University of Zakho

Metal-oxide-based heterojunction solar cells have received burgeoning research interests owing to the prospect of high efficiency, low cost, and environmental benignity. Of all the systems, ZnO heterojunctions with either NiO or CuO have received much interest for next generation photovoltaic devices. This review summarizes the material properties, fabrication methods, interface characteristics, and photovoltaic performances of ZnO/NiO and ZnO/CuO heterojunctions in a comprehensive comparison manner. ZnO, as a wide-bandgap n-type semiconducting and high electron-conductivity material, with properties including optical transparency and chemical stability, has become a good candidate for the ETL layer. Because of its large band gap and high work function, NiO can efficiently extract holes and enhance the stability of devices. These merits make ZnO/NiO hetero-junctions particularly suitable for transparent and UV-active solar cells. By comparison, CuO with a small bandgap and high absorption coefficient in the visible region can also lead to efficient light utilization of ZnO/CuO heterojunctions through type-II band alignment at the expense of becoming more susceptible to interfacial defects and environmental deterioration. In this review, we present a critical overview of physical, chemical, and green-synthesis routes, band-alignment engineering strategies, interface-defect passivation methods, and degradation mechanisms affecting the two systems. This work, which discusses the tradeoffs among optical transparency, absorption efficiency, stability and interfacial recombination inform practical design guidelines for future advances in optimizing ZnO-based heterojunction solar cell devices for next generation of scalable and environmentally friendly photovoltaic technologies.

Human skin is continuously exposed to varying environmental conditions. While it is known that the skin's biophysical properties are influenced by seasonal changes, the impact of these conditions on its electrical characteristics-particularly skin surface susceptance-remains unclear. Therefore, this study aimed to investigate the effects of seasonal variations on skin surface susceptance using a low-frequency electrical technique. The investigation was performed on 46 (23 males and 23 females) apparently healthy volunteers. Readings of electrical skin surface susceptance were taken from the volar forearm in all four seasons between autumn 2024 and June 2025. Seasonal changes had a significant effect on skin surface susceptance, with the highest values recorded in summer and the lowest in winter. In addition, a highly significant (p< 0.05,r= 0.98) positive correlation was established between seasonal temperature and the skin surface susceptance, and a significant (p< 0.05,r= -0.97) negative correlation between seasonal temperature and the skin surface susceptance was obtained. No significant differences were observed between male and female groups in response to seasonal changes, indicating that gender is an unimportant factor in this context. Our results suggest that seasonal variations should be taken into consideration when using the skin electrical technique. In addition, this will be relevant in the applications of skin sensors and dermatology.