Luminescence properties and energy transfer in Ce3+/Tb3+co-doped Y5Si3O12N oxynitride phosphors

A series of Y5Si3O12N:Ce3+ single-doped and Ce3+/Tb3+ co-doped phosphors, as potential candidates for application in tri-chromatic white LEDs, were successfully synthesized by a high temperature solid state reaction method. The addition of Li2CO3 flux (5 wt%) improved the purity of the resultant phosphors and increased their emission intensity. An intense, broad excitation band in the range of 200-400 nm with a peak at 358 nm was recorded, which suits the needs of UV LED chips. Under this excitation wavelength, intense blue emission, which peaked at 439 nm, was recorded in the Ce3+ single-doped phosphors, while two distinct luminescence bands were observed in the Ce3+/Tb3+ co-doped Y5Si3O12N phosphors: a blue one, which peaked at 439 nm and is ascribed to Ce3+ ions, and an efficient green one, which peaked at 549 nm and is assigned to 5D4→7F5 transitions in Tb3+ ions. A high luminescence quantum yield, of 85%, was achieved. The experimental results illustrate that efficient energy transfer can take place from the sensitizer Ce3+ ions to the activator Tb3+ ions in the Ce3+/Tb3+ co-doped Y5Si3O12N phosphors, through predominantly dipole-dipole interactions.