Imide-Functionalized Thiazole-Based Polymer Semiconductors: Synthesis, Structure-Property Correlations, Charge Carrier Polarity, and Thin-Film Transistor Performance

Yongqiang Shi, Han Guo, Minchao Qin, Yuxi Wang, Jiuyang Zhao, Huiliang Sun, Hang Wang, Yulun Wang, Xin Zhou, Antonio Facchetti, Xinhui Lu*, Ming Zhou, Xugang Guo

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

88 Scopus citations

Abstract

Imide-functionalized arenes, exemplified by naphthalene diimides (NDIs), perylene diimides (PDIs), and bithiophene imides (BTIs), are the most promising building blocks for constructing high-performance n-type polymers. In order to reduce the steric hindrance associated with NDI- and PDI-based polymers and to address the high-lying LUMO issue of BTI-based polymers, herein a highly electron-deficient imide-functionalized bithiazole, N-alkyl-5,5′-bithiazole-4,4′-dicarboximide (BTzI), was successfully synthesized via an efficient C-H activation. Single crystal of BTzI model compound showed a planar backbone with close π-stacking distances (3.2-3.3 Å). The N,N′-bis(2-alkyl)-2,2′-bithiazolethienyl-4,4′,10,10′-tetracarboxdiimide (DTzTI) was also used for constructing polymer semiconductors. Compared to DTzTI, BTzI is more electron-deficient, rendering it highly appealing for enabling n-type polymers. On the basis of BTzI and DTzTI, a series of polymers, including acceptor-acceptor homopolymers, and donor-acceptor and donor-acceptor-acceptor copolymers, were synthesized, which feature different contents of acceptor units in polymeric backbones. As imide content increases, the polymer FMO levels were gradually lowered, yielding a transition of charge carrier from ambipolarity to unipolar n-type in organic thin-film transistors (OTFTs). The acceptor-acceptor homopolymer PBTzI possesses the deepest LUMO/HOMO level of -3.94/-6.17 eV, enabling minimal off-current (Ioff) of 10-10-10-11 A in OTFTs. The highest electron mobility of 1.61 cm2 V-1 s-1 accompanied by small Ioff of 10-10-10-11 A and high on-current/off-current ratio (Ion/Ioff) of 107-108 was achieved from OTFTs using PDTzTI homopolymer, showing the pronounced advantages of acceptor-acceptor homopolymer approach for developing unipolar n-type polymer semiconductors. The correlations between the FMO levels and the transistor performances underscore the significance of FMO tuning for enabling unipolar electron transport. The results demonstrate that imide-functionalized thiazoles are excellent units for constructing high-performance n-type polymers. Moreover, the synthetic routes to these highly electron-deficient imide-functionalized thiazoles and the polymer structure-property correlations developed here are informative for materials invention in organic electronics.

Original languageEnglish (US)
Pages (from-to)7988-8001
Number of pages14
JournalChemistry of Materials
Volume30
Issue number21
DOIs
StatePublished - Nov 13 2018

ASJC Scopus subject areas

  • General Chemistry
  • General Chemical Engineering
  • Materials Chemistry

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