Concentration-engineered spray-deposited Si/NiO heterojunctions for self-powered UV photodetection

Self-powered ultraviolet (UV) photodetectors based on Si/NiO heterojunctions were fabricated using a cost-effective spray pyrolysis technique. The effect of precursor concentration on the structural, morphological, optical, and photodetection properties of p-NiO films deposited on n-Si substrates was systematically investigated. X-ray diffraction and X-ray photoelectron spectroscopy revealed polycrystalline films with coexisting NiO and Ni 2 O 3 phases and mixed Ni 2+ /Ni 3+ oxidation states. Surface morphology and optical reflectance were found to depend strongly on precursor concentration and film thickness. The devices exhibited pronounced rectifying behaviour and enhanced photoresponse under 395 nm illumination. A finite photocurrent at zero bias confirmed self-powered operation driven by the built-in electric field of the heterojunction. The photodetectors demonstrated good sensitivity, repeatability, detectivity, and fast response, highlighting spray-deposited Si/NiO heterojunctions as promising low-cost UV photodetectors. • Si/NiO heterojunction UV photodetectors fabricated via spray pyrolysis • Mixed NiO/Ni 2 O 3 phases confirmed with concentration-dependent microstructure • Finite photocurrent at zero bias demonstrates true self-powered operation • High sensitivity, fast response, and competitive detectivity achieved