Thermodynamic Stabilization of PbS Quantum Dots for High-Performance Short-Wave Infrared Photodetection

The development of lead sulfide (PbS) quantum dot (QD) photodetectors for short-wave infrared (SWIR) applications has been fundamentally limited by the thermodynamic instability of large PbS QD facets, which leads to aggregation and epitaxial fusion. In this work, robust thermodynamic stabilization was achieved by introducing methylammonium chloride (MACl) in PbS QD surface passivation, as validated by theoretical modeling and experimental characterization. MACl passivation reconstructed the surface energy landscape, establishing a physical barrier that suppressed PbS QD fusion and ligand re-adsorption, while extensive halide coordination minimized structural disorder and reduced sub-bandgap trap states. As a result, the optimized PbS QD photodiodes exhibited a peak external quantum efficiency of 56% and a specific detectivity of 1.12 × 1012 Jones at 1450 nm, an order-of-magnitude enhancement over control devices. This strategy enabled high-sensitivity SWIR imaging and established thermodynamic surface stabilization as a scalable avenue for advanced infrared optoelectronics.