Method for improving phosphorus expansion junction pushing of TOPCon battery

Abstract

The invention provides a method for improving phosphorus expansion junction pushing of a TOPCon battery. The method comprises the following steps of phosphorus source deposition, diffusion propulsion and cooling annealing. Wherein in the source phosphorus deposition process, the low-temperature source introduction temperature is 795-805 DEG C; the high-temperature source introduction time is 120 to 160 seconds; and during cooling and annealing, the temperature is 840-870 DEG C. According to the method for improving phosphorus expansion junction pushing of the TOPCon battery, the reaction temperature during source introduction is increased to 795-805 DEG C, the source introduction time is shortened to 780-820 s, and the high-temperature source introduction time is increased to 120-160 s, so that the doping concentration of a phosphorus deep junction is increased; furthermore, in order to avoid the situation that the tunneling oxide layer is expanded and penetrated due to the fact that the junction pushing depth is too large, the reaction temperature of cooling and aerobic propulsion is reduced. By means of the method, the phosphorus doping concentration can be increased to 2.5 E + 20 cm <-3 >-3.7 E + 20 cm <-3 >, the photoelectric conversion efficiency of the battery piece is improved, the efficiency is expected to be improved by 0.03%, and the yield is equal.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of solar cells, and particularly relates to a method for improving phosphorus diffusion and push junction of a TOPCon cell. BACKGROUND

[0002] At present, the photovoltaic industry is booming worldwide. With the rapid development of TOPCon cells, improving efficiency and reducing cost is always the main theme of solar cell development. The production efficiency of TOPCon cells is far from the theoretical efficiency in the laboratory, therefore, improving photoelectric conversion efficiency is an unchanging topic in photovoltaic technology.

[0003] In the production process of solar cells, the matching of LPCVD and phosphorus diffusion is a key point affecting the efficiency of TOPCon cells. The phosphorus diffusion process refers to the process of introducing phosphorus as a dopant into the silicon wafer through high-temperature diffusion; the core purpose is to form an N-type region in silicon to change the conductivity type and electrical properties of silicon.

[0004] Traditional phosphorus diffusion processes have many problems, for example, some processes require long-time operation at high temperatures, which not only consumes a large amount of energy, but also easily damages the substrate materials such as silicon wafers, affecting the performance and stability of the device. At the same time, the existing process is difficult to accurately control the diffusion depth and concentration distribution of phosphorus atoms, resulting in low consistency and yield of products. In addition, with the increasing requirement for the conversion efficiency of solar cells, the existing phosphorus diffusion method faces challenges in meeting high-efficiency and low-cost production. SUMMARY

[0005] The purpose of the present application is to provide a method for improving the phosphorus diffusion and push junction of a TOPCon cell, which overcomes the above technical problems existing in the prior art.

[0006] To this end, the technical solution provided by the present application is as follows:

[0007] A method for improving the phosphorus diffusion and push junction of a TOPCon cell, comprising the following steps: phosphorus source deposition, diffusion and push, and temperature reduction and annealing.

[0008] During the deposition of the phosphorus source, the low-temperature source temperature is 795-805 DEG C, and the source time is 780-820 s; the high-temperature source temperature is 820-840 DEG C, and the high-temperature source time is 120-160 s.

[0009] During temperature reduction and annealing, the temperature is first raised to 840-870 DEG C for 290-300 s, then reduced to 840-860 DEG C for 340-360 s, and finally reduced to 760-770 DEG C for 850-950 s.

[0010] Before the phosphorus source deposition, the diffusion furnace tube is leak tested at 780-800℃, by the following method:

[0011] Step 1) Vacuum pumping: close the diffusion furnace door, set the pressure of the diffusion furnace tube to 680-720mbar, and take 55-65s;

[0012] Step 2) Vacuum pumping: close the diffusion furnace door, set the pressure of the diffusion furnace tube to 120-180mbar, and take 200-210s;

[0013] Step 3) Leak testing: close the gas valve and the diaphragm pump at 120-180mbar, and check the airtightness of the diffusion furnace tube.

[0014] The specific process of phosphorus source deposition is as follows:

[0015] Step 1) Temperature rising: under the pump pressure of 120-180mbar, the temperature is raised to 795-805℃, and the nitrogen N2 flow rate is set to 2800-3200sccm to purge the internal environment of the tube, and it takes 290-300s;

[0016] Step 2) Oxidation: under the pump pressure of 120-180mbar and the temperature of 795-805℃, oxygen is introduced for oxidation, and the oxygen flow rate is 850-950sccm, and it takes 250-260s;

[0017] Step 3) Low-temperature source passing: under the pump pressure of 120-180mbar and the temperature of 795-805℃, the small nitrogen carrying POCI3 flow rate is 1600-1700sccm, the large nitrogen flow rate is 650-750sccm, and the oxygen flow rate is 650-750sccm, and it takes 780-820s;

[0018] Step 4) High-temperature source passing: under the pump pressure of 120-180mbar and the temperature of 820-830℃, the small nitrogen carrying POCI3 flow rate is 1600-1700sccm, the large nitrogen flow rate is 650-750sccm, and the oxygen flow rate is 700sccm, and it takes 120-160s.

[0019] The specific process of diffusion promotion is as follows:

[0020] Step 1) Temperature rising: the temperature is raised to 855-860℃, the large nitrogen flow rate is 1650-1700sccm, and the small nitrogen flow rate is 950-1000sccm, and it takes 230-250s;

[0021] Step 2) warming up: warming up to 878℃~879℃, large nitrogen flow is 1900sccm~2100sccm, small nitrogen flow is 950sccm~1000sccm, time is 495~500s;

[0022] Step 3) pushing: large nitrogen flow is 780sccm~820sccm, small nitrogen flow is 780~820sccm, oxygen flow is 1000sccm~1100sccm, high-temperature pushing is carried out, time is 400s~405s.

[0023] The specific process of cooling annealing is as follows:

[0024] Step 1) cooling down: temperature is reduced to 840℃~870℃, pressure is increased to 380mbar~400mbar, large nitrogen flow is 1900sccm-2100sccm, small nitrogen flow is 950sccm~1100sccm, oxygen flow is 2800sccm~3200sccm, time is 290s~300s;

[0025] Step 2) cooling down: under the pressure of 380mbar~400mbar, the flow is unchanged, the temperature is reduced to 840℃~860℃, time is 340s-360s;

[0026] Step 3) oxidation: under the temperature of 830℃~850℃ and the pressure of 380mbar~400mbar, large nitrogen flow is 780sccm~820sccm, small nitrogen flow is 950sccm~1100sccm, oxygen flow is 1450sccm~1550sccm, time is 290s~300s;

[0027] Step 4) cooling down: temperature is reduced to 760℃-770℃, large nitrogen flow is 2900sccm~3100sccm, small nitrogen flow is 1450sccm~1550sccm, time is 850s~950s.

[0028] After cooling annealing, under the temperature of 760℃-770℃ and the pressure of 1050mbar~1060mbar, the gas is filled, N2 is set to 7800mbar~8200mbar back pressure and the pipeline is purged, time is 280s~320s, the process is ended.

[0029] Phosphorus doping concentration is 2.5E+20cm -3 ~3.7E+20cm -3 .

[0030] When the pressure drop is less than 5mbar / min, the diffusion furnace tube is qualified for air tightness.

[0031] Step 2) In the oxidation process, the large nitrogen flow is 1000-1200sccm, and the small nitrogen flow is 900-1100sccm.

[0032] The beneficial effects of the present application are:

[0033] The method for improving the phosphorus diffusion and junction of the TOPCon cell provided by the present application improves the doping concentration of the phosphorus deep junction by increasing the reaction temperature during the source pass to 795-805 DEG C, reducing the source pass time to 780-820s, and increasing the high-temperature source pass time to 120-160s; further, in order to avoid the expansion of the tunneling oxide layer caused by the deep junction depth, the reaction temperature of the oxygen-containing push during the cooling is reduced.

[0034] The method can increase the phosphorus doping concentration to 2.5E+20cm -3 -3.7E+20cm -3 , improve the photoelectric conversion efficiency of the cell, and the efficiency is expected to increase by 0.03%, and the yield is flat. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 is the comparison of the phosphorus diffusion high-temperature source pass process and the ECV curve of the comparative example of the method of the present application. DETAILED DESCRIPTION

[0036] The following specific embodiments illustrate the embodiments of the present application, and those skilled in the art can easily understand other advantages and effects of the present application from the disclosure.

[0037] Reference will now be made to the drawings to describe the exemplary embodiments of the present application, however, the present application can be implemented in many different forms, and is not limited to the embodiments described herein, which are provided to fully and completely disclose the present application and to fully convey the scope of the present application to those skilled in the art. The terms used in the exemplary embodiments shown in the drawings are not limitations of the present application.

[0038] Unless otherwise defined, the terms used herein (including technical terms) have the meanings commonly understood by those skilled in the art. In addition, it is understood that the terms defined in commonly used dictionaries should be understood in the context of the relevant art and should not be understood as ideally or overly formally.

[0039] Example 1

[0040] The present application provides a method for improving the phosphorus diffusion and junction of a TOPCon cell, comprising the following steps: phosphorus source deposition, diffusion and push, and cooling and annealing;

[0041] In the source phosphorus deposition process, the low-temperature source temperature is 795-805℃, and the source time is 780-820s; the high-temperature source temperature is 820-840℃, and the high-temperature source time is 120-160s.

[0042] The silicon wafer is placed in a high-temperature diffusion furnace tube filled with a phosphorus-containing atmosphere (usually POCl3 + O2 + N2), a chemical reaction occurs on the surface of the silicon wafer, and a layer of high-concentration phosphorus atoms is deposited (forming a layer of phosphorus-silicon glass, PSG), but after deposition, the phosphorus concentration on the surface of the silicon wafer is very high but very shallow, therefore, the silicon wafer is heated again in an oxygen environment at a high temperature, and the phosphorus atoms pre-deposited on the surface are allowed to diffuse to a deeper area inside the silicon wafer, achieving the desired junction depth.

[0043] In a high-temperature oxygen environment, a layer of silicon dioxide (SiO2) will grow on the surface of the silicon wafer. This oxide layer wraps the surface PSG and can "lock" some of the phosphorus atoms, preventing them from diffusing too much to the surface during subsequent advancement, and also helping to control the final surface concentration and impurity distribution.

[0044] According to the Arrhenius equation, the rate increases exponentially with temperature, so the source temperature directly affects the diffusion rate of phosphorus, and the temperature and time together determine the junction depth of phosphorus diffusion. Therefore, the method for improving the phosphorus diffusion and junction of the TOPCon cell provided by the present application improves the reaction temperature during source to 795-805℃, reduces the source time to 780-820s, and increases the high-temperature source time to 120-160s, thereby increasing the doping concentration of the phosphorus deep junction and improving the photoelectric conversion efficiency of the cell wafer.

[0045] Example 2

[0046] Based on example 1, the present example provides a method for improving the phosphorus diffusion and junction of the TOPCon cell, wherein during the temperature reduction annealing, the temperature is first reduced to 840-870℃ for 290-300s, then reduced to 840-860℃ for 340-360s, and finally reduced to 760-770℃ for 850-950s.

[0047] In order to avoid the expansion of the tunneling oxide layer caused by the excessive depth of the junction, the reaction temperature of the temperature reduction and oxygen advancement is reduced.

[0048] The method of the present application can increase the phosphorus doping concentration to 2.5E+20cm -3 ~3.7E+20cm -3 , improve the photoelectric conversion efficiency of the cell wafer, and the efficiency is expected to increase by 0.03%, and the yield is flat.

[0049] Example 3

[0050] On the basis of embodiment 2, the embodiment provides a method for improving phosphorus extension of a TOPCon cell, comprising the following steps:

[0051] S1, vacuumizing: at 790 DEG C, closing the diffusion furnace door, setting the pressure of the diffusion furnace tube to 700 mbar, and taking 60 s;

[0052] S2, vacuumizing: at 790 DEG C, closing the diffusion furnace door, setting the pressure of the diffusion furnace tube to 150 mbar, and taking 210 s;

[0053] S3, leak checking: at 790 DEG C and 150 mbar, closing the gas valve and the diaphragm pump, checking the airtightness of the diffusion furnace tube, and taking 60 s; if the pressure drop is less than 5 mbar / min, the airtightness is qualified;

[0054] S4, temperature rising: at 150 mbar, rising the temperature to 800 DEG C, setting the nitrogen N2 flow to 3000 sccm to purge the tube environment, and taking 300 s;

[0055] S5, oxidizing: at 800 DEG C and 150 mbar, introducing oxygen for oxidation, the oxygen flow is 900 sccm, and taking 260 s;

[0056] S6, low-temperature source passing: at 800 DEG C and 150 mbar, the small nitrogen carrying POCI3 flow is 1650 sccm, the large nitrogen flow is 700 sccm, the oxygen flow is 700 sccm, and taking 790 s;

[0057] S7, high-temperature source passing: at 830 DEG C and 150 mbar, the small nitrogen carrying POCI3 flow is 1650 sccm, the large nitrogen flow is 700 sccm, the oxygen flow is 700 sccm, and taking 150 s;

[0058] S8, temperature rising: rising the temperature to 858 DEG C, the large nitrogen flow is 1700 sccm, and the small nitrogen flow is 1000 sccm, and taking 240 s;

[0059] S9, temperature rising: rising the temperature to 878 DEG C~879 DEG C, the large nitrogen flow is 2000 sccm, and the small nitrogen flow is 1000 sccm, and taking 495 s;

[0060] S10, advancing: at 878 DEG C~879 DEG C, the large nitrogen flow is 800 sccm, the small nitrogen flow is 800 sccm, the oxygen flow is 1050 sccm, and taking 405 s for high-temperature advancing;

[0061] S11, cooling: temperature is reduced to 860℃, pressure is increased to 400 mbar, large nitrogen flow is 2000 sccm, small nitrogen flow is 1000 sccm, oxygen flow is 3000 sccm, and time is 300 s;

[0062] S12, cooling: under the pressure of 400 mbar, large nitrogen flow is 2000 sccm, small nitrogen flow is 1000 sccm, oxygen flow is 3000 sccm, temperature is reduced to 850℃, and time is 350 s;

[0063] S13, oxidation: under the temperature of 840℃ and the pressure of 400 mbar, large nitrogen flow is 800 sccm, small nitrogen flow is 1000 sccm, oxygen flow is 1500 sccm, and time is 300 s;

[0064] S14, cooling: temperature is reduced to 765℃, large nitrogen flow is 3000 sccm, small nitrogen flow is 1500 sccm, and time is 900 s;

[0065] S15, after cooling and annealing, under the temperature of 765℃ and the pressure of 1050 mbar, gas is filled, N2 is set to 8000 mbar back pressure, and pipeline is purged, time is 300 s, and the process is ended.

[0066] Comparative Example 1

[0067] A method for improving phosphorus extension of a TOPCon cell, comprising the following steps:

[0068] S1, vacuumizing: under 790℃, the door of the diffusion furnace is closed, the pressure of the diffusion furnace tube is set to 700 mbar, and time is 60 s;

[0069] S2, vacuumizing: under 790℃, the door of the diffusion furnace is closed, the pressure of the diffusion furnace tube is set to 150 mbar, and time is 210 s;

[0070] S3, leak detection: under 790℃ and 150 mbar, the gas valve and the diaphragm pump are closed, the airtightness of the diffusion furnace tube is checked, time is 60 s, and the pressure drop is less than 5 mbar / min, then the airtightness is qualified;

[0071] S4, heating: under the pump pressure of 150 mbar, the temperature is increased to 800℃, the nitrogen N2 flow is set to 3000 sccm to purge the pipeline environment, and time is 300 s;

[0072] S5, oxidation: under 805℃ and 150 mbar, oxygen is introduced for oxidation, the oxygen flow is 900 sccm, and time is 260 s;

[0073] S6, low temperature source: at 805℃ and 150mbar pressure, small nitrogen carrying POCl3 flow rate is 1650sccm, large nitrogen flow rate is 700sccm, oxygen flow rate is 700sccm, time is 790s;

[0074] S7, high temperature source: at 830℃ and 150mbar pressure, small nitrogen carrying POCl3 flow rate is 1650sccm, large nitrogen flow rate is 700sccm, oxygen flow rate is 700sccm, time is 150s;

[0075] S8, temperature rise: temperature is raised to 858℃, large nitrogen flow rate is 1700sccm, small nitrogen flow rate is 1000sccm, time is 240s;

[0076] S9, temperature rise: temperature is raised to 878℃~879℃, large nitrogen flow rate is 2000sccm, small nitrogen flow rate is 1000sccm, time is 495s;

[0077] S10, advance: at 878℃~879℃ temperature, large nitrogen flow rate is 800sccm, small nitrogen flow rate is 800sccm, oxygen flow rate is 1050sccm for high temperature advance, time is 405s;

[0078] S11, temperature drop: temperature is dropped to 870℃, pressure is raised to 400mbar, large nitrogen flow rate is 2000sccm, small nitrogen flow rate is 1000sccm, oxygen flow rate is 3000sccm, time is 300s;

[0079] S12, temperature drop: at 400mbar pressure, large nitrogen flow rate is 2000sccm, small nitrogen flow rate is 1000sccm, oxygen flow rate is 3000sccm, temperature is dropped to 860℃, time is 350s;

[0080] S13, oxidation: at 840℃ and 400mbar pressure, large nitrogen flow rate is 800sccm, small nitrogen flow rate is 1000sccm, oxygen flow rate is 1500sccm, time is 300s;

[0081] S14, temperature drop: temperature is dropped to 765℃, large nitrogen flow rate is 3000sccm, small nitrogen flow rate is 1500sccm, time is 900s;

[0082] S15, after temperature drop annealing, at 765℃, pressure is 1050mbar, gas is filled, N2 is set to 8000mbar back pressure and pipeline is purged, time is 300s, process is ended.

[0083] Comparative Example 2

[0084] A TOPCon cell phosphorus diffusion method, parameters are shown in Table 1, comprising the following steps:

[0085] S1, vacuum pumping: at 790℃, close the diffusion furnace door, set the pressure of the diffusion furnace tube to 700mbar, time 60s;

[0086] S2, vacuum pumping: at 790℃, close the diffusion furnace door, set the pressure of the diffusion furnace tube to 150mbar, time 210s;

[0087] S3, leak detection: at 790℃ and 150mbar, close the gas valve and the diaphragm pump, check the airtightness of the diffusion furnace tube, time 60s; the pressure drop is less than 5mbar / min, then the airtightness is qualified;

[0088] S4, temperature rising: at 150mbar, rise to 790℃, set the nitrogen N2 flow to 3000sccm to purge the tube environment, time 300s; wherein, the small nitrogen flow is 1000sccm, and the large nitrogen flow is 2000sccm;

[0089] S5, oxidation: at 790℃ and 150mbar, oxygen is introduced for oxidation, the oxygen flow is 900sccm, time 260s;

[0090] S6, low temperature source passing: at 790℃ and 150mbar, the small nitrogen carrying POCl3 flow is 1650sccm, the large nitrogen flow is 700sccm, and the oxygen flow is 700sccm, time 890s;

[0091] S7, high temperature source passing: at 830℃ and 150mbar, the small nitrogen carrying POCl3 flow is 1650sccm, the large nitrogen flow is 700sccm, and the oxygen flow is 700sccm, time 50s;

[0092] S8, temperature rising: rise to 858℃, the large nitrogen flow is 1700sccm, and the small nitrogen flow is 1000sccm, time 240s;

[0093] S9, temperature rising: rise to 878℃~879℃, the large nitrogen flow is 2000sccm, and the small nitrogen flow is 1000sccm, time 495s;

[0094] S10, advancing: at 878℃~879℃, the large nitrogen flow is 800sccm, the small nitrogen flow is 800sccm, and the oxygen flow is 1050sccm for high temperature advancing, time 405s;

[0095] S11, temperature falling: the temperature falls to 870℃, the pressure rises to 400mbar, the large nitrogen flow is 2000sccm, the small nitrogen flow is 1000sccm, and the oxygen flow is 3000sccm, time 300s;

[0096] S12, cooling: the temperature is decreased to 860℃ at a large nitrogen flow of 2000sccm, a small nitrogen flow of 1000sccm, an oxygen flow of 3000sccm, and a pressure of 400mbar, and the time is 350s;

[0097] S13, oxidation: the temperature is 840℃ and the pressure is 400mbar, the large nitrogen flow is 800sccm, the small nitrogen flow is 1000sccm, the oxygen flow is 1500sccm, and the time is 300s;

[0098] S14, cooling: the temperature is decreased to 765℃ at a large nitrogen flow of 3000sccm, a small nitrogen flow of 1500sccm, and the time is 900s;

[0099] S15, after the annealing of cooling, the temperature is 765℃, the pressure is 1050mbar, the large nitrogen flow is 5000sccm, the small nitrogen flow is 3000sccm, and the time is 300s, and the process is ended; wherein, the back pressure of N2 is set to 8000mbar and the pipeline is purged.

[0100] Table 1 process parameters of phosphorus diffusion of the comparative examples

[0101]

[0102] In order to further illustrate the effects of the present application, the silicon wafers obtained after the phosphorus diffusion of Example 3 and Comparative Examples 1 and 2 are characterized as follows, and the results are shown in Table 2.

[0103] 1, junction depth

[0104] The depth of the phosphorus atom distribution reaching the doping concentration of the substrate is measured by electrochemical CV method.

[0105] 2, surface concentration

[0106] The carrier concentration distribution after the phosphorus diffusion is measured by electrochemical CV method.

[0107] Table 2 result characterization

[0108] Junction depth Surface concentration Example 3 0.138 μm 3.64E+20 Comparative Example 1 0.133 μm 2.47E+20 Comparative Example 2 0.135 μm 1.20E+20

[0109] Figure 1 The high-temperature source 1 corresponds to Example 3, the high-temperature source 2 corresponds to Comparative Example 1, and the switching corresponds to Comparative Example 2. From Table 2 and Figure 1It can be seen that by increasing the temperature of the first pass source (low temperature pass source) (800℃), increasing the high temperature pass source time to 150s, and reducing the reaction temperature before oxygen-promoted cooling (860℃, 850℃), the phosphorus doping concentration can be increased while avoiding the expansion of the tunneling oxide layer caused by the deep push junction depth. Compared with Comparative Example 1 and Example 3, although the temperature of the first pass source (low temperature pass source) is high (805℃) and the high temperature pass source time is 150s, the cooling temperature (annealing temperature) is high (870℃, 860℃), so the surface concentration after phosphorus doping is lower than that of Example 3 and Comparative Example 2. Figure 1 It can be seen that the inflection point is advanced, and the tunneling oxide layer is broken down, as shown in high temperature pass source 2; and although the surface concentration after phosphorus doping is high, the junction depth is less than that of Example 3 and Comparative Example 2. Comparative Example 2 is the existing phosphorus diffusion process, and the surface concentration after doping is significantly lower than that of Example 3 and Comparative Example 1.

[0110] The battery pieces corresponding to Example 3 and Comparative Example 2 were subjected to electrical performance testing, which was achieved by measuring the current-voltage (IV) characteristic curve of the solar cell or module. The core principle is based on the photoelectric effect and circuit measurement technology, combined with a steady-state light source to simulate standard light conditions, to quickly evaluate the static electrical performance of the device; including open-circuit voltage (Uoc), short-circuit current (Isc), conversion efficiency (Eta), and other static parameters; the specific standards refer to IEC 61215, IEC 61730, and other international photovoltaic module test specifications. The results are shown in Table 3.

[0111] Table 3 Electrical performance test results of battery pieces corresponding to Example 3 and Comparative Example 2

[0112] Item Eta (%) Voc (V) Isc (A) FF (%) A-rate PLNG Before switching 25.978 0.7305 13.782 85.156 97.80% 0.62% High temperature source 1 26.008 0.7308 13.781 85.264 98.08% 0.58% After switching back 25.980 0.7305 13.782 85.165 98.11% 0.82% GAP (high temperature source 1 - after switching) 0.029 0.0003 -0.001 0.104 0.12% -0.14%

[0113] As can be seen from Table 3, the present application can improve the photoelectric conversion efficiency of the battery piece by 0.03%, and the yield remains flat.

[0114] The above examples are merely illustrative of the present application and do not constitute a limitation on the scope of protection of the present application. Any design that is the same or similar to the present application falls within the scope of protection of the present application.

Claims

1. A method of improving phosphorus passivation of a TOPCon cell, characterized by: The method comprises the following steps: Phosphorus source deposition, diffusion promotion and annealing; In the source phosphorus deposition process, the low-temperature source temperature is 795-805 DEG C, and the source time is 780-820 s; the high-temperature source temperature is 820-840 DEG C, and the high-temperature source time is 120-160 s.

2. The method of claim 1, wherein the method is for improving the phosphorus passivation of a TOPCon cell. In the annealing process, the temperature is first raised to 840-870 DEG C, the time is 290-300 s; then the temperature is lowered to 840-860 DEG C, the time is 340-360 s; finally, the temperature is lowered to 760-770 DEG C, and the time is 850-950 s.

3. The method of claim 1, wherein the method is characterized by: Before the phosphorus source deposition, the diffusion furnace tube is leak tested at 780-800 DEG C, and the method is as follows: Step 1) vacuumizing: close the diffusion furnace door, set the diffusion furnace tube pressure to 680-720 mbar, and the time is 55-65 s; Step 2) vacuumizing: close the diffusion furnace door, set the diffusion furnace tube pressure to 120-180 mbar, and the time is 200-210 s; Step 3) leak testing: close the gas valve and the diaphragm pump at 120-180 mbar, and check the airtightness of the diffusion furnace tube.

4. The method of claim 1, wherein the method is for improving the phosphorus passivation of a TOPCon cell. The specific process of the phosphorus source deposition is as follows: Step 1) heating: under the pump pressure of 120-180 mbar, heat to 795-805 DEG C, and the nitrogen N2 flow rate is set to 2800-3200 sccm to purge the tube environment, and the time is 290-300 s; Step 2) oxidation: under the pump pressure of 120-180 mbar and the temperature of 795-805 DEG C, oxygen is introduced for oxidation, and the oxygen flow rate is 850-950 sccm, and the time is 250-260 s; Step 3) low-temperature source: under the pump pressure of 120-180 mbar and the temperature of 795-805 DEG C, the small nitrogen carrying POCI3 flow rate is 1600-1700 sccm, the large nitrogen flow rate is 650-750 sccm, and the oxygen flow rate is 650-750 sccm, and the time is 780-820 s; Step 4) high-temperature source: under the pump pressure of 120-180 mbar and the temperature of 820-830 DEG C, the small nitrogen carrying POCI3 flow rate is 1600-1700 sccm, the large nitrogen flow rate is 650-750 sccm, and the oxygen flow rate is 700 sccm, and the time is 120-160 s.

5. The method of claim 1, wherein the method further comprises: The specific process of the diffusion promotion is as follows: Step 1) heating: heat to 855-860 DEG C, the large nitrogen flow rate is 1650-1700 sccm, and the small nitrogen flow rate is 950-1000 sccm, and the time is 230-250 s; Step 2) heating: heat to 878-879 DEG C, the large nitrogen flow rate is 1900-2100 sccm, and the small nitrogen flow rate is 950-1000 sccm, and the time is 495-500 s; Step 3) Promotion: high-temperature promotion is performed at a large nitrogen flow of 780-820 sccm, a small nitrogen flow of 780-820 sccm, and an oxygen flow of 1000-1100 sccm for 400-405 s.

6. The method of claim 1, wherein the method further comprises: The specific process of the cooling annealing is as follows: Step 1) Cooling: the temperature is lowered to 840-870℃, the pressure is raised to 380-400 mbar, the large nitrogen flow is 1900-2100 sccm, the small nitrogen flow is 950-1100 sccm, the oxygen flow is 2800-3200 sccm, and the time is 290-300 s; Step 2) Cooling: the temperature is lowered to 840-860℃ at a pressure of 380-400 mbar and a constant flow, and the time is 340-360 s; Step 3) Oxidation: the large nitrogen flow is 780-820 sccm, the small nitrogen flow is 950-1100 sccm, and the oxygen flow is 1450-1550 sccm at a temperature of 830-850℃ and a pressure of 380-400 mbar, and the time is 290-300 s; Step 4) Cooling: the temperature is lowered to 760-770℃, the large nitrogen flow is 2900-3100 sccm, and the small nitrogen flow is 1450-1550 sccm, and the time is 850-950 s.

7. The method of claim 1, wherein the method further comprises: After the cooling annealing, the tube is filled with gas at 760-770℃ and a pressure of 1050-1060 mbar, the N2 is set to 7800-8200 sccm back pressure, the pipeline is purged, the time is 280-320 s, and the process is completed.

8. The method of claim 1, wherein the method further comprises: Phosphorus doping concentration is 2.5E+20 cm -3 ~3.7E+20 cm -3 .

9. The method of improving the phosphorus passivation of a TOPCon cell according to claim 3, characterized in that: When the pressure drop is less than 5 mbar / min, the diffusion furnace tube is qualified for air tightness.

10. The method of claim 4, wherein the method further comprises: Step 2) During the oxidation process, the large nitrogen flow is 1000-1200 sccm, and the small nitrogen flow is 900-1100 sccm.

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