Enhanced UV emission of solution processed highly transparent Alq3/ZnO hybrid thin films

Abstract

We deposited the highly transparent tris-(8-hydroxyquinoline)aluminum(Alq3)/ZnO hybrid thin films by spin-coating process. The hybrid thin film with Alq3/ZnO molar ratio of 0.5 × 10−3 exhibits the higher transparency of 90% at 550 nm and it is slightly reduced for increasing Alq3 molecules due to the adsorption of Alq3 on the ZnO grain boundaries. The adsorption of incorporated Alq3 molecules on grain boundaries of ZnO creates Alq3 capped ZnO nanoparticles in the hybrid film. The X-ray diffraction studies reveal the textured crystalline property of the films with decreased crystallite size upon increasing Alq3 content. Fourier transform infrared studies confirm the increasing content of luminescent quencher (carbonyl group) formed in Alq3 molecule for increasing Alq3 in the films. The photoluminescence study shows a fourfold enhancement in the band-edge emission (387 nm) of ZnO upon increasing Alq3 content in the hybrid films, attributing the energy transfer from Alq3 molecule to ZnO when excited by 324 nm wavelength. These studies show that the excited state energy of adsorbed Alq3 molecule may be non-radiatively transferred to ZnO via luminescence quencher, enhancing a fourfold UV emission (387 nm) of ZnO in the hybrid thin films.