title: Ultrafast dynamics of excitons in tetracene single crystals.
abstract: Ultrafast exciton dynamics in free standing 200 nm thin tetracene single crystals were studied at room temperature by femtosecond transient absorption spectroscopy in the visible spectral range. The complex spectrally overlapping transient absorption traces of single crystals were systematically deconvoluted. From this, the ultrafast dynamics of the ground, excited, and transition states were identified including singlet exciton fission into two triplet excitons. Fission is generated through both, direct fission of higher singlet states S(n) on a sub-picosecond timescale, and thermally activated fission of the singlet exciton S1 on a 40 ps timescale. The high energy Davydov component of the S1 exciton is proposed to undergo fission on a sub-picoseconds timescale. At high density of triplet excitons their mutual annihilation (triplet-triplet annihilation) occurs on a <10 ps timescale.
authors.affiliation: Laser Research Institute, Stellenbosch University, Stellenbosch 7600, South Africa.
authors.forename: Zephania
authors.initials: Z
authors.lastname: Birech
authors.affiliation: Department of Physics, University of Bayreuth, Bayreuth, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Schwoerer
authors.affiliation: Experimental Physics VI, University of Würzburg and Bavarian Center for Applied Energy Research, Würzburg, Germany.
authors.forename: Teresa
authors.initials: T
authors.lastname: Schmeiler
authors.affiliation: Experimental Physics VI, University of Würzburg and Bavarian Center for Applied Energy Research, Würzburg, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Pflaum
authors.affiliation: Laser Research Institute, Stellenbosch University, Stellenbosch 7600, South Africa.
authors.forename: Heinrich
authors.initials: H
authors.lastname: Schwoerer