Photovoltaic cell gap reflective film and preparation method and application thereof

Abstract

The invention relates to the field of photovoltaic technology, and discloses a photovoltaic cell gap reflective film and a preparation method and application thereof. The preparation method comprises the following steps: mixing a metal complexing agent and a PET material according to a mass ratio of (1-5): 100, and carrying out melt extrusion granulation to obtain PET master batches; the preparation method comprises the following steps: carrying out three-layer melt co-extrusion, two-way stretching and sizing on PET master batches, bonding resin and ionic polymer particles in specific parts by weight to obtain a base film; immersing the surface of the PET layer of the base film into a barium salt solution, adjusting the pH value of the solution system to 7-11, and stirring to enable barium ions to be fully complexed with the metal complexing agent on the surface of the PET layer; and dropwise adding a sulfate solution into the solution system, and maintaining stirring, so that the white BaSO4 layer is uniformly precipitated on the surface of the PET layer, and the gap reflective film is prepared. According to the method, the working procedures of coating, EVA film spraying, aluminum sputtering and the like are omitted, the efficiency is higher, the cost is lower, the reflectivity of the gap reflective film is high, the interlayer cohesiveness is higher, the service life of the gap reflective film is prolonged, and the reflection effect of the gap reflective film is improved.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaic technology, and in particular to a photovoltaic cell gap reflective film and a preparation method and application thereof. Background Art

[0002] The white glazed glass on the back of traditional double-glass photovoltaic modules is produced by applying a glaze coating before tempering. However, double-glass photovoltaic modules with interstitial reflective film can have their back glass tempered directly without the need for glazing, maintaining stress uniformity across the glass. This not only improves the load-bearing capacity of the photovoltaic module's back glass but also reduces the risk of glass breakage (a four-point bending test shows that the strength of the unglazed back glass is significantly higher than that of the glazed back glass).

[0003] Gap reflective film is typically made of PET (polyethylene terephthalate). Its front surface is a reflective layer, while the back surface is an adhesive layer. The adhesive layer securely adheres the gap reflective film to the back glass of the photovoltaic module. This allows the gap reflective film to replace traditional white glaze and be precisely positioned between the cells of a photovoltaic module. Furthermore, the reflective layer faces the front of the photovoltaic module, reflecting light between the cells back into the cells, increasing light absorption and utilization.

[0004] To enhance the reflective effect, the reflective layer of some interstitial reflective films utilizes materials with superior reflective properties. Experimental data shows that these materials can increase light reflectivity by approximately 10% compared to white glaze. This means that more sunlight is effectively directed into the cells, thereby increasing the power output of the entire photovoltaic module. Furthermore, to fully utilize solar resources and improve the power generation efficiency of photovoltaic cells, efforts have been made to develop enhanced reflective films for photovoltaic modules, as shown in publications CN117410365A, CN108598184B, CN109273548A, and CN116751527A. However, these reflective sheeting products can present various problems during production and long-term use. For example, the production process requires steps such as coating, rolling, laminating, and vacuum sputtering, resulting in a complex and tedious production process and expensive production equipment. Furthermore, the production process also generates various types of pollution. Furthermore, during outdoor use, the reflective aluminum layer is extremely susceptible to acid corrosion, causing a sharp drop in reflectivity. Furthermore, the encapsulating adhesive layer and microstructure layer are often made of organic materials with poor weather resistance, such as EVA (ethylene-vinyl acetate copolymer) and acrylic resin. These materials are prone to delamination, degradation, and yellowing during outdoor use, reducing the service life and reflective effect of the reflective sheeting.

[0005] In addition, existing interstitial reflective films (such as those shown in publication number CN119529695A) are also manufactured using integrated co-extrusion. However, the light management layer of such interstitial reflective films is extruded to control the gaps and form the interstitial reflective structure, making it difficult to control the positioning accuracy during the co-extrusion process. Furthermore, the interstitial reflective structure of the light management layer of such interstitial reflective films is made by mixing raw materials such as barium sulfate, a dispersant, a polar group grafted masterbatch, a UV stabilizer, and a thermal stabilizer. While this structure can avoid the corrosion resistance of the reflective aluminum layer, the light reflection effect of the reflective layer prepared by mixing barium sulfate with other raw materials is not ideal. Summary of the Invention

[0006] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a photovoltaic cell gap reflective film and a preparation method and application thereof.

[0007] Based on this, the present invention discloses a method for preparing a photovoltaic cell gap reflective film, comprising the following preparation steps:

[0008] Step 1: uniformly mixing a metal complexing agent and PET material in a mass ratio of 1-5:100, and then granulating the mixture by melt extrusion to obtain PET masterbatch;

[0009] Step 2: Place 50-100 parts by weight of PET masterbatch, 5-20 parts of adhesive resin, and 40-80 parts of ionomer particles into three hoppers of a co-extrusion device, respectively. The three layers of particles are melt-coextruded, biaxially stretched, and shaped to obtain a base film.

[0010] Step 3: Immerse the surface of the PET layer of the base film in a barium salt solution, adjust the pH value of the solution system to 7-11, and stir to allow the barium ions to fully complex with the metal complexing agent on the surface of the PET layer to form a metal complexing agent-barium ion complex;

[0011] Step 4: add sulfate solution dropwise to the solution system of step 3, maintain stirring, and allow a white BaSO4 layer to evenly precipitate on the surface of the PET layer to obtain the photovoltaic cell gap reflective film.

[0012] The metal complexing agent-barium ion complex formed in step 3 is shown in the following structure (M can be metal barium, and the metal complexing agent can be EDTA, EDTA-2Na, etc.):

[0013]

[0014] The mechanism of the white BaSO4 layer precipitating onto the surface of the PET layer is shown in the following reaction equations (1) and (2):

[0015]

[0016] For example, the structural formula of Y in reaction formulas (1) and (2) is as follows:

[0017]

[0018] Preferably, in step 1, the intrinsic viscosity of the PET material is 0.6-0.8 dL / g, the end carboxyl group range is 20-30 mol / t, and the melting point is in the range of 252-262°C; the PET material is selected from at least one of the brands Lumirror X10, Dupont 7352, FG720, and WK-821; and the PET material is dried at 160-170°C for 4-6 hours before being placed in the coextrusion equipment;

[0019] The metal complexing agent is at least one of DTPA (diethylenetriaminepentaacetic acid), CDTA (trans-1,2-cyclohexanediaminetetraacetic acid), EDTA (ethylenediaminetetraacetic acid), EDTA-2Na (disodium ethylenediaminetetraacetate), EDTA-4Na (tetrasodium ethylenediaminetetraacetate), and salts thereof. EDTA-2Na is more preferred as the metal complexing agent, considering its thermal decomposition properties and complexing properties with barium ions.

[0020] Preferably, in step 2, the adhesive resin is at least one of modified polyethylene, modified polypropylene, modified ethylene vinyl acetate copolymer, and modified ethylene acrylate resin;

[0021] The adhesive resin is selected from the brand ADMER TM AT2717, BYNEL TM 21E533, BYNEL TM 22E757, NUCREL TM 925、Plexar PX3080、 PX2250、ADMER TM NF410E, BYNEL TM 21E787、NUCREL TM At least one of AE; the adhesive resin is dried at 30-70°C for 2-5h before being placed in the co-extrusion equipment;

[0022] Ionic polymers are selected from brands Surlyn 9320, surlyn8920, Himilan TM 1557、AMPLIFY TM IO1100, NUCREL TM 0910, AMPLIFY TM At least one of IO 3801 and Aclyn 295; the ionomer is dried at 60-65° C. for 6-8 hours before being placed in the co-extrusion equipment.

[0023] Preferably, step 2 specifically includes: placing the dried PET masterbatch, adhesive resin, and ion polymer particles into three single-screw extruders of the co-extrusion equipment, respectively, adjusting the melt pump flow ratios of the three single-screw extruders to 12-20:1-4:10-20, respectively, melting the three-layer particles, and then co-extruding them at a die head temperature of 255-285°C, and quenching them with a 3-10°C cooling roller to form an amorphous thick sheet with a thickness of 0.5-1.5 mm; biaxially stretching the thick sheet with a transverse stretching ratio of 2.5-3.5 times and a longitudinal stretching ratio of 2.5-3.5 times, a preheating time of 60-150s, a stretching temperature of 100-120°C, and then shaping at a shaping temperature of 190-240°C and a shaping time of 10-30s, and obtaining the base film after cooling and trimming.

[0024] Preferably, in step 2, the base film comprises a co-extruded PET layer (30-60 μm thick), a transition adhesive layer (5-15 μm thick), and an ionomer adhesive layer (20-60 μm thick), with the transition adhesive layer and the ionomer adhesive layer sequentially laminated on the lower surface of the PET layer. The total thickness of the base film is 80-110 μm, and the thickness of the white BaSO4 layer is 8-12 μm.

[0025] Preferably, step 3 specifically includes: immersing the upper surface of the PET layer of the base film in a barium chloride solution with a concentration of 0.10-0.30 mol / L at room temperature, adjusting the pH value of the solution system to 7-11 with ammonia water, and stirring for 20-50 minutes to allow the barium ions to fully complex with the metal complexing agent on the upper surface of the PET layer; the metal complexing agent is EDTA-2Na.

[0026] Further preferably, in step 3, the pH value of the solution system is adjusted to 9.

[0027] Preferably, step 4 specifically includes: adding a Na2SO4 solution with a concentration of 0.1-0.3 mol / L to the solution system of step 3, and maintaining stirring for 5-10 minutes, so that a white BaSO4 precipitate begins to appear on the upper surface of the PET layer, continuing stirring for at least 1 hour, washing with deionized water and ethanol, and drying at 60-90°C to obtain a PET layer with a white BaSO4 layer on the upper surface as a reflective functional layer.

[0028] The present invention also discloses a photovoltaic cell gap reflective film, which is prepared by the preparation method of the photovoltaic cell gap reflective film described above in the present invention.

[0029] The present invention also discloses an application of a photovoltaic cell gap reflective film, wherein the gap reflective film is applied to the gap portion of the cell sheets in a photovoltaic module.

[0030] Compared with the prior art, the present invention has at least the following beneficial effects:

[0031] The preparation method of the present invention prepares a base film through co-extrusion integral molding, then complexes barium ions with a metal complexing agent on the surface of a PET layer to form a metal complexing agent-barium ion complex, then adds a sulfate solution, and controls the morphology of barium sulfate precipitates precipitated on the surface of the PET layer by adjusting the pH value, etc., to obtain a reflective functional layer in which a white BaSO4 layer is uniformly precipitated on the surface of the PET layer, thereby preparing a photovoltaic cell gap reflective film.

[0032] (1) The preparation method compounds ionic polymer particles (which are co-extruded to form an ionic polymer adhesive layer) with other layers (such as a transition adhesive layer co-extruded by an adhesive resin and a PET layer co-extruded by a PET masterbatch) by co-extrusion, thereby omitting the steps of coating the structural adhesive layer, EVA laminating, sputtering aluminum film, and subsequent light curing in the existing reflective film production process. The process is simpler and the cost of equipment, energy, and raw materials is reduced, thereby having the advantages of higher efficiency and lower price.

[0033] (2) Furthermore, compared to conventional sputtered aluminum interstitial reflective film, this interstitial reflective film can also achieve superior reflectivity by manipulating the morphology of the barium sulfate precipitate deposited on the surface of the PET layer. Furthermore, by depositing a white BaSO4 layer on the surface of the PET layer as a reflective functional layer instead of using a reflective aluminum layer, the present invention effectively avoids the problem of a sharp drop in reflectivity caused by the existing reflective aluminum layer being highly susceptible to acid corrosion.

[0034] (3) At the same time, the gap reflective film, formed by the transition adhesive layer and the ion polymer adhesive layer, also exhibits better bonding performance with the photovoltaic glass and PET layer than the EVA adhesive layer formed by the existing lamination. The bonding between the layers in the gap reflective film is higher, which effectively avoids the delamination problem between the reflective functional layer and the adhesive layer. The gap reflective film is not prone to delamination, degradation, yellowing, etc. during long-term outdoor use, which helps to improve its service life and reflective effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The figure is a schematic diagram of the cross-sectional structure of a photovoltaic cell gap reflective film according to the present invention.

[0036] Description of the accompanying drawings: white BaSO4 layer 1; base film 2; PET layer 21; transition bonding layer 22; ion polymer bonding layer 23. DETAILED DESCRIPTION

[0037] 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 with reference to the accompanying drawings and specific embodiments.

[0038] Example 1

[0039] A method for preparing a photovoltaic cell gap reflective film in this embodiment is described in detail in Figure 1 , comprising the following preparation steps:

[0040] Step 1, preparation of PET masterbatch: by weight, 1 part of EDTA-2Na (disodium ethylenediaminetetraacetic acid) and 99 parts of PET chips (Yizheng FG720, Sinopec) were blended, and the mixed mixture was melt-extruded and granulated through a twin-screw extruder to obtain PET masterbatch.

[0041] Step 2: By weight, 50 parts of PET masterbatch (dried at 160°C for 6 hours) and 10 parts of adhesive resin (BYNEL TM 22E757, dried at 50°C for 4 hours) and 40 parts of ionomer particles (surlyn8920, dried at 60°C for 6 hours) were respectively put into the three single-screw extruders of the co-extrusion equipment. The melt pump flow ratio of the three single-screw extruders was adjusted to 5:1:4. After the three materials were melted, they were co-extruded through a three-layer hanger-type die at a die temperature of 275°C. The materials were rapidly cooled by a 5°C chill roller and the thickness was adjusted by bolts to produce an amorphous thick sheet with a thickness of 0.9 mm. The thick sheet is biaxially stretched at a stretching temperature of 100°C, a preheating time of 60s, and a longitudinal and transverse stretching ratio of 3 times. It is then shaped at a shaping temperature of 220°C and a shaping time of 20s. After cooling and trimming, a base film 2 with a thickness of 100 μm and a three-layer structure is obtained (the base film 2 includes a PET layer 21, a transition bonding layer 22 and an ionic polymer bonding layer 23 formed by co-extrusion, and the transition bonding layer 22 and the ionic polymer bonding layer 23 are sequentially stacked on the lower surface of the PET layer 21).

[0042] Step 3: At room temperature, weigh 48.9g of BaCl2*2H2O and prepare a BaCl2 solution with a concentration of 0.20mol / L with deionized water. Immerse the upper surface of the PET layer 21 containing EDTA-2Na of the base film 2 in the BaCl2 solution, and adjust the solution system pH to 9 with ammonia water. Stir thoroughly for 30 minutes to make the BaCl2 solution 2+ Ions and EDTA on the surface of PET layer 21 2- Fully complexed.

[0043] Step 4: Add the prepared 0.2 mol / L Na2SO4 solution to the solution system of step 3 and stir for 10 minutes. A white BaSO4 precipitate begins to appear on the upper surface of the PET layer 21. Continue stirring for 1 hour, wash the surface with deionized water and ethanol, and dry at 70°C to obtain a PET layer 21 with a white BaSO4 layer 1 on the upper surface as a reflective functional layer. In this way, a photovoltaic cell gap reflective film of this embodiment (its structure is as shown) is obtained. Figure 1 As shown, the thickness of each layer of the gap reflective film is as follows: the thickness of the white BaSO4 layer 1 is 10 μm, the thickness of the PET layer 21 is 50 μm, the thickness of the transition bonding layer 22 is 10 μm, and the thickness of the ion polymer bonding layer 23 is 40 μm).

[0044] The photovoltaic cell gap reflective film of this embodiment is applied to the gap between cells in a photovoltaic module.

[0045] Example 2

[0046] The photovoltaic cell gap reflective film of this embodiment, its preparation method, and its application are all referred to in Example 1. The difference between this embodiment and Example 1 is that:

[0047] In step 4 of this embodiment, the concentration of the added Na2SO4 solution is 0.15 mol / L.

[0048] Example 3

[0049] The photovoltaic cell gap reflective film of this embodiment, its preparation method, and its application are all referred to in Example 1. The difference between this embodiment and Example 1 is that:

[0050] In step 4 of this embodiment, the concentration of the added Na2SO4 solution is 0.30 mol / L.

[0051] Example 4

[0052] The photovoltaic cell gap reflective film of this embodiment, its preparation method, and its application are all referred to in Example 1. The difference between this embodiment and Example 1 is that:

[0053] In step 3 of this embodiment, the pH value of the solution system is adjusted to 7.0 instead.

[0054] Example 5

[0055] The photovoltaic cell gap reflective film of this embodiment, its preparation method, and its application are all referred to in Example 1. The difference between this embodiment and Example 1 is that:

[0056] In step 3 of this embodiment, the pH value of the solution system is adjusted to 11 instead.

[0057] Comparative Example 1

[0058] The photovoltaic cell gap reflective film and its preparation method and application in this comparative example are all based on Example 1. The difference between this comparative example and Example 1 is that:

[0059] In this comparative example, a method for preparing a photovoltaic cell gap reflective film omits steps 3 and 4 of Example 1, and replaces step 1 with the following: 25% nano-barium sulfate (particle size 200 nm) is mixed with 75% PET chips by weight, and then melt-extruded and granulated through a twin-screw extruder to obtain the PET masterbatch of this comparative example (the PET masterbatch can be used as the reflective layer of this comparative example after co-extrusion molding in step 2); step 2 of this comparative example refers to step 2 of Example 1.

[0060] Comparative Example 2

[0061] The preparation method of a film material for a photovoltaic cell gap reflective film in this comparative example includes the following preparation steps:

[0062] EVA (Evaflex EV260) was laminated on the surface of a 50 μm thick corona-treated BOPET layer and pressed to form an EVA adhesive layer.

[0063] Performance Testing

[0064] Samples were prepared according to the standards and tested for the properties shown in Tables 1-2. The following tests were conducted, referring to GB / T2790: the adhesion between the adhesive layer of the photovoltaic cell gap reflective film in Examples 1-5 (or the EVA adhesive layer in Comparative Example 2) and the photovoltaic glass and PET layers. The test results are shown in Table 1 below (in Table 1, the adhesive layer thickness in Examples 1-5 is the sum of the thicknesses of the transition adhesive layer and the ionomer adhesive layer; the adhesive layer thickness in Comparative Example 2 is the thickness of the EVA adhesive layer):

[0065] Table 1

[0066]

[0067]

[0068] Combined with the data in Table 1, we can see that:

[0069] (1) Compared with the EVA adhesive layer formed by laminating the surface of the BOPET layer in Comparative Example 2, the adhesive layer of the gap reflective film of Examples 1-5 has significantly better adhesion to the photovoltaic glass; therefore, the gap reflective film of Examples 1-5 is not prone to delamination, degradation, yellowing, etc. during long-term outdoor use, which helps to improve the service life and reflective effect of the gap reflective film of Examples 1-5.

[0070] (2) Moreover, due to the presence of the transition adhesive layer, compared with the EVA adhesive layer formed by laminating the surface of the BOPET layer in Comparative Example 2, the gap reflective film of Examples 1-5 can also have stronger bonding performance between the ionomer adhesive layer and the PET layer through the coordinated cooperation of the transition adhesive layer and the ionomer adhesive layer, thereby effectively avoiding the delamination problem between the reflective functional layer (i.e., the PET layer with a white BaSO4 layer deposited on the upper surface of Examples 1-5) and the adhesive layer.

[0071] Adhesion was measured in accordance with GB / T 9286-2021, and reflectivity was measured in accordance with GB / T 2410-2008. The test results are shown in Table 2 below (in Table 2, the thickness of the reflective layer in Examples 1-5 is the thickness of the white BaSO4 layer):

[0072] Table 2

[0073]

[0074] Combined with the data in Table 2, we can see that:

[0075] (3) Compared with the reflective layer prepared by directly adding nano-barium sulfate into PET slices and blending and extruding them in Comparative Example 1, the reflective functional layer prepared by complex precipitation of the interstitial reflective film of Examples 1-5 (i.e., the PET layer with a white BaSO4 layer deposited on the upper surface) has a higher reflectivity in the 400-1100nm band, and at the same time reduces the adverse effect of the addition of barium sulfate on the mechanical properties of the PET layer.

[0076] (4) Comparative Examples 1-3 show that by changing the concentration of Na2SO4 solution, the 2- Already with Ba 2+ Complexed, EDTA 2- Regulated the Ba content in the solution system 2+ concentration, thus changing the SO4 2- The concentration of BaSO4 has little effect on the morphology of the white BaSO4 layer. However, in order to make full use of the ions in the solution and prevent residue, it is necessary to ensure that BaSO4 2+ With SO4 2- The concentration of NaSO4 solution is consistent, so it is more appropriate to control the concentration of the added NaSO4 solution within 0.1-0.3 mol / L.

[0077] (5) By comparing Examples 1, 4, and 5, it was found that as the pH value of the solution system in step 3 increased (e.g., from pH = 7 in Example 4 to pH = 9 in Example 1), the particle size of the barium sulfate particles in the white BaSO4 layer also increased, and the particle size distribution became narrower, presenting a uniform, nearly spherical shape. This is mainly because, as the pH value of the solution system in step 3 decreased, the EDTA 2- The more severe the acid effect, the2+ The complexing strength with EDTA-2Na is relatively weak, and the stability of the complex is poor, resulting in the presence of a large amount of free Ba ​​in the solution system. 2+ However, when the Na2SO4 solution is added, the solution system is highly supersaturated, meeting the conditions for homogeneous nucleation, and instantly forming a large number of tiny nuclei, resulting in small barium sulfate crystals and agglomeration. Therefore, if the pH value of the solution system in step 3 is too low (e.g., pH less than 7), the agglomeration of small barium sulfate crystals will be exacerbated, which is not conducive to the deposition of the white BaSO4 layer and affects the reflectivity of the interstitial reflective film.

[0078] As the pH value of the solution system in step 3 increases (such as increasing to about pH 9), Ba 2+ The stronger the complexation strength with EDTA-2Na, the slower the rate at which the complex moves toward dissociation. 2+ The supersaturation is low and the homogeneous nucleation conditions cannot be met. The barium sulfate nuclei that have already been formed can only be continuously coated to form larger barium sulfate particles. Therefore, when the pH value of the solution system in step 3 is 9 (as in Example 1), the BaSO4 is uniform and nearly spherical, and the particle size of the white BaSO4 precipitate is uniform, about 1.0 μm.

[0079] As the pH of the solution system in step 3 continues to increase (e.g., from pH = 9 in Example 1 to pH = 11 in Example 5), the balance of Na2H2Y is gradually disrupted, and the BaSO4 particles begin to shrink and aggregate. Therefore, if the pH of the solution system in step 3 is too high (e.g., pH greater than 11), the aggregation of small-sized barium sulfate crystals will be exacerbated, hindering the deposition of the white BaSO4 layer and affecting the reflectivity of the interstitial reflective film.

[0080] (6) In addition, compared with the existing gap reflective film on the market (such as the conventional sputtered aluminum gap reflective film 3M TM T81X), the reflectivity of the gap reflective films of Examples 1-5 in the 400-1100nm band is not much different, and the process of the gap reflective films of Examples 1-5 of the present invention is simpler, and the equipment, energy and raw material costs are reduced.

[0081] 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 become aware of the basic creative concepts. 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.

[0082] The technical solution provided by the present invention is introduced in detail above. Specific examples are used herein to illustrate the principles and implementation methods 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 may be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for preparing a photovoltaic cell gap reflective film, characterized in that: The method comprises the following preparation steps: Step 1: uniformly mixing a metal complexing agent and PET material in a mass ratio of 1-5:100, and then granulating the mixture by melt extrusion to obtain PET masterbatch; Step 2: Place 50-100 parts by weight of PET masterbatch, 5-20 parts of adhesive resin, and 40-80 parts of ionomer particles into three hoppers of a co-extrusion device, respectively. The three layers of particles are melt-coextruded, biaxially stretched, and shaped to obtain a base film. Step 3: Immerse the surface of the PET layer of the base film in a barium salt solution, adjust the pH value of the solution system to 7-11, and stir to allow the barium ions to fully complex with the metal complexing agent on the surface of the PET layer; Step 4: add sulfate solution dropwise to the solution system of step 3, maintain stirring, and allow a white BaSO4 layer to evenly precipitate on the surface of the PET layer to obtain the interstitial reflective film.

2. The method for preparing a photovoltaic cell gap reflective film according to claim 1, characterized in that: In step 1, the intrinsic viscosity of the PET material is 0.6-0.8 dL / g, and the PET material is selected from at least one of the brands Lumirror X10, Dupont 7352, FG720, and WK-821; the PET material is dried at 160-170° C. for 4-6 hours before being placed in the co-extrusion equipment; The metal complexing agent is at least one of DTPA, CDTA, EDTA, EDTA-2Na, EDTA-4Na and salts thereof.

3. The method for preparing a photovoltaic cell gap reflective film according to claim 1, characterized in that: In step 2, the adhesive resin is at least one of modified polyethylene, modified polypropylene, modified ethylene vinyl acetate copolymer, and modified ethylene acrylate resin; The adhesive resin is selected from the brand ADMER TM AT2717, BYNEL TM 21E533, BYNEL TM 22E757, NUCREL TM 925、Plexar PX3080、 PX2250、ADMER TM NF410E, BYNEL TM 21E787、NUCREL TM At least one of AE; the adhesive resin is dried at 30-70°C for 2-5h before being placed in the co-extrusion equipment; Ionic polymers are selected from brands Surlyn 9320, surlyn8920, Himilan TM 1557、AMPLIFY TM IO 1100, NUCREL TM 0910, AMPLIFY TM At least one of IO 3801 and Aclyn 295; the ionomer is dried at 60-65° C. for 6-8 hours before being placed in the co-extrusion equipment.

4. The method for preparing a photovoltaic cell gap reflective film according to claim 1, characterized in that: Step 2 specifically includes: placing the dried PET masterbatch, adhesive resin, and ion polymer particles into three single-screw extruders of the co-extrusion equipment, respectively, adjusting the melt pump flow ratios of the three single-screw extruders to 12-20:1-4:10-20, respectively, melting the three-layer particles, and then co-extruding the three layers at a die head temperature of 255-285°C, and quenching with a 3-10°C cooling roller to form an amorphous thick sheet with a thickness of 0.5-1.5 mm; biaxially stretching the thick sheet with a transverse stretching ratio of 2.5-3.5 times and a longitudinal stretching ratio of 2.5-3.5 times, a preheating time of 60-150s, a stretching temperature of 100-120°C, and then shaping at a shaping temperature of 190-240°C and a shaping time of 10-30s, and obtaining the base film after cooling and trimming.

5. The method for preparing a photovoltaic cell gap reflective film according to claim 1, characterized in that: In step 2, the base film includes a 30-60 μm thick PET layer, a 5-15 μm thick transition adhesive layer and a 20-60 μm thick ion polymer adhesive layer formed by co-extrusion, and the transition adhesive layer and the ion polymer adhesive layer are sequentially stacked on the lower surface of the PET layer.

6. The method for preparing a photovoltaic cell gap reflective film according to claim 1, characterized in that: Step 3 specifically includes: immersing the upper surface of the PET layer of the base film in a barium chloride solution with a concentration of 0.10-0.30 mol / L at room temperature, adjusting the pH value of the solution system to 7-11 with ammonia water, and stirring for 20-50 minutes to allow the barium ions to fully complex with the metal complexing agent on the upper surface of the PET layer; the metal complexing agent is EDTA-2Na.

7. The method for preparing a photovoltaic cell gap reflective film according to claim 6, characterized in that: In step 3, the pH value of the solution system is adjusted to 9.

8. The method for preparing a photovoltaic cell gap reflective film according to claim 1, characterized in that: Step 4 specifically includes: adding a Na2SO4 solution with a concentration of 0.1-0.3 mol / L to the solution system of step 3, and maintaining stirring for 5-10 minutes until a white BaSO4 precipitate begins to appear on the upper surface of the PET layer, continuing stirring for at least 1 hour, washing with deionized water and ethanol, and drying at 60-90°C to obtain a PET layer with a white BaSO4 layer on the upper surface as a reflective functional layer.

9. A photovoltaic cell gap reflective film, characterized in that: The photovoltaic cell gap reflective film is prepared by the method for preparing the photovoltaic cell gap reflective film according to any one of claims 1 to 8.

10. The application of the photovoltaic cell gap reflective film according to claim 9, characterized in that: The gap reflective film is applied to the gap positions of the cells in the photovoltaic module.

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