2D Structural Copper(I) Iodide Hybrid─A Promising Red-Emitting Phosphor for High-Performance WLEDs and X-ray Imaging

Currently, mainstream white light-emitting diodes (WLEDs) fabricated by combining a blue LED chip with Y 3 Al 5 O 12 :Ce 3+ yellow phosphor suffer from poor color rendering, unstable color temperature, and blue light hazards due to the lack of a red spectral component. In this study, a low-cost, easily synthesizable, nontoxic, and highly stable red-emitting Cu(I)-based hybrid material, Cu 2 I 2 (2-et-3-mepz) (2-et-3-mepz = 2-ethyl-3-methylpyrazine), is developed. This red-emitting material exhibits intense red emission under ultraviolet/blue light excitation, with an emission peak at 628 nm and CIE chromaticity coordinates of (0.628, 0.372), which are close to the standard red light. Experimental and theoretical analyses reveal that its luminescence mechanism primarily originates from hybrid metal/halide-to-ligand charge transfer ( 3 M/HLCT) and cluster-centered ( 3 CC) transitions. A WLED device fabricated by combining Cu 2 I 2 (2-et-3-mepz) with commercial blue and green phosphors achieves an Ra value as high as 93.0. Furthermore, Cu 2 I 2 (2-et-3-mepz) also exhibits excellent scintillation performance with a light yield of 12,647 photons MeV –1 . A flexible scintillation screen prepared using this material achieves a spatial resolution of 9.45 lp mm –1 , demonstrating its potential application value in X-ray imaging. This work not only achieves high-performance WLED devices but also provides a new strategy for developing low-cost, environmentally friendly red-emitting materials.