  Printed polymer electronics has held for long the promise of revolutionizing
technology by delivering distributed, flexible, lightweight and cost-effective
applications for wearables, healthcare, diagnostic, automation and portable
devices. While impressive progresses have been registered in terms of organic
semiconductors mobility, field-effect transistors (FET), the basic building
block of any circuit, are still showing limited speed of operation, thus
limiting their real applicability. So far, attempts with organic FET to achieve
the tens of MHz regime, a threshold for many applications comprising the
driving of high resolution displays, have relied on the adoption of
sophisticated lithographic techniques and/or complex architectures, undermining
the whole concept. In this work we demonstrate polymer FETs which can operate
up to 20 MHz and are fabricated by means only of scalable printing techniques
and direct-writing methods with a completely mask-less procedure. This is
achieved by combining a fs-laser process for the sintering of high resolution
metal electrodes, thus easily achieving micron-scale channels with reduced
parasitism down to 0.19 pF mm-1, and a large area coating technique of a high
mobility polymer semiconductor, according to a simple and scalable process
flow.
