Highly Stable Ni-Based Flexible Transparent Conducting Panels Fabricated by Laser Digital Patterning

A novel simple laser digital patterning process to fabricate Ni-based flexible transparent conducting panels using solution-processed nonstoichiometric nickel oxide (NiO _x ) thin films and their applications for flexible transparent devices are reported in this study. A large-scale synthesis route to produce NiO _x nanoparticle (NP) ink is also demonstrated. A low-power continuous-wave laser irradiation photothermochemically reduces and sinters selected areas of a NiO _x NP thin film to produce Ni electrode patterns. Owing to the innovative NiO _x NP ink and substantially lowered applied laser power density, Ni conductors can be fabricated, for the first time to the best of the authors' knowledge, even on a polyethylene terephthalate substrate, which is known to have one of the lowest glass-transition temperatures among polymers. The resultant Ni electrodes exhibit a high-temperature oxidation resistance up to approximately 400 °C, and high corrosion resistance in tap water and even in seawater. Moreover, a superior mechanical stability of the Ni conductors is confirmed by tape-pull, ultrasonic-bath, bending/twisting, and cyclic bending (up to 10 000 cycles) tests. Finally, flexible transparent touch screen panels and electrical heaters are fabricated with mesh-type Ni conductors to demonstrate possible applications.