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

Abstract

The embodiment of the present application relates to the photovoltaic field, and provides a solar cell, a preparation method thereof, a laminated cell and a photovoltaic module, the solar cell comprises: a silicon substrate comprising oppositely arranged first and second surfaces, the first surface comprises first and second regions arranged alternately along a first direction, and the second region comprises first and second sub-regions arranged along a second direction; the first region comprises a first doped region, the first sub-region comprises a second doped region, and the second sub-region comprises a third doped region; the doping concentration of the second doped region is greater than that of the third doped region; and a first metal gate line is electrically connected with the first doped region. The solar cell provided by the embodiment of the present application is at least beneficial to improving the problems that the silicon substrate in the prior art is prone to bending, resulting in a high fragment rate, and the deposition thickness of silicon nitride is poor in uniformity.

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] Laser etching is a critical step in the manufacturing process of solar cells. During laser etching, the silicon substrate is subjected to rapid heating and cooling, generating thermal stress that can lead to material deformation, cracking, and even breakage. This thermal stress can easily cause bending on the silicon substrate, affecting subsequent processes. For example, it can cause grid breakage during screen printing, and affect the uniformity of phosphorus diffusion sheet resistance and silicon nitride deposition thickness, thereby increasing the breakage rate and reducing the overall yield of the solar cells. 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 helps to improve the problems in the prior art where the silicon substrate bends, resulting in a high fragmentation rate, and the poor uniformity of the deposition thickness of silicon nitride and other materials.

[0004] According to some embodiments of this application, one aspect of this application provides a solar cell, comprising: a silicon substrate including a first surface and a second surface disposed opposite to each other; the first surface including a first region and a second region alternately arranged along a first direction; the second region including a first sub-region and a second sub-region arranged along a second direction; the first direction intersecting the second direction; the first region including a first doped region; the first sub-region including a second doped region; the second sub-region including a third doped region; the doping concentration of the first doped region being greater than the doping concentration of the second doped region; and the doping concentration of the second doped region being greater than the doping concentration of the third doped region; and a first metal grid line electrically connected to the first doped region.

[0005] In some embodiments, the distance from the second sub-region to the second surface is h1, and the distance from the first sub-region to the second surface is h2, wherein h1 < h2.

[0006] In some embodiments, the distance from the first region to the second surface is h3, and the distance from the first sub-region to the second surface is h2, wherein h3 ≥ h2.

[0007] In some embodiments, the doping concentration of the first doped region is greater than or equal to the doping concentration of the second doped region.

[0008] In some embodiments, the first sub-region includes a first pyramid structure, and the second sub-region includes a second pyramid structure; the height of the first pyramid structure is greater than the height of the second pyramid structure, and the direction of the height is parallel to the thickness direction of the silicon substrate.

[0009] In some embodiments, the first sub-region includes a first pyramid structure, and the second sub-region includes a second pyramid structure; the side length of the base of the first pyramid structure is greater than the side length of the base of the second pyramid structure.

[0010] In some embodiments, the solar cell satisfies at least one of the following: the height of the first pyramid structure is 0.5μm-1.5μm, the side length of the base of the first pyramid structure is 0.5μm-2.5μm, the height of the second pyramid structure is 0.3μm-1μm, and the side length of the base of the second pyramid structure is 0.5μm-2μm.

[0011] In some embodiments, the length of a single first sub-region in the second direction is 100μm-300μm.

[0012] In some embodiments, the difference between the thickness of the first region and the thickness of the first sub-region is [0.2 μm, 1 μm].

[0013] In some embodiments, the difference between the thickness of the first sub-region and the thickness of the second sub-region is [2μm, 4μm].

[0014] In some embodiments, in the second direction, there are two first sub-regions, and the second sub-region is located between the two first sub-regions.

[0015] In some embodiments, the doping concentration of the first doped region is 5e18cm. -3 -1e20cm -3 The doping concentration of the third doped region is 5e14cm. -3 -5e17cm -3 .

[0016] In some embodiments, the thickness of the second sub-region is less than the thickness of the first sub-region, and the thickness of the first region is equal to the thickness of the first sub-region.

[0017] According to some embodiments of this application, another aspect of this application provides a method for fabricating a solar cell, for fabricating any of the aforementioned solar cells, the method comprising: providing a pre-silicon substrate; diffusion on a first surface of the pre-silicon substrate; and laser scanning and etching on a portion of the pre-silicon substrate to form a silicon substrate.

[0018] In some embodiments, laser scanning of a portion of the prepared silicon substrate includes: performing a first laser scan on a first sub-region of the prepared silicon substrate; performing a second laser scan on a second sub-region of the prepared silicon substrate; wherein the scanning speed and scanning frequency of the first laser scan are greater than the scanning speed and scanning frequency of the second laser scan, and the scanning power of the first laser scan is less than the scanning power of the second laser scan.

[0019] In some embodiments, in the first laser scan, the scanning speed is 70000mm / s-90000mm / s, the scanning power is 1W-5W, and the scanning frequency is 1200kHz-1500kHz; in the second laser scan, the scanning speed is 50000mm / s-70000mm / s, the scanning power is 5W-50W, and the scanning frequency is 800kHz-1200kHz.

[0020] In some embodiments, during the second laser scanning, the scanning speed and the scanning frequency gradually decrease, while the scanning power gradually increases; or, during the second laser scanning, the scanning speed, the scanning power, and the scanning frequency remain constant.

[0021] In some embodiments, laser scanning of a portion of the prepared silicon substrate includes: controlling a laser to begin moving along a direction from the first sub-region to the second sub-region, and turning on the laser when the moving time reaches a preset time.

[0022] In some embodiments, the preset duration is 0.005s-0.015ms.

[0023] According to some embodiments of this application, another aspect of this application provides a tandem battery, including: any of the solar cells described above, or a solar cell prepared using any of the methods described above for preparing a solar cell.

[0024] According to some embodiments of this application, another aspect of this application provides a photovoltaic module, including: any of the solar cells described above, or a solar cell prepared by any of the methods described above, or the tandem cell.

[0025] The technical solution provided in this application has at least the following advantages:

[0026] A solar cell includes a silicon substrate with a first surface and a first metal grid. The first surface includes a first region and a second region, and the second region includes a first sub-region and a second sub-region. The first region includes a first doped region, the first sub-region includes a second doped region, and the second sub-region includes a third doped region. The doping concentration of the second doped region is greater than that of the third doped region. The first metal grid is electrically connected to the first doped region. Compared with the problems of high fragmentation rate due to silicon substrate bending and poor uniformity of silicon nitride deposition thickness in the prior art, this application effectively releases the stress during the laser film-opening process and reduces the occurrence of silicon substrate bending by setting first and second sub-regions with different doping concentrations on the first surface of the silicon substrate. This effectively reduces the fragmentation rate, ensures better uniformity of subsequent silicon nitride deposition thickness, and improves the yield of the cell. Attached Figure Description

[0027] 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.

[0028] Figure 1 This is a top view schematic diagram of a solar cell provided according to an embodiment of this application;

[0029] Figure 2 An embodiment provided according to this application Figure 1 A schematic diagram of the cross-sectional structure of the solar cell along the second direction;

[0030] Figure 3 This is a top view schematic diagram of another solar cell provided according to an embodiment of this application;

[0031] Figure 4 An embodiment provided according to this application Figure 3 A schematic diagram of the cross-sectional structure of the solar cell along the second direction;

[0032] Figure 5 This is a schematic cross-sectional view of a specific solar cell along a second direction according to an embodiment of this application;

[0033] Figure 6 This is a schematic cross-sectional view of a specific solar cell located in a second sub-region along a first direction, according to an embodiment of this application.

[0034] Figure 7 This is a schematic cross-sectional view of a specific solar cell located in a first sub-region along a first direction, according to an embodiment of this application.

[0035] Figure 8 This is a schematic cross-sectional view of a stacked battery according to an embodiment of this application;

[0036] Figure 9 This is a cross-sectional structural diagram of a photovoltaic module provided according to an embodiment of this application.

[0037] The above figures include the following reference numerals:

[0038] 10. Silicon substrate; 11. First region; 12. Second region; 121. First sub-region; 122. Second sub-region; 1211. First pyramid structure; 1221. Second pyramid structure; 14. First passivation layer; 15. First antireflective coating; 16. First metal grid line; 17. Tunneling oxide layer; 18. First doped conductive layer; 19. Second passivation layer; 20. Second antireflective coating; 21. Second metal grid line; 1. Solar cell; 2. Bottom cell; 22. Top cell; 23. Interconnect composite layer; 24. Cell string; 25. Encapsulating film; 26. Cover plate; 27. Backsheet material. Detailed Implementation

[0039] As is known from the background art, in the prior art, the silicon substrate will bend, resulting in a high fragmentation rate and poor uniformity of the deposition thickness of silicon nitride, etc. In order to solve the above problems, the present application provides a solar cell, a method for preparing a solar cell, a tandem cell, and a photovoltaic module.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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).

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] The terminology used in the description of the various embodiments described herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used in the description of the various embodiments and the appended claims, the term "foreword" is also intended to include the plural form unless the context clearly indicates otherwise. Components include layers, films, regions, or plates, etc.

[0049] 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.

[0050] This application provides a solar cell, such as... Figures 1 to 7 As shown, it includes:

[0051] A silicon substrate 10 includes a first surface and a second surface disposed opposite to each other. The first surface includes a first region 11 and a second region 12 arranged alternately along a first direction. The second region 12 includes a first sub-region 121 and a second sub-region 122 arranged along a second direction. The first direction intersects the second direction.

[0052] Specifically, the silicon substrate can be doped with either n-type or p-type elements. The silicon substrate material can include at least one of monocrystalline silicon, polycrystalline silicon, amorphous silicon, or microcrystalline silicon. The n-type silicon substrate is doped with n-type dopant ions, and the n-type dopant element 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 p-type elements, and the p-type dopant element can be at least one of group III elements such as boron (B), aluminum (Al), gallium (Ga), or indium (In).

[0053] Specifically, the first region is the projection area of ​​the first metal gate line (i.e., electrode) on the silicon substrate. Due to manufacturing errors, the first region may not be completely consistent with the projection area of ​​the electrode. The width of the first region is usually greater than the width of the electrode projection area. The second region is the region other than the first region, which is usually called the non-metallized region.

[0054] The first region 11 includes a first doped region, the first sub-region 121 includes a second doped region, the second sub-region 122 includes a third doped region, and the doping concentration of the second doped region is greater than the doping concentration of the third doped region.

[0055] The first metal gate line 16 is electrically connected to the first doped region.

[0056] In the above embodiments, the solar cell includes a silicon substrate with a first surface and a first metal grid. The first surface includes a first region and a second region, and the second region includes a first sub-region and a second sub-region. The first region includes a first doped region, the first sub-region includes a second doped region, and the second sub-region includes a third doped region. The doping concentration of the second doped region is greater than that of the third doped region. The first metal grid is electrically connected to the first doped region. Compared with the problems in the prior art where the silicon substrate bends, resulting in a high fragmentation rate and poor uniformity of silicon nitride deposition thickness, this application, by setting a first sub-region and a second sub-region with different doping concentrations on the first surface of the silicon substrate, can effectively release the stress during the laser film-opening process, reduce the occurrence of silicon substrate bending, thereby effectively reducing the fragmentation rate, ensuring better uniformity of subsequent silicon nitride deposition thickness, and improving the yield of the cell.

[0057] Specifically, such as Figure 1 and Figure 2 As shown, in the second direction, there can be two first sub-regions 121, and a second sub-region 122 is located between the two first sub-regions 121; as Figure 3 and Figure 4 As shown, in the second direction, the first sub-region 121 may also have only one, and this application does not impose specific restrictions on this.

[0058] It should be noted that during laser etching on a silicon substrate, rapid heating and cooling generate thermal stress, leading to material deformation, cracks, and even fracture, ultimately manifesting as bending on the silicon substrate. Existing laser etching processes achieve complete etching at both the beginning and end of the laser beam, but insufficient flatness of the silicon substrate results in bending after laser etching. This application reserves a first sub-region during the laser etching process on both the front and back sides, releasing stress at the laser edge, reducing fragmentation and bending during fabrication, and simultaneously reducing defect rates in certain processes, including the uniformity of phosphorus diffusion sheet resistance, poly deposition thickness uniformity, alumina and silicon nitride deposition thickness uniformity, and the number of broken gates during screen printing.

[0059] In one alternative embodiment, the distance from the second sub-region to the second surface is h1, and the distance from the first sub-region to the second surface is h2, where h1 < h2. In this embodiment, the thickness of the second sub-region is smaller than that of the first sub-region, which can better control the stress distribution, reduce the impact of thermal stress, reduce material deformation and crack generation, and improve the yield of the solar cell.

[0060] In another alternative embodiment, the distance from the first region to the second surface is h3, and the distance from the first sub-region to the second surface is h2, wherein h3 ≥ h2. In this embodiment, a thicker or equal-thickness first region makes the circuit connection in this region more stable in subsequent processes, such as screen printing and phosphorus diffusion, reducing the occurrence of grid breakage (circuit breakage) and improving the electrical performance of the solar cell.

[0061] In another alternative embodiment, the doping concentration of the first doped region is greater than or equal to the doping concentration of the second doped region. In this embodiment, the first doped region is the region electrically connected to the first metal gate line. A higher concentration in the first doped region can reduce the contact resistance between the metal and the semiconductor, thereby improving the current flow efficiency.

[0062] Specifically, when h3 > h2, the doping concentration of the first doped region is greater than that of the second doped region; when h3 = h2, the doping concentration of the first doped region is equal to that of the second doped region.

[0063] Specifically, the doping concentration of the first doped region is 5e18cm. -3 -1e20cm -3 The doping concentration of the third doped region is 5e14cm. -3 -5e17cm -3 The doping concentration of the second doped region is less than that of the first doped region but greater than that of the third doped region. The doping concentration of the second doped region is 5e17cm. -3 -5e20cm -3The high doping concentration in the first doped region enhances the ohmic contact for forming the first metal grid, ensuring lower contact resistance. The low doping concentration in the third doped region reduces non-radiative recombination on the battery surface, ensuring higher battery conversion efficiency and improving surface passivation, thus enhancing battery performance. The higher doping concentration in the second doped region compared to the third doped region helps reduce the resistivity of this region, thereby reducing the series resistance of the battery. The lower doping concentration in the second doped region compared to the first doped region helps suppress surface recombination while maintaining good contact performance.

[0064] Specifically, a 3D microscope or electron microscope can be used to measure the distances h3 from the first region to the second surface, h2 from the first sub-region to the second surface, and h1 from the second sub-region to the second surface. The starting point for the calculation can be the second surface of the silicon substrate, and the ending point can be the first surface of the silicon substrate. Multiple measurements of the distances from the first region to the second surface at different positions in the first direction can be taken, and the average value can be used as h3; multiple measurements of the distances from the first sub-region to the second surface at different positions in the second direction can be taken, and the average value can be used as h2; multiple measurements of the distances from the second sub-region to the second surface at different positions in the second direction can be taken, and the average value can be used as h1. When the second surface is used as the reference for the calculation, the distances must be calculated on the same plane; alternatively, the second surface can be used as the reference, and any film layer or the same horizontal plane of the silicon substrate can be used.

[0065] In another alternative, such as Figure 2 As shown, the first sub-region 121 includes a first pyramid structure 1211, and the second sub-region 122 includes a second pyramid structure 1221. The height of the first pyramid structure 1211 is greater than the height of the second pyramid structure 1221, and the direction of the height is parallel to the thickness direction of the silicon substrate 10. In this embodiment, the pyramid structure can increase the surface roughness of the silicon substrate, thereby improving the scattering and absorption efficiency of incident light; the second pyramid structure has a smaller height, and this gradual change in height helps to disperse the thermal stress during laser processing, thereby reducing material deformation and cracking.

[0066] In other embodiments, such as Figure 2 As shown, the first sub-region 121 includes a first pyramid structure 1211, and the second sub-region 122 includes a second pyramid structure 1221; the side length of the base of the first pyramid structure 1211 is greater than the side length of the base of the second pyramid structure 1221. In this embodiment, the pyramid structure can increase the surface roughness of the silicon substrate, thereby improving the scattering and absorption efficiency of incident light; the smaller side length of the base of the second pyramid structure ensures a lower reflectivity, higher light absorption, and higher photoelectric conversion efficiency of the battery.

[0067] In addition, the fact that the height and side length of the second pyramid structure are smaller than those of the first pyramid structure ensures that the reflectivity of the second pyramid structure is lower, the light absorption rate is higher, and the photoelectric conversion efficiency of the battery is higher.

[0068] According to some exemplary embodiments of this application, the solar cell satisfies at least one of the following: the height of the first pyramid structure is 0.5μm-1.5μm, the side length of the base of the first pyramid structure is 0.5μm-2.5μm, the height of the second pyramid structure is 0.3μm-1μm, and the side length of the base of the second pyramid structure is 0.5μm-2μm. In this embodiment, the pyramid structure of a specific size can effectively break the specular reflection characteristics of incident light, reduce surface reflection, and allow more light to enter the cell and participate in the photoelectric conversion process.

[0069] Specifically, the height of a pyramid structure refers to the height of the pyramid structure itself. A 3D microscope or electron microscope can be used to measure the height of a pyramid structure. When measuring the height, the starting point can be the apex of the pyramid, and the ending point can be the base. The vertical distance between the apex and the base is the height of the pyramid structure.

[0070] In other embodiments, the length of a single first sub-region in the second direction is 100μm-300μm. In this embodiment, limiting the length of the first sub-region in the second direction to 100μm-300μm is to ensure that stress can be released within an appropriate range without affecting other performance indicators of the battery.

[0071] According to some exemplary embodiments of this application, the difference between the thickness of the first region and the thickness of the first sub-region is [0.2 μm, 1 μm]. In this embodiment, by controlling the thickness of the first sub-region to be 0.2 μm to 1 μm less than the thickness of the first region, the thermal stress caused by the temperature gradient during laser film opening can be further effectively reduced, and the bending phenomenon of the silicon substrate can be further reduced.

[0072] According to some other exemplary embodiments of this application, the thickness difference between the first sub-region and the second sub-region is [2μm, 4μm]. In this embodiment, the slight difference in thickness helps to further release local stress during the laser film-opening process, further reduce bending and cracking of the silicon wafer, and thus further improve the yield of the battery.

[0073] Specifically, taking TOPCon cells as an example, such as solar cells, Figures 5 to 7As shown, the solar cell further includes a first passivation layer 14 and a first antireflective film 15 stacked sequentially on the first surface, with a first metal grid line 16 located on the first antireflective film 15. The solar cell also includes a tunneling oxide layer 17, a first doped conductive layer 18, a second passivation layer 19, a second antireflective film 20, and a second metal grid line 21 stacked sequentially on the second surface. The doping types of the first doped region, the second doped region, and the third doped region are different from the doping type of the first doped conductive layer 18. Additionally, the back surface of the solar cell may also include an oxide layer and a second doped conductive layer. The oxide layer is located on the surface of the first doped conductive layer facing away from the silicon substrate, the second doped conductive layer is located on the surface of the oxide layer facing away from the silicon substrate, and the second passivation layer is located on the surface of the second doped conductive layer facing away from the silicon substrate.

[0074] This application also provides a method for preparing a solar cell, comprising:

[0075] Step S101: Provide a prepared silicon substrate;

[0076] Step S102: Diffusion is performed on the first surface of the prepared silicon substrate.

[0077] Step S103: Laser scanning and etching are performed on a portion of the above-mentioned prepared silicon substrate to form a silicon substrate.

[0078] In the above embodiments, a preliminary silicon substrate is first provided, then diffusion is performed on the first surface of the preliminary silicon substrate, and finally laser scanning and etching are performed on the diffused portion of the preliminary silicon substrate to form a silicon substrate. Compared with the problems of high fragmentation rate due to silicon substrate bending and poor uniformity of silicon nitride deposition thickness in the prior art, this application effectively releases the stress during the laser film-opening process by setting a first sub-region and a second sub-region with different doping concentrations on the first surface of the silicon substrate, reducing the occurrence of silicon substrate bending, thereby effectively reducing the fragmentation rate, ensuring better uniformity of subsequent silicon nitride deposition thickness, and improving the yield of the battery.

[0079] Specifically, the portion of the prepared silicon substrate that has been scanned by a laser is etched to obtain the silicon substrate.

[0080] Specifically, taking TOPCon solar cells as an example, the fabrication process of solar cells is as follows: 1) Texturing the front side of an n-type pre-silicon substrate; 2) Performing boron diffusion on the front side of the n-type pre-silicon substrate to obtain a p+ emitter; 3) Performing laser etching on the front side of the n-type pre-silicon substrate (i.e., laser scanning and etching of a portion of the pre-silicon substrate) to obtain a silicon substrate with a first doped region, a second doped region, and a third doped region; 4) Performing alkaline polishing on the back side of the silicon substrate; 6) Depositing a first tunneling oxide layer and an amorphous silicon layer on the back side of the silicon substrate using LPCVD (Low Pressure Chemical Vapor Deposition), and performing phosphorus doping annealing to transform the amorphous silicon layer into an n+ poly layer (i.e., the first doped conductive layer); 7) Depositing passivation films (i.e., the first passivation layer and the second passivation layer) on the front and back sides of the silicon substrate using ALD (Atomic Layer Deposition); 8) Depositing antireflection films (i.e., the first antireflection film and the second antireflection film) on the front and back sides; 9) Printing metal grid lines (i.e., the first metal grid line and the second metal grid line) on the front and back sides.

[0081] In one alternative embodiment, laser scanning is performed on a portion of the aforementioned pre-existing silicon substrate, including: performing a first laser scan on a first sub-region of the pre-existing silicon substrate; and performing a second laser scan on a second sub-region of the pre-existing silicon substrate. The scanning speed and frequency of the first laser scan are greater than the scanning speed and frequency of the second laser scan, and the scanning power of the first laser scan is less than the scanning power of the second laser scan. In this embodiment, by performing laser scanning in stages—first scanning the first sub-region at a higher speed and frequency and a lower power, and then scanning the second sub-region at a lower speed and frequency and a higher power—the thermal stress distribution in the laser-affected zone can be effectively controlled, reducing material damage. High-speed, high-frequency, and low-power scanning is beneficial for rapid heating and reducing the heat-affected zone, while low-speed, low-frequency, and high-power scanning is beneficial for penetrating deep into the material to form a more stable doped region. This staged laser scanning technology significantly improves the battery yield, reduces the breakage rate during the fabrication process, and ensures the battery's electrical properties.

[0082] Specifically, a first laser scan is performed on a first sub-region of the prepared silicon substrate, and a second laser scan is performed on a second sub-region of the prepared silicon substrate, such that the thickness of the first sub-region corresponding to the silicon substrate is greater than the thickness of the second sub-region corresponding to the silicon substrate, but less than the thickness of the first region corresponding to the silicon substrate.

[0083] According to some exemplary embodiments of this application, in the first laser scan, the scanning speed is 70000mm / s-90000mm / s, the scanning power is 1W-5W, and the scanning frequency is 1200kHz-1500kHz; in the second laser scan, the scanning speed is 50000mm / s-70000mm / s, the scanning power is 5W-50W, and the scanning frequency is 800kHz-1200kHz. In this embodiment, by setting specific laser scanning speed, power, and frequency, effective control of the battery structure is achieved. The selection of these parameters is based on a deep understanding of the interaction mechanism between laser and materials, ensuring that the laser can accurately form the required doped region on the silicon substrate while controlling the distribution of thermal stress. This parameter setting not only improves the battery yield and reduces the breakage rate but also ensures the electrical performance of the battery.

[0084] Specifically, in the first laser scan, the scanning speed, scanning power, and scanning frequency remain unchanged along the direction from the first sub-region to the second sub-region.

[0085] Specifically, in the first laser scan, the scanning speed can be 80000mm / s, 85000mm / s, or 75000mm / s; the scanning power can be 2W, 4W, or 3W; and the scanning frequency can be 1250kHz, 1300kHz, or 1400kHz. This application does not impose any specific limitations on these parameters.

[0086] In other embodiments, during the second laser scanning, the scanning speed and scanning frequency gradually decrease, while the scanning power gradually increases; alternatively, during the second laser scanning, the scanning speed, scanning power, and scanning frequency remain constant. This embodiment provides two different second laser scanning strategies: a parameter gradient strategy and a parameter fixed strategy, to adapt to different scenarios. The parameter gradient strategy allows for more precise control of thermal stress distribution, while the parameter fixed strategy is suitable for scenarios requiring rapid stabilization. Both strategies can effectively reduce the breakage rate during the fabrication process and improve the electrical performance of the battery.

[0087] Specifically, when there are two first sub-regions in the second direction (the second sub-region is located between the two first sub-regions), in the second laser scan, the scanning speed, scanning power, and scanning frequency can remain unchanged or gradually change as the laser moves from the two edges towards the middle in the second direction. This application does not impose any specific restrictions on these parameters.

[0088] According to some other exemplary embodiments of this application, laser scanning of a portion of the aforementioned pre-existing silicon substrate includes: controlling a laser to begin moving along the direction from the first sub-region to the second sub-region, and activating the laser when the moving time reaches a preset duration. In this embodiment, by controlling the laser's moving time and activation time, the duration of laser action on the silicon substrate can be precisely managed, ensuring that the laser can only scan a specific area within a preset time period. This precise control helps reduce laser edge effects, thereby reducing thermal stress caused by excessively fast or slow laser action.

[0089] Specifically, in the case where there are two first sub-regions in the second direction (the second sub-region is located between the two first sub-regions), the laser can either move along the direction from the first first sub-region to the second sub-region and turn off the laser before moving to the second first sub-region; or it can move along the direction from the second first sub-region to the second sub-region and turn off the laser before moving to the first first sub-region.

[0090] Specifically, the laser is activated only when the movement time reaches a preset time. That is, the first sub-region of the prepared silicon substrate is not scanned by laser, but the laser is activated to scan the second sub-region. This makes the thickness of the first sub-region corresponding to the silicon substrate greater than the thickness of the second sub-region corresponding to the silicon substrate, and equal to the thickness of the first sub-region corresponding to the silicon substrate.

[0091] In practical applications, those skilled in the art can set the above-mentioned preset duration based on experience, or obtain it through multiple experiments. This application does not impose any specific restrictions on this.

[0092] According to some exemplary embodiments of this application, the preset duration is 0.005s-0.015ms. In this embodiment, setting the preset duration to 0.005s-0.015ms is to ensure that the laser action time on the material is sufficiently precise to achieve the purpose of stress release, while avoiding material damage caused by overheating. This time range is selected based on the matching study of laser action time and material thermal stress response time to ensure the best effect of laser action. This helps to improve the accuracy of laser scanning, reduce the fragmentation rate, and ensure the electrical performance of the battery.

[0093] Specifically, in existing laser etching processes, the same laser parameters are used for laser scanning and etching of the second region of a solar cell. One hundred silicon wafers were processed using both existing and the laser etching process described in this application (the laser parameters used for the first laser scan of the first sub-region in this application are the same as those used in the existing laser scan, and the etching parameters after the laser scan in this application are the same as those in the existing laser scan). The performance parameters of the processed silicon wafers are compared in Table 1.

[0094] Table 1

[0095]

[0096] In Table 1, yield rate refers to the proportion of silicon wafers that meet quality standards produced during the production process to the total number of silicon wafers produced; screen printing breakage rate refers to the proportion of metal grid lines on the front or back of the silicon wafer that are broken during the printing process to the total number of grid lines; average sheet resistance uniformity refers to the uniformity of the resistance distribution on the surface of the silicon wafer. It can be calculated by measuring the sheet resistance values ​​at multiple points on the surface of the silicon wafer, and then calculating the average value and standard deviation of the sheet resistance values ​​at these points. Sheet resistance uniformity is expressed as the average value plus or minus a certain range of standard deviation; average deposited poly thickness uniformity refers to the consistency of the thickness of the poly layer deposited on the silicon wafer. It can be calculated by measuring the poly layer thickness at multiple points on the silicon wafer, and then calculating the average thickness and the thickness deviation range. Average deposited poly thickness uniformity is expressed as the average thickness plus or minus the deviation range; average deposited antireflective film (silicon nitride) thickness uniformity refers to the consistency of the thickness of the antireflective film deposited on the silicon wafer. It can be calculated by measuring the antireflective film thickness at multiple points on the silicon wafer, and then calculating the average thickness and the thickness deviation range. Average deposited antireflective film (silicon nitride) thickness uniformity is expressed as the average thickness plus or minus the deviation range.

[0097] As can be seen from Table 1, the silicon wafers obtained by the laser thinning process of this application have better performance than those obtained by the laser thinning process of the prior art.

[0098] This application also provides a stacked battery, such as... Figure 8 As shown, it includes: any of the above-described solar cells 1, or solar cells 1 prepared by any of the above-described methods for preparing solar cells 1.

[0099] Specifically, such as Figure 8As shown, the solar cell 1 of this application serves as the bottom cell 2 of a tandem solar cell. The tandem solar cell further includes a top cell 22 and an interconnecting composite layer 23 located between the bottom cell 2 and the top cell 22. The top cell includes a first carrier transport layer, a perovskite layer, a second carrier transport layer, and a TCO (Transparent Conductive Oxide) transparent electrode stacked sequentially, wherein the first carrier transport layer is either a hole transport layer or an electron transport layer.

[0100] This application also provides a photovoltaic module, including: any of the above-described solar cells, or solar cells prepared by any of the above-described solar cell preparation methods, or the above-described tandem cells.

[0101] Specifically, such as Figure 9 As shown, the photovoltaic module includes: a battery string 24, which is formed by connecting multiple solar cells (not shown) or tandem cells (not shown) as described above; an encapsulating film 25 for covering the surface of the battery string 24; and a cover plate 26 for covering the surface of the encapsulating film 25 facing away from the battery string 24.

[0102] Specifically, the connection between batteries can be achieved through technologies such as welding and laser bonding, with the aim of converging the current generated by the batteries to form a greater output power; the encapsulating film is an important component inside the photovoltaic module, playing a role in sealing and bonding. The encapsulating film can be EVA (ethylene vinyl acetate copolymer), POE (polyolefin elastomer), or other special materials, which can effectively block the influence of external factors such as moisture and dust on the batteries, while maintaining the physical stability of the batteries; the cover plate is usually transparent tempered glass, located on the outermost layer of the photovoltaic module, directly exposed to the external environment. It not only needs to have good light transmittance and mechanical strength, but also needs to have properties such as UV protection, high temperature resistance, and impact resistance to protect the internal batteries from damage.

[0103] Specifically, such as Figure 9 As shown, the photovoltaic module also includes a backsheet material 27, which is located on the back of the photovoltaic module (i.e., the side of the cell string 24 facing away from the cover plate 26). Its main functions are insulation and waterproofing. Common backsheet materials include PVF film (polyvinyl fluoride) and PET film (polyethylene terephthalate), which can improve the durability and safety of the module.

[0104] 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 includes a first surface and a second surface disposed opposite to each other. The first surface includes a first region and a second region alternately arranged along a first direction. The second region includes a first sub-region and a second sub-region arranged along a second direction. The first direction and the second direction intersect. The first metal gate line is located in the first region; The first sub-region includes a first pyramid structure, and the second sub-region includes a second pyramid structure; The height of the first pyramid structure is greater than the height of the second pyramid structure, and the direction of the height is parallel to the thickness direction of the silicon substrate.

2. The solar cell according to claim 1, characterized in that, The distance from the first region to the second surface is h3, and the distance from the first sub-region to the second surface is h2, where h3 ≥ h2.

3. The solar cell according to claim 1, characterized in that, The distance from the second sub-region to the second surface is h1, and the distance from the first sub-region to the second surface is h2, where h1 < h2.

4. The solar cell according to claim 1, characterized in that, The first region includes a first doped region, the first metal gate line is electrically connected to the first doped region, the first sub-region includes a second doped region, the second sub-region includes a third doped region, and the doping concentration of the second doped region is greater than the doping concentration of the third doped region.

5. The solar cell according to claim 4, characterized in that, The doping concentration of the first doped region is greater than or equal to the doping concentration of the second doped region.

6. The solar cell according to any one of claims 1 to 5, characterized in that, The side length of the base of the first pyramid structure is greater than the side length of the base of the second pyramid structure.

7. The solar cell according to any one of claims 1 to 5, characterized in that, The solar cell satisfies at least one of the following: the height of the first pyramid structure is 0.5μm-1.5μm, the side length of the base of the first pyramid structure is 0.5μm-2.5μm, the height of the second pyramid structure is 0.3μm-1μm, and the side length of the base of the second pyramid structure is 0.5μm-2μm.

8. The solar cell according to any one of claims 1 to 5, characterized in that, The length of a single first sub-region in the second direction is 100μm-300μm.

9. The solar cell according to claim 2, characterized in that, The difference between the thickness of the first region and the thickness of the first sub-region is [0.2μm, 1μm].

10. The solar cell according to claim 3, characterized in that, The difference between the thickness of the first sub-region and the thickness of the second sub-region is [2μm, 4μm].

11. The solar cell according to any one of claims 1 to 5, characterized in that, In the second direction, there are two first sub-regions, and the second sub-region is located between the two first sub-regions.

12. The solar cell according to claim 4, characterized in that, The doping concentration of the first doped region is 5e18cm. -3 -1e20cm -3 The doping concentration of the third doped region is 5e14cm. -3 -5e17cm -3 .

13. A photovoltaic module, characterized in that, include: The solar cell according to any one of claims 1 to 12.

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