ABSTRACT
Electronic charge transport is a fundamental process of great importance in most areas of organic electronics whether one is studying, for instance, organic light-emitting diodes (OLEDs), organic photovoltaic (OPV) devices, or organic field-effect transistors (OFETs). Several techniques and devices have been used to investigate charge transport properties in π-conjugated organic materials with the most widely recognized technique for benchmarking charge transport being the field-effect transistor. Ando and coworkers from Mitsubishi Electric Corporation reported the first organic polymer-based field-effect transistor in 1986, using electropolymerized polythiophene prepared from 2,2′-bithiophene (Tsumura, Koezuka, and Ando, 1986). After electrochemical de-doping of the as-deposited polymer, an electrical field-effect was observed giving rise to an extracted hole mobility around 10−5 cm2/Vs and a transconductance of 3 nS. More than 30 years have passed since this report, and the field of organic electronics has matured significantly with market-ready applications such as e-paper displays and electronic sensors, not least driven by the vast improvements in understanding and control of charge transport properties in organic polymers and the shift to solution-processable materials facilitating the use of high-resolution printing technologies (Fukuda and Someya, 2017).
