Gridless back-contact solar cells, tandem solar cells and photovoltaic modules

Abstract

This application provides a gridless back-contact solar cell, a solar tandem cell, and a photovoltaic module, relating to the field of photovoltaic technology. The gridless back-contact solar cell includes a first fine grid, edge solder joints, and intermediate solder joints. The edge solder joints are located at the edge of the gridless back-contact solar cell and are disposed on the first fine grid. Multiple intermediate solder joints are arranged along a first direction between adjacent edge solder joints, each intermediate solder joint being disposed on a corresponding first fine grid. Each edge solder joint along the first direction includes a first end facing the intermediate solder joint and a second end facing away from the intermediate solder joint. The first end and the intermediate solder joint adjacent to the first end are electrically connected via a first connecting line. The second end and the first fine grid adjacent to the second end are electrically connected via a second connecting line, the width of which is greater than the width of the first connecting line. This design improves the current transmission capability and current transmission efficiency of the solar cell, thereby improving the reliability and photoelectric conversion efficiency of the solar cell.

Description

Technical Field

[0001] This application relates to the field of photovoltaic technology, specifically to gridless back-contact solar cells, solar tandem cells, and photovoltaic modules. Background Technology

[0002] Solar cells are used to convert solar energy into electrical energy. Back-contact solar cells have no grid lines blocking the front side to reduce light loss caused by grid lines. Currently, back-contact solar cells have poor current collection and transmission performance, which affects their photoelectric conversion efficiency. Summary of the Invention

[0003] In view of this, this application provides gridless back-contact solar cells, solar tandem cells, and photovoltaic modules to help solve the problem of poor current collection and transmission performance of back-contact solar cells in the prior art.

[0004] In a first aspect, embodiments of this application provide a gridless back-contact solar cell, including a first fine grid, edge solder joints, and intermediate solder joints. A plurality of the first fine grids are arranged along a first direction. The edge solder joints are located at the edges of the gridless back-contact solar cell and are disposed on the first fine grids. A plurality of intermediate solder joints are arranged along the first direction between two adjacent edge solder joints, and each intermediate solder joint is disposed on a corresponding first fine grid. Each edge solder joint along the first direction includes a first end facing the intermediate solder joint and a second end facing away from the intermediate solder joint. The first end and the intermediate solder joint adjacent to the first end are electrically connected via a first connecting line. The second end and the first fine grid adjacent to the second end are electrically connected via a second connecting line, the width of the second connecting line being greater than the width of the first connecting line.

[0005] Secondly, embodiments of this application provide a solar tandem cell, including a crystalline silicon bottom cell and a perovskite top cell. The crystalline silicon bottom cell includes the aforementioned gridless back-contact solar cell, and the perovskite top cell is electrically connected to the crystalline silicon bottom cell.

[0006] Thirdly, embodiments of this application provide a photovoltaic module. The photovoltaic module includes a cover plate, an encapsulation layer, and a battery string. The battery string includes multiple grid-less back-contact solar cells as described above, or the battery string includes multiple solar tandem cells as described above.

[0007] The beneficial effects of this application are as follows: The first end of the edge solder joint is electrically connected to the adjacent intermediate solder joint via a first connecting line. When the intermediate solder joint experiences poor welding, such as a cold solder joint, the current collected at the intermediate solder joint can be transmitted to the edge solder joint via the first connecting line, and then to the solder strip via the edge solder joint, ensuring normal and stable current transmission and thus improving the reliability of current collection and transmission in the edge region of the gridless back contact solar cell. The second end of the edge solder joint is connected to the adjacent first fine grid via a second connecting line, allowing the current on the first fine grid to be transmitted to the edge solder joint for output via the second connecting line. The second connecting line is directly electrically connected to the first fine grid, eliminating the need for additional solder joints on the first fine grid, thereby reducing current transmission loss and improving the current collection efficiency in the edge region of the gridless back contact solar cell, thus improving the photoelectric conversion efficiency of the gridless back contact solar cell. The second connecting line has a larger width to reduce current transmission loss, improve current collection efficiency, and enhance the mechanical properties of the second connecting line, thereby improving the reliability of the gridless back contact solar cell.

[0008] It should be understood that the above general description and the following detailed description are merely exemplary and do not limit this application. Attached Figure Description

[0009] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0010] Figure 1 A schematic diagram of the appearance of a gridless back-contact solar cell provided in an embodiment of this application;

[0011] Figure 2 A partial structural schematic diagram of a gridless back-contact solar cell provided in an embodiment of this application;

[0012] Figure 3 for Figure 2 A magnified view of a portion of the image;

[0013] Figure 4 A partial structural schematic diagram of a gridless back-contact solar cell provided in another embodiment of this application;

[0014] Figure 5 A partial structural schematic diagram of a gridless back-contact solar cell provided in another embodiment of this application;

[0015] Figure 6 A schematic diagram of a solar tandem cell provided in an embodiment of this application;

[0016] Figure 7 This is a schematic diagram of the structure of a photovoltaic module provided in an embodiment of this application.

[0017] Figure label:

[0018] 1000 - Photovoltaic module; 100 - Cell string; 10 - Gridless back-contact solar cell; 10a - First side; 10b - Second side; 10c - Third side; 10d - Fourth side; 10e - First corner; 10f - Second corner; 10g - Third corner; 10h - Fourth corner; 11 - First grid; 111 - First sub-connector segment; 112 - Second sub-connector segment; 113 - Third sub-connector segment; 114 - Third isolation space; 115 - Fourth isolation space; 12 - Second grid; 121 - First isolation space; 122 - Second isolation space; 123 - First part; 124 - Second part; 125 - Third part; 126 - Fourth part; 13 - Edge solder joint; 131 - First end; 132 - Second end; 133 - Third end; 134 - Fourth end; 135 - First extension; 136 - Second extension; 14 - Middle solder joint; 15 - First connecting line; 16 - Second connecting line; 17 - Third connecting line; 200 - First cover plate; 300 - Second cover plate; 400 - First encapsulation layer; 500 - Second encapsulation layer; 20 - Solar tandem cell; 21 - Crystalline silicon bottom cell; 22 - Perovskite top cell. Detailed Implementation

[0019] To better understand the technical solution of this application, the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0020] It should be understood that the described embodiments are merely some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0021] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0022] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0023] Back-contact solar cells are used to convert solar energy into electrical energy, and their front side is unobstructed by grid lines to reduce light loss caused by grid lines. Currently, the current collection and transmission performance of back-contact solar cells is relatively poor, which affects the photoelectric conversion efficiency of back-contact solar cells and thus their reliability.

[0024] like Figure 1 As shown, this application embodiment provides a gridless back-contact solar cell 10. The gridless back-contact solar cell 10 is approximately rectangular in shape, having a first side 10a and a second side 10b along a first direction X, and a third side 10c and a fourth side 10d along a second direction Y. The connection between the first side 10a and the third side 10c has a first corner 10e, the connection between the second side 10b and the third side 10c has a second corner 10f, the connection between the first side 10a and the fourth side 10d has a third corner 10g, and the connection between the second side 10b and the fourth side 10d has a fourth corner 10h. The first direction X intersects with the second direction Y. The first direction X can be the width direction of the gridless back-contact solar cell 10, and the second direction Y can be the length direction of the gridless back-contact solar cell 10. Both the first direction X and the second direction Y are perpendicular to a third direction Z, which can be the thickness direction of the gridless back-contact solar cell 10.

[0025] The aforementioned gridless back-contact solar cell can be obtained by cutting a whole cell into two, three, four, or eight slices; that is, the cell can be a sliced ​​cell. Alternatively, the aforementioned gridless back-contact solar cell can also be a whole cell.

[0026] like Figure 2 As shown, the gridless back-contact solar cell 10 includes a first fine grid 11, a second fine grid 12, an edge solder joint 13, and a center solder joint 14. Multiple first fine grids 11 and multiple second fine grids 12 are arranged alternately along a first direction X. The first fine grids 11 and second fine grids 12 are the metal electrodes of the gridless back-contact solar cell 10. The first fine grid 11 can be the positive electrode of the gridless back-contact solar cell 10, or it can also be the negative electrode. The second fine grid 12 has the opposite electrode polarity to the first fine grid 11. Both the first fine grids 11 and the second fine grid 12 can be electrically connected to a solder strip (not shown in the figure) so that the solder strip outputs the electrical energy generated by the gridless back-contact solar cell 10.

[0027] Please also refer to Figure 1Edge solder joints 13 are located at the edge of the gridless back-contact solar cell 10 and are disposed on the first fine grid 11. Edge solder joints 13 are electrically connected to the corresponding first fine grid 11 and are used to connect with solder strips (not shown in the figure). Edge solder joints 13 can be understood as solder joints closest to the side of the gridless back-contact solar cell 10. In some embodiments, edge solder joints 13 may be disposed at the first corner 10e, the second corner 10f, the third corner 10g, and the fourth corner 10h, respectively.

[0028] Multiple intermediate solder points 14 are arranged along the first direction X between two adjacent edge solder points 13. The multiple intermediate solder points 14 are respectively disposed on the corresponding first fine grid 11. Each intermediate solder point 14 is electrically connected to its corresponding first fine grid 11. The intermediate solder points 14 are also used to connect with the solder strip. That is to say, the edge solder points 13 and intermediate solder points 14 arranged along the first direction X can be connected to the same solder strip.

[0029] like Figure 3 As shown, the edge solder joint 13 includes a first end 131 facing the intermediate solder joint 14 and a second end 132 away from the intermediate solder joint 14 along the first direction X. The first end 131 and the intermediate solder joint 14 adjacent to the first end 131 are electrically connected by a first connecting line 15. The first connecting line 15 is arranged along the first direction X. The intermediate solder joint 14 adjacent to the edge solder joint 13 is the intermediate solder joint 14 closest to the first end 131 of the edge solder joint 13 among a plurality of intermediate solder joints 14. That is, the edge solder joint 13 is electrically connected to an adjacent intermediate solder joint 14 through the first connecting line 15, so that current can be transmitted between two adjacent first grids 11 through the first connecting line 15.

[0030] The second end 132 and the first fine gate 11 adjacent to the second end 132 are electrically connected by a second connecting line 16, which is arranged along the first direction X. The first fine gate 11 adjacent to the edge solder joint 13 is the first fine gate 11 of the plurality of first fine gates 11 closest to the edge solder joint 13 at the second end 132. That is, the edge solder joint 13 is electrically connected to one of the adjacent first fine gates 11 through the second connecting line 16. There is no solder joint on the first fine gate 11 adjacent to the second end 132, so the second connecting line 16 is directly electrically connected to the first fine gate 11, thereby allowing current to be transmitted between two adjacent first fine gates 11.

[0031] The second fine gate 12 is broken to form a first isolation space 121 and a second isolation space 122, which are arranged along a first direction X. The second fine gate 12 includes a first portion 123, a second portion 124, a third portion 125, and a fourth portion 126. The first portion 123 and the second portion 124 are arranged at intervals along a second direction Y, and the first isolation space 121 is located between the first portion 123 and the second portion 124. The third portion 125 and the fourth portion 126 are arranged at intervals along the second direction Y, and the second isolation space 122 is located between the third portion 125 and the fourth portion 126.

[0032] A first connecting line 15 passes through a first isolation space 121 along a first direction X to electrically connect the edge solder joint 13 to its adjacent intermediate solder joint 14. A portion of the first connecting line 15 is located within the first isolation space 121 and is spaced apart from the first portion 123 and the second portion 124 of the second fine grid 12. A second connecting line 16 passes through a second isolation space 122 to electrically connect the edge solder joint 13 to its adjacent first fine grid 11. A portion of the second connecting line 16 is located within the second isolation space 122 and is spaced apart from the third portion 125 and the fourth portion 126 of the second fine grid 12. The first isolation space 121 isolates the first connecting line 15 from the second fine grid 12, and the second isolation space 122 isolates the second connecting line 16 from the second fine grid 12, thereby reducing the possibility of a short circuit in the gridless back-contact solar cell 10 caused by contact between the first connecting line 15 and the second connecting line 16 and the second fine grid 12.

[0033] The first connecting line 15 and the second connecting line 16 mentioned above can both be formed by printing metal paste and then drying and sintering. The width of the second connecting line 16 (i.e. the size of the second connecting line 16 in the second direction Y) is greater than the width of the first connecting line 15 (i.e. the size of the first connecting line 15 in the second direction Y).

[0034] The gridless back-contact solar cell 10 in this embodiment employs gridless (OBB) technology, allowing the solder ribbon to be directly connected to the fine grid. Since no grid is required, the consumption of metal paste is reduced, thereby lowering the production cost of the gridless back-contact solar cell 10. Simultaneously, the shading area of ​​the grid lines is reduced, improving the photoelectric conversion efficiency of the gridless back-contact solar cell 10.

[0035] The first end 131 of the edge solder joint 13 is electrically connected to the adjacent intermediate solder joint 14 via the first connecting line 15. When the intermediate solder joint 14 experiences poor welding, such as a cold solder joint, the current collected at the intermediate solder joint 14 can be transmitted to the edge solder joint 13 via the first connecting line 15, and then to the solder strip via the edge solder joint 13, ensuring normal and stable current transmission. This improves the reliability of current collection and transmission in the edge region of the gridless back contact solar cell 10, thereby improving the electrical performance of the gridless back contact solar cell 10. The second end 132 of the edge solder joint 13 is connected to the adjacent first fine grid 11 via the second connecting line 16, allowing the current on the first fine grid 11 to be transmitted to the edge solder joint 13 via the second connecting line 16 for output. The second connecting line 16 is directly electrically connected to the first fine grid 11, eliminating the need for additional solder joints on the first fine grid 11, thus reducing current transmission loss and improving the current collection efficiency in the edge region of the gridless back contact solar cell 10, thereby improving the photoelectric conversion efficiency of the gridless back contact solar cell 10. Meanwhile, the second connecting line 16 is wider than the first connecting line 15 to reduce current transmission loss and improve current collection efficiency. It also improves the mechanical properties of the second connecting line 16, reduces the possibility of breakage of the second connecting line 16 during the production and operation of the gridless back contact solar cell 10, and provides a stable and reliable transmission channel for current, thereby improving the reliability of the gridless back contact solar cell 10.

[0036] In summary, the gridless back-contact solar cell 10 provided in this application improves the current transmission capability and current transmission efficiency of the gridless back-contact solar cell 10 by setting a first connecting line 15 and a second connecting line 16 electrically connected to the edge solder joint 13, thereby improving the electrical performance of the gridless back-contact solar cell 10, and further improving the reliability and photoelectric conversion efficiency of the gridless back-contact solar cell 10, so as to realize the normal and stable operation of the gridless back-contact solar cell 10.

[0037] In some embodiments, the second connecting wire can be directly connected to the solder ribbon, i.e., the second connecting wire and the solder ribbon are alloyed, so that the current on the second connecting wire can be directly transmitted to the solder ribbon, thereby shortening the current transmission path, improving the current transmission efficiency, and thus improving the photoelectric conversion efficiency of the gridless back-contact solar cell. At the same time, it increases the contact area between the solder ribbon and the gridless back-contact solar cell, thereby improving the stability and reliability of the connection between the solder ribbon and the gridless back-contact solar cell.

[0038] like Figure 3As shown, in one possible implementation, the width W1 of the first connecting line 15 satisfies: 5μm≤W1≤20μm, and the width W2 of the second connecting line 16 satisfies: 100μm≤W1≤300μm.

[0039] The width W1 of the first connecting line 15 can be 5μm, 6μm, 8μm, 10μm, 12μm, 14μm, 16μm, 18μm, or 20μm, or other values ​​within the above range. If the width of the first connecting line 15 is too small, its resistance increases, affecting the current transmission efficiency between the edge solder joint 13 and the middle solder joint 14. It also reduces the mechanical properties of the first connecting line 15, lowering its strength and making it prone to breakage during welding, encapsulation, and other processes. This disrupts the current transmission path and affects the reliability of the gridless back-contact solar cell 10. If the width of the first connecting line 15 is too large, it increases the amount of metal paste required to prepare the first connecting line 15, increasing the manufacturing cost of the gridless back-contact solar cell 10. It also increases the light-shielding area of ​​the first connecting line 15, thereby increasing the light-shielding loss and affecting the photoelectric conversion efficiency of the gridless back-contact solar cell 10. Therefore, by limiting the width of the first connecting line 15 to 5μm to 20μm, the manufacturing cost of the gridless back contact solar cell 10 is reduced, the photoelectric conversion efficiency of the gridless back contact solar cell 10 is guaranteed, and the mechanical and electrical properties of the first connecting line 15 are improved, so as to achieve stable and reliable current transmission and thus improve the reliability of the gridless back contact solar cell 10.

[0040] The width W2 of the second connecting line 16 can be 100μm, 120μm, 140μm, 160μm, 180μm, 200μm, 220μm, 240μm, 260μm, 280μm, or 300μm, or other values ​​within the above range. The width of the second connecting line 16 is much larger than the width of the first connecting line 15. By limiting the width of the second connecting line 16 to 100μm to 300μm, the resistance of the second connecting line 16 is effectively reduced, thereby achieving efficient current transmission. This improves the current collection effect in the edge region of the gridless back contact solar cell 10, reduces current loss in the edge region of the gridless back contact solar cell 10, and allows the current to be distributed more evenly. This reduces the risk of hot spots and suppresses the risk of potential-induced decay in the gridless back contact solar cell 10, thereby improving the photoelectric conversion efficiency of the gridless back contact solar cell 10. At the same time, the mechanical properties of the second connecting line 16 are improved due to its larger width, which reduces the possibility of breakage under stress such as welding pressure, thereby improving the reliability of the gridless back contact solar cell 10.

[0041] In summary, by limiting the width of the first connecting line 15 and the second connecting line 16, the electrical performance of the gridless back contact solar cell 10 can be improved while saving the amount of metal paste and reducing the production cost of the gridless back contact solar cell 10.

[0042] In other embodiments, the width W1 of the first connecting line 15 satisfies: 5μm≤W1≤20μm, or the width W2 of the second connecting line 16 satisfies: 100μm≤W2≤300μm.

[0043] like Figure 4 As shown, Figure 4 The edge of the gridless back-contact solar cell 10 is illustrated using the third side 10c as an example. In one possible implementation, the first fine grid 11 connected to the edge solder joint 13 includes a first sub-connection segment 111 and a second sub-connection segment 112. The edge solder joint 13 includes a third end 133 facing the edge of the gridless back-contact solar cell 10 and a fourth end 134 away from the edge of the gridless back-contact solar cell 10 along the second direction Y. The first sub-connection segment 111 is located on one side of the third end 133 and extends along the second direction Y to the edge of the gridless back-contact solar cell 10. The second sub-connection segment 112 is located on one side of the fourth end 134 and extends along the second direction Y away from the first sub-connection segment 111. The width of the first sub-connection segment 111 (i.e., the dimension of the first sub-connection segment 111 in the first direction X) is greater than the width of the second sub-connection segment 112 (i.e., the dimension of the second sub-connection segment 112 in the first direction X).

[0044] The first sub-connection segment 111 is used to collect the current in the edge region of the gridless back-contact solar cell 10. The first sub-connection segment 111 is electrically connected to the edge solder joint 13 to transmit the collected current to the edge solder joint 13. The second sub-connection segment 112 is used to collect the current on the side of the edge solder joint 13 away from the first sub-connection segment 111. The second sub-connection segment 112 is electrically connected to the edge solder joint 13 to transmit the collected current to the edge solder joint 13. The width of the first sub-connection segment 111 is greater than the width of the second sub-connection segment 112. By increasing the width of the first sub-connection segment 111, the current transmission and collection capabilities of the first sub-connection segment 111 are improved, enabling the current in the edge region of the gridless back-contact solar cell 10 to be effectively collected. This reduces current loss in the edge region of the gridless back-contact solar cell 10, allowing for a more uniform current distribution, reducing the risk of hot spots and suppressing potential-induced degradation, and improving the photoelectric conversion efficiency of the gridless back-contact solar cell 10.

[0045] Continue as Figure 4As shown, in one possible implementation, the width W3 of the first sub-connection segment 111 satisfies: 100μm≤W3≤350μm, and the width W4 of the second sub-connection segment 112 satisfies: 5μm≤W4≤20μm.

[0046] The width W3 of the first sub-connection segment 111 can be 100μm, 120μm, 140μm, 160μm, 180μm, 200μm, 220μm, 240μm, 260μm, 280μm, 300μm, 320μm, 340μm, or 350μm, or other values ​​within the above range. If the width of the first sub-connection segment 111 is too small, it will be difficult for the first sub-connection segment 111 to effectively collect and transmit the current in the edge region of the gridless back contact solar cell 10, resulting in current loss in the edge region of the gridless back contact solar cell 10, affecting the photoelectric conversion efficiency and reliability of the gridless back contact solar cell 10. If the width of the first sub-connector segment 111 is too large, it increases the amount of metal paste required to prepare the first fine grid 11, leading to an increase in the manufacturing cost of the gridless back-contact solar cell 10. It also increases the light-shielding area of ​​the first fine grid 11, thereby increasing the light-shielding loss caused by the first connecting line 15 and affecting the photoelectric conversion efficiency of the gridless back-contact solar cell 10. Therefore, by designing the width of the first sub-connector segment 111 to be between 100 μm and 350 μm, the current collection and transmission capabilities of the first sub-connector segment 111 are improved while the light-shielding area of ​​the first sub-connector segment 111 is reduced, thereby improving the photoelectric conversion efficiency of the gridless back-contact solar cell 10 and reducing its production cost.

[0047] The width W4 of the second sub-connection segment 112 can be 5μm, 6μm, 8μm, 10μm, 12μm, 14μm, 16μm, 18μm, or 20μm, or other values ​​within the above range. By limiting the width of the second sub-connection segment 112, stable current transmission through the second sub-connection segment 112 is ensured, while reducing the shading loss of the second sub-connection segment 112, thereby improving the photoelectric conversion efficiency of the gridless back-contact solar cell 10.

[0048] In other embodiments, the width W3 of the first sub-connection segment 111 satisfies: 100μm≤W1≤350μm, or the width W4 of the second sub-connection segment 112 satisfies: 5μm≤W1≤20μm.

[0049] Continue as Figure 4As shown, in one possible implementation, the length L1 of the first sub-connection segment 111 (i.e., the dimension of the first sub-connection segment 111 in the second direction Y) satisfies: 4mm ≤ L1 ≤ 6mm. For example, L1 can be 4mm, 4.2mm, 4.4mm, 4.6mm, 4.8mm, 5mm, 5.2mm, 5.4mm, 5.6mm, 5.8mm, or 6mm, or other values ​​within the above range. When the length of the first sub-connection segment 111 is too small, the first sub-connection segment 111 is prone to stress concentration and breakage, affecting the current collection and transmission capability of the first sub-connection segment 111. If the length of the first sub-connection segment 111 is too large, the current transmission path becomes larger, increasing resistance loss and affecting the electrical performance of the gridless back contact solar cell 10. Therefore, the length of the first sub-connection segment 111 is designed to be between 4mm and 6mm, so as to shorten the current transmission path and reduce resistance loss while ensuring the mechanical performance of the first sub-connection segment 111, thereby improving the efficiency and stability of current transmission in the first sub-connection segment 111.

[0050] like Figure 5 As shown, in one possible implementation, the first fine gate 11 connected to the edge solder joint 13 includes a third sub-connecting segment 113. Along the second direction Y, the third sub-connecting segment 113 is connected between the first sub-connecting segment 111 and the second sub-connecting segment 112. The third sub-connecting segment 113 is connected to the edge solder joint 13, and the projection of the third sub-connecting segment 113 along the third direction Z is located within the edge solder joint 13. The width of the third sub-connecting segment 113 is the same as the width of the first sub-connecting segment 111, or the width of the third sub-connecting segment 113 is the same as the width of the second sub-connecting segment 112.

[0051] Edge solder joint 13 can cover the third sub-connection segment 113, meaning that edge solder joint 13 can be formed above the third sub-connection segment 113. Edge solder joint 13 is electrically connected to the third sub-connection segment 113, thereby achieving electrical connection between edge solder joint 13 and the first sub-connection segment 111 and the second sub-connection segment 112. In some embodiments, the width of the third sub-connection segment 113 is the same as the width of the second sub-connection segment 112, i.e., the width of the third sub-connection segment 113 is smaller than the width of the first sub-connection segment 111, thereby saving the amount of metal paste used and reducing the production cost of the gridless back contact solar cell 10.

[0052] In other embodiments, the width of the third sub-connection segment 113 is the same as the width of the first sub-connection segment 111, that is, the width of the third sub-connection segment 113 is greater than the width of the second sub-connection segment 112, so as to increase the contact area between the edge solder joint 13 and the first fine grid 11, thereby improving the welding strength of the solder joint, reducing the risk of electrical connection failure of the gridless back contact solar cell 10, and thus improving the reliability of the gridless back contact solar cell 10.

[0053] like Figure 5 As shown, in one possible implementation, the area of ​​the edge solder joint 13 is larger than the area of ​​the middle solder joint 14.

[0054] Please also refer to Figure 1 During the production and operation of the gridless back-contact solar cell 10, the edge areas of the gridless back-contact solar cell 10, especially the aforementioned corners, need to bear greater stress. Therefore, the corners of the gridless back-contact solar cell 10 are prone to warping and deformation, which affects the stability of the edge solder joints 13. By increasing the area of ​​the edge solder joints 13, stress can be effectively dispersed and its fatigue resistance can be improved, thereby reducing the risk of cracking of the edge solder joints 13. This provides a reliable welding point for the solder ribbon, improves the welding strength, and thus improves the stability and reliability of the connection between the solder ribbon and the gridless back-contact solar cell 10. At the same time, increasing the area of ​​the edge solder joints 13 also improves its current transmission capability, allowing the current to be transmitted to the solder ribbon more efficiently and stably through the edge solder joints 13, thereby improving the electrical performance of the gridless back-contact solar cell 10.

[0055] Optionally, the area S1 of the edge solder joint 13 satisfies: 0.25 mm. 2 ≤S1≤4mm 2 For example, S1 can be 0.25mm. 2 0.05mm 2 0.1mm 2 0.5mm 2 1mm 2 2mm 2 3mm 2 3.5mm 2 Or 4mm 2 Of course, it can also be other values ​​within the above range. By limiting the area of ​​the edge solder joint 13, the reliability of the edge solder joint 13 is improved, the risk of cracking is reduced, and its current transmission capability is increased, thereby improving the reliability of the gridless back contact solar cell 10.

[0056] Optionally, the area S2 of the intermediate solder joint 14 satisfies: 0.1 mm. 2 ≤S2≤0.7mm 2For example, S2 can be 0.1mm. 2 0.2mm 2 0.3mm 2 0.4mm 2 0.5mm 2 0.6mm 2 or 0.7mm 2 Of course, it can also be other values ​​within the above range. By limiting the area of ​​the intermediate solder point 14, its light-blocking area is reduced, while ensuring the stability and reliability of the connection between the intermediate solder point 14 and the solder strip, so as to ensure the normal and stable transmission of current.

[0057] like Figure 5 As shown, in one possible implementation, along the first direction X, the size of the edge solder joint 13 is larger than the size of the middle solder joint 14, and along the second direction Y, the size of the edge solder joint 13 is the same as the size of the middle solder joint 14.

[0058] The edge solder joint 13 increases its size along the first direction X, thereby making its area larger than that of the middle solder joint 14. This allows the shape of the edge solder joint 13 to better match the shape of the solder strip (not shown in the figure), thereby increasing the contact area between the edge solder joint 13 and the solder strip, and thus improving the stability and reliability of the connection between the edge solder joint 13 and the solder strip.

[0059] Optionally, along the first direction X, the ratio of the dimension D1 of the edge solder joint 13 to the dimension D2 of the intermediate solder joint 14 satisfies: 2≤D1 / D2≤15. For example, the ratio of D1 to D2 can be 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15. By limiting the proportional relationship between the dimensions of the edge solder joint 13 and the intermediate solder joint 14 in the first direction X, the area ratio of the edge solder joint 13 and the intermediate solder joint 14 is kept within a reasonable range, so that the solder strip can be stably and reliably connected to the edge solder joint 13 and the intermediate solder joint 14, thereby realizing the normal and stable transmission of current.

[0060] As mentioned above, a gridless back-contact solar cell includes a first fine grid and a second fine grid, with the second fine grid and the first fine grid arranged alternately along a first direction, and the first fine grid and the second fine grid having opposite polarities. Figure 5 As shown, Figure 5The edge of the gridless back-contact solar cell 10 is illustrated using the third side 10c as an example. In one possible embodiment, the edge solder joint 13 includes a first extension 135 and a second extension 136 along the first direction X. The first extension 135 is located within a first isolation space 121 formed by the break of the second fine grid 12, and the second extension 136 is located within a second isolation space 122 formed by the break of the second fine grid 12. The second fine grid 12 located in the first isolation space 121 near the edge of the gridless back-contact solar cell 10 is electrically connected to the adjacent second fine grid 12 via a third connecting line 17. The second fine grid 12 located in the second isolation space 122 near the edge of the gridless back-contact solar cell 10 is electrically connected to the adjacent second fine grid 12 via a third connecting line 17.

[0061] The first extension 135 is connected to the first connecting line 15, and the second extension 136 is connected to the second connecting line 16. The second fine grid 12 includes a first portion 123, a second portion 124, a third portion 125, and a fourth portion 126. The first portion 123 and the second portion 124 are arranged along the second direction Y. A first isolation space 121 is located between the first portion 123 and the second portion 124. At least a portion of the structure of the first extension 135 is located within the first isolation space 121 and is spaced apart from the first portion 123 and the second portion 124 of the second fine grid 12. The first portion 123 is located on the side of the first isolation space 121 facing closer to the edge of the gridless back contact solar cell 10. The first portion 123 is electrically connected to another adjacent second fine grid 12 via a third connecting line 17. That is, the third connecting line 17 electrically connects two adjacent second fine grids 12.

[0062] The third portion 125 and the fourth portion 126 are arranged along the second direction Y. The second isolation space 122 is located between the third portion 125 and the fourth portion 126. Part of the structure of the second extension 136 is located within the second isolation space 122 and is spaced apart from the third portion 125 and the fourth portion 126 of the second grid 12. The third portion 125 is located on the side of the second isolation space 122 facing closer to the edge of the gridless back contact solar cell 10. The third portion 125 is electrically connected to another second grid 12 adjacent to it via a third connecting line 17.

[0063] The aforementioned third connecting line 17 can be formed by printing with metal paste and then drying and sintering.

[0064] As mentioned above, the edge solder joint 13 can increase its area by increasing its dimension along the first direction X. Therefore, the first extension 135 and the second extension 136 of the edge solder joint 13 can extend outward along the first direction X, that is, the first extension 135 and the second extension 136 extend towards the first isolation space 121 and the second isolation space 122, respectively. The first isolation space 121 and the second isolation space 122 can be formed by disconnecting the corresponding second grid 12. The first isolation space 121 and the second isolation space 122 serve to avoid the edge solder joint 13, providing sufficient space for the edge solder joint 13. At the same time, since the edge solder joint 13 is electrically connected to the first grid 11, the first isolation space 121 and the second isolation space 122 also serve to isolate the edge solder joint 13, reducing the risk of short circuit caused by the edge solder joint 13 contacting the second grid 12, thus ensuring the normal and stable function of the gridless back contact solar cell 10. The third connecting line 17 realizes the electrical connection between two adjacent second grids 12, reducing the possibility that the current on the second grid 12 cannot be transmitted due to the setting of the first isolation space 121 and the second isolation space 122, thereby reducing the possibility of local current loss in the gridless back contact solar cell 10, and thus improving the reliability of the low gridless back contact solar cell.

[0065] A third isolation space 114 and a fourth isolation space 115 are formed at the break of the first fine grid 11. Two third connecting lines 17 pass through the corresponding isolation spaces to realize the electrical connection between adjacent second fine grids 12. The third isolation space 114 and the fourth isolation space 115 isolate the third connecting lines 17, reducing the possibility of short circuit of the gridless back contact solar cell 10 caused by the contact between the third connecting lines 17 and the first fine grid 11.

[0066] like Figure 6 As shown, this application provides a solar tandem cell 20, including a crystalline silicon bottom cell 21 and a perovskite top cell 22. The crystalline silicon bottom cell 21 includes the above-mentioned gridless back contact solar cell, and the perovskite top cell 22 is electrically connected to the crystalline silicon bottom cell 21.

[0067] The perovskite top solar cell 22 may include a substrate, a conductive thin film, an electron transport layer (e.g., titanium dioxide), a perovskite absorber layer, a hole transport layer, and a metal electrode (not shown in the figure). Perovskite materials have a high light absorption coefficient and a long carrier diffusion distance. After the photons absorbed by the perovskite material are converted into electrons, they are easily collected by the electrodes with minimal loss, thus generating high photogenerated voltage and current, resulting in high photoelectric conversion efficiency for the perovskite top solar cell 22.

[0068] By combining the aforementioned gridless back-contact solar cell and perovskite cell into a tandem cell, a wider range of solar spectrum absorption can be achieved, thereby improving the photoelectric conversion efficiency of the tandem cell. Since the gridless back-contact solar cell has the aforementioned technical effects, the tandem module with this gridless back-contact solar cell also possesses the aforementioned technical effects, which will not be elaborated further here.

[0069] like Figure 7 As shown, this application embodiment provides a photovoltaic module 1000, which includes a cover plate, an encapsulation layer, and a cell string 100. The cell string 100 includes a plurality of the above-mentioned gridless back-contact solar cells, or the cell string 100 includes a plurality of the above-mentioned solar tandem cells 20.

[0070] The photovoltaic module 1000 is equipped with a first cover plate 200 located at the top, a second cover plate 300 located at the bottom, a first encapsulation layer 400 located between the first cover plate 200 and the battery string 100, and a second encapsulation layer 500 located between the second cover plate 300 and the battery string 100. The first cover plate 200, second cover plate 300, first encapsulation layer 400, second encapsulation layer 500, and battery string 100 are all present. These components can be arranged along the thickness direction Z of the photovoltaic module 1000 and laminated together. The first cover plate 200 can be a glass cover plate with high light transmittance. The first encapsulation layer 400 bonds the first cover plate 200 to the battery string 100, thus providing encapsulation and protection for the battery string 100. The material of the first encapsulation layer 400 can be one or more of ethylene-vinyl acetate copolymer (EVA), polyolefin elastomer (POE), and polyvinyl butyral (PVB). The second encapsulation layer 500 connects the battery layer to the second cover plate 300, also providing encapsulation and protection for the battery string 100. The material of the second encapsulation layer 500 can be one or more of EVA, POE, and PVB. The material of the second cover plate 300 can be glass, or it can be composed of multiple polymer film layers.

[0071] The above are merely optional embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A gridless back-contact solar cell, characterized in that, include: A first fine grid, wherein a plurality of the first fine grids are arranged along a first direction; Edge solder joints are located at the edge of the gridless back contact solar cell and are disposed on the first fine grid. The intermediate solder joints are arranged along the first direction between two adjacent edge solder joints, and the intermediate solder joints are respectively disposed on the corresponding first fine grid. Wherein, the edge solder joint includes a first end facing the middle solder joint and a second end away from the middle solder joint along the first direction, the first end and an intermediate solder joint adjacent to the first end are electrically connected by a first connecting line, the second end and a first fine grid adjacent to the second end are electrically connected by a second connecting line, and the width of the second connecting line is greater than the width of the first connecting line.

2. The gridless back-contact solar cell according to claim 1, characterized in that, The width W1 of the first connecting line satisfies: 5μm≤W1≤20μm, and / or; The width W2 of the second connecting line satisfies: 100μm≤W2≤300μm.

3. The gridless back-contact solar cell according to claim 1, characterized in that, The first fine grid connected to the edge solder joint includes a first sub-connection segment and a second sub-connection segment; The edge solder joint includes a third end facing the edge of the gridless back contact solar cell and a fourth end away from the edge of the gridless back contact solar cell along the second direction. The first sub-connection segment is located on one side of the third end and extends along the second direction to the edge of the gridless back contact solar cell. The second sub-connection segment is located on one side of the fourth end and extends along the second direction away from the first sub-connection segment. The width of the first sub-connection segment is greater than the width of the second sub-connection segment.

4. The gridless back-contact solar cell according to claim 3, characterized in that, The width W3 of the first sub-connection segment satisfies: 100μm≤W3≤350μm, and / or; The width W4 of the second sub-connection segment satisfies: 5μm≤W4≤20μm.

5. The gridless back-contact solar cell according to claim 3, characterized in that, The length L1 of the first sub-connection segment satisfies: 4mm≤L1≤6mm.

6. The gridless back-contact solar cell according to claim 3, characterized in that, The first fine grid connected to the edge solder joint includes a third sub-connecting segment, which connects the first sub-connecting segment and the second sub-connecting segment along the second direction; The third sub-connecting segment is connected to the edge solder joint, and the projection of the third sub-connecting segment along the third direction is located within the edge solder joint; The width of the third sub-connection segment is the same as the width of the first sub-connection segment, or the width of the third sub-connection segment is the same as the width of the second sub-connection segment.

7. The gridless back-contact solar cell according to any one of claims 1 to 6, characterized in that, The area of ​​the edge solder joint is larger than the area of ​​the middle solder joint.

8. The gridless back-contact solar cell according to claim 7, characterized in that, Along the first direction, the size of the edge solder joint is larger than the size of the middle solder joint; Along the second direction, the dimensions of the edge solder joints are the same as the dimensions of the intermediate solder joints.

9. The gridless back-contact solar cell according to claim 8, characterized in that, The gridless back-contact solar cell further includes a second fine grid, which is arranged alternately with the first fine grid along the first direction, and the first fine grid and the second fine grid have opposite properties. The edge solder joint includes a first extension and a second extension along the first direction. At least a portion of the structure of the first extension is located within a first isolation space formed by the second fine gate, and at least a portion of the structure of the second extension is located within a second isolation space formed by the second fine gate. The second fine grid located in the first isolation space near the edge of the gridless back contact solar cell is electrically connected to the adjacent second fine grid via a third connecting line. The second fine grid located in the second isolation space near the edge of the gridless back contact solar cell is electrically connected to the adjacent second fine grid via a third connecting line.

10. A solar tandem battery, characterized in that, include: A crystalline silicon bottom cell, comprising a gridless back-contact solar cell according to any one of claims 1 to 9; A perovskite top cell, wherein the perovskite top cell is electrically connected to the crystalline silicon bottom cell.

11. A photovoltaic module, characterized in that, The photovoltaic module includes a cover plate, an encapsulation layer, and a battery string, wherein the battery string includes a plurality of gridless back-contact solar cells as described in any one of claims 1 to 9, or the battery string includes a plurality of solar tandem cells as described in claim 10.

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