Effects of the surrounding medium on the photophysics of conjugated oligomers mixed with C60

摘要

Abstract: We discuss the photophysical properties of the supramolecular composites of two $pi@electron semiconductors; e.g. conjugated oligothiophenes as electron donors and Buckminsterfullerene, C60, as electron acceptor in different solvents as well as in solid composite films. Thus, the supramolecular solid state composites of these two conjugated materials exhibit an ultrafast, reversible, metastable photoinduced electron transfer and long lived charge separation. Upon changing the polarity of the surrounding media, however, we observe a profound effect on the photophysical properties of these composites in solution. Polar solvents induce electron transfer upon photoexcitation. In non-polar solvents the energy transfer is dominant. To investigate the effects of molecular ordering we embedded conjugated oligomers into nematic liquid crystals and achieved a high degree of orientation. Furthermore, in these spontaneously oriented media, the orientation of the liquid crystal host alongside with the conjugated oligomer guest can be switched upon applying an electric field. This results in dynamic switching of the polarized photoluminescence of oligomers. !11