White light emitting transparent double layer stack of Al2O3 :Eu ³⁺, Tb³⁺, and Ce³⁺ films deposited by spray pyrolysis

Aluminum oxide films doped with Tb, Ce and Eu have been deposited by spray pyrolysis using acetylacetonates as precursors. The photoluminescence emission for these films and for double layer stacks is reported. Eu and Tb doped films present the emissions associated with the radiative transitions among the electronic energy states of the triple ionized atom, being dominant the ⁵D₀ to ⁷F₂ at ∼ 612.5 nm for the Eu⁺³ ion, and the ⁵D₄ to ⁷F ₅ at ∼547.5 nm for the Tb⁺³ ion. In the case of Ce doped films, there are two broad bands associated also with the 5d to 4f transitions of this ion at∼400 and 510 nm. These films have low surface roughness lower than 3 nm, and thickness between 50 to 260 nm. The double layer stacks involved an initial Eu doped layer and a second Ce and Tb co-doped layer with different thicknesses. The films are transparent with an optical bandgap of approximately 5.63 eV, the photoluminescence of these stacks presented an overlap of the emissions corresponding to all the dopants when excited with 300 nm light, resulting in a white light emission.