Study On Preparation Process Optimization And Performance Of CsPbBr₃ Inorganic Perovskite Solar Cells

As is well known,power conversion efficiency（PCE）and long-term stability are two important performance parameters of solar cells.In recent years,the PCE of the novel organic-inorganic hybrid perovskite solar cells has been continuously enhanced,and now it reaches the level of many commercial solar cells.However,it is urgent to improve the stability of the solar cells to meet requirements of commercial applications.The current stability problem of the perovskite cells may be addressed by replacing the unstable organic-inorganic hybrid perovskite with stable inorganic perovskite.The inorganic perovskite CsPbBr₃ attracts much attention of researchers due to its high stability and achieveable synthesis technology in the atmosphere environment.But the reported PCEs of the inorganic perovskite solar cells based CsPbBr₃ are still very low.The first main reason is the narrow absorption spectra of the solar cells originating from the wide bandgap of CsPbBr₃.Secondly,the photovoltaic performances of the solar cells are also affected greatly by the microstructure of the CsPbBr₃ light absorbing layer.Therefore,this work attempts to develop efficient CsPbBr₃-based inorganic perovskite solar cells.Firstly,the optimized process for preparing CsPbBr₃ thin films was studied,and then the fabrication technology of CsPbBr₃-based solar cells was established.Secondly,some efficiency-enhanced strategies,such as solvent engineering,interface modification and spectra engineering were investigated in detail.The main work and results of the dissertation are as follows:（1）Study on the preparation process of CsPbBr₃-based inorganic perovskite cells.Based on an improved multi-step method,the high-quality CsPbBr₃ thin films were successfully synthesied in air with a relative humidity of less than 30%by controlling some key process parameters such as the number of spin-coating of CsBr solution and the annealing temperature of PbBr₂.The fabrication technology of CsPbBr₃-based solar cells was established on the base of the multi-step method for preparing CsPbBr₃ thin films.And the best PCE of CsPbBr₃-based solar cells was 7.54%.（2）Study on the effect of solvent additives in the precursor solutions on the photovoltaic performances of the solar cells and the coordination mechanism of solvent additives.The effects of N-methyl-2-pyrroli-done（NMP）and acetonitrile（ACN）additive molecules in the PbBr₂（DMF）precursor solutions on the quality of perovskite thin films were studied in detail.The mechanism of interaction between solvent additive molecules and PbBr₂ was discussed according to the results of particle-size analysis and infrared spectroscopy analysis,combined with Lewis acid-base theory.By adding NMP and ACN,the best PCE of the solar cells were increased to 9.53%and 9.22%,respectively.（3）Study on the effects of interface modification and photoactive layer on photovoltaic performances.The TiO₂/CsPbBr₃ electron transport interface was modified by introducing graphene quantum dots（GQDs）,and the electron extraction rate was improved.As a result,the PCE of the solar cells was increased to 9.18%.The absorption spectrum of the CsPbBr₃ perovskite cells was broadened to near infrared by introducing the P3HT/PbS QDs heterojunction photoactive layer,and the PCE of the solar cells was increased to 9.11%.