Phosphorus diffusion process of TOPCon battery, TOPCon battery and preparation method of TOPCon battery

Abstract

The invention belongs to the field of solar cells, and particularly relates to a phosphorus diffusion process of a TOPCon cell, the TOPCon cell and a preparation method of the TOPCon cell. The invention provides a phosphorus diffusion process of a TOPCon battery, which at least comprises first temperature rise propulsion and second temperature rise propulsion, and the temperature rise rate of the first temperature rise propulsion is smaller than that of the second temperature rise propulsion. According to the invention, by controlling the heating rate of two times of heating propulsion, slow heating propulsion is firstly carried out, and then rapid heating propulsion is carried out, the uniformity of the phosphorus concentration on the surface of the N-type silicon wafer in each temperature zone of the diffusion furnace and the consistency of the propulsion depth can be controlled, and the prepared TOPCon battery is uniform in sheet resistance and high in yield. The same batch of silicon wafers prepared by the diffusion furnace are uniform in phosphorus propelling depth and diffusion concentration, the same batch of silicon wafers are uniform in performance, and no large difference exists.

Description

Technical Field

[0001] The invention belongs to the field of solar cells, and in particular relates to a phosphorus diffusion process of a TOPCon cell, a TOPCon cell and a preparation method thereof. Background Art

[0002] At present, the photovoltaic industry is moving towards high efficiency and low cost under the background of global clean energy transformation. Among them, N-type TOPCon cells are gradually replacing traditional PERC cells and becoming the mainstream of the market due to their high conversion efficiency, low attenuation rate and bifacial power generation capabilities.

[0003] The carrier selective passivation contact technology of crystalline silicon solar cells has made significant progress in recent years. Among them, N-type TOPCon cells use polycrystalline silicon and tunnel oxide layers (such as SiO x Passivation contact structure (PTFE) is one of the advanced methods to improve the efficiency of solar cells. Specifically, the passivation contact structure includes preparing an ultra-thin tunneling oxide layer and a highly doped polysilicon thin layer on the back of the cell to form a good surface passivation. The ultra-thin oxide layer can allow the majority carrier electrons to tunnel into the polysilicon layer while blocking the recombination of minority carriers and holes. Then, the electrons are laterally transmitted in the polysilicon layer and collected by the metal, thereby greatly reducing the metal contact recombination current and improving the open circuit voltage and short circuit current of the cell. Therefore, improving the quality of the doped polysilicon layer can effectively improve the cell conversion efficiency.

[0004] The existing technology often uses phosphorus diffusion to dope phosphorus to improve the battery conversion efficiency; however, the depth and concentration of phosphorus in silicon wafers in different temperature zones of the diffusion furnace are different, and the uniformity is poor; if the phosphorus concentration is too high or the phosphorus diffusion is too deep, penetration will occur, affecting the integrity of the tunneling oxide layer and weakening the TOPCon battery's ability to select carriers; while low-concentration phosphorus diffusion is selected to avoid penetration, the phosphorus concentration reaching the tunneling oxide layer is low, making it difficult to form an N / N+ field passivation structure; this restricts the improvement of the battery conversion efficiency of the TOPCon battery. Summary of the invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the defects of the prior art in the phosphorus diffusion process, such as the uneven advancement depth and diffusion concentration of phosphorus elements in silicon wafers located in various temperature zones of the diffusion furnace, and large differences in the performance of silicon wafers prepared in the same batch, thereby providing a phosphorus diffusion process for a TOPCon battery, a TOPCon battery and a preparation method thereof.

[0006] To this end, the present invention provides the following technical solutions.

[0007] The present invention provides a phosphorus diffusion process for a TOPCon battery, which includes at least a first temperature rise advancement and a second temperature rise advancement, wherein the temperature rise rate of the first temperature rise advancement is lower than the temperature rise rate of the second temperature rise advancement.

[0008] The present invention controls the heating rate of the first heating advancement to be lower than the heating rate of the second heating advancement, first performs a slow heating advancement, and then performs a fast heating advancement, thereby greatly improving the uniformity of phosphorus concentration on the surface of the N-type silicon wafer in different temperature zones and the uniformity of diffusion concentration, so that there is no significant difference in the performance of silicon wafers produced in the same batch after phosphorus diffusion using the phosphorus diffusion process of the present invention;

[0009] The TOPCon battery prepared by the invention has uniform square resistance and high battery conversion efficiency.

[0010] In an optional embodiment, the heating rate of the first temperature increase advancement is 1-10°C / min. As an example, the heating rate of the first temperature increase advancement may be 1°C / min, 2°C / min, 3°C / min, 4°C / min, 5°C / min, 5.5°C / min, 6°C / min, 6.5°C / min, 7°C / min, 8°C / min, 9°C / min, 10°C / min, or within a range formed by any two of the above values.

[0011] In an optional embodiment, the heating rate of the second temperature increase is 15-35°C / min. As an example, the heating rate of the second temperature increase can be 15°C / min, 17°C / min, 20°C / min, 23°C / min, 25°C / min, 27°C / min, 29°C / min, 30°C / min, 33°C / min, 35°C / min, or within a range of any two of the above values.

[0012] In an optional embodiment, the heating time of the first heating advancement is 100-1000s; as an example, the heating time of the first heating advancement can be 100s, 200s, 300s, 400s, 500s, 600s, 700s, 800s, 900s, 1000s or within a range formed by any two of the above values.

[0013] In an optional embodiment, the pressure of the first temperature increase is 50-300 mbar;

[0014] In an optional embodiment, the temperature of the first temperature rise advancement is 850-880°C; as an example, the temperature of the first temperature rise advancement may be 850°C, 860°C, 865°C, 870°C, 880°C or within a range formed by any two of the above values.

[0015] It should be noted that during the first temperature increase process, the temperature of each temperature zone of the diffusion furnace (including the furnace mouth, the middle of the furnace, and the furnace tail) is kept consistent along the direction from the furnace mouth to the furnace tail.

[0016] In an optional embodiment, the nitrogen gas flow rate for the first temperature increase is 1000-5000 sccm.

[0017] In an optional embodiment, the heating time of the second heating advancement is 50-500s; as an example, the heating time of the second heating advancement can be 50s, 100s, 150s, 200s, 250s, 300s, 350s, 400s, 450s, 500s or within the range of any two of the above values.

[0018] In an optional embodiment, the pressure of the second temperature increase is 50-300 mbar;

[0019] In an optional embodiment, the temperature of the second temperature rise is 880-930°C; as an example, the temperature of the first temperature rise can be 880°C, 890°C, 900°C, 910°C, 920°C, 930°C or in a range formed by any two of the above values.

[0020] It should be noted that during the second temperature increase process, the temperature of each temperature zone of the diffusion furnace (including the furnace mouth, the middle of the furnace, and the furnace tail) is kept consistent along the direction from the furnace mouth to the furnace tail.

[0021] In an optional embodiment, the nitrogen gas flow rate for the second temperature increase is 1000-5000 sccm.

[0022] In an optional embodiment, a temperature control system is provided during the phosphorus diffusion process.

[0023] The present invention sets a temperature control system outside the diffusion furnace, and cooperates with the heating rate of the first heating advancement to be lower than the heating rate of the second heating advancement, so as to accurately control the temperature of the furnace mouth, the furnace and the furnace tail in the diffusion furnace, reduce temperature errors, and avoid excessive temperature differences in various temperature zones, which may lead to excessive differences in phosphorus doping concentrations, inconsistent doping depths, and diffusion penetration in the same batch of silicon wafers due to different temperatures in different temperature zones.

[0024] The phosphorus diffusion process is carried out in a diffusion furnace; a temperature control system is arranged outside the diffusion furnace. A temperature control system is arranged outside the diffusion furnace, which can accurately control the heating rate of each temperature zone, ensure that the temperature of each temperature zone of the diffusion furnace is consistent, and avoid the problem of large temperature difference.

[0025] In an optional embodiment, the first temperature increase process further includes: boat entry, first temperature increase, first constant temperature, first oxidation and first deposition steps;

[0026] Preferably, the parameters of the boat entry include: process time 200-500s, pressure 1000mbar, temperature controlled at 500-700°C, nitrogen flow rate 1000-5000sccm;

[0027] Preferably, the first temperature-raising parameters include: process time 100-500s, pressure 50-300mbar, temperature controlled at 500-800°C, and nitrogen flow rate 1000-5000sccm;

[0028] Preferably, the parameters of the first constant temperature include: process time 200-600s, pressure 50-300mbar, temperature controlled at 700-800°C, and nitrogen flow rate 500-3000sccm;

[0029] Preferably, a leak detection step is further included between the first heating and the first constant temperature;

[0030] The leak detection parameters include: process time 30-100s, pressure 50-300mbar, temperature controlled at 700-800°C;

[0031] Preferably, the parameters of the first oxidation include: process time 100-1000s, pressure 50-300mbar, temperature controlled at 700-800°C, nitrogen flow rate 500-3000sccm, oxygen flow rate 500-3000sccm;

[0032] Preferably, the parameters of the first deposition include: process time 500-2000 s, pressure 50-300 mbar, temperature controlled at 700-800° C., oxygen flow rate 50-1000 sccm, phosphorus oxychloride flow rate 500-3000 sccm.

[0033] In an optional embodiment, the second temperature raising and advancing step includes the steps of second constant temperature, first temperature lowering, nitrogen filling and boat exiting;

[0034] Preferably, the parameters of the second constant temperature include: process time 100-1000s, pressure 50-300mbar, temperature controlled at 900-930°C, oxygen flow rate 500-3000sccm;

[0035] Preferably, the first temperature reduction parameters include: process time 500-3000s, pressure 100-500mbar, temperature controlled at 700-800°C, nitrogen flow rate 1000-10000sccm;

[0036] Preferably, the nitrogen filling parameters include: process time 200-1000s, pressure 1000mbar, temperature controlled at 500-800°C, nitrogen flow rate 1000-10000sccm;

[0037] Preferably, the parameters of the boat exit include: process time 400-500s, pressure 1000mbar, temperature controlled at 500-700°C, and nitrogen flow rate 1000-5000sccm.

[0038] The present invention also provides a method for preparing a TOPCon battery, including phosphorus diffusion, wherein the phosphorus diffusion adopts the phosphorus diffusion process.

[0039] The present invention also provides a TOPCon battery, which is prepared according to the above preparation method.

[0040] The technical solution of the present invention has the following advantages:

[0041] 1. The phosphorus diffusion process of the TOPCon battery provided by the present invention includes at least a first temperature rise and a second temperature rise, and the heating rate of the first temperature rise is less than the heating rate of the second temperature rise. The present invention can control the uniform phosphorus concentration on the surface of the N-type silicon wafer located in each temperature zone of the diffusion furnace and the consistency of the advancement depth by controlling the heating rate of the two temperature rises, first slowly rising and advancing, and then rapidly rising and advancing, so as to control the uniformity of the phosphorus concentration on the surface of the N-type silicon wafer located in each temperature zone of the diffusion furnace and the consistency of the advancement depth, and the obtained TOPCon battery has uniform square resistance, and ensures that the phosphorus advancement depth and diffusion concentration in the same batch of silicon wafers prepared by the diffusion furnace are uniform, and the performance of the same batch of silicon wafers is uniform without large differences; wherein, the amount of phosphorus source on the surface of the N-type silicon wafer before the temperature rise is relatively large, and the phosphorus element can be more uniformly advanced into the N-type silicon wafer by slow advancement, and then the phosphorus element can be advanced to a position with a relatively consistent depth in the N-type silicon wafer by rapid temperature rise, which is helpful to obtain a battery cell with uniform phosphorus diffusion concentration and uniform square resistance.

[0042] 2. The phosphorus diffusion process of the TOPCon battery provided by the present invention is provided with a temperature control system, and cooperates with the first temperature rise advancement and the second temperature rise advancement, which can accurately control the temperature of the furnace mouth, the furnace and the furnace tail in the diffusion furnace, reduce the temperature error of the furnace mouth, the furnace and the furnace tail, and avoid temperature overshoot (the temperature difference between each temperature zone is too large), resulting in excessive difference in phosphorus element doping concentration in each temperature zone, inconsistent doping depth, and diffusion penetration. The TOPCon battery prepared by the present invention has good phosphorus diffusion uniformity and high battery conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0044] Figure 1 is an ECV result diagram of the TOPCon battery prepared in Example 1 of the present invention;

[0045] Figure 2 is an ECV result diagram of the TOPCon battery prepared in Example 2 of the present invention;

[0046] Figure 3 is an ECV result diagram of the TOPCon battery prepared in Example 3 of the present invention;

[0047] Figure 4 This is the ECV result diagram of the TOPCon battery prepared in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0048] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0049] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0050] The TOPCon cell provided by the present invention is prepared by conventional methods in the art, and a preparation process is listed here, including texturing, boron diffusion, SE (laser doping), high temperature oxidation, BSG removal, alkaline polishing, LPCVD, phosphorus diffusion, PSG removal, RCA cleaning, passivation to generate aluminum oxide, generation of silicon nitride passivation anti-reflection film, silk screen printing and other steps. Among them, phosphorus diffusion is carried out by the phosphorus diffusion process provided by the present invention.

[0051] The phosphorus diffusion process provided by the present invention performs two temperature rise advances, and controls the temperature rise rate of the first temperature rise advance to be less than the temperature rise rate of the second temperature rise advance; thereby controlling the phosphorus concentration on the surface of the N-type silicon wafer in each temperature zone of the diffusion furnace to be uniform, the advancement depth to be consistent, and the performance of the same batch of silicon wafers to be uniform. A temperature control system is further provided, which can accurately control the temperature of the furnace mouth, the furnace and the furnace tail in the diffusion furnace to avoid temperature overshoot, resulting in excessive differences in phosphorus element doping concentrations in each temperature zone, inconsistent doping depths, and diffusion penetration. The TOPCon battery thus obtained has good uniformity of square resistance and high battery conversion efficiency.

[0052] Example 1

[0053] This embodiment provides a preparation process of a TOPCon battery, wherein the phosphorus diffusion adopts the phosphorus diffusion process of the present invention, including the following steps:

[0054] (1) Take N-type silicon wafer and make texturing;

[0055] (2) Boron diffusion is performed on the front side of the N-type silicon wafer to form a P+ layer and a BSG layer; the boron source on the silicon wafer surface at the laser grating line and in the BSG is further pushed into the N-type silicon wafer to form a P++ layer;

[0056] (3) High temperature oxidation, the purpose is to achieve redistribution of boron source to form a selective emitter, grow an oxide layer on the front of the N-type silicon wafer to prevent the subsequent alkaline polishing process from damaging the PN junction;

[0057] (4) Removing the BSG layer on the side and back of the N-type silicon wafer; alkaline polishing removes the boron diffusion on the side and back of the N-type silicon wafer, while retaining the BSG layer on the front of the N-type silicon wafer;

[0058] (5) forming a tunnel oxide layer and an amorphous silicon layer on the surface of an N-type silicon wafer by LPCVD (low pressure chemical vapor deposition);

[0059] (6) Phosphorus diffusion, phosphorus doping the amorphous silicon layer on the back of the N-type silicon wafer to form an N+ layer and a PSG layer; wherein the phosphorus diffusion process includes:

[0060] Enter the boat and put several silicon wafers into the diffusion furnace, the process time is 200s, the pressure is 1000mbar, the temperature is controlled at 500-700℃, and the nitrogen flow rate is 3000sccm;

[0061] The first heating process was carried out with a process time of 450 s, a pressure of 200 mbar, a temperature of 700-750°C, and a nitrogen flow rate of 3000 sccm;

[0062] Leak detection, process time 50s, pressure 200mbar, temperature controlled at 750-800℃;

[0063] First constant temperature, process time 400s, pressure 150mbar, temperature controlled at 750-800℃, nitrogen flow rate 2000sccm;

[0064] First oxidation, process time 500s, pressure 150mbar, temperature controlled at 790°C, nitrogen flow rate 1000sccm, oxygen flow rate 2500sccm, for first oxidation;

[0065] The first deposition process was carried out with a process time of 900 s, a pressure of 150 mbar, a temperature of 790°C, an oxygen flow rate of 300 sccm, and a phosphorus oxychloride flow rate of 1500 sccm.

[0066] In the first heating advancement step, the heating time was 450 s, the pressure was 150 mbar, the temperature control system was set to a heating rate of 8°C / min, the temperature of each temperature zone of the diffusion furnace was 850°C, and the nitrogen flow rate was 2000 sccm;

[0067] The second temperature rise step was carried out with a heating time of 240 s, a pressure of 150 mbar, a heating rate of 15°C / min, a temperature of each zone of the diffusion furnace of 910°C, and a nitrogen flow rate of 2000 sccm.

[0068] The second constant temperature process was carried out with a process time of 500 s, a pressure of 150 mbar, a temperature of 910°C and an oxygen flow rate of 2000 sccm;

[0069] First cooling, process time 2000s, pressure 200mbar, temperature controlled at 760℃, nitrogen flow rate 4000sccm;

[0070] Nitrogen filling, process time 300s, pressure 1000mbar, temperature controlled at 760℃, nitrogen flow rate 4000sccm;

[0071] Out of the boat, process time 450s, pressure 1000mbar, temperature controlled at 500-700℃, nitrogen flow rate 3000sccm.

[0072] (7) Using HF to remove the PSG layer on the front and side of the N-type silicon wafer;

[0073] (8) Removing the polysilicon layer on the front and side surfaces of the N-type silicon wafer and the BSG layer on the front surface;

[0074] (9) passivating a layer of aluminum oxide on the front of the N-type silicon wafer; growing a silicon nitride passivation anti-reflection film on the back of the N-type silicon wafer;

[0075] (10) The front and back sides of the N-type silicon wafer are coated with silver paste for double-sided metallization, sintered, and light injected to produce a TOPCon cell.

[0076] Example 2

[0077] This embodiment provides a preparation process of a TOPCon battery. Compared with Embodiment 1, the only difference is that the first temperature rise step and the second temperature rise step in step (6) are different, as follows:

[0078] In the first heating advancement step, the heating time was 600 s, the pressure was 150 mbar, the heating rate was set at 6°C / min on the temperature control system, the temperature of each zone of the diffusion furnace was 850°C, and the nitrogen flow rate was 2000 sccm;

[0079] In the second temperature rise step, the heating time is 120s, the pressure is 150mbar, the heating rate is set at 25°C / min on the temperature control system, the temperature of each temperature zone of the diffusion furnace is 900°C, and the nitrogen flow rate is 2000sccm.

[0080] Example 3

[0081] This embodiment provides a preparation process of a TOPCon battery. Compared with Embodiment 1, the only difference is that the first temperature rise step and the second temperature rise step in step (6) are different, as follows:

[0082] (1) The first temperature rise step, the heating time is 720 s, the pressure is 150 mbar, the heating rate is set to 5 °C / min on the temperature control system, the temperature of each temperature zone of the diffusion furnace is 850 °C, and the nitrogen flow rate is 2000 sccm;

[0083] (2) The second temperature rise step, the heating time is 120s, the pressure is 150mbar, the heating rate is set at 30°C / min on the temperature control system, the temperature of each temperature zone of the diffusion furnace is 910°C, and the nitrogen flow rate is 2000sccm.

[0084] Comparative Example 1

[0085] This comparative example provides a preparation process of a TOPCon battery. Compared with Example 1, the only difference is that in step (6), a temperature rise step is used to replace the first temperature rise step and the second temperature rise step, as follows:

[0086] The heating step is as follows: the heating time is 900s, the pressure is 150mbar, the temperature is 850-900°C, and the nitrogen flow rate is 1500sccm.

[0087] Test Case

[0088] The performance tests of the TOPCon batteries prepared in Examples 1-3 and Comparative Example 1 were performed as follows:

[0089] (1) Tested with ECV (WAFER PROFILER CVP 21), the results are shown in Figure 1-4 ;

[0090] The results show that the diffusion concentration is the highest when the depth is 0.1 μm, which is 1×10 20 / cm 3 The phosphorus diffusion concentration and advancement depth are uniform; the phosphorus concentration uniformity of the TOPCon battery produced in Example 3 at the furnace mouth, furnace and furnace tail temperature zones is the best.

[0091] (2) The square resistance uniformity was tested using a square resistance instrument (napson RG-200PV). The results are shown in Table 1.

[0092] Table 1 Square resistance uniformity

[0093]

[0094]

[0095] It can be seen from Table 1 that the TOPCon battery produced by the phosphorus diffusion process of the present invention has better uniformity of square resistance; Comparative Example 1 only uses one temperature rise to carry out phosphorus diffusion, and its square resistance uniformity is far worse than the two-step temperature rise provided by the present invention, which is first slow temperature rise and then fast temperature rise.

[0096] (2) Battery conversion efficiency:

[0097] Table 2 Battery conversion efficiency

[0098] Example Battery conversion efficiency Example 1 26.05％ Example 2 26.10％ Example 3 26.15％ Comparative Example 1 26.01％

[0099] It can be seen from Table 2 that the battery conversion efficiency of the TOPCon battery prepared by the phosphorus diffusion process provided by the present invention is better, which is better than that of the comparative example 1 which only adopts one temperature increase, indicating that the phosphorus diffusion process provided by the present invention can significantly improve the battery conversion efficiency of the TOPCon battery; the battery conversion efficiency of the TOPCon battery prepared in each temperature zone of the furnace mouth, furnace and furnace tail of Example 3 is the highest.

[0100] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the scope of protection of the invention.

Claims

1. A phosphorus diffusion process for a TOPCon cell, characterized in that: At least a first temperature increase advancement and a second temperature increase advancement are included, and a temperature increase rate of the first temperature increase advancement is lower than a temperature increase rate of the second temperature increase advancement.

2. The phosphorus diffusion process according to claim 1, characterized in that: The heating rate of the first heating process is 1-10°C / min.

3. The phosphorus diffusion process according to claim 1 or 2, characterized in that: The heating rate of the second heating advancement is 15-35°C / min.

4. The phosphorus diffusion process according to claim 2, characterized in that: The first heating time is 100-1000s; and / or, The pressure of the first heating advancement is 50-300 mbar; and / or, The temperature of the first heating advancement is 850-880°C; and / or, The nitrogen gas flow rate during the first temperature increase is 1000-5000 sccm.

5. The phosphorus diffusion process according to claim 3, characterized in that: The heating time of the second heating advancement is 50-500s; and / or, The pressure of the second heating advancement is 50-300 mbar; and / or, The temperature of the second heating advancement is 880-930°C; and / or, The nitrogen gas flow rate during the second temperature increase is 1000-5000 sccm.

6. The phosphorus diffusion process according to claim 1, characterized in that: A temperature control system is provided when carrying out the phosphorus diffusion process.

7. The phosphorus diffusion process according to claim 4, characterized in that: The first temperature increase step also includes: first temperature increase, first constant temperature, first oxidation and first deposition steps; Preferably, the first temperature-raising parameters include: process time 100-500s, pressure 50-300mbar, temperature controlled at 500-800°C, and nitrogen flow rate 1000-5000sccm; Preferably, the parameters of the first constant temperature include: process time 200-600s, pressure 50-300mbar, temperature controlled at 700-800°C, and nitrogen flow rate 500-3000sccm; Preferably, the parameters of the first oxidation include: process time 100-1000s, pressure 50-300mbar, temperature controlled at 700-800°C, nitrogen flow rate 500-3000sccm, oxygen flow rate 500-3000sccm; Preferably, the parameters of the first deposition include: process time 500-2000 s, pressure 50-300 mbar, temperature controlled at 700-800° C., oxygen flow rate 50-1000 sccm, phosphorus oxychloride flow rate 500-3000 sccm.

8. The phosphorus diffusion process according to claim 5, characterized in that: The second temperature increase step includes a second constant temperature step and a first temperature decrease step after the second temperature increase step; Preferably, the parameters of the second constant temperature include: process time 100-1000s, pressure 50-300mbar, temperature controlled at 900-930°C, oxygen flow rate 500-3000sccm; Preferably, the first temperature reduction parameters include: process time 500-3000 s, pressure 100-500 mbar, temperature controlled at 700-800° C., and nitrogen flow rate 1000-10000 sccm.

9. A method for preparing a TOPCon battery, characterized in that: The method comprises phosphorus diffusion, wherein the phosphorus diffusion adopts the phosphorus diffusion process according to any one of claims 1 to 8.

10. A TOPCon battery, characterized in that: Prepared according to the preparation method according to claim 9.

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