ZnS is an n-type semiconductor with a wide direct band gap (3.7 eV at room temperature), and it is very suitable as a window layer in heterojunction photovoltaic solar cells. We deposited ZnS thin films on Sn-doped In2O3-coated glass substrate using pulsed electro-chemical deposition (ECD) from aqueous solutions containing Na2S2O3 and ZnSO4 with two different compositions, the first group grown from ZnSO4-rich solution, and the second grown from Na2S2O3-rich solution. We investigated electrical properties of the ZnS thin films and properties of contacts with different metals evaporated on the surfaces. We found that Au and In contacts have Ohmic-like characteristics to ZnS. Furthermore, we observed photoconductivity of the ZnS thin films by means of photoelectrochemical (PEC) measurements. We found that for both the groups of ZnS thin films, the as-deposited film shows weak photosensitivity and after annealing at 300 degrees C the photosensitivity improved. (c) 2004 Elsevier B.V. All rights reserved.