Solar cells and their preparation methods

Abstract

This application provides a solar cell and a method for fabricating the same. The method includes: providing a solar cell having a first side and a second side opposite to each other; the first side having multiple first grid lines and the second side having multiple second grid lines; obtaining the overlap index of each first grid line on the solar cell; classifying the first grid lines according to their overlap index to divide them into at least a first type of grid line and a second type of grid line; and performing a laser-assisted sintering process, wherein the process parameters used for the first type of grid lines are within a first parameter range, and the process parameters used for the second type of grid lines are within a second parameter range, wherein the maximum value of at least one parameter range in the first parameter range is less than or equal to the minimum value of the corresponding parameter range in the second parameter range. The solar cell and the method for fabricating the same provided by this application are at least beneficial for improving the yield and efficiency of solar cells.

Description

Technical Field

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

[0002] Laser-enhanced contact optimization (LECO) technology uses a high-intensity laser to irradiate the solar cell to excite charge carriers, while simultaneously applying a reverse voltage of 10V or higher to the grid lines on the cell. This generates a local current of several amperes, causing sintering and initiating interdiffusion between the silver paste and the substrate, which helps reduce the contact resistance between the metal and the semiconductor. LECO allows for a wider sintering temperature window, enables proper contact on ultra-low doped emitters, and allows for higher open-circuit voltages.

[0003] However, under-sintering or insufficient sintering can easily occur during laser-assisted sintering, leading to a decrease in the yield and efficiency of solar cells. Summary of the Invention

[0004] This application provides a solar cell and a method for its fabrication, which at least helps to improve the yield and efficiency of solar cells.

[0005] According to some embodiments of this application, one aspect of this application provides a method for fabricating a solar cell, comprising: providing a solar cell having a first surface and a second surface opposite to each other, the first surface having a plurality of first grid lines, and the second surface having a plurality of second grid lines, the first grid lines and the second grid lines extending in the same direction; obtaining an overlap index for each first grid line on the solar cell, the overlap index representing the degree of overlap between the orthographic projection of the first grid line on the first surface and the orthographic projection of the second grid line on the first surface; classifying the first grid lines according to the overlap index of each first grid line, so as to divide the first grid lines into at least a first type of grid line and a second type of grid line, wherein the overlap index corresponding to the first grid line in the first type of grid line is in a first range, the overlap index corresponding to the first grid line in the second type of grid line is in a second range, the minimum value of the first range is greater than or equal to the maximum value of the second range; performing a laser-assisted sintering process, wherein the process parameters used for the first type of grid line are in a first parameter range, the process parameters used for the second type of grid line are in a second parameter range, and the maximum value of at least one parameter range in the first parameter range is less than or equal to the minimum value of the corresponding parameter range in the second parameter range.

[0006] In some embodiments, the laser-assisted sintering process includes: each first type of gate line corresponds to a set of first parameters in a first parameter range, and each first type of gate line is individually laser-assisted sintered using its corresponding first parameters; each second type of gate line corresponds to a set of second parameters in a second parameter range, and each second type of gate line is individually laser-assisted sintered using its corresponding second parameters.

[0007] In some embodiments, the laser-assisted sintering process includes at least two laser sources. The laser power of one laser source is adjusted according to a first parameter corresponding to each of the first type of gate lines, and the laser power of the other laser source is adjusted according to a second parameter corresponding to each of the second type of gate lines.

[0008] In some embodiments, after classifying the first gate lines according to the overlap index of each first gate line, the process includes: dividing the first surface into regions to divide the first surface into at least a first region and a second region, wherein the region where a plurality of adjacent first-type gate lines are located is the first region, and the region where a plurality of adjacent second-type gate lines are located is the second region; in the step of performing laser-assisted sintering, each first region corresponds to a set of first parameters in a first parameter range, each second region corresponds to a set of second parameters in a second parameter range, each first region is laser-assisted sintered using its corresponding first parameters, and each second region is laser-assisted sintered using its corresponding second parameters.

[0009] In some embodiments, a first parameter corresponding to each first region is obtained based on the average value of the overlap index of a plurality of first-type gate lines in each first region; and a second parameter corresponding to each second region is obtained based on the average value of the overlap index of a plurality of second-type gate lines in each second region.

[0010] In some embodiments, a first parameter corresponding to each first region is obtained based on the median of the overlap indices of a plurality of first-type gate lines in each first region; and a second parameter corresponding to each second region is obtained based on the median of the overlap indices of a plurality of second-type gate lines in each second region.

[0011] In some embodiments, the laser-assisted sintering process includes at least two laser sources, one of which has a laser power corresponding to a first parameter, and the other has a laser power corresponding to a second parameter.

[0012] In some embodiments, the first range corresponds to a plurality of non-overlapping first sub-ranges, the first parameter range corresponds to a plurality of non-overlapping first sub-parameter ranges, and the first sub-ranges correspond one-to-one with the first sub-parameter ranges; the second range corresponds to a plurality of non-overlapping second sub-ranges, the second parameter corresponds to a plurality of non-overlapping second sub-parameter ranges, and the second sub-ranges correspond one-to-one with the second sub-parameter ranges.

[0013] In some embodiments, the overlap index is the ratio of the overlap width of the orthographic projection of the first gate line on the first surface to the orthographic projection of the second gate line on the first surface to the width of the first gate line.

[0014] According to some embodiments of this application, another aspect of this application also provides a solar cell, which is formed using the solar cell preparation method described in the above embodiments.

[0015] The technical solution provided in this application has at least the following advantages:

[0016] In the solar cell fabrication method provided in this application embodiment, before the laser-assisted sintering process, the first surface of the solar cell has multiple first grid lines, and the second surface of the solar cell has multiple second grid lines. The first grid lines and second grid lines are used to collect charge carriers on the first and second surfaces, respectively. The laser-assisted sintering process is used to laser-assistedly sinter the first grid lines. Before the laser-assisted sintering process, the first grid lines are not electrically connected to the structure within the solar cell, while the second grid lines are electrically connected to the structure within the solar cell before the laser-assisted sintering process. Before the laser-assisted sintering process, the overlap index of each first grid line on the solar cell is obtained, and the first grid lines are classified according to the overlap index of each first grid line to divide the first grid lines into at least a first type of grid line and a second type of grid line. The overlap degree of the first type of grid lines is greater than that of the second type of grid lines. Therefore, in the subsequent laser-assisted sintering process, the first type of grid lines are more prone to over-burning problems compared to the second type of grid lines. During the laser-assisted sintering process, laser-assisted sintering is performed on the first type of grid line and the second type of grid line using their respective first parameter range and second parameter range. The maximum value of at least one parameter range in the first parameter range is less than or equal to the minimum value of the corresponding parameter range in the second parameter range. This allows both the first type of grid line and the second type of grid line to be laser-assisted sintered under relatively matched process conditions, avoiding over-burning of the first type of grid line and under-burning of the second type of grid line, thereby improving the yield and efficiency of solar cells. Attached Figure Description

[0017] One or more embodiments are illustrated by way of example with corresponding pictures in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Unless otherwise stated, the pictures 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 technology, 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.

[0018] Figure 1A flowchart corresponding to the method for fabricating a solar cell provided in the embodiments of this application;

[0019] Figures 2 to 4 The diagram shows the structural schematics corresponding to each step of the method for fabricating a solar cell provided in the embodiments of this application. Detailed Implementation

[0020] As is known from the background technology, under-sintering or over-sintering problems are prone to occur during laser-assisted sintering, which leads to a decrease in the yield and efficiency of solar cells.

[0021] In related technologies, during laser-assisted sintering, after the grid lines are formed on the front and back sides of the solar cell, due to the difference in the number and spacing of the front and back grid lines, it is inevitable that the orthographic projections of some front grid lines on the front side of the solar cell will overlap with those of the back grid lines on the front side. To address the varying degrees of overlap between the front and back grid lines, laser-assisted sintering typically uses the same laser power and reverse current for all front grid lines. However, for front grid lines with a small overlap with the back grid lines, under-burning is likely to occur, resulting in poor electrical contact between these front grid lines and the substrate. For front grid lines with a large overlap with the back grid lines, silver can burn through the passivation layer, leading to structural damage and irreversible defects in the solar cell. Under-burned or over-burned front grid lines appear as dark stripes during electroluminescence or photoluminescence detection, affecting the efficiency and yield of the solar cell.

[0022] This application provides a method for preparing a solar cell, which at least helps to improve the yield and efficiency of the solar cell.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] The terminology used in the description of the various embodiments herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used in the description of the various embodiments and the appended claims, the term "component" is also intended to include the plural form unless the context clearly indicates otherwise.

[0027] 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.

[0028] Figure 1 The flowchart corresponds to the method for preparing a solar cell provided in the embodiments of this application. Figures 2 to 4 These are schematic diagrams illustrating the structural steps corresponding to each step of the solar cell fabrication method provided in this application embodiment. Wherein, Figure 2 A top view of a battery cell provided in an embodiment of this application; Figure 3 for Figure 2 A schematic diagram of the cross-sectional structure along the AA1 direction; Figure 4 This is a structural diagram corresponding to the step of dividing the first surface into regions provided in an embodiment of this application.

[0029] refer to Figure 1 According to some embodiments of this application, the present application provides a method for preparing a solar cell, comprising:

[0030] Step 11: Reference Figure 2 and Figure 3 A battery cell 100 is provided, the battery cell 100 having a first surface 101 and a second surface 102 opposite to each other, the first surface 101 having a plurality of first grid lines 110, and the second surface 102 having a plurality of second grid lines 120, the first grid lines 110 and the second grid lines 120 extending in the same direction.

[0031] The solar cell 100 can be any of the following: PERC cell (Passivated Emitter and Rear Cell), PERT cell (Passivated Emitter and Rear Totally-diffused cell), TOPCon cell (Tunnel Oxide Passivated Contact), or HIT / HJT cell (Heterojunction Technology).

[0032] The solar cell 100 can be a monocrystalline silicon solar cell, a polycrystalline silicon solar cell, an amorphous silicon solar cell, or a multi-component compound solar cell. Specifically, the multi-component compound solar cell can be a cadmium sulfide solar cell, a gallium arsenide solar cell, a copper indium selenide solar cell, or a perovskite solar cell.

[0033] In some embodiments, the solar cell may include a first passivation layer, a solar cell body, and a second passivation layer stacked sequentially. The surface of the first passivation layer away from the solar cell body is a first surface, and the surface of the second passivation layer away from the solar cell body is a second surface. A first grid line is located on the first passivation layer, and a second grid line is located on the second passivation layer and electrically connected to the solar cell body. The solar cell body is used to receive incident light and generate photogenerated carriers, while the first and second grid lines are used to collect these photogenerated carriers. The first and second passivation layers prevent oxidation or corrosion of the solar cell body surface, thereby improving the stability and lifespan of the solar cell. It is understood that the first grid line is not electrically connected to the solar cell body before laser sintering.

[0034] In some embodiments, the second grid line may penetrate the passivation layer and be electrically connected to the cell body, or may be electrically connected to the cell body via point contact.

[0035] The material of the first passivation layer may include at least one of aluminum oxide, silicon oxide, silicon nitride, or silicon oxynitride. The first passivation layer may be a single-layer structure or a stacked structure. For example, a single-layer structure may be a single-layer aluminum oxide film, a single-layer silicon oxide film, a single-layer silicon nitride film, or a single-layer silicon oxynitride film; a stacked structure may be composed of at least two layers selected from aluminum oxide, silicon oxide, silicon nitride, or silicon oxynitride films.

[0036] The material of the second passivation layer may include at least one of aluminum oxide, silicon oxide, silicon nitride, or silicon oxynitride. The second passivation layer may be a single-layer structure or a stacked structure. For example, a single-layer structure may be a single-layer aluminum oxide film, a single-layer silicon oxide film, a single-layer silicon nitride film, or a single-layer silicon oxynitride film; a stacked structure may be composed of at least two layers selected from aluminum oxide, silicon oxide, silicon nitride, or silicon oxynitride films.

[0037] In some embodiments, the cell body may include a substrate and an emitter stacked together, wherein the emitter may be located on the side of the substrate near the first passivation layer and in contact with the first passivation layer, or the emitter may be located on the side of the substrate near the second passivation layer and in contact with the second passivation layer. The doping element type of the emitter is opposite to that of the doping element in the substrate. For example, if the doping element in the substrate is a P-type doping element, then the doping element in the emitter is an N-type doping element; if the doping element in the substrate is an N-type doping element, then the doping element in the emitter is a P-type doping element, thus forming a PN junction with the substrate. The PN junction can receive incident light irradiating the substrate surface and generate electron-hole pairs. For example, when the substrate is an N-type substrate, the separated electrons move into the substrate, and the separated holes move into the emitter, thus forming a current.

[0038] In some embodiments, the substrate can be an N-type semiconductor substrate or a P-type semiconductor substrate. The N-type semiconductor substrate is doped with an N-type dopant element, which can be any one of group V elements such as phosphorus (P), bismuth (Bi), antimony (Sb), or arsenic (As). The P-type semiconductor substrate is doped with a P-type dopant element, which can be any one of group III elements such as boron (B), aluminum (Al), gallium (Ga), or indium (In).

[0039] In some embodiments, the substrate material may be at least one of monocrystalline silicon, polycrystalline silicon, amorphous silicon, or microcrystalline silicon.

[0040] In some embodiments, at least one surface of the substrate may have a textured structure, such as a pyramidal textured surface. This textured structure can enhance the absorption and utilization rate of incident light by the substrate, thereby improving the light conversion efficiency of the solar cell. If the solar cell is a single-sided cell, the texture can be formed only on one side of the substrate, while the other side of the substrate can be a polished surface, meaning the polished surface of the substrate is flatter than the textured surface. It should be noted that for single-sided cells, textured surfaces can also be formed on both sides of the substrate. If the solar cell is a bifacial cell, textured surfaces can be formed on both sides of the substrate.

[0041] In some embodiments, the cell body may further include a tunneling layer located on the substrate surface and a doped conductive layer located on the surface of the tunneling layer. The tunneling layer is located on the side of the substrate away from the emitter, and the doped conductive layer is located on the surface of the tunneling layer away from the substrate. The tunneling layer and the doped conductive layer are used to form a passivation contact structure. The tunneling layer can achieve a chemical passivation effect. Due to the presence of interface state defects on the substrate surface, the tunneling layer can saturate the dangling bonds on the substrate surface, reducing the defect state density and the number of recombination centers, thereby reducing the carrier recombination rate and resulting in a higher interface state density. This increased interface state density promotes the recombination of photogenerated carriers, increasing the fill factor, short-circuit current, and open-circuit voltage of the solar cell, thus improving the photoelectric conversion efficiency of the solar cell. The doped conductive layer can have a field passivation effect. It can form an electrostatic field, causing minority carriers to escape from the interface, reducing the minority carrier concentration and resulting in a lower carrier recombination rate at the substrate interface. This further improves the open-circuit voltage, short-circuit current, and fill factor of the solar cell, thereby improving the photoelectric conversion efficiency of the solar cell.

[0042] The material of the tunneling layer may include at least one of silicon oxide, silicon nitride, silicon oxynitride, silicon carbide, or magnesium fluoride.

[0043] The material of the doped conductive layer may include at least one of amorphous silicon, polycrystalline silicon, or silicon carbide. The doped conductive layer has the same doping elements as the substrate. If the substrate has P-type doping elements, then the doping elements in the doped conductive layer are also P-type; if the substrate has N-type doping elements, then the doping elements in the doped conductive layer are also N-type.

[0044] In some embodiments, the first side 101 may be one of the front or back side of the battery cell 100, and the second side 102 may be the other of the front or back side of the battery cell 100.

[0045] It should be noted that, in Figure 2 and Figure 3 In this example, taking the number of first gate lines 110 on the first surface 101 as greater than the number of second gate lines 120 on the second surface 102 as an example, this does not constitute a limitation on the number of first gate lines 110 and second gate lines 120. The number of first gate lines 110 and second gate lines 120 can be adjusted according to actual conditions. Correspondingly, the size and spacing of the first gate lines 110 and the size and spacing of the second gate lines 120 can also be adjusted according to actual conditions.

[0046] Step 12: Obtain the overlap index of each first grid line 110 on the battery cell 100. The overlap index is represented by the degree of overlap between the orthographic projection of the first grid line 110 on the first surface 101 and the orthographic projection of the second grid line 120 on the first surface 101.

[0047] For example, the overlap index can be the overlap width of the orthographic projection of the first gate line 110 on the first surface 101 and the orthographic projection of the second gate line 120 on the first surface 101; or, the overlap index can be the ratio of the overlap width of the orthographic projection of the first gate line 110 on the first surface 101 and the orthographic projection of the second gate line 120 on the first surface 101 to the width of the first gate line 110.

[0048] The overlap width refers to the width of the overlapping area between the orthographic projection of the first gate line 110 on the first surface 101 and the orthographic projection of the second gate line 120 on the first surface 101, along the extension direction perpendicular to the first gate line 110. It can be understood that when one first gate line 110 and two second gate lines 120 form two overlapping areas, the overlap width refers to the sum of the widths of the overlapping areas of the orthographic projections of the first gate line 110 on the first surface 101 and the orthographic projections of the two second gate lines 120 on the first surface 101. The width of the first gate line 110 refers to the width of the first gate line 110 itself along the extension direction perpendicular to the first gate line 110.

[0049] The following explanation uses the overlap index as the ratio of the overlap width of the orthographic projection of the first gate line 110 on the first surface 101 to the width of the first gate line 110, and does not constitute a limitation on the definition of the overlap index.

[0050] Step 13: Reference Figure 3 The first gate line 110 is classified according to the overlap index of each first gate line 110, so that the first gate line 110 is divided into at least a first class gate line 111 and a second class gate line 112. The overlap index corresponding to the first gate line 110 in the first class gate line 111 is in a first range, and the overlap index corresponding to the first gate line 110 in the second class gate line 112 is in a second range. The minimum value of the first range is greater than or equal to the maximum value of the second range.

[0051] For example, when the ratio of the overlap width of the orthographic projection of the first gate line 110 on the first surface 101 to the width of the second gate line 120 on the first surface 101 is less than or equal to 0.5, the first gate line 110 is classified as a second type gate line 112; when the ratio of the overlap width of the first gate line 110 on the first surface 101 to the width of the second gate line 120 on the first surface 101 is greater than 0.5, the first gate line 110 is classified as a first type gate line 111. Thus, the first range is represented as a range greater than 0.5 and less than or equal to 1; the second range is represented as a range greater than or equal to 0 and less than or equal to 0.5.

[0052] In some embodiments, the first range may correspond to multiple non-overlapping first sub-ranges; the second parameter may correspond to multiple non-overlapping second sub-parameter ranges. For example, when the first range is represented as a range greater than 0.5 and less than or equal to 1, the first range may correspond to three first sub-ranges: the first first sub-range is represented as a range greater than 0.5 and less than 0.6; the second first sub-range is represented as a range greater than or equal to 0.6 and less than 0.8; and the third first sub-range is represented as a range greater than or equal to 0.8 and less than or equal to 1. When the second range is represented as a range greater than or equal to 0 and less than or equal to 0.5, the second range may correspond to two second sub-ranges: the first second sub-range is represented as a range greater than or equal to 0 and less than 0.25; and the second second sub-range is represented as a range greater than or equal to 0.25 and less than or equal to 0.5.

[0053] It is understandable that the number of subranges in the first subrange can be the same as or different from the number of subranges in the second subrange.

[0054] refer to Figure 4 In some embodiments, after classifying the first gate line 110 according to the overlap index of each first gate line 110, the method may further include: dividing the first surface 101 into regions to divide the first surface 101 into at least a first region A and a second region B, wherein the region where a plurality of adjacent first-class gate lines 111 are located is the first region A, and the region where a plurality of adjacent second-class gate lines 112 are located is the second region B.

[0055] It is understandable that the number of first-class grid lines 111 in the first zone A is greater than or equal to 1; and the number of second-class grid lines 112 in the second zone B is greater than or equal to 1.

[0056] Step 14: Perform laser-assisted sintering process. The process parameters used for the first type of gate line 111 are within the first parameter range, and the process parameters used for the second type of gate line 112 are within the second parameter range. The maximum value of at least one parameter range in the first parameter range is less than or equal to the minimum value of the corresponding parameter range in the second parameter range.

[0057] In the solar cell fabrication method provided in this application embodiment, before the laser-assisted sintering process, the first surface 101 of the solar cell 100 has multiple first grid lines 110, and the second surface 102 of the solar cell 100 has multiple second grid lines 120. The first grid lines 110 and the second grid lines 120 are used to collect charge carriers on the first surface 101 and the second surface 102, respectively. The laser-assisted sintering process is used to laser-assistedly sinter the first grid lines 110. Before the laser-assisted sintering process, the first grid lines 110 are not electrically connected to the structure within the solar cell 100, while the second grid lines 120 are electrically connected to the structure within the solar cell 100 before the laser-assisted sintering process. Before the laser-assisted sintering process, the overlap index of each first grid line 110 on the solar cell 100 is obtained, and the first grid lines 110 are classified according to the overlap index of each first grid line 110, so that the first grid lines 110 are divided into at least first type grid lines 111 and second type grid lines 112. The overlap degree of the first type grid lines 111 is greater than that of the second type grid lines 112. Therefore, in the subsequent laser-assisted sintering process, the first type grid lines 111 are more likely to overburn than the second type grid lines 112. During the laser-assisted sintering process, laser-assisted sintering is performed on the first type of grid line 111 and the second type of grid line 112 using their respective first parameter range and second parameter range. The maximum value of at least one parameter range in the first parameter range is less than or equal to the minimum value of the corresponding parameter range in the second parameter range. This ensures that both the first type of grid line 111 and the second type of grid line 112 can be laser-assisted sintered under relatively matched process conditions, avoiding overburning of the first type of grid line 111 and underburning of the second type of grid line 112, thereby improving the yield and efficiency of the solar cell.

[0058] In some embodiments, the laser-assisted sintering process in step 14 includes: each first type of gate line 111 corresponds to a set of first parameters within a first parameter range, and each first type of gate line 111 is individually laser-assisted sintered using its corresponding first parameters; each second type of gate line 112 corresponds to a set of second parameters within a second parameter range, and each second type of gate line 112 is individually laser-assisted sintered using its corresponding second parameters. That is, for each first type of gate line 111, each first type of gate line 111 is matched with different first parameters according to its degree of overlap; for each second type of gate line 122, each second type of gate line 112 is matched with different second parameters according to its degree of overlap. Thus, during the laser-assisted sintering process, each first gate line 110 is individually laser-assisted sintered, and the process parameters are adjusted in real time according to the first or second parameters corresponding to each first gate line 110, so that each first gate line 110 can be matched with appropriate process parameters to achieve an appropriate degree of sintering.

[0059] In one example, the laser power of the first parameter is less than the laser power of the second parameter, and the reverse current of the first parameter is the same as the reverse current of the second parameter. In another example, the laser power of the first parameter is the same as the laser power of the second parameter, but the reverse current of the first parameter is different from the reverse current of the second parameter.

[0060] In a specific example, when each first type of gate line 111 undergoes laser-assisted sintering individually using its corresponding first parameter, and each second type of gate line 112 undergoes laser-assisted sintering individually using its corresponding second parameter, the laser power of the first parameter is less than the laser power of the second parameter, and the reverse current of the first parameter is the same as the reverse current of the second parameter. During the laser-assisted sintering process in step 14, at least two laser sources may be included. The laser power of one laser source is adjusted according to the first parameter corresponding to each first type of gate line 111, and the laser power of the other laser source is adjusted according to the second parameter corresponding to each second type of gate line 112. Thus, the laser power of one laser source is adaptively adjusted within the first parameter range according to the first parameter corresponding to each first type of gate line 111, and the power of the other laser source is adaptively adjusted within the second parameter range according to the second parameter corresponding to each second type of gate line 112. On the one hand, the two laser light sources can simultaneously perform laser-assisted sintering on the first type of gate line 111 and the second type of gate line 112, which can improve the efficiency of the laser-assisted sintering process. On the other hand, the power adjustment ranges of the two laser light sources are different, so there will be no situation where the power of the laser light sources fluctuates, which is conducive to improving the service life of the laser light sources.

[0061] In some embodiments, the number of laser sources can be greater than two, for example, three, four, six, or eight. Thus, at least two laser sources can be adaptively adjusted within a first parameter range according to the first parameter corresponding to different first-type gate lines 111, and / or, at least two laser sources can be adaptively adjusted within a second parameter range according to the second parameter corresponding to different second-type gate lines 112. Different first-type gate lines 111 can be simultaneously laser-assisted sintered using different laser sources, and different second-type gate lines 112 can be simultaneously laser-assisted sintered using different laser sources, which helps to further improve the efficiency of laser-assisted sintering.

[0062] In some embodiments, if in step 13 the first surface 101 is further divided into regions, such that it is divided into at least a first region A and a second region B; in step 14, during the laser-assisted sintering process, each first region A corresponds to a set of first parameters within a first parameter range, and each second region B corresponds to a set of second parameters within a second parameter range. Each first region A is laser-assisted sintered using its corresponding first parameters, and each second region B is laser-assisted sintered using its corresponding second parameters. That is, after classifying the first gate lines 110, the first surface 101 is divided into regions based on the position of the first type of gate line 111 or the second type of gate line 112. Thus, the first region A includes at least one first type of gate line 111, and the second region B includes at least one second type of gate line 112. During laser-assisted sintering, the first type of grid line 111 in the first region A is laser-assisted sintered using the same first parameter, and the second type of grid line 112 in the second region B is laser-assisted sintered using the same second parameter. This reduces the number of times process parameters need to be adjusted, thereby improving the efficiency of laser-assisted sintering.

[0063] In one example, the laser power of the first parameter is less than the laser power of the second parameter, and the reverse current of the first parameter is the same as the reverse current of the second parameter. In another example, the laser power of the first parameter is the same as the laser power of the second parameter, but the reverse current of the first parameter is different from the reverse current of the second parameter.

[0064] In a specific example, in step 13, the first surface 101 is divided into regions, specifically into at least a first region A and a second region B. In step 14, during the laser-assisted sintering process, each first region A corresponds to a set of first parameters within a first parameter range, and each second region B corresponds to a set of second parameters within a second parameter range. Each first region A undergoes laser-assisted sintering using its corresponding first parameters, and each second region B undergoes laser-assisted sintering using its corresponding second parameters. The laser power of the first parameters differs from that of the second parameters, while the reverse current of the first parameters is the same as that of the second parameters. During step 14, the laser-assisted sintering process may include at least two laser sources. The laser power of one laser source is adjusted according to the first parameters corresponding to each first region A, and the laser power of the other laser source is adjusted according to the second parameters corresponding to each second region B. Thus, the laser power of one laser source is adaptively adjusted within the first parameter range according to the first parameters corresponding to each first region A, and the power of the other laser source is adaptively adjusted within the second parameter range according to the second parameters corresponding to each second region B. On the one hand, the two laser light sources can simultaneously perform laser-assisted sintering on the first region A and the second region B respectively. When performing laser-assisted sintering on the first type of gate line 111 in the first region A, the laser irradiation area can be adjusted to simultaneously perform laser-assisted sintering on multiple first type of gate lines 111. When performing laser-assisted sintering on the second gate line in the second region B, the laser irradiation area can be adjusted to simultaneously perform laser-assisted sintering on multiple second type of gate lines 112. This can improve the efficiency of the laser-assisted sintering process. On the other hand, the two laser light sources have different power ranges, so there will be no situation where the power of the laser light source fluctuates, which is conducive to improving the service life of the laser light source.

[0065] In some embodiments, the number of laser sources can be greater than two, for example, three, four, six, or eight laser sources. Thus, at least two laser sources can be adaptively adjusted within a first parameter range according to the first parameter corresponding to different first regions A, and / or, at least two laser sources can be adaptively adjusted within a second parameter range according to the second parameter corresponding to different second regions B. Different first regions A can be simultaneously laser-assisted sintered using different laser sources, and different second regions B can be simultaneously laser-assisted sintered using different laser sources, which helps to further improve the efficiency of laser-assisted sintering.

[0066] In some embodiments, a first parameter corresponding to each first region A can be obtained based on the average overlap index of a plurality of first-type gate lines 111 in each first region A; and a second parameter corresponding to each second region B can be obtained based on the average overlap index of a plurality of second-type gate lines 112 in each second region B. In other embodiments, the first parameter corresponding to each first region A can be obtained based on the median of the overlap index of a plurality of first-type gate lines 111 in each first region A; and the second parameter corresponding to each second region B can be obtained based on the median of the overlap index of a plurality of second-type gate lines 112 in each second region B.

[0067] In some embodiments, if in step 13, the first range corresponds to multiple non-overlapping first sub-ranges; and the second parameter corresponds to multiple non-overlapping second sub-parameter ranges; in step 14, the first parameter range may correspond to multiple non-overlapping first sub-parameter ranges, and the second range may correspond to multiple non-overlapping second sub-ranges, with the first sub-ranges corresponding one-to-one with the first sub-parameter ranges and the second sub-ranges corresponding one-to-one with the second sub-parameter ranges.

[0068] In a specific example, taking the overlap index as the overlap width of the orthographic projections of the first gate line 110 and the second gate line 120 on the first surface 101, the first range is an overlap width greater than or equal to 0.1 μm; the second range is a range greater than or equal to 0 and less than 0.1 μm. The first range can include two first sub-ranges: the first sub-range can be greater than or equal to 0.1 μm and less than or equal to 0.2 μm, and the second sub-range can be greater than 0.2 μm. The second range can include two second sub-ranges: the first sub-range can be greater than or equal to 0 and less than or equal to 0.05 μm, and the second sub-range can be greater than 0.05 μm and less than or equal to 0.2 μm. Thus, the first second sub-range, the second second sub-range, the first first sub-range, and the second first sub-range increase sequentially. The corresponding second parameter range can correspond to two second sub-parameter ranges, and the first parameter range can correspond to two first sub-parameter ranges. Taking the constant reverse current during laser-assisted sintering as an example, the reverse current in the first second sub-parameter range, the reverse current in the second second sub-parameter range, the reverse current in the first first sub-parameter range, and the reverse current in the second first sub-parameter range are all equal. The laser power in the first second sub-parameter range is W, the laser power in the second second sub-parameter range is 0.7W to 0.9W, the laser power in the first first sub-parameter range is 0.5W to 0.7W, and the laser power in the second first sub-parameter range is 0.3W to 0.5W.

[0069] In other words, the different first gate lines 110 are divided into four levels according to the overlap index of the first gate lines 110. Each level of the first gate line 110 corresponds to the laser power of its respective level. In this way, each first gate line 110 can achieve a relatively moderate degree of sintering.

[0070] It is understandable that the first type of grid line 111 and its corresponding first parameter range, and the second type of grid line 112 and its corresponding second parameter range, can be obtained based on previous test data. The optimal parameter range for different overlap degrees of the first grid line 110 can be obtained based on multiple sets of empirical data. For example, during the testing process, a test cell is formed with first grid lines of different overlap degrees on it. Laser-assisted sintering is performed on the test cell, followed by electroluminescence or photoluminescence testing. This allows us to obtain the first grid line with a suitable sintering degree under the parameters of the laser-assisted sintering. Furthermore, by obtaining the overlap degree corresponding to this first grid line, we can obtain the correspondence between the overlap degree and the parameter range.

[0071] In the solar cell fabrication method provided in this application embodiment, before the laser-assisted sintering process, the first surface 101 of the solar cell 100 has multiple first grid lines 110, and the second surface 102 of the solar cell 100 has multiple second grid lines 120. The first grid lines 110 and the second grid lines 120 are used to collect charge carriers on the first surface 101 and the second surface 102, respectively. The laser-assisted sintering process is used to laser-assistedly sinter the first grid lines 110. Before the laser-assisted sintering process, the first grid lines 110 are not electrically connected to the structure within the solar cell 100, while the second grid lines 120 are electrically connected to the structure within the solar cell 100 before the laser-assisted sintering process. Before the laser-assisted sintering process, the overlap index of each first grid line 110 on the solar cell 100 is obtained, and the first grid lines 110 are classified according to the overlap index of each first grid line 110, so that the first grid lines 110 are divided into at least first type grid lines 111 and second type grid lines 112. The overlap degree of the first type grid lines 111 is greater than that of the second type grid lines 112. Therefore, in the subsequent laser-assisted sintering process, the first type grid lines 111 are more likely to overburn than the second type grid lines 112. During the laser-assisted sintering process, laser-assisted sintering is performed on the first type of grid line 111 and the second type of grid line 112 using their respective first parameter range and second parameter range. The maximum value of at least one parameter range in the first parameter range is less than or equal to the minimum value of the corresponding parameter range in the second parameter range. This ensures that both the first type of grid line 111 and the second type of grid line 112 can be laser-assisted sintered under relatively matched process conditions, avoiding overburning of the first type of grid line 111 and underburning of the second type of grid line 112, thereby improving the yield and efficiency of the solar cell.

[0072] Accordingly, another embodiment of this application also provides a solar cell, which is formed using the solar cell fabrication method described in the above embodiments. For parts that are the same as or corresponding to the previous embodiment, please refer to the corresponding descriptions in the foregoing embodiments; detailed descriptions will not be repeated below.

[0073] Solar cells can be any of the following: PERC cell (Passivated Emitter and Rear Cell), PERT cell (Passivated Emitter and Rear Totally-diffused Cell), TOPCon cell (Tunnel Oxide Passivated Contact Cell), or HIT / HJT cell (Heterojunction Technology).

[0074] Solar cells can be monocrystalline silicon solar cells, polycrystalline silicon solar cells, amorphous silicon solar cells, or multi-component compound solar cells. Specifically, multi-component compound solar cells can be cadmium sulfide solar cells, gallium arsenide solar cells, copper indium selenide solar cells, or perovskite solar cells.

[0075] The solar cell provided in this application embodiment is formed using the solar cell fabrication method described in the above embodiments. Before the laser-assisted sintering process, the overlap index of each first grid line on the cell is obtained, and the first grid lines are classified according to the overlap index. This classifies the first grid lines into at least a first type and a second type. The overlap of the first type of grid lines is greater than that of the second type, making them more prone to over-burning during the subsequent laser-assisted sintering process. During the laser-assisted sintering process, laser-assisted sintering is performed using corresponding first and second parameter ranges for the first and second types of grid lines, respectively. The maximum value of at least one parameter range in the first parameter range is less than or equal to the minimum value of the corresponding parameter range in the second parameter range. This ensures that both the first and second types of grid lines can be laser-assisted sintered under relatively matched process conditions, avoiding over-burning of the first type of grid lines and under-burning of the second type, thereby improving the yield and efficiency of the solar cell.

[0076] 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 method for preparing a solar cell, characterized in that, include: A battery cell is provided, the battery cell having a first side and a second side opposite to each other, the first side having a plurality of first grid lines, and the second side having a plurality of second grid lines, wherein the first grid lines and the second grid lines extend in the same direction; Obtain the overlap index of each of the first grid lines on the battery cell, whereby the overlap index represents the degree of overlap between the orthographic projection of the first grid line on the first surface and the orthographic projection of the second grid line on the first surface. The first gate lines are classified according to the overlap index of each first gate line to divide the first gate lines into at least a first type of gate line and a second type of gate line, wherein the overlap index corresponding to the first gate line in the first type of gate line is in a first range, the overlap index corresponding to the first gate line in the second type of gate line is in a second range, and the minimum value of the first range is greater than or equal to the maximum value of the second range. In the laser-assisted sintering process, the process parameters used for the first type of gate line are within a first parameter range, and the process parameters used for the second type of gate line are within a second parameter range. The maximum value of at least one parameter range in the first parameter range is less than or equal to the minimum value of the corresponding parameter range in the second parameter range. The laser-assisted sintering process includes: Each of the first type of gate line corresponds to a set of first parameters in the first parameter range. Each of the first type of gate line is individually laser-assisted sintering process using its corresponding first parameters. Each of the first type of gate line is matched with different first parameters according to its degree of overlap. Each of the second type of gate lines corresponds to a set of second parameters in the second parameter range, and each of the second type of gate lines is individually laser-assisted sintering using its corresponding second parameters; each of the second type of gate lines is matched with different second parameters according to its degree of overlap.

2. The method for preparing a solar cell according to claim 1, characterized in that, The laser-assisted sintering process includes at least two laser sources. The laser power of one laser source is adjusted according to the first parameter corresponding to each of the first type of gate lines, and the laser power of the other laser source is adjusted according to the second parameter corresponding to each of the second type of gate lines.

3. The method for preparing a solar cell according to claim 1, characterized in that, After classifying the first gate lines according to the overlap index of each first gate line, the process includes: The first surface is divided into regions, such that the first surface is divided into at least a first region and a second region. The region where a plurality of adjacent first-type gate lines are located is the first region, and the region where a plurality of adjacent second-type gate lines are located is the second region. In the step of performing laser-assisted sintering, each first region corresponds to a set of first parameters in the first parameter range, each second region corresponds to a set of second parameters in the second parameter range, each first region uses its corresponding first parameters to perform laser-assisted sintering, and each second region uses its corresponding second parameters to perform laser-assisted sintering.

4. The method for preparing a solar cell according to claim 3, characterized in that, The first parameter corresponding to each first region is obtained based on the average value of the overlap index of the plurality of first-type gate lines in each first region; the second parameter corresponding to each second region is obtained based on the average value of the overlap index of the plurality of second-type gate lines in each second region.

5. The method for preparing a solar cell according to claim 3, characterized in that, The first parameter corresponding to each first region is obtained based on the median of the overlap index of the plurality of first-type gate lines in each first region; the second parameter corresponding to each second region is obtained based on the median of the overlap index of the plurality of second-type gate lines in each second region.

6. The method for preparing a solar cell according to claim 3, characterized in that, The laser-assisted sintering process includes at least two laser sources, one of which has a laser power corresponding to the first parameter, and the other has a laser power corresponding to the second parameter.

7. The method for preparing a solar cell according to claim 1, characterized in that, The first range corresponds to multiple non-overlapping first sub-ranges, and the first parameter range corresponds to multiple non-overlapping first sub-parameter ranges. The first sub-ranges and the first sub-parameter ranges correspond one-to-one. The second range corresponds to multiple non-overlapping second sub-ranges, and the second parameter corresponds to multiple non-overlapping second sub-parameter ranges. The second sub-ranges and the second sub-parameter ranges correspond one-to-one.

8. The method for preparing a solar cell according to claim 1, characterized in that, The overlap index is the ratio of the overlap width of the orthographic projection of the first gate line on the first surface to the orthographic projection of the second gate line on the first surface, to the width of the first gate line.

9. A solar cell, characterized in that, The solar cell is formed using the solar cell preparation method as described in any one of claims 1 to 8.

Images