Solar cell, photovoltaic module and manufacturing method thereof

Abstract

The application relates to the technical field of solar cells, in particular to a solar cell, a photovoltaic module and a manufacturing method thereof. The solar cell comprises a cell body and a solder pad group. The cell body has two oppositely arranged cell surfaces. The solder pad group is arranged on at least one cell surface and comprises a plurality of solder pads arranged at intervals along a first direction. In the first direction, the solder pads at the two ends of the solder pad group are edge solder pads, and the remaining solder pads are middle solder pads. The edge solder pads are configured to be provided with a solder paste layer on the side surface away from the cell body, and the thickness of the edge solder pads is T1, the thickness of the middle solder pads is T2, and T2>T1. The application sets the solder paste layer on the edge solder pads to improve the soldering tension after the edge solder pads are soldered. The thickness of the edge solder pads is thinned to make the total thickness of the edge solder pads after the solder paste layer is printed consistent with that of the middle solder pads, so that the solder strip can fully contact the solder paste layer and the middle solder pads, thereby reducing the virtual soldering phenomenon.

Description

Technical Field

[0001] This application relates to the field of solar cell technology, and in particular to a solar cell, a photovoltaic module, and a method for manufacturing the same. Background Technology

[0002] During the manufacturing process of solar cell strings, solder ribbons are welded onto the pads of the solar cells. The solder pads and the tin layer of the solder ribbons form an alloy layer, thereby achieving mechanical and electrical connections between the solder ribbons and the solar cells. However, currently, after the solar cells are soldered, the solder joints at both ends of the pad assembly often have insufficient welding tensile strength. This makes them highly susceptible to desoldering during subsequent lamination or long-term use, which in turn affects the performance and reliability of the photovoltaic modules. Summary of the Invention

[0003] This application discloses a solar cell, a photovoltaic module, and a method for manufacturing the same, which can reduce the phenomenon of poor soldering.

[0004] To achieve the above objectives, in a first aspect, embodiments of this application disclose a solar cell, comprising: The battery body has two battery surfaces arranged opposite to each other; and, A pad group is disposed on at least one of the battery surfaces, the pad group comprising a plurality of pads spaced apart along a first direction; along the first direction, the pads located at both ends of the pad group are edge pads, and the remaining pads are center pads; Wherein, along the thickness direction of the battery body, the edge pad is configured to have a solder paste layer on the surface of the side opposite to the battery body, and the thickness of the edge pad is T1, and the thickness of the middle pad is T2, satisfying the following relationship: T2 > T1.

[0005] In a possible implementation of the first aspect, T1 is 3 μm to 6 μm; and / or, The T2 is 10 μm to 12 μm.

[0006] In one possible implementation of the first aspect, the solar cell is a bifacial solar cell.

[0007] Secondly, embodiments of this application disclose a photovoltaic module, including: A solar cell with multiple electrically connected cells, the solar cell comprising a cell body and a pad assembly, the cell body having two opposing cell surfaces, the pad assembly being disposed on at least one of the cell surfaces, the pad assembly comprising a plurality of pads spaced apart along a first direction; along the first direction, the pads located at both ends of the pad assembly are edge pads, and the remaining pads are center pads; and... A solder ribbon extends along the first direction and is connected to the pads on two solar cells to electrically connect the two solar cells; the solder ribbon includes a conductive core, a first tin alloy layer is provided between the conductive core and the edge pads, and a second tin alloy layer is provided between the conductive core and the central pads; Wherein, along the thickness direction of the battery body, the thickness of the edge pad is T1, the thickness of the middle pad is T2, and the following relationship is satisfied: T2 > T1; the thickness of the first tin alloy layer is T3, the thickness of the second tin alloy layer is T4, and the following relationship is satisfied: T3 > T4.

[0008] In a possible implementation of the second aspect, along the first direction, the portion of the solder strip that is offset from the pad is a non-soldering segment, and a solder strip tin layer is provided on the surface of the conductive core of the non-soldering segment. The conductive core accounts for 90% to 97% of the cross-sectional area in the non-welded section.

[0009] In a possible implementation of the second aspect, the thickness T5 of the solder strip tin layer is 2 μm to 5 μm; and / or, The solder strip tin layer is a tin-lead-bismuth system.

[0010] In a possible implementation of the second aspect, T3 is 10 μm to 20 μm; and / or, The T4 is 2 μm to 8 μm.

[0011] Thirdly, embodiments of this application disclose a method for manufacturing a photovoltaic module, comprising the following steps: Solder paste layer printing: A solder paste layer is printed on a solar cell; wherein the solar cell is the solar cell described in the first aspect, and the solder paste layer is printed on the side surface of the edge pad facing away from the solar cell body along the thickness direction of the cell body; Solder strip laying: Solder strips are laid on the pad assembly of the solar cell; wherein the solder strips are in partial contact with the solder paste layer; Soldering: Heating to solder the pad assembly to the solder strip; wherein a portion of the solder strip is soldered to the edge pads through the solder paste layer.

[0012] In a possible implementation of the third aspect, the thickness of the solder paste layer is T6 along the thickness direction of the battery body, satisfying the following relationship: |(T1+T6)-T2|≤3 μm.

[0013] In a possible implementation of the third aspect, the solder strip includes a conductive core and a solder strip tin layer disposed on the surface of the conductive core, the thickness of the solder strip tin layer being T5; Along the thickness direction of the battery body, the thickness of the solder paste layer is T6, which satisfies the following relationship: 10 μm≤T5+T6≤20 μm.

[0014] In a possible implementation of the third aspect, after the step of printing the solder paste layer and before the step of laying the solder ribbon, the fabrication method further includes the following steps: Pre-curing: The solar cell on which the solder paste layer is printed is heated to pre-cur the solder paste layer.

[0015] In a possible implementation of the third aspect, the solder paste layer is a tin-lead-bismuth system solder paste layer with a melting temperature of 90°C to 160°C; In the pre-curing step, the heating temperature is 55℃~75℃, and the heating time is 3 s~6 s.

[0016] In a possible implementation of the third aspect, the step of laying the solder strip further includes: A pressure fixture is placed on the solar cell on which the solder ribbon is laid, so that the solder ribbon contacts the solder paste layer and the central pad.

[0017] In a possible implementation of the third aspect, the solder strip includes a conductive core and a solder tin layer disposed on the surface of the conductive core; The conductive core accounts for 90% to 97% of the cross-sectional area of ​​the solder strip.

[0018] In a possible implementation of the third aspect, the solder strip tin layer is a tin-lead-bismuth system tin layer with a melting point of 90°C to 160°C; and / or, The thickness T5 of the solder strip tin layer is 2 μm to 5 μm; and / or, The conductive core is made of at least one of copper, aluminum, nickel, or silver.

[0019] Compared with the prior art, the beneficial effects of this application include at least the following: This application improves the solder pull strength after edge pad soldering by applying a solder paste layer on the edge pads. Furthermore, this application reduces the thickness of the edge pads so that the total thickness of the edge pads after solder paste printing is closer to that of the central pads, ensuring sufficient contact between the solder ribbon, the solder paste layer, and the central pads, thereby reducing cold solder joints.

[0020] Specifically, considering the low pull force after edge pad soldering, this application provides a solder paste layer on the surface of the edge pad facing away from the battery body. The solder paste layer can thicken the tin alloy layer between the solder ribbon and the edge pad. Since the tin alloy layer is used to achieve the mechanical connection between the solder ribbon and the edge pad, the solder pull force is roughly proportional to the thickness of the tin alloy layer. Therefore, when the tin alloy layer between the solder ribbon and the edge pad is thickened, it is beneficial to improve the solder pull force after edge pad soldering, thereby enhancing the mechanical connection between the solder ribbon and the edge pad.

[0021] Based on this, this application reduces the thickness of the edge pads. After the solder paste layer is printed on the edge pads, the total thickness of the edge pads and the solder paste layer is closer to the thickness of the central pads. When the solder ribbon is laid on the surface of the cell, the solder ribbon can make full contact with the solder paste layer and the central pads, thereby reducing the phenomenon of cold solder joints. Moreover, the reduction of the edge pad thickness helps to reduce the material cost of solar cells. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the structure of a solar cell disclosed in an embodiment of this application; Figure 2 for Figure 1 A schematic diagram of the structure of a solar cell after the solder paste layer has been printed; Figure 3 for Figure 2 A schematic diagram of the structure of a solar cell after the solder strips have been laid; Figure 4 This is a schematic diagram of the structure of a photovoltaic module disclosed in an embodiment of this application; Figure 5 for Figure 4 A magnified view of a portion of region A shown.

[0024] Explanation of reference numerals in the attached figures: 10. Solar cell; 11. Cell body; 111. Cell surface; 13. Pad assembly; 131. Edge pad; 132. Center pad; X, First direction; Z, Thickness direction of the cell body; 20. Solder strip; 20a. Non-soldering section; 21. Conductive core; 22. First tin alloy layer; 23. Second tin alloy layer; 24. Solder strip tin layer; 30. Solder paste layer. Detailed Implementation

[0025] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0026] In this application, the terms "set up," "equipped with," and "connected" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; 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, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0027] Furthermore, the terms "first," "second," etc., are primarily used to distinguish different devices, components, or parts (which may be the same or different in specific type and construction), and are not intended to indicate or imply the relative importance or quantity of the indicated devices, components, or parts. Unless otherwise stated, "a plurality of" means two or more.

[0028] In the manufacturing process of photovoltaic modules, solar cells are electrically connected by welding them to solder ribbons. However, current methods of welding solar cells to solder ribbons have the following problems: the connection strength between the welding points located on both sides of the solar cell and the solder ribbon is relatively low, and the risk of incomplete soldering and desoldering is high, which in turn affects the reliability of photovoltaic modules.

[0029] The inventors discovered that due to uneven temperature distribution in the heating field created by the welding equipment, heat dissipates more rapidly from the edges of the solar cell during welding. This leads to insufficient temperature at the edges, resulting in lower melting of the solder layer and a thinner alloy layer between the weld points and the solder strip. These thinner layers become weak points in the mechanical connection, leading to lower weld tensile strength test values. Consequently, the weld points at the edges of the solar cell are highly susceptible to detachment during subsequent lamination and operation.

[0030] To improve the welding effect of the solder joints at the edges of solar cells, current improvements involve thickening the solder strip tin layer to increase the thickness of the alloy layer between the solder joint and the solder strip, thereby increasing the welding pull strength. However, a thicker solder strip tin layer melts under the high temperatures of welding and outdoor hot spot effects, forming a large amount of tin. When the molten tin flows to the area where the fine grid is set, the silver in the fine grid reacts with the tin to form silver tin oxide (Ag3Sn). The large amount of tin causes a significant amount of silver in the fine grid to react, leading to grid breakage due to silver deficiency, which in turn causes localized blackening during EL (Electroluminescent) testing of the photovoltaic module.

[0031] Furthermore, a thicker solder layer on the solder ribbon leads to a significant increase in solder consumption, which is detrimental to cost reduction in photovoltaic modules. Moreover, a thicker solder ribbon results in a larger shading area, which in turn affects the conversion efficiency of the solar cells.

[0032] Based on the above analysis, this application provides a solar cell that improves the solder pull strength after edge pad soldering by setting a solder paste layer on the edge pads. Furthermore, this application reduces the thickness of the edge pads so that the total thickness of the edge pads after solder paste printing is closer to that of the central pads, allowing for sufficient contact between the solder ribbon, the solder paste layer, and the central pads, thereby reducing cold solder joints.

[0033] The technical solution of the present invention will now be described in conjunction with the embodiments and accompanying drawings.

[0034] Please refer to the following: Figures 1 to 3 This application discloses a solar cell 10, including a cell body 11 and a pad assembly 13. The cell body 11 has two opposing cell surfaces 111. Specifically, the two cell surfaces 111 refer to the light-receiving surface and the back-lighting surface of the cell body 11. The pad assembly 13 is disposed on at least one cell surface 111, and the pad assembly 13 includes a plurality of pads spaced apart along a first direction X. Along the first direction X, the pads located at both ends of the pad assembly 13 are edge pads 131, and the remaining pads are central pads 132.

[0035] Along the thickness direction Z of the battery body, the edge pad 131 is configured to have a solder paste layer 30 on the side surface opposite to the battery body 11, and the thickness of the edge pad 131 is T1, and the thickness of the middle pad 132 is T2, satisfying the following relationship: T2 > T1.

[0036] This application improves the solder pull force of the edge pads 131 after soldering by providing a solder paste layer 30 on the edge pads 131. Furthermore, this application reduces the thickness of the edge pads 131 so that the total thickness of the edge pads 131 after printing the solder paste layer 30 is closer to that of the central pads 132, allowing for sufficient contact between the solder ribbon 20, the solder paste layer 30, and the central pads 132, thereby reducing the occurrence of cold solder joints.

[0037] Specifically, considering the low welding pull force after welding the edge pad 131, this application provides a solder paste layer 30 on the surface of the edge pad 131 facing away from the battery body 11. The solder paste layer 30 can thicken the tin alloy layer between the solder ribbon 20 and the edge pad 131. Since the tin alloy layer is used to achieve the mechanical connection between the solder ribbon 20 and the edge pad 131, the welding pull force is roughly proportional to the thickness of the tin alloy layer. Therefore, when the tin alloy layer between the solder ribbon 20 and the edge pad 131 is thickened, it is beneficial to improve the welding pull force after welding the edge pad 131, thereby enhancing the mechanical connection between the solder ribbon 20 and the edge pad 131.

[0038] Based on this, this application reduces the thickness of the edge pad 131. After the solder paste layer 30 is printed on the edge pad 131, the total thickness of the edge pad 131 and the solder paste layer 30 is closer to the thickness of the central pad 132. When the solder ribbon 20 is laid on the surface 111 of the cell, the solder ribbon 20 can make full contact with the solder paste layer 30 and the central pad 132, thereby reducing the phenomenon of cold solder joints. Moreover, the thinning of the edge pad 131 helps to reduce the material cost of the solar cell 10.

[0039] Optionally, the thickness T1 of the edge pad 131 is 3 μm to 6 μm, for example, 3 μm, 4 μm, 5 μm, or 6 μm. This application reduces the consumption of electrode material for the edge pad 131 by controlling the thickness T1 ≤ 6 μm. The electrode material can be, for example, silver, copper, nickel, or tin. Furthermore, the total thickness of the edge pad 131 after the solder paste layer 30 is applied is still relatively thin. Since the thickness of the central pad 132 is similar to the total thickness of the edge pad 131 after the solder paste layer 30 is printed, the thickness T2 of the central pad 132 is also relatively thin, thus reducing the consumption of electrode material for the central pad 132. This application controls the thickness T1 of the edge pad 131 to be ≥ 3 μm so that the edge pad 131 is still relatively thick, thereby enabling a strong mechanical connection and stable electrical connection with the solder ribbon 20 after soldering.

[0040] Optionally, the thickness T2 of the central pad 132 is 10 μm to 12 μm, for example, 10 μm, 10.5 μm, 11 μm, 11.5 μm, or 12 μm. This application controls the thickness T2 of the central pad 132 to be ≥10 μm, so that the central pad 132 can form a strong mechanical connection and a stable electrical connection with the solder strip 20 after soldering. Controlling the thickness T2 of the central pad 132 to ≤12 μm helps reduce the consumption of electrode material for the central pad 132, thereby reducing the material cost of the solar cell 10.

[0041] Optionally, the solar cell 10 is a bifacial solar cell. Compared with a back-contact solar cell, the two polarity pads 13 of the bifacial solar cell are respectively disposed on the two cell surfaces 111, thereby achieving good insulation and reducing the risk of short circuit, and eliminating the need to print insulating adhesive.

[0042] For example, the bifacial solar cell 10 is a passivated contact solar cell (TOPCon solar cell), a heterojunction solar cell (HJT solar cell), or a perovskite tandem solar cell.

[0043] In some embodiments, the battery body includes a silicon substrate and a doped semiconductor layer and a functional layer sequentially deposited on the surface of the silicon substrate. The doped semiconductor layer is, for example, a doped polycrystalline silicon layer, a doped amorphous silicon layer, or a diffusion layer. The functional layer is, for example, a passivation layer, an antireflection layer, or a transparent conductive layer, and the material of the functional layer can be silicon oxide, aluminum oxide, silicon oxynitride, or silicon nitride. Pads are disposed on the side of the functional layer facing away from the silicon substrate.

[0044] Please refer to the above as well. Figure 4 and Figure 5 This application also discloses a photovoltaic module, including multiple electrically connected solar cells 10 and solder strips 20.

[0045] The solar cell 10 includes a cell body 11 and a pad assembly 13. The cell body 11 has two opposing cell surfaces 111. The pad assembly 13 is disposed on at least one cell surface 111 and includes a plurality of pads spaced apart along a first direction X. Along the first direction X, the pads located at both ends of the pad assembly 13 are edge pads 131, and the remaining pads are center pads 132.

[0046] The solder ribbon 20 extends along a first direction X and connects to pads 13 on two solar cells 10 to electrically connect the two solar cells 10, for example, in series or in parallel. The solder ribbon 20 includes a conductive core 21, a first tin alloy layer 22 between the conductive core 21 and the edge pad 131, and a second tin alloy layer 23 between the conductive core 21 and the central pad 132.

[0047] Along the thickness direction Z of the battery body, the thickness of the edge pad 131 is T1, and the thickness of the middle pad 132 is T2, satisfying the following relationship: T2 > T1. The thickness of the first tin alloy layer 22 is T3, and the thickness of the second tin alloy layer 23 is T4, satisfying the following relationship: T3 > T4.

[0048] The photovoltaic module of this application enhances the mechanical connection between the edge pad 131 and the solder strip 20 by increasing the thickness of the first tin alloy layer 22 between the edge pad 131 and the conductive core 21, thereby increasing the welding pull force after the edge pad 131 is welded.

[0049] Based on this, this application reduces the thickness of the edge pad 131, making the total thickness of the edge pad 131 and the first tin alloy layer 22 nearly the same as the thickness of the central pad 132. This allows the solder ribbon 20 to make full contact with both the edge pad 131 and the central pad 132, thereby reducing the occurrence of cold solder joints. Furthermore, thinning the edge pad 131 helps reduce the material cost of the solar cell 10.

[0050] Since this application enhances the solder pull force after soldering the edge pad 131 by adding a solder paste layer 30 on the edge pad 131, this application does not need to enhance the solder pull force by using a thicker solder ribbon layer 24, and can thin the solder ribbon layer 24 to reduce the silver etching reaction caused by solder, thereby reducing the risk of gate breakage in fine gates, the amount of solder consumed by the solder ribbon 20, and reducing the shielding area of ​​the solder ribbon 20.

[0051] Based on this, in some embodiments, along the first direction X, the portion of the solder ribbon 20 that is offset from the pad is a non-soldering segment 20a, and a solder ribbon tin layer 24 is disposed on the surface of the conductive core 21 of the non-soldering segment 20a. The cross-sectional area of ​​the conductive core 21 in the non-soldering segment 20a accounts for 90% to 97%, for example, 90%, 93%, 95%, or 97%. This application controls the cross-sectional area of ​​the conductive core 21 in the non-soldering segment 20a to be ≥90%, so that the resistivity of the solder ribbon 20 is close to that of the conductive core 21, which is beneficial to reducing the transmission loss of the solder ribbon 20 and thus improving the conversion efficiency of the photovoltaic module. Furthermore, the lower cross-sectional area of ​​the solder ribbon tin layer 24 in the solder ribbon 20 helps to reduce the grid breakage problem caused by the solder ribbon tin layer 24 and reduce the solder consumption of the solder ribbon 20. This application controls the cross-sectional area ratio of the conductive core 21 in the non-soldering section 20a to be ≤97%, thereby reserving a sufficient cross-sectional area ratio for the setting of the solder strip tin layer 24. The thickness of the solder strip tin layer 24 is still relatively thick, so that it can form a strong mechanical connection with the solder pad after soldering.

[0052] Alternatively, the specifications of the welding strip can be φ0.2 mm, φ0.22 mm, φ0.23 mm, φ0.24 mm, φ0.25 mm or φ0.26 mm.

[0053] Optionally, the thickness T5 of the solder ribbon tin layer 24 is 2 μm to 5 μm, for example, 2 μm, 3 μm, 4 μm, or 5 μm. This application controls the thickness T5 of the solder ribbon tin layer 24 to be ≥ 2 μm to ensure a strong mechanical connection between the solder ribbon 20 and the pad after soldering. Controlling the thickness T5 of the solder ribbon tin layer 24 to be ≤ 5 μm reduces the risk of gate breakage in fine gates, and also helps to reduce the solder consumption of the solder ribbon 20 and the obstruction area of ​​the solder ribbon 20.

[0054] Optionally, the solder strip tin layer 24 is a tin-lead-bismuth system. The tin-lead-bismuth system solder strip tin layer 24 has a lower melting point, which is beneficial for it to melt fully during soldering and form a strong mechanical connection with the solder pad.

[0055] Optionally, the thickness T3 of the first tin alloy layer 22 is 10 μm to 20 μm, for example, 10 μm, 13 μm, 15 μm, 17 μm, or 20 μm. This application controls the thickness T3 of the first tin alloy layer 22 to be ≥10 μm to ensure a sufficiently strong mechanical connection between the conductive core 21 and the edge pad 131, thereby increasing the welding pull force at the location of the edge pad 131. This application also controls the thickness T3 of the first tin alloy layer 22 to be ≤20 μm to reduce the amount of tin consumed by the photovoltaic module, and can also reduce solder balling and spike phenomena caused by excessive tin.

[0056] Optionally, the thickness T4 of the second tin alloy layer 23 is 2 μm to 8 μm, for example, 2 μm, 4 μm, 6 μm, or 8 μm. This application controls the thickness T4 of the second tin alloy layer 23 to be ≥ 2 μm to ensure a sufficiently strong mechanical connection between the conductive core 21 and the central pad 132, thereby increasing the welding pull force at the location of the central pad 132. This application controls the thickness T4 of the second tin alloy layer 23 to be ≤ 8 μm to reduce the tin consumption of the photovoltaic module.

[0057] This application also discloses a method for manufacturing a photovoltaic module, including the following steps: Solder paste layer printing: A solder paste layer 30 is printed on the solar cell 10; wherein the solar cell 10 is the solar cell 10 in any of the above embodiments. (Refer to previous section) Figure 1 and Figure 2 Along the thickness direction Z of the battery body, the solder paste layer 30 is printed on the side surface of the edge pad 131 facing away from the battery body 11.

[0058] Laying welding strips: such as Figure 3 As shown, solder ribbon 20 is laid on the pad assembly of solar cell 10; wherein, solder ribbon 20 is in partial contact with solder paste layer 30.

[0059] Soldering: Heating to solder the pad assembly to the solder ribbon; wherein, the solder ribbon is partially soldered to the edge pads through a layer of solder paste.

[0060] This application provides a solder paste layer 30 on the side of the edge pad 131 facing away from the battery body 11. The solder paste layer 30 can increase the thickness of the tin alloy layer between the solder ribbon 20 and the edge pad 131, thereby enhancing the mechanical connection between the solder ribbon 20 and the edge pad 131 and improving the welding pull force after the edge pad 131 is welded.

[0061] Based on this, this application reduces the thickness of the edge pad 131. After the solder paste layer 30 is printed on the edge pad 131, the total thickness of the edge pad 131 and the solder paste layer 30 is closer to that of the central pad 132. This allows for sufficient contact between the solder ribbon 20, the solder paste layer 30, and the central pad 132, thereby reducing the occurrence of cold solder joints. Furthermore, reducing the thickness of the edge pad 131 helps to lower the material cost of solar cells.

[0062] like Figure 3 As shown, optionally, along the thickness direction Z of the battery body, the thickness of the solder paste layer 30 is T6, satisfying the following relationship: |(T1+T6)-T2|≤3 μm, for example, 0, 0.1 μm, 0.5 μm, 1 μm, 2 μm or 3 μm. By controlling |(T1+T6)-T2|≤3 μm, after the solder paste layer 30 is printed on the edge pad 131, the total thickness T1+T6 of the edge pad 131 and the solder paste layer 30 tends to be consistent with the thickness T2 of the middle pad 132. The solder ribbon 20 can fully contact the solder paste layer 30 and the middle pad 132, thereby reducing the phenomenon of cold solder joints.

[0063] For example, the thickness of the solder paste layer is 4 μm to 8 μm, such as 4 μm, 6 μm, or 8 μm. The length of the solder paste layer can be 0.4 mm to 1.2 mm, such as 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.9 mm, 1 mm, or 1.2 mm. The width of the solder paste layer can be 0.4 mm to 1.2 mm, such as 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.9 mm, 1 mm, or 1.2 mm.

[0064] In some embodiments, such as Figure 3As shown, the solder ribbon 20 includes a conductive core 21 and a solder ribbon tin layer 24 disposed on the surface of the conductive core 21, the thickness of which is T5. Along the thickness direction Z of the battery body, the thickness of the solder paste layer 30 is T6, satisfying the following relationship: 10 μm ≤ T5 + T6 ≤ 20 μm, where T5 + T6 is, for example, 10 μm, 15 μm, or 20 μm. This application controls the total thickness of the solder paste layer 30 and the solder ribbon tin layer 24 to be ≥10 μm, so that a sufficiently thick tin alloy layer can be formed between the solder ribbon 20 and the edge pad 131, thereby enhancing the mechanical connection between the edge pad 131 and the solder ribbon 20, resulting in a stronger weld. This application controls the total thickness of the solder paste layer 30 and the solder ribbon tin layer 24 to be ≤20 μm to reduce solder consumption and avoid solder balling and spike phenomena caused by excessive solder.

[0065] It is understandable that the middle pad 132 can be soldered to the solder ribbon 20 through the solder ribbon tin layer 24, therefore, no solder paste layer is required on the middle pad 132.

[0066] In some embodiments, after the step of printing the solder paste layer and before the step of laying the solder ribbon, the manufacturing method further includes the following steps: Pre-curing: Heating the solar cell with the printed solder paste layer to pre-cur the solder paste layer.

[0067] This application pre-cures the solder paste layer so that it is cured to a certain extent but not completely solidified. The pre-cured solder paste layer enables the solder ribbon to initially adhere to the pads of the solar cell, achieving pre-positioning before soldering.

[0068] Optionally, the solder paste layer is a tin-lead-bismuth system solder paste layer with a melting temperature of 90°C to 160°C, for example, 90°C, 110°C, 130°C, 150°C or 160°C.

[0069] Furthermore, in the pre-curing step, the heating temperature is 55℃~75℃, for example, 55℃, 60℃, 65℃, 70℃ or 75℃, and the heating time is 3 s~6 s, for example, 3 s, 4 s, 5 s or 6 s.

[0070] This application controls the heating temperature and duration during pre-curing to ensure that the tin-lead-bismuth system solder paste layer is not completely solidified after pre-curing. The incompletely solidified solder paste layer retains flux, thus ensuring that the solder ribbon initially adheres to the solar cell pads after pre-curing, thereby improving the solder ribbon's positioning effect. In subsequent soldering steps, the pre-cured solder paste layer is further soldered and fixed, further enhancing the mechanical connection between the edge pads and the solder ribbon.

[0071] Furthermore, the step of laying the welding strip also includes: A pressure fixture is placed on the solar cell with solder ribbon laid on it so that the solder ribbon comes into contact with the solder paste layer and the central pad.

[0072] After the solder paste layer is pre-cured, the embodiments of this application can use a traction device to pull the solder ribbon onto the battery surface and use a pressure fixture to pre-press the solder ribbon to increase the contact area between the solder ribbon and the solder paste layer, as well as between the solder ribbon and the central pad, which is beneficial to improving the welding effect.

[0073] In some embodiments, the solder strip includes a conductive core and a solder tin layer disposed on the surface of the conductive core; wherein the cross-sectional area of ​​the conductive core in the solder strip accounts for 90% to 97%, for example, 90%, 95% or 97%.

[0074] Because this application improves the solder pull strength after edge pad soldering by setting a solder paste layer on the edge pads, it no longer needs to increase the solder pull strength by thickening the solder strip solder layer. Therefore, this application can increase the cross-sectional area ratio of the conductive core in the solder strip by thinning the solder strip solder layer. Specifically, the cross-sectional area ratio of the conductive core in the solder strip is 90%~97%, making the solder strip a thin solder strip. A thin solder strip can reduce the amount of solder consumed, thereby reducing the manufacturing cost of photovoltaic modules. It can also reduce the amount of liquid solder formed after the solder strip solder layer melts, thus reducing the risk of the fine grid being etched through by solder.

[0075] Furthermore, the high cross-sectional area of ​​the conductive core in the solder strip results in a resistivity of the solder strip close to that of the conductive core, which helps reduce transmission losses. Additionally, the smaller area of ​​the tin alloy layer formed after soldering the thin tin layer reduces light shading, thus improving the conversion efficiency of the photovoltaic module.

[0076] Optionally, the conductive core may be made of at least one of copper, aluminum, nickel or silver, which have low resistance and thus good conductivity.

[0077] Optionally, the solder strip tin layer is a tin-lead-bismuth system tin layer with a melting point of 90°C to 160°C, for example, 90°C, 110°C, 130°C, 150°C or 160°C.

[0078] It can be seen that the solder ribbon tin layer and the solder paste layer are both tin-lead-bismuth system, and their components are the same or compatible, which is conducive to improving the stability of the tin alloy layer interface, and thus conducive to forming a solid mechanical connection.

[0079] The present application will be further described below with reference to embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present application.

[0080] Example 1 This embodiment of a photovoltaic module manufacturing method includes the following steps: S1. Applying front adhesive film: Applying front adhesive film to the front cover plate.

[0081] S2. Placing the Solar Cell: Placing the solar cell on the front-side adhesive film. The solar cell includes a cell body and a set of pads. The cell body has two opposing cell surfaces. Multiple sets of pads are respectively disposed on the two cell surfaces, each set including multiple pads spaced apart along a first direction. Along the first direction, the pads at both ends of the pad set are edge pads, and the remaining pads are center pads. Along the thickness direction of the cell body, solder paste is printed on the side of the edge pads facing away from the cell body, with the edge pads having a thickness of 4 μm and the center pads having a thickness of 11 μm.

[0082] S3. Printed Solder Paste Layer: A solder paste layer is printed on the solar cell. The thickness of the solder paste layer is 7 μm, and the solder paste layer is a tin-lead-bismuth system solder paste layer with a melting temperature of 120℃.

[0083] S4. Pre-curing: The solar cell with the printed solder paste layer is heated to pre-cur the solder paste layer. The heating temperature is 70℃ and the heating time is 4 seconds.

[0084] S5. Laying the solder ribbon: Laying the solder ribbon on the pad assembly of the solar cell. The solder ribbon includes a conductive core and a solder tin layer on the surface of the conductive core. The solder tin layer is a tin-lead-bismuth system tin layer with a melting point of 130±5℃. The solder ribbon has a diameter of φ0.22 mm, a solder tin layer thickness of 3 μm, and the conductive core accounts for 94.6% of the cross-sectional area of ​​the solder ribbon.

[0085] S6. Welding: High-temperature lamp box equipment is used to heat the solar cell pads and welding strips to obtain a cell string.

[0086] S7. Lamination: A back adhesive film and a back cover are applied to the battery string, and then laminated to obtain a photovoltaic module.

[0087] Comparative Example 1 The difference between this comparative example and Example 1 is that the thickness of both the edge pads and the center pads is 11 μm, and steps S3 and S4 are not performed.

[0088] The photovoltaic modules prepared in Example 1 and Comparative Example 1 were tested, and the test results are shown in Table 1. The welding tensile strength was tested according to the standard IEC 61215-2:2021 (Design qualification and type approval of terrestrial crystalline silicon photovoltaic modules – Part 2: Test procedures), and the power was tested according to the standard IEC 60904-1:2020 (Photovoltaic devices – Part 1: Measurement of current-voltage characteristics of photovoltaic devices).

[0089] Table 1: Test results of photovoltaic modules in each embodiment and comparative example

[0090] As shown in Table 1, during the welding process of Comparative Example 1, the uneven temperature of the heat field generated by the welding equipment led to faster heat loss in the edge areas of the solar cells. This resulted in insufficient temperature in these edge areas, leading to lower melting of the solder layer on the edge pads. Consequently, the alloy layer between the edge pads and the solder strip was thinner, becoming a weak point in the mechanical connection. The welding pull force of the edge pads was only 1.75 N, lower than that of the central pads. Desoldering and cold solder joints were more common after edge pad welding, resulting in a lower yield rate and ultimately affecting the power output of the photovoltaic modules.

[0091] In contrast, Example 1 increases the solder pull force of the edge pads to 2.08 N by applying a solder paste layer on the edge pads. Furthermore, Example 1 reduces the thickness of the edge pads so that the total thickness after printing the solder paste layer on the edge pads is closer to that of the central pads. This allows the central pads to still maintain good contact with the solder strip, which is beneficial for soldering the central pads. The solder pull force of the central pads remains high, resulting in fewer soldering defects such as desoldering and cold solder joints. The yield rate of the solder joints is increased to 94.5%, thereby improving the power output of the photovoltaic modules.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application 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 therein. Such 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 this application.

Claims

1. A solar cell, characterized in that, include: The battery body has two battery surfaces that are positioned opposite to each other; as well as, A pad group is disposed on at least one of the battery surfaces, the pad group comprising a plurality of pads spaced apart along a first direction; along the first direction, the pads located at both ends of the pad group are edge pads, and the remaining pads are center pads; Wherein, along the thickness direction of the battery body, the edge pad is configured to have a solder paste layer on the surface of the side opposite to the battery body, and the thickness of the edge pad is T1, and the thickness of the middle pad is T2, satisfying the following relationship: T2 > T1.

2. The solar cell according to claim 1, characterized in that, The T1 is 3 μm to 6 μm; and / or, The T2 is 10 μm to 12 μm.

3. The solar cell according to claim 1 or 2, characterized in that, The solar cell is a bifacial solar cell.

4. A photovoltaic module, characterized in that, include: A solar cell with multiple electrically connected cells, the solar cell comprising a cell body and a pad assembly, the cell body having two opposing cell surfaces, the pad assembly being disposed on at least one of the cell surfaces, the pad assembly comprising a plurality of pads spaced apart along a first direction; along the first direction, the pads located at both ends of the pad assembly are edge pads, and the remaining pads are center pads; and... A solder ribbon extends along the first direction and is connected to the pads on two solar cells to electrically connect the two solar cells; the solder ribbon includes a conductive core, a first tin alloy layer is provided between the conductive core and the edge pads, and a second tin alloy layer is provided between the conductive core and the central pads; Wherein, along the thickness direction of the battery body, the thickness of the edge pad is T1, the thickness of the middle pad is T2, and the following relationship is satisfied: T2 > T1; the thickness of the first tin alloy layer is T3, the thickness of the second tin alloy layer is T4, and the following relationship is satisfied: T3 > T4.

5. The photovoltaic module according to claim 4, characterized in that, Along the first direction, the portion of the solder strip that is offset from the solder pad is a non-soldering segment, and a solder strip tin layer is provided on the surface of the conductive core in the non-soldering segment. The cross-sectional area of ​​the conductive core in the non-welded section accounts for 90% to 97%.

6. The photovoltaic module according to claim 5, characterized in that, The thickness T5 of the solder strip tin layer is 2 μm to 5 μm; and / or, The solder strip tin layer is a tin-lead-bismuth system.

7. The photovoltaic module according to any one of claims 4 to 6, characterized in that, The T3 is 10 μm to 20 μm; and / or, The T4 is 2 μm to 8 μm.

8. A method for manufacturing a photovoltaic module, characterized in that, Includes the following steps: Solder paste layer printing: A solder paste layer is printed on a solar cell; wherein the solar cell is the solar cell according to any one of claims 1 to 3, and the solder paste layer is printed on the side surface of the edge pad opposite to the solar cell body along the thickness direction of the cell body; Solder strip laying: Solder strips are laid on the pad assembly of the solar cell; wherein the solder strips are in partial contact with the solder paste layer; Soldering: Heating to solder the pad assembly to the solder strip; wherein a portion of the solder strip is soldered to the edge pads through the solder paste layer.

9. The manufacturing method according to claim 8, characterized in that, Along the thickness direction of the battery body, the thickness of the solder paste layer is T6, satisfying the following relationship: |(T1+T6)-T2|≤3 μm.

10. The manufacturing method according to claim 8, characterized in that, The solder strip includes a conductive core and a solder tin layer disposed on the surface of the conductive core, wherein the thickness of the solder tin layer is T5; Along the thickness direction of the battery body, the thickness of the solder paste layer is T6, which satisfies the following relationship: 10 μm≤T5+T6≤20 μm.

11. The manufacturing method according to any one of claims 8 to 10, characterized in that, After the step of printing the solder paste layer and before the step of laying the solder ribbon, the manufacturing method further includes the following steps: Pre-curing: The solar cell on which the solder paste layer is printed is heated to pre-cur the solder paste layer.

12. The manufacturing method according to claim 11, characterized in that, The solder paste layer is a tin-lead-bismuth system solder paste layer with a melting temperature of 90℃~160℃; In the pre-curing step, the heating temperature is 55℃~75℃, and the heating time is 3 s~6 s.

13. The manufacturing method according to any one of claims 8 to 10, characterized in that, The step of laying the welding strip also includes: A pressure fixture is placed on the solar cell on which the solder ribbon is laid, so that the solder ribbon contacts the solder paste layer and the central pad.

14. The manufacturing method according to any one of claims 8 to 10, characterized in that, The solder strip includes a conductive core and a solder tin layer disposed on the surface of the conductive core. The conductive core accounts for 90% to 97% of the cross-sectional area of ​​the solder strip.

15. The manufacturing method according to claim 14, characterized in that, The solder strip tin layer is a tin-lead-bismuth system tin layer with a melting point of 90℃~160℃; and / or, The thickness T5 of the solder strip tin layer is 2 μm to 5 μm; and / or, The conductive core is made of at least one of copper, aluminum, nickel, or silver.

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