Ultra-broadband emission up to 181 nm of VO4-activated yellow phosphor for white light-emitting diodes with high color rendering index

Abstract

Exploring broadband yellow phosphors capable of covering the cyan to red region is an effective approach to achieve high-performance phosphor-converted white light-emitting diodes (pc-WLEDs). Herein, we synthesized a series of VO4-activated ultra-broadband KSrP1−xVxO4 (0.1 ≤ x ≤ 1) yellow phosphors via high temperature solid-state reaction. Successive substitution of P5+ with V5+ causes a slight expansion of the lattice constant and induces several highly localized energy-levels within the forbidden band. Density functional theory calculations confirm that these newly appeared sharp-line energy-levels are attributed to the constructed VO4 anionic groups. With the optimized V5+ content, the KSrP0.7V0.3O4 phosphor exhibits an ultra-broadband yellow emission centered at 537 nm under 355 nm excitation. Impressively, its full width at half maximum is up to 181 nm, exceeding that of most reported counterparts. At 105 °C, the KSrP0.7V0.3O4 sample experiences an emission loss of 53%. A WLED device is fabricated by using phosphor blend of KSrP0.7V0.3O4 yellow phosphor and the commercial BaMgAl10O17: Eu2+ blue phosphor and a 355 nm NUV LED chip, demonstrating bright white emission with high color rendering index (CRI) of 90 and suitable correlated color temperature of 5953 K. These findings indicate that this phosphor has great potential for achieving high CRI WLEDs.