Facet‐Specific PbS Quantum Dot Passivation Using Halide Perovskites for SWIR Photodetectors

ABSTRACT PbS quantum dots (QDs) show great promise as active materials for near‐infrared photodetectors. Halide perovskites are known to efficiently passivate the surface of PbS; however, there is currently no model to explain the passivation of large QDs by perovskites, which is key to controlling their stability. In this study, we present a systematic analysis of the ligand structure of methylammonium lead iodide (MAPI)‐passivated 4‐nm PbS QDs. Through a combination of FTIR, XPS, SEM, NMR, DFT, and other techniques, we propose a comprehensive ligand model, showing that the (100) PbS facets are passivated by a MAPI monolayer and the (111) facets by a PbI ₂ monolayer. We also demonstrate that this passivation approach can be extended to other perovskite compositions. Finally, we present a proof‐of‐principle photodetector device demonstrating promising performance. Precise elucidation of the ligand structure will help optimizing the surface passivation of PbS QDs, leading to more efficient and stable photodetectors.