Multiple exciton generation (MEG) in quantum dots (QDs) has the potential to greatly increase the power conversion efficiency in solar cells and in solar-fuel production. During the MEG process, two electron–hole pairs (excitons) are created from the absorption of one high-energy photon, bypassing hot-carrier cooling via phonon emission. Here we demonstrate that extra carriers produced via MEG can be used to drive a chemical reaction with quantum efficiency above 100%. We developed a lead sulfide (PbS) QD photoelectrochemical cell that is able to drive hydrogen evolution from aqueous Na2S solution with a peak external quantum efficiency exceeding 100%. QD photoelectrodes that were measured all demonstrated MEG when the incident photon energy was larger than 2.7 times the bandgap energy. Our results demonstrate a new direction in exploring high-efficiency approaches to solar fuels.
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We would like to thank B. To and C. Xiao from NREL for the scanning electron micrographs. A. J. Nozik, J. Luther, D. Kroupa and Y. Yang are thanked for their helpful discussions. Y.Y. would like to acknowledge the support from the startup fund at New Jersey Institute of Technology. Y.Y., R.W.C., B.D.C., G.F.P., A.R.M. and M.C.B. acknowledge support from the Center for Advanced Solar Photophysics, an Energy Frontier Research Center funded by the Office of Basic Energy Sciences within the Office of Science. J.G. and J.A.T. acknowledge the solar photochemistry programme within the division of Chemical Sciences,Geosciences, and Biosciences of the Office of Basic Energy Sciences within the Office of Science. All work is supported by the Department of Energy under contract No. DE-AC36-08GO28308 to NREL.
The authors declare no competing financial interests.
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Yan, Y., Crisp, R., Gu, J. et al. Multiple exciton generation for photoelectrochemical hydrogen evolution reactions with quantum yields exceeding 100%. Nat Energy 2, 17052 (2017). https://doi.org/10.1038/nenergy.2017.52
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