Solution-Processed Hybrid Europium (II) Iodide Scintillator for Sensitive X-Ray Detection

Abstract

Lead halide perovskite nanocrystals have recently demonstrated great potential as x-ray scintillators, yet they still suffer toxicity issues, inferior light yield (LY) caused by severe self-absorption. Nontoxic bivalent europium ions (Eu 2+ ) with intrinsically efficient and self-absorption-free d–f transition are a prospective replacement for the toxic Pb 2+ . Here, we demonstrated solution-processed organic–inorganic hybrid halide BA 10 EuI 12 (BA denotes C 4 H 9 NH 4 + ) single crystals for the first time. BA 10 EuI 12 was crystallized in a monoclinic space group of P 2 1 / c , with photoactive sites of [EuI 6 ] 4− octahedra isolated by BA + cations, which exhibited high photoluminescence quantum yield of 72.5% and large Stokes shift of 97 nm. These properties enable an appreciable LY value of 79.6% of LYSO (equivalent to ~27,000 photons per MeV) for BA 10 EuI 12 . Moreover, BA 10 EuI 12 shows a short excited-state lifetime (151 ns) due to the parity-allowed d–f transition, which boosts the potential of BA 10 EuI 12 for use in real-time dynamic imaging and computer tomography applications. In addition, BA 10 EuI 12 demonstrates a decent linear scintillation response ranging from 9.21 μGy air s −1 to 145 μGy air s −1 and a detection limit as low as 5.83 nGy air s −1 . The x-ray imaging measurement was performed using BA 10 EuI 12 polystyrene (PS) composite film as a scintillation screen, which exhibited clear images of objects under x-ray irradiation. The spatial resolution was determined to be 8.95 lp mm −1 at modulation transfer function = 0.2 for BA 10 EuI 12 /PS composite scintillation screen. We anticipate that this work will stimulate the exploration of d–f transition lanthanide metal halides for sensitive x-ray scintillators.