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 sex-ithiophene 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 (similar to 100 fs) formation of intermolecular species. DOI: 10.1103/PhysRevLett.86.732.