Cyano-Functionalized Bithiophene Imide-Based n-Type Polymer Semiconductors: Synthesis, Structure-Property Correlations, and Thermoelectric Performance

Kui Feng, Han Guo, Junwei Wang, Yongqiang Shi, Ziang Wu, Mengyao Su, Xianhe Zhang, Jae Hoon Son, Han Young Woo, Xugang Guo

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)

Abstract

n-Type polymers with deep-positioned lowest unoccupied molecular orbital (LUMO) energy levels are essential for enabling n-type organic thin-film transistors (OTFTs) with high stability and n-type organic thermoelectrics (OTEs) with high doping efficiency and promising thermoelectric performance. Bithiophene imide (BTI) and its derivatives have been demonstrated as promising acceptor units for constructing high-performance n-type polymers. However, the electron-rich thiophene moiety in BTI leads to elevated LUMOs for the resultant polymers and hence limits their n-type performance and intrinsic stability. Herein, we addressed this issue by introducing strong electron-withdrawing cyano functionality on BTI and its derivatives. We have successfully overcome the synthetic challenges and developed a series of novel acceptor building blocks, CNI, CNTI, and CNDTI, which show substantially higher electron deficiencies than does BTI. On the basis of these novel building blocks, acceptor-acceptor type homopolymers and copolymers were successfully synthesized and featured greatly suppressed LUMOs (-3.64 to -4.11 eV) versus that (-3.48 eV) of the control polymer PBTI. Their deep-positioned LUMOs resulted in improved stability in OTFTs and more efficient n-doping in OTEs for the corresponding polymers with a highest electrical conductivity of 23.3 S cm-1 and a power factor of ∼10 μW m-1 K-2. The conductivity and power factor are among the highest values reported for solution-processed molecularly n-doped polymers. The new CNI, CNTI, and CNDTI offer a remarkable platform for constructing n-type polymers, and this study demonstrates that cyano-functionalization of BTI is a very effective strategy for developing polymers with deep-lying LUMOs for high-performance n-type organic electronic devices.

Original languageEnglish
Pages (from-to)1539-1552
Number of pages14
JournalJournal of the American Chemical Society
Volume143
Issue number3
DOIs
Publication statusPublished - 2021 Jan 27

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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