Evidence for Photoinduced Polaron Generation in a High Persistence Length Low Bandgap Conjugated Polymer in Solution

Using ultrafast time-resolved infrared (TRIR) spectroscopy, we studied the solution-phase excited-state structural evolution of an indacenodithiophene-<i>co</i>-benzothiadiazole polymer (C8-IDTBT). Following band gap excitation, the TRIR spectra reveal vibrational features that develop within 10 ps and decay over 4 ns. Using pulse radiolysis measurements, charge-modulation spectroscopy, and quantum-chemical calculations, the IR features are assigned to polaron pairs. Interestingly, these features appear on an evolving broad mid-IR electronic absorption background, with kinetics correlating with the formation and decay of the cation-radical vibrational bands. A three-state kinetic model successfully reproduces the spectral evolution, revealing that the polaron and exciton populations exist in dynamic equilibrium on picosecond time scales, with time constants for exciton dissociation in the range of 3-5 ps and polaron-to-exciton reformation between 20 and 100 ps, while both species decay to the ground state on much slower nanosecond time scales (∼1 ns), yielding a remarkably high polaron-generation efficiency, higher than 50%. These findings provide fundamental insights into intramolecular charge photogeneration mechanisms in conjugated polymers, demonstrating efficient bound-polaron formation in isolated polymer chains.

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Publication Details

Journal
The Journal of Physical Chemistry B
Published
2026-01-30
DOI
https://doi.org/10.1021/acs.jpcb.5c07501
Primary Topic
Organic Electronics and Photovoltaics
Type
article
Field-Weighted Citation Impact
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article

Evidence for Photoinduced Polaron Generation in a High Persistence Length Low Bandgap Conjugated Polymer in Solution

Michelle S. Vezie, Garrett LeCroy, Elham Rezasoltani, Anthony W. Parker et al.
The Journal of Physical Chemistry B
Organic Electronics and Photovoltaics
article

Evidence for Photoinduced Polaron Generation in a High Persistence Length Low Bandgap Conjugated Polymer in Solution

Michelle S. Vezie, Garrett LeCroy, Elham Rezasoltani, Anthony W. Parker, Alise Virbule, Matthew J. Bird, Sophia C. Hayes, Igor V. Sazanovich, Michael Towrie, Gregory M. Greetham, Alberto Salleo, Jarvist M. Frost, Mohammed Azzouzi, Jack F. Coker, Jenny Nelson, Hugo Bronstein, Despoina Heracleous
article en

Abstract

Using ultrafast time-resolved infrared (TRIR) spectroscopy, we studied the solution-phase excited-state structural evolution of an indacenodithiophene-<i>co</i>-benzothiadiazole polymer (C8-IDTBT). Following band gap excitation, the TRIR spectra reveal vibrational features that develop within 10 ps and decay over 4 ns. Using pulse radiolysis measurements, charge-modulation spectroscopy, and quantum-chemical calculations, the IR features are assigned to polaron pairs. Interestingly, these features appear on an evolving broad mid-IR electronic absorption background, with kinetics correlating with the formation and decay of the cation-radical vibrational bands. A three-state kinetic model successfully reproduces the spectral evolution, revealing that the polaron and exciton populations exist in dynamic equilibrium on picosecond time scales, with time constants for exciton dissociation in the range of 3-5 ps and polaron-to-exciton reformation between 20 and 100 ps, while both species decay to the ground state on much slower nanosecond time scales (∼1 ns), yielding a remarkably high polaron-generation efficiency, higher than 50%. These findings provide fundamental insights into intramolecular charge photogeneration mechanisms in conjugated polymers, demonstrating efficient bound-polaron formation in isolated polymer chains.

The Journal of Physical Chemistry BVol. 130(6)
École Polytechnique (FR), Queen Mary University of London (GB), Brookhaven National Laboratory (US), University of Cambridge (GB), University of Cyprus (CY), Research Complex at Harwell (GB), Division of Chemistry (US), Computational Physics (United States) (US), Universitas Islam Syekh Yusuf (ID), Imperial College London (GB), École Polytechnique Fédérale de Lausanne (CH), Stanford University (US)
Openalex Percentile: Top 71%
Organic Electronics and Photovoltaics
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