April 22 - 26, 2024
Seattle, Washington
May 7 - 9, 2024 (Virtual)

Event Supporters

2024 MRS Spring Meeting
SB02.12.04

Electrically Programmed Doping Gradients Optimize the Thermoelectric Power Factor of a Conjugated Polymer

When and Where

Apr 26, 2024
9:30am - 9:45am
Room 437, Level 4, Summit

Presenter(s)

Co-Author(s)

Mariavittoria Craighero1,Jian Liu1,Vandna Gupta1,Dorothea Scheunemann2,Sri Paleti1,Emmy Järsvall1,Youngseok Kim1,Kai Xu3,Juan Sebastian Reparaz3,Lambert Jan Anton Koster4,Mariano Campoy-Quiles3,Martijn Kemerink2,Anna Martinelli1,Christian Müller1

Chalmers University of Technology1,Heidelberg University2,ICMAB-CSIC3,University of Groningen4

Abstract

Mariavittoria Craighero1,Jian Liu1,Vandna Gupta1,Dorothea Scheunemann2,Sri Paleti1,Emmy Järsvall1,Youngseok Kim1,Kai Xu3,Juan Sebastian Reparaz3,Lambert Jan Anton Koster4,Mariano Campoy-Quiles3,Martijn Kemerink2,Anna Martinelli1,Christian Müller1

Chalmers University of Technology1,Heidelberg University2,ICMAB-CSIC3,University of Groningen4
Functionally graded materials (FGMs) have been 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 explored. 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 (F<sub>4</sub>TCNQ). 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 8-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.

Keywords

electrical properties | polymer

Symposium Organizers

Xiaodan Gu, University of Southern Mississippi
Chad Risko, University of Kentucky
Bob Schroeder, University College London
Natalie Stingelin, Georgia Institute of Technology

Symposium Support

Bronze
MDPI AG

Session Chairs

Chad Risko

In this Session