Band gap engineering in lead sulphur selenide (PbS_1−x Se _x ) thin films synthesized by chemical bath deposition method

Nanocrystalline PbS_1−x Se _x (0 ≤ x ≤ 1) thin films have been deposited on silica glass substrate by the chemical bath deposition technique. The deposited PbS_1−x Se _x thin films were smooth and mirror-like gray in color. The films were characterized by a variety of techniques and the effect of selenium (Se) concentration analyzed. The X-ray diffraction analyses revealed that all the PbS_1−x Se _x thin films were polycrystalline and had the face centered cubic structure. Variation in Se concentration had a significant effect on the preferred orientation of the crystallites. The lattice constant and inter planer distance increased linearly with the gradual addition of Se in the PbS_1−x Se _x thin films. Energy dispersive X-ray analysis confirmed that all the samples have stoichiometric composition. The surface morphology of the films has been examined using scanning electron microscopy. The optical absorption spectroscopy study revealed that the optical band gap of the PbS_1−x Se _x thin films tuned from near-infrared to visible region (1.32–1.08 eV) by simple and cost effective route.