High efficiency and low efficiency roll off in white phosphorescent organic light-emitting diodes by managing host structures

Abstract

High efficiency phosphorescent white organic light-emitting diodes with little efficiency roll off were developed by managing the charge transport properties of the host materials. The emitting layers were stacked at a sequence of red/blue/green from the hole transport layer side and charge injection could be easily controlled by changing the host materials in the red and green emitting layers. A high quantum efficiency of 13% was obtained at a luminance of $1000\mathrm{cd}∕{\mathrm{m}}^2$ . In addition, the quantum efficiency of the white device at low luminance was maintained up to $10000\mathrm{cd}∕{\mathrm{m}}^2$ without any decrease.