1. On the Origin of Seebeck Coefficient Inversion in Highly Doped Conducting Polymers
- Author
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Kai Xu, Tero‐Petri Ruoko, Morteza Shokrani, Dorothea Scheunemann, Hassan Abdalla, Hengda Sun, Chi‐Yuan Yang, Yuttapoom Puttisong, Nagesh B. Kolhe, José Silvestre Mendoza Figueroa, Jonas O. Pedersen, Thomas Ederth, Weimin M. Chen, Magnus Berggren, Samson A. Jenekhe, Daniele Fazzi, Martijn Kemerink, Simone Fabiano, Tampere University, Materials Science and Environmental Engineering, Xu K, Ruoko TP, Shokrani M, Scheunemann D, Abdalla H, Sun HD, Yang CY, Puttisong Y, Kolhe NB, Figueroa JSM, Pedersen JO, Ederth T, Chen WM, Berggren M, Jenekhe SA, Fazzi D, Kemerink M, and Fabiano S
- Subjects
218 Environmental engineering ,Seebeck coefficient ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,thermoelectric application ,Biomaterials ,Condensed Matter::Materials Science ,organic electrochemical transistor ,216 Materials engineering ,Condensed Matter::Superconductivity ,Electrochemistry ,thermoelectric, DFT, spectroscopy, electrochemistry, spin, polarons ,conducting polymers ,Den kondenserade materiens fysik - 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. Funding Agencies|Swedish Research CouncilSwedish Research CouncilEuropean Commission [2020-03243]; Olle Engkvists Stiftelse [204-0256]; European CommissionEuropean CommissionEuropean Commission Joint Research Centre [GA-955837, GA-799477]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [SFO-Mat-LiU 2009-00971]; Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germanys Excellence Strategy via the Excellence Cluster 3D Matter Made to OrderGerman Research Foundation (DFG) [EXC-2082/1-390761711]; Carl Zeiss Foundation; Deutsche ForschungsgemeinschaftGerman Research Foundation (DFG) [FA 1502/1-1]; National Natural Science Foundation of ChinaNational Natural Science Foundation of China (NSFC) [52173156]; Swedish Foundation for Strategic ResearchSwedish Foundation for Strategic Research [ITM17-0316]
- Published
- 2022