Acene Ring Size Optimization in Fused Lactam Polymers Enabling High n-Type Organic Thermoelectric Performance

Hu Chen, Maximilian Moser, Suhao Wang, Cameron Jellett, Karl Thorley, George T. Harrison, Xuechen Jiao, Mingfei Xiao, Balaji Purushothaman, Maryam Alsufyani, Helen Bristow, Stefaan De Wolf, Nicola Gasparini, Andrew Wadsworth, Christopher R. McNeill, Henning Sirringhaus, Simone Fabiano, Iain McCulloch

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Three n-type fused lactam semiconducting polymers were synthesized for thermoelectric and transistor applications via a cheap, highly atom-efficient, and nontoxic transition-metal free aldol polycondensation. Energy level analysis of the three polymers demonstrated that reducing the central acene core size from two anthracenes (A-A), to mixed naphthalene–anthracene (A-N), and two naphthalene cores (N-N) resulted in progressively larger electron affinities, thereby suggesting an increasingly more favorable and efficient solution doping process when employing 4-(2,3-dihydro-1,3-dimethyl-1H-benzimidazol-2-yl)-N,N-dimethylbenzenamine (N-DMBI) as the dopant. Meanwhile, organic field effect transistor (OFET) mobility data showed the N-N and A-N polymers to feature the highest charge carrier mobilities, further highlighting the benefits of aryl core contraction to the electronic performance of the materials. Ultimately, the combination of these two factors resulted in N-N, A-N, and A-A to display power factors (PFs) of 3.2 μW m–1 K–2, 1.6 μW m–1 K–2, and 0.3 μW m–1 K–2, respectively, when doped with N-DMBI, whereby the PFs recorded for N-N and A-N are among the highest reported in the literature for n-type polymers. Importantly, the results reported in this study highlight that modulating the size of the central acene ring is a highly effective molecular design strategy to optimize the thermoelectric performance of conjugated polymers, thus also providing new insights into the molecular design guidelines for the next generation of high-performance n-type materials for thermoelectric applications.
Original languageEnglish (US)
JournalJournal of the American Chemical Society
StatePublished - Dec 22 2020

Bibliographical note

KAUST Repository Item: Exported on 2020-12-24
Acknowledged KAUST grant number(s): OSR-2015-CRG4-2572, OSR-2018-CARF/CCF-3079, OSR-4106 CPF2019
Acknowledgements: The authors acknowledge generous funding from KAUST for financial support. The research reported in this publication was sponsored by funding from King Abdullah University of Science and Technology Office of Sponsored Research (OSR) under Awards OSR-2018-CARF/CCF-3079, OSR-2015-CRG4-2572, and OSR-4106 CPF2019. We acknowledge EC FP7 Project SC2 (610115), EC H2020 (643791), and EPSRC
Projects EP/G037515/1, EP/M005143/1, and EP/L016702/1. This work was performed in part at the SAXS/WAXS beamline at the Australian Synchrotron, part of ANSTO.36 S.F.acknowledges financial support from the Swedish Research Council (Grant 2016-03979), ÅForsk (Grants 18-313, 19-310), Olle Engkvists Stiftelse (Grant 204-0256), and the Advanced Functional Materials Center at Linköping University (Grant 2009-00971).


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