Research On Synthesis And Luminescence Property Of All-inorganic Lead Halide Perovskites Cs₄PbBr₆/CsPbBr₃

All-inorganic lead-halide perovskite fluorescent materials have excellent optical properties such as high photoluminescence intensity and quantum yield,large light absorption coefficient,tunable band gap,which have wide applications in the field of light-emitting diodes,solar cells and photodetectors.However,the poor stability and lead toxicity hinder the practical application of lead-halide perovskites.At present,the preparation of lead halide perovskites is mainly based on the hot-injection method,which requires high temperature reaction,protection of inert gas,and ice-water bath cooling.In contrast,a surface ligand-assisted supersaturation recrystallization method can be carried out at room temperature and does not require the harsh conditions like inert gas protection and ice-water bath cooling,which is suitable for mass production.Based on these facts,in this dissertation,surface ligand-assisted supersaturation recrystallization method was used to prepare all-inorganic lead-halide perovskite phosphors,and the influence of the surface ligand amount,solvent polarity,HBr content and rare earth ion Eu³⁺doping on the crystal phase and luminescence properties of the synthesized perovskites were studied.The main research content is divided into the following three parts:1.The introduction of surface ligands oleic acid and oleylamine（OA/OAm）during the reaction process promotes the variation of the products form Cs PbBr₃ to Cs₄PbBr₆/Cs PbBr₃ composites perovskite phosphors with intense green emission,and the quantum yield is enhanced from 0.13%to 46.74%.The emission spectra of composite perovskites is analyzed by Gaussian fitting,indicating that the green light emission of Cs₄PbBr₆/Cs PbBr₃ originates from both Cs₄PbBr₆ and Cs PbBr₃ perovskite,wherein the luminescence of Cs₄PbBr₆ originates from the exciton radiative recombination mediated by defect states,and which of Cs PbBr₃ originates from the electrons-hole recombination radiation.The energy transfer process from Cs₄PbBr₆ to Cs PbBr₃ is confirmed by the fluorescence lifetime decay of Cs₄PbBr₆ and Cs PbBr₃ in composite perovskite.2.The luminescence properties of Cs₄PbBr₆/Cs PbBr₃ composite perovskite phosphors is optimized by adjusting the polarity of the solvent which influences the ion recrystallization process in the preparation process with fixed amount of surface ligands OA/OAm.The effect of solvent polarity on the luminescence properties of composites perovskite is analyzed by the emission spectrum,fluorescence lifetime and quantum yield of Cs₄PbBr₆/Cs PbBr₃.The results show that Cs₄PbBr₆/Cs PbBr₃ composite perovskite phosphors with excellent green emission has been successfully prepared when isooctane is selected as the solvent,and the quantum yield is up to 89.28%.3.The introduction of HBr brings a Br^--rich reaction environment without the participation of ligand,which promotes the formation of Cs₄PbBr₆/Cs PbBr₃ composite perovskite phosphors.The effects of HBr amounts on the luminescence properties of composite perovskites are investigated,and the results show that the green emission increase with the increase of HBr amount.On this basis,Eu³⁺-doped Cs₄PbBr₆/Cs PbBr₃composite perovskites phosphors are prepared.Doping Eu³⁺ions can further improve the green emission intensity of the composite perovskite,and the quantum yield increases from65.74%to 90.94%.