Method for reducing laser cutting damage of TOPCon solar cells and TOPCon solar cell sheet

Abstract

The present invention provides a method for reducing laser cutting damage of TOPCon solar cells and a TOPCon solar cell sheet, and relates to the technical field of solar cells. The method for reducing laser cutting damage of TOPCon solar cells comprises: laser grooving on the front of the cell sheet after secondary boron expansion, and then depositing a passivation layer and metallized grid lines and electrodes to obtain a TOPCon solar cell sheet. The present invention can prevent internal carriers from migrating to the cutting section for recombination after laser non-destructive cutting and slicing by first laser grooving on the front of the cell sheet after secondary boron expansion and then depositing a passivation layer, thereby improving the photoelectric conversion efficiency and power of the TOPCon photovoltaic module.

Description

Technical Field

[0001] The invention relates to the technical field of solar cells, and in particular to a method for reducing laser cutting damage of a TOPCon solar cell and a TOPCon solar cell sheet. Background Art

[0002] Crystalline silicon tunnel oxide passivated contact solar cell (TOPCon) is a solar cell that uses an ultra-thin silicon oxide layer and a phosphorus-doped polysilicon layer deposited on the back to achieve a carrier-selective anti-reflection contact structure. Since TOPCon solar cells can effectively block minority hole recombination, increase minority carrier lifetime, and significantly reduce the contact recombination current of the metal and silicon substrate, they have the advantages of high open circuit voltage, high short circuit current, high conversion efficiency, good stability, and low attenuation rate, and have become one of the most promising and widely used high-efficiency photovoltaic cell technologies.

[0003] In the current manufacturing process of TOPCon solar photovoltaic modules, the TOPCon cells need to be cut into several small strips by laser non-destructive cutting technology, and then manufactured into photovoltaic modules through stacking, lamination and other process technologies. However, even if laser non-destructive cutting technology is used, the passivation layer on the front and back of the TOPCon solar cell will be damaged during the cutting process, and a bare substrate silicon wafer section will be formed. This greatly increases the carrier recombination of the solar cell on the cut section, reducing the photoelectric conversion efficiency of the TOPCon solar cell slice. Generally speaking, a laser non-destructive cutting will cause a loss of 0.15% to 0.3% in the photoelectric conversion efficiency of the TOPCon solar cell, thereby greatly reducing the photoelectric conversion efficiency of the manufactured TOPCon solar photovoltaic module. However, this part of the photoelectric efficiency loss is not specifically considered in the manufacturing process of existing TOPCon solar cells and corresponding photovoltaic modules.

[0004] Therefore, it is necessary and urgent to study and develop a method for preparing TOPCon solar cells that can reduce laser cutting damage, thereby effectively reducing the cutting damage of solar cells during laser non-destructive cutting and improving the photoelectric conversion efficiency and power of corresponding photovoltaic modules.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] The first purpose of the present invention is to provide a method for reducing laser cutting damage of TOPCon solar cells. The TOPCon solar cells treated by the method can block the internal carriers from migrating to the cutting section for recombination after laser lossless cutting and slicing, thereby improving the photoelectric conversion efficiency and power of the corresponding TOPCon photovoltaic modules.

[0007] The second object of the present invention is to provide a TOPCon solar cell sheet, which is mainly prepared by the above-mentioned method for reducing laser cutting damage of TOPCon solar cells.

[0008] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0009] The present invention provides a method for reducing laser cutting damage of a TOPCon solar cell, the method comprising:

[0010] Laser grooving is performed on the front side of the cell after secondary boron expansion, followed by deposition of a passivation layer and metallized grid lines and electrodes to obtain a TOPCon solar cell.

[0011] The laser groove is located at a width of d1 on the left and right sides of the laser cutting center axis, forming a front groove separation window with a width of 2×d1. The width of d1 is 0-0.5 mm, and d1 is not equal to 0.

[0012] Furthermore, the depth of the laser grooving is 0.5-5 μm, and the cutting width of the laser grooving is 30-150 μm.

[0013] Furthermore, the laser for the laser grooving is a green picosecond laser or an ultraviolet picosecond laser.

[0014] Furthermore, the peak power of the laser used for the laser grooving is 20-100W.

[0015] Furthermore, the laser frequency during the laser grooving process is 20 to 100 kHz;

[0016] The laser processing rate during the laser grooving process is 10-25 m / s.

[0017] Furthermore, the secondary boron-expanded cell is mainly prepared by sequentially cleaning, texturing, primary boron-expanding, laser SE, and secondary boron-expanding an N-type single crystal silicon wafer.

[0018] Furthermore, the depositing of the passivation layer includes: sequentially depositing an aluminum oxide passivation film and a silicon nitride anti-reflection film on the front side of the cell after the laser grooving.

[0019] The present invention provides a TOPCon solar cell sheet, which is mainly prepared by the above method for reducing laser cutting damage of TOPCon solar cells.

[0020] Furthermore, the method for preparing the TOPCon solar cell comprises:

[0021] (A) Preparation of intermediate cell: providing an N-type monocrystalline silicon wafer, and sequentially performing cleaning, texturing, primary boron diffusion, laser SE, and secondary boron diffusion to obtain an intermediate cell A;

[0022] (B) Laser grooving: laser grooving is performed on the front side of the intermediate cell A, wherein the grooving position is at a width of d1 on the left and right sides of the laser cutting center axis, forming a front grooving separation window with a width of 2×d1, thereby obtaining the intermediate cell B;

[0023] The width of d1 is 0-0.5 mm, and d1 is not equal to 0;

[0024] (C) Backside deposition: The borosilicate glass on the back and sides of the intermediate cell B is removed, and then a tunnel oxide layer and an intrinsic polysilicon layer are deposited on the back of the intermediate cell B, and phosphorus is diffused into the intrinsic polysilicon layer to obtain the intermediate cell C;

[0025] (D) Front deposition: The phosphosilicate glass on the front and edge of the intermediate cell C is removed and cleaned by wrapping, and then an aluminum oxide passivation film is deposited to obtain the intermediate cell D;

[0026] (E) Double-sided deposition: Silicon nitride anti-reflection film is deposited on the front and back sides of the intermediate cell D, and then metallized grid lines and electrodes are deposited on the front and back sides to obtain a TOPCon solar cell.

[0027] Furthermore, the back-deposited tunneling oxide layer in step (C) is prepared by using a low-pressure chemical vapor deposition or atomic layer deposition process.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The method for reducing the damage of laser cutting of TOPCon solar cells provided by the present invention comprises: laser grooving on the front of the cell after secondary boron expansion, and then depositing a passivation layer and metallized grid lines and electrodes to obtain a TOPCon solar cell; wherein: the position of the groove body of the laser grooving is at a width of d1 on the left and right of the laser cutting center axis, forming a front grooving separation window with a width of 2×d1, and the width of d1 is 0 to 0.5 mm. The present invention can prevent internal carriers from migrating to the cutting section for recombination after laser non-destructive cutting and slicing by first laser grooving on the front of the cell after secondary boron expansion and then depositing a passivation layer, thereby weakening the attenuation of the photoelectric conversion efficiency, opening voltage, short-circuit current and fill factor of the cell during the laser cutting process, thereby improving the photoelectric conversion efficiency and power of the corresponding TOPCon photovoltaic module.

[0030] The TOPCon solar cell provided by the present invention is mainly prepared by the above method for reducing the damage of laser cutting of TOPCon solar cells. Determined by the effect of the above method for reducing the damage of laser cutting of TOPCon solar cells, the TOPCon solar cell has a better photoelectric conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 This is a schematic diagram of the structure of the TOPCon solar cell prepared in Example 1 provided by the present invention.

[0033] Icons: 1-laser groove; 2-front silver grid wire; 3-front SiNx anti-reflection film; 4-AlOx passivation film; 5-boron-doped emitter; 6-N-type silicon substrate; 7-tunneling SiO 2 Oxide layer; 8-phosphorus-doped polysilicon layer; 9-back SiNx anti-reflection film; 10-back silver grid conductor. DETAILED DESCRIPTION

[0034] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than 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.

[0035] According to one aspect of the present invention, a method for reducing laser cutting damage of TOPCon solar cells comprises:

[0036] Laser grooving is performed on the front side of the cell after secondary boron expansion, followed by deposition of a passivation layer and metallized grid lines and electrodes to obtain a TOPCon solar cell.

[0037] The laser groove is located at a width of d1 on the left and right sides of the laser cutting center axis, forming a front groove separation window with a width of 2×d1. The width of d1 is 0-0.5 mm, and d1 is not equal to 0.

[0038] The method for reducing the damage of laser cutting of TOPCon solar cells provided by the present invention comprises: laser grooving on the front of the cell after secondary boron expansion, and then depositing a passivation layer and metallized grid lines and electrodes to obtain a TOPCon solar cell; wherein: the position of the laser grooving is at a width of d1 on the left and right of the laser cutting center axis, forming a front grooving separation window with a width of 2×d1, and the width of d1 is 0 to 0.5 mm. The present invention can prevent internal carriers from migrating to the cutting section for recombination after laser non-destructive cutting and slicing by first laser grooving on the front of the cell after secondary boron expansion and then depositing a passivation layer, thereby weakening the attenuation of the photoelectric conversion efficiency, opening voltage, short-circuit current and fill factor of the cell during the laser cutting process, thereby improving the photoelectric conversion efficiency and power of the corresponding TOPCon photovoltaic module.

[0039] The details can be summarized as follows:

[0040] (1) The method of using laser to pre-groove after the secondary boron diffusion process of the TOPCon cell and then depositing a passivation layer can prevent the carriers of the TOPCon cell from migrating to the cut surface for recombination during the subsequent cutting and manufacturing of components, effectively reducing surface recombination and interface recombination;

[0041] (2) After the second boron expansion, the passivation film deposition can also deposit aluminum oxide (AlOx) and silicon nitride (SiNx) passivation layers on the laser groove surface, which can prevent carriers from recombination on the laser groove surface;

[0042] (3) The present invention performs laser pre-grooving on both sides of the TOPCon cell cutting line to isolate the cutting line and prevent the cutting damage left on the cutting cross section during the silicon wafer cutting process from causing a decrease in the photoelectric conversion efficiency of the TOPCon cell slice.

[0043] In summary, it has been experimentally verified that the open circuit voltage, short circuit current and fill factor of the TOPCon cell that has undergone laser pre-grooving treatment in this application are repaired after one laser non-destructive cutting compared to the TOPCon cell without pre-treatment, thereby improving the photoelectric conversion efficiency of the cell and photovoltaic module.

[0044] It should be noted that the laser grooving position on the front side of the cell after secondary boron expansion in this application is the pre-grooving of the laser cutting line, and the laser grooving position does not overlap with the main and auxiliary grid lines of the TOPCon solar cell to avoid damaging the grid lines during laser cutting.

[0045] It should be noted that the width of d1 is set to 0-0.5 mm in the present application. The above width limitation is mainly to prevent the laser cutting position from overlapping with the subsequent metal grid electrode deposition part, thereby affecting the electrical performance of the solar cell strips and the components after cutting.

[0046] In a preferred embodiment of the present invention, the depth of the laser grooving is 0.5-5 μm, and the grooving cutting width of the laser grooving is 30-150 μm.

[0047] As a preferred embodiment, the depth and width limits of the laser grooving can effectively avoid the impact of cutting on the performance of the cell. For example: if the depth of the grooving is too shallow, the PN junction at the grooving position cannot be removed, and carriers will still be caused to migrate to the cutting surface for carrier recombination, which will not achieve the desired effect; while if the grooving is too deep, the structure of the solar cell itself will be damaged, and the risk of fragmentation during the manufacturing process of the solar cell will be increased. Similarly, the width setting is mainly determined by the properties of the laser itself. The smaller the diameter of the laser spot, the smaller the grooving cutting width. If the width is too small, the leakage current may increase and affect the subsequent effects. If the width is too large, the front power generation area of ​​the solar cell may be reduced, resulting in a decrease in the electrical performance of the solar cell, such as the efficiency.

[0048] It should be noted that the slotting cutting width of the laser slotting in the present application is 30-150 μm. The slotting cutting width is the diameter width of the laser spot, and this range can be appropriately scaled.

[0049] In a preferred embodiment of the present invention, the laser for laser grooving is a green picosecond laser or an ultraviolet picosecond laser.

[0050] In the above preferred embodiment, the peak power of the laser used for the laser grooving is 20-100W.

[0051] In the above preferred embodiment, the laser frequency during the laser grooving process is 20 to 100 kHz, and the laser processing rate during the laser grooving process is 10 to 25 m / s.

[0052] It should be noted that the laser peak power, laser frequency and laser processing rate of the above-mentioned laser grooving can achieve the grooving effect of the present application, and there is no need to limit the specific parameters to point values.

[0053] In a preferred embodiment of the present invention, the secondary boron-expanded cell is mainly prepared by sequentially cleaning, texturing, primary boron-expanding, laser SE, and secondary boron-expanding an N-type single crystal silicon wafer.

[0054] In a preferred embodiment of the present invention, the depositing of the passivation layer comprises: sequentially depositing an aluminum oxide passivation film and a silicon nitride anti-reflection film on the front side of the cell after laser grooving.

[0055] According to one aspect of the present invention, a TOPCon solar cell is provided. The TOPCon solar cell is mainly prepared by the above method for reducing laser cutting damage of a TOPCon solar cell.

[0056] The TOPCon solar cell provided by the present invention is mainly prepared by the above method for reducing the damage of laser cutting of TOPCon solar cells. Determined by the effect of the above method for reducing the damage of laser cutting of TOPCon solar cells, the TOPCon solar cell has a better photoelectric conversion efficiency.

[0057] In a preferred embodiment of the present invention, the method for preparing the TOPCon solar cell comprises:

[0058] (A) Preparation of intermediate cell: providing an N-type monocrystalline silicon wafer, and sequentially performing cleaning, texturing, primary boron diffusion, laser SE, and secondary boron diffusion to obtain an intermediate cell A;

[0059] (B) Laser grooving: laser grooving is performed on the front side of the intermediate cell A, wherein the grooving position is at a width of d1 on the left and right sides of the laser cutting center axis, forming a front grooving separation window with a width of 2×d1, thereby obtaining the intermediate cell B;

[0060] The width of d1 is 0-0.5 mm, and d1 is not equal to 0;

[0061] (C) Backside deposition: The borosilicate glass on the back and sides of the intermediate cell B is removed, and then a tunnel oxide layer and an intrinsic polysilicon layer are deposited on the back of the intermediate cell B, and phosphorus is diffused into the intrinsic polysilicon layer to obtain the intermediate cell C;

[0062] (D) Front deposition: The phosphosilicate glass on the front and edge of the intermediate cell C is removed and cleaned by wrapping, and then an aluminum oxide passivation film is deposited to obtain the intermediate cell D;

[0063] (E) Double-sided deposition: Silicon nitride anti-reflection film is deposited on the front and back sides of the intermediate cell D, and then metallized grid lines and electrodes are deposited on the front and back sides to obtain a TOPCon solar cell.

[0064] In a preferred embodiment of the present invention, the back-deposited tunneling oxide layer in step (C) is prepared by low-pressure chemical vapor deposition or atomic layer deposition process.

[0065] As a preferred embodiment, the tunneling oxide layer of the present application is prepared using a low-pressure chemical vapor deposition or atomic layer deposition process. The ultra-thin oxide layer deposited using the "low-pressure chemical vapor deposition or atomic layer deposition" technology can allow majority electrons to tunnel into the polysilicon layer while blocking the recombination of minority holes, causing the energy band on the surface of the silicon wafer to bend, thereby forming a field passivation effect. The probability of electron tunneling is greatly increased, the contact resistance is reduced, and the open circuit voltage and short-circuit current of the battery are increased, thereby improving the battery conversion efficiency.

[0066] The technical solution of the present invention will be further described below in conjunction with embodiments.

[0067] Example 1

[0068] A method for preparing a TOPCon solar cell, the method comprising:

[0069] 1. Select an N-type single crystal silicon wafer with a resistivity of 0.8-1.5 ohm·cm and a thickness of 150um;

[0070] Double-sided texturing of the front and back sides of the silicon substrate is performed; first, KOH and H 2 O 2 The damaged layer on the surface of the silicon wafer is removed in a mixed solution of , and then the silicon wafer is textured in a NaOH solution to form a pyramid velvet surface on the surface of the silicon wafer. The size of the pyramid velvet surface is 1 to 5 μm, and the reflectivity of the front and back surfaces should be less than 8%;

[0071] 2. Perform a boron diffusion on the front side of the N-type single crystal silicon substrate to form a PN junction;

[0072] Subsequently, a laser is used to construct a selective emitter (SE) in the front fine gate area of ​​the silicon wafer after the first boron diffusion, and then a second boron diffusion is performed to push the junction and increase the doping concentration. The depth of the boron diffusion junction is about 0.5 to 3 um.

[0073] 3. Laser grooves are made on the front side of the silicon wafer after secondary boron expansion. The grooves are made at a width of d1 on the left and right sides of the laser cutting center axis to form a front groove separation window with a width of 2×d1 to obtain an intermediate cell B, so that the cell PN junctions on both sides of the cutting center axis are separated.

[0074] The width of d1 is 0.2 mm, and the depth of the laser groove is 3.5 um.

[0075] The laser used for laser grooving is a green picosecond laser, and the peak power of the laser used for laser grooving is 20 to 100 W;

[0076] The laser frequency during the laser grooving process is 20 to 100 kHz, and the laser processing rate during the laser grooving process is 10 to 25 m / s.

[0077] 4. Remove the borosilicate glass (BSG) on the back and sides of the silicon wafer after laser grooving, then deposit a tunneling oxide layer and an intrinsic polysilicon layer on the back of the silicon wafer, and diffuse phosphorus into the intrinsic polysilicon layer to form a back phosphorus-doped N+ polysilicon layer;

[0078] The thickness of the tunnel oxide layer is 1.5 nm;

[0079] The back-deposited tunneling oxide layer is prepared by low-pressure chemical vapor deposition or atomic layer deposition process;

[0080] 5. Remove the phosphosilicate glass (PSG) on the front and edge of the silicon wafer and perform wrap-around cleaning (RCA), and then perform atomic layer deposition (ALD) coating on the front of the silicon wafer to form an aluminum oxide (AlOx) passivation film;

[0081] The thickness of the aluminum oxide passivation film is 3 nm.

[0082] 6. Depositing a silicon nitride (SiNx) anti-reflection film on the front and back sides of the silicon wafer respectively;

[0083] The thickness of the silicon nitride anti-reflection film is 85 nm.

[0084] 7. Deposit metallized grid lines and electrodes on the front and back sides of the silicon wafer respectively to form a TOPCon solar cell.

[0085] Figure 1 Schematic diagram of the structure of the TOPCon solar cell prepared in this example.

[0086] in, Figure 1 1 in the figure is laser grooved groove 1; Figure 1 Middle 2 is the front silver grid wire 2; Figure 1 3 in the middle is the front SiNx anti-reflection film 3; Figure 1 4 in the figure is AlOx passivation film 4; Figure 1 5 in it is a boron-doped emitter 5; Figure 1 6 in which is an N-type silicon substrate 6; Figure 1 7 in the figure represents the tunneling SiO2 oxide layer 7; Figure 1 8 is a phosphorus-doped polysilicon layer 8; Figure 1 9 is a back SiNx anti-reflection film 9; Figure 1 Reference numeral 10 denotes a back silver grid conductor 10 .

[0087] Example 2

[0088] This embodiment except step 3:

[0089] Except that “the width of d1 is 0.5 mm, and the depth of the laser groove is 5 um”, the rest is the same as in Example 1.

[0090] Example 3

[0091] This embodiment except step 3:

[0092] Except that “the width of d1 is 0.1 mm, and the depth of the laser groove is 0.5 um”, the rest is the same as in Example 1.

[0093] Example 4

[0094] This embodiment except step 3:

[0095] Except that “the width of d1 is 0.1 mm, and the depth of the laser groove is 5 um”, the rest is the same as in Example 1.

[0096] Example 5

[0097] This embodiment except step 3:

[0098] Except that “the width of d1 is 0.5 mm, and the depth of the laser groove is 0.5 um”, the rest is the same as in Example 1.

[0099] Example 6

[0100] This embodiment except step 4:

[0101] Except that “the thickness of the tunnel oxide layer is 2 nm;”, the rest is the same as Example 1.

[0102] Example 7

[0103] This embodiment except step 4:

[0104] Except that “the thickness of the tunnel oxide layer is 1 nm;”, the rest is the same as that of Example 1.

[0105] Example 8

[0106] This embodiment except step 5:

[0107] Except that “the thickness of the aluminum oxide passivation film is 2 nm”, the rest is the same as Example 1.

[0108] Example 9

[0109] This embodiment except step 5:

[0110] Except that “the thickness of the aluminum oxide passivation film is 5 nm”, the rest is the same as Example 1.

[0111] Example 10

[0112] This embodiment except step 6:

[0113] Except that “the thickness of the silicon nitride anti-reflection film is 75 nm”, the rest is the same as Example 1.

[0114] Embodiment 11

[0115] This embodiment except step 6:

[0116] Except that “the thickness of the silicon nitride anti-reflection film is 100 nm”, the rest is the same as Example 1.

[0117] Comparative Example 1

[0118] A method for preparing a TOPCon solar cell, the method comprising:

[0119] 1. Same as Example 1;

[0120] 2. Same as Example 1;

[0121] 3. Remove the borosilicate glass (BSG) on the back and side of the silicon wafer after secondary boron expansion, then deposit a tunneling oxide layer and an intrinsic polysilicon layer on the back of the silicon wafer, and diffuse phosphorus into the intrinsic polysilicon layer to form a back phosphorus-doped N+ polysilicon layer;

[0122] The thickness of the tunnel oxide layer is 1-2 nm;

[0123] The back-deposited tunneling oxide layer is prepared by low-pressure chemical vapor deposition or atomic layer deposition process;

[0124] 4. Same as step 5 in Example 1;

[0125] 5. Same as step 6 in Example 1;

[0126] 6. Same as step 7 in Example 1.

[0127] The difference between this comparative example and Example 1 is that the step of laser grooving the silicon wafer after the secondary boron expansion is not included.

[0128] Comparative Example 2

[0129] A method for preparing a TOPCon solar cell, the method comprising:

[0130] 1. Same as comparative example 1;

[0131] 2. Same as comparative example 1

[0132] 3. Same as comparative example 1;

[0133] 4. Same as Comparative Example 1;

[0134] 5. Same as Comparative Example 1;

[0135] 6. Same as Comparative Example 1;

[0136] 7. Laser groove the front side of the silicon wafer of the TOPCon solar cell prepared in step 6. The groove position is d1 width to the left and right of the laser cutting center axis to form a front groove separation window with a width of 2×d1 to obtain an intermediate cell B, so that the cell PN junctions on both sides of the cutting center axis are separated.

[0137] The width of d1 is 0.2 mm, and the depth of the laser groove is 3.5 um.

[0138] The laser used for laser grooving is a green picosecond laser, and the peak power of the laser used for laser grooving is 20 to 100 W;

[0139] The laser frequency during the laser grooving process is 20 to 100 kHz, and the laser processing rate during the laser grooving process is 10 to 25 m / s.

[0140] The difference between this comparative example and Example 1 is that laser grooving is performed on the front side of the cell silicon wafer after the passivation layer is deposited.

[0141] Test Example 1

[0142] In order to demonstrate that the TOPCon solar cells prepared in the present application can effectively improve the photoelectric conversion efficiency and power of the TOPCon photovoltaic modules, the photoelectric conversion efficiency of the TOPCon solar cells prepared in Example 1 of the present application and Comparative Examples 1 and 2 are tested "before laser non-destructive cutting" and "after laser non-destructive cutting" respectively.

[0143] The specific test results are as follows:

[0144]

[0145] Note: The laser non-destructive cutting is performed after the battery cell is completely prepared, for example, dividing the battery cell into three.

[0146] From the above, it can be seen that Example 1 of the present application, by first performing laser grooving on the front side of the cell after secondary boron expansion and then depositing a passivation layer, can effectively improve the photoelectric conversion efficiency of the corresponding TOPCon photovoltaic module after laser non-destructive cutting and slicing. The photoelectric conversion efficiency is only reduced by 0.12% after cutting.

[0147] In Example 2, since the slot width is too wide, the area of ​​the suede surface becomes smaller, the open circuit voltage is reduced, and thus the photoelectric conversion efficiency is reduced.

[0148] In Example 3, since the groove depth is too small, the silicon is not exposed, the deep boron diffusion is not completed in this area, and the subsequent laser cutting width and depth are higher than the groove width, resulting in the inability to prevent carriers from migrating to the cutting section for recombination.

[0149] In Example 4, since the slot width is too small, the subsequent laser cutting width is larger than the slot width, which also results in the inability to prevent carriers from migrating to the cutting cross section for recombination.

[0150] In Example 5, since the groove depth is too small, the groove position is not deeply expanded. After laser cutting, there is no PN junction and passivation film at the groove position, and the damage to the battery cell still exists.

[0151] In embodiments 6 and 7, since the tunnel oxide layer is too thin or too thick, minority carriers and electrons may recombine at the interface, thereby reducing the photoelectric conversion efficiency.

[0152] In Example 8, since the aluminum oxide passivation film is too thin, there is leakage and it cannot effectively block the intrusion of oxygen, water and harmful substances, causing damage to the battery cell.

[0153] However, the implementation method of Comparative Example 1 "does not include the step of laser grooving the silicon wafer after secondary boron expansion" performs non-destructive laser cutting after the preparation of the battery cell. After the cutting and slicing, it cannot prevent the carriers from migrating to the cut cross section for recombination, thereby reducing the open circuit voltage and fill factor of the battery cell, etc., which in turn leads to a reduction in the photoelectric conversion efficiency of the battery cell.

[0154] In the implementation method of comparative example 2, "laser grooving on the front side of the cell silicon wafer after the passivation layer is deposited", the grooving is performed after the cell is prepared, and then non-destructive laser cutting is performed. After grooving, the passivation film and PN junction on the front side of the cell are destroyed, and the open circuit voltage and the like are already affected. Laser cutting again is equivalent to laser cutting twice at the same position of a cell, and the efficiency is reduced due to grooving. Therefore, the efficiency will not change significantly after laser cutting.

[0155] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A TOPCon solar cell, characterized in that: The method for preparing the TOPCon solar cell comprises: (A) Preparation of intermediate cell: providing an N-type monocrystalline silicon wafer, and sequentially performing cleaning, texturing, primary boron diffusion, laser SE, and secondary boron diffusion to obtain an intermediate cell A; (B) Laser grooving: laser grooving is performed on the front side of the intermediate cell A, wherein the grooving position is at a width of d1 on the left and right sides of the laser cutting center axis, forming a front grooving separation window with a width of 2×d1, thereby obtaining the intermediate cell B; The width of d1 is 0-0.5 mm, and d1 is not equal to 0; (C) Backside deposition: The borosilicate glass on the back and sides of the intermediate cell B is removed, and then a tunnel oxide layer and an intrinsic polysilicon layer are deposited on the back of the intermediate cell B, and phosphorus is diffused into the intrinsic polysilicon layer to obtain the intermediate cell C; (D) Front deposition: The phosphosilicate glass on the front and edge of the intermediate cell C is removed and cleaned by wrapping, and then an aluminum oxide passivation film is deposited to obtain the intermediate cell D; (E) Double-sided deposition: Silicon nitride anti-reflection film is deposited on the front and back sides of the intermediate cell D, and then metallized grid lines and electrodes are deposited on the front and back sides to obtain a TOPCon solar cell. The back-deposited tunnel oxide layer in step (C) is prepared by low-pressure chemical vapor deposition or atomic layer deposition; The thickness of the back-deposited tunneling oxide layer is 1.5 nm; The thickness of the aluminum oxide passivation film is 3 nm.

2. The TOPCon solar cell according to claim 1, characterized in that: The depth of the laser grooving is 0.5-5 μm, and the grooving cutting width of the laser grooving is 30-150 μm.

3. The TOPCon solar cell according to claim 1, characterized in that: The laser used for the laser grooving is a green light picosecond laser or an ultraviolet picosecond laser.

4. The TOPCon solar cell according to claim 3, characterized in that: The laser peak power of the laser grooving is 20-100W.

5. The TOPCon solar cell according to claim 3, characterized in that: The laser frequency during the laser grooving process is 20 to 100 kHz; The laser processing rate during the laser grooving process is 10-25 m / s.

6. The TOPCon solar cell according to claim 1, characterized in that: The secondary boron-expanded cell is mainly prepared by sequentially cleaning, texturing, primary boron-expanding, laser SE, and secondary boron-expanding an N-type single crystal silicon wafer.

7. The TOPCon solar cell according to claim 1, characterized in that: The depositing of the passivation layer comprises: An aluminum oxide passivation film and a silicon nitride anti-reflection film are sequentially deposited on the front side of the cell after laser grooving.

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