CNN
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As summer temperatures in Osaka, Japan approach 100 degrees Fahrenheit, staff at Expo 2025 are beating the heat with their sun-powered utility vest.
Developed by Toyota Group company Toyoda Gosei and working with solar cell startup Enecoat Technologies and textile maker Seiren, the utility vest is equipped with ultra-thin, extremely flexible solar panels each weighing less than 4 grams.
These solar “films” differ from silicon panels installed in roofs and solar farms, which account for 98% of today’s solar energy market. Instead, they are made of perovskite, a family of crystals that share the same characteristic structure.
Perovskite solar cells are lighter, cheaper to produce, and can be tuned to absorb a wider range of light, including visible and near-infrared. They can even be charged “in shade, with rainy and cloudy weather.”
In the lab, Enecoat’s solar film achieves 21.2% efficiency, with about a fifth of solar energy being converted to electricity. It is currently being tested under actual conditions of the Expo.
The team collects daily data on how it responds to various climatic conditions such as solar radiation and temperature, and the performance of the mobile battery that connects it.
According to Fuki, the project is the “world’s first initiative” to integrate Perovskite Solar cells to wearables. “We hope that people who work in environments where electricity is not easily available without solar power will use it and wear it,” he adds.
Perovskites are found in nature or made in laboratories, and their use in solar cells was first demonstrated in 2009 by Japanese researchers.
In a lab setup, perovskites achieve power conversion efficiency of over 26%. This is roughly the same as today’s best-performing silicon solar panels, where efficiency limits have been achieved.
Tamotsu Horiuchi, director and chief technology officer of Enecoat Technologies, said one of the greatest benefits of Perovskites is its ability to “generate power indoors or in low-light environments.”
“Indoors, instead of sunlight, LEDs, fluorescent lights or similar lights are used to generate electricity,” says Horiuchi. And because they are more flexible and lighter than silicon panels, “you can install solar panels where they were previously impossible,” he adds.
The best isn’t the only demonstration of perovskite at the expo. Polish Company Saule Technologies deploys power street lights, security cameras, digital signage, wireless charging, and curved solar cells to “smart poles,” where Japanese company Sekisui Chemical demonstrates a 1-million solar film on the roof of the event.
At the Panasonic Group Pavilion, perovskite solar cells sandwiched between layers of glass are converted into artistic facades to provide durability, introducing the aesthetic potential of the technology.
“Current (silicon) solar panels are difficult to install in the living space,” says Yoshiteru Hara, technical director at Panasonic Pavilion at Expo 2025 Osaka. “We need to balance design with power generation efficiency.”
Japan is investing heavily in perovskite technology to achieve its ambitious goal of generating 20 gigawatts of solar energy by 2040. The country is the world’s second largest producer of iodine, an important component of perovskite, and the country’s mountainous regions limit the potential development of traditional solar farms that require vast amounts of flat land.
However, despite its benefits, perovskites break down faster than silicon when exposed to heat, moisture or ultraviolet rays, losing efficiency in years, months or weeks.
“At the moment, everyone is working on stability. That’s the only thing that perovskite lacks and we haven’t compared it to silicon yet,” says Dr. Hasini Perera, a graduate researcher at the University of Surrey’s Advanced Technology Institute, where she studies perovskite.
Researchers are looking for a variety of ways to make perovskites more durable, such as adding “stabilizing agents” and wrapping the film in protective layers such as glass. Increases the lifespan of the material by 10 times.
Another challenge with perovskites is that they contain lead. Research has shown that this can pose environmental risks, but Perera says that lead leakage is very unlikely, especially with robust encapsulation methods.
However, I only use perovskite There is still a long way to commercialize and is already improving existing panels. Last year, Oxford PV, a company spun from the Oxford University Faculty of Physics, launched the first commercial perovskite-on silicon tandem panel in the United States, providing up to 20% more energy than standalone silicon cells.
“That’s a huge step forward for Perovskite,” Perera says.
The ability to bring energy generation closer to urban areas near where Perovskite is using will also make future cities more efficient, according to Horiuchi, chief technology officer at Enecoat.
“It would be more effective to use the electricity generated there to power the building itself (on site),” says Horiuchi. With a smartwatch or smartphone. I think it’s a good thing to develop it like that. ”
