Synchrotron radiation Fourier-transform infrared absorption measurements on the single-crystal dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene

The strong coupling of charge carriers with molecular vibrations is one essential characteristic of organic semiconductor materials as molecular solids. To address this question, fundamental solid-state properties of each molecular species are demanded not only for the electronic states but also for the vibrational characteristics. In the present study, Fourier-transform infrared absorption measurements were performed on single-crystal samples of dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (DNTT) by using a linearly polarized synchrotron radiation light source. Molecular vibrational modes in a wavenumber range of 200-1600 cm⁻¹ were reasonably assigned, and the Davydov splittings of several vibrational modes were resolved demonstrating intermolecular couplings of two DNTT molecules in the unit cell.