A solar cell

Abstract

This disclosure relates to the field of photovoltaic cell technology and discloses a solar cell. The cell includes a substrate layer, a tower structure, and a reinforcing microstructure. The substrate layer includes a light-receiving surface and a backlighting surface. The tower structure is formed on the backlighting surface and includes a plurality of tower base units recessed inward from the backlighting surface. The reinforcing microstructure is disposed on one side of the backlighting surface and at least partially located within the tower structure, including a plurality of micro units protruding relative to the surface of the tower structure. In this disclosure, the tower base units are recessed relative to the backlighting surface, and the micro units are protruding relative to the surface of the tower base units. This results in the backlighting surface of the substrate layer, the surface of the tower structure, and the reinforcing microstructure exhibiting a multi-level uneven morphology, thereby reducing the surface reflectivity of the backlighting surface, increasing the internal reflection and absorption of long-wavelength light, improving the short-circuit current, and simultaneously increasing the actual contact interface between the substrate layer and the passivation layer per unit projected area, enhancing field-effect passivation, and improving the overall performance of the cell.

Description

Technical Field

[0001] This disclosure relates to the field of photovoltaic cell technology, specifically to a solar cell. Background Technology

[0002] Back-contact (BC) solar cells have become a research hotspot in the field of high-efficiency crystalline silicon solar cells due to their advantages such as no metal grid lines obstructing the front side, high theoretical conversion efficiency, and aesthetically pleasing appearance. Their core structural feature lies in arranging both p-region and n-region electrodes on the back of the cell, thereby maximizing the utilization of incident light from the front. TOPCon cells are currently the most mainstream and mass-produced high-efficiency crystalline silicon solar cells, with a passivation contact structure based on an ultra-thin tunneling oxide layer plus a doped polycrystalline silicon layer on the back side. In back-contact or TOPCon cells, the contact area (p-region or n-region) on the back side is usually polished to form a high-quality passivation contact structure and reduce the surface recombination rate. However, polished surfaces have inherent defects in optical and electrical performance: firstly, they have a high reflectivity for incident light, especially long-wavelength light, resulting in low utilization of sunlight and limiting the improvement of short-circuit current density; secondly, the specific surface area of ​​a flat surface is limited, restricting the contact area between the passivation layer and the silicon substrate, affecting the field-effect passivation effect.

[0003] To address these issues, related technologies have optimized the backside structure of solar cells. For example, a textured pyramidal surface is formed on the silicon substrate using a wet etching process. However, this pyramidal surface typically has sharp edges, which can easily lead to microcracks due to thermal stress concentration at the edges during subsequent metallization sintering and module lamination, resulting in degraded or even failed contact performance. If the sharp parts are flattened using processes such as grinding, it will affect light absorption and passivation, making it difficult to simultaneously improve the overall optical, electrical, and mechanical performance of the solar cell. Summary of the Invention

[0004] This disclosure provides a solar cell to address the problem that existing solar cells struggle to simultaneously improve optical, electrical, and mechanical properties.

[0005] In a first aspect, this disclosure provides a solar cell, comprising: a substrate layer, a tower base structure, and a reinforcing microstructure. The substrate layer includes a light-receiving surface and a back-lighting surface disposed opposite to each other. The tower base structure is formed at least on the back-lighting surface and includes a plurality of tower base units, which are recessed inward from the back-lighting surface. The reinforcing microstructure is disposed on one side of the back-lighting surface and is at least partially located within the tower base structure. The reinforcing microstructure includes a plurality of micro-units, which are protruding from the surface of the tower base structure.

[0006] Beneficial Effects: The solar cell disclosed herein simultaneously incorporates a tower base structure and a reinforcing microstructure on the backside of the substrate. The tower base structure comprises several tower base units recessed to a certain depth from the backside, and the reinforcing microstructure comprises at least several micro units formed within the tower base structure. The tower base units are recessed relative to the backside, while the micro units protrude additionally relative to the surface of the tower base units. The tower base structure presents a recessed structure relative to the backside of the substrate with a relatively flat surface free of sharp corners. Furthermore, additional protruding reinforcing microstructures are further disposed on the surface of the tower base structure. This results in a multi-level uneven morphology encompassing the backside of the substrate, the surface of the tower base structure, and the reinforcing microstructure. This significantly reduces the surface reflectivity on the backside of the substrate, increases the internal reflection and absorption of long-wavelength light, enhances the short-circuit current, and overcomes the limitations of passivation area on flat surfaces. It also increases the actual contact interface between the substrate and the passivation layer per unit projected area, enhances field-effect passivation, and ultimately improves the overall performance of the solar cell.

[0007] In one alternative implementation, the enhanced microstructure includes a first microstructure and / or a second microstructure, wherein the first microstructure includes a plurality of first microunits and the second microstructure includes a plurality of second microunits, and the size of the first microunits is larger than the size of the second microunits.

[0008] Beneficial effects: The first micro-unit can be a pyramid-shaped protrusion, formed by stress and impurity segregation during crystal growth, and its size is usually greater than 2 μm; the second micro-unit can be a spherical structure, formed by melting the oxide layer with a high-energy laser, and its size is usually less than 2 μm. That is, the first and second micro-units of different sizes and shapes form more diverse surface morphologies on the surface of the pyramid base structure, further optimizing the light absorption and passivation effect on the backlight side.

[0009] In one alternative implementation, a number of first micro-units are concentrated on the bottom and sides of the tower base structure, and a number of second micro-units are randomly distributed on the back side of the base layer.

[0010] Beneficial effects: Within the entire backlight surface of the substrate, the first micro-units are concentrated on the inner wall surface of the grooved tower base structure. The first micro-structures are basically not set on the relatively convex backlight surface around the tower base structure. Therefore, there are no obvious sharp protrusions on the outermost surface of the backlight surface, ensuring the reliability of the subsequent passivation film layer and metal connection. The second micro-structure is relatively small in size and has a relatively smooth surface. Even if it is distributed on both the inner wall surface of the tower base structure and the convex backlight surface around the tower base structure, it does not affect the contact performance of the outermost surface of the substrate, but it has a certain enhancement effect on optical performance.

[0011] In one alternative embodiment, along the thickness direction of the substrate layer and in the direction from the light-receiving surface to the backlighting surface, the size of a plurality of first micro-units in the first microstructure gradually decreases and / or the density of a plurality of first micro-units gradually decreases.

[0012] Beneficial effects: In this disclosure, several first microstructures are set in the thickness direction of the battery, that is, in the direction perpendicular to the light-receiving surface of the substrate. The closer to the light-receiving surface of the substrate, the larger their size and the greater their density. This results in more first micro-units being set in the area where the concave tower base structure is located in the entire substrate compared to other non-concave areas. Moreover, the greater the depth of the tower base unit, the more first microstructures are set inside it, thereby optimizing the carrier transport performance in the area where the tower base structure is located. At the same time, the orderly variation of the first micro-units also makes the surface morphology of the tower base structure relatively stable, which helps to further optimize the electrical and optical performance.

[0013] In one alternative implementation, the size of the first micro-unit located in the boundary region between the bottom and side surfaces of the tower base structure is larger than the size of the first micro-unit located in the middle region of the bottom surface, and / or the density of the first micro-unit located in the boundary region between the bottom and side surfaces of the tower base structure is greater than the density of the first micro-unit located in the middle region of the bottom surface.

[0014] Beneficial effects: Several first microstructures not only have a set pattern of size and density in the longitudinal direction, but also have a set pattern of size and density in the same horizontal plane. For example, the closer to the boundary region, the larger the size and the greater the density of the first microstructure. This reduces the interface abrupt change in the boundary region, avoids stress concentration and carrier accumulation, and helps to improve the overall carrier transport performance and reliability of the battery.

[0015] In one alternative embodiment, at least a portion of the tower base unit forms a stress buffer structure in the corner area between adjacent sides. The stress buffer structure includes a plurality of sequentially connected transition surfaces so that the projection of the stress buffer structure onto the base layer is stepped.

[0016] Beneficial effects: In this disclosure, the base unit as a whole can be formed into a rectangular base, with one or more smooth step-like structures formed at at least one corner of each base unit, thereby making the base unit into a polyhedral base with "missing corners". This structure has a clear crystallographic orientation or a specific radius of curvature, which can eliminate sharp corners and transform the thermomechanical stress at the contact interface from point concentration to surface distribution, thereby greatly improving the mechanical stability of the metal-semiconductor contact interface and reducing the risk of microcracks.

[0017] In one alternative implementation, at least a portion of the tower base unit includes at least two stress-buffering structures arranged diagonally.

[0018] Beneficial effects: The stress buffer structure is set diagonally, which helps to uniformly improve the crack resistance of the battery during sintering and module lamination, thereby improving the battery yield and the long-term reliability of the module under complex outdoor conditions.

[0019] In one alternative implementation, the angle between the fitting plane of the stress buffer structure and the side of the adjacent tower base structure is greater than or equal to 120°.

[0020] Beneficial effect: The angle between the fitting plane of the stress buffer structure and the side of the adjacent tower base structure is greater than or equal to 120°, which helps to ensure the stability of the stress buffer structure.

[0021] In one alternative implementation, the transition surface includes a plane or an arc surface.

[0022] Beneficial effects: Each small transition surface of the stress buffer structure can be set as a flat surface, which results in high structural consistency and simple fabrication; or it can be set as a curved surface, which improves the overall flatness of the stress buffer structure, reduces sharp edges, and is more conducive to the uniform and dense deposition of the passivation layer on the backlight surface, thereby obtaining a better surface passivation effect and improving the open circuit voltage.

[0023] In one alternative implementation, at least some adjacent tower base units are stacked at corners, and the maximum width of the stacked area is less than or equal to the average side length of the two tower base units connected to it.

[0024] Beneficial effects: Different tower base units can be stacked to improve lateral carrier transport performance. Furthermore, adjacent tower base units are stacked corner-to-corner, reducing the number of sharp corners in the tower structure, improving current collection efficiency, and contributing to further improvements in the battery's fill factor and conversion efficiency. In addition, the maximum width of the stacked region is set to be less than or equal to the average side length of the tower base units connected to it. This avoids excessive overlap that could lead to process waste. Moreover, the size of the stacked region is much smaller than the tower base units themselves, helping to provide additional, low-resistance silicon-based lateral transport paths for carriers in the back field region while maintaining the independence of the tower base units. Working in conjunction with the metal gate lines, this optimizes local current collection, thereby improving the fill factor. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the specific embodiments of this disclosure or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0026] Figure 1This is a schematic diagram of the structure of a solar cell according to an embodiment of the present disclosure; Figure 2 This is a top view of the backlit side of an embodiment of the present disclosure, which has a tower base structure and a first microstructure. Figure 3 This is a schematic diagram of the tower base unit and the first microstructure according to an embodiment of the present disclosure; Figure 4 This is an enlarged view of the first microstructure according to an embodiment of this disclosure; Figure 5 This is a top view of the backlit side of an embodiment of the present disclosure, which has a tower base structure and a second microstructure. Figure 6 This is a schematic diagram of the structure of a tower base unit with a stress buffer structure according to an embodiment of the present disclosure; Figure 7 This is a top view of the tower base unit according to an embodiment of the present disclosure.

[0027] Explanation of reference numerals in the attached figures: 1. Base layer; 101. Light-receiving surface; 102. Backlight-receiving surface; 2. Tower base structure; 201. Tower base unit; 2011. Bottom surface; 2012. Side surface; 3. Enhanced microstructure; 301, first micro-unit; 302, second micro-unit; 4. Stress buffer structure; 401. Transition surface; 5. First passivation contact structure; 501. First passivation layer; 502. First doped layer; 6. Second passivation contact structure; 601. Second passivation layer; 602. Second doped layer; 701, First transparent conductive layer; 702, Second transparent conductive layer; 801, First electrode; 802, Second electrode; 9. Passivation and anti-reflection layer. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0029] like Figures 1 to 7As shown, this disclosure provides a solar cell, including: a substrate layer 1, a tower base structure 2, and a reinforcing microstructure 3. The substrate layer 1 includes a light-receiving surface 101 and a backlight surface 102 disposed opposite to each other. The tower base structure 2 is formed at least on the backlight surface 102 and includes a plurality of tower base units 201, which are recessed inward from the backlight surface 102. The reinforcing microstructure 3 is disposed on one side of the backlight surface 102 and is at least partially located within the tower base structure 2. The reinforcing microstructure 3 includes a plurality of micro units, which are protruding from the surface of the tower base structure 2.

[0030] For example, the substrate 1 may be a silicon substrate, including a light-receiving surface 101 and a backlighting surface 102 opposite each other along the thickness direction, such as... Figure 1 As shown, the light-receiving surface 101 is provided with a passivation antireflection layer 9. The solar cell of this disclosure has a tower base structure 2 and an enhancement microstructure 3 simultaneously provided on one side of the backlight surface 102 of the substrate layer 1. The tower base structure 2 includes a plurality of tower base units 201 recessed to a certain depth from the backlight surface 102. The enhancement microstructure 3 includes a plurality of micro units formed at least within the tower base structure 2. The tower base units 201 are recessed relative to the backlight surface 102, and the micro units are additionally protruding relative to the surface of the tower base units 201. Specifically, a relatively recessed structure is formed on the backlight surface 102 of the substrate layer 1 by a wet process, and the surface of the recessed structure is relatively flat, that is, a tower base structure 2 with a relatively flat surface and no sharp corners is formed. The tower base structure 2 includes a plurality of tower base units 201 that are spaced apart or connected to each other. The tower base structure 2 makes the backlight surface 102 of the substrate layer 1 exhibit an uneven morphology, but the outermost surface is relatively flat. The specific wet process window can be as follows: 8-15 L of alkaline solution such as potassium hydroxide or sodium hydroxide, 1-8 L of polishing additive, and the balance being water; temperature 60-85℃, preferably 75-80℃, time 100-500s, preferably 150-200s; the morphology of the tower base unit 201 is controlled by adjusting the concentration of the polishing solution and the processing time. Based on this, such as... Figure 2 As shown, additional reinforcing microstructures 3 are further provided on the surface of the tower base structure 2. The reinforcing microstructures 3 are raised relative to the surface of the tower base structure 2, so that the back surface 102 of the substrate layer 1, the surface of the tower base structure 2 and the reinforcing microstructures 3 as a whole present a multi-level uneven morphology. This significantly reduces the surface reflectivity on the back surface 102 side of the substrate layer 1, increases the internal reflection and absorption of long-wavelength light, improves the short-circuit current, and breaks through the passivation area limitation of flat surface, increases the actual contact interface between the substrate layer 1 and the passivation layer per unit projected area, enhances field effect passivation, and ultimately improves the overall performance of the solar cell.

[0031] In some embodiments, the side length of the tower base unit 201 is less than or equal to 40 μm, such as 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, etc. The depth of the tower base unit 201 is less than or equal to 20 μm, such as 3 μm, 5 μm, 10 μm, 15 μm, etc.

[0032] In some embodiments, the solar cell disclosed herein can be a back-contact solar cell. The back surface 102 of the substrate 1 can include alternating first and second regions, one of which is a p-region and the other is an n-region. The solar cell further includes: a first passivation contact structure 5, a second passivation contact structure 6, a first transparent conductive layer 701, a second transparent conductive layer 702, a first electrode 801, and a second electrode 802. The first passivation contact structure 5 and the second passivation contact structure 6 are alternately disposed on the back surface 102 of the substrate 1. The doping types of the first passivation contact structure 5 and the second passivation contact structure 6 are opposite, that is, the first passivation contact structure 5 can be disposed in the first region, and the second passivation contact structure 6 can be disposed in the second region. The first transparent conductive layer 701 is disposed on the first passivation contact structure 5, and the second transparent conductive layer 702 is disposed on the second passivation contact structure 6. The first electrode 801 is disposed on the first transparent conductive layer 701 to be connected to the first passivation contact structure 5, and the second electrode 802 is disposed on the second transparent conductive layer 702 to be connected to the second passivation contact structure 6. In other embodiments, the solar cell described above may not include the first transparent conductive layer 701 and the second transparent conductive layer 702. Furthermore, there is an isolation groove between the first passivation contact structure 5 and the second passivation contact structure 6. The solar cell with the above structure is a conventional solar cell in the art, and will not be described in detail here.

[0033] For example, the first passivation contact structure 5 includes a first passivation layer 501 and a first doped layer 502 stacked together, and the second passivation contact structure 6 may include a second passivation layer 601 and a second doped layer 602 stacked together. The first passivation contact structure 5 and the second passivation contact structure 6 can employ passivation contact film layers of TOPCon cells, such as a stacked tunneling oxide layer and a doped polycrystalline silicon layer, or they can employ passivation contact film layers of heterojunction cells, such as a stacked intrinsic amorphous silicon layer and a doped amorphous silicon layer. In the first passivation contact structure 5 and the second passivation contact structure 6, one is p-type doped and the other is n-type doped. The first transparent conductive layer 701 and the second transparent conductive layer 702 can be selected from TCO-based materials; the first electrode 801 and the second electrode 802 can be made of metal paste.

[0034] In other embodiments, the solar cells described above may also be TOPCon cells, heterojunction cells, and tandem solar cells, etc., with a tower base structure 2 and an enhanced microstructure 3 formed on the surface of the silicon substrate.

[0035] like Figures 3 to 5 As shown, in some embodiments, the enhanced microstructure 3 described above includes a first microstructure and a second microstructure. The first microstructure includes a plurality of first microunits 301, and the second microstructure includes a plurality of second microunits 302. The size of the first microunits 301 is larger than the size of the second microunits 302.

[0036] For example, such as Figure 3 and Figure 4 As shown, the first micro-unit 301 described above can be at least one of pyramidal, ellipsoidal, and hemispherical shapes, formed by stress and impurity segregation during crystal growth. It can also have a size typically greater than 2 μm, preferably 2.5~12 μm, such as 3.5 μm, 5 μm, 7 μm, 10 μm, etc. Here, the pyramidal structure, because it is located in the concave region, does not affect the subsequent passivation film layer and metal contact. For example... Figure 5 As shown, the second micro-unit 302 can be spherical or sesame-seed-like, formed by melting the oxide layer with a high-energy laser. Its size is typically less than 2 μm, preferably 0.5~1.2 μm, such as 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, etc. Based on this, the first micro-unit 301 and the second micro-unit 302 of different sizes and shapes form more diverse surface morphologies on the surface of the tower base structure 2, further optimizing the light absorption and passivation effect on the backlight side 102.

[0037] Taking the first micro-unit 301 as a pyramid-shaped structure and the second micro-unit 302 as a spherical structure as an example, the following explanation is provided: The first micro-unit 301 can be a pyramid-shaped protrusion formed by crystal growth stress and impurity segregation during the deposition of a passivation film layer, such as a polycrystalline silicon layer, and subsequent high-temperature annealing, without the need for additional process steps. For example, specific process parameters include: firstly, a polycrystalline silicon layer is formed using low-pressure chemical vapor deposition (LPCVD) or plasma-enhanced chemical vapor deposition (PECVD) at a deposition temperature of 580–650 °C, a silane flow rate of 200–500 sccm, and a deposition thickness of 100–200 nm; then, doping and annealing are performed, with boron or phosphorus diffusion doping at an annealing temperature of 850–950 °C for 30–60 minutes. During annealing, metallic impurities such as Fe, Ni, and Cu, as well as oxygen precipitates, segregate towards the grain boundaries, inducing local stress concentration, thereby promoting the growth of the pyramid-shaped protrusion, i.e., the first micro-unit 301. The base of the pyramid-shaped structure has a dimension of 2 to 5 and a height of 1 to 3. The stress concentration is concentrated in the base unit 201, namely the bottom surface 2011 and the side surface 2012. The density and size of the pyramid-shaped structure are controlled by adjusting the annealing temperature and doping concentration.

[0038] The second micro-unit 302 can be obtained by utilizing the local melting of the passivation film layer, such as polycrystalline silicon, caused by excessively high laser energy during the laser grooving process. The molten material solidifies into a spherical silicon oxide / amorphous silicon composite residue under the action of surface tension. For example, specific process parameters include: using an ultraviolet picosecond laser with a wavelength of 355 nm and a pulse width of 10~20 ps, ​​and setting the laser energy density to 3.0~4.5 J / cm². 2 This is 2.5~2.8 J / cm³ higher than the energy required for conventional grooving. 2 The scanning speed was set to 5–10 m / s, and the pulse frequency to 200–500 kHz. An air or oxygen-containing atmosphere was used to promote the oxidation of the molten material, forming spherical silica particles. The size of these spherical particles was mostly less than 2 μm, typically 0.2–1.5 μm, and they were randomly distributed throughout the entire tower base structure. The size and density of the spherical structure could be controlled by adjusting the laser energy density and scanning speed; for example, the energy density could be set to 3.0–3.5 J / cm³. 2 The resulting particles range in size from 0.2 to 0.8 μm, with moderate density and an energy density of 3.5 to 4.5 J / cm³. 2 Between these conditions, the resulting particles have a size of 0.5~1.5 μm and a high density. When subjected to laser treatment, the polycrystalline silicon is instantly heated to over 1400°C, partially melting. The molten silicon shrinks into spherical shapes under the action of surface tension, and at the same time reacts with oxygen in the atmosphere, oxidizing the surface layer to form a silicon oxide shell. After rapid cooling, it solidifies into a core-shell structure, that is, spherical particles with an inner layer of amorphous silicon and an outer layer of silicon oxide.

[0039] The formation of the first micro-unit 301 and the second micro-unit 302 both originate from inherent steps in conventional solar cell manufacturing processes, such as annealing of passivation films like polycrystalline silicon and laser grooving, requiring no additional steps. By appropriately adjusting process parameters such as annealing temperature and laser energy density, a controllable and functional combination of microstructures can be formed on the surface of the tower base structure 2, achieving the dual effects of enhanced optical absorption and increased passivation interface.

[0040] Of course, in some other embodiments, the enhanced microstructure 3 may include only the first microstructure or only the second microstructure.

[0041] In some other implementations, an isolation zone can also be formed between the first region and the second region, with the isolation groove corresponding to the isolation zone. The aforementioned tower base structure 2 can be formed in all areas of the backlight surface 102, including the first region, the second region, and the isolation zone, or it can be formed only in the first and second regions. In the enhanced microstructure 3, the first micro unit 301 is formed on the tower base structure of the p region, while the second micro unit 302 is mainly formed on the tower base structure of the p region, with fewer distributions in other regions.

[0042] In some embodiments, such as Figure 2 and Figure 3 As shown, several first micro-units 301 are concentrated on the bottom surface 2011 and the side surface 2012 of the tower base structure 2; as Figure 5 As shown, several second micro-units 302 are randomly distributed on one side of the backlight surface 102 of the substrate layer 1.

[0043] That is, within the entire backlight surface 102 of the substrate layer 1, the first micro-units 301 are concentrated on the inner wall surface of the groove-shaped tower base structure 2. The first micro-structures are basically not set on the relatively convex backlight surface 102 around the tower base structure 2. Therefore, there are no obvious sharp protrusions on the outermost surface of the backlight surface 102, ensuring the reliability of the subsequent passivation film layer and metal connection. The second micro-structure is relatively small in size and has a relatively smooth surface. Even if it is distributed on the inner wall surface of the tower base structure 2 and also on the convex backlight surface 102 around the tower base structure 2, it basically does not affect the contact performance of the outermost surface of the substrate layer 1, but it has a certain enhancement effect on the optical performance.

[0044] In some embodiments, such as Figure 2 and Figure 3 As shown, along the thickness direction of the substrate layer 1 and from the light-receiving surface 101 toward the backlight surface 102, the size and density of a plurality of first micro-units 301 in the first microstructure gradually decrease.

[0045] It is known that the greater the thickness of the substrate layer 1, the more charge carriers it contains, which is more conducive to charge carrier transport. Based on this, in the thickness direction of the battery, that is, the direction perpendicular to the light-receiving surface 101 of the substrate layer 1, a number of first microstructures are provided. The closer to the light-receiving surface 101 of the substrate layer 1, the larger their size and the greater their density. This results in more first micro-units 301 being provided in the area where the concave tower base structure 2 is located in the entire substrate layer 1 compared to other non-concave areas. Moreover, the greater the depth of the tower base unit 201, the more first microstructures are provided inside it, thereby optimizing the charge carrier transport performance in the area where the tower base structure 2 is located. At the same time, the orderly variation of the first micro-units 301 also makes the surface morphology of the tower base structure 2 relatively stable, which helps to further optimize the electrical and optical performance.

[0046] Of course, in some other embodiments, the first micro-units 301 may be configured to have only size variations in the thickness direction of the substrate layer 1, or the first micro-units 301 may be configured to have only density variations in the thickness direction of the substrate layer 1, thereby simplifying the fabrication process.

[0047] In some embodiments, such as Figure 3 As shown, in the direction parallel to the backlight surface 102 of the base layer 1, or in the plane where the bottom surface 2011 of the tower base structure 2 is located, the size of the first micro-unit 301 located in the boundary area between the bottom surface 2011 and the side surface 2012 of the tower base structure 2 is larger than the size of the first micro-unit 301 located in the middle area of ​​the bottom surface 2011, and the density of the first micro-unit 301 located in the boundary area between the bottom surface 2011 and the side surface 2012 of the tower base structure 2 is also greater than the density of the first micro-unit 301 located in the middle area of ​​the bottom surface 2011.

[0048] In other words, the first microstructures not only have a set pattern of size and density in the longitudinal direction, but also have a set pattern of size and density in the same horizontal plane. For example, the closer to the boundary region, the larger the size and the greater the density of the first microstructure. This reduces the interface abrupt change in the boundary region, avoids stress concentration and carrier accumulation, and helps to improve the overall carrier transport performance and reliability of the battery.

[0049] Of course, in other embodiments, the first micro-units 301 may be configured to have only size variations in the horizontal direction, or the first micro-units 301 may be configured to have only density variations in the horizontal direction, which also helps to simplify the fabrication process.

[0050] In some embodiments, such as Figure 6 and Figure 7As shown, at least a portion of the tower base unit 201 forms a stress buffer structure 4 in the corner area between adjacent side surfaces 2012. The stress buffer structure 4 includes a plurality of sequentially connected transition surfaces 401 so that the projection of the stress buffer structure 4 on the base layer 1 is stepped.

[0051] Specifically, a stress buffer structure 4 can be formed through a wet polishing process. The wet polishing process uses a polishing slurry containing a crystal surface corrosion rate modulator, and actively forms the stress buffer structure 4 at the corners of the tower base unit 201 by controlling the corrosion kinetics. Specifically, the polishing slurry includes a main etchant, a crystal surface corrosion rate modulator, a surfactant, and a thickener. The main etchant can be potassium hydroxide with a concentration of 2-8%, and the crystal surface corrosion rate modulator can be isopropanol or ethylene glycol with a concentration of 5-15% to selectively inhibit crystal surface corrosion. The surfactant and thickener are used to improve wettability and control the diffusion boundary. The process temperature of the wet polishing process is 60-85°C, and the time is 60-300 seconds. Under the anisotropic corrosion of the polishing slurry, the corners of the base unit 201 are preferentially corroded due to their highest surface energy. The difference in corrosion rates across different crystal planes causes the corrosion front to advance in a step-like manner, forming multiple sequentially connected transition surfaces 401, constituting a stepped "corner-missing" profile. The total length of the stepped stress buffer structure 4 with the "corner-missing" shape is typically 5-30% of the side length of the base unit 201, and the radius of curvature at the corners increases from less than 0.1 μm to greater than 2 μm. The base unit 201 can be molded into a rectangular base, with one or more smooth stepped structures formed at at least one corner of each base unit 201, thus shaping the base unit 201 into a polyhedral base with a "corner-missing" shape. This structure has a clear crystallographic orientation or a specific radius of curvature, eliminating sharp corners and transforming the thermomechanical stress at the contact interface from point concentration to surface distribution, thereby greatly improving the mechanical stability of the metal-semiconductor contact interface and reducing the risk of microcracks.

[0052] In some embodiments, at least a portion of the tower base unit 201 includes at least two stress buffer structures 4 arranged diagonally.

[0053] For example, for a rectangular tower base unit 201, two stress buffer structures 4 can be arranged diagonally to uniformly improve the crack resistance of the battery during sintering and module lamination, thereby improving the battery yield and the long-term reliability of the module under complex outdoor conditions.

[0054] In some embodiments, the angle between the fitting plane of the stress buffer structure 4 and the side surface 2012 of the adjacent tower base structure 2 is greater than or equal to 120°, for example, it can be 125°, 130°, 135°, 140°, etc.

[0055] Figure 7The line 'a' shown can be used to characterize the fitting plane of the stepped stress buffer structure 4, that is, the overall tilt direction of the stress buffer structure 4. Specifically, from a top-down view, line 'a' is obtained by smoothing or fitting the lines containing the various small transition surfaces 401 that make up the stepped structure. From a three-dimensional perspective, it is used to characterize the fitting plane of the stress buffer structure 4. The angle between the fitting plane of the stress buffer structure 4 and the side surface 2012 of the adjacent tower base structure 2 is greater than or equal to 120°, which helps to ensure the stability of the stress buffer structure 4.

[0056] In some embodiments, the transition surface 401 described above includes a plane or an arc surface. That is, each small transition surface 401 of the stress buffer structure 4 can be set as a flat surface, which has high structural consistency and is simple to prepare; or it can be set as an arc surface, which improves the overall flatness of the stress buffer structure 4, reduces sharp edges, and is more conducive to the uniform and dense deposition of the passivation layer on the backlight surface 102, thereby obtaining a better surface passivation effect and improving the open circuit voltage.

[0057] In some embodiments, at least some adjacent tower base units 201 are stacked at corners, and the maximum width of the stacked area is less than or equal to the average side length of the two tower base units 201 connected thereto.

[0058] like Figure 2 As shown, different tower base units 201 can be stacked to improve lateral carrier transport performance. Furthermore, adjacent tower base units 201 are stacked in a corner-to-corner configuration, reducing the number of sharp corners in the tower base structure 2, improving current collection efficiency, and contributing to further improvements in the battery's fill factor and conversion efficiency. In addition, the maximum width of the aforementioned stacking area is also... Figure 2 The dimension shown in L is set to be less than or equal to the average side length of the tower base unit 201 connected to it. This avoids excessive overlap and process waste. Moreover, the size of the stacked area is much smaller than the tower base unit 201 itself. This helps to provide additional, low-resistance silicon-based lateral transport paths for carriers in the back field region while maintaining the independence of the tower base unit 201. Working together with the metal gate line, it optimizes local current collection and thus improves the fill factor.

[0059] Although embodiments of the present disclosure have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present disclosure, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A solar cell, characterized in that, include: The base layer (1) includes a light-receiving surface (101) and a backlight surface (102) arranged opposite to each other. A tower base structure (2) is formed at least in a portion of the backlight surface (102); the tower base structure (2) includes a plurality of tower base units (201), the tower base units (201) being recessed inward from the backlight surface (102); An enhanced microstructure (3) is disposed on one side of the backlight surface (102) and is at least partially located within the tower base structure (2); the enhanced microstructure (3) includes a plurality of micro-units, which are protruding relative to the surface of the tower base structure (2).

2. The solar cell according to claim 1, characterized in that, The enhanced microstructure (3) includes a first microstructure and / or a second microstructure, wherein the first microstructure includes a plurality of first microunits (301) and the second microstructure includes a plurality of second microunits (302), wherein the size of the first microunits (301) is larger than the size of the second microunits (302).

3. The solar cell according to claim 2, characterized in that, A number of the first micro-units (301) are concentrated on the bottom surface (2011) and the side surface (2012) of the tower base structure (2), and a number of the second micro-units (302) are randomly distributed on one side of the backlight surface (102) of the base layer (1).

4. The solar cell according to claim 2, characterized in that, Along the thickness direction of the substrate layer (1) and from the light-receiving surface (101) toward the backlight surface (102), the size of a plurality of the first micro-units (301) in the first microstructure gradually decreases and / or the density of a plurality of the first micro-units (301) gradually decreases.

5. The solar cell according to claim 2, characterized in that, The size of the first micro-unit (301) located in the boundary area between the bottom surface (2011) and the side surface (2012) of the tower base structure (2) is larger than the size of the first micro-unit (301) located in the middle area of ​​the bottom surface (2011), and / or the density of the first micro-unit (301) located in the boundary area between the bottom surface (2011) and the side surface (2012) of the tower base structure (2) is greater than the density of the first micro-unit (301) located in the middle area of ​​the bottom surface (2011).

6. The solar cell according to claim 1, characterized in that, At least a portion of the tower base unit (201) forms a stress buffer structure (4) in the corner area between adjacent sides (2012), the stress buffer structure (4) including a plurality of sequentially connected transition surfaces (401) so that the projection of the stress buffer structure (4) on the base layer (1) is stepped.

7. The solar cell according to claim 6, characterized in that, At least a portion of the tower base unit (201) includes at least two of the stress buffer structures (4) arranged diagonally.

8. The solar cell according to claim 6, characterized in that, The angle between the fitting plane of the stress buffer structure (4) and the side (2012) of the adjacent tower base structure (2) is greater than or equal to 120°.

9. The solar cell according to claim 6, characterized in that, The transition surface (401) includes a plane or an arc surface.

10. The solar cell according to claim 1, characterized in that, At least some of the tower base units (201) are stacked at corners, and the maximum width of the stacked area is less than or equal to the average side length of the two tower base units (201) connected to it.

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