Efficient hole injection by doping of hexaazatriphenylene hexacarbonitrile in hole transport layer

Hexaazatriphenylene-hexacarbonitrile (HAT) was used as a dopant in hole transport layer and hole injection properties of the HAT doped hole transport layer were studied. Hole injection was greatly improved by doping of the HAT in the hole transport material and a driving voltage was lowered by more than 3 V. Lifetime of green devices was also improved by more than three times. In addition, a high quantum efficiency of 16.8% and a power efficiency of 47 Im/W were obtained at 1000 cd/m(2) in green phosphorescent devices. (C) 2009 Elsevier B.V. All rights reserved.