Synthesis And Stability Of Cesium Lead Halide Nanocrystals

All-inorganic hybrid perovskite（CsPbX₃,X=Cl,Br,I）is a new type of material with quantum well structure and has been widely used in many fields such as light-emitting diodes and field-effect transistors.Therefore,this thesis first used different preparation methods to explore the influence of capping molecules,and the surface modifications to improve stability of photoluminescence.The thesis contains the following work:1.Based on previous studies,the influence of OPR（the proportion of adding oligomide in perovskite nanocrystals）on all-inorganic perovskite nanocrystals obtained by different preparation methods was explored.The samples were characterized by PL（emission spectrum）,Abs（absorption spectrum）,TEM（transmission electron microscope）,and XRD（X-ray diffraction spectrum）.The luminescence wavelength of CsPbBr₃ synthesized by toluene assisted precipitation and thermal injection is 530 nm,and OPR has no regulating effect.2.Reliable and stable light source in the wavelength range larger than 530 nm is lacking in the LED industry.To meet this need,we explore ways to improve the stability of CsPbI₃ nanocrystals by a core-shell approach.In the heterogeneous core-shell structure,the shell was made of CsPbBr₃ and the core was made of CsPbI₃ prepared by hot injection method.The results showed that the heterogeneous core-shell approach obtained different results depending on the solvent used.When the solvent was DMF,it resulted in a mainly CsPbBr₃ perovskite with enhanced PL and stability.On the other hand,when the solvent was Acetonitrile,it resulted in a mainly CsPbI₃ perovskite with enhanced PL but the stability was degraded.3.Continuing to explore ways to improve the stability of CsPbI₃ nanocrystals,the shell material was changed to the same CsPbI₃ as the core but made by a different method.The materials were analyzed by means of absorption spectrum,fluorescence spectrum,X-ray diffraction,scanning electron microscope and other means.It was found that this method of using the same material as core-shell structure can improve the photo-stability of CsPbI₃ nanocrystals from 3 days to 11 days.