Separation of geminate electron-hole pairs at donor-acceptor interfaces in the approximation of prescribed diffusion

Highlights: • Motion of an electron and hole at a D-A interface is considered in the diffusion model. • Smoluchowski equation is solved in the prescribed diffusion approximation. • Time-dependent survival probability of the electron-hole pair is found. • Separation probability is obtained as a function of the initial intrapair separation. - Abstract: It is generally believed that electrons and holes in organic solar cells are generated by dissociation of excitons at the interface between donor and acceptor materials in the form of geminate, coulombically bound electron-hole pairs. The further motions of electrons and holes are restricted to the acceptor material and donor material, respectively. Using the method of prescribed diffusion, we solve the Smoluchowski equation describing evolution of the spatial distribution of electrons and holes. The separation probability of electron-hole pairs is found as a function of an initial intrapair separation and external electric field.