Dithienylbenzodiimide: A new electron-deficient unit for n-type polymer semiconductors

Jianhua Chen, Xianhe Zhang, Gang Wang, Mohammad Afsar Uddin, Yumin Tang, Yulun Wang, Qiaogan Liao, Antonio Facchetti, Tobin J Marks, Xugang Guo

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11 Citations (Scopus)

Abstract

Inspired by the excellent device performance of imide-functionalized polymer semiconductors in organic electronics, a novel imide-based building block, dithienylbenzodiimide (TBDI), with fused backbone is designed and synthesized. Single-crystal structure analysis reveals that the TBDI unit features non-planar backbone conformation but with a tight π-stacking distance of 3.36 Å. By copolymerizing with various electron-rich co-units, a series of TBDI-based polymer semiconductors is synthesized and the optoelectronic, thermal, electrochemical and charge transport properties of the semiconductors are characterized. Attributed to the non-planar backbone and intrinsic electrical property of TBDI, all polymers exhibit wide bandgaps (∼2.0 eV) with low-lying HOMOs (<-5.5 eV). Organic thin-film transistors are fabricated by incorporating the TBDI-based polymers as the active layer to investigate their charge transport properties. The dithienylbenzodiimide-bithiophene copolymer shows ambipolar transport characteristics with an electron and hole mobility of 0.15 and 0.015 cm2 V-1 s-1, respectively. By incorporating weaker electron donor co-units, the dithienylbenzodiimide-thiophene and dithienylbenzodiimide-difluorobithiophene copolymers exhibit unipolar n-channel transistor performance with electron mobility up to 0.11 and 0.34 cm2 V-1 s-1, respectively. Most high-performance n-channel polymer semiconductors reported to date typically show narrow bandgaps with high-lying HOMOs, resulting in substantial p-channel performance. The new TBDI-based wide bandgap polymers with low-lying HOMOs greatly suppress p-channel performance and lead to improved Ion/Ioff ratios. The excellent n-channel performance is attributed to the strong electron-withdrawing capability of imide groups, low-lying frontier molecular orbitals, compact π-stacking distance, and a high degree of film crystallinity as confirmed by GIWAXS analysis with distinct interlamellar and π-stacking diffraction patterns. The result reveals that a building block with non-planar backbone can be utilized for constructing high crystalline polymer semiconductors with substantial charge carrier mobility. The study indicates that dithienylbenzodiimide is a promising unit for synthesizing wide bandgap polymeric semiconductors with unipolar n-channel performance.

Original languageEnglish
Pages (from-to)9559-9569
Number of pages11
JournalJournal of Materials Chemistry C
Volume5
Issue number37
DOIs
Publication statusPublished - Jan 1 2017

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ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Chemistry

Cite this

Chen, J., Zhang, X., Wang, G., Uddin, M. A., Tang, Y., Wang, Y., ... Guo, X. (2017). Dithienylbenzodiimide: A new electron-deficient unit for n-type polymer semiconductors. Journal of Materials Chemistry C, 5(37), 9559-9569. https://doi.org/10.1039/c7tc02903a