Bright Infrared Colloidal PbS Nanoplatelets with Lead Sulfobromide Shells.

We report colloidal PbS nanoplatelets synthesized in bromide-containing media that spontaneously form core/shell heterostructures with inorganic lead sulfobromide and lead bromide shells surrounding a PbS core. Band-structure measurements indicate a type-I alignment, which concentrates electrons and holes within the PbS core. These core-shell nanoplatelets exhibit near-infrared emission with a remarkably narrow photoluminescence peak of 78 meV at room temperature. The inorganic shells also act as robust passivating layers that suppress surface defect states, yielding an improved photoluminescence quantum yield and preserving emissive performance under ambient conditions. The resulting nanoplatelets are bright and air-stable, offering a solution-processable platform for infrared photonics and optoelectronics, including emitters, detectors, and integrated photonic components.