Title: Suppression of Auger Recombination in Nanostructures: Non-blinking Semiconductor Nanocrystals

Speaker: Dr. George E. Cragg, Dayton, Ohio

Date/Time: Tuesday, November 16, 2010, 1:30 pm Mountain Time       

Location: CSRI Building/Room 90 (Sandia NM)

Brief Abstract: Individual molecules and nanometer-sized crystallites exhibit large intensity fluctuations whereby their photoluminescence turns “on” and “off ” intermittently even under continuous excitation. Since a charged nanocrystal could have its photoluminescence quenched by the dominance of the non-radiative Auger mechanism, the “off ” period is believed to correspond to an interval in which the structure acquires an extra charge. Despite over a decade of research, continuously emitting nanostructures have yet to be synthesized, as a complete understanding of this charging mechanism remains elusive. However, recently fabricated CdZnSe/ZnSe graded-alloy nanocrystals individually display a non-blinking photoluminescence. Calculations show that these unique emission characteristics suggest a smooth confinement profile is associated with the graded alloy structure. Theoretically, smooth profiles would mitigate the Auger rate, thereby eliminating blinking by allowing nanocrystals to photoluminescence even in their charged state. Since Auger processes severely limit the usefulness of quantum dots and quantum wells in applications requiring a continuous output of photons, smoothly confined structures would enable breakthroughs in wide ranging applications from biological labeling to low-threshold lasers.

CSRI POC: Ann Mattsson, 505-844-9218