Ricerc@Sapienza

For the first time it is shown that the NiO films operating as
photocathodes in dye-sensitized solar cells (DSCs), alter their Xray
diffraction (XRD) pattern upon occurrence of the photoelectrochemical
reaction of reduction. In particular, it has been
observed that mesoporous NiO sensitized with Fast Green (FG)
presents splitting and broadening of its characteristic XRD
peaks after device operation in p-type DSC (p-DSC) and tandem
DSC (t-DSC). The nature of the changes in the diffraction
pattern of NiO does not vary with the magnitude of the current
passing through the p-DSC and the t-DSC with NiO photocathodes.
Such a combination of facts would indicate that the
photoelectrochemical process of holes photoinjection mediated by the sensitizer is responsible of the structural variations
in NiO photocathode. At a microscopic level, we attributed
such modifications to the reconstruction of the NiO electrode
following the realization of the dye-mediated process of
electron transfer with lattice deformation possibly due to the
inclusion of the chemisorbed sensitizer in the oxide structure.
This observation opens up a completely new direction of
research in the field of DSC and analogous devices as far as the
analysis and the understanding of the interactions dye/semiconductor
in the common operative conditions of a DSC are
concerned.