An annealing method for improving film explosion and n-type topcon cell

Abstract

The application provides an annealing method for improving film explosion and an N-type TOPCon cell, and relates to the field of solar cells. The method comprises the following steps: arranging an oxide layer on the surface of a silicon wafer subjected to micro-texturing treatment; and performing annealing under dynamic atmosphere control. The dynamic atmosphere comprises a base gas and periodic gas pulses. The concentration of hydrogen is monitored in real time during the annealing, and the pressure fluctuation frequency is dynamically adjusted. Through the synergistic effect of the dynamic atmosphere, the annealing temperature gradient, and the micro-texturing / oxide layer combination, on the one hand, hydrogen escape is inhibited, and on the other hand, residual compressive stress can be induced. Moreover, the stacking of the micro-texturing surface and the oxide layer can improve the interfacial bonding force.

Description

Technical Field

[0001] This application relates to the field of solar cells, and more particularly to an annealing method for improving film bursting and an N-type TOPCon cell. Background Technology

[0002] In the manufacturing process of TOPCon photovoltaic cells, the traditional method typically employs a combination of constant-pressure slow drawing and constant-temperature annealing for annealing. However, this existing technology has the following technical drawbacks: Insufficient control of hydrogen escape: During the annealing process, hydrogen atom diffusion is difficult to suppress effectively, resulting in damage to the film structure. Specifically, the film bursting rate exceeds 10%, which seriously affects the device yield. Thermal stress concentration problem: Due to insufficient thermodynamic matching of the annealing process, thermal stress concentration is prone to occur in the interface area, which in turn leads to interface delamination defects and reduces the long-term reliability of the battery. Limited optical performance: Existing processes do not adequately optimize the surface passivation layer, resulting in the device reflectivity remaining above 15%, which leads to reduced light absorption efficiency and affects the photoelectric conversion performance of the battery.

[0003] The fundamental problem with existing methods lies in the lack of a systematic process scheme that can synergistically optimize hydrogen diffusion suppression, thermal stress regulation, and light reflection reduction. The failure to establish an effective synergistic mechanism among the various process parameters hinders further improvements in the overall performance of TOPCon cells. Therefore, there is an urgent need to develop a new annealing process to address these technical challenges. Summary of the Invention

[0004] The purpose of this application is to provide an annealing method for improving the rupture of the film and an N-type TOPCon battery to solve the above-mentioned problems.

[0005] To achieve the above objectives, this application adopts the following technical solution: This application provides an annealing method for improving the film explosion, comprising: forming an oxide layer on the surface of a silicon wafer that has undergone microtexturing; and annealing under dynamic atmosphere control; The dynamic atmosphere includes a base gas and periodic gas pulses; The hydrogen concentration is monitored in real time during the annealing process, and the pressure fluctuation frequency is dynamically adjusted.

[0006] Optionally, the microtexturing process includes: using a microtexturing solution and treating at 70-90°C for 20-60 minutes.

[0007] Optionally, based on the total mass of the raw materials in the microtexturing solution as 100%, it includes: 10wt% NaOH 8-12%, nano-sized SiC 2-4%, surfactant 0.5-1.5%, and the balance being water; The surfactant includes fatty alcohol polyoxyethylene ether; The particle size of the nanoscale SiC is 20-100 nm.

[0008] Optionally, the textured surface Ra formed after the microtexturing process has a thickness of 100-200 nm.

[0009] Optionally, the oxide layer includes an Al2O3 layer and a SiO2 layer; The thickness of the Al2O3 layer is 4-6 nm; The thickness of the SiO2 layer is 2-4 nm.

[0010] Optionally, the pressure is 0.09-0.11 MPa during the dynamic gas regulation.

[0011] Optionally, the real-time monitoring of hydrogen concentration includes monitoring the concentration of surface hydroxyl groups of the oxide layer using online Raman spectroscopy; the concentration threshold of the surface hydroxyl groups is 2.5-3.5%.

[0012] Optionally, when the concentration of hydroxyl groups on the surface of the oxide layer is greater than 3%, the AI ​​model triggers pressure fluctuations; wherein, the pressure fluctuation frequency f = K·(OH) - ), K=4-6Hz / %.

[0013] Optionally, when the concentration of hydroxyl groups on the surface of the oxide layer is no more than 3%, the AI ​​model triggers pressure fluctuations, with a pressure fluctuation frequency of 10 Hz and a pressure fluctuation amplitude of no more than 0.02 MPa.

[0014] Optionally, the annealing is staged annealing, including: First stage: The heating rate is 2-4℃ / min to 630-670℃, and the holding time is 50-70s; Second stage: The heating rate is 6-7℃ / min to 830-870℃, and the holding time is 25-35s; The third stage: the cooling rate is 1-3℃ / min to 180-220℃, and the holding time is 15-25s; then it is allowed to cool naturally to room temperature.

[0015] Optionally, the base gas is a 5 vol% mixture of H2 and N2, with a total flow rate of 8-12 slm.

[0016] Optionally, the periodic gas pulse includes: inserting a pure H2 pulse for 8-12 seconds every 45-55°C increase in temperature, wherein the flow rate of the pure H2 pulse is 1-3 slm, triggering oxygen vacancy formation.

[0017] This application also provides an N-type TOPCon battery, the preparation method of which includes the annealing method for improving the bursting film.

[0018] Compared with the prior art, the beneficial effects of this application include: This application provides an annealing method to improve the passivation film. In this method, an oxide layer acts as a hydrogen diffusion barrier, forming a composite protective layer on the surface of a microtextured structure. A dynamic gas control system alternately introduces gases of different properties during the annealing process, periodically altering the reaction environment to suppress excessive hydrogen atom escape. A pressure fluctuation frequency adjustment module, based on real-time monitoring data, increases the pressure fluctuation amplitude when the hydrogen concentration exceeds the limit, using mechanical stress to offset thermal stress concentration. Through the synergistic effect of the dynamic atmosphere, the annealing temperature gradient, and the microtextured / oxide layer phase composite, hydrogen escape is suppressed on the one hand, and residual compressive stress is induced on the other. Furthermore, the stacking of the microtextured surface and the oxide layer enhances the interfacial bonding force. This synergistic mechanism, optimized through physical field coupling, maintains the integrity of the passivation layer while improving the interfacial bonding state. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0020] Figure 1 The SEM image of the oxide layer of the N-type TOPCon cell provided in Example 1; Figure 2 The SEM image of the oxide layer of the N-type TOPCon cell provided for Comparative Example 2. Detailed Implementation

[0021] As used in this article: "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0022] The conjunction "composed of..." excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for associated conventional impurities. When the phrase "composed of..." appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0023] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1–5” is disclosed, the described range should be interpreted as including ranges “1–4”, “1–3”, “1–2”, “1–2 and 4–5”, “1–3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0024] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0025] "Parts by mass" refers to the basic unit of measurement that expresses the mass ratio of multiple components. One part can represent any unit mass, such as 1g or 2.689g. If we say that component A has "a" parts by mass and component B has "b" parts by mass, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it can mean that the mass of component A is aK and the mass of component B is bK (where K is any number representing a multiplier). It is important to understand that, unlike parts by mass, the sum of the mass parts of all components is not limited to 100 parts.

[0026] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0027] To better explain the technical solution provided in this application, a general description of the technical solution provided in this application will be given before proceeding with specific implementation methods.

[0028] In existing technologies, the photovoltaic cell manufacturing field has long been committed to optimizing annealing processes to improve device performance. Traditional processes employ a combination of constant-pressure slow-drawing and constant-temperature annealing, but this has revealed significant drawbacks in practical applications. For example, during the high-temperature annealing process after silicon wafer surface treatment, the lack of dynamic control over the gas environment leads to uncontrollable hydrogen atom diffusion paths, uneven stress distribution within the passivation layer, and ultimately, damage to the film structure. Furthermore, fixed process parameters are difficult to match with the characteristic differences between different batches of materials, resulting in decreased interfacial bonding strength and higher light reflectivity.

[0029] To address these issues, researchers analyzed the coupling mechanism between hydrogen diffusion kinetics and thermal stress, discovering that dynamic control of the gas environment can alter the migration path of hydrogen atoms. Further investigation revealed that periodically switching reactant gases can create a gradient concentration field, effectively suppressing hydrogen atom aggregation. Based on this, they proposed synergistically applying gas control and pressure fluctuations to the annealing process, achieving dynamic optimization of process parameters through real-time monitoring and feedback. This closed-loop control strategy provides a new approach to solving interface defects.

[0030] Therefore, this application proposes an annealing method including the following steps: forming an oxide layer on the surface of a silicon wafer that has undergone microtexturing; and annealing under dynamic atmosphere control. The dynamic atmosphere includes a base gas and periodic gas pulses; The hydrogen concentration is monitored in real time during the annealing process, and the pressure fluctuation frequency is dynamically adjusted.

[0031] Compared to existing technologies, traditional constant-pressure annealing processes cannot respond to changes in hydrogen concentration in real time, leading to stress accumulation within the passivation layer. This solution introduces a dynamic gas switching and pressure fluctuation linkage mechanism to form an adaptive control system during annealing. The micro-vibrations generated by pressure fluctuations promote atomic rearrangement, while the concentration gradient formed by periodic gas switching effectively suppresses the continuity of the hydrogen diffusion path. This composite control method overcomes the limitations of single-parameter optimization.

[0032] Through the above technical solution, this application achieves directional control of the hydrogen diffusion path, reducing the risk of stress concentration within the passivation layer. The dynamic gas environment optimizes the surface passivation effect, while pressure fluctuation adjustment enhances the interfacial bonding strength. This process simultaneously improves the photoelectric conversion efficiency and long-term reliability of photovoltaic cells while maintaining the integrity of the film structure.

[0033] In one optional embodiment, the microtexturing process includes: treating with a microtexturing solution at 70-90°C for 20-60 minutes.

[0034] Specifically, in the micro-texturing process, the silicon wafer is immersed in a texturing solution and kept at 80°C for 30 minutes. Under these conditions, the active ingredients in the texturing solution undergo a controlled corrosion reaction with the silicon wafer surface, forming a textured surface structure with a specific roughness. By precisely controlling the temperature and time parameters, problems such as low texture coverage due to insufficient reaction or surface damage caused by over-reaction can be avoided.

[0035] The aforementioned technical features effectively reduce the surface reflectivity of the silicon wafer while avoiding surface defects caused by excessive etching. The uniform textured surface provides a more ideal substrate surface for subsequent oxide layer deposition, reducing interfacial stress concentration and thus lowering the risk of film bursting during annealing.

[0036] In one optional embodiment, the total mass of the raw materials in the microtexturing solution is 100%, comprising: 10wt% NaOH 8-12%, nano-sized SiC 2-4%, surfactant 0.5-1.5%, and the balance being water; The surfactant includes fatty alcohol polyoxyethylene ether; The particle size of the nanoscale SiC is 20-100 nm.

[0037] Optionally, the particle size of nanoscale SiC can be 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, or any value between 20 and 100 nm.

[0038] In one optional embodiment, the textured surface Ra formed after the microtexturing process has a thickness of 100-200 nm.

[0039] The total mass percentage of raw materials in the texturing solution refers to the mass proportion of each component in the texturing solution. This can be achieved using a premixed solution method. By controlling the ratio of sodium hydroxide to nanoscale silicon carbide, the etching rate and surface morphology control capability of the texturing solution can be adjusted. The particle size control of nanoscale silicon carbide directly affects the uniformity of the textured surface microstructure. The textured surface roughness Ra can be measured using atomic force microscopy, and this parameter is directly related to light scattering efficiency. When nanoscale silicon carbide is added to the texturing solution, it acts as hard particles, forming a uniformly distributed micron-sized depression structure on the silicon wafer surface. Simultaneously, the alkaline etching effect of sodium hydroxide and the mechanical etching effect of silicon carbide produce a synergistic effect. Under textured surface conditions with Ra = 100-200 nm, incident light undergoes multiple reflections on the surface, effectively extending the optical path and reducing reflection loss. The particle size selection of nanoscale silicon carbide must balance dispersion stability and etching efficiency. The nanoscale particle size can avoid agglomeration and blockage of the reaction interface while providing sufficient etching intensity.

[0040] In an optional embodiment, the oxide layer comprises an Al2O3 layer and a SiO2 layer; The thickness of the Al2O3 layer is 4-6 nm; The thickness of the SiO2 layer is 2-4 nm.

[0041] Optionally, the thickness of the Al2O3 layer can be 4 nm, 4.5 nm, 5 nm, 5.5 nm, 6 nm, or any value between 4 and 6 nm; the thickness of the SiO2 layer can be 2 nm, 2.5 nm, 3 nm, 3.5 nm, 4 nm, or any value between 2 and 4 nm.

[0042] An Al2O3 layer is preferentially deposited on the silicon wafer surface to form a dense passivation layer, suppressing hydrogen atom diffusion along grain boundaries through its lattice-matching properties. A SiO2 layer is then deposited on the Al2O3 layer surface, reducing incident light reflection through its refractive index gradient characteristics. The thickness ratio of the Al2O3 to SiO2 layers is optimized to achieve destructive light interference while ensuring mechanical strength. Excessive Al2O3 layer thickness increases interfacial stress, while insufficient SiO2 layer thickness reduces optical performance; the synergistic effect of both achieves a balance between interfacial stability and light absorption efficiency. In this way, this application reduces the risk of film explosion by combining the hydrogen blocking effect of the Al2O3 layer with the textured surface of the micro-textured layer, and improves the light absorption efficiency of the battery by utilizing the optical modulation properties of the SiO2 layer. The synergistic effect of the dual-layer structure effectively reduces light reflectivity while maintaining interfacial bonding strength, thereby improving the yield and photoelectric conversion performance of TOPCon batteries.

[0043] In one optional implementation, the pressure is 0.09-0.11 MPa during the dynamic gas regulation.

[0044] Optionally, the pressure during dynamic atmosphere control can be 0.09 MPa, 0.091 MPa, 0.092 MPa, 0.093 MPa, 0.094 MPa, 0.095 MPa, 0.096 MPa, 0.097 MPa, 0.098 MPa, 0.099 MPa, 0.1 MPa, 0.101 MPa, 0.102 MPa, 0.103 MPa, 0.104 MPa, 0.105 MPa, 0.106 MPa, 0.107 MPa, 0.108 MPa, 0.109 MPa, 0.11 MPa, or any value between 0.09 and 0.11 MPa.

[0045] Specifically, during the annealing process, the chamber pressure is stabilized within a set range using a pressure control module, for example, by employing a proportional-integral-derivative (PID) controller to compensate for pressure fluctuations in real time. A pressure of 0.09 MPa enhances the adsorption of reactive gases on the silicon wafer surface; while a pressure of 0.11 MPa effectively suppresses the rapid escape of hydrogen atoms. By precisely controlling the pressure parameters, a stable diffusion gradient is formed at the oxide layer interface, simultaneously reducing the impact of turbulence on the film structure. These technical features enable refined control of the gas environment during annealing, effectively reducing film structure damage caused by hydrogen atom diffusion, and mitigating thermal stress concentration by optimizing gas flow. The synergistic effect of this pressure range setting and dynamic control mechanism significantly improves the oxide layer passivation effect, laying the foundation for the subsequent formation of a stable interface structure.

[0046] In an optional implementation, the real-time monitoring of hydrogen concentration includes monitoring the concentration of surface hydroxyl groups of the oxide layer using online Raman spectroscopy; the concentration threshold of the surface hydroxyl groups is 2.5-3.5%.

[0047] Optionally, the concentration threshold of the surface hydroxyl groups can be 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, or any value between 2.5% and 3.5%.

[0048] In an optional embodiment, when the concentration of hydroxyl groups on the oxide layer surface is greater than 3%, the AI ​​model triggers pressure fluctuations to suppress excessive Si-H bond formation; wherein, the pressure fluctuation frequency f = K·(OH) - ), K=4-6Hz / %.

[0049] In one optional implementation, when the concentration of hydroxyl groups on the surface of the oxide layer is no more than 3%, the AI ​​model triggers pressure fluctuations with a frequency of 10 Hz and an amplitude of no more than 0.02 MPa.

[0050] Online Raman spectroscopy refers to an analytical method that uses laser excitation to detect molecular vibrational signals on the sample surface in real time. Specifically, it can be implemented using an in-situ detection system equipped with a fiber optic probe. This technology can non-contactly acquire chemical bond information of hydroxyl groups on the oxide layer surface. The concentration threshold of surface hydroxyl groups refers to a pre-set critical range of chemisorbent content, which can be determined by establishing a mathematical model of the relationship between hydroxyl concentration and film stress. This threshold is used to assess the stability of the interfacial chemical state during annealing. Pressure fluctuation frequency refers to the number of periodic changes in gas pressure per unit time. It can be dynamically adjusted by multiplying the proportionality coefficient K by the hydroxyl concentration deviation. This parameter is used to match the hydrogen diffusion rate control requirements of different process stages. Pressure fluctuation amplitude refers to the peak-to-valley difference in gas pressure changes, which can be limited by a linkage between a pressure limiting valve and a flow controller. This parameter is used to avoid mechanical damage to the film layer caused by sudden pressure changes.

[0051] Specifically, during the annealing process, a laser source continuously irradiates the oxide layer surface, and a Raman spectrometer collects the intensity data of the hydroxyl characteristic peaks. The real-time concentration value is calculated using the integrated area method. When the detected value exceeds 3%, the AI ​​algorithm generates a pressure fluctuation frequency adjustment command based on the concentration deviation. The proportional coefficient K converts the concentration change into a frequency adjustment value, causing the pressure fluctuation frequency to increase linearly with the increase of hydroxyl concentration. When the detected value is below or equal to 3%, the system automatically switches to the basic frequency mode, while the pressure limiting device controls the pressure fluctuation amplitude within a safe range. This process achieves dynamic matching between gas pressure parameters and interfacial chemical state through a closed-loop control system.

[0052] Through the above technical solution, this application achieves precise control of hydrogen diffusion behavior during annealing, effectively suppresses damage to the film structure caused by local hydrogen accumulation, and reduces interfacial thermal stress by dynamically optimizing pressure parameters, thereby improving the uniformity and density of the passivation layer structure.

[0053] In one optional implementation, the annealing is staged annealing, including: First stage: The heating rate is 2-4℃ / min to 630-670℃, and the holding time is 50-70s; Optionally, the heating rate of the first stage can be 2℃ / min, 3℃ / min, 4℃ / min, or any value between 2 and 4℃ / min; the heating endpoint of the first stage can be 630℃, 635℃, 640℃, 645℃, 650℃, 655℃, 660℃, 665℃, 670℃, or any value between 630 and 670℃; the holding time can be 50s, 55s, 60s, 65s, 70s, or any value between 55 and 70s.

[0054] Second stage: The heating rate is 4-6℃ / min to 830-870℃, and the holding time is 25-35s.

[0055] Optionally, the heating rate of the second stage can be 4℃ / min, 5℃ / min, 6℃ / min, or any value between 4℃ / min; the heating endpoint of the second stage can be 830℃, 835℃, 840℃, 845℃, 850℃, 855℃, 860℃, 865℃, 870℃, 875℃, 880℃, or any value between 830℃ and 870℃; the holding time can be 25s, 26s, 27s, 28s, 29s, 30s, 31s, 32s, 33s, 34s, 35s, or any value between 25s and 35s.

[0056] The third stage: the cooling rate is 1-3℃ / min to 180-220℃, and the holding time is 15-25s; then it is allowed to cool naturally to room temperature.

[0057] Optionally, the cooling rate of the third stage can be 1℃ / min, 2℃ / min, 3℃ / min, or any value between 1 and 3℃ / min; the cooling endpoint of the third stage can be 180℃, 185℃, 190℃, 195℃, 200℃, 205℃, 210℃, 215℃, 220℃, or any value between 180 and 220℃; the holding time can be 15s, 16s, 17s, 18s, 19s, 20s, 21s, 22s, 23s, 24s, 25s, or any value between 15 and 25s.

[0058] During the annealing process, the silicon wafer is first heated uniformly at a low heating rate. At this point, the hydrogen atom diffusion rate and the passivation layer recombination rate reach a dynamic equilibrium, effectively reducing local stress concentration. When the temperature reaches the intermediate stage, the heating rate is accelerated to promote the formation of a stable interface structure between the oxide layer and the silicon substrate. A short holding time is maintained at the high temperature stage to ensure sufficient crystallization of the passivation layer while avoiding excessive consumption of hydrogen atoms. The subsequent slow cooling process gradually releases the internal stress of the material, and finally, natural cooling avoids microscopic defects caused by sudden temperature changes.

[0059] Compared with existing technologies, the single temperature control mode of traditional isothermal annealing process cannot meet the dual requirements of hydrogen diffusion suppression and thermal stress elimination. In contrast, staged annealing, by controlling the temperature gradient in stages, establishes a hydrogen atom binding mechanism in the early stage of heating, optimizes the passivation layer density in the high-temperature stage, and achieves gradual stress release in the cooling stage, forming a multi-dimensional synergistic control mechanism.

[0060] Through the above technical solutions, this application can effectively reduce the uncontrolled escape of hydrogen atoms during annealing, reduce the difference in thermal expansion coefficients between the passivation layer and the substrate, and improve the interfacial bonding strength. Simultaneously, by optimizing the temperature change rate at each stage, the stability of the film structure is significantly improved while ensuring the optical performance of the passivation layer.

[0061] In one optional embodiment, the base gas is a 5 vol% mixture of H2 and N2, with a total flow rate of 8-12 slm.

[0062] During the annealing process, a mixture of hydrogen and nitrogen gases serves as the substrate environment. By precisely controlling the hydrogen concentration and total flow rate, damage to the film layer caused by excessive hydrogen escape can be suppressed, while maintaining the necessary reducing atmosphere. When the temperature gradient increases to nodes at 50 degrees Celsius intervals, short-duration, high-flow-rate pure hydrogen pulses are triggered. This operation instantaneously increases the local hydrogen concentration, promoting the reaction between oxygen atoms and hydrogen in the oxide layer, thereby forming a controllable oxygen vacancy structure in the interface region. The generation of oxygen vacancies helps reduce interfacial stress and optimizes the band structure of the surface passivation layer.

[0063] In an optional implementation, the periodic gas pulse includes: inserting a pure H2 pulse for 8-12 seconds every 45-55°C increase in temperature, wherein the flow rate of the pure H2 pulse is 1-3 slm, triggering oxygen vacancy formation.

[0064] Optionally, the temperature rise stage of the pure H2 pulse can be 45℃, 46℃, 7℃, 48℃, 49℃, 50℃, 51℃, 52℃, 53℃, 54℃, 55℃, or any value between 45℃ and 55℃; the duration of the H2 pulse can be 8s, 9s, 10s, 11s, 12s, or any value between 8s and 12s; the flow rate of the H2 pulse can be 1 slm, 1.5 slm, 2 slm, 2.5 slm, 3 slm, or any value between 1slm and 3 slm.

[0065] During the heating phase of the annealing process, a 10-second pure hydrogen pulse is superimposed on the substrate gas every 50°C increase in temperature. In this process, hydrogen molecules dissociate into active hydrogen atoms at high temperatures, which then undergo a reduction reaction with oxygen in the alumina or silicon dioxide layer, generating oxygen vacancy defects. The formation of oxygen vacancies can regulate the stress distribution within the passivation layer and simultaneously provide diffusion channels for subsequent doping elements. By controlling the hydrogen pulse flow rate to 2 slm, sufficient reactant concentration is ensured while avoiding excessive hydrogen that could cause film expansion.

[0066] Through the above technical solution, this application effectively resolves the contradiction between hydrogen diffusion control and oxygen vacancy formation during annealing. Controllable oxygen vacancy generation enhances the charge collection capability of the passivation layer, while the pulsed gas supply mode suppresses film structure damage caused by excessive hydrogen permeation. This synergistic mechanism improves the interfacial bonding strength and enhances the optical properties of the passivation layer, providing a process guarantee for the fabrication of high-performance TOPCon batteries.

[0067] This application also provides an N-type TOPCon battery, the preparation method of which includes the aforementioned improved annealing method for film bursting.

[0068] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0069] Example 1 This embodiment provides an annealing method for improving film bursting, the specific steps of which are as follows: The silicon wafer was immersed in a texturing solution at 80°C with ultrasonic-assisted dispersion (pulse mode: 2s on / 1s off, duty cycle 50%) for 25 minutes. After removal, it was rinsed sequentially with deionized water (ultrapure water resistivity ≥18.2 MΩ·cm) and dried with nitrogen to obtain a textured surface Ra=150nm. The raw materials of the texturing solution included: 10wt% NaOH, 3wt% nano-sized SiC, 1wt% fatty alcohol polyoxyethylene ether, and the balance being water. The nano-sized SiC had a particle size of 50nm.

[0070] In a dual-zone tube furnace, a microtextured silicon wafer is placed in the first zone (temperature 600℃, oxygen partial pressure 1×10⁻⁶). -2 Torr), introduce a H2O / H2 mixed gas (molar ratio 2:1), hold for 20 min to form an Al2O3 layer with a thickness of 5 nm; switch to the second temperature zone (temperature 850℃, oxygen partial pressure 5×10). -3 Torr was used to initiate plasma-assisted oxidation (power 100W, frequency 13.56MHz) for 15 minutes to generate a dense Al2O3 / SiO2 stack with a total thickness of 8nm.

[0071] The three-stage annealing process consists of three stages: Stage 1: Heating rate of 3℃ / min from room temperature to 650℃, holding time 60s; Stage 2: Heating rate of 5℃ / min to 850℃, holding time 30s; Stage 3: Cooling rate of 2℃ / min to 200℃, holding time 20s; followed by natural cooling to room temperature. The annealing process is conducted under dynamic atmosphere control, with the base gas being a 5 vol% H2 and N2 mixture at a total flow rate of 10 slm. During the heating process, a 10s pure H2 pulse with a flow rate of 2 slm is inserted every 50℃ increase to trigger oxygen vacancy formation.

[0072] During the annealing process, the pressure was controlled at 0.1 MPa, and the concentration of surface hydroxyl groups in the oxide layer was monitored using online Raman spectroscopy. A concentration threshold of 3% for surface hydroxyl groups was set. When the concentration of surface hydroxyl groups in the oxide layer exceeded 3%, the AI ​​model triggered pressure fluctuations, with the pressure fluctuation frequency f = K·(OH) - K=5Hz / %; When the concentration of hydroxyl groups on the oxide layer surface is no more than 3%, the AI ​​model triggers pressure fluctuations with a frequency of 10Hz and an amplitude of 0.02MPa.

[0073] This embodiment also provides an N-type TOPCon battery, the preparation method of which includes an annealing method to improve the bursting film.

[0074] Example 2 This embodiment provides an annealing method for improving film bursting, the specific steps of which are as follows: The silicon wafer was immersed in a texturing solution at 80°C with ultrasonic-assisted dispersion (pulse mode: 2s on / 1s off, duty cycle 50%) for 25 minutes. After removal, it was rinsed sequentially with deionized water (ultrapure water resistivity ≥18.2 MΩ·cm) and dried with nitrogen to obtain a textured surface Ra=150nm. The raw materials of the texturing solution included: 10wt% NaOH 8wt%, nano-sized SiC 3wt%, fatty alcohol polyoxyethylene ether 1wt%, and the balance being water. The nano-sized SiC had a particle size of 50nm.

[0075] In a dual-zone tube furnace, a microtextured silicon wafer is placed in the first zone (temperature 600℃, oxygen partial pressure 1×10⁻⁶). -2 Torr), introduce a H2O / H2 mixed gas (molar ratio 2:1), hold for 18 min to form an Al2O3 layer with a thickness of 4 nm; switch to the second temperature zone (temperature 850℃, oxygen partial pressure 5×10). -3 Torr was used to initiate plasma-assisted oxidation (power 100W, frequency 13.56MHz) for 12 minutes to generate a dense Al2O3 / SiO2 stack with a total thickness of 6nm.

[0076] The three-stage annealing process consists of three stages: Stage 1: Heating rate of 3℃ / min from room temperature to 630℃, holding time 60s; Stage 2: Heating rate of 5℃ / min to 830℃, holding time 30s; Stage 3: Cooling rate of 2℃ / min to 180℃, holding time 15s; followed by natural cooling to room temperature. The annealing process is conducted under dynamic atmosphere control, with the base gas being a 5 vol% H2 and N2 mixture at a total flow rate of 10 slm. During the heating process, a 10s pure H2 pulse with a flow rate of 2 slm is inserted every 50℃ increase to trigger oxygen vacancy formation.

[0077] During the annealing process, the pressure was controlled at 0.09 MPa, and the concentration of surface hydroxyl groups in the oxide layer was monitored using online Raman spectroscopy. A concentration threshold of 2.5% for surface hydroxyl groups was set. When the concentration of surface hydroxyl groups in the oxide layer exceeded 3%, the AI ​​model triggered pressure fluctuations, with the pressure fluctuation frequency f = K·(OH) - K=4Hz / %; When the concentration of hydroxyl groups on the oxide layer surface is no more than 3%, the AI ​​model triggers pressure fluctuations with a pressure fluctuation frequency of 10Hz and a pressure fluctuation amplitude of 0.02MPa.

[0078] This embodiment also provides an N-type TOPCon battery, the preparation method of which includes an annealing method to improve the bursting film.

[0079] Example 3 This embodiment provides an annealing method for improving film bursting, the specific steps of which are as follows: The silicon wafer was immersed in a texturing solution at 80°C with ultrasonic-assisted dispersion (pulse mode: 2s on / 1s off, duty cycle 50%) for 25 minutes. After removal, it was rinsed sequentially with deionized water (ultrapure water resistivity ≥18.2 MΩ·cm) and dried with nitrogen to obtain a textured surface Ra=150nm. The raw materials of the texturing solution included: 10wt% NaOH, 12wt% nano-sized SiC, 3wt% fatty alcohol polyoxyethylene ether, and the balance being water. The nano-sized SiC had a particle size of 50nm.

[0080] In a dual-zone tube furnace, a microtextured silicon wafer is placed in the first zone (temperature 600℃, oxygen partial pressure 1×10⁻⁶). -2 Torr), introduce a H2O / H2 mixed gas (molar ratio 2:1), hold for 22 min to form an Al2O3 layer with a thickness of 6 nm; switch to the second temperature zone (temperature 850℃, oxygen partial pressure 5×10). -3 Torr was used to initiate plasma-assisted oxidation (power 100W, frequency 13.56MHz) for 18 minutes to generate a dense Al2O3 / SiO2 stack with a total thickness of 10nm.

[0081] The three-stage annealing process consists of three stages: Stage 1: Heating rate of 3℃ / min from room temperature to 670℃, holding time 60s; Stage 2: Heating rate of 5℃ / min to 870℃, holding time 30s; Stage 3: Cooling rate of 2℃ / min to 220℃, holding time 25s; followed by natural cooling to room temperature. The annealing process is conducted under dynamic atmosphere control, with the base gas being a 5 vol% H2 and N2 mixture at a total flow rate of 10 slm. During the heating process, a 10s pure H2 pulse with a flow rate of 2 slm is inserted every 50℃ increase to trigger oxygen vacancy formation.

[0082] During the annealing process, the pressure was controlled at 0.11 MPa, and the concentration of surface hydroxyl groups in the oxide layer was monitored using online Raman spectroscopy. A concentration threshold of 3.5% for surface hydroxyl groups was set. When the concentration of surface hydroxyl groups in the oxide layer exceeded 3%, the AI ​​model triggered pressure fluctuations, with the pressure fluctuation frequency f = K·(OH) - K=6Hz / %; When the concentration of hydroxyl groups on the oxide layer surface is no more than 3%, the AI ​​model triggers pressure fluctuations with a frequency of 10Hz and an amplitude of 0.02MPa.

[0083] This embodiment also provides an N-type TOPCon battery, the preparation method of which includes an annealing method to improve the bursting film.

[0084] Comparative Example 1 This comparative example provides a conventional annealing process, with the specific steps as follows: S1: Texturing pretreatment with 10wt% NaOH, 18wt% sodium dodecyl sulfate, and the balance being water, followed by washing at 60℃ for 200s.

[0085] S2: Under ALD reaction conditions, at 280°C for 25 cycles, a 2nm thick layer of alumina is generated with 10 sccm of TMA and 200 sccm of ozone.

[0086] S3: Reheat temperature 580℃, oxygen partial pressure 1×10⁻⁶ -2 Torr annealing under constant temperature and pressure.

[0087] This comparative example also provides an N-type TOPCon battery prepared using a conventional annealing process.

[0088] Comparative Example 2 This comparative example provides an annealing method to improve film bursting. Compared with Example 1, the only difference is the use of a conventional texturing solution. The specific steps are as follows: The silicon wafer was immersed in a conventional texturing solution at 80°C with ultrasonic-assisted dispersion (pulse mode: 2s on / 1s off, duty cycle 50%) for 25 minutes. After removal, it was rinsed with deionized water and dried with nitrogen to obtain a textured surface Ra=300nm. The solution, calculated based on a 100% total mass of raw materials, included 10wt% NaOH, 18wt% sodium dodecyl sulfate, and pure water.

[0089] In a dual-zone tube furnace, a microtextured silicon wafer is placed in the first zone (temperature 600℃, oxygen partial pressure 1×10⁻⁶). -2 Torr), introduce a H2O / H2 mixed gas (molar ratio 2:1), hold for 20 min to form an Al2O3 layer with a thickness of 5 nm; switch to the second temperature zone (temperature 850℃, oxygen partial pressure 5×10). -3 Torr was used to initiate plasma-assisted oxidation (power 100W, frequency 13.56MHz) for 15 minutes to generate a dense Al2O3 / SiO2 stack with a total thickness of 8nm.

[0090] The three-stage annealing process consists of three stages: Stage 1: Heating rate of 3℃ / min from room temperature to 650℃, holding time 60s; Stage 2: Heating rate of 5℃ / min to 850℃, holding time 30s; Stage 3: Cooling rate of 2℃ / min to 200℃, holding time 20s; followed by natural cooling to room temperature. The annealing process is conducted under dynamic atmosphere control, with the base gas being a 5 vol% H2 and N2 mixture at a total flow rate of 10 slm. During the heating process, a 10s pure H2 pulse with a flow rate of 2 slm is inserted every 50℃ increase to trigger oxygen vacancy formation.

[0091] During the annealing process, the pressure was controlled at 0.1 MPa, and the concentration of surface hydroxyl groups in the oxide layer was monitored using online Raman spectroscopy. A concentration threshold of 3% for surface hydroxyl groups was set. When the concentration of surface hydroxyl groups in the oxide layer exceeded 3%, the AI ​​model triggered pressure fluctuations, with the pressure fluctuation frequency f = K·(OH) - K=5Hz / %; When the concentration of hydroxyl groups on the oxide layer surface is no more than 3%, the AI ​​model triggers pressure fluctuations with a frequency of 10Hz and an amplitude of 0.02MPa.

[0092] This comparative example also provides an N-type TOPCon battery, the preparation method of which includes an annealing method to improve the bursting film.

[0093] Comparative Example 3 This embodiment provides an annealing method to improve film bursting. Compared with Embodiment 1, the only difference is that dynamic atmosphere control is not added. The specific steps are as follows: The silicon wafer was immersed in a texturing solution at 80°C with ultrasonic-assisted dispersion (pulse mode: 2s on / 1s off, duty cycle 50%) for 25 minutes. After removal, it was rinsed sequentially with deionized water (ultrapure water resistivity ≥18.2 MΩ·cm) and dried with nitrogen to obtain a textured surface Ra=150nm. The texturing solution, based on a 100% total mass of raw materials, included 10wt% NaOH, 3wt% nano-sized SiC, 1wt% fatty alcohol polyoxyethylene ether, and the balance being water. The nano-sized SiC had a particle size of 50nm.

[0094] In a dual-zone tube furnace, a microtextured silicon wafer is placed in the first zone (temperature 600℃, oxygen partial pressure 1×10⁻⁶). -2 Torr), introduce a H2O / H2 mixed gas (molar ratio 2:1), hold for 30 min to form an Al2O3 layer with a thickness of 5 nm; switch to the second temperature zone (temperature 850℃, oxygen partial pressure 5×10). -3Torr was used to initiate plasma-assisted oxidation (power 100W, frequency 13.56MHz) for 15 minutes to generate a dense Al2O3 / SiO2 stack with a total thickness of 8nm.

[0095] Three-stage annealing process: First stage, the heating rate is 3℃ / min to raise the temperature from room temperature to 650℃, and the holding time is 60s; Second stage, the heating rate is 5℃ / min to raise the temperature to 850℃, and the holding time is 30s; Third stage, the cooling rate is 2℃ / min to lower the temperature to 200℃, and the holding time is 20s; then, the temperature is allowed to cool naturally to room temperature.

[0096] During the annealing process, the pressure was controlled at 0.1 MPa, and the concentration of surface hydroxyl groups in the oxide layer was monitored using online Raman spectroscopy. A concentration threshold of 3% for surface hydroxyl groups was set. When the concentration of surface hydroxyl groups in the oxide layer exceeded 3%, the AI ​​model triggered pressure fluctuations, with the pressure fluctuation frequency f = K·(OH) - K=5Hz / %; When the concentration of hydroxyl groups on the oxide layer surface is no more than 3%, the AI ​​model triggers pressure fluctuations with a frequency of 10Hz and an amplitude of 0.02MPa.

[0097] This comparative example also provides an N-type TOPCon battery, the preparation method of which includes an annealing method to improve the bursting film.

[0098] Comparative Example 4 This comparative example provides an annealing method to improve film bursting. Compared with Example 1, the only difference is that the pressure is adjusted without detecting the concentration of the solvent. The specific steps are as follows: The silicon wafer was immersed in a texturing solution at 80°C with ultrasonic-assisted dispersion (pulse mode: 2s on / 1s off, duty cycle 50%) for 25 minutes. After removal, it was rinsed sequentially with deionized water (ultrapure water resistivity ≥18.2 MΩ·cm) and dried with nitrogen to obtain a textured surface Ra=150nm. The texturing solution, based on a 100% total mass of raw materials, included 10wt% NaOH, 3wt% nano-sized SiC, 1wt% fatty alcohol polyoxyethylene ether, and the balance being water. The nano-sized SiC had a particle size of 50nm.

[0099] In a dual-zone tube furnace, a microtextured silicon wafer is placed in the first zone (temperature 600℃, oxygen partial pressure 1×10⁻⁶). -2 Torr), introduce a H2O / H2 mixed gas (molar ratio 2:1), hold for 30 min to form an Al2O3 layer with a thickness of 5 nm; switch to the second temperature zone (temperature 850℃, oxygen partial pressure 5×10). -3Torr), initiate plasma-assisted oxidation (power 100W, frequency 13.56MHz), and generate a dense Al2O3 / SiO2 stack with a total thickness of 15nm for 15 minutes.

[0100] The three-stage annealing process consists of three stages: Stage 1: Heating rate of 3℃ / min from room temperature to 650℃, holding time 60s; Stage 2: Heating rate of 5℃ / min to 850℃, holding time 30s; Stage 3: Cooling rate of 2℃ / min to 200℃, holding time 20s; followed by natural cooling to room temperature. During annealing, the pressure is controlled at 0.1MPa, and the process is conducted under dynamic atmosphere control. The base gas is a 5 vol% H2 and N2 mixture with a total flow rate of 10 slm. Every 50℃ increase in temperature, a 10s pure H2 pulse with a flow rate of 2 slm is inserted to trigger oxygen vacancy formation.

[0101] This comparative example also provides an N-type TOPCon battery, the preparation method of which includes an annealing method to improve the bursting film.

[0102] SEM analysis was used to analyze the crack density. Sample preparation: The silicon substrate was cut into 10mm×10mm samples, mechanically polished with diamond paper (2000#), and then etched with hydrofluoric acid (HF:HNO3=1:3) for 5 minutes to remove the surface oxide layer.

[0103] SEM observation: Crack morphology was imaged using a field emission scanning electron microscope (FEI Quanta 450 FEG, accelerating voltage 15 kV, working distance 10 mm). Surface morphology images were acquired using secondary electron (SE) mode. Figure 1 This is a SEM image of the oxide layer of the N-type TOPCon battery provided in Example 1. Figure 2 The SEM image of the oxide layer of the N-type TOPCon cell provided in Comparative Example 1 is shown below. The SEM image of the oxide layer in Example 1 is shown below. Figure 1 As shown, no obvious cracks are visible; the SEM image of the oxide layer in Comparative Example 2 is shown below. Figure 2 As shown, obvious microcracks are visible.

[0104] The performance of the N-type TOPCon batteries prepared in the examples and comparative examples is shown in Table 1: Table 1. Performance of N-type TOPCon batteries prepared in the examples and comparative examples.

[0105] As shown in Table 1, Examples 1-3 achieved a film burst rate of less than 2.5% by suppressing hydrogen escape through dynamic atmosphere control and stress release through microtextured surfaces (NaOH+SiC system). Example 1 reduced the interface state density, and the microtextured surface increased the optical path, resulting in a quantum efficiency of 89%. In contrast, Comparative Example 1 only experienced an increase in recombination due to hydrogen escape in 78% of cases.

[0106] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0107] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, in the foregoing claims, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. An annealing method for improving film bursting, characterized in that, include: An oxide layer is applied to the surface of a silicon wafer that has undergone micro-texturing. Annealing is performed under dynamic atmosphere control; The dynamic atmosphere includes a base gas and periodic gas pulses; The hydrogen concentration is monitored in real time during the annealing process, and the pressure fluctuation frequency is dynamically adjusted.

2. The annealing method for improving film bursting according to claim 1, characterized in that, The microtexturing process includes: using a microtexturing solution and treating at 70-90°C for 20-60 minutes.

3. The annealing method for improving the bursting film according to claim 2, characterized in that, At least one of the following conditions must be met: a. Based on the total mass of the raw materials in the microtexturing solution as 100%, it includes: 10wt% NaOH 8-12%, nano-sized SiC 2-4%, surfactant 0.5-1.5%, and the balance being water; The surfactant includes fatty alcohol polyoxyethylene ether; The particle size of the nanoscale SiC is 20-100 nm; b. The textured surface Ra formed after the microtexturing process is 100-200nm.

4. The annealing method for improving film bursting according to claim 1, characterized in that, The oxide layer includes an Al2O3 layer and a SiO2 layer; The thickness of the Al2O3 layer is 4-6 nm; The thickness of the SiO2 layer is 2-4 nm.

5. The annealing method for improving film bursting according to claim 1, characterized in that, The pressure for dynamic atmosphere control is 0.09-0.11 MPa.

6. The annealing method for improving film bursting according to claim 1, characterized in that, The real-time monitoring of hydrogen concentration includes monitoring the concentration of surface hydroxyl groups in the oxide layer using online Raman spectroscopy; the concentration threshold of the surface hydroxyl groups is 2.5-3.5%, and at least one of the following conditions is met: c. When the concentration of hydroxyl groups on the surface of the oxide layer is greater than 3%, the AI ​​model triggers pressure fluctuations; where the pressure fluctuation frequency f = K·(OH) - K=4-6Hz / % d. When the concentration of hydroxyl groups on the surface of the oxide layer is not greater than 3%, the AI ​​model triggers pressure fluctuations with a frequency of 10 Hz and an amplitude of not greater than 0.02 MPa.

7. The annealing method for improving film bursting according to claim 1, characterized in that, The annealing is staged annealing, including: First stage: The heating rate is 2-4℃ / min to 630-670℃, and the holding time is 50-70s; Second stage: The heating rate is 6-7℃ / min to 830-870℃, and the holding time is 25-35s; The third stage: the cooling rate is 1-3℃ / min to 180-220℃, and the holding time is 15-25s; then it is allowed to cool naturally to room temperature.

8. The annealing method for improving film bursting according to claim 1, characterized in that, The base gas is a 5 vol% mixture of H2 and N2, with a total flow rate of 8-12 slm.

9. The annealing method for improving film bursting according to any one of claims 1-8, characterized in that, The periodic gas pulses include: inserting a pure H2 pulse for 8-12 seconds every 45-55°C increase in temperature, wherein the flow rate of the pure H2 pulse is 1-3 slm, triggering the formation of oxygen vacancies.

10. An N-type TOPCon battery, characterized in that, The preparation method includes the annealing method for improving the bursting film as described in any one of claims 1-9.

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