title: Controlling charge separation and recombination by chemical design in donor-acceptor dyads.
abstract: Conjugated donor-acceptor block co-oligomers that self-organize into D-A mesomorphic arrays have raised increasing interest due to their potential applications in organic solar cells. We report here a combined experimental and computational study of charge transfer (CT) state formation and recombination in isolated donor-spacer-acceptor oligomers based on bisthiophene-fluorene (D) and perylene diimide (A), which have recently shown to self-organize to give a mesomorphic lamellar structure at room temperature. Using femtosecond transient absorption spectroscopy and Time-Dependent Density Functional Theory in combination with the Marcus-Jortner formalism, the observed increase of the CT lifetimes is rationalized in terms of a reduced electronic coupling between D and A brought about by the chemical design of the donor moiety. A marked dependence of the CT lifetime on solvent polarity is observed, underscoring the importance of electrostatic effects and those of the environment at large. The present investigation therefore calls for a more comprehensive design approach including the effects of molecular packing.
authors.affiliation: Institut de Physique et Chimie des Matériaux de Strasbourg & Labex NIE, Université de Strasbourg, CNRS UMR 7504, 23 rue du Loess, Strasbourg 67034, France. stefan.haacke@ipcms.unistra.fr.
authors.forename: Li
authors.initials: L
authors.lastname: Liu
authors.forename: Pierre
authors.initials: P
authors.lastname: Eisenbrandt
authors.forename: Thomas
authors.initials: T
authors.lastname: Roland
authors.forename: Matthias
authors.initials: M
authors.lastname: Polkehn
authors.forename: Pierre-Olivier
authors.initials: PO
authors.lastname: Schwartz
authors.forename: Kirsten
authors.initials: K
authors.lastname: Bruchlos
authors.forename: Beatrice
authors.initials: B
authors.lastname: Omiecienski
authors.forename: Sabine
authors.initials: S
authors.lastname: Ludwigs
authors.forename: Nicolas
authors.initials: N
authors.lastname: Leclerc
authors.forename: Elena
authors.initials: E
authors.lastname: Zaborova
authors.forename: Jérémie
authors.initials: J
authors.lastname: Léonard
authors.forename: Stéphane
authors.initials: S
authors.lastname: Méry
authors.forename: Irene
authors.initials: I
authors.lastname: Burghardt
authors.forename: Stefan
authors.initials: S
authors.lastname: Haacke