Charge Transport and Carrier Polarity Tuning by Electrolyte Gating in Nickel Benzenehexathiol Coordination Nanosheets

Coordination nanosheets (CONASHs) or conjugated metal organic frameworks (MOFs) with distinctive metal-organic bonding structures exhibit promise for electronics, sensing, and energy storage. Porous Nickel-Benzene hexathiol complex (Ni-BHT) with noteworthy conductivity was first reported a decade ago, and recent synthetic modifications produced non-porous Ni-BHT with enhanced conductivity (≈50 S cm^-1). Here the charge transport physics of such non-porous Ni-BHT films are studied with even higher conductivity (≈112 S cm^-1). In contrast to the thermally activated electrical conductivity, thermoelectric measurements suggest an intrinsic metallic nature of Ni-BHT. It is shown that it is possible to tune the Fermi level and carrier polarity in Ni-BHT by electrolyte gating; gating is initially governed by the formation of an interfacial, electric double layer and then evolves into an electrochemical (de)doping process. These findings not only contribute to a deeper understanding of charge transport in CONASHs, but also show that Fermi level tuning is an effective approach for enhancing the thermoelectric performance of CONASHs.