Inkjet printing of transparent and conductive patterns of single-walled carbon nanotubes and PEDOT-PSS composites

Transparent and conductive patterns of carboxyl functionalized single-walled carbon nanotubes (SWCNT-COOHs) and the composites of those with poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) were deposited on various substrates by inkjet printing. For low print repetitions, the PEDOT-PSS/SWCNT-COOH composite patterns show enhanced conductance as compared to the corresponding PEDOT-PSS conductors. The results suggest a decreased percolation threshold for the printed composite since the nanotubes establish electrical interconnections between the separate PEDOT-PSS (conductive phase) islands being dispersed in the insulating PSS-phase. However, the interaction between PEDOT-PSS and SWCNTs becomes insignificant and the conductivity is not enhanced by the nanotubes, when the amount of PEDOT-PSS is sufficient to form a continuous conducting phase. Up to now, patterns having sheet resistivities as low as ∼1 kΩ/□ could be achieved. Though there is a trade-off between transparency and conductivity – we achieved highly transparent patterns (∼90%) with a reasonably low resistivity of ∼10 kΩ/□. The ink and printing method proposed here offer new alternatives of conventional transparent conductive materials based on either polymers or indium oxides; and pose scaleable production of cost-effective transparent electronics.