近空间升华法制备CsPbBr3薄膜及其X射线探测性能研究

All-inorganic CsPbBr3 perovskite is an ideal novel material for high-energy radiation detection due to its high atomic number, high resistivity, high μτ value (the mobility and lifetime product), excellent chemical stability and radiation resistance. It will have a wide range of application by using CsPbBr3 films to fabricate semiconductor-type X-ray detectors with simple device structure and high quantum efficiency, which has not yet been reported. In this project, CsPbBr3 films with high quality will be prepared by using close-spaced sublimation method, which is an efficient way to deposit compact, homogeneous and large-scale films with high deposition rate. The films growth mechanism will be illuminated by analyzing the dynamic process of films formation. The forms and formation mechanisms of the defects in CsPbBr3 films prepared under different growth condition will be studied. Moreover, the relationship between defects and resistivity, μτ value of films will be explored to obtain detector-grade CsPbBr3 films with excellent carrier transport properties. The diffusion mechanism of Au in CsPbBr3 films and its effect on carrier collection efficiency of device will be studied, so as to fabricate semiconductor-type X-ray detectors based on CsPbBr3 films with high sensitivity and low lowest detectable dose rate. This project will provide theoretical and experimental basis for the application of CsPbBr3 films in the field of large-scale X-ray imaging such as medical scan and security monitoring.

全无机钙钛矿CsPbBr3材料具有原子序数高、电阻率高、μτ值（载流子迁移率和寿命的乘积）高、化学稳定性好和抗辐照能力强等优点，是一种理想的新型高能射线探测材料。采用CsPbBr3薄膜制备器件结构简单、量子效率高的半导体型X射线探测器具有广阔的应用前景，但目前还未见相关研究报道。本项目拟采用可大面积均匀致密成膜且生长速率高的近空间升华法实现高质量CsPbBr3薄膜的生长，分析薄膜的成膜动力学过程，阐明薄膜的生长机制；分析不同工艺条件下薄膜中的缺陷类型及其形成机理，探究缺陷与薄膜电阻率和μτ值的关系，获得载流子输运性质优异的探测器级CsPbBr3薄膜；研究Au在CsPbBr3中的扩散机制及其对器件载流子收集效率的影响，制备出灵敏度高、最低可探测剂量率低的CsPbBr3薄膜半导体型X射线探测器，为CsPbBr3薄膜在医学检查、安全监控等大面积X射线成像领域中的应用提供理论与实验依据。

全无机钙钛矿CsPbBr3材料具有原子序数高、电阻率高、μτ值高、化学稳定性好和抗辐照能力强等优点，是一种理想的新型高能射线探测材料。将CsPbBr3薄膜应用于X射线探测器在大面积X射线成像领域具有广阔的应用前景。本研究率先采用可大面积均匀致密成膜且生长速率高的近空间升华法制备CsPbBr3薄膜及其X射线探测器。研究结果表明，通过将CsBr和PbBr2粉末混合后直接升华难以获得CsPbBr3薄膜，而优化薄膜制备工艺后，即先将CsBr和PbBr2混合并加热合成CsPbBr3粉末后再升华可沉积出纯立方相结构的CsPbBr3薄膜。薄膜经过后退火工艺处理后，薄膜的结晶质量、晶粒尺寸和表面平整度得到了明显的改善，获取了结晶质量高、晶粒尺寸达到微米量级且薄膜致密性好的探测器级CsPbBr3薄膜。制备了共面叉指电极和电极结构的CsPbBr3薄膜光电探测器，并研究其对紫外光的探测性能，结果表明共面叉指电极结构的器件暗电流要小一个数量级，光-暗电流比要高一个数量级，CsPbBr3薄膜对紫外光的响应度为0.55A/W，紫外-可见抑制比为7.9，响应时间为230μs。利用自主设计搭建的X射线探测器性能测试系统对CsPbBr3薄膜X射线探测器的器件性能进行表征，实现了灵敏度高（67.1μCGy-1cm-2）、最低可探测剂量率低（382nGys-1）、探测效率高（42.5%）的CsPbBr3薄膜X射线探测器的制备，且器件的稳定性好，在相对湿度为50%的空气环境中，保存10天（240h）后，器件的灵敏度保持在初始值的94.6%。本项目的顺利开展，为CsPbBr3薄膜在医学检查、安全监控等大面积X射线成像领域中的应用提供一定的理论与实验依据。本研究还通过利用原创的基于连续溶质传输过程的原料自补充法制备了高性能的MAPbI3钙钛矿单晶X射线探测器，采用低成本逆温结晶法制备了光产额达119000photons/MeV的CsI单晶闪烁体。