Two-coordinate copper(I) complexes enable efficient X-ray scintillation and imaging

Abstract

Organic scintillators hold great promise for applications in high-energy radiation detection and medical diagnostics. However, their practical application is hindered by limited X-ray attenuation capacity and low exciton utilization efficiency. Here, we present a series of two-coordinate Cu(I)-based carbene-metal-amide (CMA) complexes featuring cyclic(amino)(barrelene) carbene ligands. These complexes exhibit pronounced thermally activated delayed fluorescence (TADF) from a metal-perturbed interligand charge transfer (ICT) excited state, together with high photoluminescence quantum yields of up to 0.86 and short decay lifetimes as low as 1.54 µs in thin films. Moreover, the Cu metal center significantly enhances the X-ray absorption cross-sections of these complexes. Under X-ray irradiation, these complexes display intense radioluminescence with high light yields of up to 30522 photons MeV⁻¹. The optimized scintillator screens enable high-quality X-ray imaging with a spatial resolution exceeding 16.0 line pairs mm⁻¹. This work represents the first demonstration of CMA complexes as scintillators for X-ray detection and provides a guideline for developing efficient organic X-ray scintillators.