Development of highly sensitive and ultra-fast visible-light photodetector using nano-CdS thin film

Herein, we demonstrated a highly sensitive and ultra-fast photodetector based on nano-CdS thin film synthesized via spray pyrolysis technique. The effect of variations in molar concentration of the sulfur ion sources (thiourea) on the structural and optical properties of the CdS thin films was investigated. The XRD patterns illustrate the hexagonal phase of synthesized CdS thin films with preferred (002)-orientated growth, whereas the film prepared using 0.05 M CdCl2 and 0.03 M of thiourea precursors shows nearly stoichiometric growth of film with lower strain and defect concentration. The band gap of the films was estimated from the optical absorption data which was found to be matching with the standard (2.4 eV) in the above film as compared with other films. A proto-type photodetector device fabricated in the laboratory using optimized CdS thin film shows huge photosensitivity of 104 and ultra-fast response speed of ~ 1.4 ms at 10 V. The results demonstrate the potential of application of nano-CdS thin films for photodetectors and optical switches.