REAR-CONTACT SOLAR PANELS, SOLAR MODULES, AND PHOTOVOLTA SYSTEMS

Abstract

This invention is suitable for the field of solar cell technology, providing a type of back-contact solar panel (100), battery module (200) and photovoltaic system (1000). In the back-contact solar panel (100), on the back (12) of the silicon plate (10) several spaced recessed grooves (121) are formed, to divide the back (12) of the silicon plate (10) into several alternating first (122) and second (123) regions. According to the arrangement of the first (122) and second (123) regions, the silicon sheet (10) at the edge of the first region (122) and the groove (121) has an extension (13) protruding above the groove (121), the second polar doped layer (50) is arranged stacked on top of the second tunneling layer (40) and has a predetermined distance (L) with the edge of the groove (121).

Description

Back-contact solar cells, modules and photovoltaic systems

[0001] Priority information

[0002] This application claims priority and benefits of patent applications with patent application numbers 202311238215.2 and 202322596534.2 filed with the State Intellectual Property Office of China on September 22, 2023, and the entire text of which is incorporated herein by reference. Technical Field

[0003] The present application relates to the technical field of solar cells, and in particular to a back-contact solar cell, a cell assembly, and a photovoltaic system. Background Art

[0004] A back-contact solar cell is a cell in which both the emitter and base contact electrodes are placed on the back side of the cell (non-light-receiving side). The light-receiving side of the cell is not blocked by any metal electrodes, thereby effectively increasing the short-circuit resistance of the cell.

[0005] In related technologies, to address the surface passivation issues in the recessed region on the back of back-contacted cells and reduce hydrogen-related defects in the body region, the passivated contact region requires hydrogen-passivated tunneling layer defect states. This requires the use of a high-refractive-index passivation film (such as high-refractive-index SiNx) to achieve a higher mobile hydrogen content. Excessive hydrogen entering the substrate region can cause cell degradation. Furthermore, the recessed region passivation layer (such as AlOx) is prone to negative charge field passivation. This configuration induces a surface p+ layer, creating a space charge region at the contact between the p+ layer and the n++ layer. Recombination in this region increases the junction recombination current of the cell, significantly reducing cell performance. Summary of the Invention

[0006] The present application provides a back-contact solar cell, a cell assembly and a photovoltaic system.

[0007] The present application is implemented as follows: a back-contact solar cell according to an embodiment of the present application comprises:

[0008] A silicon wafer having a front side and a back side facing each other, a plurality of grooves formed on the back side so that the back side includes a plurality of first regions and second regions alternately arranged in sequence, with adjacent first regions and second regions separated by the grooves; and the silicon wafer having an extending portion extending above the grooves at an edge of the first region and the grooves in the direction in which the first regions and the second regions are arranged.

[0009] a first tunneling layer, the first tunneling layer being stacked and covering the first region;

[0010] a first polarity doped layer, wherein the first polarity doped layer is stacked on the first tunneling layer and the extension portion;

[0011] a second tunneling layer, the second tunneling layer being stacked on the second region;

[0012] a second polarity doped layer, the second polarity doped layer being stacked on the second tunneling layer and having a preset distance from an edge of the groove; and

[0013] A passivation film layer covers the first polarity doped layer, the second polarity doped layer and the groove.

[0014] Furthermore, in the arrangement direction of the first region and the second region, the length of the extension portion is 0.2 um-50 um.

[0015] Furthermore, in the arrangement direction of the first region and the second region, the length of the extension portion is 1 um-15 um.

[0016] Furthermore, the preset distance is 0.1um-50um.

[0017] Furthermore, the preset distance is 1um-20um.

[0018] Furthermore, the surface of the second region is flush with the surface of the first region.

[0019] Furthermore, the distance between the surface of the second region and the bottom of the groove is smaller than the distance between the surface of the first region and the bottom of the groove.

[0020] Furthermore, the side surface of the groove is an inclined surface.

[0021] Furthermore, in the arrangement direction of the first region and the second region, the first polarity doped layer has a protruding portion that protrudes from the extending portion and is located above the groove.

[0022] Furthermore, in the arrangement direction of the first area and the second area, the length of the protruding portion is 0.1 um-50 um.

[0023] Furthermore, the bottom surface, the side surface of the groove and the surface of the extension portion facing the groove all have a concave-convex texture structure.

[0024] Furthermore, 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 surface of the extension portion facing the groove.

[0025] Furthermore, the silicon wafer surface between the second polarity doped layer and the edge of the groove is a polished surface and the roughness of the surface of the extension portion facing the groove is greater than the roughness of the silicon wafer surface between the second polarity doped layer and the edge of the groove.

[0026] Furthermore, the width of the groove is 2um-200um.

[0027] Furthermore, the recessed depth of the groove is 0.2um-10um.

[0028] The present application also provides a battery assembly, which includes any of the above-mentioned back-contact solar cells.

[0029] The present application also provides a photovoltaic system, which includes the above-mentioned battery assembly.

[0030] In the back-contact solar cell, battery module, and photovoltaic system of the embodiments of the present application, a plurality of grooves are formed on the back side of the silicon wafer at intervals to divide the back side of the silicon wafer into a plurality of alternating first and second regions. In the arrangement direction of the first and second regions, the silicon wafer has an extension portion extending above the groove at the edge of the first region and the groove, and the second polarity doped layer is stacked on the second tunneling layer and is spaced a predetermined distance from the edge of the groove. Thus, on the one hand, by configuring the silicon wafer with the extension portion extending above the groove, a recessed region with a small opening and a large interior can be formed on the silicon wafer, which can reduce the exchange of plasma with the outside world during the deposition of the passivation film, achieve a localized distribution of the mobile hydrogen content of the passivation film layer, and make the mobile hydrogen content of the passivation film layer lower in the groove and higher in the remaining regions, thereby achieving optimal passivation and anti-attenuation effects. On the other hand, by setting the second polarity doping layer to have a preset distance from the surface of the groove, the platform area formed can increase the mobile hydrogen content of the passivation film layer in the local area above the space charge region, thereby achieving enhanced hydrogen passivation in this area, reducing space charge region recombination, and improving battery performance.

[0031] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become obvious from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG1 is a schematic diagram of a module of a photovoltaic system provided in an embodiment of the present application;

[0033] FIG2 is a schematic diagram of a module of a battery assembly provided in an embodiment of the present application;

[0034] FIG3 is a schematic cross-sectional view of a back-contact solar cell according to an embodiment of the present application;

[0035] FIG4 is another schematic cross-sectional view of a back-contact solar cell according to an embodiment of the present application;

[0036] FIG5 is another schematic cross-sectional view of the back-contact solar cell provided in an embodiment of the present application;

[0037] FIG6 is another schematic cross-sectional view of the back-contact solar cell provided in an embodiment of the present application.

[0038] Description of main component symbols:

[0039] Photovoltaic system 1000, battery assembly 200, back-contact solar cell 100, silicon wafer 10, front side 11, back side 12, groove 121, side surface 122, first region 122, second region 123, extension portion 13, first tunneling layer 20, first polarity doped layer 30, protruding portion 31, second tunneling layer 40, second polarity doped layer 50, passivation film layer 60, first electrode 70, second electrode 80. Modes for Carrying Out the Invention

[0040] In order to make the purpose, technical solutions and advantages of the present application more clear, the present application is further described in detail below with reference to the accompanying drawings and embodiments. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application and are not to be construed as limiting the present application. In addition, it should be understood that the specific embodiments described herein are merely used to explain the present application and are not intended to limit the present application.

[0041] In the description of this application, it should be understood that the terms "thickness", "width", "up", "down", "lateral", "longitudinal", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships 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, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on this application.

[0042] 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 the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the described features. Throughout the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0043] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections, electrical connections, or mutual communication; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to internal communication between two components or the interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0044] In this application, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Moreover, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0045] The disclosure below provides many different embodiments or examples for realizing different structures of the present application. In order to simplify the disclosure of the present application, the components and settings of specific examples are described below. Of course, they are merely examples and are not intended to limit the present application. In addition, the present application may repeat reference numbers and / or reference letters in different examples. Such repetition is for the purpose of simplicity and clarity and does not in itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present application provides examples of various specific processes and materials, but those skilled in the art will appreciate the application of other processes and / or the use scenarios of other materials.

[0046] In the present application, by configuring the silicon wafer to have an extension portion extending and protruding above the groove, a recessed area with a small opening and a large interior can be formed on the silicon wafer, which can reduce the exchange of plasma with the outside world during the deposition process of the passivation film layer, thereby achieving a localized distribution of the mobile hydrogen content of the passivation film layer, making the mobile hydrogen content of the passivation film layer in the groove lower, and the mobile hydrogen content of the passivation film layer on the remaining areas higher, so as to achieve the best passivation and anti-attenuation effect. On the other hand, by configuring the second polarity doping layer to have a preset distance from the edge of the groove, the platform area formed can increase the mobile hydrogen content of the passivation film layer in the local area above the space charge region, thereby achieving enhanced hydrogen passivation in this area, reducing space charge region recombination, and improving battery performance.

[0047] Example 1

[0048] 1 and 2 , the photovoltaic system 1000 in the embodiment of the present application may include the battery assembly 200 in the embodiment of the present application, and the battery assembly 200 in the embodiment of the present application may include a plurality of back-contact solar cells 100 in the embodiment of the present application.

[0049] In some embodiments, multiple back-contact solar cells 100 in a battery assembly 200 can be connected in series in sequence to form a battery string. The battery strings can be connected in series, in parallel, or in a combination of series and parallel to achieve current bus output. For example, the connection between the battery cells can be achieved by welding welding strips, and the connection between the battery strings can be achieved by bus bars.

[0050] 3 , a back-contact solar cell 100 in an embodiment of the present application may include a silicon wafer 10 , a first tunneling layer 20 , a first polarity doped layer 30 , a second tunneling layer 40 , a second polarity doped layer 50 and a passivation film 60 .

[0051] The silicon wafer 10 has a front side 11 and a back side 12 facing each other. The back side 12 is formed with a plurality of grooves 121 arranged in an alternating pattern, such that the back side 12 includes a plurality of first regions 122 and second regions 123 arranged alternately in sequence. Adjacent first regions 122 and second regions 123 are separated by the grooves 121. For example, the first regions 122 and second regions 123 may be arranged alternately in the lateral direction of the back-contact solar cell 100, and the grooves 121 may extend in the longitudinal direction to separate adjacent first regions 122 and second regions 123.

[0052] As shown in FIG3 , in the arrangement direction of the first region 122 and the second region 123 , the silicon wafer 10 has an extension portion 13 extending and protruding above the groove 121 at the edge of the first region 122 and the groove 121 .

[0053] The first tunneling layer 20 is stacked and covered on the first region 122, and the first polarity doped layer 30 is stacked on the first tunneling layer 20 and the extension portion 13. The second tunneling layer 40 is stacked on the second region 123, and the second polarity doped layer 50 is stacked on the second tunneling layer 40 and has a predetermined distance L between it and the edge of the groove 121.

[0054] The passivation film layer 60 may cover the entire back side 12 of the silicon wafer 10 , that is, the passivation film layer 60 may cover the first polarity doped layer 30 , the second polarity doped layer 50 and the groove 121 .

[0055] In the back-contact solar cell 100, the battery assembly 200, and the photovoltaic system 1000 in the embodiments of the present application, a plurality of spaced grooves 121 are formed on the back side 12 of the silicon wafer 10 to divide the back side 12 of the silicon wafer 10 into a plurality of alternating first regions 122 and second regions 123. In the arrangement direction of the first regions 122 and the second regions 123, the silicon wafer 10 has an extension portion 13 extending and protruding above the groove 121 at the edge of the first region 122 and the groove 121. The second polarity doped layer 50 is stacked on the second tunneling layer 40 and has a preset distance L between it and the edge of the groove 121. Thus, on the one hand, by configuring the silicon wafer 10 with an extension portion 13 extending and protruding above the groove 121, a recessed region with a small opening and a large interior can be formed on the silicon wafer 10. This reduces the exchange of plasma between the passivation film layer 60 (e.g., SiNx film layer) and the outside world during deposition, thereby achieving a localized distribution of the mobile hydrogen content in the passivation film layer. This results in a lower mobile hydrogen content in the passivation film layer 60 in the groove 121 and a higher mobile hydrogen content in the remaining areas of the passivation film layer 60, thereby achieving optimal passivation and anti-attenuation effects. On the other hand, by configuring the second polarity doped layer 50 at a predetermined distance L from the edge of the groove 121 (i.e., a terrace region is formed between the second polarity doped layer 50 and the groove 121), the terrace region can increase the mobile hydrogen content of the passivation film layer 60 locally above the space charge region, thereby enhancing hydrogen passivation in this region, reducing space charge region recombination, and improving battery performance.

[0056] Specifically, in the embodiment of the present application, the front surface 11 is the side of the back-contact solar cell 100 that receives light during operation, and the back surface 12 is the side of the back-contact solar cell 100 that is not exposed to light during operation. The silicon wafer 10 can be a single-crystal silicon wafer 10 or a multi-crystal silicon wafer 10, and can be a P-type silicon wafer 10 or an N-type silicon wafer 10, without limitation. The groove 121 on the silicon wafer 10 and the extension portion 13 of the silicon wafer 10 can be formed by a combination of grooving and etching. For example, a small opening can be first formed on the silicon wafer 10, and then the opening can be etched by acid etching or alkaline etching to form a concave area with a small opening and a large interior (i.e., the groove 121), and then an extension portion 13 is formed that protrudes and extends above the groove 121, thereby reducing the exchange of plasma with the outside world during the deposition of the passivation film layer 60.

[0057] It can be understood that “there is a preset distance L between the second polarity doped layer 50 and the groove 121” means that in the arrangement direction of the first region 122 and the second region 123, there is a preset distance L between the edge of the second polarity doped layer 50 close to the groove 121 and the edge of the groove 121.

[0058] In an embodiment of the present application, the first polarity doped layer 30 may be one of a P-type doped layer and an N-type doped layer, and the second polarity doped layer 50 may be the other of a P-type doped layer and an N-type doped layer. For example, in some embodiments, the first polarity doped layer 30 may be a P-type doped layer, and the second polarity doped layer 50 may be an N-type doped layer. The first tunneling layer 20 and the second tunneling layer 40 may both be one or more combinations of a tunneling oxide layer (such as a tunneling silicon oxide layer), an intrinsic silicon carbide layer, and an intrinsic amorphous silicon layer, and no specific limitation is made here.

[0059] Specifically, the passivation film layer 60 may preferably include a stacked aluminum oxide layer and a silicon nitride layer. Of course, it may also include one or more combinations of a silicon oxynitride layer, an intrinsic silicon carbide layer, an intrinsic amorphous silicon layer and a silicon oxide layer, which is not specifically limited here.

[0060] In addition, the back-contact solar cell 100 further includes a first electrode 70 and a second electrode 80. The first electrode 70 can be disposed in the first region 122 and penetrate the passivation film layer 60 to make ohmic contact with the first polarity doped layer 30. The second electrode 80 can be disposed in the second region 123 and penetrate the passivation film layer 60 to make ohmic contact with the second polarity doped layer 50. Both the first electrode 70 and the second electrode 80 can be metal electrodes.

[0061] In the embodiments of the present application, the back side 12 of the silicon wafer 10 may be a polished surface or a textured surface. The textured surface may be, for example, a velvet surface or other surface with a relatively high roughness. Furthermore, in some embodiments, the area covered by the second polarity doped layer 50 in the second region 123 may be a polished surface, and the area not covered by the second polarity doped layer 50 in the second region 123 may be a textured surface. Of course, the area not covered by the second polarity doped layer 50 in the second region 123 may also be a polished surface. That is, the silicon wafer surface between the second polarity doped layer 50 and the edge of the groove 121 is a polished surface.

[0062] It is understood that in the embodiments of the present application, the battery assembly 200 may further include a metal frame, a backsheet, photovoltaic glass, and an adhesive film (not shown). The adhesive film may be filled between the front surface 11 and the photovoltaic glass, the back surface 12 and the backsheet, and adjacent cells of the back-contact solar cell 100. As a filler, it may be a transparent colloid with good light transmittance and aging resistance. For example, the adhesive film may be EVA film or POE film. The specific choice can be based on actual conditions and is not limited here.

[0063] Photovoltaic glass can cover the adhesive film on the front surface 11 of the back-contact solar cell 100. The photovoltaic glass can be ultra-clear glass, which has high light transmittance, high transparency, and excellent physical, mechanical, and optical properties. For example, ultra-clear glass can have a light transmittance of over 92%, protecting the back-contact solar cell 100 while minimizing the impact on its efficiency. The adhesive film can also bond the photovoltaic glass and the back-contact solar cell 100 together, providing sealing, insulation, and waterproofing for the back-contact solar cell 100.

[0064] A backsheet can be attached to the film on the back surface 12 of the back-contact solar cell 100. The backsheet protects and supports the back-contact solar cell 100, providing reliable insulation, water resistance, and aging resistance. A variety of backsheet options are available, typically including tempered glass, organic glass, and aluminum alloy TPT composite film. The specific configuration depends on the specific situation and is not limited here. The entire assembly consisting of the backsheet, back-contact solar cell 100, film, and photovoltaic glass can be mounted on a metal frame. The metal frame serves as the primary external support structure for the entire battery assembly 200 and provides stable support and installation for the battery assembly 200. For example, the metal frame can be used to mount the battery assembly 200 in the desired location.

[0065] Furthermore, in this embodiment, the photovoltaic system 1000 can be applied in photovoltaic power stations, such as ground-based power stations, rooftop power stations, and water-based power stations. It can also be applied to equipment or devices that use solar energy to generate electricity, such as user solar power supplies, solar streetlights, solar cars, and solar buildings. Of course, it is understood that the application scenarios of the photovoltaic system 1000 are not limited to these. In other words, the photovoltaic system 1000 can be applied in all fields that require solar power generation. Taking a photovoltaic power generation system network as an example, the photovoltaic system 1000 may include a photovoltaic array, a combiner box, and an inverter. The photovoltaic array may be an array combination of multiple battery assemblies 200. For example, multiple battery assemblies 200 may form multiple photovoltaic arrays. The photovoltaic arrays are connected to a combiner box, which can combine the current generated by the photovoltaic arrays. The combined current flows through the inverter to convert it into the AC power required by the mains power grid and then connects to the mains power grid to achieve solar power supply.

[0066] Example 2

[0067] In some embodiments, in the arrangement direction of the first region 122 and the second region 123 , the length of the extension portion 13 may be 0.2 μm-50 μm.

[0068] In this way, by keeping the length of the extension part 13 within this reasonable range, it can avoid the length of the extension part 13 being too short and failing to effectively reduce the exchange of plasma with the outside world during the deposition of the passivation film layer, and it can also avoid the length of the extension part 13 being too long, resulting in the opening of the groove 121 being too small and the etching process being too difficult, and it can also avoid the length of the extension part 13 being too long, resulting in easy breakage.

[0069] Specifically, in such an embodiment, the length of the extension portion 13 may be, for example, 0.2um, 0.4um, 0.6um, 0.8um, 1um, 2um, 3um, 4um, 5um, 6um, 7um, 8um, 9um, 10um, 20um, 30um, 40um, 50um or any value between 0.2um-50um.

[0070] Furthermore, according to the research and verification of the inventors of this application, in order to better prevent the extension part 13 from breaking and at the same time ensure the function of reducing the exchange of plasma with the outside world during the deposition of the passivation film layer, the length of the extension part 13 in this application is preferably in the range of 1um-15um.

[0071] Example 3

[0072] Please refer to FIG. 3 . In some embodiments, the predetermined distance L may be in the range of 0.1 um to 50 um.

[0073] In this way, setting the distance between the second polarity doping layer 50 and the groove 121 within the above-mentioned reasonable range can ensure that the platform area between the second polarity doping layer 50 and the edge of the groove 121 is at a reasonable size, which can effectively increase the mobile hydrogen content of the local passivation film layer on the platform area, thereby achieving local hydrogen passivation enhancement in this area, reducing space charge region recombination, and avoiding the preset distance L being too large, resulting in the area of ​​the second region 123 without the second polarity doping layer 50 being too large, resulting in too low carrier collection efficiency and affecting the overall efficiency of the battery.

[0074] Specifically, in the present application, the size of the preset distance L may be, for example, 0.1um, 0.2um, 0.3um, 0.4um, 0.5um, 1um, 2um, 3um, 4um, 5um, 6um, 7um, 8um, 9um, 10um, 20um, 30um, 40um, 50um or any value between 0.1um-50um.

[0075] The inventors of the present application have found through research that, in the embodiment of the present application, the preset distance L is preferably 1 μm to 20 μm, which can reduce the recombination of the space charge region while also ensuring the overall efficiency of the battery.

[0076] Example 4

[0077] Referring to FIG. 3 , in some embodiments, the surface of the second region 123 is flush with the surface of the first region 122 .

[0078] In this way, the first region 122 and the second region 123 can be directly formed using the silicon wafer 10 without performing other processes such as etching.

[0079] Example 5

[0080] 4 , in some embodiments, the distance between the surface of the second region 123 and the bottom of the groove 121 is smaller than the distance between the surface of the first region 122 and the bottom of the groove 121 . That is, the surface of the second region 123 sinks into the silicon wafer 10 .

[0081] In this way, when the second polarity doping layer 50 is an N-type doping layer, the surface of the battery will contact belts, rollers and other components during transportation in the production process, which will cause scratches on the surface. The alkali tends to etch the N-type surface at a higher rate than the P-type surface. Therefore, scratches on the N-type surface will more easily cause it to be etched away in the alkaline solution, causing failure. Therefore, by sinking the N-type surface, scratches during transportation can be avoided and the risk of failure can be reduced.

[0082] Example 6

[0083] Referring to FIG. 5 , in some embodiments, the side surface 122 of the groove 121 (ie, the bottom surface of the groove 121 connecting the surface of the first region 122 and the surface of the second region 123 ) is a slope.

[0084] In this way, there are more vertical crystal plane defects, and by forming the inclined side surface 122, the surface defect state of the groove 121 can be reduced. The formation of the inclined side surface can reduce surface recombination and improve battery performance.

[0085] Example 7

[0086] Referring to FIG. 6 , in some embodiments, in the arrangement direction of the first region 122 and the second region 123 , the first polarity doped layer 30 has a protruding extension portion 13 and a protruding portion 31 located above the groove 121 .

[0087] In this way, by setting the first polarity doping layer 30 to have a protruding portion 31 protruding above the groove 121, when depositing the second polarity doping layer 50, the local second doping layer can be selectively brought into contact with the protruding portion 31, thereby improving the subsequent electrical injection effect, and further improving the subsequent repair efficiency and repair effect of the back-contact solar cell 100.

[0088] In some embodiments, the length of the protrusion 31 may be 0.1 μm to 50 μm in the arrangement direction of the first region 122 and the second region 123. This can prevent the protrusion 31 from being too long and causing breakage.

[0089] Specifically, in the present application, the length of the protrusion 31 can be, for example, 0.1um, 0.2um, 0.3um, 0.4um, 0.5um, 1um, 2um, 3um, 4um, 5um, 6um, 7um, 8um, 9um, 10um, 20um, 30um, 40um, 50um, or any value between 0.1um and 50um, without limitation. Preferably, the length of the protrusion 31 can be 1um to 20um.

[0090] Example 8

[0091] In some embodiments, the bottom surface of the groove 121 , the side surface 1211 , and the surface of the extension portion 13 facing the groove all have a concave-convex texture structure.

[0092] In this way, by forming the concave-convex texture structure on these three surfaces, the reflection of the incident light entering the silicon wafer 10 can be increased, thereby increasing the amount of light absorbed by the battery and improving the conversion efficiency of the battery.

[0093] Furthermore, in this embodiment, the roughness of the bottom surface of the groove 121 is greater than the roughness of the side surfaces 1211 of the groove 121, and the roughness of the side surfaces 1211 of the groove 121 is greater than the roughness of the surface of the extension 13 facing the groove. In this way, by providing texture structures with different roughness levels, the wettability of the local area can be improved, thereby improving the cleaning effect when cleaning the battery cell.

[0094] In addition, in some embodiments, the surface of the silicon wafer between the second polarity doped layer 50 and the edge of the groove 121 (i.e., the surface of the above-mentioned platform area) is a polished surface and the roughness of the surface of the extension portion 13 facing the groove 121 is greater than the roughness of the silicon wafer surface between the second polarity doped layer 50 and the edge of the groove 121.

[0095] Embodiment 9

[0096] Furthermore, in some embodiments, the width of the groove 121 is 2 um-200 um.

[0097] In this way, by setting the width of the groove 121 within this reasonable range, on the one hand, it can prevent the width of the groove 121 from being too small and failing to isolate the first polarity doped layer 30 and the second polarity doped layer 50, and on the other hand, it can prevent the width of the groove 121 from being too large and causing the ineffective area of ​​the back contact solar cell 100 to be too large.

[0098] Specifically, in such an embodiment, the width of the groove 121 may be 2um, 4um, 6um, 8um, 10um, 20um, 40um, 60um, 80um, 100um, 120um, 140um, 160um, 180um, 200um or any value between 2um-200um, and is not limited here.

[0099] Example 10

[0100] In some embodiments, the recess 121 may have a depth of 0.2 um to 10 um.

[0101] In this way, setting the recessed depth of the groove 121 within a reasonable range here can avoid the groove 121 being too small, resulting in the groove 121 being unable to effectively isolate the wafer, and can also avoid the groove 121 being too deep, resulting in the strength of the silicon wafer 10 at the groove 121 being greatly reduced, thereby reducing the risk of cracks in the process of manufacturing the back-contact solar cell 100. In other words, if the groove 121 is too deep, the groove 121 will be thinner, resulting in the back-contact solar cell 100 having too low strength at the groove 121, which is prone to cracks.

[0102] Specifically, in such an embodiment, the recess depth of the groove 121 may be 0.2um, 0.4um, 0.6um, 0.8um, 1um, 2um, 3um, 4um, 5um, 6um, 7um, 8um, 9um, 10um or any value between 0.2um-10um, and is not limited here.

[0103] Throughout this specification, reference to terms such as "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with the embodiment or example is included in at least one embodiment or example of the present application. In this specification, the schematic representations 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 any one or more embodiments or examples.

[0104] In addition, the above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A back contact solar cell, characterized in that: include: A silicon wafer, wherein the silicon wafer has a front side and a back side opposite to each other, and a plurality of grooves arranged at intervals are formed on the back side so that the back side includes a plurality of first regions and second regions arranged alternately in sequence, and the adjacent first regions and second regions are separated by the grooves; in the arrangement direction of the first regions and the second regions, the silicon wafer has an extending portion extending and protruding above the groove at the edge of the first region and the groove; A first tunneling layer, the first tunneling layer is stacked and covered on the first region; A first polarity doped layer, wherein the first polarity doped layer is stacked on the first tunneling layer and the extension portion; a second tunneling layer, the second tunneling layer being stacked and arranged on the second region; A second polarity doping layer, wherein the second polarity doping layer is stacked on the second tunneling layer and has a preset distance from an edge of the groove; and A passivation film layer covers the first polarity doping layer, the second polarity doping layer and the groove.

2. The back contact solar cell according to claim 1, characterized in that: In the arrangement direction of the first region and the second region, the length of the extension portion is 0.2um-50um.

3. The back contact solar cell according to claim 2, characterized in that: In the arrangement direction of the first region and the second region, the length of the extension portion is 1 um-15 um.

4. The back contact solar cell according to claim 1, characterized in that: The preset distance is 0.1um-50um.

5. The back contact solar cell according to claim 4, characterized in that: The preset distance is 1um-20um.

6. The back contact solar cell according to claim 1, characterized in that: A surface of the second region is flush with a surface of the first region.

7. The back contact solar cell according to claim 1, characterized in that: The distance between the surface of the second region and the bottom of the groove is smaller than the distance between the surface of the first region and the bottom of the groove.

8. The back contact solar cell according to claim 1, characterized in that: The side surface of the groove is an inclined surface.

9. The back contact solar cell according to claim 1, characterized in that: In the arrangement direction of the first region and the second region, the first polarity doping layer has a protruding portion protruding from the extending portion and located above the groove.

10. The back contact solar cell according to claim 9, characterized in that: In the arrangement direction of the first area and the second area, the length of the protruding portion is 0.1um-50um.

11. The back contact solar cell according to claim 1, characterized in that: The bottom surface, the side surface of the groove and the surface of the extending portion facing the groove all have a concave-convex texture structure.

12. The back contact solar cell according to claim 11, characterized in that: 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 surface of the extension portion facing the groove.

13. The back contact solar cell according to claim 1, characterized in that: The silicon wafer surface between the second polarity doping layer and the edge of the groove is a polished surface, and the roughness of the surface of the extension portion facing the groove is greater than the roughness of the silicon wafer surface between the second polarity doping layer and the edge of the groove.

14. The back contact solar cell according to claim 1, characterized in that: The width of the groove is 2um-200um.

15. The back contact solar cell according to claim 1, characterized in that: The recessed depth of the groove is 0.2um-10um.

16. A battery assembly, characterized in that: A back-contact solar cell comprising any one of claims 1-15.

17. A photovoltaic system, characterized in that: A battery assembly comprising the battery assembly of claim 16.

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