Density-dependent excitonic properties and dynamics in 2D heterostructures consisting of boron nitride and monolayer or few-layer tungsten diselenide

The understanding of two-dimensional (2D) materials has grown tremendously, especially for isolated monolayers. Recently, complex structures formed by stacking 2D materials have attracted considerable attention. This is in part due to the fact that the properties of monolayers are known to be influenced by their surroundings. Consequently, monolayer properties are predicted to be affected by “heterostructuring”. A study involving high-charge-carrier-density effects and dynamics is presented here for monolayers of WSe2 on different substrates and heterostructures comprised of 2D h-BN and WSe2. The influence of h-BN as well as the bilayer stacking order on the spectral and dynamical properties of WSe2- monolayer emission is discussed for the low-density regime and evidenced for high-density effects such as exciton-exciton annihilation and the Mott transition.