Solar cell, preparation method thereof and photovoltaic module

Abstract

The invention relates to the field of solar cells, and discloses a solar cell and a preparation method thereof, and a photovoltaic module, the solar cell comprises a silicon substrate, a first surface and a second surface of the silicon substrate, or the first surface is provided with a second area and a first area formed by recessing towards the silicon substrate relative to the second area, a step-shaped structure is formed on the silicon substrate at the junction of the first region and the second region; the silicon substrate in the first region has a texture structure; the first passivation contact structure comprises a first dielectric layer and a first doping layer arranged on the surface of the first dielectric layer in the direction away from the silicon substrate, the first passivation contact structure is arranged in the second area, D is larger than or equal to 9: 10 and smaller than 1: 1, and the ratio of the orthographic projection width of the first passivation contact structure in the second area to the width of the first area ranges from 1: 7 to 1: 12. According to the solar cell, the absorption amount of sunlight and the carrier transmission capability are improved while the passivation effect is ensured.

Description

Technical Field

[0001] This invention relates to the field of solar cells, and more particularly to a solar cell and its preparation method, and a photovoltaic module. Background Technology

[0002] Setting a localized passivation contact structure on one side of the solar cell can improve the passivation effect of the solar cell, but it will block the first region, which will affect the light absorption effect of the textured structure, reduce the absorption and utilization rate of sunlight in the first region, and reduce the number of photogenerated carriers in the solar cell, making it difficult to effectively improve the photoelectric conversion efficiency of the solar cell. Summary of the Invention

[0003] This invention provides a solar cell and its fabrication method, as well as a photovoltaic module. While ensuring the passivation effect of the first passivation contact structure, the solar cell can effectively improve the absorption of sunlight and the transport capacity of charge carriers, thereby significantly improving the photoelectric conversion efficiency of the solar cell.

[0004] In a first aspect, embodiments of this application disclose a solar cell, the solar cell comprising:

[0005] A silicon substrate having a first surface and a second surface disposed opposite to each other, wherein the first surface and the second surface, or the first surface, each have a first region and a second region formed by recessing into the silicon substrate relative to the first region, wherein the silicon substrate at the boundary between the first region and the second region forms a stepped structure; the silicon substrate in the first region has a textured structure.

[0006] The first passivation contact structure includes a first dielectric layer and a first doped layer disposed on the surface of the first dielectric layer along a direction away from the silicon substrate. The first passivation contact structure is disposed in the second region. The ratio between the orthographic projection width of the first passivation contact structure in the second region and the width of the second region is D, where 9:10 ≤ D < 1:1. The ratio between the orthographic projection width of the first passivation contact structure in the second region and the width of the first region is 1:7 to 1:12.

[0007] Furthermore, the stepped structure has multiple groove structures on the side surface near the first passivation contact structure.

[0008] Furthermore, the depth of any of the groove structures is 1 μm to 4 μm; the distance between the center point of any of the groove structures and the edge of the groove structure is 0.5 μm to 5 μm.

[0009] Furthermore, the orthographic projection width of the first passivated contact structure in the second region is 60μm to 100μm, and the width of the first region is 700μm to 1000μm.

[0010] Furthermore, the texture structure is a pyramid-shaped structure, a pyramid-like structure, or a non-pyramid-shaped structure.

[0011] Furthermore, when the texture structure is a pyramid-shaped structure, the longest side length of the base of the pyramid-shaped structure is 1μm to 3μm; the height of the pyramid-shaped structure is 1μm to 4μm.

[0012] Furthermore, the sum of the thickness of the silicon substrate in the second region and the thickness of the first passivation contact structure is H1, and the thickness of the silicon substrate in the first region is H2. H1 and H2 satisfy: H1-H2=2μm~4μm.

[0013] Furthermore, the doping concentration of the semiconductor conductive element in the first doped layer is 2 × 10⁻⁶. 19 atoms / cm 3 ~8×10 19 atoms / cm 3 .

[0014] Furthermore, the solar cell also includes a first passivation layer, which is respectively disposed on the surface of the first doped layer away from the silicon substrate, on the surface of the stepped structure near the first passivation contact structure, on the sidewall of the stepped structure, and on the first region.

[0015] Furthermore, the silicon substrate is N-type, and the solar cell further includes a second passivation contact structure disposed on the second surface. The second passivation contact structure includes a second dielectric layer and a second doped layer. The second doped layer is disposed on the side of the second dielectric layer away from the second surface. The conductivity type of the second doped layer is N-type, and the conductivity type of the first doped layer is P-type.

[0016] Secondly, embodiments of this application disclose a method for fabricating a solar cell as described in the first aspect, the method comprising the following steps:

[0017] Provide silicon substrate;

[0018] A first passivated contact structure is formed on the first and second surfaces of the silicon substrate, or on the first surface.

[0019] The first passivated contact structure is sequentially patterned and textured to give the silicon substrate a second region and a first region that is recessed into the silicon substrate relative to the second region, and to form a stepped structure on the silicon substrate at the junction of the first region and the second region, and to form a textured structure on the silicon substrate in the first region.

[0020] Post-processing yields a solar cell as described in any of the first aspects.

[0021] Furthermore, the steps of patterning and texturing the first passivated contact structure include:

[0022] The first doped layer is processed graphically to remove a portion of the thickness of the first doped layer corresponding to the first region, so that the thickness of the first doped layer in the first region is less than the thickness of the first doped layer in the second region.

[0023] The texturing process involves etching away the first passivation contact structure in the first region and continuing to etch the silicon substrate in the first region to form the step-like structure at the junction of the first region and the second region, and to form the texture structure on the silicon substrate in the first region.

[0024] Furthermore, the first passivated contact structure is patterned using a laser etching method. The laser wavelength is 325nm to 1064nm, the laser power is 5W to 100W, the laser spot area is 20×20μm to 400×400μm, and the etching width is 500μm to 1000μm.

[0025] Furthermore, the texturing process includes the following steps:

[0026] The texturing process includes the following steps:

[0027] The surface of the solar cell is pre-cleaned to remove dirt from the surface of the solar cell;

[0028] The silicon substrate in the first region is etched to form the stepped structure on the silicon substrate at the junction of the first region and the second region, and the texture structure is formed on the silicon substrate in the first region.

[0029] The surface of the solar cell is then cleaned to remove reaction products and residual reagents.

[0030] Further, the step of preparing the first passivated contact structure includes:

[0031] The first dielectric layer and the first doped amorphous silicon layer are sequentially deposited on the first surface;

[0032] Annealing transforms the first doped amorphous silicon layer into the first doped layer, and a protective layer is formed on the first doped layer.

[0033] Furthermore, the step of providing the silicon substrate includes: first polishing the silicon substrate, and then sequentially forming a second dielectric layer and a second doped layer on the second surface of the silicon substrate;

[0034] The post-processing steps include:

[0035] Remove the protective layer on the first doped layer;

[0036] A first passivation layer is formed on the surface of the first doped layer away from the silicon substrate, on the surface of the stepped structure near the first passivation contact structure, on the sidewall of the stepped structure, and on the first region, respectively. A second functional layer is formed on the second doped layer, wherein the second functional layer is a second passivation layer and / or a second antireflection layer.

[0037] A first electrode is printed and sintered on the first passivation layer, and a second electrode is printed and sintered on the second functional layer, such that the first electrode penetrates the first passivation layer and makes ohmic contact with the first doped layer, and the second electrode penetrates the second functional layer and makes ohmic contact with the second doped layer.

[0038] Thirdly, embodiments of this application disclose a photovoltaic module, comprising: a solar cell as described in any one of the first aspects, or a solar cell prepared by any one of the preparation methods described in the second aspect.

[0039] Compared with the prior art, the beneficial effects of this application are as follows:

[0040] This application provides a solar cell and its fabrication method, as well as a photovoltaic module. A first passivated contact structure is disposed in a second region. By controlling the width ratio of the first passivated contact structure to the first region, the passivation effect of the first passivated contact structure can be fully utilized, significantly reducing recombination and promoting efficient carrier transport, thereby improving the photoelectric conversion efficiency of the solar cell. Furthermore, the light-trapping effect of the textured structure in the first region can be utilized to improve the utilization rate of sunlight. In addition, the silicon substrate at the boundary between the second and first regions of this application exhibits a stepped structure. By setting the width ratio of the orthographic projection of the first passivated contact structure in the second region to the width of the second region within the range of this application, the stepped structure not only effectively avoids the shading effect of the first passivated contact structure on the first region, further ensuring the light-trapping effect of the textured structure, but also increases the area of ​​the silicon substrate, thereby further improving the amount of sunlight captured.

[0041] In other words, this application reduces the impact of the first passivation contact structure on the amount of sunlight captured by controlling the ratio of the projected width of the first passivation contact structure in the second region to the width of the first region, thereby ensuring that the first region can achieve a good anti-reflection effect and ensuring the solar cell's ability to capture sunlight. Furthermore, by further incorporating a stepped structure and controlling the ratio of the width of the first passivation contact structure to the width of the second region, the stepped structure not only prevents the first passivation contact structure from blocking the first region but also increases the area of ​​the silicon substrate, thereby further increasing the amount of light absorbed by the solar cell and improving its photoelectric conversion efficiency.

[0042] In addition, by controlling the width of the first region, the width of the first passivation contact structure, and the width of the second region, it is possible to reduce the difficulty of printing electrodes, improve the accuracy of electrode printing, ensure a high contact area and good contact tightness between the electrode and the first doped layer, thereby helping to reduce contact resistance, reduce the resistance to carrier diffusion to the electrode, improve the carrier transport rate, and improve the photoelectric conversion efficiency of the solar cell.

[0043] In other words, by controlling the widths of the first passivation contact structure, the second region, and the first region within a specific ratio range, this application not only improves the light-shielding problem and increases the area of ​​the silicon substrate while ensuring the passivation effect of the first passivation contact structure, thereby further increasing the amount of sunlight absorbed, but also improves the carrier transport capability, thus significantly improving the photoelectric conversion efficiency of the solar cell. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1 This is a top view of a solar cell provided in an embodiment of this application;

[0046] Figure 2 This is a top-view electron microscope image of a solar cell provided in an embodiment of this application;

[0047] Figure 3 This is a solar cell provided in an embodiment of this application;

[0048] Figure 4 This is an electron microscope image of a solar cell groove structure provided in an embodiment of this application;

[0049] Figure 5This is a schematic diagram of the structure of a solar cell after depositing a second dielectric layer and a second doped layer on the back surface, as provided in an embodiment of this application.

[0050] Figure 6 This is a schematic diagram of the structure of a solar cell with borosilicate glass and a surrounding coating removed, as provided in an embodiment of this application.

[0051] Figure 7 This is a schematic diagram of the structure of a solar cell after depositing a first passivated contact structure on the light-receiving surface, as provided in an embodiment of this application.

[0052] Figure 8 This is a schematic diagram of the structure of a solar cell after graphical processing, provided in an embodiment of this application.

[0053] Figure 9 This is a schematic diagram of the structure of the solar cell after texturing treatment provided in the embodiments of this application;

[0054] Figure 10 This is a schematic diagram of the structure of a solar cell after removing the protective layer on the first doped layer, provided in an embodiment of this application.

[0055] Figure 11 This is a schematic diagram of the structure of a solar cell after depositing the first passivation layer and the second functional layer, as provided in the embodiments of this application.

[0056] Figure 12 This is a diagram showing the relationship between the sum of the thicknesses of the second region and the first passivation contact structure and the thickness of the second region, provided in an embodiment of this application.

[0057] Figure 13 This is a scanning electron microscope image of the pyramid structure provided in an embodiment of this application.

[0058] Icons: 1. Silicon substrate; 1a. First region; 1b. Second region; 11. Stepped structure; 111. Sidewall; 2. First passivation contact structure; 21. First dielectric layer; 22. First doped layer; 3. First passivation layer; 4. Second passivation contact structure; 41. Second dielectric layer; 42. Second doped layer; 5. Second functional layer; 6. First electrode; 7. Second electrode; 8. Borosilicate glass; 9. Phosphosilicate glass. Detailed Implementation

[0059] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0060] In this invention, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing the invention and its embodiments, and are not intended to limit the indicated devices, elements, or components to having a specific orientation, or to be constructed and operated in a specific orientation.

[0061] Furthermore, some of the aforementioned terms, besides indicating direction or positional relationships, may also have other meanings. For example, the term "above" may, in certain circumstances, indicate a dependency or connection. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0062] Furthermore, the terms "first," "second," etc., are primarily used to distinguish different devices, elements, or components (which may be the same or different in specific type and construction), and are not intended to indicate or imply the relative importance or quantity of the indicated devices, elements, or components. Unless otherwise stated, "a plurality of" means two or more.

[0063] The technical solutions provided by the present invention will be further described below with reference to the embodiments and accompanying drawings.

[0064] Because passivated contact structures have excellent passivation effects, fabricating them on the surface of solar cells can effectively reduce the recombination rate of charge carriers, thereby improving the photoelectric conversion efficiency of solar cells. However, the doped polycrystalline silicon layer has light-absorbing properties, which can affect the absorption of light by the solar cell. Therefore, to improve the passivation effect of the solar cell while ensuring the absorption of sunlight, a locally passivated structure is required.

[0065] However, if the width of the passivation contact structure is not designed appropriately to match the width of the first region, it will affect the passivation effect of the solar cell or the light-trapping effect of the first region. Furthermore, the applicant found that a locally long passivation contact structure can partially block the first region, thus affecting the light-trapping effect of the textured structure in the first region and making it difficult to effectively improve the solar cell's absorption and utilization rate of sunlight. Therefore, how to further improve the solar cell's utilization rate of sunlight while ensuring a balance between the passivation effect and the light-trapping effect of the first region has become a research challenge.

[0066] Based on the above problems, this application discloses a solar cell and its preparation method, as well as a photovoltaic module. This solar cell can improve the absorption of sunlight while ensuring the passivation effect, and it can also improve the carrier transport capacity, thereby improving the photoelectric conversion efficiency of the solar cell to a high extent.

[0067] The first aspect, such as Figures 1 to 3 As shown in the figure, this application discloses a solar cell, which includes:

[0068] The silicon substrate 1 has a first surface and a second surface disposed opposite to each other. The first surface and the second surface of the silicon substrate 1, or both of the first surface have a second region 1b and a first region 1a formed by indentation into the silicon substrate 1 relative to the second region 1b. The silicon substrate 1 at the junction of the first region 1a and the second region 1b forms a stepped structure 11. The silicon substrate 1 in the first region 1a has a textured structure.

[0069] The first passivation contact structure 2 includes a first dielectric layer 21 and a first doped layer 22 disposed on the surface of the first dielectric layer 21 along a direction away from the silicon substrate 1. The first passivation contact structure 2 is disposed in the second region 1b. The ratio between the orthographic projection width of the first passivation contact structure 2 in the second region 1b and the width of the second region 1b is D, where 9:10≤D<1:1. The ratio between the orthographic projection width of the first passivation contact structure 2 in the second region 1b and the width of the first region 1a is 1:7~1:12.

[0070] Wherein, the orthographic projection width of the first passivated contact structure 2 refers to the width of the first passivated contact structure 2 in the first direction (see...). Figure 1 The length of the extension in the X direction (in the first direction) and the width of the second region 1b refer to the length of the extension of the second region 1b in the first direction. The first surface and the second surface, one being the light-receiving surface of the solar cell and the other the back-lighting surface of the solar cell, can be either the first surface being the light-receiving surface of the solar cell and the second surface being the back-lighting surface of the solar cell, or the first surface being the back-lighting surface and the second surface being the light-receiving surface of the solar cell. The first region and the second region can be located on the back-lighting surface, the light-receiving surface, or both.

[0071] In a first optional embodiment, the first surface is a light-receiving surface and the second surface is a backlighting surface. The light-receiving surface of the silicon substrate is provided with a second region 1b and a first region 1a formed by recessing into the silicon substrate 1 relative to the second region 1b. Therefore, since the light-receiving surface faces the position of sunlight, by providing the above structure, the area of ​​the light-receiving surface can be sufficiently increased, and the absorption and utilization rate of sunlight can be improved.

[0072] In a second optional embodiment, the first surface is a backlight surface and the second surface is a light-receiving surface. The backlight surface of the silicon substrate is provided with a second region 1b and a first region 1a formed by recessing into the silicon substrate 1 relative to the second region 1b. As for the backlight surface of the solar cell, it can absorb sunlight reflected from the ground to the backlight surface. Therefore, by providing the above structure on the backlight surface, the utilization rate of light on the backlight surface can be effectively improved, thereby improving the photoelectric conversion efficiency of the solar cell.

[0073] In the third alternative embodiment, both the light-receiving surface and the back-lighting surface of the solar cell have the above-described structure. Therefore, it can not only effectively improve the absorption rate of sunlight on the light-receiving surface, but also improve the utilization rate of reflected light on the back-lighting surface, thereby improving the light absorption effect of the solar cell to a greater extent and improving the photoelectric conversion efficiency of the solar cell.

[0074] And, as Figure 3 As shown, the first region 1a is recessed into the silicon substrate 1 relative to the second region 1b. This can be understood as follows: with the thickness of the silicon substrate 1 corresponding to the second region 1b as a reference, the silicon substrate 1 corresponding to the first region 1a is recessed to one side of the silicon substrate 1, meaning that the thickness of the silicon substrate 1 corresponding to the first region 1a is less than the thickness of the silicon substrate 1 corresponding to the second region 1b. The silicon substrate 1 at the junction of the first region 1a and the second region 1b refers to the area where the first passivation contact structure 2 is locally provided on the second region 1b, thus exposing the silicon substrate 1 near the first region 1a in the second region 1b. The exposed silicon substrate 1 is the junction of the first region 1a and the second region 1b.

[0075] This application discloses a solar cell, such as... Figure 1 and Figure 2 As shown, the silicon substrate has a second region 1b and a first region 1a. A first passivation contact structure 2 is disposed on the second region 1b. The silicon substrate 1 at the junction of the first region 1a and the second region 1b has a stepped structure 11. Figure 2 The white area in the diagram represents the first passivation contact structure 2, and the black area represents the first region 1a. Therefore, by controlling the width of the stepped structure 11, the orthographic projection width of the first passivation contact structure 2 in the second region 1b, and the width of the first region 1a, the utilization rate of sunlight can be improved while ensuring the passivation effect.

[0076] Specifically, by controlling the ratio of the orthographic projection width of the first passivation contact structure 2 in the second region 1b to the width of the first region 1a within the range of 1:10 to 1:12, the first passivation contact structure 2 can fully exert its passivation effect, reduce carrier recombination, improve carrier transport efficiency, and ensure the amount of sunlight captured by the first region 1a. Therefore, while ensuring the passivation effect of the solar cell, the impact on the light absorption effect of the first region 1a is reduced to a relatively high extent. If the orthographic projection width of the first passivation contact structure 2 is smaller than this range, it is difficult to guarantee its passivation effect and it is difficult to effectively improve the carrier transport effect; if the orthographic projection width of the first passivation contact structure 2 is larger than the range of this application, the width of the first region 1a will be too narrow, the amount of sunlight absorbed by the first region 1a will be low, and the performance of the solar cell will be affected.

[0077] And, as Figure 3As shown, in order to further improve the absorption and utilization rate of sunlight by the solar cell, the silicon substrate 1 outside the exposed first passivation contact structure 2 is made into a stepped structure 11, so that the orthogonal projection width of the first passivation contact structure 2 in the second region 1b is smaller than the width of the second region 1b. By designing its width, not only can the first passivation contact structure 2 achieve a better passivation effect, but the amount of sunlight absorbed by the solar cell can also be further improved.

[0078] Specifically, at this width, the surface of the stepped structure 11 facing away from the silicon substrate 1 can form a better blocking effect, preventing the first passivation contact structure 2 from blocking the first region 1a. This allows the first region 1a to fully utilize its light-trapping effect. Furthermore, since the side of the stepped structure 11 can also absorb sunlight, the area of ​​the solar cell is further increased, thereby further improving the utilization rate of sunlight. If the orthographic projection width of the first passivation contact structure 2 is smaller than this range, it is difficult to guarantee the passivation effect and effectively improve the carrier transport effect. If the orthographic projection width of the first passivation contact structure 2 is larger than the range of this application, it will block the first region 1a, making it difficult to effectively improve the absorption and utilization rate of sunlight in the first region 1a.

[0079] It is important to note that while the orthographic projection width of the first passivated contact structure 2 is equal to the width of the second region 1b, improving the absorption and utilization rate of sunlight requires precise control of the processing. This significantly increases the processing difficulty, hindering mass production and making it difficult to guarantee the consistency and reliability of products processed in different batches. Ensuring processing precision requires not only the use of equipment capable of precision processing but also ensuring that the equipment can be used for precise processing under different operating environments and raw material types. This places higher demands on the processing precision of the equipment and the skills of the operators, increasing the costs of equipment maintenance and replacement, as well as the difficulty of training operators, ultimately reducing production efficiency.

[0080] In addition, by controlling the orthographic projection width of the first passivation contact structure 2 in the second region 1b, the width of the second region 1b, and the width of the stepped structure 11 within a specific range, it also helps to reduce the difficulty of printing the first electrode 6, ensuring that the first electrode 6 can be accurately printed on the first passivation contact structure 2, increasing the contact area and contact tightness between the first electrode 6 and the first passivation contact structure 2, thereby helping to reduce recombination, reduce contact resistance, and improve the carrier transport effect.

[0081] The contact resistivity of this solar cell is 0.2 mΩ·cm. 2 ~1mΩ·cm 2This further illustrates that the formation of the stepped structure can effectively reduce the contact resistivity of the solar cell and increase the carrier transport rate, which is beneficial to improving the photoelectric conversion efficiency of the solar cell. The reflectivity of the first region is 8% to 10%, and the reflectivity of the second region is 32% to 40%, indicating that the solar cell of this application can make good use of the texture structure of the first region, effectively reduce the reflectivity, and improve the utilization rate of sunlight. Furthermore, since the carrier selectivity of the first passivated contact structure is 13.8 to 14, it indicates that the first passivated contact structure has a high passivation effect, which can effectively reduce recombination and improve the carrier lifetime.

[0082] In summary, by controlling the orthographic projection width of the first passivation contact structure 2 in the second region 1b, the width of the second region 1b, and the width of the stepped structure 11 within a specific range, this application ensures that the first region 1a can fully achieve the light-trapping effect and that the first passivation contact structure 2 can exert its passivation effect. At the same time, by increasing the area of ​​the solar cell, the shading of the first region 1a is reduced, thereby further improving the absorption and utilization rate of sunlight by the solar cell. It also helps to reduce the difficulty of electrode printing, thereby helping to reduce the contact resistance between the electrode and the first passivation contact structure 2, and further improving the carrier transport effect.

[0083] Furthermore, such as Figure 4 As shown, multiple groove structures (circled in the figure) are provided on the edge of the stepped structure near the first passivation contact structure. The groove structures on the stepped structure help increase the absorption of sunlight, mainly because when sunlight is reflected within the grooves, it is reflected to other areas within the cavity of the groove structure, where the reflected light is absorbed, thus improving the utilization rate of sunlight.

[0084] Furthermore, by controlling the depth of any groove structure to be 1μm to 4μm, and the distance between the center point and the edge of any groove structure to be 0.5μm to 5μm, these parameters enable the cavity formed by the groove structure to effectively capture reflected light, reducing light escape and thus further ensuring the utilization rate of sunlight.

[0085] Wherein, the distance between the center point of any groove structure and the edge of the groove structure refers to the longest distance between the center point of the top view and the edge line of the top view when the groove structure is viewed from a top angle. In one optional embodiment, the top view is an elliptical structure, and the distance refers to the longest distance between the center point of the ellipse and the side of the ellipse; in another optional embodiment, the top view is a circular structure, and the distance refers to the radius of the circle.

[0086] Furthermore, the orthographic projection width of the first passivated contact structure in the second region is 60 μm to 100 μm, and the width of the first region is 700 μm to 1000 μm. Within this range, the first passivated contact structure can be guaranteed to have a good passivation effect, which helps to reduce the difficulty of electrode printing, reduce recombination, and improve the carrier transport efficiency. At the same time, it can avoid the situation where the first region is too small, resulting in less solar light absorption, which would make it difficult to effectively improve the photoelectric conversion efficiency of the solar cell.

[0087] Furthermore, the texture structure can be a pyramidal structure, a pyramid-like structure, or a non-pyramidal structure. When the texture structure is a pyramidal structure, the longest side length of the base of the pyramidal structure is 1 μm to 3 μm, and the height of the pyramidal structure is 1 μm to 4 μm. By controlling the parameters of the pyramidal structure within the above range, the density of the pyramidal structure is appropriate, which can effectively increase the absorption of sunlight and also help reduce interface defects, reduce carrier recombination, and increase carrier lifetime. In addition, by controlling the pyramidal structure within the above range, the reflectivity of the first region is 8% to 10%, thus effectively reducing the reflectivity of the first region and improving the absorption and utilization rate of sunlight in the first region. Furthermore, since the reflectivity of the first passivation contact structure is 35% to 40%, it indicates that the crystallinity of the first doped layer in this application is good, which can fully improve the passivation effect of the solar cell.

[0088] Furthermore, to further improve the photoelectric conversion efficiency of the solar cell, the sum of the thickness of the second region and the thickness of the first passivation contact structure is set to H1, and the thickness of the first region is set to H2, where H1 and H2 satisfy: H1-H2=2μm~4μm. When the above thickness relationship is satisfied, it not only avoids a large thickness difference leading to a small silicon substrate thickness, which would affect the absorption of sunlight by the silicon substrate and reduce photocurrent, but also avoids a small thickness difference leading to incomplete removal of the first passivation contact structure, which would affect the light absorption of the textured structure and thus affect the quality of the subsequently deposited first passivation layer, thereby affecting the passivation effect and performance of the solar cell. Furthermore, controlling the thickness within the above range also removes damage present during the fabrication process, thereby reducing leakage current and improving the photoelectric conversion efficiency of the solar cell. Additionally, the doping concentration of the semiconductor conductive element in the first doped layer is set to 2×10⁻⁶. 19 atoms / cm 3 ~8×10 19 atoms / cm 3 This doping concentration helps reduce contact resistance and increase carrier concentration, thereby improving the photoelectric conversion efficiency of solar cells.

[0089] See also Figure 3The solar cell also includes a first passivation layer 3, which is disposed on the surface of the first doped layer 22 away from the silicon substrate 1, on the surface of the stepped structure 11 near the first passivation contact structure 2, and on the first region 1a.

[0090] When the stepped structure 11 has a groove structure on the side surface near the first passivation contact structure 2, the first passivation layer 3 will also exist in the groove structure, thereby effectively passivating the defects in the groove structure and reducing the recombination of charge carriers.

[0091] Passivation layers reduce surface recombination and improve the photoelectric conversion efficiency of solar cells; the presence of antireflection layers can reduce the reflection of incident light on the one hand, and passivate it on the other hand, further improving the photoelectric efficiency of solar cells.

[0092] In a first optional embodiment, the silicon substrate 1 is N-type, and the solar cell further includes a second passivation contact structure 4 disposed on the back surface. The second passivation contact structure 4 includes a second dielectric layer 41 and a second doped layer 42. The second doped layer 42 is disposed on the side of the second dielectric layer 41 facing away from the back surface. The first passivation contact structure 2 includes a first dielectric layer 21 and a first doped layer 22. The first doped layer 22 is disposed on the side of the first dielectric layer 21 facing away from the silicon substrate 1. The conductivity type of the second doped layer 42 is P-type, and the conductivity type of the first doped layer 22 is N-type. Alternatively, in a second optional embodiment, the silicon substrate 1 is N-type, the conductivity type of the second doped layer 42 is N-type, and the conductivity type of the first doped layer 22 is P-type.

[0093] In a third optional embodiment, the silicon substrate 1 is P-type, and the solar cell further includes a second passivation contact structure 4 disposed on the back surface. The second passivation contact structure 4 includes a second dielectric layer 41 and a second doped layer 42, with the second doped layer 42 disposed on the side of the second dielectric layer 41 facing away from the back surface. The first passivation contact structure 2 includes a first dielectric layer 21 and a first doped layer 22, with the first doped layer 22 disposed on the side of the first dielectric layer 21 facing away from the silicon substrate 1. The conductivity type of the second doped layer 42 is N-type, and the conductivity type of the first doped layer 22 is P-type. Alternatively, in a fourth optional embodiment, the silicon substrate 1 is P-type, the conductivity type of the second doped layer 42 is P-type, and the conductivity type of the first doped layer 22 is N-type.

[0094] It is important to note that the passivated contact structure provides a good interface passivation effect for solar cells. The dielectric layer can be made of a variety of dielectric materials, such as at least one of silicon oxide, magnesium fluoride, amorphous silicon, polycrystalline silicon, silicon carbide, silicon nitride, silicon oxynitride, aluminum oxide, or titanium oxide. Preferably, the dielectric layer is a silicon oxide layer formed of silicon oxide, because the silicon oxide layer has excellent passivation performance, can minimize the recombination loss of minority carriers on the silicon substrate surface, and is a thin film with excellent durability for subsequent high-temperature processes.

[0095] The dielectric layer, acting as a barrier for electrons and holes, can combine with the semiconductor layer to form a passivated contact structure that prevents minority carriers from passing through. The dielectric layer can also function as a pinhole channel, allowing carriers within the solar cell to move freely. The selective passage of majority carriers through the heavily doped semiconductor layer helps reduce minority carrier recombination losses. Furthermore, the dielectric layer can act as a diffusion barrier to prevent conductive elements in the doped polycrystalline silicon layer from diffusing into the silicon substrate. Moreover, controlling the thickness of the dielectric layer to be between 0.5 nm and 4 nm helps reduce carrier transport resistance and improve transport efficiency.

[0096] Furthermore, the solar cell also includes a second functional layer 5, a first electrode 6, and a second electrode 7. The second functional layer is disposed on the side of the second doped layer 42 away from the silicon substrate 1. The first electrode 6 passes through the first passivation layer 3 and makes ohmic contact with the first doped layer 22. The second electrode 7 passes through the second functional layer 5 and makes ohmic contact with the second doped layer 42.

[0097] Secondly, embodiments of this application disclose a method for fabricating a solar cell according to the first aspect, the method comprising the following steps:

[0098] Provide silicon substrate;

[0099] A first passivated contact structure is formed on the first and second surfaces, or on the first surface, of a silicon substrate;

[0100] The first passivation contact structure is sequentially patterned and textured to give the silicon substrate a second region and a first region that is recessed into the silicon substrate relative to the second region, and to form a stepped structure on the silicon substrate at the junction of the first region and the second region, and to form a textured structure on the silicon substrate in the first region.

[0101] Post-processing yields solar cells similar to those in the first aspect.

[0102] This application employs patterning and texturing processes on the first passivation contact structure. Through the synergistic effect of these two process steps, a solar cell is fabricated that has a first region, a second region, and a stepped structure. Furthermore, the width of the orthographic projection of the first passivation contact structure in the second region, the width of the first region, and the width of the stepped structure all meet the requirements of this application. As a result, the fabricated solar cell exhibits high passivation performance, high absorption and utilization rate of sunlight, and high carrier transport efficiency.

[0103] In one alternative implementation, a schematic diagram of the solar cell is shown below. Figure 3 As shown below, Figure 3 Taking a solar cell as an example, the first surface of the solar cell is the light-receiving surface, the second surface is the backlight, and the light-receiving surface has a first region and a second region. The preparation method of the solar cell will be further explained.

[0104] Furthermore, the step of providing the silicon substrate includes:

[0105] Polish the silicon substrate to remove surface contaminants.

[0106] like Figure 5 As shown, a second dielectric layer 41 and a second doped amorphous silicon layer are sequentially deposited on the back surface of the silicon substrate 1, and then annealed to transform the second doped amorphous silicon layer into a second doped layer 42.

[0107] Specifically, the steps for polishing the silicon substrate include:

[0108] Pretreatment: The pretreatment reagents include a mixed solution of potassium hydroxide and hydrogen peroxide or sodium hydroxide and hydrogen peroxide. The volume fraction of sodium hydroxide or potassium hydroxide in the mixed solution is 1% to 6%, and the volume fraction of hydrogen peroxide is 3% to 7%. The pretreatment time is 200s to 600s.

[0109] Alkaline polishing etching: The etching reagent includes alkali and additives, and the mass fraction ratio of additives to alkali solution is 5:100 to 20:100. The alkaline polishing temperature is 60℃ to 75℃, and the alkaline polishing time is 200s to 600s. The alkali includes at least one of potassium hydroxide and sodium hydroxide, and the volume concentration of the alkali is 2% to 10%.

[0110] Polishing the silicon substrate effectively removes organic dirt, scratches, and dust particles from its surface, ensuring its cleanliness. This facilitates the subsequent deposition of passivation contact structures, resulting in a smoother film with fewer interface defects and reduced carrier recombination.

[0111] Furthermore, the steps for preparing the second dielectric layer 41 and the second doped layer 42 include:

[0112] Preparation of the second dielectric layer 41: First, the back surface of the silicon substrate 1 is oxidized under the conditions of 7600 mTorr pressure, oxygen flow rate of 10000 sccm to 50000 sccm and deposition temperature of 550℃ to 630℃ to prepare a second dielectric layer 41 with a thickness of 0.5 nm to 2 nm, and a wrap-around coating is formed on the light-receiving surface of the silicon substrate 1.

[0113] Preparation of the second doped layer 42: First, using silane as the reaction gas, a second amorphous silicon layer with a thickness of 100 nm to 500 nm is deposited under conditions of pressure of 200 mTorr to 600 mTorr and temperature of 550 °C to 630 °C; then, the second doped amorphous silicon layer is prepared by diffusion using boron trichloride or boron tribromide as the boron source. During the diffusion process, the flow ratio of boron source to oxygen is 1:3 to 1:5, the diffusion temperature is 800 °C to 900 °C, and the diffusion pressure is 100 mBar to 500 mBar; finally, oxidation treatment is performed with an oxygen flow rate of 10000 sccm to 30000 sccm and an oxidation temperature of 900 °C to 1000 °C. During this process, the second doped amorphous silicon layer is transformed into the second doped layer 42, and a wrap-around coating and borosilicate glass 8 are formed on the light-receiving surface of the silicon substrate.

[0114] The second dielectric layer 41 and the second doped layer 42 prepared by the above-described preparation process have high uniformity in thickness and fewer defects, and can fully exert the passivation effect of the second passivation contact structure 4 to improve the efficiency of carrier transport.

[0115] like Figure 6 As shown, a chain acid etching device is required to remove the borosilicate glass 8 and the surrounding coating on the light-receiving surface. Then, the light-receiving surface is polished with an alkaline solution. This step helps to prepare the first dielectric layer 21 and the first doped layer 22 on the light-receiving surface, ensuring that the first passivated contact structure 2 has a good contact effect with the silicon substrate 1.

[0116] Specifically, the steps for removing the borosilicate glass 8 and the surrounding coating include:

[0117] Acid etching of the light-receiving surface: In the acid etching step, the light-receiving surface can be etched by using a roller with liquid or by floating on water. The acid etching reagent includes a mixture of nitric acid, sulfuric acid and hydrofluoric acid. The volume fraction of nitric acid in the mixture is 40% to 70%, the volume fraction of sulfuric acid is 5% to 15%, and the volume fraction of hydrofluoric acid is 5% to 10%. The acid etching temperature is 20℃ to 30℃, and the acid etching time is 100s to 500s.

[0118] Alkaline solution polishing of the light-receiving surface: In the step of polishing the light-receiving surface with alkaline solution, potassium hydroxide or sodium hydroxide is used as the alkaline polishing solution, the volume concentration of the alkaline solution is 3% to 15%, the alkaline polishing temperature is 50℃ to 80℃, and the alkaline polishing time is 30s to 600s.

[0119] Pickling and immersion: In the pickling and immersion step, the pickling reagent includes hydrofluoric acid solution, the immersion time is 10s to 30s, and borosilicate glass with a thickness of 1nm to 5nm is removed.

[0120] The light-receiving surface obtained by using the above process steps and reagents has good surface smoothness and few defects, which is beneficial for the subsequent deposition of the first dielectric layer and the first doped layer.

[0121] Furthermore, such as Figure 7 As shown, the steps for fabricating the first passivated contact structure 2 on the light-receiving surface of the silicon substrate 1 include:

[0122] A first dielectric layer 21 and a first doped amorphous silicon layer are sequentially deposited on the light-receiving surface;

[0123] Annealing transforms the first doped amorphous silicon layer into the first doped layer 22, and a protective layer is formed on the first doped layer 22.

[0124] Specifically, the steps for preparing the first dielectric layer 21 and the first doped layer 22 include:

[0125] Preparation of the first dielectric layer 21: First, the light-receiving surface of the silicon substrate 1 is oxidized under the conditions of 7600 mTorr pressure, oxygen flow rate of 10000 sccm to 50000 sccm and deposition temperature of 550℃ to 630℃ to prepare a first dielectric layer 21 with a thickness of 0.5 nm to 2 nm, and a coating layer is formed on the back surface of the silicon substrate 1.

[0126] Preparation of the first doped layer 22: First, using silane as the reaction gas, a first amorphous silicon layer with a thickness of 100nm to 500nm is deposited under conditions of pressure of 200mTorr to 600mTorr and temperature of 550℃ to 630℃. Then, phosphorus oxychloride is used as the phosphorus source to prepare the first doped amorphous silicon layer by diffusion. During the diffusion process, the flow ratio of phosphorus source to oxygen is 1:2 to 1:3, the diffusion temperature is 800℃ to 950℃, and the diffusion pressure is 100mBar to 500mBar. Finally, oxidation treatment is performed with an oxygen flow rate of 10000sccm to 30000sccm and an oxidation temperature of 850℃ to 900℃, so that the first doped amorphous silicon layer becomes the first doped layer 22, and a wrap-around coating and a phosphorus silicon glass 9 are formed on the back surface of the silicon substrate 1, wherein the phosphorus silicon glass 9 serves as a protective layer for the first passivation contact structure.

[0127] The first dielectric layer 21 and the first doped layer 22 prepared by the above-described preparation process have high uniformity in thickness and fewer defects, and can fully exert the passivation effect of the first passivation contact structure 2 to improve the efficiency of carrier transport.

[0128] Furthermore, the steps of patterning and texturing the first passivated contact structure include:

[0129] like Figure 8 As shown, through graphical processing, a portion of the thickness of the first doped layer 22 corresponding to the first region 1a is removed, so that the thickness of the first doped layer 22 in the first region 1a is less than that of the first doped layer 22 in the second region 1b.

[0130] like Figure 9 As shown, the texturing process involves etching away the first passivation contact structure 2 in the first region 1a and continuing to etch the silicon substrate 1 in the first region 1a, so that a step-like structure 11 is formed on the silicon substrate 1 at the junction of the first region 1a and the second region 1b, and a textured structure is formed on the silicon substrate 1 in the first region 1a.

[0131] The patterning and texturing steps of the first passivation contact structure involve firstly exposing a portion of the first doped layer 22 during the patterning process, ensuring that the thickness of the exposed first doped layer 22 corresponding to the first region 1a is less than the thickness of the second region 1b. This results in the first doped layer 22 in the second region 1b exhibiting a stepped structure 11. If laser etching is used, the scattering effect of the laser will cause a thickness difference in the exposed first doped layer 22. Then, during the texturing step, this thickness difference persists and even increases with the etching depth, causing a portion of the light-receiving surface to recess into the silicon substrate 1 to form the first region 1a, while another portion forms the stepped structure 11. In other words, the combined effect of patterning and texturing facilitates the formation of the stepped structure 11 and effectively ensures that the stepped structure 11 meets the scope of this application.

[0132] Specifically, the first passivated contact structure 2 is patterned using laser etching. The laser wavelength is one of 325nm to 1064nm, the laser power is 5W to 100W, the laser spot area is 20×20μm to 400×400μm, and the etching width is 500μm to 1000μm. By controlling the laser etching parameters within the above range, the structure of the first doped layer 22 is ensured to be within the scope of this application, thereby facilitating the subsequent texturing process. The processed solar cell exhibits better passivation effect and solar light absorption capacity.

[0133] Furthermore, in order to ensure that the chemical reagents can effectively remove the first passivation contact structure on the back surface in the subsequent texturing process, the method for preparing the solar cell also includes removing the phosphosilicate glass 9 on the back surface after the step of patterning the first passivation contact structure 2 and before the step of texturing.

[0134] In this step, either a roller-carrying liquid or a water-floating method can be used. The mass concentration of the hydrofluoric acid solution is 10% to 40%, the temperature is 20℃ to 30℃, and the reaction time is 10s to 120s. Using this process and reagents, the protective layer on the back surface can be effectively removed, thereby improving the photoelectric conversion efficiency of the solar cell.

[0135] Furthermore, see the return Figure 9 The texturing process includes the following steps:

[0136] The surface of the solar cell is pre-cleaned to remove dirt and grime.

[0137] The silicon substrate 1 of the first region 1a is etched to form a stepped structure 11 at the junction of the first region 1a and the second region 1b, and a textured structure is formed on the silicon substrate 1 of the first region 1a.

[0138] The surface of the solar cell is then cleaned to remove reaction products and residual reagents.

[0139] Specifically, in the pre-cleaning step, the cleaning reagents include hydrogen peroxide and alkali. The volume ratio of alkali to hydrogen peroxide is 1:3 to 1:8, the reaction time is 100s to 500s, and the reaction temperature is 50℃ to 80℃. The alkali includes at least one of ammonia, sodium hydroxide, and potassium hydroxide. Using the above pre-cleaning process and reagents can effectively remove dirt from solar cells and has a certain repair effect on solar cells after laser patterning, thereby effectively reducing laser damage to solar cells and minimizing leakage problems.

[0140] In the etching step of the silicon substrate in the first region, when removing the first passivation contact 2 structure in the first region 1a, the etching reagent includes an alkali and an additive, with a volume ratio of alkali to additive of 1:1 to 3:1. The process temperature is 60℃ to 90℃, and the process time is 200s to 700s. The alkali includes at least one of sodium hydroxide and potassium hydroxide. Since the first passivation contact structure 2 and the second passivation contact structure 4 are provided with protective layers, texturing the solar cell can effectively avoid adverse effects on the first passivation contact structure 2 and the second passivation contact structure 4. Furthermore, the above-mentioned process conditions and reagents facilitate the formation of the first region 1a, ensuring that the obtained pyramid structure is within the scope of this application, and promoting the formation of the stepped structure 11. A groove structure is provided on the stepped structure 11, thereby effectively improving the absorption and utilization rate of sunlight.

[0141] During post-cleaning, the cleaning reagents include hydrogen peroxide and an alkali solution, specifically at least one of sodium hydroxide or potassium hydroxide, with a volume ratio of alkali solution to hydrogen peroxide of 1:3 to 1:8. The reaction time is 100 to 300 seconds, and the reaction temperature is 50°C to 80°C. The alkali includes at least one of ammonia, sodium hydroxide, and potassium hydroxide. When the reagents and processes for post-cleaning are within the above range, it helps to remove reaction products and organic residues from the pre-cleaning and texturing steps, thereby ensuring that the surface of the textured solar cell has fewer impurities and better flatness, avoiding any impact on carrier transport.

[0142] Furthermore, the post-processing steps include:

[0143] like Figure 10 As shown, the protective layer on the first doped layer 22 is removed by using a chain-type acid washing device to remove the protective layer of the phosphorosilicon glass 9 and the residual coating on the light-receiving surface. In the acid washing step, either a roller-assisted liquid feeding method or a water-based floating method can be used. The volume fraction of hydrofluoric acid is 10%–40%, the temperature is 20℃–30℃, and the reaction time is 100s–300s. Using the above process conditions and reagents, the residual phosphorosilicon glass 9, borosilicate glass 8, and coating can be effectively removed, thereby reducing leakage current and improving the photoelectric conversion efficiency of the solar cell.

[0144] like Figure 11 As shown, the first passivation layer 3 and the second functional layer 5 are prepared. The first passivation layer 3 and the second functional layer 5 each comprise an alumina layer and a silicon nitride layer, respectively. First, an alumina layer with a thickness of 2nm to 10nm is sequentially deposited on the light-receiving surface and the back-lighting surface using atomic layer deposition (ALD) at a deposition temperature of 200℃ to 300℃. Then, silicon nitride with a thickness of 70nm to 120nm is deposited on the alumina layer on both the light-receiving and back-lighting surfaces using plasma-enhanced chemical vapor deposition (PECVD) at a deposition temperature of 450℃ to 600℃ and a gas pressure of 1000mTorr to 2500mTorr. The alumina and silicon nitride layers prepared using the above process conditions exhibit good film flatness, effectively achieving passivation and anti-reflection effects, and improving the photoelectric conversion efficiency of the solar cell.

[0145] See also Figure 3 The first electrode 6 and the second electrode 7 are prepared by screen printing or electroplating on the first passivation layer 3 and the second functional layer 5, respectively. The first electrode 6 passes through the first passivation layer 3 and makes a 22-ohm contact with the first doped layer 2, and the second electrode 7 passes through the second functional layer 5 and makes a 42-ohm contact with the second doped layer 4. The conductive metals in the first electrode 6 and the second electrode 7 include metals such as Ag, Al, Cu, Ni, and Pt or their alloys.

[0146] Thirdly, embodiments of this application disclose a photovoltaic module, including: a solar cell according to the first aspect, or a solar cell prepared by the preparation method of the second aspect.

[0147] The technical solution of this application will be further explained below with reference to more specific embodiments and experimental test results.

[0148] Example 1:

[0149] This application provides a passivated contact solar cell. The silicon substrate at the junction of the first and second regions of the passivated contact solar cell forms a stepped structure. A groove structure is provided on the stepped structure. The depth of the groove is 1μm to 4μm. The distance between the center point of any groove structure and the edge of the groove structure is 1μm to 5μm. H1-H2 = 2.66μm. D is 9.5:10. The orthographic projection width of the first passivated contact structure in the second region is 80μm. The width of the first region is 900μm.

[0150] This application also provides a method for preparing the passivated contact solar cell:

[0151] The step of providing the silicon substrate includes:

[0152] Polishing: Using an N-type silicon wafer as the substrate, the surface of the N-type silicon wafer was first polished with 5% sodium hydroxide and 5% hydrogen peroxide by volume for 500 seconds. Then, the N-type silicon wafer was etched with an alkaline solution of additive and hydroxide by mass fraction of 10:100, with 5% sodium hydroxide by volume, at a reaction temperature of 70°C and a reaction time of 400 seconds.

[0153] The steps for preparing the second dielectric layer and the second doped layer include:

[0154] The second dielectric layer is prepared by first oxidizing the back surface of the silicon substrate under the conditions of 7600 mTorr pressure, oxygen flow rate of 40000 sccm and deposition temperature of 550℃ to prepare a second dielectric layer with a thickness of 2nm, and forming a wrap-around coating on the light-receiving surface of the silicon substrate.

[0155] The second doped layer is prepared by first depositing a 300 nm thick amorphous silicon layer using silane as the reactant gas at a pressure of 400 mTorr and a temperature of 630 °C. Then, the second doped amorphous silicon layer is prepared by diffusion using boron trichloride as the boron source. During the diffusion process, the flow ratio of boron source to oxygen is 1:4, the diffusion temperature is 900 °C, and the diffusion pressure is 400 mBar. Finally, oxidation treatment is performed with an oxygen flow rate of 20000 sccm and an oxidation temperature of 950 °C. In this process, the second amorphous silicon layer is transformed into the second doped layer, and a wrap-around coating and a borosilicate glass layer are formed on the light-receiving surface of the silicon substrate.

[0156] To remove the borosilicate glass and coating from the light-receiving surface: First, in the acid etching step, the light-receiving surface can be etched using a roller with liquid. The acid etching reagent includes a mixture of 50% nitric acid, 10% sulfuric acid, and 8% hydrofluoric acid by volume. The acid etching temperature is 25℃, and the acid etching time is 300s. Then, the light-receiving surface is polished using 9% sodium hydroxide by volume. The alkaline polishing temperature is 60℃, and the alkaline polishing time is 400s. Finally, hydrofluoric acid is used for acid pickling and immersion for 20s.

[0157] The steps for fabricating the first passivated contact structure on the light-receiving surface of a silicon substrate include:

[0158] To prepare the first dielectric layer, the light-receiving surface of the silicon substrate was oxidized under conditions of 7600 mTorr pressure, 30000 sccm oxygen flow rate, and 580℃ deposition temperature to prepare a first dielectric layer with a thickness of 1 nm, and a wrap-around coating was formed on the back surface of the silicon substrate.

[0159] To prepare the first doped layer, a 300 nm thick amorphous silicon layer was deposited using silane as the reactant gas at a pressure of 400 mTorr and a temperature of 580 °C. Then, phosphorus oxychloride was used as the phosphorus source for diffusion to prepare the first doped amorphous silicon layer. During the diffusion process, the flow ratio of phosphorus source to oxygen was 1:3, the diffusion temperature was 950 °C, and the diffusion pressure was 300 mBar. Finally, an oxidation treatment was performed with an oxygen flow rate of 20000 sccm and an oxidation temperature of 900 °C, which transformed the first amorphous silicon layer into the first doped layer. A wrap-around coating and a phosphosilicate glass layer were formed on the back surface of the silicon substrate, wherein the phosphosilicate glass served as a protective layer for the first passivation contact structure.

[0160] Patterning of the first passivated contact structure: The first passivated contact structure is patterned using laser etching. The laser wavelength is 532nm, the laser power is 80W, the laser spot area is 200×100μm, and the etching width is 7000μm.

[0161] Remove the phosphosilicate glass from the backlight: Use a roller to carry the liquid, with a hydrofluoric acid solution concentration of 30%, a temperature of 20℃, and a reaction time of 80s.

[0162] The steps of texture processing include:

[0163] Pre-cleaning: The cleaning reagents include hydrogen peroxide and sodium hydroxide in a volume ratio of 1:5. The reaction time is 300s and the reaction temperature is 70℃.

[0164] Etching, the etching reagents include sodium hydroxide and additives in a volume ratio of 2:1, the process temperature is 80℃, and the process time is 500s;

[0165] The subsequent cleaning process involved hydrogen peroxide and sodium hydroxide in a volume ratio of 1:6, with a reaction time of 200 seconds and a reaction temperature of 60°C.

[0166] Post-processing steps include:

[0167] The protective layer on the first doped polycrystalline silicon was removed. A chain acid washing device was used to remove the phosphorus silicon glass protective layer and the residual coating on the light-receiving surface. The volume fraction of hydrofluoric acid was 30%, the temperature was 20°C, and the reaction time was 200s.

[0168] To prepare the first passivation layer and the second functional layer, firstly, an aluminum oxide layer with a thickness of 50 nm was deposited sequentially on the light-receiving surface and the back-lighting surface using atomic layer deposition at a deposition temperature of 200 °C. Then, silicon nitride with a thickness of 900 nm was deposited on the aluminum oxide layer on the light-receiving surface and the back-lighting surface using plasma-enhanced chemical vapor deposition at a deposition temperature of 500 °C and a gas pressure of 1500 mTorr.

[0169] A first electrode and a second electrode are prepared. The first electrode and the second electrode are printed on the first passivation layer and the second functional layer, respectively. After sintering, the first electrode passes through the first passivation layer and makes ohmic contact with the first doped layer, and the second electrode passes through the second functional layer and makes ohmic contact with the second doped layer.

[0170] Structural characterization:

[0171] like Figure 12 As shown, Figure 12 The diagram shows the relationship between the thickness of the second region and the thickness of the first passivation contact structure and the thickness of the second region. H1-H2 = 2.66 μm, and the total thickness of the first passivation contact structure is approximately 301 nm. This indicates that the thickness of the stepped structure is approximately 2.3 μm, with a large lateral area, resulting in a high degree of solar energy absorption and thus contributing to improved solar cell efficiency. Figure 13 As shown, Figure 13 The image shows an electron microscope image of a pyramid structure. The pyramid structure has a high surface smoothness and small interface defects, which helps in the deposition of the first passivation layer, reduces carrier recombination, and improves the photoelectric conversion efficiency of the solar cell.

[0172] Example 2:

[0173] The only difference between this embodiment and Embodiment 1 is that H1-H2 = 1μm.

[0174] Example 3:

[0175] The only difference between this embodiment and Embodiment 1 is that H1-H2 = 4μm.

[0176] Example 4:

[0177] The only difference between this embodiment and Embodiment 1 is that the orthographic projection width of the first passivated contact structure in the second region is 80 μm, and the width of the first region is 800 μm.

[0178] Example 5:

[0179] The only difference between this embodiment and Embodiment 1 is that D is 9:10.

[0180] Comparative Example 1:

[0181] The only difference between this comparative example and Example 1 is that the entire light-receiving surface of the solar cell in this application has a textured structure, on which a boron extension layer and a first passivation layer are deposited sequentially.

[0182] Comparative Example 2:

[0183] The only difference between this comparative example and Example 1 is that the orthographic projection width of the first passivated contact structure in the second region is greater than the width of the second region.

[0184] Comparative Example 3:

[0185] The only difference between this comparative example and Example 1 is that D is 7:10.

[0186] Comparative Example 4:

[0187] The only difference between this comparative example and Example 1 is that the ratio between the orthographic projection width of the first passivated contact structure in the second region and the width of the first region is 1:14.

[0188] Performance testing

[0189] The solar cells prepared in Examples 1 to 5 and Comparative Examples 1 to 4 were subjected to the following related tests:

[0190] This application describes the performance testing of a solar cell using a Halm testing and sorting device, including open-circuit voltage, short-circuit current, and fill factor. The Halm device simulates sunlight and is equipped with electronic loads, data acquisition and calculation equipment to test the electrical performance of photovoltaic devices (including solar cells). The silicon wafer of the solar cell being tested is 182mm in size, and the calibrated light intensity is 1000±5W / m². 2 The experimental test results are as follows.

[0191] Table 1 Performance test results of solar cells

[0192]

[0193] Analysis of the data from Examples 1 to 5 and Comparative Examples 1 to 2 shows that the data from Examples 1 to 5 are superior to that of Comparative Example 1. This is because the light-receiving surface of Examples 1 to 5 has a first passivation contact structure, which effectively improves the passivation effect of the light-receiving surface, reduces carrier recombination, and improves carrier transport efficiency, thereby helping to improve the photoelectric conversion efficiency of the solar cell. The performance of Examples 1 to 5 is superior to that of Comparative Example 2. This is because the orthogonal projection width of the first passivation contact structure in the first region is smaller than the width of the first region, which helps to form a stepped structure, effectively avoiding the shading effect of the first passivation contact structure on the second region, further ensuring the light-trapping effect of the second region, and also increasing the area of ​​the light-receiving surface of the silicon substrate, thereby further improving the amount of sunlight captured.

[0194] Analysis of the data from Embodiment 1, Embodiment 5, and Comparative Example 3 shows that the performance of Embodiment 1 is better than that of Comparative Example 3. This is because D in Embodiment 1 is within the scope of this application. Therefore, the first passivated contact structure can not only fully exert the passivation effect, but also ensure the light absorption effect of the second region, thereby improving the photoelectric conversion efficiency of the solar cell to a higher extent.

[0195] Analysis of the data from Embodiment 1, Embodiment 4, and Comparative Example 4 shows that the performance of Embodiment 1 is better than that of Comparative Example 4. This is because the ratio between the orthographic projection width of the first passivation contact structure in Embodiment 1 and the width of the second region is greater than that in Comparative Example 4. Therefore, the width of the first passivation contact structure is ensured, thus guaranteeing its passivation effect. This helps to reduce recombination and improve the carrier transport capacity.

[0196] Analysis of the data from Examples 1 to 3 shows that the values ​​of H1-H2 in Examples 1 and 3 are all within the range of this application. Therefore, it is ensured that the first passivation contact structure can be completely removed, avoiding affecting the light absorption performance of the second region, thereby helping to improve the photoelectric conversion efficiency of the solar cell to a higher extent.

[0197] The solar cells and their preparation methods, as well as photovoltaic modules, disclosed in the embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are only for the purpose of helping to understand the technical solutions of the embodiments of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this invention. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A solar cell, characterized in that, The solar cell includes: A silicon substrate having a first surface and a second surface disposed opposite to each other, wherein the first surface and the second surface of the silicon substrate, or the first surface having a second region, and a first region formed by recessing into the silicon substrate relative to the second region, wherein the silicon substrate at the boundary between the first region and the second region forms a stepped structure; the silicon substrate in the first region has a textured structure. The first passivation contact structure includes a first dielectric layer and a first doped layer disposed on the surface of the first dielectric layer along a direction away from the silicon substrate. The first passivation contact structure is disposed in the second region. The ratio between the orthographic projection width of the first passivation contact structure in the second region and the width of the second region is D, where 9:10 ≤ D < 1:

1. The ratio between the orthographic projection width of the first passivation contact structure in the second region and the width of the first region is 1:7 to 1:

12.

2. The solar cell according to claim 1, characterized in that, The stepped structure has multiple groove structures on the edge of the side surface near the first passivation contact structure.

3. The solar cell according to claim 2, characterized in that, The depth of any of the groove structures is 1 μm to 4 μm; the distance between the center point of any of the groove structures and the edge of the groove structure is 0.5 μm to 5 μm.

4. The solar cell according to claim 1, characterized in that, The orthographic projection width of the first passivated contact structure in the second region is 60μm to 100μm, and the width of the first region is 700μm to 1000μm.

5. The solar cell according to claim 1, characterized in that, The texture structure is a pyramid-shaped structure, a pyramid-like structure, or a non-pyramid-shaped structure.

6. The solar cell according to claim 5, characterized in that, When the texture structure is a pyramid-shaped structure, the longest side length of the base of the pyramid-shaped structure is 1μm to 3μm; the height of the pyramid-shaped structure is 1μm to 4μm.

7. The solar cell according to claim 1, characterized in that, The sum of the thickness of the silicon substrate in the second region and the thickness of the first passivation contact structure is H1, and the thickness of the silicon substrate in the first region is H2. H1 and H2 satisfy: H1-H2=2μm~4μm.

8. The solar cell according to claim 1, characterized in that, The doping concentration of the semiconductor conductive element in the first doped layer is 2 × 10⁻⁶. 19 atoms / cm 3 ~8×10 19 atoms / cm 3 .

9. The solar cell according to any one of claims 1 to 8, characterized in that, The solar cell further includes a first passivation layer, which is disposed on the surface of the first doped layer away from the silicon substrate, on the surface of the stepped structure near the first passivation contact structure, on the sidewall of the stepped structure, and on the first region.

10. The solar cell according to any one of claims 1 to 8, characterized in that, The silicon substrate is N-type, and the solar cell further includes a second passivation contact structure disposed on the second surface. The second passivation contact structure includes a second dielectric layer and a second doped layer. The second doped layer is disposed on the side of the second dielectric layer away from the second surface. The conductivity type of the second doped layer is N-type, and the conductivity type of the first doped layer is P-type.

11. A method for preparing a solar cell, characterized in that, The preparation method includes the following steps: Provide silicon substrate; A first passivated contact structure is formed on the first and second surfaces of the silicon substrate, or on the first surface. The first passivated contact structure is sequentially patterned and textured to give the silicon substrate a second region and a first region that is recessed into the silicon substrate relative to the second region, and to form a stepped structure on the silicon substrate at the junction of the first region and the second region, and to form a textured structure on the silicon substrate in the first region. Post-processing yields the solar cell as described in any one of claims 1 to 10.

12. The preparation method according to claim 11, characterized in that, The steps of patterning and texturing the first passivated contact structure include: The first doped layer corresponding to a portion of the thickness of the first region is removed through graphical processing, so that the thickness of the first doped layer in the first region is less than the thickness of the first doped layer in the second region. The texturing process involves etching away the first passivation contact structure in the first region and continuing to etch the silicon substrate in the first region to form the step-like structure at the boundary between the first region and the second region, and to form the texture structure on the silicon substrate in the first region.

13. The preparation method according to claim 12, characterized in that, The texturing process includes the following steps: The surface of the solar cell is pre-cleaned to remove dirt from the surface of the solar cell; The silicon substrate in the first region is etched to form the stepped structure on the silicon substrate at the junction of the first region and the second region, and the texture structure is formed on the silicon substrate in the first region. The surface of the solar cell is then cleaned to remove reaction products and residual reagents.

14. The preparation method according to claim 12, characterized in that, The steps for preparing the first passivated contact structure include: The first dielectric layer and the first doped amorphous silicon layer are sequentially deposited on the first surface; Annealing transforms the first doped amorphous silicon layer into the first doped layer, and a protective layer is formed on the first doped layer.

15. The preparation method according to claim 14, characterized in that, The step of providing the silicon substrate includes: first polishing the silicon substrate, and then sequentially forming a second dielectric layer and a second doped layer on the second surface of the silicon substrate; The post-processing steps include: Remove the protective layer on the first doped layer; A first passivation layer is formed on the surface of the first doped layer away from the silicon substrate, on the surface of the stepped structure near the first passivation contact structure, on the sidewall of the stepped structure, and on the first region, respectively. A second functional layer is formed on the second doped layer, wherein the second functional layer is a second passivation layer and / or a second antireflection layer. A first electrode is printed and sintered on the first passivation layer, and a second electrode is printed and sintered on the second functional layer, such that the first electrode penetrates the first passivation layer and makes ohmic contact with the first doped layer, and the second electrode penetrates the second functional layer and makes ohmic contact with the second doped layer.

16. A photovoltaic module, characterized in that, include: The solar cell as described in any one of claims 1 to 10, or the solar cell prepared by the preparation method as described in any one of claims 11 to 15.

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