Power efficiency of organic light emitting devices (OLEDs) is inthe focus of worldwide research in order to reduce powerconsumption of displays and to improve the competitive situationof OLEDs for lighting devices. The optical properties of OLEDsare studied with the aim to enhance the fraction of light coupledout of these devices.Simulation software has been used to analyze the transfer ofinternally generated emission into usable external light modes.Results from modeling have been compared to experimental datato build trust into the validity of the results. Critical parametersinfluencing outcoupling properties have been identified. Thus,185lm/W at 1000cd/m2 have been achieved for a green PINOLEDusing a high-n substrate & half ball lens. Finally, someconclusions for the design of outcoupling enhancing means aredrawn.