Charge Transfer at the Hybrid Interfaces in the Presence of Water: A Theoretical Study

The presence of water molecules at the interfaces of dye-sensitized solar cells can hinder the excited-state charge transfer (CT), which constitutes a crucial step in solar energy harvesting by photovoltaic devices. To rationalize the impact of water adsorption on interfacial CT, this process is simulated within the time-dependent density functional theory in a model system formed by perylene-3-carboxylic acid and the TiO₂ (101) anatase surface. The adsorption of molecular water results in a moderate decrease of the CT efficiency, while dissociative adsorption of H₂O is shown to substantially reduce the electron accepting capacity of TiO₂. The amplitude of the effect depends smoothly on the amount of adsorbed water molecules, though distinct adsorption configurations contribute to it in different ways. The dissociation of the COOH anchor under the action of water species, simultaneous with the CT, results in an increased CT efficiency from the dye molecule to the TiO₂ surface.