Amphipathic Side Chain of a Conjugated Polymer Optimizes Dopant Location toward Efficient N-Type Organic Thermoelectrics.

Jian Liu, Gang Ye, Hinderikus G O Potgieser, Marten Koopmans, Selim Sami, Mohamad Insan Nugraha, Diego Rosas Villalva, Hengda Sun, Jingjin Dong, Xuwen Yang, Xinkai Qiu, Chen Yao, Giuseppe Portale, Simone Fabiano, Thomas D. Anthopoulos, Derya Baran, Remco W A Havenith, Ryan C Chiechi, L. Jan Anton Koster

Research output: Contribution to journalArticlepeer-review

86 Scopus citations

Abstract

There is no molecular strategy for selectively increasing the Seebeck coefficient without reducing the electrical conductivity for organic thermoelectrics. Here, it is reported that the use of amphipathic side chains in an n-type donor-acceptor copolymer can selectively increase the Seebeck coefficient and thus increase the power factor by a factor of ≈5. The amphipathic side chain contains an alkyl chain segment as a spacer between the polymer backbone and an ethylene glycol type chain segment. The use of this alkyl spacer does not only reduce the energetic disorder in the conjugated polymer film but can also properly control the dopant sites away from the backbone, which minimizes the adverse influence of counterions. As confirmed by kinetic Monte Carlo simulations with the host-dopant distance as the only variable, a reduced Coulombic interaction resulting from a larger host-dopant distance contributes to a higher Seebeck coefficient for a given electrical conductivity. Finally, an optimized power factor of 18 µW m$^{-1}$ K$^{-2}$ is achieved in the doped polymer film. This work provides a facile molecular strategy for selectively improving the Seebeck coefficient and opens up a new route for optimizing the dopant location toward realizing better n-type polymeric thermoelectrics.
Original languageEnglish (US)
Pages (from-to)2006694
JournalAdvanced materials (Deerfield Beach, Fla.)
DOIs
StatePublished - Dec 11 2020

Bibliographical note

KAUST Repository Item: Exported on 2020-12-14
Acknowledged KAUST grant number(s): OSR-CRG2018-3737
Acknowledgements: This study was supported by a grant from STW/NWO (VIDI 13476). This study is part of the research program of the Foundation of Fundamental Research on Matter (FOM), which is part of the Netherlands Organization for Scientific Research (NWO). This is a publication by the FOM Focus Group “Next Generation Organic Photovoltaics,” participating in the Dutch Institute for Fundamental Energy Research (DIFFER). J.D. acknowledges financial support from the China Scholarship Council. The authors thank the Center for Information Technology of the University of Groningen for their support and for providing access to the Peregrine high performance computing cluster. S.F. acknowledges the support from the Swedish Research Council (2016-03979), Olle Engkvists Stiftelse (204-0256), and the Advanced Functional Materials center at LiU (2009 00971). D.B. acknowledges the support by the King Abdullah University of Science and Technology (KAUST) Office of Sponsored Research (OSR) under Award No. OSR-CRG2018-3737. S.S. and R.W.A.H. acknowledges SURFSara for giving access to the Dutch national supercomputer Cartesius. This work was sponsored by NWO Exact and Natural Sciences for the use of supercomputer facilities (2020/ENW/00852342). The authors greatly thank dr. H.P. (Hjalmar) Permentier from Interfaculty Mass Spectrometry Center, University of Groningen for MALDI-TOF measurement.

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