Broken-gap type-III band alignment in monolayer halide perovskite/antiperovskite oxide van der Waals heterojunctions

The integration of halide perovskites with other functional materials provides a new platform for applications beyond photovoltaics, which has been realized in experiments. Here, through first-principles methods, we explore the possibility of constructing halide perovskite/antiperovskite oxide van der Waals heterostructures (vdWHs) for the first time with monolayers Rb₂CdCl₄ and Ba₄OSb₂ as representative compounds. Our calculation results reveal that the Rb₂CdCl₄/Ba₄OSb₂ vdWHs have negative binding energies and their most stable stacking possesses a rare type-III band alignment with a broken gap, which is highly promising for tunnel field-effect transistor (TFET) applications. Moreover, their electronic features can be further tuned by applying strain or an external electric field. Specifically, compressive strain can enlarge the tunneling window, while tensile strain can realize a type-III to type-II band alignment transformation. Therefore, our work provides fundamental insights into the electronic properties of Rb₂CdCl₄/Ba₄OSb₂ vdWHs and paves the way for the design and fabrication of future halide perovskite/antiperovskite-based TFETs.