Solar cells and their manufacturing methods

Abstract

This application relates to a solar cell and a method for manufacturing the same. The solar cell includes a substrate, a polycrystalline silicon layer, and multiple sub-grids. The polycrystalline silicon layer is located on one side of the substrate and includes alternating recesses and protrusions. The width of the protrusions increases sequentially along a first direction parallel to the surface of the substrate. The multiple sub-grids are located on the side of the polycrystalline silicon layer away from the substrate, and each sub-grid contacts one of the protrusions. The first direction is a direction away from the centerline of the substrate, and the extension direction of the centerline is the same as the extension direction of the protrusion. This application ensures that each sub-grid in the solar cell contacts one of the protrusions, improving the alignment accuracy between the sub-grids and the protrusions of the polycrystalline silicon layer, thereby contributing to improved efficiency and availability of the solar cell.

Description

Technical Field

[0001] This application relates to the field of solar cell technology, and in particular to a solar cell and a method for manufacturing the same. Background Technology

[0002] TOPCon (Tunnel Oxide Passivated Contact) cell technology is a solar cell technology based on the selective carrier principle, using a tunneled oxide layer for passivated contacts. Typically, TOPCon cells are built on a silicon substrate, with an ultrathin layer of silicon oxide fabricated on the back side of the cell. A thin layer of doped silicon is then deposited on the side of the ultrathin silicon oxide away from the silicon substrate to form a passivated contact structure, effectively reducing surface recombination and metal-to-metal recombination in TOPCon cells.

[0003] Generally, in laser-etched polycrystalline silicon (PMIC) technology, the larger the laser-etched area in each region and the smaller the PMIC structure, the higher the short-circuit current and the higher the bifaciality of the TOPCon cell. However, as the laser-etched area increases and the PMIC structure decreases, the risk of printing misalignment also increases, which can severely affect the efficiency and availability of the TOPCon cell. Summary of the Invention

[0004] Therefore, it is necessary to provide a solar cell and a method for manufacturing the same, so as to improve the alignment accuracy between the sub-grid and the protrusions of the polycrystalline silicon layer in the solar cell, thereby improving the efficiency and availability of the solar cell.

[0005] This application provides a solar cell, comprising:

[0006] Base;

[0007] A polycrystalline silicon layer is located on one side of the substrate. The polycrystalline silicon layer includes alternating recesses and protrusions, and the width of the protrusions increases sequentially along a first direction parallel to the surface of the substrate.

[0008] Multiple sub-gates are located on the side of the polysilicon layer away from the substrate, and each sub-gate is in contact with a protrusion.

[0009] Wherein, the first direction is the direction away from the centerline of the base, and the extension direction of the centerline is the same as the extension direction of the protrusion.

[0010] In one embodiment, along the first direction, the width variation between the two protrusions on either side of any recess is equal to a set value.

[0011] In one embodiment, the width of the recess decreases sequentially along the first direction.

[0012] In one embodiment, the minimum width of the protrusion is greater than the width of the sub-gate.

[0013] In one embodiment, the distance between any two adjacent subgates is the same.

[0014] In one embodiment, the substrate includes a silicon wafer, the side of the silicon wafer away from the polycrystalline silicon layer having a textured surface;

[0015] The solar cell also includes:

[0016] A tunneling oxide layer is located between the substrate and the polycrystalline silicon layer;

[0017] A passivation layer is located on the side of the polysilicon layer away from the substrate. The passivation layer has an opening that exposes the protrusion, and the sub-gate is disposed within the opening.

[0018] Accordingly, this application also provides a method for manufacturing a solar cell, comprising:

[0019] A substrate is provided, a polycrystalline silicon layer is formed on one side surface of the substrate, and a protective layer is formed on the polycrystalline silicon layer;

[0020] The protective layer is subjected to laser-induced film opening to form a non-contact area within the protective layer;

[0021] The non-contact area and the portion of the polysilicon layer located directly below the non-contact area are etched to form a plurality of spaced-apart recesses in the polysilicon layer. A protrusion is formed in the portion of the polysilicon layer located directly below the protective layer. The width of the protrusion increases sequentially along a first direction parallel to the surface of the substrate. The first direction is a direction away from the centerline of the substrate, and the extension direction of the centerline is the same as the extension direction of the protrusion.

[0022] A screen printing process is performed to form multiple sub-gates on the side of the polysilicon layer away from the substrate, and each sub-gate is formed on a protrusion.

[0023] In one embodiment, the process of laser molding the protective layer includes:

[0024] A laser source is provided, the laser source comprising two parallel lasers, the laser processing areas corresponding to the two lasers at least partially overlapping;

[0025] The protective layer is subjected to multiple laser-induced film-opening processes using the laser source, with each laser-induced film-opening process forming a non-contact area.

[0026] The width of the non-contact area is inversely related to the overlap area between the two laser processing areas.

[0027] In one embodiment, after etching the non-contact area and the portion of the polycrystalline silicon layer located directly below the non-contact area, and before screen printing, the method for manufacturing the solar cell further includes:

[0028] Remove the protective layer.

[0029] In one embodiment, after removing the protective layer and before performing screen printing, the method for manufacturing the solar cell further includes:

[0030] A passivation layer is formed on the side of the polysilicon layer away from the substrate;

[0031] The passivation layer is etched to form an opening in the passivation layer that exposes the protrusion.

[0032] In one embodiment, the process of forming a polycrystalline silicon layer on one side surface of the substrate includes:

[0033] A silicon wafer is provided, and the silicon wafer is texturized to form the substrate, wherein a texturized structure is formed on one side surface of the substrate;

[0034] The substrate is subjected to edge etching and backside etching to remove byproducts located on the sides of the substrate and on the surface of the substrate away from the textured structure;

[0035] A tunneling oxide layer is formed on the side of the substrate away from the velvet structure;

[0036] The polysilicon layer is formed on the side of the tunneling oxide layer away from the substrate, and the polysilicon layer is subjected to phosphorus diffusion treatment to form the phosphorus-doped polysilicon layer.

[0037] In one embodiment, after forming multiple sub-gates on the side of the polycrystalline silicon layer away from the substrate, the method of manufacturing the solar cell further includes:

[0038] The solar cell is subjected to sintering treatment;

[0039] The solar cells are then tested and sorted.

[0040] In summary, this application provides a solar cell and a method for manufacturing the same. By providing alternating recesses and protrusions within a polycrystalline silicon layer, and wherein the width of the protrusions increases sequentially along a first direction parallel to the surface of the substrate, wherein the first direction is a direction away from the centerline of the substrate, and the extension direction of the centerline is the same as the extension direction of the protrusion, each sub-grid in the solar cell contacts one of the protrusions, thereby improving the alignment accuracy between the sub-grids and the protrusions of the polycrystalline silicon layer in the solar cell, and thus helping to improve the efficiency and availability of the solar cell. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology 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.

[0042] Figure 1 This is a schematic diagram of a laser pattern for finger-shaped polycrystalline silicon in a related technology.

[0043] Figure 2 This is a schematic diagram of the structure when the sub-gate lines are misaligned during the laser printing process in a related technology.

[0044] Figure 3 This is a schematic diagram of the structure of a solar cell subjected to laser film opening according to one embodiment of this application.

[0045] Figure 4 This is a schematic diagram of the cross-sectional structure of a solar cell along a first direction, provided in one embodiment of this application.

[0046] Figure 5 A flowchart illustrating a method for manufacturing a solar cell according to one embodiment of this application.

[0047] Figure 6 This is a schematic diagram of the structure corresponding to the step of providing a substrate in the manufacturing method of a solar cell according to one embodiment of this application.

[0048] Figure 7 This is a schematic diagram of the structure corresponding to the step of laser-opening the protective layer in the manufacturing method of a solar cell provided in one embodiment of this application.

[0049] Figure 8 This is a schematic diagram of the structure corresponding to the step of etching the non-contact area and the portion of the polycrystalline silicon layer directly below it in the manufacturing method of a solar cell provided in one embodiment of this application.

[0050] Figure 9 This is a schematic diagram of the structure corresponding to the screen printing process in the manufacturing method of a solar cell provided in one embodiment of this application.

[0051] The reference numerals in the figures include: 100-substrate; 101-silicon wafer; 101a-textured structure; 102-tunneling oxide layer; 103-first doped layer; 103a-heavily doped region; 104-emitter; 110-polycrystalline silicon layer; 110a-protective layer; 110b-non-contact region; 111-recess; 111a-first recess; 111b-second recess; 112-protrusion; 112a-first protrusion; 112b-second protrusion; 113-passivation layer; 120-subgate; O-laser source. Detailed Implementation

[0052] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0053] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0054] It should be understood that when an element or layer is referred to as "on," "adjacent to," "connected to," or "coupled to" other elements or layers, it may be directly on, adjacent to, connected to, or coupled to other elements or layers, or there may be intervening elements or layers. Conversely, when an element is referred to as "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" other elements or layers, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc., may be used to describe various elements, parts, regions, layers, doping types, and / or portions, these elements, parts, regions, layers, doping types, and / or portions should not be limited by these terms. These terms are only used to distinguish one element, part, region, layer, doping type, or portion from another element, part, region, layer, doping type, or portion. Therefore, without departing from the teachings of this application, the first element, component, region, layer, doping type, or portion discussed below may be represented as a second element, component, region, layer, or portion; for example, the first doping type may be referred to as the second doping type, and similarly, the second doping type may be referred to as the first doping type; the first doping type and the second doping type are different doping types, for example, the first doping type may be P-type and the second doping type may be N-type, or the first doping type may be N-type and the second doping type may be P-type.

[0055] Spatial relation terms such as “below,” “under,” “below,” “under,” “above,” “above,” etc., are used herein to describe the relationship between one element or feature shown in the figure and other elements or features. It should be understood that, in addition to the orientation shown in the figure, spatial relation terms also include different orientations of the device in use and operation. For example, if the device in the figure is flipped, the element or feature described as “below,” “under,” or “below” will be oriented “above” the other element or feature. Therefore, the exemplary terms “below” and “under” can include both above and below orientations. Furthermore, the device may also include other orientations (e.g., rotated 90 degrees or other orientations), and the spatial descriptive terms used herein will be interpreted accordingly.

[0056] When used herein, the singular forms of “a,” “an,” and “ / the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising / including” or “having,” etc., specify the presence of the stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. Meanwhile, in this specification, the term “and / or” includes any and all combinations of the associated listed items.

[0057] TOPCon (Tunnel Oxide Passivated Contact) cell technology is a solar cell technology based on the selective carrier principle, using a tunneled oxide layer for passivated contacts. Typically, TOPCon cells are built on a silicon substrate, with an ultrathin layer of silicon oxide fabricated on the back side of the cell. A thin layer of doped silicon is then deposited on the side of the ultrathin silicon oxide away from the silicon substrate to form a passivated contact structure, effectively reducing surface recombination and metal-to-metal recombination in TOPCon cells.

[0058] When a tunneling passivation structure is used on the front or back of a TOPCon cell, silicon parasitic absorption in polycrystalline silicon severely hinders further improvements in cell efficiency. To address this issue, poly-finger technology can be employed to maintain a relatively thick polycrystalline silicon layer in the metal contact area of ​​the TOPCon cell, thereby reducing contact resistance. Furthermore, processes such as laser thinning can be used to reduce the thickness of the polycrystalline silicon layer in the non-metallic contact area of ​​the TOPCon cell, thus reducing infrared parasitic absorption and ultimately improving the short-circuit current (Isc) of the TOPCon cell.

[0059] In general, in laser-etched polycrystalline silicon, the specific morphology of the laser pattern is as follows: Figure 1 As shown. See also Figure 1 In a TOPCon cell, the laser-cut film size A1 is the same in all non-metallic contact areas, and the size A2 of the poly-finger in each metallic contact area is the same. The spacing A3 between adjacent sub-gate lines is the sum of the laser-cut film size A1 in the non-metallic contact area and the size A2 of the poly-finger (i.e., A3 = A1 + A2). Based on this, the larger the laser-cut film size A1 in each non-metallic contact area and the smaller the size of the poly-finger structure A2, the higher the short-circuit current and the higher the bifaciality of the TOPCon cell. However, as the laser-cut film size A1 in each non-metallic contact area increases and the size A2 of the poly-finger structure decreases, the risk of misalignment during laser printing also increases.

[0060] Figure 2 This is a schematic diagram illustrating the structure of a sub-grid line during laser printing in a related technology, where the solid line represents the actual printing position of the sub-grid line, and the dashed line represents the designed printing position. (See also...) Figure 2In actual printing production, the screen printing plate deforms due to continuous pressure, causing the printing sub-grids to deform sequentially and expand outwards. At this time, the expansion amount varies for different sub-grids in the TOPCon cell. Along the direction perpendicular to the extension of the sub-grids and away from the center of the laser pattern, the offset of different sub-grids from the center to the edge increases sequentially. That is, the offset of the x-th sub-grid, starting from the midpoint of the laser pattern, is Nx, and the relationship between the offsets of each sub-grid is: N1 < N2 < ... < Nx. Optionally, along the direction perpendicular to the extension of the sub-grids and away from the center of the laser pattern, the offset of different sub-grids from the center to the edge increases in an arithmetic progression.

[0061] Based on the above, within the cell area of ​​TOPCon, the actual printed positions of all sub-gate lines deviate from their designed positions. The closer to the edge of the laser pattern, the greater the deviation; conversely, the closer to the center of the laser pattern, the smaller the deviation. This indicates that the finger-shaped polycrystalline silicon layers located in the edge region (i.e., near the edge of the laser pattern) of the TOPCon cell have a significant risk of misalignment.

[0062] Generally, the alignment misalignment risk mentioned above can be avoided by increasing the size of the finger polycrystalline silicon (e.g., increasing the width of the finger polycrystalline silicon). However, the larger the size of the finger polycrystalline silicon, the smaller the size of the laser-opened film region will be, leading to an increase in infrared parasitic absorption, which will seriously affect the battery efficiency.

[0063] To address the aforementioned issues, this application provides a solar cell and a method for manufacturing the same, thereby improving the alignment accuracy between the sub-grid and the protrusions of the polycrystalline silicon layer in the solar cell, and thus enhancing the efficiency and availability of the solar cell.

[0064] Figure 3 This is a schematic diagram of the structure of a solar cell undergoing laser-assisted film opening according to one embodiment of this application. Figure 4 This is a schematic cross-sectional view of a solar cell along a first direction, provided in one embodiment of this application. (See also...) Figure 3 and Figure 4 The solar cell includes a substrate 100, a polycrystalline silicon layer 110, and multiple sub-gates 120. The polycrystalline silicon layer 110 is located on one side of the substrate 100 and includes alternating recesses 111 and protrusions 112. The width of the protrusions 112 increases sequentially along a first direction (X-direction) parallel to the surface of the substrate 100. The multiple sub-gates 120 are located on the side of the polycrystalline silicon layer 110 away from the substrate 100, and each sub-gate 120 contacts a protrusion 112. The first direction (X-direction) is the centerline away from the substrate 100. Figure 3 In the figure, AB represents the direction of the center line, and the extension direction of the center line is the same as the extension direction of the protrusion 112.

[0065] It should be noted that by increasing the width of the protrusions in the polysilicon layer along the first direction, the change in the width of the protrusions in the polysilicon layer (e.g., the increase in width along the first direction) is greater than the offset that may occur during the formation of the sub-gate by screen printing. This ensures that each sub-gate can contact a protrusion, thereby reducing or avoiding the problem of misalignment between the sub-gate and the protrusion caused by screen printing of the sub-gate.

[0066] The solar cell described above, by providing alternating recesses and protrusions within the polycrystalline silicon layer, wherein the width of the protrusions increases sequentially along a first direction parallel to the surface of the substrate, wherein the first direction is a direction away from the centerline of the substrate, and the extension direction of the centerline is the same as the extension direction of the protrusion, ensures that each sub-grid in the solar cell contacts one of the protrusions, thereby improving the alignment accuracy between the sub-grids and the protrusions of the polycrystalline silicon layer in the solar cell, thus helping to improve the efficiency and availability of the solar cell.

[0067] Continue reading Figure 3 In one embodiment, the minimum width of the protrusion 112 is greater than the width of the sub-gate 120 to ensure that the sub-gate 120 can be disposed on the surface of the protrusion 112 away from the substrate 100. Optionally, the distance between any two adjacent sub-gates 120 is the same.

[0068] It should be noted that during the actual screen printing process, the positions of the multiple sub-grids may shift due to defects in the screen printing process, resulting in a misalignment between the actual and preset positions of adjacent sub-grids in the final solar cell. However, the distance between any two adjacent sub-grids remains the same; the difference between the actual distance and the preset distance between adjacent sub-grids is the actual offset of the sub-grid. Optionally, the actual offset can be a fixed value.

[0069] Based on this, since the actual offset of the sub-grid is positively correlated with the distance between the sub-grid and the center line during the screen printing process, by increasing the width of the protrusion along the first direction, it can be ensured that the sub-grid is still formed on the protrusion after the offset, thereby improving the alignment accuracy between the sub-grid and the protrusion.

[0070] In one embodiment, the distance between the sub-gate and the center line and the actual offset of the sub-gate during screen printing can be collected and analyzed. A data model is established to obtain the quantitative relationship between the two, and the offset of each sub-gate is predicted using simulation methods. Based on the predicted offset value of each sub-gate, the width of the protrusion in the polysilicon layer is adjusted. Optionally, each sub-gate corresponds to a predicted offset value, and the relationship between each sub-gate and the protrusion it contacts is: the sum of the current sub-gate's predicted offset value P and the current sub-gate's width Q is less than or equal to the width D of the protrusion currently contacted by the sub-gate, i.e. .

[0071] In other embodiments of this application, the position of the protrusion can also be adjusted according to the predicted offset value of each sub-gate, thereby improving the alignment accuracy between the sub-gate and the protrusion without increasing the width of the protrusion, thus reducing the infrared parasitic absorption phenomenon of the solar cell, and further helping to improve the bifaciality and short-circuit current (Isc) of the solar cell. In other embodiments of this application, the specific method for obtaining the predicted offset value can be adjusted according to actual needs based on common knowledge in the art and algorithm fields, and will not be elaborated here.

[0072] In one embodiment, since the distance between any two adjacent sub-gates is the same, the two adjacent sub-gates are respectively located on two adjacent protrusions, and a recess is provided between the two adjacent protrusions, the relationship between the distance between two adjacent sub-gates and the widths of the two corresponding protrusions and the width of the recess is as follows:

[0073] ;

[0074] Where G represents the distance between two adjacent subgates. This indicates the width of the protrusion corresponding to one of the subgates. The width of the protrusion corresponding to the other subgate is represented by i, where i is a positive integer and i is greater than 1, and W represents the width of the recess between two adjacent subgates.

[0075] Based on the above relationship, in one embodiment, since the distance between any two adjacent sub-gates is the same, the width of the protrusion increases sequentially along the first direction, and therefore the width of the recess decreases sequentially along the first direction.

[0076] In one embodiment, along the first direction, the width variation between the two protrusions on either side of any recess is equal to a predetermined value. It should be emphasized that, when the centerline passes through one of the protrusions of the polysilicon layer, along the first direction, the width variation between the two protrusions on either side of any recess is equal to a predetermined value; when the centerline passes through one of the recesses of the polysilicon layer, along the first direction, except for the recess containing the centerline, the width variation between the two protrusions on either side of any other recess is equal to a predetermined value.

[0077] Optional, see below Figure 3 The centerline AB passes through the first recess 111a. Along a first direction away from the centerline AB (i.e., the X direction), the first recess 111 starting from the centerline AB is the first recess 111a, and the second recess 111 starting from the centerline AB is the second recess 111b. The width of the first recess 111a is W1, the width of the second recess 111b is W2, and so on. Therefore, the width of the nth recess starting from the centerline AB is Wn (n>0 and n is positive). (Integer); Accordingly, along the first direction away from the center line AB (i.e., the X direction), the first protrusion 112 in the polysilicon layer 110 starting from the center line AB is the first protrusion 112a, the second protrusion 112 starting from the center line AB is the second protrusion 112b, and the width of the first protrusion 112a is D1, the width of the second protrusion 112b is D2, and so on, it can be known that the width of the nth protrusion starting from the center line AB is Dn (n>0 and n is a positive integer).

[0078] It can be seen that, due to Figure 3 The centerline AB of the solar cell shown passes through the first recess 111a. Therefore, along the first direction (i.e., the X direction), except for the recess 111 containing the centerline AB (i.e., the first recess 111a), the width variation between the two protrusions 112 on both sides of any other recess 111 is equal to a set value. For example, the width variation between the two protrusions 112 on both sides of the second recess 111b (i.e., the first protrusion 112a and the second protrusion 112b) is a set value, and the width variation between the two protrusions 112 on both sides of the nth recess (i.e., the (n-1)th protrusion and the nth protrusion) is also equal to the set value. That is, Where C is a set value, n is used to represent the order of the protrusions or depressions along the first direction from the center line, and n is a positive integer and n is greater than 1.

[0079] It should be noted that in other embodiments of this application, the dimensional variation relationship of different parts within the polysilicon layer (the dimensional variation relationship includes at least the width variation relationship of different protrusions along the first direction and the width variation relationship of different recesses along the first direction) can be adjusted according to actual needs. It is only necessary to ensure that "the protrusions and the subsequently formed sub-gates can correspond one-to-one and contact each other in the direction perpendicular to the substrate". This application does not impose any restrictions on this.

[0080] See Figure 3 and Figure 4 In one embodiment, the substrate 100 includes a silicon wafer 101, the surface of the silicon wafer 101 away from the polycrystalline silicon layer 110 having a textured surface 101a; correspondingly, the solar cell also includes a tunneling oxide layer 102 and a passivation layer 113, wherein the tunneling oxide layer 102 is located between the substrate 100 and the polycrystalline silicon layer 110, and the passivation layer 113 is located on the side of the polycrystalline silicon layer 110 away from the substrate 100, and the passivation layer 113 has a passivation layer opening exposing a protrusion 112, and a sub-gate 120 is disposed within the passivation layer opening. Optionally, the material of the tunneling oxide layer 102 includes silicon oxide; the material of the passivation layer 113 includes one or more of the following materials: silicon nitride, silicon oxynitride, silicon carbonitride, titanium oxide, hafnium oxide, and aluminum oxide.

[0081] Continue reading Figure 4 In one embodiment, a first doped layer 103 is disposed in the substrate 100 near the textured structure 101a in the solar cell, and a plurality of heavily doped regions 103a are disposed in the first doped layer 103 at intervals. Optionally, the width of the heavily doped region 103a increases sequentially along a direction parallel to the surface of the substrate 100 and away from the centerline of the substrate 100 (not shown in the figure), and a plurality of emitters 104 are disposed on the side of the heavily doped region 103a away from the substrate 100, and each emitter 104 is in contact with a heavily doped region 103a to improve the alignment accuracy between the heavily doped region 103a and the emitter 104.

[0082] Figure 5 A flowchart illustrating a method for manufacturing a solar cell according to one embodiment of this application. Accordingly, see [link to relevant documentation]. Figure 5 One embodiment of this application provides a method for manufacturing a solar cell, which includes the following steps S01 to S04.

[0083] Step S01: Provide a substrate, form a polysilicon layer on one side surface of the substrate, and form a protective layer on the polysilicon layer.

[0084] Step S02: Perform laser-assisted delamination on the protective layer to form a non-contact area within the protective layer.

[0085] It should be noted that during the laser-induced film-opening process of the protective layer, multiple non-contact areas are formed within the protective layer, and the width of the non-contact areas increases sequentially along a first direction parallel to the surface of the substrate, so as to form protrusions that meet the process requirements in the next step.

[0086] Step S03: Etch the non-contact area and the portion of the polysilicon layer located directly below the non-contact area to form a plurality of spaced-apart recesses in the polysilicon layer. A protrusion is formed in the portion of the polysilicon layer located directly below the protective layer. The width of the protrusion increases sequentially along a first direction parallel to the surface of the substrate. The first direction is a direction away from the centerline of the substrate, and the extension direction of the centerline is the same as the extension direction of the protrusion.

[0087] Step S04: Perform screen printing to form multiple sub-gates on the side of the polysilicon layer away from the substrate, and each sub-gate is formed on a protrusion.

[0088] It should be noted that during the process of forming the sub-grids using screen printing, the screen will deform due to continuous pressure, causing the printed sub-grids to deform sequentially and spread in the printing direction. Therefore, along the first direction away from the center line, the potential offset of multiple sub-grids increases sequentially. At this time, since the width of the protrusions formed in step S03 increases sequentially along the first direction, the width of each protrusion can be set to be greater than the potential offset of its corresponding sub-grid. This reduces or even avoids misalignment between the sub-grids and the protrusions, improving alignment accuracy.

[0089] The solar cell manufacturing method described above forms alternating recesses and protrusions within a polycrystalline silicon layer, with the width of the protrusions increasing sequentially along a first direction parallel to the surface of the substrate. This first direction is away from the centerline of the substrate, and the extension direction of the centerline is the same as the extension direction of the protrusion. This ensures that each sub-grid in the solar cell contacts one of the protrusions, improving the alignment accuracy between the sub-grids and the protrusions of the polycrystalline silicon layer, thereby contributing to improved efficiency and availability of the solar cell.

[0090] Figures 6 to 9 This is a schematic diagram of some steps in the manufacturing method of a solar cell according to one embodiment of this application. The following is a combined description of the structural diagrams. Figures 6 to 9 This application describes in detail a method for manufacturing a solar cell according to one embodiment.

[0091] First, refer to Figure 6In one embodiment, a substrate 100 is provided, a polycrystalline silicon layer 110 is formed on one side surface of the substrate 100, and a protective layer 110a is formed on the polycrystalline silicon layer 110. Optionally, the protective layer 110a is formed on the polycrystalline silicon layer 110 using a low-pressure chemical vapor deposition (LPCVD) process. Optionally, the material of the protective layer 110a includes phosphosilicate glass (PSG).

[0092] Continue reading Figure 6 In one embodiment, the process of forming a polysilicon layer 110 on one side surface of a substrate 100 includes: providing a silicon wafer 101; texturing the silicon wafer 101 to form a substrate 100, wherein a textured structure 101a is formed on one side surface of the substrate 100; performing edge etching and back-side etching on the substrate 100 to remove byproducts (not shown) located on the side edges of the substrate 100 and on the surface of the substrate 100 away from the textured structure 101a; forming a tunneling oxide layer 102 on the side of the substrate 100 away from the textured structure 101a; forming a polysilicon layer 110 on the side of the tunneling oxide layer 102 away from the substrate 100; and performing phosphorus diffusion on the polysilicon layer 110 to form a phosphorus-doped polysilicon layer 110. Optionally, the material of the tunneling oxide layer 102 includes silicon oxide.

[0093] Next, refer to Figure 7 In one embodiment, the protective layer 110a is subjected to laser ablation to form a non-contact region 110b within the protective layer 110a. Optionally, the side surface of the substrate 100 where the protective layer 110a is formed includes the non-contact region 110b and a metal contact region (i.e., the area in the protective layer 110a other than the non-contact region 110b). The non-contact region 110b in the protective layer 110a has been modified under the action of laser during the laser ablation process, making the non-contact region 110b easier to remove in the subsequent etching process. This allows the protective layer 110a to serve as a mask for the polysilicon layer 110, ensuring the smooth progress of the subsequent etching process.

[0094] Continue reading Figure 7 In one embodiment, the process of laser mold opening of the protective layer 110a includes: providing a laser source O, the laser source O comprising two parallel laser beams (i.e., Figure 7 Lasers L1 and L2), and the laser processing areas corresponding to the two lasers (i.e. Figure 7The triangular regions corresponding to lasers L1 and L2 respectively at least partially overlap; the protective layer 110a is subjected to multiple laser-induced film-opening processes using laser source O, with each laser-induced film-opening process forming a non-contact area 110b; wherein, the width of the non-contact area 110b is equal to the overlap area between the two laser-processed regions (i.e., Figure 7 The overlapping areas of the two triangular laser processing regions in the middle show an inverse correlation.

[0095] It should be noted that by using a laser source composed of two parallel lasers to perform laser-based delamination of the protective layer, the overlap area of ​​the laser-treated regions corresponding to the two lasers can be adjusted by changing the distance between the two lasers, thereby adjusting the width of the laser-delamination area (i.e., the formed non-contact area). In this case, the laser source, as described above, employs a "double-line" design, achieving a larger delamination width, improving the applicability of the laser source, and enhancing the flexibility and controllability of the laser-based delamination process.

[0096] In one embodiment of this application, the following can also be used: Figure 7 The "double-line" laser source shown is used for laser doping. Optional, see [link / reference]. Figure 6 After forming the textured structure 101a and before forming the tunneling oxide layer 102 on the side of the substrate 100 away from the textured structure 101a, the method for manufacturing a solar cell further includes: performing a boron diffusion treatment on the substrate 100, forming a first doped layer 103 on the side of the substrate 100 where the textured structure 101a is formed; then, performing laser doping treatment on the first doped layer 103 using a "double-line" laser source to form a plurality of mutually spaced heavily doped regions 103a in the first doped layer 103, and the width of the heavily doped regions 103a increases sequentially along the first direction so that an emitter 104 can be subsequently formed on the heavily doped regions 103a.

[0097] It is important to emphasize that during the formation of the emitter, the position of the emitter prepared by screen printing may shift to varying degrees due to defects in the screen printing process, resulting in inconsistencies in the actual distance between adjacent emitters in the final solar cell. Since the actual offset of the emitter during screen printing is positively correlated with the distance between the emitter and the center line, increasing the width of the heavily doped region sequentially along the first direction ensures that the offset emitter still forms on the heavily doped region, thereby improving the alignment accuracy between the heavily doped region and the emitter.

[0098] Then refer to Figure 7 and Figure 8In one embodiment, the non-contact region 110b and the portion of the polysilicon layer 110 located directly below the non-contact region 110b are etched to form a plurality of spaced-apart recesses 111 within the polysilicon layer 110. A protrusion 112 is formed in the portion of the polysilicon layer 110 located directly below the protective layer 110a. The width of the protrusion 112 increases sequentially along a first direction (i.e., the X direction) parallel to the surface of the substrate 100. The first direction is away from the centerline of the substrate 100 (i.e., the direction of X). Figure 3 The direction of the center line AB is the same as the direction of the extension of the protrusion 112. Optionally, a wet etching process is used to etch the non-contact area 110b and the polysilicon layer 110, and an alkaline cleaning agent is used for the wet etching process.

[0099] In one embodiment, after forming the recesses and protrusions using etching, the method for manufacturing the solar cell further includes removing the remaining protective layer. Optionally, a wet cleaning process is used to remove the remaining protective layer. Optionally, the polycrystalline silicon layer after etching is a finger-shaped polycrystalline silicon layer.

[0100] See Figure 9 In one embodiment, after removing the protective layer and before screen printing, the method for manufacturing a solar cell further includes: forming a passivation layer 113 on the side of the polycrystalline silicon layer 110 away from the substrate 100; and etching the passivation layer 113 to form passivation layer openings that expose the protrusions 112.

[0101] Continue reading Figure 9 In one embodiment, a screen printing process is performed to form a plurality of sub-gates 120 on the side of the polysilicon layer 110 away from the substrate 100, and each sub-gate 120 is formed on a protrusion 112.

[0102] It is important to emphasize that in the actual screen printing process, the positions of the multiple sub-gates may shift to varying degrees due to defects in the screen printing process, resulting in inconsistencies in the actual distances between adjacent sub-gates in the final solar cell. Since the actual offset of the sub-gate is positively correlated with the distance between the sub-gate and the center line during screen printing, increasing the width of the protrusions sequentially along the first direction ensures that the offset sub-gates still form on the protrusions, thereby improving the alignment accuracy between the sub-gates and the protrusions.

[0103] In one embodiment, after forming multiple sub-gates on the side of the polycrystalline silicon layer away from the substrate, the method for manufacturing the solar cell further includes: sintering the solar cell to reduce the contact resistance of the solar cell and improve the photoelectric conversion efficiency of the solar cell; and testing and sorting the solar cell to improve the yield of the solar cell.

[0104] In summary, this application provides a solar cell and a method for manufacturing the same. By providing alternating recesses and protrusions within a polycrystalline silicon layer, and wherein the width of the protrusions increases sequentially along a first direction parallel to the surface of the substrate, wherein the first direction is a direction away from the centerline of the substrate, and the extension direction of the centerline is the same as the extension direction of the protrusion, each sub-grid in the solar cell contacts one of the protrusions, thereby improving the alignment accuracy between the sub-grids and the protrusions of the polycrystalline silicon layer in the solar cell, and thus helping to improve the efficiency and availability of the solar cell.

[0105] In the description of this specification, the references to terms such as "some embodiments," "other embodiments," "ideal embodiments," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example that are included in at least one embodiment or example of this application. In this specification, the illustrative descriptions of the above terms do not necessarily refer to the same embodiments or examples.

[0106] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features of the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0107] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for manufacturing a solar cell, characterized by, The method comprises the following steps: providing a substrate, forming a polysilicon layer on one side surface of the substrate, and forming a protective layer on the polysilicon layer; performing laser opening film processing on the protective layer to form a non-contact area in the protective layer; performing etching processing on the non-contact area and the part of the polysilicon layer located directly below the non-contact area to form a plurality of recessed parts spaced from each other in the polysilicon layer, the part of the polysilicon layer located directly below the protective layer forms a protruding part, and the width of the protruding part increases in sequence along a first direction parallel to the surface of the substrate, the first direction is away from the center line of the substrate, and the extension direction of the center line is the same as the extension direction of the protruding part; performing screen printing processing to form a plurality of auxiliary grids on the side of the polysilicon layer away from the substrate, and each auxiliary grid is formed on only one protruding part, and the extension direction of the auxiliary grid is the same as the extension direction of the protruding part; wherein the process of performing laser opening film processing on the protective layer comprises: providing a laser source, the laser source comprises two parallel lasers, and the two lasers correspond to at least partially overlapping laser processing areas respectively; performing multiple laser opening film processing on the protective layer by using the laser source, and each laser opening film processing forms a non-contact area; wherein the width of the non-contact area is inversely related to the overlapping area between the two laser processing areas.

2. The method for manufacturing a solar cell according to claim 1, wherein After performing etching processing on the non-contact area and the part of the polysilicon layer located directly below the non-contact area, and before performing screen printing processing, the method for manufacturing the solar cell further comprises: removing the remaining protective layer.

3. The method for manufacturing a solar cell according to claim 2, wherein After removing the protective layer, and before performing screen printing processing, the method for manufacturing the solar cell further comprises: forming a passivation layer on the side of the polysilicon layer away from the substrate; performing etching processing on the passivation layer to form a passivation layer opening exposing the protruding part.

4. The method for manufacturing a solar cell according to claim 1, wherein The process of forming a polysilicon layer on one side surface of the substrate comprises: providing a silicon wafer, performing texturing processing on the silicon wafer to form the substrate, and forming a textured structure on one side surface of the substrate; performing edge etching and back etching processing on the substrate to remove by-products on the side edges of the substrate and the surface of the side of the substrate away from the textured structure; forming a tunneling oxide layer on the side of the substrate away from the textured structure; forming the polysilicon layer on the side of the tunneling oxide layer away from the substrate, and performing phosphorus diffusion processing on the polysilicon layer to form a phosphorus-doped polysilicon layer.

5. The method of manufacturing a solar cell according to claim 1, wherein After forming a plurality of auxiliary grids on the side of the polysilicon layer away from the substrate, the method for manufacturing the solar cell further comprises: performing sintering processing on the solar cell; performing test sorting processing on the solar cell.

6. A solar cell produced by the method for producing a solar cell according to any one of claims 1 to 5, characterized by The solar cell comprises: a substrate; a polysilicon layer located on one side of the substrate, the polysilicon layer comprises alternating recessed parts and protruding parts, and the width of the protruding part increases in sequence along a first direction parallel to the surface of the substrate. A plurality of auxiliary grids are located on the side of the polysilicon layer away from the substrate, and each auxiliary grid is in contact with only one protruding part, and the extension direction of the auxiliary grid is the same as that of the protruding part. The first direction is a direction away from the center line of the substrate, and the extension direction of the center line is the same as that of the protruding part.

7. The solar cell according to claim 6, characterized in that, Along the first direction, the width variation between the two protruding parts on both sides of any one recessed part is equal to a set value.

8. The solar cell according to claim 6 or 7, characterized in that, Along the first direction, the width of the recessed part decreases in turn.

9. The solar cell of claim 6, wherein, The minimum width of the protruding part is greater than the width of the auxiliary grid.

10. The solar cell of claim 6, wherein, The distance between any two adjacent auxiliary grids is the same.

11. The solar cell of claim 6, wherein, The substrate comprises a silicon wafer, and the surface of the silicon wafer away from the polysilicon layer is a textured structure. The solar cell further comprises: A tunneling oxide layer is located between the substrate and the polysilicon layer. A passivation layer is located on the side of the polysilicon layer away from the substrate, the passivation layer is provided with a passivation layer opening exposing the protruding part, and the auxiliary grid is arranged in the passivation layer opening.

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