Progress Report on “From Printed Electrolyte‐Gated Metal‐Oxide Devices to Circuits”

Printed electrolyte‐gated oxide electronics is an emerging electronic technology in the low voltage regime (≤1 V). Whereas in the past mainly dielectrics have been used for gating the transistors, many recent approaches employ the advantages of solution processable, solid polymer electrolytes, or ion gels that provide high gate capacitances produced by a Helmholtz double layer, allowing for low‐voltage operation. Herein, with special focus on work performed at KIT recent advances in building electronic circuits based on indium oxide, n‐type electrolyte‐gated field‐effect transistors (EGFETs) are reviewed. When integrated into ring oscillator circuits a digital performance ranging from 250 Hz at 1 V up to 1 kHz is achieved. Sequential circuits such as memory cells are also demonstrated. More complex circuits are feasible but remain challenging also because of the high variability of the printed devices. However, the device inherent variability can be even exploited in security circuits such as physically unclonable functions (PUFs), which output a reliable and unique, device specific, digital response signal. As an overall advantage of the technology all the presented circuits can operate at very low supply voltages (0.6 V), which is crucial for low‐power printed electronics applications. Electrolyte‐gated field‐effect transistors (EGFETs) based on an indium oxide channel enable high‐performance applications with low‐voltage requirements in the printed electronics domain. Circuits consisting of EGFETs are able to already operate at supply voltages ≈0.6 V. Besides logic gates, EGFETs are used in memory as well as security circuits.