Carrier density is an important factor that affects the physical properties of materials. Tuning the carrier density by an electric field can have an important impact on the electronic, magnetic, optical, or even structural properties of a material. Controlling the carrier density in a transistor using electric fields is an important approach for tuning the electronic states of condensed matter. Recently, transistors using ionic liquids as gate dielectrics have attracted significant attention. Ionic liquids are a type of aqueous electrolyte that conducts electricity through the movement of organic cations and anions. By using ionic liquids as gate dielectrics, an electric double-layer transistor can be fabricated for material-property control. The major advantage of ionic-liquid gating is that the electric double layer formed by the cations and electrons is essentially a nanoscale parallel-plate capacitor with a very large specific capacitance. Ionic liquid technology can realise a wider tunable range of carrier density than traditional transistor technology. With the rapid development of ionic liquid technology, two paradigms, electrostatic field-effect tuning and electrochemical doping, have been recently explored. Based on several beneficial aspects of in situ, reversible, and large-scale tunability of the ionic liquid technology, we herewith make a comprehensive review of the research progress on ionic-liquid-controlled structural transition, magnetic properties, electrical transport, and thermal conduction of thin films. The future prospects of ionic-liquid-control technology for use in smart glass and artificial neural network devices have also been suggested. © 2023 Cailiao Daobaoshe/ Materials Review. All rights reserved.
