CdSe nanoplatelets show perfectly quantized thicknesses of few monolayers. They present a situation of extreme, yet well defined quantum confinement. Due to large dielectric contrast between the semiconductor and its ligand environment, interaction b
etween carriers and their dielectric images strongly renormalize bare single particle states. We discuss the electronic properties of this original system in an advanced tight-binding model, and show that Coulomb interactions, including self-energy corrections and enhanced electron-hole interaction, lead to exciton binding energies up to several hundred meVs.
A procedure to obtain single-electron wavefunctions within the tight-binding formalism is proposed. It is based on linear combinations of Slater-type orbitals whose screening coefficients are extracted from the optical matrix elements of the tight-bi
nding Hamiltonian. Bloch functions obtained for zinc-blende semiconductors in the extended-basis spds* tight-binding model demonstrate very good agreement with first-principles wavefunctions. We apply this method to the calculation of electron-hole exchange interaction, and obtain the dispersion of excitonic fine structure of bulk GaAs. Beyond semiconductor nanostructures, this work is a fundamental step toward modeling many-body effects from post-processing single particle wavefunctions within the tight-binding theory.
Based on density functional theory, the electronic and optical properties of hybrid organic/perovskite crystals are thoroughly investigated. We consider the mono-crystalline 4FPEPI as material model and demonstrate the optical process is governed by
three active Bloch states at the {Gamma} point of the reduced Brillouin zone with a reverse ordering compared to tetrahedrally bonded semiconductors. Giant spin-orbit coupling effects and optical activities are subsequently inferred from symmetry analysis.
