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

A series of Ce³⁺-, Tb³⁺- and Ce³⁺/Tb³⁺-doped La₃Si₈N₁₁O₄ phosphors were synthesized by gas-pressure sintering (GPS). The energy transfer between Ce³⁺ and Tb³⁺ 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 Ce³⁺/Tb³⁺ co-doped sample had an external quantum efficiency of 46.7%, about 5.6 times higher than the Tb-doped La₃Si₈N₁₁O₄ phosphor (8.3%). The thermal quenching of the Tb³⁺ emission in La₃Si₈N₁₁O₄:Tb,Ce was greatly reduced from 74 to 30% at 250 °C, owing to the energy transfer from Ce³⁺ to Tb³⁺. The blue-green La₃Si₈N₁₁O₄:0.01Ce,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 La₃Si₈N₁₁O₄:Ce,Tb phosphor could be a potential blue-green down-conversion luminescent material for use in UV-LED pumped wLEDs.

The peak emission intensity and thermal stability of Tb³⁺ in codoped La₃Si₈N₁₁O₄:Ce,Tb sample are strongly enhanced via Ce³⁺ to Tb³⁺ energy transfer.