DOI: https://doi.org/10.29363/nanoge.emlem.2023.004
Publication date: 18th August 2023
Colloidal quantum dots (QDs) are nanocrystals with size-dependent properties that undergo quantum confinement at the nanoscale. However, accurately describing the band alignment of core and shell materials when their size is still in the quantum confinement regime is challenging, especially if one should consider also interface and surface effects. Traditional computational methodologies to describe QDs, like the effective mass approximation, overlook the complexities of real systems. In this regard, Density Functional Theory (DFT) can describe accurately the atomistic composition of QDs, along with its electronic structure, including band gap. However, DFT models are restricted to core and shell sizes that are not aligned with those found experimentally. Furthermore, it is also common to design atomistic models of QDs that artificially introduce superficial intra-gap states that localize carriers, narrowing the band gap, and making the construction of accurate QD models more complicated.
In this work, we explore various cases of core-shell QD systems based on II-VI and III-V materials, which are comparable in size to those observed experimentally. Here, we investigate different sizes and shell thicknesses. Our aim is to examine the evolution of the band gap energy and band alignment in nanocrystals within the quantum confinement regime, considering interface and surface effects. The latter effects being mainly modulated by the use of the surface reconstruction technique. Through this work, we will demonstrate that atomistic models can effectively describe large nanocrystals when certain structural criteria are met.
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