Lead-Free Zero-Dimensional Organic-Copper(I) Halides as Stable and Sensitive X‑ray Scintillators

Low-dimensional organic–metal
halides are regarded as an
emerging class of X-ray scintillation materials, but most of the discovered
compounds are confronted with challenges of toxicity and instability.
To address these challenges, we herein report two lead-free zero-dimensional
(0D) hybrid halides, (Bmpip)2Cu2Br4 and PPh4CuBr2 single crystals, grown by the
low-cost solution-processing method. By single-crystal X-ray diffraction
refinement, the crystal structures of (Bmpip)2Cu2Br4 and PPh4CuBr2 were determined
to be orthorhombic and monoclinic crystal systems, respectively. (Bmpip)2Cu2Br4 and PPh4CuBr2 show broadband orange and yellow emissions peaking at 620 and 538
nm, respectively. Different from the emission nature of the recent
reported Cu-based halide hybrids, both (Bmpip)2Cu2Br4 and PPh4CuBr2 emit from excitons
bound to defects featuring spin-allowed transition, enabling them
to possess fast scintillation decay time of tens of nanoseconds, respectively.
In particular, the (Bmpip)2Cu2Br4 single crystal has a high photoluminescence quantum yield of 48.2%,
a high scintillation yield of 16,000 photons/MeV, and a low detection
limit of 710 nGyair/s. Due to the combination of nontoxicity,
long-term stability, and decent detection performance, (Bmpip)2Cu2Br4 could be regarded as a promising
X-ray scintillator.