Preparation And Optical Properties Of All-inorganic Perovskite Nanocrystals

In the past few years,semiconductor nanocrystals,especially the all-inorganic metal halide perovskite,have attracted wide attention due to their excellent luminescence properties,such as adjustable wide band absorption and emission spectra,narrow luminescence half peak width and high quantum yield.The preparation technologies of all-inorganic perovskite nanocrystals have constantly emerged,including thermal injection method,anion exchange method and ligand-assisted reprecipitation method,solvent thermal method and ultrasonic crystallization method etc..Various morphologies of perovskite nanocrystals such as nanospheres,nanoplates,nanowires,nanorods and nanoblocks have been successfully synthesized via these methods.Nevertheless,the current methods have difficulties in controllable growth of nanocrystals at the atomic level.This makes it a fundamental challenge to prepare uniform and high quality monodisperse all-inorganic perovskite nanocrystals samples which may weaken its luminescence performance.At the same time,the instability of perovskite is also an important limitation for its application.Therefore,choosing the right method to increase the stability of all-inorganic perovskite has become the top priority in the study of perovskite luminescence performance.This paper carries out the following three studies.1.The structure and optical properties of ultrafine Cs Pb Br₃perovskite nanowires were studied and applied for polarized light detection.The ultrafine perovskite nanowires with high quantum efficiency were synthesized with high chemical yield by introducing the pre-dissolution step to improve the traditional solvent thermal method.We have demonstrated the cubic phase structure of Cs Pb Br₃perovskite by XRD,Raman spectroscopy and TEM,and obtained bright blue emission under the excitation of 365 nm ultraviolet light.The anisotropic structure and optical properties of ultrafine Cs Pb Br₃nanowires make them a unique model for studying the polarization response of all-inorganic perovskite.We used a novel and simple method to obtain the array of self-assembly ultrafine Cs Pb Br₃nanowires,which not only provided a solution for the preparation of perovskite nanowires polarization detectors,but also enhanced the basic understanding of the polarization emission characteristics of all inorganic perovskites.2.The application of ionic crystal encapsulating all-inorganic perovskite nanocrystals in temperature detection and amplification spontaneous radiation.The all-inorganic perovskite nanocrystals with excellent optical properties were embedded into inorganic ionic crystals by using the solubility difference of each crystal in solvents.The perovskite mixed crystal with excellent luminescence properties and outstanding optical,thermal and chemical stability were synthesized.By XRD,TEM and EDS tests,we proved that the perovskite nanocrystals were successfully embedded by inorganic ionic crystals.Subsequently,the dual-mode temperature sensor was realized by Cs Pb_0.6Ni_0.1Mn_0.3Cl₃/KCl mixed crystal prepared by the above method.Meanwhile,the Cs Pb Br₃/KBr mixed crystal was excited by an 400 nm femtosecond laser to obtain ASE emission.This research opens a new way for the field of optical temperature sensors and perovskite laser emission.3.The luminescence properties and mechanism of heat treated all-inorganic two-dimensional Cs Pb₂Br₅perovskite.Pure phase,millimeter scale Cs Pb₂Br₅perovskite crystals with regular morphology,dense structure and stable chemical properties were synthesized by recrystallization method,which have been confirmed by XRD,Raman spectrum and TEM measurements.Besides,the heat treatment method was used to achieve photoluminescence?PL?emission of Cs Pb₂Br₅crystals.The effects of heat treatment regime on the PL performance of Cs Pb₂Br₅crystals was studied through PL spectra and lifetime decay.At the same time,the in situ precipitation of Cs Pb Br₃quantum dots was expounded by XRD,high resolution TEM measurements,Raman spectrum and UV-visible absorption spectra.The Cs Pb₂Br₅crystals provides a perfect matrix for the Cs Pb Br₃quantum dots so that the composite crystal achieves excellent luminescence performance and outstanding chemical stability,especially its water resistance.We took advantages of it and demonstrated its potential in X-ray detection application.