Dithiazolylthienothiophene Bisimide: A Novel Electron-Deficient Building Unit for N‑Type Semiconducting Polymers

• Published in: ACS applied materials & interfaces 2019-07, Vol.11 (26), p.23410-23416
• Main Authors: Teshima, Yoshikazu, Saito, Masahiko, Fukuhara, Tomohiro, Mikie, Tsubasa, Komeyama, Kimihiro, Yoshida, Hiroto, Ohkita, Hideo, Osaka, Itaru
• Format: Article
• Language: English
• ISSN: 1944-8244; 1944-8252
• DOI: 10.1021/acsami.9b05361

N-type (electron-transporting) semiconducting polymers are essential materials for the development of truly plastic electronic devices. Here, we synthesized for the first time dithiazolylthienothiophene bisimide (TzBI), as a new family for imide-based electron-deficient π-conjugated systems, and semiconducting polymers by incorporating TzBI into the π-conjugated backbone as the building unit. The TzBI-based polymers are found to have deep frontier molecular orbital energy levels and wide optical bandgaps compared to the dithienylthienothiophene bisimide (TBI) counterpart. It is also found that TzBI can promote the π–π intermolecular interactions of the polymer backbones relative to TBI most probably because the thiazole ring, which replaced the thiophene ring, at the end of the framework gives a more coplanar backbone. In fact, TzBI-based polymers function as the n-type semiconducting material in both organic field-effect transistor (OFET) and organic photovoltaic (OPV) devices. Notably, one of the TzBI-based polymers provides a power conversion efficiency of 3.3% in the all-polymer OPV device, which could be high for a low-molecular-weight polymer (