Synergistic optimization of luminescence in feldspar-structured blue-cyan phosphors via heterovalent K+ substitution coupled with bandgap engineering

Conventional white light-emitting diodes (WLEDs) have a cyan gap in their emission spectra, which limits their colour rendering index (CRI) and spectral continuity and thus restricts their practical potential. Here, a series of cyan-emitting Sr 0.7-x K x Al 2 Si 2 O 8 :0.3Eu 2+ (x = 0–0.35) phosphors were synthesized via a high-temperature solid-state reaction. By substituting heterovalent K + , we redshifted the emission peak and engineered the bandgap, effectively suppressing nonradiative transitions. As a result, the emission intensity at 423 K is increased from 35 % to 83 % of the room-temperature value, and the internal quantum efficiency reaches 62 %. When the optimized phosphor is combined with a near-UV chip and commercial red phosphor, a WLED with Ra = 92 and CCT = 4673 K is achieved. This strategy not only fills the gap in the cyan spectrum but also simplifies the device fabrication process, demonstrating the great promise of the present phosphor for next-generation full-visible-spectrum WLED lighting.