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.
counterion drift
conjugated polymer
organic thermoelectrics
functionally graded materials
chemical doping
Author
Jian Liu
Chalmers, Chemistry and Chemical Engineering, Applied Chemistry
Chinese Academy of Sciences
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
Spanish National Research Council (CSIC)
Juan Sebastián Reparaz
Spanish National Research Council (CSIC)
L. Jan Anton Koster
University of Groningen
M. Campoy-Quiles
Spanish National Research Council (CSIC)
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 2312549Double 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 (SSIF 2011)
Inorganic Chemistry
Materials Chemistry
Other Electrical Engineering, Electronic Engineering, Information Engineering
Condensed Matter Physics
DOI
10.1002/adfm.202312549