Conductive polythiophene-like thin film synthesized using controlled plasma processes

• Fabrication of conductive polythiophene-like films by plasma process
• Transmittance more than 80%
• 3 order conductivity enhancement with iodine doping
• Retention of monomer structure responsible for better conductivities

Transparent conductive polythiophene-like thin films were synthesized by a plasma polymerization technique using a middle range frequency (40 kHz). The effects of the variation of power and pressure on the chemical structure of the deposited film were investigated along with the effect of doping with iodine vapors on the conductivity of the films. Plasma polymerization is a low temperature process, provides deposition of thin polymer films on a wide variety of substrates, and has advantages due to non-involvement of any solvents. The chemical structure of the films was characterized using Fourier Transform Infrared Spectroscopy. The wetting properties of the films were studied using water contact angle measurements. The fragmentation of the thiophene monomer structure increased with increasing discharge power, implying that at low discharge power, the plasma phase was energy-deficient. The lower fragmentation of the monomer led to high retention of the monomer structure in the deposited films. Under various pressure conditions, the retention of the monomer structure was found to be similar as that of the deposited films. After doping with iodine vapor, a large conductivity enhancement, from 3.52 × 10− 6 to 2.3 × 10− 3 s/cm was observed. The results showed the retention of a monomer structure having conjugated bonds in the films, responsible for the enhanced conductivities.