【International Papers】Aqua-powered hybrid solar cell using amorphous conformal Ga₂O₃ thin-film

      Researchers from the Incheon National University have published a dissertation titled "Aqua-powered hybrid solar cell using amorphous conformal Ga₂O₃ thin-film" in Materials & Design.

Background

      Heterojunction interfaces–spanning solid–solid, solid–liquid and even solid–gas systems–exhibit diverse phenomena that underpin advances in electronics, photonics, and electrochemistry. In solid–solid semiconductor junctions, interfacial symmetry breaking creates a built-in electric field that governs key transport properties, such as rectification and drives photovoltage generation in devices like solar cells. By contrast, solid–liquid interfaces without dominant chemical reactions are largely shaped by ionic and molecular interactions, influencing processes such as water structuring, ionotronic devices operation, and aquavoltaic energy harvesting. Light illumination adds another layer of complexity, as photoexcited charges in the solid can modulate solid–liquid interactions. Continuous photovoltage generation at these interfaces typically requires dipole formation and dynamic charge redistribution.

Abstract

      Clean energy generation is a primary demand to neutralise carbon emissions. Photovoltaics are the best candidates for clean energy. Water is a reliable and sufficient resource for future clean energy generation, as it can be used to enhance photovoltaic performance in a hybrid system. This study design and investigates a novel aqua-voltaic hybrid solar cell by integrating an ultra-thin gallium oxide layer (2.3 nm) with a polycrystalline silicon solar cell under water-based conditions. The amorphous Ga₂O₃ layer grown by sputtering enhances optical absorption, reduces surface reflectance in the ultraviolet (UV) region, and serves as a protective barrier against environmental degradation. Photovoltaic characterisations reveal an efficiency enhancement from 19.04 % to 21.56 % in Si solar cell when Ga₂O₃ and water introduced. Under illumination, electrochemical impedance spectroscopy (EIS) exhibits capacitance and resistance, indicating strong interfacial charge dynamics. These phenomena are attributed to electronic double-layer capacitance, quantum capacitance modulation, and charge redistribution at the Ga₂O₃-water interface. The results illustrate the dual role of water in enhancing charge transport while influencing surface-state interactions, leading to improved solar cell performance. This work provides insights into the interaction of semiconductor-liquid interfaces and offers a efficient hybrid energy harvesting technologies.

Highlights

      ● A new hybrid solar cell is demonstrated by combining silicon with an ultra-thin gallium oxide layer under water-based conditions.

      ● The system shows improved light absorption, reduced surface reflection, and protection from environmental damage.

      ● Solar cell efficiency increases from 19 % to over 21 % due to enhanced charge transport and interfacial effects at the semiconductor–water interface.

      ● This study reveals the dual role of water in boosting performance and offers a pathway to future clean energy harvesting technologies.

Conclusion

      This work demonstrates the functional enhancement of a hybrid photovoltaic system that integrate water with photovoltaic cell. Singificant performance improvements are achieved when Ga₂O₃ is incorporated into polycrystalline silicon solar cells under water-based operating conditions. Designed and implemented Ga₂O₃ serves as an anti-reflective coating, increasing photon absorption and decreasing ultraviolet reflectance, while its protective properties mitigate device degradation in aqueous environments. Water further contributes to efficiency gains by interfacial capacitance, lowering recombination losses, and influencing charge carrier dynamics. Under illumination, the system exhibits complex charge transport mechanisms and distinctive impedance behavior. These findings highlight the importance of interfacial engineering in solar cells and suggest that semiconductor-liquid hybrid systems hold strong potential for next-generation photovoltaic technologies with practical applications. Furthermore, the demonstration of real-time battery charging confirms that the feasibility of this approach for sustainable energy harvesting and storage. Looking ahead, the deployment of photovoltaic systems may extend beyond land to aquatic environments, opening new pathways for solar energy utilization.