By binding photosensitive dyes to common plastic membranes and adding water, chemists have made a new type of solar power generator. The device is similar to familiar silicon photovoltaic cells, but differs in a fundamental way. Instead of being produced via electrons, its electricity comes from the motion of ions. The synthetic, light-driven proton pump has the added potential capability of taking the salt out of seawater.
The device was made from polyethylene plastic, light-absorbing dye molecules, and water. A system based on dual layers of dye-coated, ion-transporting membranes was created. When struck with light from a laser pointer — a laboratory simulation of sunlight — the dye releases ions. Positively charged protons, also known as cations, pass through one sheet, while negatively charged hydroxides, also known as anions, pass through the other. These photoactive membranes generate 60 millivolts on average, occasionally climbing to more than 100 millivolts. This represents progress toward a device that directly converts sunlight into ionic electricity, which has implications for direct desalination of seawater.
The researchers see other possible applications for the technology, including as part of a brain-computer interface system. Silicon-based devices and aqueous environments don’t mix, but the flexible, fluid-permeable structures may one day offer a way of integrating living tissue and artificial circuitry.