Design of non-periodic dielectric stacks for tailoring the emission of organic lighting-emitting diodes

The majority of photons emitted in organic light-emitting diodes are either trapped in the substrate or emitted into lossy waveguided modes. We show how optimized, non-periodic dielectric stacks inserted between the substrate and transparent anode can be used to improve the photon outcoupling efficiency by tailoring of the local photon density of states. Unlike previously demonstrated outcoupling schemes, this method does not lead to pixel blurring and maintains a Lambertian angular emission profiles within a specified cone. For small molecular weight, green-emitting devices, a 2.5-fold uniformly distributed increase in brightness is achievable for a viewing angle of 60 degrees. (c) 2007 Optical Society of America.