|June 26, 2014
Bldg. 440, A105-106
"Single-Particle Laser Spectroscopy of Semiconductor Nanocrystal Quantum Dots," by Young-Shin Park, Los Alamos National Laboratory and University of New Mexico, hosted by Gary Weiderrecht
Abstract: Size-controlled emission colors and high intrinsic photoluminescence quantum yields are among the reasons that make nanocrystal quantum dots (QDs) attractive materials for a range of applications, for examples, light-emitting diodes (LEDs), lasing, and nonclassical photon sources. One problem in all of these applications, however, is significant quenching of emission from charged- and multi-excitons due to nonradiative Auger recombination. In this process, the electron-hole recombination energy is not emitted as a photon, but rather transferred to a third carrier, finally dissipating in thermal form. Thus, the ability to harvest the emission from charged- and multi-exciton states could dramatically enhance the potential of QDs, especially for LEDs and lasing.
In this talk, I will present our recent progress on the realization of Auger suppression in two types of heterostructured QDs ("giant" and "alloyed" QDs) that are characterized by an interfacial alloy layer between the core and the shell. We found that the interfacial alloying, which makes the confinement potential "softened," can lead to significant reduction in Auger decay rates of these QDs. Auger suppression of individual QDs was quantitatively evaluated by a time-tagged, time-resolved single-photon counting technique, demonstrating high quantum yields and elongated lifetimes of biexciton states in these QDs with an interfacial alloy. I will also discuss the use of Auger-suppressed QDs for the applications of LEDs and lasers.