High-efficiency broadband cyan-green emission from Sb3 +-doped Cs2KLuCl6 toward full-spectrum white light-emitting diodes

Developing high-performance cyan-green phosphors is essential for addressing the long-standing spectral deficiency in full-spectrum white light-emitting diodes (white-LEDs). Here, we report a broadband cyan-green-emitting phosphor, Cs 2 KLuCl 6 :Sb 3+ , synthesized via a facile HCl-assisted solid-state route that supports low-temperature processing and scalable fabrication. Sb 3+ incorporation modulates the electronic structure of Cs 2 KLuCl 6 by narrowing the bandgap from 5.07 to 3.70 eV and inducing pronounced Sb-Cl-Lu orbital hybridization, which stabilizes self-trapped excitons (STEs) and promotes efficient radiative recombination. Under 330 nm excitation, the optimized phosphor exhibits intense broadband cyan-green emission centered at 513 nm with a full width at half maximum of ∼108 nm and a high photoluminescence quantum yield of 82%. The phosphor also demonstrates excellent thermal robustness, retaining 91% of its room-temperature emission intensity at 423 K, with a high thermal activation energy of 0.2874 eV. When integrated with commercial blue- and red-emitting phosphors on a 365 nm LED chip, the resulting white-LED delivers high-quality white light with a color rendering index of 92 and a correlated color temperature of 4671 K, effectively eliminating the cyan spectral gap. These results establish Cs 2 KLuCl 6 :Sb 3+ as a promising cyan-green phosphor for next-generation full-spectrum solid-state lighting.