Halogen-mediated luminescence regulation in zero-dimensional cuprous halides for high-performance solid-state lighting

Low-dimensional organic-inorganic hybrid metal halides have attracted considerable interest in solid-state lighting due to their structural tunability and excellent photophysical properties, yet the development of stable, lead-free emitters with controllable emission colors remains challenging. Herein, we synthesized two zero-dimensional (0D) cuprous halides, [EMBP]2Cu2Br4 and [EMBP]2Cu2I4 (EMBP⁺ = [4-(ethoxymethyl)benzyl]triphenylphosphonium), with high photoluminescence quantum yields of 75.69% and 57.61%, respectively. Benefiting from strong electron-phonon coupling and self-trapped exciton formation, both compounds exhibit broadband emission, with the spectral shift effectively modulated by halide substitution from Br^- to I^-. When employed as a green phosphor for white LEDs, [EMBP]2Cu2Br4 enables devices with a high color rendering index (CRI) of 83.5 and a correlated color temperature (CCT) of 6297 K, along with negligible performance degradation over 240 minutes of continuous operation. This work elucidates the halogen-mediated luminescence regulation mechanism in 0D Cu(I) halides and demonstrates their considerable potential for next-generation eco-friendly solid-state lighting.