A diketopyrrolopyrrole conjugated polymer based on 4,4ʹ-difluoro-2,2ʹ-bithiophene for organic thin-film transistors and organic photovoltaics

• Published in: Thin solid films Vol. 711; p. 138300
• Main Authors: He, Yinghui, Aïch, Badrou Reda, Lu, Jianping, Alem, Salima, Lang, Stephen, Movileanu, Raluca, Baribeau, Jean-Marc, Tao, Ye
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.10.2020
• Subjects: Fluorinated bithiophene; Fluorine substitution positions; Organic solar cells; Organic thin film transistors; Polymer semiconductors; Fluorine substitution positions; Organic thin film transistors; Polymer semiconductors; Organic solar cells; Fluorinated bithiophene
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2020.138300

•4,4ʹ-Difluoro-2,2ʹ-bithiophene (DFBT) was designed and synthesized.•A donor-acceptor copolymer of diketopyrrolopyrrole and DFBT was prepared.•Fluorination of bithiopheneat 4, 4ʹ positions has big effects on the properties.•The copolymer demonstrated a hole mobility of 0.21 cm2/VS in transistors.•The copolymer exhibited an efficiency of 3.4% with a high fill factor of 69%. The synthesis of 4,4ʹ-difluoro-2,2ʹ-bithiophene is reported and an alternating donor-acceptor copolymer of this moiety and diketopyrrolopyrrole has been prepared. This polymer has a lower highest occupied molecular orbital than its non-fluorinated analogue polymer. Organic thin film transistors based on this polymer showed p-type charge transport behavior and a hole mobility of 0.21 cm2 V−1 s−1 in bottom-gate bottom-contact devices. Organic solar cells using this polymer as donor and [6,6]-Phenyl-C71-butyric acid methyl ester as acceptor achieved a power conversion efficiency of 3.4% with a high fill factor of 69%. Our morphology analysis showed that there was a lack of long-range ordered structure in the neat polymer thin film, which could cause the inferior device performance.