Crystalline silicon solar cell metal grid line preparation method, crystalline silicon solar cell and photovoltaic module

Abstract

The invention provides a crystalline silicon solar cell metal grid line preparation method, a crystalline silicon solar cell and a photovoltaic module, and relates to the technical field of crystalline silicon solar cells. The preparation method comprises the following steps: printing a plurality of first sub-grid lines arranged in rows or columns by using a knotless screen printing plate, and curing to obtain a first target battery piece; and overprinting a second sub-grid line on each first sub-grid line by adopting a full-opening steel plate, curing and sintering. The first sub-grid lines are printed by adopting a knotless screen printing plate, and then the second sub-grid lines are overprinted by adopting a full-opening steel plate, so that the height-width ratio of the metal grid lines can be improved; the second sub-grid line is overprinted by using the full-opening steel plate, so that the shaping of the metal grid line can be assisted, the surface flatness of the metal grid line is optimized, the broken grid is reduced, the contact resistance is reduced, the formation of high-quality ohmic contact is promoted, a better narrow-line-width design space can be obtained, and the consumption of silver is reduced while the shielding of a light absorption area is reduced; and the production cost of the battery is effectively reduced.

Description

Technical Field

[0001] The present application relates to the technical field of crystalline silicon solar cells, and in particular to a method for preparing a metal grid line of a crystalline silicon solar cell, a crystalline silicon solar cell and a photovoltaic module. Background Art

[0002] Crystalline silicon solar cells are one of the most common and widely used types of solar cells on the market today. Crystalline silicon solar cells have attracted attention due to their high energy conversion efficiency, good stability and long service life. Photovoltaic heterojunction (SHJ) solar cells are a type of high-efficiency crystalline silicon solar cells. Photovoltaic heterojunction solar cells form a heterojunction by depositing an amorphous silicon film on a crystalline silicon substrate. This structure can provide excellent surface passivation and reduce the surface recombination of carriers, thereby increasing the open circuit voltage (Voc) and overall efficiency of the cell. Photovoltaic heterojunction solar cells combine the high efficiency of crystalline silicon cells with the potential for low-cost manufacturing, and are one of the current focuses of research and commercialization.

[0003] Due to the special process of photovoltaic heterojunction solar cells, they cannot be processed by high temperature process, so low temperature paste is needed to prepare metal grid lines. Compared with conventional silver paste, low temperature paste is limited by the size of powder particles, and its rheological and printing properties are biased. When used with the current mainstream knotless screen printing of the front grid lines, the fine grid width is wider and the height is lower than that of crystalline silicon cells, and the probability of grid breakage is high. The surface of the printed grid lines has ups and downs, which affects the conductive performance and thus reduces the photoelectric conversion efficiency of solar cells. In addition, the use of knotless screen printing of the front grid lines also has the problem of high silver consumption.

[0004] It should be noted that the above content is not necessarily prior art, nor is it intended to limit the scope of patent protection of this application. Summary of the invention

[0005] In view of the deficiencies in the prior art, the purpose of the present application is to provide a method for preparing metal grid lines of crystalline silicon solar cells, a crystalline silicon solar cell and a photovoltaic module. The first sub-grid line is printed by a knotless screen, and the second sub-grid line is overprinted by a fully-opened steel plate, which can effectively improve the aspect ratio of the metal grid line; the fully-opened steel plate has the characteristics of ink permeability and unobstructed. The use of the fully-opened steel plate to overprint the second sub-grid line can not only assist in shaping the metal grid line, optimize the surface flatness of the metal grid line, reduce broken grids, reduce contact resistance, and promote the formation of high-quality ohmic contact, but also obtain a better narrow line width design space, reduce the obstruction of the light absorption area while reducing the consumption of silver, thereby effectively reducing the production cost of the battery.

[0006] To achieve the above objectives, this application adopts the following technical solutions: A method for preparing a metal grid line of a crystalline silicon solar cell, comprising: Printing a plurality of first sub-grid lines arranged in rows or columns on the surface of a crystalline silicon solar cell using a knotless screen, and curing the printed circuit board to obtain a first target cell sheet; Using a fully-opened steel plate to overprint a second sub-grid line on each of the first sub-grid lines, and curing the resultant to obtain a second target cell sheet; The metal grid lines can be obtained by sintering the second target cell; Wherein, the metal gate line is composed of a plurality of sub-gate lines arranged in rows or columns; each of the sub-gate lines comprises a first sub-gate line and a second sub-gate line which are stacked in sequence.

[0007] In some implementation methods, the width of the sub-gate line is 20-50 μm; and the aspect ratio of the sub-gate line is 40-45%.

[0008] In some embodiments, the peak-to-valley height difference of the metal gate line is 4-10 μm.

[0009] In some embodiments, the paste used for the first sub-grid line and the second sub-grid line is low-temperature silver paste.

[0010] In some embodiments, the solid content of the low-temperature silver paste is controlled at 89-95%, the viscosity is controlled at 120-380 Pa·s, and the volume resistivity is ≤8X10 -6 Ω·cm.

[0011] In some embodiments, the opening angle of the knotless screen is 0°, and the mesh thickness of the knotless screen is 15-25 μm.

[0012] In some embodiments, the mesh number of the knotless screen is 360-500 meshes; the line width of the knotless screen is 7-15 μm; and the opening width of the fine grid lines on the knotless screen is 10-50 μm.

[0013] In some implementation methods, the thickness of the fully-opened steel plate is 5-20 μm; the opening width of the fine grid lines on the fully-opened steel plate is 10-50 μm.

[0014] The present application also provides a crystalline silicon solar cell, and the metal grid lines of the crystalline silicon solar cell are prepared by the above method.

[0015] The present application also provides a photovoltaic module, comprising the above-mentioned crystalline silicon solar cell.

[0016] In the technical solution of the present application, a knotless screen is used to print the first sub-grid line, and a fully-opened steel plate is used to overprint the second sub-grid line, which can effectively improve the aspect ratio of the metal grid line; the fully-opened steel plate has the characteristics of ink permeability and unobstructed. Using the fully-opened steel plate to overprint the second sub-grid line can not only assist in shaping the metal grid line, optimize the surface flatness of the metal grid line, reduce broken grids, reduce contact resistance, and promote the formation of high-quality ohmic contact, but also obtain better narrow line width design space, reduce the obstruction of the light absorption area while reducing the consumption of silver, thereby effectively reducing the production cost of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the multiple drawings represent the same or similar parts or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings only depict some embodiments disclosed in the present application and should not be regarded as limiting the scope of the present application.

[0018] Figure 1 This is a schematic diagram of the structure of the first sub-gate line prepared in an embodiment of the present application. Figure 2 Schematic diagram of the structure of the sub-gate line prepared in the embodiment of the present application.

[0019] Numbers in the figure: 1, sub-grid line; 11, first sub-grid line; 12, second sub-grid line. DETAILED DESCRIPTION

[0020] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings. In the accompanying drawings, for clarity, the sizes of layers, regions, elements and their relative sizes may be exaggerated. Wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as limitations on the present application. It should be noted that, in the absence of conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

[0021] It should be understood that when an element or layer is referred to as "on ...", "adjacent to ...", "connected to" or "coupled to" other elements or layers, it can be directly on, adjacent to, connected to or coupled to other elements or layers, or there can be intervening elements or layers. On the contrary, when an element is referred to as "directly on ...", "directly adjacent to ...", "directly connected to" or "directly coupled to" other elements or layers, there is no intervening element or layer. It should be understood that although the terms first, second, third, etc. can be used to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Therefore, without departing from the teachings of the present disclosure, the first element, component, region, layer or part discussed below can be represented as the second element, component, region, layer or part. And when the second element, component, region, layer or part is discussed, it does not mean that the present disclosure necessarily has the first element, component, region, layer or part.

[0022] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0023] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein, for example. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0024] In the present application, when it comes to a numerical interval (i.e., a numerical range), unless otherwise specified, the distribution of the optional numerical values ​​in the numerical interval is considered to be continuous, and includes the two numerical endpoints (i.e., the minimum and maximum values) of the numerical interval, and each numerical value between the two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to an integer in the numerical interval, it includes the two endpoint integers of the numerical range, and each integer between the two endpoints, which is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be merged. In other words, unless otherwise specified, the numerical range disclosed in the present application should be understood to include any and all sub-ranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. "Numerical interval" allows for broadly including quantitative intervals such as percentage intervals, ratio intervals, and ratio intervals.

[0025] The embodiments of the present application aim to provide a method for preparing metal grid lines of crystalline silicon solar cells, crystalline silicon solar cells and photovoltaic modules. The first sub-grid lines are printed by a knotless screen, and the second sub-grid lines are superimposed by a fully-opened steel plate, which can effectively improve the aspect ratio of the metal grid lines. The fully-opened steel plate has the characteristics of ink permeability and no obstruction. The use of the fully-opened steel plate to superimpose the second sub-grid lines can not only assist in shaping the metal grid lines, optimize the surface flatness of the metal grid lines, reduce broken grids, reduce contact resistance, and promote the formation of high-quality ohmic contacts, but also obtain better narrow line width design space, reduce the obstruction of the light absorption area while reducing the consumption of silver, thereby effectively reducing the production cost of the battery.

[0026] The present application provides a method for preparing a metal grid line of a crystalline silicon solar cell, comprising: Printing a plurality of first sub-grid lines arranged in rows or columns on the surface of a crystalline silicon solar cell using a knotless screen, and curing the printed circuit board to obtain a first target cell sheet; Using a fully-opened steel plate to overprint a second sub-grid line on each of the first sub-grid lines, and curing the resultant to obtain a second target cell sheet; The metal grid lines can be obtained by sintering the second target cell; Wherein, the metal gate line is composed of a plurality of sub-gate lines arranged in rows or columns; each of the sub-gate lines comprises a first sub-gate line and a second sub-gate line which are stacked in sequence.

[0027] In the embodiment of the present application, the metal grid lines are arranged in rows or columns, which can reduce the metal grid lines' shielding of light, increase the effective light-receiving area, and thereby improve the photoelectric conversion efficiency of the solar cell; the metal grid lines are arranged in rows or columns and can also reduce the material cost of the metal grid lines.

[0028] In the embodiment of the present application, when a fully-opened steel plate is used to overprint the second sub-grid line, the graphic ink permeability reaches 100%. Therefore, the first sub-grid line printed by a knotless screen has no absolute influence on the overall grid line shaping. The opening width of the fine grid line on the knotless screen can be narrowed to about 10~15μm, the printed graphic width (the width of the sub-grid line) can be narrowed to 20~30μm, the aspect ratio can reach 40~45%, the shading area is further reduced, and the contact resistance can be reduced to promote the formation of high-quality ohmic contact; and the peak-to-valley height difference on the metal grid line surface can be optimized to 4~10μm, thereby effectively reducing the metal grid line body resistance and improving battery efficiency; in the embodiment of the present application, because the opening width of the fine grid line on the knotless screen can be further narrowed, the overall silver paste single-chip consumption can be reduced by about 20% without affecting the printing effect and electrical performance.

[0029] In the embodiments of the present application, the advantages compared with the prior art are summarized as follows: when only a single-layer knotless printing technology is used to prepare metal grid lines, since the ink permeability of the knotless screen is 70% to 75%, the narrowest opening width of the fine grid lines on the knotless screen can only be designed to be about 20μm, the width of the printed pattern (the width of the sub-grid lines) is 40 to 50μm, the aspect ratio is about 30%, and the peak-to-valley height difference of the grid line surface is 10 to 20μm, and the conductive effect of preparing the metal grid lines is not good enough. When only the full-opening steel plate printing technology is used to prepare metal grid lines with a high aspect ratio, since there are no supports such as yarns in the opening area, it will cause lateral structural instability, thereby causing problems such as line expansion during the printing process. In summary, compared with the traditional single-layer knotless printing technology, the secondary printing technology of the present application has the advantages of being able to narrow the width of the prepared metal grid lines, improve the aspect ratio of the metal grid lines, reduce the peak-to-valley height difference of the metal grid lines, reduce contact resistance, and reduce silver consumption. Compared with full-opening steel plate printing technology, it has the advantage of higher process stability.

[0030] In the embodiment of the present application, the slurry used for printing the first sub-grid line can be a silver slurry. The metal grid line can be prepared on the front or back of the crystalline silicon solar cell, or on both the front and back of the crystalline silicon solar cell. The metal grid line can be prepared as needed and then sent to the sintering process. The purpose of curing after printing the first sub-grid line is to volatilize part of the organic solvent in the slurry, so that the first sub-grid line forms a solid or nearly solid state, which is convenient for overprinting the second sub-grid line. The purpose of the curing step is only to remove part of the organic solvent, so the temperature of the curing step can be set according to the actual situation, and it is sufficient to volatilize part of the organic solvent in the silver slurry. In addition, when the second target battery cell is sent to the sintering process, a suitable sintering temperature can be selected according to the slurry used for the metal grid line.

[0031] In the embodiment of the present application, a knotless screen is used to print the first sub-grid line, and a fully-opened steel plate is used to overprint the second sub-grid line, which can effectively improve the aspect ratio of the metal grid line; the fully-opened steel plate has the characteristic of ink permeability without obstruction. Using the fully-opened steel plate to overprint the second sub-grid line can not only assist in shaping the metal grid line, optimize the surface flatness of the metal grid line, reduce broken grids, reduce contact resistance, and promote the formation of high-quality ohmic contact, but also obtain better narrow line width design space, reduce light absorption area obstruction while reducing silver consumption, thereby effectively reducing the production cost of the battery.

[0032] In an optional embodiment, the width of the sub-gate line is 20~50μm (for example, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm); the aspect ratio of the sub-gate line is 40~45% (for example, 40%, 41%, 42%, 43%, 44%, 45%).

[0033] In the embodiment of the present application, adjusting the width and aspect ratio of the metal grid line can reduce the total power loss caused by the electrode design, thereby improving the photoelectric conversion efficiency of the battery and reducing the material cost of the metal grid line.

[0034] In an optional embodiment, the peak-to-valley height difference of the metal gate line is 4-10 μm (for example, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm).

[0035] In the embodiment of the present application, the peak-to-valley height difference of the metal gate line specifically refers to the vertical distance between the highest point (peak) and the lowest point (valley) of the metal gate line within a certain sampling length. Controlling the peak-to-valley height difference of the metal gate line can reduce the body resistance of the metal gate line, thereby improving the photoelectric conversion efficiency of the battery.

[0036] In an optional embodiment, the paste used for the first sub-grid line and the second sub-grid line is low-temperature silver paste. In the embodiment of the present application, the paste used for the first sub-grid line and the second sub-grid line can be low-temperature silver paste or other types of low-temperature paste. The paste used for the first sub-grid line and the second sub-grid line can be the same or different, as long as it can meet the electrode production requirements of the solar cell. The advantages of using low-temperature silver paste are: low-temperature silver paste can maintain good adhesion to the substrate after curing, meeting the mechanical strength requirements of the battery assembly; in addition, low-temperature silver paste has good chemical stability, can resist the erosion of environmental factors, and has high stability.

[0037] In an optional embodiment, the solid content of the low-temperature silver paste is controlled at 89-95% (for example, 89%, 90%, 91%, 92%, 93%, 94%, 95%), the viscosity is controlled at 120-380 Pa·s (for example, 120 Pa·s, 150 Pa·s, 200 Pa·s, 250 Pa·s, 300 Pa·s, 350 Pa·s, 380 Pa·s), and the volume resistivity is ≤8X10 -6 Ω·cm (e.g., 1X10 -6 Ω·cm、3X10 -6 Ω·cm、5X10 -6 Ω·cm、8X10 -6 Ω·cm).

[0038] In the embodiment of the present application, controlling various parameters of the low-temperature silver paste is beneficial to the shaping optimization of the metal grid line, which can further optimize the peak-to-valley height difference on the surface of the metal grid line, reduce the body resistance of the metal grid line, and thus improve the photoelectric conversion efficiency of the battery.

[0039] In an optional embodiment, the tensioning angle of the knotless screen is 0°, and the mesh thickness of the knotless screen is 15-25 μm (for example, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm).

[0040] In the embodiment of the present application, the screen angle is controlled to 0°, which can reduce the obstruction of the knotless screen to the flow of slurry and improve the printing quality. The mesh thickness of the knotless screen is controlled to control the thickness of the first sub-grid line, which is convenient for overprinting the second sub-grid line and is beneficial to the shaping optimization of the metal grid line. It can further optimize the peak-to-valley height difference on the metal grid line surface and reduce the body resistance of the metal grid line, thereby improving the photoelectric conversion efficiency of the battery.

[0041] In an optional embodiment, the mesh number of the knotless screen is 360~500 mesh (for example, 360 mesh, 400 mesh, 450 mesh, 500 mesh); the line width of the knotless screen is 7~15μm (for example, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm); the opening width of the fine grid lines on the knotless screen is 10~50μm (for example, 10μm, 20μm, 30μm, 40μm, 50μm).

[0042] In the embodiment of the present application, controlling the mesh count and wire width of the knotless screen can control the arrangement of the grid lines in the first sub-grid lines. Optimizing the arrangement of the grid lines in the first sub-grid lines can reduce the total power loss caused by the electrode design, thereby improving the photoelectric conversion efficiency of the battery and reducing the material cost of the metal grid lines.

[0043] In an optional embodiment, the thickness of the fully-open steel plate is 5~20μm (for example, 5μm, 8μm, 10μm, 12μm, 14μm, 16μm, 18μm, 20μm); the opening width of the fine grid lines on the fully-open steel plate is 10~50μm (for example, 10μm, 20μm, 30μm, 40μm, 50μm).

[0044] In the embodiment of the present application, there is no support such as yarn in the opening area of ​​the fully-open steel plate. Controlling the thickness of the fully-open steel plate can make the printing process more stable and improve the process stability.

[0045] The following specific examples further illustrate the present application, but should not be construed as limiting the present application. Without departing from the spirit and substance of the present application, modifications or replacements made to the methods, steps or conditions of the present application are within the scope of the present application.

[0046] Example 1 A method for preparing a metal grid line of a photovoltaic heterojunction cell comprises: (1) Heterojunction (HJT) cell (size 210 mm x 105 mm) after passivation but before electrode preparation; (2) Printing first sub-grid lines 11 arranged in rows on the surface of the heterojunction (HJT) cell using a knotless screen and a low-temperature silver paste, and drying at 80°C to solidify the first sub-grid lines 11 to obtain a first target cell; wherein the opening angle of the knotless screen is 0°, the mesh thickness is 15 μm, the mesh number of the knotless screen is 500 meshes, the wire width of the knotless screen is 9 μm, and the opening width of the fine grid lines on the knotless screen is 10 μm; the solid content of the low-temperature silver paste is controlled at 89%, the viscosity is controlled at 120 Pa·s, and the volume resistivity is 3X10 -6 Ω·cm; (3) A fully-opened steel plate with a thickness of 5 μm and an opening width of 10 μm for the fine grid lines is used, and a low-temperature silver paste is used to overprint a second sub-grid line 12 on each of the first sub-grid lines 11, and the second sub-grid lines 12 are cured at 80°C to obtain a second target cell; the solid content of the low-temperature silver paste is controlled at 89%, the viscosity is controlled at 120 Pa·s, and the volume resistivity is 3X10 -6 Ω·cm; (4) Sintering the second target cell at a low temperature of 180° C. to obtain a metal grid line; wherein the metal grid line is composed of a plurality of sub-grid lines 1 arranged in rows; each of the sub-grid lines 1 comprises a first sub-grid line 11 and a second sub-grid line 12 stacked in sequence; more specifically, the first sub-grid line 11 is as follows: Figure 1 As shown; sub-grid line 1 is as Figure 2As shown, each of the sub-grid lines 1 includes a first sub-grid line 11 (such as Figure 1 As shown), a second sub-gate line 12.

[0047] Example 2 A method for preparing a metal grid line of a photovoltaic heterojunction cell comprises: (1) Heterojunction (HJT) cell (size 210 mm x 105 mm) after passivation but before electrode preparation; (2) Printing first sub-grid lines 11 arranged in rows on the surface of the heterojunction (HJT) cell using a knotless screen and a low-temperature silver paste, and drying at 80°C to solidify the first sub-grid lines 11 to obtain a first target cell; wherein the opening angle of the knotless screen is 0°, the mesh thickness is 25 μm, the mesh number of the knotless screen is 430 meshes, the wire width of the knotless screen is 13 μm, and the opening width of the fine grid lines on the knotless screen is 50 μm; the solid content of the low-temperature silver paste is controlled at 95%, the viscosity is controlled at 380 Pa·s, and the volume resistivity is 5X10 -6 Ω·cm; (3) A fully-opened steel plate with a thickness of 20 μm and an opening width of 50 μm for the fine grid lines is used, and a low-temperature silver paste is used to overprint a second sub-grid line 12 on each of the first sub-grid lines 11, and the second sub-grid lines 12 are cured at 80°C to obtain a second target cell; the solid content of the low-temperature silver paste is controlled at 95%, the viscosity is controlled at 380 Pa·s, and the volume resistivity is controlled at 5X10 -6 Ω·cm; (4) Sintering the second target cell at a low temperature of 180° C. to obtain a metal grid line; wherein the metal grid line is composed of a plurality of sub-grid lines 1 arranged in rows; each of the sub-grid lines 1 comprises a first sub-grid line 11 and a second sub-grid line 12 stacked in sequence; more specifically, the first sub-grid line 11 is as follows: Figure 1 As shown; sub-grid line 1 is as Figure 2 As shown, each of the sub-grid lines 1 includes a first sub-grid line 11 (such as Figure 1 As shown), a second sub-gate line 12.

[0048] Example 3 A method for preparing a metal grid line of a photovoltaic heterojunction cell comprises: (1) Heterojunction (HJT) cell (size 210 mm x 105 mm) after passivation but before electrode preparation; (2) Printing first sub-grid lines 11 arranged in rows on the surface of the heterojunction (HJT) cell using a knotless screen and a low-temperature silver paste, and drying at 80°C to solidify the first sub-grid lines 11 to obtain a first target cell; wherein the opening angle of the knotless screen is 0°, the mesh thickness is 20 μm, the mesh number of the knotless screen is 480 meshes, the wire width of the knotless screen is 11 μm, and the opening width of the fine grid lines on the knotless screen is 20 μm; the solid content of the low-temperature silver paste is controlled at 90%, the viscosity is controlled at 180 Pa·s, and the volume resistivity is 6X10 -6 Ω·cm; (3) A fully-opened steel plate with a thickness of 10 μm and an opening width of 20 μm for the fine grid lines is used, and a low-temperature silver paste is used to overprint a second sub-grid line 12 on each of the first sub-grid lines 11, and the second sub-grid lines 12 are cured at 80°C to obtain a second target cell; the solid content of the low-temperature silver paste is controlled at 90%, the viscosity is controlled at 180 Pa·s, and the volume resistivity is controlled at 6X10 -6 Ω·cm; (4) Sintering the second target cell at a low temperature of 180° C. to obtain a metal grid line; wherein the metal grid line is composed of a plurality of sub-grid lines 1 arranged in rows; each of the sub-grid lines 1 comprises a first sub-grid line 11 and a second sub-grid line 12 stacked in sequence; more specifically, the first sub-grid line 11 is as follows: Figure 1 As shown; sub-grid line 1 is as Figure 2 As shown, each of the sub-grid lines 1 includes a first sub-grid line 11 (such as Figure 1 As shown), a second sub-gate line 12.

[0049] Example 4 The photovoltaic heterojunction cell of Example 4 was prepared by referring to the preparation method of Example 1, except that: Step (2) in Example 4 is: using a knotless screen and a low-temperature silver paste to print the first sub-grid lines 11 arranged in rows on the surface of the heterojunction (HJT) cell, drying at 80°C to solidify the first sub-grid lines 11, and obtaining a first target cell; wherein the mesh angle of the knotless screen is 0°, the mesh thickness is 10 μm, the mesh number of the knotless screen is 500 meshes, the wire width of the knotless screen is 9 μm, and the opening width of the fine grid lines on the knotless screen is 10 μm; the solid content of the low-temperature silver paste is controlled at 89%, the viscosity is controlled at 120 Pa·s, and the volume resistivity is 3X10 -6 Ω·cm.

[0050] Example 5 The photovoltaic heterojunction cell of Example 5 was prepared by referring to the preparation method of Example 1, except that: Step (2) in Example 5 is: using a knotless screen and a low-temperature silver paste to print the first sub-grid lines 11 arranged in rows on the surface of the heterojunction (HJT) cell, drying at 80°C to solidify the first sub-grid lines 11, and obtaining a first target cell; wherein the mesh angle of the knotless screen is 0°, the mesh thickness is 30 μm, the mesh number of the knotless screen is 500 meshes, the wire width of the knotless screen is 9 μm, and the opening width of the fine grid lines on the knotless screen is 10 μm; the solid content of the low-temperature silver paste is controlled at 89%, the viscosity is controlled at 120 Pa·s, and the volume resistivity is 3X10 -6 Ω·cm.

[0051] Example 6 The photovoltaic heterojunction cell of Example 6 was prepared by referring to the preparation method of Example 1, except that: Step (2) in Example 6 is: using a knotless screen and a low-temperature silver paste to print the first sub-grid lines 11 arranged in rows on the surface of the heterojunction (HJT) cell, drying at 80°C to solidify the first sub-grid lines 11, and obtaining a first target cell; wherein the mesh angle of the knotless screen is 0°, the mesh thickness is 15 μm, the mesh number of the knotless screen is 500 meshes, the wire width of the knotless screen is 9 μm, and the opening width of the fine grid lines on the knotless screen is 10 μm; the solid content of the low-temperature silver paste is controlled at 89%, the viscosity is controlled at 110 Pa·s, and the volume resistivity is 3X10 -6 Ω·cm.

[0052] Example 7 The photovoltaic heterojunction cell of Example 7 was prepared by referring to the preparation method of Example 1, except that: Step (2) in Example 7 is: using a knotless screen and a low-temperature silver paste to print the first sub-grid lines 11 arranged in rows on the surface of the heterojunction (HJT) cell, drying at 80°C to solidify the first sub-grid lines 11, and obtaining a first target cell; wherein the mesh angle of the knotless screen is 0°, the mesh thickness is 15 μm, the mesh number of the knotless screen is 500 meshes, the wire width of the knotless screen is 9 μm, and the opening width of the fine grid lines on the knotless screen is 10 μm; the solid content of the low-temperature silver paste is controlled at 89%, the viscosity is controlled at 400 Pa·s, and the volume resistivity is 3×10 -6 Ω·cm.

[0053] Example 8 The photovoltaic heterojunction cell of Example 8 was prepared by referring to the preparation method of Example 1, except that: Step (3) in Example 8 is: using a fully-opened steel plate with a thickness of 5 μm and an opening width of 10 μm for the fine grid lines, and using a low-temperature silver paste, overprinting a second sub-grid line 12 on each of the first sub-grid lines 11, and drying at 80°C to solidify the second sub-grid line 12 to obtain a second target battery cell; the solid content of the low-temperature silver paste is controlled at 89%, the viscosity is controlled at 110 Pa·s, and the volume resistivity is 3×10 -6 Ω·cm.

[0054] Example 9 The photovoltaic heterojunction cell of Example 9 was prepared by referring to the preparation method of Example 1, except that: Step (3) in Example 9 is: using a fully-opened steel plate with a thickness of 5 μm and an opening width of 10 μm for the fine grid lines, and using a low-temperature silver paste, overprinting a second sub-grid line 12 on each of the first sub-grid lines 11, and drying at 80°C to solidify the second sub-grid line 12 to obtain a second target battery cell; the solid content of the low-temperature silver paste is controlled at 89%, the viscosity is controlled at 400 Pa·s, and the volume resistivity is controlled at 3×10 -6 Ω·cm.

[0055] Comparative Example 1 A method for preparing a metal grid line of a photovoltaic heterojunction cell comprises: (1) Heterojunction (HJT) cell (size 210 mm x 105 mm) after passivation but before electrode preparation; (2) Using a knotless screen and a low-temperature silver paste to print grid lines arranged in rows on the surface of the heterojunction (HJT) cell, and drying at 80°C to solidify the grid lines to obtain a first target cell; wherein the opening angle of the knotless screen is 0°, the mesh thickness is 30 μm, the mesh number of the knotless screen is 500 mesh, the wire width of the knotless screen is 9 μm, and the opening width of the fine grid lines on the knotless screen is 20 μm; the solid content of the low-temperature silver paste is controlled at 89%, the viscosity is controlled at 120 Pa·s, and the volume resistivity is 3X10 -6 Ω·cm; (3) The first target cell is sintered at a low temperature of 180° C. to obtain a metal grid line; wherein the metal grid line is composed of a plurality of sub-grid lines arranged in rows.

[0056] Comparative Example 2 The photovoltaic heterojunction cell of Comparative Example 2 was prepared by referring to the preparation method of Comparative Example 1, except that: Step (2) in Comparative Example 2 is: using a knotless screen and a low-temperature silver paste to print grid lines arranged in rows on the surface of the heterojunction (HJT) cell, drying at 80°C to solidify the grid lines, and obtaining a first target cell; wherein the opening angle of the knotless screen is 0°, the mesh thickness is 30 μm, the mesh number of the knotless screen is 500 meshes, the wire width of the knotless screen is 9 μm, and the opening width of the fine grid lines on the knotless screen is 50 μm; the solid content of the low-temperature silver paste is controlled at 89%, the viscosity is controlled at 120 Pa·s, and the volume resistivity is 3×10 -6 Ω·cm.

[0057] Various data of the metal grid lines of the above embodiments and comparative examples were tested, and photoelectric tests were performed on the photovoltaic heterojunction cells prepared in the above embodiments and comparative examples. The test results are shown in Table 1 below.

[0058] Table 1

[0059] Referring to the test data of the above-mentioned embodiments and comparative examples, it can be known that the first sub-gridline is printed by using a knotless screen, and then the second sub-gridline is overprinted by a fully-opened steel plate, which can effectively improve the aspect ratio of the metal gridline; the fully-opened steel plate has the characteristics of ink permeability without obstruction. The use of a fully-opened steel plate to overprint the second sub-gridline can not only assist in shaping the metal gridline, optimize the surface flatness of the metal gridline, reduce the broken grid, reduce the contact resistance, and promote the formation of high-quality ohmic contact, but also obtain a better narrow line width design space, reduce the light absorption area obstruction while reducing the silver consumption, thereby effectively reducing the production cost of the battery. It should be noted that when preparing the metal gridline of the photovoltaic heterojunction battery with reference to the method of comparative examples 1-2, the opening width of the fine gridline on the knotless screen cannot be narrowed to 10μm, and the narrowest opening width of the fine gridline on the knotless screen can only reach 20μm. It can also be seen that the method of the embodiment of the present application can obtain a better narrow line width design space, reduce the light absorption area obstruction while reducing the silver consumption, thereby effectively reducing the production cost of the battery.

[0060] Referring to the test data of the above-mentioned embodiment 1 and embodiments 6-9, it can be known that controlling the various parameters of the low-temperature silver paste is beneficial to the shaping optimization of the metal grid line, which can further optimize the peak-to-valley height difference of the metal grid line surface, reduce the body resistance of the metal grid line, and thus improve the photoelectric conversion efficiency of the battery.

[0061] Referring to the detection data of the above-mentioned Examples 3 and 4-5, it can be seen that controlling the mesh thickness of the knotless screen and then controlling the thickness of the first sub-grid line facilitates the overprinting of the second sub-grid line, and is also beneficial to the shaping optimization of the metal grid line. It can further optimize the peak-to-valley height difference on the surface of the metal grid line, reduce the body resistance of the metal grid line, and thus improve the photoelectric conversion efficiency of the battery.

[0062] To sum up, the present application adopts a knotless screen to print the first sub-grid line, and then uses a fully-open steel plate to overprint the second sub-grid line, which can effectively improve the aspect ratio of the metal grid line; the fully-open steel plate has the characteristics of ink permeability and unobstructed. Using the fully-open steel plate to overprint the second sub-grid line can not only assist in the shaping of the metal grid line, optimize the surface flatness of the metal grid line, reduce broken grids, reduce contact resistance, and promote the formation of high-quality ohmic contact, but also obtain better narrow line width design space, reduce the obstruction of the light absorption area while reducing the consumption of silver, thereby effectively reducing the production cost of the battery.

[0063] The present application also provides a crystalline silicon solar cell (not shown), and the metal grid lines of the crystalline silicon solar cell are prepared by the above-mentioned sintering method.

[0064] The embodiment of the present application can provide a photovoltaic module, including the crystalline silicon solar cell in any of the above embodiments. The embodiment of the present application can provide a photovoltaic module, including the above photovoltaic module. The advantages of the above crystalline silicon solar cell are also possessed by the photovoltaic system, which will not be repeated here. The above photovoltaic system has a wide range of applications, not only limited to photovoltaic power stations, such as ground power stations, rooftop power stations and water power stations, but also includes various equipment and devices that use solar energy to generate electricity, such as user solar power supplies, solar street lights, solar cars and solar buildings. Of course, it can be understood that the application scenarios of the photovoltaic system are not limited to this, that is, the photovoltaic system can be used in all fields where solar energy is required for power generation. Taking the photovoltaic power generation system network as an example, the photovoltaic system may include a photovoltaic array, a junction box and an inverter. The photovoltaic array may be an array combination of multiple photovoltaic modules. For example, multiple photovoltaic modules may form multiple photovoltaic arrays. The photovoltaic array is connected to the junction box. The junction box can converge the current generated by the photovoltaic array. The converged current flows through the inverter and is converted into the alternating current required by the mains power grid and then connected to the mains network to realize solar power supply.

[0065] It should be noted that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. The orientation words "inside" and "outside" refer to the inside and outside relative to the outline of each component itself. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Therefore, the exemplary term "above..." can include both "above..." and "below..." orientations. The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used here are interpreted accordingly.

[0066] It should also be noted that "one embodiment", "another embodiment", "embodiment", etc. mentioned in this application refer to the specific features, structures or characteristics described in conjunction with the embodiment included in at least one embodiment generally described in this application. The same expression appearing in multiple places in the specification does not necessarily refer to the same embodiment. Further, when describing a specific feature, structure or characteristic in conjunction with any embodiment, it is claimed that the realization of such feature, structure or characteristic in conjunction with other embodiments also falls within the scope of this application.

[0067] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0068] It should also be noted that the above are only preferred embodiments of the present application, and the patent protection scope of the present application is not limited thereto. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly used in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method for preparing a metal grid line of a crystalline silicon solar cell, characterized in that: include: Printing a plurality of first sub-grid lines arranged in rows or columns on the surface of a crystalline silicon solar cell using a knotless screen, and curing the printed circuit board to obtain a first target cell sheet; Using a fully-opened steel plate to overprint a second sub-grid line on each of the first sub-grid lines, and curing the resultant to obtain a second target cell sheet; The metal grid lines can be obtained by sintering the second target cell; Wherein, the metal gate line is composed of a plurality of sub-gate lines arranged in rows or columns; each of the sub-gate lines comprises a first sub-gate line and a second sub-gate line which are stacked in sequence.

2. The method according to claim 1, characterized in that The width of the sub-gate line is 20-50 μm; the aspect ratio of the sub-gate line is 40-45%.

3. The method according to claim 1, characterized in that The peak-to-valley height difference of the metal grid line is 4-10 μm.

4. The method according to claim 1, characterized in that: The paste used for the first sub-grid line and the second sub-grid line is low-temperature silver paste.

5. The method according to claim 4, characterized in that The solid content of the low-temperature silver paste is controlled at 89-95%, the viscosity is controlled at 120-380 Pa·s, and the volume resistivity is ≤8X10 -6 Ω·cm.

6. The method according to any one of claims 1 to 5, characterized in that: The mesh angle of the knotless screen is 0°, and the mesh thickness of the knotless screen is 15-25 μm.

7. The method according to any one of claims 1 to 5, characterized in that: The mesh number of the knotless screen is 360-500 meshes; the line width of the knotless screen is 7-15 μm; and the opening width of the fine grid lines on the knotless screen is 10-50 μm.

8. The method according to any one of claims 1 to 5, characterized in that: The thickness of the fully-opened steel plate is 5-20 μm; the opening width of the fine grid lines on the fully-opened steel plate is 10-50 μm.

9. A crystalline silicon solar cell, characterized in that: The metal grid lines of the crystalline silicon solar cell are prepared by the method according to any one of claims 1 to 8.

10. A photovoltaic module, characterized in that: Comprising the crystalline silicon solar cell as claimed in claim 9.

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