Physics Colloquium - Friday, April 2nd, 2010, 3:00 P.M.

Svetlana Kilina
Center for Nonlinear Studies
Los Alamos National Laboratory

Nanotechnology represents a nexus of materials science, chemistry, physics, and engineering and is vital for the development of revolutionary applications ranging from electronics and photovoltaics to medicine. However, before advances in next generation technologies can come to fruition, understanding and control of the structure-property relationship of nanomaterials are required. Theoretical predictions based on atomistic modeling could provide valuable insight into these issues. In this talk, I first briefly overview various quantum-chemical approaches that we use for description of the morphology, optoelectronic properties, and photoexcited dynamics in novel nano-structured materials, such as carbon nanotubes, conjugated polymers, and quantum dots. Next, I focus on electron-phonon interactions in CdSe quantum dots and the impact of passivating ligands on relaxation of photoexcitation in these materials. Our simulations reveal formation of dense optically inactive states due to the surface reconstructions. Organic ligands coating the surface increase the density of such states, which have enhanced electron-phonon coupling and facilitate carrier relaxation. These results open a new prospective for understanding of fast energy relaxation mechanisms in quantum dots - a topic of general interest due to the recent focus on quantum dot-based solar cells, light-emitting diodes, field-effect transistor, etc.