Study of Electroluminescence in Cadmium Sulfide Polymer Nanocomposite Films

Nanocrystalline cadmium sulfide/Polyvinyl alcohol composite films were prepared by chemical route using Cadmium acetate and hydrogen sulfide gas as cadmium and sulfur source respectively. Poly vinyl Alcohal (PVA) used as polymer matrix. The initially loading of cadmium precursor influences the size as well as photoluminescence and electroluminescence properties of the Composite film. The films were characterized by X Ray Diffraction (XRD), Atomic Force Microscopy (AFM) and UV-Visible Absorption spectra. The X-ray Diffraction result showed that CdS nanocrystals embedded in polymer matrix were in a zinc blend cubic structure. The UVVisible absorption spectra of composite film reveal the blue shift in the band gap energy with respect to CdS bulk (2.42eV) material owing to quantum confinement effect. The Photoluminescence emission spectra show the green light emission at 510 nm arising from the defects states due to excess of cadmium or sulfur anion vacancies. Electroluminescence study indicates enhanced emission with low turn on voltage for higher loading of cadmium in polymer matrix due to increased oscillator strength. When higher electric field is applied, light emission start due to acceleration collision mechanism by charge carries inside the composite film.