Optical properties of dibenzo[d,dì3,2-b;4,5-b']dithiophene monocrystals: the effect of intermolecular interactions

The polarized UV-visible absorption spectra of dibenzo[d,d`]thieno[3,2-b;4,5-b`]dithiophene single crystals are reported and interpreted to definitively attribute the observed bands and their polarizations. The results provide information on the intermolecular interactions and on the aggregation in the condensed phase, which can be of either herringbone- or H-type, depending on the electronic transition taken into considerations, with consequences on the order and polarization of the absorption bands. A relatively easy method is also discussed to obtain information on the structural/morphological properties of different types of samples, including thin films, which have been recently proposed for high-performance organic film-effect transistors for their high ionization potential and photostability.