Physical Characterization Of Thin Films Of CuxZnySz For Photovoltaic Applications

Kesterite, Cu2ZnSn(S,Se)(4), are considered promising materials for energy conversion devices, encompassing reduced production costs and low environmental risks. The Electrochemical Atomic Layer Epitaxy (ECALE) method was used to obtain compound semiconductors, in the form of thin films, whose composition belongs to the compositional field of kesterite. Namely, CuxSy and CuxZnyS thin films were considered in this study. Films were characterised through Scanning Electron Microscopy, for film morphology, and X-ray Absorption Spectroscopy, to determine the structure of the film, the metal valence states, the nature of the coordinating ligand. In particular, films are found to always exhibit a Cu2-xS type structure, where Zn is likely tetrahedrally coordinated. The role of the two transition metal cations in modulating the overall properties of the thin layer results fundamental and it opens interesting perspectives in the chemical tuning of the photovoltaic properties.