Electronic structure and ultrafast light-induced dynamics of transition-metal sensitized, nanocrystalline-based photoelectrochemical solar cells for molecular engineering of their sensitizers

In Chapter 1, the advantages of solar electricity are presented. The dye-sensitized titanium dioxide-based Grätzel solar cell is compared and contrasted with the widely-used crystalline silicon device. The dye-sensitized cell is noted to have greater tunability in terms of sunlight absorption.; In Chapter 2, the electronic structures of the widely-used dye bis(4,4 ′-dicarboxylato-2,2′-bipyridine)-bis(isothiocyanato)ruthenium(II) are studied by Density Functional Theory (DFT) to see how its electronic structure may help make it an effective sensitizer. Low-lying occupied carboxylate-based MOs are calculated to be energetically similar to the TiO₂ valence band: this could facilitate bonding of the chromophore to the TiO₂ nanoparticle.; Dye-sensitized solar cells are studied spectroscopically in Chapter 3. Analysis of the dynamics of Ru(H₂L′) ₂(CN)₂/TiO₂, Ru(H₂L ′)₂(NCS)₂/TiO₂, Os(H₂ L′)₂(CN)₂/TiO₂ and Os(H₂L′′)₂(NCS) ₂/TiO₂ suggests charge injection from the Franck-Condon 1MLCT state occurs on the femtosecond timescale while that from the 3MLCT excited state proceeds on the picosecond time scale.; In Chapter 4, the physical properties of an iron bipyridyl complex are addressed for a prototypical example, tris(bipyridine)iron(II). Its molecular structure as determined by Density Functional Theory at the B3LYP/LACVP** level of theory is close to the experimental geometry, with the most significant difference a 0.068 Å increase in the Fe-N bond distance.; Chapter 5 presents the ultrafast excited-state dynamics of [Fe(tren(py) ₃)]2+, an iron polypyridyl complex which functions as a model of a solar cell sensitizer. Following 1A₁ → 1MLCT excitation in acetonitrile solution, the long-lived 5T₂ ligand-field state is formed in less than 1 ps. Further, the charge-transfer character of the excited state disappears with a time constant of less than 100 fs, indicating extremely rapid conversion from the charge-transfer to the ligand-field manifold. (Abstract shortened by UMI.)...