Tunable blue–green color emission and energy transfer properties of Li2CaGeO4:Ce3+, Tb3+ phosphors for near-UV white-light LEDs

Abstract

The phosphors Li2CaGeO4:Ce3+, Tb3+ were synthesized via the conventional high temperature solid state reaction method. The fluorescence and lifetime properties reveal that the energy transfer from Ce3+ to Tb3+ ions takes place in the Li2CaGeO4 host. The emission color of obtained samples can be varied from blue to green through energy transfer by simply tuning the Ce3+/Tb3+ ratio. The energy transfer mechanism was illustrated in detail. Based on concentration quenching method, the critical distance of the energy transfer was calculated to be about 14.05Å. The mechanism of energy transfer from Ce3+ to Tb3+ ions is a resonant type that occurs via dipole–quadrupole interaction. Green emission from Tb3+ can be obtained upon the excitation into Ce3+ ions (UV excitation), which indicates that Li2CaGeO4:Ce3+, Tb3+ may be a potential candidate of green emitting UV light convertible phosphor for w-LEDs.