Optimization of Thermal Annealing Effect on Sol-Gel-Driven Spin-Coated CdS Thin Films

Semiconducting nanostructured materials are preferred for optoelectronic devices due to their variable optical and electrical properties. Cadmium sulfide (CdS) thin films, due to its direct band gap, are widely used in solar cells, photodetectors, photosensors, etc. This work analyzes the effect of thermal annealing on the optical and structural properties of CdS thin films. CdS thin films are synthesized by a sol-gel spin coating technique while maintaining a constant pH level of the precursor solution. CdS thin films were annealed at 400, 450, and 500°C for 30, 60, and 90 min, respectively. The transmittance of the films varied from 60–89% in the visible region as evident from the UV analysis. The optical band gap lay in the range of 2.43–2.47 eV. The XRD and Raman analysis results reveal that the crystallinity of the CdS thin film increased with the increasing annealing temperature and time of annealing.