A back electrode for perovskite photovoltaic devices and a preparation method and application thereof

Abstract

This invention provides a back electrode for perovskite photovoltaic devices, its fabrication method, and its application, belonging to the field of perovskite photovoltaic device technology. The fabrication method of this invention includes the following steps: depositing an ITO buffer layer using a first gradient magnetron sputtering method, which includes a first initial deposition stage and a first main deposition stage performed sequentially, with the operating voltage decreasing and the sputtering power increasing sequentially in the first initial deposition stage and the first main deposition stage; and depositing an electrode layer on the ITO buffer layer. This invention improves upon the problems of damage to perovskite devices and metal diffusion in the electrode layer caused by existing magnetron sputtering processes through a gradient "soft landing" deposition process.

Description

Technical Field

[0001] This invention relates to the field of perovskite photovoltaic device technology, specifically to a back electrode for perovskite photovoltaic devices, its preparation method, and its application. Background Technology

[0002] Perovskite solar cells (PSCs), as representatives of third-generation photovoltaic technology, have received widespread attention in recent years due to their excellent photoelectric conversion efficiency and low manufacturing cost. In the device structure of perovskite cells, the back electrode plays a crucial role in collecting charge carriers and transporting them to the external circuit.

[0003] Currently, high-efficiency perovskite solar cells are typically fabricated in the laboratory using thermal evaporation processes to deposit gold (Au) or silver (Ag) as the back electrode. However, thermal evaporation equipment is expensive, material utilization is low, and the cost of precious metals is high, making it unsuitable for large-scale industrial production. Magnetron sputtering technology, due to its ability to deposit uniform films over large areas, strong adhesion, high material utilization, and ease of roll-to-roll production, is considered the preferred electrode fabrication technology for the industrialization of perovskite solar cells. Meanwhile, using inexpensive metals such as copper (Cu) and aluminum (Al) to replace gold and silver is also an inevitable trend towards cost reduction.

[0004] However, directly applying magnetron sputtering technology to the fabrication of perovskite solar cell back electrodes faces two major challenges: 1. High-energy particle damage: During magnetron sputtering, target atoms, reflected neutral particles, and high-energy ions (such as Ar) in the plasma can cause damage. + Or O - This bombardment carries high kinetic energy and bombards the substrate. Such bombardment can directly damage the fragile organic hole transport layer (such as Spiro-OMeTAD) or electron transport layer, and may even penetrate the transport layer to damage the perovskite crystal structure underneath, leading to increased interface defects, device short circuits, or a significant decrease in the fill factor (FF).

[0005] 2. Metal diffusion and chemical reaction: Inexpensive metals (such as Cu and Al) and noble metals such as silver (Ag) have high activity during sputtering and can easily diffuse into the perovskite layer, reacting with halide ions (such as forming AgI or CuI), leading to a rapid degradation of device performance.

[0006] In existing technologies, increasing the thickness of the transport layer or depositing a thicker oxide layer is usually used to resist sputtering damage, but this often increases the series resistance and reduces the battery efficiency.

[0007] For example, Chinese patent document CN120166901A discloses a wide-bandgap perovskite solar cell and its fabrication method. This perovskite solar cell includes, from bottom to top, an ITO layer, a hole transport layer, a perovskite light-absorbing film, a PEAI post-treatment salt, and a C layer. 60 The system consists of an electron transport layer, a SnO2 electron transport layer, an ITO transparent conductive electrode, and metal gate lines. The sputtering power of the ITO transparent conductive electrode is set to 50-300 W, the deposition thickness to 80-150 nm, the corresponding sputtering time to 10-30 min, and the total gas pressure to 0.3-1.0 Pa. Silver metal gate lines are deposited with a thickness of 60-200 nm using a stepped rate control; as the metal deposition thickness increases, only the rate (Å / s) is adjusted. -1 The steps are repeated sequentially. This method has the following problems: (1) ITO transparent conductive electrode 80-150nm. Excessively thick ITO layer is prone to deviating its work function from the ideal value due to factors such as stress and crystallinity changes, which will cause energy level mismatch between it and the adjacent charge transport layer. This will hinder the effective extraction of photogenerated carriers (electrons or holes), increase interfacial recombination, and directly lead to a decrease in the open circuit voltage and fill factor of the battery. Magnetron sputtering deposition of ITO is a relatively time-consuming process. Thicker ITO films require even longer sputtering times, which directly reduces equipment throughput. For industrial production, maintaining a high production cycle (e.g., processing thousands of cells per hour) is crucial. Excessively long process times cannot meet the demands of efficient roll-to-roll continuous production processes and also waste expensive targets: ITO targets contain expensive indium metal, and depositing thicker films means higher target consumption and raw material costs. The utilization rate of traditional planar targets is inherently low (approximately 20-30%), and over-deposition exacerbates this waste.

[0008] (2) ITO is sputtered with a power of 50-300W and a time of 10-30min. The low-power, gentle deposition may reduce ionic damage to the film and achieve better crystallinity and electrical properties. However, in actual industrial production, the "overall loss rate" needs to be calculated. For example, frequent opening and closing of the chamber and long-term vacuuming are not only inefficient, but also increase the risk of water and oxygen contamination from vacuum breakage, leading to a decrease in the batch qualification rate of products, which is a more serious "loss". Therefore, low-power, long-time sputtering processes are not suitable for industrial production lines.

[0009] (3) Perovskite substrates are extremely sensitive to high-energy particle bombardment. If the particle energy is too high during the initial deposition, it will directly destroy the crystal structure, leading to interface defects and seriously affecting device performance. Therefore, the primary goal of the process is "low damage". However, deposition with too low energy will result in a loose film, poor adhesion, and high resistivity, which contradicts the quality requirements of "high conductivity and high density" required for the back electrode. The above scheme only controls the rate, which is the ratio of thickness to time, and only indicates the speed of production. It has little to do with kinetic energy or bombardment damage.

[0010] Therefore, developing a back electrode fabrication process that can effectively block sputtering damage and metal diffusion while maintaining low contact resistance is key to promoting the industrialization of perovskite batteries. Summary of the Invention

[0011] In view of this, the present invention provides a back electrode for perovskite photovoltaic devices, a method for its fabrication, and its application. By using a gradient "soft landing" deposition process, the present invention improves the problems of damage to perovskite devices and metal diffusion in the electrode layer caused by existing magnetron sputtering processes.

[0012] To achieve the above objectives, the present invention provides a method for fabricating a back electrode for a perovskite photovoltaic device, comprising the following steps: An ITO buffer layer is deposited using a first gradient magnetron sputtering method, which includes a first initial deposition stage and a first main deposition stage performed sequentially. The operating voltage decreases sequentially and the sputtering power increases sequentially in the first initial deposition stage and the first main deposition stage. An electrode layer is deposited on the ITO buffer layer.

[0013] Sputtering power is primarily used to control the sputtering rate and initial particle energy. Working pressure is primarily used to control plasma density and particle scattering effects. The deposition of the ITO buffer layer in this invention is achieved through dual regulation of sputtering power and working pressure.

[0014] The first initial deposition stage uses high working pressure to increase the collision frequency between particles, which significantly reduces the kinetic energy of sputtered particles reaching the substrate. Combined with low power to reduce plasma density, this achieves a "soft landing" of the deposited atoms, avoiding physical breakdown of the underlying perovskite structure and forming a protective layer to facilitate subsequent dense deposition.

[0015] The first substrate deposition stage employs a lower operating pressure and a higher sputtering power. Lowering the operating pressure reduces particle scattering and increases the mean free path, allowing more high-energy particles to directly reach the growth surface. At this point, on the protected substrate, the higher particle energy and increased deposition rate actually promote film densification, grain growth, and crystallization, thereby significantly reducing the bulk resistance of the film and obtaining electrodes with high conductivity.

[0016] By coordinating the first initial deposition stage and the first main deposition stage, damage to the underlying perovskite structure is avoided by magnetron sputtering, and the diffusion of metal atoms from the subsequent electrode layer into the perovskite layer is blocked. At the same time, while meeting the performance requirements of perovskite photovoltaic devices, the thickness of the ITO buffer layer is reduced, making it suitable for industrial production lines.

[0017] Furthermore, an electrode layer is deposited using a second-gradient magnetron sputtering method; The second gradient magnetron sputtering method includes a second initial deposition stage and a second main deposition stage performed sequentially. The working gas pressure decreases sequentially in the second initial deposition stage and the second main deposition stage, and the sputtering power increases sequentially in the second main deposition stage.

[0018] On a substrate already protected by an ITO buffer layer, higher particle energy and increased deposition rate actually promote film densification, grain growth, and crystallization, thereby significantly reducing the bulk resistance of the film and obtaining electrodes with high conductivity. Using a second-gradient magnetron sputtering method to deposit the electrode layer facilitates better contact between the electrode layer and the ITO buffer layer, reducing the likelihood of delamination.

[0019] Furthermore, there are n transition stages between the second initial deposition stage and the second main deposition stage, where n is an integer ≥1. The sputtering power of the transition stages is between the sputtering power of the second initial deposition stage and the second main deposition stage. The operating voltage of the transition stages is not greater than the operating voltage of the second initial deposition stage and is less than that of the second main deposition stage.

[0020] The transition phase is used for a smooth transition between the initial deposition phase and the main deposition phase. The number of transition phases, n, can be set as needed.

[0021] Furthermore, the thickness of the ITO buffer layer is 2-40 nm.

[0022] With a thickness range of 2-40nm, the ITO buffer layer is made ultra-thin without affecting battery performance, while still meeting the requirement of physically isolating and blocking metal diffusion and its chemical reactions.

[0023] Furthermore, in the first initial deposition stage, an ITO planar target is driven by an RF power supply with a sputtering power of 0.3-0.5 kW and an operating pressure of 0.6-0.8 Pa. An Ar / O2 mixed gas is used, with an O2 volume content of 0.2-0.3% and a background vacuum ≤5×10⁻⁶. -4 Pa; First substrate deposition stage: The ITO rotating target is driven by a DC power supply, with a sputtering power of 0.8-1.0 kW and an operating pressure of 0.3-0.5 Pa. An Ar / O2 mixed gas is used, with an O2 volume content of 0.2-0.3% in the mixed gas, and a background vacuum ≤5×10⁻⁶. -4Pa.

[0024] By controlling the oxygen partial pressure, sputtering power, and working gas pressure, it is easier to form an ultrathin ITO layer, and it also avoids long sputtering times, making it more suitable for continuous industrial production.

[0025] Furthermore, the deposition thickness of the first initial deposition stage is 2-20 nm; the deposition thickness of the first main deposition stage is 0-20 nm.

[0026] Furthermore, the second gradient magnetron sputtering method uses a DC power supply to drive a rotating target in an inert gas atmosphere; The working gas pressure for the second initial deposition stage is 0.5-1.0 Pa, and the sputtering power is 0.7-1.0 KW; the working gas pressure for the second main deposition stage is 0.3-0.5 Pa, and the sputtering power is 1.7-2.0 KW.

[0027] Inert gases such as Ar.

[0028] Furthermore, the thickness of the second initial deposition stage is 2-40 nm; the thickness of the second main deposition stage is 0-100 nm.

[0029] The above process parameters are set to adjust the particle kinetic energy to prevent high-energy conductive atoms, such as metal atoms, from penetrating the ultrathin ITO layer. Through the synergistic effect of the gradient sputtering process of the electrode layer and the ultrathin ITO buffer layer, the damage of gradient sputtering to the soft material substrate is minimized, while ensuring the performance of the perovskite solar cell.

[0030] The second initial deposition stage uses 0.5-1.0 Pa to reduce the mean free path of the particles, allowing some thermally heated metal atoms to deposit and form a loose but soft interface layer. The second bulk deposition stage uses 0.3-0.5 Pa to ensure the bulk density of the metal film, thereby achieving a low sheet resistance close to that of bulk metal. Simultaneously, the second initial stage employs a lower sputtering power, which imparts lower kinetic energy to the sputtered particles, allowing them to "soft-land" more gently on the fragile substrate, effectively reducing sputtering bombardment damage.

[0031] Furthermore, the electrode layer is a metal electrode layer, and the material of the metal electrode layer is one of copper (Cu), silver (Ag), aluminum (Al), gold (Au) or their alloys.

[0032] Furthermore, the rotating target is a Cu target.

[0033] The first initial deposition stage and the first main deposition stage can be performed continuously or in stages; the second initial deposition stage and the second main deposition stage can also be performed continuously or in stages. The deposition of the ITO buffer layer using the first gradient magnetron sputtering method and the deposition of the electrode layer using the second gradient magnetron sputtering method are performed continuously within the vacuum chamber of the same magnetron sputtering equipment, or in a connected chamber without disrupting the vacuum environment. To prevent oxygen introduced during ITO sputtering from affecting the pure Ar atmosphere for electron layer sputtering, multiple molecular pumps are installed between the ITO and Cu target locations to evacuate and purify the gas atmosphere, while also ensuring that the nearby working gas pressure remains stable; otherwise, achieving different gas pressures and atmospheres within the connected chamber would be very difficult.

[0034] A back electrode, prepared by the aforementioned preparation method, the back electrode comprising a gradient ITO buffer layer and an electrode layer disposed on the gradient ITO buffer layer.

[0035] Furthermore, the electrode layer is a gradient electrode layer.

[0036] The back electrode is used in a perovskite solar cell, wherein the perovskite solar cell includes a perovskite semi-finished device, and the back electrode is disposed on the upper side of the perovskite semi-finished device.

[0037] Furthermore, the perovskite semi-finished device includes, from bottom to top, a substrate, a hole transport layer, a perovskite light-absorbing layer, an electron transport layer, and a SnO2 layer, with the back electrode disposed on the upper side of the SnO2 layer.

[0038] The above-described technical solution of the present invention has at least the following beneficial effects: 1. Synergistic Protection Mechanism: This invention innovatively combines "structural buffering" and "process buffering." The ultrathin ITO layer acts as the first line of defense, physically isolating and blocking metal diffusion and chemical reactions in the electron layer; the gradient sputtering process acts as the second line of defense, adjusting particle kinetic energy to prevent metal atoms in the high-energy electron layer from penetrating the ultrathin ITO layer. The synergistic effect of these two mechanisms minimizes damage to the soft material substrate caused by magnetron sputtering.

[0039] 2. Suppressing Negative Ion Damage: In the first stage of ITO deposition, a process with low oxygen partial pressure or no additional oxygen introduction is specifically employed, and the deposition thickness is strictly limited. This solves the problem of negative oxygen ions bombarding and damaging the organic transport layer (C) under the acceleration of the sheath electric field in traditional oxide sputtering. 60 The challenges of the BCP / SnO2 structure were overcome, but the electron transport capability of the transport layer was preserved.

[0040] 3. Balancing low damage and high conductivity: Gradient sputtering resolves the contradictions inherent in single-parameter sputtering. Although the initial high-pressure, low-power layer has a slightly higher resistivity, it not only protects the substrate but also improves the interfacial bonding between the metal and ITO. The subsequent low-pressure, high-power layer provides the low-resistivity transport channels required for the electrodes. The final fabricated battery not only has a high fill factor (FF) but also a low series resistance (Rs).

[0041] 4. Improved device stability: The introduced ITO buffer layer is dense and chemically stable, which can effectively suppress the intrusion of external water and oxygen and the reaction between internal halide ions and metal electrodes, significantly improving the aging stability of perovskite cells with non-noble metal electrodes (such as Cu electrodes). Attached Figure Description

[0042] Figure 1 The PSCs prepared for Example 1 and Comparative Examples 1-2 V OC diagram; Figure 2 PCE plots of PSCs prepared in Example 1 and Comparative Examples 1-2; Figure 3 The PSCs prepared for Example 1 and Comparative Examples 1-2 J SC picture; Figure 4 The PSCs prepared for Example 1 and Comparative Examples 1-2 FF picture; Figure 5 Current density-voltage (V) of PSCs prepared for Comparative Example 2 J - V Characteristic curves; Figure 6 Current density-voltage (V) of PSCs prepared for Comparative Example 1 J - V Characteristic curves; Figure 7 Current density-voltage (V) of PSCs prepared in Example 1 J - V Characteristic curves; Figure 8 PCE decay curves of PSCs prepared in Example 1 and Comparative Examples 1-2 during continuous light aging (MPPT) process; Figure 9 Comparison of photoluminescence imaging (PL Mapping) of PSCs prepared in Example 1 and Comparative Examples 1-2 before and after continuous light aging. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0044] Take the preparation of a 5×10 cm² back electrode as an example.

[0045] Example 1 A method for fabricating the back electrode of a perovskite photovoltaic device includes the following steps: An ITO buffer layer was deposited using a first-gradient magnetron sputtering method. This method includes a first initial deposition stage and a first main deposition stage. The conditions for the magnetron sputtering in the first initial deposition stage were: an ITO planar target driven by an RF power supply, a sputtering power of 0.4 kW, an operating pressure of 0.7 Pa, an Ar / O2 mixed gas with an O2 content of 0.26%, and a background vacuum ≤5°C. 10 -4 Pa, thickness 10 nm; The magnetron sputtering conditions for the first bulk deposition stage were as follows: a DC power supply driving an ITO rotating target, a sputtering power of 0.9 kW, an operating pressure of 0.4 Pa, an Ar / O2 mixed gas with an O2 content of 0.26%, and a background vacuum ≤5. 10 -4 Pa, thickness 10 nm; Electrode layers were deposited on an ITO buffer layer using a second-gradient magnetron sputtering method. This method comprises a second initial deposition stage and a second main deposition stage. The second initial deposition stage involves preparing a Cu electrode layer using magnetron sputtering under the following conditions: a Cu rotating target, a DC power supply, a sputtering power of 0.8 kW, a pure Ar atmosphere, and a base vacuum ≤ 5 × 10⁻⁶. -4 Pa, working gas pressure about 0.6 Pa, thickness 10 nm, to obtain the initial Cu electrode layer; The second stage of substrate deposition: A substrate Cu electrode layer is deposited on the initial Cu electrode layer using magnetron sputtering to obtain the back electrode. The sputtering conditions are: Cu rotating target, DC power supply, sputtering power of 1.8 kW, pure Ar atmosphere, and background vacuum ≤ 5 × 10⁻⁶. -4 Pa, working pressure approximately 0.4 Pa, thickness 70 nm.

[0046] Comparative Example 1 This comparative example is basically the same as Example 1, except that it does not include an ITO buffer layer.

[0047] A method for fabricating the back electrode of a perovskite photovoltaic device includes the following steps: Electrode layers were deposited on an ITO buffer layer using a second-gradient magnetron sputtering method. This method includes a second initial deposition stage and a second main deposition stage. The second initial deposition stage involves preparing a Cu electrode layer using magnetron sputtering under the following conditions: a Cu rotating target, a DC power supply, a sputtering power of 0.8 kW, a pure Ar atmosphere, and a base vacuum ≤ 5 × 10⁻⁶. - 4 Pa, working pressure approximately 0.6 Pa, thickness 10 nm; The second stage of substrate deposition: A substrate Cu electrode layer is deposited on the initial Cu electrode layer using magnetron sputtering to obtain the back electrode. The sputtering conditions are: Cu rotating target, DC power supply, sputtering power of 1.8 kW, pure Ar atmosphere, and background vacuum ≤ 5 × 10⁻⁶. -4 Pa, working pressure approximately 0.4 Pa, thickness 90 nm.

[0048] Comparative Example 2 A method for fabricating a back electrode includes the following steps: fabricating a Cu conductive layer using magnetron sputtering. The sputtering conditions are: Cu rotating target, DC power supply, sputtering power 1.8 kW, pure Ar atmosphere, thickness 100 nm, and base vacuum ≤ 5 × 10⁻⁶. - 4 Pa, working air pressure is about 0.4 Pa.

[0049] To verify the effects of Example 1 and Comparative Examples 1-2, the back electrodes of Examples 1-2 and Comparative Examples were applied to perovskite solar cells.

[0050] A 5×10 cm² perovskite solar cell (pin structure) was conventionally fabricated and then tested. The specific fabrication method of the perovskite solar cell includes the following steps: (1) Preparation of hole transport layer a. Prepare solar cell substrate: Etch patterns on the transparent conductive glass substrate (ITO / glass) with a laser. After etching, clean it in sequence with cleaning solution, deionized water, ethanol and isopropanol, and dry it for later use. b. Using magnetron sputtering, NiOx was sputtered onto the etched conductive substrate. The sputtering conditions were: Ni planar palladium, DC power supply 200W, 25min, carrier gas flow rate Ar:O2=200:20 (sccm). After sputtering, the substrate was annealed at 300 °C for 30min.

[0051] (2) Set up a perovskite light-absorbing layer PbI₂, CH(NH₂)₂I, PbBr₂, and NH₃CH₃Br were dissolved in a solvent of DMF:NMP = 7:1 (volume ratio, where DMF is N,N-dimethylformamide and NMP is N-methylpyrrolidone) in a molar ratio of 1.1:1:0.22:0.2 to obtain the absorber layer precursor solution. The perovskite solution was then coated onto a substrate with a hole transport layer using a slit coating method. The specific details are as follows: pre-injection volume 40 μl, pre-injection speed 9 μl / s, coating speed 5 cm / s, injection speed 1.75 μl / s, and waiting time 2s; After coating, the material is immediately transferred to a vacuum crystallization apparatus and crystallized at 20 Pa for 1 min. After removal, it is treated at 150 °C for 10 min to obtain a perovskite light-absorbing layer.

[0052] (3) Set up an electronic transport layer C 60 The light-absorbing layer was deposited on the perovskite using a vacuum thermal evaporation method, with a thickness of 20 nm.

[0053] (4) Set up a SnO2 buffer layer A SnO2 buffer layer with a thickness of approximately 20 nm was prepared on the electron transport layer using atomic layer deposition (ALD) technology.

[0054] (5) The back electrode layer is prepared using the preparation method of Example 1, Comparative Example 1 or Comparative Example 2.

[0055] The performance of the prepared perovskite solar cells was tested.

[0056] Depend on Figure 2 It can be seen that, compared with the battery using the back electrode of Comparative Example 2, the photoelectric conversion efficiency (PCE) of the battery using the back electrode of Example 1 is increased from 18.32% to 19.93%.

[0057] Depend on Figure 1-4 It can be seen that, compared with the batteries with back electrodes in Comparative Examples 1 and 2, the fill factor (FF) of the battery with the back electrode in Example 1 is significantly improved. This indicates that, during the gradient deposition of the ITO buffer layer and electron layer, by controlling the working gas pressure and sputtering power of the sputtering particles, the physical damage to the perovskite (PVK) and electron transport layer (ETL) caused by high-energy bombardment is effectively avoided. This creates a more ideal PVK / ETL / back electrode interface contact, reduces the interface barrier, and thus optimizes the carrier extraction and transport dynamics.

[0058] Depend on Figure 5-7As can be seen, the battery with the back electrode in Example 1 exhibits smoother rectification characteristics that are closer to those of an ideal diode model, corroborating the reduction in interface defect density. Notably, the JV curves of this device highly overlap under forward and reverse scans, indicating that the hysteresis effect is significantly suppressed. This phenomenon is attributed to the dense ITO buffer layer effectively blocking the ion migration channels between the metal electrode and the active layer, preventing the diffusion of Cu atoms into the perovskite layer and the chemical reactions they trigger, thereby fundamentally improving the electrochemical stability of the device.

[0059] like Figure 8 As shown, after 500 hours of continuous illumination at 30°C and maximum power point tracking (MPPT), the battery using the back electrode of Example 1 still maintained more than 90% of its initial efficiency, while the battery using the back electrode of Comparative Example 2 showed a rapid degradation trend.

[0060] To further explore the intrinsic mechanism of the stability enhancement, the study used photoluminescence imaging (PL mapping) technology for characterization.

[0061] like Figure 9 As shown, the cell using the back electrode of Example 1 exhibits a higher average fluorescence intensity, indicating a significant reduction in nonradiative recombination centers and an extended carrier lifetime, suggesting an optimized PVK / ETL / back electrode interface. Compared to the obvious local fluorescence quenching regions (i.e., "black and white spots," corresponding to high-density nonradiative recombination defects) observed in the directly sputtered sample, the PL fluorescence distribution of the cell using the back electrode of Example 1 exhibits high spatial uniformity. This result confirms that the gradient sputtering process effectively mitigates the damage to the perovskite lattice structure caused by the high-energy particle kinetic energy during direct sputtering.

[0062] In summary, the ITO buffer layer combined with gradient sputtering provides an effective strategy for solving the interface damage problem in the magnetron sputtering process, which is crucial for improving the overall performance of the components.

[0063] Example 2 A method for fabricating the back electrode of a perovskite photovoltaic device includes the following steps: An ITO buffer layer was deposited using a first-gradient magnetron sputtering method. This method includes a first initial deposition stage and a first main deposition stage. The conditions for the magnetron sputtering in the first initial deposition stage were: an ITO planar target driven by an RF power supply at a power of 0.5 kW, an operating pressure of 0.8 Pa, an Ar / O2 mixed gas with an O2 content of 0.3%, and a background vacuum ≤5°C. 10 -4 Pa, thickness 20 nm; The magnetron sputtering conditions for the first substrate deposition stage are as follows: a DC power supply drives the ITO rotating target at a power of 1.0 kW, an operating pressure of 0.5 Pa, an Ar / O2 mixed gas with an O2 content of 0.3%, and a background vacuum ≤5. 10 -4 Pa, thickness 20 nm; Electrode layers were deposited on an ITO buffer layer using a second-gradient magnetron sputtering method. This method includes a second initial deposition stage and a second main deposition stage. The second initial deposition stage involved preparing a Cu electrode layer using magnetron sputtering under the following conditions: a Cu rotating target, a DC power supply, a sputtering power of 1.0 kW, a pure Ar atmosphere, and a base vacuum ≤ 5 × 10⁻⁶. - 4 Pa, working pressure approximately 1.0 Pa, thickness 40 nm, to obtain the initial Cu electrode layer; The second stage of substrate deposition: A substrate Cu electrode layer is deposited on the initial Cu electrode layer using magnetron sputtering to obtain the back electrode. The sputtering conditions are: Cu rotating target, DC power supply, sputtering power of 2.0 kW, pure Ar atmosphere, and background vacuum ≤ 5 × 10⁻⁶. -4 Pa, working pressure approximately 0.5 Pa, thickness 100 nm.

[0064] Example 3 A method for fabricating the back electrode of a perovskite photovoltaic device includes the following steps: An ITO buffer layer was deposited using a first-gradient magnetron sputtering method. This method includes a first initial deposition stage, under the following conditions: an ITO planar target driven by an RF power supply at 0.4 kW, an operating pressure of 0.7 Pa, an Ar / O2 mixed gas with an O2 content of 0.26%, and a background vacuum ≤5°C. 10 -4 Pa, thickness 10 nm; An electrode layer was deposited on an ITO buffer layer using a second-gradient magnetron sputtering method. This second-gradient magnetron sputtering method includes a second initial deposition stage, in which a Cu electrode layer was prepared using magnetron sputtering under the following conditions: a Cu rotating target, a 0.8 kW DC power supply, a pure Ar atmosphere, and a base vacuum ≤ 5 × 10⁻⁶. -4 Pa, working pressure approximately 0.6 Pa, thickness 10 nm.

[0065] Example 4 A method for fabricating the back electrode of a perovskite photovoltaic device includes the following steps: An ITO buffer layer was deposited using a first-gradient magnetron sputtering method. This method includes a first initial deposition stage and a first main deposition stage. The conditions for the magnetron sputtering in the first initial deposition stage were: an ITO planar target driven by an RF power supply, a sputtering power of 0.3 kW, an operating pressure of 0.6 Pa, an Ar / O2 mixed gas with an O2 content of 0.2%, and a background vacuum ≤5°C. 10 -4 Pa, thickness 2nm; The magnetron sputtering conditions for the first bulk deposition stage are as follows: an ITO rotating target driven by a DC power supply, sputtering power of 0.8 kW, operating pressure of 0.3 Pa, using an Ar / O2 mixed gas with an O2 content of 0.2%, and a background vacuum ≤5. 10 -4 Pa, thickness 10 nm; Electrode layers were deposited on an ITO buffer layer using a second-gradient magnetron sputtering method. This method comprises a second initial deposition stage and a second main deposition stage. The second initial deposition stage involves preparing a Cu electrode layer using magnetron sputtering under the following conditions: a Cu rotating target, a DC power supply, a sputtering power of 0.7 kW, a pure Ar atmosphere, and a base vacuum ≤ 5 × 10⁻⁶. -4 Pa, working gas pressure about 0.5 Pa, thickness 2 nm, to obtain the initial Cu electrode layer; The second stage of substrate deposition: A substrate Cu electrode layer is deposited on the initial Cu electrode layer using magnetron sputtering to obtain the back electrode. The sputtering conditions are: Cu rotating target, DC power supply, sputtering power of 1.7kW, pure Ar atmosphere, and background vacuum ≤5×10⁻⁶. -4 Pa, working pressure approximately 0.3 Pa, thickness 50 nm.

Claims

1. A method for fabricating a back electrode for a perovskite photovoltaic device, characterized in that, Includes the following steps: An ITO buffer layer is deposited using a first gradient magnetron sputtering method, which includes a first initial deposition stage and a first main deposition stage performed sequentially. The operating voltage decreases sequentially and the sputtering power increases sequentially in the first initial deposition stage and the first main deposition stage. An electrode layer is deposited on the ITO buffer layer.

2. The preparation method according to claim 1, characterized in that, Electrode layers were deposited using a second-gradient magnetron sputtering method; The second gradient magnetron sputtering method includes a second initial deposition stage and a second main deposition stage performed sequentially. The working gas pressure decreases sequentially in the second initial deposition stage and the second main deposition stage, and the sputtering power increases sequentially in the second main deposition stage.

3. The preparation method according to claim 2, characterized in that, Between the second initial deposition stage and the second main deposition stage, there are also n transition stages, where n is an integer ≥1. The sputtering power of the transition stages is between the sputtering power of the second initial deposition stage and the second main deposition stage. The operating voltage of the transition stages is not greater than the operating voltage of the second initial deposition stage and is less than that of the second main deposition stage.

4. The preparation method according to claim 1, characterized in that, The thickness of the ITO buffer layer is 2-40nm.

5. The preparation method according to claim 1 or 4, characterized in that, The first initial deposition stage involves an ITO planar target driven by an RF power supply, with a sputtering power of 0.3-0.5 kW and an operating pressure of 0.6-0.8 Pa. An Ar / O2 mixture is used, with an O2 volume content of 0.2-0.3% and a base vacuum ≤5×10⁻⁶. -4 Pa; First substrate deposition stage: The ITO rotating target is driven by a DC power supply, with a sputtering power of 0.8-1.0 kW and an operating pressure of 0.3-0.5 Pa. An Ar / O2 mixed gas is used, with an O2 volume content of 0.2-0.3% in the mixed gas, and a background vacuum ≤5×10⁻⁶. -4 Pa.

6. The preparation method according to claim 5, characterized in that, The deposition thickness in the first initial deposition stage is 2-20 nm; the deposition thickness in the first main deposition stage is 0-20 nm.

7. The preparation method according to claim 2, characterized in that, The second-gradient magnetron sputtering method uses a DC power supply to drive a rotating target in an inert gas atmosphere; The working gas pressure for the second initial deposition stage is 0.5-1.0 Pa, and the sputtering power is 0.7-1.0 KW; the working gas pressure for the second main deposition stage is 0.3-0.5 Pa, and the sputtering power is 1.7-2.0 KW.

8. The preparation method according to claim 7, characterized in that, The thickness of the second initial deposition stage is 2-40 nm; the thickness of the second main deposition stage is 0-100 nm.

9. A back electrode for a perovskite photovoltaic device, characterized in that, Prepared by the preparation method described in any one of claims 1-8.

10. The application of the back electrode according to claim 9 in a perovskite solar cell.

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