Summer 2011 Intern Project- Nancy Trejo

ENGINEERING PLASMONICALLY SENSITIZED PHOTOVOLTAICS CELLS

Nancy Trejo
Chemical Engineering
UC Santa Barbara

Mentor: Joun (Sylvia) Lee
Faculty Advisor: Martin Moskovits
Department: Chemistry

Recently, plasmonic concentration and propagation have been used as a promising strategy for enhancing photovoltaic and photocatalytic applications. For instance, plasmonic nanostructures can be used to absorb light energies far below the semiconductor absorber energy. This has led to a new paradigm where plasmonic nanostructures can be used as photosensitizers for wide band gap semiconductors, replacing organic dyes with benefits such as high stability and electron mobility. In this study, we attempted to create one such system where wide band gap semiconducting oxides such as titanium dioxide (TiO₂) and zinc oxide (ZnO) are coated with uniform layers of gold nanoparticles (AuNP).  Specifically, we constructed n-type TiO₂ nanotubes through an anodization process and ZnO nanorods through a hydrothermal process on indium tin oxide (ITO)-coated glasses; AuNP were deposited on these nanostructures through a photoreduction synthesis and a p-type conductive polymer was spin-coat on top. Electron-hole pairs created in the AuNP are efficiently separated by the Schottky barrier at the interface of AuNP and the metal oxide. Electrons flow through metal oxides and holes are collected by the p-type conductive polymer. Structural and optical properties of the nanostructures were characterized by scanning electron microscopy (SEM) and UV-Vis-NIR spectroscopy.  The TiO₂ nanotubes were around 1.2 μm long and 40-50 nm wide and the ZnO nanorods with AuNP showed absorptions in the UV/visible range.  The photovoltaic measurements are currently in progress but we expect that combining plasmonically active materials with semiconductor oxides will enhance visible light absorption in a photovoltaic cell. 

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