Simultaneous Two-Photon Excited Fluorescence and One-Photon Excited Phosphorescence from Single Molecules of an Organometallic Complex Ir(ppy)3

We report a study of excited-state lifetimes of the phosphorescent organometallic complex Ir(ppy)3 on ensemble and a single-molecule level. With decreasing concentration, an increasingly intense fast component of 3 ns lifetime appears next to the 1.1 mus phosphorescence. Experimental evidence suggests that strong two-photon absorption followed by fluorescence is responsible for the fast lifetime component.