A single-heterojunction electrophosphorescence device with high efficiency, long lifetime and suppressive roll-off

We have demonstrated an electrophosphorescence organic light emitting device (PHOLED) with single-heterojunction to realize simultaneously high efficiency/long lifetime/suppressive roll-off. Therein, the energy barriers between the abrupt interfaces in the carrier transport path are eliminated and the effective and balanced carrier injection and transport are obtained using appropriate chemical doping of the wide band gap materials as the carrier transport layers. The optimized device realizes a maximum power efficiency of 32.1 lm/W (Current efficiency of 40.9 cd/A), which is about 3.1 times that of the referential multi-heterojunction PHOLED, especially the efficiency roll-off is effectively suppressed at the high current density. Furthermore, the operational lifetime is beyond 15 folds of the reference device. These results suggest a simple and feasible design to achieve extended lifetimes and improved efficiency for PHOLED. (C) 2012 Elsevier B.V. All rights reserved.