Long-term stable NbSe_2 nanosheet aqueous ink for printable electronics

摘要

Despite the rapid development of mass production methods of two-dimensional (2D) transition metal dichalcogenide (TMD) materials in liquid media, long-term stability of these materials in aqueous solution is a major issue. In this study, the instability of chemically exfoliated niobium diselenide (NbSe2) nanosheets (NSs) dispersed in aqueous solution is systematically investigated, and it is revealed that the instability originates from the oxidation of NbSe2 NSs in the aqueous solution, which leads to the precipitation of selenium and restacking of NbSe2 NSs, degrading the electrical property of the NbSe2 NSs. On the basis of the results, for the first time, we propose an efficient method to prevent the oxidation of NbSe2 NSs using an antioxidant (L-ascorbic acid) that effectively consumes the oxygen dissolved in the aqueous solution, rendering the NbSe2 NSs antioxidative during the redox reaction in the aqueous solution, and thereby, improving the long-term stability of the NbSe2 NS ink. Finally, we demonstrate the fabrication of a thermoelectric generator by printing process with our long-term stable NbSe2 NS ink. The thermoelectric power factor was nearly maintained up to 87% regardless of ink storage time even for 30 days.