Dielectrically Confined Stable Excitons in Few-Atom-Thick PbS Nanosheets

Two-dimensional colloidal PbS nanosheets exhibit more than one order of magnitude larger exciton binding energy than their bulk counterpart, making it possible to generate stable excitons at room temperature. It is experimentally revealed that the binding energy of the exciton increases from 26 to 68 meV as the thickness of the PbS nanosheet decreases from 4.7 to 1.2 nm. The dielectric confinement of the exciton plays a critical role in the binding-energy enhancement. The large binding energy results in a fast thickness dependent exciton radiative recombination rate, confirmed experimentally.

Automated summary

Two-dimensional colloidal PbS nanosheets have a significantly higher exciton binding energy than their bulk counterpart, allowing for the generation of stable excitons at room temperature. The binding energy of the exciton increases as the thickness of the PbS nanosheet decreases, due to dielectric confinement. This large binding energy leads to a faster exciton radiative recombination rate, which has been confirmed experimentally.