Ultrafast dynamics of excitons in tetracene single crystals

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 S-1 on a 40 ps timescale. The high energy Davydov component of the S-1 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. (C) 2014 AIP Publishing LLC.