Photovoltaic cell, photovoltaic module, and method for manufacturing photovoltaic cell

Abstract

The application relates to a photovoltaic cell, a photovoltaic module and a manufacturing method of the photovoltaic cell. The photovoltaic cell comprises a cell body, two first regions arranged at intervals along a first direction and a second region between the two first regions, the first direction being perpendicular to the thickness direction of the cell body; and a grid line comprising a plurality of welding portions arranged on the cell body and arranged at intervals along the first direction; wherein at least part of the welding portions in the second region are configured as a second material, at least part of the welding portions in the first region are configured as a first material, and only the first material comprises copper and manganese among the first material and the second material. The above photovoltaic cell, photovoltaic module and manufacturing method of the photovoltaic cell can solve the reliability problem of grid line breakage in the middle part of the photovoltaic cell and welding strip separation at the end part.

Description

Technical Field

[0001] This application relates to the field of photovoltaic cell technology, and in particular to photovoltaic cells, photovoltaic modules, and methods for manufacturing photovoltaic cells. Background Technology

[0002] With the increasing urgency of cost reduction and efficiency improvement in the photovoltaic industry, the metallization level of photovoltaic cells is constantly increasing, and cell grid lines are rapidly developing towards finer designs. While finer grid lines help improve the photoelectric conversion efficiency of cells, they also bring significant hidden dangers: during hot spot testing, the temperature in the central region of the cell can rise to 160℃-220℃, far exceeding the melting point of the solder, which can easily cause grid line breakage. Under high and low temperature cycling testing conditions, the solder ribbon end area generates significant stress due to size effects, which can easily cause the contact between the solder and the grid lines to gradually weaken, leading to desoldering. Both grid line breakage and desoldering problems directly hinder the collection and transmission of photocurrent inside the cell, increase the local resistance of the module and exacerbate heat generation, which not only significantly reduces the power generation efficiency of photovoltaic modules but also accelerates the aging and failure of internal materials, severely shortening the lifespan of the modules. Summary of the Invention

[0003] Therefore, it is necessary to provide a method for manufacturing photovoltaic cells, photovoltaic modules, and photovoltaic cells to solve the reliability problems of broken grid lines in the middle of photovoltaic cells and detached solder strips at the ends.

[0004] A photovoltaic cell, the photovoltaic cell comprising:

[0005] The battery cell body includes two first regions spaced apart along a first direction, and a second region located between the two first regions, wherein the first direction is perpendicular to the thickness direction of the battery cell body.

[0006] The grid line includes a plurality of welded portions disposed on the battery cell body, the plurality of welded portions being spaced apart along the first direction;

[0007] Wherein, at least a portion of the welded portion located in the second region is configured with a second material, and at least a portion of the welded portion located in the first region is configured with a first material, wherein only the first material includes copper and manganese.

[0008] In some embodiments, all of the welded portions located in the second region are configured to be the second material;

[0009] And / or, all of the welded portions located in the first region are configured with the first material.

[0010] In some embodiments, the copper content in the first material is 100-3000 ppmw, and the manganese content is 50-1000 ppmw.

[0011] In some embodiments, the glass powder content in the first material is not less than 2% and not more than 5%;

[0012] The glass powder content in the second material is not less than 4% and not more than 8%.

[0013] In some embodiments, the dimension of the first region along the first direction is 1 / 8 to 1 / 5 of the total dimension of the battery cell body along the first direction.

[0014] In some embodiments, the welding portion includes centipede legs or welding pads;

[0015] Alternatively, some of the welded parts may be centipede legs, and some of the welded parts may be solder pads.

[0016] In some embodiments, at least a portion of the welded portion located in the first region includes a plurality of welded segments connected in sequence, wherein at least two adjacent welded segments are arranged at an angle to each other in their length directions.

[0017] In some embodiments, the area of ​​the weld portion located in the first region covering the battery cell body is not greater than the area of ​​the weld portion located in the second region covering the battery cell body.

[0018] In some embodiments, the welded portion located in the first region is M-shaped, V-shaped, U-shaped, X-shaped, or Y-shaped.

[0019] In some embodiments, the plurality of welding segments include a first welding segment and a second welding segment arranged alternately along a second direction, wherein the length direction of the first welding segment is parallel to the first direction, the length direction of the second welding segment and the extension direction of the grid of the photovoltaic cell are both parallel to the second direction, and the second direction intersects the first direction;

[0020] The dimension of the first welded segment along the first direction is greater than the width of the fine grid, and the dimension of the second welded segment along the first direction is not greater than the width of the fine grid.

[0021] In some embodiments, the dimension of the first weld segment along the first direction is 1.5 to 4 times the width of the fine grid;

[0022] The dimension of the second welded segment along the first direction is 0.5 to 1 times the width of the fine grid.

[0023] In some embodiments, the area of ​​the welded portion located in the first region covering the battery cell body is a, wherein the sum of the areas of all the first welded segments covering the battery cell body is b, and 0.3≤b / a≤0.7.

[0024] In some embodiments, one of the plurality of welded segments is connected to the fine grid of the photovoltaic cell at the end, and the width of the welded segment at the end gradually decreases in the orientation close to the fine grid.

[0025] In some embodiments, the area of ​​the weld portion located in the first region that covers the battery cell body is greater than the area of ​​the weld portion located in the second region that covers the battery cell body.

[0026] A photovoltaic module, the photovoltaic module comprising the photovoltaic cells described above.

[0027] A method for manufacturing a photovoltaic cell, the method comprising:

[0028] A battery cell body is provided, the battery cell body including two first regions spaced apart along a first direction, and a second region located between the two first regions, the first direction being perpendicular to the thickness direction of the battery cell body;

[0029] A grid line paste is printed on the battery cell body to form a plurality of enlarged portions spaced apart along the first direction. The enlarged portions form welded portions after curing.

[0030] Wherein, at least a portion of the enlarged portion located in the second region is printed using a second paste, and at least a portion of the enlarged portion located in the first region is printed using a first paste, wherein only the first paste includes copper and manganese elements.

[0031] In some embodiments, the glass powder content in the first slurry is not less than 2% and not more than 5%;

[0032] The glass powder content in the second slurry is not less than 4% and not more than 8%.

[0033] In some embodiments, the median particle size of the silver powder in the first slurry is 1 micrometer to 1.1 micrometers;

[0034] In the second slurry, the median particle size of the silver powder is 1.3 to 1.4 micrometers.

[0035] The aforementioned photovoltaic cells, photovoltaic modules, and photovoltaic cell manufacturing methods, through differentiated material design for the welding portions of the first and second regions of the photovoltaic cell (where the first region can specifically be the end region of the cell body, and the second region can specifically be the middle region of the cell body), can specifically solve the two major problems of end desoldering and middle grid breakage existing in the prior art. Specifically, at least a portion of the welding portion of the first region uses a first material, which includes copper and manganese elements, that is, the first material is formed by curing the main grid paste (first paste), thus significantly improving the bonding force with the solder, effectively resisting the stress on the solder ribbon end during high and low temperature cycling, and minimizing the desoldering phenomenon caused by weakened contact between the solder and the grid line; at least a portion of the welding portion of the second region uses a second material, which does not include copper and manganese elements, that is, the second material is formed by curing the fine grid paste (second paste), thus making it less likely to form an excessively thick brittle and hard alloy layer with the solder under the high temperature environment of hot spot testing, reducing the generation of alloy layer cracks during cooling, thereby minimizing grid line breakage failure. The above design significantly improves the overall reliability and lifespan of the battery, ensuring the long-term stable power generation performance of the photovoltaic cell. Attached Figure Description

[0036] Figure 1 This is a top view of a battery cell in one embodiment of this application.

[0037] Figure 2 This is a magnified view of a portion of the area near the first region in one embodiment of this application.

[0038] Figure 3 This is a magnified view of a certain welded part (first welded part) in the first region of an embodiment of this application.

[0039] Figure 4 This is a schematic diagram of a welding portion (first welding portion) in the first region in one embodiment of this application.

[0040] Figure 5 This is a magnified view of a portion of the area near the first region in another embodiment of this application.

[0041] Figure 6 This is a magnified view of a certain welded part (first welded part) in the first region in another embodiment of this application.

[0042] Figure 7 This is a schematic diagram of the welded portion (first welded portion) in the first region in another embodiment of this application.

[0043] Figure 8 Stress simulation diagram when the welded part of the first region adopts the shape of the prior art.

[0044] Figure 9Stress simulation diagram when the welded part in the first region is designed as a V-shape.

[0045] Figure 10 Stress simulation diagram when the welding part of the first region is designed with an alternating arrangement of the first welding segment and the second welding segment.

[0046] Figure 11 This is a schematic diagram of the first region of a solar cell in the prior art after EL testing.

[0047] Figure 12 This is a schematic diagram of the second region of a solar cell in the prior art after EL testing.

[0048] Figure 13 This is a schematic diagram of the battery cells after EL testing in one embodiment of this application.

[0049] Figure 14 This is a flowchart of a method for manufacturing a photovoltaic cell according to one embodiment of this application.

[0050] Figure label:

[0051] 100. Cell body; 110. First region; 120. Second region; 200. Welding section; 211. Welding segment; 211a. First welding segment; 211b. Second welding segment; 300. Main grid; 400. Fine grid. Detailed Implementation

[0052] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0053] In the description of this application, it should be understood that if terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" appear, these terms indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and 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, and therefore should not be construed as a limitation of this application.

[0054] Furthermore, where the terms "first" and "second" appear, these terms are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, where the term "multiple" appears, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0055] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; 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; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0056] In this application, unless otherwise expressly specified and limited, the use of descriptions such as "above" or "below" the second feature indicates that the first and second features are in direct contact or indirect contact via an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. Similarly, "below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0057] It should be noted that if an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. If an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. If so, the terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used in this application are for illustrative purposes only and do not represent the only possible implementation.

[0058] With the increasing urgency of cost reduction and efficiency improvement in the photovoltaic industry, the metallization level of photovoltaic cells is constantly increasing, and cell grid lines are rapidly developing towards finer designs. While finer grid lines help improve the photoelectric conversion efficiency of cells, they also bring significant hidden dangers: during hot spot testing, the temperature in the central region of the cell can rise to 160℃-220℃, far exceeding the melting point of the solder, which can easily cause grid line breakage. Under high and low temperature cycling testing conditions, the solder ribbon end area generates significant stress due to size effects, which can easily cause the contact between the solder and the grid lines to gradually weaken, leading to desoldering. Both grid line breakage and desoldering problems directly hinder the collection and transmission of photocurrent inside the cell, increase the local resistance of the module and exacerbate heat generation, which not only significantly reduces the power generation efficiency of photovoltaic modules but also accelerates the aging and failure of internal materials, severely shortening the lifespan of the modules.

[0059] Based on this, embodiments of this application provide a photovoltaic cell and a photovoltaic module. By differentiating the materials used for welding to the solder strip in the end region and middle region of the photovoltaic cell, the reliability problems of grid line breakage in the middle and solder strip detachment at the end of the photovoltaic cell are solved. Specifically, at least a portion of the welding portion in the end region is printed and cured using a first paste (main grid paste), thereby improving its bonding strength with the solder, resisting the stress on the solder strip end during high and low temperature cycling, and minimizing the detachment phenomenon caused by weakened contact between the solder and the grid line; at least a portion of the welding portion in the middle region is printed and cured using a second paste (fine grid paste), which is less likely to form an excessively thick brittle and hard alloy layer with the solder under the high temperature environment of hot spot testing, and can reduce the generation of alloy layer cracks when cooling down, thereby minimizing grid breakage failure.

[0060] The above concept will now be described in detail with reference to specific embodiments and accompanying drawings.

[0061] See Figure 1 , Figure 2 and Figure 5 An embodiment of this application provides a photovoltaic cell including a cell body 100 and grid lines. The cell body 100 includes two first regions 110 spaced apart along a first direction, and a second region 120 located between the two first regions 110. The first direction is perpendicular to the thickness direction of the cell body 100. The grid lines include a plurality of welded portions 200 disposed on the cell body 100, which are spaced apart along the first direction. At least some of the welded portions 200 located in the first region 110 are configured with a first material, and at least some of the welded portions 200 located in the second region 120 are configured with a second material. Of the first and second materials, only the first material includes copper and manganese elements.

[0062] In the above embodiments, by using differentiated material design for the welding portion 200 of the first region 110 and the second region 120 of the photovoltaic cell (wherein, the first region 110 can specifically be the end region of the cell body 100, and the second region 120 can specifically be the middle region of the cell body 100), the two major problems of end desoldering and middle grid breakage existing in the prior art can be specifically solved. Specifically, at least a portion of the welded portion 200 in the first region 110 is made of a first material, which includes copper and manganese elements. This first material is formed by curing the main grid paste (first paste), thus significantly improving the bonding strength with the solder and effectively resisting the stress on the solder ribbon ends during high and low temperature cycling, minimizing the risk of desoldering due to weakened contact between the solder and the grid lines. At least a portion of the welded portion 200 in the second region 120 is made of a second material, which does not include copper and manganese elements. This second material is formed by curing the fine grid paste (second paste), thus preventing the formation of an excessively thick, brittle alloy layer with the solder under the high-temperature environment of hot spot testing. This also reduces the occurrence of alloy layer cracks during cooling, thereby minimizing the risk of grid line breakage. This design significantly improves the overall reliability and lifespan of the battery, ensuring the long-term stable power generation performance of the photovoltaic cell.

[0063] Specifically, the welded part 200 can be a centipede-like foot or a solder pad, and such structures are formed by curing the main grid / fine grid paste. Since copper and manganese are unique elements in the main grid paste, and these two elements are not present in the fine grid paste, it can be inferred from the statement that "only the first material includes copper and manganese" that the first material is cured by the main grid paste (first paste), and the second material is cured by the fine grid paste (second paste). The main grid paste is characterized by high weld pull strength, thus effectively resisting the stress on the solder strip ends during high and low temperature cycling, minimizing the risk of desoldering due to weakened contact between the solder and the grid line. The fine grid paste, due to its lower weld pull strength, is less likely to form an excessively thick, brittle, hard alloy layer with the solder under the high-temperature environment of hotspot testing, reducing the formation of alloy layer cracks during cooling, thereby minimizing grid line breakage faults.

[0064] In some embodiments, the first direction is either the length direction or the width direction of the battery cell body 100, and the second direction is the other direction, both of which are perpendicular to the thickness direction of the battery cell body 100. In the embodiment shown in the accompanying drawings, the first and second directions are perpendicular; however, in other embodiments, they may not be perpendicular but merely intersect.

[0065] See Figure 1 , Figure 2 and Figure 5The photovoltaic cell in this embodiment is a grid cell. Specifically, the grid lines include multiple main grids 300 spaced apart along a second direction and multiple fine grids 400 spaced apart along a first direction. Each main grid 300 extends along the first direction, and each fine grid 400 extends along the second direction. At the intersection of the main grids 300 and the fine grids 400, a localized enlargement is achieved during printing to form an enlarged portion. After curing, the enlarged portion forms the aforementioned weld portion 200. During string bonding, the weld portion can be used to bond with solder strips.

[0066] Alternatively, in some other embodiments, the photovoltaic cell in this application is a grid-less cell. When it is a grid-less cell, the main grid 300 is removed from the structure of the embodiment shown in the accompanying drawings, while the other structures remain basically the same.

[0067] In the foregoing embodiments, at least a portion of the welded portions 200 located in the first region 110 are configured with a first material, and at least a portion of the welded portions 200 located in the second region 120 are configured with a second material. The term "at least a portion of the welded portions 200" can be selected according to actual needs. For example, in the first region 110, a portion of the welded portions 200 near the edge of the battery cell body 100 may be made of the first material, while the remaining welded portions 200 may use conventional materials; in the second region 120, a portion of the welded portions 200 in the hot spot concentration area in the middle of the battery cell body 100 may be made of the second material, while the remaining welded portions 200 may use conventional materials.

[0068] See Figure 1 , Figure 2 and Figure 5 In some embodiments, all welded portions 200 located in the first region 110 are configured with a first material.

[0069] In the above embodiments, all welded portions 200 of the first region 110 are uniformly configured with the first material, which enables the bonding interface between all welded portions 200 and solder in the first region 110 to be uniform and consistent, eliminating stress concentration points caused by different materials of local welded portions 200. The use of the first material for all welded portions 200 in the first region 110 can form a continuous and stable solder and silver paste bonding layer. During high and low temperature cycle testing, it can resist the stress caused by the size effect in the end area of ​​the solder strip in all directions, and minimize the situation of solder contact weakening in any position of the welded portion 200 in the first region 110, thereby better solving the desoldering risk of the first region 110 and improving the structural reliability of the end of the battery cell body 100.

[0070] See Figure 1 , Figure 2 and Figure 5 In some embodiments, all welded portions 200 located in the second region 120 are configured with a second material.

[0071] In the above embodiments, all welded parts 200 in the second region 120 are uniformly configured with the second material, which enables all welded parts 200 in the second region 120 to have consistent high-temperature resistance and eliminates the problem of uneven performance caused by different materials of local welded parts 200. The use of the second material for all welded parts 200 in the second region 120 can form a continuous and stable crack-resistant structure in the high-temperature concentrated area in the middle of the cell body 100. During the cooling process, the generation of cracks in the alloy layer can be effectively reduced, and the risk of grid breakage in welded parts 200 at any position in the second region 120 can be better avoided, thereby improving the structural stability of the middle part of the cell body 100 and ensuring the efficient transmission of photocurrent.

[0072] In some embodiments, the copper content in the first material is 100-3000 ppmw, and the manganese content is 50-1000 ppmw.

[0073] In the above embodiments, by limiting the content of copper and manganese in the first material, the microstructure of the alloy layer at the welding interface can be further optimized. Controlling the copper content within the aforementioned range allows for the formation of a suitable and uniformly distributed Cu-Sn intermetallic compound between the weld and the solder, enhancing the bonding strength. Controlling the manganese content within the aforementioned range helps refine the alloy grains, improve toughness, and buffer thermal stress generated by high and low temperature cycling. The synergistic effect of these two elements further strengthens the anti-detachment performance of the weld in the first region.

[0074] Preferably, in some embodiments, the copper content is 1600-1900 ppmw and the manganese content is 300-400 ppmw.

[0075] See Figure 1 , Figure 2 and Figure 5 In some embodiments, the glass powder content in the first material is not less than 2% and not more than 5%; the glass powder content in the second material is not less than 4% and not more than 8%.

[0076] In the above embodiments, the glass powder content of the first material is limited to a range of not less than 2% and not more than 5%. The lower limit of 2% ensures the basic adhesion between the first material and the cell body 100, preventing the welded part 200 located in the first region 110 from detaching from the surface of the cell body 100 during long-term use or high and low temperature cycling. The upper limit of 5% controls the negative impact of glass powder on the solder wetting performance, ensuring that the welded part 200 and the solder always maintain a stable bonding strength. The glass powder content of the second material is limited to a range of not less than 4% and not more than 8%. The lower limit of 4% enhances the structural stability of the second material in the high-temperature environment of hot spots at 160℃-220℃, reducing the risk of alloy layer brittleness. The upper limit of 8% avoids the decrease in slurry conductivity caused by excessive glass powder content, ensuring that the welded part 200 located in the second region 120 efficiently transmits photocurrent. The above-mentioned content range limits achieve a balance between adhesion, bonding strength, and conductivity, further improving the reliability and power generation efficiency of photovoltaic cells.

[0077] Furthermore, in some embodiments, the glass powder content of the first material can be selected as 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%, and the glass powder content of the second material can be selected as 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5% or 8%.

[0078] See Figure 1 , Figure 2 and Figure 5 In some embodiments, the size of the first region 110 along the first direction is 1 / 8 to 1 / 5 of the total size of the battery cell body 100 along the first direction.

[0079] In the above embodiments, limiting the size of the first region 110 along the first direction to 1 / 8 to 1 / 5 of the total size of the battery cell body 100 along the first direction allows for more precise coverage of the stress concentration area at the end. Specifically, if the size is less than 1 / 8, it may not completely cover the stress concentration area, and some welded parts 200 within the first region 110 may still face the risk of desoldering; if the size is greater than 1 / 5, it will unnecessarily increase the amount of first material paste used, increasing the silver paste consumption per unit and the overall production cost; while setting it within the above range can better balance the above two points, achieving the dual goals of performance improvement and cost control.

[0080] Specifically, the starting point of the first region 110 is the edge of the battery cell body 100 along the first direction, and the ending point is a position extending from that edge along the first direction towards the center of the battery cell body 100, with an extension distance of 1 / 8 to 1 / 5 of the total dimension of the battery cell body 100 along the first direction. The two first regions 110 are located at the two ends of the battery cell body 100 along the first direction, and the area between them is the second region 120, as detailed in [reference needed]. Figure 1A schematic diagram of the regional division of the solar cell body 100.

[0081] Furthermore, in some embodiments, the dimension of the first region 110 along the first direction is 1 / 8, 1 / 7, 1 / 6 or 1 / 5 of the total dimension of the battery cell body 100 along the first direction.

[0082] See Figure 1 , Figure 2 and Figure 5 In some embodiments, the welding portion 200 includes centipede legs or solder pads; or, a portion of the welding portion 200 is a centipede leg and a portion of the welding portion 200 is a solder pad.

[0083] In the embodiment shown in the attached drawings, the welding part 200 is specifically a centipede leg structure. When designing the material partitions for the centipede legs, the centipede legs in the first region 110 use the first material, and the centipede legs in the second region 120 use the second material. If the welding part 200 is a pad structure, similarly, the pads in the first region 110 use the first material, and the pads in the second region 120 use the second material. In the hybrid structure, the centipede legs and pads in the first region 110 use the first material, and the centipede legs and pads in the second region 120 use the second material, ensuring the consistency of the material of the welding part 200 in the same region.

[0084] In the above embodiments, the centipede feet and / or pads located in the first region 110 are made of a first material, which can improve the wetting and bonding performance with the solder, resist the stress on the solder strip end during high and low temperature cycling, and avoid desoldering caused by weakened contact between the solder and the welded part 200. The centipede feet and / or pads located in the second region 120 are made of a second material, which is less likely to form an excessively thick and brittle alloy layer with the solder in the high temperature environment of 160℃-220℃ during hot spot testing, reducing alloy layer cracks during cooling and avoiding the risk of gate breakage. This design, without changing the original structural advantages of the welded part 200, precisely solves the problems of end desoldering and middle gate breakage through material optimization, achieving a synergistic improvement in structure and performance.

[0085] See Figure 3 , Figure 4 , Figure 6 and Figure 7 In some embodiments, at least a portion of the welded portion 200 located in the first region 110 includes a plurality of welded segments 211 connected in sequence, wherein at least two adjacent welded segments 211 are arranged at an angle to each other in their length directions.

[0086] In the above embodiments, in at least a portion of the welded portion 200 located in the first region 110, at least two adjacent welded segments 211 are arranged at an angle along their length directions. This bending shape can enhance the mechanical adsorption force on the solder and form more mechanical interlocking points with the solder, locking the solder like an anchor point and improving the bonding strength between the welded portion 200 and the solder. At the same time, the angled structure can disperse the concentrated stress generated at the end of the solder strip during high and low temperature cycling to different welded segments 211, avoiding the weakening of solder contact due to excessive stress in a single part. In addition, combined with the first material characteristics of the welded portion 200 in the first region 110, the material has excellent wetting and bonding performance with the solder. The synergistic effect of material and shape further strengthens the anti-desoldering ability of the first region 110 and ensures the structural reliability of the end of the battery cell body 100.

[0087] Furthermore, in some embodiments, the included angle between adjacent welded segments 211 is 30 degrees to 150 degrees. Within this range, sufficient mechanical adsorption sites can be formed through the bending shape, without causing structural crowding due to an excessively small included angle, or causing a decrease in the strength of the connection part of the welded segments 211 due to an excessively large included angle.

[0088] In some embodiments, the bends of adjacent welded sections 211 may be designed with a smooth transition to further reduce stress concentration.

[0089] See Figure 3 , Figure 4 , Figure 6 and Figure 7 In some embodiments, the area of ​​the welding portion 200 located in the first region 110 covering the battery cell body 100 is not greater than the area of ​​the welding portion 200 located in the second region 120 covering the battery cell body 100.

[0090] In the above embodiments, the welding part 200 of the first region 110, with the mechanical adsorption force brought by the bending structure and the high solder wettability of the first material, can effectively improve the bonding strength with the solder even if the area is not advantageous, resist the stress generated by high and low temperature cycles, and avoid desoldering. Thus, under the premise of controlling the silver paste consumption and reducing production costs, the synergistic effect of the bending segmented structure of the welding part 200 and the first material can be fully utilized to solve the end desoldering problem.

[0091] It should be noted that the area covered by the welding part 200 on the cell body 100 is the area of ​​the welding part 200 projected onto the cell body 100.

[0092] Of course, in other embodiments, if cost is not a concern, the area of ​​the welding portion 200 in the first region 110 covering the battery cell body 100 can be larger than the area of ​​the welding portion 200 in the second region 120 covering the battery cell body 100, provided that the shape is bent.

[0093] See Figures 2 to 4 In some embodiments, the weld portion 200 located in the first region 110 is M-shaped, V-shaped, U-shaped, X-shaped or Y-shaped.

[0094] In the above embodiments, the welding part 200 located in the first region 110 adopts an M-shaped, V-shaped, U-shaped, X-shaped or Y-shaped bending structure, which can form more mechanical interlocking points through its own concave and convex bending shape, enhance the mechanical adsorption force on the solder, and thus improve the bonding strength between the welding part 200 and the solder; at the same time, these bending shapes can disperse the concentrated stress generated at the end of the solder strip during high and low temperature cycling to different parts of the welding part 200, avoiding the weakening of solder contact caused by stress overload at a single location.

[0095] Figure 3 , Figure 4 In the embodiment shown, the welding portion 200 located in the first region 110 is specifically an M-shaped structure.

[0096] In addition, it should be noted that in this embodiment, the shape of the welding part 200 does not need to strictly meet the standard shape such as M-shape or V-shape in a geometric sense; it is sufficient that the overall outline matches the corresponding shape.

[0097] See Figures 5 to 7 In some embodiments, the plurality of welding segments 211 include a first welding segment 211a and a second welding segment 211b arranged alternately along a second direction. The length direction of the first welding segment 211a is parallel to the first direction, and the length direction of the second welding segment 211b is parallel to the second direction. The dimension of the first welding segment 211a along the first direction is greater than the width of the fine gate 400, and the dimension of the second welding segment 211b along the first direction is not greater than the width of the fine gate 400. The second direction is parallel to the extension direction of the fine gate 400 and intersects the first direction.

[0098] In the above embodiments, the multiple welding segments 211 adopt a structure in which the first welding segment 211a and the second welding segment 211b are arranged alternately along the second direction, and a 90-degree bending angle is formed between adjacent welding segments. This can form a stable mechanical interlocking point through regular right-angle bending, which enhances the mechanical adsorption force on the solder. At the same time, the concentrated stress generated at the end of the solder strip during high and low temperature cycling is distributed to different welding segments, avoiding the weakening of solder contact caused by stress overload in a single part. In addition, compared with the fine grid 400, the size of the first welding segment 211a along the first direction is locally increased, and the size of the second welding segment 211b along the first direction is correspondingly reduced. The size combination of the two not only realizes the construction of the bending shape, but also ensures that the overall coverage area of ​​the welding part 200 does not increase additionally due to the bending design, effectively controlling the silver paste consumption and production cost.

[0099] Further, see Figures 5 to 7 In some embodiments, the dimension of the first welding segment 211a along the first direction is 1.5 to 4 times the width of the fine gate 400; the dimension of the second welding segment 211b along the first direction is 0.5 to 1 times the width of the fine gate 400.

[0100] In the above embodiments, the size of the first welding segment 211a along the first direction is limited to 1.5 to 4 times the width of the fine grid 400, and the size of the second welding segment 211b along the first direction is limited to 0.5 to 1 times the width of the fine grid 400. This allows for precise control of the shape and proportion of the bent structure, making the mechanical interlocking points formed by the 90-degree right-angle bend more regular and stable, further enhancing the mechanical adsorption force on the solder. At the same time, this size ratio strictly limits the local increase and decrease of the welding segment, ensuring that the overall coverage area of ​​the welding part 200 will not increase additionally, effectively controlling the silver paste consumption and production cost.

[0101] It should be noted that the dimensions of each first welding segment 211a along the first direction can be all the same, or they can be set to different values ​​according to actual design requirements, as long as the dimension of each first welding segment 211a along the first direction is 1.5 to 4 times the width of the fine grid 400. Similarly, the dimensions of each second welding segment 211b along the first direction can be uniformly set to the same value, or they can differ, as long as the dimension of each second welding segment 211b along the first direction is within the range of 0.5 to 1 times the width of the fine grid 400.

[0102] See Figures 5 to 7 In some embodiments, the area of ​​the weld portion 200 located in the first region 110 covering the battery cell body 100 is a, wherein the sum of the areas of all the first weld segments 211a covering the battery cell body 100 is b, and 0.3≤b / a≤0.7.

[0103] In the above embodiments, limiting the ratio of b to a to a within the range of 0.3 to 0.7 allows for precise control of the proportion of the first welding segment 211a in the welding part 200. This avoids an excessively high proportion of the first welding segment 211a leading to an increase in the overall area of ​​the welding part 200, or an excessively low proportion weakening the stress dispersion effect. This results in a more reasonable distribution of the first welding segment 211a, which serves as the core of the mechanical interlocking point, thereby further enhancing the mechanical adsorption force on the solder. This ensures that the advantages of the bending structure are fully utilized while controlling the silver paste consumption and without increasing production costs.

[0104] It should be noted that the area 'a' of the welding part 200 covering the cell body 100 refers to its orthographic projection area on the surface of the cell body 100; the sum 'b' of the areas covered by all the first welding segments 211a in the welding part 200 is a value obtained by adding up the orthographic projection areas of all the first welding segments 211a in the welding part 200 on the surface of the cell body 100.

[0105] See Figure 3 , Figure 4 , Figure 6 and Figure 7 In some embodiments, among the plurality of welded segments 211, one located at the end is connected to the fine grid 400 of the photovoltaic cell, and the width of the welded segment 211 located at the end gradually decreases in the orientation close to the fine grid 400.

[0106] In the above embodiment, the welding segment 211 located at the end adopts a design in which the width gradually decreases in the direction of the fine gate 400, which can smoothly connect the connection part of the welding segment 211 and the fine gate 400, avoid stress concentration caused by abrupt size change, and thus reduce the probability of desoldering.

[0107] Based on the stress simulation results, it can be seen that Figure 8 When the welded part of the first region adopts the shape of the existing technology, its stress simulation diagram shows that there is a large area of ​​red high stress concentration area at the end of the welded part, which is very easy to cause solder contact weakening and desoldering failure during high and low temperature cycling. Figure 9 The stress simulation diagram shows the stress distribution when the welded portion in the first region is designed as a V-shape. Figure 10 When the welded portion of the first region is designed with an alternating arrangement of the first and second welded segments, the stress simulation diagram is compared. Figure 8 As can be seen, the area of ​​the red high-stress region at the weld end is reduced in both bending forms, effectively avoiding the problem of local stress overload. The above simulation results intuitively and powerfully demonstrate the significant advantages of the bending structure in this application embodiment in alleviating end stress concentration and improving anti-weld detachment performance.

[0108] The results of the electroluminescence (EL) test show that, Figure 11This is a schematic diagram of the first region of a battery cell after EL testing in the prior art. There are obvious irregular dark spots at its ends, which correspond to the defect locations where the solder and grid lines are desoldered. Figure 12 This is a schematic diagram of the second region of a solar cell after EL testing in the prior art. The region is covered with multiple dot-like and linear dark spots, which are abnormal current transmission areas caused by grid line breakage. Figure 13 This is a schematic diagram of the battery cells after EL testing in one embodiment of this application, for comparison. Figure 11 and Figure 12 It is clearly visible that the dark spots at the ends and center of the battery have almost completely disappeared, and the overall luminous uniformity has been significantly improved. The above EL test results directly verify that this application, through differentiated material and structural design, can solve the problems of end-soldering desoldering and middle grid breakage in photovoltaic cells, and significantly improve the structural integrity and power generation reliability of the cells.

[0109] In the aforementioned embodiments, the welding portion 200 located in the first region 110 is morphologically optimized based on a bent segmented structure. More preferably, the coverage area of ​​the welding portion 200 in the first region 110 is no greater than the coverage area of ​​the welding portion 200 in the second region 120, thereby improving the resistance to solder detachment without increasing the cost of the silver paste. In other embodiments, the bent shape design can be abandoned, and the end solder detachment problem can be solved directly by increasing the coverage area of ​​the welding portion 200 in the first region 110.

[0110] For example, in some embodiments, at least a portion of the weld portion 200 located in the first region 110 covers an area of ​​the battery cell body 100 that is larger than the area of ​​the weld portion 200 located in the second region 120 that covers the battery cell body 100.

[0111] In the above embodiments, directly increasing the coverage area of ​​the welding portion 200 in the first region 110 can increase the contact area between the welding portion 200 and the solder, thereby enhancing the bonding strength between the two, thus resisting the stress generated at the end of the solder strip during high and low temperature cycling, and preventing the solder from weakening and causing desoldering.

[0112] See Figure 1 , Figure 2 and Figure 5 The photovoltaic module provided in one embodiment of this application includes the photovoltaic cell in any of the foregoing embodiments.

[0113] See Figure 1 , Figure 2 , Figure 5 and Figure 14 One embodiment of this application provides a method for manufacturing a photovoltaic cell, including:

[0114] S100, Provide a battery cell body 100, the battery cell body 100 includes two first regions 110 spaced apart along a first direction, and a second region 120 located between the two first regions 110, the first direction being perpendicular to the thickness direction of the battery cell body 100.

[0115] S200: Print grid line paste on the cell body 100 to form a plurality of size enlargement portions spaced apart along the first direction. After curing, the size enlargement portions form a weld portion 200.

[0116] In this process, at least a portion of the enlarged size portion located in the first region 110 is printed using a first paste, and at least a portion of the enlarged size portion located in the second region 120 is printed using a second paste. Of the first paste and the second paste, only the first paste includes copper and manganese elements.

[0117] In the above embodiments, by differentially printing grid line pastes of different compositions in the first region 110 and the second region 120 of the cell body 100, the material of the welded part 200 is precisely customized, specifically solving the problems of end desoldering and middle grid breakage in photovoltaic cells. Specifically, printing a first paste containing copper and manganese elements in the first region 110, the welded part 200 formed after curing can significantly improve the bonding force with the solder, effectively resist the stress generated by high and low temperature cycles, and avoid end desoldering of the solder strip; printing a second paste that does not contain copper and manganese elements in the second region 120, the welded part 200 formed after curing can reduce the formation of a brittle hard alloy layer under the high temperature environment of hot spot testing, preventing middle grid line breakage. Moreover, this method does not require additional process steps and can be directly connected to existing photovoltaic cell mass production lines, taking into account both the needs of reliability improvement and cost reduction and efficiency improvement.

[0118] In this method, the first slurry corresponds to the first material in the aforementioned embodiments, and the second slurry corresponds to the second material. Specifically, the first slurry is cured to form the first material, and the second slurry is cured to form the second material. The composition of the slurry directly determines the core performance of the welded part 200 after curing. The enlarged part formed in the printing process is a precursor structure of the welded part 200. After curing and shaping, the enlarged part becomes the aforementioned welded part 200 used for current collection and solder strip connection. The two are different forms of the same structure at different process stages.

[0119] Furthermore, the enlarged portion formed by printing can be cured by high-temperature sintering or low-temperature drying to ultimately form a welded portion 200 with conductive and welding functions. High-temperature sintering is mostly used in the production of crystalline silicon photovoltaic cells, while low-temperature drying is suitable for photovoltaic cell types that are not resistant to high temperatures, such as heterojunction and thin-film cells.

[0120] See Figure 1 , Figure 2 and Figure 5 In some embodiments, the glass powder content in the first slurry is not less than 2% and not more than 5%, and the softening temperature is 600 to 650 degrees Celsius; the glass powder content in the second slurry is not less than 4% and not more than 8%, and the softening temperature is 500 to 550 degrees Celsius.

[0121] In the above embodiments, by limiting the upper and lower limits of the glass powder content in the first slurry and the second slurry, precise control over the material properties of the welded part 200 after curing is achieved. The content range of the first slurry ensures excellent bonding between the cured first material and the solder, effectively resisting high and low temperature cyclic stress to prevent end desoldering, and also ensures reliable adhesion between the material and the battery cell body 100. The content range of the second slurry ensures that the cured second material will not form an excessively thick, brittle, and hard alloy layer under the high temperature environment of hot spots, avoiding grid breakage in the middle, while also taking into account the conductivity of the material and not affecting the current collection and transmission efficiency of the battery.

[0122] Furthermore, in some embodiments, the glass powder content of the first slurry can be selected as 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%, and the glass powder content of the second slurry can be selected as 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5% or 8%.

[0123] In some embodiments, the first slurry may be selected from a borosilicate system ( ),Add to , The second slurry can be a lead borosilicate / bismuth borosilicate system, with the addition of... , .

[0124] See Figure 1 , Figure 2 and Figure 5 In some embodiments, more than 75% of the silver powder in the first slurry has a spherical or near-spherical morphology, and more than 75% of the silver powder in the second slurry has a flake-like or dendritic morphology.

[0125] In the above embodiments, the first slurry mainly uses spherical or near-spherical silver powder, which has good particle flowability. After curing, the first material structure formed is dense and uniform, which can significantly enhance the contact area and bonding force with the solder, improve the resistance of the welding part 200 of the first region 110 to high and low temperature cycle stress, and reduce the risk of end desoldering. The second slurry mainly uses flake or dendritic silver powder, and the conductive network formed by the overlap between particles is more stable. After curing, the second material is not prone to cracking in the high temperature environment of hot spot test. At the same time, it can inhibit the excessive growth of brittle hard alloy layer and reduce the probability of grid line breakage in the second region 120.

[0126] See Figure 1 , Figure 2 and Figure 5 In some embodiments, the median particle size of the silver powder in the first slurry is 1 micrometer to 1.1 micrometers; and the median particle size of the silver powder in the second slurry is 1.3 micrometers to 1.4 micrometers.

[0127] Specifically, the median particle size, also known as the volume average median diameter (industry term D50), refers to the particle size at which the cumulative volume percentage of silver powder reaches 50% when the silver powder is distributed in ascending order of particle size.

[0128] In the above embodiments, for the first slurry, spherical or near-spherical silver powder with a median particle size of 1 to 1.1 micrometers is used, which can improve the particle packing density of the slurry. After curing, the conductivity and bonding force of the welded part 200 of the first material are stronger, which can better resist high and low temperature cycle stress and reduce the risk of end desoldering. For the second slurry, flake or dendritic silver powder with a median particle size of 1.3 to 1.4 micrometers is used, which can enhance the overlapping effect between silver powder particles. After curing, the welded part 200 of the second material has better high temperature crack resistance and is less prone to cracking in hot spot tests. At the same time, it ensures current transmission efficiency and avoids the failure of the middle grid.

[0129] In some embodiments, the first slurry uses a high-viscosity, high-thixotropic, and slow-evaporating solvent, such as terpineol, in combination with a high molecular weight resin (such as ethyl cellulose); the second slurry uses a low-viscosity, low-thixotropic, and fast-evaporating solvent, such as ethanol, in combination with a low molecular weight resin (such as polyvinyl butyral).

[0130] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0131] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A photovoltaic cell, characterized in that, The photovoltaic cell includes: The battery cell body includes two first regions spaced apart along a first direction, and a second region located between the two first regions, wherein the first direction is one of the length direction and the width direction of the battery cell body. The grid line includes a plurality of welded portions disposed on the battery cell body, the plurality of welded portions being spaced apart along the first direction; Wherein, at least a portion of the welded portion located in the second region is configured with a second material, and at least a portion of the welded portion located in the first region is configured with a first material, the first material being a main grid material, and the second material being a fine grid material, wherein only the first material includes copper and manganese elements.

2. The photovoltaic cell according to claim 1, characterized in that, All of the welded portions located in the second region are configured with the second material; And / or, all of the welded portions located in the first region are configured with the first material.

3. The photovoltaic cell according to claim 1, characterized in that, In the first material, the content of copper is 100-3000 ppmw, and the content of manganese is 50-1000 ppmw.

4. The photovoltaic cell according to claim 1, characterized in that, The glass powder content in the first material is not less than 2% and not more than 5%; The glass powder content in the second material is not less than 4% and not more than 8%.

5. The photovoltaic cell according to claim 1, characterized in that, The dimension of the first region along the first direction is 1 / 8 to 1 / 5 of the total dimension of the battery cell body along the first direction.

6. The photovoltaic cell according to any one of claims 1 to 5, characterized in that, The welding section includes centipede legs or welding pads; Alternatively, some of the welded parts may be centipede legs, and some of the welded parts may be solder pads.

7. The photovoltaic cell according to claim 6, characterized in that, At least a portion of the welded portion located in the first region comprises a plurality of welded segments connected in sequence, wherein at least two adjacent welded segments are arranged at an angle to each other in their length directions.

8. The photovoltaic cell according to claim 7, characterized in that, The area of ​​the weld portion located in the first region covering the battery cell body is not greater than the area of ​​the weld portion located in the second region covering the battery cell body.

9. The photovoltaic cell according to claim 7 or 8, characterized in that, The welded portion located in the first region is M-shaped, V-shaped, U-shaped, X-shaped, or Y-shaped.

10. The photovoltaic cell according to claim 7 or 8, characterized in that, The plurality of welding segments include a first welding segment and a second welding segment arranged alternately along a second direction. The length direction of the first welding segment is parallel to the first direction, and the length direction of the second welding segment and the extension direction of the fine grid of the photovoltaic cell are both parallel to the second direction, and the second direction intersects the first direction. The dimension of the first welded segment along the first direction is greater than the width of the fine grid, and the dimension of the second welded segment along the first direction is not greater than the width of the fine grid.

11. The photovoltaic cell according to claim 10, characterized in that, The dimension of the first welded segment along the first direction is 1.5 to 4 times the width of the fine grid; The dimension of the second welded segment along the first direction is 0.5 to 1 times the width of the fine grid.

12. The photovoltaic cell according to claim 10, characterized in that, The area covered by the welded portion in the first region on the battery cell body is a, wherein the sum of the areas covered by all the first welded segments on the battery cell body is b, and 0.3≤b / a≤0.

7.

13. The photovoltaic cell according to claim 7, characterized in that, Of the plurality of welded segments, one located at the end is connected to the fine grid of the photovoltaic cell, and the width of the welded segment at the end gradually decreases in the direction close to the fine grid.

14. The photovoltaic cell according to claim 6, characterized in that, The area of ​​the weld portion located in the first region that covers the battery cell body is greater than the area of ​​the weld portion located in the second region that covers the battery cell body.

15. A photovoltaic module, characterized in that, The photovoltaic module includes the photovoltaic cell according to any one of claims 1 to 14.

16. A method for manufacturing a photovoltaic cell, characterized in that, The method for manufacturing the photovoltaic cell includes: A battery cell body is provided, the battery cell body including two first regions spaced apart along a first direction, and a second region located between the two first regions, the first direction being one of the length direction and the width direction of the battery cell body; A grid line paste is printed on the battery cell body to form a plurality of enlarged portions spaced apart along the first direction. The enlarged portions form welded portions after curing. Wherein, at least a portion of the enlarged size portion located in the second region is printed using a second paste, and at least a portion of the enlarged size portion located in the first region is printed using a first paste, wherein the first paste is a main grid paste, the second paste is a fine grid paste, and of the first paste and the second paste, only the first paste includes copper and manganese elements.

17. The method for manufacturing a photovoltaic cell according to claim 16, characterized in that, The glass powder content in the first slurry is not less than 2% and not more than 5%; The glass powder content in the second slurry is not less than 4% and not more than 8%.

18. The method for manufacturing a photovoltaic cell according to claim 16, characterized in that, In the first slurry, the median particle size of the silver powder is 1 micrometer to 1.1 micrometers; In the second slurry, the median particle size of the silver powder is 1.3 to 1.4 micrometers.

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