title: Fast assembly of cyanine dyes into aggregates onto [6,6]-phenyl C61-butyric acid methyl ester surfaces from organic solvents.
abstract: Supramolecular agglomerates of organic colorants based on noncovalent interactions are promising candidates for the development of sensors, optoelectronics, lighting, or photovoltaics. However, their fast and defect-free fabrication on large scales using low-cost technologies has proven elusive so far. Here, we introduce a so far unreported mechanism to induce molecular order in cyanine dyes within minutes from organic solvents by self-assembly. Spin coating blends of a cyanine dye and a soluble fullerene derivative ([6,6]-phenyl C(61)-butyric acid methyl ester (PCBM)) from apolar, aprotic solvents leads to phase-separated structures on the micrometer scale. With this superordinated phase structure, adjustment of dye aggregation is possible, leading to novel optical properties of the film emerging from dye self-assembly on the nanometer scale. In the primary process, semiporous PCBM domains act as nucleation sites for H-aggregates. H-aggregates can then be reconstructed into J-aggregates by dissolving PCBM from the film. Unexpectedly, the method even works for sterically hindered cyanine dyes that are known for their reduced tendency to aggregate. Additionally, selective removal of H-aggregates leaves a template of PCBM nanocrystals, onto which cyanine dye monomers readsorb from solution, forming H-aggregates of similar quality.
authors.affiliation: Empa, Swiss Federal Laboratories for Materials Testing and Research, Laboratory for Functional Polymers, Uberlandstr. 129, 8600 Dübendorf, Switzerland. jakob.heier@empa.ch
authors.forename: Jakob
authors.initials: J
authors.lastname: Heier
authors.forename: Rolf
authors.initials: R
authors.lastname: Steiger
authors.forename: Frank
authors.initials: F
authors.lastname: Nüesch
authors.forename: Roland
authors.initials: R
authors.lastname: Hany