Main-grid-free back contact solar cell, solar laminated cell and photovoltaic module

Abstract

The invention provides a main-grid-free back contact solar cell, a solar laminated cell and a photovoltaic module, and relates to the technical field of photovoltaics, the main-grid-free back contact solar cell comprises a first fine grid, an edge welding spot and a middle welding spot, the edge welding spot is located at the edge of the main-grid-free back contact solar cell and arranged on the first fine grid, and the middle welding spot is located at the edge of the main-grid-free back contact solar cell and arranged on the first fine grid. The plurality of middle welding spots are arranged between two adjacent edge welding spots along the first direction, the plurality of middle welding spots are respectively arranged on the corresponding first fine grids, and the edge welding spots comprise first ends facing the middle welding spots and second ends deviating from the middle welding spots along the first direction; the first end is electrically connected with the middle welding point adjacent to the first end through a first connecting line, the second end is electrically connected with the first fine grid adjacent to the second end through a second connecting line, and the width of the second connecting line is larger than that of the first connecting line. The above 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, and specifically to main-grid-free back-contact solar cells, solar tandem cells, and photovoltaic modules. Background Art

[0002] Solar cells are used to convert solar energy into electrical energy. The front side of a back-contact solar cell has no grid line obstruction, so as to reduce the shading loss caused by the grid lines. At present, the current collection and transmission performance of back-contact solar cells is poor, thus affecting the photoelectric conversion efficiency of back-contact solar cells. Summary of the Invention

[0003] In view of this, this application provides a main-grid-free back-contact solar cell, a solar tandem cell, and a photovoltaic module, which helps to solve the problem of poor current collection and transmission performance of back-contact solar cells in the prior art.

[0004] In a first aspect, an embodiment of this application provides a main-grid-free back-contact solar cell, including first fine grids, 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 main-grid-free back-contact solar cell and are disposed on the first fine grids. A plurality of the intermediate solder joints are arranged along the first direction between two adjacent edge solder joints, and a plurality of the intermediate solder joints are respectively disposed on corresponding first fine grids. Wherein, the edge solder joint includes a first end facing the intermediate solder joint and a second end facing away from the intermediate solder joint along the first direction. The first end and the intermediate solder joint adjacent to the first end are electrically connected through a first connection line. The second end and the first fine grid adjacent to the second end are electrically connected through a second connection line, and the width of the second connection line is greater than the width of the first connection line.

[0005] In a second aspect, an embodiment of this application provides a solar tandem cell, including a crystalline silicon bottom cell and a perovskite top cell. The crystalline silicon bottom cell includes the above-mentioned main-grid-free back-contact solar cell, and the perovskite top cell is electrically connected to the crystalline silicon bottom cell.

[0006] In a third aspect, an embodiment of this application provides a photovoltaic module. The photovoltaic module includes a cover plate, an encapsulation layer, and a cell string. The cell string includes a plurality of the above-mentioned main-grid-free back-contact solar cells, or the cell string includes a plurality of the above-mentioned solar tandem cells.

[0007] The beneficial effects of the present application are as follows: The first end of the edge solder joint is electrically connected to the adjacent intermediate solder joint through the first connection line. When there are problems such as poor soldering like virtual soldering between the intermediate solder joint and the solder strip, the current converging to the intermediate solder joint can be transmitted to the edge solder joint through the first connection line, and then transmitted to the solder strip through the edge solder joint to ensure the normal and stable transmission of the current, thereby improving the reliability of current collection and transmission in the edge area of the main-gridless back-contact solar cell. The second end of the edge solder joint is electrically connected to the adjacent first fine grid through the second connection line, enabling the current on the first fine grid to be output by being transmitted to the edge solder joint through the second connection line. The second connection line is directly electrically connected to the first fine grid, eliminating the need to set corresponding solder joints on the first fine grid, thereby reducing current transmission loss and improving the current collection efficiency in the edge area of the main-gridless back-contact solar cell, and further improving the photoelectric conversion efficiency of the main-gridless back-contact solar cell. The second connection line has a larger width to reduce current transmission loss, improve current collection efficiency, and enhance the mechanical properties of the second connection line, thereby improving the reliability of the main-gridless back-contact solar cell.

[0008] It should be understood that the above general description and the following detailed description are only exemplary and do not limit the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0010] Figure 1 Schematic diagram of the appearance of the main-gridless back-contact solar cell provided by an embodiment of the present application; Figure 2 Partial structural schematic diagram of the main-gridless back-contact solar cell provided by an embodiment of the present application; Figure 3 For Figure 2 partial enlarged view; Figure 4 Partial structural schematic diagram of the main-gridless back-contact solar cell provided by another embodiment of the present application; Figure 5 Partial structural schematic diagram of the main-gridless back-contact solar cell provided by yet another embodiment of the present application; Figure 6 Schematic diagram of the solar stacked cell provided by an embodiment of the present application; Figure 7 Structural schematic diagram of the photovoltaic module provided by an embodiment of the present application.

[0011] Reference Signs: 1000 - Photovoltaic module; 100 - Battery string; 10 - Main-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 fine grid; 111 - First sub-connection segment; 112 - Second sub-connection segment; 113 - Third sub-connection segment; 114 - Third isolation space; 115 - Fourth isolation space; 12 - Second fine 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 - Intermediate solder joint; 15 - First connection line; 16 - Second connection line; 17 - Third connection line; 200 - First cover plate; 300 - Second cover plate; 400 - First encapsulation layer; 500 - Second encapsulation layer; 20 - Solar laminate cell; 21 - Crystalline silicon bottom cell; 22 - Perovskite top cell. Detailed Embodiments

[0012] For a better understanding of the technical solutions of the present application, the embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0013] It should be clear that the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the protection scope of the present application.

[0014] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms of "a", "the" and "said" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0015] It should be understood that the term " / and" used herein is only a relationship describing associated objects, indicating that there can be three relationships. For example, A / and B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " herein generally represents an "or" relationship between the associated objects before and after.

[0016] Back-contact solar cells are used to convert solar energy into electrical energy, and there are no grid lines blocking their front surface to reduce the shading loss caused by the grid lines. Currently, the current collection and transmission performance of back-contact solar cells is poor, which affects the photoelectric conversion efficiency of back-contact solar cells and thus the reliability of back-contact solar cells.

[0017] As Figure 1 shown, an embodiment of the present application provides a main-gridless back-contact solar cell 10. The shape of the main-gridless back-contact solar cell 10 is approximately rectangular. It has a first side 10a and a second side 10b along the first direction X, and a third side 10c and a fourth side 10d along the second direction Y. There is a first corner 10e at the connection of the first side 10a and the third side 10c, a second corner 10f at the connection of the second side 10b and the third side 10c, a third corner 10g at the connection of the first side 10a and the fourth side 10d, and a fourth corner 10h at the connection of the second side 10b and the fourth side 10d. The first direction X intersects with the second direction Y. The first direction X can be the width direction of the main-gridless back-contact solar cell 10, and the second direction Y can be the length direction of the main-gridless back-contact solar cell 10. Both the first direction X and the second direction Y are perpendicular to the third direction Z, and the third direction Z can be the thickness direction of the main-gridless back-contact solar cell 10.

[0018] The above-mentioned main-gridless back-contact solar cell can be a two-piece, three-piece, four-piece or eight-piece obtained by cutting a whole piece of cell, that is to say, the cell can be a sliced cell. Or, the above-mentioned main-gridless back-contact solar cell can also be a whole piece of cell.

[0019] As Figure 2 shown, the main-gridless back-contact solar cell 10 includes a first fine grid 11, a second fine grid 12, edge solder joints 13 and intermediate solder joints 14. A plurality of first fine grids 11 and a plurality of second fine grids 12 are arranged alternately along the first direction X. The first fine grid 11 and the second fine grid 12 are metal electrodes of the main-gridless back-contact solar cell 10. The first fine grid 11 can be the positive electrode of the main-gridless back-contact solar cell 10, or the first fine grid 11 can also be the negative electrode of the main-gridless back-contact solar cell 10. The electrode polarity of the second fine grid 12 is opposite to that of the first fine grid 11. Both the first fine grid 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 main-gridless back-contact solar cell 10 outward.

[0020] Please refer to Figure 1, the edge solder joints 13 are located at the edge of the main-gridless back-contact solar cell 10 and are disposed on the first fine grid 11. The edge solder joints 13 are electrically connected to the corresponding first fine grids 11 and are used to connect to a solder ribbon (not shown in the figure). The edge solder joints 13 can be understood as the solder joints closest to the side edges of the main-gridless back-contact solar cell 10. In some embodiments, the edge solder joints 13 can be respectively disposed at the above-mentioned first corner 10e, second corner 10f, third corner 10g, and fourth corner 10h.

[0021] A plurality of intermediate solder joints 14 are arranged along the first direction X between two adjacent edge solder joints 13. The plurality of intermediate solder joints 14 are respectively disposed on the corresponding first fine grids 11. Each intermediate solder joint 14 is electrically connected to the corresponding first fine grid 11, and the intermediate solder joints 14 are also used to connect to a solder ribbon. That is to say, the edge solder joints 13 and the intermediate solder joints 14 arranged along the first direction X can be connected to the same solder ribbon.

[0022] As Figure 3 shown, the edge solder joint 13 includes a first end 131 facing the intermediate solder joint 14 and a second end 132 facing 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 connection line 15. The first connection 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 the plurality of intermediate solder joints 14. That is to say, the edge solder joint 13 is electrically connected to an adjacent intermediate solder joint 14 through the first connection line 15, so that current can be transmitted between two adjacent first fine grids 11 through the first connection line 15.

[0023] The second end 132 and the first fine grid 11 adjacent to the second end 132 are electrically connected by a second connection line 16. The second connection line 16 is arranged along the first direction X. The first fine grid 11 adjacent to the edge solder joint 13 is the first fine grid 11 closest to the second end 132 of the edge solder joint 13 among the plurality of first fine grids 11. That is to say, the edge solder joint 13 is electrically connected to an adjacent first fine grid 11 through the second connection line 16. There is no solder joint on the first fine grid 11 adjacent to the second end 132. Therefore, the second connection line 16 is directly electrically connected to the first fine grid 11, so that current can be transmitted between two adjacent first fine grids 11.

[0024] The second fine grid 12 is disconnected to form a first isolation space 121 and a second isolation space 122, and the first isolation space 121 and the second isolation space 122 are arranged along the first direction X. The second fine grid 12 includes a first part 123, a second part 124, a third part 125, and a fourth part 126. The first part 123 and the second part 124 are spaced apart along the second direction Y, and the first isolation space 121 is located between the first part 123 and the second part 124. The third part 125 and the fourth part 126 are spaced apart along the second direction Y, and the second isolation space 122 is located between the third part 125 and the fourth part 126.

[0025] The first connection line 15 passes through the first isolation space 121 along the first direction X to electrically connect the edge solder joint 13 and the adjacent middle solder joint 14. A partial structure of the first connection line 15 is located in the first isolation space 121 and has a certain interval from the first part 123 and the second part 124 of the second fine grid 12. The second connection line 16 passes through the second isolation space 122 to electrically connect the edge solder joint 13 and the adjacent first fine grid 11. A partial structure of the second connection line 16 is located in the second isolation space 122 and has a certain interval from the third part 125 and the fourth part 126 of the second fine grid 12. The first isolation space 121 realizes the isolation between the first connection line 15 and the second fine grid 12, and the second isolation space 122 realizes the isolation between the second connection line 16 and the second fine grid 12, thereby reducing the possibility that the first connection line 15 and the second connection line 16 come into contact with the second fine grid 12 and cause a short circuit in the main-gridless back-contact solar cell 10.

[0026] Both the above-mentioned first connection line 15 and the second connection line 16 can be formed by printing metal paste and then drying and sintering. The width of the second connection line 16 (i.e., the dimension of the second connection line 16 in the second direction Y) is greater than the width of the first connection line 15 (i.e., the dimension of the first connection line 15 in the second direction Y).

[0027] The main-gridless back-contact solar cell 10 in the embodiment of the present application adopts the main-gridless (0BB, 0 - Busbar) technology, enabling the solder ribbon to be directly connected to the fine grid. Since there is no need to set the main grid, the consumption of metal paste is reduced, thereby reducing the production cost of the main-gridless back-contact solar cell 10. At the same time, the light-shielding area of the grid lines is reduced, and the photoelectric conversion efficiency of the main-gridless back-contact solar cell 10 is improved.

[0028] Among them, the first end 131 of the edge solder joint 13 is electrically connected to the adjacent middle solder joint 14 through the first connection line 15. When there are problems such as poor soldering like virtual soldering between the middle solder joint 14 and the solder ribbon, the current converging to the middle solder joint 14 can be transmitted to the edge solder joint 13 through the first connection line 15, and then transmitted to the solder ribbon through the edge solder joint 13 to ensure the normal and stable transmission of the current, thereby improving the reliability of current collection and transmission in the edge area of the main-gridless back-contact solar cell 10, and further improving the electrical performance of the main-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 through the second connection line 16, so that the current on the first fine grid 11 can be output by being transmitted to the edge solder joint 13 through the second connection line 16. The second connection line 16 is directly electrically connected to the first fine grid 11, so that no corresponding solder joints need to be provided on the first fine grid 11, thereby reducing the current transmission loss, and at the same time improving the current collection efficiency in the edge area of the main-gridless back-contact solar cell 10, and further improving the photoelectric conversion efficiency of the main-gridless back-contact solar cell 10. At the same time, the width of the second connection line 16 is larger and greater than the width of the first connection line 15 to reduce the current transmission loss, improve the current collection efficiency, and at the same time improve the mechanical properties of the second connection line 16, reduce the possibility of the second connection line 16 breaking during the production and operation of the main-gridless back-contact solar cell 10, and provide a stable and reliable transmission channel for the current, thereby improving the reliability of the main-gridless back-contact solar cell 10.

[0029] In summary, the main-gridless back-contact solar cell 10 provided by the embodiment of the present application improves the current transmission ability and current transmission efficiency of the main-gridless back-contact solar cell 10 by setting the first connection line 15 and the second connection line 16 electrically connected to the edge solder joint 13, thereby improving the electrical performance of the main-gridless back-contact solar cell 10, and further improving the reliability and photoelectric conversion efficiency of the main-gridless back-contact solar cell 10, and realizing the normal and stable operation of the main-gridless back-contact solar cell 10.

[0030] In some embodiments, the second connection line can be directly connected to the solder ribbon, that is, the second connection line and the solder ribbon are alloyed, so that the current on the second connection line can be directly transmitted to the solder ribbon, thereby shortening the current transmission path, improving the current transmission efficiency, and further improving the photoelectric conversion efficiency of the main-gridless back-contact solar cell. At the same time, the contact area between the solder ribbon and the main-gridless back-contact solar cell is increased, thereby improving the connection stability and reliability between the solder ribbon and the main-gridless back-contact solar cell.

[0031] Such as Figure 3As shown, in a possible implementation, the width W1 of the first connection line 15 satisfies: 5μm ≤ W1 ≤ 20μm, and the width W2 of the second connection line 16 satisfies: 100μm ≤ W1 ≤ 300μm.

[0032] The width W1 of the first connection line 15 can be 5μm, 6μm, 8μm, 10μm, 12μm, 14μm, 16μm, 18μm or 20μm. Of course, it can also be other values within the above range. If the width of the first connection line 15 is too small, its resistance increases, affecting the current transmission efficiency between the edge solder joints 13 and the middle solder joints 14. At the same time, the mechanical properties of the first connection line 15 are reduced, resulting in a decrease in its strength, making the first connection line 15 prone to breakage during welding, encapsulation and other processes, destroying the current transmission path, and thus affecting the reliability of the main-gridless back-contact solar cell 10. If the width of the first connection line 15 is too large, the amount of metal paste required to prepare the first connection line 15 increases, resulting in an increase in the manufacturing cost of the main-gridless back-contact solar cell 10. At the same time, the light-shielding area of the first connection line 15 is also increased, further increasing the light-shielding loss caused by the first connection line 15 and affecting the photoelectric conversion efficiency of the main-gridless back-contact solar cell 10. Therefore, by limiting the width of the first connection line 15 to 5μm to 20μm, while reducing the manufacturing cost of the main-gridless back-contact solar cell 10 and ensuring the photoelectric conversion efficiency of the main-gridless back-contact solar cell 10, the mechanical properties and electrical properties of the first connection line 15 are improved, realizing stable and reliable current transmission, and thus improving the reliability of the main-gridless back-contact solar cell 10.

[0033] The width W2 of the second connection line 16 can be 100μm, 120μm, 140μm, 160μm, 180μm, 200μm, 220μm, 240μm, 260μm, 280μm or 300μm. Of course, it can also be other values within the above range. The width of the second connection line 16 is much larger than that of the first connection line 15. By limiting the width of the second connection line 16 to 100μm to 300μm, the resistance of the second connection line 16 is effectively reduced to achieve efficient current transmission, thereby improving the current collection effect in the edge region of the main-gridless back-contact solar cell 10, reducing the current loss in the edge region of the main-gridless back-contact solar cell 10, making the current more evenly distributed, and thus reducing the hot spot risk and inhibiting the potential-induced degradation risk of the main-gridless back-contact solar cell 10, and improving the photoelectric conversion efficiency of the main-gridless back-contact solar cell 10. At the same time, due to the large width of the second connection line 16, the mechanical properties of the second connection line 16 are improved, reducing the possibility of breakage under stress such as welding pressure, and thus improving the reliability of the main-gridless back-contact solar cell 10.

[0034] In summary, by restricting the widths of the first connection line 15 and the second connection line 16, while improving the electrical performance of the main-gridless back-contact solar cell 10, the usage amount of the metal paste is saved, and the production cost of the main-gridless back-contact solar cell 10 is reduced.

[0035] In some other embodiments, the width W1 of the first connection line 15 satisfies: 5 μm ≤ W1 ≤ 20 μm, or the width W2 of the second connection line 16 satisfies: 100 μm ≤ W2 ≤ 300 μm.

[0036] As Figure 4 shown, Figure 4 Taking the third side 10c as an example, the edge of the main-gridless back-contact solar cell 10 is schematically shown. In a possible implementation manner, 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 main-gridless back-contact solar cell 10 and a fourth end 134 facing away from the edge of the main-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 main-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).

[0037] The first sub-connection segment 111 is used to collect the current in the edge region of the main-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. Among them, 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, so that the current in the edge region of the main-gridless back-contact solar cell 10 can be effectively collected, reducing the current loss in the edge region of the main-gridless back-contact solar cell 10, making the current more evenly distributed, reducing the hot spot risk of the main-gridless back-contact solar cell 10 and suppressing the potential-induced degradation risk, and improving the photoelectric conversion efficiency of the main-gridless back-contact solar cell 10.

[0038] Continuing as Figure 4As shown, in a 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.

[0039] Among them, 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. Of course, it can also be other values within the above range. If the width of the first sub-connection segment 111 is too small, it is difficult for the first sub-connection segment 111 to effectively collect and transmit the current in the edge region of the main-gridless back-contact solar cell 10, resulting in current loss in the edge region of the main-gridless back-contact solar cell 10 and affecting the photoelectric conversion efficiency and reliability of the main-gridless back-contact solar cell 10. If the width of the first sub-connection segment 111 is too large, the amount of metal paste required for preparing the first fine grid 11 will increase, leading to an increase in the manufacturing cost of the main-gridless back-contact solar cell 10. At the same time, it also increases the light-shielding area of the first fine grid 11, and further increases the light-shielding loss caused by the first connection line 15, affecting the photoelectric conversion efficiency of the main-gridless back-contact solar cell 10. Therefore, by designing the width of the first sub-connection segment 111 between 100μm and 350μm, while improving the current collection and transmission ability of the first sub-connection segment 111, the light-shielding area of the first sub-connection segment 111 can be reduced, thereby improving the photoelectric conversion efficiency of the main-gridless back-contact solar cell 10 and reducing its production cost.

[0040] The width W4 of the second sub-connection segment 112 can be 5μm, 6μm, 8μm, 10μm, 12μm, 14μm, 16μm, 18μm or 20μm. Of course, it can also be other values within the above range. By restricting the width of the second sub-connection segment 112, the stable transmission of current through the second sub-connection segment 112 is ensured, and at the same time, the light-shielding loss of the second sub-connection segment 112 is reduced, thereby improving the photoelectric conversion efficiency of the main-gridless back-contact solar cell 10.

[0041] In some 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.

[0042] Continue as Figure 4As shown, in a 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. Of course, it can also be 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 fracture, affecting the current collection and transmission ability 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 the resistance loss and affecting the electrical performance of the main-gridless back-contact solar cell 10. Therefore, the length of the first sub-connection segment 111 is designed to be between 4mm and 6mm to shorten the current transmission path while ensuring the mechanical properties of the first sub-connection segment 111, reducing the resistance loss, and thus improving the efficiency and stability of the current transmission of the first sub-connection segment 111.

[0043] As Figure 5 shown, in a possible implementation, the first fine grid 11 connected to the edge solder joint 13 includes a third sub-connection segment 113. Along the second direction Y, the third sub-connection segment 113 is connected between the first sub-connection segment 111 and the second sub-connection segment 112. The third sub-connection segment 113 is connected to the edge solder joint 13, and the projection of the third sub-connection segment 113 along the third direction Z is located within the edge solder joint 13. The width of the third sub-connection segment 113 is the same as the width of the first sub-connection segment 111, or the width of the third sub-connection segment 113 is the same as the width of the second sub-connection segment 112.

[0044] The edge solder joint 13 can cover the third sub-connection segment 113, that is to say, the edge solder joint 13 can be formed above the third sub-connection segment 113. The edge solder joint 13 is electrically connected to the third sub-connection segment 113, thereby realizing the electrical connection between the 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, that is, the width of the third sub-connection segment 113 is less than the width of the first sub-connection segment 111, thereby saving the amount of metal paste and reducing the production cost of the main-gridless back-contact solar cell 10.

[0045] In some other embodiments, the width of the third sub-connection segment 113 is the same as that of the first sub-connection segment 111, that is, the width of the third sub-connection segment 113 is greater than that 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 facilitating the improvement of the welding strength of the solder joint, reducing the risk of electrical connection failure of the main-gridless back-contact solar cell 10, and further improving the reliability of the main-gridless back-contact solar cell 10.

[0046] As Figure 5 shown, in a possible implementation manner, the area of the edge solder joint 13 is larger than the area of the middle solder joint 14.

[0047] Please also refer to Figure 1 , during the production and operation of the main-gridless back-contact solar cell 10, in the edge region of the main-gridless back-contact solar cell 10, especially each of the above-mentioned corners needs to bear greater stress. Therefore, the corners of the main-gridless back-contact solar cell 10 are prone to warping deformation and other situations, thus affecting the stability of the setting of the edge solder joint 13. By increasing the area of the edge solder joint 13, it can effectively disperse stress and improve its anti-fatigue ability, thereby reducing the risk of cracking of the edge solder joint 13, providing a reliable welding point for the solder tape, improving the welding strength, and further improving the stability and reliability of the connection between the solder tape and the main-gridless back-contact solar cell 10. At the same time, increasing the area of the edge solder joint 13 also improves its current transmission ability, enabling the current to be transmitted to the solder tape more efficiently and stably through the edge solder joint 13, thereby improving the electrical performance of the main-gridless back-contact solar cell 10.

[0048] Optionally, the area S1 of the edge solder joint 13 satisfies: 0.25 mm 2 ≤ S1 ≤ 4 mm 2 , for example, S1 can be 0.25 mm 2 , 0.05 mm 2 , 0.1 mm 2 , 0.5 mm 2 , 1 mm 2 , 2 mm 2 , 3 mm 2 , 3.5 mm 2 or 4 mm 2 , and of course, it can also be other values within the above range. By restricting the area of the edge solder joint 13, the reliability of the edge solder joint 13 is improved, the risk of its cracking is reduced, and at the same time, its current transmission ability is increased, thereby improving the reliability of the main-gridless back-contact solar cell 10.

[0049] Optionally, the area S2 of the middle solder joint 14 satisfies: 0.1 mm 2 ≤ S2 ≤ 0.7 mm 2, for example, S2 can be 0.1 mm 2 , 0.2 mm 2 , 0.3 mm 2 , 0.4 mm 2 , 0.5 mm 2 , 0.6 mm 2 , or 0.7 mm 2 , of course, it can also be other values within the above range. By restricting the area of the middle solder joint 14, its light-shielding area is reduced, while ensuring the stability and reliability of the connection between the middle solder joint 14 and the solder ribbon, so as to ensure the normal and stable transmission of current.

[0050] As Figure 5 shown, in a possible implementation, along the first direction X, the size of the edge solder joint 13 is larger than that of the middle solder joint 14, and along the second direction Y, the size of the edge solder joint 13 is the same as that of the middle solder joint 14.

[0051] The edge solder joint 13 increases its size along the first direction X so that its area is larger than that of the middle solder joint 14, so that the shape of the edge solder joint 13 can better match the shape of the solder ribbon (not shown in the figure), so as to increase the contact area between the edge solder joint 13 and the solder ribbon, thereby improving the stability and reliability of the connection between the edge solder joint 13 and the solder ribbon.

[0052] Optionally, along the first direction X, the ratio of the size D1 of the edge solder joint 13 to the size D2 of the middle 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 restricting the proportional relationship between the sizes of the edge solder joint 13 and the middle solder joint 14 in the first direction X, the area ratio between the edge solder joint 13 and the middle solder joint 14 is kept within a reasonable range, so that the solder ribbon can be stably and reliably connected to the edge solder joint 13 and the middle solder joint 14, thereby realizing the normal and stable transmission of current.

[0053] As mentioned above, the back-contact solar cell without a main grid includes a first fine grid and a second fine grid. The second fine grid and the first fine grid are arranged alternately along the first direction, and the first fine grid and the second fine grid have opposite polarities. As Figure 5 shown, Figure 5Taking the third side 10c as an example, the edge of the back-contact solar cell 10 without main grid is illustrated. In a possible implementation, 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 disconnection of the second fine grid 12, and the second extension 136 is located within a second isolation space 122 formed by the disconnection of the second fine grid 12. The second fine grid 12 on the side of the first isolation space 121 close to the edge of the back-contact solar cell 10 without main grid is electrically connected to an adjacent second fine grid 12 through a third connection line 17. The second fine grid 12 on the side of the second isolation space 122 close to the edge of the back-contact solar cell 10 without main grid is electrically connected to an adjacent second fine grid 12 through a third connection line 17.

[0054] The first extension 135 is connected to the first connection line 15, and the second extension 136 is connected to the second connection line 16. The second fine grid 12 includes a first part 123, a second part 124, a third part 125, and a fourth part 126. The first part 123 and the second part 124 are arranged along the second direction Y. The first isolation space 121 is located between the first part 123 and the second part 124. At least part of the structure of the first extension 135 is located within the first isolation space 121 and has a certain interval from the first part 123 and the second part 124 of the second fine grid 12. The first part 123 is located on the side of the first isolation space 121 close to the edge of the back-contact solar cell 10 without main grid. The first part 123 is electrically connected to an adjacent second fine grid 12 through a third connection line 17. That is to say, the third connection line 17 electrically connects two adjacent second fine grids 12.

[0055] The third part 125 and the fourth part 126 are arranged along the second direction Y. The second isolation space 122 is located between the third part 125 and the fourth part 126. Part of the structure of the second extension 136 is located within the second isolation space 122 and has a certain interval from the third part 125 and the fourth part 126 of the second fine grid 12. The third part 125 is located on the side of the second isolation space 122 close to the edge of the back-contact solar cell 10 without main grid. The third part 125 is electrically connected to an adjacent second fine grid 12 through a third connection line 17.

[0056] The above-mentioned third connection line 17 can be formed by printing metal paste and then drying and sintering.

[0057] As described above, the edge solder joints 13 can increase their own areas by increasing their dimensions in the first direction X. Therefore, the first extension portion 135 and the second extension portion 136 of the edge solder joints 13 can extend outward in the first direction X, that is, the first extension portion 135 and the second extension portion 136 extend toward 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 fine grids 12 respectively. The first isolation space 121 and the second isolation space 122 play an avoidance role for the edge solder joints 13 to provide sufficient space for the arrangement of the edge solder joints 13. At the same time, since the edge solder joints 13 are electrically connected to the first fine grids 11, the first isolation space 121 and the second isolation space 122 also play an isolation role for the edge solder joints 13, reducing the risk of short circuit of the main-gridless back-contact solar cell 10 caused by the edge solder joints 13 contacting the second fine grids 12, so as to ensure the normal and stable operation of the main-gridless back-contact solar cell 10. The third connection lines 17 realize the electrical connection of two adjacent second fine grids 12, reducing the possibility that the current on the second fine grids 12 cannot be transmitted due to the arrangement of the above-mentioned first isolation space 121 and second isolation space 122, thereby reducing the possibility of local current loss in the main-gridless back-contact solar cell 10, and further improving the reliability of the low-main-gridless back-contact solar cell.

[0058] Third isolation spaces 114 and fourth isolation spaces 115 are formed at the disconnection positions of the first fine grids 11. Two third connection lines 17 respectively pass through the corresponding isolation spaces to realize the electrical connection between adjacent second fine grids 12. The third isolation spaces 114 and the fourth isolation spaces 115 play an isolation role for the third connection lines 17, reducing the possibility of short circuit of the main-gridless back-contact solar cell 10 caused by the third connection lines 17 contacting the first fine grids 11.

[0059] As Figure 6 shown, an embodiment of the present application provides a solar stacked 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 main-gridless back-contact solar cell, and the perovskite top cell 22 is electrically connected to the crystalline silicon bottom cell 21.

[0060] Among them, the perovskite top cell 22 may include a substrate, a conductive thin film, an electron transport layer (such as titanium dioxide), a perovskite absorption layer, a hole transport layer, and a metal electrode (not shown in the figure). The perovskite material has 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 less loss. Therefore, a high photogenerated voltage and current can be generated, making the perovskite top cell 22 exhibit a high photoelectric conversion efficiency.

[0061] By combining the above-mentioned main-gridless back-contact solar cell and perovskite cell into a tandem cell, it is possible to achieve a wider range of absorption of the solar spectrum, thereby improving the photoelectric conversion efficiency of the tandem cell. Due to the above-mentioned technical effects of the main-gridless back-contact solar cell, the tandem module with this main-gridless back-contact solar cell also has the above-mentioned technical effects, which will not be elaborated here.

[0062] As Figure 7 shown, an embodiment of the present application provides a photovoltaic module 1000, which includes a cover plate, an encapsulation layer, and a battery string 100. The battery string 100 includes a plurality of the above-mentioned main-gridless back-contact solar cells, or the battery string 100 includes a plurality of the above-mentioned solar tandem cells 20.

[0063] Among them, the cover plate at the top of the photovoltaic module 1000 is the first cover plate 200, the cover plate at the bottom of the photovoltaic module 1000 is the second cover plate 300, the encapsulation layer between the first cover plate 200 and the battery string 100 is the first encapsulation layer 400, and the encapsulation layer between the second cover plate 300 and the battery string 100 is the second encapsulation layer 500. The first cover plate 200, the second cover plate 300, the first encapsulation layer 400, the second encapsulation layer 500, and the battery string 100. The first cover plate 200, the first encapsulation layer 400, the battery string 100, the second encapsulation layer 500, and the second cover plate 300 can be arranged along the thickness direction Z of the photovoltaic module 1000 and laminated together. Among them, the first cover plate 200 can be a glass cover plate, and the first cover plate 200 has a high light transmittance. The first encapsulation layer 400 bonds the first cover plate 200 and the battery string 100 together to play a role in encapsulating and protecting 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 and the second cover plate 300, and it also plays a role in encapsulating and protecting the battery string 100. The material of the second encapsulation layer 500 can be one or more of the above-mentioned EVA, POE, and PVB. The material of the second cover plate 300 can be glass, or the second cover plate 300 can also be composed of multiple polymer film layers.

[0064] The above are only optional embodiments of the present application and are not used to limit the present application. For those skilled in the art, the present application can have various changes and modifications. Any modification, equivalent replacement, improvement, 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 without a main grid, characterized in that Including: A first set of fine grids, with multiple ones of the first set of fine grids arranged along a first direction; Edge solder joints, which are located at the edge of the main-gridless back-contact solar cell and are disposed on the first set of fine grids; Intermediate solder joints, with multiple ones of the intermediate solder joints arranged along the first direction between two adjacent ones of the edge solder joints, and multiple ones of the intermediate solder joints are respectively disposed on corresponding ones of the first set of fine grids; Wherein, the edge solder joint includes a first end facing the intermediate solder joint and a second end facing away from the intermediate solder joint along the first direction, the first end and the adjacent intermediate solder joint are electrically connected through a first connecting line, the second end and the adjacent first fine grid are electrically connected through a second connecting line, and the width of the second connecting line is greater than the width of the first connecting line.

2. The back-contact solar cell without main grid according to claim 1, wherein 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 back-contact solar cell without main grid according to claim 1, wherein 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 main-gridless back-contact solar cell and a fourth end facing away from the edge of the main-gridless back-contact solar cell along a 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 main-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, and the width of the first sub-connection segment is greater than the width of the second sub-connection segment.

4. The back-contact solar cell without a main grid 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 back-contact solar cell without main grid according to claim 3, characterized in that, The length L1 of the first sub-connection segment satisfies: 4mm ≤ L1 ≤ 6mm.

6. The back-contact solar cell without a main grid according to claim 3, wherein, The first fine grid connected to the edge solder joint includes a third sub-connection segment, and along the second direction, the third sub-connection segment is connected between the first sub-connection segment and the second sub-connection segment; The third sub-connection segment is connected to the edge solder joint, and the projection of the third sub-connection segment along a 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 back-contact solar cell without main grid according to any one of claims 1 to 6, characterized in that The area of the edge solder joint is greater than the area of the intermediate solder joint.

8. The back-contact solar cell without main grid according to claim 7, characterized in that, Along the first direction, the size of the edge solder joint is greater than the size of the intermediate solder joint; Along the second direction, the size of the edge solder joint is the same as the size of the intermediate solder joint.

9. The back-contact solar cell without main grid according to claim 8, wherein, The main-gridless back-contact solar cell further includes a second set of fine grids, the second set of fine grids and the first set of fine grids are alternately arranged along the first direction, and the first set of fine grids and the second set of fine grids have opposite polarities; The edge solder joints include a first extension portion and a second extension portion along the first direction. At least part of the structure of the first extension portion is located in a first isolation space formed by the disconnection of the second fine grid, and at least part of the structure of the second extension portion is located in a second isolation space formed by the disconnection of the second fine grid; The second fine grid located on the side of the first isolation space close to the edge of the main-gridless back-contact solar cell is electrically connected to the adjacent second fine grid through a third connection line; The second fine grid located on the side of the second isolation space close to the edge of the main-gridless back-contact solar cell is electrically connected to the adjacent second fine grid through a third connection line.

10. A solar laminated cell, characterized in that, Comprising: A crystalline silicon bottom cell, the crystalline silicon bottom cell comprising the main-gridless back-contact solar cell according to any one of claims 1 to 9; A perovskite top cell, the perovskite top cell being electrically connected to the crystalline silicon bottom cell.

11. A photovoltaic module, characterized in that, The photovoltaic module includes a cover plate, a packaging layer, and a battery string. The battery string includes a plurality of main-gridless back-contact solar cells according to any one of claims 1 to 9, or the battery string includes a plurality of the solar laminated cells according to claim 10.

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