Photovoltaic cell and photovoltaic module

Abstract

The invention relates to a photovoltaic cell and a photovoltaic module, and relates to the field of photovoltaic technology. The photovoltaic cell comprises a middle part and two edge parts, the middle part is located between the two edge parts, each edge part has a first thickness size, the middle part has a second thickness size, and the first thickness size is larger than the second thickness size. The photovoltaic cell further comprises a first step located at the edge part and a second step located at the middle part, the side wall of the first step has a first height size, the side wall of the second step has a second height size, the first height size is smaller than the second height size, and the structural strength of the edge part is relatively high. The stress concentration degree of the edge part is relatively small, the edge part is not easy to damage, and the edge part is not easy to have a leakage current path, so that the photoelectric conversion efficiency of the photovoltaic cell is relatively high, and correspondingly, the output power of the photovoltaic module is relatively high.

Description

[0001] This application is a divisional application. The original application has the application number 2025113262119 and the original application date is September 17, 2025. The entire contents of the original application are incorporated herein by reference. Technical Field

[0002] This application relates to the field of photovoltaic cell technology, and in particular to a photovoltaic cell and a photovoltaic module. Background Technology

[0003] In related technologies, photovoltaic (PV) cells are used to convert solar energy into electrical energy, and they are widely used in various applications utilizing renewable energy sources. However, the photoelectric conversion efficiency of PV cells still needs improvement. Summary of the Invention

[0004] This application provides a photovoltaic cell, which includes a middle portion and two edge portions. The middle portion is located between the two edge portions. The edge portions have a first thickness dimension, and the middle portion has a second thickness dimension. The first thickness dimension is greater than the second thickness dimension. The photovoltaic cell also includes a first step located in the edge portion and a second step located in the middle portion. The sidewall of the first step has a first height dimension, and the sidewall of the second step has a second height dimension. The first height dimension is smaller than the second height dimension.

[0005] Optionally, the ratio of the first height dimension to the second height dimension is 0.5 to 0.7.

[0006] Optionally, the first height dimension is 2 to 3 micrometers.

[0007] Optionally, the second height dimension is 3 to 4 micrometers.

[0008] Optionally, the sidewalls of the second step are steeper than the sidewalls of the first step.

[0009] Optionally, both the first step and the second step are located on the light-receiving surface of the photovoltaic cell.

[0010] Optionally, the edge portion and the middle portion are spaced apart, and the photovoltaic cell also includes an emitter, which is located between the edge portion and the middle portion.

[0011] Optionally, the photovoltaic cell further includes at least two transition portions, with at least one transition portion provided between the middle portion and one of the edge portions, and at least one transition portion also provided between the middle portion and another edge portion, the transition portions having a third thickness dimension, the third thickness dimension being smaller than the first thickness dimension and larger than the second thickness dimension.

[0012] Optionally, the photovoltaic cell also includes a third step located in the transition section, the sidewall of the third step having a third height dimension, the third height dimension being greater than the first height dimension and less than the second height dimension.

[0013] Alternatively, the sidewalls of the second step are steeper than those of the third step.

[0014] Optionally, the first step, the second step, and the third step are located on the light-receiving surface of the photovoltaic cell.

[0015] Optionally, the edge portion and the transition portion are spaced apart, the transition portion and the middle portion are spaced apart, and the photovoltaic cell also includes an emitter, with the emitter existing between the edge portion and the transition portion, and also between the transition portion and the middle portion.

[0016] Optionally, the ratio of the first thickness dimension to the second thickness dimension is 1.01 to 1.12.

[0017] Optionally, the light-receiving surface of the edge portion includes an edge velvet surface, and the light-receiving surface of the middle portion includes a middle velvet surface, wherein the size of the pyramid structure of the middle velvet surface is smaller than the size of the pyramid structure of the edge velvet surface.

[0018] Optionally, the base size of the pyramid structure with velvety edges is 3 to 4 micrometers.

[0019] Optionally, the base size of the pyramid structure with the velvet surface in the middle is 2 to 3 micrometers.

[0020] Optionally, the density of the pyramid structure on the middle pile side is greater than the density of the pyramid structure on the edge pile side.

[0021] Optionally, the height of the edge nap decreases in the direction from the edge portion toward the middle portion.

[0022] Optionally, the photovoltaic cell also includes at least two transition sections, with at least one transition section provided between the middle section and one of the edge sections, and at least one transition section also provided between the middle section and the other edge section. The light-receiving surface of the transition section includes a transition textured surface, and the size of the pyramid structure of the transition textured surface is smaller than the size of the pyramid structure of the edge textured surface.

[0023] Optionally, the density of the pyramid structure on the transition pile is greater than the density of the pyramid structure on the edge pile.

[0024] Optionally, the height of the transition velvet surface decreases in the direction from the transition portion toward the middle portion.

[0025] This application also provides a photovoltaic module, which includes a battery string, the battery string including at least two electrically connected photovoltaic cells, the photovoltaic cells being the photovoltaic cells provided in this application as described above.

[0026] The photovoltaic cell of this application exhibits relatively high structural strength at its edge, and relatively low stress concentration at the first step and surrounding area of ​​the edge. During the fabrication of photovoltaic modules, although the edge of the photovoltaic cell bears relatively greater forces and bending moments compared to other parts, it is less prone to structural damage such as cracking and edge chipping. The defect density at the edge is relatively low, and leakage current paths are less likely to occur there. Therefore, the photovoltaic cell achieves relatively high photoelectric conversion efficiency, and the photovoltaic module equipped with this cell also has relatively high output power.

[0027] It should be understood that the above general description and the following detailed description are merely exemplary and do not limit this application. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of this application, 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.

[0029] Figure 1 This is a partial structural diagram of a silicon substrate in one embodiment;

[0030] Figure 2 This is a partial structural diagram of a silicon substrate and an emitter in one embodiment;

[0031] Figure 3 This is a partial structural diagram of the silicon substrate, emitter, and modified portion in one embodiment;

[0032] Figure 4 This is a partial structural diagram of a silicon substrate and emitter after acid pickling in one embodiment;

[0033] Figure 5 This is a schematic diagram of a partial structure of a substrate after alkaline etching in one embodiment;

[0034] Figure 6 This is a partial structural diagram of the substrate, emitter, and modified portion in another embodiment;

[0035] Figure 7 This is a schematic diagram of a partial structure of the substrate after alkaline etching in another embodiment;

[0036] Figure 8 This is a partial structural diagram of the edge portion of a photovoltaic cell in one embodiment;

[0037] Figure 9 This is a schematic diagram of the scanning path of the first laser in one embodiment;

[0038] Figure 10 This is a schematic diagram of the scanning path of the first laser in another embodiment;

[0039] Figure 11 This is a partial structural diagram of the substrate after alkaline etching in another embodiment;

[0040] Figure 12 This is a partial structural diagram of the substrate after alkaline etching in another embodiment;

[0041] Figure 13 This is a schematic diagram of a partial structure of the substrate after alkaline etching in another embodiment;

[0042] Figure 14 This is a partial structural diagram of a silicon substrate and emitter after alkaline etching in one embodiment;

[0043] Figure 15 This is a partial structural diagram of the silicon substrate and emitter after alkaline etching in another embodiment;

[0044] Figure 16 This is a partial structural schematic diagram of the silicon substrate, emitter, and modified portion in another embodiment;

[0045] Figure 17 This is a partial structural diagram of the substrate after alkaline etching in yet another embodiment;

[0046] Figure 18 This is a partial structural diagram of the transition section of a photovoltaic cell in one embodiment;

[0047] Figure 19 This is a schematic diagram of a partial structure of the substrate after alkaline etching in another embodiment;

[0048] Figure 20 This is a schematic diagram of a partial structure of the substrate after alkaline etching in another embodiment;

[0049] Figure 21 This is a partial structural diagram of the silicon substrate and emitter after alkaline etching in another embodiment;

[0050] Figure 22 This is a partial structural diagram of the silicon substrate, emitter, and modified portion in another embodiment;

[0051] Figure 23 This is a schematic diagram of a partial structure of the substrate after alkaline etching in another embodiment;

[0052] Figure 24 This is a partial structural diagram of the edge and middle regions of the substrate in another embodiment;

[0053] Figure 25 This is a partial structural diagram of the edge and middle regions of the substrate in another embodiment;

[0054] Figure 26 This is a three-dimensional structural diagram of the silicon substrate and emitter after alkaline etching in another embodiment.

[0055] Figure 27 for Figure 26 A three-dimensional structural diagram of the silicon substrate and emitter from another perspective;

[0056] Figure 28 This is a schematic diagram of the structure of a silicon substrate in one embodiment;

[0057] Figure 29 This is a schematic diagram of the structure of a texturized silicon substrate in one embodiment;

[0058] Figure 30 This is a schematic diagram of the structure of a silicon substrate, an emitter, an oxide layer, and a winding layer in one embodiment;

[0059] Figure 31 This is a schematic diagram of the structure of a silicon substrate, an emitter, an oxide layer, a winding layer, and a modified portion in one embodiment;

[0060] Figure 32 This is a schematic diagram of the structure of the silicon substrate, emitter, oxide layer and winding layer after pickling in one embodiment;

[0061] Figure 33 This is a schematic diagram of the structure of the silicon substrate, emitter, oxide layer and winding layer after alkaline etching in one embodiment;

[0062] Figure 34 This is a schematic diagram of the structure of a silicon substrate, an emitter, an oxide layer, a winding layer, and borosilicate glass in one embodiment;

[0063] Figure 35 This is a schematic diagram of the structure of a silicon substrate, an emitter, an oxide layer, and borosilicate glass in one embodiment;

[0064] Figure 36 This is a schematic diagram of the structure of a silicon substrate, an emitter, an oxide layer, a borosilicate glass, a tunneling oxide layer, a phosphorus-doped silicon layer, and a phosphorus-silicon glass in one embodiment.

[0065] Figure 37 for Figure 36 A magnified view of part X in the middle;

[0066] Figure 38 for Figure 36 A magnified view of part W in the middle;

[0067] Figure 39 This is a schematic diagram of the structure of the silicon substrate, emitter, oxide layer, borosilicate glass, tunneling oxide layer, phosphorus-doped silicon layer, and phosphorosilicate glass after laser selective removal in one embodiment.

[0068] Figure 40 This is a schematic diagram of the structure of the silicon substrate, emitter, oxide layer, borosilicate glass, tunneling oxide layer, phosphorus-doped silicon layer, and phosphorus-silicon glass in one embodiment after the phosphorus-silicon glass on the light-receiving side has been removed.

[0069] Figure 41 This is a schematic diagram of the structure of the silicon substrate, emitter, oxide layer, borosilicate glass, tunneling oxide layer, phosphorus-doped silicon layer, and phosphorosilicate glass in one embodiment after the phosphorus-doped silicon layer located on the light-receiving side has been removed.

[0070] Figure 42 This is a schematic diagram of the structure of a silicon substrate, an emitter, a tunneling oxide layer, and a phosphorus-doped silicon layer in one embodiment.

[0071] Figure 43 This is a schematic diagram of the structure of a silicon substrate, an emitter, a tunneling oxide layer, a phosphorus-doped silicon layer, and a passivation layer in one embodiment;

[0072] Figure 44 This is a schematic diagram of the structure of a photovoltaic cell in one embodiment;

[0073] Figure 45 This is a schematic diagram of the structure of a photovoltaic cell in another embodiment;

[0074] Figure 46 This is a schematic diagram of the structure of a photovoltaic cell in yet another embodiment;

[0075] Figure 47 This is a schematic diagram of a photovoltaic cell in yet another embodiment;

[0076] Figure 48 This is a partial structural diagram of the edge and connecting parts of a photovoltaic cell in one embodiment;

[0077] Figure 49 This is a partial structural diagram of the transition and connection parts of a photovoltaic cell in one embodiment;

[0078] Figure 50This is a partial structural diagram of a photovoltaic cell in another embodiment;

[0079] Figure 51 This is a schematic diagram of the silicon substrate, emitter, and passivation layer in yet another embodiment;

[0080] Figure 52 This is a schematic diagram of the silicon substrate, emitter, and positive gate line in one embodiment.

[0081] Figure labeling: A - First zone, A1 - Edge zone, A2 - Middle zone, A3 - Transition zone, A 31 -First Transition Zone, A 32 - Second transition region, B-Second region, SG-Light-receiving side, BG-Backlight side, 10-Substrate, 1-Silicon substrate, 2-Emitter, 2a-Modified part, 3-Oxide layer, 23-Wrap-up layer, 4a-Borosilicate glass, 4b-Phosphosphosilicate glass, 5-Tunneling oxide layer, 6-Phosphorus-doped silicon layer, 7-Passivation layer, 8-Positive grid line, 9-Negative grid line, R-Textured surface, Q-Slanted surface, QR-Slanted textured surface, P-Non-Slanted surface, 20-Photovoltaic cell, a1-Edge part, a2-Middle part, a3-Transition part, b-Connection part, T1-First step, T2-Second step, T3-Third step, BR-Edge textured surface, ZR-Middle textured surface, GR-Transition textured surface. Detailed Implementation

[0082] To better understand the technical solutions of this application, the embodiments of this application are described in detail below with reference to the accompanying drawings. It should be understood that the described embodiments are merely some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. The terminology used in the embodiments of this application is for the purpose of describing specific embodiments only, and is not intended to limit this application. The singular forms "a," "described," and "the" used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise. It should be understood that the term "and / or" used herein is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects are in an "or" relationship.

[0083] Firstly, this application provides some embodiments of methods for preparing photovoltaic cells, relating to the field of photovoltaic cell technology. In some embodiments, the method for preparing a photovoltaic cell may include: providing, for example... Figure 1The substrate 10 shown may include a silicon substrate 1, and may have a central region A2 and two edge regions A1 distributed therebetween, with the central region A2 located between the two edge regions A1. Figure 2 As shown, emitter 2 is formed, and at this time, emitter 2 also serves as part of the structure of substrate 10. In the photovoltaic cell to be fabricated subsequently, a built-in electric field for separating photogenerated carriers can be formed between the silicon substrate 1 and emitter 2. After the emitter 2 is formed, the portion of emitter 2 located in the edge region A1 is scanned using a first laser, and the portion of emitter 2 located in the middle region A2 is scanned using a second laser, so that some portions of emitter 2 are modified by the first and second lasers, i.e., forming as shown in the diagram. Figure 3 The modified portion 2a in the edge region A1 and the modified portion 2a in the middle region A2 are shown. The energy of the first laser can be controlled to be less than the energy of the second laser. Since the depth of the modified portion 2a is positively correlated with the laser energy, the depth of the modified portion 2a in the edge region A1 is smaller than the depth of the modified portion 2a in the middle region A2. After modification, the structure of the modified portion 2a is relatively loose and its chemical reactivity is relatively high. Therefore, the portion modified by the first and second lasers within the emitter 2 can be removed by acid washing, that is, the modified portions 2a in the edge region A1 and the modified portions 2a in the middle region A2 can be removed by acid washing to form the modified portion 2a in the edge region A1 and the middle region A2, as shown in the diagram. Figure 4 In the structure shown, the thickness of the portion of emitter 2 located in the edge region A1 is greater than the thickness of the portion of emitter 2 located in the middle region A2. In other words, the thickness of the structure of substrate 10 located in the edge region A1 is greater than the thickness of the structure of substrate 10 located in the middle region A2. After acid etching, the portions of emitter 2 located in the edge region A1 and the middle region A2 are etched with alkali to remove surface laser damage and to continue etching some structures. Since the alkali etching rate of the structure of substrate 10 in the edge region A1 is the same as or close to the alkali etching rate of the structure of substrate 10 in the middle region A2, after alkali etching, as... Figure 5 As shown, the thickness H of the structure located in the edge region A1 of the substrate 10 A1 Compared to the thickness H of the structure located in the middle region A2 of substrate 10 A2 Larger.

[0084] As can be seen from the above, the photovoltaic cells prepared according to the embodiments of the photovoltaic cell preparation methods provided in this application have the following advantages: In such cases... Figure 5 The photovoltaic cell fabricated on the substrate 10 shown has a thicker edge portion than a thicker middle portion, wherein the edge portion of the photovoltaic cell is formed by... Figure 5 The substrate 10 shown is formed based on the structure located within the edge region A1, and the middle part of the photovoltaic cell is formed as shown in the figure. Figure 5 The structure of the substrate 10 shown is formed based on the structure located in the central region A2. Further details regarding specific embodiments of the photovoltaic cell structure that can be fabricated will be provided later in this document. While ensuring the structural strength of the central portion of the fabricated photovoltaic cell meets requirements, the structural strength of the edge portion of the photovoltaic cell is relatively greater, allowing it to withstand relatively larger forces and bending moments. Correspondingly, during subsequent photovoltaic module fabrication processes, such as when photovoltaic cells are wired together to form a cell string and when they are laminated to form a stack, although the edge portion of the photovoltaic cell may withstand relatively larger forces and bending moments compared to other portions, it is less prone to structural damage problems such as cracking and edge chipping. The density of defects (e.g., dangling bonds, dislocations) at the edge portion is relatively low, and leakage current paths (small currents flowing in unintended paths that do not contribute useful work) are less likely to occur at the edge portion. Therefore, the photoelectric conversion efficiency of the photovoltaic cell in the photovoltaic module is relatively high, resulting in a relatively high output power of the photovoltaic module.

[0085] In some embodiments, both the first and second lasers can be red nanolasers, which can also be called nanosecond-level pulsed lasers in the infrared band, with wavelengths ranging from 1050 nanometers (nm) to 1070 nanometers (nm), specifically 1050nm, 1055nm, 1060nm, 1065nm, or 1070nm. In other embodiments, the first and second lasers can also be ultraviolet lasers or green lasers.

[0086] In some embodiments, the comparison between the energy of the first laser and the energy of the second laser mainly involves a comparison between their energy densities. Energy density refers to the energy value per unit area, and the unit of energy density is joules per square centimeter (J / cm²). 2 In some other embodiments, the comparison between the energy of the first laser and the energy of the second laser can also be a comparison between their powers, where power refers to the energy value per unit time, and the unit of power is watts (W).

[0087] In some embodiments, such as Figures 1-5 As shown, substrate 10 mainly refers to the non-finished structure used in the preparation process to form photovoltaic cells that can be put into use. During the preparation process, the structure of substrate 10 in different states is different.

[0088] In some embodiments, such as Figures 1-5As shown, edge region A1 and middle region A2 can be separated, or they can be spaced apart. In some other embodiments, edge region A1 and middle region A2 can also be adjacent. Various distributions of edge region A1 and middle region A2 will be discussed in detail later in this document, and will not be elaborated upon here.

[0089] In some embodiments, such as Figures 1-4 As shown, silicon substrate 1 can be an N-type silicon substrate, that is, the N-type silicon substrate can be doped with at least one N-type element (the fifth main group element in the periodic table of chemical elements), such as phosphorus, arsenic, antimony and other N-type elements.

[0090] In some embodiments, such as Figures 2-4 As shown, emitter 2 can be a P-type emitter, that is, the P-type emitter can be doped with at least one P-type element (a group 3 element in the periodic table of chemical elements), such as boron, aluminum, gallium and other P-type elements.

[0091] In some embodiments, the method of forming the emitter 2 may include: in such a way as Figure 1 The silicon substrate 1 shown is diffused with a doping source on one side surface, thereby forming a doping source as shown in the figure. Figure 2 The structure shown is illustrated. The dopant source diffused into the silicon substrate 1 may contain at least one p-type element mentioned above. Furthermore, the diffusion equipment includes devices such as diffusion furnaces that utilize high temperatures to propel the dopant source from a high-concentration region to a low-concentration region.

[0092] In some embodiments, such as Figures 1-4 As shown, the method of forming the emitter 2 may include: forming the emitter 2 on the light-receiving side of the silicon substrate 1, wherein the light-receiving side of the silicon substrate 1 refers to the side of the silicon substrate 1 that is directly facing the sunlight.

[0093] In some embodiments, such as Figures 1-5 As shown, direction H can represent the thickness direction of substrate 10 and the thickness direction of the photovoltaic cell to be fabricated.

[0094] In some embodiments, the method of scanning the portion of the emitter 2 located within the edge region A1 using a first laser may include: when the portion of the emitter 2 located within the same edge region A1 is scanned by the first laser, controlling the energy of the first laser along a direction from the edge region A1 to the middle region A2 (e.g., Figure 6 The direction L1 shown increases. Under this setting, as... Figure 6 As shown, the depth of the modified portion 2a located within the edge region A1 increases along direction L1. Combined with the acid etching removal of the modified portion 2a within the edge region A1 and the alkaline etching of the portion of the emitter 2 within the edge region A1 described above, as follows... Figure 7As shown, the surface of the structure located within the edge region A1 of the substrate 10 may include an inclined surface Q. The surface of the edge portion of the photovoltaic cell fabricated based on this may also include, for example... Figure 8 The inclined surface Q is shown. In the morning or evening, although sunlight shines obliquely onto the photovoltaic cell, the incident angle θ between the normal F of the inclined surface Q at the edge of the photovoltaic cell and the direction of sunlight Y is relatively small. This relatively small incident angle θ results in a relatively low light reflectivity on the inclined surface Q at the edge of the photovoltaic cell, thus minimizing incident light loss. Therefore, the number of photogenerated carriers generated by the photovoltaic cell in the morning or evening is still relatively high, and the photoelectric conversion efficiency of the photovoltaic cell remains relatively high.

[0095] Here, the normal direction refers to the direction of the normal on the geometric surface. Additionally, from the perspective along direction H, the scanning path of the first laser scanning the portion of the emitter 2 located within the edge region A1 can be determined by... Figure 9 A hollow arrowhead in a middle triangle. Figure 9 In sub-figure (a), multiple scanning paths are perpendicular to direction L1, and the scanning directions of the multiple scanning paths are the same. The first laser scans along the scanning path away from the middle region A2 first, and then scans along the scanning path closer to the middle region A2. Figure 9 In subgraph (b), multiple scanning paths are perpendicular to direction L1, and the scanning directions of every two adjacent scanning paths are opposite. The first laser scans along the scanning path away from the middle region A2 first, and then scans along the scanning path closer to the middle region A2. Figure 9 In subgraphs (a) and (b), the energy of the first laser scanning along the scanning path away from the central region A2 is relatively low, while the energy of the first laser scanning along the scanning path closer to the central region A2 is relatively high. Figure 9 In subgraph (c), multiple scanning paths are parallel to direction L1, and the scanning direction of multiple scanning paths is the same as direction L1. The energy of the first laser scanning along each scanning path gradually increases or increases in stages along direction L1. Furthermore, direction L1 can be perpendicular to direction H.

[0096] In some embodiments, the method of scanning the portion of the emitter 2 located within the edge region A1 using a first laser may also include: when the portion of the emitter 2 located within the same edge region A1 is scanned by the first laser, controlling the energy of the first laser along a direction from the middle region A2 to the edge region A1 (e.g., ...). Figure 6 The direction L2 shown decreases, as shown in this setting, such as Figure 6As shown, the depth of the modified portion 2a located within the edge region A1 decreases along direction L2. Combined with the acid etching removal of the modified portion 2a within the edge region A1 and the alkaline etching of the portion of the emitter 2 within the edge region A1 described above, as follows... Figure 7 As shown, the surface of the structure located within the edge region A1 of the substrate 10 includes an inclined surface Q. The surface of the edge portion of the photovoltaic cell fabricated based on this may also include, for example... Figure 8 The inclined surface Q is shown. Accordingly, the number of photogenerated carriers generated by the photovoltaic cell in the morning or evening is still relatively large, and the photoelectric conversion efficiency of the photovoltaic cell is still relatively high. The specific effects have been described above and will not be repeated here.

[0097] Among them, the scanning path of the first laser scanning the portion of the emitter 2 located within the edge region A1, along the viewing angle in direction H, can be determined by... Figure 10 A hollow arrowhead in a middle triangle. Figure 10 In sub-figure (a), multiple scanning paths are perpendicular to direction L2, and the scanning directions of the multiple scanning paths are the same. The first laser scans along the scanning path closer to the middle region A2 first, and then scans along the scanning path farther from the middle region A2. Figure 10 In subgraph (b), multiple scanning paths are perpendicular to direction L2, and the scanning directions of every two adjacent scanning paths are opposite. The first laser scans along the scanning path closer to the middle region A2 first, and then scans along the scanning path farther from the middle region A2. Figure 10 In subgraphs (a) and (b), the energy of the first laser scanning along the scanning path closer to the central region A2 is relatively high, while the energy of the first laser scanning along the scanning path farther from the central region A2 is relatively low. Figure 10 In subgraph (c), multiple scanning paths are parallel to direction L2, and the scanning direction of the multiple scanning paths is the same as direction L2. The energy of the first laser scanning along each scanning path gradually decreases or decreases in stages along direction L2. In addition, direction L2 can be perpendicular to direction H.

[0098] In some embodiments, the method of scanning the portion of the emitter 2 located within the edge region A1 using a first laser may include: when the portion of the emitter 2 located within the same edge region A1 is scanned by the first laser, controlling the energy of the first laser to remain constant. Under this setup, such as... Figure 11 As shown, the non-tilted surface P of the structure located in the edge region A1 of the substrate 10 may not include the tilted surface; in other words, the non-tilted surface P is perpendicular to the direction H.

[0099] The scanning path of the first laser, which scans the portion of emitter 2 located within edge region A1 from the perspective of direction H, can be referenced. Figure 9 The scan path or Figure 10 The scanning path in the middle, or the scanning path of the first laser scanning the portion of the emitter 2 located in the edge region A1, can be bow-shaped, square-shaped, or spiral-shaped. The specific shape of the scanning path of the first laser is not limited here.

[0100] In some embodiments, the ratio of the energy of the first laser to the energy of the second laser can be controlled within the range of 0.6 to 0.7, wherein the ratio can specifically be 0.6, 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.69 or 0.7.

[0101] In some embodiments, the portion of the emitter 2 located in the edge region A1 can be scanned first using the first laser, and then the portion of the emitter 2 located in the middle region A2 can be scanned using the second laser; or, the portion of the emitter 2 located in the middle region A2 can be scanned first using the second laser, and then the portion of the emitter 2 located in the edge region A1 can be scanned using the first laser; or, the portion of the emitter 2 located in the edge region A1 can be scanned using the first laser, and the portion of the emitter 2 located in the middle region A2 can be scanned using the second laser simultaneously.

[0102] In some embodiments, a first laser may be generated using a first device, and a second laser may be generated using a second device, or the same device may be used to generate both the first and second lasers.

[0103] In some embodiments, the method of alkaline etching of the portion of the emitter 2 located within the edge region A1 and the middle region A2 may include: using an alkaline solution containing a polishing additive. Under this setup, as... Figure 5 As shown, the surfaces of the structures located in the edge region A1 and the structures located in the middle region A2 of the substrate 10 can both include polished surfaces.

[0104] In some embodiments, the method of alkaline etching of the portion of the emitter 2 located within the edge region A1 and the middle region A2 may include: using an alkaline solution containing a texturing additive. Under this setup, as... Figure 12 As shown, the surfaces of the structures located in the edge region A1 and the structures located in the middle region A2 of the substrate 10 can both include a textured surface R (a surface with multiple micron-sized pyramidal structures, also known as a light-trapping surface). Based on this, the surfaces of both the edge and middle portions of the fabricated photovoltaic cell can also include a textured surface, resulting in a relatively low light reflectivity of the photovoltaic cell and thus relatively less incident light loss. Therefore, the photovoltaic cell can generate a relatively large number of photogenerated carriers, and the photovoltaic cell has a relatively high photoelectric conversion efficiency.

[0105] If, in conjunction with the aforementioned description, the surface of the structure of the substrate 10 located within the edge region A1 also includes an inclined surface Q, then the surface of the structure of the substrate 10 located within the edge region A1 may also include, as described above... Figure 13 The tilted textured surface QR is shown. The photovoltaic cells prepared based on this still generate a relatively large number of photogenerated carriers in the morning or evening, and the photoelectric conversion efficiency of the photovoltaic cells is still relatively high. The specific effects have been described above and will not be repeated here. This article will subsequently use "alkaline solution containing texturing additives" as an example to describe "alkaline etching of the portion of emitter 2 located in the edge region A1 and the middle region A2".

[0106] In addition, the alkaline solution containing texturing additives may include at least one corrosive agent selected from sodium hydroxide (NaOH) and potassium hydroxide (KOH), and the alkaline solution containing texturing additives may include at least one slow-release agent selected from isopropyl alcohol (IPA), ethanol, and sodium silicate (Na2SiO3).

[0107] In some embodiments, after the emitter 2 is formed, the distribution of dopant sources within the emitter 2 can be a gradient distribution. Specifically, the concentration of dopant sources in the portion of the emitter 2 away from the silicon substrate 1 is relatively high, while the concentration of dopant sources in the portion of the emitter 2 close to the silicon substrate 1 is relatively low. In other words, the portion of the emitter 2 away from the silicon substrate 1 is a heavily doped region, and the portion close to the silicon substrate 1 is a lightly doped region. Under the same alkaline etching conditions, due to the reduced reactivity caused by heavy doping, the alkaline etching rate of the portion of the emitter 2 away from the silicon substrate 1 is lower than that of the portion close to the silicon substrate 1. To improve the alkaline etching rate, it is necessary to use the first laser mentioned above to scan the portion of the emitter 2 located in the edge region A1 to modify the heavily doped region of the emitter 2 located in the edge region A1, and it is necessary to use the second laser mentioned above to scan the portion of the emitter 2 located in the middle region A2 to modify the heavily doped region of the emitter 2 located in the middle region A2. After modification in the heavily doped region, the modified portion 2a is removed by acid etching. After removing the modified portion 2a, the rate of alkaline etching of the emitter 2 is relatively high. As mentioned earlier, because the energy of the first laser is less than that of the second laser, the depth of the modified portion 2a located in the edge region A1 is smaller than the depth of the modified portion 2a located in the middle region A2. After acid etching to remove the modified portion 2a, the thickness of the portion of the emitter 2 located in the edge region A1 is greater than the thickness of the portion of the emitter 2 located in the middle region A2. Under the same alkaline etching conditions, the rate of alkaline etching of the portion of the emitter 2 located in the edge region A1 is lower than the rate of alkaline etching of the portion of the emitter 2 located in the middle region A2. Therefore, after alkaline etching, as... Figure 12As shown, the size of the pyramidal structure of the textured surface R in the middle region A2 of substrate 10 is smaller than the size of the pyramidal structure of the textured surface R in the edge region A1 of substrate 10, and the density of the pyramidal structure of the textured surface R in the middle region A2 of substrate 10 is greater than the density of the pyramidal structure of the textured surface R in the edge region A1 of substrate 10. Based on this, the photovoltaic cell formed in the middle part has relatively low light reflectivity, relatively low incident light loss, a relatively large number of photogenerated carriers, and a relatively high photoelectric conversion efficiency.

[0108] In some embodiments, the method of alkaline etching of the portions of the emitter 2 located within the edge region A1 and the middle region A2 may include: alkaline etching of all portions of the emitter 2 located within the edge region A1 and alkaline etching of all portions of the emitter 2 located within the middle region A2. Under this configuration, a structure such as... Figure 14 In the structure shown, all portions of the emitter 2 located in the edge region A1 and the middle region A2 are removed. The surfaces of the silicon substrate 1 located in both the edge region A1 and the middle region A2 are etched with alkaline etching and include a textured surface R. Because all portions of the emitter 2 located in the edge region A1 are removed, leakage current paths are less likely to occur in the edge portion of the photovoltaic cell formed on this basis, resulting in a relatively high photoelectric conversion efficiency. Since the portions of the silicon substrate 1 located in both the edge region A1 and the middle region A2 are not covered by the emitter 2, the degree of parasitic absorption (light absorption without electron-hole pairs) in the photovoltaic cell formed on this basis is relatively small. Therefore, the number of photogenerated carriers generated by the photovoltaic cell is relatively large, resulting in a relatively high photoelectric conversion efficiency.

[0109] In some embodiments, the method of alkaline etching of the portion of the emitter 2 located within the edge region A1 and the middle region A2 may also include: alkaline etching of a portion of the emitter 2 located within the edge region A1, and alkaline etching of all portions within the middle region A2 of the emitter 2. Under this configuration, a structure such as... Figure 15 In the structure shown, the remaining portion of the emitter 2 located within the edge region A1 still exists and includes the textured surface R, while the surface of the portion of the silicon substrate 1 located within the middle region A2 has been etched with an alkaline agent and also includes the textured surface R. Meanwhile... Figure 15 The structure shown also illustrates that the portion of emitter 2 located in the edge region A1 is etched to a relatively small depth by alkali. Correspondingly, the degree of lattice damage to the portion of emitter 2 located in the edge region A1 is relatively small. Based on this, leakage current paths are not easily generated in the edge of the photovoltaic cell formed on this basis. Therefore, the photoelectric conversion efficiency of the photovoltaic cell is relatively large.

[0110] In some embodiments, regardless of such Figure 14 Based on the structure of substrate 10 shown, it is still based on... Figure 15 A photovoltaic cell is fabricated based on the structure of the substrate 10 shown. The thickness of the edge portion of the photovoltaic cell is always greater than the thickness of the middle portion of the photovoltaic cell.

[0111] In some embodiments, such as Figures 1-5 As shown, the substrate 10 may also have a transition region A3, which is located between the edge region A1 and the intermediate region A2. Accordingly, the fabrication method may further include scanning using a transition laser (also referred to as a third laser). Figure 2 The portion of emitter 2 shown is located within transition region A3, so that some parts of emitter 2 are modified by transition laser, i.e., forming as shown... Figure 3 The modified portion 2a within the transition region A3 is shown. The energy of the transition laser is controlled to be greater than the energy of the first laser, and the energy of the transition laser is controlled to be less than the energy of the second laser. Under this setting, the depth of the modified portion 2a within the transition region A3 is greater than the depth of the modified portion 2a within the edge region A1, and the depth of the modified portion 2a within the transition region A3 is less than the depth of the modified portion 2a within the intermediate region A2. After modification, the portion modified by the transition laser within the emitter 2 is removed by acid etching, i.e., the modified portion 2a within the transition region A3 is removed by acid etching, to form as shown... Figure 4 The structure is shown. After acid etching, the portion of emitter 2 located within transition region A3 is etched with alkali to remove surface laser damage, forming a structure as shown. Figure 5 The structure shown. In Figure 5 In the middle, the thickness H of the structure of substrate 10 located in the transition region A3 A3 The thickness H of the structure located in the edge region A1 of the substrate 10 is smaller than that of the substrate 10. A1 The thickness H of the structure of substrate 10 located in transition region A3 A3 The thickness H of the structure located in the middle region A2 of the substrate 10 is greater than that of the substrate 10. A2 If in such Figure 5 A photovoltaic cell is fabricated based on the structure of the substrate 10 shown. While ensuring the structural strength of the middle portion of the photovoltaic cell meets requirements, the transition portion of the photovoltaic cell (in...) Figure 5The structure of the substrate 10 (formed on the basis of the structure located within the transition region A3) will have relatively high structural strength, and the transition part of the photovoltaic cell can also withstand relatively large forces and bending moments. Correspondingly, in subsequent photovoltaic module manufacturing processes, such as during the process of stringing photovoltaic cells to form a cell string and during the process of laminating photovoltaic cells to form a laminate, the transition part of the photovoltaic cell is less prone to structural damage problems such as cracks, the defect density of the transition part of the photovoltaic cell is relatively low, and the transition part of the photovoltaic cell is less prone to leakage current paths. Therefore, the photoelectric conversion efficiency of the photovoltaic cell is relatively high.

[0112] In practice, the forces and bending moments borne by the edge parts of a photovoltaic cell are generally greater than those borne by the transition parts, and the forces and bending moments borne by the transition parts of a photovoltaic cell are generally greater than those borne by the middle parts.

[0113] In some embodiments, the transition laser may also be a red nano laser. In other embodiments, the transition laser may also be an ultraviolet laser or a green laser.

[0114] In some embodiments, the comparison between the energy of the first laser, the energy of the second laser, and the energy of the transition laser is primarily a comparison between their energy densities. In other embodiments, the comparison between the energy of the first laser, the energy of the second laser, and the energy of the transition laser may also be a comparison between their power.

[0115] In some embodiments, the order of using the first laser scan, the second laser scan, and the transition laser scan is not specifically limited, nor is the number of devices used to generate the first laser, the second laser, and the transition laser.

[0116] In some embodiments, such as Figures 1-5 As shown, the number of transition zones A3 can be at least two, that is, at least one transition zone A3 is provided on both sides of the intermediate zone A2.

[0117] In some embodiments, the method of scanning the portion of emitter 2 located within transition region A3 using a transition laser may include: when the portion of emitter 2 located within the same transition region A3 is scanned by the transition laser, controlling the energy of the transition laser along a direction from edge region A1 to middle region A2 (e.g., ...). Figure 16 The direction L1 shown increases. Under this setting, as... Figure 16 As shown, the depth of the modified portion 2a located within the transition region A3 increases along direction L1. Combined with the acid etching removal of the modified portion 2a within the transition region A3 and the alkaline etching of the portion of the emitter 2 within the transition region A3 described above, as follows... Figure 17As shown, the surface of the structure located within the transition region A3 of the substrate 10 includes an inclined surface Q. The surface of the transition portion of the photovoltaic cell fabricated based on this may also include, for example... Figure 18 The inclined surface Q is shown. In the morning or evening, although sunlight shines obliquely onto the photovoltaic cell, the incident angle θ between the normal F of the inclined surface Q at the transition section of the photovoltaic cell and the direction of sunlight Y is relatively small. This relatively small incident angle θ results in a relatively low light reflectivity of the inclined surface Q at the transition section of the photovoltaic cell, thus minimizing incident light loss. Therefore, the number of photogenerated carriers generated by the photovoltaic cell in the morning or evening is still relatively high, and the photoelectric conversion efficiency of the photovoltaic cell remains relatively high.

[0118] The scanning path of the transition laser scanning the portion of the emitter 2 located within the transition region A3 can be referenced. Figure 9 The scanning path of the first laser shown is not described in detail here.

[0119] In some embodiments, the method of scanning the portion of emitter 2 located within transition region A3 using a transition laser may also include: when the portion of emitter 2 located within the same transition region A3 is scanned by the transition laser, controlling the energy of the transition laser along a direction from edge region A1 to middle region A2 (e.g., ...). Figure 16 The direction L2 shown decreases. Under this setting, as... Figure 16 As shown, the depth of the modified portion 2a located within the transition region A3 decreases along direction L2. Combined with the acid etching removal of the modified portion 2a within the transition region A3 and the alkaline etching of the portion of the emitter 2 within the transition region A3 described above, as follows... Figure 17 As shown, the surface of the structure of substrate 10 located within transition region A3 includes an inclined surface Q. The surface of the edge portion of the photovoltaic cell fabricated on this basis also includes, for example, an inclined surface Q. Figure 18 The inclined surface Q is shown. Accordingly, the number of photogenerated carriers generated by the photovoltaic cell in the morning or evening is still relatively large, and the photoelectric conversion efficiency of the photovoltaic cell is still relatively high. The specific effects have been described above and will not be repeated here.

[0120] The scanning path of the transition laser scanning the portion of the emitter 2 located within the transition region A3 can be referenced. Figure 10 The scanning path of the first laser shown is not described in detail here.

[0121] In some embodiments, Figure 16 Based on the structure shown, the modified portion 2a is first removed by acid washing, and then the portion of the emitter 2 located in the transition region A3 is etched using an alkaline solution containing texturing additives, which can form a structure as shown. Figure 19The structure shown, namely the surface of the structure of substrate 10 located within the transition region A3, may include an inclined textured surface QR. The photovoltaic cell formed on this basis can still generate a relatively large number of photogenerated carriers in the morning or evening, and the photoelectric conversion efficiency of the photovoltaic cell is still relatively high. The specific effects have been described above and will not be repeated here.

[0122] In some embodiments, the method of scanning the portion of emitter 2 located within transition region A3 using a transition laser may also include: controlling the energy of the transition laser to remain constant when the portion of emitter 2 located within the same transition region A3 is scanned by the transition laser. After acid etching to remove the modified portion 2a and alkaline etching, as Figure 20 As shown, the non-tilted surface P of the structure of the substrate 10 located in the transition region A3 may not include the tilted surface. In other words, the non-tilted surface P of the structure of the substrate 10 located in the transition region A3 is perpendicular to the direction H.

[0123] The scanning path of the transition laser, which scans the portion of the emitter 2 located within the transition region A3 from the perspective of direction H, can be referenced. Figure 9 The scanning path of the first laser or Figure 10 The scanning path of the first laser, or the scanning path of the transition laser that scans the portion of the emitter 2 located within the transition region A3, can be bow-shaped, spiral-shaped, or concentric. The specific shape of the scanning path of the transition laser is not limited here.

[0124] In addition, Figure 20 In the middle, the non-tilted surface P of the structure located in the transition region A3 of the substrate 10 is a polished surface formed after etching with an alkaline solution containing polishing additives.

[0125] In some other embodiments, Figure 12 In this process, the surface of the structure located in the transition region A3 of the substrate 10 can also be a textured surface R formed after etching with an alkaline solution containing texturing additives. Because the energy of the transition laser is greater than that of the first laser, the size of the pyramid structure of the textured surface R of the structure located in the transition region A3 of the substrate 10 is smaller than the size of the pyramid structure of the textured surface R of the structure located in the edge region A1 of the substrate 10. This also results in a higher density of the pyramid structure of the textured surface R of the structure located in the transition region A3 of the substrate 10 compared to the density of the pyramid structure of the textured surface R of the structure located in the edge region A1 of the substrate 10. Based on this, the surface of the transition portion of the photovoltaic cell formed has a relatively low light reflectivity, relatively low incident light loss, a relatively high number of photogenerated carriers generated by the photovoltaic cell, and a relatively high photoelectric conversion efficiency.

[0126] In some embodiments, the entire portion of the emitter 2 located within the transition region A3 can be etched with an alkaline solution to form a shape such as Figure 14 The structure shown can also be described as follows: the portion of the silicon substrate 1 located within the transition region A3 can be left uncovered by the emitter 2. The degree of parasitic absorption of the photovoltaic cell formed on this basis is relatively small, the number of photogenerated carriers that the photovoltaic cell can generate is relatively large, and the photoelectric conversion efficiency of the photovoltaic cell is relatively high.

[0127] In some embodiments, the portion of the emitter 2 located within the transition region A3 may also be locally etched with an alkaline solution to form a shape such as Figure 15 The structure shown can also be described as follows: the remaining portion of the emitter 2 located within the transition region A3 still exists. Figure 15 The structure shown also illustrates that the portion of emitter 2 located within transition region A3 is etched to a relatively small depth by alkali. Consequently, the degree of lattice damage to the portion of emitter 2 located within transition region A3 is relatively small. Based on this, leakage current paths are less likely to occur in the transition portion of the photovoltaic cell formed. Therefore, the photoelectric conversion efficiency of the photovoltaic cell is relatively high.

[0128] In some embodiments, all portions of the emitter 2 located within the intermediate region A2 and the transition region A3 may be etched with an alkaline solution, and localized portions of the emitter 2 located within the edge region A1 may also be etched with an alkaline solution to form a shape such as Figure 21 The structure shown.

[0129] In some embodiments, Figure 14 , Figure 15 and Figure 21 A photovoltaic cell is fabricated based on the structure of the substrate 10 shown in any of the figures. The thickness of the transition portion of the fabricated photovoltaic cell is always greater than the thickness of the middle portion, and the thickness of the transition portion is always less than the thickness of the edge portion. Under this configuration, the thickness variation of the photovoltaic cell is relatively small, and stress concentration areas are less likely to exist within the photovoltaic cell. During subsequent handling, welding, and lamination processes, the photovoltaic cell is less prone to structural damage problems such as microcracks.

[0130] In some embodiments, such as Figure 22 As shown, two transition zones A3 can be set between the edge zone A1 and the middle zone A2. The transition zone A3 closer to the edge zone A1 is the first transition zone A. 31 The transition zone A3, which is close to the middle zone A2, is the second transition zone A. 32 Scanning the emitter 2 located in the first transition region A 31 The transition laser within the inner portion is the first transition laser, scanning the emitter 2 located in the second transition region A. 32The laser within the inner portion is a second transition laser, and the energy of the first transition laser can be controlled to be less than the energy of the second transition laser. Under this setting, the depth of the modified portion 2a within the edge region A1 is less than that within the first transition region A. 31 The depth of the modified portion 2a within the first transition region A 31 The depth of the modified portion 2a within is less than that in the second transition region A. 32 The depth of the modified portion 2a within the second transition region A 32 The depth of the modified portion 2a within the inner region is less than the depth of the modified portion 2a within the intermediate region A2. Based on the above, after modification, acid etching is performed to remove the modified portion 2a, followed by alkaline etching to form... Figure 23 The structure shown has a thickness H in the edge region A1 of the substrate 10. A1 The substrate 10 is located in the first transition region A. 31 The thickness H of the internal structure A31 The substrate 10 is located in the first transition region A. 31 The thickness H of the internal structure A31 The part larger than substrate 10 is located in the second transition region A. 32 The thickness H of the internal structure A32 The substrate 10 is located in the second transition region A. 32 The thickness H of the internal structure A32 The thickness H of the structure located in the middle region A2 of the substrate 10 is greater than that of the substrate 10. A2 If in Figure 23 Photovoltaic cells are fabricated based on the structure of substrate 10. The thickness of the photovoltaic cells varies relatively little, and stress concentration areas are not likely to exist within the photovoltaic cells. During subsequent handling, welding and lamination processes, the photovoltaic cells are less likely to develop structural damage problems such as microcracks.

[0131] In some other embodiments (not shown in the figures), three or more transition regions may be provided between the edge region and the middle region, or the substrate may not have transition regions located between the edge region and the middle region.

[0132] In some embodiments, such as Figures 1-7 , Figures 11-17 and Figures 19-21As shown, edge region A1, intermediate region A2, and transition region A3 can each be considered as a first region A, meaning that substrate 10 can have multiple first regions A. In addition, substrate 10 can also have multiple second regions B. These multiple first regions A and multiple second regions B can be alternately distributed along a direction perpendicular to direction H. Alternatively, it can be understood that a second region B can be positioned between edge region A1 and transition region A3, and also between transition region A3 and intermediate region A2. Regarding the distinction between first regions A and second regions B, it can be understood that in subsequent fabrication processes, the portion of the emitter 2 located within each second region B needs to make ohmic contact (or metallization contact) with the gate line (also known as an electrode). In other words, the structure of substrate 10 located within each second region B needs to include the gate line, while the structure of substrate 10 located within each first region A does not include the gate line.

[0133] In some embodiments, such as Figures 1-7 , Figures 11-17 and Figures 19-21 As shown, the number of intermediate zones A2 can be one. In some other embodiments (not shown in the figure), the number of intermediate zones A2 can be two, three or more, and a second zone B is provided between two adjacent intermediate zones A2.

[0134] In some embodiments, edge region A1 is a region that is closer to the edge of substrate 10 relative to transition region A3 and intermediate region A2. Edge region A1 may or may not correspond to the edge of substrate 10. Intermediate region A2 is a region that is closer to the middle of substrate 10 relative to edge region A1 and transition region A3. Intermediate region A2 may or may not correspond to the middle of substrate 10.

[0135] In other embodiments, the distribution of the plurality of first regions A of the substrate 10 can also be as follows: Figure 24 As shown, the substrate 10 may not have the second region B mentioned above, i.e., the edge region A1 and the transition region A3 are adjacent, and the transition region A3 and the intermediate region A2 are adjacent. The distribution of the multiple first regions A of the substrate 10 can also be as follows. Figure 25 As shown, the substrate 10 may not have the second region B mentioned above, i.e., the edge region A1 and the middle region A2 are adjacent. Figure 24 and Figure 25 The distribution of multiple first regions A shown can also be understood as follows: during the process of using laser to modify the emitter locally, acid washing to remove the modified part, and alkaline etching of the emitter, the location of the gate lines to be set later can be not specifically limited.

[0136] The following content mainly describes the substrate 10 using the example of "substrate 10 having two edge regions A1, two transition regions A3, one intermediate region A2, and four second regions B. The intermediate region A2 is located between the two edge regions A1, one transition region A3 is located between the intermediate region A2 and one edge region A1, another transition region A3 is located between the intermediate region A2 and another edge region A1, a second region B is set between one edge region A1 and one transition region A3, a second region B is set between one transition region A3 and the intermediate region A2, a second region B is set between the intermediate region A2 and another transition region A3, and a second region B is set between another transition region A3 and another edge region A1".

[0137] In some embodiments, such as Figures 26-27 As shown, the substrate 10 may have a defined first direction N and a second direction M, where the first direction N and the second direction M intersect (e.g., perpendicular or non-perpendicular), and both the first direction N and the second direction M are perpendicular to direction H. Figure 26 As shown, a portion of the substrate 10 may have the aforementioned central region A2 and two edge regions A1 distributed along the first direction N, with the central region A2 located between the two edge regions A1. Meanwhile, as... Figure 27 As shown, another portion of the substrate 10 may also have the aforementioned intermediate region A2 and two edge regions A1 distributed along the second direction M, with the intermediate region A2 located between the two edge regions A1. In this configuration, according to embodiments of some fabrication methods described above, after alkaline etching of the emitter 2, the structure of the substrate 10 will undergo the following process... Figures 26-27 As shown, the emitter 2 has a structure resembling a mesh.

[0138] In some other embodiments (not shown in the figures), the substrate may have a defined first direction and a second direction, which intersect (e.g., perpendicular or non-perpendicular), and both the first and second directions are perpendicular to the thickness direction. A portion of the substrate may have the aforementioned intermediate region and two edge regions distributed along the first direction, with the intermediate region located between the two edge regions; alternatively, another portion of the substrate may have the aforementioned intermediate region and two edge regions distributed along the second direction, with the intermediate region located between the two edge regions. Under this configuration, according to embodiments of some of the fabrication methods described above, after alkaline etching of the emitter, the structure of the substrate 10 will undergo the following process: Figure 14 ,like Figure 15 Or such as Figure 21 The state shown.

[0139] In other embodiments (not shown in the figures), the method of forming an emitter may further include: forming a doped dielectric layer on the outer surface of one side of a silicon substrate; more specifically, first depositing an intrinsic dielectric layer on the outer surface of one side of the silicon substrate, the intrinsic dielectric layer comprising at least one of polycrystalline silicon, amorphous silicon, and microcrystalline silicon, and then diffusing a dopant source into the intrinsic dielectric layer to form the doped dielectric layer. When the silicon substrate comprises an N-type element and the doped dielectric layer comprises a P-type element, the doped dielectric layer can serve as a P-type emitter. The process for depositing the intrinsic dielectric layer can include physical vapor deposition (PVD) and chemical vapor deposition (CVD). Chemical vapor deposition can include plasma-enhanced chemical vapor deposition (PECVD), low-pressure chemical vapor deposition (LPCVD), atmospheric pressure chemical vapor deposition (APCVD), and catalytic chemical vapor deposition (Cat-CVD).

[0140] In other embodiments (not shown in the figures), the method of forming the emitter may further include: depositing a doped dielectric layer containing a doped source directly on one side surface of the silicon substrate using plasma-enhanced chemical vapor deposition, thus eliminating the need for a diffusion process. When the silicon substrate includes at least one N-type element and the doped dielectric layer includes at least one P-type element, the doped dielectric layer can serve as a P-type emitter.

[0141] In some other embodiments (not shown in the figures), a tunneling oxide layer can be deposited on one side of the silicon substrate before forming the emitter, and then the emitter can be formed on the side of the tunneling oxide layer facing away from the silicon substrate. Therefore, the silicon substrate, the tunneling oxide layer, and the emitter are stacked, with the tunneling oxide layer between the silicon substrate and the emitter.

[0142] In some other embodiments (not shown in the figures), the method of forming the emitter may further include forming the emitter on the back-light side of the silicon substrate, where the back-light side of the silicon substrate refers to the side of the silicon substrate that is not exposed to sunlight. Since the emitter is not on the light-receiving side of the silicon substrate, the degree of parasitic absorption of the photovoltaic cell formed on this basis is relatively small, the number of photogenerated carriers that the photovoltaic cell can generate is relatively large, and the photoelectric conversion efficiency of the photovoltaic cell is relatively high.

[0143] The following section describes a specific embodiment of a method for preparing photovoltaic cells. The details of the preparation method are as follows:

[0144] Provide such as Figure 28 The substrate 10 shown includes a silicon substrate 1 doped with phosphorus, with a light-receiving side (SG) and a backlight side (BG) on either side. Etching is performed using an alkaline solution containing texturing additives. Figure 28 The silicon substrate 1, to form Figure 29 The substrate 10.

[0145] exist Figure 29 Based on the substrate 10, boron is diffused into the textured surface R of the silicon substrate 1 near the light-receiving side SG to form a surface like... Figure 30 The substrate 10 shown includes an emitter 2, and correspondingly, an oxide layer 3 is formed on the side of the emitter 2 facing away from the silicon substrate 1.

[0146] In such Figure 30 Based on the substrate 10, a first laser is used to scan the portion of the emitter 2 located in the edge region A1, a second laser is used to scan the portion of the emitter 2 located in the middle region A2, and a transition laser is used to scan the portion of the emitter 2 located in the transition region A3. The energy of the first laser is controlled to be less than the energy of the transition laser, and the energy of the transition laser is controlled to be less than the energy of the second laser, to form a structure as shown in the image. Figure 31 The substrate 10 shown includes the modified portion 2a. During the laser scanning of the emitter 2, the portion of the oxide layer 3 that is being scanned by the laser is incidentally removed.

[0147] In such Figure 31 Based on substrate 10, the modified portion 2a is removed by acid washing to form a substrate as shown in the figure. Figure 32 Substrate 10. In such a case... Figure 32 Based on the substrate 10, the portion of the emitter 2 located in the edge region A1, the portion located in the middle region A2, and the portion located in the transition region A3 of the emitter 2 are etched using an alkaline solution containing texturing additives to form a shape as shown in the image. Figure 33 The substrate 10. The acid washing process can utilize hydrofluoric acid (HF).

[0148] In such Figure 33 Based on the substrate 10, the substrate 10 undergoes high-temperature oxidation treatment, also known as post-boron treatment, to form a structure such as... Figure 34 The substrate 10 has borosilicate glass 4a (BSG) formed on the emitter 2, and an oxide layer 3 formed on the surface of the silicon substrate 1 near the light-receiving side SG in the middle region A2. At the same time, it also promotes the diffusion of boron in the emitter 2 into the silicon substrate 1 to increase the depth of the emitter 2.

[0149] In such Figure 34Based on the substrate 10, a chain-like single-sided acid etching process is used to remove the diffused layer 23 formed on the silicon substrate 1 near the backlight side BG during diffusion. The surface of the silicon substrate 1 near the backlight side BG is then etched using an alkaline solution containing polishing additives to form a layer such as... Figure 35 The substrate 10.

[0150] In such Figure 35 Based on the substrate 10, a structure is formed on the surface of the silicon substrate 1 near the backlight side BG. Figure 36 The photovoltaic cell consists of a stacked tunneling oxide layer 5, a phosphorus-doped silicon layer 6, and a phosphorus-silicon glass 4b (PSG). The tunneling oxide layer 5 can be formed using thermal oxidation or atomic layer deposition (ALD). The phosphorus-doped silicon layer 6 can be formed by first using low-pressure chemical vapor deposition to create an intrinsic dielectric layer (including amorphous silicon and / or polycrystalline silicon), then diffusing phosphorus into the intrinsic dielectric layer. Oxygen can be introduced during diffusion to form the phosphorus-silicon glass 4b. Furthermore, the tunneling oxide layer 5 and the phosphorus-doped silicon layer 6 can serve as a tunnel oxide passivating contact (TOPCon) structure in the photovoltaic cell to be fabricated. Additionally, as... Figure 37 and Figure 38 The magnified view shows that the tunneling oxide layer 5, the phosphorus-doped silicon layer 6, and the phosphorus-silicon glass 4b are also formed on the light-receiving side SG of the silicon substrate 1.

[0151] In such Figure 36 Based on substrate 10, a laser is used to selectively remove portions of the tunneling oxide layer 5, the phosphorus-doped silicon layer 6, and the phosphorosilicon glass 4b located on the backlight side BG of the silicon substrate 1, specifically those within the edge region A1, the middle region A2, and the transition region A3, to form a structure as shown below. Figure 39 The substrate 10.

[0152] In such Figure 39 Based on the substrate 10, a chain-like single-sided acid etching process is used to remove the phosphorosilicate glass 4b located on the light-receiving side SG of the silicon substrate 1, in order to form a structure as shown in the figure. Figure 40 The substrate 10.

[0153] In such Figure 40 Based on the substrate 10, the phosphorus-doped silicon layer 6 located on the light-receiving side SG of the silicon substrate 1 is removed by alkaline etching to form a layer such as... Figure 41 The substrate 10.

[0154] In such Figure 41Based on the substrate 10, acid etching is used to remove the oxide layer 3, borosilicate glass 4a, and tunneling oxide layer 5 on the light-receiving side SG of the silicon substrate 1, and acid etching is used to remove the phosphosilicate glass 4b on the backlight side BG of the silicon substrate 1, in order to form a substrate as shown in the figure. Figure 42 The substrate 10.

[0155] In such Figure 42 On the substrate 10, a passivation layer 7 is deposited on both sides to form a structure like... Figure 43 The substrate 10. The process for depositing the passivation layer can employ atomic layer deposition or plasma-enhanced chemical vapor deposition. Furthermore, the passivation layer may include at least one of an alumina passivation layer and a silicon nitride passivation layer.

[0156] In such Figure 43 Based on substrate 10, to form such Figure 44 The positive gate line 8 has an ohmic contact with the emitter 2, and the negative gate line 9 has an ohmic contact with the phosphorus-doped silicon layer 6. The process for forming the gate lines can include screen printing or electroplating. Additionally, laser-assisted sintering technology can be used. After the gate lines are formed, the structure of the fabricated photovoltaic cell can be as follows: Figure 44 As shown.

[0157] In other embodiments, by controlling the duration of alkaline etching of the emitter 2, the structure of the prepared photovoltaic cell can also be as follows. Figure 45 or Figure 46 As shown. Figure 44 , Figure 45 or Figure 46 The photovoltaic cell shown can be referred to as a tunnel oxide passivated contact solar cell (TOPConSolar Cell).

[0158] Of course, the embodiments of some photovoltaic cell preparation methods provided in this application can also be used to prepare other photovoltaic cells such as back contact solar cells (BC solar cells) or heterojunction solar cells.

[0159] Secondly, this application provides some embodiments of photovoltaic cells. These photovoltaic cells can be prepared using the methods described above, and therefore may also include some of the technical effects described above. In other embodiments, the photovoltaic cells may also be prepared using other methods.

[0160] In some embodiments, such as Figure 47As shown, the photovoltaic cell 20 may include a middle portion a2 and two edge portions a1 distributed along a first direction N. The middle portion a2 is located between the two edge portions a1. The first direction N is perpendicular to the direction H of the photovoltaic cell 20 (direction H is parallel to the thickness direction or the vertical direction, or in other words, direction H is perpendicular to the horizontal direction). The edge portions a1 have a first thickness dimension H. a1 The middle portion a2 has a second thickness dimension H a2 First thickness dimension H a1 Greater than the second thickness dimension H a2 While ensuring the structural strength of the middle portion a2 of the fabricated photovoltaic cell 20 meets requirements, the edge portion a1 has relatively higher structural strength and can withstand relatively larger forces and bending moments. Correspondingly, during subsequent photovoltaic module fabrication processes, such as when the photovoltaic cells 20 are wired together to form a cell string and when they are laminated to form a stack, although the edge portion a1 may withstand relatively larger forces and bending moments compared to other portions, it is less prone to structural damage such as cracking or edge chipping. The defect density in the edge portion a1 is relatively low, and leakage current paths are less likely to occur. Therefore, the photovoltaic cell 20 in the photovoltaic module has a relatively high photoelectric conversion efficiency, resulting in a relatively high output power for the photovoltaic module.

[0161] Among them, such as Figure 47 As shown, the number of intermediate portions a2 located between the two edge portions a1 can be one. In some other embodiments (not shown in the figure), in the first direction, the number of intermediate portions located between the two edge portions can be two or more.

[0162] In some embodiments, such as Figure 47 As shown, the first thickness dimension H a1 Second thickness dimension H a2 The ratio can be in the range of 1.01 to 1.12, and the specific ratio can be 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.1, 1.11 or 1.12.

[0163] In some embodiments, the first thickness dimension H a1 Second thickness dimension H a2 The ratio can also be 1.01 to 1.04, 1.04 to 1.08, or 1.08 to 1.12.

[0164] In some embodiments, such as Figure 47As shown, the photovoltaic cell 20 may further include two transition portions a3. In the first direction N, a transition portion a3 is provided between the middle portion a2 and one of the edge portions a1, and another transition portion a3 is provided between the middle portion a2 and the other edge portion a1. The transition portion a3 may have a third thickness dimension H. a3 The third thickness dimension H a3 Smaller than the first thickness dimension H a1 The third thickness dimension H a3 Greater than the second thickness dimension H a2 Under the condition that the structural strength of the middle part a2 of the photovoltaic cell 20 meets the requirements, the structural strength of the transition part a3 will also be relatively large, and the transition part a3 can withstand relatively large forces and bending moments. Accordingly, in the subsequent photovoltaic module manufacturing process, such as during the process of stringing photovoltaic cells 20 to form a cell string and during the process of laminating photovoltaic cells 20 to form a laminate, the transition part a3 is less likely to suffer structural damage problems such as cracks. The defect density of the transition part a3 is relatively low, and the transition part a3 is less likely to generate leakage current paths. Therefore, the photoelectric conversion efficiency of the photovoltaic cell 20 is relatively high. In addition, the thickness variation of the photovoltaic cell 20 is relatively small, and there are less likely to be stress concentration areas within the photovoltaic cell 20. During subsequent handling, welding, and lamination processes, the photovoltaic cell 20 is less likely to suffer structural damage problems such as microcracks.

[0165] In practice, the forces and bending moments borne by the edge portion a1 of the photovoltaic cell 20 are generally greater than those borne by the transition portion a3, and the forces and bending moments borne by the transition portion a3 of the photovoltaic cell 20 are generally greater than those borne by the middle portion a2.

[0166] In some other embodiments (not shown in the figures), the photovoltaic cell may also include multiple transition portions, with at least two transition portions provided between the middle portion and one of the edge portions in the first direction, and at least two transition portions also provided between the middle portion and another edge portion; or, the photovoltaic cell may not include transition portions.

[0167] In some embodiments, such as Figure 47As shown, the light-receiving surface of the edge portion a1 (the surface directly facing sunlight in actual use) may include an edge textured surface BR, and the light-receiving surface of the middle portion a2 may include a middle textured surface ZR. The size of the pyramid structure of the middle textured surface ZR can be smaller than the size of the pyramid structure of the edge textured surface BR, and the density of the pyramid structure of the middle textured surface ZR can be greater than the density of the pyramid structure of the edge textured surface BR. Under this configuration, the light reflectivity of the middle textured surface ZR of the middle portion a2 is relatively small, the incident light loss is relatively small, the number of photogenerated carriers generated by the photovoltaic cell 20 is relatively large, and the photoelectric conversion efficiency of the photovoltaic cell 20 is relatively high.

[0168] In some embodiments, the base size (width of the base) of the pyramid structure of the edge-textured BR can be in the range of 3 micrometers (µm) to 4 micrometers (µm), specifically 3µm, 3.2µm, 3.4µm, 3.6µm, 3.8µm, or 4µm. The base size of the pyramid structure of the center-textured ZR can be in the range of 2µm to 3µm, specifically 2µm, 2.2µm, 2.4µm, 2.6µm, 2.8µm, or 3µm.

[0169] In some embodiments, such as Figure 47 As shown, the height of the edge velvet surface BR in the vertical direction can remain constant along the direction from the edge portion a1 to the middle portion a2. In some embodiments, such as Figure 48 As shown, the height of the edge velvet surface BR in the vertical direction can be along the direction from the edge portion a1 to the middle portion a2 (e.g., Figure 48 The direction N in the middle is reduced. In this setting, the edge textured surface BR can be a sloping surface, and the number of photogenerated carriers generated by the photovoltaic cell 20 in the morning or evening is still relatively large, and the photoelectric conversion efficiency of the photovoltaic cell 20 is still relatively large. The relevant specific principles have been described above and will not be repeated here. In some other embodiments (not shown in the figure), the light-receiving surface of the edge portion may not include the edge textured surface, but may include a polished surface instead.

[0170] In some embodiments, such as Figure 47 As shown, the backlight surface (the side facing away from the light-receiving surface) of the edge portion a1 may include a polished surface, and the backlight surface of the middle portion a2 may also include a polished surface. In some other embodiments (not shown in the figures), the backlight surface of the edge portion may include a textured surface, and the backlight surface of the middle portion may include a polished surface.

[0171] In some embodiments, such as Figure 47As shown, the light-receiving surface of the transition portion a3 may include a transition textured surface GR. The size of the pyramid structure of the transition textured surface GR can be smaller than the size of the pyramid structure of the edge textured surface BR, and the density of the pyramid structure of the transition textured surface GR can be greater than the density of the pyramid structure of the edge textured surface BR. Under this configuration, the light reflectivity of the transition textured surface GR of the transition portion a3 is relatively small, the incident light loss is relatively small, the number of photogenerated carriers generated by the photovoltaic cell 20 is relatively large, and the photoelectric conversion efficiency of the photovoltaic cell 20 is relatively high.

[0172] In some embodiments, such as Figure 47 As shown, the height of the transition velvet surface GR in the vertical direction can remain unchanged along the direction from the transition portion a3 to the middle portion a2. In some embodiments, such as Figure 49 As shown, the height of the transition velvet surface GR in the vertical direction can be along the direction from the transition portion a3 to the middle portion a2 (e.g., Figure 49 The direction N in the middle is reduced. In this setting, the transition textured surface GR can be an inclined surface, and the number of photogenerated carriers generated by the photovoltaic cell 20 in the morning or evening is still relatively large, and the photoelectric conversion efficiency of the photovoltaic cell 20 is still relatively large. The relevant specific principles have been described above and will not be repeated here. In some other embodiments (not shown in the figure), the light-receiving surface of the transition part may not include the transition textured surface, but may include a polished surface instead.

[0173] In some embodiments, such as Figure 47 As shown, the backlight surface of transition portion a3 may include a polished surface. In some other embodiments (not shown in the figures), the backlight surface of the transition portion may include a textured surface.

[0174] In some embodiments, the light reflectivity of the photovoltaic cell 20 can be in the range of 9% to 14%, specifically 9%, 10%, 11%, 12%, 13%, or 14%.

[0175] In some embodiments, such as Figure 50 As shown, the light-receiving surface of the photovoltaic cell 20 may also include a first step T1 and a second step T2. The first step T1 is located at the boundary of the edge portion a1 near the middle portion a2, and the second step T2 is located at the boundary of the middle portion a2 near the edge portion a1.

[0176] In some embodiments, such as Figure 50As shown, the sidewall of the first step T1 can have a first height dimension g1, and the sidewall of the second step T2 can have a second height dimension g2. The first height dimension g1 can be smaller than the second height dimension g2. In this configuration, although the first step T1 located near the edge portion a1 may bear relatively larger forces and bending moments compared to the second step T2 located near the middle portion a2, the stress concentration of the first step T1 and its surroundings is relatively small. Structural damage problems such as cracks or edge chipping are less likely to occur in the first step T1 and its surroundings. The defect density in the first step T1 and its surroundings is relatively low, and leakage current paths are less likely to form in the first step T1 and its surroundings. Therefore, the photoelectric conversion efficiency of the photovoltaic cell 20 in the photovoltaic module is relatively high, resulting in a relatively high output power of the photovoltaic module.

[0177] The ratio of the first height dimension g1 to the second height dimension g2 can be in the range of 0.5 to 0.7, and the specific ratio can be 0.5, 0.52, 0.54, 0.56, 0.58, 0.6, 0.62, 0.64, 0.66, 0.68 or 0.7.

[0178] Furthermore, the first height dimension g1 can be in the range of 2µm to 3µm, specifically 2µm, 2.2µm, 2.4µm, 2.6µm, 2.8µm, or 3µm. The second height dimension g2 can be in the range of 3µm to 4µm, specifically 3µm, 3.2µm, 3.4µm, 3.6µm, 3.8µm, or 4µm.

[0179] In some embodiments, such as Figure 50 As shown, the sidewall of the second step T2 can be steeper than the sidewall of the first step T1. In this configuration, although the first step T1 near the edge portion a1 may experience relatively greater forces and bending moments compared to the second step T2 near the middle portion a2, the stress concentration in and around the first step T1 is relatively low. Structural damage problems such as cracks or edge chipping are less likely to occur in and around the first step T1, and the defect density in and around the first step T1 is relatively low. Leakage current paths are also less likely to form in and around the first step T1. Therefore, the photoelectric conversion efficiency of the photovoltaic cell 20 in the photovoltaic module is relatively high, resulting in a relatively high output power of the photovoltaic module.

[0180] In some embodiments, such as Figure 50 As shown, the light-receiving surface of the photovoltaic cell 20 may also include a third step T3, which may be located at the boundary of the transition portion a1 near the edge and the boundary of the transition portion a2 near the middle.

[0181] In some embodiments, such as Figure 50As shown, the sidewall of the third step T3 can have a third height dimension g3, which can be smaller than the second height dimension g2 and larger than the first height dimension g1. Under this configuration, although the third step T3 located near the transition portion a3 may bear relatively larger forces and bending moments compared to the second step T2 located near the middle portion a2, the stress concentration of the third step T3 and its surroundings is relatively small. Structural damage problems such as cracks or edge chipping are less likely to occur in the third step T3 and its surroundings, and the defect density is relatively low. Leakage current paths are also less likely to form in the third step T3 and its surroundings. Therefore, the photoelectric conversion efficiency of the photovoltaic cell 20 in the photovoltaic module is relatively high, resulting in a relatively high output power of the photovoltaic module.

[0182] In some embodiments, such as Figure 50 As shown, the sidewall of the second step T2 can be steeper than the sidewall of the third step T3, and the sidewall of the first step T1 can be steeper than the sidewall of the third step T3. Under this configuration, although the third step T3, located near the transition section a3, may bear relatively larger forces and bending moments than the second step T2, located near the middle section a2, the stress concentration in and around the third step T3 is relatively small. Structural damage problems such as cracks or edge chipping are less likely to occur in and around the third step T3, and the defect density in and around the third step T3 is relatively low. Leakage current paths are also less likely to form in and around the third step T3. Therefore, the photoelectric conversion efficiency of the photovoltaic cell 20 in the photovoltaic module is relatively high, resulting in a relatively high output power of the photovoltaic module.

[0183] In some embodiments, such as Figures 47-50 As shown, the photovoltaic cell 20 may further include multiple connecting portions b. In the first direction N, a connecting portion b may be provided between the edge portion a1 and the transition portion a3, and a connecting portion b may also be provided between the transition portion a3 and the middle portion a2. The connecting portion b may include a grid line located at the top (not shown in the figure) and a grid line located at the bottom (not shown in the figure). Either the grid line located at the top or the grid line located at the bottom can be used to collect holes, and the other can be used to collect electrons. In other words, either the grid line located at the top or the grid line located at the bottom can serve as a positive grid line, and the other can serve as a negative grid line.

[0184] In some embodiments, the edge portion a1 of the photovoltaic cell 20 may be formed based on the portion of the substrate 10 located within the edge region A1 mentioned above, the middle portion a2 of the photovoltaic cell 20 may be formed based on the portion of the substrate 10 located within the middle region A2 mentioned above, the transition portion a3 of the photovoltaic cell 20 may be formed based on the portion of the substrate 10 located within the transition region A3 mentioned above, and the connecting portion b of the photovoltaic cell 20 may be formed based on the portion of the substrate 10 located within the second region B mentioned above.

[0185] In some embodiments, such as Figures 47-50 As shown, the internal structure and materials of the photovoltaic cell 20 are not specifically limited.

[0186] In some embodiments, the specific structure of the photovoltaic cell 20 can also be as follows: Figure 44 , Figure 45 or Figure 46 The image shows a photovoltaic cell with a tunneling oxide passivation contact structure.

[0187] In some embodiments, such as Figures 44-46 As shown, silicon substrate 1 can be an N-type silicon substrate.

[0188] In some embodiments, such as Figures 44-46 As shown, emitter 2 can be a P-type emitter, and the activation doping concentration of emitter 2 can be 4E18 atom / cm². 3 Up to 7E18 atom / cm 3 Within this range, the activation doping concentration can specifically be 4E18atom / cm³. 3 5E18 atom / cm 3 6E18 atom / cm 3 Or 7E18 atom / cm 3 .

[0189] 4E18 is a simplified representation of scientific notation, which is 4 multiplied by 10 to the power of 18. Similarly, other similar values ​​are also simplified representations of scientific notation.

[0190] Additionally, atom / cm 3 It represents the number of atoms contained in one cubic centimeter.

[0191] In addition, the method for measuring the concentration of activated doping can be electrochemical capacitance-voltage profiling (ECV), or ECV analysis for short, and the equipment for measuring the concentration of activated doping can be an electrochemical analyzer, or ECV tester for short.

[0192] In some embodiments, such as Figure 46 As shown, the ratio of the area of ​​the emitter 2 to the area of ​​the light-receiving surface of the photovoltaic cell 20 can be in the range of 0.05 to 0.5, and the specific ratio can be 0.05, 0.1, 0.2, 0.3, 0.4 or 0.5.

[0193] In some embodiments, such as Figures 44-46 As shown, the tunneling oxide layer 5 may include silicon oxide (SiO2). x The tunneling oxide layer 5 is made of at least one of silicon oxynitride (SiON) and can have a thickness ranging from 0.5 nm to 5 nm, specifically 0.5 nm, 1 nm, 2 nm, 3 nm, 4 nm or 5 nm. The tunneling oxide layer can also be referred to as a tunneling dielectric layer.

[0194] In some embodiments, such as Figures 44-46 As shown, the phosphorus-doped silicon layer 6 may include at least one of polycrystalline silicon, amorphous silicon, and microcrystalline silicon. The active doping concentration of the phosphorus-doped silicon layer 6 is greater than that of the silicon substrate 1, and the active doping concentration of the phosphorus-doped silicon layer 6 can be 1E18 atom / cm 3 Up to 1E21 atom / cm 3 Within this range, the activation doping concentration can specifically be 1E18 atom / cm³. 3 1E19 atom / cm 3 1E20 atom / cm 3 Or 1E21 atom / cm 3 .

[0195] In some embodiments, such as Figures 44-46 As shown, the tunneling oxide layer 5 and the phosphorus-doped silicon layer 6 form a tunneling oxide passivation contact structure, which plays a role in chemical passivation and field passivation.

[0196] In some embodiments, such as Figures 44-46 As shown, the passivation layer 7 may include an aluminum oxide passivation layer (Al). x O y ), silicon nitride passivation layer (SiN) x At least one of the following, the passivation layer 7 can perform field passivation, chemical passivation and reduce light reflectivity.

[0197] In some embodiments, such as Figures 44-46 As shown, the positive gate line 8 is in 2-ohm contact with the emitter, and the negative gate line 9 is in 6-ohm contact with the phosphorus-doped silicon layer. Either the positive gate line 8 or the negative gate line 9 may include at least one of silver, aluminum, nickel and copper.

[0198] In some embodiments, such as Figures 44-46 As shown, the height of either the positive grid line 8 or the negative grid line 9 in the vertical direction can be in the range of 0.1µm to 20µm, and the specific height can be 0.1µm, 2µm, 4µm, 6µm, 8µm, 10µm, 12µm, 14µm, 16µm, 18µm or 20µm.

[0199] In some embodiments, such as Figures 44-46 As shown, the ratio of the area of ​​the positive grid line 8 to the area of ​​the light-receiving surface of the photovoltaic cell 20 can be in the range of 10% to 15%, specifically 10%, 11%, 12%, 13%, 14%, or 15%. The width of any positive grid line 8 can be in the range of 20µm to 200µm, specifically 20µm, 100µm, 150µm, or 200µm.

[0200] In some embodiments, such as Figures 44-46 As shown, the ratio of the area of ​​the negative grid line 9 to the area of ​​the back surface of the photovoltaic cell 20 can be in the range of 10% to 15%, specifically 10%, 11%, 12%, 13%, 14% or 15%. The width of any one of the negative grid lines 9 can be in the range of 20µm to 200µm, specifically 20µm, 100µm, 150µm or 200µm.

[0201] In some embodiments, both the positive grid line 8 and the negative grid line 9 can be directly welded to the solder ribbon to form a cell string of a photovoltaic module. In other embodiments, both the positive grid line 8 and the negative grid line 9 can serve as sub-grids. The photovoltaic cell 20 may also include a positive main grid (not shown) and a negative main grid (not shown). The positive grid line 8 is connected to the positive main grid, and the negative grid line 9 is connected to the negative main grid. The positive main grid and the negative main grid are respectively welded to the solder ribbon to form a cell string of a photovoltaic module.

[0202] In some embodiments, such as Figures 44-46 As shown, the bifaciality of photovoltaic cell 20 can be greater than or equal to 95%.

[0203] In some embodiments, as can be seen from the photovoltaic cell fabrication method and photovoltaic cell content described above, some local structures of the photovoltaic cell 20 can be as follows: Figure 51As shown, emitter 2 in the connecting portion b is in ohmic contact with the positive gate line (not shown in the figure). The thickness of emitter 2 in the connecting portion b is greater than that of emitter 2 in the transition portion a3, and the activation doping concentration of emitter 2 in the connecting portion b is greater than that of emitter 2 in the transition portion a3. The thickness of emitter 2 in the transition portion a3 monotonically increases in the left-right direction, and correspondingly, the activation doping concentration of emitter 2 in the transition portion a3 monotonically increases in the left-right direction; or, the thickness of emitter 2 in the transition portion a3 monotonically decreases in the left-right direction, and correspondingly, the activation doping concentration of emitter 2 in the transition portion a3 monotonically decreases in the left-right direction. In this configuration, the average thickness of the emitter 2 within the transition portion a3 can be relatively small. Therefore, the parasitic absorption of the emitter 2 within the transition portion a3 is relatively small, and more light is incident on the silicon substrate 1 through the emitter 2. This allows the silicon substrate 1 to generate a relatively large number of electron-hole pairs. Furthermore, a gradient electric field E can exist inside the emitter 2 within the transition portion a3. The gradient electric field E can promote the migration of holes inside the emitter 2 within the transition portion a3 along the direction of the gradient electric field E to the emitter 2 on one side within the connecting portion b, thereby reducing the carrier recombination rate and improving the photoelectric conversion efficiency of the photovoltaic cell.

[0204] The direction from the middle part a2 to the edge part a1 can be the same as the direction of the gradually changing electric field E.

[0205] In some embodiments (not shown in the figures), in addition to the photovoltaic cell mentioned above which may include a central portion and two edge portions distributed along a first direction, with the central portion located between the two edge portions in the first direction, the photovoltaic cell may also include a central portion and two edge portions distributed along a second direction, with the central portion located between the two edge portions in the second direction. The structure of the central portion in the second direction is similar to or the same as the structure of the central portion in the first direction, and the structure of the edge portions in the second direction is similar to or the same as the structure of the edge portions in the first direction. The first direction is perpendicular to the second direction.

[0206] In some embodiments, the partial structure of a photovoltaic cell can be as follows: Figure 52 As shown, the shape of the emitter 2 may include a grid pattern. In this configuration, the emitter 2 has a relatively large ability to collect holes, and the photovoltaic cell has a relatively high photoelectric conversion efficiency.

[0207] In some other embodiments (not shown in the figures), the photovoltaic cell may also be other types of photovoltaic cells such as back-contact photovoltaic cells or heterojunction photovoltaic cells.

[0208] Thirdly, this application provides some embodiments of photovoltaic modules. A photovoltaic module may include a battery string, which may include at least two electrically connected photovoltaic cells. The photovoltaic cells may be photovoltaic cells prepared using the method described above, or the photovoltaic cells may be those described above. Accordingly, the output power of the photovoltaic module is relatively large.

[0209] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A photovoltaic cell, characterized in that, The photovoltaic cell includes a middle portion and two edge portions, the middle portion being located between the two edge portions. The edge portions have a first thickness dimension, and the middle portion has a second thickness dimension. The first thickness dimension is greater than the second thickness dimension. The photovoltaic cell also includes a first step located on the edge portions and a second step located on the middle portion. The sidewall of the first step has a first height dimension, and the sidewall of the second step has a second height dimension. The first height dimension is smaller than the second height dimension.

2. The photovoltaic cell according to claim 1, characterized in that, The ratio of the first height dimension to the second height dimension is 0.5 to 0.

7.

3. The photovoltaic cell according to claim 1, characterized in that, The first height dimension is 2 micrometers to 3 micrometers.

4. The photovoltaic cell according to claim 1, characterized in that, The second height dimension is 3 to 4 micrometers.

5. The photovoltaic cell according to claim 1, characterized in that, The sidewall of the second step is steeper than the sidewall of the first step.

6. The photovoltaic cell according to claim 1, characterized in that, Both the first step and the second step are located on the light-receiving surface of the photovoltaic cell.

7. The photovoltaic cell according to claim 1, characterized in that, The edge portion and the middle portion are spaced apart, and the photovoltaic cell also includes an emitter, which is located between the edge portion and the middle portion.

8. The photovoltaic cell according to claim 1, characterized in that, The photovoltaic cell further includes at least two transition portions, with at least one transition portion provided between the middle portion and one of the edge portions, and at least one transition portion also provided between the middle portion and the other edge portion. The transition portion has a third thickness dimension, which is smaller than the first thickness dimension and larger than the second thickness dimension.

9. The photovoltaic cell according to claim 8, characterized in that, The photovoltaic cell also includes a third step located in the transition portion, the sidewall of the third step having a third height dimension, the third height dimension being greater than the first height dimension and less than the second height dimension.

10. The photovoltaic cell according to claim 9, characterized in that, The sidewall of the second step is steeper than the sidewall of the third step.

11. The photovoltaic cell according to claim 9, characterized in that, The first step, the second step, and the third step are located on the light-receiving surface of the photovoltaic cell.

12. The photovoltaic cell according to claim 8, characterized in that, The edge portion and the transition portion are spaced apart, the transition portion and the middle portion are spaced apart, the photovoltaic cell also includes an emitter, the emitter exists between the edge portion and the transition portion, and the emitter also exists between the transition portion and the middle portion.

13. The photovoltaic cell according to any one of claims 1 to 12, characterized in that, The ratio of the first thickness dimension to the second thickness dimension is 1.01 to 1.

12.

14. The photovoltaic cell according to any one of claims 1 to 12, characterized in that, The light-receiving surface of the edge portion includes an edge velvet surface, and the light-receiving surface of the middle portion includes a middle velvet surface. The size of the pyramid structure of the middle velvet surface is smaller than the size of the pyramid structure of the edge velvet surface.

15. The photovoltaic cell according to claim 14, characterized in that, The base size of the pyramid structure with the velvety edge is 3 to 4 micrometers.

16. The photovoltaic cell according to claim 14, characterized in that, The base size of the pyramid structure with the middle velvet surface is 2 to 3 micrometers.

17. The photovoltaic cell according to claim 14, characterized in that, The density of the pyramid structure on the middle pile surface is greater than the density of the pyramid structure on the edge pile surface.

18. The photovoltaic cell according to claim 14, characterized in that, The height of the edge nap decreases in the direction from the edge portion toward the middle portion.

19. The photovoltaic cell according to claim 14, characterized in that, The photovoltaic cell further includes at least two transition portions. At least one of the transition portions is provided between the middle portion and one of the edge portions, and at least one of the transition portions is also provided between the middle portion and the other edge portion. The light-receiving surface of the transition portion includes a transition textured surface, and the size of the pyramid structure of the transition textured surface is smaller than the size of the pyramid structure of the edge textured surface.

20. The photovoltaic cell according to claim 19, characterized in that, The density of the pyramid structure on the transition velvet surface is greater than the density of the pyramid structure on the edge velvet surface.

21. The photovoltaic cell according to claim 19, characterized in that, The height of the transition velvet surface decreases along the direction from the transition portion toward the middle portion.

22. A photovoltaic module, characterized in that, The photovoltaic module includes a battery string, the battery string including at least two electrically connected photovoltaic cells, the photovoltaic cells being the photovoltaic cells according to any one of claims 1 to 21.

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