Atomistic Modeling of Interfacial Electron Transfer in Dye-Sensitized Solar Cells; Exploring the Potential to Generate Solar Fuels.

摘要

In this thesis, simulations of interfacial electron transfer provide insight into the design principles of a modified dye-sensitized solar cell for water splitting. Generating solar fuels may be a solution to the growing global energy crisis. Solar energy call be stored as hydrogen fuel by splitting water into its elemental components with sunlight. Atomistic simulations of interfacial electron transfer were performed by solving the time-dependent Schrodinger equation. The simulations give insight into the mechanism and kinetics of the electron transfer process. In particular, possible designs of surface assemblies can be evaluated computationally before expensive and time consuming synthesis and device construction is attempted. A few aspects of interfacial electron transfer were investigated. The linkers acetylacetonate, hydroxamate, and phosphonate immobilize catalysts on TiO2 nanoparticles, mediate interfacial electron transfer, and are robust linkages in aqueous conditions required for water splitting. For pyridine-4-phosphonic acid on TiO2, ultrafast injection with a time scale of 460 fs was predicted. The binding mode of the phosphonate linker was found to be important, with up to 1 order of magnitude faster injection rate when attached in a bidentate mode compared to a monodentate mode. Solvent molecules, particularly water, compete with sensitizing adsorbates for close contact with the metal oxide surface creating noticeable changes in the electron transfer rate. For Rhodamine B on SnO2, the initial injection rate was slowed from 92 fs to 116 fs and the slow component of the injection was reduced from 895 fs to 1411 fs after the surface was hydrated by a few monolayers of water molecules. Long flexible bridges provide conformational flexibility and drastically reduce the electron transfer rate. For Sulforhadamine B on SnO2, adding a saturated bridge shifts injection from the picosecond to the nanosecond time scale. These results have important implications for designing devices to generate solar fuels.