Transparent Photovoltaic Arrays of ZnO/NiO Cells for Energy Harvesting

The generation and transformation of essential energy sources such as electricity, solar, wind, and thermal energy have been pivotal for human life. However, due to the limitations of conventional energy sources, the focus on renewable energy generation and its integration with human interfaces has grown significantly. Transparent photovoltaics (TPVs), which enable the direct conversion of light energy into electrical energy, have been extensively studied for applications in areas like building windows and automotive glass. Since energy usage in buildings constitutes approximately 40% of total energy consumption, the importance of building-integrated transparent photovoltaics (BITPVs) has become increasingly apparent. BITPVs offer a unique advantage by producing energy transparently without taking up additional space or obstructing visibility.
This study focuses on transparent solid-state photovoltaics utilizing transparent oxide (TO) materials for energy generation and storage. TO materials, including ZnO, ITO, AZO, IGZO, NiO, and Ga2O3, have wide energy bandgaps, allowing them to block harmful ultraviolet (UV) radiation while maintaining transparency. By absorbing UV light, these materials can protect against health risks such as skin cancer and eye diseases while preventing discoloration of furniture and interior materials. Furthermore, TO materials are non-toxic, widely available, and highly stable, making them versatile for use in diverse applications such as solar cells, displays, and light-emitting diodes (LEDs). Among these materials, ZnO and NiO were selected for use in the heterojunction of TPV devices due to their wide bandgap and superior stability.
In our research, we developed a transparent TPV device structure comprising FTO/n-ZnO/p-NiO/silver nanowires (AgNWs)/ZnO, which integrates a transparent p–n junction (ZnO/NiO) with transparent electrodes. This design minimizes the spatial footprint while optimizing electrical efficiency for energy storage when connected in arrays. To create a stable, integrated TPV device, we employed a metal sputtering method to fabricate a module array. This approach significantly increased voltage output per unit area, presenting a groundbreaking opportunity for seamless integration of TPV systems into energy storage solutions.