Phenanthro[1,2-b:8,7-b']dithiophene: A new picene-type molecule for transistor applications

A new picene-type molecule, phenanthro[1,2-b:8,7-b']dithiophene, has been synthesized for use in organic field-effect transistors (OFETs). The molecule consists of a phenanthrene core with two thiophene rings fused on the ends. This molecule can be recognized as a picene analogue. The electronic structure of the molecule was determined by its optical absorption spectrum together with a theoretical calculation based on density functional theory (DFT). The topological and electronic structures of thin films produced by direct thermal evaporation of the compounds and by deposition from a solution were characterized by optical imaging, X-ray diffraction, and atomic force microscopy. FET devices were fabricated with these thin films, and showed field-effect mobility as high as 10^-1 cm² V^-1 s^-1.