Hot carrier relaxation dynamics in non-stoichiometric CdSe quantum dots: computational insights

Gumber, Shriya; Eniodunmo, Omolola; Ivanov, Sergei A.; Kilina, Svetlana; Prezhdo, Oleg V.; Ghosh, Dibyajyoti; Tretiak, Sergei

doi:10.1039/d3ta00149k

Cited by 9 publications

(11 citation statements)

References 72 publications

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“…In contrast, the observables in the SMF and DISH methods are obtained directly from the stochastic TD-SE. The DISH method is widely used to model excited state dynamics in a broad range of systems. − …”

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confidence: 99%

Zeno and Anti-Zeno Effects in Nonadiabatic Molecular Dynamics

Gumber

Prezhdo

2023

J. Phys. Chem. Lett.

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Decoherence plays an important role in nonadiabatic (NA) molecular dynamics (MD) simulations because it provides a physical mechanism for trajectory hopping and can alter transition rates by orders of magnitude. Generally, decoherence effects slow quantum transitions, as exemplified by the quantum Zeno effect: in the limit of infinitely fast decoherence, the transitions stop. If the measurements are not sufficiently frequent, an opposite quantum anti-Zeno effect occurs, in which the transitions are accelerated with faster decoherence. Using two common NA-MD approaches, fewest switches surface hopping and decoherence-induced surface hopping, combined with analytic examination, we demonstrate that including decoherence into NA-MD slows down NA transitions; however, many realistic systems operate in the anti-Zeno regime. Therefore, it is important that NA-MD methods describe both Zeno and anti-Zeno effects. Numerical simulations of charge trapping and relaxation in graphitic carbon nitride suggest that time-dependent NA Hamiltonians encountered in realistic systems produce robust results with respect to errors in the decoherence time, a favorable feature for NA-MD simulations.

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confidence: 99%

Zeno and Anti-Zeno Effects in Nonadiabatic Molecular Dynamics

Gumber

Prezhdo

2023

J. Phys. Chem. Lett.

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“…Several experimental studies have successfully synthesized and characterized these magic-sized QDs. 29,51,[53][54][55][56] After unconstrained geometry optimization of Cd 33 Se 33 , all Cd/Se atoms become at least a 3-coordinated state and consequently exhibit a defect-free electronic gap (Fig. S1 †).…”

Section: Resultsmentioning

confidence: 99%

“…The vibrational modes give rise to enhanced electron–phonon interactions and significantly impact the energy states, band edge positions, and instantaneous band gaps of semiconductor QDs. 15,42,53,88…”

Section: Resultsmentioning

confidence: 99%

“…The inverse participation ratio (IPR) for electronic states was calculated using the formalism used by Abtew et al and some of us. 53,68,109 Here, all the computational simulations of doped QDs were performed in their neutral charge state.…”

Section: Computational Methodologymentioning

confidence: 99%

“…The vibrational modes give rise to enhanced electron-phonon interactions and significantly impact the energy states, band edge positions, and instantaneous band gaps of semiconductor QDs. 15,42,53,88 The band gap distribution of pristine Cd 33 Se 33 shows a broadened peak, revealing its considerable variation over time (section S7 and Fig. S16a †).…”

Section: Dynamic Electronic Propertiesmentioning

confidence: 99%

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The impact of spatially heterogeneous chemical doping on the electronic properties of CdSe quantum dots: insights from ab initio computation

Deswal,

Samanta,

Ghosh

2023

Nanoscale

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Ground- and Excited-State Properties of Charged Non-Stoichiometric Quantum Dots

Eniodunmo,

Gumber,

Prezhdo

et al. 2023

Chem. Mater.

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Charged excited states can accumulate on the surface of colloidal quantum dots (QDs), affecting their optoelectronic properties. In experimental samples, QDs often have non-stoichiometric structures, giving rise to cation-rich and anion-rich nanostructures. We explore the effect of charge on the ground-and excited-state properties of CdSe non-stoichiometric QDs (NS-QDs) of ∼1.5 nm in size using density functional theory calculations. We compare two cases: (i) NS-QDs with a charge introduced by direct hole or electron injection and (ii) neutral NS-QDs with one removed surface ligand (with a dangling bond). Our calculations reveal that a neutral dangling bond has an effect on the electronic structure similar to that of the electron injection for the Cd-rich NS-QDs or hole injection for the Se-rich NS-QDs. In Cd-rich structures, either the injection of an electron or the removal of a passivating ligand results in the surface-localized half-filled trap state inside the energy gap. For Se-rich structures, either the injection of a hole or the removal of a ligand introduces surface-localized unoccupied trap states inside the energy gap. As a result, the charge localization formed by these two approaches leads to an appearance of low-energy electronic transitions strongly red-shifted from the main excitonic band of NS-QDs. These transitions related to a negative charge or a dangling bond exhibit weak optical activity in Cd-rich NS-QDs. Transitions related to a positive charge or a dangling bond are optically forbidden in Se-rich NS-QDs. In contrast, electron injection in Se-rich NS-QDs strongly increases the optical activity of the lowestred-shifted charge-originated states.

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Hot carrier relaxation dynamics in non-stoichiometric CdSe quantum dots: computational insights

Abstract: Spatial confinement of charge carriers in nanosize semiconductor quantum dots (QDs) results in highly tunable, size-dependent optoelectronic properties that can be utilized in various commercial applications. Although, in such nanostructures,...

Cited by 9 publications

References 72 publications

Zeno and Anti-Zeno Effects in Nonadiabatic Molecular Dynamics

Zeno and Anti-Zeno Effects in Nonadiabatic Molecular Dynamics

The impact of spatially heterogeneous chemical doping on the electronic properties of CdSe quantum dots: insights from ab initio computation

Ground- and Excited-State Properties of Charged Non-Stoichiometric Quantum Dots

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