Light extraction from OLEDs for lighting applications through light scattering

OLEDs are gaining increasing interest for lighting applications as large-area light sources. Their lifetime and overall efficiency can be increased by the optimization of light outcoupling. In this article, scattering films on the viewer's side of the substrate to increase the outcoupling efficiency of OLEDs for lighting applications are examined. Experimental results show that the increase of outcoupling efficiency is dependent from the absolute number of scattering particles in the matrix. Theoretical considerations expect an increase of outcoupling efficiency of up to 70%. Experimental results yield an increase of outcoupling efficiency of about 22%. A software model based on raytracing to simulate light outcoupling from OLEDs through a scattering layer is introduced to gain a deeper understanding of the light extraction mechanism. We found that the scattering anisotropy factor g determined using the Henyey-Greenstein phase function and the effective absorbance of the OLED device have strong impact on outcoupling efficiency. (c) 2006 Elsevier B.V. All rights reserved.