Optoelectronic Properties of Excitonic and Biexcitonic Complexes in Metal Chalcogenide Semiconductor Nanoplatelets

Abstract

Nanoplatelets (NPLs) are of particular interest for their unique properties, they have a precisely controlled thickness of a few atomic monolayers (MLs), and lateral dimensions ranging from hundreds of nm to few nms, where quantum confinement is already felt. Additionally, NPLs are surrounded by organic ligands with weak polarizability, thus exerting a strong dielectric confine- ment that, together with the quantum confinement, serves to modulate the optical properties. The main objective of this PhD work is to study at a theoretical level the optoelectronic properties of excitonic and biexcitonic complexes in semiconductor core-only PbS and CdSe NPLs. To this end, we shall analyze the electronic structure of exciton complexes confined inside, and the resulting optical spectrum. We address through density functional theory (DFT) and k·p theory, coupled to variational and variational quantum Monte Carlo (VQMC) methods, some of the open questions that currently exist about the NPLs electronic nature.