Laser shock pressing of silver nanowires on flexible substrates to fabricate highly uniform transparent conductive electrode films

Abstract

Large surface roughness, wire-to-wire junction resistance, and poor adhesion strength of percolated silver nanowire films on polymer substrates are critical issues responsible for low shunt resistance, electron concentration, and thermal damage, resulting in the occurrence of dark spots and damage to flexible electronic devices. Therefore, the fabrication of transparent conductive electrode (TCE) thin films with high surface smoothness and enhanced film properties without the aforementioned problems is essential. Herein, we propose an innovative method to mechanically join silver nanowires on heat-sensitive polymer substrates using a laser-induced shock pressure wave generated by laser ablation of a sacrificial layer. The physical joining mechanism and film properties, that is, sheet resistance, transmittance, adhesion strength, and flexibility, were experimentally analyzed. When a high laser shock pressure was applied to the silver nanowires, plastic deformation occurred; thus, a sintered network film was fabricated through solid-state atomic diffusion at the nanowire junctions. Under optimal process conditions, the sintered films showed high resistance to the adhesion tape test (R/R 0 = 1.15), a significantly reduced surface roughness less than 6 nm, and comparable electrical conductivity (8 ± 2 ) and visible transmittance (84% ± 3%) to typical joining methods. Consequently, this work demonstrates that the laser-induced shock pressing technique has strong potential for the production of TCE metal films on heat-sensitive flexible substrates with film properties superior to those of films produced by conventional methods.