Electroluminescence of CdS nanoparticles-polyvinyl carbazole composites

Abstract

157-160In the present study thin films of CdS nanoparticle-polyvinyl carbazole (PVK) composite have been prepared using chemical method. The absorption spectra and electroluminescence of the films doped with different concentrations of CdS nanoparticle have been measured. The absorption of pure PVK film starts at 290 nm wavelength in which a peak appears at 270 nm, indicating that the optical energy gap of PVK film is 4.26 eV. The absorption onset of CdS-PVK thin films is obtained at 300 nm, which gives the band gap of CdS nanoparticles as 4.13 eV. It is observed that the current varies linearly, whereas EL intensity varies non-linearly with increasing voltage. At a particular frequency, the emission starts at a particular threshold voltage and then it increases rapidly with increasing voltage. At a particular frequency and voltage, the EL intensity of the composite increases with concentration of CdS nanoparticles in PVK polymer and attains saturation at 5% CdS concentration. It is shown that the EL of CdS-PVK composites can be explained on the basis of electron acceleration-collision mechanism