A modified polysulfide redox couple, [(CH3)4N]2S/[(CH3)4N]2Sn, in an org. solvent (3-methoxypropionitrile) was employed in CdS quantum dot-sensitized solar cells (QDSSCs), and an unprecedented energy conversion efficiency of up to 3.2% was obtained under air-mass 1.5G illumination. The quantum dots were linked to nanoporous TiO2 via covalent bonds by using thioglycolic acid, and chem. bath deposition in an org. solvent was then used to prep. the QDSSCs, facilitating high wettability and superior penetration capability of the TiO2 films. A very high fill factor of 0.89 was obsd. with the optimized QDSSCs.