Robust room temperature emissions of trion in darkish WSe 2 monolayers: effects of dark neutral and charged excitonic states

Owing to nonzero charge and spin degrees of freedom, trions offer unprecedented tunability and open new paths for applications in devices based on 2D semiconductors. However, in monolayer WSe 2 , the trion photoluminescence is commonly detected only at low temperatures and vanishes at room temperature, which undermines practical applications. To unveil how to overcome this obstacle, we have developed a comprehensive theory to probe the impact of different excitonic channels on the trion emission in WSe 2 monolayers, which combines ab initio tight-binding formalism, Bethe–Salpeter equation and a set of coupled rate equations to describe valley dynamics of excitonic particles. Through a systematic study in which new scattering channels are progressively included, we found that, besides the low electron density, strong many-body correlations between bright and dark excitonic states quenches the trion emission in WSe 2 . Therefore, the reduction of scatterings from bright to dark states is required to achieve trion emission at room temperature for experimentally accessible carrier concentrations.