Light out-coupling efficiency enhancement in organic light-emitting diodes using a multilayer stacked electrode with...

We demonstrate enhanced light out-coupling efficiency of organic light-emitting diodes by applying a multilayer stacked electrode structure consisting of fast and cost-effective sol-gel processed tantalum pentoxide (Ta₂O₅), thin layer of Au and molybdenum trioxide (MoO₃). The application of the Ta₂O₅/Au/MoO₃ electrode can modulate the optical characteristics of the device due to the optical microcavity effect. The refractive index of the sol-gel processed Ta₂O₅ thin film varied depending on the annealing temperature and reached a maximum at 400 °C (n = 2.2 at 512 nm). The influence of the refractive index of the Ta₂O₅ layer and the thickness of the multilayer electrode stack on the optical microcavity effect was systematically investigated. The device with the Ta₂O₅/Au/MoO₃ electrode, fabricated at an optimum condition based on the simulation result by calculating the photon flux, exhibited 52% enhancement in light out-coupling efficiency at 1000 cd/m² and improved color stability with the viewing angle, having near-Lambertian emission.