title: Effect of Electron-Hole Overlap and Exchange Interaction on Exciton Radiative Lifetimes of CdTe/CdSe Heteronanocrystals.
abstract: Wave function engineering has become a powerful tool to tailor the optical properties of semiconductor colloidal nanocrystals. Core-shell systems allow to design the spatial extent of the electron (e) and hole (h) wave functions in the conduction- and valence bands, respectively. However, tuning the overlap between the e- and h-wave functions not only affects the oscillator strength of the coupled e-h pairs (excitons) that are responsible for the light emission, but also modifies the e-h exchange interaction, leading to an altered excitonic energy spectrum. Here, we present exciton lifetime measurements in a strong magnetic field to determine the strength of the e-h exchange interaction, independently of the e-h overlap that is deduced from lifetime measurements at room temperature. We use a set of CdTe/CdSe core/shell heteronanocrystals in which the electron-hole separation is systematically varied. We are able to unravel the separate effects of e-h overlap and e-h exchange on the exciton lifetimes, and we present a simple model that fully describes the recombination lifetimes of heteronanostructures (HNCs) as a function of core volume, shell volume, temperature, and magnetic fields.
authors.affiliation: High Field Magnet Laboratory (HFML-EMFL), Radboud University , 6525 ED Nijmegen, The Netherlands.|Institute for Molecules and Materials, Radboud University , 6525 AJ Nijmegen, The Netherlands.
authors.forename: Andrés
authors.initials: A
authors.lastname: Granados Del Águila
authors.affiliation: Condensed Matter and Interfaces, Debye Institute for Nanomaterials Science , Princetonplein 1, 3584 CC Utrecht, The Netherlands.
authors.forename: Esther
authors.initials: E
authors.lastname: Groeneveld
authors.affiliation: High Field Magnet Laboratory (HFML-EMFL), Radboud University , 6525 ED Nijmegen, The Netherlands.|Institute for Molecules and Materials, Radboud University , 6525 AJ Nijmegen, The Netherlands.
authors.forename: Jan C
authors.initials: JC
authors.lastname: Maan
authors.affiliation: Condensed Matter and Interfaces, Debye Institute for Nanomaterials Science , Princetonplein 1, 3584 CC Utrecht, The Netherlands.
authors.forename: Celso
authors.initials: C
authors.lastname: de Mello Donegá
authors.affiliation: High Field Magnet Laboratory (HFML-EMFL), Radboud University , 6525 ED Nijmegen, The Netherlands.|Institute for Molecules and Materials, Radboud University , 6525 AJ Nijmegen, The Netherlands.
authors.forename: Peter C M
authors.initials: PC
authors.lastname: Christianen
keywords: core−shell heterostructure; electron−hole exchange; electron−hole overlap; excitons; magnetic field; nanocrystals