Nickel oxide (NiO) thin films-were prepared onto ITO/glass substrates by spin-coating, dipping and electrochemically. Studies of the morphological and structural properties of the films were done by atomic force microscopy (AFM). Photoelectrochemical and optical experiments were carried out in order to characterize the semiconductor properties of the nanostructured NiO thin films. The experiments were also done for Eosin B- and Erythrosin J-sensitized nanostructured NiO films, with the aim to visualize their potential application as photocatodes in tandem dye-sensitized solar cells (TDSSC). The NiO grown by dipping was the one presenting the best morphological properties. The photoelectrochemical results for all the bare NiO, NiO-Eosin B and NiO-Erythrosin J/electrolyte (I-2/I-) systems showed a p-type behavior. An, enhancement in the photocurrent has been observed for the systems sensitized with the dyes. For the NiO/Erythrosin J system the enhancement of the current under illumination in comparison to the dark current was about 200%. (c) 2005 Elsevier B.V. All rights reserved.