Deposition time dependent physical properties of semiconductor CuO sprayed thin films as solar absorber

This study aims to develop copper oxide (CuO) films on standard glass substrates using the spray pyrolysis technique and investigate the effect of different deposition times on their structural, morphological, wettability, optical, and electrical properties to enhance their optoelectronic characteristics. CuO thin films were fabricated at different deposition times (5 to 20 min) with a substrate temperature of 400 °C. X-ray diffraction (XRD) analysis confirmed the crystalline structure of all deposited CuO films, showing a monoclinic phase with preferential orientation along the (111) direction, indicating a well-ordered atomic arrangement. Atomic force microscopy (AFM) examination revealed the influence of deposition time on the surface morphology, with a low roughness value of 13.315 nm observed for the 10 min film compared to 19.432 nm for the 20 min film. Contact angle (CA) analysis showed a transition from hydrophilic to hydrophobic behavior as the deposition time increased, indicating significant changes in surface properties. This transition to a hydrophobic nature (CA = 105°) for the 20 min sample is important for protecting photovoltaic devices from humidity-related degradation, ensuring long-term reliable operation even in challenging conditions. The transmittance of the film in the visible region was low, indicating high absorbance of CuO. The optical gap decreased from 1.98 to 1.61 eV with increasing deposition time, making films suitable as absorber layers in solar cells. Electrical analysis showed improved conductivity with increasing deposition time, leading to a decrease in electrical resistivity (3.77 Ω.cm) and high charge density (1.269 × 10 16 cm −3 ) for the 20 min film. Therefore, the 20 min deposition film with a hydrophobic character exhibited good p -type electrical semiconductor properties and efficient absorption of solar light, making it promising for thin film solar cell applications.