  Two-dimensional materials are an emerging class of new materials with a wide
range of electrical and optical properties and potential applications.
Single-layer structures of semiconducting transition metal dichalcogenides are
gaining increasing attention for use in field-effect transistors. Here, we
report a photoluminescence switching effect based on single-layer WSe2
transistors. Dual gates are used to tune the photoluminescence intensity. In
particular, a side-gate is utilized to control the location of ions within a
solid polymer electrolyte to form an electric double layer at the interface of
electrolyte and WSe2 and induce a vertical electric field. Additionally, a
back-gate is used to apply a 2nd vertical electric field. An on-off ratio of
the light emission up to 90 was observed under constant pump light intensity.
In addition, a blue shift of the photoluminescence line up to 36 meV was
observed.
