Effects of acceptor on the performance of exciplex-based OLED

In this work, exciplex-based OLEDs (ExOLEDs) are fabricated with 1,1-bis((di-4-tolylamino)phenyl)cyclohexane (TAPC) as the donor and a series triazine derivatives, e.g., 2,4,6-tris(biphenyl-3-yl)-1,3,5-triazine (T2T), 2,4,6-tris(3-(1H-pyrazol-1-yl)phenyl)-1,3,5-triazine (3P-T2T), and 2,4,6-tris(m-(diphenylphosphinoyl)phenyl)-1,3,5-triazine (PO-T2T), as the acceptors. With different acceptors and mole ratios of donor:acceptor, the effects of the photoluminescence quantum yield (PLQY), charge carrier balance, and exciton lifetime on the EQE and efficiency roll-off are systematically investigated. It is found that the external quantum efficiency (EQE) of the ExOLEDs is primary determined by the PLQY of the mixed donor:acceptor film and tuned in a certain extent by the charge carrier balance. Furthermore, the efficiency roll-offs of different ExOLEDs are all less than 20%, which are simultaneously determined by the photoluminescence (PL) lifetime and the charge carrier balance.