Hybrid optoelectronics with colloidal nanocrystals

Abstract

In this work we present spectroscopic studies of the exciton dynamics in colloidal spherical cadmium sulfide CdS nanocrystals (NC) in the vicinity of a single indium gallium nitride InGaN quantum well (QW) in dependence of temperature. QWs of the alloy material InGaN exhibit a dependence of the exciton dimensionality on the thermal energy available. It was demonstrated that this dependence influences the rate for fluorescence resonant energy transfer from the QW to a layer of CdS-NC deposited on top of its capping layer. Investigations of different capping layer thicknesses demonstrated the dependence of the exciton dimensionality on the disorder potential of the QW.
Furthermore, spectroscopic measurements of elongated asymmetric cadmium selenide/- cadmium sulfide CdSe/CdS nanorods (NR) under the application of external magnetic and electric fields are discussed. Asymmetric CdSe/CdS-NR represent a special case of elongated NR as the analytical treatment of spherical NC can be combined with numerical methods of calculating the electron and hole energies and wave functions. The results for the excitonic fine structure splitting in these nanomaterials is used to explain the dependence of the exciton dynamics under an external magnetic field. For the first time, a separate measurement of the Zeeman splitting and the magnetic field induced spin admixture in colloidal NR was performed. Electric field mediated carrier separation in asymmetric CdSe/CdS-NR is measured in time resolved luminescence quenching experiments. Retrieval of stored excitations is demonstrated employing a synchronised ultrafast voltage pulse detection scheme.

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Identifiers

ORCID for Pavlos G. Lagoudakis: orcid.org/0000-0002-3557-5299

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