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

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) [PVKIr (ppy)3] bilayer/2,9-dimethyl-4,7-diphenyl-1, 10-phenanthroline (BCP) CaAl 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 ITOPEDOTPVK:Ir (ppy)3 blendBCPCaAl.