Nanostructures produce hidden photovoltaic cells

The discovery has been made at the Georgia Institute of Technology and could negate the need for large panels to convert sunlight to electricity and allow PV systems to be hidden from view. The development team believes that by using nanostructure arrays to increase the surface area available to convert light, it could increase efficiency and provide designers with new options for incorporating PV into vehicles, military equipment and buildings. Fabrication begins with the removal of the cladding layer from optical fibre and the application of a conductive coating to the surface, before seeding the surface with zinc oxide. A solution is then added to grow aligned zinc oxide nanowires around the fibre, and the nanowires are then coated with the dye sensitised materials that convert light to electricity. Sunlight entering the optical fibre passed into the nanowires where it interacts with the dye molecules to produce an electrical current. A liquid electrolyte between the nanowires collects the electrical charges, resulting in a hybrid nanowire / optical fibre system that the researchers claim can be up to six times as efficient as planar zinc oxide cells with the same surface area. Prof Zhong Lin Wang (pictured) from the Georgia Tech School of Materials Science and Engineering believes that by providing a larger area for gathering light, the technique would maximise the amount of energy produced from strong sunlight. He said: "In each reflection within the fibre, the light has the opportunity to interact with the nanostructures that are coated with the dye molecules. You have multiple light reflections within the fibre and multiple reflections within the nanostructures. These interactions increase the likelihood that the light will interact with the dye molecules – and that increases the efficiency. Wang added that the research will provide some new options for photovoltaic systems. He explained: "We could eliminate the aesthetic issues of PV arrays on buildings. We can also envision PV systems for providing energy to parked vehicles and for charging mobile military equipment where traditional arrays aren't practical or you wouldn't want to use them." The researchers have produced generators on optical fibre up to 20cm in length and say that the longer the light can travel along the fibre, the more 'bounces' it will make and the more it will be absorbed. Wang concluded: "This is a different way to gather power from the sun. To meet our energy needs, we need all the approaches we can get."