Dual-functional p-NiO@CuO/n-si heterostructures for MIS photodiodes under varying light intensities and photocatalytic degradation of Rhodamine-B under visible light

The NiO@CuO nanocomposite (NC) was synthesized via an ionic precipitation route and systematically characterized to confirm its structural, optical, and chemical properties. XRD revealed cubic NiO and monoclinic CuO phases with an average crystallite size of 23.25 nm, while UV–Vis analysis showed an indirect band gap of 1.29 eV. XPS further verified the elemental composition and oxidation states of Ni, Cu, and O. The cross-section revealed a well-adhered NiO@CuO particles, and TEM/SAED results showed an agglomerated, polycrystalline nature. The 30 mg NiO@CuO NC exhibited efficient photocatalytic degradation of Rhodamine-B (RhB), achieving 88.72% at pH 9 ± 0.1. Radical quenching studies confirmed ^•OH as the dominant reactive species. When fabricated as a NiO@CuO/n-Si photodiode, the device demonstrated strong photoresponse under illumination, with an ideality factor (n) of 3.84, barrier height (Ф_B) of 0.73 eV, responsivity (R) of 361.52 mA/W, and detectivity (D^*) of 2.87 × 10¹¹ Jones at 100 mW/cm². These results highlight the potential of NiO@CuO NC for photocatalytic and optoelectronic applications.