Effects of dopants on the band structure of quantum dots: A theoretical and experimental study

In this article, we present a theoretical framework that provides predictable results on band gap modifications due to the addition of dopants into CdSe quantum dots (QDs). A theoretical model is developed that predicts a lowering of the conduction band minimum (CBM) due to hybridization. We then use x-ray absorption spectroscopy (XAS) at the Cd M3-edge to determine the effects of chemical doping on the conduction band (CB) of the QD. Analysis of the XAS onset energy provides evidence for a lowering of the CBM, with our calculations yielding results comparable to experiment within 0.02 eV for tested materials. Also present in the XAS data is a distinct shift of the Cd M3-edge peak maximum as a function of particle size, suggesting this peak can be used as a tracer to probe the angular momentum resolved shifts in the CB states due to quantum confinement. Our theoretical model can model a variety of dopants and theoretically predict the shift in the energy levels, and should be generalizable towards predicting similar behavior in other materials.