Rate constant of exciton quenching of Ir(ppy)3 with hole measured by time-resolved luminescence spectroscopy

We observed the quenching of tris(2-phenylpyridinato) iridium(III) [Ir(ppy)(3)] excitons by polarons (holes or electrons) by time-resolved photoluminescence (PL) spectroscopy to clarify the dynamics of the triplet-polaron quenching of excitons. We employed a hole-only device (HOD) and an electron-only device (EOD), where the emitting layer consists of Ir(ppy)(3) doped in 4,4'-bis(carbazol-9-yl)biphenyl. Time-resolved PL spectroscopy of the EOD and HOD were measured under a constant current density. The results showed that the excitons of Ir(ppy)(3) were significantly quenched only by holes. The PL decay curves of HOD were well fitted by the biexponential function, where lifetimes (t(1) and t(2)) remain unchanged but the coefficient of each exponential term depends on hole current density. From the results, we proposed a model of exciton quenching where the exciton-hole quenching area expands with increasing hole current density. On the basis of the model, the triplet-polaron quenching rate constant K-q was determined. (C) 2016 The Japan Society of Applied Physics