Back contact photovoltaic module and preparation method thereof

Abstract

The invention relates to the field of photovoltaic technology, and discloses a back contact photovoltaic module and a preparation method thereof. The preparation method comprises the following steps: cutting a pre-crosslinked insulating adhesive film (the melting point of the pre-crosslinked insulating adhesive film is 60-80 DEG C, the pre-crosslinking degree is greater than or equal to 90%, and the insulation resistance is greater than or equal to 1.0 * 10 < 10 > omega.cm), laying the cut insulating adhesive film on the back surface of a back contact battery piece, and enabling the insulating adhesive film to cover each thin grid line on the back surface of the battery piece, main grid lines on the back surface of the battery piece and PAD points (welding points) on the main grid lines are exposed to isolate positive and negative grid lines on the back surface of the battery piece; pre-fixing the laid insulating adhesive film on the back surface of the battery piece, wherein the pre-fixing temperature is less than or equal to 80 DEG C; welding strips are laid on the main grid lines on the back face of the battery piece in the length direction of the main grid lines; and performing laser welding on the welding strips on the PAD points of the main grid lines, so that the plurality of battery pieces are welded by the welding strips and are connected in series to form a battery string. According to the preparation method, the back contact photovoltaic module with low cost and high yield can be obtained.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaic technology, and in particular to a back-contact photovoltaic module and a preparation method thereof. Background Art

[0002] With the advancement of solar cell technology, the development of high-efficiency solar cells and photovoltaic modules has received increasing attention. BC (Back Contact) cells, in particular, have attracted considerable attention from researchers both domestically and internationally due to their lack of front-side gridlines (or electrodes), high conversion efficiency, high short-circuit current, high fill factor, and aesthetically pleasing design. BC cells have become a new platform technology for the photovoltaic industry. Because BC cells have both positive and negative electrodes on the back of the cell, arranged alternately in an interdigitated pattern, BC battery modules require insulating adhesive to separate the positive and negative electrodes.

[0003] As shown in the publication number CN116995109A, the preparation method of the existing BC photovoltaic product is to lay a front adhesive film on the front cover plate; place the back contact battery on the front adhesive film, and after printing the insulating adhesive locally on the back of the back contact battery, solidify to form an insulating adhesive layer to isolate the positive and negative grid lines of the back contact battery; then print the low-temperature electrical connection material (such as low-temperature solder paste with a melting point of 90°C to 135°C) on the PAD point area of ​​the main grid line; lay a low-temperature solder tape (such as a tin-bismuth-silver system with a melting point of 90°C to 135°C) on the pre-cured low-temperature electrical connection material; then lay the back adhesive film (which is a local low-fluidity adhesive film such as a pre-cross-linked adhesive film or PVB film) and the back cover plate on the low-temperature solder tape, and enter the laminator for lamination and curing. This existing preparation method of BC photovoltaic products prints the low-temperature solder paste on the PAD point area, and after pre-curing, it is matched with the low-temperature solder tape, which can ensure the effective combination of the aluminum grid line with weak bonding force and the low-temperature solder tape, and achieve the effect of collecting current, and the natural silver paste area is better bonded.

[0004] However, this existing method for preparing BC photovoltaic products has at least the following disadvantages: 1. The equipment modification cost and material cost are high: before laying the back film, it is necessary to match the local printing of insulating glue + printing of low-temperature solder paste + laying of low-temperature solder tape, so the component end needs to add silk screen equipment to print insulating glue and solder paste. At present, the cost of silk screen equipment and both insulating glue and solder paste are relatively high. In addition, it is necessary to add additional processes such as printing and pre-curing of low-temperature solder paste. Therefore, the preparation process of the BC photovoltaic product is complicated and cumbersome, and the preparation efficiency is low, which further increases its production cost. 2. It is matched with the use of low-temperature solder tape, which is welded by conventional welding methods (infrared or bottom plate heating welding methods), and the welding accuracy of these conventional welding methods is not high; when welding by these conventional welding methods, insulating glue, low-temperature solder paste, etc. are easy to melt and flow and offset, which further affects the welding accuracy and increases the defective rate of component-end products. In addition, after conventional infrared high-temperature welding, the cell will warp due to stress (thermal expansion and contraction), which will cause cell cracks, cold solder joints and other defects, and thus lead to a decrease in the yield rate of the component end. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a back-contact photovoltaic module and a method for preparing the same, thereby reducing the cost and improving the yield.

[0006] Based on this, the present invention discloses a method for preparing a back-contact photovoltaic module, comprising the following preparation steps:

[0007] Step 1: Cut the pre-crosslinked insulating film and lay the cut insulating film on the back of the back contact battery cell so that the insulating film covers the fine grid lines on the back of the battery cell and exposes the main grid lines and PAD points on the main grid lines on the back of the battery cell to isolate the positive and negative grid lines on the back of the battery cell;

[0008] The pre-crosslinked insulating film has a melting point of 60-80°C, a pre-crosslinking degree of ≥90%, and an insulation resistance of ≥1.0*10 10 Ω.cm;

[0009] Step 2: Pre-fix the laid insulating film on the back of the battery cell at a pre-fixing temperature of ≤80°C;

[0010] Step 3: Lay the welding tape on the busbars on the back of the cell along the length of the busbars.

[0011] Step 4: Laser weld the welding ribbons at the PAD points of the main grid lines, so that several battery cells are connected in series to form a battery string.

[0012] Preferably, in step 1, the pre-crosslinked insulating film is cut into strips according to the position and shape of the main grid opening on the battery screen;

[0013] The material of the pre-crosslinked insulating film is POE insulating film.

[0014] Further preferably, in step 1, the melting point of the pre-crosslinked insulating adhesive film is 75° C. and the pre-crosslinking degree is 95%.

[0015] Preferably, in step 1, when laying the insulating film, a spacing of ≥0.3 mm is maintained between the insulating film and the main grid lines, and between the insulating film and the PAD points.

[0016] Further preferably, in step 1, when laying the insulating film, a spacing of 0.3-0.5 mm is maintained between the insulating film and the main grid lines, and between the insulating film and the PAD points.

[0017] Preferably, in step 2, the pre-fixing method is to use bottom plate heating or infrared heating of the welding platform.

[0018] Further preferably, step 2 specifically includes: treating the battery cell with the insulating film in a 70° C. oven for 5 seconds and then taking it out, so that the insulating film is pre-fixed on the back of the battery cell.

[0019] Preferably, in step 3, the soldering ribbon is a flat soldering ribbon, and its soldering temperature needs to be ≥185°C.

[0020] Preferably, in step 4, the lasers of one or more laser heads of the laser equipment are positioned on the PAD point of the main grid line to perform laser welding on the welding strip at the PAD point of the main grid line. The laser length is 3-20 cm (adjustable according to the height of the laser equipment), the laser width is 0.1-2 mm (adjustable according to the size of the PAD point of the battery cell), and the laser power is 1000-4000 W (adjustable according to the actual welding situation).

[0021] Preferably, the preparation method of a back-contact photovoltaic module of the present invention further includes step 5, laying a front packaging film on the front cover plate, and laying the front of the battery string on the front packaging film; laying the back packaging film and the back cover plate on the back of the battery string in sequence, and then laminating; installing the frame and the junction box.

[0022] The present invention also discloses a back-contact photovoltaic module, which is prepared by the method for preparing a back-contact photovoltaic module described above in the present invention.

[0023] Compared with the prior art, the present invention has at least the following beneficial effects:

[0024] The present invention lays a pre-crosslinked POE insulating film before laying the welding tape (conventional welding tape). The POE insulating film has a low melting point (60°C to 80°C), ultra-low fluidity (high pre-crosslinking degree, pre-crosslinking degree up to 90%-100%), and high insulation resistance (≥1.0*10 10 Ω.cm), and then the laid POE insulating film is pre-fixed at low temperature (pre-fixing temperature is not higher than 80°C) to the back of the battery cell to play the role of insulating and separating the positive and negative electrode grid lines (and the spacing between the pre-fixed insulating film and the main grid lines and PAD points is controlled within the range of 0.3-0.5mm), thereby replacing the process of printing insulating glue and solder paste using silk screen equipment as required by CN116995109A; and then combining the more precise laser welding process for positioning welding to replace the conventional welding process (such as infrared welding or bottom plate heating welding) of CN116995109A. In this way, the preparation method of the present invention has the following advantages:

[0025] On the one hand, there is no need to use the silk screen line equipment and insulating glue, solder paste and other materials required by CN116995109A. Compared with the low-temperature solder strip used in CN116995109A, the conventional solder strip used in the present invention has lower cost, so the equipment cost and material cost of the present invention are greatly reduced; moreover, the present invention does not need to add additional low-temperature solder paste printing, pre-curing and other processes as in CN116995109A, which can improve the production efficiency of the component and further reduce the production cost of the component.

[0026] On the other hand, the preparation method of the present invention lays an insulating film with a low melting point, high pre-crosslinking degree and high insulation, and combines it with low-temperature pre-fixing (and ensuring that the spacing between the pre-fixed insulating film and the main grid line and PAD point is controlled within the range of 0.3-0.5mm) and laser welding; therefore, during the preparation process, the pre-fixed insulating film will not be offset to ensure its better insulation effect, nor will it cause the insulating film to flow to the PAD point and cause poor welding, and the product will not warp due to thermal stress, so it can greatly improve the product yield of the back-contact photovoltaic module. Therefore, the preparation method of the present invention can obtain a back-contact photovoltaic module with both low cost and high yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the partial structure of the back side of a solar cell after being processed in step 1 of the preparation method of a back-contact photovoltaic module of the present invention.

[0028] Figure 2 for Figure 1 Schematic diagram of the local enlarged structure.

[0029] Figure 3 This is a structural schematic diagram of the laser welding process in step 4 of the method for preparing a back-contact photovoltaic module of the present invention.

[0030] Figure 4 This is a graph showing the EL (electroluminescence) test data of the back-contact photovoltaic laminate prepared in Example 1.

[0031] Figure 5 This is a graph showing the EL test data of the back-contact photovoltaic laminate prepared in Comparative Example 2.

[0032] Description of the accompanying drawings: battery cell 1; busbar 11; positive busbar 111; negative busbar 112; PAD point 12; insulating film 2; laser head 3. DETAILED DESCRIPTION

[0033] 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.

[0034] Example 1

[0035] A method for preparing a back-contact photovoltaic module according to this embodiment is described in detail in Figure 1-3 , comprising the following preparation steps:

[0036] Step 1: Place the cell 1 on the welding platform, cut the pre-crosslinked insulating film 2 into strips according to the position and shape of the main grid opening on the cell screen, and lay the cut strip insulating film 2 on the back of the cell 1 so that the laid insulating film 2 covers the fine grid lines on the back of the cell 1 and exposes the main grid lines 11 on the back of the cell 1 and the PAD points 12 on the main grid lines 11 (such as Figure 1-2 As shown), to isolate the positive and negative grid lines on the back of the battery cell 1.

[0037] In step 1, the cell 1 is a back-contact cell 1, that is, its positive and negative electrode grid lines are both located on the back of the cell 1, and the positive and negative electrode grid lines both include main grid lines 11 (such as negative electrode main grid lines 112 and positive electrode main grid lines 111) and fine grid lines (such as negative electrode fine grid lines and positive electrode fine grid lines). A number of PAD points 12 (welding points) are spaced apart on the main grid lines 11. The specific arrangement of the positive and negative electrode grid lines on the back of the cell 1 is referred to the prior art and will not be repeated here.

[0038] In step 1, the pre-crosslinked insulating film 2 is a POE insulating film (such as the POE insulating film provided by Foster Film Manufacturer), and the pre-crosslinked POE insulating film has a melting point of 75°C, a pre-crosslinking degree of 95%, and an insulation resistance of ≥1.0*10 10 Ω.cm (such as 1.0*10 14 Ω.cm).

[0039] In step 1, when laying the insulating film 2 , it is necessary to ensure that a spacing of 0.3-0.5 mm (eg, 0.3 mm) is maintained between the insulating film 2 and the busbar 11 , and between the insulating film 2 and the PAD point 12 .

[0040] Step 2: Use the bottom plate heating or infrared heating method of the welding platform to pre-fix the laid insulating film 2. The pre-fixing heating temperature is not higher than 80°C.

[0041] In step 2 of this embodiment, the specific process of pre-fixing the laid insulating film 2 is: placing the battery cell 1 with the laid insulating film 2 in a 70°C oven for 5 seconds and then taking it out to pre-fix the insulating film 2 on the back of the battery cell 1.

[0042] Due to the low melting point, ultra-low fluidity (its pre-crosslinking degree is as high as 95%), and high insulation properties of the insulating film 2, and the pre-fixing temperature of the insulating film 2 is not higher than 80°C, when the insulating film 2 is pre-fixed in step 2, the insulating film 2 will not change position (that is, during the pre-fixing process, the insulating film 2 will not be offset due to melting flow), ensuring that the pre-fixed insulating film 2 can play a better insulating role, and ensuring that the pre-fixed insulating film 2 will not flow to the PAD point 12 and have a negative impact on subsequent welding; moreover, the low-temperature pre-fixing of the insulating film 2 will not cause the battery cell 1 to warp.

[0043] Step 3: Lay flat solder strips on each busbar 11 on the back side of the solar cell 1 along the length direction of the busbar 11 .

[0044] Step 4: Adjust the angle of the laser device to locate the laser at the PAD point 12 of the main grid line 11, and laser weld the welding strip at the PAD point 12 of the main grid line 11. Through welding, several battery cells 1 are connected in series to form a battery string.

[0045] In step 4 of this embodiment, the laser length of the laser device is 6 cm, the laser width is 0.8 mm, and the laser power is 2100 W.

[0046] In step 4, the laser equipment can use one or more sets of laser heads 3 to perform laser welding to accurately weld the welding strips at the PAD points 12 of the main grid lines 11 (such as Figure 3 As shown in the figure, laser welding provides more precise positioning and minimizes thermal stress, enabling precise welding of the solder strip at the PAD point 12 of the busbar 11 without affecting other locations on the back of the cell 1. This ensures that the pre-fixed insulating film 2 is not affected by the laser (and does not damage the pre-fixed insulating film 2), further ensuring that the pre-fixed insulating film 2 provides better insulation and further preventing warping of the cell 1.

[0047] Step 5: Apply the front encapsulation film on the front cover plate, and lay the front of the battery string on the front encapsulation film; apply the back encapsulation film and the back cover plate on the back of the battery string in sequence, and then put it into the laminator for lamination at 148°C to obtain a back-contact photovoltaic laminate.

[0048] Step 6: After conventional installation work such as frame and junction box is performed on the back-contact photovoltaic laminate, the back-contact photovoltaic module of this embodiment is obtained.

[0049] Example 2

[0050] The preparation method of a back-contact photovoltaic module of this embodiment has the following preparation steps:

[0051] In step 1 of this embodiment, the pre-crosslinking degree of the pre-crosslinked insulating adhesive film is 90%.

[0052] Comparative Example 1

[0053] The preparation method of a back-contact photovoltaic module in this comparative example has the following preparation steps as specifically described in Example 1. The difference between the comparative example and the example is as follows:

[0054] In step 1 of this comparative example, the insulating film laid has a melting point of 90°C or above (such as 95°C), a pre-crosslinking degree of less than 15% (such as 10%), and an insulation resistance of less than 1.0*10 15 Ω.cm (such as 1.0*10 14 Ω.cm) of POE insulation film.

[0055] In step 2 of this comparative example, the cell with the insulating film laid thereon is placed in a 100° C. oven for 5 seconds and then taken out to pre-fix the insulating film on the back of the cell.

[0056] Comparative Example 2

[0057] The preparation method of a back-contact photovoltaic module in this comparative example has the following preparation steps as specifically described in Example 1. The difference between the comparative example and the example is as follows:

[0058] In step 4 of this comparative example, conventional infrared welding or bottom plate heating welding (such as conventional infrared welding) is used to replace the laser welding in Example 1.

[0059] Comparative Examples 3-9

[0060] Comparative Examples 3-9 are a method for preparing a back-contact photovoltaic module. The preparation steps thereof are specifically referred to Example 1. The difference between the method and the example is that:

[0061] The pre-crosslinking degrees of the pre-crosslinked insulating adhesive films in step 1 of comparative examples 3-9 were 60%, 65%, 70%, 75%, 80%, 85%, and 88%, respectively.

[0062] Performance Testing

[0063] 1. The EL (electroluminescence) test results of the back contact photovoltaic laminate prepared in step 5 of Examples 1 and 2 showed no abnormality, the power could be tested normally, and the EL test results passed (such as Figure 4 shown).

[0064] In comparative example 1, after taking out the solar cells from the oven in step 2, it was found that the laid insulating film had a high melting point and high fluidity (pre-crosslinking degree was less than 15%), and the insulating film had an increased pre-fixing temperature, so the position of the pre-fixed insulating film changed or shifted, and could not achieve the purpose of isolating the positive and negative pole grid lines, and could not play a good insulating role. Moreover, the insulating film of comparative example 1 flowed to the PAD point of the main grid line, and the subsequent welding work could not be carried out normally, resulting in the EL test result of the back contact photovoltaic laminate of comparative example 1 being NG (failed).

[0065] In Comparative Example 2, the welding range of the conventional welding process cannot be accurately controlled, and the melting point temperature of the conventional welding ribbon must be ≥185°C. Therefore, during conventional welding and when the welding range cannot be controlled, the insulating film melts, and the original laying position of the insulating film changes or shifts, making it difficult to play a good insulation role. The melting also affects the subsequent welding, resulting in the EL test result of the back contact photovoltaic laminate of Comparative Example 2 being NG (such as Figure 5 shown).

[0066] 2. We conducted multiple sets of warpage tests on the laser-welded cells of Example 1 and the conventionally welded cells of Comparative Example 2. We found that the warpage of the cells of Example 1 was significantly reduced, resulting in a passing result. Specific warpage test data is shown in Table 1 below.

[0067] Table 1

[0068]

[0069] 3. In addition, the present invention uses this low melting point, high pre-crosslinking degree and high insulation insulating film because:

[0070] ① The applicant's testing revealed that when solar cells are bonded (pre-fixed) to the adhesive film, the critical temperature at which thermal stress (thermal expansion and contraction) causes deformation and warping of the cell is approximately 80°C. When the pre-fixing temperature of the adhesive film exceeds 80°C, this leads to a mismatch in the coefficient of thermal expansion (CTE), inducing thermal stress. When this thermal stress exceeds the material's yield strength, plastic deformation or warping occurs. The lowest melting point of the particles within the adhesive film is approximately 60°C. When the pre-fixing temperature of the adhesive film is below 60°C, the film is less likely to undergo cross-linking, resulting in poor adhesion and an inability to properly pre-fix the film to the cell. Therefore, a melting point of 60°C-80°C is optimal for insulating adhesive films.

[0071] ② In addition, the applicant's tests found that: in the preparation method of the back-contact photovoltaic module of the present invention, when laying the insulating film, it is necessary to ensure that a spacing of about 0.3-0.5mm is retained between the insulating film and the busbar, and between the insulating film and the PAD point. The insulating film must also have ultra-low fluidity (≥90% pre-crosslinking degree) to ensure that the insulating film will not flow onto the busbar or PAD point during pre-fixing and affect the welding effect. After multiple sets of tests, it was verified that the pre-crosslinking degree of the insulating film reached 90% or above, and when pre-fixed at a temperature of 80°C or below, the flow distance of the insulating film will not exceed 0.3mm; the specific test data are shown in Table 2 below.

[0072] Table 2

[0073]

[0074] Referring to Table 2, it can be seen that: as the pre-crosslinking degree of the insulating film laid by Comparative Examples 3-9 and Example 2 gradually increases, the displacement distance of the insulating film pre-fixed in step 2 on the back of the battery cell becomes smaller and smaller; therefore, the insulating film pre-fixed in Example 2 can better insulate and isolate the positive and negative poles, and can effectively avoid poor welding caused by the insulating film flowing to the PAD point of the main grid line, thereby greatly improving the product yield of the back-contact photovoltaic module.

[0075] In summary, by comparing the methods for preparing back-contact photovoltaic modules of Comparative Example 1 (high melting point, low pre-crosslinking degree insulating film + laser welding process), Comparative Example 2 (low melting point, high pre-crosslinking degree and high insulation insulating film + conventional welding process), Comparative Examples 3-9 (low melting point, low pre-crosslinking degree and high insulation insulating film + laser welding process), and Examples 1-2 (low melting point, high pre-crosslinking degree and high insulation insulating film + laser welding process), it was found that:

[0076] Only when the preparation method of the back-contact photovoltaic module of Example 1-2 is adopted (the pre-fixing temperature of the insulating film does not exceed 80°C, and the spacing between the pre-fixed insulating film and the main grid line and PAD point is controlled within the range of 0.3-0.5mm, and it is combined with a conventional soldering tape), and combined with a low-melting-point, high-pre-crosslinking and high-insulation insulating film + laser welding process, can it be achieved that the cost is greatly reduced (the present invention does not require the use of silk screen equipment and insulating glue, solder paste and other materials required by CN116995109A, and the cost of the conventional soldering tape used in the present invention is lower than that of low-temperature soldering tape, and the equipment cost and material cost are greatly reduced; moreover, the present invention does not need to add additional low-temperature solder paste printing, pre-curing and other processes like CN116995109A, which can improve the module production efficiency and further reduce the module production cost), and achieve the technical effect of greatly improving the yield of the back-contact photovoltaic module, thereby obtaining a back-contact photovoltaic module with both low cost and high yield.

[0077] 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.

[0078] 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 back-contact photovoltaic module, characterized in that: The method comprises the following preparation steps: Step 1: Cut the pre-crosslinked insulating film and lay the cut insulating film on the back of the back contact battery cell so that the insulating film covers the fine grid lines on the back of the battery cell and exposes the main grid lines and PAD points on the main grid lines on the back of the battery cell to isolate the positive and negative grid lines on the back of the battery cell; The pre-crosslinked insulating film has a melting point of 60-80°C, a pre-crosslinking degree of ≥90%, and an insulation resistance of ≥1.0*10 10 Ω.cm; Step 2: Pre-fix the laid insulating film on the back of the battery cell at a pre-fixing temperature of ≤80°C; Step 3: Lay the welding tape on the busbars on the back of the cell along the length of the busbars. Step 4: Laser weld the welding ribbons at the PAD points of the main grid lines, so that several battery cells are connected in series to form a battery string.

2. The method for preparing a back-contact photovoltaic module according to claim 1, wherein: In step 1, the pre-crosslinked insulating film is cut into strips according to the position and shape of the main grid opening on the battery screen; The material of the pre-crosslinked insulating film is POE insulating film.

3. The method for preparing a back-contact photovoltaic module according to claim 1 or 2, characterized in that: In step 1, the melting point of the pre-crosslinked insulating film is 75° C. and the pre-crosslinking degree is 95%.

4. The method for preparing a back-contact photovoltaic module according to claim 1, wherein: In step 1, when laying the insulating film, a spacing of ≥0.3 mm is maintained between the insulating film and the main grid lines, and between the insulating film and the PAD points.

5. The method for preparing a back-contact photovoltaic module according to claim 4, characterized in that: In step 1, when laying the insulating film, a spacing of 0.3-0.5 mm is maintained between the insulating film and the main grid line, and between the insulating film and the PAD point.

6. The method for preparing a back-contact photovoltaic module according to claim 1, wherein: In step 2, the pre-fixing method is to use the bottom plate heating or infrared heating of the welding platform; Step 2 specifically includes: treating the cell with the insulating film in a 70° C. oven for 5 seconds and then taking it out to pre-fix the insulating film on the back of the cell.

7. The method for preparing a back-contact photovoltaic module according to claim 1, characterized in that: In step 3, the soldering ribbon is a flat soldering ribbon, and its soldering temperature needs to be ≥185°C.

8. The method for preparing a back-contact photovoltaic module according to claim 1, wherein: In step 4, the lasers of one or more laser heads of the laser equipment are positioned on the PAD point of the main grid line to perform laser welding on the welding strip at the PAD point of the main grid line. The laser length is 3-20 cm, the laser width is 0.1-2 mm, and the laser power is 1000-4000 W.

9. The method for preparing a back-contact photovoltaic module according to claim 1, characterized in that: The method further includes step 5, laying a front packaging film on the front cover plate, and laying the front of the battery string on the front packaging film; laying a back packaging film and a back cover plate on the back of the battery string in sequence, and then laminating them; and installing a frame and a junction box.

10. A back contact photovoltaic module, characterized in that: It is prepared by the method for preparing a back-contact photovoltaic module according to any one of claims 1 to 9.

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