Abstract
The ambient stability of copper oxide layers produced through thermal oxidation is a critical factor for their application in advanced photovoltaic devices. This study investigates the long-term stability of thermally grown sodium-doped copper oxides fabricated at 300 °C, 500 °C, and 700 °C. The structural, optical, and electronic properties of these oxide layers were examined after a 30-day period to understand how thermal oxidation temperature and sodium doping influence the durability and properties of copper oxide films. The results indicate that the stability of thermal copper oxide increases with oxidation temperature. The film produced at 700 °C maintained consistent optical properties, work function value, and structural integrity over time, demonstrating their robustness against environmental degradation. In contrast, the layers produced at lower temperatures (300 °C and 500 °C) showed more significant changes due to continued oxidation and adsorption from ambient.