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 (Eu2+) with intrinsically efficient and self-absorption-free d-f transition are a prospective replacement for the toxic Pb2+. Here, we demonstrated solution-processed organic-inorganic hybrid halide BA(10)EuI(12) (BA denotes C4H9NH4+) 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 [EuI6](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 similar 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 mu Gy(air) s(-1) to 145 mu Gy(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.

Automated summary

Lead halide perovskite nanocrystals have potential as x-ray scintillators, but suffer from toxicity issues and low light yield. Bivalent europium ions (Eu2+) are a prospective replacement for lead due to efficient and self-absorption-free d-f transition. Solution-processed organic-inorganic hybrid halide BA(10)EuI(12) single crystals were demonstrated for the first time, exhibiting high photoluminescence quantum yield, large Stokes shift, and appreciable light yield. BA(10)EuI(12) also showed a short excited-state lifetime, linear scintillation response, low detection limit, and clear x-ray imaging capability.