Superstretchy and efficient solar cells, courtesy of wet suit material

Solar cells made of organic molecules offer many advantages over their silicon cousins. They are thin, lightweight, flexible, and printable on large areas. But make the devices bendy, and their ability to convert light to electricity plummets. Researchers have now overcome this trade-off between efficiency and flexibility by adding chloroprene rubber—aka neoprene, the stuff of wet suits—to organic photovoltaic materials (Joule 2025, DOI: 10.1016/j.joule.2025.101996). Organic solar cells containing a mass fraction of 5% neoprene have an efficiency of 17%, which matches the current efficiency of other organic solar cells while being much more stretchable than others reported so far; by comparison, today’s best rigid devices convert 20% of light into electricity.The new cells should be easier to print on rolls and last longer in wearable devices than rubber-free ones, says Tobin J. Marks, a chemist at Northwestern University. Marks developed the devices with Antonio Facchetti of the Georgia Institute of Technology; Yifan Wang, Yahui Liu, and Zhishan Bo of Qingdao University; Hongxiang Li of Peking University; and other colleagues.Organic solar cells use two types of molecules: one absorbs light and releases electrons, and another soaks up the electrons. Separating these two types of molecules is necessary to boost their interactions and, in turn, device efficiency, Facchetti says. Typically, small, chlorinated molecules are added to the organic light-converting material for this separation, but the chlorinated molecules are volatile and escape during processing. In the new work, the researchers used chloroprene rubber for a twofer; the nonvolatile solid makes the photovoltaic layer