Heterovalent cation-exchange of CsPbBr₃ perovskite nanocrystals with enhanced stability for x-ray imaging

Metal halide perovskites have emerged as promising candidates for x-ray detection; in particular, the in-direct detectors based on perovskite scintillators have demonstrated appealing performance metrics. However, both perovskite thin films and nanocrystals still suffer from poor stability. In this work, we introduce a heterovalent cation exchange strategy to effectively modulate the optoelectronic properties of perovskite nanocrystals and further enhance their stability. Here, a portion of Pb²⁺ in perovskite nanocrystals was replaced with lead-free Sb³⁺. This is a versatile method that can be applied to cation exchange of various perovskite nanocrystals, such as CsPbX₃ and FAPbX₃, allowing for the synthesis of a wide range of mixed-cation perovskite compositions. The resulting nanocrystals exhibit relatively high photoluminescence quantum yields and improved thermal stability and water resistance. The Sb@CsPbBr₃ nanocrystals also demonstrated great potential for x-ray detection as scintillators with fast response, bright and radioluminescence, and excellent image quality.