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

Abstract

The application provides a back contact solar cell, a preparation method thereof and a photovoltaic module, and relates to the technical field of photovoltaics. The back contact solar cell comprises a silicon substrate, and the silicon substrate comprises: opposite first and second surfaces; the first surface comprises: first and second conductive regions arranged alternately in a first direction; the first conductive region has a first recessed region recessed into the silicon substrate; the first recessed region comprises: a plurality of first recesses; in a second direction, each of adjacent first recesses has a spacing; and a doped layer is located on the first surface. The application at least realizes an optimized balance of the light absorption efficiency of the silicon substrate, the contact performance of the doped layer and the current collecting grid line, and the passivation performance, and improves the efficiency of the back contact solar cell.

Description

Technical Field

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

[0002] Back-contact solar cells, due to their grid-free structure on the light-facing side, can make full use of sunlight, resulting in higher efficiency. Furthermore, the grid-free structure on the light-facing side makes the module appearance more aesthetically pleasing, thus offering broad application prospects.

[0003] In back-contact solar cells, a flat back surface of the silicon substrate is beneficial for forming a high-quality passivation film. However, an overly flat back surface is not conducive to paste contact, resulting in poor carrier transport performance and reduced cell efficiency. How to ensure good paste contact performance while maintaining high passivation performance is a pressing problem. This invention proposes a new approach and solution. Summary of the Invention

[0004] This invention provides a back-contact solar cell, its preparation method, and a photovoltaic module, aiming to solve the problem of the contradiction between high passivation performance and good paste contact performance in existing back-contact solar cells.

[0005] A first aspect of the present invention provides a back-contact solar cell, comprising:

[0006] A silicon substrate, the silicon substrate comprising: a first surface and a second surface opposite to each other; the first surface comprising: a first conductive region and a second conductive region alternately disposed along a first direction;

[0007] The first conductive region has a first pit region recessed into the silicon substrate; the first pit region includes: a plurality of first pits;

[0008] In the second direction, there is a gap between adjacent first pit regions; the second direction is different from the first direction and is perpendicular to the direction of the thickness of the silicon substrate.

[0009] A doped layer that covers the first surface;

[0010] Several collector gate lines are electrically connected to the doped layer.

[0011] In this application, firstly, the first recess is recessed into the silicon substrate, and at least a portion of the inner surface of the first recess is not perpendicular to the thickness direction of the silicon substrate. Therefore, of all light rays entering the silicon substrate from the light-facing surface, those with an incident angle less than 90° will be reflected into the silicon substrate by the aforementioned at least a portion of the inner surface and will be reflected multiple times within the silicon substrate. Compared to existing back-contact solar cells where the back surface is polished and only undergoes approximately two reflections, the number of reflections in this application is significantly more than two, increasing the light transmission distance within the silicon substrate. This increases the light absorption efficiency of the silicon substrate and improves the photoelectric conversion efficiency of the back-contact solar cell. Secondly, a doped layer covers the first surface; therefore, the surface of the doped layer facing away from the silicon substrate also has unevenness, i.e., the doped layer also has an uneven surface. Firstly, the uneven surface increases the specific surface area for contact with the electrode paste of the current collector grid, optimizing the contact performance between the doped layer and the current collector grid, and improving current conduction. Secondly, in the second direction, there is a gap between adjacent first pit regions, and the gap is flatter than the first pit region. The portion of the film layer formed on the gap in the back passivation layer has better quality, improving the compactness of the passivation layer, improving passivation performance, and reducing carrier recombination. Thirdly, the arrangement of the aforementioned first pit regions on the first conductive region with gaps along the second direction can balance the collection range or collection distance of current or carriers in the first conductive region, avoiding performance loss caused by long-distance transmission due to the concentration of pit regions, and also minimizing color difference in the appearance of the cell caused by the random occurrence of pit regions. In summary, this application achieves at least an optimized balance between the light absorption efficiency of the silicon substrate, the contact performance between the doped layer and the current collector grid, and the passivation performance, improving the efficiency of back contact solar cells, and also providing better current collection and a more aesthetically pleasing appearance.

[0012] A second aspect of the present invention provides a method for fabricating a back-contact solar cell, comprising:

[0013] A second doped layer is formed on a first surface of a silicon substrate; the first surface includes: a first conductive region and a second conductive region alternately disposed along a first direction;

[0014] The second doped layer is laser-patterned to remove the portion of the second doped layer located on the first conductive region, exposing the first conductive region and forming a first pit region recessed into the silicon substrate on the first conductive region. The first pit region includes: a plurality of first pits; in a second direction, adjacent first pits are spaced apart; the second direction is different from the first direction and is perpendicular to the direction of the thickness of the silicon substrate.

[0015] A doped layer is formed on the first surface;

[0016] Collector gate lines are formed on the doped layer.

[0017] A third aspect of the present invention provides a photovoltaic module, comprising: a battery string, the battery string comprising: a plurality of any of the aforementioned back-contact solar cells.

[0018] The aforementioned back-contact solar cells and their preparation methods have the same or similar beneficial effects as photovoltaic modules, and will not be repeated here to avoid repetition. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 A partial structural schematic diagram of the first type of back-contact solar cell in an embodiment of the present invention is shown;

[0021] Figure 2 A partial structural schematic diagram of the second type of back-contact solar cell in an embodiment of the present invention is shown;

[0022] Figure 3 A bottom view of the back-contact solar cell structure in an embodiment of the present invention is shown;

[0023] Figure 4 A partial SEM schematic diagram of a back-contact solar cell according to an embodiment of the present invention is shown;

[0024] Figure 5 A partial SEM structural diagram of another back-contact solar cell in an embodiment of the present invention is shown;

[0025] Figure 6 A cross-sectional view of a back-contact solar cell according to an embodiment of the present invention is shown.

[0026] Explanation of the attached drawing numbers:

[0027] 1-First pit region, 2-First doped layer, 3-First collector gate line, 4-Second collector gate line, 5-First bus gate line, 6-Second bus gate line, 7-First protruding particle, 8-Silicon substrate, 9-Tunneling layer, 10-Second doped layer, 11-Back passivation antireflection layer. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] This invention provides a back-contact solar cell, which is described below in conjunction with... Figures 1 to 6 This application explains the following: A back-contact solar cell includes a silicon substrate 8, a doped layer, and collector grid lines. The doped layer includes a first doped layer 2 and a second doped layer 10. The collector grid lines include a first collector grid line 3 and a second collector grid line 4. The silicon substrate can be N-type or P-type monocrystalline silicon, providing long-lived charge carriers. The silicon substrate can be obtained by cutting a silicon ingot with diamond wire. To minimize the impact of cutting marks on surface recombination, the silicon substrate can be cleaned and polished before other structural fabrication. During normal operation of the back-contact solar cell, the surface of the silicon substrate that primarily receives light is its light-facing surface, while the back-facing surface is opposite to it. The silicon substrate includes a first surface and a second surface, with the first surface being the back-facing surface and the second surface being the light-facing surface.

[0030] The first doped layer 2 and the second doped layer 10 have different doping types; one is a P-type doped layer, and the other is an N-type doped layer. The P-type doped layer can contain one or more elements from Group IIIA (e.g., boron). The N-type doped layer can contain one or more elements from Group VA (e.g., phosphorus). The materials of the N-type and P-type doped layers can include any semiconductor material such as silicon, germanium-silicon, germanium, or gallium arsenide. In terms of the arrangement of matter, the crystal phase of the doped layer can be amorphous, microcrystalline, nanocrystalline, single-crystal, or polycrystalline. The materials of the N-type and P-type doped layers can be the same or different. For example, both the N-type and P-type doped layers can be doped polycrystalline silicon. Another example: the material of the P-type doped layer can include at least one of doped amorphous silicon, doped microcrystalline silicon, and doped nanocrystalline silicon, while the material of the N-type doped layer can be doped polycrystalline silicon. Yet another example: the material of the P-type doped layer can be doped single-crystal silicon, i.e., diffused onto the surface of the P-region of a silicon substrate, while the material of the N-type doped layer can be doped polycrystalline silicon. P-type doped layers can be prepared by in-situ or ex-situ doping. N-type doped layers can also be prepared by in-situ or ex-situ doping.

[0031] Of the first collector line 3 and the second collector line 4, one is an N-type collector line and the other is a P-type collector line.

[0032] The first surface of the silicon substrate 8 includes alternating first and second conductive regions along a first direction L1, where alternation means that along the first direction L1, one first conductive region is followed by one second conductive region, and then another first conductive region. Each first conductive region has a first pit region 1 recessed into the silicon substrate, the first pit region 1 comprising a plurality of first pits; adjacent first pit regions 1 are spaced apart along a second direction L2. The second direction L2 is different from the first direction L1 and is perpendicular to the direction of the thickness of the silicon substrate. The angle between the second direction L2 and the first direction L1 is not specifically limited; for example, they can be perpendicular or nearly perpendicular.

[0033] A doped layer covers the first surface; specifically, the second doped layer 10 is located on the second conductive region. The first doped layer 2 is located on the first conductive region. Figure 6 In the first surface of the silicon substrate 8, the region corresponding to the first doped layer 2 is the first conductive region, and the region corresponding to the second doped layer 10 is the second conductive region. The first collector gate line 3 is electrically connected to the first doped layer 2, and the second collector gate line 4 is electrically connected to the second doped layer 10. The first collector gate line 3 and the second collector gate line 4 are used to collect charge carriers.

[0034] In existing back-contact solar cells, to increase the light absorption rate of the silicon substrate, the first and second conductive regions are typically flat, polished surfaces. This smooth surface reflects at least a portion of the light reaching the back surface of the silicon substrate back into the substrate, improving light utilization. However, on one hand, the light reflected back into the silicon substrate only travels approximately twice the thickness of the silicon substrate within the substrate. This short transmission distance results in low light absorption efficiency, hindering the improvement of the photoelectric conversion efficiency of the back-contact cell. On the other hand, the relatively smooth back surface of the silicon substrate and the flat surface of the doped layer formed on it lead to a small contact surface area with the collector grid lines, resulting in poor contact performance. In summary, existing back-contact solar cells suffer from low light absorption efficiency and poor contact performance, negatively impacting their overall performance.

[0035] To address the aforementioned technical problems, in this application, firstly, the first recess is recessed into the silicon substrate, and at least a portion of the inner surface of the first recess is not perpendicular to the thickness direction of the silicon substrate. Therefore, of all light rays entering the silicon substrate from the light-facing surface, those with an incident angle less than 90° will be reflected back into the silicon substrate by the aforementioned at least a portion of the inner surface, and will be reflected multiple times within the silicon substrate. Compared to existing back-contact solar cells where the back-facing surface is polished and only undergoes approximately two reflections, the number of reflections in this application is significantly more than two, increasing the light transmission distance within the silicon substrate. This increases the light absorption efficiency of the silicon substrate and improves the photoelectric conversion efficiency of the back-contact solar cell. Secondly, a doped layer covers the first surface; therefore, the surface of the doped layer facing away from the silicon substrate also has unevenness, meaning that the doped layer located on the first surface also has unevenness. On the uneven surface, the increased surface area of ​​the electrode paste in contact with the current collector grid line optimizes the contact performance between the doped layer and the current collector grid line, improving current conduction. Thirdly, in the second direction L2, adjacent first pit regions 1 are spaced apart, with the spacers being flatter than the first pit regions. The portion of the back passivation layer formed on the spacers has better quality, improving the density of the passivation layer, enhancing passivation performance, and reducing carrier recombination. Fourthly, the spaced arrangement of the first pit regions along the second direction in the first conductive region balances the collection range or distance of current or carriers in the first conductive region, avoiding performance loss due to long-distance transmission caused by concentrated pit regions, and also minimizing color differences in the cell appearance caused by random pit regions. In summary, this application achieves at least an optimized balance between the light absorption efficiency of the silicon substrate, the contact performance between the first doped layer 2 and the first current collector grid line 3, and the passivation performance, improving the efficiency of back-contact solar cells, and providing better current collection and a more aesthetically pleasing appearance.

[0036] It should be noted that some doped layers may conform to the morphology of the first surface, and / or some doped layers may not conform to the morphology of the first surface. For example, the doped layer at a deeper first pit in the first conductive region may have a roughly conformal morphology to the first pit. The doped layer at a shallower first pit in the first conductive region may have a relatively flat morphology.

[0037] It should be noted that there is no specific limit to the number of first pits in the first pit area.

[0038] Optionally, the morphology of the doped layer conforms to that of the first surface. This means that the part of the first doped layer corresponding to the first pit region may be relatively rough and have more unevenness, while the part of the first doped layer corresponding to the spacer may be relatively flat, and the second doped layer on the second conductive region may be relatively flat. Thus, in the second direction L2, good contact performance is obtained in the uneven areas, and better passivation performance is obtained in the relatively flat areas.

[0039] Optionally, in the first direction L1, there is a gap between adjacent first pit regions. Consequently, in the first direction L1, the doped layer located on the first surface also has an uneven surface. The uneven surface increases the specific surface area for contact with the electrode paste of the current collector grid, optimizes the contact performance between the doped layer and the current collector grid, and improves the current conduction effect. In addition, in the first direction L1, there is a gap between adjacent first pit regions 1. The gap is flatter than the first pit region. The portion of the film layer formed on the gap in the back passivation layer has better quality, which improves the compactness of the passivation layer, improves the passivation performance, and reduces carrier recombination. In summary, this application achieves at least an optimized balance between the light absorption efficiency of the silicon substrate, the contact performance between the first doped layer 2 and the first current collector grid 3, and the passivation performance, thereby improving the efficiency of the back contact solar cell.

[0040] Optionally, the cross-sectional shape of the first pit region, perpendicular to the thickness direction of the silicon substrate, can be one of three types: L-shaped, I-shaped, or dot-like. On the one hand, the first pit regions of the aforementioned shapes are easily formed using laser technology; on the other hand, the first pit regions of the aforementioned shapes have strong light reflection. It should be noted that the orientations of the L-shaped and I-shaped pits on the first conductive region can be the same or different, and there is no specific limitation on this.

[0041] Optionally, the first ratio is the proportion of the projected area of ​​all first pits on the first surface within a first conductive region to the area of ​​the first conductive region. For a first conductive region, this is obtained by summing the projected areas of all first pits on the first surface to get the total area, and then dividing the total area by the area of ​​the first conductive region to obtain the first ratio. Along the first direction L1, the first ratios corresponding to each first conductive region exhibit an alternating distribution of sizes. Typically, the areas of each first conductive region are approximately equal. A larger first ratio indicates that the projected size of all first pits on the first surface within the first conductive region is larger, or that there are more first pits. This indicates that the first conductive region is relatively less smooth, contributing more to the contact performance with the first doped layer and the first collector grid line, as well as the light absorption efficiency. A smaller first ratio indicates that the projected size of all first pits on the first surface within the first conductive region is smaller, or that there are fewer first pits. This indicates that the first conductive region is relatively smooth, contributing more to the passivation performance with the back passivation layer. This balances light absorption efficiency, contact performance, and passivation performance, thus improving the performance of the back contact solar cell.

[0042] Optionally, the alternating size distribution here can include: along the first direction L1, alternating between a large first proportion and a small first proportion; that is, along the first direction L1, alternating between a less uneven first conductive region, a more flat first conductive region, another less uneven first conductive region, and another more flat first conductive region. Alternatively, the alternating size distribution here can include: along the first direction L1, alternating between two large first proportions and two small first proportions; that is, along the first direction L1, alternating between two consecutive less uneven first conductive regions, two consecutive more flat first conductive regions, two consecutive less uneven first conductive regions, and two consecutive more flat first conductive regions. This alternating size distribution method is easy to implement using laser technology; furthermore, when the various structures on the first conductive region are conformally aligned with the first conductive region, the morphology distribution of the back surface of the back-contact solar cell is more aesthetically pleasing.

[0043] Optionally, in the various first proportions presented here with alternating sizes, the ratio of the larger first proportion to its adjacent smaller first proportion is greater than 1 and less than or equal to 3. Within this range, the balance between light absorption efficiency, contact performance, and passivation performance is better, thus improving the performance of the back-contact solar cell. Furthermore, it is easier to implement, and the process is relatively simple. Here, in the various proportions with alternating sizes, the larger first proportion is greater than its adjacent smaller first proportion. Whether the larger first proportion is greater than its non-adjacent smaller proportion is not specifically limited; it can be greater or less.

[0044] For example, in the various first proportions that present an alternating distribution of sizes, the ratio of the larger first proportion to its adjacent smaller first proportion can be 1.01, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.8, 2, 2.3, 2.5, 2.8, or 3.

[0045] For example, in the various first proportions that are distributed alternately in size, the larger first proportion can be 0.1%, 0.5%, 0.9%, 1%, 10%, 15%, 30%, 40%, 50%, 60%, 70%, 65%, or 80%, and the smaller first proportion can be 0.1%, 0.5%, 0.8%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50%. It should be noted that in determining the specific values ​​of the larger and smaller first proportions, the ratio of the larger first proportion to its adjacent smaller first proportion must be greater than 1 and less than or equal to 3.

[0046] Optionally, along the first direction L1, the first proportion corresponding to each first conductive region shows a gradually decreasing or gradually increasing trend, that is, along the first direction L1, each first proportion decreases or increases sequentially; or, along the first direction L1, the first proportion corresponding to each first conductive region presents a region of approximately equal size, that is, along the first direction L1, each first proportion is approximately equal in size; the changing trend of the first proportion corresponding to each first conductive region along the first direction L1 is flexible and diverse, and can be selected according to actual needs and process level.

[0047] Optionally, the first surface of the silicon substrate further includes a third conductive region, which intersects with both the first and second conductive regions. A busbar is disposed on the third conductive region, extending along a first direction L1. Figure 3 The busbars include a first busbar 5 and a second busbar 6. The first busbar 5 is electrically connected to the first collector busbar 1. The busbar extends along a first direction L1, meaning that if the busbar is straight, it extends entirely along the first direction L1; if the busbar consists of multiple segments, or contains curved sections, then some of the segments extend along the first direction L1. The first busbar 5 and the first collector busbar 1 can be electrically connected by intersecting, and the second busbar and the second collector busbar can also be electrically connected by intersecting. The third conductive region has a second recessed region recessed into the silicon substrate; the second recessed region includes a plurality of second pits, and the number of second pits in a single second recessed region is not specifically limited. Along the first direction L1, adjacent second pit regions are spaced apart. This spaced arrangement of the second pit regions along the first direction in the third conductive region balances the collection range or distance of current or charge carriers in the third conductive region, avoiding performance loss due to long-distance transmission caused by concentrated pit regions. It also minimizes color differences in the cell appearance caused by random pit occurrences. Within a third conductive region, the ratio of the projected area of ​​all second pits on the first surface to the area of ​​the third conductive region is called the second ratio. For a given third conductive region, this is obtained by summing the projected areas of all second pits on the first surface to obtain the total area, and then dividing the total area by the area of ​​the third conductive region. Along the second direction L2, the ratio of the second ratio corresponding to each third conductive region to the average of the second ratios corresponding to each third conductive region is greater than or equal to 0.97 and less than or equal to 1.03. This means that along the second direction L2, the second ratios corresponding to each third conductive region are essentially equal, resulting in a more uniform improvement in the contact performance of each third conductive region, and the process is easier to implement.

[0048] For example, along the second direction L2, the ratio of the second proportion corresponding to each third conductive region to the average value of the second proportion corresponding to each third conductive region can be 0.97, 0.98, 0.99, 1, 1.01, 1.02, or 1.03.

[0049] It should be noted that, when the first surface of the silicon substrate also includes a third conductive region, the aforementioned first ratio refers to the proportion of the projected area of ​​all first pits on the first surface within the portion of the first conductive region excluding its overlap with the third conductive region, to the total area of ​​the portion of the first conductive region excluding its overlap with the third conductive region. Simultaneously, the aforementioned second ratio refers to the proportion of the projected area of ​​all second pits on the first surface within the portion of the third conductive region excluding its overlap with the first conductive region, to the total area of ​​the portion of the third conductive region excluding its overlap with the first conductive region.

[0050] Optionally, within a third conductive region, the projected area of ​​all the second pits on the first surface accounts for a second proportion of 0.1% to 80% of the area of ​​the third conductive region. Within this range, on the one hand, the contact performance of the busbar is significantly improved, and on the other hand, it is easy to achieve through laser technology.

[0051] For example, within a third conductive region, the second proportion of the projected area of ​​all the second pits on the first surface to the area of ​​the third conductive region can be 0.1%, 1%, 3%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, or 80%.

[0052] Optionally, at the overlapping location of the first and third conductive regions, the ratio of the total projected area of ​​all first and second pits on the first surface to the area at the overlapping location of the first and third conductive regions is a third ratio. For the same third conductive region, this third ratio is greater than the second ratio. This third ratio refers to the ratio obtained by dividing the total area obtained by summing the projected areas of all first and second pits on the first surface at the overlapping location of the first and third conductive regions by the area at the overlapping location of the first and third conductive regions. In other words, the overlapping location of the third and first conductive regions is less smooth. Since both the collector grid and the bus grid are correspondingly set at this overlapping location, the contact performance of both the collector grid and the bus grid is improved. The less smooth surface effectively improves the contact performance of both the collector grid and the bus grid, thereby enhancing the performance of the back-contact solar cell.

[0053] The overlapping position of the first conductive region and the third conductive region refers to the position where the first conductive region and the third conductive region cover each other.

[0054] Optionally, for the same first conductive region and the same third conductive region, at the overlapping position of the first conductive region and the third conductive region, the ratio of the total area of ​​the projected area of ​​all first pits and all second pits on the first surface to the area at the overlapping position of the first conductive region and the third conductive region, to the ratio of the projected area of ​​all second pits in the third conductive region on the first surface to the area of ​​the third conductive region, is greater than 1 and less than or equal to 3. That is, at the corresponding position where the first conductive region and the third conductive region overlap, the surface is more uneven. This allows for an effective improvement in the contact performance of both the collector grid and the bus grid at this position, thereby improving the performance of the back contact solar cell. Moreover, the difference in unevenness is not too large, and it is easy to implement while being compatible with existing processes.

[0055] For example, for the same first conductive region and the same third conductive region, the ratio of the third ratio to the second ratio can be 1.01, 1.02, 1.02, 1.04, 1.05, 1.06, 1.08, 1.1, 1.12, 1.15, 1.16, 1.17, 1.18, 1.2, 1.5, 1.8, 2, 2.2, 2.5, 2.7, 2.9, or 3.

[0056] For example, the third percentage could be: 0.1%, 0.5%, 0.9%, 1%, 1.3%, 5%, 10%, 20%, 30%, 40%, 45%, 50%, 60%, 70%, 75%, 80%, 55%, or 90%.

[0057] Optionally, the number of first pit regions that are at least partially collinear along the second direction L2 within a first conductive region is greater than or equal to 1. These first pit regions that are at least partially collinear along the second direction L2 within a first conductive region are highly likely formed under the action of laser scanning in the same direction. The efficiency of laser formation of the first pit regions is relatively high. For example, Figure 1 Assuming this is a schematic diagram of the location of a first conductive region, then the number of first pit regions 1 that are at least partially collinear along the second direction L2 within the first conductive region is 4. However, the number could also be 1, 2, 3, 5, or even more; no specific limitation is made.

[0058] Optionally, the collector grid line includes: a first collector grid line corresponding to the location of the first conductive region, the first collector grid line including: a recessed collector grid line and / or a flat collector grid line. (Refer to...) Figure 1 At least one first recessed region 1 is provided at the corresponding position of the recessed collector grid line on the first conductive region. (Refer to...) Figure 2There is no first pit area at the corresponding position of the flat collector grid line on the first conductive region, or the flat collector grid line misses the first pit area. Both of these grid line configuration methods can satisfy the goals of increasing the contact area between the grid line and the doped layer, improving the surface adhesion between the grid line and the doped layer, and eliminating the need for strict alignment between the collector grid line and the first pit area, thereby reducing the process difficulty and improving the process window.

[0059] Optional, refer to Figure 4 and Figure 5 The space between adjacent first pit regions 1 has a first protruding particle 7 that protrudes in the direction away from the silicon substrate, and / or, between adjacent first pits, there is a second protruding particle that protrudes in the direction away from the silicon substrate. The outer surfaces of the first and second protruding particles 7 can reflect some of the light reaching the silicon substrate back to the silicon substrate, increasing the light absorption efficiency. On the other hand, the first and second protruding particles 7 and 2 also have a large specific surface area, which can increase the contact performance of the grid lines and further improve the performance of the back contact solar cell. It should be noted that... Figure 4 and Figure 5 All images are from scanning electron microscopes (SEM).

[0060] Optionally, the first protruding particle 7 and the second protruding particle can be one of four shapes: a regular pyramid, an ellipsoid, a sphere, or an irregular shape. The shapes of the first protruding particle 7 and the second protruding particle are flexible and diverse, and can be applied to various preparation methods.

[0061] Optionally, the maximum cross-sectional dimension of the first protruding particle 7 is 0.01 μm to 1 μm, and the maximum cross-sectional dimension of the first protruding particle 7 is the distance between the two farthest endpoints of the first protruding particle 7 in the projection of the first protruding particle 7 onto a plane perpendicular to the protrusion direction of the first protruding particle; the cross-section of the first protruding particle 7 is perpendicular to the protrusion direction of the first protruding particle; and / or, the minimum cross-sectional dimension of the first protruding particle 7 is 0.01 μm to 0.5 μm, and the minimum cross-sectional dimension of the first protruding particle 7 is the distance between the two closest endpoints of the first protruding particle 7 in the projection of the first protruding particle 7 onto a plane perpendicular to the protrusion direction of the first protruding particle; and / or, the height of the first protruding particle is 0.01 μm to 1 μm; the direction of the height is parallel to the protrusion direction of the first protruding particle. Alternatively, the minimum dimension of the cross-section of the first protruding particle 7 can be understood as the diameter of the smallest inscribed circle of the cross-section of the first protruding particle, and the maximum dimension of the cross-section of the first protruding particle 7 can be understood as the diameter of the largest circumscribed circle of the cross-section of the first protruding particle. The cross-section containing the minimum dimension of the first protruding particle and the cross-section containing the maximum dimension of the first protruding particle can be the same cross-section or different cross-sections. The directions of the maximum dimension of the cross-section of the first protruding particle 7 and the minimum dimension of the cross-section of the first protruding particle 7 can be parallel or intersecting, etc., without limitation. For the same first protruding particle, the maximum dimension of the cross-section is greater than or equal to the minimum dimension of the cross-section. When the size of the first protruding particle 7 is within the above range, it significantly improves the light utilization rate and contact performance, and is also easy to process and implement.

[0062] For example, the maximum cross-sectional size of the first protruding particle 7 can be 0.01μm, 0.03μm, 0.05μm, 0.1μm, 0.15μm, 0.2μm, 0.25μm, 0.3μm, 0.35μm, 0.4μm, 0.45μm, 0.5μm, 0.55μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 0.85μm, or 1μm; the minimum cross-sectional size of the first protruding particle 7 can be 0.01μm, 0.05μm, or 0.05μm. The sizes of the protruding particles are 0.1μm, 0.15μm, 0.2μm, 0.25μm, 0.3μm, 0.35μm, 0.4μm, 0.45μm, and 0.5μm; the height of the first protruding particle can be 0.01μm, 0.05μm, 0.1μm, 0.15μm, 0.2μm, 0.25μm, 0.3μm, 0.35μm, 0.4μm, 0.45μm, 0.5μm, 0.55μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, and 1μm.

[0063] It should be noted that the maximum cross-sectional dimension of the second protruding particle is 0.01 μm to 1 μm, and / or the minimum cross-sectional dimension of the second protruding particle is 0.01 μm to 0.5 μm, and / or the height of the second protruding particle is 0.01 μm to 1 μm; the determination method of the relevant dimensions of the second protruding particle is the same as the determination method of the relevant dimensions of the first protruding particle mentioned above, and will not be repeated here to avoid repetition.

[0064] Optionally, the bottom of the first recess has a third protruding particle that bulges away from the silicon substrate. The bottom of the first recess is opposite to its opening, meaning it is closer to the interior of the silicon substrate. The outer surface of this third protruding particle can reflect some of the light reaching the silicon substrate back to it, increasing light absorption efficiency and further improving the performance of the back-contact solar cell. The opening of the first recess is located at the junction of the first recess and the first conductive region, and the bottom of the first recess is closer to the second surface of the silicon substrate than its opening.

[0065] Optionally, the shape of the third protruding particle can be one of four: a quasi-pyramidal shape, a quasi-ellipsoidal shape, a quasi-spherical shape, or an irregular shape. The shape of the third protruding particle is flexible and diverse, and can be applied to various preparation methods.

[0066] Optionally, the maximum cross-sectional dimension of the third protruding particle is 0.1 μm to 5 μm; the cross-section of the third protruding particle is perpendicular to its protrusion direction; and / or, the minimum cross-sectional dimension of the third protruding particle is 0.1 μm to 3 μm; and / or, the height of the third protruding particle is 0.1 μm to 3 μm; the direction of this height is parallel to the protrusion direction of the third protruding particle. The directions of the maximum and minimum cross-sectional dimensions of the third protruding particle can be parallel or intersecting, etc., and are not limited thereto. For the same third protruding particle, the maximum cross-sectional dimension is greater than or equal to the minimum cross-sectional dimension. When the size of the third protruding particle is within the above range, the improvement in light utilization is more significant, and it is also easier to manufacture.

[0067] It should be noted that the method for determining the relevant dimensions of the third protruding particle is the same as the method for determining the relevant dimensions of the first protruding particle mentioned above. To avoid repetition, it will not be repeated here. For example, the maximum cross-sectional size of the third protruding particle can be 0.1μm, 0.3μm, 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, or 5μm; the minimum cross-sectional size of the third protruding particle can be 0.1μm, 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 1.6μm, 2.4μm, or 2.45μm; and the height of the third protruding particle can be 0.1μm, 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 1.4μm, 1.45μm, 2.55μm, 1.6μm, 2.7μm, 1.8μm, or 1.9μm.

[0068] It should be noted that the bottom of the second recess has a fourth protruding particle that bulges away from the silicon substrate. The bottom of the second recess is opposite to the opening of the second recess, which is located at the junction of the second recess and the third conductive region. The bottom of the second recess is closer to the second surface of the silicon substrate than its opening, meaning it is closer to the interior of the silicon substrate. The outer surface of this fourth protruding particle can reflect some of the light reaching the silicon substrate back to it, increasing the light absorption efficiency and further improving the performance of the back-contact solar cell. The shape of this fourth protruding particle can be one of four: a quasi-pyramidal, quasi-ellipsoidal, quasi-spherical, or irregular.

[0069] Optionally, the maximum cross-sectional dimension of the fourth protruding particle is 0.1 μm to 5 μm; the cross-section of the fourth protruding particle is perpendicular to the protrusion direction of the fourth protruding particle; and / or, the minimum cross-sectional dimension of the fourth protruding particle is 0.1 μm to 3 μm; and / or, the height of the fourth protruding particle is 0.1 μm to 3 μm; the determination method of the relevant dimensions of the fourth protruding particle is the same as the determination method of the relevant dimensions of the first protruding particle mentioned above, and will not be repeated here to avoid repetition.

[0070] Optionally, in the first direction, there are also raised particles at the intervals between adjacent second pit areas. The shape, size, etc. of these raised particles can be referenced to the first raised particles at the intervals between adjacent first pit areas, as described above, and will not be repeated here. Optionally, there are also raised particles between adjacent second pits. The shape, size, etc. of these raised particles can be referenced to the second raised particles at the intervals between adjacent first pits, as described above, and will not be repeated here.

[0071] Optionally, the first recess can be one of four shapes: a quasi-inverted pyramid, a quasi-inverted frustum, a hemispherical shape, or an irregular shape. The shape of the first recess is flexible and diverse, and can be applied to various preparation methods. The quasi-inverted pyramid here can be a quasi-inverted triangular pyramid, a quasi-inverted square pyramid, a quasi-inverted pentagonal pyramid, etc.

[0072] Optionally, the second recess can be one of four shapes: a quasi-inverted pyramid, a quasi-inverted frustum, a hemispherical shape, or an irregular shape. The shape of the second recess is flexible and diverse, and can be applied to various preparation methods. The quasi-inverted pyramid here can be a quasi-inverted triangular pyramid, a quasi-inverted square pyramid, a quasi-inverted pentagonal pyramid, etc.

[0073] Optionally, along the direction away from the silicon substrate, the cross-sectional area of ​​the first pit is increased. The cross-section of the first pit is perpendicular to the thickness direction of the silicon substrate. This facilitates the complete removal of etchant and reactive impurities used to clean the first pit after its formation, as these impurities remain within the pit, preventing leakage and other problems, thus improving the electrical performance of the back-contact solar cell. It also facilitates the subsequent fabrication of the film layer on the surface of the first conductive region, improving the film quality. Furthermore, increasing the cross-sectional area of ​​the first pit along the direction away from the silicon substrate allows at least a majority of the inner surface of the first pit to form an obtuse angle with the plane perpendicular to the thickness of the silicon substrate. This increases the reflection probability of light transmitted to the first pit and improves light utilization, further enhancing the photoelectric conversion efficiency of the back-contact cell. The method of increasing the area is not limited; it can be linear, exponential, etc.

[0074] Optionally, along the direction away from the silicon substrate, the cross-sectional area of ​​the second pit is increased, and the cross-section of the second pit is perpendicular to the direction of the thickness of the silicon substrate, having the same or similar beneficial effects as the first pit. To avoid repetition, it will not be described again here.

[0075] Optionally, the cross-sectional dimensions of the first recess are 0.01 μm to 20 μm, and this cross-section is perpendicular to the recess direction of the first recess; and / or, the depth of the first recess region is 0.01 μm to 20 μm, and the direction of this depth is parallel to the recess direction of the first recess. The cross-sectional dimensions of the first recess can be understood as the distance between the two farthest endpoints of the first recess in its projection onto a plane perpendicular to the thickness direction of the silicon substrate. Within the above-mentioned size range, the improvement in light utilization is more significant, and it is also easier to fabricate.

[0076] For example, the minimum size of the cross-section of the first pit can be 0.01μm, 0.1μm, 0.3μm, 0.5μm, 1μm, 3μm, 5μm, 8μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 10μm, 6.5μm, 11μm, 12μm, 13μm, 15μm, 16μm, 18μm, or 20μm; the maximum size of the cross-section of the first pit can be 0.5μm, 1μm, 15μm, 20μm, or 2.5μm. 3μm, 5μm, 2.4μm, 8μm, 10μm, 12μm, 17.5μm, 18μm, 20μm; the height of the first pit can be 0.01μm, 0.1μm, 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 1.4μm, 4.5μm, 5.5μm, 7μm, 9μm, 18μm, 19μm, 20μm, 10μm, 11.5μm, 13μm, 15μm, 18μm, 20μm.

[0077] Optionally, the cross-sectional dimensions of the second pit are 0.01 μm to 20 μm, and the cross-section is perpendicular to the recess direction of the second pit; and / or, the depth of the second pit region is 0.01 μm to 20 μm, having the same or similar beneficial effects as the first pit, which will not be described further here to avoid repetition.

[0078] Reference Figure 6 The back-contact solar cell further includes: a tunneling layer 9, located between the first surface and the doped layer. The tunneling layer 9 includes: a first tunneling layer located between the first conductive region and the first doped layer; the first tunneling layer is conformally oriented to the first conductive region, meaning that the position in the first tunneling layer corresponding to the first pit region on the first conductive region also has a pit region; and / or, a second tunneling layer located between the second conductive region and the second doped layer; the second tunneling layer is conformally oriented to the second conductive region. For example, Figure 6 In this process, the second conductive region is flatter than the first conductive region, thus the surface of the second tunneling layer is also relatively flat. The materials of the first and second tunneling layers can be selected from at least one of silicon oxide, silicon carbide, silicon nitride, and aluminum oxide. The aforementioned first and second tunneling layers exhibit good passivation and tunneling effects. Here, "conformal" means that where the first conductive region has pits, the corresponding positions in the first tunneling layer also have pits, and the shape of the second conductive region is similar to that of the second tunneling layer.

[0079] Optional, refer to Figure 6 The tunneling layer conforms to the doped layer, meaning the first doped layer conforms to the first tunneling layer, and the position in the first doped layer 2 corresponding to the pit region of the first tunneling layer also has a pit region; and / or, the second doped layer conforms to the second tunneling layer. For example... Figure 6In this design, the second tunneling layer is flatter than the first tunneling layer, resulting in a relatively flat surface for the second doped layer 10. Here, "conformal" means that where the first tunneling layer has pits, the corresponding locations in the first doped layer also have pits, and the second tunneling layer has a similar shape to the first doped layer. This allows the first pits in the first conductive region to be transferred to the first doped layer through the first tunneling layer, facilitating conformal design between the first doped layer and the first conductive region.

[0080] Optional, refer to Figure 6 The back-contact solar cell further includes: a back passivation antireflection layer 11; located between the doped layer and the collector grid lines, the collector grid lines penetrate the back passivation antireflection layer to make electrical contact with the doped layer; the back passivation antireflection layer may be conformal or non-conformal with the adjacent doped layer, meaning that the portion of the back passivation antireflection layer located in the first doped layer can conform to the first doped layer and may have pits, while the portion of the back passivation antireflection layer located in the second doped layer conforms to the second doped layer and is relatively flat. This back passivation antireflection layer can provide good back passivation and antireflection effects. The material of the back passivation antireflection layer can be selected from silicon oxide, silicon carbide, silicon nitride, and aluminum oxide, etc., without specific limitations.

[0081] Optional, refer to Figure 6 The first surface further includes an isolation region located between the first conductive region and the adjacent second conductive region. This isolation region can prevent short circuits within the back-contact solar cell. The isolation region has a third recessed region recessed into the silicon substrate. This third recessed region, similar to the aforementioned first recessed region, can increase light utilization. This third recessed region includes a plurality of third recesses, and the distribution and morphology of the third recesses can correspond to the distribution and morphology of the aforementioned first recesses. The morphology of this third recessed region is not specifically limited.

[0082] In this application, the second conductive region can be a polished surface or a textured surface, without specific limitations. The second surface of the silicon substrate, i.e., the light-facing surface of the silicon substrate, can be a textured surface, etc., without specific limitations. The back-contact solar cell may also include: a front passivation and antireflection layer located on the second surface, which can improve the passivation and antireflection effect on the front side, without limitations on its specific material.

[0083] This application also provides a method for fabricating a back-contact solar cell, comprising the following steps.

[0084] Step 101: A second doped layer is formed on a first surface of a silicon substrate; the first surface includes a first conductive region and a second conductive region alternately disposed along a first direction.

[0085] The first and second conductive regions are described above, and will not be repeated here to avoid repetition. The entire second doped layer can be prepared using low-pressure chemical vapor deposition (LPCVD) or plasma-enhanced chemical vapor deposition (PECVD). It should be noted that, in the case of a second tunneling layer, the second tunneling layer and the second doped layer can be prepared together. For example, dopant atoms can be diffused onto the second tunneling layer to form a boron-doped polycrystalline silicon structure and / or a phosphorus-doped polycrystalline silicon structure to form the second doped layer.

[0086] It should be noted that before preparing the second doped layer, the original silicon wafer can be subjected to alkaline polishing in a tank mill to form a tower-like morphology on the wafer surface, thus forming a silicon substrate. The original silicon wafer here can be a P-type or N-type wafer, referring to a silicon wafer cut from a silicon rod, etc. In this tower-like morphology, the cross-sectional dimensions of the tower structure can be from 5 μm to 30 μm, perpendicular to the thickness direction of the silicon substrate, and the longitudinal dimension of the tower can be from 0.01 μm to 8 μm, parallel to the thickness direction of the silicon substrate.

[0087] Step 102: Laser patterning is performed on the second doped layer to remove the portion of the second doped layer located on the first conductive region, exposing the first conductive region and forming a first pit region recessed into the silicon substrate on the first conductive region. The first pit region includes: a plurality of first pits; in a second direction, adjacent first pit regions are spaced apart; the second direction is different from the first direction and is perpendicular to the direction of the thickness of the silicon substrate.

[0088] Laser treatment is applied to the portion of the second doped layer located on or within the first conductive region. The laser energy acts on the surface phosphorus / borosilicate glass layer, producing surface modification or directly removing the portion to be eliminated. Within a first conductive region, the laser-treated pattern can be designed as a single line, double line, triple line, etc., depending on the actual laser spot size. A certain percentage of overlap can exist between different lines, and a certain percentage of overlap also exists between adjacent laser spots.

[0089] Optionally, the laser overlaps two or more times. After two or more overlaps, the location absorbs more laser energy, making it easier to remove during subsequent cleaning processes. For example, the number of laser overlaps can be 2, 3, 4, 5, 6, 7, 8, 9, or 10.

[0090] Optionally, in laser patterning: the laser wavelength selected is within the 300nm, 400nm, 500nm, 700nm, 800nm, 900nm, 1000nm, 1100nm, 1300nm, and 1400nm bands; and / or, the laser power is 15W, 25W, 30W, 45W, 40W, 55W, 60W, 75W, and 80W.

[0091] Optionally, in laser patterning: the shape of the laser spot includes at least one of the following: square, rectangle, rhombus, and circle; and / or, the longest side of the laser spot can be 100μm, 120μm, 150μm, 180μm, 190μm, 200μm, 250μm, or 300μm, and the shortest side can be 80μm, 100μm, 120μm, 150μm, 180μm, 200μm, 250μm, 280μm, or 300μm.

[0092] Optionally, the laser scanning can be at least one of single-line scanning, double-line scanning, or triple-line scanning; and / or, when the laser scanning is multi-line scanning, the overlap rate between adjacent lines can be: 3%, 4%, 5%, 10%, 30%, 40%, 50%, 60%, 70%, 80%, 55%, or 95%; and / or, the overlap rate between adjacent laser spots can be: 3%, 5%, 10%, 30%, 40%, 50%, 60%, 70%, 80%, 55%, or 95%; and / or, the energy difference of a single laser spot is: 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 5%. The small energy difference of a single laser spot makes it easy to control the formation position of the pit area.

[0093] Optionally, during the patterning process, the alkaline etching temperature in the cleaning process after laser scanning can be: 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 54℃, 68℃, or 80℃; additives need to be added during the etching process, and the main components of the additives are organic surfactants, etc.

[0094] It should be noted that this application does not specifically limit the method of forming the second pit region within the third conductive region. For example, methods such as laser can be used, and there is no specific limitation on this.

[0095] The present application will be further explained below with reference to specific embodiments.

[0096] The first step involves alkaline polishing of the N-type silicon wafer in a trough polishing machine to form a tower-based morphology on the wafer surface. The tower-based structure has a lateral dimension of 10 μm and a longitudinal dimension of 0.5 μm, resulting in a silicon substrate. The longitudinal dimension is parallel to the direction of the thickness of the silicon substrate.

[0097] The second step involves preparing a tunneling passivation structure using low-pressure chemical vapor deposition (LPCVD) and then diffusing doped atoms to form a boron-doped polycrystalline silicon structure, which constitutes the second doped layer.

[0098] Step 3: Laser patterning is performed on the portion of the second doped layer located in the first conductive region. Specifically, a double-line laser pattern with a wavelength of 532nm, a power of 50W, a near-square spot shape, and a spot size of 180×180μm is used for laser processing. The overlap rate of adjacent lines is 30%, the overlap rate between adjacent spots is 50%, and the energy difference within the spot is 3%. The laser energy acts on the surface borosilicate glass layer, producing a surface modification effect and removing part of the borosilicate glass layer.

[0099] Step 4: Alkali etching is performed in a tank etching machine to remove the second doped layer in the laser-treated area. This is followed by cleaning to remove residual additives, alkali residue, and surface metal ions. The result of this step is the formation of a first pit region recessed into the silicon substrate on the first conductive region. This first pit region includes: a plurality of first pits; and in a second direction, a gap is formed between adjacent first pits; the second direction is different from the first direction and is perpendicular to the thickness direction of the silicon substrate.

[0100] Step 5: The tunneling passivation structure is prepared by low-pressure chemical vapor deposition (LPCVD) and the doped atoms are diffused to form a phosphorus-doped polycrystalline silicon structure, which is the first doped layer.

[0101] Step 6: Laser patterning and cleaning, mainly to remove additive residues, alkali residues, surface metal ions, and other substances. During the alkali texturing process, silicon is etched by the alkali solution. Due to the anisotropic nature of the etching process, a textured pyramid structure is formed.

[0102] Step 7: Deposit oxide layers on the front and back sides of the back contact solar cell using atomic layer deposition (ALD) technology to provide passivation.

[0103] Step 8: Deposit antireflection layers on the light-facing and back-facing sides of the back-contact solar cell using plasma-enhanced chemical vapor deposition (PECVD).

[0104] Step 9: Forming electrodes by screen printing. The electrodes include: a first collector grid line and a second collector grid line. The paste printed on the first collector grid line is located in the first conductive area. Some of the first collector grid lines correspond to the positions of the first pits, while some of the first collector grid lines do not correspond to the positions of the first pits.

[0105] Step 10: Test sorting.

[0106] This application also provides a photovoltaic module comprising a plurality of cell strings, wherein each cell string includes a plurality of the aforementioned back-contact solar cells. The photovoltaic module, the back-contact solar cell, and the method for fabricating them are related and can achieve the same or similar beneficial effects; therefore, to avoid repetition, further details are omitted here.

[0107] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0108] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A back contact solar cell, characterized by, The back contact solar cell comprises: a silicon substrate comprising a first surface and a second surface opposite to the first surface; the first surface comprises first conductive regions and second conductive regions arranged alternately along a first direction; the first conductive regions have first recessed regions recessed into the silicon substrate; the first recessed regions comprise first recesses; in a second direction, the first recessed regions are spaced apart from each other; the second direction is different from the first direction and is perpendicular to the direction of the thickness of the silicon substrate; a doped layer covering the first surface; the doped layer comprises a first doped polysilicon layer and a second doped polysilicon layer; the first doped polysilicon layer covers the first conductive regions, and the second doped polysilicon layer covers the second conductive regions; a first tunneling layer is located between the first conductive regions and the first doped polysilicon layer, and a second tunneling layer is located between the second conductive regions and the second doped polysilicon layer; a plurality of collector grid lines in electrical contact with the doped layer.

2. The back contact solar cell of claim 1, wherein, The doped layer is conformal to the topography of the first surface.

3. The back contact solar cell according to claim 1, wherein: a proportion of the projected area of all the first recesses in one of the first conductive regions on the first surface to the area of the first conductive region is a first proportion; the first proportion is 0.1% to 80%.

4. The back contact solar cell of claim 1, wherein, in the first direction, the first recessed regions are spaced apart from each other.

5. The back contact solar cell according to claim 1, wherein: the first recessed regions have a cross-sectional shape perpendicular to the direction of the thickness of the silicon substrate, which is one of an L shape, an I shape, and a dot structure.

6. The back contact solar cell according to claim 1, wherein: a proportion of the projected area of all the first recesses in one of the first conductive regions on the first surface to the area of the first conductive region is a first proportion; along the first direction, the first proportions corresponding to the first conductive regions alternately increase and decrease in size.

7. The back contact solar cell of claim 6, wherein, in the first proportions alternately increasing and decreasing in size, the ratio of a large first proportion to an adjacent small first proportion is greater than 1 and less than or equal to 3.

8. The back contact solar cell of claim 1 wherein, The first surface further comprises: a plurality of third conductive regions intersecting the first conductive regions and the second conductive regions; the third conductive regions extend along the first direction; the third conductive regions have second recessed regions recessed into the silicon substrate; the second recessed regions comprise second recesses; in the first direction, the second recessed regions are spaced apart from each other; a proportion of the projected area of all the second recesses in one of the third conductive regions on the first surface to the area of the third conductive region is a second proportion; along the second direction, the ratio of the second proportion corresponding to each of the third conductive regions to the average of the second proportions corresponding to each of the third conductive regions is greater than or equal to 0.97 and less than or equal to 1.

03.

9. The back contact solar cell of claim 8, wherein, The total area of the projected area of all the first pits and all the second pits at the overlapping position of the first conductive region and the third conductive region accounts for a third proportion of the area at the overlapping position of the first conductive region and the third conductive region.

10. The back contact solar cell of claim 9, wherein, The ratio of the third proportion to the second proportion is greater than 1 and less than or equal to 3 for the same third conductive region.

11. The back contact solar cell of claim 1 wherein, The number of the first pit regions that are at least partially collinear in the second direction within one first conductive region is greater than or equal to 1.

12. The back contact solar cell of claim 1 wherein, The current collecting grid lines include first current collecting grid lines corresponding to the positions of the first conductive regions, and the first current collecting grid lines include recessed current collecting grid lines and / or flat current collecting grid lines. At least one first pit region is present at the position corresponding to the recessed current collecting grid line on the first conductive region. No first pit region is present at the position corresponding to the flat current collecting grid line on the first conductive region.

13. The back contact solar cell of claim 1 wherein, The space between adjacent first pit regions has first protruding particles protruding away from the silicon substrate; and / or, The space between adjacent first pits has second protruding particles protruding away from the silicon substrate. And / or, The bottom of the first pit has third protruding particles protruding away from the silicon substrate.

14. A method of fabricating a back contact solar cell, characterized by, It includes: Forming a second doped layer on the first surface of the silicon substrate; The first surface includes first conductive regions and second conductive regions arranged alternately in a first direction; Laser patterning the second doped layer to remove the part of the second doped layer on the first conductive region, so that the first conductive region is exposed and a first pit region recessed into the silicon substrate is formed on the first conductive region, and the first pit region includes a plurality of first pits; in a second direction, a space is formed between adjacent first pit regions; the second direction is different from the first direction and perpendicular to the direction of the thickness of the silicon substrate; Forming a doped layer on the first surface; the doped layer includes a first doped polysilicon layer and a second doped polysilicon layer; the first doped polysilicon layer covers the first conductive region, and the second doped polysilicon layer covers the second conductive region; A first tunneling layer is located between the first conductive region and the first doped polysilicon layer, and a second tunneling layer is located between the second conductive region and the second doped polysilicon layer; Forming current collecting grid lines on the doped layer.

15. A photovoltaic module, characterized by It includes: A battery string includes a plurality of back contact solar cells according to any one of claims 1 to 14.

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