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 (τ 1 and τ 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.