Effect of structural and Eu3+ amount in TiO2 semiconductor material on downconversion photoluminescence properties

Abstract

The search for new materials for application in energy production and conversion has identified inorganic oxides doped with rare earth ions as promising candidates for the construction of photovoltaic devices for energy conversion. This work presents the synthesis of TiO2 powders doped with Eu3+, using propylene glycol in the reaction medium, changing the europium percentage at 0.2, 3 and 7 mol%, and heat-treated at 700, 750, 800 and 900 °C for 8 h. The results of X-ray diffraction showed the formation of TiO2 polymorphs (anatase and rutile), both belonging to the tetragonal system and also the formation of europium titanate. The Rietveld refinement showed the deformation of the network parameters and volume of the unit cell, as well as the percent composition of the phases. Raman spectroscopy corroborated the results of XRD. Photoluminescence results showed that the synthesized materials have intense emission in the red region with the most intense band positioned at 614 nm assigned to the 5D0→7F2 transition of Eu3+ mainly in the sample with 3 mol% of Eu3+ heat-treated at 700 °C. The life time results showed that the photoluminescence of the materials are dependent on the crystalline structure, the host matrix in which the Eu3+ is localized, and the amount of the dopant in the sample. According to the results obtained in this work, the materials have the interesting downconversion effect, being a great absorber of UV–vis energy and converting that energy to the visible region. Materials with these photoluminescence properties associated with the structural properties are very interesting for use in the improvement of solar cells.