Fabrication of meso- and macro-porous Y2WO6:Eu3+ phosphor thin films by Pechini-type sol–gel dip-coating method and their characteristic optical properties.

Meso- and macro-porous Y₂WO₆:Eu³⁺ phosphor thin films were fabricated on silica glass substrates by a Pechini-type sol–gel dip-coating method. Precursor solutions for coating were prepared by mixing aqueous solutions of metal salts, ethylene glycol, and citric acid with water–alcohol solutions of a nonionic triblock copolymer (P-123) employed as a structure-directing agent. The kind of the alcohol solvents (methanol, ethanol, or isopropanol) and the amount of ethylene glycol were systematically examined because they were found to be major factors that could influence the shape and size of pores formed in the resulting thin films. The transmittance for the visible light was decreased in the thin films having macropores due to the light scattering. The red photoluminescence of the Eu³⁺ ions could be enhanced in these macro-porous thin films, especially from their surface, by a synergetic effect of increased multiple scattering and suppressed internal reflection of the emission light. The relationship between the microstructure and the optical properties of the porous Y₂WO₆:Eu³⁺ thin films was then discussed based on the experimental results. Highlights: Porous Y₂WO₆:Eu³⁺ phosphor thin films were fabricated by a Pechini-type sol–gel dip-coating method. A nonionic triblock copolymer was added to precursor solutions as a structure-directing agent. The shape and size of pores were varied by controlling organic components of precursor solutions. Red photoluminescence of Eu³⁺ was enhanced with macropores introduced in thin films. [ABSTRACT FROM AUTHOR]