Significantly enhanced photoluminescence and thermal stability of La(3)Si(8)N(11)O(4):Ce(3+),Tb(3+)via the Ce(3+) → Tb(3+) energy transfer: a blue-green phosphor for ultraviolet LEDs

A series of Ce(3+)-, Tb(3+)- and Ce(3+)/Tb(3+)-doped La(3)Si(8)N(11)O(4) phosphors were synthesized by gas-pressure sintering (GPS). The energy transfer between Ce(3+) and Tb(3+) occurred in the co-doped samples, leading to a tunable emission color from blue to green under the 360 nm excitation. The energy transfer mechanism was controlled by the dipole–dipole interaction. The Ce(3+)/Tb(3+) co-doped sample had an external quantum efficiency of 46.7%, about 5.6 times higher than the Tb-doped La(3)Si(8)N(11)O(4) phosphor (8.3%). The thermal quenching of the Tb(3+) emission in La(3)Si(8)N(11)O(4):Tb,Ce was greatly reduced from 74 to 30% at 250 °C, owing to the energy transfer from Ce(3+) to Tb(3+). The blue-green La(3)Si(8)N(11)O(4):0.01Ce,0.05Tb phosphor was testified to fabricate a warm white LED that showed a high color rendering index of 90.2 and a correlated color temperature of 3570 K. The results suggested that the co-doped La(3)Si(8)N(11)O(4):Ce,Tb phosphor could be a potential blue-green down-conversion luminescent material for use in UV-LED pumped wLEDs.