Emission dynamics and quenching of phosphors at high excitation powers

Not many phosphor materials can offer stable output under high incident light intensities for thousands of operating hours. Even the most promising LED phosphors saturate in high-power applications, that is, they show decreased light output. In this presentation, I will show our experimental efforts to understand phosphor light output under high-power illumination. The focus will be on Mn4+-doped phosphors, but also include CaAlSiN3:Eu2+ and NaYF4:Er3+,Yb3+. Time-resolved experiments with square-wave-modulated laser excitation reveal the dynamics of absorption and decay of the luminescent centers. Using the peak ratios in the Mn4+ spectrum, we track the phosphor temperature in situ, which allows us to distinguish temperature-induced effects. Finally, I will show our recent efforts to understand excited-state dynamics of an upconversion phosphor by systematically varying the photonic density of states.