Nanocrystalline mercury sulfide (HgS) thin films were deposited by chemical bath deposition (CBD) method onto the glass and fluorine doped tin oxide (FTO) coated glass substrate from an aqueous alkaline bath (pH similar to 8) at room temperature (300 K). Mercuric acetate and thiourea were used as Hg2+ and S2- ion sources, respectively. The photoelectrochemical (PEC) studies of HgS films were carried out, and the nanocrystalline films were found to be photoactive in polyiodide solution. The PEC cell configuration was p-HgS/0.1 M (KOH-KI-I-2)/C. From the current-voltage (I-V) characteristics, it is concluded that the HgS films are of p-type electrical conductivity. The photovoltaic output characteristics were used to calculate the fill factor (ff) and solar conversion efficiency (eta). The low value of eta may be due to the high value of series resistance (R-s) and interface states in the cell, which are responsible for the recombination mechanism. (c) 2006 Elsevier Ltd. All rights reserved.