Lithographic convex pattern as a wavelength-independent light extraction structure for efficient organic light-emitting diodes

Abstract

Improving light extraction efficiency is crucial for the practical use of organic light-emitting diodes (OLEDs). Despite numerous reported methods for light extraction, designing a wavelength-independent structure to effectively extract trapped photons from broadband emission OLEDs remains a challenge. In this study, we introduce a convex indium tin oxide (ITO) pattern as a straightforward and cost-efficient solution for light extraction in OLEDs. This technique involves micrometer-scale inclined planes along the ITO convex squares, disrupting the internal waveguiding of light through geometrical optics and enabling wavelength-independent light extraction. Consequently, we observe substantial enhancements in the external quantum efficiency of blue, green, red, and near-infrared OLEDs by 34.5%, 22.4%, 28.6%, and 31.3%, respectively. Moreover, the patterning method for the ITO is fully compatible with existing lithographic production lines, offering a scalable and promising approach for mass production.