Self-aligned capillarity-assisted printing of top-gate thin-film transistors on plastic

Top-gate thin-film transistors (TFTs) are fabricated on plastic using a self-aligned method based on capillarity-assisted lithography and inkjet printing, offering a promising platform for high-throughput manufacturing of flexible electronic devices. Plastic substrates are imprinted with a multi-tier structure containing capillary channels and ink receivers using a precision mold. Liquid inks are sequentially delivered to the microstructured substrate by inkjet printing, and capillary action draws the inks into a multi-tier capillary channel network designed for top-gate TFTs. The combination of imprinting, inkjet printing, and capillary flow yields self-aligned multi-layered devices without requiring precise registration for inkjet printing. The printed top-gate TFTs with Ag/Cu source and drain, poly(3-hexylthiophene) semiconducting channel, ion gel dielectric, and graphene gate electrode have desirable transfer and output characteristics, with a hole mobility of 0.48 cm² V^-1 s^-1, threshold voltage of -0.86 V, on/off current ratio of 10^4.5, and robust tolerance to bending. The top-gate geometry and careful materials selection yields devices with negligible hysteresis and sweep rate dependence, establishing the versatility and utility of this self-aligned strategy for more widespread application in printed and flexible electronics.