ARTHER EJERE

The growing demand for efficient, low-cost semiconductor materials for optoelectronic applications has driven significant interest in copper sulfide (CuS) thin films. This project successfully demonstrates the fabrication of CuS nanothin films on glass substrates using a simple and cost-effective Chemical Bath Deposition (CBD) technique, with a specific focus on investigating the influence of extended deposition times on their optical properties. Two sets of films were deposited using an aqueous solution of copper sulfate and thiourea, with deposition times of 20 hours and 24 hours, while maintaining all other parameters constant. The primary characterization technique employed was Ultraviolet-Visible (UV-Vis) Spectroscopy, which provided a detailed analysis of the films' light-matter interactions. The collected absorbance spectra, obtained with a high-resolution sampling interval of 1 nm and a measuring bandwidth of 2 nm, were used to determine key optical parameters. The results revealed that the extended deposition time significantly enhanced the optical performance of the CuS films. The film deposited for 24 hours exhibited a higher absorption coefficient across the UV-Vis-NIR spectrum and a more intense Localized Surface Plasmon Resonance (LSPR) peak in the near-infrared region (~1050 nm), confirming the formation of the covellite phase with a high density of free charge carriers. Tauc plot analysis derived from the absorbance data showed a narrowing of the direct optical band gap from 2.38 eV for the 20-hour film to 2.32 eV for the 24-hour film, attributed to increased crystallite size and reduced quantum confinement effects. In conclusion, this project establishes that a CBD deposition time of 24 hours is optimal for producing high-quality CuS thin films with superior light-harvesting capabilities and tailored optoelectronic properties. These findings provide valuable insights for the application of CBD-synthesized CuS films in devices such as solar cells, photothermal converters, and near-infrared sensors.