News & Events

When

Date - February 19, 2016
1:00 pm

What

Associate Professor
Department of Chemistry
UNC – Charlotte

“Plasmon-Enhanced Fluorescence from Trions and Biexcitons in Colloidal Quantum Dots”

Abstract:

Quantum dots (QDs) hold tremendous potential for low-cost processing and fabrication of light harvesting and other optoelectronic devices. In addition to their size-tunable electronic structure and high photo-stability, their ability to support multiple optical excitations is being explored as a strategy for developing more efficient solar cells and brighter LEDs. Metal nanoparticles are able to collect and focus light over very small length scales by forming surface plasmon oscillations of electron density. When assembled with resonant QDs they have been shown to enhance photoemission and absorption rates.

Using single particle confocal microscopy and a multi-pulse time-resolved ensemble fluorescence technique we have studied the effect of plasmonic nanostructures on the recombination dynamics of multiply excited QDs. We have shown that plasmonic coupling enhances the radiative rates of trions and biexcitons so that fluorescence can compete with non-radiative Auger processes that typically dominate the recombination processes for these states. Futhermore, using a multi-layered approach consisting of gold nanoparticles, a polyelectrolyte spacer and colloidal quantum dots, we have been able to determine the distance dependence for these interactions and demonstrate a “sweet spot” where the emission yields are maximized. In this talk we will discuss these data, demonstrate our multipulse techique and show how multi-excited states can be generated in reasonably high yields in CdSe QDs. Finally we will discuss the implication of these data for future light harvesting technologies.