Hierarchical TiO2 mesoporous sphere/graphene composites (HTMS/Gs) were prepared by incorporation proper amounts of graphene oxide (GO) into the reaction system toward hierarchical TiO2 mesoporous spheres (HTMSs). The HTMS/Gs inherit the merits of high specific surface area derived from both HTMS and graphene, as well as the well conductivity of graphene. Power conversion efficiencies (PCEs) of dye sensitized solar cells (DSSCs) using HTMS/Gs as photoanode materials were also investigated. The graphene content in HTMS/G exhibited great influence on PCE. Lower graphene content in HTMS/G showed superior dye adsorption capacity, lower charge recombination and thus higher photocurrent density over bare HTMS. However, excessive graphene promoted the recombination of photo-generated electrons, which deteriorated the PCE. Due to the high dye adsorption capacity and the prolonged electron recombination lifetime, the HTMS/G contains 5.68 wt.% graphene, denoted as HTMS/G(5.68), boosted up the short circuit current density (J(sc)) to 16.17 mA/cm(2), and a PCE of 7.19% was achieved, which is 21.8% higher than that of bare HTMS. (C) 2012 Elsevier Inc. All rights reserved.