Building-Up Relations between Intra- and Intermolecular Interactions, Miscibility, and Performance for Low-Cost, Efficient Fully Non-Fused Acceptor-Based Organic Solar Cells

Although the molecular electronic forces (e.g., intra- and intermolecular interactions) within active layers largely govern the device performance of organic solar cells (OSCs), they are complicated and less understood. In this study, we have synthesized two low-cost isomeric non-fused acceptors (TT-Naph1 and TT-Naph2) with 1-naphthyl and 2-naphthyl aromatic chains, respectively and quantified the molecular interaction-photovoltaic performance relationship. Benefiting from the enhanced dipole moment, TT-Naph2 possesses a strong dipole–dipole intermolecular interaction, while the improved backbone planarity endows TT-Naph1 with a strengthened intramolecular charge-transfer effect, which can regulate the desired blend morphology with the D18 donor polymer as a result of its low miscibility with D18. Less miscible nanostructures are more pronounced in the layer-by-layer (LBL) systems than bulk heterojunction (BHJ) ones, increasing the power conversion efficiencies (PCEs) in the sequence of TT-Naph2 BHJ < TT-Naph1 BHJ < TT-Naph2 LBL < TT-Naph1 LBL. Notably, a ternary LBL OSC based on TT-Naph1 achieved remarkable PCE of 18.41%, one of the top values for LBL-type OSCs. Our findings provide insights into the controlling effect of intra- and intermolecular interactions on the active layers for efficient non-fused acceptor-based OSCs.