Charge transport in cross-linked PEDOT:PSS near metal–insulator transition

• Published in: Journal of applied physics 2022-04, Vol.131 (15)
• Main Authors: Mohan, Arya, Anil, A. G., Ramamurthy, P. C., Menon, Reghu
• Format: Article
• Language: English
• Subjects: Applied physics; Charge transport; Crosslinking; Electric fields; Metal-insulator transition; Room temperature; Temperature dependence; Thermal conductivity
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/5.0085374

The charge transport in poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) cross-linked with divinyl sulfone (c-PEDOT:PSS) is compared with pristine PEDOT:PSS from conductivity, electric field, and frequency studies. In a cross-linked sample, the room temperature conductivity increased from 0.8 to 630 S/cm. The temperature dependence of conductivity, down to 4.2 K, is significantly weakened in a cross-linked sample. This cross-linking induced metal–insulator transition in PEDOT:PSS, as inferred from conductivity ratios ( σ r = σ 300 K / σ 4.2 K ), shows the role of modified nanomorphology in charge transport. The values of σ r for PEDOT:PSS and c-PEDOT:PSS are 6441 and 4.6, respectively. The temperature dependence of the electric-field effect on conductivity indicates that the nanoscale barriers for transport have been substantially reduced by cross-linking. Impedance spectroscopy studies suggest that the relaxation frequency in c-PEDOT:PSS is shifted to a higher frequency, and the real part decreases sharply at higher frequencies, indicating enhanced connectivity and weakened barriers between conductive PEDOT regions.