Study On Optical Properties Of Two Dimensional RP Perovskite Controlled By Different Organic Cations

As a new generation of light emitting devices,two-dimensional perovskite has been widely studied in recent years.Moreover,two-dimensional perovskite has the advantages which cannot be replaced by other traditional photoelectric materials,such as environmental stability,adjustable band gap height,easy synthesis and other excellent characteristics.Compared with three-dimensional perovskite,its natural quantum well structure and strong intrinsic exciton properties result in high fluorescence efficiency.However,strong exciton binding energy not only brings high luminescence level,but brings strong auger effect,which is unfavorable for the development and application of luminescent lighting equipment and solar cells.How to effectively use the exciton binding energy to achieve higher fluorescence efficiency is a problem to be solved at present.At the same time,the effect of different organic cations on the photoluminescence of two-dimensional RP perovskite is still unclear.This paper is mainly divided into the following two parts:1.The anisotropy of（i-BA）₂PbI₄perovskite crystals and the characteristics of in-plane and out-plane excitons were studied.（i-BA）₂PbI₄single crystals were synthesized by cooling crystallization and treated by conventional mechanical stripping.It was found a blue shift of luminescence peak and the disappearance of low-energy defect states in the exfoliated samples,which were attributed to the stronger quantum limiting effect of thin layer perovskite and the reduction of surface defect sites by exfoliating.The crystal anisotropy of（i-BA）₂PbI₄was confirmed by side excitation and polarization fluorescence detection on the crystal side,and the different properties of the intrinsic excitons in different directions were investigated.Finally,the fluorescence characteristics and carrier dynamics of the thin layer and multilayer（i-BA）₂PbI₄under high pressure were studied.Through Gaussian fitting of the photoluminescence spectra under different pressures,it was found that the photoluminescence components of the trailing state were significantly weakened.2.A variety of two-dimensional RP perovskites,including（PEA）₂PbI₄,（4F-Bz A）₂PbI₄and（S-PEA）₂PbI₄,and their Sn²⁺doped samples,were synthesized and prepared.On this basis,Sn²⁺ions are doped slightly to produce external self-trapping effect.The Elliot formula was used to fit the UV-visible absorption spectra of the samples and the Stokes shift was combined to obtain their exciton binding energy.It was found that the exciton binding energy greatly affected the migration process of the intrinsic exciton to the self-trapping region.According to fluorescence lifetime analysis,Sn²⁺doping significantly prolongs the lifetime of perovskite,improves the utilization rate of excitons,and improves the fluorescence quantum yield.Finally,the conversion relationship between free excitons and self-trapping excitons of three tin-doped samples under high pressure was investigated via high pressure.