In the present study, we report the optimization of various deposition parameters viz, bath temperature, deposition time and current density to deposit densely packed and vertically aligned ZnO nanorod thin films on cost effective substrate, i.e. steel, by electrodeposition technique. The obtained vertically aligned ZnO nanorod thin films are sensitized by CdS quantum dots (QDs) and utilized for photoelectrochemical (PEC) cell application. Effect of redox electrolyte on the PEC cell properties of CdS QDs sensitized ZnO nanorod thin films is investigated using two different electrolytes viz. polysulfide and ferro(i)cyanide.(1) CdS QDs, of around 10 nm in diameter, are synthesized by chemical bath deposition (CBD) method. The deposited ZnO nanorods having diameter in the range 100-120 nm showed hydrophobic nature, which changed to hydrophilic after CdS QDs sensitization. The maximum short circuit current density (J(sc)) and open circuit voltage (V-oc) are observed for ferro(i)cyanide electrolyte and are found to be 680 mu A cm(-2) and 520 mV, respectively, under 10 mW cm(-2) of illumination. However, better photoelectrode stability is observed for polysulfide electrolyte. (C) 2011 Elsevier Ltd. All rights reserved.