Oriented poly(3-alkylthiophene) films: absorption, photoluminescence and electroluminescence behaviour

We have found that highly regioregular poly(3-alkylthiophene) can be conveniently oriented by means of the rubbing technique. While in the absorption polarized spectra we found a dichroic ratio up to 5, depending on the wavelength, the photoluminescence and electroluminescence polarization have not the same value. A tentative explanation will be given taking into account that only the surface of the film is oriented during the rubbing process