High efficiency, solution-processed, red phosphorescent organic light-emitting diodes from a polymer doped with iridium complexes

High efficiency, solution-processed, red emissive phosphorescent organic light-emitting diodes (PhOLEDs) have been developed. The PhOLEDs utilize bis[9-ethyl-3-(4-phenylquinolin-2-yl)-9H-carbazolato-N,C2′]iridium picolinate (Et-Cvz-PhQ)2Ir(pic) and bis[9-(2-(2-methoxyethoxy)ethyl)-3-(4-phenylquinolin-2-yl)-9H-carbazolato-N,C2′]iridium picolinate (EO-Cvz-PhQ)2Ir(pic) in a nonconjugated polymer host of PVK that contains the electron transport material of OXD-7 and the hole transport material TPD. The electroluminescence (EL) spectra of the PhOLEDs parallel those of (Et-Cvz-PhQ)2Ir(pic) and (EO-Cvz-PhQ)2Ir(pic) with maxima at 608 nm and a CIE (Commission International de l’Eclairage) coordinate of (0.62, 0.38). The red emitting PhOLEDs, based on ITO/PEDOT:PSS/PVK:OXD-7:TPD:Ir complex/cathode configuration, have a maximum external quantum efficiency of 10.6% and a luminance efficiency of 17.5 cd/A. The efficiency is significantly higher than those obtained using common solution-processed red emissive PhOLEDs.