| Institution: | 1. Energy Frontier Research Center, Columbia University, New York, NY 10027;2. Department of Physics, Faculty of Mathematics and Physics, University of Ljubljana, Slovenia;3. Laboratorio TASC/IOM‐CNR, Area di ricerca, Trieste, Italy;4. Centro S3, CNR‐Istituto Nanoscienze, I‐41125 Modena, Italy;5. Department of Physics, University of Trieste, I‐34123 Trieste, Italy, Laboratorio TASC/IOM‐CNR, Area di ricerca, Trieste, Italy;6. Department of Chemistry, Columbia University, New York, NY 10027;7. Department of Electrical Engineering, Columbia University, New York, NY 10027;8. Polymers Division, National Institute of Standards and Technology, Gaithersburg, MD 20899 |
| Abstract: | While the demonstrated power conversion efficiency of organic photovoltaics (OPVs) now exceeds 10%, new design rules are required to tailor interfaces at the molecular level for optimal exciton dissociation and charge transport in higher efficiency devices. We show that molecular shape‐complementarity between donors and acceptors can drive performance in OPV devices. Using core hole clock (CHC) X‐ray spectroscopy and density functional theory (DFT), we compare the electronic coupling, assembly, and charge transfer rates at the interface between C60 acceptors and flat‐ or contorted‐hexabenzocorone (HBC) donors. The HBC donors have similar optoelectronic properties but differ in molecular contortion and shape matching to the fullerene acceptors. We show that shape‐complementarity drives self‐assembly of an intermixed morphology with a donor/acceptor (D/A) ball‐and‐socket interface, which enables faster electron transfer from HBC to C60. The supramolecular assembly and faster electron transfer rates in the shape complementary heterojunction lead to a larger active volume and enhanced exciton dissociation rate. This work provides fundamental mechanistic insights on the improved efficiency of organic photovoltaic devices that incorporate these concave/convex D/A materials. |
