PEG300-assisted synthesis and characterization of PbS nanostructured thin films

Abstract

We report here an attempt to relate the structural and optical properties of lead sulfide (PbS) nanocrystalline thin films, grown by chemical bath deposition (CBD) process at room temperature on corning glass and Si(1 0 0) substrates, with the variation of polyethylene glycol (PEG300) amount in the solution. X-ray diffraction (XRD), UV–vis spectroscopy and scanning electron microscopy (SEM) were used to characterize the samples. The concentration of PEG300 found to play crucial role in the deposition process. By making several trials, the amount of PEG300 was optimized. The transmittance of the films, for a fixed reaction time, increased from ∼30% to ∼80% with the increase of % PEG300 in the solution, indicating the formation of very thin films due to the decrease of reaction rate with the increase of the concentration of PEG300. The concentration of PEG300 not only affects the reaction rate but also the morphology of the obtained films. PbS nanoparticles were found to be oriented preferentially along the (2 0 0) plane. Particle sizes between 2.8 and 8.7 nm were obtained by varying the % of PEG300 from 0.2 to 1.5. The absorption shifts towards short wavelength compared with the bulk PbS indicated a deep blue shift as a consequence of quantum confinement. The optical band gaps found to be strongly relied to the composition of the bath deposition and increase with the increase of the PEG300 amount in the solution.