Polymer-Passivated Silver Nanowire Transparent Electrodes in Flexible PEDOT:PSS-Based Electrochromic Devices

Silver nanowire networks are a promising replacement to indium tin oxide as transparent electrodes, which are necessary components of electrochromic devices. However, silver nanowires suffer from a short lifetime due to silver corrosion. Unlike many nanowire electrode passivation materials studied in the literature, the current work focuses on an inexpensive nonconductive passivation layer, allowing the utilization of transparent polymers. Herein, a coating of a thin layer of polyurethane (PU) was used to prevent corrosion and to limit the electrode sheet resistance to an increase of only 1.8x after 6 months. PU is cheap and easy to deposit, 96% transparent across the visible and NIR regions (Atkinson, J. "Silver Nanowire Networks in Electrochromic Devices", Thesis, University of Waterloo, Waterloo, 2023), increases the mechanical flexibility of nanowire electrodes, improves nanowire adhesion, and decreases surface roughness by an average of 15 nm. The PU-passivated nanowire electrodes are integrated into mechanically flexible symmetric PEDOT:PSS-based electrochromic displays. Compared to similar devices based on ITO electrodes, the PU-passivated nanowire-based devices show higher color modulation, shorter switching times, a larger change in reflectance in the visible properties, and a longer lifetime. Most noteworthy are their far superior mechanical properties. After 50 bending cycles, the nanowire-based devices had little change in performance, whereas ITO-based devices no longer worked.