Polarized photoluminescence and electroluminescence in oriented films of regioregular poly(3-alkylthiophenes)

We report polarized photoluminescence (PL) and electroluminescence (EL) from regioregular poly(3-alkylthiophene) thin ®lms oriented by means of the rubbing technique. With a proper thermal annealing of the rubbed ®lms we have increased the anisotropy reaching values up to 8 both in PL and EL. We have evidenced that the orientation in the rubbing direction is higher for the longest conjugation segments than for the less conjugated ones. Moreover polarized PL study demonstrates that emission takes place after migration of the excitation from shorter, less oriented, to longer, more oriented conjugation segments.