A selenophene-containing near-infrared unfused acceptor for efficient organic solar cells

Unfused acceptors have attracted considerable attention due to their simple synthesis and low cost compared to their fused-ring counterparts. Herein, a simple fully unfused acceptor 2T2Se-F, with selenophene to link 2,6-di (hexyloxy)phenyl substituted bithiophene and the terminal groups of fluorinated 1,1-dicyanomethylene-3-inda-none (DFIC), was designed and synthesized. The single crystal structure of 2T2Se-F indicates that the collabo-rated pi- pi interactions from H-aggregations of molecular backbones and J-aggregations of terminal groups and terminal groups/selenophenyl rings form an ordered three-dimensional interpenetrating network. 2T2Se-F film displays near-infrared absorption with a low bandgap of 1.44 eV. After blending with the polymeric donor PM6, an impressive power conversion efficiency (PCE) of 12.17% was obtained with a high short-circuit current density of 20.63 mA cm-2 and a fill factor of 0.669, which is among the highest values for organic solar cells based on fully unfused non-fullerene acceptors so far.