All inkjet-printed electronics based on electrochemically exfoliated two-dimensional metal, semiconductor, and dielectric

Inkjet printing is a cost-effective and scalable way to assemble colloidal materials into desired patterns in a vacuum- and lithography-free manner. Two-dimensional (2D) nanosheets are a promising material category for printed electronics because of their compatibility with solution processing for stable ink formulations as well as a wide range of electronic types from metal, semiconductor to insulator. Furthermore, their dangling bond-free surface enables atomically thin, electronically-active thin films with van der Waals contacts which significantly reduce the junction resistance. Here, we demonstrate all inkjet-printed thin-film transistors consisting of electrochemically exfoliated graphene, MoS₂, and HfO₂ as metallic electrodes, a semiconducting channel, and a high-k dielectric layer, respectively. In particular, the HfO₂ dielectric layer is prepared via two-step; electrochemical exfoliation of semiconducting HfS₂ followed by a thermal oxidation process to overcome the incompatibility of electrochemical exfoliation with insulating crystals. Consequently, all inkjet-printed 2D nanosheets with various electronic types enable high-performance, thin-film transistors which demonstrate field-effect mobilities and current on/off ratios of ~10 cm² V⁻¹ s⁻¹ and >10⁵, respectively, at low operating voltage.