Low-Temperature, Solution-Based Sulfurization and Necking of PbS CQD Films

Lead sulfide colloidal quantum dots (CQDs) are a promising optoelectronic material. The optoelectronic functionality of PbS CQD films largely depends on the anionic ligands that passivate the Pb-rich surface of the CQDs' inorganic cores. Herein, we report a simple solution-based method for fabricating PbS CQD films using sulfur as the ligand. In turn, passivation of the CQDs with sulfur promotes the chemisorption of oxygen. Overall, this approach results in efficient removal of the original organic ligands and in enhanced interdot electronic coupling. The CQD films present increased p-type doping, higher majority carrier mobility, and higher photoresponsivity as compared to state-of-the-art halide-passivated CQD films. The simple postsynthetic sulfurization strategy described herein can be potentially applied in a variety of metal sulfide and selenide nanomaterials whose optoelectronic functionalities in part depend on the chalcogen to metal atomic ratio.