Photovoltaic backboard film and preparation method thereof

Abstract

The invention discloses a photovoltaic backboard film and a preparation method thereof, the photovoltaic backboard film comprises a surface layer, a support layer and a bottom layer, the preparation raw material of the surface layer comprises a first reflective filler, the preparation raw material of the support layer comprises PET and PTFE, and the first reflective filler is a high-temperature calcined ZIF-8 confinement metal particle material. The photovoltaic backboard film provided by the invention has a relatively good infrared light reflection effect, a relatively good anti-yellowing effect and a relatively good water vapor penetration resistance effect, can be relatively well adapted to an outdoor severe environment, and effectively prolongs the service life of a photovoltaic module.

Description

Technical Field

[0001] The present application relates to the field of photovoltaic cells, and in particular to a photovoltaic backplane film and a preparation method thereof. Background Art

[0002] Photovoltaic cells, as a key technology for directly converting solar energy into electricity, are playing an increasingly important role in the global energy mix. With the growing global demand for renewable energy, photovoltaic cells are gaining attention for their clean, renewable nature. They not only help reduce dependence on fossil fuels and lower greenhouse gas emissions, but also provide power solutions in remote areas and those without grid coverage. Photovoltaic cells have a wide range of applications, from large-scale ground-mounted photovoltaic power plants to residential rooftops to portable electronic devices, and their environmental and economic benefits are becoming increasingly significant. Furthermore, with technological advances, the efficiency and cost-effectiveness of photovoltaic cells are constantly improving, making them a key driver of the global energy transition.

[0003] Photovoltaic cells primarily absorb visible light and some ultraviolet light from sunlight, converting this light energy into electrical energy. However, sunlight also contains infrared light, which has lower energy and longer wavelengths, making a limited contribution to the photovoltaic cell's energy conversion efficiency. Due to the band gap limitations of photovoltaic cell materials, infrared light with wavelengths exceeding 1100 nm cannot effectively excite electrons and therefore cannot be directly converted into electrical energy. Furthermore, infrared light causes the cell panel to heat up, affecting its performance and lifespan. Therefore, photovoltaic cells need to reflect infrared light to reduce heat loss, keep the cell panel cool, and thus improve overall photoelectric conversion efficiency and stability.

[0004] The technical challenges of using infrared reflection in photovoltaic cells primarily lie in how to effectively manage and utilize infrared energy. On one hand, it is necessary to develop highly reflective materials or coatings to reduce the thermal impact of infrared radiation on the panels while not significantly reducing the absorption of visible and ultraviolet light. On the other hand, precise control of panel temperature is necessary to maintain optimal operating conditions. Furthermore, cost-effectiveness and manufacturing complexity are also important considerations for infrared reflection technology. Summary of the Invention

[0005] The purpose of this application is to provide a product having infrared light reflection performance, anti-yellowing performance and good water vapor transmission barrier properties.

[0006] To achieve the above objectives, the technical solution adopted in this application is: to provide a photovoltaic backplane film, including a surface layer, a support layer and a bottom layer, the raw materials for preparing the surface layer include a first reflective filler, the raw materials for preparing the support layer include PET and PTFE, and the first reflective filler is a high-temperature calcined ZIF-8 confined metal particle material.

[0007] As a preference, the mass proportion of the first reflective filler in the surface layer is 2% to 5%.

[0008] As another preference, the metal particles in the high-temperature calcined ZIF-8 confined metal particle material are any one or a combination of multiple of silver, gold, copper, nickel, palladium, and platinum.

[0009] As another preference, the metal particles are any one of silver and nickel, copper and nickel, silver and platinum, and platinum and nickel.

[0010] As another preferred embodiment, the preparation method of the first reflective filler is: preparing ZIF-8 powder by a hydration method, immersing the ZIF-8 powder in a metal salt solution, adding a reducing agent to reduce the metal ions, and obtaining a ZIF-8 confined metal particle material after drying, calcining the ZIF-8 confined metal particle material at a high temperature under an inert gas atmosphere, cooling the product and grinding it to obtain the first reflective filler.

[0011] As another preferred embodiment, the supporting layer is prepared from raw materials of PET and PTFE, and the mass ratio of the PET to the PTFE is (1:1) to (2:1).

[0012] As another preference, the raw materials for preparing the bottom layer include nano-silicon dioxide and anti-ultraviolet fillers.

[0013] The present application also provides a method for preparing a photovoltaic backplane film, comprising the following preparation steps: S1: preparing ZIF-8 powder by a hydration method, immersing the ZIF-8 powder in a metal salt solution, adding a reducing agent to reduce the metal ions, and obtaining a ZIF-8 confined metal particle material after drying; calcining the ZIF-8 confined metal particle material at a high temperature under an inert gas atmosphere, cooling the product and grinding it to obtain a first reflective filler; S2: mixing the first reflective filler, an antioxidant, an anti-hydrolysis agent and a PET masterbatch, and extruding the mixture in a screw rod to obtain a surface layer; S3: mixing the PET masterbatch and the PTFE masterbatch, and extruding the mixture in a screw rod to obtain a support layer; mixing the oxide, the antioxidant, the anti-hydrolysis agent, the anti-ultraviolet filler and the PET masterbatch, and extruding the mixture in a screw rod to obtain a bottom layer; melting, shaping and cooling the surface layer, the support layer and the bottom layer on a co-extrusion production line to obtain the photovoltaic backplane film.

[0014] More preferably, the high-temperature calcination temperature in step S1 is 900-1300°C.

[0015] Further preferably, the raw materials for preparing the surface layer include, by mass fraction: 2% to 5% of the first reflective filler, 1% to 3% of the antioxidant, 1% to 5% of the anti-hydrolysis agent, and the balance of the PET masterbatch.

[0016] Compared with the prior art, the present invention has the following advantages: (1) The photovoltaic backsheet film of the present application has a first reflective filler added to the surface material, which can obtain a good infrared light reflectivity; (2) The supporting layer of the photovoltaic backsheet film of the present application is a composite of PET and PFTE materials, which can achieve good anti-yellowing performance and excellent water vapor permeability resistance; (3) The photovoltaic backsheet film of the present application adds nano-silicon dioxide oxide and anti-ultraviolet filler to the raw materials for preparing the bottom layer, which gives the photovoltaic backsheet excellent anti-ultraviolet effect and anti-yellowing performance, thereby extending the service life of the photovoltaic backsheet film. DETAILED DESCRIPTION

[0017] Below, the present application is further described in conjunction with specific implementation methods. It should be noted that, under the premise of no conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0018] The terms "comprises" and "having" and any variations thereof in the specification and claims of this application are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus that includes a series of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, product or apparatus.

[0019] The present application provides a photovoltaic backplane film, including a surface layer, a support layer and a bottom layer, and the upper surface layer and the lower surface layer are both white, so that the photovoltaic backplane film of the present application appears white as a whole, which is convenient for subsequent superposition of any outer layer film to produce a photovoltaic backplane of any color.

[0020] The surface layer of the photovoltaic backsheet film of the present application is prepared from raw materials including a first reflective filler, which is a high-temperature calcined ZIF-8 confined metal particle material, and a support layer is a composite material of PET and PTFE. The bottom layer of the photovoltaic backsheet film of the present application is prepared from raw materials including oxides and UV-resistant fillers.

[0021] ZIF-8 has pores with a diameter of approximately 11.6 Å and interconnected through six-ring windows (3.5 Å) and four-ring windows. Through liquid-phase impregnation combined with in situ reduction, nanometal particles can be evenly dispersed in the ZIF-8 carrier. Moreover, the loading of metal particles does not change the morphology and size of ZIF-8, nor does it change the stability of ZIF-8.

[0022] ZIF-8 confined metal particles effectively address the dispersion issues of metal particles in PET without affecting the metal particles' infrared reflectivity. Uniformly dispersing ZIF-8, containing void-confined metal particles, in PET can eliminate the agglomeration problem of metal particles in PET. Application in photovoltaic backsheet base films can result in highly infrared reflective photovoltaic backsheets, thereby minimizing heat buildup and improving their photoelectric conversion efficiency.

[0023] After high-temperature calcination of the ZIF-8 confined metal particle material, a porous carbon material containing metal particles is obtained, which has a good specific surface area and excellent electrochemical, adsorption and photocatalytic properties.

[0024] The photovoltaic backplane film of the present application has good infrared light reflection effect, and has good anti-yellowing effect and anti-water vapor transmission effect. It can better adapt to the harsh outdoor environment and effectively extend the service life of the photovoltaic module.

[0025] In some embodiments, the first reflective filler is added in an amount of 2% to 5% by mass in the surface layer material.

[0026] In some embodiments, the metal particles confined in the internal pores of ZIF-8 are any one or a combination of silver, gold, copper, nickel, palladium, and platinum.

[0027] In some embodiments, two metal particles are simultaneously confined in the internal pores of ZIF-8, which may be any group selected from the group consisting of silver and nickel, copper and nickel, silver and platinum, and platinum and nickel.

[0028] In some embodiments, the preparation method of the first reflective filler is: preparing the ZIF-8 material by the hydration method, then immersing the ZIF-8 material in a metal salt solution, stirring for a period of time, and reducing the metal particles with a reducing agent to obtain a ZIF-8 confined metal particle material, and calcining the material at a high temperature under an inert atmosphere to obtain a high-temperature calcined ZIF-8 confined metal particle material.

[0029] In some embodiments, the high temperature calcination temperature is 900-1300°C.

[0030] In some embodiments, the raw materials for preparing the surface layer include: a first reflective filler, an antioxidant, an anti-hydrolysis agent, and PET.

[0031] In some embodiments, the supporting layer is prepared from raw materials of PET and PTFE, wherein the mass ratio of PET to PTFE is (1:1) to (2:1).

[0032] In some embodiments, the raw materials for preparing the bottom layer include: nano-silicon dioxide, an antioxidant, an anti-hydrolysis agent, an anti-ultraviolet filler, and PET. In some preferred embodiments, the particle size of the nano-silicon dioxide is 30-60 nm.

[0033] In some embodiments, the anti-hydrolysis agent is any one or more of an oxazoline compound, an epoxy compound, an aromatic carbodiimide, an aliphatic carbodiimide, and a polycarbodiimide.

[0034] In a more preferred embodiment, the anti-hydrolysis agent is an aromatic carbodiimide. Aromatic carbodiimide anti-hydrolysis stabilizers react chemically with the hydrolysis products, carboxylic acid or water, inhibiting catalytic hydrolysis and degradation, thereby extending the service life. Furthermore, aromatic carbodiimides exhibit excellent antioxidant, heat, and flame resistance, significantly improving the weatherability and aging resistance of the backsheet film, thereby ensuring a high reflectivity of the photovoltaic backsheet to sunlight.

[0035] In some embodiments, the antioxidant is an antioxidant selected from the group consisting of amine antioxidants, quinoline derivative antioxidants, hindered phenol antioxidants, phosphite antioxidants, thioester antioxidants, hydroperoxide decomposers, and heavy metal ion passivators.

[0036] In a more preferred embodiment, the antioxidants are hindered phenols and phosphite antioxidants, and the combination of the two produces a synergistic effect to improve the weather resistance and discoloration resistance of the backsheet film.

[0037] In some embodiments, the anti-ultraviolet filler is any one or a combination of titanium dioxide, benzophenone, salicylate, benzotriazole, triazine, benzoic acid, amino acid, benzoimide and nano zinc oxide.

[0038] The present application also provides a method for preparing a photovoltaic backsheet film, comprising the following preparation steps: S1: preparing ZIF-8 powder by hydration, immersing the ZIF-8 powder in a metal salt solution, adding a reducing agent to reduce the metal ions to a metal element, and drying to obtain a ZIF-8 confined metal particle material; calcining the ZIF-8 confined metal particle material at a high temperature under an inert gas atmosphere, cooling the product and grinding it to obtain a first reflective filler; S2: mixing the first reflective filler, antioxidant, anti-hydrolysis agent and PET masterbatch and extruding the mixture in a screw to obtain a surface layer; S3: Mix the PET masterbatch and the PTFE masterbatch and extrude them in a screw rod to obtain a support layer; mix the oxide, antioxidant, anti-hydrolysis agent, anti-UV filler and PET masterbatch and extrude them in a screw rod to obtain a bottom layer; melt, shape and cool the surface layer, support layer and bottom layer on a co-extrusion production line to obtain the photovoltaic backplane film of the present application.

[0039] In some embodiments, the high-temperature calcination temperature in step S1 is 900-1300°C.

[0040] In some embodiments, the surface layer comprises, by weight, 2% to 5% of a first reflective filler, 1% to 3% of an antioxidant, 1% to 5% of an anti-hydrolysis agent, and the balance PET masterbatch. In some embodiments, the support layer comprises PET masterbatch and PTFE masterbatch, with the weight ratio of PET to PTFE masterbatch being (1:1) to (2:1). In some embodiments, the bottom layer comprises, by weight, 1% to 3% of an oxide, 1% to 3% of an antioxidant, 1% to 5% of an anti-hydrolysis agent, 1% to 2% of an anti-UV filler, and the balance PET masterbatch.

[0041] The preparation method of the photovoltaic backplane film of the present application is simple and has a high success rate. The prepared photovoltaic backplane has good performance, a long service life, and certain economic adaptability.

[0042] Example 1 A photovoltaic backsheet film is prepared according to the following steps: S1: Dissolve 4.94 mmol of Zn(NO3)2·6H2O in 100 mL of methanol to obtain solution a. Dissolve 39.62 mmol of 2-methylimidazole in 100 mL of methanol to obtain solution b. Quickly pour solution a into solution b and stir at room temperature for 1 h. Centrifuge the resulting precipitate and wash it three times with methanol. Dry the washed precipitate at 60°C for 12 h to obtain a white powder, which is ZIF-8. 49.52 mg of AgNO3 was dissolved in 20 mL of deionized water, and then 22.58 mg of polyvinyl alcohol (PVA) was added. After stirring at room temperature for 1 h, 200 mg of activated ZIF-8 was added to the solution and stirred for 2 h. 4.8 mL of NaBH4 was added dropwise to the solution in an ice-water bath. After the addition was complete, the solution was stirred for 5 h. The resulting precipitate was centrifuged and washed three times with deionized water, and dried at 60 °C for 12 h to obtain Ag@ZIF-8 material. The Ag@ZIF-8 material was ground and calcined at a high temperature of 900-1300°C under inert gas protection. After cooling to room temperature, the product was taken out, washed, dried, and ground to obtain the Ag / Zn@C material, i.e., the first reflective filler. S2: 5% of a first reflective filler, 0.5% of an antioxidant, 1% of an anti-hydrolysis agent, and the remainder of PET masterbatch were mixed in a high-speed mixer, and extruded through a screw extruder at a temperature of 220°C and a speed of 15 r / min to melt-extrude and plasticize the raw materials to obtain a surface layer; S3: PET masterbatch and PTFE masterbatch were melt-blended in a mass ratio of 2:1, and the mixture was fed into an injection molding machine and injection-molded into a sheet specimen at a pressure of 50 MPa and a temperature of 200°C to obtain a support layer; 3% nano-silica, 0.5% antioxidant, 1% anti-hydrolysis agent, 1% anti-ultraviolet filler and the balance PET masterbatch were mixed in a high-speed mixer, and extruded through a screw extruder at a temperature of 220° C. and a speed of 15 r / min. The raw materials were melt-extruded and plasticized to obtain a bottom layer. The surface layer, support layer and bottom layer are transported to the backboard co-extrusion production line and extruded through a mold to obtain a sheet melt. The sheet melt is cooled and shaped by a cooling roller, and then rolled or cut to obtain the photovoltaic backboard film of the present application.

[0043] Example 2 In step S1, the silver salt is replaced with a copper salt of corresponding mass, and the Cu@ZIF-8 material is synthesized and then calcined to obtain a Cu / Zn@C material as the first reflective material. The other preparation methods are consistent with the preparation steps in Example 1.

[0044] Example 3 In step S1, the silver salt is replaced with a nickel salt of corresponding mass, and the Ni@ZIF-8 material is synthesized and then calcined to obtain a Ni / Zn@C material as the first reflective material. The other preparation methods are consistent with the preparation steps in Example 1.

[0045] Example 4 In step S1, the silver salt is replaced with nickel salt and silver salt of corresponding mass, and the Ag / Ni@ZIF-8 material is synthesized and then calcined to obtain the Ag / Ni / Zn@C material as the first reflective material. The other preparation methods are consistent with the preparation steps in Example 1.

[0046] Example 5 In step S1, the silver salt is replaced with nickel salt and copper salt of corresponding mass, and the Ni / Cu@ZIF-8 material is synthesized and then calcined to obtain Ni / Cu / Zn@C material as the first reflective material. The other preparation methods are consistent with the preparation steps in Example 1.

[0047] Comparative Example 1 In step S1, ZIF-8 material is prepared, and ZIF-8 is calcined and then mixed with silver powder to obtain Zn@C+Ag as a reflective filler. The reflective filler is added to the surface material instead of the first reflective material of the present application. The other preparation steps are consistent with the steps in Example 1 to obtain the photovoltaic backplane film of Comparative Example 1.

[0048] Comparative Example 2 In step S1, ZIF-8 material is prepared, and ZIF-8 is calcined and then mixed with copper powder to obtain Zn@C+Cu as a reflective filler. The reflective filler is added to the surface material instead of the first reflective material of the present application. The other preparation steps are consistent with the steps in Example 1 to obtain the photovoltaic backplane film of Comparative Example 2.

[0049] Comparative Example 3 In step S3, PET masterbatch and PTFE masterbatch are no longer mixed. Instead, all PET masterbatch is melted to prepare the support layer. The other preparation steps are consistent with the preparation steps in Example 1 to obtain the photovoltaic backplane film of Comparative Example 3.

[0050] Comparative Example 4 In step S1, ZIF-8 material is prepared, and ZIF-8 is calcined and mixed with nickel powder and copper powder to obtain Zn@C+Ni+Cu as a reflective filler. The reflective filler is added to the surface material instead of the first reflective material of the present application. The other preparation steps are consistent with the steps in Example 1 to obtain the photovoltaic backplane film of Comparative Example 4.

[0051] Comparative Example 5 In step S1, a ZIF-8 material is prepared, and silver and nickel are confined in the ZIF-8 material to prepare an Ag / Ni@ZIF-8 material. The Ag / Ni@ZIF-8 material is not subjected to high-temperature calcination, and is added to the surface material as a reflective filler instead of the first reflective material of the present application. The other preparation steps are consistent with the steps in Example 4 to prepare the photovoltaic backplane film of Comparative Example 5.

[0052] Performance testing The base films prepared in Examples 1 to 5 and Comparative Examples 1 to 4 were subjected to the following performance tests, and the test results are recorded in Table 1.

[0053] 1. Reflectivity The test method refers to the spectrophotometer method with an integrating sphere in the standard GB / T 29848 "Ethylene-vinyl acetate copolymer (EVA) film for photovoltaic module encapsulation". The test instrument is: UV-visible spectrophotometer, and the test conditions are: 780~1100nm.

[0054] 2. Yellowing index The test method refers to the standard GB / T2409 "Test method for yellowing index of plastics"; sample size: 100x100 mm; test conditions: 25℃, 50%RH.

[0055] 3. Water vapor transmission rate test After hydrolysis treatment at 85% relative humidity, water vapor transmission test was performed according to the test method in BG / T 26253-2010.

[0056] Table 1 Performance test results of various embodiments and comparative examples

[0057] From the analysis of the performance test results in Table 1, it can be seen that the photovoltaic backplane films prepared in each embodiment of the present application have good infrared light reflectivity, low yellowing index, and poor water vapor permeability, which can better protect photovoltaic modules outdoors and extend the service life of photovoltaic modules.

[0058] Analysis of the performance test results of Examples 1 to 5 shows that the reflectivity of two metal particles simultaneously confined in the ZIF-8 pores after high-temperature calcination is better than that of only one metal particle. Among them, the material obtained by confining silver and nickel in ZIF-8 and calcining at high temperature has the best infrared light reflectivity and better anti-yellowing performance and water vapor transmission rate.

[0059] Analysis of the performance test results of Example 1 and Comparative Examples 1, 2, and 4 shows that the metal particles are confined within the pore structure of ZIF-8 to obtain a loaded material, which is then calcined. The infrared reflectivity of the photovoltaic backplane film prepared by calcining the material is better than that of a mixture of calcined ZIF-8 material and metal powder.

[0060] Similarly, Comparative Example 5 uses ZIF-8 to simultaneously confine two metal particles, silver and nickel, but does not perform calcination. Instead, the particles are directly added to the preparation of photovoltaic backplane film materials. The infrared reflectivity obtained is not as good as that of Example 4, which is calcined after loading.

[0061] Therefore, loading metal particles in the ZIF-8 pores and then calcining them at high temperature is an important step, which has a good promoting effect on the reflectivity of infrared light. It is speculated that the reason may be that loading metal particles in the internal pores of ZIF-8 can better improve the dispersion of metal particles. After high-temperature calcination, ZIF-8 decomposes and carbonizes. ZIF-8 may be carbonized into porous carbon with a graphite phase structure, and metal particles are dispersed in the structure. Therefore, it can better improve the infrared light reflectivity, anti-yellowing performance and anti-water vapor transmission rate of the photovoltaic backplane film.

[0062] The performance test results of Example 1 and Comparative Example 3 were analyzed, in which the preparation raw materials of the support layer were changed, thereby significantly reducing the anti-yellowing performance and water vapor permeability of the photovoltaic backplane film. Therefore, when using the material calcined after ZIF-8 loaded with metal particles as the first reflective filler, PET and PTFE composite materials need to be used in the middle support layer as the middle barrier layer to block water vapor transmission and extend the service life of the photovoltaic module.

[0063] In summary, the photovoltaic backplane film of the present application adds a first reflective filler to the raw materials for preparing the surface layer, uses PET and PTFE composite materials in the support layer, and adds oxides and anti-UV fillers to the raw materials for preparing the bottom layer. The photovoltaic backplane film prepared can obtain good infrared light reflectivity and anti-yellowing and anti-water vapor transmittance properties.

[0064] The above describes the basic principles, main features, and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above-described embodiments. The above-described embodiments and the specification merely illustrate the principles of the present application. Various changes and improvements may be made to the present application without departing from the spirit and scope of the present application. These changes and improvements fall within the scope of the present application for which protection is sought. The scope of protection claimed by the present application is defined by the appended claims and their equivalents.

Claims

1. A photovoltaic backsheet film, characterized in that: It comprises a surface layer, a supporting layer and a bottom layer. The raw material for preparing the surface layer comprises a first reflective filler. The raw material for preparing the supporting layer comprises PET and PTFE. The first reflective filler is a high-temperature calcined ZIF-8 confined metal particle material.

2. The photovoltaic backsheet film according to claim 1, characterized in that: The mass percentage of the first reflective filler in the surface layer is 2% to 5%.

3. The photovoltaic backsheet film according to claim 1, characterized in that: The metal particles in the high-temperature calcined ZIF-8 confined metal particle material are any one or a combination of multiple of silver, gold, copper, nickel, palladium and platinum.

4. The photovoltaic backsheet film according to claim 3, characterized in that: The metal particles are any one of silver and nickel, copper and nickel, silver and platinum, and platinum and nickel.

5. The photovoltaic backsheet film according to claim 3, characterized in that: The preparation method of the first reflective filler is: prepare ZIF-8 powder by hydration method, immerse the ZIF-8 powder in a metal salt solution, add a reducing agent to reduce the metal ions, obtain ZIF-8 confined metal particle material after drying, calcine the ZIF-8 confined metal particle material at high temperature under an inert gas atmosphere, cool the product and grind it to obtain the first reflective filler.

6. The photovoltaic backsheet film according to claim 1, characterized in that: The supporting layer is prepared from PET and PTFE, and the mass ratio of the PET to the PTFE is (1:1) to (2:1).

7. The photovoltaic backsheet film according to claim 1, characterized in that: The raw materials for preparing the bottom layer include nano silicon dioxide and anti-ultraviolet filler.

8. A method for preparing a photovoltaic backplane film, characterized in that: The method comprises the following preparation steps: S1: preparing ZIF-8 powder by hydration method, immersing the ZIF-8 powder in a metal salt solution, adding a reducing agent to reduce metal ions, and obtaining a ZIF-8 confined metal particle material after drying; calcining the ZIF-8 confined metal particle material at high temperature under an inert gas atmosphere, cooling the product and grinding it to obtain a first reflective filler; S2: mixing the first reflective filler, antioxidant, anti-hydrolysis agent and PET masterbatch and extruding the mixture in a screw to obtain a surface layer; S3: The PET masterbatch and the PTFE masterbatch are mixed and extruded in a screw rod to obtain a support layer; the oxide, the antioxidant, the anti-hydrolysis agent, the anti-ultraviolet filler and the PET masterbatch are mixed and extruded in a screw rod to obtain a bottom layer; the surface layer, the support layer and the bottom layer are melted, shaped and cooled on a co-extrusion production line to obtain the photovoltaic backplane film.

9. The preparation method according to claim 8, characterized in that: The temperature of high temperature calcination in step S1 is 900-1300°C.

10. The preparation method according to claim 8, characterized in that: Calculated by mass fraction, the raw materials for preparing the surface layer include: 2% to 5% of the first reflective filler, 1% to 3% of the antioxidant, 1% to 5% of the anti-hydrolysis agent and the balance of the PET masterbatch.

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