Aromatic Bidentate Ligand Passivation for High-Performance PbS Quantum Dot Infrared Photodetectors

Large-sized lead sulfide (PbS) colloidal quantum dots (CQDs) face significant stability challenges in near-infrared applications due to increased surface active sites. While traditional halogen ligands achieve preliminary passivation, they are prone to dissociation under high-temperature operating conditions, leading to rapid device performance degradation. This study proposes an aromatic bidentate ligand passivation strategy based on 2-picolinic acid (2-PCA). The device demonstrates an external quantum efficiency (EQE) of 35% at 1650 nm wavelength, with responsivity and normalized detectivity reaching 0.46 A/W and 3.58 × 10¹¹ jones, respectively representing a 2.33-fold improvement over conventional halogen-passivated devices. Under thermal stress at 180 °C for 2 h, devices with 2-PCA ligands retain approximately 90% of their initial normalized EQE, marking a 15-fold improvement in stability compared to devices using halogen ligands (PbX₂, X = Br^-, I^-), which undergo nearly complete failure. This aromatic bidentate ligand passivation strategy provides a new pathway for developing high-performance infrared photodetectors with enhanced thermal stability.