title: Ultrafast decoherence dynamics govern photocarrier generation efficiencies in polymer solar cells.
abstract: All-organic-based photovoltaic solar cells have attracted considerable attention because of their low-cost processing and short energy payback time. In such systems the primary dissociation of an optical excitation into a pair of photocarriers has been recently shown to be extremely rapid and efficient, but the physical reason for this remains unclear. Here, two-dimensional photocurrent excitation spectroscopy, a novel non-linear optical spectroscopy, is used to probe the ultrafast coherent decay of photoexcitations into charge-producing states in a polymer:fullerene based solar cell. The two-dimensional photocurrent spectra are interpreted by introducing a theoretical model for the description of the coupling of the electronic states of the system to an external environment and to the applied laser fields. The experimental data show no cross-peaks in the twodimensional photocurrent spectra, as predicted by the model for coherence times between the exciton and the photocurrent producing states of 20 fs or less.
authors.affiliation: Department of Physics and Regroupement québécois sur les matériaux de pointe, Université de Montréal, C.P. 6128, Succursale centre-ville, Montréal H3C 3J7, Canada.
authors.forename: Eleonora
authors.initials: E
authors.lastname: Vella
authors.affiliation: Department of Chemistry, University of Houston, Houston, Texas 77204, USA.
authors.forename: Hao
authors.initials: H
authors.lastname: Li
authors.affiliation: Department of Physics and Regroupement québécois sur les matériaux de pointe, Université de Montréal, C.P. 6128, Succursale centre-ville, Montréal H3C 3J7, Canada.
authors.forename: Pascal
authors.initials: P
authors.lastname: Grégoire
authors.affiliation: Department of Physics, Blackett Laboratory, Imperial College London, London SW7 2AZ, United Kingdom.
authors.forename: Sachetan M
authors.initials: SM
authors.lastname: Tuladhar
authors.affiliation: Department of Physics, Blackett Laboratory, Imperial College London, London SW7 2AZ, United Kingdom.
authors.forename: Michelle S
authors.initials: MS
authors.lastname: Vezie
authors.affiliation: Department of Physics, Blackett Laboratory, Imperial College London, London SW7 2AZ, United Kingdom.
authors.forename: Sheridan
authors.initials: S
authors.lastname: Few
authors.affiliation: Department of Physics and Regroupement québécois sur les matériaux de pointe, Université de Montréal, C.P. 6128, Succursale centre-ville, Montréal H3C 3J7, Canada.
authors.forename: Claudia M
authors.initials: CM
authors.lastname: Bazán
authors.affiliation: Department of Physics, Blackett Laboratory, Imperial College London, London SW7 2AZ, United Kingdom.
authors.forename: Jenny
authors.initials: J
authors.lastname: Nelson
authors.affiliation: Department of Physics and Regroupement québécois sur les matériaux de pointe, Université de Montréal, C.P. 6128, Succursale centre-ville, Montréal H3C 3J7, Canada.|Department of Physics, Blackett Laboratory, Imperial College London, London SW7 2AZ, United Kingdom.
authors.forename: Carlos
authors.initials: C
authors.lastname: Silva-Acuña
authors.affiliation: Department of Physics and Regroupement québécois sur les matériaux de pointe, Université de Montréal, C.P. 6128, Succursale centre-ville, Montréal H3C 3J7, Canada.|Department of Chemistry, University of Houston, Houston, Texas 77204, USA.
authors.forename: Eric R
authors.initials: ER
authors.lastname: Bittner