Investigation of Structural, Optical, and Photo-Response Properties of Photochemical UV Assisted CBD-Grown CdS Thin Films

The fabrication of a cadmium sulfide (CdS) thin film has been carried out by the chemical bath deposition method under two different conditions, namely, without UV light (nonexposed) and with UV light (exposed). The thin films were found to be uniform, smooth, and homogenous under both growth conditions. Structural and microstructural studies were carried out to understand the mechanism of thin-film growth. Under both conditions, the CdS thin film was found to be face-centered cubic structured. The UV light-exposed CdS thin film acquired acicular or flower-like over structures embedded in the continuous thin film of CdS. The optical band gap increased for the UV light-exposed CdS thin film. In addition, the dark and light currents also increased around 6 times for the UV light-exposed thin film compared to the nonexposed UV light thin films. The highest photosensitivity for the nonexposed and exposed UV light CdS thin film device was ~ 200% and 230%, respectively. A decrease in the photocurrent was detected and probed as a result of traps and the recombination of electrons and holes. Our findings suggest that photoexcitation during chemical reactions could be used as an effective tool to modulate the growth process and, in turn, to tune the optoelectrical properties.