These solar cells can be bent without breaking
Liu Wenju
Solar cells that are as efficient, lightweight and flexible as conventional ones could greatly expand the use of photovoltaics.
Most solar cells in use today are based on crystalline silicon because of their high efficiency and ease of fabrication, but they crack under stress and can only be installed on flat, static surfaces. Existing bending solar cells made of other materials are alternatives, but are significantly less energy efficient.
Now, Wenzhu Liu of the Chinese Academy of Sciences in Shanghai and colleagues have developed a thin, lightweight silicon-based cell that is flexible enough to wrap itself without compromising efficiency.
The research team first created the cells by thinning solar cell silicon wafers by more than 60 percent. This makes it bend like paper, but is less efficient due to reflection. Chemically treating the surface to create microscopic pyramidal irregularities restores this efficiency, but it becomes brittle when bent. Until Liu came up with an idea to fix it.
“One day, when I tore a plastic bag for food, a small notch in the edge of the bag triggered me to wonder if the tendency of the silicon cells to fragment due to mechanical stress could be caused by sharp notches in the edge of the wafer. I wondered if it was possible,” he says.
After filming the treated cells snapping in slow motion, Liu and his team noticed that the cracks started at the edges of the cells in the grooves between the pyramids. Flexing these channels and bending the cell showed that although numerous small superficial cracks accumulated, the cell did not break and remained efficient.
Cells are light enough to be used in drones
Liu Wenju et al. (2023)
Bending cells can be easily manufactured using existing silicon wafer technology and are 95% lighter than rigid cells, so they can be used in walls without compromising the integrity of the building. Liu and his team have tested the cells in extreme environments, including Antarctica, drones flying at altitudes of 20 kilometers, and balloons with strong winds, and found that they performed as well as, and in some cases better than, rigid solar cells. I have confirmed that it works.
Kyle Frona of the University of Cambridge said the study was very impressive. “This opens up silicon to a whole other class of applications, some of which we’ve thought of, and perhaps some of which we haven’t yet considered.”
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