title: Photophysical, amplified spontaneous emission and charge transport properties of oligofluorene derivatives in thin films.
abstract: We investigate the photophysical and amplified spontaneous emission properties of a series of monodisperse solution-processable oligofluorenes functionalized with hexyl chains at the C9 position of each fluorene unit. Thin films of these oligofluorenes are then used in organic field-effect transistors and their charge transport properties are examined. We have particularly focused our attention on the influence of oligofluorene length on the absorption and steady-state fluorescence spectra, on the HOMO/LUMO energy levels, on the photoluminescence lifetime and quantum yield as well as on the amplified spontaneous emission properties and the charge carrier mobilities. Differential scanning calorimetry and X-ray diffraction measurements demonstrate that, among all oligofluorene derivatives used in this study, only the structure and morphology of the pentafluorene film is significantly modified by a thermal treatment above the glass transition temperature, resulting in a 9 nm blue-shift of the fluorescence spectrum without significant changes in the photoluminescence quantum yield and in the amplified spontaneous emission threshold. In parallel, hole field-effect mobility is significantly increased from 8.6 × 10(-7) to 3.8 × 10(-5) cm(2) V(-1) s(-1) upon thermal treatment, due to an increase of crystallinity. This study provides useful insights into the morphological control of oligofluorene thin films and how it affects their photophysical and charge transport properties. Moreover, we provide evidence that, because of the low threshold, the tunability of the amplified spontaneous emission and the photostability of the films, these oligofluorenes are promising candidates for organic solid-state laser applications.
authors.affiliation: Department of Physics, CNRS-Ewha International Research Center, Ewha Womans University, Seoul, South Korea. ribierre@opera.kyushu-u.ac.jp.
authors.forename: E Y
authors.initials: EY
authors.lastname: Choi
authors.forename: L
authors.initials: L
authors.lastname: Mazur
authors.forename: L
authors.initials: L
authors.lastname: Mager
authors.forename: M
authors.initials: M
authors.lastname: Gwon
authors.forename: D
authors.initials: D
authors.lastname: Pitrat
authors.forename: J C
authors.initials: JC
authors.lastname: Mulatier
authors.forename: C
authors.initials: C
authors.lastname: Monnereau
authors.forename: A
authors.initials: A
authors.lastname: Fort
authors.forename: A J
authors.initials: AJ
authors.lastname: Attias
authors.forename: K
authors.initials: K
authors.lastname: Dorkenoo
authors.forename: J E
authors.initials: JE
authors.lastname: Kwon
authors.forename: Y
authors.initials: Y
authors.lastname: Xiao
authors.forename: K
authors.initials: K
authors.lastname: Matczyszyn
authors.forename: M
authors.initials: M
authors.lastname: Samoc
authors.forename: D-W
authors.initials: DW
authors.lastname: Kim
authors.forename: A
authors.initials: A
authors.lastname: Nakao
authors.forename: B
authors.initials: B
authors.lastname: Heinrich
authors.forename: D
authors.initials: D
authors.lastname: Hashizume
authors.forename: M
authors.initials: M
authors.lastname: Uchiyama
authors.forename: S Y
authors.initials: SY
authors.lastname: Park
authors.forename: F
authors.initials: F
authors.lastname: Mathevet
authors.forename: T
authors.initials: T
authors.lastname: Aoyama
authors.forename: C
authors.initials: C
authors.lastname: Andraud
authors.forename: J W
authors.initials: JW
authors.lastname: Wu
authors.forename: A
authors.initials: A
authors.lastname: Barsella
authors.forename: J C
authors.initials: JC
authors.lastname: Ribierre