Back-contact solar cell, cell assembly and photovoltaic system

Abstract

The present disclosure is applicable to the technical field of solar cells. Provided are a back-contact solar cell, a cell assembly and a photovoltaic system. Several first doped layers and several second doped layers of the back-contact solar cell are alternately arranged in sequence in a first direction on a back surface of a silicon wafer, and all extend in a second direction. A first barrier layer and a first metal thin film layer are sequentially stacked on each first doped layer, and the first metal thin film layer is configured to be soldered to a solder part that is parallel to the first doped layer. A second barrier layer and a second metal thin film layer are sequentially stacked on each second doped layer, and the second metal thin film layer is configured to be soldered to a solder part that is parallel to the second doped layer. In this way, it is not necessary to provide busbars for current collection, and arranging a barrier layer below each metal thin film layer can block metal atoms during the deposition of the metal thin film layer, thereby reducing the probability of metal atoms diffusing into an underlying doped layer and silicon wafer.

Description

Back contact solar cell, cell module and photovoltaic system

[0001] The present disclosure takes the patent document with the application number 202410719534.3 and the name of "Back contact solar cell, cell string, cell module and photovoltaic system" submitted on June 4, 2024 as the priority document, the whole content of which is incorporated by reference in the present disclosure. TECHNICAL FIELD

[0002] The present disclosure relates to the technical field of solar cells, in particular to a back contact solar cell, a cell module and a photovoltaic system. BACKGROUND

[0003] Solar power generation is a sustainable clean energy source, which can convert sunlight into electrical energy by using the photovoltaic effect of semiconductor p-n junction. In a solar cell, a back contact solar cell is a cell in which the emitter electrode and the base electrode are both placed on the back surface (non-light receiving surface) of the cell. The light receiving surface of the cell has no metal electrode to block, thereby effectively increasing the short-circuit current of the cell.

[0004] When forming a cell string of a back contact solar cell, a sub-grid and a main grid are usually formed on the cell by using a patterning technology, and then the cell string is formed by welding a solder strip on the main grid to realize the stringing of the cell. In such a technical solution, a main grid needs to be additionally provided to realize current collection, and then a solder strip is welded on the main grid to realize the stringing of the cell. The cost is relatively high.

[0005] In the related art, in order to solve such a technical problem, the main grid can not be provided. However, in such a technical solution, the welding performance and welding reliability of the cell and the conductive wire are poor, and the electrical performance of the cell is also low. SUMMARY

[0006] The present disclosure provides a back contact solar cell, a cell module and a photovoltaic system.

[0007] The present disclosure is implemented in this way. The back contact solar cell of the embodiment of the present disclosure comprises:

[0008] a silicon wafer having opposite front and back surfaces;

[0009] a plurality of first doped layers and a plurality of second doped layers, the plurality of first doped layers and the plurality of second doped layers are alternately arranged in a first direction on the back surface, and the plurality of first doped layers and the plurality of second doped layers both extend in a second direction, the second direction intersects the first direction, and the doping type of the first doped layer is opposite to the doping type of the second doped layer;

[0010] a first barrier layer and a first metal thin film layer are sequentially stacked on the first doped layer, the first metal thin film layer being used for welding with a welding piece arranged above the first doped layer and parallel to the first doped layer, each of the first doped layers corresponding to at least one welding piece;

[0011] a second barrier layer and a second metal thin film layer are sequentially stacked on the second doped layer, the second metal thin film layer being used for welding with a welding piece arranged above the second doped layer and parallel to the second doped layer, each of the second doped layers corresponding to at least one welding piece.

[0012] Further, the first metal thin film layer and the second metal thin film layer each include a seed copper layer.

[0013] Further, at least one of the first metal thin film layer and the second metal thin film layer has a thickness of 60nm-150nm.

[0014] Further, at least one of the first barrier layer and the second barrier layer includes at least one of a nickel layer, a silver layer, a cobalt layer, a titanium layer and a tungsten layer.

[0015] Further, at least one of the first barrier layer and the second barrier layer has a thickness of 1nm-2um.

[0016] Further, an anti-oxidation protective layer is arranged on the first metal thin film layer and the second metal thin film layer, the anti-oxidation protective layer having an anti-oxidation capability greater than that of the first metal thin film layer and an anti-oxidation capability greater than that of the second metal thin film layer.

[0017] Further, the anti-oxidation protective layer includes at least one of a tin layer, a nickel layer and a metal oxide layer.

[0018] Further, the anti-oxidation protective layer is a magnetic layer or has a magnetic material.

[0019] Further, the anti-oxidation protective layer has a thickness of 50nm-20um.

[0020] Further, at least one of the first metal thin film layer and the second metal thin film layer includes a magnetic material.

[0021] Further, in the second direction, the first doped layer and the second doped layer each extend to both edges of the silicon wafer in the second direction.

[0022] Further, in the second direction, at least one of a ratio of a length of the first barrier layer to a length of the first doped layer and a ratio of a length of the second barrier layer to a length of the second doped layer is greater than or equal to 50%; at least one of a ratio of a length of the first metal thin film layer to a length of the first doped layer and a ratio of a length of the second metal thin film layer to a length of the second doped layer is greater than or equal to 50%.

[0023] Further, in the first direction, at least one of a ratio of a length of the first barrier layer to a length of the first doped layer, a ratio of a length of the second barrier layer to a length of the second doped layer, a ratio of a length of the first metal thin film layer to a length of the first doped layer, and a ratio of a length of the second metal thin film layer to a length of the second doped layer is 50%-150%.

[0024] Further, in the first direction, at least one of a length of the first barrier layer and a length of the second barrier layer is 5um-200um, and at least one of a length of the first metal thin film layer and a length of the second metal thin film layer is 5um-200um.

[0025] Further, an area ratio of the first barrier layer and the first metal thin film layer to the first doped layer is 0.25-1.5; and / or

[0026] an area ratio of the second barrier layer and the second metal thin film layer to the second doped layer is 0.25-1.5.

[0027] Further, the back contact solar cell further comprises a back passivation film layer which is stacked on the back surface, the back passivation film layer comprises a plurality of first grooves and a plurality of second grooves, the first grooves and the second grooves both extend along the second direction, at least part of the first doped layer is exposed from the first grooves, and at least part of the second doped layer is exposed from the second grooves;

[0028] the first barrier layer is arranged on the part of the first doped layer exposed from the first grooves, and the first metal thin film layer is arranged at the first grooves and stacked on the first barrier layer;

[0029] the second barrier layer is arranged on the part of the second doped layer exposed from the second grooves, and the second metal thin film layer is arranged at the second grooves and stacked on the second barrier layer.

[0030] Further, in the first direction, a length of the first notch is less than a length of the first doped layer, a length of the second notch is less than a length of the second doped layer, and at least one of the length of the first notch and the length of the second notch is 50-150 microns.

[0031] Further, the first metal thin film layer is completely located in the first notch, the second metal thin film layer is completely located in the second notch, and a minimum distance between a surface of the first metal thin film layer away from the silicon wafer and the back surface is less than a minimum distance between a surface of the back surface passivation film layer away from the silicon wafer and the back surface; or,

[0032] The surface of the first metal thin film layer away from the silicon wafer is flush with the surface of the back surface passivation film layer away from the silicon wafer, and the surface of the second metal thin film layer away from the silicon wafer is flush with the surface of the back surface passivation film layer away from the silicon wafer; or,

[0033] The first metal thin film layer protrudes from the back surface passivation film layer and has a first extension part extending to the back surface passivation film layer in the first direction, and the second metal thin film layer protrudes from the back surface passivation film layer and has a second extension part extending to the back surface passivation film layer in the first direction.

[0034] The present disclosure also provides a solar cell module, which includes a cell string, and the cell string includes:

[0035] A plurality of the back contact solar cell pieces described above are arranged at intervals in the second direction, the first doped layer of an Nth back contact solar cell piece corresponds to the second doped layer of an (N+1)th back contact solar cell piece in the second direction, the second doped layer of the Nth back contact solar cell piece corresponds to the first doped layer of the (N+1)th back contact solar cell piece in the second direction, and N is a positive integer.

[0036] A plurality of soldered pieces are arranged at intervals in the first direction and extend in the second direction, each of the first doped layer and the second doped layer corresponds to at least one of the soldered pieces, and the soldered pieces are soldered to the first metal thin film layer of the Nth back contact solar cell piece and to the second metal thin film layer of the (N+1)th back contact solar cell piece in the second direction.

[0037] In the first direction, the first metal thin film layer of the Nth back contact solar cell piece is electrically connected to the second metal thin film layer of the (N+1)th back contact solar cell piece through the welding piece, and the second metal thin film layer of the Nth back contact solar cell piece is not connected to the first metal thin film layer of the (N+1)th back contact solar cell piece.

[0038] In the first direction, the first metal thin film layer of the Nth back contact solar cell piece is electrically connected to the second metal thin film layer of the (N+1)th back contact solar cell piece through the welding piece, and the second metal thin film layer of the Nth back contact solar cell piece is not connected to the first metal thin film layer of the (N+1)th back contact solar cell piece.

[0039] The present disclosure also provides a photovoltaic system comprising the above-mentioned cell assembly.

[0040] In the back contact solar cell piece, the cell assembly and the photovoltaic system in the embodiments of the present disclosure, the first doped layer is sequentially stacked with the first barrier layer and the first metal thin film layer, and the second doped layer is sequentially stacked with the second barrier layer and the second metal thin film layer. The first metal thin film layer is used for welding with the welding piece arranged above the first doped layer and parallel to the first doped layer, and the second metal thin film layer is used for welding with the welding piece arranged above the second doped layer and parallel to the second doped layer. In this way, each back contact solar cell piece can be welded with the welding piece parallel to the first doped layer and the second doped layer through the first metal thin film layer and the second metal thin film layer, thereby forming a cell string without the need to set a main grid to collect current. At the same time, the welding conduction between the first doped layer and the second doped layer and the welding piece is realized through the metal thin film layer, which can ensure the welding performance and the reliability of the welding. Moreover, by arranging the barrier layer below the metal thin film layer, the metal atoms can be blocked when depositing the metal thin film layer, thereby reducing the probability of the metal atoms diffusing into the doped layer and the silicon piece below, and improving the electrical performance of the back contact solar cell piece.

[0041] Additional aspects and advantages of the present disclosure will be in part apparent and in part pointed out hereinafter. BRIEF DESCRIPTION OF DRAWINGS

[0042] FIG. 1 is a schematic diagram of a module of a photovoltaic system according to an embodiment of the present disclosure;

[0043] FIG. 2 is a schematic diagram of a module of a cell assembly according to an embodiment of the present disclosure;

[0044] FIG. 3 is a schematic diagram of a planar structure of a cell string according to an embodiment of the present disclosure;

[0045] Fig. 4 is another planar structure schematic diagram of a battery string provided by the embodiment of the present disclosure;

[0046] Fig. 5 is a planar structure schematic diagram of a back contact solar cell provided by the embodiment of the present disclosure;

[0047] Fig. 6 is a cross-sectional schematic diagram of the back contact solar cell in Fig. 5 along line VI-VI;

[0048] Fig. 7 is a cross-sectional schematic diagram of the back contact solar cell in Fig. 5 along line VII-VII;

[0049] Fig. 8 is another cross-sectional schematic diagram of a back contact solar cell provided by the embodiment of the present disclosure;

[0050] Fig. 9 is still another cross-sectional schematic diagram of a back contact solar cell provided by the embodiment of the present disclosure;

[0051] Fig. 10 is a cross-sectional schematic diagram of the back contact solar cell in Fig. 5 along line X-X;

[0052] Fig. 11 is a cross-sectional schematic diagram of the back contact solar cell in Fig. 5 along line XI-XI.

[0053] Main element symbol explanation: photovoltaic system 1000, battery assembly 200, battery string 100, back contact solar cell 10, silicon wafer 11, front surface 111, back surface 112, first doped layer 12, second doped layer 13, first barrier layer 14, first metal thin film layer 15, first extension part 151, second barrier layer 16, second metal thin film layer 17, oxidation-resistant protective layer 171, second extension part 18, back surface passivation film layer 19, first notch 191, second notch 192, spacing area 101, soldering member 20. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical solutions and advantages of the present disclosure clearer, the present disclosure will be further described in detail below in combination with the drawings and embodiments. The examples of the embodiments are shown in the drawings, wherein the same or similar reference signs represent the same or similar elements or elements with the same or similar functions throughout. It should be noted that the embodiments described below by referring to the drawings are exemplary and are only used to explain the present disclosure, and cannot be understood as a limitation on the present disclosure. In addition, it should be understood that the specific embodiments described herein are only used to explain the present disclosure and cannot be used to limit the present disclosure.

[0055] In the description of the disclosure, it needs to be understood that the terms "upper", "lower", "left", "right", "transverse", "longitudinal" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the disclosure and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the disclosure.

[0056] In addition, the terms "first", "second" are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined as "first", "second" can explicitly or implicitly include one or more of the features. In the description of the disclosure, the meaning of "several" is two or more, unless otherwise explicitly specified and limited.

[0057] In the present disclosure, unless otherwise explicitly specified and limited, "on" or "under" of the first feature to the second feature can include that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, "on", "above" and "above" of the first feature to the second feature includes that the first feature is directly above and obliquely above the second feature, or only indicates that the first feature is higher in horizontal height than the second feature. The first feature "below", "below" and "below" of the second feature includes that the first feature is directly below and obliquely below the second feature, or only indicates that the first feature is lower in horizontal height than the second feature.

[0058] The following disclosure provides many different embodiments or examples for implementing different structures of the disclosure. In order to simplify the disclosure of the disclosure, the components and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the disclosure. In addition, the present disclosure can repeatedly refer to numerals and / or reference letters in different examples, and such repetition is for the purpose of simplification and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed. In addition, the present disclosure provides examples of various specific processes and materials, but those of ordinary skill in the art can realize the application of other processes and / or the use of other materials.

[0059] Please refer to FIG. 1 and FIG. 2, the photovoltaic system 1000 in the embodiment of the present disclosure can include the battery assembly 200 in the embodiment of the present disclosure, the battery assembly 200 in the embodiment of the present disclosure can include several battery strings 100 in the embodiment of the present disclosure.

[0060] Please refer to FIG. 3 and FIG. 4, the battery string 100 in the embodiment of the present disclosure can include several back contact solar cell pieces 10 in the embodiment of the present disclosure (only 2 and 3 are shown in the figure, the number is not specifically limited in the present disclosure) and several welding pieces 20.

[0061] Please combine with FIG. 5-FIG. 7, the back contact solar cell 10 in the embodiment of the present disclosure can include a silicon wafer 11, a plurality of first doped layers 12, a plurality of second doped layers 13, a first barrier layer 14, a first metal thin film layer 15, a second barrier layer 16 and a second metal thin film layer 17.

[0062] The silicon wafer 11 has opposite front surface 111 and back surface 112, the plurality of first doped layers 12 and the plurality of second doped layers 13 are sequentially and alternately arranged on the back surface 112 along a first direction, and the plurality of first doped layers 12 and the plurality of second doped layers 13 both extend along a second direction, the second direction intersects the first direction, the doping type of the first doped layer 12 is opposite to the doping type of the second doped layer 13, one of them is a P-type doped layer, and the other is an N-type doped layer. It should be noted that in the present disclosure, in some embodiments, the first doped layer 12 and the second doped layer 13 can be directly located in the silicon wafer 11, for example, the first doped layer 12 and the second doped layer 13 can be formed by directly diffusing on the silicon wafer 11. In other embodiments, the first doped layer 12 and the second doped layer 13 can also be arranged on the silicon wafer 11, for example, they can be formed on the silicon wafer 11 by deposition. Of course, in some embodiments, one of the first doped layer 12 and the second doped layer 13 can be located in the silicon wafer 11, and the other can be located on the silicon wafer 11, which is not limited here.

[0063] As shown in FIG. 6, the first barrier layer 14 and the first metal thin film layer 15 are sequentially and laminatedly arranged on the first doped layer 12, that is, the first barrier layer 14 is laminatedly arranged on the first doped layer 12, and the first metal thin film layer 15 is laminatedly arranged on the first barrier layer 14. Each first doped layer 12 is correspondingly provided with the first barrier layer 14 and the first metal thin film layer 15. As shown in FIG. 3 and FIG. 4, the first metal thin film layer 15 is used for welding with the soldering piece 20 arranged above the first doped layer 12 and parallel to the first doped layer 12. Each first doped layer 12 corresponds to at least one soldering piece 20 (only one is shown in the figure).

[0064] As shown in FIG. 7, the second barrier layer 16 and the second metal thin film layer 17 are sequentially and laminatedly arranged on the second doped layer 13, that is, the second barrier layer 16 is laminatedly arranged on the second doped layer 13, and the second metal thin film layer 17 is laminatedly arranged on the second barrier layer 16. Each second doped layer 13 is correspondingly provided with the second barrier layer 16 and the second metal thin film layer 17. As shown in FIG. 3 and FIG. 4, the second metal thin film layer 17 is used for welding with the soldering piece 20 arranged above the second doped layer 13 and parallel to the second doped layer 13. Each second doped layer 13 corresponds to at least one soldering piece 20 (only one is shown in the figure).

[0065] Referring to FIG. 3 and FIG. 4, in the battery string 100, the plurality of back contact solar cell pieces 10 are arranged in the second direction with a spacing area 101 between two adjacent back contact solar cell pieces 10. Specifically, the second direction can be the stringing direction of the battery string 100 (i.e. the horizontal direction in FIG. 3 and FIG. 4), and the first direction can be the direction perpendicular to the stringing direction (i.e. the vertical direction in FIG. 3 and FIG. 4), and the two directions are perpendicular to each other. Of course, in other embodiments, the first direction and the second direction can also be other directions, for example, two diagonal directions of the cell piece, and the specific embodiments are not limited here.

[0066] As shown in FIG. 3 and FIG. 4, in the battery string 100, the first doped layer 12 of the Nth back contact solar cell piece 10 corresponds to the second doped layer 13 of the (N+1)th back contact solar cell piece 10 in the second direction, and the second doped layer 13 of the Nth back contact solar cell piece 10 corresponds to the first doped layer 12 of the (N+1)th back contact solar cell piece 10 in the second direction, and N is a positive integer. It can be specifically understood that, as shown in FIG. 3 and FIG. 4, in the two adjacent back contact solar cell pieces 10, the first doped layer 12 of the former cell piece and the second doped layer 13 of the latter cell piece are located on the same straight line in the second direction, and the second doped layer 13 of the former cell piece and the first doped layer 12 of the latter cell piece are located on the same straight line in the second direction.

[0067] As shown in FIG. 3 and FIG. 4, the plurality of welding pieces 20 are arranged in the first direction with a spacing and extend in the second direction, and each first doped layer 12 and each second doped layer 13 correspondingly has at least one welding piece 20 (only one is shown in the figure). In the second direction, the welding piece 20 is welded with the first metal thin film layer 15 of the Nth back contact solar cell piece 10, and the welding piece 20 is welded with the second metal thin film layer 17 of the (N+1)th back contact solar cell piece 10. That is, as shown in FIG. 3 and FIG. 4, for each welding piece 20, it is welded with the first metal thin film layer 15 and the second metal thin film layer 17 in the second direction, that is, each welding piece 20 corresponds to a plurality of first metal thin film layers 15 and second metal thin film layers 17 arranged alternately in the second direction.

[0068] As shown in FIG. 3 and FIG. 4, in the first direction, the first metal thin film layer 15 of the Nth back contact solar cell 10 is electrically connected to the second metal thin film layer 17 of the (N+1)th back contact solar cell 10 through the soldering piece 20, and the second metal thin film layer 17 of the Nth back contact solar cell 10 is not connected (i.e. not electrically connected) to the first metal thin film layer 15 of the (N+1)th back contact solar cell 10. Alternatively, in the first direction, the second metal thin film layer 17 of the Nth back contact solar cell 10 is electrically connected to the first metal thin film layer 15 of the (N+1)th back contact solar cell 10 through the soldering piece 20, and the first metal thin film layer 15 of the Nth back contact solar cell 10 is not connected (i.e. not electrically connected) to the second metal thin film layer 17 of the (N+1)th back contact solar cell 10.

[0069] In other words, in the first direction, at the interval region 101 between the two adjacent back contact solar cells 10, the odd soldering pieces in the plurality of soldering pieces 20 are disconnected, or the even soldering pieces in the plurality of soldering pieces 20 are disconnected, i.e. at the interval region 101 between the two adjacent back contact solar cells 10, every other soldering piece 20 is disconnected.

[0070] As shown in FIG. 3 and FIG. 4, taking the example of from top to bottom along the first direction, the odd soldering pieces refer to the soldering pieces 20 located at the odd positions from top to bottom (i.e. the 1st, 3rd, 5th, etc., and so on), and the even soldering pieces refer to the soldering pieces 20 located at the even positions from top to bottom (i.e. the 2nd, 4th, 6th, etc., and so on). For example, in the first direction, if the 1st soldering piece 20 is disconnected and the 2nd soldering piece 20 is not disconnected, then from top to bottom, the soldering pieces 20 at the odd positions are disconnected, and the soldering pieces 20 at the even positions are not disconnected. Similarly, if the 1st soldering piece 20 is not disconnected and the 2nd soldering piece 20 is disconnected, then from top to bottom, the soldering pieces 20 at the even positions are disconnected, and the soldering pieces 20 at the odd positions are not disconnected.

[0071] It should be noted that "disconnected" only means that the two are not connected in structure, and the embodiments in the present disclosure do not limit the way of realizing "disconnected", for example, a cutting process can be performed during manufacturing.

[0072] In addition, it should be further noted that in the embodiments of the present disclosure, the first barrier layer 14 and the second barrier layer 16 block the metal atoms in the manufacturing of the first metal thin film layer 15 and the second metal thin film layer 17 from entering the doped layer or even the silicon wafer 11, and in addition, the first barrier layer 14 and the second barrier layer 16 themselves have a conductive effect.

[0073] In the back contact solar cell 10, the cell string 100, the cell module 200 and the photovoltaic system 1000 in the embodiments of the present disclosure, the first doped layer 12 is sequentially stacked with the first barrier layer 14 and the first metal thin film layer 15, and the second doped layer 13 is sequentially stacked with the second barrier layer 16 and the second metal thin film layer 17. The first metal thin film layer 15 is used for welding with the welding member 20 arranged above the first doped layer 12 and parallel to the first doped layer 12, and the second metal thin film layer 17 is used for welding with the welding member 20 arranged above the second doped layer 13 and parallel to the second doped layer 13. In this way, each back contact solar cell 10 can be welded with the welding member 20 parallel to the first doped layer 12 and the second doped layer 13 through the first metal thin film layer 15 and the second metal thin film layer 17, thereby forming the cell string 100 without the need to arrange the main grid to collect the current. At the same time, the welding conduction between the first doped layer 12 and the second doped layer 13 and the welding member 20 is realized through the metal thin film layer (i.e. the first metal thin film layer 15 or the second metal thin film layer 17), which can ensure the welding performance and the reliability of the welding. Moreover, by arranging the barrier layer below the metal thin film layer, the metal atoms can be blocked when the metal thin film layer is deposited, thereby reducing the probability of the metal atoms diffusing into the doped layer and the silicon wafer 11 below, so as to ensure the electrical performance of the back contact solar cell 10.

[0074] Specifically, in the embodiments of the present disclosure, the first barrier layer 14, the first metal thin film layer 15, the second barrier layer 16 and the second metal thin film layer 17 can be respectively formed on the first doped layer 12 and the second doped layer 13 by PVD deposition or the like.

[0075] The first barrier layer 14 can cover the first doped layer 12, and the number of the two can be equal, and the area of the two can be equal, or the area of the first barrier layer 14 can be smaller than the area of the first doped layer 12, for example, only a part of the first doped layer 12 is slotted (e.g. the first slot) to the passivation layer (e.g. the back passivation film layer) below, and the first barrier layer 14 is located in the slot or a part of the first barrier layer 14 extends to the top of the passivation layer along the side wall of the slot, which is not limited here. The first metal thin film layer 15 can cover the first barrier layer 14 one by one, and the area of the two can be equal, or the area of the first metal thin film layer 15 can be smaller than the area of the first barrier layer 14, or the area of the first metal thin film layer 15 can be larger than the area of the first barrier layer 14, and the part of the first metal thin film layer 15 outside the first barrier layer 14 is located on the passivation layer, which is not limited here. The second barrier layer 16 and the second metal thin film layer 17 are the same, and are not described here.

[0076] In embodiments of the present disclosure, the first barrier layer 14 and the second barrier layer 16 can be formed on the first doped layer 12 and the second doped layer 13 by PVD deposition, inkjet, or the like. The first metal thin film layer 15 and the second metal thin film layer 17 can each be a metal seed layer, which can be formed on the first barrier layer 14 by PVD deposition or the like.

[0077] It can be understood that, by arranging the first barrier layer 14 and the second barrier layer 16, the probability of metal atoms diffusing into the first doped layer 12 and the second doped layer 13, or even into the silicon wafer 11, during the deposition of the first metal thin film layer 15 and the second metal thin film layer 17 can be reduced, or even completely blocked, thereby improving the minority carrier lifetime, the electrical performance of the battery, and the battery efficiency.

[0078] In some embodiments, the first metal thin film layer 15 and the second metal thin film layer 17 can be a seed copper layer, which has good solderability and a sufficiently low bulk resistance, can reduce resistance loss, and is also relatively low in cost. Of course, in other embodiments, the first metal thin film layer 15 and the second metal thin film layer 17 can also be other metal seed layers with good solderability and low resistance, such as a silver layer, a silver-aluminum alloy layer, or the like.

[0079] In embodiments of the present disclosure, the first barrier layer 14 can include at least one of a nickel layer, a silver layer, a cobalt layer, a titanium layer, and a tungsten layer.

[0080] In this way, by using these metal layers as barrier layers, the metal atoms during the deposition of the metal thin film layer can be blocked, and at the same time, the metal layers themselves are not likely to greatly reduce the minority carrier lifetime of the bulk region. Similarly, in some embodiments, the second barrier layer 16 can also include at least one of a nickel layer, a silver layer, a cobalt layer, a titanium layer, and a tungsten layer.

[0081] It can be understood that, in the present disclosure, when the first barrier layer 14 and the second barrier layer 16 are made of the same material, they can be formed by the same process. The first metal thin film layer 15 and the second metal thin film layer 17 can each be a seed copper layer, and they can also be formed by the same process.

[0082] In some embodiments, the thickness of the first metal thin film layer 15 can be 60-150 nm.

[0083] In this way, by setting the thickness of the first metal thin film layer 15 within this reasonable range, it can be effectively avoided that the thickness of the first metal thin film layer 15 is too thin to form a stable solder joint with the soldering member 20, thereby ensuring stability and reliability, and at the same time, it can also be avoided that the thickness of the first metal thin film layer 15 is too thick to greatly increase the cost.

[0084] Specifically, in such embodiments, the thickness of the first metal thin film layer 15 can be, for example, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, 105 nm, 110 nm, 115 nm, 120 nm, 125 nm, 130 nm, 135 nm, 140 nm, 145 nm, 150 nm, or any value between 60 nm and 150 nm, without limitation here specifically.

[0085] In such embodiments, the thickness of the first metal thin film layer 15 can be 80 nm to 120 nm. Specifically, it has been found by the inventors of the present disclosure that when the thickness of the first metal thin film layer 15 is less than 80 nm, although it can form a weld with the welding member 20, it is prone to cause unstable welding under the influence of external force, and if the thickness of the first metal thin film layer 15 is greater than 120 nm, it will cause a substantial increase in cost. The inventors of the present disclosure have found that by setting the thickness of the first metal thin film layer 15 in the range of 80 nm to 120 nm, which is a preferred range, it can reduce the cost to the greatest extent while ensuring the stability and reliability of the weld.

[0086] In addition, like the first metal thin film layer 15, in some embodiments, the thickness of the second metal thin film layer 17 is also 60 nm to 150 nm.

[0087] In this way, by setting the thickness of the second metal thin film layer 17 in this reasonable range, it can effectively avoid the thickness of the second metal thin film layer 17 being too thin to form a stable weld with the welding member 20, ensuring stability and reliability, while also avoiding the thickness of the second metal thin film layer 17 being too thick to cause a substantial increase in cost.

[0088] Specifically, the thickness of the second metal thin film layer 17 can be, for example, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, 105 nm, 110 nm, 115 nm, 120 nm, 125 nm, 130 nm, 135 nm, 140 nm, 145 nm, 150 nm, or any value between 60 nm and 150 nm, without limitation here specifically.

[0089] In such embodiments, the thickness of the second metal thin film layer 17 can preferably be 80-120 nm. Specifically, the inventors of the present disclosure have found through research and verification that when the thickness of the second metal thin film layer 17 is less than 80 nm, although it can form a weld with the welding piece 20, it is prone to weld instability under the influence of external force, and if the thickness of the second metal thin film layer 17 is greater than 120 nm, it will result in a substantial increase in cost. The inventors of the present disclosure have set the thickness of the second metal thin film layer 17 in the range of 80-120 nm, which is a preferred range, which can maximize the weld stability and reliability while reducing costs.

[0090] In some embodiments, the thickness of the first barrier layer 14 can be 1 nm-2 um.

[0091] In this way, setting the thickness of the first barrier layer 14 in this reasonable range can avoid the cost increase caused by the thickness of the first barrier layer 14 being too thick and avoid the poor barrier effect caused by the thickness of the first barrier layer 14 being too thin, while also avoiding a large impact on the contact resistance.

[0092] Specifically, the thickness of the first barrier layer 14 can be, for example, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 70 nm, 800 nm, 900 nm, 1 um, 1.1 um, 1.2 um, 1.3 um, 1.4 um, 1.5 um, 1.6 um, 1.7 um, 1.8 um, 1.9 um, 2 um, or any value between 0 and 2 um, specifically without limitation.

[0093] In such embodiments, the thickness of the first barrier layer 14 can preferably be 10 nm-1 um. Specifically, the inventors of the present disclosure have found through research and verification that when the thickness of the first barrier layer 14 is less than 10 nm, although it can have some barrier effect, its barrier effect is generally poor and has a large impact on the contact resistance, and if the thickness of the first barrier layer 14 is greater than 1 um, although it can achieve a better barrier effect, it will result in an increase in cost and also affect the contact resistance. The inventors of the present disclosure have set the thickness of the first barrier layer 14 in the range of 10-1 um, which is a preferred range, which can ensure the barrier effect while avoiding excessive cost and a large impact on the contact resistance, that is, setting the thickness of the first barrier layer 14 in the range of 10-1 um can balance the relationship between the barrier effect, cost, and contact resistance, thereby ensuring the efficiency of the battery piece.

[0094] In some embodiments, the thickness of the second barrier layer 16 can also be 1 nm-2 um.

[0095] In this way, by setting the thickness of the second barrier layer 16 in this reasonable range, it can avoid the second barrier layer 16 being too thick to cause cost increase and avoid the second barrier layer 16 being too thin to cause poor barrier effect, and also can avoid causing great influence on the contact resistance.

[0096] Specifically, the thickness of the second barrier layer 16 can be, for example, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 70 nm, 800 nm, 900 nm, 1 um, 1.1 um, 1.2 um, 1.3 um, 1.4 um, 1.5 um, 1.6 um, 1.7 um, 1.8 um, 1.9 um, 2 um, or any value between greater than 0 and less than 2 um, which is not particularly limited here.

[0097] In such embodiments, the thickness of the second barrier layer 16 can preferably be 10 nm-1 um. Specifically, the inventors of the present disclosure have found through research and verification that when the thickness of the second barrier layer 16 is less than 10 nm, it can have a certain barrier effect, but the barrier effect is generally poor and has a great influence on the contact resistance, and if the thickness of the second barrier layer 16 is greater than 1 um, it can achieve a better barrier effect, but it will cause cost increase and also affect the contact resistance. The inventors of the present disclosure set the thickness of the second barrier layer 16 in the range of 10 nm-1 um after research, which can ensure the barrier effect while avoiding excessive cost and great influence on the contact resistance. That is, by setting the thickness of the second barrier layer 16 in the range of 10 nm-1 um, it can balance the relationship among the barrier effect, cost, and contact resistance, thereby ensuring the efficiency of the battery piece.

[0098] Please refer to FIG. 8 and FIG. 9, in some embodiments, the first metal thin film layer 15 and the second metal thin film layer 17 can be provided with an oxidation-resistant protective layer 18, the oxidation-resistant ability of the oxidation-resistant protective layer 18 is greater than the oxidation-resistant ability of the first metal thin film layer 15, and the oxidation-resistant ability of the oxidation-resistant protective layer 18 is greater than the oxidation-resistant ability of the second metal thin film layer 17.

[0099] In this way, the anti-oxidation protective layer 18 can protect the first metal thin film layer 15 and the second metal thin film layer 17, effectively avoiding the first metal thin film layer 15 and the second metal thin film layer 17 from generating oxides due to long-time exposure to air, thus causing poor soldering performance and poor electrical conductivity, and also avoiding the phenomenon that impurities such as organic matter and dust are attached to the surface of the two metal thin film layers, thus causing poor appearance and affecting efficiency.

[0100] It can be understood that the metal thin film layer serves the functions of soldering and collecting carriers, and thus needs to be made of a relatively active metal seed layer, such as the seed copper layer described above. However, the metal seed layer with relatively high activity is prone to oxidation, thus causing poor soldering performance. Therefore, the present disclosure can effectively avoid such a situation by arranging the anti-oxidation protective layer 18 on the first metal thin film layer 15 and the second metal thin film layer 17.

[0101] Specifically, in such an embodiment, the first metal thin film layer 15 and the second metal thin film layer 17 can be a metal layer with relatively high activity, such as a seed copper layer, and the anti-oxidation protective layer 18 can be an inert metal layer, for example, in some embodiments, the anti-oxidation protective layer 18 can be at least one of a tin layer, a nickel layer, and a metal oxide layer, which can also be formed on the first metal thin film layer 15 and the second metal thin film layer 17 by PVD deposition, inkjet, or the like. Alternatively, it can be formed by heat treatment.

[0102] Of course, in other embodiments, the anti-oxidation protective layer 18 can also be an organic film layer or an inorganic film layer capable of resisting oxidation, such as an inorganic film layer with a chain structure. Specifically, it is not limited here, and is preferably an inert metal layer.

[0103] In some embodiments, the anti-oxidation protective layer 18 can be a magnetic layer. In this way, during the soldering process with the soldering piece 20, the anti-oxidation protective layer 18 can adsorb the soldering piece 20, effectively avoiding the soldering piece 20 from deviating during the soldering process, thus improving the stability and reliability of the soldering process. That is to say, the anti-oxidation protective layer 18 can effectively avoid the oxidation of the metal thin film layer while also positioning and pre-fixing the soldering piece 20 during the soldering process.

[0104] Specifically, in such an embodiment, the magnetic layer refers to a film layer that itself has a magnetic adsorption function or a film layer that has a magnetic adsorption function after being electrified, and the magnetic layer can be completely made of a magnetic material.

[0105] Of course, it can be understood that in some embodiments, the anti-oxidation protective layer 18 can not be a magnetic layer made entirely of magnetic material, but can have a magnetic material component in the anti-oxidation protective layer 18, for example, a magnetic material can be added to the inert metal layer such as the tin layer, nickel layer, and metal oxide layer described above, so that the anti-oxidation protective layer 18 can generate a magnetic attraction force on the soldering piece 20.

[0106] In addition, during the soldering process, some metal particles can be splashed, and the magnetic attraction force can be used to adsorb some metal particles, thereby reducing the surface pollution of the battery piece, improving the light absorption capacity of the battery piece, and improving the light conversion efficiency of the battery piece.

[0107] It can be understood that the anti-oxidation protective layer 18 will melt and flow during the soldering process, so in the final battery assembly 200, there can be a phenomenon that some or all areas of the first metal thin film layer 15 do not have the anti-oxidation protective layer 18 between them and the soldering piece 20.

[0108] In some embodiments, the thickness of the anti-oxidation protective layer 18 can be 50 nm-20 um. In this way, the thickness of the anti-oxidation thin film layer is set in this reasonable range, which can avoid the problem of poor anti-oxidation effect caused by too thin thickness, and can also avoid the problem of a substantial increase in cost caused by too thick thickness.

[0109] Specifically, the thickness of the anti-oxidation protective layer 18 can be, for example, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 70 nm, 800 nm, 900 nm, 1 um, 1 um, 2 um, 3 um, 4 um, 5 um, 6 um, 7 um, 8 um, 9 um, 10 um, 11 um, 12 um, 13 um, 14 um, 15 um, 16 um, 17 um, 18 um, 19 um, 20 um, or any value between 50 nm and 20 um, which is not specifically limited here.

[0110] In some embodiments, the first metal thin film layer 15 can also include a magnetic material. In this way, during the soldering process with the soldering piece 20, the first metal thin film layer 15 can also adsorb the soldering piece 20, which can effectively avoid the problem of deviation of the soldering piece 20 during the soldering process, and improve the stability and reliability of the soldering.

[0111] Similarly, in some embodiments, the second metal thin film layer 17 can also include a magnetic material, so that the second metal thin film layer 17 can generate a magnetic attraction force on the soldering piece 20.

[0112] Please refer to FIG. 3 and FIG. 4, in some embodiments, in the second direction, the first doped layer 12 and the second doped layer 13 both extend to the two edges of the silicon wafer 11 in the second direction. In this way, the area of the silicon wafer 11 can be utilized to the maximum extent, thereby improving the efficiency of the cell.

[0113] In some embodiments, in the second direction, the ratio of the length of the first barrier layer 14 to the length of the first doped layer 12 (i.e. the length in the left-right direction in the figure) is greater than 50%. The ratio of the length of the first metal thin film layer 15 to the length of the first doped layer 12 is also greater than 50%.

[0114] In this way, by setting the ratio between the length of the first barrier layer 14 and the first metal thin film layer 15 in the second direction and the length of the first doped layer 12 within the reasonable range described above, the collection efficiency of the carriers can be improved while ensuring the welding reliability, and the length of the first metal thin film layer 15 can be prevented from being too small to result in poor welding reliability.

[0115] In such embodiments, in the second direction, the length of the first barrier layer 14 and the first metal thin film layer 15 is preferably the same as the length of the first doped layer 12.

[0116] Similarly, in some embodiments, in the second direction, the ratio of the length of the second barrier layer 16 to the length of the second doped layer 13 (i.e. the length in the left-right direction in the figure) is greater than 50%, and the ratio of the length of the second metal thin film layer 17 to the length of the second doped layer 13 is also greater than 50%.

[0117] In this way, by setting the ratio between the length of the second barrier layer 16 and the second metal thin film layer 17 in the second direction and the length of the second doped layer 13 within the reasonable range described above, the collection efficiency of the carriers can be improved while ensuring the welding reliability, and the length of the second metal thin film layer 17 can be prevented from being too small to result in poor welding reliability.

[0118] In such embodiments, in the second direction, the length of the second barrier layer 16 and the second metal thin film layer 17 is preferably the same as the length of the second doped layer 13.

[0119] It should be noted that in this document, the length of each film layer in the second direction refers to the length of the area formed by the orthographic projection (i.e. the projection in the thickness direction) of each film layer on the silicon wafer 11 in the second direction. If similar descriptions appear in the following, please refer to this treatment.

[0120] In some embodiments, in the first direction, the ratio of the length of the first barrier layer 14 to the length of the first doped layer 12 is 50%-150%. The ratio of the length of the first metal thin film layer 15 to the length of the first doped layer 12 is also 50%-150%.

[0121] In this way, the ratio of the length of the first barrier layer 14 in the first direction to the length of the first doped layer 12 in the first direction can be prevented from being too small to form a stable and reliable contact with the solder ribbon, ensuring the reliability of the soldering, and can also be prevented from being too large to cause the first barrier layer 14 to shield too much of the first doped layer 12, thereby reducing the double-sided rate of the battery sheet.

[0122] It should be noted that the length of each film layer in the first direction herein refers to the length of the area formed by the orthographic projection (i.e., the projection in the thickness direction) of each film layer on the silicon wafer 11 in the first direction. If similar descriptions appear below, reference can be made to this treatment.

[0123] Specifically, in such embodiments, the ratio of the length of the first barrier layer 14 to the length of the first doped layer 12 in the first direction, and the ratio of the length of the first metal film layer 15 to the length of the first doped layer 12 in the first direction can each be, for example, any value from 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, 110%, 120%, 130%, 140%, 150%, or 50%-150%.

[0124] Further, in such embodiments, the ratio of the length of the first barrier layer 14 to the length of the first doped layer 12, and the ratio of the length of the first metal film layer 15 to the length of the first doped layer 12 can each preferably be 50%-70%. Specifically, the inventors of the present disclosure have found through research that if the above ratios are less than 50%, the length of the first metal film layer 15 in the first direction will be too small, resulting in a too-small contact area with the solder member 20 and leading to poor soldering such as a false solder. If the above ratios are set to be greater than 70%, the light-shielding area will be too large, affecting the double-sided rate. The inventors have found through research and verification that by setting the ratios in this preferred range, the soldering performance can be ensured while the double-sided rate of the battery sheet is maximized.

[0125] In some embodiments, the ratio of the length of the second barrier layer 16 to the length of the second doped layer 13 in the first direction is 50%-150%, and the ratio of the length of the second metal film layer 17 to the length of the second doped layer 13 in the first direction is 50%-150%.

[0126] In this way, the ratio of the length of the second metal thin film layer 17 and the second barrier layer 16 in the first direction to the length of the second doped layer 13 in the first direction can be prevented from being too small to form a stable and reliable contact with the solder ribbon, ensuring the reliability of the soldering, and can also be prevented from being too large to cause the second barrier layer 16 to block too much of the second doped layer 13, thereby reducing the double-sided rate of the battery sheet.

[0127] Specifically, in such embodiments, the ratio of the length of the second barrier layer 16 to the length of the first doped layer 12, and the ratio of the length of the second metal thin film layer 17 to the length of the first doped layer 12 in the first direction can each be, for example, any value from 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, 110%, 120%, 130%, 140%, 150%, or 50%-150%.

[0128] Further, in such embodiments, the ratio of the length of the second barrier layer 16 to the length of the first doped layer 12, and the ratio of the length of the second metal thin film layer 17 to the length of the first doped layer 12 in the first direction can each preferably be 50%-70%. Specifically, the inventors of the present disclosure have found through research that if the above ratios are less than 50%, the length of the second metal thin film layer 17 in the first direction will be too small, causing the contact area with the soldering piece 20 to be too small and resulting in poor soldering such as a false solder. If the above ratios are set to be greater than 70%, the light-blocking area will be too large, affecting the double-sided rate. The inventors have found through research and verification that by setting the ratios in this preferred range, the soldering performance can be ensured while the double-sided rate of the battery sheet is maximized.

[0129] In some embodiments, the length of the first barrier layer 14 and the length of the first metal thin film layer 15 in the first direction can each be 5-200um. In this way, the length of both in the first direction can be prevented from being too small to form a stable soldering contact with the solder ribbon, and can also be prevented from being too long to significantly reduce the double-sided rate.

[0130] Specifically, in such embodiments, the length of the first barrier layer 14 and the length of the first metal thin film layer 15 in the first direction can each be, for example, 5um, 10um, 20um, 30um, 40um, 50um, 60um, 70um, 80um, 90um, 100um, 110um, 120um, 130um, 140um, 150um, 160um, 170um, 180um, 190um, 200um, or any value between 5um and 200um, specifically without limitation.

[0131] In such embodiments, in the first direction, the length of the first barrier layer 14 and the length of the first metal thin film layer 15 can each be preferably 50 nm-200 nm. Specifically, the inventors of the present disclosure have found through research that if the above length is less than 50 nm, the contact area between the first barrier layer 14 and the first doped layer 12 will be too small, resulting in an increase in contact resistance, and at the same time, it will also increase the difficulty and time of slotting on the passivation film, and if the above length is greater than 200 nm, it will result in a larger light-shielding area, affecting the bifaciality. The inventors have found through research and verification that by setting the length in this preferred range, the bifaciality of the battery sheet can be maximized while reducing contact resistance and process difficulty and ensuring the welding performance with the soldering piece 20.

[0132] Similarly, in some embodiments, in the first direction, the length of the second barrier layer 16 is 5 um-200 um, and the length of the second metal thin film layer 17 is 5 um-200 um.

[0133] In this way, it can be avoided that the length of both in the first direction is too small to form stable welding contact with the solder strip, and it can also be avoided that the length of both in the first direction is too long to cause a substantial decrease in bifaciality.

[0134] Specifically, in such embodiments, the length of the second barrier layer 16 and the second metal thin film layer 17 in the first direction can be, for example, 5 um, 10 um, 20 um, 30 um, 40 um, 50 um, 60 um, 70 um, 80 um, 90 um, 100 um, 110 um, 120 um, 130 um, 140 um, 150 um, 160 um, 170 um, 180 um, 190 um, 200 um, or any value between 5 um and 200 um, which is not specifically limited here.

[0135] In such embodiments, in the first direction, the length of the second barrier layer 16 and the length of the second metal thin film layer 17 can each be preferably 50 nm-200 nm. Specifically, the inventors of the present disclosure have found through research that if the above length is less than 50 nm, the contact area between the second barrier layer 16 and the second doped layer 13 will be too small, resulting in an increase in contact resistance, and at the same time, it will also increase the difficulty and time of slotting on the passivation film, and if the above length is greater than 200 nm, it will result in a larger light-shielding area, affecting the bifaciality. The inventors have found through research and verification that by setting the length in this preferred range, the bifaciality of the battery sheet can be maximized while reducing contact resistance and process difficulty and ensuring the welding performance with the soldering piece 20.

[0136] In some embodiments, the area ratio of the first barrier layer 14 and the first metal thin film layer 15 to the first doped layer 12 is 0.25-1.5.

[0137] In this way, the area ratio of the first barrier layer 14 and the first metal thin film layer 15 can be prevented from being too small to ensure the soldering performance with the soldering member 20, and the area ratio of the first barrier layer 14 can be prevented from being too large to greatly reduce the double-sided rate.

[0138] Specifically, the area ratio of the first barrier layer 14 and the first metal thin film layer 15 to the first doped layer 12 can be, for example, 0.25, 0.5, 0.75, 1, 1.25, 1.5, or any value between 0.25 and 1.5.

[0139] Further, in order to balance the relationship between the soldering performance and the double-sided rate, the area ratio can be preferably 0.25-0.7 to ensure the soldering performance while maximizing the double-sided rate.

[0140] It should be noted that, in this article, the area ratio between the layers refers to the area ratio between the areas formed by the orthogonal projections of the layers on the silicon wafer 11. In the following, if similar descriptions appear, reference can be made to this treatment.

[0141] In some embodiments, the area ratio of the second barrier layer 16 and the second metal thin film layer 17 to the second doped layer 13 is 0.25-1.5.

[0142] In this way, the area ratio of the second barrier layer 16 and the second metal thin film layer 17 can be prevented from being too small to ensure the soldering performance with the soldering member 20, and the area ratio of the second barrier layer 16 can be prevented from being too large to greatly reduce the double-sided rate.

[0143] Specifically, the area ratio of the second barrier layer 16 and the second metal thin film layer 17 to the second doped layer 13 can be, for example, 0.25, 0.5, 0.75, 1, 1.25, 1.5, or any value between 0.25 and 1.5.

[0144] Further, in order to balance the relationship between the soldering performance and the double-sided rate, the area ratio can be preferably 0.25-0.7 to ensure the soldering performance while maximizing the double-sided rate.

[0145] Referring to FIG. 10, in some embodiments, the back contact solar cell 10 further comprises a back passivation film layer 19 laminated on the back surface 112, and a plurality of first notches 191 and a plurality of second notches 192 are formed on the back passivation film layer 19, the first notches 191 and the second notches 192 both extend along the second direction, the first doped layer 12 is at least partially exposed from the first notches 191, and the second doped layer 13 is at least partially exposed from the second notches 192;

[0146] The first barrier layer 14 is arranged on the portion of the first doped layer 12 exposed from the first notches 191, and the first metal film layer 15 is arranged at the first notches 191 and laminated on the first barrier layer 14;

[0147] The second barrier layer 16 is arranged on the portion of the second doped layer 13 exposed from the second notches 192, and the second metal film layer 17 is arranged at the second notches 192 and laminated on the second barrier layer 16.

[0148] It can be understood that, in some embodiments, a tunneling layer (not shown in FIG. 10) can also be arranged on the back surface 112 of the back contact solar cell 10. For example, the tunneling layer can be arranged between the first doped layer 12 and the silicon wafer 11, between the second doped layer 13 and the silicon wafer 11, or between the first doped layer 12 and the silicon wafer 11 and between the second doped layer and the silicon wafer 11.

[0149] In this way, by opening the first notches 191 and the second notches 192 on the back passivation film layer 19, it is convenient to form the barrier layer and the metal film layer on the first doped layer 12 and the second doped layer 13.

[0150] Specifically, in such embodiments, the area of the first notches 191 can be equal to or slightly smaller than the area of the first doped layer 12, and the area of the second notches 192 can also be preferably equal to or slightly smaller than the area of the second doped layer 13. The first notches 191 and the second notches 192 can be formed by laser slotting, etching slotting, etc., which is not limited here.

[0151] It can be understood that, in one possible example, during the manufacturing process, the barrier layer and the metal film layer can be formed at the first notches 191 and the second notches 192 by directly performing PVD deposition through a screen in the first notches 191 and the second notches 192, or the barrier layer can be deposited on the entire surface first, then the barrier layer in the regions other than the first notches 191 and the second notches 192 is etched away, then the metal film layer is deposited, and finally the metal film layer in the regions other than the first notches 191 and the second notches 192 is etched away, which is not limited here.

[0152] Further, as shown in Fig. 10, in such embodiments, the first metal film layer 15 is completely located within the first notch 191, the second metal film layer 17 is completely located within the second notch 192, and the height of the first metal film layer 15 is lower than the height of the back passivation layer 19. Alternatively, the first metal film layer 15 is flush with the back passivation layer 19, and the second metal film layer 17 is flush with the back passivation layer 19. In this way, when etching the metal film layer, only the metal film layer attached to the entire back passivation layer 19 needs to be etched.

[0153] Of course, as shown in Fig. 11, in some embodiments, the first metal film layer 15 can also protrude from the back passivation layer 19 and have a first extension portion 151 extending to the back passivation layer 19 in the first direction, and the second metal film layer 17 can also protrude from the back passivation layer 19 and have a second extension portion 171 extending to the back passivation layer 19 in the first direction. In this way, the first metal film layer 15 has the first extension portion 151 on the back passivation layer 19, and the second metal film layer 17 has the second extension portion 171 on the back passivation layer 19, which can increase the area of the metal film, thereby increasing the soldering area of the metal film and the soldering member 20 and ensuring the reliability and stability of the soldering.

[0154] In some embodiments, in the first direction, the length of the first notch 191 is less than the length of the first doped layer, and the length of the first notch 191 is 50um-150um.

[0155] In this way, it can be avoided that the first notch 191 is too large, thereby avoiding too much damage caused by the first notch 191, and ensuring the efficiency. It can also be avoided that the first notch 191 is too small, thereby avoiding that the contact area between the first blocking layer 14 and the first doped layer 12 is too small, and the contact resistance is too large. That is to say, by setting the length of the first notch 191 in the first direction within this reasonable range, the contact resistance can be avoided from being too large while reducing the damage.

[0156] Specifically, in such embodiments, the length of the first notch 191 can be, for example, 50um, 60um, 70um, 80um, 90um, 100um, 110um, 120um, 130um, 140um, 150um, or any value between 50um-150um, which is not particularly limited here. It is preferably 50um-100um.

[0157] Similarly, in some embodiments, in the first direction, the length of the second notch 192 is less than the length of the first doped layer, and the length of the second notch 192 is 50um-150um.

[0158] In this way, the second notch 192 can be prevented from being too large to cause too much damage, thereby ensuring efficiency, and can also be prevented from being too small to cause the first barrier layer 14 and the second doped layer 13 to have too small a contact area and thereby cause too large a contact resistance, that is, the length of the second notch 192 in the first direction is set within this reasonable range, which can reduce damage while avoiding too large a contact resistance.

[0159] Specifically, in such embodiments, the length of the second notch 192 may, for example, be 50 um, 60 um, 70 um, 80 um, 90 um, 100 um, 110 um, 120 um, 130 um, 140 um, 150 um, or any value between 50 um and 150 um, and is specifically not limited herein. It is preferably 50 um to 100 um.

[0160] In the description of the present specification, the description of the terms "some embodiments", "exemplary embodiments", "examples", "specific examples", or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiments or examples are included in at least one embodiment or example of the present disclosure. In the present specification, the exemplary description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0161] In addition, the above only describes the preferred embodiments of the present disclosure and is not intended to limit the present disclosure. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

1. A back contact solar cell, comprising: a silicon wafer having opposite front and back surfaces; a plurality of first doped layers and a plurality of second doped layers alternately arranged in a first direction on the back surface, and each of the plurality of first doped layers and the plurality of second doped layers extending in a second direction intersecting the first direction, the first doped layers having a doping type opposite to that of the second doped layers; a first barrier layer and a first metal thin film layer stacked in sequence on the first doped layers, the first metal thin film layer being configured to be soldered with a soldering member arranged above and parallel to the first doped layers, each of the first doped layers corresponding to at least one of the soldering members; and a second barrier layer and a second metal thin film layer stacked in sequence on the second doped layers, the second metal thin film layer being configured to be soldered with a soldering member arranged above and parallel to the second doped layers, each of the second doped layers corresponding to at least one of the soldering members. The first metal thin film layer and the second metal thin film layer each include a seed copper layer. At least one of the first metal thin film layer and the second metal thin film layer has a thickness of 60nm-150nm. At least one of the first barrier layer and the second barrier layer includes at least one of a nickel layer, a silver layer, a cobalt layer, a titanium layer, and a tungsten layer.

2. The back contact solar cell of claim 1, wherein, At least one of the first barrier layer and the second barrier layer has a thickness of 1nm-2um.

3. The back contact solar cell of claim 1, wherein, An oxidation-resistant protective layer is arranged on each of the first metal thin film layer and the second metal thin film layer, the oxidation-resistant protective layer having an oxidation resistance greater than that of the first metal thin film layer and greater than that of the second metal thin film layer.

4. The back contact solar cell of claim 1, wherein, The oxidation-resistant protective layer includes at least one of a tin layer, a nickel layer, and a metal oxide layer.

5. The back contact solar cell of claim 1, wherein, The oxidation-resistant protective layer is a magnetic layer, or the oxidation-resistant protective layer includes a magnetic material.

6. The back contact solar cell of claim 1, wherein, The oxidation-resistant protective layer has a thickness of 50nm-20um.

7. The back contact solar cell of claim 6, wherein, At least one of the first metal thin film layer and the second metal thin film layer includes a magnetic material.

8. The back contact solar cell of claim 6, wherein, In the second direction, each of the first doped layers and the second doped layers extends to both edges of the silicon wafer in the second direction.

9. The back contact solar cell of claim 6, wherein, In the second direction, at least one of a ratio of a length of the first barrier layer to a length of the first doped layer and a ratio of a length of the second barrier layer to a length of the second doped layer is greater than or equal to 50%.

10. The back contact solar cell of claim 1, wherein, At least one of a ratio of a length of the first metal thin film layer to a length of the first doped layer and a ratio of a length of the second metal thin film layer to a length of the second doped layer is greater than or equal to 50%.

11. The back contact solar cell of claim 1, wherein, ​ 12. The back contact solar cell of claim 1, wherein, ​ ​ 13. The back contact solar cell of claim 1, wherein, In the first direction, at least one of a ratio of a length of the first barrier layer to a length of the first doped layer, a ratio of a length of the second barrier layer to a length of the second doped layer, a ratio of a length of the first metal thin film layer to a length of the first doped layer, and a ratio of a length of the second metal thin film layer to a length of the second doped layer is 50%-150%.

14. The back contact solar cell of claim 1, wherein, In the first direction, at least one of a length of the first barrier layer and a length of the second barrier layer is 5um-200um, and at least one of a length of the first metal thin film layer and a length of the second metal thin film layer is 5um-200um.

15. The back contact solar cell of claim 1, wherein, The area ratio of the first barrier layer and the first metal thin film layer to the first doped layer is 0.25-1.5; and / or The area ratio of the second barrier layer and the second metal thin film layer to the second doped layer is 0.25-1.

5.

16. The back contact solar cell of claim 1, wherein, The back contact solar cell further comprises a back passivation film layer stacked on the back surface, the back passivation film layer comprises a plurality of first slots and a plurality of second slots, the first slots and the second slots both extend along the second direction, at least part of the first doped layer is exposed from the first slots, and at least part of the second doped layer is exposed from the second slots; The first barrier layer is arranged on the part of the first doped layer exposed from the first slots, and the first metal thin film layer is arranged in the first slots and stacked on the first barrier layer; The second barrier layer is arranged on the part of the second doped layer exposed from the second slots, and the second metal thin film layer is arranged in the second slots and stacked on the second barrier layer.

17. The back contact solar cell of claim 16, wherein, In the first direction, a length of the first slot is less than a length of the first doped layer, a length of the second slot is less than a length of the second doped layer, and at least one of the length of the first slot and the length of the second slot is 50um-150um.

18. The back contact solar cell of claim 16, wherein, The first metal thin film layer is completely located in the first slot, the second metal thin film layer is completely located in the second slot, and a minimum distance from a surface of the first metal thin film layer to the back surface is less than a minimum distance from a surface of the back passivation film layer to the back surface; or, a surface of the first metal thin film layer is flush with a surface of the back passivation film layer, and a surface of the second metal thin film layer is flush with the surface of the back passivation film layer; or, the first metal thin film layer protrudes from the back passivation film layer and has a first extension part extending to the back passivation film layer along the first direction, and the second metal thin film layer protrudes from the back passivation film layer and has a second extension part extending to the back passivation film layer along the first direction.

19. A solar cell module, wherein, The solar cell module comprises a cell string, and the cell string comprises: A plurality of back contact solar cell pieces according to any one of claims 1-18, a plurality of the back contact solar cell pieces are arranged in an interval along the second direction, the first doped layer of an Nth back contact solar cell piece corresponds to the second doped layer of an (N+1)th back contact solar cell piece in the second direction, the second doped layer of the Nth back contact solar cell piece corresponds to the first doped layer of the (N+1)th back contact solar cell piece in the second direction, N is a positive integer; A plurality of soldering pieces, the plurality of soldering pieces are arranged in an interval along the first direction and each extends along the second direction, each of the first doped layer and the second doped layer corresponds to at least one of the soldering pieces, the soldering pieces are soldered to the first metal thin film layer of the Nth back contact solar cell piece and to the second metal thin film layer of the (N+1)th back contact solar cell piece in the second direction; In the first direction, the first metal thin film layer of the Nth back contact solar cell piece is electrically connected to the second metal thin film layer of the (N+1)th back contact solar cell piece through the soldering piece, and the second metal thin film layer of the Nth back contact solar cell piece is not connected to the first metal thin film layer of the (N+1)th back contact solar cell piece; or, In the first direction, the second metal thin film layer of the Nth back contact solar cell piece is electrically connected to the first metal thin film layer of the (N+1)th back contact solar cell piece through the soldering piece, and the first metal thin film layer of the Nth back contact solar cell piece is not connected to the second metal thin film layer of the (N+1)th back contact solar cell piece.

20. A photovoltaic system, wherein, The battery assembly of claim 19.

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