Methods used to deposit and integrate solution-processed materials to fabricate thin film transistors by ink-jet printing are presented. We demonstrate successful integration of a complete additive process with the fabrication of simple prototype TFT backplanes on glass and on flexible plastic substrates, and we discuss the factors that make the process possible. Surface energy control of the gate dielectric layer allows printing of the metal source-drain contacts with gaps as small as 10 um as well as the polymer semiconductor whose electronic properties are very sensitive to surface energy. Silver nanoparticles are used as gate and data metals, and a polythiophene derivative (PQT-12) is used as the semiconducting layer, and the gate dielectric is a polymer. The maximum processing temperature used is 150C, making the process compatible with flexible substrates. The ION/IOFF ratio is 105106, and TFT mobilities of 0.05 cm2/Vs were obtained. The electrical stability of the all-printed transistors was compared to conventional fabrication methods and it is shown to be acceptable for array operation. Here we discuss the yield of the printing process and show arrays that are integrated with E-ink media to form flexible paper-like displays.
Arias, A. C.; Daniel, J. H.; Sambandan, S.; Ng, T.; Russo, B.; Krusor, B. S.; Street, R. A. All printed thin film transistors for flexible electronics. Organic Field Effect Transistors VII and Organic Semiconductors in Sensors and Bioelectronics; 2008 August 10; San Diego, CA. SPIE Proceedings 7054: L-1-7.