CdSe quantum dots using selenourea as selenium source in polymer matrix

In this paper we have synthesized cadmium selenide quantum dots in aqueous medium at low temperature of 80 °C through chemical route. Three different concentrations of polyvinyl alcohol (PVA) 6, 8 and 10 wt% was used as a capping agent to prevent coagulation in quantum dots. An alternative precursor selenourea was used in place of selenium powder as a selenium source. Thin film of CdSe/PVA nanocomposite was made by spin coating and characterized by UV–Vis spectroscopy; Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and Fourier transform infra red spectroscopy. For electrical measurements temperature dependent DC conductivity has been performed. From UV–Visible absorption measurement it has been observed that on increasing PVA concentration the absorption edge shifts and bandgap calculated comes out to be more than the bulk CdSe material due to quantum confinement effect. This indicates blue shift and reduction in crystallite size with increase in PVA concentration. This tunability of bandgap with size is very effective in solar cell application. SEM/TEM micrograph confirms the zero dimensional shape of the prepared quantum dot with average size in the range of 6 nm. The DC conductivity measurement shows increase in conductivity with increase in temperature which confirms semiconducting behaviour of CdSe quantum dot.