Origin of Different Photovoltaic Activities in Regioisomeric Small Organic Molecule Solar Cells: The Intrinsic Role of Charge Transfer Processes

Regioisomeric small organic molecules are recently reported to show remarkable difference in their photovoltaic activities when blended with suitable donor/acceptor counterpart. The structural difference as a result of positional diversity of the foreign substituent leads to different intermolecular interactions and dipolar orientations, and thus they acquire different morphologies. This severely influences the local transport and carrier recombination, leading to different photovoltaic power conversion efficiencies. However, the molecular level understanding relating to the carrier transfer and the associated dynamical properties remains unexplored, which could focus on the rational description of such phenomena. Herein, we apply the Marcus theory of electron transfer rates on some experimentally realized and model composite systems consisting regioisomeric molecules, which provides a general understanding of such intrinsic dynamical behavior, the precise control of which could offer better photovoltaic materials.