title: Electronic correlations in oligo-acene and -thiopene organic molecular crystals.
abstract: From first-principles calculations we determine the Coulomb interaction between two holes on oligo-acene and -thiophene molecules in a crystal, as a function of the oligomer length. The electronic polarization of the molecules that surround the charged oligomer reduces the bare Coulomb repulsion between the holes by approximately a factor of 2. The effects of relaxing the molecular geometry in the presence of holes is found to be significantly smaller. In all cases the effective hole-hole repulsion is much larger than the valence bandwidth, which implies that at high doping levels the properties of these organic semiconductors are determined by electron-electron correlations.
authors.affiliation: Faculty of Science and Technology and MESA+ Research Institute, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands.
authors.forename: Geert
authors.initials: G
authors.lastname: Brocks
authors.forename: Jeroen
authors.initials: J
authors.lastname: van den Brink
authors.forename: Alberto F
authors.initials: AF
authors.lastname: Morpurgo