COTIC-4Cl (CAS number 2328092-51-7) has a chemical structure containing an electron rich cyclopentadithiophene (CPDT) as the central donor unit flanked with alkoxythienyl units and two 2-(5,6-dichloro-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile (IC-2Cl) accepting peripheral units.
Compared to COTIC-4F, COTIC-4Cl film has an absorption that extends to near infrared (NIR) and exhibits broad absorption with a strong absorption band, which ranges from 600 to about 1400 nm. COTIC-4Cl is a ultra-narrow bandgap n-type semiconductor with an optical bandgap of ~ 1.0 eV.
COTIC-4Cl can be used for organic photodiodes to extend the spectral response range over 1000 nm. Ternary organic photodiodes photodiodes based on PCE10:COTIC-4Cl:PC71BM as active layer materials exhibited a high specific detectivity (D*) of 5 × 1012 Jones and a responsivity (R) of 0.30 A W-1 at 1100 nm.