title: Mesoscopic quantum emitters from deterministic aggregates of conjugated polymers.
abstract: An appealing definition of the term "molecule" arises from consideration of the nature of fluorescence, with discrete molecular entities emitting a stream of single photons. We address the question of how large a molecular object may become by growing deterministic aggregates from single conjugated polymer chains. Even particles containing dozens of individual chains still behave as single quantum emitters due to efficient excitation energy transfer, whereas the brightness is raised due to the increased absorption cross-section of the suprastructure. Excitation energy can delocalize between individual polymer chromophores in these aggregates by both coherent and incoherent coupling, which are differentiated by their distinct spectroscopic fingerprints. Coherent coupling is identified by a 10-fold increase in excited-state lifetime and a corresponding spectral red shift. Exciton quenching due to incoherent FRET becomes more significant as aggregate size increases, resulting in single-aggregate emission characterized by strong blinking. This mesoscale approach allows us to identify intermolecular interactions which do not exist in isolated chains and are inaccessible in bulk films where they are present but masked by disorder.
authors.affiliation: Institut für Experimentelle und Angewandte Physik, Universität Regensburg, 93053 Regensburg, Germany;
authors.forename: Thomas
authors.initials: T
authors.lastname: Stangl
authors.affiliation: Institut für Experimentelle und Angewandte Physik, Universität Regensburg, 93053 Regensburg, Germany;
authors.forename: Philipp
authors.initials: P
authors.lastname: Wilhelm
authors.affiliation: Kekulé-Institut für Organische Chemie und Biochemie, Universität Bonn, 53121 Bonn, Germany.
authors.forename: Klaas
authors.initials: K
authors.lastname: Remmerssen
authors.affiliation: Kekulé-Institut für Organische Chemie und Biochemie, Universität Bonn, 53121 Bonn, Germany.
authors.forename: Sigurd
authors.initials: S
authors.lastname: Höger
authors.affiliation: Institut für Experimentelle und Angewandte Physik, Universität Regensburg, 93053 Regensburg, Germany; jan.vogelsang@physik.uni-regensburg.de.
authors.forename: Jan
authors.initials: J
authors.lastname: Vogelsang
authors.affiliation: Institut für Experimentelle und Angewandte Physik, Universität Regensburg, 93053 Regensburg, Germany;
authors.forename: John M
authors.initials: JM
authors.lastname: Lupton
keywords: interchromophoric coupling; organic electronics; photophysics; single-molecule spectroscopy; structure–property relations