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 BAEuI (BA denotes CHNH) single crystals for the first time. BAEuI 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 BAEuI. Moreover, BAEuI shows a short excited-state lifetime (151 ns) due to the parity-allowed transition, which boosts the potential of BAEuI for use in real-time dynamic imaging and computer tomography applications. In addition, BAEuI 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 BAEuI 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 BAEuI/PS composite scintillation screen. We anticipate that this work will stimulate the exploration of transition lanthanide metal halides for sensitive x-ray scintillators.