A method of manufacturing a photovoltaic module

Abstract

The application belongs to the technical field of photovoltaic modules, and provides a preparation method of a photovoltaic module, which comprises the following steps: adding appropriate amounts of wetting agent, dispersing agent and coupling agent into a solvent and fully mixing; then adding appropriate amounts of reflective fillers with a particle size of 0.1-2 microns and uniformly dispersing; continuously adding appropriate amounts of polymer emulsion, film-forming aid and transesterification enhancer and uniformly stirring to prepare a high-reflection coating; wherein the volume concentration of the reflective fillers in the high-reflection coating is 20-80%; then spraying the high-reflection coating on the inner surface of a back plate and solidifying to form a high-reflection coating layer with a thickness of 7-10 microns; and then sequentially stacking the back plate coated with the high-reflection coating layer, EVA adhesive film, cell piece, transparent adhesive film and photovoltaic glass, heating and laminating, cross-linking and solidifying the high-reflection coating layer and the EVA adhesive film again to prepare the photovoltaic module. The prepared photovoltaic module has excellent reflectivity and peeling strength, and the output power is obviously increased, and the problems of uneven distribution of fillers, cell piece hidden cracking, white overflow and wrinkle of the existing white adhesive film are overcome.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photovoltaic modules, in particular to a preparation method of a photovoltaic module. BACKGROUND

[0002] At present, in order to improve the utilization rate of solar light by the photovoltaic module and thus improve the output power of the photovoltaic module, a white adhesive film (such as a white EVA encapsulating adhesive film) is designed. The white adhesive film is prepared by adding a white filler to improve the reflectivity of solar light. The solar light that is not absorbed and utilized by the cell sheet is reflected back to the surface of the cell sheet through the white adhesive film, and then is reabsorbed and utilized by the cell sheet.

[0003] In order to solve the overflow phenomenon of the white adhesive film, the publication CN108794870B is to add a main crosslinking agent, i.e. tert-butyl peroxyisobutyrate. Under the action of the tert-butyl peroxyisobutyrate, the main body resin with a fusion index of 15-30 g / 10 min is rapidly crosslinked. The encapsulating material is crosslinked and solidified before flowing to the front surface of the cell sheet, so as to prevent overflow. However, with the addition of the main crosslinking agent, the aging resistance of the white adhesive film will also decrease, and thus the reflectivity and adhesion of the white adhesive film will be affected.

[0004] In addition, the multi-layer structure of the white adhesive film disclosed in the publication CN210620694U increases the wrinkling phenomenon of the white EVA adhesive film during the lamination process. In addition, the white filler added in the white EVA adhesive film usually has a small particle size and is prone to agglomeration, which can easily lead to uneven dispersion of the white filler, local clumping and hardening in the white adhesive film. Therefore, during the lamination process, the cell sheet cracking rate is increased, and thus the improvement of the output power of the photovoltaic module is affected.

[0005] In addition, the high-reflective coating for the current photovoltaic backsheet (such as CN114958064A) is only fixed on the surface of the organic polymer film backsheet or the glass backsheet. The high-reflective coating is not further crosslinked and solidified with the EVA adhesive film during the subsequent heating and lamination process. Therefore, the peeling strength between the high-reflective coating and the EVA adhesive film is low, and the high-reflective coating can migrate during long-term use, which is difficult to ensure the long-term reliability of the photovoltaic module. SUMMARY

[0006] The purpose of the present application is to provide a preparation method of a photovoltaic module to overcome the shortcomings of the prior art.

[0007] Based on this, the present application discloses a preparation method of a photovoltaic module, which comprises the following preparation steps:

[0008] S1, by weight parts, the 0.1-0.3 parts of wetting agent, 0.6-0.8 parts of dispersant and 0.2-0.4 parts of coupling agent are added to 40-63 parts of solvent, mixed thoroughly; then add 15-35 parts of the particle size of 0.1-2 μm reflective filler, dispersed uniformly; continue to add 15-25 parts of polymer emulsion, 0.5-1.5 parts of film forming agent and 1-5 parts of transesterification enhancer, stirring uniformly, prepared high reflective coating;

[0009] Among them, the reflective filler is titanium dioxide, barium sulfide, zinc oxide, titanium powder, at least one of the at least one; the polymer emulsion is ethylene-vinyl acetate emulsion, vinyl acetate-acrylic acid emulsion, styrene-acrylic acid emulsion, vinyl acetate-tert-butyl vinyl acetate, pure acrylic emulsion, silicone acrylic emulsion, water-based polyurethane coating, water-based fluorocarbon coating at least one;

[0010] Among them, the volume concentration of the reflective filler in the high reflective coating is 20-80%;

[0011] S2, the high reflective coating is sprayed on the inner surface of the back plate, and the film is cured to form a high reflective coating with a thickness of 7-10 μm;

[0012] S3, the back plate, EVA film, battery piece, transparent adhesive film, photovoltaic glass are stacked in turn, heated and laminated, the high reflective coating and EVA film are crosslinked and cured again, and the photovoltaic module is prepared.

[0013] Preferably, the reflective filler is titanium dioxide with a particle size of 0.2-0.3 μm.

[0014] Further preferably, the volume concentration of the titanium dioxide in the high reflective coating is 50-60%.

[0015] Preferably, the polymer emulsion is ethylene-vinyl acetate emulsion; the transesterification enhancer is hyperbranched polyethylene glycol diacrylate with multiple vinyl groups (abbreviated as HB-PEGDA).

[0016] Further preferably, the preparation process of the hyperbranched polyethylene glycol diacrylate comprises:

[0017] (1) in a beaker, 20-40 g of PEGDA (polyethylene glycol diacrylate) monomer with an average Mn of 400-1000 g·mol -1 is transferred to a two-necked flask, the beaker is rinsed with butanone several times, the rinsing liquid is transferred to the flask, and butanone is continuously added to make the total amount of butanone in the flask 100-150 mL, stirring until completely dissolved, the concentration of PEGDA monomer is 0.2-0.5 mol·L -1 ;

[0018] (2) Then, 0.4-0.8g AIBN (azobisisobutyronitrile) and 0.5-0.8g tetraethylthiuram disulfide (DS for short) are added into the flask while stirring, the flask is sealed, argon is bubbled into the mixture in the flask for 1-2h, and then the polymerization reaction is carried out at 70-100℃ for 3-6h, the stirring rate is 100-500rpm, the reaction is stopped, air is introduced, and the temperature is cooled to room temperature;

[0019] (3) The mixed solution of hexane and diethyl ether in a volume ratio of 1:2-1:5 is pre-cooled in a refrigerator for 3-7h, and then is used to precipitate and purify the polymerization product for multiple times, and the polymerization product is dried under reduced pressure, thereby obtaining the hyperbranched polyethylene glycol diacrylate.

[0020] Further preferably, in the high-reflective coating, the addition amount of the hyperbranched polyethylene glycol diacrylate is 3-5 parts.

[0021] Preferably, in the step S1, the solvent is water, ethanol, n-butanol or butyl acetate.

[0022] Preferably, in the step S2, the back plate is a black back plate or a glass back plate.

[0023] Preferably, in the step S2, the film-forming curing condition comprises: 0.1-0.5 parts of a photoinitiator is additionally added, and ultraviolet curing is carried out for 2-5min; or hot curing is carried out at 100-200℃ for 1-5min.

[0024] Preferably, in the step S3, the heating lamination condition comprises: lamination is carried out at a heating condition of 130-150℃ for 400-1000s.

[0025] Compared with the prior art, the present application at least has the following beneficial effects:

[0026] The preparation method of the photovoltaic module of the present application uses a high-reflective coating as the main body of a polymer emulsion (such as an ethylene-vinyl acetate emulsion), and cooperates with the introduction of an ester exchange enhancer (such as HB-PEGDA) and other raw materials. In this way, because the polymer emulsion and the ester exchange enhancer that can perform an ester exchange reaction are simultaneously added to the high-reflective coating, a secondary cross-linking and curing reaction between the high-reflective coating and the EVA adhesive film during the lamination process of the photovoltaic module can be realized. The high-reflective coating that has been fixed on the inner surface of the organic high-molecular film backboard (or the glass backboard) can be firmly fixed together with the EVA adhesive film through the secondary cross-linking and curing, realizing the "integration" of the organic high-molecular film backboard (or the glass backboard), the high-reflective coating, and the EVA adhesive film. Therefore, the reflectivity and the peeling strength can be greatly improved, and the high-reflective coating can be better fixed to prevent migration, realizing the long-term reliability of the module. Further, the particle size and the volume concentration of the reflective filler in the high-reflective coating are strictly controlled. Then, the prepared high-reflective coating is sprayed on the inner surface of the organic high-molecular film backboard or the glass backboard by a spraying method (rather than a brushing method), and is cured to form a film, so as to obtain a high-reflective coating with tightly packed titanium dioxide particles on the inner surface of the organic high-molecular film backboard or the glass backboard, and the thickness of the high-reflective coating is controlled. The reflectivity and the peeling strength are further improved.

[0027] Therefore, the preparation method of the photovoltaic module of the present application can make the prepared photovoltaic module have excellent 380-1100 nm reflectivity and peeling strength, and effectively improve the output power of the photovoltaic module. Moreover, the complex process for preparing the white adhesive film is avoided, and the technical problems of uneven filler dispersion in the existing white adhesive film, leading to hidden cracks of the battery piece, and overflow, wrinkles, and the like occurring during the lamination process of the white adhesive film are solved. DETAILED DESCRIPTION

[0028] In order to make the above-mentioned objects, features, and advantages of the present application more apparent and easy to understand, the present application will be further described in detail below with specific embodiments.

[0029] The preparation method of the photovoltaic module of the present application comprises the following preparation steps:

[0030] Step 1: 0.1-0.3 parts of a wetting agent, 0.6-0.8 parts of a dispersing agent, and 0.2-0.4 parts of a coupling agent are weighed out and added to 40-63 parts of a solvent, and are fully mixed. Then, 15-35 parts of a reflective filler with a particle size of 0.1-2 μm is added and uniformly dispersed. Then, 15-25 parts of a polymer emulsion, 0.5-1.5 parts of a film-forming aid, and 1-5 parts of an ester exchange enhancer are continuously added, and are uniformly stirred to prepare a high-reflective coating.

[0031] The reflective filler is at least one of titanium white, lithopone, barium sulfide, zinc oxide, and titanium suboxide powder.

[0032] The reflective filler is an important component of the high reflective coating and cannot form a film alone. The reflective filler is generally in the form of fine powder and is uniformly dispersed in the resin, film-forming aid, and solution through stirring, grinding, high-speed dispersion, and other processes in the coating production process. After the resin and film-forming aid form a coating film, the reflective filler is uniformly dispersed in the coating film to become a functional component for reflecting sunlight.

[0033] To ensure high sunlight reflectivity, the particle size of the reflective filler used in the present application is preferably 0.2-0.3 μm, and the volume concentration of the reflective filler in the high reflective coating is preferably 50-60%, and the reflective filler is preferably titanium white.

[0034] In the present application, the particle size of the reflective filler (such as titanium white) is controlled to be 0.2-0.3 μm. The particles in this particle size range not only have strong reflectivity to sunlight, but also are beneficial to uniform dispersion in the high reflective coating of the present application. Further, the volume concentration of the reflective filler in the high reflective coating is controlled to be 50-60%. This is because: if the volume concentration of the reflective filler in the high reflective coating is low, it is not conducive to the formation of a tightly packed structure after the high reflective coating film is formed, thereby reducing the reflection and scattering effect of sunlight; and if the volume concentration of the reflective filler in the high reflective coating is high, it is not conducive to spraying, which can cause the nozzle of the spraying equipment to be easily blocked, and also affect the peel strength of the high reflective coating and the EVA adhesive film. The high reflective coating of the present application has a high sunlight reflectivity of ≥90% after the coating film is dried.

[0035] The polymer emulsion is at least one of ethylene-vinyl acetate emulsion, vinyl acetate-acrylic acid emulsion, styrene-acrylic acid emulsion, vinyl acetate-tertiary vinyl acetate, pure acrylic acid emulsion, silicone-acrylic emulsion, water-based polyurethane coating, and water-based fluorocarbon coating.

[0036] The polymer emulsion in the high reflective coating of the present application not only can bond other raw materials into a whole to form a complete coating film layer to adhere to the base surface of the backboard, but also can undergo a post-crosslinking curing reaction with the EVA adhesive film during the heating and lamination process, so that the high reflective coating layer that has been fixed on the surface of the organic high molecular film backboard (or glass backboard) can also be firmly fixed with the EVA adhesive film. The polymer emulsion used in the present application has high bonding strength and can be firmly bonded with the base of the backboard and the EVA adhesive film. The polymer emulsion is preferably ethylene-vinyl acetate emulsion.

[0037] The transesterification enhancer is a hyperbranched polyethylene glycol diacrylate. The hyperbranched polyethylene glycol diacrylate is a hyperbranched macromonomer HB-PEGDA prepared by in-situ RAFT polymerization technology, which is a hyperbranched polymer with multiple vinyl groups, and the adhesion between the high reflection coating and the EVA film is further improved by appropriate addition.

[0038] Specifically, the synthesis steps of the HB-PEGDA include: (1) weighing 20-40 g of PEGDA monomer with an average Mn of 400-1000 g·mol -1 in a beaker, transferring it to a two-necked flask, rinsing the beaker with butanone for multiple times, transferring the rinsing liquid to the flask, continuing to add butanone so that the total amount of butanone added to the flask is 100-150 mL, stirring until completely dissolved, and the concentration of the PEGDA monomer is 0.2-0.5 mol·L -1 .(2) Then, 0.4-0.8 g of AIBN and 0.5-0.8 g of tetraethylthiuram disulfide are added to the flask while stirring, the flask is sealed, argon is bubbled into the mixture in the flask for 1-2 h, and then the polymerization reaction is carried out at 70-100℃ for 3-6 h, the stirring rate is 100-500 rpm, the reaction is stopped, air is introduced, and the temperature is cooled to room temperature.(3) A mixed solution of hexane and diethyl ether with a volume ratio of 1:2-1:5 is pre-cooled in a refrigerator for 3-7 h, and then used to precipitate and purify the polymerization product for multiple times, and the polymerization product is dried under reduced pressure to obtain the hyperbranched polyethylene glycol diacrylate.

[0039] The dispersant is an interfacial active agent with both lipophilicity and hydrophilicity in the molecule, which can uniformly disperse solid particles that are difficult to dissolve, and can also prevent the settlement and agglomeration of particles. In the following example of the high reflection coating of the present application, the dispersant is selected from commercially available Dongguan Aoda Environmental Protection New Material AD8030 (in other examples of the present application, the dispersant in the high reflection coating can also be selected from other existing commonly used dispersants).

[0040] The wetting agent can reduce the surface tension or interfacial tension of the wetted substance, and its addition in the high reflection coating of the present application can improve the blending of the reflective filler and the liquid additive, and also can promote the leveling of the high reflection coating on the base surface of the back plate. In the following example of the high reflection coating of the present application, the wetting agent is selected from commercially available Dow CF-10 (in other examples of the present application, the wetting agent in the high reflection coating can also be selected from other existing commonly used wetting agents), to reduce the surface tension, increase the affinity with the reflective filler, and also improve the stability of the polymer emulsion.

[0041] The film-forming aid, also known as coagulant or coalescent, is usually a high-boiling solvent. The film-forming aid functions as a kind of "temporary" plasticizer to reduce the glass transition temperature of the polymer. Once the particles are deformed and the film-forming process is completed, the film-forming aid volatilizes from the coating film, thereby not affecting the glass transition temperature of the original polymer. The ethylene-vinyl acetate emulsion in the high-reflectance coating of the present application can form a normal film, and the addition of the film-forming aid plays a certain promoting role in the curing of the coating film. The film-forming aid in the high-reflectance coating of the following examples of the present application can be selected from the market sold by Solvay. In other examples of the present application, the film-forming aid in the high-reflectance coating can also be selected from other existing commonly used film-forming aids.

[0042] The coupling agent is a kind of compound with two different functional groups. In its molecule, it has a reactive group that can combine with inorganic materials and a reactive group that can combine with organic materials. The addition of the coupling agent can enhance the bonding strength between the high-reflectance coating after curing and the substrate of the backboard. The coupling agent in the high-reflectance coating of the following examples of the present application can be selected from the market sold by Hubei Jianghan New Material Co., Ltd. 570 silane coupling agent (in other examples of the present application, the coupling agent in the high-reflectance coating can also be selected from other existing commonly used coupling agents).

[0043] The solvent is water, ethanol, n-butanol or butyl acetate, preferably deionized water.

[0044] Step 2, the high-reflectance coating is sprayed on the inner surface of the backboard, and is cured and formed into a film to form a high-reflectance coating layer with a thickness of 7-10 μm.

[0045] Specifically, in step S2, the curing and film-forming conditions include: auxiliary addition of 0.1-0.5 parts of a photoinitiator, and ultraviolet curing for 2-5 min; or heat curing at 100-200℃ for 1-5 min.

[0046] Step 3, the backboard with the high-reflectance coating, the EVA adhesive film, the battery piece, the transparent adhesive film and the photovoltaic glass are sequentially stacked, and then are heated and laminated to make the high-reflectance coating and the EVA adhesive film crosslink and cure again, thereby obtaining a photovoltaic module.

[0047] Specifically, in step S3, the heating and lamination conditions include: lamination at a heating condition of 130-150℃ for 400-1000 s.

[0048] The following further describes each example and comparative example in detail.

[0049] Example 1

[0050] The preparation method of the photovoltaic module in this example includes the following steps:

[0051] Step 1, preparation of high reflective coating:

[0052] First, 0.2 kg of wetting agent, 0.7 kg of dispersant and 0.3 kg of coupling agent were weighed into 44.8 kg of deionized water and mixed well; then 33 kg of titanium dioxide with a particle size of 0.3 μm was added and ground and dispersed with a high-speed dispersing machine at a speed of 1500 RPM; finally, 20 kg of ethylene-vinyl acetate emulsion, 1 kg of film-forming aid and 3 kg of HB-PEGDA were added and stirred uniformly at a low speed of 500 RPM to obtain the high reflective coating. In step 1, the volume concentration of titanium dioxide in the high reflective coating was 51.6%.

[0053] In step 1, the synthesis of HB-PEGDA was as follows:

[0054] (1) 34.5 g of PEGDA monomer (average Mn = 575 g·mol -1 ) was weighed in a 50 mL beaker, transferred to a 250 mL two-necked flask, the beaker was rinsed several times with 50 mL of butanone, the rinsing liquid was transferred to the flask, butanone was continuously added, the total amount of butanone added to the flask was 150 mL, stirring until completely dissolved, the concentration of PEGDA monomer was 0.4 mol·L -1 (2) Then, 0.5517 g of AIBN (azobisisobutyronitrile) and 0.7117 g of DS (tetraethylthiuram disulfide) were added to the flask while stirring, the flask was sealed with a salt water plug and wrapped with a sealing film, argon was bubbled into the mixture in the flask for 1 h; then the polymerization reaction was carried out at 70℃ for 6 h at a rotation speed of 300 rpm; the reaction was stopped, air was introduced and cooled to room temperature. (3) The polymerization product was purified by precipitation three times with a volume ratio of 1:2 of hexane / ether solution (pre-cooled in the refrigerator for 6 h), the polymerization product was dried under reduced pressure, and the residual solvent was removed in a vacuum oven for 48 h to obtain hyperbranched polyethylene glycol diacrylate.

[0055] Step 2, the high reflective coating of step 1 was sprayed on the inner surface of the black backboard (the inner surface of the black backboard is the side of the packaging adhesive film such as high cut EVA adhesive film), and was heat cured at 150℃ for 2 min to cure the film, thereby obtaining a black backboard with a high reflective coating. In step 2, the thickness of the high reflective coating after film formation was 7-10 μm (such as 8 μm).

[0056] Step 3, the black backboard with a high reflective coating of step 2, high cut EVA adhesive film, battery sheet, high transmittance EVA adhesive film and photovoltaic glass were sequentially stacked, and were laminated under heating at 145℃ for 540 s to crosslink and cure the high reflective coating and the high cut EVA adhesive film again, thereby obtaining the photovoltaic module of the present embodiment. In step 3, the black backboard with a high reflective coating was placed on the back surface of the photovoltaic module (i.e. the back light surface of the photovoltaic module).

[0057] Example 2

[0058] The preparation method of the photovoltaic module of the present example is specifically referred to Example 1, and the difference between the present example and Example 1 is that:

[0059] In Step 2 of the present example, the high-reflective coating of Step 1 is sprayed on the inner surface of the glass backboard, and is cured into a film to obtain a glass backboard with a 7-10 μm high-reflective coating layer.

[0060] In Step 3 of the present example, the glass backboard with the high-reflective coating layer of Step 2, the high-cut EVA film, the cell sheet, the high-transmittance EVA film, and the photovoltaic glass are sequentially stacked and laminated by heating, so that the high-reflective coating layer is crosslinked and cured again with the high-cut EVA film, thereby obtaining the photovoltaic module of the present example. The glass backboard with the high-reflective coating layer is placed on the back of the photovoltaic module.

[0061] Example 3

[0062] The preparation method of the photovoltaic module of the present example is specifically referred to Example 1, and the difference between the present example and Example 1 is that:

[0063] In Step 1 of the present example, the particle size of the titanium dioxide powder added for preparing the high-reflective coating is 2 μm, and the other parameters and steps are referred to Example 1.

[0064] Example 4

[0065] The preparation method of the photovoltaic module of the present example is specifically referred to Example 1, and the difference between the present example and Example 1 is that:

[0066] In Step 1 of the present example, the added amount of the deionized water is 62.8 kg, and the added amount of the titanium dioxide powder is 15 kg, and the volume concentration of the titanium dioxide powder in the high-reflective coating is 23.5%; the other parameters and steps are referred to Example 1.

[0067] Example 5

[0068] The preparation method of the photovoltaic module of the present example is specifically referred to Example 2, and the difference between the present example and Example 2 is that:

[0069] In Step 1 of the present example, the emulsion added for preparing the high-reflective coating is pure acrylic emulsion instead of ethylene-vinyl acetate emulsion; the other parameters and steps are referred to Example 2.

[0070] Example 6

[0071] The preparation method of the photovoltaic module of the present example is specifically referred to Example 1, and the difference between the present example and Example 1 is that:

[0072] In step 1 of the present example, the added amount of HB-PEGDA for preparing the high-reflective coating is 1 kg; the remaining parameters and steps are referred to Example 1.

[0073] Comparative Example 1

[0074] The preparation method of a photovoltaic module of the present comparative example is specifically referred to Example 1, and the difference between the present comparative example and Example 1 is that:

[0075] The present comparative example omits the preparation of the high-reflective coating in step 1. Moreover, the inner surface of the black backboard of the present comparative example is not treated by spraying the high-reflective coating.

[0076] Therefore, the photovoltaic module is prepared by directly stacking and laminating the black backboard, the high-cut EVA film, the cell sheet, the high-transmittance EVA film and the photovoltaic glass in sequence.

[0077] Comparative Example 2

[0078] The preparation method of a photovoltaic module of the present comparative example is specifically referred to Comparative Example 1, and the difference between the present comparative example and Comparative Example 1 is that:

[0079] The high-cut EVA film in the photovoltaic module of Comparative Example 1 is replaced by a white EVA film, and the remaining steps are referred to Comparative Example 1 to prepare the photovoltaic module of the present comparative example.

[0080] Comparative Example 3

[0081] The preparation method of a photovoltaic module of the present comparative example is specifically referred to Example 1, and the difference between the present comparative example and Example 1 is that:

[0082] In step 2 of the present comparative example, the high-reflective coating of step 1 is brushed (instead of sprayed) on the inner surface of the black backboard; the remaining steps are referred to Example 1 to prepare the photovoltaic module of the present comparative example.

[0083] Comparative Example 4

[0084] The preparation method of a photovoltaic module of the present comparative example is specifically referred to Example 1, and the difference between the present comparative example and Example 1 is that:

[0085] In step 2 of the present comparative example, the thickness of the high-reflective coating after film formation is increased to 20-25 μm (such as 22 μm); the remaining steps are referred to Example 1 to prepare the photovoltaic module of the present comparative example.

[0086] Performance Test

[0087] The photovoltaic modules of Examples 1-4 and Comparative Examples 1-2 are respectively subjected to performance test, and the test results are shown in Table 1.

[0088] Among them, the reflectivity refers to the reflectivity of the substrate (the substrate can be specifically a black backboard or a glass backboard).

[0089] The peeling strength refers to the peeling strength between the substrate and the EVA film (such as high-cut EVA film or white EVA film). It should be noted that when the inner surface of the substrate is coated with a high-reflective coating, the high-reflective coating is directly bonded to the EVA film.

[0090] The comparative example 1 is a blank control group, and thus the photovoltaic module of the comparative example 1 has no gain power.

[0091] Table 1

[0092]

[0093] From Table 1, it can be seen that:

[0094] 1. The example 1 and the example 2 are parallel tests, which show that when the high-reflective coating is sprayed on the inner surface of different substrates (such as black backboard or glass backboard), the effect of enhancing the reflectivity is good.

[0095] 2. It is found through the comparison between the example 1 and the example 3 that, compared with adding titanium dioxide powder with a smaller particle size (such as the particle size of 0.3 μm in the example 1) in the high-reflective coating of the present application, adding titanium dioxide powder with a larger particle size (such as the particle size of 2 μm in the example 3) will reduce the reflectivity.

[0096] 3. It is found through the comparison between the example 1 and the example 4 that, compared with adding high-volume-concentration titanium dioxide powder (such as the volume concentration of 51.6% in the example 1) in the high-reflective coating of the present application, adding low-volume-concentration titanium dioxide powder (such as the volume concentration of 23.5% in the example 4) will reduce the reflectivity.

[0097] 4. It is found through the comparison between the example 1 and the example 5 that, adding polymer emulsion ethylene-vinyl acetate emulsion (as shown in the example 1) in the high-reflective coating of the present application has a better bonding effect than adding pure acrylic emulsion, and the peeling strength between the high-reflective coating and the EVA film is higher.

[0098] 5. It is found through the comparison between the example 1 and the example 6 that, by increasing the content of HB-PEGDA in the high-reflective coating of the present application, the peeling strength between the high-reflective coating and the EVA film can be further improved.

[0099] 6. Compared with the photovoltaic module of the comparative example 2 (which comprises a black backboard with no high-reflective coating sprayed on the inner surface and a white EVA film), the photovoltaic module of the example 1 of the present application (which comprises a black backboard with a high-reflective coating sprayed on the inner surface and a high-cut EVA film) has more advantages in reflectivity, peeling strength between the black backboard and the EVA film, and other properties, and has no white overflow phenomenon, and the power gain of the photovoltaic module of the example 1 is also higher than that of the comparative example 2.

[0100] 7、By comparing Example 1 with Comparative Example 3, it is found that the process of spraying high-reflective coating is easier to obtain a high-reflective coating with closely packed titanium dioxide particles on the inner surface of the substrate than the process of brushing high-reflective coating; and Example 1 has more advantages in reflectivity, peeling strength between the black backboard and EVA film, and power gain of the photovoltaic module than Comparative Example 3.

[0101] 8、By comparing Example 1 with Comparative Example 4, it is found that the high-reflective coating sprayed on the inner surface of the substrate is too thick, which leads to a decrease in the peeling strength between the high-reflective coating and the EVA film.

[0102] In summary, the preparation method of the photovoltaic module of the present application has the high-reflective coating containing the polymer emulsion (preferably ethylene-vinyl acetate emulsion) and the ester exchange enhancer HB-PEGDA which can be secondarily crosslinked with the EVA film during the heating and lamination process, and the addition amount of HB-PEGDA is controlled, the particle size and volume concentration of titanium dioxide in the high-reflective coating are strictly controlled; and the spraying method and the secondary crosslinking and solidification with the EVA film are used to firmly fix the high-reflective coating between the black backboard (or glass backboard) and the EVA film of the photovoltaic module, and the thickness of the high-reflective coating is controlled. In this way, the obtained photovoltaic module has more excellent reflectivity of 380-1100 nm and peeling strength, and the output power of the photovoltaic module can be effectively improved; and the complex process for preparing the white film is avoided, and the technical problems such as uneven filler dispersion in the existing white film, hidden cracks of the battery sheet, and overflow and wrinkles in the lamination process of the white film are solved.

[0103] Although the preferred embodiments of the embodiments of the present application have been described, those skilled in the art can make further changes and modifications to the embodiments once they know the basic creative concept. Therefore, the appended claims are intended to be interpreted as including all changes and modifications falling within the scope of the embodiments of the present application.

[0104] The above describes the technical solutions provided by the present application in detail, and the principles and implementation manners of the present application are described by applying specific examples; the above description of the embodiments is only used to help understand the method of the present application and its core idea; meanwhile, for those skilled in the art, according to the idea of the present application, the specific implementation manners and application ranges can be changed; in summary, the content of the present description should not be understood as a limitation of the present application.

Claims

1. A method of making a photovoltaic module, characterized by, It comprises the following preparation steps: S1, in parts by weight, 0.1~0.3 parts of wetting agent, 0.6~0.8 parts of dispersing agent and 0.2~0.4 parts of coupling agent are weighed and added to 40~63 parts of solvent, and mixed thoroughly; then 15~35 parts of reflective filler with a particle size of 0.1~2 μm is added, and uniformly dispersed; then 15~25 parts of polymer emulsion, 0.5~1.5 parts of film forming aid and 3~5 parts of transesterification enhancer are added, and stirred uniformly to prepare a high reflection coating; Among them, the reflective filler is titanium white powder with a particle size of 0.2~0.3 μm; the volume concentration of the titanium white powder in the high reflection coating is 50~60%; The polymer emulsion is ethylene-vinyl acetate emulsion; the transesterification enhancer is hyperbranched polyethylene glycol diacrylate with multiple vinyl groups; S2, the high reflection coating is sprayed on the inner surface of the back plate, and cured to form a high reflection coating with a thickness of 7~10 μm; S3, the back plate with the high reflection coating, EVA adhesive film, battery piece, transparent adhesive film and photovoltaic glass are stacked in sequence, and then heated and laminated to cross-link and cure the high reflection coating and the EVA adhesive film again to prepare the photovoltaic module.

2. The method of claim 1, wherein the step of applying the encapsulant is performed by a roll-to-roll process. The preparation process of the hyperbranched polyethylene glycol diacrylate comprises: (1) In a beaker, 20-40 g of PEGDA monomer with an average number average molecular weight of 400-1000 g·mol -1 was weighed and transferred to a two-mouth flask. The beaker was rinsed with butanone for several times, and the rinsing liquid was transferred to the flask. Butanone was continuously added until the total amount of butanone in the flask was 100-150 mL. After stirring until complete dissolution, the concentration of PEGDA monomer was 0.2-0.5 mol·L -1 ; (2) Then, 0.4~0.8 g of AIBN and 0.5~0.8 g of tetraethylthiuram disulfide are added to the flask while stirring, the flask is sealed, argon is bubbled into the mixture in the flask for 1~2 h, and then the polymerization reaction is carried out at 70~100℃ for 3~6 h, with a stirring rate of 100~500 rpm. Stop the reaction, pass air, and cool to room temperature; (3) The mixed solution of hexane and diethyl ether with a volume ratio of 1:2~1:5 is pre-cooled in the refrigerator for 3~7 h, and then used to precipitate and purify the polymerization product several times. The polymerization product is dried under reduced pressure to obtain the hyperbranched polyethylene glycol diacrylate.

3. The method of claim 1, wherein the step of applying the encapsulant is performed by a roll-to-roll process. In step S1, the solvent is water, ethanol, n-butanol or butyl acetate.

4. The method of claim 1, wherein the step of applying the encapsulant is performed by a roll-to-roll process. In step S2, the back plate is a black back plate or a glass back plate.

5. The method of claim 1, wherein the step of applying the encapsulant is performed by a roll-to-roll process. In step S2, the curing conditions include: auxiliary addition of 0.1~0.5 parts of photoinitiator, ultraviolet curing for 2~5 min; or heat curing at 100~200℃ for 1~5 min.

6. The method of claim 1, wherein the step of applying the encapsulant is performed by a roll-to-roll process. In step S3, the heating and lamination conditions include: lamination at a heating temperature of 130~150℃ for 400~1000 s.

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