Electrochemical Modulation of the Photophysics of Surface-Localized Trap States in Core/Shell/(Shell) Quantum Dot Films

Ward Van Der Stam*, Gianluca Grimaldi, Jaco J. Geuchies, Solrun Gudjonsdottir, Pieter T. Van Uffelen, Mandy Van Overeem, Baldur Brynjarsson, Nicholas Kirkwood, Arjan J. Houtepen

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

20 Citations (Scopus)
84 Downloads (Pure)

Abstract

In this work, we systematically study the spectroelectrochemical response of CdSe quantum dots (QDs), CdSe/CdS core/shell QDs with varying CdS shell thicknesses, and CdSe/CdS/ZnS core/shell/shell QDs in order to elucidate the influence of localized surface trap states on the optoelectronic properties. By correlating the differential absorbance and the photoluminescence upon electrochemically raising the Fermi level, we reveal that trap states near the conduction band (CB) edge give rise to nonradiative recombination pathways regardless of the CdS shell thickness, evidenced by quenching of the photoluminescence before the CB edge is populated with electrons. This points in the direction of shallow trap states localized on the CdS shell surface that give rise to nonradiative recombination pathways. We suggest that these shallow trap states reduce the quantum yield because of enhanced hole trapping when the Fermi level is raised electrochemically. We show that these shallow trap states are removed when additional wide band gap ZnS shells are grown around the CdSe/CdS core/shell QDs.

Original languageEnglish
Pages (from-to)8484-8493
Number of pages10
JournalChemistry of Materials
Volume31
Issue number20
DOIs
Publication statusPublished - 2019

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