Back contact cell, back contact laminated cell and photovoltaic module

Abstract

The utility model provides a back contact cell, a back contact laminated cell and a photovoltaic module, and the back contact cell comprises a substrate and grid lines, the grid lines comprise first grid lines, the first grid lines are arranged along a first direction, the first grid lines are provided with welding parts, the welding parts comprise a plurality of first welding parts and second welding parts, and the first welding parts and the second welding parts are arranged along the length direction of the first grid lines. The second welding parts are located at the two opposite ends of the first grid line, the first welding part is located between the two second welding parts, the size of the second welding parts is larger than that of the first welding part in the length direction of the first grid line, and the area of the first welding part is gradually increased in the direction close to the second welding parts. The first grid line is responsible for transmitting current, and the second welding part outputs current, so that the current closer to the second welding part is larger, the first welding part with larger area is smaller in resistance and higher in current bearing capacity, and the area of the first welding part is increased along the direction close to the second welding part, so that the loss in the current transmission process can be reduced, and the current transmission efficiency is improved. The power generation efficiency is improved.

Description

Technical Field

[0001] This application relates to the field of photovoltaic module technology, and in particular to a back-contact cell, a back-contact tandem cell, and a photovoltaic module. Background Technology

[0002] BC cells, short for back-contact cells, are based on IBC cells (interdigitated back-contact cells). The biggest difference between them and other crystalline silicon cell routes is that the emitter, surface field, and metal electrodes are all located on the back of the cell and are distributed in an interdigitated pattern. There are no grid lines blocking the front surface of the cell, which maximizes the use of incident light, reduces optical losses, and brings more effective power generation area. However, back-contact cells have greater losses during current collection, which reduces the cell efficiency. Utility Model Content

[0003] This application provides a back-contact battery, a back-contact stacked battery, and a photovoltaic module. The back-contact battery can improve the efficiency of the photovoltaic module and reduce losses during current transmission.

[0004] This application provides a back contact battery, comprising: a substrate; grid lines disposed on the substrate; wherein, the grid lines include a first grid line disposed along a first direction, the first grid line is provided with a welding portion, the welding portion including a plurality of first welding portions and two second welding portions, along the length direction of the first grid line, the second welding portions are located at opposite ends of the first grid line, and the first welding portions are located between the two second welding portions;

[0005] Along the length of the first grid line, the size of the second welded portion is larger than the size of the first welded portion, and along the direction closer to the second welded portion, the area of ​​the first welded portion gradually increases.

[0006] In this design, the first grid line serves as the main grid line of the back contact battery, and the second welding portion is used to transmit current to the output terminal of the back contact battery. The collected current is output through the second welding portion, therefore, the current is greater closer to the second welding portion. According to the resistance law formula R = ρL / S, where R is the resistance value, ρ is the resistivity of the material, L is the length of the conductor, and S is the cross-sectional area of ​​the conductor, it can be seen from the formula that the larger the cross-sectional area S of the conductor, the smaller the resistance R. That is, the larger the area of ​​the welding portion, the smaller its resistance. Therefore, the size of the second welding portion is made larger than the size of the first welding portion, and the area of ​​the first welding portion gradually increases along the direction closer to the second welding portion. That is, the resistance of the first welding portion is smaller closer to the second welding portion. By reducing the resistance, the loss of current flowing through each first welding portion to the second welding portion can be reduced, thereby improving the working efficiency of the back contact battery.

[0007] The second welding part located at both ends of the first grid line adopts a larger size, which can significantly enhance the connection strength of the edge area of ​​the first grid line and the connection stability between the first grid line and the welding strip. This effectively reduces the risk of warping and deformation caused by heat generated during the power generation process of the back contact battery, and ensures the stability and reliability of the back contact battery operation.

[0008] Meanwhile, the area of ​​the first welding part near the second welding part gradually increases, which can improve its welding area with the welding strip, reduce the risk of incomplete welding and missing welding, thereby improving the connection effect between the end first welding part and the back contact battery, and improving the performance of the back contact battery.

[0009] In one possible design, along the second direction, at least one of the dimensions of the first weld portion is larger than the dimension of the second weld portion.

[0010] In this scheme, along the second direction, the size of at least one first welded part is larger than the size of the second welded part. Since the current on the first grid line increases along the direction close to the second welded part, the first welded part with the increased size along the second direction can significantly improve the current conduction capability at the end of the first grid line, adapt to the current carrying requirements of the high current density region, ensure the reliability of current conduction near the second welded part, and further improve the mechanical support strength at the edge, reducing the occurrence of stress concentration at the edge.

[0011] In one possible design, the dimensional difference C between adjacent first welded portions along the second direction satisfies 0.008mm≤C≤0.015mm.

[0012] In this solution, when the difference C between adjacent first welded parts along the second direction is small, the dimensional change of the adjacent first welded parts cannot adapt to the increase in current, resulting in insufficient effective current-carrying area in the high-density current region, local temperature rise, and electrical energy being converted into heat energy and dissipated. Simultaneously, the stress dispersion effect is weakened, the strength of the back contact battery decreases, and risks such as cracking are more likely. When the difference C between adjacent first welded parts along the second direction is large, the larger area of ​​the first welded part requires more solder, resulting in solder waste. Furthermore, excessive solder is prone to flow during welding, increasing the risk of overflow and potentially causing a short circuit. In this application, the dimensional difference C between adjacent first welded parts along the second direction is limited to the range of 0.008mm to 0.015mm. The dimensional change between adjacent first welded parts is moderate, and the change in resistance adapts to the increasing characteristics of the current converging towards the second welded part, effectively reducing current heat loss. Within this range, the dimensional difference can effectively disperse stress, improve the strength of the back contact battery, reduce the risk of cracking, and control the flowability of the solder during welding, ensuring good welding results and reducing the risk of short circuits.

[0013] In one possible design, the dimensions of adjacent first welded portions change arithmetically along the second direction.

[0014] In this design, since each second grid line is connected to only one welding point on a first grid line, and the current collected by the second grid line flows into the first grid line through the welding point, the current between adjacent first welding points on the first grid line, along the direction closest to the second welding point, approximately exhibits an arithmetic progression distribution. The first welding points, whose dimensions change arithmetically along the second direction, can better adapt to the current growth gradient, match the current variation pattern, significantly reduce power loss, and optimize performance. Furthermore, the arithmetically changing first welding points can form a uniform stress distribution, further improving the strength of the back contact battery.

[0015] In one possible design, the minimum dimension of the first welded part along the second direction is L1, and the maximum dimension of the first welded part along the second direction is L2.

[0016] 0.6mm≤L2≤1.4mm, 0.2mm≤L1≤0.6mm, and / or;

[0017] The ratio of L2 to L1 satisfies: 1.5 ≤ L2 : L1 ≤ 7.

[0018] In this design, when L1 is too small, the insufficient cross-sectional area of ​​the minimum welding zone leads to severe localized heating when current passes through, resulting in excessive current loss and making the back contact battery prone to deformation due to overheating. When L1 is too large, the first welding section in the middle becomes too large, and as it increases in size towards the second welding section, the excessive size of the first welding section leads to material waste, and excessive use of solder ribbon during welding increases the risk of short circuits. When L2 is too small, the size of the first welding section is too small to withstand dense current, causing severe heating at the edges and making it prone to warping and deformation. When L2 is too large, the excessively large area of ​​the first welding section results in insufficient spacing between adjacent solder joints, making it prone to contact with the second grid line with opposite polarity during welding, increasing the risk of short circuits.

[0019] In this application, L2 is limited to 0.6mm to 1.4mm, and L1 is limited to 0.2mm to 0.6mm. The lower limit of L1 of 0.2mm can ensure that the minimum welding area maintains the necessary current conduction cross section and avoid excessive local current density due to excessive size. The upper limit of L1 of 0.6mm prevents the first welding part located in the middle area between the two second welding parts from being excessively redundant, and ensures the adaptability of the welding part area to the change of current magnitude.

[0020] The lower limit of L2 (0.6mm) ensures a safe current-carrying margin in areas with high current density near the second weld joint; the upper limit of L2 (1.4mm) reduces the risk of short circuits caused by excessive solder buildup due to an excessively large weld area. This design allows the area of ​​the first weld joint to precisely adapt to the current density variation from the center to the edge of the back contact battery, reducing current loss and improving the reliability and stability of the weld.

[0021] When the L2:L1 ratio is too small, insufficient size gradient leads to a mismatch between current carrying capacity and current growth rate, making localized areas prone to overheating due to excessive current, thus increasing the risk of chip cracking. When the L2:L1 ratio is too large, the variation between adjacent dimensions is too large, resulting in an excessively large area of ​​the first weld joint on both sides, which can easily cause solder buildup and short circuits in the back contact battery. In this application, limiting L2:L1 to 1.5 to 7 ensures that the area variation of the first weld joint matches the current variation, reducing heat loss from the current, and avoiding the risk of solder buildup due to an excessively large weld joint area, thereby improving welding reliability.

[0022] Furthermore, L1 and L2 can simultaneously satisfy 0.6mm≤L2≤1.4mm, 0.2mm≤L1≤0.6mm, and 1.5≤L2:L1≤7.

[0023] In one possible design, the number of the first welded parts is between 3 and 80.

[0024] In this design, if the number of first welded parts is too small, the spacing between adjacent first welded parts becomes too large, resulting in an excessively long current transmission path, excessive current accumulation, and a tendency to generate localized high temperatures. Furthermore, the stress dispersion effect of the welded parts is weakened, making them prone to cracking. Conversely, if the number of first welded parts is too large, the spacing between adjacent welded parts becomes too small, significantly increasing the risk of short circuits due to solder overflow during welding, thus reducing the power generation efficiency of the back contact battery. This design limits the number of first welded parts to 3 to 80, ensuring the necessary minimum node density for the current transmission path, preventing localized overheating, and ensuring sufficient spacing between adjacent first welded parts to eliminate the risk of short circuits during welding, thereby improving the power generation efficiency and lifespan of the back contact battery.

[0025] In one possible design, the first grid line includes a first connecting segment and a second connecting segment, the first connecting segment being located on the side of the second weld portion away from the first weld portion, and the second connecting segment being used to connect the first weld portion and the second weld portion or an adjacent first weld portion;

[0026] Along the direction away from the second welded part, the width of the first connecting segment gradually decreases.

[0027] In this design, since the first welding part is inconvenient to install on the side of the second welding part that is far from the first welding part, only a short first connecting segment is available. The first connecting segment is used to collect current at the edge and transmit it to the second welding part. That is, the current on the first connecting segment is larger along the direction closer to the second welding part, and the width of the first connecting segment gradually increases along the direction closer to the second welding part, adapting to the trend of current change from far away from the second welding part to near the second welding part. This design can reduce the loss of current when it moves from far away from the second welding part to near the second welding part and improve the power generation efficiency of the back contact battery.

[0028] In one possible design, the width of the first connecting segment at the end closer to the second welding part is L3, and the width at the end farther from the second welding part is L4.

[0029] 0.15mm≤L3≤0.35mm, 0.05mm≤L4≤0.25mm, and / or;

[0030] The ratio of L3 to L4 satisfies: 1.2≤L3:L4≤5.

[0031] In this design, when L3 is too small, the width of the first connection segment is insufficient, resulting in weak current carrying capacity and a risk of localized overheating and cracking. When L3 is too large, the solder coverage area is too large, increasing the risk of short circuits in adjacent circuits and affecting the power generation efficiency of the back contact battery. When L4 is too small, the first connection segment has weak resistance to edge stress, increasing the risk of breakage. When L4 is too large, excessive solder is used at the edges, resulting in solder waste. In this application, a lower limit of L3 of 0.15mm ensures the necessary current-carrying cross-section in the high-current region, preventing localized overheating; an upper limit of L3 of 0.35mm reduces the risk of solder overflow and short circuits; a lower limit of L4 of 0.05mm ensures the conductivity reliability of the thinnest part of the first connection segment, reducing the risk of breakage; and an upper limit of L4 of 0.25mm provides a moderate welding area, avoiding solder waste.

[0032] When L3:L4 is too small, the width change is too slow, resulting in insufficient coordination with the current increase and a tendency for some areas to overheat. When L3:L4 is too large, the width increases too rapidly, requiring more solder during welding. Solder buildup can easily cause short circuits, affecting the power generation efficiency of the back contact battery. The solution provided in this application limits L3:L4 to 1.2 to 5, matching the width change with the current density change. This effectively reduces heat loss during current transmission and avoids short circuits caused by solder buildup, thereby improving the power generation efficiency of the back contact battery.

[0033] Furthermore, L3 and L4 can simultaneously satisfy 0.15mm≤L3≤0.35mm, 0.05mm≤L4≤0.25mm, and 1.2≤L3:L4≤5.

[0034] In one possible design, the gate line includes a plurality of second gate lines that extend along a second direction and are spaced apart along a first direction, and the second gate lines are electrically connected to the first gate line or the welded portion;

[0035] Along the direction away from the second weld portion, the size of the second grid line located on the side of the second weld portion away from the first weld portion gradually increases along the second direction.

[0036] In this design, since the second grid line is not connected to the first grid line with opposite polarity, the second grid line is disconnected on both sides of the first grid line with opposite polarity. Furthermore, because the width of the first connecting segment decreases in the direction away from the second weld, the unused area in the second direction on both sides of the first connecting segment increases in the direction away from the second weld. Therefore, the area where the second grid line with opposite polarity can extend in the second direction increases, and the size of the second grid line can gradually increase in the second direction. The increased size of the second grid line increases its current-collecting area, enhancing its current-collecting capability and further improving the power generation efficiency of the back-contact battery.

[0037] In one possible design, the gate line includes a plurality of second gate lines, which extend along a second direction and are arranged along a first direction. The second gate lines are electrically connected to the first gate line or the welded part. The second gate line located at the outermost edge of the substrate is an edge gate line, and the remaining second gate lines are intermediate gate lines. The edge gate lines are a continuous structure, and the intermediate gate lines are broken at the positions of the first gate lines with different polarities.

[0038] The first gate line with the same polarity as the edge gate line is electrically connected to the edge gate line, and the first gate line with a different polarity from the edge gate line is connected to the edge gate line or not connected to the edge gate line through insulating adhesive.

[0039] In this design, the edge grid lines are a continuous structure, increasing the current collection area of ​​the edge grid lines. Insulating adhesive is used to insulate the edge grid lines from the first grid lines of different polarity, or to prevent the first grid lines of different polarity from connecting to the edge grid lines. This increases the current collection area while avoiding short circuits, further improving the power generation efficiency of the back contact battery.

[0040] This application provides a back-contact stacked battery, which includes a top cell and a bottom cell connected to each other. The top cell is a perovskite cell, and the bottom cell is a back-contact cell, wherein the back-contact cell is a back-contact cell according to any of the above-mentioned embodiments.

[0041] In this scheme, the back-contact tandem solar cell can be a three-terminal tandem solar cell. During the fabrication of the back-contact tandem solar cell, the top and bottom cells can be connected by directly depositing a perovskite top cell on the bottom cell. Compared to monocrystalline silicon solar cells, back-contact tandem solar cells have higher efficiency and power generation. Furthermore, back-contact tandem bottom cells using a back-contact cell as the bottom cell offer advantages such as no current mismatch, high process tolerance, and wide applicability. Simultaneously, compared to two-terminal tandem solar cells, the three-terminal tandem solar cell formed by the perovskite cell and the back-contact cell can have an additional electrode to output mismatch current, which helps ensure relatively higher power operation of the back-contact tandem solar cell, and the voltage matching requirements are less affected by solar spectrum changes than the current requirements. When the back-contact cell is used as the bottom cell, a two-terminal series structure can be constructed by using electrodes with opposite contact polarities, achieving a conversion from three-terminal to two-terminal. The back-contact cell has a textured surface; conformal deposition and growth of perovskite on this textured surface improves the utilization of incident light. Back-contact tandem cells, made using perovskite solar cells and back-contact solar cells, do not require current matching considerations and have high tolerance for the bandgap and thickness of perovskite. Three-terminal back-contact tandem cells have a wider range of applications, enabling high-power operation in various outdoor environments and better meeting practical usage needs.

[0042] This application provides a photovoltaic module, which includes at least one battery string, the battery string including any of the back-contact batteries described above or the back-contact stacked batteries described above.

[0043] In this scheme, photovoltaic modules can achieve photoelectric conversion, thereby converting the energy of sunlight into direct current (DC) electricity. A DC-DC converter can obtain electrical energy from the photovoltaic modules and output it after voltage conversion. An inverter can receive the electrical energy output from the DC-DC converter and convert it into alternating current (AC). The AC electricity is then output to the power grid through a grid-connected transformer, thus achieving grid connection of the photovoltaic power generation system.

[0044] 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

[0045] Figure 1 This is a schematic diagram of the back contact battery structure in this application;

[0046] Figure 2 for Figure 1 Enlarged view of the structure of section A;

[0047] Figure 3 for Figure 1 Enlarged view of the structure of section B;

[0048] Figure 4 This is a schematic diagram of the structure at the edge of the back contact battery substrate in this application.

[0049] Figure 5 This is a schematic diagram of the back contact stacked battery structure in this application;

[0050] Figure 6 This is a schematic diagram of the stacked battery with back contact in this application.

[0051] Explanation of reference numerals in the attached figures:

[0052] 1-Back contact stacked battery;

[0053] 11-Protective layer;

[0054] 12-Transparent conductive layer;

[0055] 13-Electron transport layer;

[0056] 14-Perovskite layer;

[0057] 15-Hole transport layer;

[0058] 16-Composite layer;

[0059] 17-Back contact battery;

[0060] 171-Base;

[0061] 172-grid line;

[0062] 1721 - First grid line;

[0063] 1721a - First connecting segment;

[0064] 1721b - Second connecting section;

[0065] 1722 - Second grid line;

[0066] 1722a - Edge grid line;

[0067] 1722b - Intermediate grid line;

[0068] 173 - Welding section;

[0069] 1731 - First Welding Section;

[0070] 1732 - Second Welding Section;

[0071] 18-Perovskite solar cells;

[0072] X - First direction;

[0073] Y - Second direction.

[0074] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. Detailed Implementation

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] As a renewable and clean energy source, solar energy has led to extensive research into photovoltaic (PV) power generation technology, resulting in the rapid development of the PV power generation industry in recent years. A typical PV power generation system includes multiple components such as PV modules, DC-DC converters, and inverters. PV modules perform photoelectric conversion, transforming the energy of sunlight into direct current (DC) electricity. DC-DC converters collect electricity from the PV modules and convert the voltage before outputting it. Inverters receive the electricity from the DC-DC converters and convert it into alternating current (AC) electricity. The AC electricity is then fed into the grid via a grid-connected transformer, thus connecting the PV power generation system to the grid. PV modules are the core component of a PV power generation system. A PV module includes at least one cell string, which contains multiple cells, such as back-contact cells or back-contact tandem cells.

[0080] BC battery stands for back contact battery. Its basic type is IBC battery (interdigitated back contact battery). The biggest difference between it and other crystalline silicon battery routes is that the emitter, surface field and metal electrode are all made on the back of the battery and are interdigitated. There are no grid lines to block the front surface of the battery, which maximizes the use of incident light, reduces optical loss, brings more effective power generation area, has high conversion efficiency, and is more aesthetically pleasing.

[0081] The structure that carries current in a solar cell is the grid line, a series of metal lines located on the surface of the cell. These are essential components of a photovoltaic cell, serving to collect and transport electrons. These grid lines are typically made of silver, aluminum, or other conductive materials and are printed or deposited onto the silicon wafer surface of the solar cell. When a photovoltaic cell is operating, sunlight shines on the silicon wafer, and the silicon material converts light energy into electrical energy, generating electrons and holes. The grid lines' role is to quickly guide these electrons to the edges of the cell so that they can be collected and utilized by external circuitry.

[0082] Specifically, there are two types of grid lines: the thicker ones are the main grid lines, which are wider metal lines responsible for collecting current from the fine grid lines and transmitting it to the battery's output. The thinner ones are the fine grid lines, which are thinner metal lines that extend from the main grid lines to the region of the battery where electron-hole pairs are generated, helping to collect electrons dispersed throughout the battery surface.

[0083] This application provides a back contact battery 17, which improves the efficiency of the back contact battery 17 by designing the welding portion 173 on the grid line 172.

[0084] This application provides a back contact battery 17, such as Figure 1 , Figure 2 As shown, the back contact battery 17 includes a substrate 171 and grid lines 172, with the grid lines 172 disposed on the substrate 171; wherein, the grid lines 172 include a first grid line 1721, the first grid line 1721 is disposed along a first direction X, the first grid line 1721 is provided with a welding portion 173, the welding portion 173 includes a plurality of first welding portions 1731 and two second welding portions 1732, along the length direction of the first grid line 1721, the second welding portions 1732 are located at both ends of the first grid line 1721, and the first welding portions 1731 are located between the two second welding portions 1732;

[0085] Along the length of the first grid line 1721, the size of the second welded portion 1732 is larger than the size of the first welded portion 1731, and along the direction closer to the second welded portion 1732, the area of ​​the first welded portion 1731 gradually increases.

[0086] In this embodiment, the first grid line 1721 serves as the main grid line 172 of the back contact battery 17 of this application embodiment. The second welding portion 1732 transmits current to the output terminal of the back contact battery 17. The collected current is output through the second welding portion 1732. Therefore, the grid line 172 closer to the second welding portion 1732 has a larger current. According to the resistance law formula R = ρL / S, where R is the resistance value, ρ is the resistivity of the material, L is the length of the conductor, and S is the cross-sectional area of ​​the conductor. According to the formula, the larger the cross-sectional area S of the conductor, the smaller the resistance R. That is, the larger the area of ​​the welding portion 1732, the smaller its resistance. Therefore, the size of the second welding part 1732 is larger than that of the first welding part 1731, and the area of ​​the first welding part 1731 gradually increases along the direction close to the second welding part 1732. That is, the closer to the second welding part 1732, the smaller the resistance of the first welding part 1731. By reducing the resistance, the loss of current flowing through each first welding part 1731 and conducted to the second welding part 1732 can be reduced, thereby improving the working efficiency of the back contact battery 17.

[0087] The second welding portion 1732 located at both ends of the first grid line 1721 is larger in size, which can significantly enhance the connection strength of the edge area of ​​the first grid line 1721 and the connection stability between the first grid line 1721 and the welding strip, effectively reducing the risk of warping and deformation caused by heat generated during the power generation process of the back contact battery 17, and ensuring the stability and reliability of the back contact battery 17.

[0088] Meanwhile, the area of ​​the first welding part 1731 near the second welding part 1732 gradually increases, which can improve its welding area with the welding strip, reduce the risk of false welding and missing welding, thereby improving the connection effect between the end first welding part 1731 and the back contact battery 17, and improving the performance of the back contact battery 17.

[0089] like Figure 1 As shown, the distribution of the first welded part 1731 between the two second welded parts 1732 at both ends exhibits a characteristic of being smaller in the middle and larger on both sides.

[0090] Specifically, the gate line 172 also includes a plurality of second gate lines 1722. The second gate lines 1722 extend along the second direction Y and are spaced apart along the first direction X. The second gate lines 1722 are electrically connected to the first gate line 1721 or the welding part 173. Along the first direction X, the polarities of adjacent second gate lines 1722 are opposite, and the polarities of adjacent first gate lines 1721 are opposite. The second gate lines 1722 are broken at the first gate lines 1721 with opposite polarities.

[0091] The second gate line 1722 is used to collect current in the second direction Y. The current collected by the second gate line 1722 flows into the first gate line 1721 at the first welded part 1731 and the second welded part 1732. The first gate line 1721 and the second gate line 1722 are connected with the same polarity, and the first gate line 1721 and the second gate line 1722 are not connected with the opposite polarity to avoid short circuit.

[0092] In some embodiments, such as Figure 1 As shown, along the second direction Y, at least one first welded portion 1731 has a larger dimension than the second welded portion 1732.

[0093] In this embodiment, along the second direction Y, at least one first weld portion 1731 has a larger size than the second weld portion 1732. Since the current on the first gate line 1721 increases along the direction close to the second weld portion 1732, the first weld portion 1731 with its larger size along the second direction Y can significantly improve the current conduction capability at the end of the first gate line 1721, adapt to the current carrying requirements of the high current density region, ensure the reliability of current conduction near the second weld portion 1732, and further improve the mechanical support strength at the edge, reducing the occurrence of stress concentration at the edge.

[0094] Meanwhile, if the size of the first welding part 1731 along the first direction X is large, it is easy for the first welding part 1731 to be connected with the second grid line 1722 with opposite polarity in the first direction X, which may cause a short circuit. Improving the first welding part 1731 along the second direction Y can prevent the occurrence of short circuit while ensuring current transmission efficiency, thereby improving the stability and reliability of the back contact battery 17.

[0095] In some embodiments, such as Figure 2 As shown, the dimensional difference C between adjacent first welded portions 1731 along the second direction Y satisfies 0.008mm≤C≤0.015mm. For example, C can be: 0.008mm, 0.009mm, 0.01mm, 0.011mm, 0.012mm, 0.013mm, 0.014mm, or 0.015mm.

[0096] When the difference C between adjacent first welded portions 1731 along the second direction Y is small, the dimensional change of the adjacent first welded portions 1731 cannot adapt to the increase in current, resulting in insufficient effective current-carrying area in the high-density current region, local temperature rise, and electrical energy being converted into heat energy and dissipated. At the same time, the stress dispersion effect is weakened, the strength of the back contact battery 17 is reduced, and risks such as cracking are more likely to occur. When the difference C between adjacent first welded portions 1731 along the second direction Y is large, the larger first welded portion 1731 requires more solder, resulting in solder waste. Moreover, excessive solder is prone to flow during the welding process, increasing the risk of overflow and easily causing short circuits. In this embodiment, the dimensional difference C between adjacent first welded portions 1731 along the second direction Y is limited to the range of 0.008mm to 0.015mm. The dimensional variation between adjacent first welded portions 1731 is moderate, and the change in resistance adapts to the growth characteristics of the current during the convergence process of the second welded portion 1732, effectively reducing the heat loss of the current. The dimensional difference within this range can effectively disperse stress, improve the strength of the back contact battery 17, reduce the risk of crack formation, and control the fluidity of the solder during the welding process, ensuring a good welding effect and reducing the risk of short circuit.

[0097] Furthermore, the dimensions of adjacent first welded portions 1731 vary arithmetically along the second direction Y.

[0098] In this embodiment, since a second grid line 1722 is connected to only one welding part 173 on a first grid line 1721, and the current collected by the second grid line 1722 flows into the first grid line 1721 through the welding part 173, the current between adjacent first welding parts 1731 on the first grid line 1721, along the direction close to the second welding part 1732, approximately exhibits an arithmetic progression distribution. The first welding parts 1731, whose dimensions change arithmetically along the second direction Y, can better adapt to the current growth gradient, match the current variation pattern, significantly reduce power loss, and optimize performance. Furthermore, the arithmetically changing first welding parts 1731 can form a uniform stress distribution, further improving the strength of the back contact battery 17.

[0099] In some embodiments, such as Figure 1 As shown, the minimum dimension of the first welded part 1731 along the second direction Y is L1, and the maximum dimension of the first welded part 1731 along the second direction Y is L2; ​​wherein, L1 and L2 satisfy: 0.6mm≤L2≤1.4mm, 0.2mm≤L1≤0.6mm. For example, L2 can be: 0.6mm, 0.65mm, 0.7mm, 0.75mm, 0.8mm, 0.85mm, 0.9mm, 0.95mm, 1mm, 1.05mm, 1.1mm, 1.15mm, 1.2mm, 1.25mm, 1.3mm, 1.35mm, 1.4mm, etc.

[0100] L1 can be: 0.2mm, 0.25mm, 0.3mm, 0.35mm, 0.4mm, 0.45mm, 0.5mm, 0.55mm, 0.6mm, etc.

[0101] When L1 is too small, the insufficient cross-sectional area of ​​the minimum welding zone leads to severe localized heating when current passes through, resulting in excessive current loss, and the back contact battery 17 is prone to deformation due to overheating. When L1 is too large, the first welding portion 1731 in the middle becomes too large, and as it increases in size towards the second welding portion 1732, the excessive size of the first welding portion 1731 causes material waste, and excessive use of solder ribbon during welding increases the risk of short circuits. When L2 is too small, the size of the first welding portion 1731 is too small to bear the dense current, causing severe heating at the edges and increasing the risk of warping and deformation. When L2 is too large, the excessive area of ​​the first welding portion 1731 results in insufficient spacing between adjacent solder joints, making it easy for it to come into contact with the second grid line 1722 with opposite polarity during welding, increasing the risk of short circuits.

[0102] In this embodiment, L2 is limited to 0.6mm to 1.4mm, and L1 is limited to 0.2mm to 0.6mm. The lower limit of L1 of 0.2mm can ensure that the minimum welding area maintains the necessary current conduction cross section and avoid excessive local current density due to the small size. The upper limit of L1 of 0.6mm prevents the first welding part 1731 located in the middle area between the two second welding parts 1732 from being excessively redundant, and ensures the adaptability of the area of ​​the welding part 173 to the changes in current magnitude.

[0103] The lower limit of L2 (0.6mm) ensures a safe current-carrying margin in the area with higher current density near the second welding section 1732; the upper limit of L2 (1.4mm) reduces the risk of short circuits caused by excessive solder buildup due to an excessively large welding area. This design allows the area of ​​the first welding section 1731 to precisely adapt to the current density variation from the center to the edge of the back contact battery 17, reducing current loss and improving the reliability and stability of the welding.

[0104] like Figure 1 As shown, the width of the center weld point is L1, which is the smallest weld point along the second direction Y, and the width of the weld points at both ends is L2, which is the largest weld point along the second direction Y. The weld points at both ends are the first weld parts 1731 closest to the second welded parts 1732, and the center weld point is the first weld part 1731 closest to the center of the line connecting the two second welded parts 1732.

[0105] The ratio of L2 to L1 can also satisfy: 1.5 ≤ L2 : L1 ≤ 7. For example, the ratio of L2 : L1 can be: 1.5, 2, 2.5, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, etc.

[0106] When the L2:L1 ratio is too small, insufficient size gradient leads to a mismatch between current carrying capacity and current growth rate, making local areas prone to overheating due to excessive current, thus increasing the risk of chip cracking. When the L2:L1 ratio is too large, the variation between adjacent dimensions is too large, resulting in an excessively large area of ​​the first welding portion 1731 on both sides, which can easily cause solder accumulation and short circuit of the back contact battery 17. In this embodiment, L2:L1 is limited to 1.5 to 7. This ensures that the area variation of the first welding portion 1731 matches the current magnitude variation, reducing current heat loss, and avoids the risk of solder accumulation due to an excessively large welding portion 1731 area, thereby improving welding reliability.

[0107] Furthermore, L1 and L2 can simultaneously satisfy 0.6mm≤L2≤1.4mm, 0.2mm≤L1≤0.6mm, and 1.5≤L2:L1≤7. The resulting technical advantages are a combination of the advantages mentioned above, which will not be elaborated here.

[0108] In some embodiments, the number of first welding parts 1731 is 3 to 80. For example, the number of first welding parts 1731 can be: 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, etc.

[0109] When the number of first welded portions 1731 is too small, the spacing between adjacent first welded portions 1731 is too large, resulting in an excessively long current transmission path, excessive current accumulation, and a tendency to generate localized high temperatures. Furthermore, the stress dispersion effect of the welded portions 173 is weakened, making them prone to cracking. When the number of first welded portions 1731 is too large, the spacing between adjacent welded portions 173 is too small, significantly increasing the risk of short circuits due to solder overflow during welding, thus reducing the power generation efficiency of the back contact battery 17. In this embodiment, the number of first welded portions 1731 is limited to 3 to 80, ensuring the necessary minimum node density of the current transmission path, avoiding excessively high local temperatures, and ensuring sufficient spacing between adjacent first welded portions 1731 to prevent short circuits during welding, thereby improving the power generation efficiency and lifespan of the back contact battery 17.

[0110] In some embodiments, such as Figure 3 As shown, the first grid line 1721 includes a first connecting segment 1721a and a second connecting segment 1721b. The first connecting segment 1721a is located on the side of the second connecting portion away from the first welding portion 1731. The second connecting segment 1721b is used to connect the first welding portion 1731 and the second welding portion 1732, or an adjacent first welding portion 1731.

[0111] Along the direction away from the second welded part 1732, the width of the first connecting section 1721a gradually decreases.

[0112] Since the second weld portion 1732 is far from the first weld portion 1731, and the first connecting segment 1721a is relatively short, it is inconvenient to install the first weld portion 1731 on the side of the grid line 172. The first connecting segment 1721a is used to collect the current at the edge and transmit the current to the second weld portion 1732. That is, the current on the first connecting segment 1721a is larger along the direction closer to the second weld portion 1732, and the width of the first connecting segment 1721a gradually increases along the direction closer to the second weld portion 1732, adapting to the trend of current change from away from the second weld portion 1732 to closer to the second weld portion 1732. This design can reduce the current loss when the current changes from away from the second weld portion 1732 to closer to the second weld portion 1732, and improve the power generation efficiency of the back contact battery 17.

[0113] Specifically, the width of the first connecting segment 1721a at the end near the second welding part 1732 is L3, and the width of the end away from the second welding part 1732 is L4; 0.15mm≤L3≤0.35mm, 0.05mm≤L4≤0.25mm. For example, L3 can be: 0.15mm, 0.18mm, 0.21mm, 0.24mm, 0.25mm, 0.27mm, 0.28mm, 0.3mm, 0.31mm, 0.33mm, 0.34mm, 0.35mm, etc. L4 can be: 0.05mm, 0.08mm, 0.09mm, 0.1mm, 0.13mm, 0.14mm, 0.15mm, 0.17mm, 0.19mm, 0.2mm, 0.24mm, 0.25mm, etc.

[0114] When L3 is too small, the width of the first connection segment 1721a is insufficient, resulting in weak current carrying capacity and a risk of localized overheating and cracking. When L3 is too large, the solder coverage area is too large, increasing the risk of short circuits in adjacent circuits and affecting the power generation efficiency of the back contact battery 17. When L4 is too small, the first connection segment 1721a has weak resistance to edge stress, increasing the risk of breakage. When L4 is too large, excessive solder is used at the edges, resulting in solder waste. In this embodiment, a lower limit of L3 of 0.15mm ensures that the high-current area has the necessary current-carrying cross-section, avoiding localized overheating; an upper limit of L3 of 0.35mm reduces the risk of solder overflow and the occurrence of short circuits; a lower limit of L4 of 0.05mm ensures the conductivity reliability of the thinnest part of the first connection segment 1721a, making it less prone to breakage; and an upper limit of L4 of 0.25mm provides a moderate welding area, avoiding solder waste.

[0115] The ratio of L3 to L4 satisfies: 1.2 ≤ L3:L4 ≤ 5. For example, L3:L4 can be: 1.2, 1.5, 1.8, 1.9, 2.0, 2.4, 2.8, 3.0, 3.5, 3.8, 3.9, 4.0, 4.2, 4.4, 4.6, 4.8, 5.0.

[0116] When L3:L4 is too small, the width change is too slow, resulting in insufficient coordination with the current increase process and a tendency for some areas to overheat. When L3:L4 is too large, the width increases too quickly, requiring more solder during welding. Solder buildup can easily cause short circuits, affecting the power generation efficiency of the back contact battery 17. The solution provided in this application limits L3:L4 to 1.2 to 5, matching the width change with the current density change. This effectively reduces heat loss during current transmission and avoids short circuits caused by solder buildup, thereby improving the power generation efficiency of the back contact battery 17.

[0117] Furthermore, L3 and L4 can simultaneously satisfy 0.15mm≤L3≤0.35mm, 0.05mm≤L4≤0.25mm, and 1.2≤L3:L4≤5. The resulting technical advantages are a combination of the advantages mentioned above, which will not be elaborated here.

[0118] In some embodiments, along the direction away from the second weld portion 1732, the size of the second gate line 1722 located on the side of the second weld portion 1732 away from the first weld portion 1731 gradually increases along the second direction Y.

[0119] Since the second grid line 1722 is not connected to the first grid line 1721 with opposite polarity, the second grid line 1722 is disconnected on both sides of the first grid line 1721 with opposite polarity. Furthermore, because the width of the first connecting segment 1721a decreases in the direction away from the second weld portion 1732, the empty area on both sides of the first connecting segment 1721a in the second direction Y increases in the direction away from the second weld portion 1732. At this time, the area where the second grid line 1722 with opposite polarity can extend in the second direction Y increases, and the size of the second grid line 1722 can gradually increase along the second direction Y. The increased size of the second grid line 1722 increases its current-collecting area, enhancing its current-collecting capability and further improving the power generation efficiency of the back contact battery 17.

[0120] In some embodiments, the second gate line 1722 located at the outermost edge of the substrate 171 is an edge gate line 1722a, and the remaining second gate lines 1722 are intermediate gate lines 1722b. The edge gate line 1722a has a continuous structure, and the intermediate gate line 1722b is broken at the position of the first gate line 1721 with a different polarity. The first gate line 1721 with the same polarity as the edge gate line 1722a is electrically connected to the edge gate line 1722a, and the first gate line 1721 with a different polarity than the edge gate line 1722a is connected to the edge gate line 1722a or not connected to the edge gate line 1722a through insulating adhesive.

[0121] In this embodiment, the edge grid line 1722a has a continuous structure, which increases the current collection area of ​​the edge grid line 1722a. Insulating glue is used to insulate the edge grid line 1722a from the first grid line 1721 with different polarity, or to prevent the first grid line 1721 with different polarity from being connected to the edge grid line 1722a. This increases the current collection area while avoiding short circuits, further improving the power generation efficiency of the back contact battery 17.

[0122] This application embodiment also provides a back-contact stacked battery 1, such as Figure 5 As shown, the back-contact tandem solar cell 1 includes a top cell and a bottom cell electrically connected to each other. The top cell is a perovskite cell 18, and the bottom cell is a back-contact cell 17, wherein the back-contact cell 17 can be any of the back-contact cells 17 involved in the above embodiments. The back-contact tandem solar cell 1 can be a three-terminal tandem solar cell. When processing the back-contact tandem solar cell 1, the top cell and the bottom cell can be connected by directly depositing the perovskite top cell on the bottom cell. Compared with single-crystal silicon solar cells, the back-contact tandem solar cell 1 has higher efficiency and power generation. Moreover, the back-contact tandem bottom cell using the back-contact cell 17 as the bottom cell has advantages such as no current mismatch, high process tolerance, and wide application scenarios. At the same time, compared with two-terminal tandem solar cells, the three-terminal tandem solar cell formed by the perovskite cell 18 and the back-contact cell 17 can have an additional electrode 7 to output the mismatch current, which is beneficial to ensure that the back-contact tandem solar cell 1 can operate at a relatively higher power, and the required voltage matching is less affected by changes in the solar spectrum than the current. When the back contact cell 17 is used as the bottom cell, a two-terminal series structure can be constructed by connecting electrodes 7 with opposite polarities, enabling a conversion from three-terminal to two-terminal operation. The back contact cell 17 has a textured surface, allowing for conformal deposition and growth of perovskite, which improves the utilization of incident light. The back contact tandem cell 1, made using the perovskite cell 18 and the back contact cell 17, eliminates the need for current matching and exhibits high tolerance for perovskite bandgap and thickness. The three-terminal back contact tandem cell 1 has a wider range of applications, enabling high-power operation in various outdoor environments and better meeting practical usage needs.

[0123] like Figure 6As shown, in one possible embodiment, the back contact stacked battery 1 consists of, from top to bottom, a protective layer 11, a transparent conductive layer 12, an electron transport layer 13, a perovskite layer 14, a hole transport layer 15, a composite layer 16, and a back contact battery 17. The transparent conductive layer 12 (transparent conductive oxide, TCO) can be an indium tin oxide layer.

[0124] The above descriptions are merely specific implementations of the embodiments of this application, but the protection scope of the embodiments of this application is not limited thereto. Any changes or substitutions within the technical scope disclosed in the embodiments of this application should be covered within the protection scope of the embodiments of this application. Therefore, the protection scope of the embodiments of this application should be determined by the protection scope of the claims.

Claims

1. A back-contact battery, characterized in that, include: Base (171); A grid line (172) is disposed on the substrate (171); The gate line (172) includes a first gate line (1721), which is arranged along a first direction (X). The first gate line (1721) is provided with a welding portion (173). The welding portion (173) includes a plurality of first welding portions (1731) and two second welding portions (1732). Along the length direction of the first gate line (1721), the second welding portions (1732) are located at opposite ends of the first gate line (1721), and the first welding portions (1731) are located between the two second welding portions (1732). Along the length of the first grid line (1721), the size of the second welded part (1732) is larger than the size of the first welded part (1731), and along the direction close to the second welded part (1732), the area of ​​the first welded part (1731) gradually increases.

2. The back contact battery according to claim 1, characterized in that, Along the second direction (Y), at least one of the first welded portions (1731) has a larger size than the second welded portion (1732).

3. The back contact battery according to claim 1, characterized in that, The dimensional difference C between adjacent first welded portions (1731) along the second direction (Y) satisfies 0.008mm≤C≤0.015mm.

4. The back contact battery according to claim 3, characterized in that, The dimensions of adjacent first welded portions (1731) vary arithmetically along the second direction (Y).

5. The back contact battery according to claim 1, characterized in that, The minimum dimension of the first welded part (1731) along the second direction (Y) is L1, and the maximum dimension of the first welded part (1731) along the second direction (Y) is L2; 0.6mm≤L2≤1.4mm, 0.2mm≤L1≤0.6mm, and / or; The ratio of L2 to L1 satisfies: 1.5 ≤ L2 : L1 ≤ 7.

6. The back contact battery according to claim 1, characterized in that, The number of the first welded parts (1731) is 3 to 80.

7. The back contact battery according to any one of claims 1 to 6, characterized in that, The first grid line (1721) includes a first connecting segment (1721a) and a second connecting segment (1721b). The first connecting segment (1721a) is located on the side of the second welded part (1732) away from the first welded part (1731). The second connecting segment (1721b) is used to connect the first welded part (1731) and the second welded part (1732) or an adjacent first welded part (1731). Along the direction away from the second welded part (1732), the width of the first connecting section (1721a) gradually decreases.

8. The back contact battery according to claim 7, characterized in that, The width of the first connecting segment (1721a) at the end near the second welding part (1732) is L3, and the width at the end away from the second welding part (1732) is L4; 0.15mm≤L3≤0.35mm, 0.05mm≤L4≤0.25mm, and / or; The ratio of L3 to L4 satisfies: 1.2≤L3:L4≤5.

9. The back contact battery according to claim 7, characterized in that, The gate line (172) includes a plurality of second gate lines (1722), which extend along a second direction (Y) and are spaced apart along a first direction (X). The second gate lines (1722) are electrically connected to the first gate line (1721) or the welding part (173). Along the direction away from the second weld portion (1732), the size of the second grid line (1722) located on the side of the second weld portion (1732) away from the first weld portion (1731) gradually increases along the second direction (Y).

10. The back contact battery according to any one of claims 1 to 6, characterized in that, The gate line (172) includes a plurality of second gate lines (1722), which extend along a second direction (Y) and are arranged along a first direction (X). The second gate lines (1722) are electrically connected to the first gate line (1721) or the welding part (173). The second gate line (1722) located at the outermost edge of the substrate (171) is the edge gate line (1722a), and the remaining second gate lines (1722) are the middle gate lines (1722b). The edge gate line (1722a) is a continuous structure, and the middle gate line (1722b) is broken at the position of the first gate line (1721) with different polarity. The first gate line (1721) with the same polarity as the edge gate line (1722a) is electrically connected to the edge gate line (1722a), and the first gate line (1721) with a different polarity from the edge gate line (1722a) is connected to the edge gate line (1722a) or not connected to the edge gate line (1722a) through insulating adhesive.

11. A back-contact stacked battery, characterized in that, The back-contact stacked battery includes a top battery and a bottom battery connected to each other. The top battery is a perovskite battery (18), and the bottom battery is a back-contact battery (17). The back-contact battery (17) is the back-contact battery (17) according to any one of claims 1 to 10.

12. A photovoltaic module, characterized in that, The photovoltaic module includes at least one battery string, the battery string including a back-contact battery (17) according to any one of claims 1 to 10 or a back-contact tandem battery (1) according to claim 11.

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