Staff at Expo 2025 in Osaka, Japan, are beating the heat with the help of ultra-thin, light, and bendy solar panels that are fitted into utility vests. Developed by the Toyota Group company Toyoda Gosei, in collaboration with solar cell startup Enecoat Technologies and textile manufacturer Seiren, the utility vests are fitted with flexible and thin solar panels that weigh just four grams. These solar panels power neck fans that keep the wearer cool.
These solar films are made out of perovskites, a family of crystals that share the same characteristic structure as silicon. Perovskite solar panels are cheaper to produce and are lighter. These materials can also absorb a broader spectrum of light, absorbing visible and near-infrared light to produce electricity. According to Shinichiro Fuki, director of the Toyoda Gosei team behind the vest, the solar panels can be charged in rainy and cloudy weather, as well as under shade.
In lab conditions, Enecoat’s solar panel has achieved an efficiency of 21.2%, converting a fifth of solar energy into electricity. Now, the material is being tested in outdoor conditions at the Expo. The team is recording data daily on how the perovskite solar panels are responding to solar radiation and temperature. The team is also collecting data about the performance of the mobile battery that it connects to. The battery is expected to fully charge in 5 to 10 hours.
According to Fuki, this marks the first instance of integrating perovskite solar panels into wearable devices. He hopes that people who work in environments where solar power is the only option to generate power will wear this utility vest.
The first instance of using perovskites in solar panels was in 2009, when a Japanese research team designed it. In lab settings, the perovskite panels have demonstrated an efficiency of 26%, comparable to that of the best-performing silicon solar panels currently in use. One of the striking properties of the perovskite is its ability to generate electricity in low-light environments or indoors.
“When indoors, instead of sunlight, the light of LEDs, fluorescent lights, or similar lights will be used to produce power,” says Horiuchi. And because they are more flexible and lightweight than silicon panels, “we can install solar panels even in places where it was impossible before,” he adds — such as roofs that can’t support silicon solar panels, which can weigh up to around 50 pounds (23 kilograms).
There are more demonstrations of perovskite solar panels apart from the vest. Polish company Saule Technologies has deployed curved solar cells on “smart poles” that power streetlights, digital signs, and security cameras. Japanese company Sekisui Chemical has demonstrated one-millimeter-thick solar panels on the roof of the event’s bus terminus.
Silicon solar panels are challenging to install in living spaces. According to Yoshiteru Hara, technical director of the Panasonic pavilion, we need to strike a balance between power generation and design.
Japan is investing heavily in perovskite technology to meet the ambitious goal of generating 20 gigawatts of solar energy by 2040. The nation is the second-largest producer of iodine, which is a key ingredient in perovskite. The mountainous terrain of Japan prevents the country from constructing solar power plants, as it requires a significant amount of flat land. Perovskite solar panels can provide a solution to this problem.
Despite the advantages, perovskite has a major flaw. This material degrades faster than silicon when exposed to heat, moisture, or UV rays. Degradation can occur in years, months, or even weeks in some cases. Scientists are working on increasing the stability of the material, the only point where silicon takes the win. To make perovskite more durable, scientists are adding “stabilizing agents” or encasing the film in protective layers of glass. Another major drawback of perovskites is the presence of lead, which is toxic. Studies have shown that if damaged, perovskites can pose an environmental risk. However, according to Dr. Hashini Perera, a postgraduate research fellow at the University of Surrey’s Advanced Technology Institute, robust encapsulation methods may mitigate lead leakage.
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