Many semiconductor devices (e.g., light emitting diodes and photovoltaics) utilize heterojunctions of doped and undoped layers or depend on gradients of electronic doping to control charge transport. Understanding of the formation and stability of gradients in doping requires an understanding of diffusion of dopants and the complex changes in polymer properties that arise during doping. Conjugated polymers can be electrically doped by strong acids, but the details of the reaction mechanism and subsequent stability are not understood. Here, we show a clear kinetic isotope effect in the doping of thin films of poly(3-hexylthiophene) (P3HT) by bis(trifluoromethane)sulfonimide (HTFSI) from solution indicating that this doping process is limited by proton transfer to the polymer. Complementary X-ray photoelectron spectroscopy and dynamic secondary ion mass spectrometry (DSIMS) depth profiling of dopant concentrations show definitive evidence of dopant enrichment at the P3HT surface. These surface-limited concentration profiles suggest that diffusivity of dopants vary inversely with dopant concentration due to doping-induced changes to the structure of the conjugated polymer.
Nguyen, Phong H., Schmithorst, Michael B., Mates, Thomas E., Segalman, Rachel A., & Chabinyc, Michael L. (2023). Diffusion of Brønsted acidic dopants in conjugated polymers. Journal of Materials Chemistry C, 11(22). https://doi.org/10.1039/d3tc00415e
Nguyen, Phong H., Schmithorst, Michael B., Mates, Thomas E., et al., "Diffusion of Brønsted acidic dopants in conjugated polymers," Journal of Materials Chemistry C 11, no. 22 (2023), https://doi.org/10.1039/d3tc00415e
@article{osti_2423898,
author = {Nguyen, Phong H. and Schmithorst, Michael B. and Mates, Thomas E. and Segalman, Rachel A. and Chabinyc, Michael L.},
title = {Diffusion of Brønsted acidic dopants in conjugated polymers},
annote = {Many semiconductor devices (e.g., light emitting diodes and photovoltaics) utilize heterojunctions of doped and undoped layers or depend on gradients of electronic doping to control charge transport. Understanding of the formation and stability of gradients in doping requires an understanding of diffusion of dopants and the complex changes in polymer properties that arise during doping. Conjugated polymers can be electrically doped by strong acids, but the details of the reaction mechanism and subsequent stability are not understood. Here, we show a clear kinetic isotope effect in the doping of thin films of poly(3-hexylthiophene) (P3HT) by bis(trifluoromethane)sulfonimide (HTFSI) from solution indicating that this doping process is limited by proton transfer to the polymer. Complementary X-ray photoelectron spectroscopy and dynamic secondary ion mass spectrometry (DSIMS) depth profiling of dopant concentrations show definitive evidence of dopant enrichment at the P3HT surface. These surface-limited concentration profiles suggest that diffusivity of dopants vary inversely with dopant concentration due to doping-induced changes to the structure of the conjugated polymer.},
doi = {10.1039/d3tc00415e},
url = {https://www.osti.gov/biblio/2423898},
journal = {Journal of Materials Chemistry C},
issn = {ISSN 2050-7526},
number = {22},
volume = {11},
place = {United States},
publisher = {Royal Society of Chemistry},
year = {2023},
month = {05}}