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- Title
On the Origin of Seebeck Coefficient Inversion in Highly Doped Conducting Polymers.
- Authors
Xu, Kai; Ruoko, Tero‐Petri; Shokrani, Morteza; Scheunemann, Dorothea; Abdalla, Hassan; Sun, Hengda; Yang, Chi‐Yuan; Puttisong, Yuttapoom; Kolhe, Nagesh B.; Figueroa, José Silvestre Mendoza; Pedersen, Jonas O.; Ederth, Thomas; Chen, Weimin M.; Berggren, Magnus; Jenekhe, Samson A.; Fazzi, Daniele; Kemerink, Martijn; Fabiano, Simone
- Abstract
A common way of determining the majority charge carriers of pristine and doped semiconducting polymers is to measure the sign of the Seebeck coefficient. However, a polarity change of the Seebeck coefficient has recently been observed to occur in highly doped polymers. Here, it is shown that the Seebeck coefficient inversion is the result of the density of states filling and opening of a hard Coulomb gap around the Fermi energy at high doping levels. Electrochemical n‐doping is used to induce high carrier density (>1 charge/monomer) in the model system poly(benzimidazobenzophenanthroline) (BBL). By combining conductivity and Seebeck coefficient measurements with in situ electron paramagnetic resonance, UV–vis–NIR, Raman spectroelectrochemistry, density functional theory calculations, and kinetic Monte Carlo simulations, the formation of multiply charged species and the opening of a hard Coulomb gap in the density of states, which is responsible for the Seebeck coefficient inversion and drop in electrical conductivity, are uncovered. The findings provide a simple picture that clarifies the roles of energetic disorder and Coulomb interactions in highly doped polymers and have implications for the molecular design of next‐generation conjugated polymers.
- Subjects
SEEBECK coefficient; CONJUGATED polymers; CONDUCTING polymers; ELECTRON paramagnetic resonance; MONTE Carlo method; CARRIER density
- Publication
Advanced Functional Materials, 2022, Vol 32, Issue 20, p1
- ISSN
1616-301X
- Publication type
Article
- DOI
10.1002/adfm.202112276