A 4-arm small molecule acceptor (SMA) 4A-DFIC was serendipitously made. Power conversion efficiencies of 15.76 % and 18.60 % were achieved in 4A-DFIC-based binary and ternary organic solar cells, respectively, setting new records for multi-arm SMA-based solar cells.
Manipulating the backbone of small molecule acceptors (SMAs) is of particular importance in developing efficient organic solar cells (OSCs). The common design is constructing 2-arm SMAs with linear or curved backbones. Herein, we report an acceptor 4A-DFIC with a 4-arm backbone unexpectedly generated in the reaction of an electron-rich aromatic diamine and hexaketocyclohexane. Single-crystal X-ray diffraction analysis indicates the rigid and twisted molecular plane and the effective molecular stacking of 4A-DFIC in solid state. 4A-DFIC shows a low band gap of 1.40 eV and excellent light-harvesting capability from visible to near-infrared region. Binary and ternary OSCs based on 4A-DFIC gave power conversion efficiencies (PCEs) of 15.76 % and 18.60 % (certified 18.1 %), respectively, which are the highest PCEs for multi-arm SMA-based OSCs to date.Zum Volltext