Архив метки: molecules

Colloquium: Quantum Dots – Artificial Atoms, Large Molecules or Small Pieces of Bulk? Insights from Time-Domain Ab Initio Studies

Quantom dots emit hoighly stable colors. image courtesy of wikipedia

Quantom dots emit hoighly stable colors. image courtesy of wikipedia

We are pleased to invite you to the Skoltech Colloquium.

When: December 18, 4:00 PM-6:00 PM

What: Quantum Dots – Artificial Atoms, Large Molecules or Small Pieces of Bulk?  Insights from Time-Domain Ab Initio Studies

Guest speaker: Oleg Prezhdo, University of Southern California

Where: Hypercube, 7th floor

Abstract: Quantum dots (QD) are quasi-zero dimensional structures with a unique combination of solid-state and atom-like properties. Unlike bulk or molecular materials, QD properties can be modified continuously by changing QD shape and size.

Often, the bulk and molecular viewpoints contradict each other. The molecular view suggests strong electron-hole and charge-phonon interactions, and slow energy relaxation due to mismatch between electronic energy gaps and phonon frequencies. The bulk view advocates that the kinetic energy of quantum confinement is greater than electron-hole interactions, that charge-phonon coupling is weak, and that the relaxation through quasi-continuous bands is rapid.

Oleg Prezhdo, University of Southern California

Oleg Prezhdo, University of Southern California

QDs exhibit new physical phenomena. The phonon bottleneck to electron energy relaxation and generation of multiple excitons can improve efficiencies of solar energy devices. The enhanced electron-hole interactions and high densities of states lead to a new electron transfer mechanism, Auger-assisted transfer, which eliminates the celebrated Marcus inverted regime and ensures consistently rapid charge separation.

The observed QD properties are complicated by presence of ligands, dopants, defects and other chemical features. Our state-of-the-art non-adiabatic molecular dynamics techniques, implemented within time-dependent density-functional-theory, allow us to model QDs at the atomistic level and in time-domain, providing a unifying description of quantum dynamics on the nanoscale.






* The Skolkovo Institute of Science and Technology (Skoltech) is a private graduate research university in Skolkovo, Russia, a suburb of Moscow. Established in 2011 in collaboration with MIT, Skoltech educates global leaders in innovation, advances scientific knowledge, and fosters new technologies to address critical issues facing Russia and the world. Applying international research and educational models, the university integrates the best Russian scientific traditions with twenty-first century entrepreneurship and innovation.


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