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Seminar: Wednesday, Nov. 7, 2012 at 3:30 pm

Multiple Exciton Generation in Lead-Salt Nanostructures
Paul D. Cunningham
U.S. Naval Research Laboratory

In a typical solar cell, only part of the energy from absorbed light is converted to electricity. Each absorbed photon produces an electron-hole pair, i.e. exciton, which ultimately cools till it possesses only the semiconductor bandgap energy. The excess energy that is typically wasted can be harnessed by exploiting multiple exciton generation, whereby the excess energy is used to excite additional excitons. This process was recently shown to be more efficient in nanocrystals than in the bulk. We have discovered that multiple exciton generation is significantly enhanced in quasi-one-dimensional nanorods compared to nanocrystals. Devices exploiting this enhancement have the potential to show enhanced photovoltaic efficiencies. I will discuss our transient absorption measurements of multiple exciton generation in PbSe nanostructures. Complications arising from the quasi-one dimensionality of these nanostructures will be explained. Multiple exciton dynamics and lifetimes will also be discussed, as well as promising future directions.

Location: Physics Bldg., Room 401