Back contact solar cell, method of manufacturing the same, stacked cell, and photovoltaic module

Abstract

The application relates to the photovoltaic technical field and provides a back contact solar cell, a preparation method thereof, a laminated cell and a photovoltaic module. The back contact solar cell comprises a substrate including oppositely arranged first and second surfaces, the second surface includes alternately arranged first and second regions, the first region includes a first rough surface and a first plane, and in the thickness direction of the substrate, the first plane is convex to the side away from the first surface relative to the first rough surface, and the second region includes a second rough surface; a first doped layer is arranged on the first region; a first electrode is electrically connected with the first doped layer, and in the thickness direction of the substrate, the first electrode at least partially overlaps with the first plane; a second doped layer is arranged on the second region, and the doping type of the second doped layer is different from that of the first doped layer; and a second electrode is electrically connected with the second doped layer.

Description

Technical Field

[0001] This application relates to the photovoltaic field, and in particular to a back-contact solar cell, its preparation method, tandem solar cells, and photovoltaic modules. Background Technology

[0002] Solar cells, as the core component for converting solar energy into electrical energy, have experienced rapid development in recent years. Among them, back-contact (BC) cells occupy an important position in the photovoltaic field due to their high photoelectric conversion efficiency and aesthetically pleasing design. BC cells achieve electrode-to-wafer contact by metallizing the back of the silicon wafer, avoiding the light blocking caused by the front metal lines in traditional cell structures, thus improving the cell's conversion efficiency. Photoelectric conversion efficiency is a core parameter of back-contact solar cells, reflecting the cell's ability to convert solar energy into electrical energy. Improving photoelectric conversion efficiency depends not only on the optimization of cell materials but also on the design of the cell's internal structure. Summary of the Invention

[0003] This application provides a back-contact solar cell, its preparation method, a tandem solar cell, and a photovoltaic module, which at least helps to improve the photoelectric conversion efficiency of the back-contact solar cell.

[0004] According to some embodiments of this application, one aspect of this application provides a back-contact solar cell, comprising: a substrate, the substrate including a first surface and a second surface disposed opposite to each other, the second surface including an alternately arranged first region and a second region, the first region including a first textured surface and a first flat surface, and in the thickness direction of the substrate, the first flat surface protrudes relative to the first textured surface on a side away from the first surface, the second region including a second textured surface; a first doped layer disposed on the first region; a first electrode electrically connected to the first doped layer, in the thickness direction of the substrate, the first electrode at least partially overlapping the first flat surface; a second doped layer disposed on the second region, the doping type of the second doped layer being different from that of the first doped layer; and a second electrode electrically connected to the second doped layer.

[0005] In some embodiments, the first velvet surface includes a plurality of first pyramid structures, and the second velvet surface includes a plurality of second pyramid structures, wherein the height of the first pyramid structure in the first velvet surface is less than the height of the second pyramid structure in the second velvet surface.

[0006] In some embodiments, the base width of the first pyramid structure in the first velvet surface is smaller than the base width of the second pyramid structure in the second velvet surface.

[0007] In some embodiments, the base width of the first pyramid structure is 0.2 μm to 1 μm; the base width of the second pyramid structure is 2 μm to 4 μm.

[0008] In some embodiments, in the thickness direction of the substrate, the distance between the first plane and the first nap is less than the distance between the second nap and the first nap.

[0009] In some embodiments, in the thickness direction of the substrate, the distance between the first plane and the first velvet surface is 0.5 μm to 2 μm, and the distance between the second velvet surface and the first velvet surface is 3 μm to 10 μm.

[0010] In some embodiments, the first doped layer is a polycrystalline silicon doped layer, and the second doped layer is an amorphous silicon doped layer, a microcrystalline silicon doped layer, or a nanocrystalline silicon doped layer. The back contact solar cell further includes: a tunneling oxide layer located between the substrate and the first doped layer; and an amorphous silicon layer located between the substrate and the second doped layer.

[0011] In some embodiments, the back-contact solar cell further includes a transparent conductive layer, the transparent conductive layer comprising: a first conductive portion located between the first doped layer and the first electrode; and a second conductive portion located between the second doped layer and the second electrode, wherein the thickness of the first conductive portion is greater than the thickness of the second conductive portion.

[0012] In some embodiments, the second region further includes a second plane, wherein the second electrode at least partially overlaps the second plane in the thickness direction of the substrate.

[0013] According to some embodiments of this application, another aspect of this application provides a method for fabricating the above-described back-contact solar cell, comprising: forming a first textured surface and a first flat surface in a first region on a second surface of a substrate; forming a first doped layer in the first region; forming a second textured surface in a second region on a second surface of the substrate; forming a second doped layer in the second region; forming a first electrode on the side of the first doped layer away from the substrate; and forming a second electrode on the side of the second doped layer away from the substrate.

[0014] In some embodiments, forming the first textured surface and the first flat surface in a first region on the second surface of the substrate includes: forming a mask layer on the second surface of the substrate, the mask layer exposing a predetermined region in the first region; forming the first textured surface in the predetermined region; and removing the mask layer to expose the first flat surface.

[0015] In some embodiments, forming the first textured surface in the designated area includes: etching the designated area to form a plurality of first pyramid structures in the designated area; forming the second textured surface in a second region on a second surface of the substrate includes: etching the second region to form a plurality of second pyramid structures in the second region; wherein the base width of the first pyramid structure is smaller than the base width of the second pyramid structure, and / or the height of the first pyramid structure is smaller than the height of the second pyramid structure.

[0016] In some embodiments, a first solution is used to etch a designated area, and a second solution is used to etch a second area. The first solution and the second solution have the same composition, and the time for etching the designated area with the first solution is less than the time for etching the second area with the second solution.

[0017] According to some embodiments of this application, another aspect of this application provides a tandem solar cell, including: a perovskite solar cell; a back-contact solar cell as described above or a back-contact solar cell prepared by the preparation method described above, wherein the perovskite solar cell is located on the light-incident side of the back-contact cell.

[0018] According to some embodiments of this application, another aspect of this application provides a tandem photovoltaic module, including: a battery string, which is formed by connecting multiple back-contact solar cells as described above, or multiple back-contact solar cells prepared by the preparation method described above, or multiple tandem solar cells as described above; 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] This application relates to the field of photovoltaic technology, and provides a back-contact solar cell, its fabrication method, a tandem solar cell, and a photovoltaic module. The back-contact solar cell includes: a substrate, comprising a first surface and a second surface disposed opposite to each other; the second surface includes alternating first and second regions; the first region includes a first textured surface and a first flat surface, and in the thickness direction of the substrate, the first flat surface protrudes relative to the first textured surface on a side away from the first surface; the second region includes a second textured surface; a first doped layer disposed on the first region; a first electrode electrically connected to the first doped layer, and in the thickness direction of the substrate, the first electrode at least partially overlaps with the first flat surface; a second doped layer disposed on the second region, the doping type of the second doped layer being different from that of the first doped layer; and a second electrode electrically connected to the second doped layer. The first and second textured surfaces increase the propagation path of light inside the battery, improving light absorption efficiency and thus enhancing the battery's photoelectric conversion efficiency and bifaciality. The first electrode and the first plane at least partially overlap in the thickness direction of the substrate; that is, at least a portion of the contact area between the surface of the first electrode facing the substrate and its adjacent film layer is planar. This optimizes the passivation contact between the first electrode and the substrate, reduces surface recombination, and ensures efficient charge carrier transport to the first electrode while improving light utilization in the first region. The first plane protrudes from the side opposite to the first textured surface relative to the first textured surface. This indicates that the formation of the first textured surface and the first plane involves texturing the area where the first plane is to be formed, rather than texturing the entire first region and then polishing the area where the first plane is to be formed. This simplifies the process and helps reduce production costs. 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 diagram of a back-contact solar cell according to an embodiment of this application;

[0023] Figure 2 This is a schematic diagram of another back-contact solar cell provided according to an embodiment of this application;

[0024] Figure 3 This is a schematic diagram of another back-contact solar cell provided according to an embodiment of this application;

[0025] Figure 4 This is a schematic flowchart illustrating a method for fabricating a back-contact solar cell according to an embodiment of this application.

[0026] Figure 5 This is a schematic diagram of a stacked battery structure provided according to an embodiment of this application;

[0027] Figure 6 This is a schematic diagram of another stacked battery structure provided according to an embodiment of this application;

[0028] Figure 7 This is a schematic diagram of another stacked battery structure provided according to an embodiment of this application;

[0029] Figure 8 This is a schematic diagram of the structure of a photovoltaic module according to an embodiment of this application.

[0030] The above figures include the following reference numerals:

[0031] 1. Substrate; 11. First region; 12. Second region; 111. First textured surface; 112. First plane; 121. Second textured surface; 122. Second plane; 21. First doped layer; 22. Second doped layer; 31. First electrode; 32. Second electrode; 41. Tunneling oxide layer; 42. Amorphous silicon layer; 5. Transparent conductive layer; 51. First conductive part; 52. Second conductive part; 100. Solar cell; 200. Encapsulating film; 300. Cover plate; 400. Perovskite solar cell; 500. Back contact solar cell. Detailed Implementation

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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).

[0036] 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", "circumferential", etc., 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 do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0037] 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. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application according to the specific circumstances.

[0038] 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.

[0039] 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.

[0040] 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 word "part" is also intended to include the plural form, unless the context clearly indicates otherwise. Components include layers, films, regions, or plates, etc.

[0041] 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.

[0042] Figure 1 This is a schematic diagram of a back-contact solar cell according to an embodiment of this application, as shown below. Figure 1 As shown, the back-contact solar cell includes a substrate 1, a first doped layer 21, a first electrode 31, a second doped layer 22, and a second electrode 32. The substrate 1 includes a first surface and a second surface disposed opposite to each other. The second surface includes alternating first regions 11 and second regions 12. The first region 11 includes a first textured surface 111 and a first flat surface 112, and in the thickness direction of the substrate 1, the first flat surface 112 protrudes relative to the first textured surface 111 towards the side opposite to the first surface. The second region 12 includes a second textured surface 121. The first doped layer 21 is disposed on the first region 11. The first electrode 31 is located on the side of the first doped layer 21 away from the substrate 1 and is electrically connected to the first doped layer 21. In the thickness direction of the substrate 1, the first electrode 31 at least partially overlaps with the first flat surface 112. The second doped layer 22 is disposed on the second region 12, and the doping type of the second doped layer 22 is different from that of the first doped layer 21. The second electrode 32 is located on the side of the second doped layer 22 away from the substrate 1 and is electrically connected to the second doped layer 22.

[0043] The back-contact solar cell provided in this application embodiment has a first region 11 and a second region 12 alternately arranged on the second surface of a substrate 1. The first region 11 is provided with a first textured surface 111 and a first flat surface 112, and the second region 12 is provided with a second textured surface 121. The first textured surface 111 and the second textured surface 121 can increase the propagation path of light inside the cell, improve the light absorption efficiency, and thus improve the photoelectric conversion efficiency and bifaciality of the cell. The first electrode 31 and the first flat surface 112 overlap at least partially in the thickness direction of the substrate 1, that is, at least a portion of the surface of the first electrode 31 facing the substrate 1 has a plane contact surface with its adjacent film layer. This is beneficial for optimizing the passivation contact between the first electrode 31 and the substrate 1, reducing surface recombination, and ensuring efficient transfer of charge carriers to the first electrode 31 while improving the light utilization rate of the first region 11. The first plane 112 protrudes to the side away from the first surface relative to the first velvet surface 111. This indicates that the first velvet surface 111 and the first plane 112 are formed by retaining the area where the first plane 112 is to be set and velveting the area where the first velvet surface 111 is to be set, rather than velveting the entire first area 11 and then polishing the area where the first plane 112 is to be formed. The process is simple and helps to reduce production costs.

[0044] The aforementioned first plane 112 protrudes away from the first surface relative to the first textured surface 111. Alternatively, in the first region 11, the distance between the first plane 112 and the first surface of the substrate 1 is a first distance, and the distance between the first textured surface 111 and the first surface of the substrate 1 is a second distance, where the first distance is greater than the second distance. The first and second distances can be measured as follows: a cross-section of the solar cell in the thickness direction is taken, and in the scanning image of this cross-section using an electron microscope (SEM), the distance between the apex of any pyramid structure in the first textured surface 111 and the first surface in the thickness direction of the substrate 1 is measured to obtain the first distance, and the distance between the first plane 112 and the first surface in the thickness direction of the substrate 1 is measured to obtain the second distance. It should be understood that the second surface of the substrate 1 is the surface on which electrodes and other structures are provided, and the surface opposite to the second surface is its first surface. The first surface is usually a textured surface. Therefore, when measuring the first distance between the first plane 112 and the first surface and the second distance between the first textured surface 111 and the first surface using the above method, a horizontal plane (perpendicular to the thickness direction of the substrate 1) intersecting with the first surface of the textured surface can be selected as a reference plane, and then the distances between the first plane 112 and the first textured surface 111 and the reference plane can be measured respectively.

[0045] It should be understood that the aforementioned first plane 112 may be formed by polishing the second surface of the substrate 1. It may not be an ideal first plane, but rather a surface with a certain texture structure but a high overall flatness.

[0046] It should also be understood that the above-mentioned overlap of the first electrode 31 and the first plane 112 in the thickness direction of the substrate 1 means that the first electrode 31 is disposed on the first plane 112 and overlaps with the first plane 112 in the thickness direction of the substrate 1. However, in actual fabrication, due to process errors, some parts of the first electrode 31 may be formed outside the range corresponding to the first plane 112. For example, when the first electrode 31 is formed by screen printing, a small amount of paste may be printed outside the first plane 112 due to process errors, resulting in a partially non-overlapping area between the first electrode 31 and the first plane 112 in the thickness direction of the substrate 1. However, this area accounts for only a small part of the first electrode 31.

[0047] It should also be understood that the thickness direction of the substrate 1 is the stacking direction of the first doped layer 21 and the substrate 1.

[0048] It should also be understood that the above-mentioned electrical connection means that the components such as the first electrode 31, the second electrode 32, the first doped layer 21 and the second doped layer 22 are conductive. When the back-contact solar cell is generating or supplying power, the components that are electrically connected to each other can conduct current to achieve electrical connection. In other cases, the components that are electrically connected to each other may only be in contact with each other without current passing through them.

[0049] The components of the aforementioned back-contact solar cell will be described in detail below.

[0050] The substrate 1 can be an N-type doped substrate or a P-type doped substrate. The material of the substrate 1 includes, but is not limited to, one of single-crystal silicon (c-Si), polycrystalline silicon (poly-Si), and amorphous silicon (a-Si). The N-type doping element includes, but is not limited to, at least one of phosphorus (P), antimony (Sb), and arsenic (As), and the P-type doping element includes, but is not limited to, at least one of boron (B), aluminum (Al), and gallium (Ga). The substrate 1 includes a first surface and a second surface. The first surface of the substrate 1 is used to face the light source (sun), that is, the first surface of the substrate 1 is the light-facing surface. The second surface is opposite to the first surface, that is, the second surface of the substrate 1 is the backlight surface. The first doped layer 21, the first electrode 31, the second doped layer 22, and the second electrode 32 are disposed on the second surface of the substrate 1, thereby minimizing the obstruction of direct sunlight and improving the utilization rate of direct sunlight.

[0051] The first region 11 and the second region 12 in the substrate 1 can be connected, or they can be spaced apart. The first region 11 and the second region 12 can also be staggered in the thickness direction of the substrate 1, which is not limited here.

[0052] The doping type of the first doped layer 21 is different from that of the second doped layer 22. The first doped layer 21 can be an N-type doped layer, and the second doped layer 22 can be a P-type doped layer, which is not limited here. The N-type doping element includes, but is not limited to, at least one of phosphorus (P), antimony (Sb), and arsenic (As), and the P-type doping element includes, but is not limited to, at least one of boron (B), aluminum (Al), and gallium (Ga).

[0053] like Figure 1 As shown, the first doped layer 21 is disposed on the first region 11, and the second doped layer 22 is disposed on the second region 12. Figure 2 This is a schematic diagram of another back-contact solar cell provided according to an embodiment of this application, as shown below. Figure 2 As shown, the second doped layer 22 may include a portion extending onto the first doped layer 21, resulting in a partial contact area between the first doped layer 21 and the second doped layer 22. This is caused by process errors during the fabrication process. The contact area between the two is small, and since the lateral transport capability of the doped layer is limited, the aforementioned contact area will not affect the normal function of the battery.

[0054] In some embodiments of this application, the first velvet surface 111 includes a plurality of first pyramid structures, and the second velvet surface 121 includes a plurality of second pyramid structures, wherein the height of the first pyramid structure is less than the height of the second pyramid structure.

[0055] It should be understood that the height of a pyramid structure refers to the maximum height from the bottom to the tip of the cross-section of the pyramid structure. The height of the pyramid structure in the velvet surface can be obtained by taking pictures of the cross-section of the velvet surface with a microscope and then measuring it. For example, multiple pyramid structures with clear structures can be selected and their heights measured, and the average of the multiple measurement results can be calculated. For example, 2, 3, 5, 7... pyramid structures can be selected for measurement, and the number of pyramid structures selected should not exceed 10.

[0056] For the same base size, a smaller pyramid height means less undulation in the pyramid structure. The height of the first pyramid structure is smaller than that of the second pyramid structure, which means that the undulation of the first textured surface 111 is less than that of the second textured surface 121. This is beneficial to improving the uniformity of the film layer formed on the first textured surface 111, especially the uniformity of thinner film layers. For example, a tunneling oxide layer is provided between the first region 11 and the first doped layer 21. Since the tunneling oxide layer usually needs to be very thin to allow charge carriers to pass through, it can only grow uniformly on a surface with high flatness. The first textured surface 111 with less undulation helps to form a more uniform tunneling oxide layer, thereby providing a consistent passivation effect in all regions and reducing surface recombination.

[0057] In some embodiments of this application, the base width of the first pyramid structure in the first velvet surface 111 is smaller than the base width of the second pyramid structure in the second velvet surface 121.

[0058] It should be understood that if the base of a pyramid structure is quadrilateral, the base width refers to the side length of that quadrilateral. If the base is a square, all four sides are equal in length, and the base width is the length of any one side of the square. If the base is rectangular, the base width usually refers to the length of either of the two shorter sides. In practical applications, the base of a pyramid structure can also be irregularly shaped. The base width can be measured by taking a cross-section of the battery and examining the SEM scan of the cross-section. This can be done by randomly selecting a sufficient number of pyramid structures with clear base structures from the SEM scan, measuring them, and then averaging the measurements. For example, 2, 3, 5, 7… pyramid structures can be selected for measurement, with the number of selected pyramid structures not exceeding 10.

[0059] The first region 11 includes multiple first pyramid structures with narrow base widths, which can reduce the undulation of the first textured surface 111, improve the uniformity of the film layer disposed on the first textured surface 111, and enhance the passivation effect. Furthermore, the first pyramid structures with narrow base widths can increase the density of scattering centers in the first textured surface 111, increasing the likelihood that light will be reflected, refracted, or scattered back into the battery for reuse, further improving the light utilization rate of the region corresponding to the first textured surface 111.

[0060] In some embodiments of this application, the first textured surface 111 and the second textured surface 121 can simultaneously satisfy the following: the base width of the first pyramid structure in the first textured surface 111 is smaller than the base width of the second pyramid structure in the second textured surface 121, and the height of the first pyramid structure in the first textured surface 111 is smaller than the height of the second pyramid structure in the second textured surface 121. In other words, the overall size of the first pyramid structure is smaller than the overall size of the second pyramid structure. As can be seen from the above embodiments, a relatively smaller base width of the pyramid structure can increase its arrangement density and increase the possibility of light reuse, while a relatively larger pyramid height can provide a larger surface area to reflect, refract, or scatter light back into the interior of the substrate 1. The first textured surface 111 and the second textured surface 121 simultaneously satisfy the above design, and the light utilization rate of the corresponding areas of the first textured surface 111 and the second textured surface 121 is enhanced, which is beneficial to improving the uniformity of the current generated by the battery in the corresponding areas and optimizing the electrical performance of the battery.

[0061] In some embodiments of this application, the base width of the first pyramid structure is 0.2μm to 1μm, and the base angle of the first pyramid structure is 45° to 60°; the base width of the second pyramid structure is 2μm to 4μm, and the base angle of the second pyramid structure is 45° to 60°. Setting the dimensions of the first and second pyramid structures within these ranges allows for appropriate light reflection, improving the light utilization rate of the corresponding areas of the first textured surface 111 and the second textured surface 121. Furthermore, the pyramid structure provides good structural stability, contributing to improved battery reliability.

[0062] The base width and bottom angle of the first and second pyramids mentioned above can be measured as follows: A cross-section is cut along the thickness direction of the battery, and an SEM scan image of this cross-section is obtained. Then, multiple pyramid structures in the SEM scan image are randomly selected to measure the width of their base cross-sections. For example, 2, 3, 5, 7... pyramid structures are selected for measurement, and the number of selected pyramid structures should not exceed 10. After removing error values ​​that are significantly larger or smaller than the base widths of other pyramid structures, the range of values ​​for the base width of the pyramid structure can be obtained. The angle between the inclined plane in the cross-section of the pyramid structure and the plane where the base is located is the bottom angle of the pyramid structure. Multiple pyramid structures in the SEM scan image are randomly selected to measure their bottom angles. For example, 2, 3, 5, 7... pyramid structures are selected for measurement, and the number of selected pyramid structures should not exceed 10. After removing error values ​​that are significantly larger or smaller than the bottom angles of other pyramid structures, the range of values ​​for the bottom angle of the pyramid structure can be obtained.

[0063] In some embodiments of this application, the distance between the first plane 112 and the first textured surface 111 in the thickness direction of the substrate 1 is smaller than the distance between the second textured surface 121 and the first textured surface 111. The smaller distance between the first plane 112 and the first textured surface 111 in the thickness direction of the substrate 1 ensures that different portions of the film layers subsequently disposed on the first plane 112 and the first textured surface 111 also have smaller distances, reducing the risk of film layer breaks or thinner films at the interface between the first plane 112 and the first textured surface 111. This allows the first textured surface 111 to be used to improve the light utilization rate of the first region 11 while ensuring that other properties of that region are not affected. The interface between the second textured surface 121 and the first textured surface 111, i.e., the interface between different doped regions, can have a relatively larger distance in the thickness direction of the substrate 1 without causing the aforementioned problems. Furthermore, a larger distance helps reduce the risk of short circuits or leakage between adjacent heterogeneously doped structures.

[0064] It should be understood that, in the thickness direction of the base 1, the distance between the first plane 112 and the first velvet surface 111 can refer to the distance between the first plane 112 and the apex of the first pyramid structure in the first velvet surface 111, and the distance between the second velvet surface 121 and the first velvet surface 111 can refer to the distance between the base of the second pyramid structure in the second velvet surface 121 and the apex of the first pyramid structure in the first velvet surface 111.

[0065] The distance between the first plane 112 and the first textured surface 111 in the thickness direction of the substrate 1 can be measured in the following way: take a cross section along the thickness direction of the battery, obtain the SEM scan image of the cross section, and then randomly select multiple positions in the SEM scan image to measure the distance between the first plane 112 and the first textured surface 111 in the thickness direction of the substrate 1. For example, select 2, 3, 5, 7... positions for measurement, and the selected positions shall not exceed 10. The average value of the measured distances can be used to obtain the distance between the first plane 112 and the first textured surface 111 in the thickness direction of the substrate 1. Similarly, the distance between the second textured surface 121 and the first textured surface 111 in the thickness direction of the substrate 1 can be measured in the following way: take a cross section along the thickness direction of the battery, obtain the SEM scan image of the cross section, and then randomly select multiple positions in the SEM scan image to measure the distance between the second textured surface 121 and the first textured surface 111 in the thickness direction of the substrate 1. For example, select 2, 3, 5, 7... positions for measurement, and the selected positions shall not exceed 10. The average value of the measured distances can be used to obtain the distance between the second textured surface 121 and the first textured surface 111 in the thickness direction of the substrate 1.

[0066] In some embodiments of this application, the distance between the first plane 112 and the first textured surface 111 in the thickness direction of the substrate 1 is 0.5μm to 2μm, for example, it can be 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1μm, 1μm, 1.2μm, 1.3μm, 1.4μm, 1.5μm, 1.6μm, 1.7μm, 1.8μm, 1.9μm, or 2μm, but is not limited thereto. The distance between the second textured surface 121 and the first textured surface 111 is 3μm to 10μm, for example, it can be 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm, 9μm, 9.5μm, or 10μm, but is not limited thereto. The spacing between the first plane 112, the first textured surface 111, and the second textured surface 121 in the thickness direction of the substrate 1 is set within the above-mentioned range, which ensures the uniformity of the film layer while providing sufficient space for the setting of the pyramid structure.

[0067] In some embodiments of this application, the first doped layer 21 is a polycrystalline silicon doped layer, and the second doped layer 22 is an amorphous silicon doped layer or a microcrystalline silicon doped layer. The back contact solar cell also includes a tunneling oxide layer 41 and an amorphous silicon layer 42. The tunneling oxide layer 41 is located at least between the substrate 1 and the first doped layer 21, and the amorphous silicon layer 42 is located between the substrate 1 and the second doped layer 22. The tunneling oxide layer 41 can be, for example, silicon oxide (SiOx). Its working principle is as follows: the tunneling oxide layer 41 provides a tunnel barrier for electrons, allowing electrons to reach the substrate 1 through the tunneling oxide layer 41 in a quantum tunneling manner. This helps to optimize charge transport, improve charge collection efficiency, and the tunneling oxide layer 41 can also reduce surface recombination and improve the lifetime of charge carriers through passivation. Therefore, the tunneling oxide layer 41 typically needs to have a very small thickness. The tunneling oxide layer 41 is disposed on the first textured surface 111 with a relatively small undulation, contacting the small-sized first pyramid structure, resulting in a tighter contact between the tunneling oxide layer 41 and the first textured surface 111, thereby improving the passivation effect of the first region 11. A portion of the tunneling oxide layer 41 is also located on the first plane 112, making the tunneling oxide layer 41 a first plane in this region, resulting in higher thickness uniformity. Since charge carriers are mainly transported from the substrate 1 to the first electrode 31 in this region, the fact that the tunneling oxide layer 41 is a first plane in this region ensures the uniformity of current transmission.

[0068] The amorphous silicon layer 42 can have a relatively larger thickness to ensure passivation effect and transmission efficiency. Since the amorphous silicon layer 42 is relatively thick, even if its growth surface (second region 12) is textured, the impact on the thickness uniformity of the amorphous silicon layer 42 is within an acceptable error range. Therefore, the second region 12 can all be textured.

[0069] In some embodiments of this application, the back contact solar cell further includes a transparent conductive layer 5, which includes a first conductive portion 51 and a second conductive portion 52. The first conductive portion 51 is located between the first doped layer 21 and the first electrode 31, and the first conductive portion 51 is in contact with the first electrode 31 with a planar contact surface. The second conductive portion 52 is located between the second doped layer 22 and the second electrode 32, and the second conductive portion 52 is in contact with the second electrode 32 with a textured contact surface.

[0070] The morphology of the surface of the transparent conductive layer 5 facing away from the substrate 1 is consistent with the surface morphology of the second side of the substrate 1, making the area where the first electrode 31 is located planar. This ensures that the current in this area is uniformly transmitted through the planar tunneling oxide layer 41, the first doped layer 21, and the first conductive part 51. The surface of the transparent conductive layer 5 facing away from the substrate 1 is textured in other areas. Combined with the back reflection function of the transparent conductive layer 5 itself, it helps to further improve the back reflection function of the back contact solar cell and improve the photoelectric conversion efficiency.

[0071] In some embodiments of this application, the thickness of the first conductive portion 51 is greater than the thickness of the second conductive portion 52, thereby adapting to the mobility difference caused by the difference in carrier type between the N-type first doped layer and the P-type second doped layer, and improving conductivity efficiency. In practical applications, it is also possible that the undulation degree of the first textured surface 111 is less than that of the second textured surface 121, resulting in the thickness of the first conductive portion 51 being greater than the thickness of the second conductive portion 52 when growing the transparent conductive layer 5.

[0072] Figure 3 This is a schematic diagram of another back-contact solar cell provided according to an embodiment of this application, as shown below. Figure 3 As shown, the second region 12 may further include a second plane 122, in which the second electrode 32 at least partially overlaps with the second plane 122 in the thickness direction of the substrate 1. By setting the region corresponding to the second electrode 32 as a plane, it is beneficial to improve the thickness uniformity of each film layer in this region, such as the thickness uniformity of the amorphous silicon layer 42, the second doped layer 22, and the second conductive portion 52, thereby improving the uniformity of current transmission and optimizing the electrical performance of the battery.

[0073] The above-mentioned overlap of the second electrode 32 and the second plane 122 at least partially means that the second electrode 32 is disposed on the second plane 122 and overlaps with the second plane 122 in the thickness direction of the substrate 1. However, in actual preparation, due to process errors, some parts of the second electrode 32 may be formed outside the range corresponding to the second plane 122. For example, when the second electrode 32 is formed by screen printing, a small part of the paste may be printed outside the second plane 122 due to process errors, resulting in a partially non-overlapping area between the second electrode 32 and the second plane 122 in the thickness direction of the substrate 1. However, this area only accounts for a small part of the second electrode 32.

[0074] Figure 4 This application provides a method for fabricating a back-contact solar cell according to an embodiment of the present application, such as... Figure 4 As shown in the embodiments of this application, the method for fabricating a back-contact solar cell includes the following steps S1 to S5:

[0075] Step S1: A first textured surface 111 and a first plane 112 are formed in the first region 11 of the second surface of the substrate 1, wherein, in the thickness direction of the substrate 1, the distance between the first plane 112 and the first surface of the substrate 1 is greater than the distance between the first textured surface 111 and the first surface of the substrate 1.

[0076] Step S2: Form a first doped layer 21 on the first region 11;

[0077] Step S3: A second textured surface 121 is formed in the second region 12 of the second surface of the substrate 1, wherein the first region 11 and the second region 12 are arranged alternately;

[0078] Step S4: A second doped layer 22 is formed on the second region 12, wherein the doping type of the second doped layer 22 is different from that of the first doped layer 21;

[0079] Step S5: A first electrode 31 is formed on the side of the first doped layer 21 away from the substrate 1, and a second electrode 32 is formed on the side of the second doped layer 22 away from the substrate 1, wherein the first electrode 31 is electrically connected to the first doped layer 21, and the second electrode 32 is electrically connected to the second doped layer 22.

[0080] Through the above preparation method, at least in the area where the first electrode 31 is set, the film layers between the first electrode 31 and the substrate 1 can have good uniformity, thereby ensuring the uniformity of current transmission.

[0081] In some embodiments of this application, step S1, namely the step of forming a first textured surface 111 and a first flat surface 112 in the first region 11 of the second surface of the substrate 1, may include the following steps S11 to S13:

[0082] Step S11: A mask layer is formed on the second surface of the substrate 1, and the mask layer exposes a designated area in the first region 11;

[0083] Step S12: Form the first velvet surface 111 in the designated area;

[0084] Step S13: Remove the mask layer to expose the first plane 112.

[0085] The process of forming the first plane 112 using a mask layer is simple and has little impact on existing processes. It avoids introducing other variables during the preparation process, such as avoiding damage or impurities caused by the process steps of first texturing the whole and then polishing or removing the texturing surface of the area corresponding to the first plane 112. This is beneficial for controlling costs and achieving mass production.

[0086] In some embodiments of this application, step S12, which is to form a first textured surface 111 in a designated area, includes: etching the designated area to form a plurality of first pyramid structures in the designated area; step S3, which is to form a second textured surface 121 in a second region 12 on a second surface of the substrate 1, includes: etching the second region 12 to form a plurality of second pyramid structures in the second region 12; wherein the first pyramid structure and the second pyramid structure satisfy at least one of the following: the base width of the first pyramid structure is smaller than the base width of the second pyramid structure, and the height of the first pyramid structure is smaller than the height of the second pyramid structure, thereby controlling the undulation of the first textured surface 111 to be lower.

[0087] In some embodiments of this application, a first solution can be used to etch a set region, and a second solution can be used to etch a second region 12. The first solution and the second solution have the same composition, and the time for etching the set region with the first solution is less than the time for etching the second region 12 with the second solution, thereby forming a first pyramid structure and a second pyramid structure of different sizes. The same solution is used, and the preparation is carried out by controlling the reaction time, which avoids the additional costs and operational complexity caused by solution switching, and also eliminates the chemical compatibility problems that may be caused between different solutions.

[0088] In some embodiments of this application, the mask layer described above may also cover the area in the second region 12 used to set the second electrode 32, exposing other areas in the second region 12. This allows a second plane 122 to be formed in the second region 12 during subsequent texturing of the second region 12, thereby further optimizing the back structure of the battery while avoiding major changes to the process and reducing costs.

[0089] Based on the same concept, embodiments of this application also provide a tandem solar cell. Figure 5 This is a schematic diagram of a stacked battery structure according to an embodiment of this application. Figure 6 This is a schematic diagram of another stacked battery structure provided according to an embodiment of this application. Figure 7 This is a schematic diagram of another stacked battery structure provided according to an embodiment of this application. Figures 5-7 As shown, the tandem solar cell includes a perovskite cell 400 and a back-contact solar cell 500. The back-contact solar cell 500 is the back-contact solar cell in any of the above embodiments. The perovskite cell 400 is located on the light-incident side of the back-contact solar cell 500, that is, the perovskite cell 400 is stacked on the back-contact solar cell 500.

[0090] In one embodiment of this application, such as Figure 5 As shown, the stacked battery is a four-terminal stacked battery. In this stacked battery, the first electrode of the back-contact solar cell 500 and the first electrode of the perovskite cell 400 serve as two electrode terminals of the stacked battery, and the second electrode of the back-contact solar cell 500 and the second electrode of the perovskite cell 400 serve as the other two electrode terminals of the stacked battery.

[0091] In another embodiment of this application, such as Figure 6As shown, the tandem battery is a three-terminal tandem battery. In this tandem battery, the back-contact solar cell 500 serves as the bottom cell, and the perovskite cell 400 serves as the top cell. The top cell and the bottom cell can be connected by directly depositing the perovskite cell 400 on the surface of the back-contact solar cell 500. Figure 6 As shown, in this tandem battery, the first and second electrodes of the back-contact solar cell serve as the two electrode terminals of the tandem battery, and one electrode of the perovskite cell 400 serves as the other electrode terminal of the tandem battery.

[0092] In another embodiment of this application, such as Figure 7 As shown, the stacked battery is a two-terminal stacked battery. In this stacked battery, the first electrode of the back-contact solar cell 500 and the first electrode of the perovskite cell 400 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.

[0093] In the aforementioned tandem solar cells, perovskite solar cells and back-contact solar cells can be mechanically stacked. In this case, the perovskite solar cells and back-contact solar cells can be connected to independent circuits without considering current matching issues. The stacking arrangement primarily saves space. Perovskite solar cells and back-contact solar cells can also be electrically connected. In this case, a conductive intermediate connection layer, such as a tunneling layer, can be provided between the perovskite solar cells and the back-contact solar cells. The tunneling effect enables carrier transport, thereby reducing the number of connection points to external circuits and simplifying the structure. The specific connection method of the perovskite solar cells and back-contact solar cells can be set according to actual needs, and this application does not limit it.

[0094] Perovskite materials, with their high absorption coefficient, wide bandgap, and tunability, excel in absorbing short-wavelength visible light, while back-contact solar cells are adept at handling long-wavelength and infrared light. This stacked configuration effectively broadens the cell's absorption range of the solar spectrum, achieving highly efficient light capture and conversion. After spectrally selective transmission through the perovskite layer, the remaining long-wavelength and infrared light portions can effectively penetrate to the absorption layer of the back-contact solar cell, where they are further absorbed and converted into electrical energy. The special structural design of the back-contact cell, including the first and second pyramid structures and optimized back-side morphology, not only improves the absorption and utilization rate of this portion of the spectrum but also ensures efficient charge transport within the cell, reducing charge loss during transport and improving the overall photoelectric conversion efficiency of the system.

[0095] Based on the same concept, this application also provides a photovoltaic module. Figure 8This is a schematic diagram of the structure of a photovoltaic module according to an embodiment of this application, as shown below. Figure 8 As shown, the photovoltaic module includes a cell string, an encapsulating film 200, and a cover plate 300.

[0096] The battery string is composed of multiple solar cells 100 connected together. The solar cells 100 are back-contact solar cells as described in the above embodiments, or back-contact solar cells prepared by the above-described method, or tandem solar cells as described above. The connection method can be series, parallel, or a combination of series and parallel connections, and is not limited here. Using the aforementioned solar cells 100 can improve the photovoltaic module's ability to cope with abnormal operating conditions and enhance its reliability.

[0097] The encapsulating film 200 is used to cover the surface of the battery string, isolating the solar cell 100 from the external environment and preventing water vapor and oxygen from corroding the solar cell, thereby improving the reliability of the module and extending its service life. The encapsulating film 200 can be made of, but is not limited to, ethylene-vinyl acetate copolymer (EVA) film, polyolefin elastomer (POE) film, etc.

[0098] The cover plate 300 is located on the surface of the encapsulating film facing away from the solar cell module. It can be used to protect its internal structure and improve reliability. The cover plate 300 can be made of materials with high hardness and good light transmittance, such as glass, so as to provide protection for the solar cell 100 while allowing as much light as possible to enter the solar cell 100 and be utilized.

[0099] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0100] 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: The base includes a first surface and a second surface disposed opposite to each other. The second surface includes alternating first regions and second regions. The first region includes a first velvet surface and a first plane. In the thickness direction of the base, the first plane protrudes from the side opposite to the first surface relative to the first velvet surface. The second region includes a second velvet surface. The first velvet surface includes a plurality of first pyramid structures. The second velvet surface includes a plurality of second pyramid structures. The height of the first pyramid structure in the first velvet surface is less than the height of the second pyramid structure in the second velvet surface. A first doped layer is disposed on the first textured surface and the first plane, wherein the first doped layer is a polycrystalline silicon doped layer; A first electrode is electrically connected to the first doped layer, and in the thickness direction of the substrate, the first electrode at least partially overlaps with the first plane; A second doped layer is disposed on the second region. The doping type of the second doped layer is different from that of the first doped layer. The second doped layer is an amorphous silicon doped layer, a microcrystalline silicon doped layer, or a nanocrystalline silicon doped layer. The second electrode is electrically connected to the second doped layer.

2. The back-contact solar cell according to claim 1, characterized in that, The base width of the first pyramid structure in the first velvet surface is smaller than the base width of the second pyramid structure in the second velvet surface.

3. The back-contact solar cell according to claim 1, characterized in that, The base width of the first pyramid structure is 0.2μm~1μm; The base width of the second pyramid structure is 2μm~4μm.

4. The back-contact solar cell according to claim 1, characterized in that, In the thickness direction of the substrate, the distance between the first plane and the first nap is less than the distance between the second nap and the first nap.

5. The back-contact solar cell according to claim 4, characterized in that, In the thickness direction of the substrate, the distance between the first plane and the first velvet surface is 0.5μm~2μm, and the distance between the second velvet surface and the first velvet surface is 3μm~10μm.

6. The back-contact solar cell according to claim 1, characterized in that, The back-contact solar cell also includes: A tunneling oxide layer is located between the substrate and the first doped layer; An amorphous silicon layer is located between the substrate and the second doped layer.

7. The back-contact solar cell according to claim 1, characterized in that, The back-contact solar cell further includes a transparent conductive layer, which comprises: A first conductive portion is located between the first doped layer and the first electrode; The second conductive portion is located between the second doped layer and the second electrode; The thickness of the first conductive part is greater than the thickness of the second conductive part.

8. The back-contact solar cell according to claim 1, characterized in that, The second region also includes a second plane, in which the second electrode at least partially overlaps with the second plane in the thickness direction of the substrate.

9. A method for fabricating a back-contact solar cell, wherein the method is used to fabricate a back-contact solar cell as described in any one of claims 1 to 8, characterized in that, include: The first velvet surface and the first plane are formed in a first region on the second surface of the substrate; The first doped layer is formed on the first region; The second velvet surface is formed in the second region on the second side of the substrate; The second doped layer is formed on the second region; The first electrode is formed on the side of the first doped layer opposite to the substrate, and the second electrode is formed on the side of the second doped layer opposite to the substrate.

10. The method for preparing a back-contact solar cell according to claim 9, characterized in that, The first textured surface and the first flat surface are formed in a first region on the second surface of the substrate, including: A mask layer is formed on the second surface of the substrate, the mask layer exposing a designated area in the first region; The first velvet surface is formed in the designated area; Remove the mask layer to expose the first plane.

11. The method for fabricating a back-contact solar cell according to claim 10, characterized in that, Forming the first textured surface in the designated area includes: etching the designated area to form a plurality of first pyramid structures in the designated area; Forming a second textured surface in a second region on a second surface of the substrate includes: etching the second region to form a plurality of second pyramid structures within the second region; Wherein, the base width of the first pyramid structure is smaller than the base width of the second pyramid structure, and / or, the height of the first pyramid structure is smaller than the height of the second pyramid structure.

12. The method for fabricating a back-contact solar cell according to claim 11, characterized in that, The designated area is etched with a first solution, and the second area is etched with a second solution. The first solution and the second solution have the same composition, and the time for etching the designated area with the first solution is less than the time for etching the second area with the second solution.

13. A tandem solar cell, characterized in that, include: Perovskite solar cells; The back-contact solar cell prepared by any one of claims 1 to 8 or by any one of claims 9 to 12, wherein the perovskite solar cell is located on the light-incident side of the back-contact solar cell.

14. 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 8, or multiple back-contact solar cells prepared by the method described in any one of claims 9 to 12, or multiple stacked solar cells as described in claim 13. 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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