Charging of colloidal nanoplatelets: effect of Coulomb repulsion on spin and optoelectronic properties

Abstract

Colloidal semiconductor nanoplatelets combine weak lateral confinement with strong Coulomb interactions, enhanced by dielectric confinement. When the platelets are charged with carriers of the same sign, this results in severe Coulomb repulsions which shape the electronic structure. To illustrate this point, the shell filling of type-I (CdSe/CdS) and type-II (CdSe/CdTe) core/crown nanoplatelets with up to 4 electrons or holes is investigated theoretically. We find that Coulomb repulsions enable addition energies exceeding room temperature thermal energy and promote the occupation of high-spin states. For charged excitons and biexcitons in CdSe/CdTe nanoplatelets, the repulsions further give rise to multi-peaked emission spectra with widely tunable (over 100 meV) energy, and a transition from type-II to quasi-type-II band profile as the number of electrons confined in the core increases. We conclude that the number of excess carriers injected in nanoplatelets is a versatile degree of freedom to modulate their magnetic and optoelectronic properties.

References in corpus (5)

• Evidence of giant oscillator strength in the exciton dephasing of CdSe nanoplatelets measured by resonant four-wave mixing
• Colloidal manganese doped ZnS nanoplatelets and their optical properties
• Excitons in core-only, core-shell and core-crown CdSe nanoplatelets: interplay between in-plane electron-hole correlation, spatial and dielectric confinement
• Singlet-Triplet Physics and Shell Filling in Carbon Nanotube Double Quantum Dots
• Magneto-optics of excitons interacting with magnetic ions in CdSe/CdMnS colloidal nanoplatelets