Abstract ZnS thin films have been successfully deposited with the same production parameters using thermionic vacuum arc technique on glass and silicon substrates. UV–Vis absorbance spectra and photoluminescence measurements were performed for the optical characterization of ZnS/glass thin film and ZnS/p-Si heterojunction device, respectively. The optical band gap is found approximately 3.78 eV. Further, electrical parameters of the device were determined for the current-voltage (I-V) measurements in dark and under illumination conditions. The open-circuit voltage and the short-circuit current values have been obtained related to illumination I-V measurements. Also, we have utilized photocurrent measurements to investigate the wavelength dependent to photosensitivity of the ZnS/p-Si heterojunction device.