Sub-picosecond time-resolved photoluminescence in substituted thiophenes

The emission properties of tetra and hexa methyl sulphanyl (SMe) substitute d sexithiophenes have been studied in solution form using time-resolved up- conversion photoluminescence technique. The SMe substituents have an electr on donating effect which compensates for the loss of pi-electron conjugatio n caused by the twisted conformation of the molecular geometry. Enhanced co njugation however does not lead to long recombination lime due to the heavy atom effect, which increases the nonradiative decay rate.