Back contact cell, back contact photovoltaic module and preparation method thereof

Abstract

The present application relates to the technical field of photovoltaic modules, and particularly relates to a back contact cell, a back contact photovoltaic module and a preparation method thereof. The back contact cell comprises a cell substrate, a bus electrode and a current collecting electrode. The bus electrode is provided with a bifurcated structure. The bifurcated structure comprises at least one connecting part extending to the side of the bus electrode. The connecting part is used for electrical connection with the current collecting electrode of the same polarity. A welding blank area is formed between each connecting part of the bifurcated structure and / or between the connecting part and the main body of the bus electrode. The spacing between the connecting part and the current collecting electrode of the opposite polarity located on the side of the bus electrode ranges from 0.4 mm to 0.8 mm. The back contact photovoltaic module comprises the above-mentioned back contact cell. The preparation method of the back contact photovoltaic module is used for preparing the above-mentioned back contact photovoltaic module. The present application provides a back contact cell, a back contact photovoltaic module and a preparation method of the back contact photovoltaic module, so that the end of the solder strip cannot be welded and fixed with the electrode, and cannot also be short-circuited with the electrode of the opposite polarity.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic module technology, and in particular to a back-contact solar cell, a back-contact photovoltaic module, and a method for preparing the same. Background Technology

[0002] As a core component of clean energy, solar cells are evolving from bifacial contact cells to back-contact cells (BC cells). Back-contact cells place both positive and negative electrodes on the back of the cell, eliminating light loss due to shading by the front grid lines and resulting in higher photoelectric conversion efficiency.

[0003] In the process of packaging back-contact batteries, solder ribbons need to be welded to the positive and negative electrodes on the back of the battery to achieve series connection of the battery cells. It is important that the ends of the solder ribbons are left free and not welded to the electrodes. This allows the welding thermal stress and mechanical stress generated by thermal cycling to be released through the free expansion and contraction of the solder ribbon ends, preventing stress concentration that could lead to microcracks or breakage on the battery cells.

[0004] In addition, since the positive and negative electrodes of the back contact battery are located on the same plane, it is necessary to ensure that the solder ribbon does not short-circuit with the opposite electrode during welding, that is, it is necessary to ensure that the end of the solder ribbon does not short-circuit with the opposite electrode.

[0005] In summary, ensuring that the end of the solder ribbon is not fixed to the electrode after being soldered to the electrode, nor short-circuited with the opposite electrode, has become a key issue that urgently needs to be addressed in the field of back contact battery technology. Summary of the Invention

[0006] The first objective of this invention is to provide a back-contact battery cell that at least prevents the end of the solder strip from being welded to the electrode or short-circuited to the opposite electrode.

[0007] A second objective of the present invention is to provide a back-contact photovoltaic module, so that the end of the solder strip will not be welded to the electrode or short-circuited with the opposite electrode.

[0008] A third objective of this invention is to provide a method for preparing a back-contact photovoltaic module, so as to further ensure that the end of the solder strip is not welded and fixed to the electrode, nor is it short-circuited with the opposite electrode.

[0009] Based on the aforementioned first objective, the present invention provides a back contact battery cell, including a battery substrate and an electrode disposed on the battery substrate. The electrode includes a bus electrode and a current collector electrode. At least one end of the bus electrode is provided with a bifurcated structure. The bifurcated structure includes at least one connecting portion extending to the side of the bus electrode. The connecting portion is used to electrically connect with the current collector electrode of the same polarity located on the side of the bus electrode. The connecting parts of the bifurcated structure and / or the connecting parts and the busbar electrode body form a welding blank area, which is an electrode-free area. The distance between the connecting portion and the current collector of opposite polarity located on the side of the bus electrode ranges from 0.4 mm to 0.8 mm.

[0010] Furthermore, along the extension direction perpendicular to the busbar electrode, the busbar electrode includes a side busbar electrode near the edge of the battery substrate and an intermediate busbar electrode located inside the side busbar electrode. The bifurcation structure on the side bus electrode includes a connecting portion that extends into the side bus electrode and connects to the current collector electrode of the same polarity on that side; and / or, the bifurcation structure on the middle bus electrode includes two connecting portions that extend to both sides of the middle bus electrode and connect to the current collector electrode of the same polarity on the same side.

[0011] Furthermore, when the bifurcated structure includes two connecting parts, the distance between the two connecting parts ranges from 0.4mm to 0.8mm.

[0012] Furthermore, along the extension direction of the bus electrode, the length of the welding blank area is S, the distance between two adjacent opposite current collectors is D, and satisfies: 3D≤S≤10D; And / or, the connection portion is spaced apart from the current collector electrode of opposite polarity located on the side of the current collector electrode.

[0013] Furthermore, along the extending direction of the bus electrode, the bus electrode includes an end gate and an intermediate gate located inside the end gate, the bifurcation structure is disposed on the end gate, and the connecting portion is electrically connected to the end gate; Wherein, the intermediate gate is a linear gate, which is arranged along the extension direction of the bus electrode; or the intermediate gate is a dot gate, including a plurality of connecting gate points, which are spaced apart along the extension direction of the bus electrode; or the intermediate gate is a composite gate formed by combining a linear gate and a dot gate.

[0014] Furthermore, when the intermediate gate is a linear gate, the linear gate is electrically connected to the collector electrode of the same polarity and is spaced apart from the collector electrode of the opposite polarity; When the intermediate gate is a dot-shaped gate, the connection gate point is located between the collector electrodes with the same polarity as the bus electrode, the collector electrodes are electrically connected through the connection gate point, and at the intermediate gate, there is a gap between the collector electrodes with the opposite polarity to the bus electrode.

[0015] By adopting the above technical solution, the back contact battery cell of the present invention has at least the following beneficial effects: It should be noted that the connecting part is used to electrically connect with the collector electrode of the same polarity located on the same side of the connecting part. That is, when only one side of the bus electrode has a collector electrode, the bifurcation structure includes only one connecting part, and the connecting part extends towards the collector electrode and forms an electrical connection with the collector electrode on this side; when both sides of the bus electrode have collector electrodes, the bifurcation structure includes two connecting parts, and the two connecting parts extend to both sides respectively and form an electrical connection with the collector electrode on the same side respectively.

[0016] In this configuration, when the bifurcation structure includes one connecting part, a welding blank area is formed between the connecting part and the main body of the busbar electrode; when the bifurcation structure includes two connecting parts, a welding blank area is formed between the two connecting parts. With this configuration, during the welding of the solder strip onto the busbar electrode, the solder strip is laid along the extension direction of the busbar electrode. When the solder strip reaches the end of the busbar electrode, because the connecting part extends laterally towards the busbar electrode, the solder strip will be laid in the welding blank area. The welding blank area is an electrode-free region, containing no busbar electrode. Therefore, the solder strip cannot be welded to the busbar electrode within the welding blank area. This allows the end of the solder strip to remain unwelded and unfixed to the busbar electrode. Consequently, the welding thermal stress and mechanical stress generated by thermal cycling can be released through the free expansion and contraction of the solder strip end, preventing stress concentration that could lead to microcracks or breakage on the battery cell.

[0017] In addition, the end of the solder strip is located in the electrode-free soldering blank area, so the solder strip will not come into contact with any electrode on the battery substrate, thus ensuring that the end of the solder strip will not short-circuit with the opposite electrode.

[0018] In summary, the back contact battery cell provided by the present invention ensures that after the solder strip is soldered to the electrode, the end of the solder strip will not be fixed to the electrode by welding, nor will it short-circuit with the opposite electrode.

[0019] Based on the second objective mentioned above, the present invention provides a back-contact photovoltaic module, which includes a solder strip and the aforementioned back-contact solar cell. The solder strip is connected to the busbar electrode, wherein the end portion of the solder strip is disposed in a welding blank area and is not welded to the busbar electrode.

[0020] Furthermore, the middle portion of the solder strip is spaced apart from the opposite polarity current collector electrode located on the side of the solder strip.

[0021] By adopting the above technical solution, the back-contact photovoltaic module of the present invention has at least the following beneficial effects: By incorporating the aforementioned back-contact solar cells within the back-contact photovoltaic module, the back-contact photovoltaic module thus possesses all the advantages of the aforementioned back-contact solar cells, which will not be elaborated upon here.

[0022] Based on the aforementioned third objective, the present invention provides a method for preparing a back-contact photovoltaic module, comprising: Laying the solder strip, the solder strip is laid on the bus electrode of the back contact cell, and the end portion of the solder strip is located in the welding blank area, and the middle portion is spaced apart from the opposite polarity current collectors located on both sides of the solder strip. The welding strip is welded to the bus electrode in the middle portion, while the end portion of the welding strip is not welded to the bus electrode.

[0023] Furthermore, the battery substrate of the back contact cell is provided with a solder pad, the solder pad is provided on the bus electrode, and the current collectors of the same polarity located on both sides of the solder strip are electrically connected through the solder pad; In the welding strip step, the middle part of the welding strip is welded to the bus electrode through the welding pad.

[0024] By adopting the above technical solution, the back-contact photovoltaic module manufacturing method of the present invention has at least the following beneficial effects: By using the back-contact photovoltaic module preparation method to prepare the aforementioned back-contact photovoltaic module, the back-contact photovoltaic module preparation method has all the advantages of the aforementioned back-contact photovoltaic module, which will not be elaborated here. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the structure of the back contact battery cell provided in an embodiment of the present invention; Figure 2 This is one of the enlarged partial structural views of the back contact battery cell provided in an embodiment of the present invention; Figure 3 for Figure 2 One of the schematic diagrams of a partial structure of the bus electrode in a back-contact solar cell; Figure 4 for Figure 2 The second schematic diagram of a partial structure of the bus electrode in the back contact cell is shown. Figure 5 for Figure 2 The diagram shows a structure with solder strips welded onto the back contact battery cell. Figure 6 This is the second enlarged view of a partial structure of the back contact battery cell provided in an embodiment of the present invention; Figure 7 for Figure 6 The diagram shows a partial structural schematic of the bus electrode in the back-contact solar cell.

[0027] Figure label: 1-Battery substrate; 2-Bus electrode; 21-Side bus electrode; 22-Intermediate bus electrode; 23-End gate; 24-Intermediate gate; 25-Connection gate point; 3-Collector; 4-Bifurcation structure; 41-Connecting part; 5- Welding blank area; 6-Welding strip; 61-End portion of welding strip; 62-Middle portion of welding strip; S - Length of the welding blank area; D - Spacing between two adjacent opposite current collector electrodes; L - Length of the bus electrode. Detailed Implementation

[0028] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0030] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0031] Please see Figure 1 and combined Figure 2 The present invention provides a back contact battery cell, which includes a battery substrate 1 and electrodes disposed on the battery substrate 1, the electrodes including a bus electrode 2 and a current collector electrode 3.

[0032] Please see below. Figure 3 At least one end of the bus electrode 2 is provided with a bifurcated structure 4. The bifurcated structure 4 includes at least one connecting portion 41 extending to the side of the bus electrode 2. The connecting portion 41 is used to electrically connect with a current collector 3 of the same polarity located on the side of the bus electrode 2. The connecting portions 41 of the bifurcated structure 4 and / or the connecting portions 41 and the body of the bus electrode 2 form a welding blank area 5, which is an electrode-free area.

[0033] It should be noted that the bus electrode 2 can be a pad, main gate, edge main gate, end line, etc., and the collector electrode 3 can be a fine gate. The connecting part 41 is used to electrically connect with the collector electrode 3 of the same polarity located on the same side of the connecting part 41. That is, when only one side of the two sides of the bus electrode 2 has a collector electrode 3, the bifurcation structure 4 includes only one connecting part 41, and the connecting part 41 extends towards the collector electrode 3 and forms an electrical connection with the collector electrode 3 on this side; when both sides of the bus electrode 2 have collector electrodes 3, the bifurcation structure 4 includes two connecting parts 41, and the two connecting parts 41 extend to both sides respectively and form an electrical connection with the collector electrode 3 on the same side respectively.

[0034] Among them, such as Figure 4 As shown, when the bifurcation structure 4 includes a connecting part 41, the connecting part 41 and the main body of the bus electrode 2 form a welding blank area 5; as Figure 3As shown, when the bifurcation structure 4 includes two connecting parts 41, a welding blank area 5 is formed between the two connecting parts 41. With this arrangement, during the welding of the solder strip 6 on the busbar electrode 2, the solder strip 6 is laid along the extension direction of the busbar electrode 2. When the solder strip 6 is laid to the end of the busbar electrode 2, since the connecting parts 41 extend to the side of the busbar electrode 2, the solder strip 6 will be laid in the welding blank area 5. The welding blank area 5 is an electrode-free area, and there is no busbar electrode 2 inside. Therefore, the solder strip 6 cannot be welded to the busbar electrode 2 in the welding blank area 5. This allows the end of the solder strip 6 to not be welded and fixed to the busbar electrode 2. Thus, the welding thermal stress and the mechanical stress generated by the thermal cycle can be released through the free expansion and contraction of the end of the solder strip 6, avoiding stress concentration that could lead to microcracks or breakage on the battery cell.

[0035] In addition, the end of the solder ribbon 6 is located in the electrode-free solder blank area 5, so the solder ribbon 6 will not come into contact with any electrode on the battery substrate 1, thus ensuring that the end of the solder ribbon 6 will not short-circuit with the opposite electrode.

[0036] In summary, the back contact battery cell provided by the present invention ensures that after the solder strip 6 is soldered to the electrode, the end of the solder strip 6 will not be fixed to the electrode by welding, nor will it short-circuit with the opposite electrode.

[0037] In addition, the distance between the connecting part 41 and the opposite polarity collector 3 located on the side of the bus electrode 2 is in the range of 0.4mm-0.8mm. For example, the distance between the connecting part 41 and the opposite polarity collector 3 located on the side of the bus electrode 2 is 0.4mm, 0.5mm, 0.6mm, 0.7mm or 0.8mm, etc.

[0038] This configuration ensures that the distance between the connecting part 41 and the opposite polarity current collector 3 located on the side of the bus electrode 2 is sufficient to prevent breakdown or short circuit between the electrodes, while also preventing the battery cell size from increasing due to excessive spacing, thus achieving a balance between insulation safety and miniaturization.

[0039] Specifically, the lower limit of the spacing range, 0.4 mm, takes into account the width of the solder strip and the deviation threshold of the welding process, ensuring that even if there is a certain misalignment during the welding process, the solder strip will not short-circuit with the opposite polarity electrode; the upper limit of the spacing range, 0.8 mm, avoids excessive spacing that would lead to an increase in cell size or waste of effective area. By limiting this range, the miniaturization of the cell design is achieved while ensuring the reliability of the welding process.

[0040] In the above embodiments, when the bifurcated structure 4 includes two connecting parts 41, the distance between the two connecting parts 41 is in the range of 0.4mm-0.8mm.

[0041] For example, the spacing between the two connecting parts 41 can be 0.4mm, 0.5mm, 0.6mm, 0.7mm, or 0.8mm. The lower limit of this spacing range, 0.4mm, takes into account the width of the solder strip and the deviation threshold of the welding process, ensuring that even with some alignment deviation during welding, the solder strip will not short-circuit or overlap with the connecting parts 41 on both sides. The upper limit of this spacing range, 0.8mm, avoids an excessively large spacing that would increase the area of ​​the welding blank area 5, thus ensuring the utilization rate of the effective area of ​​the solar cell. By limiting this numerical range, the reliability of the welding process is ensured while achieving a highly efficient design of the solar cell.

[0042] Optionally, in some embodiments of the present invention, one end of the bus electrode 2 is provided with a bifurcation structure 4, or both ends of the bus electrode 2 are provided with a bifurcation structure 4.

[0043] Preferably, both ends of the bus electrode 2 are provided with a bifurcated structure 4. This arrangement ensures that neither end of the welding strip 6 is welded to the electrode, and the welding strip 6 is in a free state throughout the entire length of the cell. This reduces the requirements for welding position accuracy and welding temperature control, widens the process window, and makes it more suitable for mass production. In addition, neither end of the welding strip 6 will short-circuit with the opposite electrode, further improving the reliability of the insulation performance in the back contact cell.

[0044] Preferably, please continue to see Figure 2 In some embodiments of the present invention, along the extension direction perpendicular to the busbar electrode 2, the busbar electrode 2 includes a side busbar electrode 21 near the edge of the battery substrate 1 and an intermediate busbar electrode 22 located inside the side busbar electrode 21; the bifurcation structure 4 on the side busbar electrode 21 includes a connecting portion 41, the connecting portion 41 extending into the side busbar electrode 21 and connecting to the current collector electrode 3 of the same polarity located on that side; and / or, the bifurcation structure 4 on the intermediate busbar electrode 22 includes two connecting portions 41, the two connecting portions 41 extending to both sides of the intermediate busbar electrode 22 respectively and connecting to the current collector electrode 3 of the same polarity located on the same side.

[0045] Optionally, in some embodiments of the present invention, the bifurcation structure 4 on the side bus electrode 21 includes a connecting portion 41, which extends into the side bus electrode 21 and connects to the collector electrode 3 of the same polarity on that side; or the bifurcation structure 4 on the middle bus electrode 22 includes two connecting portions 41, which extend to both sides of the middle bus electrode 22 and connect to the collector electrode 3 of the same polarity on the same side.

[0046] Preferably, the bifurcation structure 4 on the side bus electrode 21 includes a connecting part 41, which extends into the side bus electrode 21 and connects to the collector electrode 3 of the same polarity on that side; or the bifurcation structure 4 on the middle bus electrode 22 includes two connecting parts 41, which extend to both sides of the middle bus electrode 22 and connect to the collector electrode 3 of the same polarity on the same side.

[0047] That is, along the extension direction perpendicular to the bus electrode 2, the bus electrode 2 includes two side bus electrodes 21 and an intermediate bus electrode 22 located between the two side bus electrodes 21.

[0048] It should be noted that, due to the different positions of the busbar electrode 2 on the battery substrate 1, the presence or absence of current collector electrodes 3 on both sides varies. Therefore, this invention designs a differentiated bifurcated structure 4 for the busbar electrode 2 at different positions: the side busbar electrode 21 is located in the edge region of the battery substrate 1, with only a current collector electrode 3 of the same polarity on the inner side, and no current collector electrode 3 on the outer side, which does not need to be connected. Therefore, as... Figure 2 and Figure 4 As shown, in some embodiments of the present invention, the bifurcation structure 4 on the side bus electrode 21 includes only one connecting part 41 for connecting the inner current collector electrode 3. For example, the side bus electrode 21 on the left edge has a bifurcation structure 4 including a connecting part 41 extending to the right, i.e., into the battery. The connecting part 41 and the main body of the bus electrode 2 form a welding blank area 5. This design matches the position characteristics of the side bus electrode 21 and avoids redundant structures.

[0049] The intermediate bus electrode 22 is located in the internal region of the battery substrate 1, and there are current collector electrodes 3 of the same polarity on both sides that need to be connected, therefore... Figure 2 and Figure 3 As shown, the bifurcated structure 4 on the intermediate bus electrode 22 includes two connecting portions 41. One extends to the left to connect to the left collector electrode 3, and the other extends to the right to connect to the right collector electrode 3. The left connecting portion 41 is electrically connected to the same polarity collector electrode 3 located to the left of the bus electrode 2, and the right connecting portion 41 is electrically connected to the same polarity collector electrode 3 located to the right of the bus electrode 2. The current collected by the collector electrodes 3 on both sides flows into the same bus electrode 2. A welding blank area 5 is formed between the two connecting portions 41.

[0050] The combination of the side bus electrode 21 and the middle bus electrode 22 not only adapts to the special characteristics of the edge position, but also ensures the current collection efficiency of the internal region, thus achieving the optimal design of the entire region.

[0051] It should be noted that when the bifurcation structure 4 on the side bus electrode 21 includes a connecting part 41, the collector electrode 3 is no longer specifically provided on the outside of the connecting part 41, and only the collector electrode 3 to be connected is provided on the inside. However, due to the limitations of the alignment accuracy of the printing process, there may be a short collector electrode 3 line protruding on the outside of the side bus electrode 21, which is caused by the processing accuracy rather than the functional design.

[0052] Preferably, please refer to Figure 2 In some embodiments of the present invention, along the extension direction of the bus electrode 2, the length of the welding blank area 5 is S, the distance between two adjacent opposite current collector electrodes 3 is D, and satisfies: 3D≤S≤10D.

[0053] It should be noted that S is the length of the welding blank area 5 along the extension direction of the bus electrode 2; D is the distance between two adjacent opposite current collector electrodes 3, such as... Figure 1 As shown, D is determined by the length L of the bus electrode 2 and the number N of the same polarity collector electrodes 3, satisfying D = L / 2(N-1), where the length L of the bus electrode 2 is the total length of the bus electrode 2, including the sum of the lengths of the bifurcation structure 4, the end gate 23 and the middle gate 24.

[0054] Optionally, in some embodiments of the present invention, the length S of the welding blank area 5 is 3D, 4D, 5D, 6D, 7D, 8D, 9D or 10D, etc.

[0055] The setting of S≥3D is a necessary condition to ensure that the end of solder ribbon 6 is reliably not soldered. The end of solder ribbon 6 has a certain width and length, requiring sufficient space to ensure that it falls completely within the blank area and does not contact the bus electrode 2. The length of 3D can accommodate the typical end size of solder ribbon 6 and provides a basic positional tolerance margin. In addition, there is a certain positional error during the placement of solder ribbon 6 by automated soldering equipment, which is usually ±0.5D to ±1D. When S≥3D, even with positional deviation, the end of solder ribbon 6 can still reliably fall within the blank area and will not be mistakenly soldered onto the bus electrode 2.

[0056] Setting S ≤ 10D is a necessary condition to ensure that battery performance is not significantly affected. The total length of the bus electrode 2 is fixed. After the welding blank area 5 occupies the length at both ends, the length available for welding in the middle is [value missing]. When S is too large, it will reduce the effective welding length of the solder strip 6, which may lead to a decrease in the contact area between the solder strip 6 and the bus electrode 2, a decrease in welding pull, an extension of the current collection path, and an increase in resistance loss.

[0057] When S=3D, this dimension is the minimum reliable length to ensure that the end of the solder strip 6 is not welded. At this time, the welding blank area 5 just accommodates the end of the solder strip 6, and the edge of the end of the solder strip 6 is aligned with the edge of the welding blank area 5. Under this dimension, the end of the solder strip 6 does not contact the bus electrode 2, thus realizing the basic function of not welding the end.

[0058] When S=4D-9D, the length of the soldering blank area 5 is greater than the minimum size required at the end of the solder strip 6. Even if there is a certain positional deviation of the solder strip 6 during the automated placement process, the end of the solder strip 6 can still reliably fall within the soldering blank area 5 and will not be mistakenly soldered onto the bus electrode 2.

[0059] When S=10D, this is the maximum allowable length to ensure current collection efficiency. At this point, the weld blank area 5 occupies a large area at the end of the bus electrode 2. Although the function of not welding the end of the solder strip 6 is fully guaranteed, further increasing it will excessively reduce the effective welding length of the bus electrode 2, affecting current collection efficiency and welding reliability.

[0060] Preferably, please refer to Figure 2 In some embodiments of the present invention, the connecting portion 41 is spaced apart from the collector electrode 3 of opposite polarity located on the side of the bus electrode 2.

[0061] In other words, when only one side of the bus electrode 2 has a collector electrode 3, the bifurcation structure 4 includes only one connecting part 41, and the connecting part 41 extends towards the collector electrode 3 and is electrically connected to the same polarity collector electrode 3 on this side, while the opposite polarity collector electrodes 3 are electrically insulated by phase separation; when both sides of the bus electrode 2 have collector electrodes 3, the bifurcation structure 4 includes two connecting parts 41, which extend to both sides and are electrically connected to the same polarity collector electrodes 3 on the same side, while the opposite polarity collector electrodes 3 are electrically insulated by phase separation.

[0062] It should be noted that, on the side of the connecting part 41, there are current collectors 3 of opposite polarity, that is, current collectors 3 of opposite polarity to the current collectors 2 connected to the connecting part 41. In this application, the connecting part 41 and these current collectors 3 of opposite polarity are kept at a certain distance, and the two do not contact or connect to each other, thus forming electrical insulation.

[0063] The distance between the connecting part 41 and the opposite polarity current collector 3 can be designed according to manufacturing process precision and electrical safety requirements. In a preferred embodiment of this application, the distance is greater than the minimum resolution of the screen printing process, ensuring that the connecting part 41 and the opposite polarity current collector 3 will not accidentally come into contact due to process errors during mass production.

[0064] The spaced arrangement between the connecting part 41 and the opposite-polarity current collector 3 located on the side of the bus electrode 2 creates an air gap between them. This eliminates the need for an additional insulating layer between the connecting part 41 and the opposite-polarity current collector 3, achieving electrical insulation and preventing short circuits. This arrangement utilizes air as the insulating medium between the connecting part 41 and the opposite-polarity current collector 3, completely replacing the insulating layer used in existing technologies. This not only eliminates the printing and drying processes for insulating adhesive but also reduces the material cost of the adhesive, simplifying the process and reducing costs.

[0065] Preferably, please refer to Figure 3 In some embodiments of the present invention, along the extending direction of the bus electrode 2, the bus electrode 2 includes an end gate 23 and an intermediate gate 24 located inside the end gate 23, the bifurcation structure 4 is disposed on the end gate 23, and the connecting portion 41 is electrically connected to the end gate 23.

[0066] Please see below. Figure 3 The intermediate gate 24 is a linear gate, which is arranged along the extension direction of the bus electrode 2; or, please refer to Figure 6 and Figure 7 The intermediate gate 24 is a dot gate, including multiple connecting gate points 25, which are spaced apart along the extension direction of the bus electrode 2; or the intermediate gate 24 is a composite gate formed by combining a linear gate and a dot gate.

[0067] In other words, along the extension direction of the bus electrode 2, the bus electrode 2 sequentially includes a bifurcation structure 4, an end gate 23, an intermediate gate 24, and an end gate 23 and a bifurcation structure 4.

[0068] When the intermediate gate 24 is a linear gate, the linear gate is a continuous straight electrode that extends from one end gate 23 to the other end gate 23, forming a complete bus electrode 2 body. During operation, the current collected by the collector electrode 3 flows into the end gate 23 through the connection part 41, and then is transmitted along the direction of the bus electrode 2 through the linear gate. The continuous structure of the linear gate ensures a low-resistance current transmission path.

[0069] When the intermediate gate 24 is a dot-shaped gate, the connecting gate points 25 are discrete electrodes, arranged at intervals to form a dot matrix structure. This arrangement significantly reduces the amount of silver paste used, and the blank areas between the dots allow light to pass through, improving the power generation efficiency of the module. In addition, the dot structure can disperse welding stress.

[0070] When the intermediate gate 24 is a composite gate formed by combining a linear gate and a dot gate, for example, a linear gate is used in the region with a high current density to reduce resistance, and a dot gate is used in the region with a low current density to save silver paste.

[0071] Preferably, please refer to Figure 2 In some embodiments of the present invention, when the intermediate gate 24 is a linear gate, the linear gate is electrically connected to the collector electrode 3 of the same polarity and is spaced apart from the collector electrode 3 of the opposite polarity.

[0072] Alternatively, please see Figure 6 When the intermediate gate 24 is a dot gate, the connecting gate point 25 is located between the collector electrodes 3 of the same polarity as the bus electrode 2. The collector electrodes 3 are electrically connected through the connecting gate point 25, and at the intermediate gate 24, there is a gap between it and the collector electrodes 3 of the opposite polarity of the bus electrode 2.

[0073] When the intermediate gate 24 is a linear gate, collector electrodes 3 of the same polarity and collector electrodes 3 of opposite polarity are distributed on the side of the linear gate. The linear gate is directly electrically connected to the collector electrode 3 of the same polarity located on its side. For example, the end of the collector electrode 3 of the same polarity intersects with the linear gate, forming an electrical connection, and the current collected by the collector electrode 3 flows into the bus electrode 2. The linear gate and the collector electrode 3 of opposite polarity are kept apart and do not contact each other. For example, the collector electrode 3 of opposite polarity is disconnected near the linear gate, forming an opening, or the linear gate narrows at the projection area of ​​the collector electrode 3 of opposite polarity, ensuring that there is no electrical connection between the two.

[0074] When the intermediate gate 24 is a dot-shaped gate, each connecting gate point 25 is an island-shaped electrode, and its position corresponds to the distribution of the same polarity collector electrodes 3. The connecting gate points 25 are located between the same polarity collector electrodes 3, that is, between the ends of two adjacent same polarity collector electrodes 3. Each connecting gate point 25 is connected to two or more adjacent same polarity collector electrodes 3, realizing the electrical connection between the collector electrodes 3. Since the connecting gate points 25 are located between the same polarity collector electrodes 3, and are spaced apart from the opposite polarity collector electrodes 3 at the intermediate gate 24, the connecting gate points 25 and the opposite polarity collector electrodes 3 are kept apart and do not contact each other, ensuring electrical insulation.

[0075] Please see Figure 5 The present invention also provides a back-contact photovoltaic module, including a solder strip 6 and the aforementioned back-contact solar cell, wherein the solder strip 6 is connected to the bus electrode 2, and the end portion 61 of the solder strip is disposed in the welding blank area 5 and is not welded to the bus electrode.

[0076] With this configuration, the end portion 61 of the solder strip is located in the soldering blank area 5, so the solder strip 6 will not come into contact with any electrode on the battery substrate 1, thus ensuring that the end of the solder strip 6 will not short-circuit with the opposite electrode.

[0077] In addition, the end portion 61 of the welding strip is not fixed to any electrode, so the welding thermal stress and mechanical stress generated by thermal cycling can be released through the free expansion and contraction of the end of the welding strip 6, avoiding stress concentration that could lead to microcracks or breakage on the cell.

[0078] Preferably, please refer to Figure 5 In some embodiments of the present invention, the middle portion 62 of the solder strip is spaced apart from the opposite polarity current collector 3 located on the side of the solder strip 6.

[0079] It should be noted that there is a current collector 3 of opposite polarity on the side of the middle part of the solder strip 6, that is, a current collector 3 of opposite polarity to the current collector 2 connected to the connecting part 41. The middle part 62 of the solder strip and the current collector 3 of opposite polarity located on the side of the solder strip 6 are spaced apart so that they do not contact or connect with each other, thus forming electrical insulation.

[0080] This configuration creates an air gap between the solder ribbon 6 and the opposite-polarity current collector 3, achieving electrical insulation between them without the need for an additional insulating layer, thus preventing short circuits. The use of air as the insulating medium completely replaces the insulating layer found in existing technologies. This eliminates the need for printing and drying insulating adhesive, as well as the material cost, resulting in simplified processing and cost reduction.

[0081] The present invention also provides a method for preparing a back-contact photovoltaic module, wherein the method for preparing the back-contact photovoltaic module includes: The solder ribbon 6 is laid on the bus electrode 2 that is in back contact with the battery cell, and the end portion 61 of the solder ribbon is located in the welding blank area 5, while the middle portion is spaced apart from the opposite polarity current collectors 3 located on both sides of the solder ribbon 6.

[0082] Weld the solder strip 6, welding the middle portion 62 of the solder strip to the bus electrode 2, while leaving the end portion 61 of the solder strip unwelded to the bus electrode.

[0083] With this configuration, the end portion 61 of the solder ribbon is located in the soldering blank area 5, so the solder ribbon 6 will not come into contact with any electrode on the battery substrate 1, thus ensuring that the end of the solder ribbon 6 will not short-circuit with the opposite polarity electrode; in addition, the middle portion 62 of the solder ribbon is spaced apart from the opposite polarity current collectors 3 located on both sides of the solder ribbon 6, so that an air gap is formed between the solder ribbon 6 and the opposite polarity current collectors 3, preventing a short circuit between the middle portion 62 of the solder ribbon and the opposite polarity current collectors 3.

[0084] In summary, the end portion 61 of the solder ribbon is located in the welding blank area 5, and the middle portion is spaced apart from the opposite polarity current collectors 3 located on both sides of the solder ribbon 6. This achieves electrical insulation between the solder ribbon 6 and the opposite polarity current collectors 3 without the need for an additional insulating adhesive layer between the solder ribbon 6 and the opposite polarity current collectors 3. This completely replaces the insulating adhesive layer in the prior art, which not only eliminates the printing and drying process of the insulating adhesive but also eliminates the material cost of the insulating adhesive, achieving process simplification and cost reduction. At the same time, eliminating the insulating adhesive layer also helps to increase the light transmittance of the back of the battery and improve the light conversion efficiency of the back of the module.

[0085] In addition, only the middle part 62 of the welding strip is welded to the bus electrode 2, and the end part 61 of the welding strip is not connected to the bus electrode 2. Thus, the welding thermal stress and the mechanical stress generated by the thermal cycle can be released through the free expansion and contraction of the end of the welding strip 6, avoiding stress concentration that could lead to microcracks or breakage on the battery cell.

[0086] It should be noted that the battery substrate 1 that contacts the battery cell on the back is provided with a solder pad, which is located on the bus electrode 2, and the current collectors 3 of the same polarity located on both sides of the solder strip 6 are electrically connected through the solder pad.

[0087] Preferably, in some embodiments of the present invention, in the welding strip 6 step, the middle portion 62 of the welding strip is welded to the bus electrode 2 via a solder pad.

[0088] It should be noted that in existing technologies, before setting the solder ribbon, an insulating adhesive layer with a specific pattern needs to be printed on the battery substrate to isolate the solder ribbon from the opposite-polarity current collector electrode, thus insulating them. However, the insulating adhesive layer has a certain height, making it difficult for the solder ribbon to contact the same-polarity current collector electrode during soldering. Therefore, solder paste needs to be applied to the solder joint to achieve soldering. This process, including printing the insulating adhesive layer, applying the solder paste, and drying, is relatively complex and costly.

[0089] In some embodiments of the present invention, since the end portion 61 of the solder strip is located in the welding blank area 5 and the middle portion is spaced apart from the opposite polarity current collectors 3 located on both sides of the solder strip 6, the solder strip 6 as a whole can be electrically insulated from the opposite polarity current collectors 3. There is no need to set an insulating adhesive layer between the solder strip 6 and the opposite polarity current collectors 3, which completely replaces the use of the insulating adhesive layer in the prior art.

[0090] Therefore, since no additional insulating adhesive layer is required, the solder ribbon 6 will not be suspended during soldering, so there is no gap between the solder ribbon 6 and the bus electrode 2 of this polarity. Therefore, no additional solder paste is needed to fill the gap, and the bus electrode 2 can be made to contact and solder the solder ribbon 6. For example, the middle part 62 of the solder ribbon can be soldered to the bus electrode 2 through the solder pad. The middle part 62 of the solder ribbon can be soldered to the bus electrode 2 using the solder pad that is already on the bus electrode 2.

[0091] Among them, the pad can be the connection gate point 25 mentioned above. The two collector electrodes 3 of the same polarity are electrically connected to the bus electrode 2 through the pad, and the solder strip 6 is soldered to the bus electrode 2 through the pad.

[0092] With this setup, the back-contact photovoltaic module manufacturing method of this embodiment does not require printing an insulating adhesive layer or setting solder paste. The solder strip 6 can be directly soldered to the battery cell to form a battery string and further assembled into a photovoltaic module. This can significantly simplify the packaging process of the back-contact photovoltaic module and reduce the production cost of the module.

[0093] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A back contact battery cell, characterized in that, The battery includes a battery substrate (1) and electrodes disposed on the battery substrate (1). The electrodes include a bus electrode (2) and a current collector electrode (3). At least one end of the bus electrode (2) is provided with a bifurcated structure (4). The bifurcated structure (4) includes at least one connecting portion (41) extending to the side of the bus electrode (2). The connecting portion (41) is used to electrically connect with the current collector electrode (3) of the same polarity located on the side of the bus electrode (2). Among them, the connecting parts (41) of the bifurcated structure (4) and / or the connecting parts (41) and the main body of the bus electrode (2) form a welding blank area (5), which is an electrode-free area; The distance between the connecting part (41) and the collector electrode (3) of opposite polarity located on the side of the bus electrode (2) is in the range of 0.4mm-0.8mm.

2. The back contact battery cell according to claim 1, characterized in that, Along the extension direction perpendicular to the busbar (2), the busbar (2) includes a side busbar (21) near the edge of the battery substrate (1) and an intermediate busbar (22) located inside the side busbar (21). The bifurcation structure (4) on the side bus electrode (21) includes a connecting part (41) that extends into the side bus electrode (21) and connects to the collector electrode (3) of the same polarity on that side; and / or, the bifurcation structure (4) on the middle bus electrode (22) includes two connecting parts (41) that extend to both sides of the middle bus electrode (22) and connect to the collector electrode (3) of the same polarity on the same side.

3. The back contact battery cell according to claim 2, characterized in that, When the bifurcated structure (4) includes two connecting parts (41), the distance between the two connecting parts (41) is in the range of 0.4mm-0.8mm.

4. The back contact battery cell according to claim 1, characterized in that, Along the extension direction of the bus electrode (2), the length of the welding blank area (5) is S, the distance between two adjacent opposite current collectors (3) is D, and satisfies: 3D≤S≤10D; And / or, the connection portion (41) is spaced apart from the collector electrode (3) of opposite polarity located on the side of the bus electrode (2).

5. The back contact battery cell according to any one of claims 1-4, characterized in that, Along the extending direction of the bus electrode (2), the bus electrode (2) includes an end gate (23) and an intermediate gate (24) located inside the end gate (23), the bifurcation structure (4) is disposed on the end gate (23), and the connecting portion (41) is electrically connected to the end gate (23); Wherein, the intermediate gate (24) is a linear gate, which is arranged along the extension direction of the bus electrode (2); or the intermediate gate (24) is a dot gate, including a plurality of connecting gate points (25), which are spaced apart along the extension direction of the bus electrode (2); or the intermediate gate (24) is a composite gate formed by combining a linear gate and a dot gate.

6. The back contact battery cell according to claim 5, characterized in that, When the intermediate gate (24) is a linear gate, the linear gate is electrically connected to the collector electrode (3) of the same polarity and is spaced apart from the collector electrode (3) of the opposite polarity; When the intermediate gate (24) is a dot gate, the connection gate point (25) is located between the collector electrodes (3) of the same polarity as the bus electrode (2), the collector electrodes (3) are electrically connected through the connection gate point (25), and the intermediate gate (24) is spaced apart from the collector electrodes (3) of the opposite polarity of the bus electrode (2).

7. A back-contact photovoltaic module, characterized in that, Includes a solder strip (6) and a back contact cell as described in any one of claims 1-6, wherein the solder strip (6) is connected to the bus electrode (2), wherein the end portion (61) of the solder strip is disposed in the welding blank area (5) and is not welded to the bus electrode (2).

8. The back-contact photovoltaic module according to claim 7, characterized in that, The middle portion (62) of the solder strip is spaced apart from the opposite polarity current collector (3) located on the side of the solder strip (6).

9. A method for manufacturing a back-contact photovoltaic module, characterized in that, For preparing the back-contact photovoltaic module of claim 7 or 8, comprising: Lay the solder strip (6), lay the solder strip (6) on the bus electrode (2) of the back contact cell, and make the end portion (61) of the solder strip located in the welding blank area (5), and the middle portion is spaced apart from the opposite polarity current collectors (3) located on both sides of the solder strip (6). Welding strip (6), welding the middle part (62) of the welding strip to the bus electrode (2), and leaving the end part (61) of the welding strip unwelded to the bus electrode (2).

10. The method for preparing a back-contact photovoltaic module according to claim 9, characterized in that, The battery substrate (1) of the back contact battery cell is provided with a solder pad, which is disposed on the bus electrode (2), and the same polarity current collectors (3) located on both sides of the solder strip (6) are electrically connected through the solder pad. In the welding strip (6) step, the middle part (62) of the welding strip is welded to the bus electrode (2) through the welding pad.

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