First-Principles Investigation of the Electronic Structure and Optical Properties of NbCuO3 and Ag-Substituted Nb13AgO33 for Optoelectronic Applications

Abstract

The search for advanced semiconductor materials with improved electronic and optical properties is crucial for the development of modern optoelectronic and photocatalytic devices. In this study, density functional theory (DFT) calculations were carried out using the CASTEP code within the GGA-PBE framework to investigate the structural, electronic, and optical properties of pristine NbCuO₃ and Ag-substituted Nb₁₃AgO_33. A plane-wave cutoff energy of 450 eV and a 4×4×4 Monkhorst–Pack k-point mesh were employed throughout the calculations. Structural optimization confirms that both compounds crystallize in the triclinic P1 crystal system. The electronic band structure reveals that Ag substitution reduces the band gap from 1.08 eV to 0.83 eV, indicating enhanced electronic conductivity and easier charge-carrier excitation. TDOS and PDOS analyses show significant hybridization between Nb-d, Cu-d, Ag-d, and O-p orbitals, with Ag introducing additional electronic states near the Fermi level. Optical calculations reveal enhanced absorption, dielectric response, optical conductivity, refractive index, and reflectivity upon the incorporation of Ag. These enhancements suggest stronger interaction with visible light and improved optoelectronic performance. Overall, the results indicate that Ag substitution effectively tailors the properties of NbCuO₃, making Nb₁₃AgO₃₃ a promising material for photovoltaic, photocatalytic, and other optoelectronic applications.