Two ruthenium complexes, [Ru-II(12)(dcbpy)(NCS)(2)] Ru-II(4,5-diazafluoren-9-one)(4,4'-dicarboxy-2,2'-bipyridyl)-di(thiocyanate) [K30] and Ru(dcbpy)(3)] Ru(II)tris(4,4'-dicarboxy-2,2'-bipyridyl) [K303] have been synthesized and used in dye sensitized solar cells. The ruthenium complexes have been characterized by elemental analyses, FT-IR, UV-Vis, cyclic voltammetry and H-1 NMR spectral methods. The performance of this complexes as charge transfer photosensitizer in nc-TiO2 based dye sensitized solar cells is studied under standard AM 1.5 sunlight and by using an electrolyte consisting of 0.6 M N-methyl-N-butyl imidazolium iodide (BMII), 0.1 M Lil, 0.05 M I-2, 0.5 M 4-tert-butyl pyridine (TBP) in acetonitrile. Notably, the photo-to-electrical conversion efficiency of the DSSCs sensitized with [K30] and [K303] reaches 3.45%, and 6.33%, and the DSSC sensitized with [K303] shows better photovoltaic performances (Jsc=19.58 mA/cm(2), Voc=570 mV and FF=0.58) than [K30]. (C) 2012 Elsevier B.V. All rights reserved.