Lab Home | Phone | Search
Center for Nonlinear Studies  Center for Nonlinear Studies
 Home 
 People 
 Current 
 Affiliates 
 Alumni 
 Visitors 
 Students 
 Research 
 ICAM-LANL 
 Quantum 
 Publications 
 Publications 
 2007 
 2006 
 2005 
 2004 
 2003 
 2002 
 2001 
 2000 
 <1999 
 Conferences 
 Workshops 
 Sponsorship 
 Talks 
 Colloquia 
 Colloquia Archive 
 Seminars 
 Postdoc Seminars Archive 
 Quantum Lunch 
 CMS Colloquia 
 Q-Mat Seminars 
 Q-Mat Seminars Archive 
 Archive 
 Kac Lectures 
 Dist. Quant. Lecture 
 Ulam Scholar 
 Colloquia 
 
 Jobs 
 Students 
 Summer Research 
 Student Application 
 Visitors 
 Description 
 Past Visitors 
 Services 
 General 
 PD Travel Request 
 
 History of CNLS 
 
 Maps, Directions 
 CNLS Office 
 T-Division 
 LANL 
 
Thursday, November 01, 2012
2:00 PM - 2:45 PM
CNLS Conference Room (TA-3, Bldg 1690)

Postdoc Seminar

In Situ Studies of Photoluminescence Quenching and Photocurrent Yield in Quantum Dot Sensitized Single Crystal TiO2 and ZnO Electrodes

Doug Shepherd
MPA-CINT, CNLS

To better understand how quantum dot-quantum dot and quantum dot-surface interactions determine the overall efficiency of photovoltaic devices we have constructed an optically accessible and functional liquid junction photoelectrochemical cell. In this particular study, CdSe quantum dots are coupled to glass, single crystal TiO2, and single crystal ZnO substrates through a variety of capping ligands. This system architecture is of great interest, as the Parkinson group showed the first demonstration of multiple exciton collection with a similar architecture in 2010.[1] Correlated measurements of sensitized photocurrent and fluorescence decay time for three types of capping ligands on all three substrates show that many of these combinations have a “false” spectroscopic signature of charge transfer. That is, one would predict external current flow based on the spectroscopic measurements, yet no external current flow is detected. We also find certain capping ligand-substrate combinations promote clustering or aggregation of the quantum dots on the substrate surface as observed by atomic force microscope imaging.[2] We have previously shown that energy transfer between individual quantum dots in close physical proximity may act as an “energy sink”, possibly reducing the efficiency of quantum dots as photo-sensitizers [3]. These findings illustrate the crucial role of capping ligands on the electron transfer properties and morphology of quantum dot interfaces. In this talk, I will introduce both the relevant chemistry and photo-physics of quantum dot sensitized solar cells and discuss possible reasons for the observed false spectroscopic signature of charge transfer. REFERENCES [1] Sambur et al., Science, 2010, 330 (6000): 63-66 [2] Shepherd, Sambur, et al., J. Phys. Chem. C, 2012, 116 (39): 21069–21076 [3] Shepherd et al. J. Phys. Chem. C, 2010, 114 (35): 14831–14837

Host: Kipton Barros, T-4 and CNLS