First-principles studies of single-molecule photovoltaics

A standard pathway for sunlight to fuel conversion involves using solar photons to generate charge carriers (via the photovoltaic effect) that may then be used to drive a chemical reaction at the electrodes and generate fuel. Organic photovoltaics are promising inexpensive, lightweight alternatives to conventional solar cells. However, many of the physical processes responsible for their poor efficiencies are not well understood. Here, using first-principles calculations based on density functional theory, including the GW self-energy we examine the relationship between molecular structure and electronic level alignment at a covalent donor-acceptor interface. We compute the excitonic states of covalently-joined small molecule donor and acceptor constituents, using the Bethe-Salpeter equation. Importantly these systems use molecular fragments and combinations that should be realizable synthetically and results should be testable experimentally. Work supported in part by the DOE Helios SERC. Computational provided by NERSC.