Solar cell and its preparation method

Abstract

The present application relates to the technical field of photovoltaic power generation, and discloses a solar cell and a preparation method thereof. The solar cell therein includes a substrate and a first grid line structure and a second grid line structure located on the surface of the substrate. The first grid line structure includes a plurality of first grid lines arranged at intervals along a first direction, and a plurality of intermediate grid lines located between two adjacent first grid lines. Each first grid line extends along a second direction, the plurality of intermediate grid lines are arranged at intervals along the second direction, and there is a gap between each intermediate grid line and the first grid lines on both sides. There are a plurality of second grid line structures, and the plurality of second grid line structures are arranged at intervals along the first direction. Each second grid line structure includes 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 are arranged in a cross manner with the same first grid line. The solar cell and the preparation method thereof provided by the present application can help reduce the occurrence of welding open-circuit phenomenon.

Description

Technical Field

[0001] This application relates to the technical field of photovoltaic power generation, and particularly 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 constantly increasing. New energy can be obtained through a wide range of sources and has no polluting impact on the environment. Photovoltaic power generation can generate electric energy by obtaining the radiant energy of sunlight. Photovoltaic power generation is achieved through solar cells. Solar cells have the photovoltaic effect, that is, the photovoltaic effect, and can generate current under the irradiation of sunlight, thereby generating electricity.

[0003] When preparing solar cells, the screen printing process will be experienced. In the screen printing process, the grid line structure is formed by screen printing the electrode paste. The grid line structure is an important part of the solar cell and plays a role in 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 during the subsequent component welding process, resulting in the phenomenon of welding open circuit. Therefore, how to design the form of the grid line structure to reduce the welding open circuit phenomenon is an important issue. Summary of the Invention

[0004] The purpose of the embodiments of this application is to provide a solar cell and a method for preparing the same, which can help reduce the occurrence of welding open circuit phenomenon.

[0005] To solve the above technical problems, the embodiments of this application provide a solar cell. The solar cell includes a substrate and a first grid line structure and a second grid line structure located on the surface of the substrate. The first grid line structure includes a plurality of first grid lines arranged at intervals along a first direction, and a plurality of intermediate grid lines located between adjacent two first grid lines. Each first grid line extends along a second direction. The plurality of intermediate grid lines are arranged at intervals along the second direction. There is a gap between each intermediate grid line and the first grid lines on both sides. There are a plurality of second grid line structures, and the plurality of second grid line structures are arranged at intervals along the first direction. Each second grid line structure includes a plurality of second sub-grid lines arranged at intervals along the second direction. Each second sub-grid line extends along the first direction. The plurality of second sub-grid lines of each second grid line structure are arranged in a crosswise manner with the same first grid line. The two adjacent second sub-grid lines in the first direction are connected via the intermediate grid line. The first direction intersects with the second direction.

[0006] The embodiments of this application also provide a method for preparing the above solar cell. The preparation method includes:

[0007] Providing a substrate;

[0008] The first screen printing plate is used to print and form a first gate line structure on the substrate surface. The first screen printing plate 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;

[0009] The second screen printing plate is used to print and form a second gate line structure on the substrate surface. The second screen printing plate 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 the interval between two adjacent printing areas in the first direction corresponds to the second opening groove;

[0010] Wherein, the first direction intersects with the second direction.

[0011] The solar cell and its manufacturing method provided by the embodiment of the present application design a first gate line structure and a second gate line structure on the substrate surface. The first gate lines of the first gate line structure form main gates, and a plurality of intermediate gate lines arranged along the extension direction of the first gate lines are located between two adjacent first gate lines. The second sub-gate lines of the plurality of second gate line structures are connected through the intermediate gate lines to form sub-gates. The plurality of second sub-gate lines of each second gate line structure are arranged in a crossed manner with the same first gate line. Thereby, the overlapping position of the sub-gate connection lines is transferred, and the overlapping position of the sub-gate connection lines is transferred to between two adjacent main gates. The characteristics of the sub-gate paste can be utilized to ensure the plasticizing effect at the position where the main gate welding part is located. Furthermore, the phenomenon of welding breakage of the gate lines can be reduced. Description of the Drawings

[0012] One or more embodiments are exemplarily illustrated by the pictures in the corresponding drawings. These exemplary illustrations do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings are represented as similar elements, unless otherwise stated, the drawings in the drawings do not constitute a proportional limitation.

[0013] Figure 1 is a schematic diagram of the gate line pattern in a solar cell adopting a conventional gate line form in some cases;

[0014] Figure 2 is Figure 1 a partial enlarged schematic diagram of the shown gate line pattern;

[0015] Figure 3 is Figure 1 a schematic diagram of the structure of the main gate in the shown gate line pattern;

[0016] Figure 4 is Figure 1 a partial enlarged schematic diagram of the structure of the main gate in the shown gate line pattern;

[0017] Figure 5 isFigure 1 Schematic diagram of the structure of the auxiliary gate in the shown gate line pattern;

[0018] Figure 6 is Figure 1 Partial enlarged schematic diagram of the structure of the auxiliary gate in the shown gate line pattern;

[0019] Figure 7 Schematic diagram of the structure of a solar cell provided by some embodiments of the present application;

[0020] Figure 8 Schematic diagram of the gate line pattern in a solar cell provided by some embodiments of the present application;

[0021] Figure 9 is Figure 8 Partial enlarged schematic diagram of the structure of the shown gate line pattern;

[0022] Figure 10 is Figure 8 Schematic diagram of the structure of the first gate line in the shown gate line pattern;

[0023] Figure 11 is Figure 8 Partial enlarged schematic diagram of the structure of the first gate line in the shown gate line pattern;

[0024] Figure 12 is Figure 8 Schematic diagram of the structure of the second gate line in the shown gate line pattern;

[0025] Figure 13 is Figure 8 Partial enlarged schematic diagram of the structure of the second gate line in the shown gate line pattern;

[0026] Figure 14 is Figure 8 Schematic diagram of the structure of the middle gate line in the shown gate line pattern;

[0027] Figure 15 is Figure 8 Schematic diagram of the structure of the gradient section of the second sub-gate line in the shown gate line pattern. Detailed implementation manners

[0028] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the following will elaborate on each embodiment of this application in conjunction with the accompanying drawings. However, those of ordinary skill in the art can understand that in each embodiment of this application, many technical details are presented to help readers better understand this application. Nevertheless, even without these technical details and various changes and modifications based on the following embodiments, the technical solutions claimed in this application can still be implemented. The division of the following embodiments is for convenience of description and should not impose any limitation on the specific implementation of this application. Without conflict, the various embodiments can be combined and referenced to each other.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill 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" and any variations thereof in the specification and claims of this application and the above description of the accompanying drawings are intended to cover non-exclusive inclusion.

[0030] In the description of the embodiments of this application, unless otherwise clearly specified and limited, technical terms such as "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can also be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal communication of two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of this application can be understood according to specific circumstances.

[0031] With the continuous development of solar cell manufacturing technology, the photoelectric conversion efficiency of solar cells is also constantly improving. When manufacturing solar cells, the screen printing process is involved. Through the screen printing process, grid line electrodes are formed on the surface of the solar cell. The grid lines can be divided into main grids and sub-grids, and the sub-grids are also called fine grids. According to the number of main grids, solar cells can be divided into ultra-high main grid cells, multi-main grid cells, and no-main grid cells. The main grids usually intersect perpendicularly with the sub-grids, and the grid line electrodes can be formed on one side or both sides of the solar cell. Screen printing is carried out using a screen plate. The screen plate is designed with openings through which the printing metal paste can pass. The metal paste is usually silver paste. The metal paste is printed on the cell surface to form the main grid or sub-grid, and the required electrode pattern is obtained after sintering or drying and curing.

[0032] The fully open steel mesh screen is a screen with a 100% opening rate. The main body is no longer woven from steel wires, but made of alloy steel sheets, and the printing openings are obtained by laser grooving. The opening rate of the screen printing working area reaches 100%, that is, all printed patterns have no steel wires or other similar structures blocking. Since there is no mesh yarn blocking in the grooved area of the fully open steel mesh screen, the transmittance of the slurry can be greatly improved, saving the consumption of the slurry. At the same time, using the fully open steel mesh screen for screen printing can optimize the width of the grid lines, significantly reducing the light-shielding area on the battery surface. Moreover, the height of the grid lines after printing with the fully open steel mesh 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 lines and improve the fill factor of solar cells.

[0033] However, currently, the fully open steel mesh screen is mainly used for small-sized heterojunction batteries and the metallization printing of 0BB (Busbar, main grid; 0BB means no main grid) batteries with special component welding processes. When the fully open steel mesh screen is applied to multi-main grid batteries, such as the mainstream SMBB (Super Multi-Busbar) battery products, it will cause the plastic shaping requirements at the main grid lap / welding to not match the SMBB battery products, resulting in abnormal problems such as broken grids and poor lap at the component welding. Table 1 below shows the plastic shaping comparison of SMBB battery products at the main grid lap / welding in different situations of using conventional PI (Polyimide) screen printing and fully open steel mesh screen printing for the conventional grid line form design. Among them, the conventional grid line form is as Figure 1 and Figure 2 shown, and the solar cell adopts a gradient or I-shaped design on the main grid 100, and the sub-grid 200 laps on the main grid 100. Figure 3 and Figure 4 show the structure of the main grid 100 in the conventional grid line form. The main grid 100 includes a main grid connection line, a main pad 101 located on the main grid connection line for welding the solder tape, and a lap / welding part 102. Figure 5 and Figure 6 show the structure of the sub-grid 200 in the conventional grid line form. The sub-grid 200 includes multiple sections of sub-grid connection lines. The thickness of the screen used in the comparative experiment is 18.5 microns, and the opening width of the groove is 40 microns.

[0034] Table 1. Plastic Shaping Comparison Table of Lap / Welding at Grid Line Electrodes of Solar Cells Made with Different Screens

[0035]

[0036] It can be seen that the conventional grid line form design of SMBB battery products has a low plastic height performance when using a full-opening steel mesh screen printing, which will cause welding fusing during the process of welding the solder tape of the component, resulting in an open circuit of the current loop, manifested as blackening of EL (Electroluminescence), which is called welding broken grid. That is, the full-opening steel mesh screen does not match the current process of SMBB battery products, and the grid line form needs to be optimized to ensure the plastic effect at the position where the welding part of the main grid solder tape is located. That is to say, it is necessary to design the grid line form of the multi-main grid battery so that the full-opening steel mesh screen pattern based on the multi-main grid battery product can adapt to the process of the multi-main grid battery product and solve problems such as welding broken grid.

[0037] In order to reduce the phenomenon of welding broken grid that occurs after the solar cell uses a full-opening steel mesh screen for screen printing process, 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 for plastic shaping, and the overlapping position of the sub-grid connection line is transferred between two adjacent main grids. When performing screen printing, by using the characteristic that the electrode paste corresponding to the sub-grid has high plasticity, the plastic effect at the intersection of the sub-grid and the main grid, that is, at the position where the main grid welding part is located, is ensured. This design scheme can solve the problem of welding broken grid that occurs when the full-opening steel mesh screen technology is applied in multi-main grid battery products, and at the same time, it does not affect the efficiency wet weight, and can achieve more precise imaging refinement and more accurate alignment of the pattern. In terms of efficiency, it can ensure that the light shielding ratio is the same as that of the conventional grid line form. In terms of wet weight, it can fit the actual printing plastic shaping through the design of the screen parameters. That is, according to the actual printing morphology monitored for a long time, the expected wet weight of the fitting scheme is fitted, and the screen design parameters are adjusted.

[0038] It should be noted that in order to adapt to the functional characteristics of different grid lines, during the screen printing process, the electrode paste used for printing the main grid is different from the electrode paste used for printing the sub-grid, and each has its own required composition and ratio. The main grid paste is usually only used to ensure the welding tensile strength, and has relatively low requirements for the plastic forming ability of the paste itself. The sub-grid paste usually has good plastic forming ability, good sintering characteristics and ohmic contact characteristics. When using a full-opening steel mesh stencil for the screen printing process, due to the good paste transmittance, the plasticity of the main grid is significantly lower than that of the sub-grid. That is to say, when the solar cell adopts the conventional grid line form, the overlapping / welding part of the main grid and the main grid connection line are printed by the main grid paste, and the plasticity is poor. In actual situations, considering the paste development cost, without changing the original paste system, the overlapping position on the main grid connection line, that is, the discontinuous position of the sub-grid connection line, can be transferred between two adjacent main grids. Thus, the sub-grid connection line completely passes through the main grid, and the sub-grid paste is printed at the position where the main grid welding part is located to ensure the plastic forming effect at the position where the main grid welding part is located. By adopting the method of optimizing the grid line pattern design, it is more conducive to cost reduction and efficiency improvement.

[0039] The following will combine Figures 7 to 15 to illustrate the structure of the solar cell provided by some embodiments of the present application.

[0040] As Figures 7 to 15 shown, the solar cell provided by some embodiments of the present application includes a substrate 10 and a first grid line structure 11 and a second grid line structure 12 located on the surface of the substrate 10. The first grid line structure 11 includes a plurality of first grid lines 111 arranged at intervals along the first direction ( Figure 9 the direction shown by the arrow A in Figure 9 ), and a plurality of intermediate grid lines 112 located between two adjacent first grid lines 111. Each first grid line 111 extends along the second direction ( Figure 9 the direction shown by the arrow B in Figure 9 ). The plurality of intermediate grid lines 112 are arranged at intervals along the second direction, and there is an interval between each intermediate grid line 112 and the first grid lines 111 on both sides. There are a plurality of second grid line structures 12, and the plurality of second grid line structures 12 are arranged at intervals along the first direction. Each second grid line structure 12 includes a plurality of second sub-grid lines 121 arranged at intervals along the second direction. Each second sub-grid line 121 extends along the first direction. The plurality of second sub-grid lines 121 of each second grid line structure 12 are cross-set with the same first grid line 111, and two adjacent second sub-grid lines 121 in the first direction are connected via the intermediate grid line 112. The first direction intersects with the second direction.

[0041] The substrate 10 is the basis for forming the grid line electrodes of the solar cell, and usually a silicon substrate is used. Metal pastes can be printed on the front and back surfaces of the substrate 10 to form grid line electrodes with specific patterns. The grid line electrode printed on the front surface of the substrate 10 is the front electrode 110, and the grid line electrode printed on the back surface of the substrate 10 is the back electrode. Usually, the front surface of the substrate 10 is the light-receiving surface, receiving the solar energy brought by the directly incident light, and the back surface of the substrate 10 is the backlight surface, receiving the solar energy brought by the scattered and refracted light. The grid line electrodes 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 Taking the single-sided cell as an example for illustration. Figure 8 and Figure 9 show the grid line patterns on the surface of the solar cell.

[0042] The first grid line structure 11 and the second grid line structure 12 are formed in different regions on the surface of the substrate 10, Figure 10 and Figure 11 show the first grid line structure 11, Figure 12 and Figure 13The second gate line structure 12 is shown. The first gate line structure 11 and the second gate line structure 12 can be formed by printing using different stencils to form the main grid and the sub-grid on the surface of the solar cell. In different gate line structures, the first gate line 111 forms the main grid of the solar cell, and pads 1111 are distributed on the main grid. The second sub-gate lines 121 are connected through the intermediate gate lines 112 to form the sub-grid of the solar cell. The second sub-gate lines 121 may pass through the pads 1111 or may not pass through the pads 1111. The second sub-gate lines 121 passing through the pads 1111 may include two disconnected parts and are connected through the pads 1111 to form a path. The main grid and the sub-grid are arranged at intervals on the surface of the substrate 10, and their extending directions, i.e., the first direction and the second direction, may be two perpendicular directions or may be two directions with other included angles. The intermediate gate lines 112 and the second sub-gate lines 121 on both sides maintain a one-to-one or one-to-many correspondence relationship, that is, one intermediate gate line 112 may be connected to only one second sub-gate line 121 at one end or may be connected to multiple second sub-gate lines 121. The intermediate gate lines 112 and the second sub-gate lines 121 are arranged in the same direction, and the second sub-gate lines 121 may overlap on the intermediate gate lines 112 during printing. Thus, the discontinuous second sub-gate lines 121 are connected through the intermediate gate lines 112 to form a complete sub-grid, ensuring the formation of a path for electron movement. In actual situations, the number of main grids may be 9, 12, 13, 15, 16, 18, or 20. The number of sub-grids may be 45, 50, 55, 60, 65, 70, or 75. In addition, the solar cells provided in some embodiments of the present application may be whole cells or may be constructed in the form of half cells, and the half cells are formed by dividing the whole cell into two halves along the direction perpendicular to the main grid.

[0043] For the solar cells provided in some embodiments of the present application, the first gate line structure 11 and the second gate line structure 12 are designed on the surface of the substrate 10. The first gate line 111 of the first gate line structure 11 forms the main grid, and a plurality of intermediate gate lines 112 arranged along the extending direction of the first gate line 111 are located between two adjacent first gate lines 111. The second sub-gate lines 121 of the plurality of second gate line structures 12 are connected through the intermediate gate lines 112 to form the sub-grid. 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. Thus, the overlapping position of the sub-grid connection lines is transferred, and the overlapping position of the sub-grid connection lines is transferred between two adjacent main grids. The characteristics of the sub-grid paste can be utilized to ensure the plasticizing effect at the position where the main grid welding part is located. Furthermore, the phenomenon of welding breakage of the grid is reduced.

[0044] When using a fully open steel mesh screen for screen printing, since the main grid and the middle grid line 112 connecting the second sub-grid lines 121, i.e., the auxiliary grid connection line, are designed separately, when printing the second sub-grid lines 121 forming the auxiliary grid, the second sub-grid lines 121 can pass through the main grid and intersect with the main grid. That is, the overlapping part located at the welding tape of the main grid in the conventional design is transferred between two adjacent main grids. At the position where the welding part of the main grid is located, the auxiliary grid paste can be used for covering. By utilizing the fact that the plasticity of the auxiliary grid paste is better than that of the main grid paste, the shaping effect at the position of the main grid welding tape can be ensured, and the shaping height can be increased. Thereby ensuring the welding effect during the subsequent welding process of the solar cell and avoiding the problem of broken grid in the component welding caused by the relatively low shaping height at the welding position when using a fully open steel mesh screen for printing in the conventional grid line form.

[0045] As Figure 14 shown, each middle grid line 112 may include a middle part 1121 extending in the first direction, and a first overlapping part 1122 and a second overlapping part 1123 located at the ends of the middle part 1121. The first overlapping part 1122 and the second overlapping part 1123 are connected to the second sub-grid lines 121 in different second grid line structures 12.

[0046] The middle grid line 112 includes multiple parts, and each part 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, ensuring that two adjacent second sub-grid lines 121 in the auxiliary grid can still be connected to form a whole at a certain distance. The extending direction of the middle part 1121 is the same as that of the second sub-grid lines 121, and it can play a connecting role between two adjacent second sub-grid lines 121. Under the condition of ensuring the connection effect, the middle part 1121 can be set with a smaller width to form a narrow strip shape, so as to reduce the shading area and ensure the smoothness of the electron transmission path.

[0047] The first overlapping part 1122 and the second overlapping part 1123 are the parts providing the overlapping basis for different second sub-grid lines 121. The first overlapping part 1122 and the second overlapping part 1123 are located at both ends of the middle part 1121 and are arranged corresponding to the intervals between two adjacent second sub-grid lines 121 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 line 112, the two overlapping parts of the middle grid line 112 can extend beyond the two side edges of the second sub-grid lines 121 distributed in the width direction. So that the second sub-grid lines 121 can completely overlap within the area where the overlapping parts of the middle grid line 112 are located during printing.

[0048] It should be noted that when designing the fully open steel mesh stencil, since the openings of the slots present a 100% opening rate, discontinuous parts are provided between the slots at different positions to ensure that the stencil will not be separated into multiple parts due to the complete penetration of the slots. That is, discontinuous parts are reserved in the slot printing area. And the discontinuous part of the sub-grid connection line corresponds to the position where the intermediate grid line 112 in the first grid line structure 11 is located.

[0049] In some embodiments, both the first overlapping portion 1122 and the second overlapping portion 1123 may extend along the second direction, and the length L1 of the first overlapping portion 1122 and the second overlapping portion 1123 in the second direction is greater than the width W2 of the intermediate portion 1121 in the second direction.

[0050] That is to say, the two overlapping portions of the intermediate grid line 112 can extend along the width direction of the second sub-grid line 121. And, the length L1 of the two overlapping portions in the second direction is greater than the width W2 of the intermediate 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 intermediate portion 1121 in the second direction, the two overlapping portions can extend beyond the edge of the intermediate portion 1121 in the width direction of the second sub-grid line 121. Furthermore, it provides favorable conditions for the second sub-grid line 121 to overlap at the end of the intermediate grid line 112, ensuring the connection effect between the second sub-grid line 121 and the intermediate grid line 112.

[0051] In actual situations, the length L1 of the first overlapping portion 1122 and the second overlapping portion 1123 in the second direction can be made greater than or equal to 70 microns and less than or equal to 150 microns, and the width W1 of the first overlapping portion 1122 and the second overlapping portion 1123 in the first direction is greater than or equal to 10 microns and less than or equal to 20 microns.

[0052] By setting the two overlapping portions to be strip-shaped, while reducing the light-shielding area, the range where the overlapping portions are located can completely cover the end-slurry printing range of the second sub-grid line 121. Ensure the connection effect between the second sub-grid line 121 and the intermediate grid line 112.

[0053] Since the intermediate grid line 112 is located between two adjacent main grids and does not play a role in forming solder joints, the size of the overlapping part 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 solder joint, the area at the overlapping position on the main grid is usually set to be relatively large. In the solar cells provided in some embodiments of the present application, the grid line form is optimized. The intermediate grid line 112 is far from the solder joint position on the main grid and does not undertake the component welding function, but only provides an overlapping 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 to reduce the size, saving the use of paste material while reducing the light shielding area. Or the size can be designed within a larger range to ensure a good overlapping effect with the second sub-grid line 121. For example, the length L1 of the first overlapping part 1122 and the second overlapping part 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 overlapping part 1122 and the second overlapping part 1123 in the first direction can be 10 microns, 12 microns, 14 microns, 16 microns, 18 microns or 20 microns.

[0054] In addition, the length L2 of the middle part 1121 in the first direction can be less than or equal to 650 microns.

[0055] Compared with the conventional grid line form where it is necessary to ensure a large area at the main grid welding part, i.e., the solder joint, the improved grid line form can reduce the length dimension of the middle part 1121 of the intermediate grid line 112. Thus, effectively reducing the light shielding area and ensuring 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.

[0056] In some embodiments, the width W2 of the middle part 1121 in the second direction can be made less than the width of the second sub-grid line 121 in the second direction, and the width W2 of the middle part 1121 in the second direction is less than or equal to 40 microns.

[0057] The middle part 1121 is located at the middle position of the intermediate grid line 112 and can only play a role in transporting electrons. Therefore, the width W2 of the middle part 1121 in the second direction can be made less than the width of the second sub-grid line 121 in the second direction. At the same time, since the middle part 1121 is not used as a welding part, the width of the middle part 1121 in the second direction can be controlled within a range less than or equal to 40 microns. So as to reduce the light shielding area and save the use of electrode paste.

[0058] As a comparative illustration of the dimension design, in one example, for the main grid lap / welding part designed in the conventional grid line form, the lengths and widths of the two side parts of the I-shaped part are 150 microns and 20 microns respectively, and the lengths and widths of the middle part of the I-shaped part are 650 microns and 40 microns respectively. When the middle grid line 112 designed in the I-shaped form is located between two adjacent main grids, the dimensions of the middle grid line 112 can be designed such that the lengths and widths of the two side lap parts are 150 microns and 15 microns respectively, and the lengths and widths of the middle extending part are 500 microns and 20 microns respectively.

[0059] In actual situations, the first lap part 1122 and the second lap part 1123 can be symmetrically arranged with respect to the middle part 1121.

[0060] That is, the first lap part 1122 and the second lap part 1123 adopt the same shape and dimension design, and the first lap part 1122 and the second lap part 1123 present a symmetric form. In this way, the printing and manufacturing of the middle grid line 112 can be simplified, facilitating the design of the stencil.

[0061] In some embodiments, the distance between each middle grid line 112 and two adjacent first grid lines 111 in the first direction is equal.

[0062] That is to say, the middle grid line 112 is located at the position of the middle line of two adjacent first grid lines 111. Ensure that the lengths of each second sub-grid line 121 on both sides of the crossed first grid line 111 are consistent, facilitating the positioning during the printing of the grid lines.

[0063] In actual situations, the projected shape of the first lap part 1122 and the second lap part 1123 on the surface of the substrate 10 can be any one of a rectangle, a trapezoid, an ellipse, and a triangle.

[0064] The lap part can adopt different shapes according to the actual needs. Adopting a rectangle can simplify the printing and manufacturing of the grid lines and facilitate the opening design of the stencil. Gradient shapes such as a trapezoid and an ellipse can, while ensuring the lap effect of the second sub-grid line 121, help reduce the light-shielding area.

[0065] In some embodiments, the electrode paste of the first grid line 111 can be the same as the electrode paste of the middle grid line 112, and the electrode paste of the first grid line 111 is different from the electrode paste of the second sub-grid line 121.

[0066] That is to say, the middle grid line 112 can be printed and fabricated using the electrode paste of the same system as the main grid, and can be screen-printed through the same full-opening steel mesh stencil. Moreover, the printing and fabrication of the first grid line 111 and the middle grid line 112 can be completed synchronously, simplifying the printing and fabrication process of different grid lines. The second sub-grid line 121 can be printed and fabricated using the sub-grid electrode paste to ensure the plastic shaping effect of the solder joints at the main grid welding points.

[0067] As Figure 13 and Figure 15 shown, the middle part of each second sub-grid line 121 can have a tapered section 122 connected to the first grid line 111, and the width of at least part of the tapered section 122 in the second direction gradually increases in the direction close to the connected first grid line 111.

[0068] The tapered section 122 is designed on the second sub-grid line 121 and can be printed and fabricated using the sub-grid paste, having better plasticity. At the same time, the tapered section 122 with a changing width can form a good welding foundation for the main grid welding part, ensuring the welding effect with the welding tape.

[0069] The tapered section 122 can be located in the middle of the second sub-grid line 121. By designing the tapered section 122 in the middle of the second sub-grid line 121, the plastic shaping at the main grid welding point can be optimized, and the welding tolerance can be improved.

[0070] In addition, the length of the tapered section 122 of each second sub-grid line 121 in the first direction can be greater than or equal to 0.6 mm and less than or equal to 1.2 mm.

[0071] The tapered section 122 is located at the position of the welding part of the main grid. By controlling the length dimension of the tapered section 122, while ensuring the welding effect, the light-shielding area can be reduced, and the use of the electrode paste can be saved. In actual situations, the length of the tapered 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.

[0072] As Figure 15As shown, the tapered section 122 of the auxiliary grid can adopt a two-stage taper form. In the extending direction of the auxiliary grid connection line, the tapered 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-tapered 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 one 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 tapered section 122 can ensure excellent shaping at the main grid welding position during the printing of the auxiliary grid, effectively preventing the phenomenon of fuse breakage of the grid during the subsequent component welding process.

[0073] Table 2 below shows the comparison of the main grid welding positions when the full-opening steel mesh stencil is applied to the conventional grid line pattern and the grid line patterns provided by some embodiments of the present application. The thickness of the full-opening steel mesh stencil used in the comparative test is 18.5 μm, and the opening width of the slotted opening is 50 μm.

[0074] Table 2. Comparison table of the shaping of the welding position of the solar cell when different grid line forms are adopted

[0075]

[0076] It can be seen that the shaping height performance of the conventional grid line form design is relatively low when printed with a full-opening steel mesh stencil, which will cause a large proportion of welding grid breakage during the component welding process. After improving the grid line form, the full-opening steel mesh stencil can better adapt to the grid line printing and production of multi-main grid battery products. It can greatly increase the shaping height at the welding tape position of the main grid welding, effectively reduce the welding grid breakage phenomenon during the component welding process, and ensure that the welding tensile force of the welding tape reaches the qualified tensile force value. Therefore, without changing the original paste system of the main grid and the auxiliary grid of the solar cell, by transferring the overlapping position of the auxiliary grid connection line on the main grid, that is, the discontinuous position of the auxiliary grid connection line, to between two adjacent main grids. So that the auxiliary grid connection line completely passes through the main grid, and the auxiliary grid paste is printed at the main grid welding position, which can ensure the shaping effect of the main grid welding position.

[0077] Some embodiments of the present application also provide a preparation method for the above-mentioned solar cell, and the preparation method includes the following steps:

[0078] Step S110, provide a substrate 10.

[0079] The substrate 10 is the basis for the screen printing process, that is, printing and manufacturing the grid electrode. The substrate 10 usually adopts a silicon substrate, has a photovoltaic effect, and can generate current under the irradiation of sunlight. Thus realizing power generation.

[0080] Step S120: Use a first stencil to print and form a first gate line structure 11 on the surface of the substrate 10. The first stencil is provided with first opening slots arranged at intervals along a first direction, and a plurality of second opening slots located between two adjacent first opening slots. Each first opening slot extends along a second direction, and the plurality of second opening slots are arranged at intervals along the second direction.

[0081] The first stencil is in the form of a fully open steel mesh stencil with an opening rate of 100%. There is no mesh yarn blocking in the opening slot area, which can ensure the transmittance of the electrode paste. The first opening slots of the first stencil correspond to the printing and production of the first gate lines 111, that is, the main gates. The second opening slots correspond to the printing and production of the intermediate gate lines 112. The printing and production of the main gates and the intermediate gate lines 112 can be completed synchronously or step by step. The position of the overlapping sub-gate connection lines in the first stencil is transferred from the main gate to the middle between two adjacent main gates. The fully open steel mesh stencil pattern corresponding to the main gate includes harpoons, main gate connection lines, pads, and intermediate gate lines 112.

[0082] Step S130: Use a second stencil to print and form a second gate line structure 12 on the surface of the substrate 10. The second stencil 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 slots arranged at intervals along the second direction. Each third opening slot extends along the first direction, and the interval between two adjacent printing areas in the first direction corresponds to the second opening slot.

[0083] The second stencil is in the form of a fully open steel mesh stencil with an opening rate of 100%. There is no mesh yarn blocking in the opening slot area, which can ensure the transmittance of the electrode paste. The third opening slots of the second stencil correspond to the printing and production of the second sub-gate lines 121. A plurality of second sub-gate lines 121 located on a straight line form a sub-gate by overlapping on a plurality of intermediate gate lines 112. Moreover, the second sub-gate lines 121 printed by the second stencil cross the first gate lines 111 printed by the first stencil. Utilize the characteristic of high plasticity of the sub-gate electrode paste to ensure the plastic shaping effect of the solder joints at the main gate. Thus, problems such as broken gates during the component welding process can be avoided. The intersection of the sub-gate corresponding to the main gate in the second stencil can be designed to be gradual. The disconnection position of the sub-gate connection lines is transferred from the overlapping position on the main gate to the middle between two adjacent main gates. The fully open steel mesh stencil pattern corresponding to the sub-gate includes sub-gate connection lines.

[0084] In actual situations, solar cells can be fabricated with grid electrodes printed on both sides. When fabricating the grid electrodes by printing, a step-by-step printing process is adopted. When preparing the front electrode, first print and fabricate the front main grid and the intermediate grid line 112 of the front electrode. The number of front main grids can be 16, and the number of pads 1111 on a single front main grid is 6. Then print the front sub-grid of the front electrode, and sinter the printed substrate 10. The preparation of the back electrode is similar to that of the front electrode. First, print the back main grid and the intermediate grid line 112 of the back electrode. The number of back main grids can be 16, and the number of pads 1111 on a single back main grid is 6. Then print the back sub-grid of the back electrode, and sinter the printed substrate 10. Additionally, 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...

[0085] Those of ordinary skill in the art can understand that the above embodiments are specific examples for implementing the present application. In actual applications, various changes can be made to them in form and details without departing from the spirit and scope of the present application.

Claims

1. A solar cell, characterized in that, It includes 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 in a first direction, and a plurality of intermediate gate lines located between two adjacent first gate lines. Each first gate line extends in a second direction, the plurality of intermediate gate lines are arranged at intervals in the second direction, and there is a gap between each intermediate gate line and the first gate lines on both sides; There are a plurality of the second gate line structures, and the plurality of second gate line structures are arranged at intervals in the first direction. Each second gate line structure includes a plurality of second sub-gate lines arranged at intervals in the second direction. Each second sub-gate line extends in the first direction. The plurality of second sub-gate lines of each second gate line structure are arranged to cross the same first gate line. Two adjacent second sub-gate lines in the first direction are connected via the intermediate gate line. The first direction intersects with the second direction; The electrode paste for forming the first gate line is different from the electrode paste for forming the second sub-gate line.

2. The solar cell according to claim 1, wherein Each intermediate gate line includes an intermediate part extending in the first direction, and a first overlapping part and a second overlapping part located at the ends of the intermediate part. The first overlapping part and the second overlapping part 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, Both the first overlapping part and the second overlapping part extend in the second direction, and the lengths of the first overlapping part and the second overlapping part in the second direction are greater than the width of the intermediate part in the second direction.

4. The solar cell according to claim 3, characterized in that, The lengths of the first overlapping part and the second overlapping part in the second direction are greater than or equal to 70 microns and less than or equal to 150 microns, and the widths of the first overlapping part and the second overlapping part in the first direction are greater than or equal to 10 microns and less than or equal to 20 microns.

5. The solar cell according to claim 2, wherein, The length of the intermediate part in the first direction is less than or equal to 650 microns, and / or the width of the intermediate part in the second direction is less than the width of the second sub-gate line in the second direction, and the width of the intermediate part 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 part and the second overlapping part are symmetrically arranged with respect to the intermediate part.

7. The solar cell according to claim 2, characterized in that, The distance between each intermediate gate line and the 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 intermediate gate line.

9. The solar cell according to claim 8, wherein, The middle part of each second sub-gate line has a tapered section connected to the first gate line, and at least part of the width of the tapered section in the second direction gradually increases in the direction close to the connected first gate line.

10. The preparation method of the solar cell according to any one of claims 1 to 9, characterized in that, It includes: Providing a substrate; Using a first screen printing plate to print and form a first gate line structure on the surface of the substrate. The first screen printing plate is provided with first opening grooves arranged at intervals in the first direction, and a plurality of second opening grooves located between two adjacent first opening grooves. Each first opening groove extends in the second direction, and the plurality of second opening grooves are arranged at intervals in the second direction; Use a second stencil to print and form a second gate line structure on the surface of the substrate. The second stencil 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. A position corresponding to the second opening groove is provided at an interval between two adjacent printing areas in the first direction; Wherein, the first direction intersects with the second direction.

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