Solar cell and photovoltaic module

Abstract

The embodiment of the present application provides a solar cell and a photovoltaic cell assembly, the solar cell comprises: a semiconductor substrate; a first grid line arranged on the surface of the semiconductor substrate along a first direction; a second grid line arranged on the surface of the semiconductor substrate along a second direction, the second grid line is perpendicular to and intersects with the first grid line; the second grid line comprises: an adjacent part connected with the first grid line; an extension part connected with the adjacent part, and the adjacent part is located between the first grid line and the extension part, in parallel to the first direction, the length of the extension part is at least 0.8 of the length of the second grid line; a solder mask layer located on the surface of the second grid line and covering at least the surface of the extension part; a third grid line arranged on the surface of the semiconductor substrate along the second direction and perpendicular to the first grid line. The embodiment of the present application is favorable to improve the situation that the third grid line intersects with the first grid line in the process of manufacturing the photovoltaic cell.

Description

TECHNICAL FIELD

[0001] Embodiments of the present application relate to the field of photovoltaics, and in particular to a solar cell and a photovoltaic module. BACKGROUND

[0002] A solar cell is a kind of photoelectric semiconductor structure for generating electricity by using sunlight. It can output voltage and generate current in a loop as long as it is illuminated by light with a certain illumination condition.

[0003] Generally, a solar cell is made of a silicon wafer through production processes such as texturing, diffusion, cleaning, film plating, and screen printing. The screen printing process is to print conductive paste onto the front and / or back of the solar cell according to a certain screen pattern. The printed structure includes main grids and auxiliary grids. The auxiliary grids collect the photo-generated current generated by the solar cell to the main grids. Different solar cells are welded together to form a photovoltaic module, and the welding process mainly includes welding with a solder strip and a main grid.

[0004] However, the photoelectric conversion efficiency and service life of the current photovoltaic module need to be improved. SUMMARY

[0005] Embodiments of the present application solve the technical problem of providing a solar cell and a photovoltaic module that can improve the broken grid phenomenon in the junction area of the first grid line and the third grid line in the solar cell.

[0006] To solve the above problems, embodiments of the present application provide a solar cell, which includes a semiconductor substrate; a first grid line arranged on the surface of the semiconductor substrate along a first direction; a second grid line arranged on the surface of the semiconductor substrate along a second direction, the second grid line being perpendicular to and intersecting the first grid line, and in a direction perpendicular to the surface of the semiconductor substrate, the thickness of the second grid line being less than the thickness of the first grid line; the second grid line including: a proximal portion connected to the first grid line; an extension portion connected to the proximal portion, and the proximal portion being located between the first grid line and the extension portion, the length of the extension portion being greater than or equal to the length of the proximal portion in a direction parallel to the first direction; a solder resist layer located on the surface of the second grid line and covering at least the top surface of the extension portion; and a third grid line arranged on the surface of the semiconductor substrate along the second direction and perpendicular to the first grid line, wherein the third grid line also covers the first grid line, the solder resist layer, and the second grid line, and the third grid line is electrically connected to at least two first grid lines.

[0007] In addition, the solder resist layer covers the entire top surface of the second grid line.

[0008] In addition, in a direction perpendicular to the surface of the semiconductor substrate, the thickness of the solder resist layer is 5-10 nm.

[0009] In addition, the material of the solder resist layer comprises epoxy resin or polyester resin.

[0010] In addition, in the direction parallel to the second direction, the width of the second gate line is greater than or equal to the width of the third gate line.

[0011] In addition, in a direction perpendicular to the surface of the semiconductor substrate, the thickness of the second gate line is 0.4-1 times the thickness of the third gate line.

[0012] In addition, in a direction perpendicular to the surface of the semiconductor substrate, the thickness of the second gate line is 0.004-0.016 mm.

[0013] In addition, in the direction parallel to the second direction, the width of the second gate line is 0.02-0.05 mm.

[0014] In addition, in the direction parallel to the first direction, the length of the second gate line is 0.3-0.6 mm. In addition, the first gate line and the second gate line are integrally formed.

[0015] In addition, the first gate line comprises a flat portion and transition portions on opposite sides of the flat portion, and the surface of the transition portion is connected to the second gate line; in the direction of the flat portion pointing to the second gate line, the thickness of the transition portion in the direction perpendicular to the surface of the semiconductor substrate gradually decreases.

[0016] In addition, the embodiment of the present application further provides a photovoltaic cell assembly, comprising: a solar cell string, wherein the solar cell string is formed by electrically connecting the above-mentioned solar cell pieces.

[0017] Compared with the related art, the technical scheme provided by the embodiment of the present application has the following advantages:

[0018] In the technical solution, the second grid lines are arranged on the first grid line, and the solder resist layer is arranged on the surface of the second grid line and covers at least the top surface of the extension of the second grid line. The extension is the part of the second grid line away from the first grid line and bordering the third grid line. The second grid line is arranged to increase the thickness of the laminated structure of the first grid line and the third grid line at the bordering area, thereby reducing the probability of the solder tin of the solder strip flowing into the bordering area of the first grid line and the third grid line to separate the first grid line and the third grid line. In addition, compared with the solution of increasing the thickness of the third grid line, the solution of arranging the second grid line can save the amount of paste required for manufacturing the second grid line and the third grid line, thereby reducing the cost of the solar cell sheet. Meanwhile, the solder resist layer can prevent the solder tin of the solder strip from flowing into the bordering area of the second grid line and the third grid line, thereby preventing the disconnection of the second grid line and the third grid line. Even if the length of the second grid line is short, the risk of the disconnection of the second grid line and the third grid line can be reduced due to the arrangement of the solder resist layer. Therefore, the solar cell sheet provided by the embodiment of the present application can save the cost while effectively ensuring the quality of the solar cell sheet, so that the photovoltaic cell module manufactured by using the solar cell sheet has low cost, high photoelectric conversion efficiency, and long service life.

[0019] In addition, the orthographic projection of the second grid line on the surface of the semiconductor substrate is a first projection, the orthographic projection of the part of the third grid line directly above the second grid line on the surface of the semiconductor substrate is a second projection, the first projection coincides with the second projection, or the second projection is located in the first projection. The coincidence of the first projection and the second projection increases the thickness of the bordering area of the first grid line and the third grid line, and can also not change the light-receiving area of the solar cell sheet, thereby ensuring that the solar cell sheet has high photoelectric conversion efficiency.

[0020] In addition, the solder resist layer covers the entire top surface of the second grid line, which is conducive to further improving the ability of the solder resist layer to block the solder tin of the solder strip from flowing to the bordering area of the second grid line and the third grid line, thereby further reducing the risk of disconnection of the bordering area of the second grid line and the third grid line. BRIEF DESCRIPTION OF DRAWINGS

[0021] One or more embodiments are illustrated by way of example with reference to the drawings, which are not necessarily to scale. Unless otherwise specifically noted, the drawings show drawings in which:

[0022] Figure 1 A cross-sectional structure diagram corresponding to a photovoltaic cell structure;

[0023] Figure 2 A top view structure diagram corresponding to a solar cell sheet provided by an embodiment of the present application;

[0024] Figure 3 A top view structure schematic diagram of a first gate line connected with a second gate line provided by an embodiment of the present application;

[0025] Figure 4 A first cross-sectional structure schematic diagram of a solar cell provided by an embodiment of the present application;

[0026] Figure 5 A second cross-sectional structure schematic diagram of a solar cell provided by an embodiment of the present application;

[0027] Figure 6 A third cross-sectional structure schematic diagram of a solar cell provided by an embodiment of the present application;

[0028] Figure 7 A fourth cross-sectional structure schematic diagram of a solar cell provided by an embodiment of the present application;

[0029] Figure 8 A first cross-sectional structure schematic diagram of a photovoltaic cell module provided by an embodiment of the present application;

[0030] Figure 9 A second cross-sectional structure schematic diagram of a photovoltaic cell module provided by an embodiment of the present application. DETAILED DESCRIPTION

[0031] It is known in the background art that the photoelectric conversion efficiency and the service life of the photovoltaic cell module need to be improved.

[0032] It is found through analysis that after the photovoltaic cell module is detected by electroluminescent (EL) detection, the EL image presents a dark color, indicating that there is a problem of broken grid in the intersection area of the main grid and the auxiliary grid of the photovoltaic cell module, that is, the local or all areas of the intersection area of the main grid and the auxiliary grid are disconnected. Such a problem will directly affect the collection of photo-generated current, thereby affecting the photoelectric conversion efficiency of the photovoltaic cell module; in addition, during the use of the photovoltaic cell module with the problem of broken grid, a local hot spot phenomenon of local heating will occur at the position of the broken grid, affecting the service life of the photovoltaic cell module.

[0033] The solar cell before welding is detected by EL detection, and no problem of broken grid is found. Therefore, it is known that during the welding of the solar cell to form the photovoltaic cell module, the problem of fracture or loss of conductive material in the intersection area of the main grid and the auxiliary grid is caused.

[0034] REFERENCE Figure 1 , Figure 1A partial cross-sectional structure diagram of a photovoltaic cell assembly in the related art, the photovoltaic cell assembly comprising: a semiconductor substrate 0, a plurality of main grids 1 are present on the surface of the semiconductor substrate 0, and a sub-grid 2 intersects the main grid 1 perpendicularly; the main grid 1 has a solder ribbon melting tin 3, and the solder ribbon melting tin 3 connects the main grid 1 and a solder ribbon body 4.

[0035] During the formation of the photovoltaic cell assembly by welding, the solder ribbon melting tin 3 penetrates into the intersection area of the main grid 1 and the sub-grid 2, that is, the solder ribbon melting tin 3 separates the main grid 1 and the sub-grid 2, and the phenomenon of broken grid between the main grid 1 and the sub-grid 2 occurs. In addition, for the scheme that a lower amount of paste needs to be used in the process of manufacturing the photovoltaic cell assembly, due to the low amount of paste, the thickness of the corresponding main grid 1 and / or sub-grid 2 is also relatively low, and then the length of the corresponding interface of the intersection area is relatively short, that is, the penetration path required for the solder ribbon melting tin 3 to separate the main grid 1 and the sub-grid 2 is shortened, which will lead to a higher probability of broken grid. It can be understood that the paste is the raw material for printing the main grid 1 and the sub-grid 2, and the length of the interface refers to the length on the surface perpendicular to the semiconductor substrate 0.

[0036] To solve the above problems, an embodiment of the present application provides a solar cell, a second grid line is arranged on both sides of a first grid line, the second grid line intersects the first grid line perpendicularly, and a solder mask layer is arranged on the surface of the second grid line away from the first grid line. In this way, the thickness of the intersection area of the first grid line and the third grid line can be increased, and the solder ribbon melting tin is also blocked from flowing to the intersection area of the second grid line and the third grid line, thereby reducing the risk of broken grid in the intersection area of the second grid line and the third grid line.

[0037] To make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the embodiments of the present application will be described in detail below with reference to the drawings. However, those skilled in the art can understand that in the embodiments of the present application, many technical details are proposed in order to make the readers 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 by the present application can be implemented.

[0038] Figures 2 to 7 A corresponding structure diagram of a solar cell provided by an embodiment of the present application is shown in the figure, Figure 2 A top view structure diagram provided by an embodiment of the present application is shown in the figure; Figure 3 A top view diagram of the connection between the main grid and the sub-grid provided by an embodiment of the present application is shown in the figure; Figure 4 A first kind of cross-sectional structure diagram cut along the AA1 direction in the figure is shown in the figure; Figure 2 A second kind of cross-sectional structure diagram cut along the AA1 direction in the figure is shown in the figure; Figure 5 A third kind of cross-sectional structure diagram cut along the AA1 direction in the figure is shown in the figure; Figure 2 A fourth kind of cross-sectional structure diagram cut along the AA1 direction in the figure is shown in the figure; Figure 6 A fifth kind of cross-sectional structure diagram cut along the AA1 direction in the figure is shown in the figure; Figure 2A third cross-sectional structure diagram of the solar cell module along the direction of AA1 is shown in FIG. 3. Figure 7 For Figure 2 A fourth cross-sectional structure diagram of the solar cell module along the direction of AA1 is shown in FIG. 4.

[0039] Referring to Figures 2 to 4 In the embodiment, the solar cell includes: a semiconductor substrate 100; a first grid line 101 arranged on the surface of the semiconductor substrate 100 along a first direction; a second grid line 102 arranged on the surface of the semiconductor substrate 100 along a second direction, the second grid line 102 is perpendicular to and intersects with the first grid line 101, and the thickness of the second grid line 102 is less than the thickness of the first grid line 101 in the direction perpendicular to the surface of the semiconductor substrate 100; the second grid line 102 includes: a proximal portion 10 connected with the first grid line 101; an extension portion 11 connected with the proximal portion 10, and the proximal portion 10 is located between the first grid line 101 and the extension portion 11, and the length of the extension portion 11 is at least 0.8 times the length of the second grid line 102 in the parallel direction of the first direction; a solder resist layer 103 located on the surface of the second grid line 102 and covering at least the top surface of the extension portion 11; and a third grid line 104 arranged on the surface of the semiconductor substrate 100 along the second direction and perpendicular to the first grid line 101, wherein the third grid line 104 also covers the first grid line 101, the solder resist layer 103 and the second grid line 102, and the third grid line 104 is electrically connected with at least two first grid lines 101.

[0040] By arranging the second grid line 102 on both sides of the first grid line 101, the second grid line 102 and the third grid line 104 jointly form a secondary grid, thereby increasing the thickness of the junction area between the first grid line 101 and the secondary grid, and avoiding the problem of grid breakage between the first grid line 101 and the secondary grid during the process of forming the photovoltaic cell module. The solder resist layer 103 is arranged at the position of the extension portion of the second grid line 102, and the solder resist layer 103 is beneficial to block the flow of solder tin to the junction area of the second grid line 102 and the third grid line 104, thereby reducing the risk of grid breakage in the junction area of the second grid line 102 and the third grid line 104.

[0041] The solar cell module provided in the embodiment will be described in more detail below with reference to the accompanying drawings.

[0042] The material of the semiconductor substrate 100 is mainly single crystal silicon or polycrystalline silicon, and the semiconductor substrate 100 includes a light-receiving surface facing the sun and a back surface opposite to the light-receiving surface. Further, in some embodiments, the solar cell is a bifacial cell, and the light-receiving surface and / or the back surface in the semiconductor substrate 100 can generate photo-generated carriers; in other embodiments, the solar cell is a single-sided cell, and only the light-receiving surface of the semiconductor substrate 100 can generate photo-generated carriers.

[0043] In this embodiment, the solar cell is taken as an example of a double-sided cell, and both the light-receiving surface and the back surface of the semiconductor substrate 100 can generate photo-generated carriers. Subsequently, a plurality of solar cell pieces are welded to form a photovoltaic cell module, and the welding operation will increase the amount of new material on the surface of the solar cell piece, thereby shielding part of the surface of the semiconductor substrate 100 and reducing the photoelectric conversion efficiency of the solar cell piece. Although both the light-receiving surface and the back surface of the solar cell piece can generate photo-generated carriers, the photoelectric conversion efficiency of the back surface is lower than that of the light-receiving surface. Therefore, the welding operation can be performed on the back surface, thereby improving the photoelectric conversion efficiency of the photovoltaic cell module.

[0044] The first grid line 101 can be a main grid line for collecting the photo-generated current collected by the auxiliary grid line.

[0045] In this embodiment, the first grid line 101 is spaced apart along the first direction on the back surface of the semiconductor substrate 100. It should be noted that in other embodiments, the first grid line can also be distributed on the light-receiving surface of the semiconductor substrate. In addition, the first grid line 101 can be a solid strip or a hollow strip, and the number of first grid lines 101 can be 5-15, such as 5, 6, or 9, etc. The number of first grid lines 101 can be reasonably set according to the size of the solar cell piece. In some embodiments, the number of first grid lines 101 is set to be more than 9, so that the width of the first grid line 101 is relatively narrow, so as to save the paste. For example, the width of the first grid line can be 0.025-0.04 mm.

[0046] In this embodiment, in the parallel second direction, the width of the first grid line 101 can be 0.04 mm, and in the direction perpendicular to the surface of the semiconductor substrate 100, the thickness of the first grid line 101 can be 7-9 μm, such as 7.5 μm, 8 μm, or 8.5 μm.

[0047] The material of the first grid line 101 can use silver-containing paste. In some embodiments, the first grid line 101 can include a flat portion 13 and a transition portion 12 located on the opposite sides of the flat portion 13, and the surface of the transition portion 12 is connected to the adjacent portion 10. In the direction of the flat portion 13 pointing to the second grid line 102, the thickness of the transition portion 12 on the surface perpendicular to the semiconductor substrate 100 gradually decreases. That is, in the cross section perpendicular to the surface of the semiconductor substrate 100 and perpendicular to the extension direction of the first grid line 101, the cross-sectional shape of the first grid line 101 can be trapezoidal.

[0048] It can be understood that in other embodiments, in the cross section perpendicular to the surface of the semiconductor substrate and perpendicular to the extension direction of the first grid line, the cross-sectional shape of the first grid line can also be rectangular.

[0049] The second grid line 102 can be a first sub-grid, as a part of the sub-grid, and the third grid line 104 can be a second sub-grid, as a part of the sub-grid, and the first grid line 101 and the second grid line 102 together form the sub-grid, which is used to collect the photo-generated current generated by the photovoltaic. The second grid line 102 is arranged to increase the thickness of the paste in the junction area between the first grid line 101 and the sub-grid, that is, the thickness of the laminated structure formed by the first grid line 101 and the sub-grid in the junction area, thereby effectively avoiding the melting tin of the solder strip from melting the first grid line 101 and the sub-grid in the junction area during soldering, thereby avoiding the problem of disconnection between the first grid line 101 and the sub-grid. In addition, compared with the scheme of increasing the overall thickness of the sub-grid, in the embodiment, the thickness of only the local area of the sub-grid can be increased by arranging the second grid line 102, so that the amount of paste can be saved, and the cost of the solar cell piece can be reduced.

[0050] In the embodiment, the material of the second grid line 102 can be the same as that of the first grid line 101. In addition, referring to Figure 4 and Figure 5 , the second grid line 102 and the first grid line 101 can be an integrated structure. The integrated structure not only allows the first grid line 101 and the second grid line 102 to be printed at the same time during printing, but also allows the junction area between the first grid line 101 and the second grid line 102 to have no obvious interface, thereby further preventing the melting tin of the solder strip from penetrating into the junction area between the first grid line 101 and the second grid line 102 during the manufacture of the photovoltaic cell assembly, and thereby further improving the performance of the photovoltaic cell assembly.

[0051] It should be noted that in other embodiments, referring to Figure 6 and Figure 7 , the first grid line 101 and the second grid line 102 can not be an integrated structure, that is, the first grid line 101 and the second grid line 102 are formed by step printing. The step printing can reduce the requirements for the printing screen and can more accurately control the printing position and the printing thickness compared with the integrated structure.

[0052] The second grid line 102 is arranged on the opposite sides of the first grid line 101 along the second direction. In the embodiment, the relative arrangement density of the second grid line 102 is greater than that of the first grid line 101. Specifically, the number of the second grid line 102 can be 106-122.

[0053] In some embodiments, the length of the second busbar 102 in the parallel first direction can be 0.3mm-0.6mm, for example, 0.35mm, 0.45mm or 0.55mm. When the length of the second busbar 102 is in this range, the amount of paste required for the second busbar 102 is reduced, which in turn reduces the cost, and the path of the solder ribbon molten solder to the junction area of the second busbar 102 and the third busbar 104 is relatively long during the soldering process, thus reducing the risk of the solder ribbon molten solder melting the junction area of the second busbar 102 and the third busbar 104.

[0054] If the length of the second busbar 102 is too short, the solder ribbon molten solder is prone to flow to the junction area of the second busbar 102 and the third busbar 104 during the soldering process, causing the junction area of the second busbar 102 and the third busbar 104 to be easily melted; if the length of the second busbar 102 is too long, the amount of paste required for the second busbar 102 increases, which in turn increases the cost of the solar cell. Further, the length of the second busbar 102 can be 0.4mm-0.5mm.

[0055] In some embodiments, the width of the second busbar 102 in the parallel second direction can be greater than the width of the third busbar 104, so that even if there is a printing alignment error between the second busbar 102 and the third busbar 104, it can still be ensured that the third busbar 104 is on the top surface of the second busbar 102, and the junction area of the sub-busbar and the first busbar 101 is a stack of the second busbar 102 and the third busbar 104, rather than a single layer structure of the third busbar 104, thereby further improving the problem of preventing the junction area of the sub-busbar and the first busbar 101 from being melted.

[0056] In other embodiments, the width of the second busbar 102 in the parallel second direction can be equal to the width of the third busbar 104, i.e., from a top view, the third busbar 104 completely covers the second busbar 102 in the parallel second direction. In this way, the second busbar 102 can be prevented from blocking the light receiving area outside the third busbar 104, so that the solar cell still has a large light receiving area, thereby facilitating further improvement of the photoelectric conversion efficiency of the solar cell. In a specific embodiment, the width of the second busbar 102 in the parallel second direction can be 0.02mm-0.2mm, for example, 0.027mm, 0.035mm or 0.045mm.

[0057] In some embodiments, the thickness of the second grid line 102 in the direction perpendicular to the surface of the semiconductor substrate 100 is 0.4-1 times the thickness of the third grid line 104, for example, the thickness of the second grid line 102 is 0.5, 0.7 or 0.8 times the thickness of the third grid line 104. When the thickness of the second grid line 102 is in this range, the thickness of the second grid line 102 is moderate, so the amount of paste required for the second grid line 102 is relatively small, which is conducive to cost savings; and the thickness of the junction area of the first grid line 101 and the auxiliary grid is relatively thick, which is conducive to ensuring excellent ability to prevent the junction area of the first grid line 101 and the auxiliary grid from being fused.

[0058] Specifically, the thickness of the second grid line 102 in the direction perpendicular to the surface of the semiconductor substrate 100 can be 0.5 times the thickness of the third grid line 104.

[0059] In some specific embodiments, the thickness of the second grid line 102 in the direction perpendicular to the surface of the semiconductor substrate 100 is 0.004-0.016 mm, for example, 0.008 mm, 0.01 mm or 0.015 mm.

[0060] In addition, in some embodiments, the second grid line 102 can have a rectangular shape in the orthographic projection on the surface of the semiconductor substrate 100, that is, in the direction parallel to the second direction, the width of the end of the second grid line 102 towards the first grid line 101 is the same as the width of the end of the second grid line 102 away from the first grid line 101. The advantages of such an arrangement include: without reducing the area of the light-receiving region, the junction area of the second grid line 102 and the third grid line 104 has a laminated structure (composed of the second grid line 102 and the third grid line 104), preventing the junction area of the second grid line 102 and the third grid line 104 from having a single-layer film layer composed of the third grid line 104, thereby ensuring that the junction area of the second grid line 102 and the third grid line 104 has a relatively thick thickness, thereby reducing the probability of soldering tin from the solder strip penetrating into the second grid line 102 and the third grid line 104 during the soldering process, and further reducing the probability of the soldering tin from the solder strip fusing the junction area of the second grid line 102 and the third grid line 104.

[0061] The third grid line 104 is part of the auxiliary grid and, together with the second grid line 102, forms the auxiliary grid, which is used to collect the photo-generated current generated on the entire solar cell and transmit the photo-generated current to the first grid line 101.

[0062] Each third grid line 104 crosses a plurality of first grid lines 101 and covers the side of the first grid line 101 and the second grid line 102 away from the first grid line 101, and each third grid line 104 is electrically connected to at least two first grid lines 101. In the embodiment, the material of the third grid line 104 can be the same as that of the second grid line 102. In other embodiments, the material of the third grid line 104 can also be different from that of the second grid line 102.

[0063] In a specific embodiment, the width of the third grid line 104 in the direction parallel to the second direction can be 0.02mm-0.2mm, for example, 0.027mm, 0.035mm or 0.045mm.

[0064] Further, in some embodiments, the orthographic projection of the second grid line 102 on the surface of the semiconductor substrate 100 is a first projection, the orthographic projection of the part of the third grid line 104 above the second grid line 102 on the surface of the semiconductor substrate 100 is a second projection, and the first projection can coincide with the second projection, so that the thickness of the intersection area of the first grid line 101 and the auxiliary grid is increased, and the light receiving area of the solar cell is not changed; in other embodiments, the second projection is located in the first projection, so that even if the third grid line 104 is slightly offset during printing (i.e., the third grid line 104 is still completely in the second grid line 102 at the intersection area of the second grid line 102 and the third grid line 104), the second grid line 102 can still increase the thickness of the intersection area of the main grid and the auxiliary grid.

[0065] It can be understood that the amount of paste affects the manufacturing cost and photoelectric conversion efficiency of the solar cell. In order to improve the problem of broken grid and reduce the amount of paste, the second grid line 102 is arranged near the first grid line 101 in the area where the third grid line 104 is located before printing the third grid line 104, and then the third grid line 103 is printed on the surface of the second grid line 102 and the remaining area, so that the second grid line 102 and the third grid line 104 jointly constitute a new auxiliary grid, the length of the interface of the intersection area of the main grid and the new auxiliary grid is increased, and correspondingly, the penetration path of the solder tin of the solder strip is increased, which will reduce the probability of broken grid in the intersection area. Therefore, compared with the method of increasing the thickness of the entire third grid line 104, the method of only increasing the thickness of the second grid line 102 and keeping the thickness of the auxiliary grid unchanged in other areas can reduce the amount of paste required.

[0066] In order to further save the amount of paste, the length of the second grid line 102 is usually set to be shorter, where the length refers to the length of the third grid line 104 in the extending direction. After the second grid line 102 is set, there is a new junction area between the second grid line 102 and the third grid line 104, which is located at a position of the second grid line 102 away from the first grid line 101. In the new junction area, the solder ribbon molten tin still flows to the new junction area during the soldering process, and thus penetrates from the new junction area. Therefore, there is also a risk of grid breakage between the second grid line 102 and the third grid line 104. In addition, the shorter the length of the second grid line 102, the higher the probability of grid breakage in the new junction area. Therefore, in order to save costs while improving the problem of grid breakage of the photovoltaic module, a solder resist layer 103 is further arranged on the surface of the second grid line 102 in the embodiment, and the solder resist layer 103 at least covers the extending portion 11 of the second grid line 102. The solder resist layer 103 prevents the solder ribbon molten tin from penetrating downward from the junction area between the second grid line 102 and the third grid line 104, thereby reducing the probability of grid breakage in the junction area between the second grid line 102 and the third grid line 104.

[0067] Further, when the solar cell pieces are connected in series to form the photovoltaic module, during the process of soldering the solder ribbon and the solar cell pieces, the solder ribbon is pressed and squeezes the solder ribbon molten tin to gather in a direction away from the first grid line 101. It is found in the production process that the gathering area is the surface of the second grid line 102 away from the first grid line 101 in a direction close to the first grid line 101, and the length of the gathering area is 0.8 times the length of the second grid line.

[0068] In addition, since the solder resist layer 103 is arranged on the surface of the second grid line 102, the length of the second grid line 102 in the extending direction of the third grid line 104 can be set to be shorter, thereby facilitating further saving of the paste required by the second grid line 102 and further reducing costs. This is because even if the length of the second grid line 102 is shorter, the path of the solder ribbon molten tin penetrating into the junction area between the second grid line 102 and the third grid line 104 is shorter, but since the solder resist layer 103 prevents the penetration of the solder ribbon molten tin, it can still prevent the solder ribbon molten tin from melting the junction area between the second grid line 102 and the third grid line 104.

[0069] The second grid line 102 is divided into the adjacent portion 10 and the extending portion 11, the extending portion 11 is located on the side of the adjacent portion 10 away from the first grid line 101, and the solder resist layer 103 needs to be located at least on the top surface of the extending portion 11. It should be noted that although the second grid line 102 is divided into the adjacent portion 10 and the extending portion 11, in fact, the adjacent portion 10 and the extending portion 11 are integrally formed.

[0070] Specifically, in the direction parallel to the first direction, the length of the extension 11 is at least 0.8 of the length of the second grid line 102, and Table 1 shows the relationship between the length of the extension 11 and the probability of the occurrence of the disconnection of the second grid line 102 at the junction area with the third grid line 104.

[0071] Solder resist length Break-barrier rate Solder resist length is 100% of first sub-grid length 0％ Solder resist length is 90% of first sub-grid length 0％ Solder resist length is 82% of first sub-grid length 0％ Solder resist length is 80% of first sub-grid length 0％ Solder resist length is 78% of first sub-grid length 0.01％ Solder resist length is 76% of first sub-grid length 0.04％ Solder resist length is 74% of first sub-grid length 0.09％ Solder resist length is 72% of first sub-grid length 0.15％ Solder resist length is 70% of first sub-grid length 0.2％ Solder resist length is 60% of first sub-grid length 0.5％ No solder resist is provided 1.5％

[0072] As shown in Table 1, when the length of the extension 11 is greater than or equal to 0.8 of the length of the second grid line 102, the probability of the occurrence of the disconnection of the second grid line 102 at the junction area with the third grid line 104 is significantly reduced.

[0073] In some embodiments, the solder resist layer 103 covers the entire top surface of the extension 11 of the second grid line 102, which can improve the situation of the disconnection of the second grid line 102 at the junction area with the third grid line 104. In other embodiments, the solder resist layer 103 covers the entire top surface of the extension 11 and part of the surface of the adjacent portion 10. In addition, the solder resist layer 103 can also cover the entire top surface of the second grid line 101, i.e., the entire surface of the adjacent portion 10, which is conducive to further improving the ability of the solder resist layer 103 to block the soldering ribbon molten tin from flowing to the junction area of the second grid line 102 and the third grid line 104, thereby further reducing the risk of the disconnection of the second grid line 102 at the junction area with the third grid line 104.

[0074] In some embodiments, in the direction perpendicular to the surface of the semiconductor substrate 100, the thickness of the solder resist layer 103 is 5 nm to 10 nm, for example, 7 nm, 7.5 nm, or 8 nm, and the solder resist layer 130 is a single-layer structure. When the thickness of the solder resist layer 103 is in this range, the amount of material of the solder resist layer 103 is reduced, and the soldering ribbon molten tin is prevented from penetrating into the junction area of the second grid line 102 and the third grid line 104, thereby preventing the disconnection between the second grid line 102 and the third grid line 104.

[0075] If the thickness of the solder resist layer 103 is too thin, the solder resist layer 103 cannot completely prevent the disconnection of the second grid line 102 at the junction area with the third grid line 104 when the soldering ribbon molten tin flows to the junction area. If the thickness of the solder resist layer 103 is too thick, the material used by the solder resist layer 103 increases, which in turn increases the cost of the solar cell.

[0076] The material of the solder resist layer 103 includes epoxy resin or polyester resin and other materials. The epoxy resin and polyester resin materials themselves have the characteristics of high temperature resistance, good insulation, and printability, which can protect the junction area of the second grid line 102 and the third grid line 104, and are also convenient for production processes.

[0077] The embodiment provides a solar cell, by increasing the second grid line 102, the second grid line 102 and the third grid line 104 jointly form a sub-grid, thereby increasing the thickness of the intersection area of the first grid line 101 and the sub-grid, thereby reducing the probability that the solder of the solder strip penetrates into the intersection area of the first grid line 101 and the third grid line 104 to separate the first grid line 101 and the third grid line 104; in addition, the increased paste of the second grid line 102 is less than the thickness of the increased third grid line 104, thereby reducing the cost of the solar cell. Meanwhile, the solder resist layer 103 is arranged, the solder resist layer 103 can prevent the solder of the solder strip from penetrating into the intersection area of the second grid line 102 and the third grid line 104, thereby reducing the probability of the second grid line 102 and the third grid line 104 appearing broken grid.

[0078] Correspondingly, the embodiment of the present application also provides a photovoltaic cell module, which comprises at least two solar cell pieces provided by the above-mentioned embodiment. The photovoltaic cell module provided by the embodiment of the present application will be described below in combination with the drawings.

[0079] Figure 8 With Figure 9 is a cross-sectional structure schematic diagram of the photovoltaic cell module provided by the embodiment of the present application, Figure 8 The first grid line and the second grid line of the solar cell piece are independently formed respectively; Figure 9 The first grid line and the second grid line of the solar cell piece are formed at one time.

[0080] Reference Figure 8 And Figure 9 In the embodiment, the photovoltaic cell module comprises a solar cell string, and the solar cell string is formed by electrically connecting the at least two solar cell pieces in the above-mentioned embodiment.

[0081] Specifically, the solar cell string further comprises a solder strip 20, and the adjacent solar cell pieces are electrically connected through the solder strip 20.

[0082] In some embodiments, in parallel to the second direction, the width of the solder strip 20 is greater than the width of the first grid line 201, so that the current collection efficiency of the photovoltaic cell module can be improved, and when the solder strip 20 is slightly offset during the welding process, the surface of the first grid line 201 is still not exposed; in other embodiments, in parallel to the second direction, the width of the solder strip is equal to the width of the first grid line, so that the area of the power generation area of the cell piece is not reduced, the photoelectric conversion efficiency of the solar cell piece is ensured, and the impedance of the solder strip can be reduced, so that the transmission effect of the photo-generated carrier is better.

[0083] The solder strip 20 can include a solder strip body 206 and solder strip solder 205 surrounding the solder strip body 206. The photovoltaic cell assembly provided by the embodiment can improve the grid breakage phenomenon in the process of forming the photovoltaic cell welding. The second grid line 202 and the third grid line 204 jointly constitute a secondary grid by additionally arranging the second grid line 202 and the solder resist layer 203, thereby increasing the thickness of the junction area of the primary grid and the secondary grid, saving the cost, and reducing the grid breakage rate of the photovoltaic cell assembly from 20% to 0%. The solder resist layer 203 can prevent the solder strip solder 205 from penetrating into the junction area of the second grid line 202 and the third grid line 204, thereby reducing the probability of grid breakage of the second grid line 202 and the third grid line 204. Therefore, the photovoltaic cell assembly provided by the embodiment has the advantages of low cost, high photoelectric conversion efficiency, and long service life.

[0084] Further, the embodiment of the present application also provides a forming method of the photovoltaic cell assembly. Figure 8 and Figure 9 The forming method of the photovoltaic cell assembly includes the following steps: providing a plurality of solar cell pieces; and electrically connecting the plurality of solar cell pieces by the solder strip to form a solar cell string, i.e., the photovoltaic cell assembly.

[0085] Specifically, the solder strip 20 is used to electrically connect the adjacent solar cell pieces, and the solder strip 20 can include a solder strip body and solder strip solder 205 surrounding the solder strip body 206. In the welding process, the solder strip solder 205 penetrates from the surface of the third grid line 204 to the first grid line 201 along the junction area. Due to the increase of the second grid line 202, the length of the penetration of the solder strip solder 205 increases. The penetration length of the solder strip solder 205 is increased to improve the grid breakage between the primary grid and the secondary grid. However, the increase of the second grid line 202 forms a new junction area with the third grid line 204, and the new junction area is also prone to grid breakage. Therefore, the solder resist layer 203 is arranged on the top surface of the second grid line 202, and the solder resist layer 203 can prevent the solder strip solder 205 from flowing into the junction area of the second grid line 202 and the third grid line 204.

[0086] Since the solder resist layer 203 is made of epoxy resin or polyester resin, the material itself has good adhesion, and the quality of the contact and adhesion between the solder strip 20 and the solar cell piece can be improved.

[0087] Those skilled in the art can understand that the above-mentioned embodiments are specific embodiments for implementing the present application, and in actual application, various changes can be made in form and details without departing from the spirit and scope of the present application. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present application, and therefore the protection scope of the present application should be limited by the scope defined in the claims.

Claims

1. A solar cell, characterized by, include: Semiconductor substrate; A first gate line is arranged along a first direction on the surface of the semiconductor substrate; A second gate line is arranged along a second direction on the surface of the semiconductor substrate. The second gate line is perpendicular to and intersects the first gate line, and in the direction perpendicular to the surface of the semiconductor substrate, the thickness of the second gate line is less than the thickness of the first gate line. The second gate line includes: a neighboring portion connected to the first gate line; and an extension portion connected to the neighboring portion, wherein the neighboring portion is located between the first gate line and the extension portion, and in the direction parallel to the first direction, the length of the extension portion is at least 0.8 times the length of the second gate line. A solder resist layer, the solder resist layer being located on the surface of the second gate line and at least covering the top surface of the extension; A third gate line is arranged along the second direction on the surface of the semiconductor substrate and perpendicular to the first gate line, wherein the third gate line covers the first gate line, the solder mask layer and the second gate line, and the third gate line is electrically connected to at least two of the first gate lines; The first gate line includes a flat portion and transition portions located on opposite sides of the flat portion, and the surface of the transition portions is connected to the second gate line; wherein, in the direction from the flat portion to the second gate line, the thickness of the transition portions on the surface perpendicular to the semiconductor substrate gradually decreases.

2. The solar cell of claim 1, wherein the first and second electrodes are formed of a material selected from the group consisting of silver, aluminum, and copper. The solder resist layer covers the entire top surface of the second gate line.

3. The solar cell of claim 1, wherein the first and second electrodes are formed of a material selected from the group consisting of silver, aluminum, and copper. The thickness of the solder resist layer is 5 nm to 10 nm in a direction perpendicular to the surface of the semiconductor substrate.

4. The solar cell of claim 1, wherein the first and second electrodes are formed of a material selected from the group consisting of silver, aluminum, and copper. The material of the solder resist layer includes epoxy resin or polyester resin.

5. The solar cell as claimed in any one of claims 1 to 4, wherein the back surface of the solar cell is provided with a back surface field layer. In the direction parallel to the second direction, the width of the second gate line is greater than or equal to the width of the third gate line.

6. The solar cell as claimed in any one of claims 1 to 4, wherein the back surface of the solar cell is provided with a back surface field. In a direction perpendicular to the surface of the semiconductor substrate, the thickness of the second gate line is 0.4 to 1 times the thickness of the third gate line.

7. The solar cell as claimed in any one of claims 1 to 4, wherein the back surface of the solar cell is provided with a back surface field layer. In a direction perpendicular to the surface of the semiconductor substrate, the thickness of the second gate line is 0.004 mm to 0.016 mm.

8. The solar cell as claimed in any one of claims 1 to 4, wherein the back surface of the solar cell is provided with a back surface field layer. The width of the second gate line is 0.02mm to 0.2mm in the direction parallel to the second direction.

9. The solar cell as claimed in any one of claims 1 to 4, wherein the back surface of the solar cell is provided with a back surface field layer. The length of the second gate line is 0.3mm to 0.6mm parallel to the first direction.

10. The solar cell according to any one of claims 1 to 4, characterized in that, The first gate line and the second gate line are integrally formed.

11. A photovoltaic cell assembly, characterized by, include: A solar cell string, wherein the solar cell string is formed by electrically connecting solar cells as described in any one of claims 1 to 10.

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