Mn-doping engineering enabling non-radiative defects suppression of Cs₂ZrCl₆ nanocrystals for high-resolution X-ray...

Zero-dimensional (0D) lead-free Cs₂ZrCl₆ nanocrystals (NCs) have gained increasing attention in the photoluminescence (PL) and scintillation fields owing to their remarkable advantages such as low cost, high chemical yield, and environmental friendliness. Nevertheless, the current Cs₂ZrCl₆ NCs are plagued by low photoluminescence quantum yield (PLQY) and low light yield (LY) due to inherent defects (like chlorine vacancies), which commonly serve as traps and cause non-radiative recombination of excitons. Herein, Cs₂ZrCl₆ NCs with non-radiative defects eliminated, which have a near-unity (98.6 %) PLQY and an ultra-high LY (79,000 photons MeV^-1), were prepared via Mn doping. The experimental characterizations, including X-ray photoelectron spectroscopy (XPS), Raman, steady-state and time-resolved photoluminescence spectroscopy, confirmed the elimination of non-radiative chlorine vacancies in Mn-doped Cs₂ZrCl₆. Density functional theory calculations disclosed that the existence of chloride vacancies in Cs₂ZrCl₆ could introduce deep defect levels within the bandgap, resulting in non-radiative recombination. However, Mn doping could eliminate these trap states. Consequently, the fabricated Mn-doped Cs₂ZrCl₆ scintillator film achieved excellent performance for bendable X-ray detection and imaging, featuring an ultra-low detection limit (35.6 nGy_air s^-1) and an ultra-high spatial resolution (20 lp mm^-1). The work suggests that doping can provide an alternative solution for developing defect-free perovskites with perfect properties.