Balancing Packing Strength of End/Central Units Enables Binary Organic Solar Cells to Achieve 20.2% Efficiency

Abstract The photodynamic processes in organic solar cells (OSCs) are largely determined by the intermolecular packing of photovoltaic materials, which makes the delicate tuning of packing characteristics through molecular structural tailoring crucially important. Herein, an asymmetric acceptor of CHFN is constructed to balance the effective packing areas or packing strength of end/central units in molecular skeletons. Compared to CH6F and CH17 with the symmetric structures, asymmetric CHFN possesses the more suitable crystallinity, superior fibrillar network morphology, and facilitated charge generation/transport in blended films, thus affording a remarkable PCE of 20.23% for CHFN‐based binary OSCs, which is one of the highest efficiencies of binary OSCs based on asymmetric acceptors. This work highlights the great significance of end/central unit packing balance in achieving highly efficient OSCs.