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Abstract The structure and packing of organic mixed ionic–electronic conductors have an especially significant effect on transport properties. In operating devices, this structure is not fixed but is responsive to changes in electrochemical potential, ion intercalation, and solvent swelling. Toward this end, the steady‐state and transient structure of the model organic mixed conductor, poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), is characterized using multimodal time‐resolved operando techniques. Steady‐state operando X‐ray scattering reveals a doping‐induced lamellar expansion of 1.6 Å followed by 0.4 Å relaxation at high doping levels. Time‐resolved operando X‐ray scattering reveals asymmetric rates of lamellar structural change during doping and dedoping that do not directly depend on potential or charging transients. Time‐resolved spectroscopy establishes a link between structural transients and the complex kinetics of electronic charge carrier subpopulations, in particular the polaron–bipolaron equilibrium. These findings provide insight into the factors limiting the response time of organic mixed‐conductor‐based devices, and present the first real‐time observation of the structural changes during doping and dedoping of a conjugated polymer system via X‐ray scattering.
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This content will become publicly available on May 15, 2026
The Role of Dynamic Solvent Swelling in Electrochemical Doping of Semiconducting Polymers
Abstract Semiconducting polymers are of interest due to their solution processibility and broad electronic applications. Electrochemistry allows these wide bandgap semiconductors to be converted to conducting polymers by doping such polymers at various potentials. When polymers arep‐doped to improve their conductivity via electrochemical oxidation, various positively‐charged carriers are created, including polarons (singly‐charged) and bipolarons (doubly‐charged). Carrier creation is accompanied by anion intercalation from the electrolyte for charge balance, and this insertion requires ion mobility. In this work, poly(3‐hexylthiophene) (P3HT) with different regioregularities is used to understand the relationship between solvent swelling, which affects anion intercalation, and electrochemical doping. Cyclic voltammetry, optical absorption spectroscopy, and grazing incidence wide‐angle X‐ray scattering (GIWAXS) measurements are used to correlate the doping level with structural changes. In situ electrochemical quartz crystal microbalance (EQCM) measurements are used to quantify the swelling of the polymers dynamically during electrochemical cycling. Lastly, in situ conductivity measurements are done to measure the effect of swelling on the ionic and electronic conductivity. The results indicate that solvent swelling is required for bipolaron formation, and that swelling facilitates both the small structural changes need for polaron formation and the disordering required for bipolaron formation.
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- PAR ID:
- 10615911
- Publisher / Repository:
- Wiley-VCH
- Date Published:
- Journal Name:
- Advanced Materials Interfaces
- ISSN:
- 2196-7350
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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