Evidence for Multiple Trapping Mechanisms in Single CdSe/ZnS Quantum Dots from Fluorescence Intermittency Measurements over a Wide Range of Excitation Intensities

Cordones, Amy A.; Bixby, Teresa J.; Leone, Stephen R.

doi:10.1021/jp2001223

Cited by 46 publications

(65 citation statements)

References 47 publications

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“…The pump dependence of the blinking traces and FLID maps of a g‐NQD showing A‐type blinking are displayed in Figure a,b and c,d respectively. As observed in earlier NQD blinking studies, the g‐NQDs blink more rapidly and the PL intensity distribution widens at higher pump powers because of an increase in photo‐ionization probability. The decay of the total PL signal (black curve) at the highest pump power and the decay extracted for the highest and lowest PL intensity ranges marked in Figure d (i.e., 18–20 KHz (blue curve), 5–7 KHz (red curve), respectively) are displayed in Figure e.…”

Section: Resultssupporting

confidence: 70%

Competition between Auger Recombination and Hot‐Carrier Trapping in PL Intensity Fluctuations of Type II Nanocrystals

Mangum

Wang

Dennis

et al. 2014

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Performing time-tagged, time-correlated, single-photon-counting studies on individual colloidal nanocrystal quantum dots (NQDs), the evolution of photoluminescence (PL) intensity-fluctuation behaviors in near-infrared (NIR) emitting type II, InP/CdS core-shell NQDs is investigated as a function of shell thickness. It is observed that Auger recombination and hot-carrier trapping compete in defining the PL intensity-fluctuation behavior for NQDs with thin shells, whereas the role of hot-carrier trapping dominates for NQDs with thick shells. These studies further reveal the distinct ramifications of altering either the excitation fluence or repetition rate. Specifically, an increase in laser pump fluence results in the creation of additional hot-carrier traps. Alternately, higher repetition rates cause a saturation in hot-carrier traps, thus activating Auger-related PL fluctuations. Furthermore, it is shown that Auger recombination of negatively charged excitons is suppressed more strongly than that of positively charged excitons because of the asymmetry in the electron-hole confinement in type II NQDs. Thus, this study provides new understanding of how both NQD structure (shell thickness and carrier-separation characteristics) and excitation conditions can be used to tune the PL stability, with important implications for room-temperature single-photon generation. Specifically, the first non-blinking NQD capable of single-photon emission in the near-infrared spectral regime is described.

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Section: Resultssupporting

confidence: 70%

Competition between Auger Recombination and Hot‐Carrier Trapping in PL Intensity Fluctuations of Type II Nanocrystals

Mangum

Wang

Dennis

et al. 2014

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“…On the other hand, distributions of the OFF times(Fig. S7)can be fitted using parameters that do not significantly change for the two irradiation modes.The difference between the ON and OFF time response to the different irradiation modes can point to the involvement of multiple trap states in the emission process 33. A mechanism proposed here to account for the different blinking behavior involves the two emitting D levels(Fig.…”

mentioning

confidence: 82%

Single-particle spectroscopy of I–III–VI semiconductor nanocrystals: spectral diffusion and suppression of blinking by two-color excitation

et al. 2016

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Ternary I-III-VI semiconductor nanocrystals have been explored as non-toxic alternatives to II-VI semiconductors for optoelectronic and sensing applications, but large photoluminescence spectral width and moderate brightness restrict their practical use. Here, using single-particle photoluminescence spectroscopy on nanocrystals of (AgIn)xZn2(1-x)S2 we show that the photoluminescence band is inhomogeneously broadened and that size distribution is the dominant factor in the broadening. The residual homogeneous linewidth of individual nanocrystals reaches up to 75% of the ensemble spectral width. Single nanocrystals undergo spectral diffusion which also contributes to the inhomogeneous band. Excitation with two lasers with energies above and below the bandgap reveals coexistence of two emitting donor states within one particle. Spectral diffusion in such particles is due to temporal activation and deactivation of one such state. Filling of a trap state with a lower-energy laser enables optical modulation of photoluminescence intermittency (blinking) and leads to an almost two-fold increase in brightness.

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“…35,[43][44][45][46][47][48][49] It has been postulated that hot carriers from Auger recombination of biexcitons may contribute to the ionization events, and that the excitation power dependence under low excitation conditions is quadratic. 5,[43][44][45] However, a linear dependence has also been reported, and this indicates that traps can capture carriers directly from single excitons. [48][49][50] Here, we observe a linear dependence of the charging rate on the power for QD 6 (Figure 4b), and a quasi-quadratic dependence for QD 7 (Figure 4f).…”

Section: Exponential and Power-law Auger-blinkingmentioning

confidence: 99%

Two Mechanisms Determine Quantum Dot Blinking

et al. 2018

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Many potential applications of quantum dots (QDs) can only be realized once the luminescence from single nanocrystals (NCs) is understood. These applications include the development of quantum logic devices, single-photon sources, long-life LEDs, and single-molecule biolabels. At the single-nanocrystal level, random fluctuations in the QD photoluminescence occur, a phenomenon termed blinking. There are two competing models to explain this blinking: Auger recombination and surface trap induced recombination. Here we use lifetime scaling on core-shell chalcogenide NCs to demonstrate that both types of blinking occur in the same QDs. We prove that Auger-blinking can yield single-exponential on/off times in contrast to earlier work. The surface passivation strategy determines which blinking mechanism dominates. This study summarizes earlier studies on blinking mechanisms and provides some clues that stable single QDs can be engineered for optoelectronic applications.

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Evidence for Multiple Trapping Mechanisms in Single CdSe/ZnS Quantum Dots from Fluorescence Intermittency Measurements over a Wide Range of Excitation Intensities

Cited by 46 publications

References 47 publications

Competition between Auger Recombination and Hot‐Carrier Trapping in PL Intensity Fluctuations of Type II Nanocrystals

Competition between Auger Recombination and Hot‐Carrier Trapping in PL Intensity Fluctuations of Type II Nanocrystals

Single-particle spectroscopy of I–III–VI semiconductor nanocrystals: spectral diffusion and suppression of blinking by two-color excitation

Two Mechanisms Determine Quantum Dot Blinking

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