Back contact solar cell string and preparation method, assembly and system

Abstract

The present invention is applicable to the field of solar cell technology and provides a back-contact solar cell string, a method for manufacturing the same, a component, and a system. The back-contact solar cell string comprises: at least two solar cells, each of which includes alternating positive and negative electrode regions; an insulating layer covering each positive electrode region on one side of the solar cell and each negative electrode region on the other side of the solar cell; and a first busbar connecting two adjacent solar cells, the first busbar being electrically connected to each positive electrode region and each negative electrode region of the two adjacent solar cells not covered by the insulating layer. The back-contact solar cell string provided by the present invention solves the problems of existing solar cell string manufacturing, which require precise alignment and complex processes.

Description

Technical Field

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

[0002] Solar cells are semiconductor devices that convert light energy into electrical energy. Low production costs and high energy conversion efficiency have always been the goals of the solar cell industry. For conventional solar cells, the emitter and base contacts are located on the front and back of the cell, respectively. The front side of the cell is the light-receiving side, and the presence of metal emitter contacts on the front side will inevitably cause some incident sunlight to be reflected and blocked by the metal electrodes, resulting in some optical loss. The metal electrode coverage of the front side of a typical crystalline silicon solar cell is approximately 7%. Reducing the metal electrode coverage on the front side can directly improve the cell's energy conversion efficiency. Back-contact solar cells are designed with both the emitter and base contacts on the back side (non-light-receiving side). This leaves the light-receiving side unobstructed by any metal electrodes, effectively increasing the cell's short-circuit current. This allows for wider metal grid lines on the back side, reducing series resistance and improving fill factor. Furthermore, this unobstructed front side not only improves conversion efficiency but also enhances aesthetics. Furthermore, modules with full back-contact electrodes are easier to assemble.

[0003] Existing back-contact solar cells are connected in series into cell strings and then processed into cell modules through other processes. However, in the process of connecting the back-contact solar cells in series into cell strings, the alignment and welding between adjacent cell pieces is very difficult due to the large number and narrow line width of the emitter and base contact electrodes. When the emitter and base contact electrodes are connected during the alignment welding process, the current of the cell will be caused. Therefore, precise alignment is required during welding, and the process requirements are also relatively complex. Summary of the Invention

[0004] An object of the embodiments of the present invention is to provide a back-contact solar cell string, aiming to solve the problems of the need for precise alignment and complex manufacturing processes in conventional cell strings.

[0005] The embodiment of the present invention is implemented as follows: a back-contact solar cell string, comprising:

[0006] At least two battery cells, each of the battery cells comprising alternating positive electrode regions and negative electrode regions;

[0007] an insulating layer covering each positive electrode region on one side of the battery cell and each negative electrode region on the other side thereof; and

[0008] A first bus bar connecting two adjacent battery cells, wherein the first bus bar is electrically connected to each positive electrode region and negative electrode region of the two adjacent battery cells that are not covered by the insulating layer.

[0009] Furthermore, welding points are provided on the positive electrode region and the negative electrode region of the battery cell that are electrically connected to the first bus bar.

[0010] Furthermore, conductive glue or solder paste is provided at the connection parts between the first bus bar and the positive electrode area and the negative electrode area in the battery cell.

[0011] Furthermore, the first bus bar is provided with conductive glue or solder paste.

[0012] Furthermore, the first bus bar includes a main body portion and extension portions extending from the main body portion and connected to the positive electrode region and the negative electrode region.

[0013] Furthermore, a reflective structure is provided on the main body.

[0014] Furthermore, the reflective structure is a rough texture structure, or a reflective layer coated on the main body or a reflective film attached thereto.

[0015] Furthermore, the reflective film is an aluminum film.

[0016] Furthermore, the reflective structure is located in the gap area between two adjacent solar cells.

[0017] Furthermore, the insulating layer is insulating glue.

[0018] Furthermore, the first bus bar is a pressure-sensitive conductive tape or a welding tape.

[0019] Furthermore, the battery string further includes a second bus bar located at an end of the solar cell string, and the second bus bar is electrically connected to the positive electrode region or the negative electrode region of the battery cell located at the end that is not covered by the insulating layer.

[0020] Furthermore, the number of the welding points is 2-20.

[0021] Another embodiment of the present invention aims to provide a battery assembly, which includes the back-contact solar cell string as described above.

[0022] Another embodiment of the present invention aims to provide a photovoltaic system, which includes the battery assembly described above.

[0023] Another embodiment of the present invention is to provide a method for preparing a back-contact solar cell string, the method comprising:

[0024] An insulating layer is provided on each positive electrode region on one side of the battery cell and each negative electrode region on the other side thereof;

[0025] The first bus bar is connected to each positive electrode region and negative electrode region of two adjacent battery cells that are not covered by the insulating layer.

[0026] Furthermore, the step of connecting the first bus bar to each positive electrode region and negative electrode region of two adjacent battery cells that are not covered by the insulating layer includes:

[0027] Disposing conductive glue or solder paste on the first bus bar;

[0028] The first bus bar is connected to each positive electrode region and negative electrode region not covered with the insulating layer in two adjacent battery cells by conductive glue or solder paste.

[0029] Furthermore, the step of connecting the first bus bar to each positive electrode region and negative electrode region of two adjacent battery cells that are not covered by the insulating layer includes:

[0030] A main grid or a wire connected to each positive electrode region or negative electrode region not covered with the insulating layer is provided on the battery cell;

[0031] Connect the first bus bar to the main grids or wires in two adjacent battery cells.

[0032] Furthermore, the step of connecting the first bus bar to each positive electrode region and negative electrode region of two adjacent battery cells that are not covered by the insulating layer includes:

[0033] Setting welding points on each positive electrode region and negative electrode region of the battery cell that is not covered by the insulating layer;

[0034] The first bus bar is connected to welding points of each positive electrode region and negative electrode region of two adjacent battery cells that are not covered by the insulating layer.

[0035] Furthermore, the method further comprises:

[0036] The second bus bar is connected to each positive electrode region or negative electrode region of the battery sheet located at the end portion and not covered by the insulating layer.

[0037] The back-contact solar cell string provided by the embodiment of the present invention covers the positive or negative regions on the cell that do not require electrical connection with an insulating layer, and at the same time, directly connects to all the positive and negative regions on the cell by using a first bus bar. Due to the provision of the insulating layer, the positive or negative regions that do not require electrical connection are insulated from the first bus bar through the insulating layer, while the positive or negative regions that require electrical connection are directly electrically connected to the first bus bar, thereby reducing the requirement for precise alignment during string production and simplifying the process, solving the problem of precise alignment and complex process during the production of existing cell strings. At the same time, by providing a reflective structure on the first bus bar, light can be reflected back into the glass on the manufactured cell assembly, and then reflected by the glass to the adjacent cell, so that the adjacent cell can absorb the light irradiated on the first bus bar, thereby increasing the secondary reflection utilization of the light irradiated on the cell assembly and improving power. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 1 is a schematic structural diagram of a back-contact solar cell string provided by one embodiment of the present invention;

[0039] Figure 2 is a schematic structural diagram of a back-contact solar cell string provided by another embodiment of the present invention;

[0040] Figure 3 is a schematic structural diagram of a back-contact solar cell string provided by another embodiment of the present invention;

[0041] Figure 4 is a schematic structural diagram of a back-contact solar cell string provided by yet another embodiment of the present invention;

[0042] Figure 5 is a schematic structural diagram of a back-contact solar cell string provided by yet another embodiment of the present invention;

[0043] Figure 6 is a schematic structural diagram related to a first bus bar in a back-contact solar cell string provided by one embodiment of the present invention;

[0044] Figure 7 This is a flow chart of a method for preparing a back-contact solar cell string provided by another embodiment of the present invention. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. 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.

[0046] In the present invention, unless otherwise expressly specified or limited, the terms "installed," "connected," "connected," "fixed," and the like should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to mechanical connections or electrical connections; they may refer to direct connections or indirect connections through an intermediate medium; and they may refer to internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances. The term "and / or" as used herein includes any and all combinations of one or more of the relevant listed items.

[0047] The present invention covers the positive or negative regions on the battery cell that do not require electrical connection with an insulating layer, and at the same time, uses a first bus bar that can be directly connected to all the positive and negative regions on the battery cell. Due to the provision of the insulating layer, the positive or negative regions that do not require electrical connection are insulated from the first bus bar through the insulating layer, while the positive or negative regions that require electrical connection are directly electrically connected to the first bus bar, thereby reducing the need for precise alignment during string production and simplifying the process, solving the problem of precise alignment and complex process in existing battery string production. At the same time, by providing a reflective structure on the first bus bar, light can be reflected back into the glass on the manufactured battery assembly, and then reflected by the glass to the adjacent battery cell, so that the adjacent battery cell can absorb the light irradiated on the first bus bar, thereby increasing the secondary reflection utilization of the light irradiated on the battery assembly and improving power.

[0048] Example 1

[0049] See also Figure 1 , is a schematic structural diagram of a back-contact solar cell string provided by an embodiment of the present invention. For ease of description, only the parts related to the embodiment of the present invention are shown. The back-contact solar cell string provided by the embodiment of the present invention includes:

[0050] At least two battery cells, each battery cell comprising alternating positive electrode regions 11 and negative electrode regions 12;

[0051] an insulating layer 13 covering each positive electrode region 11 on one side of the cell and each negative electrode region 12 on the other side thereof; and

[0052] The first bus bar 14 connecting two adjacent battery cells is electrically connected to each positive electrode region 11 and negative electrode region 12 of the two adjacent battery cells that are not covered by the insulating layer 13 .

[0053] In one embodiment of the present invention, the back contact solar cell string is a cell string formed by connecting at least two cells (i.e., back contact solar cells) in series through respective first bus bars 14 disposed between each two cells. The cell string may include two cells, three cells, or other number of cells connected in series. Figure 1 、 Figure 3 、 Figure 4 ,and Figure 5 As shown, it shows a battery string composed of two battery cells connected in series. At this time, a first bus bar 14 is provided to connect two adjacent battery cells; Figure 2 As shown, in other embodiments of the present invention, a battery string consisting of three battery cells connected in series is shown. In this case, two first bus bars 14 are required to be provided so that each of them is connected to its two adjacent battery cells. It is understandable that the battery string can also be connected in series with other numbers of battery cells according to actual use needs. Not all of them are shown in this figure, and they are arranged according to actual needs. The battery cells located at the two ends of the battery string are defined as end battery cells, and when the battery string is a plurality of battery cells connected in series, the battery cells connected in series between the two end battery cells are defined as internal battery cells.

[0054] As one example of the present invention, the cell comprises, from top to bottom, the following: a front passivation and anti-reflection layer, a silicon substrate, a back tunneling layer, an N-type doped region and a P-type doped region arranged at intervals, a back passivation layer, and a cell electrode; wherein the N-type doped region and the P-type doped region are alternately arranged on the lower surface of the back tunneling layer; the cell electrode comprises a positive electrode fine grid line and a negative electrode fine grid line, wherein the positive electrode fine grid line is electrically connected to the P-type doped region to form a positive electrode region 11, and the negative electrode fine grid line is electrically connected to the N-type doped region to form a negative electrode region 12. It is understandable that in other embodiments of the present invention, the cell structure can also be set to other structures, which are not limited here. However, it should be noted that in any type of cell structure, the positive electrode fine grid line is provided in the P-type doped region to form the positive electrode region 11, and the negative electrode fine grid line is provided in the N-type doped region to form the negative electrode region 12, and the positive electrode region 11 and the negative electrode region 12 are both provided on the back of the cell. When printing the positive and negative fine grid lines, they can be arranged to extend to the ends of the battery cell, or a certain distance can be left between the ends of the positive and negative fine grid lines and the ends of the battery cell.

[0055] Furthermore, in one embodiment of the present invention, Figure 1As shown, it is a back view of a battery string, which includes a plurality of positive electrode regions 11 and negative electrode regions 12 arranged alternately. Each of the positive electrode regions 11 and negative electrode regions 12 is substantially parallel to the edge of the battery cell and is arranged alternately. Each of the battery cells is substantially rectangular, wherein the substantially rectangular battery cell can be, for example, a square or another rectangular shape, and can have standard corners, cut corners or rounded corners. It is set according to actual production needs and is not specifically limited here. At the same time, the number of the positive electrode regions 11 and the negative electrode regions 12 is determined according to the actual size of the battery cell, the width and distance of the positive electrode fine grid lines and the negative electrode fine grid lines, and is not specifically limited here.

[0056] Furthermore, in one embodiment of the present invention, Figures 1 to 5 As shown, each positive electrode region 11 on one side of each cell is covered with an insulating layer 13, and each negative electrode region 12 on the other side is covered with an insulating layer 13. Specifically, if the insulating layer 13 is applied to each positive electrode region 11 on the left side of each cell, then the insulating layer 13 is also applied to each negative electrode region 12 on the right side of each cell. In one embodiment of the present invention, the insulating layer 13 may be an insulating adhesive, a non-conductive tape or film, or another suitable non-conductive shielding cover or cap. The insulating layer 13 may comprise materials such as polypropylene, polyethylene, or polyimide, and may also include an acrylic adhesive layer. The insulating layer 13 may be circular, square, triangular, or other shapes, and is used to insulate the covered positive electrode region 11 or negative electrode region 12 from the outside. The shape and material of the insulating layer 13 can be determined based on actual usage requirements, and the material and shape of the insulating layer 13 are not specifically limited herein. The preferred insulating layer 13 can be diffused outward from the end of the positive electrode region 11 or the negative electrode region 12 to be covered, and the insulating layer 13 can be applied from the end of the positive electrode region 11 to the end of the battery cell. In this case, one area on one side of the battery cell (the positive electrode region 11 or the negative electrode region 12) is covered with the insulating layer 13, while the other area is not covered with the insulating layer 13. This allows the area not covered by the insulating layer 13 to be electrically connected to the outside world, while the area covered by the insulating layer 13 is insulated from the outside world.

[0057] It should be noted that, in order to realize the series connection between the battery cells, it is specifically connected from one polarity of a battery cell to the other polarity of the next adjacent battery cell through the first bus bar 14, so that the battery cells are interconnected. Therefore, when the battery cells are connected in series through the first bus bar 14 in this embodiment, the first bus bar 14 is electrically connected to the positive electrode regions 11 and the negative electrode regions 12 of the two adjacent battery cells that are not covered with the insulating layer 13. That is, for example, when both battery cells are set to cover the insulating layer 13 on the positive electrode regions 11 on the left and the negative electrode regions 12 on the right, at this time Due to the provision of the insulating layer 13, the right side of the end cell on the left side is insulated from the first bus bar 14 by the provision of the insulating layer 13, while the positive regions 11 not covered by the insulating layer 13 are electrically connected to the first bus bar 14. Correspondingly, due to the provision of the insulating layer 13, the left side of the end cell on the right side is insulated from the first bus bar 14 by the provision of the insulating layer 13, while the negative regions 12 not covered by the insulating layer 13 are electrically connected to the first bus bar 14, so that the positive region 11 of the end cell on the left side is connected to the negative region 12 of the adjacent end cell on the right side through the first bus bar 14. It should be noted that at this time, the connection range of the first bus bar 14 when connecting to the two adjacent cell cells does not exceed the coverage range of the insulating layer 13, so that the first bus bar 14 is insulated from the positive region 11 or the negative region 12 covered by the insulating layer 13. At this time, the current at the negative electrode area 12 of the end battery cell on the left flows from the inside of the battery cell to the adjacent positive electrode area 11, and the positive electrode area 11 is electrically connected to the first bus bar 14. At this time, the current at the positive electrode area 11 of the end battery cell on the left flows to the negative electrode area 12 of the end battery cell on the right through the first bus bar 14, and flows to the adjacent positive electrode area 11 through the inside of the end battery cell on the right, so that the battery cells are finally connected in series. It can be understood that when there are 3 or other numbers of battery cells, the battery cells are also electrically connected through their respective first bus bars 14, so that each first bus bar 14 is respectively connected to each positive electrode area 11 and each negative electrode area 12 of the corresponding two adjacent battery cells that are not covered with the insulating layer 13, and each first bus bar 14 is electrically connected to each positive electrode area 11 on the left side and to each negative electrode area 12 on the right side, thereby realizing the series connection between each battery cell, so that the current can flow from one battery cell to the next adjacent battery cell through the first bus bar 14 in sequence, and finally the current is extracted.

[0058] Furthermore, in one embodiment of the present invention, Figure 3As shown, each positive electrode region 11 and negative electrode region 12 on each battery cell that is not covered with the insulating layer 13 can be directly electrically connected to the first bus bar 14. At this time, the connection portion between the first bus bar 14 and the positive electrode region 11 and negative electrode region 12 in the battery cell is provided with a conductive glue or solder paste 15. Among the optional arrangements, one of the methods is to directly apply a conductive glue or solder paste 15 on each positive electrode region 11 and negative electrode region 12 on the battery cell that is not covered with the insulating layer 13. At this time, the first bus bar 14 can contact the battery cell when connected. Conductive glue or solder paste 15 is applied to achieve better electrical and physical connection with each positive electrode area 11 and negative electrode area 12 to be connected. However, since the conductive glue or solder paste 15 needs to be applied on each positive electrode area 11 and negative electrode area 12 not covered by the insulating layer 13 in turn, the arrangement method is relatively cumbersome. At the same time, the conductive glue or solder paste 15 needs to be applied with sufficient accuracy to avoid the conductive glue or solder paste 15 being applied to the adjacent positive electrode area 11 or negative electrode area 12 covered by the insulating layer 13 and causing a short circuit. Figure 6 As shown, another way is to coat the first bus bar 14 with a conductive glue or solder paste 15, that is, the conductive glue or solder paste 15 is set on the first bus bar 14. At this time, the range of the conductive glue or solder paste 15 set on the first bus bar 14 is controlled not to exceed the range covered by the insulating layer 13. Therefore, when the conductive glue or solder paste 15 is set on the first bus bar 14, it can be directly and continuously arranged on the periphery of the entire first bus bar 14. At this time, when the first bus bar 14 is connected to the battery cell, the first bus bar 14 can be connected to the battery cell through the conductive glue or solder paste 15 and the battery cell not covered by the insulating layer 13. Each positive electrode area 11 or negative electrode area 12 is better electrically connected, and due to the setting of the insulating layer 13, even if the conductive glue or solder paste 15 set on the first bus bar 14 covers the insulating layer 13, it will not be electrically connected to the negative electrode area 12 or the positive electrode area 11 covered by the insulating layer 13. At this time, the negative electrode area 12 or the positive electrode area 11 covered by the insulating layer 13 is sequentially covered with the insulating layer 13, the conductive glue or solder paste 15, and the first bus bar 14. Therefore, the method of coating the conductive glue or solder paste 15 on the first bus bar 14 can realize convenient and fast process operation.

[0059] Furthermore, in one embodiment of the present invention, Figure 4As shown, each battery cell is further provided with a main grid or wire 16 connected to each positive electrode region 11 or negative electrode region 12 not covered with the insulating layer 13. For example, when each positive electrode region 11 on one side of the battery cell is covered with the insulating layer 13, each negative electrode region 12 not covered with the insulating layer 13 can be connected through the main grid or wire 16, so that the current on each negative electrode region 12 is converged to the main grid or wire 16. At this time, the first bus bar 14 is electrically connected to the positive electrode regions 11 and negative electrode regions 12 in the two adjacent battery cells that are not covered with the insulating layer 13 mainly through connection with the main grid or wire 16. At this time, due to the effect of the insulating layer 13, the positive electrode regions 11 or negative electrode regions 12 covered by the insulating layer 13 will not be connected to the first bus bar 14. Correspondingly, referring to the above, the connection parts between the first bus bar 14 and the positive electrode regions 11 and negative electrode regions 12 in the battery cell are provided with conductive glue or solder paste 15. Specifically, the conductive glue or solder paste 15 can be coated on the main grid or wire 16, or the conductive glue or solder paste 15 can be directly coated on the first bus bar 14. Further, in one embodiment of the present invention, as Figure 1 As shown, during cell fabrication, each positive electrode region 11 of the same polarity can be offset to one side, while each negative electrode region 12 can be offset to the other side. For example, an insulating layer 13 is coated on each positive electrode region 11 on the left side of the cell, and an insulating layer 13 is coated on each negative electrode region 12 on the right side. In this case, each negative electrode region 12 is positioned closer to the left side, while each positive electrode region 11 is positioned closer to the right side. This allows the negative electrode region 12 on the left side to extend beyond the positive electrode region 11 coated with the insulating layer 13. Therefore, when connected to the positive electrode region 11 via a busbar or conductive wire 16, the negative electrode region 12 on the left side does not contact the positive electrode region 11. This ensures that the positive electrode region 11 is both insulated from the outside by being covered by the insulating layer 13 and prevented from contacting the busbar or conductive wire 16 by being offset. Of course, in other embodiments of the present invention, each positive electrode region 11 and each negative electrode region 12 can be regularly and alternately arranged on the back side of the cell. In this case, the insulating layer 13 must be coated first, followed by the busbar or conductive wire 16.

[0060] Furthermore, in one embodiment of the present invention, Figure 1 、 Figure 2 ,and Figure 5As shown, each cell may further be provided with a welding point 17 (pad) on the busbar or conductor 16. That is, welding points 17 are provided on the positive electrode region 11 and the negative electrode region 12 of the cell electrically connected to the first busbar 14. In this case, multiple welding points 17 are provided on the busbar or conductor 16, so that the welding points 17 can better connect the cell to the first busbar 14 electrically and physically. The number of welding points 17 is 2-20, that is, not all positive electrode regions 11 or negative electrode regions 12 on the cell electrically connected to the first busbar 14 are provided with welding points 17. Welding points 17 may be provided on some positive electrode regions 11 or negative electrode regions 12, while the remaining positive electrode regions 11 or negative electrode regions 12 are directly connected to the busbar or conductor 16. At this time, the first bus bar 14 is electrically connected to the positive electrode areas 11 and negative electrode areas 12 in the two adjacent battery cells that are not covered with the insulating layer 13 by respectively connecting through the respective solder joints 17 and the main grid or wire 16. At this time, due to the effect of the insulating layer 13, the positive electrode areas 11 or negative electrode areas 12 covered by the insulating layer 13 will not be connected to the first bus bar 14. Correspondingly, referring to the above, the connection parts of the first bus bar 14 and the positive electrode areas 11 and negative electrode areas 12 in the battery cells are provided with conductive glue or solder paste 15, which can be specifically coated on the solder joints 17, or directly coated on the first bus bar 14.

[0061] Furthermore, in one embodiment of the present invention, the first bus bar 14 is a pressure-sensitive conductive tape or a welding tape, and the first bus bar 14 includes a main body 141 and extensions 142 extending from the main body 141 and connected to the positive electrode region 11 and the negative electrode region 12. Figure 1 As shown, each extension portion 142 extends from the main body portion 141 and presents a finger or comb shape. At this time, the corresponding welding points 17 are staggered so that the welding points 17 provided on the positive electrode region 11 required for electrical connection of one battery cell correspond to the welding points 17 provided on the negative electrode region 12 required for electrical connection of the adjacent battery cell, so that the first bus bar 14 is connected to each welding point 17 accordingly. At this time, since each extension portion 142 is only connected to each positive electrode region 11 or negative electrode region 12 in the battery cell that is not covered by the insulating layer 13, and is not connected to the adjacent negative electrode region 12 or positive electrode region 11 covered by the insulating layer 13, it is possible to achieve physical disconnection between the first bus bar 14 and the negative electrode region 12 or positive electrode region 11 covered by the insulating layer 13 on the basis of the insulating layer 13, thereby avoiding the problem of short circuit when the insulating layer 13 does not completely cover the negative electrode region 12 or the positive electrode region 11 and is connected to the first bus bar 14. Of course, it is optional, such as Figure 5As shown, its various extensions can also be extended and merged into one, that is, its first bus bar 14 can be a main body and two extensions extending from both ends of the main body, wherein the extensions are connected to the corresponding positive electrode areas 11 or negative electrode areas 12 that are not covered by the insulating layer. At this time, due to the action of the insulating layer 13, the positive electrode areas 11 or negative electrode areas 12 covered by the insulating layer 13 will not be connected to the first bus bar 14.

[0062] Furthermore, in one embodiment of the present invention, Figure 6 As shown, a reflective structure 143 is provided on the main body 141 , and the reflective structure 143 is located in the gap area between two adjacent solar cells. Specifically, since adjacent battery cells are not completely tightly fitted together when the battery cells are assembled into a battery assembly, a certain gap area exists between the adjacent battery cells. In this embodiment, a reflective structure 143 is provided on the main body 141, and the reflective structure 143 is located in the gap area between the adjacent battery cells. Therefore, when the first bus bar 14 is connected to the adjacent battery cells, the extensions 142 at both ends of the main body 141 are electrically connected to the positive electrode regions 11 and the negative electrode regions 12 in the adjacent battery cells that are not covered with the insulating layer 13. The reflective structure 143 on the main body 141 is accommodated in the gap area between the adjacent battery cells. Therefore, when the battery assembly is in use, when light passes through the glass on the battery assembly and reaches the first bus bar 14, the light is reflected back to the glass by the reflective structure 143, and then reflected by the glass to the adjacent battery cell. Therefore, the adjacent battery cell can absorb the light irradiated on the first bus bar 14, thereby increasing the secondary reflection utilization of the light irradiated on the battery assembly and improving the power.

[0063] Specifically, the reflective structure 143 is a rough textured structure, or a reflective layer or film applied to the main body 141. The reflective film can be aluminum film, glass bead reflective film, or micro-prismatic reflective film. The rough textured structure includes, but is not limited to, a mechanically polished surface, a random pyramid shape, an inverted pyramid shape, a spherical crown shape, a V-groove shape, and structures intermediate thereto. The reflective layer and film are retroreflective materials capable of achieving a reflective effect, and are configured based on actual usage needs and are not specifically limited herein.

[0064] Furthermore, in one embodiment of the present invention, the battery string also includes a second bus bar 18 located at the end of the solar cell string. The second bus bar 18 is electrically connected to the positive electrode region 11 and the negative electrode region 12 of the end cell that are not covered by the insulating layer 13. Specifically, there are two second bus bars 18, one located at each end of the two end cell. They serve as the two electrodes of the entire battery string. In other words, the current directed in each positive electrode region 11 and negative electrode region 12 of each cell is connected in series through each first bus bar 14 to the two second bus bars 18 at the end. The second bus bar 18 can be electrically connected to each positive electrode area 11 or negative electrode area 12 not covered with the insulating layer 13 through a wire. Of course, it can also be directly connected to the battery cell after the conductive glue or solder paste 15 is set as described in the first bus bar 14, so as to form an electrical connection between the second bus bar 18 and the positive electrode area 11 and the negative electrode area 12 of the battery cell located at the end that is not covered with the insulating layer 13. The specific connection is described with reference to the electrical connection between the first bus bar 14 and the adjacent battery cell, which will not be repeated here.

[0065] In an embodiment of the present invention, an insulating layer is used to cover the positive or negative regions on the battery cell that do not require electrical connection, and a first bus bar is used to directly connect to all the positive and negative regions on the battery cell. Due to the provision of the insulating layer, the positive or negative regions that do not require electrical connection are insulated from the first bus bar through the insulating layer, while the positive or negative regions that require electrical connection are directly electrically connected to the first bus bar. This reduces the need for precise alignment during string production and simplifies the process, solving the problem of precise alignment and complex process during existing battery string production. At the same time, a reflective structure is provided on the first bus bar, so that light can be reflected back into the glass on the manufactured battery assembly, and then reflected by the glass to the adjacent battery cell, so that the adjacent battery cell can absorb the light irradiated on the first bus bar, thereby increasing the secondary reflection utilization of the light irradiated on the battery assembly to increase power.

[0066] Example 2

[0067] See also Figure 7 , is a flow chart of a method for preparing a back-contact solar cell string according to a second embodiment of the present invention. For ease of explanation, only the portion related to the embodiment of the present invention is shown. The method is used to prepare the back-contact solar cell string according to the aforementioned embodiment. Specifically, the method includes:

[0068] Step S11, providing an insulating layer on each positive electrode region on one side of the battery cell and each negative electrode region on the other side thereof;

[0069] In one embodiment of the present invention, Figures 1 to 5 As shown, the back side of the cell is provided with a positive electrode region and a negative electrode region, wherein the positive electrode region includes a P-type doped region and a positive electrode fine grid line provided on the P-type doped region, and the negative electrode region includes an N-type doped region and a negative electrode fine grid line provided on the N-type doped region. Since the series connection between the various cell cells is achieved, it is necessary to electrically connect one polarity on one cell cell with the other polarity on the adjacent cell cell. Therefore, in order to avoid the problem of short circuit caused by the positive and negative electrode regions on the cell cells being connected during the connection process, an insulating layer is mainly provided on the cell cell, so that the positive electrode region or the negative electrode region that does not need to be electrically connected is insulated from the outside. Specifically, if the negative electrode regions on the right side of one of the cell cells need to be electrically connected to the outside, an insulating layer is coated on each positive electrode region on the right side of the cell cell. Specifically, the insulating layer can be an insulating material such as polypropylene, polyethylene, or polyimide. The process of coating the insulating layer can be completed by a printing process to ensure the accuracy and quality of the coating. Of course, the shape of the coated insulating layer can be circular, square, triangular or other shapes, and it can be used to achieve insulation between the covered positive electrode area or negative electrode area and the outside, and is not specifically limited here.

[0070] Step S21, connecting the first bus bar to each positive electrode region and negative electrode region not covered by the insulating layer in two adjacent battery cells;

[0071] In one embodiment of the present invention, after insulating layers are respectively provided on each positive electrode region on one side of the battery cell and each negative electrode region on the other side thereof, the positive electrode regions and negative electrode regions not covered with the insulating layer in the two adjacent battery cells are connected through a first bus bar, so that the two adjacent batteries are electrically connected through the first bus bar to achieve series connection.

[0072] Specifically, the step of connecting the first bus bar to the positive electrode regions and the negative electrode regions of two adjacent battery cells that are not covered by the insulating layer can be achieved by:

[0073] Method 1: Apply conductive glue or solder paste to each positive electrode area and negative electrode area not covered by the insulating layer in the battery cell;

[0074] The first bus bar is connected to each positive electrode region and negative electrode region not covered with the insulating layer in two adjacent battery cells by conductive glue or solder paste.

[0075] Method 2: Apply conductive glue or solder paste on the first bus bar;

[0076] The first bus bar is connected to each positive electrode region and negative electrode region not covered with the insulating layer in two adjacent battery cells by conductive glue or solder paste.

[0077] Among them, in method one, it specifically involves sequentially coating conductive glue or solder paste on each positive electrode region and negative electrode region of the battery cell that are not covered by the insulating layer. Then, a first busbar is connected to two adjacent battery cells. At this time, a heating welding method such as hot melt welding, laser welding, infrared welding, or electromagnetic welding is used to melt the conductive glue or solder paste and then solidify it, thereby electrically and physically connecting the first busbar to each positive electrode region and negative electrode region of the two adjacent battery cells that are not covered by the insulating layer. In method two, it is largely the same as the above method, except that the conductive glue or solder paste is directly applied to the first busbar. In this case, the area of ​​the conductive glue or solder paste applied to the first busbar is controlled to not exceed the area covered by the insulating layer.

[0078] Method 1 requires sequentially applying conductive glue or solder paste to each positive and negative electrode region not covered by the insulating layer, making the arrangement more complicated. It also requires sufficient precision when applying the conductive glue or solder paste to avoid short circuits caused by coating adjacent positive or negative electrode regions covered by the insulating layer. Method 2, on the other hand, only requires applying the conductive glue or solder paste to the first busbar, making the process more convenient and faster. Therefore, in embodiments of the present invention, method 2 is preferred for connecting the first busbar to each positive and negative electrode region not covered by the insulating layer in two adjacent battery cells.

[0079] Furthermore, the step of connecting the first bus bar to each positive electrode region and negative electrode region not covered by the insulating layer in two adjacent battery cells further includes:

[0080] A main grid or a wire connected to each positive electrode region or negative electrode region not covered with the insulating layer is provided on the battery cell;

[0081] Connect the first bus bar to the main grids or wires in two adjacent battery cells.

[0082] By providing busbars or wires capable of collecting current on each positive or negative electrode region not covered by the insulating layer, the current on each positive or negative electrode region not covered by the insulating layer can be collected on the busbars or wires, and then connected to the busbars or wires in two adjacent battery cells via a first busbar. At this time, due to the effect of the insulating layer, the positive or negative electrode regions covered by the insulating layer will not be connected to the first busbar, thereby achieving series connection of adjacent battery cells. Specifically, the connection method can be implemented using the method described in the second method above.

[0083] Furthermore, the step of connecting the first bus bar to each positive electrode region and negative electrode region not covered by the insulating layer in two adjacent battery cells further includes:

[0084] Setting welding points on each positive electrode area and negative electrode area of ​​the battery cell that is not covered by the insulating layer;

[0085] The first bus bar is connected to welding points of each positive electrode region and negative electrode region not covered by the insulating layer in two adjacent battery slices.

[0086] Each cell may also have welding points on the busbar or conductors. The first busbar is then connected to each welding point, thereby connecting the first busbar to each positive electrode region and negative electrode region of two adjacent cells that are not covered by the insulating layer. Specifically, this connection can be achieved using the method described in Method 2 above.

[0087] Step S31, connecting the second bus bar to each positive electrode region or negative electrode region of the battery cell located at the end portion and not covered by the insulating layer;

[0088] Among them, by connecting the positive electrode areas or negative electrode areas not covered by the insulating layer in the end battery cells of the battery string to the second bus bar, the current collected on each battery cell is finally converged to the second bus bar to form the battery string. It can be understood that the above steps can be specifically that the second bus bar is electrically connected to the positive electrode areas or negative electrode areas not covered by the insulating layer through a wire, or it can be described with reference to the above-mentioned first bus bar connection method, which will not be repeated here.

[0089] Example 3

[0090] A third embodiment of the present invention further provides a battery assembly, which includes the back-contact solar cell string described in the above embodiment.

[0091] Specifically, the assembly process of the battery assembly includes the following:

[0092] Cell sorting: Due to the high degree of randomness in solar cell production lines, the performance of the cells produced varies. In order to effectively combine cells with consistent or similar performance, they should be sorted according to the performance parameters measured by battery testing to improve cell utilization and produce qualified battery components. Battery testing is to test the output parameters (current and voltage) of the battery.

[0093] Serial connection: The individual battery cells are prepared according to the preparation method described in the aforementioned method embodiment, so as to be connected in series to form the battery string described in the aforementioned device embodiment.

[0094] Lamination: After the back is connected and passed the inspection, the glass, cut EVA film / POE film, battery string, EVA film / POE film, glass fiber, and backplane / glass are laid from bottom to top in sequence. During the laying process, the relative positions of the battery string and glass and other materials are ensured, and the distance between the battery cells is adjusted.

[0095] Module lamination: The stacked cells are placed in a laminator, the air in the components is extracted by vacuuming, and then the EVA is heated to melt and bond the cells, glass and back panel together. Finally, the components are cooled and removed.

[0096] Trimming: During lamination, EVA melts and extends outward due to pressure and solidifies to form burrs, so the burrs are trimmed after lamination is completed.

[0097] Framing: Attaching an aluminum frame to the module increases its strength, further seals the battery assembly, and extends the battery life. The gap between the frame and the glass assembly is filled with silicone resin, and the frames are connected with angle bonds.

[0098] Bonding junction box: Bond a box to the leads on the back of the module to facilitate the connection between the battery and other devices or between batteries.

[0099] Component testing: Test and calibrate the output power of the battery, test its output characteristics, and determine the quality level of the component.

[0100] High-voltage test: A certain voltage is applied between the component frame and the electrode lead to test the component's pressure resistance and insulation strength to ensure that the component is not damaged under harsh natural conditions (such as lightning strikes).

[0101] Example 4

[0102] A fourth embodiment of the present invention further provides a photovoltaic system, comprising the battery assembly as described in the above embodiments.

[0103] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A back contact solar cell string, characterized in that: include: At least two battery cells, each of the battery cells comprising alternating positive electrode regions and negative electrode regions; an insulating layer covering each positive electrode region on one side of the battery cell and each negative electrode region on the other side thereof; and a first bus bar connecting two adjacent battery cells, wherein the first bus bar is electrically connected to each positive electrode region and negative electrode region of the two adjacent battery cells that are not covered by the insulating layer; The first bus bar comprises: a main body portion, the main body portion extending to the edges of two adjacent battery cells; a plurality of pairs of extensions, each pair of extensions comprising two extensions located on opposite sides of the main body in a transverse direction, and the two extensions in each pair of extensions being symmetrically arranged about the main body; The positive electrode regions or negative electrode regions on both sides of each battery cell that are not covered by the insulating layer are connected together by wires, and the wires extend parallel to the longitudinal direction of the main body; Welding points are provided on the positive and negative regions of the battery cell that are electrically connected to the first bus bar. The first bus bar is connected to two adjacent battery cells through multiple welding points, the wires, and multiple pairs of extensions, and each extension is connected to a corresponding welding point.

2. The back contact solar cell string according to claim 1, wherein: Conductive glue or solder paste is provided at the connection parts between the first bus bar and the positive electrode area and the negative electrode area in the battery cell.

3. The back contact solar cell string according to claim 2, wherein: Conductive glue or solder paste is provided on the first bus bar.

4. The back-contact solar cell string according to claim 1, wherein: A reflection structure is provided on the main body.

5. The back contact solar cell string according to claim 4, wherein: The reflective structure is a rough texture structure, or a reflective layer coated on the main body or a reflective film attached thereto.

6. The back contact solar cell string according to claim 5, wherein: The reflective film is an aluminum film.

7. The back-contact solar cell string according to claim 4, wherein: The reflective structure is located in the gap area between two adjacent battery cells.

8. The back-contact solar cell string according to claim 1, wherein: The insulating layer is insulating glue.

9. The back contact solar cell string according to claim 1, wherein: The first bus bar is a pressure-sensitive conductive tape or a welding tape.

10. The back contact solar cell string according to claim 1, wherein: The battery string further includes a second bus bar located at an end of the solar cell string, and the second bus bar is electrically connected to a positive electrode region or a negative electrode region of the battery cell located at the end that is not covered by the insulating layer.

11. The back contact solar cell string according to claim 1, wherein: The number of the welding points is 2-20.

12. A battery assembly, characterized in that: The battery assembly comprises a back-contact solar cell string as claimed in any one of claims 1 to 11.

13. A photovoltaic system, characterized in that: The photovoltaic system includes the battery assembly according to claim 12.

14. A method for preparing a back-contact solar cell string, characterized in that: The method comprises: An insulating layer is provided on each positive electrode region on one side of the battery cell and each negative electrode region on the other side thereof; Connecting the first bus bar to each positive electrode region and negative electrode region of two adjacent battery cells that are not covered by the insulating layer; The first bus bar comprises: a main body portion, the main body portion extending to the edges of two adjacent battery cells; a plurality of pairs of extensions, each pair of extensions comprising two extensions located on opposite sides of the main body in a transverse direction, and the two extensions in each pair of extensions being symmetrically arranged about the main body; The positive electrode regions or negative electrode regions on both sides of each battery cell that are not covered by the insulating layer are connected together by wires, and the wires extend parallel to the longitudinal direction of the main body; Welding points are provided on the positive and negative regions of the battery cell that are electrically connected to the first bus bar. The first bus bar is connected to two adjacent battery cells through multiple welding points, the wires, and multiple pairs of extensions, and each extension is connected to a corresponding welding point.

15. The method for preparing a back contact solar cell string according to claim 14, wherein: The step of connecting the first bus bar to each positive electrode region and negative electrode region of two adjacent battery cells that are not covered by the insulating layer includes: Disposing conductive glue or solder paste on the first bus bar; The first bus bar is connected to each positive electrode region and negative electrode region not covered with the insulating layer in two adjacent battery cells by conductive glue or solder paste.

16. The method for preparing a back contact solar cell string according to claim 14, wherein: The method further comprises: The second bus bar is connected to each positive electrode region or negative electrode region of the battery sheet located at the end portion and not covered by the insulating layer.

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