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.