Dye-sensitized solar 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 (TiO_2) particles of a few nanometers in size, coated with a monolayer of charge-transfer dye to sensitize the film for light harvesting. In the present authors' review, the principal role of the TiO_2 photoanode is emphasized by a detailed presentation of its characterization by different experimental methods, while the photoelectric responses of the cells, a work which is still in progress, are indicated in the references cited. Hydrolysis of Ti(IV)-isopropoxide in isopropanol by the addition of water is a suitable chemical reaction for the production of nanosized TiO_2. The properties of nanosized TiO_2 can be modified by the hydrolysis catalyst, pH of the solution, temperature, presence of complexing ligand and the colloidal state of TiO_2 precursor. In the present work, the microstructural properties of nanosized TiO_2 were studied by HREM, ED, XRD, SAXS and Raman spectroscopy. HREM was used to determine both grain and pore sizes. Electron diffraction and X-ray diffraction provided evidence of nanocrystalline anatase and brookite phases. The grain sizes of the anatase and brookite phases changed from (5±1) to (12±3) nm with an increase of the treating temperature up to 773 K, as shown by XRD. An method of determining nanosized TiO_2 grain size based on low-frequency Raman scattering, is presented
