TOPCon battery, preparation method thereof and boron diffusion equipment

Abstract

The invention provides a TOPCon battery and a preparation method thereof, and boron diffusion equipment, and the preparation method of the TOPCon battery comprises the steps: providing a silicon substrate, placing the silicon substrate in a boron diffusion furnace, introducing nitrogen into a furnace mouth region of the boron diffusion furnace, introducing oxygen and boron trichloride into the boron diffusion furnace, introducing nitrogen gas into the furnace mouth region of the boron diffusion furnace, introducing nitrogen gas into the furnace mouth region of the boron diffusion furnace, introducing nitrogen gas into the furnace mouth region of the boron diffusion furnace, and introducing nitrogen gas into the furnace mouth region of the boron diffusion furnace, the ratio of the flow of the oxygen to the flow of the boron trichloride is alpha, and alpha is more than or equal to 3.5 and less than or equal to 4.5. The nitrogen can quickly purge reaction byproducts in a low-temperature area of the furnace mouth, and sufficient oxygen is provided to completely oxidize boron trichloride into a gaseous boron oxide precursor before the boron trichloride enters a high-temperature reaction area, so that the generation of viscous low-temperature boron oxide due to insufficient oxidation is avoided; and the generation and deposition of boron oxide crystals at the furnace mouth are inhibited from two dimensions of mass transfer process and chemical reaction completeness, and the yield and average photoelectric conversion efficiency of the TOPCon battery can be remarkably improved.

Description

Technical Field

[0001] This application relates to the field of solar cell technology, specifically to a TOPCon cell and its preparation method, and a boron diffusion device. Background Technology

[0002] TOPCon (Tunneling Oxide Passivated Contact) cells, as the mainstream technology for high-efficiency N-type crystalline silicon solar cells, rely heavily on the boron diffusion process in the front-side P-type emitter region, which is crucial for determining the cell's photoelectric conversion efficiency and yield. In the boron diffusion process of TOPCon cells, boron trichloride (BCl3) is typically used as the boron source. Boron atoms are incorporated into the silicon substrate by controlling the reaction between oxygen and BCl3. Atmosphere control in the boron diffusion furnace area is critical to ensuring process stability.

[0003] In related technologies, crystals are prone to form at the furnace mouth of boron diffusion furnaces. These crystals not only accumulate at the furnace mouth, affecting the uniformity of airflow and diluting the concentration of boron source, thus reducing the uniformity of the boron diffusion process, but also cause crystal peeling to directly contaminate the silicon substrate, leading to defects in the solar cells. At the same time, the continuous formation of crystals forces the production line to frequently stop to clean the furnace mouth, significantly reducing equipment utilization and capacity. It also leads to low sheet resistance concentration and large fluctuations in photoelectric conversion efficiency of TOPCon cells, seriously restricting the stability and economic benefits of TOPCon cell mass production. Summary of the Invention

[0004] The purpose of this application is to provide a TOPCon battery and its preparation method, as well as a boron diffusion device, to solve the technical problem that crystallization easily occurs at the furnace mouth of the boron diffusion furnace in related technologies.

[0005] In a first aspect, this application provides a method for preparing a TOPCon battery, comprising: A silicon substrate is provided, and the silicon substrate is placed in a boron diffusion furnace; Nitrogen gas is introduced into the furnace mouth area of ​​the boron diffusion furnace, and the flow rate of the nitrogen gas is in the range of 800 sccm-1200 sccm; Oxygen and boron trichloride are introduced into the boron diffusion furnace, and the ratio of the flow rate of oxygen to the flow rate of boron trichloride is α, wherein α satisfies: 3.5≤α≤4.5.

[0006] In the TOPCon battery fabrication method provided in this application, a silicon substrate is provided and placed in a boron diffusion furnace. Nitrogen gas is introduced into the furnace opening area of ​​the boron diffusion furnace, with a flow rate ranging from 800 sccm to 1200 sccm. Oxygen and boron trichloride are introduced into the boron diffusion furnace, with the ratio of the oxygen flow rate to the boron trichloride flow rate being α, where α satisfies the condition: 3.5 ≤ α ≤ 4.5. Controlling the nitrogen flow rate at the furnace mouth of the boron diffusion furnace to 800-1200 sccm creates a high-intensity protective gas curtain, rapidly purging reaction byproducts (such as chlorine and boron oxide aerosols) from the low-temperature zone at the furnace mouth. Simultaneously, it isolates the furnace from external air disturbances, effectively preventing byproducts from lingering and condensing at the furnace mouth. Limiting the oxygen-to-boron trichloride flow ratio α to 3.5 ≤ α ≤ 4.5 provides sufficient oxygen to ensure complete oxidation of boron trichloride into gaseous boron oxide precursors before entering the high-temperature reaction zone, preventing the formation of viscous low-temperature boron oxides due to incomplete oxidation. This synergistic effect of high purging and high oxidation thoroughly suppresses the formation and deposition of boron oxide crystals at the furnace mouth from both the perspectives of mass transfer and chemical reaction completeness. This reduces silicon wafer contamination and cell defects caused by crystal shedding, improves the uniformity and stability of the boron diffusion process, significantly reduces equipment downtime due to crystal cleaning, and significantly improves the yield and average photoelectric conversion efficiency of TOPCon cells.

[0007] The flow rate of nitrogen is in the range of 950 sccm-1050 sccm; the ratio α of the flow rate of oxygen to the flow rate of boron trichloride satisfies: 3.8 ≤ α ≤ 4.2.

[0008] The flow rate of nitrogen is 1000 sccm, and the ratio α of the flow rate of oxygen to the flow rate of boron trichloride is 4.

[0009] The preparation method further includes: The boron diffusion furnace is heated to a temperature range of 860℃-950℃.

[0010] This includes: A collection device is provided at the tail gas outlet of the boron diffusion furnace, and the collection device is capable of collecting by-reactants; The furnace opening area of ​​the boron diffusion furnace is provided with a heat insulation layer, which can keep the furnace opening area of ​​the boron diffusion furnace warm.

[0011] Wherein, the step of introducing nitrogen gas into the furnace mouth area of ​​the boron diffusion furnace includes: Nitrogen gas is introduced simultaneously through multiple sets of air inlets, which are evenly distributed around the circumference of the furnace flange of the boron diffusion furnace. The gas injection direction of each set of air inlets is towards the inside of the furnace opening.

[0012] Secondly, this application provides a TOPCon battery, which is prepared by the same method used to prepare the TOPCon battery.

[0013] Thirdly, this application provides a boron diffusion apparatus for preparing TOPCon batteries. The boron diffusion apparatus includes a boron diffusion furnace, a nitrogen supply device, a boron source supply device, an oxygen supply device, and a control unit. The nitrogen supply device is connected to the furnace opening area of ​​the boron diffusion furnace and is used to introduce nitrogen into the furnace opening. The boron source supply device is used to supply boron trichloride into the boron diffusion furnace. The oxygen supply device is used to supply oxygen into the boron diffusion furnace. The control unit is electrically connected to the nitrogen supply device, the boron source supply device, and the oxygen supply device, respectively, and is configured to execute the preparation method of the TOPCon battery to control the flow rate of nitrogen, the flow-to-volume ratio of oxygen and boron trichloride, and the temperature inside the boron diffusion furnace.

[0014] The control unit further includes a flow detection module and a temperature detection module; The flow detection modules are respectively installed in the pipelines of the nitrogen supply device, the boron source supply device, and the oxygen supply device, and are used to detect the flow value of each gas in real time. The temperature detection module is installed in the furnace mouth area and the reaction zone inside the boron diffusion furnace to detect the temperature value in real time. The control unit can dynamically adjust the flow rate of each gas and the temperature inside the furnace based on the detection results of the flow detection module and the temperature detection module.

[0015] The boron diffusion equipment also includes a furnace mouth crystallization monitoring module, which includes an optical imaging sensor. The furnace mouth crystallization monitoring module is located at the furnace mouth observation window of the boron diffusion furnace and is used to capture images of the furnace mouth area in real time. The control unit is electrically connected to the furnace mouth crystallization monitoring module. It can analyze the crystallization situation at the furnace mouth based on images and dynamically adjust the flow rate and volume ratio of nitrogen, oxygen and boron trichloride when the amount of crystallization exceeds a preset threshold. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Figure 1 This is a flowchart of a TOPCon preparation method provided in the embodiments of this application; Figure 2This is a flowchart of step S400 in a TOPCon preparation method provided in this application embodiment; Figure 3 This is a flowchart of step S210 in a TOPCon preparation method provided in this application embodiment; Figure 4 This is a simplified structural diagram of a boron diffusion device provided in an embodiment of this application; Figure 5 This application provides a control frame for a boron diffusion device. Figure 1 ; Figure 6 This application provides a control frame for a boron diffusion device. Figure 2 .

[0017] Label Explanation: Boron diffusion equipment 100, boron diffusion furnace 10, nitrogen supply device 20, boron source supply device 30, oxygen supply device 40, control unit 50, flow detection module 60, temperature detection module 70, furnace mouth crystallization monitoring module 80. Detailed Implementation

[0018] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0019] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion.

[0020] In this specification, for convenience, terms such as "middle," "upper," "lower," "front," "rear," "vertical," "horizontal," "top," "bottom," "inner," and "outer" are used to indicate orientation or positional relationships in conjunction with the accompanying drawings. This is solely for the purpose of facilitating the description and simplification, and does not imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this disclosure. The positional relationships of the constituent elements may be appropriately varied depending on the orientation of the constituent elements being described. Therefore, the use of terms not limited to those described in the specification may be appropriately replaced as needed.

[0021] In this specification, unless otherwise expressly specified and limited, the terms "installation," "connection," and "joint" shall be interpreted broadly. For example, they may refer to a fixed connection, a detachable connection, or an integral connection; a mechanical connection or an electrical connection; a direct connection or an indirect connection via an intermediate component, or a connection within two components. Those skilled in the art will understand the meaning of these terms in this disclosure as appropriate.

[0022] TOPCon (Tunneling Oxide Passivated Contact) cells, as the mainstream technology for high-efficiency N-type crystalline silicon solar cells, rely heavily on the boron diffusion process in the front-side P-type emitter region, which is crucial for determining the cell's photoelectric conversion efficiency and yield. In the boron diffusion process of TOPCon cells, boron trichloride (BCl3) is typically used as the boron source. Boron atoms are incorporated into the silicon substrate by controlling the reaction between oxygen and BCl3. Atmosphere control in the boron diffusion furnace area is critical to ensuring process stability.

[0023] In related technologies, crystals are prone to form at the furnace mouth of boron diffusion furnaces. These crystals not only accumulate at the furnace mouth, affecting the uniformity of airflow and diluting the concentration of boron source, thus reducing the uniformity of the boron diffusion process, but also cause crystal peeling to directly contaminate the silicon substrate, leading to defects in the solar cells. At the same time, the continuous formation of crystals forces the production line to frequently stop to clean the furnace mouth, significantly reducing equipment utilization and capacity. It also leads to low sheet resistance concentration and large fluctuations in photoelectric conversion efficiency of TOPCon cells, seriously restricting the stability and economic benefits of TOPCon cell mass production.

[0024] To suppress furnace mouth crystallization, the industry generally controls the flow rate of protective nitrogen at the boron diffusion furnace mouth at around 600 sccm and the oxygen to boron trichloride flow ratio at around 3.0. However, significant technical defects still exist under these parameters: on the one hand, the gas curtain purging intensity formed by the 600 sccm furnace mouth nitrogen flow rate is insufficient, failing to quickly remove reaction byproducts such as chlorine and boron oxide aerosols generated in the low-temperature zone of the furnace mouth, causing byproducts to easily remain at the furnace mouth and condense and deposit; on the other hand, the oxygen source ratio of around 3.0 cannot provide sufficient oxygen for the oxidation reaction of BCl3, resulting in insufficient oxidation of BCl3 before entering the high-temperature reaction zone, easily forming viscous low-temperature boron oxides.

[0025] Please refer to Figure 1 , Figure 1 This is a flowchart of a TOPCon preparation method provided in the embodiments of this application.

[0026] This application provides a method for preparing TOPCon batteries to solve the technical problem that crystallization easily occurs at the furnace mouth of boron diffusion furnaces in related technologies.

[0027] This application provides a method for fabricating a TOPCon solar cell, which includes steps S100, S200, and S300. TOPCon is an abbreviation for Tunnel Oxide Passivated Contact, and the TOPCon solar cell is a tunnel oxide passivated contact cell, currently the mainstream high-efficiency N-type crystalline silicon solar cell in the photovoltaic field.

[0028] It should be noted that the fabrication method of TOPCon cells mainly includes the following steps: silicon wafer pretreatment, front junction formation (boron diffusion), back TOPCon structure fabrication, front passivation and anti-reflection film, metallization, and testing and sorting. Steps S100, S200, and S300 in this application are mainly parts of the front junction formation (boron diffusion) step and should not be construed as limiting this application. Specifically, the boron diffusion step is a process in TOPCon cell manufacturing where boron trichloride (BCl3) is used as a boron source to deposit boron atoms through diffusion.

[0029] The specific descriptions of steps S100, S200, and S300 are as follows.

[0030] S100: Provide a silicon substrate and place the silicon substrate in a boron diffusion furnace.

[0031] The silicon substrate is an N-type monocrystalline silicon wafer specifically designed for TOPCon batteries. Before being placed in the furnace, it needs to undergo pretreatment (texturing, RCA cleaning, cutting and removing damaged layers, etc.) to ensure that the silicon wafer surface is clean, free of impurities and damage, and to avoid impurities interfering with the subsequent boron diffusion reaction or causing battery defects.

[0032] The pretreated silicon substrate is placed in the reaction chamber of the boron diffusion furnace, which places it in a closed and controllable high-temperature reaction environment. The boron diffusion furnace provides a stable space carrier for the subsequent introduction of boron trichloride, oxygen, and nitrogen and the diffusion reaction, ensuring that the reaction occurs only in the preset area (the front side of the silicon substrate).

[0033] S200: Nitrogen gas is introduced into the furnace mouth area of ​​the boron diffusion furnace, and the flow rate of the nitrogen gas is in the range of 800 sccm-1200 sccm.

[0034] It should be noted that in conventional boron diffusion processes, the nitrogen flow rate at the furnace inlet is approximately 600 sccm, which is insufficient for timely removal of reaction byproducts (such as Cl2 and B2O3 aerosols) in the low-temperature zone at the furnace inlet. Here, sccm is a unit of gas flow rate, representing standard milliliters per minute.

[0035] This application enhances the purging and dilution capabilities of nitrogen by increasing the nitrogen flow rate to 800-1200 sccm. Nitrogen can be uniformly introduced along the furnace flange or door, rapidly carrying away any small amounts of B2O3 aerosol, incompletely reacted intermediates, and byproducts such as Cl2 that may be generated in the furnace opening area, preventing them from accumulating, condensing, and depositing as hard crystals. Furthermore, the uniform introduction of nitrogen along the furnace flange or door forms a protective gas curtain, isolating the boron diffusion furnace from external air (preventing interference from ambient air during the furnace reaction) and stabilizing the temperature and gas composition at the furnace opening.

[0036] The flow rate of nitrogen is in the range of 800 sccm-1200 sccm. Preferably, the flow rate of nitrogen is in the range of 950 sccm-1050 sccm. The flow rate of nitrogen in this range can ensure the purging effect without diluting the concentration of boron trichloride in the furnace due to excessive nitrogen flow rate, thus avoiding insufficient boron diffusion.

[0037] Optionally, the flow rate of the nitrogen gas can be 800 sccm, or 810 sccm, or 820 sccm, or 850 sccm, or 860 sccm, or 890 sccm, or 900 sccm, or 920 sccm, or 940 sccm, or 950 sccm, or 980 sccm, or 1000 sccm, or 1010 sccm, or 1030 sccm, or 1050 sccm, or 1070 sccm, or 1090 sccm, or 1100 sccm, or 1120 sccm, or 1140 sccm, or 1150 sccm, or 1160 sccm, or 1180 sccm, or 1200 sccm, or other values ​​within the range of 800 sccm to 1200 sccm. This application does not impose any restrictions on this.

[0038] Furthermore, the flow rate of the nitrogen gas is within the range of 800 sccm-1200 sccm. It should be noted that the flow rate of the nitrogen gas can remain constant or vary within the range of 800 sccm-1200 sccm, and this application does not impose any restrictions on this.

[0039] S300: Oxygen and boron trichloride are introduced into the boron diffusion furnace, wherein the ratio of the flow rate of oxygen to the flow rate of boron trichloride is α, and α satisfies: 3.5≤α≤4.5.

[0040] It should be noted that the oxygen source ratio is the ratio of the flow rate of oxygen to the flow rate of boron trichloride, and the ratio of the flow rate of oxygen to the flow rate of boron trichloride is α. In other words, the oxygen source ratio is α. It should be noted that when α is 3.5, the corresponding oxygen source ratio is 3.0:1, meaning the ratio of the flow rate of oxygen to the flow rate of boron trichloride is 3.0:1; when α is 4.5, the corresponding oxygen source ratio is 4.5:1, meaning the ratio of the flow rate of oxygen to the flow rate of boron trichloride is 4.5:1. This application does not impose any limitations on this ratio.

[0041] In conventional processes, the oxygen source ratio is approximately 3.0:1. Insufficient oxygen can easily lead to incomplete oxidation of boron trichloride and the formation of viscous boron oxide and other solid deposits in the furnace mouth area of ​​the boron diffusion furnace.

[0042] This application increases the oxygen source ratio to 3.5:1-4.5:1 (3.5≤α≤4.5), ensuring sufficient oxygen without excess (avoiding excessive oxidation that could damage the silicon substrate's surface) and guaranteeing complete oxidation of boron trichloride.

[0043] Based on the core reaction equation 4BCl3+3O2=2B2O3+6Cl2, sufficient oxygen O2 ensures that boron trichloride (BCl3) is fully mixed with O2 and completely oxidized into gaseous B2O3 precursor before entering the high-temperature reaction zone of the furnace. This avoids the formation of easily deposited boron oxides due to insufficient oxidation in the low-temperature furnace mouth zone.

[0044] Gaseous B2O3 reaches the surface of the silicon substrate with the gas flow and reacts with Si: 2B2O3 + 3Si = 3SiO2 + 4B. Boron atoms are uniformly incorporated into the front side of the silicon substrate to form the core of the P-type emitter region TOPCon cell PN junction.

[0045] The ratio α of the oxygen flow rate to the boron trichloride flow rate satisfies: 3.5≤α≤4.5. Preferably, the ratio α of the oxygen flow rate to the boron trichloride flow rate satisfies: 3.8≤α≤4.2. This range can balance oxidation completeness and process stability, and avoid excessively high α leading to excessively high local oxygen O2 concentration, causing excessive oxidation of the silicon substrate surface.

[0046] Optionally, the ratio α of the oxygen flow rate to the boron trichloride flow rate can be 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, or other values ​​within the range of 3.5-4.5, and this application does not limit it.

[0047] It should be noted that this application does not restrict the order of steps S100, S200 and S300. Steps S100, S200 and S300 can be performed simultaneously or at different times, and this should not be construed as a limitation on this application.

[0048] In the TOPCon battery fabrication method provided in this application, a silicon substrate is provided and placed in a boron diffusion furnace. Nitrogen gas is introduced into the furnace opening area of ​​the boron diffusion furnace, and the flow rate of the nitrogen gas is in the range of 800 sccm-1200 sccm. Oxygen and boron trichloride are introduced into the boron diffusion furnace, and the ratio of the flow rate of the oxygen gas to the flow rate of the boron trichloride gas is α, wherein α satisfies: 3.5≤α≤4.5. Controlling the nitrogen flow rate at the furnace mouth of the boron diffusion furnace to 800 sccm-1200 sccm creates a high-intensity protective gas curtain, rapidly purging reaction byproducts (such as chlorine and boron oxide aerosols) from the low-temperature zone at the furnace mouth. Simultaneously, it isolates the furnace from external air disturbances, effectively preventing byproducts from lingering and condensing at the furnace mouth. Limiting the oxygen-to-boron trichloride flow ratio α to 3.5 ≤ α ≤ 4.5 provides sufficient oxygen to ensure complete oxidation of boron trichloride into gaseous boron oxide precursors before entering the high-temperature reaction zone, preventing the formation of viscous low-temperature boron oxides due to incomplete oxidation. This synergistic effect of high purging and high oxidation thoroughly suppresses the formation and deposition of boron oxide crystals at the furnace mouth from both the perspectives of mass transfer and chemical reaction completeness. This reduces silicon wafer contamination and cell defects caused by crystal shedding, improves the uniformity and stability of the boron diffusion process, significantly reduces equipment downtime due to crystal cleaning, and significantly improves the yield and average photoelectric conversion efficiency of TOPCon cells.

[0049] Further, in one embodiment, the oxygen flow rate ranges from 240 sccm to 720 sccm. Optionally, the oxygen flow rate can be 240 sccm, or 260 sccm, or 280 sccm, or 300 sccm, or 310 sccm, or 330 sccm, or 350 sccm, or 370 sccm, or 400 sccm, or 420 sccm, or 450 sccm, or 470 sccm, or 500 sccm, or 530 sccm, or 550 sccm, or 580 sccm, or 600 sccm, or 650 sccm, or 700 sccm, or 720 sccm, or other values ​​within the range of 240 sccm to 720 sccm. This application does not limit this.

[0050] Furthermore, in one embodiment, the flow rate of boron trichloride is in the range of 80 sccm-160 sccm. Optionally, the flow rate of boron trichloride can be 80 sccm, 90 sccm, 100 sccm, 110 sccm, 120 sccm, 130 sccm, 140 sccm, 150 sccm, 160 sccm, or other values ​​in the range of 80 sccm-160 sccm. This application does not limit this value.

[0051] Please refer to Table 1, which shows the single-factor influence of nitrogen flow rate at the furnace inlet when the oxygen source ratio is fixed at 4:1: Table 1. Experimental comparison of nitrogen flow rates at the furnace inlet when oxygen source ratio is 4:1.

[0052] Table 1 shows the single-factor effect of nitrogen flow rate at the furnace inlet when the oxygen source ratio is fixed at 4:1. That is, the oxygen source ratio (oxygen: boron trichloride) is kept constant at 4:1, and only the nitrogen flow rate at the furnace inlet is changed (600 sccm, 800 sccm, 1000 sccm, 1200 sccm), and the changes in furnace inlet crystallization, sheet resistance concentration and cell efficiency are observed.

[0053] In the comparative example (nitrogen flow rate at the furnace inlet was 600 sccm), severe crystallization occurred at the furnace inlet, requiring shutdown for cleaning. Examples 1-3 (800 sccm-1200 sccm): As the nitrogen flow rate increased, the crystallization at the furnace inlet progressed from slight to almost clean and then to no crystallization, but the sheet resistance concentration (90% within ±5Ω) and cell efficiency (26.15%) showed no significant changes.

[0054] It should be noted that the sheet resistance concentration ±5Ω is a key indicator for measuring the uniformity of sheet resistance in the P-type emitter region during the boron diffusion process of photovoltaic cells. Its core meaning is: in the sheet resistance test of the P-type emitter region on the front side of the silicon wafer, the proportion of silicon wafers whose sheet resistance value falls within the range of ±5Ω of the standard sheet resistance value to the total number of silicon wafers tested.

[0055] In summary, high-flow-rate nitrogen (800 sccm-1200 sccm) can effectively purge byproducts at the furnace mouth and inhibit crystallization. However, when the oxygen source ratio is fixed, the nitrogen flow rate has limited effect on improving the sheet resistance uniformity and cell efficiency of TOPCon cells.

[0056] Please refer to Table 2, which shows the single-factor influence of the oxygen source ratio when the nitrogen flow rate at the furnace inlet is fixed at 1000 sccm: Table 2. Experimental comparison of various oxygen source ratios when the nitrogen flow rate at the furnace inlet is 1000 sccm.

[0057] Table 2 shows the single-factor effect of the oxygen source ratio when the nitrogen flow rate at the furnace inlet is fixed at 1000 sccm. That is, the nitrogen flow rate at the furnace inlet is kept constant at 1000 sccm, and only the oxygen source ratio (3:1, 3.5:1, 4:1, 4.5:1) is changed to observe the changes in furnace inlet crystallization, sheet resistance concentration and cell efficiency.

[0058] Among them, the comparative example (oxygen source ratio 3:1): severe crystallization at the furnace mouth, sheet resistance concentration of only 80%, and cell efficiency of 26.14%. Example 1 (oxygen source ratio 3.5:1): slight crystallization, sheet resistance concentration increased to 90%, and efficiency of 26.15%. Example 2 (oxygen source ratio 4:1): virtually no hard crystallization, sheet resistance concentration reached 95%, and efficiency of 26.16%; Example 3 (oxygen source ratio 4.5:1): clean and free of crystallization, but sheet resistance concentration dropped back to 90%, and efficiency of 26.15%.

[0059] In summary, an oxygen source ratio in the range of 3.5:1 to 4.5:1 can promote the complete oxidation of boron trichloride and reduce crystallization; among them, 4:1 is the optimal oxygen source ratio, which can simultaneously achieve low crystallization, high sheet resistance uniformity of TOPCon cells, and high cell efficiency.

[0060] Please refer to Table 3, which verifies the synergistic effect of simultaneous changes in nitrogen flow rate and oxygen source ratio at the furnace inlet: Table 3. Experimental comparison when nitrogen flow rate and oxygen source ratio at the furnace inlet change simultaneously.

[0061] Table 3 shows the verification of the synergistic effect of simultaneous changes in nitrogen flow rate and oxygen source ratio at the furnace inlet. That is, the nitrogen flow rate and oxygen source ratio at the furnace inlet are adjusted simultaneously to simulate the multi-factor synergistic scenario of the actual process and observe the comprehensive effect.

[0062] Among them, the comparative example (nitrogen flow rate 600 sccm + oxygen source ratio 3:1): severe crystallization, sheet resistance concentration 80%, efficiency 26.14%; Example 1 (nitrogen flow rate 800 sccm + oxygen source ratio 3.5:1): slight crystallization, sheet resistance concentration 90%, efficiency 26.15%; Example 2 (nitrogen flow rate 1000 sccm + oxygen source ratio 4:1): virtually no hard crystallization, sheet resistance concentration 95%, efficiency 26.16% (optimal combination); Example 3 (nitrogen flow rate 1200 sccm + oxygen source ratio 4.5:1): clean and no crystallization, sheet resistance concentration 90%, efficiency 26.15%.

[0063] In summary, the synergistic optimization of nitrogen flow rate and oxygen source ratio is the key. Relying on a single parameter (such as high nitrogen or high oxygen) cannot simultaneously achieve complete suppression of crystallization, optimal sheet resistance uniformity, and highest efficiency. The combination of a nitrogen flow rate of 1000 sccm and an oxygen source ratio of 4:1 is the optimal solution for balancing the three.

[0064] Through single-factor and multi-factor synergistic experiments, it can be clearly seen that: the nitrogen flow rate at the furnace inlet (800 sccm-1200 sccm) is the key to physical purging and rapid removal of by-products; the oxygen source ratio (3.5:1-4.5:1) is the key to chemical oxidation and ensuring complete reaction of boron trichloride; the synergistic effect of the two (especially the combination of nitrogen flow rate of 1000 sccm and oxygen source ratio of 4:1) can thoroughly suppress furnace inlet crystallization from both the mass transfer process and chemical reaction dimensions, while maximizing the improvement of process uniformity and battery efficiency.

[0065] Please refer to Figure 2 , Figure 2 This is a flowchart of step S400 in a TOPCon preparation method provided in an embodiment of this application.

[0066] In one embodiment, the method for preparing a TOPCon battery further includes step S400, which is described in detail below.

[0067] S400: The boron diffusion furnace is heated to a temperature range of 860℃-950℃.

[0068] Step S400 is the core step in the boron diffusion process of TOPCon cells, controlling the thermodynamic conditions of the reaction. Boron diffusion is achieved by the migration of boron atoms in the silicon lattice at high temperatures, and temperature is the key factor determining the diffusion rate, depth, and uniformity. The higher the temperature, the more intense the thermal motion of boron atoms, the greater the diffusion coefficient, and the thicker and deeper P-type emitter region (the core of the PN junction of TOPCon cells) can be formed in the same amount of time.

[0069] The boron diffusion furnace operates at a high temperature of 860℃-950℃, providing sufficient thermodynamic conditions for the oxidation reaction "4BCl3 + 3O2 = 2B2O3 + 6Cl2". This ensures the complete oxidation of the boron source into a gaseous precursor, avoiding the formation of easily deposited viscous boron oxides at low temperatures. Temperatures that are too low (e.g., below 860℃) will result in insufficient diffusion, excessively high sheet resistance and shallow depth of the P-type emitter region, affecting the carrier separation efficiency of the PN junction. Temperatures that are too high (e.g., above 950℃) may cause silicon wafer lattice damage and excessive impurity diffusion, thus reducing the battery's carrier lifetime.

[0070] Furthermore, the boron diffusion furnace operates at a high temperature of 860℃-950℃, and the high flow rate of nitrogen (800 sccm-1200 sccm) maintains the turbulent flow of gas within the furnace, preventing airflow stratification caused by localized temperature gradients and ensuring uniform distribution of boron source and oxygen within the furnace. The combination of high temperature and a high oxygen source ratio (3.5:1-4.5:1) makes the oxidation reaction of BCl3 more complete, allowing the generated gaseous B2O3 to rapidly diffuse to the silicon wafer surface, reducing the deposition of intermediate products in the low-temperature zone at the furnace opening.

[0071] Furthermore, maintaining a temperature range of 860℃-950℃ within the boron diffusion furnace allows for more uniform diffusion of boron atoms within the silicon wafer, thereby increasing the sheet resistance concentration of the P-type emitter region and ensuring consistent electrical performance between and within cells. A suitable diffusion temperature optimizes the depth and doping concentration of the PN junction, maximizing the separation and collection efficiency of photogenerated carriers, ultimately improving the average conversion efficiency of TOPCon cells.

[0072] Optionally, the temperature inside the boron diffusion furnace can be 860°C, 870°C, 880°C, 890°C, 900°C, 910°C, 920°C, 930°C, 940°C, 950°C, or other temperatures within the range of 860°C to 950°C. This application does not impose any restrictions on this.

[0073] It should be noted that this application does not restrict the order of steps S100, S200, S300, and S400. Steps S100, S200, S300, and S400 can be performed simultaneously or at different times, and this should not be construed as a limitation on this application.

[0074] During boron diffusion, boron trichloride (BCl3) reacts with oxygen (O2) to produce gaseous boron oxide (B2O3), while also generating byproducts such as chlorine (Cl2). Furthermore, boron oxide aerosols not completely purged from the furnace opening may also be emitted with the exhaust gas. Chlorine (Cl2) is a toxic and highly corrosive gas; direct emission will pollute the atmosphere and harm the health of operators. Chlorine (Cl2) and boron oxide aerosols can corrode exhaust gas pipes, valves, and downstream equipment, shortening their service life. If byproducts accumulate and circulate within the system, they may conversely affect the purity of the furnace atmosphere and interfere with the uniformity of boron diffusion.

[0075] In one embodiment, in the method for preparing the TOPCon battery, a collection device may be provided at the tail gas outlet of the boron diffusion furnace, the collection device being capable of collecting byproducts.

[0076] The collection device can be equipped with an alkaline absorption unit, for example, filled with sodium hydroxide (NaOH) solution or other alkaline absorbents. Utilizing the acidic properties of Cl2, it converts Cl2 into harmless salts and water, achieving efficient removal. Furthermore, the collection device can be equipped with a filter element or a gas-liquid separator to intercept boron oxide aerosols carried in the exhaust gas, preventing them from clogging the pipes.

[0077] The process temperature in the reaction zone of the boron diffusion furnace is 860℃-950℃. However, due to its proximity to the furnace door and flange (directly exposed to the external environment), heat is easily dissipated rapidly at the furnace opening, resulting in a significantly lower temperature zone at the furnace opening compared to the interior. Incompletely oxidized BCl3 intermediates or gaseous B2O3 precursors rapidly condense in this low-temperature zone at the furnace opening due to the sudden temperature drop, transforming from a gaseous state into a solid, viscous boron oxide, which then deposits at the furnace opening to form hard crystals. Furthermore, the large temperature difference between the furnace opening and the interior causes localized airflow temperature fluctuations, interfering with the purging effect of the nitrogen curtain and the uniformity of mixing boron trichloride (BCl3) and oxygen (O2), further exacerbating the crystallization risk.

[0078] In one embodiment, in the method for preparing TOPCon batteries, a heat insulation layer may be provided in the furnace mouth area of ​​the boron diffusion furnace, the heat insulation layer being able to keep the furnace mouth area of ​​the boron diffusion furnace warm.

[0079] An insulation layer is installed in the furnace mouth area of ​​the boron diffusion furnace to prevent the temperature in the furnace mouth area from becoming too low, reducing the probability of boron oxide condensing into a solid state due to a sudden drop in temperature, and thus reducing the possibility of crystal formation caused by temperature factors. Furthermore, it can reduce heat loss caused by heat dissipation from the furnace mouth, prevent the infiltration of cold air from the outside or the escape of hot air from the furnace, maintain the temperature stability of the nitrogen gas curtain at the furnace mouth, and ensure that the purging and isolation effects of nitrogen are not affected by temperature fluctuations.

[0080] The furnace opening temperature is more uniform after heat preservation, avoiding a sharp drop in the BCl3 oxidation reaction rate due to local low temperature. It also helps to achieve complete oxidation of BCl3 with a high oxygen source ratio (3.5:1-4.5:1) and reduces the formation of easily deposited intermediate products.

[0081] Please refer to Figure 3 , Figure 3 This is a flowchart of step S210 in a TOPCon preparation method provided in an embodiment of this application.

[0082] In one embodiment, step S200 introduces nitrogen gas into the furnace mouth area of ​​the boron diffusion furnace, and may further include step S210, which is described in detail below.

[0083] S210: Multiple sets of air inlets are used to simultaneously introduce nitrogen gas. The multiple sets of air inlets are evenly distributed around the circumference of the furnace flange of the boron diffusion furnace. The gas injection direction of each set of air inlets is towards the inside of the furnace opening.

[0084] Multiple sets of air inlets are evenly arranged around the flange circumference, and each set of air inlets sprays towards the inside of the furnace opening. Nitrogen gas is sprayed out synchronously from all sides of the furnace opening and converges towards the center, forming a continuous and dense annular air curtain (rather than scattered airflow) in the furnace opening area.

[0085] A nitrogen gas curtain prevents external impurities such as oxygen and dust from entering the furnace, thus avoiding interference with the oxidation reaction of BCl3 and preventing the escape of the high-temperature atmosphere from the furnace. The nitrogen gas curtain forms a barrier, preventing byproducts such as Cl2 and boron oxide aerosols generated inside the furnace from escaping into areas like the furnace flange gaps and edges; instead, they are rapidly expelled by the nitrogen gas.

[0086] The evenly distributed air inlets cover all areas of the furnace opening (including weak areas such as the gaps between the flange and the furnace door, and the edge of the furnace opening, which are difficult to reach with traditional single-point air inlets). The inner spray direction of each set of air inlets ensures that the nitrogen gas flow can reach the core area of ​​the furnace opening directly, rather than escaping along the flange surface. Byproducts in all areas can be quickly swept away by nitrogen, with no blind spots, thus completely eliminating the possibility of crystallization depositing locally at the furnace opening from a spatial perspective.

[0087] Nitrogen is introduced into multiple air inlets simultaneously, avoiding local airflow turbulence caused by single-point air intake. The nitrogen flow field at the furnace opening is more stable and will not disturb the mixing ratio of boron trichloride (BCl3) and oxygen (O2) in the furnace. This ensures the stability of the oxidation reaction under a high oxygen source ratio (3.5:1-4.5:1), thereby improving the uniformity of sheet resistance of the P-type emitter region of the silicon wafer.

[0088] This application also provides a TOPCon battery, which is prepared by the same method as the TOPCon battery, and the average photoelectric conversion efficiency of the TOPCon battery is higher than 26.15%.

[0089] During the fabrication of the TOPCon cell provided in this application, the generation and deposition of boron oxide crystals at the furnace opening can be suppressed in the boron diffusion process. This reduces silicon wafer contamination and cell defects caused by crystal peeling, improves the uniformity and stability of the boron diffusion process, reduces the frequency of equipment downtime due to crystal cleaning, and significantly improves the yield and average photoelectric conversion efficiency of the TOPCon cell.

[0090] Please refer to Figure 4 , Figure 4 This is a simplified structural diagram of a boron diffusion device provided in an embodiment of this application.

[0091] This application also provides a boron diffusion apparatus 100 for preparing TOPCon batteries. The boron diffusion apparatus 100 includes a boron diffusion furnace 10, a nitrogen supply device 20, a boron source supply device 30, an oxygen supply device 40, and a control unit 50. The nitrogen supply device 20 is connected to the furnace opening area of ​​the boron diffusion furnace 10 and is used to introduce nitrogen into the furnace opening. The boron source supply device 30 is used to supply boron trichloride into the boron diffusion furnace 10. The oxygen supply device 40 is used to supply oxygen into the boron diffusion furnace 10. The control unit 50 is electrically connected to the nitrogen supply device 20, the boron source supply device 30, and the oxygen supply device 40, and the control unit 50 is configured to execute the preparation method of the TOPCon battery to control the nitrogen flow rate, the flow-to-volume ratio of oxygen and boron trichloride, and the temperature inside the boron diffusion furnace 10.

[0092] The boron diffusion furnace 10 serves as the physical core of the entire boron diffusion process, providing a sealed, high-temperature resistant reaction chamber suitable for high-temperature diffusion requirements of 860℃-950℃. It also features a pre-designed structure with circumferential air inlets at the furnace mouth flange and mounting positions for the insulation layer, and is compatible with optimization measures such as multiple air inlets for nitrogen purging and furnace mouth insulation.

[0093] The nitrogen supply device 20 is directly connected to the furnace mouth area and is specifically designed to provide nitrogen purging services for the furnace mouth in steps S200 and S210. The nitrogen supply device 20 can stably output a nitrogen flow rate of 800 sccm-1200 sccm and can adapt to a structure with multiple sets of circumferentially distributed air inlets, ensuring that the nitrogen forms a uniform annular gas curtain. This hardware solution addresses the problems of insufficient nitrogen purging flow rate and uneven distribution in traditional equipment.

[0094] The boron source supply device 30 and the oxygen supply device 40 are independent gas supply modules: they support precise adjustment of the flow-volume ratio of oxygen to boron trichloride within the range of 3.5:1 to 4.5:1, ensuring the stable achievement of a high oxygen source ratio in terms of hardware, and avoiding the defects of large errors in manual adjustment of oxygen source ratio in traditional equipment.

[0095] The control unit 50 can convert the parameter requirements of the preparation method into automated instructions. The control unit 50 is electrically connected to each supply device and the furnace heating system, and can preset and execute parameter ranges of nitrogen flow rate 800sccm-1200sccm, oxygen source ratio 3.5-4.5, and temperature 860-950℃, and can calibrate flow rate and temperature deviations in real time.

[0096] The boron diffusion equipment 100 approved in this application is used to prepare TOPCon cells. In the boron diffusion process, the generation and deposition of boron oxide crystals at the furnace mouth can be suppressed, which reduces silicon wafer contamination and cell defects caused by crystal peeling, improves the uniformity and stability of the boron diffusion process, reduces the frequency of downtime of the boron diffusion equipment 100 due to crystal cleaning, and can significantly improve the yield and average photoelectric conversion efficiency of TOPCon cells.

[0097] Please refer to Figure 5 , Figure 5 This application provides a control frame for a boron diffusion device. Figure 1 .

[0098] In one embodiment, the control unit 50 further includes a flow detection module 60 and a temperature detection module 70; the flow detection module 60 is respectively installed in the pipelines of the nitrogen supply device 20, the boron source supply device 30, and the oxygen supply device 40, and is used to detect the flow rate of each gas in real time; the temperature detection module 70 is installed in the furnace mouth area and the furnace reaction zone of the boron diffusion furnace 10, and is used to detect the temperature in real time; the control unit 50 can dynamically adjust the flow rate of each gas and the furnace temperature according to the detection results of the flow detection module 60 and the temperature detection module 70.

[0099] The flow detection module 60 can accurately capture real-time deviations in gas flow. Specifically installed in the pipelines of the nitrogen supply device 20, the boron source supply device 30, and the oxygen supply device 40, it can collect the instantaneous flow value of each gas stream in real time. This overcomes the drawback of traditional equipment that lacks real-time verification after setting the flow rate, providing real-time feedback on the deviation between the actual flow rate and the preset value. For example, if the nitrogen supply device 20 is set to 1000 sccm, but the actual flow rate is only 900 sccm due to pipeline pressure fluctuations, the flow detection module 60 can immediately capture this deviation and transmit it to the control unit 50.

[0100] The temperature detection module 70 can be installed in both the furnace opening area and the furnace reaction zone. The temperature detection module 70 is arranged in a dual-point configuration: the furnace opening temperature sensor monitors the temperature of the insulation layer and the gas curtain area, while the sensor in the furnace reaction zone monitors the temperature of the boron diffusion core. Simultaneously, it captures temperature changes in the low-temperature zone at the furnace opening related to crystallization and the high-temperature zone inside the furnace related to diffusion. For example, if the furnace opening temperature decreases or the furnace temperature decreases, the temperature detection module 70 can provide real-time feedback on the temperature deviation.

[0101] The control unit 50 receives real-time data from the two modules and automatically adjusts the hardware output according to a preset algorithm, forming a closed loop of detection-comparison-correction. For example, if the actual nitrogen flow rate is 750 sccm (below the lower limit of 800 sccm), the control unit 50 automatically increases the output power of the nitrogen supply device 20 to supplement the flow rate to 800-1000 sccm, ensuring the intensity of the furnace inlet gas curtain purging. If the oxygen source ratio is 3.2:1 (below the lower limit of 3.5:1), the boron trichloride flow rate is kept constant, and the flow rate of the oxygen supply device 40 is slightly increased; or the oxygen flow rate is kept constant, and the boron trichloride flow rate is slightly decreased until the oxygen source ratio returns to above 3.5:1. If the furnace temperature is 850℃ (below the lower limit of 860℃), the control unit 50 activates the compensation power of the furnace heating system, gradually raising the temperature to the range of 860℃-950℃, while avoiding excessively rapid heating that could damage the silicon wafer lattice.

[0102] Please refer to Figure 6 , Figure 6 This application provides a control frame for a boron diffusion device. Figure 2 .

[0103] In one embodiment, the boron diffusion equipment 100 further includes a furnace mouth crystallization monitoring module 80. The furnace mouth crystallization monitoring module 80 includes an optical imaging sensor and is positioned at the furnace mouth observation window of the boron diffusion furnace 10 for real-time image capture of the furnace mouth area. The control unit 50 is electrically connected to the furnace mouth crystallization monitoring module 80 and can analyze the furnace mouth crystallization situation based on the images. When the crystallization amount exceeds a preset threshold, it dynamically adjusts the flow rate of nitrogen, the flow rate and volume ratio of oxygen and boron trichloride.

[0104] The furnace mouth crystallization monitoring module 80 is located at the furnace mouth observation window of the boron diffusion furnace 10. The observation window is equipped with a high-temperature resistant and corrosion-resistant lens, suitable for conditions involving high furnace mouth temperatures and a small amount of corrosive byproducts. The furnace mouth crystallization monitoring module 80 can employ an industrial-grade optical imaging sensor, possessing characteristics of high-temperature resistance and dust interference resistance. It can capture high-definition images of the furnace mouth area in real time, with a sampling frequency of up to 1 time / minute (adjustable according to operating conditions during mass production). The furnace mouth crystallization monitoring module 80 can directly capture the visual characteristics of furnace mouth crystallization, including the presence, distribution, area ratio, and thickness of crystals.

[0105] The control unit 50 has a built-in image recognition algorithm with preset crystallization judgment criteria and threshold parameters. The algorithm automatically identifies the visual characteristics of hard boron oxide crystals in the image (such as white / light yellow deposit patches, contrast differences with the metal surface of the furnace opening, etc.), converts the crystallization state into quantifiable indicators (such as "the proportion of crystallization area to the visible area of ​​the furnace opening" and "the proportion of areas with crystallization thickness exceeding 0.5mm"), and sets preset thresholds (such as "the proportion of crystallization area ≥ 5%" is the threshold for intervention).

[0106] For example, if the crystallization area accounts for ≥5% (not reaching the shutdown threshold), prioritize increasing the nitrogen flow rate at the furnace inlet: increase it from the current value (e.g., 1000 sccm) to 1100-1200 sccm to enhance the gas curtain purging force and quickly remove uncured byproducts; fine-tune the oxygen source ratio: slightly increase it from the current value (e.g., 4.0:1) to 4.1:1-4.2:1 to enhance the complete oxidation of BCl3 and reduce the formation of new crystals; simultaneously check the temperature data: if the furnace inlet temperature is low, link the heating unit of the insulation layer to raise the temperature to avoid byproduct condensation. If crystallization is concentrated in a certain area of ​​the furnace inlet, only increase the nitrogen flow rate at the inlet on that side (e.g., from 1000 sccm to 1100 sccm) to avoid process fluctuations caused by adjusting the flow rate around the entire circumference. When the crystallization area is ≥10% (close to the shutdown threshold), adjust the nitrogen flow rate to 1200 sccm (upper limit); adjust the oxygen source ratio to 4.3:1-4.5:1; slightly increase the furnace temperature (e.g., from 900℃ to 920℃) to accelerate the BCl3 oxidation reaction rate.

[0107] Traditional equipment relies solely on flow rate and temperature parameters to indirectly assess crystallization risk. However, in actual mass production, situations may arise where parameters meet standards but crystallization still occurs at the furnace mouth (e.g., partial failure of the furnace mouth insulation layer or insufficient purging due to blockage of the air inlet). In contrast, the crystallization monitoring module directly captures the crystallization state, accurately identifying scenarios where parameters are normal but results are abnormal, thus enabling full-scenario control of crystallization.

[0108] The control unit 50 adjusts parameters only when the amount of crystallization exceeds the threshold, and fine-tunes them in the order of adjusting nitrogen first (physical purging), then oxygen source ratio (chemical oxidation), and finally temperature, rather than directly maximizing the parameters. This avoids crystal accumulation and prevents excessive parameter adjustment from causing a decrease in the uniformity of boron diffusion, thus balancing crystallization inhibition and process stability in the boron diffusion process.

[0109] In this application, the terms "embodiment" and "implementation" mean that a specific feature, structure, or characteristic described in connection with an embodiment can be included in at least one embodiment of this application. The appearance of these phrases in various locations throughout the specification does not necessarily refer to the same embodiment, nor are they independent or alternative embodiments mutually exclusive with other embodiments. Those skilled in the art will understand, explicitly and implicitly, that the embodiments described in this application can be combined with other embodiments. Furthermore, it should be understood that the features, structures, or characteristics described in the various embodiments of this application can be arbitrarily combined to form another embodiment that does not depart from the spirit and scope of the technical solution of this application, provided there is no contradiction between them.

[0110] The above description represents some embodiments of this application. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this application, and these improvements and modifications are also considered to be within the scope of protection of this application.

Claims

1. A method for preparing a TOPCon battery, characterized in that, include: A silicon substrate is provided, and the silicon substrate is placed in a boron diffusion furnace; Nitrogen gas is introduced into the furnace mouth area of ​​the boron diffusion furnace, and the flow rate of the nitrogen gas is in the range of 800 sccm-1200 sccm; Oxygen and boron trichloride are introduced into the boron diffusion furnace, and the ratio of the flow rate of oxygen to the flow rate of boron trichloride is α, wherein α satisfies: 3.5≤α≤4.

5.

2. The preparation method according to claim 1, characterized in that, The flow rate of the nitrogen gas is in the range of 950 sccm-1050 sccm; the ratio α of the flow rate of the oxygen gas to the flow rate of the boron trichloride gas satisfies: 3.8 ≤ α ≤ 4.

2.

3. The preparation method according to claim 1, characterized in that, The flow rate of nitrogen is 1000 sccm, and the ratio α of the flow rate of oxygen to the flow rate of boron trichloride is 4.

4. The preparation method according to any one of claims 1-3, characterized in that, The preparation method further includes: The boron diffusion furnace is heated to a temperature range of 860℃-950℃.

5. The preparation method according to any one of claims 1-3, characterized in that, include: A collection device is provided at the tail gas outlet of the boron diffusion furnace, and the collection device is capable of collecting by-reactants; The furnace opening area of ​​the boron diffusion furnace is provided with a heat insulation layer, which can keep the furnace opening area of ​​the boron diffusion furnace warm.

6. The preparation method according to any one of claims 1-3, characterized in that, The process of introducing nitrogen gas into the furnace mouth area of ​​the boron diffusion furnace includes: Nitrogen gas is introduced simultaneously through multiple sets of air inlets, which are evenly distributed around the circumference of the furnace flange of the boron diffusion furnace. The gas injection direction of each set of air inlets is towards the inside of the furnace opening.

7. A TOPCon battery, characterized in that, The TOPCon battery is prepared by the method for preparing the TOPCon battery according to any one of claims 1-6.

8. A boron diffusion apparatus for preparing TOPCon batteries, characterized in that, The boron diffusion equipment includes a boron diffusion furnace, a nitrogen supply device, a boron source supply device, an oxygen supply device, and a control unit. The nitrogen supply device is connected to the furnace opening area of ​​the boron diffusion furnace and is used to introduce nitrogen into the furnace opening. The boron source supply device is used to supply boron trichloride into the boron diffusion furnace. The oxygen supply device is used to supply oxygen into the boron diffusion furnace. The control unit is electrically connected to the nitrogen supply device, the boron source supply device, and the oxygen supply device, respectively, and is configured to perform the TOPCon battery preparation method according to any one of claims 1-6, to control the nitrogen flow rate, the flow-to-volume ratio of oxygen and boron trichloride, and the temperature inside the boron diffusion furnace.

9. The boron diffusion apparatus according to claim 8, characterized in that, The control unit also includes a flow detection module and a temperature detection module; The flow detection modules are respectively installed in the pipelines of the nitrogen supply device, the boron source supply device, and the oxygen supply device, and are used to detect the flow value of each gas in real time. The temperature detection module is installed in the furnace mouth area and the reaction zone inside the boron diffusion furnace to detect the temperature value in real time. The control unit can dynamically adjust the flow rate of each gas and the temperature inside the furnace based on the detection results of the flow detection module and the temperature detection module.

10. The boron diffusion apparatus according to claim 8, characterized in that, The boron diffusion equipment also includes a furnace mouth crystallization monitoring module, which includes an optical imaging sensor. The furnace mouth crystallization monitoring module is located at the furnace mouth observation window of the boron diffusion furnace and is used to capture images of the furnace mouth area in real time. The control unit is electrically connected to the furnace mouth crystallization monitoring module. It can analyze the crystallization situation at the furnace mouth based on images and dynamically adjust the flow rate and volume ratio of nitrogen, oxygen and boron trichloride when the amount of crystallization exceeds a preset threshold.

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