Solar cell, method for manufacturing solar cell, and photovoltaic module

Abstract

This application relates to a solar cell, a method for fabricating a solar cell, and a photovoltaic module. The solar cell includes: a substrate having a first surface; and a marking code located on the first surface, the marking code including a plurality of pits, at least some of which include a plurality of steps arranged in a stepped manner along a direction perpendicular to the first surface; in the direction perpendicular to the first surface, the cross-sectional area of ​​each of the at least some pits gradually increases in the direction parallel to the first surface, and the cross-sectional area at the bottom of the pit is the smallest. This at least helps to improve the light reflection performance of the pits, thereby making the features of the pits constituting the marking code easier to identify and improving the accuracy of marking code identification.

Description

Technical Field

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

[0002] Fossil fuels cause air pollution and have limited reserves, while solar energy has advantages such as being clean, pollution-free, and abundant. Therefore, solar energy is gradually becoming the core clean energy source to replace fossil fuels. Due to the excellent photoelectric conversion efficiency of solar cells, solar cells have become the focus of development for clean energy utilization.

[0003] To improve the photoelectric conversion efficiency of solar cells, optimizing their structural design and material composition is a fundamental approach. To achieve this optimization, traceability of process information during solar cell manufacturing is essential. A common method is to add coded markings to the cells, and then, by identifying these markings, traceability of the manufacturing process and procedures can be achieved.

[0004] However, the accuracy of cell identification and information traceability is limited in the current process of achieving traceability of cell manufacturing processes. Summary of the Invention

[0005] This application provides a solar cell, a method for preparing a solar cell, and a photovoltaic module, which at least helps to improve the accuracy of solar cell identification and process information traceability.

[0006] This application provides a solar cell, comprising: a substrate having a first surface; a marking code located on the first surface, the marking code including a plurality of pits, at least some of the pits including a plurality of steps arranged in a stepwise manner along a direction perpendicular to the first surface; in the direction perpendicular to the first surface, each of the at least some pits has a progressively increasing cross-sectional area in a direction parallel to the first surface, and the cross-sectional area at the bottom of the pit is the smallest.

[0007] Additionally, the first surface includes an edge region surrounding each of the pits and a flat region adjacent to the edge region, wherein the height difference between the edge region and the flat region is 0 to 5 μm in a direction perpendicular to the first surface.

[0008] In addition, the number of steps in the plurality of steps is 12 to 20.

[0009] In addition, in the direction parallel to the first surface, the width of any one of the plurality of steps is 1 μm to 2 μm; and in the direction perpendicular to the first surface, the height of any one of the plurality of steps is 0.2 μm to 0.6 μm.

[0010] Additionally, the depth of the pit is 4 μm to 8 μm in the direction perpendicular to the first surface.

[0011] Additionally, the maximum length of the pit is 40 μm to 70 μm in a direction parallel to the first surface.

[0012] In addition, the substrate has a front side and a back side, with the first surface being the back side of the substrate.

[0013] Accordingly, this application also provides a method for fabricating a solar cell, comprising: providing a substrate, the substrate including a first surface; forming an original marking code consisting of a plurality of recessed points on the first surface; texturing the substrate to form a textured structure covering the first surface and the original marking code; cleaning the textured structure on the original marking code to form a marking code consisting of a plurality of pits, at least some of the pits including a plurality of steps arranged in a stepwise manner along a direction perpendicular to the first surface; in the direction perpendicular to the first surface, the cross-sectional area of ​​each of the at least some pits gradually increases in the direction parallel to the first surface, and the cross-sectional area of ​​the bottom of the pit is the smallest.

[0014] In addition, the substrate has a front and a back side, and the first surface is the back side of the substrate; the step of cleaning the original mark code includes: cleaning the first surface to remove the velvet structure on the original mark code and on the first surface.

[0015] In addition, the step of forming the mark code includes: laser etching the first surface to form the plurality of recessed points, the plurality of recessed points constituting the original mark code.

[0016] In addition, the laser etching process parameters include: laser wavelength of 1059nm to 1065nm, pulse duration of 10 to 100ns, pulse repetition frequency of 500kHz to 2000kHz, and laser power percentage of 70% to 75%.

[0017] Accordingly, this application also provides a stacked photovoltaic module, including: a battery string, which is formed by connecting multiple solar cells as described above; an encapsulation layer for covering the surface of the battery string; and a cover plate for covering the surface of the encapsulation layer away from the battery string.

[0018] The technical solution provided in this application has at least the following advantages:

[0019] In the solar cell provided in this application embodiment, during the cell fabrication process, a marking code is first formed on the first surface of the solar cell substrate by a combination of multiple pits. At least some of the pits forming the marking code include multiple steps arranged in a stepwise manner along a direction perpendicular to the first surface. That is, the pit walls are composed of stepwise steps along a direction perpendicular to the first surface, and the cross-sectional area of ​​the pit gradually increases from the bottom to the top of the pit in the direction parallel to the first surface. By utilizing pits whose walls are composed of stepwise steps arranged in a direction perpendicular to the first surface to generate the marking code, the light reflection performance of the pits is improved by the stepwise arrangement of steps, thereby making the features of the pits constituting the marking code easier to identify. This reduces the illumination requirements during the marking code identification process and improves the accuracy of marking code identification. Constructing the marking code using pits with a gradually increasing cross-sectional area from bottom to top reduces damage to the substrate during marking code formation while maximizing the light-receiving area of ​​the pits, facilitating accurate identification of the pits and the marking code. Attached Figure Description

[0020] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations do not constitute a limitation on the embodiments, and unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0021] Figure 1 This is a schematic diagram of the structure of a solar cell provided in one embodiment of this application;

[0022] Figure 2 A top view of a recess provided in an embodiment of this application;

[0023] Figure 3 A cross-sectional view of a solar cell provided in an embodiment of this application;

[0024] Figure 4 This is a schematic diagram of another solar cell structure provided in an embodiment of this application;

[0025] Figure 5 A flowchart of a solar cell fabrication method provided in another embodiment of this application;

[0026] Figure 6 This is a schematic diagram of the structure of a photovoltaic module provided in another embodiment of this application. Detailed Implementation

[0027] As can be seen from the background technology, the accuracy of cell identification and information traceability in the current process of achieving traceability of cell manufacturing process information in solar cells is limited.

[0028] One embodiment of this application provides a solar cell. During the cell manufacturing process, a marking code is first formed on a first surface of a substrate. The marking code consists of multiple pits, and at least some of the pits constituting the marking code include multiple steps arranged in a stepwise manner along a direction perpendicular to the first surface. That is, the marking code is made using pits with multiple steps arranged in a stepwise manner on the pit walls. The multiple steps arranged in a stepwise manner on the pit walls improve the light reflection performance of the pits, thereby making the features of the pits easier to identify. This reduces the light requirements of the marking code during the identification process and improves the accuracy and adaptability of the marking code identification. Along the direction perpendicular to the first surface, the cross-sectional area of ​​each pit gradually increases along the direction parallel to the first surface, and the cross-sectional area at the bottom of the pit is the smallest. That is, the marking code is constructed using pits with a gradually decreasing cross-sectional area from the top to the bottom of the pit. This minimizes damage to the substrate during the pit formation process while allowing the pits to have a large light-receiving area, facilitating accurate identification of the pits and the marking code.

[0029] 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.

[0030] One embodiment of this application provides a solar cell, referencing... Figures 1 to 3 ,in, Figure 1 This is a schematic diagram of the structure of the first surface of a solar cell. Figure 2 The diagram shows a structure in which the pit wall comprises multiple stepped recesses arranged in a stepwise manner along a direction perpendicular to the first surface. Figure 3 This is a schematic diagram of a partial cross-sectional structure of a solar cell. The X-direction is perpendicular to the first surface, and the Y-direction is parallel to the first surface.

[0031] The solar cell includes: a substrate 100 having a first surface 101; a marking code 102 located on the first surface 101, the marking code 102 including a plurality of pits 103, at least some of the pits 103 including a plurality of steps 310 arranged in a stepwise manner along a direction perpendicular to the first surface 101; in the direction perpendicular to the first surface 101, each of the at least some pits 103 has a progressively increasing cross-sectional area in a direction parallel to the first surface 101, and the cross-sectional area at the bottom of the pit is the smallest.

[0032] The multiple pits 103 constituting the marker code 102 can be formed by processes such as laser etching. During the formation of the pits 103, multiple steps 310 arranged in a stepwise manner along the direction perpendicular to the first surface 101 are formed on the pit wall of the pit 103. The multiple steps 310 are used to improve the light reflection performance of the pits 103, so that the features of the pits 103 can be more accurately identified under the same incident light conditions. This reduces the lighting conditions that the feature recognition of the constructed marker code 102 needs to meet, and reduces the difficulty of feature acquisition and encoding recognition of the marker code 102 under the same external conditions. This reduces the difficulty of recognizing the marker code 102 while improving the recognition accuracy of the marker code 102. In the process of constructing the pit 103 containing multiple steps, the cross-sectional area of ​​the pit 103 is gradually increased in the direction perpendicular to the first surface 101 and in the direction parallel to the first surface 101, and the cross-sectional area at the bottom of the pit is minimized. That is, the pit 103 is constructed into a shape with a larger top area and a smaller bottom area. This minimizes the damage to the substrate 100 during the construction of the marker code 102 through the pit 103, while ensuring that the pit 103 has a larger light-receiving area to facilitate the identification of the pit 103 and improve the accuracy of feature acquisition and coding recognition of the marker code 102.

[0033] It should be understood that the size of the cross-sectional area of ​​the pit 103 in the direction parallel to the first surface 101 is related to the number of steps contained between the cross-section and the bottom of the pit. When the number of steps increases, the cross-sectional area increases accordingly. When the number of steps does not change, the cross-sectional area remains unchanged. Therefore, in the direction perpendicular to the first surface 101, the cross-sectional area of ​​the pit 103 in the direction parallel to the first surface 101 gradually increases.

[0034] It is worth mentioning that among the multiple pits 103 forming the mark code 102, all pits 103 may have pit walls composed of multiple steps 310, or only some pits 103 may have pit walls composed of multiple steps 310. All pits 103 may have a larger top area and a smaller bottom area, or only some pits 103 may have a larger top area and a smaller bottom area. This application embodiment does not impose any restrictions on this.

[0035] Furthermore, the substrate 100 is used to receive incident light and generate photogenerated carriers. In some embodiments, the substrate 100 can be a silicon substrate, and the material of the silicon substrate can include at least one of monocrystalline silicon, polycrystalline silicon, amorphous silicon, or microcrystalline silicon. In other embodiments, the material of the substrate 100 can also be silicon carbide, organic materials, or multi-component compounds. Multi-component compounds can include, but are not limited to, materials such as perovskite, gallium arsenide, cadmium telluride, and copper indium selenide.

[0036] In some embodiments, the tag code 102 includes a QR code, a barcode, or identification characters.

[0037] During the creation of the marker code 102, one or more combinations of QR codes, barcodes, and identification characters can be used as the marker code 102, depending on the requirements of the subsequent recognition method or specific recognition scenario. The marker code 102 is then formed on the first surface 101 using processes such as laser engraving and chemical etching. For example, a high-quality carbon dioxide pulsed laser beam can be used. After spot processing, beam expansion, and focusing, and with computer control of parameters such as laser beam energy output, frequency output, and scanning speed, a laser beam is formed to scan the first surface 101, creating a marker code 102 composed of multiple pits 103 on the first surface 101. By selecting one or more combinations of codes as the marker code 102 according to specific application scenarios and recognition needs, the adaptability and practicality of the marker code 102 to different scenarios are improved.

[0038] refer to Figures 1 to 4 In some embodiments, the first surface 101 includes an edge region 110 surrounding each recess 103 and a flat region 120 adjacent to the edge region 110. The height difference between the edge region 110 and the flat region 120 is 0 to 5 μm in a direction perpendicular to the first surface 101.

[0039] During the construction of the marking and coding 102, due to laser thermal effects or etching residues, protrusions composed of molten silicon or etching residues can easily form on the first surface 101 of the substrate 100. Furthermore, these protrusions around the pits 103 cannot be completely removed during subsequent cell fabrication processes. If the height of the protrusions around the pits 103 is too large, it can cause abnormal wear on the stencil during the screen printing process, reducing the stencil's lifespan and affecting the screen printing effect.

[0040] In other words, if the protrusions around the pit 103 protrude too high from the first surface 101, for example, if the protrusion height is 5.5μm, 6μm, or 8μm, the protrusions can easily damage the screen printing plate used in the screen printing process. Therefore, during the production of the marking code 102, after the pit 103 is formed, the protrusion height of the edge area 110 surrounding the pit 103 on the first surface 101 is adjusted by cleaning or particle blowing. That is, the height of the edge area 110 protruding from the first surface 101 in a direction perpendicular to the first surface 101 is adjusted so that the height difference between the edge area 110 and the adjacent flat area 120 in a direction perpendicular to the first surface 101 is 0 to 5μm. For example, the height difference between the edge region 110 and the flat region 120 can be adjusted to 0, 0.5μm, 0.75μm, 1μm, 1.5μm, 2.25μm, 2.5μm, 3μm, 3.45μm, 4.5μm, or 4.8μm, thereby reducing the interference of the construction of the marking code 102 on the subsequent manufacturing process of the solar cell, while reducing the wear of the screen in the screen printing process, and thus reducing the cost of solar cell manufacturing.

[0041] It is worth mentioning that the edge region 110 refers to a portion of the first surface 101 adjacent to the edge of the pit 103. The width of the edge region 110 is 0.5μm to 4μm. That is, the area formed by extending outward from any point on the edge of the pit 103 on the first surface 101 along a direction parallel to the first surface 101, from 0.5μm to 4μm, constitutes the edge region 110. If the width of the edge region 110 is too small, some protrusions may not be completely cleaned. If the width of the edge region 110 is too large, it may cause additional damage to the non-protruding parts. Therefore, the width of the edge region 110 is set in the range of 0.5μm to 4μm, for example, 0.5μm, 0.75μm, 1μm, 1.5μm, 2μm, 3μm, or 3.75μm, to ensure accurate cleaning of the protrusions around the pit 103 while avoiding additional damage to the substrate 100.

[0042] In some embodiments, the plurality of steps 310 includes 12 to 20 steps 310.

[0043] During the fabrication of the recess 103, the number of steps 310 contained in the recess 103 affects its light reflection capability. If the number of steps 310 in the recess 103 is too small, the arrangement of the steps 310 in the recess 103 is too sparse, and the concave-convex structure formed between each level of steps 310 mainly functions to trap light, resulting in limited improvement in the light reflection capability of the recess 103. If the number of steps 310 in the recess 103 is too large, the arrangement of the steps 310 in the recess 103 is too dense, the concave-convex structure formed between each level of steps 310 is not obvious, and the recess wall of the recess 103 tends to be smooth, which also makes it difficult to effectively improve the light reflection capability of the recess 103.

[0044] Therefore, during the fabrication of the recess 103, when setting the steps 310, the number of steps 310 formed in the recess 103, i.e., the number of steps, is set to 12 to 20, for example, 12, 13, 15, 17, or 18. By setting the number of steps 310 contained in the recess 103 to an appropriate value, it avoids the situation where the number of steps 310 is too small, resulting in a sparse arrangement of steps 310, and the uneven structure formed by the steps 310 acts as a light trapping mechanism. At the same time, it also avoids the situation where the number of steps 310 is too large, resulting in an overly dense arrangement of steps 310, so that the recess walls of the recess 103 tend to be smooth and flat, ensuring that the light reflection capability of the recess 103 can be effectively improved.

[0045] It is important to understand that the number of steps 310 contained in the recess 103 refers to the number of steps in the stepped staircase. Along the direction perpendicular to the first surface 101, the interval between each step 310 and the first surface 101 is obtained. Since steps 310 with the same interval can be regarded as the same level, the number of different interval sizes contained in the obtained interval is counted, and the number of different interval sizes is used as the number of steps in the stepped staircase.

[0046] refer to Figures 1 to 3 In some embodiments, the width of any one of the plurality of steps 310 is 1 μm to 2 μm in a direction parallel to the first surface 101.

[0047] Along the direction parallel to the first surface 101, the width of the step 310 refers to the tread width of the step 310, which is the interval w1 between the two edges of the step 310 in the cross-sectional view. During the fabrication of the recess 103, the width w1 of each step 310 in the multiple steps 310 included will affect the number of steps 310 that can be arranged in the recess 103. If the width w1 of each step 310 is too large, the number of steps 310 that can be arranged in the recess 103 will be too small, resulting in the steps 310 in the recess 103 being too sparsely arranged. The concave and convex structure formed between each level of steps 310 will mainly play the role of trapping light, and the improvement of the light reflection capability of the recess 103 will be limited. When the width w1 of each step 310 is too small, the number of steps 310 that can be arranged in the pit 103 is too large, resulting in the arrangement of each step 310 in the pit 103 being too tight. The concave-convex structure formed between each step 310 is not obvious, and the pit wall of the pit 103 tends to be smooth, which also makes it difficult to effectively improve the light reflection capability of the pit 103.

[0048] Therefore, during the fabrication of the pit 103, when setting the steps 310, the width w1 of each step 310 is set in the range of 1μm to 2μm. For example, the width w1 of the step 310 is set to 1.1μm, 1.25μm, 1.4μm, 1.5μm, 1.65μm, 1.75μm, 1.8μm or 1.9μm, etc. By setting the width w1 of each step 310 to an appropriate value, it is possible to avoid the pit 103 containing too few steps 310 due to the excessive width of the step 310, which would cause the concave and convex structures between the steps 310 to trap light and fail to effectively improve the light reflection capability of the pit 103. At the same time, it is also possible to avoid the pit 103 containing too many steps 310 due to the excessive width of the step 310, which would cause the pit wall of the pit 103 to become too smooth and flat, with limited improvement in light reflection capability. This ensures that the light reflection capability of the pit 103 can be effectively improved as much as possible.

[0049] It is worth mentioning that among the multiple steps 310 included in the recess 103, the width w1 of each step 310 can be the same or different. The specific size of the width w1 of the step 310 can be set as needed, and this application embodiment does not limit it.

[0050] refer to Figures 1 to 3 In some embodiments, the height of any one of the plurality of steps 310 is 0.2 μm to 0.6 μm in a direction perpendicular to the first surface 101.

[0051] In the direction perpendicular to the first surface 101, the height of the step 310 refers to the riser height of the step 310, which is the interval h1 between the two edges of the step 310 in the cross-sectional view. During the fabrication of the recess 103, the height h1 of each step 310 in the multiple steps 310 will affect the number of steps 310 that can be arranged in the recess 103. If the height h1 of each step 310 is too large, the number of steps 310 that can be arranged in the recess 103 will be too small, resulting in the steps 310 in the recess 103 being too sparsely arranged. The concave-convex structure formed between each level of steps 310 will mainly play the role of trapping light, and the improvement of the light reflection capability of the recess 103 will be limited. When the height h1 of each step 310 is too small, the number of steps 310 that can be arranged in the pit 103 is too large, resulting in the arrangement of each step 310 in the pit 103 being too tight. The concave and convex structure formed between each step 310 is not obvious, and the pit wall of the pit 103 tends to be smooth, which also makes it difficult to effectively improve the light reflection capability of the pit 103.

[0052] Therefore, during the fabrication of the pit 103, when setting the steps 310, the height h1 of each step 310 is set in the range of 0.2μm to 0.6μm. For example, the height h1 of the steps 310 can be set to 0.25μm, 0.3μm, 0.35μm, 0.375μm, 0.4μm, 0.45μm, 0.5μm, or 0.575μm, etc. By setting the height h1 of each step 310 to an appropriate value, it is possible to avoid the pit 103 containing too few steps 310 due to excessive step height, which would cause the uneven structure between steps 310 to trap light and fail to effectively improve the light reflection capability of the pit 103. At the same time, it is also possible to avoid the pit 103 containing too many steps 310 due to excessive step height, which would cause the pit wall of the pit 103 to become too smooth and flat, limiting the improvement of light reflection capability. This ensures that the light reflection capability of the pit 103 can be effectively improved.

[0053] It is worth mentioning that among the multiple steps 310 included in the pit 103, the height h1 of each step 310 can be the same or different. The height h1 of the step 310 can be set according to specific application scenarios and needs, and this application embodiment does not limit this.

[0054] In some embodiments, the width of any one of the plurality of steps 310 is 1 μm to 2 μm in the direction parallel to the first surface 101, and the height of any one of the plurality of steps 310 is 0.2 μm to 0.6 μm in the direction perpendicular to the first surface 101.

[0055] Since the riser height and tread width of each step 310 in the multiple steps 310, i.e., the height h1 of the step 310 in the direction perpendicular to the first surface 101 and the width w1 of the step 310 in the direction parallel to the first surface 101, both affect the number of steps 310 contained in the recess 103, and the larger the riser height and tread width, the smaller the number of steps 310 that can be contained in the recess 103. Therefore, when both the riser height and tread width are too large, the recess 103 contains too few steps 310, causing the concave and convex structures between the steps 310 to trap light, failing to effectively improve the light reflection capability of the recess 103; when both the riser height and tread width are too small, the recess 103 contains too many steps 310, the concave and convex structures formed between each step 310 are not obvious, and the recess wall of the recess 103 tends to be smooth, which also makes it difficult to effectively improve the light reflection capability of the recess 103.

[0056] To control the number of steps 310 contained in the pit 103 within a suitable range, the width w1 of each step 310 can be set within the range of 1μm to 2μm, and the height h1 of each step 310 can be set within the range of 0.2μm to 0.6μm. For example, the height h1 of each step 310 can be set to 0.25μm, 0.3μm, 0.35μm, 0.375μm, 0.4μm, 0.45μm, 0.5μm, or 0.575μm, while the width w1 of each step 310 can be set to 1.1μm, 1.25μm, 1.4μm, 1.5μm, 1.65μm, 1.75μm, 1.8μm, or 1.9μm, thereby effectively improving the light reflection capability of the pit 103.

[0057] refer to Figures 1 to 3 In some embodiments, the total width of the plurality of steps 310 in a direction parallel to the first surface 101 is 10 μm to 20 μm.

[0058] Along the direction parallel to the first surface 101, the total width of the plurality of steps 310 is the sum of the tread widths of the plurality of steps 310 included in one side wall of the recess 103, that is, the interval W between the starting and ending positions of the plurality of steps 310 included in one side wall of the recess in the cross-sectional view. During the setting of the recess 103, the number of steps 310 included in the recess wall of the recess 103 is related not only to the width of each step 310, but also to the total width W of the plurality of steps 310. When the width of the steps 310 is the same, if the total width W is too large, the number of steps 310 that can be arranged in the pit 103 will be too large, resulting in the arrangement of each level of steps 310 in the pit 103 being too dense. The concave and convex structure formed between each level of steps 310 will not be obvious, and the pit wall of the pit 103 will tend to be smooth, making it difficult to effectively improve the light reflection capability of the pit 103. If the total width W is too small, the arrangement of steps 310 in the pit 103 will be too sparse, and the concave and convex structure formed between each level of steps 310 will mainly play the role of trapping light, and the improvement of the light reflection capability of the pit 103 will also be limited.

[0059] Therefore, during the fabrication of the pit 103, the total width W of the multiple steps 310 is set within the range of 10μm to 20μm, for example, 10.5μm, 11μm, 12.5μm, 14μm, 15μm, 16.75μm, 17.5μm, or 19.5μm. By setting the total width W of the multiple steps 310 within a suitable range, the number of steps 310 contained in the pit 103 is moderate, effectively improving the light reflection capability of the pit 103, reducing the difficulty of identifying the pit 103, and facilitating the identification of the pit 103.

[0060] refer to Figures 1 to 3 In some embodiments, the depth of the pit 103 is 4 μm to 8 μm in the direction perpendicular to the first surface 101.

[0061] In the direction perpendicular to the first surface 101, the depth of the pit 103 refers to the distance the pit 103 extends into the substrate 100, that is, the distance H between the deepest point a of the pit 103 inside the substrate 100 and the first surface 101. The function of the pit 103 is to form a marking code 102, so that the features of the marking code 102 can be accurately identified. If the depth H of the pit 103 is too small, the features of the pit 103 itself are not obvious and it is difficult to identify after the incident light is reflected. If the depth H of the pit 103 is too large, the formation of the pit 103 will cause greater damage to the substrate 100, resulting in a decrease in the open circuit voltage of the substrate 100 and affecting the photoelectric conversion efficiency of the solar cell.

[0062] Therefore, during the fabrication of the pit 103, the depth H of the pit 103 is set within the range of 4μm to 8μm, for example, 4.25μm, 4.75μm, 5μm, 5.5μm, 6.25μm, 6.75μm, 7.5μm, or 7.8μm. By setting the depth H of the pit 103 within a suitable range, it is ensured that the pit 103 has sufficient depth to accurately identify the features of the pit 103 and the marking code 102, while reducing the impact of the formation of the pit 103 on the open-circuit voltage and photoelectric conversion efficiency of the solar cell.

[0063] It should be understood that during the production of the mark code 102, the depth H of each pit 103 in the direction perpendicular to the first surface 101 can be the same or different. The specific depth H of each pit 103 can be selected and set according to the characteristics of the mark code 102 and the specific needs of the application scenario. This application embodiment does not limit this.

[0064] refer to Figures 1 to 3 In some embodiments, the maximum length of the pit 103 is 40 μm to 70 μm in a direction parallel to the first surface 101.

[0065] In the direction parallel to the first surface 101, the maximum length of the recess 103 refers to the maximum distance L between any two points of the recess 103 on the first surface 101. During the setting of the recess 103, if the maximum length L of the recess 103 is set too small, the light-receiving area of ​​the recess 103 will be limited. Even if the recess 103 has good light reflection capability, it will be difficult to accurately identify the recess 103 due to the limited light-receiving area. If the maximum length L of the recess 103 is set too large, the light-receiving area of ​​the recess 103 will be large enough, but this will result in an excessively large mold opening area on the substrate 100, leading to excessive opening pressure loss of the solar cell and a decrease in the photoelectric conversion efficiency of the solar cell.

[0066] Therefore, during the fabrication of the recess 103, the maximum length L of the recess 103 is set to 40μm to 70μm, for example, 41μm, 45μm, 50μm, 55μm, 57.5μm, 62μm, or 67.5μm. By setting the maximum length L of the recess 103 within a suitable range, the recess 103 has a sufficiently large light-receiving area, facilitating the identification of the recess 103, while reducing the molding area of ​​the substrate 100, thus avoiding increased opening voltage loss and decreased photoelectric conversion efficiency due to an excessively large molding area.

[0067] It is worth mentioning that during the production of the mark code 102, the maximum length L of each pit 103 along the direction parallel to the first surface 101 can be the same or different. The maximum length L of each pit 103 can be selected and set according to the characteristics of the mark code 102 and the specific needs of the application scenario. This application embodiment does not limit this.

[0068] refer to Figure 1 In some embodiments, the substrate 100 has a front side and a back side, and the first surface 101 is the back side of the substrate 100.

[0069] During the setting of the marker code 102, if the marker code 102 is placed on the front side of the substrate 100, since the front side of the solar cell usually has light-trapping structures in the shape of pyramids, a large incident angle of the light source is required for the identification of the marker code 102. The incident angle refers to the angle between the incident light and the first surface 101. However, if the marker code 102 is placed on the back side of the substrate 100, since there are no light-trapping structures on the back side, there is no need for an excessively high incident angle; a low incident angle is also acceptable. A large incident angle refers to an incident angle greater than or equal to 45 degrees. By placing the marker code 102 on the back side of the substrate 100, the difficulty of identifying the marker code 102 is reduced, while the accuracy of the identification is improved.

[0070] It is worth mentioning that during the process of setting the marker code 102, the marker code 102 can also be set on the front side of the substrate 100, and then the light-trapping structure in the area where the marker code is located can be selectively removed, so that there is no light-trapping structure in the area where the marker code 102 is located, thereby reducing the recognition difficulty of the marker code 102.

[0071] In the solar cell provided in this application embodiment, multiple steps 310 are formed on the wall of the pit 103 and arranged in a stepwise manner along the direction perpendicular to the first surface 101. The multiple steps 310 are used to improve the light reflection performance of the pit 103, so that the features of the pit 103 can be more accurately identified under the same incident light conditions. This reduces the illumination conditions that the feature recognition of the constructed tag code 102 needs to meet, and reduces the difficulty of feature acquisition and encoding recognition of the tag code 102 under the same external conditions. While reducing the difficulty of tag code 102 recognition, the recognition accuracy of tag code 102 is improved. In the process of constructing the pit 103 containing multiple steps, the cross-sectional area of ​​the pit 103 is gradually increased in the direction perpendicular to the first surface 101 and in the direction parallel to the first surface 101, and the cross-sectional area at the bottom of the pit is minimized. That is, the pit 103 is constructed into a shape with a larger top area and a smaller bottom area. This minimizes the damage to the substrate 100 during the construction of the marker code 102 through the pit 103, while ensuring that the pit 103 has a larger light-receiving area to facilitate the identification of the pit 103 and improve the accuracy of feature acquisition and coding recognition of the marker code 102.

[0072] Accordingly, another embodiment of this application also provides a method for fabricating a solar cell, which can be referred to... Figure 5 ,include:

[0073] refer to Figure 1 and Figure 5 A substrate 100 is provided, the substrate 100 including a first surface 101.

[0074] On the first surface 101, an original mark code consisting of multiple recessed points is formed.

[0075] During the creation of the mark code 102, an original mark code consisting of multiple recessed points is formed on the first surface 101 according to the outline and features of the mark code 102.

[0076] In some embodiments, the marker code 102 can be formed by laser etching on the first surface 101 to form multiple recessed points, which constitute the original marker code. That is, according to the target outline and features of the marker code 102, multiple recessed points are formed on the first surface 101 by laser etching to form the original marker code.

[0077] It is worth mentioning that in the process of forming the original mark code composed of multiple indentations, not only laser etching can be used to etch the substrate 100, but other processes such as chemical etching can also be used for etching.

[0078] In some embodiments, during the formation of the original marker code using laser etching, the laser etching process parameters include: a laser wavelength of 1059 nm to 1065 nm, a pulse duration of 10 to 100 ns, a pulse repetition frequency of 500 kHz to 2000 kHz, and a laser power percentage of 70% to 75%. By setting the laser parameters as described above, combined with the movement of the substrate 100, multiple recesses with a diameter of 40 μm to 70 μm, a depth of 4 μm to 8 μm, a pit edge protrusion height of no more than 3 μm, and a width of no more than 4 μm can be formed on the first surface 101. This ensures that the morphological characteristics of the original marker code and the marker code 102 match as closely as possible, improving the accuracy of the marker code 102 formation.

[0079] The substrate 100 is textured to form a textured surface structure covering the first surface 101 and the original mark encoding.

[0080] After forming an original mark code consisting of multiple recessed points on the first surface 101 of the substrate 100, a flocking process is performed on the substrate 100 to form a flocked structure covering the first surface 101 and the original mark code.

[0081] It is worth mentioning that the substrate 100 has a front and a back side. The first surface 101 can be the front side or the back side of the substrate 100. When the first surface 101 is the back side of the substrate 100, the substrate 100 is double-sided texturing. When the first surface 101 is the front side of the substrate 100, the substrate 100 can be texturized only on the front side.

[0082] refer to Figures 1 to 5 The velvet structure on the original mark code is cleaned to form a mark code 102 consisting of multiple pits 103.

[0083] After forming a textured structure covering the first surface 101 and the original mark code, the textured structure on the original mark code is cleaned. During the formation of the recessed points, the portion of the recessed point in contact with the first surface 101 may form a protruding portion protruding from the first surface 101 due to molten silicon or etching residue. Therefore, after forming the original mark code, a textured structure is formed on the first surface 101 and the original mark code. Then, by cleaning the textured structure, the textured structure and the protrusions at the edges of the recessed points are removed together, forming a pit 103. Due to the texturing and textured structure cleaning, based on the characteristics of the textured structure base, at least a portion of the pits 103 include multiple steps 310 arranged in a stepwise manner along a direction perpendicular to the first surface 101.

[0084] Furthermore, to avoid excessive mold opening losses in the battery cell due to the formation of the marking code 102, during the initial marking code formation process, the cross-sectional area of ​​the formed recesses gradually increases in the direction perpendicular to the first surface 101, while the cross-sectional area of ​​the pit bottom located inside the substrate 100 is the smallest. Due to the characteristics of the tower base, the pit walls of the recesses 103 are composed of multiple stepped structures 310 arranged in a progressive manner. Therefore, in the direction perpendicular to the first surface 101, at least some of the formed recesses 103 have a gradually increasing cross-sectional area in the direction parallel to the first surface 101, while the cross-sectional area of ​​the pit bottom is the smallest.

[0085] It is worth mentioning that the cleaning methods for the velvet structure include chemical cleaning, particle blowing cleaning, etc. The cleaning method can be selected according to specific needs, and this application embodiment does not limit this.

[0086] In some embodiments, the substrate 100 has a front side and a back side, and the first surface 101 is the back side of the substrate 100; the step of cleaning the original mark code includes: cleaning the first surface 101 to remove the velvet structure on the original mark code and on the first surface 101.

[0087] When the first surface 101 is the back side of the substrate 100, the textured surface on the back is not needed in the finished product. Therefore, to simplify the cleaning of the textured surface on the original marking code, the first surface 101 can be cleaned directly. When the first surface 101 is the front side of the substrate 100, the textured surface on the front side needs to be retained. Therefore, a protective film can be formed on the area of ​​the first surface 101 not covered by the original marking code, and then the original marking code can be cleaned with textured material.

[0088] It is not difficult to see that this embodiment is a solar cell fabrication method embodiment corresponding to the solar cell structure embodiment. The details in this embodiment are also applicable to the solar cell structure embodiment, and similarly, the details in the solar cell structure embodiment are also applicable to this embodiment.

[0089] Accordingly, embodiments of this application also provide a photovoltaic module, referencing Figure 6 The photovoltaic module includes: a cell string, which is formed by connecting multiple solar cells 610 provided in the above embodiments; an encapsulation layer 620 for covering the surface of the cell string; and a cover plate 630 for covering the surface of the encapsulation layer 620 away from the cell string. The solar cells 610 are electrically connected in a whole or in multiple segments to form multiple cell strings, and the multiple cell strings are electrically connected in series and / or parallel.

[0090] Specifically, in some embodiments, multiple battery strings can be electrically connected via conductive strips 640. The encapsulation layer 620 covers the front and back of the solar cell 610. Specifically, the encapsulation layer 620 can be an organic encapsulation film such as ethylene-vinyl acetate copolymer (EVA) film, polyethylene octene copolymer elastomer (POE) film, or polyethylene terephthalate (PET) film. In some embodiments, the cover plate 630 can be a light-transmitting cover plate such as a glass cover plate or a plastic cover plate. Specifically, the surface of the cover plate 630 facing the encapsulation layer 620 can be an uneven surface, thereby increasing the utilization rate of incident light.

[0091] Although this application discloses preferred embodiments as described above, it is not intended to limit the claims. Any person skilled in the art can make several possible changes and modifications without departing from the concept of this application. Therefore, the scope of protection of this application should be determined by the scope defined in the claims of this application.

[0092] Those skilled in the art will understand that the above embodiments are specific examples of implementing this application, and in practical applications, various changes in form and detail can be made without departing from the spirit and scope of this application. Any person skilled in the art can make various alterations and modifications without departing from the spirit and scope of this application; therefore, the scope of protection of this application should be determined by the scope defined in the claims.

Claims

1. A solar cell, characterized by, include: A substrate having a first surface; The marking code located on the first surface includes a plurality of pits, at least a portion of which include a plurality of steps arranged in a stepwise manner along a direction perpendicular to the first surface, the plurality of steps forming a stepped structure arranged sequentially along the depth direction on the pit wall of the pit. In the direction perpendicular to the first surface, the cross-sectional area of ​​each of the at least some pits gradually increases in the direction parallel to the first surface, and the cross-sectional area at the bottom of the pit is the smallest.

2. The solar cell according to claim 1, characterized in that, The first surface includes an edge region surrounding each of the pits and a flat region adjacent to the edge region, wherein the height difference between the edge region and the flat region is 0 to 5 μm in a direction perpendicular to the first surface.

3. The solar cell according to claim 1, characterized in that, The plurality of steps comprises 12 to 20 steps.

4. The solar cell according to claim 1, characterized in that, In the direction parallel to the first surface, the width of any one of the plurality of steps is 1 μm to 2 μm; in the direction perpendicular to the first surface, the height of any one of the plurality of steps is 0.2 μm to 0.6 μm.

5. The solar cell according to claim 1, characterized in that, The depth of the pit is 4 μm to 8 μm in a direction perpendicular to the first surface.

6. The solar cell according to claim 1, characterized in that, The maximum length of the pit is 40 μm to 70 μm in a direction parallel to the first surface.

7. The solar cell according to any one of claims 1 to 6, characterized in that, The substrate has a front and a back side, with the first surface being the back side of the substrate.

8. A method for preparing a solar cell, characterized in that, include: A substrate is provided, the substrate including a first surface; On the first surface, an original mark code consisting of multiple indentations is formed; The substrate is flocked to form a flocked structure covering the first surface and the original mark encoding; The velvet structure on the original mark code is cleaned to form a mark code consisting of multiple pits. At least some of the multiple pits include multiple steps arranged in a stepwise manner along a direction perpendicular to the first surface. The multiple steps form a stepped structure arranged sequentially along the depth direction on the pit wall. In the direction perpendicular to the first surface, the cross-sectional area of ​​each of the at least some pits gradually increases in the direction parallel to the first surface, and the cross-sectional area at the bottom of the pit is the smallest.

9. The method for preparing a solar cell according to claim 8, characterized in that, The substrate has a front side and a back side, with the first surface being the back side of the substrate; The step of cleaning the original mark code includes: cleaning the first surface to remove the velvet structure on the original mark code and on the first surface.

10. The method for preparing a solar cell according to claim 8, characterized in that, The step of forming the mark code includes: laser etching the first surface to form the plurality of recessed points, the plurality of recessed points constituting the original mark code.

11. The method for preparing a solar cell according to claim 10, characterized in that, The laser etching process parameters include: laser wavelength of 1059nm to 1065nm, pulse duration of 10 to 100ns, pulse repetition frequency of 500kHz to 2000kHz, and laser power percentage of 70% to 75%.

12. A photovoltaic module, characterized in that, include: A battery string, wherein the battery string is formed by connecting a plurality of solar cells according to any one of claims 1 to 7; Encapsulation layer, the encapsulation layer being used to cover the surface of the battery string; A cover plate for covering the surface of the encapsulation layer away from the battery string.

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