CdSe/ZnS quantum dot intermittency in N,N′-diphenyl-N,N′-bis(3-methylphenyl)-(1,1′-biphenyl)-4,4′-diamine (TPD)

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

doi:10.1016/j.cplett.2011.11.051

Cited by 26 publications

(8 citation statements)

References 40 publications

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“…At sub-Bohr dimensions, mobile charge carriers will frequently sample the QD surface and core as well as the host medium surrounding the QD. As such, interfacial states arising from unterminated bonds , and the QD host dielectric mismatch, , along with trap states on ligands , and in the host, , will all influence charge-carrier transport and recombination at the nanoscale.…”

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confidence: 99%

Sizing Up Excitons in Core–Shell Quantum Dots via Shell-Dependent Photoluminescence Blinking

Fisher

Osborne

2017

ACS Nano

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Semiconductor nanocrystals or quantum dots (QDs) are now widely used across solar cell, display, and bioimaging technologies. While advances in multishell, alloyed, and multinary core-shell QD structures have led to improved light-harvesting and photoluminescence (PL) properties of these nanomaterials, the effects that QD-capping have on the exciton dynamics that govern PL instabilities such as blinking in single-QDs is not well understood. We report experimental measurements of shell-size-dependent absorption and PL intermittency in CdSe-CdS QDs that are consistent with a modified charge-tunnelling, self-trapping (CTST) description of the exciton dynamics in these nanocrystals. By introducing an effective, core-exciton size, which accounts for delocalization of charge carriers across the QD core and shell, we show that the CTST models both the shell-depth-dependent red-shift of the QD band gap and changes in the on/off-state switching statistics that we observe in single-QD PL intensity trajectories. Further analysis of CdSe-ZnS QDs, shows how differences in shell structure and integrity affect the QD band gap and PL blinking within the CTST framework.

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confidence: 99%

Sizing Up Excitons in Core–Shell Quantum Dots via Shell-Dependent Photoluminescence Blinking

Fisher

Osborne

2017

ACS Nano

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“…When exciting near E g , the local minima in the EED of the PL QYs could result in further misinterpretations. Thus, whether characterizing the growth or passivation of colloidal QDs, monitoring energy transfer using QDs as donors or acceptors, , investigating blinking and charging dynamics within QDs, ,− or simply measuring the PL QYs of QD samples, correctly characterizing the EED of the PL QYs is essential for developing accurate interpretations of the results.…”

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confidence: 99%

Excitation Energy Dependence of the Photoluminescence Quantum Yields of Core and Core/Shell Quantum Dots

Hoy

Morrison

Steinberg

et al. 2013

J. Phys. Chem. Lett.

118

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The photoluminescence (PL) intensity of semiconductor quantum dots (QDs) is routinely monitored to track the chemical and physical properties within a sample or device incorporating the QDs. A dependence of the PL quantum yields (QYs) on the excitation energy could lead to erroneous conclusions but is commonly not considered. We summarize previous evidence and present results from two methodologies that confirm the possibility of a dependence of the PL QYs on the excitation energy. The data presented indicate that PL QYs of CdSe and CdSe/ZnS QDs suspended in toluene are highest for excitation just above the band gap, Eg, of each. The PL QYs decrease with increasing excitation energies up to 1 eV above Eg. The PL intensity decay profiles recorded for these samples at varying emission and excitation energies indicate that the changes in the PL QYs result from the nonradiative relaxation pathways sampled as the charge carriers relax down to the band edge.

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“…In the present study, we are focusing on the truncated part (exponential part) of the PDDs of ON- and OFF-events indicating the process such as trapping-induced charging (Auger photoionization) and detrapping-induced discharging (neutralization), respectively. The diffusion-controlled electron transfer (DCET) model proposed by Marcus and co-workers explains that the inverse of truncation time is equal to the energetic parameters of the corresponding process with a unit of s –1 , indicating that the process follows first-order kinetics. , The truncated power-law model has been widely used by several groups wherein the inverse of ON- and OFF-event truncation time is related to trapping and detrapping rates, both having a unit of second inverse. ,− In the present case, the PDDs are fitted with the ubiquitous truncated power-law (TPL) function, P ON ( t ) for the ON-state (eq ) and P OFF ( t ) for OFF-states (eq ) as where m represents the power-law exponent and τ c the truncation time (ON and OFF in the superscripts represent corresponding ON- and OFF-events, respectively). The function mentioned above describes a blinking process that can be modeled by a power-law function at the short times and an exponential function at the longer times (traces in the right column, Figure ).…”

Section: Resultsmentioning

confidence: 99%

“…In PDD analysis, the ON-to-OFF-transition (τ c ON ) and OFF-to-ON-transition (τ c OFF ) disclose the information about the trapping and detrapping kinetics, respectively. The charge trapping rate constant ( k t ) is calculated by taking the inverse of τ c ON , while the detrapping rate constant ( k d ) is obtained by the inverse of τ c OFF . ,,− The ratio of τ c ON to τ c OFF is equivalent to k d / k t in a single QD. The values for the power-law exponents for ON- and OFF-events of the four sets of QDs are provided in Table S2.…”

Section: Resultsmentioning

confidence: 99%

Core-Size-Dependent Trapping and Detrapping Dynamics in CdSe/CdS/ZnS Quantum Dots

2021

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The fascinating optoelectronic properties of semiconductor quantum dots (QDs) originate from the quantum confinement effect; i.e., the band gap increases as the size decreases. Another significant parameter dictating the photophysics of QD is the dynamics of trapping and detrapping from the trap-states, but it is nonetheless less understood. To understand these aspects, herein we investigate the photoluminescence (PL) fluctuations in CdSe QDs using time-resolved PL spectroscopy by systematically varying its core size, maintaining a constant shell thickness by coating with CdS followed by ZnS. The probability density distribution of ON- and OFF-events of QDs is constructed from the PL trajectories and fitted with the truncated power-law from which the trapping (k t) and detrapping (k d) rate constants are estimated. The increase in φPL observed with the increase in core size of CdSe at the ensemble level is related to the enhanced k d/k t and charge carrier wave function localization in the core. Indeed, the band gap decreases as the core size increases, bringing the trap-states close to the band edge positions, leading to an efficient detrapping of carriers. The fluorescence lifetime-intensity distribution plots revealed the presence of a high-intensity and high-lifetime component due to neutral exciton recombination and a low-intensity and low-lifetime component due to trap-induced Auger recombination. The decay kinetics in a single QD is further modeled using a pre-equilibrium approximation.

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CdSe/ZnS quantum dot intermittency in N,N′-diphenyl-N,N′-bis(3-methylphenyl)-(1,1′-biphenyl)-4,4′-diamine (TPD)

Cited by 26 publications

References 40 publications

Sizing Up Excitons in Core–Shell Quantum Dots via Shell-Dependent Photoluminescence Blinking

Sizing Up Excitons in Core–Shell Quantum Dots via Shell-Dependent Photoluminescence Blinking

Excitation Energy Dependence of the Photoluminescence Quantum Yields of Core and Core/Shell Quantum Dots

Core-Size-Dependent Trapping and Detrapping Dynamics in CdSe/CdS/ZnS Quantum Dots

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