The optical emission properties of alpha-sexithiophene single crystal
have been studied using photoluminescence (PL), time resolved PL and t
emperature dependent PL spectroscopy. Contrary to the absorption spect
rum the photoluminescence measured on the same sample shows broad and
structureless emission with a temperature dependence pointing to therm
ally activated defect state emission. The temperature dependence of th
e photoluminescence and the time-resolved photoluminescence measuremen
ts support this scenario.