Tinted Car Windows to Produce Power with Translucent Solar Cells

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The recently developed technology to produce power with a translucent solar cell while blocking heat is anticipated to realize multiple applications for vehicle tinting and building windows and doors. 

The translucent solar cell technology was developed by a team led by Prof. Yoo Seunghyup of the School of Electrical Engineering at KAIST.   

The technology is characterized by the ability to generate electricity while allowing penetration of visible rays and selectively reflecting infrared rays (heat rays). 

Due to the very nature of solar cells to produce power by absorbing light, the translucent cells that penetrating light are bound to result in reduced efficiency. It is difficult to produce the existing commercialized solar cells based on crystalline silicon in translucent forms.

For photoelectric conversion, the research team used a perovskite, which comprises organic and inorganic composites and is regarded as a future solar cell material, and also used transparent electrodes on both sides to complete a translucent solar cell.   

In particular, the transparent electrode on one side applied metal-based multilayered thick films with a dielectric-metal-dielectric structure that the research team has applied to electronic devices for years.  

Light usually cannot penetrate metals. To address this issue, the researchers realized transparent electrodes by making thin films that are only tens of nanometers thick and placing upon them dielectric layers with a high refractive index to reduce reflection.

By precisely adjusting the thickness of each layer of the transparent electrodes, the research team completed the design to allow penetration of visual rays and reflect the invisible rays.   

From measurement results, the researchers found that the new solar cells recorded a 7.4% average penetration ratio of visible rays, which is a similar level to vehicle tinting films, and 13.3% photoelectric conversion efficiency. In addition, the total solar energy rejection (TSER) to evaluate the performance of tinting films was 89.6%, similar to the performance of expensive tinting films.   

 “With additional optical design, the solar cells we developed can have different colors and be made in film types,” explained Prof. Yoo. “Then we will be able to upgrade the aesthetic and smart aspects of the windows of vehicles and buildings.”  

This research was jointly conducted with the research team led by Prof. Park Nam-Gyu of the School of Chemical Engineering at Sungkyunkwan University.  

The study was sponsored by KAIST’s climate change research hub project, and the outcomes were published as a cover feature of the July 20 issue of Advanced Energy Materials, with the title “Empowering Semi-Transparent Solar Cells with Thermal-Mirror Functionality.”