Photoactive iron pyrite (FeS2) thin film layers have been synthesized by a simple method involving the reaction of Fe3O4 or Fe2O3 with elemental sulfur. The films were formed on a variety of different substrate materials by converting or sulfurizing iron oxide layers. The subsequent sulfur treatment of the oxide layers consisted of exposure of the films to gaseous sulfur in open or closed ampules at 350°C for 0.5-2 h. The morphology, composition and photoactivity of the films produced were checked using X-ray diffraction, X-ray photoelectron spectroscopy (ESCA), optical absorption, steady state and transient photoconductivity. The best films showed good crystallinity and purity with concurrent photoconductivity and photoelectrochemical response. The ability of this technique to produce photoactive material can be explained by interpretation of the Gibbs ternary phase diagram for the FeOS system, and may be related to the production of photoactive pyrite in nature. A discussion is made as to the future improvement of the solar cell response by proper optimization of geometric and configurational properties.
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