Excitation dynamics in ?-sexithiophene single crystals and UHV-grown films

We have investigated the disorder-determined optical properties of ?-sexithiophene by comparing measurements of an evaporated film and a single crystal. We observed for the first time sharp lines in absorption and photoluminescence from both samples representing the intrinsic electronic properties of the material. The time-integrated emission spectra of both samples are dominated by radiative trap emission, which is more pronounced in the film due to the higher degree of disorder