Two side chain conjugated polythiophene copolymer: poly[3-(5'-octylthienylenevinyl) thiophene]-thiophene (P1) and poly(3-[4-(2-ethyl-hexyloxy)-phenylvinyl]-thiophene)-thiophene (P2) were synthesized. Polymer photovoltaic solar cells using P1 and P2 as donor and a high LUMO energy level fullerene derivative indene-C-60 bisadduct (IC(60)BA) as acceptor were demonstrated. The polymer solar cells (PSCs) based P1/IC(60)BA and P2/IC(60)BA showed enhanced open circuit voltage (V-oc) of 0.89 and 0.88 V respectively, in comparison with that of P1/PC61BM and P2/PC61BM as 0.58 and 0.56 V. respectively. The improved V-oc of IC(60)BA as acceptor in PSCs is benefited from the higher LUMO energy levels of the C-60 derivatives. The power conversion efficiency of the PSCs based on P1/IC(60)BA and P2/IC(60)BA were 0.32% and 0.35%, respectively. (C) 2011 Elsevier Ltd. All rights reserved.