Significantly enhanced photoluminescence and thermal stability of La3Si8N11O4:Ce3+,Tb3+ via the Ce3+ → Tb3+ energy transfer: a blue-green phosphor for ultraviolet LEDs

摘要

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.