Abstract:
A photosensor is an electronic component that detects the presence of visible light,
infrared transmission (IR), and/or ultraviolet (UV) energy. A photosensor which
changes its electrical capacitance in the presence of visible light was developed based
on the photo-dielectric effect of Cadmium Sulphide (CdS). This photosensor was
fabricated by depositing a CdS thin film on Fluorine-doped Tin Oxide glass (FTO
glass). FTO acts as the front electrical contact and an aluminum sheet acts as the back
contact, where a 2.0)im - 3.0)im thick CdS thin film acts as the photo-dielectric
material. Chemical bath deposition method was used for CdS fabrication and the CdS
thin film with optimum photovoltaic and micro structural properties was obtained at a
bath temperature interval of 40 - 45 °C, annealing temperature of 180-220 °C. Film
thickness was varied by adjusting deposition time and the number of coatings.
Thickness variations were determined using a Scanning Electron Microscope (SEM).
The transmittance and absorbance spectra are recorded in the range of 200 nm - 1100
nm. CdS thin film fabricated under optimum conditions resulted in a bandgap in the
range of 2.30 eV-2.40 eV, which is closely agreeing to the theoretical value of 2.42eV.
The photo-capacitance and photoconductivity were measured in a frequency range of
1 kHz to 5 MHz in dark and illuminated conditions. The Cole-Cole plots were
analyzed to identify the most sensitive operational frequency for the device.
Citation:
Kumari, T.I.D., Jayasumana, M.A.S.D., & Attygalle, D. (2019). Development of a photosensor based on photo dielectric effect of cadmium sulphide
[Abstract]. In V. Sivahar & H.S. Sitinamaluwa (Eds.), Dreams to reality through innovative materials (p. 3). Department of Materials Science and Engineering, University of Moratuwa.