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

A new selenophene-contaning fully unfused acceptor 2T2Se-F is developed. Multiple intermolecular π−π interactions, from J-aggregations between terminal groups and between the terminal groups with selenophenyl rings, and H-aggregations between molecular backbones form an ordered three-dimensional interpenetrating charge-transfer network for 2T2Se-F. The combination of the 1,8-diiodooctane (DIO) and thermal annealing (TA) treatment led to higher crystallinity, dominant face-on molecular orientation, suitable phase separation, and finer morphologies, which contributed to more efficient charge dissociation and suppressed charge recombination, and larger carrier mobilities. A power conversion efficiency of 12.17% is obtained, which is among the highest values for fully unfused acceptors. [Display omitted] •An efficient fully unfused acceptor 2T2Se-F containing selenophene.•Combined H- and J-aggregation and multiple non-covalent interactions.•An excellent PCE of 12.17% for 2T2Se-F:PM6-based 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-indanone (DFIC), was designed and synthesized. The single crystal structure of 2T2Se-F indicates that the collaborated π−π 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.