On the role of driving force in molecular photocells

Exciton diffusion in organic solar cells constitutes a major issue for the next generation of photovoltaic devices, where the competition between driving force and Coulomb attraction constitutes a decisive issue. In this article, such diffusion is investigated by means of a two-dimensional lattice with impurities, originated from an electron-hole attractive Hubbard model. Calculations of the quantum efficiency were carried out by using an effective channel method combined with a real-space renormalization one in order to address conducting leads in molecular photocells. The results show a splitting of the exciton band confirmed by analytical solutions, which leads to an enhanced total quantum efficiency and a shift of its maximum into the strong attractive interaction region when the driving force increases.