Effects of Side-Chain Interdigitation on Stability: An Environmentally, Electrically, and Thermally Stable Semiconducting Polymer

A polymeric semiconductor, poly­(3,6-dihexyl-[2,2′]­bi­[thieno­[3,2-b]­thiophene]) (PDHTT), was synthesized and tested as an active layer in organic thin film transistors (OTFTs). This semiconductor showed considerable potential for use in commercial electronic devices because of its superior characteristics, particularly its good stability. PDHTT-based OTFTs exhibited high stability in air, retaining their initial performance after exposure to 70% relative humidity for 50 days; they were also stable under repeated electrical stress and even after exposure to temperatures as high as 250 °C. We attribute the remarkable stability of PDHTT OTFTs to the relatively low highest occupied molecular orbital (5.1 eV) level of the polymer and its highly interdigitated structure in the thin film state.