Role of intermolecular charge delocalization on electron transport in fullerene aggregates

Electron transfer in fullerene aggregates plays a key role in organic solar cells and organic transistors. Electron transfer overcoming a potential barrier is proposed to occur during the charge separation in organic solar cells. We analyze the electron transfers in C-60 aggregates using quantum dynamics calculations based on a first-principles parameterization, where the transfer integral and the vibronic coupling of C-60 aggregates are determined using density functional theory. We particularly focus on the role of intermolecular charge delocalization on the electron transfer from lower-to higher-potential sites. The quantum coherence between coupled C-60 molecules stabilizes the polaron delocalized over several molecules, in conjunction with the relaxation of the intermolecular coordinates, thereby facilitating electron transport ascending the potential.