Yellow-emissive organic copper(I) halide single crystals with [Cu4I4] cubane unit as efficient X-ray scintillators

Recently, low-dimensional copper(I)-based halide has been considered as a potential substitute for its lead-based counterpart due to its environmental friendliness, facile preparation and superior luminescence performance. In particular, as a representative efficient luminescent material, it shows great potential as a scintillator for X-ray detection. Herein, three organic copper(I) halide single crystals were grown by incorporating a conjugated organic cation (4-benzylpyridine, 4-bzpy) with copper(I) iodide modules. The three compounds exhibit distinct crystal structure and properties. Notably, the zero-dimensional cubane-like (4-bzpy)4Cu4I4 shows a broadband emission with near-unity photoluminescence quantum yield (∼99.7%) and a large Stokes shift (∼216 nm). More importantly, it demonstrates an obvious X-ray response with a high light yield (∼60 948 photons per MeV) and a perfect linear relationship with the dose rate under X-ray irradiation. The highly efficient emission of (4-bzpy)4Cu4I4 clusters mainly originates from the ligand-to-core charge transfer state. This work not only provides further understanding of the importance of crystal structure in the properties of organic copper(I) halides, but also facilitates the design and fabrication of high-performance X-ray scintillators.