Photovoltaic cell and preparation method thereof

Abstract

The invention relates to a photovoltaic cell and a preparation method of the photovoltaic cell. The photovoltaic cell comprises: a substrate having a textured surface, the textured surface comprising a plurality of first pyramids and a plurality of second pyramids, the plurality of second pyramids being arranged between the plurality of first pyramids; the tower footing size of the second pyramid is larger than that of the first pyramid, and the tower height of the second pyramid is larger than that of the first pyramid. According to the invention, the scattering capability of broadband light can be enhanced, the problem that the traditional single-scale pyramid texture surface is insufficient in scattering of long-wave light is effectively improved, and the light capturing and absorbing effects of the photovoltaic cell are improved; the dual-scale pyramid suede can be better matched with the passivation contact layer, so that the surface recombination phenomenon is reduced, and the high open-circuit voltage of the photovoltaic cell can be maintained; the second pyramid can also provide an adaptive contact basis for the metal electrode, and the contact resistance between the electrode and the substrate is reduced. Therefore, the photoelectric conversion efficiency of the photovoltaic cell can be effectively improved.

Description

Technical Field

[0001] This application relates to the field of photovoltaic technology, and in particular to a photovoltaic cell and a method for preparing a photovoltaic cell. Background Technology

[0002] With the development of solar cell technology, texturing has become one of the key technologies to improve photoelectric conversion efficiency. It reduces light reflection and enhances light absorption by forming a pyramid texture on the substrate surface, thereby improving the photoelectric conversion efficiency of photovoltaic cells.

[0003] Optimizing the pyramidal textured surface of the substrate is of great significance for further improving the photoelectric conversion efficiency of photovoltaic cells. Summary of the Invention

[0004] Based on this, a photovoltaic cell and a method for preparing a photovoltaic cell are provided to improve the photoelectric conversion efficiency of the photovoltaic cell.

[0005] The present invention provides a photovoltaic cell, comprising: a substrate having a textured surface, the textured surface comprising a plurality of first pyramids and a plurality of second pyramids, the plurality of second pyramids being arranged between the plurality of first pyramids; wherein the base size of the second pyramids is larger than the base size of the first pyramids, and the height of the second pyramids is greater than the height of the first pyramids.

[0006] According to one embodiment of the present invention, the top of the second pyramid forms a smooth top surface.

[0007] According to one embodiment of the invention, it further includes an electrode that contacts at least a portion of the smooth top surface of the second pyramid.

[0008] According to one embodiment of the present invention, the distance from the smooth top surface to the side of the substrate opposite to the velvet surface is greater than or equal to the distance from the top of the first pyramid to the side of the substrate opposite to the velvet surface.

[0009] According to one embodiment of the present invention, the velvet surface forms a plurality of first regions spaced apart and a second region located outside the first regions, a plurality of second pyramids are formed in the first regions, and a plurality of first pyramids are formed in the second regions.

[0010] According to one embodiment of the present invention, the first region is distributed in an array on the velvet surface according to a preset pattern.

[0011] According to one embodiment of the present invention, the height of the first pyramid is 0.5 μm-2 μm; and / or, the density of the first pyramid in the second region is 10. 6 pcs / cm 2 -107 pcs / cm 2 .

[0012] According to one embodiment of the present invention, the height of the second pyramid is 3μm-10μm.

[0013] According to one embodiment of the present invention, it further includes a passivation layer located on the velvety surface.

[0014] The present invention also provides a method for fabricating a photovoltaic cell, comprising the following steps: providing a substrate; performing a first texturing process on the surface of the substrate to form a textured surface, the textured surface comprising a plurality of first pyramids; preparing a mask covering a second region of the textured surface to expose a first region of the textured surface outside the second region; performing a second texturing process on the first region to form a second pyramid located in the first region, wherein the base size of the second pyramid is larger than the base size of the first pyramid, and the height of the second pyramid is larger than the height of the first pyramid; depositing a passivation layer on the textured surface; printing electrode paste and sintering to form an electrode, the electrode being in contact with at least a portion of the second pyramid.

[0015] According to one embodiment of the present invention, before depositing a passivation layer on the velvet surface, the method further includes: performing a rapid thermal oxidation treatment or an ozone treatment to passivate the sidewalls of the second pyramid and forming a smooth top surface on the top of the second pyramid.

[0016] According to one embodiment of the present invention, the process parameters of the first texturing process include: providing a first etching solution to the substrate surface, the first etching solution etching the substrate surface; wherein, the first etching solution contains 1%-3% sodium hydroxide by mass, 5%-10% isopropanol by mass, a process temperature of 70℃-85℃, and a process duration of 5min-10min; or, the first etching solution contains hydrofluoric acid, nitric acid, and water in a volume ratio of 1:3:5, a process temperature of 25℃-40℃, and a process duration of 5min-10min.

[0017] According to one embodiment of the present invention, the process parameters of the second texturing process include: providing a second etching solution to the first region of the texturing surface, the second etching solution etching the first region of the texturing surface; wherein the second etching solution contains hydrofluoric acid, nitric acid and water in a volume ratio of 1:3:5, contains a surfactant by mass percentage of 0.1%-0.5%, the process temperature is 20℃-25℃, and the process time is 30s-120s.

[0018] According to one embodiment of the present invention, the step of preparing a mask covering a second region of the textured surface to expose a first region of the textured surface outside the second region includes: coating the textured surface with photoresist; performing photoresist patterning to form periodic openings, the openings having a diameter of 2μm-8μm and a spacing of 10μm-30μm, wherein the location of the openings forms the first region, and the region outside the openings forms the second region.

[0019] The aforementioned photovoltaic cell and its fabrication method, by setting multiple first pyramids and multiple second pyramids arranged between the first pyramids on the textured surface of the substrate, wherein the base size of the second pyramids is larger than that of the first pyramids and the height of the second pyramids is greater than that of the first pyramids, can form a dual-scale hybrid pyramid textured surface structure. This structure can enhance the scattering ability of broadband light, effectively improve the problem of insufficient scattering of long-wavelength light by traditional single-scale pyramid textured surfaces, reduce light reflection on the substrate surface, improve the light capture and absorption effect of the photovoltaic cell, and thus help to increase the short-circuit current. At the same time, the reasonable distribution of the dual-scale pyramid textured surface can better adapt to the passivation contact layer, reduce surface recombination, and help maintain the high open-circuit voltage of the photovoltaic cell. In addition, the second pyramids can also provide a suitable contact base for the metal electrodes, reduce the contact resistance between the electrodes and the substrate, avoid excessive damage to the passivation layer, and ensure the stability of the electrical performance of the photovoltaic cell. Therefore, this application can effectively improve the photoelectric conversion efficiency of photovoltaic cells. Attached Figure Description

[0020] Figure 1 This is a partial cross-sectional schematic diagram of a photovoltaic cell according to an embodiment of this application.

[0021] Figure 2 This is a partial cross-sectional schematic diagram of a photovoltaic cell according to another embodiment of this application.

[0022] Figure 3 This is a partial cross-sectional schematic diagram of a photovoltaic cell according to another embodiment of this application.

[0023] Figure 4 This is a schematic diagram showing the distribution of the first and second pyramids in a photovoltaic cell according to an embodiment of this application.

[0024] Figure 5 This is one of the flowcharts of a photovoltaic cell preparation method according to an embodiment of this application.

[0025] Figure 6 This is a second flowchart of a photovoltaic cell fabrication method according to an embodiment of this application.

[0026] Figure label:

[0027] 100, Substrate; 110, First Region; 120, Second Region;

[0028] 200. The First Pyramid;

[0029] 300. The Second Pyramid; 310. Smooth Top Surface;

[0030] 400, Electrode;

[0031] 500, passivation layer;

[0032] 600. Mask. Detailed Implementation

[0033] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0034] In the description of this application, it should be understood that if terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" appear, these terms indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0035] Furthermore, where the terms "first" and "second" appear, these terms 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. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, where the term "multiple" appears, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0036] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0037] In this application, unless otherwise expressly specified and limited, the use of descriptions such as "above" or "below" the second feature indicates that the first and second features are in direct contact or indirect contact via an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. Similarly, "below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0038] It should be noted that if an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. If an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. If so, the terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used in this application are for illustrative purposes only and do not represent the only possible implementation.

[0039] See Figure 1 One embodiment of this application provides a photovoltaic cell including a substrate 100. The substrate 100 has a textured surface, which includes a plurality of first pyramids 200 and a plurality of second pyramids 300, with the plurality of second pyramids 300 arranged between the plurality of first pyramids 200. The base size of the second pyramid 300 is larger than the base size of the first pyramid 200, and the height of the second pyramid 300 is greater than the height of the first pyramid 200.

[0040] For example, a textured surface is formed on the light-receiving surface of the substrate 100, which is the main surface of the photovoltaic cell that receives external light. This arrangement ensures that light can directly enter the pyramid structure of the textured surface, reducing the loss of light caused by passing through other structures before reaching the textured surface and improving the incident efficiency of light.

[0041] Multiple first pyramids 200 are distributed over most of the velvet surface, forming the main structure of the velvet surface. The first pyramids 200 can cover the main light-receiving area of ​​the velvet surface and perform sufficient multiple reflections on the incident short-wavelength light. Multiple second pyramids 300 are scattered between adjacent first pyramids 200. This arrangement will not excessively occupy the distribution space of the first pyramids 200, ensuring the normal functioning of the main function of the first pyramids 200, while allowing the second pyramids 300 to fully exert their function of increasing the absorption of long-wavelength light.

[0042] The first pyramid 200 has a smaller base and lower height. This smaller size allows the first pyramid 200 to form a dense distribution on the textured surface. This dense distribution allows incident short-wavelength (300nm-800nm) light to undergo multiple reflections on the textured surface, reducing direct reflection losses of short-wavelength light and increasing the absorption ratio of short-wavelength light, thereby improving the utilization efficiency of photovoltaic cells for short-wavelength light. The second pyramid 300 has a larger base and higher height. This larger size allows the second pyramid 300 to form a relatively prominent structure on the textured surface. This prominent structure can have a stronger scattering effect on incident long-wavelength (800nm-1200nm) light, changing the propagation direction of long-wavelength light and guiding more long-wavelength light into the interior of the textured surface or the adjacent surface of the first pyramid 200, further reducing the reflection of long-wavelength light and compensating for the insufficient scattering of long-wavelength light by traditional single-scale pyramid textured surfaces.

[0043] When external light enters the velvet surface, short-wavelength light comes into contact with the densely distributed first pyramids 200. After multiple reflections by the first pyramids 200, most of the short-wavelength light is reflected into the interior of the velvet surface or onto the surface of adjacent first pyramids 200, and is eventually absorbed by the substrate 100. Long-wavelength light comes into contact with the second pyramids 300 distributed between the first pyramids 200. The second pyramids 300 scatter the long-wavelength light through their larger structural size, changing the propagation direction of the long-wavelength light, so that the long-wavelength light that would otherwise be easily reflected can be guided more into the interior of the substrate 100 and absorbed by the substrate 100.

[0044] This dual-scale pyramidal textured surface structure effectively reduces the reflection of short-wavelength light through the first pyramid 200 and the second pyramid 300, thereby capturing a wide range of light wavelengths. This significantly reduces reflection losses across different wavelengths and improves the overall light absorption efficiency of the photovoltaic cell. Simultaneously, the rational distribution of the first and second pyramids 200 ensures that their respective functions do not interfere with each other, guaranteeing synergistic optimization of short-wavelength and long-wavelength optical performance. This provides strong support for improving the short-circuit current of the photovoltaic cell, ultimately contributing to higher overall photoelectric conversion efficiency.

[0045] In addition, the dual-scale pyramid textured surface structure can be better adapted to the passivation layer 500, electrode 400 and other structures, reducing the impact on the optical performance of the textured surface during the subsequent structure preparation process, and further ensuring the stability of the overall performance of the photovoltaic cell.

[0046] Combination Figure 2 According to one embodiment of the present invention, a smooth top surface 310 is formed on the top of the second pyramid 300. The smooth top surface 310 is a flat surface obtained by processing the top of the second pyramid 300.

[0047] Optionally, a smooth transition is formed between the smooth top surface 310 and the sidewall of the second pyramid 300, without any obvious sharp edges or protrusions, and the smooth top surfaces 310 of multiple second pyramids 300 are at approximately the same height in the textured surface. The smooth top surface 310 is located at the highest end of the second pyramid 300 and is the part where the second pyramid 300 may come into contact with the external structure. After the second pyramid 300 is formed, the sharp top portion is removed, transforming the sharp tip into a flat surface, providing a stable foundation for subsequent structural contact. It is worth noting that the smooth top surface 310 can be planar or approximately planar; for example, the smooth top surface 310 can be a convex or concave curved surface with an arc-shaped cross-section.

[0048] The smooth top surface 310 can avoid the problem of uneven coverage of the passivation layer 500 caused by the sharp tip, so that the passivation layer 500 covers the top of the second pyramid 300 more evenly and improves the passivation effect. Secondly, the smooth top surface provides a larger and more stable contact area for subsequent possible electrode 400 contact, reducing contact resistance fluctuations.

[0049] Combination Figure 3 According to one embodiment of the present invention, the photovoltaic cell further includes an electrode 400, which contacts at least a portion of the smooth top surface 310 of the second pyramid 300. The electrode 400 is a conductive structure for conducting internal current within the photovoltaic cell and is made of a metallic material with good conductivity. The electrode 400 may selectively contact a portion of the smooth top surface 310 of the second pyramid 300 according to current conduction requirements and the overall structural arrangement. The smooth top surface 310 of the second pyramid 300 in contact with the electrode 400 is typically arranged along the extension direction of the electrode 400 to ensure uniform current collection.

[0050] After the photovoltaic cell absorbs light and generates charge carriers, the charge carriers migrate inside the substrate 100 and are eventually led out through the electrode 400 that contacts the smooth top surface 310 of the second pyramid 300, thus completing the current collection and transmission.

[0051] When electrode 400 contacts the smooth top surface 310 of the second pyramid 300, the flatness of the smooth top surface 310 can be used to form a stable physical and electrical connection. Compared with contact with sharp structures, this effectively reduces contact resistance and energy loss in current transmission. When electrode 400 contacts part of the second pyramid 300, it can prevent electrode 400 from excessively covering the textured surface and affecting light incidence. While ensuring effective current output, it can also maximize the preservation of the optical absorption area of ​​the textured surface, thus balancing optical and electrical performance.

[0052] According to one embodiment of the present invention, the distance from the smooth top surface 310 to the side of the substrate 100 away from the velvet surface is greater than or equal to the distance from the top of the first pyramid 200 to the side of the substrate 100 away from the velvet surface.

[0053] The side of the substrate 100 facing away from the textured surface is the non-light-receiving surface. The distance from the smooth top surface 310 to this non-light-receiving surface is the overall height of the second pyramid 300 from the smooth top surface 310 to the non-light-receiving surface; the distance from the top of the first pyramid 200 to this non-light-receiving surface is the overall height of the first pyramid 200 from its top to the non-light-receiving surface.

[0054] When the distance from the smooth top surface 310 to the non-lit surface is greater than the distance from the top of the first pyramid 200 to the non-lit surface, the overall height of the second pyramid 300 is higher than that of the first pyramid 200; when the two distances are equal, the smooth top surface 310 of the second pyramid 300 and the top of the first pyramid 200 are at the same horizontal height.

[0055] The distance from the smooth top surface 310 to the side of the substrate 100 away from the textured surface is greater than or equal to the distance from the top of the first pyramid 200 to the side of the substrate 100 away from the textured surface. This can be achieved by controlling the parameters of the two texturing processes. When the height of the smooth top surface 310 is greater than the height of the top of the first pyramid 200, the second pyramid 300 forms a relatively protruding structure, which can more effectively scatter long-wave light and guide more long-wave light into the interior of the textured surface or the surface of the first pyramid 200, thereby improving the long-wave absorption efficiency. At the same time, the protruding smooth top surface 310 also facilitates the precise alignment of the electrode 400. When the two heights are equal, the overall height of the textured surface is flatter, reducing the problem of uneven deposition of the passivation layer 500, improving the coverage quality of the passivation layer 500, and reducing surface recombination to maintain a high open-circuit voltage.

[0056] Combination Figure 4 According to one embodiment of the present invention, a plurality of first regions 110 and a second region 120 located outside the first regions 110 are formed in a velvet pattern. A plurality of second pyramids 300 are formed in the first regions 110 and a plurality of first pyramids 200 are formed in the second regions 120.

[0057] The first region 110 of the velvet surface is a pre-planned area for forming the second pyramid 300. Multiple first regions 110 are discontinuously distributed on the velvet surface and spaced apart from each other. The second region 120 is the remaining area of ​​the velvet surface excluding all the first regions 110. These regions are interconnected to form the main body of the velvet surface. Each first region 110 is an independent small area, dispersed in the second region 120. The second pyramid 300 is within the first region 110 and does not exceed the range of the first region 110. The first pyramid 200 is within the second region 120.

[0058] It is worth noting that within each first region 110, there may be more than two second pyramids 300, or there may be only one second pyramid 300; no specific limitation is made here.

[0059] This correspondence between regional division and pyramid formation can be achieved through a masking process during the flocking process. Specifically, a mask is used to cover the second region 120, exposing only the first region 110 for a second flocking process. This causes the first region 110 to form the second pyramid 300, while the second region 120 retains the first pyramid 200 formed during the first flocking process. By defining the boundary between the first region 110 and the second region 120 using a mask, the two flocking processes are applied to different regions, ultimately forming corresponding pyramid structures in different areas, achieving an orderly distribution of the two types of pyramids on the flocked surface.

[0060] This method of dividing the area into different pyramids enables the orderly distribution of the second pyramid 300, avoiding uneven optical performance caused by random distribution and ensuring consistent light absorption in all parts of the textured surface. Concentrating the second pyramid 300 in the first area 110 facilitates precise alignment between the subsequent electrode 400 and the second pyramid 300, reducing the possibility of contact between the electrode 400 and the first pyramid 200 and avoiding affecting the optical function of the first pyramid 200.

[0061] According to one embodiment of the present invention, the first region 110 is arranged in an array on the pile surface according to a preset pattern. The preset pattern array distribution means that the first region 110 is arranged on the pile surface according to a predetermined fixed pattern, forming a neat and orderly distribution. This array distribution can take many forms, such as arranging the first region 110 evenly into multiple rows and columns along the length and width of the pile surface, with equal spacing between adjacent rows and columns of the first region 110; it can also be arranged according to a geometric pattern, such as setting the first region 110 at the vertices of a regular hexagon to form a hexagonal array.

[0062] In this distribution, the size and shape of each first region 110 remain consistent, and the spacing between any two adjacent first regions 110 is also the same. This array distribution is achieved by preparing a mask with a corresponding array pattern. The opening pattern on the mask perfectly matches the array distribution pattern of the first regions 110. When the mask covers the pile surface, the exposed area at the opening is the first region 110 distributed according to the array. Using the mask with the array pattern, the distribution pattern of the first region 110 is transferred to the pile surface, so that the subsequent second pile fabrication is carried out only in these regularly distributed opening areas, ultimately forming a second pyramid 300 distributed according to a preset pattern.

[0063] The first region 110 is arranged in a pre-defined array, which ensures that the second pyramid 300 is evenly distributed on the textured surface, ensuring consistent long-wave scattering capability in all parts, avoiding insufficient local light absorption, and improving the stability of optical performance. The regular array distribution facilitates the automated alignment of the subsequent electrode 400 fabrication. The electrode 400 pattern can be matched with the array pattern of the first region 110, achieving precise contact through automated equipment, improving production efficiency and alignment accuracy. The neat array distribution is conducive to the consistent control of process parameters during the texturing process. The texturing environment of each first region 110 is more similar, ensuring that the second pyramid 300 is highly consistent in size and morphology, improving batch consistency and reducing performance fluctuations.

[0064] According to one embodiment of the present invention, the height of the first pyramid 200 is 0.5μm-2μm, for example, the height of the first pyramid is 0.5μm, 0.7μm, 0.9μm, 1μm, 12μm, 1.5μm, 1.8μm, 2μm, etc.; and / or, the density of the first pyramid 200 within the second region 120 is 10. 6 pcs / cm 2 -10 7 pcs / cm 2 For example, the density of the first pyramid 200 within the second region 120 is 10. 6 pcs / cm 2 2.5×10 6 pcs / cm 2 5×10 6 pcs / cm 2 7.5×10 6 pcs / cm 2 Or 10 7 pcs / cm 2 wait.

[0065] The height of the first pyramid 200 refers to the vertical distance from its base to its top, and the density of the first pyramid 200 within the second region 120 refers to the number of first pyramids 200 distributed per unit area within the second region 120. The height and density of the first pyramid 200 are controlled through the first texturing process, such as adjusting parameters like the composition of the texturing solution, texturing temperature, and time, to control the growth height and quantity of the first pyramid 200 to meet preset requirements.

[0066] The first pyramid 200 of appropriate height can provide sufficient reflection path for short-wavelength light, allowing it to be reflected multiple times between the first pyramids 200, reducing the proportion of light directly reflected off the velvet surface; the first pyramid 200 of appropriate density can ensure that short-wavelength light, no matter where it is incident in the second region 120, will encounter the first pyramid 200 and be reflected, avoiding increased local reflectivity due to the sparseness of the first pyramid 200.

[0067] The height of the first pyramid 200 is in the range of 0.5μm-2μm, which can extend the propagation path and residence time of short-wavelength light within the substrate 100, increase the probability of absorption by the substrate 100, and reduce reflection loss. The density of the first pyramid 200 in the second region 120 is 10 6 pcs / cm 2 -10 7 pcs / cm 2 Within the specified range, this avoids blank areas in the second region 120 that are not covered by the first pyramid 200, further reducing short-wave reflectivity. The two work synergistically to maximize the absorption efficiency of photovoltaic cells for short-wave light, supporting increased short-circuit current, while simultaneously laying the optical performance foundation for the second region 120 as the main surface area.

[0068] According to one embodiment of the present invention, the height of the second pyramid 300 is 3μm-10μm, for example, the height of the second pyramid 300 is 3μm, 6μm, 9μm or 10μm. The height of the second pyramid 300 refers to the vertical distance from its bottom to its top. This height is controlled by adjusting the second texturing process, for example, by adjusting the action time of the second etching solution, reaction conditions, etc., to control the growth height of the second pyramid 300 to achieve the preset requirements. When the second pyramid 300 has a smooth top surface 310, the height can be the vertical distance from the bottom of the second pyramid 300 to the smooth top surface 310. The height control can be achieved by adjusting the second texturing process and the sidewall passivation process of the second pyramid 300.

[0069] In this embodiment, the height of the second pyramid 300 is 3μm-10μm, which can effectively enhance the scattering ability of long-wavelength light, reduce direct reflection loss, and improve long-wavelength absorption efficiency. The height of the second pyramid 300 matches the height of the first pyramid 200, which can avoid unevenness of the textured surface due to excessive height difference, reduce the problem of uneven deposition of the passivation layer 500, and improve the coverage quality of the passivation layer 500. The appropriate height also facilitates the subsequent contact between the electrode 400 and the smooth top surface 310, ensuring stable contact of the electrode 400, reducing contact resistance, and ensuring effective current conduction.

[0070] According to one embodiment of the present invention, the photovoltaic cell further includes a passivation layer 500 located on the textured surface. The passivation layer 500 is a thin film structure having the function of reducing carrier recombination on the surface of the substrate 100, and is made of a material with good insulation and chemical stability. The passivation layer 500 can be a single-layer structure or a multilayer structure, and the material of the passivation layer 500 can include at least one of alumina, silicon oxide, silicon nitride, or silicon oxynitride.

[0071] Optionally, the passivation layer 500 completely covers the textured surface, including the entire surface of the first pyramid 200, the entire surface of the second pyramid 300, and the transition area between the first region 110 and the second region 120, ensuring that the textured surface has no exposed substrate 100 surface, and that the passivation layer 500 is tightly attached to the textured surface without obvious gaps or peeling areas.

[0072] The substrate 100 has a large number of dangling bonds on its surface. These dangling bonds can capture charge carriers and cause charge carrier recombination, reducing the open-circuit voltage and short-circuit current of the photovoltaic cell. After the passivation layer 500 covers the textured surface, it can combine with the dangling bonds on the surface of the substrate 100, reducing the number of dangling bonds. At the same time, it blocks the influence of external impurities on the surface of the substrate 100, significantly reducing the charge carrier recombination rate on the surface of the substrate 100 and extending the charge carrier lifetime.

[0073] The passivation layer 500 effectively reduces carrier recombination on the substrate 100 surface, minimizes carrier transport losses, and improves the open-circuit voltage of the photovoltaic cell. This is because a lower surface recombination rate allows more carriers to participate in current formation, maintaining a higher potential difference. Furthermore, the passivation layer 500 protects the pyramid structure from damage during subsequent processes, maintaining its integrity and ensuring undamaged optical performance. In addition, the passivation layer 500 also provides some anti-reflection protection, working in conjunction with the pyramid structure to reduce light reflection and further improve light absorption efficiency. Simultaneously, the passivation layer 500 completely covers the textured surface, preventing excessive obstruction of electrical connections when the electrode 400 contacts the smooth top surface 310, thus ensuring effective current transport between the electrode 400 and the substrate 100 and achieving synergistic optimization of optical and electrical performance.

[0074] Combination Figure 5 and Figure 6The present invention also provides a method for preparing a photovoltaic cell, comprising the following steps:

[0075] S100, providing substrate 100.

[0076] Optionally, after providing the substrate 100, the method further includes:

[0077] Clean the substrate 100, for example, by using RCA standard cleaning, and remove surface contaminants and the natural oxide layer by SC-1 (Standard Clean 1) cleaning and SC-2 (Standard Clean 2) cleaning;

[0078] The substrate 100 is surface activated by immersing it in hydrofluoric acid at a mass percentage of 1%-2% for 30-60 seconds to form a hydrogen-terminated surface.

[0079] S200: A first texturing process is performed on the surface of the substrate 100 to form a textured surface, which includes multiple first pyramids 200.

[0080] Optionally, the process parameters for the first texturing process include: providing a first etching solution to the surface of the substrate 100, wherein the first etching solution etches the surface of the substrate 100; wherein the mass percentage of sodium hydroxide in the first etching solution is 1%-3%, the mass percentage of isopropanol is 5%-10%, the process temperature is 70℃-85℃, and the process duration is 5min-10min; or, the first etching solution contains hydrofluoric acid, nitric acid, and water in a volume ratio of 1:3:5, the process temperature is 25℃-40℃, and the process duration is 5min-10min.

[0081] The first texturing process involves applying a first etching solution to the surface of the substrate 100. The etching solution chemically reacts with the substrate 100 surface to form multiple first pyramids 200. The first etching solution reacts chemically with the substrate 100 material, selectively etching the surface. Due to the anisotropic corrosion characteristics of the substrate 100 material, the etching rate varies across different crystal orientations on the substrate 100 surface. This difference causes pyramid-shaped protrusions, i.e., the first pyramids 200, to gradually form on the substrate 100 surface.

[0082] During the etching process, the etching solution uniformly covers the entire surface of the substrate 100, ensuring that all parts of the substrate 100 surface can be etched to form a uniformly distributed first pyramid 200. At the same time, the reaction conditions are controlled to adjust the growth of the first pyramid 200, ensuring that it has a suitable height and density to meet the subsequent optical performance requirements.

[0083] The first pyramid 200 formed during the first texturing process can construct an anti-reflection structure for short-wavelength light on the surface of the substrate 100. After short-wavelength light is incident, it undergoes multiple reflections between the first pyramids 200, increasing the propagation path within the substrate 100, reducing the proportion of direct reflection, and improving the short-wavelength absorption efficiency, thus laying the foundation for increased short-circuit current. At the same time, the uniformly distributed first pyramids 200 can ensure consistent anti-reflection effects across different parts of the substrate 100 surface, avoiding local light absorption differences and improving optical performance stability. Furthermore, the structurally complete and regularly shaped first pyramids 200 can provide a good substrate for the subsequent second texturing process to form the second pyramid 300, ensuring the stable formation of the second pyramid 300 between the first pyramids 200 without affecting the original structure and function of the first pyramid 200.

[0084] S300, prepare a mask 600 covering a second region 120 of the velvet surface, and expose a first region 110 outside the second region 120 of the velvet surface.

[0085] Optionally, a mask 600 covering a second region 120 of the textured surface is prepared on the textured surface, and the first region 110 of the textured surface located outside the second region 120 is exposed by: coating the textured surface with photoresist; performing photoresist patterning to form periodic openings with a diameter of 2μm-8μm and a spacing of 10μm-30μm, wherein the location of the openings forms the first region 110, and the region outside the openings forms the second region 120.

[0086] When preparing the textured mask 600, a layer of photoresist is first uniformly coated on the entire textured surface. The photoresist is a material that is sensitive to specific light. After coating, it can completely cover every part of the textured surface, including the first pyramid 200 and the surface after the first texture, forming a continuous photoresist film.

[0087] Next, the coated photoresist is patterned. This process involves transferring a pre-defined pattern, consistent with the distribution pattern of the first region 110, onto the photoresist through exposure. Following this, a development process removes the exposed portions of the photoresist, retaining the unexposed areas, ultimately forming periodic openings on the photoresist film. The positions and distribution patterns of these openings on the photoresist completely correspond to the pre-defined first region 110. The locations of these openings are the first region 110 that will be exposed subsequently. The retained portion of the photoresist covers the textured second region 120, preventing the subsequent etching solution from contacting the second region 120.

[0088] By coating photoresist and patterning it to form a mask 600, the precise division of the first region 110 and the second region 120 can be achieved, ensuring that the position, size, and distribution pattern of the first region 110 meet the preset requirements, providing a precise positional basis for the second pyramid 300. Secondly, the photoresist mask 600 has a good shielding effect, which can effectively prevent the solution during the second etching from contacting the second region 120, avoiding corrosion and damage to the first pyramid 200. In addition, the photoresist patterning process can achieve complex and regular opening patterns, meeting the requirement that the first region 110 is distributed according to a preset pattern. At the same time, this process has high precision and repeatability, which is conducive to large-scale mass production, improves product batch consistency, and reduces the impact of process fluctuations on product performance.

[0089] S400, a second texturing process is performed in the first region 110 to form a second pyramid 300 located in the first region 110, wherein the base size of the second pyramid 300 is larger than the base size of the first pyramid 200, and the height of the second pyramid 300 is greater than the height of the first pyramid 200.

[0090] Optionally, the process parameters for the second texturing process include: providing a second etching solution to the first region 110 of the texturing surface, wherein the second etching solution etches the first region 110 of the texturing surface; wherein the second etching solution contains hydrofluoric acid, nitric acid and water in a volume ratio of 1:3:5, contains a surfactant by mass percentage of 0.1%-0.5%, the process temperature is 20℃-25℃, and the process duration is 30s-120s.

[0091] The second texturing process involves etching only the first region 110 of the textured surface created in the first texturing process to form the second pyramid 300. Before the second texturing, a mask 600 is prepared on the textured surface, covering the second region 120 and exposing only the first region 110. A second etching solution is then applied to the exposed first region 110, reacting chemically only with the substrate 100 surface of the first region 110 to further etch it. Since the first region 110 has already formed a basic textured structure after the first texturing, the second etching solution will perform deeper selective etching in this region. Utilizing the anisotropic etching characteristics of the substrate 100 material, a larger and taller pyramid structure, the second pyramid 300, is gradually formed within the first region 110. During the etching process, the range and degree of action of the second etching solution are controlled to ensure that the second pyramid 300 is formed only in the first region 110, and that the size and height of the second pyramid 300 meet the preset requirements without damaging the first pyramid 200 in the surrounding second region 120.

[0092] The second texturing process forms the second pyramid 300 only in the first region 110, allowing for precise control over its position and avoiding uneven optical performance caused by random distribution. The larger and taller second pyramid 300 effectively scatters long-wavelength light, compensating for the insufficient long-wavelength scattering capability of the first pyramid 200, improving long-wavelength absorption efficiency, and further increasing short-circuit current. The second etching solution does not affect the first pyramid 200 in the second region 120, allowing it to continue its short-wavelength anti-reflection function. This achieves synergy between the two pyramid functions, ensuring good absorption of the full spectrum of light by the photovoltaic cell, while also creating conditions for precise contact between the subsequent electrode 400 and the second pyramid 300, improving electrical performance stability.

[0093] In this embodiment, after forming the second pyramid 300 located in the first region 110, the mask 600 of the second region 120 is removed, for example, by wet etching or plasma ashing process.

[0094] S500, deposit a passivation layer 500 on the velvet surface.

[0095] S600, print electrode 400 paste, and sinter to form electrode 400, electrode 400 being in contact with at least a portion of second pyramid 300. Electrode 400 paste is a metal paste, which may include at least one of silver, copper, tin, gold, lead, or nickel.

[0096] According to one embodiment of the present invention, before depositing the passivation layer 500 on the textured surface, the method further includes:

[0097] S410, Perform rapid thermal oxidation or ozone treatment to passivate the sidewalls of the second pyramid 300, and form a smooth top surface 310 on the top of the second pyramid 300.

[0098] This processing step is performed after the second texturing and before the deposition of the passivation layer 500. The object of the processing is the second pyramid 300 formed after the second texturing. After the processing is completed, the defects on the sidewalls of the second pyramid 300 are repaired and a smooth structure is formed on the top before the subsequent deposition of the passivation layer 500.

[0099] Rapid thermal oxidation treatment involves placing the textured substrate 100 in a high-temperature environment and introducing an oxidizing gas, causing the surface of the substrate 100 to react with the oxidizing gas to form an oxide layer; ozone treatment involves placing the substrate 100 in an ozone-containing environment and using the strong oxidizing properties of ozone to treat the sidewalls and top of the second pyramid 300.

[0100] In both processes, on the one hand, the oxidizing material reacts with the defects (such as dangling bonds, impurity atoms, etc.) on the sidewall surface of the second pyramid 300, filling these defects and achieving passivation of the sidewall; on the other hand, the process slightly oxidizes or etches the top of the second pyramid 300, removing the sharp part at the top and transforming the sharp top into a flat and smooth top surface 310.

[0101] The passivation of the sidewalls of the second pyramid 300 reduces carrier recombination centers on the sidewall surface, lowers the carrier recombination rate, and extends carrier lifetime, thereby improving the open-circuit voltage of the photovoltaic cell. Forming a smooth top surface 310 avoids uneven coverage of the passivation layer 500 caused by sharp tips, improving the overall coverage quality of the passivation layer 500. It also provides a good foundation for subsequent electrode 400 contact, reducing contact resistance and ensuring effective current transmission. Furthermore, this treatment step does not significantly affect the structure and performance of the first pyramid 200, maintaining its short-wave anti-reflection effect and achieving simultaneous optimization of electrical and optical performance.

[0102] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0103] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A photovoltaic cell, characterized in that, include: A substrate having a textured surface, the textured surface comprising a plurality of first pyramids and a plurality of second pyramids, the plurality of second pyramids being arranged between the plurality of first pyramids; The base dimensions of the second pyramid are larger than those of the first pyramid, and the height of the second pyramid is greater than that of the first pyramid.

2. The photovoltaic cell according to claim 1, characterized in that, The top of the second pyramid has a smooth surface.

3. The photovoltaic cell according to claim 2, characterized in that, Also includes: An electrode that is in contact with at least a portion of the smooth top surface of the second pyramid.

4. The photovoltaic cell according to claim 2 or 3, characterized in that, The distance from the smooth top surface to the side of the substrate opposite to the velvet surface is greater than or equal to the distance from the top of the first pyramid to the side of the substrate opposite to the velvet surface.

5. The photovoltaic cell according to any one of claims 1 to 3, characterized in that, The velvet surface forms a plurality of first regions spaced apart and a second region located outside the first regions, with a plurality of second pyramids formed in the first regions and a plurality of first pyramids formed in the second regions.

6. The photovoltaic cell according to claim 5, characterized in that, The first region is distributed in an array on the velvet surface according to a preset pattern.

7. The photovoltaic cell according to claim 5, characterized in that, The height of the first pyramid is 0.5μm-2μm; And / or, the density of the first pyramid within the second region is 10. 6 pcs / cm 2 -10 7 pcs / cm 2 .

8. The photovoltaic cell according to claim 5, characterized in that, The height of the second pyramid is 3μm-10μm.

9. The photovoltaic cell according to any one of claims 1 to 3, characterized in that, Also includes: A passivation layer is located on the velvety surface.

10. A method for preparing a photovoltaic cell, characterized in that, Includes the following steps: Provide substrate; A first texturing process is performed on the surface of the substrate to form a texturized surface, the texturized surface comprising a plurality of first pyramids; A mask is prepared on the velvet surface to cover a second region of the velvet surface, exposing a first region of the velvet surface outside the second region; A second texturing process is performed in the first region to form a second pyramid located in the first region, wherein the base size of the second pyramid is larger than the base size of the first pyramid, and the height of the second pyramid is greater than the height of the first pyramid. A passivation layer is formed by depositing material on the textured surface; The electrode paste is printed and sintered to form an electrode that is in contact with at least a portion of the second pyramid.

11. The method for preparing a photovoltaic cell according to claim 10, characterized in that, Before depositing the passivation layer on the textured surface, the method further includes: The sidewalls of the second pyramid are passivated by rapid thermal oxidation or ozone treatment, forming a smooth top surface at the top of the second pyramid.

12. The method for preparing a photovoltaic cell according to claim 10 or 11, characterized in that, The process parameters for the first texturing process include: A first etching solution is provided to the surface of the substrate, and the first etching solution etches the surface of the substrate; In the first etching solution, the mass percentage of sodium hydroxide is 1%-3%, the mass percentage of isopropanol is 5%-10%, the process temperature is 70℃-85℃, and the process time is 5min-10min; or... The first etching solution contains hydrofluoric acid, nitric acid and water in a volume ratio of 1:3:5, the process temperature is 25℃-40℃, and the process time is 5min-10min.

13. The method for preparing a photovoltaic cell according to claim 10 or 11, characterized in that, The process parameters for the second flocking process include: A second etching solution is provided to the first region of the velvet surface, and the second etching solution etches the first region of the velvet surface. The second etching solution contains hydrofluoric acid, nitric acid and water in a volume ratio of 1:3:5, contains surfactants at a mass percentage of 0.1%-0.5%, has a process temperature of 20℃-25℃, and a process duration of 30s-120s.

14. The method for preparing a photovoltaic cell according to claim 10 or 11, characterized in that, The step of preparing a mask covering a second region of the velvet surface, exposing a first region of the velvet surface outside the second region, includes: Photoresist is coated onto the textured surface; Photoresist patterning is performed to form periodic openings with a diameter of 2μm-8μm and a spacing of 10μm-30μm. The location of the openings forms the first region, and the region outside the openings forms the second region.

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