title: The separation of vibrational coherence from ground- and excited-electronic states in P3HT film.
abstract: Concurrence of the vibrational coherence and ultrafast electron transfer has been observed in polymer/fullerene blends. However, it is difficult to experimentally investigate the role that the excited-state vibrational coherence plays during the electron transfer process since vibrational coherence from the ground- and excited-electronic states is usually temporally and spectrally overlapped. Here, we performed 2-dimensional electronic spectroscopy (2D ES) measurements on poly(3-hexylthiophene) (P3HT) films. By Fourier transforming the whole 2D ES datasets (S(λ1,T̃2,λ3)) along the population time (T̃2) axis, we develop and propose a protocol capable of separating vibrational coherence from the ground- and excited-electronic states in 3D rephasing and nonrephasing beating maps (S(λ1,ν̃2,λ3)). We found that the vibrational coherence from pure excited electronic states appears at positive frequency (+ν̃2) in the rephasing beating map and at negative frequency (-ν̃2) in the nonrephasing beating map. Furthermore, we also found that vibrational coherence from excited electronic state had a long dephasing time of 244 fs. The long-lived excited-state vibrational coherence indicates that coherence may be involved in the electron transfer process. Our findings not only shed light on the mechanism of ultrafast electron transfer in organic photovoltaics but also are beneficial for the study of the coherence effect on photoexcited dynamics in other systems.
authors.affiliation: Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6, Canada.
authors.forename: Yin
authors.initials: Y
authors.lastname: Song
authors.affiliation: Department of Materials and Centre for Plastic Electronics, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom.
authors.forename: Christoph
authors.initials: C
authors.lastname: Hellmann
authors.affiliation: Department of Materials and Centre for Plastic Electronics, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom.
authors.forename: Natalie
authors.initials: N
authors.lastname: Stingelin
authors.affiliation: Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6, Canada.
authors.forename: Gregory D
authors.initials: GD
authors.lastname: Scholes