Effective Use of Electrically Insulating Units in Organic Semiconductor Thin Films for High-Performance Organic Transistors

The electrical properties of organic semiconductors (OSCs), whether they are conjugated small molecules or polymers, can be tailored by incorporating electrically insulating units (EIUs), which are organic moieties consisting of nonconjugated units. EIUs can be introduced to a thin film by synthetically connecting them to the otherwise conjugated OSC molecules or by blending them in as separate EIU molecules with the OSCs during the thin-film fabrication process. The engineered EIUs are capable of imparting various additional functions to the OSC thin film and improving their electrical properties. In this review article, a comprehensive overview of various effects of EIUs on OSC thin films and their consequent electrical performance when used as active layers in organic field-effect transistors (OFETs) is provided. A broad range of studies of the synthetic approaches of incorporating EIUs, such as those using side chains, block copolymers, and conjugation-break spacers, and of the blending approaches with organic insulators is discussed. Finally, a brief summary and perspectives for future research in this field are presented.