A back contact cell assembly and photovoltaic system

Abstract

The application relates to the technical field of solar cells, and particularly discloses a back contact cell module and a photovoltaic system. The cell module comprises: a plurality of cell pieces arranged along a first direction; a plurality of grid lines arranged on each cell piece, including first polarity grid lines and second polarity grid lines, wherein the first polarity grid lines and the second polarity grid lines are arranged to extend along a second direction; and a plurality of solder strips arranged at least partially on a side of the grid lines away from the cell pieces, and each solder strip is arranged to extend along the first direction. The number N of the solder strips electrically connected with the first polarity grid lines or the second polarity grid lines on a single cell piece is determined according to the cross-sectional area of the solder strips on the cell piece, the copper content of the base layer of the solder strips on the cell piece, the length of the cell piece and the width of the cell piece, so that the electrical loss and the optical loss caused by the solder strips are effectively reduced, and the comprehensive power of the cell module is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solar cells, in particular to a back contact cell module and a photovoltaic system. BACKGROUND

[0002] The back contact cell has the advantage of unique electrode layout, which concentrates the positive and negative grid lines on the back of the cell, avoiding the optical loss caused by the front electrode shielding in the traditional cell structure. However, with the iterative evolution of photovoltaic technology, the existing back contact cell technology has gradually developed to a mature stage, and the efficiency improvement is facing significant bottlenecks, making it increasingly difficult to break through in the actual industrialization process.

[0003] In the back contact cell module, the solder strip is electrically connected with the positive or negative grid line of the solar cell to build an electrical connection network. However, as a key bridge for current transmission in the cell module, the solder strip will cause a certain degree of electrical loss and optical loss, resulting in a decrease in the overall power output of the cell module to the outside. SUMMARY

[0004] The purpose of the present application is to provide a back contact cell module and a photovoltaic system in view of the existing technical situation.

[0005] In the present application, after research and testing, the length L and width W of the cell, the copper content β of the solder strip base layer, the cross-sectional area S of the solder strip on the cell, and the number N of solder strips are introduced as core influencing parameters, and based on the correlation and influence size between the parameters, the relationship functions I and II are constructed. When the relevant parameters of the back contact cell module satisfy the relationship functions, the electrical loss and optical loss caused by the solder strip can be effectively reduced, the overall power of the cell module is improved, and the parameters in the relationship functions are easy to obtain, and the scheme is easy to implement.

[0006] To achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0007] Firstly, the present application provides a back contact cell module, comprising:

[0008] a plurality of cell pieces arranged along a first direction;

[0009] a plurality of grid lines provided on each of the cell pieces, including a plurality of first polarity grid lines and second polarity grid lines with opposite polarity and staggered arrangement along the first direction, the first polarity grid lines and the second polarity grid lines are arranged along a second direction, and the first direction and the second direction are arranged transversely;

[0010] a plurality of solder strips provided at least partially on the side of the grid lines away from the cell pieces, and each of the solder strips is arranged along the first direction;

[0011] The number N of the solder strips conductively connected to the first polarity grid line or the second polarity grid line on a single piece of the battery piece is determined according to a cross-sectional area of the solder strip on the battery piece, a copper content of a base layer of the solder strip on the battery piece, a length of the battery piece, and a width of the battery piece.

[0012] In some embodiments, N min ≤N≤N max , where N is a positive integer, N min satisfies the formula I, N max satisfies the formula II,

[0013] The formula I is:

[0014] ,

[0015] The formula II is:

[0016] ,

[0017] In the formula, S is the cross-sectional area of the solder strip on the battery piece, in mm 2 ; β is the copper content of the base layer of the solder strip on the battery piece; L is the length of the battery piece, in cm; and W is the width of the battery piece, in cm.

[0018] In some embodiments, in the formula I and / or the formula II, the value of S is: 0 mm 2 <S≤0.187 mm 2 .

[0019] In some embodiments, in the formula I and / or the formula II, the value of S is: 0.12 mm 2 ≤S≤0.16 mm 2 .

[0020] In some embodiments, the cross-sectional profile of the solder strip is any one of a circle, a rectangle, a waist hole, and an oblate circle.

[0021] In some embodiments, in the formula I and / or the formula II, the value of β is: 0≤β≤100%.

[0022] In some embodiments, in the formula I and / or the formula II, the value of β is: 50%≤β≤100%.

[0023] In some embodiments, the solder strip further comprises a tin-containing layer covering at least part of the surface of the base layer.

[0024] In some embodiments, the base layer comprises a core layer and a cladding layer, the cladding layer is arranged on at least part 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.

[0025] Alternatively, the base layer is made of pure copper or copper alloy.

[0026] In some embodiments, the battery piece is a whole battery piece or a sub-piece of the whole battery piece.

[0027] In some embodiments, a battery string is included, the battery string comprises a plurality of battery pieces arranged along a first direction, and a first battery piece and a second battery piece are arranged adjacently on the same battery string.

[0028] The solder strip comprises a series solder strip for electrically connecting the adjacent battery pieces.

[0029] One end of the same series solder strip is connected to the first polarity grid line on any one of the first battery piece or the second battery piece, and the other end is connected to the second polarity grid line on the other of the first battery piece or the second battery piece.

[0030] The number N1 of the series solder strips on the first battery piece that are electrically connected to the first polarity grid line is equal to the number N2 of the series solder strips on the second battery piece that are electrically connected to the second polarity grid line.

[0031] In some embodiments, the series solder strip comprises a plurality of first series solder strips arranged along a second direction and a plurality of second series solder strips arranged along the second direction, and in the first direction, the first series solder strips and the second series solder strips are arranged alternately, and in the second direction, the first series solder strips and the second series solder strips are arranged staggeredly.

[0032] On the whole battery piece, the first polarity grid line is electrically connected to any one of the first series solder strip or the second series solder strip, and the second polarity grid line is electrically connected to the other of the first series solder strip or the second series solder strip.

[0033] In some embodiments, comprising:

[0034] The bus bar is arranged along the second direction;

[0035] The solder strip comprises a bus solder strip for electrically connecting the bus bar and the battery piece.

[0036] At least part of the same bus solder strip is electrically connected to the bus bar, and at least part of the bus solder strip is electrically connected to the first polarity grid line or the second polarity grid line on the battery piece.

[0037] In some embodiments, each of the battery pieces comprises a substrate having a first surface and a second surface arranged oppositely,

[0038] a doped layer arranged between the second surface and the gate lines, the doped layer comprising a plurality of first doped regions and second doped regions arranged alternately along a first direction, the first doped regions being electrically connected with at least part of the first polarity gate lines, and the second doped regions being electrically connected with at least part of the second polarity gate lines.

[0039] In some embodiments, the adjacent battery pieces are arranged on the same plane and are arranged at intervals, or,

[0040] The adjacent battery pieces are at least partially stacked.

[0041] Secondly, the application provides a photovoltaic system comprising the above-mentioned back contact battery assembly.

[0042] The application has the following advantages:

[0043] 1) In actual use, the problem of the comprehensive power reduction of the battery assembly caused by the solder strip is affected by multiple factors, and there is a correlation between the factors. Specifically, when the length and width of the battery piece change, the photo-generated current generated by the battery changes, the length of the solder strip on the battery piece, the number of the solder strip that can be placed, and the like also change, causing the optical loss and electrical loss caused by the solder strip to change. When the power loss caused by the solder strip is constant, the solder strip with high resistance needs a larger cross-sectional area and a larger number than the solder strip with low resistance, and there is a nonlinear relationship between the cross-sectional area, the number, and the resistance characteristics of the solder strip. In the application, through multiple researches and tests, the number N of the solder strip on the battery piece that is electrically connected with the first polarity gate line or the second polarity gate line is determined according to the cross-sectional area of the solder strip on the battery piece, the copper content of the base layer of the solder strip on the battery piece, the length of the battery piece, and the width of the battery piece, thereby effectively reducing the optical loss and electrical loss caused by the solder strip and improving the comprehensive power of the battery assembly.

[0044] 2) In the application, the length L and the width W of the battery piece, the copper content β of the base layer of the solder strip, the cross-sectional area S of the solder strip on the battery piece, and the number N of the solder strip are introduced as multiple core influencing parameters, and based on the correlation and influence size between the parameters, the relationship functions of formula I and formula II are constructed. When the related parameters of the back contact battery assembly satisfy the relationship functions, the optical loss and electrical loss caused by the solder strip can be effectively reduced, thereby improving the comprehensive power of the battery assembly, and each parameter in the relationship functions is easy to obtain, and the scheme is easy to implement.

[0045] Meanwhile, the skilled in the art can obtain the value range of the number of solder strips required to realize higher comprehensive power according to the above relationship function, reduce the difficulty of confirming the number of solder strips, and reduce the number of tests. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 A structure schematic diagram of a battery string of a back contact battery assembly according to an embodiment of the present application.

[0047] Figure 2 A structure schematic diagram of a monolithic cell according to an embodiment of the present application.

[0048] Figure 3 A minimum value N of the number of solder strips of a single polarity on a monolithic cell according to an embodiment of the present application min and a maximum value N max of the number of solder strips of a single polarity on a monolithic cell according to an embodiment of the present application

[0049] Figure 4 A minimum value N of the number of solder strips of a single polarity on a monolithic cell according to an embodiment of the present application min and a maximum value N max of the number of solder strips of a single polarity on a monolithic cell according to an embodiment of the present application

[0050] Figure 5 A minimum value N of the number of solder strips of a single polarity on a monolithic cell according to an embodiment of the present application min and a maximum value N max of the number of solder strips of a single polarity on a monolithic cell according to an embodiment of the present application

[0051] Figure 6 A minimum value N of the number of solder strips of a single polarity on a monolithic cell according to an embodiment of the present application min of the number of solder strips of a single polarity on a monolithic cell according to an embodiment of the present application

[0052] Figure 7 A schematic diagram of a solder strip according to an embodiment of the present application.

[0053] Figure 8 A schematic diagram of a solder strip according to an embodiment of the present application.

[0054] Figure 9 A schematic diagram of a solder strip according to an embodiment of the present application.

[0055] Figure 10 A schematic diagram of a solder strip according to an embodiment of the present application.

[0056] Figure 11The schematic view of the cross section of the solder strip of the embodiment of the present application is rectangular (the base layer does not contain the cladding layer).

[0057] Figure 12 The partial enlarged view of the cross section of the battery piece of the embodiment of the present application.

[0058] Figure 13 The structural schematic view of a back contact battery assembly of the embodiment of the present application.

[0059] Figure 14 The structural schematic view of a back contact battery assembly (the busbar is hidden in the back of the battery piece) of the embodiment of the present application. DETAILED DESCRIPTION

[0060] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. The examples of the embodiments are shown in the drawings, wherein the same or similar notations represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application. In addition, it should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0061] In the description of the present application, the terms "first", "second", etc. are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second", etc. can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of", "several" is two or more, unless otherwise explicitly specified and limited.

[0062] In the description of the present application, unless otherwise explicitly specified and limited, "on" or "under" of the first feature to the second feature can include that the first feature and the second feature are in direct contact, or the first feature and the second feature are not in direct contact but are in contact through another feature between them.

[0063] In the description of the present application, unless otherwise explicitly specified and limited, the first feature and the second feature are "electrically connected" or "electrically connected", which means that the electric charge can move between them to form an electrically conductive path. It can be that the first feature and the second feature are in direct contact, or the first feature and the second feature are in contact through another feature between them, or the two are connected together by mechanical means such as welding, crimping, clamping, plugging, etc. to achieve mechanical positioning and electrically conductive connection. Exemplarily, the grid line and the solder strip can be electrically connected through the solder pad, solder paste, etc., but are not limited thereto.

[0064] It can be understood that the solder strip itself has electrical conductivity but no polarity, in the present application, for the convenience of description, the polarity of the solder strip refers to its polarity on a certain battery piece, the polarity of the solder strip on a certain battery piece is consistent with the polarity of the grid line collected by it on the battery piece, and correspondingly, the opposite grid line is the grid line whose polarity is opposite to the grid line collected by it on the battery piece, for example, the solder strip is welded with the grid line of the positive electrode on a certain battery piece, and the polarity of the solder strip on the battery piece is positive, and correspondingly, the opposite grid line is the grid line of the negative electrode.

[0065] Firstly, referring to FIGS. 1-3, Figure 1 and Figure 2 the present application provides a back contact battery assembly, comprising:

[0066] a plurality of battery pieces 1 arranged along a first direction;

[0067] a plurality of grid lines 2 provided on each battery piece 1, including a plurality of first polarity grid lines 212 and second polarity grid lines 222 with opposite polarity and staggered arrangement along the first direction, the first polarity grid lines 212 and the second polarity grid lines 222 are arranged along a second direction, and the first direction and the second direction are arranged crossly;

[0068] a plurality of solder strips 3 at least partially provided on the side of the grid lines 2 away from the battery piece 1, and each solder strip 3 is arranged along the first direction;

[0069] The number N of the solder strips 3 electrically connected with the first polarity grid lines 212 or the second polarity grid lines 222 on a single battery piece 1 is determined according to the cross-sectional area of the solder strips 3 on the battery piece 1, the copper content of the base layer of the solder strips 332 on the battery piece 1, the length of the battery piece 1 and the width of the battery piece 1.

[0070] In actual use, the problem of power reduction of the battery assembly caused by the solder strip is affected by many factors, and there is a correlation between the influencing factors, specifically, when the length and width of the battery piece 1 change, the photogenerated current generated by the battery changes, the length of the solder strip 3 on the battery piece 1, the number of the solder strip 3 that can be placed also changes, resulting in changes in optical loss and electrical loss caused by the solder strip 3, and when the power loss caused by the solder strip 3 is constant, the solder strip 3 with high resistance material needs larger cross-sectional area and more number compared with the solder strip 3 with low resistance material, and the cross-sectional area, number and resistance characteristics of the solder strip 3 show a nonlinear relationship. In the present application, the number N of the solder strips electrically connected with the first polarity grid lines 212 or the second polarity grid lines 222 on the battery piece 1 is determined according to the cross-sectional area of the solder strips 3 on the battery piece 1, the copper content of the base layer of the solder strips 332 on the battery piece 1, the length of the battery piece 1 and the width of the battery piece 1, thereby effectively reducing the optical loss and electrical loss caused by the solder strip and improving the overall power of the battery assembly.

[0071] In some embodiments, N min ≤N≤N max wherein N is a positive integer, N min satisfies formula I, N max satisfies formula II,

[0072] Formula I is:

[0073] ,

[0074] Formula II is:

[0075] ,

[0076] In the formula, S is the cross-sectional area of the solder strip 3 on the battery piece 1 (here, the cross-sectional area refers to the cross-sectional area of a single solder strip 3), in mm 2 ; β is the copper content of the base layer 32 of the solder strip 3 on the battery piece 1 (here, it refers to the copper content of the base layer 32 corresponding to a single solder strip 3); L is the length of the battery piece 1, in cm; W is the width of the battery piece 1, in cm.

[0077] It can be understood that formula I and formula II use upward rounding processing for the final numerical value.

[0078] In the formula, the copper content refers to the proportion of the mass of copper in the base layer 32 of the solder strip 3 to the total mass of the base layer 32.

[0079] It can be understood that N refers to the number of solder strips 3 of a single polarity (i.e., solder strips 3 conductively connected to the first polarity grid line 212 or solder strips 3 conductively connected to the second polarity grid line 222) on a single battery piece 1, N min is the minimum value of the number of solder strips 3 of a single polarity on a single battery piece 1, N max is the maximum value of the number of solder strips 3 of a single polarity on a single battery piece 1.

[0080] In the formula, the first direction and the second direction are arranged in a cross manner, in one embodiment, the first direction and the second direction are perpendicular to each other, and in another embodiment, the first direction and the second direction can also not be perpendicular to each other. Further, the first direction can be a direction parallel to the length direction of the battery piece 1, or a direction parallel to the width direction of the battery piece 1.

[0081] In actual use, the battery assembly comprehensive power reduction problem caused by the solder strip 3 is affected by multiple factors, and there is a correlation between the influencing factors. Specifically, when the length and width of the battery sheet 1 change, the photogenerated current generated by the battery changes, the length of the solder strip 3 on the battery sheet 1, the number of the solder strip 3 that can be placed, and the like also change, causing the optical loss and electrical loss caused by the solder strip 3 to change. When the power loss caused by the solder strip 3 is constant, the solder strip 3 of high-resistance material needs a larger cross-sectional area and more quantity than the solder strip 3 of low-resistance material, and the cross-sectional area, quantity, and resistance characteristics of the solder strip 3 present a nonlinear relationship. In the present application, through multiple researches and tests, the length L and width W of the battery sheet 1, the copper content β of the base layer 32 of the solder strip 3, the cross-sectional area S of the solder strip 3 on the battery sheet 1, and the quantity N of the solder strip 3 are introduced as multiple core influencing parameters, and based on the correlation and influence size between the parameters, the relationship functions I and II are constructed. When the related parameters of the back contact battery assembly satisfy the relationship functions, the optical loss and electrical loss caused by the solder strip 3 can be effectively reduced, and the comprehensive power of the battery assembly is improved. Moreover, the parameters in the relationship functions are easy to obtain, and the scheme is easy to implement.

[0082] Meanwhile, in actual operation, the staff often needs to use professional detection equipment to accurately measure various parameters of the battery sheet, and then repeatedly calculates and verifies combined with experience and various tests to determine the appropriate number of solder strips. This process not only consumes a lot of time and labor costs, but also requires a high level of professional skills of the staff. Once the operation is wrong or the judgment is inaccurate, the comprehensive power of the battery assembly may be reduced due to improper solder strip setting, affecting the performance of the battery assembly. In the present application, the technical personnel only need to obtain the value range of the number of solder strips 3 required to achieve a higher comprehensive power according to the above relationship functions, thereby reducing the difficulty of confirming the number of solder strips 3 and reducing the number of tests.

[0083] Through tests, when the related parameters of the back contact battery assembly satisfy the relationship functions, the comprehensive power loss caused by the solder strip 3 can be reduced by 4W~15W, and the conversion efficiency of the battery assembly can be improved by 0.62%~1.69%, breaking through the bottleneck of the current battery assembly efficiency improvement.

[0084] It can be understood that the battery sheet 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 corner with a chamfer, which is set according to actual production needs and is not specifically limited herein. When the corners of the battery sheet 1 are rounded or chamfered, in the formula I and / or the formula II, the length of the battery sheet 1 is measured based on the length dimension of the remaining area excluding the corner, and the width of the battery sheet 1 is measured based on the width dimension of the remaining area excluding the corner.

[0085] In some embodiments, the value of S in Formula I and / or Formula II is: 0 mm 2 <S≤0.187mm 2 .

[0086] 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 0.187mm 2 However, it is not limited to this.

[0087] The influence of the cross-sectional area S of the solder strip 3 on the overall power induced by the solder strip 3 is reflected to some extent in Equations I and II, specifically the effect of the cross-sectional area S of the solder strip 3 on the number of solder strips 3 (N). min / N max For the impact of ), see Figure 3 As shown, it illustrates the minimum value N of the number of single-polarity solder strips 3 when all other parameters remain consistent (taking a cell 1 length L of 182 mm, a cell 1 width W of 94 mm, and a copper content β of the base layer 32 of solder strip 3 of 50% as an example). min and maximum value N max The trend of N changing with the cross-sectional area S of the solder strip 3 shows that when the cross-sectional area S of the solder strip 3 is small, min N max The difference between the two decreases significantly with the increase of the cross-sectional area S of the solder strip 3. When the cross-sectional area S of the solder strip 3 is large, N min N max And the decreasing trend of the difference between the two slows down, N min and N maxThe curve tends to be flat, thus, by properly increasing the cross-sectional area S of the welding strip 3, the number of welding strips 3 used can be reduced, which is conducive to increasing the overall power of the battery assembly and improving the battery conversion efficiency. Meanwhile, properly increasing the cross-sectional area S of the welding strip 3 can reduce the range of the number of welding strips 3 required, which is conducive to reducing the difficulty of determining the number of welding strips 3 and reducing the number of tests. However, the cross-sectional area S of the welding strip 3 should not be too large, otherwise, unnecessary material costs will be increased, and the optical loss will be increased, which will affect the conversion efficiency.

[0088] In some embodiments, preferably, the value of S in formula I and / or formula II is 0 mm 2 ≤S≤0.16mm 2 .

[0089] 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 In this range, the battery assembly can have relatively high overall power and low material cost, which is more conducive to industrialized production of products.

[0090] For example, the value of S in formula I and / or formula II is 0.12 mm 2 , 0.13 mm 2 , 0.14 mm 2 , 0.15 mm 2 or 0.16 mm 2 , but not limited thereto.

[0091] In some embodiments, the cross-sectional profile of the welding strip 3 is any one of a circular shape, a rectangular shape, a waist hole shape, and a flat round shape.

[0092] In some embodiments, the value of β in formula I and / or formula II is 0≤β≤100%.

[0093] For example, β can be 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 100%, but not limited thereto.

[0094] The influence of the copper content β of the base layer 32 of the welding strip 3 on the overall power induced by the welding strip 3 is reflected to some extent in the influence of the copper content β of the base layer 32 of the welding strip 3 on the number (N min / N max ) of the welding strip 3, as shown in FIG. 4, which shows the minimum value N Figure 4 of the number of welding strips 3 of a single polarity when the other parameters remain unchanged (for example, the length L of the battery sheet 1 is 182 mm, the width W of the battery sheet 1 is 94 mm, and the cross-sectional area S of the welding strip 3 is 0.1).min and maximum value N max The change trend of the minimum value N Figure 5 and the maximum value N Figure 6 are shown in FIGS. 1-3, which show the minimum value N min and the maximum value N max of the number of solder strips 3 of a single polarity under different copper content β of the base layer 32 of the solder strip 3 when other parameters remain unchanged (for example, the length L of the battery piece 1 is 182 mm, and the width W of the battery piece 1 is 94 mm). Figure 4 Figure 5 and Figure 5 It can be seen that N min and N max tend to decrease with the increase of the copper content β of the base layer 32 of the solder strip 3, and the copper content β of the base layer 32 of the solder strip 3 affects the sensitivity of N min and N max to the cross-sectional area S of the solder strip 3. The greater the copper content β of the base layer 32 of the solder strip 3, the stronger the change of N min and N max with the cross-sectional area S of the solder strip 3.

[0095] In some embodiments, preferably, the value of β in formula I and / or formula II is 50%≤β≤100%.

[0096] For example, β can be 50%, 55%, 58%, 60%, 65%, 68%, 70%, 75%, 78%, 80%, 85%, 88%, 90%, 95%, 98%, or 100%, but is not limited thereto.

[0097] Within this range, the battery assembly can have relatively high overall power and low material cost, which is more conducive to industrial production of products.

[0098] In some embodiments, as shown in FIG. 4, the solder strip 3 further comprises a tin-containing layer 31 covering at least part 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 to reduce the risk of short circuit caused by tinization while ensuring the welding effect. For example, 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, or the like, but is not limited thereto. Figures 7 to 11 In the first embodiment, as shown in FIG. 5, the base layer 32 comprises a core layer and a cladding layer. The cladding layer is arranged on at least part of the surface of the core layer. The material of the core layer is pure aluminum or an aluminum alloy, and the material of the cladding layer is pure copper or a copper alloy.

[0099] Figures 7 to 10 In the first embodiment, as shown in FIG. 5, the base layer 32 comprises a core layer and a cladding layer. The cladding layer is arranged on at least part of the surface of the core layer. The material of the core layer is pure aluminum or an aluminum alloy, and the material of the cladding layer is pure copper or a copper alloy. ​​

[0100] Exemplarily, the aluminum alloy can be an aluminum-copper alloy, an aluminum-manganese alloy, an aluminum-silicon alloy, etc., but is not limited thereto.

[0101] Exemplarily, the copper alloy can be brass, bronze, cupronickel, phosphor bronze, etc., but is not limited thereto.

[0102] Compared with using copper material as the base layer 32, using copper material coated with aluminum material as the base layer 32 can effectively reduce the material cost of the solder strip 3.

[0103] In a second embodiment, as shown in Figure 11 The base layer 32 is made of pure copper or a copper alloy, that is, the base layer 32 does not have the above-mentioned cladding layer.

[0104] In some embodiments, the battery piece 1 is a whole battery piece 1 or a split of the whole battery piece 1.

[0105] Exemplarily, the specification of the whole battery piece 1 can be 158.75mm x 158.75mm, 156mm x 156mm, 166mm x 166mm, 182mm x 182mm, 182mm x 188mm, 182mm x 199mm, or 210mm x 210mm, etc., but is not limited thereto.

[0106] A single whole battery piece 1 can be divided into a plurality of splits. Exemplarily, the split can be a half piece, a three-split piece, a four-split piece, or a six-split piece, etc., but is not limited thereto.

[0107] In some embodiments, as shown in Figure 1 , Figures 12 to 14 The battery string 10 includes a plurality of battery pieces 1 arranged along a first direction, and the same battery string 10 is provided with a first battery piece and a second battery piece arranged adjacently.

[0108] The solder strip 3 includes a series solder strip 33 for electrically connecting the adjacent battery pieces 1, and the adjacent battery pieces 1 in the same battery string 10 can be connected in series through the series solder strip 33.

[0109] One end of the same series solder strip 33 is connected to the first polarity grid line 212 on any one of the first battery piece or the second battery piece, and the other end is connected to the second polarity grid line 222 on the other of the first battery piece or the second battery piece.

[0110] The number N1 of the series solder strips 33 on the first battery piece electrically connected to the first polarity grid line 212 is equal to the number N2 of the series solder strips 33 on the second battery piece electrically connected to the second polarity grid line 222.

[0111] In some embodiments, as shown in Figure 1As shown, the series welding strip 33 includes a plurality of first series welding strips 331 arranged along the second direction and a plurality of second series welding strips 332 arranged along the second direction, and in the first direction, the first series welding strips 331 and the second series welding strips 332 are arranged alternately, and in the second direction, the first series welding strips 331 and the second series welding strips 332 are arranged staggeredly.

[0112] On the monolithic cell 1, the first polarity grid line 212 is conductively connected with any one of the first series welding strip 331 or the second series welding strip 332, and the second polarity grid line 222 is conductively connected with the other one of the first series welding strip 331 or the second series welding strip 332.

[0113] It can be understood that in the battery string 10, the battery string 10 can include two cell 1s in series, three cell 1s in series, or other more number of cell 1s in series, and the number of cell 1s in series can be determined according to actual use.

[0114] For example, in one battery string 10, the Nth cell 1, the N+1th cell 1, and the N+2th cell 1 are arranged in sequence along the first direction, wherein the first polarity grid line 212 on the Nth cell 1 and the second polarity grid line 222 on the N+1th cell 1 are connected by a plurality of first series welding strips 331 arranged along the second direction, and one end of the same first series welding strip 331 is connected to the first polarity grid line 212 on the Nth cell 1, and the other end is connected to the second polarity grid line 222 on the N+1th cell 1, and the first polarity grid line 212 on the N+1th cell 1 and the second polarity grid line 222 on the N+2th cell 1 are connected by a plurality of second series welding strips 332 arranged along the second direction, and one end of the same second series welding strip 332 is connected to the first polarity grid line 212 on the N+1th cell 1, and the other end is connected to the second polarity grid line 222 on the N+2th cell 1.

[0115] In some embodiments, the material of the grid line 2 can be silver, copper, aluminum, silver alloy, or copper alloy, but is not limited thereto, and the grid line 2 can be a single material layer or a composite of multiple material layers, which is not limited herein. The number of the first polarity grid line 212 and the second polarity grid line 222 can be determined according to the actual area of the cell 1, the width of the first polarity grid line 212 itself, the width of the second polarity grid line 222 itself, and the distance between them, which is not limited herein.

[0116] In some embodiments, the cross section of the grid line 2 can be trapezoidal (regular trapezoidal or inverted trapezoidal from the first face 111 to the second face 112), rectangular, etc., but is not limited thereto.

[0117] In some embodiments, the grid lines 2 can be formed by any one of a screen printing process, an electroplating process or a stacked grid process, but are not limited thereto.

[0118] In some embodiments, as shown in Figure 1 , Figure 13 and Figure 14 , the battery string 10 comprises:

[0119] The bus bar 4 is arranged to extend along the second direction;

[0120] The solder strip 3 comprises a bus bar solder 34 for electrically connecting the bus bar 4 and the battery tab 1;

[0121] At least a part of the bus bar solder 34 is electrically connected with the bus bar 4, and at least a part of the bus bar solder 34 is electrically connected with the first polarity grid line 212 or the second polarity grid line 222 on the battery tab 1.

[0122] In a first embodiment, as shown in Figure 13 , the battery tab 1 at any one end of the battery string 10 along the first direction is referred to as an end battery tab, and the bus bar 4 can be arranged beside any one end of the battery string 10 along the first direction, at this time, the first section of the bus bar solder 34 is arranged on the end battery tab at the end of the battery string 10, and is electrically connected with the first polarity grid line 212 or the second polarity grid line 222 on the end battery tab; in a second embodiment, as shown in Figure 14 , the bus bar 4 can also be arranged on the back of the battery tab 1 to hide the bus bar 4, for example, the bus bar 4 can be arranged on the end battery tab, and the bus bar 4 is electrically connected with the bus bar solder 34 on the end battery tab, and the bus bar 4 and the female solder strip 3 and the female grid line on the end battery tab are insulated from each other by an insulating material; or, the bus bar 4 can be arranged at the edge position of the battery tab 1 adjacent to the end battery tab, one end of the bus bar solder 34 is electrically connected with the first polarity grid line 212 or the second polarity grid line 222 on the end battery tab, and the other end is electrically connected with the bus bar 4.

[0123] Further, the bus bar 4 can comprise an end bus bar for realizing series connection between a plurality of battery strings 10 or a middle bus bar for realizing parallel connection between a plurality of battery strings 10, and the specific arrangement can refer to the prior art, which will not be described here.

[0124] In some embodiments, the bus bar 4 can comprise a core material and a surface layer covering at least a part of the surface of the core material, wherein the material of the core material can be any one of pure copper, copper alloy, aluminum or aluminum alloy, and the material of the surface layer can be pure tin or tin alloy, but is not limited thereto.

[0125] In some embodiments, as shown in Figure 1 , Figure 2 and Figure 12As shown, each battery piece 1 comprises a substrate 11 having a first surface 111 and a second surface 112 oppositely arranged,

[0126] A doped layer 12 is arranged between the second surface 112 and the gate line 2, and the doped layer 12 comprises a plurality of first doped regions 121 and second doped regions 122 arranged alternately along the first direction, the first doped regions 121 are electrically connected with at least part of the first polarity gate line 212, and the second doped regions 122 are electrically connected with at least part of the second polarity gate line 222.

[0127] The substrate 11 has a first surface 111 and a second surface 112 oppositely arranged, one of which is a light-receiving surface (generally corresponding to the front surface of the substrate 11), and the other is a back light surface (generally corresponding to the back surface of the substrate 11). In this specification, the first surface 111 is the light-receiving surface, and the second surface 112 is the back light surface. The light-receiving surface generally refers to the surface that receives light, and the surface can also be provided with a passivation layer, an anti-reflection layer and the like commonly used in the art, but is not limited thereto. In some embodiments, the light-receiving surface can also be provided with a textured surface. It should be noted that in some embodiments, light incident through the back light surface can also be absorbed to generate photocurrent. In addition, in actual application, the material and conductive type of the substrate 11 are not specifically limited. For example, the substrate 11 can be a silicon substrate, such as single crystal silicon, microcrystalline silicon, polycrystalline silicon or amorphous silicon, or a germanium-silicon substrate, a germanium substrate or a gallium arsenide substrate, but is not limited thereto. The conductive type can be N-type or P-type.

[0128] It can be understood that, in terms of conductive type, the polarity of the first doped region 121 and the polarity of the second doped region 122 can be the same as or opposite to the polarity of the substrate 11, as long as the polarity of the first doped region 121 is opposite to the polarity of the second doped region 122. The material of any one of the first doped region 121 or the second doped region 122 is single crystal silicon, microcrystalline silicon, polycrystalline silicon or amorphous silicon doped with III group element (such as B, Ga or In) impurities, and the material of the other is single crystal silicon, microcrystalline silicon, polycrystalline silicon or amorphous silicon doped with V group element (such as P, As, Sb) impurities.

[0129] It can be understood that the side of the doped layer 12 away from or towards the substrate 11 can also be provided with a passivation layer (not shown). For example, in some embodiments, an ultrathin tunneling oxide layer can be provided between the polycrystalline silicon doped layer 12 and the single crystal silicon substrate 11 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 and the like are sequentially deposited on the doped layer 12, and then the gate line 2 is formed by photolithography, etching and the like, so that the gate line 2 and the doped layer 12 are in good electrical contact and physical isolation through the passivation layer, but are not limited thereto.

[0130] In some embodiments, the adjacent battery pieces 1 are arranged on the same plane and are arranged in intervals, or

[0131] The adjacent battery pieces 1 are at least partially stacked (i.e., laminated).

[0132] Secondly, the application provides a photovoltaic system comprising the back contact battery assembly.

[0133] The plurality of battery assemblies can be connected in series or in parallel through the junction box to form the photovoltaic system. The photovoltaic system can be applied in photovoltaic power stations, such as ground power stations, roof power stations, water surface power stations, etc., and can also be applied in devices or apparatuses that utilize solar energy to generate electricity, such as user solar power sources, solar street lamps, solar cars, solar buildings, etc. Of course, it can be understood that the application scenarios of the photovoltaic system are not limited to this, that is, the photovoltaic system can be applied in all fields that need to utilize solar energy to generate electricity. Taking a photovoltaic power generation system network as an example, the photovoltaic system can include a photovoltaic array, a combiner box, and an inverter. The photovoltaic array can be an array combination of a plurality of battery assemblies. For example, a plurality of battery assemblies can form a plurality of photovoltaic arrays. The photovoltaic arrays are connected to the combiner box. The combiner box can combine the currents generated by the photovoltaic arrays. The combined current flows through the inverter to convert into alternating current required by the power grid, and then is connected to the power network to realize solar power supply.

[0134] The application will be further described below in conjunction with the accompanying drawings and embodiments:

[0135] Firstly, the application provides a back contact battery assembly, comprising:

[0136] a plurality of battery pieces arranged along a first direction;

[0137] a plurality of grid lines arranged on each battery piece, including a plurality of first polarity grid lines and second polarity grid lines with opposite polarities and staggered arrangement along the first direction, the first polarity grid lines and the second polarity grid lines are arranged along a second direction, and the first direction and the second direction are arranged in a cross manner;

[0138] a plurality of solder strips arranged at least partially on a side of the grid lines away from the battery pieces, and each solder strip is arranged along the first direction;

[0139] On a single battery piece, the number N of solder strips conductively connected to the first polarity grid lines or the second polarity grid lines is: N min ≤N≤N max , wherein N is a positive integer, N min satisfies formula I, N max satisfies formula II,

[0140] Formula I is:

[0141] ,

[0142] Equation II is:

[0143] ,

[0144] In the formula, S is the cross-sectional area of ​​the solder strip on the battery 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.

[0145] In each embodiment, the values ​​of S, β, L, and W in Equations I and II are shown in the table below. After calculation using Equations I and II, two values ​​N1 and N2 that conform to the above-mentioned range of N values ​​are selected. The specific settings for each embodiment are as follows:

[0146]

[0147] Control group:

[0148] The difference between the control group and the above embodiment is that, in each control group, the number of solder ribbons conductively connected to the first polarity grid line or the second polarity grid line on a single battery cell is n. Each control group takes two values, n1 and n2, and the value of n is outside the range of N values ​​in the embodiments where S, β, L, and W have the same values. Specifically, the specific settings for each control group are as follows:

[0149]

[0150] The simulation results of the overall efficiency output values ​​of the battery modules corresponding to the control group and the experimental group are shown below:

[0151] Among them, the comprehensive power P comp =P front +P rear *α;

[0152] In the formula, P comp P represents the combined power output of the front and back sides of the photovoltaic module under STC. front For the positive power of the photovoltaic module under STC, P rear The back-side power of the photovoltaic module under STC is α, and the reflection coefficient is uniformly taken as 0.1.

[0153]

[0154] The experimental results show that when the relevant parameters of the back contact battery module satisfy the relationship function constructed in this invention, the electrical and optical losses caused by the solder strip are lower, thereby improving the overall efficiency of the battery module and enhancing its conversion efficiency.

[0155] In the description of the application, reference to "some embodiments", "an example", "exemplary", or "for example" means that a particular feature, structure, material, or characteristic being referred to is included in at least one embodiment or example of the application. The appearances of the above terms in various places in the specification are not necessarily all referring to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments or examples.

[0156] The above descriptions are only the preferred embodiments of the present application and are not intended to limit the present application in any form. Although the present application has been described as above with the preferred embodiments, it is not intended to limit the present application, and any skilled person in the art can make some changes or modifications to the above-mentioned technical content with the prompt as equivalent embodiments with equivalent changes, but as long as it does not deviate from the technical solution of the present application, any simple modification, equivalent change and modification of the above embodiments according to the technical essence of the present application are still within the scope of the present application.

Claims

1. A back contact cell assembly, characterized by, The application relates to a battery string, which comprises a plurality of battery pieces arranged along a first direction, a plurality of grid lines arranged on each battery piece, a plurality of solder strips arranged on at least one side of the grid lines away from the battery piece, and a plurality of bus bars arranged along a second direction. The plurality of grid lines comprise a plurality of first polarity grid lines and a plurality of second polarity grid lines with opposite polarity and staggered arrangement along the first direction, and the first polarity grid lines and the second polarity grid lines are arranged along a second direction. The number N of the solder strips electrically connected to the first polarity grid lines or the second polarity grid lines on a single battery piece is determined according to the cross-sectional area of the solder strips on the battery piece, the copper content of the base layer of the solder strips on the battery piece, the length of the battery piece, and the width of the battery piece. The formula I is as follows: The formula II is as follows: N min ≤N≤N max wherein N is a positive integer, N min satisfies formula I, N max satisfies formula II, The cross-sectional profile of the solder strip is any one of a circle, a rectangle, a waist hole, and an oblate circle. ， In the formula I and / or the formula II, the value of beta is 0<=beta<=100%. ， where S is the cross-sectional area of the solder ribbon on the cell piece in mm 2 ; β is the copper content of the base layer of the solder ribbon on the cell piece; L is the length of the cell piece in cm; and W is the width of the cell piece in cm.

2. A back contact solar cell assembly according to claim 1, wherein, S in the formula I and / or the formula II has the value: 0 mm 2 S≤0.187 mm 2 .

3. A back contact solar cell assembly according to claim 2, wherein, In the formula I and / or the formula II S has the value: 0.12 mm 2 ≤ S ≤ 0.16 mm 2 .

4. A back contact solar cell assembly according to claim 1, wherein, In the formula I and / or the formula II, the value of beta is 50%<=beta<=100%.

5. A back contact solar cell assembly as set forth in Claim 1, wherein, The solder strip further comprises a tin-containing layer covering at least part of the surface of the base layer.

6. A back contact solar cell assembly according to claim 5, wherein, The base layer comprises a core layer and a cladding layer arranged on at least part of the surface of the core layer, the material of the core layer is pure aluminum or aluminum alloy, and the material of the cladding layer is pure copper or copper alloy.

7. A back contact solar cell assembly as set forth in Claim 1, wherein, Alternatively, the material of the base layer is pure copper or copper alloy.

8. A back contact solar cell assembly according to claim 1, wherein, The battery piece is a whole battery piece or a split battery piece of the whole battery piece. The battery string comprises a plurality of battery pieces arranged along a first direction, and adjacent first battery pieces and second battery pieces are arranged on the same battery string.

9. A back contact solar cell assembly according to claim 1, wherein, The solder strip comprises a series solder strip for electrically connecting adjacent battery pieces.

10. A back-contact battery assembly according to claim 1, characterized in that, One end of the series solder strip is connected to the first polarity grid line on any one of the first battery piece or the second battery piece, and the other end is connected to the second polarity grid line on the other one of the first battery piece or the second battery piece. The series solder strip comprises a plurality of first series solder strips arranged along a second direction and a plurality of second series solder strips arranged along the second direction, and the first series solder strips and the second series solder strips are staggered arranged along the first direction and staggered arranged along the second direction. On a single battery piece, the first polarity grid line is electrically connected to any one of the first series solder strip or the second series solder strip, and the second polarity grid line is electrically connected to the other one of the first series solder strip or the second series solder strip.

11. A back contact solar cell assembly according to claim 10, wherein, The application relates to a battery string, which comprises a plurality of battery pieces arranged along a first direction, a plurality of grid lines arranged on each battery piece, a plurality of solder strips arranged on at least one side of the grid lines away from the battery piece, and a plurality of bus bars arranged along a second direction. Each battery piece comprises a base body with a first surface and a second surface arranged oppositely, 12. A back contact solar cell assembly according to claim 1, wherein, ​ ​ ​ ​ 13. A back contact solar cell assembly according to claim 1, wherein, ​ A doped layer is arranged between the second surface and the gate lines, and the doped layer comprises a plurality of first doped regions and second doped regions staggered along a first direction, the first doped regions being electrically connected to at least part of the first-polarity gate lines, and the second doped regions being electrically connected to at least part of the second-polarity gate lines.

14. A back contact solar cell assembly according to claim 1, wherein, The adjacent battery pieces are arranged on the same plane and are spaced apart, or The adjacent battery pieces are at least partially stacked.

15. A photovoltaic system characterized by, A back contact battery assembly comprising any one of the back contact battery assemblies according to any one of claims 1 to 14.

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