Laser digital patterning of finely-structured flexible copper electrodes using copper oxide nanoparticle ink produced by a scalable synthesis method

We present a facile and simple method for synthesizing a large-scale, well-dispersed, and high-concentration CuOx nanoparticle (NP) ink. CuOx thin films with ultrafine surfaces were fabricated using the synthesized NP ink by spin coating, which cannot be achieved using commercial NPs. The CuOx NP thin films were subjected to a subsequent laser digital patterning process, yielding finely-structured Cu electrodes on various polymer substrates with the minimum resistivity of 10.5 mu Omega cm due to the laser-induced reductive sintering (LRS) phenomenon. Arbitrary Cu electrode patterns were directly generated on various flexible substrates under ambient conditions without any templating process. Cu-grid transparent conducting panels with a low sheet resistance (8.45 Omega sq(-1)) and high transmittance (87.4% at 550 nm) were prepared. Furthermore, the effect of the amount of polyvinylpyrrolidone, which was used as a dispersing and reducing agent in the NP ink, on the LRS phenomenon was analyzed in detail. Mechanical bending and twisting, cyclic bending, and tape pull tests confirmed the superior electromechanical stability of the Cu electrodes. The long-term oxidation resistance of the Cu electrodes under ambient conditions and the limiting temperature of oxidation resistance were also examined. Finally, a Cubased flexible transparent touchscreen panel was demonstrated as a possible application.