Back contact battery assembly and photovoltaic system

Abstract

The invention relates to the technical field of solar cells, and particularly discloses a back contact cell module and a photovoltaic system, and the cell module comprises a plurality of cell sheets which are arranged along a first direction; the grid lines are arranged on the battery pieces and comprise first polarity grid lines and second polarity grid lines, and the first polarity grid lines and the second polarity grid lines extend in the second direction; the plurality of welding strips are at least partially arranged on one side, back on to the battery piece, of the grid line, and each welding strip extends along the first direction; on a single battery piece, the number N of the welding strips in conductive connection with the first polarity grid line or the second polarity grid line is determined according to the sectional area of the welding strip on the battery piece, the copper content of the base layer of the welding strip on the battery piece, the length of the battery piece and the width of the battery piece, so that electrical loss and optical loss caused by the welding strips are effectively reduced; and the comprehensive power of the battery assembly is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a back-contact cell assembly and a photovoltaic system. Background Art

[0002] Back-contact cells, with their unique electrode layout, concentrate the positive and negative grid lines on the back of the cell, avoiding the optical losses caused by front-side electrode shading in traditional cell structures. However, with the iterative evolution of photovoltaic technology, existing back-contact cell technology has gradually developed to a mature stage, and its efficiency improvement faces significant bottlenecks. In the actual industrialization process, efficiency breakthroughs are becoming increasingly difficult.

[0003] In back-contact solar modules, solder ribbons are electrically connected to the positive or negative grid lines of the solar cell to form an electrical connection network. However, as a key bridge for current transmission within the solar module, the solder ribbons introduce a certain degree of electrical and optical losses, resulting in a decrease in the overall power output of the solar module. Summary of the Invention

[0004] The purpose of the present invention is to provide a back-contact battery assembly and a photovoltaic system in view of the existing technical status.

[0005] In the present invention, after extensive research and experiments, multiple core influencing parameters are introduced, including the length L and width W of the battery cell, the copper content β of the soldering ribbon base layer, the cross-sectional area S of the soldering ribbon on the battery cell, and the number N of soldering ribbons. Based on the correlation and influence of each parameter, the relationship functions of Formula I and Formula II are constructed. When the relevant parameters of the back-contact battery assembly meet the relationship function, the electrical loss and optical loss caused by the soldering ribbon can be effectively reduced, and the comprehensive power of the battery assembly can be improved. In addition, the parameters in the relationship function are easy to obtain, and the solution is easier to implement.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: First, the present invention provides a back contact battery assembly, comprising: A plurality of battery cells are arranged along a first direction; a plurality of grid lines disposed on each of the battery cells, including a plurality of first polarity grid lines and second polarity grid lines having opposite polarities and arranged alternately along a first direction, wherein the first polarity grid lines and the second polarity grid lines both extend along a second direction, and the first direction and the second direction are intersected; a plurality of welding strips, at least partially disposed on a side of the grid line facing away from the solar cell, and each of the welding strips extending along the first direction; On a single cell, the number N of the soldering strips conductively connected to the first polarity grid line or the second polarity grid line is determined based on the cross-sectional area of the soldering strip on the cell, the copper content of the base layer of the soldering strip on the cell, the length of the cell, and the width of the cell.

[0007] In some embodiments, N min ≤N≤N max , where N is a positive integer, N min Satisfying formula I, N max Satisfying formula II, Formula I is: , Formula II is: , Where S is the cross-sectional area of the solder strip on the cell, in mm 2 ; β is the copper content of the base layer of the solder strip on the battery cell; L is the length of the battery cell, in cm; W is the width of the battery cell, in cm.

[0008] In some embodiments, the value of S in Formula I and / or Formula II is: 0 mm 2 <S≤0.187mm 2 .

[0009] In some embodiments, the value of S in Formula I and / or Formula II is: 0.12 mm 2 ≤S≤0.16mm 2 .

[0010] In some embodiments, the cross-sectional profile of the welding strip is any one of circular, rectangular, waist-shaped and oblate.

[0011] In some embodiments, the value of β in Formula I and / or Formula II is: 0≤β≤100%.

[0012] In some embodiments, the value of β in Formula I and / or Formula II is: 50%≤β≤100%.

[0013] In some embodiments, the soldering ribbon further includes a tin-containing layer, and the tin-containing layer covers at least a portion of the surface of the base layer.

[0014] In some embodiments, the base layer includes a core layer and a cladding layer, the cladding layer is provided on at least a portion of the surface of the core layer, the core layer is made of pure aluminum or an aluminum alloy, and the cladding layer is made of pure copper or a copper alloy; Alternatively, the base layer is made of pure copper or copper alloy.

[0015] In some embodiments, the battery cell is a whole battery cell or a slice of the whole battery cell.

[0016] In some embodiments, a battery string is included, wherein the battery string includes a plurality of battery cells arranged along a first direction, and a first battery cell and a second battery cell are adjacently arranged on the same battery string; The welding strips include series welding strips for conductively connecting adjacent battery cells; One end of the same series welding ribbon is connected to the first polarity grid line on either the first battery cell or the second battery cell, and the other end is connected to the second polarity grid line on the other of the first battery cell or the second battery cell; The number N1 of the series welding ribbons on the first cell that are conductively connected to the first polarity grid line is equal to the number N2 of the series welding ribbons on the second cell that are conductively connected to the second polarity grid line.

[0017] In some embodiments, the series welding ribbons include a plurality of first series welding ribbons arranged along the second direction and a plurality of second series welding ribbons arranged along the second direction, and in the first direction, the first series welding ribbons and the second series welding ribbons are arranged alternately, and in the second direction, the first series welding ribbons and the second series welding ribbons are arranged in an alternating manner; On the single cell, the first polarity grid line is conductively connected to either the first series welding ribbon or the second series welding ribbon, and the second polarity grid line is conductively connected to the other of the first series welding ribbon or the second series welding ribbon.

[0018] In some embodiments, including: A bus bar extending along the second direction; The welding ribbon includes a busbar welding ribbon for conductively connecting the busbar and the battery cell; At least a portion of the same busbar is conductively connected to the busbar, and at least a portion of the same busbar is conductively connected to the first polarity grid line or the second polarity grid line on the battery cell.

[0019] In some embodiments, each of the battery cells includes a substrate having a first surface and a second surface disposed opposite to each other. A doped layer is provided between the second surface and the gate line, the doped layer including a plurality of first doped regions and second doped regions staggered along a first direction, the first doped regions being conductively connected to at least a portion of the first polarity gate line, and the second doped regions being conductively connected to at least a portion of the second polarity gate line.

[0020] In some embodiments, adjacent battery cells are arranged on the same plane and spaced apart, or, Adjacent battery cells are at least partially stacked.

[0021] Secondly, the present invention provides a photovoltaic system including the above-mentioned back-contact cell assembly.

[0022] The beneficial effects of the present invention are: 1) In actual use, the problem of reduced overall power of the battery assembly caused by the soldering ribbon is subject to multiple constraints and influences, and there is a correlation between the various influencing factors. Specifically, when the length and width of the battery cell change, the photocurrent generated by the battery changes, and the length of the soldering ribbon on the battery cell, the number of soldering ribbons that can be placed, etc. also change accordingly, causing the optical loss and electrical loss caused by the soldering ribbon to change. When the power loss caused by the soldering ribbon is constant, the soldering ribbon made of high-resistance material requires a larger cross-sectional area and a larger number than the soldering ribbon made of low-resistance material, and the cross-sectional area, number, and resistance characteristics of the soldering ribbon show a nonlinear relationship. In the present invention, after extensive research and testing, the number N of soldering ribbons conductively connected to the first polarity grid line or the second polarity grid line on the battery cell is determined based on the cross-sectional area of the soldering ribbon on the battery cell, the copper content of the base layer of the soldering ribbon on the battery cell, the length of the battery cell, and the width of the battery cell, thereby effectively reducing the optical loss and electrical loss caused by the soldering ribbon and improving the overall power of the battery assembly.

[0023] 2) In the present invention, multiple core influencing parameters such as the length L and width W of the battery cell, the copper content β of the solder ribbon base layer, the cross-sectional area S of the solder ribbon on the battery cell, and the number N of solder ribbons are introduced. Based on the correlation and influence of each parameter, the relationship functions of Formula I and Formula II are constructed. When the relevant parameters of the back-contact battery assembly meet the relationship function, the optical loss and electrical loss caused by the solder ribbon can be effectively reduced, thereby improving the comprehensive power of the battery assembly. In addition, the parameters in the relationship function are easy to obtain, and the solution is easier to implement.

[0024] At the same time, technicians only need to use the above-mentioned relationship function to obtain the range of values of the number of solder strips required to achieve a higher comprehensive power, which reduces the difficulty of confirming the number of solder strips and reduces the number of tests. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the structure of a battery string of a back-contact battery assembly according to an embodiment of the present invention.

[0026] Figure 2 Schematic diagram of the structure of a single cell according to an embodiment of the present invention.

[0027] Figure 3 The minimum number N of solder strips of a single polarity on a single cell of the present invention ismin and the maximum value N max The trend diagram of the change with the cross-sectional area S of the welding strip.

[0028] Figure 4 The minimum number N of solder strips of a single polarity on a single cell of the present invention is min and the maximum value N max The trend chart of the change with the copper content of the base layer of the welding strip.

[0029] Figure 5 The minimum number N of solder strips of a single polarity on a single cell in an embodiment of the present invention under the conditions of different solder strip base copper contents β is min and the maximum value N max The trend diagram of the change with the cross-sectional area S of the welding strip.

[0030] Figure 6 The minimum number N of solder strips of a single polarity on a single cell in an embodiment of the present invention under the conditions of different solder strip base copper contents β is min The trend diagram of the change with the cross-sectional area S of the welding strip.

[0031] Figure 7 Schematic diagram of a welding strip having a circular cross section according to an embodiment of the present invention.

[0032] Figure 8 Schematic diagram of a case where the cross section of the soldering strip according to an embodiment of the present invention is oblate.

[0033] Figure 9 Schematic diagram of a welding strip having a waist-shaped cross section according to an embodiment of the present invention.

[0034] Figure 10 This is a schematic diagram of a welding strip according to an embodiment of the present invention having a rectangular cross-section (the base layer includes the covering layer).

[0035] Figure 11 This is a schematic diagram of a welding strip according to an embodiment of the present invention having a rectangular cross-section (the base layer does not include a covering layer).

[0036] Figure 12 This is a partially enlarged view of the cross section of a battery cell according to an embodiment of the present invention.

[0037] Figure 13 This is a schematic structural diagram of a back-contact battery assembly according to an embodiment of the present invention.

[0038] Figure 14 This is a schematic structural diagram of a back-contact battery assembly (the busbar is hidden on the back of the battery cell) according to an embodiment of the present invention. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and are not to be construed as limiting the present invention. In addition, it should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0040] In the description of the present invention, the terms "first," "second," etc. are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature defined as "first," "second," etc. may explicitly or implicitly include one or more of the described features. In the description of the present invention, "plurality" or "several" means two or more, unless otherwise specifically defined.

[0041] In the description of the present invention, unless otherwise clearly stipulated and limited, a first feature being “above” or “below” a second feature may include the first feature and the second feature being in direct contact, or may include the first feature and the second feature not being in direct contact but being in contact through another feature between them.

[0042] In the description of the present invention, unless otherwise clearly stipulated and limited, the "conductive connection" or "electrical connection" between the first feature and the second feature means that electric charge can move between them to form a conductive path. The first feature and the second feature may be in direct contact, or the first feature and the second feature may be in contact through another feature between them, or the two may be connected together by mechanical means such as welding, crimping, clamping, and plugging to achieve mechanical positioning and conductive connection. For example, the gate line and the welding strip can be electrically connected through a welding pad, solder paste, etc., but is not limited to this.

[0043] It can be understood that the welding ribbon itself is conductive but not polar. In the present invention, for the convenience of description, the polarity of the welding ribbon refers to its polarity on a certain battery cell. The polarity of the welding ribbon on a certain battery cell is consistent with the polarity of the grid lines collected on the battery cell. Correspondingly, its opposite-sex grid lines are grid lines with opposite polarity to the grid lines collected on the battery cell. For example, if the welding ribbon is welded to the positive grid line on a certain battery cell, the polarity of the welding ribbon on the battery cell is positive, and correspondingly, its opposite-sex grid line is the negative grid line.

[0044] First, see Figure 1 and Figure 2 As shown, the present invention provides a back contact battery assembly, comprising: A plurality of battery cells 1 are arranged along a first direction; A plurality of grid lines 2 are provided on each cell 1, including a plurality of first polarity grid lines 212 and second polarity grid lines 222 having opposite polarities and arranged alternately along a first direction. The first polarity grid lines 212 and the second polarity grid lines 222 are both extended along a second direction, and the first direction and the second direction are intersected. A plurality of welding strips 3, at least partially disposed on a side of the grid line 2 facing away from the solar cell 1, and each welding strip 3 extending along a first direction; On a single cell 1, the number N of solder strips 3 conductively connected to the first polarity grid line 212 or the second polarity grid line 222 is determined based on the cross-sectional area of the solder strip 3 on the cell 1, the copper content of the base layer of the solder strip 332 on the cell 1, the length of the cell 1, and the width of the cell 1.

[0045] In actual use, the problem of reduced overall power of the battery assembly caused by the soldering ribbon 3 is subject to multiple constraints and influences, and there are correlations between the various influencing factors. Specifically, when the length and width of the battery cell 1 change, the photocurrent generated by the battery changes, and the length and number of soldering ribbons 3 that can be placed on the battery cell 1 also change accordingly, resulting in changes in the optical loss and electrical loss caused by the soldering ribbon 3. When the power loss caused by the soldering ribbon 3 is constant, soldering ribbons 3 made of high-resistance materials require larger cross-sectional areas and more in number than soldering ribbons 3 made of low-resistance materials, and the cross-sectional area, number, and resistance characteristics of the soldering ribbon 3 exhibit a nonlinear relationship. In the present invention, the number N of soldering ribbons conductively connected to the first polarity grid lines 212 or the second polarity grid lines 222 on the battery cell 1 is determined based on the cross-sectional area of the soldering ribbon 3 on the battery cell 1, the copper content of the base layer of the soldering ribbon 332 on the battery cell 1, the length of the battery cell 1, and the width of the battery cell 1, thereby effectively reducing the optical loss and electrical loss caused by the soldering ribbon and improving the overall power of the battery assembly.

[0046] In some embodiments, N min ≤N≤N max , where N is a positive integer, N min Satisfying formula I, N max Satisfying formula II, Formula I is: , Formula II is: , Where S is the cross-sectional area of the solder ribbon 3 on the cell 1 (the cross-sectional area here refers to the cross-sectional area of a single solder ribbon 3), in mm 2 ; β is the copper content of the base layer 32 of the solder ribbon 3 on the battery cell 1 (here refers to the copper content of the base layer 32 corresponding to a single solder ribbon 3); L is the length of the battery cell 1, in cm; W is the width of the battery cell 1, in cm.

[0047] It can be understood that in Formula I and Formula II, the final values are rounded up.

[0048] The copper content refers to the ratio of the mass of copper in the base layer 32 of the soldering strip 3 to the total mass of the base layer 32 .

[0049] It is understandable that N refers to the number of soldering strips 3 of a single polarity (i.e., soldering strips 3 conductively connected to the first polarity grid lines 212 or soldering strips 3 conductively connected to the second polarity grid lines 222) on a single cell 1. min N is the minimum number of solder strips 3 of a single polarity on a single cell 1. max It is the maximum number of solder ribbons 3 of a single polarity on a single solar cell 1 .

[0050] The first direction and the second direction are arranged to intersect each other. In one embodiment, the first direction and the second direction are perpendicular to each other. In another embodiment, the first direction and the second direction may not be perpendicular to each other. Furthermore, the first direction may be parallel to the length direction of the battery cell 1 or parallel to the width direction of the battery cell 1.

[0051] During actual use, the problem of the overall power reduction of the battery assembly caused by the welding ribbon 3 is subject to multiple constraints and influences, and there is also a correlation between the various influencing factors. Specifically, when the length and width of the battery cell 1 change, the photocurrent generated by the battery changes, and the length of the welding ribbon 3 on the battery cell 1, the number of welding ribbons that can be placed, etc. also change accordingly, resulting in changes in the optical loss and electrical loss caused by the welding ribbon 3. When the power loss caused by the welding ribbon 3 is constant, the welding ribbon 3 made of high-resistance material requires a larger cross-sectional area and more quantity than the welding ribbon 3 made of low-resistance material, and the cross-sectional area, quantity and resistance characteristics of the welding ribbon 3 show a nonlinear relationship. In the present invention, after extensive research and experiments, multiple core influencing parameters are introduced, including the length L and width W of the battery cell 1, the copper content β of the base layer 32 of the solder ribbon 3, the cross-sectional area S of the solder ribbon 3 on the battery cell 1, and the number N of solder ribbons 3. Based on the correlation and influence of each parameter, the relationship functions of Formula I and Formula II are constructed. When the relevant parameters of the back-contact battery assembly meet the relationship function, the optical loss and electrical loss caused by the solder ribbon 3 can be effectively reduced, thereby improving the comprehensive power of the battery assembly. In addition, the parameters in the relationship function are easy to obtain, and the solution is easier to implement.

[0052] Furthermore, in actual operation, personnel often rely on specialized testing equipment to accurately measure various cell parameters. Determining the appropriate number of solder ribbons requires repeated calculations and verification, combined with experience and various tests. This process is not only time-consuming and labor-intensive, but also requires a high level of professional expertise. A single operational error or inaccurate judgment can lead to a decrease in the overall power of the battery assembly due to improper solder ribbon placement, impacting its performance. In the present invention, technicians can simply use the aforementioned relationship function to determine the range of values for the number of solder ribbons 3 required to achieve a high overall power, reducing the difficulty of determining the number of solder ribbons 3 and the number of trials.

[0053] Experiments have shown that when the relevant parameters of the back-contact battery module meet this relationship function, the comprehensive power loss caused by the welding ribbon 3 can be reduced by 4W~15W, and the battery module conversion efficiency can be increased by 0.62%~1.69%, breaking through the current bottleneck of battery module efficiency improvement.

[0054] It can be understood that the battery cell 1 can be square or rectangular, and the corners can each independently be a standard corner (i.e., a 90° right angle), a rounded corner, or a chamfered corner. It is set according to actual production needs and is not specifically limited here. When the corners of the battery cell 1 are rounded corners or chamfered corners, in Formula I and / or Formula II, the length of the battery cell 1 is based on the length dimension of the remaining area avoiding the location of the corner, and the width is based on the width dimension of the remaining area avoiding the location of the corner.

[0055] In some embodiments, the value of S in Formula I and / or Formula II is: 0 mm 2 <S≤0.187mm 2 .

[0056] For example, S is 0.01 mm 2 , 0.02mm 2 , 0.03mm 2 , 0.04mm 2 , 0.05mm 2 , 0.06mm 2 , 0.07mm 2 , 0.08mm 2 , 0.09mm 2 , 0.10mm 2 , 0.11mm 2 , 0.12mm 2 , 0.13mm 2 , 0.14mm 2 , 0.15mm 2 , 0.16mm 2 , 0.18mm 2 or 0.187mm2 , but not limited to this.

[0057] The influence of the cross-sectional area S of the welding strip 3 on the comprehensive power caused by the welding strip 3 is reflected to a certain extent in the relationship between the cross-sectional area S of the welding strip 3 and the number of welding strips 3 (N min / N max ), see Figure 3 As shown, it shows that when the other parameters remain the same (taking the length L of the cell 1 as 182 mm, the width W of the cell 1 as 94 mm, and the copper content β of the base layer 32 of the soldering ribbon 3 as 50% as an example), the minimum number N of soldering ribbons 3 of a single polarity is min and the maximum value N max The trend of the change with the cross-sectional area S of the welding strip 3 is that when the cross-sectional area S of the welding strip 3 is small, N min 、N max The difference between the two decreases significantly with the increase of the cross-sectional area S of the welding strip 3. When the cross-sectional area S of the welding strip 3 is large, N min 、N max The decreasing trend of the difference between the two slows down, N min and N max The curve tends to be flat. Therefore, by appropriately increasing the cross-sectional area S of the soldering ribbon 3, the number of soldering ribbons 3 used can be reduced, which is beneficial to increasing the comprehensive power of the battery assembly and improving the battery conversion efficiency. At the same time, appropriately increasing the cross-sectional area S of the soldering ribbon 3 can narrow the range of the required number of soldering ribbons 3, which is beneficial to reducing the difficulty of confirming the number of soldering ribbons 3 and reducing the number of tests. However, the cross-sectional area S of the soldering ribbon 3 should not be too large, otherwise it will increase unnecessary material costs and easily lead to increased optical losses, affecting the conversion efficiency.

[0058] In some embodiments, preferably, the value of S in Formula I and / or Formula II is: 0 mm 2 <S≤0.16mm 2 .

[0059] In some embodiments, more preferably, the value of S in Formula I and / or Formula II is: 0.12 mm 2 ≤S≤0.16mm 2 Within this range, battery components can achieve both relatively high comprehensive power and low material cost, which is more conducive to the industrial production of products.

[0060] For example, in Formula I and / or Formula II, the value of S is 0.12 mm 2 , 0.13mm 2 , 0.14mm 2 , 0.15mm 2 or 0.16mm 2 , but not limited to this.

[0061] In some embodiments, the cross-sectional profile of the welding ribbon 3 is any one of a circular shape, a rectangular shape, a waist-shaped shape, and an oblate shape.

[0062] In some embodiments, the value of β in Formula I and / or Formula II is: 0≤β≤100%.

[0063] Illustratively, β may be 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 100%, but is not limited thereto.

[0064] The influence of the copper content β of the base layer 32 of the welding strip 3 on the comprehensive power caused by the welding strip 3 is reflected to a certain extent in the relationship between the copper content β of the base layer 32 of the welding strip 3 and the number of welding strips 3 (N min / N max ), see Figure 4 As shown, it shows that when the other parameters remain the same (taking the length L of the battery cell 1 as 182mm, the width W of the battery cell 1 as 94mm, and the cross-sectional area S of the welding ribbon 3 as 0.1 as an example), the minimum number N of welding ribbons 3 of a single polarity min and the maximum value N max The trend of the change of the copper content β of the base layer 32 of the welding strip 3 is shown in FIG. Figure 5 and Figure 6 As shown, it shows that when the other parameters remain the same (taking the length L of the battery cell 1 as 182 mm and the width W of the battery cell 1 as 94 mm as an example), the minimum number N of the single polarity soldering ribbon 3 under the conditions of different copper content β of the base layer 32 of the soldering ribbon 3 min and the maximum value N max The trend of change with the cross-sectional area S of the welding strip 3. Figure 4 、 Figure 5 and Figure 5 As shown, it can be seen that N min and N max As the copper content β of the base layer 32 of the welding strip 3 increases, it shows a decreasing trend. At the same time, the copper content β of the base layer 32 of the welding strip 3 will affect N min and N max The sensitivity of the cross-sectional area S of the soldering strip 3 is increased. The larger the copper content β of the soldering strip 3 base layer 32 is, the higher the N min and N max The more intense the change in the cross-sectional area S of the welding strip 3.

[0065] In some embodiments, preferably, the value of β in Formula I and / or Formula II is: 50%≤β≤100%.

[0066] Illustratively, β may be 50%, 55%, 58%, 60%, 65%, 68%, 70%, 75%, 78%, 80%, 85%, 88%, 90%, 95%, 98% or 100%, but is not limited thereto.

[0067] Within this range, battery components can have both relatively high comprehensive power and low material cost, which is more conducive to the industrial production of products.

[0068] In some embodiments, see Figures 7 to 11 As shown, the soldering strip 3 also includes a tin-containing layer 31, which covers at least a portion of the surface of the base layer 32. The material of the tin-containing layer 31 can be pure tin or a tin alloy. Preferably, the material of the tin-containing layer 31 is a tin alloy, which can reduce the tin content while ensuring the welding effect, so as to reduce the short circuit risk easily caused by the tin oxidation phenomenon. Exemplarily, the tin alloy can be a tin-lead alloy, a tin-silver-copper alloy, a tin-bismuth alloy, a tin-zinc alloy, a tin-silver alloy, a tin-copper alloy, etc., but is not limited thereto.

[0069] In a first embodiment, see Figures 7 to 10 As shown, the base layer 32 includes a core layer and a cladding layer. The cladding layer is provided on at least a portion of the surface of the core layer. The core layer is made of pure aluminum or aluminum alloy, and the cladding layer is made of pure copper or copper alloy.

[0070] For example, the aluminum alloy may be an aluminum-copper alloy, an aluminum-manganese alloy, an aluminum-silicon alloy, etc., but is not limited thereto.

[0071] For example, the copper alloy may be brass, bronze, nickel silver, phosphor bronze, etc., but is not limited thereto.

[0072] Compared with simply using copper as the base layer 32 , using copper coated with aluminum as the base layer 32 can effectively reduce the material cost of the welding strip 3 .

[0073] In the second embodiment, see Figure 11 As shown, the base layer 32 is made of pure copper or copper alloy, that is, the base layer 32 does not have the aforementioned coating layer.

[0074] In some embodiments, the battery cell 1 is a whole battery cell 1 or a slice of a whole battery cell 1 .

[0075] For example, the specifications of the entire battery cell 1 may be 158.75mm×158.75mm, 156mm×156mm, 166mm×166mm, 182mm×182mm, 182mm×188mm, 182mm×199mm or 210mm×210mm, etc., but are not limited thereto.

[0076] A single whole cell 1 can be divided into multiple slices. For example, the slices can be half slices, three-quarter slices, four-quarter slices, six-quarter slices, etc., but not limited thereto.

[0077] In some embodiments, see Figure 1 、 Figures 12 to 14 As shown, it includes a battery string 10, the battery string 10 includes a plurality of battery cells 1 arranged along a first direction, and a first battery cell and a second battery cell arranged adjacent to each other are provided on the same battery string 10; The welding strips 3 include series welding strips 33 for conductively connecting adjacent battery cells 1. Adjacent battery cells 1 in the same battery string 10 can be connected in series via the series welding strips 33. One end of the same series welding ribbon 33 is connected to the first polarity grid line 212 on either the first cell or the second cell, and the other end is connected to the second polarity grid line 222 on the other of the first cell or the second cell. The number N1 of the series welding ribbons 33 conductively connected to the first polarity grid lines 212 on the first cell is equal to the number N2 of the series welding ribbons 33 conductively connected to the second polarity grid lines 222 on the second cell.

[0078] In some embodiments, see Figure 1 As shown, the series welding ribbon 33 includes a plurality of first series welding ribbons 331 arranged along the second direction and a plurality of second series welding ribbons 332 arranged along the second direction, and in the first direction, the first series welding ribbons 331 and the second series welding ribbons 332 are alternately arranged, and in the second direction, the first series welding ribbons 331 and the second series welding ribbons 332 are staggered; On the single cell 1 , the first polarity grid line 212 is conductively connected to either the first serial ribbon 331 or the second serial ribbon 332 , and the second polarity grid line 222 is conductively connected to the other of the first serial ribbon 331 or the second serial ribbon 332 .

[0079] It is understandable that in the battery string 10, the battery string 10 may include two battery cells 1 connected in series, three battery cells 1 connected in series, or any other greater number of battery cells 1. The specific number of battery cells 1 to be connected in series can be determined based on actual usage.

[0080] For example, in a battery string 10, the Nth battery cell 1, the N+1th battery cell 1, and the N+2th battery cell 1 are sequentially arranged along the first direction, wherein the first polarity grid line 212 on the Nth battery cell 1 and the second polarity grid line 222 on the N+1th battery cell 1 are connected in series via a plurality of first series welding ribbons 331 arranged along the second direction, and one end of the same first series welding ribbon 331 is connected to the first polarity grid line 212 on the Nth battery cell 1, and the other end is connected to the first polarity grid line 212 on the Nth battery cell 1. The end is connected to the second polarity grid line 222 on the N+1th battery cell 1, the first polarity grid line 212 on the N+1th battery cell 1 and the second polarity grid line 222 on the N+2th battery cell 1 are connected in series through a plurality of second series welding ribbons 332 arranged along the second direction, and one end of the same second series welding ribbon 332 is connected to the first polarity grid line 212 on the N+1th battery cell 1, and the other end is connected to the second polarity grid line 222 on the N+2th battery cell 1.

[0081] In some embodiments, the material of the gate lines 2 can be silver, copper, aluminum, a silver alloy, or a copper alloy, but is not limited thereto. The gate lines 2 can be a single layer of material or a composite of multiple layers of material, and are not limited thereto. The number of first polarity gate lines 212 and second polarity gate lines 222 can be determined based on the actual area of the cell 1, the width of the first polarity gate lines 212, the width of the second polarity gate lines 222, and the distance between the first polarity gate lines 212 and the second polarity gate lines 222, and are not specifically limited thereto.

[0082] In some embodiments, the cross section of the gate line 2 may be trapezoidal (a regular trapezoid or an inverted trapezoid from the first surface 111 toward the second surface 112 ), rectangular, etc., but is not limited thereto.

[0083] In some embodiments, the gate line 2 may be formed by any one of a screen printing process, an electroplating process, or a gate stacking process, but is not limited thereto.

[0084] In some embodiments, see Figure 1 、 Figure 13 and Figure 14 As shown, including: The bus bar 4 is extended along the second direction; The welding ribbon 3 includes a busbar welding ribbon 34 for conductively connecting the busbar 4 and the battery cell 1; At least a portion of the same busbar ribbon 34 is conductively connected to the busbar 4 , and at least a portion of the same busbar ribbon 34 is conductively connected to the first polarity grid line 212 or the second polarity grid line 222 on the cell 1 .

[0085] In the first embodiment, see Figure 13As shown, the cell 1 at any end of the cell string 10 in the first direction is recorded as the end cell, and the bus bar 4 can be arranged on the side of any end of the cell string 10 in the first direction. In this case, the first segment of the busbar 34 is arranged on the end cell at the end of the cell string 10 and is conductively connected to the first polarity grid line 212 or the second polarity grid line 222 on the end cell; in the second embodiment, see Figure 14 As shown, the bus bar 4 can also be set on the back side of the battery cell 1 to hide the bus bar 4. For example, the bus bar 4 can be set on the end battery cell, and the bus bar 4 is conductively connected to the bus bar 34 on the end battery cell, and the bus bar 4 and the heterogeneous welding strip 3 and the heterogeneous grid line on the end battery cell are insulated from each other by insulating material; or, the bus bar 4 can be set at the edge position of the battery cell 1 adjacent to the end battery cell, one end of the bus bar 34 is conductively connected to the first polarity grid line 212 or the second polarity grid line 222 on the end battery cell, and the other end is conductively connected to the bus bar 4.

[0086] Furthermore, the busbar 4 may include an end busbar for realizing series connection between multiple battery strings 10 or an intermediate busbar for realizing parallel connection between multiple battery strings 10 . The specific configuration thereof may refer to the prior art and will not be described in detail here.

[0087] In some embodiments, the busbar 4 may include a core material and a surface layer covering at least a portion of the surface of the core material, wherein the core material may be made of pure copper, copper alloy, aluminum or aluminum alloy, and the surface layer may be made of pure tin or tin alloy, but is not limited thereto.

[0088] In some embodiments, see Figure 1 、 Figure 2 and Figure 12 As shown, each battery cell 1 includes a substrate 11 having a first surface 111 and a second surface 112 disposed opposite to each other. The doped layer 12 is disposed between the second surface 112 and the gate line 2. The doped layer 12 includes a plurality of first doped regions 121 and second doped regions 122 that are staggered along a first direction. The first doped regions 121 are conductively connected to at least a portion of the first polarity gate line 212, and the second doped regions 122 are conductively connected to at least a portion of the second polarity gate line 222.

[0089] The substrate 11 has a first surface 111 and a second surface 112 disposed opposite each other, one of which is a light-receiving surface (commonly referred to as the front surface of the substrate 11), and the other is a light-receiving surface (commonly referred to as the back surface of the substrate 11). In this specification, the first surface 111 is referred to as the light-receiving surface, and the second surface 112 is referred to as the back surface. The light-receiving surface generally refers to the side that receives light. Its surface may also be provided with a passivation layer, an anti-reflection layer, etc., as is common in the art, but is not limited thereto. In some embodiments, the light-receiving surface may also be provided with a velvet surface. It should be noted that in some embodiments, light incident through the back surface may be absorbed to generate a photocurrent. Furthermore, in actual applications, the embodiments of the present invention do not specifically limit the material and conductivity type of the substrate 11. For example, the substrate 11 may be a silicon substrate, such as single crystal silicon, microcrystalline silicon, polycrystalline silicon, or amorphous silicon, or may be a silicon germanium substrate, a germanium substrate, or a gallium arsenide substrate, but is not limited thereto. Its conductivity type may be N-type or P-type.

[0090] It is understood that, in terms of conductivity, the polarity of the first doping region 121 and the polarity of the second doping region 122 can be the same as or opposite to the polarity of the substrate 11. It is only necessary to ensure that the polarity of the first doping region 121 is opposite to the polarity of the second doping region 122. Either the first doping region 121 or the second doping region 122 can be made of single crystal silicon, microcrystalline silicon, polycrystalline silicon, or amorphous silicon doped with impurities of a Group III element (e.g., B, Ga, or In), while the other can be made of single crystal silicon, microcrystalline silicon, polycrystalline silicon, or amorphous silicon doped with impurities of a Group V element (e.g., P, As, Sb).

[0091] It is understandable that a passivation layer (not shown) may also be provided on the side of the doped layer 12 facing away from the substrate 11 or on the side facing the substrate 11. For example, in some embodiments, an ultra-thin tunneling oxide layer may be provided between the doped layer 12 made of polycrystalline silicon and the substrate 11 made of single crystal silicon as a passivation layer to improve the passivation effect of the battery and reduce the recombination of carriers on the surface of the substrate 11. In some embodiments, a passivation layer, an anti-reflection layer, etc. are sequentially deposited on the doped layer 12, and then a gate line 2 is formed by processes such as photolithography and etching, so that the gate line 2 and the doped layer 12 are in good electrical contact and physically isolated through the passivation layer, but the present invention is not limited thereto.

[0092] In some embodiments, adjacent cells 1 are arranged on the same plane and spaced apart, or, Adjacent battery cells 1 are at least partially stacked (ie, laminated).

[0093] Secondly, the present invention provides a photovoltaic system including the above-mentioned back-contact cell assembly.

[0094] In particular, multiple battery modules can be connected in series or in parallel through a junction box to form a photovoltaic system. This photovoltaic system can be used in photovoltaic power stations, such as ground power stations, rooftop power stations, water-surface power stations, etc., and can also be used in equipment or devices that use solar energy to generate electricity, such as user solar power supplies, solar street lights, solar cars, solar buildings, etc. Of course, it is understandable that the application scenarios of the photovoltaic system are not limited to this. In other words, the photovoltaic system can be used in all fields that require solar power generation. Taking the photovoltaic power generation system network as an example, the photovoltaic system may include a photovoltaic array, a junction box, and an inverter. The photovoltaic array can be an array combination of multiple battery modules. For example, multiple battery modules can form multiple photovoltaic arrays. The photovoltaic array is connected to a junction box, which can combine the current generated by the photovoltaic array. The combined current flows through the inverter to convert it into the AC power required by the mains power grid and then connect to the mains power network to achieve solar power supply.

[0095] The present invention will be further described below with reference to the accompanying drawings and embodiments: First, the present invention provides a back contact battery assembly, comprising: A plurality of battery cells are arranged along a first direction; A plurality of grid lines are provided on each battery cell, including a plurality of first polarity grid lines and second polarity grid lines having opposite polarities and arranged alternately along a first direction, wherein the first polarity grid lines and the second polarity grid lines are both extended along a second direction, and the first direction and the second direction are intersected; A plurality of welding strips, at least partially disposed on a side of the grid line facing away from the solar cell, and each welding strip extending along a first direction; On a single cell, the number N of solder strips conductively connected to the first polarity grid lines or the second polarity grid lines is: min ≤N≤N max , where N is a positive integer, N min Satisfying formula I, N max Satisfying formula II, Formula I is: , Formula II is: , Where S is the cross-sectional area of the solder strip on the cell, in mm 2 ; β is the copper content of the base layer of the solder strip on the battery cell; L is the length of the battery cell, in cm; W is the width of the battery cell, in cm.

[0096] In each embodiment, the values of S, β, L, and W in Formula I and Formula II are shown in the following table. After calculation by Formula I and Formula II, two values N1 and N2 that meet the above-mentioned N value range are taken. The specific settings of each embodiment are as follows:

[0097] Control group: The difference between the control group and the above embodiment is that in each control group, on a single cell, the number of solder strips conductively connected to the first polarity grid line or the second polarity grid line is n, and n in each control group takes two values n1 and n2, and the value of n is a value outside the range of N in the embodiment with the same values of S, β, L and W. Specifically, the specific settings of each control group are as follows:

[0098] The simulation results of the comprehensive efficiency output values of the battery components corresponding to the control group and the experimental group are as follows: Among them, the comprehensive power P comp =P front +P rear *α; Where, P comp P is the combined power of the front and back of the photovoltaic module under STC, front is the front power of the photovoltaic module under STC, P rear is the back power of the photovoltaic module under STC, and the α reflection coefficient is uniformly taken as 0.1.

[0099]

[0100] It can be seen from the experimental results that when the relevant parameters of the back-contact battery assembly meet the relationship function constructed by the present invention, the electrical loss and optical loss caused by the welding strip are lower, thereby improving the overall efficiency of the battery assembly and enhancing the conversion efficiency of the battery assembly.

[0101] Throughout this specification, reference to terms such as "some embodiments," "exemplary," "example," or "for example" means that a specific feature, structure, material, or characteristic described in conjunction with an embodiment or example is included in at least one embodiment or example of the present application. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0102] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may, without departing from the scope of the technical solution of the present invention, make some changes or modifications to equivalent embodiments using the technical contents suggested above. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of the solution of the present invention.

Claims

1. A back contact battery assembly, characterized in that: include: A plurality of battery cells are arranged along a first direction; a plurality of grid lines disposed on each of the battery cells, including a plurality of first polarity grid lines and second polarity grid lines having opposite polarities and arranged alternately along a first direction, wherein the first polarity grid lines and the second polarity grid lines both extend along a second direction, and the first direction and the second direction are intersected; a plurality of welding strips, at least partially disposed on a side of the grid line facing away from the solar cell, and each of the welding strips extending along the first direction; On a single cell, the number N of the soldering strips conductively connected to the first polarity grid line or the second polarity grid line is determined based on the cross-sectional area of the soldering strip on the cell, the copper content of the base layer of the soldering strip on the cell, the length of the cell, and the width of the cell.

2. A back contact battery assembly according to claim 1, characterized in that: N min ≤N≤N max , where N is a positive integer, N min Satisfying formula I, N max Satisfying formula II, Formula I is: ， Formula II is: ， Where S is the cross-sectional area of the solder strip on the cell, in mm 2 ; β is the copper content of the base layer of the solder strip on the battery cell; L is the length of the battery cell, in cm; W is the width of the battery cell, in cm.

3. A back contact battery assembly according to claim 2, characterized in that: In the formula I and / or the formula II, the value of S is: 0 mm 2 <S≤0.187mm 2 .

4. A back contact battery assembly according to claim 3, characterized in that: In the formula I and / or the formula II, the value of S is: 0.12 mm 2 ≤S≤0.16mm 2 .

5. The back contact battery assembly according to claim 1, characterized in that: The cross-sectional profile of the welding strip is any one of circular, rectangular, waist-shaped and oblate.

6. The back contact battery assembly according to claim 1, characterized in that: In the formula I and / or the formula II, the value of β is: 0≤β≤100%.

7. A back contact battery assembly according to claim 6, characterized in that: In the formula I and / or the formula II, the value of β is: 50%≤β≤100%.

8. The back contact battery assembly according to claim 1, characterized in that: The soldering ribbon further includes a tin-containing layer, which covers at least a portion of the surface of the base layer.

9. The back contact battery assembly according to claim 1, characterized in that: The base layer includes a core layer and a cladding layer, wherein the cladding layer is provided on at least a portion of the surface of the core layer, the core layer is made of pure aluminum or an aluminum alloy, and the cladding layer is made of pure copper or a copper alloy; Alternatively, the base layer is made of pure copper or copper alloy.

10. The back contact battery assembly according to claim 1, characterized in that: The battery cell is a whole battery cell or a slice of the whole battery cell.

11. The back contact battery assembly according to claim 1, characterized in that: The battery string includes a plurality of battery cells arranged along a first direction, and a first battery cell and a second battery cell are provided adjacent to each other on the same battery string; The welding strips include series welding strips for conductively connecting adjacent battery cells; One end of the same series welding ribbon is connected to the first polarity grid line on either the first battery cell or the second battery cell, and the other end is connected to the second polarity grid line on the other of the first battery cell or the second battery cell.

12. The back contact battery assembly according to claim 11, characterized in that: The series welding strips include a plurality of first series welding strips arranged along the second direction and a plurality of second series welding strips arranged along the second direction, and in the first direction, the first series welding strips and the second series welding strips are arranged alternately, and in the second direction, the first series welding strips and the second series welding strips are arranged alternately; On the single cell, the first polarity grid line is conductively connected to either the first series welding ribbon or the second series welding ribbon, and the second polarity grid line is conductively connected to the other of the first series welding ribbon or the second series welding ribbon.

13. The back contact battery assembly according to claim 1, characterized in that: include: A bus bar extending along the second direction; The welding ribbon includes a busbar welding ribbon for conductively connecting the busbar and the battery cell; At least a portion of the same busbar is conductively connected to the busbar, and at least a portion of the same busbar is conductively connected to the first polarity grid line or the second polarity grid line on the battery cell.

14. The back contact battery assembly according to claim 1, characterized in that: Each of the battery cells includes a substrate having a first surface and a second surface that are oppositely disposed. A doped layer is provided between the second surface and the gate line, the doped layer including a plurality of first doped regions and second doped regions staggered along a first direction, the first doped regions being conductively connected to at least a portion of the first polarity gate line, and the second doped regions being conductively connected to at least a portion of the second polarity gate line.

15. The back contact battery assembly according to claim 1, characterized in that: The adjacent battery cells are arranged on the same plane and spaced apart, or, Adjacent battery cells are at least partially stacked.

16. A photovoltaic system, characterized in that: Comprising a back contact battery assembly according to any one of claims 1 to 15.

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