Alkyl chain extension as a route to novel thieno[3,2-b ]thiophene flanked diketopyrrolopyrrole polymers for use in organic solar cells and field effect transistors

The synthesis and characterization of four new donor-acceptor type semiconducting polymers based on the electron-deficient diketopyrrolopyrrole unit for use in photovoltaic devices are reported. The extended 2-decyl-1-tetradecyl alkyl chain (C₁₀C₁₂) is utilized to provide a valuable route toward enhanced solubility. The resultant soluble DPP polymers were synthesized in high polymer molecular weights with a larger range of accessible comonomer units. Bulk heterojunction solar cells containing these polymers show promising device performance with efficiencies around 4%. Organic thin film transistor devices with high ambipolar hole mobilities of >0.1 cm² V^-1 s^-1 are also reported.