Band Alignment and Optical Properties of 1D/2D Sb2Se3/PtSe2 Heterojunctions

The heterojunction between two materials brought into contact, for example, in the form of vertical van der Waals heterostructures, exhibits interesting features offering functionalities to devices stimulated by light. We report in this article an investigation of the optical and electronic properties of the heterojunction formed between Sb2Se3, a material with a promising role in photovoltaics characterized by one-dimensional (1D) topology (ribbons), and an emerging two-dimensional (2D) material, PtSe2, exhibiting unique optical properties for photoelectronics and photonics. The controlled growth of PtSe2 on Sb2Se3 underlayer takes place using a transfer-free process by low-temperature selenization of 1-2 nm Pt films thermally evaporated on Sb2Se3 ultrathin substrates. X-ray photoelectron spectroscopy (XPS) data analyzed in the context of the Kraut method provided an estimate for the band offsets at the interface. The valence band offset and the conduction band offset of the PtSe2/Sb2Se3 heterojunction were found to be -0.25 and 1.0 eV, respectively, indicating a type-II heterojunction. The ultrabroad optical absorption of the heterojunction and the protection offered by PtSe2 to Sb2Se3, against oxidation of the latter, render this particular heterojunction a robust candidate for applications in photovoltaics. Finally, the current study of a heterojunction between materials of different dimensionalities may pave the way for a rational design in the field of trans-dimensional heterostructures.