Phonon-Driven Energy Relaxation in PbS/CdS and PbSe/CdSe Core/Shell Quantum Dots

Lystrom, Levi; Tamukong, Patrick; Mihaylov, Deyan; Kilina, Svetlana

doi:10.1021/acs.jpclett.0c00845

Cited by 12 publications

(11 citation statements)

References 74 publications

(144 reference statements)

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“…All these PbSe QDs and corresponding core/shell QDs show Stokes shifts of ca. 30–40 nm, which are similar to the literature reports. ,, The observed red shift during shell growth may be explained by the quasi-type II band alignment of PbSe/CdS QDs. , With the increase of the CdS shell, the delocalization of either electron or hole wave function into a shell layer induced the red shift. , …”

Section: Resultssupporting

confidence: 89%

Colloidal Synthesis of Giant Shell PbSe-Based Core/Shell Quantum Dots in Polar Solvent: Cation Exchange versus Epitaxial Growth

et al. 2020

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Shell thickness control of core/shell quantum dots (QDs) plays an important role in determining their optical properties as well as the corresponding device performance. PbSebased core/shell QDs are attractive near-infrared (NIR) light emitters for photonic and optoelectronic applications. We herein report the colloidal synthesis of giant shell PbSe-based core/shell QDs through controllable reactions between preformed PbSe QDs and Cd 2+ ions in polar solvents. The preformed PbSe QDs experienced cation-exchange reaction in N,N-dimethylformamide (DMF), while they underwent epitaxial growth of CdS shell in dimethyl sulfoxide (DMSO). The cation exchange of preformed PbSe QDs in DMF result in PbSe/CdSe core/shell QDs with similar size (ca. 6.3 nm) but tunable shell thickness from 0.5 to 2.9 nm. In comparison, the epitaxial growth of preformed PbSe QDs in DMSO produce PbSe/CdS core/shell QDs in DMSO with average core size of ∼5.7 nm but tunable shell thickness from 0.5 to 3.1 nm. These resulting PbSe-based core/shell QDs show tunable photoluminescence emission of 1393−1744 nm for PbSe/CdSe core/shell QDs and 1566−1719 nm for PbSe/CdS core/ shell QDs. The cation exchange and epitaxial growth reactions of preformed PbSe QDs were further investigated by comparing the interactions between solvents and cation ions through nuclear magnetic resonance (NMR) measurements. The interactions between Cd 2+ and DMSO are stronger than that of DMF, while the interactions between Pb 2+ and DMSO are weaker than that of DMF. The difference accounts for the reaction transition from cation exchange to epitaxial growth, providing alternative route for fabricating shell controllable PbSe-based core/shell QDs.

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Section: Resultssupporting

confidence: 89%

Colloidal Synthesis of Giant Shell PbSe-Based Core/Shell Quantum Dots in Polar Solvent: Cation Exchange versus Epitaxial Growth

et al. 2020

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“…Nonadiabatic dynamics (NAD) is a powerful tool for predicting the coupled evolution of electrons and nuclei. It can be used to detail excited state processes in chemical systems, such as hot carrier cooling, − electron–hole recombination, − and carrier–carrier and carrier–phonon scattering . Multiple trajectory surface hopping (TSH) approaches are available nowadays for modeling NAD, − with methods like Tully’s fewest switches surface hopping (FSSH) algorithm being among the most adopted ones.…”

Section: Introductionmentioning

confidence: 99%

“…Despite the simplicity of the TSH approaches, their application to modeling NAD in nanoscale systems and periodic solids is still prohibitively expensive. To enable such simulations, two key approximations are widely used: (a) the Neglect-of-Back-Reaction Approximation (NBRA) of Craig, Duncan, and Prezhdo, − which neglects the response of nuclear evolution to the change of electronic states upon photoexcitation or excited state decay; (b) the single-particle (SP) approximation in modeling electronic excited states, where the state energies and nonadiabatic couplings (NACs) are computed using the properties of 1-electron molecular orbitals (MOs) such as Kohn–Sham (KS) orbitals, ,,− semiempirical or ab initio MOs, ,− and individual excited Slater determinants (SDs) built out of these types of SP orbitals. , …”

Section: Introductionmentioning

confidence: 99%

Nonadiabatic Dynamics in Si and CdSe Nanoclusters: Many-Body vs Single-Particle Treatment of Excited States

Smith

Shakiba

Akimov

2021

J. Chem. Theory Comput.

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In this work, we report a new nonadiabatic molecular dynamics methodology that incorporates many-body (MB) effects in the treatment of electronic excited states in extended atomistic systems via linear-response time-dependent density functional theory (TD-DFT). The nonradiative dynamics of excited states in Si 75 H 64 and Cd 33 Se 33 nanocrystals is studied at the MB (TD-DFT) and single-particle (SP) levels to reveal the role of MB effects. We find that a MB description of the excited states qualitatively changes the structure of coupling between the excited states, leading to larger nonadiabatic couplings and accelerating the dynamics by a factor of 2−4. The dependence of excited state dynamics in these systems on the surface hopping/decoherence methodology and the choice of the dynamical basis is investigated and analyzed. We demonstrated that the use of special "electron-only" or "hole-only" excitation bases may be advantageous over using the full "electron−hole" basis of SP states, making the computed dynamics more consistent with the one obtained at the MB level.

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“…Depending on the level of theory used and the size of the systems studied, such calculations may be quite expensive. Conventionally, few-picosecond trajectories are computed for systems of few hundreds of atoms while using Kohn–Sham (KS) orbitals and pure functionals such as the Perdew–Burke–Ernzerhof (PBE). ,,− Recently, we have extended this procedure to go beyond the KS picture via the time-dependent density functional theory (TD-DFT) calculations of excited states and computing the corresponding couplings. , However, one major drawback of such an approach is that the TD-DFT still relies on the short-ranged exchange component of the PBE functional and hence is incapable of fully capturing excitonic effects. To capture such effects, the TD-DFT calculations with hybrid functionals are desirable.…”

mentioning

confidence: 99%

Extending the Time Scales of Nonadiabatic Molecular Dynamics via Machine Learning in the Time Domain

Akimov

2021

J. Phys. Chem. Lett.

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A novel methodology for direct modeling of long-time scale nonadiabatic dynamics in extended nanoscale and solid-state systems is developed. The presented approach enables forecasting the vibronic Hamiltonians as a direct function of time via machine-learning models trained directly in the time domain. The use of periodic and aperiodic functions that transform time into effective input modes of the artificial neural network is demonstrated to be essential for such an approach to work for both abstract and atomistic models. The best strategies and possible limitations pertaining to the new methodology are explored and discussed. An exemplary direct simulation of unprecedentedly long 20 picosecond trajectories is conducted for a divacancy-containing monolayer black phosphorus system, and the importance of conducting such extended simulations is demonstrated. New insights into the excited states photophysics in this system are presented, including the role of decoherence and model definition.

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Phonon-Driven Energy Relaxation in PbS/CdS and PbSe/CdSe Core/Shell Quantum Dots

Cited by 12 publications

References 74 publications

Colloidal Synthesis of Giant Shell PbSe-Based Core/Shell Quantum Dots in Polar Solvent: Cation Exchange versus Epitaxial Growth

Colloidal Synthesis of Giant Shell PbSe-Based Core/Shell Quantum Dots in Polar Solvent: Cation Exchange versus Epitaxial Growth

Nonadiabatic Dynamics in Si and CdSe Nanoclusters: Many-Body vs Single-Particle Treatment of Excited States

Extending the Time Scales of Nonadiabatic Molecular Dynamics via Machine Learning in the Time Domain

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