Molecular Stacking Regulation of Organic Semiconductors Via Intermolecular Interaction Enables High‐Performance Organic Solar Cells

Abstract The ordered π ‐stacking with face‐on orientation and uniform phase separation in active layer is essential to develop high‐performance organic solar cells (OSCs). Differing from phase separation optimization, it is challenging to regulate the molecular stacking of organic semiconductors during the film‐formation process. In this contribution, a universal strategy is established to simultaneously optimize the π ‐stacking and aggregation of organic semiconductors via intermolecular interaction with solid additive. It is demonstrated that the strong intermolecular interaction between solid additive and organic semiconductors is a critical factor in molecular stacking regulation. Benefitting from the more ordered molecular stacking of active layer aroused by the additive treatment, significantly improved photovoltaic performance can be realized in OSCs. Particularly, an outstanding power‐conversion efficiency (PCE) of 20.04% is achieved in the D18:N3:AQx‐2F‐based device treated by thioxanthene, while the control device without additive treatment yields a much lower PCE of 19.00%.