Thermally oxidized gallium nanoparticles as broadband antireflective coatings for GaAs solar cells

The development of efficient and scalable antireflective coatings (ARCs) remains a critical challenge for maximizing the performance of III-V solar cells. Here, we introduce a simple and robust method to fabricate gallium oxide nanoparticles (Ga x Oᵧ-NPs) as broadband ARCs via thermal oxidation of self-assembled hemispherical gallium nanoparticles (Ga-NPs) directly deposited on GaAs substrates. Complete crystalline oxidation and preservation of nanoparticle morphology are confirmed by transmission and scanning electron microscopy, ensuring the structural integrity necessary for reliable optical performance. Reflectance measurements show a ≈30% reduction across the 280–900 nm range compared to bare GaAs. Effective medium approximation simulations, based on AFM-derived coverage and NP height profiles, reproduce the experimental reflectance spectra and validate the graded-index behavior of the nanostructured layer. When implemented on GaAs solar cells, Ga x Oᵧ-NPs yield reproducible enhancements in external quantum efficiency and short-circuit current density, with average improvements of ∼10%. Control experiments confirm that these gains arise solely from the presence of the oxidized NPs. This work establishes thermally oxidized Ga x Oᵧ-NPs as a scalable, plasmon-free ARC solution, offering compatibility with standard device processing and a promising route for light management in III–V photovoltaics. • Facile synthesis of Ga oxide nanoparticles via thermal oxidation of Ga-NPs • Hemispherical Ga-based NPs fully oxidized preserving morphology • Nanoparticles serve as broadband antireflective coatings on GaAs • Reflectance reduced by ∼30%, enhancing solar cell performance 10% • Effective medium simulations validate graded-index antireflective layer