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.