Researchers triple efficiency of organic solar cells

Led by electrical engineer Stephen Chou, the Princeton team used a nanostructured 'sandwich' of metal and plastic to overcome the two primary challenges that cause solar cells to lose energy: light reflecting from the cell, and the inability to fully capture light. The sandwich - called a subwavelength plasmonic cavity – consists of five very thin layers. On top is the window layer made of extremely fine metal mesh, through which the sunlight first passes. Next is a layer of transparent plastic, followed by a layer of semiconductive material. This is topped by a layer of titanium oxide, with a layer of aluminum sitting at the bottom of the stack. The combined thickness of all five layers is just 230nm. This distance, along with the spacing and diameter of the holes in the mesh, is said to be shorter than the wavelength of the sunlight itself, allowing only 4% of the light to be reflected, and up to 96% to be absorbed. Chou claims the solar cells are ready for commercial use and can be manufactured cost effectively in wallpaper size sheets.