2009 MICS Schedule

September 8, 2009
Sarah Altschuler


September 15, 2008
Trevor Courtney (Jonas Group)
Pump Probe Spectroscopic Studies of Lead Sulfide Quantum Dots 

One proposed route to efficient photovoltaic devices seeks to utilize solar photons with energy in excess of twice the material bandgap to produce additional carriers per incident photon.  It has been hypothesized that this process, known as carrier multiplication (CM), is aided by increased coupling between excitons, a relaxation of bulk selection rules, and slower carrier cooling in quantum dots (QD) – all effects of quantum confinement.  Three mechanisms for CM have been proposed to explain time resolved transient absorption experiments that show, for excitation above a frequency threshold, increased bleaching at the band gap.  This increased bleach decays on the same timescale as the Auger recombination observed after multi-photon excitation, which suggests CM (Klimov, Nozik), but this interpretation is controversial in light of spontaneous emission experiments (Bawendi).  I will introduce our lab’s 20-fs time resolution pump-probe spectroscopy experiments – outlining the experimental setup and our methods to probe the optically excited hot electron precursor to CM in PbS QDs and to quantify the Auger recombination rate in the QDs.  I will comment on current findings regarding the hot exciton studies and the kinetics relationship between bulk and QD Auger recombination.      

September 22, 2009
No Meeting

September 29, 2009
Ice Cream Soical

Come meet and network with graduate students and post docs.

October 6, 2009
Kevin Dean (Palmer/Jimenez Groups)

October 13, 2009
AJ Vasiliou (Ellison Group)

October 20, 2009
Barbara Dix (Volkamer Group)

October 27, 2009
Rebecca Montange (Perkins Group/JILA)

November 3, 2009
Chris Adams (Weber Group/JILA)

November 10, 2009
Delphine Farmer

November 17, 2008
Marta Kapala (Vaida Group)

December 1, 2008
Andrea Edwards (Batey Group)

 

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