高稳定铜基钙钛矿结构设计及X-ray成像应用研究

【作者】 周维；

【导师】 刘碧桃； 彭玲玲；

【作者基本信息】 昆明理工大学 ， 材料工程（专业学位）， 2023， 硕士

【摘要】 X射线成像在医疗、工业无损探测、安检和核安全探测等领域被广泛应用,闪烁体作为能量转换层是X射线成像系统中的一个重要组件,它可以有效地将高能X射线转换为可见光。新型钙钛矿闪烁体由于其可调谐的发射波长、高的X射线吸收、高光效、快衰减以及易制备等特点而展现出巨大的应用潜力,但普遍存在环境稳定性差的问题,以及微纳米晶闪烁体的器件封装问题,限制了钙钛矿闪烁体的商业应用。针对以上问题,本文聚焦于闪烁性能优异的Cs₃Cu₂Cl₅与Cs₃Cu₂I₅无铅钙钛矿闪烁体,通过便捷的方法制备高质量、高分辨率的微纳米晶材料,深入探究其光致发光与辐射发光性能,并提出微波后处理修复和复合有机聚合物两种策略来实现在X射线成像中的长期稳定和可重复性应用。本工作为实现无铅钙钛矿闪烁体的高稳定性应用提供了两种新的思路,进一步推动了钙钛矿闪烁体的商业应用进程,具体内容如下:（1）采用热注射法制备了大尺寸、高结晶性、亚微米级的片状Cs₃Cu₂Cl₅钙钛矿晶体,从而获得了致密的Cs₃Cu₂Cl₅闪烁体膜。对其光物理性能以及辐射发光性能进行了相关表征,结果表明Cs₃Cu₂Cl₅可以实现72.1%的光致发光量子效率（PLQY）、小的自吸收和高达20 lp mm^-1的成像分辨率。为解决器件长期使用不稳定的问题,本工作引入了一种便捷高效的微波修复策略。通过短时间的简单微波处理,使高湿度环境中易被湿度侵蚀破坏的Cs₃Cu₂Cl₅晶体再结晶,进而重筑闪烁体膜的晶体结构,再现其光致发光（PL）与辐射发光（RL）性能,可以分别恢复至初始强度的97.3%和95.4%。结果表明,通过每隔一天对Cs₃Cu₂Cl₅闪烁体膜的微波处理,可以有效延长其在X射线成像应用中的工作寿命至30天,实现了Cs₃Cu₂Cl₅闪烁体膜在X射线成像中的长期稳定应用。（2）以本征稳定性更好的Cs₃Cu₂I₅钙钛矿作为闪烁体材料进行了相应研究。本工作引入了一种两步退火策略,通过控制原位结晶旋涂法中两次退火过程的温度和时间,精准实现Cs₃Cu₂I₅晶体在聚甲基丙烯酸甲酯（PMMA）基体中先原位成核结晶再原位生长,制备了可以长期稳定成像应用的Cs₃Cu₂I₅@PMMA闪烁体膜。研究结果表明,所制备的Cs₃Cu₂I₅@PMMA闪烁体膜具有高的结晶度、大的尺寸（10×10 cm）、优异的柔韧性、高稳定的发光性能（PLQY=64%）、高效的辐射发光性能和高质量的X射线成像分辨(12.5 lp mm^-1)。Cs₃Cu₂I₅@PMMA闪烁体膜多功能成像应用结果表明,该闪烁体膜不仅可以对不同复杂结构的物体进行清晰准确的成像识别;也具有高效的工作稳定性,可以在60天内保持其稳定的X射线成像质量;还可以实现柔性成像,闪烁体膜的柔性贴覆有效地保证了X射线成像结果的准确性。综上所述,本论文为制备高质量闪烁体膜提供了两种有效思路,满足了新型闪烁体的多维度需求,为钙钛矿闪烁体的商业应用提供了参考。更多还原

【Abstract】 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.更多还原