The energy transfer from Eu2+ to Tb3+ in Ca10K(PO4)7 and its application in green light emitting diode

A novel green phosphor, Ca10K(PO4)7:Eu2+,Tb3+,K+, is synthesized by high temperature solid-state reaction. The photoluminescence properties show that there is an efficient energy transfer from Eu2+ to Tb3+ where Eu2+ ions exhibit a strong excitation band between 350 and 420 nm, matching well with the dominant emission band of (n)-UV (390–420 nm) LED, and Tb3+ ions give an intense green emitting light. A green LED with CIE chromaticity coordinates (x = 0.283, y = 0.383) were fabricated by coating the Ca10K(PO4)7:Eu2+,Tb3+,K+ phosphor onto (n)-UV chip emitting at 398 nm. These results demonstrate that Tb3+ ion with low 4f–4f absorption efficiency in (n)-UV region can play a role of activator in narrow green emitting phosphor potentially useful in (n)-UV GaN-based LED through efficient energy feeding by allowed 4f–5d absorption of Eu2+ with high oscillator strength.