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Seminar Abstract

"Plasmon-enhanced Solar Energy Conversion to Fuels"

Isabell Thomann, Materials Science and Engineering, Stanford University

Mar 08 2012 1:25 PM in B-75 Amundson Hall

Future generations of photoelectrodes must employ cheap, earth-abundant absorber materials in order to provide a large-scale source of clean energy. These materials tend to have poor electrical transport properties and exhibit carrier diffusion lengths which are significantly shorter than the absorption depth of light. As a result, many photo-excited carriers are generated too far from a reactive surface, and recombine instead of participating in solar-to-fuel conversion reactions.

I will present our recent results on the use of noble metal nanoparticles to enhance the efficiency of solar fuel generation. I will illustrate how collective electron oscillations, known as surface plasmons, in such small structures and optical interference effects in multilayer photo-electrodes can be engineered to strongly concentrate sunlight close to the electrode/liquid interface. This enhances the generation of photocarriers, precisely where the relevant reactions take place.

By comparing spectral features in the enhanced photocurrent spectra to full-field electromagnetic simulations, the contribution of surface plasmon excitations is verified. When metal core - dielectric shell particles are used, we could show an increase of the total, wavelength-integrated photocurrent by 10% in an operating photoelectrochemical cell. These results open the door to the optimization of a wide variety of photocatalytic processes by leveraging the rapid advances in the field of plasmonics.

I will end with a brief outlook on my future research plans, which will leverage my experience in ultra-fast spectroscopy and nanophotonics to develop novel tools for controlling and monitoring photocatalytic processes.