Porous TiO2: Electron transport and application to dye sensitized injection solar cells

Porous TiO2 (anatase, rutile) belongs to the class of materials with very l ow drift mobility of electrons (10(-4)-10(-7) cm/Vs). The drift mobility is limited by traps being responsible for the slow interparticle charge trans fer. The deep traps are generated at the TiO2 surface in oxygen deficient a tmosphere and should be avoided in dye sensitized injection solar cells sin ce they increase the saturation current. Another group of defects is relate d to disorder in the bulk TiO2. The disorder is much stronger for anatase t han for rutile. The respective optical bandgap of the undisturbed anatase i s 3.45 eV. The disorder related defects do not limit the efficiency of the dye sensitized injection solar cell. The current dependent barrier height h as been shown to be important as a limiting factor for the energy conversio n efficiency in dye sensitized injection solar cells at moderate light inte nsity.