Researchers Develop Solar Window Thanks to Hole Punching

The solar cells demonstrated power conversion efficiency of as much as 12.2%.
Donna Fuscaldo

Forget rooftop solar panels to generate energy, South Korean researchers think solar windows will be a driver of adoption in the future. 

But to make it a reality the solar windows would need to overcome some challenges, including a reddish hue produced by transparent solar cells and a reduction in efficiency when placed vertically.


Solar windows closer to becoming a reality 

A team of researchers led by Kwanyong Seo, a professor of chemical engineering at the Ulsan National Institute of Science and Technology (UNIST), came up with a new method to make solar windows by punching tiny holes into the crystalline silicon wafers. They believe their work will pave the way to the development someday of solar windows. 

"Crystalline silicon (c-Si) is one of the best candidates to develop transparent solar cells with high efficiency and stability because conventional c-Si solar cells are known to exhibit high efficiency and long-term stability compared with other solar cells. However, the opaque characteristic of the c-Si wafer hinders the development of transparent solar cells using c-Si," the team of researcher wrote in a paper published in Journal Joule. "We present a novel approach to develop neutral-colored transparent c-Si solar cells that exhibit the highest efficiency among neutral-colored transparent solar cells developed to date." 

Solar windows have 12% efficiency, closing in on solar panels

To overcome the challenges the researchers developed a neutral-colored transparent c-SI substrate using a 200-μm-thick c-Si wafer which is known for being opaque that was combined with microhole-shaped light transmission windows.  Solar cells made using the method demonstrated power conversion efficiency of as much as 12.2% A solar panel has efficency of about 20%. 

Transparent c-Si Substrate
Transparent c-Si Substrate. Source: Joule 

The researchers developed the light transmission windows by taking into account the hole diameters in which visible light wavelengths can be transmitted. They are effective as windows because the efficiency doesn't decline if they are placed vertically. That isn't the case with traditional solar cells. According to one report if a solar cell is placed vertically it may lose as much as 30% of its efficiency.  The aim of the researchers is to increase efficiency to 15%. 

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