Highly Efficient Organic Solar Cells Based on S,N-Heteroacene Non-Fullerene Acceptors

Two novel non-fullerene acceptors, SN6IC and SN6IC-4F, based on an S,N-heteroacene backbone were designed and synthesized. The cyclopentadiene fragments of commonly used acceptors were replaced with pyrrole rings to improve the electron-donating ability to increase the energy levels of the molecules. Both acceptors match well with the absorption and energy levels of the polymer donor PBDB-T, and PBDB-T:SN6IC-4F-based solar cells showed an excellent power conversion efficiency of 13.2%, with a relatively small V_OC loss of 0.54 eV. This study proves that the introduction of a nitrogen atom to replace the sp³-hybridized carbon in the fused ring is very effective for making highly efficient NFAs to further improve the performance of organic solar cells.