Highly Conductive Semitransparent Graphene Circuits Screen‐Printed from Water‐Based Graphene Oxide Ink

The use of graphene materials as conductive inks for flexible and transparent electronics is promising, but challenged by the need for stabilizers, specialized organic solvents, and/or high temperature annealing, severely limiting performance or compatibility with substrates and printing techniques. Here, the development of a scalable water‐based graphene oxide ink is reported that can be screen‐printed on flexible plastic substrates and subsequently reduced using a 1:1 mixture of trifluoroacetic acid and hydroiodic acid, thereby creating an electric circuit. The reduced prints exhibit low sheet resistance of 327 Ω sq⁻¹ for thin semitransparent layers with 37% transmittance. This methodology with postprinting chemical reduction outperforms high temperature annealing, thereby eliminating the need for such a step, which is incompatible with flexible plastic substrates. The strategy relies on low cost, industrially compatible chemicals and can be scaled up for low cost manufacture of roll‐to‐roll printed electronics.