Solar cell, preparation method thereof and photovoltaic module

Abstract

The embodiment of the invention relates to the photovoltaic field, and provides a solar cell and a preparation method thereof, and a photovoltaic module. The first doping layer is positioned on the front surface of the substrate, and the first doping layer is doped with one of N-type ions or P-type ions; the second doping layer is located on the side wall of the substrate, and the second doping layer is doped with one of N-type ions or P-type ions; the tunneling layer covers the back surface of the substrate; the third doping layer covers the surface of the tunneling layer, and the third doping layer is doped with the other one of the N-type ions or the P-type ions; the front surface passivation layer is located on the surface, away from the front surface, of the first doping layer; the back surface passivation layer covers the surface, far away from the back surface, of the third doping layer; a front electrode; a back surface electrode; the hot spot effect of the solar cell can be improved.

Description

Technical Field

[0001] The present disclosure relates to the field of photovoltaics, and particularly to a solar cell, a preparation method thereof, and a photovoltaic module. Background Art

[0002] Photovoltaic power generation refers to the conversion of solar energy into electrical energy through the photovoltaic effect of semiconductors. For example, TOPCON (Tunnel Oxide Passivated Contact) cells have received increasing attention due to their good photovoltaic conversion performance.

[0003] TOPCON cells are a type of tunnel oxide passivated contact solar cell technology based on the principle of selective carriers. In TOPCON solar cells, the selective transport of carriers is achieved by forming a passivated contact structure on the substrate surface. The passivated contact structure includes a tunneling layer and a doped conductive layer.

[0004] Currently, the hot spot effect of TOPCON cells is difficult to solve. Summary of the Invention

[0005] Embodiments of the present disclosure provide a solar cell, a preparation method thereof, and a photovoltaic module, which can at least improve the hot spot effect of the solar cell.

[0006] According to some embodiments of the present disclosure, on the one hand, an embodiment of the present disclosure provides a solar cell, including: a substrate, the substrate including a relative front surface and a back surface and side walls located between the front surface and the back surface; a first doped layer, the first doped layer being located on the front surface of the substrate, the first doped layer being doped with one of N-type ions or P-type ions; a second doped layer, the second doped layer being located on the side walls of the substrate, the second doped layer being doped with one of N-type ions or P-type ions; a tunneling layer, the tunneling layer covering the back surface of the substrate; a third doped layer, the third doped layer covering the surface of the tunneling layer, the third doped layer being doped with the other of N-type ions or P-type ions; a front passivation layer, the front passivation layer being located on the surface of the first doped layer away from the front surface; a back passivation layer, the back passivation layer covering the surface of the third doped layer away from the back surface; a front electrode, the front electrode being located on the front passivation layer and being in electrical contact with the first doped layer; a back electrode, the back electrode being in electrical contact connection with the third doped layer.

[0007] In some embodiments, the thickness of the second doped layer in the direction perpendicular to the front surface and pointing to the back surface is 800 nm to 2 μm.

[0008] In some embodiments, the second doped layer does not contact the tunneling layer.

[0009] According to some embodiments of the present disclosure, on the other hand, an embodiment of the present disclosure provides a method for manufacturing a solar cell, including: providing a substrate, the substrate including an opposite front surface and a back surface and sidewalls located between the front surface and the back surface; performing a first doping process, the first doping process converting a part of the substrate into a first doping layer, the first doping layer surrounding the surface of the substrate, the first doping layer including a first doping portion on the front surface, a second doping portion on the sidewalls, and a third doping portion on the back surface, the first doping layer being doped with one of N-type ions or P-type ions; performing a laser treatment, the laser treatment irradiating the sidewalls of the substrate to convert the second doping portion and a part of the region of the substrate adjacent to the second doping portion into a second doping layer; removing the third doping portion until the back surface of the substrate is exposed; forming a tunneling layer, the tunneling layer covering the back surface of the substrate; forming a third doping layer, the third doping layer covering the surface of the tunneling layer, the third doping layer being doped with the other of N-type ions or P-type ions; forming a front passivation layer, the front passivation layer being located on the surface of the first doping layer away from the front surface; forming a back passivation layer, the back passivation layer covering the surface of the third doping layer away from the back surface; forming a front electrode, the front electrode being located on the front passivation layer and in electrical contact with the first doping layer; forming a back electrode, the back electrode being in electrical contact with the third doping layer.

[0010] In some embodiments, after performing the laser treatment, it further includes: performing a post-oxidation process, the post-oxidation process including: a diffusion stage, in the diffusion stage, the second doping layer and a part of the region of the substrate adjacent to the second doping layer are converted into a fourth doping layer; an oxidation stage, in the oxidation stage, a part of the fourth doping layer is converted into a sidewall oxide layer.

[0011] In some embodiments, in the same process step of removing the first doping layer located on the back surface, it further includes: removing the sidewall oxide layer.

[0012] In some embodiments, the process parameters of the post-oxidation process include: the process temperature is 1000°C to 1200°C, and the process duration is 2000s to 10000s.

[0013] In some embodiments, after removing the first doping layer located on the back surface, it further includes: performing an etching process, the etching process being used to remove a part of the second doping layer in a direction from the back surface towards the front surface.

[0014] In some embodiments, the process parameters of the laser treatment include: the laser type is ultraviolet light, green light or red light, the laser frequency is 400KHz to 1200KHz, the laser spot diameter is 80μm to 200μm, and the laser energy is 1W to 500W.

[0015] According to some embodiments of the present disclosure, on the other hand, an embodiment of the present disclosure further provides a photovoltaic module, including: a battery string, the battery string includes: a plurality of solar cells as described above, or a plurality of solar cells formed by the manufacturing method including the solar cells as described above; a welding ribbon, the welding ribbon is electrically connected to at least two of the solar cells to serially connect adjacent solar cells; an encapsulation film, the encapsulation film is used to cover the surface of the battery string; a cover plate, the cover plate is used to cover the surface of the encapsulation film away from the battery string.

[0016] The technical solution provided by the embodiment of the present disclosure has at least the following advantages: Utilize the negative effect that the substrate on the sidewall is converted into a second doped portion during the process of forming the first doped layer on the front surface, and form a second doped layer on the sidewall based on the second doped portion, so as to construct a leakage channel on the sidewall of the solar cell. The leakage performance of the solar cell can also be increased through the leakage channel, thereby improving the hot spot effect of the solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] One or more embodiments are exemplarily illustrated by the pictures in the corresponding drawings. These exemplary illustrations do not limit the embodiments. Unless otherwise stated, the figures in the drawings do not constitute a proportional limitation; in order to more clearly illustrate the technical solutions in the embodiments of the present disclosure or in the conventional technology, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the following described drawings are only some embodiments of the present disclosure. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0018] Figures 1 to 6 It is a schematic structural diagram corresponding to each step of a preparation method of a solar cell provided by an embodiment of the present disclosure;

[0019] Figure 7 It is a schematic structural diagram of a solar cell provided by an embodiment of the present disclosure;

[0020] Figure 8 It is another schematic structural diagram of a solar cell provided by an embodiment of the present disclosure;

[0021] Figure 9 It is a partial three-dimensional structural schematic diagram of a photovoltaic module provided by an embodiment of the present disclosure;

[0022] Figure 10 It is a schematic cross-sectional structure diagram of a photovoltaic module provided by an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] As can be seen from the background art, in current TOPCon cells, there may be poor contact in some cells, resulting in local heating of the solar cell. In severe cases, the solar cell may be burned out, causing the solar cell to fail.

[0024] In the embodiment of the present disclosure, during the process of forming the first doped layer on the front surface, there will be a negative effect that the substrate on the sidewall is converted into the second doped part. Based on the second doped part on the sidewall, a second doped layer is formed, thereby constructing a leakage channel on the sidewall of the solar cell. Through the leakage channel, the leakage performance of the solar cell can also be increased, thereby improving the hot spot effect of the solar cell.

[0025] In the description of the embodiment of the present disclosure, technical terms such as "first" and "second" are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order or primary-secondary relationship of the indicated technical features. In the description of the embodiment of the present disclosure, the meaning of "a plurality" is more than two, unless otherwise clearly and specifically defined.

[0026] Referring to "embodiment" herein means that the specific features, structures or characteristics described in connection with the embodiment may be included in at least one embodiment of the present disclosure. The appearance of this phrase in various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0027] In the description of the embodiment of the present disclosure, the term "and / or" is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can mean: the existence of A, the simultaneous existence of A and B, and the existence of B. In addition, the character " / " in this article generally represents an "or" relationship between the associated objects before and after.

[0028] In the description of the embodiment of the present disclosure, the term "a plurality" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0029] In the description of the embodiment of the present disclosure, the orientation or positional relationship indicated by technical terms such as "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the embodiment of the present disclosure and simplifying the description, rather than indicating or implying that the indicated device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the embodiment of the present disclosure.

[0030] In the description of the embodiments of the present disclosure, unless otherwise clearly defined and limited, technical terms such as "installation", "connection", "connection", "fixation", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can also be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and can be the communication inside two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present disclosure can be understood according to specific circumstances.

[0031] In the corresponding drawings of the embodiments of the present disclosure, for better understanding and description, the thickness and area of the layer are enlarged. When describing a component (such as a layer, film, region, or substrate) on or on the surface of another component, the component can be "directly" on the surface of the other component, or there can be a third component between the two components. On the contrary, when describing a component on the surface of another component or when another component is formed or provided on the surface of a component, it means that there is no third component between the two components. In addition, when describing a component "substantially" formed on another component, it means that the component is not formed on the entire surface (or front surface) of the other component, nor on a partial edge of the entire surface.

[0032] In the description of the embodiments of the present disclosure, when a certain component "includes" another component, unless otherwise specified, other components are not excluded, and other components may further be included. In addition, when components such as layers, films, regions, or plates are referred to as "on / at" another component, it can be "directly on" the other component (that is, on the surface of the other component and there is no other component between the two), or there can be another component therebetween. In addition, when components such as layers, films, regions, or plates are "directly located" on another component, or when components such as layers, films, regions, or plates are located on the surface of another component, it means that there is no other component therebetween.

[0033] The terms used in the description of the various embodiments herein are only for describing specific embodiments and are not intended to be limiting. As used in the description of the various embodiments and the appended claims, "the component" is also intended to include the plural form, unless the context clearly indicates otherwise. Among them, the component includes components such as layers, films, regions, or plates.

[0034] The following will elaborate on the embodiments of the present disclosure in conjunction with the drawings. However, those of ordinary skill in the art can understand that in the embodiments of the present disclosure, many technical details are presented for the reader to better understand the present disclosure. However, even without these technical details and various changes and modifications based on the following embodiments, the technical solutions claimed in the present disclosure can still be implemented.

[0035] Reference Figures 1 to 6 , Figures 1 to 6 is a schematic structural diagram corresponding to each step of a method for manufacturing a solar cell provided in an embodiment of the present disclosure.

[0036] In some embodiments, the method for manufacturing a solar cell may include: providing a substrate 100, the substrate 100 including a relative front surface 110 and a back surface 120 and a sidewall 130 located between the front surface 110 and the back surface 120.

[0037] The method for manufacturing a solar cell may further include: performing a first doping process, the first doping process converting a part of the substrate 100 into a first doping layer 101, the first doping layer 101 surrounding the surface of the substrate 100, the first doping layer 101 including a first doping portion 111 located on the front surface 110, a second doping portion 121 located on the sidewall 130, and a third doping portion 131 located on the back surface 120, and the first doping layer 101 being doped with one of N-type ions or P-type ions.

[0038] The method for manufacturing a solar cell may further include: performing a laser treatment, the laser treatment irradiating the sidewall 130 of the substrate 100 to convert the second doping portion 121 and a partial area of the substrate 100 adjacent to the second doping portion 121 into a second doping layer 102.

[0039] The method for manufacturing a solar cell may further include: removing the third doping portion 131 until the back surface 120 of the substrate 100 is exposed.

[0040] The method for manufacturing a solar cell may further include: forming a tunneling layer 103, the tunneling layer 103 covering the back surface 120 of the substrate 100.

[0041] The method for manufacturing a solar cell may further include: forming a third doping layer 104, the third doping layer 104 covering the surface of the tunneling layer 103, and the third doping layer 104 being doped with the other of N-type ions or P-type ions.

[0042] The method for manufacturing a solar cell may further include: forming a front passivation layer 105, the front passivation layer 105 being located on the surface of the first doping layer 101 away from the front surface 110.

[0043] The method for manufacturing a solar cell may further include: forming a back passivation layer 106, the back passivation layer 106 covering the surface of the third doping layer 104 away from the back surface 120.

[0044] The method for manufacturing a solar cell may further include: forming a front electrode 107, the front electrode 107 being located on the front passivation layer 105 and being in electrical contact with the first doping layer 101.

[0045] The method for preparing a solar cell may further include: forming a back electrode 108, and the back electrode 108 is in contact electrical connection with the third doped layer 104.

[0046] In the embodiment of the present disclosure, by using the negative effect that the substrate 100 on the sidewall 130 is converted into the second doped portion 121 during the process of forming the first doped layer 101 on the front surface 110, the second doped layer 102 is formed on the sidewall 130 based on the second doped portion 121, so as to construct a leakage channel on the sidewall 130 of the solar cell. The leakage performance of the solar cell can also be increased through the leakage channel, thereby improving the hot spot effect of the solar cell.

[0047] Reference Figure 1 , Figure 1 is a schematic structural diagram of a substrate provided by an embodiment of the present disclosure.

[0048] A substrate 100 is provided, and the substrate 100 has opposite front surface 110 and back surface 120. In some embodiments, if the solar cell is a single-sided cell, the front surface 110 of the substrate 100 can be used as the light-receiving surface for receiving incident light, and the back surface 120 is used as the backlight surface. In some embodiments, if the solar cell is a double-sided cell, both the front surface 110 and the back surface 120 of the substrate 100 can be used as the light-receiving surfaces and can be used to receive incident light. It can be understood that the backlight surface referred to in the embodiments of the present disclosure can also receive incident light, but the degree of receiving incident light is weaker than that of the light-receiving surface, so it is defined as the backlight surface.

[0049] In some embodiments, a texturing process can be performed on at least one of the front surface 110 or the back surface 120 of the substrate 100 to form a textured surface on at least one of the front surface 110 or the back surface 120 of the substrate 100. In this way, the absorption utilization rate of the front surface 110 and the back surface 120 of the substrate 100 for incident light can be enhanced. In some embodiments, the textured surface can be a pyramid textured surface. As a common textured surface, the pyramid textured surface not only reduces the reflectivity of the surface of the substrate 100, but also forms an optical trap, enhances the absorption effect of the substrate 100 on incident light, and improves the photoelectric conversion efficiency of the solar cell.

[0050] Specifically, if the solar cell is a single-sided cell, a textured surface can be formed on the light-receiving surface of the substrate 100, for example, it can be a pyramid textured surface, and the backlight surface of the substrate 100 can be a polished surface, that is, the backlight surface of the substrate 100 is flatter than the light-receiving surface. It should be noted that for a single-sided cell, a textured surface can also be formed on both the light-receiving surface and the backlight surface of the substrate 100.

[0051] If the solar cell is a double-sided cell, textured surfaces can be formed on both the light-receiving surface and the backlight surface of the substrate 100.

[0052] Combined reference Figure 1 and Figure 2 , Figure 2 to form a first doped layer on the basis of Figure 1 .

[0053] In some embodiments, the first doping process may be to place the substrate 100 in a diffusion furnace, introduce a doping source gas, and allow doping ions to diffuse into the substrate 100 in a high-temperature environment. The ambient temperature and diffusion time in the diffusion furnace can be controlled according to requirements to finally form the sheet resistance of the solar cell.

[0054] It can be understood that the first doping process is used to form the first doped layer 101 on the front surface 110. However, during the entire process, since there is no shielding on the sidewalls 130 and the bottom surface of the substrate 100, and a doping source gas is introduced, the gas molecules will undergo free diffusion. Therefore, the first doped layer 101 will be formed on both the sidewalls 130 and the back surface 120 of the substrate 100.

[0055] In the related process, the second doped portion 121 on the sidewall 130 and the third doped portion 131 on the back surface 120 are both etched and removed, and then subsequent process steps are carried out. However, in the embodiments of the present disclosure, the second doped portion 121 on the sidewall 130 is used as a basis to construct a leakage channel on the sidewall 130 of the solar cell to improve the hot spot effect of the formed solar cell. On the one hand, the problem of forming the second doped portion 121 on the sidewall 130 can be solved, and on the other hand, the reliability of the formed solar cell is also improved.

[0056] Reference Figure 3 , Figure 3 to form a second doped layer on the basis of Figure 2 .

[0057] In some embodiments, after the first doping process, the second doped portion 121 on the sidewall 130 is also laser-treated. The laser treatment causes the carriers on the second doped portion 121 to diffuse into the substrate 100 to form the second doped layer 102. It can be understood that for the second doped portion 121 on the sidewall 130, since the second doped portion 121 is a by-product of forming the first doped layer 101 on the front surface 110, the diffusion uniformity of the second doped portion 121 itself and its performance as a leakage channel are not good. By performing laser treatment, on the one hand, the carriers are caused to diffuse into the substrate 100 by laser treatment, thereby forming a second doped layer 102 with a higher doping concentration and a deeper junction depth. On the other hand, the diffusion of the carriers is made more uniform by laser treatment, thereby improving the reliability of the second doped layer 102.

[0058] In some embodiments, the process parameters of the laser treatment include: the laser type is ultraviolet, green or red light, the laser frequency is 400KHz to 1200KHz, such as 500KHz, 600KHz, 700KHz, 1000KHz or 1100KHz, etc., the laser spot diameter is 80μm to 200μm, such as 100μm, 120μm, 150μm, 180μm or 190μm, etc., and the laser energy is 1W to 500W, such as 10W, 50W, 100W, 200W, 300W or 400W, etc. Under these process parameters, the doping ions can be controlled to diffuse towards the inside of the substrate 100, so as to complete the formation of the second doped layer 102. Moreover, under these process parameters, the uniformity of the doping concentration in the formed second doped layer 102 can be improved, thereby improving the reliability of the formed second doped layer 102.

[0059] In some embodiments, the process parameters of the laser treatment further include: the laser type is picosecond or nanosecond laser, and the laser scanning speed is 3000m / s - 50000m / s.

[0060] Reference Figure 4 , Figure 4 For the post-oxidation process on the basis of Figure 3 .

[0061] In some embodiments, after the laser treatment, it further includes: performing a post-oxidation process, and the post-oxidation process includes: a diffusion stage, in which the second doped layer 102 and a part of the substrate 100 adjacent to the second doped layer 102 are converted into a fourth doped layer 109; an oxidation stage, in which a part of the fourth doped layer 109 is converted into a sidewall oxide layer 200. By setting the diffusion stage, the carriers in the second doped layer 102 on the sidewall 130 can continue to diffuse towards the inside of the substrate 100, so as to increase the diffusion depth of the carriers on the sidewall 130, thereby further improving the performance of the leakage channel on the sidewall 130; by setting the oxidation stage, on the one hand, the oxidation stage can precipitate the doping ions that have not advanced into the substrate 100, thereby improving the reliability of the formed fourth doped layer 109. On the other hand, during the laser treatment process, inevitably, damage will be caused to the solar cell, that is, damage will exist on the formed second doped layer 102. By setting the oxidation stage, the damaged part can also be oxidized and repaired, thereby improving the reliability of the formed solar cell.

[0062] In some embodiments, the process parameters of the post-oxidation process may include: the process temperature is 1000°C to 1200°C, such as 1050°C, 1080°C, 1120°C, 1170°C or 1190°C, etc., and the process duration is 2000s to 10000s, such as 3000s, 4000s, 5500s, 6700s, 8900s or 9300s, etc.

[0063] For the formed fourth doped layer 109, the higher the process temperature, the faster the diffusion rate of the doped ions, and it is difficult to control the thickness of the formed fourth doped layer 109. The lower the process temperature, the slower the formation rate of the fourth doped layer 109 and the longer the process duration. Therefore, setting the process temperature to 1000°C to 1200°C can improve the formation rate of the fourth doped layer 109 while facilitating the control of the thickness of the fourth doped layer 109.

[0064] Similarly, the longer the process duration, the deeper the diffusion depth of the formed ions, which will affect the light absorption ability of the formed solar cell. The shorter the process duration, the thinner the thickness of the formed fourth doped layer 109, which will affect the leakage ability of the fourth doped layer 109. Therefore, setting the process duration to 2000s to 10000s can avoid affecting the photoelectric conversion efficiency of the solar cell while controlling the fourth doped layer 109 to an appropriate thickness.

[0065] In some embodiments, oxygen and inert gas are also introduced during the post-oxidation process. Oxygen is introduced to form the sidewall oxide layer 200 and to repair the damage on the surface of the fourth doped layer 109 to a certain extent. Introducing inert gas can also provide a reaction environment for the solar cell, thereby improving the reliability of the formed solar cell.

[0066] In some embodiments, the diffusion stage and the oxidation stage can be carried out separately. For example, oxygen can be introduced differently first to allow the doped ions to diffuse into the substrate 100 for a period of time, and then oxygen is introduced to enter the oxidation stage. In other embodiments, the diffusion stage and the oxidation stage can also be carried out simultaneously, that is, while the doped ions are diffusing into the interior of the substrate 100, the formed fourth doped layer 109 is oxidized.

[0067] In some embodiments, during the oxidation stage, the front passivation layer 105 is formed in the same process step so that the sheet resistance of the front passivation layer 105 is 30Ω / sq 2 ~500Ω / sq 2 . By forming the front passivation layer 105 while forming the sidewall oxide layer 200, the process steps can be reduced. Moreover, the sheet resistance of the formed front passivation layer 105 can be adjusted to be within 30Ω / sq 2 ~500Ω / sq 2Thereby enabling the formation of the front passivation layer 105 to have a good passivation effect.

[0068] Reference Figure 5 , Figure 5 For performing a back grinding process on the basis of Figure 4 .

[0069] In some embodiments, the third doping portion 131 located on the back surface 120 can be removed by back grinding. The back grinding can chemically remove the third doping portion 131 on the back surface 120 by etching with an etching solution, or can physically remove the third doping portion 131 on the back surface 120 directly by grinding.

[0070] In some embodiments, in the same process step of removing the first doping layer 101 located on the back surface 120, it further includes: removing the sidewall oxide layer 200.

[0071] It can be understood that, in some embodiments, a post-oxidation process is performed after the laser treatment, and a sidewall oxide layer 200 is formed on the sidewall 130 of the substrate 100. Therefore, for the formed solar cell, this part of the sidewall oxide layer 200 has no practical significance. Moreover, this part of the oxide layer is actually the sidewall oxide layer 200 formed after the surface layer after the laser treatment is oxidized. Therefore, for this part of the sidewall oxide layer 200, it has certain defects. Therefore, removing the sidewall oxide layer 200 in the same process step of removing the first doping layer 101 located on the back surface 120 can also improve the reliability of the formed solar cell.

[0072] In some embodiments, the sidewall oxide layer 200 can also act as a protective layer to protect the fourth doping layer 109, so that the fourth doping layer 109 can be avoided from being etched in the process of removing the first doping layer 101 on the back surface 120, thereby improving the reliability of the formed solar cell.

[0073] In some embodiments, after removing the first doping layer 101 located on the back surface 120, it further includes: performing an etching process, and the etching process is used to remove a part of the second doping layer 102 in the direction from the back surface 120 to the front surface 110. By etching a part of the second doping layer 102, the second doping layer 102 can also be spaced apart from the subsequent formed tunneling layer 103 and the third doping layer 104, thereby controlling the leakage current ability of the second doping layer 102 and avoiding affecting the photoelectric conversion efficiency of the formed solar cell.

[0074] It can be understood that the above-mentioned removal of a part of the second doping layer 102 refers to the process of directly performing the etching process without performing the post-oxidation process. If the post-oxidation process is also performed, the etching process can be to remove a part of the fourth doping layer 109 in the direction from the back surface 120 to the front surface 110.

[0075] Reference Figure 6 , Figure 6 Based on Figure 5 , a tunneling layer, a third doping layer, a back passivation layer, a front electrode, and a back electrode are formed.

[0076] In some embodiments, the tunneling layer 103 and the third doping layer 104 can be formed in a back-to-back manner. It should be noted that the back-to-back manner means that the surfaces of two solar cells are closely attached. Taking the formation of the tunneling layer 103 as an example, the fronts 110 of the two solar cells are closely attached to each other, so that the backs 120 of the two solar cells face outward. At this time, the tunneling layer 103 is formed on the exposed surfaces of the two solar cells. It can be understood that since the fronts 110 of the two solar cells are not exposed, the tunneling layer 103 will not be formed on the fronts 110 of the solar cells.

[0077] After the tunneling layer 103 and the third doping layer 104 are formed, the wrap-around coatings located on the front 110 and the wrap-around coatings located on the sidewalls 130 can be etched away. It can be understood that when the third doping layer 104 is formed, the wrap-around coatings will inevitably be formed on the front 110 and the wrap-around coatings will be formed on the sidewalls 130 of the substrate 100. At this time, the wrap-around coatings on the front 110 and the wrap-around coatings on the sidewalls 130 are removed by etching, so as to avoid affecting the performance of the solar cell.

[0078] In some embodiments, it further includes forming a front passivation layer 105 on the front 110 and a back passivation layer 106 on the back 120. After the front passivation layer 105 and the back passivation layer 106 are formed on the front 110 and the back 120, the front electrode 107 and the back electrode 108 are formed by screen printing and sintering.

[0079] In the embodiments of the present disclosure, the negative effect that the substrate 100 on the sidewall 130 is converted into the second doping portion 121 during the process of forming the first doping layer 101 on the front 110 is utilized, and the second doping layer 102 is formed on the sidewall 130 based on the second doping portion 121, so as to construct a leakage channel on the sidewall 130 of the solar cell. The leakage performance of the solar cell can also be increased through the leakage channel, thereby improving the hot spot effect of the solar cell.

[0080] Another embodiment of the present disclosure further provides a solar cell, which can be formed by the preparation method of the solar cell in the above-mentioned part or all of the embodiments. The solar cell provided in another embodiment of the present disclosure will be described below with reference to the accompanying drawings. It should be noted that for the same or corresponding parts in the foregoing embodiments, reference may be made to the corresponding descriptions in the foregoing embodiments, and the following will not be repeated.

[0081] Reference Figure 7 AndFigure 8 , Figure 7 is a schematic structural diagram of a solar cell provided by an embodiment of the present disclosure; Figure 8 is another schematic structural diagram of a solar cell provided by an embodiment of the present disclosure.

[0082] In some embodiments, the solar cell may include: a substrate 100, the substrate 100 includes a relative front surface 110 and a back surface 120 and a side wall 130 located between the front surface 110 and the back surface 120.

[0083] The solar cell may further include: a first doping layer 101, the first doping layer 101 is located on the front surface 110 of the substrate 100, and the first doping layer 101 is doped with one of N-type ions or P-type ions.

[0084] The solar cell may further include: a second doping layer 102, the second doping layer 102 is located on the side wall 130 of the substrate 100, and the second doping layer 102 is doped with one of N-type ions or P-type ions.

[0085] The solar cell may further include: a tunneling layer 103, the tunneling layer 103 covers the back surface 120 of the substrate 100.

[0086] The solar cell may further include: a third doping layer 104, the third doping layer 104 covers the surface of the tunneling layer 103, and the third doping layer 104 is doped with the other of N-type ions or P-type ions.

[0087] The solar cell may further include: a front passivation layer 105, the front passivation layer 105 is located on the surface of the first doping layer 101 away from the front surface 110.

[0088] The solar cell may further include: a back passivation layer 106, the back passivation layer 106 covers the surface of the third doping layer 104 away from the back surface 120.

[0089] The solar cell may further include: a front electrode 107, the front electrode 107 is located on the front passivation layer 105 and is in electrical contact with the first doping layer 101.

[0090] The solar cell may further include: a back electrode 108, the back electrode 108 is in contact electrical connection with the third doping layer 104.

[0091] A topcon cell is formed by a substrate 100, a first doping layer 101, a tunneling layer 103, a third doping layer 104, a front passivation layer 105, a back passivation layer 106, a front electrode 107 and a back electrode 108. A second doping layer 102 is provided on the sidewall 130 of the solar cell, and a leakage structure of the sidewall 130 of the topcon cell is formed by the second doping layer 102 to improve the hot spot effect of the topcon cell and improve the reliability of the solar cell.

[0092] In some embodiments, the solar cell may further include a fourth doping layer 109. The fourth doping layer 109 is located between the second doping layer 102 and the substrate 100. The fourth doping layer 109 and the second doping layer 102 together form a leakage channel of the sidewall 130 of the solar cell. By providing the fourth doping layer 109, the leakage performance of the solar cell can be improved.

[0093] In some embodiments, the thickness of the second doping layer 102 in the direction perpendicular to the front surface 110 and pointing to the back surface 120 is 800 nm to 2 μm.

[0094] For the second doping layer 102, the thickness of the second doping layer 102 is proportional to the leakage ability of the second doping layer 102. Similarly, if the thickness of the second doping layer 102 is too thick, the electrical performance of the solar cell will be poor. Therefore, setting the thickness of the second doping layer 102 in the direction perpendicular to the front surface 110 and pointing to the back surface 120 to be 800 nm to 2 μm can ensure the electrical performance of the solar cell while making the second doping layer 102 have a certain thickness, thereby improving the reliability of the solar cell.

[0095] In some embodiments, the second doping layer 102 does not contact the tunneling layer 103. That is to say, the second doping layer 102 does not directly contact the tunneling layer 103. In this way, when a leakage channel is constructed between the second doping layer 102 and the third doping layer 104, the leakage ability of the second doping layer 102 will not be too strong, thereby avoiding excessive influence of the second doping layer 102 on the electrical performance of the solar cell.

[0096] Reference Figure 8 , the second doping layer 102 contacts the tunneling layer 103, and the second doping layer 102 and the third doping layer 104 leak electricity through the tunneling layer 103. Compared with the scheme of controlling the second doping layer 102 not to contact the tunneling layer 103, the process steps can be reduced, and damage during the etching of the second doping layer 102 can be avoided, and the reliability of the solar cell can be improved.

[0097] Another embodiment of the present disclosure further provides a photovoltaic module. The photovoltaic module may be formed by the preparation method of the solar cells in some or all of the above embodiments, or include the solar cells in some or all of the above embodiments. Hereinafter, the photovoltaic module provided by another embodiment of the present disclosure will be described with reference to the accompanying drawings. It should be noted that for the same or corresponding parts in the foregoing embodiments, reference may be made to the corresponding descriptions in the foregoing embodiments, which will not be repeated hereinafter.

[0098] Reference Figure 9 and Figure 10 , wherein, Figure 9 is a partial three-dimensional structural schematic diagram of a photovoltaic module; Figure 10 is Figure 9 a cross-sectional structural schematic diagram along the section direction MM1.

[0099] The photovoltaic module may include: a battery string, the battery string includes: a plurality of solar cells 40 in some or all of the above embodiments, or solar cells 40 formed by the manufacturing method of the solar cells in some or all of the above embodiments; a welding ribbon 402, the welding ribbon 402 is electrically connected to at least two solar cells 40 to serially connect the adjacent solar cells 40; an encapsulation film 41, used to cover the surface of the battery string; a cover plate 42, used to cover the surface of the encapsulation film 41 facing away from the battery string.

[0100] In some embodiments, the encapsulation film 41 includes a first encapsulation layer and a second encapsulation layer. The first encapsulation layer covers one of the front or back surfaces of the solar cell 40, and the second encapsulation layer covers the other of the front or back surfaces of the solar cell 40. Specifically, at least one of the first encapsulation layer or the second encapsulation layer may be an organic encapsulation film such as a polyvinyl butyral (PVB) film, an ethylene-vinyl acetate copolymer (EVA) film, a polyethylene octene co-elastic body (POE) film, or a polyethylene terephthalate (PET) film, or at least one of the first encapsulation layer or the second encapsulation layer may also be an EP film, an EPE film, or a PVP film. Among them, the EP film refers to a co-extruded film composed of an EVA film and a POE film stacked, the EPE film refers to a co-extruded film formed by sequentially stacking an EVA film + a POE film + an EVA film, and the PVP film refers to a co-extruded film formed by stacking a POE film + an EVA film + a POE film. The co-extruded film can be prepared by extruding one or more raw materials onto another film that has been made in the process of film processing, or by bonding different types of films that have been made together.

[0101] In some cases, there is still a demarcation line between the first encapsulation layer and the second encapsulation layer before lamination. After the lamination process, when forming the photovoltaic module, there will no longer be the concept of the first encapsulation layer and the second encapsulation layer, that is, the first encapsulation layer and the second encapsulation layer have formed an integral encapsulation adhesive film 41.

[0102] In some embodiments, the cover plate 42 can be a cover plate with a light-transmitting function such as a glass cover plate or a plastic cover plate. Specifically, the surface of the cover plate 42 facing the encapsulation adhesive film 41 can be a concave-convex surface or a suede surface including a plurality of protruding structures, so as to increase the utilization rate of incident light. The cover plate 42 includes a first cover plate and a second cover plate. The first cover plate is opposite to the first encapsulation layer, and the second cover plate is opposite to the second encapsulation layer.

[0103] Those of ordinary skill in the art can understand that the above embodiments are specific examples for implementing the present disclosure. In actual applications, various changes can be made in form and details without departing from the spirit and scope of the embodiments of the present disclosure. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the embodiments of the present disclosure. Therefore, the protection scope of the embodiments of the present disclosure should be subject to the scope defined by the claims.

Claims

1. A solar cell, characterized in that: include: a substrate, the substrate comprising opposite front and back surfaces and a sidewall located between the front and back surfaces; A first doping layer, the first doping layer is located on the front side of the substrate, and the first doping layer is doped with one of N-type ions or P-type ions; a second doping layer, the second doping layer being located on a sidewall of the substrate, the second doping layer being doped with one of N-type ions or P-type ions; A tunneling layer, the tunneling layer covering the back side of the substrate; a third doping layer, the third doping layer covering a surface of the tunneling layer, the third doping layer being doped with the other of N-type ions or P-type ions; A front passivation layer, the front passivation layer is located on a surface of the first doped layer away from the front surface; a back passivation layer, the back passivation layer covering a surface of the third doped layer away from the back surface; a front electrode, the front electrode being located on the front passivation layer and electrically contacting the first doping layer; A back electrode is electrically connected to the third doping layer.

2. The solar cell according to claim 1, characterized in that: The thickness of the second doping layer in a direction perpendicular to the front side and pointing to the back side is 800 nm to 2 μm.

3. The solar cell according to claim 1, characterized in that The second doped layer does not contact the tunneling layer.

4. A method for preparing a solar cell, characterized in that: include: Providing a substrate, the substrate comprising opposite front and back surfaces and a sidewall located between the front and back surfaces; Performing a first doping process, wherein the first doping process converts a portion of the substrate into a first doping layer, wherein the first doping layer surrounds a surface of the substrate, wherein the first doping layer includes a first doping portion located on the front side, a second doping portion located on the sidewall, and a third doping portion located on the back side, and wherein the first doping layer is doped with one of N-type ions or P-type ions; Performing laser processing, wherein the laser processing irradiates the sidewall of the substrate to convert the second doped portion and a partial area of ​​the substrate adjacent to the second doped portion into a second doped layer; removing the third doped portion until the back side of the substrate is exposed; forming a tunneling layer, wherein the tunneling layer covers the back side of the substrate; forming a third doping layer, wherein the third doping layer covers a surface of the tunneling layer, and the third doping layer is doped with the other of N-type ions or P-type ions; forming a front passivation layer, wherein the front passivation layer is located on a surface of the first doped layer away from the front surface; forming a back passivation layer, wherein the back passivation layer covers a surface of the third doped layer away from the back surface; forming a front electrode, the front electrode being located on the front passivation layer and electrically contacting the first doping layer; A back electrode is formed, wherein the back electrode is in electrical contact with the third doping layer.

5. The method for preparing a solar cell according to claim 4, characterized in that: After the laser treatment, the method further includes: performing a post-oxidation process, wherein the post-oxidation process includes: a diffusion stage, during which the second doping layer and a partial area of ​​the substrate adjacent to the second doping layer are converted into a fourth doping layer; and an oxidation stage, during which a portion of the fourth doping layer is converted into a sidewall oxide layer.

6. The method for preparing a solar cell according to claim 5, characterized in that: The same process step of removing the first doping layer located at the back side also includes: removing the sidewall oxide layer.

7. The method for preparing a solar cell according to claim 5, characterized in that: The process parameters of the post-oxidation process include: a process temperature of 1000° C. to 1200° C., and a process time of 2000s to 10000s.

8. The method for preparing a solar cell according to claim 4, characterized in that: After removing the first doped layer located on the back side, the method further includes: performing an etching process, wherein the etching process is used to remove a portion of the second doped layer along a direction from the back side to the front side.

9. The method for preparing a solar cell according to claim 4, characterized in that: The process parameters of the laser treatment include: the laser type is purple light, green light or red light, the laser frequency is 400KHz to 1200KHz, the laser spot diameter is 80μm to 200μm, and the laser energy is 1W to 500W.

10. A photovoltaic module, characterized in that: include: A battery string, the battery string comprising: a plurality of solar cells according to any one of claims 1 to 3, or a plurality of solar cells formed by the method for manufacturing a solar cell according to any one of claims 4 to 9; a welding ribbon, The welding ribbon is electrically connected to at least two of the solar cells to connect the adjacent solar cells in series; A packaging film, the packaging film is used to cover the surface of the battery string; A cover plate is used to cover the surface of the packaging film away from the battery string.

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