A pentacyclic S,N-heteroacene based electron acceptor with strong near-infrared absorption for efficient organic solar cells.

A novel non-fullerene acceptor-donor-acceptor (A-D-A) structured small molecule acceptor material with fused ring N-alkyl dithieno[3,2-b:2',3'-d]pyrrole (DTP) as the central donor unit and ((2-(5,6-difluoro-)3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile) (EG-2F) as the terminal acceptor units, named DTP-C17-4F, was designed and synthesized. DTP-C17-4F demonstrates strong near-infrared absorption, suitable energy levels, a good film morphology and high electron mobility, resulting in an outstanding short-circuit current density of 21.17 mA cm-2 without additives for organic photovoltaics.