Simple Non-Fused Electron Acceptors Leading to Efficient Organic Photovoltaics.

Despite the remarkable progress achieved in recent years, organic photovoltaics (OPVs) still need work to approach the delicate balance between efficiency, stability, and cost. Herein, two fully non-fused electron acceptors, PTB4F and PTB4Cl, are developed via a two-step synthesis from single aromatic units. The introduction of a two-dimensional chain and halogenated terminals for these non-fused acceptors plays a synergistic role in optimizing their solid stacking and orientation, thus promoting an elongated exciton lifetime and fast charge-transfer rate in bulk heterojunction blends. As a result, PTB4Cl, upon blending with PBDB-TF polymer, has enabled single-junction OPVs with power conversion efficiencies of 12.76 %, representing the highest values among the reported fully unfused electron acceptors so far.