When you think of solar panels, one of the first things that likely come to mind are solid, flat square slabs destined to find their place under the sun on a rooftop or at a solar farm. But the technology is steadily evolving to become more flexible, and a team of scientists at Pusan National University in Korea has recently developed a prototype solar cell that is fully foldable.

The rigid quality of current solar cells makes it difficult to store them in large numbers or get the tech into everyday appliances such as phones, vehicles, and indoor devices. The only way to allow this technology to be integrated within these items is to make it foldable so it bends at will repeatedly without breaking. This feat, however, cannot be achieved by using traditional conducting materials used in solar cells.

“Unlike merely flexible electronics, foldable devices are subject to much harsher deformations, with folding radii as small as 0.5 mm,” says Professor Il Jeon, one of the study’s authors. “This is not possible with conventional ultra-thin glass substrates and metal oxide transparent conductors, which can be made flexible but never fully foldable.”

To address this problem, the research team identified a promising solution — using single-walled carbon nanotube (SWNT) films, which have high transparency and mechanical resilience. The resulting prototype, which is just seven micrometers thick and can fold to a radius of just 0.5 mm, exceeded the team’s expectations. The device was able to withstand over 10,000 folding cycles without breaking, exhibited 80 percent transparency, and achieved a power conversion efficiency of 15.2 percent.

“The obtained results are some of the best among those reported thus far for flexible solar cells, both in terms of efficiency and mechanical stability,” says Jeon.