Non-destructive method of spectroscopic ellipsometry (SE) from IR to FUV was
applied to study PEDOT/PSS thin films deposited by spin coating from aqueous
dispersions of the material with different N,N-Dimethylformamide (DMF)
volume percent. In our work we used the Tauc-Lorentz model to describe the
dielectric function of PEDOT/PSS:DMF films in the Vis-FUV energy region.
First, the spectrum analysis showed that the thickness and the fundamental
band gap Eg of the film is being decreased with the increase of DMF
content in the dispersion. Taking into account that the heating temperature
is below the boiling point of DMF we assume that DMF molecules are
incorporated in the film volume and act as dopants. Further more, this means
that carrier concentration is being increased and thus we have higher
electrical conductivity. The existence of DMF molecules in the film proved
from FTIR SE, which can probe the bonding structure of the materials. The
results showed lowering of peak intensity assigned to PEDOT/PSS and
appearing of peaks assigned to DMF in the imaginary part of spectrum. In
conclusion, SE is a potential tool for the evaluation of electronic
properties for conductive polymers.