Solar cell, method of manufacturing the same, stacked cell, and photovoltaic module

Abstract

This application relates to the photovoltaic field, providing a solar cell, its fabrication method, a tandem cell, and a photovoltaic module. The solar cell includes: a silicon substrate having opposing first and second surfaces; a composite structure layer located on the first surface, the composite structure layer including an antireflection layer and an ultraviolet absorption layer, wherein the ultraviolet absorption layer and the antireflection layer are stacked along a first direction, the refractive index of the ultraviolet absorption layer decreases in the first direction, the refractive index of the antireflection layer decreases in the first direction, the refractive index of the ultraviolet absorption layer is greater than the refractive index of the antireflection layer, and the first direction is the direction from the second surface to the first surface. The solar cell provided by this application embodiment can at least improve the photoelectric conversion efficiency of the solar cell.

Description

Technical Field

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

[0002] Solar cells, as clean and renewable energy semiconductor devices, convert light energy into electrical energy through the photovoltaic effect. When light shines on the surface of the cell, photons excite electrons in the semiconductor layer, forming an electric current and completing the photoelectric conversion. However, current solar cells lack sufficient passivation performance under strong ultraviolet radiation. Summary of the Invention

[0003] This application provides a solar cell, a method for preparing a solar cell, a tandem cell, and a photovoltaic module, which at least help improve the photoelectric conversion efficiency of the solar cell.

[0004] According to some embodiments of this application, a solar cell is provided, comprising: a silicon substrate having opposing first and second surfaces; a composite structure layer located on the first surface, the composite structure layer comprising an antireflection layer and an ultraviolet absorption layer, wherein the ultraviolet absorption layer and the antireflection layer are stacked along a first direction, the refractive index of the ultraviolet absorption layer decreases in the first direction, the refractive index of the antireflection layer decreases in the first direction, the refractive index of the ultraviolet absorption layer is greater than the refractive index of the antireflection layer, and the first direction is the direction from the second surface to the first surface.

[0005] In some embodiments, the composite structure layer further includes a field passivation layer located between the silicon substrate and the ultraviolet absorption layer.

[0006] In some embodiments, the first surface has a first region and a second region alternately arranged along a second direction, and the solar cell further includes a first doped conductive layer and a second doped conductive layer, wherein the first doped conductive layer is located on the second surface and has a first doping type; the second doped conductive layer is located in the first region and has a second doping type, and the first doping type is opposite to the second doping type.

[0007] In some embodiments, the second surface has a third region and a fourth region alternately arranged along a second direction, and the solar cell further includes a first doped conductive layer and a second doped conductive layer, wherein the first doped conductive layer is located in the fourth region and has a first doping type; the second doped conductive layer is located in the third region and has a second doping type, wherein the first doping type is opposite to the second doping type.

[0008] In some embodiments, the antireflection layer includes a first antireflection layer and a second antireflection layer, wherein the first antireflection layer is located between the ultraviolet absorption layer and the second antireflection layer, the refractive index of the first antireflection layer is 1.95~2.1, and the refractive index of the second antireflection layer is 1.75~1.95.

[0009] In some embodiments, the refractive index of the ultraviolet absorbing layer is in the range of 2.25 to 2.68.

[0010] In some embodiments, the material of the ultraviolet absorption layer includes TiO2, wherein the atomic ratio of Ti to O is (1:1.7) to (1:2), the ultraviolet absorption layer includes a plurality of absorber sublayers, which are stacked sequentially in the first direction, and the atomic ratio of Ti to O in the absorber sublayers decreases.

[0011] In some embodiments, the atomic ratio of Ti to O in the absorber sublayer decreases by 7% to 8%.

[0012] In some embodiments, the atomic ratio of Ti in the absorber layer furthest from the silicon substrate to Si in the first antireflection layer of the antireflection layer is (1:6) to (1:5).

[0013] According to some embodiments of this application, another aspect of this application provides a method for preparing a solar cell, comprising: providing a silicon substrate; using a first deposition process to gradually reduce the flow ratio of a titanium precursor source and an oxidant to form an ultraviolet absorption layer on one side of the silicon substrate; and using a second deposition process to form an antireflection layer on the ultraviolet absorption layer.

[0014] In some embodiments, the flow ratio of the titanium precursor source to the oxidant is (1:5) to (1:8).

[0015] In some embodiments, the temperature of the second deposition process is 400°C to 500°C.

[0016] In some embodiments, before forming the ultraviolet absorption layer, an atomic layer deposition process is used to form a field passivation layer on the silicon substrate, wherein the temperature of the atomic layer deposition process is 250°C to 300°C.

[0017] According to some embodiments of this application, a tandem battery is provided, comprising: a bottom battery, which is the solar cell described above, or a solar cell prepared by the method for preparing the solar cell described above; and a top battery located on the bottom battery.

[0018] According to some embodiments of this application, a photovoltaic module is provided, comprising: a battery string, which is formed by connecting multiple solar cells described above, or by connecting solar cells prepared by the method described above, or by connecting multiple stacked cells 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 facing away from the battery string.

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

[0020] The solar cell of this application includes a composite structure layer comprising an antireflective layer and an ultraviolet (UV) absorption layer, which are stacked along a first direction. The refractive index of the antireflective layer decreases along this first direction, meaning the refractive index of the antireflective layer farther from the silicon substrate is lower than that of the antireflective layer closer to the silicon substrate. When the solar cell forms a photovoltaic module, an encapsulation structure, typically a glass cover, is placed on the antireflective layer farther from the silicon substrate. The glass cover has a higher refractive index relative to air. The lower refractive index of the antireflective layer farther from the silicon substrate can match the refractive index of the glass cover, reducing light reflection and scattering at the interface of the antireflective layer and decreasing the time light spends at this interface. This suppresses parasitic absorption at the interface and improves the cell's conversion efficiency. The increased refractive index of the antireflective layer closer to the silicon substrate, making it closer to the UV absorption layer, reduces interface reflection when light exits the antireflective layer and reaches the UV absorption layer with its higher refractive index, thus improving the cell's light absorption efficiency. The antireflective layer acts as a protective layer for the ultraviolet (UV) absorption layer, reducing damage caused by direct UV exposure and maintaining its UV absorption performance. The refractive index of the UV absorption layer increases from the side closest to the antireflective layer to the side closest to the silicon substrate. This change reduces the refractive index difference between the UV absorption layer and the antireflective layer, decreasing interface reflection and improving the cell's light absorption efficiency. Furthermore, the higher refractive index region strongly absorbs UV light, reducing the damaging effects of UV light on the cell's internal structure and improving its stability and efficiency. Through the synergistic effect of the antireflective layer and the UV absorption layer, the photoelectric conversion efficiency of the solar cell is improved. 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] Figures 1 to 4 This is a schematic cross-sectional view of the TOPCon solar cell provided in an embodiment of this application.

[0023] Figures 5 to 8 A cross-sectional structural diagram of a back-contact solar cell provided in an embodiment of this application;

[0024] Figure 9 A schematic flowchart illustrating a method for fabricating a solar cell according to an embodiment of this application;

[0025] Figure 10 for Figure 9 A schematic diagram of the substrate cross-sectional structure after providing the silicon substrate and before preparing the ultraviolet absorption layer in the fabrication method of solar cells;

[0026] Figure 11 In order to be in Figure 10 A schematic diagram of the substrate cross-section structure after the ultraviolet absorption layer is prepared on the field passivation layer formed in the middle;

[0027] Figure 12 In order to be in Figure 11 A schematic diagram of the substrate cross-section structure after an antireflection layer is prepared on the ultraviolet absorption layer formed in the process;

[0028] Figure 13 A cross-sectional structural diagram of a stacked battery provided in an embodiment of this application;

[0029] Figure 14 This is a cross-sectional structural diagram of a photovoltaic module provided in an embodiment of this application.

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

[0031] 10. Silicon substrate; 20. Composite structure layer; 21. Ultraviolet absorption layer; 22. Antireflection layer; 23. Field passivation layer; 24. Oxide layer; 211. First sub-absorber layer; 212. Second sub-absorber layer; 213. Third sub-absorber layer; 221. First antireflection layer; 222. Second antireflection layer; 231. First passivation layer; 232. Second passivation layer; 233. Third passivation layer; 30. First doped conductive layer; 40. Second doped conductive layer; 50. Back passivation layer; 60. First electrode; 70. Second electrode; 80. Bottom cell; 90. Top cell; 100. Solar cell; 101. Encapsulating film; 102. Cover plate; 103. Conductive strip; A. First region; B. Second region; C. Third region; D. Fourth region;

[0032] 11. Silicon substrate; 200. Composite structure layer; 210. Ultraviolet absorption layer; 220. Antireflection layer; 230. Field passivation layer; 240. Oxide layer; 2110. First sub-absorber layer; 2120. Second sub-absorber layer; 2130. Third sub-absorber layer; 2210. First antireflection layer; 2220. Second antireflection layer; 2310. First passivation layer; 2320. Second passivation layer; 2330. Third passivation layer; 31. First doped conductive layer; 41. Second doped conductive layer; 51. Back passivation layer; 61. First electrode; 71. Second electrode. Detailed Implementation

[0033] As the background technology indicates, solar cells, as a clean and renewable energy semiconductor device, convert light energy into electrical energy through the photovoltaic effect. When light shines on the surface of the cell, photons excite electrons in the semiconductor layer of the cell, forming an electric current, thus completing the photoelectric conversion. However, the passivation effect of current solar cells under strong ultraviolet radiation is insufficient.

[0034] This application provides a solar cell, a method for preparing a solar cell, a tandem cell, and a photovoltaic module.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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).

[0039] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0040] In the description of the embodiments of this application, unless otherwise expressly specified and limited, the technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] According to some embodiments of this application, a solar cell is provided, such as... Figures 1 to 4 As shown, the TOPCon solar cell includes: a silicon substrate 10 having opposing first and second surfaces; a composite structure layer 20 located on the first surface, the composite structure layer 20 including an ultraviolet absorption layer 21 and an antireflection layer 22, wherein the ultraviolet absorption layer 21 and the antireflection layer 22 are stacked along a first direction X, the refractive index of the ultraviolet absorption layer 21 decreases in the first direction X, the refractive index of the antireflection layer 22 decreases in the first direction X, the refractive index of the ultraviolet absorption layer 21 is greater than the refractive index of the antireflection layer 22, and the first direction X is the direction from the second surface to the first surface. Figures 5 to 8 As shown, the back-contact solar cell includes: a silicon substrate 11 having opposing first and second surfaces; a composite structure layer 200 located on the first surface, the composite structure layer 200 including an ultraviolet absorption layer 210 and an antireflection layer 220, wherein the ultraviolet absorption layer 210 and the antireflection layer 220 are stacked along a first direction X, the refractive index of the ultraviolet absorption layer 210 decreases in the first direction X, the refractive index of the antireflection layer 220 decreases in the first direction X, the refractive index of the ultraviolet absorption layer 210 is greater than the refractive index of the antireflection layer 220, and the first direction X is the direction from the second surface to the first surface.

[0046] By introducing a composite structure layer into the solar cell, comprising an antireflective layer and an ultraviolet (UV) absorption layer, with the UV absorption layer and antireflective layer stacked along a first direction, the refractive index of the antireflective layer decreases in this first direction. Specifically, the refractive index of the antireflective layer farther from the silicon substrate is lower than that of the antireflective layer closer to the silicon substrate. The resulting solar cell has an encapsulation structure on the antireflective layer farther from the silicon substrate, typically a glass cover. The lower refractive index of the antireflective layer farther from the silicon substrate matches the refractive index of the glass cover, reducing reflection and scattering at the interface when light enters the antireflective layer from the glass cover. This reduces the time light spends at the interface, suppressing parasitic absorption and improving the cell's conversion efficiency. Conversely, the increased refractive index of the antireflective layer closer to that of the UV absorption layer reduces interface reflection when light exits the antireflective layer to the UV absorption layer with its higher refractive index, further improving the cell's light absorption efficiency. The antireflective layer acts as a protective layer for the ultraviolet (UV) absorption layer, reducing damage caused by direct UV exposure and maintaining its UV absorption performance. The refractive index of the UV absorption layer increases from the side closest to the antireflective layer to the side closest to the silicon substrate. This change reduces the refractive index difference between the UV absorption layer and the antireflective layer, decreasing interface reflection and improving the cell's light absorption efficiency. Furthermore, the higher refractive index region strongly absorbs UV light, reducing the damaging effects of UV light on the cell's internal structure and improving its stability and efficiency. Through the synergistic effect of the antireflective layer and the UV absorption layer, the photoelectric conversion efficiency of the solar cell is improved.

[0047] In the above embodiments, the silicon substrate material can be an elemental semiconductor material. Specifically, the elemental semiconductor material is composed of a single element, such as silicon. The elemental semiconductor material can be monocrystalline, polycrystalline, amorphous, or microcrystalline (a state simultaneously possessing both monocrystalline and amorphous states is called microcrystalline). For example, silicon can be at least one of monocrystalline silicon, polycrystalline silicon, amorphous silicon, or microcrystalline silicon.

[0048] In the above embodiments, the silicon substrate material can also be a compound semiconductor material. Common compound semiconductor materials include, but are not limited to, silicon germanide, silicon carbide, gallium arsenide, indium gallium dihydrogen phosphate, perovskite, cadmium telluride, and copper indium selenide. The silicon substrate can also be a sapphire silicon substrate, a silicon-on-insulator substrate, or a germanium-silicon-on-insulator substrate.

[0049] In the above embodiments, the N-type silicon substrate is doped with an N-type dopant element, which can be at least one of group V elements such as phosphorus (P), bismuth (Bi), antimony (Sb), or arsenic (As). The P-type silicon substrate is doped with a P-type dopant element, which can be at least one of group III elements such as boron (B), aluminum (Al), gallium (Ga), or gallium (In). Optionally, the thickness of the N-type silicon substrate can be 100 μm to 210 μm, such as 130 μm, 170 μm, and 190 μm.

[0050] In the above embodiments, the first surface of the silicon substrate is the front side and the second surface is the back side, that is, the solar cell is a single-sided cell, the front side can be used as the light-receiving surface to receive incident light, and the back side is used as the back light surface.

[0051] The first surface and the second surface mentioned above can be flat surfaces or non-flat surfaces, that is, the first surface can be a flat surface or a non-flat surface, the second surface can be a flat surface or a non-flat surface, and the first surface and the second surface can be the same or different.

[0052] In the above embodiments, both the first and second surfaces are non-flat surfaces. Non-flat surfaces can increase internal reflection of incident light, thereby further improving the light utilization efficiency of the solar cell. More specifically, the cross-section of the non-flat surface along the first predetermined direction is a line segment. This line segment can include at least one of straight segments and curved segments; that is, the line segment can be composed of straight segments, curved segments, or a combination of both. In the case where only straight segments are used, the line segment is composed of multiple sequentially connected straight segments. The first predetermined direction is the thickness direction of the silicon substrate.

[0053] The composite passivation layer of this application can be used in TOPCon batteries, such as in some embodiments. Figures 1 to 4 As shown, the solar cell can be a TOPCon cell. The first surface has a first region A and a second region B alternately arranged along the second direction Y. The solar cell also includes a first doped conductive layer 30 and a second doped conductive layer 40. The first doped conductive layer 30 is located on the second surface and has a first doping type. The second doped conductive layer 40 is located in the first region A and has a second doping type. The first doping type is opposite to the second doping type.

[0054] In the above embodiments, the first region refers to the region in the battery where electrodes are formed, also known as the metal region. The second region is the region in the battery other than the first region, also known as the non-metal region.

[0055] The composite passivation layer of this application can be used in back contact batteries, such as in some embodiments. Figures 5 to 8As shown, the solar cell can be a back-contact cell. The second surface has a third region C and a fourth region D alternately arranged along the second direction Y. The solar cell also includes a first doped conductive layer 31 and a second doped conductive layer 41. The first doped conductive layer 31 is located in the fourth region D and has a first doping type; the second doped conductive layer 41 is located in the third region C and has a second doping type. The first doping type is the opposite of the second doping type. The composite passivation layer of this application can be applied to TOPCon cells, back-contact cells, and their stacked cells, and has a wide range of applications.

[0056] In the above embodiments, the first doped conductive layer and the second doped conductive layer can be doped polysilicon layers, silicon carbide layers, or composite layers of doped polysilicon and silicon carbide layers. For example, they can be only silicon carbide or only polysilicon, or they can be doped materials of silicon carbide and polysilicon. When the first doped conductive layer is doped polysilicon (Doped poly-Si), it can serve as a field passivation layer, forming band bends on the silicon wafer surface to achieve selective carrier transport and reduce recombination losses. The thickness of the first doped conductive layer and the second doped conductive layer can be 80nm~100nm, such as 80nm and 95nm. The specific thickness and material are not limited in this application and can be selected according to the actual situation.

[0057] In the above embodiments, such as Figures 1 to 4 As shown, in the case of the aforementioned solar cell being a TOPCon cell, the cell also has a back passivation layer 50; as Figures 5 to 8 As shown, in the case of a back-contact solar cell, the cell also has a back passivation layer 51. The back passivation layer suppresses carrier recombination at the interface, thus avoiding the reduction in photocurrent caused by carrier recombination and ensuring high photoelectric conversion efficiency. Optionally, the material of the back passivation layer can be a single-layer or composite film such as alumina, silicon nitride, silicon oxide, and silicon oxynitride. For example, if the back passivation layer is a single-layer film, it can be an alumina single-layer film, a silicon nitride single-layer film, a silicon oxide single-layer film, or a silicon oxynitride single-layer film; if the back passivation layer is a multi-layer film, it can be a composite film of alumina and silicon oxide, or a composite film of alumina, silicon oxide, and silicon nitride. Of course, the material of the back passivation layer in this application is not limited to the above-mentioned materials; those skilled in the art can select any suitable material to form the back passivation layer of this application according to the actual situation. Optionally, the thickness of the back passivation layer in this application can be 70nm~90nm, which can further ensure a reduction in the defect state density on the surface of the solar cell, reduce the probability of electron and hole recombination on the surface, and thus improve the photoelectric conversion efficiency.

[0058] In the above embodiments, such as Figures 1 to 4 As shown, in the case of the aforementioned solar cell being a TOPCon cell, the cell further includes a first electrode 60 and a second electrode 70. The first electrode 60 is located on the side of the first doped conductive layer 30 facing away from the silicon substrate 10, and the second electrode 70 is located on the side of the second doped conductive layer 40 facing away from the silicon substrate 10; Figures 5 to 8 As shown, in the case of a back-contact solar cell, the cell further includes a first electrode 61 and a second electrode 71. The first electrode 61 is located on the side of the first doped conductive layer 31 facing away from the silicon substrate 11, and the second electrode 71 is located on the side of the second doped conductive layer 41 facing away from the silicon substrate 11. The materials of the first and second electrodes can be independently selected from copper, silver, nickel, or aluminum. This application does not limit the materials and thicknesses of the first and second electrodes; those skilled in the art can select appropriate materials and thicknesses to form the first and second electrodes according to actual conditions.

[0059] In some embodiments, such as Figures 2 to 4 As shown, in the case of a TOPCon solar cell, the antireflection layer 22 includes a first antireflection layer 221 and a second antireflection layer 222, wherein the first antireflection layer 221 is located between the ultraviolet absorption layer 21 and the second antireflection layer 222; as Figures 6 to 8As shown, in the case of a back-contact solar cell, the antireflection layer 220 includes a first antireflection layer 2210 and a second antireflection layer 2220, wherein the first antireflection layer 2210 is located between the ultraviolet absorption layer 210 and the second antireflection layer 2220. Specifically, in the direction from the second surface to the first surface, the refractive index of the first antireflection layer varies from 1.95 to 2.1, and the refractive index of the second antireflection layer varies from 1.75 to 1.95. The material of the first antireflection layer can be SiNx, the thickness can be 50 nm, and the atomic ratio of Si to N can be (1:1.2) to (1:1.4); the material of the second antireflection layer can be SiOx, the thickness can be 30 nm, and the atomic ratio of Si to N can be (1:1.7) to (1:1.9). The refractive index of the second antireflective layer is close to that of the glass cover plate (n=1.5) of the solar cell. It can serve as a transition layer for light entering the cell from the glass cover plate, reducing light reflection and scattering at the interface of the second antireflective layer, decreasing light residence time, and suppressing parasitic absorption at the interface. The refractive index of the first antireflective layer is greater than that of the second antireflective layer but less than that of the ultraviolet absorption layer. It can serve as a transition layer for light entering the ultraviolet absorption layer 21 from the second antireflective layer, reducing light reflection and scattering at the interface of the ultraviolet absorption layer, suppressing interface absorption. Through the antireflective layer, most of the light can be smoothly transmitted to the ultraviolet absorption layer and enter the cell, reducing light waste and allowing the cell to absorb more light. Furthermore, using the above-mentioned double-layer antireflective layer, the weighted average reflectance of the cell is 2.1% (300~1200nm wavelength), which is lower than the weighted average reflectance of the single-layer antireflective layer (4.5%). This reduces light reflection, retains more light for the cell, and increases the photocurrent gain of the cell by approximately 0.8 mA / cm².

[0060] In the visible and near-infrared spectral range, the outermost material of the antireflection layer, SiOx, has a lower light absorption coefficient than the outermost material of the antireflection layer, SiNx. This means that the SiOx layer can transmit more light while absorbing less light energy, which can reduce light loss between the encapsulation material and the battery surface.

[0061] In some embodiments, such as Figures 1 to 4 As shown, in the case of a TOPCon solar cell, the composite structure layer 20 further includes a field passivation layer 23, which is located between the silicon substrate 10 and the ultraviolet absorption layer 21. Figures 5 to 8As shown, in the case of a back-contact solar cell, the composite structure layer 200 further includes a field passivation layer 230, which is located between the silicon substrate 11 and the ultraviolet absorption layer 210. The thickness of the field passivation layer can be 6 nm to 10 nm, which can suppress carrier recombination at the interface. This avoids the problem of reduced photocurrent caused by carrier recombination, thereby ensuring high photoelectric conversion efficiency of the cell. Figures 1 to 4 As shown, the composite structure layer 20 of the TOPCon cell also includes an oxide layer 24, which is located between the silicon substrate 10 and the field passivation layer 23; as Figures 5 to 8 As shown, the composite structure layer 200 of the back contact battery also includes an oxide layer 240, which is located between the silicon substrate 11 and the field passivation layer 230. The oxide layer material can be at least one of silicon oxide, silicon oxynitride, titanium oxide, and silicon nitride, and its thickness can be 1-5 nm. The oxide layer 240 can passivate dangling bonds on the surface of the silicon substrate, reducing surface recombination centers and improving battery performance.

[0062] In the above embodiments, the atomic ratio of Ti in the ultraviolet absorption layer to Al in the field passivation layer can be (2:5) to (9:20). The material of the field passivation layer can include Al2O3, and the material of the ultraviolet absorption layer can include TiO2. The atomic ratio of Ti to Al can be selected as 3:7, which allows for better formation of Ti-O-Al bonds at the interface between the field passivation layer and the ultraviolet absorption layer. The bond energy of the Ti-O-Al bond is approximately 6.2 eV, which is greater than the bond energy of the Ti-O-Ti bond in the TiO2 layer (5.8 eV), resulting in a more stable structure and suppressing interface defects. The coefficient of thermal expansion increases gradually from the field passivation layer to the ultraviolet absorption layer: the coefficient of thermal expansion of the Al2O3 layer is 8 × 10⁻⁶. -6 The coefficient of thermal expansion of the Ti3AlOx layer formed at the interface between the field passivation layer and the ultraviolet absorption layer is 8.2 × 10⁻⁶ K. -6 / K, the coefficient of thermal expansion of the TiO2 layer is 9×10. -6 / K, which can reduce the thermal stress of the battery (by about 40%).

[0063] In some embodiments, such as Figures 3 to 4 As shown, in the case of a TOPCon solar cell, the field passivation layer 23 includes a first passivation layer 231, a second passivation layer 232, and a third passivation layer 233; as Figures 7 to 8As shown, in the case of a back-contact solar cell, the field passivation layer 230 includes a first passivation layer 2310, a second passivation layer 2320, and a third passivation layer 2330. The first, second, and third passivation layers are stacked sequentially in the first direction X. The first passivation layer can be made of SiO2 with a thickness of 1-2 nm and an atomic ratio of Si to O of 1:2. The second passivation layer can be made of Al2O3 with a thickness of 3-5 nm and an atomic ratio of Al to O of 2:3. The third passivation layer can be made of SiON with a thickness of 2-3 nm and an atomic ratio of Si, O, and N of 1:0.6:0.4. Setting the material, thickness, and atomic ratio of the third passivation layer within the above ranges allows for better film density and a diffusion coefficient of less than 10. -16 cm 2 The charge density of the second passivation layer can be controlled within the range of -3 × 10⁻⁶ ppm, preventing excessive penetration of H₂ gas into the second passivation layer during film fabrication and maintaining the structural stability of the field passivation layer. Setting the material, thickness, and atomic ratio of the second passivation layer to the range described above allows for control of the charge density of the film within this range. 12 cm -2 This suppresses electron recombination and improves the field passivation effect of negative charges. Setting the material, thickness, and atomic ratio of the first passivation layer within the above range can reduce the lattice mismatch rate between the SiO2 film and the Al2O3 film to 1.2%, thereby reducing the interface state density.

[0064] In some embodiments, the refractive index of the ultraviolet absorption layer ranges from 2.25 to 2.68. Setting the refractive index of the ultraviolet absorption layer to this range can better reduce the refractive index difference between the ultraviolet absorption layer and the antireflective layer, reduce interface reflection, improve the battery's light absorption efficiency, and the region with a high refractive index has a strong ability to absorb ultraviolet rays, reducing the damage of ultraviolet light to the battery's interior and improving the battery's stability and efficiency.

[0065] In some embodiments, the material of the ultraviolet absorbing layer includes TiO2, wherein the atomic ratio of Ti to O is (1:1.7) to (1:2), such as... Figure 4 As shown, the ultraviolet absorption layer 21 of the TOPCon battery includes multiple absorber sublayers. In the first direction X, the multiple absorber sublayers are stacked sequentially, and the atomic ratio of Ti to O in the absorber sublayers decreases. Specifically, in the first direction X, the multiple absorber sublayers may include a first sub-absorbent layer 211, a second sub-absorbent layer 212, and a third sub-absorbent layer 213 stacked sequentially. Figure 8As shown, the ultraviolet absorption layer 210 of the back contact battery includes multiple absorber sublayers. In the first direction X, the multiple absorber sublayers are stacked sequentially, and the atomic ratio of Ti to O in the absorber sublayers decreases. Specifically, in the first direction X, the multiple absorber sublayers may include a first sub-absorber layer 2110, a second sub-absorber layer 2120, and a third sub-absorber layer 2130 stacked sequentially. The thickness of the first sub-absorber layer can be 3 nm, the refractive index can be 2.52~2.68, and the atomic ratio of Ti to O can be (1:1.7)~(1:1.9); the thickness of the second sub-absorber layer can be 5 nm, the refractive index can be 2.38~2.52, and the atomic ratio of Ti to O can be (1:1.9)~(1:1.95); the thickness of the third sub-absorber layer can be 4 nm, the refractive index can be 2.25~2.38, and the atomic ratio of Ti to O can be (1:1.95)~(1:2). Setting the thickness, refractive index, and Ti / O atomic ratio of the third sub-absorbing layer within the aforementioned range can reduce light reflection at the interface of the third sub-absorbing layer, resulting in a film layer with a density less than 10. 17 cm -3 Low oxygen vacancies reduce photogenerated carrier recombination; by setting the thickness, refractive index, and Ti / O atomic ratio of the third absorber layer within the aforementioned ranges, the carrier mobility of the film can be approximately 15 cm⁻¹. 2 / V•s, balancing absorption and carrier transport; setting the thickness, refractive index, and atomic ratio of Ti to O of the first sub-absorber layer within the aforementioned range can make the film layer Ti-rich. 3+ The oxygen vacancy concentration is approximately 5 × 10⁻⁶. 19 cm -3 This enhances the efficiency of ultraviolet absorption.

[0066] In the above embodiments, the overall thickness of the ultraviolet absorption layer can be 9nm~15nm. Setting the thickness of the ultraviolet absorption layer within this range allows for the absorption of more ultraviolet light while maintaining a suitable battery size, reducing the damaging effects of ultraviolet light on the battery's interior and further improving the photoelectric conversion efficiency of the solar cell.

[0067] In some embodiments, the atomic ratio of Ti to O in the absorber sublayer decreases by 7% to 8%. Setting the atomic ratio of Ti to O in the absorber sublayer to the above range can improve the band gradient (conduction band shift of 0.2 eV), drive the directional migration of photogenerated electrons, and improve the photoelectric conversion efficiency of the cell.

[0068] In some embodiments, the absorber layer furthest from the silicon substrate is the third absorber layer, and the atomic ratio of Ti in the third absorber layer to Si in the first antireflection layer of the antireflection layer is (1:6) to (1:5). Optionally, the Ti:Si ratio is 1:4, and Si-O-Ti bonds (infrared peak position 920 cm⁻¹) can be formed at the interface between the ultraviolet absorber layer and the first antireflection layer. This allows the refractive index to gradually change from the refractive index of the ultraviolet absorber layer to the refractive index of the first antireflection layer, reducing interface reflection. With this setting, the interface recombination rate at this interface is approximately 10 cm / s, which is significantly lower than that of traditional mechanical interfaces (above 100 cm / s).

[0069] The technical solutions of this application can be used in photovoltaic cells such as gridless (OBB, Zero Busbar) or multi-busbar (MBB, MULTI-BUSBAR) all-back contact cells, all-back contact cells (IBC, Interdigitated Back Contact), all-back contact solar cells (ABC, All Back Contact), composite passivated back contact cells (HPBC, Hybrid Passivated Back Contact), emitter and rear passivated cells (PERC, Passivated Emitter and Rear Cell), tunneling oxide passivated contact cells (TOPCon, Tunnel Oxide Passivated Contact), TOPCon-IBC (Interdigitated Back Contact, IBC) cells, crystalline silicon heterojunction solar cells (HJT, Heterojunction with Intrinsic Thin-layer), perovskite tandem cells, and flexible cells.

[0070] According to some embodiments of this application, a method for preparing a solar cell is provided, such as... Figure 9 As shown, it includes:

[0071] Step S1: As Figure 10 As shown, a silicon substrate 11 is provided;

[0072] Specifically, the silicon substrate can be an elemental semiconductor material, a compound semiconductor material, or a sapphire substrate. Specifically, the elemental semiconductor material is composed of a single element, such as silicon. The elemental semiconductor material can be monocrystalline, polycrystalline, amorphous, or microcrystalline (a state simultaneously possessing both monocrystalline and amorphous states is called microcrystalline). For example, silicon can be at least one of monocrystalline silicon, polycrystalline silicon, amorphous silicon, or microcrystalline silicon. Compound semiconductor materials include, but are not limited to, silicon germanide, silicon carbide, gallium arsenide, indium gallium dihydrogen phosphate, perovskite, cadmium telluride, and copper indium selenide.

[0073] Step S2: As Figure 10 and Figure 11 As shown, the first deposition process is used to gradually reduce the flow ratio of titanium precursor source and oxidant to form an ultraviolet absorption layer 210 on one side of the silicon substrate.

[0074] Specifically, such as Figure 10 As shown, before preparing the ultraviolet absorption layer, an oxide layer 240 and a field passivation layer 230 are first prepared on one side of the silicon substrate 11. In some embodiments, the field passivation layer is formed on the silicon substrate using atomic layer deposition (ALD) at a temperature of 250°C to 300°C. Specifically, the temperature can be 250°C, 280°C, or 300°C. More specifically, the material of the oxide layer 240 is deposited on the silicon substrate 11 using the ALD process. The material undergoes a chemical reaction to generate the oxide layer. The material of the oxide layer 240 can be SiO2. The specific reaction principle is as follows: in an environment of 250°C, silane (SiH4) reacts with O2 to generate SiO2. The thickness of the oxide layer 240 can be 1 nm to 5 nm. This can passivate the dangling bonds on the surface of the silicon substrate 11, reduce surface recombination centers, and improve the performance of the battery. The field passivation layer 230 is deposited on the oxide layer 240 using the ALD process. The material undergoes a chemical reaction to generate the field passivation layer 230. The field passivation layer 230 can be a single-layer film or a multi-layer module. When the field passivation layer 230 is a single-layer film, the material can be Al2O3. The specific reaction principle can be: in an environment of 300℃, trimethylaluminum (TMA) reacts with H2O to generate Al2O3. The thickness of the field passivation layer 230 can be 6nm~10nm. Figure 10 The field passivation layer 230 shown is a multilayer film, including a first passivation layer 2310, a second passivation layer 2320, and a third passivation layer 2330. The materials can be SiO2, Al2O3, and SiON, respectively, with thicknesses of 1 nm~2 nm, 3 nm~5 nm, and 2 nm~3 nm, respectively. The aforementioned field passivation layer 230 can suppress carrier recombination at the interface, thus avoiding the problem of reduced photocurrent caused by carrier recombination, thereby ensuring high photoelectric conversion efficiency of the battery.

[0075] Specifically, such as Figure 11As shown, the ultraviolet absorption layer 210 can be prepared on the field passivation layer 230 using PECVD technology. Under conditions of TiCl4 and O2 as precursors, a reaction temperature of 400℃, and a gas pressure of 200Pa, the atomic ratio of Ti and O in the ultraviolet absorption layer 210 can be controlled to achieve a gradual change in the refractive index. The ultraviolet absorption layer 210 includes a first sub-absorption layer 2110, a second sub-absorption layer 2120, and a third sub-absorption layer 2130, wherein the first sub-absorption layer 2110, the second sub-absorption layer 2120, and the third sub-absorption layer 2130 are sequentially stacked in the first direction X.

[0076] Step S3: As Figure 12 As shown, an antireflection layer 220 is formed on the ultraviolet absorption layer 210 using a second deposition process.

[0077] Specifically, such as Figure 12 As shown, an antireflection layer 220 can be prepared on the ultraviolet absorption layer using a PECVD process. The antireflection layer 220 may include a first antireflection layer 2210 and a second antireflection layer 2220. In some embodiments, the temperature of the second deposition process is 400℃~500℃. Specifically, the temperature can be 450℃ or 480℃, etc. More specifically, the first antireflection layer 2210 is prepared on the ultraviolet absorption layer 210 by introducing a SiH4 / NH3 / H2 mixed gas (ratio can be 1:4:2) at a deposition temperature of 450℃. The second antireflection layer 2220 is prepared on the first antireflection layer 2210 by introducing a SiH4 / NO2 / H2 mixed gas (ratio can be 1:8:2) at a deposition temperature of 450℃. After these two layers are prepared, the film is annealed at 400℃ for 30 minutes in a nitrogen atmosphere to promote the migration of hydrogen atoms to the interface. This forms the composite structure layer 200.

[0078] Figures 10 to 12 The diagram shown is a fabrication structure diagram of the composite structure layer in the back contact battery. The fabrication of the composite structure layer in the TOPCon battery is the same as that in the back contact battery, and will not be described again in this application.

[0079] In some embodiments, the flow ratio of the titanium precursor source to the oxidant is (1:5) to (1:8). The titanium precursor can be TiCl4, and the oxidant can be O2. The flow ratio is gradually increased during the preparation of the ultraviolet absorption layer, thus producing an ultraviolet absorption layer with increasing Ti and O atomic ratios and decreasing refractive index. This reduces the refractive index difference between the ultraviolet absorption layer and the antireflective layer with a lower refractive index, reducing interfacial reflection of light. Furthermore, the region with a high refractive index has a strong absorption capacity for ultraviolet light, reducing the damage of ultraviolet light to the battery's interior and improving the battery's stability and efficiency.

[0080] According to embodiments of this application, a stacked battery is also provided, such as... Figure 13 As shown, it includes: a bottom cell 80, which is the solar cell described above, or a solar cell prepared by the method described above; and a top cell 90, located on the bottom cell.

[0081] In some embodiments, the first transport layer can be either an electron transport layer or a hole transport layer, and the second transport layer can be either an electron transport layer or a hole transport layer. For example, the first transport layer is an electron transport layer and the second transport layer is a hole transport layer, or the first transport layer is a hole transport layer and the second transport layer is an electron transport layer.

[0082] According to embodiments of this application, a photovoltaic module is also provided, such as... Figure 14 As shown, the system includes: a battery string, which is formed by connecting multiple solar cells 100 as described above, or by connecting multiple solar cells 100 prepared by the above-described method, or by connecting multiple tandem solar cells as described above; an encapsulating film 101 for covering the surface of the battery string; and a cover plate 102 for covering the surface of the encapsulating film 101 facing away from the battery string. The solar cells 100 can be electrically connected to each other via conductive strips 103, which are welded to electrodes on the solar cells 100.

[0083] The aforementioned encapsulating film can be an organic encapsulating film such as polyvinyl butyral (PVB) film, ethylene-vinyl acetate copolymer (EVA) film, polyvinyl octene elastomer (POE) film, or polyethylene terephthalate (PET) film. Alternatively, at least one of the first or second encapsulating layer can also be an EP film, EPE film, or PVP film. Specifically, EP film refers to a co-extruded film composed of stacked EVA and POE films; EPE film refers to a co-extruded film formed by sequentially stacking EVA, POE, and EVA films; and PVP film refers to a co-extruded film formed by stacking POE, EVA, and POE films. The co-extruded film can be manufactured by sequentially extruding one or more raw materials onto another pre-made film during the film processing, or by bonding different types of pre-made films together.

[0084] The aforementioned cover plate can be a glass cover plate, a plastic cover plate, or other cover plate with light-transmitting function. Specifically, the surface of the cover plate facing the encapsulating film can be an uneven surface or a textured surface containing multiple raised structures, which can increase the utilization rate of incident light.

[0085] The preparation method of the solar cell described above in this application will be specifically described below with reference to specific embodiments and comparative examples.

[0086] Example 1

[0087] This application provides a method for preparing a solar cell, comprising:

[0088] A silicon substrate is provided, having opposing first and second surfaces, wherein the silicon substrate is a silicon wafer with a thickness of 150 μm;

[0089] An oxide layer was prepared on the first surface using the ALD process at a reaction temperature of 250℃. The oxide layer was made of SiO2 and had a thickness of 1 nm.

[0090] A field passivation layer was prepared on the oxide layer using the ALD process. The field passivation layer includes a first sub-passivation layer, a second sub-passivation layer, and a third sub-passivation layer. The materials of the first sub-passivation layer, the second sub-passivation layer, and the third sub-passivation layer are SiO2, Al2O3, and SiON, respectively, and their thicknesses are 1 nm, 3 nm, and 2 nm, respectively. The reaction temperature is 300 °C.

[0091] A UV absorption layer was prepared on a field passivation layer using PECVD. The UV absorption layer includes a first sub-absorption layer, a second sub-absorption layer, and a third sub-absorption layer. Specifically, the flow ratio of TiCl4 to O2 in the first sub-absorption layer was 1:5, the atomic ratio of Ti to O in the first sub-absorption layer was 1:1.8, and the refractive index was 2.68. In the second sub-absorption layer, the flow ratio was 1:6, the atomic ratio of Ti to O in the second sub-absorption layer was 1:1.9, and the refractive index was 2.52. In the third sub-absorption layer, the flow ratio was 1:8, the atomic ratio of Ti to O in the third sub-absorption layer was 1:95, and the refractive index was 2.45. The reaction temperature was 400℃, the atmospheric pressure was 200 Pa, the material of the UV absorption layer was TiO2, and the thickness of the UV absorption layer was 12 nm.

[0092] An antireflection layer was fabricated on an ultraviolet absorption layer using PECVD. The antireflection layer includes a first antireflection layer and a second antireflection layer. The first antireflection layer is made of Si3N4 and has a thickness of 50 nm. The refractive index changes from 1.95 to 2 in the direction from the second surface to the first surface. The second antireflection layer is made of SiO2 and has a refractive index change from 1.75 to 1.85 in the direction from the second surface to the first surface. The thickness is 30 nm, and the deposition temperature is 450 °C.

[0093] A first doped conductive layer is formed on the second surface. The doping type is N-type and the thickness is 80 nm.

[0094] A second doped conductive layer is formed in a first region on the first surface. The doping type is P-type and the thickness is 80 nm.

[0095] A first electrode and a second electrode are formed on the side of the first doped conductive layer and the second doped conductive layer away from the silicon substrate, respectively. The material of the first electrode and the second electrode is Ag, and the thickness of each electrode is 10 μm.

[0096] Example 2

[0097] This application provides a method for preparing a solar cell, comprising:

[0098] The difference from Example 1 is that, in the direction from the second surface to the first surface, the refractive index of the first antireflection layer changes from 1.95 to 2.1, and the refractive index of the second antireflection layer changes from 1.75 to 1.95.

[0099] Example 3

[0100] This application provides a method for preparing a solar cell, comprising:

[0101] The difference from Example 1 is that, in the direction from the second surface to the first surface, the refractive index of the first antireflection layer changes from 1.95 to 2.3, and the refractive index of the second antireflection layer changes from 1.75 to 2.05.

[0102] Example 4

[0103] This application provides a method for preparing a solar cell, comprising:

[0104] The difference from Example 1 is that the atomic ratio of Ti in the third sub-absorbing layer to Si in the first antireflection layer is 1:4.

[0105] Example 5

[0106] This application provides a method for preparing a solar cell, comprising:

[0107] The difference from Example 4 is that the atomic ratio of Ti in the third sub-absorbing layer to Si in the first antireflection layer is 1:5.

[0108] Example 6

[0109] This application provides a method for preparing a solar cell, comprising:

[0110] The difference from Example 4 is that the atomic ratio of Ti in the third sub-absorbing layer to Si in the first antireflection layer is 1:6.

[0111] Example 7

[0112] This application provides a method for preparing a solar cell, comprising:

[0113] The difference from Example 4 is that the atomic ratio of Ti in the third sub-absorbing layer to Si in the first antireflection layer is 1:7.

[0114] Example 8

[0115] This application provides a method for preparing a solar cell, comprising:

[0116] The difference from Example 4 is that the atomic ratio of Ti in the third sub-absorbing layer to Si in the first antireflection layer is 1:8.

[0117] Example 9

[0118] This application provides a method for preparing a solar cell, comprising:

[0119] The difference from Example 1 is that the refractive index of the first sub-absorbing layer is 2.52, and the atomic ratio of Ti to O is 1:1.9; the refractive index of the third sub-absorbing layer is 2.38, and the atomic ratio of Ti to O is 1:1.95.

[0120] Example 10

[0121] This application provides a method for preparing a solar cell, comprising:

[0122] The difference from Example 1 is that the refractive index of the first sub-absorbing layer is 2.88, and the atomic ratio of Ti to O is 1:1.7; the refractive index of the third sub-absorbing layer is 2.25, and the atomic ratio of Ti to O is 1:2.

[0123] Comparative Example 1

[0124] A method for preparing a solar cell, comprising:

[0125] The difference from Example 1 is that the refractive index of the ultraviolet absorption layer is fixed at 2.5.

[0126] Comparative Example 2

[0127] A method for preparing a solar cell, comprising:

[0128] The difference from Example 1 is that there is no ultraviolet absorption layer.

[0129] Comparative Example 3

[0130] A method for preparing a solar cell, comprising:

[0131] The difference from Comparative Example 2 is that the antireflective layer is a single-layer structure, the material is Si3N4, and the refractive index is fixed at 1.95.

[0132] Comparative Example 4

[0133] A method for fabricating a solar cell, comprising:

[0134] The difference from Example 1 is that the antireflection layer is a single-layer structure, the material is Si3N4, and the refractive index is fixed at 1.95.

[0135] The performance of solar cells prepared using the methods described in Examples 1-10 and Comparative Examples 1-4 was tested. TOPCon solar cells were used as an example. The test results are shown in Table 1.

[0136] Table 1

[0137] Absorbance (L / (g·cm)) Light reflectance % Conversion efficiency % Example 1 1.25 2.1 25.7 Example 2 1.2 2.2 25.5 Example 3 1.21 2.3 25.4 Example 4 1.25 2.1 25.6 Example 5 1.23 2.2 25.4 Example 6 1.24 2.3 25.5 Example 7 1.22 2.4 25.2 Example 8 1.23 2.5 25.1 Example 9 1.245 2.35 25.15 Example 10 1.28 2.2 25.6 Comparative Example 1 1.24 2.5 25.0 Comparative Example 2 0.95 2.3 25.2 Comparative Example 3 0.1 4.0 24.5 Comparative Example 4 1.2 4.5 24.8

[0138] Among them, absorbance indicates the ability to absorb ultraviolet light; reflectance indicates the degree to which incident light is reflected. The higher the reflectance, the more incident light is reflected, and the less light the battery can use; conversion efficiency represents the battery's working efficiency.

[0139] As shown in Table 1 above, Example 12, compared to Example 1, adjusted the refractive index and atomic ratio of the first sub-absorber layer, further improving absorbance. Compared to Comparative Example 2, Example 1 significantly improved the battery's absorption capacity for ultraviolet light, and compared to Comparative Example 3, Example 1 showed a significantly lower light reflectance, allowing more light to enter the battery. Compared to Example 3, Examples 1-2, by setting the refractive index range of the first and second antireflection layers, reduced the battery's light reflectance, allowing more light to enter and be converted by the battery. Compared to Examples 7-8, Examples 4-6 adjusted the atomic ratio of Ti to Si between the third sub-absorber layer and the first antireflection layer, reducing the recombination rate at the interface between the third sub-absorber layer and the first antireflection layer, thereby improving the battery's photoelectric conversion efficiency. Examples 1, 9, and 10, by adjusting the refractive index range in the ultraviolet absorber layer (the range from the transition of the first sub-absorber layer to the second sub-absorber layer and the third sub-absorber layer), show that the overall effect of absorbance and light reflectance is better than Comparative Example 1. Analysis shows that the solar cell of this application has improvements in light absorption, light reflection, and photoelectric conversion efficiency.

[0140] 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 solar cell, characterized in that, include: A silicon substrate having opposing first and second surfaces; A composite structure layer is located on the first surface. The composite structure layer includes an antireflection layer and an ultraviolet absorption layer, wherein the ultraviolet absorption layer and the antireflection layer are stacked along a first direction. The refractive index of the ultraviolet absorption layer decreases in the first direction, and the refractive index of the antireflection layer also decreases in the first direction. The refractive index of the ultraviolet absorption layer is greater than that of the antireflection layer. The first direction is the direction from the second surface to the first surface. The material of the ultraviolet absorption layer is TiO2, wherein the atomic ratio of Ti to O is (1:1.7) to (1:2). The ultraviolet absorption layer includes multiple absorber sublayers, which are stacked sequentially in the first direction. The material of the multiple absorber sublayers is also TiO2. A first doped conductive layer is located on the second surface, and the first doped conductive layer is a doped polycrystalline silicon layer.

2. The solar cell according to claim 1, characterized in that, The composite structure layer further includes a field passivation layer, which is located between the silicon substrate and the ultraviolet absorption layer.

3. The solar cell according to claim 1, characterized in that, The first surface has a first region and a second region alternately arranged along a second direction. The solar cell further includes a first doped conductive layer and a second doped conductive layer, wherein the first doped conductive layer is located on the second surface and has a first doping type; the second doped conductive layer is located in the first region and has a second doping type, and the first doping type is opposite to the second doping type.

4. The solar cell according to claim 3, characterized in that, The second surface has a third region and a fourth region alternately arranged along a second direction. The solar cell further includes a first doped conductive layer and a second doped conductive layer. The first doped conductive layer is located in the fourth region and has a first doping type. The second doped conductive layer is located in the third region and has a second doping type. The first doping type is opposite to the second doping type.

5. The solar cell according to claim 1, characterized in that, The antireflection layer includes a first antireflection layer and a second antireflection layer, wherein the first antireflection layer is located between the ultraviolet absorption layer and the second antireflection layer, the refractive index of the first antireflection layer is 1.95~2.1, and the refractive index of the second antireflection layer is 1.75~1.

95.

6. The solar cell according to claim 1, characterized in that, The refractive index of the ultraviolet absorption layer is in the range of 2.25 to 2.

68.

7. The solar cell according to claim 1, characterized in that, The atomic ratio of Ti to O in the absorber layer decreases.

8. The solar cell according to claim 7, characterized in that, The atomic ratio of Ti to O in the absorber sublayer decreases by 7% to 8%.

9. The solar cell according to claim 7, characterized in that, The atomic ratio of Ti in the absorber layer furthest from the silicon substrate to Si in the first antireflection layer of the antireflection layer is (1:6) to (1:5).

10. A method for preparing a solar cell, characterized in that, The method for preparing a solar cell according to any one of claims 1 to 9 comprises: Provide silicon substrate; Using a first deposition process, the flow ratio of titanium precursor source and oxidant is gradually reduced to form an ultraviolet absorption layer on one side of the silicon substrate. A second deposition process is used to form an antireflection layer on the ultraviolet absorption layer.

11. The preparation method according to claim 10, characterized in that, The flow rate ratio of the titanium precursor source to the oxidant is (1:5) to (1:8).

12. The preparation method according to claim 10, characterized in that, The temperature of the second deposition process is 400℃~500℃.

13. The preparation method according to claim 10, characterized in that, Before forming the ultraviolet absorption layer, a field passivation layer is formed on the silicon substrate using an atomic layer deposition process, wherein the temperature of the atomic layer deposition process is 250°C to 300°C.

14. A stacked battery, characterized in that, include: The base cell is a solar cell according to any one of claims 1 to 9, or a solar cell prepared by the method of preparing a solar cell according to any one of claims 10 to 13; The top battery is located on the bottom battery.

15. A photovoltaic module, characterized in that, include: A battery string is formed by connecting multiple solar cells as described in any one of claims 1 to 9, or by connecting multiple solar cells prepared by the method of preparing solar cells as described in any one of claims 10 to 13, or by connecting multiple stacked cells as described in claim 14. An encapsulating film is used to cover the surface of the battery string; A cover plate is used to cover the surface of the encapsulating film that faces away from the battery string.

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