The Preparation And Photovoltaic Application Of All-Inorganic Perovskite Films With High-Quality

Metal halide perovskite materials have achieved unprecedented rapid development and delivered a more than 25%certified efficiency,becoming the most potential photovoltaic device for commercialization.However,due to the high thermal volatility of organic cations,the long-term instability of the organic-inorganic hybrid perovskite display quite low long-term stability.The substitution of organic cations（MA or FA）by inorganic Cs cation could avoid the thermal volatility of organic cations,thereby greatly improving the photostability and thermal stability of the perovskite layer.Cs PbI₃,as one of these all inorganic perovskite displaying a suitable band gap（1.7 e V）and an absorption edge near 730 nm,is very suitable as a photoactive layer for photovoltaics.However,Cs PbI₃ is a thermodynamically stable cubic phase perovskite only at temperatures above 325°C.It is challenging to prepare high quality Cs PbI₃ film,which results in extremely lower performance of all-inorganic solar cells than organic counterpart.Here in this dissertation,we develop strategies for preparation of high quality all-inorganic perovskite films and high-performance photovoltaic devices by pre-treatment and modulation of precursors.1.Cs PbI₃ perovskite precursor film was prepared by the traditional one-step solution method,and then further subject to PEAI pre-treatment,which results in the transformation from one-dimensional（DMAPbI₃）and two-dimensional（PEA₂Cs Pb₂I₇）perovskite to three-dimensional perovskite and realize high crystalline Cs PbI₃ film,as evidenced by SEM,UV-vis,XRD,photoluminescence,etc..The photovoltaic devices based on such Cs PbI₃ film delivers an efficiency of 17.08%and much enhanced stability.2.We regulate the perovskite crystallization process by adjusting the composition of the perovskite precursor solution,preparing high-quality all-inorganic Cs PbI₂Br perovskite films at low temperature.First,the Pb Br₂（DMSO）and Pb Br₂（DMSO）adduct was synthesized and used as precursors for the preparation of perovskite solutions,instead of Pb Br₂and PbI₂.It was found that the crystallinity of Cs PbI₂Br and power conversion efficiency（PCE）of solar cell based on these Cs PbI₂Br films was much enhanced,delivering an PCE of 14.31%.The effects of different precursors and perovskite solution components on the crystallization process of Cs PbI₂Br perovskite were analyzed,and the internal mechanism of Cs PbI₂Br perovskite crystallization was explored.