Radiative suppression of exciton–exciton annihilation in a two-dimensional semiconductor

Abstract

Two-dimensional (2D) semiconductors possess strongly bound excitons, opening novel opportunities for engineering light–matter interaction at the nanoscale. However, their in-plane confinement leads to large non-radiative exciton–exciton annihilation (EEA) processes, setting a fundamental limit for their photonic applications. In this work, we demonstrate suppression of EEA via enhancement of light–matter interaction in hybrid 2D semiconductor–dielectric nanophotonic platforms, by coupling excitons in WS2 monolayers with optical Mie resonances in dielectric nanoantennas. The hybrid system reaches an intermediate light–matter coupling regime, with photoluminescence enhancement factors up to 102. Probing the exciton ultrafast dynamics reveal suppressed EEA for coupled excitons, even under high exciton densities >1012 cm−2. We extract EEA coefficients in the order of 10−3, compared to 10−2 for uncoupled monolayers, as well as a Purcell factor of 4.5. Our results highlight engineering the photonic environment as a route to achieve higher quantum efficiencies, for low-power hybrid devices, and larger exciton densities, towards strongly correlated excitonic phases in 2D semiconductors.