Photoluminescence and Radiation Luminescence in a Hybrid Cuprous (I) Halide: (4,4-Difluoro-bipiperidinium)₃Cu₂I₅

Copper (I) based halide scintillators have received high attention due to their high light yield. At the same time, researchers are increasingly interested in exploring organic-inorganic hybrid copper(I) based halides, due to the diversity and tunability of structures. Here, we describe high-efficiency photoluminescence and X-ray excited luminescence in (DFPD)(3)Cu2I5 (1) (DFPD=4,4-difluoro-bipiperidinium). 1 is comprised of a unique [Cu2I5](3-) cluster, which have typical structure allowing high-transition-probability self-trapped exciton emission (one Cu+ ion adopts the tetrahedral coordination geometry, the other trigonal planar coordination geometry, the Cu-Cu distance (2.574 angstrom) is short). Accordingly, 1 shows efficient yellow-green photoluminescence with the maximum at 527 nm, a full-width at half-maximum of 99.2 nm, a large Stokes shift of 214 nm (1.6 eV) and a quantum yield of 77.15 %. Polycrystalline 1 can also convert high-energy X-ray photons into UV-visible pulsed fluorescence with the light yield of 5000 photons/MeV. This finding plays a valuable role in the development of organic-inorganic hybrid copper(I) based scintillators.