A Combined Experimental and Numerical Study on Copper Oxide Thin Films: Oxygen Flow-Driven Phase Tuning and Solar Cell Efficiency

This study investigates copper oxide thin films, deposited by reactive DC magnetron sputtering at room temperature, for use as absorber layers in thin-film solar cells. Films are synthesized under varying oxygen flow rates (16–33%). Structural analysis (X-ray diffraction, Raman) reveals a phase transition from mixed Cu₄O₃CuO to phase-pure monoclinic CuO at 23% oxygen, correlating with enhanced crystallinity. Atomic force microscope shows oxygen flow-influenced film morphology, correlating with crystallite growth. Optical properties vary with oxygen flow: lower flows improve absorption, while higher flows increase transmittance, indicating reduced defect density. The optical bandgap ranges from 1.73 to 1.98 eV in line with phase changes. X-ray photoelectron spectroscopy further confirms the presence of Cu₄O₃ at low oxygen flows and CuO at high oxygen flows, validating the observed phase evolution. Hall measurements demonstrate that oxygen flow significantly tunes the electrical properties, with optimal values observed at 23–28% oxygen. Using these parameters, SCAPS-1D simulations of TiO₂/CuO solar cells predict a 22.8% power conversion efficiency and 89.3% fill factor for a 5 μm CuO layer with a 1.73 eV bandgap. Overall, the findings demonstrate the precise control over CuO thin film properties through oxygen flow tuning, underscoring their considerable potential for high-efficiency solar energy applications.