Radiative lifetime of localized excitons in transition-metal dichalcogenides

Disorder derived from defects or strain in monolayer TMDs can lead to a\ndramatic change in the physical behavior of the interband excitations,\nproducing inhomogeneous spectral broadening and localization; leading to\nradiative lifetime increase. In this study, we have modeled the disorder in the\nsurface of the sample through a randomized potential in monolayer WSe2. We show\nthat this model allows us to simulate the spectra of localized exciton states\nas well as their radiative lifetime. In this context, we give an in depth study\nof the influence of the disorder potential parameters on the optical properties\nof these defects through energies, density of states, oscillator strengths,\nphotoluminescence (PL) spectroscopy and radiative lifetime at low temperature\n(4K). We demonstrate that localized excitons have a longer emission time than\nfree excitons, in the range of tens of picoseconds or more, and we show that it\ndepends strongly on the disorder parameter and dielectric environment. Finally,\nin order to prove the validity of our model we compare it to available\nexperimental results of the literature.\n