Highly Efficient Green-Emitting Phosphors BaYBO with Low Thermal Quenching Due to Fast Energy Transfer from Ce to Tb.

This paper demonstrates a highly thermally stable and efficient green-emitting BaYBO:Ce, Tb phosphor prepared by high-temperature solid-state reaction. The phosphor exhibits a blue emission band of Ce and green emission lines of Tb upon Ce excitation in the near-UV spectral region. The effect of Ce to Tb energy transfer on blue to green emission color tuning and on luminescence thermal stability is studied in the samples codoped with 1% Ce and various concentrations (0-40%) of Tb. The green emission of Tb upon Ce excitation at 150 °C can keep, on average, 92% of its intensity at room temperature, with the best one showing no intensity decreasing up to 210 °C for 30% Tb. Meanwhile, Ce emission intensity only keeps 42% on average at 150 °C. The high thermal stability of the green emission is attributed to suppression of Ce thermal de-excitation through fast energy transfer to Tb, which in the green-emitting excited states is highly thermally stable such that no lifetime shortening is observed with raising temperature to 210 °C. The predominant green emission is observed for Tb concentration of at least 10% due to efficient energy transfer with the transfer efficiency approaching 100% for 40% Tb. The internal and external quantum yield of the sample with Tb concentration of 20% can be as high as 76% and 55%, respectively. The green phosphor, thus, shows attractive performance for near-UV-based white-light-emitting diodes applications.