Comparison of ex-situ solid and liquid iodine doping methods at different temperatures to improve electrical properties of polythiophene nanostructure films synthesized by atmospheric pressure plasma process

Despite advancements in research on conducting polymers, obtaining stable conductivity in thin films remains challenging. Although ex-situ iodine (I₂) doping methods have exhibited promise, they often result in unstable conductivity with increasing exposure time. This study aimed to produce polythiophene (PTh) nanostructure films with stable electrical conductivity through optimized ex-situ I₂-doping techniques using a newly fabricated atmospheric pressure plasma reactor for PTh deposition. I₂ charge carriers in the form of solid and liquid were separately incorporated into the PTh at room temperatures and 60 °C. FE-SEM, EDS, and FT-IR revealed an enhanced molecular structure, the distribution of element and functional chemical composition of the doped PTh nanostructure films, respectively. Compared to solid I₂ doping, the liquid-doped PTh exhibited improved electrical conductivity and stable conductivity over a long period. The results also proved promising for reliable applications in electronic devices, making ex-situ liquid I₂ doping a good technique.