Modeling the electronic and optical processes in organic solar cells: Density functional theory and beyond

We describe some of the computational methodologies that are being used in our research group to develop a better understanding of the geometric and electronic structure at the organic-organic interfaces present in the active layer. We focus, in particular, on the nature of the excitons that are formed upon photoexcitation of small-gap conjugated polymers and on the exciton-dissociation and charge-transfer processes at donor-acceptor interfaces. The local morphology at the pentacene-C₆₀ interface is discussed on the basis of molecular dynamics simulations.