Positive film structure for improving UV attenuation of TOPCon battery and preparation method

Abstract

The invention discloses a positive film structure for improving UV attenuation of a TOPCon battery and a preparation method, and relates to the technical field of TOPCon batteries, the positive film structure comprises a silicon oxycarbide passivation anti-reflection film deposited on the front surface of a silicon wafer, a SiOC low-folding layer, a SiOC silicon-carbon-rich layer, a SiOC transition layer and a SiOC oxygen-rich layer are sequentially arranged from the surface of the silicon wafer to the outside, the film thickness, the atomic percentage and the refractive index of each layer are in specific ranges, and the thickness of the silicon oxycarbide passivation anti-reflection film is larger than that of the silicon oxycarbide passivation anti-reflection film. The SiOC low-folding layer is used for playing a role in stress buffering, the SiOC silicon-carbon-rich layer is used for resisting UV decomposition and playing a role in passivation, the SiOC transition layer is used for playing roles in stress buffering and optical optimization, and the SiOC oxygen-rich layer is used for resisting environmental corrosion and playing a role in optical optimization. According to the positive film structure, silicon oxycarbide is introduced into the positive film layer of the battery piece, through the synergistic effect of the four layers of SiOC films, ultraviolet dissociation can be resisted, dangling bonds can be reduced, the four-layer gradient refractive index structure can achieve wide spectrum matching and improve the light absorption efficiency, oxygen atoms and carbon atoms are matched to reduce the interface state density, and the UV attenuation resistance is improved on the basis that the electrical performance is kept.

Description

Technical Field

[0001] This invention relates to the field of TOPCon battery technology, specifically to a positive film structure and preparation method for improving UV degradation in TOPCon batteries. Background Technology

[0002] The current front-side film design of TOPCon batteries mainly adopts a composite structure of silicon nitride (SiNx), silicon oxynitride (SiON), or silicon oxide (SiO2). These film structures are rich in hydrogen, and effective hydrogen passivation is achieved through Si-H bonds or NH bonds, thereby improving the passivation effect and electrical performance of the battery. However, in practical applications, TOPCon batteries are exposed to ultraviolet (UV) radiation for a long time, and the Si-H bonds and NH bonds are prone to breakage, resulting in the formation of dangling bonds. Dangling bonds reduce the passivation effect of the film, which in turn affects the open-circuit voltage (Uoc) and short-circuit current (Isc) of the battery, ultimately leading to battery performance degradation and problems such as insufficient bond energy and high interface state density.

[0003] Based on this, a positive film structure and preparation method for improving UV degradation of TOPCon batteries are provided, which can eliminate the drawbacks of existing technical solutions. Summary of the Invention

[0004] The purpose of this invention is to provide a positive film structure and preparation method for improving UV degradation of TOPCon batteries, so as to solve the problems in the prior art where the design of the front film layer of TOPCon batteries leads to battery performance degradation, insufficient bond energy and high interface state density.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A positive film structure for improving UV degradation in TOPCon solar cells includes a silicon oxycarbon passivation antireflective film deposited on the front side of a silicon wafer. The silicon oxycarbon passivation antireflective film is configured as a multilayer composite film structure with different component ratios. The silicon oxycarbon passivation antireflective film comprises, from the silicon wafer surface outwards, the following components:

[0007] The SiOC low-refractive-index layer is used to buffer stress. The SiOC low-refractive-index layer has a C atom percentage of 4-7%, an O atom percentage of 50-70%, and a Si atom percentage of 25-40%. The film thickness of the SiOC low-refractive-index layer is 1-5 nm, and the refractive index is 1.60-1.90.

[0008] The SiOC silicon-rich carbon layer is used to resist UV decomposition and passivate. The SiOC silicon-rich carbon has a C atom percentage of 8-10%, an O atom percentage of 35-45%, and a Si atom percentage of 40-50%. The SiOC silicon-rich carbon layer has a film thickness of 2-15 nm and a refractive index of 2.15-2.35.

[0009] The SiOC transition layer serves as a stress buffer and optical optimization layer. The SiOC transition layer has a C atom percentage of 5-8%, an O atom percentage of 45-55%, and a Si atom percentage of 35-45%. The SiOC transition layer has a film thickness of 8-30 nm and a refractive index of 2.05-2.25.

[0010] The SiOC oxygen-rich layer is used for environmental corrosion resistance and optical optimization. The SiOC oxygen-rich layer has a C atom percentage of 2-4%, an O atom percentage of 50-70%, and a Si atom percentage of 25-40%. The film thickness of the SiOC oxygen-rich layer is 8-30 nm, and the refractive index is 1.90-2.10.

[0011] Preferably, the total thickness of the silicon dioxide passivation antireflective film is 60–90 nm.

[0012] Preferably, the refractive index of the silicon dioxide passivation antireflection film is 1.90 to 2.15, and gradient antireflection matching is achieved in the spectral range of 300 to 1100 nm.

[0013] A method for preparing a positive membrane structure includes the following steps:

[0014] S1. A trough-type machine is used to perform surface cleaning and texturing operations on raw N-type silicon wafers of different sizes to remove contaminants from the silicon wafer surface and form a pyramid structure. The height of the pyramid structure is 0.7–1.3 μm, the width is 1.2–2.0 μm, and the number is 180,000–280,000 per cm. 2 ;

[0015] S2. A boron source is introduced into a tube diffusion furnace to perform a boron diffusion operation on the silicon wafer processed in step S1. A layer of borosilicate glass is formed on the surface of the silicon wafer. The diffusion sheet resistance of the boron diffusion operation is 300 to 450 Ω.

[0016] S3. Remove the borosilicate glass from the surface of the silicon wafer with hydrofluoric acid, and control the thickness of the pyramid base of the pyramid structure to 6-18 μm through mechanical back polishing.

[0017] S4. After polishing, an ultrathin oxide passivation structure is deposited on the back side of the silicon wafer. During the deposition, a portion of the ultrathin oxide passivation structure diffuses to the front side of the silicon wafer.

[0018] S5. Perform high-temperature crystallization treatment on the silicon wafer, annealing at 890-930℃ for 2500-3500s to convert amorphous silicon into polycrystalline silicon.

[0019] S6. Remove the ultrathin oxide passivation structure on the front side of the silicon wafer described in step S4 by wet etching;

[0020] S7. Deposit an aluminum oxide passivation layer on the front side of the silicon wafer, wherein the thickness of the aluminum oxide passivation layer is 3-15 nm;

[0021] S8. Deposit a silicon dioxide passivation antireflection film on the surface of the alumina passivation layer of the silicon wafer to prepare a positive film structure;

[0022] S9. A silicon nitride passivation layer is deposited on the back side of the silicon wafer, wherein the thickness of the silicon nitride passivation layer is 60-90 nm and the refractive index is 2.05-2.25;

[0023] S10. The deposited silicon wafer is subjected to electrode printing operation and high-temperature sintering to form ohmic contacts, thereby obtaining the TOPCon cell structure.

[0024] Preferably, the ultrathin oxide passivation structure in step S4 includes a tunneling oxide layer and a poly layer, wherein the thickness of the tunneling oxide layer is 1-3 nm and the thickness of the poly layer is 60-200 nm.

[0025] Preferably, the deposition is performed using a PECVD process.

[0026] Preferably, the preparation of the positive membrane structure in step S8 specifically includes:

[0027] S81. The graphite boat loaded with silicon wafers is sent into the furnace chamber of the PECVD equipment;

[0028] S82. Turn on the heating and auxiliary heating for 200-600 seconds to raise the internal temperature of the furnace cavity to 300-500℃.

[0029] S83. Evacuate the furnace cavity for 120-200 seconds and control the gas pressure at 0-20 mTorr.

[0030] S84. Perform the deposition of the first film: Introduce SiH4, CO2 and C2H4 gases into the furnace chamber. Set the flow rate of SiH4 gas to 200-2000 sccm, the flow rate of CO2 gas to 3000-6000 sccm, the flow rate of C2H4 gas to 3000-6000 sccm, and the total flow rate of the gases to 6000-14000 sccm. Set the pressure in the furnace chamber to 1200-1800 mTorr. Set the deposition time to 10-50 s. After the deposition operation is completed, a SiOC low-refractive-index layer is formed on the front side of the silicon wafer.

[0031] S85. Perform the deposition of the second film: Introduce SiH4, CO2 and C2H4 gases into the furnace chamber. Set the flow rate of SiH4 gas to 2000-3500 sccm, the flow rate of CO2 gas to 1000-3000 sccm, and the flow rate of C2H4 gas to 3000-6000 sccm. Control the total flow rate of the gases to 6000-12500 sccm. Set the pressure in the furnace chamber to 1000-1800 mTorr. Set the deposition time to 30-150 s. After the deposition operation is completed, a SiOC silicon-rich carbon layer is formed on the surface of the SiOC low-refractive layer.

[0032] S86. Perform the deposition of the third layer film: Introduce SiH4, CO2 and C2H4 gases into the furnace chamber. Set the flow rate of SiH4 gas to 1000-2500 sccm, the flow rate of CO2 gas to 2000-4000 sccm, and the flow rate of C2H4 gas to 2000-4000 sccm. Control the total flow rate of the gases to 5000-10500 sccm. Set the pressure in the furnace chamber to 1000-1700 mTorr. Set the deposition time to 100-250 s. After the deposition operation is completed, a SiOC transition layer is formed on the surface of the SiOC silicon-rich carbon layer.

[0033] S87. Perform the deposition of the fourth film: Introduce SiH4, CO2 and C2H4 gases into the furnace chamber. Set the flow rate of SiH4 gas to 500-1500 sccm, the flow rate of CO2 gas to 3000-5000 sccm, and the flow rate of C2H4 gas to 1000-3000 sccm. Control the total flow rate of the gases to 4500-9500 sccm. Set the pressure in the furnace chamber to 800-1400 mTorr. Set the deposition time to 100-250 s. After the deposition operation is completed, a SiOC oxygen-rich layer is formed on the surface of the SiOC transition layer, and a positive film structure is then deposited and prepared.

[0034] S88. Evacuate the furnace cavity again for 120-200 seconds and control the gas pressure at 0-20 mTorr.

[0035] S89. Introduce N2 into the furnace cavity. The flow rate of N2 is set to 30,000 to 50,000 sccm, and the ventilation time is set to 100 to 300 seconds, until the pressure inside the furnace cavity is restored to 10,000 mTorr atmospheric pressure.

[0036] S810. Open the furnace door of the PECVD equipment, remove the silicon wafers and graphite boats that have completed the film-forming operation from the furnace, and proceed to the next process.

[0037] Preferably, the temperature inside the furnace cavity in steps S83-S87 is controlled at 300-500℃.

[0038] Preferably, the radio frequency power of the PECVD equipment in steps S84-S87 is 10000~16000W.

[0039] Preferably, in steps S84-S87, the RF pulse switching ratio of the PECVD equipment is adjusted to 1:15 to 1:30.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0041] This positive film structure for improving UV degradation in TOPCon cells enhances overall cell performance by introducing silicon dioxide (SiO2) into the positive film layer. Since the Si-OC bond energy is greater than the Si-H and NH bond energies, it effectively resists the dissociation of ultraviolet photons, reduces dangling bond formation, and facilitates improvement in UV degradation. By designing a four-layer gradient refractive index structure, gradient matching from 300 to 1100 nm can be achieved, improving the cell's light absorption efficiency. Oxygen atoms fill silicon dangling bonds, while carbon atoms suppress oxygen diffusion; their interaction reduces the interface state density. While maintaining the cell's original electrical performance, it improves UV degradation resistance, optical performance, and environmental stability, demonstrating promising application prospects. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the structure of the TOPCon battery cell of the present invention.

[0043] Figure 2 This is a schematic diagram of the positive membrane structure of the present invention.

[0044] Figure 3 This is a schematic diagram of the steps of the present invention.

[0045] Figure 4 This is a flowchart illustrating step S8 of the present invention. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0047] In this embodiment, as Figure 1 and Figure 2 As shown, a positive film structure for improving UV degradation in TOPCon cells includes a silicon oxycarbonate (SiOC) passivation antireflection film deposited on the front side of a silicon wafer. The SiOC passivation antireflection film is configured as a multilayer composite film structure with different component ratios. The SiOC passivation antireflection film includes, from the silicon wafer surface outwards, the following components:

[0048] SiOC low-refractive-index layer is used to buffer stress. The percentage of C atoms in the SiOC low-refractive-index layer is 4-7%, the percentage of O atoms is 50-70%, the percentage of Si atoms is 25-40%, the film thickness of the SiOC low-refractive-index layer is 1-5 nm, and the refractive index is 1.60-1.90.

[0049] The SiOC silicon-rich carbon layer is used to resist UV decomposition and passivate. The percentage of C atoms in the SiOC silicon-rich carbon is 8-10%, the percentage of O atoms is 35-45%, and the percentage of Si atoms is 40-50%. The film thickness of the SiOC silicon-rich carbon layer is 2-15 nm, and the refractive index is 2.15-2.35.

[0050] The SiOC transition layer serves as a stress buffer and optical optimization layer. The SiOC transition layer has a C atom percentage of 5-8%, an O atom percentage of 45-55%, and a Si atom percentage of 35-45%. The SiOC transition layer has a film thickness of 8-30 nm and a refractive index of 2.05-2.25.

[0051] The SiOC oxygen-rich layer is used for environmental corrosion resistance and optical optimization. The SiOC oxygen-rich layer has a C atom percentage of 2-4%, an O atom percentage of 50-70%, and a Si atom percentage of 25-40%. The film thickness of the SiOC oxygen-rich layer is 8-30 nm, and the refractive index is 1.90-2.10.

[0052] Specifically, such as Figure 2As shown, the positive film structure consists of a SiOC low-refractive-index layer, a SiOC silicon-rich carbon layer, a SiOC transition layer, and a SiOC oxygen-rich layer. The silicon carbide oxycarbon (SiOC) passivation antireflection film adopts a four-layer composite structure with different component ratios. Each layer achieves differentiated functions by adjusting the atomic percentages of carbon (C), oxygen (O), and silicon (Si) and process parameters. The four layers must be deposited sequentially from the silicon wafer surface outwards. If the layer order is changed, the UV attenuation resistance will decrease. The refractive index of the four layers from the bottom layer to the surface is 1.60–1.90 → 2.15–2.35 → 2.05–2.25 → 1.90–2.10, forming a continuously changing refractive index profile to avoid scattering loss caused by abrupt interface changes. The SiOC low-refractive-index layer matches the incident light with its low refractive index (1.60–1.90) and is close to the silicon wafer surface to reduce interface reflection. The high oxygen content in the SiOC silicon-rich carbon layer fills the silicon dangling bonds, thereby reducing the interface state density. It can also act as a stress buffer layer to alleviate the mechanical mismatch between the subsequent film layer and the silicon substrate. The high carbon content in the SiOC silicon-rich carbon layer enhances the Si-OC bond density (~4.5 eV), and the bond energy is higher than that of the traditional Si-H bond energy (~3.1 eV), resulting in stronger resistance to UV dissociation. The high silicon content effectively improves the carrier transport efficiency. The SiOC transition layer can balance optical and stress characteristics. The refractive index in the range of 2.05 to 2.25 is within the gradient transition range, effectively reducing interlayer light scattering. Carbon atoms inhibit oxygen diffusion and stabilize the passivation interface. The high oxygen content in the SiOC oxygen-rich layer forms a dense protective layer, resisting corrosion from moisture, acids, alkalis, and other environments. The refractive index in the range of 1.90 to 2.10 matches the external medium, further reducing surface reflection.

[0053] Among them, such as Figure 2 As shown, the total thickness of the silicon dioxide passivation antireflection film is 60–90 nm, the refractive index of the silicon dioxide passivation antireflection film is 1.90–2.15, and gradient antireflection matching is achieved in the spectral range of 300–1100 nm;

[0054] Specifically, within the solar spectrum range of 300–1100 nm, a thickness range of 60–90 nm can satisfy the 1 / 4 wavelength antireflection condition (i.e., film thickness ≈ λ / 4n, where λ is the incident light wavelength and n is the refractive index), thereby maximizing light absorption. If the film is too thin (film thickness < 60 nm), the passivation layer may not be fully covered, and the dangling bonds may not be sufficiently passivated. If the film is too thick (film thickness > 90 nm), stress cracks may be introduced or the risk of carrier recombination may be increased. The thickness range of 60–90 nm matches the uniformity of the PECVD deposition process, ensuring the controllability of mass production.

[0055] The refractive index *n* is a measure of the speed of light in a medium. The refractive index of silicon oxycarbonate (SiOC) passivation antireflective coatings is designed to be 1.90–2.15. The refractive index of silicon differs greatly from that of air. 硅≈3.5~4.0, n 空气 ≈1.0, the impedance gradient needs to be achieved by using the refractive index of the intermediate refractive index layer, namely the silicon carbide (SiOC) passivation antireflection film, to reduce Fresnel reflection. By adjusting the thickness ratio of each layer, the overall refractive index can be stabilized at 1.90 to 2.15, thus achieving broadband optimization.

[0056] Among them, such as Figure 3 and Figure 4 As shown, a method for preparing a positive membrane structure includes the following steps:

[0057] S1. A tank-type machine is used to perform surface cleaning and texturing operations on raw N-type silicon wafers of different sizes to remove contaminants such as organic matter and metallic impurities from the silicon wafer surface, forming a pyramid structure. The height of the pyramid structure is 0.7–1.3 μm, the width is 1.2–2.0 μm, and the number is 180,000–280,000 per cm. 2 The pyramid-shaped velvet structure reduces light reflection and enhances light absorption;

[0058] S2. Introduce a boron source, which can be BBr3, into the tubular diffusion furnace to perform high-temperature diffusion and form a p+ emitter. Perform boron diffusion operation on the silicon wafer processed in step S1 to form a layer of borosilicate glass on the surface of the silicon wafer. The diffusion sheet resistance of the boron diffusion operation is 300-450Ω. This step can form a pn junction to provide a separation electric field for photogenerated carriers in the battery.

[0059] S3. Remove the borosilicate glass (BSG) from the surface of the silicon wafer with hydrofluoric acid. Through mechanical back-side polishing, control the thickness of the pyramid base to 6-18 μm. This step can remove impurities and optimize the substrate quality of the back-side passivation layer deposition.

[0060] S4. Using PECVD process, an ultrathin oxide passivation structure is deposited on the back side of the polished silicon wafer. The ultrathin oxide passivation structure includes a tunneling oxide layer and a poly layer. The thickness of the tunneling oxide layer is 1-3 nm, and the thickness of the poly layer is 60-200 nm. During deposition, a portion of the ultrathin oxide passivation structure will diffuse to the front side of the silicon wafer. However, this portion of the oxide layer may affect the subsequent passivation quality. Therefore, it is removed by wet etching in step S6. The tunneling oxide layer can reduce carrier recombination, and the poly layer can provide field effect passivation.

[0061] S5. Perform high-temperature crystallization treatment on the silicon wafer, annealing at 890-930℃ for 2500-3500s to convert amorphous silicon into polycrystalline silicon. This step can improve the conductivity and passivation effect of the poly layer.

[0062] S6. Remove the ultrathin oxide passivation structure on the front side of the silicon wafer in step S4 by wet etching. In step S4, poly and silicon oxide are deposited on the back side of the silicon wafer. Some of the poly and silicon oxide will be wrapped around to the front side, which is called PSG and poly wrap-around plating. Wet etching can remove the phosphorus silicon glass (PSG) and poly-Si residues on the front side due to the back side deposition process, avoid front side film contamination, and ensure the quality of the subsequent passivation layer.

[0063] S7. Deposit an aluminum oxide passivation layer on the front side of the silicon wafer. The thickness of the aluminum oxide passivation layer is 3-15 nm. This step can provide excellent chemical passivation and reduce the interface state density.

[0064] S8. Deposit a silicon dioxide passivation antireflection film on the surface of the alumina passivation layer of the silicon wafer to prepare a positive film structure;

[0065] S9. Deposit a silicon nitride passivation layer on the back side of the silicon wafer. The thickness of the silicon nitride passivation layer is 60-90 nm and the refractive index is 2.05-2.25. This step can protect the back metallization area.

[0066] S10. The deposited silicon wafer is subjected to electrode printing, followed by high-temperature sintering to form ohmic contacts, thereby obtaining the TOPCon cell structure. The TOPCon cell structure is as follows: Figure 1 As shown, the high-temperature sintering temperature is set to 800-900℃, and this step can collect photocurrent.

[0067] Among them, such as Figure 3 and Figure 4 As shown, the deposition was performed using the PECVD process;

[0068] Specifically, PECVD is a plasma-enhanced chemical vapor deposition process with a deposition temperature of 300–500°C. This avoids damage to the passivation structure of the poly layer on the back of the TOPCon cell caused by high temperature. By exciting the reactive gas with radio frequency plasma, monolayer film growth can be completed within 10–250 seconds. By adjusting the flow rate ratio of SiH4, CO2, and C2H4 gases, the atomic percentage of C, O, and Si can be precisely controlled. Increasing the CO2 gas flow rate increases the percentage of O atoms, and increasing the C2H4 gas flow rate increases the percentage of C atoms.

[0069] Among them, such as Figure 4 As shown, the preparation of the positive membrane structure in step S8 specifically includes:

[0070] S81. Send the graphite boat loaded with silicon wafers into the furnace chamber of the PECVD equipment, ensuring that the front side of the silicon wafers is facing up. The graphite boat must be resistant to high temperatures (≤500℃) to avoid contaminating the film layer.

[0071] S82. Turn on the heating and auxiliary heating for 200-600s to raise the temperature inside the furnace cavity to 300-500℃. If the temperature is higher than 500℃, there is a possibility that the poly-Si passivation layer on the back side may be damaged. If the temperature is lower than 300℃, there is a possibility that the film layer may not be dense enough.

[0072] S83. Evacuate the furnace cavity for 120-200 seconds to control the gas pressure at 0-20 mTorr, remove residual gas in the furnace cavity, avoid oxidation pollution, and provide a pure environment for subsequent gas reactions.

[0073] S84. Perform the deposition of the first film: Introduce SiH4, CO2 and C2H4 gases into the furnace chamber. Set the flow rate of SiH4 gas to 200-2000 sccm, the flow rate of CO2 gas to 3000-6000 sccm, the flow rate of C2H4 gas to 3000-6000 sccm, the total flow rate of the gases to 6000-14000 sccm, the pressure in the furnace chamber to 1200-1800 mTorr, and the deposition time to 10-50 s. After the deposition operation is completed, a SiOC low-refractive layer is formed on the front side of the silicon wafer.

[0074] S85. Perform the deposition of the second film: Introduce SiH4, CO2 and C2H4 gases into the furnace chamber. Set the flow rate of SiH4 gas to 2000-3500 sccm, the flow rate of CO2 gas to 1000-3000 sccm, and the flow rate of C2H4 gas to 3000-6000 sccm. Control the total flow rate of the gas to 6000-12500 sccm. Set the pressure in the furnace chamber to 1000-1800 mTorr. Set the deposition time to 30-150 s. After the deposition operation is completed, a SiOC silicon-rich carbon layer is formed on the surface of the SiOC low-refractive layer.

[0075] S86. Perform the deposition of the third layer: Introduce SiH4, CO2 and C2H4 gases into the furnace chamber. Set the flow rate of SiH4 gas to 1000-2500 sccm, the flow rate of CO2 gas to 2000-4000 sccm, and the flow rate of C2H4 gas to 2000-4000 sccm. Control the total flow rate of the gases to 5000-10500 sccm. Set the pressure in the furnace chamber to 1000-1700 mTorr. Set the deposition time to 100-250 s. After the deposition operation is completed, a SiOC transition layer is formed on the surface of the SiOC silicon-rich carbon layer.

[0076] S87. Deposition of the fourth layer: SiH4, CO2 and C2H4 gases are introduced into the furnace chamber. The flow rate of SiH4 gas is set to 500-1500 sccm, the flow rate of CO2 gas is set to 3000-5000 sccm, and the flow rate of C2H4 gas is set to 1000-3000 sccm. The total flow rate of the gas is controlled at 4500-9500 sccm. The pressure in the furnace chamber is set to 800-1400 mTorr. The deposition time is 100-250 s. After the deposition operation is completed, a SiOC oxygen-rich layer is formed on the surface of the SiOC transition layer, and then a positive film structure is prepared by deposition.

[0077] S88. Evacuate the furnace cavity again for 120-200 seconds, and control the gas pressure at 0-20 mTorr to remove reaction byproducts such as CH4 and H2 gas.

[0078] S89. Introduce N2 into the furnace cavity. Set the flow rate of N2 to 30,000 to 50,000 sccm and the ventilation time to 100 to 300 seconds until the pressure inside the furnace cavity is restored to 10,000 mTorr atmospheric pressure to avoid film oxidation when the vacuum is broken.

[0079] S810. Open the furnace door of the PECVD equipment, remove the silicon wafer and graphite boat that have completed the film-forming operation from the furnace, and proceed to the next process.

[0080] Specifically, deposition is performed using plasma-enhanced chemical vapor deposition (PECVD). In steps S83-S87, the temperature within the furnace chamber is controlled between 300 and 500°C. When the temperature is within this range, a decrease in temperature can retain more Si-H bonds. In steps S84-S87, the pressure within the furnace chamber is between 800 and 1800 mTorr. When the pressure is within this range, an increase in pressure can increase the film density and reduce stress. In steps S84-S87, the RF power of the PECVD equipment is between 10000 and 160 kW. When the RF power is within this range, increasing the RF power can increase the deposition rate. In steps S84-S87, the RF pulse switching ratio of the PECVD equipment is adjusted to 1:15 to 1:30 to reduce ion bombardment damage and keep the film stress below 500 MPa. Conventional film stress is higher than 1000 MPa. The RF frequency of the PECVD process can be adjusted to 13.56 MHz according to actual environmental requirements, the electrode spacing is set to 10-20 mm, and the plasma power density is set to 0.5-1.5 W / cm². 2 ;

[0081] Specifically, as shown in Tables 1 and 2 below, Tables 1 and 2 contain comparative data on film performance. In the tables, Eta represents electrical performance, Uoc represents open-circuit voltage, Isc represents short-circuit current, Rs represents series resistance, Rsh represents parallel resistance, FF represents fill factor, IRev2 represents reverse current, and UV60 represents ultraviolet attenuation rate. The conventional group represents the original silicon wafer structure, while the experimental group represents the silicon wafer structure containing silicon oxycarbon (SiOC) passivation antireflection film. Inter-wafer uniformity refers to the consistency of the same film layer or performance parameters between different silicon wafers and can be used to measure the carbon deposited on different silicon wafers. The difference in parameters such as thickness and refractive index of silicon oxide passivation antireflection film; intra-wafer uniformity refers to the consistency of film layers or performance parameters at different locations on the same silicon wafer, such as the fluctuation of parameters such as thickness and refractive index of silicon oxide passivation antireflection film in different areas of the same silicon wafer surface; EL yield refers to the proportion of qualified cells to the total number of cells tested in electroluminescence testing, used to detect whether there are defects in cells, such as cracks, fragments, short circuits, open circuits, etc. The conventional group and the experimental group use the same testing standards, such as the same wavelength range and test duration;

[0082] According to the data, the total thickness of the conventional group and the experimental group is the same, ensuring optical interference conditions. Compared with the refractive index of the conventional group, the experimental group has a wider gradient. The multilayer design can achieve a wide spectral matching of 300-1100nm. Compared with the reflectivity of the conventional group, the lower limit of the experimental group's range is reduced by 0.1%, indicating that the experimental group has better performance in reducing light reflection. There is no significant difference in the inter-cell uniformity and intra-cell uniformity between the conventional group and the experimental group. The electrical efficiency, short-circuit current, fill factor, reverse current, and EL yield of the experimental group are slightly higher than those of the conventional group, indicating that the cells of the experimental group have fewer defects during the production process and better cell quality. The positive film rework rate is slightly lower than that of the conventional group. The parallel resistance of the experimental group is higher than that of the conventional group, indicating that the battery performance of the experimental group is better. The UV decay rate of the experimental group is significantly lower than that of the conventional group, indicating that the battery of the experimental group performs better in resisting UV decay. The open-circuit voltage and series resistance of the two groups are the same, with no significant difference.

[0083] Table 1

[0084]

[0085] Table 2

[0086]

[0087] In summary, by controlling the refractive index and gradient multilayer structure design of the silicon oxycarbon (SiOC) passivation antireflection film, the light absorption in the wavelength range of 300–1100 nm is maximized, while the reflectivity is stabilized at 2.4–3.6%. Experimental data show that the film thickness, refractive index, reflectivity range, and uniformity of the positive film structure in this scheme are consistent with the original structure. However, the efficiency of the positive film structure in this scheme is slightly better than that of the original structure. Rework of the positive film is normal, and the EL yield is normal. By introducing the silicon oxycarbon (SiOC) film layer, the stability of the Si-OC bond is utilized to effectively resist ultraviolet light dissociation and reduce the generation of dangling bonds. Under UV irradiation, the traditional Si-H and N... H bonds are prone to breakage, resulting in dangling bonds. In contrast, the Si-OC bonds in the multilayer SiOC composite structure require high-energy dissociation (UV photon energy > 4.5 eV) to reduce the UV60 decay rate and prevent passivation degradation. This reduces the UV60 decay rate from 2.40% in the conventional group to 1.20% in the experimental group, an improvement of 50%, meeting the industry requirement of <1.5%. This effectively improves the UV decay of TOPCon cells. While maintaining the original electrical performance (Eta efficiency 26.89%), this positive film structure significantly enhances the UV decay resistance of TOPCon cells, while also considering optical, passivation, and process feasibility, making it a valuable application.

[0088] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A positive film structure for improving UV degradation in TOPCon batteries, characterized in that, This includes a silicon dioxide passivation antireflective film deposited on the front side of a silicon wafer. The silicon dioxide passivation antireflective film is configured as a multilayer composite film structure with different component ratios. From the silicon wafer surface outwards, the silicon dioxide passivation antireflective film comprises: The SiOC low-refractive-index layer is used to buffer stress. The SiOC low-refractive-index layer has a C atom percentage of 4-7%, an O atom percentage of 50-70%, and a Si atom percentage of 25-40%. The film thickness of the SiOC low-refractive-index layer is 1-5 nm, and the refractive index is 1.60-1.

90. The SiOC silicon-rich carbon layer is used to resist UV decomposition and passivate. The SiOC silicon-rich carbon has a C atom percentage of 8-10%, an O atom percentage of 35-45%, and a Si atom percentage of 40-50%. The SiOC silicon-rich carbon layer has a film thickness of 2-15 nm and a refractive index of 2.15-2.

35. The SiOC transition layer serves as a stress buffer and optical optimization layer. The SiOC transition layer has a C atom percentage of 5-8%, an O atom percentage of 45-55%, and a Si atom percentage of 35-45%. The SiOC transition layer has a film thickness of 8-30 nm and a refractive index of 2.05-2.

25. The SiOC oxygen-rich layer is used for environmental corrosion resistance and optical optimization. The SiOC oxygen-rich layer has a C atom percentage of 2-4%, an O atom percentage of 50-70%, and a Si atom percentage of 25-40%. The film thickness of the SiOC oxygen-rich layer is 8-30 nm, and the refractive index is 1.90-2.

10.

2. The positive film structure for improving UV degradation of TOPCon batteries according to claim 1, characterized in that, The total thickness of the silicon dioxide passivation antireflective film is 60–90 nm.

3. The positive film structure for improving UV degradation of TOPCon batteries according to claim 2, characterized in that, The refractive index of the silicon dioxide passivation antireflection film is 1.90 to 2.15, and it achieves gradient antireflection matching in the 300 to 1100 nm spectral range.

4. A method for preparing a positive film structure according to any one of claims 1-3, characterized in that, Includes the following steps: S1. A trough-type machine is used to perform surface cleaning and texturing operations on raw N-type silicon wafers of different sizes to remove contaminants from the silicon wafer surface and form a pyramid structure. The height of the pyramid structure is 0.7–1.3 μm, the width is 1.2–2.0 μm, and the number is 180,000–280,000 per cm. 2 ; S2. A boron source is introduced into a tube diffusion furnace to perform a boron diffusion operation on the silicon wafer processed in step S1. A layer of borosilicate glass is formed on the surface of the silicon wafer. The diffusion sheet resistance of the boron diffusion operation is 300 to 450 Ω. S3. Remove the borosilicate glass from the surface of the silicon wafer with hydrofluoric acid, and control the thickness of the pyramid base of the pyramid structure to 6-18 μm through mechanical back polishing. S4. After polishing, an ultrathin oxide passivation structure is deposited on the back side of the silicon wafer. During the deposition, a portion of the ultrathin oxide passivation structure diffuses to the front side of the silicon wafer. S5. Perform high-temperature crystallization treatment on the silicon wafer, annealing at 890-930℃ for 2500-3500s to convert amorphous silicon into polycrystalline silicon. S6. Remove the ultrathin oxide passivation structure on the front side of the silicon wafer described in step S4 by wet etching; S7. Deposit an aluminum oxide passivation layer on the front side of the silicon wafer, wherein the thickness of the aluminum oxide passivation layer is 3-15 nm; S8. Deposit a silicon dioxide passivation antireflection film on the surface of the alumina passivation layer of the silicon wafer to prepare a positive film structure; S9. A silicon nitride passivation layer is deposited on the back side of the silicon wafer, wherein the thickness of the silicon nitride passivation layer is 60-90 nm and the refractive index is 2.05-2.25; S10. The deposited silicon wafer is subjected to electrode printing operation and high-temperature sintering to form ohmic contacts, thereby obtaining the TOPCon cell structure.

5. The method for preparing a positive film structure for improving UV degradation of TOPCon cells according to claim 4, characterized in that, The ultrathin oxide passivation structure in step S4 includes a tunneling oxide layer and a poly layer. The thickness of the tunneling oxide layer is 1-3 nm, and the thickness of the poly layer is 60-200 nm.

6. The method for preparing a positive film structure for improving UV degradation of TOPCon cells according to claim 4, characterized in that, The deposition was performed using the PECVD process.

7. The method for preparing a positive film structure for improving UV degradation of TOPCon cells according to claim 4, characterized in that, The preparation of the positive membrane structure in step S8 specifically includes: S81. The graphite boat loaded with silicon wafers is sent into the furnace chamber of the PECVD equipment; S82. Turn on the heating and auxiliary heating for 200-600 seconds to raise the internal temperature of the furnace cavity to 300-500℃. S83. Evacuate the furnace cavity for 120-200 seconds and control the gas pressure at 0-20 mTorr. S84. Perform the deposition of the first film: Introduce SiH4, CO2 and C2H4 gases into the furnace chamber. Set the flow rate of SiH4 gas to 200-2000 sccm, the flow rate of CO2 gas to 3000-6000 sccm, the flow rate of C2H4 gas to 3000-6000 sccm, and the total flow rate of the gases to 6000-14000 sccm. Set the pressure in the furnace chamber to 1200-1800 mTorr. Set the deposition time to 10-50 s. After the deposition operation is completed, a SiOC low-refractive-index layer is formed on the front side of the silicon wafer. S85. Perform the deposition of the second film: Introduce SiH4, CO2 and C2H4 gases into the furnace chamber. Set the flow rate of SiH4 gas to 2000-3500 sccm, the flow rate of CO2 gas to 1000-3000 sccm, and the flow rate of C2H4 gas to 3000-6000 sccm. Control the total flow rate of the gases to 6000-12500 sccm. Set the pressure in the furnace chamber to 1000-1800 mTorr. Set the deposition time to 30-150 s. After the deposition operation is completed, a SiOC silicon-rich carbon layer is formed on the surface of the SiOC low-refractive layer. S86. Perform the deposition of the third layer film: Introduce SiH4, CO2 and C2H4 gases into the furnace chamber. Set the flow rate of SiH4 gas to 1000-2500 sccm, the flow rate of CO2 gas to 2000-4000 sccm, and the flow rate of C2H4 gas to 2000-4000 sccm. Control the total flow rate of the gases to 5000-10500 sccm. Set the pressure in the furnace chamber to 1000-1700 mTorr. Set the deposition time to 100-250 s. After the deposition operation is completed, a SiOC transition layer is formed on the surface of the SiOC silicon-rich carbon layer. S87. Perform the deposition of the fourth film: Introduce SiH4, CO2 and C2H4 gases into the furnace chamber. Set the flow rate of SiH4 gas to 500-1500 sccm, the flow rate of CO2 gas to 3000-5000 sccm, and the flow rate of C2H4 gas to 1000-3000 sccm. Control the total flow rate of the gases to 4500-9500 sccm. Set the pressure in the furnace chamber to 800-1400 mTorr. Set the deposition time to 100-250 s. After the deposition operation is completed, a SiOC oxygen-rich layer is formed on the surface of the SiOC transition layer, and a positive film structure is then deposited and prepared. S88. Evacuate the furnace cavity again for 120-200 seconds and control the pressure at 0-20 mTorr. S89. Introduce N2 into the furnace cavity. The flow rate of N2 is set to 30,000 to 50,000 sccm, and the ventilation time is set to 100 to 300 seconds, until the pressure inside the furnace cavity is restored to 10,000 mTorr atmospheric pressure. S810. Open the furnace door of the PECVD equipment, remove the silicon wafers and graphite boats that have completed the film-forming operation from the furnace, and proceed to the next process.

8. The method for preparing a positive film structure for improving UV degradation of TOPCon cells according to claim 7, characterized in that, In steps S83-S87, the temperature inside the furnace cavity is controlled between 300 and 500°C.

9. The method for preparing a positive film structure for improving UV degradation of TOPCon cells according to claim 7, characterized in that, In steps S84-S87, the radio frequency power of the PECVD equipment is 10000~16000W.

10. The method for preparing a positive film structure for improving UV degradation of a TOPCon battery according to claim 9, characterized in that, In steps S84-S87, the RF pulse switching ratio of the PECVD equipment is adjusted to 1:15 to 1:30.

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