Photoluminescence and electrical impedance measurements on alloyed Zn(1−x)CdxS nanocrystals

A series of wurtzite Zn(1−x)CdxS (x = 0, 0.25, 0.5, 0.75 and 1) nanocrystals with average crystallite size of 1.98, 1.82, 1.80, 2.04 and 2.51 nm, respectively, have been synthesized by simple solvothermal microwave heating method. The photoluminescence yield is found to be higher in the case of alloyed nanocrystals (x = 0.25, 0.5, 0.75) as compared to ZnS (x = 0) and CdS (x = 1). The optical emission is tuned from blue (440 nm) to orange (575 nm) with the increase of Cd composition in Zn(1−x)CdxS nanocrystal. The impedance analysis for Zn(1−x)CdxS nanocrystals has been measured as a function of frequency and temperature. The real and imaginary part of complex impedance plots exhibit semicircle behavior in the complex plane. The AC activation energies of ZnS, Zn0.75Cd0.25S, Zn0.5Cd0.5S, Zn0.25Cd0.75S and CdS nanocrystals were calculated from electrical conductivity analysis and are found to be 0.188, 0.378, 0.456, 0.284 and 0.255 eV, respectively. The conductivity of the alloyed nanocrystals was higher than that of ZnS and CdS.

Figure optionsDownload as PowerPoint slideHighlights
► High yield synthesis of Zn–Cd–S QDs. is achieved by solvothermal-microwave heating.
► The samples are highly crystalline and the average particle size is ∼3.5 nm.
► High luminescent quantum yield and narrow emission spectral widths are obtained.
► High conduction activation energy is observed in the case of Zn–Cd coexisting QDs.