Study On Stability Of Lead Halide Perovskite Nanocrystals

Due to super-long carrier diffusion length,high absorption coefficient,tunable bandgap,etc,lead-based halide perovskite has been a research hotspot of photoelectric functional materials in recent years.However,one limitation of the application of perovskite materials in photoelectric devices is the stability of perovskite NCs themselves,which is caused by its ionicity.On this basis,this work mainly focuses on the stability of lead-halide perovskite NCs and improves the stability by modification of surface ligands and introduction of inorganic matrix.Firstly,it is proposed to introduce hyperbranched polyamidoamine?PAMAM?dendrimers with two different generations?G0 and G4?instead of oleic acid?OA?to synthesize CH₃NH₃PbBr₃ perovskite NCs with high photoluminescence?PL?quantum yields?QY?above 70%and a new record of stability.The results indicate that PAMAM ligands outside perovskite NCs can dramatically slow down the speed of halide exchange and thus the halide exchange resistance of perovskite NCs can be dramatically improved.Compared to traditional OA-capped NCs,PAMAM-capped perovskite NCs are excellent in water-resistance and moisture-resistance.In view of slow halide exchange speed,excellent water and moisture stability,PAMAM dendrimers-capped perovskite NCs and their mixture are available as color conversion single layer in fabrication of long-term stable light-emitting diodes?LED?.Secondly,a post-passivation method of trioctylphosphine?TOP?to synthesize CsPbI₃perovskite NCs with excellent phase stability is proposed.The TOP-capped CsPbI₃ perovskite NCs do not undergo phase transformation??phase to?phase?and its relative PL intensity remains 80%in high humidity,which indicates that phase stability of CsPbI₃ NCs has been substantially improved after treated by TOP.It is also verified that F^-can quicken the phase transformation of CsPbI₃ perovskite NCs.