Electric Field-Induced Emission Enhancement and Modulation in Individual CdSe Nanowires

Vietmeyer, Felix; Tchelidze, Tamar; Tsou, Veronica; Jankó, Boldizsár; Kuno, Masaru

doi:10.1021/nn3033997

Cited by 28 publications

(25 citation statements)

References 53 publications

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“…45À48 Hole trapping in CdSe nanocrystals was found to be related to poor surface passivation and Cd vacancies 36 and was shown to cause fast nonradiative recombination of the excitons with time constants on the order of 10 ps. 49,50 In the CdSe NPLs, it is expected that there might arise both surface traps and Cd vacancies, leading to interband hole trap states, which may rapidly quench the excitons nonradiatively. 15 Previously, blinking was also reported in the NPLs, suggesting that nonemissive or dark states arise in the NPL populations.…”

Section: Resultsmentioning

confidence: 99%

Stacking in Colloidal Nanoplatelets: Tuning Excitonic Properties

et al. 2014

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Cataloged from PDF version of article.Colloidal semiconductor quantum wells, also commonly known as nanoplatelets (NPLs), have arisen among the most promising materials for light generation and harvesting applications. Recently, NPLs have been found to assemble in stacks. However, their emerging characteristics essential to these applications have not been previously controlled or understood. In this report, we systematically investigate and present excitonic properties of controlled column-like NPL assemblies. Here, by a controlled gradual process, we show that stacking in colloidal quantum wells substantially increases exciton transfer and trapping. As NPLs form into stacks, surprisingly we find an order of magnitude decrease in their photoluminescence quantum yield, while the transient fluorescence decay is considerably accelerated. These observations are corroborated by ultraefficient Forster resonance energy transfer (FRET) in the stacked NPLs, in which exciton migration is estimated to be in the ultralong range (>100 nm). Homo-FRET (i.e., FRET among the same emitters) is found to be ultraefficient, reaching levels as high as 99.9% at room temperature owing to the close-packed collinear orientation of the NPLs along with their large extinction coefficient and small Stokes shift, resulting in a large Forster radius of similar to 13.5 nm. Consequently, the strong and long-range homo-FRET boosts exciton trapping in nonemissive NPLs, acting as exciton sink centers, quenching photoluminescence from the stacked NPLs due to rapid nonradiative recombination of the trapped excitons. The rate-equation-based model, which considers the exciton transfer and the radiative and nonradiative recombination within the stacks, shows an excellent match with the experimental data. These results show the critical significance of stacking control in NPL solids, which exhibit completely different signatures of homo-FRET as compared to that in colloidal nanocrystals due to the absence of inhomogeneous broadening

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Section: Resultsmentioning

confidence: 99%

Stacking in Colloidal Nanoplatelets: Tuning Excitonic Properties

et al. 2014

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“…As those robust excitons are stable at room temperature and still efficiently polarizable, there is great application potential for field-dependent photoluminescence (PL) nanoemitters or modulators. While field-controlled electroabsorption based modulators have been studied intensively both in experiment and theory, ,,− field-dependent photoluminescence (PL) nanoemitters − have been mostly discussed on a qualitative or semiquantitative level. However, these studies investigated field effects on Wannier excitons with rather weak exciton binding energy in contrast to the nanoplatelets.…”

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confidence: 99%

Time-Resolved Stark Spectroscopy in CdSe Nanoplatelets: Exciton Binding Energy, Polarizability, and Field-Dependent Radiative Rates

et al. 2016

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We present a study of the application potential of CdSe nanoplatelets (NPLs), a model system for colloidal 2D materials, as field-controlled emitters. We demonstrate that their emission can be changed by 28% upon application of electrical fields up to 175 kV/cm, a very high modulation depth for field-controlled nanoemitters. From our experimental results we estimate the exciton binding energy in 5.5 monolayer CdSe nanoplatelets to be E = 170 meV; hence CdSe NPLs exhibit highly robust excitons which are stable even at room temperature. This opens up the possibility to tune the emission and recombination dynamics efficiently by external fields. Our analysis further allows a quantitative discrimination of spectral changes of the emission energy and changes in PL intensity related to broadening of the emission line width as well as changes in the intrinsic radiative rates which are directly connected to the measured changes in the PL decay dynamics. With the developed field-dependent population model treating all occurring field-dependent effects in a global analysis, we are able to quantify, e.g., the ground state exciton transition dipole moment (3.0 × 10 Cm) and its polarizability, which determine the radiative rate, as well as the (static) exciton polarizability (8.6 × 10 eV cm/kV), all in good agreement with theory. Our results show that an efficient field control over the exciton recombination dynamics, emission line width, and emission energy in these nanoparticles is feasible and opens up application potential as field-controlled emitters.

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“…[8][9][10][11][12][13][14][15] However, the photophysical properties of Qdots subjected to an external electric field and in particular the behavior at the single nanocrystal level have received somewhat sporadic attention. [16][17][18][19] A Qdot can interact with an external electric field in several ways. A Qdot can be placed in a capacitor-like geometry such as in a light emitting diode device, where the electric field is applied between two parallel electrodes, 7,20 herein named external electric field.…”

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confidence: 99%

Charge trapping and de-trapping in isolated CdSe/ZnS nanocrystals under an external electric field: indirect evidence for a permanent dipole moment

et al. 2015

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Single nanoparticle studies of charge trapping and de-trapping in core/shell CdSe/ZnS nanocrystals incorporated into an insulating matrix and subjected to an external electric field demonstrate the ability to reversibly modulate the exciton dynamics and photoluminescence blinking while providing indirect evidence for the existence of a permanent ground state dipole moment in such nanocrystals. A model assuming the presence of energetically deep charge traps physically aligned along the direction of the permanent dipole is proposed in order to explain the dynamics of nanocrystal blinking in the presence of a permanent dipole moment.

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Electric Field-Induced Emission Enhancement and Modulation in Individual CdSe Nanowires

Cited by 28 publications

References 53 publications

Stacking in Colloidal Nanoplatelets: Tuning Excitonic Properties

Stacking in Colloidal Nanoplatelets: Tuning Excitonic Properties

Time-Resolved Stark Spectroscopy in CdSe Nanoplatelets: Exciton Binding Energy, Polarizability, and Field-Dependent Radiative Rates

Charge trapping and de-trapping in isolated CdSe/ZnS nanocrystals under an external electric field: indirect evidence for a permanent dipole moment

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