Color stable and low driving voltage white organic light-emitting diodes with low efficiency roll-off achieved by selective hole transport buffer layers

White organic light-emitting diodes (WOLEDs) showing high color stability, low operating voltage, high efficiency and low efficiency roll-off by adopting different hole transport buffer layers which also behaves as electron/exciton blocking layers (EBL) have been developed. The characteristics of WOLEDs based on blue-green and orange phosphors could be easily manipulated by hole transport buffer layer, which tailors charge carrier transportation and energy transfer. Our WOLEDs show low operating voltages, 100 cd/m(2) at 3.2 V. 1000 cd/m(2) at 3.7 V and 10000 cd/m(2) at 4.8 V, respectively, and achieve a current efficiency of 35.0 cd/A, a power efficiency of 29.0 lm/W at a brightness of 1000 cd/m(2), and a low efficiency roll-off 8.7% calculated from the maximum efficiency value to that of 5000 cd/m(2). Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved.