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Title page for ETD etd-03232017-171910


Type of Document Dissertation
Author Erwin, William Robert
Author's Email Address wrerwin1@gmail.com
URN etd-03232017-171910
Title Shape Controlled Plasmonic Nanostructures for Light Harvesting Applications
Degree PhD
Department Chemical Engineering
Advisory Committee
Advisor Name Title
Rizia Bardhan, Ph.D. Committee Chair
Cary L. Pint, Ph.D. Committee Member
G. Kane Jennings, Ph.D Committee Member
Paul E. Laibinis, Ph.D. Committee Member
Keywords
  • solar
  • plasmonics
  • nanotechnology
Date of Defense 2017-03-17
Availability unrestricted
Abstract
In the search for economically feasible renewable energy sources, the conversion of solar energy into electricity is highly attractive to replace depleting fossil fuels and mitigate high oil prices. While promising, solar harvesting technology does not compete with fossil fuels due to low power conversion efficiency (PCE) and high cost of processing, both of which remain a tremendous challenge. Through experiments and simulations, this PhD thesis investigates the use of metal nanostructures (MNS) for enhancement of PCE in photoelectrochemical solar cells and organic photovoltaics. In the presence of incident light, noble MNS support a localized surface plasmon resonance (LSPR) which are collective oscillations of the metal’s conduction electrons. Upon decoherence, LSPRs give rise to a collection of radiative and non-radiative effects, which can be harnessed to improve the light harvesting efficiency of various types of solar devices. In this work, we investigate the incorporation of colloidal plasmonic MNS into organic photovoltaics (OPVs) and photoelectrochemical water splitting electrodes as a route to improve PCE. A fundamental understanding of the interactions of plasmonic nanostructures with incident electromagnetic fields and subsequent field modulation in surrounding photovoltaic materials is paramount to achieve high PCE in solar devices. In particular this thesis examines how the shape and composition of MNS and the resulting radiative and non-radiative effects impacts the efficiency and charge transfer processes in solar devices. Our results show a 14x improvement in external quantum efficiency in photoelectrochemical water splitting with the incorporation of Au-Ag core-shell nanocrystals (Au-AgNCs) – 2.3x higher than enhancement achieved via incorporation of Au nanospheres. We attribute enhancement to improved radiative field enhancement achieved due to the “lightning rod effect,” resulting from nanostructure’s edges and corners. In OPVs, we observed an 11% enhancement in PCE via the incorporation of Au-AgNCs. Using numerical solvers to approximate solutions to Maxwell’s Equations, we learn that while the light capture in the absorbing layer is not increased, it is augmented such that charge transport is favorable, thus increasing PCE. Further, we explore the use of nanostructured electrodes for photoelectrochemical light harvesting. We find that it is possible to replace traditional platinum electodes with silicon-carbon hybrid electrodes to fabricate highly efficient platinum free dye-sensitized solar cells
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