TOPCon solar cell and preparation method and application thereof

Abstract

The invention discloses a TOPCon solar cell and a preparation method and application thereof, and belongs to the technical field of solar cells. The preparation method of the TOPCon solar cell provided by the invention comprises the following steps: S1, arranging an Al2O3 thin film on the front surface of a pretreated silicon wafer by adopting a first ALD method; the first ALD method comprises the following steps: preheating for the first time, and circularly introducing an aluminum precursor, introducing inert gas, introducing an oxygen precursor and purging; s2, arranging a positive film on the surface of the Al2O3 thin film by adopting a second ALD method; the second ALD method includes second preheating and deposition of a positive film. By limiting specific parameters, the TOPCon solar cell which is low in black edge proportion and excellent in electrical performance can be obtained. The invention also provides an application of the TOPCon solar cell.

Description

Technical Field

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

[0002] As a new type of solar cell, TOPCon solar cells have become a new hot spot in the solar energy field in recent years.

[0003] The front side of a TOPCon solar cell is typically coated with an aluminum oxide passivation film and a silicon nitride anti-reflection film, in that order. Due to the complementary and self-limiting nature of atomic deposition (ALD), which enables excellent film thickness uniformity, conformality, and precision, and boasts a wider process temperature window, ALD is typically used to deposit the Al2O3 thin film used in TOPCon solar cells, aiming to provide excellent surface passivation for N-type solar cells. The main steps in ALD deposition of Al2O3 thin films are as follows: 1) TMA, an aluminum source gas, enters the chamber and chemically adsorbs onto the substrate surface, forming new surface functional groups. The reaction is saturated, and unreacted TMA and the reaction byproduct methane are purged with high-purity nitrogen, completing the first half-reaction. 2) Water vapor enters the reaction chamber as an oxygen source and fully reacts with the new groups formed in the first half-reaction. High-purity nitrogen is then used to purge the unreacted water vapor and byproducts from the chamber, completing the second half-reaction. This cycle repeats until the desired film thickness is achieved. The film contains a significant amount of hydrogen, which chemically passivates the silicon wafer surface.

[0004] However, the film bursting phenomenon that occurs during the ALD process of preparing Al2O3 thin films can lead to low efficiency and black edge problems in the battery, seriously affecting the battery's photoelectric conversion efficiency and yield rate. Currently, there is still a lack of systematic principle analysis and comprehensive solution research on this problem. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a method for preparing a TOPCon solar cell, which can effectively reduce the EL black edge ratio and improve the open circuit voltage and conversion efficiency of the TOPCon solar cell.

[0006] The present invention also provides a TOPCon solar cell prepared by the above preparation method.

[0007] The present invention also provides applications of the TOPCon solar cell.

[0008] According to an embodiment of the first aspect of the present invention, a method for preparing a TOPCon solar cell is provided, the method comprising the following steps:

[0009] S1 provides a pretreated silicon wafer; the front side of the pretreated silicon wafer is velvet;

[0010] Producing an Al2O3 thin film on the front surface of the pretreated silicon wafer using a first ALD method;

[0011] The first ALD method includes a first preheating, and a cyclic introduction of an aluminum precursor, an inert gas, an oxygen precursor, and a purge;

[0012] The first preheating temperature is 220-300°C and the duration is ≥700s;

[0013] The number of cycles performed is 27 to 40 weeks;

[0014] S2. A positive film is provided on the surface of the Al2O3 film by a second ALD method;

[0015] The second ALD method includes a second preheating and deposition of the positive film;

[0016] The temperature of the second preheating is 440-550°C.

[0017] The preparation method according to the embodiment of the present invention has at least the following beneficial effects:

[0018] The preparation method provided by the present invention can significantly inhibit aluminum oxide film explosion and the black edge problem of TOPCon solar cells by controlling the parameters in the preparation process of Al2O3 thin film and positive film, and ultimately significantly improve the electrochemical performance of the resulting TOPCon solar cell.

[0019] According to some embodiments of the present invention, the method for obtaining a pre-processed silicon wafer includes the following steps:

[0020] The n-type silicon wafer is sequentially subjected to texturing, front boron diffusion, SE treatment, oxidation treatment, BSG removal treatment, alkaline polishing, Poly-Si deposition, annealing, PSG removal treatment and RCA cleaning.

[0021] The thickness of the n-type silicon wafer is 120-140 μm, for example, about 130 μm.

[0022] The size of the n-type silicon wafer is a standard size, for example, about 210 mm×210 mm.

[0023] The resistivity of the n-type silicon wafer is 0.9-1.6 Ω·cm; for example, it may be about 1.0 Ω·cm, 1.2 Ω·cm, 1.4 Ω·cm or about 1.5 Ω·cm.

[0024] The texturing is to form a velvet surface similar to a positive pyramid on the front and back surfaces of the n-type silicon wafer.

[0025] The front boron diffusion is to perform preliminary boron doping on one side surface of the n-type silicon wafer after texturing, and determine the doped side surface as the front side.

[0026] The SE treatment and oxidation treatment are to use laser energy to promote the diffusion of boron atoms in the silicon wafer in the local area on the front side of the component obtained by diffusing boron on the front side to perform heavy doping. Oxidation protects the SE area (the local area on the front side) and plays a role in high-temperature junction pushing.

[0027] The purpose of the BSG removal and alkali polishing is to etch the back and side borosilicate glass wraps formed on the components obtained by oxidation treatment for insulation treatment; the velvet surface on the back will be etched away at the same time.

[0028] The poly-Si deposition and annealing treatment will sequentially form a tunneling oxide layer, an amorphous silicon layer and a mask layer on the back side of the component obtained by the alkali polishing treatment; the amorphous silicon layer is annealed to form a doped polysilicon layer.

[0029] The PSG removal process and RCA cleaning can remove the edge wrap and front BSG, and remove the back protection layer (the mask layer).

[0030] The present invention does not strictly limit the specific preparation process of the above steps. In actual production, corresponding adjustments can be made according to performance requirements, available test conditions, and industry standards.

[0031] According to some embodiments of the present invention, the pre-processed silicon wafer comprises a stacked n-type silicon wafer, a tunneling oxide layer and a polysilicon layer from the front to the back; the front side of the n-type silicon wafer is a velvet surface and is doped with boron.

[0032] According to some embodiments of the present invention, in step S1, the first preheating temperature is 250-270°C. For example, it can be approximately 255°C, 260°C, or 265°C. If the temperature is too low, the amount of residual hydrogen in the aluminum oxide film will be affected, significantly reducing the efficiency of the resulting TOPCon solar cell. If the temperature is too high, it may negatively impact the structure of other layers.

[0033] According to some embodiments of the present invention, in step S1, the first preheating period is 700-800 seconds. Specifically, it can be approximately 750 seconds. Extending this period will not negatively affect the performance of the resulting TOPCon solar cell, but will also not significantly positively impact it. Therefore, within this range, high-performance TOPCon solar cells can be obtained without affecting production schedules.

[0034] According to some embodiments of the present invention, in step S1, the first ALD method is cycled 30 to 35 times. For example, it can be 31, 32, 33, or 34 times. While maintaining a certain thickness of the Al2O3 film, if the number of cycles is below the above range, the thickness will increase with each cycle, which will affect the uniformity of the aluminum oxide and result in poor on-chip passivation. As a result, the efficiency of the TOPCon solar cell will decrease to a certain extent.

[0035] The mechanism of step S1 is as follows: At room temperature and pressure, aluminum precursors, such as colorless, transparent liquid TMA (trimethylaluminum), are highly reactive and react violently with water to produce methane. H2O is a colorless, odorless liquid at room temperature. When temperatures exceed 100°C, it evaporates into water vapor and is a recognized clean energy source in nature. The current ALD process for preparing Al2O3 thin films begins with TMA undergoing a chemical adsorption reaction with the substrate to form new radicals. Water vapor then undergoes a new chemical adsorption reaction with the new radicals. This completes a cycle; after multiple cycles, an aluminum oxide film of a certain thickness is obtained.

[0036] According to some embodiments of the present invention, step S1 includes the following steps: S1a. first preheating;

[0037] S1b. Water pretreatment:

[0038] S1c. Deposition of aluminum precursor;

[0039] S1d. Inert gas purge;

[0040] S1e. Oxygen precursor reaction;

[0041] S1f. Inert gas purge;

[0042] S1g. Repeat steps S1c to S1f;

[0043] S1h. Purge the chamber with nitrogen; then evacuate, fill with nitrogen, and return the pressure to the boat.

[0044] According to some embodiments of the present invention, in step S1b, the water pretreatment includes cyclically introducing water vapor and nitrogen purging. The water vapor aeration time is 5 to 10 seconds, for example, specifically about 7 seconds; the water vapor flow rate is 200 to 300 sccm, for example, specifically about 250 sccm; the nitrogen purge time is 10 to 15 seconds, for example, specifically about 10 seconds; during the nitrogen purge, the nitrogen flow rate is 200 to 300 sccm, for example, specifically about 250 sccm; and the above steps are repeated 1 to 3 times, for example, specifically 2 times.

[0045] According to some embodiments of the present invention, in step S1c, the aluminum precursor includes TMA.

[0046] According to some embodiments of the present invention, in step S1c, the deposition of the aluminum precursor includes introducing the aluminum precursor into the chamber, wherein the aluminum precursor is introduced for a ventilation time of 5 to 8 seconds, for example, specifically about 6 seconds, and the flow rate of the aluminum precursor is 200 to 300 sccm, for example, specifically about 250 sccm.

[0047] According to some embodiments of the present invention, in step S1d, the inert gas purge uses at least one of nitrogen and argon; the flow rate of the inert gas used is 200 to 300 sccm, for example, specifically about 250 sccm; the ventilation time of the inert gas used is 10 to 13 s, for example, specifically about 11 s or about 12 s.

[0048] According to some embodiments of the present invention, in step S1e, the oxygen precursor used includes water.

[0049] According to some embodiments of the present invention, in step S1e, the reaction of the oxygen precursor is specifically performed by introducing water vapor into the chamber. Specifically, the water vapor flow rate is 200 to 300 sccm, for example, about 250 sccm, and the water vapor introduction time is 5 to 10 seconds, for example, about 7 seconds.

[0050] The parameter selection ranges of step S1f and step S1d are the same; in a specific embodiment, the selected values ​​of the parameters may be the same or different.

[0051] According to some embodiments of the present invention, in step S2, the second preheating is performed using a nine-temperature zone device to control the temperature, wherein the temperature settings of the nine temperature zones are, in order: 440-550°C, 440-550°C, 415-510°C, 400-495°C, 435-530°C, 445-540°C, 445-540°C, 425-520°C, and 425-520°C. Although the set temperature of the intermediate temperature zone is lower than the target temperature, the desired temperature can still be reached due to heat radiation from adjacent temperature zones; that is, the temperatures of different temperature zones are maintained at substantially the same level.

[0052] According to some embodiments of the present invention, in step S2, the second preheating temperature is 520-540°C, for example, about 525°C, 530°C, or about 535°C.

[0053] Correspondingly, the temperature ranges of the nine temperature zones are 520-540°C, 520-540°C, 490-510°C, 475-485°C, 510-530°C, 520-530°C, 520-540°C, 500-520°C and 500-520°C. Further:

[0054] The temperature of the first temperature zone is about 525°C, 530°C or about 535°C;

[0055] The temperature of the second temperature zone is about 525°C, 530°C or about 535°C;

[0056] The temperature of the third temperature zone is about 495°C, 500°C or about 505°C;

[0057] The temperature of the fourth temperature zone is about 480° C. or about 485° C.;

[0058] The temperature of the fifth temperature zone is about 515° C., 520° C., or about 525° C.;

[0059] The temperature of the sixth temperature zone is about 525℃;

[0060] The temperature of the seventh temperature zone is about 525° C., 530° C., or about 535° C.;

[0061] The temperature of the eighth temperature zone is about 505° C., 510° C., or about 515° C.;

[0062] The temperature of the ninth temperature zone is about 505°C, 510°C or about 515°C.

[0063] According to some embodiments of the present invention, in step S2, the second preheating time is 800-1000 seconds, for example, about 850 seconds, 900 seconds, or about 950 seconds.

[0064] According to some embodiments of the present invention, in step S2, the positive film includes a first silicon nitride film layer, a second silicon nitride film layer, a third silicon nitride film layer, a first silicon oxynitride film layer, a second silicon oxynitride film layer, and a silicon oxide film layer stacked starting from the Al2O3 film. The order of refractive index is: first silicon nitride film layer > third silicon nitride film layer > second silicon nitride film layer; and first silicon oxynitride film layer > second silicon oxynitride film layer.

[0065] According to some embodiments of the present invention, the method for preparing the first silicon nitride film layer includes introducing SiH4 and NH3 at a volume flow ratio of 1:3-4, setting the pressure to 1650-1750 mtorr, the RF power frequency to 35-45 kHz, the RF power to 13800 W-14200 W, the reaction time to 50-70 seconds, and the duty cycle to 1:12-13. Specifically, the temperature may be approximately 440° C. or approximately 450° C.; the SiH4 and NH3 flow ratio to 1:3.5-3.8; the pressure to approximately 1700 mtorr; the RF power frequency to approximately 40 kHz; the RF power to approximately 14000 W; the reaction time to approximately 60 seconds; and the duty cycle to approximately 1:12.5.

[0066] According to some embodiments of the present invention, the method for preparing the second silicon nitride film layer includes introducing SiH4 and NH3 at a volume flow ratio of 1:6-7, setting the pressure to 1700-1800 mtorr, the RF power frequency to 35-45 kHz, the RF power to 15600 W-16100 W, the reaction time to 100-120 seconds, and the duty cycle to 1:12-13. Specifically, the temperature may be approximately 480° C., 495° C., or approximately 510° C.; the flow ratio of SiH4 and NH3 to 1:6.4-6.5; the pressure setting to approximately 1750 mtorr; the RF power frequency to approximately 40 kHz; the RF power to approximately 14600 W; the reaction time to approximately 110 seconds; and the duty cycle to approximately 1:12.5.

[0067] According to some embodiments of the present invention, the method for preparing the third silicon nitride film layer includes introducing SiH4 and NH3 at a volume flow ratio of 1:8-9, setting the pressure to 1700-1800 mtorr, the RF power frequency to 35-45 kHz, the RF power to 1700-17500 W, the reaction time to 220-230 seconds, and the duty cycle to 1:11-12. Specifically, the temperature may be approximately 480° C., 495° C., or approximately 510° C.; the SiH4 and NH3 flow ratio to 1:8.5-8.7; the pressure to approximately 1750 mtorr; the RF power frequency to approximately 40 kHz; the RF power to approximately 17200 W; the reaction time to approximately 225 seconds; and the duty cycle to approximately 1:11.5.

[0068] According to some embodiments of the present invention, the method for preparing the first silicon oxynitride film layer includes introducing SiH4, NH3, and N2O at a volume flow ratio of 1:3.5-4.5:5-5.5, setting the pressure to 1100-1200 mtorr, the RF power frequency to 35-45 kHz, the RF power to 14800 W-15450 W, the reaction time to 150-170 s, and the duty cycle to 1:19-21. Specifically, the temperature may be approximately 480° C., 495° C., or approximately 510° C.; the flow ratio of SiH4, NH3, and N2O to 1:4:5.2; the pressure setting to approximately 1150 mtorr; the RF power frequency to approximately 40 kHz; the RF power to approximately 15000 W; the reaction time to approximately 160 s; and the duty cycle to approximately 1:20.

[0069] According to some embodiments of the present invention, the method for preparing the second silicon oxynitride film layer includes introducing SiH4, NH3, and N2O at a volume flow ratio of 1:4.5 to 5:8 to 8.5, setting the pressure to 1200 to 1300 mtorr, the RF power frequency to 35 to 45 kHz, the RF power to 14800 W to 15450 W, the reaction time to 120 to 140 seconds, and the duty cycle to 1:19 to 21. Specifically, the temperature may be approximately 480° C., 495° C., or approximately 510° C.; the flow ratio of SiH4, NH3, and N2O to 1:4.9 to 8.2; the pressure setting to approximately 1250 mtorr; the RF power frequency to approximately 40 kHz; the RF power to approximately 15000 W; the reaction time to approximately 130 seconds; and the duty cycle to approximately 1:20.

[0070] According to some embodiments of the present invention, the method for setting the silicon oxide film layer includes introducing SiH4 and N2O with a volume flow ratio of 1:10 to 11, setting the pressure to 1050 to 1150 mtorr, the RF power frequency of 35 to 45 kHz, the RF power of 14000 W to 14650 W, the reaction time of 120 to 140 s, and the duty cycle of 1:19 to 21; wherein the specific temperature can be approximately 480°C, 495°C or approximately 510°C; the flow ratio of SiH4 and N2O is 1:10.5 to 10.8; the pressure is set to approximately 1100 mtorr; the RF power frequency is approximately 40 kHz; the RF power is approximately 14500 W; the reaction time is approximately 130 s, and the duty cycle is approximately 1:20.

[0071] According to some embodiments of the present invention, the preparation temperature of the positive film is the same as the second preheating temperature.

[0072] According to some embodiments of the present invention, step S2 further comprises nitrogen purging, vacuuming, and nitrogen back-pressure removal from the boat after depositing the positive film.

[0073] According to some embodiments of the present invention, the preparation method further comprises the following steps performed after step S2:

[0074] S3. A back film is provided on the back of the component obtained in step S2;

[0075] S4. Electrodes are provided on the front and back surfaces of the component obtained in step S3.

[0076] According to some embodiments of the present invention, in step S4, the electrode is provided by screen printing.

[0077] According to some embodiments of the present invention, the preparation method further includes post-processing after step S4. The post-processing includes sintering, light injection, and laser sintering. The specific operation of the post-processing is not strictly limited by the present invention and can be adjusted in actual production based on experience, required results, and available experimental conditions.

[0078] According to an embodiment of the second aspect of the present invention, there is provided a TOPCon solar cell produced by the production method provided in an embodiment of the first aspect of the present invention.

[0079] Since the TOPCon solar cell adopts all the technical solutions of the preparation method of the above embodiment, it has at least all the beneficial effects brought by the technical solutions of the above embodiment. That is, the obtained TOPCon solar cell has a low black edge ratio and excellent electrical performance.

[0080] According to some embodiments of the present invention, the TOPCon solar cell includes a stacked back film, an amorphous silicon layer, a tunneling oxide layer, an n-type silicon wafer, an Al2O3 thin film, and a front film; a boron-doped region is provided on the front side of the n-type silicon wafer; and electrodes are embedded on the front and back sides of the TOPCon solar cell, respectively.

[0081] According to an embodiment of the third aspect of the present invention, there is provided an application of the TOPCon solar cell provided by the embodiment of the second aspect of the present invention in photovoltaic power stations, construction fields and electronic equipment.

[0082] Since the application adopts all the technical solutions of the TOPCon solar cell of the above embodiment, it has at least all the beneficial effects brought by the technical solutions of the above embodiment.

[0083] Unless otherwise specified, the term “about” in the present invention actually means that the error is allowed to be within the range of ±2%, for example, about 100 actually means 100±2%×100.

[0084] Unless otherwise specified, “between” in the present invention includes the number itself, for example, “between 2 and 3” includes the endpoint values ​​2 and 3.

[0085] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0086] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which:

[0087] Figure 1 Schematic diagram of the structure of the TOPCon solar cell obtained in Example 1 of the present invention.

[0088] Figure 2 This is the PL image of a normal TOPCon solar cell obtained in Comparative Example 1 of the present invention.

[0089] Figure 3 This is the EL image of a normal TOPCon solar cell obtained in Comparative Example 1 of the present invention.

[0090] Figure 4 This is a PL image of the black-edge sheet of the TOPCon solar cell obtained in Comparative Example 1 of the present invention.

[0091] Figure 5 This is the EL image of the black-edge sheet of the TOPCon solar cell obtained in Comparative Example 1 of the present invention.

[0092] Figure 6 This is a comparison chart of EQE-IQE of the normal TOPCon solar cell and the black-edge TOPCon solar cell obtained in Comparative Example 1 of the present invention.

[0093] Figure 7 This is a microscope picture of the black-edge sheet of the TOPCon solar cell obtained in Comparative Example 1 of the present invention.

[0094] Figure 8 The EL black edge ratios of multiple batches of TOPCon solar cells produced using the technical solutions provided in Example 2 (left) and Example 1 (right) of the present invention.

[0095] Figure 9 1 is a UOC box plot of the TOPCon solar cells obtained in Examples 2 to 5 of the present invention.

[0096] Figure 10 1 is a box plot of Isc of the TOPCon solar cells obtained in Examples 2 to 5 of the present invention.

[0097] Figure 11 FF box plot of the TOPCon solar cells obtained in Examples 2 to 5 of the present invention.

[0098] Figure 121 is a PCE box plot of the TOPCon solar cells obtained in Examples 2 to 5 of the present invention.

[0099] Figure 13 It is the UOC box plot of the TOPCon solar cells obtained in Example 2 and Examples 6 to 8 of the present invention.

[0100] Figure 14 1 is a box plot of Isc of the TOPCon solar cells obtained in Example 2 and Examples 6 to 8 of the present invention.

[0101] Figure 15 FF box plots of the TOPCon solar cells obtained in Example 2 and Examples 6 to 8 of the present invention.

[0102] Figure 16 1 is a PCE box plot of the TOPCon solar cells obtained in Example 2 and Examples 6 to 8 of the present invention.

[0103] Figure 17 This is a diagram of the deposition mechanism of the Al2O3 film in the preparation method provided by the present invention.

[0104] Reference numerals:

[0105] Electrode 100 , back film 200 , polysilicon layer 300 , tunneling oxide layer 400 , n-type silicon wafer 500 , boron-doped region 510 , Al 2 O 3 film 600 , and positive film 700 . DETAILED DESCRIPTION

[0106] The following will clearly and completely describe the concept and technical effects of the present invention in conjunction with the embodiments to fully understand the purpose, features and effects of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0107] In the description of the present invention, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the exemplary expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0108] Example 1

[0109] In this example, a TOPCon solar cell was prepared. The specific steps are as follows:

[0110] S0. Obtain pre-processed silicon wafer:

[0111] The n-type silicon wafer 500 is sequentially subjected to texturing, front boron diffusion, SE treatment, oxidation treatment, BSG removal treatment, alkaline polishing, Poly-Si deposition, annealing, PSG removal treatment and RCA cleaning.

[0112] Boron diffusion on the front side, combined with SE treatment and oxidation treatment, forms a boron-doped region 510;

[0113] Poly-Si is deposited and annealed to form a tunnel oxide layer 400 and a polysilicon layer 300 , as well as a mask layer that needs to be removed later.

[0114] The n-type silicon wafer is a Czochralski silicon wafer with a thickness of 130±10μm, an area of ​​approximately 210mm×210mm, and a resistivity of 0.9 to 1.6Ω·cm (multiple n-type silicon wafers are used in the same furnace, i.e., the same batch, and this resistivity is the statistical range of the resistivity of multiple n-type silicon wafers).

[0115] S1. Using a first ALD method, an Al2O3 film 600 is formed on the front surface of the component obtained in step S1. The first ALD method includes the following steps:

[0116] S1a first preheating: the step S1 resulting single component inserted into the full boat cavity: the full boat silicon wafer placed on the carrier to the cavity operation open; the cavity is evacuated preheating constant temperature, set the temperature to 270 ℃, constant temperature time 700s;

[0117] S1b water pretreatment: In step S1a, water vapor is introduced into the chamber, the ventilation time is 7s, the flow rate is 250sccm; the nitrogen purge time is 12s, the flow rate is 250sccm, and the cycle is repeated 2 times;

[0118] S1c into the chamber of step S1b of the aluminum precursor (TMA), deposited on the preheated pretreated silicon wafer surface, the ventilation time is 6s, the flow rate is 250sccm;

[0119] S1d. An inert protective gas (eg, nitrogen) is introduced at a flow rate of 250 sccm for a ventilation time of 11 s.

[0120] S1e. An oxygen precursor (water vapor) is introduced for reaction with the aluminum precursor of step S1c at a flow rate of 250 sccm for 7 s.

[0121] S1f. An inert protective gas is introduced for purging excess oxygen precursor in step S1e at a flow rate of 250 sccm for 12s.

[0122] S1g. Repeat steps S1c to S1f for 30 cycles.

[0123] S1h. Purge the chamber with nitrogen; then evacuate, fill with nitrogen, and return the pressure to the boat.

[0124] The mechanism of step S1 is as follows Figure 17 As shown, it is a chemical reaction that only limits the adsorption interface. The mechanism reaction formula is as follows:

[0125] 2Al(CH3)3+3H2O→Al2O3+6CH4.

[0126] S2. A positive film 700 is provided on the surface of the Al2O3 film of the component obtained in step S1 by a second ALD method;

[0127] The second ALD method includes the following steps:

[0128] S2a second preheating: The components obtained in step S1 are loaded into a graphite boat and placed on a silicon carbide paddle and fed into a quartz tube;

[0129] The quartz tube is preheated and maintained at a constant temperature by evacuating the chamber, with the target temperature set at 520°C. In actual production, a nine-zone device is used to control the temperature, with the specific nine zones set at 520°C, 520°C, 490°C, 475°C, 510°C, 520°C, 520°C, 500°C, and 500°C. Although the temperature of the middle zone is set lower, it can still reach the desired temperature due to heat radiation from adjacent zones. The constant temperature time is 900s.

[0130] S2b depositing a first silicon nitride film layer: controlling the temperature in step S2a; passing a volume flow ratio of 1: 3.8 SiH4 and NH3, the pressure was set to 1700mtorr, the RF power frequency was 40kHz, the RF power was set to 13800W before the boat, after the boat was set to 14200W, the reaction time was 60s, the duty cycle of the front boat was set to 1: 12, and the duty cycle of the rear boat was set to 1: 13;

[0131] S2c. Deposition of a second silicon nitride film layer: The temperature was controlled as in step S2a, and SiH4 and NH3 were introduced at a volume flow ratio of 1:6.4. The pressure was set to 1750mtorr, the RF power frequency was 40kHz, the RF power was set to 15680W before the boat, and 16100W after the boat, the reaction time was 110s, the duty cycle of the front boat was set to 1:12, and the duty cycle of the rear boat was set to 1:13;

[0132] S2d. Deposition of a third silicon nitride film layer: The temperature was controlled as in step S2a, and SiH4 and NH3 were introduced at a volume flow ratio of 1:8.7. The pressure was set to 1750mtorr, the RF power frequency was 40kHz, the RF power was set to 17200W for the front boat, and 17200W for the rear boat, the reaction time was 225s, the front boat duty cycle was set to 1:11, and the rear boat duty cycle was set to 1:12;

[0133] S2e. Deposition of a first silicon oxynitride film layer: Controlling the temperature as in step S2a, introducing SiH4 and NH3 and N2O at a volume flow ratio of 1:4:5.2, the pressure was set to 1150mtorr, the RF power frequency was 40kHz, the RF power was set to 14800W for the front boat, 15450W for the rear boat, the reaction time was 160s, the front boat duty cycle was set to 1:20, and the rear boat duty cycle was set to 1:20;

[0134] S2f. Deposition of a second silicon oxynitride film layer: The temperature was controlled as in step S2a, and SiH4 and NH3 and N2O were introduced at a volume flow ratio of 1:4.9:8.2. The pressure was set to 1250mtorr, the RF power frequency was 40kHz, the RF power was set to 14800W for the front boat, and 15450W for the rear boat. The reaction time was 130s, the front boat duty cycle was set to 1:20, and the rear boat duty cycle was set to 1:20;

[0135] S2g. Deposition of a silicon oxide film: The temperature was controlled as in step S2a, and the volume flow ratio of SiH4 and N2O was 1:10.8. The pressure was set to 1100mtorr, the RF power frequency was 40kHz, the RF power was set to 14000W before the boat, and after the boat was set to 14650W, the reaction time was 130s, the duty cycle of the front boat was set to 1:20, and the duty cycle of the rear boat was set to 1:20;

[0136] S2h. Nitrogen purge, vacuum, fill with nitrogen to back pressure and exit the boat.

[0137] S3. A back film 200 is provided on the back of the component obtained in step S2;

[0138] S4. Electrodes 100 are provided on the front and back surfaces of the component obtained in step S3 by screen printing.

[0139] S5. Perform sintering, light injection and laser sintering on the component obtained in step S4.

[0140] The structural diagram of the TOPCon solar cell obtained in this example is as follows Figure 1As shown, the TOPCon solar cell comprises a back film 200, a polysilicon layer 300, a tunneling oxide layer 400, an n-type silicon wafer 500, an Al2O3 film 600, and a front film 700. A boron-doped region 510 is provided on the front surface of the n-type silicon wafer 500. Electrodes 100 are embedded on the front and back surfaces of the TOPCon solar cell.

[0141] Example 2

[0142] This example prepares a TOPCon solar cell, which differs from Example 1 in that:

[0143] (1) In step S1g, the number of cycles is 33.

[0144] (2) In step S2a, the target temperature of the second preheating is 465°C; the corresponding temperature zones are set as: 465°C, 465°C, 435°C, 420°C, 455°C, 465°C, 465°C, 445°C, and 445°C.

[0145] Example 3

[0146] This example prepares a TOPCon solar cell, which differs from Example 2 in that:

[0147] (1) In step S1g, the number of cycles is 30.

[0148] Example 4

[0149] This example prepares a TOPCon solar cell, which differs from Example 2 in that:

[0150] (1) In step S1a, the constant temperature duration is 800s.

[0151] Example 5

[0152] This example prepares a TOPCon solar cell, which differs from Example 2 in that:

[0153] (1) In step S1a, the constant temperature is 250°C.

[0154] Example 6

[0155] This example prepares a TOPCon solar cell, which differs from Example 2 in that:

[0156] (1) In step S2a, the second preheating temperature is 520°C; the corresponding temperature zones are set as: 520°C, 520°C, 490°C, 475°C, 510°C, 520°C, 520°C, 500°C, and 500°C.

[0157] Example 7

[0158] This example prepares a TOPCon solar cell, which differs from Example 2 in that:

[0159] (1) In step S2a, the second preheating temperature is 530°C; the corresponding temperature zones are set as follows: 530°C, 530°C, 500°C, 485°C, 520°C, 530°C, 530°C, 510°C, and 510°C.

[0160] Example 8

[0161] This example prepares a TOPCon solar cell, which differs from Example 2 in that:

[0162] (1) In step S2a, the second preheating temperature is 540°C; the corresponding temperature zones are set as: 540°C, 540°C, 510°C, 495°C, 530°C, 530°C, 540°C, 520°C, and 520°C.

[0163] Test Example 1

[0164] This example tests the various properties of normal films and black-edge films in the traditional process (Example 2) in order to clarify the root cause of the black edges.

[0165] This example first tested the appearance of a normal cell (no obvious black edge) and two TOPCon solar cells with obvious black edges (hereinafter referred to as black edge cells) in Example 2 (traditional process). The test method was visual inspection. Specifically, the PL (photoluminescence) and EL (electroluminescence) images of the normal cell are as follows: Figures 2-3 As shown; the PL (photoluminescence) and EL (electroluminescence) images of the black edge film are as follows Figures 4-5 As shown; the arrows in the figure indicate the positions of the black edges.

[0166] Depend on Figure 3 and Figure 5 The figure shows that the EL black edge is perpendicular to the main grid direction; and the black position is the same as that shown in the PL image; the combination of the two shows that the cause of the black edge is the abnormal passivation problem of the TOPCon solar cell.

[0167] In order to further explore the cause of the EL black edge, the EL black edge area of ​​the TOPCon solar cell observed above was tested for EQE, using a quantum efficiency test system for testing, and an IV test system for electrical performance parameter testing; the results showed that the difference in the EQE curve between the EL black edge area (the corresponding area of ​​the black-edge cell) and the normal area (the corresponding area of ​​the normal cell) was mainly concentrated in the short-wave band (350nm~500nm). Compared with normal cells, the open circuit voltage (Uoc) loss of TOPCon solar cells with black edges was about 3.6mv, the short circuit current (Isc) loss was 20mA, and the fill factor (FF) was low by 0.55. This shows that the black edge caused by the ALD film explosion has a significant negative impact on the electrical performance of the TOPCon solar cell, and is one of the important factors leading to cell inefficiency; the above results combined can rule out that the EL black edge is caused by the back process of the TOPCon solar cell, and confirm that the EL black edge is mainly generated on the front of the TOPCon solar cell. The specific EQE test results are as follows Figure 6 The electrical performance parameters are shown in Table 1.

[0168] Table 1 Electrical performance data of normal and black TOPCon solar cells

[0169] type Eta (%) Uoc(V) Isc(A) Ff(%) Rsh(Ω) Rs(Ω) IRev2(A) Normal film 26.9 0.7403 16.007 86.69 2430 0.00057 0.0344 Black edge piece 1 26.49 0.7358 15.988 85.99 2434 0.00063 0.0590 Black edge film 2 26.46 0.7376 15.985 86.28 2345 0.00060 0.1184

[0170] In Table 1, Eta represents the battery conversion efficiency, Uoc represents the open circuit voltage, Isc represents the short circuit current, ff represents the fill factor, Rsh represents the parallel resistance, Rs represents the series resistance, and IRev2 represents the leakage current.

[0171] Furthermore, this example also tested the three cells mentioned above using a Suns-Voc test system. The results showed that the J01 value of the EL black-bordered cell was higher than that of normal cells, indicating a surface abnormality. However, the J02 value was the same as that of normal cells, indicating that there was no abnormality in the junction area. Therefore, it can be preliminarily determined that the surface passivation process (positive film process) caused the EL black border. The specific results are shown in Table 2.

[0172] Table 2 Suns-voc data sheet for EL black-edged TOPCon batteries

[0173] type Voc(V) <![CDATA[J01(A / cm 2 )]]> <![CDATA[J02(A / cm 2 ) <!-- 9 -->]]> Normal film 0.742 1.09E-14 1E-11 Black edge film 1 0.723 2.32E-14 1E-11 Black edge film 2 0.736 1.42E-14 1E-11

[0174] In Table 2, Voc represents the open-circuit voltage. J01 represents the saturation current density 1, which is generally correlated with the bulk recombination current density. It reflects the recombination of carriers through recombination centers within the active region of the cell (e.g., within the silicon wafer). Increased bulk recombination results in an increased J01 value. J02 represents the saturation current density 2, which is generally correlated with the surface recombination current. It reflects the recombination of carriers at the cell surface (e.g., at the interface between the silicon wafer and the passivation layer or electrodes). Increased surface recombination results in an increased J02 value. Both J01 and J02 are directly read from the Suns-Voc flash test system.

[0175] This example also analyzed the front side of the TOPCon solar cell with the EL black edge. The microscope image shows that there are white bright spots on the blue background, which is preliminarily confirmed to be caused by the explosion of the aluminum oxide process in the front ALD setting. The microscope image of the explosion shows abnormal structural features, and at the same time, it is manifested as a black edge phenomenon at the edge of the battery on a macro scale. In the photoluminescence (PL) test image, the luminescence of the black edge area is significantly different from that of the normal area, indicating that the explosion has changed the recombination of carriers and the optical properties inside the battery. The specific test results are as follows Figure 7 shown.

[0176] Based on the above tests and inferences, it is obvious that the EL black edge is produced on the front of the battery, mainly in the ALD and positive film processes.

[0177] Test Example 2

[0178] This example tested the EL black edge ratio and electrochemical performance of the TOPCon solar cells obtained in Examples 1-8. The specific testing method was as follows: 786 TOPCon solar cells were tested in one batch, and the data were statistically analyzed to obtain the median value. The results from three batches were averaged. In Example 2, two batches were tested under the same conditions, hereafter referred to as Example 2-1 and Example 2-2.

[0179] The results of EL black edge are shown in Table 3 and Figure 8 The electrochemical test results are shown in Table 4 and Figures 9 to 16 shown.

[0180] Table 3 EL black edge statistics results

[0181]

[0182]

[0183] The results show that reducing the number of ALD cycles during aluminum oxide film deposition (Examples 2 and 3) can reduce the EL black edge ratio to a certain extent. Prolonging the holding time before ALD aluminum oxide deposition (Examples 2 and 4) does not significantly reduce the EL black edge ratio. However, reducing the holding temperature before ALD aluminum oxide deposition (Examples 2 and 5) does reduce the EL black edge ratio to a certain extent. Increasing the holding temperature before positive film deposition (Examples 2 and Examples 6-8) gradually reduces the black edge ratio.

[0184] At the same time, the results show that the white bright spots (i.e., film bursts) in Examples 3 and 6 under the microscope have also disappeared, which also indirectly verifies that the cause of the EL black edge is due to the ALO X The black edge and low efficiency caused by the explosion of the film, so to improve this kind of EL black edge degradation, it is necessary to start from ALO X Only by working together with the positive film can the production line yield be effectively improved.

[0185] By comparing the results of Example 2-1 and Example 2-2, it can be seen that by adopting the preparation method provided by the present invention, if the same experimental parameters are maintained, the same or equivalent technical effects can be obtained, that is, the preparation method provided by the present invention has good reproducibility.

[0186] By comparing the results of Example 1 with those of other examples, it can be seen that there is a significant synergistic effect between the number of cycles when ALD is used to prepare the aluminum oxide film and the preheating temperature when preparing the positive film. The combination of the two can significantly reduce the black edge ratio of TOPCon solar cells.

[0187] Table 4 Electrochemical performance results of TOPCon solar cells obtained in Example

[0188]

[0189] The open circuit voltage UOC and conversion efficiency Eta of Example 3 are slightly higher than those of Example 2. From the EL results and electrical performance results, it can be considered that reducing the number of cycles of the ALD method for preparing aluminum oxide thin films (step S1) from 33 to 30 is an effective improvement measure. The experimental efficiency of Examples 4 and 5 is 0.009 to 0.018% lower than that of the production line, which is reflected in the open circuit voltage being 0.0002 to 0.0006V lower. Figures 8-12 It can also be seen that the overall data of Example 3 is relatively concentrated and has good discreteness.

[0190] The positive film temperature was experimentally adjusted (Example 2 and Examples 6 to 8). In Example 6, the temperature was increased from 465°C to 520°C, and the efficiency was improved by 0.055 compared with Example 2, mainly reflected in the increase of the fill factor FF by 0.28. The efficiency of Examples 7 and 8 was 0.027 to 0.036% lower than that of Example 2, and both the open circuit voltage and the fill factor were lost.

[0191] Combining the results of Example 1 and other examples, it can be seen that by reducing the number of cycles in step S1g, maintaining a low insulation time, and appropriately increasing the temperature of the second preheating and positive film preparation, the black edge problem of TOPCon solar cells can be significantly suppressed and their comprehensive electrical performance can be improved.

[0192] In summary, ALO X Film explosion is the key factor leading to low efficiency and black edges of batteries. Its principle involves many aspects such as process parameters and film characteristics. ALO can be effectively reduced by optimizing process parameters, improving process monitoring and quality control, and other measures. X The TOPCon solar cell fabrication method can significantly improve the overall performance of the resulting TOPCon solar cell, thus enabling its widespread application in photovoltaic power plants, construction, and electronic devices.

[0193] While the embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to the embodiments described above. Various modifications may be made within the scope of knowledge possessed by a person skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof may be combined with one another unless there is a conflict.

Claims

1. A method for preparing a TOPCon solar cell, characterized in that: The preparation method comprises the following steps: S1 provides a pretreated silicon wafer; the front side of the pretreated silicon wafer is velvet; Producing an Al2O3 thin film on the front surface of the pretreated silicon wafer using a first ALD method; The first ALD method includes a first preheating, and a cyclic introduction of an aluminum precursor, an inert gas, an oxygen precursor, and a purge; The first preheating temperature is 220-300°C and the duration is ≥700s; The number of cycles performed is 27 to 40 weeks; S2. A positive film is provided on the surface of the Al2O3 film by a second ALD method; The second ALD method includes a second preheating and deposition of the positive film; The temperature of the second preheating is 440-550°C.

2. The preparation method according to claim 1, characterized in that The method for obtaining the pre-treated silicon wafer comprises the following steps: The n-type silicon wafer is sequentially subjected to texturing, front boron diffusion, SE treatment, oxidation treatment, BSG removal treatment, alkaline polishing, Poly-Si deposition, annealing, PSG removal treatment and RCA cleaning; And / or, the pre-treated silicon wafer comprises an n-type silicon wafer, a tunneling oxide layer and a polysilicon layer stacked from the front side to the back side; the front side of the n-type silicon wafer is a velvet surface and is doped with boron.

3. The preparation method according to claim 1, characterized in that The preparation method further comprises the following steps after step S2: S3. A back film is provided on the back of the component obtained in step S2; S4. Electrodes are provided on the front and back surfaces of the component obtained in step S3.

4. The preparation method according to any one of claims 1 to 3, characterized in that In step S1, the temperature of the first preheating is 250-270°C; and / or, in step S1, the duration of the first preheating is 700-800s.

5. The preparation method according to any one of claims 1 to 3, characterized in that In step S1, the first ALD method is cycled 30 to 35 times.

6. The preparation method according to any one of claims 1 to 3, characterized in that In step S2, the temperature of the second preheating is 520-540°C.

7. The preparation method according to any one of claims 1 to 3, characterized in that In step S2, the second preheating time is 800 to 1000 seconds.

8. The preparation method according to any one of claims 1 to 3, characterized in that In step S2, the positive film includes a first silicon nitride film layer, a second silicon nitride film layer, a third silicon nitride film layer, a first silicon oxynitride film layer, a second silicon oxynitride film layer and a silicon oxide film layer stacked starting from the Al2O3 film.

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

10. Use of the TOPCon solar cell according to claim 9 in photovoltaic power stations, buildings and electronic equipment.

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