Korean researchers have created a textile-based organic photovoltaic cell that can be stitched into fabric and used as a wearable power source for personal electronic devices.
Organic photovoltaics (OPVs) have been of interest to researchers for years, but recently, they entered the commercial and industrial sectors, for use in energy harvesting applications. OPVs are flexible, easy to produce and lightweight, allowing companies to develop and deploy self-powered wireless sensors at a low cost. But, a collaboration between Kyung Hee University and Samsung Advanced Institute of Technology may have an impact on a very different audience – individual consumers. Published in Nano Energy [DOI: 10.1016 /j.nanoen.2014.06.017], the team report on the development of a textile-based OPV that can be stitched directly into clothing, and could be used to power the next-generation of wearable devices.
Producing power from materials that are both lightweight and flexible, involves complex materials engineering. Recent work on photovoltaic wires (fibres that act as individual solar cells) has shown potential, but the process remains slow and costly. And film-based OPVs have shown low compatibility with textiles. Dukhyun Choi and his team took a different approach, by developing an inexpensive polymer-blend-based OPV, which sits on a large-area woven textile electrode that can be stitched directly onto standard textiles.
Choi and his team developed a novel fibre architecture for the electrode materials. Consisting of polyethylene terephthalate (PET), coated with copper, nickel and gold, each individual fibre is 10um in diameter, and flexible enough to be assembled into bundles. These bundles were then woven into a 5cm2 square and added to the fabric of a child’s t-shirt. The fibre was found to be mechanically durable, but that it formed into a curved surface, rather than the ideal flat electrode surface. The OPV itself consists of layers of oxides and two blended polymers, with a thin layer of indium tin oxide (ITO) acting as the top electrode.
Although the textile-based OPV performed well mechanically, its power conversion efficiency was found to be relatively low, at ~1.8%. The team believe that this can be explained by the poor contact between the textile electrode and the polymer OPV. However, their device showed a short circuit current density higher than that of a typical OPV. With some design changes, the team believe that their approach will open the way to a power source for next-generation of wearable electronics.