- Maria A. Izquierdo, Zernike Institute for Advanced Materials, University of Groningen, the Netherlands
Organic photovoltaics (OPVs), unlike inorganic ones, lead to an exciton or bound electron-hole pair after absorption of a photon. The generation of free charges then depends on the exciton binding energy and the absorption properties of the materials used. In the modelling of more efficient OPVs, we have combined a conjugated polymer with a fullerene derivative in bulk heterojunction architectures .In such architectures, the excitons formed on the absorber polymer are separated through electron transfer process that lead to charge transfer (CT) states at the interface of the polymer and fullerene based molecule. We have computed the energies of the CT and fully charge separated (CS) states in bulk heterojunctions by using Density Functional Theory and its Time Dependent extension, coupled with the Discrete Reaction Field method as implemented in the Amsterdam Density Functional modeling suite. Our preliminary results are in line with experimental ones; especially good agreement in terms of the CT state energies has been found. Our results also indicate that the environment stabilizes the CS states. Further computations of the electron transfer rates and potential energy surfaces are intended.