High-efficiency white phosphorescent organic light-emitting devices with greenish-blue and red-emitting layers

Abstract

We demonstrate high-efficiency white light emission from a phosphorescent organic light-emitting device with greenish-blue and red emissive layers. Bis{2-[3,5-bis(trifluoromethyl)phenyl]-pyridinato-N,C2′}iridium(III)picolinate [(CF3ppy)2Ir(pic)] and bis{2-[2′-benzo(4,5-a)thienyl]pyridinato-N,C3′}iridium(III)acetylacetonate were employed for the greenish-blue and red phosphorescent materials for the emissive layers. To enhance the emission efficiency of (CF3ppy)2Ir(pic), 4,4′-bis(9-carbazolyl)-2,2′-dimethyl-biphenyl was used as the charge-transporting host. White light emission was obtained by controlling the layer thickness and the concentration of each phosphorescent material in the emissive layers. A maximum external quantum efficiency of 12%, a luminance efficiency of 18 cd/A, and a maximum power efficiency of 10 lm/W were achieved at a current density of 0.01 mA/cm2. This high efficiency is primarily attributed to the improvement of greenish-blue emission efficiency due to the strong confinement of triplet excitons on the (CF3ppy)2Ir(pic) molecules.