Stable, highly conductive and orthogonal silver nanowire networks via zwitterionic treatment

Abstract

Silver nanowires (AgNWs) are the most important transparent electrodes for flexible optoelectronics. Their high aspect ratio and metallic nature make them tend to aggregate and yield inhomogeneous conducting films, which is detrimental to device performance. Here, a zwitterionic molecule was introduced into AgNW suspensions to tackle these drawbacks. The anionic part of the zwitterionic molecule absorbs on the surface of AgNWs, while the cations help the homogeneous dispersion of AgNWs in suspensions. More importantly, the cations generate electrostatic repulsion, which forces the AgNWs to form orthogonal networks with cut-off angles approaching 90°. These perfect AgNW networks showed superior photoelectric performance (with a sheet resistance of ∼11.8 Ω cm⁻² and transmittance at 550 nm of ∼94.4%) and excellent storage stability. As a demonstration of their application, a flexible transparent electrode was fabricated via semi-embedding the AgNW networks in a polyimide substrate and applied to flexible organic solar cells, which exhibit superior mechanical stability (maintaining > 92% of the initial efficiency after 30 000 bending cycles at a small radius of 1 mm). Therefore, stable, highly conductive and orthogonal AgNW networks can be obtained via zwitterionic treatment and show potential in flexible optoelectronics.