Inkjet-Printed MoS2 Nanoplates on Flexible Substrates for High-Performance Field Effect Transistors and Gas Sensing Applications

Owing to the simplicity, scalability, and cost efficiency, solution-processable two-dimensional (2D) semiconductors have attracted great interest in electronic applications, especially as the channel material for field-effect transistors (FETs). Inkjet printing is a lithography-free technique to achieve drop-on-demand patterning of solution-processable 2D ink. However, thus far, inkjet-printed 2D FETs exhibit limited performance due to the coffee-ring effect and consequent discontinuity of the printed 2D material films. Here, we report high-performance and flexible inkjet-printed MoS2 FETs with high mobilities and high on/off ratios and their gas sensing applications. By preparing high-quality MoS2 ink comprised of MoS2 nanoplates using electrochemical exfoliation and then applying a binary solvent comprised of 2-butanol and isopropanol, the obtained ink was printed to form a continuous and relatively uniform MoS2 film, and high-performance printed MoS2 FETs were demonstrated, with mobilities of 11 cm2 V-1 s-1 and on/off ratios of 106. Furthermore, low-voltage gate modulation was achieved by applying an ion gel gate, and robust electrical performance under tensile strain was observed for the ion gel-gated MoS2 FETs printed on flexible substrates. As the printed MoS2 film is abundant in edge sites and sulfur vacancies, we further demonstrated our MoS2 FETs as high-performance gas sensors with a limit of detection of 10 ppb for NO2 and 0.5 ppm for NH3, together with a fast recovery rate.