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

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 ) with intrinsically efficient and self-absorption-free transition are a prospective replacement for the toxic Pb . Here, we demonstrated solution-processed organic-inorganic hybrid halide BA EuI (BA denotes C H NH ) single crystals for the first time. BA EuI was crystallized in a monoclinic space group of 2 / , with photoactive sites of [EuI ] 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 EuI . Moreover, BA EuI shows a short excited-state lifetime (151 ns) due to the parity-allowed transition, which boosts the potential of BA EuI for use in real-time dynamic imaging and computer tomography applications. In addition, BA EuI demonstrates a decent linear scintillation response ranging from 9.21 μGy s to 145 μGy s and a detection limit as low as 5.83 nGy s . The x-ray imaging measurement was performed using BA EuI 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 at modulation transfer function = 0.2 for BA EuI /PS composite scintillation screen. We anticipate that this work will stimulate the exploration of transition lanthanide metal halides for sensitive x-ray scintillators.