Hybrid Copper-Nanowire-Reduced-Graphene-Oxide Coatings: A "Green Solution" Toward Highly Transparent, Highly Conductive, and Flexible Electrodes for (Opto)Electronics.

This study reports a novel green chemistry approach to assemble copper-nanowires/reduced-graphene-oxide hybrid coatings onto inorganic and organic supports. Such films are robust and combine sheet resistances (<30 Ω sq-1 ) and transparencies in the visible region (transmittance > 70%) that are rivalling those of indium-tin oxide. These electrodes are suitable for flexible electronic applications as they show a sheet resistance change of <4% after 10 000 bending cycles at a bending radius of 1.0 cm, when supported on polyethylene terephthalate foils. Significantly, the wet-chemistry method involves the preparation of dispersions in environmentally friendly solvents and avoids the use of harmful reagents. Such inks are processed at room temperature on a wide variety of surfaces by spray coating. As a proof-of-concept, this study demonstrates the successful use of such coatings as electrodes in high-performance electrochromic devices. The robustness of the electrodes is demonstrated by performing several tens of thousands of cycles of device operation. These unique conducting coatings hold potential for being exploited as transparent electrodes in numerous optoelectronic applications such as solar cells, light-emitting diodes, and displays.