Preparation And Optical Properties Of All Inorganic Perovskites Cs_nPbBr_n+2 Micro-nanostructures

In recent years,the organic-inorganic hybrid perovskites(CH3NH3PbX3,X = Cl,Br,I)materials have attracted much attention,because of its high light absorption coefficient,low cost and easy preparation,etc.However,the poor environmental stability and thermal stability limits the development of organic-inorganic perovskites.All inorganic perovskites have better environmental stability and thermal stability.Furthermore,all inorganic perovskites materials have the advantages of high photoluminescence quantum efficiency,tunable bandgap,narrow line width and low temperature solution synthesis.All inorganic perovskites materials are one of the most promising luminescent materials,which can be used to fabricate solar cell,nano-laser,LED,etc.This dissertation mainly investigated the preparation and characterization of all inorganic perovskites CsPbBr3 and its derivatives Cs4PbBr6.The differences of luminescence mechanism between the Cs4PbBr6 and CsPbBr3 were analyzed.Finally,the anionic in the all inorganic perovskites CsPbX3 and Cs4PbX6 were mixed to obtained tunable emission.The main research results are summarized as follows:1.The all inorganic perovskites CsPbBr3 micro-nano structure was synthesized by low temperature thermal evaporation of precursor solutioin.The structure,morphology and optical properties of samples were characterized by X-ray diffraction,scanning electron microscopy,absorption spectra,photoluminescence and Raman spectroscopy.The optical properties of the samples after anion exchange were studied.Through a similar method,we obtained novel Cs4PbBr6 micro-nano structure.After the time-resolved photoluminescence spectra,variable temperature PL and Raman characterization,we found that the fluorescence quantum yield of Cs4PbBr6 is one order of magnitude higher than that of CsPbBr3.2.Through the careful analysis of the multiple experiment results,we assigned that CsPbBr3 nanocrystals are embedded in the stable Cs4PbBr6 microlattice matrix.Different ratio of precursor PbBr2/CsBr can produce different content of embedded CsPbBr3 nanocrystalline.Due to the discrete[PbBr6]4-octahedron model and the quantum confined effect in Cs4PbBr6,the CsPbBr3 nanocrystals embedded in Cs4PbBr6 micro-nano lattice matrix has enhanced luminescence intensity compared with pure CsPbBr3 microcrystals.Furthermore,after storage for two months in the air,Cs4PbBr6 microcrystals still have almost the same performance with that of as-prepared,which demonstrates better air stability.This method can be extended to synthesis of stable iodine-based all inorganic perovskites.Using Csl to instead of CsBr to miscibility withPbBr2 precursor,we can obtain the obvious enhancement of luminescence peak around 688nm while reduced significantly peak intensity of 515nm,which is helpful for the realization of air stable iodine-based perovskites materials used in solar cells.