Korea University Develops ‘Transparent Solar Window’ Technology That Generates Electricity Day and Night

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Harnessing Both Sunlight and Indoor Lighting… Overcoming Limits of Transparency, Efficiency, and Color Reproduction Simultaneously

A research team led by Professor Jeon Yong-seok of the Department of Convergence Energy Engineering and the Graduate School of Energy and Environment at Korea University (KU) has developed a “Transparent Solar Window Technology” that maintains window-like transparency while producing power 24 hours a day, regardless of time or weather.

The study, conducted in collaboration with researchers from Korea Aerospace University and the Korea Institute of Science and Technology (KIST), presents a next-generation architectural energy technology where the building envelope itself generates power.

Existing transparent solar cells faced structural limitations: increasing transparency lowered power generation efficiency, while increasing efficiency dimmed the field of view. Furthermore, color distortion during the light absorption process made them difficult to apply as actual windows. The research team resolved these trade-offs through an innovative structural design.

Structural Innovation: Distributed Bragg Reflectors (DBR)

The team designed a hybrid structure combining a Distributed Bragg Reflector (DBR) with bifacial silicon solar cells. This structure allows visible light perceived by humans to pass through while selectively reflecting invisible near-infrared light and directing it toward the solar cells.

Through this, they managed to maintain indoor brightness and visibility while boosting power generation efficiency. Notably, the solar window module recorded a light transmittance of 75.6%, providing a sense of openness similar to standard windows, and a Color Rendering Index (CRI) of 93.8%, achieving color reproduction close to natural light. This is considered a significant achievement in virtually eliminating the color distortion issue typical of transparent solar cells.

24-Hour Power Generation: Day and Night

Another core feature of this technology is its ability to generate power day and night. By utilizing the characteristics of bifacial solar cells, the system absorbs sunlight during the day and captures light from indoor sources like LEDs or fluorescent lamps at night. This enables a stable power supply that is less dependent on weather or sunlight conditions.

[Photo of the Research Team / Provided by Korea University]

The research team believes this 24-hour generation structure will drastically expand the application of Building-Integrated Photovoltaics (BIPV).

Professor Jeon Yong-seok explained, “This achievement proves that we can actively utilize invisible energy sources while maintaining window transparency.” He suggested the potential for expansion into various industrial sectors, including Zero-Energy Buildings (ZEB), as well as windows for electric and autonomous vehicles. This study is being evaluated as a technical turning point that satisfies the three conditions of transparency, power generation efficiency, and color reproduction, blurring the lines between energy production and architectural design.

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