Hexagonal CuAlO2 for advanced optoelectronics: Insights from first-principles structural, electronic and optical analysis

In this study, we employ first-principles simulations based on density functional theory (DFT) with a Hubbard U correction (LDA[Formula: see text]U) to investigate the structural, electronic and optical properties of delafossite CuAlO 2 in its hexagonal 2H phase. Our calculations yield optimized lattice parameters in good agreement with experimental data, revealing an indirect electronic band gap of approximately 2.4[Formula: see text]eV and an optical band gap of about 1.9[Formula: see text]eV. The optical properties of CuAlO2-2H reveal strong anisotropy, driven by its layered delafossite structure. The dielectric function shows a dominant absorption peak at [Formula: see text]4.4[Formula: see text]eV for light polarized perpendicular to the c-axis ([Formula: see text], attributed to O 2p [Formula: see text] Cu 3d interband transitions, while the parallel component ([Formula: see text] exhibits a weaker, blue-shifted peak around 5.0–5.2[Formula: see text]eV, linked to O 2p [Formula: see text] Cu 3p transitions. This anisotropy results in a higher static dielectric constant (1.7 versus 1.2), enhanced optical conductivity in the perpendicular direction and strong birefringence (3.67) and linear dichroism (5.21). The absorption coefficient, extinction coefficient and reflectivity spectra confirm a pronounced absorption edge near 3.2[Formula: see text]eV and strong UV absorption near 5[Formula: see text]eV, with up to 21% reflectivity, underscoring the material’s directional and energy-dependent optical behavior.