Solar Cells and Photovoltaic Modules

Abstract

SUMMARY OF THE DISCLOSURE Embodiments of the invention relate to the field of photovoltaic power generation and, in particular, disclose solar cells and photovoltaic modules. [Solution] Here, the solar cell includes a substrate, a front electrode provided on the front surface of the substrate, and a back electrode provided on the back surface of the substrate, the front electrode has a plurality of front main grids and a plurality of front sub-grids, each front sub-grid is electrically connected to the plurality of front main grids, the number of front main grids is 6 to 20, the number of front sub-grids is 45 to 75, the back electrode has a plurality of back surface main grids and a plurality of back surface sub-grids, each back surface sub-grid is electrically connected to the plurality of back surface main grids, the number of back surface main grids is 6 to 20, the number of back surface sub-grids is 50 to 80, and at least one of the plurality of front main grids has 4 to 10 first spot welds.

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS) This application claims priority to Chinese patent application No. 202210784277.2, entitled “Solar Cell and Photovoltaic Module,” filed on June 28, 2022, the entire disclosure of which is incorporated herein by reference.

[0002] FIELD OF THEINVENTION FIELD OF THE DISCLOSURE Embodiments of the present invention relate to the field of photovoltaic power generation, and in particular to solar cells and photovoltaic modules. [Background technology]

[0003] With the development of photovoltaic power generation technology, the power generation efficiency of solar cells is constantly improving. In particular, with the emergence of bifacial solar cells, both sides of the solar cell are used simultaneously, and power can be generated not only from the light directly incident on the front side of the solar cell, but also from the light scattered and refracted on the back side of the solar cell, which effectively increases the power generation efficiency of solar cells.

[0004] In solar cells, grid line electrodes are formed by printing with paste. Since the cost of printing paste is high, it is important to reduce the unit consumption of printing paste in order to reduce the cost of solar cells. However, in some cases, the area of ​​spot welds in grid line electrodes in solar cells is large, which is disadvantageous to reducing the unit consumption of printing paste in solar cells. Summary of the Invention

[0005] SUMMARY OF THE DISCLOSURE Embodiments of the present application aim to provide solar cells and photovoltaic modules.

[0006] In an embodiment of the present application, a solar cell is provided, the solar cell including a substrate, a front electrode provided on a front surface of the substrate, and a back electrode provided on a back surface of the substrate, the front electrode includes a plurality of front main grids and a plurality of front sub-grids, each of the front sub-grids being electrically connected to the plurality of front main grids, the number of the front main grids being 6 to 20, the number of the front sub-grids being 45 to 75, the back electrode includes a plurality of back main grids and a plurality of back sub-grids, each of the back sub-grids being electrically connected to the plurality of back main grids, the number of the back main grids being 6 to 20, and the number of the back sub-grids being 50 to 80, at least one of the plurality of front main grids has 4 to 10 first spot welds, and at least one of the plurality of back main grids has 4 to 10 corresponding second spot welds, and an area of ​​the first spot welds is smaller than an area of ​​the corresponding second spot welds.

[0007] In an embodiment of the present application, a photovoltaic module is further provided, the photovoltaic module including a battery string, a sealing adhesive film, and a cover plate, the battery string being formed by connecting a plurality of solar cells, each solar cell including a substrate, a front electrode provided on a front surface of the substrate, and a back electrode provided on a back surface of the substrate, the front electrode including a plurality of front main grids and a plurality of front sub-grids, each front sub-grid being electrically connected to the plurality of front main grids, the number of the front main grids being 6 to 20, the number of the front sub-grids being 45 to 75, the back electrode including a plurality of back main grids and a plurality of back sub-grids being electrically connected to the plurality of front main grids, and a front sub-grid, each of which is electrically connected to a plurality of back main grids, the number of the back main grids being 6 to 20, the number of the back sub-grids being 50 to 80, at least one of the plurality of front main grids having 4 to 10 first spot welds and at least one of the plurality of back main grids having 4 to 10 corresponding second spot welds, an area of ​​the first spot welds being smaller than an area of ​​the corresponding second spot welds, a sealing adhesive film being used to cover a surface of the battery string, and a cover plate being used to cover a surface of the sealing adhesive film facing away from the battery string.

[0008] In some embodiments, the plurality of first spot welds include two third spot welds located on the edges of the front main grid and a plurality of fourth spot welds located between the two third spot welds, where the area of ​​the third spot welds is greater than the area of ​​the fourth spot welds, and the plurality of second spot welds include two fifth spot welds located on the edges of the back main grid and a plurality of sixth spot welds located between the two fifth spot welds, where the area of ​​the fifth spot welds is greater than the area of ​​the sixth spot welds.

[0009] In some embodiments, the area of ​​the third spot weld is no more than 2 / 3 the area of ​​the fifth spot weld.

[0010] In some embodiments, the third spot weld and the fifth spot weld are both rectangular, and the ratio of the length of the third spot weld to the length of the fifth spot weld and the ratio of the width of the third spot weld to the width of the fifth spot weld are both greater than 2 / 3 and less than 1.

[0011] In some embodiments, the area of ​​the fourth spot weld is no more than 2 / 3 the area of ​​the sixth spot weld.

[0012] In some embodiments, the third spot weld and the fourth spot weld are both rectangular, the length and width of the third spot weld are 0.5 mm to 0.7 mm and 0.9 mm to 1.1 mm, respectively, and the length and width of the fourth spot weld are 0.3 mm to 0.5 mm and 0.7 mm to 0.9 mm, respectively.

[0013] In some embodiments, the fifth spot weld and the sixth spot weld are both rectangular, the fifth spot weld has a length and width of 0.7 mm to 0.9 mm and 1.1 mm to 1.3 mm, respectively, and the sixth spot weld has a length and width of 0.5 mm to 0.7 mm and 0.7 mm to 0.9 mm, respectively.

[0014] In some embodiments, the length of the first spot weld in the first direction is less than or equal to 2 / 3 of the length of the corresponding second spot weld in the first direction, and the first direction is parallel to the extension direction of the front main grid.

[0015] In some embodiments, the length of the first spot weld in the first direction is greater than the width of the front main grid, and the length of the second spot weld in the first direction is greater than the width of the back main grid.

[0016] In some embodiments, the pitch between adjacent first spot welds and the pitch between adjacent second spot welds are both between 15 mm and 20 mm. [Brief description of the drawings]

[0017] One or more embodiments are illustratively illustrated in the accompanying drawing figures, but these illustrative illustrations are not intended to be limiting of the embodiments, and in the accompanying drawing figures, like reference numbers refer to similar parts and, unless otherwise noted, the drawings are not drawn to scale. [Figure 1] FIG. 1 is a diagram showing the structure of a solar cell according to some embodiments of the present application. [Diagram 2] FIG. 2 is a diagram showing the structure of a front electrode in a solar cell according to some embodiments of the present application. [Diagram 3] FIG. 3 is an enlarged view of the structure of part A in FIG. [Figure 4] FIG. 4 is a diagram showing the structure of a back electrode in a solar cell according to some embodiments of the present application. [Diagram 5] FIG. 5 is an enlarged view of the structure of part B in FIG. [Figure 6] FIG. 6 shows the pattern of the main grid of the front electrode as the solar cell according to some embodiments of the present application is printed step by step. [Figure 7] FIG. 7 shows the sub-grid pattern of the front electrode as the solar cell according to some embodiments of the present application is printed step by step. [Figure 8] FIG. 8 shows the pattern of the main grid of the back electrode as the solar cell according to some embodiments of the present application is printed step by step. [Figure 9] FIG. 9 shows the sub-grid pattern of the back electrode as the solar cell according to some embodiments of the present application is printed step by step. [Figure 10] FIG. 10 is a diagram showing a cross-sectional structure of a photovoltaic module according to some embodiments of the present application. [Figure 11] FIG. 11 is a diagram showing a cross-sectional structure of another photovoltaic module according to some embodiments of the present application. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] In the solar cell and photovoltaic module provided by the embodiment of the present application, the area of ​​the first spot welds on the front main grid is smaller than the area of ​​the corresponding second spot welds on the back main grid, thereby reducing the unit consumption of printing paste during the manufacture of the solar cell. By adopting a method in which the areas of the corresponding spot welds on the front and back sides are the same, it is possible to avoid the soldering tension between the back spot welds and the PV ribbon being significantly smaller than the soldering tension between the corresponding spot welds on the front side and the PV ribbon. In addition, after reducing the area of ​​the first spot welds on the front main grid, the soldering tension between the first spot welds and the PV ribbon can still meet the requirements. Therefore, by reducing the area of ​​the first spot welds on the front main grid, the soldering tension between the front and back spot welds of the substrate and the PV ribbon can be both required, and the unit consumption of printing paste for the solar cell can be reduced.

[0019] In some embodiments, the plurality of first spot welds includes two third spot welds located at the ends of the front main grid and a plurality of fourth spot welds located between the two third spot welds, the area of ​​the third spot welds being greater than the area of ​​the fourth spot welds. The plurality of second spot welds includes two fifth spot welds located at the ends of the back main grid and a plurality of sixth spot welds located between the two fifth spot welds, the area of ​​the fifth spot welds being greater than the area of ​​the sixth spot welds. In this way, by making the area of ​​the spot welds at the ends of the main grid greater than the area of ​​the spot welds located in the middle of the main grid, it is possible to effectively prevent poor soldering or misalignment of soldering at the ends of the main grid.

[0020] In some embodiments, the area of ​​the third spot weld is 2 / 3 or less than the area of ​​the fifth spot weld. By making the area of ​​the third spot weld 2 / 3 or less than the area of ​​the fifth spot weld, the soldering tension between the third spot weld and the PV ribbon can be kept within a range close to the soldering tension between the fifth spot weld and the PV ribbon. This allows the soldering tension between the front and back spot welds and the PV ribbon to meet the requirements, while minimizing the unit consumption of the printing paste for the solar cell.

[0021] In some embodiments, the third spot weld and the fifth spot weld are both rectangular, and the ratio of the length of the third spot weld to the length of the fifth spot weld and the ratio of the width of the third spot weld to the width of the fifth spot weld are both greater than 2 / 3 and less than 1. This allows the area of ​​the third spot weld to be kept equal to or less than 2 / 3 of the area of ​​the fifth spot weld by simultaneously reducing the length and width dimensions of the third spot weld.

[0022] In some embodiments, the area of ​​the fourth spot weld is 2 / 3 or less than the area of ​​the sixth spot weld. By making the area of ​​the fourth spot weld 2 / 3 or less than the area of ​​the sixth spot weld, the soldering tension between the fourth spot weld and the PV ribbon can be kept within a range close to the soldering tension between the sixth spot weld and the PV ribbon. This allows the soldering tension between the front and back spot welds and the PV ribbon to meet the requirements while minimizing the unit consumption of the solar cell printing paste.

[0023] In some embodiments, the length of the first spot weld in the first direction is no more than 2 / 3 of the length of the corresponding second spot weld in the first direction, and the first direction is parallel to the extension direction of the front main grid, thereby significantly reducing the soldering tension between the first spot weld and the PV ribbon by reducing the dimension of the first spot weld in the first direction.

[0024] In some embodiments, the length of the first spot weld in the first direction is greater than the width of the front main grid, and the length of the second spot weld in the first direction is greater than the width of the back main grid, such that the spot welds can protrude from both sides of the main grid in the extension direction of the main grid, which helps with positioning when soldering the PV ribbons.

[0025] In some embodiments, the pitch between adjacent first spot welds and the pitch between adjacent second spot welds are both 15 mm to 20 mm, which avoids the effect on the soldering process caused by the pitch between adjacent spot welds being too small, and avoids the effect on the connection of PV ribbons in solar cells caused by the pitch between adjacent spot welds being too large.

[0026] Hereinafter, each embodiment of the present disclosure will be described in detail with reference to the drawings. However, as will be understood by those skilled in the art, in order to allow the reader to better understand the present application, many technical details are proposed in each embodiment of the present disclosure, but the technical solution that the present disclosure seeks to protect can be realized without these technical details and various changes and modifications based on the following embodiments.

[0027] In order to clarify the purpose, technical solution and advantages of the embodiments of the present application, the embodiments of the present application will be described in detail below in conjunction with the drawings. However, as can be understood by those skilled in the art, many technical details are proposed in the embodiments of the present application in order to allow the reader to better understand the present application, but the technical solution claimed for protection by the present application can be realized without these technical details and various changes and modifications based on the following embodiments. The division of the following embodiments is for the convenience of explanation and does not constitute a limitation on the specific embodiments of the present application. The embodiments can be combined with or referenced to each other without discrepancy.

[0028] In bifacial solar cells, grid line electrodes are provided on both the front and back surfaces of the substrate. The grid line electrodes on the front and back surfaces of the solar cell substrate are both provided with main grids and sub-grids that intersect (usually perpendicular to each other), and the main grids and sub-grids are generally printed using a metal paste (usually silver paste) to obtain a desired pattern, and then sintered to form the desired pattern. The sub-grids in the grid line electrodes are used to guide the current, and the main grids in the grid line electrodes are used to collect and merge the currents in the sub-grids. In order to increase the power generation efficiency of solar cells and reduce costs, multi-busbar technology (MBB, Multi-Busbar) is usually adopted, that is, multiple main grids are printed simultaneously on the front and back surfaces of the substrate, and the number of main grids is usually 9 or more, for example, 9 main grids, 12 main grids, 13 main grids, 15 main grids, 16 main grids, 18 main grids, or 20 main grids. The multi-busbar technology reduces the number of sub-grids by increasing the number of main grids, thereby expanding the pitch between the sub-grids and reducing costs. By reducing the sub-grid width, the shading area and the unit consumption of silver paste are reduced, and by installing spot welding parts on the main grid, the soldering accuracy and soldering tension strength when soldering the solar cell and the PV ribbon are ensured.

[0029] In solar cells using multi-busbar technology, the design of the main grids on the front and back of the substrate is almost the same, and the spot weld area of ​​the main grid is set large to ensure that the soldering tension between the solar cell and the PV ribbon meets the requirements, and to comprehensively consider the factors of soldering misalignment.

[0030] In some cases, the areas of the spot welds on the front and back of the solar cell substrate are both large, and the soldering tensile strength requirements can be met, so the method of maintaining the corresponding spot welds on the front and back is basically adopted. However, according to the test results, when the areas of the corresponding spot welds on the front and back of the substrate are the same, the soldering tensile strength between the spot welds on the back of the substrate and the PV ribbon is only about 70% of the soldering tensile strength between the corresponding spot welds on the front and PV ribbon. In other words, when the method of maintaining the areas of the corresponding spot welds on the front and back of the substrate is adopted, the soldering tensile strength between the spot welds on the front of the substrate and the PV ribbon and the soldering tensile strength between the corresponding spot welds on the back of the substrate and the PV ribbon are obviously different. The reason for this significant difference is the difference in the soldering methods adopted on the front and back of the substrate and the system of electrode paste printed on the front and back of the substrate. In practice, after the solar cell is transferred to the soldering station, the PV ribbons on the front and back of the substrate are heated by infrared lamps to carry out soldering. However, in order to prevent heat loss, the soldering board on the back side of the board has a certain temperature preservation, and the heat dissipation on the back side of the board is not timely, so the PV ribbon on the back side of the board is not cooled in a timely manner during soldering, which ultimately leads to the PV ribbon on the back side of the solar cell board exhibiting a low tensile strength. In addition, in reality, the types of printing paste on the front and back sides of the board are different, and different types of printing paste have different composition components, which leads to different soldering tensile strengths of the PV ribbons at different spot welds on the front and back sides of the board.

[0031] The correspondence of the spot welds refers to the positional correspondence of the spot welds in the main grids on the front and back of the board in the direction perpendicular to the board. In practice, the spot welds in the main grids on the front and back of the board may be in strict positional correspondence in the direction perpendicular to the board (the projections of the two in the direction perpendicular to the board at least partially overlap) or may be shifted by a certain distance. In the case of being shifted, it is possible to avoid hidden cracks and fragments in the solar cell due to overlapping of soldering stress concentration areas on the board. In addition, the spot welds in the main grids on the front and back of the board may be in strict correspondence in terms of quantity or may differ within a certain range.

[0032] The test results show that, when the corresponding spot welds on the front and back of the board and the soldering tension of the PV ribbon meet the requirements at the same time, the area of ​​the spot welds on the front of the board can be reduced to reduce the unit consumption of the printing paste for the solar cell. In addition, when the soldering tension of the spot welds on the front of the board and the soldering tension of the PV ribbon and the soldering tension of the spot welds on the back of the board are kept the same, the reduction rate of the area of ​​the spot welds on the front side compared with the area of ​​the corresponding spot welds on the back side can reach more than 1 / 3. In this way, after reducing the area of ​​the spot welds on the front side, not only can the unit consumption of the printing paste for the solar cell be reduced, but the soldering tension of the spot welds on the front side and the PV ribbon on the PV ribbon does not affect the reliability requirement, that is, the soldering tension of the spot welds on the front side and the PV ribbon on the PV ribbon can still meet the requirement.

[0033] Therefore, some embodiments of the present application include a substrate 10, a front electrode 20 provided on a front surface of the substrate 10, and a rear electrode 30 provided on a rear surface of the substrate 10, the front electrode 20 having a plurality of front main grids 21 and a plurality of front sub-grids 22, each front sub-grid 22 being electrically connected to a plurality of front main grids 21, the number of the front main grids 21 being 6 to 20, the number of the front sub-grids 22 being 45 to 75, the rear electrode 30 having a plurality of rear main grids 31 and a plurality of rear sub-grids 32, A solar cell is provided in which each back surface sub-grid 32 is electrically connected to a plurality of back surface main grids 31, the number of back surface main grids 31 is 6 to 20, the number of back surface sub-grids 32 is 50 to 80, at least one of the plurality of front surface main grids 21 has 4 to 10 first spot welds 211, and at least one of the plurality of back surface main grids 31 has corresponding 4 to 10 second spot welds 311, and the area of ​​the first spot welds 211 is smaller than the area of ​​the corresponding second spot welds 311.

[0034] The number of front subgrids 22 is 35 to 100, and the number of back subgrids 32 is 38 to 120. The number of front subgrids 22 may be 35 to 46, 46 to 58, 58 to 69, 69 to 81, 81 to 90, or 90 to 100. The number of back subgrids 32 may be 38 to 49, 49 to 64, 64 to 73, 73 to 89, 89 to 108, or 108 to 120. The number of front subgrids 22 may be 35, 41, 45, 50, 55, 60, 65, 70, 75, 83, 91, or 99. The number of rear surface subgrids 32 may be 39, 44, 48, 50, 55, 60, 65, 70, 75, 83, 91, 99, 112 or 120.

[0035] The substrate 10 is the basis for forming the grid line electrode of the solar cell, and is usually a silicon substrate. Metal paste can be printed on the front and back surfaces of the substrate 10 to form grid line electrodes with a specific pattern. The grid line electrode printed on the front surface of the substrate 10 is the front electrode 20, and the grid line electrode printed on the back surface of the substrate 10 is the back electrode 30. Usually, the front surface of the substrate 10 is the light receiving surface, which receives solar energy from directly incident light, and the back surface of the substrate 10 is the backlight surface, which receives solar energy from scattered and refracted light. In practice, the number of the front main grid 21 and the back main grid 31 may be 9, 12, 13, 15, 16, 18 or 20. The number of the front sub-grid 22 may be 45, 50, 55, 60, 65, 70 or 75. The number of rear sub-grids 32 may be 50, 55, 60, 65, 70, 75, or 80. The solar cell provided by some embodiments of the present application may be configured in the form of an integrated cell or a half-split cell. A half-split cell is formed by splitting an integrated cell into two along a direction perpendicular to the main grid.

[0036] The width of the front subgrid 22 is between 10 μm and 80 μm. The width of the front subgrid 22 may be between 10 μm and 22 μm, between 22 μm and 34 μm, between 34 μm and 46 μm, between 46 μm and 58 μm, between 58 μm and 70 μm, between 70 μm and 80 μm, or between 20 μm and 60 μm. The width of the front subgrid 22 may be 13 μm, 19 μm, 26 μm, 35 μm, 47 μm, 61 μm, or 73 μm.

[0037] The height of the front subgrid 22 is between 6 μm and 18 μm. The height of the front subgrid 22 may be between 6 μm and 9.3 μm, between 9.3 μm and 12.4 μm, between 12.4 μm and 15.1 μm, or between 15.1 μm and 18 μm. The height of the front subgrid 22 may be 6.1 μm, 7.3 μm, 8.2 μm, 9.5 μm, 10.4 μm, 11.1 μm, 12.6 μm, 14.6 μm, 16.3 μm, 17.6 μm, or 18 μm.

[0038] The width of the rear surface sub-grid 32 is 10 μm to 80 μm. The width of the rear surface sub-grid 32 may be 10 μm to 23 μm, 23 μm to 33 μm, 33 μm to 45 μm, 45 μm to 54 μm, 54 μm to 68 μm, 68 μm to 80 μm, or 20 μm to 60 μm. The width of the rear surface sub-grid 32 may be 12 μm, 21 μm, 28 μm, 38 μm, 52 μm, 63 μm, or 78 μm.

[0039] The height of the rear surface sub-grid 32 is 6 μm to 18 μm. The height of the rear surface sub-grid 32 may be 6 μm to 9.1 μm, 9.1 μm to 12.3 μm, 12.3 μm to 15.6 μm, or 15.6 μm to 18 μm. The height of the rear surface sub-grid 32 may be 6.2 μm, 7.1 μm, 8.3 μm, 9.4 μm, 10.1 μm, 11.3 μm, 12.7 μm, 14.8 μm, 16.4 μm, 17.1 μm, or 18 μm.

[0040] The width of the front main grid 21 is 15 μm to 100 μm. The width of the front main grid 21 may be 15 μm to 24 μm, 24 μm to 42 μm, 42 μm to 53 μm, 53 μm to 65 μm, 65 μm to 82 μm, 82 μm to 100 μm, or 18 μm to 80 μm. The width of the front main grid 21 may be 18 μm, 26 μm, 38 μm, 51 μm, 69 μm, 81 μm, or 98 μm.

[0041] The height of the front main grid 21 is 3 μm to 12 μm. The height of the front main grid 21 may be 3 μm to 5.3 μm, 5.3 μm to 8.4 μm, 8.4 μm to 10.1 μm, or 10.1 μm to 12 μm. The height of the front main grid 21 may be 3.1 μm, 4.3 μm, 5.2 μm, 6.5 μm, 7.4 μm, 8.1 μm, 9.6 μm, 10.6 μm, 11.3 μm, 11.6 μm, or 12 μm.

[0042] The width of the rear surface main grid 31 is 15 μm to 100 μm. The width of the rear surface main grid 31 may be 15 μm to 26 μm, 26 μm to 43 μm, 43 μm to 54 μm, 54 μm to 66 μm, 66 μm to 84 μm, 84 μm to 100 μm, or 18 μm to 80 μm. The width of the rear surface main grid 31 may be 18 μm, 26 μm, 38 μm, 51 μm, 69 μm, 81 μm, or 98 μm.

[0043] The height of the rear surface main grid 31 is 3 μm to 12 μm. The height of the rear surface main grid 31 may be 3 μm to 4.1 μm, 4.1 μm to 6.3 μm, 6.3 μm to 8.6 μm, or 8.6 μm to 12 μm. The height of the rear surface main grid 31 may be 3.2 μm, 4.1 μm, 5.3 μm, 6.4 μm, 7.1 μm, 8.3 μm, 9.7 μm, 10.8 μm, 11.4 μm, or 12 μm.

[0044] In addition, the number of spot welds in a solar cell should not be too large. If the number of spot welds is too large, the unit consumption of printing paste will be too large, and the light-shielding area will be too large. In the sealing process of a photovoltaic module, if the number of spot welds is too large, it will also affect the soldering process. If the grid line electrode has 4 to 10 spot welds, the unit consumption of printing paste can be saved and the light-shielding area can be avoided to be too large. In practice, the first spot welds 211 in the front main grid 21 may be 4, 5, 7, 9 or 10, and the second spot welds 311 in the back main grid 31 may be 4, 5, 7, 9 or 10.

[0045] Furthermore, the correspondence between the first spot weld 211 and the second spot weld 311 refers to whether the projections of the first spot weld 211 and the second spot weld 311 in the direction perpendicular to the substrate 10 at least partially overlap, or whether the first spot weld 211 and the second spot weld 311 are in the same range of the grid position section, for example, the range of the leading and trailing spot welds or the range of the middle spot weld. The range of the leading and trailing spot welds includes spot welds that are within 10% of the length of the solar cell from the end of the main grid, and the location of the middle spot weld is outside of 10% of the length of the solar cell from the end of the main grid.

[0046] In the solar cell provided by some embodiments of the present application, the area of ​​the first spot welds 211 on the front main grid 21 is smaller than the area of ​​the corresponding second spot welds 311 on the back main grid 31, thereby reducing the unit consumption of printing paste during the manufacture of the solar cell. This maintains the areas of the corresponding spot welds on the front and back sides to be consistent, thereby avoiding the soldering tension between the back spot welds and the PV ribbon being significantly smaller than the soldering tension between the corresponding spot welds on the front side and the PV ribbon. In addition, after reducing the area of ​​the first spot welds 211 on the front main grid 21, the soldering tension between the first spot welds 211 and the PV ribbon still meets the requirements. Therefore, by reducing the area of ​​the first spot welds 211 on the front main grid 21, the soldering tension between the front and back spot welds of the substrate 10 and the PV ribbons can be both met, while reducing the unit consumption of printing paste for the solar cell.

[0047] In some embodiments of the present application, the plurality of first spot welds 211 may include two third spot welds 2111 located at an edge of the front main grid 21 and a plurality of fourth spot welds 2112 located between the two third spot welds 2111, where the area of ​​the third spot welds 2111 is greater than the area of ​​the fourth spot welds 2112. The plurality of second spot welds 311 may include two fifth spot welds 3111 located at an edge of the back main grid 31 and a plurality of sixth spot welds 3112 located between the two fifth spot welds 3111, where the area of ​​the fifth spot welds 3111 is greater than the area of ​​the sixth spot welds 3112.

[0048] 1 to 5, the third spot weld 2111 and the fifth spot weld 3111 are spot welds located at the ends of the main grid, and the fourth spot weld 2112 and the sixth spot weld 3112 are spot welds located at intermediate positions between both ends of the main grid. The area of ​​the third spot weld 2111 is larger than the area of ​​the fourth spot weld 2112, and the area of ​​the fifth spot weld 3111 is larger than the area of ​​the sixth spot weld 3112. In other words, the area of ​​two spot welds located at the ends of the same main grid is larger than the area of ​​another spot weld located between the two spot welds at the ends.

[0049] By making the area of ​​the spot welds located at the ends of the front main grid 21 and the back main grid 31 larger than the area of ​​the spot welds located in the middle, it is possible to effectively prevent poor soldering or misalignment of the soldering at the ends of the front main grid 21 and the back main grid 31 and to ensure the soldering effect between the ends of the front main grid 21 and the back main grid 31 and the PV ribbons.

[0050] Continuing to refer to Figures 3 and 5, the ends of the front main grid 21 and the back main grid 31 both have a branch electrode structure. By making the ends of the front main grid 21 and the back main grid 31 into a branch structure, the front sub-grid 22 which is cut close to the outside and the back sub-grid 32 which is cut close to the outside can be avoided from the PV ribbons, and the risk of hidden cracks and soldering defects at the ends of the grid line electrodes can be reduced when sealing the photovoltaic module.

[0051] In addition, test results show that while maintaining the soldering tension of the corresponding spot welds on the front and back sides of the substrate 10 and the PV ribbon consistent, the reduction ratio of the area of ​​the front spot welds to the area of ​​the corresponding spot welds on the back side can reach more than 1 / 3. In an embodiment where the spot welds are generally rectangular, the areas of the leading and trailing spot welds on the back side main grid 31 of the substrate 10 can be 0.70 mm 2 ~1.20mm 2 The area of ​​the leading and trailing spot welds in the front main grid 21 of the substrate 10 may be 0.40 mm 2 ~0.70mm 2 The area of ​​the intermediate spot welds in the rear main grid 31 of the substrate 10 may be 0.35 mm 2 ~0.70mm 2 The area of ​​the middle spot welds in the front main grid 21 of the substrate 10 may be 0.20 mm 2 ~0.45mm 2 may be also possible.

[0052] Thus, in some embodiments of the present application, the area of ​​the third spot weld 2111 may be ⅔ or less than the area of ​​the fifth spot weld 3111.

[0053] That is, the area of ​​the leading and trailing spot welds located at the ends of the front main grid 21 is no more than 2 / 3 of the area of ​​the leading and trailing spot welds located at the ends of the back main grid 31. By reducing the area of ​​the third spot weld 2111 to no more than 2 / 3 of the area of ​​the fifth spot weld 3111, the soldering tensile strength between the corresponding spot welds on the front and back of the substrate 10 and the PV ribbon can be kept in a close range, and the soldering tensile strength between the front and back spot welds and the PV ribbon can all be met, while minimizing the unit consumption of printing paste for solar cells.

[0054] As shown in Figures 3 and 5, the third spot weld 2111 and the fifth spot weld 3111 can both be set to a rectangular shape, and the ratio of the length of the third spot weld 2111 to the length of the fifth spot weld 3111, and the ratio of the width of the third spot weld 2111 to the width of the fifth spot weld 3111 are both greater than 2 / 3 and less than 1.

[0055] Typically, the shape of the spot weld is rectangular, the length of the spot weld refers to the dimension of the spot weld in the extension direction of the main grid, and the width of the spot weld refers to the dimension of the spot weld in the extension direction of the sub-grid, and the width of the spot weld is larger than the length to ensure accuracy in aligning with the PV ribbons.

[0056] By making the ratio of the length of the third spot weld 2111 to the length of the fifth spot weld 3111, and the ratio of the width of the third spot weld 2111 to the width of the fifth spot weld 3111 both greater than 2 / 3 and less than 1, the area of ​​the third spot weld 2111 can be reduced to a range that is less than 2 / 3 of the area of ​​the fifth spot weld 3111.

[0057] In other embodiments, the spot welds may be diamond or triangular in shape, and the spot welds on the front and back sides may be the same or different in shape.

[0058] Additionally, the area of ​​the fourth spot weld 2112 may be ⅔ or less of the area of ​​the sixth spot weld 3112 .

[0059] In other words, the area of ​​the middle spot weld located at the middle of the front main grid 21 is ⅔ or less of the area of ​​the middle spot weld located at the middle of the back main grid 31. Similarly, by making the area of ​​the fourth spot weld 2112 ⅔ or less of the area of ​​the sixth spot weld 3112, the soldering tensile force between the fourth spot weld 2112 and the PV ribbon can be kept close to the soldering tensile force between the sixth spot weld 3112 and the PV ribbon. Because the area of ​​the spot weld located at the middle of the grid line electrode is small, the area of ​​the spot weld can be reduced simply by reducing the dimension of the spot weld in one direction.

[0060] In some embodiments, the third spot weld 2111 and the fourth spot weld 2112 may both be rectangular, with the length (dimension shown as L1 in FIG. 3) and width (dimension shown as W1 in FIG. 3) of the third spot weld 2111 being 0.5 mm to 0.7 mm and 0.9 mm to 1.1 mm, respectively, and the length (dimension shown as L2 in FIG. 3) and width (dimension shown as W2 in FIG. 3) of the fourth spot weld 2112 being 0.3 mm to 0.5 mm and 0.7 mm to 0.9 mm, respectively.

[0061] In addition, the fifth spot weld 3111 and the sixth spot weld 3112 may both be rectangular, and the length (dimension shown as L3 in Figure 5) and width (dimension shown as W3 in Figure 5) of the fifth spot weld 3111 are 0.7 mm to 0.9 mm and 1.1 mm to 1.3 mm, respectively, and the length (dimension shown as L4 in Figure 5) and width (dimension shown as W4 in Figure 5) of the sixth spot weld 3112 are 0.5 mm to 0.7 mm and 0.7 mm to 0.9 mm, respectively.

[0062] In some embodiments of the present application, the length of the first spot weld 211 in the first direction is less than 2 / 3 of the length of the corresponding second spot weld 311 in the first direction, and the first direction is parallel to the extension direction of the front main grid 21.

[0063] That is, the dimension of the first spot weld 211 in the extension direction of the front main grid 21 is at least ⅓ smaller than the dimension of the corresponding second spot weld 311 in the extension direction of the front main grid 21. Note that it is mainly the dimension of the spot weld in the extension direction of the main grid that affects the soldering tensile force between the spot weld and the PV ribbon. Therefore, by focusing on reducing the dimension of the first spot weld 211 in the extension direction of the main grid, it is possible to achieve a significant effect of reducing the soldering tensile force between the first spot weld 211 and the PV ribbon.

[0064] In addition, the length in the first direction of the first spot welds 211 may be greater than the width of the front main grid 21, and the length in the first direction of the second spot welds 311 may be greater than the width of the back main grid 31.

[0065] By making the dimension of the spot weld in the extension direction of the main grid larger than the width of the main grid, the spot weld can be made to protrude from both sides of the main grid in the extension direction of the main grid, which helps with positioning when welding the PV ribbons.

[0066] In some embodiments of the present application, the pitch between adjacent first spot welds 211 and the pitch between adjacent second spot welds 311 may both be between 15 mm and 20 mm.

[0067] The pitch between adjacent spot welds refers to the distance between two adjacent spot welds. By keeping the pitch between adjacent first spot welds 211 and the pitch between adjacent second spot welds 311 within the range of 15 mm to 20 mm, it is possible to avoid the pitch between adjacent spot welds being too small to affect the soldering process, and to avoid the pitch between adjacent spot welds being too large to affect the connection effect between the PV ribbon and the solar cell.

[0068] Also, the solar cell provided by some embodiments of the present application may be manufactured in the form of a half-split cell. That is, the solar cell on which the grid line electrodes are printed is cut into two pieces along the symmetrical axis of the two front electrodes 20, and then the two pieces are connected to form the solar cell. When printing the grid line electrodes, a step-by-step printing process can be adopted. When manufacturing the front electrode 20, the front main grid 21 of the front electrode 20 is printed first (as shown in FIG. 6 ). The number of the front main grid 21 may be 16, and the number of the first spot welds 211 in one front main grid 21 is six (including two rectangular third spot welds 2111 and four rectangular fourth spot welds 2112). The third spot welds 2111 at the end (near the branch) of the front main grid 21 are 0.6 mm long and 1.0 mm wide, and the fourth spot welds 2112 at the middle position of the front main grid 21 are 0.4 mm long and 0.8 mm wide. Then, the front sub-grid 22 of the front electrode 20 is printed (as shown in FIG. 7), and the printed substrate 10 is sintered. The manufacturing method of the rear electrode 30 is similar to that of the front electrode 20. First, the rear main grid 31 of the rear electrode 30 is printed (as shown in FIG. 8). The number of the rear main grid 31 may be 16, and the number of the second spot welds 311 in one rear main grid 31 is six (including two rectangular fifth spot welds 3111 and four rectangular sixth spot welds 3112). The fifth spot welds 3111 at the end (near the branch) of the rear main grid 31 are 0.8 mm long and 1.2 mm wide, and the sixth spot welds at the middle position of the rear main grid 31 are 0.6 mm long and 0.8 mm wide. Then, the rear sub-grid 32 of the rear electrode 30 is printed (as shown in FIG. 9), and the printed substrate 10 is sintered.

[0069] Table 1 below shows the test results of the soldering tensile strength between each of the front and back spot welds and the PV ribbon after the area of ​​the front spot welds of the solar cell substrate 10 according to some embodiments of the present application is reduced. Here, the area of ​​the leading and trailing spot welds (i.e., the third spot weld 2111) of the front main grid 21 located on the front side of the substrate 10 is 0.6 mm 2 The area of ​​the middle spot weld (i.e., the fourth spot weld 2112) of the front main grid 21 located on the front side of the substrate 10 is 0.32 mm 2 The area of ​​the leading and trailing spot welds (i.e., the fifth spot welds 3111) of the rear main grid 31 located on the rear surface of the substrate 10 is 0.96 mm 2 The area of ​​the middle spot weld (i.e., the sixth spot weld 3112) of the rear main grid 31 located on the rear surface of the substrate 10 is 0.48 mm 2 The leading and trailing spot welds are the first and sixth spot welds, and the middle spot welds are the second to fifth spot welds. The number of front main grids 21 and back main grids 31 in a single solar cell is 16, and three front main grids 21 and three back main grids 31 were selected to explain the results of the tensile force test. The acceptable tensile force values ​​for the front and back spot welds of the substrate 10 are both 0.8 N. The minimum allowable spot weld area is 0.10 mm 2 The minimum allowable length of a spot weld is 0.2 mm, and the minimum allowable width of a spot weld is 0.5 mm.

[0070] Table 1: Record of soldering tensile strength test results after reducing the area of ​​the front spot welds according to the embodiments of the present application JPEG0007604676000001.jpg74161

[0071] At the same time, Table 2 below shows the results of soldering tensile strength tests conducted in a manner that keeps the areas of corresponding spot welds on the front and back of the boards in some comparative examples consistent. The areas of the leading and trailing spot welds of the front main grid located on the front of the board and the leading and trailing spot welds of the back main grid located on the back of the board are both 0.96 mm 2 The areas of the intermediate spot welds of the front main grid located on the front side of the board and the intermediate spot welds of the rear main grid located on the rear side of the board are both 0.48 mm 2 The leading and trailing spot welds are the first and sixth spot welds, and the middle spot welds are the second to fifth spot welds. The number of rear main grids and front main grids of a single solar cell is 16, and three front main grids 21 and three rear main grids 31 were selected from them to explain the results of the tensile force test.

[0072] Table 2: Results of soldering tensile test for comparative example where the areas of the corresponding spot welds on the front and back sides are the same JPEG0007604676000002.jpg72161

[0073] Comparing the tensile test results of the PV ribbons at different spot welds in Table 1 and Table 2, it can be seen that when the areas of the corresponding spot welds on the front and back sides of the substrate 10 are the same, the tensile test results of the PV ribbons at the spot welds on the front main grid 21 are obviously larger than the tensile test results of the PV ribbons at the spot welds on the back main grid 31. At the same time, in some embodiments of the present application, after reducing the area of ​​the spot welds on the front main grid 21, the tensile test results of the PV ribbons at the spot welds on the front main grid 21 and the tensile test results of the PV ribbons at the spot welds on the back main grid 31 can be kept in a close range. In addition, the reduction ratio of the area of ​​the spot welds on the front main grid 21 to the area of ​​the corresponding spot welds on the back main grid 31 can reach more than 1 / 3.

[0074] Table 3 below shows test results of the soldering tensile strength between each front and back spot weld and PV ribbon after the area of ​​the front spot weld of the solar cell substrate 10 according to some embodiments of the present application is reduced to a small range. Here, the areas of the leading and trailing spot welds (i.e., the third spot weld 2111) and the middle spot weld (i.e., the fourth spot weld 2112) of the front main grid 21 located on the front side of the substrate 10 are all 0.15 mm 2 The areas of the first and last spot welds (i.e., the fifth spot weld 3111) and the middle spot weld (i.e., the sixth spot weld 3112) of the rear main grid 31 located on the rear surface of the substrate 10 are all 0.25 mm 2 The leading and trailing spot welds are the first and sixth spot welds, and the middle spot welds are the second to fifth spot welds. The number of front main grids 21 and back main grids 31 of a single solar cell is 16 each, and three front main grids 21 and three back main grids 31 were selected from them to explain the results of the tensile force test.

[0075] Table 3: Results of soldering tensile strength test after reducing the area of ​​the front spot welds according to the embodiment of the present application JPEG0007604676000003.jpg81161

[0076] Tables 4 and 5 below show the results of solder tensile strength tests of the spot welds and PV ribbons in several comparative examples where the areas of the front and back spot welds of the battery substrate 10 are the same. Here, Table 4 shows the results of solder tensile strength tests of the front and back spot welds of the substrate 10 (including the first spot weld 211 of the front main grid 21 and the second spot weld 311 of the back main grid 31) where the areas of both are 0.25 mm 2The tensile test results were obtained when the number of front main grids 21 and back main grids 31 in a single solar cell was 16, and three front main grids 21 and three back main grids 31 were selected from the total to explain the tensile test results. Table 5 shows that the areas of the front and back spot welds of the substrate 10 (including the first spot welds 211 of the front main grid 21 and the second spot welds 311 of the back main grid 31) were both 0.15 mm 2 The number of front main grids 21 and rear main grids 31 in a single solar cell is 16 each, and three front main grids 21 and three rear main grids 31 were selected from them to explain the results of the tensile test.

[0077] Table 4. The areas of the front and back spot welds in the comparative example are both 0.15 mm 2 Soldering tension test result record table when JPEG0007604676000004.jpg73161

[0078] Table 5. The front and back spot weld areas of the comparative example are both 0.25 mm 2 Soldering tension test result record table when JPEG0007604676000005.jpg74161

[0079] From the tensile test results of the PV ribbons at different spot welds in Table 4, it can be seen that when the spot weld area of ​​the front main grid 21 is small, the tensile test results of the PV ribbons at different spot welds of the front main grid 21 can still meet the requirements. On the other hand, when the spot weld area of ​​the back main grid 31 is small, the tensile test results of the PV ribbons at some spot welds of the back main grid 31 may not meet the requirements.

[0080] In addition, Table 5 shows the tensile test results of the PV ribbon at different spot welds when the areas of the front and back spot welds of the substrate 10 are the same in some forms. Comparing the tensile test results of the PV ribbon at different spot welds in Tables 3, 4 and 5, it can be seen that when the area of ​​the back spot welds of the substrate 10 is constant, the area of ​​the front spot welds of the substrate 10 can be reduced at a certain rate relative to the area of ​​the back spot welds. This shows that the unit consumption of the printing paste can actually be reduced by reducing the area of ​​the front spot welds of the substrate 10. In addition, while reducing the unit consumption of the printing paste, the soldering tensile strength of the different spot welds on the front and back of the substrate 10 and the PV ribbons do not affect the requirement.

[0081] As shown in FIG. 10 and FIG. 11 , some embodiments of the present application further provide a photovoltaic module including a battery string 100, a sealing adhesive film 200, and a cover plate 300, in which the battery string 100 is formed by connecting a plurality of solar cells 110, and each solar cell 110 adopts the solar cell of the above embodiment, that is, each solar cell 110 includes a substrate 10, a front electrode 20 provided on the front surface of the substrate 10, and a back electrode 30 provided on the back surface of the substrate 10, the front electrode 20 includes a plurality of front main grids 21 and a plurality of front sub-grids 22, each front sub-grid 22 is electrically connected to a plurality of front main grids 21, the number of the front main grids 21 is 6 to 20, the number of the front sub-grids 22 is 45 to 75, and the back electrode 30 is a plurality of solar cells 110. the rear surface main grid 31 and a plurality of rear surface sub-grids 32, each of which is electrically connected to the plurality of rear surface main grids 31, the number of the rear surface main grids 31 being 6 to 20, the number of the rear surface sub-grids 32 being 50 to 80, at least one of the plurality of front surface main grids 21 having 4 to 10 first spot welds 211, at least one of the plurality of rear surface main grids 31 having corresponding 4 to 10 second spot welds 311, the area of ​​the first spot welds 211 being smaller than the area of ​​the corresponding second spot welds 311, the sealing adhesive film 200 being used to cover a surface of the battery string 100, and the cover plate 300 being used to cover a surface of the sealing adhesive film 200 facing away from the battery string 110.

[0082] Here, the solar cell 110 in FIG. 10 is arranged along a direction inclined with respect to the cover plate 300, while the solar cell 110 in FIG.

[0083] In the cell string 100 used in the photovoltaic module, the area of ​​the first spot weld 211 on the front main grid 21 of each solar cell 110 is smaller than the area of ​​the corresponding second spot weld 311 on the back main grid 31, thereby reducing the unit consumption of printing paste for the solar cells. This avoids the situation where the soldering tensile force between the back spot weld and the PV ribbon is significantly smaller than the soldering tensile force between the corresponding front spot weld and the PV ribbon when a method is used in which the areas of the corresponding front and back spot welds are the same.

[0084] Those skilled in the art will understand that the above embodiments are specific examples of realizing the present application, but that in practice various changes in form and details are possible without departing from the spirit and scope of the present application.

Claims

1. A substrate, a front electrode provided on a front surface of the substrate, and a rear electrode provided on a rear surface of the substrate, the front electrode includes a plurality of front main grids and a plurality of front sub-grids, each of the front sub-grids is electrically connected to a plurality of the front main grids, and the number of the front main grids is 6 to 20; the rear electrode includes a plurality of rear main grids and a plurality of rear sub-grids, each of the rear sub-grids is electrically connected to a plurality of the rear main grids, and the number of the rear main grids is 6 to 20; an end of the front main grid and an end of the rear main grid have a branch electrode structure; At least one of the plurality of front main grids has 4 to 10 first spot welds, and at least one of the plurality of back main grids has 4 to 10 corresponding second spot welds, the area of ​​the first spot welds being smaller than the area of ​​the corresponding second spot welds; the plurality of first spot welds include two third spot welds located at ends of the front main grid and a plurality of fourth spot welds located between the two third spot welds, an area of ​​the third spot welds being larger than an area of ​​the fourth spot welds; the second spot welds include two fifth spot welds located at ends of the rear main grid and a plurality of sixth spot welds located between the two fifth spot welds, the fifth spot welds having an area larger than an area of ​​the sixth spot welds; an area of ​​the third spot weld is 2 / 3 or less of an area of ​​the fifth spot weld; the third spot weld and the fifth spot weld are both rectangular, and a ratio of a length of the third spot weld to a length of the fifth spot weld and a ratio of a width of the third spot weld to a width of the fifth spot weld are both greater than 2 / 3 and less than 1; The area of ​​the fourth spot weld is 2 / 3 or less of the area of ​​the sixth spot weld. A solar cell characterized by:

2. The third spot weld and the fourth spot weld are both rectangular, the length and width of the third spot weld are 0.5 mm to 0.7 mm and 0.9 mm to 1.1 mm, respectively, and the length and width of the fourth spot weld are 0.3 mm to 0.5 mm and 0.7 mm to 0.9 mm, respectively. The solar cell according to claim 1 .

3. The fifth spot weld and the sixth spot weld are both rectangular, the fifth spot weld has a length and a width of 0.7 mm to 0.9 mm and 1.1 mm to 1.3 mm, respectively, and the sixth spot weld has a length and a width of 0.5 mm to 0.7 mm and 0.7 mm to 0.9 mm, respectively. The solar cell according to claim 1 .

4. a length of the first spot weld in a first direction is ⅔ or less of a length of the corresponding second spot weld in the first direction, and the first direction is parallel to an extension direction of the front main grid; The solar cell according to claim 1 .

5. a length of the first spot weld in the first direction is greater than a width of the front main grid, and a length of the second spot weld in the first direction is greater than a width of the rear main grid; The solar cell according to claim 4 .

6. The pitch between adjacent first spot welds and the pitch between adjacent second spot welds are both 15 mm to 20 mm. The solar cell according to claim 1 .

7. the number of the front subgrids is between 35 and 100, and the number of the back subgrids is between 38 and 120; The solar cell according to claim 1 .

8. the width of either the front subgrid or the back subgrid is between 10 μm and 80 μm; The solar cell according to claim 1 or 7.

9. the width of either the front sub-grid or the back sub-grid is between 20 μm and 60 μm; The solar cell according to claim 1 or 7.

10. the height of either the front subgrid or the back subgrid is between 6 μm and 18 μm; The solar cell according to claim 1 or 7.

11. The width of either the front main grid or the back main grid is 15 μm to 100 μm; The solar cell according to claim 1 .

12. The width of either the front main grid or the back main grid is 18 μm to 80 μm. The solar cell according to claim 1 or 11.

13. The height of either the front main grid or the back main grid is 3 μm to 12 μm. The solar cell according to claim 1 or 11.

14. A battery string, a sealing adhesive film, and a cover plate, the battery string is formed by connecting a plurality of solar cells, each of the solar cells includes a substrate, a front electrode provided on a front surface of the substrate, and a back electrode provided on a back surface of the substrate, the front electrode includes a plurality of front main grids and a plurality of front sub-grids, each of the front sub-grids is electrically connected to a plurality of the front main grids, the number of the front main grids is 6 to 20, the back electrode includes a plurality of back main grids and a plurality of back sub-grids, each of the back sub-grids is electrically connected to a plurality of the back main grids, the number of the back main grids is 6 to 20, an end of the front main grid and an end of the back main grid have a branch electrode structure, At least one of the plurality of front main grids has 4 to 10 first spot welds, and at least one of the plurality of back main grids has 4 to 10 corresponding second spot welds, the area of ​​the first spot welds being smaller than the area of ​​the corresponding second spot welds; the plurality of first spot welds include two third spot welds located at ends of the front main grid and a plurality of fourth spot welds located between the two third spot welds, an area of ​​the third spot welds being larger than an area of ​​the fourth spot welds; the second spot welds include two fifth spot welds located at ends of the rear main grid and a plurality of sixth spot welds located between the two fifth spot welds, the fifth spot welds having an area larger than an area of ​​the sixth spot welds; an area of ​​the third spot weld is 2 / 3 or less of an area of ​​the fifth spot weld; the third spot weld and the fifth spot weld are both rectangular, and a ratio of a length of the third spot weld to a length of the fifth spot weld and a ratio of a width of the third spot weld to a width of the fifth spot weld are both greater than 2 / 3 and less than 1; an area of ​​the fourth spot weld is 2 / 3 or less of an area of ​​the sixth spot weld; The sealing adhesive film is used to cover the surface of the battery string, The cover plate is used to cover the surface of the sealing adhesive film that is away from the battery string. A photovoltaic module comprising:

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