Luminescence characteristics and energy transfer of Eu2+/Tb3+ doped single phase multi-color phosphor

The investigation on single phase multi-color phosphors is highly meaningful for near-ultraviolet chip based white light emitting diodes. In this work, a series of Eu²⁺ and Tb³⁺ singly doped and Eu²⁺/Tb³⁺ codoped Sr₅(PO₄)₃Cl phosphors were synthesized via a high-temperature solid state reaction method. The luminescence spectra and decay curves of Eu²⁺ and Tb³⁺ singly doped samples were discussed, the optimal doping concentrations were determined. Thanks to the spectra overlap between Eu²⁺ and Tb³⁺, nonradiative energy transfer from Eu²⁺ to Tb³⁺ was investigated. It is found electric dipole-dipole interaction played the main role for the energy transfer in codoped samples, the highest energy transfer efficiency was calculated to be 60.98%. Tunable emissions are observed for codoped samples by adjusting doping concentration. The thermal quenching properties were discussed and the activation energy (ΔE) was estimated in the present work.