Design and Fabrication of Printed Organic Thin-Film Transistor Active Matrix

Abstract

As an alternative to rigid devices, soft electronics are pursuing large-area, high-density, and highly reliable devices. However, it is challenging to fabricate organic transistor-based soft electronics with high density and high yield with high uniformity on a large-area flexible substrate using printing technology. We adopt two strategies to solve these bottlenecks. An array pattern is modified for high density of transistors avoiding electrical short by monolithically integrate crossing interconnections. Then, for 100% yield and high uniformity, organic semiconductor (OSC) drying temperature and OSC nozzle-printing pressure are optimized with ~ 275 nm of thin parylene gate insulator to fully block leakage current. As a result, 80 printed transistors are integrated on a 25 × 20 mm2 flexible parylene substrate with 100% yield. Transistors show high uniformity of three major parameters, which are observed as 0.198±0.046 cm2·V-1·s-1 for average saturation mobility, -1.72±0.21 V for average threshold voltage, and 5.12±0.2 for average logarithmic on/off ratio. We utilize the data of transistor active matrix to compare and verify our custom-built array auto characterization system. An error in an algorithm for current range transition impeded accurate measurement. By modifying the algorithm, the system shows high accuracy compared to a conventional semiconductor analyzer. These results represent significant progress in the fabrication of printed organic thin-film transistor array on a biocompatible flexible substrate, which makes it a promising candidate for next-generation backplane of soft electronics.