Fabrication of low haze silver nanowire flexible transparent electrode

Abstract

In this work, a modified polyol synthesis by adding KBr and by replacing the AgCl with NaCl seed was used to obtain high quality silver nanowires with long aspect ratios with an average length of 13.5 um in length and 62.5 nm in diameter. The silver nanowires suspended in methanol solution after removing any unwanted particles using a glass filter system were then deposited on a flexible polycarbonate substrate using an electrostatic spray system. Transmittance of 92.1% at wavelength of 550 nm with sheet resistance of 20 Ohm/sq and haze of 4.9% were measured for the electrostatic sprayed silver nanowire transparent electrode. However, transparent electrodes that consist of a network of silver nanowires are known to display significantly high haze due to the geometry and the high scattering efficiency of the silver nanowire. In this work, a methodology in reducing the haze by coating the silver nanowires with a thin layer of Au by galvanic exchange in solution was demonstrated. Silver nanowires dispersed in methanol with an average length and diameter of $13.0 \mu m$ and 60 nm, respectively, were subjected to $[Au(en)_2]Cl_3$ galvanic displacement reaction to coat the surface of the silver nanowire with a thin layer of Au. Our reported galvanic exchange conditions were mild enough to gently replace the outer diameter of the silver while preserving the length of the nanowires. The optimized Au/Ag core-shell nanowires were electrostatically coated on polycarbonate substrate to evaluate the electrical and optical properties that revealed a clear reduction in haze of 2-4 % for the total transmittance and sheet resistance range of 80-90% and 8.8-36.8 Ohm/sq., respectively.