Characterization of Erbium and Ytterbium Co-doped TiO2 Synthesized Using the Sol-gel Process for Photon Up-conversion Applications

Abstract

TiO2-based up-conversion materials dually doped with 0.2%Er3+ and 10/12%Yb3+ were synthesized using the sol-gel method. The samples were subjected to a calcination process at 500 °C for 2 hr. X-ray diffraction, scanning electron microscopy, UV-VIS diffuse reflectance spectroscopy, and X-Ray Photoelectron Spectroscopy were employed to investigate the effect of dopant concentration on the morphology, crystal structure, and up-conversion properties of the prepared samples. The results indicate that the prepared doped samples retained the anatase TiO2 crystalline phase and did not show any significant difference in morphology. Moreover, the band gap energy of TiO2 was found to decrease from the typical 3.2 eV (pristine TiO2) to 3.17 and 3.03 eV for the 0.2%Er3+ with 10 and 12%Yb3+ dopants, respectively, which can be attributed to the presence of Yb4f valence edge states. The Er4f state exhibited a transition absorption state in the near-infrared light range, indicating its crucial role in the potential up-conversion mechanism of the prepared doped samples.