IEICO-4F is a low band-gap and low energy-loss material showing an A-D-A type structure with extra thiophenes as spacers between the acceptor and donor units. The structure has an electron-donating fused five-member-ring indaceno[1,2-b:5,6-b′]dithiophene (IDT) core, terminated by two electron-withdrawing units, 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile (IC-2F). IEICO-4F extends into the near infrared (NIR) region with maximum absorption around 860 nm, 200 nm red-shifted compared to ITIC.
