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/m2 at 3.2 V, 1000 cd/m2 at 3.7 V and 10000 cd/m2 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/m2, and a low efficiency roll-off 8.7% calculated from the maximum efficiency value to that of 5000 cd/m2.

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► We have investigated WOLEDs with different hole transport buffer layers.
► WOLEDs with low operating voltage and high color stability are demonstrated.
► WOLEDs with low efficiency roll-off are achieved utilizing an additional orange EML.