Efficient and color stable phosphorescent white organic light-emitting devices based on an ultra wide band-gap host

We report high efficiency phosphorescent white organic light-emitting devices (WOLEDs) employing single emissive layer (EML) based on an ultra wide band-gap host. Effective exciton/charge confinement and balanced recombination within EML was achieved by employing adequate interlayer and stepwise hole-transporting layer (step HTL) system. Moreover, this step HTL system lower driving voltage of WOLEDs, therefore power efficiency was enhanced over 40%. These WOLEDs showed external quantum, and power efficiencies of 17.6%, and 37.5 lm/W at 100 cd/m(2) without outcoupling enhancements. We also found that these WOLEDs; exhibited little change of color coordinate from 100 to 10,000 cd/m(2). Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.