Cu-doped ZnO (Zn1
xCuxO, x ¼ 0.00, 0.01, 0.02, 0.03, 0.04, 0.05) nanocrystals were synthesized by icebath
assisted sonochemical method. X-ray diffraction (XRD) analysis of the undoped and Cu-doped
ZnO nanostructures reveals the formation of ZnO hexagonal wurtzite structure for all samples which
confirm the incorporation of Cu2þ ions into the ZnO lattice by substitution. Increasing the Cu concentration
resulted in a contraction of the bond length and the unit cell volume, whereas, the crystallite size
increases by the doping induced grain growth. High-resolution transmission electron microscopy
(HRTEM) images show that the morphology of the pure and doped samples consists of mixtures of
nanorods and nanosheets. The increase of Cu content leads to an improvement of a preferable growth
direction and an increase of both the lengths and diameters of the nanorods. Analysis of the optical
absorption spectra shows that incorporation of Cu ions into the ZnO lattice leads to a red shift of the
optical band gap from 3.45 eV to 3.35 eV and the exciton peak from 3.35 to 3.24 eV. The photoluminescence
(PL) spectrum of the undoped ZnO nanopowders at excitation wavelength (lex) ¼ 325 nm,
reveals near band edge UV emission and defect-related blue and green emission, whereas, the PL
spectrum at lex ¼ 380 nm exhibits only defect-related green and red emission. The incorporation of Cu
leads to a decrease of the PL intensity due to the increase of nonradiative recombination centers. To
explain the mechanism of the PL emission and to identify the different trapping and recombination levels
in the ZnO nanopowders, energy band diagrams were suggested. Raman spectroscopy analysis show that
the increase of Cu content leads to an increase in the number of defects in the ZnO lattice. The direct
current (DC) electrical conductivity measurement reveals a presence of different shallow and deep
trapping levels. In addition, an increase of the electrical conductivity with increasing the Cu content in
ZnO lattice was observed and can be ascribed to the decrease in the activation energy.