Scientists from the RIKEN Center for Emergent Matter Science and the University of Tokyo have developed a new type of ultra-thin photovoltaic device. The solar cells are coated on both sides with stretchable and waterproof films and are – according to RIKEN - able to provide electricity from sunlight even after being soaked in water or being stretched and compressed.

According to Takao Someya, leader of the research group, the solar cells could provide energy for electric devices which are worn on the body, e.g. sensors that record heartbeats and body temperature in order to provide early warning of medical problems.

The members of the research group developed extremely thin and flexible organic photovoltaic cells. The ultra-thin device was placed onto acrylic-based elastomer and the top side of the device was coated with an identical elastomer, giving it a coating on both sides to prevent water infiltration. The elastomer, while allowing light to enter, prevented water and air from leaking into the cells, making them more long-lasting than previous experiments.

The device has an energy efficiency of 7.9 percent, producing 7.86 milliwatts per square centimeter, as the current density was 13.8 milliamperes per square centimeter at 0.57 volts, based on a simulated sunlight of 100 milliwatts per square centimeter. The scientists soaked it in water for two hours, and found that the efficiency decreased by just 5.4 percent. After compressing by nearly half for twenty cycles while placing drops of water on it, it still had 80 percent of the original efficiency.

The work »Stretchable and waterproof elastomer-coated organic photovoltaics for washable electronic textile applications«, is published in Nature Energy (10.1038/s41560-017-0001-3).