Microstructural Evolution Dominates the Changes in the Thermal Conductivity of Conjugated Polymers Upon Doping
Journal article, 2025
In this study, the correlation between the changes in microstructure of conjugated polymers upon doping and their concomitant thermal transport properties is elucidated. Eight conjugated polymers across distinct doping systems are examined: molecular dopants, Lewis acid type dopants, and ion-exchange systems. These findings indicate that, upon doping, there is a decrease in out-of-plane thermal conductivity for five polymers characterized by high structural order, such as those based on thiophene, diketopyrrolopyrrole, and terthiophene-naphthalimide copolymers. Conversely, for polymers with less ordered structures, including regioregular poly(3-hexylthiophene) and thiophene-based polymers with oligoether side chains, an increase in out-of-plane thermal conductivity is observed. To elucidate these trends, several hypotheses are examined: i) enhanced intrinsic thermal anisotropy originating from backbone orientation, ii) variations in the crystalline to amorphous fraction, and (iii) alloying effects resulting from dopant incorporation. Grazing incidence wide-angle X-ray scattering reveals that in-plane alignment exerts a direct influence on both in-plane and out-of-plane thermal conductivities. Photooxidation experiments provide further insights into the role of alloy scattering. Ultimately, the in-plane thermoelectric figure of merit is ascertained for two diketopyrrolopyrrole-based polymers, underscoring the critical importance of measuring thermal and electrical properties in the same orientation to ensure precise thermoelectric evaluation.
electrical doping
semiconducting polymers
thermal transport
anisotropy
organic thermoelectrics
Author
Jiali Guo
Spanish National Research Council (CSIC)
Kai Xu
Spanish National Research Council (CSIC)
Jesika Asatryan
University of A Coruña
Matías J. Alonso-Navarro
Rey Juan Carlos University (URJC)
Complutense University
Osnat Zapata-Arteaga
King Abdullah University of Science and Technology (KAUST)
Mariavittoria Craighero
Chalmers, Chemistry and Chemical Engineering, Applied Chemistry
Aleksandr Perevedentsev
Spanish National Research Council (CSIC)
Renee Kroon
Linköping University
Chalmers, Chemistry and Chemical Engineering, Applied Chemistry
María Mar Ramos
Rey Juan Carlos University (URJC)
José L. Segura
Complutense University
Jaime Martín
University of A Coruña
Christian Müller
Chalmers, Chemistry and Chemical Engineering, Applied Chemistry
Juan Sebastián Reparaz
Spanish National Research Council (CSIC)
M. Campoy-Quiles
Spanish National Research Council (CSIC)
Advanced Functional Materials
1616-301X (ISSN) 16163028 (eISSN)
Vol. In PressHybrid and Organic Thermoelectric Systems (HORATES)
European Commission (EC) (EC/H2020/955837), 2021-03-01 -- 2025-02-28.
Subject Categories (SSIF 2025)
Polymer Chemistry
Condensed Matter Physics
Physical Chemistry
DOI
10.1002/adfm.202510822