Antimony selenide solar cells are an emerging thin-film technology of growing interest. They benefit from a direct ~1.17eV bandgap, containing no scarce materials, have a simple phase chemistry and an interesting 1D nanoribbon grain structure. Despite the first respectable device efficiency being reported as recently as 2014 and the relative paucity of research, they have already reached efficiencies of 6.5% in excess of other widely studied binary compounds such as SnS. Due to the nascent nature of the technology the optimal cell structure is still to be determined and as a result number of n-type partner layers such as ZnO, CdS and TiO2 have thus far been reported.
In this work we compare devices based on two Sb2Se3 deposition routes, thermal evaporation and close space sublimation, to examine the influence of the n-type partner layer and the interface on device performance. Our results show that while CdS is a suitable partner layer for thermally evaporated Sb2Se3 devices (efficiencies >4%) for CSS deposited layers CdS is unsuitable (<2.5% efficiency). In contrast TiO2 layers are highly effective for CSS material (>5.5% efficiency) but are unsuited to thermally evaporated Sb2Se3 devices (<1% efficiency). We will demonstrate this is due to the degree of S/Se interdiffusion at the interface and thereby linked to the Sb2Se3 deposition process. Device performance will be linked to XPS analysis of band alignments, cross sectional TEM of the interface and deep level transient spectroscopy (DLTS) analysis of defect composition in complete cell structures.