Circuits and Applications for Organic Electronics - A Bottom-Contact Organic-Thin-Film-Transistor for Flexible Display Application

摘要

A bottom-contact organic-thin-film-transistor (BC OTFT) is a promising device for display application on a flexible substrate. Conventional fine lithography can be easily applicable to BC OTFT's, eventually enabling higher resolution displays. There are, however, several hurdles for BC OTFT's to achieve higher resolution. We will discuss this issue quantitatively based on the active-matrix display circuitry. A simple FET model with parasitic elements was precisely applied to pentacene-based OTFT's. Two dominant limiting factors were quantitatively revealed to be intrinsic carrier mobility and contact resistance between source, drain and a conducting channel. Improvement in the intrinsic carrier mobility was achieved by optimizing the conditions of surface treatment of a gate dielectric film and deposition conditions of pentacene. We drastically improved the ohmic contact by using a novel metallization process with self-assembled monolayer and achieving direct ohmic contacts with a few molecular layer channels. With these technologies, we achieved BC OTFT's with the extrinsic mobility over 1.1cm{sup}2/V-s, on-off current ratio of 106 and sub threshold slope of 0.3V/decade. These results provide a promising solution for the realization of a flexible display.