Highly efficient and stable organic light-emitting diodes

Doped and undoped multilayer organic light-emitting diodes containing copper phthalocyanine as the hole-injection layer, aromatic diamines as the hole-transport layers and (tris(8-hydroxy-quinoline)aluminum) as the electron-injection, electron-transport, and emitting layer were fabricated. The influence of the individual layer thicknesses and doping locations (electron-transport layer and/or hole-transport layer) on the current-voltage characteristics, luminous efficiency, and stability was investigated. Optimization of these parameters led to highly efficient (above 8 lm/W) and stable organic light-emitting diodes.