Photoluminescence processes in τ-phase Dy3+/Tb3+-codoped Ba1.3Ca0.7SiO4 phosphors for solid-state lighting

The τ-phase-Ba1.3Ca0.7SiO4 phosphors co-doped with 3 mol% Dy3+ and ~1-5
mol% Tb3+ trivalent rare-earth ions were prepared by the gel-combustion
method. The structure-property relation of the samples was examined by
X-ray diffraction, scanning electron microscopy, and spectrophotometer.
Here, the effect of Tb3+’s concentration on the spectroscopic properties
of Dy3+/Tb3+ co-doped Ba1.3Ca0.7SiO4 phosphors was explored by using the
photoluminescence excitation, emission, and decay curves. Importantly, the
photonic energy transfer from (Dy3+: 4F9/2 + Tb3+: 7F6) to (Dy3+: 6H15/2 +
Tb3+:5D4) was observed, in which the Dy3+ ions acts as a light-emitting
donor whereas the Tb3+ ions as a light-absorbing acceptor, resulting in an
enhanced emission from the co-doped Ba1.3Ca0.7SiO4: Dy3+/Tb3+ phosphors.
Finally, the chromaticity coordinates were determined from the measured
emission spectra, locating at the green and white light regions. This
observation indicates that the characteristic emission color could be
tuned from white to green by varying Tb3+ concentrations under ultraviolet
light.