Electron Transfer at Molecule-Metal Oxide Interfaces for Applications in Dye-Sensitized Devices

Designing systems that can allow for increased control of electron transfer processes at dye-semiconductor interfaces is useful in a wide variety of applications, but specifically in the field of dye-sensitized devices such as dye-sensitized solar cells and dye-sensitized photodetectors. In trying to maximize regeneration rates and minimize recombination rates in DSSCs through metal ion coordination to the non-surface bound carboxylate groups of the dye, it was discovered that doing so can ideally slow recombination rates, however it was unclear if the additional steric effects or charge of the metal ion were the cause of this behavior. Using three differently charge mediators it was ultimately discovered that electrostatics may influence regeneration rates, but steric bulk of the components used ultimately had a greater effect on the overall device performance. With this result in hand and contemplating on the simple geometric restrictions imposed by the mesoporous nature of high surface area metal oxide substrates, we sought to determine the role porosity has on multilayer assembly loading, electrolyte diffusion, and subsequent device performance. Through modifying the porosity of the film through sintering procedure modifications and loading the film with dye molecules, it was found that porosity should be considered when designing multimolecular architectures as to have enough space to load the number of components desired and leave room for mediator diffusion. Finally, a prototype dye-sensitized photodetector was designed with efficient charge separation characteristics in the red to infrared wavelength range. This device utilized the same device structure as DSSCs and the performance metrics for the device were measured and reported for this first of its kind device. Seeking to improve the devices performance through applying an external bias, it was determined that the metal oxide had to be shifted from TiO2 to ITO and insulating layers of atomically thin metal oxides were added in order to stabilize the performance of the device under bias.