Preparation and Characterization of CdS and PbS Chalcogenides Compounds and n-CdS/p-PbS photodiode

Abstract

In this study, a chemical bath deposition method (CBD) is used to synthesize CdS nanocrystalline thin films onto FTO substrate using two temperatures of 70 and 80 ºC for 1h of preparation time. PbS nanocrystalline thin films are also prepared using CBD using temperature of 35 ºC for 2h. XRD measurements confirmed that the prepared CdS and PbS thin films are polycrystalline with hexagonal phase for CdS and cubic for PbS. Scanning Electron Microscope images show increasing particles size of CdS thin films with increasing temperature of preparation and the films became more adherent on the substrates without pinholes or vacancies. Optical properties are investigated through UV-Visible Spectroscopy and found decreasing in the transmittance of prepared thin films with increasing temperature. Energy band gap calculated for CdS and PbS nanocrystalline thin films found with values higher than bulk value indicating to due to the quantum confinement effect. Photoluminescence spectra of prepared CdS nanocrystalline thin films appeared sharp emission beak at around 550 nm for all samples indicating high crystallinity. Photoresponse 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 of 16833, responsivity of 1.44 mAW−1, and a low rise/fall time of 0.284/0.298 s.