Innovative back-contact for Sb2Se3-based thin film solar cells

Among the most promising material for thin-film photovoltaics, Sb2Se3 (ASe) plays a pivotal role, being constituted of Earth-abundant elements and owing to its optical and electrical properties. Recently, ASe solar cells exhibited relatively good photovoltaic performances, reaching a considerable efficiency close to 9 %. Despite these remarkable results, much is still to be investigated, particularly regarding the active materials, interfaces, and electrical contacts. In this study we propose an alternative back contact for ASe solar cells. It is based on Fe, S and O elements, and was deposited at room temperature by radiofrequency magnetron sputtering. XRD and Raman measurements revealed that it is actually made of two materials: Fe3O4, in orthorhombic and cubic phases and FeS in troilite phase. This material provided an ohmic contact on top of the ASe film; its contact resistivity, extrapolated from current vs voltage characteristics of complete ASe-based solar cells, was estimated to be 0.8Ω·cm2. Monitoring the photovoltaic parameters, we observed a negligible average change after three months.