Proton‐Mediated Phase Control in Flexible and Transparent Mott Transistors

Abstract To meet the development of wearable and energy‐efficient flexible electronics, multifunctional oxide film on soft substrate and its versatile phase control are in demand. Here, flexible VO 2 film is directly deposited on mica via van der Waals epitaxy, exhibiting pronounced metal‐insulator (MI) transition and infrared (IR) switching properties. Using a rubbery solid ionic gel as gate insulator, a fully flexible and transparent VO 2 ‐channel Mott transistor is successfully demonstrated. The prototype Mott transistor processes excellent mechanical flexibility and giant on/off current ratio of ≈10 5 % even at room temperature. Highly reversible suppression of MI transition is realized by applying small gate voltages and the nonvolatile phase modulation suggests an electrochemical reaction mechanism. X‐ray diffraction and secondary‐ion mass spectroscopy analyses, together with theoretical calculation, confirm that electrically controlled phase transformation is mainly caused by reversible and nonvolatile proton (H + ) doping into VO 2 lattices. Significant modulation of IR transmittance (>40%) is observed in the VO 2 Mott transistor, which is attributed to electrically driven phase transition between insulating VO 2 and metallic H x VO 2 phases. The flexible and transparent Mott transistor provides a good platform for proton‐mediated Mottronics and realizes novel electric control of optical characteristics, showing a promising application for flexible energy‐saving smart windows.