The effects of light and electrostatic doping on the carrier dynamics of transition metal dichalcogenides

Transition metal dichalcogenides (TMDs) are atomically thin semiconductors combined with van der Waals forces with unique properties that make them excellent for optoelectronic and photovoltaic applications. These materials, in both bulk and monolayer, have a variety of ultrafast photoinduced processes such as scattering, exciton formation, charge transfer and carrier recombination that can be studied with ultrafast transient absorption spectroscopy. Despite extensive previous research on the photophysical processes in these materials, the impact of a gate voltage via ionic-liquid gating on the carrier dynamics in these experiments remains limited. Ionic-liquid gating forms an electric double layer that acts as an electrostatic doping mechanism that creates even higher electric fields and charge densities than solid gate dielectrics and allows precise control over carrier concentration alongside photoexcitation. Our study uses ionic liquid gating to adjust the carrier concentration in TMDs such as MoS₂, altering photoinduced carrier dynamics as revealed by femtosecond transient absorption.