High-efficiency monochrome organic light emitting diodes employing enhanced microcavities

We demonstrate enhanced light outcoupling from bottom emitting monochrome high-efficiency red, green, and blue organic light emitting diodes by adding silver layers on the indium tin oxide (ITO) anode. The devices contain the phosphorescent emitting dyes tris(2-phenylpyridine)iridium and iridium(III)bis[2-methyldibenzo-(f, h)quinoxaline](acetylacetonate), and the blue singlet emitter 2,$2′$⁠,7,$7′$-tetrakis 2,2-(diphenylvinyl)spiro-9,$9′$-bifluorene. We follow the $p-i-n$ doping concept to increase the power efficiencies. We reach 81 lm/W for red, 101 lm/W for green, and 4.0 lm/W for blue color. These efficiencies are improved by up to a factor of 2.3 compared to standard ITO devices, which we attribute to microcavity amplification between the cathode and the Ag layer.