Role of defects in the anomalous photoconductivity in ZnO nanowires

The anomalous photocurrent decay in aqueous solution grown ZnO nanowires (NWs) under steady ultraviolet light illumination have been investigated. The photocurrent growth-decay measurements using the above-band and subband gap light excitation energies in the as-grown and annealed NWs show that while a V-Zn-related defect complex is formed by the surface adsorbed H2O molecules, a faster carrier trapping by the surface adsorbed O-2 molecules and a slower carrier recombination at the defect, Zn-i cause the photocurrent decay under steady illumination supported by the results of the photocurrent spectra and photoluminescence measurements. The predicted mechanism has been explained through a model.