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(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 P2(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.