Method for preventing TOPCon solar cell boron diffusion furnace door flange from rusting

Abstract

The invention discloses a method for preventing a TOPCon solar cell boron diffusion furnace door flange from rusting. The problem of silicon wafer pollution caused by flange rusting is solved through environment control, hardware adjustment and technological parameter optimization. The method comprises the following specific steps: controlling the temperature and humidity of a workshop to be 23 + / -3 DEG C, 40-50%, and ensuring that no process cooling water leaks from a machine; the flow of flange cooling water is reduced from 7 L / min to 5 L / min, and a short air inlet pipe in a 1.8 m furnace is adopted to replace a long air inlet pipe; when the source is introduced, the nitrogen at the furnace mouth is adjusted to 700 sccm, the source-carrying nitrogen is adjusted to 5500 sccm, the boron chloride is adjusted to 120 sccm, the deposition pressure is increased to 220 mbar, and the post-oxygen temperature is reduced to 1020 DEG C. According to the method, the concentration of boron chloride is reduced from 4.88% to 1.76%, and a low-concentration shallow PN junction is formed. Through optimization, the service life of the flange is prolonged to more than 100 days, the yellowing abnormity of a silicon wafer is reduced, the maintenance period of a diaphragm pump is prolonged from 30 days to 50 days, the conversion efficiency of the battery is improved by more than 0.04%, and the method is suitable for a TOPCon battery boron diffusion process.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cell production processes, and in particular to a method for preventing rusting of a furnace door flange used in boron diffusion of TOPCon solar cells. The method solves the problems of silicon wafer contamination and efficiency reduction caused by rusting of the furnace door flange during the boron diffusion process by means of environmental control, hardware optimization, and process parameter adjustment. Background Art

[0002] During the boron diffusion process for N-type TOPCon cells, the furnace door flange, which fits over the outer ring of the quartz furnace tube, is susceptible to yellow-brown rust after about a month of use. Rust particles contaminate the quartz tube and silicon wafers, introducing deep-level recombination centers, reducing minority carrier lifetime and cell conversion efficiency. In severe cases, they can cause the silicon wafer to appear abnormally yellow (normally a uniform, deep blue).

[0003] The reasons that lead to rusting of furnace door flanges are generally as follows: First, the influence of the internal and external environment of the machine, such as high humidity in the workshop and inside the machine, poor fresh air circulation, especially during the cooling and shutdown period of the machine, which is more likely to worsen; second, the influence of equipment hardware, such as long air intake mode, process cooling water leakage, cooling water flow and temperature, and the escape of byproducts such as boron chloride, boron oxide, and chlorine in the quartz furnace tube when the furnace door is often open; third, the influence of the process formula, such as the furnace tube pressure, the amount of boron chloride used, and the distribution of the gas field and temperature field in the tube. By controlling the external environment, modifying the equipment hardware, and optimizing the process formula, the rusting of the furnace door flange can be effectively improved. Under the conditions of continuous and uninterrupted production, the furnace door flange has been used for more than 100 days with a bright appearance and no rust, and the yellowing of flakes after boron expansion has been basically eliminated. Summary of the Invention

[0004] The core objective of this invention is to provide a method for preventing rust from occurring in the door flanges of TOPCon solar cell boron diffusion furnaces. By utilizing environmental control, hardware optimization, and process parameter adjustments, this method extends the service life of the door flanges, reduces silicon wafer contamination, and improves solar cell conversion efficiency.

[0005] An embodiment of the present invention provides a method for preventing rusting of a TOPCon solar cell boron diffusion furnace door flange, comprising the following steps:

[0006] Step 1: Environmental control, control the temperature and humidity in the workshop and optimize the sealing of the machine;

[0007] Step 2: Adjust the hardware conditions, optimize the flange cooling water flow rate, and improve the air intake method;

[0008] Step 3: Optimize process parameters, adjust gas flow and concentration; shallow junction low concentration doping.

[0009] In some embodiments of the present invention, the above-mentioned environmental control step includes:

[0010] Workshop temperature and humidity control: Through the air conditioning system and fresh air circulation, the workshop temperature is maintained at 23±3℃ and the humidity is controlled at 40%-50%;

[0011] Optimize machine sealing: ensure that the machine exhaust system is normal and the process cooling water pipes and valves are leak-free.

[0012] In some embodiments of the present invention, the hardware condition adjustment step includes:

[0013] Optimize the flange cooling water flow rate: reduce the flange cooling water flow rate from 7L / min to 5L / min, set the flow rate lower limit to 2L / min less than the actual value, and set the temperature upper limit to 50°C;

[0014] Improvement of air intake method: the 2.8m long air intake pipe at the furnace mouth was changed to a 1.8m short air intake pipe in the furnace.

[0015] In some embodiments of the present invention, the process parameter optimization step includes adjusting gas flow and concentration, adjusting deposition pressure and temperature, and shallow junction low-concentration doping.

[0016] In some embodiments of the present invention, the above-mentioned gas flow rates and concentrations are adjusted as follows: when the source is turned on, the furnace mouth nitrogen flow rate is increased from 0 sccm to 700 sccm, the source-carrying nitrogen flow rate is increased from 2600 sccm to 5500 sccm, the oxygen flow rate is reduced from 600 sccm to 500 sccm, the boron chloride flow rate is reduced from 200 sccm to 120 sccm, and the boron chloride concentration is reduced from 4.88% to 1.76%.

[0017] In some embodiments of the present invention, the above-mentioned deposition pressure and temperature are adjusted as follows: the deposition pressure is increased from 160 mbar to 220 mbar, and the post-oxygen peak temperature is reduced from 1050° C. to 1020° C.

[0018] In some embodiments of the present invention, the shallow junction low-concentration doping is achieved by reducing the amount of boron chloride to 120 sccm and increasing the deposition pressure to 220 mbar.

[0019] The embodiments of the present invention have at least the following advantages or beneficial effects:

[0020] This invention adjusts the external environmental temperature and humidity, the PCW flow rate of the machine, and the process recipe parameters. Without changing the hardware, by adjusting pressure, gas, and temperature, BCL3 consumption is reduced while significantly reducing rust on the furnace door flange, achieving a service life of over 100 days while maintaining a bright, rust-free exterior. Furthermore, a PN junction with a lower doping concentration and shallower junction depth is achieved, resulting in the following advantages:

[0021] The present invention improves the probability of collecting photogenerated carriers: the surface of the solar cell is directly irradiated by sunlight, and the positive surface area is the area where the most photogenerated carriers are generated. The shallower PN junction, that is, closer to the cell surface, can increase the probability of collecting photogenerated carriers, thereby improving the short-circuit current and open-circuit voltage of the photovoltaic cell, and ultimately improving the conversion efficiency of the cell;

[0022] This invention improves minority carrier lifetime: In the photovoltaic effect, minority carrier lifetime is one of the key factors affecting cell efficiency. Excessively high doping concentrations can lead to severe lattice distortion and increased defects, reducing carrier diffusion length and lifetime, and negatively impacting open-circuit voltage and short-circuit current. Therefore, by reducing the boron doping concentration, the minority carrier lifetime can be increased, thereby increasing the short-circuit current and open-circuit voltage of photovoltaic cells, ultimately improving the cell's conversion efficiency.

[0023] This invention reduces metal contamination: Through the above-mentioned rust-proof measures, rust on the furnace door flange is greatly reduced, thereby reducing the penetration and contamination of the furnace tubes and silicon wafers by metal ions. These metal ions can diffuse into the silicon wafer during the process, introducing some deep energy levels in the silicon wafer's band gap and becoming recombination centers for photogenerated carriers, thereby shortening the minority carrier lifetime and seriously reducing the conversion efficiency of the solar cell.

[0024] The present invention enhances UV attenuation performance: Photovoltaic cells are affected by factors such as ultraviolet light and ambient temperature during use, causing their performance to gradually decay. The step-by-step deposition technology according to the temperature gradient can increase the effective doping rate of boron atoms, reduce interstitial atoms, improve the stability of photovoltaic cells, enhance their resistance to ultraviolet light attenuation, and extend the service life of the battery.

[0025] The present invention optimizes the spectral response characteristics: low-concentration shallow junction doping technology can optimize the spectral response characteristics of photovoltaic cells, increase their absorptivity within a specific wavelength range, and thus improve the conversion efficiency of the cells.

[0026] The present invention reduces the oxygen and temperature in the high-temperature oxidation step, increases the extraction pressure, and reduces the furnace tube load to a great extent, thereby increasing the furnace tube quartz life and saving operating costs.

[0027] The present invention forms a full-chain anti-corrosion system covering the workshop environment, equipment hardware, and process through the synergistic effect of environmental control, hardware optimization, and process parameter adjustment, systematically solving the problem of furnace door flange rust.

[0028] In the present invention, the ambient water vapor content is reduced by controlling the workshop temperature and humidity (23±3°C, 40%-50%), thereby inhibiting the electrochemical corrosion of the flange; the machine sealing is optimized to prevent cooling water leakage, thereby avoiding the reaction of moisture with the boron source to generate corrosive boric acid, which directly corresponds to the technical details of claim 2.

[0029] The present invention controls the flange cooling water flow rate to 5L / min and sets a safety threshold to reduce seal wear and leakage caused by water flow impact, thereby reducing the risk of flange corrosion from long-term water contact. A 1.8m short air intake pipe is used to change the gas flow direction, allowing boron chloride to diffuse in the middle of the furnace tube, reducing direct erosion and corrosion of the furnace mouth flange. The hardware modification directly targets the defects of the original long air intake process.

[0030] In the present invention, the boron chloride concentration is reduced from 4.88% to 1.76% (200 sccm→120 sccm), thereby reducing the content of corrosive active substances in the gas phase. At the same time, nitrogen gas (700 sccm) at the furnace mouth forms a gas curtain to block the escape of the boron source. This dual effect reduces the frequency of the flange contact with the corrosive gas.

[0031] In the present invention, the deposition pressure is increased to 220 mbar, and the diffusion of boron chloride to the furnace mouth is suppressed by increasing the gas pressure in the tube; the post-oxygen temperature is reduced to 1020°C to reduce the high-temperature oxidation reaction rate of the flange metal and oxygen, corresponding to the temperature and pressure control parameters of claim 6.

[0032] In the present invention, a shallow PN junction is formed by using a low boron chloride dosage (120 sccm) and a high deposition pressure (220 mbar), thereby reducing lattice distortion caused by high-concentration doping, reducing the channels for metal ions to diffuse into the silicon wafer, and indirectly suppressing the contamination of the silicon wafer by flange rust powder, reflecting the technical effect of coordinated optimization of process parameters.

[0033] The present invention directly corresponds to the combined effects of environmental control to reduce water vapor corrosion, hardware optimization to reduce mechanical damage, and process adjustment to reduce chemical corrosion.

[0034] The maintenance period of the diaphragm pump of the present invention is extended from 30 days to 50 days, thanks to the reduction of pump load by increased deposition pressure; the service life of the quartz furnace tube is extended because the post-oxygen temperature is reduced to reduce thermal stress damage. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0036] Figure 1 It is a principle block diagram of the present invention;

[0037] Figure 2 This is a comparison diagram of the ECV curve of the present invention. DETAILED DESCRIPTION

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0039] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0040] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0041] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprises" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further limitations, an element defined by the sentence "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device that includes the element.

[0042] In the description of the embodiments of the present invention, "a plurality of" means at least two.

[0043] In the description of the embodiments of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0044] like Figure 1The embodiment of the present invention discloses a method for preventing rusting of the door flange of a TOPCon solar cell boron diffusion furnace, which comprises the following steps:

[0045] Step 1: Environmental control, control the temperature and humidity in the workshop and optimize the sealing of the machine;

[0046] Step 2: Adjust the hardware conditions, optimize the flange cooling water flow rate, and improve the air intake method;

[0047] Step 3: Optimize process parameters, adjust gas flow and concentration; shallow junction low concentration doping.

[0048] In this embodiment, the above-mentioned environmental control step includes:

[0049] Workshop temperature and humidity control: Through the air conditioning system and fresh air circulation, the workshop temperature is maintained at 23±3℃ and the humidity is controlled at 40%-50%;

[0050] Optimize machine sealing: ensure that the machine exhaust system is normal and the process cooling water pipes and valves are leak-free.

[0051] In this embodiment, the hardware condition adjustment step includes:

[0052] Optimize the flange cooling water flow rate: reduce the flange cooling water flow rate from 7L / min to 5L / min, set the flow rate lower limit to 2L / min less than the actual value, and set the temperature upper limit to 50°C;

[0053] Improvement of air intake method: the 2.8m long air intake pipe at the furnace mouth was changed to a 1.8m short air intake pipe in the furnace.

[0054] In this embodiment, the process parameter optimization steps include adjusting gas flow and concentration, adjusting deposition pressure and temperature, and shallow junction low-concentration doping.

[0055] In this embodiment, the above-mentioned gas flow rates and concentrations are adjusted as follows: when the source is turned on, the furnace mouth nitrogen flow rate is increased from 0 sccm to 700 sccm, the source-carrying nitrogen flow rate is increased from 2600 sccm to 5500 sccm, the oxygen flow rate is reduced from 600 sccm to 500 sccm, the boron chloride flow rate is reduced from 200 sccm to 120 sccm, and the boron chloride concentration is reduced from 4.88% to 1.76%.

[0056] In this embodiment, the deposition pressure and temperature are adjusted as follows: the deposition pressure is increased from 160 mbar to 220 mbar, and the post-oxygen peak temperature is reduced from 1050° C. to 1020° C.

[0057] In this embodiment, the shallow junction low-concentration doping is achieved by reducing the amount of boron chloride to 120 sccm and increasing the deposition pressure to 220 mbar.

[0058] Example 1:

[0059] Environmental Control:

[0060] The temperature and humidity in the workshop are strictly controlled at 23°C and 45% respectively. The air conditioning system monitors and records the temperature and humidity data every hour.

[0061] The machine exhaust system wind speed is maintained at 5m / s. The process cooling water (PCW) pipeline is leak tested using helium mass spectrometry, and the leakage rate is less than 1×10 -9 Pa·m 3 / s.

[0062] Hardware Adjustment:

[0063] The flange cooling water flow is precisely adjusted to 5L / min, the flow meter accuracy is 0.1L / min, and the flow lower limit is set to 3L / min with sound and light alarm;

[0064] The air intake method was changed to a short air intake pipe in the 1.8m furnace. The pipe mouth was located 1 / 3 of the distance from the center axis of the quartz furnace tube to the furnace mouth, and the gas inlet angle was 30° to the axial direction of the furnace tube.

[0065] Process parameters:

[0066] Source stage: furnace door nitrogen (DoorN2) 700sccm, source nitrogen (BN2) 5500sccm, oxygen (BO2) 500sccm, boron chloride (BCl3) 120sccm, gas mixing uniformity error <±2%;

[0067] The deposition pressure is 220 mbar, and the pressure fluctuation is ≤±1 mbar by adjusting the pumping speed of the diaphragm pump;

[0068] The post-oxygen peak temperature is 1020℃, and the PID temperature control system is used to control the heating rate within 5℃ / min.

[0069] Test results:

[0070] After 125 days of continuous use, the flange had no visible rust on the surface, and the metal luster was uniform under a 3D microscope (500 times), with a roughness of Ra = 0.6μm;

[0071] The abnormal yellowing rate of silicon wafers is 0.2%, the dark wafer rate of EL detection is 0.05%, and the battery conversion efficiency is 26.94% (an increase of 0.041% compared with the original process);

[0072] The maintenance cycle of the diaphragm pump has been extended to 52 days, and the service life of the quartz furnace tube has reached 800 batches (the original process was 600 batches).

[0073] Comparative Example 1:

[0074] Environmental control: Workshop temperature 28°C, humidity 60%, PCW pipe leakage rate 5×10 -8 Pa·m 3 / s;

[0075] Hardware configuration: 2.8m long air inlet pipe, flange cooling water flow rate 7L / min;

[0076] Process parameters: BCl3 = 200 sccm, deposition pressure 160 mbar, post-oxygen temperature 1050°C, furnace mouth nitrogen 0 sccm.

[0077] Test results:

[0078] The flange had large areas of rust after 28 days of use (coverage > 60%), and the surface roughness Ra = 2.1μm;

[0079] The yellowing rate of silicon wafers is 3.5%, the dark film rate of EL detection is 0.8%, and the conversion efficiency is 26.89%;

[0080] The diaphragm pump needs maintenance every 28 days, and the quartz furnace tube has a lifespan of 500 batches.

[0081] Example 2:

[0082] Technical features:

[0083] Environmental Control:

[0084] The workshop humidity was raised to 50% (upper limit), the temperature was 23°C, the machine exhaust system was operating normally, but there was a slight leakage in the PCW pipe (leakage rate 1×10 -8 Pa·m 3 / s).

[0085] Hardware Adjustment:

[0086] The flange cooling water flow rate is 6 L / min (the lower limit alarm is not triggered), and the installation position of the 1.8 m short air intake pipe is consistent with that in Example 1.

[0087] Process parameters:

[0088] Source pass stage: BCl3 = 120 sccm, deposition pressure 220 mbar, post-oxygen temperature 1020°C, and other gas flow rates are the same as in Example 1.

[0089] Test results:

[0090] After 85 days of use, sporadic rust spots appeared on the edge of the furnace mouth (area accounting for <1%), with a roughness of Ra = 0.8μm;

[0091] The yellowing rate of silicon wafers is 0.9%, and the conversion efficiency is 26.91% (an increase of 0.012% compared to the original process);

[0092] The maintenance cycle of the diaphragm pump is 40 days. Because the ambient humidity is close to the upper limit and there is a small amount of water leakage, the corrosion rate is increased by about 30% compared with Example 1.

[0093] Comparative Example 2:

[0094] Technical features:

[0095] Environmental control: workshop temperature 23°C, humidity 40%, PCW pipeline no leakage;

[0096] Hardware configuration: 2.8m long air intake pipe and 7L / min cooling water flow rate are used;

[0097] Process parameters: BCl3 = 200 sccm, deposition pressure 160 mbar, post-oxygen temperature 1050 °C.

[0098] Test results:

[0099] The flange showed rust spots (coverage rate of about 10%) after 42 days of use, which was 14 days later than that of Comparative Example 1. However, the long air inlet pipe still caused the boron source to flush the furnace mouth.

[0100] The yellowing rate of the silicon wafer was 2.8% (a decrease of 20% compared with Comparative Example 1), and the conversion efficiency was not significantly improved;

[0101] The maintenance cycle of the diaphragm pump is 30 days, and the hardware and process defects are not resolved, so the anti-corrosion effect is limited.

[0102] Example 3:

[0103] Technical features:

[0104] Environmental Control:

[0105] The temperature and humidity in the workshop were out of control (temperature 26°C, humidity 58%), and the PCW pipes of the machines were leaking seriously (leakage rate 5×10 - 8 Pa·m 3 / s).

[0106] Hardware Adjustment:

[0107] The original 2.8m long air inlet pipe is used, and the flange cooling water flow rate is maintained at 7L / min.

[0108] Process parameters:

[0109] Source pass stage: DoorN2 = 700 sccm, BN2 = 5500 sccm, BCl3 = 120 sccm, deposition pressure 220 mbar, post-oxygen temperature 1020°C.

[0110] Test results:

[0111] After 60 days of use, the rust coverage of the flange reached 15%, mainly concentrated in the area where the furnace mouth contacts the quartz tube;

[0112] The yellowing rate of silicon wafers was 1.2%, and the conversion efficiency was 26.90% (a 0.001% improvement over the original process). The environmental out-of-control situation offset some of the effects of process optimization.

[0113] The maintenance cycle of the diaphragm pump is 38 days. Since the hardware and control environment have not been modified, the corrosion load of the equipment is still high.

[0114] Comparative Example 3:

[0115] Technical features:

[0116] Environmental control: workshop temperature 23°C, humidity 45%, no PCW leakage;

[0117] Hardware adjustment: 1.8m short air intake pipe, flange cooling water flow 5L / min;

[0118] Process parameters: BCl3 = 200 sccm (not reduced), deposition pressure 220 mbar, post-oxygen temperature 1020°C.

[0119] Test results:

[0120] Rust spots appeared on the flange after 75 days of use (coverage rate 5%). Because the boron chloride concentration did not decrease, there was still slight corrosion at the furnace mouth.

[0121] The yellowing rate of the silicon wafer is 2.2%, which is 37% lower than that of Comparative Example 1, but higher than 0.3% of Example 1;

[0122]

[0123] In summary, the present invention systematically solves the core problem of rusting of the furnace door flange in the TOPCon battery boron diffusion process through the synergistic effect of environmental control, hardware adjustment and process parameter optimization, and all technical indicators are significantly improved.

[0124] It will be apparent to those skilled in the art that the present application is not limited to the details of the exemplary embodiments described above and that the present application can be implemented in other specific forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the present application is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

Claims

1. A method for preventing rust on the door flange of a TOPCon solar cell boron diffusion furnace, characterized in that The following steps are involved: Step 1: Environmental control, control the temperature and humidity in the workshop and optimize the sealing of the machine; Step 2: Adjust the hardware conditions and optimize the flange cooling water flow; Improve the air intake method; Step 3: Optimize process parameters, adjust gas flow and concentration; shallow junction low concentration doping.

2. The method for preventing rusting of a TOPCon solar cell boron diffusion furnace door flange according to claim 1, characterized in that: The environmental control step comprises: Workshop temperature and humidity control: Through the air conditioning system and fresh air circulation, the workshop temperature is maintained at 23±3℃ and the humidity is controlled at 40%-50%; Optimize machine sealing: ensure that the machine exhaust system is normal and the process cooling water pipes and valves are leak-free.

3. The method for preventing rusting of a TOPCon solar cell boron diffusion furnace door flange according to claim 1, characterized in that: The hardware condition adjustment step includes: Optimize the flange cooling water flow rate: reduce the flange cooling water flow rate from 7L / min to 5L / min, set the flow rate lower limit to 2L / min less than the actual value, and set the temperature upper limit to 50°C; Improvement of air intake method: the 2.8m long air intake pipe at the furnace mouth was changed to a 1.8m short air intake pipe in the furnace.

4. The method for preventing rusting of a TOPCon solar cell boron diffusion furnace door flange according to claim 1, characterized in that: The process parameter optimization steps include gas flow and concentration adjustment, deposition pressure and temperature adjustment, and shallow junction low-concentration doping.

5. The method for preventing rusting of the door flange of a TOPCon solar cell boron diffusion furnace according to claim 4, characterized in that: The gas flow and concentration are adjusted as follows: when the source is turned on, the furnace mouth nitrogen flow is increased from 0 sccm to 700 sccm, the source nitrogen flow is increased from 2600 sccm to 5500 sccm, the oxygen flow is reduced from 600 sccm to 500 sccm, the boron chloride flow is reduced from 200 sccm to 120 sccm, and the boron chloride concentration is reduced from 4.88% to 1.76%.

6. The method for preventing rusting of a TOPCon solar cell boron diffusion furnace door flange according to claim 4, characterized in that: The deposition pressure and temperature were adjusted as follows: the deposition pressure was increased from 160 mbar to 220 mbar, and the post-oxygen peak temperature was reduced from 1050° C. to 1020° C.

7. The method for preventing rusting of a TOPCon solar cell boron diffusion furnace door flange according to claim 4, characterized in that: The shallow junction low concentration doping is achieved by reducing the amount of boron chloride to 120 sccm and increasing the deposition pressure to 220 mbar.

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