(Invited) Charge Carrier Generation and Transport in Semiconducting Polymer Blends Exposed to Electrochemical Environments

• Published in: Meeting abstracts (Electrochemical Society) Vol. MA2025-01; no. 33; p. 1633
• Main Authors: Ferguson, Andrew J, Kopcha, William, Mohapatra, Aiswarya Abhisek, Li, Shuya, Carr, Joshua, Rumbles, Garry, Miller-Link, Elisa, Greenaway, Ann L, Gish, Melissa, Reid, Obadiah
• Format: Journal Article
• Language: English
• Published: The Electrochemical Society, Inc 11.07.2025
• DOI: 10.1149/MA2025-01331633mtgabs
• ISSN: 2151-2043

Invited Presentation: Pi-conjugated semiconducting polymers have garnered attention for a variety of electronic and optoelectronic applications, such as field-effect transistors, thermoelectric generators, and photovoltaic devices. In these systems, the charge carrier dynamics are primarily governed by the properties of the polaron and the polymer microstructure. More recently, there has been growing interest in the suitability of these polymer for electrochemical transistors and (photo)electrochemical applications, where the understanding is further complicated by the presence of ions and solvent molecules, as well as the dynamic transport of these species into, and out of, the semiconducting polymer. Here, we use employ steady-state and transient spectroscopic techniques to probe charge carrier generation, transport, and recombination processes in electrochemical environments in an all-polymer blend of PTB7-Th and P(NDI2OD-T2). We demonstrate that the intrinsic carrier lifetime is short in a ‘dry’ PTB7-Th:P(NDI2OD-T2) blend, but the presence of electrolyte salts, and even water, results in a slight increase in the carrier yield, lifetime and mobility, despite minimal water uptake. These observations point to stabilization of the separated charge carriers by a combination of coulomb interactions with polar molecules/counterions and an increase in the dielectric constant. The carrier lifetime can be further enhanced by overcoating the blend with a NDI-T2 polymer appended with glycolated side chains to enhance the hydrophilicity and increase water/ion uptake. Incorporation of electrochemical techniques enables in-situ spectroscopic measurements that mimic operando conditions, allowing exploration of the carrier photophysics under application of a bias. Our observations will provide a better understanding of the factors that control the carrier dynamics in these compositionally complex systems and will have implications for their viability and optimization for (photo)electrochemical applications. PTB7-Th = poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b']dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl] P(NDI2OD-T2) = N2200 = poly{[N,N'-bis(2-octyldodecyl)naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)}