Porous TiO2: Electron Transport and Application to Dye Sensitized Injection Solar Cells

Abstract

Porous TiO2 (anatase, rutile) belongs to the class of materials with very low drift mobility of electrons (10—4–10—7 cm/Vs). The drift mobility is limited by traps being responsible for the slow interparticle charge transfer. The deep traps are generated at the TiO2 surface in oxygen deficient atmosphere and should be avoided in dye sensitized injection solar cells since they increase the saturation current. Another group of defects is related to disorder in the bulk TiO2. The disorder is much stronger for anatase than for rutile. The respective optical bandgap of the undisturbed anatase is 3.45 eV. The disorder related defects do not limit the efficiency of the dye sensitized injection solar cell. The current dependent barrier height has been shown to be important as a limiting factor for the energy conversion efficiency in dye sensitized injection solar cells at moderate light intensity.