Controlled electron injection and transport at materials interfaces in dye sensitized solar cells

Abstract

Dye-sensitized solar cells (DSSCs) generate excitons (bound electron-hole pairs) upon absorption of photon from the sunlight and undergo dissociation at the donor/acceptor materials interface to create free electrons and holes. Major challenges in DSSCs until now have been to achieve maximum exciton generation followed by dissociation, electrons injection and transportation with minimum recombination, which are controlled by the dye/metal oxide, dye/electrolyte, and metal oxide/electrolyte interfaces. Researchers have been focusing on improving these materials interfaces in DSSCs by using novel materials (doped metal oxides, wider spectral range dyes, and low viscous gel, ionic electrolytes and low molecular weight organic hole conductors), and introducing new semiconductor morphologies (nanofibers, rods, wires, core–shell). With the current effort by researchers, TiO 2/Ruthenium complex (N3 dye)-based liquid state DSSC have reached an efficiency of 11%, whereas TiO 2/Ruthenium complex (N719 dye)/Solid electrolyte-based solid state DSSC have achieved an efficiency of ∼4%. As numerous materials have been the focal point in DSSCs, it is necessary to have an overall understanding on the materials interfaces and their influence on the performance of the solar cell. This review focuses on the metal oxides and metal oxide/dye interface that control the electron injection and transport for improving the efficiency of DSSCs.