of crosslinking, so that the fluidity of the two layers of EVA resin during lamination of photovoltaic modules is greatly reduced, so as to effectively prevent the nano silver wire layer from being destroyed due to the high fluidity of the EVA resin during lamination, and effectively improve the reliability of the thermally conductive composite encapsulation film and photovoltaic modules.

[0032] For example, by controlling the amount of the cross-linking agent tert-butyl peroxide-2-ethylhexyl carbonate, the auxiliary cross-linking agent triallyl isocyanurate and the auxiliary cross-linking agent ethoxylated trimethylolpropane triacrylate added to the phase change thermal storage adhesive layer and the thermal conductive adhesive layer, the pre-cross-linking reaction between the EVA resins in the two layers can be promoted during the electron irradiation process, so that the thermal conductive composite packaging adhesive film can reach the desired pre-cross-linking degree.

[0033] The present invention also discloses a photovoltaic module, comprising a photovoltaic front panel, a first packaging film, a solar cell, a second packaging film and a photovoltaic back panel stacked in sequence; the first packaging film and / or the second packaging film is a thermally conductive composite packaging film as described above in the present invention, and the phase change heat storage adhesive layer is in contact with the solar cell.

[0034] Compared with the prior art, the present invention has at least the following beneficial effects:

[0035] The thermally conductive composite packaging adhesive film of the present invention can (1) effectively prevent the nano silver wire layer from being damaged due to the high fluidity of the EVA resin during lamination by pre-crosslinking the composite packaging adhesive film, thereby improving the reliability of the thermally conductive composite packaging adhesive film; (2) can also improve the volume resistivity of the thermally conductive composite packaging adhesive film by arranging the nano silver wire layer between the phase change heat storage adhesive layer and the thermally conductive adhesive layer, and by combining the phase change heat storage adhesive layer with paraffin microcapsules as the phase change heat storage material, thereby effectively improving the wet leakage and insulation performance between the thermally conductive composite packaging adhesive film and the battery cell, thereby effectively improving The reliability of photovoltaic modules; (3) through the cooperation of the three layers of phase change thermal storage glue layer, nano silver wire layer and thermal conductive glue layer, the battery cell can be cooled more quickly and efficiently, and the lateral heat transfer can be promoted, which effectively reduces the risk of hot spots in photovoltaic modules and increases power generation. In addition, the heat storage performance of the phase change thermal storage glue layer can be used to reduce the duration and probability of photovoltaic modules being covered by snow or frost at night, further increasing the power generation of photovoltaic modules; (4) It can also effectively prevent the liquid paraffin from seeping out of the microcapsule shell during the phase change process, effectively avoiding the delamination problem between the composite encapsulation film and the battery cell.

[0036] Therefore, the thermally conductive composite encapsulation film of the present invention has good moisture resistance, insulation, heat storage, high-efficiency cooling, anti-delamination and anti-nano silver wire damage effects, so it can effectively improve the power generation and reliability of photovoltaic modules. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 The cross-sectional structure diagram of a thermally conductive composite packaging adhesive film of the present invention is shown in FIG.

[0038] Description of the accompanying drawings: phase change heat storage glue layer 11; nano silver wire layer 12; thermal conductive glue layer 13. DETAILED DESCRIPTION

[0039] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below in conjunction with specific implementation methods.

[0040] Example 1

[0041] A thermally conductive composite packaging film of this embodiment, see Figure 1 , including a phase change heat storage adhesive layer 11, a nano silver wire layer 12 and a thermal conductive adhesive layer 13 stacked in sequence; the phase change heat storage adhesive layer 11 contacts the solar cell, and the thermal conductive adhesive layer 13 contacts the photovoltaic back panel or the photovoltaic front panel.

[0042] Among them, the thickness of the phase change heat storage glue layer 11 is 0.3mm; the phase change heat storage glue layer 11 includes a first resin and a phase change heat storage material and a first auxiliary agent dispersed in the first resin, the phase change heat storage material is paraffin microcapsule, and the addition amount of paraffin microcapsule is 20% of the mass of the first resin, the phase change melting point range of the paraffin microcapsule is 35-40℃, the thermal enthalpy value is greater than 160KJ / KG, and the heat resistance temperature is greater than 200℃.

[0043] Further, the first auxiliary agent includes, by mass percentage of the first resin, 0.6% of tert-butyl peroxy-2-ethylhexyl carbonate, 0.5% of triallyl isocyanurate, 0.5% of ethoxylated trimethylolpropane triacrylate, 0.3% of γ-methacryloxypropyltrimethoxysilane, 0.15% of bis(2,2,6,6-tetramethylpiperidinyl)sebacate and 0.05% of triethylene glycol bis[β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate].

[0044] The nano silver wire layer 12 is formed by crisscrossing nano silver wires, and the thickness of the nano silver wire layer 12 is 150 nm; the diameter of the nano silver wires used in the nano silver wire layer 12 is 50-70 nm and the length is 20-30 um.

[0045] The thickness of the thermal conductive adhesive layer 13 is 0.2 mm. The thermal conductive adhesive layer 13 includes a second resin, a thermal conductive material dispersed in the second resin, and a second auxiliary agent. The amount of the thermal conductive material added is 10% of the mass of the second resin.

[0046] Furthermore, the thermally conductive material includes inorganic thermally conductive particles and vinyltrimethoxysilane coated on the outer layer of the inorganic thermally conductive particles, and the added amount of vinyltrimethoxysilane is 2% of the mass of the thermally conductive material. The particle size range of the thermally conductive material is 0.1-10um; the inorganic thermally conductive particles are boron nitride.

[0047] Further, the second auxiliary agent includes 0.6% of tert-butyl peroxy-2-ethylhexyl carbonate, 0.5% of triallyl isocyanurate, 0.5% of ethoxylated trimethylolpropane triacrylate, 0.3% of γ-methacryloxypropyltrimethoxysilane, 0.15% of bis(2,2,6,6-tetramethylpiperidinyl)sebacate and 0.05% of triethylene glycol bis[β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate] in terms of mass percentage of the second resin.

[0048] Specifically, the first resin and the second resin are both ethylene-vinyl acetate copolymer (EVA).

[0049] The thermally conductive composite packaging film is a composite packaging film that has been pre-crosslinked, and the pre-crosslinking degree of the composite packaging film is 15%.

[0050] A photovoltaic module of the present embodiment includes a photovoltaic front panel, a first packaging film, a solar cell, a second packaging film and a photovoltaic back panel stacked in sequence from top to bottom; wherein the first packaging film and the second packaging film are a thermally conductive composite packaging film described above in the present embodiment, and the phase change heat storage adhesive layer 11 is in contact with the solar cell, and the thermal conductive adhesive layer 13 is in contact with the photovoltaic back panel or the photovoltaic front panel; the photovoltaic front panel is glass.

[0051] Example 2

[0052] The present embodiment is a thermally conductive composite encapsulation adhesive film and a photovoltaic module, see Example 1 for details, and the difference between the present embodiment and Example 1 is that:

[0053] In the thermally conductive composite packaging film of the present embodiment, the thickness of the phase change heat storage adhesive layer 11 is 0.4 mm, and the added amount of paraffin microcapsules is 25% of the mass of the first resin; the thickness of the nano silver wire layer 12 is 200 nm; the thickness of the thermally conductive adhesive layer 13 is 0.1 mm, and the added amount of the thermally conductive material is 20% of the mass of the second resin, and the inorganic thermally conductive particles are aluminum nitride; the pre-crosslinking degree of the composite packaging film of the present embodiment is 20%.

[0054] Example 3

[0055] The present embodiment is a thermally conductive composite encapsulation adhesive film and a photovoltaic module, see Example 1 for details, and the difference between the present embodiment and Example 1 is that:

[0056] In the thermally conductive composite packaging film of the present embodiment, the thickness of the phase change heat storage adhesive layer 11 is 0.4 mm, and the amount of paraffin microcapsules added is 30% of the mass of the first resin; the thickness of the nano silver wire layer 12 is 250 nm; the thickness of the thermally conductive adhesive layer 13 is 0.1 mm, and the amount of thermally conductive material added is 30% of the mass of the second resin, and the inorganic thermally conductive particles are silicon carbide; the pre-crosslinking degree of the composite packaging film of the present embodiment is 25%.

[0057] Comparative Example 1

[0058] A packaging film in this comparative example has only one transparent EVA adhesive layer with a thickness of 0.5 mm; the transparent EVA adhesive layer includes EVA resin and an auxiliary agent dispersed in the EVA resin. The formula composition of the auxiliary agent specifically refers to the first auxiliary agent or the second auxiliary agent in Example 2.

[0059] A photovoltaic module of this comparative example, see Example 2 for details, which differs from Example 2 in that:

[0060] The first packaging film and the second packaging film are the packaging films described above in this comparative example.

[0061] Comparative Example 2

[0062] A packaging adhesive film in this comparative example has only one thermal conductive EVA adhesive layer with a thickness of 0.5 mm; the thermal conductive EVA adhesive layer is specifically referred to as the thermal conductive adhesive layer 13 in Example 2.

[0063] A photovoltaic module of this comparative example, see Example 2 for details, which differs from Example 2 in that:

[0064] The first packaging film and the second packaging film are the packaging films described above in this comparative example.

[0065] Comparative Example 3

[0066] A packaging film in this comparative example is a composite packaging film having a two-layer structure, one layer is a transparent EVA layer with a thickness of 0.25 mm, and the other layer is a thermally conductive EVA layer with a thickness of 0.25 mm; wherein the transparent EVA layer specifically refers to the transparent EVA layer in comparative example 1, and the thermally conductive EVA layer specifically refers to the thermally conductive EVA layer in comparative example 2.

[0067] A photovoltaic module of this comparative example, see Example 2 for details, which differs from Example 2 in that:

[0068] The first packaging film and the second packaging film are the packaging films described above in this comparative example; the transparent EVA adhesive layer contacts the solar cell sheet, and the thermal conductive EVA adhesive layer contacts the photovoltaic back sheet or the photovoltaic front sheet.

[0069] Comparative Example 4

[0070] A packaging film in this comparative example is a composite packaging film having a two-layer structure, one layer is a phase-change heat storage EVA adhesive layer with a thickness of 0.4 mm, and the other layer is a thermal conductive EVA adhesive layer with a thickness of 0.1 mm; its phase-change heat storage EVA adhesive layer and thermal conductive EVA adhesive layer are specifically referred to the phase-change heat storage adhesive layer 11 and the thermal conductive adhesive layer 13 of Example 2 respectively; and the composite packaging film is also a composite packaging film after pre-crosslinking treatment, and its pre-crosslinking degree is also referred to Example 2.

[0071] A photovoltaic module of this comparative example, see Example 2 for details, which differs from Example 2 in that:

[0072] The first packaging film and the second packaging film are the packaging films described above in this comparative example; the phase-change heat storage EVA adhesive layer contacts the solar cell sheet, and the heat conductive EVA adhesive layer contacts the photovoltaic back panel or photovoltaic front panel.

[0073] Comparative Example 5

[0074] The encapsulation film and photovoltaic module of this comparative example are specifically referred to Example 2, and the difference between this comparative example and Example 2 is that the composite encapsulation film of this comparative example is not pre-crosslinked.

[0075] Comparative Example 6

[0076] A packaging film in this comparative example has only one phase-change heat storage EVA adhesive layer with a thickness of 0.5 mm; the phase-change heat storage EVA adhesive layer specifically refers to the phase-change heat storage adhesive layer 11 in Example 2.

[0077] A photovoltaic module of this comparative example, see Example 2 for details, which differs from Example 2 in that:

[0078] The first packaging film and the second packaging film are the packaging films described above in this comparative example.

[0079] Comparative Example 7

[0080] A packaging film in this comparative example is a composite packaging film having a three-layer structure, wherein the first layer is a phase change heat storage adhesive layer with a thickness of 0.4 mm, the second layer is a nano silver wire layer with a thickness of 200 nm, and the third layer is a phase change heat storage adhesive layer with a thickness of 0.1 mm; the phase change heat storage adhesive layer and the nano silver wire layer are specifically referred to in Example 2; and the composite packaging film is also a composite packaging film after pre-crosslinking treatment, and its pre-crosslinking degree is also referred to in Example 2.

[0081] A photovoltaic module of this comparative example, see Example 2 for details, which differs from Example 2 in that:

[0082] The first packaging film and the second packaging film are the packaging films described above in this comparative example.

[0083] Performance Testing

[0084] The performance tests were conducted on the encapsulation films and photovoltaic modules of Examples 1-3 and Comparative Examples 1-7. The test data are shown in Table 1 below:

[0085] Table 1

[0086]

[0087]

[0088] From Table 1, we can see that:

[0089] It can be seen from the test data of Example 2 and Comparative Examples 1-3 that the thermally conductive composite encapsulation film of Example 2 of the present invention not only ensures that the encapsulation film has a higher volume resistivity and meets the requirements of wet leakage and insulation performance of photovoltaic modules; the power generation of photovoltaic modules is also improved more than that of Comparative Examples 1-3; the effect of reducing the hot spot temperature of photovoltaic modules is also superior to that of Comparative Examples 1-3; and the phase change heat storage material of paraffin microcapsules solidifies and releases heat at a temperature higher than the ambient temperature, which also reduces the duration and probability of photovoltaic modules being covered by snow or frost.

[0090] It can be seen from the test data of Example 2 and Comparative Example 4 that the nano silver wire layer 12 has high thermal conductivity and lateral heat dissipation performance, and can quickly and significantly reduce the temperature of the battery cell at the hot spot; and, although the conductivity of the nano silver wire layer 12 is particularly outstanding, in the thermally conductive composite packaging film of Example 2, the nano silver wire layer 12 is arranged between the phase change heat storage adhesive layer 11 and the thermally conductive adhesive layer 13, which can not only improve the cooling effect of the thermally conductive composite packaging film on the battery cell, but also ensure the moisture leakage resistance and insulation performance requirements of the thermally conductive composite packaging film, thereby improving the power generation and reliability of the photovoltaic module.

[0091] It can be seen from the test data of Example 2 and Comparative Example 5 that after pre-crosslinking, the nano silver wire layer 12 will not be damaged during lamination of the photovoltaic module and can maintain its integrity; without pre-crosslinking, the nano silver wire layer 12 will be damaged during lamination, which will lead to an increase in the hot spot temperature of the photovoltaic module and a decrease in the increase in the power generation of the photovoltaic module.

[0092] It can be seen from the test data of Example 2, Comparative Example 2, Comparative Example 4, Comparative Example 6 and Comparative Example 7 that, when the total thickness of the EVA adhesive layer of the encapsulation film remains unchanged (the total thickness of the EVA adhesive layer is 0.5 mm), the thermally conductive composite encapsulation film of Example 2 of the present invention, through the coordination of the three-layer structure of the phase change heat storage adhesive layer, the nano silver wire layer and the thermally conductive adhesive layer, can not only effectively improve the insulation and wet leakage performance degradation problems caused by the application of the thermally conductive EVA adhesive layer in photovoltaic modules, but also has unique advantages in improving the power generation of photovoltaic modules and reducing the hot spot temperature of photovoltaic modules.

[0093] It can be seen from the test data of Examples 1-3 and Comparative Examples 1-7 that after pre-crosslinking, the adhesion between the thermally conductive composite encapsulation film and the glass and the backplane will decrease, but the peel strength with the glass will still be much higher than the national standard GB / T29848-2018 requirement of >60N / cm, and the peel strength with the backplane will still be much higher than the national standard GB / T31034-2014 requirement of ≥40N / cm. Therefore, the pre-crosslinked thermally conductive composite encapsulation film still has good adhesion with the glass and the backplane, which can effectively prevent the delamination of the film and the glass or the backplane when the component is running outdoors.

[0094] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the embodiments of the present invention.

[0095] The technical solution provided by the present invention is introduced in detail above. Specific examples are used in this article to illustrate the principle and implementation mode of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation mode and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A thermally conductive composite packaging film, characterized in that: It is a pre-crosslinked composite encapsulation adhesive film, which includes a phase change heat storage adhesive layer in contact with the solar cell sheet, a nano silver wire layer, and a heat conductive adhesive layer in contact with the photovoltaic back panel or photovoltaic front panel. The phase-change heat storage adhesive layer includes a first resin and a phase-change heat storage material dispersed in the first resin, wherein the phase-change heat storage material is paraffin microcapsules, and the addition amount of the paraffin microcapsules is 20-30% of the mass of the first resin; The thermally conductive adhesive layer includes a second resin and a thermally conductive material dispersed in the second resin, and the amount of the thermally conductive material added is 10%-30% of the mass of the second resin; Wherein, the first resin and the second resin are both ethylene-vinyl acetate copolymer; The pre-crosslinking degree of the composite packaging film is controlled at 15-25%.

2. The thermally conductive composite packaging film according to claim 1, characterized in that: The thickness of the phase change heat storage glue layer is 0.3-0.4 mm.

3. A thermally conductive composite packaging film according to claim 1 or 2, characterized in that: The phase change melting point of the paraffin microcapsule is in the range of 35-40°C, the thermal enthalpy value is greater than 160KJ / KG, and the heat resistance temperature is greater than 200°C.

4. The thermally conductive composite packaging film according to claim 1, characterized in that: The diameter of the nano silver wires used in the nano silver wire layer is 50-70nm and the length is 20-30um.

5. A thermally conductive composite packaging film according to claim 1 or 4, characterized in that: The thickness of the nano silver wire layer is 150-250nm.

6. The thermally conductive composite packaging film according to claim 1, characterized in that: The thermal conductive material comprises inorganic thermal conductive particles and vinyl trimethoxy silane coated on the outer layer of the inorganic thermal conductive particles, and the added amount of the vinyl trimethoxy silane is 1.5-3% of the mass of the thermal conductive material.

7. The thermally conductive composite packaging film according to claim 6, characterized in that: The inorganic thermally conductive particles are one or more of aluminum nitride, boron nitride and silicon carbide.

8. A thermally conductive composite packaging film according to claim 1, 6 or 7, characterized in that: The thickness of the thermal conductive adhesive layer is 0.1-0.2 mm; the particle size range of the thermal conductive material is 0.1-10 um.

9. The thermally conductive composite packaging film according to claim 1, characterized in that: The phase-change heat storage adhesive layer and the heat conductive adhesive layer are both added with an auxiliary agent accounting for 2-3% of the mass of the ethylene-vinyl acetate copolymer of the respective layers.

10. The thermally conductive composite packaging film according to claim 9, characterized in that: The auxiliary agent includes 0.6% of tert-butyl peroxy-2-ethylhexyl carbonate, 0.5% of triallyl isocyanurate, 0.5% of ethoxylated trimethylolpropane triacrylate, 0.3% of γ-methacryloxypropyltrimethoxysilane, 0.15% of bis(2,2,6,6-tetramethylpiperidinyl)sebacate and 0.05% of triethylene glycol bis[β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate] in terms of the mass percentage of the ethylene-vinyl acetate copolymer in the respective layers.

11. A photovoltaic module, comprising a photovoltaic front panel, a first encapsulation film, a solar cell, a second encapsulation film and a photovoltaic back panel stacked in sequence; characterized in that: The first packaging film and / or the second packaging film is a thermally conductive composite packaging film as claimed in any one of claims 1 to 10, and the phase change heat storage adhesive layer is in contact with the solar cell.

Images