Unique physico-chemical characteristics of TiO₂ containing rhenium for advanced energy storage and optoelectronic devices

Introducing rhenium (Re) into inorganic semiconductor compounds offers an effective approach to enhancing their performance in green energy and optoelectronic applications. A detailed understanding of this mechanism is essential for tuning the intrinsic properties of such materials. In this work, we synthesized and characterized both simple and complex inorganic compound in pellet and thin-film forms, systematically examining the effects of varying dopant levels on structural, optical, and electrical properties. The materials were analyzed using X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM, TEM), X-ray photoelectron spectroscopy (XPS), impedance spectroscopy (IS), and UV–visible spectroscopy. XRD confirmed the anatase phase for all samples, with higher Re concentrations slightly reducing crystallite size while improving homogeneity and densification. XPS revealed the formation of Ti³⁺ states and oxygen vacancies, which are critical in modifying the electronic structure and facilitating charge transport. Impedance measurements demonstrated semiconducting behavior, with decreasing resistance at elevated temperatures, consistent with thermally activated conduction. Optical characterization showed a redshift in the absorption edge and a decrease in the bandgap from 3.10 eV (undoped) to 2.80 eV (4 % Re-doped), attributed to defect-induced intermediate states and impurity bands. Additionally, the films exhibited a high dielectric constant and non-Debye relaxation behavior, reflecting a distribution of relaxation times due to grain boundaries and intrinsic defects. Overall, this study highlights how controlled addition of Re can effectively tailor the structural, optical, and electrical characteristics of providing valuable guidance for its implementation in advanced energy storage, photocatalysis, and optoelectronic devices.