High luminescence efficiency of multi-valley excitonic complexes in heavily doped WSe2 monolayer

TL;DR

This study demonstrates that heavily doped WSe2 monolayers exhibit significantly enhanced photoluminescence due to multi-particle excitonic complexes, achieving quantum yields over 50%, which opens new avenues for efficient atomically thin light emitters.

Contribution

It reveals that high electron doping in WSe2 monolayers boosts excitonic emission efficiency, surpassing previous low-yield levels and enabling new optoelectronic applications.

Findings

Photoluminescence intensity increases with doping level.

Quantum yield exceeds 50% at high electron densities.

Multi-particle excitonic complexes dominate emission in doped regimes.

Abstract

Monolayers of group-VI transition-metal dichalcogenides (TMDs) are two-dimensional semiconductors that exhibit exceptionally strong light-matter coupling yet typically suffer from low emission quantum yields. In this letter, we investigate the heavily n-doped regime of a WSe$_2$ monolayer and show that multi-particle excitonic complexes produce photoluminescence signals up to two orders of magnitude stronger than in the neutral state. Time-resolved photoluminescence and differential reflectivity measurements reveal that the quantum yield rises with carrier density and exceeds 50% for electron concentrations above 10$^{13}$ cm$^{-2}$. These findings establish TMD monolayers as a platform for exploring excitonic complexes in high-density electron gases and point toward new opportunities for efficient, atomically thin light emitters.