Method of manufacturing a solar cell, solar cell, stacked cell and photovoltaic module

Abstract

This invention provides a method for fabricating a solar cell, a solar cell, a tandem solar cell, and a photovoltaic module, relating to the photovoltaic field. The solar cell substrate has first and second doped regions and an isolation region. The isolation region is partially disposed inside the semiconductor substrate and has a structure characterized by a wide bottom and a narrow opening, designed as a two-section groove structure, including a first section structure and a second section structure with an opening at one end, and the inner wall surface of the second section structure has a textured surface. The ratio D1 of the single maximum vertical projection area of ​​the second section structure on the cell to the single vertical projection area of ​​the first section structure on the cell is 1 < D1 ≤ 3, and the ratio D2 of the total maximum vertical projection area of ​​the second section structure on the cell to the area of ​​the first or second surface where the isolation region is located is 0.2 < D2 ≤ 0.8. Through the above design, the specific surface area of ​​the textured surface of the solar cell can be increased, increasing the number of reflections and refractions of light, thereby improving the bifaciality of the cell and its module.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic technology, specifically to a method for preparing a solar cell, a solar cell, a tandem cell, and a photovoltaic module. Background Technology

[0002] With the increasing global demand for renewable energy, photovoltaic power generation technology has developed rapidly. Among them, bifacial solar cells, which can generate electricity by simultaneously utilizing direct sunlight incident on the front and scattered and reflected light incident on the back, can significantly increase the power generation per unit area of ​​photovoltaic modules and have become an important technological direction for reducing the levelized cost of electricity (LCOE) of photovoltaic power generation.

[0003] In the performance evaluation system of solar cells, the bifaciality, which is the ratio of the power generation efficiency on the back side to that on the front side, is a key performance indicator for measuring its overall power generation capacity. A higher bifaciality means a stronger ability of the module to utilize ambient light, such as ground reflection, atmospheric scattering, and reflections between bifacial module arrays, resulting in a more significant overall power generation gain. Currently, to improve cell conversion efficiency, industry research focuses primarily on optimizing the passivation layer on the cell surface, controlling the doping concentration and depth of doped regions, and developing finer grids and low-resistivity materials for metal electrodes. These studies have effectively improved the basic photoelectric conversion efficiency on both the front and back sides of the cell.

[0004] However, existing technologies have certain limitations in their focus on improving bifaciality. Besides improving the conversion efficiency of the active regions on the front and back sides, the internal structural design of the solar cell, especially the structure of the isolation region within the doped area, also has a significant impact on bifaciality.

[0005] Currently, traditional isolation zone designs are mostly quite simple, generally employing straight-walled structures with equal width at the top and bottom, or trapezoidal isolation slots with an opening width greater than the bottom width, created using methods such as laser grooving. These structural designs primarily aim to achieve electrical isolation, neglecting their potential in optical performance. Specifically, these conventional structures limit the internal space of the isolation zone, failing to provide sufficient reflection and refraction interfaces for incident light. When light, especially scattered light incident from the back or front of the battery, enters the isolation zone, due to the lack of an effective multiple reflection mechanism, most of the light escapes directly from the isolation zone before fully interacting with the battery's active layer, resulting in the loss of this light energy before it is effectively converted into electrical energy. This optical loss limits the battery's ability to capture weak light and backscattered light, thus becoming a bottleneck for improving bifaciality.

[0006] Limited by this, the bifaciality of mainstream bifacial solar cells is currently concentrated between 70% and 85%. With the photovoltaic industry's increasingly urgent demand for high-power modules and the pressure to achieve lower levelized cost of electricity (LCOE), the market urgently needs high-efficiency bifacial cell technologies that can stably achieve bifacialities of over 90%. Therefore, how to achieve a breakthrough in bifaciality through cell structure innovation, especially the optimized design of the isolation zone, to maximize the utilization of light entering that area, has become a pressing technical challenge in the current photovoltaic technology field. Summary of the Invention

[0007] 1. The technical problem that the invention aims to solve Existing bifacial solar cells primarily focus on improving the conversion efficiency of the active regions on the front and back sides when increasing bifaciality, neglecting the structural design of the internal isolation zone, which significantly affects bifaciality. Currently, the limited space within the isolation zone causes light entering it to escape before fully interacting with the active layer, thus limiting the cell's ability to capture weak light and backscattered light, creating a bottleneck in bifaciality improvement. This invention aims to optimize the structure of the internal isolation zone to fully utilize the light entering the isolation zone and improve the cell's bifaciality.

[0008] 2. Technical Solution To achieve the above objectives, the technical solution provided by this invention is as follows: In a first aspect, the present invention provides a solar cell, comprising a semiconductor substrate; The semiconductor substrate has a first surface and a second surface disposed opposite to each other, at least one surface of the semiconductor substrate is provided with a doped region, and at least one of the doped regions is provided with an isolation region. The isolation region extends from the reference surface into the semiconductor substrate and is configured as a two-segment trench structure. The two-segment trench structure includes a first segment structure with one end open and a second segment structure connected to the first segment structure. The first segment structure extends from the reference surface to the surface of the semiconductor substrate, and the second segment structure extends from the surface of the semiconductor substrate into the semiconductor substrate. The inner wall surface of the second segment structure is a textured surface. The reference surface is defined as the surface of the doped region away from the semiconductor substrate. For the isolation region, the ratio of the maximum vertical projection area of ​​the second segment structure of a single isolation region on the semiconductor substrate surface to the maximum vertical projection area of ​​the first segment structure on the semiconductor substrate surface is defined as D1, and the ratio of the total maximum vertical projection area of ​​the second segment structure of all isolation regions on the first or second surface on the semiconductor substrate surface to the area of ​​the isolation region on the first or second surface is defined as D2, then 1 < D1 ≤ 3, 0.2 < D2 ≤ 0.8.

[0009] Preferably, 0.2 < D2 ≤ 0.5, for example, values ​​of 0.3, 0.4, and 0.5.

[0010] Furthermore, the second segment of the isolation zone has a cross-sectional shape that is either an inverted trapezoid or an arc with a central angle greater than 180° along the direction perpendicular to the isolation zone. Naturally, the cross-sectional dimension of the first segment of the isolation zone along the direction perpendicular to the isolation zone is smaller than that of the second segment. That is, the isolation zone primarily forms a structure where the second segment is wider and the first segment is narrower. This allows light entering from the opening in the first segment to undergo multiple reflections and full interaction with the battery active layer within the second segment, successfully converting light energy into electrical energy, thereby improving the bifaciality.

[0011] Furthermore, for any of the isolation regions, let L1 be the vertical projection length of the first segment of the structure on the semiconductor substrate surface along the direction perpendicular to the extension of the isolation region, and L2 be the vertical projection length of the second segment of the structure on the semiconductor substrate surface along the direction perpendicular to the extension of the isolation region. Then, 30μm ≤ L1 ≤ 500 μm, 30μm < L2 < 500μm, and L2 > L1. This numerical setting allows the proportion of the isolation region to be within a reasonable range, working together with the doped regions on both sides to balance the lateral transport distance of charge carriers inside the semiconductor substrate.

[0012] Optionally, L1 can be 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, 200μm, 300μm or 400μm; preferably, 100μm≤L1≤400μm.

[0013] Optionally, L2 can be 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, 120μm, 220μm, 320μm or 410μm; preferably, 120μm < L2 < 420μm.

[0014] Furthermore, the felted structure on the inner wall of the second section of the isolation zone is composed of several pyramid bases, with a distribution density of 20,000 to 50,000 bases per mm. 2 Furthermore, the size of any of the pyramid bases is 0.1~4μm and the height is 0.1~4μm.

[0015] Furthermore, the maximum vertical height of the isolation region extending vertically from the reference surface into the semiconductor substrate is defined as H1, then 0.5μm≤H1≤5μm; for example, the value can be 1μm, 2μm, 3μm, 4μm, or 5μm. The value of H1 can reduce the curvature of the semiconductor substrate after the isolation region is trenched, improve the cell yield, and also avoid cell efficiency loss due to excessively low current and fill factor.

[0016] Optionally, along the thickness direction of the semiconductor substrate, the heights of the first doped region and the second doped region disposed on the same surface of the semiconductor substrate are equal or unequal; optionally, the areas of the first doped region and the second doped region disposed on the same surface of the semiconductor substrate are equal or unequal.

[0017] Optionally, the substrate of the semiconductor substrate is a semiconductor substrate, and the type of the semiconductor substrate is selected from intrinsic semiconductor, N-type semiconductor or P-type semiconductor.

[0018] Furthermore, it also includes a passivation antireflection layer, which covers the outer surface of the semiconductor substrate and the surface of the isolation region; wherein the outer surface of the semiconductor substrate includes the first surface, the second surface, and the outer side surface of the semiconductor substrate; The passivation antireflection layer is Al2O3 / SiN. x The Al2O3 / SiN stacked structure x In the stacked structure, the thickness of the Al2O3 layer is 3~10nm, and the thickness of the SiNx layer is 60~100nm.

[0019] Furthermore, the solar cell is a back-contact solar cell; The semiconductor substrate has the doped region on only one surface. The doped region includes alternating first doped regions and second doped regions with opposite polarities. The isolation region is disposed between any adjacent first doped regions and second doped regions.

[0020] Furthermore, the solar cell is a bifacial solar cell; The first and second surfaces of the semiconductor substrate are respectively provided with the doped regions, the doped regions on the same surface have the same polarity, the doped regions on different surfaces have opposite polarities, and at least one of the doped regions on one side of the semiconductor substrate is provided with the isolation region.

[0021] Optionally, the first doped region and the second doped region with opposite polarities include: when the semiconductor substrate of the semiconductor substrate is an N-type semiconductor, the first doped region is P-type doped and the second doped region is N-type doped; when the semiconductor substrate of the semiconductor substrate is a P-type semiconductor, the first doped region is N-type doped and the second doped region is P-type doped.

[0022] Optionally, the first doped region and the second doped region have different doping characteristics; the doping characteristics refer to the characteristics associated with doping, including at least one of doping concentration and doping element type.

[0023] Optionally, the surfaces of the first and second doped regions can be either textured or polished to allow for matching to electrode requirements in practical applications. When the surface of the doped region is a relatively smooth polished surface, it can better match the metal electrode, reducing the risk of grid breakage. A polished surface structure can be obtained through alkaline polishing. When the surface of the doped region is textured, it can ensure the light-trapping effect of the cell, increase the absorption of sunlight, reduce reflectivity, increase short-circuit current, and improve the photoelectric conversion efficiency of the solar cell.

[0024] Optionally, the velvet structure may be obtained by velvet processes such as acid velvet, alkali velvet, mechanical velvet, electrochemical velvet, reactive ion etching velvet, laser velvet, and mask velvet.

[0025] In a second aspect, the present invention provides a method for preparing a solar cell, comprising: The steps of polishing or texturing the first and second surfaces of a semiconductor substrate; The steps of forming a doped region on at least one surface of a polished or texturized semiconductor substrate and forming an isolation region in at least one doped region; The steps involved in forming a velvety texture at the target location within the isolation zone; The step of depositing a passivation antireflection layer on the outer surface of the semiconductor substrate and the surface of the isolation region; The steps involve printing corresponding metal electrodes in the doped region, followed by sintering and light injection to obtain a solar cell. The isolation region extends from the reference surface into the semiconductor substrate and is configured as a two-segment trench structure. The two-segment trench structure includes a first segment open at one end and a second segment connected to the first segment. The first segment extends from the reference surface to the surface of the semiconductor substrate, and the second segment extends from the surface of the semiconductor substrate into the interior of the semiconductor substrate. The inner wall of the second segment has a textured surface. The reference surface is defined as the surface of the doped region away from the semiconductor substrate, and the target location is the inner wall of the second segment of the isolation region. The ratio of the maximum vertical projected area of ​​the second segment structure of a single isolation region on the semiconductor substrate surface to the maximum vertical projected area of ​​the first segment structure on the semiconductor substrate surface is defined as D1, and the ratio of the total maximum vertical projected area of ​​the second segment structure of the isolation region on the first or second surface to the area of ​​the isolation region on the first or second surface is defined as D2. Then, 1 < D1 ≤ 3, 0.2 < D2 ≤ 0.8. By increasing the relative area of ​​the textured surface of the isolation region without increasing the opening area of ​​the isolation region, the number of reflections and refractions of light in the second segment structure of the isolation region is increased. This allows the textured surface structure to capture more photons, thereby improving the utilization rate of ground-reflected light by the cell and obtaining a high bifaciality solar cell.

[0026] Furthermore, the isolation region is formed by at least one or more of laser etching, wet etching, or slurry etching.

[0027] Furthermore, the second segment of the isolation zone has a cross-sectional shape that is either an inverted trapezoid or an arc with a corresponding central angle greater than 180° along the direction perpendicular to the extension of the isolation zone.

[0028] Furthermore, for any of the isolation regions formed, the vertical projection length of the first segment structure on the semiconductor substrate surface along the first direction is defined as L1, and the vertical projection length of the second segment structure on the semiconductor substrate surface along the first direction is defined as L2. Then, 30μm≤L1≤500μm, 30μm<L2<500μm, and L2>L1; wherein, the first direction is the direction in which the battery surface extends perpendicular to the isolation region.

[0029] Furthermore, the textured surface is formed by etching with a potassium hydroxide or sodium hydroxide solution of 0.5-2.5% by mass at 60-80°C for 350-650 seconds.

[0030] A third aspect of the present invention provides a stacked battery, characterized in that it comprises: The top cell is a perovskite cell, a cadmium sulfide solar cell, a copper indium gallium selenide solar cell, or a gallium arsenide solar cell; the intermediate connecting layer; the bottom cell is a solar cell prepared by the method of preparing a solar cell proposed in the first aspect of the present invention or the method of preparing a solar cell proposed in the second aspect of the present invention; the top cell, the intermediate connecting layer, and the bottom cell are stacked and connected.

[0031] In a fourth aspect, the present invention provides a photovoltaic module comprising a solar cell as proposed in the first aspect of the present invention, or comprising a solar cell prepared by the method for preparing a solar cell as proposed in the second aspect of the present invention, or comprising a tandem cell as proposed in the third aspect of the present invention.

[0032] 3. Beneficial effects Compared with the prior art, the technical solution provided by this invention has the following advantages: The solar cell fabrication method, solar cell, tandem cell, and photovoltaic module disclosed in this invention optimize the internal structure design of the isolation region, providing sufficient reflection and refraction interfaces for light incident on the isolation region, thereby improving the cell's ability to capture weak light and backscattered light, and thus solving the bottleneck problem of bifaciality improvement from the perspective of cell structure design. Since the opening size, internal morphology, and overall shape of the solar cell isolation region are key parameters affecting cell efficiency, reliability, and process cost, the isolation region is designed as a two-segment trench structure extending vertically from a reference plane into the semiconductor substrate. This two-segment trench structure includes a first segment structure with one end open, extending from the reference plane to the surface of the semiconductor substrate, and a second segment structure connected to the first segment structure, extending from the surface of the semiconductor substrate into the semiconductor substrate. By limiting the projected area of ​​the two-segment trench structure on the semiconductor substrate surface, its length in the direction perpendicular to the isolation region, and designing the inner wall structure of the second segment structure, the function of the isolation region is optimized.

[0033] First, the projected area of ​​the two-segment trench structure of the isolation region on the semiconductor substrate surface is defined, and the inner wall structure of the second segment structure is designed. By defining the ratio of the maximum vertical projected area of ​​the second segment structure of a single isolation region on the semiconductor substrate surface to the maximum vertical projected area of ​​the first segment structure on the semiconductor substrate surface as D1, and the ratio of the total maximum vertical projected area of ​​the second segment structure of all isolation regions on the first or second surface to the surface area of ​​the isolation region as D2, and limiting 1 < D1 ≤ 3 and 0.2 < D2 ≤ 0.8, the second segment structure has a larger internal space than the first segment structure. By combining the internal surface of the second segment structure with a textured surface, the number of reflections and refractions of light entering the isolation zone from the surface of the solar cell is increased, thereby increasing the interaction time between the light and the active layer of the cell and improving the light utilization rate. Secondly, the length of the two-segment groove structure in the direction perpendicular to the isolation zone is limited to ensure that the light entering the isolation zone can be confined within the second segment structure. That is, for any isolation zone, the vertical projection length of the first segment structure on the semiconductor substrate surface along the direction perpendicular to the extension of the isolation zone is defined as L1, and the vertical projection length of the second segment structure on the semiconductor substrate surface along the first direction is defined as L2. The lengths are limited to 30μm≤L1≤500μm, 30μm<L2<500μm, and L2>L1.

[0034] In addition, by arranging the isolation region portion of the two-section groove structure within the semiconductor substrate, this invention can not only improve the bifaciality of solar cells, but also avoid electrode paste overflow across regions while optimizing the carrier transport path. Combined with the above-mentioned isolation region structural design, this invention fully solves the problem that existing technologies only consider the front and back active regions and ignore the isolation region design when improving the bifaciality of solar cells, breaking the conventional design and overcoming the bottleneck of bifaciality improvement. Attached Figure Description

[0035] Figure 1 This is a cross-sectional view of the solar cell proposed in Embodiment 1 of the present invention along the direction of extension of the isolation region; Figure 2 This is a cross-sectional view of the solar cell proposed in Embodiment 5 of the present invention along the direction of extension of the isolation region; Figure 3 This is a cross-sectional view of the solar cell proposed in Embodiment 9 of the present invention along the direction of extension of the isolation region; Figure 4 This is a cross-sectional view of the solar cell proposed in Comparative Example 1 of the present invention along the direction of extension of the isolation region; Figure 5 This is a cross-sectional view of the solar cell proposed in Comparative Example 3 of the present invention along the direction of extension of the isolation region.

[0036] The specific meanings of each mark in the diagram are as follows: 10 - Semiconductor substrate; 20 - First doped region; 21 - First tunneling layer; 22 - First doped layer; 30 - Second doped region; 31 - Second tunneling layer; 32 - Second doped layer; 41 - Passivation and antireflection layer; 51 - First electrode; 52 - Second electrode; 61 - First segment structure; 62 - Second segment structure. Detailed Implementation

[0037] To further understand the content of this invention, a detailed description of the invention will be provided in conjunction with the accompanying drawings.

[0038] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0039] In the description of this invention, it should be understood that if terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" appear, these terms indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0040] Furthermore, where the term "and / or" appears, "and / or" merely describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship. Where the terms "first" and "second" appear, these terms are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" or "second" may explicitly or implicitly include at least one of those features. In the description of this invention, where the term "multiple" appears, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0041] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0042] In this invention, unless otherwise explicitly specified and limited, the use of descriptions such as "above" or "below" the second feature indicates that the first and second features are in direct contact, or indirect contact via an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. Similarly, "below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0043] It should be noted that if an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. If an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. Where applicable, the terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used in this invention are for illustrative purposes only and do not represent the only possible implementation. The following disclosure provides many different embodiments or examples for implementing different structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. Of course, these are merely examples and are not intended to limit the invention. Furthermore, reference values ​​and / or reference letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. The invention will be further described below with reference to embodiments.

[0044] A solar cell is a device that converts sunlight into electrical energy. Specifically, when a solar cell is in operation, sunlight shines on the semiconductor PN junction of the solar cell, forming new electron-hole pairs. Under the influence of the built-in electric field of the PN junction, photogenerated holes flow to the P-region, and photogenerated electrons flow to the N-region. When the circuit is connected, an electric current is generated.

[0045] In back-contact solar cells, an isolation region is often placed between the P-region and the N-region to effectively prevent short-circuit conduction. In other bifacial doped solar cells, the doped regions are also localized to reduce parasitic absorption; the undoped regions between these localized doped regions are also referred to as isolation regions. However, if the opening width of the isolation region is too wide, it will reduce the printable area of ​​the metal electrode, requiring higher printing precision, and will also increase the lateral transport distance of photogenerated carriers in the isolation region, increasing the series resistance of the cell and thus reducing cell efficiency. Conversely, if the opening width of the isolation region is narrow, the proportion of the doped region area increases, and the parasitic absorption generated by the polycrystalline silicon layer increases accordingly, leading to a decrease in current.

[0046] Therefore, this invention aims to overcome the bottleneck of improving the bifaciality of solar cells by designing an isolation region structure, while ensuring the series resistance and efficiency of the cells.

[0047] Specifically, the solar cell disclosed in this invention includes a semiconductor substrate 10; the semiconductor substrate 10 has a first surface and a second surface disposed opposite to each other, at least one surface of the semiconductor substrate 10 is provided with a doped region, and at least one of the doped regions is provided with an isolation region; wherein, the first surface is a light-receiving surface and the second surface is a backlight surface, or the first surface is a backlight surface and the second surface is a light-receiving surface; In specific implementation, whether doped regions are provided on the first and second surfaces, and the polarity selection of the doped regions, needs to be designed according to the type of solar cell. Optionally, the doped regions include a first doped region 20 and a second doped region 30 with opposite polarities. The positions of the first doped region 20 and the second doped region 30, as well as the design of the isolation region, differ for different types of solar cells. For example, when the solar cell is a back-contact solar cell, the semiconductor substrate 10 has the doped regions on only one surface. The doped regions include alternating first doped regions 20 and second doped regions 30 with opposite polarities, and the isolation region is provided between any adjacent first doped regions 20 and second doped regions 30. When the solar cell is a bifacial solar cell, the first and second surfaces of the semiconductor substrate 10 are respectively provided with the doped regions. The doped regions on the same surface have the same polarity, and the doped regions on different surfaces have opposite polarities. Furthermore, the isolation region is provided on the doped regions on at least one side of the semiconductor substrate 10. For example, the first surface of the semiconductor substrate 10 is entirely provided with first doped regions 20, and the second surface is entirely provided with second doped regions 30. The second doped regions 30 and the isolation region are arranged alternately on the second surface.

[0048] The isolation region extends vertically from the reference plane into the semiconductor substrate 10 and is configured as a two-segment trench structure. The two-segment trench structure includes a first segment 61 with one open end and a second segment 62 connected to the first segment 61. The first segment 61 extends from the reference plane to the surface of the semiconductor substrate 10, and the second segment 62 extends from the surface of the semiconductor substrate 10 into the interior of the semiconductor substrate 10. The inner wall surface of the second segment 62 has a textured surface. The reference plane is defined as the surface of the doped region away from the semiconductor substrate 10. The textured surface of the inner wall surface of the second segment 62 may be designed to consist of several pyramid bases, with a pyramid base distribution density of 20,000 to 50,000 units / mm². 2 Furthermore, the size of any of the pyramid bases is 0.1~4μm and the height is 0.1~4μm.

[0049] For the isolation region, the ratio of the maximum vertical projection area of ​​the second segment structure 62 of a single isolation region on the surface of the semiconductor substrate 10 to the maximum vertical projection area of ​​the first segment structure 61 on the surface of the semiconductor substrate 10 is defined as D1, and the ratio of the total maximum vertical projection area of ​​the second segment structure 62 of all isolation regions on the first or second surface to the area of ​​the isolation region on the first or second surface is defined as D2. Then, 1 < D1 ≤ 3, 0.2 < D2 ≤ 0.8. In summary, on the one hand, by setting the area as described above, the isolation region of the two-segment groove structure forms a structure with a wide bottom and a narrow opening, so that light entering the second segment structure 62 of the isolation region through the opening is reduced to reduce light dissipation; on the other hand, by setting the area in combination with the textured structure of the inner wall of the second segment structure, the specific surface area of ​​the solar cell textured surface is increased, thereby increasing the number of reflections and refractions of light on the inner wall of the second segment structure, so that the light can be fully converted into electrical energy after contacting the active layer of the cell, thus improving the bifaciality.

[0050] To ensure the cell efficiency of the solar cell and the function of the isolation region, for any of the isolation regions, the vertical projection length of the first segment structure 61 on the surface of the semiconductor substrate 10 along the direction perpendicular to the extension of the isolation region is defined as L1, and the vertical projection length of the second segment structure 62 on the surface of the semiconductor substrate 10 along the direction perpendicular to the extension of the isolation region is defined as L2. Then, 30μm≤L1≤500μm, 30μm<L2<500μm, and L2>L1.

[0051] An isolation zone that forms a structure with a wide bottom and a narrow opening can be designed as follows: The first segment structure 61 of the isolation zone is designed as a rectangle along the cross-sectional shape perpendicular to the extension direction of the isolation zone, and the second segment structure 62 of the isolation zone is designed as an inverted trapezoid or an arc with a corresponding central angle greater than 180° along the cross-sectional shape perpendicular to the extension direction of the isolation zone; both of these structures of the second segment structure 62 conform to the structural characteristics of the isolation zone with a wide bottom and a narrow opening.

[0052] The solar cell with the above structure can be fabricated by the following steps, including polishing or texturing the first and second surfaces of the semiconductor substrate 10; The steps of forming a doped region on at least one surface of a polished or texturized semiconductor substrate 10 and forming an isolation region in at least one doped region; The steps involved in forming a velvety texture at the target location within the isolation zone; The step of depositing a passivation antireflection layer on the outer surface of the semiconductor substrate and the surface of the isolation region; The steps involve printing corresponding metal electrodes in the doped region, followed by sintering and light injection to obtain a solar cell.

[0053] The following detailed description, in conjunction with the specific embodiments shown in the accompanying drawings, further illustrates the method for preparing solar cells, solar cells, tandem cells, and photovoltaic modules disclosed in this invention.

[0054] Example 1 Figure 1 The diagram shows a structure of a solar cell according to the present invention, a back-contact solar cell, wherein the first segment 61 of the isolation region has a rectangular cross-sectional shape along the direction perpendicular to the extension of the isolation region, and the second segment 62 has an inverted trapezoidal cross-sectional shape along the direction perpendicular to the extension of the isolation region; the back surface of the back-contact solar cell, i.e., the second surface, is provided with doped regions; the doped regions include alternating first doped regions 20 and second doped regions 30 with opposite polarities, and the isolation region is disposed between any adjacent first doped regions 20 and second doped regions 30.

[0055] Example 1: The fabrication steps of the solar cell include: S1. Polishing the first and second surfaces of the semiconductor substrate 10 using an alkaline solution; wherein the polishing solution used for polishing is a mixed solution of potassium hydroxide with a mass fraction of 1.5% and polishing additive with a mass fraction of 0.5%. S2. A first tunneling layer 21, a first doped layer 22 and a first oxide layer are sequentially stacked on the second surface of the semiconductor substrate 10; wherein, the first tunneling layer 21, the first doped layer 22 and the first oxide layer at the predetermined first doped region 20 position constitute the first doped region 20. S3. The first tunneling layer 21, the first doped layer 22, and the first oxide layer of the second doped region 30 and the isolation region are removed by first laser etching and first wet etching solution; in the first laser etching, the laser's interaction angle with the surface of the semiconductor substrate 10 is 60°, the laser power is 75W, the first wet etching solution is a potassium hydroxide or sodium hydroxide solution with a mass fraction of 3.0%, the etching temperature is 70°C, and the etching time is 150s; S4. A second tunneling layer 31, a second doped layer 32, and a second oxide layer are sequentially stacked on the surface of the semiconductor substrate 10; wherein, the second tunneling layer 31, the second doped layer 32, and the second oxide layer at the predetermined second doped region 30 position constitute the second doped region 30. S5. The second tunneling layer 31, the second doped layer 32, and the second oxide layer of the first doped region 20 and the isolation region are removed by the second laser etching and the second wet etching solution, and a textured structure is formed in the isolation region of the semiconductor substrate 10; in the second laser etching, the laser's interaction angle with the surface of the semiconductor substrate 10 is 120°, the laser power is 50W, the second wet etching solution is a mixture of potassium hydroxide with a mass fraction of 0.5% and texturing additive with a mass fraction of 0.5%, the etching temperature is 70℃, and the etching time is 400s; S6. Deposit a passivation antireflection layer 41 on the surface of the semiconductor substrate 10; wherein the passivation antireflection layer is Al2O3 / SiN x Layered structure, Al2O3 layer thickness 5nm, SiN x Layer thickness 80nm; S7. Print corresponding metal electrodes, including a first electrode 51 and a second electrode 52, in the first doped region 20 and the second doped region 30 of the semiconductor substrate 10. After sintering and light injection, a solar cell is obtained, denoted as cell A. The substrate of battery A is an N-type semiconductor, which has advantages such as high minority carrier lifetime and good weak light response. The first doped region 20 is P-type doped and the second doped region 30 is N-type doped. The doping element of the P-type doping is one or more of IIIA and the doping element of the N-type doping is one or more of VA. The specific types are not limited. The area of ​​the second doped region 30 of battery A is larger than the area of ​​the first doped region 20 to increase the current and passivation level of the second surface of battery A. Based on steps S1 and S3, the surfaces of the first doped region 20 and the second doped region 30 are set as polished planar structures.

[0056] For the isolation region, the vertical projection length of the first segment structure 61 on the surface of the semiconductor substrate 10 along the direction perpendicular to the extension of the isolation region is L1, and L1 is 300 μm; the vertical projection length of the second segment structure 62 on the surface of the semiconductor substrate 10 along the direction perpendicular to the extension of the isolation region is L2, and L2 is 450 μm. The ratio of the maximum vertical projection area of ​​the second segment structure 62 of a single isolation region on the surface of the semiconductor substrate 10 to the maximum vertical projection area of ​​the first segment structure 61 on the surface of the semiconductor substrate 10 is D1, and D1 is 1.5; the ratio of the total maximum vertical projection area of ​​the second segment structures 62 of all isolation regions on the second surface to the area of ​​the isolation region on the second surface is D2, and D2 is 0.5. Along the thickness direction of the semiconductor substrate 10, the maximum vertical height H1 of the isolation region extending vertically from the reference surface into the semiconductor substrate 10 is 5 μm.

[0057] Example 2 The structure of the solar cell disclosed in Example 2 is similar to Figure 1 Similarly, the first segment structure 61 of the isolation region has a rectangular cross-sectional shape along the direction perpendicular to the extension of the isolation region, and the second segment structure 62 has an inverted trapezoidal cross-sectional shape along the direction perpendicular to the extension of the isolation region. The preparation steps of the solar cell in Example 2 are the same as those in Example 1, except that the ratio D2 of the total area of ​​the maximum vertical projection of the second segment structure 62 of all isolation regions on the surface of the semiconductor substrate 10 to the area of ​​the surface where the isolation region is located is adjusted to 0.3. The solar cell finally obtained is denoted as cell B.

[0058] Example 3 The structure of the solar cell disclosed in Example 3 is similar to Figure 1 Similarly, the first segment 61 of the isolation region has a rectangular cross-sectional shape along the direction perpendicular to the extension of the isolation region, and the second segment 62 has an inverted trapezoidal cross-sectional shape along the direction perpendicular to the extension of the isolation region. The preparation steps of the solar cell in Example 3 are the same as those in Example 1, except that the laser's interaction angle with the surface of the semiconductor substrate 10 is 50° in the first laser etching and 130° in the second laser etching. The solar cell finally obtained is denoted as cell C.

[0059] The isolation region structure parameters of battery C are as follows: The vertical projection length of the first segment 61 on the surface of the semiconductor substrate 10 along the direction perpendicular to the extension of the isolation region is L1, and L1 is 250 μm; the vertical projection length of the second segment 62 on the surface of the semiconductor substrate 10 along the direction perpendicular to the extension of the isolation region is L2, and L2 is 480 μm. The ratio of the maximum vertical projection area of ​​the second segment 62 of a single isolation region on the surface of the semiconductor substrate 10 to the maximum vertical projection area of ​​the first segment 61 on the surface of the semiconductor substrate 10 is D1, and D1 is 1.92; the ratio of the total maximum vertical projection area of ​​the second segment 62 of all isolation regions on the second surface to the surface area of ​​the isolation region is D2, and D2 is 0.6. Along the thickness direction of the semiconductor substrate 10, the maximum vertical height H1 of the isolation region extending vertically from the reference surface into the semiconductor substrate 10 is 4 μm.

[0060] Example 4 The structure of the solar cell disclosed in Example 4 is similar to Figure 1 Similarly, the first segment structure 61 of the isolation region has a rectangular cross-sectional shape along the direction perpendicular to the extension of the isolation region, and the second segment structure 62 has an inverted trapezoidal cross-sectional shape along the direction perpendicular to the extension of the isolation region. The fabrication steps of the solar cell in Example 4 are the same as in Example 3, except that the ratio D2 of the total area of ​​the maximum vertical projection of the second segment structure 62 of all isolation regions on the surface of the semiconductor substrate 10 to the surface area of ​​the isolation region is adjusted to 0.3. The final solar cell is denoted as cell D.

[0061] Example 5 Figure 2 The diagram shows another structure of the solar cell of the present invention, wherein the first segment 61 of the isolation region has a rectangular cross-sectional shape along the direction perpendicular to the extension of the isolation region, and the second segment 62 has a circular arc shape with a corresponding central angle greater than 180° along the direction perpendicular to the extension of the isolation region; the resulting solar cell is denoted as cell E.

[0062] For the isolation region, the vertical projection length of the first segment structure 61 on the surface of the semiconductor substrate 10 along the direction perpendicular to the extension of the isolation region is L1, and L1 is 350 μm; the vertical projection length of the second segment structure 62 on the surface of the semiconductor substrate 10 along the direction perpendicular to the extension of the isolation region is L2, and L2 is 400 μm. The ratio of the maximum vertical projection area of ​​the second segment structure 62 of a single isolation region on the surface of the semiconductor substrate 10 to the maximum vertical projection area of ​​the first segment structure 61 on the surface of the semiconductor substrate 10 is D1, and D1 is 1.14; the ratio of the total maximum vertical projection area of ​​the second segment structures 62 of all isolation regions on the first or second surface to the area of ​​the surface where the isolation region is located is D2, and D2 is 0.5. Along the thickness direction of the semiconductor substrate 10, the maximum vertical height H1 of the isolation region extending vertically from the reference surface into the semiconductor substrate 10 is 5 μm.

[0063] Example 6 The structure of the solar cell disclosed in Example 6 is similar to Figure 2 Similarly, the first segment structure 61 of the isolation region has a rectangular cross-sectional shape along the direction perpendicular to the extension of the isolation region, and the second segment structure 62 has an arc shape with a corresponding central angle greater than 180° along the direction perpendicular to the extension of the isolation region. The difference between Example 6 and Example 5 is that the ratio D2 of the total area of ​​the maximum vertical projection of the second segment structure 62 of all isolation regions on the surface of the semiconductor substrate 10 to the area of ​​the surface where the isolation region is located is adjusted to 0.3. The solar cell finally obtained is denoted as cell F.

[0064] Example 7 The structure of the solar cell disclosed in Example 7 is similar to Figure 2 Similarly, the first section of the isolation zone 61 has a rectangular cross-sectional shape along the direction perpendicular to the extension of the isolation zone, and the second section of the isolation zone 62 has a circular arc shape with a corresponding central angle greater than 180° along the direction perpendicular to the extension of the isolation zone. The final solar cell is denoted as cell G.

[0065] The isolation region structure parameters of battery G are as follows: The vertical projection length of the first segment 61 on the surface of semiconductor substrate 10 along the direction perpendicular to the extension of the isolation region is L1, and L1 is 100 μm; the vertical projection length of the second segment 62 on the surface of semiconductor substrate 10 along the direction perpendicular to the extension of the isolation region is L2, and L2 is 200 μm. The ratio of the maximum vertical projection area of ​​the second segment 62 of a single isolation region on the surface of semiconductor substrate 10 to the maximum vertical projection area of ​​the first segment 61 on the surface of semiconductor substrate 10 is D1, and D1 is 2; the ratio of the total maximum vertical projection area of ​​the second segment 62 of all isolation regions on the second surface to the surface area of ​​the isolation region is D2, and D2 is 0.55. Along the thickness direction of semiconductor substrate 10, the maximum vertical height H1 of the isolation region extending vertically from the reference surface into the semiconductor substrate 10 is 4 μm.

[0066] Example 8 The structure of the solar cell disclosed in Example 8 is similar to Figure 2 Similarly, the first segment structure 61 of the isolation region has a rectangular cross-sectional shape along the direction perpendicular to the extension of the isolation region, and the second segment structure 62 has an arc shape with a corresponding central angle greater than 180° along the direction perpendicular to the extension of the isolation region. The difference between Example 8 and Example 7 is that the ratio D2 of the total area of ​​the maximum vertical projection of the second segment structure 62 of all isolation regions on the surface of the semiconductor substrate 10 to the area of ​​the surface where the isolation region is located is adjusted to 0.3. The solar cell finally obtained is denoted as cell H.

[0067] Example 9 Figure 3 The diagram shows another structure of the solar cell of the present invention, a bifacial solar cell, wherein a first doped region 20 is formed on a first surface of a semiconductor substrate and a second doped region 30 is formed on a second surface, and electrodes of the same polarity are disposed on the same cell surface; an isolation region is disposed on the second surface, alternating with the second doped region 30, wherein the first segment structure 61 of the isolation region has a rectangular cross-sectional shape along the direction perpendicular to the extension of the isolation region, and the second segment structure 62 has an inverted trapezoidal cross-sectional shape along the direction perpendicular to the extension of the isolation region; optionally, the isolation region may also be disposed in the second doped region 30 in other ways.

[0068] Example 9: The fabrication steps of the solar cell include: S1. The first and second surfaces of the semiconductor substrate 10 are texturized using an alkaline solution; wherein the texturizing solution is a mixed solution of potassium hydroxide with a mass fraction of 1.5% and texturizing additive with a mass fraction of 0.5%. S2. A first doped layer 22 and a first oxide layer are sequentially stacked on the first surface of the semiconductor substrate 10; wherein, the first doped layer 22 and the first oxide layer at the predetermined first doped region 20 position constitute the first doped region 20. S3. A second tunneling layer 31, a second doped layer 32, and a second oxide layer are sequentially stacked on the second surface of the semiconductor substrate 10; wherein, the second doped layer 32 and the second oxide layer at the predetermined second doped region 30 position constitute the second doped region 30. S4. Part of the second tunneling layer 31, the second doped layer 32, and the second oxide layer on the second surface of the semiconductor substrate 10 are removed by two first laser etchings and one first wet etching solution to obtain an isolation region; the laser angles relative to the surface of the semiconductor substrate 10 in the two first laser etchings are 60° and 120°, respectively, and the laser power is 75W in both cases; the first wet etching solution is a mixture of 3.0% potassium hydroxide or sodium hydroxide solution and 0.5% texturing additive, the etching temperature is 70°C, and the etching time is 150s; S5. A passivation antireflection layer 41 is deposited on the surface of the semiconductor substrate 10; wherein the passivation antireflection layer is Al2O3 / SiN. x Layered structure, Al2O3 layer thickness 5nm, SiN x Layer thickness 80nm; S6. Print corresponding metal electrodes, including a first electrode 51 and a second electrode 52, in the first doped region 20 and the second doped region 30 of the semiconductor substrate 10. After sintering and light injection, a solar cell is obtained, denoted as cell I. The substrate of battery I is an N-type semiconductor, which has advantages such as high minority carrier lifetime and good weak light response; the first doped region 20 is P-type doped and the second doped region 30 is N-type doped. The doping element of the P-type doping is one or more of IIIA and the doping element of the N-type doping is one or more of VA. The specific types are not limited; and based on step S1, the surfaces of the first doped region 20 and the second doped region 30 of battery I are set with a textured surface structure.

[0069] For the isolation region, the vertical projection length of the first segment structure 61 on the surface of the semiconductor substrate 10 along the direction perpendicular to the extension of the isolation region is L1, and L1 is 300 μm; the vertical projection length of the second segment structure 62 on the surface of the semiconductor substrate 10 along the direction perpendicular to the extension of the isolation region is L2, and L2 is 450 μm. The ratio of the maximum vertical projection area of ​​the second segment structure 62 of a single isolation region on the surface of the semiconductor substrate 10 to the maximum vertical projection area of ​​the first segment structure 61 on the surface of the semiconductor substrate 10 is D1, and D1 is 1.5; the ratio of the total maximum vertical projection area of ​​the second segment structures 62 of all isolation regions on the second surface to the area of ​​the isolation region on the second surface is D2, and D2 is 0.5. Along the thickness direction of the semiconductor substrate 10, the maximum vertical height H1 of the isolation region extending vertically from the reference surface into the semiconductor substrate 10 is 5 μm.

[0070] Comparative Example 1 Figure 4 The solar cell fabricated for Comparative Example 1 is denoted as Cell J. Cell J differs from Cell A of Example 1 only in the morphology of the isolation region. Specifically, the first segment structure 61 and the second segment structure 62 of Cell J are configured as straight-walled structures with equal width at the top and bottom along the direction perpendicular to the extension of the isolation region, i.e., L1=L2=300μm for the rectangular cell J. The ratio of the maximum vertical projection area of ​​the second segment structure 62 of a single isolation region on the surface of the semiconductor substrate 10 to the maximum vertical projection area of ​​the first segment structure 61 on the surface of the semiconductor substrate 10 is D1, where D1 is 1. The ratio of the total maximum vertical projection area of ​​the second segment structures 62 of all isolation regions on the first or second surface to the surface area of ​​the isolation region is D2, where D2 is 0.3. Along the thickness direction of the semiconductor substrate 10, the maximum vertical height H1 of the isolation region extending vertically from the reference surface into the semiconductor substrate 10 is 4 μm.

[0071] Comparative Example 2 The difference between Comparative Example 2 and Example 1 lies only in the morphology of the isolation region and the angle of laser action on the surface of the semiconductor substrate 10. The resulting solar cell is denoted as cell K. Specifically, the first segment 61 and the second segment 62 of cell K are set as trapezoids along the direction perpendicular to the extension of the isolation region, and L1 is much larger than L2; the angle of laser action relative to the surface of the semiconductor substrate 10 in the first laser etching is 130°, and the angle of laser action relative to the surface of the semiconductor substrate 10 in the second laser etching is 50°. For the isolation region, the vertical projection length of the first segment structure 61 on the surface of the semiconductor substrate 10 along the direction perpendicular to the extension of the isolation region is L1, and L1 is 480 μm; the vertical projection length of the second segment structure 62 on the surface of the semiconductor substrate 10 along the direction perpendicular to the extension of the isolation region is L2, and L2 is 250 μm. The ratio of the maximum vertical projection area of ​​the second segment structure 62 of a single isolation region on the surface of the semiconductor substrate 10 to the maximum vertical projection area of ​​the first segment structure 61 on the surface of the semiconductor substrate 10 is D1, and D1 is 0.52; the ratio of the total maximum vertical projection area of ​​the second segment structures 62 of all isolation regions on the first or second surface to the area of ​​the surface where the isolation region is located is D2, and D2 is 0.65. Along the thickness direction of the semiconductor substrate 10, the maximum vertical height H1 of the isolation region extending vertically from the reference surface into the semiconductor substrate 10 is 5 μm.

[0072] Comparative Example 3 Figure 5 The solar cell prepared for Comparative Example 3 differs from that of Example 9 only in the morphology of the isolation region. Specifically, the first segment structure 61 and the second segment structure 62 of Comparative Example 3 are set as straight-walled structures with equal width at the top and bottom along the direction perpendicular to the extension of the isolation region, i.e., rectangular. The resulting solar cell is denoted as cell L. The lengths of cell L are L1 = L2 = 300 μm. The ratio of the maximum vertical projection area of ​​the second segment structure 62 of a single isolation region on the surface of the semiconductor substrate 10 to the maximum vertical projection area of ​​the first segment structure 61 on the surface of the semiconductor substrate 10 is D1, where D1 is 1. The ratio of the total maximum vertical projection area of ​​the second segment structures 62 of all isolation regions on the first or second surface to the surface area of ​​the isolation region is D2, where D2 is 0.5. The maximum vertical height H1 of the isolation region extending vertically from the reference surface into the semiconductor substrate 10 along the thickness direction of the semiconductor substrate 10 is 5 μm.

[0073] The solar cell samples prepared in Examples 1-9 and Comparative Examples 1, 2 and 3 were subjected to the following experiments to detect various cell performance parameters of each sample, including open-circuit voltage, short-circuit current, fill factor, conversion efficiency and other parameters measured and calculated using an IV tester. The measured electrical performance data are shown in Table 2 below.

[0074] Table 1 shows the specific differences in the process and structural parameters of the isolation region on the battery prepared in Examples 1-9 and Comparative Examples 1-3.

[0075] Table 2 shows the battery performance data of the embodiments and comparative examples provided by the present invention.

[0076] Combining Examples 1, 3, 5, 7, and 9 shown in Table 1, and Comparative Examples 1-3, the battery performance data in Table 2 shows that different types of solar cells can achieve a balance in various aspects such as short-circuit risk, carrier transport, parasitic absorption, and optical performance on the second side of the solar cell by reasonably setting the overall shape, opening width, maximum width inside the isolation zone, and isolation zone depth. This results in a bifaciality exceeding 90%. Compared to conventional equal-width groove isolation zones, the maximum increase in bifaciality for back-contact solar cells can reach 5%, and for bifacial solar cells, it can reach 5.2%. Compared to conventional trapezoidal groove isolation zones, the maximum increase in bifaciality for back-contact solar cells can reach 6.6%. This represents a breakthrough in the bottleneck of solar cell bifaciality.

[0077] Further comparative analysis of the battery performance data from Examples 1 and 2, 3 and 4, 5 and 6, 7 and 8 revealed that reducing the number of isolation zones with the same structure in solar cells significantly impacts their optical performance, leading to a decrease in bifaciality. This is because a smaller isolation zone reduces the number of reflections and refractions of light, thus decreasing the interaction time between light and the active layer and consequently slightly reducing light utilization. Therefore, while a smaller D2 value slightly reduces the bifaciality of the solar cell, it remains higher than that of solar cells with conventional equal-width slot isolation zones and conventional trapezoidal slot isolation zones.

[0078] It should be noted that, in addition to the inverted trapezoidal and arc-shaped structures given in the embodiments, the overall structure of the isolation zone can also be any other shape. As long as the key feature satisfies the "wide bottom and narrow opening" scheme, it falls within the technical scope of this invention. That is, along the direction parallel to the extension of the isolation zone, the single maximum vertical projection area inside the isolation zone on the battery surface is greater than the single vertical projection area of ​​the isolation zone opening on the battery surface.

[0079] Example 10 This embodiment discloses a tandem solar cell, including a top cell, which is a perovskite solar cell, a cadmium sulfide solar cell, a copper indium gallium selenide solar cell, or a gallium arsenide solar cell; an intermediate connecting layer; and a bottom cell, which is a solar cell provided in any of the above embodiments; the top cell, the intermediate connecting layer, and the bottom cell are stacked and connected; wherein, the intermediate connecting layer can be a transparent conductive layer.

[0080] The bottom cell is selected from the solar cells provided in any of the foregoing embodiments. The structure and preparation process are the same as those of the corresponding embodiments. Please refer to the corresponding descriptions of the foregoing embodiments. They will not be described in detail below.

[0081] Example 11 This embodiment discloses a photovoltaic module, which includes the solar cell provided in any of the foregoing embodiments, or the photovoltaic module includes the tandem cell provided in the foregoing embodiments. For the parts of the selected solar cell or tandem cell that are the same as those in the foregoing embodiments, please refer to the corresponding descriptions in the foregoing embodiments; detailed descriptions will not be repeated below.

[0082] The present invention and its embodiments have been described above illustratively. This description is not restrictive and is merely one embodiment of the present invention, and is not actually limited thereto. Therefore, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the present invention, such designs should fall within the protection scope of the present invention.

Claims

1. A solar cell, characterized in that, Including semiconductor substrates; The semiconductor substrate has a first surface and a second surface disposed opposite to each other, at least one surface of the semiconductor substrate is provided with a doped region, and at least one of the doped regions is provided with an isolation region. The isolation region extends from the reference surface into the semiconductor substrate and is configured as a two-segment trench structure. The two-segment trench structure includes a first segment structure with one end open and a second segment structure connected to the first segment structure. The first segment structure extends from the reference surface to the surface of the semiconductor substrate, and the second segment structure extends from the surface of the semiconductor substrate into the semiconductor substrate. The inner wall surface of the second segment structure is a textured surface. The reference surface is defined as the surface of the doped region away from the semiconductor substrate. For the isolation region, the ratio of the maximum vertical projection area of ​​the second segment structure of a single isolation region on the semiconductor substrate surface to the maximum vertical projection area of ​​the first segment structure on the semiconductor substrate surface is defined as D1, and the ratio of the total maximum vertical projection area of ​​the second segment structure of all isolation regions on the first or second surface on the semiconductor substrate surface to the area of ​​the isolation region on the first or second surface is defined as D2, then 1 < D1 ≤ 3, 0.2 < D2 ≤ 0.

8.

2. The solar cell according to claim 1, characterized in that, The second section of the isolation zone has a cross-sectional shape that is either an inverted trapezoid or an arc with a corresponding central angle greater than 180° along the direction perpendicular to the extension of the isolation zone.

3. The solar cell according to claim 1, characterized in that, For any of the isolation regions, the vertical projection length of the first segment structure on the semiconductor substrate surface along the direction perpendicular to the extension of the isolation region is defined as L1, and the vertical projection length of the second segment structure on the semiconductor substrate surface along the direction perpendicular to the extension of the isolation region is defined as L2. Then, 30μm≤L1≤500μm, 30μm<L2<500μm, and L2>L1.

4. The solar cell according to claim 1, characterized in that, The velvet-like structure on the inner wall of the second section of the isolation zone consists of several pyramid bases, with a distribution density of 20,000 to 50,000 pyramid bases per mm. 2 Furthermore, the size of any of the pyramid bases is 0.1~4μm and the height is 0.1~4μm.

5. The solar cell according to claim 1, characterized in that, Define the maximum vertical height of the isolation region extending vertically from the reference plane into the semiconductor substrate as H1, then 0.5μm≤H1≤5μm.

6. The solar cell according to claim 1, characterized in that, It also includes a passivation antireflection layer, which covers the outer surface of the semiconductor substrate and the surface of the isolation region; wherein, the outer surface of the semiconductor substrate includes the first surface, the second surface and the outer side surface of the semiconductor substrate; The passivation antireflection layer is Al2O3 / SiN. x The Al2O3 / SiN stacked structure x In the stacked structure, the thickness of the Al2O3 layer is 3~10nm, and the thickness of the SiNx layer is 60~100nm.

7. The solar cell according to claim 1, characterized in that, The solar cell is a back-contact solar cell; The semiconductor substrate has the doped region on only one surface. The doped region includes alternating first doped regions and second doped regions with opposite polarities. The isolation region is disposed between any adjacent first doped regions and second doped regions.

8. The solar cell according to claim 1, characterized in that, The solar cell is a bifacial solar cell; The first and second surfaces of the semiconductor substrate are respectively provided with the doped regions, the doped regions on the same surface have the same polarity, the doped regions on different surfaces have opposite polarities, and at least one of the doped regions on one side of the semiconductor substrate is provided with the isolation region.

9. A method for preparing a solar cell, characterized in that, include: The steps of polishing or texturing the first and second surfaces of a semiconductor substrate; The steps of forming a doped region on at least one surface of a polished or texturized semiconductor substrate and forming an isolation region in at least one doped region; The steps involved in forming a velvety texture at the target location within the isolation zone; The step of depositing a passivation antireflection layer on the outer surface of the semiconductor substrate and the surface of the isolation region; The steps involve printing corresponding metal electrodes in the doped region, followed by sintering and light injection to obtain a solar cell. The isolation region extends from the reference surface into the semiconductor substrate and is configured as a two-segment trench structure. The two-segment trench structure includes a first segment open at one end and a second segment connected to the first segment. The first segment extends from the reference surface to the surface of the semiconductor substrate, and the second segment extends from the surface of the semiconductor substrate into the interior of the semiconductor substrate. The inner wall of the second segment has a textured surface. The reference surface is defined as the surface of the doped region away from the semiconductor substrate, and the target location is the inner wall of the second segment of the isolation region. The ratio of the maximum vertical projection area of ​​the second segment structure of a single isolation region on the semiconductor substrate surface to the maximum vertical projection area of ​​the first segment structure on the semiconductor substrate surface is defined as D1, and the ratio of the total maximum vertical projection area of ​​the second segment structure of the isolation region on the semiconductor substrate surface on the first or second surface to the area of ​​the isolation region on the first or second surface is defined as D2. Then 1 < D1 ≤ 3 and 0.2 < D2 ≤ 0.

8.

10. The method for preparing a solar cell according to claim 9, characterized in that, The second section of the isolation zone has a cross-sectional shape that is either an inverted trapezoid or an arc with a corresponding central angle greater than 180° along the direction perpendicular to the extension of the isolation zone.

11. The method for preparing a solar cell according to claim 9, characterized in that, For any of the isolation regions formed, the vertical projection length of the first segment structure on the semiconductor substrate surface along the first direction is defined as L1, and the vertical projection length of the second segment structure on the semiconductor substrate surface along the first direction is defined as L2. Then, 30μm≤L1≤500μm, 30μm<L2<500μm, and L2>L1; wherein, the first direction is the direction in which the battery surface extends perpendicular to the isolation region.

12. A stacked battery, characterized in that, include: Top cell, which can be a perovskite cell, cadmium sulfide solar cell, copper indium gallium selenide solar cell, or gallium arsenide solar cell; Intermediate connection layer; The base cell is a solar cell as described in any one of claims 1 to 8 or a solar cell prepared by the method described in any one of claims 9 to 11; The top battery, the intermediate connecting layer, and the bottom battery are stacked and connected.

13. A photovoltaic module, characterized in that, The photovoltaic module comprises a solar cell according to any one of claims 1 to 8, or the photovoltaic module comprises a solar cell prepared by the method of preparing a solar cell according to any one of claims 9 to 11, or the photovoltaic module comprises a tandem cell according to claim 12.

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