Electrically Programmed Doping Gradients Optimize the Thermoelectric Power Factor of a Conjugated Polymer
Journal article, 2024

Functionally graded materials (FGMs) are widely explored in the context of inorganic thermoelectrics, but not yet in organic thermoelectrics. Here, the impact of doping gradients on the thermoelectric properties of a chemically doped conjugated polymer is studied. The in-plane drift of counterions in moderate electric fields is used to create lateral doping gradients in films composed of a polythiophene with oligoether side chains, doped with 2,3,5,6-tetrafluoro-tetracyanoquinodimethane (F4TCNQ). Raman microscopy reveals that a bias voltage of as little as 5 V across a 50 µm wide channel is sufficient to trigger counterion drift, resulting in doping gradients. The effective electrical conductivity of the graded channel decreases with bias voltage, while an overall increase in Seebeck coefficient is observed, yielding an up to eight-fold enhancement in power factor. Kinetic Monte Carlo simulations of graded films explain the increase in power factor in terms of a roll-off of the Seebeck coefficient at high electrical conductivities in combination with a mobility decay due to increased Coulomb scattering at high dopant concentrations. Therefore, the FGM concept is found to be a way to improve the thermoelectric performance of not yet optimally doped organic semiconductors, which may ease the screening of new materials as well as the fabrication of devices.

functionally graded materials

chemical doping

organic thermoelectrics

counterion drift

conjugated polymer

Author

Jian Liu

Chinese Academy of Sciences

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry

Mariavittoria Craighero

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry

Vandna Kumari Gupta

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry

Dorothea Scheunemann

Heidelberg University

Sri Harish Kumar Paleti

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry

Emmy Järsvall

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry

Youngseok Kim

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry

Kai Xu

Institute of Material Science of Barcelona (ICMAB)

Juan Sebastián Reparaz

Institute of Material Science of Barcelona (ICMAB)

L. Jan Anton Koster

University of Groningen

M. Campoy-Quiles

Institute of Material Science of Barcelona (ICMAB)

M. Kemerink

Heidelberg University

Anna Martinelli

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry

Christian Müller

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry

Advanced Functional Materials

1616-301X (ISSN) 16163028 (eISSN)

Vol. 34 18 2312549

Double Doping of Semiconducting Polymers

Swedish Research Council (VR) (2018-03824), 2018-01-01 -- 2021-12-31.

Hybrid and Organic Thermoelectric Systems (HORATES)

European Commission (EC) (EC/H2020/955837), 2021-03-01 -- 2025-02-28.

Subject Categories

Inorganic Chemistry

Materials Chemistry

Other Electrical Engineering, Electronic Engineering, Information Engineering

Condensed Matter Physics

DOI

10.1002/adfm.202312549

More information

Latest update

5/11/2024