Role of complexing agents on chemicalbath deposited PbS thin film characterization

In the present work, lead sulphide thin films have been grown on soda lime glass substrates by chemical bath deposition technique using three different complexing agents, namely triethanolamine, diethanolamine and hexamine. Aqueous solutions of lead acetate complexed with the above mentioned ligands were used as cationic precursor and thioacetamide as anionic precursor. The structural, morphological, optical and electrical properties of the as-prepared samples were investigated and compared by means of X-ray diffraction (XRD), Scanning electron microscopy (SEM), optical and electrical studies. The films were well crystallized and highly adherent to the substrate with face centered cubic structure. The average crystallite size was found to be in the range 15-20nm. The SEM micrographs showed variations in morphology. Optical studies revealed that the direct band gap energy was in the range of 1.65-2.27eV. The transmittance and reflectance in IR region was respectively in the range of 14%-47% and 25-45%. Optical constants of all films were determined by absorbance and reflection measurements. The room temperature conductivity of the PbS thin films were in the range 9.67×10⁻⁹ (Ω-Cm)⁻¹-3.29×10⁻⁶(Ω-Cm)⁻¹. The optical band gap energy has inverse relation with grain size and electrical conductivity is closely related to structural parameters like grain size, crystallinity and microstrain. PbS thin film using hexamine as complexing agent was proved to be the best in structural, optical and electrical properties. In this attempt we establish that the use of different complexing agents have immense effect on structural, morphological, optoelectronic and transport properties of PbS thin films.