[Reading Science] 24-Hour Power Generation Achieved: Transparent Photovoltaic Windows Developed to Produce Electricity Regardless of Time or Weather

Utilizing Sunlight by Day and Indoor Lighting by Night
Overcoming the Limits of Transparency, Efficiency, and Color Rendering All at Once

Domestic researchers have developed photovoltaic window technology that is as transparent as glass but can generate electricity both day and night. This is seen as a significant advancement in next-generation energy production methods that utilize building exteriors and windows.

The research team led by Professor Yongseok Jeon of the Department of Integrated Energy Engineering and the Graduate School of Energy and Environment (Green School) at Korea University, in collaboration with teams from Korea Aerospace University and the Korea Institute of Science and Technology (KIST), announced the development of a "transparent photovoltaic window technology" that maintains transparency while enabling 24-hour power generation.

Research paper image. Distributed Bragg Reflector (DBR)-Silicon Hybrid Photovoltaic Window Structure. Provided by the research team.

Conventional transparent solar cells have structural limitations: increasing transparency reduces power generation efficiency, while increasing efficiency makes them too dark to be used as windows. Additionally, thin-film solar cells often cause color distortion during the light absorption process, posing significant challenges for their application in building-integrated photovoltaics (BIPV).

To address these issues, the research team designed a new structure that combines a Distributed Bragg Reflector (DBR) with a bifacial silicon solar cell. This structure allows visible light to pass through as it would with ordinary glass, while selectively reflecting only the invisible near-infrared light toward the solar cell. As a result, the system maintains window-like brightness while simultaneously improving power generation efficiency.

In particular, by utilizing the characteristics of bifacial solar cells, the team implemented a "24-hour power generation system" that absorbs sunlight during the day and indoor lighting such as LEDs and fluorescent lamps at night to generate electricity. Unlike conventional solar power, which is highly dependent on time and weather, this technology stands out for its ability to use both indoor and outdoor lighting as energy sources.

Research team photo. From the left, Yongseok Jeon, Professor at Korea University Graduate School of Energy and Environment (Green School) (corresponding author), Myunghoon Shin, Professor at Korea Aerospace University (corresponding author), Hyungdeok Ko, PhD at KIST Nanophotonic Systems Research Center (corresponding author). Provided by Korea University.

The photovoltaic window module developed by the research team achieved a light transmittance of 75.6%, ensuring brightness similar to that of real windows. It also attained a color rendering index (CRI) of 93.8%, effectively solving the chronic color distortion problem of existing transparent solar cells.

Professor Yongseok Jeon of Korea University stated, "This study demonstrates that it is possible to utilize not only invisible infrared light but also indoor lighting as an energy source while maintaining window transparency," adding, "This technology can be expanded to various industries, including zero-energy buildings as well as windows for electric vehicles and mobility applications."

The results of this research were published online on November 21 in the international energy journal "Joule" (IF=35.4) under the title "Scalable hybrid solar window with high transparency, high efficiency, and superior color rendering," and were officially published on December 17. The study was supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP) under the Ministry of Trade, Industry and Energy.