title: Langmuir-Schaeffer films from a pi-pi stacking perylenediimide dye: organization and charge transfer properties.
abstract: The organization of pi-pi 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 approximately 30 monomers. Intermolecular photoinduced energy and electron transfer processes in C(60)|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 C(60). 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 C(60) as an electron donor.
authors.affiliation: Department of Chemistry and Bioengineering, Tampere University of Technology, Tampere, Finland. antti.tolkki@tut.fi
authors.forename: Antti
authors.initials: A
authors.lastname: Tolkki
authors.forename: Elina
authors.initials: E
authors.lastname: Vuorimaa
authors.forename: Vladimir
authors.initials: V
authors.lastname: Chukharev
authors.forename: Helge
authors.initials: H
authors.lastname: Lemmetyinen
authors.forename: Petri
authors.initials: P
authors.lastname: Ihalainen
authors.forename: Jouko
authors.initials: J
authors.lastname: Peltonen
authors.forename: Volker
authors.initials: V
authors.lastname: Dehm
authors.forename: Frank
authors.initials: F
authors.lastname: Würthner