title: Relaxation dynamics of photoexcited excitons in rubrene single crystals using femtosecond absorption spectroscopy.
abstract: The relaxation dynamics of an exciton in rubrene was investigated by femtosecond absorption spectroscopy. Exciton relaxation to a self-trapped state occurs via the coherent oscillation with 78 cm(-1) due to a coupled mode of molecular deformations with phenyl-side-group motions and molecular displacements. From the temperature dependence of the decay time of excitons, the energy necessary for an exciton to escape from a self-trapped state is evaluated to be ~35 meV (~400 K). As a result, a self-trapped exciton is stable at low temperatures. At room temperature, excitons can escape from a self-trapped state and, subsequently, they are dissociated to charged species. The exciton dissociation mechanism is discussed on the basis of the results.
authors.affiliation: Department of Advanced Materials Science, University of Tokyo, Kashiwa, Chiba, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Tao
authors.forename: N
authors.initials: N
authors.lastname: Ohtani
authors.forename: R
authors.initials: R
authors.lastname: Uchida
authors.forename: T
authors.initials: T
authors.lastname: Miyamoto
authors.forename: Y
authors.initials: Y
authors.lastname: Matsui
authors.forename: H
authors.initials: H
authors.lastname: Yada
authors.forename: H
authors.initials: H
authors.lastname: Uemura
authors.forename: H
authors.initials: H
authors.lastname: Matsuzaki
authors.forename: T
authors.initials: T
authors.lastname: Uemura
authors.forename: J
authors.initials: J
authors.lastname: Takeya
authors.forename: H
authors.initials: H
authors.lastname: Okamoto