Designing Efficient Non-Fullerene Acceptors by Tailoring Extended Fused-Rings with Electron-Deficient Groups

In the past two years, non-fullerene acceptors including polymers and small molecules have become the focus of many research efforts. Fullerene-free organic solar cells (OSCs) have shown efficiencies of up to 6.8% for solution-processed devices, and even up to 8.4% for vacuum-deposited devices, which have been significantly improved relative to those disclosed 2 years ago (generally <4%). Non-fullerene acceptor materials are a new focus in the OSC field. Tailoring extended fused-rings with electron-deficient groups is an effective strategy for design of acceptors. Here, very recent developments in several systems of fused ring-based electron acceptors, such as halogenated (sub or subna)phthalocyanine, imide-functionalized rylene, and linear fused-rings end capped with electron deficient blocks, are reviewed.