Photoconductivity and photoluminescence of ZnO nanoparticles synthesized via co-precipitation method

Photoconductivity and photoluminescence studies of ZnO nanoparticles (NPs) synthesized by co-precipitation method capped with thioglycerol are carried out. The effect of annealing at 300 degrees C is also studied. The transmission electron micrograph (TEM) and X-ray diffraction (XRD) pattern confirm the hexagonal wurtzite structure of ZnO nanoparticles. The UV-vis absorption spectrum of ZnO NPs shows blue shift of absorption peak as compared to bulk ZnO. The photoluminescence (PL) spectra of assynthesized ZnO NPs show band edge emission as well as blue-green emission. After annealing band edge emission is quenched. Photocurrent is found to vary super linearly at high voltage for both assynthesized as well as annealed ZnO NPs. Time resolved rise and decay photocurrent spectra are found to exhibit anomalous photoconductivity for as-synthesized as well as annealed ZnO NPs wherein the photocurrent decreases even during steady illumination. (C) 2011 Elsevier B.V. All rights reserved.