Solvent effects on the characteristics of conductive and luminescent polymers

The electrical conductivity of ES film which was cast first in EB form followed by doping by HC1 was in the metallic range (20 S/cm) while that cast from m-cresol was in the range of semiconductor (8×10−4 S/cm). On the other hand, PPy film cast from m-cresol showed higher conductivity (1.3×10−4 S/cm) than the film cast from NMP solution(~10−10 S/cm). This is because the polymer chains in the film cast from a good solvent have more expanded structures than the those in the film cast from a poor solvent. The PL-intensity of P3ATʹs increased as the solvent becomes poorer. In a good solvent, as the P3AT chains have expanded structures with longer π-conjugation lengths, the excitons can migrate to quenching sites relatively easily lowering the luminescence efficiency. Conversely, in a poor solvent, the they have compact structures confining the excitons in relatively shorter segments of the chain. Thus the excitons would have more chances to relax via an emissive route. results indicate that the solvent-solute interactions have significant impacts on the luminescence of the film cast from the solution. It must be emphasized that, in the manufacturing of the devices utilizing such characteristics, the impacts of the solvents should be considered seriously.