title: Polymorphism in new thienothiophene-thiazolothiazole organic semiconductors.
abstract: Charge transport in organic semiconductors is heavily influenced by their solid-state packing. To separate intermolecular packing effects from molecular electronic effects, we have synthesized two polymorphs of crystalline thienothiophene-thiazolothiazole trimers and studied them by DFT calculations, optical spectroscopy, single-crystal X-ray diffraction and charge-transport measurements in field-effect transistors. One polymorph was found to be a p-type semiconductor with a hole mobility of 3.3×10(-3) cm(2)  V(-1)  s(-1) , while the other was insulating. The different charge-transport behavior and optical properties of the two polymorphs are strongly related to the topology of their π-stacks. Subtle differences between the polymorphs, including S⋅⋅⋅S close contacts and bond-length alternation are also discussed for their possible effects on charge transport.
authors: Department of Chemistry and Centre for Self-Assembled Chemical Structures, McGill University, 801 Sherbrooke St. West, Montreal QC, H3A 0B8 (Canada).
authors: Julia A
authors: JA
authors: Schneider
authors: Hayden
authors: H
authors: Black
authors: Hua-Ping
authors: HP
authors: Lin
authors: Dmitrii F
authors: DF
authors: Perepichka
keywords: organic field-effect transistors; polymorphism; single crystals; thiazolothiazole; thienothiophene