Oxynitride-Encapsulated Silver Nanowire Transparent Electrode with Enhanced Thermal, Electrical, and Chemical Stability.

Abstract

Silver nanowire (AgNW) networks have been explored as a promising technology for transparent electrodes due to their solution-processability, low-cost implementation, and excellent trade-off between sheet resistance and transparency. However, their large-scale implementation in applications such as solar cells, transparent heaters, and display applications has been hindered by their poor thermal, electrical, and chemical stability. In this work, we present reactive sputtering as a method for fast deposition of metal oxynitrides as an encapsulant layer on AgNWs. Because O2 cannot be used as a reactive gas in the presence of oxidation-sensitive materials such as Ag, N2 is used under moderate sputtering base pressures to leverage residual H2O on the sample and chamber to deposit Al, Ti, and Zr oxynitrides (AlOxNy, TiOxNy, and ZrOxNy) on Ag nanowires on glass and polymer substrates. All encapsulants improve AgNW networks' electrical, thermal, and chemical stability. In particular, AlOxNy-encapsulated networks present exceptional chemical stability (negligible increase in resistance over 7 days at 80% relative humidity and 80 °C) and transparency (96% for 20 nm films on AgNWs), while TiOxNy demonstrates exceptional thermal and electrical stability (stability up to over temperatures 100 °C more than that of bare AgNW networks, with a maximum areal power density of 1.72 W/cm2, and no resistance divergence at up to 20 V), and ZrOxNy presents intermediate properties in all metrics. In summary, a novel method of oxynitride deposition, leveraging moderate base pressure reactive sputtering, is demonstrated for AgNW encapsulant deposition, which is compatible with roll-to-roll processes that are operated at commercial scales, and this technique can be extended to arbitrary, vacuum-compatible substrates and device architectures.