Quantum Dots (QDs) show promise for many technological applications, including photocatalysis and photovoltaics. However, their photophysical properties are sensitive to surface oxidation, resulting in uncontrollable luminescence quenching. Using density functional theory (DFT) and time dependent DDFT (TDDFT), we simulate the oxidation process on the surface of Pb16Se16 and Pb68S68 QDs and its effect on their electronic and optical properties. When oxygen is substituted for Se/S ions, the electronic properties of the QD are insignificantly perturbed. In contrast, if oxygen is adsorbed on the QD surface and coordinated with two Pb ions, it introduces additional unoccupied states inside the QD's bandgap, so called mid-gap states. Such states are hybridized between the oxygen and the QD's surface atoms and contribute to the lowest-energy optically dark or semi-dark transitions resulting in quenching of luminescence of QDs. In contrast, if the oxygen is coordinated with Se/S and Pb ions on the surface, the mid-gap states are not present and the optical transitions are similar to those of the non-oxidized QDs.

Oxidation of PbSe and PbS quantum dots: Theoretical insights

247th National Meeting (2014)

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