Two-Color Antibunching from Band-Gap Engineered Colloidal Semiconductor Nanocrystals

Deutsch, Zvicka; Schwartz, Osip; Tenne, Ron; Popovitz‐Biro, Ronit; Oron, Dan

doi:10.1021/nl300638t

Cited by 48 publications

(75 citation statements)

References 24 publications

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“…In contrast, the anticorrelation in frequency, which we will qualify as "frequency antibunching" in agreement with the literature [33], reflects only anticorrelations of intensities, which can be linked or not to a quantum character of the emission. Our main theme in this paper is illustrated in Fig.…”

Section: Frequency-resolved Mandel Parametersupporting

confidence: 87%

Optimization of photon correlations by frequency filtering

2015

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Section: Frequency-resolved Mandel Parametersupporting

confidence: 87%

Optimization of photon correlations by frequency filtering

2015

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“…17 These QDs exhibited the ultimate proof of dual emission from a single nanoparticle, that is, correlated photon statistics of two emission colors (“two-color antibunching”). 4 The first demonstrations of these effects used a QD–QD asymmetric heterostructure geometry, based on tip growth on a seeded rod. 4 In CdSe:Te/CdS/CdZnSe doped-core/rod/dot nanoparticles, the CdS rod served as a thick tunneling barrier between the Te-doped CdSe well and the CdZnSe well only for the holes.…”

Section: Toward Colloidal Double Quantum Dotsmentioning

confidence: 99%

“…4 The first demonstrations of these effects used a QD–QD asymmetric heterostructure geometry, based on tip growth on a seeded rod. 4 In CdSe:Te/CdS/CdZnSe doped-core/rod/dot nanoparticles, the CdS rod served as a thick tunneling barrier between the Te-doped CdSe well and the CdZnSe well only for the holes. 4 In contrast, since the conduction band is nearly flat, excited electrons can interact with holes excited at either side of the rod.…”

Section: Toward Colloidal Double Quantum Dotsmentioning

confidence: 99%

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Colloidal Double Quantum Dots

et al. 2016

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ConspectusPairs of coupled quantum dots with controlled coupling between the two potential wells serve as an extremely rich system, exhibiting a plethora of optical phenomena that do not exist in each of the isolated constituent dots. Over the past decade, coupled quantum systems have been under extensive study in the context of epitaxially grown quantum dots (QDs), but only a handful of examples have been reported with colloidal QDs. This is mostly due to the difficulties in controllably growing nanoparticles that encapsulate within them two dots separated by an energetic barrier via colloidal synthesis methods. Recent advances in colloidal synthesis methods have enabled the first clear demonstrations of colloidal double quantum dots and allowed for the first exploratory studies into their optical properties. Nevertheless, colloidal double QDs can offer an extended level of structural manipulation that allows not only for a broader range of materials to be used as compared with epitaxially grown counterparts but also for more complex control over the coupling mechanisms and coupling strength between two spatially separated quantum dots.The photophysics of these nanostructures is governed by the balance between two coupling mechanisms. The first is via dipole–dipole interactions between the two constituent components, leading to energy transfer between them. The second is associated with overlap of excited carrier wave functions, leading to charge transfer and multicarrier interactions between the two components. The magnitude of the coupling between the two subcomponents is determined by the detailed potential landscape within the nanocrystals (NCs).One of the hallmarks of double QDs is the observation of dual-color emission from a single nanoparticle, which allows for detailed spectroscopy of their properties down to the single particle level. Furthermore, rational design of the two coupled subsystems enables one to tune the emission statistics from single photon emission to classical emission. Dual emission also provides these NCs with more advanced functionalities than the isolated components. The ability to better tailor the emission spectrum can be advantageous for color designed LEDs in lighting and display applications. The different response of the two emission colors to external stimuli enables ratiometric sensing. Control over hot carrier dynamics within such structures allows for photoluminescence upconversion.This Account first provides a description of the main hurdles toward the synthesis of colloidal double QDs and an overview of the growing library of synthetic pathways toward constructing them. The main discoveries regarding their photophysical properties are then described in detail, followed by an overview of potential applications taking advantage of the double-dot structure. Finally, a perspective and outlook for their future development is provided.

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“…For example, CdSe/CdS core/shell tetrapods have exhibited luminescence from higher-energy transitions that appear to involve unrelaxed electrons. 46 Emission from higher-energy transitions has also been observed for heterostructures that have been engineered to provide two spatially separate potential minima for carriers; 47,48 for CdSe/ZnS/CdSe core/shell/shell nanocrystals, in particular, transient-absorption measurements also provide evidence for inhibited electron relaxation.…”

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confidence: 99%

Controlling the spatial location of photoexcited electrons in semiconductor CdSe/CdS core/shell nanorods

et al. 2013

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It is commonly assumed that, after an electron-hole pair is created in a semiconductor by absorption of a photon, the electron and hole rapidly relax to their respective lowest-energy states before recombining with one another. In semiconductor heterostructure nanocrystals, however, intraband relaxation can be inhibited to the point where recombination occurs primarily from an excited state. We demonstrate this effect using time-resolved optical measurements of CdSe/CdS core/shell nanorods. For nanorods with large CdSe cores, an electron photoexcited into the lowest-energy state in the core remains in the core, and an electron photoexcited into an excited state in the CdS shell remains in the shell, until the electron recombines with the hole. This provides a means of controlling the spatial location of photoexcited electrons by excitation energy. The control over electron localization is explained in terms of slow relaxation into the lowest-energy electron state in the nanorods, on time scales slower than electron-hole recombination. The observation of inhibited relaxation suggests that a simple picture of band alignment is insufficient for understanding charge separation in semiconductor heterostructures.

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Two-Color Antibunching from Band-Gap Engineered Colloidal Semiconductor Nanocrystals

Cited by 48 publications

References 24 publications

Optimization of photon correlations by frequency filtering

Optimization of photon correlations by frequency filtering

Colloidal Double Quantum Dots

Controlling the spatial location of photoexcited electrons in semiconductor CdSe/CdS core/shell nanorods

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