Oxidation-Resistant Cu-Based Nanowire Transparent Electrodes Activated by an Exothermic Reduction Reaction

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This article describes an approach to making highly stable copper nanowire networks on any type of substrates. These nanostructured materials are highly sought after for, among other applications, the development of next-generation flexible electronics. Their high susceptibility to oxidation in air currently limits their use in the real world. Here, we develop a multistep chemical method to fabricate transparent electrodes (TEs) using Cu-based bimetallic NW networks on various substrates at room temperature. First, we synthesized homogeneous core@shell copper@nickel (Cu@Ni) NWs using a one-pot colloidal approach. After their deposition on a substrate, we exploited the exothermic nature of the reaction between the Ni oxide and hydrazine to eliminate the naturally formed metal oxide moieties and interlock the NW junctions of the network. Electrical measurements, at the single junction level, indicate that the exothermic reaction induces a reduction of resistance by up to 4 orders of magnitude. On a macroscopic scale, the resulting Cu-based NW networks feature an optical transmittance of 80% in the visible region and a sheet resistance of 10 Ω/sq with a record stability of over 2 years. This process offers a simple and efficient strategy for fabricating cost-effective, long-life electronic devices, as illustrated by a proof-of-concept integrating an optimized Cu@Ni-based TE as a flexible transparent heater.