Thumbnail image of graphical abstract

Organic photovoltaic devices, schematically shown in the bottom left of the cover image, are gaining popularity as alternatives to more expensive inorganic photovoltaics. The active layers in these cells are most commonly composed of a polymer (donor) and fullerene (acceptor) blend. The work by Christopher Arntsen, Randa Reslan, Samuel Hernandez, Yi Gao, and Daniel Neuhauser on page 1885 presents a simple method for efficiently calculating electron transfer in large molecules and applies it to various fullerene derivatives, which are the most popular electron acceptors in organic photovoltaic devices. PCBM, shown in the top right of the image, represents one of the most notable examples of this class of molecules.