Effects of Counter-Ion Size on Delocalization of Carriers and Stability of Doped Semiconducting Polymers

TitleEffects of Counter-Ion Size on Delocalization of Carriers and Stability of Doped Semiconducting Polymers
Publication TypeJournal Article
Year of Publication2020
AuthorsThomas, Elayne M., Kelly A. Peterson, Alex H. Balzer, Dakota Rawlings, Natalie Stingelin, Rachel A. Segalman, and Michael L. Chabinyc
JournalAdvanced Electronic Materials
Abstract

Since doped polymers require a charge‐neutralizing counter‐ion to maintain charge neutrality, tailored and high degrees of doping in organic semiconductors requires an understanding of the coupling between ionic and electronic carrier motion. A method of counter‐ion exchange is utilized using the polymeric semiconductor poly[2,5‐bis(3‐tetradecylthiophen‐2‐yl)thieno[3,2‐b]thiophene] ‐C14 to deconvolute the effects of ionic/polaronic interactions with the electrical properties of doped semiconducting polymers. In particular, exchanging the counter‐ions of the dopant nitrosonium hexafluorophosphate enables investigation into the role of counter‐ion size from 5.2 to 8.2 Å in diameter. The orientational order of the polymeric crystallites is not affected with this exchange process while effectively modifying the counter‐ion distance to the charge carrier. Doped films have electrical conductivities of 320 S cm−1 and are not sensitive to an increased ion‐polaron distance. It is posited that other factors dominate the electrical properties at a device scale, such as the morphology and presence of domain boundaries. Interestingly, the temperature stability of the doped film can be drastically improved with the use of counter‐ions containing less labile bonds. This platform serves as a unique way to retain the morphology of polymeric thin films while studying charge interactions at the local scale.

URLhttps://doi.org/10.1002/aelm.202000595
DOI10.1002/aelm.202000595