Cloaking Contacts on Large-Area Organic Light-Emitting Diodes

Abstract

Metallic contact grids on top of large-area organic light-emitting diodes (OLEDs) are important for laterally homogenized current spreading leading to a lower series resistance and reduced large-scale brightness gradients. However, the contacts are also visible by unwanted shadows, i.e., by spatially inhomogeneous Lambertian light emission. In this paper, inspired by recent work on diffuse-light core-shell invisibility cloaking, a practical tailored distribution of light scattering centers is designed on top of an OLED to homogenize its light emission. Numerical solutions of the light-diffusion equation as well as Monte Carlo ray-tracing simulations are presented. The blueprint is verified by experiments on a scaled-up model structure. The contacts can be made "invisible" in emission while maintaining large light throughput.