Preparation And Physical Properties Of All-inorganic Cesium Lead Halide Perovskite Nanostructures

In recent years,due to the excellent optical properties,organic-inorganic hybrid CH3NH3PbX3(X=Cl,Br,I)perovskite materials with low cost,high carrier mobility and large optical absorption coefficient are widely concerned.However,organic-inorganic hybrid perovskite structures are prepared difficultly and the organic components are easily decomposed under humid or oxygen atmosphere,resulting a poor environmental stability.In contrast,all-inorganic perovskite nanomaterial CsPbX3(X=Cl,Br,I)have no organic components,containing stable structure,adjustable band gap,high fluorescence quantum efficiency and good stability,make them have broad application prospects in light-emitting diodes,photodetectors and solar cells.However,owing to inherent ionic properties,there are much work need to be done for CsPbX3(X=Cl,Br,I)nanostructures in terms of structural stability and quantum yield.In this dissertation,to solve the main problems of all-inorganic CsPbX3(X=Cl,Br,I)perovskite nanostructures,works in improving the photoelectric properties of materials and structural stability are as follows:1.We prepared size-controlled CsPbBr3 nanocrystals through a hot-injection method.The PL spectra showed that emission peaks had a red-shift as increasing the reaction temperature,indicating the synthesis temperature have a greater influence on the size of perovskite nanocrystals.Combining with the time-resolved fluorescence spectra,we had further analyzed the luminescence mechanism and the dynamic process of photogenerated carriers of CsPbBr3 nanocrystals.2.By changing the proportion and composition of halogen elements,CsPbX3(X=Cl,Br,I)nanocrystals with good dispersibility are prepared at 160?.The emission wavelengths could be adjusted from 406 to 680 nm,which almost covered the entire visible spectra.Excitation spectra and tiny Stokes shift indicated that the quantum dots origin from bound exciton recombination.Time-resolved spectra showed 1-6 ns lifetimes and high fluorescence quantum efficiency of the samples.In addition,after a post-annealing at 80? for CsPbBr3 quantum dots,we found they still exhibited stable cubic phase and fluorescence decay lifetimes,indicating a good thermal stability of the prepared nanocrystals.3.Colloidal perovskite CsPbBr3/TiO2 core/shell composite nanocrystals were synthesized at room temperature.Compared with the single-component CsPbBr3 nanocrystals,the size of the composite nanocrystals was about 9.2 nm and the FWHM was 15 nm.Time-resolved spectra showed that the lifetime of CsPbBr3/TiO2 core/shell composite nanocrystals were about 2.52 ns and exhibited excellent optical properties.After a post-annealing at 80?,it was found that the emission peak and fluorescence lifetime of CsPbBr3/TiO2 nanocrystals remained unchanged,indicating the prepared composite nanocrystals have a strong stability.