Effect of electric field on the photoluminescence intensity of single CdSe nanocrystals

Park, Soo‐Young; Link, Stephan; Miller, William L.; Gesquiere, Andre J.; Barbara, Paul F.

doi:10.1016/j.chemphys.2007.06.025

Cited by 81 publications

(105 citation statements)

References 26 publications

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“…Indeed, although many of the proposed models for blinking are based on charging processes, an alternative class of models based on fluctuating nonradiative rates 16,17,31,32 has also been proposed. In these models, blinking is associated with opening and closing certain nonradiative exciton recombination pathways involving localized surface states.…”

Section: Discussionmentioning

confidence: 99%

Collective fluorescence enhancement in nanoparticle clusters

et al. 2011

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many nanoscale systems are known to emit light intermittently under continuous illumination. In the fluorescence of single semiconductor nanoparticles, the distributions of bright and dark periods ('on' and 'off' times) follow Lévy statistics. Although fluorescence from single-quantum dots and from macroscopic quantum dot ensembles has been studied, there has been little study of fluorescence from small ensembles. Here we show that blinking nanorods (nRs) interact with each other in a cluster, and the interactions affect the blinking statistics. The ontimes in the fluorescence of a nR cluster increase dramatically; in a cluster with N nRs, the maximum on-time increases by a factor of N or more compared with the combined signal from N well-separated nRs. our study emphasizes the use of statistical properties in identifying the collective dynamics. The scaling of this interaction-induced increase of on-times with number of nRs reveals a novel collective effect at the nanoscale.

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Section: Discussionmentioning

confidence: 99%

Collective fluorescence enhancement in nanoparticle clusters

et al. 2011

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“…S9) as expected for the Stark effect. The intensity drop is partly attributed to field-induced dissociation of electron-hole pairs and their subsequent participation in non-radiative recombination processes 34,35 (such as Auger recombination). From our numerical simulations, we find that the central beam for the asymmetric slit-groove structure (Fig.…”

Section: Confocal Scanning Images Of the Collimated Fluorescent Emissmentioning

confidence: 99%

Plasmonic beaming and active control over fluorescent emission

Jun

Huang²,

Brongersma³

2011

Nat Commun

194

185

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nanometallic optical antennas are rapidly gaining popularity in applications that require exquisite control over light concentration and emission processes. The search is on for highperformance antennas that offer facile integration on chips. Here we demonstrate a new, easily fabricated optical antenna design that achieves an unprecedented level of control over fluorescent emission by combining concepts from plasmonics, radiative decay engineering and optical beaming. The antenna consists of a nanoscale plasmonic cavity filled with quantum dots coupled to a miniature grating structure that can be engineered to produce one or more highly collimated beams. Electromagnetic simulations and confocal microscopy were used to visualize the beaming process. The metals defining the plasmonic cavity can be utilized to electrically control the emission intensity and wavelength. These findings facilitate the realization of a new class of active optical antennas for use in new optical sources and a wide range of nanoscale optical spectroscopy applications.

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“…In contrast, above 4 V, the PL intensity decreases monotonically with increasing bias, tracking the decrease in EQE of the QD-LED. The correspondence between the decreasing PL intensities and EQE with applied bias identifies the change in the QD luminescence efficiency to be sufficient to explain the QD-LED roll-off behavior.Reduction of PL efficiency in QD thin films has been previously measured when QDs are heated [8], charged (Auger recombination) [9], or placed under a strong electric field [10,11]. We eliminate temperature effects on the QD PL efficiency, as measurement of the operating temperature of our QD-LEDs with an infrared camera shows a change of no more than a few degrees, which is not sufficient to affect the PL efficiency and explain the roll-off.…”

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confidence: 99%

Origin of Efficiency Roll-Off in Colloidal Quantum-Dot Light-Emitting Diodes

et al. 2013

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We study the origin of efficiency roll-off (also called ''efficiency droop'') in colloidal quantum-dot light-emitting diodes through the comparison of quantum-dot (QD) electroluminescence and photoluminescence. We find that an electric-field-induced decrease in QD luminescence efficiency-and not charge leakage or QD charging (Auger recombination)-is responsible for the roll-off behavior, and use the quantum confined Stark effect to accurately predict the external quantum efficiency roll-off of QD light-emitting diodes. DOI: 10.1103/PhysRevLett.110.217403 PACS numbers: 85.60.Jb, 85.35.Be, 85.60.Bt Quantum-dot light-emitting diodes (QD-LEDs), which capitalize on the excellent color saturation and high photoluminescence efficiency of colloidal QDs, offer the prospect of a new generation of display technologies [1]. However, these devices suffer from decreasing efficiency [measured as the ratio of the number of photons emitted out of the QD-LED to the number of electrons injected into the device, per unit time, known as external quantum efficiency (EQE)] at high current densities. This behavior, termed efficiency roll-off or efficiency droop, is a problem that affects most types of LEDs [2][3][4]. The origin of the efficiency roll-off continues to be a topic of debate and understanding its cause is essential to developing highbrightness, high current density QD-LEDs. In this Letter, we investigate the origins of the roll-off behavior in QD-LEDs by performing simultaneous measurements of electroluminescence (EL) and photoluminescence (PL) intensities of a QD-LED, which pinpoint the cause to be a decrease in QD luminescence efficiency. Comparison of EL and PL spectra reveals that strong electric fields are responsible for the reduced QD luminescence, and the quantum confined Stark effect (QCSE) and transient PL measurements consistently explain the observed phenomena.The device structure investigated was a QD-LED with organic-inorganic hybrid charge transport layers that has recently attracted attention owing to its record high EQE and brightness [2]. The device was fabricated on a glass substrate coated with indium tin oxide and has the structure: ITO ð150nmÞ=ZnO ð50 nmÞ=QDs ð30 nmÞ=4, 4-bis(carbazole-9-yl) biphenyl (CBP) ð100 nmÞ=MoO 3 ð10 nmÞ=Al (100 nm). ZnO was radio-frequency sputtered, QDs were spin-cast out of chloroform, and CBP, MoO 3 , and Al were thermally evaporated. We used CdSe-ZnCdS core-shell QDs with a peak PL wavelength of 610 nm, provided by QD Vision, Inc. Current density and normalized EQE for a typical device are shown in Fig. 1(a). The EQE peaks at 2% for 4 V applied bias and rolls-off by 50% by 8 V. The energy band diagram of the device is shown in the inset and is based on literature values [4][5][6][7].The decrease in EQE at high biases may be a result of either charge carriers leaking out of the QD layer or a reduction in QD luminescence efficiency. To identify which of these two mechanisms dominates, we perform a simultaneous EL-PL experiment and monitor the relative PL efficiency of t...

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Effect of electric field on the photoluminescence intensity of single CdSe nanocrystals

Cited by 81 publications

References 26 publications

Collective fluorescence enhancement in nanoparticle clusters

Collective fluorescence enhancement in nanoparticle clusters

Plasmonic beaming and active control over fluorescent emission

Origin of Efficiency Roll-Off in Colloidal Quantum-Dot Light-Emitting Diodes

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