Langmuir−Schaeffer Films from a π−π Stacking Perylenediimide Dye: Organization and Charge Transfer Properties

• Published in: Langmuir Vol. 26; no. 9; pp. 6630 - 6637
• Main Authors: Tolkki, Antti, Vuorimaa, Elina, Chukharev, Vladimir, Lemmetyinen, Helge, Ihalainen, Petri, Peltonen, Jouko, Dehm, Volker, Würthner, Frank
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 04-05-2010
• Subjects: Chemistry; Colloidal state and disperse state; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Fullerenes and related materials; diamonds, graphite; General and physical chemistry; Materials science; Materials: Nano-and Mesostructured Materials, Polymers, Gels, Liquid Crystals, Composites; Physics; Specific materials; Surface physical chemistry; Monolayer; Atomic force microscopy; Compression; Dyes; Organization; Stacking; Film; Spin; Fluorescence; Hydrophobic interaction; Electron transfer; Langmuir method; Thin film; Transients; Monomer; Charge transfer; Steady state; Thickness; Lifetime; Preparation; Fullerenes; Aggregate; Energy transfer; Electron acceptor; Electron donor
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la903978y

The organization of π−π stacking perylenediimide (PDI) derivative, PDI12, was studied in solution and in thin films. Films were prepared with the Langmuir−Schaeffer (LS) method and characterized by means of AFM, optical profilometry, steady-state absorption, emission, fluorescence lifetime, and transient photovoltage measurements. The columnar aggregates observed previously in PDI12 solutions and in spin-coated films persist also in LS films. Because of the specific conditions during the preparation of the LS film, i.e., hydrophobic interactions and lateral compression, the columnar aggregates seem to organize with their long axis perpendicular to the layer plane whereas in spin-coated films the columns were oriented parallel to the layer plane. According to AFM and profilometer results, the thickness of LS monolayer of PDI12 is 10 nm, indicating that it consists mainly of aggregates, each containing ∼30 monomers. Intermolecular photoinduced energy and electron transfer processes in C60|PDI12 double layer junction were studied. The fluorescence lifetime of PDI12 film is exceptionally long, but the quenching is very efficient in the presence of C60. In charge transfer studies, long-lived photovoltage signal was observed for the double layer. Results of this work indicate that PDI12 acts as an electron acceptor and fullerene C60 as an electron donor.