Polycrystalline iron sulphide based semiconductors for solar energy conversion

Potentialities of iron sulphide semiconductors for solar energy conversion have been outlined. Iron sulphide semiconductors have been characterized with respect to their bulk (XRD, EDAX), surface (XPS) and electronic (UV-Vis reflectance spectroscopy) structure. Materials have been formed into electrodes by screen-printing and have been thermally activated under different conditions. Synthetic polycrystalline pyrite activated in air-hydrogen atmosphere showed the highest efficiency for solar energy conversion in polyiodide electrolyte. Distinguishing characteristics of these materials are due to the optimal absorption and charge transfer properties at the electrode-electrolyte interface. From parallel experiments carried out on pyrrhotite and natural pyrite-based semiconductors, it was derived that the latter characteristics are related to favourable substoichiometric surface sites and to the formation of an iron oxide bulk phase in the semiconductors.