Study On The Optimization Of Perovskite Thin Film And Its Device Properties Based On Vapor-Solid Reaction Method

Perovskite solar cells have the characteristics of low exciton binding energy（20-30 me V）,long carrier diffusion length（>1μm）and adjustable band gap,which show a wide application prospect in photovoltaic power generation.Just 14 years of time,the photoelectric conversion efficiency of organic-inorganic hybrid perovskite solar cell laboratory has reached 25.7%,but its commercialization process is still restricted by many critical problems.At present,most of the high efficiency perovskite solar devices are prepared based on solution method.The preparation conditions of this method are relatively strict,and more toxic solvents are used in the preparation process,which make it an obstacle to industrialization.Vacuum evaporation method can greatly reduce the use of toxic solvent and produce high quality perovskite films.In this paper,perovskite thin films(Cs_xFA_1-xPb I_3-yBr_y)were prepared by vapor-solid reaction method.The properties of perovskite thin films prepared by different processes and assembled into batteries were studied by phase characterization and photoelectric properties characterization.This lays a solid foundation for the subsequent assembly of large-area batteries.The main research results are as follows:（1）The dense layer Ti O₂ prepared by water bath deposition method was used as the electron transport layer.The optimal thickness was obtained by exploring the deposition time of water bath,and the optimal device efficiency was 13.1%.The effect of FAI-FACl multistage atmosphere gas on perovskite absorption layer was investigated.It was found that the phase of perovskite film prepared under the condition of FAI-FACl multistage atmosphere is more pure,the grain size is larger and more uniform,and the device efficiency is increased to 14.4%.（2）The influence of substrate temperature on the preparation of Cs Br/Pb I₂ composite films and perovskite films during evaporation process was studied.The results show that the substrate preheating can improve the high crystallinity of Cs Br/Pb I₂ composite films,and then affect the quality of Cs_xFA_1-xPb I_3-yBr_y films.When the substrate temperature is 110℃,the Cs Br/Pb I₂composite thin film has high crystallinity.The perovskite thin film prepared by vapor-solid reaction has the characteristics of large grain and no pinhole,and its optical test shows high broadband absorption and low radiation recombination.The maximum efficiency of the prepared battery device can reach 17.1%.（3）By soaking Cs Br/Pb I₂ composite precursor film in Gu SCN solution and introducing mixed perovskite Gu Pb I_3-x（SCN）_x,the effect of mixed perovskite Gu Pb I_3-x（SCN）_x on the crystallization of perovskite film in vapor-solid reaction was studied.The results show that the mixed perovskite Gu Pb I_3-x（SCN）_x provides nucleation sites during chemical vapor deposition of perovskite films,thereby improving the diffusion reaction rate of FAI atmosphere in precursor films and obtaining high quality films.When the solution concentration of Gu SCN is1.6 mg/m L and the immersion time is one minute,the prepared perovskite films have good crystallization and morphology,and the photoelectric conversion efficiency of the prepared devices increases from 14.85%to 16.21%.