Back contact solar cell, preparation method thereof and photovoltaic module

Abstract

The invention provides a back contact solar cell, a preparation method thereof and a photovoltaic module, and relates to the field of photovoltaic technology. The back contact solar cell comprises a silicon substrate, wherein the silicon substrate comprises a first surface and a second surface which are opposite; the first surface comprises first conductive regions and second conductive regions which are alternately arranged in the first direction; the first conductive region is provided with a first pit region which is recessed into the silicon substrate; the first pit area comprises a plurality of first pits; in the second direction, a gap is formed between every two adjacent first pits; the doped layer is located on the first surface. According to the back contact solar cell, optimization and balance of the light absorption efficiency of the silicon substrate, the contact performance of the doping layer and the collector grid lines and the passivation performance are at least achieved, and the efficiency of the back contact solar cell is improved.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaic technology, and in particular to a back-contact solar cell and a preparation method thereof, and a photovoltaic module. Background Art

[0002] Back-contact solar cells can make full use of sunlight due to their structure without grid lines on the light-facing side, making them more efficient. In addition, due to their structure without grid lines on the light-facing side, the appearance of the component end is more beautiful, so they have broad application prospects.

[0003] The flat backlight surface of the silicon substrate in the back-contact solar cell is conducive to the formation of a high-quality passivation film layer. However, an overly flat back surface is not conducive to the contact of the slurry, resulting in poor carrier transport performance and reduced cell efficiency. How to ensure high passivation performance while having good slurry contact performance is a problem that needs to be solved urgently. The present invention proposes a new thinking direction and solution. Summary of the invention

[0004] The present invention provides a back-contact solar cell and a preparation method thereof and a photovoltaic module, aiming to solve the problem of the contradiction between high passivation performance and good slurry contact performance in the 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: first conductive areas and second conductive areas alternately arranged along a first direction;

[0007] The first conductive region has a first concave region that is concave into the silicon substrate; the first concave region includes: a plurality of first concave pits;

[0008] In the second direction, there is a gap between adjacent first pit areas; the second direction is different from the first direction, and both are perpendicular to the direction where the thickness of the silicon substrate is located;

[0009] a doping layer, wherein the doping layer covers the first surface;

[0010] A plurality of collector grid lines are in electrical contact with the doped layer.

[0011] In the present application, on the first aspect, the first pit is recessed into the silicon substrate, and at least part of the inner surface of the first pit is not perpendicular to the direction of the thickness of the silicon substrate. Therefore, among all the light rays entering the silicon substrate from the light-facing surface of the silicon substrate, the light rays with an incident angle less than 90° will be reflected into the silicon substrate through the at least part of the inner surface mentioned above, and will be reflected multiple times in the silicon substrate. Compared with the existing back-contact solar cells in which the backlight surface is a polished surface and only has approximately two reflections, the number of reflections in the present application is significantly more than 2 times, which increases the transmission distance of light in the silicon substrate, thereby increasing the light absorption efficiency of the silicon substrate and improving the photoelectric conversion efficiency of the back-contact solar cell. On the second aspect, the doping layer covers the first surface, and therefore, there are also unevenness on the surface of the doping layer away from the silicon substrate, that is, the doping layer also has an uneven surface. On the one hand, the uneven surface increases the specific surface area in contact with the electrode slurry of the collector grid line, optimizes the contact performance between the doping layer and the collector grid line, and improves the current conduction effect; on the third hand, in the second direction, there is a gap between the adjacent first pit areas, the gap is flatter than the first pit area, and the quality of the part of the film layer formed on the gap in the back passivation layer is better, which improves the density of the passivation layer, improves the passivation performance, and reduces the carrier recombination; on the fourth hand, the above-mentioned first pit areas on the first conductive area have a gap arrangement along the second direction, which can balance the collection range or collection distance of the current or carriers in the first conductive area, avoid the performance loss caused by the long-distance transmission caused by the concentration of the pit areas, and can also minimize the color difference in the appearance of the battery cell caused by the random appearance of the pit areas. In summary, the present application at least achieves the optimal balance of the light absorption efficiency of the silicon substrate, the contact performance of the doping layer and the collector grid line, and the passivation performance, improves the efficiency of the back contact solar cell, and has a better current collection effect and is more beautiful.

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

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

[0014] Laser patterning is performed on the second doped layer to remove a portion of the second doped layer located on the first conductive region, so that the first conductive region is exposed and a first concave pit region is formed on the first conductive region and is concave into the silicon substrate, wherein the first concave pit region includes: a plurality of first concave pits; spaces are formed between adjacent first concave pits in a second direction; the second direction is different from the first direction and is perpendicular to a direction where the thickness of the silicon substrate is located;

[0015] forming a doped layer on the first surface;

[0016] A collector grid line is formed on the doped layer.

[0017] According to a third aspect of the present invention, there is provided a photovoltaic module, comprising: a cell string, wherein the cell string comprises: a plurality of any of the aforementioned back-contact solar cells.

[0018] The above-mentioned back-contact solar cell and its preparation method and photovoltaic module have the same or similar beneficial effects, and in order to avoid repetition, they are not described again here. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative labor.

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

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

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

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

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

[0025] Figure 6 A schematic cross-sectional structure diagram of a back-contact solar cell in an embodiment of the present invention is shown.

[0026] Description of the accompanying drawings:

[0027] 1-first pit area, 2-first doped layer, 3-first collector grid line, 4-second collector grid line, 5-first bus grid line, 6-second bus grid line, 7-first protruding particles, 8-silicon substrate, 9-tunneling layer, 10-second doped layer, 11-back passivation anti-reflection layer. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] The present invention provides a back contact solar cell, which is combined with Figures 1 to 6 , explaining the present application. The back-contact solar cell comprises: a silicon substrate 8, a doping layer and a collector grid line. The doping layer comprises: a first doping layer 2 and a second doping layer 10. The collector grid line comprises: a first collector grid line 3 and a second collector grid line 4. The silicon substrate can be N-type monocrystalline silicon or P-type monocrystalline silicon, which can provide long-life carriers; the silicon ingot can be cut by diamond wire to obtain a silicon substrate; in order to minimize the influence of the cutting line marks on the surface recombination, the silicon substrate can be surface cleaned and polished before preparing other structures. During the normal operation of the back-contact solar cell, the surface of the silicon substrate that mainly receives light is its light-facing surface, and the backlight surface is opposite to the light-facing surface. The silicon substrate comprises a first surface and a second surface relative to each other, the first surface is the backlight surface of the silicon substrate, and the second surface is the light-facing surface of the silicon substrate.

[0030] The first doping layer 2 and the second doping layer 10 have different doping types, one of which is a P-type doping layer and the other is an N-type doping layer. The P-type doping layer may contain one or more of the IIIA group elements (for example, boron). The N-type doping layer may contain one or more of the VA group elements (for example, phosphorus). The materials of the N-type doping layer and the P-type doping layer may include any semiconductor material such as silicon, silicon germanium, germanium or gallium arsenide. In terms of the arrangement of the material, the crystal phase of the doping layer may be amorphous, microcrystalline, nanocrystalline, single crystal or polycrystalline. Among them, the materials of the N-type doping layer and the P-type doping layer may be the same or different. For example: the materials of the N-type doping layer and the P-type doping layer may both be doped polycrystalline silicon. For another example: the material of the P-type doping layer may include at least one of doped amorphous silicon, doped microcrystalline silicon and doped nanocrystalline silicon, and the material of the N-type doping layer may be doped polycrystalline silicon. For another example: the material of the P-type doping layer may be doped single crystal silicon, that is, diffused and formed on the surface of the P region of the silicon substrate, and the material of the N-type doping layer may be doped polycrystalline silicon. The P-type doped layer can be prepared by in-situ doping or ex-situ doping. The N-type doped layer can also be prepared by in-situ doping or ex-situ doping.

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

[0032] The first surface of the silicon substrate 8 includes: a first conductive area and a second conductive area alternately arranged along the first direction L1, where the alternation means that along the first direction L1, a first conductive area is followed by a second conductive area, and then a first conductive area is distributed in this way. The first conductive area has a first pit area 1 that is recessed into the silicon substrate, and the first pit area 1 includes a plurality of first pits; in the second direction L2, there is a gap between adjacent first pit areas 1. The second direction L2 is different from the first direction L1, and both are perpendicular to the direction where the thickness of the silicon substrate is located. The angle between the second direction L2 and the first direction L1 is not specifically limited, for example, they can be perpendicular to each other, or nearly perpendicular.

[0033] The doping layer covers the first surface, and specifically, the second doping layer 10 is located on the second conductive region. The first doping layer 2 is located on the first conductive region. Figure 6 In the first surface of the silicon substrate 8, the area corresponding to the first doped layer 2 is the first conductive area, and the area corresponding to the second doped layer 10 is the second conductive area. The first collector gate line 3 is in electrical contact with the first doped layer 2, and the second collector gate line 4 is in electrical contact with the second doped layer 10. The first collector gate line 3 and the second collector gate line 4 are used to collect carriers.

[0034] In order to increase the light absorption rate of the silicon substrate, the first conductive region and the second conductive region of the existing back-contact solar cell are usually flat polished surfaces, so that at least part of the light reaching the backlight surface of the silicon substrate can be reflected back into the silicon substrate through the smooth polished surface, thereby improving the utilization rate of light. However, on the one hand, the transmission distance of the light reflected back into the silicon substrate by the backlight surface of the silicon substrate is only approximately equal to twice the thickness of the silicon substrate, and the transmission distance of light in the silicon substrate is short, resulting in low light absorption efficiency of the silicon substrate, which is not conducive to improving the photoelectric conversion efficiency of the back-contact solar cell. On the other hand, the backlight surface of the silicon substrate is relatively smooth, and the surface of the doping layer formed thereon is also relatively flat, and the contact specific surface area with the collector grid line is small, and the contact performance is poor. In summary, the existing back-contact solar cells have low light absorption efficiency and poor contact performance, which affects the performance of the back-contact solar cells.

[0035] In response to the above technical problems, in the present application, on the first hand, the first pit is recessed into the silicon substrate, and at least part of the inner surface of the first pit is not perpendicular to the direction of the thickness of the silicon substrate. Therefore, among all the light rays entering the silicon substrate from the light-facing surface of the silicon substrate, the light rays with an incident angle less than 90° will be reflected back into the silicon substrate through the above at least part of the inner surface, and will be reflected multiple times in the silicon substrate. Compared with the existing back-contact solar cells in which the backlight surface is a polished surface and only has approximately two reflections, the number of reflections in the present application is significantly more than 2 times, which increases the transmission distance of light in the silicon substrate, thereby increasing the light absorption efficiency of the silicon substrate and improving the photoelectric conversion efficiency of the back-contact solar cell. On the second hand, the doped layer covers the first surface, and therefore, there are also unevenness on the surface of the doped layer away from the silicon substrate, that is, the doped layer located on the first surface also has unevenness. On the uneven surface, the uneven surface increases the specific surface area in contact with the electrode paste of the collector grid line, optimizes the contact performance between the doped layer and the collector grid line, and improves the current conduction effect; thirdly, in the second direction L2, there are intervals between the adjacent first pit areas 1, the intervals are flatter than the first pit areas, and the quality of the partial film layer formed on the intervals in the back passivation layer is good, which improves the compactness of the passivation layer, improves the passivation performance, and reduces the carrier recombination; fourthly, the above-mentioned first pit areas on the first conductive area have an interval arrangement along the second direction, which can balance the collection range or collection distance of the current or carriers in the first conductive area, avoid the performance loss caused by the long-distance transmission caused by the concentration of the pit areas, and can also reduce the color difference in the appearance of the battery cell caused by the random appearance of the pit areas as much as possible. In summary, the present application at least achieves the optimization balance of the light absorption efficiency of the silicon substrate, the contact performance of the first doped layer 2 and the first collector grid line 3, and the passivation performance, improves the efficiency of the back contact solar cell, and has a better current collection effect and is more beautiful.

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

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

[0038] Optionally, the doping layer is conformal to the morphology of the first surface, that is, the portion of the first doping layer corresponding to the first pit area may be rougher and have more unevenness, the portion of the first doping layer corresponding to the interval may be relatively flat, and the second doping layer on the second conductive area may be relatively flat, so that in the second direction L2, good contact performance is obtained at the unevenness and better passivation performance is obtained at the relatively flat position.

[0039] Optionally, in the first direction L1, there are gaps between adjacent first pit areas, and then in the first direction L1, the doping layer located on the first surface also has an uneven surface, and the uneven surface increases the specific surface area in contact with the electrode slurry of the collector grid line, optimizes the contact performance between the doping layer and the collector grid line, and improves the current conduction effect; in addition, in the first direction L1, there are gaps between adjacent first pit areas 1, and the gaps are flatter than the first pit areas. The quality of the partial film layer formed on the gap in the back passivation layer is better, which improves the density of the passivation layer, improves the passivation performance, and reduces carrier recombination. In summary, the present application at least achieves the optimal balance of the light absorption efficiency of the silicon substrate, the contact performance of the first doping layer 2 and the first collector grid line 3, and the passivation performance, and improves the efficiency of the back contact solar cell.

[0040] Optionally, in the first concave region, the cross-section perpendicular to the direction of the thickness of the silicon substrate is in one of the following shapes: L-shaped, I-shaped, and dot-shaped. On the one hand, the first concave region of the above shape is easy to form by laser, and on the other hand, the first concave region of the above shape has a strong reflection effect on light. It should be noted that, on the first conductive region, the orientations of the L-shaped and I-shaped can be the same or different, and there is no specific limitation on this.

[0041] Optionally, the proportion of the projection area of ​​all the first pits on the first surface in a first conductive region to the area of ​​the first conductive region is the first proportion. For a first conductive region, here the projection areas of all the first pits on it on the first surface are summed to obtain the total area, and then the total area is divided by the area of ​​the first conductive region to obtain the first proportion. Along the first direction L1, the first proportions corresponding to the various first conductive regions are distributed alternately in size. Usually, the areas of the various first conductive regions are roughly equal. The first proportion is larger, indicating that the projection size of all the first pits on the first surface in the first conductive region is larger, or the number of the first pits is larger, and the first conductive region is relatively more uneven, which contributes more to the contact performance with the first doping layer and the first collector grid line, and the light absorption efficiency. The first proportion is smaller, indicating that the projection size of all the first pits on the first surface in the first conductive region is smaller, or the number of the first pits is smaller, and the first conductive region is relatively flat, which contributes more to the improvement of the passivation performance with the back passivation layer. The light absorption efficiency, contact performance and passivation performance are all taken into account, which can improve the performance of the back contact solar cell.

[0042] Optionally, the size alternating distribution here may include: along the first direction L1, a large first ratio followed by a small first ratio is alternately distributed, that is, along the first direction L1, a relatively uneven first conductive area, then a relatively flat first conductive area, then a relatively uneven first conductive area, and then a relatively flat first conductive area are alternately distributed; or, the size alternating distribution here may include: along the first direction L1, two large first ratios, followed by two small first ratios are alternately distributed, that is, along the first direction L1, two consecutive relatively uneven first conductive areas, followed by two consecutive relatively flat first conductive areas, then two consecutive relatively uneven first conductive areas, and then two consecutive relatively flat first conductive areas are alternately distributed. The above size alternating distribution mode is easy to realize through laser technology on the one hand, and on the other hand, when each structure on the first conductive area is conformal with the first conductive area, the morphological distribution law of the backlight surface of the back contact solar cell is more beautiful.

[0043] Optionally, among the first ratios that are alternately distributed in size, the ratio of the large first ratio to the small first ratio adjacent to it is greater than 1 and less than or equal to 3. Within this range, the ratio of the two can achieve better light absorption efficiency, contact performance, and passivation performance, which can improve the performance of back-contact solar cells. On the other hand, it is easy to implement and the process is relatively simple. Among the ratios that are alternately distributed in size, the large first ratio is greater than the small first ratio adjacent to it. Whether the large first ratio is greater than the small ratio that is not adjacent to it is not specifically limited, and it can be greater or less than it.

[0044] For example, among the first proportions that are alternating in size here, the ratio of a large first proportion to its adjacent small 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 another example, among the first proportions of alternating large and small distributions, the large first proportion may be 0.1%, 0.5%, 0.9%, 1%, 10%, 15%, 30%, 40%, 50%, 60%, 70%, 65%, 80%, and the small first proportion may be 0.1%, 0.5%, 0.8%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%. It should be noted that in the process of determining the specific values ​​of the large first proportion and the small first proportion, it is necessary to satisfy that the ratio of the large first proportion to its adjacent small first proportion is greater than 1 and less than or equal to 3.

[0046] Optionally, along the first direction L1, the first ratios corresponding to the various first conductive areas present a trend of gradually decreasing or increasing, that is, along the first direction L1, the various first ratios decrease or increase successively; alternatively, along the first direction L1, the first ratios corresponding to the various first conductive areas present approximately equal areas, that is, along the first direction L1, the various first ratios are basically equal in size; along the first direction L1, the changing trends of the first ratios corresponding to the various first conductive areas are flexible and diverse, and can be selected accordingly according to actual needs and process levels.

[0047] Optionally, the first surface of the silicon substrate further includes: a third conductive region, the third conductive region intersects with the first conductive region and the second conductive region, a busbar line is disposed on the third conductive region, and the busbar line extends along the first direction L1, referring to Figure 3 , the busbar lines include a first busbar line 5 and a second busbar line 6. The first busbar line 5 is electrically connected to the first collector gate line 1; the busbar line extends along the first direction L1, which means that if the busbar line is a straight line, all the busbar lines extend along the first direction L1, and if the busbar line is composed of multiple line segments, or the busbar line contains a curved portion, then the line segment portion of the busbar line has a portion extending along the first direction L1. Here, the first busbar line 5 and the first collector gate line 1 can be electrically connected by intersecting, and here, the second busbar line and the second collector gate line can be electrically connected by intersecting. The third conductive area has a second pit area that is recessed into the silicon substrate; the second pit area includes: a plurality of second pits, and the number of second pits in a second pit area is not specifically limited. In the first direction L1, there is a gap between adjacent second pit areas, and the above-mentioned second pit areas on the third conductive area are arranged in a gap along the first direction, which can balance the collection range or collection distance of the current or carriers in the third conductive area, avoid the performance loss caused by the long-distance transmission caused by the concentration of the pit areas, and can also reduce the color difference in the appearance of the battery cell caused by the random appearance of the pit areas as much as possible. In a third conductive area, the proportion of the projection area of ​​all second pits on the first surface to the area of ​​the third conductive area is the second proportion. For a third conductive area, here is to sum up the projection areas of all second pits on the first surface to obtain the total area, and then divide the total area by the area of ​​the third conductive area to obtain the second proportion. Along the second direction L2, the ratio of the second proportion corresponding to each third conductive area to the mean value of the second proportion corresponding to each third conductive area is greater than or equal to 0.97 and less than or equal to 1.03, that is, along the second direction L2, the second proportions corresponding to each third conductive area are basically equal, so the contact performance of each third conductive area is improved more evenly, and the process is easy to implement.

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

[0049] It should be noted that, in the case where the first surface of the silicon substrate further includes a third conductive region, the aforementioned first ratio refers to the ratio of the projection area of ​​all first pits on the first surface in a portion other than the overlapped portion of the first conductive region and the third conductive region to the area of ​​the first conductive region other than the overlapped portion of the first conductive region and the third conductive region. At the same time, the aforementioned second ratio refers to the ratio of the projection area of ​​all second pits on the first surface in a portion other than the overlapped portion of the third conductive region and the first conductive region to the area of ​​the third conductive region other than the overlapped portion of the first conductive region and the first conductive region.

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

[0051] For example, in a third conductive region, the second proportion of the projection area of ​​all 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 corresponding position where the first conductive region and the third conductive region overlap, the total area of ​​the projection area of ​​all the first pits and all the second pits on the first surface accounts for a third ratio of the area at the overlapping position of the first conductive region and the third conductive region, and for the same third conductive region, the third ratio is greater than the second ratio. The third ratio refers to: at the corresponding position where the first conductive region and the third conductive region overlap, the total area obtained by summing the projection area of ​​all the first pits on the first surface and the projection area of ​​all the second pits on the first surface is divided by the area at the overlapping position of the first conductive region and the third conductive region, and the ratio is obtained. That is to say, at the corresponding position where the third conductive region and the first conductive region overlap, it is more uneven. Since the collector grid line and the bus grid line are both correspondingly arranged at the overlapping position, the contact performance of the collector grid line and the bus grid line is improved here. The more unevenness here can effectively improve the contact performance of the collector grid line and the bus grid line at the same time, thereby improving the performance of the back contact solar cell.

[0053] The overlapping position of the first conductive region and the third conductive region refers to a 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 total area of ​​the projection areas of all the first pits and all the second pits on the first surface accounts for a third proportion of the area at the overlapping position of the first conductive region and the third conductive region, and the ratio of the projection areas of all the second pits in the third conductive region on the first surface to the second proportion of the area of ​​the third conductive region is greater than 1 and less than or equal to 3. That is, at the corresponding overlapping position of the first conductive region and the third conductive region, the surface is more uneven, and thus the contact performance of the collector grid line and the bus grid line can be effectively improved at this position, thereby improving the performance of the back-contact solar cell, and the difference in unevenness is not too large, and it is easy to implement on the basis of compatibility 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 another example, the third ratio may be: 0.1%, 0.5%, 0.9%, 1%, 1.3%, 5%, 10%, 20%, 30%, 40%, 45%, 50%, 60%, 70%, 75%, 80%, 55%, 90%.

[0057] Optionally, the number of first pit regions at least partially collinear along the second direction L2 in a first conductive region is greater than or equal to 1, the first pit regions at least partially collinear along the second direction L2 in a first conductive region are most likely formed under the action of laser scanning in the same direction, the number of first pit regions at least partially collinear along the second direction L2 in a first conductive region is greater than or equal to 1, and the efficiency of laser forming the first pit regions is high. For example, Figure 1 Assuming that this is a schematic diagram of a first conductive region, the number of first concave regions 1 at least partially collinear along the second direction L2 in the first conductive region is 4. It can also be 1, 2, 3, 5 or even more, which is not specifically limited.

[0058] Optionally, the collector grid line includes: a first collector grid line corresponding to the position of the first conductive region, and the first collector grid line includes: a concave collector grid line and / or a flat collector grid line. Figure 1 , at least one first concave pit region 1 is provided at a position corresponding to the concave collector gate line on the first conductive region. Figure 2There is no first pit area at the position corresponding to the flat collector gate line on the first conductive area, or the flat collector gate line misses the above-mentioned first pit area. The two gate line settings can meet the purpose of increasing the contact area between the gate line and the doping layer, improving the surface bonding force between the gate line and the doping layer, and eliminating the need for strict alignment of the collector gate line and the first pit area, thereby reducing the process difficulty and improving the process window.

[0059] Optional, see Figure 4 and Figure 5 The intervals between adjacent first pit areas 1 have first protruding particles 7 protruding in a direction away from the silicon substrate, and / or, between adjacent first pits, there are second protruding particles protruding in a direction away from the silicon substrate. The outer surfaces of the first protruding particles 7 and the second protruding particles can reflect part of the light reaching the silicon substrate back to the silicon substrate, thereby increasing the light absorption efficiency. On the other hand, the first protruding particles 7 and the second protruding particles here also have a large specific surface area, which can increase the contact performance of the gate line and further improve the performance of the back contact solar energy. It should be noted that Figure 4 and Figure 5 All are scanning electron microscope (SEM) images.

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

[0061] Optionally, the maximum dimension of the cross section of the first protruding particle 7 is 0.01 μm to 1 μm, and the maximum dimension of the cross section of the first protruding particle 7 is the distance between the two farthest endpoints of the first protruding particle 7 in the projection of a plane perpendicular to the protruding direction of the first protruding particle; the cross section of the first protruding particle 7 is perpendicular to the protruding direction of the first protruding particle; and / or, the minimum dimension of the cross section of the first protruding particle 7 is 0.01 μm to 0.5 μm, and the minimum dimension of the cross section of the first protruding particle 7 is the distance between the two closest endpoints of the first protruding particle 7 in the projection of a plane perpendicular to the protruding 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 protruding 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 minimum 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 maximum circumscribed circle of the cross section of the first protruding particle. The cross section where the minimum dimension of the cross section of the first protruding particle is located can be the same cross section as the cross section where the maximum dimension of the cross section of the first protruding particle is located, or a different cross section. The maximum dimension of the cross section of the first protruding particle 7 and the direction where the minimum dimension of the cross section of the first protruding particle 7 are located 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. The size of the first protruding particle 7 is within the above range. On the one hand, it has a more obvious effect on improving the utilization rate of light and the contact performance, and on the other hand, it is easy to process and realize.

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

[0063] It should be noted that the maximum dimension of the cross section of the second raised particles here is 0.01μm to 1μm, and / or the minimum dimension of the cross section of the second raised particles is 0.01μm to 0.5μm, and / or the height of the second raised particles is 0.01μm to 1μm; the method for determining the relevant dimensions of the second raised particles is the same as the method for determining the relevant dimensions of the aforementioned first raised particles. In order to avoid repetition, they will not be repeated here.

[0064] Optionally, the bottom of the first pit has a third protruding particle protruding in a direction away from the silicon substrate; the bottom of the first pit is opposite to the opening of the first pit, that is, the bottom of the first pit is closer to the inside of the silicon substrate, and the outer surface of the third protruding particle can reflect part of the light reaching the silicon substrate back to the silicon substrate, thereby increasing the light absorption efficiency and further improving the performance of the back contact solar energy. The opening of the first pit is located at the junction of the first pit and the first conductive area, and the bottom of the first pit is closer to the second surface of the silicon substrate than the opening of the first pit.

[0065] Optionally, the shape of the third protruding particles is one of a regular pyramid, an ellipsoid, a sphere, and an irregular shape. The shape of the third protruding particles is flexible and diverse, and can be applied to a variety of preparation methods.

[0066] Optionally, the maximum dimension of the cross section of the third raised particle is 0.1 μm to 5 μm; the cross section of the third raised particle is perpendicular to the raised direction of the third raised particle; and / or the minimum dimension of the cross section of the third raised particle is 0.1 μm to 3 μm; and / or the height of the third raised particle is 0.1 μm to 3 μm; the direction of the height is parallel to the raised direction of the third raised particle. The maximum dimension of the cross section of the third raised particle and the direction of the minimum dimension of the cross section of the third raised particle can be parallel or intersecting, etc., without limitation. For the same third raised particle, the maximum dimension of the cross section is greater than or equal to the minimum dimension of the cross section. The size of the third raised particle is within the above range, which has a more obvious effect on improving the utilization rate of light, and is easy to process and realize on the other hand.

[0067] It should be noted that the method for determining the relevant dimensions of the third protruding particles is the same as the method for determining the relevant dimensions of the aforementioned first protruding particles. In order to avoid repetition, it will not be repeated here. For example, the maximum dimension of the cross section of the third raised particle may be 0.1 μm, 0.3 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, or 5 μm; the minimum dimension of the cross section of the third raised particle may be 0.1 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 1.6 μm, 2.4 μm, or 2.45 μm; the height of the third raised particle may be 0.1 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 1.4 μm, 1.45 μm, 2.55 μm, 1.6 μm, 2.7 μm, 1.8 μm, or 1.9 μm.

[0068] It should be noted that the bottom of the second pit has a fourth protruding particle protruding in the direction away from the silicon substrate; the bottom of the second pit is opposite to the opening of the second pit, the opening of the second pit is located at the junction of the second pit and the third conductive area, and the bottom of the second pit is closer to the second surface of the silicon substrate than the opening of the second pit, that is, the bottom of the second pit is closer to the inside of the silicon substrate, and the outer surface of the fourth protruding particle can reflect part of the light reaching the silicon substrate back to the silicon substrate, thereby increasing the light absorption efficiency and further improving the performance of the back contact solar energy. The shape of the fourth protruding particle is one of the four shapes of a regular pyramid, an ellipsoid, a sphere, and an irregular shape.

[0069] Optionally, the maximum dimension of the cross section of the fourth raised particle is 0.1 μm to 5 μm; the cross section of the fourth raised particle is perpendicular to the protrusion direction of the fourth raised particle; and / or the minimum dimension of the cross section of the fourth raised particle is 0.1 μm to 3 μm; and / or the height of the fourth raised particle is 0.1 μm to 3 μm; the method for determining the relevant dimensions of the fourth raised particle is the same as the method for determining the relevant dimensions of the aforementioned first raised particle, and in order to avoid repetition, it will not be repeated here.

[0070] Optionally, in the first direction, there are also protruding particles at the intervals between adjacent second pit areas, and the shape, size, etc. of the protruding particles can refer to the first protruding particles at the intervals between the aforementioned adjacent first pit areas, which will not be repeated here. Optionally, there are also protruding particles between adjacent second pits, and the shape, size, etc. of the protruding particles can refer to the second protruding particles at the intervals between the aforementioned adjacent first pits, which will not be repeated here.

[0071] Optionally, the first concave pit is one of the following shapes: a quasi-inverted pyramid, a quasi-inverted prism, a hemispherical shape, and an irregular shape. The shape of the first concave pit is flexible and can be applied to a variety of preparation methods. The quasi-inverted pyramid here can be a quasi-inverted triangular pyramid, a quasi-inverted quadrangular pyramid, a quasi-inverted pentagonal pyramid, and the like.

[0072] Optionally, the second pit is one of the following shapes: a quasi-inverted pyramid, a quasi-inverted prism, a hemispherical shape, and an irregular shape. The shape of the second pit is flexible and can be applied to a variety of preparation methods. The quasi-inverted pyramid here can be a quasi-inverted triangular pyramid, a quasi-inverted quadrangular pyramid, a quasi-inverted pentagonal pyramid, and the like.

[0073] Optionally, the cross-sectional area of ​​the first pit increases along the direction away from the silicon substrate, and the cross-sectional area of ​​the first pit is perpendicular to the direction of the thickness of the silicon substrate, which is conducive to the complete discharge of the etchant and reaction impurities used to clean the first pit after the first pit is formed, and is conducive to preventing leakage and other problems caused by the above-mentioned etchant and reaction impurities remaining in the first pit, thereby improving the electrical performance of the back-contact solar cell. At the same time, it is also conducive to the subsequent preparation of the film layer formed on the surface of the first conductive area, and the film formation quality of the film layer can be improved. In addition, along the direction away from the silicon substrate, the cross-sectional area of ​​the first pit increases, and the angle between at least most of the inner surface of the above-mentioned first pit and the plane perpendicular to the thickness of the silicon substrate is an obtuse angle, which can increase the reflection probability of the light transmitted to the first pit, and improve the utilization rate of the light, and further improve the photoelectric conversion efficiency of the back-contact battery. The increase method here is not limited, and can be linear increase, exponential increase, etc.

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

[0075] Optionally, the size of the cross section of the first pit is: 0.01μm to 20μm, and the cross section is perpendicular to the concave direction of the first pit; and / or, the depth of the first pit area is 0.01μm to 20μm; the direction of the depth is parallel to the concave direction of the first pit. The size of the cross section of the first pit can be understood as the distance between the two farthest endpoints in the projection of the first pit on the plane perpendicular to the thickness direction of the silicon substrate. When the size of the first pit is within the above range, the effect of improving the utilization rate of light is more obvious, and on the other hand, it is easy to process and realize.

[0076] For example, the minimum size of the cross section of the first pit can be 0.01 μm, 0.1 μm, 0.3 μm, 0.5 μm, 1 μm, 3 μm, 5 μm, 8 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 10 μm, 6.5 μm, 11 μm, 12 μm, 13 μm, 15 μm, 16 μm, 18 μm, 20 μm; the maximum size of the cross section of the first pit can be 0.5 μm, 1 μm, 15 μm, 20 μm, 2.5 μm, 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 size of the cross section of the second pit is: 0.01μm to 20μm, and the cross section is perpendicular to the recessed direction of the second pit; and / or the depth of the second pit area is 0.01μm to 20μm, which has the same or similar beneficial effects as the first pit, and will not be repeated here to avoid repetition.

[0078] Reference Figure 6 , the back contact solar cell further comprises: a tunneling layer 9, the tunneling layer 9 is located between the first surface and the doped layer, and the tunneling layer 9 comprises: a first tunneling layer, located between the first conductive region and the first doped layer; the first tunneling layer is conformal to the first conductive region, that is, 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 conformal to the second conductive region. For example, Figure 6 In the embodiment, the second conductive region is flatter than the first conductive region, so the surface of the second tunneling layer is also relatively flat. The materials of the first tunneling layer and the second tunneling layer can be selected from at least one of silicon oxide, silicon carbide, silicon nitride and aluminum oxide, and the first tunneling layer and the second tunneling layer have good passivation tunneling effect. Conformal here means that where there are pits in the first conductive region, there are pits at the corresponding positions of the first tunneling layer, and the second conductive region is similar in shape to the second tunneling layer.

[0079] Optional, see Figure 6 , the tunneling layer is conformal to the doping layer, that is, the first doping layer is conformal to the first tunneling layer, and the position of the first doping layer 2 corresponding to the pit area of ​​the first tunneling layer also has a pit area; and / or, the second doping layer is conformal to the second tunneling layer. For example, Figure 6In the embodiment, the second tunnel layer is flatter than the first tunnel layer, so the surface of the second doping layer 10 is also relatively flat. Conformal here means that where there is a pit in the first tunnel layer, there is also a pit at the corresponding position of the first doping layer, and the second tunnel layer is similar in shape to the second doping layer. Here, the first pit on the first conductive region is transferred to the first doping layer through the first tunnel layer, which makes it easy to achieve conformal between the first doping layer and the first conductive region.

[0080] Optional, see Figure 6 , the back contact solar cell also includes: a back passivation anti-reflection layer 11; located between the doped layer and the collector grid line, the collector grid line will penetrate the back passivation anti-reflection layer and make electrical contact with the doped layer; the back passivation anti-reflection layer is conformal or non-conformal with the doped layer adjacent to it, that is, the portion of the back passivation anti-reflection layer located in the first doped layer can be conformal with the first doped layer and may have pits, and the portion of the back passivation anti-reflection layer located in the second doped layer is conformal with the second doped layer and is relatively flat. The back passivation anti-reflection layer can provide good back passivation and anti-reflection effects. The material of the back passivation anti-reflection layer can be selected from silicon oxide, silicon carbide, silicon nitride and aluminum oxide, etc., and there is no specific limitation on this.

[0081] Optional, see Figure 6 The first surface also includes: an isolation region between the first conductive region and the second conductive region adjacent thereto, the isolation region can avoid short circuits in the back contact solar cell, the isolation region has a third concave region recessed into the silicon substrate, the third concave region here is similar to the aforementioned first concave region and can increase light utilization. The third concave region here includes a plurality of third concave pits, the distribution mode, morphology, etc. of the third concave pits can correspond to the distribution mode, morphology, etc. of the aforementioned first concave pits, and the morphology of the third concave region here is not specifically limited.

[0082] In the present application, the second conductive area may be a polished surface or a velvet structure, which is not specifically limited. The second surface of the silicon substrate, that is, the light-facing surface of the silicon substrate, may be a velvet structure, etc., which is also not specifically limited. The back-contact solar cell may also include: a front passivation anti-reflection layer located on the second surface, the front passivation anti-reflection layer may improve the passivation anti-reflection effect of the front side, and its specific material is not limited.

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

[0084] Step 101: forming a whole second doping layer on a first surface of a silicon substrate; the first surface comprises: first conductive regions and second conductive regions alternately arranged along a first direction.

[0085] The first conductive region and the second conductive region here refer to the above-mentioned related records, and will not be described again to avoid repetition. The second doped layer can be prepared by: low pressure chemical vapor deposition technology (LPCVD) or plasma enhanced chemical vapor deposition technology (PECVD). It should be noted that in the case of having a second tunneling layer, the second tunneling layer and the second doped layer can be prepared together, for example, doping atoms are diffused on the second tunneling layer to form a boron-doped polysilicon structure or / and a phosphorus-doped polysilicon structure to form a second doped layer.

[0086] It should be noted that before preparing the second doping layer, the original silicon wafer can also be subjected to alkali polishing in a slot machine to form a tower base morphology on the surface of the silicon wafer to form a silicon substrate. The original silicon wafer here can be a P-type original silicon wafer or an N-type original silicon wafer, and the original silicon wafer refers to a silicon wafer cut from a silicon rod or the like. In the tower base morphology here, the size of the cross section of the tower base structure can be 5 μm to 30 μm, and the cross section is perpendicular to the direction of the thickness of the silicon substrate, and the longitudinal dimension of the tower base can be 0.01 μm to 8 μm, and the longitudinal dimension is parallel to the direction of the thickness of the silicon substrate.

[0087] Step 102, laser patterning 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 on the first conductive region that is recessed into the silicon substrate, wherein the first pit region includes: a plurality of first pits; in a second direction, gaps are formed between adjacent first pit regions; the second direction is different from the first direction and is perpendicular to the direction in which the thickness of the silicon substrate is located.

[0088] The laser processes the portion of the second doped layer located on or within the first conductive region, and the laser energy acts on the surface phosphorus / borosilicate glass layer to produce a surface modification effect, or directly remove the portion to be eliminated. In a first conductive region, the laser processing pattern can be designed as a single line, a double spliced ​​line, a triple spliced ​​line, etc., according to the actual laser spot size. There can be a certain percentage of overlap between different spliced ​​lines, and there is also a certain percentage of overlap between adjacent spots.

[0089] Optionally, the number of laser overlaps is greater than or equal to 2 times. After greater than or equal to 2 times, the position absorbs more laser energy and is easier to clean in the subsequent cleaning process. For example, the number of laser overlaps can be 2 times, 3 times, 4 times, 5 times, 6 times, 7 times, 8 times, 9 times, and 10 times.

[0090] Optionally, in laser patterning: the light wave selected by the laser is light within the band of 300nm, 400nm, 500nm, 700nm, 800nm, 900nm, 1000nm, 1100nm, 1300nm, and 1400nm; and / or the power of the laser 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 square, rectangle, prism, and circle; and / or the longest side of the laser spot can be 100μm, 120μm, 150μm, 180μm, 190μm, 200μm, 250μm, 300μm, and the shortest side can be 80μm, 100μm, 120μm, 150μm, 180μm, 200μm, 250μm, 280μm, 300μm.

[0092] Optionally, the laser scanning is at least one of single-line scanning, double-line scanning, and 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%, 95%; and / or, the overlap rate between adjacent laser spots can be: 3%, 5%, 10%, 30%, 40%, 50%, 60%, 70%, 80%, 55%, 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%, 5%, the energy difference of a single laser spot is small, and it is easy to control the formation position of the pit area.

[0093] Optionally, during the patterning process, in the cleaning process after laser scanning, the alkaline etching temperature can be: 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 54°C, 68°C, 80°C; 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 in the present application, there is no specific limitation on the method for forming the second concave pit region in the third conductive region. For example, laser and other methods may be used, and there is no specific limitation on this.

[0095] The present application is further explained below in conjunction with specific embodiments.

[0096] In the first step, the N-type original silicon wafer is subjected to alkali polishing in a slot machine to form a tower base morphology on the surface of the silicon wafer. The horizontal dimension of the tower base structure is 10μm; the vertical dimension of the tower base is 0.5μm, and the silicon base is obtained, and the vertical dimension is parallel to the direction of the thickness of the silicon base.

[0097] Step 2: Prepare a tunnel passivation structure through low pressure chemical vapor deposition technology (LPCVD) and diffuse doping atoms to form a boron-doped polysilicon structure, that is, form a second doping layer.

[0098] Step 3: The portion of the second doped layer located in the first conductive region is subjected to laser patterning. Specifically, a double stitching line with a wavelength of 532nm, a power of 50W, a spot shape of a quasi-square, and a spot size of 180×180μm is used for laser processing. The overlap rate of adjacent stitching 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 to produce a surface modification effect and remove part of the borosilicate glass layer.

[0099] Step 4: Perform alkali etching in a slot machine to wash away the second doping layer in the laser processing area, and then perform cleaning to mainly remove additive residues, alkali residues, surface metal ions and other substances. As a result of this step, a first pit area is formed on the first conductive area, which is concave into the silicon substrate. The first pit area includes: a plurality of first pits; in the second direction, spaces are formed between adjacent first pits; the second direction is different from the first direction, and both are perpendicular to the direction of the thickness of the silicon substrate.

[0100] Step 5: Prepare a tunnel passivation structure through low pressure chemical vapor deposition technology (LPCVD) and diffuse doping atoms to form a phosphorus-doped polysilicon structure, that is, form a first doping layer.

[0101] Step 6: Laser patterning and cleaning, mainly to remove additive residues, alkali residues, surface metal ions and other substances. In the alkali texturing process, silicon is corroded by alkali solution, and because the etching process of the chemical solution is anisotropic, a velvet pyramid structure is formed.

[0102] Step 7: Use atomic layer deposition technology (ALD) to deposit an oxide layer on the front and back of the back-contact solar cell to provide a passivation effect.

[0103] Step 8: Use plasma enhanced chemical vapor deposition technology (PECVD) to deposit anti-reflection layers on the light-facing side and the back-light side of the back-contact solar cell respectively.

[0104] Step 9: Form an electrode by screen printing, the electrode comprising: a first collector grid line and a second collector grid line, the slurry printed on the first collector grid line is located in the first conductive area, part of the first collector grid line corresponds to the first pit position, and part of the first collector grid line does not correspond to the first pit position.

[0105] Step 10: Test sorting.

[0106] The present application also provides a photovoltaic module, including a plurality of cell strings, wherein the cell strings include a plurality of any of the aforementioned back-contact solar cells. The photovoltaic module, the back-contact solar cell, and the preparation method thereof may be mutually referenced and can achieve the same or similar beneficial effects, and will not be described in detail here to avoid repetition.

[0107] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0108] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation modes, which are merely illustrative rather than restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are within the protection of the present invention.

Claims

1. A back contact solar cell, characterized in that: include: A silicon substrate, the silicon substrate comprising: a first surface and a second surface opposite to each other; the first surface comprising: first conductive areas and second conductive areas alternately arranged along a first direction; The first conductive region has a first concave region that is concave into the silicon substrate; the first concave region includes: a plurality of first concave pits; In the second direction, there is a gap between adjacent first pit areas; the second direction is different from the first direction, and both are perpendicular to the direction where the thickness of the silicon substrate is located; a doping layer, wherein the doping layer covers the first surface; A plurality of collector grid lines are in electrical contact with the doped layer.

2. The back contact solar cell according to claim 1, characterized in that: The doped layer conforms to the topography of the first surface.

3. The back contact solar cell according to claim 1, characterized in that: The ratio of the projection area of ​​all the first pits on the first surface in one first conductive region to the area of ​​the first conductive region is a first ratio; The first ratio is 0.1% to 80%.

4. The back contact solar cell according to claim 1, characterized in that: In the first direction, there is a gap between adjacent first pit areas.

5. The back contact solar cell according to claim 1, characterized in that; The first pit region has a cross-sectional shape perpendicular to the direction in which the thickness of the silicon substrate is located, which is one of an L-shaped structure, an I-shaped structure, and a dot-shaped structure.

6. The back contact solar cell according to claim 1, characterized in that: The ratio of the projection area of ​​all the first pits on the first surface in one first conductive region to the area of ​​the first conductive region is a first ratio; Along the first direction, the first proportions corresponding to the first conductive areas are distributed in alternating sizes.

7. The back contact solar cell according to claim 6, characterized in that: Among the first ratios that are alternately distributed in size, the ratio of a large first ratio to its adjacent small first ratio is greater than 1 and less than or equal to 3.

8. The back contact solar cell according to claim 1, characterized in that: The first surface also includes: A plurality of third conductive regions intersecting the first conductive region and the second conductive region; the third conductive region extending along the first direction; the third conductive region having a second concave pit region concave into the silicon substrate; the second concave pit region comprising: a plurality of second concave pits; in the first direction, there is a gap between adjacent second concave pit regions; The ratio of the projection area of ​​all the second pits on the first surface in one of the third conductive regions to the area of ​​the third conductive region is a second ratio; Along the second direction, a ratio of the second ratio corresponding to each of the third conductive regions to an average of the second ratio 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 according to claim 8, characterized in that: At the overlapping position of the first conductive region and the third conductive region, the ratio of the total area of ​​the projection areas of all the first pits and all the second pits on the first surface to the area at the overlapping position of the first conductive region and the third conductive region is a third ratio; for the same third conductive region, the third ratio is greater than the second ratio.

10. The back contact solar cell according to claim 9, characterized in that: For the same first conductive region and the same third conductive region, a ratio of the third ratio to the second ratio is greater than 1 and less than or equal to 3.

11. The back contact solar cell according to claim 1, characterized in that: The number of the first recessed areas at least partially collinear along the second direction in one of the first conductive areas is greater than or equal to 1.

12. The back contact solar cell according to claim 1, characterized in that: The collector grid lines include: a first collector grid line corresponding to the position of the first conductive area; the first collector grid lines include: a concave collector grid line and / or a flat collector grid line; There is at least one first concave pit area at a position corresponding to the concave collector gate line on the first conductive area; There is no first concave region at a position corresponding to the flat collector gate line on the first conductive region.

13. The back contact solar cell according to claim 1, characterized in that: The intervals between adjacent first pit areas have first protruding particles protruding in a direction away from the silicon substrate; and / or, Second protruding particles protruding in a direction away from the silicon substrate are provided between adjacent first pits; and / or, The bottom of the first pit has third protruding particles protruding in a direction away from the silicon substrate; the bottom of the first pit is opposite to the opening of the first pit.

14. A method for preparing a back contact solar cell, characterized in that ,,include: A second doped layer is formed on a first surface of the silicon substrate; the first surface comprises: first conductive areas and second conductive areas alternately arranged along a first direction; Laser patterning is performed on the second doped layer to remove a portion of the second doped layer located on the first conductive region, so that the first conductive region is exposed and a first concave pit region is formed on the first conductive region and is concave into the silicon substrate, wherein the first concave pit region includes: a plurality of first concave pits; in a second direction, intervals are formed between adjacent first concave pit regions; the second direction is different from the first direction and is perpendicular to a direction where the thickness of the silicon substrate is located; forming a doped layer on the first surface; A collector grid line is formed on the doped layer.

15. A photovoltaic module, characterized in that: include: A cell string, comprising: the back-contact solar cells according to any one of claims 1 to 14.

Images