Solar cells and solar modules

Abstract

This invention provides solar cells and solar modules that improve the photoelectric conversion efficiency of solar cells by balancing the light confinement effect and passivation performance of the silicon substrate's side surface. [Solution] The silicon substrate 10 includes opposing first surfaces 11 and second surfaces 12, and a side surface 13 connecting the first surface 11 and the second surface 12, wherein at least one side surface 13 of the silicon substrate 10 includes a plurality of first texture regions A11 and second texture regions A12. Each of the first texture regions A11 includes a plurality of first pyramidal structures, and the second texture region A12 includes a second pyramidal structure. The structural dimensions of the second pyramidal structures are larger than the structural dimensions of the first pyramidal structures, and the second texture regions A12 are located between adjacent first texture regions A11. A passivation layer (not shown) covers the first texture regions A11 and second texture regions A12 on at least one side surface 13.

Description

Technical Field

[0001] This application relates to the technical field of photovoltaic power generation, and specifically to solar cells and solar modules.

Background Art

[0002] Solar cells can convert light energy into electrical energy, which is of great significance for energy development and environmental protection. Batteries made of single-crystalline silicon occupy a large share in the photovoltaic power generation industry because they have advantages such as high conversion efficiency and mature technology. To reduce production costs, thinning of silicon wafers has become an inevitable trend. However, in thin silicon wafers, the light absorption rate of the substrate decreases and the number of photo-generated carriers decreases. As the thinning of silicon wafers progresses, how to further improve the light absorption of battery cells is an urgent issue to be solved. In the prior art, by providing a pyramidal texture surface structure on the side surface of a solar cell, the light confinement effect on the side surface is enhanced and the light absorption of the solar cell is increased. However, such a structure affects the coating quality of the passivation layer on the side surface of the solar cell, reduces the passivation performance of the solar cell, and affects the efficiency of the solar cell.

Summary of the Invention

Problems to be Solved by the Invention

[0003] The object of this application is to provide a solar cell and a solar module that control the form of the side surface of the solar cell to balance the light confinement effect and the passivation performance of the side surface and improve the photoelectric conversion efficiency of the solar cell.

Means for Solving the Problems

[0004] To achieve the above objective, in a first embodiment, the present application provides a solar cell. The solar cell includes a silicon substrate and a passivation layer, the silicon substrate including opposing first and second surfaces and a plurality of sides connecting the first and second surfaces. At least one side includes a plurality of first texture regions and a plurality of second texture regions, each of the first texture regions includes a plurality of first pyramidal structures, and the second texture regions include a plurality of second pyramidal structures. The structural dimensions of the second pyramidal structures are greater than the structural dimensions of the first pyramidal structures. The second texture regions are located between adjacent first texture regions. The passivation layer covers the first and second texture regions on at least one of the sides.

[0005] In some embodiments, the second texture region extends between the first texture regions in one or more forms, such as linear, polylinear, or curved.

[0006] In some embodiments, the stretching direction of the second texture region is not parallel to the thickness direction of the solar cell, and / or the stretching directions of at least two second texture regions are set to be parallel.

[0007] In some embodiments, the second texture region includes a prism-like structure, and the length range of the prism-like structure is between 200 nm and 6 μm.

[0008] In some embodiments, the structural dimensions of the first pyramidal structure range from 0.05 μm to 2 μm.

[0009] In some examples, the structural dimensions of the second pyramidal structure range from 2 μm to 6 μm.

[0010] In some embodiments, the side surface includes a first region, the first region is connected to a first surface, both the first texture region and the second texture region are provided in the first region, and the width of the first region is between 20% and 100% of the width of the side surface.

[0011] In some embodiments, the side surface includes a first region and a second region, both of which are provided in the first region, the second region is connected to the second surface side, and the second region includes a plurality of base structures.

[0012] In some embodiments, the boundary line between the first and second regions is curved, and a depression is provided near the boundary line in the second region.

[0013] In some embodiments, the width of the recessed region in the thickness direction of the silicon substrate is 0% to 60% of the width of the second region.

[0014] In some embodiments, the shape of the depression includes one or more of the following: inverted pyramidal, inverted hemispherical, or stepped, and / or the cross-sectional area of ​​the depression gradually increases along the direction perpendicular to the side.

[0015] In some embodiments, the diameter of the cross-section of the depression on the side surface is 0.1 μm or more and 5 μm or less, and / or the depth of the depression is 0.05 μm or more and 2 μm or less.

[0016] In some embodiments, the passivation layer includes, in the direction away from the silicon substrate, an aluminum oxide layer and a silicon nitride layer provided in sequence.

[0017] In the solar cell described above, the first pyramidal structure in the first texture region enhances the light confinement effect on the sides of the solar cell, thereby improving the light utilization rate of the solar cell. While the first pyramidal structure with small structural dimensions increases the surface roughness of the sides, which is unfavorable for the coating quality of the subsequent passivation layer on the sides of the solar cell, in the embodiment of this application, a second pyramidal structure is further designed to be formed in the second texture region. The larger structural dimensions of the second pyramidal structure provide a larger surface area than the first pyramidal structure, providing a larger coating area for the subsequent coating and improving the coating quality. Therefore, a mixed structure of multiple first pyramidal structures and multiple second pyramidal structures can better balance the passivation effect and light confinement effect on the sides of the solar cell, thereby improving the photoelectric conversion efficiency of the solar cell.

[0018] In a second aspect, this application provides a solar module, which includes a plurality of solar cells electrically connected to one another, the solar cells being the solar cells provided in the first aspect of this application. [Brief explanation of the drawing]

[0019] [Figure 1] This is a schematic diagram illustrating the distribution of the texture structure on the side surface of a solar cell according to one embodiment of this application. [Figure 2] This is a schematic diagram of the structure of a solar cell according to one embodiment of this application. [Figure 3] Figure 2 is a schematic diagram of the structure of the silicon substrate in a solar cell. [Figure 4] Figure 2 is a schematic diagram illustrating the distribution of the texture structure of the silicon substrate in the solar cell. [Figure 5] This is a scanning electron microscope image of the side surface of a solar cell according to one embodiment of this application. [Figure 6] This is another scanning electron microscope image of the side of a solar cell according to one embodiment of this application. [Figure 7] This is a scanning electron microscope image of the first surface of a solar cell according to one embodiment of this application. [Figure 8]It is a schematic diagram of the structural dimensions of the pyramid structure and the structural dimensions of the base structure in the solar cell of one embodiment of the present application.

Embodiments for Carrying Out the Invention

[0020] In order to make the technical problems, technical solutions, and beneficial effects to be solved by the present application clearer and easier to understand, the present application will be described in more detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only for interpreting the present invention and not for limiting the present application.

[0021] Hereinafter, embodiments of the present application will be described in detail. The embodiments are shown in the drawings, where the same or similar reference numerals represent the same or similar elements or elements having the same or similar functions from beginning to end. The embodiments described below with reference to the drawings are exemplary and are only for interpreting the embodiments of the present application and should not be understood as limiting the present application.

[0022] In the description of the embodiments of the present application, the orientation or positional relationship indicated by terms such as "center", "vertical direction", "horizontal direction", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. is based on the drawings and is only for the convenience of explaining and simplifying the description of the embodiments of the present application. It does not indicate or imply that the described device or element must have a specific orientation and be configured and operate in a specific orientation, so it should not be understood as limiting the present application.

[0023] In the description of the embodiments of the present application, the terms "first" and "second" are only for the purpose of explanation and should not be understood as indicating or suggesting relative importance or implicitly indicating the number of the indicated technical features. Thus, the features limited by "first" and "second" may explicitly or implicitly include one or more of the above features.

[0024] In the description of the embodiments of this application, unless otherwise specified, "multiple" means two or more.

[0025] In the description of the embodiments of this application, unless otherwise specified, the terms “attachment,” “connection,” and “connection” should be understood in a broad sense, for example, a fixed connection, a removable or integral connection, a mechanical connection, an electrical connection or a connection that can communicate with each other, a direct connection, an indirect connection via an intermediate mediator, or an internal communication between two elements or an interaction relationship between two elements.

[0026] A person skilled in the art will be able to understand the specific meaning of the above terms in this application, depending on the specific circumstances.

[0027] Refer to Figures 1 and 2. The solar cell 100 includes a silicon substrate 10, and the silicon substrate 10 may be an N-type silicon substrate or a P-type silicon substrate.

[0028] Specifically, the silicon substrate 10 includes opposing first surfaces 11 and second surfaces 12, and a side surface 13 connecting the first surface 11 and the second surface 12.

[0029] The battery type of solar cell 100 is not limited to those shown in Figure 2. Specifically, the battery type of solar cell 100 may be a tunnel oxide passivated contact back contact (TBC) battery, a tunnel oxide passivated contact (TOPCon) battery, or a hybrid back contact battery. Here, a hybrid back contact battery refers to a back contact battery in which the N region and P region correspond to a tunnel passivated contact structure and a heterojunction contact structure, respectively, or a back contact battery in which the N region and P region correspond to a tunnel passivated contact structure and a passivation emitter structure, respectively. The silicon substrate of solar cell 100 may be an N-type raw silicon wafer or a P-type raw silicon wafer.

[0030] The structure of the silicon substrate 10 will be described in detail below. Figure 3 is a schematic diagram of the structure of the silicon substrate 10 of the solar cell 100 in Figure 2. As shown in Figure 3, the silicon substrate 10 has a roughly rectangular parallelepiped shape. The side surface 13 includes a first side surface 131, a second side surface 132, a third side surface 133, and a fourth side surface 134 that are connected in sequence. The first side surface 131 and the third side surface 133 are provided opposite each other. The second side surface 132 and the fourth side surface 134 are provided opposite each other.

[0031] Figure 4 is a schematic diagram of the texture structure distribution of the silicon substrate 10 of the solar cell 100 in Figure 2. Figure 5 is a scanning electron microscope image of the side surface 13 of the solar cell 100 according to one embodiment of this application.

[0032] Referring to Figures 1 to 5, a plurality of pyramidal structures T11 are provided on at least one side surface 13 of the silicon substrate 10. Specifically, the plurality of pyramidal structures T11 include a plurality of first pyramidal structures and a plurality of second pyramidal structures. More specifically, the distribution of the plurality of pyramidal structures T11 causes at least one side surface 13 of the silicon substrate 10 to include a plurality of first texture regions A11 and a plurality of second texture regions A12. Each of the first texture regions A11 includes a plurality of first pyramidal structures. The second texture regions A12 include a second pyramidal structure. The structural dimensions of the second pyramidal structures are larger than the structural dimensions of the first pyramidal structures. The second texture regions A12 are located between adjacent first texture regions A11. The solar cell 100 includes a passivation layer (not shown), which covers the first texture regions A11 and the second texture regions A12 on at least one side surface 13.

[0033] It should be explained that, in the embodiments of this application, the structural dimensions of the first pyramid structure refer to one of the lengths of the base, width, or diagonal of the first pyramid structure, and / or the height of the first pyramid structure. The structural dimensions of the second pyramid structure refer to one of the lengths of the base, width, or diagonal of the second pyramid structure, and / or the height of the second pyramid structure.

[0034] In related technologies, a base texture structure is formed on the side surface of the silicon substrate of a solar cell. This base texture structure can improve the coating quality of the passivation layer on the side surface, but it increases the light reflectivity, reducing the light absorption performance of the solar cell. Alternatively, a pyramidal texture surface structure of a single dimensional range is formed on the side surface of the silicon substrate of a solar cell. This texture surface structure can improve the light confinement effect on the side surface of the silicon substrate, but it increases the roughness of the side surface of the silicon substrate, which is detrimental to improving the passivation performance on the side surface of the silicon substrate.

[0035] In contrast, in the embodiment of this application, the side surface 13 of the solar cell 100 includes a plurality of pyramidal structures T11. The first pyramidal structure in the first textured region A11 enhances the light confinement effect on the side surface of the solar cell 100 and can improve the light utilization rate of the solar cell 100. Furthermore, in the embodiment of this application, a second pyramidal structure is designed to be formed in the second textured region A12. The larger structural dimensions of the second pyramidal structure provide a larger surface area than the first pyramidal structure, providing a larger coating area for the subsequent passivation layer coating, improving the coating quality of the passivation layer and enhancing the passivation performance of the side surface 13. For this reason, compared to base textured structures or pyramidal structures with a single structural dimension in related technologies, the mixed structure of a plurality of first pyramidal structures and a plurality of second pyramidal structures can better balance the passivation effect and light confinement effect on the side surface of the solar cell and can improve the photoelectric conversion efficiency of the solar cell.

[0036] In some embodiments, the passivation layer further covers areas on the side surface 13 other than the first texture region A11 and the second texture region A12.

[0037] In some embodiments, referring to Figure 2, the solar cell 100 further includes a first dielectric layer 20, a first doped conductive layer 30, a second dielectric layer 40, and a second doped conductive layer 50.

[0038] The first dielectric layer 20 and the second dielectric layer 40 are alternately provided on the second surface 12. The first doped conductive layer 30 is located on the opposite side of the first dielectric layer 20 from the silicon substrate 10. The second doped conductive layer 50 is located on the opposite side of the second dielectric layer 40 from the silicon substrate 10.

[0039] The first doped conductive layer 30 and the second doped conductive layer 50 have opposite conductivity types. The conductivity type of the first doped conductive layer 30 may be N-type, and the conductivity type of the second doped conductive layer 50 may be P-type. Alternatively, the conductivity type of the first doped conductive layer 30 may be P-type, and the conductivity type of the second doped conductive layer 50 may be N-type.

[0040] Space regions are formed between the first dielectric layer 20 and the second dielectric layer 40, and between the first doped conductive layer 30 and the second doped conductive layer 50, thereby electrically isolating the first doped conductive layer 30 and the second doped conductive layer 50. It should be noted that, in practical situations, space regions can be placed to achieve electrical isolation, but other methods may be employed without placing space regions if electrical isolation between film layers or regions of different doping types can be achieved.

[0041] The materials for the first dielectric layer 20 and the second dielectric layer 40 may be, but are not limited to, materials such as silicon oxide, aluminum oxide, titanium oxide, or intrinsic amorphous silicon. The materials for the first doped conductive layer 30 and the second doped conductive layer 50 may be, but are not limited to, materials such as doped polycrystalline silicon or doped amorphous silicon.

[0042] The passivation layer covers at least one side 13 as well as the first surface 11 and / or the second surface 12. Specifically, the passivation layer covers at least one side 13 and the first surface 11 of the solar cell 100, or the passivation layer covers at least one side 13 and the second surface 12 of the solar cell 100, or the passivation layer covers at least one side 13, the first surface 11 and the second surface 12 of the solar cell 100. If the passivation layer covers the second surface 12, the passivation layer covers the side of the first doped conductive layer 30 opposite to the silicon substrate 10 and the side of the second doped conductive layer 50 opposite to the silicon substrate 10.

[0043] The passivation layer material may be one or more of the following materials: aluminum oxide, silicon nitride, silicon oxynitride, etc., but is not limited to these. It is used to passivate the surface of the silicon substrate 10 or the functional layer, and to reduce or remove reflected light on the surface of the solar cell 100, thereby improving the utilization rate of sunlight by the solar cell 100 and improving the photoelectric conversion efficiency.

[0044] In some embodiments, the passivation layer includes a sequentially arranged aluminum oxide layer and a silicon nitride layer. The thickness range of the aluminum oxide layer is 4 nm to 10 nm (for example, 4 nm to 6 nm, 6 nm to 8 nm, 8 nm to 10 nm, etc.). The silicon nitride layer may be a single layer or a multilayer structure with different refractive indices, and the thickness range of the silicon nitride layer is 50 nm to 100 nm (for example, 50 nm to 60 nm, 60 nm to 70 nm, 70 nm to 80 nm, 80 nm to 90 nm, 90 nm to 100 nm, etc.).

[0045] The passivation layer reduces the number of recombination centers on the surface of the silicon substrate or other film layers through field passivation or chemical passivation, thereby reducing carrier recombination phenomena on the battery surface and improving battery efficiency. Furthermore, the outermost passivation layer can reduce sunlight reflection and enhance the battery's light absorption capacity. For example, the aluminum oxide layer saturates unbonded sites on the surface of side 13, reducing the interfacial state density and passivating the side. The silicon nitride layer protects the aluminum oxide layer, enables internal reflection, and can improve the light utilization rate of the solar cell.

[0046] In some embodiments, the thickness of the silicon nitride layer on side surface 13 is greater than the thickness of the silicon nitride layer on the first surface 11 or the second surface 12. In comparison, side surface 13 has a much smaller area than the first surface 11 or the second surface 12, and the coating quality of the passivation layer is not as good as on the first surface 11 or the second surface 12. Therefore, a thicker silicon nitride layer can maximize the continuity of the silicon nitride coating covering the side surface, providing protection and passivation effects to the aluminum oxide layer and side surface 13, as well as light reflection.

[0047] In some embodiments, the second texture region A12 extends between the first texture regions A11 in one or more forms, such as linearly, polylinearly, and / or curvedly. Furthermore, the extension direction of the second texture region A12 is not parallel to the thickness direction of the solar cell 100, and / or the extension directions of at least two second texture regions A12 are set to be parallel.

[0048] As described above, this contributes to improving the regularity of the morphological changes on the sides of the solar cell 100, further improving the uniformity of the film layer formed based on the sides of the solar cell 100, and thereby improving the passivation effect on the sides of the solar cell 100.

[0049] Specifically, side surface 13 has a first region A1 connected to the first surface 11. Both the first texture region A11 and the second texture region A12 are provided in the first region A1. The structural dimensions of the first pyramidal structure of the pyramidal structure T11 are in the range of 0.05 μm to 2 μm. The structural dimensions of the second pyramidal structure of the pyramidal structure T11 are in the range of 2 μm to 6 μm.

[0050] For example, the dimensional range of the base of the first pyramidal structure and / or the dimensional range of the height of the first pyramidal structure in pyramidal structure T11 is 0.05 μm or more and 2 μm or less (for example, 0.05 μm or more and 0.1 μm or less, 0.1 μm or more and 0.5 μm or less, 0.5 μm or more and 1.1 μm or less, 1.1 μm or more and 1.3 μm or less, 1.3 μm or more and 1.5 μm or less, 1.5 μm or more and 1.8 μm or less, 1.8 μm or more and 2 μm or less, etc.). The dimensional range of the base of the second pyramidal structure and / or the dimensional range of the height of the second pyramidal structure in pyramidal structure T11 is 2 μm or more and 6 μm or less (2 μm or more and 2.3 μm or less, 2.3 μm or more and 2.8 μm or less, 2.8 μm or more and 3.3 μm or less, 3.3 μm or more and 4 μm or less, 4 μm or more and 5 μm or less, 5 μm or more and 6 μm or less, etc.).

[0051] The embodiments of this application will be described in more detail below with reference to Figure 5.

[0052] As shown in Figure 5, the second texture region A12 extends in a broken line between the first texture regions A11. Furthermore, the extension direction of the second texture region A12 is not parallel to the thickness direction of the solar cell 100.

[0053] It should be explained that Figure 5 shows two second texture regions A12 with solid lines, and only a portion of the second texture region A12 is shown in Figure 5. In actual applications, the number of second texture regions A12 on side 13 includes, but is not limited to, the number of second texture regions A12 shown with black lines, and the size and extension direction of the second texture region A12 are not limited to the shape of the second texture region A12 shown with solid lines.

[0054] The angle between the stretching direction of the second texture region A12 and the thickness direction D1 of the solar cell 100 is calculated using the same rule and refers to the angle between the stretching direction of the second texture region A12 and the thickness direction D1 of the solar cell 100 in the counterclockwise (or clockwise) direction.

[0055] In some embodiments, the orthographic projections of the second pyramidal structure on side 13 overlap.

[0056] Furthermore, the second texture region A12 further includes multiple prism-like structures T12 (as shown by the dotted elliptical region in Figure 5). Compared to a pyramidal texture surface structure, the prism-like structures T12 can provide a flatter surface than the first pyramidal structure, and the prism-like structures T12 have a larger surface area, providing a larger deposition area for the subsequent passivation layer deposition. Therefore, the prism-like structures T12 can contribute to further improvement of the quality of the subsequent coating. For this reason, compared to a single texture surface structure or base structure in related technologies, the mixed structure of multiple first pyramidal structures, multiple second pyramidal structures, and multiple prism-like structures T12 can better balance the passivation effect and light confinement effect on the side surface 13 of the solar cell 100.

[0057] In some examples, the length range of the prism-like structure T12 is 200 nm to 6 μm (for example, 200 nm to 500 nm, 500 nm to 1 μm, 1 μm to 3 μm, 3 μm to 5 μm, 5 μm to 6 μm, etc.).

[0058] It should be explained that the length of the prism-like structure T12 refers to the distance from the lowest end to the highest end of the prism-like structure T12 in the direction of its inclination.

[0059] In some embodiments, some prism-like structures T12 include a prismatic base and a roughly pyramidal upper section connected to the base. Some prism-like structures T12 are roughly prismatic overall.

[0060] Side 13 further includes the second region A2. The second region A2 is connected to the side of the first region A1 that is closer to the second surface 12.

[0061] Figure 6 is another scanning electron microscope image of a side view 13 of a solar cell 100 according to one embodiment of the present application. As shown in Figure 6, the second region A2 includes a plurality of base structures T13.

[0062] The second region A2, which has multiple base structures T13, contributes to increasing the specific surface area of ​​the side surface of the solar cell 100, thereby increasing the specific surface area of ​​the subsequent coating film layer and improving the passivation effect on the side surface of the solar cell 100 by the passivation layer. Furthermore, the passivation performance after coating the base structure T13 of the second region A2 becomes better, and the passivation performance in the part close to the second surface 12 becomes better, reducing the possibility of carrier recombination at the edge of the solar cell 100 and contributing to an improvement in the performance of the solar cell 100.

[0063] By combining this with the process, the problem of excessive etching of the second surface 12 can be improved, and in the solar cell 100 of the embodiment of this application, by providing a second region A2 on the side surface, the passivation performance of the solar cell 100 can be improved while reducing excessive etching of the functional layer of the second surface by the etching solution.

[0064] In some embodiments, the base structure may be a recessed structure on the surface of the side 13, and the shape of its bottom or projection of the opening may be rectangular, rhombic, parallelogram, substantially rectangular, substantially rhombic, or substantially parallelogram. The shape of the base structure T13 includes one of a square or substantially square.

[0065] For example, the lateral dimension of the base structure T13 is in the range of 10 μm to 30 μm (for example, 10 μm to 12 μm, 12 μm to 13 μm, 13 μm to 14.5 μm, 14.5 μm to 15 μm, 15 μm to 20 μm, 20 μm to 25 μm, 25 μm to 28 μm, 28 μm to 30 μm, etc.). Specifically, the lateral dimension of the base structure T13 is the maximum distance at the base bottom surface of the base structure T13.

[0066] For example, the vertical height range of the base of the base structure T13 is 0.01 μm or more and 8 μm or less (for example, 0.01 μm or more and 0.05 μm or less, 0.05 μm or more and 0.1 μm or less, 0.1 μm or more and 0.4 μm or less, 0.4 μm or more and 0.5 μm or less, 0.5 μm or more and 0.7 μm or less, 0.7 μm or more and 1 μm or less, 1 μm or more and 1.3 μm or less, 1.3 μm or more and 1.5 μm or less, 1.5 μm or more and 1.8 μm or less, 1.8 μm or more and 2.3 μm or less, 2.3 μm or more and 2.8 μm or less, 2.8 μm or more and 3.3 μm or less, 3.3 μm or more and 4 μm or less, 4 μm or more and 5 μm or less, 5 μm or more and 6 μm or less, 6 μm or more and 7 μm or less, 7 μm or more and 8 μm or less, etc.).

[0067] In some embodiments, the base structure T13 may not be fully visible in the second region A2.

[0068] In some embodiments, the boundary line between the first region A1 and the second region A2 is curved, a depression R is provided near the boundary line in the second region A2, and in the thickness direction of the silicon substrate 10, the width of the region where the depression R is provided is 0% to 60% of the width of the second region A2 (for example, 0% to 10%, 10% to 20%, 20% to 30%, 30% to 40%, 40% to 50%, 50% to 60%, etc.).

[0069] In some embodiments, the shape of the recess R includes one or more of the following: inverted pyramidal, inverted hemispherical, and stepped.

[0070] In some embodiments, the cross-sectional area of ​​the recess R gradually increases along the direction perpendicular to the side surface 13.

[0071] In some embodiments, the diameter of the cross-section of the recess R on the side surface 13 is 0.1 μm or more and 5 μm or less (for example, 0.1 μm or more and 1 μm or less, 1 μm or more and 1.5 μm or less, 1.5 μm or more and 2 μm or less, 2 μm or more and 3.5 μm or less, 3.5 μm or more and 5 μm or less, etc.).

[0072] Specifically, the diameter of the cross-section of the recess R on the side surface 13 is the diameter of the cross-section furthest from the bottom surface of the recess R. In other words, it is the diameter of the cross-section of the opening of the recess R.

[0073] The diameter of the depression R can be obtained by a three-dimensional microscope or a scanning electron microscope, and the depth of the depression R can be obtained by scanning with a three-dimensional microscope.

[0074] By providing the recess R at the boundary between the first region A1 and the second region A2, the morphology of the first region A1 and the second region A2 tends to change transitionally, reducing the prominent undulations on the side surface 13 and contributing to improved coating quality at subsequent boundary lines. Furthermore, the recess R located in the second region A2 can also partially enhance the light confinement effect of incident light.

[0075] In some examples, the depth of the recess R is between 0.05 μm and 2 μm (for example, between 0.05 μm and 0.1 μm, between 0.1 μm and 0.5 μm, between 0.5 μm and 1 μm, between 1 μm and 1.5 μm, between 1.5 μm and 2 μm, etc.).

[0076] In some embodiments, the distribution ratio of the first region A1 to the side surface 13 in the direction extending from the first surface 11 to the second surface 12 is between 20% and 100%. Specifically, the distribution ratio of the first region A1 to the side surface 13 in the direction extending from the first surface 11 to the second surface 12 refers to the ratio of the length of the first region A1 in the thickness direction of the solar cell 100 to the thickness of the solar cell 100. More specifically, the length of the first region A1 in the thickness direction of the solar cell 100 refers to the vertical distance from the intersection of the first surface 11 and the side surface 13 to the lowest point of the boundary line between the first region A1 and the second region A2 in the thickness direction of the solar cell 100.

[0077] In some embodiments, the first region A1 has a width X (shown in Figure 4) in the direction extending from the first surface 11 to the second surface 12. The ratio of the width X of the first region A1 to the thickness L (shown in Figure 4) of the silicon substrate 10 is in the range of 20% to 100% (for example, 20% to 35%, 35% to 40%, 40% to 55%, 55% to 70%, 70% to 80%, 80% to 85%, 85% to 90%, 90% to 95%, 95% to 100%, etc.).

[0078] As described above, the minimum value of the proportion range of the first region A1 ensures that the pyramidal structure T11 is distributed on the side surface 13, thereby enhancing the light confinement effect of the side surface 13. The maximum value of the proportion range ensures that the pyramidal structure T11 satisfies the light confinement effect, while also ensuring sufficient area for the second texture region A12 to extend between the first texture regions A11, thereby increasing the surface area of ​​the side surface having the first texture region and improving the coating quality of the passivation layer.

[0079] In some embodiments, when combined with the process, the proportion of the first region A1 can ensure that the film layer to be cleaned on the first surface 11 is completely removed during the chain etching process, providing a good surface base for subsequent processes such as texturing and coating. At the same time, the proportion of the first region A1 can improve the problem of excessive etching of the film layer on the back surface (second surface 12) during the chain etching process.

[0080] In some embodiments, the proportion of the first region A1 to the side surface 13 reaches 80% to 100%, so that the multiple pyramidal structures T11 and the multiple prism-like structures T12 are distributed over most of the side surface 13, and even throughout the entire surface. Furthermore, the multiple pyramidal structures T11 and the multiple prism-like structures T12 on the side surface 13 contribute to improving the light confinement effect and passivation performance of the solar cell 100, as well as balancing the relationship between the two, ultimately improving the battery efficiency of the solar cell 100.

[0081] In some embodiments, the distribution ratio of the second region A2 to the side surface 13 in the direction extending from the second surface 12 to the first surface 11 is greater than 0 and 80% or less. Specifically, the ratio of the width (LX) of the second region A2 to the thickness L of the silicon substrate 10 in the direction extending from the second surface 12 to the first surface 11 is between 0 and 80% (for example, 0% to 5%, 5% to 10%, 10% to 15%, 15% to 18%, 18% to 20%, 20% to 35%, 35% to 40%, 40% to 55%, 55% to 70%, 70% to 80%, etc.).

[0082] If the ratio of the width (LX) of the second region A2 to the thickness L of the silicon substrate 10 is too small, the risk of over-etching of the functional layer on the second surface 12 increases. If this ratio is too large, it becomes difficult to ensure the wrap-around removal effect of the first surface 11. As a result, the possibility of minute defects occurring between layers due to the difference in lateral etching efficiency between the functional layer and the silicon substrate 10 is reduced, the problem of recombination in the final battery is mitigated, the passivation effect of the battery is enhanced, and the battery efficiency is improved.

[0083] In some embodiments, the side surface 13 is composed of a first region A1 and a second region A2. That is, in each side surface 13, in the direction extending from the second surface 12 to the first surface 11, the sum of the distribution ratio of the first region A1 to the side surface 13 and the distribution ratio of the second region A2 to the side surface 13 is 100%.

[0084] In some embodiments, the second region A2 is formed on at least one of the first side surface 131, the second side surface 132, the third side surface 133, and the fourth side surface 134. That is, the second region A2 (in other words, the structure in which the polished surface and the base structure T13 coexist) may be formed on any one, any two, any three, or any four of the first side surface 131, the second side surface 132, the third side surface 133, and the fourth side surface 134.

[0085] In some embodiments, the second region A2 may not be present on the first side surface 131, the second side surface 132, the third side surface 133, and the fourth side surface 134.

[0086] Figure 7 is a scanning electron microscope image of the first surface 11 of a solar cell 100 according to one embodiment of this application. As shown in Figure 7, the first surface 11 has a plurality of third pyramidal structures T21, which enhance the light confinement effect on the side of the solar cell 100 where the first surface 11 is located.

[0087] It should be explained that the sizes of the third pyramidal structure T21 on the first face 11 and the pyramidal structure T11 on the side 13 are not exactly the same, and there is a difference in their sizes.

[0088] For example, the dimensional range of the base of the third pyramidal structure T21 is 0.05 μm to 2 μm (for example, 0.05 μm to 0.1 μm, 0.1 μm to 0.5 μm, 0.5 μm to 1.1 μm, 1.1 μm to 1.3 μm, 1.3 μm to 1.5 μm, 1.5 μm to 1.8 μm, 1.8 μm to 2 μm, etc.).

[0089] For example, the height range of the third pyramidal structure T21 is between 0.1 μm and 2 μm (for example, between 0.1 μm and 0.5 μm, between 0.5 μm and 1 μm, between 1 μm and 1.3 μm, between 1.3 μm and 1.5 μm, between 1.5 μm and 1.8 μm, between 1.8 μm and 2 μm, etc.). If the lateral dimensions and vertical height of the base of the third pyramidal structure T21 are not appropriate, the secondary reflection of light by the third pyramidal structure T21 will be insufficient, increasing the reflectivity of the textured surface and reducing the light absorption performance of the battery.

[0090] Specifically, the orthographic projection shape of the base of the pyramidal structure T11 on side 13 and the orthographic projection shape of the third pyramidal structure T21 on the first face 11 may be a regular quadrilateral or an irregular polygon. If it is a regular quadrilateral, referring to Figure 8(a), the structural dimensions of the base of the pyramidal structure T11 and the third pyramidal structure T21 are the length of the longest diagonal of the base of the pyramidal structure d1 or the longest side length d2. If it is an irregular quadrilateral, the side lengths and diagonal lengths of the base of the pyramidal structure T11 and the third pyramidal structure T21 are not absolute but are artificially defined to characterize the dimensions of the base. For example, the side lengths of the base of the pyramidal structure T11 and the third pyramidal structure T21 may be defined as the side length of the longest side of the irregular quadrilateral, and the diagonal lengths of the base of the pyramidal structure T11 and the third pyramidal structure T21 may be defined as the length of the longest diagonal of the irregular quadrilateral. The heights of pyramidal structure T11 and the third pyramidal structure T21 are defined as the height from the apex to the base of the pyramidal structure. The above is merely an illustrative explanation, and it is understood that in practice, the height can be flexibly defined according to actual needs.

[0091] It should be explained that both the pyramidal structure T11 and the third pyramidal structure T21 are distributed in various sizes, and the dimensions mentioned above represent the structural dimensions of pyramidal structure T11 and / or the structural dimensions of the third pyramidal structure T21 that are relatively uniformly distributed within the interface observed by magnifying the texture surface on the first face 11 or side surface 13. Furthermore, Figure 8(a) is a schematic diagram of the measurement method and does not have a direct correlation with the actual base morphology of pyramidal structure T11 and the actual base morphology of the third pyramidal structure T21.

[0092] Specifically, as shown in Figure 8(b), the method for measuring the bottom surface dimension of the base of the base structure T13 is to take the larger of the diagonal lengths d3 and d4 of the base in a direction parallel to the bottom surface of the base structure T13, and the method for measuring the vertical height of the base of the base structure T13 is to take the difference in height between the bottom surface of the base structure T13 and the plane of the side surface 13.

[0093] It should be explained that the base structure T13 is distributed in various sizes, and the dimensions mentioned above represent the size of the base of the base structure T13 that is relatively uniformly distributed within the interface observed by magnifying the texture surface on the side surface 13. Also, Figure 8(b) is a schematic diagram of the measurement method and does not directly correlate with the actual base morphology of the base structure T13.

[0094] Embodiments of this application further provide a solar module, which includes a plurality of solar cells electrically connected to one another, the solar cells being any of the embodiments described above.

[0095] In some embodiments, the method for manufacturing the solar cell of the above embodiment includes the following steps S10 to S60.

[0096] Depending on different needs, the order of some steps or substeps of the solar cell manufacturing method may be changed, and some steps or substeps may be omitted or combined.

[0097] In step S10, a silicon substrate is provided that includes opposing first and second surfaces and a side surface connecting the first and second surfaces, and a base structure is formed on the first surface, the second surface and the side surface.

[0098] Specifically, this silicon substrate may be a P-type or N-type unprocessed silicon wafer. The silicon substrate is subjected to alkaline polishing using a slot machine to form a base structure on the surface of the silicon substrate. This base structure includes a structure in which the polished surface and the base structure coexist; in other words, this base structure is a base structure that has undergone polishing treatment.

[0099] For example, the range of the lateral dimensions of the base of the base structure formed in step S10 is 10 μm to 30 μm (for example, 10 μm to 12 μm, 12 μm to 13 μm, 13 μm to 14.5 μm, 14.5 μm to 15 μm, 15 μm to 20 μm, 20 μm to 25 μm, 25 μm to 28 μm, 28 μm to 30 μm, etc.).

[0100] For example, the range of vertical height of the base structure formed in step S10 is 0.01 μm to 8 μm (for example, 0.01 μm to 0.05 μm, 0.05 μm to 0.1 μm, 0.1 μm to 0.4 μm, 0.4 μm to 0.5 μm, 0.5 μm to 0.7 μm, 0.7 μm to 1 μm, 1 μm to 1.3 μm, 1.3 μm to 1.5 μm, 1.5 μm to 1.8 μm, 1.8 μm to 2.3 μm, 2.3 μm to 2.8 μm, 2.8 μm to 3.3 μm, 3.3 μm to 4 μm, 4 μm to 5 μm, 5 μm to 6 μm, 6 μm to 7 μm, 7 μm to 8 μm, etc.).

[0101] For example, the base of the base structure formed in step S10 is rectangular, with dimensions of 15 μm × 14.5 μm, and the vertical dimension of the base of the base structure is 0.5 μm.

[0102] In step S20, a dielectric layer and a doped conductive layer are sequentially formed on the second surface, side surface, and at least a portion of the first surface of the silicon substrate, with the doped conductive layer located on the side of the dielectric layer away from the silicon substrate. The doped conductive layer may be a doped polycrystalline silicon layer.

[0103] Specifically, a passivation layer (e.g., silicon oxide or aluminum oxide) is fabricated by low-pressure chemical vapor deposition (LPCVD) or plasma-enhanced chemical vapor deposition (PECVD), and doped atoms are diffused to form a boron-doped polycrystalline silicon structure and / or a phosphorus-doped polycrystalline silicon structure. The dielectric layer and the doped polycrystalline silicon layer cover the second surface, several side surfaces, and a portion of the first surface.

[0104] The dielectric layers formed in step S20 are the first dielectric layer and the second dielectric layer described above.

[0105] In step S20, the doped atom diffusion step is performed at least once. In some embodiments, the doped atom diffusion step may be performed two or more times.

[0106] In step S30, the dielectric layer and doped polycrystalline silicon layer located on the first surface are removed, and at least a portion of the dielectric layer and doped polycrystalline silicon layer located in the first region close to the first surface on the side surface is removed.

[0107] In step S30, the dielectric layer and doped polycrystalline silicon layer on all or part of the first surface and side surfaces are etched off using a chain etching apparatus.

[0108] Specifically, a silicon substrate on which a dielectric layer and a doped polycrystalline silicon layer are formed is set in a chain etching apparatus, and the silicon substrate is brought into contact with the etching solution used in the chain etching apparatus with its first surface facing downwards, so that the etching solution covers at least a portion of the dielectric layer and doped polycrystalline silicon layer on the sides.

[0109] In some embodiments, the distribution ratio of the first region to the side surface in the direction extending from the first surface to the second surface is between 20% and 100%.

[0110] For example, 85% of the side (closer to the first surface) is in full contact with the etching solution, while 15% of the side (closer to the second surface) is not in contact with the etching solution.

[0111] In step S40, a first region and / or a second region are formed on the side surface.

[0112] A pyramidal structure is formed by alkaline texturing. By controlling the type of additive and reaction time, the size of the pyramidal structure can be controlled to form a first pyramidal structure and a second pyramidal structure, or the first and second pyramidal structures can be formed separately by stepwise texturing.

[0113] During the alkaline texturing process, the exposed surface of the silicon substrate on the sides is corroded by the alkaline solution, forming a textured surface pyramidal structure. On the other hand, in the areas where the surface of the silicon substrate is not exposed, the dielectric layer (e.g., silicon dioxide) and the alkaline solution hardly react under the process conditions. Therefore, no textured surface is formed on the surface of the silicon substrate in these areas during texturing, and it exhibits a base structure.

[0114] For example, in the alkaline texturing process, the first surface of the silicon substrate and 85% of the sides near the surface are alkaline etched, forming a combined structure of a first texture region and a second texture region. The remaining 15% of the sides near the back surface are protected by a dielectric layer and a doped polycrystalline silicon layer, preventing the formation of a pyramidal structure, and allowing the base structure to be observed.

[0115] In step S50, a passivation layer and a reflection reduction layer are formed.

[0116] Specifically, passivation layers can be deposited on certain sides of the first surface, certain sides of the second surface, and multiple sides of a silicon substrate using atomic layer deposition (ALD) to impart a passivation effect. Reflection reduction layers can be deposited on certain sides of the first surface, certain sides of the second surface, and multiple sides of a silicon substrate using plasma-enhanced chemical vapor deposition. The textured surface pyramidal structure on the surface and the combination of textured surface pyramidal structures and bases on the sides can be observed after the passivation layers and reflection reduction layers have been formed.

[0117] In step S60, electrodes are formed.

[0118] Specifically, electrodes can be formed by screen printing. The combination of the textured pyramidal structure on the surface and the textured pyramidal structure and base structure on the sides can be observed after electrode printing.

[0119] In summary, the side surface of the solar cell in the embodiment of this application includes a plurality of first pyramidal structures, a plurality of second pyramidal structures, and a plurality of prism-like structures. The first pyramidal structures in the first texture region enhance the light confinement effect on the side surface of the solar cell, thereby improving the light utilization rate of the solar cell. Furthermore, by designing to form second pyramidal structures in the second texture region, the larger structural dimensions of the second pyramidal structures provide a larger surface area than the first pyramidal structures, providing a larger coating area for subsequent coatings and improving coating quality. Therefore, a mixed structure of a plurality of first pyramidal structures and a plurality of second pyramidal structures can better balance the passivation effect and light confinement effect on the side surface of the solar cell, thereby improving the photoelectric conversion efficiency of the solar cell.

[0120] Furthermore, compared to the pyramidal textured surface structure, the prism-like structure of the second textured region has a larger surface area, providing a larger deposition area for the subsequent passivation layer. As a result, the mixed structure of the first pyramidal structure, the second pyramidal structure, and the prism-like structure can better balance the passivation and light confinement effects on the sides of the solar cell compared to the single textured surface structure in related technologies.

[0121] The embodiments described above are for illustrative purposes only and do not limit the present application. Although this application has been described in detail with reference to the above preferred embodiments, those skilled in the art should understand that the technical solutions of this application can be modified or replaced with equivalent substitutes without departing from the spirit and scope of the technical solutions of this application. [Explanation of Symbols]

[0122] 100 solar cells 10 Silicon substrate 11 Page 1 12 Side 2 13 Side view 131 First aspect 132 Second aspect 133 Third aspect 134 Fourth aspect 20 First Dielectric Layer 30 First doped conductive layer 40 Second dielectric layer 50 Second doped conductive layer A1 1st area A11 First Texture Area A12 Second Texture Area A2 2nd area T11 Pyramid structure T12 Prismatic structure T13 Base structure T21 Third Pyramid Structure R recess D1 Thickness direction of the silicon substrate

Claims

1. The silicon substrate includes a silicon substrate and a passivation layer, the silicon substrate includes opposing first and second surfaces and a plurality of sides connecting the first and second surfaces, At least one of the aforementioned sides includes a plurality of first texture regions and second texture regions, each of the first texture regions includes a plurality of first pyramidal structures, and the second texture region includes a plurality of second pyramidal structures. The structural dimensions of the second pyramidal structure are larger than those of the first pyramidal structure. The second texture region is located between adjacent first texture regions. A solar cell characterized in that the passivation layer covers the first texture region and the second texture region on at least one of the sides.

2. The solar cell according to claim 1, characterized in that the second texture region extends between the first texture regions in one or more forms, which are linear, polylinear, or curved.

3. The solar cell according to claim 2, characterized in that the stretching direction of the second texture region is not parallel to the thickness direction of the solar cell, and / or the stretching directions of at least two of the second texture regions are set to be parallel.

4. The solar cell according to claim 1, characterized in that the second texture region includes a prism-like structure, and the length range of the prism-like structure is 200 nm or more and 6 μm or less.

5. The solar cell according to claim 1, characterized in that the structural dimensions of the first pyramidal structure are in the range of 0.05 μm or more and 2 μm or less.

6. The solar cell according to claim 1, characterized in that the structural dimensions of the second pyramidal structure are in the range of 2 μm to 6 μm.

7. The solar cell according to claim 1, characterized in that the side surface includes a first region, the first region is connected to the first surface, both the first texture region and the second texture region are provided in the first region, and the width of the first region is 20% or more and 100% or less of the width of the side surface.

8. The solar cell according to claim 1, characterized in that the side surface includes a first region and a second region, both the first texture region and the second texture region are provided in the first region, the second region is connected to the second surface side, and the second region includes a plurality of base structures.

9. The solar cell according to claim 8, characterized in that the boundary line between the first region and the second region is curved, and a depression is provided in the second region at a position close to the boundary line.

10. The solar cell according to claim 9, characterized in that, in the thickness direction of the silicon substrate, the width of the region in which the depression is provided is 0% or more and 60% or less of the width of the second region.

11. The solar cell according to claim 9, wherein the shape of the recess includes one or more of the following: an inverted pyramidal shape, an inverted hemispherical shape, and a stepped shape, and / or the cross-sectional area of ​​the recess gradually increases along the direction perpendicular to the side surface.

12. The solar cell according to claim 9, characterized in that the diameter of the cross-section of the recess on the side surface is 0.1 μm or more and 5 μm or less, and / or the depth of the recess is 0.05 μm or more and 2 μm or less.

13. The solar cell according to claim 1, characterized in that, in the direction away from the silicon substrate, the passivation layer includes an aluminum oxide layer and a silicon nitride layer provided in order.

14. A solar module comprising a plurality of solar cells electrically connected to each other, wherein each solar cell is a solar cell according to any one of claims 1 to 13.

Images