Bond-Mode Engineering in Copper(I) Halides: From Excitation-Dependent Luminescence to High-Resolution X-Ray Imaging Screens.

Abstract

Copper(I)-based halides are promising for X-ray detection due to their excellent scintillation efficiency and solution processability. However, the structure-property relationship remains elusive, and their practical viability for X-ray imaging is largely unverified. In this work, we employ a bond‑mode control strategy to synthesize two compounds from the same amine precursor: ionic (4‑ATHP)₂CuI₃ and coordinative (4‑ATHP)₄Cu₄I₄ (4-ATHP = 4-Aminotetrahydropyran), providing a model system to study their photophysics and underlying mechanism. (4‑ATHP)₂CuI₃ adopts a unique 1D crystal structure with alternating arrangement of Cu₂I₆ dimers, which shows excitation‑dependent dual emissions. Experimental and calculation results indicate that the dual emissions originate from the Cu₂I₆ dimer with a different Cu─Cu bond length. In contrast, the (4‑ATHP)₄Cu₄I₄ shows single emission centered at 635 nm, in which the organic component contributes to the excited state. The ionic (4‑ATHP)₂CuI₃ achieves a much higher light yield (55 923 photons/MeV) than that of the coordinative counterpart (31 866 photons/MeV). Furthermore, a large‑area flexible film (15 × 20 cm²) based on (4‑ATHP)₂CuI₃ delivers a spatial resolution of 20 lp/mm. Critically, integrating this film into a CMOS imager demonstrates superior dynamic imaging without afterglow, outperforming the commercialized CsI: Tl screen. This study not only deciphers the bond‑mode‑dependent photophysics but also validates a commercial‑grade scintillator, paving the way for high‑performance X‑ray imaging materials.