Towards Photocurrent Production By Gold Nanoarrays with Self-Assembled Monolayer Coatings
Master of Science
This thesis proposes to use optical rectennae (rectifying antennae) for generating electricity by harvesting solar energy. Rectennae have theoretical efficiency over 90%, well above that of current photovoltaic devices. They could be built by arraying nano- antennae combined with a self-assembled monolayer for DC current rectification. Gold nanoarrays were built to absorb light by plasmonic resonance by depositing a gold layer on CdSe tetrapods or directly growing nanowires via template synthesis; various alkanethiolates were explored as rectifying units. The tunneling properties of alkanethiolates on gold nanoarrays were examined by electrochemical analysis. Preliminary photocurrent tests show that electric currents can be induced at different optical frequencies depending on the aspect ratios of the nanoarrays. However, gold contributes as an enhancement rather than an active material. Furthermore, by fitting the impedance spectroscopy data with equivalent electric circuits, the calculated tunneling barrier of the self-assembled monolayer on gold nanoarrays is ten times lower than on gold film, suggesting that the monolayer formed on gold nanoarrays is defective and cannot serve as a practical rectifying barrier. This concept will need further investigation to lead to an applicable photovoltaic cell.
Applied sciences; Chemical engineering; Nanotechnology