Understanding the kinetics and energetics of interfacial electron transfer in molecular systems is crucial for the development of a broad array of technologies, including photovoltaics, solar fuel systems and energy storage. The Marcus formulation for electron transfer relates the thermodynamic driving force and reorganization energy for charge transfer between a given donor/acceptor pair to the kinetics and yield of electron transfer. Here we investigated the influence of the thermodynamic driving force for photoinduced electron transfer (PET) between single-walled carbon nanotubes (SWCNTs) and fullerene derivatives by employing time-resolved microwave conductivity as a sensitive probe of interfacial exciton dissociation. For the first time, we observed the Marcus inverted region (in which driving force exceeds reorganization energy) and quantified the reorganization energy for PET for a model SWCNT/acceptor system. The small reorganization energies (about 130 meV, most of which probably arises from the fullerene acceptors) are beneficial in minimizing energy loss in photoconversion schemes.
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We especially thank N. Kopidakis and R. Larsen for helpful discussions. R.I., K.S.M., A.J.F, G.R. and J.L.B. were funded by the Solar Photochemistry Program, Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences, US Department of Energy (Grant DE-AC3608GO28308). T.T.C., B.W.L., O.V.B. and S.H.S. acknowledge funding from the National Science Foundation (Grants CHE-1012468 and CHE-1362302).
The authors declare no competing financial interests.
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Ihly, R., Mistry, K., Ferguson, A. et al. Tuning the driving force for exciton dissociation in single-walled carbon nanotube heterojunctions. Nature Chem 8, 603–609 (2016). https://doi.org/10.1038/nchem.2496
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