High‐Efficiency All‐Small‐Molecule Organic Solar Cells Based on New Molecule Donors with Conjugated Symmetric/Asymmetric Hybrid Cyclopentyl‐Hexyl Side Chains

Abstract All small molecule organic solar cells (ASM‐OSCs) have numerous advantages but lower power conversion efficiencies (PCEs) than their polymer equivalents, which is largely due to the suboptimal nanoscale network structure in a bulk heterojunction (BHJ). Herein, new small molecule donors with symmetric/asymmetric hybrid cyclopentyl‐hexyl side chains are designed, accounting for manipulated intermolecular interactions and BHJ morphology. Theoretical and experimental results reveal that the asymmetric cyclopentyl‐hexyl side chains modification has a significant influence on potential energy surface and intermolecular interaction that can ensure preferable molecular assembly and regulate the D/A interfacial energetics, thus boosting the exciton dissociation and charge transport when pairing with a wide‐used acceptor L8‐BO. Concurrently, a nanoscale bicontinuous interpenetrating network with optimal domain size can be fully evolved in the BHJ layer. As a consequence, the As‐TCp‐based binary device achieves a superior PCE of 16.46% in comparison to that of the controlled symmetric counterparts S‐BF (14.92%) and A‐TCp (15.77%), and ranks one of best performance among ASM‐OSCs. This study demonstrates that precise manipulation of the cyclo‐alkyl chain in combination with the asymmetric 2D side chain strategy is an effective synergistic approach to control intermolecular interaction and nanoscale bicontinuous phase separation for achieving high‐performance ASM‐OSCs.