Efficient green phosphor realized by Ce3+→Tb3+ energy transfer in Li3Sc2(PO4)3 for ultraviolet white light-emitting diodes

Abstract

A series of Ce³⁺/Tb³⁺ doped Li₃Sc₂(PO₄)₃ phosphors has been obtained using high temperature solid state reactions. Density functional theory (DFT) calculations using the CASTEP module have given an insight into the bandgap and electronic structures of the hosts. The phase formation and the crystal structure of the prepared samples were verified using X-ray diffraction and Rietveld structure refinement analysis. Samples singly doped with Ce³⁺ ions had an intense emission centered at 350 nm under UV light irradiation, while samples singly doped with Tb³⁺ ions exhibited a typical green emission under 230 nm irradiation. Efficient Ce³⁺→Tb³⁺ energy transfer can cause the Li₃Sc₂(PO₄)₃:Ce³⁺,Tb³⁺ samples to have an intense green emission at very low Tb³⁺ concentrations under 285 nm excitation, making Li₃Sc₂(PO₄)₃:Ce³⁺,Tb³⁺ an efficient UV-excited green phosphor. The mechanism and critical distance for Ce³⁺→Tb³⁺ energy transfer in the phosphor were determined by detailed luminescence decay curve analysis utilizing the I–H model. Moreover, a WLED device was fabricated using our prepared green phosphor.