Dye-sensitized solar cells: management of photoelectrons

Dye-sensitized solar cells (DSC) consist of a dye-adsorbed nano-structured TiO/sub 2/ electrode as an electron emitter and iodide/tri-iodide redox electrolyte as a hole transport layer. The nano-structure of TiO/sub 2/ electrodes with a huge surface area (roughness factor=/spl sim/1000) contributes to the effective light harvest by the dye molecules on the surface. They can be sandwiched between two transparent conducting glasses at ordinary pressure, giving the solar cell devices a favorable cost performance. The sensitizing dye molecules on TiO/sub 2/ inject photo-generated electrons into the TiO/sub 2/ electrode with femto-second rate and photo-generated holes into the semi-conducting electrolyte with nano-second rate, indicating directional electron flow in DSC. The effective transport of electrons both in the electrolyte and in the TiO/sub 2/ layer contribute to high fill factor of DSC, leading to the high photon-to-current conversion efficiency. This paper focuses on the mechanism and management of the electron transport in TiO/sub 2/ for fabrication of the high efficient DSC devices.