The team at the RIKEN Center for Emergent Matter Science (CEMS) and the University of Tokyo used a material called PNTz4T on a 1μm thick parylene film. The cell was then placed onto acrylic-based elastomer and the top side of the device was coated with an identical elastomer to prevent water and air from leaking into the cell.
The cell has an efficiency of 7.9% and produces a current of 7.86 mW/cm 2 at 0.57 volts, based on a simulated sunlight of 100 mW/cm 2. The elastomer protects the cell so that the efficiency decreased by just 5% after two hours in water, with a similar small fall (to 80%) after being folded in half (52% mechanical compression) for 20 cycles with 100 minutes of water exposure.
“We were very gratified to find that our device has great environmental stability while simultaneously having a good efficiency and mechanical robustness," said Kenjiro Fukuda of the RIKEN Center for Emergent Matter Science. "We very much hope that these washable, lightweight and stretchable organic photovoltaics will open a new avenue for use as a long-term power source system for wearable sensors and other devices.”