Research in photoelectrochemical solar cells received a boost in 1991 when O’Regan and Grätzel reported an energy conversion efficiency of about 7% for a regenerative photoelectrochemical cell based on dye-sensitized, nanostructured TiO₂ [1].  The solar cell is based on a large surface area, nanostructured, porous metal oxide electrode covered with adsorbed dye molecules.  The metal oxide is transparent to visible light, and efficient absorption of sun light occurs by the dye sensitizer.  Absorption of a photon by a dye molecule is followed by electron transfer from the dye to the metal oxide conduction band, and subsequent electron transport to the back contact.  The oxidized dye molecule is regenerated by a reducing agent in solution, and the reducing agent is regenerated at the counter electrode.  Hence, a photocurrent can flow without net changes in the chemistry.

After more than a decade, the efficiency of these cells now stands at more than 10%.  Several metal oxide materials have been tried, many new dyes have been synthesized, the solution chemistry has been improved, and a variety of redox couples have been investigated.  In addition, detailed mechanisms have been proposed for the charge separation process, loss processes, and charge transport in the photoelectrochemical cell.  In this paper, the progress and recent developments in dye-sensitized solar cells (DSSCs) research will be reviewed.