Efficient Outcoupling of Organic Light-Emitting Devices Using a Light-Scattering Dielectric Layer

It has long been a challenge to develop a highly efficient outcoupling method for organic light-emitting diodes that is independent of wavelength and viewing angle, as well as being nonintrusive into the device structure. Here, we demonstrate a transparent, top emitting structure integrated with a high index of refraction waveguide layer and a rough, dielectric diffuse reflector that eliminates plasmonic, waveguide, and substrate modes without introducing wavelength and viewing-angle dependence. The simple outcoupling structure increases the external quantum efficiency from 15 +/- 2% to 37 +/- 4% compared to an analogous device with a metal mirror, corresponding to a 2.5-fold enhancement without requiring the use of additional outcoupling structures such as microlens arrays or index matching layers to extract substrate modes. The method is potentially suitable for low-cost, solid-state lighting due to its simplicity and high outcoupling efficiency.