The Research On Exciton-polaritons And Electron-hole Plasma In Metal Halide Perovskites

Due to many excellent optoelectronic properties,metal halide perovskite materials have great application potentials in the field of optoelectronic devices and integration technology.With the realization of a series of high-performance optical and optoelectronic devices based on perovskite materials,researchers have aroused great interest in the study of its photophysical phenomena and mechanisms.The dynamic mechanism of quasi-particles such as carriers and excitons in a material is closely related to its electrical and optical properties.An in-depth understanding of the related photophysical properties and mechanisms in perovskite materials will help feedback material preparation and device optimization and design.For this reason,this dissertation focuses on two kinds of optical excitation phenomena in metal halide perovskite materials:exciton-polarization excimer and electron-hole plasma.The main research contents are as follows:(1)We prepared layered high-quality two-dimensional(2D)Ruddlesden-Popper(RP)perovskites(BA)₂(MA)_n-1Pb_nI_3n+1(n=3,4).Since the layered material itself can form a good microcavity,we can observe the strong light-matter interaction and exciton-polariton related phenomena in the 2D RP perovskites at room temperature.Through angle-resolved PL spectroscopy,the exciton-polaritons in 2D RP perovskites under different effective cavity resonance conditions was studied.Based on the analysis of the experimental data with the coupled harmonic oscillator model,the Rabi splitting of160 me V and 180 me V in the n=3 and n=4 materials were obtained.At the same time,based on the Hopfield coefficients of different exciton-polariton modes,it reveals the transition process of exciton-polariton from exciton dominance to photon dominance.The research of this thesis realizes exciton-polaritons in high-quality 2D RP perovskite,which is very important for basic photo-physics research and the application of perovskite-based polariton devices.(2)We established a model describing the carrier and exciton process of perovskite,which can be used to calculate the carrier density dependent exciton behaviors that changes from the excitons to the electron-hole plasma related phenomena as the carrier concentration increases to the threshold,namely"Mott density".Using this model,we have calculated the Mott density of all-inorganic Cesium Lead Bromide nanowires grown by chemical vapor deposition.The results obtained by our model are consistent with those reported in the literature.Meanwhile,using this method,we have calculated a series of organic-inorganic hybrid perovskite materials(FAPb I₃,MAPb I_3-xCl_x,MAPb I₃,FAPb Br₃,MAPb Br₃)under different temperature conditions.The results obtained are well in line with the variation trend due to the different material properties.Finally,we discussed how to calculate the photogenerated carrier density under single-photon and two-photon excitation in the experiment.The study of electron-hole plasma behavior in perovskite materials has built an important foundation for the design and preparation of new functional optoelectronic devices.