Temperature activated de-trapping processes in vacuum deposited sexithiophene thin films

Photoluminescence (PL) emission spectra of sexithiophene (6T) thin films grown on different substrates by organic molecular beam deposition (OMBD) are studied in the range of temperature from 300 to 7 K. Besides the two vibronic progressions detectable between 300 and 50 K, related to the radiative recombination of the free exciton and to a structural defect state, a new emission is observed at temperatures lower than 40 K, whose origin is discussed in terms of exciton bound to a structural defects.