High-Mobility Flexible Transistors with Low-Temperature Solution-Processed Tungsten Dichalcogenides
Tian Carey, Oran Cassidy, Kevin Synnatschke, Eoin Caffrey, James Garcia, Shixin Liu, Harneet Kaur, Adam G. Kelly, Jose Munuera, Cian Gabbett, Domhnall O’Suilleabhain, Jonathan N. Coleman
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.