How charge trapping affects the conductivity of electrochemically doped poly(3-hexylthiophene) films
- 18 October 2021
- journal article
- research article
- Published by AIP Publishing in Applied Physics Letters
- Vol. 119 (16), 163301
- https://doi.org/10.1063/5.0056484
Abstract
Electrochemical doping is an elegant method of controlling the doping level and charge carrier densities of conjugated polymer films and enhancing their thermoelectric figure of merit. Applying this doping technique to films of poly(3-hexylthiophene) (P3HT) results in conductivities with values as high as 200 S/cm. The stability of the doped films in the solid state can be probed by UV-vis-NIR spectroscopy. We found that the choice of the conducting salt in the liquid electrolyte exerts a strong influence over the conductivity. Using TBAPF6 and LiClO4 provides highest conductivities for P3HT films, while LiTFSI and TBABF4 show overall lower performance. This effect is also reflected in cyclic voltammetry measurements coupled with in situ spectroscopy. Overall lower reversibility upon multiplex cycling in LiTFSI and TBABF4 electrolytes suggests strong charge trapping effects, which one might attribute to a considerable fraction of charges (holes/ions) remaining in the films after charge/discharge cycles. The salts with stronger charge irreversibility in the electrochemistry experiments show the poorer solid state conductivities. Our conclusion is that one should carefully choose the electrolyte to ensure good percolation pathways and delocalized charge transport throughout doped films.Keywords
Funding Information
- Carl Zeiss Foundation (IQST)
- Natural Sciences and Engineering Research Council of Canada (RGPIN-2015-05981)
- Natural Sciences and Engineering Research Council of Canada (Green Electronics)
- Deutsche Forschungsgemeinschaft (project 358283783 (CRC1333))
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