Reduced graphene oxide with a highly restored π-conjugated structure for inkjet printing and its use in all-carbon transistors

An inkjet-printed graphene film is of great importance for next-generation flexible, low cost and high performance electronic devices. However, due to the limitation of the inkjet printing process, the electrical conductivity of inkjet-printed graphene films is limited to ~10 S·cm^–1, and achieving a high conductivity of the printed graphene films remains a big challenge. Here, we develop a "weak oxidation–vigorous exfoliation" strategy to tailor graphene oxide (GO) for meeting all the requirements of highly conductive inkjet-printed graphene films, including a more intact carbon plane and suitable size. The π-conjugated structure of the resulting graphene has been restored to a high degree, and its printed films show an ultrahigh conductivity of ~420 S·cm^–1, which is tens of times higher than previously reported results, suggesting that, aside from developing a highly efficient reduction method, tuning the GO structure could be an alternative way to produce high quality graphene sheets. Using inkjet-printed graphene patterns as source/drain/gate electrodes, and semiconducting single-walled carbon nanotubes (SWCNTs) as channels, we fabricated an all-carbon field effect transistor which shows excellent performance (an on/off ratio of ~10⁴ and a mobility of ~8 cm²·V^–1·s^–1) compared to previously reported CNT-based transistors, promising the use of nanocarbon materials, graphene and SWCNTs in printed electronics, especially where high performance and flexibility are needed.