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Thanks to the development of acceptor–donor–acceptor (A–D–A) type electron acceptors, organic solar cells (OSCs) have achieved marvelous progress in recent years. However, a systematic investigation about the structure–efficiency relationship is still highly desired to better understand the working mechanisms inside a bulk heterojunction (BHJ). In this study, new acceptors with the synergistic effect of side chain and unilateral π‐bridge strategy are designed, accounting for lower energy loss, expanded absorption, modulated intermolecular interactions and BHJ morphology. As a consequence, the resultant A–D–π–A acceptor ID‐C6Ph‐ST‐4F based binary solar cell receives an impressive efficiency up to 15.36%, much greater than the A–D–A analog ID‐C6Ph‐4F (10.75%), and ranks the best among all small molecular acceptors with symmetric or asymmetric π‐bridges. The results highlight the promising manipulation of phenylalkyl side chain and unilateral π‐bridge on intermolecular interactions among acceptor molecules and interactions between donor and acceptor (D/A) molecules. Superior interactions among acceptor molecules are an essential precondition to ensure preferable molecular assembly for charge transport, and meanwhile, moderately enhanced D/A interactions are also crucial for proper phase‐separation networks with efficient exciton dissociation and charge generation. [ABSTRACT FROM AUTHOR]

Promoted by uninterrupted materials and device innovation, organic solar cells have achieved impressive development. However, the complicated intermolecular interactions inside active layers are less understood. Herein, the intermolecular interactions are studied from the dual perspectives of acceptor/acceptor (A/A) and donor/acceptor (D/A), and how these interactions synergistically control the final efficiencies. Three small molecular acceptors (SMAs) are designed with different end‐caps, which manipulate the crystallinity and electrostatic potential (ESP) distributions of acceptors, and accordingly, the A/A and D/A intermolecular interactions. The results show that SMA LA17 with low A/A interactions exhibits inferior performance around 12%, owing to its strong D/A interaction with donor PM6, which shapes too miscible morphology and increases charge recombination. Instead, LA16 with strong A/A interactions and moderate D/A interactions delivers improved bulk‐heterojunction (BHJ) networks, and therefore, enhances charge transport and diminishes geminate or trap‐assisted charge recombination. Consequently, PM6:LA16 records the competitive efficiency of up to 13.74% among the three systems. Therefore, this study deepens the synergistic or balancing effect of the D/A and A/A interactions on BHJ blends for efficient organic solar cells. [ABSTRACT FROM AUTHOR]

Ternary organic solar cells (TOSCs) offer a facile and efficient approach to increase the power conversion efficiencies (PCEs). However, the critical roles that guest components play in complicated ternary systems remain poorly understood. Herein, two acceptors named LA1 and LA9 with differing crystallinity are investigated. The overly crystalline LA9 induces large self‐aggregates in PM6:LA9 binary system, resulting in a lower PCE (13.12%) compared to PM6:LA1 device (13.89%). Encouragingly, both acceptors are verified as efficient guest candidates into the host binary PM6:NCBDT‐4Cl (PCE = 13.48%) and afford markedly improved PCEs up to 15.39% and 15.75% in LA1 and LA9 ternary devices, respectively. Interestingly, the higher crystallinity LA9 reveals smaller interaction energies with both the host acceptor and donor PM6. Compared to LA1, the appropriate mutual interactions in the LA9 ternary system not only induces the orderly crystallinity of PM6 but also better compatibility with the host acceptor, generating further optimized molecular orientations and ternary morphology. Therefore, enhanced charge transport and minimized recombination loss are detected in LA9 ternary devices, affording the most competitive performance among Y6‐sbsent TOSCs. This work suggests that complicated intermolecular interactions should be seriously considered when fabricating state‐of‐the‐art multiple components OSCs. [ABSTRACT FROM AUTHOR]