Defect-passivated Te-doped Cs2HfCl6 perovskite microcrystals with high efficiency and robust stability for X-ray imaging

Lead-free vacancy-ordered double perovskites are promising scintillator candidates for X-ray imaging due to their excellent photoluminescence and low afterglow. However, the defect-related nonradiative recombination will decrease their photoluminescence intensity as well as scintillation performance. In this work, a facile room-temperature recrystallization approach was used to prepare high-quality Cs 2 HfCl 6 :1% Te perovskites microcrystals with suppressed defects via in situ ligand passivation with cationic quaternary ammonium surfactants. By tuning the chain length of ligands, dodecyltrimethylammonium chloride (DTAC) passivated Cs 2 HfCl 6 :1% Te possesses a high photoluminescence quantum yield (PLQY) up to 73.87%, which is higher than that of didodecyldimethylammonium chloride (DDAC) passivated Cs 2 HfCl 6 :1% Te. The improved performances of perovskites were further clarified by density functional theory (DFT) computations, which reveal that a larger binding energy for DTAC (−2.069 eV) exceeds that of DDAC (−1.891 eV). The Cs 2 HfCl 6 :1% Te (DTAC) exhibits a high spatial resolution (10 lp mm −1 ) and notable light yield (19,693 photons MeV −1 ). This study provides an effective strategy for defect suppression in perovskite scintillators, facilitating their use in high-resolution X-ray imaging.