TOPCon solar cell and preparation method and application thereof

Abstract

The invention relates to a TOPCon solar cell and a preparation method and application thereof. According to the preparation method, in the boron diffusion step, the pressure ranges from 100 mbar to 260 mbar, the temperature ranges from 810 DEG C to 840 DEG C, the boron source flow ranges from 210 sccm to 240 sccm, the nitrogen flow ranges from 2000 sccm to 6000 sccm, the oxygen flow ranges from 400 sccm to 800 sccm, the time ranges from 300 s to 500 s, the surface peak concentration ranges from 8.8 * 10 < 19 > cm <-3 > to 1.2 * 10 < 20 > cm <-3 >, and the junction depth ranges from 0.2 micrometer to 0.4 micrometer; in the SE laser doping step, the laser spot width is 80 to 100 microns, the laser power is 60 to 75 W, the laser wavelength is 200 to 1200 nm, the laser frequency is 100000 to 140000 KHz, and the scanning speed is 10 to 100 m / s. According to the preparation method, damage to the surface of the cell can be effectively reduced during superposition of SE laser doping, and then the efficiency of the TOPCon solar cell can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a TOPCon solar cell and a preparation method and application thereof. Background Art

[0002] The theoretical conversion efficiency limit of PERC solar cells is 24.5%, while the current average mass production efficiency has reached 23.2%, which is close to the theoretical limit of its efficiency, making it difficult to significantly improve the efficiency of PERC solar cells. In addition, the current mass production efficiency of TOPCon solar cells has exceeded 25%, which has better economic benefits than PERC solar cells and is the mainstream development direction in the future.

[0003] In order to further improve the efficiency of TOPCon solar cells and enhance the competitiveness of products, superimposing laser doped selective emitters (SE laser doping) in the production process is an inevitable choice. Although the process flow of SE laser doping is simple and easy to implement, directly superimposing the SE laser doping process in the existing production process of TOPCon solar cells will damage the cell, increase the reflectivity after SE laser doping, and thus reduce the efficiency of the cell. Summary of the invention

[0004] Based on this, it is necessary to provide a TOPCon solar cell and its preparation method and application to address the above problems. The preparation method can reduce the reflectivity increase when SE laser doping is superimposed, thereby improving the efficiency of the TOPCon solar cell.

[0005] The present invention provides a method for preparing a TOPCon solar cell, wherein the boron diffusion step and the SE laser doping step in the preparation method respectively meet the following conditions:

[0006] In the boron diffusion step, the pressure is 100 mbar-700 mbar, the temperature is 800°C-850°C, the boron source flow rate is 180 sccm-300 sccm, the nitrogen flow rate is 2000 sccm-20000 sccm, the oxygen flow rate is 500 sccm-3000 sccm, and the time is 100 s-500 s, so that the surface peak concentration is 8.8×10 19 cm -3 -1.2×10 20 cm -3 , the junction depth is 0.2μm-0.4μm;

[0007] In the SE laser doping step, the laser spot width is 80μm-100μm, the laser power is 60W-75W, the laser wavelength is 200nm-1200nm, the laser frequency is 100000KHz-140000KHz, and the scanning speed is 10m / s-100m / s.

[0008] In one embodiment, during the boron diffusion step, the surface peak concentration is 8.8×10 19 cm -3 -1.2×10 20 cm -3 , the junction depth is 0.25 μm-0.4 μm.

[0009] In one embodiment, in the boron diffusion step, the pressure is 100 mbar-260 mbar, the temperature is 810°C-840°C, the boron source flow rate is 200 sccm-260 sccm, the nitrogen flow rate is 2000 sccm-6000 sccm, the oxygen flow rate is 400 sccm-800 sccm, and the time is 300s-500s.

[0010] In one embodiment, in the SE laser doping step, the laser spot width is 80 μm-100 μm, the laser power is 60 W-75 W, the laser wavelength is 800 nm-1400 nm, the laser frequency is 100000 KHz-140000 KHz, and the scanning speed is 24 m / s-28 m / s.

[0011] In one embodiment, in the SE laser doping step, when the laser spot width is 80 μm, the laser power is 60 W-70 W.

[0012] In one embodiment, in the SE laser doping step, when the laser spot width is 100 μm, the laser power is 65W-75W.

[0013] In one embodiment, in the boron diffusion step, the boron source is selected from boron trichloride.

[0014] In one embodiment, in the SE laser doping step, the laser is selected from nanosecond laser.

[0015] A TOPCon solar cell prepared by the above-mentioned preparation method.

[0016] An application of the TOPCon solar cell as described above in a photovoltaic module.

[0017] In the preparation method of the TOPCon solar cell described in the present invention, by controlling the process parameters in the boron diffusion step, the surface peak concentration and the junction depth in the boron diffusion step can be controlled, and the amount of unactivated boron element deposited in the boron-rich layer can be reduced, thereby reducing the BO-Si chemical bonds on the surface of the silicon wafer. Furthermore, by controlling the laser parameters in the SE laser doping step, the damage to the velvet pyramid structure of the silicon wafer can be reduced, the increase in reflectivity after SE laser doping can be reduced, and the conversion efficiency of the TOPCon solar cell can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 : are scanning electron microscope images of silicon wafer velvet, in which e is a scanning electron microscope image of silicon wafer velvet after boron diffusion but not SE laser doping in Example 2, f is a scanning electron microscope image of silicon wafer velvet doped with SE laser in Example 2, g is a scanning electron microscope image of silicon wafer velvet doped with SE laser in Comparative Example 2, and h is a scanning electron microscope image of silicon wafer velvet doped with SE laser in Comparative Example 3;

[0019] Figure 2 : are scanning electron microscope images of the velvet surface of the silicon wafer, in which a is a scanning electron microscope image of the velvet surface of the silicon wafer after boron diffusion but not SE laser doping in Example 5, b is a scanning electron microscope image of the velvet surface of the silicon wafer after SE laser doping in Example 5, c is a scanning electron microscope image of the velvet surface of the silicon wafer after SE laser doping in Example 4, and d is a scanning electron microscope image of the velvet surface of the silicon wafer after SE laser doping in Comparative Example 4. DETAILED DESCRIPTION

[0020] For ease of understanding of the present invention, the present invention will be described more fully below with reference to relevant embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0022] The present invention provides a method for preparing a TOPCon solar cell. The method adds an SE laser doping step to the existing TOPCon solar cell preparation method. In order to avoid the superimposed SE laser doping causing significant damage to the cell, the reflectivity increase after SE laser doping is large, resulting in reduced efficiency of the TOPCon solar cell. The boron diffusion step and the SE laser doping step in the preparation method of the present invention respectively meet the following conditions:

[0023] In the boron diffusion step, the pressure is 100 mbar-260 mbar, the temperature is 810°C-840°C, the boron source flow rate is 200 sccm-260 sccm, the nitrogen flow rate is 2000 sccm-6000 sccm, the oxygen flow rate is 400 sccm-800 sccm, and the time is 300 s-500 s, so that the surface peak concentration is 8.8×10 19 cm -3 -1.2×10 20 cm -3 , the junction depth is 0.2μm-0.4μm;

[0024] In the SE laser doping step, the laser spot width is 80μm-100μm, the laser power is 60W-75W, the laser wavelength is 200nm-1200nm, the laser frequency is 100000KHz-140000KHz, and the scanning speed is 10m / s-100m / s.

[0025] The study found that during the SE laser doping process, the BO-Si chemical bond is easier to be destroyed than the Si-O chemical bond. Therefore, the more unactivated boron element deposited in the boron-rich layer, the more BO-Si chemical bonds there are on the surface of the silicon wafer. The greater the increase in reflectivity after SE laser doping, the lower the efficiency.

[0026] In this regard, the present invention can control the surface peak concentration and junction depth in the boron diffusion step by controlling the process parameters in the boron diffusion step, and reduce the amount of unactivated boron element deposited in the boron-rich layer, thereby reducing the BO-Si chemical bonds on the surface of the silicon wafer. Furthermore, by controlling the laser parameters in the SE laser doping step, the damage to the velvet pyramid structure of the silicon wafer can be reduced, and the increase in reflectivity after SE laser doping can be reduced. Therefore, the present invention can improve the conversion efficiency of TOPCon solar cells through the coordination of the boron diffusion step and the SE laser doping step.

[0027] In one embodiment, in the boron diffusion step, the pressure is 100 mbar-260 mbar, the temperature is 810°C-840°C, the boron source flow rate is 200 sccm-260 sccm, the nitrogen flow rate is 2000 sccm-6000 sccm, the oxygen flow rate is 400 sccm-800 sccm, and the time is 300 s-500 s, so that the surface peak concentration can be further controlled to be 8.8×10 19 cm -3 -1.2×10 20 cm -3 The junction depth is 0.25 μm-0.4 μm, and the amount of unactivated boron element deposited in the boron-rich layer is further reduced, so that the BO-Si chemical bonds on the surface of the silicon wafer can be further reduced. Furthermore, combined with the laser parameters in the SE laser doping step of the present invention, the damage to the velvet pyramid structure of the silicon wafer can be further reduced, and the increase in reflectivity after SE laser doping can be further reduced. Therefore, the coordination effect of the boron diffusion step and the SE laser doping step can be further improved, and the conversion efficiency of the TOPCon solar cell can be improved.

[0028] Optionally, in the boron diffusion step, the boron source is selected from boron trichloride.

[0029] In one embodiment, in the SE laser doping step, the laser spot width is 80μm-100μm, the laser power is 60W-75W, the laser wavelength is 800nm-1400nm, the laser frequency is 100000KHz-140000KHz, and the scanning speed is 24m / s-28m / s. The laser parameters in the SE laser doping step can better cooperate with the boron diffusion step, further reduce the damage to the velvet pyramid structure of the silicon wafer, and further reduce the increase in reflectivity after SE laser doping, thereby further improving the conversion efficiency of the TOPCon solar cell.

[0030] Optionally, a suitable laser power may be selected according to the width of the laser spot to further improve the coordination effect between the boron diffusion step and the SE laser doping step, further reduce the increase in reflectivity after SE laser doping, and improve the conversion efficiency of the TOPCon solar cell.

[0031] For example, when the laser spot width is 80 μm, the laser power is 60W-70W; when the laser spot width is 100 μm, the laser power is 65W-75W.

[0032] The present invention does not limit the selection of laser in the SE laser doping step, and the laser can be selected according to actual conditions. In one embodiment, the laser is selected from nanosecond laser.

[0033] The present invention also provides a TOPCon solar cell prepared by the above-mentioned preparation method. The TOPCon solar cell prepared by the preparation method has excellent electrical properties such as open circuit voltage, short circuit current, fill factor, etc. and high conversion efficiency.

[0034] The present invention also provides an application of the TOPCon solar cell as described above in a photovoltaic module. Since the TOPCon solar cell has excellent cell conversion efficiency, the conversion efficiency of the photovoltaic module is improved.

[0035] Hereinafter, the TOPCon solar cell and its preparation method and application will be further described through the following specific examples.

[0036] Example 1

[0037] S1, providing an N-type silicon wafer, cleaning the N-type silicon wafer to remove surface damage and performing double-sided texturing to form a pyramid texturing structure.

[0038] S2, double insertion is performed on the silicon wafer after texturing, and then boron diffusion is performed on the front side of the silicon wafer. The pressure during boron diffusion is 200mbar, the temperature is 820℃, the boron trichloride flow rate is 210sccm, the nitrogen flow rate is 2700sccm, the oxygen flow rate is 540sccm, and the time is 410s to form a PN junction. The peak concentration of the surface after boron diffusion is 1.06×10 20 cm -3 , the junction depth is 0.31μm.

[0039] S3, SE laser doping was performed on the boron diffusion surface to produce a laser square pattern. The laser spot width was 100μm, the laser power was 65W, the laser wavelength was 1064nm, the laser frequency was 120000KHz, and the scanning speed was 25m / s. The reflectivity changes before and after SE laser doping were monitored.

[0040] S4, back-to-back double insertion of the SE laser doped silicon wafers, and oxidation of the SE laser doped surface.

[0041] S5, removing the borosilicate glass (BSG) on the back side of the silicon wafer and polishing the back side of the silicon wafer.

[0042] S6, growing a tunneling layer and an intrinsic layer (poly-si) on the polished surface of the silicon wafer by a low-pressure chemical vapor deposition process.

[0043] S7, phosphorus diffusion is performed on the intrinsic layer.

[0044] S8, remove the phospho-silicate glass (PSG) on the back side of the silicon wafer and perform RCA cleaning on the front side of the silicon wafer.

[0045] S9, passivation of the front side of the silicon wafer by atomic layer deposition.

[0046] S10, performing a coating passivation process on the front and back sides of the silicon wafer.

[0047] S11, screen printing and sintering to obtain TOPCon solar cells.

[0048] Example 2

[0049] S1, providing an N-type silicon wafer, cleaning the N-type silicon wafer to remove surface damage and performing double-sided texturing to form a pyramid texturing structure.

[0050] S2, double insertion is performed on the silicon wafer after texturing, and then boron diffusion is performed on the front side of the silicon wafer. The pressure during boron diffusion is 200mbar, the temperature is 820℃, the boron trichloride flow rate is 210sccm, the nitrogen flow rate is 2700sccm, the oxygen flow rate is 540sccm, and the time is 410s to form a PN junction. The peak concentration of the surface after boron diffusion is 1.06×10 20 cm -3 , the junction depth is 0.31μm.

[0051] S3, SE laser doping was performed on the boron diffusion surface to produce a laser square pattern. The laser spot width was 100μm, the laser power was 70W, the laser wavelength was 1064nm, the laser frequency was 120000KHz, and the scanning speed was 25m / s. The reflectivity changes before and after SE laser doping were monitored.

[0052] Steps S4-S11 are performed with reference to Example 1.

[0053] Example 3

[0054] S1, providing an N-type silicon wafer, cleaning the N-type silicon wafer to remove surface damage and performing double-sided texturing to form a pyramid texturing structure.

[0055] S2, double insertion is performed on the silicon wafer after texturing, and then boron diffusion is performed on the front side of the silicon wafer. The pressure during boron diffusion is 200mbar, the temperature is 820℃, the boron trichloride flow rate is 210sccm, the nitrogen flow rate is 2700sccm, the oxygen flow rate is 540sccm, and the time is 410s to form a PN junction. The peak concentration of the surface after boron diffusion is 1.06×10 20 cm -3 , the junction depth is 0.31μm.

[0056] S3, SE laser doping was performed on the boron diffusion surface to produce a laser square pattern. The laser spot width was 100μm, the laser power was 75W, the laser wavelength was 1064nm, the laser frequency was 120000KHz, the scanning speed was 25m / s, and the reflectivity changes before and after SE laser doping were monitored.

[0057] Steps S4-S11 are performed with reference to Example 1.

[0058] Example 4

[0059] S1, providing an N-type silicon wafer, cleaning the N-type silicon wafer to remove surface damage and performing double-sided texturing to form a pyramid texturing structure.

[0060] S2, double insertion is performed on the silicon wafer after texturing, and then boron diffusion is performed on the front side of the silicon wafer. The pressure during boron diffusion is 200mbar, the temperature is 820℃, the boron trichloride flow rate is 210sccm, the nitrogen flow rate is 2700sccm, the oxygen flow rate is 540sccm, and the time is 410s to form a PN junction. The peak concentration of the surface after boron diffusion is 1.06×10 20 cm -3 , the junction depth is 0.31μm.

[0061] S3, SE laser doping is performed on the boron diffusion surface to produce a laser square pattern. The laser spot width is 100μm, the laser power is 60W, the laser wavelength is 1200nm, the laser frequency is 120000KHz, and the scanning speed is 25m / s. The reflectivity changes before and after SE laser doping are monitored.

[0062] Steps S4-S11 are performed with reference to Example 1.

[0063] Example 5

[0064] S1, providing an N-type silicon wafer, cleaning the N-type silicon wafer to remove surface damage and performing double-sided texturing to form a pyramid texturing structure.

[0065] S2, double insertion is performed on the silicon wafer after texturing, and then boron diffusion is performed on the front side of the silicon wafer. The pressure during boron diffusion is 200mbar, the temperature is 820℃, the boron trichloride flow rate is 210sccm, the nitrogen flow rate is 2700sccm, the oxygen flow rate is 540sccm, and the time is 410s to form a PN junction. The peak concentration of the surface after boron diffusion is 1.06×10 20 cm -3 , the junction depth is 0.31μm.

[0066] S3, SE laser doping was performed on the boron diffusion surface to produce a laser square pattern. The laser spot width was 100μm, the laser power was 70W, the laser wavelength was 1064nm, the laser frequency was 120000KHz, and the scanning speed was 25m / s. The reflectivity changes before and after SE laser doping were monitored.

[0067] Steps S4-S11 are performed with reference to Example 1.

[0068] Example 6

[0069] S1, providing an N-type silicon wafer, cleaning the N-type silicon wafer to remove surface damage and performing double-sided texturing to form a pyramid texturing structure.

[0070] S2, double insertion is performed on the silicon wafer after texturing, and then boron diffusion is performed on the front side of the silicon wafer. The pressure during boron diffusion is 200mbar, the temperature is 810℃, the boron trichloride flow rate is 210sccm, the nitrogen flow rate is 2700sccm, the oxygen flow rate is 540sccm, and the time is 410s to form a PN junction. The peak concentration of the surface after boron diffusion is 8.8×10 19 cm -3 , the junction depth is 0.25μm.

[0071] S3, perform SE laser doping on the boron diffusion surface to produce a laser square pattern, with a laser spot width of 80μm, a laser power of 70W, a laser wavelength of 1064nm, a laser frequency of 120000KHz, and a scanning speed of 25m / s, and monitor the reflectivity changes before and after SE laser doping.

[0072] Steps S4-S11 are performed with reference to Example 1.

[0073] Comparative Example 1

[0074] S1, providing an N-type silicon wafer, cleaning the N-type silicon wafer to remove surface damage and performing double-sided texturing to form a pyramid texturing structure.

[0075] S2, double insertion is performed on the silicon wafer after texturing, and then boron diffusion is performed on the front side of the silicon wafer. The pressure during boron diffusion is 200mbar, the temperature is 820℃, the boron trichloride flow rate is 270sccm, the nitrogen flow rate is 2700sccm, the oxygen flow rate is 540sccm, and the time is 410s to form a PN junction. The peak concentration of the surface after boron diffusion is 1.14×10 20 cm -3 , the junction depth is 0.38μm.

[0076] S3, SE laser doping was performed on the boron diffusion surface to produce a laser square pattern. The laser spot width was 100μm, the laser power was 70W, the laser wavelength was 1064nm, the laser frequency was 120000KHz, and the scanning speed was 25m / s. The reflectivity changes before and after SE laser doping were monitored.

[0077] Steps S4-S11 are performed with reference to Example 1.

[0078] Comparative Example 2

[0079] S1, providing an N-type silicon wafer, cleaning the N-type silicon wafer to remove surface damage and performing double-sided texturing to form a pyramid texturing structure.

[0080] S2, double insertion is performed on the silicon wafer after texturing, and then boron diffusion is performed on the front side of the silicon wafer. The pressure during boron diffusion is 200mbar, the temperature is 820℃, the boron trichloride flow rate is 170sccm, the nitrogen flow rate is 2700sccm, the oxygen flow rate is 540sccm, and the time is 410s to form a PN junction. The peak concentration of the surface after boron diffusion is 8×10 19 cm -3 , the junction depth is 0.22μm.

[0081] S3, SE laser doping was performed on the boron diffusion surface to produce a laser square pattern. The laser spot width was 100μm, the laser power was 70W, the laser wavelength was 1064nm, the laser frequency was 120000KHz, and the scanning speed was 25m / s. The reflectivity changes before and after SE laser doping were monitored.

[0082] Steps S4-S11 are performed with reference to Example 1.

[0083] Comparative Example 3

[0084] S1, providing an N-type silicon wafer, cleaning the N-type silicon wafer to remove surface damage and performing double-sided texturing to form a pyramid texturing structure.

[0085] S2, double insertion is performed on the silicon wafer after texturing, and then boron diffusion is performed on the front side of the silicon wafer. The pressure during boron diffusion is 200mbar, the temperature is 820℃, the boron trichloride flow rate is 250sccm, the nitrogen flow rate is 2700sccm, the oxygen flow rate is 540sccm, and the time is 410s to form a PN junction. The peak concentration of the surface after boron diffusion is 1.1×10 20 cm -3 , the junction depth is 0.36μm.

[0086] S3, SE laser doping was performed on the boron diffusion surface to produce a laser square pattern. The laser spot width was 100μm, the laser power was 70W, the laser wavelength was 1064nm, the laser frequency was 120000KHz, and the scanning speed was 25m / s. The reflectivity changes before and after SE laser doping were monitored.

[0087] Steps S4-S11 are performed with reference to Example 1.

[0088] The scanning electron microscope images of the textured surface of the silicon wafer after SE laser doping in Example 2, Comparative Example 2 and Comparative Example 3 are as follows: Figure 1 As shown in the figure, it can be seen that compared with the silicon wafer not doped with SE laser, the damage to the pyramid surface of the silicon wafer after SE laser doping in Comparative Examples 2 and 3 is more serious.

[0089] Comparative Example 4

[0090] S1, providing an N-type silicon wafer, cleaning the N-type silicon wafer to remove surface damage and performing double-sided texturing to form a pyramid texturing structure.

[0091] S2, double insertion is performed on the silicon wafer after texturing, and then boron diffusion is performed on the front side of the silicon wafer. The pressure during boron diffusion is 200mbar, the temperature is 820℃, the boron trichloride flow rate is 240sccm, the nitrogen flow rate is 2700sccm, the oxygen flow rate is 540sccm, and the time is 410s to form a PN junction. The peak concentration of the surface after boron diffusion is 1.06×10 20 cm -3 , the junction depth is 0.31μm.

[0092] S3, SE laser doping was performed on the boron diffusion surface to produce a laser square pattern. The laser spot width was 100μm, the laser power was 80W, the laser wavelength was 1064nm, the laser frequency was 120000KHz, and the scanning speed was 25m / s. The reflectivity changes before and after SE laser doping were monitored.

[0093] Steps S4-S11 are performed with reference to Example 1.

[0094] The scanning electron microscope images of the textured surface of the silicon wafer after SE laser doping in Example 4, Example 5 and Comparative Example 4 are as follows: Figure 2 As shown in the figure, it can be seen that compared with the silicon wafer that has not been doped with SE laser, the damage to the pyramid surface of the silicon wafer in Comparative Example 4 after SE laser doping is more serious.

[0095] Comparative Example 5

[0096] S1, providing an N-type silicon wafer, cleaning the N-type silicon wafer to remove surface damage and performing double-sided texturing to form a pyramid texturing structure.

[0097] S2, double insertion is performed on the silicon wafer after texturing, and then boron diffusion is performed on the front side of the silicon wafer. The pressure during boron diffusion is 200mbar, the temperature is 820℃, the boron trichloride flow rate is 210sccm, the nitrogen flow rate is 2700sccm, the oxygen flow rate is 540sccm, and the time is 410s to form a PN junction. The peak concentration of the surface after boron diffusion is 1.06×10 20 cm -3 , the junction depth is 0.31μm.

[0098] S3, SE laser doping is performed on the boron diffusion surface to produce a laser square pattern. The laser spot width is 100μm, the laser power is 50W, the laser wavelength is 1064nm, the laser frequency is 120000KHz, and the scanning speed is 25m / s. The reflectivity changes before and after SE laser doping are monitored.

[0099] Steps S4-S11 are performed with reference to Example 1.

[0100] Comparative Example 6

[0101] S1, providing an N-type silicon wafer, cleaning the N-type silicon wafer to remove surface damage and performing double-sided texturing to form a pyramid texturing structure.

[0102] S2, double insertion is performed on the silicon wafer after texturing, and then boron diffusion is performed on the front side of the silicon wafer. The pressure during boron diffusion is 200mbar, the temperature is 820℃, the boron trichloride flow rate is 210sccm, the nitrogen flow rate is 2700sccm, the oxygen flow rate is 540sccm, and the time is 410s to form a PN junction. The peak concentration of the surface after boron diffusion is 1.06×10 20 cm -3 , the junction depth is 0.31μm.

[0103] S3, SE laser doping was performed on the boron diffusion surface to produce a laser square pattern. The laser spot width was 70μm, the laser power was 70W, the laser wavelength was 200nm, the laser frequency was 120000KHz, the scanning speed was 25m / s, and the reflectivity changes before and after SE laser doping were monitored.

[0104] Steps S4-S11 are performed with reference to Example 1.

[0105] Comparative Example 7

[0106] S1, providing an N-type silicon wafer, cleaning the N-type silicon wafer to remove surface damage and performing double-sided texturing to form a pyramid texturing structure.

[0107] S2, double insertion is performed on the silicon wafer after texturing, and then boron diffusion is performed on the front side of the silicon wafer. The pressure during boron diffusion is 200mbar, the temperature is 820℃, the boron trichloride flow rate is 210sccm, the nitrogen flow rate is 2700sccm, the oxygen flow rate is 540sccm, and the time is 410s to form a PN junction. The peak concentration of the surface after boron diffusion is 1.06×10 20 cm -3 , the junction depth is 0.31μm.

[0108] S3, SE laser doping was performed on the boron diffusion surface to produce a laser square pattern. The laser spot width was 120μm, the laser power was 70W, the laser wavelength was 1200nm, the laser frequency was 120000KHz, the scanning speed was 25m / s, and the reflectivity changes before and after SE laser doping were monitored.

[0109] Steps S4-S11 are performed with reference to Example 1.

[0110] Comparative Example 8

[0111] Comparative Example 8 was carried out with reference to Example 1, except that the SE laser doping in step S2 was not performed.

[0112] The amount of unactivated boron in the TOPCon solar cells obtained in Examples 1-6 and Comparative Examples 1-8 after boron diffusion and the reflectivity before and after SE laser doping were tested. The test results are shown in Table 1.

[0113] Reflectivity test: Use a D8 reflectivity meter to test the reflectivity of the silicon wafer before and after SE laser doping, and take the average value after three tests.

[0114] The open circuit voltage (Uoc), short circuit current (Isc), ohmic internal resistance (Rs), parallel resistance (Rsh), fill factor (FF) and conversion efficiency (Eta) of the TOPCon solar cells obtained in Examples 1-6 and Comparative Examples 1-8 were tested using a halm tester. The test results are shown in Table 2.

[0115] Table 1

[0116]

[0117]

[0118] Table 2

[0119]

[0120] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0121] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing a TOPCon solar cell, characterized in that, in the preparation method, the boron diffusion step and the SE laser doping step respectively meet the following conditions: In the boron diffusion step, the pressure is 100 mbar - 700 mbar, the temperature is 800 °C - 850 °C, the boron source flow rate is 180 sccm - 300 sccm, the nitrogen flow rate is 2000 sccm - 20000 sccm, the oxygen flow rate is 500 sccm - 3000 sccm, and the time is 100 s - 500 s, so that the surface peak concentration is 8.8×10 19 cm -3 -1.2×10 20 cm -3 , and the junction depth is 0.2 μm - 0.4 μm; In the SE laser doping step, the laser spot width is 70μm - 120μm, the laser power is 60W - 75W, the laser wavelength is 200nm - 1400nm, the laser frequency is 80000KHz - 160000KHz, and the scanning speed is 10m / s - 100m / s.

2. The preparation method according to claim 1, characterized in that, In the boron diffusion step, the surface peak concentration is 8.8×10 19 cm -3 -1.2×10 20 cm -3 , and the junction depth is 0.25 μm - 0.4 μm.

3. The preparation method according to claim 2, characterized in that, In the boron diffusion step, the pressure is 100mbar - 260mbar, the temperature is 810°C - 840°C, the boron source flow rate is 200sccm - 260sccm, the nitrogen flow rate is 2000sccm - 6000sccm, the oxygen flow rate is 400sccm - 800sccm, and the time is 300s - 500s.

4. The preparation method according to any one of claims 1 - 3, characterized in that, In the SE laser doping step, the laser spot width is 80μm - 100μm, the laser power is 60W - 75W, the laser wavelength is 800nm - 1400nm, the laser frequency is 100000KHz - 140000KHz, and the scanning speed is 24m / s - 28m / s.

5. The preparation method according to claim 4, characterized in that, In the SE laser doping step, when the laser spot width is 80μm, the laser power is 60W - 70W.

6. The preparation method according to claim 4, characterized in that, In the SE laser doping step, when the laser spot width is 100μm, the laser power is 65W - 75W.

7. The preparation method according to any one of claims 1 - 3, characterized in that, In the boron diffusion step, the boron source is selected from boron trichloride.

8. The preparation method according to any one of claims 1 - 3, characterized in that, In the SE laser doping step, the laser is selected from nanosecond lasers.

9. A TOPCon solar cell prepared by the preparation method according to any one of claims 1 - 8.

10. An application of the TOPCon solar cell according to claim 9 in a photovoltaic module.

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