posted on 2015-12-24, 00:00authored byOlga A. Syzgantseva, Martti Puska, Kari Laasonen
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.