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.

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 Proceedings of SPIE - The International Society for Optical Engineering. SPIE [10.1117/12.2273713].

Effects of surface and interface traps on exciton and multi-exciton dynamics in core/shell quantum dots

Minotto, A
2017

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.
slide + paper
Auger recombination; Excitons; Photophysics; Quantum Dots; Trapping
English
Physical Chemistry of Semiconductor Materials and Interfaces XVI 2017
2017
Proceedings of SPIE - The International Society for Optical Engineering
9781510611535
2017
10348
1034816
none
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 Proceedings of SPIE - The International Society for Optical Engineering. SPIE [10.1117/12.2273713].
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/340905
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