An A-D-A′-D-A type unfused nonfullerene acceptor for organic solar cells with approaching 14%efficiency

In recent years,power conversion efficiency(PCE)of organic solar cells(OSCs)has made significant improvement.A large number of studies were reported to achieve high PCEs through exploring new active layer materials,especially the high efficiency fused ring acceptors(FRAs).Compared with FRAs,another type of so-called unfused-ring acceptors(UFAs),possessing some advantages such as simple synthesis and low cost,have attracted a lot of attention.Herein,a new UFA BTzO-4F,incorporating with a benzotriazole moiety and S···O intramolecular noncovalent interactions,has been successfully synthesized.The photovoltaic device based on PBDB-T:BTzO-4F achieved a record PCE of 13.8%for UFAs,which indicates that introducing the benzotriazole moiety is an effective strategy for high quality acceptors.Thus,these findings of this work demonstrate the great potential of UFAs for high performance OSCs.

Simple non-fullerene electron acceptors with unfused core for organic solar cells

Two simple electron acceptors based on unfused bithiophene core and 1,1-dicyanomethylene-3-indanone end group were easily prepared via three synthetic steps. These acceptors exhibited broad absorption in the range of 300 nm to 800 nm, aligned energy levels and high crystallinity. When combined with a wide band gap donor polymer in non-fullerene solar cells, an initial power conversion efficiency of 2.4% was achieved. The relatively low efficiencies were due to the large phase separation in blended thin films, which is originated from their high aggregation tendency in thin films. Our results suggest that these electron acceptors with unfused core are promising candidates for commercial application of solar cells due to the low cost starting materials and facile synthesis.