Impact of solvent selection and temperature on porosity and resistance of printed self-reducing silver inks

Reactive metal inks have the potential to replace particle-based inks for printed metals and electrodes. Recent advances in self-reducing silver inks have dropped the reduction temperature from >180 °C down to room temperature. However, most reactive inks are printed at room temperature and sintered at an elevated temperature to achieve good electrical resistivity. In this work, we demonstrate that low electrical resistivity (1.8 μΩcm) can be achieved by adjusting solvent selection and printing at slightly elevated temperatures. This work examines the impact of solvent type and substrate temperature on the resulting morphology and electrical properties of silver films printed with a self-reducing silver-diamine ink. We show that morphology, porosity, and media resistivity can be controlled to produce a dense film without sintering. The porosity was adjusted from 93% down to 50% and the media resistivity two orders of magnitude from 180 μΩcm down to 1.8 μΩcm. The lowest media resistivity was found for a 10:1-EtOH:Ag ink printed at 66 °C. Overall, this process demonstrates that highly conductive silver films can be printed at low temperatures with broad control over morphology and without post-print annealing. Reactive inks print silver with controllable porosity.