Copper's Role in the Photoluminescence of AgCu InS Nanocrystals, from Copper-Doped AgInS ( x ∼ 0) to CuInS ( x = 1).

A series of AgCu InS nanocrystals (NCs) spanning from 0 ≤ x ≤ ∼1 was synthesized by partial cation exchange to identify copper's contributions to the electronic structure and spectroscopic properties of these NCs. Discrete midgap states appear above the valence band upon doping AgInS NCs with Cu (small x). Density functional theory calculations confirm that these midgap states are associated with the 3d valence orbitals of the Cu impurities.