A square-planar platinum(II) based dye containing 4,4'-dicarboxy-2,2'-bipyridine and quinoxaline-2,3-dithiolate ligands achieves efficient sensitization of nanocrystalline TiO2 solar cells over a wide visible range, generating a short-circuit photocurrent of 6.14 mA cm(-2) and an open-circuit potential of 600 mV under simulated AM 1.5 solar irradiation, with a solar energy conversion efficiency of 2.6%.