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 organic vapor deposition)-grown ZnO nanorod array (ZnO-N) or a mesoporous film prepared from ZnO colloids (ZnO-C) as the working electrode was compared. The electrodes were of similar thickness (2 ím) 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 ís). Thus, the morphology of the working ZnO electrode plays a key role for the electron transport properties. Highly ordered nanostructures of ZnO,1 TiO2,2 and other wide band gap semiconductors are promising alternatives to the mesoporous nanoparticle thin films that are currently used for dye-sensitized solar cells (DSSCs) and other devices. DSSCs prepared from colloidal solutions are characterized by complex interfaces.3 The possibility to employ a well-defined semicon-ductor layer morphology in DSSCs is attractive, as it could allo