Deep blue, cyan, orange-red, and white multicolor emissions generated by Bi3+/Eu3+ activated KBaYSi2O7 luminescent materials for white light-emitting diodes

Abstract

A variety of Bi3+ and/or Eu3+ doped KBaYSi2O7 phosphors with deep blue, cyan, orange-red, and white light multicolor emissions have been fabricated by a Pechini sol-gel (PSG) method. The KBaYSi2O7:Bi3+ phosphors exhibit an intense cyan emission or a unique narrow deep blue emission when excited by different wavelengths, which may bridge the cyan gap or act as a promising deep blue phosphor for white light-emitting diodes (WLEDs). The tunable multicolor emissions can be achieved by changing the Bi3+ doping concentrations. The Bi3+/Eu3+ co-doped KBaYSi2O7 phosphors display intrinsic emissions of Bi3+ and Eu3+ and an energy transfer process between Bi3+ and Eu3+ can be detected. The luminescence colors of KBaYSi2O7:Bi3+,Eu3+ regularly shift from blue, through cold and warm white, finally toward orange-red by adjusting the relative doping concentrations of Bi3+ and Eu3+. The single-phase white light-emitting material can be generated in both cold and warm white regions by simply varying the Eu3+ doping concentrations. Furthermore, three kinds of WLEDs devices are fabricated by KBaYSi2O7:Bi3+ or KBaYSi2O7:Bi3+,Eu3+ phosphors, which can exhibit dazzling white light emissions with eminent CIE coordinates, correlated color temperature, and color rendering index. The result offers direct evidence that the as-synthesized phosphors may be potentially applied in WLEDs and solid-state lighting.