VATIS UPDATE Article

Scientists from RIKEN, Japan, and the University of Tokyo, Japan, have developed ultra-thin photovoltaics wrapped in stretchable and waterproof films, which can continue to generate solar electricity even after being soaked in water or being exposed to mechanical stress, such as cleaning in a washing machine. As ultra-thin and stretchable material that can be woven into wearable textiles is often permeable, the scientists have come up with a coating made of acrylic-based elastomer, which prevents water infiltration, while allowing light in.

The researchers have subjected the photovoltaics to a variety of tests, finding first that it had a strong energy efficiency of 7.9%, producing a current of 7.86 mW/cm², as the current density was 13.8 mA/cm² at 0.57 V, based on a simulated sunlight of 100 mW/cm². The efficiency of double-side-coated devices decreases only by 5.4% after immersion in water for 120 minutes. Furthermore, the efficiency of the devices remains at 80% of the initial value even after 52% mechanical compression for 20 cycles with 100 minutes of water exposure.

The extremely thin and flexible organic photovoltaic cell is based on material called PNTz4T, which the scientists had developed in earlier work. “These cells could be used to provide power to health monitors woven into clothing, which are able to record heartbeats and body temperature, and provide early warning of medical problems. These healthcare textile-implantable devices need a steady power supply of several milliwatts or more to continuously collect data,” said Takao Someya, at University of Tokyo.