Back contact cell and module

Abstract

The present disclosure is applicable to the technical field of photovoltaics, and provides a back contact cell and a module. A plurality of grooves are formed in the back surface of a silicon wafer. In first regions, the silicon wafer has first extension portions extending and protruding above the grooves. Second polarity doped layers are on second tunneling layers and have a preset distance from edges of the grooves, the second polarity doped layers having second extension portions extending in directions towards the grooves.

Description

Back contact cells and modules

[0001] Cross-references

[0002] This disclosure incorporates, in its entirety, Chinese Patent Application No. 202422659489.5, filed on October 31, 2024, entitled “A Back Contact Cell, Cell Module and Photovoltaic System”. Technical Field

[0003] This disclosure pertains to the field of photovoltaic technology, and particularly relates to a back-contact solar cell and module. Background Technology

[0004] A back-contact solar cell is a type of solar cell in which both the emitter and base contact electrodes are placed on the back (non-light-receiving surface) of the cell. The light-receiving surface of this cell is not obstructed by any metal electrodes, thereby effectively increasing the efficiency of the solar cell.

[0005] In related technologies, to address the surface passivation problem in the grooved region on the back of a back-contact battery and reduce hydrogen-related defects in the bulk region, the passivation contact region requires defect states in the hydrogen passivation tunneling layer. This necessitates the use of a high-refractive-index passivation film (e.g., high-refractive-index SiNx) to achieve better mobile hydrogen content. However, excessive hydrogen entering the substrate region can lead to battery degradation. Simultaneously, the passivation layer in the grooved region (e.g., AlOx) is prone to generating negatively charged field passivation. This configuration induces a surface p+ layer, and a space charge region is generated at the contact between the p+ layer and the n++ layer. Recombination in this region increases the junction recombination current of the battery, significantly reducing battery performance.

[0006] Public content

[0007] This disclosure provides a back-contact solar cell and a module, which aims to solve the technical problems of large battery degradation and reduced battery performance in back-contact solar cells in the related art.

[0008] This disclosure is achieved by providing a back-contact solar cell comprising:

[0009] A silicon substrate has a backlight surface and a light-facing surface arranged opposite to each other. A first region and a second region are alternately arranged on the backlight surface of the silicon substrate, and a groove is provided between adjacent first regions and second regions.

[0010] The first tunnel layer is stacked and covered on the first area;

[0011] A first polar doped layer is stacked on a first tunneling layer, and the first polar doped layer has a first extension portion extending toward the groove.

[0012] The second tunnel layer is stacked on the second region;

[0013] A second polar doped layer is stacked on the second tunneling layer, and the side of the second polar doped layer has a first spacing distance from the sidewall of the groove. The side of the second polar doped layer away from the silicon substrate extends a second extension portion toward the groove.

[0014] A passivation film layer covers a first polar doped layer, a second polar doped layer, and a groove.

[0015] In some implementations, the second extension does not extend above the groove.

[0016] In some implementations, the passivation film layer surrounds the second extension.

[0017] In some embodiments, the sidewall of the second tunneling layer is flush with the sidewall of the connected second polar doped layer, the passivation film layer covers the silicon substrate, and there is a second gap distance between the passivation film layer covering the bottom surface of the second extension and the passivation film layer covering the silicon substrate, the second gap distance being less than 150 nm.

[0018] In some embodiments, along the arrangement direction of the first region and the second region, the length of the first extension is greater than the length of the second extension.

[0019] In some embodiments, the length of the first extension portion is 0.5 μm-3 μm along the arrangement direction of the first and second regions.

[0020] In some embodiments, the length of the second extension is less than or equal to 200 nm along the arrangement direction of the first and second regions.

[0021] In some implementations, the surface of the second region is flush with the surface of the first region.

[0022] In some implementations, the distance between the surface of the second region and the bottom of the groove is less than the distance between the surface of the first region and the bottom of the groove.

[0023] In some implementations, the sides of the groove are beveled.

[0024] In some embodiments, the surface of the second extension facing the groove has an uneven structure.

[0025] In some embodiments, the roughness of the bottom surface of the groove is greater than the roughness of the side surface of the groove, and the roughness of the side surface of the groove is greater than the roughness of the surfaces of the first extension and the second extension that are away from the groove.

[0026] In some implementations, the width of the groove is 2μm-200μm.

[0027] In some embodiments, the recess depth of the groove is 0.2 μm-10 μm.

[0028] This disclosure also provides a battery assembly including the aforementioned back-contact solar cell.

[0029] This disclosure also provides a photovoltaic system including the aforementioned battery module.

[0030] The beneficial effects achieved by this disclosure include: by providing a first extension portion extending above the groove, a recessed area with a small opening and a large interior is formed at the groove. This reduces the exchange between plasma and the external environment during the deposition of the passivation film, achieving a localized distribution of the mobile hydrogen content in the passivation film, thus achieving optimal passivation and anti-attenuation effects. Simultaneously, the second extension portion allows the passivation film to cover the underlying structure more uniformly and comprehensively, increasing the contact area between the passivation film and the underlying structure and improving the passivation effect. The enhanced passivation effect helps reduce leakage current, which significantly contributes to the stability of long-term performance and the improvement of cell efficiency. Furthermore, the first and second extension portions increase the reflection of incident light entering the silicon substrate, improving cell efficiency. Attached Figure Description

[0031] Figure 1 is a cross-sectional structural diagram of the back contact battery cell provided in an embodiment of this application;

[0032] Figure 2 is another cross-sectional structural diagram of the back contact battery cell provided in an embodiment of this application;

[0033] Figure 3 is another cross-sectional structural diagram of the back contact battery cell provided in the embodiment of this application;

[0034] Figure 4 is another cross-sectional structural diagram of the back contact battery cell provided in the embodiment of this application;

[0035] Figure 5 is a physical image view of the back contact battery cell provided in the embodiment of this application.

[0036] Explanation of reference numerals in the attached figures: 100, back contact solar cell; 101, silicon substrate; 1011, third extension portion; 110, first region; 120, second region; 130, groove; 102, first tunneling layer; 103, first polar doped layer; 1031, first extension portion; 104, second tunneling layer; 105, second polar doped layer; 1051, second extension portion; 106, passivation film layer; 107, first electrode; 108, second electrode. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. Examples of 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. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this disclosure, and should not be construed as limiting this disclosure. Furthermore, it should be understood that the specific embodiments described herein are merely for explaining this disclosure and are not intended to limit this disclosure.

[0038] In the description of this disclosure, it should be understood that the terms “length”, “width”, “upper”, “lower”, “left”, “right”, “horizontal”, “top”, “bottom”, etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this disclosure and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this disclosure.

[0039] 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 features. In the description of this disclosure, "a plurality of" means two or more, unless otherwise explicitly specified.

[0040] In the description of this disclosure, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linkage" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this disclosure according to the specific circumstances.

[0041] In this disclosure, 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 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 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.

[0042] The following disclosure provides numerous different embodiments or examples for implementing various structures of this disclosure. 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 disclosure. 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 disclosure, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0043] This disclosure includes a first extension portion extending above the groove, creating a recessed area with a small opening and a large interior. This reduces plasma exchange with the external environment during passivation film deposition, achieving a localized distribution of mobile hydrogen content in the passivation film for optimal passivation and anti-degradation effects. Simultaneously, a second extension portion allows the passivation film to cover the underlying structure more uniformly and comprehensively, increasing the contact area between the passivation film and the underlying structure and improving the passivation effect. This enhanced passivation helps reduce leakage current, significantly contributing to long-term performance stability and cell efficiency improvement. Furthermore, the first and second extension portions increase the reflection of incident light entering the silicon substrate, improving cell efficiency.

[0044] Example 1

[0045] As shown in Figures 1 and 5, this embodiment provides a back-contact solar cell 100, comprising:

[0046] A silicon substrate 101 has a backlight surface and a light-facing surface disposed opposite to each other. A first region 110 and a second region 120 are alternately disposed on the backlight surface of the silicon substrate 101, and a groove 130 is disposed between adjacent first regions 110 and second regions 120.

[0047] The first tunnel layer 102 is stacked and covered on the first region 110;

[0048] A first polar doped layer 103 is stacked on the first tunneling layer 102, and the first polar doped layer 103 has a first extension portion 1031 extending toward the groove 130.

[0049] The second tunnel layer 104 is stacked on the second region 120;

[0050] A second polar doped layer 105 is stacked on the second tunneling layer 104. The side of the second polar doped layer 105 has a first spacing distance from the sidewall of the groove 130. A second extension portion 1051 extends from the side of the second polar doped layer 105 away from the silicon substrate 101 toward the groove 130.

[0051] The passivation film 106 covers the first polar doped layer 103, the second polar doped layer 105, and the groove 130.

[0052] The silicon substrate 101 has two main surfaces: a light-facing surface and a back-lighting surface. The light-facing surface directly faces the sunlight, while the back-lighting surface is on the other side. The two surfaces are positioned opposite each other.

[0053] Two distinct regions, a first region 110 and a second region 120, are arranged alternately on the backlight surface of the silicon substrate 101. Specifically, a plurality of first regions 110 and a plurality of second regions 120 are arranged alternately along a first direction, and both the first regions 110 and 120 extend along a second direction, which intersects the first direction. The first regions 110 and 120 may be arranged alternately along the lateral direction of the silicon substrate 101 and both extend along the longitudinal direction; that is, the first direction may be the lateral direction of the back contact battery, and the second direction may be the longitudinal direction of the back contact battery, and the two are perpendicular to each other. Of course, in other embodiments, the first direction and the second direction may also be other directions, for example, they may each be the diagonal direction of the silicon substrate 101, and no specific limitation is made here.

[0054] A groove 130 is provided between adjacent first regions 110 and second regions 120. The groove 130 extends along a second direction and the extension direction of the groove 130 is consistent with the extension direction of the first regions 110 and second regions 120. The groove 130 separates the adjacent first regions 110 and second regions 120.

[0055] A first tunneling layer 102 and a first polar doped layer 103 are sequentially stacked in the first region 110. The first extension portion 1031 of the first polar doped layer 103 extends from the first region 110 to above the groove 130, and the projection of the first extension portion 1031 falls into the groove 130. A second tunneling layer 104 and a second polar doped layer 105 are sequentially stacked in the second region 120. There is a predetermined distance L between the sidewall of the second polar doped layer 105 (excluding the second extension portion 1051) and the edge of the groove 130, that is, there is a platform region between the second polar doped layer 105 and the groove 130. In this way, the formed platform region can increase the mobile hydrogen content of the passivation film layer 106 in the upper local area of ​​the space charge region, thereby achieving hydrogen passivation enhancement in this region, reducing space charge recombination, and improving battery performance.

[0056] The second polar doped layer 105 extends a second extension portion 1051 toward the groove on the side away from the silicon substrate 101, and the second extension portion 1051 protrudes from the sidewall of the second polar doped layer 105. The first polar doped layer 103 and the second polar doped layer 105 form a region with different electrical characteristics, supporting the formation of the PN junction and the separation of charge carriers.

[0057] The passivation film 106 can cover the entire back surface of the silicon substrate 101, that is, the passivation film 106 can cover the sidewalls of the first polar doped layer 103, the second polar doped layer 105, the first tunneling layer 102, the second tunneling layer 104, and the groove 130.

[0058] The presence of the first extension portion 1031 obstructs the opening of the groove 130, creating a recessed area with a small opening and a large interior at the groove 130. This reduces plasma exchange between the passivation film layer 106 (e.g., a SiNx film layer) and the external environment during deposition, achieving a localized distribution of mobile hydrogen content in the passivation film layer 106, thus achieving optimal passivation and anti-degradation effects. The presence of the first extension portion 1031 and the second extension portion 1051 allows the passivation film layer 106 to more uniformly and comprehensively cover the underlying structure (the silicon substrate 101 and the first tunneling layer 102 and the second tunneling layer 104 placed on the silicon substrate 101, as well as the corresponding doped layers), including the first extension portion 1031, the second extension portion 1051, and the groove 130, increasing the contact area between the passivation film layer 106 and the underlying structure. This enhances the passivation effect. The enhanced passivation effect helps reduce leakage current, which significantly contributes to the stability of long-term performance and the improvement of cell efficiency. Furthermore, providing the first extension portion 1031 and the second extension portion 1051 can increase the reflection of incident light entering the silicon substrate 101 and improve battery efficiency.

[0059] Specifically, the silicon substrate 101 can be a monocrystalline silicon substrate 101 or a polycrystalline silicon substrate 101, and it can be a P-type silicon substrate or an N-type silicon substrate; no specific limitation is made here. The groove 130 on the silicon substrate 101 can be formed by a combination of grooving and etching. For example, a small opening can be formed on the silicon substrate 101 first, and then the opening can be etched by acid etching or alkaline etching to form the final groove 130.

[0060] In some embodiments, the passivation film 106 may include a stacked aluminum oxide layer and a silicon nitride layer. Of course, it may also include one or more combinations of silicon oxynitride layer, intrinsic silicon carbide layer, intrinsic amorphous silicon layer and silicon oxide layer, without any specific limitation.

[0061] Understandably, the first polar doped layer 103 can be either a P-type doped layer or an N-type doped layer, and the second polar doped layer 105 can be either a P-type doped layer or an N-type doped layer. For example, in some embodiments, the first polar doped layer 103 can be a P-type doped layer, the second polar doped layer 105 can be an N-type doped layer, and the first tunneling layer 102 and the second tunneling layer 104 can both be one or more combinations of tunneling oxide (e.g., tunneling silicon oxide layer), intrinsic silicon carbide layer, and intrinsic amorphous silicon layer, without any specific limitations.

[0062] In addition, the back contact solar cell 100 also has a first electrode 107 and a second electrode 108. The first electrode 107 can be disposed in the first region 110 and penetrate the passivation film layer 106 to make ohmic contact with the first polar doped layer 103. The second electrode 108 can be disposed in the second region 120 and penetrate the passivation film layer 106 to make ohmic contact with the second polar doped layer 105. Both the first electrode 107 and the second electrode 108 can be metal electrodes.

[0063] Specifically, the back surface of the silicon substrate 101 may include a polished surface or a textured surface, and the textured surface may be a surface with high roughness such as a velvety surface. Further, in some embodiments, the area of ​​the second region 120 covered by the second polar doped layer 105 may be a polished surface, and the area of ​​the second region 120 not covered by the second polar doped layer 105 may be a textured surface. Of course, the area of ​​the second region 120 not covered by the second polar doped layer 105 may also be a polished surface, that is, the silicon wafer surface between the second polar doped layer 105 and the edge of the groove 130 is a polished surface.

[0064] In some embodiments, as shown in FIG4, the silicon substrate 101 may have a third extension portion 1011 extending and protruding above the groove 130 at the edge of the first region 110 and the groove 130, the projection of which falls into the groove 130. A first tunneling layer 102 is stacked and covered on the first region 110 and the third extension portion 1011, and a first polar doped layer 103 and the first extension portion 1031 are stacked and disposed on the first tunneling layer 102.

[0065] In some embodiments, the first extension 1031 has a protrusion that extends further above the groove 130 than the third extension 1011.

[0066] Example 2

[0067] Based on Embodiment 1, the second extension portion 1051 does not extend above the groove 130.

[0068] Thus, the projection of the second extension 1051 cannot fall into the groove 130. This maintains the functional independence of the first region 110 and the second region 120, avoids unnecessary interference between different doped regions, and reduces the electric field shielding effect inside the cell. This layout helps carriers to be transported more efficiently from the silicon substrate to the electrodes, maximizing current collection efficiency.

[0069] Example 3

[0070] As shown in Figure 1, based on Example 1, the passivation film layer 106 surrounds the second extension portion 1051.

[0071] The passivation film 106 reduces carrier recombination on the surface of the second extension 1051, further reducing electron recombination caused by surface defects, thereby improving battery performance. Exemplarily, the passivation film 106 can provide a chemically and electrically passivated environment, effectively reducing the surface recombination rate.

[0072] In some embodiments, the sidewall of the second tunneling layer 104 is flush with the sidewall of the connected second polar doped layer 105, the passivation film layer 106 covers the silicon substrate 101, and there is a second gap distance H between the passivation film layer 106 covering the bottom surface of the second extension portion 1051 and the passivation film layer 106 covering the silicon substrate 101, the second gap distance being less than 150 nm.

[0073] The sidewalls of the second tunneling layer 104 are flush with the sidewalls of the connected second polar doped layer 105 (the sidewalls of the non-second extension portion 1051 of the second polar doped layer 105), which helps to reduce the influence of irregular structures on carrier transport, ensures that current can be transported on a relatively smooth path, and improves the electrical performance and efficiency of the device. Since the sidewalls of the second polar doped layer 105 and the sidewalls of the groove 130 have a first gap distance, that is, there is a partial exposed silicon substrate 101, the passivation film layer 106 covers the exposed silicon substrate 101.

[0074] The bottom surface of the second extension 1051 refers to the surface of the second extension 1051 facing the silicon substrate 101. A second gap distance exists between the passivation film layer covering the bottom surface of the second extension 1051 and the passivation film layer 106 covering the silicon substrate 101. This second gap distance is less than 150 nm. This tight gap control ensures that the exposed area is minimized, passivation is maximized, and unnecessary surface recombination is reduced.

[0075] Example 4

[0076] Based on Embodiment 1, along the arrangement direction of the first region 110 and the second region 120, the length of the first extension portion 1031 is greater than the length of the second extension portion 1051.

[0077] In the direction from the first region 110 to the second region 120, the length of the first extension 1031 located on both sides of the same groove 130 is greater than that of the second extension 1051. This asymmetric design is optimized for charge separation and collection processes. The longer extension means a larger contact area in the corresponding region, which can effectively promote charge collection. The longer first extension 1031 corresponds to the region where minority carriers are concentrated (such as electrons or holes). By increasing the contact area of ​​this part, the path for carriers to be transported from the silicon substrate 101 to the external circuit becomes more efficient, reducing resistive losses.

[0078] The asymmetric extensions also help optimize the potential gradient, allowing charge to flow more efficiently from one side to the other by adjusting the potential difference between different regions. This structural design improves the light response of different regions, thereby ensuring the matching of output currents in each part of the overall circuit for higher conversion efficiency.

[0079] Example 5

[0080] Based on Embodiment 1, along the arrangement direction of the first region 110 and the second region 120, the length of the first extension portion 1031 is 0.5μm-3μm.

[0081] Thus, controlling the length of the first extension 1031 within this reasonable range can prevent the first extension 1031 from being too short and thus failing to effectively reduce the exchange of plasma with the outside world during the deposition of the passivation film 106. It can also prevent the extension from being too long, which would result in the opening of the groove 130 being too small and the etching process being too difficult. At the same time, it can also prevent the extension from being too long, which would make it prone to breakage.

[0082] Specifically, in such embodiments, the length of the extended portion can be any value between 0.2μm, 0.3μm, 0.4μm, 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, or 0.2μm-50μm.

[0083] Example 6

[0084] Based on Embodiment 1, along the arrangement direction of the first region 110 and the second region 120, the length of the second extension portion 1051 is less than or equal to 200 nm.

[0085] Thus, keeping the length of the second extension 1051 within this reasonable range can prevent the length of the second extension 1051 from being too large, which would increase the resistance in the path and reduce the overall conductivity and efficiency of the device.

[0086] Specifically, in such embodiments, the length of the extended portion can be any value between 200nm, 190nm, 180nm, 170nm, 160nm, 150nm, 140nm, 130nm, 120nm, 110nm, 100nm, 90nm, 80nm, 70nm, 60nm, 50nm, 40nm, 30nm, 20nm, 10nm, or 0-200nm.

[0087] Example 7

[0088] As shown in Figure 1, in some embodiments, the surface of the second region 120 is flush with the surface of the first region 110.

[0089] In this way, the first region 110 and the second region 120 can be formed directly using the silicon substrate 101 without the need for other processes such as etching.

[0090] Example 8

[0091] As shown in Figure 3, in some embodiments, the distance between the surface of the second region 120 and the bottom of the groove 130 is less than the distance between the surface of the first region 110 and the bottom of the groove 130.

[0092] Thus, when the second polar doped layer 105 is an N-type doped layer, the surface of the battery will come into contact with components such as belts and rollers during the transportation process of the battery. These components will cause scratches on the surface. The etching rate of alkaline solution on N-type surface is higher than that on P-type surface. Therefore, scratches on N-type surface will be more likely to be etched away in alkaline solution, causing failure. Therefore, by sinking the N-type surface, scratches during transportation can be avoided, reducing the risk of failure.

[0093] Example 9

[0094] As shown in Figure 2, in some embodiments, the side surface of the groove 130 (that is, the surface where the bottom surface of the groove 130 connects the surface of the first region 110 and the surface of the second region 120) is an inclined surface. The inclined surface is a surface that is not perpendicular to the bottom surface of the groove 130.

[0095] Thus, there are more vertical crystal plane defects, but by forming inclined side surfaces, the surface defect states of the groove 130 can be reduced. Forming inclined side surfaces can reduce surface recombination and improve battery performance.

[0096] Example 10

[0097] Based on Embodiment 1, the surface of the second extension portion 1051 facing the groove 130 has an uneven structure.

[0098] In this way, by forming a textured structure on the surface, the reflection of incident light entering the silicon substrate 101 can be increased, thereby increasing the amount of light absorbed by the battery and improving the battery's conversion efficiency.

[0099] Example 11

[0100] Based on Embodiment 1, the roughness of the bottom surface of the groove 130 is greater than the roughness of the side surface of the groove 130, and the roughness of the side surface of the groove 130 is greater than the roughness of the surfaces of the first extension portion 1031 and the second extension portion 1051 that are away from the groove 130.

[0101] In this way, by setting texture structures with different roughness, the wettability of local areas can be improved, thus enhancing the cleaning effect when cleaning battery cells.

[0102] Furthermore, in some embodiments, the silicon wafer surface between the second polar doped layer 105 and the edge of the groove 130 is a polished surface, and the roughness of the surface of the extended portion facing the groove 130 is greater than the roughness of the silicon wafer surface between the second polar doped layer 105 and the edge of the groove 130.

[0103] Example 12

[0104] Furthermore, in some embodiments, the width of the groove 130 is 2μm-200μm.

[0105] Thus, by setting the width of the groove 130 within this reasonable range, on the one hand, the width of the groove 130 can be avoided from being too small and failing to function as an isolation layer between the first polar doped layer 103 and the second polar doped layer 105; on the other hand, the width of the groove 130 can be avoided from being too large and causing the ineffective area of ​​the back contact solar cell 100 to be too large.

[0106] Specifically, in such an embodiment, the width of the groove 130 can be any value between 2μm, 4μm, 6μm, 8μm, 10μm, 20μm, 40μm, 60μm, 70μm, 100μm, 110μm, 140μm, 160μm, 170μm, 180μm or 2μm-200μm, and is not limited herein.

[0107] Example 13

[0108] In some embodiments, the recess depth of the groove 130 may be 0.2 μm-10 μm.

[0109] Thus, setting the recess depth of the groove 130 within this reasonable range can avoid the groove 130 being too shallow, which would prevent it from effectively providing isolation, and it can also avoid the groove 130 being too deep, which would greatly reduce the strength of the silicon substrate 101 at the groove 130, thereby reducing the risk of cracking during the fabrication of the back contact solar cell 100. In other words, if the groove 130 is too deep, it will be thinner at the groove 130 position, resulting in the back contact solar cell 100 having too low strength at the groove 130, which is prone to cracking.

[0110] Specifically, in such an embodiment, the recess depth of the groove 130 can be any value between 0.2μm, 0.4μm, 0.6μm, 0.8μm, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm or 0.2μm-10μm, and is not limited here.

[0111] Example 14

[0112] This embodiment provides a battery assembly, including the back-contact solar cell described in the above embodiment.

[0113] The battery module may also include a metal frame, a backsheet, photovoltaic glass, and an encapsulant film (not shown in the figures). The encapsulant film may be filled between the front side 11 of the back-contact solar cell 100 and the photovoltaic glass, the back side and the backsheet, and adjacent cells. As a filler, it may be a transparent colloid with good light transmittance and aging resistance. For example, the encapsulant film may be an EVA film or a POE film, and the specific choice can be made according to the actual situation. There are no restrictions here.

[0114] Photovoltaic glass can be applied to the encapsulant film on the front side 11 of the back contact solar cell 100. The photovoltaic glass can be ultra-clear glass, which has high light transmittance, high transparency, and superior physical, mechanical, and optical properties. For example, the light transmittance of ultra-clear glass can reach over 92%. It can protect the back contact solar cell 100 with minimal impact on its efficiency. Simultaneously, the encapsulant film bonds the photovoltaic glass and the back contact solar cell 100 together, providing sealing, insulation, waterproofing, and moisture protection for the back contact solar cell 100.

[0115] The backsheet can be attached to the adhesive film on the back of the back-contact solar cell 100. The backsheet provides protection and support for the back-contact solar cell 100, and offers reliable insulation, water resistance, and aging resistance. Multiple options are available for the backsheet, typically including tempered glass, acrylic glass, aluminum alloy TPT composite adhesive film, etc., and the specific choice is determined based on the specific circumstances and is not limited here. The backsheet, back-contact solar cell 100, adhesive film, and photovoltaic glass can be mounted on a metal frame. The metal frame serves as the main external support structure for the entire battery module, providing stable support and installation. For example, the battery module can be installed at the desired location using the metal frame.

[0116] The beneficial effects of the battery assembly in this embodiment are equivalent to those of the back-contact solar cell 100 described above, and will not be repeated here.

[0117] Example 15

[0118] This embodiment provides a photovoltaic system, including the battery module described in the above embodiment.

[0119] Photovoltaic systems can be applied in photovoltaic power plants, such as ground-mounted, rooftop, and floating power plants, as well as in equipment or devices that utilize solar energy to generate electricity, such as user solar power supplies, solar streetlights, solar cars, and solar buildings. Of course, it's understandable that the application scenarios of photovoltaic systems are not limited to these; that is, photovoltaic systems can be applied in all fields that require solar energy to generate electricity. Taking a photovoltaic power generation network as an example, a photovoltaic system can include photovoltaic arrays, combiner boxes, and inverters. A photovoltaic array can be a combination of multiple battery modules; for example, multiple battery modules can form multiple photovoltaic arrays. The photovoltaic arrays are connected to combiner boxes, which collect the current generated by the photovoltaic arrays. The collected current flows through an inverter and is converted into AC power required by the mains grid before being connected to the mains grid to achieve solar power supply.

[0120] The beneficial effects of the photovoltaic system in this embodiment are equivalent to the beneficial effects of the battery module described above, and will not be repeated here.

[0121] The above are merely preferred embodiments of this disclosure and are not intended to limit this disclosure. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this disclosure should be included within the scope of protection of this disclosure.

Claims

1. A back-contact solar cell, comprising: A silicon substrate having a backlight surface and a light-facing surface disposed opposite to each other, with a first region and a second region alternately disposed on the backlight surface of the silicon substrate, and a groove disposed between adjacent first regions and second regions. A first tunneling layer is stacked and covered on the first region; A first polar doped layer is stacked on the first tunneling layer, and the first polar doped layer has a first extension portion extending toward the groove; The second tunneling layer is stacked on the second region; A second polar doped layer is stacked on the second tunneling layer, and the side of the second polar doped layer has a first spacing distance from the sidewall of the groove, and the side of the second polar doped layer away from the silicon substrate extends into the groove as a second extension portion. and A passivation film layer covering the first polar doped layer, the second polar doped layer, and the groove.

2. The back-contact solar cell as described in claim 1, wherein, The second extension does not extend above the groove.

3. The back-contact solar cell as described in claim 1, wherein, The passivation film layer surrounds the second extension portion.

4. The back-contact solar cell as described in claim 3, wherein, The sidewall of the second tunneling layer is flush with the sidewall of the connected second polar doped layer. The passivation film covers the silicon substrate. There is a second gap distance between the passivation film covering the bottom surface of the second extension and the passivation film covering the silicon substrate. The second gap distance is less than 150 nm.

5. The back-contact solar cell as described in claim 1, wherein, Along the arrangement direction of the first region and the second region, the length of the first extension portion is greater than the length of the second extension portion.

6. The back-contact solar cell as described in claim 1, wherein, Along the arrangement direction of the first region and the second region, the length of the first extension portion is 0.5μm-3μm.

7. The back-contact solar cell as described in claim 1, wherein, Along the arrangement direction of the first region and the second region, the length of the second extension is less than or equal to 200 nm.

8. The back-contact solar cell as described in claim 1, wherein, The surface of the second region is flush with the surface of the first region.

9. The back-contact solar cell as claimed in claim 1, wherein, The distance between the surface of the second region and the bottom of the groove is less than the distance between the surface of the first region and the bottom of the groove.

10. The back-contact solar cell as claimed in claim 1, wherein, The side of the groove is a slope.

11. The back-contact solar cell as claimed in claim 1, wherein, The surface of the second extension facing the groove has an uneven structure.

12. The back-contact solar cell as claimed in claim 1, wherein, The roughness of the bottom surface of the groove is greater than the roughness of the side surface of the groove, and the roughness of the side surface of the groove is greater than the roughness of the surfaces of the first extension portion and the second extension portion away from the groove.

13. The back-contact solar cell as claimed in claim 1, wherein, The width of the groove is 2μm-200μm.

14. The back-contact solar cell as claimed in claim 1, wherein, The groove has a depth of 0.2μm-10μm.

15. A battery assembly comprising a back-contact solar cell according to any one of claims 1-14.

16. A photovoltaic system comprising the battery module of claim 15.

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