Green photoluminescence from highly oriented ZnO thin film for photovoltaic application

We report here the fabrication of ZnO nanoparticles embedded on glass substrate by sol–gel and spin coating technique. Transmission electron microscope images revealed that the thin film is composed of ZnO nanoparticles. X-ray diffraction data confirms that the fabricated ZnO nanoparticles have hexagonal unit cell structure. The ZnO nanocrystals of the thin film are oriented along the c-axis of the hexagonal unit cell. UV–vis absorption spectroscopy shows that the absorption occurring at 373 nm in the ZnO thin film. The band gap was calculated from the absorption data and found to be 3.76 eV. This band gap enhancement occurs due to size effect in the nanoscale regime. Room temperature photoluminescence spectrum shows strong green emission at 530 nm owing to the singly ionized oxygen vacancy. This green emission was further investigated by annealing the thin film at different temperature. This singular green emission will be very useful in optoelectronic and nanophotonic devices.