Regular Article

Synthesis and characterization of nanocrystalline CdS thin films for highly photosensitive self-powered photodetector

¹ Institute of Nano-Optoelectronics Research and Technology (INOR), School of Physics, Universiti Sains Malaysia, 11800 Penang, Malaysia
² Departments of Pharmacology and Toxicology, College of Pharmacy, University of Kufa, Najaf, Iraq

^a e-mail: mhjusm@gmail.com

Received: 6 August 2015
Revised: 23 October 2015
Accepted: 1 March 2016
Published online: 1 April 2016

Abstract

A self-powered highly photosensitive photodetector based on a nanocrystalline CdS thin film was fabricated using a microwave-assisted chemical bath deposition. In this study, highly uniform nanocrystalline CdS thin films were grown on Si(1 0 0) substrates from aqueous solutions of cadmium chloride (CdCl₂) and thiourea [SC(NH₂)₂], which served as cadmium Cd²⁺ and sulfur S^2- ions sources, respectively. Structural, morphological and optical analysis revealed that good-quality nanocrystalline CdS thin films were synthesized. Current-voltage (I-V) measurements of the fabricated photodetector showed a significant sensitivity to visible light at zero applied voltage, indicating that the fabricated device is a self-powered photodetector. The device was highly photosensitive to low-power visible light; it showed a sensitivity of 97.2 × 10³ to (1.20 mW/cm²⁾ 500-nm light, without an external bias. Photoresponse measurements demonstrated the highly reproducible characteristics of the fabricated photodetector with rapid response and baseline recovery time. This work introduces a simple and low-cost method for fabricating a rapid-response, highly photosensitive photodetector with zero power consumption. The mechanism of self-powered photodetectors is discussed.