Effects of composition modulation on the type of band alignments for Pd2Se3/CsSnBr3 van der waals heterostructure: A transition from type I to type II

Constructing perovskite-based van der Waals heterostructures (vdWHs) have rapidly advanced the field of optoelectronics and solar cells due to their unprecedented property to integrate excellent characteristics of different materials. In general, the perovskite-based vdWHs have various functional properties due to their different band alignments for Type I, Type II and Type III. However, it is challenging to realize the flexible switch of band alignments in heterostructure for diverse applications. In this paper, we systematically investigate the electronic and optical properties of novel heterostructure system composed of emerging two-dimensional material Pd2Se3 and all-inorganic halide perovskite CsSnBr3 for the first time. A Type I-Type II transition of band alignments in Pd2Se3/CsSnBr3 vdWH is achieved by partly replacing the Pd atom in Pd2Se3 monolayer with Ni atom, facilitating the highly efficient separation of photo-generated carriers. Meanwhile, the heavy hole effective mass along [1 0 0] direction is greatly reduced due to the transition of band alignment, which will improve the photoelectric conversion efficiency. Our works indicate that such a controllable band alignment of Pd2Se3/CsSnBr3 heterostructure holds a significant potential for future photoelectric applications.