title: Intermolecular charge transfer between heterocyclic oligomers. Effects of heteroatom and molecular packing on hopping transport in organic semiconductors.
abstract: For electron or hole transfer between neighboring conducting polymer strands or oligomers, the intrinsic charge-transfer rate is dictated by the charge-resonance integral and by the reorganization energy due to geometric relaxation. To explain conduction anisotropy and other solid-state effects, a multivariate, systematic analysis of bandwidth as a function of intermolecular orientations is undertaken for a series of oligoheterocycles, using first-principles methods. While cofacial oligomers show the greatest bandwidths at a given intermolecular C-C contact distance, for a fixed center-to-center intermolecular distance, tilted pi-stacking increases pi-overlap (particularly for LUMO orbitals) and decreases electrostatic repulsion, yielding optimum tilt angles for packing of approximately 40-60 degrees at small intermolecular separations. The calculations also reveal that bandwidths and intrinsic mobilities of holes and electrons in conjugated oligoheterocycles can be quite comparable.
authors.affiliation: Department of Chemistry, Northwestern University, Evanston, Illinois 60208-3113, USA.
authors.forename: Geoffrey R
authors.initials: GR
authors.lastname: Hutchison
authors.forename: Mark A
authors.initials: MA
authors.lastname: Ratner
authors.forename: Tobin J
authors.initials: TJ
authors.lastname: Marks