Zinc Grid Based Transparent Electrodes for Organic Photovoltaics

Abstract

Zinc is the fifth most electrically conductive metal and is available at a fraction of the cost of the most widely used transparent electrode materials; silver, indium-tin oxide, and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate, but has been surprisingly overlooked as a current carrying element in organic photovoltaics. Here, a transparent flexible electrode based on an embedded zinc grid with ≈1 µm linewidth is reported and its utility as a drop-in replacement for indium-tin oxide coated glass electrodes in model organic photovoltaic devices is demonstrated. The zinc grids are fabricated using the unconventional approach of condensation coefficient modulation, using a micro-contact printed patterned layer of poly(perfluorooctylmethylmethacrylate) to resist zinc condensation in the gaps between grid lines, together with a copper acetylacetonate seed layer to nucleate zinc condensation where grid lines are required. Density functional theory calculations of the strength of the interaction between zinc atoms and this fluorinated polymer provide fundamental insight into why the latter is so effective at resisting zinc condensation. The resulting zinc grid is embedded in a flexible polymer support and transferred to a flexible plastic substrate by delamination, which enables recovery and reuse of the fluorinated polymer.