Characteristics of emissive bilayers in electrophosphorescent organic light-emitting diodes

New electrophosphorescent organic light-emitting diodes were fabricated by polymer/Ir(ppy)3 bilayers. Already several groups have reported polymer systems that show efficient energy transfer from a polymer host to an organometallic guest. We have fabricated a phosphorescent polymer light-emitting device with fac tris(2-phenylpyridine)iridium [Ir(ppy)3] as a triplet emissive layer on a poly(vinylcarbazole) (PVK) layer. The emission spectrum of the bilayer device exhibited pure Ir(ppy)3 emission, which indicates that the efficient energy transfer from PVK layer to Ir(ppy)3 layer. Our bilayer device system shows a lower driving voltage and a higher current density than those of the general blended device.