Stable polythiophene semiconductors incorporating thieno[2,3-6]thiophene

This work describes a new design methodology that allows the preparation of air stable, semiconducting thiophene polymers with high charge carrier mobilities. The incorporation of thieno[2,3-b]thiophene into a polythiophene backbone introduces cross-conjugated double bonds that disfavor full delocalization, leading to high ionization potential in comparison to a fully conjugated polythiophene, with no reduction in charge carrier mobility. The resulting solution processable polymers exhibit charge carrier mobilities up to 0.15 cm²/V s and on/off ratios greater than 10⁵ when measured in air. Transistors exhibit lifetimes of several months in air with no encapsulation necessary.