Transient photoluminescent response with three decay lifetimes of phosphorescent organic molecule Ir(ppy)3 doped in polycarbonate

A calculation has been done to explain the temperature dependence of photoluminescence (PL) lifetime of fac tris(2-phenylpyridine) iridium (Ir(ppy)3) observed in polycarbonate (PC) at 8-295 K. Taking into account (1) three zero-field splitting substates in the lowest-energy triplet state and (2) one-phonon non-radiative transitions among these substates, the rate equations have been obtained for the populations of these substates. We derived the PL time response with three PL lifetimes, which increase with decreasing temperature from 300 K to 1 K. A good agreement has been obtained between the calculated PL lifetimes and the observed ones.