Development and Improvement of Quantum Dot Sensitized Solar Cell Architectures

Abstract

Chemistry

Development and Improvement of Quantum Dot-Sensitized Solar Cell Architectures

Shawn M. Rosson

Thesis under the direction of Professor Sandra J. Rosenthal

Nanostructured photovoltaic devices constructed with inexpensive materials such as TiO2 and ZnO were fabricated, characterized, and tested. These devices employed semiconductor nanocrystals as light harvesters that were deposited using electrophoretic deposition, spin-coating, and drop-casting. TiO2 nanotube architectures were previously bound to the titanium substrate, but other metals such as aluminum or gold will give better charge transfer and transport. By removing the nanotubes from titanium, these other metals can be deposited onto the nanotubes by evaporation. We have achieved the removal of nanotubes from their substrate, which demonstrates the possibility for many new architectures. I have also described a study to determine the concentration of nanocrystals on the nanotubes that can be done using these free-standing films that is not possible for bound nanotubes. The maximum efficiency achieved in this work is 6 x 10-4 %. The mechanics and theory behind how devices function and can be improved are detailed, including the application of Marcus Theory to our device structure. Explanations as to why the device efficiency is low with ways to potentially improve the efficiency are also given. The limitations in the device architecture described in this thesis should be overcome by discovering the ideal interactions between the materials as determined by band-gap alignment, maximizing the amount of light that can be converted to usable energy, and reducing charge trapping and recombination within the materials once light is absorbed.