Bozio, R;
Righetto, M;
Minotto, A;
(2017)
Effects of surface and interface traps on exciton and multi-exciton dynamics in core/shell quantum dots.
In: Bronstein, HA and Deschler, F and Bakulin, AA, (eds.)
Proceedings of SPIE Physical Chemistry of Semiconductor Materials and Interfaces XVI;.
SPIE: San Diego, CA, United States.
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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.
| Type: | Proceedings paper |
|---|---|
| Title: | Effects of surface and interface traps on exciton and multi-exciton dynamics in core/shell quantum dots |
| Event: | Conference on Physical Chemistry of Semiconductor Materials and Interfaces XVI |
| Location: | San Diego, CA |
| Dates: | 06 August 2017 - 09 August 2017 |
| ISBN-13: | 978-1-5106-1153-5 |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1117/12.2273713 |
| Publisher version: | http://dx.doi.org/10.1117/12.2273713 |
| Language: | English |
| Additional information: | This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions. |
| Keywords: | Science & Technology, Physical Sciences, Technology, Chemistry, Physical, Materials Science, Multidisciplinary, Physics, Atomic, Molecular & Chemical, Chemistry, Materials Science, Physics, Quantum Dots, Excitons, Photophysics, Trapping, Auger recombination, LIGHT-EMITTING DEVICES, SEMICONDUCTOR NANOCRYSTALS, CORE, CDSE, HOT, EXCITATION, EMISSION, BLINKING, YIELDS |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10044176 |
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