Full In-Place Printing of Flexible Electrolyte-Gated CNT-TFTs
The vast majority of research in the printed electronics space is invested into the development of RFID antennae, sensors, and transistors to facilitate the growth of ubiquitous electronics for the Internet-of-Things (IoT) [1]. Despite an intensive research effort over the past 20 years, a streamlined, direct-write, print-on-demand fabrication process, similar to the likes of today's 3D printing technologies (where the substrate never leaves the printing stage), has yet to be developed. The challenges preventing printed electronics from reaching such a point today are, in part, the high process temperature requirements imposed by inorganic nanoparticle-based inks. Recent work has shown that increasing the aspect ratio of nanostructures in an ink results in the reduction of its process temperature requirements [2], which is a major step towards the development of print-on-demand electronics. Utilizing these findings, in past work we have demonstrated substrate-gated, partially in-place printed thin-film transistors (TFTs) at low-temperatures using rigid Si substrates for gate and dielectric [3]. However, the demonstration of a fully in-place printed flexible TFT technology, where the source, drain, gate, dielectric, and semiconductor are all printed, is necessary for the further development of print-on-demand electronics. In this work, we demonstrate fully in-place printed TFTs on flexible substrates. This is achieved using materials and inks amenable to low-temperature processing, which include semiconducting carbon nanotubes (s-CNTs), conductive silver nanowires (AgNW), and an ionic gel (IG) dielectric, resulting in high-performance, low-voltage devices with a maximum process temperature of only 80°C.
