Multifunctional Ga2O3 Protective Layer for Enhanced Underwater Silicon Solar Cells

Si solar cells operated in underwater environments suffer from substantial optical reflection losses and performance degradation due to interfacial instability and thermal effects.This study introduces a multifunctional gallium oxide (Ga 2 O 3 ) interfacial layer that enhances optical coupling and interfacial robustness simultaneously.The Ga 2 O 3 layer (n ≈ 1.8-1.9)enables step-index matching between water (n ≈ 1.33) and silicon (n ≈ 3.5), thereby mitigating reflection losses.In addition, its wide bandgap (≈ 4.8 eV) effectively blocks high-energy ultraviolet (UV) radiation, thereby suppressing photo-induced degradation during underwater operation.The amorphous Ga 2 O 3 film, which is synthesized via a low-power sputtering process.To evaluate its efficacy, the optical reflectance and photovoltaic performances of the fabricated devices were systematically characterized under simulated underwater conditions.The sputtered film contributes to an improved interfacial quality and serves as a physical barrier against moisture penetration.With an optimized thickness of 20 nm, the Ga 2 O 3 -coated device achieved a power conversion efficiency of 20.7% underwater, corresponding to an improvement of 8.4% compared with conventional Si reference devices (19.1%) tested under identical underwater conditions.These findings demonstrate a practical approach to developing highperformance and reliable underwater photovoltaic systems.