Conformation Locking of Simple Nonfused Electron Acceptors Via Multiple Intramolecular Noncovalent Bonds to Improve the Performances of Organic Solar Cells

Through the molecular isomerization strategy, three simple nonfused electron acceptors (AOT1, AOT2, and AOT3) are synthesized by altering the position of the isooctyloxy group on the bridging thienyl group. The number of intramolecular O···S noncovalent bonds of the three acceptors is two for AOT1, three for AOT2, and four for AOT3. With the multiple O···S interactions, the molecular backbone of AOT3 can be locked tightly, and thus, AOT3 possesses more confirmed conformation, which is beneficial for the J-aggregation. Compared with AOT1 and AOT2, AOT3 exhibits stronger crystallinity, narrower band gap, and better solubility. When pairing AOT3 with polymer donor PCE10, the blend film can form smaller domain sizes, a smoother surface, and a tighter π–π stacking. Therefore, photovoltaic devices based on PCE10:AOT3 blends give a power conversion efficiency of 6.59%, higher than that based on PCE10:AOT2 (4.06%) and PCE10:AOT1 (3.31%) blends. This study shows that ensuring the presence of multiple noncovalent bonds to tightly lock the conformation of simple nonfused electron acceptors is vital to improve the performances of organic solar cells.