Semiconductor quantum dot sensitized TiO₂ mesoporous solar cells

Dye-sensitized solar cells (DSSCs) have attracted significant attention throughout the world from both academic and industrial fields as a promising alternative to conventional solid-state photovoltaic devices since a report by O’Regan and Grätzel in 1991 [1]. To improve the overall efficiency and long-term stability of DSSCs, several groups have investigated various sensitizers, photoanode materials, counterelectrodes, and redox systems. Light absorbers, such as transition metal complexes and organic molecules, have been designed and tested in DSSCs. In these cells the photoexcited dye injects electrons into the conduction band of TiO2, then the oxidized dye cations are regenerated by electron donation from the electrolyte or, alternatively, by hole injection into an organic hole transporting material for the solid-state counterpart [2, 3]. Although the results obtained so far are very impressive, further improvements in both efficiency and stability by introducing new materials and engineering their interfaces are anticipated. Inorganic semiconducting materials “quantum dots (QDs)” are attracting increasing attention because of their technological importance in solar energy conversion, light emitting diodes, and sensor applications [4]. The attractive properties of QDs, i.e., their size dependent optical, electronic, and mechanical properties, coupled with the available synthetic protocols allow these materials to be integrated into various types of solar cell. In this chapter we focus mainly on incorporating the QDs into mesoscopic TiO2 based solar cells.