Thermally Induced Exciton Diffusion and Dissociation in Organic Semiconductors

By introducing the thermal effect on pi-electrons with Fermi-Dirac distribution and atomic nuclei with Boltzmann distribution, we study exciton diffusion and dissociation in an organic polymer with nonuniform temperature distribution in the framework of the tight-binding model. It is found that the thermal effect can make the electron-hole separation in an exciton, and the separation becomes apparent with increasing temperature. Especially, by applying a linear-gradient temperature distribution along the polymer, we further study the nonuniform thermal field on the exciton behaviors. We obtain that the exciton will migrate along the chain with the direction toward the high-temperature region. Based on this, we propose a physical mechanism for a built-in thermal field to assist exciton diffusion and dissociation, which provides a new tunneling to enhance the efficiency of organic solar cells.