Tuning the Photophysical Properties of Colloidal Two-Dimensional Nanoplatelets*

Two-dimensional colloidal semiconductor nanoplatelets (NPLs) are promising optoelectronic materials with outstanding photophysical properties, such as large optical cross-sections and high photoluminescence quantum yield.
Using first-principles density functional theory calculations, we demonstrate strong tunability of NPL band edge energies through surface passivation by common organic molecules. We develop a simple quantitative electrostatic theory describing this effect through dipole-dipole interactions mediated by platelet-ligand interactions and ligand-dependent dielectric function. Finally, using parameter-free self-energies and an effective mass model of the excitons, we show that the band-edge tunability of NPLs together with the strong dependence of the optical bandgap of NPL on thickness can lead to favorable, and controlled tunability of photochemical and optoelectronic properties.