Temperature Dependence of Photoluminescence Lifetime and Quantum Efficiency in Neat fac-Ir(ppy)3 Thin Films

Abstract

Temperature dependences of lifetime and intensity of photoluminescence have been investigated in neat fac-Ir(ppy)3 thin films, which have a nonradiative decay channel due to aggregate quenching. Both temperature dependences can be well understood by a model which consists of three substates of the triplet metal-to-ligand-charge-transfer (3MLCT) state and a nonemissive state. Good agreement between the experimental results and the calculations based on the model suggests that nonradiative decay occurs through a higher lying excited state in fac-Ir(ppy)3 molecules, and that the nonemissive excited state has a decay rate of 3.1×109 s-1 and is located at 0.12 eV above the lowest substate of the 3MLCT state.