Fluctuations in the Photoluminescence Excitation Spectra of Individual Semiconductor Nanocrystals
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Date
2024-05-09
Publication Type
Journal Article
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yes
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Abstract
Most single quantum emitters display non-steady emission properties. Models that explain this effect have primarily relied on photoluminescence measurements that reveal variations in intensity, wavelength, and excited-state lifetime. While photoluminescence excitation spectroscopy could provide complementary information, existing experimental methods cannot collect spectra before individual emitters change in intensity (blink) or wavelength (spectrally diffuse). Here, we present an experimental approach that circumvents such issues, allowing the collection of excitation spectra from individual emitters. Using rapid modulation of the excitation wavelength, we collect and classify excitation spectra from individual CdSe/CdS/ZnS core/shell/shell quantum dots. The spectra, along with simultaneous time-correlated single-photon counting, reveal two separate emission-reduction mechanisms caused by charging and trapping, respectively. During bright emission periods, we also observe a correlation between emission red-shifts and the increased oscillator strength of higher excited states. Quantum-mechanical modeling indicates that diffusion of charges in the vicinity of an emitter polarizes the exciton and transfers the oscillator strength to higher-energy transitions.
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published
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Journal / series
Volume
15 (18)
Pages / Article No.
4844 - 4850
Publisher
American Chemical Society
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Subject
Diffusion; Energy; Oscillation; Quantum dots; Quantum mechanics
Organisational unit
03875 - Norris, David J. / Norris, David J.
Notes
Funding
339905 - Quantum-Dot Plasmonics and Spasers (EC)