High efficiency in two color and three color phosphorescent white organic light-emitting diodes using a 2,7-substituted 9-phenylcarbazole derivative as the host material

High efficiency two color and three color phosphorescent white organic light-emitting diodes (PHWOLEDs) were developed using 2,7-bis(diphenylphosphino)-9-phenyl-9H-carbazole (PPO27) as the host material for blue phosphorescent emitting layer. High external quantum efficiency of 20.1% was achieved in the two color PHWOLEDs with red: blue co-doped single emitting layer and high external quantum efficiency of 20.8% was obtained in the three color PHWOLEDs with stacked structure of red: blue co-doped and green emitting layers. The PPO27 host material was effective as the host material for the red: blue co-doped emitting layer and could give high quantum efficiency in two color and three color PHWOLEDs. (C) 2011 Elsevier B.V. All rights reserved.