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High-efficiency silicon solar cells go on a roll

DAILY SCIENCE

High-efficiency silicon solar cells go on a roll

Lightweight and flexible, these solar cells could power airships and drones, or be easily integrated into electric vehicles and building facades
June 1, 2023

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Solar panels are powering an increasing number of homes around the world as solar power prices go down. Americans alone installed enough solar panels in 2022 to power 22 million homes. But those shiny blue solar panels remain relegated to rooftops because they are rigid and bulky.

Now, researchers have developed a way to make flexible solar cells that are just as efficient as their conventional rigid counterparts. “We hope that this will further motivate development of applications such as self-powered aircraft and energy production in buildings and vehicles,” wrote Wenzhu Liu and Zhengxin Liu of the Shanghai Institute of Microsystem and Information Technology in China in a research highlight about the new manufacturing process they report in the journal Nature.

Scientists first developed solar cells almost 70 years ago. The most efficient commercial solar cells, which convert sunlight into the most electricity, are made from crystalline silicon wafers. These are also the most robust, able to withstand extreme climates. Thinner, flexible solar cells that exist today are made of materials that are either not very efficient or that deteriorate in heat and humidity.

Flat, stiff crystalline silicon solar panels have limited applications, though. They could not, for instance, be used in solar-powered aerial vehicles, or be integrated into building facades or mounted on cars to provide energy. But researchers have been unable to make flexible crystalline silicon solar cells, because the silicon wafers used to make the cells are mechanically brittle.

Powered by flexible and lightweight high-efficiency silicon solar module mounted on its curved wing, a drone can fly 20 km high for long-duration tasks.

Liu, Liu and colleagues set out to develop high-efficiency flexible solar cells from crystalline silicon. They treated silicon wafers using two techniques to reduce brittleness. One was a wet chemical process, involving acid, and the other a dry heat-based process. After the treatment, the wafers could be shaken without breaking, “like sheets of flexible paper,” the researchers write.

Using the pliable wafers, the team made 15 centimeters-wide solar cells that had an efficiency of more than 24 percent, about the same as that of commercial solar cells. These flexible cells could be rolled up into a tube just like a sheet of paper.

To showcase the novelty and use of these cells, the researchers assembled them into large 1m x 1m modules, and installed these lightweight, flexible, modules on a drone that could fly at a height of 20km for a long time.

Source: Liu, W., Liu, Y., Yang, Z. et al. Flexible solar cells based on foldable silicon wafers with blunted edges. Nature, 2023.

Image: Nature, Chinese Academy of Sciences, Creative Commons License CC BY 4.0

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