Chemistry Reference
In-Depth Information
Fig. 6 Photoactive dyad
obtained by covalent
bonding of Ruthenium
porphyrin derivative with
amphiphilic features and a
fulleropyrrolidine
octadecylamine (ODA) and arachidic acid (AA), are often co-spread together with
the photoactive species. This approach prevents the rapid annihilation between the
triplet porphyrin state and the fulleropyrrolidine that governs the fate of the excited
state in the dyad ruthenium porphyrin derivative-bridge-fulleropyrrolidine.
The isotherm curves of the AA/donor-acceptor co-spread floating film reported in
Fig.
6
suggested that the dyad molecules were gradually squeezed out of the acid
monolayer as a consequence of the barrier pressure. The LB deposition was
repeated on different substrates, and a Y-type transfer was ever obtained; the
thickness of the solid film confirmed a uniform dispersion of dyad molecules in
the cadmium arachidate matrix. The dyad molecules were adequately separated
from each other, and electron and energy transfer from the excited state of
ruthenium functionalized porphyrin toward the acceptor element took place as
pointed out by the transient absorption spectrophotometry.
In many cases, the strong
interactions between porphyrins and fullerenes
induce the formation of a very rigid floating film that cannot be transferred by the
LB method; hence, it is generally substituted by its horizontal variation, which is
the Langmuir-Schaefer (LS) technique [
6
]. A covalent bonded C
60
-Ni porphyrin
dyad (Fig.
7
) was transferred by means of the LS method, and the efficiency of the
solar cell was compared with a layer-by-layer (LbL) C
60
-Ni porphyrin photo-device
[
20
]. More packed films and the preferential arrangement of the molecules of the
dyad induced by the LS technique allowed to reach a double efficiency if compared
to LbL device, highlighting the role of the deposition technique in the performance
of a solar cell.
Tkachenco et al. used octadecylamine as well as a spacer and insulator layer
[
23
]: they demonstrated that when a fulleropyrrolidine and a porphyrin bounded
with a long linker were transferred by Y-type LB method, dyads of different layers
were in close contact to each other, and intermolecular energy transfer between
π
-
π
