Manipulation of Band Alignment in Two-Dimensional Vertical WSe2/BA2PbI4Ruddlesden-Popper Perovskite Heterojunctions via DefectEngineering

Transition metal dichalcogenides (TMDs), two-dimensional (2D) layeredRuddlesden-Popper perovskite material, and their heterojunctions have attracted a great dealof interest in optoelectronic applications. Although various approaches for modulating theirproperties and applications have been demonstrated, knowledge of the interface band alignmentand defect engineering on the TMD/2D perovskite heterojunction is still lacking. Herein, theoptoelectronic properties and defect engineering of the WSe2/BA2PbI4heterojunction havebeen investigated with density functional theory simulations. Wefind that the WSe2/BA2PbI4van der Waals heterojunction maintains an indirect bandgap and S-scheme alignment,facilitating the efficient splitting of light excited carriers across the interface. Importantly, wefind that defect engineering could manipulate the band alignment. The introduction of the BAvacancies could switch the interface from the S-scheme to the typical type II interface, whereasSe vacancies would facilitate recombination at the S-scheme interface. Our work proves that theinterfacial properties of heterojunctions can be regulated by defect modulation to addressdifferent optoelectronic applications.