Transparent and conductive silver nanowires networks printed by laser-induced forward transfer

Networks of silver nanowires (Ag-NWs) can be electrically conductive and optically transparent at the same time. Thus, Ag-NWs are promising candidates for substituting transparent and conductive oxides like indium-tin-oxide. Direct-write methods for printing patterns are suitable in order to reduce the amount of material used with respect to actual deposition methods on large areas that require post-processing steps. In this work, we study the laser-induced forward transfer of Ag-NWs with the aim of printing conductive patterns that appear invisible at naked eye. A Nd:YAG laser system delivering 150 ns pulses at 1064 nm wavelength was coupled with a scan head for printing the Ag-NWs at different pulse energies (0.20-0.45 mJ). It has been found that the area coverage of Ag-NWs, which is directly related with the optical an electrical properties of the patterns, increases as the laser pulse energy increases. A sheet resistance of 140 Omega/sq. is reached when printing at the highest pulse energy tested. As a proof-of-concept, we printed simple circuits with a pair of invisible electrodes connecting an LED on glass with a transmittance of 98.8%, a haze of 0.5%, a reflectance below 0.1% and a sheet resistance of 340 Omega/sq.