Effect of Steric Hindrance at the Anthracene Core on the Photovoltaic Performance of Simple Nonfused Ring Electron Acceptors.

Solving the contradiction between good solubility and dense packing is a challenge in designing high-performance nonfullerene acceptors. Herein, two simple nonfused ring electron acceptors ( o -AT-2Cl and m -AT-2Cl ) carrying ortho - or meta -substituted hexyloxy side chains can be facilely synthesized in only three steps. The two ortho -substituted phenyl side chains in o -AT-2Cl cannot freely rotate due to a big steric hindrance, which endows the acceptor with good solubility. Moreover, o -AT-2Cl displays a more ordered packing than m -AT-2Cl as revealed by the absorption measurement. When blended with polymer donor D18 for the fabrication of organic solar cells (OSCs), o -AT-2Cl -based devices exhibit a favorable morphology, more efficient exciton dissociation, and better charge transport. Consequently, the optimal OSCs based on D18: o -AT-2Cl exhibit a power conversion efficiency (PCE) of 12.8%, which is significantly higher than the moderate PCE (7.66%) for D18: m -AT-2Cl -based devices. Remarkably, o -AT-2Cl shows a higher figure-of-merit value compared with classic high-efficiency fused ring electron acceptors. As a result, our research succeeds in obtaining nonfused ring acceptors with cost-effective photovoltaic performance and provides a valuable experience for simultaneously improving solubility as well as ensuring ordered packing of acceptors through regulating the steric hindrance via changing the position of substituents.