A review on counter electrode materials in dye-sensitized solar cells

Dye-sensitized solar cells (DSCs) present promising low-cost alternatives to the conventional silicon (Si)based solar cells. A DSC consists of several components, the most prominent being a titanium dioxide/metal oxide-based photoanode, a dye, an electrolyte and a counter electrode. The photoexcited electrons from the dye diffuse through the TiO2 network in the photoanode and go to the counter electrode which generally consists of platinum (Pt) sputtered onto a fluorine-doped tin oxide (FTO) plate. The Pt in the counter electrode helps in the regeneration of dyes by catalysing the I- regeneration from the I-3(-) species in the redox couple. The morphology of Pt, its surface roughness, nature of the exposed facet, etc. play a crucial role in determining the overall efficiency of a DSC device. With Pt being a costly noble metal, reasonable efforts have been made to find cheaper alternatives. The review presented below gives a succinct summary of the materials in use as counter electrodes in DSCs, with a conclusion and future prospects section.