Document Type : Research Paper
Abstract
Copper–zinc–tin–sulphide (CZTS) is an environmentally friendly and earth-abundant semiconductor material with significant potential for photovoltaic and optoelectronic applications. In this study, CZTS thin films were deposited on fluorine-doped tin oxide (FTO) substrates using electrochemical deposition followed by spin coating and high-temperature thermal annealing. The influence of annealing temperature on the structural, optical, morphological, and electrical properties of the films was investigated at 150 °C, 300 °C, and 320 °C. The optical band gap values obtained from Tauc plot analysis decreased significantly from 3.80 eV at 150 °C to 2.26 eV at 300 °C and further to 2.23 eV at 320 °C, indicating enhanced visible-light absorption and improved semiconductor behavior with increasing annealing temperature. The XRD results revealed progressive improvement in crystallinity, with the film annealed at 320 °C exhibiting the highest degree of crystal ordering and the most intense diffraction peaks. SEM micrographs showed a transition from small, irregularly distributed grains at 150 °C to larger, more compact, and uniformly distributed grains at 320 °C, confirming enhanced grain growth and reduced defect density. Hall-effect measurements indicated improved electrical conductivity, higher carrier mobility, and lower resistivity as the annealing temperature increased. Optical studies further demonstrated that the 320 °C sample possessed the highest absorbance and lowest transmittance among the investigated films, reflecting superior light-harvesting capability. Thermal annealing significantly enhanced the crystallinity, grain growth, optical absorption, and electrical performance of the CZTS thin films. The sample annealed at 320 °C exhibited the most favorable optoelectronic properties, demonstrating its suitability for thin-film solar cells, photodetectors, and other advanced optoelectronic devices.
