Organic n‑Channel Transistors Based on [1]Benzothieno[3,2‑b]benzothiophene–Rylene Diimide Donor–Acceptor Conjugated Polymers

• Published in: ACS applied materials & interfaces 2018-09, Vol.10 (38), p.32444-32453
• Main Authors: Samanta, Suman Kalyan, Song, Inho, Yoo, Jong Heun, Oh, Joon Hak
• Format: Article
• Language: English
• ISSN: 1944-8244; 1944-8252
• DOI: 10.1021/acsami.8b10831

Improving the charge-carrier mobility of conjugated polymers is important for developing high-performance, solution-processed optoelectronic devices. Although [1]­benzothieno­[3,2-b]­benzothiophene (BTBT) has been frequently used as a high-performance p-type small molecular semiconductor and employed a few times as a building block for p-type conjugated polymers, it has never been explored as a donor moiety for high-performance n-type conjugated polymers. Here, BTBT has been conjugated with either n-type perylene diimide (PDI) or naphthalene diimide (NDI) units to generate a donor–acceptor copolymer backbone, for the first time. Charge-transport measurements of organic field-effect transistors show n-type dominant behaviors, with the electron mobility reaching ∼0.11 cm2 V–1 s–1 for PDI–BTBT and ∼0.050 cm2 V–1 s–1 for NDI–BTBT. The PDI–BTBT mobility value is one of the highest among the PDI-containing polymers. The high π–π stacking propensity of BTBT significantly improves the charge-carrier mobility in these polymers, as supported by atomic force microscopy and grazing incidence X-ray diffraction analyses. Phototransistor applications of these polymers in the n-type mode show highly sensitive photoresponses. Our findings demonstrate that incorporation of the BTBT donor unit within the rylene diimide acceptor-based conjugated polymers can improve the molecular ordering and electron mobility.