Enhanced structural, optical, electrical, photocatalytic, and scavengers test of Er-doped ZnO thin films via dip coating for optoelectronic and environmental applications under UV and sunlight exposure

This study explores the impact of erbium (Er) doping on the structural, optical, electrical, and photocatalytic properties of ZnO thin films synthesized via the sol-gel dip-coating method. X-ray diffraction (XRD) confirms a hexagonal wurtzite structure, with peak shifts indicating strain induced by Er incorporation. Notably, a secondary Er-related phase emerges at higher doping levels (10 % and 15 %), suggesting the solubility limit of Er in the ZnO matrix. Scanning electron microscopy (SEM) reveals that moderate doping (2–5 %) improves film uniformity, while excessive Er content (10 % and above) leads to porosity and grain boundary defects. Photoluminescence (PL) spectra show enhanced near-band-edge (NBE) emission (405–416 nm) with increasing Er content, peaking at 15 %, while defect-related emissions (486 nm and 528 nm) indicate changes in charge trapping mechanisms. Electrical analysis via impedance spectroscopy demonstrates improved conductivity, with a decrease in parallel resistance (Rp) up to 10 % Er, followed by an increase at 15 % due to excess defect formation. Photocatalytic experiments using methylene blue (MB) under UV and sunlight irradiation reveal enhanced degradation efficiency, with 2 % Er-doped ZnO performing best under UV light and 10 % Er showing optimal performance under sunlight. Kinetic analysis follows a pseudo-first-order reaction model, Scavenger experiments confirm that hydroxyl radicals (•OH) playing a dominant role under UV irradiation. These results highlight the critical role of Er solubility in tuning ZnO’s properties, making Er-doped ZnO a promising material for optoelectronic applications and environmental remediation.