Influence of dielectric environment on exciton and bi-exciton properties in colloidal, type II quantum dots

We present theoretical calculations of type II CdSe/CdTe quantum dots systems. We use an 8-band k.p Hamiltonian that includes spin-orbit interaction, strain, and first order piezoelectric effects. Exciton and bi-exciton states are found using the configuration interaction (CI) method that explicitly includes the effects of the Coulomb interaction, as well as exchange and correlation effects between many-electron configurations. We study convergence of the CI Hamiltonian with respect to the number of single particle states used in creation of the Hamiltonian. We show that there is a very strong correlation between the dielectric constant of the environment and exciton and bi-exciton energies

Theoretical studies of excitons in type II CdSe/CdTe quantum dots

We present a method for calculating exciton and bi-exciton energies in type-II colloidal quantum dots. Our methodology is based on an 8-band k p Hamiltonian of the zinc- blend structure, which incorporates the effects of spin-orbit interaction, strain between the core and the shell and piezoelectric potentials. Exciton states are found using the configuration interaction (CI) method that explicitly includes the effects of Coulomb interaction, as well as exchange and correlation between many-electron configurations. We pay particular attention to accurate modelling of the electrostatic interaction between quasiparticles. The model includes surface polarization and self-polarization effects due to the large difference in dielectric constants at the boundary of the QD

Design of core/shell colloidal quantum dots for MEG solar cells

Semiconductor quantum dots (QDs) are the subject of intensive research worldwide due to a number of novel properties, which make them of interest for both fundamental science and technological applications. QDs are of particular interest for solar cell applications due to their ability to increase efficiency via the generation of multiexcitons from a single photon. The efficiency of multiexciton generation (MEG) in colloidal QDs is determined by the competition between MEG and other hot electron-cooling processes. Core/shell QDs with type-II band alignment offers extra degrees of freedom in mediating both the optical dipoles and the Coulomb interaction between charges in such structures for the benefit of elevated MEG efficiency