Regioregular poly[3-(3,6-dioxaheptyl)thiophene] (PDHT) has been synthesized by Grignard metathesis (GRIM). The UV–vis absorption spectrum of spin-cast films of PDHT presents a well-resolved vibrational fine structure typical of well-ordered polymers. The characterization of bulk heterojunction solar cells fabricated using PCBM as acceptor shows that PDHT leads to power conversion efficiencies in ca 4–5 times lower than that obtained with regioregular poly(3-hexylthiophene) (P3HT). In contrast, the characterization of bilayer solar cells realized by thermal evaporation of C60 on spin-cast polymer films shows that PDHT leads to performances similar or even better than P3HT both before and after thermal treatment.