Over 19% Efficiency Organic Solar Cells by Regulating Multidimensional Intermolecular Interactions.

Research on organic solar cells (OSCs) has progressed through material innovation and device engineering. However, well-known and ubiquitous intermolecular interactions, and particularly their synergistic effects, have received little attention. Herein, we investigate the complicated relationship between photovoltaic conversion and multidimensional intermolecular interactions in the active layers. These interactions are dually regulated by side-chain isomerization and end-cap engineering of the acceptors. The phenylalkyl featured acceptors (LA-series) exhibited stronger crystallinity with preferential face-on interactions relative to the alkylphenyl attached isomers (ITIC-series). In addition, the PM6 and LA-series acceptors exhibited moderate donor/acceptor (D/A) interactions compared to those of the strongly interacting PM6/ITIC-series pairs, which helped to enhance phase separation and charge transport. Consequently, the output efficiencies of all LA series acceptors were over 14%. Moreover, LA-series acceptors showed appropriate compatibility, host/guest interactions, and crystallinity relationships with BTP-eC9, thereby leading to uniform and well-organized "alloy-like" mixed phases. In particular, the highly crystalline LA23 further optimized multiple interactions and ternary microstructures, which resulted in a high efficiency of 19.12%. Thus, these results highlight the importance of multidimensional intermolecular interactions in the photovoltaic performance of OSCs. This article is protected by copyright. All rights reserved.