Electronic structure, optical properties, rectification, and solar photocatalytic performance of CuGeO₃ oxide...

Orthorhombic CuGeO₃ oxide nanostructures were synthesized using a microwave-assisted thermal method and systematically investigated through experimental characterization and first-principles density functional theory (DFT) calculations. X-ray diffraction and spectroscopic analyses confirmed the formation of phase-pure, highly crystalline CuGeO₃ with homogeneous elemental distribution and stable Cu²⁺ and Ge⁴⁺ oxidation states. The optimized crystal structure showed good agreement with the experimental lattice parameters, while DFT calculations revealed a direct bandgap of 2.62 eV with the valence band dominated by O 2p states and the conduction band primarily composed of hybridized Cu 3d and Ge 4p orbitals. UV-Vis spectroscopy yielded an experimental bandgap of 2.53 eV based on a direct-transition Tauc analysis, demonstrating strong ultraviolet-blue light absorption. Under 405 nm illumination, the fabricated devices exhibited stable asymmetric rectifying characteristics, reproducible current switching behavior, and distinct resistance modulation, confirming reliable optoelectronic performance despite minor device-to-device variations. Band-edge analysis indicates that photogenerated electrons and holes generate reactive oxygen species, including superoxide (O₂ ^-) and hydroxyl (OH) radicals, which promote photocatalytic degradation. Consequently, the CuGeO₃ nanostructures achieved approximately 87% degradation of methylene blue within 60 min under simulated solar irradiation. The combined experimental and theoretical investigation suggests that CuGeO₃ oxide nanostructures possess promising electronic, optical, rectifying, and photocatalytic properties, making them attractive candidates for ultraviolet optoelectronic devices and environmental remediation.