Ultrafast Exciton Dynamics in CdxHg(1-x)Te alloy Quantum Dots

Marina A. Leontiadou; Ali Al-Otaify; Stephen V. Kershaw; Olga Zhovtiuk; Sergii Kalytchuk; Derrick Mott; Shinya Maenosono; Andrey L. Rogach; David J. Binks

doi:10.1016/j.chemphys.2016.02.003

Ultrafast Exciton Dynamics in Cd_xHg_(1-x)Te alloy Quantum Dots

Marina A. Leontiadou^*, Ali Al-Otaify, Stephen V. Kershaw, Olga Zhovtiuk, Sergii Kalytchuk, Derrick Mott, Shinya Maenosono, Andrey L. Rogach, David J. Binks

^*Corresponding author for this work

Research output: Journal Publications and Reviews › RGC 21 - Publication in refereed journal › peer-review

13 Citations (Scopus)

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Abstract

Ultrafast transient absorption spectroscopy is used to investigate sub-nanosecond exciton dynamics in Cd_xHg₍₁_-_x₎Te alloy colloidal quantum dots. A bleach was observed at the band gap due to state-filling, the mono-exponential decay of which had a characteristic lifetime of 91 ± 1 ps and was attributed to biexciton recombination; no evidence of surface-related trapping was observed. The rise time of the bleach, which is determined by the rate at which hot electrons cool to the band-edge, ranged between 1 and 5 ps depending on the pump photon energy. Measuring the magnitude of the bleach decay for different pump fluences and wavelengths allowed the quantum yield of multiple exciton generation to be determined, and was 115 ± 1% for pump photons with energy equivalent to 2.6 times the band gap.

Original language	English
Pages (from-to)	25-30
Journal	Chemical Physics
Volume	469-470
Online published	24 Feb 2016
DOIs	https://doi.org/10.1016/j.chemphys.2016.02.003
Publication status	Published - 1 May 2016

Research Keywords

CdHgTe alloy quantum dot
Femtosecond transient absorption spectroscopy
Multiple exciton generation

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title = "Ultrafast Exciton Dynamics in CdxHg(1-x)Te alloy Quantum Dots",

abstract = "Ultrafast transient absorption spectroscopy is used to investigate sub-nanosecond exciton dynamics in CdxHg(1-x)Te alloy colloidal quantum dots. A bleach was observed at the band gap due to state-filling, the mono-exponential decay of which had a characteristic lifetime of 91 ± 1 ps and was attributed to biexciton recombination; no evidence of surface-related trapping was observed. The rise time of the bleach, which is determined by the rate at which hot electrons cool to the band-edge, ranged between 1 and 5 ps depending on the pump photon energy. Measuring the magnitude of the bleach decay for different pump fluences and wavelengths allowed the quantum yield of multiple exciton generation to be determined, and was 115 ± 1% for pump photons with energy equivalent to 2.6 times the band gap.",

keywords = "CdHgTe alloy quantum dot, Femtosecond transient absorption spectroscopy, Multiple exciton generation",

author = "Leontiadou, {Marina A.} and Ali Al-Otaify and Kershaw, {Stephen V.} and Olga Zhovtiuk and Sergii Kalytchuk and Derrick Mott and Shinya Maenosono and Rogach, {Andrey L.} and Binks, {David J.}",

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doi = "10.1016/j.chemphys.2016.02.003",

language = "English",

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T1 - Ultrafast Exciton Dynamics in CdxHg(1-x)Te alloy Quantum Dots

AU - Leontiadou, Marina A.

AU - Al-Otaify, Ali

AU - Kershaw, Stephen V.

AU - Zhovtiuk, Olga

AU - Kalytchuk, Sergii

AU - Mott, Derrick

AU - Maenosono, Shinya

AU - Rogach, Andrey L.

AU - Binks, David J.

PY - 2016/5/1

Y1 - 2016/5/1

N2 - Ultrafast transient absorption spectroscopy is used to investigate sub-nanosecond exciton dynamics in CdxHg(1-x)Te alloy colloidal quantum dots. A bleach was observed at the band gap due to state-filling, the mono-exponential decay of which had a characteristic lifetime of 91 ± 1 ps and was attributed to biexciton recombination; no evidence of surface-related trapping was observed. The rise time of the bleach, which is determined by the rate at which hot electrons cool to the band-edge, ranged between 1 and 5 ps depending on the pump photon energy. Measuring the magnitude of the bleach decay for different pump fluences and wavelengths allowed the quantum yield of multiple exciton generation to be determined, and was 115 ± 1% for pump photons with energy equivalent to 2.6 times the band gap.

AB - Ultrafast transient absorption spectroscopy is used to investigate sub-nanosecond exciton dynamics in CdxHg(1-x)Te alloy colloidal quantum dots. A bleach was observed at the band gap due to state-filling, the mono-exponential decay of which had a characteristic lifetime of 91 ± 1 ps and was attributed to biexciton recombination; no evidence of surface-related trapping was observed. The rise time of the bleach, which is determined by the rate at which hot electrons cool to the band-edge, ranged between 1 and 5 ps depending on the pump photon energy. Measuring the magnitude of the bleach decay for different pump fluences and wavelengths allowed the quantum yield of multiple exciton generation to be determined, and was 115 ± 1% for pump photons with energy equivalent to 2.6 times the band gap.

KW - CdHgTe alloy quantum dot

KW - Femtosecond transient absorption spectroscopy

KW - Multiple exciton generation

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U2 - 10.1016/j.chemphys.2016.02.003

DO - 10.1016/j.chemphys.2016.02.003

M3 - RGC 21 - Publication in refereed journal

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VL - 469-470

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JO - Chemical Physics

JF - Chemical Physics

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