  Quantum dot (QD) assemblies are nanostructured networks made from aggregates
of QDs and feature improved charge and energy transfer efficiencies compared to
discrete QDs. Using first-principles many-body perturbation theory, we
systematically compare the electronic and optical properties of two types of
CdS QD assemblies that have been experimentally investigated: QD gels, where
individual QDs are covalently connected via di- or poly-sulfide bonds, and QD
nanocrystals, where individual QDs are bound via van der Waals interactions.
Our work illustrates how the electronic, excitonic, and optical properties
evolve when discrete QDs are assembled into 1D, 2D, and 3D gels and
nanocrystals, as well as how the one-body and many-body interactions in these
systems impact the trends as the dimensionality of the assembly increases.
Furthermore, our work reveals the crucial role of the covalent di- or
poly-sulfide bonds in the localization of the excitons, which highlights the
difference between QD gels and QD nanocrystals.
