Screen printing plate assembly, patterned electrode and solar cell

Abstract

The utility model relates to the technical field of solar cells, in particular to a printing screen assembly, a patterned electrode and a solar cell. The printing screen assembly comprises a first printing screen and a second printing screen, wherein the first printing screen comprises a main grid pattern structure and a first harpoon line pattern structure arranged at the end part of the main grid pattern structure; the second printing screen comprises an auxiliary grid pattern structure and a second harpoon line pattern structure, and part of the auxiliary grid pattern structure intersects with the second harpoon line pattern structure; wherein the main grid pattern structure is perpendicular to the auxiliary grid pattern structure, and the first harpoon line pattern structure and the second harpoon line pattern structure form a harpoon pattern structure. According to the printing screen assembly, the grid breaking probability of a fish fork structure during graphical electrode printing of a solar cell can be effectively reduced, especially the grid breaking probability of adjacent fish fork lines corresponding to the same main grid, and the quality of the solar cell is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of solar cells, in particular to a printing screen component, a graphic electrode and a solar cell. Background Art

[0002] Printing quality is an important factor affecting the quality of solar cells and is related to the yield and efficiency of the cell production line.

[0003] At present, the multi-busbar technology has been promoted and further developed to more busbars. There are more and more harpoon structures in the positive and back structures of solar cells, and the width of the harpoon line is getting thinner and thinner. During the printing process, it is easy to have problems such as current collection failure caused by the broken harpoon structure, which affects the quality of solar cells. Utility Model Content

[0004] The purpose of the embodiments of the present application is to provide a printed screen assembly, a patterned electrode and a solar cell, which can effectively reduce the probability of broken grids of the harpoon structure when printing the patterned electrode of the solar cell, especially the probability of broken grids of adjacent harpoon lines corresponding to the same main grid, thereby improving the quality of the solar cell.

[0005] In a first aspect, an embodiment of the present application provides a printing screen assembly for printing a patterned electrode of a solar cell, the printing screen assembly comprising:

[0006] A first printing screen, the first printing screen comprising a main grid pattern structure and a first harpoon line pattern structure provided at an end of the main grid pattern structure;

[0007] a second printing screen, the second printing screen comprising a secondary grid pattern structure and a second harpoon line pattern structure, a portion of the secondary grid pattern structure intersecting with the second harpoon line pattern structure;

[0008] The main grid pattern structure and the secondary grid pattern structure are perpendicular to each other, and the first harpoon line pattern structure and the second harpoon line pattern structure form a harpoon pattern structure.

[0009] Furthermore, the first printing screen further comprises a pad pattern structure connected to the main grid pattern structure, the pad pattern structure is used for printing to form a pad, the pad is used for connecting the secondary grid obtained by printing the secondary grid pattern structure, and / or the pad is used for connecting the harpoon structure obtained by printing the harpoon pattern structure;

[0010] Alternatively, the second printing screen also includes a pad graphic structure connected to the secondary grid graphic structure, the pad graphic structure is used to print to form a pad, the pad is used to connect the main grid obtained by printing the main grid graphic structure, and / or the pad is used to connect the harpoon structure obtained by printing the harpoon graphic structure.

[0011] Furthermore, the mesh number of the second printing screen is greater than that of the first printing screen, the line diameter of the second printing screen is smaller than that of the first printing screen, and the film thickness of the second printing screen is greater than that of the first printing screen.

[0012] Optionally, the mesh number of the first printing screen is 430-520 mesh, the wire diameter of the first printing screen is 13.0μm-15.0μm, and the film thickness of the first printing screen is 2.0μm-4.0μm; and / or, the mesh number of the second printing screen is 500-600 mesh, the wire diameter of the second printing screen is 10.5μm-13.0μm, and the film thickness of the second printing screen is 3.0μm-4.0μm.

[0013] As a preferred implementation, the film thickness of the second printing screen in the intersection area of ​​the second harpoon line pattern structure and the secondary grid pattern structure is greater than the film thickness of the second printing screen in other areas.

[0014] In a second aspect, an embodiment of the present application provides a patterned electrode, which is printed using the printed screen assembly as described in the first aspect, and includes a first patterned electrode prepared using the first printed screen and a second patterned electrode prepared using the second printed screen, the first patterned electrode includes a main grid and a first harpoon line, the second patterned electrode includes a secondary grid and a second harpoon line, the main grid and the secondary grid are perpendicular to each other, and the first harpoon line and the second harpoon line form a harpoon structure.

[0015] Furthermore, the patterned electrode also includes a pad, and the pad includes a first pad and a second pad, the first pad is arranged at the intersection of the main grid, the auxiliary grid, and the harpoon structure; the second pad is arranged at the intersection of the main grid and the auxiliary grid.

[0016] Furthermore, the opening width of the harpoon structure is 1.0 mm to 2.0 mm.

[0017] As a preferred implementation, the opening width of the harpoon structure is 1.5 mm to 1.7 mm.

[0018] Furthermore, the line width of the first harpoon line is 25.0 μm to 45.0 μm, and the line width of the second harpoon line is 25.0 μm to 45.0 μm.

[0019] As a preferred implementation, the line width of the first harpoon line is 25.0 μm to 30.0 μm, and the line width of the second harpoon line is 25.0 μm to 30.0 μm.

[0020] In a third aspect, an embodiment of the present application provides a solar cell, wherein the solar cell includes a patterned electrode printed by the printing screen assembly described in the first aspect, or the solar cell includes the patterned electrode described in the second aspect.

[0021] Compared with the prior art, the beneficial effects of the embodiments of the present application are:

[0022] In an embodiment of the present application, a printing screen assembly for printing a graphic electrode of a solar cell includes a first printing screen having a first harpoon line graphic structure and a second printing screen having a second harpoon line graphic structure, and two printing screens are used to achieve the purpose of printing two harpoon lines in the harpoon structure separately. In the present application, by using two screens to print the two harpoon lines of the same harpoon structure respectively, the screen graphic structures corresponding to the adjacent harpoon lines corresponding to the same main grid are not blocked at the same time, which effectively avoids the problem of current collection being blocked due to the simultaneous break of the adjacent harpoon lines corresponding to the same main grid. Furthermore, the dry slurry blocking area is random and not fixed during the printing process, and two screens are used for printing, which greatly reduces the probability of the entire harpoon and the adjacent harpoon lines corresponding to the same main grid being broken at the same time. In summary, the embodiments of the present application divide the screen graphic structure corresponding to the harpoon structure into a first harpoon graphic structure and a second harpoon graphic structure through the design of the printed screen assembly, thereby effectively reducing the probability of broken grids of adjacent harpoon lines corresponding to the same main grid and the overall harpoon structure during the solar cell screen printing process, thereby reducing the probability of poor battery quality caused by the inability to collect current due to broken grids. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0024] Figure 1 It is a schematic diagram of the phenomenon of broken grid in the patterned electrode;

[0025] Figure 2 It is a schematic diagram of the principle of the effect of different types of broken grids of patterned electrodes on solar cells;

[0026] Figure 3 This is a comparison between a solar cell with a patterned electrode and a solar cell with a broken grid and a solar cell with a normal grid line;

[0027] Figure 4 is a schematic diagram of the structure of a printing screen assembly provided in an embodiment of the present application;

[0028] Figure 5 yes Figure 4The enlarged schematic diagram at A in the middle;

[0029] Figure 6 yes Figure 4 The enlarged schematic diagram of point B in the middle;

[0030] Figure 7 This is a schematic diagram of a patterned electrode printed by a printing screen assembly provided in an embodiment of the present application;

[0031] Figure 8 yes Figure 7 Enlarged schematic diagram at point C in the middle.

[0032] Reference numerals:

[0033] 1. First printed screen; 11. Main grid pattern structure; 12. First harpoon line pattern structure; 2. Second printed screen; 21. Sub-grid pattern structure; 22. Second harpoon line pattern structure; 31. First pad pattern structure; 32. Second pad pattern structure; 4. Patterned electrode; 41. Main grid; 42. Sub-grid; 43. Harpoon structure; 431. First harpoon line; 432. Second harpoon line; 44. Pad; 441. First pad; 442. Second pad. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0035] In the present application, the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings. These terms are mainly used to better describe the present application and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation.

[0036] In addition, some of the above terms may be used to express other meanings in addition to indicating orientation or positional relationship. For example, the term "on" may also be used to express a certain dependency or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in this application can be understood according to specific circumstances.

[0037] In addition, the terms "installed", "set", "provided with", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection, or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be an internal connection between two devices, elements, or components. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0038] In addition, the terms "first", "second", etc. are mainly used to distinguish different devices, elements or components (the specific types and structures may be the same or different), and are not used to indicate or imply the relative importance and quantity of the indicated devices, elements or components. Unless otherwise specified, "plurality" means two or more.

[0039] The technical solution provided in this application will be further described below in conjunction with embodiments and drawings.

[0040] During the screen printing process of the patterned electrode of the solar cell, the harpoon graphic structure and the main grid graphic structure or the sub-grid graphic structure are printed together using the printing screen printing paste in the related technology to obtain the corresponding patterned electrode. However, during the printing process of the patterned electrode of the solar cell, the movement of the scraper pushes the paste to overflow to the two sides of the screen graphic. After a certain period of time, due to the static state and the volatilization of the organic solvent in the paste, block-shaped dry paste is formed. Further, due to the movement and vibration of the machine, the dry paste falls off on both sides of the screen graphic. The positions on both sides of the screen graphic correspond to the positions of the harpoon lines. During the printing process, the movement direction of the scraper is perpendicular to the direction of the array of the harpoon graphic structure, and then the fallen dry paste is pushed to move to the side of the screen graphic. Therefore, the positions on both sides of the screen graphic are particularly prone to blockage, and then when printing the patterned electrode, the following problems occur. Figure 1 The linear continuous broken grid shown.

[0041] In the patterned electrode, the broken gate type can be divided into three types according to the broken gate line, and the effects of different gate line types on solar cells are also different. Figure 2 As shown, Figure 2 The figure shows three types of broken grids and their impact on solar cells. The first type of broken grid is that the adjacent harpoon lines corresponding to the same main grid are broken at the same time, and are classified as defective cells. Figure 2The right half of the harpoon line in the leftmost harpoon structure and the left half of the harpoon line in another harpoon structure adjacent to the harpoon structure are broken at the same time. In this case, the carriers of the sub-gate cannot be transmitted through any harpoon line, and the current collection is poor, then the photoelectric conversion efficiency is reduced, and the quality of the battery cell is degraded. In the second and third types of broken gates, the adjacent harpoon lines corresponding to the same main gate are not broken at the same time. Although the conversion efficiency is reduced, the battery can still collect the current collected by the sub-gate at the harpoon structure, and will not be classified as a defective cell. In summary, if the adjacent harpoon lines corresponding to the same main gate are not broken at the same time, although the photoelectric conversion efficiency will be reduced, it will not be classified as a defective cell; and if the adjacent harpoon lines corresponding to the same main gate are broken at the same time, it will be classified as a defective cell. Using the printed screen in the related technology, the resulting graphic electrode appears as follows Figure 1 The line type shown is broken continuously, that is, the adjacent harpoon lines corresponding to the same main grid are broken at the same time, which leads to poor current collection, and the corresponding positions of solar cells and battery modules are not collected and blackened, resulting in poor quality, such as Figure 3 shown.

[0042] Through in-depth analysis of the above-mentioned problems, the embodiments of the present application provide a printed screen assembly, a patterned electrode and a solar cell, which divide the harpoon graphic structure into a first harpoon line graphic structure and a second harpoon line graphic structure, which are arranged on different screens to reduce the impact of broken grid on the quality of solar cells.

[0043] In a first aspect, the present application provides a printing screen assembly for printing a patterned electrode of a solar cell, such as Figures 4 to 6 As shown, the printing screen assembly includes:

[0044] The first printing screen 1 comprises a main grid pattern structure 11 and a first harpoon line pattern structure 12 arranged at the end of the main grid pattern structure 11;

[0045] The second printing screen 2 includes a secondary grid pattern structure 21 and a second harpoon line pattern structure 22, and a portion of the secondary grid pattern structure 21 intersects with the second harpoon line pattern structure 22;

[0046] The main grid pattern structure 11 and the secondary grid pattern structure 21 are perpendicular to each other, and the first harpoon line pattern structure 12 and the second harpoon line pattern structure 22 form a harpoon pattern structure.

[0047] The first harpoon line graphic structure 12 and the second harpoon line graphic structure 22 refer to the graphic structures of half a harpoon, one of which is the left half harpoon line graphic structure and the other is the right half harpoon line graphic structure. The first harpoon line graphic structure 12 and the second harpoon line graphic structure 22 constitute a complete harpoon graphic structure.

[0048] In an embodiment of the present application, a printing screen assembly for printing a graphic electrode of a solar cell includes a first printing screen 1 having a first harpoon line graphic structure 12 and a second printing screen 2 having a second harpoon line graphic structure, and two printing screens are used to achieve the purpose of printing two harpoon lines in the harpoon structure separately. In the present application, by using two screens to print the two harpoon lines of the same harpoon structure respectively, the screen graphic structures corresponding to the adjacent harpoon lines corresponding to the same main grid are not blocked at the same time, which effectively avoids the problem of current collection being blocked due to the simultaneous breakage of adjacent harpoon lines. Furthermore, the dry slurry blocking area is random and not fixed during the printing process, and the use of two screens for printing greatly reduces the probability of the entire harpoon and the adjacent harpoon lines corresponding to the same main grid being broken at the same time. In summary, the embodiments of the present application divide the screen graphic structure corresponding to the harpoon structure into a first harpoon line graphic structure 12 and a second harpoon line graphic structure 22 through the design of the printed screen assembly, thereby effectively reducing the probability of broken grids of adjacent harpoon lines corresponding to the same main grid and the overall harpoon structure during the solar cell screen printing process, thereby reducing the probability of poor battery quality caused by the inability to collect current due to broken grids.

[0049] Furthermore, the main grid slurry and the sub-grid slurry are slurries with different functions. During printing, the printing speed and static drying time of the scraper are basically the same. By not replacing the main grid slurry and the sub-grid slurry at the same time, the slurries in the two screens will not become block dry slurries at the same time, which can further reduce the probability of simultaneous breakage of adjacent harpoon lines corresponding to the same main grid.

[0050] The printing screen assembly and its effects in this application are further described below in combination with a mathematical model.

[0051] The mathematical model is established as follows:

[0052] (1) The time for the slurry to become dry slurry is t, and the machine movement speed and mechanical vibration of the main grid and the auxiliary grid are the same, that is, the number of cells printed on the main grid screen and the auxiliary grid screen in the same time is the same.

[0053] (2) When the non-dry pulp of the fish fork is not smooth in ink penetration, due to the block of dry pulp on the side of the screen, the movement of the scraper will form the following Figure 1 Linear harpoon breakage. Assuming that the probability of adjacent harpoon lines corresponding to the same main grid breaking due to the movement of the scraper on the dry pulp during printing is a%, in actual production, a% ≤ 0.5%.

[0054] Case 1: Within a certain period of time, when the harpoon graphic structure is located on the main grid screen and is printed together with the secondary grid, or when the harpoon graphic structure is located on the secondary grid screen and is printed together with the main grid, the probability of the adjacent harpoon lines corresponding to the same main grid being broken at the same time due to the static slurry forming dry slurry shedding is a%, and a%≤0.5%. Assuming that the number of cells printed by the main grid screen is N1, and the number of cells printed by the secondary grid screen is N2 per unit time, N1+N2=N, and N is the total number of cells printed per unit time, then the number of defective cells with adjacent harpoon lines corresponding to the same main grid being broken at the same time is N×t×a%.

[0055] Case 2: Printing is performed using the printing screen assembly described in this application, then:

[0056] N1: the number of cells printed on the first printing screen per unit time;

[0057] N2: the number of cells printed on the second printing screen per unit time;

[0058] N1+N2=N.

[0059] The probability of adjacent harpoon lines corresponding to the same main grid is a%×a%, and the number of defective cells is (N1+N2)×t×a%×a%, and N1≈N2 (the number of cells printed in the same time is the same). In practice, because a%≤0.5%, a%×a%<a%.

[0060] Assuming t is 10 hours and 3500 solar cells are printed per hour, then:

[0061] In case 1, no matter the main grid and the harpoon structure are printed at the same time and then the secondary grid is printed, or the secondary grid and the harpoon structure are printed at the same time and then the main grid is printed, the number of solar cells with both left and right harpoons broken at the same time is: 10×3500×0.5%=175pcs.

[0062] In case 2, that is, using the printing screen assembly described in the present application, the left and right harpoon lines are printed separately using different screens, then the number of cells with the left and right harpoon lines broken at the same time is: 10×3500×0.5%×0.5%=87pcs.

[0063] That is, through the design of the printed screen assembly in the embodiment of the present application, the number of defective battery cells with both left and right harpoons broken at the same time was reduced by 175-87=88 pieces, that is, through the improvement of the present application, the defective rate of both left and right harpoons broken at the same time was reduced by half.

[0064] Furthermore, the present application is approximately as follows: the probability of the left and right harpoon lines breaking at the same time is reduced by at least 2 times or more, and the multiple relationship depends on a%, that is, the smaller a%, the greater the multiple.

[0065] In summary, the embodiment of the present application divides the harpoon line into a first harpoon line and a second harpoon line and prints them separately through the design of the printed screen assembly, thereby reducing the number of broken grids of adjacent harpoon lines corresponding to the same main grid. That is, the number of broken harpoon grids can be reduced through the improved solution of the present application.

[0066] For example, Figure 1 As shown, the electrodes are printed using the same printing screen, which can easily cause the adjacent harpoon lines corresponding to the same main grid to break due to the clogging of the mesh holes by dry slurry in the knife lowering and knife retracting positions. By using the printing screen assembly described in the present application, the harpoon structure is divided into the first harpoon line and the second harpoon line for printing, which greatly reduces the probability of adjacent harpoon lines corresponding to the same main grid breaking at the same time.

[0067] The first printing screen 1 also includes a pad pattern structure connected to the main grid pattern structure 11, and the pad pattern structure includes a first pad pattern structure 31 and a second pad pattern structure 32. Figure 7 , Figure 8 As shown, the pad pattern structure is used to print and form a pad 44, and the pad 44 is used to connect the secondary grid 42 obtained by printing the secondary grid pattern structure 21, and / or the pad 44 is used to connect the harpoon structure 43 obtained by printing the harpoon pattern structure;

[0068] Alternatively, the second printing screen 2 also includes a pad graphic structure connected to the secondary grid graphic structure 21, the pad graphic structure is used to print and form a pad 44, the pad 44 is used to connect the main grid 41 obtained by printing the main grid graphic structure 11, and / or the pad 44 is used to connect the harpoon structure 43 obtained by printing the harpoon graphic structure.

[0069] The soldering pad 44 can be a first soldering pad 441 arranged at the intersection of the main grid 41, the auxiliary grid 42, and the harpoon structure 43, or a second soldering pad 442 arranged at the intersection of the main grid 41 and the auxiliary grid 42. The graphic structures corresponding to the first soldering pad 441 and the second soldering pad 442 can be both arranged on the first printed screen 1, or both arranged on the second printed screen 2, or respectively arranged on the first printed screen 1 and the second printed screen 2. The present application does not impose any restrictions on this.

[0070] The mesh number of the second printing screen 2 is greater than that of the first printing screen 1 , the line diameter of the second printing screen 2 is smaller than that of the first printing screen 1 , and the film thickness of the second printing screen 2 is greater than that of the first printing screen 1 .

[0071] In solar cells, the secondary grid mainly collects the photocurrent generated in the solar cell. The secondary grid is electrically connected to the main grid, and the current collected by the secondary grid is collected and exported to the external circuit. Compared with the main grid, the secondary grid has more grid lines and smaller grid line width. A larger number of grid lines shortens the lateral current transmission path, reduces the series resistance, and increases the fill factor and output power, which is beneficial to improving the current collection efficiency; while a smaller grid line width can help reduce shading losses, improve short-circuit current and photoelectric conversion efficiency. Therefore, secondary grid printing requires a finer screen than main grid printing, with a smaller wire diameter, more mesh count, and a thicker screen film. A thicker screen film can make the mesh more complete and regular, so that it has a higher resolution when printing and forms a clearer graphic.

[0072] As an embodiment, the mesh number of the first printing screen 1 is 430-520 meshes, the line diameter of the first printing screen 1 is 13.0μm-15.0μm, and the film thickness of the first printing screen 1 is 2.0μm-4.0μm; and / or, the mesh number of the second printing screen 2 is 500-600 meshes, the line diameter of the second printing screen 2 is 10.5μm-13.0μm, and the film thickness of the second printing screen 2 is 3.0μm-4.0μm. Using the printing screen assembly, a fine graphic structure can be obtained to achieve fine printing of a patterned electrode. For example, using the printing screen assembly, a harpoon structure with a width of 20μm-40μm can be printed.

[0073] Exemplarily, the mesh count of the first printing screen 1 can be any value within the above range, including but not limited to 430 mesh, 450 mesh, 470 mesh, 480 mesh, 500 mesh, 520 mesh, etc.; the line diameter of the first printing screen 1 can be any value within the above range, including but not limited to 13.0μm, 13.2μm, 13.5μm, 13.8μm, 14.2μm, 14.6μm, 15.0μm, etc.; the film thickness of the first printing screen 1 can be any value within the above range, including but not limited to 2.0μm, 2.4μm, 2.5μm, 2.8μm, 3.0μm, 3.3μm, 3.6μm, 4.0μm, etc. The mesh count of the second printing screen 2 can be any value within the above range, including but not limited to 500 mesh, 505 mesh, 508 mesh, 510 mesh, 517 mesh, 520 mesh, 580 mesh, 600 mesh, etc.; the line diameter of the second printing screen 2 can be any value within the above range, including but not limited to 10.5μm, 10.7μm, 10.9μm, 11.2μm, 12.5μm, 13.0μm, etc.; the film thickness of the second printing screen 2 can be any value within the above range, including but not limited to 3.0μm, 3.2μm, 3.4μm, 3.5μm, 3.8μm, 4.0μm, etc.

[0074] As a preferred embodiment, the film thickness of the second printing screen 2 in the intersection area of ​​the second harpoon line pattern structure 22 and the secondary grid pattern structure 21 is greater than the film thickness of the second printing screen 2 in other areas.

[0075] Among them, the other areas of the second printed screen refer to: any other areas except the intersection area of ​​the second harpoon line graphic structure 22 and the secondary grid graphic structure 21, for example, it can be the area of ​​the secondary grid graphic structure 21 that does not intersect with the second harpoon line graphic structure 22, and when there is a pad graphic structure on the second printed screen, it can also be the pad graphic structure area. It can be understood that due to the movement of the scraper, the positions on both sides of the screen pattern, i.e., the areas corresponding to the harpoon graphic structure, have more slurry and are prone to broken grids, especially the secondary grid and harpoon structures that are thinner than the main grid. The film thickness of the intersection area of ​​the second harpoon line graphic structure 22 and the secondary grid graphic structure 21 is set higher than that of other areas. The thicker film can penetrate more slurry, further reducing the probability of broken grids.

[0076] In a second aspect, the present application provides a patterned electrode 4, which is printed using the printing screen assembly of the first aspect. Figures 4 to 6 Schematic diagram of the relevant structure of the printing screen components, and Figure 7 and Figure 8 Schematic diagram of the structure related to the patterned electrode, the patterned electrode 4 includes a first patterned electrode prepared using a first printed screen 1 and a second patterned electrode prepared using a second printed screen 2, the first patterned electrode includes a main grid 41 and a first harpoon line 431, the second patterned electrode includes a sub-grid 42 and a second harpoon line 432, the main grid 41 and the sub-grid 42 are perpendicular to each other, and the first harpoon line 431 and the second harpoon line 432 form a harpoon structure.

[0077] The patterned electrode further includes a pad 44 , which includes a first pad 441 and a second pad 442 . The first pad 441 is disposed at the intersection of the main grid 41 , the auxiliary grid 42 , and the harpoon structure 43 ; the second pad 442 is disposed at the intersection of the main grid 41 and the auxiliary grid 42 .

[0078] The above-mentioned patterned electrodes can realize the collection of carriers and the conduction of current. Specifically, the auxiliary grid 42 has good ohmic contact with the solar cell substrate, which can effectively collect carriers and form current; the auxiliary grid 42 and the main grid 41 are perpendicular to each other, and the collected current can be conducted to the main grid 41 through the pad 44, and then the current is conducted through the harpoon structure 43.

[0079] Further, the opening width of the harpoon structure 43 is 1.0 mm to 2.0 mm. The opening of the harpoon structure 43 can provide an appropriate conductive contact area to ensure that the current can be smoothly conducted through the harpoon structure 43. Exemplarily, the opening width of the harpoon structure 43 can be any point value within the above range, including but not limited to 1.0 mm, 1.1 mm, 1.3 mm, 1.4 mm, 1.6 mm, 1.8 mm, 2.0 mm, etc. Among them, the opening width of the harpoon structure is defined as the maximum width of adjacent harpoon lines corresponding to the same main grid in the direction perpendicular to the main grid.

[0080] As a preferred embodiment, the opening width of the harpoon structure 43 is 1.5 mm to 1.7 mm. Controlling the opening width of the harpoon structure 43 within the above range helps to reduce the gap between the positive and negative electrodes and the diaphragm while ensuring smooth current conduction, thereby improving the utilization rate of the active material of the electrode and the energy density of the battery. Exemplarily, the opening width of the harpoon structure 43 can be any point value within the above range, including but not limited to 1.5 mm, 1.6 mm, 1.7 mm, etc.

[0081] Further, the line width of the first harpoon line 431 is 25.0 μm to 45.0 μm, and the line width of the second harpoon line 432 is 25.0 μm to 45.0 μm. Exemplarily, the line width of the first harpoon line 431 can be any value within the above range, including but not limited to 25.0 μm, 26.2 μm, 29.6 μm, 32.5 μm, 38.8 μm, 45.0 μm, etc. The line width of the second harpoon line 432 can be any value within the above range, including but not limited to 25.0 μm, 26.3 μm, 29.1 μm, 32.7 μm, 38.9 μm, 45.0 μm, etc.

[0082] As a preferred embodiment, the line width of the first harpoon line 431 is 25.0 μm to 30.0 μm, and the line width of the second harpoon line 432 is 25.0 μm to 30.0 μm. Exemplarily, the line width of the first harpoon line 431 can be any value within the above range, including but not limited to 25.0 μm, 26.1 μm, 27.2 μm, 27.9 μm, 28.8 μm, 30.0 μm, etc. The line width of the second harpoon line 432 can be any value within the above range, including but not limited to 25.0 μm, 26.3 μm, 27.1 μm, 27.7 μm, 28.9 μm, 30.0 μm, etc.

[0083] On the one hand, the harpoon line needs to have a certain width to carry current. A harpoon line that is too thin may cause uneven current conduction or low current conduction efficiency. On the other hand, the thinner the harpoon line, the easier it is to break the grid during printing, and the higher the requirements for the printing process. In the embodiment of the present application, by printing the two harpoon lines of the harpoon structure 43 separately, the harpoon line width can be 25.0μm to 30.0μm and the probability of grid breaking is very low. A smaller line width can provide a smaller metallization area, so that the contact area between the electrode structure and the solar cell substrate becomes smaller, reducing metal contact recombination and reducing the blocking of sunlight, thereby improving the photoelectric conversion efficiency. Further, it also reduces the consumption of slurry during printing.

[0084] In a third aspect, an embodiment of the present application provides a solar cell, wherein the solar cell includes a patterned electrode 4 printed by the printing screen assembly of the first aspect, or the solar cell includes the patterned electrode 4 of the second aspect.

[0085] The effect of the printed screen assembly in the embodiment of the present application is further explained below in combination with the printed screen assembly provided in the embodiment of the present application and the method for preparing solar cells using a conventional printed screen.

[0086] Example 1

[0087] This embodiment provides a printing screen assembly, which includes:

[0088] The first printing screen includes: a main grid pattern structure, a first harpoon line pattern structure, a first pad pattern structure and a second pad pattern structure, wherein the first harpoon line pattern structure is arranged at the end of the main grid pattern structure, wherein the first printing screen is a polyimide knotless screen, the screen mesh number is 480 meshes, the yarn diameter is 14.0 μm, and the film thickness is 3.0 μm; the width of the first harpoon line is 45 μm;

[0089] The second printing screen includes a sub-grid graphic structure and a second harpoon line graphic structure, and part of the sub-grid graphic structure intersects with the second harpoon line graphic structure, wherein the second printing screen adopts a high-precision polyimide knotless screen with a screen mesh of 520 meshes, a yarn diameter of 13.0 μm, a film thickness of 4.0 μm, and a second harpoon line width of 45 μm.

[0090] The main grid graphic structure and the secondary grid graphic structure are perpendicular to each other, the first harpoon line graphic structure and the second harpoon line graphic structure constitute a harpoon graphic structure, the first pad graphic structure is arranged at the intersection of the main grid graphic structure, the harpoon graphic structure, and the secondary grid graphic structure, and the second pad graphic structure is arranged at the intersection of the main grid graphic structure and the secondary grid graphic structure; the opening width of the harpoon graphic structure is 1.8 mm.

[0091] Example 2

[0092] The difference between this embodiment and embodiment 1 is that the mesh number, line diameter and film thickness of the second printing screen in this embodiment are the same as those of the first printing screen, which are 480 mesh, 14.0 μm line diameter and 3.0 μm film thickness.

[0093] Example 3

[0094] The difference between this embodiment and embodiment 1 is that the film thickness of the second printing screen in this embodiment is 2 μm thicker in the intersection area of ​​the secondary grid pattern structure and the second harpoon line pattern structure than in other areas.

[0095] <Preparation Example Battery>

[0096] The steps of preparing a solar cell using the printed screen assembly provided in Examples 1 to 5 are as follows:

[0097] ①Texturing: Use single crystal N-type silicon wafers and use alkali to texturize the front and back sides to form a velvet pyramid light-trapping structure.

[0098] ②Diffusion: Boron trichloride and the textured silicon wafer are reacted at high temperature to diffuse on the front side to form a PN emitter junction. After diffusion, the square resistance of the thin layer on the front surface is 90Ω / □~110Ω / □.

[0099] ③ Laser SE: Using the BSG layer formed during the diffusion process, laser doping is performed on the metallized area of ​​the positive electrode gate line on the front side of the silicon wafer after diffusion to form a heavily doped area, thereby realizing a selective emitter structure on the front side of the silicon wafer. The block resistance of the heavily doped area is between 70 and 100Ω / □, and the number of gate lines is 160 to 200.

[0100] ④ Oxidation, BSG removal, and alkaline polishing: The diffused silicon wafer is passed through oxygen at high temperature to form an oxide layer. For the thermally oxidized silicon wafer, hydrofluoric acid is used to remove the BSG generated on the back and surrounding areas. The back and edges of the silicon wafer after BSG removal are polished, and the BSG on the front is removed at the same time.

[0101] ⑤Prepare the back passivation contact structure: deposit a thin layer of silicon oxide and a phosphorus-doped polysilicon layer in sequence on the back surface after alkaline polishing.

[0102] ⑥ Annealing and RCA cleaning: Heat treatment is performed at 910°C to crystallize the polysilicon layer on the back side; and the phosphorus-doped polysilicon layer that is plated on the front side is removed.

[0103] ⑦Preparation of passivation anti-reflection film:

[0104] Positive film: Aluminum oxide film is deposited on the front side using atomic layer deposition (ALD);

[0105] A silicon nitride anti-reflection film is deposited on the surface after the aluminum oxide film layer is deposited by plasma-enhanced chemical vapor deposition (PECVD).

[0106] Back film: A silicon nitride film is deposited on the surface after the phosphorus-doped polysilicon layer is deposited using the PECVD method.

[0107] ⑧Printing patterned electrodes:

[0108] Preparation of the back main grid and the first harpoon line: using the first printing screen, the back first harpoon line and the main grid are printed synchronously on the surface of the silicon wafer;

[0109] Preparation of the back secondary grid and the second harpoon line: Using the second printing screen, the first harpoon line on the back is printed synchronously with the secondary grid and overprinted on the main grid.

[0110] Preparation of the front main grid and the first harpoon line: using the first printing screen, the front first harpoon line and the main grid are printed synchronously on the surface of the silicon wafer;

[0111] Preparation of the front secondary grid and the second harpoon line: The front second harpoon line is printed synchronously with the secondary grid and overprinted on the main grid.

[0112] ⑨ High temperature sintering: The lower layer of silver paste is co-fired with the crystalline silicon cell to attach and solidify the lower layer on the crystalline silicon cell. The sintering peak setting temperature is 820℃~870℃, and the actual temperature is 720℃~760℃.

[0113] ①0 Light injection: The sintered cell is subjected to light injection treatment.

[0114] Finished products: Test, sort, package and store finished battery cells.

[0115] <Preparation of Comparative Example Battery>

[0116] The difference between Comparative Example 1 and Example 1 is only in step ⑧, during printing, the main grid and the harpoon structure are printed simultaneously, as follows:

[0117] Preparation of the back main grid and harpoon structure: The back harpoon structure is printed on the silicon wafer surface simultaneously with the main grid;

[0118] Preparation of back auxiliary grid: The back auxiliary grid is overprinted on the main grid;

[0119] Preparation of the front main grid and harpoon structure: The front harpoon structure is printed on the silicon wafer surface simultaneously with the main grid;

[0120] Preparation of front sub-grid: The front sub-grid is overprinted on the main grid.

[0121] The defective rate test was conducted on the solar cells made by the printed screen assembly in Examples 1-3 and Comparative Example 1. The test results are listed in Table 1.

[0122] Table 1 Performance test results of solar cells

[0123] Defective rate (%) Example 1 0.32％ Example 2 0.29％ Example 3 0.25％ Comparative Example 1 0.8％

[0124] It can be seen from the above table that, compared with Comparative Example 1, using the printed screen assembly in the embodiment of the present application and printing the two harpoon lines of the same harpoon structure using two screens respectively can effectively reduce the defective rate of solar cells and improve the quality of solar cells.

[0125] By comparing Example 1 and Example 2, it can be found that, using the printed screen assembly in the embodiment of the present application, further setting the mesh number of the second printed screen to be greater than the mesh number of the first printed screen, the wire diameter of the second printed screen to be smaller than the wire diameter of the first printed screen, and the film thickness of the second printed screen to be greater than the film thickness of the first printed screen, compared with using the first printed screen and the second printed screen with the same mesh number, wire diameter, and film thickness, the defective rate of the solar cell is lower;

[0126] By comparing Example 1 and Example 3, it can be found that setting the film thickness of the second printed screen in the intersection area of ​​the second harpoon line pattern structure and the secondary grid pattern structure to be greater than the film thickness of the second printed screen in other areas can also reduce the battery defect rate.

[0127] The above is a detailed introduction to the printed screen assembly, patterned electrode and solar cell disclosed in the embodiments of the present application. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the technical solutions and core ideas of the embodiments of the present application. At the same time, for those of ordinary skill in the art, according to the ideas of the embodiments of the present application, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as limiting the embodiments of the present application.

Claims

1. A printing screen assembly for printing a patterned electrode of a solar cell, characterized in that: The printing screen assembly comprises: A first printing screen, the first printing screen comprising a main grid pattern structure and a first harpoon line pattern structure provided at an end of the main grid pattern structure; a second printing screen, the second printing screen comprising a secondary grid pattern structure and a second harpoon line pattern structure, a portion of the secondary grid pattern structure intersecting with the second harpoon line pattern structure; The main grid pattern structure and the secondary grid pattern structure are perpendicular to each other, and the first harpoon line pattern structure and the second harpoon line pattern structure form a harpoon pattern structure.

2. The printing screen assembly according to claim 1, characterized in that: The first printing screen further comprises a pad pattern structure connected to the main grid pattern structure, the pad pattern structure is used for printing to form a pad, the pad is used for connecting the secondary grid obtained by printing the secondary grid pattern structure, and / or the pad is used for connecting the harpoon structure obtained by printing the harpoon pattern structure; Alternatively, the second printing screen also includes a pad graphic structure connected to the secondary grid graphic structure, the pad graphic structure is used to print to form a pad, the pad is used to connect the main grid obtained by printing the main grid graphic structure, and / or the pad is used to connect the harpoon structure obtained by printing the harpoon graphic structure.

3. The printing screen assembly according to claim 1, characterized in that: The mesh number of the second printing screen is greater than that of the first printing screen, the line diameter of the second printing screen is smaller than that of the first printing screen, and the film thickness of the second printing screen is greater than that of the first printing screen.

4. The printing screen assembly according to claim 3, characterized in that: The mesh number of the first printing screen is 430-520 meshes, the line diameter of the first printing screen is 13.0 μm-15.0 μm, and the film thickness of the first printing screen is 2.0 μm-4.0 μm; and / or, The mesh number of the second printing screen is 500-600 meshes, the line diameter of the second printing screen is 10.5 μm-13.0 μm, and the screen film thickness is 3.0 μm-4.0 μm.

5. The printing screen assembly according to any one of claims 1 to 4, characterized in that: The film thickness of the second printing screen in the intersection area of ​​the second harpoon line pattern structure and the secondary grid pattern structure is greater than the film thickness of the second printing screen in other areas.

6. A patterned electrode, characterized in that: The patterned electrode is printed using the printing screen assembly described in any one of claims 1 to 5, and the patterned electrode includes a first patterned electrode prepared using the first printing screen and a second patterned electrode prepared using the second printing screen, the first patterned electrode includes a main grid and a first harpoon line, the second patterned electrode includes a secondary grid and a second harpoon line, the main grid and the secondary grid are perpendicular to each other, and the first harpoon line and the second harpoon line form a harpoon structure.

7. The patterned electrode according to claim 6, characterized in that: The patterned electrode further includes a pad, which includes a first pad and a second pad. The first pad is disposed at the intersection of the main grid, the auxiliary grid, and the harpoon structure; the second pad is disposed at the intersection of the main grid and the auxiliary grid.

8. The patterned electrode according to claim 6, characterized in that: The opening width of the harpoon structure is 1.0 mm to 2.0 mm.

9. The patterned electrode according to claim 8, characterized in that: The opening width of the harpoon structure is 1.5 mm to 1.7 mm.

10. The patterned electrode according to claim 6, characterized in that: The line width of the first harpoon line is 25.0 μm to 45.0 μm, and the line width of the second harpoon line is 25.0 μm to 45.0 μm.

11. The patterned electrode according to claim 10, characterized in that: The line width of the first harpoon line is 25.0 μm to 30.0 μm, and the line width of the second harpoon line is 25.0 μm to 30.0 μm.

12. A solar cell, characterized in that: The solar cell comprises a patterned electrode printed by the printing screen assembly according to any one of claims 1 to 5, or the solar cell comprises a patterned electrode according to any one of claims 6-11.

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