Optical, Electrical and Photovolatic Characterisation of Amorphous and Polycrystalline Iron Disilicide

The photovoltaics industry is enjoying the highest level of growth in its relatively short history due, partly, to the so called looming energy crisis. However, the technology has yet to reach parity with fossil fuels that will allow it to be instituted as a major contributor to global energy demand. As a result of this, research and development into improving technologies is also enjoying similar growth. Much of this research focuses on the development of improved materials, be it from a photoefficiency, cost or availability point of view (usually a combination of all three). This work will focus reports on characterisation work that has been performed on a potentially exciting material, iron disilicide, which has the possibility of fulfilling the above requirements. In its amorphous form, it offers inexpensive deposition combined with high absorption coefficients and an appropriate energy band-gap value (~0.9eV) to be used as a photovoltaic material. However, its electrical characteristics have yet to be rigorously investigated. In this thesis, the results of optical, structural and, primarily, electrical characterisation of amorphous iron disilicide is reported. The materials properties have been investigated as a function of synthesis method, including ion beam mixing of Fe/ Si discrete layers and sputtering of iron/ silicon targets. The effects of intrinsic material parameters, such as atomic composition, as well as post deposition processing such as thermal treatment have been investigated. Its ability to form rectifying junctions required for photovoltaic power generation is reported. It is shown that ion beam mixing is unlikely to become a viable synthesis route for the material. The silicide, in its amorphous form, is shown to consistently exhibits n-type conduction, irrespective of post deposition treatment. Heterostructures formed with p-type crystalline silicon have been shown to possess rectifying properties, with photovoltaic action having been observed in such junctions, and its suitability as a photovoltaic material qualified, and largely dismissed. Initial investigations into forms of the material that may possess improved viability have been carried out and reported.