Application Of Lead Free Perovskite Materials In X-ray Imaging

Since its discovery,X-rays have been widely used in medical diagnosis,as well as in industrial flaw detection and security inspection.The physical properties of the detection materials（scintillators）used in X-ray imaging directly determine the performance of X-ray detection,which plays a vital role in medical X-ray CT imaging and safety inspection.In recent years,organic-inorganic hybrid perovskites have shown good application prospect in X-ray detection by virtue of their intrinsic properties such as tunable band gap,large atomic number and large density.In particular,the all-inorganic lead halide perovskite has become the focus of X-ray imaging research because of its good stability and higher photoluminescence quantum efficiency（PLQY）than traditional scintillator.However,the soluble toxic lead contained in it will cause damage to the environment and human body.Therefore,this thesis aims to explore a series of scintillator materials suitable for X-ray imaging with high PLQY,high radioluminescence yield,low cost and environmental friendliness.The essay mainly carries out the following three works:An inorganic non-lead perovskite material,Rb₂Ag Br₃ micron rod,with a diameter of 0.4-1μm,presents green light under the irradiation of a deep ultraviolet fluorescent lamp（254 nm）.The photoluminescence emission peak of Rb₂Ag Br₃ micron rod is about514 nm,PLQY is only 5.46%and Stokes shift is about 254 nm.The prepared Rb₂Ag Br₃micron rod has a radioluminescence yield close to that of reported Cs Pb Br₃ under the excitation of X-ray.Therefore,scintillator films based on Rb₂Ag Br₃ were prepared on the substrate of optical fiber panel and used in X-ray transmission imaging.Finally,the image of iron wire was successfully obtained.The Cs Ag Cl₂ microcrystal,a lead-free perovskite material,was studied and successfully applied to X-ray transmission imaging based on Cs Ag Cl₂ scintillator.The prepared Cs Ag Cl₂ microcrystal is a vertical cube with a diameter of 0.4-0.8μm.The photoluminescence emission peak of Cs Ag Cl₂ is 570 nm,and the Stokes shift is 310 nm.Compared with Rb₂Ag Br₃,the PLQY of Cs Ag Cl₂ micron crystal is slightly increased,which is 8.15%.Under 80 k V and 70μA,the radioluminescence yield of Cs Ag Cl₂ is 97%higher than that of Cs Pb Br₃,which is more suitable for X-ray imaging.Finally,the Cs Ag Cl₂-based scintillation screen was successfully used to image the metal and plastic.X-ray application of lead-free copper-based Cs₃Cu₂I₅ perovskite nanocrystals has been studied.The prepared Cs₃Cu₂I₅ nanocrystals have a 59%PLQY and excellent stability over three months.Furthermore,the Cs₃Cu₂I₅ nanocrystals have a high radioluminescence yield under X-ray excitation at 80 k V and 70μA,and is also higher than that of Rb₂Ag Br₃ and Cs Ag Cl₂ perovskite materials previously prepared.Due to the excellent radioluminescence properties of Cs₃Cu₂I₅ nanocrystals,we studied the conventional transmission imaging of Cs₃Cu₂I₅ nanocrystals and the performance of a scintillator screen as a tomography.