DTT-DDQ Mixed-Stack Organic Charge-Transfer Crystals with Near-Infrared Absorption

Dithieno[3,2-b:2′,3′-d]thiophene (DTT) is a common molecular motif in organic
electronics.
We find that it forms a 1:1 charge-transfer complex (CTC) with the
electron acceptor 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ).
The 1:1 complex has an alternating donor/acceptor mixed-stack structure,
and an intense near-infrared absorption band. Vibrational spectroscopy
and electronic structure calculations are used to further understand
the partial ionization induced by the DTT/DDQ complex.