Study of the Optical Properties of Thin Films Deposited on Glass Substrates Using Chemical Bath Deposition in Ile-Ife

Background: Thin film technology is foundational to solar cell fabrication, optical coatings, and semiconductor device manufacturing. Chemical bath deposition is a low-cost, scalable technique well-suited to laboratory settings in developing countries. Aim: This study investigated the optical properties of zinc sulphide thin films deposited on glass substrates using chemical bath deposition at Obafemi Awolowo University, Ile-Ife, South West Nigeria. Methods: Thin films were deposited at bath temperatures of 50, 60, and 70 degrees Celsius. Film thickness was measured using a Tolansky interferometric method. Optical transmittance and absorbance were characterised using a UV-Vis spectrophotometer in the wavelength range of 300 to 900 nanometres. Bandgap energy was estimated from Tauc plots. Results: Films deposited at 70 degrees Celsius showed the highest transmittance of 82% in the visible range. Optical bandgap values ranged from 3.54 to 3.71 eV, consistent with reported values for zinc sulphide. Film thickness increased with deposition temperature. Conclusion: Zinc sulphide films deposited via chemical bath deposition exhibit favourable optical properties for photovoltaic window layer applications. The study supports further investigation of doped films to tune optical and electrical characteristics. Keywords: thin films, chemical bath deposition, optical properties, zinc sulphide, Ile-Ife.