KIST develops shape-shifting solar cell that folds and stretches like paper

- 3D solar system built on origami principles achieves stable power output

- Performance holds after 500% deformation and 1,000 repeated cycles

A demonstration of electrode durability. [Provided by KIST]

South Korean researchers have developed a next-generation solar technology that generates electricity stably even when folded or stretched like paper. The advance is expected to significantly expand urban solar power by allowing solar cells to be installed freely on curved building facades and in confined spaces.

The Korea Institute of Science and Technology announced Thursday that a research team led by Lee Philip, director of its Next-Generation Solar Cell Research Center, has developed a "three-dimensional solar metamaterial structure" that maintains power-generation performance while freely changing shape.

Conventional solar systems are mostly built in flat-panel form, making them difficult to install on complex structures such as curved surfaces or protruding elements. Flexible solar cells also faced a separate problem: stretching them significantly either reduced the effective cell area or broke electrical connections.

The research team overcame these limitations by applying the principles of "kirigami" — the art of cutting and folding paper — and "origami," the art of paper folding. The key innovation was designing both the structure and the electrodes simultaneously so that pulling or folding the structure causes it to deform into a pre-designed shape while maintaining electrical connections throughout.

The team also developed a new electrode by anchoring thin silver nanowires to the surface of the structure and combining them with a flexible indium-gallium liquid metal. The silver nanowires maintain the current-carrying pathways while the liquid metal fills gaps in the conductive network.

This design prevents electrical interruptions even when the solar structure is stretched significantly or folded. The team also implemented a technology that allows solar cell modules to be attached and detached without complex wiring.

A mechanical metamaterial system using a modular design that enables large-area scaling and compatibility with a variety of surfaces. [Provided by KIST]

In testing, the solar system showed almost no change in power-generation performance at a deformation rate of 500 percent and maintained its performance after 1,000 repeated deformation cycles.

In a separate configuration with densely arranged solar cells, the team secured a solar cell area equivalent to up to 225 percent of the flat installation footprint. Even when stretched by about 100 percent, the system successfully maintained a solar cell area equal to the original installation footprint.

Durability tests also yielded positive results. No performance degradation was observed after the electrodes were stored indoors for about two years, and the system operated stably through 10,000 repeated folding cycles. The ability to reconfigure electrical connections after replacing a solar cell module also makes the system easier to maintain.

The most promising application for the technology is building-integrated photovoltaic systems. Because solar cells can be fitted to the varying sizes and shapes of exterior walls on different buildings, the technology can extend power generation to spaces where conventional flat-panel solar cells could not reach.

The research team is pursuing commercialization work that combines actual solar cell modules with the modular structure. The team also plans to develop materials with the durability to withstand strong winds and rain, secure mounting capabilities, and fire safety.

Going forward, the team plans to expand the technology's applications to portable power devices that can be folded compactly for storage and unfolded when needed, as well as to vehicles and other mobile platforms. Over the longer term, the technology is expected to find use in space-deployable solar systems, where solar cells folded during launch are unfurled in orbit.

"We plan to combine the modular structural technology we developed earlier with actual solar cell modules to pursue commercialization for architectural use, and then broaden the scope to mobile platforms and deployable systems," said Hwang Seok-jun, a KIST researcher.

"This research is significant in that it involved the simultaneous design of structural movement, form, and electrical function," said Lee Philip, the center director.

The findings were published in the latest issue of the international journal Advanced Materials.

nbgkoo@heraldcorp.com