Multifunctional Properties of Rare Earth Doped AlXO₂ Delafossites for Energy Applications

Cu-based delafossite compounds AlXO₂ (X = Cu, Eu, Er) have emerged as technologically important materials for optoelectronic applications due to their unique combination of p-type conductivity and tunable electronic properties. Our comprehensive investigation reveals that these materials exhibit small direct band gaps ranging from 1.2 to 1.8 eV, ideal for solar energy conversion. First-principles calculations demonstrate strong p-d hybridization, characterized by exchange constants N₀β = − 0.19, − 0.12, − 0.14 and N₀α = 0.16, 0.24, 0.31 for Cu, Eu, and Er variants, respectively, indicating dominant exchange field contributions to their magnetic behavior. Optical property analysis in the 0–14 eV range shows significant anisotropy in absorption coefficients and dielectric functions, with notable birefringence effects. Remarkably, these materials demonstrate hydrogen storage capacities of 4.5–5.48 wt%, while thermoelectric calculations predict a figure of merit (ZT) of 0.55 at 600 K. The synergistic combination of favorable optoelectronic properties, magnetic tunability, and energy storage capabilities positions these delafossites as promising candidates for next-generation photovoltaic, spintronic, and energy storage applications. These findings provide fundamental insights into structure–property relationships in ternary oxides while demonstrating their potential for multifunctional device applications.