Enhanced open-circuit voltage of two side chain conjugated polythiophene derivatives blended with indene-C60 bisadduct

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-C60 bisadduct (IC60BA) as acceptor were demonstrated. The polymer solar cells (PSCs) based P1/IC60BA and P2/IC60BA showed enhanced open circuit voltage (Voc) 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 Voc of IC60BA as acceptor in PSCs is benefited from the higher LUMO energy levels of the C60 derivatives. The power conversion efficiency of the PSCs based on P1/IC60BA and P2/IC60BA were 0.32% and 0.35%, respectively.