Bulklike Hot Carrier Dynamics in Lead Sulfide Quantum Dots

Cho, Byungmoon; Peters, William K.; Hill, Robert J.; Courtney, Trevor L.; Jonas, David M.

doi:10.1021/nl1010349

Cited by 82 publications

(117 citation statements)

References 61 publications

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“…Fortunately these assumptions can be tested experimentally. In our previous study of NC spectator effects pumping was conducted high in the inter-band continuum since there the cross section for absorption is unaffected by the existence of other excitons [18,32]. This provides a trivial method for ensuring an equal dose of additional excitons deposited in samples with or without spectators.…”

Section: Resultsmentioning

confidence: 99%

Spin Blockades to Relaxation of Hot Multiexcitons in Nanocrystals

Ghosh

Dehnel

Fabian

et al. 2019

J. Phys. Chem. Lett.

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The rates of elementary photophysical processes in nanocrystals, such as carrier cooling, multiexciton generation, Auger recombination etc., are determined by monitoring the transient occupation of the lowest exciton band. The underlying assumption is that hot carriers relax rapidly to their lowest quantum level. Using femtosecond transient absorption spectroscopy in CdSe/CdS nanodots we challenge this assumption. Results show, that in nanodots containing a preexisting cold "spectator exciton", only half of the photoexcited electrons relax directly to the band-edge and the rest are blocked in an excited state due to Pauli exclusion. Full relaxation occurs only after˜15 ps, as the blocked electrons flip spin. This requires review of numerous studies unaware of this ubiquitous and novel effect, which may facilitate hot carrier energy utilization as well.arXiv:1809.08581v2 [cond-mat.mes-hall]

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Section: Resultsmentioning

confidence: 99%

Spin Blockades to Relaxation of Hot Multiexcitons in Nanocrystals

Ghosh

Dehnel

Fabian

et al. 2019

J. Phys. Chem. Lett.

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“…Qualitative discrepancies between the predictions of the effective mass model and results from quantum chemical calculations have been described previously. 50,51 The idea that highly energetic electron-hole pairs are bulk-like and largely localized on a length scale smaller than that of the quantum dot has been put forward previously for PbS 52 and PbSe 53 QDs. Experiments on CdSe/CdS dot-in-rod structures have also been interpreted to show long-lived exciton localization in the CdS shell.…”

Section: Figure 7 Experimental (Black) and Calculated (Red) Frequencmentioning

confidence: 99%

Electron–Phonon Coupling in CdSe/CdS Core/Shell Quantum Dots

et al. 2015

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Resonance Raman spectra and excitation profiles have been measured and semiquantitatively modeled for core/shell quantum dots consisting of 2.7 nm diameter zincblende CdSe cores and thin (0.5 nm) or thick (1.6 nm) CdS shells. The Raman spectra show previously reported trends of increased peak frequency for both the CdSe and the CdS longitudinal optical (LO) phonons with increasing shell thickness. We also find a strong dependence of the peak CdS frequency on excitation energy and a large discrepancy between the experimental frequency of the CdSe+CdS combination band and the sum of the corresponding fundamental frequencies. This suggests that the dominant transitions at high excitation energies are localized on either the CdSe core or the CdS shell and thereby cannot enhance combination band transitions between core and shell. The CdS to CdSe Raman intensity ratios at high excitation energies further support this picture. The electron-phonon coupling for the CdSe LO phonon in the lowest excitonic transition is slightly weaker in the core/shell structures than in pure CdSe quantum dots, contrary to expectations for the Fröhlich coupling mechanism. Possible explanations for this discrepancy are discussed.

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“…Recent advances in the fabrication of quantum dots (QDs) have provided new approaches for enhancing photo cell efficiencies. [4][5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Heat fluctuations and coherences in a quantum heat engine

2012

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We consider finite sized atomic systems with varying number of particles which have dipolar interactions among them and also under the collective driving and dissipative effect of thermal photon environment. Fo-cusing on the simple case of two atoms, we investigate the impact of different parameters of the model on the coherence contained in the system. We observe that even though the system is initialized in a completely incoherent state, it evolves to a state with a finite amount of coherence and preserve that coherence in the long-time limit in the presence of thermal photons. We propose a novel scheme to utilize the created coherence in order to change the thermal state of a single two-level atom by repeatedly interacting it with a coherent atomic beam. Finally, we discuss the scaling of coherence as a function of the number of particles in our system up to N = 7.

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Bulklike Hot Carrier Dynamics in Lead Sulfide Quantum Dots

Cited by 82 publications

References 61 publications

Spin Blockades to Relaxation of Hot Multiexcitons in Nanocrystals

Spin Blockades to Relaxation of Hot Multiexcitons in Nanocrystals

Electron–Phonon Coupling in CdSe/CdS Core/Shell Quantum Dots

Heat fluctuations and coherences in a quantum heat engine

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