Hybrid layers of ZnO/lanthanide complexes with high visible luminescences

Zinc oxide based luminescent thin films, prepared at mild temperature conditions and from solutions, with controllable wavelength light emission are of great interest for use in light emitting devices. In the present work mixed ZnO/organic heterocyclic ligand thin films are grown by an electrochemical method. The organic component is codeposited with electroprecipitated ZnO. It is shown that the incorporation of the ligand, a bipyridine dicarboxylate, is due to the presence of the carboxylate groups which allow the anchoring to zinc oxide. The films are macroporous and fibrous. These conducting layers are rendered luminescent by a subsequent adsorption step of different lanthanide ions. The emission wavelength can be adjusted by changing the cation and an intense red emission is observed under UV light illumination with Eu3+ whereas the luminescence is green with Tb3+. Finally, promising results are presented on the stabilization of the emission intensity during storage in air of these hybrid structures by a subsequent treatment with phenanthroline.