Solar cell and preparation method thereof

Abstract

The invention relates to the technical field of photovoltaic power generation, and discloses a solar cell and a preparation method thereof. The solar cell comprises a substrate, a first grid line structure and a second grid line structure, wherein the first grid line structure and the second grid line structure are located on the surface of the substrate. The first grid line structure comprises a plurality of first grid lines arranged at intervals in the first direction and a plurality of middle grid lines located between every two adjacent first grid lines, each first grid line extends in the second direction, the multiple middle grid lines are arranged at intervals in the second direction, and intervals exist between each middle grid line and the first grid lines on the two sides. The plurality of second grid line structures are arranged at intervals along the first direction, each second grid line structure comprises a plurality of second sub-grid lines arranged at intervals along the second direction, each second sub-grid line extends along the first direction, and the plurality of second sub-grid lines of each second grid line structure and the same first grid line are arranged in a crossed manner. According to the solar cell and the preparation method thereof provided by the invention, the occurrence of a welding broken gate phenomenon can be reduced.

Description

Technical Field

[0001] The present application relates to the field of photovoltaic power generation technology, and in particular to a solar cell and a method for preparing the same. Background Art

[0002] With the continuous development of new energy power generation technology, the proportion of new energy power generation is increasing. There are many ways to obtain new energy without polluting the environment. Photovoltaic power generation can generate electricity by obtaining the radiation energy of sunlight. Photovoltaic power generation is achieved through solar cells. Solar cells have the photovoltaic effect, that is, the photovoltaic effect, which can generate current under the irradiation of sunlight. Thus generating electricity.

[0003] When preparing solar cells, they will go through the screen printing process. In the screen printing process, the grid line structure is formed by screen printing electrode slurry. The grid line structure is an important part of the solar cell, which plays the role of collecting and transmitting electrons. The screen is designed according to the form of the grid line structure. The characteristics of the grid line structure formed by the screen printing process affect the welding effect in the subsequent component welding process, and the phenomenon of welding broken grid occurs. Therefore, how to design the form of the grid line structure to reduce the phenomenon of welding broken grid is an important issue. Summary of the invention

[0004] The purpose of the embodiments of the present application is to provide a solar cell and a method for manufacturing the same, which can help reduce the occurrence of welding grid breakage.

[0005] To solve the above technical problems, an embodiment of the present application provides a solar cell. The solar cell includes a substrate and a first gridline structure and a second gridline structure located on the surface of the substrate. The first gridline structure includes a plurality of first gridlines arranged at intervals along a first direction, and a plurality of intermediate gridlines located between two adjacent first gridlines, each first gridline extends along a second direction, a plurality of intermediate gridlines are arranged at intervals along the second direction, and each intermediate gridline has a gap with the first gridlines on both sides. There are multiple second gridline structures, and the plurality of second gridline structures are arranged at intervals along the first direction, each second gridline structure includes a plurality of second sub-gridlines arranged at intervals along the second direction, each second sub-gridline extends along the first direction, and the plurality of second sub-gridlines of each second gridline structure are arranged crosswise with the same first gridline, and two second sub-gridlines adjacent to each other in the first direction are connected via the intermediate gridline, and the first direction intersects with the second direction.

[0006] The embodiment of the present application further provides a method for preparing the above-mentioned solar cell, the preparation method comprising: providing a substrate; A first grid line structure is formed by printing on the surface of the substrate using a first screen, wherein the first screen is provided with first opening grooves arranged at intervals along a first direction, and a plurality of second opening grooves located between two adjacent first opening grooves, each first opening groove extends along a second direction, and the plurality of second opening grooves are arranged at intervals along the second direction; A second grid line structure is formed by printing on the surface of the substrate using a second screen, wherein the second screen is provided with a plurality of printing areas arranged at intervals along the first direction, each printing area is provided with a plurality of third opening grooves arranged at intervals along the second direction, each third opening groove extends along the first direction, and is provided correspondingly to the second opening groove at the interval between two adjacent printing areas in the first direction; The first direction intersects with the second direction.

[0007] The solar cell and the preparation method thereof provided by the embodiment of the present application are designed with a first grid line structure and a second grid line structure on the surface of the substrate. The first grid line of the first grid line structure forms a main grid, and a plurality of intermediate grid lines arranged along the extension direction of the first grid line are located between two adjacent first grid lines. The second sub-grid lines of the plurality of second grid line structures are connected through the intermediate grid lines to form a secondary grid. The plurality of second sub-grid lines of each second grid line structure are arranged crosswise with the same first grid line. Thus, the overlapping position of the secondary grid connection line is shifted, and the overlapping position of the secondary grid connection line is shifted to between two adjacent main grids. The characteristics of the secondary grid slurry can be utilized to ensure the shaping effect at the location of the main grid welding portion. Thereby reducing the phenomenon of welding broken grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] One or more embodiments are exemplarily described by pictures in the corresponding drawings, and these exemplified descriptions do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings represent similar elements, and unless otherwise stated, the figures in the drawings do not constitute proportional limitations.

[0009] Figure 1 is a schematic diagram of a gridline pattern in a solar cell using a conventional gridline form in some cases; Figure 2 yes Figure 1 A partial enlarged schematic diagram of the grid line pattern shown; Figure 3 yes Figure 1 A schematic diagram of the structure of the main grid in the grid line pattern shown; Figure 4 yes Figure 1 A schematic diagram of a partially enlarged structure of a main grid in the grid line pattern shown; Figure 5 yes Figure 1 A schematic diagram of the structure of the auxiliary grid in the grid line pattern shown; Figure 6 yes Figure 1A schematic diagram of a partially enlarged structure of a secondary grid in the grid line pattern shown; Figure 7 is a schematic diagram of the structure of a solar cell provided in some embodiments of the present application; Figure 8 is a schematic diagram of a grid line pattern in a solar cell provided in some embodiments of the present application; Fig. 9 yes Figure 8 A schematic diagram of a partially enlarged structure of the grid line pattern shown; Fig.10 yes Figure 8 A schematic diagram of a first gate line structure in the gate line pattern shown; Fig.11 yes Figure 8 A partial enlarged schematic diagram of a first gate line structure in the gate line pattern shown; Fig.12 yes Figure 8 A schematic diagram of a second gate line structure in the gate line pattern shown; Fig.13 yes Figure 8 A partial enlarged schematic diagram of a second gate line structure in the gate line pattern shown; Fig.14 yes Figure 8 A schematic diagram of the structure of the middle grid line in the grid line pattern shown; Fig.15 yes Figure 8 A schematic structural diagram of the gradient segment of the second sub-grid line in the grid line pattern shown. DETAILED DESCRIPTION

[0010] To make the purpose, technical scheme and advantages of the embodiments of the present application clearer, each embodiment of the present application will be described in detail below in conjunction with the accompanying drawings. However, it will be appreciated by those skilled in the art that in each embodiment of the present application, many technical details are proposed in order to enable the reader to better understand the present application. However, even without these technical details and various changes and modifications based on the following embodiments, the technical scheme claimed in the present application can also be implemented. The division of the following embodiments is for the convenience of description, and the specific implementation of the present application should not constitute any limitation, and the various embodiments can be combined with each other and referenced to each other without contradiction.

[0011] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0012] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected" 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, and it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0013] With the continuous development of solar cell preparation technology, the photoelectric conversion efficiency of solar cells is also constantly improving. When preparing solar cells, they will undergo a screen printing process. The screen printing process forms a grid electrode on the surface of the solar cell. The grid line can be divided into a main grid and a sub-grid. The sub-grid is also called a fine grid. According to the number of main grids, solar cells can be divided into super-multi-main grid cells, multi-main grid cells, and no main grid cells. The main grid usually intersects the sub-grid vertically, and the grid electrode can be formed on one side or both sides of the solar cell. Screen printing is carried out using a screen, and the screen is designed with openings for the printed metal paste to pass through. The metal paste is usually silver paste. The metal paste is printed on the surface of the battery to form a main grid or a sub-grid, and the required electrode pattern is obtained after sintering or drying and curing.

[0014] The fully-opened steel plate screen is a screen with a 100% opening rate. The main body is no longer woven from steel wire, but alloy steel sheets are used, and the printing openings are obtained by laser slotting. The opening rate of the screen printing working area is 100%, that is, the entire printed pattern is not blocked by steel wire or other similar structures. Since the fully-opened steel plate screen has no mesh blocking in the slotted area, the transmittance of the slurry can be greatly improved, saving the consumption of slurry. At the same time, the use of a fully-opened steel plate screen for screen printing can optimize the width of the grid line and greatly reduce the shading area on the surface of the battery. In addition, the height of the grid line after printing with a fully-opened steel plate screen is uniform and flat, and the height fluctuation is significantly lower than that of traditional screen printing. It can significantly reduce the resistance of the grid line and improve the fill factor of solar cells.

[0015] However, currently, fully-opened steel screens are mainly used for metallization printing of small-sized heterojunction cells and 0BB (Busbar; 0BB means no busbar) cells with special component welding processes. When fully-opened steel screens are applied to multi-busbar cells, such as mainstream SMBB (Super Multi-Busbar) battery products, the shaping requirements of the busbar overlap / welding will not match those of SMBB battery products, resulting in abnormal problems such as broken grids and poor overlap in component welding. Table 1 below shows the comparison of shaping of SMBB battery products at the busbar overlap / welding under different circumstances of conventional grid line design using conventional PI (Polyimide) screen printing and fully-opened steel screen printing. Among them, conventional grid line forms such as Figure 1 and Figure 2 As shown, the solar cell is in the form of a gradient or I-shaped design on the main grid 100 , and the auxiliary grid 200 is overlapped on the main grid 100 . Figure 3 and Figure 4 The structure of the main grid 100 in a conventional grid line form is shown. The main grid 100 includes a main grid connection line and a main pad 101 located on the main grid connection line and used for welding a welding strip, and a lap / welding portion 102 . Figure 5 and Figure 6 The structure of the auxiliary grid 200 in the conventional grid line form is shown, and the auxiliary grid 200 includes a plurality of sections of auxiliary grid connection lines. The thickness of the screen used in the comparative test is 18.5 microns, and the opening width of the slot is 40 microns.

[0016] Table 1. Comparison of the overlapping / welding shapes of solar cells when using different screens to make grid electrodes

[0017] It can be seen that the conventional grid line form design of SMBB battery products has a low molding height when using full-open steel plate screen printing, which will cause welding melting during the process of welding the welding strip of the component, thereby causing the current circuit to be broken, which is manifested as EL (Electroluminescence) blackening, which is called welding broken grid. That is, the full-open steel plate screen does not match the current process of SMBB battery products, and the grid line form needs to be optimized to ensure the molding effect at the welding position of the main grid welding strip. In other words, the grid line form of multi-main grid batteries needs to be designed so that the full-open steel plate screen pattern based on multi-main grid battery products can adapt to the process of multi-main grid battery products to solve problems such as welding broken grid.

[0018] In order to reduce the phenomenon of welding broken grids that occur in solar cells after the screen printing process using a full-open steel plate screen, some embodiments of the present application provide a solar cell. The grid line form of the solar cell is optimized, the printing of the main grid welding part is optimized, and the overlapping position of the auxiliary grid connection line is transferred to between two adjacent main grids. When screen printing is performed, the high plasticity of the electrode slurry corresponding to the auxiliary grid is utilized to ensure the shaping effect at the intersection of the auxiliary grid and the main grid, that is, at the location of the main grid welding part. This design scheme can solve the problem of welding broken grids that occurs when the full-open steel plate screen technology is applied to multi-main grid battery products without affecting the efficiency wet weight, and can achieve more precise image refinement and more accurate alignment of the graphics. In terms of efficiency, it can ensure that the shading ratio is consistent with the conventional grid line form. In terms of wet weight, the actual printing shaping can be fitted through screen parameter design. That is, based on the actual printing morphology monitored for a long time, the expected wet weight of the fitting scheme is adjusted to adjust the screen design parameters.

[0019] It should be noted that, in order to adapt to the functional characteristics of different grid lines, when performing the screen printing process, the electrode paste used for printing the main grid is different from the electrode paste used for printing the secondary grid, and each has its own required components and proportions. The main grid paste is usually only used to ensure the welding tension, and the requirements for the paste's own plasticity are relatively low. The secondary grid paste usually has better plasticity, good sintering characteristics and ohmic contact characteristics. When using a full-opening steel plate screen for screen printing, the plasticity of the main grid is significantly lower than that of the secondary grid due to the good slurry transmittance. In other words, when the solar cell adopts the conventional grid line form, the main grid overlap / welding part is printed together with the main grid connection line by the main grid paste, and the plasticity is poor. In actual situations, considering the slurry development cost, without changing the original slurry system, the overlap position on the main grid connection line, that is, the discontinuous position of the secondary grid connection line, can be transferred between two adjacent main grids. Therefore, the auxiliary grid connection line can pass through the main grid completely, and the auxiliary grid paste is printed at the location of the main grid welding part to ensure the shaping effect at the location of the main grid welding part. By adopting the method of optimizing the grid line pattern design, it is more conducive to reducing costs and improving efficiency.

[0020] Combine the following Figures 7 to 15 The structure of the solar cell provided by some embodiments of the present application is described.

[0021] like Figures 7 to 15 As shown, the solar cell provided by some embodiments of the present application includes a substrate 10 and a first gridline structure 11 and a second gridline structure 12 located on the surface of the substrate 10. The first gridline structure 11 includes a first direction ( Fig. 9 A plurality of first gate lines 111 are arranged in a spaced relationship along the second direction (in the direction indicated by the arrow A in the middle), and a plurality of intermediate gate lines 112 are located between two adjacent first gate lines 111. Each first gate line 111 is arranged along the second direction (in the direction indicated by the arrow A in the middle). Fig. 9The first direction is the direction indicated by the arrow B in the middle, and the plurality of middle gate lines 112 are arranged at intervals along the second direction, and there is a gap between each middle gate line 112 and the first gate lines 111 on both sides. There are a plurality of second gate line structures 12, and the plurality of second gate line structures 12 are arranged at intervals along the first direction, and each second gate line structure 12 includes a plurality of second sub-gate lines 121 arranged at intervals along the second direction, and each second sub-gate line 121 extends along the first direction, and the plurality of second sub-gate lines 121 of each second gate line structure 12 are arranged to cross the same first gate line 111, and two second sub-gate lines 121 adjacent to each other in the first direction are connected via the middle gate line 112. The first direction crosses the second direction.

[0022] The substrate 10 is the basis for forming the grid electrode of the solar cell, and a silicon substrate is usually used. Metal paste can be printed on the front and back of the substrate 10 to form a grid electrode with a specific pattern. The grid electrode printed on the front of the substrate 10 is the front electrode 110, and the grid electrode printed on the back of the substrate 10 is the back electrode. Usually, the front of the substrate 10 is the light-receiving surface, which receives the solar energy brought by the directly incident light, and the back of the substrate 10 is the backlight surface, which receives the solar energy brought by the scattered and refracted light. The grid electrode can be printed on one side or both sides of the substrate 10 to form a single-sided cell or a double-sided cell. Figure 7 Take a single-sided battery as an example. Figure 8 and Fig. 9 The gridline pattern on the surface of the solar cell is shown.

[0023] The first gate line structure 11 and the second gate line structure 12 are formed in different areas on the surface of the substrate 10. Fig.10 and Fig.11 shows a first gate line structure 11, Fig.12 and Fig.13The second grid line structure 12 is shown. The first grid line structure 11 and the second grid line structure 12 can be printed and formed using different screens to form a main grid and a secondary grid on the surface of the solar cell. In different grid line structures, the first grid line 111 forms the main grid of the solar cell, and pads 1111 are distributed on the main grid. The second sub-grid line 121 is connected through the middle grid line 112 to form the secondary grid of the solar cell. The second sub-grid line 121 may pass through the pad 1111 or may not pass through the pad 1111. The second sub-grid line 121 passing through the pad 1111 may include two disconnected parts, which are connected through the pad 1111 to form a passage. The main grid and the secondary grid are arranged at intervals on the surface of the substrate 10, and the extension directions of the two, that is, the first direction and the second direction, can be two directions perpendicular to each other, or two directions with other angles. The middle grid line 112 maintains a one-to-one or one-to-many correspondence with the second sub-grid lines 121 on both sides, that is, one middle grid line 112 can be connected to only one second sub-grid line 121 at one end, or it can be connected to multiple second sub-grid lines 121. The arrangement direction of the middle grid line 112 is the same as that of the second sub-grid lines 121, and the second sub-grid lines 121 can be overlapped on the middle grid line 112 when printing. Thereby, the intermittent second sub-grid lines 121 are connected to form a complete secondary grid through the middle grid line 112 to ensure the formation of a path for electron movement. In actual situations, the number of main grids can be 9, 12, 13, 15, 16, 18 or 20. The number of secondary grids can be 45, 50, 55, 60, 65, 70 or 75. In addition, the solar cell provided in some embodiments of the present application can be a whole cell, or it can be constructed in the form of a half cell, and the half cell is formed by dividing the whole cell into two halves along a direction perpendicular to the main grid.

[0024] In the solar cell provided by some embodiments of the present application, a first grid line structure 11 and a second grid line structure 12 are designed on the surface of the substrate 10. The first grid line 111 of the first grid line structure 11 forms a main grid, and a plurality of intermediate grid lines 112 arranged along the extension direction of the first grid line 111 are located between two adjacent first grid lines 111. The second sub-grid lines 121 of the plurality of second grid line structures 12 are connected through the intermediate grid lines 112 to form a secondary grid. The plurality of second sub-grid lines 121 of each second grid line structure 12 are arranged crosswise with the same first grid line 111. Thus, the overlapping position of the secondary grid connection line is shifted, and the overlapping position of the secondary grid connection line is shifted between two adjacent main grids. The characteristics of the secondary grid slurry can be utilized to ensure the shaping effect at the location of the main grid welding portion. Thereby reducing the phenomenon of welding broken grid.

[0025] When a full-opening steel plate screen is used for screen printing, since the main grid and the middle grid line 112 connected to the second sub-grid line 121, that is, the auxiliary grid connection line, are designed separately, when the second sub-grid line 121 of the auxiliary grid is printed, the second sub-grid line 121 can pass through the main grid and intersect with the main grid. That is, the overlapped portion located at the welding strip of the main grid in the conventional design is transferred to between two adjacent main grids. The auxiliary grid slurry can be used to cover the welding part of the main grid. The plasticity of the auxiliary grid slurry is better than that of the main grid slurry to ensure the molding effect at the location of the main grid welding strip and increase the molding height. Thereby ensuring the welding effect of the solar cell in the subsequent welding process, avoiding the problem of broken grid in component welding caused by the low molding height at the welding point when the conventional grid line form is printed using a full-opening steel plate screen.

[0026] like Fig.14 As shown, each middle gate line 112 may include a middle portion 1121 extending along the first direction, and a first overlap portion 1122 and a second overlap portion 1123 located at the ends of the middle portion 1121. The first overlap portion 1122 and the second overlap portion 1123 are connected to the second sub-gate lines 121 in different second gate line structures 12.

[0027] The middle grid line 112 includes a plurality of parts, each of which plays a different role. The middle part 1121 is the longer part of the middle grid line 112, forming the main structure of the middle grid line 112. The middle part 1121 can ensure the overall length of the middle grid line 112, and ensure that the two adjacent second sub-grid lines 121 in the auxiliary grid can still be connected to form a whole through the middle grid line 112 when they are spaced at a certain distance. The extension direction of the middle part 1121 is the same as the extension direction of the second sub-grid line 121, and can play a connecting role between the two adjacent second sub-grid lines 121. While ensuring the connection effect, the middle part 1121 can be set to a smaller width to form a narrower strip to reduce the shading area and ensure the smooth flow of the electron transmission path.

[0028] The first overlap portion 1122 and the second overlap portion 1123 are parts that provide an overlap basis for different second sub-grid lines 121. The first overlap portion 1122 and the second overlap portion 1123 are located at both ends of the middle portion 1121, and are arranged corresponding to the interval between two second sub-grid lines 121 adjacent in the first direction. In actual situations, in order to ensure the connection effect between the second sub-grid lines 121 and the middle grid lines 112, the two overlap portions of the middle grid lines 112 can be made to exceed the two side edges of the second sub-grid lines 121 distributed along the width direction. This allows the second sub-grid lines 121 to completely overlap in the area where the overlap portions of the middle grid lines 112 are located when printing.

[0029] It should be noted that when designing the full-opening steel plate screen, since the slot opening presents a 100% opening rate, discontinuities are set between the slots at different positions to ensure that the screen will not be separated into multiple parts due to the complete penetration of the slots. That is, discontinuities are reserved in the slot printing area. The discontinuities of the secondary grid connection lines correspond to the positions of the middle grid lines 112 in the first grid line structure 11.

[0030] In some embodiments, the first overlapping portion 1122 and the second overlapping portion 1123 may both extend along the second direction, and a length L1 of the first overlapping portion 1122 and the second overlapping portion 1123 in the second direction is greater than a width W2 of the middle portion 1121 in the second direction.

[0031] That is to say, the two overlapping portions of the middle grid line 112 can extend along the width direction of the second sub-grid line 121. Moreover, the length L1 of the two overlapping portions in the second direction is greater than the width W2 of the middle portion 1121 in the second direction. By making the length L1 of the first overlapping portion 1122 and the second overlapping portion 1123 in the second direction greater than the width W2 of the middle portion 1121 in the second direction, the two overlapping portions can be made to extend beyond the edge of the middle portion 1121 in the width direction of the second sub-grid line 121. This provides favorable conditions for the second sub-grid line 121 to overlap the end of the middle grid line 112, thereby ensuring the connection effect between the second sub-grid line 121 and the middle grid line 112.

[0032] In actual situations, the length L1 of the first overlap portion 1122 and the second overlap portion 1123 in the second direction can be greater than or equal to 70 microns and less than or equal to 150 microns, and the width W1 of the first overlap portion 1122 and the second overlap portion 1123 in the first direction can be greater than or equal to 10 microns and less than or equal to 20 microns.

[0033] By setting the two overlapping portions in a strip shape, the light shielding area can be reduced while the range where the overlapping portions are located can completely cover the end paste printing range of the second sub-grid line 121, thereby ensuring the connection effect between the second sub-grid line 121 and the middle grid line 112.

[0034] Since the middle grid line 112 is located between two adjacent main grids and does not play the role of forming a welding point, the size of the overlap portion can be appropriately reduced and set within a smaller range. In the conventional grid line form, in order to ensure the welding area at the welding point, the area at the overlap position on the main grid is usually set larger. In the solar cell provided in some embodiments of the present application, the grid line form is optimized. The middle grid line 112 is far away from the welding point position on the main grid and does not play the component welding function, but only provides an overlap basis between two adjacent second sub-grid lines 121 to form a complete current loop. Therefore, the size can be designed within a smaller range, reducing the size, while saving slurry materials, reducing the shading area. The size can also be designed within a larger range to ensure a good overlap effect with the second sub-grid line 121. For example, the length L1 of the first overlap portion 1122 and the second overlap portion 1123 in the second direction can be 70 microns, 90 microns, 110 microns, 130 microns or 150 microns, and the width W1 of the first overlap portion 1122 and the second overlap portion 1123 in the first direction can be 10 microns, 12 microns, 14 microns, 16 microns, 18 microns or 20 microns.

[0035] In addition, a length L2 of the middle portion 1121 in the first direction may be less than or equal to 650 micrometers.

[0036] Compared with the conventional grid line form, it is necessary to ensure that the main grid welding part, that is, the welding point has a larger area. The grid line form after the improved design can reduce the length size of the middle part 1121 of the middle grid line 112. Then the shading area is effectively reduced to ensure the photoelectric conversion efficiency of the solar cell. That is, the length L2 of the middle part 1121 in the first direction can be controlled within 650 microns, such as 600 microns, 610 microns, 620 microns, 630 microns, 640 microns or 650 microns.

[0037] In some embodiments, the width W2 of the middle portion 1121 in the second direction may be smaller than the width of the second sub-gate line 121 in the second direction, and the width W2 of the middle portion 1121 in the second direction may be smaller than or equal to 40 micrometers.

[0038] The middle portion 1121 is located in the middle of the middle grid line 112, and can only play the role of transmitting electrons. Therefore, the width W2 of the middle portion 1121 in the second direction can be made smaller than the width of the second sub-grid line 121 in the second direction. At the same time, since the middle portion 1121 is not used as a welding part, the width of the middle portion 1121 in the second direction can be controlled within a range of less than or equal to 40 microns, so as to reduce the shading area and save the use of electrode slurry.

[0039] As a comparative illustration of the size design, in one example, the dimensions of the main grid overlap / weld portion of the conventional grid line design are that the length and width of the two side portions of the I-shaped are 150 microns and 20 microns respectively, and the length and width of the middle portion of the I-shaped are 650 microns and 40 microns respectively. When the middle grid line 112 designed in the shape of an I is located between two adjacent main grids, the dimensions of the middle grid line 112 can be designed such that the length and width of the overlap portions on both sides are 150 microns and 15 microns respectively, and the length and width of the middle extension portion are 500 microns and 20 microns respectively.

[0040] In actual situations, the first overlapping portion 1122 and the second overlapping portion 1123 may be symmetrically arranged with respect to the middle portion 1121 .

[0041] That is, the first overlap portion 1122 and the second overlap portion 1123 are designed with the same shape and size, and the first overlap portion 1122 and the second overlap portion 1123 are symmetrical. In this way, the printing and production of the middle grid line 112 can be simplified, and the design of the screen can be facilitated.

[0042] In some embodiments, the distances between each intermediate gate line 112 and two adjacent first gate lines 111 in the first direction are equal.

[0043] That is, the middle grid line 112 is located at the middle line of two adjacent first grid lines 111. It is ensured that the length of each second sub-grid line 121 on both sides of the crossed first grid line 111 is consistent, which is convenient for positioning when printing the grid lines.

[0044] In actual situations, the projection shapes of the first overlapping portion 1122 and the second overlapping portion 1123 on the surface of the substrate 10 may be any one of a rectangle, a trapezoid, an ellipse and a triangle.

[0045] The overlapping portion can be in different shapes according to the actual situation. A rectangular shape can simplify the printing of the grid line and facilitate the opening design of the screen. A gradual shape such as a trapezoid or an ellipse can help reduce the shading area while ensuring the overlapping effect of the second sub-grid line 121.

[0046] In some embodiments, the electrode paste of the first gate line 111 may be the same as the electrode paste of the middle gate line 112 , and the electrode paste of the first gate line 111 is different from the electrode paste of the second sub-gate line 121 .

[0047] That is to say, the middle grid line 112 can be printed and manufactured using the same electrode paste system as the main grid, and can be screen printed using the same full-opening steel plate screen. In addition, the printing and manufacturing of the first grid line 111 and the middle grid line 112 can be completed simultaneously, simplifying the printing and manufacturing process of different grid lines. The second sub-grid line 121 can be printed and manufactured using the auxiliary grid electrode paste to ensure the plastic effect of the solder joint at the main grid welding point.

[0048] like Fig.13 and Fig.15 As shown, each second sub-gridline 121 may have a gradient segment 122 connected to the first gridline 111 in the middle, and the width of at least part of the gradient segment 122 in the second direction gradually increases in a direction approaching the connected first gridline 111 .

[0049] The gradient section 122 is designed on the second sub-grid line 121 and can be printed with auxiliary grid paste, which has better plasticity. At the same time, the gradient section 122 with varying width can form a good welding foundation for the main grid welding part to ensure the welding effect with the welding strip.

[0050] The gradient section 122 may be located in the middle of the second sub-grid line 121 . By designing the gradient section 122 in the middle of the second sub-grid line 121 , the shaping of the main grid welding position may be optimized and the welding tolerance may be improved.

[0051] In addition, the length of the gradient section 122 of each second sub-grid line 121 in the first direction may be greater than or equal to 0.6 mm and less than or equal to 1.2 mm.

[0052] The gradient section 122 is located at the welding portion of the main grid. By controlling the length of the gradient section 122, the shading area can be reduced while ensuring the welding effect, and the use of electrode paste can be saved. In actual situations, the length of the gradient section 122 in the first direction can be 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm or 1.2 mm.

[0053] like Fig.15As shown, the gradient section 122 of the auxiliary grid can adopt a two-level gradient form. In the extension direction of the auxiliary grid connection line, the gradient section 122 has a first section, a second section and a third section respectively. The first section and the third section located on both sides are set in a width gradient form, and the second section located in the middle is set in a width constant form. The length La of the first section is equal to the length Lc of the third section. In an example, the length La of the first section and the length Lc of the third section can be designed to be 0.3 mm, and the length Lb of the second section can be designed to be 0.37 mm. At the same time, the minimum width of the first section and the third section is designed to be 0.01 mm, the maximum width is designed to be 0.04 mm, and the width of the second section is designed to be 0.04 mm. The gradient section 122 can ensure excellent shaping at the main grid welding point when printed on the auxiliary grid, and effectively prevent the phenomenon of fuse and broken grid in the subsequent component welding process.

[0054] Table 2 below compares the main grid welding when the full-opening steel plate is applied to conventional grid pattern and the grid pattern provided by some embodiments of the present application. The full-opening steel plate used in the comparative test has a thickness of 18.5 microns and a slotted opening width of 50 microns.

[0055] Table 2. Comparison of welding shape of solar cells using different grid lines

[0056] It can be seen that the conventional grid line form design has a low molding height when using full-opening steel plate screen printing, which will cause a large proportion of welding broken grid phenomenon during the component welding process. After improving the grid line form, the full-opening steel plate screen can better adapt to the grid line printing and production of multi-busbar battery products. It can greatly increase the molding height at the position of the main grid welding strip, effectively reduce the welding broken grid phenomenon that occurs during the component welding process, and ensure that the welding tension of the strip reaches the qualified tension value. Therefore, without changing the original slurry system of the main grid and the secondary grid of the solar cell, the overlapping position of the secondary grid connection line on the main grid, that is, the interrupted position of the secondary grid connection line, is transferred to between two adjacent main grids. Thereby, the secondary grid connection line passes through the main grid completely, and the secondary grid slurry is printed at the main grid welding point, which can ensure the molding effect at the main grid welding point.

[0057] Some embodiments of the present application also provide a method for preparing the above solar cell, the preparation method comprising the following steps: Step S110 , providing a substrate 10 .

[0058] The substrate 10 is the basis for screen printing, that is, printing and manufacturing the gate electrode. The substrate 10 is usually a silicon substrate, which has a photovoltaic effect and can generate current under the irradiation of sunlight, thereby realizing power generation.

[0059] Step S120, using a first screen to print and form a first gate line structure 11 on the surface of the substrate 10, the first screen is provided with first opening grooves arranged at intervals along a first direction, and a plurality of second opening grooves located between two adjacent first opening grooves, each first opening groove extends along a second direction, and the plurality of second opening grooves are arranged at intervals along the second direction.

[0060] The first screen is in the form of a fully open steel screen with an opening rate of 100%. There is no mesh blocking the opening slot area, which can ensure the transmittance of the electrode slurry. The first opening slot of the first screen corresponds to the first grid line 111, that is, the printing and production of the main grid, and the second opening slot corresponds to the printing and production of the intermediate grid line 112. The printing and production of the main grid and the intermediate grid line 112 can be completed simultaneously or in steps. The position of the overlapping secondary grid connection line in the first screen is transferred from the main grid to the middle of the two adjacent main grids. The fully open steel screen graphics corresponding to the main grid include a harpoon, a main grid connection line, a pad, and an intermediate grid line 112.

[0061] Step S130, using a second screen to print on the surface of the substrate 10 to form a second gate line structure 12, the second screen is provided with a plurality of printing areas arranged at intervals along the first direction, each printing area is provided with a plurality of third opening grooves arranged at intervals along the second direction, each third opening groove extends along the first direction, and is provided corresponding to the second opening groove at the interval between two adjacent printing areas in the first direction.

[0062] The second screen adopts the form of a fully open steel plate screen with an opening rate of 100%. There is no mesh obstruction in the opening slot area, which can ensure the transmittance of the electrode slurry. The third opening slot of the second screen corresponds to the printing production of the second sub-grid line 121. A plurality of second sub-grid lines 121 located in a straight line are overlapped on a plurality of intermediate grid lines 112 to form a secondary grid. In addition, the second sub-grid lines 121 formed by the second screen printing are crossed with the first grid lines 111 formed by the first screen printing. The high plasticity of the secondary grid electrode slurry is utilized to ensure the shaping effect of the solder joints at the main grid welding. Thereby avoiding problems such as welding broken grids during component welding. The secondary grid in the second screen can be designed to be gradually changed at the intersection of the main grid, and the disconnection position of the secondary grid connection line is transferred from the overlap position on the main grid to the middle of the two adjacent main grids. The fully open steel plate screen pattern corresponding to the secondary grid includes the secondary grid connection line.

[0063] In actual situations, the solar cell can be printed on both sides to form grid electrodes. When printing and manufacturing the grid electrodes, a step-by-step printing process is adopted. When preparing the front electrode, the front main grid and the middle grid line 112 of the front electrode are first printed and manufactured. The number of the front main grid can be 16, and the number of the pads 1111 on the single front main grid is 6. Then the front sub-grid of the front electrode is printed, and the printed substrate 10 is sintered. The preparation of the back electrode is similar to that of the front electrode. The back main grid and the middle grid line 112 of the back electrode are first printed. The number of the back main grid can be 16, and the number of the pads 1111 on the single back main grid is 6. Then the back sub-grid of the back electrode is printed, and the printed substrate 10 is sintered. In addition, the solar cell after printing the grid electrodes can be cut into two pieces along the symmetry axis of the two front electrodes, and then the two pieces are connected to form.

[0064] Those skilled in the art will appreciate that the above-mentioned embodiments are specific examples for implementing the present application, and in actual applications, various changes may be made thereto in form and detail without departing from the spirit and scope of the present application.

Claims

1. A solar cell, characterized in that: It comprises a substrate and a first gate line structure and a second gate line structure located on the surface of the substrate; The first gate line structure includes a plurality of first gate lines arranged at intervals along a first direction, and a plurality of middle gate lines located between two adjacent first gate lines, each of the first gate lines extends along a second direction, the plurality of middle gate lines are arranged at intervals along the second direction, and each of the middle gate lines has an interval with the first gate lines on both sides; There are multiple second gate line structures, and the multiple second gate line structures are arranged at intervals along the first direction. Each of the second gate line structures includes multiple second sub-gate lines arranged at intervals along the second direction. Each second sub-gate line extends along the first direction. The multiple second sub-gate lines of each second gate line structure are cross-arranged with the same first gate line. Two adjacent second sub-gate lines in the first direction are connected via the middle gate line, and the first direction intersects with the second direction.

2. The solar cell according to claim 1, characterized in that Each of the middle gate lines includes a middle portion extending along the first direction, and a first overlapping portion and a second overlapping portion located at ends of the middle portion, wherein the first overlapping portion and the second overlapping portion are connected to the second sub-gate lines in different second gate line structures.

3. The solar cell according to claim 2, characterized in that: The first overlapping portion and the second overlapping portion both extend along the second direction, and the lengths of the first overlapping portion and the second overlapping portion in the second direction are greater than the width of the middle portion in the second direction.

4. The solar cell according to claim 3, characterized in that: The length of the first overlapping portion and the second overlapping portion in the second direction is greater than or equal to 70 microns and less than or equal to 150 microns, and the width of the first overlapping portion and the second overlapping portion in the first direction is greater than or equal to 10 microns and less than or equal to 20 microns.

5. The solar cell according to claim 2, characterized in that: The length of the middle portion in the first direction is less than or equal to 650 microns, and / or the width of the middle portion in the second direction is less than the width of the second sub-gate line in the second direction, and the width of the middle portion in the second direction is less than or equal to 40 microns.

6. The solar cell according to claim 2, characterized in that: The first overlapping portion and the second overlapping portion are symmetrically arranged with respect to the middle portion.

7. The solar cell according to claim 2, characterized in that: The distance between each of the intermediate gate lines and two adjacent first gate lines in the first direction is equal.

8. The solar cell according to claim 1, characterized in that The electrode paste of the first gate line is the same as the electrode paste of the middle gate line, and the electrode paste of the first gate line is different from the electrode paste of the second sub-gate line.

9. The solar cell according to claim 8, characterized in that Each of the second sub-grid lines has a gradient segment connected to the first grid line in the middle, and the width of at least a portion of the gradient segment in the second direction gradually increases in a direction approaching the connected first grid line.

10. A method for preparing a solar cell according to any one of claims 1 to 9, characterized in that: include: providing a substrate; A first grid line structure is formed by printing on the surface of the substrate using a first screen, wherein the first screen is provided with first opening grooves arranged at intervals along a first direction, and a plurality of second opening grooves located between two adjacent first opening grooves, each of the first opening grooves extending along a second direction, and a plurality of the second opening grooves arranged at intervals along the second direction; A second grid line structure is formed by printing on the surface of the substrate using a second screen, wherein the second screen is provided with a plurality of printing areas arranged at intervals along the first direction, each of the printing areas is provided with a plurality of third opening grooves arranged at intervals along the second direction, each of the third opening grooves extends along the first direction, and the interval between two adjacent printing areas in the first direction is provided with a corresponding second opening groove; The first direction intersects with the second direction.

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