Molecular Tautomerization on the Surface of Monolayer MoS ₂ for Field‐Effect Transistors with Ultra‐High Mobilities and On–Off Ratios

The inherent contradiction between carrier mobility and gate performance constrains the advancement of monolayer MoS 2 (1L‐MoS 2 ) field‐effect transistors (FETs). Herein, we show that the tautomerization of organic molecules on the surface of 1L‐MoS 2 simultaneously improves the carrier concentration and minimizes the leakage current. This tautomeric molecule comprises a pyridin‐2‐ol structure and two tert‐butyltriphenylamine groups (named tTPA‐PyOH). tTPA‐PyOH molecules anchored on the defect‐state Mo atoms passivate the defects and donate electrons to 1L‐MoS 2 , resulting in n‐doping. 1L‐MoS 2 lowers the enol‐keto tautomerization energy barrier of tTPA‐PyOH, and the as‐generated cationic ketone configuration exhibits a p‐doping effect on 1L‐MoS 2 . The tautomerization behavior can be manipulated by electrical stimulation of FET devices. Therefore, the 1L‐MoS 2 ‐tTPA‐PyOH FETs simultaneously achieve ultra‐high mobility (up to 165.1 cm 2 V −1 s −1 ), large on‐off ratios (exceeding 10 10 ), and outstanding stability under ambient conditions. This study unlocks the potential of molecular tautomerization for electronic property regulation of 2D semiconductors.