Facet oriented coupling stabilizes PbS quantum dots for infrared LEDs

PbS quantum dots (QDs) are excellent infrared semiconductor materials for solution-processed optoelectronic devices. However, poor resistance to moisture, oxygen, and photobleaching cast a shadow over the development of optoelectronic devices based on PbS QDs. Here, we present a strategy for enhancing the stability of PbS QDs through <i>in situ</i> lead halide (PbX₂, X = Cl, Br, I) induced facet coupling. The addition of PbX₂ ligands has been observed to effectively reduce the Stokes shift of PbS QDs with increasing atomic radius of the halide, suggesting that the PbX₂ ligands effectively passivate the surface of the QDs. Further analysis of the morphology and crystal facets of PbS QDs reveals that PbX₂ ligands can induce coupling of the (200) crystal facet. Consequently, the surface passivation and coupling of non-polar crystal facets result in the demonstration of robust resistance to moisture, oxygen, and photobleaching by PbS-PbI₂ QDs. No notable alterations in the absorption spectrum were discerned following exposure to UV irradiation and prolonged air exposure. Infrared LEDs based on PbS-PbX₂ QDs exhibited enhanced current density and achieved a maximum irradiance of 5.06 W sr^-1 m^-2.This strategy offers a promising solution to the stability issue of infrared nanomaterials and devices.