CN218827184U

CN218827184U - Solar cell backboard

Info

Publication number: CN218827184U
Application number: CN202223148872.1U
Authority: CN
Inventors: 吴培服; 吴迪; 孙化斌; 臧辉; 张迪
Original assignee: Jiangsu Shuangxing Color Plastic New Materials Co Ltd
Current assignee: Jiangsu Shuangxing Color Plastic New Materials Co Ltd
Priority date: 2022-11-25
Filing date: 2022-11-25
Publication date: 2023-04-07
Anticipated expiration: 2032-11-25

Abstract

The application discloses a solar cell backboard, which comprises a base film, an adhesive layer and a weather-resistant film, wherein the base film comprises a base material layer, two online coating layers are respectively arranged on the surfaces of two sides of the base material layer, and a barrier layer is formed on the outer sides of the online coating layers in a sputtering manner; the substrate layer includes transmission membrane and heat conduction membrane, is formed with a plurality of equidistant parallel arrangement's prism structure on the transmission membrane, and the prism structure outside is formed with one deck metal reflection stratum through vacuum sputtering, has filled the heat conduction glue in the sunken cavity between heat conduction membrane and the metal reflection stratum, and the heat conduction membrane is connected as an organic wholely through the heat conduction glue with the metal reflection stratum. The solar cell backboard can not only collect light, but also enlarge the reflection area by arranging the substrate layer with the reflection prism structure of the physical structure. The metal reflecting layer on the back of the reflecting prism structure not only has a reflecting effect, but also increases the heat dissipation area and the heat conduction efficiency. In addition, the base film has excellent barrier properties by providing a barrier layer.

Description

Solar cell backboard

Technical Field

The present application relates to a solar cell back sheet.

Background

CN 114536906A discloses a black photovoltaic backplate, including black layer, undercoating, supporting layer and the skin that sets gradually from inside to outside. The position of the black layer corresponds to the cell gap of the photovoltaic module; the inner coating is white and is used for reflecting light; the support layer contains a thermally conductive filler. The black layer in the prior art mainly plays a role in beauty, reflects little light and is difficult to fold to the cell for utilization. The white inner coating on the inner side of the battery piece is a surface mainly reflecting light rays and is mainly made of materials with poor heat conductivity, such as white titanium dioxide, glass beads and resin. However, the particles such as titanium dioxide and glass beads have a diffuse reflection effect, a large amount of light is actually absorbed by the inner coating, the thermal conductivity of the inner coating is relatively poor, and the efficiency of conducting the absorbed heat to the supporting layer is low. This prior art's backplate, the ability that relies on internal coating reflection light is limited, and the efficiency of heat conduction for the supporting layer is lower, and the leakproofness of coating is also relatively poor.

Disclosure of Invention

The present application addresses the problem of providing a solar cell backsheet that reduces or avoids the aforementioned problems.

In order to solve the technical problem, the application provides a solar cell back plate which comprises a base film close to the back surface of a solar cell piece and a weather-resistant film positioned on the outer side of the base film, wherein the weather-resistant film and the base film are bonded into a whole through a bonding layer; the base film comprises a base material layer, two side surfaces of the base material layer are respectively provided with an online coating layer, and the outer side of the online coating layer is sputtered to form a barrier layer; the solar cell comprises a substrate layer and a plurality of solar cell sheets, wherein the substrate layer comprises a transmission film facing one side of each solar cell sheet and a heat conduction film far away from one side of each solar cell sheet, a plurality of prism structures which are arranged in parallel at equal intervals are formed on the transmission film, each prism structure consists of a body part with an isosceles triangle section and a fin extending upwards from the top of the body part, a metal reflection layer is formed on the outer side of each prism structure through vacuum sputtering, heat conduction glue is filled in a concave cavity between each heat conduction film and the corresponding metal reflection layer, the heat conduction films and the corresponding metal reflection layers are connected into a whole through the heat conduction glue, and the thickness of each base film is 120-250 micrometers; the thickness of the weather-resistant film is 45-72 mu m; the thickness of the adhesive layer is 5-10 μm.

Preferably, the isosceles triangle of the cross-section of the body portion of the prism structure has a base length of 20 to 30 μm, an apex angle of 45 to 135 degrees, and a height of 25 to 50 μm.

Preferably, the thickness of the substrate layer is 120-250 μm, the thickness of the in-line coating layer is 0.1-0.3 μm, and the thickness of the barrier layer is 200nm.

Preferably, the height of the fin is 15 to 50 μm, and the thickness is 2 to 10 μm.

Preferably, the thickness of the transmission film is 40 to 60 μm.

The solar cell backboard can not only collect light, but also enlarge the reflection area by arranging the substrate layer with the reflection prism structure of the physical structure. The metal reflecting layer on the back of the reflecting prism structure not only has a reflecting effect, but also increases the heat dissipation area and the heat conduction efficiency. In addition, the base film has excellent barrier properties by providing a barrier layer.

Drawings

The drawings are only for purposes of illustrating and explaining the present application and are not to be construed as limiting the scope of the present application.

Fig. 1 shows a schematic cross-sectional view of a solar cell backsheet according to an embodiment of the present application.

Figure 2 shows a schematic cross-sectional view of a base film that can be used in a solar cell backsheet of the present application, according to one embodiment of the present application.

Fig. 3 shows a schematic cross-sectional view of a base film that can be used in a solar cell backsheet of the present application, according to another embodiment of the present application.

Fig. 4 shows an exploded perspective schematic view of a base film that can be used in the solar cell backsheet of the present application, according to yet another embodiment of the present application.

Fig. 5 is a partially enlarged schematic view of a base film that may be used in the solar cell back sheet of the present application according to still another embodiment of the present application.

Detailed Description

In order to more clearly understand the technical features, objects, and effects of the present application, embodiments of the present application will now be described with reference to the accompanying drawings. Wherein like parts are given like reference numerals.

As shown in fig. 1, the present application proposes a solar cell back sheet, which includes a base film 100 adjacent to a back surface of a solar cell (not shown in the figure) and a weather-resistant film 200 located outside the base film 100, wherein the weather-resistant film 200 and the base film 100 are integrally bonded by an adhesive layer 300. In a specific embodiment, the total thickness of the backing plate is about 170-332 μm; the thickness of the base film 100 is about 120 to 250 μm; the weatherable film 200 has a thickness of about 45-72 μm; the adhesive layer 300 has a thickness of about 5 to 10 μm.

The adhesive layer 300 may be a conventional EVA adhesive, or an ultraviolet light curing adhesive. The weather-resistant film 200 may be preferably prepared using a PVDF film, and for example, a commercially available PVDF film having a thickness of 20 to 30 μm may be used, or a PVDF film may be formed by adding an ultraviolet absorber, an abrasion-resistant filler, and the like to PVDF raw material particles in an amount of 90% by mass or more, melt-co-extruding the PVDF raw material particles, and then biaxially stretching the PVDF raw material particles.

The weather-resistant film on the outer side of the solar cell backboard can provide good environmental erosion resistance, and the base film on the inner side has good insulating property and mechanical property. In the back sheet of the prior art cited in the background art, the base film only serves as a simple support, the reflection and heat transfer of the transmitted light rays need to be realized by other coatings, the process is complex, the coating structure is unstable, and the back sheet is easy to age and delaminate under the condition of long-term heating.

In one embodiment of the present application, the base film 100 may be made of a PET film, which may be a single-layer or multi-layer structure that is biaxially stretched. The PET film can provide excellent insulation, water resistance, mechanical properties and dimensional stability. However, for solar cells, especially for CI (G) S flexible solar cells, which are mainstream products, the requirements for the back sheet are high due to the process characteristics of the solar cells requiring stronger barrier property to protect the internal circuits, and the barrier property is usually required to be 10 ^-3 g/m ² Day level. The general idea behind enhancing the barrier properties is to increase the thickness of the material, which results in increased material costs, while increasing the unit weight and decreasing the flexibility of the material, too thick a material also results in slippage leakage when the edges of the sheet are bent.

In view of this, in one embodiment of the base film 100 shown in fig. 2, the base film 100 includes a substrate layer 101, an in-line coating layer 102 is formed on both surfaces of the substrate layer 101, and a barrier layer 103 is formed on the outside of the in-line coating layer 102 by sputtering. The substrate layer 101 has a thickness of about 120 to 250 μm, and may be formed of, for example, 188 μm biaxially oriented PET film having a single layer structure, or may be formed by laminating a plurality of films (as will be described in further detail below). The barrier layer 23 is preferably made of silicon dioxide; the thickness was 200nm.

The barrier property of the substrate layer 101 can be improved by the barrier layer 103, the thickness of the substrate layer 101 does not need to be increased, and the adaptability of the flexible solar cell is improved. In order to improve the surface smoothness and the adhesion of the barrier layer 103, it is preferable to perform an in-line coating process on both surfaces of the base layer 101 before the formation of the barrier layer 103 by sputtering, and to form an in-line coating layer 102 having a thickness of preferably 0.1 to 0.3 μm on each of both sides.

The online coating can be directly through online coating machine with the coating of chemical article on the substrate layer in the production process of substrate layer 101, and online coating can be directly formed in the later stage of the production process of substrate layer, need not launch the operation again with the coiled material, and the coating forms evenly, fast, efficient, and is with low costs.

In one embodiment, the primer solution forming the in-line coating layer 102 can be applied to the thick sheet before or during the stretching of the polyester film forming the substrate layer 101, and then the primer solution applied to the surface of the thick sheet is cured at a high temperature during the stretching process to form the in-line coating layer 102 as the thick sheet is stretched to a film with a desired thickness.

In one embodiment, the in-line coating layer 102 is formed by uniformly mixing acrylic resin, silica nanoparticles having a particle size of 5-10nm, 1,4-dioxane, polyethylene oxide, and ethylene-vinyl acetate copolymer into a primer solution, and then curing by in-line coating.

Specifically, the mass ratios of the components of the online coating layer 102 are, respectively, acrylic resin: silica nanoparticles: 1,4-dioxane: polyethylene oxide: the ethylene-vinyl acetate copolymer is 100: (10-15): (20 to 30): (10-15): (5-10). Wherein the ethylene-vinyl acetate copolymer can be ethylene-vinyl acetate copolymer which is sold by Mitsui corporation of Japan and has the trade name of Evaflex 550, and the mass percentage of the contained vinyl acetate polymer is 14 percent.

According to the weight parts of the raw materials in the following table, on-line coating layers are respectively prepared on the two side surfaces of a 188-micron biaxially oriented PET film, and then a layer of barrier layer made of silicon dioxide is respectively sputtered on the outer sides of the on-line coating layers.

	Example 1	Example 2	Example 3	Example 4	Example 5
						Acrylic resin	100	100	100	100	100
Silica nanoparticles	10	11.5	12.5	13.5	15
						1,4-dioxane	20	22	25	28	30
Polyethylene oxide	10	12	13	14	15
						Ethylene-vinyl acetate copolymer	5	6	7.5	8	10
On-line coating layer thickness (nm)	100	150	200	250	300
						Thickness of barrier layer (nm)	200	200	200	200	200

As a comparison, barrier layers of 200nm thick silica were formed by sputtering directly on both side surfaces of a 188 μm biaxially oriented PET film as comparative examples. The 180 degree peel force (N/25 mm) of the barrier layers of examples 1-5 was measured to be 34.5%, 36.2%, 35.1%, 34.8%, and 36.1% higher than the comparative examples, respectively.

Further, as shown in fig. 3, the present application proposes another embodiment of a base film that can be used in the solar cell backsheet of the present application, and similar to the embodiment shown in fig. 2, the base film 100 of the present embodiment also includes a substrate layer 101, an in-line coating layer 102 is respectively disposed on both sides of the substrate layer 101, and a barrier layer 103 is formed on the outside of the in-line coating layer 102 by sputtering. Unlike the embodiment shown in fig. 2, the substrate layer 101 of the present embodiment is formed by laminating a plurality of films, and the on-line coating layer 102 and the barrier layer 103 may have the same structure and composition as those of the previous embodiment. Only the substrate layer 101 of the multilayer composite structure of the present embodiment will be described in detail below.

As shown in fig. 3-5, the substrate layer 101 of the present embodiment includes a transmission film 1 facing one side of the solar cell and a heat conduction film 2 away from one side of the solar cell, wherein the transmission film 1 is formed with a plurality of prism structures 3 arranged in parallel at equal intervals, the prism structures 3 are composed of a body portion 31 with an isosceles triangle cross section and fins 32 extending upward from the top of the body portion 31 (see fig. 3 in particular), a metal reflection layer 4 is formed on the outer side of the prism structures 3 by vacuum sputtering, a concave cavity between the heat conduction film 2 and the metal reflection layer 4 is filled with a heat conduction glue 5, and the heat conduction film 2 and the metal reflection layer 4 are connected into a whole through the heat conduction glue 5. In fig. 3, the thickness of the fin 32 is exaggerated for clarity, and the actual thickness is small, substantially concentrated at the apex of the body portion 31, and does not substantially destroy the triangular cross-sectional shape of the body portion 31.

The substrate layer 101 of the application adopts a multilayer composite structure, a reflection prism structure of a physical structure is arranged between the diaphragms (the transmission film 1 and the heat conduction film 2) of the two-layer overall structure, light rays at different angles can be converged to be reflected, the reflection surface deflected by the angle can not only converge the light rays, but also enlarge the reflection area. The metal reflecting layer on the back of the reflecting prism structure not only has a reflecting function, but also has a heat conduction function, and the reflecting surface is bent along with the reflecting surface, so that the reflectivity is increased, and the heat dissipation area is also increased. In addition, in order to further enlarge the heat dissipation area, the top of the body part of the prism structure is extended with the fins, and the metal reflection layer is formed on the surfaces of the fins, so that the fins attached with the metal reflection layer become heat dissipation fins, and the heat dissipation area and the heat conduction efficiency are further enlarged.

The transmission film 1 can be made of PET with light transmittance of more than 85%, the heat conduction film 2 can be made of PET added with heat conduction filler, and the PET film with a double-layer structure can provide excellent insulation, water resistance, mechanical property and dimensional stability. The transmission film 1 and the heat conduction film 2 integrally package the middle prism structure, the metal reflection layer 4 sputtered on the back of the prism structure isolates the heat dissipation structure on the outer side, the bent metal reflection layer 4 prolongs the isolation channel, and the water resistance and the air tightness are enhanced.

In a particular embodiment, the prismatic structure 3 is made of uv curable acrylic. The metallic reflective layer 4 may be formed by sputtering metallic silver having excellent reflection effect and heat conduction effect. The heat conductive adhesive 5 may be made of an ultraviolet-curable acrylic resin to which a heat conductive filler is added, or, in order to avoid poor ultraviolet curing effect due to influence of the heat conductive filler on light transmittance, the heat conductive adhesive 5 is preferably made of a thermosetting resin to which a heat conductive filler is added.

The solar panel is usually fixed and non-adjustable after installation, so that the efficiency is greatly influenced by the irradiation direction of sunlight, generally speaking, the efficiency of direct sunlight is the largest, but the time is short, and the irradiation direction is inclined for a large period of time. The prism structure is arranged and formed in the substrate layer 101, light rays enter the prism structure and then are reflected by the metal reflecting layer on the outer side on the inclined triangular edge, the reflected light rays are gradually collected to the bottom of the triangle and finally are reflected back to the direction perpendicular to the solar cell piece as far as possible, and therefore even if the inclined light rays can be collected and reflected for use, and therefore the utilization rate of sunlight is improved. In addition, for the flexible solar cell laid on the roof, the efficiency of the stripes of the prism structure pointing to the south and north directions is better, and the utilization rate of light rays in the morning, evening and east-west directions can be improved. For the flexible solar cell laid on the vertical wall, the efficiency of the stripes of the prism structure pointing to the east-west direction is better, and the utilization rate of light rays obliquely irradiating the wall from the top when the sunlight is strongest at noon can be improved.

The method for manufacturing the solar cell back sheet of the present application is described in further detail below with reference to the accompanying drawings. As described above, the solar cell back sheet of the present application includes the base film 100 adjacent to the back surface of the solar cell sheet and the weather-resistant film 200 located outside the base film 100, and the weather-resistant film 200 and the base film 100 are integrally bonded by the adhesive layer 300. The base film 100 comprises a base material layer 101, an online coating layer 102 is respectively arranged on two side surfaces of the base material layer 101, and a barrier layer 103 is formed on the outer side of the online coating layer 102 in a sputtering mode. Substrate layer 101 is including facing transmission film 1 of solar wafer one side and keeping away from heat conduction membrane 2 of solar wafer one side, be formed with a plurality of equidistant parallel arrangement's prism structure 3 on the transmission film 1, prism structure 3 comprises body part 31 that the cross-section is isosceles triangle and the fin 32 that upwards extends from body part 31's top, prism structure 3 outside is formed with one deck metal reflection stratum 4 through vacuum sputtering, it has heat-conducting glue 5 to fill in the sunken cavity between heat conduction membrane 2 and the metal reflection stratum 4, heat conduction membrane 2 is connected as an organic wholely through heat-conducting glue 5 with metal reflection stratum 4.

Further, the manufacturing method of the present application includes a manufacturing step of the base film 100, and an adhering step of the base film 100 and the weather-resistant film 200. Wherein the preparation of the base film 100 comprises:

first, a transmission film 1 is provided on a side facing the solar cell sheet, and an in-line coating layer 102 and a barrier layer 103 are formed on one side surface thereof. In one embodiment, a PET chip is used as a raw material for preparing a PET film, a single-layer thick sheet is obtained by melt extrusion, the sheet is longitudinally stretched into a film after preheating, a mixture of components constituting the on-line coating layer of the present application is coated on one side of the film on line by a coater after longitudinally stretching, and then the film is transversely stretched, shaped, cooled and wound, so that the on-line coating layer 102 is formed on the surface of the film, and then a barrier layer 103 made of silica is formed on the outer side of the on-line coating layer 102 by sputtering, so that a transmission film 1 with the on-line coating layer 102 and the barrier layer 103 is obtained for standby. The thickness of the transmission film 1 is preferably 40-60 μm, and the visible light transmittance is 85% -95%.

Meanwhile, a heat conducting film 2 is provided on the side far away from the solar cell sheet, and an in-line coating layer 102 and a barrier layer 103 are formed on one side surface of the heat conducting film. In one embodiment, a PET chip and 5 to 10wt% of heat conductive filler particles are used as raw materials for preparing a PET film, a single-layer thick sheet is obtained through melt extrusion, the raw material is longitudinally stretched into a film after preheating, the mixture of the components constituting the on-line coating layer of the present application is coated on one side of the film in an on-line manner through a coating machine after longitudinally stretching, then the on-line coating layer 102 is transversely stretched, shaped, cooled and rolled, and then the on-line coating layer 102 is formed on the surface of the film, and a barrier layer 103 made of silica is formed on the outer side of the on-line coating layer 102 in a sputtering manner, so that the heat conductive film 2 with the on-line coating layer 102 and the barrier layer 103 is obtained for standby. In a specific embodiment, the thermally conductive filler may be one or a mixture of boron nitride, graphite, and graphene, preferably boron nitride.

Then, on the side of the transmission film 1 where the in-line coating layer 102 and the barrier layer 103 are not formed, a plurality of equally spaced prism structures 3 arranged in parallel are cured, the prism structures 3 being composed of a body portion 31 having an isosceles triangle-shaped cross section and fins 32 extending upward from the top of the body portion 31. For example, a roller having a pattern matching the shape of the prism structure may be used, the uv-curable acrylic resin may be applied to the roller, the transmission film 1 may be pressed and rolled along the surface of the roller while the uv-curable acrylic resin is pressed onto the transmission film 1 in accordance with the shape of the prism structure, and then the uv-curable acrylic resin may be cured by irradiating uv light to form the prism structure 3 of a desired shape on the transmission film 1. The base of the isosceles triangle forming the cross section of the body portion 31 of the prism structure 3 has a length of 20 to 30 μm, a vertex angle of 60 to 120 degrees and a height of 25 to 50 μm, and the minimum gap between adjacent prism structures 3 is 0 to 50 μm. The height of the fin 32 is 15 to 50 μm, and the thickness is 2 to 10 μm.

Thereafter, a metal reflective layer 4 is formed on the prism structure 3 by vacuum sputtering. For example, a layer of metallic silver having a thickness of 2-10 μm may be formed on the prism structure 3 by vacuum sputtering, and since the thickness of the metallic reflective layer 4 is formed to be relatively very thin, the metallic reflective layer 4 is not shown in fig. 2 and 3.

Then, filling heat-conducting glue 5 in the concave cavity at the outer side of the metal reflecting layer 4, and attaching the heat-conducting film 2 to the outer sides of the metal reflecting layer 4 and the filled heat-conducting glue 5; the side of the heat conductive film 2 where the line coating layer 102 and the barrier layer 103 are not formed is bonded to the metal reflective layer 4. Preferably, the heat conducting glue 5 is filled in the concave cavity at the outer side of the metal reflecting layer 4, and simultaneously the heat conducting glue outside the top of the metal reflecting layer 4 is scraped by a scraper, so that the filled heat conducting glue 5 is flush with the top of the metal reflecting layer 4, and gaps are eliminated, and the bonding between the attached layers is ensured to be firmer, as shown in fig. 3.

And finally, curing the heat-conducting glue 5, and connecting the heat-conducting film 2 and the metal reflecting layer 4 into a whole through the heat-conducting glue 5 while curing the heat-conducting glue 5, thereby preparing the base film 100. In one embodiment, as described above, the heat conductive adhesive 5 may be made of an ultraviolet-curable acrylic resin to which a heat conductive filler is added, and thus the heat conductive adhesive 5 may be cured by irradiating ultraviolet light through the heat conductive film 2. Alternatively, since the heat conductive filler is added to both the heat conductive film 2 and the heat conductive paste 5, in consideration of the problem of light transmittance, it is preferable that the heat conductive paste 5 is made of a thermosetting resin to which the heat conductive filler is added, and the heat conductive paste 5 is cured by heating. The heat-conducting glue 5 can be any commercially available bonding resin with a heat-conducting function, or can be prepared by purchasing a heat-conducting filler and adding the heat-conducting filler into the existing bonding resin. In a specific embodiment, the thermally conductive filler may be one or a mixture of boron nitride, graphite, and graphene, preferably boron nitride. The heat-conducting adhesive 5 is preferably a thermosetting resin having a thermal conductivity of 20-25W/(m.K).

The bonding step of the base film 100 and the weather-resistant film 200 includes: one side of the heat conductive film 2 of the base film 100 is integrally bonded to the weather-resistant film 200 through the adhesive layer 300, wherein the weather-resistant film 200 may be formed of PVDF-based PVDF film. The PVDF film can be a commercially available PVDF film with the thickness of 20-30 mu m, or PVDF raw material particles with the mass content of more than or equal to 90 percent are added with an ultraviolet absorber, a wear-resistant filler and the like, and the PVDF film is formed by melt co-extrusion and then bidirectional stretching.

Examples 6 to 8

A substrate layer of the base film, which was used for the solar cell back sheet of the present application, was prepared according to the parameters shown in the following table.

Comparative examples 6 to 8

Comparative examples 6-8 use a single layer PET film as the base film and the white coating of the second mesh layer referenced CN 114156357A as the reflective coating, with relevant reflection parameters as follows.

	Comparative example 6	Comparative example 7	Comparative example 8
				Thickness of PET film layer	250	250	250
Thickness of the reflection coating	15	10	1

The parametric properties of the examples were measured and compared as follows.

The test is carried out by referring to GJB 5023.1A-2012 material and a coating reflectivity and emissivity test method.

As can be seen from the comparison of the performance parameters of the embodiment, the mechanical performance, the reflectivity, the stripping performance, the heat conductivity and the like of the base material layer for the solar cell backboard are greatly improved.

It should be appreciated by those skilled in the art that while the present application is described in terms of several embodiments, not every embodiment includes only a single embodiment. Such descriptions are merely for clarity reasons and should be understood by those skilled in the art as a whole and the technical solutions involved in the embodiments should be considered as being combinable with each other into different embodiments to understand the scope of the present application.

The above description is only illustrative of the present invention and is not intended to limit the scope of the present invention. Any equivalent alterations, modifications and combinations that may be made by those skilled in the art without departing from the spirit and principles of this application shall fall within the scope of this application.

Claims

1. A solar cell backboard comprises a base film close to the back of a solar cell and a weather-resistant film positioned on the outer side of the base film, wherein the weather-resistant film and the base film are bonded into a whole through a bonding layer; the film is characterized in that the base film comprises a base material layer, two side surfaces of the base material layer are respectively provided with an online coating layer, and the outer side of the online coating layer is sputtered to form a barrier layer; the solar cell comprises a substrate layer and a plurality of solar cell sheets, wherein the substrate layer comprises a transmission film facing one side of each solar cell sheet and a heat conduction film far away from one side of each solar cell sheet, a plurality of prism structures which are arranged in parallel at equal intervals are formed on the transmission film, each prism structure consists of a body part with an isosceles triangle section and a fin extending upwards from the top of the body part, a metal reflection layer is formed on the outer side of each prism structure through vacuum sputtering, heat conduction glue is filled in a concave cavity between each heat conduction film and the corresponding metal reflection layer, the heat conduction films and the corresponding metal reflection layers are connected into a whole through the heat conduction glue, and the thickness of each base film is 120-250 micrometers; the thickness of the weather-resistant film is 45-72 mu m; the thickness of the adhesive layer is 5-10 μm.

2. The backsheet according to claim 1, wherein the isosceles triangle of the cross-section of the body portion of the prism structure has a length of a base of 20 to 30 μm, an apex angle of 45 to 135 degrees, and a height of 25 to 50 μm.

3. The backsheet according to claim 2, wherein the thickness of the substrate layer is 120 to 250 μm, the thickness of the in-line coating layer is 0.1 to 0.3 μm, and the thickness of the barrier layer is 200nm.

4. The backing sheet of claim 3 wherein the fins have a height of 15 to 50 μm and a thickness of 2 to 10 μm.

5. The backsheet according to claim 4, wherein the transmission film has a thickness of 40 to 60 μm.