Slide Image: A diagram showing how a dye-sensitized solar cell works. Nanoparticles of titanium dioxide are coated with a dye that absorbs a wide range of light waves from the sun. Then they are applied to a conducting glass electrode immersed in an electrolyte solution containing iodine molecules and a second (platinum) electrode. The cells generate electricity when the energy captured by the dye excites an electron in the dye molecule. The electron is injected into a titanium dioxide particle and diffuses toward the glass electrode; from there, a wire carries it to the external circuit. The circuit closes when electrons return to the platinum electrode and attach to iodine molecules, which diffuse across the electrolyte, returning to and regenerating the dye.

Credit: Alex Agrios, Northwestern University