Light scattering and photosensitivity characteristics of nanocrystalline Zn1−xCdxS (0 ≤ x ≤ 0.9) films for photosensor diode application

Nanocrystalline Zn1−xCdxS (0 ≤ x ≤ 0.9) thin films were synthesized by low cost dip coating technique for optoelectronic application. Optical absorption characteristics of the prepared films were investigated by spectrophotometric measurements and the values of the optical band gap and Urbach energy were determined. The optical absorption measurements indicate that the absorption mechanism is due to allowed direct transitions and Urbach energy values changes with Cd-content. Quantum confinement in strained films with various Cd content values was investigated and the optical results showed that the average diameter of nanoparticles ranges from 5.7 nm to 14.5 nm. Values of the absorption edge were found to shift toward the higher wavelength region and hence the direct band gap energy varies from 4.00 eV for the ZnS film and 2.55 eV for the Zn0.1Cd0.9S film. A light scattering model of the films was explained by the simplest model on the basis of Rayleigh scattering theory. Heterojunctions of Zn1−xCdxS (0 ≤ x ≤ 0.9)/p-Si showed photovoltaic and photosensing characteristics depending on the Cd-content. The main photovoltaic parameters were investigated as a function of Cd content under illumination of 100 mW/cm2.