Enhanced Light Extraction from Mechanically Flexible, Nanostructured Organic Light-Emitting Diodes with Plasmonic Nanomesh Electrodes

Abstract

Characteristics of light extraction from nanostructured organic light-emitting diodes (OLEDs) incorporating plasmonic metal nanomesh anodes are investigated for achieving high-performance, flexible OLEDs. Given that flexibility of devices is limited by rigid and fragile constituents such as indium tin oxide electrodes, alternative transparent, and flexible electrodes including nanomesh-type metal films have been widely studied, where high transparency, low resistance, and good flexiblity were regarded as essential requirements of high-performance flexible applications due to the expectation that they are closely related to the device performance. However, here it is reported that a metal nanomesh optimized for high transmittance cannot promise high device efficiency when it is used as an anode of OLEDs. Systematic experiments together with analytic simulations elucidate that the surface plasmon loss is singnificantly reduced by metallic cathode nanostructures that were inherently formed from a periodic nanomesh anode, which results in huge enhancement of the light extraction, though the optimal period of the nanomesh anode for high light extraction is inconsistent with that for high transmittance. Further performance characterization of nanostructured OLEDs with metal nanomesh anodes provides insight into strategies to realize highly efficient flexible OLEDs.