Probing the Metal Oxide Local Environment for Thermochromic and Photovoltaic Applications

Energy demand is predicted to increase by 28% between 2015 and 2040, placing strain on the current reserves of petroleum, coal and natural gas. There are two different approaches to alleviating the demand on Earth’s natural resources: increase energy efficiency or utilize renewable resources. Vanadium dioxide (VO2) thermochromic windows passively modulate infrared (IR) transparency, aiding in reducing undesirable heat exchange from outside to indoors. This occurs through a semiconductor to metal transition upon heating which is coupled with an optical change from IR transparent to IR absorbing, respectively. The metallic phase exhibits a plasmon resonance and we can control the local environment by embedding the VO2 nanoparticles in a high refractive index material (i.e. a polymer) where the plasmon absorption intensity increases as does the overall device performance. Alternatively, to increase the production of renewable energy, p-type dye sensitized solar cells (DSSCs) are studied as a precursor to tandem devices for solar fuel production. A novel p-type semiconductor (photocathode), lead titanate was identified through a material informatics approach and utilized in fundamental studies of the semiconductor-electrolyte interaction. By tuning the electrolyte composition to increase the concentration of an efficient electron scavenger, I2, the photocurrent and fill factor approximately doubled resulting in a four-fold increase in power conversion efficiency. Simply changing the concentration of I2, and electron scavenger, in the electrolyte allows for more efficient charge separation at the semiconductor-chromophore-electrolyte interface, which improves two of the most problematic device performance metrics in p-type DSSCs, low photocurrent and low fill factor.Doctor of Philosoph