Silver nanowire transparent electrodes have received much attention as a replacement for indium tin oxide, particularly in organic solar cells. In this paper, we show that when silver nanowire electrodes conduct current at levels encountered in organic solar cells, the electrodes can fail in as little as 2 days. Electrode failure is caused by Joule heating which causes the nanowires to breakup and thus create an electrical discontinuity in the nanowire film. More heat is created, and thus failure occurs sooner, in more resistive electrodes and at higher current densities. Suggestions to improve the stability of silver nanowire electrodes are given.

The emerging area of e-textiles requires electrically conductive threads. We demonstrate that nylon, polyester, and cotton threads can be made conductive by coating their surfaces with random networks of solution-synthesized silver nanowires. A resistance per unit length of 0.8 Ω cm⁻¹ was achieved and can be varied through the density of the nanowire coating. Because the nanowires are 35 nm in diameter, and the mesh structure does not cover the entire surface like a thin-film, less metal is used compared to conventional silver-coated conductive threads. This leads to a much lower weight and mechanically flexible coating. The functionality of the thread as a heater and the fabrication of stretchable conductive thread are also demonstrated.

Silver nanowire transparent electrodes have shown considerable potential to replace conventional transparent conductive materials. However, in this report we show that Joule heating is a unique and serious problem with these electrodes. When conducting current densities encountered in organic solar cells, the average surface temperature of indium tin oxide (ITO) and silver nanowire electrodes, both with sheet resistances of 60 ohms/square, remains below 35 °C. However, in contrast to ITO, the temperature in the nanowire electrode is very non-uniform, with some localized points reaching temperatures above 250 °C. These hotspots accelerate nanowire degradation, leading to electrode failure after 5 days of continuous current flow. We show that graphene, a commonly used passivation layer for these electrodes, slows nanowire degradation and creates a more uniform surface temperature under current flow. However, the graphene does not prevent Joule heating in the nanowires and local points of high temperature ultimately shift the failure mechanism from nanowire degradation to melting of the underlying plastic substrate. In this paper, surface temperature mapping, lifetime testing under current flow, post-mortem analysis, and modelling illuminate the behaviour and failure mechanisms of nanowires under extended current flow and provide guidelines for managing Joule heating.

Variables such as nanowire diameter and density are found to have a significant effect on the degradation of silver nanowires.

A procedure for joining polyol-synthesized silver nanowires in air using current-induced Joule heat welding is reported. Using a common probe station and photolithographically patterned gold electrodes, the welding process is completed using a common semiconductor analyzer. A unique two-step procedure eliminates the dielectric barrier at the point of contact without damaging the nanowires away from the junction. This procedure is designed for metal–metal contacts where a strong dielectric intermediate layer might exist, which can occur with metals prone to oxidation or corrosion in air, or as a result of the electrode deposition process. Ohmic connections are also established in cases where there is an initial gap between two nanowires.

Silver nanowire (AgNW) transparent electrodes show promise as an alternative to indium tin oxide (ITO). However, these nanowire electrodes degrade in air, leading to significant resistance increases. We show that passivating the nanowire surfaces with small organic molecules of 11-mercaptoundecanoic acid (MUA) does not affect electrode transparency contrary to typical passivation films, and is inexpensive and simple to deposit. The sheet resistance of a 32 nm diameter silver nanowire network coated with MUA increases by only 12% over 120 days when exposed to atmospheric conditions but kept in the dark. The increase is larger when exposed to daylight (588%), but is still nearly two orders of magnitude lower than the resistance increase of unpassivated networks. The difference between the experiments performed under daylight versus the dark exemplifies the importance of testing passivation materials under light exposure.