Cuprous-Hybrid Metal Halides with Multimode Self-Trapped Excitons Enable Full-Spectrum White-Light Emission with Considerable Color Stability

Zero-dimensional (0D) cuprous-based metal halides have recently gained prominence as advanced luminescent materials owing to their structural tunability and distinctive broadband self-trapped exciton (STE) emission. Herein, a 0D structure, ETPA 2 Cu 2 Br 2 I 2 (ETPA + = ethyltripropylammonium) crystal, was synthesized via a solution growth method. The rigid dimer [Cu 2 Br 2 I 2 ] 2–, formed due to the mixed-halide effect, effectively suppresses nonradiative recombination at room temperature. Temperature-dependent photoluminescence and Raman spectroscopic analyses systematically reveal dual STE emission channels originating from multimode vibronic coupling, achieving full-visible-spectrum white light emission with Commission Internationale de l’Éclairage (CIE) coordinates (0.3337, 0.3449) and a near-unity photoluminescence quantum yield of 95.94%. A prototype white LED fabricated with a 295 nm UV chip exhibits a high color rendering index (CRI = 88.4) and warm-white emission, demonstrating its potential for next-generation solid-state lighting and visible light communication systems.