A new fullerene derivative, biindene-C-70 monoadduct (BC(70)MA), was synthesized by [4+2] cycloaddition reaction between 1,1'-biindene and C-70, for the application as acceptor in polymer solar cells (PSCs). BC(70)MA is soluble in common organic solvents such as tetrahydrofuran, chloroform, toluene, o-dichlorobenzene, etc., and shows stronger absorption in the visible region and a slightly up-shifted lowest unoccupied molecular orbital (LUMO) energy level than that of PCBM. PSCs were fabricated with BC(70)MA as acceptor and poly(3-hexylthiophene) (P3HT) as donor for investigating the photovoltaic properties of BC(70)MA. The power conversion efficiency of the PSC based on P3HT/BC(70)MA (1:1, w/w) with the additive of 3% octane-1,8-dithiol and thermal annealing at 110 degrees C for 10 min reached 3.44% with open circuit voltage of 0.64 V, short circuit current of 8.02 mA/cm(2) and fill-factor of 0.67, under the illumination of AM1.5, 100 mW/cm(2). (C) 2011 Elsevier B.V. All rights reserved.