Dye-sensitized cells differ from conventional semiconductor devices in that they separate the function of light absorption from charge carrier transport. The device is based on a 10-μm thick optically transparent film of titanium dioxide particles of a few nanometers in size, coated with a monolayer of charge-transfer dye to sensitize the film for light harvesting. The nano-size properties of TiO 2 obtained by the sol-gel method have been studied by Raman spectrometry, X-ray diffraction, high-resolution electron microscopy and small-angle X-ray scattering. Grain sizes and distributions obtained by these four methods agreed, varing from 4 to 12 nm with the temperature of TiO 2 calcination.