Preparation of nanocrystalline PbS thin films and effect of Sn doping and annealing on their structural and optical properties

Highlights: ► We deposited nanocrystalline PbS thin films by chemical bath deposition technique. ► We examined the effect of Sn doping and annealing on their structural and optical properties. ► The crystallite size increases with increasing doping concentration in pure PbS. ► The band gap of pure PbS was 1.8 eV which is higher than bulk PbS. ► Band gap reduces with increasing doping concentration in pure PbS. -- Abstract: Nanocrystalline PbS and Sn doped PbS thin films were successfully deposited on suitably cleaned glass substrate at constant room temperature, using the chemical bath deposition technique. Before, adding Sn doping content, the pure PbS thin films were deposited at room temperature for several dipping times to optimize the deposition time. After deposition, the films were also annealed at 400 °C for 1 h in air. The crystal structures of the films were determined by X-ray diffraction studies. The films were adherent to the substrate and well crystallized according to cubic structure with the preferential orientation (2 0 0). The crystallite size of the pure PbS thin films at optimized deposition time 30 min was found to be 40.4 nm, which increased with Sn content in pure PbS thin film. The surface roughness was measured by AFM studies. The band gaps of the films were determined by transmission spectra. Experiments showed that the growth parameters, doping and annealing, influenced the crystal structure, and optical properties of the films.