Solder strip and photovoltaic module

Abstract

The invention relates to the field of photovoltaic technology, in particular to a solder strip and a photovoltaic module, the solder strip comprises an inner core and a shell, the inner core comprises a plurality of bending sections which are continuously arranged, the shell wraps the outer side of the inner core, and the curvature of the solder strip is smaller than the minimum curvature of the bending sections. According to the invention, the thermal expansion coefficients of the battery piece and the welding strip are different, and when the external temperature changes, the bending section can stretch or retract to compensate the difference value of the size change of the battery piece and the welding strip, thereby preventing the welding strip from falling off from the bonding pad due to the overlarge drawing force, causing the photo-generated current generated by the battery piece not to be effectively led out, and improving the reliability of the battery piece. And the photoelectric conversion efficiency of the battery piece is influenced. The housing can protect the inner core, isolate the contact between the inner core and air and water vapor, and make the bending degree of the solder strip smaller, so that the contact area between the solder strip and the bonding pad is larger, the connection strength between the solder strip and the bonding pad is higher, and the solder strip is not easy to fall off from the bonding pad.

Description

Technical Field

[0001] The present application relates to the field of photovoltaic technology, and in particular to a welding ribbon and a photovoltaic module. Background Art

[0002] Photovoltaic modules consist of cells and solder ribbons. The cells are equipped with solder pads, and the solder ribbons are connected to the cells via the solder pads. A single solder ribbon connects two adjacent cells to conduct the photocurrent generated by the cells for human use.

[0003] Because the thermal expansion coefficients of the soldering ribbon and the solar cell are different, when the external temperature changes, the difference in the size change of the solar cell and the soldering ribbon causes the connection point between the soldering ribbon and the soldering pad to be subjected to a large pulling force, making the soldering ribbon easy to fall off from the soldering pad, resulting in the inability to effectively extract the photocurrent, thereby affecting the photoelectric conversion efficiency of the photovoltaic module. Summary of the Invention

[0004] The present application provides a soldering ribbon and a photovoltaic module, which are used to solve the technical problem that the soldering ribbon is easily detached from the solar cell when the external temperature changes.

[0005] A welding strip provided in an embodiment of the present application includes an inner core and an outer shell, wherein the inner core includes a plurality of continuously arranged curved segments, the outer shell is wrapped around the outer side of the inner core, and the curvature of the welding strip is less than the minimum curvature of the curved segments.

[0006] In a possible design, the diameter of the welding strip remains unchanged along the extending direction of the welding strip.

[0007] In a possible design, the welding strip extends along a straight line.

[0008] In a possible design, the cross-sectional shape of the welding strip is circular, elliptical, triangular or rectangular.

[0009] In a possible design, the diameter d1 of the inner core satisfies: 100 μm ≤ d1 ≤ 400 μm; and / or the diameter d2 of the welding strip satisfies: 105 μm ≤ d2 ≤ 500 μm.

[0010] In a possible design, a minimum distance d3 between the outer circumference of the inner core and the outer circumference of the outer shell satisfies: 5 μm≤d3≤100 μm.

[0011] In a possible design, along the extension direction of the welding strip, the length L of the bent section satisfies: 1 mm ≤ L ≤ 20 mm.

[0012] In a possible design, the inner core is a copper wire and the outer shell is a tin layer.

[0013] A photovoltaic module provided in an embodiment of the present application includes solar cells and the aforementioned welding ribbon, wherein the welding ribbon connects adjacent solar cells.

[0014] In a possible design, the curved segment includes a first curved segment and a second curved segment, the first curved segment is connected to the battery cell, and the second curved segment is not connected to the battery cell; the second curved segment is provided between adjacent first curved segments.

[0015] In a possible design, between adjacent first curved segments, the number n of the second curved segments satisfies: 1≤n≤20.

[0016] In a possible design, the curvature of the first curved segment is smaller than the curvature of the second curved segment.

[0017] In the present application, the thermal expansion coefficient of the battery cell is different from that of the solder strip. By making the inner core have multiple curved sections, when the external temperature changes, the curved sections can stretch or retract to compensate for the difference in size changes between the battery cell and the solder strip, thereby preventing the solder strip from being subjected to excessive pulling force and falling off from the solder pad, resulting in the inability to effectively extract the photocurrent generated by the battery cell, thereby affecting the photoelectric conversion efficiency of the battery cell.

[0018] The outer shell wrapped around the outside of the inner core can protect the inner core, isolate the inner core from contact with air and water vapor, and make the curvature of the welding ribbon less than the minimum curvature of the bending section, that is, the curvature of the welding ribbon is less than the curvature of the bending section. The smaller curvature of the welding ribbon makes the contact area between the welding ribbon and the welding pad larger, the connection strength between the welding ribbon and the welding pad is higher, and it is not easy to fall off from the welding pad. At the same time, the smaller curvature of the welding ribbon can facilitate welding the welding ribbon to the welding pad, reducing the difficulty of connecting the welding ribbon to the battery cell. Furthermore, during the lamination process, the curved welding ribbon and the curved section can release the stress caused by the inconsistent thermal stress between the welding ribbon and the battery cell, reduce the degree of warping of the battery cell, and thus reduce the probability of battery cell fragmentation and breakage.

[0019] It should be understood that the foregoing general description and the following detailed description are merely illustrative and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic structural diagram of a photovoltaic module provided in this application in one embodiment; Figure 2 for Figure 1 Schematic diagram of the structure of the battery cell and the welding ribbon; Figure 3 This is a schematic structural diagram of another embodiment of the photovoltaic module provided by the present application, wherein the cell is a back-contact cell; Figure 4This is a schematic structural diagram of another embodiment of the photovoltaic module provided by the present application, wherein the cell is a back-contact stacked cell; Figure 5 for Figure 3 、 Figure 4 Schematic diagram of the structure of the battery cell and the welding ribbon; Figure 6 for Figure 1 A schematic structural diagram of a battery cell in one embodiment; Figure 7 for Figure 1 A schematic structural diagram of a battery cell in another embodiment; Figure 8 A schematic structural diagram of a welding strip provided in this application in one embodiment; Figure 9 A schematic structural diagram of the welding strip provided in this application in another embodiment; Figure 10 for Figure 9 The solder strips and Figure 6 Schematic diagram of the structure of the battery cells in the figure.

[0021] Reference numerals: 1- welding strip; 11-inner core; 11a-first curved section; 11b-second curved section; 12-housing; 2-battery cell; 21-first grid line; 22-second grid line; 23- soldering pad; 3-front packaging structure; 4-front film layer; 5-back film layer; 6-Back side packaging structure.

[0022] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application. DETAILED DESCRIPTION

[0023] In order to better understand the technical solution of the present application, the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0024] It should be clear that the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0025] The terms used in the embodiments of the present application are for the purpose of describing specific embodiments only and are not intended to limit the present application. The singular forms "a", "an", "the" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise.

[0026] It should be understood that the term "and / or" as used herein is merely a description of the relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, or B exists alone. Furthermore, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0027] It should be noted that the directional words such as "upper", "lower", "left", and "right" described in the embodiments of the present application are described based on the angles shown in the accompanying drawings and should not be understood as limiting the embodiments of the present application. In addition, in the context, it should be understood that when it is mentioned that an element is connected to another element "on" or "under", it can not only be directly connected to the other element "on" or "under", but also be indirectly connected to the other element "on" or "under" through an intermediate element.

[0028] The present invention provides a photovoltaic module, comprising cells 2 and a soldering ribbon 1, wherein the soldering ribbon 1 connects adjacent cells 2 to form a cell string. The cells 2 have a front side and a back side that are opposite each other along their thickness direction Z. The front side is the light-receiving side of the cells 2, and the back side is the back side of the cells 2 that is not exposed to light.

[0029] Figure 1 This is a schematic structural diagram of a photovoltaic module provided in this application in one embodiment. Figure 2 for Figure 1 Schematic diagram of the structure of the battery cell 2 and the welding ribbon 1. Figure 1 and Figure 2 As shown, for a cell 2 in which the positive and negative grid lines are located on the front and back sides respectively, such as a Passivated Emitter Rear Cell (PERC), a Tunnel Oxide Passivated Contact (TOPCON), a Heterojunction with Intrinsic Thin-layer (HIT), a Perovskite Solar Cell (PSC), etc., the soldering ribbon 1 extends from the front side of one cell 2 to the back side of another cell 2 or from the back side of one cell 2 to the front side of another cell 2 to achieve connection between adjacent cells 2.

[0030] For PERC cells, along the thickness direction, the PERC cell includes the front surface metal silver electrode, the front surface silicon nitride passivation layer, the phosphorus layer emitter, the P-type base silicon layer, the local aluminum back field, the metal aluminum back electrode, the back passivation layer (Al2O3 / SiN x PERC cells use a passivation film to passivate the back surface, replacing the all-aluminum back surface field. This enhances the internal back reflection of light in the silicon substrate, reduces the recombination rate on the back surface, and increases the photoelectric conversion efficiency of the cell by 0.5%-1%.

[0031] A TOPCon cell, along its thickness, consists of a silver electrode, a front silicon nitride passivation layer, a boron-doped emitter, an N-type base silicon layer, a diffused doped layer, an ultrathin silicon oxide layer, doped polysilicon, silicon nitride, and a silver electrode. The back of the cell consists of an ultrathin silicon oxide layer (1nm-2nm) and a phosphorus-doped microcrystalline amorphous hybrid silicon thin film, which together form a passivated contact structure. This structure blocks minority carrier-hole recombination, improving the cell's open-circuit voltage and short-circuit current. The ultrathin oxide layer allows majority electrons to tunnel into the polysilicon layer while blocking minority carrier-hole recombination. The excellent passivation effect of the ultrathin silicon oxide and heavily doped silicon film causes surface band bending of the silicon wafer, creating a field passivation effect. This significantly increases the probability of electron tunneling and reduces contact resistance, thereby increasing the cell's open-circuit voltage and short-circuit current, and thus improving the cell's photoelectric conversion efficiency.

[0032] For HIT batteries, along their thickness direction, the HIT batteries include a front low-temperature silver electrode, a front conductive film, an N-type amorphous silicon film, an intrinsic amorphous silicon film, an N-type base silicon layer, an intrinsic amorphous silicon film, a P-type amorphous silicon film, a back conductive film, and a back low-temperature silver electrode.

[0033] For a PSC cell, along its thickness, the perovskite cell consists of a substrate material, a conductive film, an electron transport layer (titanium dioxide), a perovskite absorption layer (hole transport layer), and a metal cathode. Perovskite materials have a high light absorption coefficient and a long carrier diffusion distance. After the photons absorbed by the perovskite material are converted into electrons, they are easily collected by the electrode with minimal loss. This can generate a high photogenerated voltage and current, making perovskites exhibit high photoelectric conversion efficiency.

[0034] Figure 3 This is a schematic structural diagram of another embodiment of the photovoltaic module provided in this application, wherein the cell 2 is a back-contact cell. Figure 4 This is a schematic structural diagram of another embodiment of the photovoltaic module provided in the present application, wherein the cell 2 is a back-contact stacked cell. Figure 5 for Figure 3 、 Figure 4 Schematic diagram of the structure of the battery cell 2 and the welding ribbon 1. Figures 3 to 5 As shown, for a cell 2 with both the positive and negative grid lines located on the back, such as a back contact cell (BC), a back contact stacked cell, etc., the welding ribbon 1 extends from the back of one cell 2 to the back of another cell 2 to achieve connection between adjacent cells 2.

[0035] For BC cells, the emitter, surface field and metal electrode are all set on the back of the cell and distributed in a cross-finger manner. The front of the cell 2 uses SiN x / SiO x The double-layer anti-reflection passivation film eliminates metal electrode obstruction on the front of the cell, allowing the cell 2 to receive more incident light, reducing optical losses and improving photoelectric conversion efficiency. BC cells can also be further categorized as interdigitated back contact (IBC), heterojunction back contact (HBC), and tunnel oxide back contact (TBC).

[0036] For back-contact tandem cells, the back-contact tandem cell includes a top cell, an intermediate connecting layer, and a bottom cell. The intermediate connecting layer connects between the bottom and top cells. The top cell can be a perovskite cell, a cadmium telluride solar cell, a copper indium gallium selenide solar cell, or a gallium arsenide solar cell. The bottom cell is a BC cell. The intermediate connecting layer can be selected from transparent materials with a high refractive index, such as transparent conductive metal oxide thin film (ITO). An effective intermediate connecting layer needs to have high light transmittance to reduce light reflection and absorption at the connecting layer interface, as well as good conductivity to reduce the impact of series resistance on device performance.

[0037] like Figure 1 、 Figure 3 and Figure 4 As shown, the photovoltaic module also includes: a front encapsulation structure 3, a front film layer 4, a back film layer 5, and a back encapsulation structure 6. The front encapsulation structure 3, the front film layer 4, the back film layer 5, and the back encapsulation structure 6 encapsulate the cell string to ensure the photovoltaic module has high mechanical strength, reduce the impact of hail impact, wind, mechanical vibration, etc. on the back-contact photovoltaic module, and improve the sealing of the back-contact photovoltaic module, enhancing its corrosion resistance and safety.

[0038] Specifically, the front encapsulation structure 3 and the back encapsulation structure 6 can be made of a rigid material such as tempered glass, polyethylene terephthalate (PET), or polycarbonate (PC), or a flexible material such as polyvinyl fluoride (PVF), ethylene-tetrafluoroethylene copolymer (ETFE), or polyvinylidene fluoride (PVDF). These materials have high light transmittance, which can improve the photoelectric conversion efficiency of the back-contact photovoltaic module and ensure the power output of the back-contact photovoltaic module. The front film layer 4 and the back film layer 5 can be one of the materials such as ethylene-vinyl acetate copolymer (EVA), polyolefin elastomer (POE), polyvinyl butyral (PVB), EVA-POE-EVA co-extruded film (EPE), and EVA-POE co-extruded film (EP).

[0039] The following is a detailed discussion using a cell 2 in which the positive and negative grid lines are located on the front and back sides, respectively, as an example.

[0040] Figure 6 for Figure 1 A schematic diagram of the structure of the battery cell 2 in one embodiment. Figure 6 As shown, the cell 2 has a first grid line 21 extending along a first direction X and a second grid line 22 extending along a second direction Y. Exemplarily, the first grid line 21 is a main grid, and the second grid line 22 is a fine grid. The first grid line 21 is thicker than the second grid line 22, i.e., a main grid cell. Multiple first grid lines 21 are spaced apart along the second direction Y, and multiple second grid lines 22 are spaced apart along the first direction X. Each first grid line 21 is connected to multiple second grid lines 22. The photocurrent generated by the cell 2 can be collected by the second grid lines 22, and the photocurrent collected by the second grid lines 22 can be collected by the first grid lines 21. A soldering pad 23 is provided on the first grid line 21, and a soldering ribbon 1 is soldered to the soldering pad 23 to connect the soldering ribbon 1 to the first grid line 21. The photocurrent in the first grid line 21 can flow through the soldering pad 23 to the soldering ribbon 1, thereby conducting current out of the cell 2.

[0041] Specifically, the plurality of pads 23 are arranged at intervals along the first direction X. The pads 23 may contact the second gate lines 22 or may be disposed between two second gate lines 22 .

[0042] Among them, the first direction X and the second direction Y are both perpendicular to the thickness direction Z of the battery cell 2. Exemplarily, one of the first direction X and the second direction Y is the length direction of the battery cell 2, and the other is the width direction of the battery cell 2. The first direction X and the second direction Y are perpendicular to each other.

[0043] Figure 7 for Figure 1 A schematic diagram of the structure of the battery cell 2 in another embodiment. Figure 7 As shown, the cell 2 has only a second grid line 22 extending along the second direction Y. That is, the cell 2 does not have a first grid line 21, i.e., it does not have a busbar cell. A soldering pad 23 is provided on the second grid line 22, allowing the soldering ribbon 1 to be directly connected to the second grid line 22. The photocurrent collected by the second grid line 22 can flow directly to the soldering ribbon 1 through the soldering pad 23, thereby conducting the current away from the cell 2.

[0044] Figure 8 This is a schematic structural diagram of the welding strip 1 provided in this application in one embodiment. Figure 8 As shown, the soldering ribbon 1 includes an inner core 11 and an outer shell 12. The inner core 11 includes a plurality of continuously arranged curved segments. The outer shell 12 wraps around the outer side of the inner core 11. The curvature of the soldering ribbon 1 is less than the minimum curvature of the curved segment.

[0045] When the external temperature changes, the photovoltaic module also obeys the physical law of thermal expansion and contraction. The thermal expansion coefficient of the battery cell 2 is different from that of the welding strip 1. By making the inner core 11 have multiple bending sections, when the external temperature changes, the bending sections can stretch or retract to compensate for the difference in size changes between the battery cell 2 and the welding strip 1, preventing the welding strip 1 from being subjected to excessive pulling force and falling off from the pad 23, resulting in the photocurrent generated by the battery cell 2 cannot be effectively extracted, affecting the photoelectric conversion efficiency of the battery cell 2.

[0046] The outer shell 12 wrapped around the outer surface of the inner core 11 can protect the inner core 11, isolating the inner core 11 from contact with air and moisture, and ensuring that the curvature of the soldering ribbon 1 is less than the minimum curvature of the curved section. That is, the curvature of the soldering ribbon 1 is less than the curvature of the curved section. The smaller curvature of the soldering ribbon 1 increases the contact area between the soldering ribbon 1 and the soldering pad 23, and the connection strength between the soldering ribbon 1 and the soldering pad 23 is higher, making it less likely to fall off the soldering pad 23. At the same time, the smaller curvature of the soldering ribbon 1 facilitates soldering of the soldering ribbon 1 to the soldering pad 23, reducing the difficulty of connecting the soldering ribbon 1 to the battery cell 2.

[0047] Furthermore, after the cells 2 are connected into a cell string via the soldering ribbon 1, a front film layer 4 and a front encapsulation structure 3 are placed on the front of the cell string, and a back film layer 5 and a back encapsulation structure 6 are placed on the back of the cell string. Lamination is then performed under a certain temperature and pressure to connect the front encapsulation structure 3, the front film layer 4, the cell string, the back film layer 5, and the back encapsulation structure 6 into a single unit. During the lamination process, the curved soldering ribbon 1 and its curved sections can release stress caused by the inconsistent thermal stress between the soldering ribbon 1 and the cell 2, reducing the degree of warping of the cell 2 and, in turn, reducing the probability of cell 2 fragmentation or breakage.

[0048] like Figure 8 As shown, the diameter of the solder ribbon 1 remains constant along its extension direction, thereby ensuring a more uniform force on the cell 2 from the solder ribbon 1. This prevents stress concentration caused by local diameter variations in the solder ribbon 1, which could lead to fragmentation or breakage of the cell 2. Furthermore, a solder ribbon 1 with a consistent diameter is easier to produce, has lower production costs, and has a controllable elongation.

[0049] It can be understood that the unchanged diameter of the welding ribbon 1 along the extension direction of the welding ribbon 1 means that the diameter of the welding ribbon 1 changes slightly, and the change in the diameter of the welding ribbon 1 is difficult to be observed with the naked eye.

[0050] Figure 9 This is a schematic structural diagram of the welding strip 1 provided in this application in another embodiment. Figure 9 As shown, the soldering ribbon 1 extends in a straight line. When the soldering ribbon 1 is placed on the battery cell 2, the soldering ribbon 1 can contact the soldering pad 23, thereby facilitating soldering between the soldering ribbon 1 and the soldering pad 23. Furthermore, the soldering ribbon 1 extending in a straight line is easy to produce and has a low production cost.

[0051] like Figure 9 As shown, the diameter d1 of the inner core 11 satisfies: 100 μm≤d1≤400 μm. For example, the diameter d1 of the inner core 11 can be: 100μm, 112μm, 115μm, 110μm, 120μm, 130μm, 140μm, 150μm, 160μm, 170μm, 180μm, 190μm, 200μm, 210μm, 220μm, 230μm, 240μm, 250μm, 260μm, 270μm, 280μm, 290μm, 300μm, 310μm, 320μm, 330μm, 340μm, 350μm, 360μm, 370μm, 380μm, 390μm, 395μm, 398μm, 400μm, etc.

[0052] The diameter d1 of the inner core 11 should be neither too large nor too small. If the diameter d1 of the inner core 11 is too large (for example, greater than 400 μm), the amount of inner core 11 used increases, increasing the cost of the soldering ribbon 1. If the diameter of the inner core 11 is too small (for example, less than 100 μm), the resistance of the soldering ribbon 1 increases, reducing the conductive performance of the soldering ribbon 1. Therefore, the diameter d1 of the inner core 11 should be selected within a reasonable range.

[0053] like Figure 9 As shown, the diameter d2 of the soldering ribbon 1 satisfies: 105 μm ≤ d2 ≤ 500 μm. For example, the diameter d2 of the soldering ribbon 1 can be: 105 μm, 106 μm, 108 μm, 110 μm, 115 μm, 118 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, 200 μm, 210 μm, 220 μm, 230 μm, 240 μm, 250 μm, 260 μm, 270 μm, 280 μm, 290 μm, 300 μm, 310 μm, 320 μm, 330 μm, 340 μm, 350 μm, 360 μm, 370 μm, 380 μm, 390 μm, 400 μm, 410 μm, 420 μm, 430 μm, 440 μm, 450 μm, 460 μm, 470 μm, 480 μm, 490 μm, 500 μm, 510 μm, 520 μm, 530 μm, 540 μm, 550 μm, 560 μm, 570 μm, 580 μm, 590 μm, 600 μm, 610 μm, 620 μm, 630 μm, 640 μm 70μm, 280μm, 290μm, 300μm, 310μm, 320μm, 330μm, 340μm, 350μm, 360μm, 370μm, 380μm, 3 90μm, 400μm, 410μm, 420μm, 430μm, 440μm, 450μm, 460μm, 470μm, 480μm, 490μm, 500μm, etc.

[0054] The diameter d2 of the soldering ribbon 1 should be neither too large nor too small. If the diameter d2 of the soldering ribbon 1 is too large (for example, greater than 500 μm), the cost of the soldering ribbon 1 increases, and the area of ​​the soldering ribbon 1 blocking the solar cell 2 increases, affecting the photovoltaic conversion efficiency of the solar cell 2. If the diameter d2 of the soldering ribbon 1 is too small (for example, less than 105 μm), the resistance of the soldering ribbon 1 increases, and the conductivity of the soldering ribbon 1 decreases. Therefore, the diameter d2 of the soldering ribbon 1 should be selected within a reasonable range.

[0055] like Figure 9 As shown, the minimum distance d3 between the outer circumference of the inner core 11 and the outer circumference of the outer shell 12 satisfies: 5 μm≤d3≤100 μm. For example, the minimum distance d3 between the outer peripheral surface of the inner core 11 and the outer peripheral surface of the outer shell 12 can be specifically: 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 12 μm. , 15μm, 18μm, 20μm, 22μm, 25μm, 28μm, 30μm, 32μm, 35μm, 38μm, 40μm, 42μm, 45μm m, 48μm, 50μm, 52μm, 55μm, 58μm, 60μm, 62μm, 65μm, 68μm, 70μm, 72μm, 75μm, 78 μm, 80μm, 82μm, 85μm, 88μm, 90μm, 92μm, 95μm, 96μm, 97μm, 98μm, 99μm, 100μm, etc.

[0056] The minimum distance d3 between the outer circumference of the inner core 11 and the outer circumference of the outer shell 12 should be neither too large nor too small. If the minimum distance d3 between the outer circumference of the inner core 11 and the outer circumference of the outer shell 12 is too large (for example, greater than 100 μm), the diameter d2 of the welding ribbon 1 will be too large, increasing the cost of the welding ribbon 1 and increasing the area blocked by the welding ribbon 1 on the solar cell 2, affecting the photovoltaic conversion efficiency of the solar cell 2. If the minimum distance d3 between the outer circumference of the inner core 11 and the outer shell 12 is too small (for example, less than 5 μm), the outer shell 12 will be easily worn at its thinnest point, exposing the inner core 11 and making it susceptible to damage. Therefore, the minimum distance d3 between the outer circumference of the inner core 11 and the outer shell 12 should be selected within a reasonable range.

[0057] like Figure 9 As shown, along the extension direction of the welding ribbon 1, the length L of the bent section satisfies the following: 1 mm ≤ L ≤ 20 mm. For example, the length L of the bent section can be: 1 mm, 1.2 mm, 1.5 mm, 1.8 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, 5.5 mm, 6 mm, 6.5 mm, 7 mm, 7.5 mm, 8 mm, 8.5 mm, 9 mm, 9.5 mm, 10 mm, 10.5 mm, 11 mm, 11.5 mm, 12 mm, 12.5 mm, 13 mm, 13.5 mm, 14 mm, 14.5 mm, 15 mm, 15.5 mm, 16 mm, 16.5 mm, 17 mm, 17.5 mm, 18 mm, 18.5 mm, 19 mm, 19.2 mm, 19.5 mm, 19.8 mm, 20 mm, etc.

[0058] Along the extension direction of the solder ribbon 1, the length L of the bend section should be neither too long nor too short. If the length L of the bend section is too long (for example, greater than 20 mm), the length of the bend section is greater than the distance between adjacent solder pads 23. As the external temperature changes, the bend section's effectiveness in compensating for the difference in size between the cell 2 and the solder ribbon 1 becomes less effective. Consequently, the solder ribbon 1 cannot be effectively prevented from being pulled off the solder pads 23 due to excessive pulling force. This results in the inability to effectively extract the photocurrent generated by the cell 2, affecting the photoelectric conversion efficiency of the cell 2. If the length L of the bend section is too short (for example, less than 1 mm), more inner cores 11 are required per unit length of the solder ribbon 1, increasing the cost of the solder ribbon 1. Therefore, the length L of the bend section should be selected within a reasonable range.

[0059] In the above embodiment, the inner core 11 is a copper wire and the outer shell 12 is a tin layer. The copper wire has good electrical conductivity, which reduces the loss of current during transmission. The tin layer has good corrosion resistance and welding performance, and there is no need to grind the welding strip 1 before welding, which can simplify the welding process. The tin layer can also fill the tiny gap between the copper wire and the pad 23, reducing the contact resistance between the welding strip 1 and the pad 23. In addition, the melting point of the tin layer is lower than the melting point of the copper wire, which reduces the temperature required for welding, is not easy to damage the battery cell 2, and is conducive to reducing the cost required for welding. It can be understood that the inner core 11 can also be other materials with good electrical conductivity, and the outer shell 12 can also be other materials with good corrosion resistance and welding performance.

[0060] In the above embodiments, the cross-sectional shape of the soldering ribbon 1 can be circular, elliptical, triangular, or rectangular. For example, when the cross-sectional shape of the soldering ribbon 1 is circular, the soldering ribbon 1 has the advantage of less obstruction of the solar cell 2, facilitating production. For example, when the cross-sectional shape of the soldering ribbon 1 is rectangular, the soldering ribbon 1 has the advantage of being less likely to roll relative to the soldering pad 23 before soldering, facilitating securing the soldering ribbon 1 during soldering.

[0061] Figure 10 for Figure 9 The solder strip 1 and Figure 6 Schematic diagram of the structure of the battery cell 2. Figure 10 As shown, the curved sections include a first curved section 11a and a second curved section 11b. The first curved section 11a is connected to the cell 2, while the second curved section 11b is not. Second curved sections 11b are located between adjacent first curved sections 11a. The second curved sections 11b improve the ability of the soldering ribbon 1 to compensate for the dimensional differences between the cell 2 and the soldering ribbon 1, further preventing the soldering ribbon 1 from being pulled off the soldering pad 23 due to excessive pulling force. This would prevent the photovoltaic current generated by the cell 2 from being effectively extracted, thus affecting the photovoltaic conversion efficiency of the cell 2.

[0062] Specifically, between adjacent first curved segments 11 a , the number n of second curved segments 11 b satisfies: 1≤n≤20.

[0063] Exemplarily, between adjacent first curved segments 11a, the number n of second curved segments 11b satisfies: 1≤n≤6, which is suitable for busbar-free cells with a smaller distance between adjacent pads 23. For example, the number n of second curved segments 11b is 1, 2, 3, 4, 5, or 6.

[0064] Exemplarily, between adjacent first bending segments 11a, the number n of second bending segments 11b satisfies: 5≤n≤20, so that it is suitable for main-grid batteries with a larger distance between adjacent pads 23. For example, the number n of second bending segments 11b is 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20.

[0065] The number n of second curved segments 11b between adjacent first curved segments 11a should be neither too many nor too few. If the number n of second curved segments 11b is too large (e.g., greater than 20), the curvature of the second curved segments 11b is greater, requiring more inner cores 11 per unit length of the solder ribbon 1, resulting in a larger diameter d2 of the solder ribbon 1. This, in turn, increases the cost of the solder ribbon 1 and the area of ​​the solder ribbon 1 blocking the solar cell 2, thereby affecting the photovoltaic conversion efficiency of the solar cell 2. If the number n of second curved segments 11b is too small (e.g., there is no second curved segment 11b between adjacent first curved segments 11a, i.e., the number of second curved segments 11b is zero), the solder ribbon 1 is less able to compensate for the difference in size between the solar cell 2 and the solder ribbon 1, and cannot effectively prevent the solder ribbon 1 from being pulled off the solder pad 23 due to excessive pullout force. Therefore, the number n of second curved segments 11b between adjacent first curved segments 11a should be within a reasonable range.

[0066] Preferably, the curvature of the first bending segment 11a is smaller than the curvature of the second bending segment 11b, that is, the bending degree of the first bending segment 11a is smaller than the bending degree of the second bending segment 11b, so that when the external temperature changes, the extension or retraction distance of the first bending segment 11a is smaller, and the extension or retraction distance of the second bending segment 11b is larger, thereby improving the connection reliability between the first bending segment 11a and the solder pad 23.

[0067] It can be understood that the curvatures of the plurality of first curved segments 11 a may be the same or different, and the curvatures of the plurality of second curved segments 11 b may be the same or different.

[0068] Further, such as Figure 10 As shown, each curved segment has two vertices, that is, each first curved segment 11a has two vertices, and each second curved segment 11b has two vertices. Along the first direction X, the distance between the two vertices of the first curved segment 11a is greater than the distance between the two vertices of the second curved segment 11b.

[0069] Of the two vertices of the first curved section 11 a , one is higher and the other is lower. The higher vertex is defined as a wave crest, and the lower vertex is defined as a wave trough.

[0070] Exemplarily, along the extension direction of the welding strip 1, the projections of the crests of multiple first bending segments 11a coincide with each other, and the projections of the troughs of multiple first bending segments 11a coincide with each other, that is, the minimum distances between the multiple first bending segments 11a and the outer peripheral surface of the welding strip 1 are the same; similarly, along the extension direction of the welding strip 1, the projections of the crests of multiple second bending segments 11b coincide with each other, and the projections of the troughs of multiple second bending segments 11b coincide with each other, that is, the minimum distances between the multiple first bending segments 11a and the outer peripheral surface of the welding strip 1 are the same.

[0071] Optionally, along the extension direction of the welding strip 1 , the projection of the crest of the first curved segment 11 a coincides with the projection of the crest of the second curved segment 11 b , and the projection of the trough of the first curved segment 11 a coincides with the projection of the trough of the second curved segment 11 b .

[0072] Optionally, along the extension direction of the welding strip 1, the projection of the wave crest of the first bending segment 11a and the projection of the wave crest of the second bending segment 11b do not overlap, including: the projection of the wave crest of the first bending segment 11a and the projection of the wave crest of the second bending segment 11b are spaced apart in the radial direction of the welding strip 1, and the projection of the wave crest of the first bending segment 11a and the projection of the wave crest of the second bending segment 11b are spaced apart in the circumferential direction of the welding strip 1.

[0073] Optionally, the projection of the trough of the first bending segment 11a and the projection of the trough of the second bending segment 11b do not overlap, including: the projection of the trough of the first bending segment 11a and the projection of the trough of the second bending segment 11b are spaced apart in the radial direction of the welding strip 1, and the projection of the trough of the first bending segment 11a and the projection of the trough of the second bending segment 11b are spaced apart in the circumferential direction of the welding strip 1.

[0074] Exemplarily, along the extension direction of the welding strip 1, the projections of the crests of the multiple first bending segments 11a do not overlap, including: the projections of the crests of the multiple first bending segments 11a are spaced apart in the radial direction of the welding strip 1 and spaced apart in the circumferential direction of the welding strip 1; along the extension direction of the welding strip 1, the projections of the troughs of the multiple first bending segments 11a do not overlap, including: the projections of the troughs of the multiple first bending segments 11a are spaced apart in the radial direction of the welding strip 1 and spaced apart in the circumferential direction of the welding strip 1.

[0075] Along the extension direction of the welding strip 1, the projections of the crests of the multiple second curved segments 11b do not overlap, including: the projections of the crests of the multiple second curved segments 11b are spaced apart in the radial direction of the welding strip 1 and spaced apart in the circumferential direction of the welding strip 1; along the extension direction of the welding strip 1, the projections of the troughs of the multiple second curved segments 11b do not overlap, including: the projections of the troughs of the multiple second curved segments 11b are spaced apart in the radial direction of the welding strip 1 and spaced apart in the circumferential direction of the welding strip 1.

[0076] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A welding strip, characterized in that: The welding strip (1) comprises an inner core (11) and an outer shell (12), wherein the inner core (11) comprises a plurality of continuously arranged curved segments, and the outer shell (12) is wrapped around the outer side of the inner core (11), and the curvature of the welding strip (1) is smaller than the minimum curvature of the curved segments.

2. The welding strip according to claim 1, characterized in that Along the extension direction of the welding strip (1), the diameter of the welding strip (1) remains unchanged.

3. The welding strip according to claim 1, characterized in that The welding strip (1) extends along a straight line.

4. The welding strip according to claim 1, characterized in that The cross-sectional shape of the welding strip (1) is circular, elliptical, triangular or rectangular.

5. The welding strip according to claim 1, characterized in that The diameter d1 of the inner core (11) satisfies: 100 μm ≤ d1 ≤ 400 μm; And / or, the diameter d2 of the welding strip (1) satisfies: 105 μm≤d2≤500 μm.

6. The welding strip according to claim 1, characterized in that The minimum distance d3 between the outer circumference of the inner core (11) and the outer circumference of the outer shell (12) satisfies the following conditions: 5 μm≤d3≤100 μm.

7. The welding strip according to claim 1, characterized in that Along the extension direction of the welding strip (1), the length L of the bending section satisfies: 1 mm ≤ L ≤ 20 mm.

8. The welding strip according to any one of claims 1 to 7, characterized in that: The inner core (11) is a copper wire, and the outer shell (12) is a tin layer.

9. A photovoltaic module, characterized in that: The photovoltaic module comprises a cell (2) and a welding ribbon (1) according to any one of claims 1 to 8, wherein the welding ribbon (1) connects adjacent cells (2).

10. The photovoltaic module according to claim 9, characterized in that: The bending section comprises a first bending section (11a) and a second bending section (11b), the first bending section (11a) is connected to the battery cell (2), and the second bending section (11b) is not connected to the battery cell (2); The second curved section (11b) is located between adjacent first curved sections (11a).

11. The photovoltaic module according to claim 10, characterized in that: Between adjacent first curved sections (11a), the number n of the second curved sections (11b) satisfies: 1≤n≤20.

12. The photovoltaic module according to claim 10, characterized in that: The curvature of the first curved section (11a) is smaller than the curvature of the second curved section (11b).

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