P-175: Enhanced Outcoupling of Light from Organic Light-Emitting Diodes by Microlens Arrays Based on Breath-Figure Template

We present a bottom-up method of fabricating microlens arrays based on a template of close-packed microvoids created by self-assembly and subsequent evaporation of condensed water droplets on the surface of a polymer solution exposed to humid air. The pattern of microvoids is transferred to an optically transparent, thermally curable elastomer to form the microlens array. The method offers advantages over conventional top-down microfabrication approaches in terms of easy fabrication, high fill factor, and near-optimum shape of the microlenses. Attachment of the microlens array to the glass substrate of an OLED device results in a significant increase in total emission and external quantum efficiency. These experimental results are compared to the predictions of a hybrid ray optics/wave optics model that can be used to gain further understanding and to help optimize the system.