【Epitaxy Papers】Surface Wettability Engineering of Ga₂O₃ Thin Films by Oblique Angle Electron-Beam Deposition for Transparent Self-Cleaning Photovoltaic Coatings

      Researchers from Manipal University Jaipur have published a dissertation titled " Surface Wettability Engineering of Ga₂O₃ Thin Films by Oblique Angle Electron-Beam Deposition for Transparent Self-Cleaning Photovoltaic Coatings " in Physica B: Condensed Matter.

Abstract

      The buildup of dust and environmental contaminants on photovoltaic (PV) module surfaces significantly reduces power conversion efficiency, especially in humid and dusty environmental conditions. In this study, nanostructured gallium oxide (Ga₂O₃) thin films are developed as stable, transparent, and naturally hydrophilic self-cleaning coatings for photovoltaic use. Ga₂O₃ thin films were deposited on silicon substrates via electron-beam evaporation under oblique-angle deposition (OAD) conditions at incidence angles (α) of 0°, 10°, and 20°, allowing control over film morphology, phase composition, optical transparency, and surface wettability. Structural analysis shows a shift from mixed α/β-Ga₂O₃ phases at lower deposition angles to phase-pure, thermodynamically stable β-Ga₂O₃ at α = 20°. Microscopy analysis reveals a systematic change from dense, compact films to nanostructured morphologies with increasing α, driven by atomic shadowing and reduced adatom mobility. All the films exhibit low reflectance in the visible range, indicating minimal optical losses for PV window applications. The optical bandgap measures 4.5 eV for the phase-pure β-Ga₂O₃ film deposited at α = 20°. Urbach energy analysis shows an increase in band-tail states in the α = 20° film, linked to higher surface defect density associated with nanostructure formation. Wettability tests reveal a shift toward hydrophilic behavior as the deposition angle increases, with the highest wettability observed for the film deposited at α = 20°. The combination of wide bandgap, reduced reflectance (in the visible range), and improved wettability makes the nanostructured β-Ga₂O₃ thin film suitable as a self-cleaning window layer for PV modules. This deposition approach is adaptable to glass substrates for practical integration in PV modules and needs further investigation.

DOI：

https://doi.org/10.1016/j.physb.2026.418760