Titanium dioxide is by far the most utilized semiconductor for dye-sensitized solar cells (DSSCs). However, in the last years zinc oxide has been also studied as an interesting alternative to TiO₂. ZnO presents similar photoelectrochemical and transport properties to TiO₂. Nevertheless, the efficiency of ZnO-based solar cells still remains far from their TiO₂ counterparts.
The low performance of ZnO cells has been attributed to poor sensitisation with the most common Ruthenium-based dyes. In addition to that, it has been reported that ZnO performs particularly well when sensitised with organic dyes. These dyes have the advantages of being much cheaper than those based in a precious metal such as ruthenium.
In this work, the photovoltaic properties of nanostructured ZnO electrodes sensitised with xanthene dyes are explored. We have used Eosin-Y, Eosin-B and Mercurochrome and compared their performance with respect the N719 Ruthenium dye. We observe that these dyes sensitise efficiently commercial ZnO nanopowder and yield efficiencies that are, in general, more than a half of those provided by N719. We have prepared polymer-sealed cells and measured the stability of the devices under 2-sun illumination at short circuit. They show very good stability properties.
In summary, the combination of a versatile metal oxide as ZnO and cheap organic dyes similar to those utilized in this work should be considered as a promising alternative in the field of dye-sensitised solar cells.