Naphthodithiophene Diimide-Based Copolymers: Ambipolar Semiconductors in Field-Effect Transistors and Electron Acceptors with Near-Infrared Response in Polymer Blend Solar Cells

Kyohei Nakano, Masahiro Nakano, Bo Xiao, Erjun Zhou, Kaori Suzuki, Itaru Osaka, Kazuo Takimiya, Keisuke Tajima

Research output: Contribution to journalArticle

63 Citations (Scopus)

Abstract

New π-conjugated copolymers based on naphtho[2,3-b:6,7-b′]dithiophene-4,5,9,10-diimide (NDTI) combined with thiophene, thienothiophene, or dithienothiophene units are synthesized and used in field-effect transistors (FETs) and organic solar cells (OSCs). The low-lying lowest unoccupied molecular orbital (LUMO) and high-lying highest occupied molecular orbital (HOMO) levels of the polymers contribute to reducing injection barriers for both electrons and holes, resulting in ambipolar operation of FET devices. The charge mobilities were strongly affected by the molecular orientation of the copolymers, and the highest electron mobility of 0.26 cm2/(V s) was observed for the copolymer with thienothiophene unit with edge-on orientation. On the other hand, OSCs with PTB7 as the electron donor polymer and the copolymers as the acceptor showed a broad photoresponse extending to the near-IR region, and the highest power conversion efficiency of over 3.5% was obtained for the copolymer with dithienothiophene unit that showed the favorable face-on orientation in the neat thin film, though the effect of the molecular orientations in OSCs was not as clear as in OFETs owing to the lower crystallinity of the mixed films.

Original languageEnglish
Pages (from-to)1752-1760
Number of pages9
JournalMacromolecules
Volume49
Issue number5
DOIs
Publication statusPublished - 2016 Mar 9
Externally publishedYes

ASJC Scopus subject areas

  • Organic Chemistry
  • Polymers and Plastics
  • Inorganic Chemistry
  • Materials Chemistry

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