In this paper, a simple and non-poisonous "surfactant treatment" method to prepare graphene oxide (GO) in organic solvents with good dispersibility was presented. As the surfactant molecules, didodecyldimethyla-mmonium bromide (DDAB) was attached onto the GO sheets via ionic interactions by mild sonication, the obtained GO:DDAB nanocomposites were then blended into copolymer Poly(3-hexylthiophene-2,5-diyl) (P3HT) [6,6]: -Phenyl C-61 butyric acid methyl ester (PC61BM) as the active layer to fabricate bulk-heterojunction (BHJ) organic solar cells ITO/PEDOT:PSS/P3HT:PC61BM:(GO:DDAB)/Ca/Al. The concentration of GO:DDAB in the active layer, a maximum power conversion efficiency (PCE) of 3.67% was obtained by blending 0.5 mg/mL GO:DDAB in the active layer, showing an efficiency increment of 13.35% as compared with that of the control device without doping GO:DDAB. The optimized OPVs with PTB7:PC71BM by adding GO:DDAB shows the PCE of 7.96%. Therefore, it paves a way to get high efficiency organic photovoltaic cells by directly blending surfactant -treated graphene oxide in organic solvent. (C) 2016 Elsevier B.V. All rights reserved.