Solar cell, preparation method thereof and photovoltaic module

Abstract

The invention discloses a solar cell, a preparation method thereof and a photovoltaic module, and relates to the field of photovoltaic technology. The solar cell comprises an ultraviolet cut-off layer, a first doped silicon layer, a silicon substrate, a tunneling layer and a second doped silicon layer which are sequentially stacked, and the ultraviolet cut-off layer comprises an aluminum nitride layer. The solar cell further comprises a first electrode and a second electrode, the first electrode is connected to the first doped silicon layer, and the second electrode is connected to the second doped silicon layer. In the embodiment of the invention, the ultraviolet cut-off layer comprises the aluminum nitride layer, so that the damage of high-energy deep ultraviolet light to the silicon substrate can be effectively blocked, the anti-UV attenuation performance of the solar cell is improved, and meanwhile, the photoelectric conversion efficiency is also improved.

Description

Technical Field

[0001] This application relates to the field of photovoltaic technology, and more specifically, to a solar cell, a method for its fabrication, and a photovoltaic module. Background Technology

[0002] As the global energy structure shifts towards solar photovoltaic power generation, market demand for module power continues to rise. The problem of ultraviolet-induced degradation (UV degradation) in N-type cells poses a serious threat to product quality and market competitiveness. The impact of UV degradation on photovoltaic cells is mainly reflected in three aspects: high-energy ultraviolet light cannot be effectively utilized, leading to reduced power generation efficiency; the physicochemical reactions induced by ultraviolet light are accompanied by photothermal effects, and excessive heat accelerates the aging and damage of cell materials; and ultraviolet-induced oxidation reactions lead to cell corrosion and damage.

[0003] Currently, the mainstream solutions to address the UV degradation problem in tunneling oxide passivated contact (TOPCon) batteries include using multilayer antireflective coatings (such as silicon nitride / silicon oxynitride / alumina composite films). These solutions improve the UV resistance of TOPCon batteries by increasing the alumina layer thickness and adjusting the refractive index of silicon nitride. However, these measures inevitably lead to efficiency losses such as hydrogen passivation loss, reduced effective minority carrier lifetime, and photocurrent loss, while also raising reliability concerns. Therefore, improving the UV degradation effect of TOPCon batteries has become a key challenge restricting the lifespan of advanced N-type TOPCon battery products, and the industry urgently needs to overcome these technological bottlenecks. Summary of the Invention

[0004] The purpose of this application is to provide a solar cell, a method for its fabrication, and a photovoltaic module, which can effectively improve the UV degradation problem of solar cells, maintain high photoelectric conversion efficiency, and have better reliability.

[0005] The embodiments of this application can be implemented as follows: In a first aspect, this application provides a solar cell, comprising an ultraviolet cutoff layer, a first doped silicon layer, a silicon substrate, a tunneling layer, and a second doped silicon layer stacked sequentially, wherein the ultraviolet cutoff layer includes an aluminum nitride layer, and the solar cell further includes a first electrode and a second electrode, the first electrode being connected to the first doped silicon layer, and the second electrode being connected to the second doped silicon layer.

[0006] In an optional embodiment, the ultraviolet cutoff layer further includes an aluminum oxide layer, with an aluminum nitride layer disposed on the side of the aluminum oxide layer opposite to the first doped silicon layer.

[0007] In an optional embodiment, the thickness of the alumina layer is 2nm to 8nm.

[0008] In an optional implementation, the thickness of the aluminum nitride layer is 2 nm to 5 nm.

[0009] In an optional embodiment, the solar cell further includes a first antireflection layer and a second antireflection layer, wherein the first antireflection layer is disposed on the side of the ultraviolet cutoff layer opposite to the first doped silicon layer, and the second antireflection layer is disposed on the side of the second doped silicon layer opposite to the tunneling layer.

[0010] In an optional implementation, the thickness of the first antireflection layer is 60 nm to 90 nm; And / or, the thickness of the second antireflective layer is 60nm~90nm.

[0011] In an optional embodiment, the materials of the first antireflection layer and the second antireflection layer are selected from one or more of silicon nitride, silicon oxynitride, and silicon oxide.

[0012] In an optional embodiment, the silicon substrate is N-type single-crystal silicon, the first doped silicon layer is a boron diffusion layer, and the second doped silicon layer is N-type doped polycrystalline silicon.

[0013] Secondly, this application provides a method for preparing a solar cell according to any of the foregoing embodiments, comprising: Obtaining a silicon substrate; A first doped silicon layer is fabricated on the front side of a silicon substrate, and a tunneling layer and a second doped silicon layer are fabricated on the back side of the silicon substrate. An ultraviolet cutoff layer is deposited on the first doped silicon layer, wherein the aluminum nitride layer in the ultraviolet cutoff layer is obtained by plasma-enhanced atomic layer deposition. A first electrode connected to a first doped silicon layer and a second electrode connected to a second doped silicon layer are fabricated.

[0014] In an optional embodiment, during the deposition of the aluminum nitride layer, the deposition temperature is 200℃~400℃, the pressure is 100pa~200pa, the deposition power is 8000w~12000w, and the reaction gases include trimethylaluminum and ammonia.

[0015] Thirdly, this application provides a photovoltaic module, including a solar cell of any of the embodiments of the first aspect, or a solar cell prepared by a method of preparing a solar cell of any of the embodiments of the second aspect.

[0016] The beneficial effects of the solar cells, their fabrication methods, and photovoltaic modules provided in this application include: The solar cell provided in this application embodiment includes a UV cutoff layer, a first doped silicon layer, a silicon substrate, a tunneling layer, and a second doped silicon layer stacked sequentially, wherein the UV cutoff layer includes an aluminum nitride layer. The solar cell also includes a first electrode and a second electrode, the first electrode being connected to the first doped silicon layer and the second electrode being connected to the second doped silicon layer. In this application embodiment, the UV cutoff layer includes an aluminum nitride layer with a bandgap of 6.2 eV, corresponding to a cutoff absorption wavelength of 200 nm. It intrinsically absorbs deep ultraviolet light below 200 nm and exhibits strong absorption in the 200-300 nm ultraviolet region, effectively blocking high-energy deep ultraviolet light from damaging the silicon substrate. This not only improves the solar cell's UV degradation resistance but also enhances its photoelectric conversion efficiency. Furthermore, the ultraviolet (UV) cutoff layer also includes an aluminum oxide layer. Aluminum nitride has a refractive index of 2.25–2.35 at a wavelength of 300 nm (UV), while aluminum oxide has a refractive index of 1.76–1.82 at the same wavelength. In the 300 nm–400 nm UV band, the aluminum nitride layer can match the refractive index of the aluminum oxide layer, creating a larger refractive index difference (up to 0.43–0.59), thus increasing the reflectivity of UV light. Moreover, aluminum nitride and aluminum oxide have similar coefficients of thermal expansion; therefore, the stress generated between the layers of the UV cutoff layer is lower when facing temperature changes, making it less susceptible to damage from thermal shock and thus exhibiting better reliability.

[0017] The method for preparing solar cells provided in this application is used to prepare the aforementioned solar cells, thus enabling the acquisition of solar cells with better UV degradation resistance. The photovoltaic module provided in this application includes the aforementioned solar cells, thus exhibiting better UV degradation resistance and maintaining high photoelectric conversion efficiency even after exposure to ultraviolet radiation. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of a solar cell in one embodiment of this application; Figure 2 This is a flowchart of a method for preparing a solar cell in one embodiment of this application.

[0020] Icons: 110 - Silicon substrate; 120 - First doped silicon layer; 130 - Tunneling layer; 140 - Second doped silicon layer; 150 - Ultraviolet cutoff layer; 151 - Alumina layer; 152 - Aluminum nitride layer; 160 - First antireflection layer; 170 - Second antireflection layer; 210 - First electrode; 220 - Second electrode. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0022] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0023] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0024] In the description of this application, it should be noted that if terms such as "upper," "lower," "inner," or "outer" are used to indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the invention is usually placed during use, they are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0025] Furthermore, the terms "first" and "second" are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0026] It should be noted that, where there is no conflict, the features in the embodiments of this application can be combined with each other.

[0027] Taking N-type TOPCon solar cells as an example, the mechanism of ultraviolet light-induced degradation mainly includes the following three points: (1) Passivation damage: Under ultraviolet irradiation, electrons in the conduction band of silicon (Si) are injected into the second tunneling layer (material is SiO2), resulting in a significant increase in recombination centers at the Si / SiO2 interface. This process directly destroys the suppression effect of the tunneling layer on charge carriers by changing the fixed charge density at the interface and increasing the defect density on the silicon surface, thereby reducing the minority carrier lifetime of the battery surface.

[0028] (2) Hot carriers destroy the passivation layer: High-energy photons generated by ultraviolet radiation excite valence band electrons to jump to the conduction band and above. The hot electrons formed break through the interface barrier due to their high mobility and energy and are injected into the interface, thereby destroying the passivation layer and increasing the interface state density.

[0029] (3) Chemical passivation loss: Ultraviolet light irradiation destroys the Si-H bonds at the interface, triggering secondary hydrogen distribution, excessive generation of surface hydrogen atom groups, and aggravating carrier recombination.

[0030] To improve the problem of ultraviolet light-induced degradation in batteries, existing technologies typically employ multilayer antireflective coatings (such as SiN). x / Si x O y The N / Al2O3 composite film improves the UV resistance of TOPCon cells by increasing the thickness of the alumina layer and adjusting the refractive index of silicon nitride. Silicon nitride (SiN...) x The band gap of silicon oxynitride (SiO2) is approximately 3.8 eV to 4.2 eV. It mainly absorbs ultraviolet light with wavelengths <350 nm, while its absorption rate of UV light in the 350 nm to 400 nm band is only relatively low. x O y The band gap of nitrogen (N) varies with oxygen content (3.5 eV~4.0 eV), exhibiting limited absorption of ultraviolet light near 365 nm. Furthermore, oxygen defects in the film can lead to absorption peaks in the 280 nm~320 nm band, potentially triggering photodegradation of the film itself. While alumina (Al2O3) has a band gap of 6.0 eV, pure Al2O3 films absorb less than 10% of ultraviolet light in the 300 nm~400 nm range. This absorption primarily relies on photochemical reactions of hydroxyl (-OH) groups under ultraviolet light, but this reaction leads to the consumption of hydroxyl groups, causing a gradual decrease in passivation performance after ultraviolet irradiation. Increasing the alumina thickness can enhance ultraviolet absorption, thereby reducing UV damage to the silicon surface and improving the battery's UV degradation resistance. However, the large amount of hydrogen in the alumina film also poses a risk of film explosion, damaging the passivation layer and resulting in electrical performance loss.

[0031] To address at least one deficiency in the aforementioned related technologies, embodiments of this application provide a solar cell whose ultraviolet cutoff layer includes an aluminum oxide layer and an aluminum nitride layer, which can effectively absorb ultraviolet light, alleviate UV degradation of the solar cell, and also have better reliability.

[0032] Figure 1 This is a schematic diagram of a solar cell in one embodiment of this application. Figure 1 As shown, the solar cell provided in this embodiment includes a UV cutoff layer 150, a first doped silicon layer 120, a silicon substrate 110, a tunneling layer 130, and a second doped silicon layer 140 stacked sequentially. The UV cutoff layer 150 includes an aluminum nitride layer 152. The solar cell also includes a first electrode 210 and a second electrode 220, with the first electrode 210 connected to the first doped silicon layer 120 and the second electrode 220 connected to the second doped silicon layer 140.

[0033] Furthermore, the ultraviolet cutoff layer 150 also includes an aluminum oxide layer 151, and an aluminum nitride layer 152 is disposed on the side of the aluminum oxide layer 151 opposite to the first doped silicon layer 120.

[0034] Furthermore, the solar cell also includes a first antireflection layer 160 and a second antireflection layer 170. The first antireflection layer 160 is disposed on the side of the ultraviolet cut-off layer 150 opposite to the first doped silicon layer 120, and the second antireflection layer 170 is disposed on the side of the second doped silicon layer 140 opposite to the tunneling layer 130. The first antireflection layer 160 and the second antireflection layer 170 are located on the outermost side of the solar cell and serve a protective function. At the same time, the antireflection layers can reduce the reflection of external light after it hits the surface of the solar cell, thereby allowing more light to enter the interior of the solar cell to participate in photoelectric conversion, thus improving the efficiency of the solar cell.

[0035] In this embodiment, the solar cell is a tunneling oxide passivated contact cell, also known as a TOPCon cell. Specifically, the silicon substrate 110 is N-type monocrystalline silicon, the first doped silicon layer 120 is a boron diffusion layer, and the second doped silicon layer 140 is N-type doped polycrystalline silicon (such as phosphorus doped silicon).

[0036] In this embodiment, the tunneling layer 130 is silicon oxide. The core function of the tunneling layer 130 in the TOPCon cell is to achieve efficient selective carrier transport through the quantum tunneling effect, while providing excellent surface passivation to reduce unnecessary electron-hole recombination. Furthermore, it works synergistically with the doped polycrystalline silicon layer to form an optimized charge-selective contact structure, thereby significantly improving the cell's photoelectric conversion efficiency and long-term stability.

[0037] Optionally, the materials of the first antireflection layer 160 and the second antireflection layer 170 are selected from one or more of silicon nitride, silicon oxynitride, and silicon oxide. For example, the first antireflection layer 160 includes a silicon nitride layer, a silicon oxynitride layer, and a silicon oxide layer stacked sequentially, wherein the silicon nitride layer is connected to the ultraviolet cutoff layer 150, the silicon oxynitride layer is disposed on the side of the silicon nitride layer opposite to the ultraviolet cutoff layer 150, and the silicon oxide layer is disposed on the side of the silicon oxynitride layer opposite to the silicon nitride layer.

[0038] Furthermore, the structure of the second antireflection layer 170 can be consistent with the structure of the first antireflection layer 160. Optionally, in the second antireflection layer 170, the silicon nitride layer, the silicon oxynitride layer, and the silicon oxide layer are stacked sequentially from the direction closest to the silicon substrate 110 to the direction furthest from the silicon substrate 110.

[0039] In this embodiment, the aluminum nitride layer 152 in the ultraviolet cutoff layer 150 has a bandgap of 6.2 eV, corresponding to a cutoff absorption wavelength of 200 nm. It intrinsically absorbs deep ultraviolet light below 200 nm and exhibits strong absorption of ultraviolet light in the 200 nm to 300 nm range. This effectively blocks high-energy deep ultraviolet light from damaging the aluminum oxide layer 151 and the silicon substrate 110, improving both the UV degradation resistance of the solar cell and the photoelectric conversion efficiency. The refractive index of aluminum nitride at 300 nm (ultraviolet) is 2.25–2.35, and that of aluminum oxide at 300 nm (ultraviolet) is 1.76–1.82. The reflectivity R can be calculated using the Fresnel formula: R = ((n2-n1) / (n2+n1)). 2 Where n2 is the refractive index of aluminum nitride and n1 is the refractive index of aluminum oxide. In the ultraviolet band of 300nm~400nm, the aluminum nitride layer 152 can match the refractive index of the aluminum oxide layer 151 to form a large refractive index difference (up to 0.43~0.59), which can increase the reflectivity of ultraviolet light and reduce the ultraviolet light entering the silicon substrate 110, thereby improving the resistance to UV attenuation and reducing the performance degradation caused by UV attenuation.

[0040] In this application, the aluminum oxide layer 151 is located between the aluminum nitride layer 152 and the first doped silicon layer 120, and is in direct contact with the first doped silicon layer 120, so that the aluminum oxide layer 151 can fully exert the field passivation effect (alumina field passivation can act within 2nm of the silicon surface). If the positions of the aluminum oxide layer 151 and the aluminum nitride layer 152 are interchanged, the field passivation of the aluminum oxide layer 151 will fail, and the electrical performance will be reduced.

[0041] When the first antireflective layer 160 comprises a silicon nitride layer, a silicon oxynitride layer, and a silicon oxide layer stacked sequentially, the aluminum nitride layer 152 can contact the silicon nitride layer in the first antireflective layer 160. For a wavelength of 589 nm (visible light), aluminum nitride has a refractive index of 2.1 to 2.2, and silicon nitride (SiN...)...x The refractive index is 1.85~2.2 (varying with x value). The refractive indices of aluminum nitride and silicon nitride are close in the visible light region and have overlapping intervals, which can form gradient matching, reduce the reflection loss of visible light at the film interface, and thus allow more visible light to enter the solar cell, thereby improving the photoelectric conversion efficiency.

[0042] Furthermore, aluminum nitride is deposited at around 300℃, exhibits a polycrystalline hexagonal wurtzite structure, and has a preferred orientation along the c-axis (perpendicular to the substrate). Its coefficient of thermal expansion in the direction parallel to the c-axis is 5.3 × 10⁻⁶. -6 / ℃. Alumina is deposited at temperatures around 250℃~300℃, is amorphous, and has a coefficient of thermal expansion of 5×10⁻⁶. -6 / ℃~6×10 -6 The specific value (°C) depends on the crystal phase, thickness, defects, and substrate material, and can be adjusted through process parameters. It is evident that aluminum nitride and aluminum oxide have similar coefficients of thermal expansion. Therefore, when facing temperature changes, the stress generated between the UV cutoff layer 150 is relatively low, making it less susceptible to damage from thermal shock. This results in better reliability and contributes to a longer lifespan for solar cells.

[0043] Optionally, the thickness of the alumina layer 151 is 2nm to 8nm, such as any value or any two values ​​between 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, and 8nm; optionally, the thickness of the aluminum nitride layer 152 is 2nm to 5nm, such as any value or any two values ​​between 2nm, 3nm, 4nm, and 5nm. The aluminum nitride layer 152 is the core film layer for ultraviolet (UV) cutoff. If it is too thin, it cannot effectively cut off UV radiation; however, if it is too thick, the slurry will not easily corrode through this film during electrode sintering, resulting in poor contact between the electrode and the doped silicon layer, leading to a significant decrease in electrical performance. Therefore, the film thicknesses of the alumina layer 151 and the aluminum nitride layer 152 must be adjusted reasonably while ensuring no impact on electrical performance. In a specific embodiment, the thickness of the alumina layer 151 is 2.8nm, and the thickness of the aluminum nitride layer 152 is 2nm. Optionally, the thickness of both the first antireflection layer 160 and the second antireflection layer 170 can be 60nm~90nm.

[0044] In this embodiment, the first electrode 210 and the second electrode 220 can be made of metals or alloys with excellent conductivity, such as copper, silver, and molybdenum.

[0045] Figure 2 This is a flowchart illustrating a method for fabricating a solar cell in one embodiment of this application. Figure 2 As shown in the embodiments of this application, the method for fabricating a solar cell includes: Step S100: Obtain silicon substrate 110.

[0046] In this embodiment, a wet texturing process can be used to form a textured surface on the silicon substrate 110, which is then cleaned before subsequent film preparation.

[0047] In step S200, a first doped silicon layer 120 is formed on the front side of the silicon substrate 110, and a tunneling layer 130 and a second doped silicon layer 140 are formed on the back side of the silicon substrate 110.

[0048] High-temperature boron diffusion can be performed on the front side of the silicon substrate 110 to form a first doped silicon layer 120. The back side of the silicon substrate 110 is etched to remove the borosilicate glass (BSG) formed by the boron diffusion process and the winding diffusion, and then a tunneling layer 130 and a second doped silicon layer 140 can be fabricated on the back side of the silicon substrate 110.

[0049] Optionally, the tunneling layer 130 is prepared using plasma-enhanced chemical vapor deposition (PECVD); optionally, in the preparation process of the tunneling layer 130, the nitrous oxide flow rate is 5000 sccm~20000 sccm, the pressure is 100~500 Pa, and the radio frequency power is 5000~20000 W.

[0050] Optionally, the second doped silicon layer 140 is prepared using plasma-enhanced chemical vapor deposition (PECVD). Optionally, in the preparation process of the second doped silicon layer 140, the silane flow rate is 1000 sccm~5000 sccm, the hydrogen flow rate is 5000 sccm~20000 sccm, the phosphine flow rate is 100 sccm~2000 sccm, the pressure is 100 Pa~500 Pa, the RF power is 5000 W~20000 W, and the phosphorus doping concentration is 1 × 10⁻⁶. 20 atoms / cm 3 ~1×10 22 atoms / cm 3 .

[0051] After the second doped silicon layer 140 is fabricated, it can be annealed at 850℃~920℃ for 30min~60min to activate the phosphorus doping in the second doped silicon layer 140.

[0052] Optionally, after the second doped silicon layer 140 is fabricated, a wet process can be used to remove the phosphosilicate glass (PSG) on the front and sides.

[0053] In step S300, an ultraviolet cutoff layer 150 is deposited on the first doped silicon layer 120, wherein the aluminum nitride layer 152 in the ultraviolet cutoff layer 150 is obtained by plasma-enhanced atomic layer deposition.

[0054] Further, step S300 specifically includes depositing an aluminum oxide layer 151 on the first doped silicon layer 120 by atomic layer deposition process, and depositing an aluminum nitride layer 152 on the aluminum oxide layer 151 by plasma-enhanced atomic layer deposition process to form an ultraviolet cutoff layer 150.

[0055] In this embodiment, an atomic layer deposition (ALD) process can be used to prepare a thin, uniform, and dense alumina layer 151. Especially in the case of a textured surface, the ALD process can ensure that the thickness of the alumina layer 151 is uniform at the grooves and peaks of the textured surface. The ALD process can achieve atomic-level thickness control, with the film thickness determined only by the number of reaction cycles, with precision down to the angstrom level. When the required thickness of the alumina layer 151 is extremely thin, this precision allows for optimization of the optimal alumina layer 151 thickness to achieve the best field-effect passivation and chemical passivation effects.

[0056] In this embodiment, a thin, uniform, and dense aluminum nitride layer 152 can be prepared using plasma-enhanced atomic layer deposition (PEALD). This process is applicable to multiple gas sources (providing various precursors), enabling high-efficiency deposition with minimal damage to the substrate. PEALD allows for precise thickness control, producing films with uniform thickness, clear interfaces, and extremely high quality, thus achieving precise ultraviolet light cutoff.

[0057] Optionally, in the process of preparing aluminum nitride layer 152 using plasma-enhanced atomic layer deposition, the deposition temperature is 200℃~400℃, the pressure is 100pa~200pa, the deposition power is 8000w~12000w, and the reaction gases are trimethylaluminum (TMA) and ammonia (NH3).

[0058] After the UV cutoff layer 150 is deposited, a PECVD process can be used to fabricate a first antireflection layer 160 on the front side and a second antireflection layer 170 on the back side. Optionally, the fabrication method of the antireflection layer includes sequentially fabricating a silicon nitride layer, a silicon oxynitride layer, and a silicon oxide layer to obtain the first antireflection layer 160 and the second antireflection layer 170 of the composite layer structure.

[0059] Step S400: Fabricate a first electrode 210 connected to the first doped silicon layer 120 and a second electrode 220 connected to the second doped silicon layer 140.

[0060] Optionally, a first electrode 210 and a second electrode 220 are formed by screen printing and sintering. The first electrode 210 burns through the first antireflection layer 160 and the ultraviolet cutoff layer 150, thereby connecting to the first doped silicon layer 120; the second electrode 220 burns through the second antireflection layer 170, thereby connecting to the second doped silicon layer 140.

[0061] In this embodiment, by using an aluminum nitride layer 152 as part of the UV cutoff layer 150 in the TOPCon cell and optimizing the deposition process of the aluminum nitride layer 152, the degradation problem of existing solar cells under UV irradiation can be improved, enhancing the cell's UV degradation resistance, interface stability, and photoelectric conversion efficiency. The high hardness, chemical stability, and optical properties of aluminum nitride make it an ideal material for the UV cutoff layer 150. Combined with optimized fabrication processes and interface treatment methods, the performance of the solar cell is enhanced.

[0062] The table below compares the performance of the solar cells in Examples 1-4 of this application with that of Comparative Example 1. In Examples 1-4, the thicknesses of the aluminum nitride layer 152 in the UV cutoff layer 150 are 2 nm, 3 nm, 4 nm, and 5 nm, respectively, and the thickness of the aluminum oxide layer 151 is 5 nm in all examples. All other structural parameters and fabrication processes are identical. Comparative Example 1 uses only aluminum oxide as the UV cutoff layer, with a thickness of 7 nm. The specific testing method is as follows: After testing the cell efficiency Eta, the cells are simultaneously placed in a UV light test chamber, and the UV conditions are set to an irradiance of 600 W / m² according to the IEC (International Electrotechnical Commission) UV30 test standard. 2 The irradiation temperature was 40°C, and the cumulative irradiation was 30 kW·h. After the experiment, the battery efficiency of each embodiment and comparative example will be tested.

[0063]

[0064] By comparing and analyzing the relevant data in the table above, it can be seen that by using a combination of alumina layer 151 and aluminum nitride layer 152 as the ultraviolet cutoff layer 150, the UV30 degradation of the solar cell can be reduced to as low as 0.8%. Compared with the traditional scheme (Comparative Example 1), the UV degradation rate is reduced by 25% after using aluminum nitride layer 152. Therefore, it can be seen that the solar cell provided in this application can effectively improve the UV degradation problem, improve the UV resistance of the solar cell, and enable the solar cell to maintain high photoelectric conversion efficiency after UV irradiation.

[0065] This application also provides a photovoltaic module (not shown in the figure), which includes the solar cell provided in the above embodiments.

[0066] In summary, the solar cell provided in this application embodiment includes a UV cutoff layer 150, a first doped silicon layer 120, a silicon substrate 110, a tunneling layer 130, and a second doped silicon layer 140 stacked sequentially. The UV cutoff layer 150 includes an aluminum nitride layer 152. The solar cell also includes a first electrode 210 and a second electrode 220, with the first electrode 210 connected to the first doped silicon layer 120 and the second electrode 220 connected to the second doped silicon layer 140. In this application embodiment, the UV cutoff layer 150 includes an aluminum nitride layer 152. The aluminum nitride has a bandgap of 6.2 eV, corresponding to a cutoff absorption wavelength of 200 nm. It intrinsically absorbs deep ultraviolet light below 200 nm and exhibits strong absorption in the 200 nm to 300 nm ultraviolet region, effectively blocking high-energy deep ultraviolet light from damaging the aluminum oxide layer 151 and the silicon substrate 110. This not only improves the solar cell's UV degradation resistance but also enhances its photoelectric conversion efficiency. Furthermore, the ultraviolet cutoff layer 150 also includes an aluminum oxide layer 151. Aluminum nitride has a refractive index of 2.25–2.35 at a wavelength of 300 nm (ultraviolet), while aluminum oxide has a refractive index of 1.76–1.82 at the same wavelength. In the 300 nm–400 nm ultraviolet band, the aluminum nitride layer 152 can match the refractive index of the aluminum oxide layer 151, creating a larger refractive index difference (up to 0.43–0.59), which increases the reflectivity of ultraviolet light. Moreover, aluminum nitride and aluminum oxide have similar coefficients of thermal expansion; therefore, when faced with temperature changes, the stress generated between the film layers of the ultraviolet cutoff layer 150 is low, making it less susceptible to damage from thermal shock and thus exhibiting good reliability.

[0067] The method for preparing solar cells provided in this application is used to prepare the aforementioned solar cells, thus enabling the acquisition of solar cells with better UV degradation resistance. The photovoltaic module provided in this application includes the aforementioned solar cells, thus exhibiting better UV degradation resistance and maintaining high photoelectric conversion efficiency even after exposure to ultraviolet radiation.

[0068] 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 scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. A solar cell, characterized in that, The solar cell includes a UV cutoff layer, a first doped silicon layer, a silicon substrate, a tunneling layer, and a second doped silicon layer stacked sequentially. The UV cutoff layer includes an aluminum nitride layer. The solar cell also includes a first electrode and a second electrode, with the first electrode connected to the first doped silicon layer and the second electrode connected to the second doped silicon layer.

2. The solar cell according to claim 1, characterized in that, The ultraviolet cutoff layer further includes an aluminum oxide layer, and the aluminum nitride layer is disposed on the side of the aluminum oxide layer opposite to the first doped silicon layer.

3. The solar cell according to claim 2, characterized in that, The thickness of the alumina layer is 2nm~8nm.

4. The solar cell according to claim 1, characterized in that, The thickness of the aluminum nitride layer is 2nm~5nm.

5. The solar cell according to claim 1, characterized in that, The solar cell further includes a first antireflection layer and a second antireflection layer. The first antireflection layer is disposed on the side of the ultraviolet cutoff layer opposite to the first doped silicon layer, and the second antireflection layer is disposed on the side of the second doped silicon layer opposite to the tunneling layer.

6. The solar cell according to claim 5, characterized in that, The thickness of the first antireflective layer is 60nm~90nm; And / or, the thickness of the second antireflective layer is 60nm~90nm.

7. The solar cell according to claim 5, characterized in that, The materials of the first antireflection layer and the second antireflection layer are selected from one or more of silicon nitride, silicon oxynitride and silicon oxide.

8. A method for preparing a solar cell according to any one of claims 1-7, characterized in that, include: Obtaining a silicon substrate; A first doped silicon layer is formed on the front side of the silicon substrate, and a tunneling layer and a second doped silicon layer are formed on the back side of the silicon substrate. An ultraviolet cutoff layer is deposited on the first doped silicon layer, wherein the aluminum nitride layer in the ultraviolet cutoff layer is obtained by plasma-enhanced atomic layer deposition. A first electrode is fabricated that is connected to the first doped silicon layer and a second electrode is fabricated that is connected to the second doped silicon layer.

9. The method for preparing a solar cell according to claim 8, characterized in that, During the deposition of the aluminum nitride layer, the deposition temperature is 200℃~400℃, the pressure is 100pa~200pa, the deposition power is 8000w~12000w, and the reaction gases include trimethylaluminum and ammonia.

10. A photovoltaic module, characterized in that, The solar cell includes any one of claims 1-7, or the solar cell prepared by the method of claim 8 or 9.

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