Large Tunability of Band Edges and Band Gaps in Colloidal Nanoplatelets

Colloidal semiconductor nanoplatelets (NPLs) are quasi-two-dimensional nanostructures, that exhibit outstanding physical and chemical properties for optoelectronic applications. Using first-principles density functional theory calculations, we demonstrate large tunability of NPLs band edge energies over a range of 5 eV through surface passivation by common organic molecules, and how this could be leveraged in controlling the functionality in mixed-dimensional heterojunctions and photocatalysis[1]. Meanwhile, ligands induce up to 300 meV band gap shifts, in addition to the shifts by quantum confinement dictated by the number of atomic layers in thickness. We developed simple quantitative theory describing the independent tunability of band edge and band gap shifts in terms of ligand-induced surface dipole, and strain, respectively, which can be used for controlled modification of photochemistry and optoelectronic properties for NPLs.
[1] Q. Zhou et al., Nano Lett. 2019, 19, 10, 7124-7129.