Preparation And Exciton Kinetics Of Two-dimensional Metal Halide Perovskite

Metal halide perovskite has attracted much attention in the field of photovoltaic devices due to its excellent light absorption coefficient,optical quantum yield,chemical composition adjustable band gap width,long diffusion distance and fluorescence life.However,due to the limitation of structure and dimension,the environmental stability and photoelectric performance of 3D perovskite need to be improved in long-term operation.With the development of a series of low-dimensional materials,perovskite materials gradually tend to be low-dimensional,and it is found that low-dimensional perovskite can not only make up for the deficiency of structure and performance of body perovskite.Due to the change of dimension,low-dimensional perovskite has many unique photoelectric properties.In this paper,2D pure inorganic metal halide perovskite was synthesized by chemical vapor deposition and its basic optical properties were studied.Organic-inorganic hybrid perovskite（BA）₂（CH₃NH₃）_n-1Pb_nI_3n+1microcrystals were prepared by liquid phase method.The exciton behavior dynamics of（BA）₂（CH₃NH₃）_n-1Pb_nI_3n+1nanosheets were studied after the microcrystals were pretreated,and the internal exciton behavior of（BA）₂Pb I₄was effectively modulated by external electric field.The specific research content is as follows:（1）Ultrathin CsPbBr₃nanosheets were prepared by chemical vapor deposition（CVD）.High quality CsPbBr₃nanosheets were prepared by adjusting gas flow rate,concentration of reaction source（relative position of magnetic boat）and reaction temperature.Experimental results show that when the flow rate of argon gas is about 30 sccm.The heating rate was 24℃/min,and the sample quality was higher when the temperature was increased to550℃for 75 min.The changes of band gap and optical properties of CsPbBr₃nanosheets with different thicknesses were investigated by atomic force microscopy（AFM）and optical characterization,and the optimal fluorescence lifetime of CsPbBr₃nanosheets at a certain thickness was verified.（2）The lasing behavior of the prepared CsPbBr₃nanosheet was characterized,and the special configuration of the randomly growing CsPbBr₃nanowire-nanosheet was found.The optical waveguide behavior of the CsPbBr₃nanowire and the optical waveguide coupling lasing behavior of the CsPbBr₃nanowire and the optical waveguide was preliminatively explored.（3）（BA）₂（CH₃NH₃）_n-1Pb_nI_3n+1quasi-two-dimensional materials with different n values were prepared by inverse solvent diffusion method.The high purity and high quality of the materials were verified by the basic phase characterization and optical characterization.The effects of different factors on the behavior dynamics of organic-inorganic hybrid perovskite excitons were studied by changing a single variable（temperature）,single quantum well thickness（n value）,and different continuous quantum well thickness).（4）The（BA）₂（CH₃NH₃）_n-1Pb_nI_3n+1nanosheets with n=1 were selected for electric-field modulated exciton diffusion.A device configuration perpendicular to the direction of organic-inorganic stacking was constructed using h-BN and thin graphene with good light transmission,and the exciton behavior was modulated by applied gate pressure（BA）₂Pb I₄.After removing the applied electric field,the device can be restored.In the case of no tunneling effect,the applied electric field can be applied repeatedly and the device will not be damaged.