Fast electron transport in metal organic vapor deposition grown dye-sensitized ZnO nanorod solar cells

The electron transport in dye-sensitized solar cells with a MOCVD (metal org. vapor deposition)-grown ZnO nanorod array (ZnO-N) or a mesoporous film prepd. from ZnO colloids (ZnO-C) as the working electrode was compared. The electrodes were of similar thickness (2 μm) and sensitized with zinc(II) meso-tetrakis(3-carboxyphenyl)porphyrin, while the electrolyte was I-/I3- in 3-methoxypropionitrile. Electron transport in the ZnO-C cells was comparable with that found for colloidal TiO2 films (transport time ∼ 10 ms) and was light intensity dependent. Electron transport in solar cells with ZnO-N electrodes was about 2 orders of magnitude faster (∼30 μs). Thus, the morphol. of the working ZnO electrode plays a key role for the electron transport properties.