High-pressure study of picosecond exciton dynamics in solid C60

Photoexcitation dynamics in films of C60 and Zn phthalocyanine with a layered nanostructure

We elucidate photoexcitation dynamics in C(60) and zinc phthalocyanine (ZnPc) from picoseconds to milliseconds by transient absorption and time-resolved terahertz spectroscopy. Autoionization of C(60) is a precursor to photocarrier generation. Decay of the terahertz signal is due to decreasing photocarrier mobility over the first 20 ps and thereafter reflects recombination dynamics. Singlet diffusion rates in C(60) are determined by modeling the rise of ground state bleaching of ZnPc absorption following C(60) excitation. Recombination dynamics transform from bimolecular to monomolecular as the layer thickness is reduced, revealing a metastable exciplex at the C(60)/ZnPc interface with a lifetime of 150 μs.

Ultrafast formation of nonemissive species via intermolecular interaction in single crystals of conjugated molecules

We investigate the influence of interchain interactions on the photoluminescence processes in a sexithiophene single crystal by applying hydrostatic pressure. We perform transient photoluminescence spectroscopy in the time domain of 100 fs for pressures up to 60 kbar. The combined use of steady-state and time-resolved optical spectroscopies allows us to show that the pressure-induced quenching of the photoluminescence is caused by an ultrafast (approximately 100 fs) formation of intermolecular species.