Modulating the Rise and Decay Dynamics of Upconversion Luminescence through Controlling Excitations.

Different from organic dye/quantum dot possessing one luminescent center, upconversion luminescence (UCL) is actually a statistic of temporal behaviors of countless individual activators. Our experimental results have shown that the rise and decay dynamics of UCL is directly associated with the relative contribution of sensitizer-to-activator energy transfer and energy migration among sensitizers, which can be physically modulated by simply tuning the excitation laser. Therefore, dynamic UCL with record-wide 20-fold lifetime, ≈70-fold red-to-green intensity ratio, and reversibly definable emission color is easily realized by just modulating the excitation laser. Moreover, this generally applicable strategy only requires a simplest-possible UCL system whereas prevalent material engineering such as complicated composition design, sophisticated core-shell construction, or tedious chemical synthesis, is no longer needed.