Preparation And Optical Properties Of CsPbBr₃ Nanowires

CsPbX3(X = Cl,Br,I)with the perovskite crystal structure has received considerable attention and is developing rapidly in the past few years.CsPbX3 perovskites with unique optical and electronic properties have demonstrated remarkable potential as building blocks in various applications,such as in photodetectors,light-emitting diodes,solar cells and lasers.Up to now,various CsPbX3 perovskites with tunable composition and morphology,including zero-dimensional quantum dots,one-dimensional nanowires,and two-dimensional nanoplates,have been successfully prepared.Up to now,two main approaches have been proposed for preparation of CsPbBr3 nanoparticles,which are the hot-injection route and the ligand-assisted reprecipitation(LARP)technique.However,there are still some problems to be solved,such as complicated synthetic route and poor nuclear reaction rate.Therefore,it is urgent to find a simple method to prepare CsPbBr3 and control the size and optical properties simply and effectively.In this thesis,the preparation,properties and size effects of CsPbBr3 nanomaterials were explored and studied in detail.1.One-step synthesis of ultrathin CsPbBr3 NWs at room temperature and optical propertiesWe introduce a one-step colloidal method to synthesize ultrathin CsPbBr3 nanowires with diameter?2.5n m.Instead of pre-dissolving the metal precursors in a good solvent,we added CsBr and PbBr2 solid powders directly into a mixture of oleic acid(OA),oleylamine(OM)and acetone with vigorous stirring.The solid metal precursors slowly dissolved and formed small CsPbBr3 nanoparticles(NPs).The new synthesis method is relatively simple and has less surface defects than the traditional thermal injection method and LARP method reported previously.Therefore,the electron and hole can effectively and directly compound luminescence,showing excellent luminescence properties and higher photoluminescence quantum yield(PLQY).In this work,a new method for the preparation of ultrathin nanowires of perovskite is proposed,which provides a new way for the study and preparation of nanowires.2.Tuning the size and composition of CsPbBr3 NWs and optical propertiesBy controlling the reaction conditions,the diameter of the nanowires can be adjusted from 2.5 nm to 32 nm.For width increasing from 2.5 nm to 5.3 nm,the thickness increasing is owing to the layer-by-layer deposition of the metal precursors For nanowires growing from 6.5 nm to 32 nm,the growth may be induced by attachment of these thin nanowires,more defects are induced in the growth process.Due to the strong quantum confinement effects,the optical properties can be tuned from purple to green with different nanowires widths.The composition and optical properties can also be tuned across the entire visible range through an anion-exchange process with good nanowire morphology preservation.Our study provides a facile,reliable method for controlled synthesis of 1D perovskite nanowires,which may offer a new platform for their fundamental studies and optoelectronic applications.