Front composite passivation anti-uv attenuation film and preparation method and application thereof

Abstract

The application relates to the field of photovoltaic technology, and discloses a front composite passivation anti-reflection film layer with anti-ultraviolet attenuation and a preparation method and application thereof. The front composite passivation anti-reflection film layer is prepared by sequentially arranging an aluminum oxide layer, a SiCxNy layer and a silicon nitride layer from bottom to top in a cooperative manner, the C / N atomic ratio of the SiCxNy layer is controlled to be 1.0-3.5:1, the C / N atomic ratio of the SiCxNy layer gradually increases from the side of the aluminum oxide layer to the side of the silicon nitride layer, and the thickness of the SiCxNy layer is 5-20 nm. Therefore, the front composite passivation anti-reflection film layer has excellent anti-ultraviolet attenuation, low solar reflectivity, high visible light transmittance, good passivation effect, low recombination and carrier transport optimization, and can effectively improve the anti-ultraviolet attenuation performance of a photovoltaic cell from the root cause, effectively solve the UV attenuation problem, and help improve the open-circuit voltage, short-circuit current density, fill factor, photoelectric conversion efficiency and other electrical properties of the photovoltaic cell.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic technology, specifically to a front-side composite passivation antireflection film layer for resisting ultraviolet degradation, its preparation method, and its application. Background Technology

[0002] TOPCon (Tunnel Oxide Passivated Contact) cells, as one of the mainstream technologies for high-efficiency crystalline silicon photovoltaic cells, have the core advantage of achieving extremely low surface recombination rate and high-efficiency carrier transport through a back-side passivated contact structure of "ultra-thin tunnel oxide (SiO2) layer + polycrystalline silicon (poly-Si) layer", thus breaking through the bottleneck of photoelectric conversion efficiency of traditional photovoltaic cells.

[0003] With the widespread application of TOPCon cells in the photovoltaic market, the performance degradation caused by ultraviolet (UV) radiation in outdoor environments has become increasingly prominent. Under prolonged outdoor UV exposure, TOPCon cells experience performance degradation (i.e., "UV degradation"), a phenomenon closely related to their material properties and structural design, and a key reliability issue that the industry needs to address. UV radiation has a short wavelength and high energy, making it highly destructive to photovoltaic cell structures. When TOPCon cells are exposed to UV radiation, a series of complex physicochemical changes occur within them:

[0004] On the one hand, when UV photon energy exceeds 3.5 eV (wavelength less than 360 nm), it breaks the Si-H bonds at the silicon nitride-Si interface in photovoltaic cells, generating dangling bonds, reducing passivation quality, increasing emitter saturation current, and decreasing carrier lifetime, leading to surface passivation degradation. On the other hand, UV irradiation induces carrier injection, altering impurity charge states and mobility, and combining to form bulk defect centers, affecting photovoltaic cell performance. Furthermore, the hot electrons generated by UV radiation, when exceeding the interface barrier, damage the passivation layer, increasing the interface state density. These combined effects lead to a decrease in the open-circuit voltage, short-circuit current, and fill factor of TOPCon cells, ultimately reducing the photovoltaic cell's photoelectric conversion efficiency and severely impacting its long-term reliability and power generation efficiency. Therefore, ultraviolet radiation can disrupt the chemical bonds or interface states of the passivation layer, leading to increased carrier recombination. Current solutions for UV degradation at the cell level include:

[0005] 1. Silicon nitride (SiN) protective layer: When depositing a silicon nitride anti-reflective layer on the front side (light-receiving side) of a photovoltaic cell, the nitrogen and hydrogen content of the silicon nitride (such as hydrogen-rich silicon nitride) is adjusted to enhance its ability to block ultraviolet rays and reduce the penetration of UV rays into the passivation layer.

[0006] 2. Double-layer or multi-layer passivation design: For example, Al2O3 film or SiOxNy film is superimposed on the passivation contact structure to suppress interfacial recombination by utilizing the negative fixed charge characteristics of Al2O3, while blocking ultraviolet rays (as shown in publication number CN114512611A).

[0007] 3. Improve the process of polycrystalline silicon (poly-Si) layer: control the crystallinity and doping uniformity of poly-Si through in-situ doping or annealing process to reduce UV-induced defects (as shown in publication number JP2020509688A).

[0008] 4. Nanocrystalline silicon (nc-Si) as a replacement for traditional poly-Si layers: Nanocrystalline silicon has a lower defect density, which can reduce UV-induced carrier trapping (as shown in publication number WO2021164587A1). However, compared with poly-Si, nanocrystalline silicon also presents the following new problems:

[0009] (1) Grain boundary scattering problem: Nanocrystalline silicon is composed of nanocrystals embedded in an amorphous matrix. Grain boundary scattering will lead to a decrease in carrier transport efficiency. (2) Difference in optical properties: Although nanocrystalline silicon can achieve photoluminescence through rare earth doping, its bandgap tunable range (1.2-2.4 eV) is still smaller than that of polycrystalline silicon, resulting in limited absorption of visible light in specific wavelength bands. All of these will lead to a decrease in the electrical performance of the battery. (3) Fabrication process limitations: The fabrication of nanocrystalline silicon thin films requires special processes such as ion beam sputtering, which is more expensive than conventional polycrystalline silicon deposition methods.

[0010] While adjusting the crystallinity and doping uniformity of poly-Si can passively reduce UV-induced defects, it cannot fundamentally block or eliminate ultraviolet light. Furthermore, relying solely on hydrogen-rich silicon nitride, Al2O3 films, or SiOxNy films is ineffective in blocking ultraviolet light and cannot effectively solve the UV attenuation problem at its root. Summary of the Invention

[0011] The purpose of this invention is to overcome the shortcomings of the prior art and provide a front-side composite passivation antireflective film layer with anti-ultraviolet decay, its preparation method and application.

[0012] Based on this, the present invention discloses a front composite passivation antireflection film layer for resisting ultraviolet decay, comprising a silicon nitride layer, a SiCxNy layer and an aluminum oxide layer stacked sequentially from top to bottom; the aluminum oxide layer is in contact with the silicon surface;

[0013] The C / N atomic ratio of the SiCxNy layer is controlled between 1.0 and 3.5:1, and the C / N atomic ratio of the SiCxNy layer shows a gradient change that gradually increases from the alumina layer side to the silicon nitride layer side; the thickness of the SiCxNy layer is 5-20 nm.

[0014] Preferably, the bandgap of the SiCxNy layer is controlled at 2.0-3.0 eV; the C atom concentration of the SiCxNy layer is controlled at 5-40%, and the C atom concentration of the SiCxNy layer shows a gradually increasing gradient change from the alumina layer side to the silicon nitride layer side.

[0015] More preferably, the SiCxNy layer includes a lower layer region, an intermediate transition layer region, and an upper layer region distributed sequentially from bottom to top.

[0016] More preferably, the lower layer region is disposed on the side close to the alumina layer, and the thickness of the lower layer region is 1-5 nm; the C atom concentration of the lower layer region is controlled in the range of 5-10%, its C / N atom ratio is controlled in the range of 1-1.5:1, and its band gap is controlled in the range of 2.0-2.2 eV.

[0017] More preferably, the thickness of the intermediate transition layer is 2-10 nm; the C atom concentration of the intermediate transition layer is controlled in the range of 10-30%, the C / N atom ratio is controlled in the range of 1.5-2.5:1, and the band gap is controlled in the range of 2.2-2.7 eV.

[0018] More preferably, the thickness of the upper layer is 2-5 nm; the C atom concentration of the upper layer is controlled in the range of 30-40%, the C / N atom ratio is controlled in the range of 2.5-3.5:1, and the band gap is controlled in the range of 2.7-3.0 eV.

[0019] Preferably, the thickness of the silicon nitride layer is 60-80 nm; the thickness of the aluminum oxide layer is 1-8 nm.

[0020] This invention also discloses a method for preparing a front-side composite passivation antireflection film layer with anti-ultraviolet fading, comprising the following steps:

[0021] S1. Prepare an aluminum oxide layer on the silicon surface;

[0022] S2. A SiCxNy layer is prepared on the upper surface of the alumina layer using a co-deposition method of plasma-enhanced atomic layer deposition (PE-ALD).

[0023] S3. Prepare a silicon nitride layer on the upper surface of the SiCxNy layer.

[0024] Preferably, before preparing the silicon nitride layer in step S3, the method further includes: treating the upper surface of the SiCxNy layer with H2 plasma to reduce interface defects between the SiCxNy layer and the silicon nitride layer; the power of the H2 plasma treatment is 80-150W, the time is 20-50s, and the flow rate of H2 is 10-15sccm.

[0025] The present invention also discloses an application of a front composite passivation antireflection film layer for resisting ultraviolet degradation, wherein the front composite passivation antireflection film layer is applied to photovoltaic cells.

[0026] Compared with the prior art, the present invention has at least the following beneficial effects:

[0027] In the front composite passivation antireflection film layer of the present invention: (1) The silicon nitride layer is located on the top layer of the front composite passivation antireflection film layer, which can achieve the effects of reducing visible light reflectivity, hydrogen passivation and repairing defects; moreover, the silicon nitride layer has high transmittance to ultraviolet light, which allows ultraviolet light to penetrate the silicon nitride layer and be absorbed by the SiCxNy layer, avoiding the direct irradiation of ultraviolet light on the silicon surface and causing its surface defects to be activated, thereby effectively avoiding UV attenuation.

[0028] (2) The bandgap of the SiCxNy layer (2.0-3.0 eV) can be continuously adjusted with the C / N atomic ratio. Therefore, by adjusting the C / N atomic ratio (making the C / N atomic ratio in the SiCxNy layer gradually increase from the alumina layer side to the silicon nitride layer side), the ultraviolet light absorption range can be controllably extended, achieving efficient absorption of near- and far-ultraviolet light (200-400 nm). Moreover, the smaller C / N atomic ratio of the SiCxNy layer on the alumina layer side (close to the silicon surface) can reduce the carrier injection barrier, optimize carrier transport, reduce the accumulation of electron-hole pairs at the interface, and improve the open-circuit voltage. In addition, the SiCxNy layer (refractive index n≈2.6) can serve as a refractive index transition layer from the silicon surface (refractive index n≈3.4) to the silicon nitride layer (refractive index n≈2.0), which helps to reduce the solar reflectivity at the interface.

[0029] (3) The alumina layer is located at the bottom of the front composite passivation antireflection film layer and is in direct contact with the silicon surface. It can play a chemical passivation role and enhance field effect passivation, reducing recombination. At the same time, the silicon nitride layer, SiCxNy layer and alumina layer have high transmittance to visible light (400-1100nm), which can effectively ensure that visible light passes through the front composite passivation antireflection film layer and enters the silicon surface, where it is absorbed and utilized, achieving high photoelectric conversion efficiency.

[0030] Therefore, the front composite passivation antireflection film layer of the present invention requires the coordinated cooperation of an alumina layer, a SiCxNy layer (with the C / N atomic ratio in the SiCxNy layer gradually increasing from the alumina layer side to the silicon nitride layer side) and a silicon nitride layer stacked sequentially from bottom to top, in order to achieve excellent anti-UV degradation performance, low solar reflectivity, high visible light transmittance, good passivation effect, low recombination, and optimized carrier transport properties. This effectively improves the anti-UV degradation performance of photovoltaic cells from the root, effectively solves the UV degradation problem, and helps to improve the open-circuit voltage, short-circuit current density, fill factor, photoelectric conversion efficiency and other electrical properties of photovoltaic cells. Attached Figure Description

[0031] Figure 1 This is a schematic cross-sectional view of a TOPCon battery with a front composite passivation antireflection film layer that resists ultraviolet degradation, according to this embodiment.

[0032] Figure 2 The TOPCon cells of Example 1 and Comparative Examples 1-3 were subjected to a UV irradiation of 15 kWh / m². 2 A graph showing the changes in electrical performance parameters over time.

[0033] Figure 3 The TOPCon cells of Example 1 and Comparative Examples 1-3 were subjected to a UV irradiation of 35 kWh / m². 2 A graph showing the changes in electrical performance parameters over time.

[0034] Figure 4 The TOPCon cells of Example 1 and Comparative Examples 1-3 were subjected to a UV irradiation of 45 kWh / m². 2 A graph showing the changes in electrical performance parameters over time.

[0035] Figure 5 The TOPCon cells of Example 1 and Comparative Examples 1-3 were subjected to a UV irradiation of 60 kWh / m². 2 A graph showing the changes in electrical performance parameters over time.

[0036] Explanation of reference numerals: 1. Front electrode; 2. Front silicon nitride layer; 3. SiCxNy layer; 4. Alumina layer; 5. P+ emitter; 6. Silicon substrate; 7. Tunneling oxide layer; 8. N-type polycrystalline silicon layer; 9. Back silicon nitride layer; 10. Back electrode. Detailed Implementation

[0037] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] A front-side composite passivation antireflective film layer for resisting ultraviolet fading according to the present invention, see [link to relevant documentation]. Figure 1It includes an alumina layer 4, a SiCxNy layer 3 (Si-CN alloy layer) and a silicon nitride layer 2, which are stacked sequentially from bottom to top.

[0039] In this process, the alumina layer 4 serves as an interface layer, directly contacting the silicon surface (such as the silicon substrate 6 or the emitter formed by doped polycrystalline silicon), and the thickness of the alumina layer 4 is preferably 1-8 nm. The alumina layer 4 mainly plays the following roles in the front-side composite passivation antireflection film layer:

[0040] 1. Chemical passivation and interface stability: The alumina layer 4 forms stable Si-O bonds through dangling bonds between its oxygen atoms and the silicon surface, which can reduce the surface state density from 10 12 cm -2 The magnitude dropped to 10 10 cm -2 The following provides stable chemical passivation and improves the interfacial stability between the alumina layer 4 and the silicon surface.

[0041] If the alumina layer 4 is missing in the front composite passivation antireflection film, the SiCxNy layer 3 will directly contact the silicon surface. Interface defects (such as Si-C non-ideal bonds) will cause the surface recombination rate to surge from <10cm / s to >100cm / s, which will significantly reduce the open-circuit voltage of the photovoltaic cell.

[0042] 2. Enhanced field-effect passivation: The negative charge density of alumina layer 4 (≈-1×10⁻⁶) 12 cm -2 An electric field pointing into the bulk is formed on the surface of crystalline silicon to repel minority carriers (such as electrons in p-type silicon) and further suppress interfacial recombination.

[0043] In this structure, the SiCxNy layer 3 serves as the functional layer, formed by co-depositing SiH4, CH4, and NH3 via PE-ALD (plasma-enhanced atomic layer deposition). The thickness of the entire SiCxNy layer 3 is preferably 5-20 nm. Furthermore, the C / N atomic ratio (i.e., the x / y ratio) of the entire SiCxNy layer 3 is controlled within 1.0-3.5:1, and the bandgap of the entire SiCxNy layer 3 is controlled within 2.0-3.0 eV.

[0044] Increasing the C / N atomic ratio of SiCxNy layer 3 (correspondingly, increasing the C atom concentration in SiCxNy layer 3) increases the band gap of SiCxNy layer 3. The band gap (2.0-3.0 eV) of SiCxNy layer 3 is continuously adjustable with the C / N atomic ratio. Therefore, by adjusting the C / N atomic ratio, the ultraviolet light absorption range can be controllably extended, achieving efficient absorption of near- and far-ultraviolet light (200-400 nm).

[0045] The concentration of C atoms in SiCxNy layer 3 shows a gradually increasing gradient distribution from the alumina layer 4 side to the silicon nitride layer 2 side (i.e., a gradient distribution from low C atom concentration to high C atom concentration); that is, the C / N atom ratio in SiCxNy layer 3 shows a gradually increasing gradient change from the alumina layer 4 side to the silicon nitride layer 2 side.

[0046] For example, the entire SiCxNy layer can be divided into at least three layer regions distributed sequentially from bottom to top: the lower layer region, the intermediate transition layer region, and the upper layer region.

[0047] The lower region is located on the side close to the alumina layer 4. The C atom concentration in the lower region is controlled in the range of 5-10%. At this time, the C / N atomic ratio is controlled in the range of 1-1.5:1. The band gap of the lower region is 2.0-2.2eV. At this time, the SiCxNy layer 3 is closer to silicon nitride. Its main function is to reduce the carrier injection barrier.

[0048] The intermediate transition layer is located between the lower and upper layers. The C atom concentration in the intermediate transition layer is controlled within the range of 10-30%, and the C / N atom ratio is controlled within the range of 1.5-2.5:1. The band gap of the intermediate transition layer is 2.2-2.7 eV, which is mainly used to achieve optical refractive index transition and reduce interface reflection.

[0049] The upper region is located on the side closest to the silicon nitride layer 2. The C atom concentration in the upper region is controlled within the range of 30-40%, and the C / N atom ratio is controlled within the range of 2.5-3.5:1. The band gap of the upper region is 2.7-3.0 eV. At this time, the SiCxNy layer 3 is closer to SiC and mainly plays the role of enhancing the absorption of ultraviolet light and the transmission of visible light.

[0050] Therefore, the core functions of this SiCxNy layer 3 include:

[0051] 1. Ultraviolet absorption and gradient refractive index matching:

[0052] Ultraviolet absorption: The SiCxNy layer 3 (bandgap 2.7-3.0eV) with a high C / N atomic ratio (2.5-3.5:1) on the silicon nitride layer 2 can effectively absorb ultraviolet rays of 200-400nm, preventing them from penetrating to the silicon surface and causing carrier recombination.

[0053] Refractive index transition: The refractive index gradient design from the surface of crystalline silicon (refractive index n≈3.4) to the surface of SiCxNy layer 3 (refractive index n≈2.6) and then to silicon nitride layer 2 (refractive index n≈2.0) can reduce the interfacial solar reflectivity from 15% of the single-layer silicon nitride layer 2 to <5%.

[0054] 2. Carrier transport optimization: The C / N atomic ratio of the SiCxNy layer 3 on the side of the alumina layer 4 (close to the silicon surface) is small, which can reduce the carrier injection barrier and reduce the accumulation of electron-hole pairs at the interface.

[0055] However, if the C / N atomic ratio of the SiCxNy layer 3 in the front composite passivation antireflection film layer exhibits a gradually decreasing gradient change from the alumina layer 4 side to the silicon nitride layer 2 side (i.e., a gradient distribution from high C atom concentration to low C atom concentration), the following problems will arise:

[0056] 1. Interfacial recombination enhancement: The high C atom concentration (i.e., high C / N atomic ratio) of the SiCxNy layer 3 on the alumina layer 4 side (close to the crystalline silicon surface) leads to an excessively wide bandgap (≈2.7-3.0eV), significantly increasing the carrier injection barrier, enhancing surface recombination, and reducing Voc (open circuit voltage) and short-wavelength response.

[0057] 2. Refractive index mismatch: It is difficult to achieve a smooth transition of refractive index from the surface of crystalline silicon (refractive index n≈3.4) to the surface of SiCxNy layer 3 (refractive index n≈2.6) and then to silicon nitride layer 2 (refractive index n≈2.0), which increases reflection and absorption losses and weakens the optical benefits in the ultraviolet band.

[0058] 3. Reduced UV absorption: If the SiCxNy layer 3 with high C atom concentration is mainly distributed on the side of the alumina layer 4, the UV absorption of the SiCxNy layer 3 on the side of the silicon nitride layer 2 will be insufficient; and the increased UV transmittance will make it easier to damage the interface between the SiCxNy layer 3 and the alumina layer 4, which is not conducive to improving the UV absorption stability.

[0059] 4. Damaged hydrogen passivation: If the hydrogen content in the SiCxNy layer 3 changes in the opposite gradient, hydrogen is more likely to escape outward during annealing, making it difficult to effectively passivate the silicon interface and affecting minority carrier lifetime and decay suppression.

[0060] Furthermore, the thickness of the SiCxNy layer 3 was designed to be 5-20 nm, which is the result of comprehensively considering its core functions (ultraviolet absorption, refractive index transition, and carrier transport optimization) and film stability.

[0061] Ultraviolet absorption depends on a sufficiently thick SiCxNy layer 3 to ensure sufficient absorption of 200-400nm ultraviolet light (following the Lambert-Beer law, the absorption increases with increasing thickness, but there is a saturation threshold).

[0062] Furthermore, the refractive index from the crystalline silicon surface (refractive index n≈3.4) to the silicon nitride layer 2 (refractive index n≈2.0) needs to be smoothly transitioned through the SiCxNy layer 3 (refractive index n≈2.6). Insufficient thickness will lead to discontinuous refractive index transition.

[0063] Furthermore, since SiCxNy layer 3 is an amorphous alloy, excessive thickness can lead to the accumulation of internal defects (such as dangling bonds and microvoids), which in turn increases the number of recombination centers. Therefore, if the thickness of SiCxNy layer 3 deviates from the range of 5-20 nm, it will directly affect the realization of the function of SiCxNy layer 3, as detailed below:

[0064] If the thickness of the SiCxNy layer 3 is less than 5nm (taking 3nm as an example), it will lead to:

[0065] (1) Significant decrease in ultraviolet absorption capacity: The thickness of the SiCxNy layer 3 decreased from 5-20nm to 3nm, which led to a decrease in its absorption rate of 200-300nm short-wave ultraviolet light from >90% to <50% (mainly due to insufficient absorption pathways), resulting in more ultraviolet light penetrating into the crystalline silicon substrate 6 and inducing the formation of oxygen vacancies (O2) in the silicon substrate 6. v ) and silicon self-interstitial atoms (Si i Photoexcitation by the SiCxNy layer reduces the bulk recombination lifetime. Furthermore, reducing the thickness of the SiCxNy layer 3 from 5-20 nm to 3 nm leads to a more significant decrease in absorption of long-wavelength ultraviolet light (300-400 nm) (absorption rate drops to <30%), resulting in a decrease in the UV responsivity (R0) of the photovoltaic cell. uv (Decrease >40%)

[0066] (2) Refractive index gradient breakage and sudden increase in reflectivity: SiCxNy layer 3 with a thickness of less than 5nm cannot form a complete gradient distribution of "low C atom concentration → high C atom concentration" (at least 5nm is required to achieve a continuous change of C atom concentration from 5% to 30%), resulting in a sudden change in the refractive index of SiCxNy layer 3 from the alumina layer 4 side to the silicon nitride layer 2 side, and the interface reflectivity increases from <5% to >15% (especially in the 400-500nm visible light region), with a short-circuit current density (Jsc) loss of >3mA / cm. 2 The refractive index smoothly decreases from about 3.5 at the silicon surface, through about 2.6 at the SiCxNy layer 3, and about 2.0 at the silicon nitride layer 2, to the refractive index of air, which can control the light reflection loss to below 5%.

[0067] (3) Deterioration of film interface stability: The excessively thin SiCxNy layer 3 cannot effectively buffer the stress difference between the alumina layer 4 (hard and brittle) and the silicon nitride layer 2 (tough), causing the film adhesion to drop sharply from >50MPa to <20MPa. After 100 hours of damp heat test (85℃ / 85%RH), the film is prone to peeling, and the efficiency decreases by >10%.

[0068] However, if the thickness of the SiCxNy layer 3 is greater than 20nm (taking 30nm as an example), it will lead to:

[0069] (1) Excessive visible light absorption and significant loss of Jsc: The absorption of SiCxNy layer 3 in the 300-400nm ultraviolet region is close to saturation (>95%), but when its thickness increases to 30nm, its absorption rate in the 400-500nm visible light region increases from <5% to >20%, resulting in a decrease in visible light transmittance and a Jsc loss of >2mA / cm 2 .

[0070] (2) Accumulation of bulk defects and deterioration of passivation performance: The defect density of the amorphous SiCxNy layer 3 increases linearly with the increase of thickness (the defect state density D increases by 10 nm for every 10 nm increase). it Increase by approximately 5×10 9 cm -2 When the thickness is 30nm, the D of SiCxNy layer 3 it Up to 5×10 9 cm -2 Surface recombination rate (S) e When the speed increases from <10cm / s to >50cm / s, the open-circuit voltage (Voc) loss is >30mV.

[0071] (3) Excessive film stress reduces process feasibility: The internal stress of the SiCxNy layer 3 increases exponentially with thickness (approximately -200MPa at 5nm, -500MPa at 20nm, and -800MPa at 30nm). Excessive thickness leads to cell bending >50μm (standard <20μm), making the cells prone to breakage during subsequent cutting (breakage rate increases from <1% to >10%). In addition, the deposition time of SiCxNy layer 3 is prolonged (the deposition time of a 30nm thick SiCxNy layer 3 is 1.5 times that of a 20nm thick layer), reducing production efficiency by 30% and increasing costs by approximately 20%.

[0072] Among them, silicon nitride layer 2, as the top layer of the entire front-side composite passivation and antireflection film, preferably has a thickness of 60-80 nm. Its main function is to further reduce reflection and provide hydrogen passivation. Furthermore, short-time H2 plasma treatment at the interface between SiCxNy layer 3 and silicon nitride layer 2 can reduce interface defects. Details are as follows:

[0073] 1. Hydrogen passivation and defect repair: Hydrogen atoms (H content ≈ 10-15 at%) in silicon nitride layer 2 can diffuse to the interface between SiCxNy layer 3 and the crystalline silicon surface, passivating dangling bonds and grain boundary defects, thus increasing the bulk recombination lifetime (τ). eff The improvement was from ~1μs to >10μs.

[0074] 2. Anti-reflection and mechanical protection: The 60-80nm thick silicon nitride layer 2 and SiCxNy layer 3 form optical interference, which further reduces the visible light reflectivity (<3%), while providing mechanical support to resist film cracking in humid and hot environments.

[0075] In summary, the front composite passivation antireflection film of the present invention, with the silicon nitride layer 2 located on the top layer of the front composite passivation antireflection film, can achieve reduced visible light reflectivity, hydrogen passivation, and defect repair. Moreover, the silicon nitride layer 2 has high ultraviolet transmittance, allowing ultraviolet light to penetrate the silicon nitride layer 2 and be absorbed by the SiCxNy layer 3, avoiding direct ultraviolet light irradiation on the silicon surface and thus preventing the activation of surface defects, thereby effectively avoiding the problem of UV attenuation.

[0076] Increasing the C / N atomic ratio of SiCxNy layer 3 (increasing the C atom concentration in SiCxNy layer 3) leads to an increase in the band gap of SiCxNy layer 3. Therefore, the band gap (2.0-3.0 eV) of SiCxNy layer 3 can be continuously adjusted with the C / N atomic ratio. Thus, by adjusting the C / N atomic ratio (making the C / N atomic ratio in SiCxNy layer 3 gradually increase from the alumina layer 4 side to the silicon nitride layer 2 side), the ultraviolet light absorption range can be controllably extended, achieving efficient absorption of near- and far-ultraviolet light (200-400 nm). Moreover, the smaller C / N atomic ratio of SiCxNy layer 3 on the alumina layer 4 side (closer to the crystalline silicon surface) can lower the carrier injection barrier, optimize carrier transport, and reduce the accumulation of electron-hole pairs at the interface. In addition, the SiCxNy layer 3 (refractive index n≈2.6) can serve as a refractive index transition layer between the crystalline silicon surface (refractive index n≈3.4) and the silicon nitride layer 2 (refractive index n≈2.0), which helps to reduce the solar reflectivity at the interface.

[0077] The alumina layer 4 is located at the bottom of the front composite passivation antireflection film layer, directly contacting the silicon surface. It can achieve a chemical passivation effect and enhance field-effect passivation, reducing recombination. At the same time, the silicon nitride layer 2, SiCxNy layer 3, and alumina layer 4 have high transmittance to visible light (400-1100nm), which can effectively ensure that visible light passes through the front composite passivation antireflection film layer and enters the silicon surface, where it is absorbed and utilized, achieving high photoelectric conversion efficiency.

[0078] Therefore, the front composite passivation antireflection film layer of the present invention requires the coordinated cooperation of an alumina layer 4, a SiCxNy layer 3 (with the C / N atomic ratio in the SiCxNy layer 3 gradually increasing from the alumina layer 4 side to the silicon nitride layer 2 side) and a silicon nitride layer 2 stacked sequentially from bottom to top, in order to achieve excellent anti-ultraviolet degradation performance, low solar reflectivity, high visible light transmittance, good passivation effect, low recombination, and optimized carrier transport properties, thereby helping to improve the electrical performance of photovoltaic cells such as open-circuit voltage, short-circuit current density, fill factor, and photoelectric conversion efficiency.

[0079] However, if the front-side composite passivation antireflection film layer is only paired with a silicon nitride layer 2 + a SiCxNy layer 3 (while lacking an aluminum oxide layer 4 that directly contacts the silicon surface), the following defects are likely to occur:

[0080] (1) Interface recombination runaway: The lack of chemical passivation by alumina results in a large surface state density at the interface between the SiCxNy layer 3 and the crystalline silicon, which leads to an increased surface recombination rate and a decrease in the open-circuit voltage of the photovoltaic cell.

[0081] (2) Insufficient UV absorption: The transmittance of silicon nitride layer 2 in the 200-300nm band is >80%, which cannot effectively block short-wave ultraviolet rays, resulting in a decrease of >30% in the UV responsivity of the battery.

[0082] However, if the front-side composite passivation antireflection film layer is only paired with a SiCxNy layer 3 + an alumina layer 4, the following defects are likely to occur:

[0083] (1) Lack of hydrogen passivation: The SiCxNy layer 3 itself does not contain hydrogen, and the hydrogen diffusion coefficient of the alumina layer 4 itself is extremely low (<10). -20 cm 2 / s), which prevents volume defects (such as dislocations) from being effectively passivated.

[0084] (2) High reflectivity: Without a 60-80nm thick silicon nitride layer 2, optical interference between the 60-80nm thick silicon nitride layer 2 and the SiCxNy layer 3 cannot be achieved, resulting in high visible light reflectivity (especially in the 400-700nm visible light region).

[0085] The present invention discloses a method for preparing a front-side composite passivation antireflective film layer with anti-ultraviolet fading, comprising the following steps:

[0086] S1. Prepare an aluminum oxide layer on the silicon surface (it is prepared by referring to existing deposition methods, such as atomic layer deposition, so it will not be described in detail).

[0087] S2. A SiCxNy layer is prepared on the upper surface of the alumina layer using a plasma-enhanced atomic layer deposition co-deposition method.

[0088] S3. Prepare a silicon nitride layer on the upper surface of the SiCxNy layer.

[0089] Before preparing the silicon nitride layer in step S3, the method further includes: treating the upper surface of the SiCxNy layer with H2 plasma to reduce the interface defects between the SiCxNy layer and the silicon nitride layer.

[0090] The present invention relates to an application of a front composite passivation antireflection film layer for resisting ultraviolet degradation, wherein the front composite passivation antireflection film layer is applied to a photovoltaic cell; for example, the front composite passivation antireflection film layer is applied to a TOPCon cell to replace the front film layer structure on the silicon surface (such as silicon substrate 6 or emitter formed by doped polycrystalline silicon).

[0091] The present invention provides a photovoltaic module comprising a photovoltaic cell with a front composite passivation antireflection film layer for resisting ultraviolet degradation as described above.

[0092] The following are specific embodiments of the present invention: a front-side composite passivation antireflective film layer for resisting ultraviolet fading, its preparation method, and its application:

[0093] Example 1

[0094] This embodiment describes the application of a front composite passivation antireflection film layer for resisting ultraviolet degradation. This front composite passivation antireflection film layer is applied to a TOPCon battery to replace the front film layer structure on the silicon surface (emitter).

[0095] The TOPCon battery specifically includes the following structure (e.g.) Figure 1 (As shown): Silicon substrate 6; The front side (i.e., the top, the light-receiving surface) of silicon substrate 6 consists of a P+ emitter 5, a front composite passivation antireflection film layer and a front electrode 1, the lower end of which passes through the front composite passivation antireflection film layer and makes an ohmic contact with the P+ emitter 5; The back side (i.e., the bottom, the backlighting surface) of silicon substrate 6 consists of a conventional passivation contact structure (which includes a tunneling oxide layer 7 and an N-type polysilicon layer 8 arranged from top to bottom), a back silicon nitride layer 9 and a back electrode 10, the upper end of which passes through the back silicon nitride layer 9 and makes an ohmic contact with the N-type polysilicon layer 8.

[0096] It should be noted that this embodiment only improves the front-side film structure of the silicon surface (emitter) of a conventional TOPCon cell (using the front-side composite passivation antireflection film of this embodiment). Therefore, apart from the front-side composite passivation antireflection film, the other structures and fabrication processes of the TOPCon cell in this embodiment are the same as those of existing conventional TOPCon cells, and will not be described in detail here.

[0097] This embodiment provides a front-side composite passivation antireflection film layer for resisting ultraviolet decay, which includes a front-side silicon nitride layer 2, a SiCxNy layer 3, and an aluminum oxide layer 4 stacked sequentially from top to bottom. The aluminum oxide layer 4 contacts the upper surface (front side) of the P+ emitter 5.

[0098] In this embodiment, the thickness of the front silicon nitride layer 2 is 70 nm.

[0099] In this embodiment, the SiCxNy layer 3 is located between the front silicon nitride layer 2 and the aluminum oxide layer 4. The band gap of the SiCxNy layer 3 is continuously adjustable with the C / N atomic ratio. Therefore, by adjusting the C / N atomic ratio, efficient absorption of near and far ultraviolet rays (200-400nm) can be achieved, thereby enhancing the anti-ultraviolet degradation performance of the photovoltaic cell.

[0100] Specifically, the C / N atomic ratio in the SiCxNy layer 3 exhibits a gradually increasing gradient change from the alumina layer 4 side to the front silicon nitride layer 2 side.

[0101] In this embodiment, the thickness of the alumina layer 4 is 6 nm.

[0102] This embodiment describes a method for preparing a front-side composite passivation and antireflection film layer that resists ultraviolet degradation, comprising the following steps:

[0103] Step 1: Prepare an aluminum oxide layer 4 on the silicon surface (emitter) using conventional atomic layer deposition.

[0104] Step 2: SiCxNy layer 3 is prepared on the upper surface of alumina layer 4 using PE-ALD (plasma-enhanced atomic layer deposition) co-deposition method. In practice, in addition to adjusting the C / N atomic ratio of each region of SiCxNy layer 3 by adjusting the flow rate of the gas (i.e., the precursor), the C / N atomic ratio of each region can also be controlled by adjusting the power and the precursor pulse time.

[0105] In step 2, the total deposition thickness of the SiCxNy layer 3 is 15 nm, and the PE-ALD co-deposition method is used. The specific deposition process of the SiCxNy layer 3 is as follows:

[0106] The precursors were SiH4 (10 sccm), CH4, and NH3 (20 sccm), the deposition temperature was 250℃, and the plasma power was uniformly 140±10W (e.g., 140W) when depositing the SiCxNy layer.

[0107] The SiCxNy layer 3 (upper region) near the alumina layer 4 has a C atom concentration of 7%, a CH4 flow rate of 12 sccm, a thickness of 5 nm, and is cycled 50 times (0.05-0.08 nm / cycle). The C / N atom ratio is 1.1:1, and the band gap is 2.0 eV. The single-cycle precursor pulse times for this upper region are as follows: the total single-cycle time is 17 s, and the timing sequence is: SiH4 pulse 3 s → Ar purge 2 s → CH4 pulse 3 s → Ar purge 2 s → NH3 pulse 4 s → Ar purge 3 s.

[0108] The SiCxNy layer 3 in the intermediate transition region has a C atom concentration of 12-30%, a CH4 flux of 28 sccm, a thickness of 8 nm, and is cycled 150 times (0.05-0.08 nm / cycle). The C / N atom ratio is 1.7:1, and the band gap is about 2.3 eV. The single-cycle precursor pulse times in this intermediate transition region are as follows: the total single-cycle time is 19 s, and the timing sequence is: SiH4 pulse 3 s → Ar purge 2 s → CH4 pulse 5 s → Ar purge 2 s → NH3 pulse 4 s → Ar purge 3 s.

[0109] The SiCxNy layer 3 (lower region), located near the front silicon nitride layer 2, has a C atom concentration of 38%, a CH4 flow rate of 32 sccm, a thickness of 2 nm, and undergoes 50 cycles (0.05-0.08 nm / cycle). The C / N atom ratio is 3.2:1, and the band gap is 2.9 eV. The single-cycle precursor pulse times for this lower region are as follows: total single-cycle time 20 s, with the sequence: SiH4 pulse 3 s → Ar purge 2 s → CH4 pulse 6 s → Ar purge 2 s → NH3 pulse 4 s → Ar purge 3 s. The CH4 pulse time is the longest, suitable for the highest CH4 flow rate of 32 sccm.

[0110] Immediately after the SiCxNy layer 3 was deposited, a short-term H2 plasma treatment (i.e., interface treatment) was performed in the chamber. The H2 plasma power was 90W, the H2 flow rate was 13sccm, and the treatment time was 35s, reducing the interface defect density to 5×10⁻⁶. 11 cm -2 The purpose of this study is to reduce reflection, increase hydrogen passivation, and reduce interface defects, thereby providing a low-defect interface for the subsequent deposition of the front-side silicon nitride layer 2.

[0111] Step 3: Prepare a front-side silicon nitride layer 2 on the upper surface of the SiCxNy layer 3 using PECVD (plasma-enhanced chemical vapor deposition).

[0112] In step 3, the deposition process of the front silicon nitride layer 2 is as follows:

[0113] The silicon nitride layer 2 on the front side has a silicon source of SiH4 (30 sccm) and a nitrogen source of NH3 (60 sccm), with a deposition thickness of 70 nm and a refractive index of 2.05.

[0114] The above structure is used to prepare a TOPCon battery with a front composite passivation antireflection film layer that resists ultraviolet decay in this embodiment. The preparation steps not described in detail can be referred to the existing conventional N-type TOPCon battery preparation process, so they are not described in detail here.

[0115] A photovoltaic module according to this embodiment includes a TOPCon cell with a front composite passivation antireflection film layer for resisting ultraviolet degradation, as described above in this embodiment.

[0116] Comparative Example 1

[0117] This comparative example describes a front-side composite passivation antireflective film layer for resisting ultraviolet degradation, its preparation method, and its application in TOPCon cells and photovoltaic modules. All examples refer to Example 1, but differ from Example 1 in that:

[0118] The total deposition thickness of the SiCxNy layer in this comparative example is 3 nm. The specific deposition process for obtaining the 3 nm thick SiCxNy layer using the PE-ALD co-deposition method is as follows:

[0119] The precursors are SiH4 (10 sccm), CH4, and NH3 (20 sccm). The deposition temperature is 250℃, and the plasma power is uniformly 110±10W (e.g., 110W). The processes for different regions are as follows:

[0120] The SiCxNy layer (upper region) near the alumina layer has a C atom concentration of 8%, a CH4 flux of 13 sccm, a thickness of 1 nm, and undergoes 15 cycles (0.05-0.08 nm / cycle). The C / N atom ratio is 1.2:1, and the band gap is 2.1 eV. The total cycle time is 12 s, with the timing sequence being: SiH4 pulse 2 s → Ar purge 1 s → CH4 pulse 3 s → Ar purge 1 s → NH3 pulse 3 s → Ar purge 2 s. The relatively short total cycle time is suitable for the thin-layer deposition requirement of 15 cycles, and the high power ensures sufficient CH4 fragmentation at 13 sccm.

[0121] The SiCxNy layer in the intermediate transition region has a C atom concentration of 19%, a CH4 flow rate of 45 sccm, a thickness of 1 nm, and undergoes 20 cycles (0.05-0.08 nm / cycle). The C / N atom ratio is 1.7:1, and the band gap is 2.3 eV. The total single-cycle time is 15 s, with the timing sequence being: SiH4 pulse 2 s → Ar purge 1 s → CH4 pulse 6 s → Ar purge 1 s → NH3 pulse 3 s → Ar purge 2 s. The CH4 pulse is extended to 6 s to match the 45 sccm CH4 flow rate, rapidly increasing the C atom concentration to 19%.

[0122] The SiCxNy layer (lower region) near the front silicon nitride layer has a C atom concentration of 25%, a CH4 flow rate of 60 sccm, a thickness of 1 nm, and is cycled 15 times (0.05-0.08 nm / cycle). The C / N atom ratio is 3.0:1, and the band gap is 2.8 eV. The total cycle time is 16 s, with the timing sequence being: SiH4 pulse 2 s → Ar purge 1 s → CH4 pulse 7 s → Ar purge 1 s → NH3 pulse 3 s → Ar purge 2 s. The CH4 pulse time is the longest, suitable for a CH4 flow rate of 60 sccm, meeting the requirements of a C atom concentration of 25% and a C / N ratio of 3.0:1. Other process parameters are consistent with Example 1.

[0123] Comparative Example 2

[0124] This comparative example describes a front-side composite passivation antireflective film layer for resisting ultraviolet degradation, its preparation method, and its application in TOPCon cells and photovoltaic modules. All examples refer to Example 1, but differ from Example 1 in that:

[0125] The total deposition thickness of the SiCxNy layer in this comparative example is 25 nm. This 25 nm thick SiCxNy layer was fabricated using the PE-ALD co-deposition method. The specific deposition process for this SiCxNy layer is as follows:

[0126] The precursors were SiH4 (10 sccm), CH4, and NH3 (20 sccm), and the deposition temperature was 250℃. SiC was then deposited. x N γ During the layering process, the plasma power is uniformly set at 140±10W (e.g., 140W), and the processes for different zones are as follows:

[0127] The SiCxNy layer (upper region) near the alumina layer has a C atom concentration of 9%, a CH4 flow rate of 14 sccm, a thickness of 7 nm, and undergoes 80 cycles (0.05-0.08 nm / cycle). The C / N atom ratio is 1.3:1, and the band gap is 2.2 eV. The single-cycle precursor pulse times are as follows: total single-cycle time 17 s, timing sequence: SiH4 pulse 3 s → Ar purge 2 s → CH4 pulse 3 s → Ar purge 2 s → NH3 pulse 4 s → Ar purge 3 s. Low power reduces thick film stress, and the pulse time is adapted to a CH4 flow rate of 14 sccm to ensure a C atom concentration of 9%.

[0128] The SiCxNy layer in the intermediate transition region has a C atom concentration of 15-32%, a CH4 flow rate of 28 sccm, a thickness of 15 nm, and undergoes 260 cycles (0.05-0.08 nm / cycle). The C / N atom ratio is 2.5:1, and the band gap is 2.3-2.7 eV. The total time for a single cycle is 19 s, with the timing sequence being: SiH4 pulse 3 s → Ar purge 2 s → CH4 pulse 5 s → Ar purge 2 s → NH3 pulse 4 s → Ar purge 3 s. Consistent with the intermediate transition region of Example 1, a CH4 flow rate of 28 sccm is matched to achieve a gentle gradient of C atom concentration from 15-32%.

[0129] The SiCxNy layer (lower region) near the front silicon nitride layer has a C atom concentration of 36%, a CH4 flow rate of 31 sccm, a thickness of 3 nm, and undergoes 80 cycles (0.05-0.08 nm / cycle). The C / N atom ratio is 3.1:1, and the band gap is 2.8 eV. The total cycle time is 19.5 s, with the timing sequence being: SiH4 pulse 3 s → Ar purge 2 s → CH4 pulse 5.5 s → Ar purge 2 s → NH3 pulse 4 s → Ar purge 3 s. The CH4 pulse is slightly shorter than in Example 1, adapted to a CH4 flow rate of 31 sccm, and meets the requirement of a C atom concentration of 36%. Other process parameters are consistent with Example 1.

[0130] Comparative Example 3

[0131] This comparative example describes a method for preparing a photovoltaic cell that uses the existing mass-produced conventional N-type TOPCon cell preparation process.

[0132] The photovoltaic cell obtained in this comparative example has a structure that is similar to the TOPCon cell structure of Example 1. The difference between the photovoltaic cell obtained in this example and the TOPCon cell structure of Example 1 is as follows:

[0133] An aluminum oxide layer and a silicon nitride layer are sequentially deposited on the front side of the P+ emitter (while omitting the SiCxNy layer in the front composite passivation antireflection film layer of Example 1).

[0134] Performance testing

[0135] UVID tests were performed on the TOPCon batteries of Example 1 and Comparative Examples 1-3, and the test results are shown in Table 1 below. Figure 2-5 As shown:

[0136] Table 1

[0137] Comparative Example 3 / / / / Comparative Example 1 (3nm) 1.50 -3.0 0.0003 -0.0188 Example 1 (15nm) 1.00 0.0 0.0002 0.0006 Comparative Example 2 (25nm) -35.00 -2.2 -0.0050 -0.0278

[0138] Table 1 shows the differences in initial electrical performance between Comparative Examples 1-2 and Example 1 and Comparative Example 3, using Comparative Example 3 (i.e., existing mass-produced conventional N-type TOPCon batteries) as a reference.

[0139] Where ΔVoc, ΔIsc, ΔFF, and Δη represent the changes in open-circuit voltage, short-circuit current density, fill factor, and photoelectric conversion efficiency, respectively.

[0140] Combining Table 1 and Figure 2-5 This reveals that TOPCon batteries can withstand 15-60 kWh / m³ at an ambient temperature of 65°C. 2 Evolution of electrical properties under ultraviolet irradiation:

[0141] 1. The electrical performance degradation trend of the TOPCon batteries in Example 1 and Comparative Examples 1-2 after ultraviolet irradiation is better than that in Comparative Example 3.

[0142] 2. The SiCxNy layer in the front composite passivation antireflection film of Comparative Example 1 is thinner (3nm), which causes more ultraviolet light to penetrate and reach the silicon substrate, triggering photoexcitation of oxygen vacancies and interstitial atoms in the silicon substrate, reducing the bulk recombination lifetime, and thus causing UV decay in the TOPCon cell of Comparative Example 1 (compared to Example 1).

[0143] 3. The SiCxNy layer in the front composite passivation antireflection film of Comparative Example 2 is thicker (25nm), which leads to a decrease in visible light transmittance, resulting in a significant loss of Isc in the TOPCon cell of Comparative Example 2 (compared to Example 1), and UV degradation.

[0144] 4. Compared with Comparative Examples 1-3, the C atom concentration (from the aluminum oxide layer side to the front silicon nitride layer side) of the TOPCon cell in Example 1 (with a SiCxNy layer thickness of 15nm in its front composite passivation antireflection film) has a uniform gradient transition from low to high, which reduces the carrier injection barrier and fully absorbs ultraviolet light. The interface H2 plasma treatment further reduces defects, thus significantly improving its UV resistance performance.

[0145] Therefore, based on the TOPCon battery's ability to withstand 15-60 kWh / m at an ambient temperature of 65°C... 2 The evolution of electrical properties under ultraviolet irradiation shows that:

[0146] As the irradiance increases to 60 kWh / m 2 The TOPCon battery of Comparative Example 1 (SiCxNy layer thickness of 3nm) showed a significant UV degradation trend, followed by Comparative Example 2 (SiCxNy layer thickness of 25nm). Example 1 (SiCxNy layer thickness of 15nm) showed the most ideal UV degradation trend and its anti-UV degradation performance was significantly improved.

[0147] Although preferred embodiments of the present invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of the present invention.

[0148] The technical solution provided by the present invention has been described in detail above. Specific examples have been used to illustrate the principle and implementation of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A front-side composite passivation antireflective film layer with UV fading resistance, characterized in that, It includes a silicon nitride layer, a SiCxNy layer, and an aluminum oxide layer stacked sequentially from top to bottom; the aluminum oxide layer is in contact with the silicon surface; The C / N atomic ratio of the SiCxNy layer is controlled between 1.0 and 3.5:1, and the C / N atomic ratio of the SiCxNy layer shows a gradient change that gradually increases from the alumina layer side to the silicon nitride layer side; the thickness of the SiCxNy layer is 5-20 nm. The bandgap of the SiCxNy layer is controlled at 2.0-3.0 eV; the C atom concentration of the SiCxNy layer is controlled at 5-40%, and the C atom concentration of the SiCxNy layer shows a gradually increasing gradient from the alumina layer side to the silicon nitride layer side.

2. The anti-UV attenuation front composite passivation antireflection film layer according to claim 1, characterized in that, The SiCxNy layer comprises a lower layer region, an intermediate transition layer region, and an upper layer region distributed sequentially from bottom to top.

3. The anti-UV attenuation front composite passivation antireflection film layer according to claim 2, characterized in that, The lower layer region is located on the side close to the alumina layer, and the thickness of the lower layer region is 1-5 nm. The C atom concentration of the lower layer region is controlled in the range of 5-10%, the C / N atom ratio is controlled in the range of 1-1.5:1, and the band gap is controlled in the range of 2.0-2.2 eV.

4. The anti-UV attenuation front composite passivation antireflection film layer according to claim 2, characterized in that, The thickness of the intermediate transition layer is 2-10 nm; the C atom concentration of the intermediate transition layer is controlled in the range of 10-30%, the C / N atom ratio is controlled in the range of 1.5-2.5:1, and the band gap is controlled in the range of 2.2-2.7 eV.

5. The anti-UV attenuation front composite passivation antireflection film layer according to claim 2, characterized in that, The thickness of the upper layer is 2-5 nm; the C atom concentration of the upper layer is controlled in the range of 30-40%, the C / N atom ratio is controlled in the range of 2.5-3.5:1, and the band gap is controlled in the range of 2.7-3.0 eV.

6. The anti-UV attenuation front composite passivation antireflection film layer according to claim 1, characterized in that, The thickness of the silicon nitride layer is 60-80 nm; the thickness of the aluminum oxide layer is 1-8 nm.

7. A method for preparing a front-side composite passivation antireflective film layer with UV fading resistance according to any one of claims 1-6, characterized in that, Includes the following steps: S1. Prepare an aluminum oxide layer on the silicon surface; S2. A SiCxNy layer is prepared on the upper surface of the alumina layer using a plasma-enhanced atomic layer deposition co-deposition method. S3. Prepare a silicon nitride layer on the upper surface of the SiCxNy layer.

8. The method for preparing a front-side composite passivation antireflective film layer with anti-ultraviolet attenuation according to claim 7, characterized in that, Before preparing the silicon nitride layer in step S3, the method further includes: treating the upper surface of the SiCxNy layer with H2 plasma to reduce the interface defects between the SiCxNy layer and the silicon nitride layer; the power of the H2 plasma treatment is 80-150W, the time is 20-50s, and the flow rate of H2 is 10-15sccm.

9. The application of the anti-ultraviolet fading front composite passivation antireflection film layer according to any one of claims 1-6, characterized in that, The aforementioned front composite passivation antireflection film is applied to photovoltaic cells.

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