Persistent Photoconductivity in Single Crystals of the High Temperature Polymorph of alpha-Sexithiophene

We have found persistent photoconductivity in alpha-sexithiophene single crystals and its properties and the charge transport in this material are studied in the temperature range from 100 to 340 K. Persistent photoconductivity is observed even above room temperature and the decrease in time of the conductivity can be described by a stretched exponential which lasts at low temperature for more than 10 sup 6 s. A thermal activation energy of 0.44 eV is observed for the relaxation time of the decay. Moreover, the persistent photoconductivity can be quenched by a strong electric field. The origin of these effects is discussed assuming metastable defect relaxations.