Synthesis,Structure,and Optical Properties Of Lead-Free Organic-Inorganic Hybrid Halides

Organic–inorganic lead-halide perovskites have attracted extensive attention due to their outstanding photophysical properties,such as high photoluminescence quantum yield（PLQY）,large absorption,and high carrier mobility,as well as their simple synthesis method and low preparation cost.Lead-halide perovskite is an emerging semiconducting material that have promising in a variety of optoelectronic applications,for example,photovoltaic cells,laser technologies,light-emitting diodes（LEDs）,etc.However,the intrinsic toxicity of lead limits its large-scale and extensive applications.Therefore,it is of great significance to design and develop lead-free perovskite.Firstly,we synthesize three new lead-free organic-inorganic zinc halides,(C₈H₁₂N)₂Zn Br₄,(C₉H₁₄N)₂Zn Br₄,and(C₉H₁₄NO)₂Zn Br₄ by the slow solvent evaporation method.All the compounds are zero-dimensional（0D）,and all the compounds exhibit similar broadband white photoluminescence and good air stability.The steady-state and transient-state fluorescence spectra manifest that the broadband white emissions of these compounds originate from the organic molecules.Then,we synthesize a new lead-free organic–inorganic tin（IV）bromide hybrid（4-APEA）₂SnBr₆ through the slow cooling crystallization process.（4-APEA）₂SnBr₆exhibits broadband yellow photoluminescence under the excitation of 365 nm UV light,and PLQY is 27%.The temperature-dependent fluorescence spectra and time-resolved photoluminescence decay indicate the yellow emission originates from self-trapping excitons.The bare（4-APEA）₂SnBr₆ shows impressive emission stability and thermal stability in the air.The excellent stability is profit from the stable valence state and few defect state densities.Finally,based on the previous chapter,we synthesize a new lead-free organic–inorganic tin（IV）bromide hybrid（4-APEACl）₂SnCl₆by the slow cooling crystallization process.Under the excitation of 365 nm,（4-APEACl）₂SnCl₆ exhibits a broad orange emission located at 582 nm.Especially,the PLQY of orange emission is37%,which is higher than most reported hybrid Sn⁴⁺-based metal halides.Moreover,（4-APEACl）₂SnCl₆ exhibits relatively good stability in the air.The structurally distorted[SnCl₆]^2-octahedron causes self-trapping excitons,resulting in orange emission.