Interplay of Excitonic Complexes in $p$-Doped WSe$_2$ Monolayers

TL;DR

This study investigates how excitonic complexes in p-doped WSe2 monolayers influence photoluminescence, revealing optimal doping levels for brightest emission and explaining the underlying scattering mechanisms.

Contribution

It provides a qualitative model explaining the doping-dependent behavior of excitonic complexes and photoluminescence in WSe2 monolayers.

Findings

Maximum photoluminescence at moderate p-doping levels

Decrease in dark trion signals with increased doping

Increase in bright trion signals with doping

Abstract

WSe$_2$ monolayers with variable doping are an ideal system to study two-dimensional excitonic complexes. Here, we find that the strongest photoluminescence from bright neutral excitons occurs at moderate $p$-doping levels, owing to a rapid decrease of signal from positive dark trions and a slow increase of signal from positive bright trions with growing $p$-concentrations. We explain our observations with a qualitative model, in which the scattering rate of bright excitons into dark complexes is enhanced by exciton localization, while the scattering rate into positive bright trions increases with $p$-doping level.