Tunable luminescent chromaticity of CaZnOS: Bi3+, Eu3+ with white emitting based on energy transfer

Abstract

A series of Bi3+ or Eu3+ ion single doped and Bi3+ and Eu3+ co-doped CaZnOS phosphors were synthesized via high temperature solid state method. Under ultraviolet (UV) excitation, CaZnOS: Bi3+ has an intense emission band ranged from 400 to 600 nm owing to the 3P1,0 → 1S0 transition of Bi3+. And CaZnOS: Eu3+ shows superior red emissions due to the characteristic 5D0 → 7FJ (J = 1, 2, 3, 4) transitions of Eu3+. Tunable emission chromaticity from cyan, white, yellow to red is obtained by regulating the proportion of Eu3+ in CaZnOS Bi3+, Eu3+. The energy transfer mechanism from Bi3+ to Eu3+ was confirmed to be a quadrupole-quadrupole interaction based on the overlap of emission band of Bi3+ and excitation band of Eu3+ combined with the luminescent lifetime measurement. In addition, CaZnOS: 2.5 mol% Bi3+, 3 mol% Eu3+ phosphor with optimized concentrations has standard white light chromaticity coordinates (0.315, 0.323) and activation energy about 0.372 eV, which reflects its potential application in ultraviolet-chip excited white light emitting diodes (W-LEDs).