Solar cell and manufacturing method thereof

Abstract

The embodiment of the invention relates to the photovoltaic field, and provides a solar cell piece and a manufacturing method thereof, the solar cell piece comprises a substrate, the substrate comprises a front surface and a back surface which are opposite, the front surface is provided with a pyramid suede structure, the back surface is provided with a tower footing structure, and the specific surface area of the tower footing structure is smaller than that of the pyramid suede structure; dangling bonds exist in the substrate; the first tunneling layer at least covers part of the back surface, the first tunneling layer is made of a hollow titanium dioxide material, a plurality of transmission gaps exist in the hollow titanium dioxide material, the transmission gaps are used for transmitting carriers and doping ions, and the hollow titanium dioxide material is bonded with dangling bonds in the substrate; the second tunneling layer covers the surface of the first tunneling layer; the doped conductive layer covers the surface of the second tunneling layer; the passivation layer covers the surface of the doped conductive layer; the back electrode is electrically connected with the doped conductive layer. The photoelectric conversion efficiency of the solar cell can be improved.

Description

Technical Field

[0001] The present disclosure relates to the field of photovoltaics, and particularly to a solar cell and a method for manufacturing the same. Background Art

[0002] Photovoltaic power generation refers to the conversion of solar energy into electrical energy through the photovoltaic effect of semiconductors. For example, TOPCON (Tunnel Oxide Passivated Contact) cells have received increasing attention due to their good photoelectric conversion performance.

[0003] TOPCON cells are a type of tunnel oxide passivated contact solar cell technology based on the principle of selective carriers. In TOPCON solar cells, a passivated contact structure is formed on the surface of the substrate to achieve selective transport of carriers.

[0004] Currently, it is necessary to improve the performance of solar cells. Summary of the Invention

[0005] Embodiments of the present disclosure provide a solar cell and a method for manufacturing the same, which can at least improve the photoelectric conversion efficiency of the solar cell.

[0006] According to some embodiments of the present disclosure, on the one hand, an embodiment of the present disclosure provides a solar cell, including: a substrate, the substrate includes opposite front and back surfaces, the front surface has a pyramid texture structure, the back surface has a tower base structure, the specific surface area of the tower base structure is smaller than the specific surface area of the pyramid texture structure, and there are dangling bonds in the substrate; a first tunneling layer, the first tunneling layer at least covers part of the back surface, the material of the first tunneling layer is hollow titanium dioxide material, there are a plurality of transmission gaps in the hollow titanium dioxide material, the transmission gaps are used for transmitting carriers and doping ions, and the hollow titanium dioxide material is bonded to the dangling bonds in the substrate; a second tunneling layer, the second tunneling layer covers the surface of the first tunneling layer; a doped conductive layer, the doped conductive layer covers the surface of the second tunneling layer; a passivation layer, the passivation layer covers the surface of the doped conductive layer; a back electrode, the back electrode is electrically connected to the doped conductive layer.

[0007] In some embodiments, the tower base structure includes: a tower top and a side surface extending from the tower top towards the back surface of the substrate, and the density of the first tunneling layer covering the surface of the tower top is greater than the density of the first tunneling layer covering the side surface.

[0008] In some embodiments, the specific surface area of the tower base structure is 1.01 - 1.04.

[0009] In some embodiments, the thickness of the first tunneling layer is within 3 nm.

[0010] In some embodiments, the substrate includes alternately arranged first regions and second regions. The orthographic projection of the first tunneling layer on the surface of the substrate is located in the first regions, and the orthographic projection of the back electrode on the surface of the substrate is located in the second regions.

[0011] In some embodiments, the specific surface area of the tower base structure located in the second regions is larger than that of the tower base structure located in the first regions.

[0012] In some embodiments, the orthographic projection of the second tunneling layer on the surface of the substrate is also located in the second regions.

[0013] In some embodiments, the doping ions contained in the doped conductive layer are also embedded in the transmission gap.

[0014] According to some embodiments of the present disclosure, on the other hand, the present disclosure also provides a method for manufacturing a solar cell, including: providing a substrate, the substrate includes opposite front and back surfaces, the front surface has a pyramid texture structure, the back surface has a tower base structure, the specific surface area of the tower base structure is larger than that of the pyramid texture structure, and there are dangling bonds in the substrate; forming a first tunneling layer, the first tunneling layer at least covers part of the back surface, the material of the first tunneling layer is a hollow titanium dioxide material, there are a plurality of transmission gaps in the hollow titanium dioxide material, the transmission gaps are used for transmitting carriers and doping ions, and the hollow titanium dioxide material is bonded to the dangling bonds in the substrate; forming a second tunneling layer, the second tunneling layer covers the surface of the first tunneling layer; forming a doped conductive layer, the doped conductive layer covers the surface of the second tunneling layer; forming a passivation layer, the passivation layer covers the surface of the doped conductive layer; forming a back electrode, the back electrode is electrically connected to the doped conductive layer.

[0015] In some embodiments, the method for forming the doped conductive layer includes: forming a polysilicon layer on the surface of the second tunneling layer, and then converting the polysilicon layer into the doped conductive layer by means of high-temperature diffusion; during the high-temperature diffusion process, the first tunneling layer is also subjected to crystallization treatment.

[0016] The technical solutions provided by the embodiments of the present disclosure have at least the following advantages: on the one hand, a tower base structure with a smaller specific surface area is arranged on the back surface, thereby improving the flatness of the back surface of the substrate. A flatter back surface is more suitable for the deposition of hollow titanium dioxide materials, and thus can cooperate with the first tunneling layer to improve the density and uniformity of the first tunneling layer; on the other hand, the hollow titanium dioxide material can increase the light incident into the substrate, improve the photoelectric conversion efficiency of the solar cell, and moreover, the bonding of the hollow titanium dioxide material with the dangling bonds in the substrate can passivate the surface of the substrate, thereby reducing the recombination of carriers in the substrate and improving the photoelectric conversion efficiency of the solar cell. Description of the Drawings

[0017] One or more embodiments are exemplarily illustrated by the pictures in the corresponding drawings. These exemplary illustrations do not limit the embodiments unless otherwise stated. The figures in the drawings do not constitute a proportional limitation; in order to more clearly illustrate the technical solutions in the embodiments of the present disclosure or in the conventional technology, the drawings required to be used in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present disclosure. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0018] Figure 1 It is a cross-sectional view of a solar cell provided by an embodiment of the present disclosure; Figure 2 It is a top view of a first tunneling layer provided by an embodiment of the present disclosure; Figure 3 It is a cross-sectional view of a solar cell provided by another embodiment of the present disclosure; Figure 4 It is a cross-sectional view of a solar cell provided by still another embodiment of the present disclosure; Figure 5 It is an enlarged structural schematic diagram of a solar cell provided by an embodiment of the present disclosure; Figure 6 It is a flowchart of a manufacturing method of a solar cell provided by an embodiment of the present disclosure.

[0019] Description of the Reference Numerals: 100, substrate; 110, front surface; 120, back surface; 130, pyramid texture structure; 140, tower base structure; 101, first tunneling layer; 111, transmission gap; 102, doped conductive layer; 103, passivation layer; 104, back electrode; 105, emitter; 106, second passivation layer; 107, front electrode; 108, second tunneling layer.

[0020] 200. Substrate; 210. Front surface; 220. Back surface; 230. Pyramidal suede structure; 240. Tower base structure; 201. First tunneling layer; 202. Doped conductive layer; 203. Passivation layer; 204. Back electrode; 205. Emitter; 206. Second passivation layer; 207. Front electrode; 208. Second tunneling layer.

[0021] 300. Substrate; 310. Front surface; 320. Back surface; 330. Pyramidal suede structure; 340. Tower base structure; 301. First tunneling layer; 302. Doped conductive layer; 303. Passivation layer; 304. Back electrode; 305. Emitter; 306. Second passivation layer; 307. Front electrode; 308. Second tunneling layer. Detailed implementation manners

[0022] As can be seen from the background art, it is necessary to improve the photoelectric conversion efficiency of solar cell wafers at present.

[0023] An embodiment of the present disclosure provides a solar cell wafer. On the one hand, a tower base structure with a smaller specific surface area is arranged on the back surface, thereby improving the flatness of the back surface of the substrate. A flatter back surface is more suitable for the deposition of hollow titanium dioxide materials, so that it can cooperate with the first tunneling layer to improve the density and uniformity of the first tunneling layer; on the other hand, the hollow titanium dioxide material can increase the light incident into the substrate, improve the photoelectric conversion efficiency of the solar cell wafer, and moreover, the bonding of the hollow titanium dioxide material with the dangling bonds in the substrate can passivate the surface of the substrate, thereby reducing the recombination of carriers in the substrate and improving the photoelectric conversion efficiency of the solar cell wafer.

[0024] In the description of the embodiments of the present disclosure, technical terms such as "first" and "second" are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order or primary-secondary relationship of the indicated technical features. In the description of the embodiments of the present disclosure, "a plurality" means more than two, unless otherwise specifically and clearly defined.

[0025] Referring to "embodiments" herein means that the specific features, structures or characteristics described in connection with the embodiments may be included in at least one embodiment of the present disclosure. The phrase appears in various places in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0026] In the description of the embodiments of the present disclosure, the term "and / or" is merely a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: the existence of A, the simultaneous existence of A and B, and the existence of B. In addition, the character " / " in this article generally represents an "or" relationship between the associated objects before and after.

[0027] In the description of the embodiments of the present disclosure, the term "plurality" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0028] In the description of the embodiments of the present disclosure, the orientation or positional relationship indicated by technical terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the embodiments of the present disclosure and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present disclosure.

[0029] In the description of the embodiments of the present disclosure, unless otherwise clearly specified and limited, technical terms such as "installation", "connection", "connection", "fixation", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can also be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and can be the communication inside two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present disclosure can be understood according to specific circumstances.

[0030] In the corresponding drawings of the embodiments of the present disclosure, for better understanding and convenience of description, the thickness and area of the layer are enlarged. When describing a component (such as a layer, film, region, or substrate) on or on the surface of another component, the component can be "directly" on the surface of the other component, or there can be a third component between the two components. On the contrary, when describing a component on the surface of another component or when a surface of a component forms or is provided with another component, it means that there is no third component between the two components. In addition, when describing a component "substantially" formed on another component, it means that the component is not formed on the entire surface (or front surface) of the other component, nor on a partial edge of the entire surface.

[0031] In the description of the embodiments of the present disclosure, when a component "includes" another component, unless otherwise specified, other components are not excluded, and other components may be further included. In addition, when a component such as a layer, film, region, or plate is referred to as being "on / located on" another component, it may 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 exist in between. In addition, 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 means that no other components are located in between.

[0032] The terms used in the description of the various embodiments described herein are only used to describe specific embodiments and are not intended to be limiting. As used in the description of the various embodiments described and in the appended claims, "the components" are also intended to include plural forms unless the context clearly indicates otherwise. Among them, components include components such as layers, films, regions, or plates.

[0033] The following will describe the various embodiments of the present disclosure in detail with reference to the accompanying drawings. However, it will be appreciated by those skilled in the art that in the various embodiments of the present disclosure, many technical details are provided in order to enable the reader to better understand the present disclosure. However, even without these technical details and various changes and modifications based on the following embodiments, the technical solutions claimed in the present disclosure can be implemented.

[0034] refer to Figure 1 , Figure 2 and Figure 5 ,in, Figure 1 A cross-sectional view of a solar cell provided in accordance with an embodiment of the present disclosure; Figure 2 A top view of a first tunneling layer provided in one embodiment of the present disclosure; Figure 5 An enlarged schematic diagram of the structure of a substrate surface provided in one embodiment of the present disclosure.

[0035] In some embodiments, the solar cell may include: a substrate 100, the substrate 100 includes a relative front side 110 and a back side 120, the front side 110 has a pyramid velvet structure 130, the back side 120 has a tower base structure 140, the specific surface area of ​​the tower base structure 140 is smaller than the specific surface area of ​​the pyramid velvet structure 130, and there are hanging bonds in the substrate 100.

[0036] The solar cell may further include: a first tunneling layer 101, the first tunneling layer 101 at least covers a portion of the back side 120, the material of the first tunneling layer 101 is a hollow titanium dioxide material, there are a plurality of transmission gaps 111 in the hollow titanium dioxide material, the transmission gaps 111 are used to transmit carriers and doped ions, and the hollow titanium dioxide material is bonded to the dangling bonds in the substrate 100.

[0037] The solar cell may further include: a second tunneling layer 108, and the second tunneling layer 108 covers the surface of the first tunneling layer 101.

[0038] The solar cell may further include: a doped conductive layer 102, and the doped conductive layer 102 covers the surface of the second tunneling layer 108.

[0039] The solar cell may further include: a passivation layer 103, and the passivation layer 103 covers the surface of the doped conductive layer 102.

[0040] The solar cell may further include: a back electrode 104, and the back electrode 104 is electrically connected to the doped conductive layer 102.

[0041] An embodiment of the present disclosure provides a solar cell. On the one hand, a tower base structure 140 with a smaller specific surface area is provided on the back surface 120, thereby improving the flatness of the back surface 120 of the substrate 100. The flatter back surface 120 is more suitable for the deposition of the hollow titanium dioxide material, so that it can cooperate with the first tunneling layer 101 to improve the density and uniformity of the first tunneling layer 101. On the other hand, the hollow titanium dioxide material can increase the light incident on the substrate 100, improve the photoelectric conversion efficiency of the solar cell, and the bonding of the hollow titanium dioxide material with the dangling bonds in the substrate 100 can passivate the surface of the substrate 100, thereby reducing the recombination of carriers in the substrate 100 and improving the photoelectric conversion efficiency of the solar cell.

[0042] The substrate 100 has opposite front surface 110 and back surface 120. In some embodiments, the solar cell is a single-sided cell, then the front surface 110 of the substrate 100 can be used as the light-receiving surface for receiving incident light, and the back surface 120 is used as the backlight surface. In some embodiments, the solar cell is a double-sided cell, then both the front surface 110 and the back surface 120 of the substrate 100 can be used as the light-receiving surfaces and can be used for receiving incident light. It can be understood that the backlight surface referred to in the embodiments of the present disclosure can also receive incident light, but the degree of receiving incident light is weaker than that of the light-receiving surface, so it is defined as the backlight surface.

[0043] In some embodiments, a texturing process may be performed on at least one of the front surface 110 or the back surface 120 of the substrate 100 to form a textured surface structure on at least one of the front surface 110 or the back surface 120 of the substrate 100. In this way, the absorption and utilization rate of incident light on the front surface 110 and the back surface 120 of the substrate 100 can be enhanced.

[0044] The pyramid matte structure 130 can be formed on the front surface 110 and the back surface 120 of the substrate 100 simultaneously first, and then the pyramid matte structure 130 on the back surface 120 of the substrate 100 is processed to form the tower base structure 140. By forming the tower base structure 140, the roughness of the back surface 120 can be reduced, facilitating the deposition of hollow titanium dioxide. It can be understood that if the hollow titanium dioxide material is directly deposited on the pyramid matte structure 130, the compactness of the formed first tunneling layer 101 will be poor, and the tunneling effect of the first tunneling layer 101 will be poor, affecting the photoelectric conversion efficiency of the solar cell.

[0045] In some embodiments, the specific surface area of the tower base structure 140 is 1.01 - 1.04. It can be understood that the smaller the specific surface area of the tower base structure 140, the higher the flatness of the back surface 120, and the higher the flatness, the more convenient it is for the subsequent formation of the first tunneling layer 101. However, the smaller the specific surface area of the tower base structure 140, the greater the process difficulty of forming the tower base structure 140. Setting the specific surface area of the tower base structure 140 to 1.01 - 1.04 can reduce the process difficulty of forming the tower base structure 140 while facilitating the formation of the first tunneling layer 101.

[0046] It can be understood that the specific surface area here refers to the ratio of the surface area of the tower base structure 140 to the area of the orthographic projection of the tower base structure 140 on the surface of the substrate 100. The surface area of the tower base structure 140 can be calculated by scanning the tower base structure 140 with a scanning electron microscope and integrating. The projected area of the tower base structure 140 can be obtained by scanning the projected pattern of the tower base structure 140 with a scanning microscope and directly calculating the projected area of the tower base structure 140.

[0047] Reference Figure 5 It can be seen that the surface of the tower base structure after treatment is smoother. The edges of the tower base structure surface are of different depths, the edges with darker colors have greater roughness, and the edges with lighter colors have smaller roughness. Figure 5 The edges and boundaries of the tower base structure in [] become less obvious. Thus, it indicates that the back surface of the substrate becomes smoother, facilitating the formation of the first tunneling layer.

[0048] The hollow titanium dioxide material refers to a material with a cavity inside and a titanium dioxide shell. The cavity can be single-layer or multi-layer (such as a core-shell structure). The hollow titanium dioxide material can achieve multiple reflections of ultraviolet and visible light in the internal cavity, thereby increasing the light utilization rate, improving the light absorption ability of the substrate 100, and improving the photoelectric conversion efficiency of the solar cell.

[0049] In some embodiments, the transmission gap 111 does not refer to the cavity of the hollow titanium dioxide material, but refers to the tiny voids in the first tunneling layer 101. The tiny voids in the first tunneling layer 101 are used to transmit the carriers in the substrate 100, thereby completing the transmission of carriers.

[0050] In some embodiments, the size of the transmission gap 111 can be 1 nm to 5 nm, such as 2 nm, 3 nm, or 4 nm, etc. For the first tunneling layer 101, the larger the transmission gap 111, the better the transmission effect of the carriers. However, the larger the transmission gap 111, the uniformity of the first tunneling layer 101 itself will be affected, and the light emission ability of the first tunneling layer 101 will also be affected. Therefore, controlling the size of the transmission gap 111 in the formed first tunneling layer 101 to be 1 nm to 5 nm can improve the photoelectric conversion efficiency of the solar cell while considering the reliability of the first tunneling layer 101 itself.

[0051] In some embodiments, the particle size of the hollow titanium dioxide material is 200 nm to 600 nm, such as 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, or 550 nm, etc. The smaller the particle size of the hollow titanium dioxide material, the higher the density and uniformity of the formed first tunneling layer 101, and the stronger the ability to improve the light reflection ability of the back surface 120 and saturate the dangling bonds in the substrate 100. Similarly, the smaller the particle size of the hollow titanium dioxide material, the higher the process difficulty of forming the hollow titanium dioxide material. Therefore, setting the particle size of the hollow titanium dioxide material to be 200 nm to 600 nm takes into account the process difficulty of forming the solar cell while considering the improvement of the performance of the solar cell by the first tunneling layer 101.

[0052] In some embodiments, the tower base structure 140 includes: a tower top and a side surface extending from the tower top towards the back surface 120 of the substrate 100. The density of the first tunneling layer 101 covering the surface of the tower top is greater than the density of the first tunneling layer 101 covering the side surface. For the hollow titanium dioxide material, it is easier to form on a flatter surface, and the formed first tunneling layer 101 is denser. The denser first tunneling layer 101 will inhibit the carrier recombination of the tower base structure 140, while the side surface of the tower base structure 140 with poor density can facilitate the tunneling of carriers.

[0053] It can be understood that during the process of measuring the density of the first tunneling layer 101, it can be feedback from the side through the corrosion process. For example, after forming the first tunneling layer 101, through corrosion, and always paying attention to whether the corrosion is completed, and the density of different positions can be reflected from the side through the time required for corrosion.

[0054] In some embodiments, the thickness of the first tunneling layer 101 formed on the top of the tower is also greater than that of the first tunneling layer 101 formed on the side. It can be understood that for the back surface 120, the top of the tower is more likely to be in direct contact with the doped conductive layer 102. Therefore, the first tunneling layer 101 on the top of the tower is set to be thicker to reduce carrier recombination at the top of the tower. Moreover, the first tunneling layer 101 on the top of the tower is thicker and the first tunneling layer 101 on the side is thinner. Coupled with the hollow titanium dioxide material, local enhanced tunneling and overall optimized transmission can be achieved.

[0055] In some embodiments, the thickness of the first tunneling layer 101 is within 3 nm, for example, 1 nm, 1.5 nm, 2 nm or 2.5 nm. It can be understood that for the first tunneling layer 101, the greater the thickness of the first tunneling layer 101, the greater the ability of the hollow titanium dioxide material to improve the light reflection ability of the first tunneling layer 101. However, if the thickness of the first tunneling layer 101 is too large, the parasitic absorption phenomenon of the first tunneling layer 101 may increase, which is not conducive to improving the photoelectric conversion efficiency of the solar cell. Therefore, the thickness of the first tunneling layer 101 is set within 3 nm to avoid the parasitic absorption of the first tunneling layer 101 affecting the photoelectric conversion efficiency of the solar cell while considering improving the light absorption ability of the substrate 100.

[0056] The material of the second tunneling layer 108 can be silicon dioxide, aluminum oxide, etc. Taking the material of the second tunneling layer 108 as silicon dioxide as an example, the difference between the silicon dioxide material and the substrate 100 material is small, and the lattice matching degree is high, which will reduce the contact resistance of the metal region, thereby further improving the performance of the solar cell.

[0057] The concentration of the doped ions diffused from the doped conductive layer 102 into the second tunneling layer 108 is greater than the concentration of the doped ions diffused from the doped conductive layer 102 into the first tunneling layer 101.

[0058] By setting the first tunneling layer 101 and the second tunneling layer 108 in cooperation, the reliability of the second tunneling layer 108 can be improved on the premise of the same thickness of the tunneling layer. It can be understood that in the related art, taking the thickness of the tunneling layer as 5 nm as an example, with the formation of the doped conductive layer, the doped ions will enter the substrate through the tunneling layer. Due to the certain thickness of the tunneling layer, some doped ions will remain in the tunneling layer, and the remaining problem will be more serious in the part closer to the substrate, which will cause the doped ions to affect the reliability of the tunneling layer. In the present disclosure, by setting the first tunneling layer 101 and the second tunneling layer 108 in cooperation, the thicknesses of the first tunneling layer 101 and the second tunneling layer 108 can be reduced respectively, and the reliability of the second tunneling layer 108 can be improved. Since the first tunneling layer 101 is made of hollow titanium dioxide material, the doped ions can easily pass through the first tunneling layer 101 and enter the substrate, thereby reducing the influence of the doped ions on the second tunneling layer 108.

[0059] In some embodiments, doping ions contained in the doped conductive layer 102 are also embedded in the transmission gap 111. It can be understood that during the formation of the doped conductive layer 102, some doping ions diffuse into the first tunneling layer 101, resulting in some doping ions being embedded in the transmission gap 111 within the first tunneling layer 101. Thus, the doping ions can be used to capture carriers, facilitating the transmission of carriers.

[0060] The concentration of the doping ions embedded in the transmission gap 111 can be 2E19 Atoms / cm 3 ~5E19 Atoms / cm 3 . If the concentration of the doping ions embedded in the transmission gap 111 is too high, it may affect the carrier recombination ability of the first tunneling layer 101. Therefore, it is necessary to control the concentration of the doping ions in the transmission gap 111 to avoid affecting the performance of the solar cell.

[0061] The doping element concentration in the doped conductive layer 102 can be greater than the doping element concentration of the substrate 100 to form a sufficiently high potential barrier on the back surface 120 of the substrate 100. This potential barrier can induce the bending of the energy band on the back surface 120, realizing the aggregation of majority carriers (also known as majority carriers) and the depletion of minority carriers (also known as minority carriers) on the back surface 120, reducing the carrier recombination on the back surface 120. The first tunneling layer 101 can cause an asymmetric shift in the energy band on the back surface 120, making the potential barrier for majority carriers in the carriers lower than the potential barrier for minority carriers in the carriers. Therefore, the majority carriers can more easily undergo quantum tunneling through the first tunneling layer 101 to be transmitted into the doped conductive layer 102, while the minority carriers are difficult to pass through the first tunneling layer 101, achieving the selective transmission of carriers. In addition, the first tunneling layer 101 also has a chemical passivation effect. Specifically, due to the interface state defects at the interface between the substrate 100 and the first tunneling layer 101, the interface state density on the back surface 120 is relatively large. The increase in the interface state density promotes the recombination of photo-generated carriers, reducing the fill factor, short-circuit current, and open-circuit voltage of the solar cell, and thus resulting in a relatively low photoelectric conversion efficiency of the solar cell.

[0062] The doped conductive layer 102 also has a field passivation effect. Specifically, the doped conductive layer 102 forms an electrostatic field pointing into the substrate 100 on the back surface 120 of the substrate 100, causing the minority carriers to escape from the interface, thereby reducing the minority carrier concentration, decreasing the carrier recombination rate at the interface of the substrate 100, increasing the open-circuit voltage, short-circuit current, and fill factor of the solar cell, and enhancing the photoelectric conversion efficiency of the solar cell.

[0063] The material of the doped conductive layer 102 can include at least one of amorphous silicon, polycrystalline silicon, or silicon carbide.

[0064] The passivation layer 103 can play a good passivation role for the back surface 120 of the substrate 100. For example, it can chemically passivate the dangling bonds on the back surface 120 well, saturate the dangling bonds on the back surface 120, reduce the defect state density of the back surface 120, and inhibit the carrier recombination on the back surface 120.

[0065] The material of the passivation layer 103 can be one of silicon oxide, aluminum oxide, silicon nitride, or silicon oxynitride.

[0066] The passivation layer 103 can be a single-layer structure or a multi-layer structure. For a multi-layer structure, the materials of different layers can be different from each other, or the materials of some layers can be the same and different from the materials of other layers. For example, the passivation layer 103 can be a multi-layer structure of a silicon nitride layer and an aluminum oxide layer.

[0067] The solar cell can further include: a back electrode 104, the back electrode 104 is electrically connected to the doped conductive layer 102, the majority carriers in the substrate 100 tunnel through the first tunneling layer 101 into the doped conductive layer 102, the majority carriers transmitted into the doped conductive layer 102 are then transmitted into the back electrode 104 in electrical contact with the doped conductive layer 102, and are collected by the back electrode 104.

[0068] The solar cell can further include: an emitter 105, the emitter 105 covers the front surface 110 of the substrate 100, the doping element type of the emitter 105 is opposite to the doping element type of the substrate 100, and forms a PN junction with the substrate 100. In some embodiments, the material of the emitter 105 is the same as the material of the substrate 100.

[0069] The solar cell can further include: a second passivation layer 106, the second passivation layer 106 is located on the surface of the emitter 105 away from the substrate 100, plays a good passivation role for the front surface 110 of the substrate 100, reduces the defect state density of the front surface 110 of the substrate 100, and preferably inhibits the carrier recombination on the front surface 110 of the substrate 100. The second passivation layer 106 can also achieve a good antireflection effect, reduce the reflection of the incident light by the front surface 110 of the substrate 100, and improve the utilization rate of the incident light by the substrate 100.

[0070] The material of the second passivation layer 106 can be at least one of silicon oxide, aluminum oxide, silicon nitride, or silicon oxynitride.

[0071] In some embodiments, the second passivation layer 106 can be a single-layer structure. In some embodiments, the second passivation layer 106 can also be a multi-layer structure, and the materials of the layers in the multi-layer structure can be different from each other, or the materials of some layers can be different from each other, and the materials of the remaining layers can be the same. For example, the second passivation layer 106 can be a multi-layer structure of a silicon nitride layer and an aluminum oxide layer.

[0072] The solar cell may further include: a front electrode 107, which is electrically connected to the emitter 105 and is used to collect carriers.

[0073] Through testing, it is found in the embodiments of the present disclosure that the photoelectric conversion efficiency of the solar cell is increased by 0.05 - 0.10%, the Isc (short-circuit current) is increased by 30 mA, the bifaciality is increased by 3%, the dark saturation current density (J0) is decreased, and the short-wavelength light reflection ability of the back surface 120 is significantly improved. The bifaciality refers to the ratio of the power generation ability of the back surface 120 to that of the front surface 110 under standard test conditions (STC).

[0074] On the one hand, in the embodiments of the present disclosure, a tower base structure 140 with a smaller specific surface area is provided on the back surface 120, thereby improving the flatness of the back surface 120 of the substrate 100. A flatter back surface 120 is more suitable for the deposition of the hollow titanium dioxide material, and thus can cooperate with the first tunneling layer 101 to improve the density and uniformity of the first tunneling layer 101; on the other hand, the hollow titanium dioxide material can increase the light incident into the substrate 100, improve the photoelectric conversion efficiency of the solar cell, and moreover, the bonding of the hollow titanium dioxide material with the dangling bonds in the substrate 100 can passivate the surface of the substrate 100, thereby reducing the recombination of carriers in the substrate 100 and improving the photoelectric conversion efficiency of the solar cell.

[0075] On the other hand, in this embodiment, the first tunneling layer 101 covers the entire back surface 120, which is convenient for the manufacturing process of the entire solar cell and can maximize the performance of the hollow titanium dioxide material, thereby further passivating the substrate 100.

[0076] Another embodiment of the present disclosure also provides another solar cell. Different from the above embodiment, the structural morphologies of the first tunneling layer and the second tunneling layer are different. The solar cell in another embodiment of the present disclosure will be described below with reference to the accompanying drawings. The same or corresponding parts as those in the above embodiment can refer to the above embodiment and will not be described in detail below.

[0077] Refer to Figure 3 , Figure 3 which is a schematic structural diagram of another solar cell provided by another embodiment of the present disclosure.

[0078] In some embodiments, the substrate 200 includes alternately arranged first regions and second regions. The orthographic projection of the first tunneling layer 201 on the surface of the substrate 200 is located in the first region, and the orthographic projection of the back electrode 204 on the surface of the substrate 200 is located in the second region. In other words, the first region is the non-metal region, and the second region is the metal region. The back electrode 204 is formed at the corresponding position of the metal region. The first tunneling layer 201 only covers the surface of the non-metal region. It can be understood that during the formation of the back electrode 204, there may be a situation where the back electrode 204 penetrates through the doped conductive layer 202 and contacts the first tunneling layer 201, which will damage the passivation effect. Moreover, the resistance value of the hollow titanium dioxide material is relatively large, which may increase the contact resistance of the metal region and is not conducive to the transport of carriers in the solar cell.

[0079] In some embodiments, the specific surface area of the tower base structure 240 located in the second region is larger than the specific surface area of the tower base structure 240 located in the first region. In other words, the specific surface area of the tower base structure 240 in the metal region is larger than the specific surface area of the tower base structure 240 in the non-metal region. Setting the specific surface area of the tower base structure 240 in the metal region to be larger can facilitate the transport of carriers at the corresponding position in the metal region.

[0080] It can be understood that the formation process of the tower base structure 240 is as follows: First, a pyramid texture structure 230 is formed on the back surface 220, and then the pyramid texture structure 230 is etched to form the tower base structure 240. For the tower base structure 240 in the metal region, a thin layer of protective layer can be formed at the corresponding position in the metal region. Then, during the formation of the tower base structure 240, the protective layer at the corresponding position in the metal region will be etched first, and then the pyramid texture structure 230 will be etched, while the tower base structure 240 in the non-metal region will directly etch the pyramid texture structure 230, so that two tower base structures 240 with different morphologies will be formed on the back surface 220.

[0081] In some embodiments, the specific surface area of the tower base structure 240 in the metal region can be 1.03 - 1.05, and the specific surface area of the tower base structure 240 in the non-metal region can be 1 - 1.03. Since the first tunneling layer is not formed in the metal region, the specific surface area of the tower base structure 240 in the metal region can be increased to facilitate the increase of the contact area between the doped conductive layer 202 and the substrate 200, which can facilitate the transport of carriers.

[0082] In this embodiment, both the first tunneling layer 201 and the second tunneling layer 208 only cover the first region. That is to say, the doped conductive layer 202 is in direct contact with the substrate 200 to directly collect the carriers in the substrate 200 through the doped conductive layer 202, which can reduce the obstruction of the first tunneling layer 201 and the second tunneling layer 208 to the carrier collection and improve the efficiency of carrier transport.

[0083] It should be noted that the front surface 210, the passivation layer 203, the emitter 205, the second passivation layer 206, and the front electrode 207 in this embodiment correspond one by one to the front surface 110, the passivation layer 103, the emitter 105, the second passivation layer 106, and the front electrode 107 in the above embodiment, and will not be elaborated here.

[0084] Another embodiment of the present disclosure further provides a solar cell. Different from the above embodiment, the structural morphologies of the first tunneling layer and the second tunneling layer are different. Hereinafter, the solar cell in another embodiment of the present disclosure will be described with reference to the accompanying drawings. The same or corresponding parts as those in the above embodiment can refer to the above embodiment and will not be elaborated hereinafter.

[0085] Reference Figure 4 , Figure 4 is a schematic structural diagram of a solar cell provided by another embodiment of the present disclosure.

[0086] Reference Figure 4 , in some embodiments, the solar cell further includes: the positive projection of the second tunneling layer 308 on the surface of the substrate 300 also coincides with the positive projection of the back electrode 304 on the surface of the substrate 300. The second tunneling layer 308 cooperates with the first tunneling layer 301 to increase the light absorption capacity of the substrate 300 by using the first tunneling layer 301 and reduce the contact resistance of the metal region by using the second tunneling layer 308, thereby further improving the performance of the solar cell.

[0087] In other words, the thickness of the second tunneling layer 308 in the second region is greater than the thickness of the second tunneling layer 308 in the first region.

[0088] In this embodiment, the first tunneling layer 301 only covers the first region, and the second tunneling layer 308 covers the first region and the second region. Due to the characteristics of the hollow titanium dioxide material, the tunneling performance of the hollow titanium dioxide material is weaker than that of the second tunneling layer 308, and the insulating performance of the hollow titanium dioxide material is stronger, which may affect the ability of the back electrode 304 to collect carriers. Controlling the first tunneling layer 301 to only cover the non-metal region can improve the passivation effect of the first tunneling layer 301 on the substrate 300 and the light absorption capacity of the substrate 300 while avoiding affecting the carrier transport of the solar cell, and can further improve the performance of the solar cell.

[0089] It should be noted that the front surface 310, the back surface 320, the doped conductive layer 302, the passivation layer 303, the emitter 305, the second passivation layer 306, and the front electrode 307 in this embodiment correspond one by one to the front surface 110, the back surface 120, the doped conductive layer 102, the passivation layer 103, the emitter 105, the second passivation layer 106, and the front electrode 107 in the above embodiment, and will not be elaborated here.

[0090] Another embodiment of the present disclosure further provides a method for manufacturing a solar cell, which can be used to form the above-mentioned solar cell. The method for manufacturing the solar cell provided by another embodiment of the present disclosure will be described below with reference to the accompanying drawings. It should be noted that for the same or corresponding parts as those in the foregoing embodiments, reference may be made to the corresponding descriptions in the foregoing embodiments, and details will not be repeated hereinafter.

[0091] Refer to Figure 6 , Figure 6 which is a flowchart of the method for manufacturing a solar cell provided by an embodiment of the present disclosure.

[0092] The method for manufacturing a solar cell may include: providing a substrate, the substrate including opposite front and back surfaces, the front surface having a pyramid texture structure, the back surface having a tower base structure, the specific surface area of the tower base structure being larger than that of the pyramid texture structure, and dangling bonds existing in the substrate.

[0093] The method for manufacturing a solar cell may include: forming a first tunneling layer, the first tunneling layer covering at least a part of the back surface, the material of the first tunneling layer being hollow titanium dioxide material, there being a plurality of transmission gaps between the hollow titanium dioxide materials, the transmission gaps being used for transmitting carriers and doping ions, and the hollow titanium dioxide material being bonded to the dangling bonds in the substrate.

[0094] The method for manufacturing a solar cell may include: forming a second tunneling layer, the second tunneling layer covering the surface of the first tunneling layer.

[0095] The method for manufacturing a solar cell may include: forming a doped conductive layer, the doped conductive layer covering the surface of the second tunneling layer.

[0096] The method for manufacturing a solar cell may include: forming a passivation layer, the passivation layer covering the surface of the doped conductive layer.

[0097] The method for manufacturing a solar cell may include: forming a back electrode, the back electrode being electrically connected to the doped conductive layer.

[0098] In some embodiments, the method for forming the substrate may include: performing a texturing process to form a pyramid structure on the front and back surfaces of the substrate; performing a back polishing process to polish the back surface and removing the tips of some of the pyramid structures by grinding to form a tower base structure; performing an ablation process to further etch the tower base structure on the back surface, thereby further reducing the specific surface area of the tower base structure.

[0099] The texturing process is to etch the surface of the substrate through an alkaline solution to etch the substrate along the crystal orientation, thereby forming a pyramid structure. The back grinding process is to further etch the pyramid structure through an alkaline solution with an additive to form a base structure. The ablation process is to further ablate the base structure through an acidic solution with an oxidizing additive to form a base structure with a lower specific surface area. For the ablation process, the oxidizing additive can oxidize the uneven parts on the back surface, that is, the sides and the top of the base structure, and then the oxidized part of the base structure is removed through the acidic solution.

[0100] Taking the material of the substrate as silicon as an example, the ablation process is that silicon is oxidized to silicon dioxide by the oxidizing additive, and then the silicon dioxide is reduced to silicate by the acidic solution, thereby removing part of the base structure of the substrate.

[0101] In some embodiments, the method for forming the first tunneling layer includes: forming a mask layer, the mask layer covering part of the substrate, and the orthographic projection of the mask layer on the substrate surface being directly opposite to the orthographic projection of the back electrode on the substrate surface; covering the hollow titanium dioxide material on the part of the back surface not covered by the mask layer through the sol-gel method; performing a sintering process to form the first tunneling layer on the back surface; removing the mask layer. By using the method of forming the mask layer, it is possible to avoid forming the first tunneling layer on the part where the back electrode is directly opposite to the substrate, so that the hollow titanium dioxide material can be offset from the corresponding position of the electrode, thus avoiding affecting the carrier transport, and the sol-gel method can facilitate the formation of a transport gap on the first tunneling layer.

[0102] In some embodiments, the sol-gel method can form the first tunneling layer by low-temperature sintering at a process temperature of 50°C to 100°C. The sol-gel method is a method of preparing materials by hydrolyzing and polycondensing a precursor to form a sol, and then converting it into a gel.

[0103] In some embodiments, the method for forming the doped conductive layer includes: forming an amorphous silicon layer on the surface of the second tunneling layer, and then converting the amorphous silicon layer into a doped conductive layer by high-temperature diffusion; during the high-temperature diffusion process, the first tunneling layer is also crystallized. On the one hand, the first tunneling layer is crystallized by using the high-temperature diffusion process, which can reduce the process steps of the manufacturing method of the solar cell chip. On the other hand, crystallizing the first tunneling layer can improve the light reflection ability and surface field passivation ability of the first tunneling layer.

[0104] In some embodiments, the process temperature of high-temperature diffusion can be 800°C to 900°C, such as 800°C, 810°C, 820°C, 830°C, 840°C, 850°C, 860°C, 870°C, 880°C, 890°C or 900°C. Using 800°C to 900°C can facilitate the control of the diffusion of ions into the amorphous silicon while crystallizing the first tunneling layer, thereby further improving the light reflection ability and surface passivation ability of the first tunneling layer.

[0105] Those of ordinary skill in the art can understand that the above embodiments are specific embodiments for implementing the present disclosure. In actual applications, various changes can be made in form and details without departing from the spirit and scope of the embodiments of the present disclosure. Any person skilled in the art can make various modifications and changes without departing from the spirit and scope of the embodiments of the present disclosure. Therefore, the protection scope of the embodiments of the present disclosure should be subject to the scope defined by the claims.

Claims

1. A solar cell, characterized in that: include: A substrate, the substrate comprising a front side and a back side opposite to each other, the front side having a pyramid velvet structure, the back side having a tower base structure, the specific surface area of ​​the tower base structure being smaller than the specific surface area of ​​the pyramid velvet structure, and dangling bonds existing in the substrate; A first tunneling layer, wherein the first tunneling layer at least covers a portion of the back surface, the material of the first tunneling layer is a hollow titanium dioxide material, a plurality of transmission gaps exist in the hollow titanium dioxide material, the transmission gaps are used to transmit carriers and doped ions, and the hollow titanium dioxide material is bonded to the dangling bonds in the substrate; a second tunneling layer, wherein the second tunneling layer covers a surface of the first tunneling layer; a doped conductive layer, wherein the doped conductive layer covers a surface of the second tunneling layer; a passivation layer, the passivation layer covering a surface of the doped conductive layer; A back electrode is electrically connected to the doped conductive layer.

2. The solar cell according to claim 1, characterized in that: The tower base structure includes: a tower top and a side surface extending from the tower top toward the back surface of the base, and the density of the first tunneling layer covering the surface of the tower top is greater than the density of the first tunneling layer covering the side surface.

3. The solar cell according to claim 1, characterized in that: The specific surface area of ​​the tower base structure is 1.01-1.

04.

4. The solar cell according to claim 1, characterized in that: The thickness of the first tunneling layer is within 3 nm.

5. The solar cell according to claim 1, characterized in that: The substrate includes a first region and a second region that are alternately arranged, the orthographic projection of the first tunneling layer on the surface of the substrate is located in the first region, and the orthographic projection of the back electrode on the surface of the substrate is located in the second region.

6. The solar cell according to claim 5, characterized in that: The specific surface area of ​​the tower base structure located in the second region is greater than the specific surface area of ​​the tower base structure located in the first region.

7. The solar cell according to claim 5, characterized in that: The orthographic projection of the second tunneling layer on the substrate surface is also located in the second region.

8. The solar cell according to claim 1, characterized in that: The transmission gap is also embedded with doping ions contained in the doped conductive layer.

9. A method for manufacturing a solar cell, characterized in that: include: Providing a substrate, the substrate comprising a front side and a back side opposite to each other, the front side having a pyramid velvet structure, the back side having a tower base structure, the specific surface area of ​​the tower base structure being greater than the specific surface area of ​​the pyramid velvet structure, and dangling bonds existing in the substrate; Forming a first tunneling layer, wherein the first tunneling layer at least covers a portion of the back surface, wherein the material of the first tunneling layer is a hollow titanium dioxide material, wherein a plurality of transmission gaps exist in the hollow titanium dioxide material, wherein the transmission gaps are used to transmit carriers and doped ions, and wherein the hollow titanium dioxide material is bonded to dangling bonds in the substrate; forming a second tunneling layer, wherein the second tunneling layer covers a surface of the first tunneling layer; forming a doped conductive layer, wherein the doped conductive layer covers a surface of the second tunneling layer; forming a passivation layer, wherein the passivation layer covers the surface of the doped conductive layer; A back electrode is formed, wherein the back electrode is electrically connected to the doped conductive layer.

10. The method for manufacturing a solar cell according to claim 9, characterized in that: The method for forming the doped conductive layer includes: forming a polysilicon layer on the surface of the second tunneling layer, and then converting the polysilicon layer into the doped conductive layer by high temperature diffusion; During the high-temperature diffusion process, the first tunneling layer is also crystallized.

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