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Changyong Cao1

1, Michigan State University, East Lansing, Michigan, United States

Nanomaterials offer an attractive solution to the challenges faced for low-cost printed electronics, with applications ranging from additively manufactured sensors to wearables. While many reports have presented “fully printed” thin-film transistors (TFTs) from carbon nanotubes (CNTs), they have all used non-printing techniques to form some portion of the devices, compromising the benefits of throughput and on-the-fly customization that an exclusively printed process offers. Here we report hysteresis-free carbon nanotube TFTs (CNT-TFTs) fabricated entirely using an aerosol jet printing technique; this includes the printing of all layers: semiconducting CNTs, metallic electrodes and insulating gate dielectrics, using the same printer. One of the foremost challenges to a completely printed CNT-TFT approach has been the difficulty of obtaining a robust printed dielectric. We show that, under appropriate printing conditions, a now commercially available dielectric ink can be reliably printed and yield negligible hysteresis and low threshold voltage in CNT-TFTs. Conditions were optimized for printing on both rigid and flexible substrates, including insight into the trade-offs between top- and bottom-gate device geometries. Flexible CNT-TFTs on Kapton film demonstrate minimal variations in performance for over 1000 cycles of bending tests with curvature radii down to 1 mm. New insights are also gained concerning the role of charge trapping in Si substrate-supported devices, where exposure to high substrate fields results in irreversible degradation. With all of the benefits that CNT-TFTs offer for the field of low-cost, multi-functional electronics, this result is a critical step forward as it enables a completely additive, maskless method to fully print CNT-TFTs of direct relevance for the burgeoning areas of flexible/foldable, wearable, and biointegrated electronics.

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