Nonlinear Photoluminescence in Atomically Thin Layered WSe2 Arising from Diffusion-Assisted Exciton-Exciton Annihilation

TL;DR

This study reveals how long-distance exciton diffusion and diffusion-assisted exciton-exciton annihilation lead to nonlinear photoluminescence in monolayer WSe2, advancing understanding of multi-exciton dynamics in 2D materials.

Contribution

It introduces a diffusion-assisted exciton-exciton annihilation model that explains nonlinear PL behavior and long-range exciton diffusion in monolayer WSe2.

Findings

Nonlinear saturation of PL with increasing excitation power

Exciton diffusion reaching several micrometers

Diffusion-assisted exciton-exciton annihilation explains observed behavior

Abstract

We studied multi-exciton dynamics in monolayer WSe2 using nonlinear photoluminescence (PL) spectroscopy and Monte Carlo simulations. We observed strong nonlinear saturation behavior of exciton PL with increasing excitation power density, and long-distance exciton diffusion reaching several micrometers. We demonstrated that the diffusion-assisted exciton-exciton annihilation model accounts for the observed nonlinear PL behavior. The long-distance exciton diffusion and subsequent efficient exciton-exciton annihilation process determined the unusual multi-exciton dynamics in atomically thin layered transition metal dichalcogenides.