Novel donor acceptor alternating polymers containing an electron-rich five-membered ring in azulene as a donor unit and diketopyrrolopyrrole or 2,1,3-benzothiadiazole unit as an acceptor unit were synthesized. The azulene-based copolymers displayed broad absorption bands in the visible region. The photovoltaic devices consisting of the polymer and a fullerene derivative ([70]PCBM) showed power conversion efficiencies up to 0.39% under simulated AM 1.5G irradiation of 100 mW cm(-2).