Back contact solar cells, cell assemblies, and photovoltaic systems

Abstract

The application belongs to the technical field of photovoltaics, and discloses a back contact solar cell, a cell module and a photovoltaic system. The back contact solar cell comprises a silicon substrate, the silicon substrate has a light-receiving surface and a non-light-receiving surface arranged oppositely, and the non-light-receiving surface has a P region and an N region; the P region is provided with a plurality of first grooves, and at least part of the first grooves overlap with each other to form a first overlapping region; and the N region is provided with a plurality of second grooves, and at least part of the second grooves overlap with each other to form a second overlapping region. The plurality of first grooves and the plurality of second grooves that overlap with each other can increase the roughness of the P region and the N region, the roughness of the entire non-light-receiving surface is uniformly increased, and when the silicon substrate is conveyed by a roller, the slip between the silicon substrate and the roller can be avoided, the problems of uneven running and stacking of the silicon wafer can be eliminated, the production rhythm can be prevented from being affected and the silicon substrate structure can be prevented from being damaged, the yield of the cell wafer is improved, and meanwhile, the P region and the N region are both provided with grooves, which is helpful to improve the photoelectric conversion efficiency of the solar cell.

Description

Technical Field

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

[0002] In back-contact solar cell modules, since the positive and negative electrodes of the cells are on their back side (non-light-receiving surface), there is no need to weld grid lines to conduct current on the light-receiving surface. The light-receiving area is increased compared to ordinary solar cells, which helps to improve the photoelectric conversion efficiency of the photovoltaic system.

[0003] In the fabrication of back-contact solar cells, the non-light-receiving surface of the cell is primarily polished, requiring all or part of the silicon substrate to be a flat, polished surface. This facilitates the deposition of the passivation antireflection film, resulting in fewer carrier recombination sites and higher photoelectric conversion efficiency. However, in actual production, an overly flat polished silicon substrate surface leads to lower surface roughness, such as... Figure 1 As shown, during wet cleaning and etching using a chain machine, insufficient friction between silicon wafer 1′ and roller 2′ causes slippage, resulting in uneven running of silicon wafer 1′ on roller 2′ and wafer stacking. This affects subsequent production cycle time and damages the structure of silicon wafer 1′, leading to defective solar cells and increased production costs. Furthermore, an overly smooth polished surface of the silicon substrate can also affect the photoelectric conversion efficiency of the solar cells.

[0004] Therefore, there is an urgent need for a back-contact solar cell, battery module, and photovoltaic system to solve the aforementioned problems in the existing technology. Summary of the Invention

[0005] The purpose of this invention is to provide a back-contact solar cell, a battery module, and a photovoltaic system that, without affecting the passivation effect of the silicon wafer surface, avoids slippage between the silicon wafer and the roller, eliminates problems of misaligned silicon wafers and stacking, and improves the photoelectric conversion efficiency of the solar cell.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, a back-contact solar cell is provided, comprising a silicon substrate having a light-receiving surface and a non-light-receiving surface disposed opposite to each other, the non-light-receiving surface having a P-region and an N-region;

[0008] The P region is provided with a plurality of first grooves, and at least some of the first grooves overlap each other to form a first overlapping region;

[0009] The N region is provided with a number of second grooves, and at least some of the second grooves overlap each other to form a second overlapping region.

[0010] As an optional solution of the back contact solar cell provided by the application, the surface of the second groove is provided with at least one third groove.

[0011] As an optional solution of the back contact solar cell provided by the application, the surface of the second groove is provided with a plurality of third grooves, and there is a spacing between adjacent third grooves or the third grooves are mutually overlapped to form a third overlapping area.

[0012] As an optional solution of the back contact solar cell provided by the application, the distance between the two farthest points in the orthographic projection of the third groove on the silicon substrate is 0.5 μm to 20 μm.

[0013] As an optional solution of the back contact solar cell provided by the application, the number of third grooves provided in a single second groove is 4 to 30.

[0014] As an optional solution of the back contact solar cell provided by the application, at least part of the first grooves are distributed in a linear array to form a first array structure.

[0015] And / or, at least part of the second grooves are distributed in a linear array to form a second array structure.

[0016] As an optional solution of the back contact solar cell provided by the application, at least one first array structure penetrates the P region.

[0017] And / or, at least one second array structure penetrates the N region.

[0018] As an optional solution of the back contact solar cell provided by the application, an isolation region is provided between the P region and the N region, at least one first array structure and at least one second array structure are collinear, and the collinear position passes through the isolation region.

[0019] As an optional solution of the back contact solar cell provided by the application, the back contact solar cell has a cutting region, and the first array structure and the second array structure are collinear in the cutting region.

[0020] As an optional solution of the back contact solar cell provided by the application, the P region is provided with a first electrode, and the first array structure is arranged at an angle with the first electrode.

[0021] And / or, the N region is provided with a second electrode, and the second array structure is arranged at an angle with the second electrode.

[0022] As an optional solution of the back contact solar cell provided by the application, the angle between the first array structure and the first electrode is greater than 0° and less than or equal to 15° or greater than or equal to 90° and less than or equal to 105°.

[0023] And / or, the included angle between the second array structure and the second electrode is greater than 0° and less than or equal to 15° or greater than or equal to 90° and less than or equal to 105°.

[0024] As an optional solution of the back contact solar cell provided by the application, the P region is provided with a plurality of the first array structures, which are arranged in parallel or at an included angle with each other.

[0025] And / or, the N region is provided with a plurality of the second array structures, which are arranged in parallel or at an included angle with each other.

[0026] As an optional solution of the back contact solar cell provided by the application, the area of the first overlapping region is A1, the area of the orthographic projection of the first groove on the silicon substrate is B1, and the ratio of A1 to B1 is 15% to 90%.

[0027] And / or, the area of the second overlapping region is A2, the area of the orthographic projection of the second groove on the silicon substrate is B2, and the ratio of A2 to B2 is 15% to 90%.

[0028] As an optional solution of the back contact solar cell provided by the application, the distance between the two farthest points in the orthographic projection of the first groove on the silicon substrate is 5 μm to 40 μm.

[0029] And / or, the distance between the two farthest points in the orthographic projection of the second groove on the silicon substrate is 5 μm to 40 μm.

[0030] As an optional solution of the back contact solar cell provided by the application, the depth of the first groove is 0.05 μm to 2.5 μm.

[0031] And / or, the depth of the second groove is 0.05 μm to 2.5 μm.

[0032] As an optional solution of the back contact solar cell provided by the application, the orthographic projection of the first groove on the silicon substrate is N-sided or at least partially curved in outline.

[0033] And / or, the orthographic projection of the second groove on the silicon substrate is N-sided or at least partially curved in outline.

[0034] Wherein, N is a positive integer greater than or equal to 3.

[0035] In a second aspect, a cell assembly is provided, comprising the back contact solar cell as described above.

[0036] In a third aspect, a photovoltaic system is provided, comprising the cell assembly as described above.

[0037] Advantages of the present application:

[0038] The present application provides a back contact solar cell, a cell module and a photovoltaic system, a first groove is arranged in the P region of the non-light-receiving surface of the silicon substrate of the cell, and a second groove is arranged in the N region, the P region increases the edge and height difference due to the mutual overlap of the first grooves, thereby increasing the roughness of the P region, the N region increases the edge and height difference due to the mutual overlap of the second grooves, thereby increasing the roughness of the N region, the roughness of the entire non-light-receiving surface of the silicon substrate is uniformly increased by increasing the roughness of the P region and the N region, and the silicon substrate and the roller can be prevented from slipping when conveying through the roller structure, the problems of uneven running and stacking of the silicon wafer are eliminated, the production rhythm is prevented from being affected and the structure of the silicon substrate is prevented from being damaged, and the yield of the cell wafer is improved.

[0039] In addition, since the P region and the N region of the non-light-receiving surface are both provided with rough groove structures, when photons reach the non-light-receiving surface, diffuse reflection occurs instead of specular reflection, the probability of the photons returning to the silicon substrate and the propagation path length in the cell are increased, and the light absorption of the cell is improved. The rough groove structures arranged in the P region and the N region can increase the actual surface area of the non-light-receiving surface, the area of the PN junction is increased, thereby realizing more area separation and carrier (electron and hole) collection, shortening the average distance that the carriers need to diffuse to the PN junction region, reducing the recombination probability of the carriers, improving the carrier collection efficiency, and helping to improve the short-circuit current of the solar cell. Moreover, since the surface area of the non-light-receiving surface of the silicon substrate is uniformly increased, the surface area of the passivation contact structure arranged on the non-light-receiving surface in the subsequent process is increased, thereby increasing the contact area between the electrode and the passivation contact structure of the cell, enhancing the adhesion of the electrode, reducing the contact resistance, improving the collection efficiency of the electrode for the carriers, and improving the photoelectric conversion efficiency of the solar cell. Furthermore, since groove structures are made in the P region and the N region of the non-light-receiving surface, the optical and electrical properties of the entire non-light-receiving surface are uniformly and balancedly enhanced, and the collection ability for electrons and holes is improved, thereby avoiding the mismatching problem caused by the optimization of a single region and the non-optimization of another region. BRIEF DESCRIPTION OF DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the description of the embodiments of the present application will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art according to the contents of the embodiments of the present application and the drawings without creating any inventive labor.

[0041] Figure 1 is a schematic diagram of conveying a silicon wafer on a roller of a chain machine in the prior art;

[0042] Figure 2 is a first electron micrograph of the silicon substrate provided by the embodiment of the present application;

[0043] Figure 3 is a first electron micrograph of the P region of the silicon substrate provided by the embodiment of the present application;

[0044] Figure 4 is a schematic diagram of a first array structure of the P region of the silicon substrate provided by the embodiment of the present application;

[0045] Figure 5 is an electron micrograph of the N region of the silicon substrate provided by the embodiment of the present application;

[0046] Figure 6 is a schematic diagram of a second array structure of the N region of the silicon substrate provided by the embodiment of the present application;

[0047] Figure 7 is a schematic diagram of the transmission of the silicon substrate on the roller structure of the chain machine provided by the embodiment of the present application;

[0048] Figure 8 is a second electron micrograph of the silicon substrate provided by the embodiment of the present application;

[0049] Figure 9 is a second electron micrograph of the P region of the silicon substrate provided by the embodiment of the present application;

[0050] Figure 10 is an electron micrograph of the first groove of the P region provided by the embodiment of the present application;

[0051] Figure 11 is an electron micrograph of the second groove of the N region provided by the embodiment of the present application.

[0052] Figure 1 in which:

[0053] 1', silicon wafer; 2', roller.

[0054] Figures 2 to 11 in which:

[0055] 100, silicon substrate; 200, roller structure;

[0056] 1, P region; 2, N region; 3, isolation region; 4, cutting area; 5, first electrode; 6, second electrode;

[0057] 11, first groove; 12, first overlapping area; 10, first array structure;

[0058] 21, second groove; 22, second overlapping area; 23, third groove; 24, third overlapping area; 20, second array structure. DETAILED DESCRIPTION

[0059] The technical solutions of the present application will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0060] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the accompanying drawings can be arranged and designed in various different configurations.

[0061] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative labor are within the scope of protection of the present application.

[0062] It should be noted that: similar reference numerals and letters represent similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0063] In the description of the present application, it should be noted that the terms "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the present application is usually placed, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second", "third" and the like are only used for differentiation in description, and cannot be understood as indicating or implying relative importance. In the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0064] In the description of the present application, it should also be noted that, unless otherwise explicitly specified and limited, the terms "provided", "connected", "fixed" should be understood broadly, for example, can be fixedly connected, can be detachably connected, or integrally connected; can be mechanically connected, or electrically connected. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

[0065] In the present application, unless otherwise explicitly specified and limited, "on" or "under" of a first feature to a second feature can include that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, "on", "above" and "over" of a first feature to a second feature includes that the first feature is directly above and obliquely above the second feature, or only means that the first feature is higher than the second feature in horizontal height. "Under", "below" and "underneath" of a first feature to a second feature includes that the first feature is directly below and obliquely below the second feature, or only means that the first feature is lower than the second feature in horizontal height.

[0066] In the present application, the term "and / or", only describes the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which can represent the three cases of A alone, A and B together, and B alone. In addition, the character " / " in the present application generally represents that the front and rear associated objects are in an "or" relationship.

[0067] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference signs represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as a limitation of the present application.

[0068] The present embodiment provides a back contact solar cell, which comprises a silicon substrate 100. The silicon substrate 100 has a light receiving surface (front surface) and a non-light receiving surface (back surface) arranged oppositely, and for the back contact solar cell, the electrodes for collecting carriers are arranged on the non-light receiving surface, so that the light receiving surface has a larger area to receive light.

[0069] As shown in Figure 2 , the non-light receiving surface of the silicon substrate 100 has a P region 1 and an N region 2. In combination with Figure 3 and Figure 4 , the P region 1 is distributed with a plurality of first grooves 11, and at least part of the first grooves 11 overlap each other to form a first overlapping area 12. Referring to Figure 3 , the adjacent two first grooves 11 at the positions C and D marked in the figure increase the edge and height difference on the P region 1 of the non-light receiving surface after overlapping each other, so that the roughness of the P region 1 is increased. In combination with Figure 5 and Figure 6 , the N region 2 is distributed with a plurality of second grooves 21, and at least part of the second grooves 21 overlap each other to form a second overlapping area 22.

[0070] It can be understood that the first grooves 11 between adjacent ones can be spaced apart or can overlap with each other. In the P region 1 of the non-light-receiving surface, only a part of the first grooves 11 can overlap with each other, or all the first grooves 11 can overlap with adjacent ones. The second grooves 21 between adjacent ones can be spaced apart or can overlap with each other. In the N region 2 of the non-light-receiving surface, only a part of the second grooves 21 can overlap with each other, or all the second grooves 21 can overlap with adjacent ones.

[0071] The back contact solar cell provided by the embodiment is provided with the first grooves 11 in the P region 1 of the non-light-receiving surface of the silicon substrate 100 and the second grooves 21 in the N region 2. Since the first grooves 11 overlap with each other, the P region 1 can increase the edges and height differences, thereby increasing the roughness of the P region 1. Since the second grooves 21 overlap with each other, the N region 2 can increase the edges and height differences, thereby increasing the roughness of the N region 2. By increasing the roughness of the P region 1 and the N region 2, the roughness of the entire non-light-receiving surface of the silicon substrate 100 can be uniformly increased, as shown in FIG. 6. When the silicon substrate 100 is conveyed by the roller structure 200, the slipping between the silicon substrate 100 and the roller can be avoided, the silicon wafer can be prevented from being misaligned or stacked, the production rhythm can be prevented from being affected and the structure of the silicon substrate 100 can be prevented from being damaged, and the yield of the solar cell can be improved. Figure 7

[0072] In addition, since the P region 1 and the N region 2 of the non-light-receiving surface are both provided with the rough groove structure, when the photons reach the non-light-receiving surface, the diffuse reflection can occur instead of the specular reflection, the probability of the photons returning into the silicon substrate 100 and the propagation path length in the cell can be increased, and the light absorption of the cell can be improved. The rough groove structure provided in the P region 1 and the N region 2 can increase the actual surface area of the non-light-receiving surface, the area of the PN junction can be increased, thereby more area separation and carrier (electron and hole) collection can be achieved, the average distance of the carriers to be diffused to the PN junction region can be shortened, the recombination probability of the carriers can be reduced, the carrier collection efficiency can be improved, and the short-circuit current of the solar cell can be improved. Moreover, since the surface area of the non-light-receiving surface of the silicon substrate 100 is uniformly increased, the surface area of the passivation contact structure subsequently provided on the non-light-receiving surface can be improved, the contact area between the electrode and the passivation contact structure of the cell can be improved, the adhesion of the electrode can be enhanced, the contact resistance can be reduced, the carrier collection efficiency of the electrode can be improved, and the photoelectric conversion efficiency of the solar cell can be improved. Furthermore, since the groove structure is made in the P region 1 and the N region 2 of the non-light-receiving surface, the optical and electrical properties of the entire non-light-receiving surface can be uniformly and balancedly improved, and the collection ability of the electrons and holes can be improved, thereby avoiding the mismatching problem caused by the optimization of a single region.

[0073] As shown in FIG. 6, the first grooves 11 and the second grooves 21 can be arranged in a staggered manner. Figure 4 ​As shown, in the two adjacent first grooves 11 with overlap, the area of the first overlap region 12 formed is A1, the area of the orthographic projection of the first groove 11 on the silicon substrate 100 is B1, and the ratio of A1 to B1 is defined as the overlap rate of the adjacent first grooves 11, which is in the range of 15% to 90%. Limiting the overlap rate of the adjacent first grooves 11 to be in the range of 15% to 90% can on one hand prevent the length of the edge formed by the overlap of the grooves in the P area 1 from being too short to cause no obvious increase in roughness, so that the slipping phenomenon still exists between the silicon substrate 100 and the roller structure 200, and the problems of uneven film running and film stacking are not obviously improved, and on the other hand, can prevent the length of the edge formed by the overlap of the grooves in the P area 1 from being too long to cause excessive increase in roughness, thereby affecting the passivation effect of the non-light-receiving surface.

[0074] Exemplarily, the overlap rate of the adjacent first grooves 11 can be 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, and the like, but is not limited to the above listed values and ranges.

[0075] As shown, Figure 6 As shown, in the two adjacent second grooves 21 with overlap, the area of the second overlap region 22 formed is A2, the area of the orthographic projection of the second groove 21 on the silicon substrate 100 is B2, and the ratio of A2 to B2 is defined as the overlap rate of the adjacent second grooves 21, which is in the range of 15% to 90%. Limiting the overlap rate of the adjacent second grooves 21 to be in the range of 15% to 90% can on one hand prevent the length of the edge formed by the overlap of the grooves in the N area 2 from being too short to cause no obvious increase in roughness, so that the slipping phenomenon still exists between the silicon substrate 100 and the roller structure 200, and the problems of uneven film running and film stacking are not obviously improved, and on the other hand, can prevent the length of the edge formed by the overlap of the grooves in the N area 2 from being too long to cause excessive increase in roughness, thereby affecting the passivation effect of the non-light-receiving surface.

[0076] Exemplarily, the overlap rate of the adjacent second grooves 21 can be 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, and the like, but is not limited to the above listed values and ranges.

[0077] In some optional embodiments, the distance between the two farthest points in the orthographic projection of the first groove 11 on the silicon substrate 100 is 5 μm to 40 μm. This size limitation makes the size of the first groove 11 moderate, so that the P area 1 is distributed with a suitable density of the first grooves 11, avoiding that the number of the first grooves 11 is too small to cause no obvious increase in roughness, and avoiding that the number of the first grooves 11 is too large to cause excessive increase in roughness and affect the passivation effect.

[0078] Exemplarily, the distance between the two farthest points in the orthographic projection of the first groove 11 on the silicon substrate 100 can be 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, etc., but is not limited to the above listed values and value ranges.

[0079] In some optional embodiments, the distance between the two farthest points in the orthographic projection of the second groove 21 on the silicon substrate 100 is 5 μm to 40 μm. This size limitation makes the size of the second groove 21 moderate, so that the N region 2 is distributed with a proper density of the second groove 21, avoiding that too few second grooves 21 result in an insignificant increase in roughness, and avoiding that too many second grooves 21 result in too much increase in roughness and affect the passivation effect.

[0080] Exemplarily, the distance between the two farthest points in the orthographic projection of the second groove 21 on the silicon substrate 100 can be 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, etc., but is not limited to the above listed values and value ranges.

[0081] In some embodiments, the orthographic projection of the first groove 11 on the silicon substrate 100 and the orthographic projection of the second groove 21 on the silicon substrate 100 are both N-sided shapes, where N is a positive integer greater than or equal to 3. The N-sided first groove 11 and the N-sided second groove 21 have regular shapes, can form relatively flat edges to increase roughness, and can be formed in the P region 1 and the N region 2, respectively, by means of the same process (e.g., etching by etching liquid).

[0082] Exemplarily, referring to Figure 4 and Figure 6 , the orthographic projection of the first groove 11 on the silicon substrate 100 and the orthographic projection of the second groove 21 on the silicon substrate 100 are both quadrilaterals, i.e., N is 4. Of course, in other embodiments, they can also be triangles, pentagons, hexagons, etc., which are not listed one by one.

[0083] In other embodiments, the orthographic projection of the first groove 11 on the silicon substrate 100 and the orthographic projection of the second groove 21 on the silicon substrate 100 have at least partially curved outlines, such as the orthographic projections of both being circular, elliptical or other regular or irregular shapes containing curved outlines, which are not limited here.

[0084] In the embodiment, the orthographic projection of the first groove 11 on the silicon substrate 100 and the orthographic projection of the second groove 21 on the silicon substrate 100 are both quadrilaterals. The distance between the two most distant points in the orthographic projection of the first groove 11 on the silicon substrate 100 is the diagonal length of the first groove 11, and the distance between the two most distant points in the orthographic projection of the second groove 21 on the silicon substrate 100 is the diagonal length of the second groove 21. The diagonal lengths of the two are between 5 μm and 40 μm.

[0085] In some embodiments of the present application, as shown in Figure 5 and Figure 6 The surface of the second groove 21 is provided with at least one third groove 23. By forming the third groove 23 on the surface of the second groove 21, the number of edges formed on the surface of the second groove 21 can be increased, so that the surface roughness of the N region 2 is increased. That is, by providing the third groove 23 in the second groove 21, the roughness of the N region 2 can be greater than the roughness of the P region 1. By setting the roughness of the N region 2 to be greater than the roughness of the P region 1, the light will be scattered back into the cell no matter whether it reaches the P region 1 or the N region 2, the path length of the light in the cell is prolonged, the light absorption rate is significantly increased, the light trapping capability of the entire back surface of the cell is improved, and the photoelectric conversion efficiency is improved. Moreover, the entire back surface of the cell can be processed by the same process (such as wet etching or dry etching) to form the textured structure of the groove, which simplifies the manufacturing process and reduces the production complexity and cost.

[0086] It should be noted that although the roughness of the N region 2 is greater than the roughness of the P region 1, the roughness of the N region 2 should be limited within a range that does not affect the passivation effect.

[0087] It should be noted that the roughness can be measured by the number of edges formed in the N region 2 and the P region 1. The more the number of edges, the greater the roughness. Since the third groove 23 is provided in the second groove 21 in the N region 2, edges can be formed in the region where the second groove 21 is located, while the first groove 11 in the P region 1 does not contain small grooves. Therefore, the total number of edges in the N region 2 is greater than the total number of edges in the P region 1, so that the roughness of the N region is greater than the roughness of the P region 1.

[0088] It should be emphasized that in the embodiment, the sizes of the first groove 11 and the second groove 21 are approximately the same. If the second groove 21 does not contain the third groove 23, the roughness of the N region 2 and the P region 1 is almost the same.

[0089] The number of edges can be obtained by microstructure analysis technology. The microstructure of the silicon substrate can be photographed by a microscope, and the number of edges can be counted.

[0090] Furthermore, the surface of the second groove 21 is provided with a plurality of third grooves 23, and there are gaps between adjacent third grooves 23 or they overlap to form a third overlapping region 24. The overlapping third grooves 23 can increase the number of edges distributed in the second groove 21, so that more positions in the second groove 21 form a height difference, thereby increasing the surface roughness of region N 2.

[0091] like Figure 5 and Figure 6 As shown, the third groove 23 has a distinct boundary. Figure 5 The boundary of the third groove 23 in each second groove 21 can be clearly seen in the electron microscope image shown.

[0092] For example, the distance between the two farthest points of the third groove 23 in the orthographic projection on the silicon substrate 100 is 0.5 μm to 20 μm. This size limitation makes the size of the third groove 23 moderate, so that the third groove 23 is distributed in a suitable density within the second groove 21 of the N region 2, avoiding the situation where the number of third grooves 23 is too small, resulting in an insignificant increase in roughness, and avoiding the situation where the number of third grooves 23 is too large, resulting in an excessive increase in roughness and affecting the passivation effect.

[0093] For example, the distance between the two farthest points in the orthographic projection of the third groove 23 onto the silicon substrate 100 can be 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 5μm, 8μm, 10μm, 11μm, 15μm, 17μm, 18μm, 20μm, etc., but is not limited to the values ​​and ranges listed above.

[0094] In some embodiments, the number of third grooves 23 provided in a single second groove 21 is 4 to 30, which ensures that the number of edges in the second groove 21 can be increased to a certain extent, thereby increasing the roughness of the N region 2, and avoiding the problem that the roughness of the N region 2 is too large due to the excessive number of edges in the second groove 21, which would affect the passivation effect.

[0095] For example, the number of third grooves 23 provided in a single second groove 21 can be 4, 7, 8, 11, 14, 19, 22, 25, 28, 33, 37, 38, or 40. However, it is not limited to the specific numbers and ranges listed. Furthermore, the number of third grooves 23 in each second groove 21 can be the same or different, and the specific number can be odd or even; there is no strict limitation here.

[0096] In some embodiments, the third recess 23 has a projection on the silicon substrate 100 in the shape of a polygon with M sides, where M is a positive integer greater than or equal to 3. For example, the third recess 23 has a projection on the silicon substrate 100 in the shape of a quadrilateral, i.e. M is 4. The distance between the two most distant points in the projection of the third recess 23 on the silicon substrate 100 is the diagonal length of the third recess 23, which is in the range of 0.5 μm to 20 μm.

[0097] In other embodiments, the projection of the third recess 23 on the silicon substrate 100 has an outer contour that is at least partially curved, such as a circular, elliptical or other regular or irregular shape that contains a curved outer contour, which is not limited herein.

[0098] As shown in FIG. 1, at least some of the first recesses 11 are arranged in a linear array to form a first array structure 10. As shown in FIG. 2, at least some of the second recesses 21 are arranged in a linear array to form a second array structure 20. By forming a plurality of recesses in the P region 1 to form the first array structure 10 and a plurality of second recesses 21 in the N region 2 to form the second array structure 20, the roughness of the P region 1 and the N region 2 can be uniformly increased, and the topography of the non-light-receiving surface of the silicon substrate 100 can be more regular as a whole. Figure 3 Figure 5 As shown in FIG. 1, at least some of the first recesses 11 are arranged in a linear array to form a first array structure 10. As shown in FIG. 2, at least some of the second recesses 21 are arranged in a linear array to form a second array structure 20. By forming a plurality of recesses in the P region 1 to form the first array structure 10 and a plurality of second recesses 21 in the N region 2 to form the second array structure 20, the roughness of the P region 1 and the N region 2 can be uniformly increased, and the topography of the non-light-receiving surface of the silicon substrate 100 can be more regular as a whole.

[0099] In the first array structure 10, adjacent first recesses 11 can have a gap therebetween or can overlap each other to form a first overlapping region 12. Further, some or all of the first recesses 11 in the first array structure 10 overlap each other. In the second array structure 20, adjacent second recesses 21 can have a gap therebetween or can overlap each other to form a second overlapping region 22. Further, some or all of the second recesses 21 in the second array structure 20 overlap each other.

[0100] As shown in FIG. 1, at least some of the first recesses 11 are arranged in a linear array to form a first array structure 10. As shown in FIG. 2, at least some of the second recesses 21 are arranged in a linear array to form a second array structure 20. By forming a plurality of recesses in the P region 1 to form the first array structure 10 and a plurality of second recesses 21 in the N region 2 to form the second array structure 20, the roughness of the P region 1 and the N region 2 can be uniformly increased, and the topography of the non-light-receiving surface of the silicon substrate 100 can be more regular as a whole. Figure 3 Figure 5 As shown in FIG. 1, at least some of the first recesses 11 are arranged in a linear array to form a first array structure 10. As shown in FIG. 2, at least some of the second recesses 21 are arranged in a linear array to form a second array structure 20. By forming a plurality of recesses in the P region 1 to form the first array structure 10 and a plurality of second recesses 21 in the N region 2 to form the second array structure 20, the roughness of the P region 1 and the N region 2 can be uniformly increased, and the topography of the non-light-receiving surface of the silicon substrate 100 can be more regular as a whole.

[0101] Of course, the first array structure 10 can not extend through the P region 1, and the second array structure 20 can not extend through the N region 2.

[0102] ​​In some embodiments, region P1 is provided with a plurality of first array structures 10, which are arranged parallel to each other or at an angle. Among the plurality of first array structures 10 in region P1, they may all be parallel to each other, all be arranged at an angle, or some of the first array structures 10 may be parallel to each other and some of the first array structures 10 may be arranged at an angle.

[0103] In some embodiments, region N 2 is provided with a plurality of second array structures 20, which are arranged parallel to each other or at an angle. Among the plurality of second array structures 20 in region N 2, they may all be parallel to each other, all be arranged at an angle, or some of the second array structures 20 may be parallel to each other and some of the second array structures 20 may be arranged at an angle.

[0104] like Figure 2 As shown, the non-light-receiving surface of the silicon substrate 100 is provided with a plurality of P-regions 1 and a plurality of N-regions 2, which are alternately distributed in sequence, and an isolation region 3 is provided between the P-regions 1 and N-regions 2 to achieve automatic isolation between different regions. At least one first array structure 10 and at least one second array structure 20 are collinear, and their collinear positions pass through the isolation region 3. That is, the first array structure 10 and the second array structure 20 located on the same straight line penetrate through the P-regions 1 and N-regions 2, and the roughness of the non-light-receiving surface can be uniformly increased in the direction of extension of this straight line.

[0105] Specifically, the back-contact solar cell has a cutting region 4, and cutting along this region allows the cell to be slicing. The first array structure 10 and the second array structure 20 are collinear in the cutting region 4; that is, there is a row of grooves in the cutting region 4 that runs through the P-region 1 and the N-region 2, creating a weak line at this location. When slicing, stress preferentially spreads along this row of grooves, resulting in a neater and more controllable final breakage of the cell. Moreover, the collinear grooves in the cutting region 4 result in a larger surface area at the cut edge, providing sufficient light reflection and trapping capabilities, minimizing the loss of effective optical area caused by cutting, and helping to maintain a high short-circuit current.

[0106] like Figure 2 and Figure 8 As shown, a first electrode 5 is disposed in region P1, and a second electrode 6 is disposed in region N2. The first electrode 5 and the second electrode 6 have different polarities and are used to collect charge carriers. See also Figure 3 , Figure 5 as well as Figure 9The first array structure 10 is set at an angle to the first electrode 5. The second array structure 20 is set at an angle to the second electrode 6. After photons are absorbed on the front side of the battery, charge carriers (electrons and holes) are generated. The charge carriers diffuse laterally within the silicon substrate 100 and are collected at the positions of the first electrode 5 and the second electrode 6 on the non-light-receiving surface. The longer the diffusion path of the charge carriers, the greater the recombination probability. Since the first array structure 10 and the first electrode 5 are set at an angle, and the second array structure 20 and the second electrode 6 are set at an angle, the grooves of the two array structures can form a high-speed channel for charge carriers, allowing the charge carriers to first diffuse longitudinally into the nearest array structure and then be transported to the electrode, shortening the diffusion path of the charge carriers and reducing the recombination probability.

[0107] In some embodiments, the angle α between the first array structure 10 and the first electrode 5 is greater than 0° and less than or equal to 15°, and the angle β between the second array structure 20 and the second electrode 6 is greater than 0° and less than or equal to 15°. This limitation of the angle range allows the first array structure 10 and the second array structure 20 to extend further, thereby forming more edges and height difference positions in their extension direction, which helps to increase the roughness of the entire non-light-receiving surface.

[0108] In other embodiments, the angle α between the first array structure 10 and the first electrode 5 is greater than or equal to 90° and less than or equal to 105°, and the angle β between the second array structure 20 and the second electrode 6 is greater than or equal to 90° and less than or equal to 105°. This limitation of the angle range allows the first array structure 10 and the second array structure 20 to greatly shorten the carrier diffusion path and significantly reduce the carrier recombination probability.

[0109] like Figure 10 As shown, the depth h1 of the first groove 11 is 0.05μm to 2.5μm. For the overlapping first grooves 11, the depth h1 is the height difference formed by the overlap. The height difference is limited to the range of 0.05μm to 2.5μm, so that it is not too small and the increase in roughness is not obvious, nor too large and the non-light-receiving surface is too rough and thus affects the passivation effect.

[0110] For example, the depth h1 of the first groove 11 is 0.05μm, 0.1μm, 0.15μm, 0.17μm, 0.2μm, 0.4μm, 0.5μm, 0.8μm, 1μm, 1.2μm, 1.5μm, 1.8μm, 1.9μm, 2μm, 2.1μm, 2.2μm, 2.5μm, etc., but is not limited to the listed values ​​and ranges.

[0111] like Figure 11As shown, the depth h2 of the second groove 21 is 0.05 μm to 2.5 μm. For the second grooves 21 overlapping with each other, the depth h2 is the height difference formed by the overlapping, which is limited in the range of 0.05 μm to 2.5 μm, so as not to be too small to cause the roughness to increase unobviously, or too large to cause the non-light-receiving surface to be too rough and affect the passivation effect.

[0112] Exemplarily, the depth h2 of the second groove 21 is 0.05 μm, 0.1 μm, 0.15 μm, 0.17 μm, 0.2 μm, 0.4 μm, 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.8 μm, 1.9 μm, 2 μm, 2.1 μm, 2.2 μm, 2.5 μm, etc., but is not limited to the listed values and ranges.

[0113] The embodiment also provides a battery assembly comprising the back contact solar cell as described above. Since the back contact solar cell has a high yield and a high photoelectric conversion efficiency, the quality of the battery assembly can be improved, the production cost can be reduced, and the battery assembly has a high photoelectric conversion efficiency. It should be noted that the battery assembly has the same or similar beneficial effects as the back contact solar cell described above, and the relevant parts between the two can be referred to each other. In order to avoid repetition, it will not be described here.

[0114] The embodiment also provides a photovoltaic system comprising at least one battery assembly as described above. Since the photovoltaic system comprises the battery assembly with a high yield and a high photoelectric conversion efficiency, the power generation efficiency can be improved, and the construction cost can be reduced.

[0115] The photovoltaic system can be applied in a photovoltaic power station, such as a ground power station, a roof power station, a water surface power station, etc., or can be applied in a device or apparatus using solar energy to generate electricity, such as a user solar power source, a solar street lamp, a solar car, a solar building, etc. Of course, it can be understood that the application scenarios of the photovoltaic system are not limited to this, that is, the photovoltaic system can be applied in all fields requiring solar energy to generate electricity. Taking a photovoltaic power generation system network as an example, the photovoltaic system can comprise a photovoltaic array, a combiner box, and an inverter, the photovoltaic array can be an array combination of a plurality of battery assemblies, for example, a plurality of battery assemblies can form a plurality of photovoltaic arrays, the photovoltaic arrays are connected to the combiner box, the combiner box can combine the currents generated by the photovoltaic arrays, the combined current flows through the inverter to convert into an alternating current required by a power grid, and then is connected to a power network to realize solar power supply.

[0116] Obviously, the above embodiments of the present application are merely exemplary but not intended to limit the embodiments of the present application. Various obvious changes, re-adjustments and substitutions can be made by those skilled in the art without departing from the scope of the present application. It is not necessary or possible to enumerate all the embodiments. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the claims of the present application.

Claims

1. A back-contact solar cell, characterized in that, Includes a silicon substrate (100), the silicon substrate (100) having a light-receiving surface and a non-light-receiving surface disposed opposite to each other, the non-light-receiving surface having a P region (1) and an N region (2); The P region (1) is provided with a plurality of first grooves (11), and at least some of the first grooves (11) overlap each other to form a first overlapping region (12). The N region (2) is provided with a number of second grooves (21), and at least some of the second grooves (21) overlap each other to form a second overlapping region (22). The surface of the second groove (21) is provided with a plurality of third grooves (23), which can form an edge in the area where the second groove (21) is located; There is a gap between adjacent third grooves (23) or they overlap to form a third overlapping area (24); The distance between the two furthest points of the third groove (23) in the orthographic projection on the silicon substrate (100) is 0.5μm to 20μm.

2. The back-contact solar cell according to claim 1, characterized in that, The number of the third grooves (23) provided in a single second groove (21) is 4 to 30.

3. The back-contact solar cell according to claim 1, characterized in that, At least a portion of the first grooves (11) are arranged in a linear array to form a first array structure (10); And / or, at least a portion of the second groove (21) is distributed in a linear array to form a second array structure (20).

4. The back-contact solar cell according to claim 3, characterized in that, At least one of the first array structures (10) penetrates the P region (1); And / or, at least one of the second array structures (20) extends through the N region (2).

5. The back-contact solar cell according to claim 3, characterized in that, An isolation zone (3) is provided between the P region (1) and the N region (2), at least one of the first array structures (10) and at least one of the second array structures (20) are collinear, and the collinear positions pass through the isolation zone (3).

6. The back-contact solar cell according to claim 5, characterized in that, The back-contact solar cell has a cut area (4), and the first array structure (10) and the second array structure (20) are collinear in the cut area (4).

7. The back-contact solar cell according to claim 3, characterized in that, The P region (1) is provided with a first electrode (5), and the first array structure (10) is arranged at an angle to the first electrode (5); And / or, the N region (2) is provided with a second electrode (6), and the second array structure (20) is arranged at an angle to the second electrode (6).

8. The back-contact solar cell according to claim 7, characterized in that, The angle between the first array structure (10) and the first electrode (5) is greater than 0° and less than or equal to 15° or greater than or equal to 90° and less than or equal to 105°; And / or, the angle between the second array structure (20) and the second electrode (6) is greater than 0° and less than or equal to 15° or greater than or equal to 90° and less than or equal to 105°.

9. The back-contact solar cell according to claim 3, characterized in that, The P region (1) is provided with a plurality of the first array structures (10), which are arranged parallel to each other or at an angle. And / or, the N region (2) is provided with a plurality of the second array structures (20), which are parallel to each other or at an angle to each other.

10. The back-contact solar cell according to any one of claims 1-9, characterized in that, The area of ​​the first overlapping region (12) is A1, and the orthographic projection area of ​​the first groove (11) on the silicon substrate (100) is B1. The ratio of A1 to B1 is 15% to 90%. And / or, the area of ​​the second overlapping region (22) is A2, the orthographic projection area of ​​the second groove (21) on the silicon substrate (100) is B2, and the ratio of A2 to B2 is 15% to 90%.

11. The back-contact solar cell according to any one of claims 1-9, characterized in that, The distance between the two farthest points of the first groove (11) in the orthographic projection on the silicon substrate (100) is 5 μm to 40 μm; And / or, the distance between the two furthest points of the second groove (21) in the orthographic projection on the silicon substrate (100) is 5 μm to 40 μm.

12. The back-contact solar cell according to any one of claims 1-9, characterized in that, The depth of the first groove (11) is 0.05μm to 2.5μm; And / or, the depth of the second groove (21) is 0.05μm to 2.5μm.

13. The back-contact solar cell according to any one of claims 1-9, characterized in that, The orthographic projection of the first groove (11) onto the silicon substrate (100) is an N-sided shape or the outer contour is at least partially curved; And / or, the orthographic projection of the second groove (21) onto the silicon substrate (100) is N-sided or the outer contour is at least partially curved; Where N is a positive integer greater than or equal to 3.

14. A battery assembly, characterized in that, Including the back-contact solar cell as described in any one of claims 1-13.

15. A photovoltaic system, characterized in that, Includes the battery assembly as described in claim 14.

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