Novel cyan‐emitting KBaScSi2O7:Eu2+ phosphors with ultrahigh quantum efficiency and excellent thermal stability for WLEDs

Abstract Owing to the conventional phosphor‐converted white LEDs (pc‐WLEDs) generally suffer from blue‐green cavity, thus, developing an appropriate phosphors covering both the blue and green regions in their emission spectra are very urgent. Herein, a novel Sc silicate phosphor, KBaScSi 2 O 7 :Eu 2+ (KBSS:Eu 2+ ), has been successfully designed and prepared via a solid‐state reaction. The crystal structure, luminescent properties, thermal quenching, quantum efficiency as well as its application in UV‐pumped WLEDs have been investigated systematically. The KBSS:Eu 2+ phosphor exhibits a strong and broad excitation band ranging from 290 to 450 nm, and gives a sufficient cyan emission of 488 nm with a full‐width half‐maximum (FWHM) of 70 nm, which filled the blue‐green cavity. Importantly, the optimized KBSS:Eu 2+ phosphor possesses an ultrahigh quantum efficiency (QE) up to 91.3% and an excellent thermal stability retaining 90% at 423 K with respect to that measured at room temperature. Finally, the as‐fabricated UV‐based WLEDs device, with only coupled the mixture of KBSS:Eu 2+ cyan phosphor and CaAlSiN 3 :Eu 2+ red ones to a commercial 365nm UV chip, exhibits a satisfactory color‐rendering index (Ra = 88.6), correlated color temperature (CCT = 3770K), and luminous efficiency (LE = 21 lm/W).