Two C-60 derivatives, biindene-C-60 monoadduct (BC(60)MA) and biindene-C-60 bisadduct (BC(60)BA), were synthesized by an one-pot reaction of 1, l'-biindene and C-60, for the application as acceptor materials in Polymer Solar Cells (PSCs). The two C-60 derivatives possess good solubility in toluene and o-dichlorobenzene, and the solubility of BC(60)BA is even better than that of BC(60)MA. The electrochemical properties and the LUMO energy levels of the two fullerene derivatives were investigated by cyclic voltammetry. The LUMO energy levels of BC(60)MA and BC(60)BA were 0.06 and 0.17 eV higher (up-shifted) than that of PCBM, respectively. The PSCs based on P3HT as donor and BC(60)MA or BC(60)BA as acceptorexhibited higher V-oc of 0.68 and 0.82 V, respectively, which is benefited from the higher LUMO energy levels of the C-60 derivatives. The power conversion efficiency of the PSC based on P3HT/BC(60)MA was 2.21% after annealing at 140 degrees C for 5 min. (C) 2010 Elsevier B.V. All rights reserved.