High-Mobility Flexible Transistors with Low-Temperature Solution-Processed Tungsten Dichalcogenides

Abstract

High Resolution Image Download MS PowerPoint Slide The investigation of high-mobility two-dimensional (2D) flakes beyond molybdenum disulfide (MoS 2 ) will be necessary to create a library of high-mobility solution-processed networks that conform to substrates and remain functional over thousands of bending cycles. Here we report electrochemical exfoliation of large-aspect-ratio (>100) semiconducting flakes of tungsten diselenide (WSe 2 ) and tungsten disulfide (WS 2 ) as well as MoS 2 as a comparison. We use Langmuir–Schaefer coating to achieve highly aligned and conformal flake networks, with minimal mesoporosity (∼2–5%), at low processing temperatures (120 °C) and without acid treatments. This allows us to fabricate electrochemical transistors in ambient air, achieving average mobilities of μ MoS 2 ≈ 11 cm 2 V –1 s –1, μ WS 2 ≈ 9 cm 2 V –1 s –1, and μ WSe 2 ≈ 2 cm 2 V –1 s –1 with a current on/off ratios of I on / I off ≈ 2.6 × 10 3, 3.4 × 10 3, and 4.2 × 10 4 for MoS 2, WS 2, and WSe 2, respectively. Moreover, our transistors display threshold voltages near ∼0.4 V with subthreshold slopes as low as 182 mV/dec, which are essential factors in maintaining power efficiency and represent a 1 order of magnitude improvement in the state of the art. Furthermore, the performance of our WSe 2 transistors is maintained on polyethylene terephthalate (PET) even after 1000 bending cycles at 1% strain.