Solution-based deposition of transparent Eu-doped titanium oxide thin films for potential security labeling and UV screening

Transparent titanium oxide thin films attract enormous attention from the scientific community because of their prominent properties, such as low-cost, chemical stability, and optical transparency in the visible region. In this study, we developed an easy and scalable solution-based process for the deposition of transparent TiOx thin films on glass substrates. We showed that the proposed method is also suitable for the fabrication of metal-doped TiOx thin films. As proof-of-the-concept, europium Eu(III) ions were introduced into TiOx film. A photoluminescence (PL) study revealed that Eu-doped TiOx thin films showed strong red luminescence associated with⁵D₀→⁷F_j relaxation transitions in Eu (III). We found that prepared TiOx thin films significantly reduce the transmittance of destructive UV radiation; a feature that can be useful for the protection of photovoltaic devices. In addition, transparent and luminescent TiOx thin films can be utilized for potential security labeling.