Aqueous Route to Phthalocyanine–Fullerene Composites with Regular Structure

Abstract

Random mixtures of phthalocyanines (Pcs) with fullerene C₆₀ are currently exploited as active layers in organic solar cells. Therefore, spatially regular Pc–C₆₀ 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 C₆₀. Specifically, this work reports on the mixing behavior of cobalt <i>tetrakis</i>(3-amino-5-<i>tert</i>-butyl)­phthalocyanine (CoPc^#) with fullerene C₆₀. A composite film (CoPc^#/C₆₀ = 1:2, mol) was prepared by the Langmuir–Schaefer technique from a floating layer with double-decker architecture, where the CoPc^# monolayer was interlinked with the C₆₀ submonolayer by the clustered water. This film was structurally analyzed and compared with the CoPc^# 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 C₆₀ 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^# 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 C₆₀ molecules