Electrophosphorescent devices from a poly(9-vinylcarbazole)/tris(2-phenylpyridine)iridium(III) bilayer with a concentration gradient

Abstract

Electrophosphorescence and the dynamics of charge carrier recombination in poly(9-vinylcarbazole) (PVK)/tris(2-phenylpyridine)iridium [Ir-(ppy)(3)] bilayer electroluminescence devices were investigated. Because the second layer [Ir-(ppy)(3)] is spin cast from a solvent that slightly swells the PVK layer, the two layers are partially intermixed at the bilayer interface. Indium tin oxide (ITO)/3,4-polyethylenedioxythiophene-polystyrenesulfonate (PEDOT)/[PVK/Ir(ppy)(3)] bilayer/2,9-dimethyl-4,7-diphenyl-1, 10-phenanthroline (BCP)/Ca/Al ultilayer devices showed similar emission intensity and color quality to those of the PVK: Ir(ppy)(3) blended device. However, turn-on and driving voltage were decreased dramatically compared with those of the ITO/PEDOT/PVK: Ir(ppy)(3) blend/BCP/Ca/Al. (c) 2007 American Institute of Physics.