Carbon-Oxygen-Bridged Ladder-Type Building Blocks for Highly Efficient Nonfullerene Acceptors.

Recently, acceptor-donor-acceptor (A-D-A) small molecules have emerged as promising nonfullerene acceptors (NFAs) for organic solar cells and have attracted great attention. The carbon-bridged (C-bridged) ladder-type D unit plays a crucial role in developing high-performance A-D-A NFAs. However, the medium electron-donating capability of C-bridged units is unfavorable for making NFAs with strong light-harvesting capability. In this regard, carbon-oxygen-bridged (CO-bridged) ladder-type units present advantages in developing strong light-absorbing NFAs. Here, recent progress in the newly emerging CO-bridged NFAs is highlighted. The synthetic methods for the polycyclic CO-bridged building blocks are introduced. The photovoltaic performance for CO-bridged NFAs is summarized and discussed. Perspectives on developing high-performance CO-bridged-NFA-based solar cells are made.