DFT Calculations of Structure and Optical Properties in Wide Band-Gap Semiconductor Clusters for Dye-Sensitized Solar Cells

We report results of a computational study of TiO2 clusters to understand their structure and optical properties as well as the binding and charge transfer from organic dyes to such clusters. We perform density functional theory calculations of several coumarin-based and oligomethine cyanine-based dyes as well as complex systems consisting of the dye bound to a TiO2 cluster. We provide the electronic structure of the dyes alone and adsorbed to the cluster, and discuss the matching with the solar spectrum. We display the energy level diagrams and the electron density of the key molecular orbitals and analyze the electron transfer from the dye to the oxide.