Preparation And Photoelectric Properties Of Cs₂AgBiX₆（X=Cl,Br）inorganic Halide Double Perovskite Materials

Cs₂AgBiX₆（X=Cl,Br）inorganic halide double perovskite material is a new catalytic material.Because of its unique optical properties,tunable band structure,high photoelectric conversion efficiency and strong light absorption ability,it is widely used in various catalytic fields.It is of great significance to study the preparation methods and optoelectronic properties of Cs₂AgBiX₆（X=Cl,Br）inorganic halide double perovskite materials.The size,doping and coating of Cs₂AgBiX₆（X=Cl,Br）inorganic halide double perovskite materials and their optoelectronic properties were studied in this paper.the samples were characterized and analyzed by field emission scanning electron microscopy（SEM）,x-ray diffraction（XRD）,uv absorption spectroscopy（UV-Vis）,specific surface area measurement method（BET）,and surface photovoltage spectroscopy was used to explore the transport behavior of their photogenerated charge carriers.The main research work includes the following three aspects:（1）Different size Cs₂AgBiX₆（X=Cl,Br）inorganic halide double perovskites were prepared by melt crystallization and water bath methods.The experimental results show that the size of the material has a great influence on the photoelectric properties of Cs₂AgBiX₆（X=Cl,Br）,that is,the smaller the size,the higher the separation efficiency of photogenerated electron-hole pairs,and the faster the degradation of methyl orange by ultraviolet lamp,which indicates that the catalytic activity is higher.（2）Cs₂AgBiCl₆materials doped with different Na were prepared by melting crystallization by adjusting the input of sodium citrate.The theoretical results show that the doping of Na has a great influence on the valence and conduction band positions of Cs₂AgBiCl₆,and the high density of Na doping can change the indirect band gap properties of Cs₂AgBiCl₆materials into direct band gap properties.The experimental results show that Na may be doped into the Cs₂AgBiCl₆material,which affects the lattice structure of the Cs₂AgBiCl₆material.According to the surface photovoltage data,the peak value of the photovoltage curve is constantly blue-shifted with the increasing amount of Na doping.The photocatalytic properties of the obtained materials were further explored by using the degradation of methylene blue as the probe.Compared with the pure Cs₂AgBiCl₆and pure Cs₂Na Bi Cl₆materials,the Na doped Cs₂AgBiCl₆materials prepared in this paper better photocatalytic properties.（3）The TiO₂coated Cs₂AgBiCl₆composites were successfully prepared using tetrabutyl titanate as the coating material by the combination of melt crystallization and ligand assisted precipitation.The experiments show that the TiO₂is attached to the surface of the Cs₂AgBiCl₆material.Compared with the pure Cs₂AgBiCl₆,the TiO₂@Cs₂AgBiCl₆composite has higher specific surface area and longer photogenerated carrier lifetime,so in the photocatalytic degradation reaction a good stabilizing effect on the Cs₂AgBiCl₆material in the photocatalytic degradation reaction of rhodamine.