Preparation And Fluorescence Performance Of CsPbBr₃ And Cs₄PbBr₆ Quantum Dots

In recent years,cesium-lead-bromine（Cs-Pb-Br）inorganic perovskite quantum dots have attracted the attention of researchers as a new type of material.Such perovskite quantum dots have excellent photoelectric properties,such as high quantum efficiency,narrow emission peak.The green wavelength fluorescence peaks of zero-dimensional（0D）Cs₄PbBr₆has been debated continuously in the study of Cs-Pb-Br inorganic perovskite.Three-dimensional（3D）CsPbBr₃is the only perovskite material that has been confirmed to have intrinsic photoluminescence,so some researchers believe that the green wavelength fluorescence peaks of 0D Cs₄PbBr₆is due to the presence of the impruty CsPbBr₃;other researchers consider that it is produced by the defective state of 0D Cs₄PbBr₆itself.In this thesis.In addition,it is of great significance to the research and development of inorganic perovskite quantum dots devices to the study of the stability of inorganic perovskite quantum dots under changes in the external environment,such as temperature and light other conditions.In this thesis,the above problems are designed to study the experiments,and the main research points of this paper are as follows:（1）The green fluorescence peaks of 3D CsPbBr₃and 0D Cs₄PbBr₆perovskites were researched in depth.It was found that there were significant differences between the two in terms of absorption band edge,exciton absorption,PL peak position,PL full width at half maximum（FWHM）and PL lifetime.Therefore,it can be assumed that the green fluorescent peak of 0D Cs₄PbBr₆perovskite is not produced by impurities in 3D CsPbBr₃.（2）The thermal stability of 3D CsPbBr₃quantum dots and 0D Cs₄PbBr₆quantum dots at300K-360K was studied.In this paper,by setting the heating group and the cooling group,comparing the changes in the PL spectrum during the process of rising and cooling,it is found that the PL characteristic peak intensity of 3D CsPbBr₃quantum dots and 0D Cs₄PbBr₆quantum dots decreases rapidly in the heating process,and the PL characteristic peak intensity rises during the cooling,and the PL peak position remains unchanged.This shows that the structure of 3D CsPbBr₃quantum dots and 0D Cs₄PbBr₆quantum dots is damaged in the high temperature environment,resulting in a decrease in their PL intensity,so the PL intensity cannot be restored after the temperature is reduced.（3）The the stability of 3D CsPbBr₃quantum dots and 0D Cs₄PbBr₆quantum dots at different temperatures（low temperature and room temperature）,gaseous environments and light are researched.This paper preserves two kinds of quantum dots in five different external environments.it is found that under the above three factors,illumination has the greatest impact on the stability of perovskite quantum dots,which will cause the phenomenon of reducing the peak intensity of its PL characteristics,redshift of PL spectra and absorption,and downward shift of absorption spectrum below the absorption boundary.This shows that prolonged illumination will cause the concentration of CsPbBr₃quantum dots and Cs₄PbBr₆quantum dots to decrease,and the size of the quantum dots will be converted a blocky material.