Preparation And Scintillation Properties Of All-inorganic Halide Perovskites And Their Thin Films

As a non-destructive detection means,X-ray imaging detection has been widely used in high-energy physics,industry,medical imaging,security,scientific research,and other fields.Depending on the detection method,X-ray imaging detection is divided into direct detection and indirect detection.In direct detection,the semiconductor directly converts high-energy radiation information into electrical signals and then read out the high-resolution images.Indirect detection requires the use of scintillation materials,which are a kind of energy conversion materials that can convert high-energy rays（X-rays,βrays,γrays,etc.）or particles（αparticles,neutrons,etc.）into low-energy ultraviolet or visible light,and then the low energy light information is transmitted to the photodiode for photoelectric conversion,in order to read the X-ray images.The development of next generation high performance scintillation materials is becoming more and more urgent due to the lower cost of indirect detection and the problems of high preparation costs,complex processes and long afterglow times of traditional commercial scintillators such as Lu₂（1-x）Y_2xSi O₅（LYSO）or Cs I:Tl.All inorganic halide perovskites and metal halide materials¹ have become the focus of research on new scintillation materials due to their excellent photoluminescence efficiency,high photoluminescence quantum yield,adjustable luminescence wavelength,low synthesis cost and short synthesis time.However,there are still some deficiencies on synthesis methods and film making in the current research reports.The problems of poor scintillation performance,the difficulty in scaling up synthesis,and thin scintillation film thickness in the current film preparation have limited the practical application of perovskite and metal halide.In view of the above background and problems,this paper explored the synthesis methods and thin film preparation processes of perovskite and its related compounds,and prepared thin films with large area,sub millimeter thickness,good uniformity and flatness,and uniform luminescence.The imaging tests were conducted using all inorganic halide perovskite and metal halide scintillator thin films combined with practical indirect X-ray imaging detectors.The following main results were achieved:（1）Rod-like crystals of K₂CuCl₃ was prepared by the saturated solution slow cooling method and K₂Cu Br₃polycrystalline powder was prepared by the reverse solvent method.The luminescence peak of K₂CuCl₃ was 386 nm and the PLQY reached 99.91%.The luminescence peak of K₂Cu Br₃ was 383 nm and the PLQY reached 93.54%.The X-ray yield of the K₂CuCl₃ sample is estimated to 16800 Ph/Me V,and K₂Cu Br₃,25100 Ph/Me V.The prepared K₂CuCl₃-PDMS（PDMS,Polydimethylsiloxane）and K₂Cu Br₃-PDMS films were coupled with an indirect X-ray imaging detector for testing and obtaining X-ray imaging images.The results show that K₂CuCl₃ and K₂Cu Br₃ are feasible in X-ray imaging applications,and the resolution can reach 2.00 lp/mm.（2）Cs₃Cu₂Cl₅ scintillator powder was prepared by aqueous solvent mixing with saturated precursor.The powder precipitation of Cs₃Cu₂Cl₅ was obtained by mixing saturated Cs Cl aqueous solution with saturated CuCl hydrochloric acid solution（molar ratio Cs Cl:CuCl=3:2）.This method can be used for large-scale green synthesis experiments,and the product yield of Cs₃Cu₂Cl₅ can reach to 77%,and the PLQY is 96.65%.The photoluminescence peak of 529 nm is higher than that of the common blue-violet system materials,resulting in a photon yield of 59900 photons/Me V,which is comparable with the existing commercial scintillator Cs I:Tl.By combining Cs₃Cu₂Cl₅-PDMS film with X-ray imaging detector,the imaging resolution can reach 4 lp/mm,which is the upper limit of the detector,and proved the potential of perovskite and its related compounds in X-ray imaging applications.At the same time,the synthesis method can also be synthesized in other systems,and has a certain generalization.（3）By direct ultrasonic spraying of CsPbBr₃ perovskite nanocrystalline solution and in situ preparation of Cs₃Cu₂Cl₅ precursor solution,CsPbBr₃ scintillation films and Cs₃Cu₂Cl₅scintillation films without polymer adhesive were prepared,which made the proportion of scintillation materials per unit volume higher and achieved the purpose of reducing light dispersion and improving resolution.It is of great significance to prepare perovskite and its related compounds scintillation thin films in the future.