title: Theory and simulation of organic solar cell model compounds: from atoms to excitons.
abstract: We approach the electronic properties of a simple model of organic solar cells, a binary mixture of αα'-oligothiophenes and buckminsterfullerene, from a theoretical and numerical perspective. Close-packed model geometries are generated using a Monte Carlo method, the electronic structure is described by a reparametrized semiempirical Pariser-Parr-Pople Hamiltonian. All electronic properties, such as optical absorption spectra, tightly-bound charge transfer states and exciton bands, arise from the same atomistic Hamiltonian using a configuration interaction method involving single excitations. The absorption spectra are dominated by intramolecular contributions, whereas in the optical gap low-lying charge transfer states are predicted. The efficiency of the solar cell crucially depends on the structure of the charge-transfer exciton bands and on the relaxation mechanism. We discuss how these findings may help improve the design of organic solar cells from an excitonic view.
authors.affiliation: Institut für Physikalische Chemie, Universität Freiburg, Albertstraße 23a, D-79104 Freiburg im Breisgau, Germany.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Lampe
authors.forename: Thorsten
authors.initials: T
authors.lastname: Koslowski