Novel tunable green-red-emitting oxynitride phosphors co-activated with Ce, Tb, and Eu: photoluminescence and energy transfer.

A series of novel Ce, Tb and Eu ion doped YSiAlON-based oxynitride phosphors were synthesized by the solid-state method and characterized by X-ray powder diffraction, scanning electron microscopy, photoluminescence, lifetimes and thermo-luminescence. The excitation of the Ce/Tb co-doped and Ce/Tb/Eu tri-doped phosphor with near-UV radiation results in strong linear Tb green and Eu red emission. The occurrence of Ce-Tb and Ce-Tb-Eu energy transfer processes is responsible for the bright green or red luminescence. The Tb ion acting as an energy transfer bridge can alleviate MMCT quenching between the Ce-Eu ion pairs. The lifetime measurements demonstrated that the energy-transfer mechanisms of Ce→ Tb and Tb→ Eu are dipole-quadrupole and quadrupole-quadrupole interactions, respectively. The temperature dependent luminescence measurements showed that as-prepared green/red phosphors have good thermal stability against temperature quenching. The obtained results indicate that these phosphors might serve as promising candidates for n-UV LEDs.