Back contact solar cell, method of manufacturing the same, and photovoltaic module

Abstract

The embodiment of the present application relates to the field of photovoltaics, and provides a back contact solar cell, a preparation method thereof and a photovoltaic module. The back contact solar cell comprises: a substrate, a back surface side of the substrate comprising a first doped region and a second doped region staggered with each other; a first doped layer located in the first doped region; a first grid line located on a side of the first doped layer away from the substrate and electrically connected with the first doped layer; a second doped layer opposite to the first doped layer in a doping type, comprising a first part located in the second doped region and a second part located in the first doped region, the first part and the second part being disconnected; and a second grid line located on a side of the first part away from the substrate and conductively connected with the first part, the second grid line being opposite to the first grid line in polarity.

Description

Technical Field

[0001] This application relates to the photovoltaic field, and in particular to a back-contact solar cell, its preparation method, and a photovoltaic module. Background Technology

[0002] Back-contact solar cells have all electrodes located on the back of the cell, with no metal grid lines obstructing the front, which can greatly improve light absorption and photoelectric conversion efficiency. Currently, hot spot effect is a major problem affecting the reliability of back-contact solar cells.

[0003] Hot spot effect refers to the phenomenon where some cells in a solar cell module cannot receive enough sunlight due to shading, dust accumulation, or performance degradation, resulting in less current. Meanwhile, other cells connected in series continue to generate current, causing the shaded cell to act as a load, consuming the energy generated by the other cells and leading to localized overheating. The occurrence of hot spot effect may reduce the performance and lifespan of back-contact solar cells.

[0004] The information disclosed above in the background section is only intended to enhance the understanding of the background art of the art described herein. Therefore, the background art may contain certain information that does not constitute prior art known to those skilled in the art in this country. Summary of the Invention

[0005] This application provides a back-contact solar cell, its fabrication method, and a photovoltaic module to mitigate the hot spot effect in back-contact solar cells.

[0006] To achieve the above objectives, a first aspect of this application provides a back-contact solar cell, comprising: a substrate, wherein a back side of the substrate includes a first doped region and a second doped region offset from each other; a first doped layer located within the first doped region; a first grid line located on the side of the first doped layer away from the substrate and electrically connected to the first doped layer; a second doped layer with a doping type opposite to that of the first doped layer, comprising a first portion located within the second doped region and a second portion located within the first doped region, wherein the first portion and the second portion are disconnected; and a second grid line located on the side of the first portion away from the substrate and electrically connected to the first portion, wherein the polarity of the second grid line is opposite to that of the first grid line; wherein the second portion is located between the first doped layer and the first grid line, and the second portion is electrically connected to a portion of the first doped layer and a portion of the first grid line, respectively.

[0007] In some embodiments of this application, the second part includes at least one sub-part, and when the second part includes multiple sub-parts, the multiple sub-parts are spaced apart along the linewidth direction of the corresponding first gate line.

[0008] In some embodiments of this application, the plurality of sub-parts include at least one of a first type of sub-part and a second type of sub-part; wherein the extension direction of the first type of sub-part is the same as the extension direction of the first gate line, and the first type of sub-part is a continuous strip structure; the second type of sub-part includes a plurality of portions arranged along the extension direction of the first gate line.

[0009] In some embodiments of this application, the sub-part satisfies at least one of the following: the edge of the orthographic projection of the sub-part on the substrate is a straight line; at least a portion of the edge of the orthographic projection of the sub-part on the substrate has a protrusion or a depression.

[0010] In some embodiments of this application, the first gate line is at least one of a main gate and a sub-gate.

[0011] In some embodiments of this application, the second doped layer further includes: a third portion, wherein a first end of the third portion is located in the second doped region and is connected to the first portion, and the third portion extends along the sidewall of the first doped layer to the side of the first doped layer opposite to the substrate, and a second end of the third portion is located in the first doped region and is spaced apart from the second portion and the first gate line.

[0012] In some embodiments of this application, the ratio of the total width of the sub-parts connected to the same first gate line in the linewidth direction of the first gate line to the linewidth of the first gate line is less than or equal to 25%.

[0013] In some embodiments of this application, the back-contact solar cell further includes: a conductive layer located on the side of the first doped layer and the second doped layer away from the substrate; the conductive layer includes a first conductive portion located in the first doped region and a second conductive portion located in the second doped region; the first conductive portion and the second conductive portion are disconnected; the thickness of the second conductive portion is greater than the thickness of the second doped layer; a portion of the second conductive portion covers the second portion; and a portion of the second conductive portion fills the gap between adjacent sub-parts.

[0014] A second aspect of this application also provides a method for fabricating a back-contact solar cell, comprising: forming a first doped region and a second doped region on the back side of a substrate, the first doped region and the second doped region being offset from each other; forming a first initial doped layer on one side of the back side of the substrate, and removing the first initial doped layer located in the second doped region using a laser process to form a first doped layer located in the first doped region; forming a second initial doped layer on one side of the back side of the substrate and the first doped layer, and removing a portion of the second initial doped layer located in the first doped region using a laser process to form a second doped layer, the second doped layer comprising a first portion located in the second doped region and a second portion located in the first doped region, the first portion and the second portion being disconnected; forming a first grid line on the side of the first doped layer and the second portion away from the substrate, respectively, and forming a second grid line on the side of the first portion away from the substrate, wherein the second portion is electrically connected to a portion of the first doped layer and a portion of the first grid line, respectively, and the orthographic projection of the first grid line on the substrate covers the orthographic projection of the second portion on the substrate.

[0015] In some embodiments of this application, the removal of a portion of the second initial doped layer located within the first doped region using a laser process includes: adjusting the laser to form a plurality of laser spots spaced apart along a first predetermined direction on the second initial doped layer; and moving each of the laser spots along a second predetermined direction to remove a portion of the second initial doped layer located within the first doped region, wherein the second predetermined direction intersects with the first predetermined direction.

[0016] In some embodiments of this application, the step of adjusting the laser to form a plurality of laser spots arranged at intervals along a first predetermined direction on the second doped layer further includes: adjusting the laser to further form a plurality of laser spots arranged along a second predetermined direction on the second initial doped layer, wherein any two adjacent laser spots arranged along the second predetermined direction have a gap or are edge-connected.

[0017] A third aspect of this application also provides a photovoltaic module, comprising: a battery string, formed by connecting back-contact solar cells of any of the above embodiments or back-contact solar cells prepared by the preparation method of any of the above embodiments; an encapsulating film for covering the surface of the battery string; and a cover plate for covering the surface of the encapsulating film away from the battery string.

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

[0019] This application relates to the field of photovoltaic technology, and provides a back-contact solar cell, its fabrication method, and a photovoltaic module. The back-contact solar cell includes: a substrate, with a first doped region and a second doped region offset from each other on one side of the substrate; a first doped layer located within the first doped region; a first grid line located on the side of the first doped layer away from the substrate and electrically connected to the first doped layer; a second doped layer with a doping type opposite to the first doped layer, including a first portion located within the second doped region and a second portion located within the first doped region, the first portion and the second portion being disconnected; and a second grid line located on the side of the first portion away from the substrate and electrically connected to the first portion, the second grid line having the opposite polarity to the first grid line; wherein the second portion is located between the first doped layer and the first grid line, and the second portion is electrically connected to a portion of the first doped layer and a portion of the first grid line, respectively. The second doped layer includes a first part located within the second doped region and a second part located within the first doped region. The first part can perform the function of collecting charge carriers, while the second part is in contact with the first doped layer. Since the doping types of the two are opposite, their contact will form a reverse leakage structure, causing leakage in the corresponding area. This leakage phenomenon can improve the ability of back-contact solar cells to cope with abnormal operating conditions. For example, if part of the cell is shaded, the shaded area will not generate current, but will instead act as a load to consume the current of other normally generating areas. This will lead to local heating, i.e., hot spot effect. By setting the above-mentioned reverse leakage structure, the current in each area of ​​the cell can be balanced to a certain extent, reducing the impact of the shaded area on the entire cell, alleviating the hot spot problem, and improving the thermal stability of the cell. Attached Figure Description

[0020] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Unless otherwise stated, the drawings in the accompanying drawings do not constitute a limitation on scale. In order to more clearly illustrate the technical solutions in the embodiments of this application or in the conventional art, 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.

[0021] Figure 1 This is a schematic diagram of a back-contact solar cell according to an embodiment of this application;

[0022] Figure 2 This is a schematic diagram of another back-contact solar cell provided according to an embodiment of this application;

[0023] Figure 3 This is a schematic diagram of another back-contact solar cell provided according to an embodiment of this application;

[0024] Figure 4 This is a schematic flowchart illustrating a method for fabricating a solar cell according to an embodiment of this application.

[0025] Figure 5 This is a schematic diagram of the cross-sectional structure of a photovoltaic module according to an embodiment of this application.

[0026] The above figures include the following reference numerals:

[0027] 1. Substrate; 11. First doped region; 12. Second doped region; 13. Spacer region; 2. First doped layer; 3. First grid line; 4. Second doped layer; 41. First portion; 42. Second portion; 43. Third portion; 420. Sub-part; 5. Second grid line; 6. Conductive layer; 61. First conductive part; 62. Second conductive part; 71. First passivation layer; 72. Second passivation layer; 100. Back contact solar cell; 200. Encapsulating film; 300. Cover plate. Detailed Implementation

[0028] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise expressly defined.

[0029] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0030] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A exists, A and B exist simultaneously, and B exists. In addition, the character " / " in this document generally indicates that the related objects before and after it have an "or" relationship.

[0031] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0032] In the description of the embodiments of this application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0033] In the description of the embodiments of this application, unless otherwise expressly specified and limited, the technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0034] In the accompanying drawings corresponding to the embodiments of this application, the thickness and area of ​​the layers are enlarged for better understanding and ease of description. When describing a component (such as a layer, film, region, or substrate) on or on the surface of another component, the component may be "directly" located on the surface of the other component, or there may be a third component between the two components. Conversely, when describing a component on the surface of another component, or when another component is formed or disposed on the surface of a component, it indicates that there is no third component between the two components. Furthermore, when describing a component as being "generally" formed on another component, it means that the component is not formed on the entire surface (or front surface) of the other component, nor is it formed on a portion of the edge of the entire surface.

[0035] In the description of the embodiments of this application, when a component "includes" another component, other components are not excluded unless otherwise stated, and other components may be further included. Furthermore, when a component such as a layer, film, region, or plate is referred to as being "on / located" on another component, it can be "directly on" the other component (i.e., located on the surface of the other component with no other components between them), or another component may be present therein. Moreover, when a component such as a layer, film, region, or plate is "directly located" on another component, or when a component such as a layer, film, region, or plate is located on the surface of another component, it indicates that no other components are located therein.

[0036] The terminology used in the description of the various embodiments herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used in the description of the various embodiments and the appended claims, the term "part" is also intended to include the plural form unless the context clearly indicates otherwise. Components include layers, films, regions, or plates, etc.

[0037] The embodiments of this application will now be described in detail with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the embodiments of this application to facilitate a better understanding of the application. However, the technical solutions claimed in this application can be implemented even without these technical details and various variations and modifications based on the following embodiments.

[0038] Figure 1 This is a schematic diagram of a back-contact solar cell according to an embodiment of this application. Figure 1 As shown, the back contact solar cell includes a substrate 1, a first doped layer 2, a second doped layer 4, a first grid line 3, and a second grid line 5. The above components will be described in detail below.

[0039] The substrate 1 includes a front side and a back side. The front side of the substrate 1 is set to face the light source (e.g., the sun). The first doped layer 2, the second doped layer 4, the first gate line 3, and the second gate line 5 are set on one side of the back side of the substrate 1, thereby minimizing the obstruction of direct light from the front side and improving the utilization rate of direct light from the front side.

[0040] The back side of substrate 1 includes a first doped region 11 and a second doped region 12 that are staggered from each other. It is understood that the staggering of the first doped region 11 and the second doped region 12 means that the orthographic projection of the first doped region 11 onto substrate 1 does not overlap with the orthographic projection of the second doped region 12 onto substrate 1. Figure 1 As shown, the edges of the first doped region 11 and the second doped region 12 can be connected. It should be understood that the first doped region 11 and the second doped region 12 described above are only used to represent two regions in the battery for setting different types of doped layers, and do not represent the doping type of the substrate 1. In the following text, for a film layer disposed on the back side of the substrate 1, if the orthographic projection of the film layer on the substrate 1 falls within the first doped region 11, then the film layer is said to be located within the first doped region 11; if the orthographic projection of the film layer on the substrate 1 falls within the second doped region 12, then the film layer is said to be located within the second doped region 12.

[0041] The first doped layer 2 is located within the first doped region 11, and the first gate line 3 is located on the side of the first doped layer 2 away from the substrate 1 and is electrically connected to the first doped layer 2, so that the first gate line 3 can guide the carriers collected by the first doped layer 2 to the external circuit.

[0042] The second doped layer 4 includes a first portion 41 located within the second doped region 12 and a second portion 42 located within the first doped region 11. The first portion 41 and the second portion 42 are disconnected. The first portion 41 is located within the second doped region 12, and the second gate line 5 is located on the side of the first portion 41 facing away from the substrate 1 and is electrically connected to the first portion 41. Thus, the second gate line 5 can be used to guide the charge carriers collected by the first portion 41 to an external circuit. The second portion 42 of the second doped layer 4 is located between the first doped layer 2 and the first gate line 3, and the second portion 42 is electrically connected to a portion of the first doped layer 2 and a portion of the first gate line 3, respectively. The disconnection between the first portion 41 and the second portion 42 isolates the regions in the first doped layer 2 and the second doped layer 4 used for transporting charge carriers to the corresponding gate lines, avoiding interference with the normal use of the battery.

[0043] The second doped layer 4 described above has the opposite doping type to the first doped layer 2 described above, and the first gate line 3 described above has the opposite polarity to the second gate line 5 described above. For example, if the first doped layer 2 is a P-type doped layer and the second doped layer 4 is an N-type doped layer, then the first doped layer 2 is used to collect holes, the first gate line 3 is used to guide the holes collected by the first doped layer 2 to the external circuit, the first portion 41 of the second doped layer 4 is used to collect electrons, and the second gate line 5 is used to guide the electrons collected by the first portion 41 of the second doped layer 4 to the external circuit. Alternatively, if the first doped layer 2 is an N-type doped layer and the second doped layer 4 is a P-type doped layer, then the first doped layer 2 is used to collect electrons, the first gate line 3 is used to guide the electrons collected by the first doped layer 2 to the external circuit, the second doped layer 4 is used to collect holes, and the second gate line 5 is used to guide the holes collected by the first portion 41 of the second doped layer 4 to the external circuit. No further limitation is made here.

[0044] In this embodiment, the second doped layer 4 includes a first portion 41 located in the second doped region 12 and a second portion 42 located in the first doped region 11. The first portion 41 can perform the function of collecting charge carriers, while the second portion 42 is in contact with the first doped layer 2. Since the doping types of the two are opposite, their contact will form a reverse leakage structure, resulting in leakage in the corresponding area. This leakage phenomenon can improve the ability of the back contact solar cell to cope with abnormal operating conditions. For example, if part of the cell is shaded, the shaded area will not generate current, but will consume the current of other normally generating areas as a load. This will lead to local heating, i.e., hot spot effect. By setting the above-mentioned reverse leakage structure, the current of each area of ​​the cell can be balanced to a certain extent, reducing the impact of the shaded area on the entire cell, alleviating the hot spot problem, and improving the thermal stability of the cell.

[0045] It should be understood that the second part 42 is only in contact with and electrically connected to a portion of the first doped layer 2 and a portion of the first gate line 3, ensuring that there are still some areas in contact with and electrically connected between the first doped region 11 and the first gate line 3. Furthermore, the contact area between the second part 42 and the first gate line 3 and the first doped layer 2 should be small enough to ensure that the areas in contact with and electrically connected between the first doped region 11 and the first gate line 3 meet their requirements for carrier transport efficiency.

[0046] In some embodiments of this application, the ratio of the contact area between the second portion 42 and the first grid line 3 to the area of ​​the orthogonal projection of the first grid line 3 onto the substrate 1 is less than or equal to 25%. By setting this ratio within the aforementioned range, the area occupied by the second portion 42 is not excessively large; that is, the space occupied by the reverse leakage structure in the battery is not excessively large. This mitigates the hot spot effect while preventing the reverse leakage structure from occupying too much space, which would reduce the effective power generation area of ​​the battery, thus ensuring that the photoelectric conversion efficiency of the battery remains at a suitable level. In some embodiments of this application, the ratio of the contact area between the second portion 42 and the first grid line 3 to the area of ​​the orthogonal projection of the first grid line 3 onto the substrate 1 is less than or equal to 10% to ensure that the photoelectric conversion efficiency of the battery remains at a high level.

[0047] Figure 2 This is a schematic diagram of another back-contact solar cell provided according to an embodiment of this application.

[0048] like Figure 1 and Figure 2 As shown, the second portion 42 of the second doped layer 4 may include at least one sub-part, for example, the second portion 42 may include such as Figure 1 A sub-part 420 as shown, or including as Figure 2 The embodiments shown may include two sub-sections 420, or may include more sub-sections 420; the embodiments of this application are not limited herein. When the second part 42 includes multiple sub-sections 420, the multiple sub-sections 420 are arranged at intervals along the linewidth direction of the corresponding first gate line 3.

[0049] In this embodiment, the sub-part 420 of the second part 42 is formed based on the process of forming the second doped layer 4. The second doped layer 4 is formed by first depositing the entire layer and then laser etching it. That is, an initial second doped layer is first formed, and then the initial second doped layer is laser etched to form the pattern of the second doped layer 4. In actual production, multiple laser beams are usually used simultaneously to achieve large-area etching and ensure production efficiency.

[0050] In traditional back-contact solar cells, the second doped layer is only set within the second doped region. Therefore, it is necessary to remove the portion of the initial second doped layer located within the first doped region. To avoid leaving the second doped layer within the first doped region, multiple laser beams are used to strike the cell, forming multiple laser spots. Adjacent laser spots may overlap, causing local areas of the cell to be irradiated with double energy. This leads to a sharp rise in temperature in that area. Excessive temperature may cause thermal deformation and melting of the material. After cooling, irregular protrusions and depressions may form, affecting the stability of the cell.

[0051] In the embodiments of this application, to form each sub-part 420, at least in the area where the first gate line 3 is to be set, there needs to be a gap between the multiple laser spots used to etch the second doped layer 4, so that the material at the spot gaps retains to form the sub-part 420 of the second portion 42 described above. It can be seen that, in the embodiments of this application, by providing the second portion 42 located in the first doped region 11 in the second doped layer 4, the area of ​​laser spot overlap during the formation of the second doped layer 4 can be reduced, thereby reducing the thermal effect caused by heat accumulation, reducing damage to the cell during laser processing, and improving the reliability of the back-contact solar cell.

[0052] When the second part 42 mentioned above includes multiple sub-parts 420, the multiple sub-parts 420 are arranged at intervals along the linewidth direction of the first grid line 3. The dispersed sub-parts 420 can more accurately control the magnitude and distribution of reverse leakage current, avoiding current overload or uneven degradation of battery performance due to a single large leakage area. Furthermore, the arrangement of multiple sub-parts 420 can more effectively form multiple bypasses in the event of local obstruction or failure, thereby reducing the hot spot effect, protecting other parts of the battery from damage, and preventing other sub-parts from being affected by a problem in one sub-part, thereby improving the reliability and durability of the entire battery structure.

[0053] In some embodiments of this application, the width of the sub-part 420 in the linewidth direction of the first grid line 3 is less than or equal to 10% of the linewidth of the first grid line 3, in order to avoid an excessively large reverse leakage area from adversely affecting battery performance. For example, the width of the sub-part 420 in the linewidth direction of the first grid line 3 is greater than 0 and less than 10 μm, and the linewidth of the first grid line 3 is 180~220 μm.

[0054] In some embodiments of this application, the aforementioned plurality of sub-parts 420 may include a first type of sub-part. The extension direction of the first type of sub-part is the same as the extension direction of the first gate line 3, and the first type of sub-part is a continuous strip structure. The continuous and strip-shaped first type of sub-part is beneficial to improving the continuity of current transmission, ensuring a more uniform current distribution on the entire battery, reducing the probability of hot spot effect, and the continuous strip design of the first type of sub-part simplifies the path planning of laser etching, making laser operation more precise and controllable, and avoiding the process complexity and errors that may be caused by non-strip structures.

[0055] In some embodiments of this application, the aforementioned plurality of sub-parts 420 may include a second type of sub-part. This second type of sub-part comprises multiple portions arranged along the extension direction of the first gate line 3. That is, the second type of sub-part is a segmented design, forming multiple distributed reverse leakage structures. This allows the heat source to be dispersed to multiple smaller areas when the battery is partially blocked, thereby effectively reducing heat accumulation in each part and mitigating the hot spot effect. In practical applications, the aforementioned second type of sub-part may also be formed due to errors in the laser etching process. For example, factors such as the laser beam focus failing to remain at a predetermined position, unstable or improperly adjusted laser power, and the precision of the motion control system of the laser etching equipment can cause different etching degrees at different locations, resulting in the aforementioned structure of the second type of sub-part.

[0056] In practical applications, the aforementioned multiple sub-parts 420 may include the first type of sub-parts, or may only include the second type of sub-parts, or may include both the first type of sub-parts and the second type of sub-parts simultaneously; no limitation is made here. Allowing multiple sub-parts 420 to include segmented second type sub-parts reduces the stringent requirements on the fabrication precision of each sub-part 420, which helps to reduce production difficulty and cost, and improve production efficiency.

[0057] In some embodiments of this application, the edge of the orthographic projection pattern of the sub-part 420 on the substrate 1 can be a straight line. For example, the extension direction of the straight line is consistent with the extension direction of the first grid line 3 to form a sub-part 420 with a straight edge. The movement direction of the laser spot is also a straight line. The straight movement path has lower requirements for the laser motion control system, reduces the need for a precision positioning system, helps to reduce equipment costs and operational complexity, and can more accurately control the energy distribution of the laser spot. Moreover, it does not require frequent changes in the movement direction or speed of the laser, which helps to improve production efficiency.

[0058] In some embodiments of this application, at least a portion of the edge of the orthographic projection pattern of the sub-part 420 on the substrate 1 has protrusions or depressions. These protrusions or depressions can be caused by process errors in laser etching, such as uneven energy distribution of the laser spot or limitations in equipment precision. The embodiments of this application allow for the presence of these edge protrusions or depressions. Even with minor fluctuations or deviations during laser etching, the performance of the solar cell can be maintained within an acceptable range, improving process tolerance. This reduces stringent requirements on laser energy, beam shape, and equipment precision, simplifies the adjustment and control of process parameters, and helps reduce production costs and process complexity. Furthermore, the protrusions or depressions at the edge of the sub-part 420 can trap light. Multiple reflections and refractions at the edge of the sub-part 420 increase the residence time and path length of light within the cell, improving light absorption and thus enhancing the photoelectric conversion efficiency and bifaciality of the back-contact solar cell.

[0059] In practical applications, the multiple sub-parts 420 may include multiple linear sub-parts 420 as described above, or multiple sub-parts 420 with protrusions and depressions as described above, or may simultaneously include both linear sub-parts 420 and sub-parts 420 with protrusions and depressions as described above, to meet the needs of different products.

[0060] In some embodiments of this application, the first gate line 3 can be the main gate line, that is, the second portion 42 of the second doped layer 4 is disposed between the main gate line and the first doped layer 2. The main gate line, as the current confluence channel in the battery, primarily functions to collect and discharge the current gathered by the sub-gate lines. The area where the main gate line is disposed is a sensitive region for hot spot effects due to its high current density. The aforementioned reverse leakage structure between the main gate line and the first doped layer 2 can mitigate the hot spot effect to a greater extent. Furthermore, since the main gate line typically has a wider linewidth, the sub-part 420 of the aforementioned second portion 42 can also be correspondingly wider, thus appropriately reducing the precision control requirements in the laser etching process, thereby reducing production difficulty and cost.

[0061] In some embodiments of this application, the first gate line 3 can be a sub-gate line, that is, the second portion 42 of the second doped layer 4 is disposed between the sub-gate line and the first doped layer 2. The sub-gate line is more uniformly and densely distributed in the battery. The aforementioned reverse leakage structure between the sub-gate line and the first doped layer 2 helps to manage the current distribution more precisely and prevents hot spots from being generated in the sub-gate line area due to local overload.

[0062] In practical applications, the second part 42 of the second doped layer 4 can be disposed only between the sub-gate line and the first doped layer 2, or only between the main gate line and the first doped layer 2, or simultaneously between the sub-gate line and the first doped layer 2 and the main gate line and the first doped layer 2, to meet the needs of different products.

[0063] In some embodiments of this application, such as Figure 1 and Figure 2 As shown, the second doped layer 4 also includes a third portion 43. The first end of the third portion 43 is located in the second doped region 12 and is connected to the first portion 41. The third portion 43 extends along the sidewall of the first doped layer 2 to the side of the first doped layer 2 away from the substrate 1. The second end of the third portion 43 is located in the first doped region 11 and is spaced apart from the second portion 42 and the first gate line 3. During laser etching, due to limitations in the precision of laser control, some areas of the initial second doped layer in the first doped region 11 (excluding the second portion 42) are difficult to remove by the laser, thus forming the aforementioned third portion 43. The third portion 43 is spaced apart from the second portion 42 to avoid causing a larger area of ​​leakage, and the third portion 43 does not cover the surface of the first doped layer 2 too much, ensuring that the battery can work normally. This setting, while ensuring reliable battery performance, does not impose overly stringent precision requirements on the laser etching process, meeting the requirements for mass production.

[0064] In some embodiments of this application, such as Figure 1 and Figure 2 As shown, the back-contact solar cell also includes a conductive layer 6. The conductive layer 6 is located on the side of the first doped layer 2 and the second doped layer 4 away from the substrate 1. The conductive layer 6 includes a first conductive portion 61 located in the first doped region 11 and a second conductive portion 62 located in the second doped region 12. The first conductive portion 61 and the second conductive portion 62 are disconnected to avoid mutual interference between the transport paths of charge carriers of different polarities. The thickness of the second conductive portion 62 is greater than the thickness of the second doped layer 4. Thus, part of the second conductive portion 62 covers the second portion 42, and part of the second conductive portion 62 fills the gaps between adjacent sub-parts. This structure shows that placing the second doped layer 4 in the first doped region 11 in this application has no impact on the process technology of the conductive layer 6. The aforementioned reverse leakage structure can be formed while minimizing design and process costs, thereby improving the reliability of the back-contact solar cell. For example, the thickness of the second doped layer 4 is 12~15nm, and the thickness of the conductive layer 6 is 100~110nm.

[0065] Figure 3 This is a schematic diagram of another back-contact solar cell provided according to an embodiment of this application, as shown below. Figure 3 As shown, with Figure 2The difference in the illustrated embodiment is that a spacer region 13 can also be provided between the first doped region 11 and the second doped region 12. The spacer region 13 ensures sufficient insulation between the first portion 41 of the first doped layer 2 and the second doped layer 4, clearly defining the current transmission path; that is, the current must be transmitted through the gate line or conductive layer, rather than through direct contact between the doped layers, thereby reducing carrier recombination losses between doped layers of different polarities. It is understood that, as Figure 1 The embodiment shown can also have the above-described interval 13, which will not be described in detail here.

[0066] The design of disposing the second doped layer 4 in the first doped region 11 in the above embodiments of this application can be applied to various types of back-contact solar cells, and the above design has good versatility. For example, the back-contact solar cell of this application can be a hybrid back-contact solar cell, that is, one of the first doped layer 2 and the second doped layer 4 is a polycrystalline silicon doped layer and the other is an amorphous silicon doped layer; or, the back-contact solar cell of this application can be a tunneling barrier back-contact solar cell, that is, both the first doped layer 2 and the second doped layer 4 are polycrystalline silicon doped layers.

[0067] like Figure 1 , Figure 2 and Figure 3 As shown, in embodiments of this application, the back-contact solar cell may further include a first passivation layer 71 and a second passivation layer 72. The first passivation layer 71 is located between the substrate 1 and the first doped layer 2, and the second passivation layer 72 is located between the substrate 1 and the second doped layer 4. Exemplarily, when the first doped layer 2 is a polycrystalline silicon doped layer and the second doped layer 4 is an amorphous silicon doped layer, the first passivation layer 71 is a tunneling oxide layer formed of silicon oxide (SiOx) material, and the second passivation layer 72 is an amorphous silicon layer. When the first doped layer 2 is entirely polycrystalline silicon doped layer, both the first passivation layer 71 and the second passivation layer 72 are tunneling oxide layers formed of silicon oxide (SiOx) material.

[0068] Based on the same concept, this application also provides a method for fabricating the back-contact solar cell in any of the above embodiments. Figure 4 This is a schematic flowchart illustrating a method for fabricating a solar cell according to an embodiment of this application, as shown below. Figure 4 As shown, the method for fabricating a solar cell may specifically include the following steps S1 to S4:

[0069] Step S1: A first doped region 11 and a second doped region 12 are formed on the back side of the substrate 1, and the first doped region 11 and the second doped region 12 are staggered from each other;

[0070] Step S2: A first initial doped layer is formed on one side of the back side of the substrate 1, and the first initial doped layer located in the second doped region 12 is removed by laser process to form a first doped layer 2 located in the first doped region 11.

[0071] Step S3: A second initial doped layer is formed on one side of the back side of the first doped layer 2 and the substrate 1, and a portion of the second initial doped layer located in the first doped region 11 is removed using a laser process to form a second doped layer 4. The second doped layer 4 includes a first portion 41 located in the second doped region 12 and a second portion 42 located in the first doped region 11. The first portion 41 and the second portion 42 are disconnected.

[0072] Step S4: A first gate line 3 is formed on the side of the first doped layer 2 and the second part 42 away from the substrate 1, and a second gate line 5 is formed on the side of the first part 41 away from the substrate 1. The second part 42 is electrically connected to a part of the first doped layer 2 and a part of the first gate line 3, respectively. The orthographic projection of the first gate line 3 on the substrate 1 covers the orthographic projection of the second part 42 on the substrate 1.

[0073] In steps S1 to S4 above, the patterns of the first doped layer 2 and the second doped layer 4 are formed by laser etching. Laser etching can precisely form the first doped layer 2 and the second doped layer 4 in a set area. In the step of forming the second doped layer 4, a portion of the second doped layer material is retained in the first doped region 11 to form the second part 42 mentioned above, thereby forming the aforementioned reverse leakage structure. This preparation method does not require adding any steps to the original back contact solar cell process, but only requires slight adjustments in the step of forming the second doped layer 4. Without increasing the process complexity and production cost, the reliability of the back contact solar cell is improved by forming a reverse leakage structure, which meets the requirements of mass production.

[0074] In some examples of this application, the above-described removal of a portion of the second initial doped layer located within the first doped region 11 using a laser process includes the following steps S31 and S32:

[0075] Step S31: Adjust the laser to form multiple laser spots spaced apart along a first predetermined direction on the second initial doped layer;

[0076] Step S32: Move each laser spot along the second set direction to remove part of the second initial doped layer located in the first doped region 11, wherein the second set direction intersects with the first set direction.

[0077] After completing steps S31 and S32, the areas in the first doped region 11 not covered by the laser spot can form the sub-parts 420 of the second part 42 to form a reverse leakage structure. Since the multiple laser spots arranged along the first set direction are spaced apart, there is no thermal damage problem caused by laser spot overlap at least in the first set direction. The above preparation method only adjusts the laser arrangement. For existing battery production lines, only the laser link needs to be adjusted, without modifying other process steps. This helps to lower the threshold for technology upgrades, save time and costs for re-verification and adjustment of the entire production chain, and enable new technologies to be integrated into existing industrial production more quickly.

[0078] In some embodiments of this application, the first setting direction can be the linewidth direction of the first gate line 3, and the second setting direction can be the extension direction of the first gate line 3. If the laser energy is stable and the precision is higher, a sub-part 420 with a straight edge can be formed in the aforementioned embodiment. If the laser energy is allowed to fluctuate or the precision is slightly lower, a sub-part 420 with a raised or recessed edge can be formed in the aforementioned embodiment, or a second type of sub-part can be formed in the aforementioned embodiment. The specific sub-part can be determined according to the actual product requirements and production capacity.

[0079] The spacing between adjacent laser spots in the first set direction can be less than or equal to 10% of the width of the laser spot in the first set direction, so as to avoid the sub-part 420 being too large and affecting the performance of the battery during normal operation. For example, the width of the laser spot in the first set direction can be 80~120μm, and the spacing between adjacent laser spots in the first set direction is greater than 0 and less than or equal to 10μm.

[0080] In some embodiments of this application, step S31 further includes: adjusting the laser to form a plurality of laser spots arranged along a second predetermined direction on the second initial doped layer, wherein any two adjacent laser spots arranged along the second predetermined direction have a gap or are edge-connected. That is, the laser forms a plurality of laser spots arranged in an array along the first predetermined direction and the second predetermined direction on the second initial doped layer, and any two adjacent laser spots do not overlap, thereby avoiding thermal damage caused by excessive local laser energy. The gap between the laser spots in the first predetermined direction can be used to form the aforementioned reverse leakage structure, and since the moving direction of the laser spots is also the aforementioned second predetermined direction, even if there is a gap between the laser spots in the aforementioned second predetermined direction, there will be no material residue in the second predetermined direction, ensuring that the preset second doped layer pattern can be formed.

[0081] In some embodiments of this application, before forming the first doped layer 2 using a laser process in step S2, the above method may further include: forming a first initial passivation layer on the back side of the substrate 1, that is, forming the first initial passivation layer and the first initial doped layer sequentially on the back side of the substrate 1, and then removing the first initial doped layer and the first initial passivation layer located in the second doped region 12 simultaneously by a laser process, forming the first doped layer 2 and the first passivation layer 71 with the same pattern, thereby simplifying the process steps.

[0082] In some embodiments of this application, before forming the second doped layer 4 using a laser process in step S3, the above method may further include: forming a second initial passivation layer on the back side of the first doped layer 2 and the substrate 1, that is, forming the second initial passivation layer and the second initial doped layer sequentially on the back side of the first doped layer 2 and the substrate 1, and then forming the second passivation layer 72 and the second doped layer 4 simultaneously through a laser process, thereby simplifying the process.

[0083] When the first initial passivation layer and the second initial passivation layer are made of the same material, an initial passivation layer can be formed on the substrate 1, and then a pattern of the first passivation layer 71 and the second passivation layer 72 can be formed on the initial passivation layer using a laser process, and then the first doped layer 2 and the second doped layer 4 can be prepared sequentially.

[0084] In some embodiments of this application, a textured surface can be formed in the second doped region 12 to improve the utilization rate of light by the battery. The textured surface in the second doped region 12 can be formed by a texturing process after the first doped layer 2 is formed in step S2. In the same step, a textured surface on the front side of the battery can also be formed.

[0085] In some embodiments of this application, such as Figure 3 The interval 13 shown can be formed by laser grooving in step S1 above. The interval 13 can be a textured surface or a flat surface, and there is no limitation here.

[0086] In some embodiments of this application, the steps S3 and S4 described above may further include: forming a conductive layer 6 on the side of the first doped layer 2 and the second doped layer 4 facing away from the substrate 1. Exemplarily, an initial conductive layer can be formed first, and then the initial conductive layer can be patterned using a laser process to form the conductive layer 6. The conductive layer 6 includes a first conductive portion 61 located within the first doped region 11 and a second conductive portion 62 located within the second doped region 12.

[0087] It is understood that the first initial passivation layer, the first initial doped layer, the second initial passivation layer, the second initial doped layer, the initial passivation layer, and the initial conductive layer mentioned above can all be formed in one layer using a deposition process.

[0088] Based on the same concept, this application also provides a photovoltaic module. Figure 5 This is a schematic cross-sectional view of a photovoltaic module according to an embodiment of this application, as shown below. Figure 5 As shown, the photovoltaic module includes a cell string, an encapsulating film 200, and a cover plate 300.

[0089] The battery string is composed of multiple back-contact solar cells 100 connected together. The back-contact solar cells 100 are the back-contact solar cells in the above embodiments or the back-contact solar cells prepared by the above preparation method. The connection method can be series, parallel, or a combination of series and parallel, and is not limited here. Using the above-mentioned back-contact solar cells 100 can improve the photovoltaic module's ability to cope with abnormal operating conditions and enhance its reliability.

[0090] The encapsulating film 200 is used to cover the surface of the battery string, isolating the back contact solar cell 100 from the external environment and preventing water vapor and oxygen from corroding the solar cell, thereby improving the reliability of the module and extending its service life. The encapsulating film 200 can be made of, but is not limited to, ethylene-vinyl acetate copolymer (EVA) film, polyolefin elastomer (POE) film, etc.

[0091] The cover plate 300 is located on the surface of the encapsulating film facing away from the solar cell module. It can be used to protect the internal structure and improve reliability. The cover plate 300 can be made of materials with high hardness and good light transmittance, such as glass, so as to provide protection for the back contact solar cell 100 while allowing as much light as possible to enter the back contact solar cell 100 for utilization.

[0092] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0093] Those skilled in the art will understand that the above embodiments are specific examples of implementing this application, and in practical applications, various changes in form and detail can be made without departing from the spirit and scope of this application. Any person skilled in the art can make various alterations and modifications without departing from the spirit and scope of this application; therefore, the scope of protection of this application should be determined by the scope defined in the claims.

Claims

1. A back contact solar cell, characterized by, The application relates to a substrate, which comprises: a back side of the substrate comprising a first doped region and a second doped region staggered with each other; a first doped layer located in the first doped region; a first gate line located on a side of the first doped layer away from the substrate and electrically connected with the first doped layer; a second doped layer opposite to the first doped layer in doping type, comprising a first part located in the second doped region and a second part located in the first doped region, the first part and the second part being disconnected; a second gate line located on a side of the first part away from the substrate and electrically connected with the first part, the second gate line being opposite to the first gate line in polarity; wherein the second part is located between the first doped layer and the first gate line, and the second part is electrically connected with a partial area of the first doped layer and a partial area of the first gate line respectively.

2. The back contact solar cell of claim 1, wherein, The second part comprises at least one sub-part, and when the second part comprises a plurality of sub-parts, the plurality of sub-parts are arranged in intervals along a width direction of the corresponding first gate line.

3. The back contact solar cell of claim 2, wherein, The plurality of sub-parts comprise at least one of a first type of sub-part and a second type of sub-part; wherein the first type of sub-part has the same extension direction as the first gate line, and the first type of sub-part is a continuous strip structure; the second type of sub-part comprises a plurality of parts arranged along the extension direction of the first gate line.

4. The back contact solar cell according to claim 2 or 3, characterized in that, The sub-part satisfies at least one of the following conditions: an edge of a projection of the sub-part on the substrate is a straight line; at least part of the edge of the projection of the sub-part on the substrate has a protrusion or a recess.

5. The back contact solar cell of claim 1, wherein, The first gate line is at least one of a main gate and a sub-gate.

6. The back contact solar cell of claim 1, wherein, The second doped layer further comprises: a third part, a first end of the third part being located in the second doped region and connected with the first part, and the third part extending along a side wall of the first doped layer to a side of the first doped layer away from the substrate, a second end of the third part being located in the first doped region and arranged in intervals with the second part and the first gate line.

7. The back contact solar cell of claim 1 wherein, A ratio of a contact area of the second part with the first gate line to an area of a projection of the first gate line on the substrate is less than or equal to 25%.

8. The back contact solar cell of claim 2, wherein, Further comprising: a conductive layer located on a side of the first doped layer and the second doped layer away from the substrate, the conductive layer comprising a first conductive part located in the first doped region and a second conductive part located in the second doped region, the first conductive part and the second conductive part being disconnected, a thickness of the second conductive part being greater than a thickness of the second doped layer, part of the second conductive part covering the second part, and part of the second conductive part filling intervals between adjacent sub-parts.

9. A method of producing a back contact solar cell as claimed in any one of claims 1 to 8, characterized in that, The application further relates to a manufacturing method of the substrate, which comprises: forming the first doped region and the second doped region on a back side of the substrate, the first doped region and the second doped region being staggered with each other; forming a first initial doped layer on a side of the substrate, and removing the first initial doped layer located in the second doped region by a laser process to form the first doped layer located in the first doped region. forming a second initial doping layer on a side of the first doping layer and a back side of the substrate, and removing part of the second initial doping layer located in the first doping region by a laser process to form a second doping layer, the second doping layer comprising a first part located in the second doping region and a second part located in the first doping region, the first part and the second part being disconnected; forming a first gate line on a side of the first doping layer and the second part away from the substrate, and forming a second gate line on a side of the first part away from the substrate, wherein the second part is electrically connected to a partial region of the first doping layer and a partial region of the first gate line respectively, and a normal projection of the first gate line on the substrate covers a normal projection of the second part on the substrate.

10. The method of producing a back contact solar cell according to claim 9, wherein the step of removing part of the second initial doping layer located in the first doping region by a laser process comprises: adjusting the laser to form a plurality of laser spots on the second initial doping layer along a first set direction; moving each of the laser spots along a second set direction to remove part of the second initial doping layer located in the first doping region, wherein the second set direction intersects the first set direction.

11. The method of producing a back contact solar cell according to claim 10, wherein the step of adjusting the laser to form a plurality of laser spots on the second initial doping layer along a first set direction further comprises: adjusting the laser to form a plurality of laser spots on the second initial doping layer along the second set direction, wherein any two adjacent laser spots among the plurality of laser spots along the second set direction have a spacing or an edge joint.

12. A photovoltaic module, characterized by comprise: a battery string connected by a plurality of back contact solar cells as claimed in any one of claims 1-8 or prepared by the method for preparing a back contact solar cell as claimed in any one of claims 9-11; an encapsulating adhesive film for covering a surface of the battery string; a cover plate for covering a surface of the encapsulating adhesive film away from the battery string.

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