Back contact solar cell, cell string, cell module and photovoltaic system

Abstract

The utility model is suitable for the technical field of solar cells, and provides a back contact solar cell piece, a cell string, a cell assembly and a photovoltaic system, and a plurality of first doped layers and a plurality of second doped layers of the back contact solar cell piece are alternately arranged on the back surface of a silicon wafer in sequence along a first direction and extend along a second direction. The first barrier layer and the first metal film layer are sequentially stacked on the first doping layer. And the first metal film layer is used for welding a welding piece parallel to the first doping layer. The second barrier layer and the second metal film layer are sequentially stacked on the second doping layer, and the second metal film layer is used for being welded with a welding piece parallel to the second doping layer. Therefore, current collection can be realized without arranging a main gate, and the barrier layer is arranged below the metal thin film layer, so that metal atoms can be blocked when the metal thin film layer is deposited, and the probability that the metal atoms diffuse into a doping layer and a silicon wafer below is reduced.

Description

Technical Field

[0001] This application relates to the field of solar cell technology, and in particular to a back-contact solar cell, a cell string, a cell module, and a photovoltaic system. Background Technology

[0002] Solar cell power generation is a sustainable and clean energy source that utilizes the photovoltaic effect of semiconductor pn junctions to convert sunlight into electrical energy. Among solar cells, back-contact solar cells are those where both the emitter and base contact electrodes are placed on the back of the cell (the non-light-receiving surface). Since the light-receiving surface of this cell is not obstructed by any metal electrodes, this effectively increases the short-circuit current of the cell.

[0003] When forming a cell string from a back-contact solar cell, the sub-busbars and main busbars are typically created on the cells using patterning techniques. Then, solder strips are welded onto the main busbars to connect the cells in series. This approach requires additional main busbars for current collection, and the series connection of cells via solder strips is relatively expensive.

[0004] In related technologies, a main grid can be omitted to solve this technical problem. However, in such a solution, the welding performance and reliability between the solar cells and conductive wires are poor, and the electrical performance of the solar cells is also low. Utility Model Content

[0005] This application provides a back-contact solar cell, a cell string, a cell module, and a photovoltaic system.

[0006] This application is implemented as follows: the back-contact solar cell in the embodiments of this application includes:

[0007] A silicon wafer having opposing front and back sides;

[0008] A plurality of first doped layers and a plurality of second doped layers are alternately disposed on the back side along a first direction and all extend along a second direction, the second direction intersecting the first direction, and the doping types of the first doped layers and the second doped layers are opposite.

[0009] 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 is used for welding to a weldment disposed above and parallel to the first doped layer. Each first doped layer corresponds to at least one weldment.

[0010] 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 is used to weld to a weldment disposed above the second doped layer and parallel to the second doped layer. Each second doped layer corresponds to at least one weldment.

[0011] Furthermore, the first metal thin film layer and the second metal thin film layer include a seed copper layer.

[0012] Furthermore, the thickness of the first metal thin film layer is 60nm-150nm; and / or

[0013] The thickness of the second metal thin film layer is 60nm-150nm.

[0014] Furthermore, the first barrier layer comprises at least one of a nickel layer, a silver layer, a cobalt layer, a titanium layer, or a tungsten layer; and / or

[0015] The second barrier layer includes at least one of a nickel layer, a silver layer, a cobalt layer, a titanium layer, or a tungsten layer.

[0016] Furthermore, the thickness of the first barrier layer is 1 nm-2 μm; and / or

[0017] The thickness of the second barrier layer is 1nm-2um.

[0018] Furthermore, both the first metal thin film layer and the second metal thin film layer are provided with an antioxidant protective layer, and the antioxidant protective layer has a greater antioxidant capacity than the first metal thin film layer and the second metal thin film layer.

[0019] Furthermore, the antioxidant protective layer includes at least one of a tin layer, a nickel layer, and a metal oxide layer.

[0020] Furthermore, the antioxidant protective layer is a magnetic layer; or the antioxidant protective layer contains magnetic materials.

[0021] Furthermore, the thickness of the antioxidant protective layer is 50nm-20um.

[0022] Furthermore, the first metal thin film layer includes a magnetic material, and / or the second metal thin film layer includes a magnetic material.

[0023] Furthermore, in the second direction, both the first doped layer and the second doped layer extend to the two edges of the silicon wafer in the second direction.

[0024] Furthermore, in the second direction, the ratio of the length of the first barrier layer to the length of the first doped layer is greater than or equal to 50%, and the ratio of the length of the first metal thin film layer to the length of the first doped layer is greater than or equal to 50%; and / or

[0025] In the second direction, the ratio of the length of the second barrier layer to the length of the second doped layer is greater than or equal to 50%, and the ratio of the length of the second metal thin film layer to the length of the second doped layer is greater than or equal to 50%.

[0026] Furthermore, in the first direction, the length ratio of the first barrier layer to the first doped layer is 50%-150%, and the length ratio of the first metal thin film layer to the first doped layer is 50%-150%; and / or

[0027] In the first direction, the ratio of the length of the second barrier layer to the length of the second doped layer is 50%-150%, and the ratio of the length of the second metal thin film layer to the length of the second doped layer is 50%-150%.

[0028] Furthermore, in the first direction, the length of the first barrier layer is 5µm-200µm, and the length of the first metal thin film layer is 5µm-200µm; and / or

[0029] In the first direction, the length of the second barrier layer is 5um-200um, and the length of the second metal thin film layer is 5um-200um.

[0030] Furthermore, 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

[0031] 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.

[0032] Furthermore, the back contact solar cell also includes a back passivation film layer stacked on the back side, on which a plurality of first slots and a plurality of second slots are formed, the first slots and the second slots both extending along the second direction, the first doped layer being exposed at least partially from the first slots, and the second doped layer being exposed at least partially from the second slots.

[0033] The first barrier layer is disposed on the portion of the first doped layer exposed from the first slot, and the first metal thin film layer is disposed at the first slot and stacked on the first barrier layer.

[0034] The second barrier layer is disposed on the portion of the second doped layer exposed from the second slot, and the second metal thin film layer is disposed at the second slot and stacked on the second barrier layer.

[0035] Furthermore, in the first direction, the length of the first groove is less than the length of the first doped layer, and the length of the first groove is 50µm-150µm; and / or

[0036] In the first direction, the length of the second slot is less than the length of the second doped layer, and the length of the second slot is 50um-150um.

[0037] Furthermore, the first metal thin film layer is completely located within the first slot, the second metal thin film layer is completely located within the second slot, and the height of the first metal thin film layer is lower than the height of the back passivation film layer; or,

[0038] The first metal thin film layer is flush with the back passivation film layer, and the second metal thin film layer is flush with the back passivation film layer; or...

[0039] The first metal thin film layer protrudes from the back passivation film layer and has a first extension portion extending along the first direction onto the back passivation film layer, and the second metal thin film layer protrudes from the back passivation film layer and has a second extension portion extending along the first direction onto the back passivation film layer.

[0040] This application also provides a battery string, the battery string comprising:

[0041] The back-contact solar cell according to any one of the preceding claims, wherein a plurality of back-contact solar cells are arranged at intervals along the second direction, the first doped layer of the Nth back-contact solar cell and the second doped layer of the (N+1)th back-contact solar cell correspond to each other in the second direction, and the second doped layer of the Nth back-contact solar cell and the first doped layer of the (N+1)th back-contact solar cell correspond to each other in the second direction, where N is a positive integer; and

[0042] A plurality of welded components are arranged at intervals along the first direction and all extend along the second direction. Each first doped layer and each second doped layer corresponds to at least one welded component. The welded component is welded to the first metal thin film layer of the Nth back contact solar cell and to the second metal thin film layer of the N+1th back contact solar cell in the second direction.

[0043] In the first direction, the first metal film layer of the Nth back-contact solar cell is electrically connected to the second metal film layer of the (N+1)th back-contact solar cell via a welded joint, and the second metal film layer of the Nth back-contact solar cell is not connected to the first metal film layer of the (N+1)th back-contact solar cell; or...

[0044] In the first direction, the second metal thin film layer of the Nth back contact solar cell is electrically connected to the first metal thin film layer of the N+1th back contact solar cell via a welded joint, and the first metal thin film layer of the Nth back contact solar cell is not connected to the second metal thin film layer of the N+1th back contact solar cell.

[0045] This application also provides a battery assembly comprising a plurality of the aforementioned battery strings.

[0046] This application also provides a photovoltaic system, which includes the above-described battery components.

[0047] In the back-contact solar cell, cell string, cell module, and photovoltaic system of this application embodiment, a first barrier layer and a first metal thin film layer are sequentially stacked on a first doped layer, and a second barrier layer and a second metal thin film layer are sequentially stacked on a second doped layer. The first metal thin film layer is used for welding to a welding component disposed above and parallel to the first doped layer, and the second metal thin film layer is used for welding to a welding component disposed above and parallel to the second doped layer. Thus, each back-contact solar cell can be welded to a welding component parallel to the first and second doped layers via the first and second metal thin film layers to form a cell string, eliminating the need for a main grid for current collection. Simultaneously, the metal thin film layer ensures welding conductivity between the first and second doped layers and the welding component, guaranteeing welding performance and reliability. Furthermore, by providing a barrier layer below the metal thin film layer, it can block metal atoms during the deposition of the metal thin film layer while maintaining electrical conductivity, reducing the probability of metal atoms diffusing into the underlying doped layer and silicon wafer, thereby improving the electrical performance of the back-contact solar cell.

[0048] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the photovoltaic system provided in the embodiments of this application.

[0050] Figure 2 This is a schematic diagram of a battery assembly provided in an embodiment of this application.

[0051] Figure 3 This is a schematic diagram of the planar structure of the battery string provided in an embodiment of this application;

[0052] Figure 4 This is another planar structural schematic diagram of the battery string provided in the embodiments of this application;

[0053] Figure 5 This is a schematic diagram of the planar structure of the back-contact solar cell provided in an embodiment of this application;

[0054] Figure 6 yes Figure 5 A cross-sectional view of the back-contact solar cell along line VI-VI;

[0055] Figure 7 yes Figure 5 A schematic cross-sectional view of the back-contact solar cell along line VII-VII;

[0056] Figure 8 This is another cross-sectional schematic diagram of the back-contact solar cell provided in the embodiments of this application;

[0057] Figure 9 This is another cross-sectional schematic diagram of the back-contact solar cell provided in the embodiments of this application;

[0058] Figure 10 yes Figure 5 A cross-sectional schematic diagram of the back-contact solar cell along line XX;

[0059] Figure 11 yes Figure 5 A schematic cross-sectional view of the back-contact solar cell along line XI-XI.

[0060] Explanation of key component symbols:

[0061] Photovoltaic system 1000, battery module 200, battery string 100, back contact solar cell 10, silicon wafer 11, front side 111, back side 112, first doped layer 12, second doped layer 13, first barrier layer 14, first metal thin film layer 15, second barrier layer 16, second metal thin film layer 17, anti-oxidation protective layer 18, back passivation film layer 19, first slot 191, second slot 192, spacing region 101, welded component 20. Detailed Implementation

[0062] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. It should be noted that the embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application. Furthermore, it should be understood that the specific embodiments described herein are merely for explaining this application and are not intended to limit this application.

[0063] In the description of this application, it should be understood that the terms "upper", "lower", "left", "right", "lateral", "longitudinal", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0064] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this application, "several" means two or more, unless otherwise explicitly specified.

[0065] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0066] The following disclosure provides numerous different embodiments or examples for implementing various structures of this application. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the scope of this application. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, various specific examples of processes and materials are provided in this application, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0067] Please see Figure 1 and Figure 2 The photovoltaic system 1000 in this application embodiment may include the battery module 200 in this application embodiment, and the battery module 200 in this application embodiment may include a plurality of battery strings 100 in this application embodiment.

[0068] Please see Figure 3 and Figure 4 The battery string 100 in this application embodiment may include several back contact solar cells 10 (only 2 and 3 are shown in the figure, and the number is not specifically limited in this application) and several welded parts 20.

[0069] Please combine Figures 5-7 The back-contact solar cell 10 in this embodiment may 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.

[0070] The silicon wafer 11 has a front side 111 and a back side 112. A plurality of first doped layers 12 and a plurality of second doped layers 13 are alternately disposed on the back side 112 along a first direction and extend along a second direction, which intersects the first direction. The first doped layers 12 and 13 have opposite doping types; one is a P-type doped layer and the other is an N-type doped layer. It should be noted that in some embodiments of this application, the first doped layer 12 and the second doped layer 13 may both be directly located within the silicon wafer 11. For example, they can be formed by diffusion directly onto the silicon wafer 11. In other embodiments, the first doped layer 12 and the second doped layer 13 may both be disposed on the silicon wafer 11. For example, they can both 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 may be located within the silicon wafer 11, and the other may be located on the silicon wafer 11; no specific limitation is made here.

[0071] like Figure 6 As shown, the first barrier layer 14 and the first metal thin film layer 15 are sequentially stacked on the first doped layer 12. That is, the first barrier layer 14 is stacked on the first doped layer 12, and the first metal thin film layer 15 is stacked 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. Figure 3 and Figure 4As shown, the first metal thin film layer 15 is used to weld to the weldment 20 disposed above and parallel to the first doped layer 12, and each first doped layer 12 corresponds to at least one weldment 20 (only one is shown in the figure).

[0072] like Figure 7 As shown, the second barrier layer 16 and the second metal thin film layer 17 are sequentially stacked on the second doped layer 13. That is, the second barrier layer 16 is stacked on the second doped layer 13, and the second metal thin film layer 17 is stacked 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. Figure 3 and Figure 4 As shown, the second metal thin film layer 17 is used to weld to the weldment 20 disposed above and parallel to the second doped layer 13, and each second doped layer 13 corresponds to at least one weldment 20 (only one is shown in the figure).

[0073] Please see Figure 3 and Figure 4 In the battery string 100, a plurality of back-contact solar cells 10 can be arranged at intervals along a second direction, with a gap region 101 between adjacent back-contact solar cells 10. Specifically, the second direction can be the stringing direction of the battery string 100 (i.e., Figure 3 and Figure 4 The horizontal direction in the middle), the first direction can be the direction perpendicular to the serial connection direction (i.e., the horizontal direction in the middle). Figure 3 and Figure 4 The first and second directions are perpendicular to each other (the longitudinal direction of the cell). Of course, in other embodiments, the first and second directions can also be other directions, such as the two diagonal directions of the battery cell, which are not limited here.

[0074] like Figure 3 and Figure 4 As shown, in the battery string 100, the first doped layer 12 of the Nth back-contact solar cell 10 corresponds to the second doped layer 13 of the (N+1)th back-contact solar cell 10 in the second direction, and the second doped layer 13 of the Nth back-contact solar cell 10 corresponds to the first doped layer 12 of the (N+1)th back-contact solar cell 10 in the second direction, where N is a positive integer. Specifically, this can be understood as follows: Figure 3 and Figure 4 As shown, in two adjacent back-contact solar cells 10, the first doped layer 12 of the preceding cell and the second doped layer 13 of the following cell are substantially on the same straight line in the second direction, and the second doped layer 13 of the preceding cell and the first doped layer 12 of the following cell are substantially on the same straight line in the second direction.

[0075] like Figure 3 and Figure 4 As shown, a plurality of welded components 20 are spaced apart along a first direction and extend in a second direction. At least one welded component 20 is correspondingly disposed on each first doped layer 12 and each second doped layer 13 (only one is shown in the figure). In the second direction, the welded component 20 is welded to the first metal thin film layer 15 of the Nth back-contact solar cell 10, and the welded component 20 is welded to the second metal thin film layer 17 of the (N+1)th back-contact solar cell 10. That is, as... Figure 3 and Figure 4 As shown, for each welded component 20, it is welded to the first metal thin film layer 15 and the second metal thin film layer 17 in the second direction, that is, each welded component 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.

[0076] Among them, such as Figure 3 and Figure 4 As shown, in the first direction, the first metal thin film layer 15 of the Nth back-contact solar cell 10 and the second metal thin film layer 17 of the (N+1)th back-contact solar cell 10 are electrically connected via a solder joint 20, while the second metal thin film layer 17 of the Nth back-contact solar cell 10 and the first metal thin film layer 15 of the (N+1)th back-contact solar cell 10 are not connected (i.e., not electrically connected). Alternatively, in the first direction, the second metal thin film layer 17 of the Nth back-contact solar cell 10 and the first metal thin film layer 15 of the (N+1)th back-contact solar cell 10 are electrically connected via a solder joint 20, while the first metal thin film layer 15 of the Nth back-contact solar cell 10 and the second metal thin film layer 17 of the (N+1)th back-contact solar cell 10 are not connected (i.e., not electrically connected).

[0077] In other words, in the interval region 101 between two adjacent back-contact solar cells 10, in the first direction, an odd number of welded parts 20 are disconnected, or an even number of welded parts 20 are disconnected. That is to say, in the interval region 101 between two adjacent back-contact solar cells 10, every other welded part 20 is disconnected.

[0078] like Figure 3 and Figure 4As shown, taking the first direction from top to bottom as an example, odd-numbered welded parts refer to welded parts 20 located at odd-numbered positions from top to bottom (i.e., the 1st, 3rd, 5th, etc., and so on), while even-numbered welded parts refer to welded parts 20 located at even-numbered positions from top to bottom (i.e., the 2nd, 4th, 6th, etc., and so on). For example, in the first direction, if the 1st welded part 20 breaks but the 2nd welded part 20 does not, then from top to bottom, welded parts 20 at odd-numbered positions break, while welded parts 20 at even-numbered positions do not. Similarly, if the 1st welded part 20 does not break but the 2nd welded part 20 breaks, then from top to bottom, welded parts 20 at even-numbered positions break, while welded parts 20 at odd-numbered positions do not.

[0079] It should be noted that "disconnection" only means that the two are not structurally connected. The embodiments in this application do not limit the way to achieve "disconnection". For example, a cutting process can be carried out during the manufacturing process.

[0080] Furthermore, it should be noted that in the embodiments of this application, the function of the first barrier layer 14 and the second barrier layer 16 is to prevent metal atoms in the fabrication 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. In addition, the first barrier layer 14 and the second barrier layer 16 themselves have a conductive function.

[0081] In the back-contact solar cell 10, cell string 100, cell module 200, and photovoltaic system 1000 of this application embodiment, a first barrier layer 14 and a first metal thin film layer 15 are sequentially stacked on the first doped layer 12, and a second barrier layer 16 and a second metal thin film layer 17 are sequentially stacked on the second doped layer 13. The first metal thin film layer 15 is used to weld to a welding component 20 disposed above and parallel to the first doped layer 12, and the second metal thin film layer 17 is used to weld to the welding component 20 disposed above and parallel to the second doped layer 13. Thus, each back-contact solar cell 10 can be welded to the welding component 20 parallel to the first and second doped layers 12 and 13 through the first metal thin film layer 15 and the second metal thin film layer 17, thereby forming a cell string 100 without the need for a main grid to collect current. Simultaneously, the first and second doped layers 12 and the welding component 20 are connected through the metal thin film layer, ensuring welding performance and reliability. Furthermore, by setting a barrier layer below the metal thin film layer, it can block metal atoms during the deposition of the metal thin film layer while achieving electrical conduction, thereby reducing the probability of metal atoms diffusing into the doped layer and silicon wafer 11 below, thus ensuring the electrical performance of the back contact solar cell 10.

[0082] Specifically, in the embodiments of this application, 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 all be formed on the first doped layer 12 and the second doped layer 13 respectively by means of PVD deposition or the like.

[0083] The first barrier layer 14 can cover the first doped layer 12. The number of both layers is equal, and their areas 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 portion of the first doped layer 12 may have grooves (as described below) formed in the passivation layer (the back passivation film layer). The first barrier layer 14 may be located within the groove, or a portion of the first barrier layer 14 may extend along the sidewall of the groove to the top passivation layer. Specific details are not limited here. The first metal thin film layer 15 can cover the first barrier layer 14 in a one-to-one correspondence. Their areas can be equal, or the area of ​​the first metal thin film layer 15 may be smaller than the area of ​​the first barrier layer 14, or the area of ​​the first metal thin film layer 15 may be larger than the first barrier layer 14. The portion of the first metal thin film layer 15 outside the first barrier layer 14 is located on the passivation layer. Specific details are not limited here. The second barrier layer 16 and the second metal thin film layer 17 are similar and will not be described in detail here.

[0084] In the embodiments of this application, 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 means of PVD deposition, inkjet printing, etc. The first metal thin film layer 15 and the second metal thin film layer 17 can both be metal seed layers, which can be formed on the first barrier layer 14 by means of PVD deposition, etc.

[0085] It is understandable that by setting 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, can be reduced or even completely blocked during the deposition of the first metal thin film layer 15 and the second metal thin film layer 17, thereby improving minority carrier lifetime, battery electrical performance and battery efficiency.

[0086] In some embodiments, the first metal thin film layer 15 and the second metal thin film layer 17 are preferably seed copper layers. Seed copper layers have good welding performance and sufficiently low bulk resistance, which can reduce resistance loss and also have low 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 low welding performance and low resistance, such as silver layers, silver-aluminum alloy layers, etc.

[0087] In embodiments of this application, the first barrier layer 14 may include at least one of a nickel layer, a silver layer, a cobalt layer, a titanium layer, or a tungsten layer.

[0088] Thus, by using these metal layers as barrier layers, metal atoms can be blocked during the deposition of the metal thin film layer, while also minimizing the likelihood of a significant reduction in the minority carrier lifetime of the bulk region. Similarly, in some embodiments, the second barrier layer 16 may also include at least one of a nickel layer, a silver layer, a cobalt layer, a titanium layer, or a tungsten layer.

[0089] It is understood that in this application, when the first barrier layer 14 and the second barrier layer 16 are made of the same material, they can be formed using the same process. The first metal thin film layer 15 and the second metal thin film layer 17 are preferably both seed copper layers, and they can also be formed using the same process.

[0090] In some embodiments, the thickness of the first metal thin film layer 15 may be 60nm-150nm.

[0091] Thus, by setting the thickness of the first metal thin film layer 15 within this reasonable range, it is possible to effectively avoid the first metal thin film layer 15 being too thin and unable to form a stable weld with the weldment 20, thus ensuring stability and reliability. At the same time, it is also possible to avoid the first metal thin film layer 15 being too thick, which would lead to a significant increase in cost.

[0092] Specifically, in such embodiments, the thickness of the first metal thin film layer 15 can be, for example, any value between 60nm, 65nm, 70nm, 75nm, 80nm, 85nm, 90nm, 95nm, 100nm, 105nm, 110nm, 115nm, 120nm, 125nm, 130nm, 135nm, 140nm, 145nm, 150nm, or 60nm-150nm, and is not limited herein.

[0093] In such an embodiment, the thickness of the first metal thin film layer 15 is preferably 80nm-120nm. Specifically, through research and verification by the inventors of this application, it has been found that when the thickness of the first metal thin film layer 15 is less than 80nm, although it can form a weld with the weldment 20, it is easily unstable under the influence of external forces. If the thickness of the first metal thin film layer 15 is greater than 120nm, it will lead to a significant increase in cost. After research, the inventors of this application have set the thickness of the first metal thin film layer 15 within the preferred range of 80nm-120nm, which can reduce costs while ensuring welding stability and reliability to the greatest extent.

[0094] In addition, similar to the first metal thin film layer 15, in some embodiments, the thickness of the second metal thin film layer 17 is also 60nm-150nm.

[0095] Thus, by setting the thickness of the second metal thin film layer 17 within this reasonable range, it is possible to effectively avoid the second metal thin film layer 17 being too thin and unable to form a stable weld with the weldment 20, thus ensuring stability and reliability. At the same time, it is also possible to avoid the second metal thin film layer 17 being too thick, which would lead to a significant increase in cost.

[0096] Specifically, the thickness of the second metal thin film layer 17 can be, for example, any value between 60nm, 65nm, 70nm, 75nm, 80nm, 85nm, 90nm, 95nm, 100nm, 105nm, 110nm, 115nm, 120nm, 125nm, 130nm, 135nm, 140nm, 145nm, 150nm, or 60nm-150nm, and is not limited here.

[0097] In such an embodiment, the thickness of the second metal thin film layer 17 is preferably 80nm-120nm. Specifically, through research and verification by the inventors of this application, it has been found that when the thickness of the second metal thin film layer 17 is less than 80nm, although it can form a weld with the weldment 20, it is easily unstable under the influence of external forces. If the thickness of the second metal thin film layer 17 is greater than 120nm, it will lead to a significant increase in cost. After research, the inventors of this application have set the thickness of the second metal thin film layer 17 within the preferred range of 80nm-120nm, which can reduce costs while ensuring welding stability and reliability to the greatest extent.

[0098] In some embodiments, the thickness of the first barrier layer 14 may be 1 nm-2 μm.

[0099] By setting the thickness of the first barrier layer 14 within this reasonable range, we can avoid the increased cost caused by an excessively thick first barrier layer 14, and avoid the inability to achieve a good barrier effect due to an excessively thin first barrier layer 14. At the same time, we can also avoid a significant impact on the contact resistance.

[0100] Specifically, the thickness of the first barrier layer 14 can be, for example, any value between 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 70nm, 800nm, 900nm, 1um, 1.1um, 1.2um, 1.3um, 1.4um, 1.5um, 1.6um, 1.7um, 1.8um, 1.9um, 2um, or greater than 0 and less than 2um, without any specific limitation here.

[0101] In such an embodiment, the thickness of the first barrier layer 14 is preferably 10 nm-1 μm. Specifically, through research and verification by the inventors of this application, it has been found that when the thickness of the first barrier layer 14 is less than 10 nm, although it can achieve a certain barrier effect, the barrier effect is generally weak, and it has a significant impact on the contact resistance. On the other hand, if the thickness of the first barrier layer 14 is greater than 1 μm, although it can achieve a better barrier effect, it will lead to increased costs and also affect the contact resistance. After research, the inventors of this application have set the thickness of the first barrier layer 14 within the preferred range of 10 nm-1 μm. This can ensure the barrier effect while avoiding excessive costs and a significant impact on the contact resistance. In other words, setting the thickness of the first barrier layer 14 within the range of 10 nm-1 μm can balance the relationship between barrier effect, cost, and contact resistance, thereby ensuring the efficiency of the solar cell.

[0102] In some embodiments, the thickness of the second barrier layer 16 may also be 1 nm-2 μm.

[0103] By setting the thickness of the second barrier layer 16 within this reasonable range, we can avoid the increased cost caused by an excessively thick second barrier layer 16, and avoid the inability to achieve a good barrier effect due to an excessively thin second barrier layer 16. At the same time, we can also avoid a significant impact on the contact resistance.

[0104] Specifically, the thickness of the second barrier layer 16 can be, for example, any value between 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 70nm, 800nm, 900nm, 1um, 1.1um, 1.2um, 1.3um, 1.4um, 1.5um, 1.6um, 1.7um, 1.8um, 1.9um, 2um, or greater than 0 and less than 2um, without any specific limitation here.

[0105] In such an embodiment, the thickness of the second barrier layer 16 is preferably 10 nm-1 μm. Specifically, through research and verification by the inventors of this application, it has been found that when the thickness of the second barrier layer 16 is less than 10 nm, although it can achieve a certain barrier effect, the barrier effect is generally weak, and it has a significant impact on the contact resistance. If the thickness of the second barrier layer 16 is greater than 1 μm, although it can achieve a better barrier effect, it will lead to increased costs and also affect the contact resistance. After research, the inventors of this application have set the thickness of the second barrier layer 16 within the preferred range of 10 nm-1 μm. This can ensure the barrier effect while avoiding excessive costs and a significant impact on the contact resistance. In other words, setting the thickness of the second barrier layer 16 within the range of 10 nm-1 μm can balance the relationship between barrier effect, cost, and contact resistance, thereby ensuring the efficiency of the solar cell.

[0106] Please see Figure 8 and Figure 9 In some embodiments, an antioxidant protective layer 18 may be stacked on both the first metal thin film layer 15 and the second metal thin film layer 17, and the antioxidant protective layer 18 has a greater antioxidant capacity than the first metal thin film layer 15 and the second metal thin film layer 17.

[0107] Thus, the antioxidant protective layer 18 can protect the first metal thin film layer 15 and the second metal thin film layer 17, effectively preventing the first metal thin film layer 15 and the second metal thin film layer 17 from being exposed to the air for a long time to generate oxides, which would lead to a deterioration in welding performance and electrical conductivity. At the same time, it can also prevent the appearance of organic matter, dust and other impurities from adhering to the surface of the two, which would lead to poor appearance and affect efficiency.

[0108] Understandably, the metal thin film layer serves the function of welding and collecting charge carriers, requiring a relatively active metal seed layer for fabrication, such as the seed copper layer mentioned above. However, highly active metal seed layers are prone to oxidation, leading to a deterioration in subsequent welding performance. Therefore, this application effectively avoids this situation by providing an anti-oxidation protective layer 18 on the first metal thin film layer 15 and the second metal thin film layer 17.

[0109] Specifically, in such embodiments, the first metal thin film layer 15 and the second metal thin film layer 17 can be highly reactive metal layers, such as a seed copper layer, while the antioxidant protective layer 18 can be an inert metal layer. For example, in some embodiments, the antioxidant protective layer 18 can be at least one of a tin layer, a nickel layer, and a metal oxide layer, and it can also be formed on the first metal thin film layer 15 and the second metal thin film layer 17 by PVD deposition, inkjet printing, or other methods. Alternatively, it can be formed by heat treatment.

[0110] Of course, in other embodiments, the antioxidant protective layer 18 may also be an organic or inorganic film layer capable of resisting oxidation, such as an inorganic film layer with a chain structure. The specific type is not limited here, but an inert metal layer is preferred.

[0111] In some embodiments, the antioxidant protective layer 18 may be a magnetic layer. In this way, during the welding process with the weldment 20, the antioxidant protective layer 18 can adsorb the weldment 20, which can effectively prevent the weldment 20 from shifting during the welding process, improve the stability and reliability of the welding. That is to say, the antioxidant film layer 18 can not only effectively prevent the metal film layer from oxidizing, but also position and pre-fix the weldment 20 during the welding process.

[0112] Specifically, in such embodiments, the magnetic layer refers to a film layer that has magnetic adsorption function itself or a film layer that has magnetic adsorption function after being energized. The magnetic layer can be made entirely of magnetic materials.

[0113] Of course, it is understood that in some embodiments, the antioxidant protective layer 18 may not be a magnetic layer made entirely of magnetic materials, but may contain magnetic material components. For example, magnetic materials may be added to inert metal layers such as tin layer, nickel layer and metal oxide layer as described above, so that the antioxidant protective layer 18 can generate magnetic attraction to the weldment 20.

[0114] In addition, some metal particles may be spattered during the welding process. The magnetic attraction can be used to attract some of these metal particles, thereby reducing surface contamination of the solar cells, improving the light absorption capacity of the solar cells, and increasing the light conversion efficiency of the solar cells.

[0115] It is easy to understand that the antioxidant protective layer 18 will melt and flow during the welding process. Therefore, in the final battery assembly 200, there may be a phenomenon where the antioxidant protective layer 18 is not present between some or all areas of the first metal thin film layer 15 and the welded part 20.

[0116] In some embodiments, the thickness of the antioxidant protective layer 18 can be 50 nm to 20 μm. Setting the thickness of the antioxidant film layer within this reasonable range avoids both insufficient anti-oxidation effect due to excessive thickness and significant cost increase due to excessive thickness.

[0117] Specifically, the thickness of the antioxidant protective layer 18 can be, for example, any value between 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 70nm, 800nm, 900nm, 1um, 1um, 2um, 3um, 4um, 5um, 6um, 7um, 8um, 9um, 10um, 11um, 12um, 13um, 14um, 15um, 16um, 17um, 18um, 19um, 20um, or 50nm-20um, and is not limited here.

[0118] In some embodiments, the first metal thin film layer 14 may also include a magnetic material. Thus, during the welding process with the weldment 20, the first metal thin film layer 14 can also adsorb the weldment 20, effectively preventing the weldment 20 from shifting during welding and improving the stability and reliability of the welding.

[0119] Similarly, in some embodiments, the second metal thin film layer 16 may also include a magnetic material, thereby enabling the first metal thin film layer 16 to generate a magnetic attraction force on the weldment 20.

[0120] Please see Figure 3 and Figure 4 In some embodiments, in the second direction, both the first doped layer 12 and the second doped layer 13 extend to the two edges of the silicon wafer 11 in the second direction. This maximizes the utilization of the area of ​​the silicon wafer 11, thereby improving the efficiency of the solar cell.

[0121] 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%.

[0122] Thus, by setting the ratio between the length of the first barrier layer 14 and the length of the first metal thin film layer 15 in the second direction and the length of the first doped layer 12 within the above-mentioned reasonable range, the carrier collection efficiency can be improved while ensuring welding reliability, and the welding reliability can be avoided if the length of the first metal thin film layer 15 is too small.

[0123] In such an embodiment, in the second direction, the lengths of the first barrier layer 14 and the first metal thin film layer 15 are preferably the same as the length of the first doped layer 12.

[0124] 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 (that is, 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%.

[0125] Thus, 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 above-mentioned reasonable range, the carrier collection efficiency can be improved while ensuring welding reliability, and the poor welding reliability caused by the second metal thin film layer 17 being too short can be avoided.

[0126] In such an embodiment, in the second direction, the lengths of the second barrier layer 16 and the second metal thin film layer 17 are preferably the same as the length of the second doped layer 13.

[0127] It should be noted that the length of each film layer in the second direction in this article refers to the length of the region formed by the orthographic projection of each film layer on the silicon wafer 11 (i.e., the projection along the thickness direction) in the second direction. If a similar description appears in the following text, please refer to this document for understanding.

[0128] In some embodiments, in the first direction, the length ratio of the first barrier layer 14 to the length of the first doped layer 12 is 50%-150%. The length ratio of the first metal thin film layer 15 to the length of the first doped layer 12 is also 50%-150%.

[0129] In this way, the ratio of the length of the first metal thin film layer 15 and the first barrier layer 14 in the first direction to the length of the first doped layer 12 in the first direction is avoided from being too small, which would prevent them from forming a stable and reliable contact with the solder strip and ensure the reliability of the welding. At the same time, 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 is also avoided from being too large, which would cause the first barrier layer 14 to block too much of the first doped layer 12 and reduce the bifaciality of the cell.

[0130] It should be noted that the length of each film layer in the first direction in this article refers to the length of the region formed by the orthographic projection of each film layer on the silicon wafer 11 (i.e., the projection along the thickness direction) in the first direction. If a similar description appears in the following text, please refer to this document for understanding.

[0131] Specifically, in such 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, and the ratio of the length of the first metal thin film layer 15 to the length of the first doped layer 12, can be any value among 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, 110%, 120%, 130%, 140%, 150%, or 50%-150%.

[0132] Furthermore, 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 thin film layer 15 to the length of the first doped layer 12, are preferably 50%-70%. Specifically, the inventors of this application have discovered through research that if the above ratios are less than 50%, the length of the first metal thin film layer 15 in the first direction will be too small, resulting in a small contact area with the weldment 20 and thus poor welding such as incomplete soldering. Conversely, if the above ratios are set to be greater than 70%, the light-shielding area will be too large, affecting the bifaciality. After research and verification, the inventors found that by setting the ratios within this preferred range, the bifaciality of the solar cell can be maximized while ensuring welding performance.

[0133] In some embodiments, in the first direction, the length ratio of the second barrier layer 16 to the length of the second doped layer 13 is 50%-150%, and the length ratio of the second metal thin film layer 17 to the length of the second doped layer 13 is 50%-150%.

[0134] 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 avoided, which would prevent them from forming a stable and reliable contact with the solder ribbon and ensure the reliability of the welding. At the same time, the ratio of the length of the second barrier layer 16 in the first direction to the length of the second doped layer 13 in the first direction can also be avoided, which would prevent the second barrier layer 16 from blocking too much of the second doped layer 13 and thus reducing the bifaciality of the solar cell.

[0135] Specifically, in such embodiments, in the first direction, 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, can be any value among, for example, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, 110%, 120%, 130%, 140%, 150%, or 50%-150%.

[0136] Furthermore, 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, are preferably 50%-70%. Specifically, the inventors of this application have discovered 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, resulting in a small contact area with the weldment 20 and causing poor welding such as incomplete soldering. If the above ratios are set to be greater than 70%, the light-shielding area will be too large, affecting the bifaciality. After research and verification, the inventors found that by setting the ratios within this preferred range, the bifaciality of the solar cell can be maximized while ensuring welding performance.

[0137] In some embodiments, in the first direction, the length of the first barrier layer 14 can be 5µm-200µm, and the length of the first metal thin film layer 15 can be 5µm-200µm. This avoids the situation where the lengths of both layers in the first direction are too small, which would prevent them from forming a stable welding contact with the solder strip, and also avoids the situation where the lengths of both layers in the first direction are too long, which would result in a significant decrease in the double-sided ratio.

[0138] Specifically, in such an embodiment, the lengths of the first barrier layer 14 and the first metal thin film layer 15 in the first direction can be, for example, any value between 5um, 10um, 20um, 30um, 40um, 50um, 60um, 70um, 80um, 90um, 100um, 110um, 120um, 130um, 140um, 150um, 160um, 170um, 180um, 190um, 200um, or 5um-200um, without any specific limitation herein.

[0139] In such an embodiment, in the first direction, the length of the first barrier layer 14 and the length of the first metal thin film layer 15 are preferably both 50nm-200nm. Specifically, the inventors of this application have found through research that if the length is less than 50nm, it will result in an excessively small contact area between the first barrier layer 14 and the first doped layer 12, leading to increased contact resistance. It will also increase the difficulty and time of trenching on the passivation film. Conversely, if the length is greater than 200nm, it will result in a larger light-shielding area, affecting the bifaciality. After research and verification, the inventors found that by setting the length within this preferred range, the bifaciality of the solar cell can be maximized while reducing contact resistance and process difficulty and ensuring welding performance with the weldment 20.

[0140] Similarly, in some embodiments, in the first direction, the length of the second barrier layer 16 is 5um-200um, and the length of the second metal thin film layer 17 is 5um-200um.

[0141] In this way, we can avoid the two materials being too short in the first direction, which would prevent them from forming a stable welding contact with the welding strip, and we can also avoid the two materials being too long in the first direction, which would lead to a significant decrease in the double-sided ratio.

[0142] Specifically, in such an embodiment, the length of the second barrier layer 16 and the second metal thin film layer 17 in the first direction can be, for example, any value between 5um, 10um, 20um, 30um, 40um, 50um, 60um, 70um, 80um, 90um, 100um, 110um, 120um, 130um, 140um, 150um, 160um, 170um, 180um, 190um, 200um or 5um-200um, and is not limited herein.

[0143] In such an embodiment, in the first direction, the length of the second barrier layer 16 and the length of the second metal thin film layer 17 are preferably both 50nm-200nm. Specifically, the inventors of this application have found through research that if the length is less than 50nm, the contact area between the second barrier layer 16 and the second doped layer 13 will be too small, resulting in increased contact resistance. This also increases the difficulty and time required for trenching on the passivation film. Conversely, if the length is greater than 200nm, the light-shielding area will be too large, affecting the bifaciality. After research and verification, the inventors found that by setting the length within this preferred range, the bifaciality of the solar cell can be maximized while reducing contact resistance and process difficulty and ensuring welding performance with the weldment 20.

[0144] 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.

[0145] In this way, the area ratio of the first barrier layer 14 and the first metal film layer 15 can be avoided from being too small, which would prevent them from being unable to guarantee the welding performance with the weldment 20. It can also prevent the area ratio of the first barrier layer 14 from being too large, which would result in a significant decrease in the double-sided ratio.

[0146] 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, any value between 0.25, 0.5, 0.75, 1, 1.25, 1.5 or 0.25-1.5.

[0147] Furthermore, in order to balance the relationship between welding performance and double-sided ratio, and to maximize the double-sided ratio while ensuring welding performance, the area ratio can preferably be 0.25-0.7.

[0148] It should be noted that, in this article, the area ratio between each layer refers to the ratio of the areas formed by the orthographic projection of each layer onto the silicon wafer 11. If a similar description appears in the following text, please refer to this document for understanding.

[0149] 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.

[0150] In this way, the area ratio of the second barrier layer 16 and the second metal thin film layer 17 can be avoided from being too small, which would prevent them from being unable to guarantee the welding performance with the weldment 20. It can also be avoided from the area ratio of the second barrier layer 16 being too large, which would result in a significant decrease in the double-sided ratio.

[0151] 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, any value between 0.25, 0.5, 0.75, 1, 1.25, 1.5 or 0.25-1.5.

[0152] Furthermore, in order to balance the relationship between welding performance and double-sided ratio, and to maximize the double-sided ratio while ensuring welding performance, the area ratio can preferably be 0.25-0.7.

[0153] Please see Figure 10 In some embodiments, the back contact solar cell 10 further includes a back passivation film layer 19 stacked on the back surface 112. The back passivation film layer 19 has a plurality of first slots 191 and a plurality of second slots 192 formed thereon. The first slots 191 and the second slots 192 both extend along a second direction. The first doped layer 12 is exposed at least partially from the first slot 191, and the second doped layer 13 is exposed at least partially from the second slot 192.

[0154] The first barrier layer 14 is disposed on the portion of the first doped layer 12 exposed from the first slot 191, and the first metal thin film layer 15 is disposed at the first slot 191 and stacked on the first barrier layer 14.

[0155] The second barrier layer 16 is disposed on the portion of the second doped layer 13 exposed from the second slot 192, and the second metal thin film layer 17 is disposed at the second slot 192 and stacked on the second barrier layer 16.

[0156] It is understood that, in some embodiments, a tunneling layer may also be provided on the back surface 111 of the back-contact solar cell 10. Figure 10 (Not shown in the image). For example, the tunneling layer can be disposed between the first doped layer 12 and the silicon wafer 11, or between the second doped layer 13 and the silicon wafer 11, or both the first doped layer 12 and the silicon wafer 11 and the second doped layer and the silicon wafer 11 can have tunneling layers.

[0157] Thus, by opening the first slot 191 and the second slot 192 on the back passivation film layer 19, it is convenient to form a barrier layer and a metal thin film layer in the first doped layer 12 and the second doped layer 13.

[0158] Specifically, in such an embodiment, the area of ​​the first slot 191 may be equal to or slightly smaller than the area of ​​the first doped layer 12, and the area of ​​the second slot 192 may preferably be equal to or slightly smaller than the area of ​​the second doped layer 13. The first slot 191 and the second slot 192 may be formed by laser grooving, etching, or other methods, and no specific limitations are imposed here.

[0159] Understandably, in one possible example, during the manufacturing process, PVD deposition can be performed directly at the first slot 191 and the second slot 192 using a screen, thereby forming a barrier layer and a metal thin film layer at the first slot 191 and the second slot 192. Alternatively, a screen can be omitted, and a barrier layer can be deposited on the entire surface first, then the barrier layer in areas other than the first slot 191 and the second slot 192 can be etched away, followed by the deposition of the metal thin film layer, and finally the metal thin film layer in areas other than the first slot 191 and the second slot 192 can be etched away. The specific method is not limited here.

[0160] Furthermore, such as Figure 10 As shown, in this embodiment, the first metal thin film layer 15 is completely located within the first groove 191, and the second metal thin film layer 17 is completely located within the second groove 192. The height of the first metal thin film layer 15 is lower than the height of the back passivation film layer 19. Alternatively, the first metal thin film layer 15 is flush with the back passivation film layer 19, and the second metal thin film layer 17 is flush with the back passivation film layer 19. In this way, when etching the metal thin film layer, only the metal thin film layer attached to the entire back passivation film layer 19 needs to be etched.

[0161] Of course, please see Figure 11 In some embodiments, the first metal thin film layer 15 may also protrude from the back passivation film layer 19 and have a first extension portion 151 extending along the first direction onto the back passivation film layer 19, and the second metal thin film layer 17 may protrude from the back passivation film layer 19 and have a second extension portion 152 extending along the first direction onto the back passivation film layer 19. Thus, the first metal thin film layer 15 has a first extension portion 151 on the back passivation film layer 19, and the second metal thin film layer 17 has a second extension portion 152 on the back passivation film layer 19. This can increase the area of ​​the metal thin film, thereby increasing the welding area between the metal thin film and the weldment 20, and ensuring the reliability and stability of the welding.

[0162] In some embodiments, in the first direction, the length of the first slot 191 is less than the length of the first doped layer, and the length of the first slot 191 is 50um-150um.

[0163] In this way, the damage caused by making the first slot 191 too large can be avoided, thus ensuring efficiency. It can also prevent the contact area between the first barrier layer 14 and the first doped layer 12 from being too small, resulting in excessive contact resistance. In other words, by setting the length of the first slot 191 in the first direction within this reasonable range, damage can be reduced while avoiding excessive contact resistance.

[0164] Specifically, in such an embodiment, the length of the first slot 191 can be, for example, any value between 50um, 60um, 70um, 80um, 90um, 100um, 110um, 120um, 130um, 140um, 150um, or 50um-150um, and is not limited herein. It is preferably 50um-100um.

[0165] Similarly, in some embodiments, in the first direction, the length of the second slot 192 is less than the length of the first doped layer, and the length of the second slot 192 is 50um-150um.

[0166] In this way, the damage caused by making the second slot 192 too large can be avoided, thus ensuring efficiency. It can also be avoided that the contact area between the first barrier layer 14 and the second doped layer 13 is too small, resulting in excessive contact resistance, if the second slot 192 is made too small. In other words, by setting the length of the second slot 192 in the first direction within this reasonable range, damage can be reduced while avoiding excessive contact resistance.

[0167] Specifically, in such an embodiment, the length of the second slot 192 can be, for example, any value between 50um, 60um, 70um, 80um, 90um, 100um, 110um, 120um, 130um, 140um, 150um, or 50um-150um, and is not limited herein. It is preferably 50um-100um.

[0168] In the description of this specification, the references to terms such as "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with the described embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0169] Furthermore, the above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A back-contact solar cell, characterized in that, include: A silicon wafer having opposing front and back sides; A plurality of first doped layers and a plurality of second doped layers are alternately disposed on the back side along a first direction and all extend along a second direction, the second direction intersecting the first direction, and the doping types of the first doped layers and the second doped layers are opposite. 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 is used to weld to a weldment disposed above the first doped layer and parallel to the first doped layer. Each first doped layer corresponds to at least one weldment. and 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 is used to weld to a weldment disposed above the second doped layer and parallel to the second doped layer. Each second doped layer corresponds to at least one weldment.

2. The back-contact solar cell according to claim 1, characterized in that, The first metal thin film layer and the second metal thin film layer include a seed copper layer.

3. The back-contact solar cell according to claim 1, characterized in that, The thickness of the first metal thin film layer is 60nm-150nm; and / or The thickness of the second metal thin film layer is 60nm-150nm.

4. The back-contact solar cell according to claim 1, characterized in that, The first barrier layer includes at least one of a nickel layer, a silver layer, a cobalt layer, a titanium layer, or a tungsten layer; and / or The second barrier layer includes at least one of a nickel layer, a silver layer, a cobalt layer, a titanium layer, or a tungsten layer.

5. The back-contact solar cell according to claim 1, characterized in that, The thickness of the first barrier layer is 1 nm-2 μm; and / or The thickness of the second barrier layer is 1nm-2um.

6. The back-contact solar cell according to claim 1, characterized in that, An antioxidant protective layer is stacked on both the first metal thin film layer and the second metal thin film layer, and the antioxidant capacity of the antioxidant protective layer is greater than that of the first metal thin film layer and the second metal thin film layer.

7. The back-contact solar cell according to claim 6, characterized in that, The antioxidant protective layer includes at least one of a tin layer, a nickel layer, and a metal oxide layer.

8. The back-contact solar cell according to claim 6, characterized in that, The antioxidant protective layer is a magnetic layer; or the antioxidant protective layer contains magnetic materials.

9. The back-contact solar cell according to claim 6, characterized in that, The thickness of the antioxidant protective layer is 50nm-20um.

10. The back-contact solar cell according to claim 1, characterized in that, The first metal thin film layer includes a magnetic material, and / or the second metal thin film layer includes a magnetic material.

11. The back-contact solar cell according to claim 1, characterized in that, In the second direction, both the first doped layer and the second doped layer extend to the two edges of the silicon wafer in the second direction.

12. The back-contact solar cell according to claim 1, characterized in that, In the second direction, the ratio of the length of the first barrier layer to the length of the first doped layer is greater than or equal to 50%, and the ratio of the length of the first metal thin film layer to the length of the first doped layer is greater than or equal to 50%; and / or In the second direction, the ratio of the length of the second barrier layer to the length of the second doped layer is greater than or equal to 50%, and the ratio of the length of the second metal thin film layer to the length of the second doped layer is greater than or equal to 50%.

13. The back-contact solar cell according to claim 1, characterized in that, In the first direction, the length ratio of the first barrier layer to the first doped layer is 50%-150%, and the length ratio of the first metal thin film layer to the first doped layer is 50%-150%; and / or In the first direction, the ratio of the length of the second barrier layer to the length of the second doped layer is 50%-150%, and the ratio of the length of the second metal thin film layer to the length of the second doped layer is 50%-150%.

14. The back-contact solar cell according to claim 1, characterized in that, In the first direction, the length of the first barrier layer is 5µm-200µm, and the length of the first metal thin film layer is 5µm-200µm; and / or In the first direction, the length of the second barrier layer is 5um-200um, and the length of the second metal thin film layer is 5um-200um.

15. The back-contact solar cell according to claim 1, characterized in that, 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 according to claim 1, characterized in that, The back contact solar cell further includes a back passivation film layer stacked on the back side, and a plurality of first slots and a plurality of second slots are formed on the back passivation film layer. The first slots and the second slots both extend along the second direction. The first doped layer is exposed at least partially from the first slot, and the second doped layer is exposed at least partially from the second slot. The first barrier layer is disposed on the portion of the first doped layer exposed from the first slot, and the first metal thin film layer is disposed at the first slot and stacked on the first barrier layer. The second barrier layer is disposed on the portion of the second doped layer exposed from the second slot, and the second metal thin film layer is disposed at the second slot and stacked on the second barrier layer.

17. The back-contact solar cell according to claim 16, characterized in that, In the first direction, the length of the first slot is less than the length of the first doped layer, and the length of the first slot is 50µm-150µm; and / or In the first direction, the length of the second slot is less than the length of the second doped layer, and the length of the second slot is 50um-150um.

18. The back-contact solar cell according to claim 16, characterized in that, The first metal thin film layer is completely located within the first slot, the second metal thin film layer is completely located within the second slot, and the height of the first metal thin film layer is lower than the height of the back passivation film layer; or... The first metal thin film layer is flush with the back passivation film layer, and the second metal thin film layer is flush with the back passivation film layer; or, The first metal thin film layer protrudes from the back passivation film layer and has a first extension portion extending along the first direction onto the back passivation film layer, and the second metal thin film layer protrudes from the back passivation film layer and has a second extension portion extending along the first direction onto the back passivation film layer.

19. A battery string, characterized in that, include: The back-contact solar cell according to any one of claims 1-18, wherein a plurality of back-contact solar cells are arranged at intervals along the second direction, the first doped layer of the Nth back-contact solar cell and the second doped layer of the (N+1)th back-contact solar cell correspond to each other in the second direction, and the second doped layer of the Nth back-contact solar cell and the first doped layer of the (N+1)th back-contact solar cell correspond to each other in the second direction, where N is a positive integer; and A plurality of welded components are arranged at intervals along the first direction and all extend along the second direction. Each first doped layer and each second doped layer corresponds to at least one welded component. The welded component is welded to the first metal thin film layer of the Nth back contact solar cell and to the second metal thin film layer of the N+1th back contact solar cell in the second direction. In the first direction, the first metal film layer of the Nth back-contact solar cell is electrically connected to the second metal film layer of the (N+1)th back-contact solar cell via a welded joint, and the second metal film layer of the Nth back-contact solar cell is not connected to the first metal film layer of the (N+1)th back-contact solar cell; or... In the first direction, the second metal thin film layer of the Nth back contact solar cell is electrically connected to the first metal thin film layer of the N+1th back contact solar cell via a welded joint, and the first metal thin film layer of the Nth back contact solar cell is not connected to the second metal thin film layer of the N+1th back contact solar cell.

20. A battery assembly, characterized in that, Includes several battery strings as described in claim 19.

21. A photovoltaic system, characterized in that, Includes the battery assembly as described in claim 20.

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