Preparation Of Inorganic Perovskite Single Crystaland Study On Optical Structure Of Thin Films

Perovskite is a semiconductor material with direct band gap which has high absorption coefficient in visible range.As a functional layer material for perovskite solar cells,it has great potential for application.The power conversion efficiency of perovskite solar cells has increased from 3.8%in 2009 to 22.1%in 2017.Perovskite materials also have the advantages of long carrier diffusion distance,tunable band gap,long carrier lifetime,simple preparation process,and so on.Except for the application in perovskite solar cells,it can also be widely used in perovskite light emitting diode,perovskite microlaser,photodetector and metasurface of optical gain.Up to now,the organic-inorganic hybrid perovskite has been studied extensively and deeply.However,due to its poor thermal stability and easily destroyed structure by water,the preparation and optoelectronic properties of inorganic perovskite single crystals and optical structure of perovskite thin films are studied in this dissertation.The preparation conditions of inorganic perovskite single crystals are analyzed.It is proposed to change the volatilization direction and growth environment pressure of antisolvent dichloromethane?CH₂Cl₂?to avoid the rapid supersaturation precipitation of perovskite single crystal from solution,and to slow down the growth rate of perovskite single crystal.A high quality inorganic perovskite?CsPbBr₃?single crystal is prepared by an improved one-step solution method.Its roughness is only 1.02 nm measured by atomic force microscope?AFM?.The absorption band edges of all-inorganic perovskite single crystals are measured and the bandgap is calculated to be Eg=2.296 eV.Using femtosecond laser at 400 nm to pump all-inorganic perovskite single crystals,it can be found that the laser mode is a whispering gallery mode?WGM?and has a lower laser threshold of 6.2?J·cm^-2.Br^-ion directional migration in perovskite single crystals is studied by introducing the built-in electric field into perovskite single crystals using electron beam lithography?EBL?technique which provides guidance suggestions for improving the performance of perovskite solar cells.In this dissertation,the structure color of all-inorganic perovskite?CsPbIBr₂?thin film grating is also studied.By hydrophilic treatment of indium tin oxide?ITO?glass substrate,controlling the value of water and oxygen below 0.1 ppm,argon protection,and so on,the yield of all-inorganic perovskite film is over 90%and the roughness of all-inorganic perovskite film is less than 10 nm.Using COMSOL Multiphysics software to simulate,the grating structure size of thin film structure color in visible light band is designed.Based on the simulation results,the grating structure of perovskite thin films is prepared by electron beam lithography?EBL?technique and plasma coupled etching technique.The phase transition of perovskite film between perovskite phase and non-perovskite phase is realized by controlling the temperature and humidity of the environment.Changing the refractive index of perovskite film can realize color conversion.This provides a good idea for color conversion of perovskite materials and can be used in display devices or humidity detection devices to some extent.