Highly efficient bilayer red phosphorescent organic light-emitting devices with solution-processed emission layer

We have developed highly efficient bilayer red phosphorescent organic light-emitting devices (OLEDs) using a solution processed poly(N-vinylcarbazole) (PVK) host layer doped with tris(2-phenyl-1-quinoline)indium(111) [Ir(phq)(3)] molecules. PVK was mixed with Ir(phq)3 molecules of 0.2 - 10 wt% in a chlorobenzene solution and spin-coated in order to prepare the emission layer. 3-(4-biphenyl)-4-phenyl-5-(4-tert-butylpheny1)-1,2,4-triazole (TAZ) was used as an electron transport material. The electrical conduction, emission, and efficiency characteristics of the OLEDs with a resultant structure of ITO/PVK:Ir(phq)(3)/TAZ/LiF/Alwere investigated. The maximum current efficiency and external quantum efficiency were 19.5 cd/A and 10.5%, respectively, in the device with 1% Ir(phq)(3) doped PVK host layer.