Journal
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
Volume 143, Issue 3, Pages 1539-1552Publisher
AMER CHEMICAL SOC
DOI: 10.1021/jacs.0c11608
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Funding
- National Natural Science Foundation of China [22005135, 51903117]
- Shenzhen Basic Research Fund [JCYJ20190809162003662, JCYJ20180504165709042]
- National Research Foundation (NRF) of Korea [NRF - 2016M1A2A2940911, 2019R1A6A1A11044070]
- Center for Computational Science and Engineering at SUSTech
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In this study, a series of novel acceptor building blocks, CNI, CNTI, and CNDTI, were successfully developed by introducing strong electron-withdrawing cyano functionality on BTI and its derivatives. Based on these novel building blocks, high-performance n-type polymers with deep-positioned LUMOs were synthesized, showing excellent stability and doping efficiency. These polymers exhibit the highest electrical conductivity of 23.3 S m-1 and a power factor of up to 10 mu W m-1 K-2, which are among the highest values reported for solution-processed molecularly n-doped polymers.
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 m(-1) and a power factor of similar to 10 mu W 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.
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