Ultrafast excited state dynamics in 3,4,9,10-perylene tetracarboxylic dianhydride (PTCDA) thin films

Ultrafast decay dynamics of the excited state in the thin films of 3,4,9,10-perylene tetracarboxylic dianhydride (PTCDA) have been directly observed by using fs time-resolved two-photon photoelectron spectroscopy. The lifetimes were measured up to the excess energy of 2 eV above the S1 state. The highly excited state presumably S2 decays with τ=70±2 fs and S1 with τ=360±12 fs. The extremely short lifetimes indicate that those excited states undergo very fast non-radiative decay, which is consistent with low fluorescence quantum yields in the S1 manifold.