Tunable white-light emission and energy transfer in single-phase Bi3+,Eu3+ co-doped Ba9Y2Si6O24 phosphors for UV w-LEDs

In this paper, a series of Bi 3+ and Eu 3+ single-doped as well as Bi 3+ ,Eu 3+ co-doped Ba 9 Y 2 Si 6 O 24 samples were synthesized through a simple high-temperature solid-state reaction method. Their crystal structures, morphologies, luminescent properties, temperature-dependent emission spectra , decay curves and quantum efficiencies were investigated in detail. Upon ultraviolet light excitation, Bi 3+ single-doped samples exhibited blue and green emissions peaking at 408 and 501 nm, corresponding to the 3 P 1 – 1 S 0 transition of Bi 3+ ions. The spectral analysis indicated that there were two different luminescent centers of Bi 3+ ions due to different occupancies in Ba 9 Y 2 Si 6 O 24 host lattice. And the highest quantum efficiency can reach 64.5% in Ba 9 Y 2 Si 6 O 24 :0.024Bi 3+ phosphor. The remarkable spectral overlap between the emission spectra of Bi 3+ ions and the excitation spectra of Eu 3+ ions indicated the exist of energy transfer from Bi 3+ to Eu 3+ . The efficient energy transfer from Bi 3+ to Eu 3+ has been investigated in detail and resulted in that tunable and white-light emission can be obtained by modulating Eu 3+ doping concentration. White emission can be realized with the CIE coordinates of (0.357, 0.345) and quantum efficiency of 57.6% for Ba 9 Y 2 Si 6 O 24 :0.024Bi 3+ ,0.02Eu 3+ . The above results demonstrate that Ba 9 Y 2 Si 6 O 24 :Bi 3+ ,Eu 3+ may be a potential candidate for ultraviolet (UV) driven white light-emitting diodes (w-LEDs).