An Optically Flat Conductive Outcoupler Using Core/Shell Ag/ZnO Nanochurros

Abstract

Transparent conductive electrodes (TCEs) featuring a smooth surface are indispensable for preserving pristine electrical characteristics in optoelectronic and transparent electronic devices. For high-efficiency organic light emitting diodes (OLEDs), a high outcoupling efficiency, which is crucial, is only achieved by incorporating a wavelength-scale undulating surface into a TCE layer, but this inevitably degrades device performance. Here, an optically flat, high-conductivity TCE composed of core/shell Ag/ZnO nanochurros (NCs) is reported embedded within a resin film on a polyethylene terephthalate substrate, simultaneously serving as an efficient outcoupler and a flexible substrate. The ZnO NCs are epitaxially grown on the {100} planes of a pentagonal Ag core and the length of ZnO shells is precisely controlled by the exposure time of Xe lamp. Unlike Ag nanowires films, the Ag/ZnO NCs films markedly boost the optical tunneling of light. Green-emitting OLEDs (2.78 x 3.5 mm(2)) fabricated with the Ag/ZnO TCE exhibit an 86% higher power efficiency at 1000 cd m(-2) than ones with an Sn-doped indium oxide TCE. A full-vectorial electromagnetic simulation suggests the suppression of plasmonic absorption losses within their Ag cores. These results provide a feasibility of multifunctional TCEs with synthetically controlled core/shell nanomaterials toward the development of high-efficiency LED and solar cell devices.