Scalable Coating and Properties of Transparent, Flexible, Silver Nanowire Electrodes

TLDR

The study investigates scalable fabrication and performance of transparent, flexible silver nanowire electrodes. The authors employ a synthesis of long, thin silver nanowires, a scalable fabrication process, and an electrochemical gold coating to reduce junction resistance and improve sheet resistance and transmittance. The resulting electrodes achieve 20 Ω/sq with ~80 % specular transmittance, 8 Ω/sq with 80 % diffusive transmittance, superior near‑infrared transparency, a large diffusive‑specular transmittance contrast, excellent bending durability, and conductance gains from mechanical pressing, meeting flexible‑electronics and solar‑cell requirements.

Abstract

We report a comprehensive study of transparent and conductive silver nanowire (Ag NW) electrodes, including a scalable fabrication process, morphologies, and optical, mechanical adhesion, and flexibility properties, and various routes to improve the performance. We utilized a synthesis specifically designed for long and thin wires for improved performance in terms of sheet resistance and optical transmittance. Twenty Ω/sq and ∼80% specular transmittance, and 8 ohms/sq and 80% diffusive transmittance in the visible range are achieved, which fall in the same range as the best indium tin oxide (ITO) samples on plastic substrates for flexible electronics and solar cells. The Ag NW electrodes show optical transparencies superior to ITO for near-infrared wavelengths (2-fold higher transmission). Owing to light scattering effects, the Ag NW network has the largest difference between diffusive transmittance and specular transmittance when compared with ITO and carbon nanotube electrodes, a property which could greatly enhance solar cell performance. A mechanical study shows that Ag NW electrodes on flexible substrates show excellent robustness when subjected to bending. We also study the electrical conductance of Ag nanowires and their junctions and report a facile electrochemical method for a Au coating to reduce the wire-to-wire junction resistance for better overall film conductance. Simple mechanical pressing was also found to increase the NW film conductance due to the reduction of junction resistance. The overall properties of transparent Ag NW electrodes meet the requirements of transparent electrodes for many applications and could be an immediate ITO replacement for flexible electronics and solar cells.