Solar cell, cell assembly and photovoltaic system

Abstract

The invention is suitable for the technical field of solar cells, and provides a back contact solar cell, a cell assembly and a photovoltaic system, and the solar cell comprises a silicon wafer which comprises a first edge, a second edge, a third edge and a fourth edge; the first mark is arranged on the back face of the silicon wafer and comprises a first sub-mark close to the first edge, a second sub-mark close to the second edge and a third sub-mark close to the third edge, and the area of the first sub-mark is larger than that of the second sub-mark; wherein the first sub-mark, the second sub-mark and the third sub-mark respectively correspond to a first side latch, a second side latch and a bottom side latch of the first wet flower basket used by the first wet etching process. According to the solar cell, the first mark is arranged, so that manual judgment of generation reasons of battery appearance defects can be assisted, manual quick finding of the generation reasons of the battery appearance defects can be facilitated, and the production efficiency of the solar cell can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and particularly relates to a solar cell, a battery module and a photovoltaic system. Background Art

[0002] A solar cell is a device that directly converts light energy into electrical energy through the photovoltaic effect or the photochemical effect. During the manufacturing process of a solar cell, the back surface of the silicon wafer of the solar cell usually needs to be prepared into a polished surface by using a wet etching process.

[0003] In the prior art, in the wet etching process of a solar cell, the silicon wafer is usually placed into a wet basket through the opening of the wet basket, and then the wet basket with the silicon wafer is placed into the tank of a wet batch etching machine for the wet etching process. However, the wet etching process may cause poor appearance of the silicon wafer of the solar cell. Since a solar cell often has a central symmetry or axial symmetry structure, when the appearance of the solar cell is poor during the wet etching process, it is impossible to know how the cell is placed in the wet basket during the wet etching process, which is not convenient for troubleshooting the cause of the poor appearance of the cell during the wet etching process. Summary of the Invention

[0004] The present invention provides a solar cell, aiming to solve the problem in the prior art that it is inconvenient to troubleshoot the cause of the poor appearance of the cell during the wet etching process.

[0005] The present invention provides a solar cell, comprising:

[0006] A silicon wafer, the silicon wafer includes a first edge and a second edge oppositely arranged along a first direction, a third edge and a fourth edge oppositely arranged along a second direction, and the first direction intersects with the second direction;

[0007] A first mark disposed on the back surface of the silicon wafer, the first mark includes a first sub-mark close to the first edge, a second sub-mark close to the second edge, and a third sub-mark close to the third edge, and the area of the first sub-mark is larger than the area of the second sub-mark; wherein, the first sub-mark, the second sub-mark, and the third sub-mark respectively correspond to the first side teeth, the second side teeth, and the bottom side teeth of the first wet basket used in the first wet etching process.

[0008] In the present invention, a first mark is provided on the back surface of a silicon wafer. The first edge, the second edge, and the third edge of the silicon wafer are respectively marked by a first sub-mark, a second sub-mark, and a third sub-mark. The first sub-mark, the second sub-mark, and the third sub-mark correspond to the first side teeth, the second side teeth, and the bottom side teeth of the first wet flower basket. According to the first sub-mark, the second sub-mark, and the third sub-mark, it is possible to know the placement manner of the silicon wafer in the first wet flower basket in the first wet etching process. At the same time, combined with the placement manner of the first wet flower basket in the wet tank machine, it is possible to assist manual judgment of the cause of the appearance defect of the battery, help manual quickly find the cause of the defective production, and is beneficial to improving the production efficiency of solar cells.

[0009] Preferably, the solar cell is a back-contact solar cell. The back surface of the silicon wafer includes a plurality of first regions arranged at intervals. The first region is a P-type region or an N-type region. The first sub-mark is located in the first region close to the first edge. The second sub-mark is located in the first region close to the second edge. The third sub-mark is located in the first region at the middle position of the silicon wafer.

[0010] In the present invention, on the one hand, by using the corresponding relationship between the first mark and the teeth of the wet flower basket, it is possible to assist manual judgment of the cause of the appearance defect. On the other hand, by using the first mark, it is possible to help manual distinguish the P-type region or the N-type region of the back-contact solar cell, which is beneficial to distinguishing the P region and the N region during the production process and is convenient for manual to distinguish the P region or the N region according to the position of the first mark.

[0011] Preferably, it further includes:

[0012] A second mark provided on the back surface of the silicon wafer. The second mark includes at least one fourth sub-mark close to the first edge, at least one fifth sub-mark close to the second edge, and at least one sixth sub-mark close to the fourth edge. Among them, the fourth sub-mark, the fifth sub-mark, and the sixth sub-mark correspond to the first side teeth, the second side teeth, and the bottom side teeth of the second wet flower basket used in the second wet etching process.

[0013] In the present invention, by providing a second mark on the back surface of the silicon wafer and using the corresponding relationship between the second mark and the teeth of the second wet flower basket, it is possible to know the placement manner of the flower basket in the second wet etching process of the silicon wafer. According to the specific placement manner of the flower basket in the second wet etching process of the silicon wafer, it is possible to assist manual judgment that the appearance defect of the battery corresponds to the direction of the flower basket in the second wet etching process, thereby assisting manual judgment of the cause of the appearance defect, being beneficial to improving the fault troubleshooting efficiency, and improving the production efficiency of the battery.

[0014] Preferably, the back surface of the silicon wafer further includes a plurality of second regions arranged at intervals, the first region and the second region are arranged alternately in sequence, and one of the first region and the second region is a P-type region and the other is an N-type region;

[0015] The fourth sub-mark is located in the second region close to the first edge, the fifth sub-mark is located in the second region close to the second edge, and the sixth sub-mark is located in the second region at the middle position of the silicon wafer.

[0016] The present invention utilizes the corresponding relationship between the second mark and the teeth of the second wet flower basket, which can assist manual judgment of the cause of appearance defects; on the other hand, it is convenient for manual distinction of the P region or the N region according to the positions of the first mark and the second mark, and can avoid misplacement when the back-contact solar cell is assembled into a photovoltaic module.

[0017] Preferably, the first region includes a first non-marked area that does not correspond to the first mark, and the maximum base size of the region where the first mark is located is smaller than the maximum base size of the first non-marked area.

[0018] The present invention realizes the identification function of the first mark by controlling the maximum base size of the region where the first mark is located to be smaller than the maximum base size of the first non-marked area, and is prepared by a wet etching process, having a small surface recombination loss of the battery, and can maintain good battery efficiency of the solar cell.

[0019] Preferably, the second region includes a second non-marked area that does not correspond to the second mark, and the maximum base size of the region where the second mark is located is smaller than the maximum base size of the second non-marked area.

[0020] The present invention realizes the identification function of the second mark by controlling the maximum base size of the region where the second mark is located to be smaller than the maximum base size of the second non-marked area, utilizes the difference in base size, and is prepared by a wet etching process, having a small surface recombination loss of the battery, and can maintain good battery efficiency of the solar cell.

[0021] Preferably, the first region is a P-type region and the second region is an N-type region; the base size of the region where the first mark is located is larger than the base size of the region where the second mark is located.

[0022] The present invention controls the base size of the P-type region to be larger than the base size of the N-type region, so that the mark in the P-type region is flatter than the mark in the N-type region, which can reduce the influence of the first mark on the passivation performance of the P-type region and ensure good battery efficiency.

[0023] Preferably, the base size of the region where the first mark is located is 5-20 microns, and the base size of the first non-marked area is 10-40 microns.

[0024] The present invention controls the base size of the first mark to be 5-20 microns, and the base size of the first non-marked area to be 10-40 microns. The cooperative design of the base of the first mark and the base of the first non-marked area can not only increase the roughness of the first mark and improve the identification degree, but also enable both the first mark and the first non-marked area to have small surface recombination losses and have a good passivation effect.

[0025] Preferably, the base size of the area where the second mark is located is 3-15 microns, and the base size of the second non-marked area is 5-50 microns.

[0026] The present invention controls the base size of the area where the second mark is located to be 3-15 microns, and the length of the base size of the second non-marked area to be 5-50 microns. The cooperative design of the base of the area where the second mark is located and the base of the second non-marked area can not only increase the identification degree of the second mark, but also ensure that both the second mark and the second non-marked area have small surface recombination losses and have a good passivation effect.

[0027] Preferably, the first sub-mark and the fourth sub-mark are alternately arranged in sequence along the first edge; the second sub-mark and the fifth sub-mark are alternately arranged in sequence along the second edge.

[0028] The present invention controls the first sub-mark and the fourth sub-mark to be alternately arranged in sequence along the first edge, and the second sub-mark and the fifth sub-mark to be alternately arranged in sequence along the second edge, so that the surface recombination losses of the first mark and the second mark with different morphologies are evenly distributed, the influence brought by the recombination losses is reduced, and the battery efficiency is improved.

[0029] Preferably, the number of the first sub-marks is one, and the first sub-mark is offset from the center of the first edge; and / or the number of the second sub-marks is one, and the second sub-mark is offset from the center of the second edge; and / or the number of the third sub-marks is one, and the third sub-mark is offset from the center of the third edge.

[0030] The present invention controls the first mark to be offset from the center position of the silicon wafer edge, which can reduce the surface recombination loss and ensure good battery efficiency on the premise of realizing the identification function.

[0031] Preferably, the number of the fourth sub-marks is one, and the fourth sub-mark is offset from the center of the first edge; and / or the number of the fifth sub-marks is one, and the fifth sub-mark is offset from the center of the second edge; and / or the number of the sixth sub-marks is one, and the sixth sub-mark is offset from the center of the fourth edge.

[0032] The present invention controls the central position of the second mark offset from the edge, which can reduce the surface recombination loss and ensure good cell efficiency on the premise of realizing the identification function.

[0033] Preferably, the number of the first sub - marks is N 1 pieces, N 1 is greater than or equal to 2, the length of the first edge is D 1 , and the distance from the first sub - mark near the end of the first edge to the end of the first edge is less than one - (N 1 + 1) - th of D 1 ;

[0034] The number of the second sub - marks is N 2 pieces, N 2 is greater than or equal to 2, the length of the second edge is D 2 , and the distance from the second sub - mark near the end of the second edge to the end of the second edge is less than one - (N 2 + 1) - th of D 2 ;

[0035] The number of the third sub - marks is N 3 pieces, N 3 is greater than or equal to 2, the length of the third edge is D 3 , and the distance from the third sub - mark near the end of the third edge to the end of the third edge is less than one - (N 3 + 1) - th of D 3 ;

[0036] The present invention controls the first mark to be located at the corner position of the cell as much as possible, which is beneficial to reducing the surface recombination loss caused by the first - mark design and thus beneficial to ensuring good cell efficiency.

[0037] Preferably, the number of the fourth sub - marks is N 4 pieces, N 4 is greater than or equal to 2, the length of the first edge is D 1 , and the distance from the fourth sub - mark near the end of the first edge to the end of the first edge is less than one - (N 1 + 1) - th of D 4 ;

[0038] The number of the fifth sub - marks is N 5 pieces, N 5 is greater than or equal to 2, the length of the second edge is D 2 , and the distance from the fifth sub - mark near the end of the second edge to the end of the second edge is less than one - (N 2 + 1) - th of D 5 ;

[0039] The number of the sixth sub - marks is N 6 pieces, and N 6 is greater than or equal to 2. The length of the fourth edge is D 4 , and the distance from the sixth sub - mark near the end of the fourth edge to the end of the fourth edge is less than one - (N 4 + 1)th of D 6 .

[0040] The present invention controls the second mark to be as close as possible to the corner position of the cell, which is beneficial to reducing the surface recombination loss caused by the design of the second mark, and thus is beneficial to ensuring good cell efficiency.

[0041] Preferably, the total area of the first mark accounts for 0.15% - 0.65% of the total area of the first region, which can ensure that the back surface of the silicon wafer has a small surface recombination loss, has a good passivation effect, and realizes the balance of the two effects.

[0042] Preferably, the area of the second mark accounts for 0.15% - 0.65% of the total area of the second region, which can ensure that the back surface of the silicon wafer has a small surface recombination loss, has a good passivation effect, and realizes the balance of the two effects.

[0043] Preferably, the width of the first mark gradually decreases from the edge of the silicon wafer to the center of the silicon wafer, which can reduce the recombination loss brought by the design of the first mark to the middle region of the silicon wafer, and on the premise of realizing the good identification function of the first mark, thus minimizing the cell surface recombination loss caused by the first mark.

[0044] Preferably, the width of the second mark gradually decreases from the edge of the silicon wafer to the center of the silicon wafer, which can reduce the recombination loss brought by the design of the second mark to the middle region of the silicon wafer, and on the premise of realizing the good identification function of the second mark, thus minimizing the cell surface recombination loss caused by the second mark.

[0045] The present invention also provides a battery module, including the above - mentioned solar cell.

[0046] The present invention also provides a photovoltaic system, including the above - mentioned battery module. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 is a schematic diagram of the back surface of a solar cell provided by an embodiment of the present invention;

[0048] Figure 2 is a schematic diagram of the placement of a silicon wafer of a solar cell during the first wet etching process provided by an embodiment of the present invention;

[0049] Figure 3The back view of the second solar cell provided by the embodiment of the present invention;

[0050] Figure 4 The layout diagram of the silicon wafer of the second solar cell provided by the embodiment of the present invention during the second wet etching process. Detailed implementation manners

[0051] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0052] A solar cell provided by an embodiment of the present invention sets a first mark on the back of a silicon wafer, and uses a first sub-mark, a second sub-mark, and a third sub-mark to mark the first edge, the second edge, and the third edge of the silicon wafer respectively. The first sub-mark, the second sub-mark, and the third sub-mark correspond to the first side teeth, the second side teeth, and the bottom side teeth of the first wet flower basket respectively. According to the first sub-mark, the second sub-mark, and the third sub-mark on the solar cell, it is possible to know the placement method of the silicon wafer of the solar cell in the first wet flower basket during the first wet etching process. At the same time, combined with the placement method of the first wet flower basket in the wet etching machine tank, it is possible to assist manual judgment of the causes of battery appearance defects, help manual quickly find the reasons for the battery's poor appearance, and is conducive to improving the production efficiency of solar cells.

[0053] Please refer to Figure 1 and Figure 2 , an embodiment of the present invention provides a solar cell, including:

[0054] A silicon wafer 1, the silicon wafer 1 includes a first edge 11 and a second edge 12 oppositely arranged along a first direction X, and a third edge 13 and a fourth edge 14 oppositely arranged along a second direction Y. The first direction X intersects with the second direction Y;

[0055] A first mark provided on the back of the silicon wafer 1, the first mark includes a first sub-mark 21 close to the first edge 11, a second sub-mark 22 close to the second edge 12, and a third sub-mark 23 close to the third edge 13. The area of the first sub-mark 21 is larger than the area of the second sub-mark 22; the first sub-mark 21, the second sub-mark 22, and the third sub-mark 23 respectively correspond to the first side teeth 51, the second side teeth 52, and the bottom side teeth 53 of the first wet flower basket 5 used in the first wet etching process.

[0056] In the embodiments of the present invention, the solar cell can be a double-sided contact solar cell or a back contact solar cell. The back side of the silicon wafer 1 is the side facing away from the sunlight when the solar cell is working. The first edge 11, the second edge 12, and the third edge 13 of the silicon wafer 1 are respectively marked with the first sub-mark 21, the second sub-mark, and the third sub-mark, and are obtained by wet etching using the first side teeth 51, the second side teeth 52, and the bottom side teeth 53 on the first side of the first wet flower basket as masks. In the first wet etching process, according to the placement method of the silicon wafer 1 in the first wet flower basket 5 and the placement method of the first wet flower basket 5 in the tank of the wet etching machine, the corresponding relationship among the silicon wafer, the first wet flower basket, and the tank of the wet etching machine is established, so as to assist manual judgment of whether the appearance defects of the battery correspond to the direction of the first wet flower basket and the direction in the tank of the wet etching machine in the first wet etching process, which is beneficial to assisting manual judgment of the causes of battery appearance defects, improving the troubleshooting efficiency, and improving the production efficiency.

[0057] Specifically, as Figure 2 shown, the first wet etching process uses the first wet flower basket 5. The first wet flower basket 5 includes a bottom side, a first side and a second side arranged oppositely, and an opening opposite to the bottom side. The first side teeth 51 are arranged on the rod of the first side, the second side teeth 52 are arranged on the rod of the second side, and the bottom side teeth 53 are arranged on the rod of the bottom side. In the first wet etching process, the first edge 11 of the silicon wafer 1 is placed on the first side teeth 51 of the first wet flower basket 5, the second edge 12 of the silicon wafer 1 is placed on the second side teeth 52 of the first wet flower basket 5, and the third edge 13 of the silicon wafer 1 is placed on the bottom side teeth 53 of the first wet flower basket 5.

[0058] As Figure 2 shown, after the first wet flower basket 5 is placed into the tank of the wet etching machine for the wet process, since the first side teeth 51, the second side teeth 52, and the bottom side teeth 53 of the first wet flower basket 5 respectively cover half of the areas of the first sub-mark 21, the second sub-mark 22, and the third sub-mark 23, the etching rate of the areas of the first sub-mark 21, the second sub-mark 22, and the third sub-mark 23 is less than that of other areas of the silicon wafer 1. Therefore, the first side teeth 51, the second side teeth 52, and the bottom side teeth 53 of the first wet flower basket respectively form flower basket tooth marks at the corresponding positions on the silicon wafer 1, that is, the first sub-mark 21, the second sub-mark 22, and the third sub-mark 23 are formed. Among them, the number and shape of the first sub-mark 21 are the same as those of the first side teeth of the first wet flower basket; the number and shape of the first sub-mark 21 are the same as the number and shape of the first side teeth 51 of the first wet flower basket 5; the number and shape of the second sub-mark 22 are the same as the number and shape of the second side teeth 52 of the first wet flower basket 5; the number and shape of the third sub-mark 23 are the same as the number and shape of the bottom side teeth 53 of the first wet flower basket 5. Figure 1It is shown that there are two of the first sub - marker 21, the second sub - marker 22, and the third sub - marker 23 respectively.

[0059] In the embodiment of the present invention, since the first marker 21 on the first edge 11 of the silicon wafer 1 corresponds to the first side teeth 51 of the first wet basket 5, the first marker 21 on the second edge 12 of the silicon wafer 1 corresponds to the second side teeth 52 of the first wet basket 5, the first marker 21 on the third edge 13 of the silicon wafer 1 corresponds to the bottom side teeth 53 of the first wet basket 5, and the fourth edge 14 of the silicon wafer 1 without the first marker 21 corresponds to the opening of the first wet basket 5. Moreover, the area of the first sub - marker 21 is larger than that of the second sub - marker 22, and the first edge 11 where the first sub - marker 21 is located corresponds to the bottom side inside the tank of the wet type tank machine. Thus, it is possible to know how the silicon wafer 1 is placed in the first wet basket according to the first marker 21 on the silicon wafer 1. At the same time, according to the placement method of the first wet basket 5 inside the tank of the wet type tank machine, it can assist manual judgment of the reasons for the appearance defects of the battery.

[0060] As Figure 2 shown, in the first wet etching process, when the first wet basket 5 is placed inside the tank of the tank machine, the opening and the bottom side teeth of the first wet basket 5 are distributed left - and - right inside the tank, and the first side teeth and the second side teeth of the first wet basket 5 are distributed up - and - down inside the tank. At the same time, since the first marker corresponding to the bottom of the tank of the silicon wafer 1 is relatively obvious and has a larger area, and the first marker corresponding to the upper part inside the tank of the tank machine of the silicon wafer 1 is relatively light and has a smaller area. After the first wet etching process, the first sub - marker 21, the second sub - marker 22, and the third sub - marker 23 formed on the silicon wafer 1 respectively correspond to the first side teeth 51, the second side teeth 52, and the bottom side teeth 53 of the first wet basket 5 used in the first wet etching process, and the first sub - marker 21, the second sub - marker 22, and the third sub - marker 23 formed on the silicon wafer 1 respectively correspond to the bottom side of the tank of the tank machine, the upper side of the tank, and the side of the tank, that is, the first edge 11, the second edge 12, the third edge 13, and the fourth edge 14 of the silicon wafer 1 respectively correspond to the bottom side of the tank, the upper side of the tank, one side of the tank, and the other side of the tank.

[0061] For example, when there are traces of appearance liquid residue near the second edge 12 of the silicon wafer 1, according to the positions of the first sub - marker 21, the second sub - marker 22, and the third sub - marker 23 and the area size relationship between the first sub - marker 21 and the second sub - marker 22, it can be known that the first sub - marker 21, the second sub - marker 22, and the third sub - marker 23 respectively correspond to the bottom side of the tank of the tank machine, the upper side of the tank, and the side of the tank. It can be known that there are traces of appearance liquid residue on the upper side of the tank of the tank machine on the second edge 12 of the silicon wafer 1. It can be known that the reason for this appearance defect may be caused by the upper side of the tank of the tank machine. For example, it may be that when the basket in the polishing tank is lifted, the upper edge of the silicon wafer 1 dries quickly, causing the reaction products to adsorb on the upper edge of the silicon wafer 1. Thus, the reason can be inferred based on this and further investigated.

[0062] For another example, when black spots diverging from the first edge 11 of the silicon wafer 1 towards the middle of the silicon wafer 1 are found in the EL defect test, it can be determined that the side where the EL defect black spots are generated is the lower side in the groove. At the same time, this fixed position corresponds to the liquid medicine circulation pipe at the bottom of the groove, and it is very likely that the liquid medicine flushed out from this circulation pipe causes it.

[0063] For another example, when airflow-like EL defects are found on the third edge 13 or the fourth edge 14 of the silicon wafer 1 during the test, according to the corresponding relationship among the solar cell, the wet flower basket, and the groove of the trough machine, it can be determined that it is caused by one side in the groove. Combining the airflow-like EL defect morphology, it is very likely caused by gas. And in the wet trough machine, only the drying groove contains gas, and the hot air duct in the groove just corresponds to these two abnormal edges. Therefore, it is determined that the EL defect of the battery is caused by the pollution of the gas in the drying groove.

[0064] Therefore, in the embodiment of the present invention, a first mark is set on the back surface of the silicon wafer 1, and the first sub-mark 21, the second sub-mark 22, and the third sub-mark 23 respectively correspond to the first side teeth 51, the second side teeth 51, and the bottom side teeth 53 of the first wet flower basket 5. By using the corresponding relationship between the first mark and the teeth of the first wet flower basket 5, the placement method of the flower basket of the silicon wafer 1 in the first wet etching process can be known. According to the specific placement method of the flower basket of the silicon wafer 1 in the first wet etching process, it can assist manual judgment that the appearance defect of the battery corresponds to the direction where the flower basket is located in the first wet etching process, thereby assisting manual judgment of the cause of the appearance defect, which is beneficial to improving the troubleshooting efficiency and the battery production efficiency.

[0065] As an embodiment of the present invention, the solar cell is a back-contact solar cell. The back surface of the silicon wafer 1 includes a plurality of first regions 3 arranged at intervals, and the first regions 3 are P-type regions or N-type regions; the first sub-mark 21 is located in the first region 3 near the first edge 11, the second sub-mark 22 is located in the first region 3 near the second edge 12, and the third sub-mark 23 is located in the first region 3 at the middle position of the silicon wafer 1.

[0066] In this embodiment, the solar cell is a back-contact solar cell. The back surface of the silicon wafer 1 includes a plurality of first regions 3, and the first regions 3 are P-type regions or N-type regions; wherein, the first mark is set in the P-type region or the N-type region. On the one hand, by using the corresponding relationship between the first mark and the teeth of the wet flower basket, it assists manual judgment of the cause of the appearance defect; on the other hand, using the first mark can help manual distinction between the P-type region and the N-type region of the back-contact solar cell, which is beneficial to distinguishing the P region and the N region during the production process, facilitating manual distinction between the P region and the N region according to the position of the first mark, and can avoid misplacement when the back-contact solar cell is assembled into a battery module.

[0067] Among them, the first sub - marker 21 can be located in a first region 3 near the first edge 11, or can be simultaneously located in two or more first regions 3 near the first edge 11; the second sub - marker 22 is located in a first region 3 near the second edge 12, or can be simultaneously located in two or more first regions 3 near the first edge 11; the third sub - marker 23 is located in a first region 3 at the middle position of the silicon wafer 1, or can be located in two or more first regions 3 at the middle position of the silicon wafer 1. Among them, Figure 1 As shown, the first sub - marker 21 is located in two first regions 3 near the first edge 11, the second sub - marker 22 is simultaneously located in two first regions 3 near the second edge 12, and the third sub - marker 23 is located in two first regions 3 at the middle position of the silicon wafer 1.

[0068] Please refer to Figure 3 and Figure 4 , as an embodiment of the present invention, further includes:

[0069] A second marker provided on the back surface of the silicon wafer 1, the second marker includes at least one fourth sub - marker 41 near the first edge 11, at least one fifth sub - marker 42 near the second edge 12, and at least one sixth sub - marker 44 near the fourth edge 14, and the fourth sub - marker 41, the fifth sub - marker 42, and the sixth sub - marker 44 respectively correspond to the first side teeth 61, the second side teeth 62, and the bottom side teeth 64 of the second wet flower basket 6.

[0070] Among them, the placement method of the silicon wafer 1 in the first wet flower basket and the placement method of the silicon wafer 1 in the second wet flower basket can be the same or different; the placement method of the first wet flower basket in the slot of the trough - type machine and the placement method of the second wet flower basket in the slot of the trough - type machine can be the same or different.

[0071] For example, as shown in Figure 2 and Figure 4 , the placement method of the silicon wafer 1 in the first wet flower basket and the placement method of the silicon wafer 1 in the second wet flower basket differ by 90 degrees, that is, the silicon wafer 1 is in the first position in the first wet flower basket, and the silicon wafer 1 is in the second position in the second wet flower basket. The first position rotates 90 degrees clockwise to reach the second position. The placement method of the first wet flower basket in the slot of the trough - type machine and the placement method of the second wet flower basket in the slot of the trough - type machine also differ by 90 degrees. The first wet flower basket is in the first position in the slot of the trough - type machine, and at this time the opening of the first wet flower basket faces right; the second wet flower basket is in the second position in the slot of the trough - type machine, and at this time the opening of the second wet flower basket faces up.

[0072] Since the carrier is in the first position when the first mark is formed in the first wet etching process and in the second position when the second mark is formed in the second wet etching process, there will be differences in the etching rate when etching the silicon wafer 1 with chemical liquid. For example, under the etching of the chemical liquid, the etching rate of forming the first mark on the surface of the silicon wafer 1 is greater than that of forming the second mark on the surface of the silicon wafer 1.

[0073] In some specific applications, there are certain differences in the solutions, reaction temperatures, and reaction times used in the first wet etching process and the second wet etching process, making the difference between the first mark and the second mark more obvious and facilitating the identification of the first mark and the second mark.

[0074] For example, the first wet etching process uses potassium hydroxide with a concentration of 1-3% and an additive concentration of 0.5-1.5%, a reaction temperature of 60-80 degrees, and a reaction time of 100-400 seconds; the second wet etching process uses potassium hydroxide with a concentration of 3-10% and an additive concentration of 0.5-1.5%, a reaction temperature of 70-90 degrees, and a reaction time of 100-300 seconds.

[0075] Similarly, in the embodiment of the present invention, by setting the second mark on the back of the silicon wafer 1, and the fourth sub-mark 41, the fifth sub-mark 42, and the sixth sub-mark 44 respectively correspond to the first side teeth 61, the second side teeth 62, and the bottom side teeth 63 of the second wet carrier 6. Using the corresponding relationship between the second mark and the teeth of the second wet carrier, it is possible to know the placement method of the carrier when the silicon wafer 1 is in the second wet etching process. According to the specific placement method of the carrier when the silicon wafer 1 is in the second wet etching process, it can assist manual judgment that the appearance defect of the battery corresponds to the direction where the carrier is located in the second wet etching process, thereby assisting manual judgment of the cause of the appearance defect, which is beneficial to improving the fault troubleshooting efficiency and the battery production efficiency.

[0076] The second wet etching process uses the second wet carrier to place the silicon wafer 1. The second wet carrier 6 also includes a bottom side, a first side and a second side arranged oppositely, and an opening opposite to the bottom side. The rod on the first side of the second wet carrier is provided with the first side teeth 61, the rod on the second side is provided with the second side teeth 62, and the rod on the bottom side is provided with the bottom side teeth 64. During the second wet etching process, the first edge 11 of the silicon wafer 1 is placed on the first side teeth 61 of the second wet carrier, the second edge 12 of the silicon wafer 1 is placed on the second side teeth 62 of the second wet carrier, and the fourth edge 14 of the silicon wafer 1 is placed on the bottom side teeth 64 of the second wet carrier.

[0077] Such as Figure 4As shown in the figure, in the second wet etching process, when the second wet carrier basket is placed in the tank of the tank-type machine, the basket opening and the bottom-side teeth of the second wet carrier basket are distributed vertically in the tank, and the first-side teeth and the second-side teeth of the second wet carrier basket are distributed horizontally in the tank of the tank-type machine. Therefore, after the second wet etching process, the fourth sub-mark 41, the fifth sub-mark 42, and the sixth sub-mark 44 formed on the silicon wafer 1 respectively correspond to the first-side teeth, the second-side teeth, and the bottom-side teeth of the second wet carrier basket used in the second wet etching process, that is, the first edge 11, the second edge 12, the third edge 13, and the fourth edge 14 formed on the silicon wafer 1 respectively correspond to the first side, the second side, the upper side, and the bottom side of the tank of the tank-type machine.

[0078] For example, when it is determined that the cause of the defective appearance is caused by the second wet etching process and there are traces of appearance chemical liquid residues on the third edge 13 of the silicon wafer 1, it can be known that the cause of this appearance defect may be the upper side of the tank of the tank-type machine. For example, it may be that when the silicon wafer 1 is lifted in the polishing tank basket, the upper edge of the silicon wafer 1 dries quickly, causing the reaction products to adsorb on the upper edge of the silicon wafer 1, and then the cause can be inferred based on this for further investigation.

[0079] Another example is that when it is determined that the cause of the defective appearance is caused by the second wet etching process and black spots diverging from the fourth edge 14 of the silicon wafer 1 towards the middle of the silicon wafer 1 are found in the EL defect test, it can be determined that the side where the EL defective black spots are generated is the lower side in the tank, and at the same time, this fixed position corresponds to the chemical liquid circulation pipe at the bottom of the tank. It is very likely that the chemical liquid flushed out from this circulation pipe is the cause.

[0080] Another example is that when it is determined that the cause of the defective appearance is caused by the second wet etching process and EL defects in the shape of airflows are found on the first edge 11 or the second edge 12 of the silicon wafer 1 during the test. According to the corresponding relationship among the battery wafer, the wet carrier basket, and the tank of the tank-type machine, it can be determined that it is caused by one side in the tank. Combining the EL defect morphology in the shape of airflows, it is very likely to be caused by gas. And only the drying tank in the wet tank-type machine has gas, and the hot air ducts in the tank just correspond to these two abnormal edges, so it is determined that the EL defect of the battery is caused by the pollution of the gas in the drying tank.

[0081] Please refer to Figure 3 , as an embodiment of the present invention, the back surface of the silicon wafer 1 further includes a plurality of second regions 4 arranged at intervals, the first region 3 and the second region 4 are arranged alternately in sequence, and one of the first region 3 and the second region 4 is a P-type region and the other is an N-type region;

[0082] The fourth sub-mark 41 is located in the second region 4 near the first edge 11, the fifth sub-mark 42 is located in the second region 4 near the second edge 12, and the sixth sub-mark 44 is located in the second region 4 at the middle position of the silicon wafer 1.

[0083] In this embodiment, on the one hand, the corresponding relationship between the second mark and the teeth of the second wet flower basket 6 can assist manual judgment of the cause of appearance defects. On the other hand, since the second mark is set in the second area 3 and the second mark is set in the second area 4, the second mark can help manual further distinguish the P-type area or N-type area of the back-contact solar cell, which is beneficial to distinguish the P area and N area during the production process, facilitate manual distinction of the P area or N area according to the positions of the first mark and the second mark, and can avoid misplacement when the back-contact solar cell is assembled into a photovoltaic module.

[0084] As an embodiment of the present invention, the first area 3 includes a first non-marked area 30 that does not correspond to the first mark, and the maximum base size of the area where the first mark is located is smaller than the maximum base size of the first non-marked area 30.

[0085] In this embodiment, the first area 3 includes the area where the first mark is located and the first non-marked area 30, and both the area where the first mark is located and the first non-marked area 30 are polished surfaces. The maximum base size of the area where the first mark is located is the length of the longest diagonal of the largest base of the area where the first mark is located, and the maximum base size of the first non-marked area 30 is the length of the longest diagonal of the largest base of the area where the first non-marked area is located.

[0086] In this embodiment, by controlling the maximum base size of the area where the first mark is located to be smaller than the maximum base size of the first non-marked area, two different polished morphologies of the first mark 21 and the first non-marked area 30 can be formed through the wet etching process and the semi-mask process. By using the difference in the two base sizes of the first mark 21 and the first non-marked area 30, the first mark 21 can be formed in the first area 3, avoiding physical damage to the silicon wafer 1 caused by the high temperature of laser marking, reducing the cracking rate of the silicon wafer 1 during subsequent processing; moreover, the first mark and the first non-marked area 30 formed by wet etching can reduce the surface damage degree of the silicon wafer 1, and have a small surface recombination loss of the battery on the premise of realizing the identification function of the first mark, and can maintain the good battery efficiency of the solar cell.

[0087] As an embodiment of the present invention, the second area 4 includes a second non-marked area 40 that does not correspond to the second mark, and the maximum base size of the area where the second mark is located is smaller than the maximum base size of the second non-marked area 40.

[0088] In this embodiment, the second area 4 includes the area where the second mark is located and the second non-marked area 40, and both the second mark and the second non-marked area 40 are set as polished surfaces. The maximum base size of the area where the second mark is located is the length of the longest diagonal of the largest base of the area where the second mark is located, and the maximum base size of the second non-marked area 40 is the length of the longest diagonal of the largest base of the area where the second non-marked area 40 is located.

[0089] In this embodiment, the maximum base size of the area where the second mark is located is controlled to be smaller than the maximum base size of the second non-marked area 40. Two different polished morphologies of the second mark and the second non-marked area can be formed through a wet etching process and a semi-mask process. By using the difference in the base sizes of the second mark and the second non-marked area, the second mark can be formed in the second area 4, avoiding physical damage to the silicon wafer 1 caused by the high temperature of laser marking, and reducing the cracking rate of the silicon wafer 1 during subsequent processing. Moreover, the second mark and the second non-marked area 40 formed by wet etching can reduce the surface damage degree of the silicon wafer 1. On the premise of realizing the identification function of the second mark, it has a small surface recombination loss of the battery and can maintain good battery efficiency of the solar cell.

[0090] As an embodiment of the present invention, the first area 3 is a P-type area, and the second area 4 is an N-type area; the maximum base size of the area where the first mark is located is larger than the maximum base size of the area where the second mark is located.

[0091] The present invention controls the maximum base size of the area where the first mark is located to be larger than the maximum base size of the area where the second mark is located, so that the base size of the P-type area is larger than that of the N-type area, and the mark of the P-type area is flatter than that of the N-type area, which can reduce the influence of the first mark on the passivation performance of the P-type area and ensure good battery efficiency.

[0092] As an embodiment of the present invention, the base size of the area where the first mark is located is 5-20 microns, and the base size of the first non-marked area 30 is 10-40 microns.

[0093] In this embodiment, the base size of the first mark is 5-20 microns, and the base size of the first non-marked area is 10-40 microns. The base of the first mark and the base of the first non-marked area are designed in cooperation, which can not only increase the roughness of the first mark and improve the identification degree, but also make both the first mark and the first non-marked area 30 have a small surface recombination loss and have a good passivation effect.

[0094] For example, the base size of the area where the first mark is located can be any value among 5 microns, 5.5 microns, 6 microns, 6.2 microns, 7 microns, 7.5 microns, 9 microns, 9.6 microns, 10 microns, 11 microns, 13 microns, 14 microns, 15 microns, 16 microns, 17 microns, 18 microns, 19 microns, 20 microns; the base size of the first non-marked area 30 can be any value among 10 microns, 10.2 microns, 11 microns, 12 microns, 12.3 microns, 14 microns, 14.8 microns, 15 microns, 16 microns, 18 microns, 20 microns, 22 microns, 25 microns, 26 microns, 27 microns, 28 microns, 30 microns, 32 microns, 34 microns, 35 microns, 37 microns, 38 microns, 39 microns, 40 microns.

[0095] As an embodiment of the present invention, the base size of the tower in the area where the second mark is located is 3 to 15 micrometers, and the base size of the second non-marked area 40 is 5 to 50 micrometers.

[0096] In this embodiment, the base size of the tower in the area where the second mark is located is set to 3 to 15 micrometers, and the length of the base size of the second non-marked area 40 is set to 5 to 50 micrometers. The cooperative design of the bases of the area where the second mark is located and the second non-marked area can not only increase the identification degree of the second mark, but also ensure that both the second mark and the second non-marked area have relatively small surface recombination losses and have a good passivation effect.

[0097] For example, the base size of the second mark can be any value among 3 micrometers, 3.5 micrometers, 4 micrometers, 5 micrometers, 7 micrometers, 7.5 micrometers, 9 micrometers, 9.2 micrometers, 10 micrometers, 11 micrometers, 13 micrometers, 14 micrometers, 15 micrometers; the base size of the second non-marked area 40 can be any value among 5 micrometers, 6 micrometers, 8 micrometers, 10 micrometers, 12 micrometers, 14 micrometers, 15 micrometers, 16 micrometers, 18 micrometers, 20 micrometers, 22 micrometers, 25 micrometers, 26 micrometers, 27 micrometers, 28 micrometers, 30 micrometers, 32 micrometers, 34 micrometers, 35 micrometers, 37 micrometers, 38 micrometers, 39 micrometers, 40 micrometers, 45 micrometers, 47 micrometers, 48 micrometers, 50 micrometers.

[0098] As an embodiment of the present invention, the first sub-mark 21 and the fourth sub-mark 41 are alternately arranged in sequence along the first edge 11; the second sub-mark 22 and the fifth sub-mark 42 are alternately arranged in sequence along the second edge 12.

[0099] In this embodiment, the first sub-mark 21 and the fourth sub-mark 41 are alternately arranged in sequence along the first edge 11, and the second sub-mark 22 and the fifth sub-mark 42 are alternately arranged in sequence along the second edge 12, so that the surface recombination losses of the first mark and the second mark with different morphologies are evenly distributed, the influence brought by the recombination losses is reduced, and the battery efficiency is improved.

[0100] As an embodiment of the present invention, the number of the first sub-marks 21 is one, and the first sub-mark 21 is arranged offset from the center of the first edge 11; and / or, the number of the second sub-marks 22 is one, and the second sub-mark 22 is arranged offset from the center of the second edge 12; and / or, the number of the third sub-marks 23 is one, and the third sub-mark 23 is arranged offset from the center of the third edge 13.

[0101] In this embodiment, when the number of the first sub - markers 21 is one, the first sub - marker 21 is offset from the center of the first edge 11. Compared with the case where the first sub - marker 21 is disposed at the center of the first edge 11, the surface recombination loss caused by the first sub - marker 21 can be reduced. On the premise of realizing the identification function, the surface recombination loss brought by the first sub - marker 21 can be minimized as much as possible to ensure good cell efficiency. Similarly, when the number of the second sub - markers 22 is one, the second sub - marker 22 is offset from the center of the second edge 12. Compared with the case where the second sub - marker 22 is disposed at the center of the second edge 12, the surface recombination loss caused by the second sub - marker 22 can be reduced. When the number of the third sub - markers 23 is one, the third sub - marker 23 is offset from the center of the third edge 13. Compared with the case where the third sub - marker 23 is disposed at the center of the third edge 13, the surface recombination loss caused by the third sub - marker 23 can be reduced.

[0102] Of course, in some other embodiments, when the number of the first sub - markers 21 is one, the first sub - marker 21 is located at the center of the first edge 11. When the number of the second sub - markers 22 is one, the second sub - marker 22 is located at the center of the second edge 12. When the number of the third sub - markers 23 is one, the third sub - marker 23 is located at the center of the third edge 13.

[0103] As an embodiment of the present invention, the number of the fourth sub - markers 41 is one, and the fourth sub - marker 41 is offset from the center of the first edge 11; and / or the number of the fifth sub - markers 42 is one, and the fifth sub - marker 42 is offset from the center of the second edge 12; and / or the number of the sixth sub - markers 44 is one, and the sixth sub - marker 44 is offset from the center of the fourth edge 14.

[0104] In this embodiment, when the number of the fourth sub - markers 41 is one, the fourth sub - marker 41 is offset from the center of the first edge 11. Compared with the case where the fourth sub - marker 41 is disposed at the center of the first edge 11, the surface recombination loss caused by the fourth sub - marker 41 can be reduced. On the premise of realizing the identification function, the surface recombination loss brought by the fourth sub - marker 41 can be minimized as much as possible to ensure good cell efficiency. Similarly, when the number of the fifth sub - markers 42 is one, the fifth sub - marker 42 is offset from the center of the second edge 12. Compared with the case where the fifth sub - marker 42 is disposed at the center of the second edge 12, the surface recombination loss caused by the fifth sub - marker 42 can be reduced. When the number of the sixth sub - markers 44 is one, the sixth sub - marker 44 is offset from the center of the fourth edge 14. Compared with the case where the sixth sub - marker 44 is disposed at the center of the fourth edge 14, the surface recombination loss caused by the sixth sub - marker 44 can be reduced.

[0105] Of course, in some other embodiments, when the number of the fourth sub - markers 41 is one, the fourth sub - marker 41 is located at the center of the first edge 11; when the number of the fifth sub - markers 42 is one, the fifth sub - marker 42 is located at the center of the second edge 12; when the number of the fifth sub - markers 42 is one, the fifth sub - marker 42 is located at the center of the fourth edge 14.

[0106] As an embodiment of the present invention, the number of the first sub - markers 21 is N 1 pieces, and N 1 is greater than or equal to 2. The length of the first edge 11 is D 1 , and the distance from the first sub - marker 21 near the end of the first edge 11 to the end of the first edge 11 is less than one - (N 1 + 1) - th of D 1 ;

[0107] The number of the second sub - markers 22 is N 2 pieces, and N 2 is greater than or equal to 2. The length of the second edge 12 is D 2 , and the distance from the second sub - marker 22 near the end of the second edge 12 to the end of the second edge 12 is less than one - (N 2 + 1) - th of D 2 ;

[0108] The number of the third sub - markers 23 is N 3 pieces, and N 3 is greater than or equal to 2. The length of the third edge 13 is D 3 , and the distance from the third sub - marker 23 near the end of the third edge 13 to the end of the third edge 13 is less than one - (N 3 + 1) - th of D 3 .

[0109] In this embodiment, the specific values of N 1 , N 2 , and N 3 are not limited and can be flexibly set according to actual needs; the specific lengths of D 1 , D 2 , and D 3 are not limited and can be set according to the actual size of the battery cell. The distance from the first sub - marker 21 near the end of the first edge 11 to the end of the first edge 11 being less than one - (N 1 + 1) - th of D 1 can be understood as: the distance from the first sub - marker 21 near the first end of the first edge 11 to the first end of the first edge 11 is less than one - (N 1 + 1) - th of D 1 , and the distance from the first sub - marker 21 near the second end of the first edge 11 to the second end of the first edge 11 is less than one - (N 1 + 1) - th of D1 One over (N + 1), such that the second sub - mark 22 near the end of the second edge 12 is located as close as possible to the corner position of the cell, which is conducive to reducing the surface recombination loss caused by the first mark design, and thus conducive to ensuring good cell efficiency. Similarly, the distance from the second sub - mark 22 near the end of the second edge 12 to the end of the second edge 12 is less than one over (N + 1) of D 2 of (N 2 + 1) is understood as: the distance from the second sub - mark 22 near the first end of the second edge 12 to the first end of the second edge 12 is less than one over (N + 1) of D 2 of (N 2 + 1), and the distance from the second sub - mark 22 near the second end of the second edge 12 to the second end of the second edge 12 is less than one over (N + 1) of D 2 of (N 2 + 1); the distance from the third sub - mark 23 near the end of the third edge 13 to the end of the third edge 13 is less than one over (N + 1) of D 3 of (N 3 + 1) is understood as that the distance from the third sub - mark 23 near the first end of the third edge 13 to the first end of the third edge 13 is less than one over (N + 1) of D 3 of (N 3 + 1), and the distance from the third sub - mark 23 near the second end of the third edge 13 to the second end of the third edge 13 is less than one over (N + 1) of D 3 of (N 3 + 1), which is conducive to reducing the surface recombination loss caused by the design of the second sub - mark 22 and the third sub - mark 23, and thus conducive to ensuring good cell efficiency.

[0110] For example, the number of the first sub - marks 21 is 2. The distance from the first sub - mark 21 near the first end of the first edge 11 to the first end of the first edge 11 is less than one - half of D 1 and the distance from the first sub - mark 21 near the second end of the first edge 11 to the second end of the first edge 11 is less than one - half of D 1 ; the number of the first sub - marks 21 is 3. The distance from the first sub - mark 21 near the first end of the first edge 11 to the first end of the first edge 11 is less than one - quarter of D 1 and the distance from the first sub - mark 21 near the second end of the first edge 11 to the second end of the first edge 11 is less than one - quarter of D 1 of D.

[0111] As an embodiment of the present invention, the number of the fourth sub - marks 41 is N 4 pieces, N 4 is greater than or equal to 2, and the length of the first edge 11 is D 1, the distance from the fourth sub - mark 41 near the end of the first edge 11 to the end of the first edge 11 is less than one - (N + 1)th of D 1 of (N 4 + 1);

[0112] The number of the fifth sub - marks 42 is N 5 pieces, N 5 is greater than or equal to 2, the length of the second edge 12 is D 2 , the distance from the fifth sub - mark 42 near the end of the second edge 12 to the end of the second edge 12 is less than one - (N + 1)th of D 2 of (N 5 + 1);

[0113] The number of the sixth sub - marks 44 is N 6 pieces, N 6 is greater than or equal to 2, the length of the fourth edge 14 is D 4 , the distance from the sixth sub - mark 44 near the end of the fourth edge 14 to the end of the fourth edge 14 is less than one - (N + 1)th of D 4 of (N 6 + 1).

[0114] In this embodiment, the specific values of N 4 , N 5 , N 6 are not limited, and can be flexibly set according to actual needs. Similarly, the fourth sub - mark 41, the fifth sub - mark 42, and the sixth sub - mark 44 in this embodiment are also preferably located at the corner positions of the cell, which is beneficial to reducing the surface recombination loss caused by the design of the fourth sub - mark 41, the fifth sub - mark 42, and the sixth sub - mark 44, and is beneficial to ensuring good cell efficiency.

[0115] As an embodiment of the present invention, the total area of the first mark accounts for 0.15% - 0.65% of the total area of the first region 3.

[0116] In this embodiment, the area of the first mark accounts for 0.15% - 0.65% of the first region 3, that is, the sum of the areas of the first sub - mark 21, the second sub - mark 22, and the third sub - mark 23 accounts for 0.15% - 0.65% of the total area of the first region 3. It can not only achieve better identification of the first mark, but also ensure that the back surface of the silicon wafer 1 has less surface recombination loss, has a better passivation effect, and realizes the balance of the two effects.

[0117] As an embodiment of the present invention, the area of the second mark accounts for 0.15% - 0.65% of the total area of the second region 4.

[0118] In this embodiment, the area of the second mark accounts for 0.15% - 0.65% of the second region 4, that is, the sum of the areas of the fourth sub - mark 41, the fifth sub - mark 42, and the sixth sub - mark 44 accounts for 0.15% - 0.65% of the total area of the second region 4. This can not only achieve better identification of the second mark, but also ensure that the back surface of the silicon wafer 1 has less surface recombination loss, has a better passivation effect, and realizes the balance of the two effects.

[0119] As an embodiment of the present invention, the first region 31 is a P - type region, and the second region 42 is an N - type region; the area of the first mark is smaller than the area of the second mark.

[0120] In this embodiment, the P - type region is the region where a P - type doped polysilicon layer is provided, and the N - type region is the region where an N - type doped polysilicon layer is provided. The sum of the areas of the first sub - mark 21, the second sub - mark 22, and the third sub - mark 23 is smaller than the sum of the areas of the fourth sub - mark 41, the fifth sub - mark 42, and the sixth sub - mark 44. Since the passivation performance of the P - type doped layer is worse than that of the N - type region doped layer, the area of the first mark in the P - type region is smaller than the area of the second mark in the N - type region. In this way, the surface recombination loss of the first mark can be made smaller than that of the second mark, so as to balance the passivation performance of the P - type region and the N - type region and further improve the battery efficiency.

[0121] Among them, the ratio of the area of the second mark to the area of the first mark can be set flexibly. For example, the ratio of the area of the second mark to the area of the first mark can be 1.2 - 1.5, so as to reasonably design the area of the first mark in the P - type region and the area of the second mark in the N - type region. In this way, it can not only maintain the good passivation performance of the P - type region and the N - type region, but also improve the local roughness of the P - type region and the N - type region, reduce the local light reflectivity of the P - type region and the N - type region, and thus improve the battery efficiency.

[0122] As an embodiment of the present invention, the width of the first mark gradually decreases from the edge of the silicon wafer 1 towards the center of the silicon wafer 1.

[0123] In this embodiment, the first mark can preferably be triangular or trapezoidal. Since the recombination loss at the edge of the silicon wafer 1 is large and the middle region of the silicon wafer 1 is small, because the width of the first mark gradually decreases from the edge of the silicon wafer 1 towards the center of the silicon wafer 1, the surface recombination loss caused by the first mark to the battery gradually decreases from the edge of the silicon wafer 1 towards the center of the silicon wafer 1, which can reduce the recombination loss brought by the first mark design to the middle region of the silicon wafer 1. On the premise of realizing the good identification function of the first mark, the surface recombination loss of the battery caused by the first mark can be minimized as much as possible.

[0124] As an embodiment of the present invention, the width of the second mark gradually decreases from the edge of the silicon wafer 1 towards the center of the silicon wafer 1.

[0125] In this embodiment, the second mark is preferably triangular or trapezoidal. Since the edge recombination loss of the silicon wafer 1 is large and the middle area of the silicon wafer 1 is small, and since the width of the second mark gradually decreases from the edge of the silicon wafer 1 towards the center of the silicon wafer 1, the surface recombination loss caused by the second mark to the battery gradually decreases from the edge of the silicon wafer 1 towards the center of the silicon wafer 1, which can reduce the recombination loss brought by the second mark design to the middle area of the silicon wafer 1. On the premise of realizing the good identification function of the second mark, the surface recombination loss of the battery caused by the first mark can be minimized as much as possible.

[0126] As an embodiment of the present invention, the number of the first sub - marks 21 and the second sub - marks 22 is each 1 to 5; the number of the third sub - marks 23 is 1 to 3.

[0127] Among them, the number of the first sub - marks 21, the second sub - marks 22, and the third sub - marks 23 corresponds to the number of teeth of the first wet - type flower basket used in the first wet etching process. Among them, the number of the first sub - marks 21 and the second sub - marks 22 is preferably 1 to 5; the number of the third sub - marks 23 is preferably 1 to 3, which can not only realize the better identification function of the first mark, facilitate manual understanding of the corresponding relationship between each edge of the battery cell and the four directions of the first wet - type flower basket in the first wet etching process, but also facilitate the investigation of the causes of defective battery appearance.

[0128] For example, the number of the first sub - marks 21 and the second sub - marks 22 is each set to 1, and the number of the third sub - marks 23 is set to 1; or for another example, the number of the first sub - marks 21 and the second sub - marks 22 is each set to 2, and the number of the third sub - marks 23 is set to 2.

[0129] As an embodiment of the present invention, the number of the fourth sub - marks 41 and the fifth sub - marks 42 is 1 to 5; the number of the sixth sub - marks 44 is 1 to 3.

[0130] For example, the number of the fourth sub - marks 41 and the fifth sub - marks 42 is each set to 1, and the number of the sixth sub - marks 44 is set to 1; or for another example, the number of the fourth sub - marks 41 and the fifth sub - marks 42 is each set to 2, and the number of the sixth sub - marks 44 is set to 2.

[0131] The embodiment of the present invention also provides a battery module, which includes the solar cell of the above - mentioned embodiment. It should be noted that this battery module has the same or similar beneficial effects as the above - mentioned solar cell, and the relevant parts between the two can be referred to each other. To avoid repetition, it will not be elaborated here.

[0132] In this embodiment, multiple solar cells in the battery assembly can be connected in series in sequence to form a battery string, thereby achieving the series connection and confluence output of current. For example, the connection of the battery cells can be achieved by setting up solder tapes (bus bars, interconnection bars), conductive backplates, etc.

[0133] It can be understood that in such an embodiment, the battery assembly may further include a metal frame, a backplate, photovoltaic glass, and a glue film. The glue film can be filled between the front and back of the solar cells, as well as between the photovoltaic glass and adjacent battery cells. As a filler, it can be a transparent colloid with good light transmittance and aging resistance. For example, the glue film can be an EVA glue film or a POE glue film, and the specific choice can be made according to the actual situation and is not limited here.

[0134] The photovoltaic glass can cover the glue film on the front of the solar cells. The photovoltaic glass can be ultra-white glass, which has a high light transmittance, high transparency, and excellent physical, mechanical, and optical properties. For example, the light transmittance of the ultra-white glass can reach more than 92%, and it can protect the solar cells without significantly affecting their efficiency. At the same time, the glue film can bond the photovoltaic glass and the solar cells together, and the presence of the glue film can seal and insulate the solar cells and prevent water and moisture.

[0135] The backplate can be attached to the glue film on the back of the solar cells. The backplate can protect and support the solar cells, and has reliable insulation, water resistance, and aging resistance. The backplate can have multiple choices and is usually tempered glass, plexiglass, aluminum alloy TPT composite glue film, etc., and its specific settings can be determined according to the specific situation and are not limited here. The whole composed of the backplate, solar cells, glue film, and photovoltaic glass can be set on the metal frame. The metal frame is the main external support structure of the entire solar cell assembly and can stably support and install the solar cell assembly. For example, the solar cell assembly can be installed at the required installation position through the metal frame.

[0136] The embodiment of the present invention also provides a photovoltaic system, which includes the battery assembly of the above embodiment. It should be noted that this photovoltaic system has the same or similar beneficial effects as the above-mentioned solar cells, and the relevant parts between the two can be referred to each other. To avoid repetition, it will not be elaborated here.

[0137] In this embodiment, the photovoltaic system can be applied in a photovoltaic power station, such as a ground power station, a rooftop power station, a water surface power station, etc., or can also be applied to equipment or devices that utilize solar energy for power generation, such as a user solar power supply, a solar street lamp, a solar vehicle, a solar building, and so on. Of course, it can be understood that the application scenarios of the photovoltaic system are not limited to this, that is to say, the photovoltaic system can be applied in all fields that require solar power generation. Taking the photovoltaic power generation system network as an example, the photovoltaic system can include a photovoltaic array, a busbar box, and an inverter. The photovoltaic array can be an array combination of multiple solar cell modules. For example, multiple solar cell modules can form multiple photovoltaic arrays. The photovoltaic arrays are connected to the busbar box, and the busbar box can collect the current generated by the photovoltaic arrays. The collected current flows through the inverter and is converted into alternating current required by the commercial power grid and then connected to the commercial power grid to achieve solar power supply.

[0138] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A solar cell, characterized in that: include: A silicon wafer, the silicon wafer comprising a first edge and a second edge arranged opposite to each other along a first direction, and a third edge and a fourth edge arranged opposite to each other along a second direction, wherein the first direction intersects with the second direction; A first mark is arranged on the back side of the silicon wafer, the first mark includes a first sub-mark close to the first edge, a second sub-mark close to the second edge, and a third sub-mark close to the third edge, and the area of ​​the first sub-mark is larger than the area of ​​the second sub-mark; wherein the first sub-mark, the second sub-mark, and the third sub-mark respectively correspond to the first side tooth, the second side tooth, and the bottom side tooth of the first wet flower basket used in the first wet etching process.

2. The solar cell according to claim 1, characterized in that The solar cell is a back-contact solar cell, the back side of the silicon wafer includes a plurality of first regions spaced apart from each other, the first regions being P-type regions or N-type regions; the first sub-mark is located within the first region close to the first edge, the second sub-mark is located within the first region close to the second edge, and the third sub-mark is located within the first region in the middle of the silicon wafer.

3. The solar cell according to claim 2, characterized in that: Also includes: A second mark is arranged on the back side of the silicon wafer, the second mark includes at least one fourth sub-mark close to the first edge, at least one fifth sub-mark close to the second edge, and at least one sixth sub-mark close to the fourth edge; wherein the fourth sub-mark, the fifth sub-mark, and the sixth sub-mark correspond to the first side tooth, the second side tooth, and the bottom side tooth of the second wet flower basket used in the second wet etching process.

4. The solar cell according to claim 2, characterized in that: The back side of the silicon wafer further includes a plurality of second regions, wherein the first regions and the second regions are alternately arranged in sequence, and one of the first regions and the second regions is a P-type region and the other is an N-type region; The fourth sub-mark is located in the second region close to the first edge, the fifth sub-mark is located in the second region close to the second edge, and the sixth sub-mark is located in the second region in the middle of the silicon wafer.

5. The solar cell according to claim 2, characterized in that: The first area includes a first non-marking area that does not correspond to the first mark, and the maximum tower base size of the area where the first mark is located is smaller than the maximum tower base size of the first non-marking area.

6. The solar cell according to claim 4, characterized in that: The second area includes a second non-marking area that does not correspond to the second mark, and the maximum tower base size of the area where the second mark is located is smaller than the maximum tower base size of the second non-marking area.

7. The solar cell according to claim 4, characterized in that: The first region is a P-type region, and the second region is an N-type region; the maximum tower base size of the region where the first mark is located is greater than the maximum tower base size of the region where the second mark is located.

8. The solar cell according to claim 5, characterized in that: The base size of the tower in the area where the first mark is located is 5 to 20 microns, and the base size of the tower in the first non-mark area is 10 to 40 microns.

9. The solar cell according to claim 7, characterized in that: The size of the tower base in the area where the second mark is located is 3 to 15 microns, and the size of the tower base in the second non-mark area is 5 to 50 microns.

10. The solar cell according to claim 3, characterized in that: The first sub-mark and the fourth sub-mark are arranged alternately in sequence along the first edge; the second sub-mark and the fifth sub-mark are arranged alternately in sequence along the second edge.

11. The solar cell according to claim 3, characterized in that: The number of the first sub-mark is one, and the first sub-mark is offset from the center of the first edge; and / or, the number of the second sub-mark is one, and the second sub-mark is offset from the center of the second edge; and / or, the number of the third sub-mark is one, and the third sub-mark is offset from the center of the third edge.

12. The solar cell according to claim 3, characterized in that: The number of the fourth sub-mark is one, and the fourth sub-mark is offset from the center of the first edge; and / or, the number of the fifth sub-mark is one, and the fifth sub-mark is offset from the center of the second edge; and / or, the number of the sixth sub-mark is one, and the sixth sub-mark is offset from the center of the fourth edge.

13. The solar cell according to claim 1, characterized in that The number of the first sub-marks is N1, N1 is greater than or equal to 2, the length of the first edge is D1, and the distance between the first sub-mark close to the end of the first edge and the end of the first edge is less than one (N1+1)th of D1; The number of the second sub-marks is N2, N2 is greater than or equal to 2, the length of the second edge is D2, and the distance between the second sub-mark close to the end of the second edge and the end of the second edge is less than one (N2+1)th of D2; The number of the third sub-marks is N3, N3 is greater than or equal to 2, the length of the third edge is D3, and the distance from the third sub-mark close to the third edge end to the third edge end is less than one (N3+1)th of D3.

14. The solar cell according to claim 3, characterized in that: The number of the fourth sub-marks is N4, N4 is greater than or equal to 2, the length of the first edge is D1, and the distance between the fourth sub-mark close to the end of the first edge and the end of the first edge is less than one (N4+1)th of D1; The number of the fifth sub-marks is N5, N5 is greater than or equal to 2, the length of the second edge is D2, and the distance between the fifth sub-mark close to the end of the second edge and the end of the second edge is less than one (N5+1)th of D2; The number of the sixth sub-marks is N6, N6 is greater than or equal to 2, the length of the fourth edge is D4, and the distance from the sixth sub-mark close to the fourth edge end to the fourth edge end is less than one (N6+1)th of D4.

15. The solar cell according to claim 2, characterized in that: The total area of ​​the first marks accounts for 0.15% to 0.65% of the total area of ​​the first region.

16. The solar cell according to claim 3, characterized in that: The area of ​​the second mark accounts for 0.15% to 0.65% of the total area of ​​the second region.

17. The solar cell according to claim 1, characterized in that The width of the first mark gradually decreases from the edge of the silicon wafer to the center of the silicon wafer.

18. The solar cell according to claim 3, characterized in that: The width of the second mark gradually decreases from the edge of the silicon wafer to the center of the silicon wafer.

19. A battery assembly, characterized in that: Comprising the solar cell according to any one of claims 1 to 18.

20. A photovoltaic system, characterized in that: Comprising a battery assembly as claimed in claim 19.

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