A theoretical investigation of the dye-redox mediator interaction in dye-sensitized photovoltaic cells

A theoretical study of the electronic properties and the reactivity toward I^-/I₃^- of some M(bpy)₂L₂ complexes (M=Ru and Os, L=CN and SCN and bpy=2,2′-bipyridine), both in the gas-phase and in aqueous solution is presented. All the calculations have been carried out using a hybrid density functional approach (PBE0) and solvent effects have been included using a polarizable continuum model (CPCM). The donor-acceptor intermolecular hardness and the electrophilicity indexes have been chosen as molecular descriptors in order to discriminate the relative reactivity of the different species in the different phases. In particular, solvation significantly affects the reactivity of the considered species.