Direct Patterned Printing Method of Top-Contact ITO Electrodes for Solution-Processed Metal Oxide Thin-film Transistors

Abstract

The electrodes of metal oxide thin-film transistors (TFTs) can be printed in a practical way by using a solution-based approach, which could be useful for flexible displays and wearable sensors. We have proposed a technique that uses a simple bar coater and selective wettability to enable spontaneous direct patterned printing of top-contact conductive In−Sn−O (ITO) electrodes. We developed ITO inks that were tuned to produce well-defined printed structures and have minimal sheet resistance in order for this to happen. These inks were used to directly modify the surface wettability of the metal oxide semiconductor using photopatterning of the surface modification layer. In our experiments, a directly printed ITO demonstrated a good electrical resistivity of 0.04 Ω cm. In addition, the minimum patterned line width of 10 μm was obtained via developed printed methods. Furthermore, the TFTs incorporating top-contact ITO source/drain electrodes printed using our proposed method on an In−Zn−O semiconductor, which was fabricated through direct photopatterning and solution processing, demonstrated excellent switching performance. They displayed minimal hysteresis, 6 cm 2 /V s of saturated electron mobility, −2.5 V of threshold voltage, and an on− off ratio greater than 10 7 . The introduction of this spontaneous direct printing method is anticipated to significantly contribute to the broader utilization of printed electronics.