Balancing Solvent Polarity and Drying‐Kinetics for Processing Non‐Fullerene Acceptors towards High Performance Organic Solar Cells

In recent years, the emergence of high‐efficiency non‐fullerene acceptors (NFAs) has pushed the power conversion efficiency (PCE) beyond 19% in organic solar cells (OSCs). For solution processing of the photoactive layers, the study of solvent properties on device performance has become a hot research topic towards up‐scaling. Here, we reveal the key roles of balancing solvent polarity and drying kinetics for processing of small molecular NFAs towards high performance organic solar cells. We demonstrate that the synergistic effect of solvent polarity and drying kinetics significantly affects the multi‐length scale morphology of solid films and photovoltaic performance. Furthermore, the self‐assembly of NFAs in solution and the resulting thin film microstructures induced by electrostatic interactions with polarized additives are even more sensitive to the solvent polarity and drying kinetics. Finally, the optimized devices achieve an outstanding PCE of 18.54% by fine tuning the microstructure with polar solvent and fast drying kinetics to form improved molecular packing and structure size. Our work provides a novel view and deeper insights into the general selection rules of solvents towards solution processing of high‐performance non‐fullerene organic solar cells.This article is protected by copyright. All rights reserved.