Back-contact solar cells, modules and photovoltaic systems

Abstract

The present application relates to the technical field of solar cells, and provides a back-contact solar cell, a battery assembly and a photovoltaic system. In the back-contact solar cell, the first busbar line is continuous at the first edge series connection area and the second series connection area. A first groove is formed on the substrate. The first edge busbar line is closer to the first edge than the first edge series connection area. A first insulating layer is provided on the portion of the first busbar line corresponding to the first series connection area. The first insulating layer is at least partially arranged in the first groove. The height of the first insulating layer is flush with the height of the second welding section, or the height of the first insulating layer is less than the height of the second welding section, or the height of the first insulating layer is greater than the height of the second welding section, and the height difference between the first insulating layer and the second welding section is less than or equal to 15um. In this way, by setting the first groove, the influence caused by the cold solder joint can be reduced, thereby ensuring the efficiency of the back-contact solar cell.

Description

Technical Field

[0001] The present application relates to the technical field of solar cells, and in particular, to a back-contact solar cell, a battery module, and a photovoltaic system. Background Art

[0002] A back-contact solar cell is a type of cell in which both the P-type doping layer and the N-type doping layer are disposed on the back surface of a silicon wafer, and there is no shielding of metal electrodes on the front surface, which has a higher short-circuit current and conversion efficiency.

[0003] In the related art, the back surface of the back-contact solar cell is provided with alternately arranged grid lines. In order to reduce the use of paste and transmission loss, a solder ribbon can be directly used in the battery module to form an electrical connection with the grid lines of the cell to achieve current collection and output. However, in such a technical solution, since it is necessary to provide an insulating glue at the heteropolar grid lines intersecting with the solder ribbon to avoid leakage, however, the setting of the insulating glue easily causes the phenomenon of poor soldering during the soldering process of the solder ribbon, affecting the performance of the back-contact solar cell. Summary of the Invention

[0004] The present application provides a back-contact solar cell, a battery module, and a photovoltaic system.

[0005] The present application is implemented as follows. The back-contact solar cell according to an embodiment of the present application includes:

[0006] A substrate having opposite front and back surfaces, the back surface having opposite first and second edges in a first direction, the back surface having a plurality of first series connection regions and a plurality of second series connection regions, and in the first direction, the first series connection regions and the second series connection regions are alternately arranged. The plurality of first series connection regions include a first edge series connection region closest to the first edge, and there is no second series connection region between the first edge series connection region and the first edge. In the first edge series connection region, a first groove is formed on the substrate;

[0007] A plurality of first grid lines and a plurality of second grid lines alternately arranged along a second direction on the back surface, the second direction intersecting the first direction. The first grid lines and all the second grid lines are cross-arranged with the first series connection regions and the second series connection regions. The first grid lines include first welding segments located in the second series connection regions, and the second grid lines include second welding segments located in the first series connection regions; the plurality of first grid lines include a plurality of first collecting grid lines and at least one first busbar grid line. The first collecting grid lines are discontinuous at the first edge series connection region and continuous at the second series connection regions. The first busbar grid line is continuous at the first edge series connection region and a part of the first busbar grid line is located in the first groove. The second grid lines are continuous at the first edge series connection region;

[0008] A first edge bus bar, the first edge bus bar being closer to the first edge than the first edge series connection region, the first edge bus bar being electrically connected to at least a part of the first collection grid lines and electrically connected to the first bus bar grid line; and

[0009] A first insulating layer, the first insulating layer being at least partially disposed in the first groove and on the first bus bar grid line, wherein, in the direction from the front side towards the back side, the height of the first insulating layer is flush with the height of the second welding section, or the height of the first insulating layer is less than the height of the second welding section, or the height of the first insulating layer is greater than the height of the second welding section and the height difference between the first insulating layer and the second welding section is less than or equal to 15 um.

[0010] Furthermore, the recessed depth of the first groove is less than one half of the thickness of the substrate.

[0011] Furthermore, the first insulating layer is completely located within the first groove.

[0012] Furthermore, the substrate includes a silicon substrate, a plurality of first doping layers, a plurality of second doping layers, and a back surface passivation film layer, the silicon substrate having opposite first and second surfaces, the first doping layers and the second doping layers both being disposed on the second surface, a plurality of the first doping layers and a plurality of the second doping layers being alternately arranged along a second direction, the back surface passivation film layer being at least stacked on the first doping layers and the second doping layers, the first grid line being correspondingly disposed with the first doping layer and at least partially penetrating the back surface passivation film layer to make conductive contact with the first doping layer, the second grid line being correspondingly disposed with the second doping layer and at least partially penetrating the back surface passivation film layer to make conductive contact with the second doping layer;

[0013] Wherein, the first groove penetrates through the back surface passivation film layer and the first doping layer so that the silicon substrate is exposed from the first groove, and the portion of the first bus bar grid line located within the first groove contacts the silicon substrate; or

[0014] At a position corresponding to the first bus bar grid line in the first edge series connection region, a first indentation groove is formed on the silicon substrate, and the first doping layer and the back surface passivation film layer are both recessed towards the side where the front surface is located at the first indentation groove to form the first groove on the substrate.

[0015] Furthermore, the first edge bus bar is electrically connected to all of the first collection grid lines; or

[0016] The first edge busbar is electrically connected to some of the first collecting grid lines, and the number of the first collecting grid lines not electrically connected to the first edge busbar is less than or equal to 4.

[0017] Furthermore, the number of the first busbar grid lines is multiple, and the substrate has a third edge and a fourth edge in the second direction;

[0018] Among the first grid lines and the second grid lines, the grid line closest to the third edge is the first busbar grid line, and / or the grid line closest to the fourth edge is the first busbar grid line.

[0019] Furthermore, the substrate has a third edge and a fourth edge in the second direction;

[0020] At the junction where the first grid line closest to the third edge is connected to the first edge busbar, the first edge busbar has a first convex portion protruding toward the third edge side; and / or

[0021] At the junction where the first grid line closest to the fourth edge is connected to the first edge busbar, the first edge busbar has a second convex portion protruding toward the fourth edge side.

[0022] Furthermore, the width of the first busbar grid line is greater than the width of the portion of the first collecting grid line outside the second series connection region.

[0023] Furthermore, several of the second series connection regions include a second edge series connection region closest to the first edge; the first busbar grid line includes a first busbar segment located between the second edge series connection region and the first edge;

[0024] wherein, the width of the first busbar segment is greater than the width of the portion of the rest of the first busbar grid line outside the second series connection region; and / or

[0025] A first busbar layer is provided on the first busbar segment.

[0026] Furthermore, the width of the first busbar layer is greater than the width of the portion of the first collecting grid line outside the second series connection region.

[0027] Furthermore, the width of the first edge busbar is greater than the width of the portion of the first collecting grid line outside the second series connection region.

[0028] Furthermore, the distance between the first edge series connection region and the first edge is greater than or equal to 2 mm and less than or equal to 20 mm.

[0029] Further, some of the second connection regions include a third edge connection region closest to the second edge, and there is no such first connection region between the third edge connection region and the second edge. In the third edge connection region, a second groove is formed on the substrate;

[0030] Some of the second gate lines include a plurality of second collection gate lines and at least one second bus bar gate line. The second collection gate lines are discontinuous at the third edge connection region and continuous at the first connection region. The second bus bar gate line is continuous at the third edge connection region and the first connection region, and part of the second bus bar gate line is located in the second groove. The first gate line is continuous at the third edge connection region;

[0031] The back-contact solar cell further includes:

[0032] A second edge bus bar, which is closer to the second edge than the third edge connection region. The second edge bus bar is electrically connected to at least part of the second collection gate lines and is electrically connected to the second bus bar gate line;

[0033] A second insulating layer, which is at least partially disposed in the second groove and on the second bus bar gate line. The number of the second insulating layers corresponds to the number of the second bus bar gate lines. Wherein, in the thickness direction of the back-contact solar cell, the height of the second insulating layer is flush with the height of the first welding segment, or the height of the second insulating layer is less than the height of the first welding segment, or the height of the second insulating layer is greater than the height of the first welding segment and the height difference between the second insulating layer and the first welding segment is less than or equal to 15um.

[0034] Further, the depression depth of the second groove is less than one-half of the thickness of the substrate.

[0035] Further, the second insulating layer is completely located in the second groove.

[0036] Further, the substrate includes a silicon substrate, a plurality of first doping layers, a plurality of second doping layers, and a back surface passivation film layer. The silicon substrate has opposite first and second surfaces. The first doping layers and the second doping layers are both disposed on the second surface. A plurality of the first doping layers and a plurality of the second doping layers are alternately arranged along the second direction. The back surface passivation film layer is at least stacked on the first doping layers and the second doping layers. The first gate line is correspondingly disposed with the first doping layer and at least partially penetrates the back surface passivation film layer to make conductive contact with the first doping layer. The second gate line is correspondingly disposed with the second doping layer and at least partially penetrates the back surface passivation film layer to make conductive contact with the second doping layer;

[0037] Wherein, the second groove penetrates through the back passivation film layer and the second doping layer, so that the silicon substrate is exposed from the second groove, and the part of the second bus bar located in the second groove contacts the silicon substrate; or

[0038] At a position corresponding to the second edge series connection area and the second bus bar, a second recessed groove is formed on the silicon substrate, and both the second doping layer and the back passivation film layer are recessed toward the side where the front side is located at the second recessed groove, so as to form the second groove on the substrate.

[0039] Furthermore, the second edge bus bar is electrically connected to all the second collection grid lines; or

[0040] The second edge bus bar is electrically connected to some of the second collection grid lines, and the number of the second collection grid lines not electrically connected to the second edge bus bar is less than or equal to 4.

[0041] Furthermore, the substrate has a third edge and a fourth edge in the second direction, the second edge bus bar includes an intermediate bus bar section, a first edge bus bar section and a second edge bus bar section, the intermediate bus bar section, the first edge bus bar section and the second edge bus bar section all extend along the second direction, the intermediate bus bar section is closer to the second edge than the first edge bus bar section and the second edge bus bar section, the first edge bus bar section is arranged close to the third edge, and the second edge bus bar section is arranged close to the fourth edge;

[0042] The second edge bus bar further includes a first connection section and a second connection section, the first connection section and the second connection section both extend along the first direction, the first connection section connects the intermediate bus bar section and the first edge bus bar section, and the second connection section connects the intermediate bus bar section and the second edge bus bar section;

[0043] Wherein, the first edge bus bar section connects the two second grid lines closest to the third edge. At the junction of the first edge bus bar section and the first connection section, the first edge bus bar section has a third convex portion protruding toward the fourth edge side, and the first connection section has a fourth convex portion protruding toward the first edge side. At the junction of the intermediate bus bar section and the first connection section, the intermediate bus bar section has a fifth convex portion protruding toward the third edge side, and the first connection section has a sixth convex portion protruding toward the second edge; and / or

[0044] The second edge busbar section is connected to the two second grid lines closest to the fourth edge. At the junction of the second edge busbar section and the second connection section, the second edge busbar section has a seventh convex portion protruding toward the third edge side, and the second connection section has an eighth convex portion protruding toward the first edge side. At the junction of the middle busbar section and the second connection section, the middle busbar section has a ninth convex portion protruding toward the fourth edge side, and the second connection section has a tenth convex portion protruding toward the second edge.

[0045] Further, the width of the second busbar grid line is greater than the width of the portion of the second collection grid line outside the first series connection area.

[0046] Further, several of the first series connection areas include a fourth edge series connection area closest to the second edge; the second busbar grid line includes a second busbar section located between the fourth edge series connection area and the second edge;

[0047] The width of the second busbar section is greater than the width of the portion of the rest of the second busbar grid line outside the first series connection area; and / or

[0048] A second busbar layer is provided on the second busbar section.

[0049] Further, the width of the second busbar layer is greater than the width of the portion of the second collection grid line outside the first series connection area.

[0050] Further, the width of the second edge busbar line is greater than the width of the portion of the second collection grid line outside the first series connection area.

[0051] Further, the distance between the third edge series connection area and the second edge is greater than or equal to 2 mm and less than or equal to 20 mm.

[0052] The present application also provides a battery assembly, which includes several back-contact solar cells as described in any one of the above.

[0053] The present application also provides a photovoltaic system, which includes the above battery assembly.

[0054] In the back-contact solar cell, cell module, and photovoltaic system according to the embodiments of the present application, the first collection grid line is discontinuous at the first edge connection area and continuous at the second connection area, the first busbar grid line is continuous at the first edge connection area and the second connection area, and the second grid line is continuous at the first edge connection area. The first edge busbar is closer to the first edge than the first edge connection area, and the first edge busbar is electrically connected to at least part of the first collection grid line and electrically connected to the first busbar grid line. The first insulating layer is disposed at the first groove within the first edge connection area, and the first insulating layer is at least partially disposed within the first groove and located on the first busbar grid line. The height of the first insulating layer is flush with the height of the second welding section, or the height of the first insulating layer is less than the height of the second welding section, or the height of the first insulating layer is greater than the height of the second welding section, and the height difference between the first insulating layer and the second welding section is less than or equal to 15 μm. Thus, by providing the first edge busbar and the first busbar grid line, the current collected by at least part of the isolated segment of the first grid line located between the first edge connection area and the first edge can be collected and fed to the same-polarity solder strip within the second connection area adjacent to the first edge connection area, effectively avoiding the occurrence of hidden cracks caused by welding at the first edge of the back-contact solar cell while ensuring the efficiency of the back-contact solar cell. At the same time, by forming the first groove on the substrate and at least partially disposing the first insulating layer within the first groove, the height of the first insulating layer is less than the height of the second welding section, or the first insulating layer is flush with the second welding section, or the height of the first insulating layer is greater than the height of the second welding section and the height difference therebetween is less than or equal to 15 μm. This can ensure insulation between the solder strip and the first busbar grid line while reducing or even eliminating the height difference between the first insulating layer and the grid line welding section, thereby reducing the risk of false soldering caused by the first insulating layer and minimizing the impact of false soldering on the back-contact solar cell, improving the performance of the back-contact solar cell.

[0055] Additional aspects and advantages of the present application will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 is a schematic diagram of a module of a photovoltaic system provided by an embodiment of the present application;

[0057] Figure 2 is a schematic diagram of a module of a cell module provided by an embodiment of the present application;

[0058] Figure 3 is a schematic plan view of a back-contact solar cell provided by an embodiment of the present application;

[0059] Figure 4 is Figure 3Partial enlarged schematic view of the back-contact solar cell in [IV];

[0060] Figure 5 is Figure 4 Schematic cross-sectional structure diagram of the back-contact solar cell along line V-V in [ ];

[0061] Figure 6 is Figure 4 Schematic cross-sectional structure diagram of the back-contact solar cell along line VI-VI in [ ];

[0062] Figure 7 is Figure 4 Partial enlarged schematic view of the back-contact solar cell in [VII];

[0063] Figure 8 is Figure 4 Partial enlarged schematic view of the back-contact solar cell in [VIII];

[0064] Figure 9 is Figure 4 Partial enlarged schematic view of the back-contact solar cell in [IX];

[0065] Figure 10 is Figure 3 Partial enlarged schematic view of the back-contact solar cell in [X];

[0066] Figure 11 is Figure 10 Schematic cross-sectional structure diagram of the back-contact solar cell along line XI-XI in [ ];

[0067] Figure 12 is Figure 10 Schematic cross-sectional structure diagram of the back-contact solar cell along line XII-XII in [ ];

[0068] Figure 13 is Figure 10 Partial enlarged schematic view of the back-contact solar cell in [XIII];

[0069] Figure 14 is Figure 10 Partial enlarged schematic view of the back-contact solar cell in [XIV];

[0070] Figure 15 is Figure 10 Partial enlarged schematic view of the back-contact solar cell in [XV];

[0071] Figure 16 It is another planar structure schematic diagram of the back-contact solar cell provided by the embodiments of the present application.

[0072] Main element symbol description:

[0073] Photovoltaic system 1000;

[0074] Battery module 200;

[0075] Back-contact solar cell 100, substrate 10, front side 11, back side 12, first edge 121, second edge 122, third edge 123, fourth edge 124, first series connection region 13, first edge series connection region 131, fourth edge series connection region 132, second series connection region 14, second edge series connection region 141, third edge series connection region 142, first groove 15, second groove 16;

[0076] Silicon substrate 101, first surface 1011, second surface 1012, first doping layer 102, second doping layer 103, back surface passivation film layer 104;

[0077] First grid line 20, first collecting grid line 21, first bus bar 22, first bus bar segment 221, first welding segment 201; First grid line protrusion 202, second grid line 30, second collecting grid line 31, second bus bar 32, second bus bar segment 321, second welding segment 301, second grid line protrusion 302;

[0078] First edge bus bar 40, first protrusion 41, second protrusion 42, first insulating layer 50, first auxiliary connection line 60, first bus bar layer 70, second auxiliary connection line 90;

[0079] Second edge bus bar 110, first edge bus bar segment 111, second edge bus bar segment 112, middle bus bar segment 113, first connection segment 114, second connection segment 115, third protrusion 1101, fourth protrusion 1102, fifth protrusion 1103, sixth protrusion 1104, seventh protrusion 1105, eighth protrusion 1106, ninth protrusion 1107, tenth protrusion 1108, second insulating layer 120, third auxiliary connection line 130, second bus bar layer 140, fourth auxiliary connection line 160; Fifth auxiliary connection line 170, sixth auxiliary connection line 180, seventh auxiliary connection line 190, eighth auxiliary connection line 1100. Detailed implementation manners

[0080] In order to make the objectives, technical solutions and advantages of the present application clearer and more understandable, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. The examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions from beginning to end. It should be noted that the embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and should not be construed as a limitation to the present application. In addition, it should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0081] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "lateral", "longitudinal", etc. is based on the orientation or positional relationship shown in the drawings. These are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present application.

[0082] In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more features. In the description of the present application, the meaning of "a number of" is two or more, unless otherwise specifically defined.

[0083] In the present application, unless otherwise clearly specified and limited, the first feature being "on" or "under" the second feature may include the first and second features being in direct contact, or may include the first and second features not being in direct contact but being in contact through additional features therebetween. Moreover, the first feature being "above", "over" and "on top of" the second feature includes the first feature being directly above and obliquely above the second feature, or merely indicating that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "underneath" the second feature includes the first feature being directly below and obliquely below the second feature, or merely indicating that the first feature has a lower horizontal height than the second feature.

[0084] The following disclosure provides many different embodiments or examples for implementing different structures of the present application. To simplify the disclosure of the present application, the components and settings of specific examples are described below. Of course, they are only examples and are not intended to limit the present application. In addition, the present application may repeat reference numerals and / or reference letters in different examples. Such repetition is for the purpose of simplification and clarity and does not itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present application provides examples of various specific processes and materials, but those of ordinary skill in the art may be aware of the application of other processes and / or the use scenarios of other materials.

[0085] Please refer to Figure 1 and Figure 2, the photovoltaic system 1000 in the embodiments of the present application may include the battery module 200 in the embodiments of the present application, and the battery module 200 in the embodiments of the present application may include a plurality of back-contact solar cells 100 in the embodiments of the present application. In the embodiments of the present application, a plurality of back-contact solar cells 100 in the battery module 200 may be connected in series to form a plurality of cell strings, and each cell string may be connected in series, in parallel, or in a series-parallel combination to achieve the current confluence output. For example, the connection between each cell can be realized by welding a solder tape, and the connection between each cell string can be realized by a bus bar. In some embodiments, each cell string may form a cell array, and then be encapsulated together with a front plate, a front encapsulant film, a back encapsulant film, and a back plate to form the battery module 200.

[0086] In the embodiments of the present application, the back-contact solar cell 100 may be a main-gridless back-contact solar cell. Please refer to Figures 3 - 7 , the back-contact solar cell 100 in the embodiments of the present application may include a substrate 10, a plurality of first grid lines 20, a plurality of second grid lines 30, a first edge bus bar 40, and a first insulating layer 50.

[0087] As Figures 3 - 7 shown, the substrate 10 has opposite front and back surfaces 11 and 12. The back surface 12 of the substrate 10 has opposite first and second edges 121 and 122 in a first direction, and the back surface 12 has a plurality of first connection areas 13 and a plurality of second connection areas 14. The first connection areas 13 and the second connection areas 14 are respectively used for arranging the positive and negative solder tapes. That is to say, one of the first connection areas 13 and the second connection areas 14 is a positive connection area, and the other is a negative connection area.

[0088] As Figure 3 and Figure 4 shown, in the first direction, the first connection areas 13 and the second connection areas 14 are alternately arranged. The plurality of first connection areas 13 include a first edge connection area 131 closest to the first edge 121, and there is no second connection area 14 between the first edge connection area 131 and the first edge 121. That is to say, as Figure 3 and Figure 4 shown, among the first connection areas 13 and the second connection areas 14, the connection area closest to the first edge 121 is the first connection area 13, and this first connection area 13 is denoted as the first edge connection area 131, and there are no other connection areas between the first edge connection area 131 and the first edge 121. As Figure 6 shown, a first groove 15 is formed on the substrate 10 within the first edge connection area 131.

[0089] As Figure 3As shown, a plurality of first grid lines 20 and a plurality of second grid lines 30 are alternately arranged along a second direction on the back surface 12, and the second direction intersects the first direction. All the first grid lines 20 and all the second grid lines 30 intersect with the first series connection region 13 and the second series connection region 14, that is, the first series connection region 13 and the second series connection region 14 both extend along the second direction to intersect with the first grid lines 20 and the second grid lines 30. In some embodiments, the first direction and the second direction can be respectively the longitudinal direction and the transverse direction of the back contact solar cell 100, and the two are perpendicular to each other. For example, in Figure 3 the example shown, the first direction is the transverse direction of the back contact solar cell 100, and the second direction is the longitudinal direction of the back contact solar cell 100. Of course, in other embodiments, the first direction and the second direction can also be other directions, such as the two diagonal directions of the back contact solar cell 100, and specific details are not limited herein.

[0090] The first grid line 20 (including the first collecting grid line 21 and the first bus bar 22 hereinafter) includes a first welding section 201 located in the second series connection region 14, that is, the first grid line 20 is continuous in each second series connection region 14 and has a first welding section 201 for welding with a solder tape at the second series connection region 14. The second grid line 30 (including the second collecting grid line 31 and the second bus bar 32 hereinafter) includes a second welding section 301 located in the first series connection region 13 (including the first edge series connection region 131), that is, the second grid line 30 is continuous in each first series connection region 13 and has a second welding section 301 for welding with a solder tape at the first series connection region 13.

[0091] The plurality of first grid lines 20 may include a plurality of first collecting grid lines 21 and at least one first bus bar 22. The first collecting grid line 21 is discontinuous at the first edge series connection region 131 and continuous at the second series connection region 14. The first bus bar 22 is continuous at both the first edge series connection region 131 and the second series connection region 14. The second grid line 30 is continuous at the first edge series connection region 131. That is, the first grid line 20 includes at least two types of grid lines, one is the first collecting grid line 21, and the other is the first bus bar 22. The first collecting grid line 21 is discontinuous at the first edge series connection region 131, and the first bus bar 22 is continuous at the first edge series connection region 131. The second grid line 30 is also continuous at the first edge series connection region 131. In the battery module 200, the solder tape in the first series connection region 13 (including the first edge series connection region 131) is used to connect with the second grid line 30 to realize the current collection output of the second grid line 30, and the solder tape in the second series connection region 14 is used to be welded and connected with the first grid line 20 to realize the current collection output of the first grid line 20.

[0092] As Figure 6As shown, a part of the first busbar 22 is located in the first groove 15. In some embodiments, in the second direction, the first busbar 22 may extend along a sidewall of the first groove 15 to the bottom of the first groove 15 and extend out of the first groove 15 from the other sidewall of the first groove 15.

[0093] The part of the first busbar 22 corresponding to the first groove 15 does not fill the entire first groove 15, that is, in the thickness direction of the back-contact solar cell 100, the height of the part of the first busbar 22 corresponding to the first groove 15 is less than the height of the opening of the first groove 15.

[0094] As Figure 3 shown, the first edge busbar 40 is closer to the first edge 121 than the first edge series connection region 131, and the first edge busbar 40 is electrically connected to at least a part of the first collecting grid line 21 and electrically connected to the first busbar 22.

[0095] Specifically, in order to avoid the battery from having a hidden crack caused by welding at the edge position of the first edge 121, the first edge busbar 40 is not used for welding. It is used to collect the current of the part of the first collecting grid line 21 between the first edge series connection region 131 and the first edge 121, and then collect the current through the first busbar 22 to the same-polarity solder strip in the second series connection region 14 adjacent to the first edge series connection region 131 (that is, Figure 3 and Figure 4 the leftmost second series connection region 14 in ), so as to collect the current of the grid line segment in the edge region of the first grid line 20 at the first edge 121, improving the efficiency of the back-contact solar cell 100. If the first edge busbar 40 and the first busbar 22 are not provided, it will cause the part of the first grid line 20 between the first edge series connection region 131 and the first edge 121 to form an isolated grid line segment, resulting in the inability to collect the current of this part.

[0096] As Figure 3 and Figure 6 shown, the first insulating layer 50 is disposed at the first groove 15 in the first edge series connection region 131. The first insulating layer 50 is at least partially disposed in the first groove 15 and located on the first busbar 22. That is, the first insulating layer 50 is provided on the part of the first busbar 22 located in the first groove 15, and the first insulating layer 50 is at least partially disposed in the first groove 15. The first insulating layer 50 is provided to insulate the different-polarity solder strip in the first edge series connection region 131 from the first busbar 22 to avoid short circuit.

[0097] Among them, in the thickness direction of the back-contact solar cell 100 (i.e., the direction in which the front surface 11 faces the back surface 12), the height of the first insulating layer 50 is flush with the height of the second welding section 301, or the height of the first insulating layer 50 is less than the height of the second welding section 301, or the height of the first insulating layer 50 is greater than the height of the second welding section 301, and the height difference between the first insulating layer 50 and the second welding section 301 is less than or equal to 15 μm.

[0098] In the back-contact solar cell 100, the battery module 200, and the photovoltaic system 1000 according to the embodiments of the present application, the first collecting grid line 21 is discontinuous at the first edge series connection area 131 and continuous at the second series connection area 14, the first bus bar 22 is continuous at the first edge series connection area 131 and the second series connection area 14, and the second grid line 30 is continuous at the first edge series connection area 131. The first edge bus line 40 is closer to the first edge 121 than the first edge series connection area 131, and the first edge bus line 40 is electrically connected to at least a part of the first collecting grid line 21 and electrically connected to the first bus bar 22. The first insulating layer 50 is disposed at the first groove 15 within the first edge series connection area 131, and the first insulating layer 50 is at least partially disposed within the first groove 15 and located on the first bus bar 22. The height of the first insulating layer 50 is flush with the height of the second welding section 301, or the height of the first insulating layer 50 is less than the height of the second welding section 301, or the height of the first insulating layer 50 is greater than the height of the second welding section 301, and the height difference between the first insulating layer 50 and the second welding section 301 is less than or equal to 15 μm. In this way, by providing the first edge bus line 40 and the first bus bar 22, the current collected by at least a part of the first grid line 20 located between the first edge series connection area 131 and the first edge 121 can be collected and merged into the same-polarity solder tape within the second series connection area 14 adjacent to the first edge series connection area 131, which can effectively avoid causing hidden cracks during welding at the first edge 121 of the back-contact solar cell 100 while ensuring the efficiency of the back-contact solar cell 100. At the same time, by forming the first groove 15 on the substrate 10 and disposing the first insulating layer 50 at least partially within the first groove 15, the height of the first insulating layer 50 is less than the height of the second welding section 301, or the first insulating layer 50 is flush with the second welding section 301, or the height of the first insulating layer 50 is greater than the height of the second welding section 301 and the height difference between the two is less than or equal to 15 μm. In this way, while achieving insulation between the solder tape and the first bus bar 22, the height difference between the first insulating layer 50 and the grid line welding section can be reduced or even eliminated, thereby reducing the risk of false soldering caused by the first insulating layer 50, reducing the impact of false soldering on the back-contact solar cell 100, and improving the performance of the back-contact solar cell 100.

[0099] Specifically, as shown above, it is not difficult to understand that in the present application, the first edge busbar 40 is not used for welding, but only for current transmission and busbar connection. The function of the first busbar grid line 22 is to collect and transmit current. From Figure 3 and Figure 4 it can be seen that in the examples shown in Figure 3 and Figure 4 , if the first edge busbar 40 and the first busbar grid line 22 are not provided, the first grid line 20 is disconnected at the first edge series connection area 131. The current of at least some of the isolated grid line segments of the first grid line 20 located between the first edge series connection area 131 and the first edge 121 cannot be collected. Therefore, by providing the first edge busbar 40 and the first busbar grid line 22, the current of at least some of the isolated grid line segments of the first grid line 20 in this edge area can be collected and transmitted to the solder strip provided in the adjacent second series connection area 14, thereby effectively avoiding efficiency loss.

[0100] And due to the continuous arrangement of the first busbar grid line 22 in the first edge series connection area 131, in order to prevent the solder strip on the first edge series connection area 131 from contacting the first busbar grid line 22 and causing a short circuit, a first insulating layer 50 (such as insulating glue) needs to be provided at the position corresponding to the first busbar grid line 22 in the first edge series connection area 131. However, in such a case, when the first groove 15 is not opened, the height of the first insulating layer 50 is higher than the height of the second welding section 301 of the second grid line 30. That is, in the thickness direction, the protruding height of the first insulating layer 50 is higher than the height of the second welding section 301 of the second grid line 30. In such a case, the solder strip in the first edge series connection area 131 is likely to be poorly welded to the second grid line 30 during the welding process, resulting in the inability to effectively collect the current on some of the second grid lines 30 (especially the second grid line 30 adjacent to the first busbar grid line 22, which has the greatest possibility of poor welding). Based on this, in the present application, by opening the first groove 15 on the substrate 10 and disposing the first insulating layer 50 at least partially in the first groove 15, the height of the first insulating layer 50 is made flush with or less than the height of the second welding section 301 or the height difference between the first insulating layer 50 and the second welding section 301 is less than 15 μm, which can reduce or even eliminate the risk of poor welding, thereby improving the welding reliability and ensuring the performance of the back contact solar cell 100.

[0101] Furthermore, in some embodiments, the number of the first busbar grid lines 22 can be multiple, the number of the first insulating layers 50 corresponds to the number of the first busbar grid lines 22, and the number of the first grooves 15 can correspond to the number of the first insulating layers 50. In this way, the risk of poor welding caused by all the first insulating layers 50 can be reduced or even eliminated.

[0102] Of course, in some possible embodiments, only some of the first busbar lines 22 may be correspondingly provided with the first grooves 15, that is, the first grooves 15 are only formed below only some of the first insulating layers 50, and the first grooves 15 are not formed in other positions. In such a case, it can solve the problem of poor soldering caused by some of the first insulating layers 50.

[0103] When the height of the first insulating layer 50 is greater than the height of the second welding section 301, the height difference between the two can be 1um, 2um, 3um, 4um, 5um, 9um, 7um, 8um, 9um, 10um, 11um, 12um, 13um, 14um, 15um or any value between 0 - 15um.

[0104] In some embodiments, when the height of the first insulating layer 50 is greater than the height of the second welding section 301, the height difference between the first insulating layer 50 and the second welding section 301 is preferably less than 8um, such as 0.5um, 1um, 2um, 3um, 4um, 5um, 9um, 7um, 8um. Specifically, through repeated research and verification by the inventors of the present application, it is found that by preferably setting the height difference between the two within the preferred range of less than 8um, the risk of poor soldering caused by the first insulating layer 50 can be basically completely eliminated.

[0105] Furthermore, in the embodiments of the present application, as Figure 5 and Figure 6 shown, the substrate 10 may include a silicon substrate 101, several first doping layers 102, several second doping layers 103, and a back passivation film layer 104. The silicon substrate 101 has opposite first surface 1011 and second surface 1012. The first doping layers 102 and the second doping layers 103 are both disposed on the second surface 1012. Several first doping layers 102 and several second doping layers 103 are alternately arranged along the second direction. The back passivation film layer 104 is at least stacked on the first doping layers 102 and the second doping layers 103. In some embodiments, the back passivation film layer 104 may cover the entire second surface 1012, that is, the first doping layers 102, the second doping layers 103, and the regions of the second surface 1012 where no doping layer is provided are all stacked with the back passivation film layer 104.

[0106] It can be seen therefrom that, in the substrate 10, the surface on the side where the first surface 1011 is located is the front surface 11 of the substrate 10, and the side where the second surface 1012 is located is the back surface of the substrate 10. Of course, in some embodiments, in the substrate 10, a first passivation layer (not shown in the figure) may be further disposed between the first doping layer 102 and the silicon substrate 101. The first passivation layer may be, for example, a tunneling layer, an intrinsic amorphous silicon layer or other film layers. A second passivation layer (not shown in the figure) may also be disposed between the second doping layer 103 and the silicon substrate 101. The second passivation layer may be, for example, a tunneling layer, an intrinsic amorphous silicon layer or other film layers.

[0107] In the back-contact solar cell 100, the first grid lines 20 correspond to the first doping layer 102 one by one, and the second grid lines 30 correspond to the second doping layer 103 one by one. One of the first doping layer 102 and the second doping layer 103 may be a P-type doping layer, and the other may be an N-type doping layer. In some embodiments, the first grid lines 20 may all penetrate through the back surface passivation film layer 104 to form a full contact with the first doping layer 102, or the first grid lines 20 may only partially penetrate through the back surface passivation film layer 104 to form a local metallization contact with the first doping layer 102. Specifically, there is no limitation here.

[0108] That is to say, in the embodiments of the present application, the first grid lines 20 are correspondingly disposed with the first doping layer 102 and at least partially penetrate through the back surface passivation film layer 104 to make electrical contact with the first doping layer 102, and the second grid lines 30 are correspondingly disposed with the second doping layer 103 and at least partially penetrate through the back surface passivation film layer 104 to make electrical contact with the second doping layer 103.

[0109] Please refer to Figure 3 and Figure 4 , in some embodiments, the back-contact solar cell 100 is a main-gridless back-contact solar cell. Among the plurality of first grid lines 20, the first collecting grid line 21 is disconnected at the first series connection region 13 and continuous at the second series connection region 14, and the first bus bar grid line 22 is continuous at the first edge series connection region 131 and disconnected at the remaining first series connection regions 13 and continuous at the second series connection region 14.

[0110] Such as Figure 3 、 Figure 4 and Figure 7As shown, in such a case, as described above, the first grid line 20 (including the first collecting grid line 21 and the first bus bar 22) includes a first welding section 201 corresponding to the second series connection area 14. That is, the first grid line 20 is continuous at each second series connection area 14 and has a first welding section 201 for welding with a solder strip at the second series connection area 14. The second grid line 30 (including the second collecting grid line 31 and the second bus bar 32 hereinafter) includes a second welding section 301 corresponding to the first series connection area 13 (including the first edge series connection area 131). That is, the second grid line 30 is continuous at each first series connection area 13 and has a second welding section 301 for welding with a solder strip at the first series connection area 13.

[0111] In some embodiments, in the first collecting grid line 21, the width of the first welding section 201 (i.e., the length in the second direction) may be greater than the width of the remaining part. In this way, the contact area between the first collecting grid line 21 and the solder strip can be increased, and the welding stability can be improved.

[0112] In some embodiments, the first welding section 201 may be a double-layer structure. Specifically, in some embodiments, the first grid line 20 may include a first collecting layer penetrating through the back passivation film layer 104 and a first welding layer stacked on the first collecting layer and not penetrating through the back passivation film layer 104.

[0113] In some embodiments, the first collecting layer may be continuous at the second series connection area 14 and discontinuous at the first series connection area 13. The first welding layer may be disposed at the second series connection area 14 and on the first collecting layer. In such a case, in the first grid line 20, the portion corresponding to the first welding layer is the first welding section 201.

[0114] Of course, in some other embodiments, the first welding section 201 may be a single-layer structure. In such a case, the first collecting layer is discontinuous at both the second series connection area 14 and the first series connection area 13. The first welding layer is disposed at the second series connection area 14 and electrically connected to the two ends formed by the first collecting layer at the second series connection area 14. It is not difficult to understand that in these cases, the portion corresponding to the first welding layer is the first welding section 201.

[0115] In some embodiments, the width of the first welding layer may be set to be greater than the width of the first collecting layer, where the width refers to the length of both in the second direction. In this way, the welding area during welding can be increased, and the welding reliability can be improved.

[0116] In some embodiments, the second welding section 301 may also be a double-layer structure. Specifically, in some embodiments, the second grid line 30 may include a second collecting layer penetrating through the back passivation film layer 104 and a second welding layer stacked on the second collecting layer and not penetrating through the back passivation film layer 104.

[0117] In some embodiments, the second collection layer may be continuous at the first connection area 13 and discontinuous at the second connection area 14. The second welding layer may be disposed at the first connection area 13 and on the second collection layer. In such a case, in the second gate line 30, the portion corresponding to the second welding layer is the second welding segment 301.

[0118] Of course, in other embodiments, the second collection layer may also be discontinuous at both the first connection area 13 and the second connection area 14. The second welding layer is disposed at the first connection area 13 and is electrically connected to the two ends formed by the second collection layer at the first connection area 13. It is not difficult to understand that in these cases, the portion corresponding to the second welding layer is the second welding segment 301.

[0119] In some embodiments, the width of the second welding layer may also be set to be greater than the width of the second collection layer, where the width refers to the length of both in the second direction.

[0120] In some embodiments, the depression depth of the first groove 15 is less than one-half of the thickness of the substrate 10. Specifically, the "depression depth" refers to: in the thickness direction, the distance between the bottom surface of the first groove 15 and the outermost surface of the back passivation film layer 104 facing away from the back surface 12, that is, the distance between the bottom surface of the first groove 15 and the back surface 12 of the substrate 10.

[0121] In this way, by setting the depth of the first groove 15 within a reasonable range, the risk of false soldering caused by the first insulating layer 50 can be reduced or even eliminated, while avoiding a too large depression depth that may greatly reduce the strength of the back contact solar cell 100.

[0122] Specifically, in such a case, the depression depth of the first groove 15 may be, for example, one-third, one-fourth, one-fifth, etc. of the thickness of the substrate 10.

[0123] In some embodiments, the first groove 15 may penetrate through the back passivation film layer 104 and the first doping layer 102, so that the silicon substrate 101 is exposed from the first groove 15. The portion of the first bus bar 22 located in the first groove 15 is in contact with the silicon substrate 101. In this way, after the substrate 10 is fabricated, the first groove 15 can be directly formed on the substrate 10 by etching (such as laser etching, etc.), without inserting an etching and grooving process during the preparation of the substrate 10.

[0124] Specifically, in such a case, a complete substrate 10 may be provided first, and then grooving treatment may be directly performed at the position on the substrate 10 where the first insulating layer 50 needs to be placed, then the first gate line 20 and the second gate line 30 are printed, and then the first insulating layer 50 is disposed at the first groove 15.

[0125] Of course, in some other embodiments, at a position on the silicon substrate 101 corresponding to the first edge connection region 131 and the first bus bar 22, a first recessed groove may be formed on the silicon substrate 101. Both the first doped layer 102 and the back passivation film layer 104 are recessed toward the side where the front surface 11 is located at the first recessed groove, so as to form a first groove 15 on the substrate 10.

[0126] Specifically, in such a case, during the manufacturing process, before preparing the first doped layer 102, a first recessed groove may be opened at a position on the silicon substrate 101 where the first doped layer 102 needs to be prepared and the first insulating layer 50 needs to be placed. Then, the first doped layer 102 and the back passivation film layer 104 are prepared to form the substrate 10. Since the first recessed groove is opened on the silicon substrate 101, the above-mentioned first groove 15 can be correspondingly formed on the substrate 10. Then, the first gate line 20 and the second gate line 30 are printed, and then the first insulating layer 50 is disposed at the first groove 15.

[0127] Please refer to Figure 3 、 Figure 4 and Figure 6 , in some embodiments, the back-contact solar cell 100 may further include a first auxiliary connection line 60. The first auxiliary connection line 60 may be disposed within the first edge connection region 131. In the second direction, at least one side of the first bus bar 22 is provided with the first auxiliary connection line 60. The first auxiliary connection line 60 connects at least two second gate lines 30 located on the same side of the first bus bar 22. Among them, as Figure 4 and Figure 6 shown, in some embodiments, preferably, at least two second gate lines 30 connected to the first auxiliary connection line 60 include the second gate line 30 adjacent to the first bus bar 22 (i.e., Figure 3 and Figure 4 the second gate line 30 closest to the first bus bar 22 in

[0128] Thus, by providing the first auxiliary connection line 60, the risk of poor soldering caused by the first insulating layer 50 can be further reduced. Even if poor soldering occurs between the second gate line 30 near the first insulating layer 50 and the solder tape due to the provision of the first insulating layer 50, due to the existence of the first auxiliary connection line 60, the poor soldered second gate line 30 can also achieve current confluence output through the first auxiliary connection line 60, reducing the impact caused by poor soldering, thereby ensuring the efficiency of the back-contact solar cell 100.

[0129] As Figure 3 and Figure 4 shown, in the embodiments of the present application, in order to minimize the impact of poor soldering as much as possible, when there are second gate lines 30 on both sides of the first bus bar 22, it is preferred to provide first auxiliary connection lines 60 on both sides of the first bus bar 22 simultaneously.

[0130] In some embodiments, the width of the first bus bar 22 (i.e., the length in the second direction) can be greater than the width of the portion of the first collecting grid line 21 outside the second series connection region 14 (i.e., the portion of the first collecting grid line 21 other than the first welding segment 201) (i.e., the length in the second direction).

[0131] Thus, since the first bus bar 22 needs to undertake the function of current confluence and transmission, therefore, setting the width of the first bus bar 22 wider can reduce the transmission loss during the current confluence process and improve the efficiency.

[0132] In addition, as Figure 3 , Figure 4 and Figure 7 shown, in the embodiments of the present application, in the first bus bar 22, it is continuous only at the first edge series connection region 131, and is disconnected at other first series connection regions 13. At the same time, the first bus bar 22 is continuous at the second series connection region 14 and has a first welding segment 201 at the second series connection region 14. Only the segment of the first bus bar 22 closest to the first edge 121 undertakes the current confluence function. Therefore, in some embodiments, in order to save the paste to reduce the cost, only this part of the grid line segment can be set wider. In such a case, please refer to Figure 3 , Figure 4 and Figure 7 , several second series connection regions 14 may include a second edge series connection region 141 closest to the first edge 121. The first bus bar 22 may include a first current confluence segment 221 located between the second edge series connection region 141 and the first edge 121. In some embodiments, the width of the first current confluence segment 221 (i.e., the length in the second direction) can be greater than the width of the remaining portion of the first bus bar 22 outside the second series connection region 14 (i.e., the portion other than the first current confluence segment 221 and other than the first welding segment 201).

[0133] Thus, by only setting the width of the first bus bar segment 221 wider, the use of paste can be reduced while reducing the bus bar transmission loss, thereby reducing costs.

[0134] Specifically, as described above, in such an embodiment, the first bus bar line 22 is continuous at the second edge series connection region 141 and has a first welding segment 201 at the second edge series connection region 141. The first bus bar segment 221 can collect current to the solder tape provided at the second edge series connection region 141, and only setting a part of the first bus bar segment 221 wider can reduce the use of paste. In such a case, the first bus bar segment 221 penetrates the back passivation film layer 104 and contacts the first doping layer 102.

[0135] Please refer to Figure 7 , in some other embodiments, a first bus bar layer 70 may be provided on the first bus bar segment 221. Thus, by providing the first bus bar layer 70 on the first bus bar segment 221, it is equivalent to increasing the cross-sectional area of the first bus bar segment 221, which can also reduce the transmission loss. At the same time, the first bus bar layer 70 can be made of a paste with a lower cost than that of the first bus bar segment 221, which can reduce costs.

[0136] Specifically, in such an embodiment, the first bus bar layer 70 can be made of a non-burn-through paste. The first bus bar layer 70 does not penetrate the back passivation film layer 104 and contacts the first doping layer 102. The paste cost of the first bus bar layer 70 is lower than that of the first bus bar segment 221. It can be understood that since the first bus bar layer 70 is provided on the first bus bar segment 221, it is also not necessary to widen the first bus bar segment 221, and the purpose of reducing the transmission loss can also be achieved.

[0137] Further, in such an embodiment, the width (the length in the second direction) of the first bus bar layer 70 can be greater than the width (the length in the second direction) of the part of the first collecting grid line 21 outside the second series connection region 14 (that is, the part of the first collecting grid line 21 other than the first welding segment 201). Thus, by increasing the width of the first bus bar layer 70, the transmission capacity can be further improved and the transmission loss can be reduced.

[0138] Specifically, in such an embodiment, the width of the first bus bar layer 70 can be the same as the width of the first welding segment 201. In this article, the width of the first welding segment 201 refers to the length of the first welding segment 201 in the second direction. As shown above, when the width of the first welding layer is greater than the width of the first collecting layer, the width of the first welding segment 201 is the width of the first welding layer (that is, the length in the second direction). For similar descriptions that appear below, this can be referred to for understanding.

[0139] In this way, it can be ensured that no significant transmission loss will occur during the current collection process. At the same time, during the printing process, the first current collection layer 70 can be printed simultaneously with the first welding layer at the first welding section 201. When using the same screen printing, there is no need to open screen slots of different sizes on the screen, saving manufacturing processes and reducing manufacturing difficulty.

[0140] Please refer to Figure 7 , in some embodiments, the width (the length in the first direction) of the first edge current collection line 40 may be greater than the width (the length in the second direction) of the portion of the first collection grid line 21 that is outside the second series connection region 14 (i.e., the portion of the first collection grid line 21 other than the first welding section 201).

[0141] In this way, since the first edge current collection line 40 needs to undertake the function of current collection and transmission, setting the width of the first edge current collection line 40 wider can also reduce the transmission loss during the current collection process and improve efficiency.

[0142] Specifically, in such an embodiment, the width of the first edge current collection line 40 may be the same as the width of the first welding section 201. In this way, it can be ensured that no significant current collection loss will occur during the current collection process. At the same time, during printing, only screen slots of the same size need to be opened on the screen to print the three simultaneously, which can effectively save manufacturing processes and reduce manufacturing difficulty.

[0143] In addition, please continue to refer to Figure 7 , in some embodiments, the width (the length in the first direction) of the first auxiliary connection line 60 may be greater than the width (the length in the second direction) of the portion of the first collection grid line 21 that is outside the second series connection region 14 (i.e., the portion of the first collection grid line 21 other than the first welding section 201).

[0144] In this way, since the first auxiliary connection line 60 functions to transmit and collect current when a virtual weld occurs, setting the width of the first auxiliary connection line 60 wider can also reduce the transmission loss during the current collection process and improve efficiency.

[0145] In some embodiments, the width of the first auxiliary connection line 60 may be the same as the width of the first edge current collection line 40.

[0146] Please refer to Figure 3 and Figure 4 , in some embodiments, the first edge current collection line 40 is electrically connected to all the first collection grid lines 21.

[0147] In this way, the current collected by the isolated grid line segments between the first edge series connection region 131 and the first edge 121 in all the first collection grid lines 21 can be collected, maximizing the efficiency of the back contact solar cell 100.

[0148] Of course, in some embodiments, the first edge bus bar 40 may also be electrically connected to only a part of the first collection grid lines 21. In such a case, the number of the first collection grid lines 21 not electrically connected to the first edge bus bar 40 is less than or equal to 4. In this way, even if some of the first collection grid lines 21 are not connected to the first edge bus bar 40, the number is small and will not cause excessive efficiency loss and product defects.

[0149] In some embodiments, the first auxiliary connection line 60 is connected to 2 - 20 second grid lines 30. In this way, by setting the number of the second grid lines 30 connected to the first auxiliary connection line 60 within this reasonable range, the influence brought by false soldering can be reduced or even eliminated as much as possible.

[0150] In the embodiments of the present application, the number of the first bus grid lines 22 may be a single one. In such a case, the first auxiliary connection line 60 may be provided only on one side of the first bus grid line 22, or the first auxiliary connection line 60 may be provided on both sides of the first bus grid line 22. Specifically, there is no limitation here. When there are second grid lines 30 on both sides of the first bus grid line 22, it is preferred to provide the first auxiliary connection line 60 on both sides.

[0151] In addition, it should be noted that in the present application, when the number of the first bus grid lines 22 is multiple, the first auxiliary connection line 60 may also be provided only on one side or both sides of only some of the first bus grid lines 22, while the first auxiliary connection line 60 may not be provided on both sides of the remaining first bus grid lines 22. In such a case, it can also solve the problem of false soldering at some positions. In the present application, it is preferred that the first auxiliary connection line 60 is provided on both sides of each first bus grid line 22. Of course, if the first bus grid line 22 is located at the third edge 123, only the first auxiliary connection line 60 needs to be provided on one side of the first bus grid line 22.

[0152] Of course, please refer to Figure 3 and Figure 4 , in some embodiments, the number of the first bus grid lines 22 may also be multiple. Setting multiple first bus grid lines 22 can shorten the current bus path, effectively reduce the bus transmission loss, and improve the efficiency.

[0153] In such a case, a first auxiliary connection line 60 is provided between adjacent two first bus grid lines 22, and the first auxiliary connection line 60 located between adjacent two first bus grid lines 22 is connected to all the second grid lines 30 located between adjacent two first bus grid lines 22.

[0154] Thus, connecting all the second grid lines 30 between two adjacent first bus grid lines 22 with the first auxiliary connection line 60 can basically completely eliminate the influence caused by poor soldering and improve the efficiency of the back-contact solar cell 100 as much as possible.

[0155] Specifically, in such an embodiment, the number of the first bus grid lines 22 in the back-contact solar cell 100 can be selected according to the actual situations such as the size of the cell and the loss during the transmission process, and no limitation is imposed herein.

[0156] Please refer to Figure 3 and Figure 4 as well as Figure 8 and Figure 9 , in some embodiments, the number of the first bus grid lines 22 is multiple, and the substrate 10 has a third edge 123 and a fourth edge 124 in the second direction. Among the first grid lines 20 and the second grid lines 30, the grid line closest to the third edge 123 is the first bus grid line 22, and / or the grid line closest to the fourth edge 124 is the first bus grid line 22.

[0157] Thus, setting the grid lines located at the third edge 123 and / or the fourth edge 124 as the first bus grid lines 22 can achieve current collection at the edge position and also reduce the range affected by poor soldering.

[0158] Specifically, as Figure 3 and Figure 4 shown, in such an embodiment, in addition to the first bus grid lines 22 at the third edge 123 and / or the fourth edge 124, several first bus grid lines 22 can also be arranged in the middle region. A first auxiliary connection line 60 is arranged between every two adjacent first bus grid lines 22, and the first auxiliary connection line 60 connects all the second grid lines 30 between two adjacent first bus grid lines 22. In this way, the influence caused by poor soldering can be basically completely eliminated, and the efficiency of the back-contact solar cell 100 can be ensured to the greatest extent.

[0159] Of course, it can be understood that in some embodiments, among the first grid lines 20 and the second grid lines 30, the grid line closest to the third edge 123 can also be the first collection grid line 21. In such a case, the first auxiliary connection line 60 between the first bus grid line 22 closest to the third edge 123 and the third edge 123 is connected to all the second grid lines 30 between the first bus grid line 22 closest to the third edge 123 and the third edge 123, that is, changing the first bus grid line 22 closest to the third edge 123 in Figure 3 and Figure 4 to the first collection grid line 21.

[0160] In some embodiments, among the first gate line 20 and the second gate line 30, the gate line closest to the fourth edge 124 may also be the first collecting gate line 21. The first auxiliary connection line 60 between the first busbar gate line 22 closest to the fourth edge 124 and the fourth edge 124 is connected to all the second gate lines 30 between the first busbar gate line 22 closest to the fourth edge 124 and the fourth edge 124. That is, change the first busbar gate line 22 closest to the third edge 123 in Figure 3 and Figure 4 to the first collecting gate line 21.

[0161] In this way, the gate line closest to the third edge 123 and / or the fourth edge 124 is set as the first collecting gate line 21, and the first busbar gate line 22 is only set in the middle area. It is not necessary to provide the first insulating layer 50 at the positions of the third edge 123 and the fourth edge 124, reducing the use of insulating glue and lowering the cost. At the same time, in such a case, by making the above-mentioned connection settings for the first auxiliary connection line 60 between the first busbar gate line 22 closest to the third edge 123 and the third edge 123, the virtual soldering influence brought by the first insulating layer 50 can be basically completely eliminated.

[0162] Please refer to Figure 4 and Figure 8 . In some embodiments, the substrate 10 has a third edge 123 and a fourth edge 124 in the second direction. At the junction where the first gate line 20 closest to the third edge 123 is connected to the first edge busbar 40, the first edge busbar 40 has a first convex portion 41 protruding toward the third edge 123.

[0163] Please refer to Figure 4 and Figure 9 . In some embodiments, at the junction where the first gate line 20 closest to the fourth edge 124 is connected to the first edge busbar 40, the first edge busbar 40 has a second convex portion 42 protruding toward the fourth edge 124.

[0164] In this way, the settings of the first convex portion 41 and the second convex portion 42 can provide redundancy for the first edge busbar 40 at the corner of the back-contact solar cell 100 located at the first edge 121, avoiding poor contact between the first edge busbar 40 and the first gate line 20 closest to the third edge 123 due to inaccurate printing during the printing process, resulting in incomplete filling of the paste at the corner.

[0165] Specifically, in such a case, in some embodiments, the first grid lines 20 closest to the third edge 123 and the fourth edge 124 can both be the first bus grid lines 22. In such a case, when a first bus layer 70 is provided on the first bus grid line 22, the first edge bus line 40 and the first bus layer 70 can be directly printed integrally, and the first convex portion 41 and the second convex portion 42 are provided at the intersection of the two to ensure the integrity of printing and filling and ensure good contact between the two.

[0166] In addition, as Figure 8 and Figure 9 shown, in some embodiments, in the back-contact solar cell 100, chamfers are formed at the intersections of the first edge 121 with the third edge 123 and the fourth edge 124, and the first grid lines 20 are correspondingly provided at the chamfers. Therefore, as Figure 8 and Figure 9 shown, in order to realize the connection between the first edge bus line 40 and the first grid line 20, the first edge bus line 40 has bending portions at both chamfers. Of course, it can be understood that in some embodiments, if the back-contact solar cell 100 does not have chamfers, there is no need to provide bending portions.

[0167] Please refer to Figure 8 and Figure 9 , in some embodiments, at the junction of the first grid line 20 (including the first collecting grid line 21 and the first bus grid line 22) and the first edge bus line 40, at least part of the first grid line 20 has a first grid line convex portion 202 that protrudes toward the first edge 121 side compared with the first edge bus line 40.

[0168] In this way, through the setting of the first grid line convex portion 202, the stability of the electrical connection between the first grid line 20 and the first edge bus line 40 can be ensured, and effectively avoid the phenomenon that part of the first grid line 20 cannot form a stable contact with the first edge bus line 40 due to printing accuracy during the printing process.

[0169] Please refer to Figure 3 , Figure 4 and Figure 7 , in some embodiments, several second series connection regions 14 include a second edge series connection region 141 closest to the first edge 121 (i.e., the second series connection region 14 adjacent to the first edge series connection region 131). The first grid line 20 is continuous at the second edge series connection region 141, the second grid line 30 is discontinuous at the second edge series connection region 141, and the back-contact solar cell 100 further includes a second auxiliary connection line 90. The second auxiliary connection line 90 is provided in the second edge series connection region 141, and in the second direction, the second auxiliary connection line 90 connects the first bus grid line 22 and at least one first collecting grid line 21 located on one side of the first bus grid line 22.

[0170] Thus, by providing the second auxiliary connection line 90 within the second edge connection area 141, it is possible to effectively avoid the phenomenon that the solder tape within the second edge connection area 141 has poor soldering or poor contact at the first busbar line 22, resulting in the inability to collect the current transmitted from the first busbar line 22.

[0171] Specifically, as Figure 4 and Figure 7 shown, in such an embodiment, the number of the second auxiliary connection lines 90 may be the same as the number of the first busbar lines 22, and the two correspond one by one. When the first busbar line 22 is located at the middle position (i.e., there are first collection grid lines 21 on both sides of the first busbar line 22), the second auxiliary connection line 90 connects the first busbar line 22 and also connects two first collection grid lines 21 adjacent to the first busbar line 22 (i.e., the first collection grid lines 21 located on both sides of and adjacent to the first busbar line 22).

[0172] When the grid line closest to the third edge 123 is the first busbar line 22, the first busbar line 22 has the first collection grid line 21 on only one side. In such a case, the second auxiliary connection line 90 connected to the first busbar line 22 located at the third edge 123 connects at least the first collection grid line 21 adjacent to the first busbar line 22, and the number of the first collection grid lines 21 connected by the second auxiliary connection line 90 is 1 - 6. For example, in Figure 3 and Figure 4 , the second auxiliary connection line 90 connects 6 first collection grid lines 21 closest to the third edge 123, and specific details are not limited herein.

[0173] Similarly, when the grid line closest to the fourth edge 124 is the first busbar line 22, the first busbar line 22 has the first collection grid line 21 on only one side. In such a case, the second auxiliary connection line 90 connected to the first busbar line 22 located at the fourth edge 124 connects at least the first collection grid line 21 adjacent to the first busbar line 22, and the number of the first collection grid lines 21 connected by the second auxiliary connection line 90 is 1 - 6. For example, in Figure 3 and Figure 4 , the second auxiliary connection line 90 connects 6 first collection grid lines 21 closest to the fourth edge 124, and specific details are not limited herein.

[0174] In some embodiments, the width of the second auxiliary connection line 90 (the length in the first direction) may be greater than the width of the portion of the first collecting grid line 21 outside the second series connection region 14 (i.e., the portion of the first collecting grid line 21 other than the first welding section 201) (the length in the second direction). Thus, since the second auxiliary connection line 90 functions to transmit and converge current when a virtual weld occurs at the first busbar 22, setting the width of the second auxiliary connection line 90 to be wider can also reduce the transmission loss during the current convergence process and improve the efficiency.

[0175] In some embodiments, the distance between the first edge series connection region 131 and the first edge 121 is greater than or equal to 2 mm and less than or equal to 20 mm.

[0176] Thus, it is possible to avoid the distance between the first edge series connection region 131 and the first edge 121 being too small, resulting in the welding position being too close to the first edge 121 and causing a hidden crack in the back contact solar cell 100, reducing the risk of hidden cracks. It is also possible to avoid the distance between the first edge series connection region 131 and the first edge 121 being too large, which may cause the length of the isolated grid line segment between the first edge series connection region 131 and the first edge 121 to be too long, resulting in excessive loss during the transmission path.

[0177] Specifically, in such an embodiment, the distance between the first edge series connection region 131 and the first edge 121 may be, for example, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, 20 mm or any value between 2 mm and 20 mm, and is not specifically limited herein.

[0178] Please refer to Figure 3 and Figures 10 - 13 , in some embodiments, a plurality of second series connection regions 14 include a third edge series connection region 142 closest to the second edge 122. There is no first series connection region 13 between the third edge series connection region 142 and the second edge 122. That is to say, as Figure 3 and Figure 10 shown, among the first series connection region 13 and the second series connection region 14, the series connection region closest to the second edge 122 is the second series connection region 14, and this second series connection region 14 is represented as the third edge series connection region 142. There are no other series connection regions between the third edge series connection region 142 and the second edge 122. As Figure 12 shown, within the third edge series connection region 142, a second groove 16 is formed on the substrate 10.

[0179] A plurality of second grid lines 30 includes a plurality of second collecting grid lines 31 and at least one second bus bar 32. The second collecting grid lines 31 are discontinuous at the third edge connection area 142 and continuous at the first connection area 13. The second bus bar 32 is continuous at the third edge connection area 142, and the first grid line 20 is continuous at the second edge connection area 141.

[0180] That is, the second grid line 30 includes at least two types of grid lines. One is the second collecting grid line 31, and the other is the second bus bar 32. The second collecting grid line 31 is discontinuous at the third edge connection area 142, and the second bus bar 32 is continuous at the third edge connection area 142. The first grid line 20 is also continuous at the third edge connection area 142.

[0181] The second bus bar 32 is partially located in the second groove 16. In some embodiments, in the second direction, the second bus bar 32 may extend along one side wall of the second groove 16 to the bottom of the second groove 16 and extend out of the second groove 16 from the other side wall of the second groove 16. The portion of the second bus bar 32 corresponding to the second groove 16 does not fill the entire second groove 16. That is, in the thickness direction of the back contact solar cell 100, the height of the portion of the second bus bar 32 corresponding to the second groove 16 is less than the height of the opening of the second groove 16.

[0182] The back contact solar cell 100 may further include a second edge bus bar 110 and a second insulating layer 120. The second edge bus bar 110 is closer to the second edge 122 than the third edge connection area 142. The second edge bus bar 110 is electrically connected to at least a part of the second collecting grid lines 31 and electrically connected to the second bus bar 32.

[0183] Specifically, in order to avoid the battery from having a hidden crack caused by welding at the edge position of the second edge 122, the second edge bus bar 110 is not used for welding. It is used to collect the current of the part of the second collecting grid lines 31 between the third edge connection area 142 and the second edge 122, and then converge the current to the first connection area 13 adjacent to the third edge connection area 142 (i.e., Figure 3 and Figure 10 the rightmost first connection area 13 in

[0184] such as Figure 3 and Figure 12As shown, the second insulating layer 120 is disposed in the second groove 16 within the third edge series connection region 142. The second insulating layer 120 is at least partially disposed within the second groove 16 and is located on the second bus bar 32. That is, the second insulating layer 120 is provided on the portion of the second bus bar 32 that is within the second groove 16, and the second insulating layer 120 is at least partially disposed within the second groove 16. The second insulating layer 120 is provided to insulate the differently polarized solder tapes within the third edge series connection region 142 from the second bus bar 32 to avoid short circuits.

[0185] Wherein, in the thickness direction of the back contact solar cell 100 (i.e., the direction in which the front surface 11 faces the back surface 12), the height of the second insulating layer 120 is flush with the height of the first welding section 201, or the height of the second insulating layer 120 is less than the height of the first welding section 201, or the height of the second insulating layer 120 is greater than the height of the first welding section 201, and the height difference between the second insulating layer 120 and the first welding section 201 is less than or equal to 15 um.

[0186] Thus, by providing the second edge bus line 110 and the second bus bar 32, the current collected by at least a part of the isolated section of the second grid line 30 located between the third edge series connection region 142 and the second edge 122 can be collected and fed to the same polarized solder tape within the second series connection region 14 adjacent to the third edge series connection region 142. While effectively avoiding the formation of hidden cracks caused by welding at the second edge 122 of the back contact solar cell 100, the efficiency of the back contact solar cell 100 is ensured. At the same time, by forming the second groove 16 on the substrate 10 and disposing the second insulating layer 120 at least partially within the second groove 16, the height of the second insulating layer 120 is less than the height of the first welding section 201, or the second insulating layer 120 is flush with the first welding section 201, or the height of the second insulating layer 120 is greater than the height of the first welding section 201 and the height difference between the two is less than or equal to 15 um. This can reduce or even eliminate the height difference between the second insulating layer 120 and the grid line welding section, thereby reducing the risk of false soldering caused by the second insulating layer 120, further reducing the impact of false soldering on the back contact solar cell 100, and improving the performance of the back contact solar cell 100.

[0187] Specifically, as shown above, it is not difficult to understand that in the present application, the second edge bus line 110 is not used for welding. It is only used for current transmission and collection. The function of the second bus bar 32 is for collection and transmission. Figure 3 and Figure 10 It can be seen that in Figure 3 and Figure 10In the illustrated example, if the second edge bus line 110 and the second bus grid line 32 are not provided, the second grid line 30 is disconnected at the third edge series connection area 142, and the current of at least a part of the grid line segments of the second grid line 30 located between the third edge series connection area 142 and the second edge 122 cannot be collected. Therefore, by providing the second edge bus line 110 and the second bus grid line 32, the current of at least a part of the isolated grid line segments of the second grid line 30 in this edge area can be collected and transmitted to the solder strip provided in the adjacent second series connection area 14, thereby effectively avoiding efficiency loss.

[0188] Due to the continuous provision of the second bus grid line 32 in the third edge series connection area 142, in order to avoid short circuit caused by the contact between the solder strip on the third edge series connection area 142 and the second bus grid line 32, a second insulating layer 120 (such as insulating glue) needs to be provided at the position corresponding to the third edge series connection area 142 of the second bus grid line 32. However, in such a case, when the second groove 16 is not opened, the height of the second insulating layer 120 is higher than the height of the first welding section 201 of the second grid line 30, that is, in the thickness direction, the protruding height of the second insulating layer 120 is higher than the height of the first welding section 201 of the second grid line 30. In such a case, the solder strip in the third edge series connection area 142 is prone to poor soldering with the second grid line 30 during the welding process, resulting in the inability to effectively collect the current on part of the second grid line 30 (especially the second grid line 30 adjacent to the second bus grid line 32, which has the greatest possibility of poor soldering). Based on this, in this application, a second groove 16 is opened on the substrate 10, and the second insulating layer 120 is at least partially provided in the second groove 16, so that the height of the second insulating layer 120 is flush with or less than the height of the first welding section 201 or the height between the second insulating layer 120 and the first welding section 201 is less than 15um, which can reduce or even eliminate the risk of poor soldering, thereby improving the reliability of welding and ensuring the performance of the back contact solar cell 100.

[0189] Furthermore, in some embodiments, the number of the second bus grid lines 32 can be multiple, the number of the second insulating layers 120 corresponds to the number of the second bus grid lines 32, and the number of the second grooves 16 can correspond to the number of the second insulating layers 120. In this way, the risk of poor soldering brought by all the second insulating layers 120 can be reduced or even eliminated. Of course, in some possible embodiments, only part of the second bus grid lines 32 may be correspondingly provided with the second grooves 16, that is, only part of the second insulating layers 120 are provided with the second grooves 16 below, and the second grooves 16 are not opened at other positions. In such a case, it can solve the problem of poor soldering brought by part of the second insulating layers 120.

[0190] When the height of the second insulating layer 120 is greater than the height of the first welding section 201, the height difference between the two can be 1um, 2um, 3um, 4um, 5um, 9um, 7um, 8um, 9um, 10um, 11um, 12um, 13um, 14um, 15um or any value between 0 - 15um.

[0191] In some embodiments, when the height of the second insulating layer 120 is greater than the height of the first welding section 201, the height difference between the second insulating layer 120 and the first welding section 201 is preferably less than 8um, such as 0.5um, 1um, 2um, 3um, 4um, 5um, 9um, 7um, 8um. Specifically, after repeated research and verification by the inventors of the present application, it is found that by preferably setting the height difference between the two within the range of less than 8um, the risk of false soldering caused by the second insulating layer 120 can be basically completely eliminated.

[0192] In some embodiments, the recessed depth of the second groove 16 is less than half of the thickness of the substrate 10. Specifically, the "recessed depth" refers to: in the thickness direction, the distance between the bottom surface of the second groove 16 and the outermost surface of the back passivation film layer 104 facing away from the back surface 12, that is, the distance between the bottom surface of the second groove 16 and the back surface 12 of the substrate 10.

[0193] In this way, setting the depth of the second groove 16 within this reasonable range can reduce or even eliminate the risk of false soldering caused by the second insulating layer 120 while avoiding a too large recessed depth that may greatly reduce the strength of the back - contact solar cell 100.

[0194] Specifically, in such a case, the recessed depth of the second groove 16 can be, for example, one - third, one - fourth, one - fifth, etc. of the thickness of the substrate 10.

[0195] In some embodiments, the second groove 16 can penetrate through the back passivation film layer 104 and the second doping layer 103 so that the silicon substrate 101 is exposed from the second groove 16, and the part of the first bus bar 22 located in the second groove 16 is in contact with the silicon substrate 101. In this way, after the substrate 10 is fabricated, the second groove 16 can be directly formed on the substrate 10 by etching (such as laser etching, etc.), without inserting an etching and grooving process during the preparation process of the substrate 10.

[0196] Specifically, in such a case, a complete substrate 10 can be provided first, then grooving treatment is directly performed at the position on the substrate 10 where the second insulating layer 120 needs to be placed, then the first grid line 20 and the second grid line 30 are printed, and then the second insulating layer 120 is provided at the second groove 16.

[0197] Of course, in some other embodiments, a second recessed groove may also be formed in the silicon substrate 101 at a position corresponding to the first edge connection region 131 and the first bus bar line 22. The second doped layer 103 and the back passivation film layer 104 are both recessed toward the side where the front surface 11 is located at the second recessed groove, so as to form a second groove 16 on the substrate 10.

[0198] Specifically, in such a case, during the manufacturing process, before preparing the second doped layer 103, a second recessed groove may be first opened in the silicon substrate 101 at a position where the second doped layer 103 needs to be prepared and the second insulating layer 120 needs to be placed, and then the second doped layer 103 and the back passivation film layer 104 are prepared to form the substrate 10. Since the second recessed groove is opened in the silicon substrate 101, the above-mentioned second groove 16 can be correspondingly formed on the substrate 10. Then, the first grid line 20 and the second grid line 30 are printed, and then the second insulating layer 120 is provided at the second groove 16.

[0199] Please refer to Figure 3 、 Figure 10 and Figure 12 In some embodiments, the back contact solar cell 100 may further include a third auxiliary connection line. The third auxiliary connection line 130 is disposed in the third edge connection region 142. In the second direction, the third auxiliary connection line 130 is provided on at least one side of the second bus bar line 32. The third auxiliary connection line 130 connects at least two first grid lines 20 located on the same side of the second bus bar line 32. Among them, in some embodiments, it is preferred that the at least two first grid lines 20 connected to the third auxiliary connection line 130 include the first grid line 20 adjacent to the second bus bar line 32 (i.e., Figure 3 and Figure 10 the first grid line 20 closest to the second bus bar line 32 among them). That is to say, in some embodiments, the third auxiliary connection line 130 preferably connects the first grid line 20 closest to the second bus bar line 32, and the third auxiliary connection line 130 also connects at least one of the remaining first grid lines 20 located on the same side as the second grid line 30. That is, the third auxiliary connection line 130 preferably connects at least the first grid line 20 adjacent to the second bus bar line 32 and at least one of the remaining first grid lines 20 on the same side.

[0200] In this way, through the setting of the third auxiliary connection line 130, the risk of virtual soldering caused by the second insulating layer 120 can be further reduced. Even if virtual soldering occurs between the first grid line 20 near the second insulating layer 120 and the solder tape due to the setting of the second insulating layer 120, due to the existence of the third auxiliary connection line 130, the first grid line 20 with virtual soldering can also achieve current confluence output through the third auxiliary connection line 130, reducing the impact caused by virtual soldering, thereby ensuring the efficiency of the back contact solar cell 100.

[0201] Please refer to Figure 3 and Figure 10 , in some embodiments, the back-contact solar cell 100 is a main-gridless back-contact solar cell. Among several second grid lines 30, the second collecting grid line 31 is disconnected at the second series connection region 14 and continuous at the first series connection region 13. The second busbar grid line 32 is continuous at the third edge series connection region 142 and disconnected at the remaining second series connection regions 14, and is continuous at the first series connection region 13.

[0202] As Figure 3 and Figure 10 shown, in the embodiments of the present application, in order to minimize the impact of virtual soldering as much as possible, when there are first grid lines 20 on both sides of the second busbar grid line 32, it is preferred that third auxiliary connection lines 130 are provided on both sides of the second busbar grid line 32 simultaneously.

[0203] In some embodiments, in the second collecting grid line 31, the width of the second welding segment 301 (i.e., the length in the second direction) can be greater than the width of the remaining part. In this way, the contact area between the second collecting grid line 31 and the solder tape can be increased, improving the stability of soldering.

[0204] In some embodiments, the width of the second busbar grid line 32 (i.e., the length in the second direction) can be greater than the width of the part of the second collecting grid line 31 outside the first series connection region 13 (i.e., the part of the second collecting grid line 31 other than the second welding segment 301) (i.e., the length in the second direction).

[0205] In this way, since the second busbar grid line 32 needs to undertake the function of current collection and transmission, therefore, setting the width of the second busbar grid line 32 wider can reduce the transmission loss during the current collection process and improve the efficiency.

[0206] In addition, in the embodiments of the present application, in the second busbar grid line 32, it is continuous only at the third edge series connection region 142 and is disconnected at the other second series connection regions 14. At the same time, the second busbar grid line 32 is continuous at the first series connection region 13 and has a second welding segment 301 at the first series connection region 13. Only the section of the second busbar grid line 32 closest to the first edge 121 undertakes the current collection function. Therefore, in some embodiments, in order to save the paste to reduce the cost, only this part of the grid line segment can be set wider. In such a case, please refer to Figure 3 , Figure 10 and Figure 13, a plurality of first connection regions 13 may include a fourth edge connection region 132 closest to the first edge 121. The second busbar 32 may include a second busbar section 321 located between the fourth edge connection region 132 and the first edge 121, and the width of the second busbar section 321 (i.e., the length in the second direction) is greater than the width of the remaining part of the second busbar 32 outside the first connection region 13 (i.e., the part of the second busbar 32 other than the second busbar section 321 and the second welding section 301).

[0207] In this way, only by setting the width of the second busbar section 321 wider, the use of paste can be reduced while reducing the busbar transmission loss, thereby reducing costs.

[0208] Specifically, as described above, in such an embodiment, the second busbar 32 is continuous at the fourth edge connection region 132 and has a second welding section 301 at the fourth edge connection region 132. The second busbar section 321 can collect current to the solder tape provided at the fourth edge connection region 132, and only setting a part of the second busbar section 321 wider can reduce the use of paste. In such a case, the second busbar section 321 penetrates the back passivation film layer 104 and contacts the second doping layer 103.

[0209] Please refer to Figure 13 , in some other embodiments, a second busbar layer 140 may be provided on the second busbar section 321. In this way, by providing the second busbar layer 140 on the second busbar section 321, it is equivalent to increasing the cross-sectional area of the second busbar section 321, which can also reduce the transmission loss. At the same time, the second busbar layer 140 can be made of a paste with a lower cost than the second busbar section 321, which can reduce costs.

[0210] Specifically, in such an embodiment, the second busbar layer 140 may be made of a non-burn-through paste. The second busbar layer 140 does not penetrate the back passivation film layer 104 and contacts the first doping layer 102. The paste cost of the second busbar layer 140 is lower than that of the second busbar section 321. It can be understood that since the second busbar layer 140 is provided on the second busbar section 321, it is also not necessary to widen the second busbar section 321, and the purpose of reducing the transmission loss can also be achieved.

[0211] Furthermore, in such an embodiment, the width (the length in the second direction) of the second busbar layer 140 may be greater than the width (the length in the second direction) of the part of the second collecting busbar 31 outside the first connection region 13 (i.e., the part of the second collecting busbar 31 other than the second welding section 301). In this way, by increasing the width of the second busbar layer 140, the transmission capacity can be further improved and the transmission loss can be reduced.

[0212] Specifically, in such an embodiment, the width of the second bus layer 140 may be the same as the width of the second welding section 301. Herein, the width of the second welding section 301 refers to the length of the second welding section 301 in the second direction. As shown above, when the width of the second welding layer is greater than the width of the second collection layer, the width of the second welding section 301 is the width of the second welding layer (i.e., the length in the second direction). For similar descriptions hereinafter, reference may be made to this for understanding. Herein, the width of the second welding section 301 may be the same as the width of the first welding section 201.

[0213] In this way, it can be ensured that there will be no significant transmission loss during the bus bar process. At the same time, during the printing process, the second bus layer 140 and the first welding layer can be printed simultaneously. When using the same screen printing, there is no need to open screen printing slots of different sizes on the screen, saving manufacturing processes and reducing manufacturing difficulty.

[0214] Please refer to Figure 13 , in some embodiments, the width (the length in the first direction) of the second edge bus line 110 is greater than the width (the length in the second direction) of the portion of the second collection grid line 31 outside the first series connection area 13 (i.e., the portion of the second collection grid line 31 other than the second welding section 301).

[0215] In this way, since the second edge bus line 110 needs to undertake the bus bar transmission function, therefore, setting the width of the second edge bus line 110 wider can also reduce the transmission loss during the bus bar process and improve efficiency.

[0216] Specifically, in such an embodiment, the width of the second edge bus line 110 may be the same as the width of the second welding section 301. In this way, it can be ensured that there will be no significant bus bar loss during the bus bar process. At the same time, during printing, only screen printing slots of the same size need to be opened on the screen to print the three simultaneously, which can effectively save manufacturing processes and reduce manufacturing difficulty.

[0217] In addition, please continue to refer to Figure 13 , in some embodiments, the width (the length in the first direction) of the third auxiliary connection line 130 is greater than the width (the length in the second direction) of the portion of the second collection grid line 31 outside the first series connection area 13 (i.e., the portion of the second collection grid line 31 other than the second welding section 301).

[0218] In this way, since the third auxiliary connection line 130 functions to transmit and bus bar the current when virtual soldering occurs, therefore, setting the width of the third auxiliary connection line 130 wider can also reduce the transmission loss during the bus bar process and improve efficiency.

[0219] In some embodiments, the width of the third auxiliary connection line 130 may be the same as the width of the second edge bus bar 110.

[0220] Please refer to Figure 3 and Figure 10 , in some embodiments, the second edge bus bar 110 is electrically connected to all the second collection grid lines 31. In this way, the current collected by the isolated grid line segments of all the second collection grid lines 31 located between the third edge series connection area 142 and the second edge 122 can be converged, maximizing the efficiency of the back contact solar cell 100.

[0221] Of course, in some embodiments, the second edge bus bar 110 may also be electrically connected to some of the second collection grid lines 31. In such a case, the number of the second collection grid lines 31 not electrically connected to the second edge bus bar 110 is less than or equal to 4. In this way, even if some of the second collection grid lines 31 are not connected to the second edge bus bar 110, the number is small and will not cause excessive efficiency loss and product defects.

[0222] In some embodiments, the third auxiliary connection line 130 is connected to 2 - 20 first grid lines 20. By setting the number of the first grid lines 20 connected to the third auxiliary connection line 130 within this reasonable range, the influence brought by soldering voids can be reduced or even eliminated as much as possible.

[0223] In the embodiments of the present application, the number of the second bus bars 32 may be a single one. In such a case, the third auxiliary connection line 130 may be provided only on one side of the second bus bar 32, or may be provided on both sides of the second bus bar 32. Specifically, there is no limitation here. When there are first grid lines 20 on both sides of the second bus bar 32, it is preferred to provide the third auxiliary connection line 130 on both sides.

[0224] In addition, it should be noted that in the present application, when the number of the second bus bars 32 is multiple, the third auxiliary connection line 130 may also be provided only on one side or both sides of some of the second bus bars 32, while the third auxiliary connection line 130 may not be provided on both sides of the remaining second bus bars 32. In such a case, it can also solve the problem of soldering voids at some positions. In the present application, it is preferred that the third auxiliary connection line 130 is provided on both sides of each second bus bar 32.

[0225] Of course, please refer to Figure 3 and Figure 10 , in some embodiments, the number of the second bus bars 32 may also be multiple. Setting multiple second bus bars 32 can shorten the current converging path, effectively reduce the converging transmission loss, and improve the efficiency.

[0226] In such a case, a third auxiliary connection line 130 is provided between every two adjacent second busbar lines 32, and the third auxiliary connection line 130 located between two adjacent second busbar lines 32 is connected to all the first grid lines 20 located between the two adjacent second busbar lines 32.

[0227] In this way, by connecting the third auxiliary connection line 130 to all the first grid lines 20 between two adjacent second busbar lines 32, the influence brought by the virtual soldering can be basically and completely eliminated, and the efficiency of the back-contact solar cell 100 can be improved as much as possible.

[0228] Of course, in some alternative embodiments, the third auxiliary connection line 130 may also be provided only on one side of the second busbar line 32, and specific details are not limited herein.

[0229] Specifically, in such an embodiment, the number of the second busbar lines 32 in the back-contact solar cell 100 can be selected according to the actual conditions such as the size of the cell and the loss during the transmission process, and specific details are not limited herein.

[0230] Please refer to FIG. Figure 3 and Figure 10 as well as Figure 14 and Figure 15 , in some embodiments, the number of the second busbar lines 32 is multiple, and the substrate 10 has a third edge 123 and a fourth edge 124 in the second direction. Among the second grid lines 30 and the first grid lines 20, the grid line closest to the third edge 123 can be the first grid line 20, and the third auxiliary connection line 130 between the second busbar line 32 closest to the third edge 123 and the third edge 123 is connected to all the first grid lines 20 between the second busbar line 32 closest to the third edge 123 and the third edge 123.

[0231] Among the second grid lines 30 and the first grid lines 20, the grid line closest to the fourth edge 124 can also be the first grid line 20, and the third auxiliary connection line 130 between the second busbar line 32 closest to the fourth edge 124 and the fourth edge 124 is connected to all the first grid lines 20 between the second busbar line 32 closest to the fourth edge 124 and the fourth edge 124.

[0232] In this way, by making the above connection settings for the third auxiliary connection line 130 between the second busbar line 32 closest to the third edge 123 and the third edge 123, the virtual soldering influence brought by the second insulating layer 120 can also be basically and completely eliminated.

[0233] Please refer to Figure 10 , Figure 14 and Figure 15, in some embodiments, the second edge bus bar 110 may include an intermediate bus bar segment 113, a first edge bus bar segment 111, and a second edge bus bar segment 112. The intermediate bus bar segment 113, the first edge bus bar segment 111, and the second edge bus bar segment 112 all extend along the second direction. As Figure 12 shown, the three may be arranged in parallel at intervals along the first direction. The intermediate bus bar segment 113 is closer to the second edge 122 than the first edge bus bar segment 111 and the second edge bus bar segment 112.

[0234] The first edge bus bar segment 111 is disposed close to the third edge 123, and the second edge bus bar segment 112 is disposed close to the fourth edge 124. The second edge bus bar 110 further includes a first connection segment 114 and a second connection segment 115. The first connection segment 114 and the second connection segment 115 both extend along the first direction. The first connection segment 114 connects the intermediate bus bar segment 113 and the first edge bus bar segment 111, and the second connection segment 115 connects the intermediate bus bar segment 113 and the second edge bus bar segment 112;

[0235] wherein, the first edge bus bar segment 111 connects the two second gate lines 30 closest to the third edge 123. At the junction of the first edge bus bar segment 111 and the first connection segment 114, the first edge bus bar segment 111 has a third convex portion 1101 protruding toward the fourth edge 124 side, and the first connection segment 114 has a fourth convex portion 1102 protruding toward the first edge 121 side. At the junction of the intermediate bus bar segment 113 and the first connection segment 114, the intermediate bus bar segment 113 has a fifth convex portion 1103 protruding toward the third edge 123 side, and the first connection segment 114 has a sixth convex portion 1104 protruding toward the second edge 122; and / or

[0236] The second edge bus bar segment 112 connects the two second gate lines 30 closest to the fourth edge 124. At the junction of the second edge bus bar segment 112 and the second connection segment 115, the second edge bus bar segment 112 has a seventh convex portion 1105 protruding toward the third edge 123 side, and the second connection segment 115 has an eighth convex portion 1106 protruding toward the first edge 121 side. At the junction of the intermediate bus bar segment 113 and the second connection segment 115, the intermediate bus bar segment 113 has a ninth convex portion 1107 protruding toward the fourth edge 124 side, and the second connection segment 115 has a tenth convex portion 1108 protruding toward the second edge 122.

[0237] Thus, when there is a chamfer at the connection of the second edge 122 with the third edge 123 and the fourth edge 124, by setting the second-edge bus bar line 110 into a structure of 3 vertical segments + 2 horizontal straight segments, the chamfer can be avoided, reducing the printing difficulty. At the same time, by setting corresponding convex portions at the junctions of the respective bus bar segments, redundancy can be set at the corners of the second edge 122, avoiding poor contact between the respective bus bar segments caused by inaccurate printing during the printing process, resulting in incomplete filling of the paste at the corners and thus preventing the formation of a complete filling.

[0238] Of course, it can be understood that in some embodiments, when a chamfer is formed at the intersection of the second edge 122 with the third edge 123 and the fourth edge 124, the second-edge bus bar line 110 can also be set in the same manner as the first-edge bus bar line 40 (for example, having a bent portion), and specific details are not limited herein. Of course, it can be understood that in some embodiments, if there is no chamfer in the back-contact solar cell 100, only a second-edge bus bar line 110 extending vertically and continuously along the second direction needs to be set.

[0239] Please refer to Figure 14 and Figure 15 , in some embodiments, at the junction of the second grid lines 30 (including the second collecting grid lines 31 and the second bus bar grid lines 32) and the second-edge bus bar line 110, at least a part of the second grid lines 30 all have a second-grid-line convex portion 302 protruding towards the first edge 121 side compared to the second-edge bus bar line 110.

[0240] Thus, by setting the second-grid-line convex portion 302, the stability of the electrical connection between the second grid lines 30 and the second-edge bus bar line 110 can be ensured, effectively avoiding the phenomenon that due to printing accuracy reasons during the printing process, some of the second grid lines 30 cannot form a stable contact with the second-edge bus bar line 110.

[0241] Please refer to Figure 3 , Figure 10 and Figure 13 , in some embodiments, several first series connection regions 13 may further include a fourth-edge series connection region 132 closest to the second edge 122 (i.e., the first series connection region 13 adjacent to the third-edge series connection region 142). The second grid lines 30 are continuous at the fourth-edge series connection region 132, the first grid lines 20 are discontinuous at the fourth-edge series connection region 132, and the back-contact solar cell 100 may further include a fourth auxiliary connection line 160. The fourth auxiliary connection line 160 is disposed within the fourth-edge series connection region 132, and in the second direction, the fourth auxiliary connection line 160 connects the second bus bar grid line 32 and at least one second collecting grid line 31 on one side of the second bus bar grid line 32.

[0242] Thus, by providing the fourth auxiliary connection line 160 within the fourth edge connection region 132, it is possible to effectively avoid the phenomenon that the current transmitted from the second busbar line 32 cannot be collected due to poor soldering or poor contact of the solder tape within the fourth edge connection region 132 at the second busbar line 32.

[0243] Specifically, as Figure 10 and Figure 13 shown, in such an embodiment, the number of the fourth auxiliary connection lines 160 may be the same as the number of the second busbar lines 32, with one-to-one correspondence. When the second busbar line 32 is in the middle position (i.e., there are second collection grid lines 31 on both sides of the second busbar line 32), the fourth auxiliary connection line connects the second busbar line 32 and two adjacent second collection grid lines 31 (i.e., the second collection grid lines 31 on both sides of and adjacent to the second busbar line 32).

[0244] In some embodiments, the width (length in the first direction) of the fourth auxiliary connection line 160 is greater than the width (length in the second direction) of the portion of the second collection grid line 31 outside the first connection region 13 (i.e., the portion of the second collection grid line 31 other than the second soldering section 301). Thus, since the fourth auxiliary connection line 160 functions to transmit and converge current when poor soldering occurs at the second busbar line 32, setting the width of the fourth auxiliary connection line 160 wider can also reduce the transmission loss during the converging process and improve the efficiency.

[0245] In some embodiments, the distance between the third edge connection region 142 and the second edge 122 is greater than or equal to 2 mm and less than or equal to 20 mm.

[0246] Thus, it is possible to avoid the distance between the third edge connection region 142 and the second edge 122 being too small, resulting in the welding position being too close to the second edge 122 and causing the back-contact solar cell 100 to have a hidden crack, reducing the risk of hidden cracks. It is also possible to avoid the distance between the third edge connection region 142 and the second edge 122 being too large, which may cause the length of the isolated grid line segment between the third edge connection region 142 and the second edge 122 to be too long, resulting in excessive loss during the transmission path.

[0247] Specifically, in such an embodiment, the distance between the third edge connection region 142 and the second edge 122 may be, for example, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, 20 mm or any value between 2 mm and 20 mm, and is not specifically limited herein.

[0248] In the above embodiments, the polarity of the third edge connection region 142 is opposite to that of the first edge connection region 131, and the structures of the two edges of the back contact solar cell 100 in the first direction are different and asymmetric. It can be understood that in some possible embodiments, the polarity of the third edge connection region 142 may also be the same as that of the first edge connection region 131. In such a case, the structures of the two edges of the back contact solar cell 100 in the first direction are the same and symmetric. That is to say, in such a case, in the back contact solar cell 100, the two connection regions closest to the second edge 122 are symmetric with the first edge connection region 131 and the second edge connection region 141. Structures such as bus bars and auxiliary connection lines are also provided on one side of the second edge 122, which are completely symmetric with one side of the first edge 121. For the sake of brevity, the specific structures are not described herein.

[0249] Please refer to Figure 3 , in some embodiments, the substrate 10 has a third edge 123 and a fourth edge 124 in the second direction. The first connection region 13 further includes a fifth auxiliary connection line 170 and a sixth auxiliary connection line 180. The fifth auxiliary connection line 170 connects N second grid lines 30 closest to the third edge 123, and the sixth auxiliary connection line 180 connects M second grid lines 30 closest to the fourth edge 124, where N and M are both greater than or equal to 2 and less than or equal to 8.

[0250] In some embodiments, the second connection region 14 includes a seventh auxiliary connection line 190 and an eighth auxiliary connection line 1100. The seventh auxiliary connection line 190 connects P first grid lines closest to the third edge, and the eighth auxiliary connection line 1100 connects Q first grid lines closest to the fourth edge, where P and Q are both greater than or equal to 2 and less than or equal to 8.

[0251] In this way, by respectively providing the fifth auxiliary connection line 170 and the sixth auxiliary connection line 180 at positions in the first connection region 13 close to the third edge 123 and the fourth edge 124, that is, by respectively providing the fifth auxiliary connection line 170 and the sixth auxiliary connection line 180 at the head and tail ends of the solder tape in the first connection region 13, the problem that the solder tape on the first connection region 13 is soldered falsely at the starting and ending solder points, resulting in the inability to collect the current of some grid lines, can be effectively avoided. Similarly, by respectively providing the seventh auxiliary connection line 190 and the eighth auxiliary connection line 1100 at positions in the second connection region 14 close to the third edge 123 and the fourth edge 124, that is, by respectively providing the seventh auxiliary connection line 190 and the eighth auxiliary connection line 1100 at the head and tail ends of the solder tape in the second connection region 14, the problem that the solder tape on the second connection region 14 is soldered falsely at some positions of the starting and ending solder points, resulting in the inability to collect the current of some grid lines, can be effectively avoided.

[0252] Specifically, as Figure 3 shown, in some embodiments, the fifth auxiliary connection line 170 in the first edge connection area 131 can be an integrated shared structure with the first auxiliary connection line 60 closest to the third edge 123 in the first edge connection area 131, and the sixth auxiliary connection line 180 in the first edge connection area 131 can be an integrated shared structure with the first auxiliary connection line 60 closest to the fourth edge 124 in the first edge connection area 131.

[0253] The seventh auxiliary connection line 190 in the second edge connection area 141 can be an integrated shared structure with the second auxiliary connection line 90 closest to the third edge 123 in the second edge connection area 141, and the eighth auxiliary connection line 1100 in the second edge connection area 141 can be an integrated shared structure with the second auxiliary connection line 90 closest to the fourth edge 124 in the second edge connection area 141.

[0254] The seventh auxiliary connection line 190 in the third edge connection area 142 can be an integrated shared structure with the third auxiliary connection line 130 closest to the third edge 123 in the third edge connection area 142, and the eighth auxiliary connection line 1100 in the third edge connection area 142 can be an integrated shared structure with the third auxiliary connection line 130 closest to the fourth edge 124 in the third edge connection area 142.

[0255] The fifth auxiliary connection line 170 in the fourth edge connection area 132 can be an integrated shared structure with the fourth auxiliary connection line 160 closest to the third edge 123 in the fourth edge connection area 132, and the sixth auxiliary connection line 180 in the fourth edge connection area 132 can be an integrated shared structure with the fourth auxiliary connection line 160 closest to the fourth edge 124 in the fourth edge connection area 132.

[0256] As for the first connection area 13 and the second connection area 14 located between the second edge connection area 141 and the fourth edge connection area 132, only the corresponding auxiliary connection lines need to be set at the corresponding positions of the edges.

[0257] Please refer to Figure 16 , in some embodiments, in the first connection area 13, X first gate lines 20 closest to the third edge 123 are discontinuous at the first connection area 13, Y first gate lines 20 closest to the fourth edge 124 are discontinuous at the first connection area 13, the width of the discontinuous area formed by the X first gate lines 20 closest to the third edge 123 gradually increases in the direction towards the third edge 123, the width of the discontinuous area formed by the Y first gate lines 20 closest to the fourth edge 124 gradually increases in the direction towards the fourth edge 124, where X and Y are both greater than or equal to 2;

[0258] Within the second series connection region 14, W second grid lines 30 closest to the third edge 123 are discontinuous at the second series connection region 14, and Z second grid lines 30 closest to the fourth edge 124 are discontinuous at the second series connection region 14. The width of the discontinuous region formed by the W second grid lines 30 closest to the third edge 123 gradually increases in the direction towards the third edge 123, and the width of the discontinuous region formed by the Z second grid lines 30 closest to the fourth edge 124 gradually increases in the direction towards the fourth edge 124, where both W and Z are greater than or equal to 2.

[0259] In this way, by setting the discontinuous regions of the grid lines at both ends of the solder strip to gradually increase towards the edge, it is possible to effectively avoid the large offsets that are prone to occur at both ends of the solder strip during the welding process, which may cause it to come into contact with the grid lines of the opposite polarity, thus ensuring the reliability and stability of the welding.

[0260] In the description of this specification, the descriptions with reference to terms such as "some embodiments", "schematic embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiments or examples are included in at least one embodiment or example of the present application. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiments or examples. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0261] In addition, the above are only the preferred embodiments of the present application and are not used to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A back contact solar cell, characterized in that: include: A substrate, wherein the substrate has a front side and a back side opposite to each other, the back side has a first edge and a second edge opposite to each other in a first direction, the back side has a plurality of first series connection areas and a plurality of second series connection areas, in the first direction, the first series connection areas and the second series connection areas are alternately arranged, the plurality of first series connection areas include a first edge series connection area closest to the first edge, there is no second series connection area between the first edge series connection area and the first edge, and a first groove is formed on the substrate in the first edge series connection area; A plurality of first grid lines and a plurality of second grid lines arranged on the back side are alternately arranged along a second direction, the second direction intersects with the first direction, the first grid lines and all the second grid lines are arranged to intersect with the first series connection area and the second series connection area, the first grid lines include a first welding section located in the second series connection area, and the second grid lines include a second welding section located in the first series connection area; the plurality of first grid lines include a plurality of first collecting grid lines and at least one first bus grid line, the first collecting grid line is discontinuous at the first edge series connection area and continuous at the second series connection area, the first bus grid line is continuous at the first edge series connection area and the first bus grid line is partially located in the first groove, and the second grid line is continuous at the first edge series connection area; a first edge bus line, the first edge bus line being closer to the first edge than the first edge series connection region, the first edge bus line being electrically connected to at least a portion of the first collector gate line and to the first bus gate line; and A first insulating layer, the first insulating layer is at least partially arranged in the first groove and located on the first bus line, wherein, in the direction from the front side to the back side, the height of the first insulating layer is flush with the height of the second welding section, or the height of the first insulating layer is less than the height of the second welding section, or the height of the first insulating layer is greater than the height of the second welding section and the height difference between the first insulating layer and the second welding section is less than or equal to 15um.

2. The back contact solar cell according to claim 1, characterized in that: The depression depth of the first groove is less than half of the thickness of the substrate.

3. The back contact solar cell according to claim 1, characterized in that: The first insulating layer is completely located in the first groove.

4. The back contact solar cell according to claim 1, characterized in that The substrate comprises a silicon substrate, a plurality of first doped layers, a plurality of second doped layers and a back passivation film layer, the silicon substrate has a first surface and a second surface opposite to each other, the first doped layers and the second doped layers are both arranged on the second surface, the plurality of first doped layers and the plurality of second doped layers are alternately arranged along a second direction, the back passivation film layer is at least stacked on the first doped layers and the second doped layers, the first gate line is arranged corresponding to the first doped layers and at least partially penetrates the back passivation film layer and is in conductive contact with the first doped layers, and the second gate line is arranged corresponding to the second doped layers and at least partially penetrates the back passivation film layer and is in conductive contact with the second doped layers; Wherein, the first groove penetrates the back passivation film layer and the first doping layer, so that the silicon substrate is exposed from the first groove, and the portion of the first busbar line located in the first groove is in contact with the silicon substrate; or A first recessed groove is formed on the silicon substrate at a position corresponding to the first busbar line in the first edge series region, and the first doping layer and the back passivation film layer are both recessed toward the front side at the first recessed groove to form the first groove on the substrate.

5. The back contact solar cell according to claim 1, characterized in that: The first edge bus line is electrically connected to all the first collecting gate lines; or The first edge bus line is electrically connected to a portion of the first collecting gate lines, and the number of the first collecting gate lines that are not electrically connected to the first edge bus line is less than or equal to four.

6. The back contact solar cell according to claim 1, characterized in that: The number of the first busbar lines is plural, and the substrate has a third edge and a fourth edge in the second direction; Among the first gate lines and the second gate lines, the gate line closest to the third edge is the first bus gate line, and / or the gate line closest to the fourth edge is the first bus gate line.

7. The back contact solar cell according to claim 1, characterized in that The substrate has a third edge and a fourth edge in the second direction; At the junction where the first gate line closest to the third edge is connected with the first edge bus line, the first edge bus line has a first protrusion protruding toward the third edge; and / or At a junction where the first gate line closest to the fourth edge is connected to the first edge bus line, the first edge bus line has a second protrusion protruding toward the fourth edge.

8. The back contact solar cell according to claim 1, characterized in that: The width of the first bus gate line is greater than the width of a portion of the first collecting gate line located outside the second series connection region.

9. The back contact solar cell according to claim 1, characterized in that: The plurality of second series connection regions include a second edge series connection region closest to the first edge; the first busbar line includes a first bus segment located between the second edge series connection region and the first edge; Wherein, the width of the first bus segment is greater than the width of the remaining portion of the first bus grid line located outside the second series connection area; and / or A first busbar layer is provided on the first busbar segment.

10. The back contact solar cell according to claim 9, characterized in that: The width of the first bus layer is greater than the width of a portion of the first collecting gate line located outside the second series connection area.

11. The back contact solar cell according to claim 1, characterized in that: The width of the first edge bus line is greater than the width of a portion of the first collecting gate line located outside the second series connection region.

12. The back contact solar cell according to claim 1, characterized in that: A distance between the first edge series connection area and the first edge is greater than or equal to 2 mm and less than or equal to 20 mm.

13. The back contact solar cell according to claim 1, characterized in that: The plurality of second series connection areas include a third edge series connection area closest to the second edge, the third edge series connection area and the second edge have no first series connection area between them, and a second groove is formed on the substrate in the third edge series connection area; The plurality of second gate lines include a plurality of second collecting gate lines and at least one second bus gate line, the second collecting gate lines are discontinuous at the third edge series connection area and continuous at the first series connection area, the second bus gate lines are continuous at the third edge series connection area and the first series connection area and the second bus gate lines are partially located in the second groove, and the first gate lines are continuous at the third edge series connection area; The back contact solar cell further comprises: a second edge bus line, the second edge bus line being closer to the second edge than the third edge series connection region, the second edge bus line being electrically connected to at least a portion of the second collecting grid line and to the second bus grid line; and A second insulating layer, the second insulating layer is at least partially arranged in the second groove and located on the second bus bar, the number of the second insulating layers corresponds to the number of the second bus bar, wherein, in the thickness direction of the back contact solar cell, the height of the second insulating layer is flush with the height of the first welding section, or the height of the second insulating layer is less than the height of the first welding section, or the height of the second insulating layer is greater than the height of the first welding section and the height difference between the second insulating layer and the first welding section is less than or equal to 15um.

14. The back contact solar cell according to claim 13, characterized in that: The recessed depth of the second groove is less than half of the thickness of the substrate.

15. The back contact solar cell according to claim 13, characterized in that: The second insulating layer is completely located in the second groove.

16. The back contact solar cell according to claim 13, characterized in that The substrate comprises a silicon substrate, a plurality of first doped layers, a plurality of second doped layers and a back passivation film layer, the silicon substrate has a first surface and a second surface opposite to each other, the first doped layers and the second doped layers are both arranged on the second surface, the plurality of first doped layers and the plurality of second doped layers are alternately arranged along a second direction, the back passivation film layer is at least stacked on the first doped layers and the second doped layers, the first gate line is arranged corresponding to the first doped layers and at least partially penetrates the back passivation film layer and is in conductive contact with the first doped layers, and the second gate line is arranged corresponding to the second doped layers and at least partially penetrates the back passivation film layer and is in conductive contact with the second doped layers; wherein the second groove penetrates the back passivation film layer and the second doping layer, so that the silicon substrate is exposed from the second groove, and a portion of the second busbar line located in the second groove is in contact with the silicon substrate; or A second recessed groove is formed on the silicon substrate at a position corresponding to the second edge series region and the second busbar line, and the second doping layer and the back passivation film layer are both recessed toward the front side at the second recessed groove to form the second groove on the substrate.

17. The back contact solar cell according to claim 13, characterized in that: The second edge bus line is electrically connected to all the second collecting gate lines; or The second edge bus line is electrically connected to a portion of the second collecting gate lines, and the number of the second collecting gate lines that are not electrically connected to the second edge bus line is less than or equal to four.

18. The back contact solar cell according to claim 13, characterized in that: The substrate has a third edge and a fourth edge in the second direction, the second edge bus line includes a middle bus section, a first edge bus section and a second edge bus section, the middle bus section, the first edge bus section and the second edge bus section all extend along the second direction, the middle bus section is closer to the second edge than the first edge bus section and the second edge bus section, the first edge bus section is arranged close to the third edge, and the second edge bus section is arranged close to the fourth edge; The second edge bus line further includes a first connecting section and a second connecting section, the first connecting section and the second connecting section both extend along the first direction, the first connecting section connects the middle bus section and the first edge bus section, and the second connecting section connects the middle bus section and the second edge bus section; Wherein, the first edge bus section connects two of the second grid lines closest to the third edge, and at the junction of the first edge bus section and the first connecting section, the first edge bus section has a third convex portion protruding toward the fourth edge, and the first connecting section has a fourth convex portion protruding toward the first edge, and at the junction of the middle bus section and the first connecting section, the middle bus section has a fifth convex portion protruding toward the third edge, and the first connecting section has a sixth convex portion protruding toward the second edge; and / or The second edge bus section connects the two second grid lines closest to the fourth edge. At the junction of the second edge bus section and the second connecting section, the second edge bus section has a seventh protrusion protruding toward the third edge, and the second connecting section has an eighth protrusion protruding toward the first edge. At the junction of the middle bus section and the second connecting section, the middle bus section has a ninth protrusion protruding toward the fourth edge, and the second connecting section has a tenth protrusion protruding toward the second edge.

19. The back contact solar cell according to claim 13, characterized in that: The width of the second bus gate line is greater than the width of a portion of the second collecting gate line located outside the first series connection region.

20. The back contact solar cell according to claim 13, characterized in that The first series connection regions include a fourth edge series connection region closest to the second edge; the second busbar line includes a second bus segment located between the fourth edge series connection region and the second edge; The width of the second bus segment is greater than the width of the remaining portion of the second bus grid line located outside the first series connection region; and / or A second bus layer is provided on the second bus section.

21. The back contact solar cell according to claim 20, characterized in that: The width of the second bus layer is greater than the width of a portion of the second collecting gate line located outside the first series connection area.

22. The back contact solar cell according to claim 13, characterized in that: The width of the second edge bus line is greater than the width of a portion of the second collecting gate line located outside the first series connection region.

23. The back contact solar cell according to claim 13, characterized in that: A distance between the third edge series connection area and the second edge is greater than or equal to 2 mm and less than or equal to 20 mm.

24. A battery assembly, characterized in that: A back-contact solar cell comprising any one of claims 1-23.

25. A photovoltaic system, characterized in that: A battery assembly comprising the battery assembly of claim 24.

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