Measurement of the Radiative and Nonradiative Decay Rates of Single CdSe Nanocrystals through a Controlled Modification of their Spontaneous Emission

Brokmann, Xavier; Coolen, Laurent; Dahan, Maxime; Hermier, Jean-Pierre

doi:10.1103/physrevlett.93.107403

Cited by 211 publications

(239 citation statements)

References 22 publications

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“…For an emission energy of 2.08 eV γ nrad = 0.017±0.006 ns −1 and γ hom rad = 0.065 ± 0.005 ns −1 giving a quantum efficiency of 80 ± 5 %. In figure 10 a) the nonradiative decay rate γ nrad and homogeneous radiative decay rate γ hom rad are shown as a function of the emission energy together with the result found by Brokmann et al [19] for ensembles. The nonradiative decay rate increases with emission energy or equivalently decreases with quantum dot size.…”

Section: Discussionmentioning

confidence: 99%

“…The emission rate will be affected by emission which is reflected at the interface and leads to a controlled modification of the local density of states (LDOS) allowing us to separate radiative and nonradiative decay rate components. This technique has been pioneered by Drexhage for dye molecules [15] and used to determine quantum efficiency of Si nanocrystals [16], erbium ions [17], epitaxially grown InAs quantum dots [18] and colloidal CdSe quantum dots [19,20].…”

Section: Introductionmentioning

confidence: 99%

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Size-dependent oscillator strength and quantum efficiency of CdSe quantum dots controlled via the local density of states

et al. 2009

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We study experimentally time-resolved emission of CdSe quantum dots in an environment with a controlled local density of states (LDOS). The decay rate is measured versus frequency and as a function of distance to a mirror. We observe a linear relation between the decay rate and the LDOS, allowing us to determine the size-dependent quantum efficiency and oscillator strength. We find that the quantum efficiency decreases with increasing emission energy mostly due to an increase in nonradiative decay. For the first time, we manage to obtain the oscillator strength of the important class of CdSe quantum dots. The oscillator strength varies weakly with frequency in agreement with behavior of quantum dots in the strong confinement limit. Surprisingly, the measured absolute values are a factor of 5 below theoretically calculated values. Our results are relevant for applications of CdSe quantum dots in spontaneous emission control and cavity quantum electrodynamics. * URL: www.photonicbandgaps.com arXiv:0808.3191v1 [physics.optics]

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Size-dependent oscillator strength and quantum efficiency of CdSe quantum dots controlled via the local density of states

et al. 2009

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“…First, the single molecule fluorescence QY is very well defined for CdSe QDs (closely related to CdTe QDs). Indeed, correlated AFM and fluorescence imaging, 199 fluorescence correlation spectroscopy, 200 and dielectric-dependent photoluminescence studies 201 have all demonstrated that the fluorescence QY approaches unity for individual bright QDs. Therefore, although the ensemble CdTe QD QY is ~70%, we can assume that the maximum fluorescence counts in a given time trace correspond to a single CdTe QD QY of ~100%.…”

Section: Single Molecule Fluorescence Quantum Yield Of Qdsmentioning

confidence: 99%

Photophysics of Individual Single-Walled Carbon Nanotubes

2008

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Single-walled carbon nanotubes (SWNTs) are cylindrical graphitic molecules that have remained at the forefront of nanomaterials research since 1991, largely due to their exceptional and unusual mechanical, electrical, and optical properties. The motivation for understanding how nanotubes interact with light (i.e., SWNT photophysics) is both fundamental and applied. Individual nanotubes may someday be used as superior near-infrared fluorophores, biological tags and sensors, and components for ultrahigh-speed optical communications systems. Establishing an understanding of basic nanotube photophysics is intrinsically significant and should enable the rapid development of such innovations. Unlike conventional molecules, carbon nanotubes are synthesized as heterogeneous samples, composed of molecules with different diameters, chiralities, and lengths. Because a nanotube can be either metallic or semiconducting depending on its particular molecular structure, SWNT samples are also mixtures of conductors and semiconductors. Early progress in understanding the optical characteristics of SWNTs was limited because nanotubes aggregate when synthesized, causing a mixing of the energy states of different nanotube structures. Recently, significant improvements in sample preparation have made it possible to isolate individual nanotubes, enabling many advances in characterizing their optical properties. In this Account, single-molecule confocal microscopy and spectroscopy were implemented to study the fluorescence from individual nanotubes. Single-molecule measurements naturally circumvent the difficulties associated with SWNT sample inhomogeneities. Intrinsic SWNT photoluminescence has a simple narrow Lorentzian line shape and a polarization dependence, as expected for a one-dimensional system. Although the local environment heavily influences the optical transition wavelength and intensity, single nanotubes are exceptionally photostable. In fact, they have the unique characteristic that their single molecule fluorescence intensity remains constant over time; SWNTs do not “blink” or photobleach under ambient conditions. In addition, transient absorption spectroscopy was used to examine the relaxation dynamics of photoexcited nanotubes and to elucidate the nature of the SWNT excited state. For metallic SWNTs, very fast initial recovery times (300–500 fs) corresponded to excited-state relaxation. For semiconducting SWNTs, an additional slower decay component was observed (50–100 ps) that corresponded to electron–hole recombination. As the excitation intensity was increased, multiple electron–hole pairs were generated in the SWNT; however, these e−h pairs annihilated each other completely in under 3 ps. Studying the dynamics of this annihilation process revealed the lifetimes for one, two, and three e−h pairs, which further confirmed that the photoexcitation of SWNTs produces not free electrons but rather one-dimensional bound electron–hole pairs (i.e., excitons). In summary, nanotube photophysics is a rapidly developing area o...

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“…The emission efficiency is assessed by the quantum yield (QY) which is given by the ratio between the radiative decay rate and the total decay rate due to radiative and non-radiative relaxations. Excitons in high quality CdSe structures have a QY close to unity 21,22 , while the trion state exhibits a QY ranging from 15 to 50% in this specific sample 11 .…”

Section: Flickeringmentioning

confidence: 99%

Effect of charging on CdSe/CdS dot-in-rods single-photon emission

et al. 2014

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The photon statistics of CdSe/CdS dot-in-rods nanocrystals is studied with a method involving post-selection of the photon detection events based on the photoluminescence count rate. We show that flickering between two states needs to be taken into account to interpret the single-photon emission properties. With post-selection we are able to identify two emitting states: the exciton and the charged exciton (trion), characterized by different lifetimes and different second order correlation functions. Measurements of the second order autocorrelation function at zero delay with postselection shows a degradation of the single photon emission for CdSe/CdS dot-in-rods in a charged state that we explain by deriving the neutral and charged biexciton quantum yields.

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Measurement of the Radiative and Nonradiative Decay Rates of Single CdSe Nanocrystals through a Controlled Modification of their Spontaneous Emission

Cited by 211 publications

References 22 publications

Size-dependent oscillator strength and quantum efficiency of CdSe quantum dots controlled via the local density of states

Size-dependent oscillator strength and quantum efficiency of CdSe quantum dots controlled via the local density of states

Photophysics of Individual Single-Walled Carbon Nanotubes

Effect of charging on CdSe/CdS dot-in-rods single-photon emission

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