We present a detailed description of the direct charge injection mechanism in a coupled dye−TiO 2 nanoparticle (NP) using a full quantum dynamical simulation framework. The method employed here is based on a timedependent tight-binding model to describe the system under nonequilibrium conditions. By using this tool, we performed a simulation showing a full timedependent picture of the photoabsorption process in type-II dye-sensitized solar cells (direct charge injection mechanism from the dye to the TiO 2 NP). This task is accomplished by tuning the frequency of an applied sinusoidal time-dependent electric field with the frequency of the dye−TiO 2 NP's main absorption peak. We find that during the field irradiation there is a net charge transfer from the dye to the NP superposed with a typical charge oscillation due to absorption of radiant energy.

Optical properties of TiO(2) nanoclusters (with more than 30 TiO(2) units) were calculated within a fully atomistic quantum dynamic framework. We use a time dependent tight-binding model to describe the electronic structure of TiO(2) nanoclusters in order to compute their optical properties. We present calculated absorption spectra for a series of nanospheres of different radii and crystal structures. Our results show that bare TiO(2) nanoclusters have the same adsorption edge for direct electronic transition independently of the crystal structure and the nanocluster size. We report values of the adsorption edge of around 3.0 eV for all structures analyzed. In the present work we demonstrate that, for small clusters, both the direct transition absorption edge and the blue shifting phenomena are masked by thermal disorder.

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