Study On Synthesis And Photoluminesence Properties Of Perovskite Nanoplates

In recent years,the organic-inorganic hybridized perovskites,with the organic groups embedded in the mineral crystal lattice on the molecule level,have attracted widespread attention due to their advantages including high absorption coefficients,direct bandgap,long carrier lifetimes,balanced electron/hole mobility and so on.Besides,the excellent optical and electrical properties of perovskites enable them to find suitable applications in other optoelectronic devices,such as light emission diodes,lasers,photodetectors,and field-effect transistors.Although the perovskite thin films with fair performance could be produced through the classic one-step or two-steps spin-coating processes,the products of polycrystalline perovskites limit the applications to a certain degree.Compared to their polycrystalline counterparts,single crystalline perovskites with higher crystalline quality,less crystal defects,lower trap density,and longer carrier lifetimes,are more promising.In this work,the synthesis of regular single crystalline lead iodide nanoplatelets are carried out based on the physical vapor phase deposition method.Different lead iodide nanoplatelets are obtained by tuning the location of the mica substrate along with the temperature of the tube furnace.The rules of size,thickness,density of the lead iodide nanoplatelets at varied deposition conditions are analyzed according to the crystal growth principles.It was claimed in literature that the photoluminescence of lead iodide could be obtained only at a low temperature(lower than 200 K).Here,at room temperature,using a 325 nm continuous-wave laser with a beam waist of ~200 micrometers,we successfully obtained the photoluminescence spectra of lead iodide nanoplatelets,which possess two apparent peaks due to the biexcitons and the inelastic scattering of excitons,respectively.Here,we first synthesized lead iodide nanoplatelets with well-defined crystal boundaries and then successfully conversed the pre-grown lead iodide template into perovskite nanoplatelets by placing the substrate exactly above the methyl iodide amine powder in Ar gas condition with all valves of the quartz tube closed.Based on our home-made microscope system which can provide photoluminescence spectra of an individual platelet excited by a continuous-wave laser at 325 nm,we measured the photoluminescence spectra of different perovskite nanoplatelets and observed the whispering gallery modes over the spontaneous emission band.Our work contributes to the development of perovskite optoelectronic devices.