Back contact solar cell, preparation method, laminated cell and photovoltaic module

Abstract

The embodiment of the invention relates to the photovoltaic field, and provides a back contact solar cell, a preparation method, a laminated cell and a photovoltaic module. The back contact solar cell comprises a substrate, the substrate is provided with a first surface and a second surface which are opposite to each other, the second surface comprises first regions and second regions which are alternately arranged, each first region comprises a first pyramid structure, and the top of each first pyramid structure is provided with a groove; the first doped conductive layer is located in the first region; the second doped conductive layer is located in the second region, and the doping type of the second doped conductive layer is different from that of the first doped conductive layer; the first electrode is electrically connected with the first doped conductive layer, the first electrode and the groove are overlapped in a first direction, and the first direction is the arrangement direction of the substrate and the first doped conductive layer; and the second electrode is electrically connected with the second doped conductive layer. The back contact solar cell provided by the embodiment of the invention at least can improve the photoelectric conversion efficiency of the solar cell.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of photovoltaics, and in particular to a back contact solar cell, a preparation method, a stacked cell and a photovoltaic module. BACKGROUND

[0002] In the existing back contact solar cell technology, a pyramid texture structure is usually adopted to improve the photoelectric conversion efficiency. The design of this kind of structure aims to reduce the direct reflection of light by increasing the surface area, so that more light can be absorbed and then converted into electrical energy. However, the traditional pyramid structure has certain limitations in practical application, which limits the further improvement of the cell conversion efficiency. SUMMARY

[0003] The present application provides a back contact solar cell, a preparation method, a stacked cell and a photovoltaic module, which at least helps to improve the cell conversion efficiency of the back contact cell.

[0004] According to some embodiments of the present application, the present application provides a back contact solar cell, comprising: a substrate, the substrate having opposite first and second surfaces, the second surface comprising first and second regions arranged alternately, the first region comprising a first pyramid structure, the top of the first pyramid structure having a groove; a first doped conductive layer located in the first region; a second doped conductive layer located in the second region, the second doped conductive layer being different from the first doped conductive layer in doping type; a first electrode electrically connected with the first doped conductive layer, the first electrode overlapping with the groove in a first direction, the first direction being the arrangement direction of the substrate and the first doped conductive layer; and a second electrode electrically connected with the second doped conductive layer.

[0005] In some embodiments, at least part of the second region comprises a second pyramid structure, the second pyramid structure being different from the first pyramid structure.

[0006] In some embodiments, the depth of the groove is 50nm-200nm, the width of the groove is 200nm-600nm, the direction of the depth is parallel to the first direction, and the direction of the width is perpendicular to the first direction.

[0007] In some embodiments, the angle between the extension planes of two non-adjacent sides of the first pyramid structure is 60°-135°.

[0008] In some embodiments, the first surface comprises a third pyramid structure, the third pyramid structure is terrace-like, comprising a tapered structure and a stepped structure, the stepped structure is located at the outer periphery of the tapered structure and in contact with the tapered structure, the stepped structure comprises a plurality of steps, the step comprises a slope surface and a step surface, the step surface is in contact with one side of the slope surface away from the second surface.

[0009] In some embodiments, the angle between the slope surface and the step surface is 60°-90°.

[0010] In some embodiments, the angle between the slope surface and the step surface is 135°-150°.

[0011] In some embodiments, the angle between the slope surface and the surface on which the base of the third pyramid structure is located is 30°-60°.

[0012] In some embodiments, the number of steps is 3-8.

[0013] In some embodiments, the height of the third pyramid structure is 650 nm-820 nm, and the width of the base of the third pyramid structure is 2.2 μm-3.7 μm.

[0014] In some embodiments, the distance between two adjacent step surfaces is 30 nm-70 nm.

[0015] In some embodiments, the first doped conductive layer is a doped amorphous silicon layer or a doped microcrystalline silicon layer, and the second doped conductive layer is a doped polysilicon layer.

[0016] According to some embodiments of the present application, another aspect of the present application provides a preparation method of the back contact solar cell, comprising: providing an initial substrate, the initial substrate has a first surface and a second surface opposite to each other, and the second surface comprises first regions and second regions arranged alternately; sequentially performing selective etching, first cleaning, texturing, second cleaning and acid washing on the second surface of the initial substrate to form a first pyramid structure with a groove at the top of the tower in the first regions, thereby obtaining a substrate; forming a first doped conductive layer on the first regions of the substrate, and forming a second doped conductive layer on the second regions of the substrate, the second doped conductive layer being different from the first doped conductive layer in doping type; forming a first electrode electrically connected to the first doped conductive layer, and forming a second electrode electrically connected to the second doped conductive layer, the first electrode and the groove overlap in a first direction, and the first direction is the arrangement direction of the substrate and the first doped conductive layer.

[0017] According to some embodiments of this application, another aspect of this application provides a tandem battery, including: any of the back-contact solar cells described above; and a perovskite battery electrically connected to the back-contact solar cell.

[0018] According to some embodiments of this application, another aspect of this application provides a photovoltaic module, including: a battery string, formed by connecting multiple back-contact solar cells of any one of the described methods, or back-contact solar cells prepared by the described method, or stacked cells; an encapsulating film for covering the surface of the battery string; and a cover plate for covering the surface of the encapsulating film away from the battery string.

[0019] The technical solution provided in this application has at least the following advantages:

[0020] In the back-contact solar cell of this application, a first pyramid structure with a groove at the top is provided on the first region of the second surface. This allows a portion of the projection of the first electrode on the second surface to lie within the groove, increasing the effective contact area between the first electrode and the pyramid textured surface. This reduces contact resistance, improves electrode contact performance, and increases the fill factor and open-circuit voltage of the cell, thus enhancing the cell conversion efficiency of the back-contact solar cell. Furthermore, the groove design at the top of the first pyramid structure increases the number of internal reflections of light, allowing more incident light to be absorbed by the cell, significantly improving the photoelectric conversion efficiency. Attached Figure Description

[0021] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Unless otherwise stated, the drawings in the accompanying drawings do not constitute a limitation on scale. In order to more clearly illustrate the technical solutions in the embodiments of this application or in the conventional art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic cross-sectional view of a back-contact solar cell provided in one embodiment of this application;

[0023] Figure 2 This is a top-view SEM (scanning electron microscope) image of a first pyramid structure provided in one embodiment of this application;

[0024] Figure 3 This is a cross-sectional schematic diagram of a first pyramid structure provided in one embodiment of this application;

[0025] Figure 4This is a top-view SEM image of a third pyramid structure provided in one embodiment of this application;

[0026] Figure 5 This is a schematic diagram of a third pyramid structure provided in one embodiment of this application;

[0027] Figure 6 This is a cross-sectional schematic diagram of a third pyramid structure provided in one embodiment of this application;

[0028] Figure 7 This is a cross-sectional schematic diagram of another third pyramid structure provided in one embodiment of this application;

[0029] Figure 8 This is a schematic diagram of a stacked battery provided in one embodiment of this application;

[0030] Figure 9 This is a schematic diagram of another stacked battery structure provided in one embodiment of this application;

[0031] Figure 10 This is a schematic diagram of another stacked battery provided in one embodiment of the present application;

[0032] Figure 11 This is a schematic diagram of the structure of a photovoltaic module provided in one embodiment of this application.

[0033] The above figures include the following reference numerals:

[0034] 10. Substrate; 11. First pyramid structure; 12. Groove; 13. First doped conductive layer; 14. Second doped conductive layer; 15. First electrode; 16. Second electrode; 17. Third pyramid structure; 18. Amorphous silicon layer; 19. First transparent conductive layer; 20. Tunneling oxide layer; 21. Second transparent conductive layer; 22. First region; 23. Second region; 100. Back contact solar cell; 200. Perovskite solar cell; 500. Cell string; 501. Encapsulating film; 502. Cover plate. Detailed Implementation

[0035] The textured back surface structure of traditional back-contact solar cells results in insufficient contact area between the electrodes and the textured surface, leading to increased contact resistance. Irregular distribution of contact points also increases contact resistance, which in turn affects the fill factor and open-circuit voltage of the cell, ultimately reducing photoelectric conversion efficiency.

[0036] Based on the aforementioned problems, this application provides a back-contact solar cell, a fabrication method, a tandem cell, and a photovoltaic module. The back-contact solar cell of this application includes: a substrate having opposing first and second surfaces, the second surface comprising alternating first and second regions, the first region comprising a first pyramid structure with a groove at the apex; a first doped conductive layer located in the first region; a second doped conductive layer located in the second region, the second doped conductive layer having a different doping type than the first doped conductive layer; and a first electrode electrically connected to the first doped conductive layer, the first electrode overlapping the groove in a first direction, the first direction being the arrangement direction of the substrate and the first doped conductive layer.

[0037] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0038] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0039] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A exists, A and B exist simultaneously, and B exists. In addition, the character " / " in this document generally indicates that the related objects before and after it have an "or" relationship.

[0040] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0041] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0042] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" 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. For those skilled in the art, the specific meaning of the terms in the embodiments of this application can be understood according to the specific circumstances.

[0043] In the accompanying drawings corresponding to the embodiments of this application, the thickness and area of ​​the layers are enlarged for better understanding and ease of description. When describing a component (such as a layer, film, region, or substrate) on or on the surface of another component, the component may be "directly" located on the surface of the other component, or there may be a third component between the two components. Conversely, when describing a component on the surface of another component, or when another component is formed or disposed on the surface of a component, it indicates that there is no third component between the two components. Furthermore, when describing a component as being "generally" formed on another component, it means that the component is not formed on the entire surface (or front surface) of the other component, nor is it formed on a portion of the edge of the entire surface.

[0044] In the description of the embodiments of this application, when a component "includes" another component, other components are not excluded unless otherwise stated, and other components may be further included. Furthermore, when a component such as a layer, film, region, or plate is referred to as being "on / located" on another component, it can be "directly on" the other component (i.e., located on the surface of the other component with no other components between them), or another component may be present therein. Moreover, when a component such as a layer, film, region, or plate is "directly located" on another component, or when a component such as a layer, film, region, or plate is located on the surface of another component, it indicates that no other components are located therein.

[0045] The terminology used in the description of the various embodiments herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used in the description of the various embodiments and the appended claims, the term "part" is also intended to include the plural form unless the context clearly indicates otherwise. Components include layers, films, regions, or plates, etc.

[0046] Unless otherwise stated, "substantially identical" within the range of measurement tolerances or manufacturing errors is equivalent to "identical" or "equal" in the description of the embodiments of this application.

[0047] The embodiments of this application will now be described in detail with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the embodiments of this application to facilitate a better understanding of the application. However, the technical solutions claimed in this application can be implemented even without these technical details and various variations and modifications based on the following embodiments.

[0048] One embodiment of this application provides a back-contact solar cell. Figure 1 An exemplary schematic diagram of a back-contact solar cell according to an embodiment of this application is shown, such as... Figure 1 As shown, the back-contact solar cell includes:

[0049] Substrate 10, having opposing first and second surfaces, the second surface comprising alternating first regions 22 and second regions 23, the first region 22 comprising a first pyramid structure 11, such as... Figure 2 and Figure 3 As shown, the top of the first pyramid structure 11 has a groove 12;

[0050] Specifically, the first surface is the light-receiving surface of the back-contact solar cell, i.e., the surface that receives direct sunlight, and the second surface is the back-lighting surface of the back-contact solar cell. The first region 22 and the second region 23 have different doping types; that is, when the first region 22 is a P-type doped region, the second region 23 is an N-type doped region, and vice versa. Optionally, the doping type of the first region 22 is different from the doping type of the substrate 10, and the doping type of the second region 23 is the same as the doping type of the substrate 10. In one specific embodiment, the substrate 10 is an N-type substrate 10, and the doping element of the N-type substrate 10 is at least one of phosphorus, arsenic, antimony, and bismuth; the first region 22 is a P-type doped region, and the second region 23 is an N-type doped region. The first pyramid structure 11 has a base and a top located on the base, and the end of the top away from the base has the groove 12, making the first pyramid structure 11 a pyramid with an open top. There can be multiple first pyramid structures 11.

[0051] The first doped conductive layer 13 is located in the first region 22;

[0052] Specifically, the doping type of the first doped conductive layer 13 is the same as the doping type of the first region 22.

[0053] The second doped conductive layer 14 is located in the second region 23, and the doping type of the second doped conductive layer 14 is different from that of the first doped conductive layer 13.

[0054] Specifically, the doping type of the second doped conductive layer 14 is the same as the doping type of the second region 23.

[0055] The first electrode 15 is electrically connected to the first doped conductive layer 13. The first electrode 15 overlaps with the groove 12 in a first direction, which is the arrangement direction of the substrate 10 and the first doped conductive layer 13.

[0056] Specifically, overlap in the first direction refers to the overlap between the projection of the first electrode 15 onto the first doped conductive layer 13 and the projection of the groove 12 onto the first doped conductive layer 13. This overlap can be a complete coincidence of the first electrode 15 and the groove 12 in the first direction. Alternatively, the overlap can be a partial coincidence of the first electrode 15 and the groove 12 in the first direction. Partial coincidence includes three cases: first, a portion of the first electrode 15 coincides with a portion of the groove 12 in the first direction; second, the first electrode 15 is located within the groove 12 in the first direction; and third, the groove 12 is located within the first electrode 15 in the first direction. Optionally, at least a portion of the projection of the first electrode 15 may be located within all of the grooves 12, meaning the projection of the first electrode 15 can be entirely located within the grooves 12; or the projection of the first electrode 15 may be partially located within the grooves 12, with the remaining portion located on the first region 22 outside the grooves 12.

[0057] The second electrode 16 is electrically connected to the second doped conductive layer 14.

[0058] Specifically, the projection of the second electrode 16 onto the second surface overlaps with the second region 23. In this field, since the connecting material is conductive, when the back-contact solar cell is generating or supplying power, there is an electrical connection between the first electrode 15 and the first doped conductive layer 13, and an electrical connection between the second electrode 16 and the second doped conductive layer 14.

[0059] In the embodiments described herein, the back-contact solar cell of this application has a first pyramid structure with a groove at the top on the first region of the second surface. This allows a portion of the projection of the first electrode on the second surface to lie within the groove, increasing the effective contact area between the first electrode and the pyramid textured surface. This reduces contact resistance, improves electrode contact performance, and increases the fill factor and open-circuit voltage of the cell, thus enhancing the cell conversion efficiency of the back-contact solar cell. Furthermore, the groove design at the top of the first pyramid structure increases the number of internal reflections of light, allowing more incident light to be absorbed by the cell, significantly improving the photoelectric conversion efficiency.

[0060] For example, the surface of the first pyramid structure 11 with a groove 12 at the top is relatively complex, forming numerous acute angles and sides. When light is incident on such a surface, it will be reflected multiple times on the sidewalls at different angles. Each reflection changes the direction of the light, thereby extending the propagation path of the light within the cell. This extended optical path means more photons have the opportunity to be absorbed by the cell material and converted into current, a key factor in improving photoelectric conversion efficiency. The various sides of the groove 12 in the first pyramid structure 11 are tilted at different angles. This multi-angle arrangement increases the possibility of various incident angles when light contacts the cell surface. The different angled sides can capture and guide light rays incident at various angles, allowing the light to be refracted and reflected multiple times inside the cell, rather than simply reflected directly from the surface, thus increasing the probability of light absorption. The groove 12 design at the top also reduces the possibility of light being reflected directly from the top of the pyramid, thereby increasing the probability of photons being captured and converted into electrical energy, and thus improving the photoelectric conversion efficiency of the solar cell.

[0061] For example, the groove 12 can be an elliptical groove, a circular groove, a rectangular groove, a trapezoidal groove, a cross-shaped groove, a V-shaped groove, a groove with other polygonal shapes, or an irregularly shaped opening.

[0062] In some embodiments, such as Figure 1 As shown, the second region 23 is a polished surface. In this embodiment, since the second region 23 has a very thin tunneling oxide layer 20, the second region 23 of the back contact solar cell adopts a polished surface design instead of a pyramid textured surface design. This avoids the problem that the pyramid textured surface is not conducive to the deposition of the tunneling oxide layer, thus affecting the open circuit voltage. The polished surface of the second region 23 ensures that a relatively uniform tunneling oxide layer can be formed on it.

[0063] In other embodiments, at least a portion of the second region 23 includes a second pyramid structure (not shown in the figure), which differs from the first pyramid structure. This embodiment addresses the specific performance requirements of different regions by setting a different pyramid structure in the second region 23 compared to the first region 22, effectively capturing and guiding light incident on the second region 23, thereby further improving the photoelectric conversion efficiency of the solar cell.

[0064] For example, the second pyramid structure can be a conventional pyramid structure, i.e., a pyramidal structure without a groove at the top. Specifically, the second pyramid structure can include a regular pyramidal structure or an inclined pyramidal structure.

[0065] In some embodiments, such as Figure 2 andFigure 3 As shown, the depth of the groove 12 is 50nm~200nm, and the width of the groove 12 is 200nm~600nm. The direction of the depth is parallel to the first direction, and the direction of the width is perpendicular to the first direction. This range not only further increases the internal reflection of light and effectively reduces light reflection loss, but also further ensures the stability of the pyramid structure and good contact of the metal electrodes. Specifically, by controlling the depth and width of the groove 12, the scattering and absorption of incident light on the surface of the solar cell can be promoted, thereby further improving the photoelectric conversion efficiency. At the same time, the design of the groove 12 also improves the uniformity of film deposition, especially at the groove 12 at the top of the pyramid, which helps to further reduce the contact resistance, thereby further improving the fill factor and open-circuit voltage of the cell.

[0066] In one embodiment, the dimensions of the pyramid groove are obtained by measuring the depth and width of the groove in the SEM top view.

[0067] Among other alternatives, such as Figure 2 and Figure 3 As shown, the included angle α between the extended surfaces of two non-adjacent sides of the first pyramid structure 11 is 60°~135°. That is, the apex angle of the first pyramid structure 11 is 60°~135°. For example, this included angle can be 60°, 70°, 80°, 90°, 100°, 110°, 120°, 130°, or 135°, etc. The 60°~135° apex angle design allows light to be scattered over a wider range of angles, ensuring that photons undergo multiple internal reflections within the solar cell, increasing the optical path length, and thus improving the photoelectric conversion efficiency.

[0068] For example, the method for testing the included angle α between the extended surfaces of two non-adjacent sides of the first pyramid structure 11 is as follows: obtain a SEM cross-sectional view of the first pyramid structure 11, extend the sides of the first pyramid structure 11 in the SEM cross-sectional view by drawing auxiliary lines, and use a protractor to measure the included angle α between the extended lines.

[0069] According to some other alternatives of this application, such as Figure 2 and Figure 3As shown, the angle b between the side of the first pyramid structure 11 and the plane where the base is located is 45°~60°. For example, the angle between the side of the first pyramid structure 11 and the plane where the base is located can be 45°, 48°, 50°, 52°, 55°, 58°, or 60°, etc. In this application, the tilt angle design of 45°~60° can form multiple scattering and refraction on the surface of the pyramid structure, effectively reducing direct reflection of light and improving the light incident utilization rate. The pyramid structure within this angle range ensures that most incident light undergoes multiple reflections within the solar cell, increasing the optical path length and thus improving the light absorption rate.

[0070] In some embodiments, such as Figure 1 , Figures 4 to 7 As shown, the first face includes a third pyramid structure 17, which is terraced and includes a conical structure and a step structure. The step structure is located on the outer periphery of the conical structure and is in contact with the conical structure. The step structure includes multiple steps arranged continuously. Each step includes a slope (also called a riser) and a step surface (also called a tread). The step surface is in contact with the side of the slope away from the second face. In this embodiment, a terraced pyramid structure is formed on the front side of the back-contact solar cell. This pyramid structure includes layers of upward-sloping steps. When light is incident on the front side of the back-contact solar cell, part of the light directly penetrates into the cell contents, is quickly absorbed, and converted into electrical energy. Another part of the light is reflected by the surface of the third pyramid structure 17 and guided to the inner structure of the cell for re-absorption, realizing multi-level utilization of light energy and maximizing light absorption efficiency. Furthermore, due to the introduction of the layered step structure, the flatness of the pyramid structure surface is reduced, which effectively reduces specular reflection and increases diffuse reflection. Diffuse reflection allows light to be scattered over a wider range of angles, increasing the optical path length and further promoting the absorption and conversion of light energy. This significantly reduces the reflectivity of the front side of the back-contact solar cell, allowing more light energy to be captured and utilized by the cell, thus improving the photoelectric conversion efficiency.

[0071] Specifically, the third pyramid structure is obtained by forming multiple steps on the surface of a pyramidal structure. The steps are arranged in an orderly manner on the surface of the pyramidal structure, similar to the shape of a terraced field.

[0072] The synergistic effect of the first "terraced" pyramid and the second open pyramid not only improves the photoelectric conversion efficiency of the battery, but also improves the uniformity and contact performance of the subsequently deposited film, reduces the contact resistance, optimizes the transport path of photogenerated carriers, and reduces energy loss.

[0073] In one exemplary solution, such as Figure 6As shown, the angle c between the slope and the step surface is 60°~90°. That is, the angle between the step surface and the slope is an acute angle. Specifically, the angle between the slope and the step surface can be 60°, 65°, 70°, 75°, 80°, 85°, or 90°, etc. The acute angle design of the slope and step surfaces increases the surface roughness, which helps to scatter the incident light over a wider range of angles, increasing diffuse reflection, reducing specular reflection, and promoting multipath absorption of light. This angle range also helps to increase the optical path length, ensuring that photons stay in the silicon material for a longer time, thereby improving the light absorption efficiency and having a direct positive impact on the photoelectric conversion efficiency.

[0074] In another example scenario, such as Figure 7 As shown, the angle c between the slope and the step surface is 135°~150°. That is, the angle between the step surface and the slope is an obtuse angle. Specifically, the angle between the slope and the step surface can be 135°, 138°, 140°, 145°, 147°, or 150°, etc. The design of the large-angle slope and step surface can significantly enhance the light scattering effect, especially for light rays parallel to the surface. This light scattering mechanism at this angle helps to extend the path of photons inside the solar cell, increasing their interaction opportunities with silicon materials, thereby improving light absorption and photoelectric conversion efficiency. This obtuse angle range can also more effectively break the straight-line propagation of light, reducing the possibility of direct reflection from the surface of the solar cell, further ensuring maximum absorption of incident light and reducing energy loss of unused light.

[0075] In some embodiments, such as Figure 6 and Figure 7 As shown, the angle d between the slope and the surface where the base of the third pyramid structure 17 is located is 30°~60°. For example, the angle between the slope and the surface where the base is located can be 30°, 40°, 50°, or 60°, etc. This angle design optimizes the light absorption characteristics of the battery cell surface. By precisely controlling the geometric parameters of the textured pyramid structure, the incident angle range of light on the battery surface is effectively increased, light reflection is reduced, and the light capture capability is enhanced.

[0076] In one exemplary embodiment, the angle between the slope and the surface where the base of the third pyramid structure 17 is located is 45°.

[0077] For example, the specific testing methods for the angle b between the side of the first pyramid structure 11 and the plane where the base is located, the angle c between the slope and the step surface, and the angle d between the slope and the surface where the base of the third pyramid structure 17 is located are as follows: Obtain SEM cross-sectional views of the first pyramid structure 11 and the third pyramid structure 17. Measure the angle b between the hypotenuse of the first pyramid structure 11 and the plane where the base is located in the SEM cross-sectional view using a protractor. Measure the angle c between the slope and the step surface of the third pyramid structure 17 in the SEM cross-sectional view using a protractor. Measure the angle d between the slope and the plane where the base is located in the SEM cross-sectional view using a protractor.

[0078] According to some specific implementation methods of this application, such as Figures 5 to 7 As shown, the number of steps is 3 to 8. In other words, the terraced pyramid structure consists of 3 to 8 consecutive steps. Since the number of steps needs to be considered in relation to the difficulty and controllability of the manufacturing process, this application sets the number of steps between 3 and 8. This provides sufficient structural complexity to optimize the light absorption path without being overly complex, which could make the texturing process difficult to control and increase uncertainty in the production process.

[0079] Specifically, the method for testing the number of steps in the terraced pyramid structure is as follows: obtain the SEM top view and cross-sectional view of the third pyramid structure 17, and count the steps of the third pyramid structure 17 by combining the SEM top view and cross-sectional view to obtain the number of steps.

[0080] Optionally, such as Figure 5 As shown, the height D2 of the third pyramid structure 17 is 650nm~820nm, and the base width D1 of the third pyramid structure 17 is 2.2μm~3.7μm. For example, the height of the third pyramid structure 17 can be 650nm, 700nm, 750nm, 800nm, or 820nm, etc. The base width of the third pyramid structure 17 can be 2.2μm, 2.5μm, 3μm, 3.5μm, or 3.7μm, etc. In this embodiment, the height of 650nm~820nm is within the optimal photon capture range, ensuring that the light path length is long enough to fully absorb visible light of different wavelengths, while reducing insufficient absorption of near-infrared light and excessive absorption of ultraviolet light, thus avoiding energy waste in the photoelectric conversion process. The base width design of 2.2µm~3.7µm balances the amount of silicon material used and the light absorption efficiency of the structure. Setting the tower height and base width within the specified range ensures both optimized light absorption of the structure and process stability and operational feasibility during manufacturing. This helps simplify the manufacturing process, reduce process difficulty, and improve production efficiency and yield.

[0081] It should be noted that the base width D1 of the third pyramid structure 17 is the width of the longest side of the pyramid base.

[0082] Specifically, the test method for the base width D1 and height D2 of the third pyramid structure 17 is as follows: take a SEM cross-sectional view of the third pyramid structure 17, and measure the base width and height of the third pyramid structure 17 in the SEM cross-sectional view to obtain the values ​​of D1 and D2 respectively.

[0083] In some embodiments, such as Figure 5 As shown, the distance D3 between two adjacent step surfaces is 30nm~70nm. For example, the distance between two adjacent step surfaces can be 30nm, 40nm, 50nm, 60nm, or 70nm, etc. The distance between two adjacent step surfaces is the length of the slope connecting the two adjacent step surfaces. This application controls the distance between step surfaces at the nanoscale, which can not only finely control the scattering behavior of light on the surface, but also take into account the process stability and operational feasibility during manufacturing. This helps to simplify the manufacturing process, reduce process difficulty, and improve production efficiency and yield. The 30nm~70nm scale can match the wavelength of the incident light, and enhance the scattering of light through the light interference effect, thereby reducing the direct reflection of light and improving the light capture efficiency.

[0084] Specifically, the method for testing the distance D3 between two adjacent step surfaces is as follows: take a SEM cross-sectional view of the third pyramid structure 17, and obtain the distance D3 by measuring the slope length connecting the adjacent pyramid step surfaces in the SEM cross-sectional view.

[0085] In one exemplary embodiment, the first doped conductive layer 13 is a doped amorphous silicon layer or a doped microcrystalline silicon layer, and the second doped conductive layer 14 is a doped polycrystalline silicon layer. In this embodiment, the doped amorphous silicon layer or the doped microcrystalline silicon layer, serving as the first doped conductive layer 13, possesses excellent passivation properties, effectively reducing surface recombination and increasing the open-circuit voltage (Voc) of the solar cell, thereby improving the overall photoelectric conversion efficiency. The doped polycrystalline silicon layer, serving as the second doped conductive layer 14, has good carrier transport properties, providing a low-resistance path, promoting rapid electron or hole transport, reducing carrier recombination losses, and improving the short-circuit current (Isc) and fill factor (FF) of the solar cell.

[0086] Based on this, such as Figure 1As shown, the back-contact solar cell further includes: an amorphous silicon layer 18 located between the first doped conductive layer 13 and the substrate 10; a first transparent conductive layer 19 located between the first doped conductive layer 13 and the first electrode 15, and in contact with the first electrode 15; a tunneling oxide layer 20 located between the second doped conductive layer 14 and the substrate 10; and a second transparent conductive layer 21 located between the second doped conductive layer 14 and the second electrode 16, and in contact with the second electrode 16. In other words, the back-contact solar cell of this application can utilize the design of doped conductive layers and transparent conductive layers, which helps to optimize the collection and transport of charge carriers (electrons and holes), reduce the series resistance of the cell, and improve the short-circuit current (Isc). The introduction of the amorphous silicon layer 18 and the tunneling oxide layer 20 provides excellent surface and bulk passivation effects, reduces the surface recombination rate, and further improves the open-circuit voltage of the cell.

[0087] In the actual fabrication process, intrinsic amorphous silicon is used as the material for the amorphous silicon layer 18. However, due to the diffusion of other doped layers, the amorphous silicon layer 18 contains doped elements and is not a truly intrinsic layer. In this application, the doping concentration of the amorphous silicon layer 18 ranges from 1E19 to 5E20 cm⁻¹. -3 .

[0088] The first pyramid structure 11 is provided in the first region 22 of the back contact battery, which can improve the uniformity of the film layer deposited on the first region 22, ensure the uniformity of the thickness of the intrinsic passivation film layer deposited by CVD, improve the passivation quality, and the first transparent conductive layer 19 deposited by PVD can be uniformly covered in the groove 12 of the first pyramid structure 11, improve the transmission capability, reduce the contact resistance, and effectively reduce laser damage during the subsequent laser crystallization of the first region 22.

[0089] Optionally, the thickness of the tunneling oxide layer 20 is 1.2~1.5 nm.

[0090] Another aspect of this application provides a method for fabricating the aforementioned back-contact solar cell, comprising the following steps:

[0091] Step S201: Provide an initial substrate having opposing first and second surfaces, the second surface including alternating first and second regions;

[0092] Step S202: Selective etching, first cleaning, texturing, second cleaning and acid washing are performed sequentially on the second side of the initial substrate to form a first pyramid structure with a groove at the top of the first region, thereby obtaining the substrate;

[0093] Step S203: A first doped conductive layer is formed on the first region of the substrate, and a second doped conductive layer is formed on the second region of the substrate, wherein the doping type of the second doped conductive layer is different from that of the first doped conductive layer.

[0094] Step S204: Form a first electrode electrically connected to the first doped conductive layer, and form a second electrode electrically connected to the second doped conductive layer. The first electrode overlaps with the groove in a first direction, which is the arrangement direction of the substrate and the first doped conductive layer.

[0095] In the above embodiment, an initial substrate is first provided; then, the first region of the second surface of the initial substrate is etched to form a first pyramid structure with a groove at the top, thus obtaining the substrate; a first doped conductive layer is then formed on the first region of the substrate, and a second doped conductive layer is formed on the second region of the substrate; finally, a first electrode electrically connected to the first doped conductive layer is formed, such that the projection of the first electrode on the second surface is at least partially located in the groove, and a second electrode electrically connected to the second doped conductive layer is formed. This method increases the effective contact area between the first electrode and the pyramid textured surface by forming a first pyramid structure with a groove at the top on the first region of the second surface of the substrate, and by setting a portion of the projection of the first electrode on the second surface to be located in the groove. This reduces contact resistance, improves electrode contact performance, and increases the fill factor and open-circuit voltage of the solar cell, which is beneficial for improving the cell conversion efficiency of back-contact solar cells. Furthermore, the groove design at the top of the first pyramid structure increases the number of internal reflections of light, thereby allowing more incident light to be absorbed by the solar cell, significantly improving the photoelectric conversion efficiency.

[0096] Furthermore, the method further includes: sequentially performing selective etching, a first cleaning, texturing, a second cleaning, and acid pickling on the first surface of the substrate to form a plurality of third pyramid structures on the first surface of the substrate. The third pyramid structure is terraced and includes a conical structure and a step structure. The step structure is located on the outer periphery of the conical structure and is in contact with the conical structure. The step structure includes a plurality of steps, and each step includes a slope and a step surface. The step surface is in contact with the side of the slope away from the second surface.

[0097] It should be noted that the additive components used in the flocking process of the first pyramid structure and the third pyramid structure are different. In one specific embodiment, the additive used in the first pyramid structure is Topband EP32V65, and the additive used in the third pyramid structure is Shichuang TS53V01.

[0098] For example, the first cleaning refers to cleaning the substrate with a resist remover, then cleaning the substrate with an alkaline solution, and finally cleaning the substrate with an acidic solution. The second cleaning refers to cleaning the substrate with an acidic solution first and then cleaning the substrate with ultrapure water.

[0099] The fabrication time for the first pyramid structure and the third pyramid structure can be 400 seconds to 600 seconds, respectively.

[0100] In one embodiment, the specific fabrication process of the back-contact solar cell may include the following steps:

[0101] Step S1: Silicon wafer cleaning and polishing;

[0102] Step S2: SiOx tunneling oxygen layer preparation + poly deposition;

[0103] Step S3: Phosphorus diffusion;

[0104] Step S4: Backside SiOx / SiNx mask;

[0105] Step S5: Backside patterning, removing the mask and PSG from the P area;

[0106] Step S6: Remove PSG from one side of the front with HF solution;

[0107] Step S7: Double-sided etching and texturing. By adjusting the texturing process, the structure of the pyramid body is changed, forming the first pyramid structure in the P area on the back and the third pyramid structure on the front.

[0108] Step S8: Remove the back N-region mask with HF solution and clean with PSG;

[0109] Step S9: Front passivation layer (AlOx, SiOx, a-Si:H(i) etc.);

[0110] Step S10: Front antireflection layer (SiNx: SiNxOy: SiOx, etc.);

[0111] Step S11: Chain-type back-side plating removal;

[0112] Step S12: Cleaning the battery cells;

[0113] Step S13: Deposit a-Si:H(i) passivation layer on the back side at low temperature (<250°C);

[0114] Step S14: Deposit an a-Si:H(p) doped layer on the back side at low temperature (<250°C);

[0115] Step S15: Backside graphical removal of the i+p layer in region N;

[0116] Step S16: Deposit TCO (single-layer or multi-layer film such as ITO, IWO, ITiO, SnOx, AZO, etc.) thin film on the back side;

[0117] Step S17: Ink etching or laser patterning is applied to the TCO film to form an isolation region;

[0118] Step S18: Metallization and optical injection.

[0119] Another aspect of this application provides a tandem battery, including: any of the back-contact solar cells described above; and a perovskite battery electrically connected to the back-contact solar cell.

[0120] In one embodiment, such as Figure 8 As shown, the stacked battery is a four-terminal stacked battery. In this stacked battery, the first electrode of the back-contact solar cell 100 and the first electrode of the perovskite cell 200 serve as two electrode terminals of the stacked battery, and the second electrode of the back-contact solar cell 100 and the second electrode of the perovskite cell 200 serve as the other two electrode terminals of the stacked battery.

[0121] In another embodiment, such as Figure 9 As shown, the tandem solar cell is a three-terminal tandem solar cell. In this tandem solar cell, the back-contact solar cell 100 serves as the bottom cell, and the perovskite cell 200 serves as the top cell. The top cell and the bottom cell can be connected by directly depositing the perovskite cell 200 on the first surface of the back-contact solar cell 100. Figure 9 As shown, in this stacked cell, the first and second electrodes of the back-contact solar cell serve as the two electrode terminals of the stacked cell, and one electrode of the perovskite cell 200 serves as the other electrode terminal of the stacked cell.

[0122] Specifically, the first side of the back-contact solar cell 100 is the light-receiving side of the cell.

[0123] In another embodiment, such as Figure 10 As shown, the stacked battery is a two-terminal stacked battery. In this stacked battery, the first electrode of the back-contact solar cell 100 and the first electrode of the perovskite cell 200 are electrically connected to serve as one electrode terminal of the stacked battery, and the first electrode and the second electrode of the back-contact solar cell are electrically connected to serve as the other electrode terminal of the stacked battery.

[0124] In another aspect, this application also provides a photovoltaic module, such as... Figure 11As shown, the photovoltaic module includes: a battery string 500, which is formed by connecting multiple back-contact solar cells of any one of the above methods, or back-contact solar cells prepared by the above method, or stacked cells; an encapsulating film 501 for covering the surface of the battery string 500; and a cover plate 502 for covering the surface of the encapsulating film 501 that is away from the surface of the battery string 500.

[0125] To enable those skilled in the art to better understand the technical solution of this application, the structure of the back contact solar cell of this application will be described in detail below with reference to specific embodiments.

[0126] Example 1

[0127] This embodiment provides a back-contact solar cell, including:

[0128] The N-type substrate has opposing front and back sides. The back side includes alternating P and N regions. The P regions include multiple first pyramid structures with grooves at the top. The N regions are polished surfaces. The front side includes multiple terraced third pyramid structures. The average depth of the grooves in the first pyramid structures on the back side is 50 nm to 200 nm, the average width of the grooves in the first pyramid structures is 200 nm to 600 nm, the average angle between the side surface of the first pyramid structure and the plane where the base is located is 45° to 60°, the average angle between the extended surfaces of two non-adjacent side surfaces of the first pyramid structure is 60° to 135°, the average angle between the slope surface of the third pyramid structure and the surface where the base is located is 30° to 60°, the average height of the third pyramid structure is 650 nm to 820 nm, the average width of the base of the third pyramid structure is 2.2 μm to 3.7 μm, the average distance between two adjacent step surfaces is 30 nm to 70 nm, and the average number of steps in the third pyramid structure is 3 to 8.

[0129] An amorphous silicon layer, a P-type doped conductive layer, and a first transparent conductive layer are sequentially stacked on the P-region;

[0130] A tunneling oxide layer, an N-type doped conductive layer, and a second transparent conductive layer are sequentially stacked on the N-region.

[0131] A first electrode is located on the first transparent conductive layer. In a first direction, at least a portion of the first electrode is located in the groove. The first direction is the arrangement direction of the substrate and the P-type doped conductive layer.

[0132] The second electrode is located on the second transparent conductive layer, and the second electrode is located in the N region in the first direction.

[0133] Comparative Example 1

[0134] This embodiment provides a back-contact solar cell. The only difference between this cell and Embodiment 1 is that the pyramid structure in the P-region and on the front is a pyramidal structure, and the top of the pyramid structure has no groove and no steps.

[0135] The performance of the back-contact solar cells in Example 1 and Comparative Example 1 was tested, and the test results are shown in Table 1:

[0136] Table 1

[0137]

[0138] As can be seen from the experimental data, the open-circuit voltage, short-circuit current, fill factor, and cell conversion efficiency of the back-contact solar cell of Embodiment 1 of this application are all higher than those of Comparative Example 1. Therefore, the technical solution of this application brings significant performance improvement to the design and manufacturing of back-contact solar cells, demonstrating the effectiveness and superiority of the technical solution of this application.

[0139] 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 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.

[0140] As can be seen from the above description, the embodiments described in this application achieve the following technical effects:

[0141] In the back-contact solar cell of this application, a first pyramid structure with a groove at the top is provided on the first region of the second surface. This allows a portion of the projection of the first electrode on the second surface to lie within the groove, increasing the effective contact area between the first electrode and the pyramid textured surface. This reduces contact resistance, improves electrode contact performance, and increases the fill factor and open-circuit voltage of the cell, thus enhancing the cell conversion efficiency of the back-contact solar cell. Furthermore, the groove design at the top of the first pyramid structure increases the number of internal reflections of light, allowing more incident light to be absorbed by the cell, significantly improving the photoelectric conversion efficiency.

[0142] Those skilled in the art will understand that the above embodiments are specific examples of implementing this application, and in practical applications, various changes in form and detail can be made without departing from the spirit and scope of this application. Any person skilled in the art can make various alterations and modifications without departing from the spirit and scope of this application; therefore, the scope of protection of this application should be determined by the scope defined in the claims.

Claims

1. A back-contact solar cell, characterized in that, include: A substrate having opposing first and second surfaces, the second surface comprising alternating first and second regions, the first region comprising a first pyramid structure having a groove at the top of the pyramid structure; A first doped conductive layer is located in the first region; A second doped conductive layer is located in the second region, and the doping type of the second doped conductive layer is different from that of the first doped conductive layer. The first electrode is electrically connected to the first doped conductive layer, and the first electrode overlaps with the groove in a first direction, which is the arrangement direction of the substrate and the first doped conductive layer. The second electrode is electrically connected to the second doped conductive layer.

2. The back-contact solar cell according to claim 1, characterized in that, At least a portion of the second region includes a second pyramid structure, which is different from the first pyramid structure.

3. The back-contact solar cell according to claim 1, characterized in that, The groove has a depth of 50nm to 200nm and a width of 200nm to 600nm. The direction of the depth is parallel to the first direction, and the direction of the width is perpendicular to the first direction.

4. The back-contact solar cell according to claim 1, characterized in that, The included angle between the extended faces of two non-adjacent sides of the first pyramid structure is 60° to 135°.

5. The back-contact solar cell according to claim 1, characterized in that, The first face includes a third pyramid structure, which is terraced and includes a conical structure and a step structure. The step structure is located on the outer periphery of the conical structure and is in contact with the conical structure. The step structure includes multiple steps, and each step includes a slope and a step surface. The step surface is in contact with the side of the slope away from the second face.

6. The back-contact solar cell according to claim 5, characterized in that, The angle between the slope and the step is 60° to 90°.

7. The back-contact solar cell according to claim 5, characterized in that, The angle between the slope and the step is 135°~150°.

8. The back-contact solar cell according to claim 6 or 7, characterized in that, The angle between the slope and the surface where the base of the third pyramid structure is located is 30° to 60°.

9. The back-contact solar cell according to claim 5, characterized in that, The number of steps is 3 to 8.

10. The back-contact solar cell according to claim 5, characterized in that, The height of the third pyramid structure is 650nm~820nm, and the width of the base of the third pyramid structure is 2.2μm~3.7μm.

11. The back-contact solar cell according to claim 5, characterized in that, The distance between two adjacent step surfaces is 30nm~70nm.

12. The back-contact solar cell according to any one of claims 1 to 7 and 9 to 11, characterized in that, The first doped conductive layer is a doped amorphous silicon layer or a doped microcrystalline silicon layer, and the second doped conductive layer is a doped polycrystalline silicon layer.

13. A method for preparing a back-contact solar cell, used to prepare the back-contact solar cell according to any one of claims 1 to 12, characterized in that, include: An initial substrate is provided, the initial substrate having opposing first and second surfaces, the second surface comprising alternating first and second regions; The second side of the initial substrate is selectively etched, first cleaned, texturized, second cleaned and acid-washed in sequence to form a first pyramid structure with a groove at the top of the first region, thus obtaining the substrate. A first doped conductive layer is formed on the first region of the substrate, and a second doped conductive layer is formed on the second region of the substrate, wherein the doping type of the second doped conductive layer is different from that of the first doped conductive layer. A first electrode electrically connected to the first doped conductive layer and a second electrode electrically connected to the second doped conductive layer are formed. The first electrode overlaps with the groove in a first direction, which is the arrangement direction of the substrate and the first doped conductive layer.

14. A stacked battery, characterized in that, include: Back-contact solar cell according to any one of claims 1 to 12; The perovskite cell is electrically connected to the back-contact solar cell.

15. A photovoltaic module, characterized in that, include: A battery string is formed by connecting multiple back-contact solar cells as described in any one of claims 1 to 12, or back-contact solar cells prepared by the method for preparing back-contact solar cells as described in claim 13, or stacked cells as described in claim 14. An encapsulating film is used to cover the surface of the battery string; A cover plate is used to cover the surface of the encapsulating film that faces away from the battery string.

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