Research On The Structure Design Of Highly Stable Copper-based Perovskite And Its Application In X-ray Imagin

X-ray imaging is widely used in medical,industrial nondestructive detection,security and nuclear safety detection.Scintillator is an important component in X-ray imaging system as an energy conversion layer,which can effectively convert high-energy X-rays into visible light.New perovskite scintillators show great application potential due to their tunable emission wavelength,high X-ray absorption,high luminescence efficiency,fast decay and easy preparation.However,the common problems of poor environmental stability and device encapsulation of micro-and nanocrystalline scintillators limit the commercial applications of perovskite scintillators.To address these problems,this paper focuses on Cs₃Cu₂Cl₅ and Cs₃Cu₂I₅ lead-free perovskite scintillators with excellent scintillation performance,prepares high-quality,high-resolution micro-nanocrystalline materials by convenient methods,deeply investigates their photoluminescence and radioluminescence properties.We have proposed two strategies,microwave post-treatment restoration and composite organic polymer,to achieve long-term stability and reproducible X-ray imaging.This work provides two new ideas to realize the high stability application of lead-free perovskite scintillators and further promote the process of commercial application of perovskite scintillators,as follows.（1）Large-size,highly crystalline,submicron-sized sheets of Cs₃Cu₂Cl₅ scintillators were prepared by hot-injection method,resulting in dense Cs₃Cu₂Cl₅ scintillator films.The photophysical properties as well as the radioluminescence properties were characterized correlatively,and the results showed that Cs₃Cu₂Cl₅ could achieve 72.1%photoluminescence quantum yield（PLQY）,small self-absorption and imaging resolution up to 20 lp mm^-1.To address the problem of long-term device instability,a convenient and efficient microwave repair strategy is introduced in this work.Through a short time simple microwave treatment,the Cs₃Cu₂Cl₅ crystals,which are easily damaged by humidity erosion in high humidity environment,are recrystallized,and then the crystal structure of the scintillator film is reconstructed to reproduce its photoluminescence（PL）and radioluminescence（RL）properties,which can be restored to 97.3%and 95.4%of the initial intensity.The results show that the microwave treatment of Cs₃Cu₂Cl₅ scintillator films every other day can effectively extend their working life in X-ray imaging applications up to 30 days,achieving long-term stable applications of Cs₃Cu₂Cl₅ scintillator films in X-ray imaging.（2）Cs₃Cu₂I₅ perovskite with better intrinsic stability were investigated accordingly as scintillator materials.In this paper,a two-step annealing strategy was introduced to precisely realize the in situ nucleation and crystallization of Cs₃Cu₂I₅ crystals in polymethyl methacrylate（PMMA）matrix followed by in-situ growth by controlling the temperature and time during the two annealing processes of the in situ crystallization spin coating.The prepared Cs₃Cu₂I₅@PMMA scintillator films can be used for long-term stable imaging applications.The results of the study showed that Cs₃Cu₂I₅@PMMA scintillator films have high crystallinity,large size（10×10 cm）,excellent flexibility,highly stable luminescence（PLQY=64%）,efficient radioluminescence and high quality X-ray imaging resolution(12.5 lp mm^-1).The multifunctional imaging applications of Cs₃Cu₂I₅@PMMA scintillator films show that the film can not only provide clear and accurate imaging recognition of objects with different complex structures,it also has efficient working stability and can maintain its stable imaging quality within 60 days.And it can achieve flexible imaging,the flexible lamination of the scintillator film effectively ensures the accuracy of the X-ray imaging.In summary,this paper provides two effective way for the preparation of high-quality scintillator films that meet the multidimensional needs of novel scintillators and provides a reference for the commercial application of perovskite scintillators.