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Proceedings Paper

Effects of surface and interface traps on exciton and multi-exciton dynamics in core/shell quantum dots
Author(s): Renato Bozio; Marcello Righetto; Alessandro Minotto
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Paper Abstract

Exciton interactions and dynamics are the most important factors determining the exceptional photophysical properties of semiconductor quantum dots (QDs). In particular, best performances have been obtained for ingeniously engineered core/shell QDs. We have studied two factors entering in the exciton decay dynamics with adverse effects for the luminescence efficiency: exciton trapping at surface and interface traps, and non-radiative Auger recombination in QDs carrying either net charges or multiple excitons. In this work, we present a detailed study into the optical absorption, fluorescence dynamics and quantum yield, as well as ultrafast transient absorption properties of CdSe/CdS, CdSe/Cd0.5Zn0.5S, and CdSe/ZnS QDs as a function of shell thickness. It turns out that de-trapping processes play a pivotal role in determining steady state emission properties. By studying the excitation dependent photoluminescence quantum yields (PLQY) in different CdSe/CdxZn1-xS (x = 0, 0.5, 1) QDs, we demonstrate the different role played by hot and cold carrier trapping rates in determining fluorescence quantum yields. Finally, the use of global analysis allows us untangling the complex ultrafast transient absorption signals. Smoothing of interface potential, together with effective surface passivation, appear to be crucial factors in slowing down both Auger-based and exciton trapping recombination processes.

Paper Details

Date Published: 24 August 2017
PDF: 10 pages
Proc. SPIE 10348, Physical Chemistry of Semiconductor Materials and Interfaces XVI, 1034816 (24 August 2017); doi: 10.1117/12.2273713
Show Author Affiliations
Renato Bozio, Univ. degli Studi di Padova (Italy)
Marcello Righetto, Univ. degli Studi di Padova (Italy)
Alessandro Minotto, Univ. degli Studi di Padova (Italy)
Univ. College London (United Kingdom)

Published in SPIE Proceedings Vol. 10348:
Physical Chemistry of Semiconductor Materials and Interfaces XVI
Hugo A. Bronstein; Felix Deschler, Editor(s)

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