Eu2+-doping induced phase transformation and blue–cyan luminescence in KAlSi3O8 phosphors

Cyan-emitting phosphors are essential to compensate for the emission gap of conventional white light-emitting diodes (WLEDs) in the 480–500 nm range, thus considerably increasing the color rendering index (Ra) and gamut coverage to achieve high-quality full-spectrum lighting. In this work, we developed a phase-tunable Eu 2+ -doped KAlSi 3 O 8 multiphase phosphor via a solid-state reaction, in which controlled Eu 2+ doping (0.000–0.040) induced a phase transition and generated dual emission centers, resulting in a remarkable redshift from 406 nm to 480 nm with a broadened full width at half maximum (FWHM) (67 → 177 nm) to cover the blue–cyan–green regions. The combination of a 365 nm near-UV (NUV) LED chip, KAlSi 3 O 8 :0.040Eu 2+ , and commercial red phosphor yields a white LED device with a high color rendering index (Ra) of 96.1 and chromaticity coordinates of (0.3276, 0.3350). These results demonstrate that this blue–cyan phosphor not only simplifies the fabrication process of white LEDs but also effect ively compensates for the cyan spectral gap, making it a promising candidate material for NUV phosphor-converted WLEDs.