Pressure-Dependent Light Emission of Charged and Neutral Excitons in Monolayer MoSe₂

Tailoring the excitonic properties in two-dimensional monolayer transition metal dichalcogenides (TMDs) through strain engineering is an effective means to explore their potential applications in optoelectronics and nanoelectronics. Here we report pressure-tuned photon emission of trions and excitons in monolayer MoSe₂ via a diamond anvil cell (DAC) through photoluminescence measurements and theoretical calculations. Under quasi-hydrostatic compressive strain, our results show neutral (X⁰) and charged (X^-) exciton emission of monolayer MoSe₂ can be effectively tuned by alcohol mixture vs inert argon pressure transmitting media (PTM). During this process, X^- emission undergoes a continuous blue shift until reaching saturation, while X⁰ emission turns up splitting. The pressure-dependent charging effect observed in alcohol mixture PTM results in the increase of the X^- exciton component and facilitates the pressure-tuned emission of X^- excitons. This substantial tunability of X^- and X⁰ excitons in MoSe₂ can be extended to other 2D TMDs, which holds potential for developing strained and optical sensing devices.