Electrical, morphological and electronic properties of inkjet printed PEDOT:PSS

Electrical and morphological properties of inkjet printed (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) thin-films samples have been explored using dimethyl sulfoxide as conduction enhancing cosolvent. Room temperature conductivity increased by a factor of 10³ to ~140 S cm^-1 on the addition of 5% DMSO, Hall probe analysis demonstrated a decrease in contact resistance from 10⁶Ω to 10⁴Ω whilst variable-temperature conductivity analysis shows an increase in VRH exponent from 0.25 to 0.5 signifying a charge transport evolution from Mott Variable Range Hopping in 3-dimensions to a pseudo 1-dimensional Variable Range Hopping. XPS analysis verified an increase in surface PEDOT to PSS ratio from 0.39 (0_wt% DMSO) to 0.5 (5_wt% DMSO) with an associated increase in PEDOT grain size from 11nm to 31nm, derived from electric field force microscopy. Concurrently the addition of DMSO acted as a foaming suppressor in samples containing the processing additive Surfynol 2502 with pristine samples matching the surface roughness of spin cast references.