Strain-enhanced trion emission in monolayer WS2 modulated by an ion-gel electrochemical gate

The abundant light–matter interactions in monolayer WS2 make the manipulation of exciton states a fascinating endeavor. Utilizing photoluminescence spectroscopy, we investigated strain-induced red shifts and trion enhancement in a WS2 monolayer on a PET/PVA substrate with a Li+ ion-gel electrolyte gate. A notable red shift of the exciton emission peak was observed, increasing by ∼41 meV/%, up to a maximum strain of 2.5%. The combination of ion-gel and strain effectively modulated the radiative recombination, leading to a significant enhancement of the trion peak, with IXT/IX0 rising from 0.95 to 13.12 under 1.21% strain and 6.8 × 1012 cm−2 electron concentration. This enhancement is attributed to strain-induced changes in scattering channels between valleys and indirect bandgap excitation processes. Our study underscores the potential of coupling strain and ion-gate-induced doping for tuning excitonic behaviors in flexible quantum devices.