In the first part of the present work, the structural, elemental and optical properties of PbS and PbS:Ni(3%) thin films synthesized by chemical bath deposition (CBD) technique on glass substrates at room temperature were analyzed by x-ray diffraction (XRD), energy dispersive x-ray (EDX) and absorption measurements, respectively. It was determined that the particle size of PbS:Ni(3%) thin film in the presence of Ni additive material is smaller than that of PbS although both thin films have the same structure (cubic phase). A similar result was achieved using the data obtained as a result of the optical measurements. Moreover, when the PbS thin film was doped with Ni, its energy band gap was observed to be wider. In the second part; the photovoltaic properties of FTO/Zn2SnO4/PbS and FTO/Zn2SnO4/PbS: Ni(3%) thin films were investigated by performing incident photon-tocurrent efficiency (IPCE) and current density (J)- voltage (V) measurements, respectively, using Zn2SnO4 coated on FTO conductive glasses instead of glass susbtrates. Based on the data obtained from both measurements, it was observed that the Ni dopant significantly enhance the performance of the PbS-based solar cell devices.