Preparation and room temperature photoluminescence characterization of PbS/Si(100) thin films

PbS nanoparticles and smooth nanocrystalline thin films (nc-PbS) were prepared by chemical precipitation from aqueous solutions. Polyethylene oxide and isopropyl alcohol were used as additives in the aqueous solution, which results in the enhancement of the blue luminescence of PbS thin films. The introduction of isopropyl reduced the grain size and increases the optical gap of the PbS particles. The size of PbS particles was estimated to be ~ 3.5 nm. The broad emission bands exhibited were composed by a multiple overlapping peaks. The photoluminescence (PL) intensity was significantly influenced by the excitation wavelength. Indeed, intense blue luminescence was obtained under 230 nm compared to that obtained under 325 nm excitation wavelength. The PL emission from PbS nanoparticles was less intense than the luminescence of PbS thin films. The high PL intensity of the thin films was attributed to the lower density of defects introduced in the thin films during the chemical bath deposition growth process compared the defects density of PbS powder.