Aqueous
Route to Phthalocyanine–Fullerene Composites
with Regular Structure
- Publication date
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Abstract
Random mixtures of phthalocyanines
(Pcs) with fullerene C<sub>60</sub> are currently exploited as active
layers in organic solar cells.
Therefore, spatially regular Pc–C<sub>60</sub> heterostructures,
not designed so far, are of great interest as molecularly mixed donor–acceptor
phases for further improving the device performance. Here we investigate
the prospects to create such heterostructures by fine intermixing
of π-rich Pcs with fullerene C<sub>60</sub>. Specifically, this
work reports on the mixing behavior of cobalt <i>tetrakis</i>(3-amino-5-<i>tert</i>-butyl)phthalocyanine (CoPc<sup>#</sup>) with fullerene C<sub>60</sub>. A composite film (CoPc<sup>#</sup>/C<sub>60</sub> = 1:2, mol) was prepared by the Langmuir–Schaefer
technique from a floating layer with double-decker architecture, where
the CoPc<sup>#</sup> monolayer was interlinked with the C<sub>60</sub> submonolayer by the clustered water. This film was structurally
analyzed and compared with the CoPc<sup>#</sup> film used as a reference.
The latter film is found to be constructed from the 2-stack dye aggregates,
which are assembled in the χ-phase mode, randomly oriented,
and loosely packed. In the composite film, the C<sub>60</sub> molecules
tend to intercalate into the interaggregate voids, making the aggregates
consolidate and align in the vertical direction. Accordingly, the
delamination process, which freely occurs in the pristine dye film,
is inhibited in the composite. All aggregative features of CoPc<sup>#</sup> indicate that both structure and arrangement of the dye aggregates
are determined by water-assisted H bonding via the primary amine groups.
This kind of interaction is of use for tailoring Pc-based frameworks
capable to host the C<sub>60</sub> molecules