Shape Matters: Effect of 1D, 2D, and 3D Isovolumetric Quantum Confinement in Semiconductor Nanoparticles

Abstract

Semiconductor nanoparticles (NPs) are a class of nanoscopic materials with highly tunable optical and electronic properties. The electronic density of states of these NPs depends strongly on both shape and size and has allowed semiconductor NPs to be tailored for applications in various fields including photovoltaics, solid-state lighting, and biological labeling. This work presents investigation of the effect of shape on excitonic properties of electronically excited NPs. Specifically, this work focuses on isovolumetric NPs and addresses the question of how optical properties of NPs are impacted by isovolumetic deformation of NP shapes. The effects of three shapes, representing 1D, 2D, and 3D quantum confinement, for three sizes and four semiconductor materials (CdSe, CdS, CdTe, and PbS) were studied. The electronic excitation in these NPs was described using electron–hole (eh) quasiparticle representation, and exciton binding energies, eh-joint probabilities, and eh-separation distances were calculated using the eh explicitly correlated Hartree–Fock method. The calculations demonstrated that increased anisotropy in the confinement potential resulted in decreased exciton binding energy in the NPs. Within a specific volume, it was found that nanorods exhibited lower exciton binding energies than did nanodisks and that nanodisks exhibited lower exciton binding energies than nanospheres of identical volume. In contrast, the trend for eh-joint probability was found to be opposite that of exciton binding energies. These results demonstrate that a relatively small change in NP structure can result in a substantial change in the excitonic properties of these nanomaterials.