Influence of the Cadmium Sulfide Chemical Bath Deposition Temperature on Cadmium Sulfide/Zinc Oxide Thin Films

Abstract

The spin-coating method has been employed for nanostructured crystalline zinc oxide (ZnO) thin film preparation on FTO glass substrates. Cadmium sulfide (CdS) layers were then deposited on the surface via the chemical bath deposition method. To investigate the effect of the formation of the CdS layer on ZnO/FTO, the deposition of these layers was performed at three different temperatures (40, 60, and 80 °C). The synthesized CdS/ZnO composite was found to have homogenously distributed crystalline grains of both ZnO and CdS. The uniform distribution of the grains and the equal molar ratio of the two components resulted in excellent optical and photocatalytic performance. Analysis of CdS/ZnO thin films was performed using XRD analysis, UV-vis spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and linear sweep voltammetry. The best optical, morphological, and electrical properties and the highest photocurrent value of the CdS/ZnO thin films were obtained when the CdS layers were formed at 60 °C. X-ray diffraction characterization revealed that CdS/ZnO thin films crystallized into hexagonal wurtzite ZnO and cubic CdS. The crystallite size of ZnO and CdS/ZnO was ~38 nm and ~19 nm, respectively. The band gap calculated for CdS/ZnO, formed at different temperatures, varies from 2.05 to 2.15 eV.