Study On The Growth And Optoelectronic Properties Of Lead-Free Double Perovskite Single Crystals

Metal halide perovskite materials have attracted intense research interests in recent years because of their excellent photoelectric characteristics.Unfortunately,lead halide perovskites have not been widely commercialized because they generally contain toxic lead and display intrinsically unstable in crystallographic structure,which accordingly gives rise to decompose in ambient environment.Lead-free,non-toxic double perovskite materials,i.e.,A₂M^IM^?X₆,show excellent environmental stability and good photoelectric properties,enabling its wide applications in various optoelectronic devices.Compared with the double perovskite polycrystalline thin films,single crystal has lower defect density,higher carrier mobility and longer carrier diffusion length,and these excellent photoelectric characteristics enable double perovskite single crystal to have potential application in the field of optoelectronics.In this study,an emerging lead-free double perovskite single crystal with stable internal structure was designed and grown,i.e.,Cs₂Ag Fe Cl₆ double perovskite single crystal.It is found that the crystal structure and electron structure of Cs₂Ag Fe Cl₆ can be effectively regulated by means of In³⁺or Na⁺substitution engineering.The prepared Cs₂Ag In_xFe_1-xCl₆?0?x?1?and Cs₂Na_xAg_1-xFe Cl₆?0?x?1?perovskite single crystal have strong absorption capacity in the range of 450-800 nm.And Cs₂Ag In_xFe_1-xCl₆?0?x?1?perovskite single crystal has excellent luminescence performance in the range of 600-750 nm.The photoluminescence quantum yield?PLQY?after doping is significantly improved by 167 times compared with pure Cs₂Ag Fe Cl₆ perovskite material.The crystal structure of a series of new double perovskite single crystals was resolved and analyzed,and the energy band structure,state density and charge density distribution were obtained by density functional theory?DFT?calculation.Both theory and experiment show that the photoelectric performance of Cs₂Ag Fe Cl₆perovskite monocrystalline material can be effectively improved,e.g.,the density of defect states can be reduced,and the transport capacity of carriers can be enhanced.This study laid a foundation for the application of new Cs₂Ag Fe Cl₆ double perovskite materials in the fields of photovoltaic,luminescence and catalysis.At the same time,it provides new ideas for the design and development of new non-toxic and stable perovskite materials.