Solar cell, stacked cell, and photovoltaic module

Abstract

This application relates to the field of solar cells and discloses a solar cell, a tandem solar cell, and a photovoltaic module. The solar cell includes: a substrate having a first surface and a second surface disposed opposite each other along its thickness direction; a functional film layer covering the first and second surfaces of the substrate; the first surface includes at least one first textured region and at least one second textured region alternately arranged along a first horizontal direction, the first horizontal direction being perpendicular to the thickness direction; the first textured region includes a plurality of first protrusions, and the second textured region includes a plurality of second protrusions; there is a height difference between the average height of the first protrusions and the average height of the second protrusions; a transition surface is formed between the first textured region and the second textured region, the transition surface having a non-linear curved extension along a second horizontal direction, the second horizontal direction being perpendicular to both the first horizontal direction and the thickness direction. This application can improve mechanical strength and the uniformity of stress distribution.

Description

Technical Field

[0001] This application relates to the field of solar cell technology, and in particular to a solar cell, a tandem cell, and a photovoltaic module. Background Technology

[0002] With the accelerated transition from traditional fossil fuels and the increasing demand for sustainable development, solar cells, as a clean and renewable energy technology, are increasingly becoming an important component of the energy system. A solar cell is essentially a semiconductor device that directly converts solar energy into electrical energy. Its working principle is based on the photovoltaic effect: when sunlight shines on the cell, photon energy excites electron-hole pairs (i.e., charge carriers) to be generated inside the semiconductor. These charge carriers then separate under the influence of a built-in electric field, forming a potential difference. By effectively extracting these charge carriers through the metal electrodes on the front and back of the cell, direct current can be generated for use in external circuits, thus achieving the efficient conversion and utilization of solar energy into electrical energy.

[0003] In related technologies, when different textured regions are formed on the surface of a silicon wafer through methods such as step-by-step texturing, masking, or changing local reaction conditions, the transition surfaces between these regions typically exhibit a flat, steep, or regular zigzag shape. This rigid, unnatural boundary shape leads to uneven mechanical strength and stress distribution, which can easily cause stress concentration, resulting in film peeling and cell cracking, thereby affecting the long-term reliability of the cell. Summary of the Invention This application provides a solar cell, a tandem cell, and a photovoltaic module that can improve mechanical strength and the uniformity of stress distribution.

[0004] To solve the above-mentioned technical problems, one technical solution adopted in this application is: to provide a solar cell, comprising: A substrate having a first surface and a second surface disposed opposite to each other along the thickness direction; A functional film layer, including a passivation film layer and an antireflection film layer, wherein the functional film layer covers the first surface and the second surface of the substrate; The first surface includes at least one first pile area and at least one second pile area arranged alternately along a first horizontal direction, the first horizontal direction being perpendicular to the thickness direction, the first pile area including a plurality of first protrusion structures, the second pile area including a plurality of second protrusion structures, and a height difference between the average height of the first protrusion structure and the average height of the second protrusion structure. A transition surface is formed between the first velvet area and the second velvet area. The transition surface extends in a non-linear curved shape along the second horizontal direction, which is perpendicular to both the first horizontal direction and the thickness direction.

[0005] According to one embodiment of the present invention, the average height of the first protrusion structure located on the transition surface of the first velvet area is less than the average height of the first protrusion structure located on the non-transition surface; and / or, the average height of the second protrusion structure located on the transition surface of the second velvet area is less than the average height of the second protrusion structure located on the non-transition surface.

[0006] According to one embodiment of the present invention, the transition surface is formed by the side or top of the first protrusion structure and / or the second protrusion structure, and the transition surface has a surface that extends continuously along the second horizontal direction.

[0007] According to one embodiment of the present invention, the cross-sectional profile of the transition surface includes at least one of a circular arc, an elliptical arc, a wavy line, and an irregular polygonal line.

[0008] According to one embodiment of the present invention, on the transition surface, at least a portion of the vertex regions of the first protrusion structure and / or the second protrusion structure are formed with a cavity recessed along the thickness direction, the opening of the cavity is located on the upper surface of the protrusion structure, the bottom of the cavity is located inside the protrusion structure, and the cross-sectional profile of the cavity exhibits a monotonically decreasing trend in the direction from the opening to the bottom.

[0009] According to one embodiment of the present invention, within the transition surface, starting from the boundary line between the transition surface and the first velvet area or the second velvet area, extending along the first horizontal direction toward a direction away from the boundary line, the opening area of ​​the cavity exhibits a monotonically decreasing trend.

[0010] According to one embodiment of the present invention, the depth of the cavity and the length of the opening are both less than 5 micrometers; and / or, the angle between the sidewall of the cavity and the first surface is 10° to 130°.

[0011] According to one embodiment of the present invention, the shape of the cavity includes at least one of an inverted pyramid shape, an inverted cone shape, and an inverted frustum shape; and / or, the shape of the first protrusion structure and / or the second protrusion structure includes at least one of a pyramid, a truncated pyramid, a frustum pyramid, and a cone.

[0012] To solve the above-mentioned technical problems, another technical solution adopted in this application is: to provide a stacked battery, comprising: Top cell, which can be a perovskite cell, cadmium telluride solar cell, copper indium gallium selenide solar cell, or gallium arsenide solar cell; Intermediate connecting layer; and The bottom battery is the aforementioned solar cell; The top battery, the intermediate connecting layer, and the bottom battery are stacked and connected.

[0013] To solve the above-mentioned technical problems, another technical solution adopted in this application is: including the solar cell or the tandem cell.

[0014] The beneficial effects of this application are as follows: The solar cell of this application forms a transition surface between the first textured area and the second textured area. This transition surface extends in a non-linear curved shape along the second horizontal direction. On the one hand, it makes the transition between textured areas more natural and smooth, transforming the traditional rigid and unnatural boundary shape into a gradual stress buffer zone, which facilitates a smooth stress transition and avoids stress concentration caused by abrupt changes in height. On the other hand, the curved extension shape of the transition surface makes the protruding structures of the first textured area and the second textured area form a mechanical structure that interlocks and supports each other on the transition surface, enhancing the overall structure's shear resistance and bending resistance. This solves the problem of uneven mechanical strength and stress distribution caused by local discontinuity due to an overly abrupt transition surface. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of a solar cell according to an embodiment of this application.

[0016] Figure 2 for Figure 1 A schematic diagram of the transition surface of a solar cell.

[0017] Figure 3 This is a partial structural schematic diagram of a solar cell according to another embodiment of this application.

[0018] Figure 4 for Figure 3 A schematic diagram of the transition surface of a solar cell.

[0019] Figure 5 This is a scanning electron microscope image of a solar cell according to an embodiment of this application.

[0020] Figure 6 for Figure 5 A magnified schematic diagram of a portion of region A.

[0021] Figure 7 The diagram shows the structure of the cavity in the solar cell according to an embodiment of this application, wherein (a) is an inverted pyramid shape, (b) an inverted cone shape, (c) an inverted frustum shape, (d) a pinhole shape, and (e) an irregular shape.

[0022] Figure 8 This is a schematic diagram of the structure of a solar cell according to another embodiment of this application.

[0023] Figure 9 This is a schematic diagram of the structure of the battery string in the photovoltaic module according to an embodiment of this application.

[0024] Figure 10 This is a schematic diagram of the structure of a photovoltaic module according to an embodiment of this application. Detailed Implementation

[0025] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0026] The terms "first," "second," and "third" in this application are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first," "second," or "third" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified. All directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative positional relationships and movements between components in a specific orientation (as shown in the figures). If the specific orientation changes, the directional indications also change accordingly. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or devices.

[0027] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0028] like Figures 1 to 10 As shown, this is a solar cell 100 provided in an embodiment of this application.

[0029] like Figure 1As shown, the solar cell 100 of this application embodiment includes a substrate 11 and a functional film layer 12 covering the substrate 11. The substrate 11 has a first surface 11a and a second surface 11b disposed opposite to each other along its thickness direction S1. The functional film layer 12 covers the first surface 11a and the second surface 11b of the substrate 11. The functional film layer 12 includes a passivation film layer covering the substrate 11 and an anti-reflection film layer covering the passivation film layer.

[0030] The first surface 11a is the front surface, and the second surface 11b is the back surface. The first surface 11a includes at least one first napped area 13 and at least one second napped area 14 arranged alternately along the horizontal direction S2, wherein the horizontal direction S2 is perpendicular to the thickness direction S1. The number of first napped areas 13 and second napped areas 14 on the first surface 11a can be the same or different. Since the first napped areas 13 and second napped areas 14 can be formed using different napping process parameters, differences can be formed in structure or size.

[0031] The first velvet area 13 includes a plurality of first protrusions, and the second velvet area 14 includes a plurality of second protrusions. The shapes of the first protrusions include at least one of a pyramid, a truncated pyramid, a frustum, and a cone, and the shapes of the second protrusions include at least one of a pyramid, a truncated pyramid, a frustum, and a cone. It can be understood that the shapes and sizes of the first and second protrusions can be the same or different, and the density of the first protrusions in the first velvet area 13 can be the same or different from the density of the second protrusions in the second velvet area 14. This embodiment uses the example where both the first and second protrusions are pyramidal in shape for illustration.

[0032] like Figure 1 As shown, there is a height difference ΔH between the average height of the first protrusion structure and the average height of the second protrusion structure. This can be understood as follows: along the thickness direction S1, the heights of multiple first protrusion structures can be the same or different, and the heights of multiple second protrusion structures can be the same or different. The height of the first protrusion structure is the distance between its top and the first surface 11a, and the height of the second protrusion structure is the distance between its top and the first surface 11a. Therefore, the average height of the first protrusion structure is the average of the distances between its top and the first surface 11a, and the average height of the second protrusion structure is the average of the distances between its top and the first surface 11a.

[0033] As one implementation method, such as Figure 1As shown, the average height of the first protrusion structure is higher than that of the second protrusion structure. Traditional protrusion structures with uniform height create a repetitive, periodic stress field on a macroscopic scale, meaning that the mechanical strength is the same in different areas of the battery surface. When the battery is subjected to external forces (such as thermal stress, wind pressure, or hail impact), all protrusion structures vibrate or deform with similar amplitudes, easily triggering resonance effects and leading to overall structural fatigue. In the embodiments of this application, when external stress (such as thermal expansion) acts on the solar cell 100, the first protrusion structure (i.e., the high protrusion area) preferentially undergoes minor deformation, absorbing and dissipating most of the stress energy. The second protrusion structure (i.e., the low protrusion area) acts as a rigid framework, maintaining the stability of the overall structure. This hardness gradient effectively prevents the initiation and propagation of microcracks. Due to the non-periodicity in height and distribution of the high and low protrusion areas, their response frequencies to external excitations (such as vibration or wind pressure) differ. This breaks the condition of synchronous vibration or resonance in a uniform structure, making the structure of the solar cell 100 more stable under dynamic loads and extending its fatigue life.

[0034] Furthermore, in a uniformly textured surface, some short-wavelength light may escape through the gaps in the raised structure due to an excessively large grazing angle, and the uniformly textured surface does not scatter long-wavelength light sufficiently, resulting in a significant amount of light being reflected or lost through transmission. The embodiments of this application, by setting textured surface regions of different heights, can optimize the absorption of light of different wavelengths. The height difference between the first textured surface region 13 and the second textured surface region 14 allows short-wavelength and long-wavelength light to obtain optimal absorption paths in different regions, thereby optimizing light absorption efficiency.

[0035] like Figure 2 As shown, a transition surface 15 is formed between the first velvet area 13 and the second velvet area 14. The transition surface 15 extends in a non-linear curved shape along the second horizontal direction S3. It can be understood that the first velvet area 13 and the second velvet area 14 are not connected by a rigid boundary such as a step or a straight line, but rather form a transition surface 15 that extends in a non-linear curved shape along the second horizontal direction S3.

[0036] In one embodiment, the transition surface 15 is formed by the side or top of the first protrusion structure and / or the second protrusion structure, and the transition surface 15 has a surface that extends continuously along the second horizontal direction S3.

[0037] For example, the transition surface 15 is formed by the side surface of the first protruding structure and the side surface of the second protruding structure, with the splicing surface continuous and unbroken, meeting the requirements of the bent extension shape. In another example, the transition surface 15 is formed by the side surface of the first protruding structure and the top of the second protruding structure. In another example, the transition surface 15 is formed by the top of the first protruding structure and the side surface of the second protruding structure. In yet another example, the transition surface 15 is formed by the top of the first protruding structure and the top of the second protruding structure.

[0038] In one implementation, the transition surface 15 extends discontinuously along the second horizontal direction S3, presenting an overall closed or near-closed structure. For example, the transition surface 15 includes breaks, gaps, or pores, which are connected by a smooth substrate, giving the transition surface 15 an overall closed profile resembling an island or bubble wall. That is, the transition surface 15 separates and surrounds the first textured area 13 and the second textured area 14.

[0039] Furthermore, the projection of the contour of the transition surface 15 onto any cross section perpendicular to the thickness direction S1 is a smooth curve, and the cross-sectional contour of the transition surface 15 includes at least one of circular arcs, elliptical arcs, wavy lines, and irregular broken lines. It can be understood that the transition surface 15 can be a single contour or a mixture of multiple contours, such as a mixture of circular arcs and elliptical arcs, a mixture of wavy lines and elliptical arcs, or a mixture of circular arcs and wavy lines.

[0040] The embodiments of this application form a transition surface 15 between the first velvet area 13 and the second velvet area 14. This transition surface 15 extends in a non-linear curved shape along the second horizontal direction S3. On the one hand, this makes the transition between the velvet areas more natural and smooth, transforming the traditional rigid and unnatural boundary shape into a gradual stress buffer zone, facilitating a smooth stress transition and avoiding stress concentration caused by abrupt changes in height, thereby improving the adhesion and reliability of the functional film layer 12. On the other hand, the curved extension shape of the transition surface 15 causes the protruding structures of the first velvet area 13 and the second velvet area 14 to form a mechanical structure that interlocks and interlaces to support each other on the transition surface 15, enhancing the overall structure's shear resistance and bending resistance. This solves the problem of uneven mechanical strength and stress distribution caused by local discontinuity due to the overly abrupt transition surface 15.

[0041] In one embodiment, the average height of the first protrusion structure located on the transition surface 15 on the first velvet area 13 is less than the average height of the first protrusion structure located on the non-transition surface.

[0042] For example, such as Figure 3As shown, in the first velvet area 13, the average height H1 of the first protrusion structure on the non-transition surface (the area away from the transition surface 15) is 1.2 μm, and the average height H2 of the first protrusion structure on the transition surface 15 (the area near the second velvet area 14) is 0.9 μm, with a height difference of 0.3 μm between the two.

[0043] This configuration creates a height difference between the first protrusion structure of the transition surface 15 and the first protrusion structure of the non-transition surface. When the solar cell 100 is subjected to external force or thermal stress, the first protrusion structure of the transition surface 15 is more likely to undergo elastic deformation, absorb stress, and avoid stress concentration on the non-transition surface. This solves the problem of stress concentration caused by excessive height of the first protrusion structure of the transition surface 15, which leads to peeling off from the functional film layer 12.

[0044] In one embodiment, the average height of the second protrusion structure located on the transition surface 15 on the second velvet area 14 is less than the average height of the second protrusion structure located on the non-transition surface.

[0045] For example, such as Figure 3 As shown, in the second velvet area 14, the average height H3 of the second protrusion structure on the non-transition surface (the area away from the transition surface 15) is 0.8 μm, and the average height H4 of the second protrusion structure on the transition surface 15 (the area near the first velvet area 13) is 0.6 μm, with a height difference of 0.2 μm between the two.

[0046] This configuration creates a height difference between the second protrusion structure of the transition surface 15 and the protrusion structure of the non-transition surface. When the solar cell 100 is subjected to external force or thermal stress, the second protrusion structure of the transition surface 15 is more likely to undergo elastic deformation, absorb stress, and avoid stress concentration on the non-transition surface. This solves the problem of stress concentration caused by excessive height of the second protrusion structure of the transition surface 15, which leads to peeling off from the functional film layer 12.

[0047] In some embodiments, such as Figures 3 to 6 As shown, on the transition surface 15, at least a portion of the first protrusion structure and / or the vertex region of the second protrusion structure are formed with a cavity 16 recessed along the thickness direction. The opening of the cavity 16 is located on the upper surface of the protrusion structure, and the bottom of the cavity 16 is located inside the protrusion structure. The cross-sectional profile of the cavity 16 shows a monotonically decreasing trend from the opening to the bottom.

[0048] This can be understood as the opening of cavity 16 being located at the top of the pyramid, and the outline of the opening can be a concave arc.

[0049] In some embodiments, such as Figure 7 As shown, the shape of cavity 16 includes at least one of the following: inverted pyramid shape, inverted cone shape, inverted frustum shape, pinhole shape, and irregular shape.

[0050] As one implementation method, such as Figure 8 As shown, the first and second protruding structures are pyramids, and the cavity 16 is shaped like a double inverted pyramid. It can be understood that the cavity 16 is formed by two concentric inverted pyramid-shaped contours with opposite apexes; from the opening to the bottom, it first undergoes a contraction of a larger inverted pyramid, followed by a further contraction of a smaller inverted pyramid, and the overall cross-sectional contour shows a step-like or smooth continuous monotonous decreasing trend.

[0051] In some embodiments, such as Figure 3 As shown, the depth H of cavity 16 and the length L of opening are both less than 5 μm. The depth H of cavity 16 refers to the vertical distance from the plane of the opening (i.e., the first surface 11a) downwards to the lowest point of the bottom of cavity 16. For example, the depth of cavity 16 can be 1 μm, 2 μm, 3 μm, or 4 μm. The length L of opening refers to the maximum linear dimension of the opening of cavity 16 on its plane (i.e., the first surface 11a). For example, the length L of opening can be 1 μm, 2 μm, 3 μm, or 4 μm. For cavities 16 with regular geometric shapes (such as inverted pyramids or inverted cones), the length L of opening is the maximum diameter or diagonal of the opening profile; for irregular shapes, it is the distance between the two farthest points on the opening boundary.

[0052] In this embodiment, plasma dry etching or reactive ion etching processes can be used to achieve precise control of the depth H and opening length L of the cavity 16. The design of the cavity 16 minimizes the weakening of the mechanical strength of the substrate material, avoiding the risk of silicon wafer embrittlement or breakage due to over-etching. At the same time, the small opening size can reduce the number of stress concentration sources, thereby improving the overall fatigue resistance of the battery.

[0053] As one implementation method, such as Figure 3 As shown, the angle θ between the sidewall of cavity 16 and the first surface 11a is 10° to 130°. This angle θ is defined as the acute or obtuse angle (absolute value) between the sidewall of cavity 16 and the plane containing the opening of cavity 16 (i.e., the first surface 11a). For cavities 16 with regular geometric shapes (such as inverted pyramids or inverted cones), the angle θ is the angle between the sidewall and the plane containing the opening (i.e., the first surface 11a). For example, the angle for an inverted pyramid cavity is 54.7°; the angle for an inverted cone cavity can be any value (depending on the shape of the etching mask opening).

[0054] When the included angle θ is too small (close to 0°), the sidewalls of cavity 16 tend to be vertical, and the difference between the opening area and the bottom area of ​​cavity 16 is too large, which may make it difficult to completely remove residues at the bottom during the etching process, forming etching dead corners. In addition, an excessively small included angle θ will reduce the light-trapping efficiency of cavity 16, because light is easily reflected directly out of cavity 16 along the vertical sidewalls. When the included angle θ is too large (close to 180°), the sidewalls of cavity 16 tend to be horizontal, and the shape of cavity 16 is close to a shallow pit or groove, losing the light-trapping characteristics of the inverted cone structure. An excessively large included angle θ may also lead to increased lateral drilling during the etching process, damaging the integrity of adjacent structures. Therefore, in this embodiment, the preferred range of included angle θ is 30° to 90°. Within this range, cavity 16 can maintain good light multiple reflection characteristics while avoiding local stress concentration caused by excessively steep sidewalls or a decrease in mechanical strength caused by excessively gentle sidewalls.

[0055] like Figure 3 As shown, cavities 16 recessed along the thickness direction S1 are formed at the apex regions of the first and second protruding structures on the transition surface 15. In the transition surface 15 region, an inverted pyramid-shaped cavity 16 can be formed at the apex region of the protruding structure using laser etching or chemical wet etching. The cavity 16 has a depth H of 2.5 μm, an opening length L of 1.8 μm, and an angle θ between the sidewall of the cavity 16 and the first surface 11a is 54.7°. In conventional solid protruding structures, stress is directly transmitted through the solid material under load, easily leading to stress concentration at the root. The cavity 16 in this embodiment forms a hollow support for the protruding structure. When external force is applied to this region, the sidewall of the cavity 16 undergoes slight elastic deformation, enhancing its resistance to bending. Furthermore, the cavity 16 structure on the transition surface 15 can further increase multiple reflections of light, improving light absorption efficiency.

[0056] In some embodiments, such as Figure 5 As shown, within the transition surface 15, starting from the boundary line between the transition surface 15 and the first textured area 13 or the second textured area 14, the opening area of ​​the cavity 16 extends horizontally in a direction away from the boundary line along the horizontal direction S2, exhibiting a monotonically decreasing trend. This can be understood as the cavity 16 not being uniformly distributed throughout the entire transition surface 15, but rather extending horizontally in a direction away from the boundary line between the transition surface 15 and the first textured area 13 or the second textured area 14, with the opening area of ​​the cavity 16 decreasing as the horizontal distance increases. In this embodiment, the distribution of the cavity 16 can be achieved through a mask pattern gradient method, an etching time gradient control method, or a laser energy / scanning speed gradient method. A gradient cavity distribution allows for a smooth transition of stress from the boundary to the interior, thereby improving mechanical reliability. Furthermore, a gradient light inlet optimizes the light absorption path, thereby improving photoelectric conversion efficiency.

[0057] One embodiment of this application provides a stacked battery, which includes a top battery, an intermediate connecting layer and a bottom battery, wherein the intermediate connecting layer is connected between the top battery and the bottom battery.

[0058] The top cell is one of a perovskite cell, a cadmium telluride solar cell, a copper indium gallium selenide solar cell, or a gallium arsenide solar cell, and the bottom cell is the aforementioned solar cell 100.

[0059] In some implementations, the interlayer can be a transparent material with a high refractive index. To reduce light reflection and absorption at the interlayer interface and achieve good conductivity to minimize the impact of series resistance on device performance, the interlayer typically needs to have high light transmittance. For example, the interlayer can be a transparent conductive metal oxide thin film (ITO).

[0060] One embodiment of this application provides a photovoltaic module 200. Please refer to [link / reference]. Figure 9 and Figure 10 As shown, it includes a battery string 201, an encapsulating film 202, and a cover plate 203. Please refer to [the provided text]. Figure 9 As shown, the battery string 201 is formed by connecting multiple solar cells 100 as described above, or the battery string 201 is formed by connecting multiple stacked cells as described above; the encapsulating film 202 is used to cover the surface of the battery string 201; the cover plate 203 is used to cover the surface of the encapsulating film 202 away from the surface of the battery string 201.

[0061] In some embodiments, multiple solar cells 100 can be electrically connected to each other by solder strips 20, which are connected to each pair of adjacent solar cells 100. The solder strips 20 are connected to the front surface of the first solar cell 100 and the back surface of the second solar cell 100, respectively.

[0062] In some embodiments, the solar cells 100 may be spaced apart, and during string bonding, the solder strip 20 extends from the front surface of the first solar cell 100 to the gap, passes through the gap, and extends to the back surface of the second solar cell 100.

[0063] In some embodiments, no gap is provided between the solar cells 100, that is, two adjacent solar cells 100 overlap each other.

[0064] In some embodiments, the encapsulating film 202 includes a first encapsulating film and a second encapsulating film. The first encapsulating film covers one of the front or back sides of the solar cell 100, and the second encapsulating film covers the other of the front or back sides of the solar cell 100. Specifically, at least one of the first or second encapsulating film can be an organic encapsulating film such as polyvinyl butyral (PVB) film, ethylene-vinyl acetate copolymer (EVA) film, polyvinyl octene coelastomer (POE) film, or polyethylene terephthalate (PET) film.

[0065] Example 1 The method for preparing the solar cell in Example 1 includes the following steps: Step 1-1: Provide a texturized N-type silicon wafer. The front surface of the N-type silicon wafer has a first protrusion structure, which is a third pyramid. The average size of the third pyramid is 2μm to 4μm, the average height of the third pyramid is 1.2μm, and the density of the first protrusion structure is 300,000 / mm². 2 .

[0066] Steps 1-2 involve boron diffusion doping of the N-type silicon wafer to form an initial doped layer on the positive surface of the N-type silicon wafer. The sheet resistance of the positive surface after boron diffusion doping is 100-200 Ω / □.

[0067] Steps 1-3 involve using an ultraviolet picosecond laser with a wavelength of 266nm to 355nm, setting a repetition rate of 500kHz to 1MHz, and applying a laser energy density of 0.5 to 1 MHz to the first textured region of the boron-diffused N-type silicon wafer. The first textured region is surface activated; a laser is used to perform laser delamination on the second textured region of the boron-diffused N-type silicon wafer to initially remove at least a portion of the initial doped layer in the second textured region, obtaining a first solar cell intermediate. The laser provided is an ultraviolet picosecond laser (wavelength 266nm to 355nm, spot diameter 200μm to 300μm, frequency 600kHz, scanning speed 50m / s to 60m / s, pulse width 6ps to 15ps, energy density 0.1~3). By adjusting the energy focusing of the laser spot through a diffractive optical element (DOE), the direction and distribution of light are changed, thereby controlling the ratio of energy at the center of the laser spot to energy at the edge of the laser spot. This ensures that the energy ratio between the center and the edge of the laser spot is less than 0.8 or greater than 1.2. When the energy of the laser spot is not uniform, a groove structure is formed. Laser preprocessing is performed on the transition area adjacent to the first textured area and the groove structure through staggered splicing and edge-blurred laser scanning. The offset of the center of the adjacent laser spot is 70% to 90% of the laser spot diameter. By adjusting the Q switch or acousto-optic modulator, the energy at the edge of the laser spot is attenuated by 20% to 40% relative to the center (i.e., edge blurring).

[0068] Steps 1-4 involve using an alkaline etching solution to perform alkaline etching on the first battery cell intermediate to remove at least a portion of the initial doped layer thickness in the second textured area, thereby forming a groove structure. After alkaline etching, the depth of the groove structure (the height difference between the laser-etched area and the non-laser-etched area) is 0.3 μm to 18 μm. During the alkaline etching process, secondary texturing is also performed on the bottom surface of the groove to form a second textured surface in the laser-etched area, and secondary texturing is performed on the sidewalls of the groove to form a second protruding structure, thus obtaining the second battery cell intermediate. The alkaline etching solution is prepared by mixing an alkaline solution and an alkaline etching additive. The alkaline solution is a 49% NaOH solution, and the volume ratio of the alkaline solution to the total volume of the alkaline etching solution is 5% to 10%. The alkaline etching additive is in liquid form, and the volume ratio of the alkaline etching additive to the total volume of the alkaline etching solution is 0.5% to 1%. The alkaline etching additive is a product manufactured by Shaoxing Topband New Energy Co., Ltd., with the model number TB22BV03. The second velvet surface includes a second raised structure, which is a first pyramid. The average size of the first pyramid is 2μm to 4μm, the average height of the first pyramid is 1μm, and the density of the first pyramid is 360,000 / mm². 2 .

[0069] Steps 1-5 involve oxidizing the second solar cell intermediate to oxidize the initial doped layer of at least a portion of the thickness in the first textured region to form a first oxide layer, and to form a second oxide layer of at least a portion of the thickness on the bottom surface and sidewalls of the groove in the second textured region. The oxidation conditions are as follows: oxygen is introduced at a flow rate of 20,000 to 80,000 sccm at 800–1050°C for 1–4 hours to oxidize the second solar cell intermediate; the first oxide layer is borosilicate glass with a thickness of 80 nm to 120 nm, and the second oxide layer is also borosilicate glass with a thickness of 80 nm to 120 nm; simultaneously, a third oxide layer is formed on the back surface, also made of borosilicate glass with a thickness of 80 nm to 120 nm. During the oxidation process, the PN junction in the first textured region is advanced. After oxidation, the depth of the PN junction in the first textured region is 2.0 μm to 2.5 μm, and the surface concentration of boron in the first textured region is 5E17. ~1E21 .

[0070] Steps 1-6 involve removing the borosilicate glass from the back surface of the second solar cell intermediate using hydrofluoric acid (HF), followed by alkaline polishing and etching of the back surface of the intermediate with an alkaline polishing solution to expose a clean, flat, and parasitic-free N-type monocrystalline silicon surface. The dimensions of the base after etching are 3μm to 30μm. The alkaline polishing solution is prepared by mixing water, an alkaline solution, and an alkaline polishing additive. The alkaline solution is a 49% NaOH solution, and the volume ratio of the alkaline solution to the total volume of the alkaline polishing solution is 5% to 10%. The alkaline polishing additive is liquid, and the volume ratio of the additive to the total volume of the alkaline polishing solution is 0.5% to 3%. The alkaline polishing additive is a product manufactured by Jiaxing Xiaochen Photovoltaic Technology Co., Ltd., model AT37-2. The base is a structure formed after the back surface is polished. The base is a concave structure that extends into the substrate, with a certain depth of concavity along the thickness direction of the substrate. The base dimension can be the average value of the side length of the base.

[0071] Steps 1-7: A tunneling oxide layer and a polycrystalline silicon layer are sequentially formed on the back surface of the second solar cell intermediate. The polycrystalline silicon layer is then phosphorus-doped to obtain a phosphorus-doped polycrystalline silicon layer (Poly). The thickness of the tunneling oxide layer is 0.6 nm to 3 nm, the thickness of the phosphorus-doped polycrystalline silicon layer (Poly) is 40 nm to 220 nm, and the phosphorus doping surface concentration is 1E18. up to 8E21 During this process, a portion of the phosphorus-doped polycrystalline silicon layer forms a fourth oxide layer, which is a phosphorus-silicon glass with a thickness of 20 nm to 50 nm.

[0072] Steps 1-8 involve removing the first and second oxide layers on the front surface using an acid solution. The acid solution is an HF solution with a volume concentration of 5-20%, and the acid treatment time is 20-80 seconds. Then, an alkaline etching solution is used to remove the polycrystalline silicon layer coated on the front surface. The alkaline solution is prepared by mixing water, NaOH solution, and a decoupling additive. The NaOH solution has a NaOH mass concentration of 49%, and the volume ratio of the NaOH solution to the total volume of the alkaline solution is 2-8%. The decoupling additive is in liquid form, and the volume ratio of the decoupling additive to the total volume of the alkaline solution is 1%. The decoupling additive is a commercial product, model PR21V03, manufactured by Shaoxing Topband New Energy Co., Ltd. The alkaline solution temperature is 60-75℃, and the alkaline treatment time is 220-480 seconds. Finally, an acid solution is used to remove the fourth oxide layer on the back surface and the remaining oxide layer on the front surface. The acid solution is an HF solution with a volume concentration of 5-20%, and the acid treatment time is 20-80 seconds.

[0073] Steps 1-9 involve passivating the second battery cell intermediate to form passivation layers on the front and back surfaces, and then forming an anti-reflection layer covering the passivation layers to obtain the battery cell. The passivation layer can be aluminum oxide with a thickness of 1 nm to 18 nm, and the anti-reflection layer can be silicon nitride with a thickness of 50 nm to 150 nm.

[0074] Steps 1-10: Print and sinter the first electrode on the front surface of the solar cell to form a first electrode, and print and sinter the second electrode on the back surface of the solar cell to form a second electrode, thus obtaining a solar cell.

[0075] The solar cell prepared in Example 1 has a boron doping concentration (surface) of 4.75E17 at the bottom of the groove. .

[0076] Example 2 The structure of the solar cell in Example 2 is basically the same as that in Example 1, except that in steps 1-4, the intermediate of the second cell is placed in an HF solution with a mass concentration of 2%~5%. In a mixed acid solution (volume ratio of 1:3 to 1:5), the treatment time is 30 to 60 seconds. Due to the more severe lattice damage and higher chemical reactivity in the laser pretreatment region (transition surface), isotropic accelerated corrosion occurs in this region in the mixed acid solution, thereby forming corrosion pits (i.e., cavities) that extend from the vertex regions of at least a portion of the first protrusion structure and at least a portion of the vertex regions of the second protrusion structure into the interior of the first and second protrusion structures.

[0077] In Example 2, the boron doping concentration (surface) at the bottom of the groove in the solar cell is 3E17. .

[0078] Comparative Example 1 The structure of the solar cell in Comparative Example 1 is basically the same as that in Example 1, except that the laser misalignment splicing and edge blurring process in steps 1-3 are omitted, and in steps 1-4, a standard isotropic etching process is used to avoid forming a curved extension shape on the transition surface, so that the first textured area and the second textured area are directly connected to form a sharp straight physical boundary.

[0079] Performance testing The performance of the solar cells from Examples 1-2 and Comparative Example 1 was compared and tested. The test conditions were as follows: (1) Use a three-point bending tester to perform bending tests and record the maximum bending force, the maximum force point deformation, and the maximum bending strength.

[0080] (2) Using a pulsed solar simulator, the photoelectric conversion efficiency (Eta), fill factor (FF), open-circuit voltage (Voc), and short-circuit current (Isc) of the battery were measured at an ambient temperature of 25℃, an AM1.5 atmosphere mass, and a solar irradiance of 1000 W / m². The test results are shown in Table 1. Table 1 is a comparison table of performance test results between the examples and the comparative examples.

[0081] Comparative analysis shows that Example 2 has the highest photoelectric conversion efficiency, while the comparative example has the lowest. Example 2 shows an improvement of approximately 0.9% compared to Comparative Example 1, indicating that the combination of the transition surface and the cavity effectively reduces optical or electrical recombination losses, thus improving the overall conversion efficiency of the cell. Furthermore, the electrical performance of Example 2 is also superior to that of Example 1, indicating that the presence of the cavity further enhances electrical performance. Moreover, compared to Comparative Example 1, Example 2 shows a 59.2% increase in maximum bending force, a 78.0% increase in maximum deformation, and a 31.1% increase in maximum bending strength. This demonstrates that the continuously bending transition surface significantly improves the bending resistance and overall mechanical strength of the solar cell, effectively suppressing film peeling and substrate cracking caused by stress concentration. Compared to Example 1, the cavity in Example 2 creates a hollow support structure for the protruding structure, which helps to enhance deformation and bending resistance.

[0082] The above are merely embodiments of this application and do not limit the scope of this patent application. Any equivalent structural or procedural changes made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of this application.

Claims

1. A solar cell, characterized in that, include: A substrate having a first surface and a second surface disposed opposite to each other along the thickness direction; A functional film layer, including a passivation film layer and an antireflection film layer, wherein the functional film layer covers the first surface and the second surface of the substrate; The first surface includes at least one first pile area and at least one second pile area arranged alternately along a first horizontal direction, the first horizontal direction being perpendicular to the thickness direction, the first pile area including a plurality of first protrusion structures, the second pile area including a plurality of second protrusion structures, and a height difference between the average height of the first protrusion structure and the average height of the second protrusion structure. A transition surface is formed between the first velvet area and the second velvet area. The transition surface extends in a non-linear curved shape along the second horizontal direction, which is perpendicular to both the first horizontal direction and the thickness direction. On the transition surface, at least a portion of the vertex regions of the first protrusion structure and / or the second protrusion structure have cavities recessed along the thickness direction.

2. The solar cell according to claim 1, characterized in that, The average height of the first protrusion on the transition surface of the first velvet area is less than the average height of the first protrusion on the non-transition surface; and / or, the average height of the second protrusion on the transition surface of the second velvet area is less than the average height of the second protrusion on the non-transition surface.

3. The solar cell according to claim 1, characterized in that, The transition surface is formed by the side or top of the first protrusion structure and / or the second protrusion structure, and the transition surface has a surface that extends continuously along the second horizontal direction.

4. The solar cell according to claim 3, characterized in that, The cross-sectional profile of the transition surface includes at least one of circular arc, elliptical arc, wavy line, and irregular polygonal line.

5. The solar cell according to claim 1, characterized in that, The opening of the cavity is located on the upper surface of the protruding structure, the bottom of the cavity is located inside the protruding structure, and the cross-sectional profile of the cavity shows a monotonically decreasing trend from the opening to the bottom.

6. The solar cell according to claim 5, characterized in that, Within the transition surface, starting from the boundary line between the transition surface and the first or second velvet area, extending along the first horizontal direction toward a direction away from the boundary line, the opening area of ​​the cavity exhibits a monotonically decreasing trend.

7. The solar cell according to claim 5, characterized in that, The depth of the cavity and the length of the opening are both less than 5 micrometers; and / or, the angle between the sidewall of the cavity and the first surface is 10° to 130°.

8. The solar cell according to claim 5, characterized in that, The cavity shape includes at least one of an inverted pyramid, an inverted cone, and an inverted frustum; and / or, the shape of the first protrusion structure and / or the second protrusion structure includes at least one of a pyramid, a truncated pyramid, a frustum, and a cone.

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

10. A photovoltaic module, characterized in that, It includes the solar cell according to any one of claims 1 to 8, or the tandem cell according to claim 9.

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