A topcon cell, a preparation method thereof and a photovoltaic system

Abstract

The application provides a TOPCon cell and a preparation method thereof and a photovoltaic system, and relates to the field of solar cells. The TOPCon cell comprises a P-type silicon-based substrate and an N+ layer. The surface of the P-type silicon-based substrate extends in a direction away from the P-type silicon-based substrate and comprises, in sequence from the P-type silicon-based substrate, an N+ emitter layer, a silicon oxide layer, a first aluminum oxide layer, and a second aluminum oxide layer. The first aluminum oxide layer comprises a boron-doped aluminum oxide layer, and the second aluminum oxide layer comprises a phosphorus-doped aluminum oxide layer. The TOPCon cell adopts a double-layer gradient-doped aluminum oxide structure. The first aluminum oxide layer close to the P-type silicon-based substrate is a nanocrystalline aluminum oxide doped with boron, the B-O bond is used to enhance the interface chemical passivation, and the density of silicon dangling bonds is reduced. The second aluminum oxide layer close to the N+ emitter layer is an amorphous aluminum oxide doped with phosphorus. The phosphorus doping concentration gradient decreases, the electric field distribution can be controlled by P doping, and the hole recombination is inhibited.

Description

Technical Field

[0001] This application relates to the field of solar cells, and more particularly to a TOPCon cell, its fabrication method, and a photovoltaic system. Background Technology

[0002] In the field of crystalline silicon solar cell technology, the tunneling oxide passivated contact (TOPCon) structure has attracted widespread attention due to its excellent prospects. Among them, the performance of the passivation layer is one of the core factors determining the key electrical parameters of TOPCon cells, such as open-circuit voltage (Voc) and fill factor (FF).

[0003] Currently, single-layer alumina (Al2O3) films are widely used as passivation layers, but significant technical bottlenecks still exist in practical applications: (1) The challenge of balancing charge density and interface state density: A single alumina layer cannot simultaneously achieve the optimal balance between high negative fixed charge density (to effectively suppress electron recombination at the interface) and low interface state density (to reduce carrier recombination loss), resulting in inherent performance limitations. (2) Stress concentration and structural failure risk: When the thickness of the alumina layer exceeds a certain threshold (usually >30 nm), significant lattice mismatch stress is easily generated inside the film. This stress concentration may not only cause cracks in the passivation layer itself, but also induce potential leakage channels, seriously threatening the long-term reliability and stability of the device. (3) Insufficient compatibility with large-area fabrication processes: The traditional atomic layer deposition (ALD) technique for preparing alumina layers typically has a low single-cycle deposition rate (<1 nm / cycle). This characteristic makes it extremely challenging to achieve uniform control of thickness and passivation quality on large-area silicon wafers, restricting the efficiency and yield of industrialization.

[0004] Therefore, given the shortcomings of existing single-layer alumina passivation layers in terms of charge regulation capability, mechanical stability, and process adaptability, and considering the lack of exploration of bilayer alumina gradient doping structures in existing optimization schemes, there is an urgent need in this field to develop a novel bilayer alumina passivation structure. This structure must possess excellent passivation performance (high negative charge density, low interface state density) to maximize battery efficiency, while also exhibiting good process controllability and adaptability for large-area fabrication, to meet the urgent needs of the industrialization of high-efficiency TOPCon batteries. Summary of the Invention

[0005] The purpose of this application is to provide a TOPCon cell, its preparation method, and a photovoltaic system to solve the above-mentioned problems.

[0006] To achieve the above objectives, this application adopts the following technical solution: This application provides a TOPCon cell, comprising: a P-type silicon substrate and an N+ layer; In the N+ layer, the surface of the P-type silicon substrate extending away from the P-type silicon substrate includes, in sequence: an N+ emitter layer, a silicon oxide layer, a first aluminum oxide layer, and a second aluminum oxide layer. The first alumina layer includes a boron-doped alumina layer; the second alumina layer includes a phosphorus-doped alumina layer.

[0007] Optionally, the thickness of the silicon oxide layer is 1.5-2.5 nm.

[0008] Optionally, the thickness of the first alumina layer is 5-8 nm.

[0009] Optionally, the thickness of the second alumina layer is 10-15 nm.

[0010] Optionally, the boron concentration gradient distribution in the first alumina layer is 1×10⁻⁶. 16 -5×10 17 cm -3 .

[0011] Optionally, the phosphorus concentration gradient distribution in the second alumina layer is 5 × 10⁻⁶. 17 -1×10 16 cm -3 .

[0012] This application also provides a method for preparing a TOPCon battery, comprising: In the N+ direction of the P-type silicon substrate, a first treatment is performed to prepare the N+ emitter layer; a second treatment is performed on the surface of the N+ emitter layer to prepare the silicon oxide layer; a third treatment is performed on the surface of the silicon oxide layer to prepare the first aluminum oxide layer; and a fourth treatment is performed on the surface of the first aluminum oxide layer to obtain the second aluminum oxide layer.

[0013] Optionally, the first process includes: preparing an N+ emitter layer silicon wafer by POCl3 diffusion and performing phosphorus doping, with a phosphorus oxychloride flow rate of 800-1200 sccm / min, an oxygen flow rate of 600-700 sccm / min, a pressure of 150-170 mbar, a time of 15-21 min, and a temperature of 785-805℃; then heating the silicon wafer to 880-890℃ and advancing it for 23-27 min, with the thickness of the phosphorus silicate glass on the surface being 20-30 nm.

[0014] Optionally, the second process includes: preparing a silicon oxide layer with a thickness of 15-2.5 nm by means of: an oxygen flow rate of 33-38 L / min, a pressure of 65000-75000 Pa, a time of 4-6 min, and a temperature of 600-610 °C.

[0015] Optionally, the third process includes: preparing a first alumina layer at a temperature of 190-290°C using a dual-precursor alternating pulse method; The pulse sequence is as follows: TMA 8-12ms, H2O 3-7ms, B2H6 3-7ms, N2 10-30ms; the number of cycles is 18-22; the flow rate of TMA is 5-15 sccm, the flow rate of H2O is 1000-3000 sccm, and the flow rate of B2H6 is 0.5-2 sccm.

[0016] Optionally, the fourth process includes: preparing a second alumina layer at a temperature of 190-290°C using alternating pulses of dual precursors and plasma-assisted treatment; The pulse sequence is as follows: TMA 8-12ms, H2O 3-7ms, PH3 3-7ms, N2 10-30ms; the number of cycles is 38-42; the flow rate of TMA is 10-20 sccm, the flow rate of H2O is 1500-3500 sccm, the flow rate of PH3 is 1-3 sccm; and the plasma power is 50-200W.

[0017] Optionally, the preparation method further includes annealing activation, which includes rapid thermal annealing and hydrogen-assisted annealing performed sequentially.

[0018] Optionally, the conditions for rapid thermal annealing are: a temperature of 400-440℃, a mixed gas with a volume ratio of N2:H2 of 8.2-9:1, a flow rate of 222-555 sccm, and a time of 2-4 min. Optionally, the hydrogen-assisted annealing conditions are: a temperature of 630-670℃ and a time of 4-6 minutes; The gas atmosphere for hydrogen-assisted annealing, calculated with its total volume as 100%, includes 80-90% N2 and 10-20% H2.

[0019] This application also provides a photovoltaic system including the TOPCon battery.

[0020] Compared with the prior art, the beneficial effects of this application include: The TOPCon cell provided in this application employs a dual-layer gradient-doped alumina structure. The first alumina layer, near the p-type silicon substrate, is boron-doped nanocrystalline alumina with an increasing boron doping concentration gradient. This enhances interfacial chemical passivation through BO bonds and reduces silicon dangling bond density. The second alumina layer, near the N+ emitter layer, is phosphorus-doped amorphous alumina with a decreasing phosphorus doping concentration gradient. This allows for the regulation of the electric field distribution using p-doping, suppressing hole recombination. A synergistic passivation mechanism is also employed: on one hand, the boron-doped layer repairs silicon surface defects, while the phosphorus-doped layer passivates the polycrystalline silicon / alumina interface; on the other hand, the charge densities of the two layers are superimposed (total charge density > 1 × 10⁻⁶). 14 cm -2 This forms a double barrier structure, enhancing the selective transport of charge carriers.

[0021] The preparation method provided in this application employs alternating pulse deposition of dual precursors to prepare a high-quality alumina passivation layer. On the one hand, it enables sub-nanometer precision film thickness control, and the self-limiting surface reaction characteristics ensure that the film maintains a thickness deviation of <1% on complex three-dimensional structures and large-size silicon wafers (>210 mm), meeting the stringent requirements of high-efficiency batteries for passivation layer consistency. On the other hand, the layer-by-layer growth mechanism forms a pore-free, dense Al2O3 film, effectively blocking metal ion diffusion and enabling the formation of a steep Al2O3 / Si interface on the silicon surface, significantly reducing the interface state density (down to <10). 11 eV -1 cm -2 Furthermore, by precisely controlling the alumina stoichiometry (Al / O), Al2O3 deposited by ALD can generate a high-density negative fixed charge (>10). 12 cm -2 This induces a strong passivation effect on the silicon surface, significantly increasing the open-circuit voltage (Voc). Attached Figure Description

[0022] 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.

[0023] Figure 1 A schematic diagram of the TOPCon battery prepared for an example; Figure 2 The TOPCon battery prepared for this example.

[0024] The main labeling information is as follows: 1-P-type silicon substrate; 2-N+ emitter layer; 3-silicon oxide layer; 4-first aluminum oxide layer; 5-second aluminum oxide layer. Detailed Implementation

[0025] 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.

[0026] 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.

[0027] 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.

[0028] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0029] "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.

[0030] "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).

[0031] To better explain the technical solution provided in this application, the technical solution will be described in its entirety before proceeding with specific implementation methods.

[0032] The purpose of this application is to provide a TOPCon cell, its preparation method, and a photovoltaic system, which have the advantages of optimizing the charge regulation capability of the passivation layer, improving mechanical stability, and enhancing process adaptability.

[0033] In a first aspect, this application provides a TOPCon cell, comprising: a P-type silicon substrate and an N+ layer; In the N+ layer, the surface of the P-type silicon substrate extending away from the P-type silicon substrate includes, in sequence: an N+ emitter layer, a silicon oxide layer, a first aluminum oxide layer, and a second aluminum oxide layer. The first alumina layer includes a boron-doped alumina layer; the second alumina layer includes a phosphorus-doped alumina layer.

[0034] In this battery, a P-type silicon substrate serves as the core material, forming the basic structure of a PN junction through doping. The N+ emitter layer, formed through phosphorus diffusion, establishes the potential field required for carrier separation. The silicon oxide layer acts as a tunneling dielectric layer, allowing selective carrier transport. A boron-doped alumina layer, by introducing boron, modulates the charge characteristics of alumina, creating a high-density negative charge at the interface. A phosphorus-doped alumina layer, through phosphorus doping, alters the band structure of alumina, reducing the interface state density. The layered structure achieves charge complementarity through the gradient distribution of different dopants, while simultaneously mitigating internal stress by utilizing differences in material thermal expansion. Specifically, the N+ emitter layer constructed on the surface of the P-type silicon substrate forms a PN junction to generate photogenerated carriers. The silicon oxide layer, acting as a tunneling layer, allows electron tunneling while blocking hole recombination. The boron-doped alumina layer, located near the silicon interface, effectively repels minority carriers due to its high negative charge density, suppressing interface recombination. The outer phosphorus-doped alumina layer, through N-type doping, modulates the interface band bending, reducing the surface state density. The gradient doping of two layers of alumina creates a continuous transition in charge distribution, avoiding recombination losses caused by abrupt charge changes at the interface. The layered deposition process allows for independent control of the thickness of each layer, and the passivation performance and stress distribution can be optimized by adjusting deposition parameters.

[0035] Traditional single-layer alumina passivation layers suffer from a trade-off between charge density and interface state density. This solution, however, achieves synergistic optimization of both through a bilayer gradient doping structure. The stress concentration problem in existing single-layer alumina layers is effectively mitigated in this solution by addressing the difference in thermal expansion coefficients between the different doped layers. Stepwise deposition, compared to continuous single-layer deposition, is more advantageous for controlling the thickness and doping concentration of each layer, thus improving the uniformity of large-area fabrication.

[0036] Through the above technical solutions, this application effectively balances the charge density and interface state density of the passivation layer, suppressing carrier recombination losses. The layered structure design reduces internal stress in the thin film, avoiding leakage problems caused by crack formation. The stepwise deposition process provides feasibility for independent control of each functional layer, enhances process adaptability, and meets the mass production requirements of high-efficiency batteries.

[0037] In one alternative embodiment, the thickness of the silicon oxide layer is 1.5-2.5 nm.

[0038] Optionally, the thickness of the silicon oxide layer can be 1.5 nm, 1.6 nm, 1.7 nm, 1.8 nm, 1.9 nm, 2 nm, 2.1 nm, 2.2 nm, 2.3 nm, 2.4 nm, 2.5 nm, or any value between 1.5 and 2.5 nm.

[0039] In one alternative embodiment, the thickness of the first alumina layer is 5-8 nm.

[0040] Optionally, the thickness of the first alumina layer can be 5nm, 5.5nm, 6nm, 6.5nm, 7nm, 7.5nm, 8nm, or any value between 5 and 8nm.

[0041] In one optional embodiment, the thickness of the second alumina layer is 10-15 nm.

[0042] Optionally, the thickness of the second alumina layer can be 10nm, 10.5nm, 11nm, 11.5nm, 12nm, 12.5nm, 13nm, 13.5nm, 14nm, 14.5nm, 15nm, or any value between 10-15nm.

[0043] The silicon oxide layer refers to the tunneling oxide layer deposited on the surface of the silicon substrate, and its thickness control directly affects the carrier tunneling efficiency and surface passivation effect. The first alumina layer is a boron-doped alumina layer, and its thickness is limited to alleviate lattice mismatch stress. The second alumina layer is a phosphorus-doped alumina layer, which can be prepared by plasma-assisted atomic layer deposition combined with phosphorus source pulses. Its upper limit thickness control avoids stress accumulation caused by excessive overall structure thickness.

[0044] Specifically, by controlling the thickness of the silicon oxide layer within a specific range, the interfacial recombination rate is reduced while ensuring effective carrier tunneling. The first alumina layer has a thickness of 5-8 nanometers. While maintaining a high negative charge density, the reduced single-layer thickness alleviates lattice mismatch stress and prevents crack formation. The second alumina layer has a thickness of 10-15 nanometers. While maintaining passivation performance, the layered thickness design ensures that the total thickness does not exceed the critical stress threshold. This gradient thickness distribution matches the cycle number control requirements of the atomic layer deposition process, improving the uniformity of large-area fabrication by reducing the difference in the number of deposition cycles per cycle.

[0045] Traditional single-layer alumina passivation layers are prone to stress concentration when their thickness exceeds 30 nanometers, leading to decreased mechanical stability. Layered structures, by decomposing the total thickness into two gradient layers, disperse stress concentration areas through differentiated thickness distribution while maintaining a constant total thickness. Existing single-layer alumina technologies struggle to balance charge density and interface state density in their doping concentration distribution, while bilayer structures achieve directional distribution of dopants by confining boron and phosphorus doping to separate layers. Through the above technical solutions, this application effectively balances the contradiction between high negative charge density and low interface state density. Gradient thickness design disperses lattice mismatch stress, preventing passivation layer structural failure. The layer thickness range matches the cycle number control characteristics of atomic layer deposition, improving the thickness uniformity of large-area fabrication. Boron and phosphorus doped layers achieve elemental concentration gradient distribution within their respective thickness ranges, optimizing the charge control capability of the passivation layer.

[0046] In an optional embodiment, the boron concentration gradient distribution in the first alumina layer is 1×10⁻⁶. 16 -5×10 17 cm -3 .

[0047] In an optional embodiment, the phosphorus concentration gradient distribution in the second alumina layer is 5 × 10⁻⁶. 17 -1×10 16 cm -3 .

[0048] The boron concentration gradient distribution refers to a gradual decrease in boron doping concentration within the alumina layer, achieved by adjusting the combination of boron source pulse count and deposition temperature. This gradient distribution allows for high doping concentration near the interface to enhance the negative fixed charge density, while the concentration gradually decreases away from the interface to alleviate lattice stress. The phosphorus concentration gradient distribution refers to a gradual increase in phosphorus doping concentration within the alumina layer, achieved by adjusting the phosphorus source injection rate and plasma treatment time. This gradient distribution enhances field-effect passivation through high surface doping concentration, while low-concentration doping at the bottom layer prevents bandgap with the silicon oxide layer.

[0049] Specifically, the boron-doped layer generates a strong electric field effect through high-concentration doping in the near-interface region, effectively suppressing electron recombination, while the decreasing concentration distribution towards the surface reduces lattice distortion. The phosphorus-doped layer generates an additional electric field through high-concentration doping at the surface, enhancing the attraction of charge carriers, while the low-concentration doping at the bottom maintains bandgap matching with the silicon oxide layer. The synergistic effect of these two gradient distributions allows the passivation layer to maintain high charge density while reducing interface state density, and to release internal stress in the film through the concentration gradient.

[0050] Through the above technical solution, this application achieves an optimized balance between the charge density of the passivation layer and the interface state density, effectively reducing the recombination loss of charge carriers at the interface, while avoiding the risk of mechanical failure caused by thin film stress concentration, and improving the long-term stability of the passivation structure.

[0051] Secondly, this application also provides a method for preparing a TOPCon battery, the method comprising: In the N+ direction of the P-type silicon substrate, a first treatment is performed to prepare the N+ emitter layer; a second treatment is performed on the surface of the N+ emitter layer to prepare the silicon oxide layer; a third treatment is performed on the surface of the silicon oxide layer to prepare the first aluminum oxide layer; and a fourth treatment is performed on the surface of the first aluminum oxide layer to obtain the second aluminum oxide layer.

[0052] The first treatment involves forming a heavily doped region on the silicon substrate surface through phosphorus diffusion, specifically using a POCl3 diffusion process. The N+ emitter layer formed in this step provides a carrier transport interface for the subsequent passivation layer. The second treatment involves generating an ultrathin dielectric layer on the N+ emitter layer surface through oxidation, specifically using a conventional thermal oxidation method. This silicon oxide layer acts as a tunneling layer, reducing interfacial recombination losses. The third treatment involves constructing a boron-doped alumina layer on the silicon oxide layer surface through atomic layer deposition, specifically using an alternating pulsed dual-precursor method. The introduction of boron enhances the surface field effect. The fourth treatment involves constructing a phosphorus-doped alumina layer on the first alumina layer surface through plasma-assisted deposition, specifically using alternating deposition of phosphorus-containing and alumina precursors. The gradient distribution of phosphorus helps alleviate film stress. A stepwise deposition process was used to construct a gradient-doped bilayer alumina structure, resolving the conflict between interfacial passivation and mechanical stability while improving process controllability. The N+ emitter layer formed in the first treatment provides a matching carrier transport interface for the subsequent passivation layer; the silicon oxide layer generated in the second treatment acts as a tunneling layer, effectively reducing interfacial recombination losses; the boron-doped alumina layer prepared in the third treatment utilizes the negative charge of boron to enhance the surface field effect; and the phosphorus-doped alumina layer prepared in the fourth treatment achieves stress buffering with the underlying material through the gradient distribution of phosphorus. This approach avoids lattice mismatch caused by excessive single-layer thickness and achieves an optimized balance between charge density and interfacial state density through the synergistic effect of the two layers.

[0053] In an optional embodiment, the first process includes: preparing an N+ emitter layer silicon wafer by POCl3 diffusion and performing phosphorus doping, with a phosphorus oxychloride flow rate of 800-1200 sccm / min, an oxygen flow rate of 600-700 sccm / min, a pressure of 150-170 mbar, a time of 15-21 min, and a temperature of 785-805℃; then heating the silicon wafer to 880-890℃ and advancing it for 23-27 min, with the thickness of the phosphorus-silicon glass on the surface being 20-30 nm.

[0054] Optionally, the thickness of the surface phosphosilicate glass can be 20nm, 21nm, 22nm, 23nm, 24nm, 25nm, 26nm, 27nm, 28nm, 29nm, 30nm, or any value between 20nm and 30nm.

[0055] During the POCl3 diffusion process, by precisely controlling the reaction temperature and gas partial pressure, a high-concentration doped layer of phosphorus atoms is formed on the silicon substrate surface, while simultaneously generating a 20-30 nm thick phosphosilicate glass layer. This thickness range is set to provide sufficient phosphorus source to ensure that the doping concentration of the N+ emitter layer reaches the threshold requirement, while avoiding excessively thick phosphosilicate glass that could cause interface stress accumulation or impurity residue during subsequent silicon oxide layer deposition. When the phosphosilicate glass thickness is less than 20 nm, insufficient phosphorus source supply may occur, reducing doping efficiency; when the thickness exceeds 30 nm, physical defects will form at the interface, increasing the difficulty of subsequent cleaning processes. By limiting the thickness of the phosphosilicate glass layer within this range, a smooth and low-defect substrate interface can be provided for the deposition of the silicon oxide and aluminum oxide layers after the N+ emitter layer is prepared.

[0056] In an optional embodiment, the second process includes: preparing a silicon oxide layer with a thickness of 15-2.5 nm at an oxygen flow rate of 33-38 L / min, a pressure of 65000-75000 Pa, a time of 4-6 min, and a temperature of 600-610 °C.

[0057] Optionally, the oxygen flow rate can be 33 L / min, 34 L / min, 35 L / min, 36 L / min, 7 L / min, 38 L / min, or any value between 33 and 38 L / min; the pressure can be 65000 Pa, 66000 Pa, 67000 Pa, 68000 Pa, 69000 Pa, 70000 Pa, 71000 Pa, 72000 Pa, 73000 Pa, 74000 Pa, 75000 Pa, or any value between 65000 and 75000 Pa; the second treatment time can be 4 min, 4.5 min, 5 min, 5.5 min, 6 min, or 4-6 min. Any value between min; the reaction temperature can be 600℃, 601℃, 602℃, 603℃, 604℃, 605℃, 606℃, 607℃, 608℃, 609℃, 610℃, or any value between 600℃ and 610℃.

[0058] In an optional embodiment, the third process includes: preparing a first alumina layer at a temperature of 190-290°C using a dual-precursor alternating pulse method; The pulse sequence is as follows: TMA 8-12ms, H2O 3-7ms, B2H6 3-7ms, N2 10-30ms; the number of cycles is 18-22; the flow rate of TMA is 5-15 sccm, the flow rate of H2O is 1000-3000 sccm, and the flow rate of B2H6 is 0.5-2 sccm.

[0059] The dual-precursor alternating pulse method refers to the layer-by-layer deposition of alumina by alternately introducing trimethylaluminum and water as precursors. This can be achieved by precisely controlling the gas flow using a timing control module in the atomic layer deposition equipment, and by periodically switching precursors to achieve atomic-level thickness control. The diborane pulse method involves simultaneously introducing diborane gas during alumina deposition. This can be achieved by adjusting the dopant gas concentration using a mass flow meter, introducing boron in situ during each alumina layer growth to form a gradient doped structure. The nitrogen purging step involves introducing nitrogen after each precursor pulse to remove reaction byproducts. This can be achieved using high-purity nitrogen in conjunction with a vacuum pump system to ensure the purity of each reaction step. The cycle count is controlled to 20, which means precisely controlling the total film thickness by setting the number of deposition cycles. This can be achieved automatically using a cycle counter in the deposition equipment, ensuring film uniformity while avoiding stress accumulation due to excessive thickness.

[0060] Trimethylaluminum reacts with water at a set temperature to form an alumina monolayer. During each deposition cycle, diborane decomposes and releases boron atoms into the alumina lattice. By precisely controlling the pulse timing and gas flow rate of trimethylaluminum, water, and diborane, a boron concentration gradient gradually decreasing from the bottom to the surface is formed within the alumina layer. A nitrogen purging step effectively removes unreacted precursors and byproducts, ensuring precise control of the stoichiometry for each deposition layer. The 20-cycle setting maintains the total film thickness at the nanometer level, meeting the charge density requirements of the passivation layer while avoiding the lattice mismatch problem inherent in traditional thick films. This method achieves a gradient distribution of boron doping concentration within the alumina layer, effectively balancing the conflicting requirements of high negative charge density and low interface state density. Precise control of the film thickness avoids the mechanical stress generated by traditional thick film deposition, improving the structural stability of the passivation layer. The synergistic control of pulse timing and gas flow rate gives this process excellent large-area uniformity, meeting the stringent repeatability requirements of industrial production.

[0061] In an optional embodiment, the fourth process includes: preparing a second alumina layer at a temperature of 190-290°C using alternating pulses of dual precursors and plasma-assisted treatment; The pulse sequence is as follows: TMA 8-12ms, H2O 3-7ms, PH3 3-7ms, N2 10-30ms; the number of cycles is 38-42; the flow rate of TMA is 10-20 sccm, the flow rate of H2O is 1500-3500 sccm, the flow rate of PH3 is 1-3 sccm; and the plasma power is 50-200W.

[0062] The dual-precursor alternating pulse method refers to constructing the alumina matrix framework through the alternating introduction of trimethylaluminum and water vapor, while simultaneously introducing phosphine pulses for in-situ doping. Specifically, a time-divided pulse sequence can be used to control the precursor contact order, avoiding particulate contamination from gas-phase side reactions. Plasma-assisted treatment involves generating active particles by exciting the reactive gas with radio frequency energy. Specifically, plasma with a power range of 50-200 watts can be used to bombard the deposition surface, promoting chemical bond recombination and eliminating unsaturated dangling bonds. Pulse timing control involves setting a nitrogen purging step after each precursor pulse to maintain the cleanliness of the thin film deposition process. Setting the number of cycles to 40 means controlling the total film thickness through the product of the number of cycles and the thickness of a single deposition. Specifically, the thickness of the second alumina layer can be adjusted to reach the target range by regulating the number of cycles.

[0063] Alternating pulses of trimethylaluminum and water vapor deposit alumina lattice layer by layer on the substrate surface, while phosphine pulses simultaneously introduce phosphorus dopant atoms during alumina formation. A nitrogen purging step effectively removes unreacted residual precursors, preventing film porosity caused by gas-phase nucleation. Plasma energy applied to the deposition surface allows phosphorus atoms to integrate more fully into the alumina lattice, while eliminating structural defects at grain boundaries. The matching relationship between the number of cycles and the deposition rate ensures precise controllability of the film thickness; 40 cycles correspond to a thickness range of 10-15 nanometers. This process combination results in a gradient distribution of phosphorus concentration from the surface inwards, while plasma energy alleviates internal stress in the film. This method achieves high-quality deposition of phosphorus-doped alumina layers, significantly improving film density and doping uniformity. Plasma energy effectively reduces interface state density, and the gradient doping structure enhances carrier transport efficiency. Controllable process parameters ensure consistent film thickness over large areas, while pulse timing design suppresses impurity aggregation and optimizes film stress distribution. This preparation method ensures the simultaneous improvement of the electrical properties and mechanical stability of the passivation layer while maintaining a high deposition rate.

[0064] In an optional embodiment, the preparation method further includes annealing activation, which comprises sequential rapid thermal annealing and hydrogen-assisted annealing.

[0065] In one optional embodiment, the temperature is 400-440°C, and a mixed gas with a volume ratio of N2:H2 of 8.2-9:1 is introduced, the flow rate of the mixed gas is 222-555 sccm, and the time is 2-4 min.

[0066] In one optional embodiment, the hydrogen-assisted annealing conditions are: a temperature of 630-670°C and a time of 4-6 minutes.

[0067] The gas atmosphere for hydrogen-assisted annealing, calculated with its total volume as 100%, includes 80-90% N2 and 10-20% H2.

[0068] The two-stage annealing process optimizes the passivation layer performance by first applying a low-temperature, then a high-temperature annealing. The rapid thermal annealing stage is performed at 420°C. The nitrogen-dominated mixed gas environment suppresses lattice distortion in the alumina layer during heating, while a small amount of hydrogen is incorporated to facilitate the initial activation of boron and phosphorus dopants in the alumina lattice and provide a structural buffer for subsequent high-temperature processing. The hydrogen-assisted annealing stage raises the temperature to 650°C. Maintaining the nitrogen-hydrogen mixed gas environment, the high temperature promotes deep diffusion of dopants and lattice reconstruction. Simultaneously, hydrogen reduces the interface state density by passing off dangling bonds at the passivation interface. This two-stage annealing sequence, with its logic of first stabilizing the structure at low temperature and then deeply activating it at high temperature, avoids the risk of stress cracking in the alumina layer caused by a single high-temperature treatment while ensuring precise control of the doping gradient distribution.

[0069] This application also provides a photovoltaic system including the TOPCon battery.

[0070] 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.

[0071] Example 1 This embodiment provides a TOPCon battery: like Figure 1 As shown, the surface of the P-type silicon substrate 1 extending away from the P-type silicon substrate includes the following sequentially arranged components: N+ emitter layer 2: 25nm; Silicon oxide layer 3: 2nm; The first alumina layer is 4:5 nm thick, with a boron concentration gradient distribution of 1×10⁻⁵ nm. 16 -5×10 17 cm -3 ; The second alumina layer is 5:10 nm thick, with a phosphorus concentration gradient distribution of 5 × 10⁻⁶. 17 -1×10 16 cm -3 ; This embodiment also provides a method for preparing a TOPCon battery, the specific steps of which are as follows: The N-type crystalline silicon substrate is cleaned, the damaged layer is removed, and texturing is performed to form a random pyramid structure on the silicon wafer surface.

[0072] A nano-sized RS-ALD system was used for ALD equipment at a temperature of 240℃, with a mixed gas of trimethylaluminum and boron source (B2H6) introduced; the pulse sequence was: TMA 10ms, H2O 5ms, B2H6 5ms, N2 20ms; the number of cycles was 20; the flow rate of TMA was 10 sccm, the flow rate of H2O was 2000 sccm, and the flow rate of B2H6 was 1.25 sccm.

[0073] At 240℃, the phosphorus source was switched to PH3, with the following pulse sequence: TMA 10ms, H2O 5ms, PH3 5ms, N2 20ms; the number of cycles was 40; the flow rate of TMA was 15 sccm, the flow rate of H2O was 2500 sccm, and the flow rate of PH3 was 2 sccm; the plasma power was 100W. Plasma-assisted enhancement of PO bond formation reduced the interfacial state density.

[0074] Rapid thermal annealing and hydrogen-assisted annealing were performed sequentially: a N2 / H2 mixed gas (volume ratio 9:1) was introduced at 420℃ for 3 minutes to activate B / P doping and repair lattice defects; then, annealing was carried out at 650℃ for 5 minutes in an H2 / N2 atmosphere (H2 content 10%) to improve the density of the passivation layer.

[0075] Subsequently, following conventional methods, laser grooving is performed to form selective emitter contacts, metal electrodes are screen-printed, and co-sintering is completed to obtain a TOPCon cell, such as... Figure 2 As shown.

[0076] Example 2 This embodiment provides a TOPCon battery: The surface of the P-type silicon substrate 1 extends away from the P-type silicon substrate and includes the following sequentially arranged components: N+ emitter layer 2: 20nm; Silicon oxide layer 3: 1.5nm; The first alumina layer is 4:5 nm thick, with a boron concentration gradient distribution of 1×10⁻⁵ nm. 16 -5×10 17 cm -3 ; The second alumina layer is 5:10 nm thick, with a phosphorus concentration gradient distribution of 5 × 10⁻⁶. 17 -1×10 16 cm -3 ; This embodiment also provides a method for preparing a TOPCon battery, the specific steps of which are as follows: The N-type crystalline silicon substrate is cleaned, the damaged layer is removed, and texturing is performed to form a random pyramid structure on the silicon wafer surface.

[0077] A nano-sized RS-ALD system was used for ALD equipment at a temperature of 190℃, with a mixture of trimethylaluminum and boron source (B2H6) gas introduced; the pulse sequence was: TMA 10ms, H2O 5ms, B2H6 5ms, N2 20ms; the number of cycles was 20; the flow rate of TMA was 5 sccm, the flow rate of H2O was 1000 sccm, and the flow rate of B2H6 was 0.5 sccm.

[0078] At 190℃, the phosphorus source was switched to PH3, with the following pulse sequence: TMA 10ms, H2O 5ms, PH3 5ms, N2 20ms; the number of cycles was 40; the flow rate of TMA was 10 sccm, the flow rate of H2O was 1500 sccm, and the flow rate of PH3 was 1 sccm; the plasma power was 100W. Plasma-assisted enhancement of PO bond formation reduced the interfacial state density.

[0079] Rapid thermal annealing and hydrogen-assisted annealing were performed sequentially: a N2 / H2 mixed gas (volume ratio 9:1) was introduced at 420℃ for 3 minutes to activate B / P doping and repair lattice defects; then, annealing was carried out at 650℃ for 5 minutes in an H2 / N2 atmosphere (H2 content 10%) to improve the density of the passivation layer.

[0080] Subsequently, following conventional methods, laser grooving was performed to form selective emitter contacts, metal electrodes were screen-printed, and co-sintering was completed to obtain TOPCon cells.

[0081] Example 3 This embodiment provides a TOPCon battery: The surface of the P-type silicon substrate 1 extends away from the P-type silicon substrate and includes the following sequentially arranged components: N+ emitter layer 2: 30nm; Silicon oxide layer 3: 2.5nm; The first alumina layer is 4:5 nm thick, with a boron concentration gradient distribution of 1×10⁻⁵ nm. 16 -5×10 17 cm -3 ; The second alumina layer is 5:10 nm thick, with a phosphorus concentration gradient distribution of 5 × 10⁻⁶. 17 -1×10 16 cm -3 ; This embodiment also provides a method for preparing a TOPCon battery, the specific steps of which are as follows: The N-type crystalline silicon substrate is cleaned, the damaged layer is removed, and texturing is performed to form a random pyramid structure on the silicon wafer surface.

[0082] The RS-ALD system-type ALD device was used with a temperature of 290℃ and a mixed gas of trimethylaluminum and boron source (B2H6) was introduced. The pulse sequence was: TMA 10ms, H2O 5ms, B2H6 5ms, N2 20ms; the number of cycles was 20; the flow rate of TMA was 15 sccm, the flow rate of H2O was 3000 sccm, and the flow rate of B2H6 was 2 sccm.

[0083] At 290℃, the phosphorus source was switched to PH3, with the following pulse sequence: TMA 10ms, H2O 5ms, PH3 5ms, N2 20ms; the number of cycles was 40; the flow rate of TMA was 20 sccm, the flow rate of H2O was 3500 sccm, and the flow rate of PH3 was 3 sccm; the plasma power was 100W. Plasma-assisted enhancement of PO bond formation reduced the interfacial state density.

[0084] Rapid thermal annealing and hydrogen-assisted annealing were performed sequentially: a N2 / H2 mixed gas (volume ratio 9:1) was introduced at 420℃ for 3 minutes to activate B / P doping and repair lattice defects; then, annealing was carried out at 650℃ for 5 minutes in an H2 / N2 atmosphere (H2 content 10%) to improve the density of the passivation layer.

[0085] Subsequently, following conventional methods, laser grooving was performed to form selective emitter contacts, metal electrodes were screen-printed, and co-sintering was completed to obtain TOPCon cells.

[0086] Comparative Example 1 This comparative example provides a TOPCom battery: The surface of the P-type silicon substrate extending away from the P-type silicon substrate includes the following sequentially arranged elements: N+ emitter layer: 25nm; Silicon oxide layer: 2nm; Alumina layer: 5.5nm; This comparative example also provides a method for preparing a TOPCon battery, the specific steps of which are as follows: The N-type crystalline silicon substrate is cleaned, the damaged layer is removed, and texturing is performed to form a random pyramid structure on the silicon wafer surface.

[0087] An alumina layer was deposited using an unconventional ALD method.

[0088] Rapid thermal annealing and hydrogen-assisted annealing were performed sequentially: a N2 / H2 mixed gas (volume ratio 9:1) was introduced at 420℃ for 3 minutes to activate B / P doping and repair lattice defects; then, annealing was carried out at 650℃ for 5 minutes in an H2 / N2 atmosphere (H2 content 10%) to improve the density of the passivation layer.

[0089] Subsequently, following conventional methods, laser grooving was performed to form selective emitter contacts, metal electrodes were screen-printed, and co-sintering was completed to obtain TOPCon cells.

[0090] Comparative Example 2 This comparative example provides a TOPCon battery: The surface of the P-type silicon substrate extending away from the P-type silicon substrate includes the following sequentially arranged elements: N+ emitter layer: 25nm; Silicon oxide layer: 2nm; First alumina layer: 5nm, boron concentration gradient distribution is 1×10⁻⁶ 16 -5×10 17 cm -3 ; This comparative example also provides a method for preparing a TOPCon battery, the specific steps of which are as follows: The N-type crystalline silicon substrate is cleaned, the damaged layer is removed, and texturing is performed to form a random pyramid structure on the silicon wafer surface.

[0091] A nano-sized RS-ALD system was used for ALD equipment at a temperature of 240℃, with a mixed gas of trimethylaluminum and boron source (B2H6) introduced; the pulse sequence was: TMA 10ms, H2O 5ms, B2H6 5ms, N2 20ms; the number of cycles was 20; the flow rate of TMA was 10 sccm, the flow rate of H2O was 2000 sccm, and the flow rate of B2H6 was 1.25 sccm.

[0092] Rapid thermal annealing and hydrogen-assisted annealing were performed sequentially: a N2 / H2 mixed gas (volume ratio 9:1) was introduced at 420℃ for 3 minutes to activate B / P doping and repair lattice defects; then, annealing was carried out at 650℃ for 5 minutes in an H2 / N2 atmosphere (H2 content 10%) to improve the density of the passivation layer.

[0093] Subsequently, following conventional methods, laser grooving was performed to form selective emitter contacts, metal electrodes were screen-printed, and co-sintering was completed to obtain TOPCon cells.

[0094] Comparative Example 3 This comparative example provides a TOPCon battery. The surface of the P-type silicon substrate extending away from the P-type silicon substrate includes the following sequentially arranged elements: N+ emitter layer: 25nm; Silicon oxide layer: 2nm; Second alumina layer: 10 nm, phosphorus concentration gradient distribution is 5 × 10⁻⁶ 17 -1×10 16 cm -3 ; This comparative example also provides a method for preparing a TOPCon battery, the specific steps of which are as follows: The N-type crystalline silicon substrate is cleaned, the damaged layer is removed, and texturing is performed to form a random pyramid structure on the silicon wafer surface.

[0095] A nano-sized RS-ALD system-type ALD device was used. Trimethylaluminum and phosphorus source PH3 were introduced at a temperature of 240℃. The pulse sequence was: TMA 10ms, H2O 5ms, PH3 5ms, N2 20ms; the number of cycles was 40; the flow rate of TMA was 15 sccm, the flow rate of H2O was 2500 sccm, the flow rate of PH3 was 2 sccm; and the plasma power was 100W.

[0096] Rapid thermal annealing and hydrogen-assisted annealing were performed sequentially: a N2 / H2 mixed gas (volume ratio 9:1) was introduced at 420℃ for 3 minutes to activate B / P doping and repair lattice defects; then, annealing was carried out at 650℃ for 5 minutes in an H2 / N2 atmosphere (H2 content 10%) to improve the density of the passivation layer.

[0097] Subsequently, following conventional methods, laser grooving was performed to form selective emitter contacts, metal electrodes were screen-printed, and co-sintering was completed to obtain TOPCon cells.

[0098] The electrical performance of the TOPCon batteries prepared in the examples and comparative examples is shown in Table 1: Table 1 shows the electrical performance of the TOPCon batteries prepared in the examples and comparative examples.

[0099] As shown in Table 1, the structures and parameters of Examples 1 / 2 / 3 are all within the scope of the design of this patent, with an efficiency improvement of more than 0.35% and an open-circuit voltage significantly higher than that of conventional batteries by 3mV; Comparative Examples 2 and 3 are single-doped alumina structures, with no significant improvement in open-circuit voltage; This further proves that the synergistic effect of gradient doped bilayer alumina achieves an optimized balance between charge density and interface state density.

[0100] 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.

[0101] 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. A TOPCon battery, characterized in that, include: P-type silicon substrate, N+ layer; In the N+ layer, the surface of the P-type silicon substrate extending away from the P-type silicon substrate includes, in sequence: an N+ emitter layer, a silicon oxide layer, a first aluminum oxide layer, and a second aluminum oxide layer. The first alumina layer includes a boron-doped alumina layer; the second alumina layer includes a phosphorus-doped alumina layer.

2. The TOPCon battery according to claim 1, characterized in that, At least one of the following conditions must be met: a. The thickness of the silicon oxide layer is 1.5-2.5 nm; b. The thickness of the first alumina layer is 5-8 nm; c. The thickness of the second alumina layer is 10-15 nm.

3. The TOPCon battery according to claim 1 or 2, characterized in that, At least one of the following conditions must be met: d. the boron concentration gradient distribution in the first aluminum oxide layer is 1 x 10 16 -5 x 10 17 cm -3 -1 e. the phosphorous concentration gradient distribution in the second aluminum oxide layer is 5 x 10 17 -1 x 10 16 cm -3 .

4. A method for preparing a TOPCon battery according to any one of claims 1-3, characterized in that, include: The N+ emitter layer is prepared by performing a first process in the N+ direction of the P-type silicon substrate; The silicon oxide layer is prepared by performing a second treatment on the surface of the N+ emitter layer. The first alumina layer is prepared by performing a third treatment on the surface of the silicon oxide layer; the second alumina layer is obtained by performing a fourth treatment on the surface of the first alumina layer.

5. The method for preparing a TOPCon battery according to claim 4, characterized in that, The first process includes: preparing an N+ emitter layer silicon wafer by POCl3 diffusion and performing phosphorus doping, with a phosphorus oxychloride flow rate of 800-1200 sccm / min, an oxygen flow rate of 600-700 sccm / min, a pressure of 150-170 mbar, a time of 15-21 min, and a temperature of 785-805℃; then heating the silicon wafer to 880-890℃ and advancing it for 23-27 min, with the thickness of the phosphorus silicate glass on the surface being 20-30 nm.

6. The method for preparing a TOPCon battery according to claim 4, characterized in that, The second process includes: preparing a silicon oxide layer with a thickness of 15-2.5 nm by using an oxygen flow rate of 33-38 L / min, a pressure of 65000-75000 Pa, a time of 4-6 min, and a temperature of 600-610 °C.

7. The method for preparing a TOPCon battery according to claim 4, characterized in that, The third process includes: preparing a first alumina layer at a temperature of 190-290°C using an alternating pulse method with dual precursors; The pulse sequence is as follows: TMA 8-12ms, H2O 3-7ms, B2H6 3-7ms, N2 10-30ms; the number of cycles is 18-22; the flow rate of TMA is 5-15 sccm, the flow rate of H2O is 1000-3000 sccm, and the flow rate of B2H6 is 0.5-2 sccm.

8. The method for preparing a TOPCon battery according to claim 4, characterized in that, The fourth process includes: preparing a second alumina layer at a temperature of 190-290°C using alternating pulses of dual precursors and plasma-assisted treatment. The pulse sequence is as follows: TMA 8-12ms, H2O 3-7ms, PH3 3-7ms, N2 10-30ms; the number of cycles is 38-42; the flow rate of TMA is 10-20 sccm, the flow rate of H2O is 1500-3500 sccm, the flow rate of PH3 is 1-3 sccm; and the plasma power is 50-200W.

9. The method for preparing a TOPCon battery according to any one of claims 4-8, characterized in that, The preparation method further includes annealing activation, which comprises sequential rapid thermal annealing and hydrogen-assisted annealing, and satisfies at least one of the following conditions: A. The conditions for rapid thermal annealing are: a temperature of 400-440℃, a mixed gas with a volume ratio of N2:H2 of 8.2-9:1, a flow rate of 222-555 sccm, and a time of 2-4 min; B. The conditions for hydrogen-assisted annealing are: temperature 630-670℃, time 4-6 min; The gas atmosphere for hydrogen-assisted annealing, calculated with its total volume as 100%, includes 80-90% N2 and 10%-20% H2.

10. A photovoltaic system, characterized in that, Includes the TOPCon battery as described in any one of claims 1-3.

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