Study On Photoelectric Performance And Stability Of CsPbI_3-xBr_x Inorganic Perovskite Solar Cell

Organic-inorganic hybrid perovskite materials have received extensive attention from researchers in recent years due to their excellent photoelectric properties and low manufacturing costs.However,the organic components in the system are easily affected by external conditions such as light,heat,and humidity.Decomposition occurs,leading to serious degradation of device power conversion efficiency(PCE)over time in the external environment,which greatly restricts the industrialization process of perovskite solar cells.In the perovskite solar cells,if the active layer of the perovskite with ABX₃ structure is replaced by inorganic Cs ions at the A site of the traditional hybrid perovskite with mechylamine ions,problems such as poor thermal stability and A-site ion migration caused by hydrogen bonding in the methylamine perovskite can be effectively avoided,and the stability of the perovskite can be comprehensively improved.At present,the most concerned inorganic perovskite materials are CsPb Br₃ and CsPbI₃.Among them,CsPb Br₃ has excellent stability in the atmospheric environment,but the wide band gap of 2.3 e V limits the improvement of cell efficiency.CsPbI₃ has a suitable band gap of 1.73 e V,but the thermodynamic instability of?-CsPbI₃ with high photoactivity is one of the bottlenecks hindering its further development.It is expected to obtain inorganic perovskite with both efficiency and stability by doping CsPbI_3-xBr_x inorganic perovskite with certain halogen at X site.Moreover,the ratio of halogen at X site can effectively control the band gap of perovskite and its capture of light,thus improving the performance of the device.Therefore,the paper takes CsPbI_3-xBr_x inorganic perovskite as the research object,from optimizing the composition of inorganic perovskite,precursor concentration,annealing temperature,introducing polymer to modify the surface during the preparation process,and using inorganic carbon(C)as the conductive layer.The introduction of Cs I modification and control components has systematically improved the photoelectric performance and stability of inorganic perovskite solar cells.First,the traditional one-step spin coating method was used to prepare CsPbI_3-xBr_xinorganic perovskite with adjustable band gap,and the influence of the phase structure and light absorption of the film under different components was explored.ITO/Sn O₂/CsPbI_3-xBr_x/Spiro/Ag structure solar cell devices were assembled,and the photoelectric performance test was carried out.It is found that when the composition is CsPbIBr₂,the assembled devices have higher photoelectric efficiency and better stability.On this basis,the photoelectric performance of the CsPbIBr₂ perovskite device was further optimized by changing the CsPbIBr₂ precursor concentration and annealing temperature.It was found that when the CsPbIBr₂ precursor concentration was 1.2 M and the annealing temperature was 220°C,the photoelectric performance of the device was greatly improved.The best photoelectric conversion efficiency reaches 8.14%,but CsPbIBr₂ perovskite is prone to spontaneous phase transition at room temperature,there are still challenges in device stability.In view of the phase instability problem of the above-mentioned CsPbIBr₂ perovskite device,first of all,learn from the idea of improving the stability of the perovskite film in the traditional hybrid perovskite device.The perovskite film was prepared by adding hydrophobic strong polyvinylpyrrolidone(PVP)and polyacrylonitrile(PAN)polymers into the CsPbIBr₂precursors,respectively,and then assembled into solar cell.XRD and FTIR test results show that PVP and PAN are attached to the surface of the perovskite grains,which effectively prevents the perovskite from being corroded by moisture in the environment,but the extra grain boundaries formed by them also hinder the effective transport of carriers and sacrifice improved certain device performance.By optimizing the amount of PVP doping and the annealing temperature of PAN doping,the surface coverage of the doped perovskite and the crystallinity of the crystal are improved,and the device performance is improved by 4%and 13%.From the perspective of improving the overall stability of the device,the screen printing method is further used to replace the hydroscopicity and expensive organic hole small molecules(Spiro-OMe TAD)and precious metal electrodes with extremely hydrophobic carbon electrodes to assemble ITO/Sn O₂/CsPbIBr₂/C structure solar cell,it was found that the carbon-based perovskite solar cell was placed in an environment of 20%-55%humidity for 23 days,and the efficiency remained 88.7%of the initial value,while the Spiro-based device efficiency dropped below 1%on day 15.The use of carbon-based devices shows extremely high stability.Furthermore,based on the use of carbon electrodes,the effect of different annealing temperatures on CsPbI₂Br perovskite was explored,and the annealing temperature was successfully reduced from 250°C to 160°C,and the device achieved an efficiency of 11.8%,providing the possibility for efficient and stable preparation of flexible devices.Finally,from the perspective of further optimizing the photoelectric performance and stability of the device,a certain Cs I methanol solution was introduced on the CsPbIBr₂ film and assembled into a perovskite cell with an ITO/Sn O₂/Cs I-CsPbIBr₂/C structure.It is found that this method not only effectively suppresses Pb⁴⁺in the inorganic perovskite film that affects the performance of the device,but also improves the crystallinity and film density of the film,and effectively solves the problem of poor film formation quality of the CsPbIBr₂ film prepared by the traditional solution method.Furthermore,by changing the concentration and dropping amount of the Cs I methanol solution,the device efficiency was successfully increased to 13.8%while maintaining stability.It provides important help for the preparation of efficient and stable inorganic perovskite solar cells.