This talk is concerned with a novel approach in the context of material design for (organic) photovoltaics. We consider a quantum-mechanical model for a prescribed distribution of positive charges (atomic cores) and a corresponding set of orbitals describing the negative charges (electrons). In the ground state, all orbitals up to HOMO are occupied and all higher orbitals starting from LUMO are unoccupied. By a light-induced excitation, the electronic system may end up in the first excited state where HOMO is unoccupied but LUMO is occupied. Our aim is to maximize this light-induced spatial charge transfer from HOMO to LUMO as a function of the underlying nuclear charge distribution. Concerning optimal charge transfer, we will review a general existence proof for the corresponding mathematical optimization problem. Numerical simulations are carried out for a 1D chain of atoms and illustrate the applicability of this approach. This work is part of a joint project with Gero Friesecke.