Nucleophilic Covalent Ligands Enable Simultaneous Surface Reconstruction and Passivation of Colloidal InSb Quantum...

Indium antimonide (InSb) colloidal quantum dots (CQDs) are promising candidates for short-wave infrared (SWIR) photodetectors due to their large Bohr exciton radius and tunable bandgap in the 0.6-1.3 eV range. However, the formation of metal oxides on InSb surfaces during synthesis impedes charge transport, necessitating CQD resurfacing strategies for integration into photodetectors. Previous reports achieved progress in device efficiency by resurfacing these CQDs with acid-halide sequential treatments, but the device operating stability remains unsatisfactory. Herein, we report a solution-phase strategy for surface reconstruction and passivation of InSb CQDs using sulfur-based nucleophilic covalent ligands. We find that short-chain thiol molecules remove surface metal oxides through nucleophilic attack and enable robust passivation of In and Sb via strong covalent bonds, whereas metal sulfides are less effective at oxide removal and passivation. Consequently, the thiolate-passivated CQDs exhibit a tenfold decrease in trap state density compared to controls and remain structurally and optically stable for 5 months. We demonstrate InSb CQD SWIR photodetectors that realize a high external quantum efficiency (EQE) of 28% at 1450 nm, with the highest operating stability among reported CQD SWIR photodetectors, retaining 95% of performance following 300 h of biased and illuminated operation.