Ink-jet printed highly conductive pristine graphene patterns achieved with water-based ink and aqueous doping processing

We report an efficient inkjet printing of water-based pristine GNPs graphene ink and a facile aqueous halogen doping process that provides significant and thermally stable conductivity enhancement of printed patterns. Highly concentrated aqueous graphene ink populated by few-layer pristine graphene flakes is obtained by means of scalable shear exfoliation process with the aid of bromine intercalation. The as-printed GNP films which has been merely treated by drying at 100 °C exhibits DC conductivity (σ_DC) of ∼1400 S/m likely due to bromine doping effect. This value is significantly increased to ∼3 × 10⁴ S/m when an additional treatment by means of dipping in aqueous iodine solution is applied prior to the drying. As contrast, σ_DC is increased to ∼2.4 × 10⁴ S/m when a mere annealing at elevated temperature in air is employed. When the aqueous iodine doping process and annealing at elevated temperature is combined, an unprecedented value of σ_DC ∼10⁵ S/m is achieved. The availability of water-based GNPs inks and low-temperature doping scheme for efficient and reliable conductivity enhancement has offered a pathway for the application of GNPs in different printed electronics devices.