title: Directional charge separation in isolated organic semiconductor crystalline nanowires.
abstract: One of the fundamental design paradigms in organic photovoltaic device engineering is based on the idea that charge separation is an extrinsically driven process requiring an interface for exciton fission. This idea has driven an enormous materials science engineering effort focused on construction of domain sizes commensurate with a nominal exciton diffusion length of order 10 nm. Here, we show that polarized optical excitation of isolated pristine crystalline nanowires of a small molecule n-type organic semiconductor, 7,8,15,16-tetraazaterrylene, generates a significant population of charge-separated polaron pairs along the π-stacking direction. Charge separation was signalled by pronounced power-law photoluminescence decay polarized along the same axis. In the transverse direction, we observed exponential decay associated with excitons localized on individual monomers. We propose that this effect derives from an intrinsic directional charge-transfer interaction that can ultimately be programmed by molecular packing geometry.
authors.affiliation: Department of Chemistry, University of Massachusetts, Amherst Massachusetts 01003, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Labastide
authors.affiliation: Department of Chemistry, University of Massachusetts, Amherst Massachusetts 01003, USA.
authors.forename: H B
authors.initials: HB
authors.lastname: Thompson
authors.affiliation: Department of Chemistry, University of Massachusetts, Amherst Massachusetts 01003, USA.
authors.forename: S R
authors.initials: SR
authors.lastname: Marques
authors.affiliation: Department of Polymer Science and Engineering, University of Massachusetts, Amherst Massachusetts 01003, USA.
authors.forename: N S
authors.initials: NS
authors.lastname: Colella
authors.affiliation: Department of Polymer Science and Engineering, University of Massachusetts, Amherst Massachusetts 01003, USA.
authors.forename: A L
authors.initials: AL
authors.lastname: Briseno
authors.affiliation: Department of Chemistry, University of Massachusetts, Amherst Massachusetts 01003, USA.|Department of Physics, University of Massachusetts, Amherst Massachusetts 01003, USA.
authors.forename: M D
authors.initials: MD
authors.lastname: Barnes