Electrodeposited polymer encapsulated nickel sulphide thin films: frequency switching material

Polyvinylpyrrolidone (PVP) encapsulated nickel sulfide (NiS) thin films have been synthesized electro-chemically from aqueous solution of hydrated nickel chloride (NiC(l)2, 6H(2)O), thioacetamide (CH3C(S) NH2) (TAA) and polyvinylpyrrolidone (PVP). Surface modification of nickel sulfide (NiS) thin films was achieved by this polymer encapsulation. X-ray diffraction (XRD), high resolution transmission electron microscope (HRTEM), field emission scanning electron microscopy (FESEM) and Energy dispersive X-radiation( EDAX) techniques were used for the characterization of thin films. Infrared spectroscopy (IR) confirmed the formation of polymer encapsulated semiconductor. Frequency switching generation study shows that the encapsulated material could be used as a frequency switching device that generates a frequency similar to 50 Hz under 1 Sun illumination. Encapsulation with PVP causes surface modification that reduces the surface states and barrier height. As a result, the width of the depletion region decreases. So the number of electron-hole pairs increases. Consequently, the number of excitons and exciton related emission increases and this leads to reduction of recombination process and shows photo induced frequency switching phenomenon. (C) 2014 Elsevier B.V. All rights reserved.