Y6 (BTP-4F) is a highly conjugated organic semiconductor. It is composed of a fused thienothienopyrrolo-thienothienoindole (TTP-TTI) core base and 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile (2FIC) end units. These 2FIC end units are believed to promote intermolecular interactions and enhance optical absorption.